Effects of arsenic on telomerase and telomeres in relation to cell proliferation and apoptosis in human keratinocytes and leukemia cells in vitro

Early life exposure to mercury and relationships with telomere length and mitochondrial DNA content in European children

BACKGROUND

Telomere length (TL) and mitochondrial function expressed as mitochondrial DNA copy number (mtDNAcn) are biomarkers of aging and oxidative stress and inflammation, respectively. Methylmercury (MeHg), a common pollutant in fish, induces oxidative stress. We hypothesized that elevated oxidative stress from exposure to MeHg decreases mtDNAcn and shortens TL.

METHODS

Study participants are 6-11-year-old children from the HELIX multi-center birth cohort study, comprising six European countries. Prenatal and postnatal total mercury (THg) concentrations were measured in blood samples, TL and mtDNAcn were determined in child DNA. Covariates and confounders were obtained by questionnaires. Robust regression models were run, considering sociodemographic and lifestyle covariates, as well as fish consumption. Sex, ethnicity, and fish consumption interaction models were also run.

RESULTS

We found longer TL with higher pre- and postnatal THg blood concentrations, even at low-level THg exposure according to the RfD proposed by the US EPA. The prenatal association showed a significant linear relationship with a 3.46 % increase in TL for each unit increased THg. The postnatal association followed an inverted U-shaped marginal non-linear relationship with 1.38 % an increase in TL for each unit increased THg until reaching a cut-point at 0.96 μg/L blood THg, from which TL attrition was observed. Higher pre- and postnatal blood THg concentrations were consistently related to longer TL among cohorts and no modification effect of fish consumption nor children's sex was observed. No association between THg exposure and mtDNAcn was found.

DISCUSSION

We found evidence that THg is associated with TL but the associations seem to be time- and concentration-dependent. Further studies are needed to clarify the mechanism behind the telomere changes of THg and related health effects.

Natural peloids originating from subsea depths of 200 m in the hupo basin, South Korea: physicochemical properties for potential pelotherapy applications

The present study firstly reports surface sediment from the subsea depth of 200 m as a potential natural peloid. The fine-silt sediment exhibited a consistent clay mineral composition dominated by illite, chlorite, kaolinite, and diatomite. The most abundant clay mineral was illite/mica, with other minerals loosely packed in a face-to-face orientation. The thermal conductivity, specific heat capacity, and cation-exchange capacity of the sediment were in the range 0.855-0.885 W/m K, 2.718-2.821 J/g °C, and 23.06-32.96 cmol/kg, respectively. The concentrations of most toxic elements in the sediment were considerably lower than the limits set by domestic cosmetic regulations and other international standards. The analyzed samples exhibited similar properties to those of previously reported peloids, thus making them suitable for use in the field of pelotherapy; furthermore, the consistency in data across a wide peloid-distribution area is expected to enable economically viable mining. Future investigations should aim to to evaluate the long-term effects on the skin, the bioavailability of potentially hazardous substances, and the therapeutic efficacy for various skin conditions.

Arsenic-Induced Cardiovascular Diseases and their Correlation with Mitochondrial DNA Copy Number, Deletion, and Telomere Length in Bangladeshi Population

Arsenic contamination is a global health concern, primarily through contaminated groundwater and its entry into the food chain. The association between arsenic exposure and cardiovascular diseases (CVDs) is particularly alarming due to CVDs being the leading cause of death worldwide. Arsenic exposure has also been linked to changes in telomere length, mitochondrial DNA copy number (mtDNAcn), and deletion, further increasing the risk of CVDs. We aimed to determine whether arsenic exposure alters telomere length and mtDNAcn and deletion in a total of 50 CVD patients who underwent open heart surgery hailed from known arsenic-affected and unaffected areas in Bangladesh. Amount of arsenic was determined from the collected nails and cardiac tissues. Relative telomere length and mtDNAcn and deletion were quantified by qRT-PCR. The patients from arsenic-contaminated areas had higher average arsenic deposits in their fingers and toenails (P < 0.05) and higher cardiac tissue injury scores (P < 0.05). Moreover, approximately 1.5-fold shorter telomere length (P < 0.05, r =  - 0.775), 1.2-fold decreased mtDNAcn (P < 0.05, r = - 0.797), and an 81-fold higher amount of mitochondrial DNA deletion (P < 0.05, r = 0.784) were observed in the patients who had higher arsenic deposition in their nails. Higher levels of arsenic exposure were found to be linked to shorter telomere length, decreased mtDNAcn, and increased mitochondrial DNA deletion in the patients from As-affected areas. It can also be anticipated that the correlation of arsenic exposure with telomere length, mtDNAcn, and deletion can be used as biomarkers for early diagnosis of arsenic-induced cardiovascular diseases.

