SIRT1 promotes differentiation of normal human keratinocytes

Identification of an exosomal miRNA-mRNA regulatory network contributing to methotrexate efficacy

OBJECTIVE

Methotrexate (MTX) is an economic and effective medicine treatment for psoriasis. Extracellular vesicle (EV) miRNA biomarkers related to its efficiency have been identified in various diseases. Whether certain miRNA profiles are associated with psoriasis treatment is unknown. In order to determine specific miRNA biomarkers for MTX effectiveness prediction and the severity of psoriasis, our study looked at the variations in circulating EV miRNA profiles before and after MTX therapy.

METHODS

Plasma EV isolation and next-generation sequencing were performed to identify differentially expressed EV miRNAs between GRs (n = 14) and NRs (n = 6). Univariate and multiple linear regression analyses were performed to evaluate the correlation between PASI scores and miRNA expression levels.

RESULTS

15 miRNAs out of a total profile of 443 miRNAs were substantially different between GRs and NRs at baseline, 4 of them (miR-199a-5p, miR-195-5p, miR-196a-5p, and miR-1246) have the potential to distinguish between GRs and NRs [area under the curve (AUC) ≥ 0.70, all P < 0.05]. KEGG pathway analyses revealed differentially expressed miRNAs to potentially target immune-related pathways. SIRT1 was discovered to be a target of miR-199a-5p and involved in MAPK signaling pathway. MiR-191-5p and miR-21-5p expression levels have been discovered to positively correlate with PASI scores[P < 0.05].

CONCLUSION

This pilot investigation found that miR-199a-5p, miR-195-5p, miR-196a-5p, and miR-1246 might be prospective biomarkers to predict the efficacy of MTX, and that miR-191-5p and miR-21-5p were correlated with psoriasis severity. Five of them previously reported to be involved in MAPK signaling pathway, indicating a potential role of MTX in delaying the progression of psoriatic inflammation.

SIRT1 regulates endoplasmic reticulum stress-related organ damage

Endoplasmic reticulum (ER) stress plays a key role in the pathogenesis of several organ damages. Studies show that excessive ER stress (ERS) can destroy cellular homeostasis, causing cell damage and physiological dysfunction in various organs. In recent years, Sirtuin1 (SIRT1) has become a research hotspot on ERS. Increasing evidence suggests that SIRT1 plays a positive role in various ERS-induced organ damage via multiple mechanisms, including inhibiting cellular apoptosis and promoting autophagy. SIRT1 can also alleviate liver, heart, lung, kidney, and intestinal damage by inhibiting ERS. We discuss the possible mechanism of SIRT1, explore potential therapeutic targets of diseases, and provide a theoretical basis for treating ERS-related diseases.

A Novel Handrub Tablet Loaded with Pre- and Post-Biotic Solid Lipid Nanoparticles Combining Virucidal Activity and Maintenance of the Skin Barrier and Microbiome

OBJECTIVE

This study aimed to develop a holobiont tablet with rapid dispersibility to provide regulation of the microbiota, virucidal activity, and skin barrier protection.

METHODS

A 23 factorial experiment was planned to define the best formulation for the development of the base tablet, using average weight, hardness, dimensions, swelling rate, and disintegration time as parameters to be analyzed. To produce holobiont tablets, the chosen base formulation was fabricated by direct compression of prebiotics, postbiotics, and excipients. The tablets also incorporated solid lipid nanoparticles containing postbiotics that were obtained by high-pressure homogenization and freeze-drying. The in vitro virucidal activity against alpha-coronavirus particles (CCoV-VR809) was determined in VERO cell culture. In vitro analysis, using monolayer cells and human equivalent skin, was performed by rRTq-PCR to determine the expression of interleukins 1, 6, 8, and 17, aquaporin-3, involucrin, filaggrin, FoxO3, and SIRT-1. Antioxidant activity and collagen-1 synthesis were also performed in fibroblast cells. Metagenomic analysis of the skin microbiome was determined in vivo before and after application of the holobiont tablet, during one week of continuous use, and compared to the use of alcohol gel. Samples were analyzed by sequencing the V3-V4 region of the 16S rRNA gene.

RESULTS

A handrub tablet with rapid dispersibility was developed for topical use and rinse off. After being defined as safe, the virucidal activity was found to be equal to or greater than that of 70% alcohol, with a reduction in interleukins and maintenance or improvement of skin barrier gene markers, in addition to the reestablishment of the skin microbiota after use.

CONCLUSIONS

The holobiont tablets were able to improve the genetic markers related to the skin barrier and also its microbiota, thereby being more favorable for use as a hand sanitizer than 70% alcohol.

Insufficient SIRT1 in macrophages promotes oxidative stress and inflammation during scarring

Macrophage is a critical regulator in wound healing and scar formation, and SIRT1 is related to macrophage activation and polarization, while the specific mechanism is still unclear. To explore the specific effects of SIRT1 in scarring, we established a skin incision mouse model and LPS-induced inflammation cell model. The expression of SIRT1 in tissue and macrophage was detected, and the level of SIRT1 was changed to observe the downstream effects. LPS-induced macrophages with or without SIRT1 deficiency were used for TMT-based quantitative proteomic analysis. SIRT1 was suppressed in scar while increased in macrophages of scar tissue. And macrophages were proven to be necessary for wound healing. In the early stage of wound healing, knockout of SIRT1 in macrophage could greatly strengthen inflammation and finally promote scarring. NADH-related activities and oxidoreductase activities were differentially expressed in TMT-based quantitative proteomic analysis. We confirmed that ROS production and NOX2 level were elevated after LPS stimulation while the Nrf2 pathway and the downstream proteins, such as Nqo-1 and HO-1, were suppressed. In contrast, the suppression of SIRT1 strengthened this trend. The NF-κB pathway was remarkably activated compared with the control group. Insufficient increase of SIRT1 in macrophage leads to over activated oxidative stress and activates NF-κB pathways, which then promotes inflammation in wound healing and scarring. Further increasing SIRT1 in macrophages could be a promising method to alleviate scarring. KEY MESSAGES: SIRT1 was suppressed in scar while increased in macrophages of scar tissue. Inhibition of SIRT1 in macrophage leads to further activated oxidative stress. SIRT1 is negatively related to oxidative stress in macrophage. The elevation of SIRT1 in macrophage is insufficient during scarring.

The Role of Sirtuins in the Pathogenesis of Psoriasis

Psoriasis is the most common chronic inflammatory skin disease with a genetic basis. It is characterised by keratinocyte hyperproliferation, parakeratosis and inflammatory cell infiltration. Psoriasis negatively affects a patient's physical and emotional quality of life. Sirtuins (SIRTs; silent information regulators) are an evolutionarily conserved group of enzymes involved in the post-translational modification of proteins, including deacetylation, polyADP-ribosylation, demalonylation and lipoamidation. SIRTs are involved in a number of cellular pathways related to ageing, inflammation, oxidative stress, epigenetics, tumorigenesis, the cell cycle, DNA repair and cell proliferation, positioning them as an essential component in the pathogenesis of many diseases, including psoriasis. Activation of SIRT1 counteracts oxidative-stress-induced damage by inhibiting the mitogen-activated protein kinases (MAPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signal transducer and activator of transcription 3 (STAT3) pathways and may mitigate pathological events in psoriasis. There is a significant reduction in the expression of SIRT1, SIRT2, SIRT3, SIRT4 and SIRT5 and an increase in the expression of SIRT6 and SIRT7 in psoriasis. The aim of the review is to draw the attention of physicians and scientists to the importance of SIRTs in dermatology and to provide a basis and impetus for future discussions, research and pharmacological discoveries to modulate SIRT activity. In light of the analysis of the mode of action of SIRTs in psoriasis, SIRT1-SIRT5 agonists and SIRT6 and SIRT7 inhibitors may represent new therapeutic options for the treatment of psoriasis.

