Arsenic-induced Skin Research Articles

Genetic susceptible locus in NOTCH2 interacts with arsenic in drinking water on risk of type 2 diabetes.

BackgroundChronic exposure to arsenic in drinking water is associated with increased risk of type 2 diabetes mellitus (T2DM) but the underlying molecular mechanism remains unclear.ObjectivesThis study evaluated the interaction between single nucleotide polymorphisms (SNPs) in genes associated with diabetes and arsenic exposure in drinking water on the risk of developing T2DM.MethodsIn 2009–2011, we conducted a follow up study of 957 Bangladeshi adults who participated in a case-control study of arsenic-induced skin lesions in 2001–2003. Logistic regression models were used to evaluate the association between 38 SNPs in 18 genes and risk of T2DM measured at follow up. T2DM was defined as having a blood hemoglobin A1C level greater than or equal to 6.5% at follow-up. Arsenic exposure was characterized by drinking water samples collected from participants' tubewells. False discovery rates were applied in the analysis to control for multiple comparisons.ResultsMedian arsenic levels in 2001–2003 were higher among diabetic participants compared with non-diabetic ones (71.6 µg/L vs. 12.5 µg/L, p-value <0.001). Three SNPs in ADAMTS9 were nominally associated with increased risk of T2DM (rs17070905, Odds Ratio (OR) = 2.30, 95% confidence interval (CI) 1.17–4.50; rs17070967, OR = 2.02, 95%CI 1.00–4.06; rs6766801, OR = 2.33, 95%CI 1.18–4.60), but these associations did not reach the statistical significance after adjusting for multiple comparisons. A significant interaction between arsenic and NOTCH2 (rs699780) was observed which significantly increased the risk of T2DM (p for interaction = 0.003; q-value = 0.021). Further restricted analysis among participants exposed to water arsenic of less than 148 µg/L showed consistent results for interaction between the NOTCH2 variant and arsenic exposure on T2DM (p for interaction = 0.048; q-value = 0.004).ConclusionsThese findings suggest that genetic variation in NOTCH2 increased susceptibility to T2DM among people exposed to inorganic arsenic. Additionally, genetic variants in ADAMTS9 may increase the risk of T2DM.

Epigenetic Modifications of DAPK and p16 Genes Contribute to Arsenic-Induced Skin Lesions and Nondermatological Health Effects

Over 26 million people in West Bengal, India, are exposed to very high levels of arsenic through drinking water, leading to several deleterious endpoints including cancers. To elucidate the role of promoter methylation in arsenic-induced dermatological and nondermatological health effects, methylation status of p16 and DAPK genes was determined. A case-control study was conducted involving 72 individuals with arsenic-induced skin lesions (cases) and 50 individuals without skin lesions (controls), having similar arsenic exposure through drinking water. Methylation status was determined by bisulfite conversion of genomic DNA and methylation-specific PCR. Expression of the genes was determined by real-time PCR and Western blot analysis. Associations between the promoter methylation status and nondermatological health effects were determined from epidemiological survey data. Significant hypermethylation was found in the promoters of both DAPK and p16 genes in the cases compared with the controls resulting in downregulation of both the genes in the cases. There was a 3.4-fold decrease in the expression of death-associated protein kinase and 2.2-fold decrease in gene expression of p16 in the cases compared to the controls, the lowest expression being in the cancer tissues. Promoter hypermethylation of the genes was also associated with higher risk of developing arsenic-induced skin lesions, peripheral neuropathy, ocular and respiratory diseases. This study for the first time makes an attempt to correlate epigenetic modifications of the tumor suppressor genes with dermatological and nondermatological health outcomes in a population chronically exposed to arsenic.