Analysis of MsTERT Gene Expression Profile in Alfalfa (Medicago sativa) Indicates Their Response to Abiotic Stress and Seed Aging

Seed aging is always taken as a crucial factor for vigor loss due to delayed seed germination and seedling growth, which limits hay production. Many studies have found that telomeres are closely related to abiotic stress and seed vigor. However, the molecular mechanism of telomeres' response to abiotic stress, seed vigor, and the maintenance mechanism of plant telomere homeostasis still remain unclear. Alfalfa (Medicago sativa) enjoys the title of "King of Forage", and is an important protein forage for the dairy industry as planted in the world. This comprehensive investigation was performed to explore the molecular characterization, phylogenetic relationship, and gene expression analysis of MsTERT under abiotic stress and during seed aging in alfalfa. In this study, MsTERT was identified from the 'Zhongmu 1' alfalfa genome and encoded a coding sequence (CDS) of 3615 bp in length, consisting of telomerase- RNA-Binding Domain (RBD) and Reverse Transcriptase (RT) domains, 1024 amino acids, an isoelectric point of 9.58, and a relative molecular mass of 138.94 kD. Subcellular localization showed that MsTERT was mainly localized in the nucleus and mitochondria. The results of the expression profile showed that MsTERT was observed to respond to various stress conditions such as salt (100 mmol/L NaCl) and drought (20% PEG 6000). Furthermore, exogenous hormones IAA, ABA, and GA3 showed the potential to affect MsTERT expression. Additionally, MsTERT also responded to seed aging. Our results revealed a marginal but significant association between relative telomere length, MsTERT expression, and seed germination percentage, suggesting that the length of telomeres was shortened, and expression of MsTERT decreased with alfalfa seed aged. These results provide some evidence for the hypothesis of relative telomere length and/or TERT expression serving as biomarkers of seed aging. Although this finding is helpful to offer a new way to elucidate the molecular mechanism of vigor loss in alfalfa seed, further investigation is required to elucidate the molecular mechanism by which the MsTERT gene regulates seed vigor.

SIRT1/P53 pathway is involved in the Arsenic induced aerobic glycolysis in hepatocytes L-02 cells

Arsenic is a known human carcinogen. Low doses of arsenic can induce cell proliferation, but the mechanism remains elusive. Aerobic glycolysis, also known as the Warburg effect, is one of the characteristics of tumour cells and rapidly proliferating cells. P53 is a tumour suppressor gene that has been shown to be a negative regulator of aerobic glycolysis. SIRT1 is a deacetylase that inhibits the function of P53. In this study, we found that P53 was involved in low dose of arsenic-induced aerobic glycolysis through regulating HK2 expression in L-02 cells. Moreover, SIRT1 not only inhibited P53 expression but also decreased the acetylation level of P53-K382 in arsenic-treated L-02 cells. Meanwhile, SIRT1 influenced the expression of HK2 and LDHA, which then promoted arsenic-induced glycolysis in L-02 cells. Therefore, our study demonstrated that the SIRT1/P53 pathway is involved in arsenic-induced glycolysis, thereby promoting cell proliferation, which provides theoretical basis for enriching the mechanism of arsenic carcinogenesis.