DNA methylation regulates Sirtuin 1 expression in osteoarthritic chondrocytes

PURPOSE

Sirtuin 1 (SIRT1) comprises a major anti-aging longevity factor with multiple protective effects on chondrocyte homeostasis. Previous studies have reported that downregulation of SIRT1 is linked to osteoarthritis (OA) progression. In this study, we aimed to investigate the role of DNA methylation on SIRT1 expression regulation and deacetylase activity in human OA chondrocytes.

MATERIALS AND METHODS

Methylation status of SIRT1 promoter was analyzed in normal and OA chondrocytes using bisulfite sequencing analysis. CCAAT/enhancer binding protein alpha (C/EBPα) binding to SIRT1 promoter was assessed by chromatin immunoprecipitation (ChIP) assay. Subsequently, C/EBPα's interaction with SIRT1 promoter and SIRT1 expression levels were evaluated after treatment of OA chondrocytes with 5-Aza-2'-Deoxycytidine (5-AzadC). Acetylation and nuclear levels of nuclear factor kappa-B p65 subunit (NF-κΒp65) and expression levels of selected OA-related inflammatory mediators, interleukin 1β (IL-1β) and IL-6 and catabolic genes (metalloproteinase-1 (MMP-1) and MMP-9) were evaluated in 5-AzadC-treated OA chondrocytes with or without subsequent transfection with siRNA against SIRT1.

RESULTS

Hypermethylation of specific CpG dinucleotides on SIRT1 promoter was associated with downregulation of SIRT1 expression in OA chondrocytes. Moreover, we found decreased binding affinity of C/EBPα on the hypermethylated SIRT1 promoter. 5-AzadC treatment restored C/EBPα's transcriptional activity inducing SIRT1 upregulation in OA chondrocytes. Deacetylation of NF-κΒp65 in 5-AzadC-treated OA chondrocytes was prevented by siSIRT1 transfection. Similarly, 5-AzadC-treated OA chondrocytes exhibited decreased expression of IL-1β, IL-6, MMP-1 and MMP-9 which was reversed following 5-AzadC/siSIRT1 treatment.

CONCLUSIONS

Our results suggest the impact of DNA methylation on SIRT1 suppression in OA chondrocytes contributing to OA pathogenesis.

The critical importance of epigenetics in autoimmune-related skin diseases

Autoimmune-related skin diseases are a group of disorders with diverse etiology and pathophysiology involved in autoimmunity. Genetics and environmental factors may contribute to the development of these autoimmune disorders. Although the etiology and pathogenesis of these disorders are poorly understood, environmental variables that induce aberrant epigenetic regulations may provide some insights. Epigenetics is the study of heritable mechanisms that regulate gene expression without changing DNA sequences. The most important epigenetic mechanisms are DNA methylation, histone modification, and noncoding RNAs. In this review, we discuss the most recent findings regarding the function of epigenetic mechanisms in autoimmune-related skin disorders, including systemic lupus erythematosus, bullous skin diseases, psoriasis, and systemic sclerosis. These findings will expand our understanding and highlight the possible clinical applications of precision epigenetics approaches.

Safe and Effective Antioxidant: The Biological Mechanism and Potential Pathways of Ergothioneine in the Skin

Ergothioneine, a sulfur-containing micromolecular histidine derivative, has attracted increasing attention from scholars since it was confirmed in the human body. In the human body, ergothioneine is transported and accumulated specifically through OCTN-1, especially in the mitochondria and nucleus, suggesting that it can target damaged cells and tissues as an antioxidant. It shows excellent antioxidant, anti-inflammatory effects, and anti-aging properties, and inhibits melanin production. It is a mega antioxidant that may participate in the antioxidant network system and promote the reducing glutathione regeneration cycle. This review summarizes studies on the antioxidant effects of ergothioneine on various free radicals in vitro to date and systematically introduces its biological activities and potential mechanisms, mostly in dermatology. Additionally, the application of ergothioneine in cosmetics is briefly summarized. Lastly, we propose some problems that require solutions to understand the mechanism of action of ergothioneine. We believe that ergothioneine has good prospects in the food and cosmetics industries, and can thus meet some needs of the health and beauty industry.

Influence of narrow-band ultraviolet B therapy on sirtuin 1 expression in lesional skin of patients with chronic plaque psoriasis: Relation to clinical improvement and interferon-γ expression

BACKGROUND

Reduced sirtuin 1 (Sirt1) expression in psoriasis was previously reported, and its activation was associated with disease improvement. Narrow-band ultraviolet B (NB-UVB) downregulates several pro-inflammatory cytokines such as interferon-γ (IFN-γ) and influences keratinocyte differentiation in psoriasis.

OBJECTIVES

The aim of this study was to study the in vivo influence NB-UVB treatment on Sirt1 expression in psoriatic skin in relation to disease improvement and IFN-γ expression.

METHODS

Twenty-six patients with chronic plaque psoriasis were evaluated, and psoriasis area severity index (PASI) was calculated. Skin biopsies were taken from lesional skin of the patients before and after 3 months of treatment with NB-UVB and from 26 controls, where the distribution and immunohistochemistry (IHC) scores of Sirt1 and IFN-γ were determined.

RESULTS

After 3 months of treatment, Sirt1 distribution and epidermal IHC score were significantly higher, whereas Sirt1 dermal IHC score and IFN-γ distribution, epidermal and dermal IHC scores were significantly lower than the pre-treatment values. Before and after 3 months of NB-UVB therapy, PASI showed a significant negative correlation with Sirt1 distribution and epidermal IHC score; and a significant positive correlation with interferon-γ distribution and epidermal IHC score. Moreover, Sirt1 distributions were negatively correlated with the corresponding interferon-γ distributions. Conclusions The detected upregulation of epidermal Sirt1 following NB-UVB therapy possibly represents another mechanism by which NB-UVB can act in psoriasis and also highlights the role of Sirt1 upregulation in psoriasis treatment.

Screening of Plant-Derived Natural Extracts to Identify a Candidate Extract Capable of Enhancing Lipid Synthesis in Keratinocytes

BACKGROUND

Reduced lipid content in the stratum corneum is a major cause of skin-barrier dysfunction in various pathological conditions. Promoting lipid production is a potential strategy to improve skin-barrier function. Recent evidence supports the beneficial effects of adiponectin on lipid metabolism and senescence in keratinocytes.

OBJECTIVE

This study aimed to investigate whether plant extracts can enhance skin-barrier function.

METHODS

We screened fruit and herb extracts that enhance the lipid synthesis of keratinocytes via AMP-activated protein kinase (AMPK) activation and SIRT1 signaling in the adiponectin pathway. The levels of major lipid synthesis enzymes and transcription factors as well as epidermal barrier lipids involved in adiponectin-associated epidermal barrier formation were evaluated in the herbal extracts- or adiponectin-treated human epidermal keratinocyte and equivalent models. The mRNA expression of major lipid synthesis enzymes increased following treatment with Lycii Fructus , Prunus tomentosa , and Melia toosendan extracts.

RESULTS

The expression of transcription factors SIRT1, liver X receptor α, peroxisome proliferator-activated receptors (PPARs), and sterol regulatory element-binding proteins (SREBPs) were upregulated. Levels of free fatty acids, cholesterol, and ceramides were elevated. The expression of keratinocyte differentiation markers increased. In particular, among fruit extracts with a detectable effect, Melia toosendan induced the highest expression of lipid synthase.

CONCLUSION

These results indicate that Melia toosendan is a promising candidate for improving skin-barrier function.

Transcriptome profiling in psoriasis: NB-UVB treatment-associated transcriptional changes and modulation of autoinflammation in perilesional skin in early-phase disease

BACKGROUND

Psoriasis is a chronic inflammatory skin condition. It is widely treated with phototherapy using narrowband ultraviolet B (NB-UVB). The therapeutic mechanisms of NB-UVB, however, remain unclear, particularly in the early phases of the disease.

