Arsenic Exposure Groups Research Articles

AMPKα is active in autophagy of endothelial cells in arsenic-induced vascular endothelial dysfunction by regulating mTORC1/p70S6K/ULK1

Cardiovascular disease (CVD) is the most common cause of death, environmental factors, such as arsenic, playing an important role in the progress of CVD. Vascular endothelial dysfunction (VED) is a crucial early feature for CVD, inorganic arsenic (iAs) can induce autophagy in various cells. However, the role of endothelial autophagy has rarely been studied in VED triggered by arsenic. Total of one hundred and twenty healthy male C57BL/6J mice weighing 18–22 g were randomly divided into an arsenic-exposure group and a control group for 3, 6, 9, and 12 weeks. The results showed that, independent of the exposure period, autophagy markers of p-ATG16L1 levels and Beclin 1 contents in the aortic arch endothelium increased significantly compared with those of the corresponding control group. And different exposure duration decreased NO contents in the serum significantly. Combined with the histological changes that endothelial injury aggravated gradually with the increasing exposure period, suggesting that under exposure to iAs over 9 weeks, VED was remarkably induced, and consistant high levels of endothelial autophagy may play an important role. Additionally, levels of p-AMPKα/AMPKα increased significantly and p-mTORC1/mTORC1 levels decreased remarkably in the aortic arch endothelium. Then, a NaAsO2-induced-VED in vitro model was used to explore the mechanism of arsenic-induced endothelial autophagy. Similarly, p-AMPKα/AMPKα level significantly increased, and p-mTORC1/mTORC1 level remarkably decreased induced by 30 μmol/L NaAsO2 in HUAECs. Further, an AMPK inhibitor (Compound C) pre-treatment prior to arsenic exposure reversed the increased autophagy level, and alleviated the endothelial dysfunction in HUVECs, as shown by the significant increase in the intracellular NO content and the cell vitality. Mechanistically, we revealed that AMPKα is active in autophagy of endothelial cells in arsenic-induced VED by regulating mTORC1/p70S6K/ULK1. The present study provide a new promising target for prevention and control arsenic-associated CVD.

Preliminary study on the effect of fecal microbiota transplantation on neurobehavior and gut microbiota of offspring rats exposed to arsenic

Objective: To explore the effects of fecal microbiota transplantation (FMT) on neurobehavior and gut microbiota of arsenic-exposed offspring rats. Methods: In April 2021, Thirty-six SPF SD rats aged 8 weeks were seleted, rats were ranked by weight and divided into four groups according to randomized block design, namely control group, arsenic exposure group (As group) , arsenic+normal saline group (As+NaCl group) and As+FMT group, 6 females and 3 males in each group. Fecal microbiota fluid were provided by feces of rats in control group. Rats drank tap water containing 75 mg/L sodium arsenite for one week and then were caged together. The arsenic exposure was terminated until the pups were born. Female rats with vaginal plug were treated with fecal microbiota fluid via gavage during neurodevelopmental teratogenic window period. The volume of gavage was 1 ml/100 g with once every two days, for a total of three times. Weight alterations of offspring rats were recorded every week after weaning, and when offspring rats grew up for 6 weeks, Morris test and open field experiment was used to observe learning and memory abilities, as well as neurobehavioral performance of autonomous exploration and tension, respectively. 16S rDNA sequencing technology was used to detect microbiota diversities in fecal samples of rats in As group and As+FMT group. Results: Compared with the control group, the ratio of swimming distance and staying time in the target quadrant and the times of crossing the platform of rats in As group decreased significantly, and the motor distance, times entering central zone and the number of grid crossing of rats decreased significantly (P<0.05) . Compared with As group, the ratio of swimming distance in target quadrant, the motor distance in central zone and times entering central zone of rats in As+FMT group were evidently increased (P<0.05) . The analysis of fecal microbiota diversities showed that, at the phyla level, the relative abundance of Bacteroidetes in feces of rats in As+FMT group was higher than that in As group (68.34% vs 60.55%) , while the relative abundance of Firmicutes was lower than that in As group (28.02% vs 33.48%) . At the genus level, the relative abundance of Prevotella in As+FMT group was significantly higher than that in As group, becoming the dominant genus (42.08% vs 21.78%) . Additionally, compared with As group, a total of 22 genus were increased with 21 decreased genus in As+FMT group (P<0.05) . LEfSe analysis showed that dominant genuses in As+FMT group were Prevotella and UCG_005, and their relative abundance was significantly higher than that of As group (P<0.05) . Conclusion: FMT may alleviate the impaired learning and memory ability and anxiety like behavior of the offspring rats exposed to arsenic, and improve the disrupted gut microbiota.