Arsenic causing gallbladder cancer disease in Bihar

In recent times Gallbladder cancer (GBC) incidences increased many folds in India and are being reported from arsenic hotspots identified in Bihar. The study aims to establish association between arsenic exposure and gallbladder carcinogenesis. In the present study, n = 200 were control volunteers and n = 152 confirmed gallbladder cancer cases. The studied GBC patient's biological samples-gallbladder tissue, gallbladder stone, bile, blood and hair samples were collected for arsenic estimation. Moreover, n = 512 gallbladder cancer patients blood samples were also evaluated for the presence of arsenic to understand exposure level in the population. A significantly high arsenic concentration (p < 0.05) was detected in the blood samples with maximum concentration 389 µg/L in GBC cases in comparison to control. Similarly, in the gallbladder cancer patients, there was significantly high arsenic concentration observed in gallbladder tissue with highest concentration of 2166 µg/kg, in gallbladder stones 635 µg/kg, in bile samples 483 µg/L and in hair samples 6980 µg/kg respectively. Moreover, the n = 512 gallbladder cancer patient's blood samples study revealed very significant arsenic concentration in the population of Bihar with maximum arsenic concentration as 746 µg/L. The raised arsenic concentration in the gallbladder cancer patients' biological samples-gallbladder tissue, gallbladder stone, bile, blood, and hair samples was significantly very high in the arsenic exposed area. The study denotes that the gallbladder disease burden is very high in the arsenic exposed area of Bihar. The findings do provide a strong link between arsenic contamination and increased gallbladder carcinogenesis.

Telomeres susceptibility to environmental arsenic exposure: Shortening or lengthening?

Maintaining telomere length plays a crucial role in regulating cellular life span. Telomere lengthening or shortening is one of the important biomarkers which could predict the preceding or present diseases. Meanwhile, the impact of environmental arsenic exposure on telomere length has increasingly concerned. Although previous studies demonstrated the effects of arsenic on telomere length, the findings were unclear on whether telomere shortens or lengthens by arsenic exposure. Thus, this manuscript summarized and discussed the telomere length alteration following arsenic exposure and the possible does-response effect of arsenic on telomere length. The present review suggested that different age groups may respond differently to arsenic exposure, and the dose-response effect of arsenic could be a critical factor in its effect on telomere length. Moreover, speciation analysis of arsenic could be more informative in identifying the effect of arsenic on telomere length.

Telomeres and anthropogenic disturbances in wildlife: A systematic review and meta-analysis

Human-driven environmental changes are affecting wildlife across the globe. These challenges do not influence species or populations to the same extent and therefore a comprehensive evaluation of organismal health is needed to determine their ultimate impact. Evidence suggests that telomeres (the terminal chromosomal regions) are sensitive to environmental conditions and have been posited as a surrogate for animal health and fitness. Evaluation of their use in an applied ecological context is still scarce. Here, using information from molecular and occupational biomedical studies, we aim to provide ecologists and evolutionary biologists with an accessible synthesis of the links between human disturbances and telomere length. In addition, we perform a systematic review and meta-analysis on studies measuring telomere length in wild/wild-derived animals facing anthropogenic disturbances. Despite the relatively small number of studies to date, our meta-analysis revealed a significant small negative association between disturbances and telomere length (-0.092 [-0.153, -0.031]; n = 28; k = 159). Yet, our systematic review suggests that the use of telomeres as a biomarker to understand the anthropogenic impact on wildlife is limited. We propose some research avenues that will help to broadly evaluate their suitability: (i) further causal studies on the link between human disturbances and telomeres; (ii) investigating the organismal implications, in terms of fitness and performance, of a given telomere length in anthropogenically disturbed scenarios; and (iii) better understanding of the underlying mechanisms of telomere dynamics. Future studies in these facets will help to ultimately determine their role as markers of health and fitness in wildlife facing anthropogenic disturbances.

Testing the Limit: Evaluating Drinking Water Arsenic Regulatory Levels Based on Adverse Pregnancy Outcomes in Bangladesh

(1) Background: Arsenic (As) is a common drinking water contaminant that is regulated as a carcinogen. Yet, As is a systemic toxicant and there is considerable epidemiological data showing As adversely impacts reproductive health. This study used data from a birth cohort in Bangladesh (2008−2011) to examine associations between drinking water As levels and reproductive outcomes. (2) Methods: Pregnant individuals (n = 1597) were enrolled at <16 weeks gestation and drinking water As was measured. Participants with live births (n = 1130) were propensity score matched to participants who experienced miscarriage (n = 132), stillbirth (n = 72), preterm birth (n = 243), and neonatal mortality (n = 20). Logistic regression was used to examine drinking water As recommendations of 50, 10, 5, 2.5, and 1 µg/L on the odds of adverse birth outcomes. (3) Results: The odds of miscarriage were higher for pregnant women exposed to drinking water ≥2.5 versus <2.5 µg As/L [adjusted odds ratio (OR) 1.90, 95% Confidence Interval (CI): 1.07−3.38)]. (4) Conclusions: These preliminary findings suggest a potential threshold where the odds of miscarriage increases when drinking water As is above 2.5 µg/L. This concentration is below the World Health Organizations and Bangladesh’s drinking water recommendations and supports the re-evaluation of drinking water regulations.