OBJECTIVE

To investigate the mechanisms underlying the effects of NB-UVB on psoriasis in a model of perilesional psoriasis.

METHODS

Psoriatic patients that received NB-UVB treatment and were evaluated with the psoriasis area and severity index were included in the study. Skin biopsies obtained before and after treatment were subjected to RNA sequencing (RNA-seq) and Ingenuity Pathway Analyses for genome-wide transcriptome profiling to gain further insights into the signaling pathways underlying the improvement of psoriasis with therapeutic intervention.

RESULTS

Our findings revealed that NB-UVB treatment may exert its effects by suppressing nuclear factor kappa B, which leads to upregulation of the sirtuin signaling pathway, as well as by decreasing the function of major upstream regulators associated with proinflammatory and inflammatory cytokines, which blocks the expression of downstream toll-like receptors. Psoriasis improvement after NB-UVB treatment was associated with decreased expression of NFKBIZ, SERPINB4, ATG13, and CTSS and increased expression of SKP1 gene. Our results also highlighted the expression of proposed genes associated with the modulation of autoinflammation.

CONCLUSIONS

To the best of our knowledge, this is the first study to apply advanced molecular techniques to explore the effects of phototherapy on psoriasis in the early-phase, providing new insights into the disease pathogenesis and novel genetic information for the development of new therapeutic modalities and potential treatment targets.

Inverse correlation between the expression of AMPK/SIRT1 and NAMPT in psoriatic skin: A pilot study

PURPOSE

Epidermal hyperplasia and the involvement of immune cells characterize the clinical picture of psoriasis. Among the several factors involved, attention has been focused on sirtuin 1 (SIRT1) - a deacetylase endowed with a variety of functions including the control of metabolic and inflammatory processes-, and on nicotinamide phosphoribosyltransferase (NAMPT), important for SIRT1 activation and involved in inflammatory events. The aim of the study was to analyze changes of SIRT1 and NAMPT expression in psoriatic skin.

PATIENTS AND METHODS

Samples from healthy controls and psoriatic patients were subjected to immunohistochemical analysis.

RESULTS

A strong downregulation of SIRT1 expression was observed in skin samples from psoriatic patients compared to healthy controls. This was accompanied by a parallel reduction of adenosine monophosphate-activated kinase (AMPK) expression and, more strikingly, by the disappearance of cells immunolabeled for its active, phosphorylated form (pAMPK). In both cases, analysis of the distribution of immunopositive cells revealed a shift towards reduced intensity of staining. In contrast, NAMPT expression was upregulated in psoriatic samples in line with its pro-inflammatory role. This was again more visible with an intensity-based distribution analysis that evidenced a shift towards more intensely immunostained cell populations.

CONCLUSIONS

The present data correlate in the same samples the expression of SIRT1, pAMPK/AMPK and NAMPT in psoriasis and open the way for novel pharmacological targets in the treatment of the disease.

Oxidative Stress Induced by High Salt Diet—Possible Implications for Development and Clinical Manifestation of Cutaneous Inflammation and Endothelial Dysfunction in Psoriasis vulgaris

Although oxidative stress is recognized as an important effector mechanism of the immune system, uncontrolled formation of reactive oxygen and nitrogen species promotes excessive tissue damage and leads to disease development. In view of this, increased dietary salt intake has been found to damage redox systems in the vessel wall, resulting in endothelial dysfunction associated with NO uncoupling, inflammation, vascular wall remodeling and, eventually, atherosclerosis. Several studies have reported increased systemic oxidative stress accompanied by reduced antioxidant capacity following a high salt diet. In addition, vigorous ionic effects on the immune mechanisms, such as (trans)differentiation of T lymphocytes are emerging, which together with the evidence of NaCl accumulation in certain tissues warrants a re-examination of the data derived from in vitro research, in which the ionic influence was excluded. Psoriasis vulgaris (PV), as a primarily Th17-driven inflammatory skin disease with proven inflammation-induced accumulation of sodium chloride in the skin, merits our interest in the role of oxidative stress in the pathogenesis of PV, as well as in the possible beneficial effects that could be achieved through modulation of dietary salt intake and antioxidant supplementation.

Anxiety and Cognition in Cre- Collagen Type II Sirt1 K/O Male Mice

Introduction

Using transgenic collagen type II-specific Sirt1 knockout (CKO) mice we studied the role of Sirt1 in nutritional induced catch up growth (CUG) and we found that these mice have a less organized growth plate and reduced efficiency of CUG. In addition, we noted that they weigh more than control (CTL) mice. Studying the reason for the increased weigh, we found differences in activity and brain function.

Methods

Several tests for behavior and activity were used: open field; elevated plus maze, Morris water maze, and home cage running wheels. The level of Glu- osteocalcin, known to connect bone and brain function, was measured by Elisa; brain Sirt1 was analyzed by western blot.

Results

We found that CKO mice had increased anxiety, with less spatial memory, learning capabilities and reduced activity in their home cages. No significant differences were found between CKO and CTL mice in Glu- osteocalcin levels; nor in the level of brain SIRT1.

Discussion/Conclusion

Using transgenic collagen type II-specific Sirt1 knockout (CKO) mice we found a close connection between linear growth and brain function. Using a collagen type II derived system we affected a central regulatory mechanism leading to hypo activity, increased anxiety, and slower learning, without affecting circadian period. As children with idiopathic short stature are more likely to have lower IQ, with substantial deficits in working memory than healthy controls, the results of the current study suggest that SIRT1 may be the underlying factor connecting growth and brain function.

FGF21 promotes migration and differentiation of epidermal cells during wound healing via SIRT1-dependent autophagy

BACKGROUND AND PURPOSE

Migration and differentiation of epidermal cells are essential for epidermal regeneration during wound healing. Fibroblast growth factor 21 (FGF21) plays key roles in mediating a variety of biological activities. However, its role in skin wound healing remains unknown.

EXPERIMENTAL APPROACH

Fgf21 knockout (Fgf21 KO) mice were used to determine the effect of FGF21 on wound healing. The source of FGF21 and its target cells were determined by immunohistochemistry, immunoblotting, and ELISA assay. Moreover, Sirt1^flox/flox and Atg7^flox/flox mice were constructed and injected with the epidermal-specific Cre virus to elucidate the underlying mechanisms. Migration and differentiation of keratinocytes were evaluated in vitro by cell scratch assays, immunofluorescence, and qRT-RCR. The effects were further assessed when SIRT1, ATG7, ATG5, BECN1, and P53 were silenced. Interactions between SIRT1 and autophagy-related genes were assessed using immunoprecipitation assays.

KEY RESULTS

FGF21 was active in fibroblasts and promoted migration and differentiation of keratinocytes following injury. After wounding, SIRT1 expression and autophagosome synthesis were lower in Fgf21 KO mice. Depletion of ATG7 in keratinocytes counteracted the FGF21-induced increases in migration and differentiation, suggesting that autophagy is required for the FGF21-mediated pro-healing effects. Furthermore, epithelial-specific Sirt1 knockout abolished the FGF21-mediated improvements of autophagy and wound healing. Silencing of SIRT1 in keratinocytes, which decreased deacetylation of p53 and autophagy-related proteins, revealed that FGF21-induced autophagy during wound healing was SIRT1-dependent.

CONCLUSIONS AND IMPLICATIONS

FGF21 is a key regulator of keratinocyte migration and differentiation during wound healing. FGF21 may be a novel therapeutic target to accelerate would healing.

