Polymorphisms in XPD (Asp312Asn and Lys751Gln) genes, sunburn and arsenic-related skin lesions

Systematic review on gene-sun exposure interactions in skin cancer

BACKGROUND

The risk of skin cancer is determined by environmental factors like ultraviolet radiation (UVR), personal habits like time spent outdoors and genetic factors. This review aimed to survey existing studies in gene-environment (GxE) interaction on skin cancer risk, and report on GxE effect estimates.

METHODS

We searched Embase, Medline (Ovid) and Web of Science (Core Collection) and included only primary research that reported on GxE on the risk of the three most common types of skin cancer: basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. Quality assessment followed the Newcastle-Ottawa Scale. Meta-analysis was not possible because no two studies examined the same interaction. This review was registered on PROSPERO (CRD42021238064).

RESULTS

In total 260 records were identified after exclusion of duplicates. Fifteen studies were included in the final synthesis-12 used candidate gene approach. We found some evidence of GxE interactions with sun exposure, notably, with MC1R, CAT and NOS1 genes in melanoma, HAL and IL23A in BCC and HAL and XRCC1 in SCC.

CONCLUSION

Sun exposure seems to interact with genes involved in pigmentation, oxidative stress and immunosuppression, indicating that excessive UV exposure might exhaust oxidative defence and repair systems differentially, dependent on genetic make-up. Further research is warranted to better understand skin cancer epidemiology and develop sun exposure recommendations. A genome-wide approach is recommended as it might uncover unknown disease pathways dependent on UV radiation.

GYY4137 Attenuates Sodium Deoxycholate-Induced Intestinal Barrier Injury Both In Vitro and In Vivo

Objectives

Substantial studies have demonstrated that an elevated concentration of deoxycholic acid (DCA) in the colonic lumen may play a critical role in the pathogenesis of intestinal barrier dysfunction and inflammatory bowel disease (IBD). The purpose of this study was to investigate the protective effects of GYY4137, as a novel and synthetic H₂S donor, on the injury of intestinal barrier induced by sodium deoxycholate (SDC) both in vivo and in vitro.

Methods

In this study, Caco-2 monolayers and mouse models with high SDC concentration in the lumen were used to study the effect of GYY4137 on intestinal barrier dysfunction induced by SDC and its underlying mechanisms.

Results

In Caco-2 monolayers, a short period of addition of SDC increased the permeability of monolayers obviously, changed distribution of tight junctions (TJs), and improved the phosphorylation level of myosin light chain kinase (MLCK) and myosin light chain (MLC). However, pretreatment with GYY4137 markedly ameliorated the SDC-induced barrier dysfunction. Being injected with GYY4137 could enable mice to resist the SDC-induced injury of the intestinal barrier. Besides, GYY4137 promoted the recovery of the body weight and intestinal barrier histological score of mice with the gavage of SDC. GYY4137 also attenuated the decreased expression level of TJs in mice treated with SDC.

Conclusion

Taken together, this research suggests that GYY4137 preserves the intestinal barrier from SDC-induced injury via suppressing the activation of P-MLCK-P-MLC2 signaling pathway and increasing the expression level of tight junctions.

Association between the ERCC2 Asp312Asn polymorphism and risk of cancer

Cancer is the leading cause of death in economically developed countries and the second leading cause of death in developing countries. The relationship between genetic polymorphisms and the risk of cancers has been widely researched. Excision repair cross-complementing group 2 (ERCC2) gene plays important roles in the nucleotide excision repair pathway. There is contrasting evidence on the association between the ERCC2 Asp312Asn polymorphism and the risk of cancer. We conducted a comprehensive meta-analysis in order to assess the correlation between these factors. We searched the PubMed, EMBASE, Science Direct, Web of Science, and CNKI databases for studies published from January 1, 2005 to January 1, 2016. Finally, 86 articles with 38,848 cases and 48,928 controls were included in the analysis. The overall analysis suggested a significant association between the ERCC2 Asp312Asn polymorphism and cancer risk. Furthermore, control source, ethnicity, genotyping method, and cancer type were used for subgroup analysis. The result of a trial sequential analysis indicated that the cumulative evidence is adequate; hence, further trials were unnecessary in the overall analysis for homozygote comparison. In summary, our results suggested that ERCC2 Asp312Asn polymorphism is associated with increased cancer risk. A significantly increased cancer risk was observed in Asian populations, but not in Caucasian populations. Furthermore, the ERCC2 Asp312Asn polymorphism is associated with bladder, esophageal, and gastric cancers, but not with breast, head and neck, lung, prostate, and skin cancers, and non-Hodgkin lymphoma. Further multi-center, well-designed studies are required to validate our results.

