 Closeup of a proteasome core complex with ubiquitin molecules
After "deep-diving" into autophagy and impaired autophagy, one of the twelve hallmarks of aging, it makes sense to shine some light on its equally important (however not so famous) partner in cellular housekeeping: the proteasome. It ́s primary function is breaking down proteins that are no longer needed, damaged, or misfolded [1]. Similar to autophagy, it is our body's and skin's very own trash and recycling system, working 24/7 to keep our cells healthy and functioning [2]. The human body is composed of approximately 16-20% protein by weight. This percentage can vary based on factors like age, sex, and overall body composition. Skin, is particularly rich in proteins, about 25-30% of the total protein in the human body is found in the skin and the dry weight of skin is approximately 70% protein. Loss of proteostasis (balance of protein synthesis, folding, and degradation) is one of the twelve hallmarks of aging and the proteasome is an important mechanism within the proteostasis network [3].
THE PROTEASOME The proteasome is a large, barrel-shaped protein complex found in all eukaryotic cells, responsible for the degradation of intracellular proteins [4]. It plays a crucial role in maintaining cellular homeostasis by selectively breaking down short-lived, damaged, or misfolded proteins [5]. The 26S proteasome consists of a 20S core particle and one or two 19S regulatory particles [6]. Proteins targeted for degradation are typically tagged with ubiquitin molecules, which are recognized by the 19S regulatory particle, allowing the protein to be unfolded and fed into the 20S core for proteolysis [7]. The ubiquitination process provides a highly selective mechanism for targeting proteins for degradation in comparison to other systems like lysosomes. Proteasomal degradation is an ATP-dependent process:
▌Maintaining protein quality control [12] ▌Regulating cellular processes by controlling protein levels ▌Recycling amino acids for new protein synthesis The proteasome is involved in numerous vital cellular processes, including: ▌Cell cycle regulation ▌Transcriptional control ▌Immune responses ▌Neuronal plasticity Its proper function is essential for cellular health, and dysfunction of the proteasome system has been implicated in various diseases, including neurodegenerative disorders and cancer. The proteostasis network The proteostasis network (PN) is a complex system of cellular machinery that maintains the integrity of the proteome consisting of collaborating systems to ensure proper protein folding, repair damaged proteins and eliminate those beyond repair. ▌Molecular chaperones and co-chaperones ▌The ubiquitin-proteasome system (UPS) ▌Autophagy machinery ▌Translational machinery 
PROTEASOME VS AUTOPHAGY
Complementary cleaning and recycling systems While the proteasome primarily handles short-lived and soluble proteins, autophagy is responsible for degrading long-lived proteins, protein aggregates, and even entire organelles [13]. The proteasome plays critical roles in cell cycle control, gene expression, protein quality control, and immune responses, while other systems like autophagy are more involved in bulk degradation and cellular remodeling. The systems are not entirely independent and often work together to maintain cellular health [14]. The ubiquitin-proteasome system (UPS) and autophagy interact through various mechanisms:
PROTEASOME AND EPIGENETICS The proteasome also plays a significant role in epigenetics - the study of heritable changes in gene expression that don't involve changes to the underlying DNA sequence and recognised as one of the hallmarks of aging [19]. The proteasome influences epigenetics through several mechanisms: ▌Histone regulation + modification: The proteasome degrades histones, proteins that package DNA, influencing chromatin structure and gene accessibility [20].. ▌Transcription factor control + regulation: By regulating the levels of transcription factors, the proteasome indirectly affects gene expression patterns [21]. ▌Epigenetic modifier turnover + DNA methylation: The proteasome controls the levels of enzymes that modify histones and DNA, such as histone deacetylases (HDACs) and DNA methyltransferases (DNMTs) [22]. ▌Non-proteolytic functions: Some proteasome subunits have been found to directly interact with chromatin, suggesting a more direct role in gene regulation [23]. These interactions create a complex feedback loop between protein degradation and gene expression, highlighting the proteasome's far-reaching influence on cellular function PROTEASOME AND (SKIN) HEALTH The proteasome is likely present in skin cells and in extracellular fluids associated with skin, such as sweat and plays a vital role in maintaining health and skin quality by regulating the turnover of various proteins. Proteins are fundamental to life for several reasons:
Important proteins in skin and the human body based on their overall impact and prevalence:
▌accelerated aging of skin cells ▌reduced collagen production and increased breakdown ▌impaired elastin function ▌wrinkles, sagging and loss of elasticity ▌impaired wound healing and barrier function ▌increased susceptibility to UV damage and DNA damage [26] Or more skin conditions like:
PROTEASOME AND CELLULAR SENESCENCE The proteasome plays a crucial role in preventing cellular senescence, a state of permanent cell cycle arrest associated with aging:
PROTEASOME AND IMMUNE FUNCTION The proteasome is integral to immune system function:
Glycosylated proteins Proteins connected to sugar molecules, known as glycosylated proteins, can be targeted by the proteasome: ▌Ubiquitin-Proteasome System (UPS) is capable of degrading many types of glycoproteins [29]. ▌However, hyperglycemia (high blood sugar) can impair proteasome function. Glucose-derived compounds like methylglyoxal (MGO) can modify proteasome subunits, reducing their activity [29]. Amyloids The proteasome's relationship with amyloids (involved in for example Alzheimer's disease) is more complex. The proteasome can degrade some amyloid precursor proteins and smaller amyloid aggregates [30]. However, larger amyloid fibrils often overwhelm or inhibit the proteasome: ▌Amyloid aggregates can clog the entrance to the proteasome's catalytic core. ▌Some amyloids can directly inhibit proteasome activity. INFLUENCERS PROTEASOME ACTIVITY Challenges in protein clearance Several factors can hinder the proteasome's ability to clear modified or aggregated proteins: Glycation: Advanced glycation end products (AGEs) formed in hyperglycemic conditions can modify the proteasome, reducing its activity [29]. Oxidative stress: Often associated with aging and disease, it can damage both proteins and proteasomes [29]. Aging: Proteasome activity generally declines with age, reducing the cell's capacity to clear problematic proteins [30]. The proteasome's activity is sensitive to pH changes: ▌Optimal pH range for proteasome function is typically between 7.5-8.0. ▌Acidic conditions tend to inhibit proteasome activity, while alkaline conditions can enhance it to a certain extent. ▌Skin pH, which is typically slightly acidic (around 4.7-5.75), may influence extracellular proteasome activity. Oxidative stress has complex effects on the proteasome system in skin: ▌Mild oxidation (hormesis) can stimulate proteasomal degradation, while severe oxidation inhibits it ▌Oxidative stress can cause the 26S proteasome to disassemble into its 20S core and 19S regulatory components [25] ▌In skin, oxidative stress from UV radiation or environmental pollutants may affect proteasome function ▌Severely oxidized proteins may form non-degradable aggregates that can bind to and inhibit the proteasome [24] ▌Oxidative stress can reduce cellular ATP levels, affecting the ATP-dependent 26S proteasome function [25] ▌Oxidative stress can alter the association of chaperone proteins like HSP70 with the proteasome, affecting its function