Proliferation Increasing Genetic Engineering in Human Corneal Endothelial Cells: A Literature Review

The corneal endothelium is the inner layer of the cornea. Despite comprising only a monolayer of cells, dysfunction of this layer renders millions of people visually impaired worldwide. Currently, corneal endothelial transplantation is the only viable means of restoring vision for these patients. However, because the supply of corneal endothelial grafts does not meet the demand, many patients remain on waiting lists, or are not treated at all. Possible alternative treatment strategies include intracameral injection of human corneal endothelial cells (HCEnCs), biomedical engineering of endothelial grafts and increasing the HCEnC density on grafts that would otherwise have been unsuitable for transplantation. Unfortunately, the limited proliferative capacity of HCEnCs proves to be a major bottleneck to make these alternatives beneficial. To tackle this constraint, proliferation enhancing genetic engineering is being investigated. This review presents the diverse array of genes that have been targeted by different genetic engineering strategies to increase the proliferative capacity of HCEnCs and their relevance for clinical and research applications. Together these proliferation-related genes form the basis to obtain a stable and safe supply of HCEnCs that can tackle the corneal endothelial donor shortage.

Restoring NAD+ by NAMPT is essential for the SIRT1/p53-mediated survival of UVA- and UVB-irradiated epidermal keratinocytes

Nicotinamide adenine dinucleotide (NAD⁺) is a crucial coenzyme in energy production. The imbalance of NAD⁺ synthesis has been found to trigger age-related diseases, such as metabolic disorders, cancer, and neurodegenerative diseases. Also, UV irradiation induces NAD⁺ depletion in the skin. In mammals, nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in the NAD⁺ salvage pathway and essential for NAD⁺ homeostasis. However, but few studies have focused on the role of NAMPT in response to UV irradiation. Here, we show that NAMPT prevents NAD⁺ depletion in epidermal keratinocytes to protect against the mild-dose UVA and UVB (UVA/B)-induced proliferation defects. We showed that poly(ADP-ribose) polymerase (PARP) inhibitor rescued the NAD⁺ depletion in UVA/B-irradiated human keratinocytes, confirming that PAPR transiently exhausts cellular NAD⁺ to repair DNA damage. Notably, the treatment with a NAMPT inhibitor exacerbated the UVA/B-induced loss of energy production and cell viability. Moreover, the NAMPT inhibitor abrogated the sirtuin-1 (SIRT1)-mediated deacetylation of p53 and significantly inhibited the proliferation of UVA/B-irradiated cells, suggesting that the NAMPT-NAD⁺-SIRT1 axis regulates p53 functions upon UVA/B stress. The supplementation with NAD⁺ intermediates, nicotinamide mononucleotide and nicotinamide riboside, rescued the UVA/B-induced phenotypes in the absence of NAMPT activity. Therefore, NAD⁺ homeostasis is likely essential for the protection of keratinocytes from UV stress in mild doses. Since the skin is continuously exposed to UVA/B irradiation, understanding the protective role of NAMPT in UV stress will help prevent and treat skin photoaging.

Glycyrrhizin improves the pathogenesis of psoriasis partially through IL-17A and the SIRT1-STAT3 axis

Background

The anti-inflammatory effect of glycyrrhizin has been widely recognized, while the specific mechanism of glycyrrhizin in psoriasis remains poorly understood.

Results

In the imiquimod-induced mouse model of psoriasis (IMD), we found that glycyrrhizin can substantially improve the adverse symptoms in mice. The hematoxylin-eosin staining results showed that glycyrrhizin can also improve the pathological state of skin cells in IMD mice. Using enzyme-linked immunosorbent assay (ELISA), we found that glycyrrhizin substantially inhibited the expression of IL-17A and IFN-γ in the serum of IMD mice. In order to simulate the effect of IL-17A on keratinocytes in psoriasis, we treated HaCaT cells with 100 ng/mL IL-17A (IL-17A-HaCaT cells) for 48 h. Then, using cell-counting kit-8 (CCK-8) and ELISA assays, we found that glycyrrhizin inhibited the proliferation of IL-17A-HaCaT cells and reversed the promotion of IL-6, CCL20, and TNF-α induced by IL-17A. Further, western blotting (WB) results indicated that glycyrrhizin promoted the expression of SIRT1 and inhibited the expression of STAT3 and phosphorylated STAT3 (p-STAT3). By treating IL-17A-HaCaT cells with EX-527 (a potent and selective inhibitor of SIRT1), combined with CCK-8 and WB experiments, we initially found that EX-527 inhibited the proliferation of IL-17A-HaCaT cells and promoted the expression of STAT3, p-STAT3, and acetylated STAT3 (a-STAT3). However, when glycyrrhizin was added at the same time, the proliferation of IL-17A-HaCaT cells increased, and the expression of STAT3, p-STAT3, and a-STAT3 reduced. We then knocked down the expression of SIRT1 via small interfering RNA in IL-17A-HaCaT cells, and the results were consistent with those of EX-527.

Conclusions

Together, these results indicated that glycyrrhizin improved psoriasis by inhibiting the expression of IL-17A and IFN-γ in vivo and suppressed the proliferation of IL-17A-HaCaT cells and the expression of STAT3, p-STAT3, and a-STAT3 by upregulating SIRT1 in vitro.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00421-z.

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.

Epigenetic-modifying therapies: An emerging avenue for the treatment of inflammatory skin diseases

Epigenetic modifications include DNA methylation, histone modification and the action of microRNAs. These mechanisms coordinate in complex networks to control gene expression, thereby regulating key physiological processes in the skin and immune system. Recently, researchers have turned to the epigenome to understand the pathogenesis of inflammatory skin diseases. In psoriasis and atopic dermatitis, epigenetic modifications contribute to key pathogenic events such as immune activation, T-cell polarization and keratinocyte dysfunction. These discoveries have introduced new possibilities for the treatment of skin diseases; unlike genetics, epigenetic alterations are readily modifiable and potentially reversible. In this viewpoint essay, we summarize the current state of epigenetic research in inflammatory skin diseases and propose that targeting the histone machinery is a promising avenue for the development of new therapies for psoriasis and atopic dermatitis. Expanding on the progress that has already been made in the field of cancer epigenetics, we discuss existing epigenetic-modifying tools that can be applied to the treatment of inflammatory skin diseases and consider future directions for investigation in order to allow for the widespread clinical application of such therapies.

Cartilage -specific knockout of Sirt1 significantly reduces bone quality and catch-up growth efficiency

BACKGROUND

Spontaneous catch-up (CU) growth occurs when a growth-restricting factor is resolved. However, its efficiency is sometimes inadequate and growth deficits remain permanent. The therapeutic toolbox for short stature is currently very limited, thus, finding new regulatory pathways is important for the development of novel means of treatment. Our previous studies using a nutrition-induced CU growth model showed that the level of sirtuin-1 (Sirt1) was significantly increased in food-restricted animals and decreased during CU growth.

AIM

This study sought to investigate the role of Sirt1 in modulating the response of the epiphyseal growth plate (EGP) to nutritional manipulation.

METHOD

Collagen type II-specific Sirt1 knockout (CKO) mice were tested for response to our CU growth model consisting of a period of food restriction followed by re-feeding.

RESULTS

The transgenic CKO mice weighed more than the control (CTL) mice, their EGP was higher and less organized, specifically at the resting and proliferative zones, leading to shorter bones. Ablation of Sirt1 in the chondrocytes was found to have a dramatic effect on bone mineralization on micro-CT analysis. The CKO mice were less responsive to the nutritional manipulation, and their CU growth was less efficient. They remained shorter than the CTL mice who corrected the food restriction-induced growth deficit during the re-feeding period.

CONCLUSIONS

Sirt1 appears to be important for normal regulation of the EGP. In its absence, the EGP is less organized and CU growth is less efficient. These results suggest that SIRT1 may serve as a novel therapeutic target for short stature.

