The role of altered nucleotide excision repair and UVB-induced DNA damage in melanomagenesis

Narrow-band UVB radiation triggers diverse changes in the gene expression and induces the accumulation of M1 macrophages in human skin

BACKGROUND

The underlying molecular mechanisms that determine the biological effects of UVB radiation exposure on human skin are still only partially comprehended.

OBJECTIVES

Our goal is to examine the human skin transcriptome and related molecular mechanisms following a single exposure to UVB in the morning versus evening.

METHODS

We exposed 20 volunteer females to four-fold standard erythema doses (SED4) of narrow-band UVB (309-313 nm) in the morning or evening and studied skin transcriptome 24 h after the exposure. We performed enrichment analyses of gene pathways, predicted changes in skin cell composition using cellular deconvolution, and correlated cell proportions with gene expression.

RESULTS

In the skin transcriptome, UVB exposure yielded 1384 differentially expressed genes (DEGs) in the morning and 1295 DEGs in the evening, of which the most statistically significant DEGs enhanced proteasome and spliceosome pathways. Unexposed control samples showed difference by 321 DEGs in the morning vs evening, which was related to differences in genes associated with the circadian rhythm. After the UVB exposure, the fraction of proinflammatory M1 macrophages was significantly increased at both timepoints, and this increase was positively correlated with pathways on Myc targets and mTORC1 signaling. In the evening, the skin clinical erythema was more severe and had stronger positive correlation with the number of M1 macrophages than in the morning after UVB exposure. The fractions of myeloid and plasmacytoid dendritic cells and CD8 T cells were significantly decreased in the morning but not in the evening.

CONCLUSIONS

NB-UVB-exposure causes changes in skin transcriptome, inhibiting cell division, and promoting proteasome activity and repair responses, both in the morning and in the evening. Inflammatory M1 macrophages may drive the UV-induced skin responses by exacerbating inflammation and erythema. These findings highlight how the same UVB exposure influences skin responses differently in morning versus evening and presents a possible explanation to the differences in gene expression in the skin after UVB irradiation at these two timepoints.

Decoding the synergistic potential of MAZ-51 and zingerone as therapy for melanoma treatment in alignment with sustainable development goals

Melanoma, an invasive class of skin cancer, originates from mutations in melanocytes, the pigment-producing cells. Globally, approximately 132,000 new cases are reported each year, and in South Africa, the incidence stands at 2.7 per 100,000 people, signifying a worrisome surge in melanoma rates. Therefore, there is a need to explore treatment modalities that will target melanoma's signalling pathways. Melanoma metastasis is aided by ligand activity of transforming growth factor-beta 1 (TGF-β1), vascular endothelial growth factor-C (VEGF-C) and C-X-C chemokine ligand 12 (CXCL12) which bind to their receptors and promote tumour cell survival, lymphangiogenesis and chemotaxis. (3-(4-dimethylaminonaphthelen-1-ylmethylene)-1,3-dihydroindol-2-one) MAZ-51 is an indolinone-based molecule that inhibits VEGF-C induced phosphorylation of vascular endothelial growth factor receptor 3 (VEGFR-3). Despite the successful use of conventional cancer therapies, patients endure adverse side effects and cancer drug resistance. Moreover, conventional therapies are toxic to the environment and caregivers. The use of medicinal plants and their phytochemical constituents in cancer treatment strategies has become more widespread because of the rise in drug resistance and the development of unfavourable side effects. Zingerone, a phytochemical derived from ginger exhibits various pharmacological properties positioning it as a promising candidate for cancer treatment. This review provides an overview of melanoma biology and the intracellular signalling pathways promoting cell survival, proliferation and adhesion. There is a need to align health and environmental objectives within sustainable development goals 3 (good health and well-being), 13 (climate action) and 15 (life on land) to promote early detection of skin cancer, enhance sun-safe practices, mitigation of environmental factors and advancing the preservation of biodiversity, including medicinal plants. Thus, this review discusses the impact of cytostatic cancer drugs on patients and the environment and examines the potential use of phytochemicals as adjuvant therapy.

CD133-Dependent Activation of Phosphoinositide 3-Kinase /AKT/Mammalian Target of Rapamycin Signaling in Melanoma Progression and Drug Resistance

Melanoma frequently harbors genetic alterations in key molecules leading to the aberrant activation of PI3K and its downstream pathways. Although the role of PI3K/AKT/mTOR in melanoma progression and drug resistance is well documented, targeting the PI3K/AKT/mTOR pathway showed less efficiency in clinical trials than might have been expected, since the suppression of the PI3K/mTOR signaling pathway-induced feedback loops is mostly associated with the activation of compensatory pathways such as MAPK/MEK/ERK. Consequently, the development of intrinsic and acquired resistance can occur. As a solid tumor, melanoma is notorious for its heterogeneity. This can be expressed in the form of genetically divergent subpopulations including a small fraction of cancer stem-like cells (CSCs) and non-cancer stem cells (non-CSCs) that make the most of the tumor mass. Like other CSCs, melanoma stem-like cells (MSCs) are characterized by their unique cell surface proteins/stemness markers and aberrant signaling pathways. In addition to its function as a robust marker for stemness properties, CD133 is crucial for the maintenance of stemness properties and drug resistance. Herein, the role of CD133-dependent activation of PI3K/mTOR in the regulation of melanoma progression, drug resistance, and recurrence is reviewed.

Role of reactive oxygen species in ultraviolet-induced photodamage of the skin

Reactive oxygen species (ROS), such as superoxides (O2 •-) and hydroxyl groups (OH·), are short-lived molecules containing unpaired electrons. Intracellular ROS are believed to be mainly produced by the mitochondria and NADPH oxidase (NOX) and can be associated with various physiological processes, such as proliferation, cell signaling, and oxygen homeostasis. In recent years, many studies have indicated that ROS play crucial roles in regulating ultraviolet (UV)-induced photodamage of the skin, including exogenous aging, which accounts for 80% of aging. However, to the best of our knowledge, the detailed signaling pathways, especially those related to the mechanisms underlying apoptosis in which ROS are involved have not been reviewed previously. In this review, we elaborate on the biological characteristics of ROS and its role in regulating UV-induced photodamage of the skin.