Individual susceptibility to arsenic-induced diseases: the role of host genetics, nutritional status, and the gut microbiome

Arsenic (As) contamination in water or food is a global issue affecting hundreds of millions of people. Although As is classified as a group 1 carcinogen and is associated with multiple diseases, the individual susceptibility to As-related diseases is highly variable, such that a proportion of people exposed to As have higher risks of developing related disorders. Many factors have been found to be associated with As susceptibility. One of the main sources of the variability found in As susceptibility is the variation in the host genome, namely, polymorphisms of many genes involved in As transportation, biotransformation, oxidative stress response, and DNA repair affect the susceptibility of an individual to As toxicity and then influence the disease outcomes. In addition, lifestyles and many nutritional factors, such as folate, vitamin C, and fruit, have been found to be associated with individual susceptibility to As-related diseases. Recently, the interactions between As exposure and the gut microbiome have been of particular concern. As exposure has been shown to perturb gut microbiome composition, and the gut microbiota has been shown to also influence As metabolism, which raises the question of whether the highly diverse gut microbiota contributes to As susceptibility. Here, we review the literature and summarize the factors, such as host genetics and nutritional status, that influence As susceptibility, and we also present potential mechanisms of how the gut microbiome may influence As metabolism and its toxic effects on the host to induce variations in As susceptibility. Challenges and future directions are also discussed to emphasize the importance of characterizing the specific role of these factors in interindividual susceptibility to As-related diseases.

Arsenic-induced promoter hypomethylation and over-expression of ERCC2 reduces DNA repair capacity in humans by non-disjunction of the ERCC2-Cdk7 complex

Arsenic in drinking water is of critical concern in West Bengal, India, as it results in several physiological symptoms including dermatological lesions and cancers. Impairment of the DNA repair mechanism has been associated with arsenic-induced genetic damage as well as with several cancers. ERCC2 (Excision Repair Cross-Complementing rodent repair, complementation group 2), mediates DNA-repair by interacting with Cdk-activating kinase (CAK) complex, which helps in DNA proof-reading during transcription. Arsenic metabolism alters epigenetic regulation; we tried to elucidate the regulation of ERCC2 in arsenic-exposed humans. Water, urine, nails, hair and blood samples from one hundred and fifty seven exposed and eighty eight unexposed individuals were collected. Dose dependent validation was done in vitro using HepG2 and HEK-293. Arsenic content in the biological samples was higher in the exposed individuals compared with the content in unexposed individuals (p < 0.001). Bisulfite-modified methylation specific PCR showed a significant (p < 0.0001) hypomethylation of the ERCC2 promoter in the arsenic-exposed individuals. Densitometric analysis of immunoblots showed a nearly two-fold increase in expression of ERCC2 in exposed individuals, but there was an enhanced genotoxic insult as measured by micronuclei frequency. Immuno-precipitation and western blotting revealed an increased (p < 0.001) association of Cdk7 with ERCC2 in highly arsenic exposed individuals. The decrease in CAK activity was determined by observing the intensity of Ser(392) phosphorylation in p53, in vitro, which decreased with an increase in arsenic dose. Thus we infer that arsenic biotransformation leads to promoter hypomethylation of ERCC2, which in turn inhibits the normal functioning of the CAK-complex, thus affecting DNA-repair; this effect was highest among the arsenic exposed individuals with dermatological lesions.

Xeroderma pigmentosum genes and melanoma risk

Xeroderma pigmentosum is a rare autosomal recessive disease that is associated with a severe deficiency in nucleotide excision repair. The presence of a distinct the nucleotide excision repair (NER) mutation signature in melanoma suggests that perturbations in this critical repair process are likely to be involved with disease risk. We hypothesized that persons with polymorphic NER gene(s) are likely to have reduced NER activity and are consequently at an increased risk of melanoma development. We assessed the association between 94 SNPs within seven XP genes (XPA-XPG) and the melanoma risk in the Polish population. We genotyped 714 unselected melanoma patients and 1,841 healthy adults to determine if there were any polymorphisms differentially represented in the disease group. We found that a significantly decreased risk of melanoma was associated with the Xeroderma pigmentosum complementation (XPC) rs2228000_CT genotype (odds ratio [OR] = 0.15; p < 0.001) and the rs2228000_TT genotype (OR = 0.11; p < 0.001) compared to the reference genotype. Haplotype analysis within XPC revealed the rs2228001_A + G1475A_G + G2061A_A + rs2228000_T + rs3731062_C haplotype (OR = 0.26; p < 0.05) was associated with a significantly decreased disease risk. The haplotype analysis within the Xeroderma pigmentosum group D (XPD) showed a modest association between two haplotypes and a decrease in melanoma risk. There were no major differences between the prevalence of the XP polymorphisms among young or older patients with melanoma. Linkage disequilibrium of XPC: rs2228001, G1475A, G2061A, rs2228000 and rs3731062 was found. The data from our study support the notion that only XPC and XPD genes are associated with melanoma susceptibility.

Functional polymorphisms in XRCC-1 and APE-1 contribute to increased apoptosis and risk of ulcerative colitis

OBJECTIVE

The present study was designed to investigate the role of X-ray cross-complementing group 1 (XRCC1) and apurinic/apyrimidinic endonuclease 1 (APE1) polymorphisms in apoptosis and the risk of ulcerative colitis (UC).

