Exposure of human melanocytes to UVB twice and subsequent incubation leads to cellular senescence and senescence-associated pigmentation through the prolonged p53 expression

Impact of nicotine-free and nicotine-rich flavored electronic cigarette refill liquids on primary human melanocyte function

In this study, five popular EC liquid flavors-strawberry, banana, vanilla, tobacco, and menthol-were examined on human melanocyte functions. Each flavored e-liquid (in 80/20 PG/VG vehicle) was tested without or with 18 mg/mL nicotine. The effects of PG/VG and nicotine-containing vehicles were also evaluated. Results revealed that nicotine-free and nicotine-containing e-liquids had comparable cytotoxicity, with menthol> > banana> tobacco> vanilla> strawberry. This cytotoxicity was unrelated to either nicotine or the vehicle. PG/VG (1 and 2 %) increased melanin production without influencing cellular tyrosinase activity. The flavored e-liquids did not further affect melanin production, suggesting that the vehicle's effect, not the flavor, was responsible for the increased melanin production. Interestingly, nicotine at 2 % in the vehicle restored the stimulated melanin production to the control. Flavors suppressed cellular tyrosinase activity, with vanilla and banana flavors robustly inhibiting it. Vanilla and banana e-liquids also enhanced reactive oxygen species (ROS) production, which did not originate from the vehicle or nicotine-containing vehicle. Banana e-liquid with nicotine lowered ROS generation compared to nicotine-free banana e-liquid. Common flavors in e-liquids can cause cytotoxicity and influence melanogenesis even without nicotine, indicating that the use of ECs may not completely avoid the harmful effects of cigarette smoking. Further studies are warranted to investigate e-liquid aerosol effects on melanocytes.

Senescence as a molecular target in skin aging and disease

Skin aging represents a multifactorial process influenced by both intrinsic and extrinsic factors, collectively known as the skin exposome. Cellular senescence, characterized by stable cell cycle arrest and secretion of pro-inflammatory molecules, has been implicated as a key driver of physiological and pathological skin aging. Increasing evidence points towards the role of senescence in a variety of dermatological diseases, where the accumulation of senescent cells in the epidermis and dermis exacerbates disease progression. Emerging therapeutic strategies such as senolytics and senomorphics offer promising avenues to target senescent cells and mitigate their deleterious effects, providing potential treatments for both skin aging and senescence-associated skin diseases. This review explores the molecular mechanisms of cellular senescence and its role in promoting age-related skin changes and pathologies, while compiling the observed effects of senotherapeutics in the skin and discussing the translational relevance.

Senescence in the ageing skin: a new focus on mTORC1 and the lysosome

Ageing is defined as the progressive loss of tissue function and regenerative capacity and is caused by both intrinsic factors i.e. the natural accumulation of damage, and extrinsic factors i.e. damage from environmental stressors. Cellular senescence, in brief, is an irreversible exit from the cell cycle that occurs primarily in response to excessive cellular damage, such as from ultraviolet (UV) exposure and oxidative stress, and it has been comprehensively demonstrated to contribute to tissue and organismal ageing. In this review, we will focus on the skin, an organ which acts as an essential protective barrier against injury, insults, and infection. We will explore the evidence for the existence and contribution of cellular senescence to skin ageing. We discuss the known molecular mechanisms driving senescence in the skin, with a focus on the dysregulation of the master growth regulator, mechanistic Target of Rapamycin Complex 1 (mTORC1). We explore the interplay of dysregulated mTORC1 with lysosomes and how they contribute to senescence phenotypes.

A novel microcapsule composite Spherulites Peony Superior Retinol mitigates UVB-induced skin damage in vitro and in vivo

Skin serves as our outermost barrier, protecting our bodies from various environmental damages. Increasing research has revealed that UVB is a primary factor for extrinsic aging. This study explored the role of a novel microcapsule composite Spherulites Peony Superior Retinol (SPSR) on skin damage induced by UVB. SPSR exhibited a capacity to eliminate UVB-induced ROS. By measurement of cyclobutane pyrimidine dimers (CPD) and comet assay, the results implied that SPSR mitigates DNA damage from oxidative damage caused by UVB. In addition, UVB radiation typically leads to an increase in inflammatory factors within the skin. Decreased gene expressions of interleukin-1α and TNF-α have been observed in HaCaT cells. Moreover, a decreased gene expression of extracellular matrix (ECM)-related protein, including fibronectin (FN1), Col1A1, and Col3A1 caused by UVB was mitigated by SPSR. Furthermore, the clinical trials with 30 volunteers confirmed the significant relief and antiwrinkle effects of the cosmetic formulation containing 0.1% SPSR. These findings implied the promising potential of SPSR as a comprehensive solution for combating the detrimental effects of UVB exposure and maintaining skin health.

