Integration of transcriptomics and spatial biology analyses reveals Galactomyces ferment filtrate promotes epidermal interconnectivity via induction of keratinocyte differentiation, proliferation and cellular bioenergetics.

OBJECTIVE: Human skin is the first line of defence from environmental factors such as solar radiation and is susceptible to premature ageing, including a disruption in epidermal differentiation and homeostasis. We evaluated the impact of a Galactomyces Ferment Filtrate (GFF) on epidermal differentiation and response to oxidative stress. METHODS: We used transcriptomics, both spatial and traditional, to assess the impact of GFF on epidermal biology and homeostasis in keratinocytes (primary or immortalized) and in ex vivo skin explant tissue. The effect of GFF on cell adhesion rates, cellular ATP levels and proliferation rates were quantitated. Oxidative phosphorylation and glycolytic rates were measured under normal and stress-induced conditions. RESULTS: Transcriptomics from keratinocytes and ex vivo skin explants from multiple donors show GFF induces keratinocyte differentiation, skin barrier development and cell adhesion while simultaneously repressing cellular stress and inflammatory related processes. Spatial transcriptomics profiling of ex vivo skin indicated basal keratinocytes at the epidermal-dermal junction and cornifying keratinocytes in the top layer of the epidermis as the primary cell types influenced by GFF treatment. Additionally, GFF significantly increases crosstalk between suprabasal and basal keratinocytes. To support these findings, we show that GFF can significantly increase cell adhesion and proliferation in keratinocytes. GFF also protected overall cellular bioenergetics under metabolic or oxidative stress conditions. CONCLUSION: Our findings provide novel insights into cellular differences and epidermal spatial localization in response to GFF, supporting previous findings that this filtrate has a significant impact on epidermal biology and homeostasis, particularly on spatially defined crosstalk. We propose that GFF can help maintain epidermal health by enhancing keratinocyte crosstalk and differentiation/proliferation balance as well as promoting an enhanced response to stress.

Suppressed basal mitophagy drives cellular aging phenotypes that can be reversed by a p62-targeting small molecule.

Selective degradation of damaged mitochondria by autophagy (mitophagy) is proposed to play an important role in cellular homeostasis. However, the molecular mechanisms and the requirement of mitochondrial quality control by mitophagy for cellular physiology are poorly understood. Here, we demonstrated that primary human cells maintain highly active basal mitophagy initiated by mitochondrial superoxide signaling. Mitophagy was found to be mediated by PINK1/Parkin-dependent pathway involving p62 as a selective autophagy receptor (SAR). Importantly, this pathway was suppressed upon the induction of cellular senescence and in naturally aged cells, leading to a robust shutdown of mitophagy. Inhibition of mitophagy in proliferating cells was sufficient to trigger the senescence program, while reactivation of mitophagy was necessary for the anti-senescence effects of NAD precursors or rapamycin. Furthermore, reactivation of mitophagy by a p62-targeting small molecule rescued markers of cellular aging, which establishes mitochondrial quality control as a promising target for anti-aging interventions.

Targeting the autophagy-NAD axis protects against cell death in Niemann-Pick type C1 disease models.

Impairment of autophagy leads to an accumulation of misfolded proteins and damaged organelles and has been implicated in plethora of human diseases. Loss of autophagy in actively respiring cells has also been shown to trigger metabolic collapse mediated by the depletion of nicotinamide adenine dinucleotide (NAD) pools, resulting in cell death. Here we found that the deficit in the autophagy-NAD axis underpins the loss of viability in cell models of a neurodegenerative lysosomal storage disorder, Niemann-Pick type C1 (NPC1) disease. Defective autophagic flux in NPC1 cells resulted in mitochondrial dysfunction due to impairment of mitophagy, leading to the depletion of both the reduced and oxidised forms of NAD as identified via metabolic profiling. Consequently, exhaustion of the NAD pools triggered mitochondrial depolarisation and apoptotic cell death. Our chemical screening identified two FDA-approved drugs, celecoxib and memantine, as autophagy activators which effectively restored autophagic flux, NAD levels, and cell viability of NPC1 cells. Of biomedical relevance, either pharmacological rescue of the autophagy deficiency or NAD precursor supplementation restored NAD levels and improved the viability of NPC1 patient fibroblasts and induced pluripotent stem cell (iPSC)-derived cortical neurons. Together, our findings identify the autophagy-NAD axis as a mechanism of cell death and a target for therapeutic interventions in NPC1 disease, with a potential relevance to other neurodegenerative disorders.