Re: "Use of Arsenic-Induced Palmoplantar Hyperkeratosis and Skin Cancers to Predict Risk of Subsequent Internal Malignancy"

Re: "Use of Arsenic-Induced Palmoplantar Hyperkeratosis and Skin Cancers to Predict Risk of Subsequent Internal Malignancy"

Association of NALP2 polymorphism with arsenic induced skin lesions and other health effects

Prolonged consumption of arsenic-laden water above the threshold limit of 10μg/L causes a plethora of dermatological and non-dermatological multi-organ health problems, including cancer and death. Among several mechanisms of arsenic-induced toxicity and carcinogenicity studied so far, role of arsenic in impairment of immune system is less understood. Epidemiological data, animal model as well as cell line based studies have indicated that arsenic targets immune system and is associated with characteristic immunosupression, which may further adversely affect respiratory function. However, to the best of our knowledge, there is no study with respect to arsenic susceptibility investigating the role of genetic variation having immunological function. Hence, we have recruited a total of 432 arsenic-exposed individuals, of which 219 individuals with characteristic arsenic-induced skin lesions (cases) and 213 individuals without arsenic-induced skin lesion(controls), from arsenic-exposed districts of West Bengal, India. To find any probable association between arsenicism and the exonic single nucleotide polymorphisms (SNPs) in NALP2 gene, an important component of inflammasome complex, we screened the entire coding region (exon) in all the study participants. Among 9 SNPs found in NALP2 gene, the A1052E polymorphism (at least with one minor allele), was significantly overrepresented in controls and hence implies decreased risk toward the development of skin lesions [OR=0.67, 95% CI: 0.46–0.97]. Since, development of non-dermatological health effects are also important factor to properly look into, we have attempted to correlate the genetic variation of NALP2 with the extent of cytogenetic damage as measured by chromosomal aberration assay and adverse health effects including peripheral neuropathy, eye problem and respiratory diseases in the study population. We observed individuals with the protective genotype had less chromosomal aberration (p<0.05), and were also less susceptible toward arsenic-related respiratory diseases [OR=0.47; 95%CI: 0.23–0.89]. These findings suggest that NALP2 A1052E SNP plays an important role toward development of arsenic-induced skin lesions, chromosomal damage and respiratory diseases.

Use of Arsenic-Induced Palmoplantar Hyperkeratosis and Skin Cancers to Predict Risk of Subsequent Internal Malignancy

Hyperpigmentation, hyperkeratoses, and Bowen's disease are hallmarks of chronic arsenic exposure. The association between arsenic-induced skin lesions and subsequent internal cancers is examined by using a community-based prospective study. The cohort was enrolled from an arseniasis-endemic area in southwestern Taiwan, where 2,447 residents participated in skin examinations during the late 1980s. The number of participants diagnosed with hyperpigmentation was 673; with hyperkeratosis, 243; and with skin cancer (Bowen's disease or non-melanoma skin cancer), 378. Newly diagnosed internal cancers were ascertained through linkage with National Cancer Registry profiles. Cox regression was performed to estimate hazard ratios with 95% confidence intervals for potential risk predictors. Compared with participants without skin lesions, patients affected with skin cancers had a significantly increased risk of lung cancer (hazard ratio = 4.64, 95% confidence interval: 2.92, 7.38) and urothelial carcinoma (hazard ratio = 2.02, 95% confidence interval: 1.23, 3.30) after adjustment for potential confounders and cumulative arsenic exposure. Hyperkeratosis is significantly associated with an increased lung cancer risk (hazard ratio = 2.76, 95% confidence interval: 1.35, 5.67). A significant interactive effect on lung cancer risk between hyperkeratosis and cigarette smoking was identified, which suggests that patients with hyperkeratosis who have been exposed to arsenic should cease smoking.

Oxidative DNA damage of peripheral blood polymorphonuclear leukocytes, selectively induced by chronic arsenic exposure, is associated with extent of arsenic-related skin lesions