Ultraviolet Light Causes Skin Cell Senescence: From Mechanism to Prevention Principle

The skin is an effective protective barrier that significantly protects the body from damage caused by external environmental factors. Furthermore, skin condition significantly affects external beauty. In today's era, which is of material and spiritual prosperity, there is growing attention on skincare and wellness. Ultraviolet radiation is one of the most common external factors that lead to conditions like sunburn, skin cancer, and skin aging. In this review, several mechanisms of UV-induced skin cell senescence are discussed, including DNA damage, oxidative stress, inflammatory response, and mitochondrial dysfunction, which have their own characteristics and mutual effects. As an illustration, mitochondrial dysfunction triggers electron evasion and the generation of more reactive oxygen species, leading to oxidative stress and the activation of the NLRP3 inflammasome, which in turn causes mitochondrial DNA (mt DNA) damage. Based on the current mechanism, suitable prevention and treatment strategies are proposed from sunscreen, dietary, and experimental medications respectively, aimed at slowing down skin cell aging and providing protection from ultraviolet radiation. The effects of ultraviolet rays on skin is summarized, offering insights and directions for future studies on mechanism of skin cell senescence, with an anticipation of discovering more effective prevention and cure methods.

Deciphering the role of skin aging in pigmentary disorders

Skin aging is a complex biological process involving intrinsic and extrinsic factors. Skin aging contains alterations at the tissue, cellular, and molecular levels. Currently, there is increasing evidence that skin aging occurs not only in time-dependent chronological aging but also plays a role in skin pigmentary disorders. This review provides an in-depth analysis of the impact of skin aging on different types of pigmentary disorders, including both hyperpigmentation disorders such as melasma and senile lentigo and hypopigmentation disorders such as vitiligo, idiopathic guttate hypomelanosis and graying of hair. In addition, we explore the mechanisms of skin aging on pigmentation regulation and suggest several potential therapeutic approaches for skin aging and aging-related pigmentary disorders.

Exposure to Radiofrequency Electromagnetic Fields Enhances Melanin Synthesis by Activating the P53 Signaling Pathway in Mel-Ab Melanocytes

The skin is the largest body organ that can be physiologically affected by exposure to radiofrequency electromagnetic fields (RF-EMFs). We investigated the effect of RF-EMFs on melanogenesis; Mel-Ab melanocytes were exposed to 1760 MHz radiation with a specific absorption rate of 4.0 W/kg for 4 h/day over 4 days. Exposure to the RF-EMF led to skin pigmentation, with a significant increase in melanin production in Mel-Ab melanocytes. The phosphorylation level of cAMP response element binding protein (CREB) and the expression of microphthalmia-associated transcription factor (MITF), which regulate the expression of tyrosinase, were significantly increased in Mel-Ab after RF-EMF exposure. Interestingly, the expression of tyrosinase was significantly increased, but tyrosinase activity was unchanged in the RF-EMF-exposed Mel-Ab cells. Additionally, the expression of p53 and melanocortin 1 receptor (MC1R), which regulate MITF expression, was significantly increased. These results suggest that the RF-EMF induces melanogenesis by increasing phospho-CREB and MITF activity. Importantly, when Mel-Ab cells were incubated at 38 °C, the melanin production and the levels of tyrosinase significantly decreased, indicating that the increase in melanin synthesis by RF-EMF exposure is not due to a thermal effect. In conclusion, RF-EMF exposure induces melanogenesis in Mel-Ab cells through the increased expression of tyrosinase via the activation of MITF or the phosphorylation of CREB, which are initiated by the activation of p53 and MC1R.

Skin Structure, Physiology, and Pathology in Topical and Transdermal Drug Delivery

Several industries are increasingly focused on enhancing the delivery of active ingredients through the skin to optimize therapeutic outcomes. By facilitating the penetration of active ingredients through the skin barrier, these enhancers can significantly improve the efficacy of various formulations, ranging from skincare products to therapeutic agents targeting systemic circulation. As the understanding of skin physiology and the mechanisms of drug absorption deepen, these industries are adopting permeation enhancers more widely, ultimately leading to better patient outcomes and expanded treatment options. However, the structure and physiological function of the skin can vary according to different factors, such as the area of the body and between individuals. These variations, along with external environmental exposures, aging and pathological conditions, introduce complexities that must be carefully considered when designing effective delivery systems. Considering the intricacies of skin structure and physiology, tailoring systems to account for regional differences, individual variability, and changes induced by environmental factors or disease is critical to optimizing therapeutic outcomes. This review discusses the features of skin structure, physiology, and pathologies, as well as the application of permeation enhancers in these contexts. Furthermore, it addresses the use of animal skin models in transdermal delivery and dermatological studies, along with the latest developments in this field.