The combination of allantoin, bisabolol, D-panthenol and dipotassium glycyrrhizinate mitigates UVB-induced PGE2 synthesis by keratinocytes.

OBJECTIVE: Erythema, characterized by the redness of the skin, is a common skin reaction triggered by various endogenous and exogenous factors. This response is often a result of the activation of underlying inflammatory mechanisms within the skin. The objective of this study is to investigate the potential benefits of applying a combination of skincare ingredients, namely allantoin, bisabolol, D-panthenol and dipotassium glycyrrhizinate (AB5D), in the modulation of inflammatory factors associated with erythema. Additionally, the study aims to elucidate the mechanisms by which these ingredients exert their combined actions to alleviate erythema-associated inflammation. METHODS: Human epidermal keratinocytes were exposed to UVB and subsequently treated with AB5D. Transcriptomics profiling was performed to analyse the dose-response effect of AB5D treatment on keratinocytes. The quantitation of inflammatory mediators, including PGE2 , IL-1α, IL-6, IL-8, IL-1RA and TNFα, was performed on cultured media. Additionally, the oxygen radical absorbance capacity (ORAC) assay was carried out to evaluate the total antioxidant capacity of both individual ingredients and the AB5D combination. To assess the in-vitro antioxidant effects of AB5D against UVB-induced oxidative stress in hTERT keratinocytes, real-time quantitation of mitochondrial superoxide was measured through live-cell imaging. RESULTS: The application of AB5D to UVB-exposed keratinocytes downregulated gene sets associated with inflammatory responses, highlighting the anti-inflammatory properties of AB5D. Specifically, AB5D effectively reduced the production of PGE2 , leading to the downregulation of inflammatory cytokines. Moreover, our findings indicate that AB5D exhibits antioxidative capabilities, functioning as both an antioxidant agent and a regulator of antioxidant enzyme expression to counteract the detrimental effects of cellular oxidative stress. CONCLUSION: We demonstrated that AB5D can reduce UVB-induced PGE2 , IL-1α, IL-6, IL-8, IL-1RA and TNFα as well as mitochondrial superoxide. These findings suggest that AB5D may alleviate erythema by modulating inflammation via PGE2 and through antioxidation mechanisms.

L'érythème, caractérisé par une rougeur sur la peau, est une réaction cutanée fréquente déclenchée par divers facteurs endogènes et exogènes. Il s'agit d'une réponse qui résulte souvent de l'activation des mécanismes inflammatoires sous-jacents dans la peau. OBJECTIF: cette étude vise à étudier les bénéfices potentiels de l'application d'une association d'ingrédients de soins cutanés, à savoir l'allantoïne, le bisabolol, le D-panthénol et le glycyrrhizinate dipotassique (AB5D) dans la modulation des facteurs inflammatoires associés à l'érythème. En outre, l'étude vise à élucider les mécanismes par lesquels ces ingrédients exercent leurs actions combinées pour soulager l'inflammation associée à l'érythème. MÉTHODES: les kératinocytes épidermiques humains ont été exposés aux UVB et traités par la suite par AB5D. Un profilage transcriptomique a été effectué pour analyser l'effet dose-réponse du traitement par AB5D sur les kératinocytes. La quantification des médiateurs inflammatoires, y compris PGE2, IL-1α, IL-6, IL-8, IL-1RA et TNFα, a été effectuée sur des milieux de culture. En outre, le dosage de la capacité d'absorption des radicaux oxygénés (Oxygen Radical Absorbance Capacity, ORAC) a été effectué pour évaluer la capacité antioxydante totale des deux ingrédients individuels et de l'association AB5D. Pour évaluer les effets antioxydants in vitro de l'AB5D contre le stress oxydatif induit par les UVB dans les kératinocytes hTERT, on a mesuré la quantification en temps réel du superoxyde mitochondrial par des tests d'imagerie des cellules vivantes. RÉSULTATS: l'application de l'AB5D aux ensembles de gènes régulés à la baisse exposés aux kératinocytes UVB associés à des réponses inflammatoires, a mis en évidence les propriétés anti-inflammatoires de l'AB5D. Plus précisément, l'AB5D a efficacement réduit la production de PGE2, entraînant une régulation négative des cytokines inflammatoires. En outre, nos résultats indiquent que l'AB5D présente des capacités antioxydantes. Il fonctionne à la fois comme un agent antioxydant et comme un régulateur de l'expression enzymatique antioxydante pour contrer les effets néfastes du stress oxydatif cellulaire. CONCLUSION: nous avons montré que l'AB5D pouvait réduire la PGE2 induite par les UVB, l'IL-1α, l'IL-6, IL-8, IL-1RA et le TNFα, ainsi que le superoxyde mitochondrial. Ces résultats suggèrent que l'AB5D pourrait soulager l'érythème en modulant l'inflammation via la PGE2 et via des mécanismes d'antioxydation.