Dermal bioaccessibility and cytotoxicity of heavy metals in urban soils from a typical plateau city: Implication for human health

The dermal exposure of heavy metals in contaminated urban soils poses huge environmental health risks globally. However, their dermal bioaccessibility and adverse effects on human skin cells were not fully understood. In this study, we measured the total and dermal bioaccessibility of Cr, As, Cd, Pb, and Cu in four selected urban soil samples from Kunming, Yunnan, China, and evaluated the cellular responses of these bioaccessible extracts on human keratinocytes (HaCaT). Among all the metals, only As in Soil-3 (S3) exceeded Chinese risk screening and Yunnan background values at 38.2 mg/kg. The average concentrations of Cr, As, Cd, Pb, and Cu in all soil samples were 47.79, 15.50, 3.11, 104.27, and 180.29 mg/kg respectively. Although relatively high concentrations of heavy metals were detected in soil samples, the highest dermal bioaccessibility of Cd was 3.57% with others' being lower than 1%. The bioaccessible dermal-absorbed doses (DADs) of Cr, As, Cd, Pb, and Cu from soils reflected acceptable health risks since all DADs were below the corresponding derived dermal reference values. However, the toxic data showed the extracts of S3 and S4 presented certain cytotoxicity in HaCaT cells, indicating the existing models based on dermal bioaccessibility and DADs may be not accurate enough to assess their human health risk. Taken together, the human health risk assessment should be modified by taking their skin cytotoxicity into account.

Urinary arsenic and relative telomere length in 5-7 year old children in Bangladesh

BACKGROUND

Telomere length has been associated with the occurrence and progression of common chronic and age-related diseases, and in younger populations, may represent a biomarker of disease susceptibility. Early childhood is a critical period for telomere biology as this period is characterized by a rapid decline in telomere length due to a large turnover of highly proliferative cells and may represent a period of unique sensitivity to environmental insults. Arsenic (As) exposure has been associated with both telomere lengthening and shortening in adults and children and some evidence suggests the effects may differ by level and timing of exposure.

OBJECTIVES

Given the lack of clarity across studies, we investigated the association between urinary As and leukocyte telomere length among 476 five- to seven-year-old children enrolled in the Bangladesh Environmental Research in Children's Health (BiRCH) cohort.

METHODS

In a series of multivariable models, adjusted for key covariates, we examined associations between urinary As and relative telomere length (RTL) of whole blood DNA.

RESULTS

We observed small but consistent, negative associations between urinary As and RTL, such that a doubling of urinary As was associated with a -0.017 (95% CI: -0.030, -0.005; p = 0.0056) decrease in RTL, in fully adjusted models. We also observed a somewhat stronger inverse relationship between urinary As concentration and RTL among children born to fathers ≥ 30 years of age at the time of birth, than those < 30 years; however, we did not observe a statistically significant interaction.

DISCUSSION

Our study suggests that As influences RTL, with detectable associations in early to mid-childhood. Further studies are needed to confirm our findings and investigate the potential long-term impacts of telomere shortening in childhood on later life health outcomes. Additional studies exploring how dose and timing of exposure may relate to RTL are critical to understanding As's relationship to telomere length.

Associations between polyfluoroalkyl substance and organophosphate flame retardant exposures and telomere length in a cohort of women firefighters and office workers in San Francisco

BACKGROUND

Environmental chemical exposures can affect telomere length, which in turn has been associated with adverse health outcomes including cancer. Firefighters are occupationally exposed to many hazardous chemicals and have higher rates of certain cancers. As a potential biomarker of effect, we assessed associations between chemical exposures and telomere length in women firefighters and office workers from San Francisco, CA.