Ataxia Telangiectasia Mutated Signaling Delays Skin Pigmentation upon UV Exposure by Mediating MITF Function toward DNA Repair Mode

Skin pigmentation is paused after sun exposure; however, the mechanism behind this pausing is unknown. In this study, we found that the UVB-induced DNA repair system, led by the ataxia telangiectasia mutated (ATM) protein kinase, represses MITF transcriptional activity of pigmentation genes while placing MITF in DNA repair mode, thus directly inhibiting pigment production. Phosphoproteomics analysis revealed ATM to be the most significantly enriched pathway among all UVB-induced DNA repair systems. ATM inhibition in mouse or human skin, either genetically or chemically, induces pigmentation. Upon UVB exposure, MITF transcriptional activation is blocked owing to ATM-dependent phosphorylation of MITF on S414, which modifies MITF activity and interactome toward DNA repair, including binding to TRIM28 and RBBP4. Accordingly, MITF genome occupancy is enriched in sites of high DNA damage that are likely repaired. This suggests that ATM harnesses the pigmentation key activator for the necessary rapid, efficient DNA repair, thus optimizing the chances of the cell surviving. Data are available from ProteomeXchange with the identifier PXD041121.

The role of APOBEC3-induced mutations in the differential evolution of monkeypox virus

Recent studies show that newly sampled monkeypox virus (MPXV) genomes exhibit mutations consistent with Apolipoprotein B mRNA Editing Catalytic Polypeptide-like3 (APOBEC3)-mediated editing compared to MPXV genomes collected earlier. It is unclear whether these single-nucleotide polymorphisms (SNPs) result from APOBEC3-induced editing or are a consequence of genetic drift within one or more MPXV animal reservoirs. We develop a simple method based on a generalization of the General-Time-Reversible model to show that the observed SNPs are likely the result of APOBEC3-induced editing. The statistical features allow us to extract lineage information and estimate evolutionary events.

The role of APOBEC3-induced mutations in the differential evolution of monkeypox virus

Recent studies show that newly sampled monkeypox virus (MPXV) genomes exhibit mutations consistent with Apolipoprotein B mRNA Editing Catalytic Polypeptide-like3 (APOBEC3)-mediated editing, compared to MPXV genomes collected earlier. It is unclear whether these single nucleotide polymorphisms (SNPs) result from APOBEC3-induced editing or are a consequence of genetic drift within one or more MPXV animal reservoirs. We develop a simple method based on a generalization of the General-Time-Reversible (GTR) model to show that the observed SNPs are likely the result of APOBEC3-induced editing. The statistical features allow us to extract lineage information and estimate evolutionary events.

DNA repair pathways in breast cancer: from mechanisms to clinical applications

BACKGROUND

Breast cancer (BC) is a complex disease with various subtypes and genetic alterations that impact DNA repair pathways. Understanding these pathways is essential for developing effective treatments and improving patient outcomes.

AREA COVERED

This study investigates the significance of DNA repair pathways in breast cancer, specifically focusing on various pathways such as nucleotide excision repair, base excision repair, mismatch repair, homologous recombination repair, non-homologous end joining, fanconi anemia pathway, translesion synthesis, direct repair, and DNA damage tolerance. The study also examines the role of these pathways in breast cancer resistance and explores their potential as targets for cancer treatment.

CONCLUSION

Recent advances in targeted therapies have shown promise in exploiting DNA repair pathways for BC treatment. However, much research is needed to improve the efficacy of these therapies and identify new targets. Additionally, personalized treatments that target specific DNA repair pathways based on tumor subtype or genetic profile are being developed. Advances in genomics and imaging technologies can potentially improve patient stratification and identify biomarkers of treatment response. However, many challenges remain, including toxicity, resistance, and the need for more personalized treatments. Continued research and development in this field could significantly improve BC treatment.

Preventive Effect of Pharmaceutical Phytochemicals Targeting the Src Family of Protein Tyrosine Kinases and Aryl Hydrocarbon Receptor on Environmental Stress-Induced Skin Disease

The skin protects our body; however, it is directly exposed to the environment and is stimulated by various external factors. Among the various environmental factors that can threaten skin health, the effects of ultraviolet (UV) and particulate matter (PM) are considered the most notable. Repetitive exposure to ultraviolet and particulate matter can cause chronic skin diseases such as skin inflammation, photoaging, and skin cancer. The abnormal activation of the Src family of protein tyrosine kinases (SFKs) and the aryl hydrocarbon receptor (AhR) in response to UV and/or PM exposure are involved in the development and aggravation of skin diseases. Phytochemicals, chemical compounds of natural plants, exert preventive effects on skin diseases through the regulation of various signaling pathways. Therefore, this review aims to highlight the efficacy of phytochemicals as potential nutraceuticals and pharmaceutical materials for the treatment of skin diseases, primarily by targeting SFK and AhR, and to explore the underlying mechanisms of action. Future studies are essential to validate the clinical potential for the prevention and treatment of skin diseases.

DNA damage and somatic mutations in mammalian cells after irradiation with a nail polish dryer

Ultraviolet A light is commonly emitted by UV-nail polish dryers with recent reports suggesting that long-term use may increase the risk for developing skin cancer. However, no experimental evaluation has been conducted to reveal the effect of radiation emitted by UV-nail polish dryers on mammalian cells. Here, we show that irradiation by a UV-nail polish dryer causes high levels of reactive oxygen species, consistent with 8-oxo-7,8-dihydroguanine damage and mitochondrial dysfunction. Analysis of somatic mutations reveals a dose-dependent increase of C:G>A:T substitutions in irradiated samples with mutagenic patterns similar to mutational signatures previously attributed to reactive oxygen species. In summary, this study demonstrates that radiation emitted by UV-nail polish dryers can both damage DNA and permanently engrave mutations on the genomes of primary mouse embryonic fibroblasts, human foreskin fibroblasts, and human epidermal keratinocytes.