Early onset of senescence and imbalanced epidermal homeostasis across the decades in photoexposed human skin: Fingerprints of inflammaging.

Inflammaging is a theory of ageing which purports that low-level chronic inflammation leads to cellular dysfunction and premature ageing of surrounding tissue. Skin is susceptible to inflammaging because it is the first line of defence from the environment, particularly solar radiation. To better understand the impact of ageing and photoexposure on epidermal biology, we performed a system biology-based analysis of photoexposed face and arm, and photoprotected buttock sites, from women between the ages of 20s to 70s. Biopsies were analysed by histology, transcriptomics, and proteomics and skin surface biomarkers collected from tape strips. We identified morphological changes with age of epidermal thinning, rete ridge pathlength loss and stratum corneum thickening. The SASP biomarkers IL-8 and IL-1RA/IL1-α were consistently elevated in face across age and cis/trans-urocanic acid were elevated in arms and face with age. In older arms, the DNA damage response biomarker 53BP1 showed higher puncti numbers in basal layers and epigenetic ageing were accelerated. Genes associated with differentiation and senescence showed increasing expression in the 30s whereas genes associated with hypoxia and glycolysis increased in the 50's. Proteomics comparing 60's vs 20's confirmed elevated levels of differentiation and glycolytic-related proteins. Representative immunostaining for proteins of differentiation, senescence and oxygen sensing/hypoxia showed similar relationships. This system biology-based analysis provides a body of evidence that young photoexposed skin is undergoing inflammaging. We propose the presence of chronic inflammation in young skin contributes to an imbalance of epidermal homeostasis that leads to a prematurely aged appearance during later life.

Autophagy promotes cell survival by maintaining NAD levels.

Autophagy is an essential catabolic process that promotes the clearance of surplus or damaged intracellular components. Loss of autophagy in age-related human pathologies contributes to tissue degeneration through a poorly understood mechanism. Here, we identify an evolutionarily conserved role of autophagy from yeast to humans in the preservation of nicotinamide adenine dinucleotide (NAD) levels, which are critical for cell survival. In respiring mouse fibroblasts with autophagy deficiency, loss of mitochondrial quality control was found to trigger hyperactivation of stress responses mediated by NADases of PARP and Sirtuin families. Uncontrolled depletion of the NAD(H) pool by these enzymes ultimately contributed to mitochondrial membrane depolarization and cell death. Pharmacological and genetic interventions targeting several key elements of this cascade improved the survival of autophagy-deficient yeast, mouse fibroblasts, and human neurons. Our study provides a mechanistic link between autophagy and NAD metabolism and identifies targets for interventions in human diseases associated with autophagic, lysosomal, and mitochondrial dysfunction.

Nicotinamide Prevents UVB- and Oxidative Stress‒Induced Photoaging in Human Primary Keratinocytes.

Nicotinamide (NAM), a NAM adenine dinucleotide precursor, is known for its benefits to skin health. Under standard culture conditions, NAM delays the differentiation and enhances the proliferation of human primary keratinocytes, leading to the maintenance of stem cells. In this study, we investigated the effects of NAM on photoaging in two-dimensional human primary keratinocyte cultures and three-dimensional organotypic epidermal models. In both models, we found that UVB irradiation and hydrogen peroxide induced human primary keratinocyte premature terminal differentiation and senescence. In three-dimensional organotypics, the phenotype was characterized by a thickening of the granular layer expressing filaggrin and loricrin, but thinning of the epidermis overall. NAM limited premature differentiation and ameliorated senescence, as evidenced by the maintenance of lamin B1 levels in both models, with decreased lipofuscin staining and reduced IL-6/IL-8 secretion in three-dimensional models, compared to those in UVB-only controls. In addition, DNA damage observed after irradiation was accompanied by a decline in energy metabolism, whereas both effects were partially prevented by NAM. Our data thus highlight the protective effects of NAM against photoaging and oxidative stress in the human epidermis and pinpoint DNA repair and energy metabolism as crucial underlying mechanisms.