METHODS

We measured serum concentrations of polyfluoroalkyl substances (PFAS), urinary metabolites of flame retardants, including organophosphate flame retardants (OPFRs), and telomere length in peripheral blood leukocytes in women firefighters (N = 84) and office workers (N = 79) who participated in the 2014-15 Women Workers Biomonitoring Collaborative. Multiple linear regression models were used to assess associations between chemical exposures and telomere length.

RESULTS

Regression results revealed significant positive associations between perfluorooctanoic acid (PFOA) and telomere length and perfluorooctanesulfonic acid (PFOS) and telomere length among the whole cohort. Models stratified by occupation showed stronger and more significant associations among firefighters as compared to office workers. Among firefighters in models adjusted for age, we found positive associations between telomere length and log-transformed PFOA (β (95%CI) = 0.57(0.12, 1.02)), PFOS (0.44 (0.05, 0.83)), and perfluorodecanoic acid (PFDA) (0.43 (0.02, 0.84)). Modeling PFAS as categories of exposure showed significant associations between perfluorononanoic acid (PFNA) and telomere length among firefighters. Significant associations between OPFR metabolites and telomere length were seen for bis (1,3-dichloro-2-propyl) phosphate (BDCPP) and telomere length among office workers (0.21(0.03, 0.40)) and bis (2-chloroethyl) phosphate (BCEP) and telomere length among firefighters (- 0.14(- 0.28, - 0.01)). For OPFRs, the difference in the direction of effect by occupational group may be due to the disparate detection frequencies and concentrations of exposure between the two groups and/or potential unmeasured confounding.

CONCLUSION

Our findings suggest positive associations between PFAS and telomere length in women workers, with larger effects seen among firefighters as compared to office workers. The OPFR metabolites BDCPP and BCEP are also associated with telomere length in firefighters and office workers. Associations between chemical exposures and telomere length reported here and by others suggest mechanisms by which these chemicals may affect carcinogenesis and other adverse health outcomes.

Effects of co-administration of arsenic trioxide and Schiff base oxovanadium complex on the induction of apoptosis in acute promyelocytic leukemia cells

Acute promyelocytic leukaemia (APL) is commonly treated with arsenic trioxide (As2O3) that has many side effects. Given the increasing trend of studies on beneficial therapeutic properties of synthetic compounds containing vanadium, the present study sought to use Schiff base oxovanadium complex to reduce the needed concentration of arsenic trioxide. The HL-60 cell line, which is a model of APL, was selected and the effects of arsenic trioxide and Schiff base oxovanadium complex were individually and simultaneously evaluated on the cell viability by the MTT assay. Flow cytometry and Real-time RT-PCR were also performed to investigate the rate of apoptosis and the expression of P53 and P21 genes, respectively. The IC50 of arsenic trioxide and Schiff base oxovanadium complex on Hl-60 cells was 8.37 ± 0.36 µM and 34.12 ± 1.52 µg/ml, respectively. At the simultaneous administration of both compounds, the maximum decrease in the cell viability was seen in co-administration of 40 µg/ml of Schiff base oxovanadium complex and 0.001 µM of arsenic trioxide. Real-time RT-PCR indicated that the co-administration of Schiff base oxovanadium complex 40 µg/ml and arsenic trioxide 0.001 µM could increase the expression of P53 and P21 genes by 3.76 ± 0.19 and 6.57 ± 1.29 fold change, respectively to the control sample. The flow cytometry studies also indicated that this co-administration could induce apoptosis up to 67% ± 0.9% significantly higher than the control sample. The use of Schiff base oxovanadium complex could significantly reduce the required dose of arsenic trioxide to induce apoptosis in HL-60 cells.