Construction of Prognostic Risk Model of Patients with Skin Cutaneous Melanoma Based on TCGA-SKCM Methylation Cohort

Skin cutaneous melanoma (SKCM) is a common malignant skin cancer. Early diagnosis could effectively reduce SKCM patient's mortality to a large extent. We managed to construct a model to examine the prognosis of SKCM patients. The methylation-related data and clinical data of The Cancer Gene Atlas- (TCGA-) SKCM were downloaded from TCGA database. After preprocessing the methylation data, 21,861 prognosis-related methylated sites potentially associated with prognosis were obtained using the univariate Cox regression analysis and multivariate Cox regression analysis. Afterward, unsupervised clustering was used to divide the patients into 4 clusters, and weighted correlation network analysis (WGCNA) was applied to construct coexpression modules. By overlapping the CpG sites between the clusters and turquoise model, a prognostic model was established by LASSO Cox regression and multivariate Cox regression. It was found that 9 methylated sites included cg01447831, cg14845689, cg20895058, cg06506470, cg09558315, cg06373660, cg17737409, cg21577036, and cg22337438. After constructing the prognostic model, the performance of the model was validated by survival analysis and receiver operating characteristic (ROC) curve, and the independence of the model was verified by univariate and multivariate regression. It was represented that the prognostic model was reliable, and riskscore could be used as an independent prognostic factor in SKCM patients. At last, we combined clinical data and patient's riskscore to establish and testify the nomogram that could determine patient's prognosis. The results found that the reliability of the nomogram was relatively good. All in all, we constructed a prognostic model that could determine the prognosis of SKCM patients and screened 9 key methylated sites through analyzing data in TCGA-SKCM dataset. Finally, a prognostic nomogram was established combined with clinical diagnosed information and riskscore. The results are significant for improving the prognosis of SKCM patients in the future.

Mitotic Activation Around Wound Edges and Epithelialization Repair in UVB-Induced Capsular Cataracts

Purpose

Ultraviolet B (UVB) has been well documented to induce capsular cataracts; however, the mechanism of the lens epithelial cell-mediated repair process after UVB irradiation is not fully understood. The purpose of this study was to better understand lens epithelial cell repair after UVB-induced epithelium damage.

Method

C57BL/6J mice were irradiated by various doses of UVB. Lens morphology and lens capsule opacity were monitored by slit lamp, darkfield microscopy, and phase-contrast microscopy. Lens epithelial cell mitotic activation and cell apoptosis were measured by immunohistochemistry. Lens epithelial ultrastructure was analyzed by transmission electron microscopy.

Results

UVB irradiation above a dose of 2.87 kJ/m2 triggered lens epithelial cell apoptosis and subcapsular cataract formation, with a ring-shaped structure composed of multilayered epithelial cell clusters manifesting a dense ring-shaped capsular cataract. The epithelial cells immediately outside the edge of the ring-shaped aggregates transitioned to mitotically active cells and performed wound healing through the epithelialization process. However, repairs ceased when lens epithelial cells made direct contact, and scar-like tissue in the center of the anterior capsule remained even by 6 months after UVB irradiation.

Conclusions

Our present study demonstrates that normally quiescent lens epithelial cells can be reactivated for epithelialization repair in response to UV-induced damage.

The link of ERCC2 rs13181 and ERCC4 rs2276466 polymorphisms with breast cancer in the Bangladeshi population

BACKGROUND

Breast cancer (BC) is the most common disease in women and the leading cause of death from cancer globally. Epidemiological studies examined that nucleotide excision repair genes ERCC2 (rs13181) and ERCC4 (rs2276466) SNPs might increase cancer risk. Based on the previous investigation, this study was conducted to explore the correlation between these polymorphisms and BC susceptibility in Bangladeshi women.

METHODS AND RESULTS

Between January 2019 and January 2020, 140 blood samples were collected from female patients histologically diagnosed with BC, and 111 female controls were recruited from non-cancer subjects. Genotyping was performed applying the PCR-RFLP method, and all statistical analyzes were conducted using SPSS, version 25.0. Comparison of characteristics and clinicopathological features between ERCC2 rs13181 and ERCC4 rs2276466 carriers and non-carriers showed no significant link with BC. Analysis of ERCC2 rs13181 with the risk of BC showed that the GG genotype and G allele carriers showed a fourfold and 1.78-fold higher risk (OR 4.00, P = 0.001 and OR 1.78, P = 0.002) that are statistically significant. In addition, the patients with combined TG+GG genotype revealed a 2.09-fold increased chance (OR 2.09, P = 0.020) BC development. Analysis of recessive model (GG vs. TT+TG) also depicted 2.74-times significantly higher risk (OR 2.74, P = 0.002). On the other hand, ERCC4 rs2276466 polymorphism did not show any significant association with BC (P > 0.05).

CONCLUSIONS

Our findings show that ERCC2 rs13181 is linked to an elevated risk of BC. Our study also shows that ERCC4 rs2276466 polymorphism has no substantial risk of BC in the Bangladeshi population.

Recent Advances in Phenolic Metabolites and Skin Cancer

Skin cancer represents any tumor development from the cutaneous structures within the epidermis, dermis or subcutaneous tissue, and is considered to be the most prevalent type of cancer. Compared to other types of cancer, skin cancer is proven to have a positive growth rate of prevalence and mortality. There are available various treatments, including chemotherapy, immunotherapy, radiotherapy and targeted therapy, but because of the multidrug resistance development, a low success has been registered. By this, the importance of studying naturally occurring compounds that are both safe and effective in the chemoprevention of skin cancer is emphasized. This review focuses on melanoma because it is the deadliest form of skin cancer, with a significantly increasing incidence in the last decades. As chemopreventive agents, we present polyphenols and their antioxidant activity, anti-inflammatory effect, their ability to balance the cell cycle and to induce apoptosis and their various other effects on skin melanoma. Besides chemoprevention, studies suggest that polyphenols can have treating abilities in some conditions. The limitations of using polyphenols are also pointed out, which are related to their poor bioavailability and stability, but as the technology is well developed, it is possible to augment the efficacy of polyphenols in the case of melanoma.