Arsenic-induced lung inflammation and fibrosis in a rat model: Contribution of the HMGB1/RAGE, PI3K/AKT, and TGF-β1/SMAD pathways

An increasing number of studies have shown that arsenic exposure increases the risk of lung cancer as well as a variety of non-malignant respiratory diseases, including bronchitis and tracheobronchitis. HMGB1 is widely expressed in a variety of tissues and cells and is involved in the pathological processes of many lung diseases through binding to the corresponding receptors and activating the downstream signaling pathways. However, the exact role of HMGB1/RAGE in arsenic-induced lung injury remains unknown. The aim of this study was to investigate whether HMGB1/RAGE and its activated downstream pathways are involved in the process of arsenic exposure-induced lung injury in rats. In this study, an animal model of oral exposure to arsenic was induced using 2.5, 5 and 10 mg/kg NaAsO2. The results showed that capillary permeability (LDH, TP, ACP, and AKP) was increased in the arsenic exposure groups, resulting in cell damage; this was accompanied by acute inflammation marked by significant neutrophil infiltration. Meanwhile, obvious histopathological damage, including thickening of the lung epithelium, increased infiltration of inflammatory cells, rupture of the alveolar wall, swelling of the mitochondria, and chromatin agglutination was observed by H&E staining and transmission electron microscopy. Furthermore, the results confirmed that the expressions of HMGB1 and RAGE in lung tissue were enhanced, and protein expression of PI3K, p-AKT, IL-1β, IL-18, and MMP-9 was increased in lung homogenates from the arsenic-exposed groups compared to the control group. Finally, Masson's staining results revealed arsenic-induced fibrosis and collagen deposition. Moreover, a significant increase in key fibrosis factors, including TGF-β1, p-SMAD2, p-SMAD3, and SMAD4 was observed in the lung homogenates in arsenic-exposed groups. In conclusion, the current study demonstrates that sub-chronic arsenic exposure triggers the inflammatory response and collagen fiber deposition in rat lung tissue. The potential mechanism may be closely related to activation of the pro-inflammatory-related HMGB1/RAGE pathway and initiation of the PI3K/AKT and TGF-β1/SMAD pathways.

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

Assessing potential mechanisms of arsenic-induced skin lesions and cancers: Human and in vitro evidence

Environmental exposure to arsenic is a major public health challenge worldwide. In detailing the hallmark signs of chronic arsenic exposure, previous studies have shown that epigenetic and immune dysfunction are associated with arsenic-induced skin lesions; however, knowledge regarding interactions between the mechanisms listed above is limited. In this study, a total of 106 skin samples were collected over the past 20 years. Based on the presence or absence of high arsenic exposure, the participants were divided into arsenic exposure (72) and reference (34) groups. Additionally, the arsenic exposure group was further divided into the non-cancer group (31, including skin hyperpigmentation and hyperkeratosis) and the skin cancer group (41, including Bowen’s disease, basal cell carcinoma and squamous cell carcinoma) according to a skin histopathological examination. First, the associations among miR-155, NF-AT1 with immunological dysfunction and arsenic-induced skin lesions and carcinogenesis were confirmed using these skin samples. In the arsenic-exposed group, miR-155–5p, keratin 1(Krt1), keratin 10 (Krt10), and keratin 6c (Krt6c) were significantly increased in the skin (p < 0.05), while NF-AT1, interleukin-2 (IL-2), and interferon-γ (IFN-γ) were significantly decreased (p < 0.05). Clear correlations were observed among these factors (p < 0.05). In immortalized human keratinocytes, silencing and overexpression of NF-AT1 could alter the expression and secretion of immunological dysfunction indicators (IL-2 and IFN-γ) that are induced by arsenic exposure (p < 0.05); however, miR-155–5p levels did not change significantly (p > 0.05). The miR-155–5p mimic and inhibitor could regulate the NF-AT1-mediated immunological dysfunction caused by arsenic (p < 0.05). Our study provides some limited evidence that miR-155–5p regulates the NF-AT1-mediated immunological dysfunction that is involved in the pathogenesis and carcinogenesis of arsenic. The second major finding was that Krt1 and Krt10 are markers of hyperkeratosis caused by arsenic, and Krt6c is a potential biomarker that can reflect arsenic carcinogenesis.