There is increasing evidence that oxidative stress is an important risk factor for arsenic-related diseases. Peripheral blood leukocytes constitute an important defense against microorganisms or pathogens, while the research on the impact of chronic arsenic exposure on peripheral blood leukocytes is much more limited, especially at low level arsenic exposure. The purpose of the present study was to explore whether chronic arsenic exposure affects oxidative stress of peripheral blood leukocytes and possible linkages between oxidative stress and arsenic-induced skin lesions. 75 male inhabitants recruited from an As-endemic region of China were investigated in the present study. The classification of arsenicosis was based on the degree of skin lesions. Arsenic levels were measured in drinking water and urine by Atomic Fluorescence Spectroscopy. Urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) was tested by Enzyme-Linked Immunosorbent Assay. 8-OHdG of peripheral blood leukocytes was evaluated using immunocytochemical staining. 8-OHdG-positive reactions were only present in polymorphonuclear leukocytes (PMNs), but not in monocytes (MNs). The 8-OHdG staining of PMN cytoplasm was observed in all investigated populations, while the 8-OHdG staining of PMN nuclei was frequently found along with the elevated amounts of cell debris in individuals with skin lesion. Urinary arsenic levels were increased in the severe skin lesion group compared with the normal group. No relationship was observed between drinking water arsenic or urine 8-OHdG and the degree of skin lesions. These findings indicated that the target and persistent oxidative stress in peripheral blood PMNs may be employed as a sensitive biomarker directly to assess adverse health effects caused by chronic exposure to lower levels of arsenic.

Abstract 2925: Genome-wide association study identifies 10q24.32 variants associated with arsenic metabolism and premalignant skin lesion risk in Bangladesh

Abstract Arsenic is a class-I human carcinogen, and arsenic contamination of drinking water is a serious public health issue in many countries, increasing risk for a wide array of diseases, including cancers of the bladder, kidney, lung, and skin. There is inter-individual variation in arsenic metabolism efficiency and susceptibility to arsenic toxicity, however the basis of this variation in not well understood. Here, we have performed the first genome-wide association study (GWAS) of arsenic-related phenotypes to identify genetic determinants of arsenic metabolism and gene-arsenic interactions influencing risk for arsenic-induced premalignant skin lesions (a classical sign of arsenic toxicity). Using data on urinary arsenic metabolite concentrations and genome-wide single nucleotide polymorphisms (SNPs) for 1,313 arsenic-exposed Bangladeshi individuals, we identified genome-wide significant association signals (P&amp;lt;5x10^-8) for urinary concentrations of both monomethylarsonic (MMA) and dimethylarsinic (DMA) in a large linkage disequilibrium block containing the AS3MT gene (arsenite methyltransferase; 10q24.32), with five genetic variants showing strong evidence independent association. In a follow-up analysis of 1,085 individuals with premalignant skin lesions and 1,794 controls population-based, we show that one of these five variants (rs9527, which is associated with DMA%) is associated with arsenical skin lesion risk (P=0.0005). Using a subset of individuals with prospectively measured arsenic metabolites (n=769), we show that rs9527 interacts with arsenic exposure to influence skin lesion risk (P=0.01). The direction of the observed association is consistent with the prevailing hypothesis that DMA is the less toxic than MMA. To evaluate the functional role of the five identified SNPs, we conducted expression quantitative trait locus (eQTL) analyses of genome-wide expression data from 950 individual's lymphocyte RNA. Our results suggest that several of our lead SNPs represent cis-eQTLs for AS3MT (P=10^-12) or neighboring gene C10orf32 (P=10^-44). This is an intriguing finding in part because C10orf32 and AS3MT are known to be involved in read-through transcription, producing a transcript that is presumed to be non-functional. To our knowledge, this is the largest genetic association study of arsenic metabolites to date, the only GWAS of arsenic-related traits, and the first to implicate 10q24.32 variants in both arsenic metabolism and arsenical skin lesion risk. Our results suggest that MMA% and DMA% have distinct genetic determinants and support hypothesis that DMA is the less toxic of these two methylated arsenic species. These results have potential translational implications for the prevention and treatment of arsenic-associated toxicities, including several types of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2925. doi:1538-7445.AM2012-2925

Genome-Wide Association Study Identifies Chromosome 10q24.32 Variants Associated with Arsenic Metabolism and Toxicity Phenotypes in Bangladesh