Conjunctival melanoma: New insights in tumour genetics and immunology, leading to new therapeutic options

Recent developments in oncology have led to a better molecular and cellular understanding of cancer, and the introduction of novel therapies. Conjunctival melanoma (CoM) is a rare but potentially devastating disease. A better understanding of CoM, leading to the development of novel therapies, is urgently needed. CoM is characterized by mutations that have also been identified in cutaneous melanoma, e.g. in BRAF, NRAS and TERT. These mutations are distinct from the mutations found in uveal melanoma (UM), affecting genes such as GNAQ, GNA11, and BAP1. Targeted therapies that are successful in cutaneous melanoma may therefore be useful in CoM. A recent breakthrough in the treatment of patients with metastatic cutaneous melanoma was the development of immunotherapy. While immunotherapy is currently sparsely effective in intraocular tumours such as UM, the similarities between CoM and cutaneous melanoma (including in their immunological tumour micro environment) provide hope for the application of immunotherapy in CoM, and preliminary clinical data are indeed emerging to support this use. This review aims to provide a comprehensive overview of the current knowledge regarding CoM, with a focus on the genetic and immunologic understanding. We elaborate on the distinct position of CoM in contrast to other types of melanoma, and explain how new insights in the pathophysiology of this disease guide the development of new, personalized, treatments.

2-acetylphenothiazine protects L929 fibroblasts against UVB-induced oxidative damage

Ultraviolet B (UVB) light corresponds to 5% of ultraviolet radiation. It is more genotoxic and mutagenic than UVA and causes direct and indirect cellular damage through the generation of reactive oxygen species (ROS). Even after radiation, ROS generation may continue through activation of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) enzyme. Long-term exposure can progress to premature skin aging and photocarcinogenesis. To prevent damage that is caused by UVB radiation, several studies have focused on the topical administration of compounds that have antioxidant properties. 2-Acetylphenothiazine (ML171) is a potent and selective inhibitor of NOX1. The present study investigated the antioxidant potential and photoprotective ability of ML171 in UVB-irradiated L929 fibroblasts. ML171 had considerable antioxidant activity in both the DPPH^• and xanthine/luminol/xanthine oxidase assays. ML171 did not induce cytotoxicity in L929 fibroblasts and increased the viability of UVB-irradiated cells. ML171 also inhibited ROS production, the enzymatic activity of NOX, depolarization of the mitochondrial membrane, and DNA damage. Additionally, ML171 protected cell membrane integrity and induced fibroblast migration. These results suggest that the incorporation of ML171 in topical administration systems may be a promising strategy to mitigate UVB-induced oxidative damage in L929 fibroblasts.

Chromosomal abnormalities and dysregulated DNA repair gene expression in farmers exposed to pesticides

Exposure to pesticides is considered a major factor underlying increased risk of hematological disorders in agricultural workers due to its carcinogenic potential. However, genotoxic impact of pesticides in DNA integrity of bone marrow stem cells (BMSC) of farmers exposed is not yet well known. We evaluated presence of chromosomal abnormalities (CA) and mRNA expression of DNA repair targets (ATM, BRCA1, BRCA2, RAD51, XRCC5, XRCC6, LIG4, CSA, CSB, XPA, XPC, XPG) in 90 bone marrow samples of farmers divided into three groups: commercial farming (CF), family farming (FF) and organic farming (OF). Our results showed that farmers in CF (72.7 %) and FF (27.3 %) groups had significantly higher values of CA when compared to OF group (0.0 %; p = 0.003). CF showed lower XPG (p = 0.008), CSA (p < 0.001), ATM (p = 0.036) and LIG4 (p = 0.004) mRNA expression than OF. FF presented lower XPG (p = 0.012) and LIG4 (p = 0.004) expression than OF. CF + FF individual with ≥12 years of exposure to pesticides showed decreased mRNA expression of XPC (p = 0.001), XPG (p = 0.010), CSB (p = 0.05), ATM (p = 0.030) and LIG4 (p = 0.044) than those who have been exposed for <12 years. CF + FF with CA showed a lower expression of BRCA2 when compared to CF + FF group without CA (p = 0.007). These results highlight that genotoxic exposure to pesticides negatively affects expression profile of important DNA repair genes in BMSC, favoring irreparable chromosomal lesions.

The deacetylase SIRT6 promotes the repair of UV-induced DNA damage by targeting DDB2

The NAD+-dependent deacetylase and mono-ADP-ribosyl transferase SIRT6 stabilizes the genome by promoting DNA double strand break repair, thereby acting as a tumor suppressor. However, whether SIRT6 regulates nucleotide excision repair (NER) remains unknown. Here, we showed that SIRT6 was recruited to sites of UV-induced DNA damage and stimulated the repair of UV-induced DNA damage. Mechanistic studies further indicated that SIRT6 interacted with DDB2, the major sensor initiating global genome NER (GG-NER), and that the interaction was enhanced upon UV irradiation. SIRT6 deacetylated DDB2 at two lysine residues, K35 and K77, upon UV stress and then promoted DDB2 ubiquitination and segregation from chromatin, thereby facilitating downstream signaling. In addition, we characterized several SIRT6 mutations derived from melanoma patients. These SIRT6 mutants ablated the stimulatory effect of SIRT6 on NER and destabilized the genome due to (i) partial loss of enzymatic activity (P27S or H50Y), (ii) a nonsense mutation (R150*) or (iii) high turnover rates (G134W). Overall, we demonstrate that SIRT6 promotes NER by deacetylating DDB2, thereby preventing the onset of melanomagenesis.

Integrating DNA damage response and autophagy signalling axis in ultraviolet-B induced skin photo-damage: a positive association in protecting cells against genotoxic stress

The skin acts as both physical as well as an immunological barrier against hazardous agents from the outside environment and protects the internal organs against damage. Skin ageing is a dynamic process caused by the influence of various external factors, including damage from ultraviolet (UV-B) radiation, which is known as photo-ageing, and due to internal chronological mechanisms. A normal ageing process requires several orchestrated defense mechanisms to diverse types of stress responses, the concomitant renewal of cellular characteristics, and the homeostasis of different cell types that directly or indirectly protect the integrity of skin. Cumulative oxidative and endoplasmic reticulum (ER) stress responses and their adverse impact on biological systems in the skin are a common mechanism of the ageing process, negatively impacting DNA by causing mutations that lead to many physiological, functional, and aesthetic changes in the skin, culminating in the development of many diseases, including photo-damage and photo-carcinogenesis. Exposure of the skin to ultraviolet-(B) elicits the activation of signal transduction pathways, including DNA damage response, autophagy, and checkpoint signal adaptations associated with clearing radiation-induced DNA damage. Recent experimental reports suggest that autophagy is involved in maintaining skin homeostasis upon encountering different stresses, notably genotoxic stress. It has also been revealed that autophagy positively regulates the recognition of DNA damage by nucleotide excision repair and that skin ageing is associated with defects in the autophagy process. Moreover, autophagy is constitutively active in the skin epithelium, imparting protection to skin cells against a diverse range of outside insults, thus increasing resistance to environmental stressors. It has also been found that the stress-induced suppression of the autophagy response in experimental settings leads to enhanced apoptosis during photo-ageing upon UV-B exposure and that the maintenance of homeostasis depends on cellular autophagy levels. More recent reports in this domain claim that relieving the oxidative-stress-mediated induction of the ER stress response upon UV-B irradiation protects skin cells from photo-damage effects. The integration of autophagy and the DNA damage response under genotoxic stress is being considered as a meaningful partnership for finding novel molecular targets and devising suitable therapeutic strategies against photo-ageing disorders. Here, we summarize and review the current understanding of the mechanisms governing the intricate interplay between autophagy and the DNA damage response and its regulation by UV-B, the roles of autophagy in regulating the cellular response to UV-B-induced photodamage, and the implications of the modulation of autophagy as a meaningful partnership in the treatment and prevention of photoaging disorders.