Histone Deacetylase 1 and Sirtuin 1 Expression in Psoriatic Skin: A Comparison between Guttate and Plaque Psoriasis

Abnormal histone modification by histone deacetylases (HDACs), including HDAC1 and sirtuin 1 (SIRT1), has been reported to play an important role in the pathogenesis of psoriasis by altering cell proliferation, differentiation, and inflammation. However, findings on the expression level of HDACs in psoriatic skin lack consistency. We assessed the expression of HDAC1, SIRT1, p63, and proliferating cell nuclear antigen (PCNA) in skin tissues from 23 patients with psoriasis (15 with plaque psoriasis and eight with guttate psoriasis) and five healthy individuals using immunohistochemistry, and analyzed their associations with clinical phenotypes of the disease. The expression of HDAC1 and keratinocyte proliferative markers, such as p63 and PCNA significantly increased, whereas that of SIRT1 decreased in the basal layer (p < 0.05) of the patients with psoriasis compared to those in healthy controls. Among the patients with psoriasis, expression of HDAC1, p63, and PCNA was significantly higher in plaque psoriasis than in guttate psoriasis. There was no significant differences in the level of SIRT1 between the two clinical phenotypes. The findings of this study suggest that histone modifications are involved in the pathogenesis of psoriasis and may contribute to the formation of clinical phenotypes.

Clinical and in vitro evaluation of new anti-redness cosmetic products in subjects with winter xerosis and sensitive skin

Objective

To demonstrate the in vitro activities of panthenol, palmitoylethanolamide (PEA), and niacinamide (NAM) and determine the biophysical properties, clinical safety, tolerability together with efficacy of two developmental anti‐redness (AR) formulations containing these ingredients, in alleviating facial redness associated with winter xerosis in healthy volunteers with sensitive skin.

Methods

The anti‐inflammatory and skin protective properties of panthenol, PEA and NAM were evaluated in vitro. The physical properties of the AR formulations were analysed using measurement of water vapour transport rate (WVTR) and infrared spectroscopy. Clinical studies were performed between the months of December and April (2014–2015) with efficacy assessed during the winter. Facial redness, irritation, sensitization potential, photo‐irritation, and photo‐sensitization were evaluated. Self‐assessed adverse reactions were reported in diaries of use.

Results

Panthenol and PEA reduced prostaglandin E₂, interleukin‐6, and thymic stromal lymphopoietin levels in vitro, while NAM induced nicotinamide adenine dinucleotide (NAD) levels and the keratinocyte differentiation markers: filaggrin (2‐fold increase, P < 0.001), loricrin (2‐fold increase, P < 0.05), involucrin (2 fold increase, P < 0.001) & peroxisomal proliferator activated receptor‐alpha (1.5 fold increase, P < 0.05). The two AR products exhibited low WVTR vs. no treatment (P < 0.001) and displayed an ordered lipid structure. The day cream formulation protected against ultraviolet B radiation in vitro. A total of 382 participants were included in clinical studies which showed the AR formulations significantly improved facial redness associated with winter xerosis (Day 29 mean change from baseline: AR day cream 0.77 (P < 0.001); AR serum 0.67 (P < 0.001)). No irritation, sensitization, photo‐irritation, photo‐sensitization or product‐related adverse reactions were observed or reported in the clinical studies.

Conclusion

The new products significantly improved skin redness associated with winter xerosis in participants with self‐perceived sensitive skin. Both products were well tolerated with a suitable safety profile for topical use in subjects with sensitive skin.

s-HBEGF/SIRT1 circuit-dictated crosstalk between vascular endothelial cells and keratinocytes mediates sorafenib-induced hand-foot skin reaction that can be reversed by nicotinamide

Hand-foot skin reaction (HFSR), among the most significant adverse effects of sorafenib, has been limiting the clinical benefits of this frontline drug in treating various malignant tumors. The mechanism underlying such toxicity remains poorly understood, hence the absence of effective intervention strategies. In the present study, we show that vascular endothelial cells are the primary cellular target of sorafenib-induced HFSR wherein soluble heparin-binding epidermal growth factor (s-HBEGF) mediates the crosstalk between vascular endothelial cells and keratinocytes. Mechanistically, s-HBEGF released from vascular endothelial cells activates the epidermal growth factor receptor (EGFR) on keratinocytes and promotes the phosphorylation of c-Jun N-terminal kinase 2 (JNK2), which stabilizes sirtuin 1 (SIRT1), an essential keratinization inducer, and ultimately gives rise to HFSR. The administration of s-HBEGF in vivo could sufficiently induce hyper-keratinization without sorafenib treatment. Furthermore, we report that HBEGF neutralization antibody, Sirt1 knockdown, and a classic SIRT1 inhibitor nicotinamide could all significantly reduce the sorafenib-induced HFSR in the mouse model. It is noteworthy that nicotinic acid, a prodrug of nicotinamide, could substantially reverse the sorafenib-induced HFSR in ten patients in a preliminary clinical study. Collectively, our findings reveal the mechanism of vascular endothelial cell-promoted keratinization in keratinocytes and provide a potentially promising therapeutic strategy for the treatment of sorafenib-induced HFSR.

Role of Resveratrol in Regulating Cutaneous Functions

Protective role of the skin is against external insults and maintenance of electrolyte homeostasis of the body. Cutaneous dysfunction can account for the development of both cutaneous and systemic disorders. Thus, improvements in cutaneous functions can benefit a number of extracutaneous and cutaneous functions. Resveratrol, a natural ingredient, displays multiple benefits for various systems/organs, including the skin. The benefits of resveratrol for cutaneous functions include stimulation of keratinocyte differentiation and antimicrobial peptide expression, inhibition of keratinocyte proliferation and cutaneous inflammation, UV protection, anticancer, antiaging, and inhibition of melanogenesis. The mechanisms of action of resveratrol include activation of sirtuin 1 and nuclear factor erythroid 2-related factor 2, and inhibition of mitogen-activated protein kinase signaling. Evidence suggests that topical resveratrol could be a valuable alternative not only for daily skin care, but also for the prevention and treatment of various cutaneous disorders. This review summarizes the benefits of resveratrol for cutaneous functions.

Salidroside inhibits MAPK, NF-κB, and STAT3 pathways in psoriasis-associated oxidative stress via SIRT1 activation

Objectives: To unveil the role of SIRT1 in limiting oxidative stress in psoriasis and to further discuss the therapeutic prospects of salidroside in psoriasis.

Methods: Literature from 2002 to 2019 was searched with “psoriasis”, “oxidative stress”, “SIRT1”, “salidroside” as the key words. Then, Oxidative stress in psoriasis and the role of SIRT1 were summarized and the potential role of salidroside in the disease was speculated.

Results: Oxidative stress might contribute to the pathogenesis of psoriasis. High levels of ROS produced during oxidative stress lead to the release of inflammatory mediators, that, in turn, induce angiogenesis and excessive proliferation of keratinocytes. SIRT1 is a member of the sirtuin family, of which the activation lead to the inhibition of such oxidative stress signaling pathways MAPK, NF-κB, and STAT3, down-regulation of inflammatory factors, suppression of inflammation and keratinocyte hyperproliferation, and inhibition of angiogenesis. Salidroside, the main ingredient of Rhodiola, is known to exert antioxidant roles, which has been attributed to SIRT1 activation.

Conclusion: Salidroside might inhibit oxidative stress singling pathways via SIRT1 activation, and could be as an ideal candidate for management of psoriasis.