The Keratinocyte in the Picture Cutaneous Melanoma Microenvironment

Melanoma progression is a multistep evolution from a common melanocytic nevus through a radial superficial growth phase, the invasive vertical growth phase finally leading to metastatic dissemination into distant organs. Melanoma aggressiveness largely depends on the propensity to metastasize, which means the capacity to escape from the physiological microenvironment since tissue damage due to primary melanoma lesions is generally modest. Physiologically, epidermal melanocytes are attached to the basement membrane, and their adhesion/migration is under the control of surrounding keratinocytes. Thus, the epidermal compartment represents the first microenvironment responsible for melanoma spread. This complex process involves cell-cell contact and a broad range of secreted bioactive molecules. Invasion, or at the beginning of the microinvasion, implies the breakdown of the dermo-epidermal basement membrane followed by the migration of neoplastic melanocytic cells in the superficial papillary dermis. Correspondingly, several experimental evidences documented the structural and functional rearrangement of the entire tissue surrounding neoplasm that in some way reflects the atypia of tumor cells. Lastly, the microenvironment must support the proliferation and survival of melanocytes outside the normal epidermal-melanin units. This task presumably is mostly delegated to fibroblasts and ultimately to the self-autonomous capacity of melanoma cells. This review will discuss remodeling that occurs in the epidermis during melanoma formation as well as skin changes that occur independently of melanocytic hyperproliferation having possible pro-tumoral features.

miR-656-3p inhibits melanomas in vitro and in vivo by inducing senescence via inhibiting LMNB2

BACKGROUND

Ultra-Violet Radiation (UVR) is the most significant exogenous contributor to skin aging. UVB causes the senescence of melanocytes, which results in a permanent arrest in the proliferative process. Senescence is also regarded as a physiological tumor-suppressing mechanism of normal cells. However, the mechanism of the relationship between melanocyte senescence and melanoma was not sufficiently clarified.

METHODS

Melanocytes and melanoma cells were irradiated with UVB for the indicated time. The miRNA expression profile of melanocytes were obtained by miRNA sequencing and confirmed by real-time PCR. Cell count kit-8 assays, cell cycle assays were also employed to explore the effect of miR-656-3p and LMNB2 on senescence. Dual-luciferase reporter assays were applied to determine the miRNA targets. Finally, a xenograft model and a photoaging model of mice were conducted to verified the function of miR-656-3p in vivo.

RESULTS

Melanoma cells did not alter into a senescence stage and the expressions of miR-656-3p had no significant changes under the same intensity of UVB radiation. miR-656-3p appeared to be upregulated in melanocytes rather than melanoma cells after UVB radiation. miR-656-3p could promote the photoaging of human primary melanocytes by targeting LMNB2. Finally, overexpression of miR-656-3p significantly induced senescence and inhibited the growth of melanomas in vitro and in vivo.

CONCLUSION

Our work not only demonstrated the mechanism by which miR-656-3p induced the senescence of melanocytes but also proposed a treatment strategy for melanomas by using miR-656-3p to induce senescence.

Identification of lncRNA-miRNA-mRNA Regulatory Network and Therapeutic Agents for Skin Aging by Bioinformatics Analysis

Skin aging is the most intuitive manifestation of aging. Skin aging inevitably leads to cosmetic and psychological problems, and even diseases. The present study aims to research the pathological and molecular mechanisms underlying skin aging and identify the therapeutic agents for reversing skin aging. Two available gene expression datasets (GSE55118 and GSE72264) for skin aging were downloaded from Gene Expression Omnibus, followed by bioinformatic analyses performed on the datasets. Firstly, 169 crucial mRNAs, 27 crucial miRNAs and 50 crucial lncRNAs closely related to skin aging were identified by weighted gene co-expression network analysis. Then, function Enrichment Analysis performed by Metascape database showed that skin aging involves a variety of biological functions, such as detection of stimulus, response to steroid hormone and water channel activity, regulation of muscle contraction. Next, ten hub genes including AQP4, TRPM8, TBR1, NTSR2, MPPED1, BARHL2, PAX9, CPN1, CES3, and CHGB were screened out by the protein-protein interaction analysis. Next, the "lncRNA-miRNA-mRNA" network and the "lncRNA-miRNA-hub mRNA" network were constructed to explore the competing endogenous RNAs mechanism of skin aging. Finally, ten significant potential small molecules mitigating skin aging were screened using CMAP platform, including tretinoin, pifithrin, selamectin, entinostat, bretazenil, syringic-acid, BRD-K96475865, emedastine, abacavir, and rotenone, and their reliability was verified by molecular docking experiments. The present study provided basis for revealing the molecular mechanism of skin aging and identified the potential candidate drugs for mitigating skin aging.