MATERIALS AND METHODS

Blood samples from 384 unrelated subject (age range 18-65 years; 171 with UC, 213 healthy controls) were collected after colonoscopy. Genomic DNA was isolated and genotyped for XRCC1 Arg399Gln and APE1 Asp148Glu using a confronting two-pair primers polymerase chain reaction. Apoptosis and intracellular reactive oxygen species (ROS) levels in peripheral blood mononuclear cells were measured using annexin-V and H(2)DCFDA assay, respectively.

RESULTS

The frequency of genotype Arg399Gln (heterozygous) of XRCC1 gene was significantly higher in patients with UC than the controls (odds ratio [OR] 1.73; 95% confidence interval [CI] 1.13-2.64; p = 0.01). Similarly the genotypic frequency of APE1 Asp148Glu showed statistically significant incidence among UC subjects (OR 1.54; 95% CI 1.02-2.33; p = 0.04). Polymorphism in XRCC1 Arg399Gln and APE1 Asp148Glu together considerably increased the risk of UC (OR 2.303; 95% CI 1.43-3.69; p = 0.0007). ROS levels were high in UC subjects compared with controls (p = 0.01).

CONCLUSION

Polymorphisms in XRCC1 Arg399Gln and APE1 Asp148Glu significantly increased the rate of apoptosis and risk of ulcerative colitis.

Arsenic geochemistry and human health in South East Asia

Arsenic occurs naturally in many environmental components and enters the human body through several exposure pathways. Natural enrichment of arsenic may result in considerable contamination of soil, water, and air. Arsenic in groundwater can exceed values hundreds of time higher than the concentration recommended for drinking water. Such exposure levels indicate a serious potential health risk to individuals consuming raw groundwater. Human activities that have an impact on the environment may increase the distribution of inorganic arsenic. Abandoned mines are of great concern due to the extremely high arsenic concentrations detected in mine drainage and tailings. Diet, drinking water, air, soil, and occupational exposures are all sources of inorganic arsenic for humans. Interdisciplinary efforts to better characterize the transport of arsenic and reactants that facilitate their release to the environment are important for human health studies. Multi-disciplinary efforts are needed to study diet, infectious disease, genetics, and cultural practices unique to each region to better understand human health risk and to design public health interventions.

Association of genetic variation in cystathionine-beta-synthase and arsenic metabolism

Variation in individual susceptibility to arsenic-induced disease may be partially explained by genetic differences in arsenic metabolism. Mounting epidemiological evidence and in vitro studies suggest that methylated arsenic metabolites, particularly monomethylarsonic (MMA3), are more acutely toxic than inorganic arsenic; thus, MMA3 may be the primary toxic arsenic species. To test the role of genetic variation in arsenic metabolism, polymorphisms in genes involved in one-carbon metabolism [methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), cystathionine-beta-synthase (CBS), thymidylate synthase (TYMS), dihydrofolate reductase (DHFR), serine hydroxymethyltransferase 1 (SHMT1)] and glutathione biosynthesis [glutathione-S-transferase omega 1 (GSTO1)] were examined in an arsenic-exposed population to determine their influence in urinary arsenic metabolite patterns. In 142 subjects in Cordoba Province, Argentina, variant genotypes for CBS rs234709 and rs4920037 SNPs compared with wild-type homozygotes were associated with 24% and 26% increases, respectively, in the mean proportion of arsenic excreted as monomethylarsonic acid (%MMA). This difference is within the range of differences in %MMA seen between people with arsenic-related disease and those without such disease in other studies. Small inverse associations with CBS rs234709 and rs4920037 variants were also found for the mean levels of the proportion of arsenic excreted as dimethylarsinous acid (%DMA). No other genetic associations were found. These findings are the first to suggest that CBS polymorphisms may influence arsenic metabolism in humans and susceptibility to arsenic-related disease.

Genetic variations associated with interindividual sensitivity in the response to arsenic exposure

People are exposed to arsenic compounds environmentally, occupationally or therapeutically. In some areas, where arsenic is present in high proportions in the drinking water, this exposure represents an important health concern. Chronic exposure to arsenic leads to hyperkeratosis and loss of skin pigmentation, as well as to significant increases of different types of cancer in skin, lung, bladder and liver; in addition, other pathologies, such as vascular diseases, hepatotoxicity and diabetes, have also been related to arsenic exposure. Since high interindividual variability is observed among people exposed to equivalent doses, genetic susceptibility factors have been postulated to be involved. When inorganic arsenic enters into the body it undergoes metabolic conversion, in a process where methylation plays a crucial role. Trivalent forms, both inorganic and organic, are the most toxic and genotoxic and, for this reason, metabolic variations owing to variant alleles in genes involved in such a process have been the aim of several studies. Genes involved in other mechanisms, such as antioxidant defense and DNA-repair lesions, among others, have also been the subject of association studies. A survey of those studies related to individual susceptibility is summarized here. Results with genes involved in folate one-carbon metabolism and in arsenic transport across the cell membrane provide promising data for future studies.