Arsenic contamination of drinking water is a major public health issue in many countries, increasing risk for a wide array of diseases, including cancer. There is inter-individual variation in arsenic metabolism efficiency and susceptibility to arsenic toxicity; however, the basis of this variation is not well understood. Here, we have performed the first genome-wide association study (GWAS) of arsenic-related metabolism and toxicity phenotypes to improve our understanding of the mechanisms by which arsenic affects health. Using data on urinary arsenic metabolite concentrations and approximately 300,000 genome-wide single nucleotide polymorphisms (SNPs) for 1,313 arsenic-exposed Bangladeshi individuals, we identified genome-wide significant association signals (P<5×10−8) for percentages of both monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) near the AS3MT gene (arsenite methyltransferase; 10q24.32), with five genetic variants showing independent associations. In a follow-up analysis of 1,085 individuals with arsenic-induced premalignant skin lesions (the classical sign of arsenic toxicity) and 1,794 controls, we show that one of these five variants (rs9527) is also associated with skin lesion risk (P = 0.0005). Using a subset of individuals with prospectively measured arsenic (n = 769), we show that rs9527 interacts with arsenic to influence incident skin lesion risk (P = 0.01). Expression quantitative trait locus (eQTL) analyses of genome-wide expression data from 950 individual's lymphocyte RNA suggest that several of our lead SNPs represent cis-eQTLs for AS3MT (P = 10−12) and neighboring gene C10orf32 (P = 10−44), which are involved in C10orf32-AS3MT read-through transcription. This is the largest and most comprehensive genomic investigation of arsenic metabolism and toxicity to date, the only GWAS of any arsenic-related trait, and the first study to implicate 10q24.32 variants in both arsenic metabolism and arsenical skin lesion risk. The observed patterns of associations suggest that MMA% and DMA% have distinct genetic determinants and support the hypothesis that DMA is the less toxic of these two methylated arsenic species. These results have potential translational implications for the prevention and treatment of arsenic-associated toxicities worldwide.

Classification accuracy and cut point selection

In biomedical research and practice, quantitative tests or biomarkers are often used for diagnostic or screening purposes, with a cut point established on the quantitative measurement to aid binary classification. This paper introduces an alternative to the traditional methods based on the Youden index and the closest-to-(0, 1) criterion for threshold selection. A concordance probability evaluating the classification accuracy of a dichotomized measure is defined as an objective function of the possible cut point. A nonparametric approach is used to search for the optimal cut point maximizing the objective function. The procedure is shown to perform well in a simulation study. Using data from a real-world study of arsenic-induced skin lesions, we apply the method to a measure of blood arsenic levels, selecting a cut point to be used as a warning threshold.

Effects of sodium arsenite on hypermethylation, transcription and expression of O6-methylguanine-DNA methyltransferase gene in HaCaT cells

Objective To investigate the DNA methylation feature and DNA methylation regulation to its transcription and expression of O6-methylguanine-DNA methyltransferase gene (MGMT) in NaAsO2-treated HaCaT cells. Methods HaCaT cells were treated 72 hours at intervals and repeatedly by 3.13, 6.25,12.50, and 25.00 μmol/L NaAsO2, MGMT gene promoter region was amplified in the transcription initiation site - 329 - + 93 region by bisulfate-sequencing polymerase chain reaction (BSP), the mRNA transcription and the protein expression of MGMT was detected by real-time quantitative PCR and Western blotting. NaAsO2-untreated HaCaT cell was set as a blank control, and human epidermal squamous carcinoma cell strain A431 was set as a positive control. Results Among the groups of HaCaT cells treated with 3.13, 6.25, 12.50 and 25.00 μmol/L NaAsO2, the positive rates of the DNA methylation of promoter region in MGMT gene were 0.63%(l/160), 6.25% (10/160), 10.63%( 17/160) and 18.75% (30/160), respectively, and methylated CpG sites were mainly located in - 249--146 region relative to transcription start site. There was no DNA methylation in the blank control. There were significant differences between the blank control and the NaAsO2-treated cells (x2 = 76.687, P< 0.05). Average levels of MGMT mRNA were 1.518 31 ± 0.180 54, 1.425 22 ± 0.180 39, 1.014 54 ± 0.096 79 and 0.887 72 ± 0.020 00, respectively among the groups of HaCaT cells treated with 3.13, 6.25, 12.50 and 25.00 μmol/L NaAsO2, compared with the blank control cells(1.198 29 ± 0.159 97), there were significant differences(F = 37.359, P < 0.05). Average levels of MGMT protein were 1.174 47 ± 0.064 75, 0.848 83 ± 0.057 01, 0.471 63 ± 0.023 34 and 0.240 34 ± 0.014 43, respectively among the groups of HaCaT cells treated with 3.13, 6.25, 12.50 and 25.00 μmol/L NaAsO2, compared with the blank control cells (1.066 19 ± 0.061 24), there were significant differences(F = 20.687, P < 0.05). Conclusions Arsenic can cause CpC island hypermethylation in the promoter region of MGMT gene, which results in inhibited MGMT mRNA transcription and protein expression. It might be one of the important mechanisms of arsenic-induced skin lesion. Key words: Arsenic; DNA methylation; Transcription, genetic; Proteins; O6-methylguanineDNA methyltransferase gene