Role of Glutathione-S-Transferase Polymorphism on Arsenic-Induced Protein Carbonylation and Urinary Deoxy Guanosine Status

Oxidative stress is significantly associated with chronic arsenic exposure in persons exposed to moderate-to-high level of environmental arsenic. However, the response varies widely among persons within similar exposure level. To study whether Glutathione-S-Transferase (GST) gene polymorphism plays any pivotal role in this variation, total number of 115 chronic arsenic-exposed study subjects without arsenic-induced cancer from School of Tropical Medicine, Kolkata and from arsenic-exposed districts of West Bengal were recruited for this study. Concentration of arsenic in their urine and water, extent of clinical manifestation, GST status and protein carbonylation, and 8-oxo-2′-deoxyguanosine status were determined. Genetic polymorphism of GSTM1 and T1 were significantly associated (p < 0.05) with degree of protein carbonylation and 8-oxo-2′-deoxyguanosine in moderate-to-high degree of arsenic exposure groups. Persons having null genotype have significantly increased level of protein carbonylation and 8-oxo-2′-deoxyguanosine in comparison to persons with GSTM1 or GSTT1 non-null genotype of the same arsenic exposure group. Degree of protein carbonylation and urinary 8-oxo-2-deoxyguanosine is positively correlated with GST null genotype.

Effects of Proanthocyanidins on Arsenic Methylation Metabolism and Efflux in Human Hepatocytes L-02.

This study investigated the effects of proanthocyanidins (PC) on arsenic methylation metabolism and efflux in human hepatocytes (L-02), as well as the relationships between PC and GSH, MRP1 and other molecules. Cells were randomly divided into blank control group, arsenic trioxide exposure group (ATO, As2O3, 25μmol/L), and PC-treated arsenic exposure group (10, 25, 50mg/L). After 24/48h, the contents of different forms of arsenic were determined, and the methylation indexes were calculated. Intracellular S-adenosyl methionine (SAM), arsenic (+3 oxidation state) methyltransferase (AS3MT), multidrug resistance-associated protein 1 (MRP1), and reduced glutathione (GSH) were ascertained. Changing trends were observed and the correlation between arsenic metabolism and efflux related factors and arsenic metabolites was analyzed. We observed that cells showed increased levels of content/constituent ratio of methyl arsenic, primary/secondary methylation index, methylation growth efficiency/rate, and the difference of methyl arsenic content in cells and culture medium (P<0.05, resp.). Compared with ATO exposure group, the intracellular SAM content in PC-treated group decreased, and the contents of GSH, AS3MT, and MRP1 increased (P<0.05, resp.). There was a positive correlation between the content of intracellular GSH/AS3MT and methyl arsenic. The content of MRP1 was positively correlated with the difference of methyl arsenic content in cell and culture medium; conversely, the SAM content was negatively correlated with intracellular methyl arsenic content (P<0.05, resp.). Taken together, these results prove that PC can promote arsenic methylation metabolism and efflux in L-02 cells, which may be related to the upregulation of GSH, MRP1, and AS3MT levels by PC.

Effect and mechanism of cyclooxygenase-2 on sodium arsenic-induced microglia activation in mice