External environmental agents influence telomere length and telomerase activity by modulating internal cellular processes: Implications in human aging

External environment affects cellular physiological processes and impact the stability of our genome. The most important structural components of our linear chromosomes which endure the impact by these agents, are the chromosomal ends called telomeres. Telomeres preserve the integrity of our genome by preventing end to end fusions and telomeric loss through by inhibiting DNA damage response (DDR) activation. This is accomplished by the presence of a six membered shelterin complex at telomeres. Further, telomeres cannot be replicated by normal DNA polymerase and require a special enzyme called telomerase which is expressed only in stem cells, few immune cells and germ cells. Telomeres are rich in guanine content and thus become extremely prone to damage arising due to physiological processes like oxidative stress and inflammation. External environmental factors which includes various physical, biological and chemical agents also affect telomere homeostasis by increasing oxidative stress and inflammation. In the present review, we highlight the effect of these external factors on telomerase activity and telomere length. We also discuss how the external agents affect the physiological processes, thus modulating telomere stability. Further, we describe its implication in the development of aging and its related pathologies.

The Dual Role of ROS in Hematological Malignancies: Stem Cell Protection and Cancer Cell Metastasis

BACKGROUND AND OBJECTIVE

Reactive oxygen species (ROS) play crucial role in hematopoiesis, regulation of differentiation, self-renewal, and the balance between quiescence and proliferation of hematopoietic stem cells (HSCs). The HSCs are a small population of undifferentiated cells that reside in the bone marrow (BM) and can undergo self-renewal by giving rise to mature cells.

METHODS

Relevant literature was identified through a PubMed search (2000-2019) of English-language papers using the following terms: reactive oxygen species, hematopoietic stem cell, leukemic stem cell, leukemia and chemotherapy.

RESULTS

HSCs are very sensitive to high levels of ROS and increased production of ROS have been attributed to HSC aging. HSC aging induced by both cell intrinsic and extrinsic factors is linked to impaired HSC self-renewal and regeneration. In addition, the elevated ROS levels might even trigger differentiation of Leukemic stem cells (LSCs) and ROS may be involved in the initiation and progression of hematological malignancies, such as leukemia.

CONCLUSION

Targeting genes involved in ROS in LSCs and HSCs are increasingly being used as a critical target for therapeutic interventions. Appropriate concentration of ROS may be an optimal therapeutic target for treatment of leukemia during chemotherapy, but still more studies are required to better understanding of the of ROS role in blood disorders.

Associations between polyfluoroalkyl substance and organophosphate flame retardant exposures and telomere length in a cohort of women firefighters and office workers in San Francisco

BACKGROUND

Environmental chemical exposures can affect telomere length, which in turn has been associated with adverse health outcomes including cancer. Firefighters are occupationally exposed to many hazardous chemicals and have higher rates of certain cancers. As a potential marker of effect, we assessed associations between chemical exposures and telomere length in women firefighters and office workers from San Francisco, CA.

METHODS

We measured serum levels of polyfluoroalkyl substances (PFAS), urinary metabolites of flame retardants, including organophosphate flame retardants (OPFRs), and telomere length in peripheral blood leukocytes in women firefighters and office workers who participated in the 2014-15 Women Workers Biomonitoring Collaborative. Multiple linear regression models were used to assess associations between chemical exposures and telomere length.

RESULTS

Regression results revealed significant positive associations between perfluorooctanoic acid (PFOA) and telomere length and perfluorooctanesulfonic acid (PFOS) and telomere length among the whole cohort. Models stratified by occupation showed stronger and more significant associations among firefighters as compared to office workers. Among firefighters in models adjusted for age, we found positive associations between telomere length and log-transformed PFOA ( β (95%CI) = 0.57(0.12, 1.02)), PFOS (0.44 (0.05, 0.83)), and perfluorodecanoic acid (PFDA) (0.43 (0.02, 0.84)). Modeling PFAS as categories of exposure showed significant associations between perfluorononanoic acid (PFNA) and telomere length among firefighters. Significant associations between OPFR metabolites and telomere length were seen for bis(1,3-dichloro-2-propyl) phosphate (BDCPP) and telomere length among office workers (0.21(0.03, 0.40)) and bis(2-chloroethyl) phosphate (BCEP) and telomere length among firefighters (-0.14(-0.28, -0.01)). For OPFRs, the difference in the direction of effect by occupational group may be due to the disparate detection frequencies and levels of exposure between the two groups and/or potential unmeasured confounding.

CONCLUSION

Our findings suggest positive associations between PFAS and telomere length in women workers, with larger effects seen among firefighters as compared to office workers. The OPFR metabolites BDCPP and BCEP are also associated with telomere length in firefighters and office workers. Associations between chemical exposures and telomere length reported here and by others suggest mechanisms by which these chemicals may affect carcinogenesis and other adverse health outcomes.