Cellular damage, including wounding, drives C. elegans stress-induced sleep

Across animal phyla, sleep is associated with increased cellular repair, suggesting that cellular damage may be a core component of sleep pressure. In support of this notion, sleep in the nematode Caenorhabditis elegans can be triggered by damaging conditions, including noxious heat, high salt, and ultraviolet light exposure. It is not clear, however, whether this stress-induced sleep (SIS) is a direct consequence of cellular damage, or of a resulting energy deficit, or whether it is triggered simply by the sensation of noxious conditions. Here, we show that thermosensation is dispensable for heat-induced sleep, that osmosensation is dispensable for salt-induced sleep, and that wounding is also a sleep trigger, together indicating that SIS is not triggered by sensation of noxious environments. We present evidence that genetic variation in cellular repair pathways impacts sleep amount, and that SIS involves systemic monitoring of cellular damage. We show that the low-energy sensor AMP-activated protein kinase (AMPK) is not required for SIS, suggesting that energy deficit is not the primary sleep trigger. Instead, AMPK-deficient animals display enhanced SIS responses, and pharmacological activation of AMPK reduces SIS, suggesting that ATP-dependent repair of cellular damage mitigates sleep pressure.

Induction of Autophagy by Baicalin Through the AMPK-mTOR Pathway Protects Human Skin Fibroblasts from Ultraviolet B Radiation-Induced Apoptosis

Background

Baicalin, a natural product isolated from Scutellaria radix, has been reported to exert anti-oxidant and anti-apoptotic effects on skin, but the underlying mechanism remains poorly understood. This study aimed to investigate the possible mechanism of anti-UVB effect of baicalin in human skin fibroblasts.

Methods

Cell proliferation was estimated by CCK-8 Kit. Apoptotic incidence was detected by flow cytometry with Annexin V-PE/PI apoptosis detection kit. Autophagy was determined by the evaluation of fluorescent LC3 puncta and Western blotting. Cell signalling was analysed by Western blotting.

Results

Baicalin exerted cytoprotective effects in UVB-induced HSFs. Moreover, baicalin increased autophagy and suppressed UVB-induced apoptosis of HSFs. Pretreatment with 3-MA, an autophagy inhibitor, attenuated baicalin-induced HSFs autophagy and promoted apoptosis. Baicalin activated AMPK, which leads to suppression of basal mTOR activity in cultured HSFs. Administration of compound C, an AMPK inhibitor, abrogated AMPK phosphorylation and increased mTOR phosphorylation and apoptosis compared with baicalin alone.

Conclusion

Taken together, these results indicate the important role of mTOR inhibition in UVB protection by baicalin and provide a new target and strategy for better prevention of UV-induced skin disorders.

Supplementation with 5-formyltetrahydrofolate alleviates ultraviolet B-inflicted oxidative damage in folate-deficient zebrafish

Ultraviolet (UV) is an omnipresent environmental carcinogen transmitted by sunlight. Excessive UV irradiation has been correlated to an increased risk of skin cancers. UVB, the most mutagenic component among the three UV constituents, causes damage mainly through inducing DNA damage and oxidative stress. Therefore, strategies or nutrients that strengthen an individual's resistance to UV-inflicted harmful effects shall be beneficial. Folate is a water-soluble B vitamin essential for nucleotides biosynthesis, and also a strong biological antioxidant, hence a micronutrient with potential of modulating individual's vulnerability to UV exposure. In this study, we investigated the impact of folate status on UV sensitivity and the protective activity of folate supplementation using a zebrafish model. Elevated reactive oxygen species (ROS) level and morphological injury were observed in the larvae exposed to UVB, which were readily rescued by supplementing with folic acid, 5-formyltetrahydrofolate (5-CHO-THF) and N-acetyl-L-cysteine (NAC). The UVB-inflicted abnormalities and mortality were worsened in Tg(hsp:EGFP-γGH) larvae displaying folate deficiency. Intriguingly, only supplementation with 5-CHO-THF, as opposed to folic acid, offered significant and consistent protection against UVB-inflicted oxidative damage in the folate-deficient larvae. We concluded that the intrinsic folate status correlates with the vulnerability to UVB-induced damage in zebrafish larvae. In addition, 5-CHO-THF surpassed both folic acid and NAC in preventing UVB-inflicted oxidative stress and injury in our current experimental zebrafish model.

Dietary compounds and cutaneous malignant melanoma: recent advances from a biological perspective

Cutaneous malignant melanoma is a heterogeneous disease, being the consequence of specific genetic alterations along several molecular pathways. Despite the increased knowledge about the biology and pathogenesis of melanoma, the incidence has grown markedly worldwide, making it extremely important to develop preventive measures. The beneficial role of correct nutrition and of some natural dietary compounds in preventing malignant melanoma has been widely demonstrated. This led to numerous studies investigating the role of several dietary attitudes, patterns, and supplements in the prevention of melanoma, and ongoing research investigates their impact in the clinical management and outcomes of patients diagnosed with the disease. This article is an overview of recent scientific advances regarding specific dietary compounds and their impact on melanoma development and treatment.

