MicroRNA-129-5p-regulated microglial expression of the surface receptor CD200R1 controls neuroinflammation.

CD200R1 is an inhibitory surface receptor expressed in microglia and blood macrophages. Microglial CD200R1 is known to control neuroinflammation by keeping the microglia in resting state, and therefore, tight regulation of its expression is important. CCAAT/enhancer-binding protein ß (CEBPß) is the known regulator of CD200R1 transcription. In the present study, our specific intention was to find a possible posttranscriptional regulatory mechanism of CD200R1 expression. Here we investigated a novel regulatory mechanism of CD200R1 expression following exposure to an environmental stressor, arsenic, combining in silico analysis, in vitro, and in vivo experiments, as well as validation in human samples. The in silico analysis and in vitro studies with primary neonatal microglia and BV2 microglia revealed that arsenic demethylates the promoter of a microRNA, miR-129-5p, thereby increasing its expression, which subsequently represses CD200R1 by binding to its 3'-untranslated region and shuttling the CD200R1 mRNA to the cytoplasmic-processing body in mouse microglia. The role of miR-129-5p was further validated in BALB/c mouse by stereotaxically injecting anti-miR-129. We found that anti-miR-129 reversed the expression of CD200R1, as well as levels of inflammatory molecules IL-6 and TNF-α. Experiments with a CD200R1 siRNA-induced loss-of-function mouse model confirmed an miR-129-5p→CD200R1→IL-6/TNF-α signaling axis. These main findings were replicated in a human cell line and validated in human samples. Taken together, our study revealed miR-129-5p as a novel posttranscriptional regulator of CD200R1 expression with potential implications in neuroinflammation and related complications.

SILAC-based quantitative proteomic analysis reveals widespread molecular alterations in human skin keratinocytes upon chronic arsenic exposure.

Chronic exposure to arsenic is associated with dermatological and nondermatological disorders. Consumption of arsenic-contaminated drinking water results in accumulation of arsenic in liver, spleen, kidneys, lungs, and gastrointestinal tract. Although arsenic is cleared from these sites, a substantial amount of residual arsenic is left in keratin-rich tissues including skin. Epidemiological studies suggest the association of skin cancer upon arsenic exposure, however, the mechanism of arsenic-induced carcinogenesis is not completely understood. We developed a cell line based model to understand the molecular mechanisms involved in arsenic-mediated toxicity and carcinogenicity. Human skin keratinocyte cell line, HaCaT, was chronically exposed to 100 nM sodium arsenite over a period of 6 months. We observed an increase in basal ROS levels in arsenic-exposed cells. SILAC-based quantitative proteomics approach resulted in identification of 2111 proteins of which 42 proteins were found to be overexpressed and 54 downregulated (twofold) upon chronic arsenic exposure. Our analysis revealed arsenic-induced overexpression of aldo-keto reductase family 1 member C2 (AKR1C2), aldo-keto reductase family 1 member C3 (AKR1C3), glutamate-cysteine ligase catalytic subunit (GCLC), and NAD(P)H dehydrogenase [quinone] 1 (NQO1) among others. We observed downregulation of several members of the plakin family including periplakin (PPL), envoplakin (EVPL), and involucrin (IVL) that are essential for terminal differentiation of keratinocytes. MRM and Western blot analysis confirmed differential expression of several candidate proteins. Our study provides insights into molecular alterations upon chronic arsenic exposure on skin.

Arsenic toxicity and epimutagenecity: the new LINEage.

Global methylation pattern regulates the normal functioning of a cell. Research have shown arsenic alter these methylation landscapes within the genome leading to aberrant gene expression and inducts various pathophysiological outcomes. Long interspersed nuclear elements (LINE-1) normally remains inert due to heavy methylation of it's promoters, time and various environmental insults, they lose these methylation signatures and begin retro-transposition that has been associated with genomic instability and cancerous outcomes. Of the various high throughput technologies available to detect global methylation profile, development of LINE-1 methylation index shall provide a cost effect-screening tool to detect epimutagenic events in the wake of toxic exposure in a large number of individuals. In the present review, we tried to discuss the state of research and whether LINE-1 methylation can be considered as a potent epigenetic signature for arsenic toxicity.

Reduced LINE-1 methylation is associated with arsenic-induced genotoxic stress in children.