Current Understanding of the Role of Senescent Melanocytes in Skin Ageing

Melanocytes reside within the basal epidermis of human skin, and function to protect the skin from ultraviolet light through the production of melanin. Prolonged exposure of the skin to UV light can induce irreparable DNA damage and drive cells into senescence, a sustained cell cycle arrest that prevents the propagation of this damage. Senescent cells can also be detrimental and contribute to skin ageing phenotypes through their senescence-associated secretory phenotype. Senescent cells can act in both an autocrine and paracrine manner to produce widespread tissue inflammation and skin ageing. Recently, melanocytes have been identified as the main senescent cell population within the epidermis and have been linked to a variety of skin ageing phenotypes, such as epidermal thinning and the presence of wrinkles. However, the literature surrounding melanocyte senescence is limited and tends to focus on the role of senescence in the prevention of melanoma. Therefore, this review aims to explore the current understanding of the contribution of senescent melanocytes to human skin ageing.

Application of traditional Chinese medicine as skin depigmentation agents

Traditional Chinese medicine (TCM) has been frequently used as skin lightning agents. However, the mechanism of action of their effect is unclear. The present study aims to evaluate anti-tyrosinase activity of 10 commonly used TCM on mushroom (ab), human (hs) and mouse melanoma B16F0 (mm) tyrosinase (TYR) respectively. The results showed that at 1.0 mg/mL, extracts from Rosa rugosa Thumb, Morus alba L. and Paeonia lactiflora Pall were active against both abTYR and hsTYR (>50% inhibition), extracts from Bletilla striata (Thunb.) Rchb. F., Centella asiatica (L.) Urb, Cynanchum atratum L., Rosa canina L., Rhus chinensis Mill. and Glycyrrhiza urolensis Fisch. Ex DC. inhibited either abTYR or hsTYR (>50%), while extract from Tribulus terrestris L. had no/minimal activity (<10% inhibition). When treated with melanoma B16F0 cells, M. alba also significantly reduced mmTYR activity (70% at 250 μg/mL) and melanin content (50% at 250 μg/mL). These findings demonstrated inhibitory effects of 9 TCM against TYR and hence support their application as skin lightning agents. Our results also showed discrepancies in TYR activity from different sources, suggesting a testing regime of combining abTYR, hsTYR and mmTYR when developing depigmentation agents for human application.

Skin-Aging Pigmentation: Who Is the Real Enemy?

Skin aging is induced and sustained by chronological aging and photoaging. Aging skin pigmentation such as mottled pigmentation (senile lentigo) and melasma are typical signs of photoaging. The skin, like other human organs, undergoes cellular senescence, and senescent cells in the skin increase with age. The crosstalk between melanocytes as pigmentary cells and other adjacent types of aged skin cells such as senescent fibroblasts play a role in skin-aging pigmentation. In this review, we provide an overview of cellular senescence during the skin-aging process. The discussion also includes cellular senescence related to skin-aging pigmentation and the therapeutic potential of regulating the senescence process.

Anti-Melanogenesis Activity of Crocodile (Crocodylus siamensis) White Blood Cell Extract on Ultraviolet B-Irradiated Melanocytes

Ultraviolet (UV) radiation generates a range of biological effects in the skin, which includes premature skin aging, hyperpigmentation, and cancer. Therefore, the development of new effective agents for UV-related skin damage remains a challenge in the pharmaceutical industry. This study aims to test the inhibitory effect of crocodile white blood cell (cWBC) extract, a rich source of bioactive peptides, on ultraviolet B (UVB)-induced melanocyte pigmentation. The results showed that cWBC (6.25-400 μg/mL) could inhibit tyrosinase without adduct formation by 12.97 ± 4.20% on average. cWBC pretreatment (25-100 μg/mL) had no cytotoxicity and reduced intracellular melanin to 111.17 ± 5.20% compared with 124.87 ± 7.43 for UVB condition. The protective role of cWBC pretreatment against UVB was exhibited by the promotion of cell proliferation and the prevention of UVB-induced morphological change as observed from F actin staining. The decrease of microphthalmia-associated transcription factor expression levels after cWBC pretreatment might be a mechanism by which cWBC suppresses UVB-induced pigmentation. These results suggest that cWBC could be beneficial for the prevention of UVB-induced skin pigmentation.