Extensive loss of cell-cycle and DNA repair genes in an ancient lineage of bipolar budding yeasts

Cell-cycle checkpoints and DNA repair processes protect organisms from potentially lethal mutational damage. Compared to other budding yeasts in the subphylum Saccharomycotina, we noticed that a lineage in the genus Hanseniaspora exhibited very high evolutionary rates, low Guanine-Cytosine (GC) content, small genome sizes, and lower gene numbers. To better understand Hanseniaspora evolution, we analyzed 25 genomes, including 11 newly sequenced, representing 18/21 known species in the genus. Our phylogenomic analyses identify two Hanseniaspora lineages, a faster-evolving lineage (FEL), which began diversifying approximately 87 million years ago (mya), and a slower-evolving lineage (SEL), which began diversifying approximately 54 mya. Remarkably, both lineages lost genes associated with the cell cycle and genome integrity, but these losses were greater in the FEL. E.g., all species lost the cell-cycle regulator WHIskey 5 (WHI5), and the FEL lost components of the spindle checkpoint pathway (e.g., Mitotic Arrest-Deficient 1 [MAD1], Mitotic Arrest-Deficient 2 [MAD2]) and DNA-damage-checkpoint pathway (e.g., Mitosis Entry Checkpoint 3 [MEC3], RADiation sensitive 9 [RAD9]). Similarly, both lineages lost genes involved in DNA repair pathways, including the DNA glycosylase gene 3-MethylAdenine DNA Glycosylase 1 (MAG1), which is part of the base-excision repair pathway, and the DNA photolyase gene PHotoreactivation Repair deficient 1 (PHR1), which is involved in pyrimidine dimer repair. Strikingly, the FEL lost 33 additional genes, including polymerases (i.e., POLymerase 4 [POL4] and POL32) and telomere-associated genes (e.g., Repressor/activator site binding protein-Interacting Factor 1 [RIF1], Replication Factor A 3 [RFA3], Cell Division Cycle 13 [CDC13], Pbp1p Binding Protein [PBP2]). Echoing these losses, molecular evolutionary analyses reveal that, compared to the SEL, the FEL stem lineage underwent a burst of accelerated evolution, which resulted in greater mutational loads, homopolymer instabilities, and higher fractions of mutations associated with the common endogenously damaged base, 8-oxoguanine. We conclude that Hanseniaspora is an ancient lineage that has diversified and thrived, despite lacking many otherwise highly conserved cell-cycle and genome integrity genes and pathways, and may represent a novel, to our knowledge, system for studying cellular life without them.

Macroenvironment-gene-microenvironment interactions in ultraviolet radiation-induced melanomagenesis

Cutaneous malignant melanoma is one of the few major cancers that continue to exhibit a positive rate of increase in the developed world. A wealth of epidemiological data has undisputedly implicated ultraviolet radiation (UVR) from sunlight and artificial sources as the major risk factor for melanomagenesis. However, the molecular mechanisms of this cause-and-effect relationship remain murky and understudied. Recent efforts on multiple fronts have brought unprecedented expansion of our knowledge base on this subject and it is now clear that melanoma is caused by a complex interaction between genetic predisposition and environmental exposure, primarily to UVR. Here we provide an overview of the effects of the macroenvironment (UVR) on the skin microenvironment and melanocyte-specific intrinsic (mostly genetic) landscape, which conspire to produce one of the deadliest malignancies.

Draft Genome Sequence of the UV-Resistant Antarctic Bacterium Sphingomonas sp. Strain UV9

We report the draft genome sequence of the Antarctic UV-resistant bacterium Sphingomonas sp. strain UV9. The strain has a genome size of 4.25 Mb, a 65.62% GC content, and 3,879 protein-coding sequences.

We report the draft genome sequence of the Antarctic UV-resistant bacterium Sphingomonas sp. strain UV9. The strain has a genome size of 4.25 Mb, a 65.62% GC content, and 3,879 protein-coding sequences. Among others, genes encoding the resolving of the DNA damage produced by the UV irradiation were identified.

DNA Damage and Deficiencies in the Mechanisms of Its Repair: Implications in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a perplexing and potentially severe disease, the pathogenesis of which is yet to be understood. SLE is considered to be a multifactorial disease, in which genetic factors, immune dysregulation, and environmental factors, such as ultraviolet radiation, are involved. Recently, the description of novel genes conferring susceptibility to develop SLE even in their own (monogenic lupus) has raised the interest in DNA dynamics since many of these genes are linked to DNA repair. Damage to DNA induces an inflammatory response and eventually triggers an immune response, including those targeting self-antigens. We review the evidence that indicates that patients with SLE present higher levels of DNA damage than normal subjects do and that several proteins involved in the preservation of the genomic stability show polymorphisms, some of which increase the risk for SLE development. Also, the experience from animal models reinforces the connection between DNA damage and defective repair in the development of SLE-like disease including characteristic features such as anti-DNA antibodies and nephritis. Defining the role of DNA damage response in SLE pathogenesis might be strategic in the quest for novel therapies.

Mediator MED23 Links Pigmentation and DNA Repair through the Transcription Factor MITF

DNA repair is related to many physiological and pathological processes, including pigmentation. Little is known about the role of the transcriptional cofactor Mediator complex in DNA repair and pigmentation. Here, we demonstrate that Mediator MED23 plays an important role in coupling UV-induced DNA repair to pigmentation. The loss of Med23 specifically impairs the pigmentation process in melanocyte-lineage cells and in zebrafish. Med23 deficiency leads to enhanced nucleotide excision repair (NER) and less DNA damage following UV radiation because of the enhanced expression and recruitment of NER factors to chromatin for genomic stability. Integrative analyses of melanoma cells reveal that MED23 controls the expression of a melanocyte master regulator, Mitf, by modulating its distal enhancer activity, leading to opposing effects on pigmentation and DNA repair. Collectively, the Mediator MED23/MITF axis connects DNA repair to pigmentation, thus providing molecular insights into the DNA damage response and skin-related diseases.