Early life exposure to arsenic has profound effect towards development of arsenic induced toxic outcomes. Some districts in the state of West Bengal, India are highly affected by arsenic, mainly through ground water. In children, not much of the toxic outcomes like dermatological lesions are observed but it is thought that the exposure leads to transient alteration in their biological processes that leads to various deleterious health effects later on. We evaluated the global methylation status by analyzing the LINE-1 methylation profile in children from arsenic exposed region between the age group 5-15 years along with the cytogenetic stress induced by arsenic as measured by lymphocyte micronucleus (MN) frequency. A total of 52 arsenic exposed and 32 unexposed children were analyzed. Whole blood DNA was used to measure the LINE-1 methylation by qRT-MSP. We found a significant association of MN-frequency in exposed individuals with highly depleted LINE-1 methylation compared to the exposed individuals with near baseline (which was comparable to unexposed control) methylation index as well as with those with the hypermethylated LINE-1 promoters. From our results, we interpret that LINE-1 methylation index may serve as a potent global epigenetic mark to detect the degree of arsenic genotoxicity at a very early age. We propose that this may be utilized to determine the extent of toxic influence exerted by arsenic, from a very early age.

Arsenic exposure through drinking water leads to senescence and alteration of telomere length in humans: A case-control study in West Bengal, India.

Arsenic (As) induces pre-malignant and malignant dermatological lesions, non-dermatological health effects and cancers in humans. Senescence involves telomere length changes and acquisition of senescence-associated secretory phenotype (SASP), which promotes carcinogenesis. Though in vitro studies have shown that As induces senescence, population based studies are lacking. We investigated the arsenic-induced senescence, telomere length alteration and its contribution towards development of As-induced skin cancer. The study participants included 60 each of As-exposed individuals with skin lesion (WSL), without skin lesions (WOSL) and 60 unexposed controls. Exposure assessment of drinking water and urine was done. SA ß-gal activity, ELISA, and quantification of senescence proteins, alternative lengthening of telomere (ALT) associated proteins and telomerase activity were performed. Relative telomere length (RTL) was determined by qPCR. A significantly higher number of senescent cells, over-expression of p53 and p21 were observed in the As-exposed individuals when compared to unexposed. SASP markers, MMP-1/MMP-3 were significantly higher in the WSL but not IL-6/IL-8. A significant increase of RTL was observed in the WSL group, which was telomerase-independent but exhibited an over-expression of ALT associated proteins TRF-1 and TRF-2 with higher increase in TRF-2. An increased risk for developing As-induced skin lesions was found for individuals having RTL greater than 0.827 (odds ratio, 13.75; 95% CI: 5.66-33.41; P < 0.0001). Arsenic induces senescence in vivo, but the SASP markers are not strictly over-expressed in the As-induced skin lesion group, whereas telomerase-independent elongation of telomere length might be useful for predicting the risk of development of As-induced skin lesions.

Antimutagenic and anticancer activity of Darjeeling tea in multiple test systems.

BACKGROUND: Darjeeling tea, a most popular variety of black tea, though consumed by the people in different parts of world but its beneficial health effects have not been investigated in details. In this study, the antimutagenic and anticancer effect of Darjeeling tea extract (DTE) has been evaluated. METHODS: Antimutagenic activity of the DTE was carried out in two different strains of Salmonella typhimurium by AMES test against a known mutagen benzo[a]pyrene (B[a]P) with S9 activation. Moreover, anticlastogenic property of DTE was also measured by micronuclei formation (MN) against B[a]P with S9 activation in human lymphocytes. The anticancer activity of the same was studied on U937 cell line. Here, Human PBMCs were used as the normal cell control to identify selective anticancer activity of the extract against U937 cells. RESULTS: The results showed significant antimutagenic activity on bacterial strains. A significant decrease in MN was also observed in the DTE treated human lymphocyte cultures pretreated with B[a]P when compared with B[a]P treated cultures alone. The study clearly exhibited anticancer activity of the extract on U937 cell line. Further studies also revealed that apoptosis induction is an important mechanism behind the anticancer effect of DTE. CONCLUSION: Overall, this study indicates that DTE has significant antimutagenic and anticancer activities on bacterial and mammalian cells respectively.

Targeting 'histone mark': Advanced approaches in epigenetic regulation of telomere dynamics in cancer.