Objective To investigate the effect and mechanism of cyclooxygenase-2 (COX-2) on sodium arsenic-induced microglia activation in mice. Methods Twenty of C57BL/6J male mice were randomly divided into a control group supplied with tap water and an arsenic exposure group administered with drinking water containing 50 mg/L sodium arsenite (NaAsO 2 ) continuously for 12 weeks to establish a chronic arsenic exposure model. Morris water maze was used to test learning and memory ability of the mice. Hematoxylin-eosin (HE) staining and transmission electron microscopy were used to observe pathological changes of neuron and ultrastructure in hippocampus. Immunofluorescence microscopy was used to determine expression of ionized calcium-binding adapter molecule 1 (IBA-1) in hippocampus. The protein expressions of IBA-1, COX-2, transcription factor nuclear factor kappa-Bp65 (NF- κ Bp65) were detected with Western blot. The concentration of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF- α ) was measured with enzyme-linked immunosorbent assay (ELISA). Results Compared to the control group, the mice with arsenic exposure had significantly increased escape latency time (50.79 ± 12.30 vs. 29.01 ± 18.10 seconds) but decreased effectively traveled distance (9.34 ± 2.34 vs. 11.78 ± 1.25 centimeters) (both P < 0.05l). Pathological changes such as disarrangement of cells, edema and nuclei atrophy were observed in the hippocampus of arsenic exposed mice. The protein expression of IBA-1 was increased in arsenic exposed mice based on observation of green fluorescence aggregation with fluorescence microscope. In comparison with those in hippocampus of the control mice, significantly higher levels of IBA-1 (1.01 ± 0.12 vs. 0.75 ± 0.13), NF- κ Bp65 (1.23 ± 0.11 vs. 0.86 ± 0.14), COX-2 (1.14 ± 0.13 vs. 0.74 ± 0.12), IL-6 (93.61 ± 3.18 vs. 43.37 ± 1.11 pg/mL) and TNF- α (604.00 ± 25.02 vs. 198.46 ± 9.93 pg/mL) were detected in arsenic exposed mice ( P < 0.05 for all). Conclusion Chronic arsenic exposure-induced learning and memory impairment are associated with the activation of microglia by the activation of NF- κ B and the increase in the secretion of pro-inflammatory cytokines by upregulation of COX-2 in mice 【摘 要】 目的 探讨环氧合酶-2（COX-2）在亚砷酸钠诱导小鼠小胶质细胞活化中的作用及机制。 方法 建立慢性小鼠饮水砷暴露模型，将 20 只 C57BL/6J 雄性小鼠随机分为对照组（自来水）和砷暴露组（50 mg/L NaAsO 2 ），连续自由饮水暴露 12 周。Morris 水迷宫实验检测小鼠学习记忆能力；苏木精-伊红染色和透射电镜观察海马区神经元病理变化及超微结构改变；免疫荧光检测海马区离子钙结合配适分子-1（IBA-1）表达；蛋白印迹法（WB）检测海马区 IBA-1、COX-2、核因子 κ B p65（NF- κ B p65）蛋白表达；酶联免疫吸附法（ELISA）检测海马区白细胞介素-6（IL-6）和肿瘤坏死因子 α （TNF- α ）表达。 结果 与对照组小鼠[逃避潜伏期（29.01 ± 18.10）s、有效停留距离（11.78 ± 1.25）cm]比较，砷暴露组小鼠逃避潜伏期[（50.79 ± 12.30）s]延长，有效停留距离明显缩短[（9.34 ± 2.34）cm]（ P < 0.05）；砷暴露组小鼠海马区出现细胞排列紊乱、水肿、皱缩等病理改变，荧光显微镜下 IBA-1 绿色荧光表达增多。与对照组[IBA-1 （0.75 ± 0.13）、NF- κ B p65（0.86 ± 0.14）、COX-2（0.74 ± 0.12）表达水平及 IL-6（43.37 ± 1.11）pg/mL、TNF- α （198.46 ± 9.93）pg/mL 含量]比较，砷暴露组小鼠海马 IBA-1（1.01 ± 0.12）、NF- κ Bp65（1.23 ± 0.11）、COX-2（1.14 ± 0.13）表达水平及 IL-6 和 TNF-α 含量[分别为（93.61 ± 3.18）、（604.00 ± 25.02）pg/mL]明显升高，差异均具有统计学意义（ P < 0.05）。 结论 慢性砷暴露导致小鼠学习记忆损伤机制可能与小胶质细胞活化，激活 NF- κ B 上调 COX-2 分泌促炎性细胞因子，促进神经炎症有关。

Exposure to arsenic during embryogenesis impairs olfactory sensory neuron differentiation and function into adulthood

Arsenic is a contaminant of food and drinking water. Epidemiological studies have reported correlations between arsenic exposure and neurodevelopmental abnormalities, such as reduced sensory functioning, while in vitro studies have shown that arsenic reduces neurogenesis and alters stem cell differentiation. The goal of this study was assess whether arsenic exposure during embryogenesis reduced olfactory stem cell function and/or numbers, and if so, whether those changes persist into adulthood. Killifish (Fundulus heteroclitus) embryos were exposed to 0, 10, 50 or 200 ppb arsenite (AsIII) until hatching, and juvenile fish were raised in clean water. At 0, 2, 4, 8, 16, 28 and 40 weeks of age, odorant response tests were performed to assess specific olfactory sensory neuron (OSN) function. Olfactory epithelia were then collected for immunohistochemical analysis of stem cell (Sox2) and proliferating cell numbers (PCNA), as well as the number and expression of ciliated (calretinin) and microvillus OSNs (Gαi3) at 0, 4, 16 and 28 weeks. Odorant tests indicated that arsenic exposure during embryogenesis increased the start time of killifish responding to pheromones, and this altered start time persisted to 40 weeks post-exposure. Response to the odorant taurocholic acid (TCA) was also reduced through week 28, while responses to amino acids were not consistently altered. Immunohistochemistry was used to determine whether changes in odorant responses were correlated to altered cell numbers in the olfactory epithelium, using markers of proliferating cells, progenitor cells, and specific OSNs. Comparisons between response to pheromones and PCNA + cells indicated that, at week 0, both parameters in exposed fish were significantly reduced from the control group. At week 28, all exposure are still significantly different than control fish, but now with higher PCNA expression coupled with reduced pheromone responses. A similar trend was seen in the comparisons between Sox2-expressing progenitor cells and response to pheromones, although Sox2 expression in the 28 week-old fish only recovers back to the level of control fish rather than being significantly higher. Comparisons between calretinin expression (ciliated OSNs) and response to TCA demonstrated that both parameters were reduced in the 200 ppb arsenic-exposed fish in at weeks 4, 16, and 28. Correlations between TCA response and the number of PCNA + cells revealed that, at 28 weeks of age, all arsenic exposure groups had reductions in response to TCA, but higher PCNA expression, similar to that seen with the pheromones. Few changes in Gαi3 (microvillus OSNs) were seen. Thus, it appears that embryonic-only exposure to arsenic has long-term reductions in proliferation and differentiation of olfactory sensory neurons, leading to persistent effects in their function.