Sebocytes contribute to melasma onset

Melasma is a hyperpigmentary disorder with photoaging features, whose manifestations appear on specific face areas, rich in sebaceous glands (SGs). To explore the SGs possible contribution to the onset, the expression of pro-melanogenic and inflammatory factors from the SZ95 SG cell line exposed to single or repetitive ultraviolet (UVA) radiation was evaluated. UVA up-modulated the long-lasting production of α-MSH, EDN1, b-FGF, SCF, inflammatory cytokines and mediators. Irradiated SZ95 sebocyte conditioned media increased pigmentation in melanocytes and the expression of senescence markers, pro-inflammatory cytokines, and growth factors regulating melanogenesis in fibroblasts cultures. Cocultures experiments with skin explants confirmed the role of sebocytes on melanogenesis promotion. The analysis on sebum collected from melasma patients demonstrated that in vivo sebocytes from lesional areas express the UVA-activated pathways markers observed in vitro. Our results indicate sebocytes as one of the actors in melasma pathogenesis, inducing prolonged skin cell stimulation, contributing to localized dermal aging and hyperpigmentation.

Protooncogene MYC drives human melanocyte melanogenesis and senescence

In spite of extensive research and advances on the molecular biology of melanoma, the process of melanocytic differentiation or its relationship with proliferation is poorly understood. The role of proto-oncogenes in normal melanocyte biology is also intriguing. Proto-oncogene MYC is overexpressed in 40% of melanomas. It has been suggested that MYC can mediate senescence bypass in malignant melanocytes, an important event in melanoma development, likely in cooperation with other oncogenic pathways. However, despite the apparent importance of MYC in melanoma, its functions in normal melanocytes are unknown. We have overexpressed MYC in freshly isolated human primary melanocytes and studied the effects on melanocytic proliferation and differentiation. MYC promoted a transient activation of melanocytes including cell cycle entry, DNA damage and cell migration. Subsequently, MYC induced melanogenesis, increased cellular size and complexity and senescence. Interestingly, we also found strong expression of MYC in regions of human nevi displaying high pigmentation and high expression of senescence marker p16. The results altogether show that MYC drives melanocytic differentiation and suggest that senescence is associated with differentiation. We discuss the implications into the mechanisms governing melanocytic differentiation and the development of melanoma.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

Heptapeptide Isolated from Isochrysis zhanjiangensis Exhibited Anti-Photoaging Potential via MAPK/AP-1/MMP Pathway and Anti-Apoptosis in UVB-Irradiated HaCaT Cells

Marine microalgae can be used as sustainable protein sources in many fields with positive effects on human and animal health. DAPTMGY is a heptapeptide isolated from Isochrysis zhanjiangensis which is a microalga. In this study, we evaluated its anti-photoaging properties and mechanism of action in human immortalized keratinocytes cells (HaCaT). The results showed that DAPTMGY scavenged reactive oxygen species (ROS) and increase the level of endogenous antioxidants. In addition, through the exploration of its mechanism, it was determined that DAPIMGY exerted anti-photoaging effects. Specifically, the heptapeptide inhibits UVB-induced apoptosis through down-regulation of p53, caspase-8, caspase-3 and Bax and up-regulation of Bcl-2. Thus, DAPTMGY, isolated from I. zhanjiangensis, exhibits protective effects against UVB-induced damage.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Cellular Senescence and Inflammaging in the Skin Microenvironment

Cellular senescence and aging result in a reduced ability to manage persistent types of inflammation. Thus, the chronic low-level inflammation associated with aging phenotype is called “inflammaging”. Inflammaging is not only related with age-associated chronic systemic diseases such as cardiovascular disease and diabetes, but also skin aging. As the largest organ of the body, skin is continuously exposed to external stressors such as UV radiation, air particulate matter, and human microbiome. In this review article, we present mechanisms for accumulation of senescence cells in different compartments of the skin based on cell types, and their association with skin resident immune cells to describe changes in cutaneous immunity during the aging process.