NCM 1921, a Mixture of Several Ingredients, Including Fatty Acids and Choline, Attenuates Atopic Dermatitis in 1-Chloro-2,4-Dinitrobenzene-Treated NC/Nga Mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease in humans. In this study, we evaluated the effects of a mixture (NCM 1921) of omega-3 butter, omega-3 beef tallow oil, omega-3 lard oil, caprylic acid, lauric acid, choline, and Fe on AD in 1-chloro-2,4-dinitrobenzene (DNCB)-treated NC/Nga mice. NCM 1921 significantly ameliorated the macroscopic and microscopic signs and reduced skin thickness and mast cell incorporation in the skin lesions of mice with DNCB-induced AD. Furthermore, it reduced serum immunoglobulin E levels; reduced the number of IgE-producing B cells, peripheral blood mononuclear cells, white blood cells, and differential white blood cells; and increased the number of lymphocytes. NCM 1921 normalized the total cell number in dorsal skin tissue, the axillary lymph node, and spleen following DNCB exposure and reduced the number of CD23+/B220+ cells in the axillary lymph node and CD3+ cells in dorsal skin tissue. Moreover, it reduced the levels of interleukin (IL)-4 and IL-13 but increased the levels of interferon-γ in anti-CD3–stimulated splenocytes. Immunohistofluorescence staining showed that NCM 1921 treatment significantly increased claudin1, filaggrin, and Sirt1 protein expressions in AD skin lesions. These results suggest that NCM 1921 could be a valuable remedy for the treatment of AD.

Epigenetics of Psoriasis

Psoriasis is a chronic and recurrent inflammatory skin disease, involving the rapid proliferation and abnormal differentiation of keratinocytes and activation of T cells. It is generally accepted that the central pathogenesis of psoriasis is a T cell-dominant immune disorder affected by multiple factors including genetic susceptibility, environmental factors, innate and adaptive immune responses, etc. However, the exact etiology is largely unknown. In recent years, epigenetic involvements, such as the DNA methylation, chromatin modifications, and noncoding RNA regulation are reported to be critical for the pathogenesis of psoriasis. However, the interplay between these factors has only recently been started to be unraveled. Notably, inhibitors of enzymes that work in epigenetic modifications, such as DNA methyltransferases and histone deacetylases, are beginning to appear in the clinical setting to restore normal epigenetic patterns (Generali et al. in J Autoimmun 83:51-61, 2017), providing novel therapeutic potential as novel treatment targets for psoriasis. Indeed, medications previously used to treat autoimmune diseases have later been discovered to exert their action via epigenetic mechanisms. Herein, we review the findings on epigenetics associated with psoriasis, and discuss future perspectives in this field.

Niacinamide and 12-hydroxystearic acid prevented benzo(a)pyrene and squalene peroxides induced hyperpigmentation in skin equivalent

Skin surface is constantly exposed to environmental and secreted stressors such as UV, air pollution and peroxidized sebum. The current study aims to use reconstructed human skin equivalents to demonstrate topical stressor-induced hyperpigmentation and evaluate bioactives' potential protective effect. Given that polycyclic aromatic hydrocarbons are representative airborne particle-bound organic compounds with known relevance to pigmentation pathways, benzo(a)pyrene was selected as surrogate environmental toxin. On the other hand, squalene monohydroperoxides are well-characterized sebum peroxidation product under UV and pollutant exposure, thus are used as another representative skin stressor. With 3-day continuous exposure, 30 pmol/cm² of benzo(a)pyrene and 3.4 nmol/cm² of squalene monohydroperoxides induced significant viability loss, inflammatory response, and approximately 10 shades of pigmentation increase in pigmented living skin equivalents. At the same time, pretreatment and co-treatment with 12-hydroxystearic acid (12-HSA, 20 μmol/L) or niacinamide (5 mmol/L) ameliorated such stressor-induced consequences. Niacinamide was particularly effective against benzo(a)pyrene damage, probably as a substrate for important NAD+ dependent detoxification pathways, while 12-HSA was potent against squalene monohydroperoxides through barrier enhancing, anti-inflammatory, and anti-oxidative mechanisms. In summary, topical stressor-induced hyperpigmentation was achieved in vitro, with known bioactives showing protective benefits.

Adiponectin Enhances Human Keratinocyte Lipid Synthesis via SIRT1 and Nuclear Hormone Receptor Signaling

Adiponectin is known to have beneficial effects on lipid and insulin metabolism, wound healing, and cellular senescence, but its effect on skin barrier formation remains unknown. We investigated the effects of adiponectin on keratinocyte lipid synthesis with respect to skin barrier function. Lipid staining revealed an adiponectin-mediated increase in keratinocyte intracellular and reconstructed epidermal lipid content. Moreover, significant increases in the levels of ceramide and its downstream metabolites (sphingosine and sphingosine-1-phosphate) following adiponectin stimulation were detected using liquid chromatography-mass spectrometry. Expression levels of keratinocyte differentiation markers were also increased. Adiponectin also increased expression of lipid biosynthesis enzymes (fatty acid synthase, HMG-CoA reductase, and serine palmitoyltransferase), nuclear hormone receptors (peroxisome proliferator-activated receptors and liver X receptors), and the adiponectin signal molecule SIRT1. Suppression of SIRT1, liver X receptor-α, or peroxisome proliferator-activated receptor-α downregulated the expression of lipid synthetic enzymes, decreasing lipid content. Inhibition of adiponectin receptors decreased expression of nuclear hormone receptors, SIRT1, lipid-synthesizing enzymes, and sphingolipids. Thus, activation of adiponectin signaling increases the expression of transcription factors, including SIRT1, liver X receptor-α, and peroxisome proliferator-activated receptor-α, enhancing lipid synthesis and keratinocyte cell differentiation and possibly aiding in the maintenance of skin barrier homeostasis.

AHR Regulates Metabolic Reprogramming to Promote SIRT1-Dependent Keratinocyte Differentiation

Activation of the transcription factor, AHR, in normal human epidermal keratinocytes increased AHR binding in the gene regions of the glucose transporter, SLC2A1, and the glycolytic enzyme, ENO1. This increased chromatin binding corresponded with AHR-dependent decreases in levels of SLC2A1 and ENO1 mRNA, protein, and activities. Studies of the ENO1 promoter showed activation of the AHR decreases the transcription of ENO1. Glycolysis was lowered by activation of the AHR as measured by decreases in glucose uptake and the production of pyruvate and lactate. Levels of ATP were also decreased. Downregulation of glucose metabolism, either by activation of the AHR, inhibition of glycolysis, inhibition of glucose transport, or inhibition of enolase, increased SIRT1 protein levels in normal human epidermal keratinocytes and the immortalized keratinocyte cell line, N/TERT-1. This increase in SIRT1 was abrogated by the addition of exogenous pyruvate. Moreover, keratinocyte differentiation in response to downregulation of glycolysis, either by activation of the AHR, inhibition of glucose transport, or inhibition of enolase, was dependent on SIRT1. These results indicate that regulation of glycolysis controls keratinocyte differentiation, and that activation of the AHR, by lowering the expression of SLC2A1 and ENO1, can determine this fate.

SULFATION PATHWAYS: Potential benefits of a sulfated resveratrol derivative for topical application

Resveratrol (RSV) is a polyphenolic compound with antioxidant, anti-inflammatory and anti-aging properties partly associated with sirtuin 1 (SIRT1)-activation in the skin. However, poor water solubility may limit RSV efficacy. This work aimed to clarify the interest of a new synthetic water-soluble RSV derivative (resveratrol glucoside sulfate, RSV-GS) for topical application. Resveratrol glucoside sulfate was synthesized using microwave-assisted sulfation. Cytotoxicity assays were performed with the keratinocyte HaCaT cell line, using MTT reduction, neutral red uptake, Alamar Blue/resazurin reduction, trypan blue exclusion and measurement of ATP concentration. Western blotting was used to evaluate SIRT1 protein content. Regarding SIRT1 binding, an in silico docking study was performed, using AutoDock Vina. Our results showed that the synthetic derivative RSV-GS was 1000 times more soluble in water than RSV and its non-sulfated glucoside. No relevant decrease in HaCaT cell viability was observed for concentrations up to 5 mM for RSV-GS, and up to 500 μM for resveratrol glucoside, while a significant decrease in HaCaT viability occurred from 100 μM for RSV. RSV-GS and RSV showed a similar behavior regarding protective effect against oxidative stress-induced cytotoxicity. SIRT1 protein content increased after treatment with 500 μM of RSV-GS and 100 μM of RSV. Moreover, in silico studies predicted that RSV-GS binds more stably to SIRT1 with a lower binding free energy than RSV. Although these results support the possible use of RSV-GS in topical formulations, in vivo safety and efficacy studies are needed before considering the use of RSV-GS in commercial products.

