Cellular metabolic pathways of aging in dogs: could p53 and SIRT1 be at play?

Aging and cancer seem to be closely associated, such that cancer is generally considered a disease of the elderly in both humans and dogs. Additionally, cancer is a metabolic shift in itself towards aerobic glycolysis. Larger dog breeds with shorter lifespans, and increased glycolytic cellular metabolic rates, die of cancer more often than smaller breeds. The tumor suppressor p53 factor is a key suppressor oncogene, and the p53 pathway arrests cellular proliferation and prevents DNA mutations from accumulating during cellular stress. The p53 pathway is also associated with the control of cellular metabolism to prevent cellular metabolic shifts common to cancerous phenotypes. SIRT1 deacetylates the p53 tumor suppressor protein, downregulating p53 via effects on stability and activity during stress. Here, we used primary fibroblast cells from small and large puppies and old dogs. Using UV radiation to upregulate the p53 system (100 J/m2), control cells and UV-treated cells were used to measure aerobic and glycolytic metabolic rates using a Seahorse XFe96 oxygen flux analyzer. We also quantified p53 expression and SIRT1 concentration in canine primary fibroblasts before and after UV treatment. We demonstrate that, due to a higher p53 nuclear to cytoplasmic ratio in large breed dogs after UV treatment, p53 could have a more regulatory effect on large breed dogs' metabolism compared with smaller breeds. Thus, there may be a link between p53 upregulation and inhibition of glycolysis in large breed dogs during times of cellular stress compared with small breed dogs. However, SIRT1 concentrations decrease with age in domestic dogs of both size classes, suggesting a possible release of inhibition of p53 through the SIRT1 pathway with age. This may lead to increased incidences of cancer, especially due to the more pronounced upregulation of p53 with cellular stress.

Oroxylin A ameliorates ultraviolet radiation-induced premature skin aging by regulating oxidative stress via the Sirt1 pathway

Skin is susceptible to premature aging in response to ultraviolet (UV) radiation-induced oxidative stress, which can ultimately result in aberrant aging or age-related disorders. Accordingly, strategies that can be adopted to mitigate oxidative stress may contribute to protecting skin from induced aging-related damage, thereby offering promising approaches for the treatment of skin diseases and disorders. In this regard, oroxylin A (OA), a natural flavonoid isolated from certain plants used in traditional Chinese medicine, is considered to have notable antioxidant, anti-inflammatory, and anti-apoptotic properties, and is often used to treat certain inflammatory diseases. To date, however, there has been comparatively little research on the effects of OA with respect skin aging. In this study, we utilized UV radiation-induced mouse and cellular models of aging to assess the efficacy of OA in protecting against skin aging. Subsequently, to elucidate the potential mechanisms underlying the protective effect of OA on skin aging, we performed molecular docking analysis to investigate the involvement of the anti-aging gene Sirt1, which was further confirmed on the basis of Sirt1 gene silencing. We accordingly demonstrated that by promoting an increase in the expression of Sirt1, OA can contribute to suppressing UV-induced skin photo-aging in cells/mice by reducing oxidative stress. Furthermore, we established that by activating Sirt1, OA can also promote the dissociation of Nrf2 from Keap1 and its subsequent nuclear translocation. Collectively, our findings in this study reveal OA to be an effective natural compound that can be administered to delay the aging of skin triggered by UV, both in vivo and in vitro, by binding to Sirt1 to promote the deacetylation and nuclear translocation of Nrf2, thereby contributing to a reduction in oxidative stress. These findings may this provide a therapeutic target for the prevention of skin aging or aging-induced skin diseases.

Long Non-coding RNA H19-Overexpressing Exosomes Ameliorate UVB-Induced Photoaging by Upregulating SIRT1 Via Sponging miR-138

UVB-induced photoaging is characterized by wrinkle formation, slackness and senile plaques, affecting the health and beauty of human being. Our previous study revealed that exosomes derived from adipose-derived stem cells (ADSCs) could efficiently alleviate UVB-induced photodamage. However, the functional ingredients in exosomes were undefined. LncRNA H19, one of the well-researched lncRNAs in exosomes, exhibits multiple physiological effects. This study aims to demonstrate the photo-protective role of lncRNA H19 on skin photoaging in UVB-irradiated human skin fibroblasts cells (HSFs) and Kunming mice. LncRNA H19-overexpressing exosomes (H19-Exo) were isolated from the supernatant of ADSCs infected with lncRNA H19-loaded lentivirus. The results showed that H19-Exo significantly inhibited MMPs production, DNA damage and ROS generation while enhancing procollagen type I synthesis in UVB-irradiated HSFs. Meanwhile, H19-Exo markedly reversed epidermal thickening and collagen degradation in UVB-irradiated mice. Furthermore, luciferase reporter assays indicated that lncRNA H19 acted as a sponge for miR-138 expression, and SIRT1 was targeted by miR-138. Evidence from both in vitro and in vivo studies also revealed that H19-Exo could enhance SIRT1 expression by knocking down miR-138. In conclusion, lncRNA H19 served as a therapeutic candidate in treating UVB-induced skin photoaging by upregulation of SIRT1 via miR-138.

Identification of key circadian rhythm genes in skin aging based on bioinformatics and machine learning

Skin aging is often accompanied by disruption of circadian rhythm and abnormal expression of circadian rhythm-related genes. In this study, we downloaded skin aging expression datasets from the GEO database and utilized bioinformatics and machine learning methods to explore circadian rhythm genes and pathways involved in skin aging, revealing the pathological and molecular mechanisms of skin aging. Results showed that 39 circadian rhythm-related genes (CRGs) were identified in skin aging, and these CRGs were enriched in signaling pathways such as glucagon signaling pathway, insulin resistance, thyroid hormone signaling pathway, and adipocytokine signaling pathway. Three key skin aging-related CRGs, SIRT1, ARNTL, and ATF4, were identified based on machine learning. Additionally, we found that skin aging was associated with infiltration of immune cells including NK cells activated, Macrophages M1, Mast cells resting, T cells CD4 memory activated, and Macrophages M2, and the expression of the three key skin aging-related CRGs was correlated with these immune cells. Finally, SIRT1, ARNTL, and ATF4 were all down-regulated in skin aging and had a good ability to distinguish young skin tissue from aging skin tissue. In conclusion, three key CRGs, including SIRT1, ARNTL, and ATF4, which are closely related to skin aging, were obtained based on bioinformatics and machine learning technology screening. These three key CRGs were potential risk genes for skin aging and also associated with changes in the immune microenvironment in skin aging. The language used in this paragraph follows the guidelines for scientific writing specified by SCI, making it clear and concise.