and assembly [25] Temperature can significantly impact proteasome function: ▌The optimal temperature for proteasome activity is typically around 37°C (human body temperature) [27] ▌Higher temperatures may initially increase proteasome activity but can eventually lead to denaturation and loss of function. ▌Low temperatures reduce proteasome activity by slowing down enzymatic reactions. ▌Skin, being exposed to environmental temperature changes, may experience fluctuations in proteasome activity. MAINTAIN AND IMPROVE PROTEASOME Several strategies can help maintain and improve proteasomal function: Exercise: Regular physical activity has been shown to enhance proteasome activity. Diet: ▌Protein: Ensuring adequate intake of high-quality proteins provides the building blocks for maintaining a healthy proteome ▌Polyphenols: Found in green tea, berries, and red wine, can stimulate proteasome function. ▌Omega-3 fatty acids: May help maintain proteasome activity and reduce oxidative stress. ▌Sulforaphane (found in broccoli sprouts): Activates Nrf2, which enhances proteasome function. ▌Spermidine: This natural polyamine has been shown to enhance autophagy and improve proteostasis. ▌Curcumin: This compound from turmeric has been shown to enhance proteostasis and have anti-aging effects ▌Caloric restriction or intermittent fasting: May enhance proteasome activity and promote cellular health. Stress management: Chronic stress can impair proteasome function, so stress reduction techniques will be beneficial. Adequate sleep: Crucial for cellular repair and protein homeostasis. Skincare + ingredients: ▌Sun protection: Use broad-spectrum sunscreens to protect skin from photo-damage, which can impair proteasome function. ▌Retinoids: May enhance proteasome activity in skin cells. ▌Peptides: Certain peptides have been shown to stimulate proteasome function. ▌Licochalcone A: Activates Nrf2, which in turn enhances proteasome function. ▌Niacinamide: Supports proteasome function and improves skin barrier health. In-office treatments: ▌Low-level laser therapy: May improve proteasome function in skin cells. ▌Chemical peels: Can stimulate cellular renewal and potentially enhance proteasome activity. MISCELLANEOUS PROTEASOME FACTS ▌Ancient origins: Proteasomes are found in all three domains of life (bacteria, archaea, and eukaryotes), suggesting they evolved over 2 billion years ago. ▌Rapid recyclers: A single proteasome can degrade about 2 million proteins over its lifetime. ▌Circadian rhythm regulation: The proteasome plays a crucial role in maintaining our body's internal clock by degrading clock proteins at specific times. ▌Stress response: Under stress conditions, cells can form large assemblies of proteasomes called "proteasome storage granules" to quickly respond to changing protein degradation needs. The role of the proteasome in protein quality control, cellular regulation, interplay with autophagy, epigenetics, telomeres, cell senescence and more, makes it a key player in maintaining our health and beauty and an interesting target for new strategies to enhance longevity [28], health span and beauty span. Always consult a qualified healthcare professional to determine what the most suitable approach is for your needs and rejuvenation or regeneration goals. Take care! Anne-Marie References: [1] Glickman MH, Ciechanover A. Physiol Rev. 2002;82(2):373-428. [2] Lecker SH, et al. Annu Rev Biochem. 2006;75:629-649. [3] López-Otín C, et al. Cell. 2013;153(6):1194-1217. [4] Tanaka K. Proc Jpn Acad Ser B Phys Biol Sci. 2009;85(1):12-36. [5] Goldberg AL. Nature. 2003;426(6968):895-899. [6] Finley D. Annu Rev Biochem. 2009;78:477-513. [7] Pickart CM, Cohen RE. Nat Rev Mol Cell Biol. 2004;5(3):177-187. [8] Hershko A, Ciechanover A. Annu Rev Biochem. 1998;67:425-479. [9] Thrower JS, et al. EMBO J. 2000;19(1):94-102. [10] Smith DM, et al. Mol Cell. 2005;20(5):687-698. [11] Groll M, et al. Nature. 1997;386(6624):463-471. [12] Balch WE, et al. Science. 2008;319(5865):916-919. [13] Mizushima N, Komatsu M. Cell. 2011;147(4):728-741. [14] Dikic I. Trends Biochem Sci. 2017;42(11):873-886. [15] Ding WX, et al. Am J Pathol. 2007;171(2):513-524. [16] Zhao J, et al. Cell Metab. 2015;21(6):898-911. [17] Pandey UB, et al. Nature. 2007;447(7146):859-863. [18] Korolchuk VI, et al. Mol Cell. 2010;38(1):17-27. [19] Greer EL, Shi Y. Nat Rev Genet. 2012;13(5):343-357. [20] Qian MX, et al. Cell. 2013;153(5):1012-1024. [21] Muratani M, Tansey WP. Nat Rev Mol Cell Biol. 2003;4(3):192-201. [22] Gu B, Lee MG. Mol Cell. 2013;49(6):1134-1146. [23] Geng F, et al. Proc Natl Acad Sci USA. 2012;109(5):1437-1442. [24] Bach SV, et al. Biomol Concepts. 2016;7(4):215-227. doi:10.1515/bmc-2016-0016 [25] Bonea D, et al. BMC Plant Biol. 2021;21:486. doi:10.1186/s12870-021-03234-9 [26] Minoretti P, et al. Cureus. 2024;16(1):e52548. doi:10.7759/cureus.52548 [27] Groll M, et al. Nat Struct Biol. 2005;12(11):1062-1069. doi:10.1038/nsmb1006 [28] Galatidou S, et al. Mol Hum Reprod. 2024;30(7):gaae023. doi:10.1093/molehr/gaae023 [29=41] Queisser MA, et al. Hyperglycemia impairs proteasome function by methylglyoxal. Diabetes. 2010 [28=42] Mao, Y. Structure and Function of the 26S Proteasome. In: Harris, J.R., Marles-Wright, J. Macromolecular Protein Complexes III. Springer, 2021. [29=43] Schipper-Krom, S. Visualizing Proteasome Activity and Intracellular Localization. Front. Mol. Biosci. 6, 2019. [30=44] Lifespan.io. Loss of Proteostasis. Lifespan.io Topics. Accessed 2024.
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 The process of autophagy in which a lysosome engulfs and digests excess or damaged cellular material.
Autophagy was initially classified under "altered proteostasis" as part of the hallmarks of aging. However as autophagy is involved in various other aspects of aging, such as DNA repair and metabolism, it's now seen as an "integrative hallmark". Autophagy is the cell´s way of cleaning up and recycling it´s own parts to maintain health and efficiency [1] by breaking down various parts of the cell, such as proteins, fats, and small structures called organelles. This breakdown happens in special compartments within the cell called lysosomes, which contain enzymes that can digest these cellular components. Impaired autophagy is a cause of aging and not just a consequence. When the efficiency of autophagy declines, it contributes to the accumulation of damaged cellular components, affecting other hallmarks of aging and the progression of health and beauty (skin health) problems [1][2].
SIMPLIFIED HOW AUTOPHAGY WORKS ▌Initiation: The process begins when a cell is under stress, such as during nutrient deprivation or oxidative stress. ▌Formation of the autophagosome: A double-membrane structure called a phagophore forms and expands to engulf damaged or unnecessary cellular components. ▌Encapsulation: The phagophore completely surrounds the targeted cellular material, forming a sealed vesicle called an autophagosome. ▌Fusion with lysosome: The autophagosome travels through the cell and fuses with a lysosome, forming an autophagolysosome - see picture below ▌Breakdown and recycling: Inside the autophagolysosome, lysosomal enzymes break down the captured cellular material into basic building blocks like amino acids, fatty acids, and nucleotides. ▌Reuse of materials: The broken-down components are released back into the cell's cytoplasm, where they can be reused to build new cellular structures or generate energy. THREE MAIN TYPES OF AUTOPHAGY
Various impairments in these autophagy mechanisms can occur: ▌Autophagosome formation ▌Decreased lysosomal function ▌Impaired fusion of autophagosomes with lysosomes ▌Accumulation of non-degradable material in lysosomes These impairments lead to the accumulation of damaged cellular components, contributing to the aging process. CONSEQUENCES DECLINE AUTOPHAGIC ACTIVITY
 Illustration showing the fusion of a lysosome (upper left) with an autophagosome during the process of autophagy.