The vitamin A ester retinyl propionate has a unique metabolic profile and higher retinoid-related bioactivity over retinol and retinyl palmitate in human skin models.

Human skin is exposed daily to environmental stressors, which cause acute damage and inflammation. Over time, this leads to morphological and visual appearance changes associated with premature ageing. Topical vitamin A derivatives such as retinol (ROL), retinyl palmitate (RPalm) and retinyl propionate (RP) have been used to reverse these changes and improve the appearance of skin. This study investigated a stoichiometric comparison of these retinoids using in vitro and ex vivo skin models. Skin biopsies were treated topically to compare skin penetration and metabolism. Treated keratinocytes were evaluated for transcriptomics profiling and hyaluronic acid (HA) synthesis and treated 3D epidermal skin equivalents were stained for epidermal thickness, Ki67 and filaggrin. A retinoic acid receptor-alpha (RARα) reporter cell line was used to compare retinoid activation levels. Results from ex vivo skin found that RP and ROL have higher penetration levels compared with RPalm. RP is metabolized primarily into ROL in the viable epidermis and dermis whereas ROL is esterified into RPalm and metabolized into the inactive retinoid 14-hydroxy-4,14-retro-retinol (14-HRR). RP treatment yielded higher RARα activation and HA synthesis levels than ROL whereas RPalm had a null effect. In keratinocytes, RP and ROL stimulated similar gene expression patterns and pathway theme profiles. In conclusion, RP and ROL show a similar response directionality whereas RPalm response was inconsistent. Additionally, RP has a consistently higher magnitude of response compared with ROL or RPalm.

Metabolic dysfunction in human skin: Restoration of mitochondrial integrity and metabolic output by nicotinamide (niacinamide) in primary dermal fibroblasts from older aged donors.

Alterations in metabolism in skin are accelerated by environmental stressors such as solar radiation, leading to premature aging. The impact of aging on mitochondria is of interest given their critical role for metabolic output and the finding that environmental stressors cause lowered energy output, particularly in fibroblasts where damage accumulates. To better understand these metabolic changes with aging, we performed an in-depth profiling of the expression patterns of dermal genes in face, forearm, and buttock biopsies from females of 20-70 years of age that encode for all subunits comprising complexes I-V of the mitochondrial electron transport chain. This complements previous preliminary analyses of these changes. "Oxidative phosphorylation" was the top canonical pathway associated with aging in the face, and genes encoding for numerous subunits had decreased expression patterns with age. Investigations on fibroblasts from older aged donors also showed decreased gene expression of numerous subunits from complexes I-V, oxidative phosphorylation rates, spare respiratory capacity, and mitochondrial number and membrane potential compared to younger cells. Treatment of older fibroblasts with nicotinamide (Nam) restored these measures to younger cell levels. Nam increased complexes I, IV, and V activity and gene expression of representative subunits. Elevated mt-Keima staining suggests a possible mechanism of action for these restorative effects via mitophagy. Nam also improved mitochondrial number and membrane potential in younger fibroblasts. These findings show there are significant changes in mitochondrial functionality with aging and that Nam treatment can restore bioenergetic efficiency and capacity in older fibroblasts with an amplifying effect in younger cells.

A population-based gene expression signature of molecular clock phase from a single epidermal sample.