Phycocyanin Protects Against UVB-induced Apoptosis Through the PKC α/βII-Nrf-2/HO-1 Dependent Pathway in Human Primary Skin Cells

Phycocyanin (Pc) is one of the active pigment constituents of Spirulina microalgae. It has been used for its potent antioxidant and anti-inflammatory properties. However, the protective effects of Pc against ultraviolet-B (UVB)-induced primary skin cells damage are still undefined. In the present study, we investigated whether Pc prevented UVB-induced apoptotic cell death in human dermal fibroblasts (HDF) and human epidermal keratinocytes (HEK). Pc induced the transcription of heme oxygenase-1 (HO-1). Furthermore, Pc treatments resulted in a marked increase in nuclear factor erythroid-derived 2 (NF-E2)-like 2 (Nrf-2) nuclear translocation. Also, Pc protected UVB induced apoptosis and reduced the p53 and Bax levels, as well as caspase-3 activation. Pc treatment showed a significantly enhanced effect on the phosphorylation of protein kinase C (PKC) α/β II, but not that of p38 mitogen-activated protein kinase (MAPK) or Akt. Induction of HO-1 induced by Pc was suppressed by Go6976, a selective inhibitor of PKC α/β II. In addition, knockdown of HO-1 by small interfering (siRNA) caused a significant increase in poly (ADP-ribose) polymerase 1 (PARP-1) cleavage and caspase-3 activation after Pc pretreatment. Taken together, our results demonstrate that Pc-induced expression of HO-1 is mediated by the PKC α/β II-Nrf-2/HO-1 pathway, and inhibits UVB-induced apoptotic cell death in primary skin cells.

Hydrogen gas mediates ascorbic acid accumulation and antioxidant system enhancement in soybean sprouts under UV-A irradiation

The soybean sprout is a nutritious and delicious vegetable that is rich in ascorbic acid (AsA). Hydrogen gas (H2) may have potential applications in the vegetable processing industry. To investigate whether H2 is involved in the regulation of soybean sprouts AsA biosynthesis under UV irradiation, we set 4 different treatments: white light(W), W+HRW, UV-A and UV-A+HRW. The results showed that H2 significantly blocked the UV-A-induced accumulation of ROS, decreased TBARS content and enhanced SOD and APX activity in soybean sprouts. We also observed that the UV-A induced accumulation of AsA was enhanced more intensely when co-treated with HRW. Molecular analyses showed that UV-A+HRW significantly up-regulated AsA biosynthesis and recycling genes compared to UV-A in soybean sprouts. These data demonstrate that the H2 positively regulates soybean sprouts AsA accumulation under UV-A and that this effect is mediated via the up-regulation of AsA biosynthesis and recycling genes.

Autophagy in UV Damage Response

UV radiation exposure from sunlight and artificial tanning beds is the major risk factor for the development of skin cancer and skin photoaging. UV-induced skin damage can trigger a cascade of DNA damage response signaling pathways, including cell cycle arrest, DNA repair and, if damage is irreparable, apoptosis. Compensatory proliferation replaces the apoptotic cells to maintain skin barrier integrity. Disruption of these processes can be exploited to promote carcinogenesis by allowing the survival and proliferation of damaged cells. UV radiation also induces autophagy, a catabolic process that clears unwanted or damaged proteins, lipids and organelles. The mechanisms by which autophagy is activated following UV exposure, and the functions of autophagy in UV response, are only now being clarified. Here, we summarize the current understanding of the mechanisms governing autophagy regulation by UV, the roles of autophagy in regulating cellular response to UV-induced photodamage and the implications of autophagy modulation in the treatment and prevention of photoaging and skin cancer.

Apigenin prevents ultraviolet-B radiation induced cyclobutane pyrimidine dimers formation in human dermal fibroblasts

Exposure to solar ultraviolet-B (UVB) radiation leads to the formation of cyclobutane pyrimidine dimers (CPDs). We investigated the protective effect of apigenin against UVB-induced CPDs formation in human dermal fibroblasts cells (HDFa). For this purpose, HDFa cells were treated with apigenin (15μM) prior to UVB irradiation (20mJ/cm²); DNA damage and subsequent molecular end points were observed. Exposure to UVB radiation increased significant CPDs formation in HDFa cells and the frequencies of CPDs were reduced by treatment with apigenin (15μM). UVB-induced CPDs downregulates the expression of nucleotide excision repair (NER) genes such as xeroderma pigmentosum complementation group C, B, G and F (XPC, XPB, XPG and XPF), transcription factor II human (TFIIH) and excision repair cross-complementation group 1 (ERCC1) in HDFa cells. Conversely, apigenin treatment restored UVB-induced loss of NER proteins in HDFa cells, which indicates its preventive effect against CPDs formation. Besides, single low dose UVB-exposure induced nuclear fragmentation, apoptotic frequency and apoptotic proteins expression (Bax and Caspase-3) have been prevented by the apigenin pretreatment. Furthermore, apigenin exhibits strong UV absorbance property and showed 10.08 SPF value. Thus, apigenin can protect skin cells against UVB-induced CPDs formation probably through its sunscreen effect. Hence, apigenin can be considered as an effective protective agent against UV induced skin damages.

Photo-enzymatic repair of UVB-induced DNA damage in the two-spotted spider mite Tetranychus urticae

Ambient ultraviolet-B (UVB) radiation induces lethal effects in the two-spotted spider mite Tetranychus urticae, whereas photoreactivation by irradiation with ultraviolet-A and visible light (VIS) plays an important role to increase survival of mites irradiated by UVB. The physiological mechanisms and ecological significance of photoreactivation in terrestrial arthropods have not been shown clearly. We verified the biological impact and accumulation of DNA lesions by UVB irradiation and the repair of them by photoreactivation in T. urticae larvae. Survival of UVB-irradiated larvae decreased with increasing UVB dose, but recovered remarkably with VIS exposure after UVB irradiation (photoreactivation). The DNA lesions, cyclobutane pyrimidine dimers (CPDs) and 6-4 pyrimidine-pyrimidine photoproducts (6-4PPs) linearly increased with the UVB dose. The CPDs were repaired after exposure to VIS, whereas the frequency of 6-4PPs was unaffected by VIS; CPD photolyase genes, but not (6-4) photolyase genes, have been found in the T. urticae genome. Therefore, DNA damage and CPD photo enzymatic repair (PER) is significant for survival in this mite under ambient UVB radiation. Unexpectedly, gene expression of CPD photolyase was unaffected by irradiation with UVB and VIS. Instead, expression of xeroderma pigmentosum A (XPA) was increased by irradiation. XPA is a core factor in nucleotide excision repair (NER), which is a repair system unrelated to photo energy. The relationship between gene expression and enzymatic repair remains unclear. To elucidate the PER process in T. urticae, further study will be necessary on the gene expression patterns and molecular functions of CPD photolyase in PER and of XPA in NER.