Polymorphisms in the TNF-α and IL10 Gene Promoters and Risk of Arsenic-Induced Skin Lesions and Other Nondermatological Health Effects

In West Bengal, India, at present, more than 26 million people are exposed to arsenic through drinking water. Among them, only 15-20% manifest arsenic-induced noncancerous, precancerous, and cancerous skin lesions, indicating that genetic variants play important role in arsenic susceptibility. Chronic arsenic exposure has been associated with impairment of immune systems in the exposed individuals. Because cytokines are important immune mediators, alteration in expression of these gene products may lead to arsenic-specific disease manifestations. The aim of the present work was to investigate the association between the TNF-α-308G>A (rs1800629) and IL10 -3575T>A (rs1800890) polymorphisms and arsenic-induced dermatological and nondermatological health outcomes. A case-control study was conducted in West Bengal, India, involving 207 cases with arsenic-induced skin lesions and 190 controls without skin lesions having similar arsenic exposure. The polymorphisms were determined using conventional PCR-sequencing method. ELISA was done to determine the serum levels of the two cytokines tumor necrosis factor α (TNF-α) and interleukin 10 (IL10). Associations between the polymorphisms studied and nondermatological health effects in the study subjects were determined from our epidemiological survey data. Individuals with GA/AA (-308 TNF-α) and TA/AA (-3575 IL10) genotypes were at higher risk of developing arsenic-induced skin lesions, ocular, and respiratory diseases. Also the -308 TNF A allele corresponded to a higher production of TNF-α, and -3575 IL10 A allele corresponded to a lower production of IL10. Thus, the polymorphisms studied impart significant risk toward development of arsenic-induced dermatological and nondermatological health effects in the chronically exposed population of West Bengal, India.

Precancerous and non-cancer disease endpoints of chronic arsenic exposure: The level of chromosomal damage and XRCC3 T241M polymorphism

Genetic variants are expected to play an important role in arsenic susceptibility. Our previous study revealed deficient DNA repair capacity to be a susceptibility factor for arsenicism. T241M polymorphism in XRCC3 (a homologous recombination repair pathway gene) is widely studied for its association with several cancers. We have investigated the association of XRCC3 T241M polymorphism with arsenic-induced precancerous and non-cancer disease outcomes. The present study evaluated the association of T241M polymorphism with arsenic-induced skin lesions, peripheral neuropathy (neurodegenerative changes), conjunctivitis and other ocular diseases. A case-control study was conducted in West Bengal, India, involving 206 cases with arsenic-induced skin lesions and 215 controls without arsenic-induced skin lesions having similar arsenic exposure. XRCC3 T241M polymorphism was determined using conventional PCR-sequencing method. Chromosomal aberration assay, arsenic-induced neuropathy and ocular diseases were also evaluated. The data revealed that presence of at least one Met allele (Met/Met or Thr/Met) was protective towards development of arsenic-induced skin lesions [OR = 0.45, 95% CI: 0.30–0.67], peripheral neuropathy [OR = 0.49; 95%CI: 0.30–0.82] and conjunctivitis [OR = 0.60; 95%CI: 0.40–0.92]. A significant correlation was also observed between protective genotype and decreased frequency of chromosomal aberrations. Thus the results indicate the protective role of Met allele against the arsenic-induced skin lesions, chromosomal instability, peripheral neuropathy and conjunctivitis.