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.

Melatonin protects skin keratinocyte from hydrogen peroxide-mediated cell death via the SIRT1 pathway

Melatonin (N-acetyl-5-methoxytryptamine), which is primarily synthesized in and secreted from the pineal gland, plays a pivotal role in cell proliferation as well as in the regulation of cell metastasis and cell survival in a diverse range of cells. The aim of this study is to investigate protection effect of melatonin on H₂O₂-induced cell damage and the mechanisms of melatonin in human keratinocytes. Hydrogen peroxide dose-dependently induced cell damages in human keratinocytes and co-treatment of melatonin protected the keratinocytes against H₂O₂-induced cell damage. Melatonin treatment activated the autophagy flux signals, which were identified by the decreased levels of p62 protein. Inhibition of autophagy flux via an autophagy inhibitor and ATG5 siRNA technique blocked the protective effects of melatonin against H₂O₂-induced cell death in human keratinocytes. And we found the inhibition of sirt1 using sirtinol and sirt1 siRNA reversed the protective effects of melatonin and induces the autophagy process in H₂O₂-treated cells. This is the first report demonstrating that autophagy flux activated by melatonin protects human keratinocytes through sirt1 pathway against hydrogen peroxide-induced damages. And this study also suggest that melatonin could potentially be utilized as a therapeutic agent in skin disease.

Adiponectin Upregulates Filaggrin Expression via SIRT1-Mediated Signaling in Human Normal Keratinocytes

Background

Filaggrin (FLG) is the major component of the epidermal granular layer and binds to and condenses the keratin cytoskeleton. FLG thus contributes to cell compaction and serves as a natural moisturizing factor by promoting unfolding and degradation into hygroscopic amino acids. Loss or downregulation of FLG has been shown to result in a weak stratum corneum, which causes water loss and increases the possibility of skin barrier-related seizure. Adiponectin (Acrp30) contributes to the functional recovery of somatic cells, including human normal epidermal keratinocytes (NHEKs).

Objective

To investigate the effect of Acrp30 in FLG expression and identifying its signal transduction mechanism.

Methods

Normal human keratinocytes were treated with Acrp30 and the levels of FLG were examined. Silent mating type information regulation 2 homolog (SIRT)-targeting siRNA and aryl hydrocarbon receptor nuclear translocator (ARNT)-targeting siRNA were used to identify the role of various signal transduction pathway components.

Results

Acrp30 upregulated SIRT1 and ARNT expression in NHEKs, resulting in increased FLG expression. Treatment with both SIRT1-targeting siRNA and ARNT-targeting siRNA blocked Acrp30 stimulation and silenced FLG expression.

Conclusion

Adiponectin upregulates FLG expression through a SIRT1-mediated pathway. Our results suggest that Acrp30 is a promising agent for skin barrier permeability improvement.

Expression of sirtuins 1, 6, tumor necrosis factor, and interferon-γ in psoriatic patients

Sirtuins (SIRT) have been regarded as culprits in the pathogenesis of various diseases. Their exact role has not been explained. This study aimed to assess the expression of SIRT1, SIRT6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in psoriatic patients. Thirty psoriatic patients and 22 controls were enrolled. Clinical examination and Psoriasis Area and Severity Index (PASI) were obtained. Two skin biopsies (lesional, peri-lesional) and one from controls were obtained. Tissue levels of SIRT1, SIRT6, TNF-α, and IFN-γ were measured using ELISA. SIRT1 was significantly lower in lesional skin with gradual increase in perilesional followed by control skin (P <0.001). SIRT6, TNF-α, and IFN-γ were significantly higher in lesional than perilesional and control skin (P <0.001). Significant positive correlations were found between SIRT1 and TNF-α, IFN-γ and between SIRT6 and TNF-α in peri-lesional skin. SIRT1 and SIRT6 are potentially involved in the pathogenesis of psoriasis. Modulating their action could offer a novel therapy for such disease.

Induction of differentiation in psoriatic keratinocytes by propylthiouracil and fructose

Psoriasis is characterized by uncontrolled proliferation and poor differentiation. Sirtuin1 (SIRT1) a class III deacetylase, crucial for differentiation in normal keratinocytes, is reduced in psoriasis. Down regulated SIRT1 levels may contribute to poor differentiation in psoriasis. In addition, the levels of early differentiation factors Keratin1 (K1) and Keratin10 (K10) are depleted in psoriasis. We attempted to study a possible effect of fructose, a SIRT1 upregulator and Propylthiouracil (PTU) to augment differentiation in psoriatic keratinocytes. Keratinocytes were cultured from lesional biopsies obtained from psoriatic patients and control cells were obtained from patients undergoing abdominoplasty. Cells were treated with fructose and PTU individually. K1 and K10 transcript levels were measured to evaluate early differentiation; SIRT1 protein expression was also studied to decipher its role in the mechanism of differentiation. The K1, K10 transcript levels, SIRT1 protein and transcript levels in fructose treated psoriatic keratinocytes were improved. This suggests keratinocyte differentiation was induced by fructose through SIRT1 upregulation. Whereas PTU induced differentiation, as confirmed by improved K1, K10 transcript levels followed a non-SIRT1 mechanism. We conclude that the use of fructose and PTU may be an adjunct to the existing therapies for psoriasis.

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Fructose induces differentiation of psoriatic keratinocytes through SIRT1 upregulation.

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Propylthiouracil (PTU) improves K1 and K10 to induce differentiation in psoriasis.

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Fructose and PTU can be used as adjunct to existing therapies for psoriasis.

Adiponectin corrects premature cellular senescence and normalizes antimicrobial peptide levels in senescent keratinocytes

Stress-induced premature senescence or aging causes dysfunction in the human somatic system. Adiponectin (Acrp30) plays a role in functional recovery, especially with adenosine 3',5'-monophosphate (AMP)-activated protein kinase (AMPK) and silent mating type information regulation 2 homolog 1 (SIRT1). Acrp30 stimulation reduced the premature senescence positive ratio induced by hydrogen peroxide (H2O2) and restituted human β-defensin 2 (hBD-2) levels in senescent keratinocytes. Acrp30 recovered AMPK activity in senescent keratinocytes and increased SIRT1 deacetylation activity. As a result, FoxO1 and FoxO3 transcription activity was recovered. Additionally, Acrp30 stimulation suppresses NFκB p65, which induces abnormal expression of hBD-2 induced by H2O2. In the present study, we have shown that Acrp30 reduces premature senescence and recovers cellular function in keratinocytes. These results suggest a role for Acrp30 as an anti-aging agent to improve impaired skin immune barriers.