GENERAL CAUSES IMPAIRED AUTOPHAGY - HEALTH
Disruption of key regulatory pathways Autophagy is tightly regulated by several molecular pathways, and disruption of these can impair the process: ▌Nutrient sensing pathways: Inhibition of AMPK and SIRT1 or activation of mTOR can suppress autophagy initiation [1][5]. ▌Mutations affecting proteins like ULK1, Atg13, or other autophagy-related genes can disrupt autophagosome formation [5]. ▌Dysregulation of transcription factor TFEB, which controls expression of autophagy and lysosomal genes, can impair the process [1][5]. Defects in autophagosome formation or maturation Problems with the machinery involved in forming or maturing autophagosomes can impair autophagy: ▌Disruption of membrane sources like the ER or mitochondria can affect autophagosome formation [6]. ▌Mutations affecting proteins involved in autophagosome-lysosome fusion, like Dynein, can block completion of autophagy [6]. Lysosomal dysfunction Since lysosomes are crucial for the degradation step of autophagy, lysosomal defects can severely impair the process: ▌Lysosomal storage disorders, like Pompe disease, directly impair the degradative capacity of lysosomes [1]. ▌Accumulation of undegraded material in lysosomes can overwhelm their function over time [1]. Cellular stress and damage Various cellular stressors can both induce and potentially overwhelm autophagy: ▌Oxidative stress and mitochondrial dysfunction can both trigger and potentially impair autophagy if severe [7][8]. ▌Accumulation of protein aggregates, as seen in neurodegenerative diseases, can overwhelm autophagic capacity [6][7]. Metabolic imbalances Disruptions in cellular metabolism can impair autophagy: ▌Chronic exposure to excess nutrients, like in obesity or alcoholic liver disease, can suppress autophagy through mTOR activation [1][5]. ▌Energy deficits can potentially impair autophagy if severe enough to disrupt basic cellular functions [5]. In many cases, impaired autophagy results from a combination of these factors, often creating a vicious cycle where initial dysfunction leads to further cellular stress and damage, progressively worsening autophagic impairment over time [1][7][8]. This is particularly evident in age-related and neurodegenerative diseases, where multiple factors converge to disrupt cellular homeostasis and autophagic function. SKIN AGING Autophagy impairment contributes significantly to skin aging through multiple mechanisms: [9] ▌Reduced collagen and elastin production by fibroblasts ▌Accumulation of damaged ECM components ▌Altered keratinocyte differentiation and reduced barrier function (thinning) ▌Reduced stem cell function and altered cellular metabolism ▌Accumulation of cellular damage and reduced stress resistance Impaired autophagy in fibroblasts and keratinocytes leads to wrinkles and reduced skin elasticity [10][11] and more visible signs of aging skin. SKIN SPECIFIC CAUSES IMPAIRED AUTOPHAGY - BEAUTY Autophagy decline was observed in both intrinsic and extrinsic skin aging [12]. Oxidative stress and environmental factors Skin cells are constantly exposed to environmental stressors that can impair autophagy: ▌Ultraviolet (UV) radiation is a major factor that can disrupt autophagy in skin cells, particularly keratinocytes and melanocytes [13][14]. ▌Reactive oxygen species (ROS) generated from various environmental factors can deactivate key autophagy regulators like Akt and mTORC1, leading to impaired autophagy initiation [15]. Aging and senescence As skin cells age, their autophagic capacity tends to decline: ▌Premature skin aging is associated with decreased autophagy in various skin cell types [13]. ▌Senescence of mesenchymal cells in the dermis is linked to impaired autophagy and contributes to skin aging [14]. Dysregulation of autophagy pathways Several molecular pathways can become dysregulated, leading to impaired autophagy: ▌Mutations or alterations in autophagy-related genes (ATGs) can disrupt the formation of autophagosomes and impair the process [15][16]. ▌Dysfunction of the mTORC1 signaling pathway, a key regulator of autophagy, can lead to autophagy impairment [17]. Cellular energy imbalances Disruptions in cellular metabolism can impair autophagy in skin cells: ▌Low cellular energy levels (high AMP/ATP ratio) can abnormally trigger AMPK activation, disrupting normal autophagy regulation [17]. ▌Nutrient imbalances can affect mTORC1 activity, which is crucial for proper autophagy function [17]. Inflammatory processes Chronic inflammation in the skin can interfere with normal autophagy: ▌Inflammatory skin conditions like psoriasis and atopic dermatitis are associated with impaired autophagy in various skin cell types [16][17]. Lysosomal dysfunction Since lysosomes are crucial for the final stages of autophagy, their dysfunction can severely impair the process: ▌Accumulation of undegraded material in lysosomes, which can occur with aging or in certain skin conditions, can overwhelm lysosomal function and impair autophagy completion [15][14]. ROLE OF UV AND BLUE LIGHT IN AUTOPHAGY IMPAIRMENT IMPLICATIONS FOR SKIN HEALTH AND PHOTOAGING UV Radiation and autophagy: UV exposure has a complex effect on autophagy in skin cells. Acute UV exposure activates autophagy as a protective mechanism. This process helps degrade oxidized lipids and metabolic wastes, potentially slowing photoaging. However, chronic UV exposure leads to autophagy impairment and accelerated skin aging [13]. UV radiation modulates several signaling pathways involved in regulating autophagy: [14] [18] 1. mTOR (mechanistic target of rapamycin): A negative regulator of autophagy 2. AMPK (AMP-activated protein kinase): Promotes autophagy 3. PI3K/Akt pathway: Influences autophagy regulation 4. p53: Plays a role in UV-induced autophagy response UV exposure also affects the expression and activity of autophagy-related genes like Atg5, Atg7, and LC3 [14]. The UV-induced DNA damage and oxidative stress contribute significantly to autophagy dysfunction over time. Blue light and autophagy: ▌Blue light induces approximately 50% of the oxidative stress in skin cells compared to UV. ▌It penetrates deeper into the skin, affecting both epidermal keratinocytes and dermal fibroblasts. ▌Prolonged exposure may lead to autophagy impairment, contributing to premature skin aging and pigmentation issues. Molecular mechanisms and key players: [14] Several molecular mechanisms and key players are involved in the UV-autophagy relationship:
AUTOPHAGY AND DNA REPAIR Autophagy plays a crucial role in maintaining cellular homeostasis and genomic stability, particularly in skin health and DNA repair [19]. When UVB radiation hits our skin, it activates AMPK, which in turn boosts the autophagy process in our cells [18]. This mechanism is essential for repairing various types of DNA damage, including broken DNA strands, small structural changes, and errors that occur during DNA replication [20]. Autophagy positively regulates the recognition of DNA damage by nucleotide excision repair (NER) and enhances the repair of UV-induced lesions, particularly through the removal of oxidized proteins and lipids [21]. By responding to various DNA lesions and regulating multiple aspects of the DNA damage response (DDR), autophagy helps maintain the integrity of our genetic material and promotes overall skin health. IMPACT ON SKIN CELLS The skin, being the largest organ, is significantly affected by impaired autophagy, which impacts various skin cells differently, leading to visible signs of aging such as wrinkles, reduced skin thickness, and pigmentation changes. Ethnic differences in autophagy capacity may influence susceptibility to skin damage [12]. Autophagy has different effects in three categories of skin cells: [13] ▌stem cells: autophagy supports self-renewal and quiescence. Declining autophagy can lead to stem cell loss over time. ▌short-lived differentiating cells: like keratinocytes, autophagy contributes to differentiation processes like cornification but is less impacted by aging. ▌long-lived differentiated cells (hair follicles and sweat glands): autophagy maintains cell survival and function. Decreased autophagy leads to accumulation of damaged components. The roles of autophagy in skin aging are complex and cell type-specific [13]. Keratinocytes Keratinocytes, the primary cell type in the epidermis, rely heavily on autophagy for differentiation and barrier function [16]. Different autophagy proteins showed distinct localization patterns in the epidermis [12]. LC3 and ATG9L1 were enriched in granular layers, while ATG5-ATG12 and ATG16L1 were in basal/spinous layers [12]. Autophagy plays a critical role in keratinocyte cornification, the process by which these cells form the outermost layer of the skin. Autophagy protects keratinocytes against UV-induced DNA damage and inflammation, potentially slowing photoaging [13]. Impaired autophagy in keratinocytes can lead to: ▌Reduced barrier function ▌Increased susceptibility to environmental stressors [14] ▌Altered epidermal differentiation ▌Accumulation of damaged proteins and organelles ▌Increased DNA damage, senescence, and aberrant lipid composition after oxidative stress [14][22]. mTOR inhibition directly promoted keratinocyte differentiation [12]. Fibroblasts Dermal fibroblasts are responsible for producing extracellular matrix (ECM) components, including collagen and elastin. Fibroblast autophagy helps clear lipofuscin (age pigment) and damaged proteins that accumulate with age. Autophagy impairment in fibroblasts can result in: ▌Reduced proteostasis and ECM production (collagen and elastin production) [13] ▌Accumulation of senescent cells and DNA damage [13] ▌Increased matrix metalloproteinase (MMP) activity, leading to ECM degradation ▌Altered cellular metabolism and energy production ▌Accumulation of autophagosomes, resulting in the deterioration of dermal integrity and skin fragility [10][11] These changes contribute to