The role of sirtuins in dermal fibroblast function

The sirtuins are a family of seven proteins that perform a variety of dermatological functions and help maintain both the structure and function of the skin. More specifically, the sirtuins have been shown to be altered in multiple dermal cell types including dermal fibroblasts. The functions of dermal fibroblasts are extensive, and include playing a significant role in wound healing as well as helping to maintain the integrity of the skin. As dermal fibroblasts age, they can undergo a state of permanent cell cycle arrest, known as cellular senescence. This senescent process can occur as a result of various stressors, including oxidative stress, ultraviolet radiation -induced stress, and replicative stress. In recent years, there has been a growing interest in both enhancing the cutaneous fibroblast’s ability to facilitate wound healing and altering fibroblast cellular senescence. Thus, in this review, we examine the relationship between sirtuin signaling and dermal fibroblasts to understand how this family of proteins may modulate skin conditions ranging from the wound healing process to photocarcinogenesis associated with fibroblast senescence. Additionally, we offer supporting data from experiments examining the relationship between fibroblast senescence and sirtuin levels in an oxidative stress model indicating that senescent dermal fibroblasts exhibit diminished sirtuin levels. Furthermore, we survey the research on the role of sirtuins in specific dermatological disease states that where dermal fibroblast function has been implicated. Finally, we conclude with outlining potential clinical applications of sirtuins in dermatology. In sum, we find that the literature on the involvement of sirtuins in dermal fibroblasts is limited, with research still in its early stages. Nevertheless, intriguing preliminary findings merit additional investigation into the clinical implications of sirtuins in dermatology.

Post-Translational Modifications Evoked by Reactive Carbonyl Species in Ultraviolet-A-Exposed Skin: Implication in Fibroblast Senescence and Skin Photoaging

Photoaging is an accelerated form of aging resulting from skin exposure to ultraviolet (UV) radiation. UV-A radiation deeply penetrates the dermis and triggers the generation of reactive oxygen species (ROS) which promotes damage to DNA, lipids and proteins. Lipid peroxidation results from the oxidative attack of polyunsaturated fatty acids which generate a huge amount of lipid peroxidation products, among them reactive carbonyl species (RCS) such as α, β-unsaturated hydroxyalkenals (e.g., 4-hydroxynonenal), acrolein or malondialdehyde. These highly reactive agents form adducts on free NH2 groups and thiol residues on amino acids in proteins and can also modify DNA and phospholipids. The accumulation of RCS-adducts leads to carbonyl stress characterized by progressive cellular and tissular dysfunction, inflammation and toxicity. RCS-adducts are formed in the dermis of skin exposed to UV-A radiation. Several RCS targets have been identified in the dermis, such as collagen and elastin in the extracellular matrix, whose modification could contribute to actinic elastosis lesions. RCS-adducts may play a role in fibroblast senescence via the modification of histones, and the sirtuin SIRT1, leading to an accumulation of acetylated proteins. The cytoskeleton protein vimentin is modified by RCS, which could impair fibroblast motility. A better identification of protein modification and carbonyl stress in the dermis may help to develop new treatment approaches for preventing photoaging.

Nicotinamide Mononucleotide and Coenzyme Q10 Protects Fibroblast Senescence Induced by Particulate Matter Preconditioned Mast Cells

Particulate matter (PM) pollutants impose a certain degree of destruction and toxicity to the skin. Mast cells in the skin dermis could be activated by PMs that diffuse across the blood vessel after being inhaled. Mast cell degranulation in the dermis provides a kind of inflammatory insult to local fibroblasts. In this study, we evaluated human dermal fibroblast responses to conditioned medium from KU812 cells primed with PM. We found that PM promoted the production of proinflammatory cytokines in mast cells and that the cell secretome induced reactive oxygen species and mitochondrial reactive oxygen species production in dermal fibroblasts. Nicotinamide mononucleotide or coenzyme Q10 alleviated the generation of excessive ROS and mitochondrial ROS induced by the conditioned medium from PM-activated KU812 cells. PM-conditioned medium treatment increased the NF-κB expression in dermal fibroblasts, whereas NMN or Q10 inhibited p65 upregulation by PM. The reduced sirtuin 1 (SIRT 1) and nuclear factor erythroid 2-related Factor 2 (Nrf2) expression induced by PM-conditioned medium was reversed by NMN or Q10 in HDFs. Moreover, NMN or Q10 attenuated the expression of senescent β-galactosidase induced by PM-conditioned KU812 cell medium. These findings suggest that NMN or Q10 ameliorates PM-induced inflammation by improving the cellular oxidative status, suppressing proinflammatory NF-κB, and promoting the levels of the antioxidant and anti-inflammatory regulators Nrf2 and SIRT1 in HDFs. The present observations help to understand the factors that affect HDFs in the dermal microenvironment and the therapeutic role of NMN and Q10 as suppressors of skin aging.

Age-Related Changes in the Fibroblastic Differon of the Dermis: Role in Skin Aging

Skin aging is a multi-factorial process that affects nearly every aspect of skin biology and function. The processes developing in the skin during aging are based on fundamental molecular mechanisms associated with fibroblasts, the main cellular population of the dermis. It has been revealed that the amount of fibroblasts decreases markedly with age and their functional activity is also reduced. This inevitably leads to a decrease in the regenerative abilities of the skin and the progression of its aging. In this review we consider the mechanisms underlying these processes, mainly the changes observed with age in the stem/progenitor cells that constitute the fibroblastic differon of the dermis and form their microenvironment (niches). These changes lead to the depletion of stem cells, which, in turn, leads to a decrease in the number of differentiated (mature) dermal fibroblasts responsible for the production of the dermal extracellular matrix and its remodeling. We also describe in detail DNA damages, their cellular and systemic consequences, molecular mechanisms of DNA damage response, and also the role of fibroblast senescence in skin aging.

Photoprotective effects of Sargassum thunbergii on ultraviolet B-induced mouse L929 fibroblasts and zebrafish

BACKGROUND

Chronic exposure to ultraviolet B (UVB) causes a series of adverse skin reactions, such as erythema, sunburn, photoaging, and cancer, by altering signaling pathways related to inflammation, oxidative stress, and DNA damage. Marine algae have abundant amounts and varieties of bioactive compounds that possess antioxidant and anti-inflammatory properties. Thus, the objective of this study was to investigate the photoprotective effects of an ethanol extract of Sargassum thunbergii.

METHODS

Sargassum thunbergii phenolic-rich extract (STPE) was prepared, and its activity against UVB damage was evaluated using L929 fibroblast cells and zebrafish. STPE was extracted and purified by 40% ethanol and macroporous resin XDA-7. Reactive oxygen species (ROS) and antioxidant markers, such as superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde (MDA) content were analyzed. The effect of STPE on UVB-induced inflammation was determined by inflammatory cytokine gene and protein expression. The expression of signaling molecules in the Nuclear Factor KappaB (NF-κB) pathway was determined by western blotting. DNA condensation was analyzed and visualized by Hoechst 33342 staining. In vivo evaluation was performed by tail fin area and ROS measurement using the zebrafish model.