Severe arsenic poisoning: one of the largest man-made catastrophies

More than 50 million people in Bangladesh are at risk of arsenic-induced disease (Ahmad 2001; Bae et al. 2002). In the 1970s, a nationwide WHO-initiated campaign switched water from ponds and open dug wells to groundwater as a source of drinking water. About 4 million wells have been installed for this purpose. Indeed, this measure reduced waterborne diseases, such as gastrointestinal diseases and infant mortality, as a consequence of drinking bacterialcontaminated water. However, the natural contamination of the groundwater with arsenic because of its contact with arsenic-rich rocks was neglected. Meanwhile, at least 100,000 people have been observed with skin lesions caused by arsenic; however, the real number is probably much higher. Arsenic poisoning is not limited to populations in Bangladesh. In Chile, arsenic in drinking water has been linked to lung and bladder cancer (Orellana 2001). Cases of severe arsenic poisoning as a consequence of Wres fueled with high-arsenic coal have also been reported in Guizhou Province in China (Finkelman et al. 1999; Chen et al. 2007, 2009; Lin et al. 2010b). The alarming extent of arseniasis due to drinking water naturally contaminated with arsenic is illustrated by the fact that more than 2 million rural residents in Chinese mainland are at risk (Lin et al. 2010a). Large studies in an area with more than 2,000 arsenic-related skin lesions have shown that the XPD/ ERCC2 G23591A and A35931C polymorphisms modulate the risk for arsenic-induced skin disease (Lin et al. 2010a). Also the GSTP1 A1578G and the GSTM1 polymorphisms might be susceptibility factors for arsenic-related skin lesions (Lin et al. 2007; 2006). Because of the high relevance and consequences of arsenic poisoning to many of the world’s populations, the toxic mechanisms of arsenic have been a central topic in the Archives of Toxicology (Wang et al. 2009; Xi et al. 2009; Juarez-Reyes et al. 2009; Mahmud et al. 2009; Naraharisetti et al. 2008; Beyersmann and Hartwig 2008; Manna et al. 2008; Kobayashi et al. 2008). The editors are happy that Ingrid Druwe and Richard Vaillancourt from The University of Arizona College of Pharmacy, Tucson, have accepted our invitation and reviewed the most up-to-date information available on how arsenate and arsenite inXuence signal transduction:

Molecular interaction between arsenic hydrate microcrystals and the cell-surface endopeptidase CD10 (neprilysin) – A possible link to the development of renal and cutaneous malignancies upon occupational exposure to arsenic compounds?

Arsenic poisoning has become a worldwide public health concern since arsenic is recognized as a human carcinogen although the detailed mechanisms of carcinogenesis related to arsenic exposure are not completely understood at present. In particular, the skin and the kidneys are prone to neoplastic transformation upon occupational exposure of the human body to inorganic arsenic compounds. The cell-surface endopeptidase CD10 is variably expressed in cutaneous and renal malignancies, and due to this expression profile, might theoretically be implicated in arsenic-induced skin and renal neoplasias. From the functional point of view, CD10 conveys important anti-tumorigenic effects brought about by the inactivation of neuropeptide growth factors implicated in cancer progression. Placing the focus on the structural composition of arsenic hydrate microcrystals encountered in the cellular microenvironment, the present hypothesis suggests so far neglected molecular interactions between arsenic microcrystals and membrane-bound CD10 to be implicated in arsenic-induced carcinogenesis.