the formation of wrinkles and loss of skin elasticity [14]. Melanocytes Melanocytes, responsible for skin pigmentation, are particularly sensitive to autophagy impairment [13]. Autophagy defects disturb melanosome biogenesis and transport, leading to pigmentation disorders. Autophagy-deficient melanocytes display a senescence-associated secretory phenotype (SASP), contributing to inflammation and pigmentation changes [23]. Declining melanocyte autophagy may contribute to age-related pigmentation changes and hair graying. The consequences of impaired autophagy: ▌Accumulation of damaged melanosomes ▌Altered melanin production and distribution ▌Increased susceptibility to oxidative stress, inflammation and senescence ▌Pigmentation disorders like vitiligo and hyperpigmentation Stem cells Skin stem cells, including those in hair follicles and the interfollicular epidermis, rely on autophagy for maintenance and function. Impaired autophagy in stem cells can lead to: ▌Reduced self-renewal capacity ▌Altered differentiation potential ▌Accumulation of damaged cellular components ▌Premature stem cell exhaustion These effects contribute to reduced skin regeneration and repair capacity with age [14]. Sweat glands and sebaceous glands Autophagy is essential for normal sebum production in sebaceous glands (long-lived cells) and in sweat glands suppresses accumulation of lipofuscin ("age pigment") during aging and maintains gland function [13]. Autophagy plays a crucial role in the function of sweat glands and sebaceous glands. Impairment can result in: ▌Reduced sweat production, affecting thermoregulation ▌Altered sebum composition and production - can affect skin barrier function and contribute to conditions like acne [24] ▌Increased susceptibility to infections and skin disorders Merkel cells Autophagy regulates serotonin signaling in Merkel cells and may impact age-related changes in touch sensation [13]. Hair follicles In hair follicles, (long lived cells) autophagy promotes hair growth [14] and may counteract age-related hair loss when pharmacologically activated [13]. PIGMENTATION Dysregulation of autophagy in melanocytes affects melanin synthesis and transfer, leading to pigmentation disorders [23]. Autophagy activity correlates with skin lightness measurements and plays a role in melanosome degradation in keratinocytes . autophagy proteins like LC3, p62, ATG9L1, ATG5-ATG12 and ATG16L1 were decreased in hyperpigmented skin, while mTORC1 activity was increased in hyperpigmented elbow skin [12]. Autophagy impairment can lead to various pigmentation disorders: [12] ▌Hyperpigmentation: Accumulation of damaged melanosomes and altered melanin distribution ▌Hypopigmentation: Potential link to vitiligo through increased melanocyte sensitivity to oxidative stress ▌Uneven skin tone: Dysregulation of melanin production and transfer to keratinocytes Restoring autophagy (inhibiting mTORC1 with Torin 1) improved both pigmentation (maintaining skin color uniformity) and epidermal differentiation (barrier function) [12] and could be a therapeutic approach for photoaging and hyperpigmentation. PIGMENTATION ISSUES 1. Senile Lentigo (Age Spots): Studies have shown that autophagy declines in hyperpigmented skin areas such as senile lentigocompared to even-toned skin [12]. This decline in autophagy is associated with increased melanin deposition and melanocyte proliferation in the epidermis [13]. The impaired autophagy in these areas also correlates with reduced levels of late epidermal differentiation markers like filaggrin and loricrin [13]. 2. Photoaging: Ultraviolet (UV) radiation, a major cause of photoaging, affects autophagy in skin cells. While UV exposure initially increases autophagy as a protective mechanism, chronic exposure leads to impaired autophagic function. This impairment contributes to the accumulation of damaged cellular components and oxidized proteins, accelerating the photoaging process [14][12]. 3. Xerotic hyperpigmentation: In areas of skin with severe xerosis (dry skin) and hyperpigmentation, an exacerbated decline in autophagy has been observed. This decline is accompanied by severe dehydration and barrier defects, showing correlations with deteriorating skin physiological conditions [13=10]. The impaired autophagy in these areas contributes to both pigmentation abnormalities and compromised epidermal differentiation. These examples demonstrate that impaired autophagy is associated with various aspects of skin aging, including pigmentation changes, barrier function decline, and altered epidermal differentiation. The decline in autophagic activity appears to be both a result of aging processes and a contributing factor to the progression of skin aging symptoms [12][13][14]. SOLAR ELASTOSIS Solar elastosis is characterized by the accumulation of abnormal elastotic material (broken elastin fibres due to sun damage) in the dermis. While not directly linked to impaired autophagy, the loss of autophagy and/or it's housekeeping partner proteasome could be a contributing factor. 1. Autophagy is crucial for cellular homeostasis: Autophagy is described as "an essential cellular process that maintains balanced cell life" and is responsible for "clearing surplus or damaged cell components notably lipids and proteins" [12]. 2. Impaired autophagy in photoaging: Loss of autophagy leads to both photodamage and the initiation of photoaging in UV exposed skin [12][18]. 3. UV radiation affects autophagy: UV exposure can both stimulate and impair autophagy, depending on the circumstances. For example, repeated UVA radiation negatively affects the autophagy process in fibroblasts due to modifications in lysosomal functioning [25]. 4. Accumulation of damaged components: When autophagy is impaired, there's a reduced ability to clear damaged cellular components. This could include broken down elastin fibres. The proteasome and autophagy work closely together in cleaning up and recycling proteins like elastin. 5. Chronic inflammation: Photoaging is characterized by a chronic inflammatory response, which can be exacerbated by defects in autophagy. In turn, defects in autophagy have also been shown to cause severe inflammatory reaction in the skin [12]. AUTOPHAGY FAT CELLS Autophagy in fat cells, or adipocytes, plays a significant role in regulating adipose tissue biology and metabolism. 1. Role in adipose tissue biology: Autophagy is crucial for maintaining cellular homeostasis in adipose tissue by degrading and recycling cellular components. It influences adipogenic differentiation and affects the size and function of adipose tissue depots [26]. 2. Influence of obesity: In obesity, autophagy is often altered. Adipocytes in obese individuals show increased autophagic activity, which is associated with enhanced lipid mobilization and metabolic activity [27]. This process can be influenced by proinflammatory cytokines, leading to selective degradation of lipid droplet proteins like Perilipin 1 [27]. 3. Adipocyte browning: Autophagy is involved in the browning of white adipose tissue, which is associated with increased energy expenditure and protection against obesity [28]. Suppression of autophagy can block adipogenesis and lipid accumulation, indicating its role in fat storage and metabolism [28]. 4. Response to fasting: During fasting, autophagy is upregulated in adipose tissue to promote fat breakdown and support metabolic processes like ketogenesis [29]. This response involves the regulation of genes that influence autophagic activity. 5. Regulation by mTOR: The mTOR signaling pathway is a major regulator of autophagy in adipocytes. Under conditions of nutrient deprivation or stress, mTOR activity is inhibited, leading to the activation of autophagy [17]. AUTOPHAGY AND INSULIN RESISTANCE Activation of autophagy is beneficial for improving insulin sensitivity without compromising insulin production [30][31]. Impaired autophagy as a cause of insulin resistance 1. Accumulation of cellular debris: When autophagy is impaired, damaged organelles and proteins accumulate in cells, leading to cellular stress and inflammation that can contribute to insulin resistance [32]. 2. ER stress: Autophagy inhibition can cause severe endoplasmic reticulum stress in adipocytes, which can suppress insulin receptor signaling and contribute to peripheral insulin resistance [33]. 3. Mitochondrial dysfunction: Impaired autophagy can lead to accumulation of damaged mitochondria, which can disrupt cellular metabolism and contribute to insulin resistance [32]. 4. Reduced insulin signaling: Knockdown of autophagy genes like Atg7 in adipocytes can reduce insulin-stimulated phosphorylation of insulin receptor subunits and IRS-1, directly impairing insulin signaling [33]. Insulin resistance as a cause of impaired autophagy 1. Hyperinsulinemia: Chronic exposure to high insulin levels, as seen in insulin-resistant states, can suppress autophagy through activation of mTORC1 and inhibition of FoxO1 [30]. 2. Nutrient excess: The excess nutrients associated with obesity and insulin resistance can inhibit autophagy through mTORC1 activation [32][33]. 3. Altered gene expression: Insulin resistance can downregulate the expression of genes encoding major autophagy components, further impairing autophagic function [34]. Bidirectional relationship The relationship between insulin resistance and impaired autophagy often creates a vicious cycle: 1. Initial insulin resistance can lead to suppression of autophagy. 2. Impaired autophagy then exacerbates cellular stress and dysfunction. 3. This cellular dysfunction further worsens insulin resistance. 4. The cycle continues, progressively worsening both conditions [32][33]. Tissue-specific effects The relationship between autophagy and insulin sensitivity can vary depending on the tissue: 1. In insulin-responsive tissues like muscle, liver, and adipose tissue, moderate activation of autophagy can improve insulin sensitivity by reducing cellular stress and inflammation [30][32]. 