Telomere integrity is required for the maintenance of genome stability and prevention of oncogenic transformation of cells. Recent evidence suggests the presence of epigenetic modifications as an important regulator of mammalian telomeres. Telomeric and subtelomeric regions are rich in epigenetic marks that regulate telomere length majorly through DNA methylation and post-translational histone modifications. Specific histone modifying enzymes play an integral role in establishing telomeric histone codes necessary for the maintenance of structural integrity. Alterations of crucial histone moieties and histone modifiers cause deregulations in the telomeric chromatin leading to carcinogenic manifestations. This review delves into the significance of histone modifications and their influence on telomere dynamics concerning cancer. Additionally, it highlights the existing research gaps that hold the potential to drive the development of therapeutic interventions targeting the telomere epigenome.

Human urothelial micronucleus assay to assess genotoxic recovery by reduction of arsenic in drinking water: a cohort study in West Bengal, India.

Chronic exposure to arsenic through drinking water affects nearly 26 million individuals in West Bengal, India. Cytogenetic biomarkers like urothelial micronucleus (MN) are extensively used to monitor arsenic exposed population. In 2004-2005, 145 arsenic exposed individuals and 60 unexposed controls were surveyed of which 128 exposed individuals and 54 unexposed controls could be followed up in 2010-2011. In 2004-2005, the extent of arsenic content in the drinking water was 348.23 ± 102.67 µg/L, which was significantly lowered to 5.60 ± 10.83 µg/L in 2010-2011. Comparing the data obtained between 2004-2005 and 2010-2011, there was a significant decline in the MN frequency, when assayed in 2010-2011 compared to 2004-2005. Hence, we infer that urothelial MN can be utilized as a good biomarker in detecting remedial effects from toxicity of the low dose of arsenic through drinking water.

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.

Arsenic exposure through drinking water increases the risk of liver and cardiovascular diseases in the population of West Bengal, India.

BACKGROUND: Arsenic is a natural drinking water contaminant affecting 26 million people in West Bengal, India. Chronic arsenic exposure causes cancer, cardiovascular disease, liver disease, neuropathies and ocular diseases. The aims of the present study were to assess bioindicators of hepatocellular injury as indicated by the levels of liver enzymes, to determine the auto immune status, as indicated by the amounts of anti-nuclear antibodies (ANA) and anti-dsDNA antibodies in their serum, and to predict cardiovascular risk in the arsenic exposed population. METHODS: Effect of chronic arsenic exposure on liver was determined by liver function tests. Autoimmune status was measured by measuring ANA and anti-dsDNA in serum. Inflammatory cytokines associated with increased cardiovascular disease risk, IL6, IL8 and MCP-1 were determined. RESULTS: Our results indicated that serum levels of bilirubin, alanine transaminase, aspartate transaminase, alkaline phosphatase and ANA were increased in the arsenic exposed population. Serum levels of IL6 and IL8 also increased in the arsenic exposed group. CONCLUSIONS: Chronic arsenic exposure causes liver injury, increases the serum levels of autoimmune markers and imparts increased cardiovascular risk.

Comparative antimutagenic and anticancer activity of three fractions of black tea polyphenols thearubigins.

Antimutagenic and anticancer effects of black tea polyphenols theaflavins (TF) and thearubigins (TR) have previously been reported. TR is a complex mixture of polyphenols. In this study, our interest was to fractionate TR and to study the antimutagenic and anticancer activities of the fractions. Three fractions of TR, namely TR-1, TR-2, and TR-3, were isolated by chromatographic processes. Antimutagenic activity of these 3 fractions was carried out on 4 Salmonella strains by Ames assay. Anticancer activity was studied on human leukemic cells U937. Our findings clearly indicated antimutagenic and anticancer activities of the TR-1, TR-2, and TR-3 fractions on Salmonella strains and on U937 cells, respectively. However, all 3 fractions, at or below 100 µg/ml dose, did not show any significant toxic effects on the normal human cells (peripheral blood mononuclear cells). TR-2 was found to be the most active fraction among the 3. Flow cytometric and confocal microscopic studies further indicate that apoptosis induction could be an important mechanism behind the anticancer effects of these fractions. To our knowledge, this study is the first attempt to describe the antimutagenic and anticancer activity of TR fractions, and it also suggests that TR-2 is the most active component of TR.

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.