RESULTS

The total polyphenol content of STPE was 72%. STPE reduced ROS content in L929 cells, improved SOD and CAT activities, and significantly reduced MDA content, thereby effectively alleviating UVB radiation-induced oxidative damage. STPE inhibited the mRNA and protein expression of TNF-α, IL-6, and IL-1α. STPE reversed DNA condensation at concentrations of 20 and 40 μg/mL compared with the UVB control. Moreover, STPE inhibited NF-κB signaling pathway activation and alleviated DNA agglutination in L929 cells after UVB irradiation. Additionally, 1.67 μg/mL STPE significantly increased the tail fin area in zebrafish, and 0.8-1.6 μg/mL STPE effectively eliminated excessive ROS after UVB radiation.

CONCLUSIONS

STPE inhibited UVB-induced oxidative stress, inflammatory cytokine expression, and DNA condensation via the downregulation of the NF-κB signaling pathway, suggesting that it prevents UVB-induced photodamage, and has potential for clinical development for skin disease treatment.

Resistance to chemical carcinogenesis induction via a dampened inflammatory response in naked mole-rats

Naked mole-rats (NMRs) have a very low spontaneous carcinogenesis rate, which has prompted studies on the responsible mechanisms to provide clues for human cancer prevention. However, it remains unknown whether and how NMR tissues respond to experimental carcinogenesis induction. Here, we show that NMRs exhibit extraordinary resistance against potent chemical carcinogenesis induction through a dampened inflammatory response. Although carcinogenic insults damaged skin cells of both NMRs and mice, NMR skin showed markedly lower immune cell infiltration. NMRs harbour loss-of-function mutations in RIPK3 and MLKL genes, which are essential for necroptosis, a type of necrotic cell death that activates strong inflammation. In mice, disruption of Ripk3 reduced immune cell infiltration and delayed carcinogenesis. Therefore, necroptosis deficiency may serve as a cancer resistance mechanism via attenuating the inflammatory response in NMRs. Our study sheds light on the importance of a dampened inflammatory response as a non-cell-autonomous cancer resistance mechanism in NMRs.

Naked mole rats are found to be resistant to cancer development through dampened inflammatory response due to genetically determined impaired necroptosis, with essential necroptosis genes RIPK3 and MLKL containing mutations causing premature stop codons.

Role of the SENP1-SIRT1 pathway in hyperoxia-induced alveolar epithelial cell injury

Bronchopulmonary dysplasia (BPD) is a common complication in preterm infants, and its main pathogenesis partly involves oxidative stress. A large number of studies have shown that silent information regulator 1 (SIRT1) plays a protective role in oxidative stress. SUMO-specific protease 1 (SENP1) is vital in the nucleoplasmic distribution of SIRT1 under stress. However, whether the SENP1-SIRT1 pathway is involved in the hyperoxic lung injury is unknown. Therefore, this study aimed to explore the role and related mechanisms of the SENP1-SIRT1 pathway in hyperoxic lung injury. Peripheral blood mononuclear cells (PBMCs) from infants with BPD and SENP1-silenced alveolar epithelial cells were used as research models. PBMCs were isolated from the peripheral blood of premature infants. Next, the SENP1-silenced human alveolar epithelial cells were used to verify the role of the SENP1-SIRT1 pathway in vitro. The results indicated that the ROS level and the mRNA and protein expression of SENP1 increased in PBMCs of infants with BPD, but the expression of SIRT1 decreased in the nucleus and increased in the cytoplasm, and then the expression of acetyl-p53 (Ac-p53) increased. In the hyperoxic alveolar epithelial cell injury model, it seemed that hyperoxia could induce the same variation trend in the SENP1-SIRT1 pathway as in infants with BPD and then increased the expression of Ac-p53 and BAX, and cell apoptosis. Furthermore, silencing SENP1 could alleviate these hyperoxia-induced changes. These results suggested that SENP1 played an important role in hyperoxia-induced lung injury. It could regulate the expression and nucleoplasmic distribution of SIRT1 to inhibit its deacetylase activity, and then promoted cell apoptosis. Hence, SENP1 may become a potential intervention target of BPD in the future.

HucMSC exosome-delivered 14-3-3ζ alleviates ultraviolet radiation-induced photodamage via SIRT1 pathway modulation

Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-ex) are nano-sized membrane-bound vesicles that have been reported to facilitate skin regeneration and repair. However, the roles played by hucMSC-ex in ultraviolet (UV) radiation-induced skin photodamage and the underlying mechanisms remain unknown. To investigate the functions of hucMSC-ex in a rat model of acute skin photodamage, immunofluorescence and immunohistochemical staining, quantitative real-time-polymerase chain reaction (qRT-PCR), western blot, and gene silencing assays were performed. We found that the in vivo subcutaneous injection of hucMSC-ex elicited antioxidant and anti-inflammatory effects against UV radiation-induced DNA damage and apoptosis. Further studies showed that the sirtuin 1 (SIRT1) expression level in skin keratinocytes (HaCaT) decreased in a time- and dose-dependent manner under in vitro UV radiation induced-oxidative stress conditions, which could be reversed by treatment with hucMSC-ex. The activation of SIRT1 significantly attenuated UV- and H₂O₂-induced cytotoxic damage by inhibiting oxidative stress and promoting the activation of autophagy. Our study found that 14-3-3ζ protein, which was delivered by hucMSC-ex, exerted a cytoprotective function via the modulation of a SIRT1-dependent antioxidant pathway. Collectively, our findings indicated that hucMSC-ex might represent a new potential agent for preventing or treating UV radiation-induced skin photodamage and aging.

Sirtuin 1 and Skin: Implications in Intrinsic and Extrinsic Aging-A Systematic Review

Skin, as the outermost organ of the body, is constantly exposed to both intrinsic and extrinsic causative factors of aging. Intrinsic aging is related to compromised cellular proliferative capacity, and may be accelerated by harmful environmental influences with the greatest significance of ultraviolet radiation exposure, contributing not only to premature aging, but also to skin carcinogenesis. The overall skin cancer burden and steadily increasing global antiaging market provide an incentive for searching novel targets to improve skin resistance against external injury. Sirtuin 1, initially linked to extension of yeast and rodent lifespan, plays a key role in epigenetic modification of proteins, histones, and chromatin by which regulates the expression of genes implicated in the oxidative stress response and apoptosis. The spectrum of cellular pathways regulated by sirtuin 1 suggests its beneficial impact on skin aging. However, the data on its role in carcinogenesis remains controversial. The aim of this review was to discuss the relevance of sirtuin 1 in skin aging, in the context of intrinsic factors, related to genetic premature aging syndromes, as well as extrinsic modifiable ones, with the assessment of its future application. PubMed were searched from inception to 4 January 2021 for relevant papers with further search carried out on ClinicalTrials.gov. The systematic review included 46 eligible original articles. The evidence from numerous studies proves sirtuin 1 significance in both chronological and premature aging as well as its dual role in cancer development. Several botanical compounds hold the potential to improve skin aging symptoms.