Panax ginseng-Derived Extracellular Vesicles Facilitate Anti-Senescence Effects in Human Skin Cells: An Eco-Friendly and Sustainable Way to Use Ginseng Substances

Ginseng is a traditional herbal medicine in eastern Asian countries. Most active constituents in ginseng are prepared via fermentation or organic acid pretreatment. Extracellular vesicles (EVs) are released by most organisms from prokaryotes to eukaryotes and play central roles in intra- and inter-species communications. Plants produce EVs upon exposure to microbes; however, their direct functions and utility for human health are barely known, except for being proposed as delivery vehicles. In this study, we isolated EVs from ginseng roots (GrEVs) or the culture supernatants of ginseng cells (GcEVs) derived from Panax ginseng C.A. Meyer and investigated their biological effects on human skin cells. GrEV or GcEV treatments improved the replicative senescent or senescence-associated pigmented phenotypes of human dermal fibroblasts or ultraviolet B radiation-treated human melanocytes, respectively, by downregulating senescence-associated molecules and/or melanogenesis-related proteins. Based on comprehensive lipidomic analysis using liquid chromatography mass spectrometry, the lipidomic profile of GrEVs differed from that of the parental root extracts, showing significant increases in 70 of 188 identified lipid species and prominent increases in diacylglycerols, some phospholipids (phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine), and sphingomyelin, revealing their unique vesicular properties. Therefore, our results imply that GEVs represent a novel type of bioactive and sustainable nanomaterials that can be applied to human tissues for improving tissue conditions and targeted delivery of active constituents.

Clinical brightening efficacy and safety of Melasolv™ (3,4,5-trimethoxy cinnamate thymol ester, TCTE) in Southeast Asian women

BACKGROUND

Skin darkening because of increased and irregular synthesis of melanin causes melasma, solar lentigo, and freckles. Melasolv™, produced in the early 2000s, shows potent depigmenting effect and has low cytotoxicity. It has been used as a brightening agent in cosmetics for decades.

AIMS

This study was conducted to investigate whether Melasolv™ is effective for the skin of ASEAN (Southeast Asia) women.

METHODS

We recruited ASEAN women in Singapore and divided them into two groups (active group vs. placebo group). Melasolv^™ and placebo formulations were applied twice a day for 12 weeks. The changes in the pigmented spots were visually evaluated by an expert and assessed using a spectrophotometer and Mexameter at 0, 4, 8, and 12 weeks.

RESULTS

The visual evaluation revealed significant improvements, in both size and color intensity, in the active group compared with those in the placebo group at 12 weeks. In the spectrophotometric evaluation, the L* value of the pigmented spots in the active group was significantly higher than that in the placebo group at 12 weeks. Similar results were obtained in the evaluation using the Mexameter. After 12 weeks, the melanin index of the pigmented spots significantly decreased, and it was significantly higher than that in the placebo group. There was no significant change in the erythema index. In the image analysis, there were no significant differences in skin color brightness and evenness in the active group compared with those in the placebo group.

CONCLUSION

Melasolv^™ can be effective used for skin brightening.

Possible treatment for UVB-induced skin injury: Anti-inflammatory and cytoprotective role of metformin in UVB-irradiated keratinocytes

BACKGROUND

Excessive inflammation and cell death induced by ultraviolet (UV) cause skin photodamage. Metformin possesses anti-inflammatory and cytoprotective effects. However, whether metformin inhibits inflammation and cell death in UVB-induced acute skin damage is unclear.

OBJECTIVE

To evaluate the anti-inflammatory and cytoprotective effects of metformin in vitro and in vivo. Furthermore, its potential mechanism has been explored.

METHODS

Transcriptome sequencing and multiplex cytokines analysis were used to evaluate the validity of in vitro UVB-induced acute damage keratinocyte model and anti-inflammatory effects of metformin. We also determined the expression and nuclear translocation of CCAAT/enhancer-binding protein beta (C/EBPβ), an important transcriptional factor of Interleukin-1beta (IL-1β). Cell viability and cell death of keratinocytes were evaluated upon UVB irradiation in the presence or absence of metformin. 0.6% metformin cream was applied on UVB-irradiated mice to explore its pharmacological effects in vivo.

RESULTS

Transcriptional landscape of 50 mJ/cm² UVB-irradiated HaCaT cells is typical of UVB-induced acute damage keratinocyte model in vitro. Metformin alleviated transcription and secretion of IL-1β, Tumor Necrosis Factor-alpha, and Fibroblast Growth Factor 2, expression and nuclear translocation of C/EBPβ in this model. Metformin also protected keratinocytes from cell death caused by UVB-induced cellular secretions, which contributed to its cytoprotective effects. Topical administration of 0.6% metformin cream alleviated UVB-induced skin damage in mice.

CONCLUSION

We proved the protective roles of metformin in UVB-challenged keratinocytes and UVB-irradiated mice, which indicated the potential value of metformin in topical therapy against skin photodamage.

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

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

The bright and dark side of skin senescence. Could skin rejuvenation anti-senescence interventions become a "bright" new strategy for the prevention of age-related skin pathologies?