BACKGROUND: For circadian medicine to influence health, such as when to take a drug or undergo a procedure, a biomarker of molecular clock phase is required--one that is easily measured and generalizable across a broad population. It is not clear that any circadian biomarker yet satisfies these criteria. METHODS: We analyzed 24-h molecular rhythms in human dermis and epidermis at three distinct body sites, leveraging both longitudinal (n = 20) and population (n = 154) data. We applied cyclic ordering by periodic structure (CYCLOPS) to order the population samples where biopsy time was not recorded. With CYCLOPS-predicted phases, we used ZeitZeiger to discover potential biomarkers of clock phase. RESULTS: Circadian clock function was strongest in the epidermis, regardless of body site. We identified a 12-gene expression signature that reported molecular clock phase to within 3 h (mean error = 2.5 h) from a single sample of epidermis--the skin's most superficial layer. This set performed well across body sites, ages, sexes, and detection platforms. CONCLUSIONS: This research shows that the clock in epidermis is more robust than dermis regardless of body site. To encourage ongoing validation of this putative biomarker in diverse populations, diseases, and experimental designs, we developed SkinPhaser--a user-friendly app to test biomarker performance in datasets ( https://github.com/gangwug/SkinPhaser ).

Niacinamide mitigates SASP-related inflammation induced by environmental stressors in human epidermal keratinocytes and skin.

OBJECTIVE: To evaluate whether niacinamide (Nam) can mitigate production of inflammatory and senescence-related biomarkers induced by environmental stressors. METHODS: Human epidermal keratinocytes were exposed to UVB, urban dust, diesel exhaust and cigarette smoke extract and treated with Nam or vehicle control. Full thickness 3-D skin organotypic models were exposed to a combination of UVB and PM2.5 and treated with Nam or vehicle control. Quantitation of the SASP-related inflammatory mediators PGE2 , IL-6 and IL-8 was performed on cultured media. UVB-exposed keratinocytes treated with and without Nam were immunostained for the senescence biomarker Lamin B1 (LmnB1). Transcriptomics profiling of cigarette smoke extract effects on keratinocytes was performed. A double-blind, placebo-controlled clinical was conducted on 40 female panellists that were pretreated on back sites for two weeks with 5% Nam or vehicle and then exposed to 1.5 minimal erythemal dose (MED) solar-simulated radiation (SSR). Treated sites were compared with non-treated exposed sites for erythema and the skin surface IL-1αRA/IL-1α inflammatory biomarkers. RESULTS: Ultraviolet B induced synthesis of PGE2 , IL-8 and IL-6 and reduced LmnB1 levels in keratinocytes. Urban dust and diesel exhaust only stimulated synthesis of IL-8 whereas cigarette smoke extract only stimulated levels of PGE2 . In all exposures, treatment with Nam significantly mitigated synthesis of the inflammatory mediators and restored levels of UVB-reduced LmnB1. In the 3D skin equivalent model, Nam reduced IL-8 levels stimulated by a combination of topical PM2.5 and UV exposure. In a UV challenge clinical, pretreatment with 5% Nam reduced erythema and skin surface IL-1αRA/IL-1α inflammatory biomarkers that were induced by SSR. CONCLUSION: Since it is known that Nam has anti-inflammatory properties, we tested whether Nam can inhibit environmental stress-induced inflammation and senescence-associated secretory phenotype (SASP) biomarkers. We show Nam can reduce PGE2 , IL-6 and IL-8 levels induced by environmental stressors. Additionally, in vivo pretreatment with Nam can reduce UV-induced erythema and skin surface inflammatory biomarkers. These findings add to the body of evidence that Nam can mitigate the skin's inflammatory response elicited by environmental stressors. This supports Nam can potentially inhibit senescence and premature ageing and thereby maintain skin's functionality and appearance.