Evaluation of the serum catalase and myeloperoxidase activities in chronic arsenic-exposed individuals and concomitant cytogenetic damage.

Chronic arsenic exposure through contaminated drinking water is a major environmental health issue. Chronic arsenic exposure is known to exert its toxic effects by a variety of mechanisms, of which generation of reactive oxygen species (ROS) is one of the most important. A high level of ROS, in turn, leads to DNA damage that might ultimately culminate in cancer. In order to keep the level of ROS in balance, an array of enzymes is present, of which catalase (CAT) and myeloperoxidase (MPO) are important members. Hence, in this study, we determined the activities of these two enzymes in the sera and chromosomal aberrations (CA) in peripheral blood lymphocytes in individuals exposed and unexposed to arsenic in drinking water. Arsenic in drinking water and in urine was used as a measure of exposure. Our results show that individuals chronically exposed to arsenic have significantly higher CAT and MPO activities and higher incidence of CA. We found moderate positive correlations between CAT and MPO activities, induction of CA and arsenic in urine and water. These results indicate that chronic arsenic exposure causes higher CAT and MPO activities in serum that correlates with induction of genetic damage. We conclude that the serum levels of these enzymes might be used as biomarkers of early arsenic exposure induced disease much before the classical dermatological symptoms of arsenicosis begin to appear.

Comparison of drinking water, raw rice and cooking of rice as arsenic exposure routes in three contrasting areas of West Bengal, India.

Remediation aimed at reducing human exposure to groundwater arsenic in West Bengal, one of the regions most impacted by this environmental hazard, are currently largely focussed on reducing arsenic in drinking water. Rice and cooking of rice, however, have also been identified as important or potentially important exposure routes. Quantifying the relative importance of these exposure routes is critically required to inform the prioritisation and selection of remediation strategies. The aim of our study, therefore, was to determine the relative contributions of drinking water, rice and cooking of rice to human exposure in three contrasting areas of West Bengal with different overall levels of exposure to arsenic, viz. high (Bhawangola-I Block, Murshidibad District), moderate (Chakdha Block, Nadia District) and low (Khejuri-I Block, Midnapur District). Arsenic exposure from water was highly variable, median exposures being 0.02 µg/kg/d (Midnapur), 0.77 µg/kg/d (Nadia) and 2.03 µg/kg/d (Murshidabad). In contrast arsenic exposure from cooked rice was relatively uniform, with median exposures being 0.30 µg/kg/d (Midnapur), 0.50 µg/kg/d (Nadia) and 0.84 µg/kg/d (Murshidabad). Cooking rice typically resulted in arsenic exposures of lower magnitude, indeed in Midnapur, median exposure from cooking was slightly negative. Water was the dominant route of exposure in Murshidabad, both water and rice were major exposure routes in Nadia, whereas rice was the dominant exposure route in Midnapur. Notwithstanding the differences in balance of exposure routes, median excess lifetime cancer risk for all the blocks were found to exceed the USEPA regulatory threshold target cancer risk level of 10(-4)-10(-6). The difference in balance of exposure routes indicate a difference in balance of remediation approaches in the three districts.

Mutagenic, Genotoxic and Immunomodulatory effects of Hydroxychloroquine and Chloroquine: a review to evaluate its potential to use as a prophylactic drug against COVID-19.

Hydroxychloroquine (HCQ) and Chloroquine (CQ) are two anti-malarial drugs that are now being extensively used by front-line healthcare workers and other common people as a prophylactic drug against the Corona Virus Disease - 19 (COVID-19) in India and as well as in many parts of the world. While only a few in vitro studies have pointed to some efficacy of these drugs as a prophylactic against COVID-19, to date, there are no clinical studies that have established any clinical efficacy of these drugs as a prophylactic. These drugs are commonly used for the treatment of Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE) because of its immunomodulatory effects. Previously, we have evaluated the genetic toxicology of different drugs and chemicals including antimalarial drug CQ both in vitro and in vivo. Thus, we recognize the need to critically review the mutagenic, genotoxic, and immunomodulatory effects of these drugs, to find out whether it is safe to use as a prophylactic drug against COVID-19. Existing literature suggests that CQ can induce mutagenic and genotoxic effects in multiple test systems and both the drugs have immunomodulatory effects. There was no data available to evaluate the mutagenicity and genotoxicity for HCQ. However, during metabolism about 60% of both the drugs remain unchanged and about 40% of the drugs are metabolized into two metabolites, desethylchloroquine and bisdesethylchloroquine by the action of the cytochrome P450 (CYP) enzymes in the liver. Both HCQ and CQ are immunomodulatory drugs and have the potential to suppress normal immune system activation. In this review, we have elucidated the mechanism of immunomodulation by both HCQ and CQ and highlighted the mutagenic and genotoxic effects from the available literature. This article is written with the sole objective that the reader will be able to recognize the adverse effects of these drugs when consumed by healthy individuals as a prophylactic. Current literature indicates that healthy individuals should refrain from the use of these drugs until further investigation.