The number of senescent cells in the skin is increasing with age. Numerous studies have attempted to elucidate the role of these cells in normal aging of the skin as well as in age-related skin conditions. In recent years, attempts have also been made to find treatments that aim either to cleanse the skin tissues of senescent cells or to neutralize their effects (referred to as senolytics and senomorphics respectively) and thus prevent the consequences, particularly on the skin's appearance in advanced age. Through this review, we have tried to gather data on the role of senescent cells in the skin, in treatments aimed at removing them, and we are asking a reasonable question as to whether anti-senescence treatments may contribute to the protection against age-related skin pathologies, including skin cancer, such as non-melanoma skin cancer, in addition to their involvement in skin rejuvenation.

Effect of Konjac Glucomannan (KGM) on the Reconstitution of the Dermal Environment against UVB-Induced Condition

Skin layers serve as a barrier against unexpected critical changes in the body due to environmental factors. Excessive ultraviolet (UV) B exposure increases the levels of age-related factors, leading to senescent cells and damaged skin tissues. Widely used as a dietary supplement, konjac (Amorphophallus konjac) glucomannan (KGM) has shown skin regeneration potential in patch or sheet form with anti-inflammatory or immunosuppressive effects. However, the ability of KGM to reconstitute senescent/damaged skin following UV radiation has not been explored. Here, we demonstrate that KGM alleviates skin damage by increasing the proportion of young cell populations in UVB-exposed senescent human epidermal primary melanocytes. Young cell numbers increased depending on KGM dosage, but the senescent cells were not removed. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis showed that mRNA and protein levels of age- and pigmentation-related factors decreased in a manner dependent on the rate at which new cells were generated. Moreover, an analysis of mRNA and protein levels indicated that KGM facilitated youth by increasing cell proliferation in UVB-damaged human fibroblasts. Thus, KGM is a highly effective natural agent for maintaining skin homeostasis by promoting the reconstitution of the dermal environment against UVB-induced acute senescence or skin damage.

Skin photo-protection with phytochemicals against photo-oxidative stress, photo-carcinogenesis, signal transduction pathways and extracellular matrix remodeling-An overview

Excessive exposure of skin to UV radiation triggers the generation of oxidative stress, inflammation, immunosuppression, apoptosis, matrix-metalloproteases production, and DNA mutations leading to the onset of photo ageing and photo-carcinogenesis. At the molecular level, these changes occur via activation of several protein kinases as well as transcription pathways, formation of reactive oxygen species, and release of cytokines, interleukins and prostaglandins together. Current therapies available on the market only provide limited solutions and exhibit several side effects. The present paper provides insight into scientific studies that have elucidated the positive role of phytochemicals in counteracting the UV-induced depletion of antioxidant enzymes, increased lipid peroxidation, inflammation, DNA mutations, increased senescence, dysfunctional apoptosis and immune suppression. The contribution of phytochemicals to the downregulation of expression of oxidative-stress sensitive transcription factors (Nrf2, NF-Kb, AP-1 and p53) and protein kinases (MSK, ERK, JNK, p38 MAPK, p90RSK2 and CaMKs) involved in inflammation, apoptosis, immune suppression, extracellular matrix remodelling, senescence, photo ageing and photo-carcinogenesis, is also discussed. Conclusively, several phytochemicals hold potential for the development of a viable solution against UV irradiation-mediated photo ageing, photo-carcinogenesis and related manifestations.

Effects of hydrogen peroxide, doxorubicin and ultraviolet irradiation on senescence of human dental pulp stem cells

OBJECTIVE

The objective of this study was to evaluate the ability of three distinct agents on the induction of senescence in human dental pulp stem cells (DPSCs).

DESIGN

DPSCs from three separate donors were treated with H₂O₂, doxorubicin and ultraviolet (UV) irradiation. The response of the cells to the three agents was assayed by specific staining for SA-βGal, RT-qPCR and flow cytometry.

RESULTS

The results showed that incubation with 100 μM H₂O₂ and 20 nM Doxorubicin for seven days led to senescence in all donors' cells equally. Interestingly, UV irradiation for just one minute was sufficient to induce senescence in the cells. The SA-βGal positive senescent cells were arrested in G₁ phase and their S phase was significantly reduced as analyzed by flow cytometry. Significant increment in p21 and BTG1 expression and decrement in CCND1 expression also confirmed the cells have been arrested and get senescent via p53-p21 pathway.

CONCLUSION

All three agents successfully triggered senescence in the cells. There was no significant difference in the capacity of the three donor's cells for senescence. To avoid premature senescence in stem cell in vitro, it is recommended to avoid unnecessary exposure of the cell to fluorescent and UV light. Moreover, to prevent ROS production, we recommend using a separate incubator with low oxygen content for cell culture, if possible.