2. In pancreatic β-cells, however, excessive autophagy can reduce insulin storage and secretion, potentially worsening glucose intolerance despite improved peripheral insulin sensitivity [30]. PREVENTION AND TREATMENT OPTIONS Targeting nutrient-sensing pathways (mTORC1, AMPK, SIRT1) can enhance autophagic activity and mitigate age-related cellular damage [4][35][36] The most efficient and evidence-based methods to improve autophagy are: 1. Intermittent fasting (IF): ▌The 16/8 method (16 hours fasting, 8 hours eating window) is commonly recommended [37][38]. ▌Alternate-day fasting and the 5:2 diet (5 days normal eating, 2 days restricted calories) are also effective [38][39]. ▌Fasting periods of 18-72 hours show increasing benefits for autophagy [37]. Fasting a lot is not recommended for women in their reproductive age, the use of geroprotectors (a few mentioned under point 6) are more suitable. 2. Calorie restriction (CR): [4] ▌Reducing daily calorie intake by 10-40% can trigger autophagy [38]. ▌Long-term calorie restriction increases the expression of autophagy-related genes [40]. 3. Exercise: [4] ▌Both aerobic exercise and resistance training stimulate autophagy [37][41]. ▌Aerobic exercise (lower intensity, longer duration) may be more effective for autophagy than high-intensity exercise [37]. 4. Ketogenic diet: ▌A high-fat, low-carb diet can mimic fasting effects and trigger autophagy [41]. 5. Sleep: ▌Good quality sleep supports autophagy, as it follows the sleep-wake cycle [41]. 6. Specific nutrients and supplements: ▌Spermidine (naturally occurring in our body and food) has been shown to enhance autophagy [40][42] and is on top of the list. ▌Resveratrol, found in red wine and grapes, may induce autophagy [40] (in very high doses), however there are contradicting study outcomes. ▌Curcumin (from turmeric) has shown potential in animal studies [41]. ▌Green tea contains compounds that may support autophagy [40]. ▌GlyNAC - more information below 7. Stress management: ▌Chronic stress can interfere with autophagy, so stress reduction techniques like meditation or yoga may be beneficial [38]. 8. Pharmacological Interventions: ▌Several antidiabetic medicines and other pharmacological agents are being explored to modulate autophagy and slow aging [3][4]. ▌Genetic approaches to upregulate autophagy-related genes (e.g., ATG7, BECN1) are being investigated as potential therapeutic strategies for neurodegenerative diseases [35][43]. 9. Hormetic stress activates autophagy: Hormesis influences and activates autophagy through various mechanisms, contributing to cellular stress resistance and potential health benefits. ▌Hormesis appears to be executed by a variety of physiological cellular processes, including autophagy that cooperatively interact and converge [44]. ▌Hormetic heat shock activates autophagy in human RPE cells [45]. Heat shock factor 1 (HSF1) plays a role in hormetic autophagy activation [46=73]. HHS enhances the expression of fundamental autophagy-associated genes in ARPE-19 cells through the activation of HSF1 [45]. ▌Inhibition of mTOR (mechanistic target of rapamycin) is a key pathway for hormetic autophagy activation. Inhibition of mTOR (specifically dephosphorylation of mTOR complex 1) triggers augmented autophagy [44]. ▌Hormetic autophagy contributes to stress resistance, longevity, and improved proteostasis [46]. 10. Sunscreen: I promote the use of sunscreens, particularly ones with the natural compounds Licochalcone A (powerful anti-oxidant, Nrf2 activator, Glutathione stimulator and MMP1 inhibitor) [47][48][49][50] and Glycerrhetinic Acid (supports DNA repair) [51]. The regular use of sunscreen can decrease the risk of impaired autophagy in skin: ▌Reduction of oxidative stress: By blocking UV rays, sunscreen helps prevent the generation of excessive ROS, which can impair autophagy [18]. ▌Prevention of DNA damage: Sunscreen protects skin cells from UV-induced DNA damage, which can interfere with autophagy-related gene expression [18][21]. ▌Maintenance of cellular homeostasis: By reducing overall UV-induced stress on skin cells, sunscreen helps maintain the balance necessary for proper autophagy function [21]. Several studies have demonstrated the link between UV protection and autophagy preservation. A study published in the Journal of Investigative Dermatology showed that UV radiation can dysregulate autophagy in skin cells, and that protecting against UV exposure can help maintain normal autophagy function [21]. Research published in the International Journal of Molecular Sciences highlighted that sunscreen use can prevent UV-induced damage to autophagy-related proteins and pathways in skin cells [18]. A review in Frontiers in Pharmacology discussed how sunscreen, as part of a comprehensive photoprotection strategy, can help preserve autophagy function in skin by reducing overall UV-induced cellular stress [21]. By using sunscreen regularly, individuals can significantly reduce their risk of impaired autophagy in skin cells, contributing to overall skin health and slowing the photoaging process. 11. Red light therapy: Red light therapy, particularly at a wavelength of 660 nm, has been shown to promote autophagy, the cellular process of cleaning out damaged cells and regenerating healthier ones. Studies indicate that this therapy can enhance autophagy in various contexts, such skin health [57]. Additionally, red light therapy is often used in combination with fasting to further boost cellular repair processes associated with autophagy. Red light activates autophagy in retinal cells: Studies have shown that red light exposure can activate multiple steps of the autophagy process in retinal pigment epithelium (RPE) cells. It increases autophagy-related proteins and promotes the formation of autophagosomes [58]. 12. Polynucleotides: 1. DNA damage response: DNA damage can trigger autophagy as a protective mechanism. Polynucleotides, particularly damaged DNA, can activate autophagy pathways [59]. 2. RNA-mediated regulation: Certain RNA molecules, such as microRNAs and long non-coding RNAs, can modulate autophagy-related gene expression and signaling pathways [59]. 13. Exosomes: Exosomes have a complex relationship with autophagy: 1. Autophagy regulation: Exosomes can carry proteins and RNAs that influence autophagy in recipient cells. For example, some exosomal microRNAs can target autophagy-related genes [59]. 2. Protein content alteration: Autophagy modulators can significantly alter the protein content of phosphatidylserine-positive extracellular vesicles (PS-EVs), including exosomes, produced by cancer cells [59]. 3. Signaling molecules: Exosomes can contain important signaling molecules like SQSTM1 and TGFβ1 pro-protein, which are involved in autophagy regulation [59]. 4. Intercellular communication: Exosomes derived from cells treated with autophagy modulators can influence the metabolism and phenotype of recipient cells [59]. 5. Autophagy-related protein transport: Exosomes can carry autophagy-related proteins like LC3-II, potentially transferring autophagic capabilities between cells [59]. The relationship between exosomes and autophagy is bidirectional. Autophagy can also influence exosome production and content. The specific effects may vary depending on the cell type, physiological context, and the particular polynucleotides or exosomes involved. GLYNAC AND AUTOPHAGY GlyNAC, a combination of glycine and N-acetylcysteine, has shown promising effects on various aspects of cellular health, including autophagy. Glutathione synthesis and oxidative stress GlyNAC supplementation has been shown to improve glutathione (GSH = body's master antioxidant) synthesis and reduce oxidative stress [52][53][54]. GSH is a crucial antioxidant that plays a role in regulating autophagy and DNA repair. By improving GSH levels, GlyNAC may indirectly support autophagic processes [52][53]. Aging hallmarks GlyNAC supplementation has been shown to improve multiple hallmarks of aging, including mitochondrial dysfunction, oxidative stress, and inflammation [52][53][54].[55].These improvements may indirectly support autophagic processes, as these hallmarks are interconnected with autophagy regulation [1][2]. Direct evidence on autophagy While direct evidence of GlyNAC's effect on autophagy is limited, some studies provide insights: 1. In a study on HIV patients, GlyNAC supplementation improved mitophagy markers, suggesting a potential role in enhancing selective autophagy of mitochondria [53]. 2. N-acetylcysteine, a component of GlyNAC, has been shown to induce autophagy in various cellular models, potentially through its antioxidant properties and effects on mTOR signaling [56]. Potential mechanisms The potential mechanisms by which GlyNAC might influence autophagy include: 1. Reduction of oxidative stress, which can promote autophagy induction [52][53][54]. 2. Improvement of mitochondrial function, which is closely linked to mitophagy regulation [7][8][52][53]. 3. Modulation of nutrient-sensing pathways, such as mTOR, which are key regulators of autophagy [53][56]. Future directions While the evidence suggests that GlyNAC supplementation may have beneficial effects on cellular processes related to autophagy, more direct research is needed to fully elucidate its impact on autophagic flux and regulation. By improving autophagy, we're not just investing in our appearance, but in the fundamental processes that keep our body healthy. Always consult a qualified healthcare professional to determine what the most suitable approach is for your needs and rejuvenation or regeneration goals. Take care! Anne-Marie
References:
[1] Aman, Y., et al. (2021). Autophagy in healthy aging and disease. Nature Aging, 1(8), 634-650. [2] Rubinsztein, D. C., et al. (2011). Autophagy and aging. Cell, 146(5), 682-695. [3] Kaushik, S. et al. (2021). Autophagy and the hallmarks of aging. Ageing Research Reviews, 72. [4] Kitada, M., & Koya, D. (2021). Autophagy in metabolic disease and ageing. Nature Reviews Endocrinology, 17, 647 - 661. [5] Ichimiya T et al. Autophagy and Autophagy-Related Diseases: A Review. Int J Mol Sci. 2020 [6] Budini M. et al. Front. Mol. Neurosci. Autophagy and Its Impact on Neurodegenerative Diseases: New Roles for TDP-43 and C9orf72 (2017). [7] Niture S. et al. Int. J. Hepatol. Emerging Roles of Impaired Autophagy in Fatty Liver Disease and Hepatocellular Carcinoma (2021) [8] Edens B.M. et al. Front. Cell. Neurosci. Impaired Autophagy and Defective Mitochondrial Function in Motor Neuron Degeneration (2016) [9] Jeong D et al. The Role of Autophagy in Skin Fibroblasts, Keratinocytes, Melanocytes, and Epidermal Stem Cells. J Invest Dermatol. 2020 [10] Kim H et al. (2018). Autophagy in Human Skin Fibroblasts: Impact of Age. International Journal of Molecular Sciences, 19 [11] Tashiro K. et al. Biochem. Biophys. Res. Commun. Age-related disruption of autophagy in dermal fibroblasts modulates ECM (2014) [12] Wang M et al. Autophagy: Multiple Mechanisms to Protect Skin from Ultraviolet Radiation-Driven Photoaging. Oxid Med Cell Longev. 2019 [13] Murase D. et al. Int. J. Mol. Sci. Autophagy Declines with Premature Skin Aging Altering Skin Pigmentation and Epidermal Diff. (2020). [14] Eckhart Leopold, Tschachler Erwin , Gruber Florian Autophagic Control of Skin Aging Frontiers in Cell and Developmental Biology 2019 [15] Lin Y. et al. Front. Immunol. The multifaceted role of autophagy in skin autoimmune disorders (2024). [16] Kim HJ, Park J, Kim SK, Park H, Kim JE, Lee S. Autophagy: Guardian of Skin Barrier. 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[25] Gromkowska-Kępka K.J. et al. J. Cosmet. Dermatol. The impact of ultraviolet radiation on skin photoaging: in vitro studies review (2021). [26] Romero M, Zorzano A. Role of autophagy in the regulation of adipose tissue biology. Cell Cycle. 2019 [27] Ju L. et al. Cell Death Dis. Obesity-associated inflammation triggers autophagy-lysosomal response in adipocytes (2019) [28] Seung-Hyun Ro et al. Front. Physiol., 28 January 2019 Autophagy in Adipocyte Browning: Emerging Drug Target for Intervention in Obesity [29] Furthering fat loss in the fasting response - EurekAlert! Peer reviewed publication Osaka University 2022 [30] Yamamoto S et al. Autophagy Differentially Regulates Insulin Production and Insulin Sensitivity. Cell Rep. 2018 [31] Ning Wang et al. Autophagy: Playing an important role in diabetes and its complications, Medicine in Drug Discovery 2024 [32] Frendo-Cumbo S. et al. Front. Cell Dev. Biol. Communication Between Autophagy and Insulin Action (2021). 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Mitochondria are the "powerhouses" or "lungs" of our cells and bioenergetic semi-autonomous organelles with their own genomes and genetic systems. [1] They are responsible for generating the energy that fuels a wide range of cellular processes in the skin, including cell signaling, pigmentation, wound healing, barrier integrity [2], metabolism and quality control. [3] Mitochondria exist in each cell of the body and are generally inherited exclusively from the mother. Their primary role is cellular respiration; a process converting the energy in nutrients (like glucose) into a usable form of energy called ATP or Adenosine Triphosphate. Mitochondria are particularly abundant in the skin, reflecting the skin's high metabolic demand. When the functionality of mitochondria is impaired or declines, it impacts skin's vitality, health and beauty. Mitochondrial dysfunction is 1 of the 12 hallmarks of skin ageing.
The skin is particularly susceptible to mitochondrial stress due to its constant exposure to environmental insults, such as UV radiation, pollution, and other oxidative stressors. These factors can damage mitochondrial DNA, leading to increased production of reactive oxygen species (ROS) and disrupting the delicate balance of cellular processes. [4] In aged post-mitotic cells, heavily lipofuscin-loaded lysosomes perform poorly, resulting in the enhanced accumulation of defective mitochondria, which in turn produce more reactive oxygen species causing additional damage (the mitochondrial-lysosomal axis theory). [5] Optimal mitochondrial function is indispensable for sustaining the specialized functions of each cell type, like keratinocyte differentiation, fibroblast ECM production, melanocytes melanin production and distribution, immune cell surveillance, sebocytes and adipocytes. [6] Mitochondrial dysfunction is both directly and indirectly linked to chronological ageing and photo-ageing. [7] As mitochondrial function declines, the skin's ability to regenerate and repair itself is decreased. [2] This results in visible signs of aging, such as wrinkles, loss of elasticity, dryness, uneven pigmentation, melasma, age spots, lipomas, impaired wound healing. [2-4-5-8-9] Mitochondrial dysfunction also has been implicated in skin conditions like acne, eczema, lupus, psoriasis, vitiligo, atopic dermatitis and even skin cancer. [10] Ageing is associated with changes in mitochondrial morphology, including [6] ▌Hyperfusion or increased fragmentation ▌Loss of mitochondrial connectivity [11-7] ▌Decline in the efficiency of oxidative phosphorylation, leading to reduced ATP production ▌Decline mitochondrial membrane potential (ΔΨM) ▌Compromised cellular energy metabolism ▌Reduced mitochondrial turnover (downregulated biogenesis) ▌Impaired mitochondrial quality control such as mitophagy (removal of damaged mitochondria through autophagy) [6] These alterations are related to the increased production of ROS exhibited by mitochondria during ageing, the accumulation of which causes oxidative damage to mitochondrial and cell components contributing to cellular senescence. [12] Good mitochondrial function or metabolism: [7] ▌Redox homeostasis: (the way of reducing oxidative stress) - mitochondrial respiration and ROS production are essential for keratinocyte differentiation ▌ATP production: Adenosine Triphosphate provides energy to drive and support many processes in living cells (and GTP) ▌Respiration: mitochondrial respiration is the most important generator of cellular energy ▌Biogenesis: allows cells to meet increased energy demands, to replace degraded mitochondria and is essential for the adaptation of cells to stress [6] ▌Calcium homeostasis ▌Cellular growth ▌Programmed cell death (apoptosis) reducing cell senescence [13] ▌Mitochondrial protein synthesis: mitochondria typically produce 13 proteins encoded by mitochondrial DNA (mtDNA) Dysfunctional Mitochondria: [7] ▌Oxidative stress ▌Decreased ATP levels ▌Dysfunctional OXPHOS: Oxidative phosphorylation, a metabolic pathway in which enzymes oxidize nutrients to release stored chemical energy in the form of ATP ▌Altered mitochondrial biogenesis ▌Calcium imbalance ▌Cell death Mitochondrial proteins Mitochondria contain >1,100 different proteins (MitoCoP) that often assemble into complexes and supercomplexes such as respiratory complexes and preprotein translocases. The chaperones Heat Shock Proteins HSP60-HSP10 are the most abundant mitochondrial proteins. [3] Small heat shock proteins form a chaperone system that operates in the mitochondrial intermembrane space. Depletion of small heat shock proteins leads to mitochondrial swelling and reduced respiration. [14] Mitochondrial hyperpigmentation Emerging research has shed light on the intricate relationship between mitochondrial dysfunction and the development of hyperpigmentation, a condition characterized by the overproduction and uneven distribution of melanin in the skin. One of the key mechanisms underlying this connection is the role of mitochondria in the regulation of melanogenesis, the process by which melanin is synthesized. Mitochondria are involved in the production of various cofactors and signaling molecules that are essential for the activity of tyrosinase, the rate-limiting enzyme in melanin synthesis. [15] When mitochondrial function is impaired, it can lead to an imbalance in the production and distribution of these cofactors and signaling molecules, ultimately resulting in the overproduction and uneven deposition of melanin in the skin. [15] This can manifest itself as age spots, melasma, and other forms of hyperpigmentation. The link between mitochondrial dysfunction and hyperpigmentation has been further supported by studies on genetic disorders that involve mitochondrial dysfunction, such as mitochondrial DNA depletion syndrome. In these conditions, patients often exhibit a range of pigmentary skin changes, including patchy hyper- and hypopigmentation, as well as reticular pigmentation. [16] Mitochondrial crosstalk and exosomes Mitochondria can crosstalk and move beyond cell boundaries. [17] Mitochondria-derived material might be transferred to neighboring cells in the form of cell-free mitochondria or included in extracellular vesicles [18-19]. This process supports cellular repair and contributes to vital mitochondrial functions. Besides restoring stressed cells and damaged tissues due to mitochondrial dysfunction, intercellular mitochondrial transfer also occurs under physiological and pathological conditions. [20] The transfer of active mitochondria from mesenchymal stem cells (MSCs) has been identified as a repair mechanism for rejuvenating damaged skin fibroblasts. [21] MITOCHONDRIAL SUPPORT Move According Martin Picard phD being physically active is a protective factor against almost everything health related. Exercise stimulates the production of mitochondria as more energy is required. Be hungry sometimes If there is too much supply of energy acquired via food leads to mass shrinking of mitochondria or fragmentation. Don´t over-eat, be calorie neutral and sometimes being calorie deficient is good for mitochondria. Maintain a healthy weight, preferably with a mediterranean diet containing phenolic and polyphenolic compounds (increase