Epigenetic regulations in alternative telomere lengthening: Understanding the mechanistic insight in arsenic-induced skin cancer patients.

Telomere integrity is considered to be one of the primary mechanisms during malignant transformation. Arsenic, a group 1 carcinogenic metalloid, has been reported to cause telomere lengthening in a telomerase-independent manner. Recent studies suggest a significant role for epigenetic modifications in regulating telomeric length and integrity. Here, we have explored the role of epigenetic deregulation in alternative lengthening of telomeres (ALT) in arsenic-exposed skin cancer tissues and corresponding non-tumor tissues. The relative telomere length (RTL) was analyzed by qRT-PCR using 2-ΔΔCt method. The subtelomeric methylation pattern of the four chromosomes (7q, 18p, 21q and XpYp) were analysed by Methylation Specific PCR (MSP) in 40 pairs of arsenic exposed skin cancer tissues and its corresponding control. The role of constitutive heterochromatin histone marks in the regulation of telomere length (TL) was analyzed by targeted ELISA. A 2-fold increase of relative telomere length in 85% of the arsenic-induced skin cancer tissues was observed. Among the four chromosomes, subtelomere of XpYp was found to be hypermethylated (p < 0.001) whereas 18p was hypomethylated (p < 0.01). Additionally, the level of H4K20me3, a heterochromatic mark was found to be significantly down-regulated (p < 0.0003), and inversely correlated with telomere length indicating loss of heterochromatinization of telomeric DNA. These observations highlight the novel role of epigenetic regulation in the maintenance of constitutive heterochromatin structure at telomere. Alteration in subtelomeric DNA methylation patterns and depletion of H4K20me3 might lead to loss of heterochromatinization resulting in arsenic-induced telomeric elongation. We provide novel data indicating possible alternative determinants of telomere elongation through epigenetic modifications during arsenic-induced skin carcinogenesis which could be used as early 'epimarkers' in the near future. The findings provide new insights about the mechanism of arsenic-induced carcinogenesis.

Role of oxidation-triggered activation of JNK and p38 MAPK in black tea polyphenols induced apoptotic death of A375 cells.

Theaflavins (TF) and thearubigins (TR) are the major polyphenols of black tea. Our previous study revealed that TF- and TR-induced apoptosis of human malignant melanoma cells (A375) is executed via a mitochondria-mediated pathway. In our present study we observed the role of the three most important MAPK (ERK, JNK, and p38) in TF- and TR-induced apoptosis. TF and TR treatment of A375 cells led to sustained activation of JNK and p38 MAPK but not ERK, suggesting that JNK and p38 are the effector molecules in this polyphenol-induced cell death. This idea was further supported by subsequent studies in which JNK and p38 activation was inhibited by specific inhibitors. Significant inhibition was found in TF- and TR-treated A375 cell death pretreated with JNK- or p38-specific inhibitors only. Further, we have found that TF and TR treatment induces a time-dependent increase in intracellular reactive oxygen species generation in A375 cells. Interestingly, treatment with the antioxidant N-acetyl cystein inhibits TF- and TR-induced JNK and p38 activation as well as induction of cell death in A375 cells. We also provide evidence demonstrating the critical role of apoptosis signal-regulating kinase 1 in TF- and TR-induced apoptosis in A375 cells. Taken together our results strongly suggest that TF and TR induce apoptotic death of A375 cells through apoptosis signal-regulating kinase 1, MAPK kinase, and the JNK-p38 cascade, which is triggered by N-acetyl cystein intracellular oxidative stress.

Chronic arsenic exposure impairs macrophage functions in the exposed individuals.