Extracts of Jasminum sambac flowers fermented by Lactobacillus rhamnosus inhibit H2 O2 - and UVB-induced aging in human dermal fibroblasts

Ultraviolet (UV) irradiation is a crucial factor that leads to skin photoaging and results in increased DNA damage, oxidative stress, and collagen degradation. Jasmine flowers have been utilized as a traditional medicine in Asia to treat various diseases, including dermatitis, diarrhea, and fever. Furthermore, the fermented broth of Lactobacillus rhamnosus has been reported to exert protective effects on the skin. In the present study, jasmine flower extract was fermented with L. rhamnosus. We investigated the antioxidant and collagen-promoting effects on UVB/H₂ O₂ -induced HS68 dermal fibroblast cell damage. The results indicated that treatment with the fermented flower extracts of Jasminum sambac (F-FEJS) could enhance the viability of HS68 cells. Furthermore, the UVB/H₂ O₂ -induced excessive production of reactive oxygen species, degradation of collagen, activation of MAPKs, including P38, ERK, and JNK, and premature senescence were remarkably attenuated by F-FEJS in dermal fibroblast cells. The nuclear accumulation of p-c-jun, which is downstream of MAPK, and the inactivation of p-smad2/3, which is one of the crucial transcription factors that enhance collagen synthesis, were reversed in response to F-FEJS treatment in UVB/H₂ O₂ -exposed cells. Notably, the expression of antioxidant genes, such as HO-1, and the nuclear translocation of Nrf2 were further enhanced by F-FEJS in UVB/H₂ O₂ -treated cells. Interestingly, the F-FEJS-induced increase in ARE luciferase activity indicated the activation of Nrf2/ARE signaling. In conclusion, our findings demonstrated that F-FEJS can effectively ameliorate UVB/H₂ O₂ -induced dermal cell aging and may be considered a promising ingredient in skin aging therapy.

Cellular Senescence and the Senescence-Associated Secretory Phenotype as Drivers of Skin Photoaging

Chronic exposure to UVR is known to disrupt tissue homeostasis, accelerate the onset of age-related phenotypes, and increase the risk for skin cancer-a phenomenon defined as photoaging. In this paper, we review the current knowledge on how UV exposure causes cells to prematurely enter cellular senescence. We describe the mechanisms contributing to the accumulation of senescent cells in the skin and how the persistence of cellular senescence can promote impaired regenerative capacity, chronic inflammation, and tumorigenesis associated with photoaging. We conclude by highlighting the potential of senolytic drugs in delaying the onset and progression of age-associated phenotypes in the skin.

Effect of lemon peel flavonoids on UVB-induced skin damage in mice

By establishing an effective ultraviolet B (UVB) radiation model of skin damage in mice, the effect of lemon peel flavonoids (LPF) on skin damage was explored. UVB skin damage in UV-irradiated mice was simulated, and animal models were established. Serum parameters were measured using kits, skin sections were stained with hematoxylin-eosin (H&E) and Masson, and quantitative polymerase chain reaction (qPCR) was used to detect the expression of skin tissue-related mRNA. The experimental results showed that LPF increased the activity of catalase (CAT) and superoxide dismutase (SOD) oxidases in serum of mice with UVB-induced skin damage and decreased MDA, interleukin-1β (IL-1β), IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α) levels. Pathological observation indicated that LPF alleviated the skin tissue lesions caused by UVB. LPF upregulated the mRNA expression of SOD1, SOD2, CAT, nuclear factor erythroid-2 related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and inhibitor of NF-κB alpha (IκB-α) and downregulated the expression of nuclear factor kappa B (NF-κB), p38 MAPK, and cyclooxygenase-2 (COX-2) in the skin tissue of skin-damaged mice. There was a greater protective effect of LPF on the skin as compared to vitamin C (VC) at the same application concentration, and the effect of LPF was positively correlated with the concentration. High performance liquid chromatography (HPLC) analysis showed that LPF contained five flavonoid compounds, namely isomangiferin, rutin, astragalin, naringin, and quercetin. We demonstrated that flavonoids from LPF exhibit an excellent skin protection effect with satisfactory application value.

Nectandrin B-mediated activation of the AMPK pathway prevents cellular senescence in human diploid fibroblasts by reducing intracellular ROS levels

Nectandrin B (NecB) is a bioactive lignan compound isolated from Myristica fragrans (nutmeg), which functions as an activator of AMP-activated protein kinase (AMPK). Because we recently found that treatment with NecB increased the cell viability of old human diploid fibroblasts (HDFs), the underlying molecular mechanism was investigated. NecB treatment in old HDFs reduced the activity staining of senescence-associated β-galactosidase and the levels of senescence markers, such as the Ser¹⁵ phosphorylated p53, caveolin-1, p21^waf1, p16^ink4a, p27^kip1, and cyclin D1. NecB treatment increased that in S phase, indicating a enhancement of cell cycle entry. Interestingly, NecB treatment ameliorated age-dependent activation of AMPK in old HDFs. Moreover, NecB reversed the age-dependent expression and/or activity changes of certain sirtuins (SIRT1-5), and cell survival/death-related proteins. The transcriptional activity of Yin-Yang 1 and the expression of downstream proteins were elevated in NecB-treated old HDFs. In addition, NecB treatment exerted a radical scavenging effect in vitro, reduced cellular ROS levels, and increased antioxidant enzymes in old HDFs. Moreover, NecB-mediated activation of the AMPK pathway reduced intracellular ROS levels. These results suggest that NecB-induced protection against cellular senescence is mediated by ROS-scavenging through activation of AMPK. NecB might be useful in ameliorating age-related diseases and extending human lifespan.

Shedding Light on the Effects of Calorie Restriction and its Mimetics on Skin Biology

During the aging process of an organism, the skin gradually loses its structural and functional characteristics. The skin becomes more fragile and vulnerable to damage, which may contribute to age-related diseases and even death. Skin aging is aggravated by the fact that the skin is in direct contact with extrinsic factors, such as ultraviolet irradiation. While calorie restriction (CR) is the most effective intervention to extend the lifespan of organisms and prevent age-related disorders, its effects on cutaneous aging and disorders are poorly understood. This review discusses the effects of CR and its alternative dietary intake on skin biology, with a focus on skin aging. CR structurally and functionally affects most of the skin and has been reported to rescue both age-related and photo-induced changes. The anti-inflammatory, anti-oxidative, stem cell maintenance, and metabolic activities of CR contribute to its beneficial effects on the skin. To the best of the author’s knowledge, the effects of fasting or a specific nutrient-restricted diet on skin aging have not been evaluated; these strategies offer benefits in wound healing and inflammatory skin diseases. In addition, well-known CR mimetics, including resveratrol, metformin, rapamycin, and peroxisome proliferator-activated receptor agonists, show CR-like prevention against skin aging. An overview of the role of CR in skin biology will provide valuable insights that would eventually lead to improvements in skin health.