Role of Pigment Epithelium-Derived Factor in Arsenic-Induced Vascular Endothelial Dysfunction in a Rat Model.

Water-borne arsenicosis is caused by the consumption of excess levels of inorganic arsenic from drinking water and is a worldwide public health issue. Arsenic exposure has recently attracted extensive attention due to its damage to the cardiovascular system. Vascular endothelial dysfunction (VED) is recognized as an important cause of cardiovascular diseases. Pigment epithelium-derived factor (PEDF) plays an important role in maintaining endothelial function, and our previous studies suggested that PEDF may have role in arsenic-induced damage. In the present study, we established subchronic arsenic exposure (3months) rat model from drinking water at doses of 0, 2mg/L, 10mg/L, and 50mg/L, respectively. The results showed that the endothelial cells of the aortic arch were obviously damaged, the apoptosis rate increased, the vWF and iNOS levels increased, and the NO and TNOS levels significantly decreased in the arsenic exposure groups. Regardless of serum or aortic arch endothelium, PEDF levels in the arsenic exposure groups decreased compared to the control group. The oxidative stress level and key proteins associated with apoptosis such as Fas, FasL, P53, and p-p38 were then detected to explore the detailed mechanisms. The results showed that the P53 and p-p38 levels significantly increased in the 10mg/L and 50mg/L groups compared to the control group. The MDA content in the arsenic exposure groups increased markedly, whereas the SOD activity decreased significantly with the increased arsenic dose. Taken together, our study is the first to find that PEDF plays a protective role in arsenic-induced endothelial dysfunction through anti-oxidation and anti-apoptosis, and p38 and P53 may be promising target proteins.

Effects of sodium arsenite exposure on activation and extracellular matrix secretion of human hepatic stellate cells

Objective: To explore the effects of sodium arsenite (NaAsO(2)) exposure on the activation and extracellular matrix secretion of human hepatic stellate cells, and to provide a theoretical basis for the mechanism study of arsenic induced hepatic fibrosis. Methods: Different doses of NaAsO(2) (0.0, 0.1, 1.0, 10.0, 50.0, 100.0 μmol/L) were exposed to human hepatic stellate cell line (Lx-2) for 24, 48 and 72 huors. CCK-8 assay was used to measure cell viability and IC(50) of NaAsO(2) on Lx-2 was then calculated; According to IC(50) results, 0.000, 1.875, 3.750, 7.500, and 15.000 μmol/L of NaAsO(2) were exposed to Lx-2 cells for 24 hours, besides, 7.500 μmol/L of NaAsO(2) was exposed to Lx-2 cells for 0, 12, 24, 48, and 72 hours, then collected cells and culture supernatant; HSC activation-related protein, including α-smooth muscle actin (α-SMA), and transforming growth factor-β1 (TGF-β1) expression levels were detected by Western blot analysis, the main extracellular matrix including laminin (LN) , hyaluronic acid (HA), collagen Ⅳ (COL-Ⅳ) and procollagen Ⅲ(P Ⅲ NP) secretion level was detected by Elisa assay. Results: CCK-8 assay showed that the cell viability of Lx-2 cells were increased obviously at low doses (≤1.0 μmol/L) of arsenic exposure, especially at 48 and 72 h. In contrast, with the increasing doses of arsenic exposure, the survival rate of Lx-2 cell was decreased gradually, and the survival rate of the high-dose (50, 100 μmol/L) arsenic exposure group at 24, 48 and 72 h were significantly lower than 0.0 μmol/L group, P<0.05. The IC(50) of NaAsO(2) on Lx-2 cells at 24, 48, 72 h were calculated as 72.75, 48.19 and 29.95 μmol/L, respectively; The expression levels of HSC activation-related protein showed that, after treated with 1.875, 3.750, 7.500, 15.000 μmol/L NaAsO(2) for 24 h, α-SMA and TGF-β1 protein level were higher than 0.000 μmol/L group. The increased expression of α-SMA and TGF-β1 protein were most significant in 7.500 μmol/L NaAsO(2) group (P<0.05). In addition, the expression levels of α-SMA and TGF-β1 also showed a time-dependent increasing in Lx-2 cells after treated with 7.500 μmol/L NaAsO(2) for 0, 12, 24, 48 and 72 h; Elisa assay showed that after treated with 1.875, 3.750, 7.500, 15.000 μmol/L NaAsO(2) for 24 h, the secretion levels of HA, LN, COL-Ⅳ and PⅢNP were obvious higher than 0.000 μmol/L group (P<0.05). Moreover, the secretion levels of HA, LN, COL-Ⅳ and P Ⅲ NP also showed a time-dependent increased manner in Lx-2 cells after exposed to 7.500 μmol/L NaAsO(2) for 0, 12, 24, 48 and 72 h (P<0.05). Conclusion: NaAsO(2) exposure to Lx-2 cells can upregulate the expression level of HSC activation-related proteins, induce its further activation, then increase ECM secretion level.