mitochondrial function and number) nitrate rich vegetables, soybeans and cacao beans. Mitohormesis In model organisms, lifespan can be improved by compromising mitochondrial function, which induces a hormetic response (“mitohormesis”), provided that this inhibition is partial and occurs early during development. Feel good Feeling good (positivity), especially at night, has a scientifically proven positive effect on mitochondrial health index, it is even a predictive factor. Q10 or Coenzyme Q10 (CoQ10) Q10 is part of the mitochondrial respiration chain and essential for cellular energy production. About 95% of our cellular energy is generated with support of Q10, which is produced by the human body itself. During skin ageing, both the cellular energy production and levels of Q10 are declined. Q10 is a powerful anti-oxidant [22], thus protecting cells from oxidative stress and damage and has proven to be able to "rescue" senescent cells by decreasing elevated senescent markers like p21 levels and β-Galactosidases positive cell numbers (in-vitro). Q10 is bio-active, increasing collagen type I and elastin production. [23] Q10 can be supplemented via nutrition, however also via topical application and is considered an evidence based active ingredient in skin care products. Ubiquinol (reduced form) shows higher bioavailability compared to ubiquinone (oxidized form). [23] Pyrroloquinoline quinone (PQQ) Q10 improves the energy in the mitochondria, however PQQ has shown to increase the number of mitochondria and a redox maestro. I´ve written a full post about this compound, which can be found as skincare ingredient and supplement. Read more about PQQ Glutathione Glutathione is formed in cell's cytoplasm from glutamic acid, cysteine and glycine. It is present in 2 forms: reduced (GSH) and oxidized (GSSG). Reduced GSH is an active anti-oxidant, while the presence of inactive GSSG is increased under oxidative stress. The ratio between GSH and GSSH is considered a measure of oxidative stress. Glutathione participates in redox reactions, acts as co-factor of many anti-oxidant enzymes and is the most important non-enzymatic anti-oxidant, essential for synthesis of proteins and DNA. Low Glutathione results in accelerated ageing and inflammatory skin diseases. Mitochondrial glutathione (mGSH) is the main line of defense for the maintenance of the appropriate mitochondrial redox environment to avoid or repair oxidative modifications leading to mitochondrial dysfunction and cell death. [24] Glutathione can be increased via supplementation via precursors cysteine or N-acetylcysteine (not recommended for pregnant women), a combination of Glycine and NAC (called GlyNAC) part of the popular "power of three" supplementation, or the reduced form of Glutathione itself, or increased via topical active ingredients like Licochalcone A. [25] I´ve written about GlyNAC in my post on autophagy. Nicotinamide NR nicotinamide ribosome which is the precursor of NMN nicotinamide mononucleotide which is the precursor of NAD+ nicotinamide adenine dinucleotide all could have a protective effect on mitochondria. Nicotinamide adenine dinucleotide is present in living organisms as ions NAD+ and NADP+ and in reduced forms NADH and NADPH. NADH is a cofactor of processes inside mitochondria: ▌ATP production ▌Activation of "youth proteins" sirtuins ▌Activation of PARP Poly (ADP-ribose) polymerase, a family of proteins involved in many cellular processes such as DNA repair, genomic stability and programmed cell death ▌Reduction of ROS (free radicals) NAD levels as lowered during ageing. [26] One of the fans of NMN supplementation is Harvard Professor David Sinclair, best known for his work on understanding why we age and how to slow its effects and also featured in my article about hormesis. There are about 14 studies done to date with NMN supplementation in humans, one of which was done by Professor Sinclair. NMN supplementation does raise NAD levels, however there aren't substantial proven health benefits, unless you are unhealthy. Resveratrol Although systemically Resveratrol promotes mitochondrial biogenesis. [27] Other data shows that UVA (14 J/cm(2)) along with resveratrol causes massive oxidative stress in mitochondria. As a consequence of oxidative stress, the mitochondrial membrane potential decreases which results in opening of the mitochondrial pores ultimately leading to apoptosis in human keratinocytes. [28] Magnesium Magnesium supplementation has been shown to improve mitochondrial function by increasing ATP production, decreasing mitochondrial ROS and calcium overload, and repolarizing mitochondrial membrane potential. There are many forms of Magnesium, however Citrate, Malate and Orotate are particularly good for energy. L-Carnitine Placebo-controlled trials have shown positive effects of L-Carnitine supplementation on both pre-frail subjects and elderly men. The effect is possibly mediated by counteracting age-related declining L-carnitine levels which may limit fatty acid oxidation by mitochondria. NEW Ergothioneine (EGT) Ergothioneine (EGT) is a sulfur-containing amino acid derivative known for its antioxidant properties, particularly in mitochondria. It is transported into cells and mitochondria via the OCTN1 transporter, where it helps reduce reactive oxygen species (ROS) and maintain cellular homeostasis [29]. EGT binds to and activates 3-mercaptopyruvate sulfurtransferase (MPST), enhancing mitochondrial respiration and exercise performance [30]. It also protects against oxidative stress and inflammation, potentially benefiting conditions like neurodegenerative diseases [31]. Melatonin Not much talked about when it comes to mitochondria, however should not be ignored as mitochondria can benefit significantly from melatonin supplementation. 1. Antioxidant protection: Melatonin acts as a powerful antioxidant within mitochondria, scavenging free radicals and reducing oxidative damage to mitochondrial DNA and proteins [32][34]. 2. Regulation of mitochondrial homeostasis: Melatonin helps maintain electron flow, efficiency of oxidative phosphorylation, ATP production, and overall bioenergetic function of mitochondria [32][34]. 3. Preservation of respiratory complex activities: Melatonin helps maintain the activities of mitochondrial respiratory complexes, which are crucial for energy production [32][34]. 4. Modulation of calcium influx: Melatonin regulates calcium influx into mitochondria, helping prevent calcium overload which can be damaging [32][34]. 5. Protection of mitochondrial permeability transition: Melatonin helps regulate the opening of the mitochondrial permeability transition pore, which is important for maintaining mitochondrial integrity [32][34]. 6. Enhancement of mitochondrial fusion: Melatonin promotes mitochondrial fusion, which is part of the quality control process for maintaining healthy mitochondria [33]. 7. Promotion of mitophagy: Melatonin enhances the removal of damaged mitochondria through mitophagy, helping maintain a healthy mitochondrial population [33]. 8. Reduction of nitric oxide generation: Melatonin decreases nitric oxide production within mitochondria, which can be damaging in excess [32][34]. 9. Selective uptake by mitochondria: Melatonin is selectively taken up by mitochondrial membranes, allowing it to exert its protective effects directly within these organelles [34]. 10. Support of mitochondrial biogenesis: Some studies suggest melatonin may promote the formation of new mitochondria [33]. The key antioxidants used by mitochondria are Glutathione (GSH), Glutathione peroxidase (GPx), Coenzyme Q10 (CoQ10), Superoxide dismutase (SOD), Melatonin, Vitamin C (ascorbate) and Vitamin E (α-tocopherol). Red light therapy By incorporating red light therapy into your skin care routine, you can help to counteract the damaging effects of mitochondrial dysfunction and support the skin's natural renewal processes. As we continue to explore the 12 hallmarks of ageing, I am confident that we will gain even more valuable insights and develop breakthrough innovations that will improve skin quality, health, beauty and vitality. Always consult a qualified healthcare professional or dermatologist to determine what the most suitable approach is for your particular skin condition and rejuvenation goals. Take care! Anne-Marie References
Many of the skin regenerating or rejuvenating treatments, like energy based devices in the doctors-office are based on the principle to cause controlled damage and therewith provocation of a skin rejuvenating repair response. One of the fascinating mechanisms behind laser "damage" is the heat shock response leading to increased production of regenerating heat shock proteins (HSPs). Heat shock proteins respond to heat stress, are crucial cellular defence mechanisms against stress (environmental and physiological), act as chaperones, aiding in protein folding, prevention of protein damage, cellular protection and repair, with other words HSPs play a crucial role in proteostasis. [1]
HEAT SHOCK PROTEINS AND OX-INFLAMMAGEING UV radiation and blue light cause oxidative stress and inflammation, and can overwhelm skin's own capacity to counteract the increased formation of reactive oxygen species (ROS) and inflammatory mediators. Chronic oxidative stress state and chronic low grade of inflammation are hallmarks of skin ageing and their combination can be called ox-inflammageing. Oxidative stress and inflammation alter cellular signal transduction pathways and thereby the expression of the ECM genes as well as the structure of the ECM proteins like collagen, fibronectin and elastin. Their reduced expression and increased degradation manifests eventually at the skin surface as wrinkles, loss of firmness, and elasticity. Heat shock proteins are chaperone proteins that facilitate the formation of the ECM and prevention of molecular oxidative damage or degradation and are classified based on their molecular weights.