CO2 lattice laser reverses skin aging caused by UVB

The carbon dioxide (CO₂) lattice laser has been successfully used to treat facial skin photoaging induced by UV light. In this study, we analyzed the effect of CO₂ lattice laser irradiation on skin photoaging, and investigated the underlying mechanisms. Our results demonstrate that the laser promoted collagen synthesis and proliferation of primary human skin fibroblasts, inhibited cell senescence, and induced expression of superoxide dismutase (SOD) and the signaling protein SMAD3. In addition, this laser reversed cell cycle arrest and fibroblast apoptosis induced by UVB irradiation, and restored fibroblast proliferation inhibited by SMAD3 silencing. Using a rat model of photoaging, our results show that the laser increased collagen expression and dermal thickness, demonstrating that the CO₂ lattice laser has a profound therapeutic effect on photoaged skin. Together, our in vitro and in vivo data show that the CO₂ lattice laser can reverse the skin aging caused by UVB, and indicate that this effect is mediated through SMAD3.

SIRT1 and aging related signaling pathways

Aging is a biological phenomenon in which the structure and function of organisms declining with the increasing of age. It has become a major risk factor of human diseases, including diabetes, cancers, cardiovascular diseases and neurodegenerative diseases. Silencing information regulator 2 related enzyme 1(sirtuin1, SIRT1) is an NAD⁺-dependent deacetylase, which has been reported to be involved in the regulation of cellular senescence and aging. The expression of SIRT1 is diminished with aging in mice. By contrast, increased expression of SIRT1 is sufficient to extend lifespan in yeast, caenorhabditis elegans and mice. In this review, the relationship between SIRT1 and aging and various signaling networks associated with aging, including NF-κB, AMPK, mTOR, P53, PGC1α, and FoxOs will be discussed. Meanwhile, the potential therapeutic strategies of targeting SIRT1 to anti-aging are also addressed.

Antioxidant and Cytoprotective Effects of (-)-Epigallocatechin-3-(3″-O-methyl) Gallate

Reactive oxygen species (ROS) are generated from diverse cellular processes or external sources such as chemicals, pollutants, or ultraviolet (UV) irradiation. Accumulation of radicals causes cell damage that can result in degenerative diseases. Antioxidants remove radicals by eliminating unpaired electrons from other molecules. In skin health, antioxidants are essential to protect cells from the environment and prevent skin aging. (-)-Epigallocatechin-3-(3″-O-methyl) gallate (3″Me-EGCG) has been found in limited oolong teas or green teas with distinctive methylated form, but its precise activities have not been fully elucidated. In this study, we examined the antioxidant roles of 3″Me-EGCG in keratinocytes (HaCaT cells). 3″Me-EGCG showed scavenging effects in cell and cell-free systems. Under H₂O₂ exposure, 3″Me-EGCG recovered cell viability and increased the expression of heme oxygenase 1 (HO-1). Under ultraviolet B (UVB) and sodium nitroprusside (SNP) exposure, 3″Me-EGCG protected keratinocytes and regulated the survival protein AKT1. By regulating the AKT1/NF-κB pathway, 3″Me-EGCG augmented cell survival and proliferation in HaCaT cells. These results indicate that 3″Me-EGCG exhibits antioxidant properties, resulting in cytoprotection against various external stimuli. In conclusion, our findings suggest that 3″Me-EGCG can be used as an ingredient of cosmetic products or health supplements.

Coenzyme Q10 protects hepatocytes from ischemia reperfusion-induced apoptosis and oxidative stress via regulation of Bax/Bcl-2/PUMA and Nrf-2/FOXO-3/Sirt-1 signaling pathways

Coenzyme Q₁₀ (CoQ₁₀) is a component of the mitochondrial electron transport chain and regarded as a strong anti-oxidant agent. In this study, we focused on the mechanistic insights involved in the hepato-protective effects of CoQ₁₀ against hepatic ischemia reperfusion (IR) injury. Our results revealed that CoQ₁₀ significantly improved hepatic dysfunctions and oxidative stress caused by IR injury. Interestingly, as compared to IR subjected rat, CoQ₁₀ inhibited apoptosis by marked down-regulation of both Bax and PUMA genes while the level of Bcl-2 gene was significantly increased. Moreover, CoQ₁₀ up-regulated PI3K, Akt and mTOR protein expressions while it inhibited the expression of both GSK-3β and β-catenin. Additionally, CoQ₁₀ restored oxidant/antioxidant balance via marked activated Nrf-2 protein as well as up-regulation of both Sirt-1 and FOXO-3 genes. Moreover, CoQ₁₀ strongly inhibited inflammatory response through down-regulation of NF-κB-p65 and decrease both JAK1 and STAT-3 protein expressions with a subsequent modulating circulating inflammatory cytokines. Furthermore, histopathological analysis showed that CoQ₁₀ remarkably ameliorated the histopathological damage induced by IR injury. Taken together, our results suggested and proved that CoQ₁₀ provided a hepato-protection against hepatic IR injury via inhibition of apoptosis, oxidative stress, inflammation and their closed related pathways.

The effect of aging in primary human dermal fibroblasts

Skin aging is a complex process, and alterations in human skin due to aging have distinct characteristic as compared to other organs. The aging of dermal cells and the biological mechanisms involved in this process are key areas to understand skin aging. A large number of biological mechanisms, such as decreasing of protein synthesis of extracellular matrix or increasing of degradation, are known to be altered through skin aging. However, environmental influence can accelerate this characteristic phenotype. In this study, we analyzed primary human dermal fibroblasts in three different in-vitro aging models—UVB irradiation and accelerated proliferation of human dermal fibroblasts from young donors as well as from elderly donors—for the gene expression of COL1A1, COL1A2, COL3A1, COL4A1, COL7A1, MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP12, MMP13, MMP14, TIMP1, TIMP2, TIMP3, TIMP4, IL1B, IL1A, IL6, IL8, IL10, PTGS2, TP53, CASP3, LMNA, SIRT1. We compared the gene expression levels with young control. Furthermore, the behavior of skin fibroblasts was also evaluated using cell growth rate. The findings reveal that the gene expression levels in skin fibroblasts was altered in the process of aging in all three in-vitro aging models, and the cell growth rate was reduced, suggesting that these methods can be employed to understand skin aging mechanisms as well as drug discovery screening method.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Epigenetic Regulation of Skin Cells in Natural Aging and Premature Aging Diseases

Skin undergoes continuous renewal throughout an individual’s lifetime relying on stem cell functionality. However, a decline of the skin regenerative potential occurs with age. The accumulation of senescent cells over time probably reduces tissue regeneration and contributes to skin aging. Keratinocytes and dermal fibroblasts undergo senescence in response to several intrinsic or extrinsic stresses, including telomere shortening, overproduction of reactive oxygen species, diet, and sunlight exposure. Epigenetic mechanisms directly regulate skin homeostasis and regeneration, but they also mark cell senescence and the natural and pathological aging processes. Progeroid syndromes represent a group of clinical and genetically heterogeneous pathologies characterized by the accelerated aging of various tissues and organs, including skin. Skin cells from progeroid patients display molecular hallmarks that mimic those associated with naturally occurring aging. Thus, investigations on progeroid syndromes strongly contribute to disclose the causal mechanisms that underlie the aging process. In the present review, we discuss the role of epigenetic pathways in skin cell regulation during physiologic and premature aging.