Postnatal low-concentration arsenic exposure induces autism-like behavior and affects frontal cortex neurogenesis in rats

This study aimed to explore the effects of postnatal low-concentration arsenic exposure on learning, social skills and frontal cortex neurogenesis in rats. Water-based arsenic exposure rat models were established on postnatal days 4–10 (P4-P10). The experimental animals were divided into four groups: the control group, a 15 μg/L As2O3 water group, a 30 μg/L As2O3 water group, and a 45 μg/L As2O3 water group. Cognitive function was examined with the Morris water maze, anxiety-like behavior with the open field test and light-dark box test, and social skills with a social interaction test. The frontal cortices of pups from each experimental group were sectioned at various time points after arsenic exposure. The morphologies and neurogenesis of the neurons in the frontal cortices were observed by hematoxylin-eosin staining, Nissl staining, and doublecortin (DCX) immunostaining. Significant positive correlations between arsenic concentration and deficits in learning and social skills were found, and the arsenic exposure groups showed significant increases in anxiety-like behavior compared with the control group (all Ps<0.05). Abnormal morphologic changes in the external granular layer and external pyramidal layer were positively correlated with the water arsenic concentration in the acute phase of arsenic exposure. However, at five weeks after arsenic exposure, the frontal cortex morphology was restored. Moreover, immunohistochemistry revealed that compared to the control group, the groups that were exposed to arsenic exhibited significantly higher levels of DCX expression in the external granular and external pyramidal layers (all Ps<0.001). Furthermore, the 30 μg/L and 45 μg/L arsenic exposure groups still showed some DCX expression at five weeks after exposure. In conclusion, postnatal low-concentration arsenic exposure impaired learning and social skills and increased anxiety-like behaviors, and abnormal frontal cortex neurogenesis may be the mechanism underlying these effects.

Effect of Arsenic on Intracellular Calcium & Redox Homeostasis

A range of environmental agents causes tissue injury that has been attributed to reactive oxygen species (ROS). Altered ROS production is commonly originated from the mitochondria and is associated with dysregulation of calcium (Ca2+) homeostasis and mitochondrial apoptosis. However, the causative pathways remain largely unknown because the fundamental roles of mitochondria in cell survival, cell signaling and dynamics are commonly mediated through local communication between mitochondria and other organelles, which have been difficult to directly monitor. Our aim is to develop fluorescent protein-based tools allowing sensitive and specific measurements of ROS and [Ca2+] at the mitochondria-endoplasmic reticulum (ER) interface. Applying these novel tools, we have studied the effects of environmental stress caused by arsenicon local mitochondria-ER communication and its impact for cell signaling, and cell physiology in primary mouse hepatocytes. Either acute addition (30 µM) or prolonged, overnight exposure (3 µM) to sodium arsenite has induced an increase in ROS. Upon prolonged arsenic exposure, these alterations were accompanied by a significant decrease in the cytoplasmic calcium signal to an IP3-linked agonist: a decrease was observed in the fraction of responsive cells, in the amplitude of the response as well as in the sustained phase. Regarding the acute effect of arsenic, we observed a progressive increase of the basal cytoplasmic [Ca2+] with a decrease in the amplitude of the IP3-linked calcium signal. Neither acute nor prolonged arsenic exposure impaired mitochondrial calcium uptake. Nevertheless, we documented increased mitochondrial calcium content in the prolonged arsenic exposure group. In conclusion, the results suggest that an initial component of the arsenic-induced hepatocyte injury is increased ROS, which is associated with impaired local mitochondria-ER calcium communication.