Restoration of sirt1 function by pterostilbene attenuates hypoxia-reoxygenation injury in cardiomyocytes

Restoration of blood supply to ischemic myocardium causes cardiomyocyte damage, a process known as ischemia-reperfusion injury. Excess reactive oxygen species and intracellular calcium contribute to cell damage but the involvement of sirt1, a versatile protein deacetylase in reperfusion-induced cell damage remains unknown. Here, we found that hypoxia-reoxygenation, an in vitro model of ischemia-reperfusion injury, induced H9c2 cardiomyocyte apoptosis as revealed by caspase-3 assay, Hoechst 33258 staining, flow cytometric analysis and JC-1 staining. Molecular docking analysis showed that, pterostilbene, a natural dimethyl ether derivative of resveratrol, binds to the enzymatic active pocket of sirt1. Importantly, application of pterostilbene at low concentrations of 0.1-3.0 μM rescued H9c2 cells from apoptosis, an effect comparable with resveratrol at 20 μM. Mechanistically, pterostilbene exerted its cardioprotective effects via 1) stimulation of sirt1 activity, since pretreatment of H9c2 cells with splitomicin, an antagonist of sirt1, removed the effects of pterostilbene, and 2) enhancement of sirt1 expression. Therefore, the present study demonstrates that activation of sitr1 during ischemia-reperfusion is cardioprotective and that the natural compound-pterostilbene-could be used therapeutically to alleviate ischemia-reperfusion injury.

The Deacetylase Sirtuin 1 Regulates Human Papillomavirus Replication by Modulating Histone Acetylation and Recruitment of DNA Damage Factors NBS1 and Rad51 to Viral Genomes

Human papillomaviruses (HPV) regulate their differentiation-dependent life cycles by activating a number of cellular pathways, such as the DNA damage response, through control of post-translational protein modification. Sirtuin 1 (SIRT1) is a protein deacetylase that modulates the acetylation of a number of cellular substrates, resulting in activation of pathways controlling gene expression and DNA damage repair. Our studies indicate that SIRT1 levels are increased in cells containing episomes of high-risk HPV types through the combined action of the E6 and E7 oncoproteins. Knockdown of SIRT1 in these cells with shRNAs impairs viral activities including genome maintenance, amplification and late gene transcription, with minimal effects on cellular proliferation ability. Abrogation of amplification was also seen following treatment with the SIRT1 deacetylase inhibitor, EX-527. Importantly, SIRT1 binds multiple regions of the HPV genome in undifferentiated cells, but this association is lost upon of differentiation. SIRT1 regulates the acetylation of Histone H1 (Lys26) and H4 (Lys16) bound to HPV genomes and this may contribute to regulation of viral replication and gene expression. The differentiation-dependent replication of high-risk HPVs requires activation of factors in the Ataxia Telangiectasia Mutated (ATM) pathway and SIRT1 regulates the recruitment of both NBS1 and Rad51 to the viral genomes. These observations demonstrate that SIRT1 is a critical regulator of multiple aspects of the high-risk HPV life cycle.

Human papillomaviruses regulate their differentiation-dependent life cycles by activating a number of cellular pathways, such as the DNA damage response, through control of post-translational protein modification. Sirtuin 1 (SIRT1) is a protein deacetylase that regulates the acetylation of a number of cellular substrates, resulting in activation of pathways involved in gene expression and DNA damage repair. We report here that SIRT1 protein levels are elevated in cells stably maintaining genomes of oncogenic HPVs and that SIRT1 knockdown impairs genome maintenance, productive replication and late gene transcription. The DNA damage sensing and repair pathways are critical for the HPV viral life cycle and members of this pathway, such as NBS1 and Rad51, are targets of SIRT1. Our studies demonstrate that SIRT1 binds the HPV genome and regulates both viral chromatin remodeling as well as binding of members of the homologous repair pathway to viral DNA. These findings demonstrate that binding of SIRT1 to the HPV genome is necessary for histone deacetylation and recruitment of DNA damage repair factors and is a critical step in the HPV life cycle.

Resveratrol ameliorates imiquimod-induced psoriasis-like skin inflammation in mice

Background

The polyphenol resveratrol has anti-inflammatory effects in various cells, tissues, animals and human settings of low-grade inflammation. Psoriasis is a disease of both localized and systemic low-grade inflammation. The Sirtuin1 enzyme thought to mediate the effects of resveratrol is present in skin and resveratrol is known to down regulate NF-κB; an important contributor in the development of psoriasis. Consequently we investigated whether resveratrol has an effect on an Imiquimod induced psoriasis-like skin inflammation in mice and sought to identify candidate genes, pathways and interleukins mediating the effects.

Methods

The study consisted of three treatment groups: A control group, an Imiquimod group and an Imiquimod+resveratrol group. Psoriasis severity was assessed using elements of the Psoriasis Area Severity Index, skin thickness measurements, and histological examination. We performed an RNA microarray from lesional skin and afterwards Ingenuity pathway analysis to identify affected signalling pathways. Our microarray was compared to a previously deposited microarray to determine if gene changes were psoriasis-like, and to a human microarray to determine if findings could be relevant in a human setting.

Results

Imiquimod treatment induced a psoriasis-like skin inflammation. Resveratrol significantly diminished the severity of the psoriasis-like skin inflammation. The RNA microarray revealed a psoriasis-like gene expression-profile in the Imiquimod treated group, and highlighted several resveratrol dependent changes in relevant genes, such as increased expression of genes associated with retinoic acid stimulation and reduced expression of genes involved in IL-17 dependent pathways. Quantitative PCR confirmed a resveratrol dependent decrease in mRNA levels of IL-17A and IL-19; both central in developing psoriasis.

Conclusions

Resveratrol ameliorates psoriasis, and changes expression of retinoic acid stimulated genes, IL-17 signalling pathways, IL-17A and IL-19 mRNA levels in a beneficial manner, which suggests resveratrol, might have a role in the treatment of psoriasis and should be explored further in a human setting.

Loss of sirtuin 1 (SIRT1) disrupts skin barrier integrity and sensitizes mice to epicutaneous allergen challenge

BACKGROUND

Skin barrier integrity requires a highly coordinated molecular system involving the structural protein filaggrin (FLG). Mutational loss of the skin barrier protein FLG predisposes subjects to the development of atopic dermatitis (AD).

OBJECTIVE

We sought to determine the role of sirtuin 1 (SIRT1) in skin barrier function, FLG expression, and development of AD.

METHODS

Skin histology of mice with skin-specific SIRT1 deletion and wild-type control animals was examined by using hematoxylin and eosin staining. Protein and mRNA abundance was analyzed by means of immunoblotting, immunohistochemistry, immunofluorescence, and RT-PCR. Serum antibody levels were assessed by means of ELISA.

RESULTS

Here we show that FLG is regulated by the protein deacetylase SIRT1 and that SIRT1 is critical for skin barrier integrity. Epidermis-specific SIRT1 ablation causes AD-like skin lesions in mice, and mice with epidermal SIRT1 deletion are sensitive to percutaneous challenge by the protein allergen ovalbumin. In normal human keratinocytes and mouse skin SIRT1 knockdown or genetic deletion downregulates FLG, and regulation of FLG expression by SIRT1 requires the deacetylase activity of SIRT1. SIRT1 also promotes activation of the aryl hydrocarbon receptor, and the aryl hydrocarbon receptor ligand restores FLG expression in SIRT1-inhibited cells. Compared with normal human skin, SIRT1 is downregulated in both AD and non-AD lesions.

CONCLUSION

Our findings demonstrate a critical role of SIRT1 in skin barrier maintenance, open up new opportunities to use SIRT1 as a pharmacologic target, and might facilitate the development of mechanism-based agents for AD prevention and therapy.

Genetic and epigenetic basis of psoriasis pathogenesis

Psoriasis is a chronic inflammatory skin disease whose prevalence varies among different populations worldwide. It is a complex multi-factorial disease and the exact etiology is largely unknown. Family based studies have indicated a genetic predisposition; however they cannot fully explain the disease pathogenesis. In addition to genetic susceptibility, environmental as well as gender and age related factors were also been found to be associated. Recently, imbalances in epigenetic networks are indicated to be causative elements in psoriasis. The present knowledge of epigenetic involvement, mainly the DNA methylation, chromatin modifications and miRNA deregulation is surveyed here. An integrated approach considering genetic and epigenetic anomalies in the light of immunological network may explore the pathogenesis of psoriasis.