Mushroom extract inhibits ultraviolet B-induced cellular senescence in human keratinocytes

Mushrooms possess various bioactivities and are used as nutritional supplements and medicinal products. Twenty-nine bioactive components have been extracted recently from mushrooms grown in Nepal. In this study, we evaluated the ability of these mushroom extracts to augment SIRT1, a mammalian SIR2 homologue localized in cytosol and nuclei. We established a system for screening food ingredients that augment the SIRT1 promoter in HaCaT cells, and identified a SIRT1-augmenting mushroom extract (number 28, Trametes versicolor). UVB irradiation induced cellular senescence in HaCaT cells, as evidenced by increased activity and expression of cellular senescence markers including senescence-associated β-galactosidase, p21, p16, phosphorylated p38, and γH2AX. Results clearly showed that the mushroom extract (No. 28) suppressed the ultraviolet B irradiation-induced cellular senescence in HaCaT cells possibly through augmenting SIRT1 expression.

Sirt1 Protects against Oxidative Stress-Induced Apoptosis in Fibroblasts from Psoriatic Patients: A New Insight into the Pathogenetic Mechanisms of Psoriasis

Psoriasis, a multisystem chronic disease characterized by abnormal keratinocyte proliferation, has an unclear pathogenesis where systemic inflammation and oxidative stress play mutual roles. Dermal fibroblasts, which are known to provide a crucial microenvironment for epidermal keratinocyte function, represented the selected experimental model in our study which aimed to clarify the potential role of SIRT1 in the pathogenetic mechanisms of the disease. We firstly detected the presence of oxidative stress (lipid peroxidation and total antioxidant capacity), significantly reduced SIRT1 expression level and activity, mitochondrial damage and apoptosis (caspase-3, -8 and -9 activities) in psoriatic fibroblasts. Upon SIRT1 activation, redox balance was re-established, mitochondrial function was restored and apoptosis was no longer evident. Furthermore, we examined p38, ERK and JNK activation, which was strongly altered in psoriatic fibroblasts, in response to SIRT1 activation and we measured caspase-3 activity in the presence of specific MAPK inhibitors demonstrating the key role of the SIRT1 pathway against apoptotic cell death via MAPK modulation. Our results clearly demonstrate the involvement of SIRT1 in the protective mechanisms related to fibroblast injury in psoriasis. SIRT1 activation exerts an active role in restoring both mitochondrial function and redox balance via modulation of MAPK signaling. Hence, SIRT1 can be proposed as a specific tool for the treatment of psoriasis.

The skin protective effects of compound K, a metabolite of ginsenoside Rb1 from Panax ginseng

BACKGROUND

Compound K (CK) is a ginsenoside, a metabolite of Panax ginseng. There is interest both in increasing skin health and antiaging using natural skin care products. In this study, we explored the possibility of using CK as a cosmetic ingredient.

METHODS

To assess the antiaging effect of CK, RT-PCR was performed, and expression levels of matrix metalloproteinase-1, cyclooxygenase-2, and type I collagen were measured under UVB irradiation conditions. The skin hydrating effect of CK was tested by RT-PCR, and its regulation was explored through immunoblotting. Melanin content, melanin secretion, and tyrosinase activity assays were performed.

RESULTS

CK treatment reduced the production of matrix metalloproteinase-1 and cyclooxygenase-2 in UVB irradiated NIH3T3 cells and recovered type I collagen expression level. Expression of skin hydrating factors-filaggrin, transglutaminase, and hyaluronic acid synthases-1 and -2-were augmented by CK and were modulated through the inhibitor of κBα, c-Jun N-terminal kinase, or extracellular signal-regulated kinases pathway. In the melanogenic response, CK did not regulate tyrosinase activity and melanin secretion, but increased melanin content in B16F10 cells was observed.

CONCLUSION

Our data showed that CK has antiaging and hydrating effects. We suggest that CK could be used in cosmetic products to protect the skin from UVB rays and increase skin moisture level.

Programming of Cell Resistance to Genotoxic and Oxidative Stress

Different organisms, cell types, and even similar cell lines can dramatically differ in resistance to genotoxic stress. This testifies to the wide opportunities for genetic and epigenetic regulation of stress resistance. These opportunities could be used to increase the effectiveness of cancer therapy, develop new varieties of plants and animals, and search for new pharmacological targets to enhance human radioresistance, which can be used for manned deep space expeditions. Based on the comparison of transcriptomic studies in cancer cells, in this review, we propose that there is a high diversity of genetic mechanisms of development of genotoxic stress resistance. This review focused on possibilities and limitations of the regulation of the resistance of normal cells and whole organisms to genotoxic and oxidative stress by the overexpressing of stress-response genes. Moreover, the existing experimental data on the effect of such overexpression on the resistance of cells and organisms to various genotoxic agents has been analyzed and systematized. We suggest that the recent advances in the development of multiplex and highly customizable gene overexpression technology that utilizes the mutant Cas9 protein and the abundance of available data on gene functions and their signal networks open new opportunities for research in this field.

Photoaging protective effects of BIOGF1K, a compound-K-rich fraction prepared from Panax ginseng

BACKGROUND

BIOGF1K, a compound-K-rich fraction, has been shown to display anti-inflammatory activity. Although Panax ginseng is widely used for the prevention of photoaging events induced by UVB irradiation, the effect of BIOGF1K on photoaging has not yet been examined. In this study, we investigated the effects of BIOGF1K on UVB-induced photoaging events.

METHODS

We analyzed the ability of BIOGF1K to prevent UVB-induced apoptosis, enhance matrix metalloproteinase (MMP) expression, upregulate anti-inflammatory activity, reduce sirtuin 1 expression, and melanin production using reverse transcription-polymerase chain reaction, melanin content assay, tyrosinase assay, and flow cytometry. We also evaluated the effects of BIOGF1K on the activator protein-1 signaling pathway, which plays an important role in photoaging, by immunoblot analysis and luciferase reporter gene assays.

RESULTS

Treatment of UVB-irradiated NIH3T3 fibroblasts with BIOGF1K prevented UVB-induced cell death, inhibited apoptosis, suppressed morphological changes, reduced melanin secretion, restored the levels of type I procollagen and sirtuin 1, and prevented mRNA upregulation of MMP-1, MMP-2, and cyclo-oxygenase-2; these effects all occurred in a dose-dependent manner. In addition, BIOGF1K markedly reduced activator-protein-1-mediated luciferase activity and decreased the activity of mitogen-activated protein kinases (extracellular response kinase, p38, and C-Jun N-terminal kinase).

CONCLUSION

Our results strongly suggest that BIOGF1K has anti-photoaging activity and that BIOGF1K could be used in anti-aging cosmeceutical preparations.