Impact of Smoking and Chewing Tobacco on Arsenic-Induced Skin Lesions

BackgroundWe recently reported that the main reason for the documented higher prevalence of arsenic-related skin lesions among men than among women is the result of less efficient arsenic metabolism.ObjectiveBecause smoking has been associated with less efficient arsenic methylation, we aimed to elucidate interactions between tobacco use and arsenic metabolism for the risk of developing skin lesions.MethodsWe used a population-based case–referent study that showed increased risk for skin lesions in relation to chronic arsenic exposure via drinking water in Bangladesh and randomly selected 526 of the referents (random sample of inhabitants > 4 years old; 47% male) and all 504 cases (54% male) with arsenic-related skin lesions to measure arsenic metabolites [methylarsonic acid (MA) and dimethylarsinic acid (DMA)] in urine using high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICPMS).ResultsThe odds ratio for skin lesions was almost three times higher in the highest tertile of urinary %MA than in the lowest tertile. Men who smoked cigarettes and bidis (locally produced cigarettes; 33% of referents, 58% of cases) had a significantly higher risk for skin lesions than did nonsmoking men; this association decreased slightly after accounting for arsenic metabolism. Only two women smoked, but women who chewed tobacco (21% of referents, 43% of cases) had a considerably higher risk of skin lesions than did women who did not use tobacco. The odds ratio (OR) for women who chewed tobacco and who had ≤ 7.9 %MA was 3.8 [95% confidence interval (CI), 1.4–10] compared with women in the same MA tertile who did not use tobacco. In the highest tertile of %MA or %inorganic arsenic (iAs), women who chewed tobacco had ORs of 7.3 and 7.5, respectively, compared with women in the lowest tertiles who did not use tobacco.ConclusionThe increased risk of arsenic-related skin lesions in male smokers compared with nonsmokers appears to be partly explained by impaired arsenic methylation, while there seemed to be an excess risk due to interaction between chewing tobacco and arsenic metabolism in women.

Aberrant cytokeratin expression during arsenic-induced acquired malignant phenotype in human HaCaT keratinocytes consistent with epidermal carcinogenesis

Inorganic arsenic is a known human skin carcinogen. Chronic arsenic exposure results in various human skin lesions, including hyperkeratosis and squamous cell carcinoma (SCC), both characterized by distorted cytokeratin (CK) production. Prior work shows the human skin keratinocyte HaCaT cell line, when exposed chronically for >25 weeks to a low level of inorganic arsenite (100 nM) results in cells able to produce aggressive SCC upon inoculation into nude mice. In the present study, CK expression analysis was performed in arsenic-exposed HaCaT cells during the progressive acquisition of this malignant phenotype (0–20 weeks) to further validate this model as relevant to epidermal carcinogenesis induced by arsenic in humans. Indeed, we observed clear evidence of acquired cancer phenotype by 20 weeks of arsenite exposure including the formation of giant cells, a >4-fold increase in colony formation in soft agar and a ∼2.5-fold increase in matrix metalloproteinase-9 secretion, an enzyme often secreted by cancer cells to help invade through the local extra-cellular matrix. During this acquired malignant phenotype, various CK genes showed markedly altered expression at the transcript and protein levels in a time-dependent manner. For example, CK1, a marker of hyperkeratosis, increased up to 34-fold during arsenic-induced transformation, while CK13, a marker for dermal cancer progression, increased up to 45-fold. The stem cell marker, CK15, increased up to 7-fold, particularly during the later stages of arsenic exposure, indicating a potential emergence of cancer stem-like cells with arsenic-induced acquired malignant phenotype. The expression of involucrin and loricrin, markers for keratinocyte differentiation, increased up to 9-fold. Thus, during arsenic-induced acquired cancer phenotype in human keratinocytes, dramatic and dynamic alterations in CK expression occur which are consistent with the process of epidermal carcinogenesis helping validate this as an appropriate model for the study of arsenic-induced skin cancer.

Chronic exposure of arsenic via drinking water and its adverse health impacts on humans

Worldwide chronic arsenic (As) toxicity has become a human health threat. Arsenic exposure to humans mainly occurs from the ingestion of As contaminated water and food. This communication presents a review of current research conducted on the adverse health effects on humans exposed to As-contaminated water. Chronic exposure of As via drinking water causes various types of skin lesions such as melanosis, leucomelanosis, and keratosis. Other manifestations include neurological effects, obstetric problems, high blood pressure, diabetes mellitus, diseases of the respiratory system and of blood vessels including cardiovascular, and cancers typically involving the skin, lung, and bladder. The skin seems to be quite susceptible to the effects of As. Arsenic-induced skin lesions seem to be the most common and initial symptoms of arsenicosis. More systematic studies are needed to determine the link between As exposure and its related cancer and noncancer end points.