OBJECTIF: Évaluer si le niacinamide (Nam) peut atténuer la production de biomarqueurs inflammatoireset liés à la sénescence induits par les facteurs de stress environnementaux. MÉTHODES: Leskératinocytes épidermiques H uman ont été exposés aux UVB, à la poussière urbaine, aux gaz d'échappement diesel et à l'extrait de fumée de cigarette et traités avec nam ou contrôle de véhicule. Les modèles organotypic de peau 3D de pleine épaisseur ont été exposés à une combinaison d'UVB et de PM2.5 et traités avec nam ou commande de véhicule. La quantitation des médiateurs inflammatoires liés à la SASP PGE2 ,IL-6 et IL-8 a été réalisée sur des médias cultivés. Les kératinocytes exposés aux UVB traités avec et sans Nam étaient immunotachés pour le biomarqueur de sénescence Lamin B1 (LmnB1). Le profilage de transcriptomique des effets d'extrait de fumée de cigarette sur les kératinocytes a été exécuté. Un placebo contrôlé clinique à double insu a été menée sur 40 panélistes féminins qui ont été prétraités sur les sites arrière pendant deux semaines avec 5% Nam ou véhicule, puis exposés à 1,5 dose erythémique minimale (MED) rayonnement solaire simulé (SSR). Les sites traités ont été comparés à des sites exposés non traités pour l'érythème et la surface de la peau IL-1▫RA/IL-1▫ biomarqueurs inflammatoiress. RÉSULTATS: Synthèse induite par UVB des niveaux de PGE2, IL-8 et IL-6 et réduit de LmnB1 dans les kératinocytes. La poussière urbaine et les gaz d'échappement diesel n'ont stimulé que la synthèse de l'IL-8 alors que l'extrait de fumée de cigarette ne stimulait que les niveaux de PGE2 . Dans toutes les expositions, le traitement avec Nam a significativement atténué la synthèse des médiateurs inflammatoires et les niveaux restaurés de LmnB1 UVB-réduit. Dans le modèle équivalent de la peau 3D, Nam a réduit les niveaux d'IL-8 stimulés par une combinaison de PM combination of topical PM 2.5 topique et d'exposition aux UV. Dans un uv-défi clinique, prétraitement avec 5% Nam réduit érythème et la surface de la peau IL-1▫RA/IL-1▫ biomarqueurs inflammatoires qui ont été induits par SSR. CONCLUSION: Puisqu'il est connu que Nam a des propriétés anti-inflammatoires, nous avons testé si Nam peut inhiber l'inflammation induite par le stressenvironnementaltion et les biomarqueurs sécrétoires sécrétoires sécrétoires (SASP) associés à la sénescence. We montrent Nam peut réduire PGE2 ,IL-6, et IL-8 niveaux induits par les facteurs de stress environnementaux. En outre, le prétraitement in vivo avec Nam peut réduire l'érythème induit par les UV et les biomarqueurs inflammatoires de surface de la peau. Ces résultats ajoutent à l'oody bde la preuve que Nam peut atténuer la réponse inflammatoire de la peau provoquée par lesfacteurs de stress environnementaux. Cela soutient Nam peut potentiellement inhiber la sénescence et le vieillissement prématuré et ainsi maintenir la fonctionnalité de la peau et l'apparence.

Nicotinamide Metabolism Modulates the Proliferation/Differentiation Balance and Senescence of Human Primary Keratinocytes.

Nicotinamide (NAM) is the main precursor of nicotinamide adenine dinucleotide (NAD+), a coenzyme essential for DNA repair, glycolysis, and oxidative phosphorylation. NAM has anti-aging activity on human skin, but the underlying mechanisms of action are unclear. Using 3-dimensional organotypic skin models, we show that NAM inhibits differentiation of the upper epidermal layers and maintains proliferation in the basal layer. In 2-dimensional culture, NAM reduces the expression of early and late epidermal differentiation markers and increases the proliferative capacity of human primary keratinocytes. This effect is characterized by elevated clonogenicity and an increased proportion of human primary keratinocyte stem cell (holoclones) compared to controls. By contrast, preventing the conversion of NAM to NAD+ using FK866 leads to premature human primary keratinocyte differentiation and senescence, together with a dramatic drop in glycolysis and cellular adenosine triphosphate levels while oxidative phosphorylation is moderately affected. All these effects are rescued by addition of NAM, known to compete with FK866, which suggests that conversion to NAD+ is part of the mechanistic response. These data provide insights into the control of differentiation, proliferation, and senescence by NAM and NAD+ in skin. They may lead to new therapeutic advances for skin conditions characterized by dysregulated epidermal homeostasis and premature skin aging, such as photoaging.

Population-level rhythms in human skin with implications for circadian medicine.

Skin is the largest organ in the body and serves important barrier, regulatory, and sensory functions. The epidermal layer shows rhythmic physiological responses to daily environmental variation (e.g., DNA repair). We investigated the role of the circadian clock in the transcriptional regulation of epidermis using a hybrid experimental design, in which a limited set of human subjects (n = 20) were sampled throughout the 24-h cycle and a larger population (n = 219) were sampled once. We found a robust circadian oscillator in human epidermis at the population level using pairwise correlations of clock and clock-associated genes in 298 epidermis samples. We then used CYCLOPS to reconstruct the temporal order of all samples, and identified hundreds of rhythmically expressed genes at the population level in human epidermis. We compared these results with published time-series skin data from mice and found a strong concordance in circadian phase across species for both transcripts and pathways. Furthermore, like blood, epidermis is readily accessible and a potential source of biomarkers. Using ZeitZeiger, we identified a biomarker set for human epidermis that is capable of reporting circadian phase to within 3 hours from a single sample. In summary, we show rhythms in human epidermis that persist at the population scale and describe a path to develop robust single-sample circadian biomarkers.