Significance of the Melanocortin 1 and Endothelin B Receptors in Melanocyte Homeostasis and Prevention of Sun-Induced Genotoxicity

The membrane bound melanocortin 1 receptor (MC1R), and the endothelin B receptor (ENDBR) are two G-protein coupled receptors that play important roles in constitutive regulation of melanocytes and their response to ultraviolet radiation (UVR), the main etiological factor for melanoma. The human MC1R is a G_s protein-coupled receptor, which is activated by its agonists α-melanocyte stimulating hormone (α-melanocortin; α-MSH) and adrenocorticotropic hormone (ACTH). The ENDBR is a G_q coupled-receptor, which is activated by Endothelin (ET)-3 during embryonic development, and ET-1 postnatally. Pigmentation and the DNA repair capacity are two major factors that determine the risk for melanoma. Activation of the MC1R by its agonists stimulates the synthesis of eumelanin, the dark brown photoprotective pigment. In vitro studies showed that α-MSH and ET-1 interact synergistically in the presence of basic fibroblast growth factor to stimulate human melanocyte proliferation and melanogenesis, and to inhibit UVR-induced apoptosis. An important function of the MC1R is reduction of oxidative stress and activation of DNA repair pathways. The human MC1R is highly polymorphic, and MC1R variants, particularly those that cause loss of function of the expressed receptor, are associated with increased melanoma risk independently of pigmentation. These variants compromise the DNA repair and antioxidant capacities of human melanocytes. Recently, activation of ENDBR by ET-1 was reported to reduce the induction and enhance the repair of UVR-induced DNA photoproducts. We conclude that α-MSH and ET-1 and their cognate receptors MC1R and ENDBR reduce the risk for melanoma by maintaining genomic stability of melanocytes via modulating the DNA damage response to solar UVR. Elucidating the response of melanocytes to UVR should improve our understanding of the process of melanomagenesis, and lead to effective melanoma chemoprevention, as well as therapeutic strategies.

A meta-analysis of XPC Lys939Gln polymorphism and melanoma susceptibility

BACKGROUND

It has been reported that polymorphisms of XPC Lys939Gln may affect the risk of melanom. However, the results have been inconsistent.We performed a comprehensive meta-analysis to determine the association between XPC Lys939Gln polymorphism and melanoma susceptibility.

METHODS

Based on comprehensive searches of the MEDLINE, EMBASE and ISI Web of knowledge, China National Knowledge Infrastructure (CNKI) and Wanfang Database, we identified eligible studies about the association between XPC Lys939Gln polymorphism and melanoma risk.

RESULTS

A total of 4631 cases and 5111 controls in studies were included in this meta-analysis. All studies were conducted in Caucasian populations. Allele model (Gln vs. Lys: P = 0.22; OR = 1.07, 95% CI = 0.96-1.18), and homozygous model (Gln/Gln vs. Lys/Lys: P = 0.66; OR = 1.03, 95% CI = 0.91-1.17) did not show increased risk of developing melanoma. Similarly, dominant model Gln/Gln and Gln/Lys vs. Lys/Lys: P = 0.07; OR = 1.17, 95% CI = 0.99-1.40) and recessive model (Gln/Gln vs. Gln/Lys and Lys/Lys: P = 0.67; OR = 1.03, 95% CI = 0.90-1.19) failed to show increased risk of developing melanoma.

CONCLUSION

Our pooled data suggest that there was no evidence for a major role of XPC Lys939Gln polymorphism in the pathogenesis of melanoma.

Protective Effect of Diphlorethohydroxycarmalol against Ultraviolet B Radiation-Induced DNA Damage by Inducing the Nucleotide Excision Repair System in HaCaT Human Keratinocytes

We investigated the protective properties of diphlorethohydroxycarmalol (DPHC), a phlorotannin, against ultraviolet B (UVB) radiation-induced cyclobutane pyrimidine dimers (CPDs) in HaCaT human keratinocytes. The nucleotide excision repair (NER) system is the pathway by which cells identify and repair bulky, helix-distorting DNA lesions such as ultraviolet (UV) radiation-induced CPDs and 6-4 photoproducts. CPDs levels were elevated in UVB-exposed cells; however, this increase was reduced by DPHC. Expression levels of xeroderma pigmentosum complementation group C (XPC) and excision repair cross-complementing 1 (ERCC1), which are essential components of the NER pathway, were induced in DPHC-treated cells. Expression of XPC and ERCC1 were reduced following UVB exposure, whereas DPHC treatment partially restored the levels of both proteins. DPHC also increased expression of transcription factor specificity protein 1 (SP1) and sirtuin 1, an up-regulator of XPC, in UVB-exposed cells. DPHC restored binding of the SP1 to the XPC promoter, which is reduced in UVB-exposed cells. These results indicate that DPHC can protect cells against UVB-induced DNA damage by inducing the NER system.

Ultraviolet Radiation-Induced Cytogenetic Damage in White, Hispanic and Black Skin Melanocytes: A Risk for Cutaneous Melanoma

Cutaneous Melanoma (CM) is a leading cause of cancer deaths, with reports indicating a rising trend in the incidence rate of melanoma among Hispanics in certain U.S. states. The level of melanin pigmentation in the skin is suggested to render photoprotection from the DNA-damaging effects of Ultraviolet Radiation (UVR). UVR-induced DNA damage leads to cytogenetic defects visualized as the formation of micronuclei, multinuclei and polymorphic nuclei in cells, and a hallmark of cancer risk. The causative relationship between Sun exposure and CM is controversial, especially in Hispanics and needs further evaluation. This study was initiated with melanocytes from White, Hispanic and Black neonatal foreskins which were exposed to UVR to assess their susceptibility to UVR-induced modulation of cellular growth, cytogenetic damage, intracellular and released melanin. Our results show that White and Hispanic skin melanocytes with similar levels of constitutive melanin are susceptible to UVR-induced cytogenetic damage, whereas Black skin melanocytes are not. Our data suggest that the risk of developing UVR-induced CM in a skin type is correlated with the level of cutaneous pigmentation and its ethnic background. This study provides a benchmark for further investigation on the damaging effects of UVR as risk for CM in Hispanics.