Premature senescence in human melanocytes after exposure to solar UVR: An exosome and UV-miRNA connection

Ultraviolet radiation (UVR) can play two roles: induce cellular senescence and convert skin melanocytes into melanoma. To assess whether this conversion might rely on melanocytes having to first acquire a senescent phenotype, we studied the effects of physiological doses of UVR (UVA + UVB) on quiescent melanocytes in vitro. Repeated doses of UVR induced these melanocytes into a senescent-like state. Additionally, these cells secrete exosomes with specific miRNAs that differ in quantity from those of the un-irradiated melanocytes. Many of the exosomal miRNAs that were differentially enriched regulated genes comprising a "senescence core signature" and encoding factors of the senescence-messaging secretome (SASP), while a subset of the differentially reduced miRNAs targeted DNA repair genes that have been experimentally shown to be repressed in senescent melanocytes. Thus, the selection of specific miRNAs by exosomes and their release from melanocytes after exposure to UVR have activities in inducing these cells into premature senescence.

Pomegranate Juice and Extract Consumption Increases the Resistance to UVB-induced Erythema and Changes the Skin Microbiome in Healthy Women: a Randomized Controlled Trial

In vitro and animal studies have demonstrated that topical application and oral consumption of pomegranate reduces UVB-induced skin damage. We therefore investigated if oral pomegranate consumption will reduce photodamage from UVB irradiation and alter the composition of the skin microbiota in a randomized controlled, parallel, three-arm, open label study. Seventy-four female participants (30–45 years) with Fitzpatrick skin type II-IV were randomly assigned (1:1:1) to 1000 mg of pomegranate extract (PomX), 8 oz of pomegranate juice (PomJ) or placebo for 12 weeks. Minimal erythema dose (MED) and melanin index were determined using a cutometer (mexameter probe). Skin microbiota was determined using 16S rRNA sequencing. The MED was significantly increased in the PomX and PomJ group compared to placebo. There was no significant difference on phylum, but on family and genus level bacterial composition of skin samples collected at baseline and after 12 week intervention showed significant differences between PomJ, PomX and placebo. Members of the Methylobacteriaceae family contain pigments absorbing UV irradiation and might contribute to UVB skin protection. However, we were not able to establish a direct correlation between increased MED and bacterial abundance. In summary daily oral pomegranate consumption may lead to enhanced protection from UV photodamage.

On-off switching of cell cycle and melanogenesis regulation of melanocytes by non-thermal atmospheric pressure plasma-activated medium

Non-thermal atmospheric pressure (NAP) plasma has demonstrated potential in biomedical applications, such as cancer treatment, bactericidal sterilization, and cell growth promotion or inhibition. In this study, for the first time, we demonstrated on–off switching of cell cycle progression and regulated melanogenesis in normal human skin melanocytes by NAP plasma-activated medium (PAM). The melanocytes were exposed to NAP plasma at durations varying from 0 to 20 min, and the effects of PAM on cell proliferation, cell cycle progression, and melanogenesis were investigated. Although PAM showed no cytotoxicity, the proliferation of melanocytes was inhibited. The melanocyte cell cycle was arrested by PAM for a relatively short period (48 h), after which it recovered slowly. PAM promoted melanogenesis through the activation of the enzymes tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2. These effects seem to be related to reactive oxygen species induced by PAM. Our finding that PAM modulates the cell cycle may provide insight into the recurrence of cancer. The regulation of the melanogenesis of melanocytes may facilitate the control of skin tone without incurring negative side effects.

RNA-Seq analysis revealed genes associated with UV-induced cell necrosis through MAPK/TNF-α pathways in human dermal fibroblast cells as an inducer of premature photoaging

Exposing the skin to solar UV radiation induces cascades of signaling pathways and biological alterations such as redox imbalance, suppression of antioxidant genes and programmed cell death. Therefore, the aim of this study was to use RNA-Seq to unravel the effects of UV radiation on Normal Human Adult Fibroblast cells (NHDF). Cells were exposed to UV (20 mJ/cm2 for 3 mins) and incubated for 24 h. Total mRNA from the cells generated libraries of 72,080,648 and 40,750,939 raw reads from UV-treated and control cells respectively. Of the differentially expressed genes (DEGs) produced 2,007 were up-regulated and 2,791 were down-regulated (fold change ≥2, p < 0.05). The expression of 4 genes was validated with RT-qPCR. Chemokine signaling pathways in cancer were significantly activated and antioxidant genes were down-regulated. This study applied Next Generation Sequencing technology to reveal the genes and pathways involved in UV-induced human dermal fibroblast cells necrosis.