The evolving role of the NAD+/nicotinamide metabolome in skin homeostasis, cellular bioenergetics, and aging.

Human skin is exposed to daily environmental insults, particularly solar radiation, that triggers a range of molecular responses. These perturbations to the normal homeostatic state can lead to cellular dysfunction and, ultimately, impacts tissue integrity and accelerates skin aging (photoaging). One of the responses is increased oxidative stress which has been shown to disrupt cellular bioenergetics. This can be detected by depletion of the nucleotide energy metabolites NAD+ and ATP as both an acute transient decrease and, over time, a more permanent chronic reduction due in part to cumulative damage of mitochondria. NAD+ and its primary precursor nicotinamide have been known for some time to impact skin homeostasis based on linkages to dietary requirements, treatment of various inflammatory conditions, photoaging, and prevention of cancer. Cellular NAD+ pools are known to be lower in aged skin and treatment with nicotinamide is hypothesized to restore these levels, thereby mitigating cellular bioenergetics dysfunction. In dermal fibroblasts, nicotinamide is able to protect against oxidative stress to glycolysis, oxidative phosphorylation as well as increase mitochondrial efficiency via sirtuin-dependent selective mitophagy. Recent research has found that NAD+ cellular pools are more dynamic than previously thought, oscillating in tandem with free nicotinamide, and serves as a regulatory point and feedback loop in cellular metabolism regulation, maintenance of mitochondrial efficiency, and circadian rhythmicity. Since UV-induced oxidative stress in skin can disrupt these processes, continued molecular understanding of the role of NAD+ and nicotinamide in skin biology is important to identify interventions that would help maintain its normal homeostatic functions and efficient cellular bioenergetics.

Male skin care: shaving and moisturization needs.

Historically, most cosmetic and medical cosmetic research has been focused on the female consumer. Advancements in the development of grooming instruments as well as changing consumer habits and attitudes toward male cosmetic skin care needs support the need to develop a deeper understanding of male skin biology and how that can be used to improve the quality of life relative to societal interactions. Male skin biology has been found to have unique properties that are distinct from females and have a significant impact on the way males groom and maintain their overall appearance. Research to date has found that male skin has a different response profile to such environmental insults as UV, heat, and stress that is based not on just differences in cosmetic or dermatological product usage but also on underlying biological differences. These differences are discussed with the implications to a broader understanding of male facial skin care needs that spans from daily grooming practices to overall health status that impacts higher incidence rate of skin cancer among males. This highlights that male skin care has a holistic need to ensure proper grooming and sunscreen moisturizer usage.

Niacinamide: A B vitamin that improves aging facial skin appearance.

BACKGROUND: In multiple chronic clinical studies, topical niacinamide (vitamin B3) has been observed to be well tolerated by skin and to provide a broad array of improvements in the appearance of aging facial skin (eg, reduction in the appearance of hyperpigmentated spots and red blotchiness). OBJECTIVE: To clinically determine the effect of topical niacinamide on additional skin appearance and property end points (wrinkles, yellowing, and elasticity). METHODS: Female white subjects (N = 50) with clinical signs of facial photoaging (fine lines and wrinkles, poor texture, and hyperpigmented spots) applied 5% niacinamide to half of the face and its vehicle control to the other half twice daily for 12 weeks (double blind, left-right randomized). Facial images and instrumental measures were obtained at baseline and at 4-week intervals. RESULTS: Analyses of the data revealed a variety of significant skin appearance improvement effects for topical niacinamide: reductions in fine lines and wrinkles, hyperpigmented spots, red blotchiness, and skin sallowness (yellowing). In addition, elasticity (as measured via cutometry) was improved. Corresponding mechanistic information is presented. CONCLUSION: In addition to previously observed benefits for topical niacinamide, additional effects were identified (improved appearance of skin wrinkles and yellowing and improved elasticity).