An Extract from the Plant Deschampsia antarctica Protects Fibroblasts from Senescence Induced by Hydrogen Peroxide

The Antarctic plant Deschampsia antarctica (DA) is able to survive in extreme conditions thanks to its special mechanism of protection against environmental aggressions. In this work, we investigated whether an aqueous extract of the plant (EDA) retains some of its defensive properties and is able to protect our skin against common external oxidants. We evaluated EDA over young human fibroblasts and exposed to H2O2, and we measured cell proliferation, viability, and senescence-associated β-galactosidase (SA-β-Gal). We also tested the expression of several senescence-associated proteins including sirtuin1, lamin A/C, the replicative protein PCNA, and the redox protein thioredoxin 2. We found that EDA promoted per se cell proliferation and viability and increased the expression of anti-senescence-related markers. Then, we selected a dose of H2O2 as an inductor of senescence in human fibroblasts, and we found that an EDA treatment 24 h prior H2O2 exposure increased fibroblast proliferation. EDA significantly inhibited the increase in SA-β-Gal levels induced by H2O2 and promoted the expression of sirtuin 1 and lamin A/C proteins. Altogether, these results suggest that EDA protects human fibroblasts from cellular senescence induced by H2O2, pointing to this compound as a potential therapeutic agent to treat or prevent skin senescence.

Exogenous nicotinamide supplementation and moderate physical exercise can attenuate the aging process in skeletal muscle of rats

Nicotinamide (NAM) could enhance the availability of NAD+ and be beneficial to cell function. However, NAM can inhibit the activities of SIRT1 and PARP. The effect of NAM supplementation on the aging process is not well known. In the present study exogenous NAM (1-0.5% in drinking water) was supplemented for 5 weeks and in the last 4 weeks moderate treadmill running was given to 5 mo and 28 mo old rats. The content of SIRT1 was not effected by NAM treatment alone. However, the activity of SIRT1, judged from the acetylated p53/p53 ratio, increased in both NAM treated age groups, suggesting beneficial effects of exogenous NAM. This was confirmed by the finding of increased PGC-1α and pCREB/CREB ratio in the gastrocnemius muscle of old but not young NAM treated animals. Our data suggest NAM administration can attenuate the aging process in skeletal muscle of rats, but NAM administration together with exercise training might be too great challenge to cope with in the old animals, since it leads to decreased levels of SIRT1.

Sirtuins in Skin and Skin Cancers

The sirtuins are a family of proteins that comprise class III of the histone deacetylases. These NAD+-dependent proteins have been found to be intricately involved in a variety of important and skin-relevant cellular functions and processes, including aging, UV damage response, oxidative stress, and wound repair. In addition, recent research is unraveling the role of sirtuins in a variety of skin diseases, including melanoma and nonmelanoma skin cancers. In this review, we provide a discussion on the potential roles and implications of different sirtuins in skin-specific cellular processes, which may have relevance to skin health and skin diseases. Based on the available literature, the sirtuins appear to be important targets in the management of a variety of skin diseases from cosmetic (e.g., skin aging) to fatal conditions (e.g., melanoma).

SIRT1 activation mediates heat-induced survival of UVB damaged Keratinocytes

Background

Exposure to heat stress after UVB irradiation induces a reduction of apoptosis, resulting in survival of DNA damaged human keratinocytes. This heat-mediated evasion of apoptosis appears to be mediated by activation of SIRT1 and inactivation of p53 signalling. In this study, we assessed the role of SIRT1 in the inactivation of p53 signalling and impairment of DNA damage response in UVB plus heat exposed keratinocytes.

Results

Activation of SIRT1 after multiple UVB plus heat exposures resulted in increased p53 deacetylation at K382, which is known to affect its binding to specific target genes. Accordingly, we noted decreased apoptosis and down regulation of the p53 targeted pro-apoptotic gene BAX and the DNA repair genes ERCC1 and XPC after UVB plus heat treatments. In addition, UVB plus heat induced increased expression of the cell survival gene Survivin and the proliferation marker Ki67. Notably, keratinocytes exposed to UVB plus heat in the presence of the SIRT1 inhibitor, Ex-527, showed a similar phenotype to those exposed to UV alone; i.e. an increase in p53 acetylation, increased apoptosis and low levels of Survivin.

Conclusion

This study demonstrate that heat-induced SIRT1 activation mediates survival of DNA damaged keratinocytes through deacetylation of p53 after exposure to UVB plus heat

Electronic supplementary material

The online version of this article (doi:10.1186/s12895-017-0060-y) contains supplementary material, which is available to authorized users.

Melatonin regulates the aging mouse hippocampal homeostasis via the sirtuin1-FOXO1 pathway

Sirtuin1 (SIRT1) and forkhead box transcription factor O subfamily 1 (FOXO1) play vital roles in the maintenance of hippocampal neuronal homeostasis during aging. Our previous study showed that melatonin, a hormone mainly secreted by the pineal gland, restored the impaired memory of aged mice. Age-related neuronal energy deficits contribute to the pathogenesis of several neurodegenerative disorders. An attempt has been made to determine whether the effect of melatonin is mediated through the SIRT1-FOXO1 pathways. The present results showed that aged mice (22 months old) exhibited significantly downregulated SIRT1, FOXO1, and melatonin receptors MT1 and MT2 protein expression but upregulated tumor suppressor protein 53 (p53), acetyl-p53 protein (Ac-p53), mouse double minute 2 homolog (MDM2), Dickkopf-1 (DKK1) protein expression in mouse hippocampus compared with the young group. Melatonin treatment (10 mg/kg, daily in drinking water for 6 months) in aged mice significantly attenuated the age-induced downregulation of SIRT1, FOXO1, MT1 and MT2 protein expression and attenuated the age-induced increase in p53, ac-p53, MDM2, and DKK1 protein and mRNA expression. Melatonin decreased p53 and MDM2 expression, which led to a decrease in FOXO1 degradation. These present results suggest that melatonin may help the hippocampal neuronal homeostasis by increasing SIRT1, FOXO1 and melatonin receptors expression while decreasing DKK1 expression in the aging hippocampus. DKK1 can be induced by the accumulation of amyloid β (Aβ) which is the major hallmark of Alzheimer's disease.