HEAT SHOCK PROTEINS AND PROTEOME Proteostasis, or protein homeostasis, refers to the balance between protein synthesis (like collagen, fibronectin and elastin), folding, and degradation. As we age, this balance is disrupted, leading to the accumulation of misfolded and aggregated proteins [10]. Loss of proteostasis is another hallmark of aging and HSPs play a crucial role in maintaining proteostasis through several mechanisms: 1. Protein folding: HSPs assist in the proper folding of newly synthesised proteins and refolding of misfolded proteins [10][11]. 2. Protein degradation: HSPs collaborate with the ubiquitin-proteasome system and autophagy to target misfolded proteins for degradation [10][12]. 3. Stress response: Under stress conditions, HSPs are upregulated to protect cells from protein damage and maintain cellular functions [13][14]. HSP-70 and HSP-90 are particularly important in protein folding and refolding, while small HSPs are involved in preventing protein aggregation [11][14]. Several studies have provided evidence supporting the potential of HSPs as an intervention to improve proteostasis: lifespan extension: [15], neuroprotection (HSP70), stress resistance and cellular survival [13][14], protein aggregation prevention (small HSPs) [11][14], autophagy regulation and particularly HSP70 is crucial for cellular protein quality control [16]. STIMULATION OF REJUVENATING HEAT SHOCK PROTEINS Heat shock protein synthesis can be initiated not only by heat but also by many chemical and physical stimuli, such as heavy metals, amino acid analogues, oxidative stress, viral infection and UV and ionizing irradiation. [17] Exercise and hormesis: Mild stress induced by exercise or other hormetic interventions has been shown to upregulate HSPs and improve proteostasis. Laser Laser treatments have been shown to induce a heat shock response in the skin from epithelial cells to deeper connective tissues, leading to the production of heat shock proteins. This response is characterized by the temporary changes in cellular metabolism, release of growth factors, and increased cell proliferation and thus contribute to tissue regeneration and rejuvenation. [17] CBD It has been proven that a large number of genes belonging to the heat shock protein super-family were up-regulated following cannabidiol (CBD) treatment. [18] UV radiation Ultraviolet radiation (UV)‐induced cell death and sunburn cell formation can be inhibited by previous heat shock exposure and UV itself can induce HSP expression. However, levels of HSP-27 have been found to be elevated in sun‐protected aged skin indicating a link between HSP-27 expression and age‐dependent epidermal alterations. [19] I would recommend daily protection from UV radiation and blue light (or high energy visible light). Ultrasound Ultrasound exposure at different frequencies, intensities, and exposure times can induce HSP-72 expression. Higher ultrasound frequencies, such as 10 MHz, have been found to significantly increase HSP-72 levels. Additionally, increasing the temperature during ultrasound exposure has shown to enhance HSP-72 expression. Interestingly, ultrasound at 1 MHz was unable to induce HSP-72 significantly, while 10 MHz ultrasound induced HSP-72 after 5 minutes of exposure. [16] Radiofrequency Radiofrequency has been shown to increase HSP-70 and decrease melanin synthesis and tyrosinase activity. [20] RF-US treatment significantly increased levels of HSP47 proteins. [21] Red & near infra red light Although I've not seen much peer reviewed published evidence, red light and near infra red light therapy may release the HSPs in the skin if tissue reaches >42 - 45 degrees (even for 8 - 10 seconds). Nicotinamide Nicotinamide and its derivatives have been found to stimulate the expression of heat shock proteins, including HSP-27, HSP-47, HSP-70, and HSP-90 in the skin. These proteins play as mentioned before an essential role in collagen production, skin protection, skin health and rejuvenation. [6] NAD as nutrient interestingly has proven to tweak the epigenome by modulating DNMT1 enzymatic DNA methylation and cell differentiation. [22] In topical applications an ingredient called Dihydromyricetin also called Epicelline® has been successful in inhibiting DNMT1 enzyme activity biochemical assays. [23] Stimulation of heat shock proteins offers a promising and novel invasive, non invasive and topical approach for skin regeneration, rejuvenation, reduction of ox-inflammageing and prevention of loss of proteostasis. Always consult a qualified healthcare professional or dermatologist to determine the most suitable approach for your particular skin condition and rejuvenation goals. Take care! Anne-Marie References
One of the people I follow ever since I started to work on skin epigenetics back in 2017 and longevity is Harvard professor David Sinclair. He is best known for his (sometimes controversial) work on understanding why we age and how to slow its effects. He was talking about hormesis, a phenomenon where exposure to low doses of stressors induces beneficial effects. A hormetic (cellular defense) response can modulate ageing processes by activating genes related to maintenance and repair pathways through mild stress exposure in our body and skin, leading to enhanced longevity (thus anti-ageing) and health. [1 - 2]
Originating from the early 2000s, the concept of hormesis has evolved to evidenced based dermatological applications. [3] Various factors, including environmental stressors, lifestyle choices, and genetic predispositions, can influence the hormetic responses in skin cells. Understanding these influences is essential for optimizing skin health and beauty through hormetic pathways. Many terms are used for hormetic responses in the scientific literature, including the Arndt-Schulz Law, biphasic dose response, U-shaped dose response, preconditioning/adaptive response, overcompensation responses, rebound effect, repeat bout effect, steeling effect, among others. [4] Ageing is an emergent, epigenetic and a meta-phenomenon, not controlled by a single mechanism. Cellular damage has three primary sources: [3]
Effective homeodynamic space or buffering capacity (body's ability to maintain stability or balance in changing conditions) is characterized by:
Stress response is a reaction to physical, chemical, or biological factors (stressors) aimed at counteracting, adapting, and surviving, is a critical component of the homeodynamic space. There are seven main cellular stress response pathways:
Hormetins can be categorized into three types:
Hallmarks of aging benefiting from hormesis 1. Loss of proteostasis Hormetic stress can upregulate heat shock proteins (HSPs) and other molecular chaperones, improving protein folding and maintenance. [9] This directly supports proteostasis, which is crucial for cellular (skin) health and longevity. 2. Mitochondrial dysfunction Mild stress can stimulate mitochondrial biogenesis and improve mitochondrial function, potentially counteracting age-related mitochondrial decline.[9] 3. Cellular senescence Hormetic interventions may help clear senescent cells or prevent their accumulation, though this effect is less direct and requires further research. [8] 4. Deregulated nutrient sensing Hormetic stressors like caloric restriction or intermittent fasting can improve nutrient sensing pathways, particularly involving sirtuins and AMPK. [9] 5. Epigenetic alterations Some hormetic stressors can influence epigenetic markers, potentially reversing age-related epigenetic changes. [8] 6. Stem cell exhaustion Mild stress may stimulate stem cell activity and regeneration, though this effect varies depending on the type and intensity of the stressor. [9] 7. Altered intercellular communication Hormesis can modulate inflammatory responses and improve intercellular signaling, potentially addressing the "inflammaging" phenomenon. [8][9] Being aware of the phenomenon of hormesis can result in discovering the usefulness of new compounds, or synergistic effects of combining hormetic treatments which otherwise may have been rejected due to their effects of stress induction. What is bad for us in excess, can be beneficial in moderation, or (quote): "What doesn't kill you makes you stronger". [6]. The future of hormesis in dermatology holds great promise for innovative interventions, advanced hormetic technologies or personalized skin care regimens. Always consult a qualified healthcare professional or dermatologist to determine the most suitable approach for your particular (skin) condition and rejuvenation goals. Take care! Anne-Marie
Read more:
The impact of senescent zombie cells on skin ageing The role of heat shock proteins in skin rejuvenation Neurocosmetics, the skin-brain connection & neuro-ageing The role of the lymphatic system in ageing skin The power of light and photo-biomodulation Bio-stimulators Skin glycation Exosomes References
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