DNA repair deficiency leads to susceptibility to develop arsenic-induced premalignant skin lesions

DNA repair deficiency leads to susceptibility to develop arsenic-induced premalignant skin lesions

Folate Deficiency, Hyperhomocysteinemia, Low Urinary Creatinine, and Hypomethylation of Leukocyte DNA Are Risk Factors for Arsenic-Induced Skin Lesions

BackgroundArsenic methylation relies on folate-dependent one-carbon metabolism and facilitates urinary As elimination. Clinical manifestations of As toxicity vary considerably among individuals and populations, and poor methylation capacity is thought to confer greater susceptibility.ObjectiveAfter determining that folate deficiency, hyperhomocysteinemia, and low urinary creatinine are associated with reduced As methylation, and that As exposure is associated with increased genomic methylation of leukocyte DNA, we asked whether these factors are associated with As-induced skin lesion risk among Bangladeshi adults.MethodsWe conducted a nested case–control study of 274 cases who developed lesions 2 years after recruitment, and 274 controls matched to cases for sex, age, and water As.ResultsThe odds ratios and 95% confidence intervals (CIs) for development of skin lesions for participants who had low folate (< 9 nmol/L), hyperhomocysteinemia (men, > 11.4 μmol/L; women, > 10.4 μmol/L), or hypomethylated leukocyte DNA at recruitment (< median) were 1.8 (95% CI, 1.1–2.9), 1.7 (95% CI, 1.1–2.6), and 1.8 (95% CI, 1.2–2.8), respectively. Compared with the subjects in the first quartile, those in the third and fourth quartiles for urinary creatinine had a 0.4-fold decrease in the odds of skin lesions (p < 0.01).ConclusionsThese results suggest that folate deficiency, hyperhomocysteinemia, and low urinary creatinine, each associated with decreased As methylation, are risk factors for As-induced skin lesions. The increased DNA methylation associated with As exposure previously observed, and confirmed among controls in this study, may be an adaptive change because hypomethylation of leukocyte DNA is associated with increased risk for skin lesions.

Gastronomical Delight: Micronutrients Protect against Arsenic Lesions

Studies in South Asia suggest that antioxidants may mediate many of the dermatologic symptoms associated with exposure to arsenic in drinking water. Nonetheless, the mitigating effects of diet on arsenic-related premalignant skin lesions are largely unknown, particularly in the context of the typical Bangladeshi diet. A new cross-sectional study using baseline data from the Health Effects of Arsenic Longitudinal Study (HEALS), 2000–2002, is the first systematic, population-based attempt to assess the association between micronutrient intake and the prevalence of arsenic-induced skin lesions [EHP 116:1056–1062; Zablotska et al.]. As many as a third of the people living in Bangladesh have been exposed to arsenic-tainted water levels above the national limit of 50 ppb, with many levels as high as 800 ppb. Several studies have shown an association between drinking arsenic-rich water and development of skin lesions, a common outward sign of chronic arsenic exposure. HEALS is a population-based prospective cohort study in Araihazar, Bangladesh, using individual-level time-weighted measures of arsenic exposure via drinking water. The present study relied on detailed daily diet information obtained from all participants using a food frequency questionnaire along with U.S. Department of Agriculture nutritional tables. The analyses were aimed at clarifying the effects of the B vitamin group and antioxidants (vitamins A, C, and E) on the risk of arsenic-related skin lesions. Because supplements and food fortification are rare in Bangladesh, only dietary intakes of these micronutrients were considered. Skin lesions were identified among 10,628 subjects according to a structured clinical protocol during screening that was confirmed with further clinical review. Dietary intake of B1, B6, and B9 and all three antioxidants significantly reduced the risk of arsenic-related skin lesions. For example, for individuals with the highest vitamin intake, the risk of arsenic-induced skin lesions was significantly reduced by 60% for vitamin E. The investigators conclude that intakes of B vitamins and antioxidants at doses greater than the current recommended daily amounts for Bangladesh might lower the risk of arsenic-related skin lesions. However, the research team observed that there was a high prevalence of micronutrient deficiency in Bangladesh, with the potential protective modifying effects of these vitamins restricted to the medium and upper consumption levels. Public health measures to assist this population may need to include either supplementation or food fortification to achieve a significant degree of protection from chronic arsenic exposures.