Taurine Normalizes the Levels of Se, Cu, Fe in Mouse Liver and Kidney Exposed to Arsenic Subchronically.

To evaluate the benefits of taurine on the homeostasis of trace elements induced by toxic metals, we investigated the concentration of Selenium (Se), Copper (Cu), Iron (Fe) and Manganese (Mn) in mouse liver and kidney after arsenic exposure for 2 months. The experimental animals were divided into control group, arsenic exposure group (1, 2, 4 ppm) and taurine protective group randomly. Concentrations of serum, liver and kidney trace elements such as Se, Cu, Fe, Mn were measured by Inductively Coupled Plasma-Mass Spectrometry. Our results showed that the concentration of Cu was higher, however, the concentration of Se and Fe was lower in mice liver and kidney exposed to arsenic. The levels of Se, Cu, Fe were alleviated by co-administered with taurine. Furthermore, there was no difference in the concentration of Mn between the three groups. Our finding suggests that taurine may relieve the disturbed levels of Se, Cu and Fe in liver and kidney induced by arsenic.

Specific histone modification responds to arsenic-induced oxidative stress

To explore whether specific histone modifications are associated with arsenic-induced oxidative damage, we recruited 138 arsenic-exposed and arsenicosis subjects from Jiaole Village, Xinren County of Guizhou province, China where the residents were exposed to arsenic from indoor coal burning. 77 villagers from Shang Batian Village that were not exposed to high arsenic coal served as the control group. The concentrations of urine and hair arsenic in the arsenic-exposure group were 2.4-fold and 2.1-fold (all P<0.001) higher, respectively, than those of the control group. Global histone modifications in human peripheral lymphocytes (PBLCs) were examined by ELISA. The results showed that altered global levels of H3K18ac, H3K9me2, and H3K36me3 correlated with both urinary and hair-arsenic levels of the subjects. Notably, H3K36me3 and H3K18ac modifications were associated with urinary 8-OHdG (H3K36me3: β=0.16; P=0.042, H3K18ac: β=−0.24; P=0.001). We also found that the modifications of H3K18ac and H3K36me3 were enriched in the promoters of oxidative stress response (OSR) genes in human embryonic kidney (HEK) cells and HaCaT cells, providing evidence that H3K18ac and H3K36me3 modifications mediate transcriptional regulation of OSR genes in response to NaAsO2 treatment. Particularly, we found that reduced H3K18ac modification correlated with suppressed expression of OSR genes in HEK cells with long term arsenic treatment and in PBLCs of all the subjects. Taken together, we reveal a critical role for specific histone modification in response to arsenic-induced oxidative damage.

Altered Hepatic Transport by Fetal Arsenite Exposure in Diet-Induced Fatty Liver Disease.

Non-alcoholic fatty liver disease can result in changes to drug metabolism and disposition potentiating adverse drug reactions. Furthermore, arsenite exposure during development compounds the severity of diet-induced fatty liver disease. This study examines the effects of arsenite potentiated diet-induced fatty liver disease on hepatic transport in male mice. Changes were detected for Mrp2/3/4 hepatic transporter gene expression as well as for Oatp1a4/2b1/1b2. Plasma concentrations of Mrp and Oatp substrates were increased in arsenic exposure groups compared with diet-only controls. In addition, murine embryonic hepatocytes and adult primary hepatocytes show significantly altered transporter expression after exposure to arsenite alone: a previously unreported phenomenon. These data indicate that developmental exposure to arsenite leads to changes in hepatic transport which could increase the risk for ADRs during fatty liver disease.

Evaluation of aortic elasticity parameters in arsenic exposed workers.

One of the major complications of arsenic on human health is hypertension. Arsenic-related hypertension and negative effects of arsenic on arterial system such as oxidative stress and vasoconstriction/vasorelaxation imbalance may lead to impair aortic elasticity. The aim of this study was to evaluate the effects of arsenic on aortic elasticity parameters including aortic strain and distensibility. One hundred twelve (112) workers were occupationally exposed to arsenic and 60 healthy control subjects were enroled. All patients underwent transthoracic echocardiography for detecting aortic strain and aortic distensibility. There were no differences in baseline demographic and echocardiographic characteristics between the groups. Aortic strain (10.3±3.9 vs 12.1±2.7%, P=0.001) and aortic distensibility (0.45±0.17 vs 0.54±0.15 cm2 per dyn, P=0.001) were decreased in arsenic-exposure group compared with controls. Urinary arsenic level was found to be negatively and significantly correlated with aortic strain (r=-0.306, P=0.001) and aortic distensibility (r=-0.259, P=0.006). Duration of arsenic exposure was also found to be negatively and significantly correlated with aortic strain (r=-0.386, P<0.001) and aortic distensibility (r=-0.333, P<0.001). This study suggests that arsenic exposure is related to impairment of aortic elasticity parameters even in subjects without overt cardiovascular disease.