FGF21 represses cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 signaling pathway in an AMPK-dependent manner

Cerebrovascular aging has a high relationship with stroke and neurodegenerative disease. In the present study, we evaluated the influence of fibroblast growth factor 21 (FGF21) on angiotensin (Ang II)-mediated cerebrovascular aging in human brain vascular smooth muscle cells (hBVSMCs). Ang II induced remarkable aging-phenotypes in hBVSMCs, including enhanced SA-β-gal staining and NBS1 protein expression. First, we used immunoblotting assay to confirm protein expression of FGF21 receptor (FGFR1) and the co-receptor β-Klotho in cultured hBVSMCs. Second, we found that FGF21 treatment partly prevented the aging-related changes induced by Ang II. FGF21 inhibited Ang II-enhanced ROS production/superoxide anion levels, rescued the Ang II-reduced Complex IV and citrate synthase activities, and suppressed the Ang II-induced meprin protein expression. Third, we showed that FGF21 not only inhibited the Ang II-induced p53 activation, but also blocked the action of Ang II on Siah-1-TRF signaling pathway which is upstream factors for p53 activation. At last, either chemical inhibition of AMPK signaling pathway by a specific antagonist Compound C or knockdown of AMPKα1/2 isoform using siRNA, successfully abolished the anti-aging action of FGF21 in hBVSMCs. These results indicate that FGF21 protects against Ang II-induced cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 activation in an AMPK-dependent manner, and highlight the therapeutic value of FGF21 in cerebrovascular aging-related diseases such as stroke and neurodegenerative disease.

MicroRNA-34a affects chondrocyte apoptosis and proliferation by targeting the SIRT1/p53 signaling pathway during the pathogenesis of osteoarthritis

Osteoarthritis (OA) is the most prevalent degenerative joint disease with multifactorial etiology caused by risk factors such as ageing, obesity and trauma. Previously, it was reported that the inhibition of microRNA-34a (miR-34a) may reduce rat chondrocyte apoptosis induced by IL-1β, whereas the molecular mechanism and the role of miR-34a in human chondrocyte as well as in OA progression remains to be determined. In the current study, using MTT, luciferase reporter assays and western blot analysis we identified that miR-34a was upregulated while silent information regulator 1 (SIRT1) was inhibited in chondrocytes from 12 OA patients compared with healthy chondrocytes from 10 trauma amputees. Overexpression of miR-34a promoted apoptosis and inhibited cell proliferation in human chondrocytes. Transfection with miR-34a mimic inhibited SIRT1 expression, which attenuated the deacetylation of p53, leading to the upregulation of Bax and downregulation of Bcl-2. Furthermore, results from the western blot analysis and luciferase reporter assay demonstrated that SIRT1 was directly regulated by miR-34a in human chondrocytes. A rat model of OA was induced through anterior cruciate ligament transection and medial meniscus resection (ACLT+MMx). The results showed that the intra-articular injection of lentiviral vector encoding anti-miR-34a sequence effectively ameliorated the progression of OA. The results suggest that miR-34a has a crucial role in the pathogenesis of OA through direct regulation of the SIRT1/p53 signaling pathway and serves as a potential therapeutic target of OA.

The Photoprotective Effect of S-Methylmethionine Sulfonium in Skin

S-Methylmethionine sulfonium (SMMS) was reported to have wound-healing effects; we therefore have investigated the photoprotective effect of SMMS in the present study. SMMS increased the viability of keratinocyte progenitor cells (KPCs) and human dermal fibroblasts (hDFs) following ultraviolet B (UVB) irradiation, and reduced the UVB-induced apoptosis in these cells. SMMS increased the phosphorylation of extracellular signal-regulated kinases (ERK), and the inhibitor of the mitogen-activated protein kinase pathway significantly decreased the SMMS-induced viability of KPCs and hDFs. In addition, SMMS attenuated the UVB-induced reactive oxygen species (ROS) generation in KPCs and hDFs. SMMS induced the collagen synthesis and reduced the matrix metalloproteinase-1 expression in UVB-irradiated hDFs. In animal studies, application of 5% and 10% SMMS before and after UVB-irradiation significantly decreased the UVB-induced erythema index and depletion of Langerhans cells. In summary, SMMS protects KPCs and hDFs from UVB irradiation, and reduces UVB-induced skin erythema and immune suppression. Therefore, SMMS can be used as a cosmetic raw material, and protect skin from UVB.

Globular Adiponectin Causes Tolerance to LPS-Induced TNF-α Expression via Autophagy Induction in RAW 264.7 Macrophages: Involvement of SIRT1/FoxO3A Axis

Adiponectin, an adipokine predominantly produced from adipose tissue, exhibited potent anti-inflammatory properties. In particular, it inhibits production of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), in macrophages. Autophagy, an intracellular self-digestion process, has been recently shown to regulate inflammatory responses. In the present study, we investigated the role of autophagy induction in the suppression of Lipopolysaccharide (LPS) -induced TNF-α expression by globular adiponectin (gAcrp) and its potential mechanisms. Herein, we found that gAcrp treatment increased expression of genes related with autophagy, including Atg5 and microtubule-associated protein light chain (LC3B), induced autophagosome formation and autophagy flux in RAW 264.7 macrophages. Similar results were observed in primary macrophages isolated peritoneum of mice. Interestingly, inhibition of autophagy by pretreatment with Bafilomycin A1 or knocking down of LC3B gene restored suppression of TNF-α expression, tumor necrosis factor receptor- associated factor 6 (TRAF6) expression and p38MAPK phosphorylation by gAcrp, implying a critical role of autophagy induction in the development of tolerance to LPS-induced TNF-α expression by gAcrp. We also found that knocking-down of FoxO3A, a forkhead box O member of transcription factor, blocked gAcrp-induced expression of LC3II and Atg5. Moreover, gene silencing of Silent information regulator 1 (SIRT1) blocked both gAcrp-induced nuclear translocation of FoxO3A and LC3II expression. Finally, pretreatment with ROS inhibitors, prevented gAcrp-induced SIRT1 expression and further generated inhibitory effects on gAcrp-induced autophagy, indicating a role of ROS production in gAcrp-induced SIRT1 expression and subsequent autophagy induction. Taken together, these findings indicate that globular adiponectin suppresses LPS-induced TNF-α expression, at least in part, via autophagy activation. Furthermore, SIRT1-FoxO3A axis plays a crucial role in gAcrp-induced autophagy in macrophages.

Humulus japonicus extract exhibits antioxidative and anti-aging effects via modulation of the AMPK-SIRT1 pathway

The perennial herb, Humulus japonicus, has been previously described as possessing potential antituberculosis and anti-inflammatory properties. In the present study, the anti-aging activity of ethanol extracts from the leaves of H. japonicus (HJE) was evaluated in yeast and human fibroblast cells. In addition, the antioxidant activity of HJE was analyzed using free radical scavenging assays. Furthermore, the mechanism underlying the hypothesized HJE-associated extension of lifespan was investigated, and the results indicated that HJE was able to extend the lifespan of yeast cells. Further experiments demonstrated that HJE upregulated the longevity-associated proteins, sirtuin 1 and AMP-activated protein kinase, and effectively inhibited the generation of reactive oxygen species (ROS). In addition, the antioxidative potential of the active constituents of HJE, including luteolin, luteolin 7-glycoside, quercetin and quercitrin, was evaluated and the results demonstrated that these flavonoids were able to scavenge ROS in cell-free and intracellular systems. In summary, the results revealed that HJE possessed the potential for antioxidative activity; however, further in vivo investigations are required with the aim of developing safe, high-efficacy anti-aging agents.