INTRODUCTION: Owing to the established roles of human macrophages in immune defense, we investigated the effect of chronic arsenic exposure upon these major hematopoietic cells in 70 arsenic-exposed individuals with skin lesions and 64 unexposed individuals. METHODS: Human monocyte-derived macrophages were prepared from peripheral blood mononuclear cells, by culture of the adherent cells for 6 days in medium supplemented with granulocyte-monocyte colony stimulating factor. Parameters studied included cell adhesion capacity, expression of CD54 and F-actin, nitric oxide production, phagocytic capacity, and effect of arsenic on Rho A-ROCK pathway. RESULTS: In macrophages of exposed individuals when compared to unexposed group, there was cell rounding accompanied with a significant (p < 0.001) loss of cell adhesion capacity, decrease in nitric oxide production, impaired phagocytic capacity, and decreased CD 54 and F-actin expression. Additionally, chronic arsenic exposure affected Rho A-ROCK pathway which in turn impaired macrophage functions. DISCUSSION AND CONCLUSION: These altogether could contribute significantly to arsenic-induced immunosuppression observed in the arsenic-exposed individuals.

MicroRNAs play an important role in contributing to arsenic susceptibility in the chronically exposed individuals of West Bengal, India.

Arsenic exposure by groundwater contamination is a menace which threatens more than 26 million individuals of West Bengal. Interestingly, with similar levels of arsenic exposure, only 15-20% of the population show arsenic-induced skin lesions, the hallmarks of chronic arsenic toxicity, but the rest do not. In this study, our aim was to identify whether microRNAs (miRNA) have any role to play in causing such arsenic susceptibility. Global plasma miRNA profiling was done in 12 arsenic-exposed individuals with skin lesions and 12 exposed individuals without skin lesions. Two hundred two miRNAs were found to be differentially regulated between the two study groups. Results were validated by quantitative real-time PCR in 30 exposed subjects from each of the groups, which showed that among others miR-21, miR-23a, miR-27a, miR-122, miR-124, miR-126, miR-619, and miR-3613 were significantly upregulated and miR-1282 and miR-4530 were downregulated in the skin lesion group compared with the no skin lesion group. Bioinformatic analyses predicted that these altered miRNAs have targets in 7 different biochemical pathways, including glycerophospholipid metabolism, colorectal cancer, glycosphingolipid biosynthesis, T cell receptor signaling, and neurotrophin signaling pathways; glycerophospholipid metabolism pathway being the most enriched pathway. Association study show that these microRNAs contribute significantly to the increased prevalence of other non-dermatological health effects like conjunctival irritations of the eyes and respiratory distress in the study subjects. To our knowledge, this is the first study of its kind involving miRNA expressions contributing to arsenic susceptibility in the exposed population of West Bengal.

Molecular mechanism of black tea polyphenols induced apoptosis in human skin cancer cells: involvement of Bax translocation and mitochondria mediated death cascade.

Theaflavins (TF) and thearubigins (TR) are the most exclusive polyphenols of black tea. Even though few previous reports showed the anticancer effects of TF through apoptosis, the potential effect of TR has not been appraised. This study investigated the induction of apoptosis in human skin cancer cells after treatment of TF and TR. We report that both TF and TR could exert inhibition of A431 (human epidermoid carcinoma) and A375 (human malignant melanoma) cell proliferation without adversely affecting normal human epidermal keratinocyte cells. Growth inhibition of A375 cells occurred through apoptosis, as evident from cell cycle arrest at G(0)/G(1) phase, increase in early apoptotic cells, externalization of phosphatidylserine and DNA fragmentation. In our pursuit to dissect the molecular mechanism of TF- and TR-induced apoptosis in A375 cells, we investigated whether cell death is being mediated by mitochondria. In our system, Bax translocation to mitochondria persuaded depolarization of mitochondrial membrane potential, cytochrome c release in cytosol and induced activation of caspase-9, caspase-3 and poly (ADP-ribose) polymerase cleavage. Our intricate investigations on apoptosis also explained that TF and TR augmented Bax:Bcl2 ratio, up-regulated the expression of p53 as well as p21 and inhibited phosphorylation of the cell survival protein Akt. Furthermore, TF and TR elicited intracellular reactive oxygen species generation in A375 cells. These observations raise speculations that TF as well as TR might exert chemopreventive effect through cell cycle arrest and induction of apoptogenic signals via mitochondrial death cascade in human skin cancer cells.