Role of Glutathione-S-Transferase Polymorphism on Arsenic Induced DNA Hypermethylation

People chronically exposed to environmental arsenic through their drinking water experience various arsenic induced clinical manifestations and there is modulation of methylation level in their genome. However the response varies widely among persons. The present manuscript deals with the evaluation of role of individual's GST status in altering the degree of DNA methylation after chronic arsenic exposure in human. To study whether Glutathione-S-Transferase (GST) gene polymorphism plays any role in this variation, a total of 92 study subjects were recruited from the villages of southern region of West Bengal, India. Concentration of arsenic in their urine and water, extent of clinical manifestation, GST status and p53 and p16 gene promoter methylation status were determined. Results showed that genetic polymorphism of GSTM1 and T1 were significantly associated (p<0.05) with degree of methylation in p53 and p16 gene promoter region and urinary arsenic in higher exposure group. Persons having null genotype have significantly decreased urinary arsenic and increased DNA methylation level relative to persons with GSTM1 or GSTT1 nonnull genotype of same arsenic exposure group. In the present work we are therefore trying to show that individual's GST polymorphic status may alter the degree of DNA methylation after arsenic exposure.

Sex-specific patterns and deregulation of endocrine pathways in the gene expression profiles of Bangladeshi adults exposed to arsenic contaminated drinking water

Arsenic contamination of drinking water occurs globally and is associated with numerous diseases including skin, lung and bladder cancers, and cardiovascular disease. Recent research indicates that arsenic may be an endocrine disruptor. This study was conducted to evaluate the nature of gene expression changes among males and females exposed to arsenic contaminated water in Bangladesh at high and low doses. Twenty-nine (55% male) Bangladeshi adults with water arsenic exposure ranging from 50 to 1000μg/L were selected from the Folic Acid Creatinine Trial. RNA was extracted from peripheral blood mononuclear cells for gene expression profiling using Affymetrix 1.0 ST arrays. Differentially expressed genes were assessed between high and low exposure groups for males and females separately and findings were validated using quantitative real-time PCR. There were 534 and 645 differentially expressed genes (p<0.05) in the peripheral blood mononuclear cells of males and females, respectively, when high and low water arsenic exposure groups were compared. Only 43 genes overlapped between the two sexes, with 29 changing in opposite directions. Despite the difference in gene sets both males and females exhibited common biological changes including deregulation of 17β-hydroxysteroid dehydrogenase enzymes, deregulation of genes downstream of Sp1 (specificity protein 1) transcription factor, and prediction of estrogen receptor alpha as a key hub in cardiovascular networks. Arsenic-exposed adults exhibit sex-specific gene expression profiles that implicate involvement of the endocrine system. Due to arsenic's possible role as an endocrine disruptor, exposure thresholds for arsenic may require different parameters for males and females.

Environmental arsenic exposure and microbiota in induced sputum.

Arsenic exposure from drinking water is associated with adverse respiratory outcomes, but it is unknown whether arsenic affects pulmonary microbiota. This exploratory study assessed the effect of exposure to arsenic in drinking water on bacterial diversity in the respiratory tract of non-smokers. Induced sputum was collected from 10 subjects with moderate mean household water arsenic concentration (21.1 ± 6.4 ppb) and 10 subjects with low household water arsenic (2.4 ± 0.8 ppb). To assess microbiota in sputum, the V6 hypervariable region amplicons of bacterial 16s rRNA genes were sequenced using the Ion Torrent Personal Genome Machine. Microbial community differences between arsenic exposure groups were evaluated using QIIME and Metastats. A total of 3,920,441 sequence reads, ranging from 37,935 to 508,787 per sample for 316 chips after QIIME quality filtering, were taxonomically classified into 142 individual genera and five phyla. Firmicutes (22%), Proteobacteria (17%) and Bacteriodetes (12%) were the main phyla in all samples, with Neisseriaceae (15%), Prevotellaceae (12%) and Veillonellacea (7%) being most common at the genus level. Some genera, including Gemella, Lactobacillales, Streptococcus, Neisseria and Pasteurellaceae were elevated in the moderate arsenic exposure group, while Rothia, Prevotella, Prevotellaceae Fusobacterium and Neisseriaceae were decreased, although none of these differences was statistically significant. Future studies with more participants and a greater range of arsenic exposure are needed to further elucidate the effects of drinking water arsenic consumption on respiratory microbiota.