Interaction effects of environmental response gene polymorphisms and benzene exposure on telomere length in shoe-making workers

Benzene is a globally occurring environmental and occupational pollutant that causes leukemia. To better understand telomere length (TL) as a function of benzene toxicity, we recruited 294 shoe-making workers and 102 controls from Wenzhou, China in 2011. Biomarkers of TL, cytokinesis-block micronucleus (MN) frequency, and white blood cells (WBC) were measured. In total, 18 polymorphic sites in environmental response genes, including metabolic and DNA repair genes, were analyzed. Results indicate that benzene exposure led to a longer TL at a threshold of 32 mg/m³-year of cumulative exposure dose (CED). Furthermore, the TL was longer in members of the damaged group, when evaluated for MN frequency (P < 0.001) and reduced WBC (P < 0.001), than in those of the normal group. Workers carrying genotype TT (β = 0.32, P = 0.042) in rs3212986 of ERCC1 and genotype TC (β = 0.24, P = 0.082) in rs1051740 of mEH exon3 were associated with a longer TL as compared to the wild-type group. TA (β = -0.53, P < 0.001) in rs6413432 of CYP2E1 was associated with a shorter TL. Benzene exposure interacted with the TA type in rs6413432 (β = 0.003, 95% CI: 0, 0.006, P = 0.042) and the CC type in rs1051740 (β = 0.007, 95% CI: 0.001, 0.013, P = 0.015) after adjusting for confounding factors. Our results indicate that benzene induces an increase in TL at a threshold of CED ≥32mg/m³-year. Rs1051740, rs3212986, and rs6413432 were found to be involved in benzene-induced telomere growth; in particular, rs1051740 and rs6413432 interacted with the benzene exposure, resulting in an extended TL.

Phase I clinical trial of KML001 monotherapy in patients with advanced solid tumors

BACKGROUND

We evaluated the tolerability, pharmacokinetics (PK) and preliminary efficacy of KML001, an oral trivalent arsenical, as a monotherapy in patients with advanced solid tumors.

RESEARCH DESIGN AND METHODS

With a standard 3 + 3 design for dose-escalation stage, the planned dose levels of KML001 were 5, 7.5, 10, 12.5, and 15 mg/day for 28 days. Once the maximum tolerated dose was determined, 22 subjects were additionally enrolled for dose-expansion stage. PK analysis was performed in the 5, 10, and 15 mg/day cohort at the dose-escalation stage and also at the dose-expansion stage. Moreover, response was assessed using the standard RECIST 1.1.

RESULTS

A total of 45 Korean subjects were enrolled. No DLT was reported at the dose-escalation stage. Three DLTs, two cases of prolonged QTc interval and one of neutropenia, were reported in the 12.5 mg/day cohort at the dose-expansion stage. Higher total daily doses up to 12.5 mg/day of KML001 resulted in higher trough plasma concentrations. Among the 18 subjects who completed 2 cycles of therapy, 15 had progressive disease and 3 had stable disease.

CONCLUSIONS

Doses equal to or greater than 10 mg/day KML001 alone were tolerable and produced plasma concentrations higher than biologically relevant targets.

Nanofiltration for Arsenic Removal: Challenges, Recent Developments, and Perspectives

Arsenic (As) removal is of major significance because inorganic arsenic is highly toxic to all life forms, is a confirmed carcinogen, and is of significant environmental concern. As contamination in drinking water alone threatens more than 150 million people all over the world. Therefore, several conventional methods such as oxidation, coagulation, adsorption, etc., have been implemented for As removal, but due to their cost-maintenance limitations; there is a drive for advanced, low cost nanofiltration membrane-based technology. Thus, in order to address the increasing demand of fresh and drinking water, this review focuses on advanced nanofiltration (NF) strategy for As removal to safeguard water security. The review concentrates on different types of NF membranes, membrane fabrication processes, and their mechanism and efficiency of performance for removing As from contaminated water. The article provides an overview of the current status of polymer-, polymer composite-, and polymer nanocomposite-based NF membranes, to assess the status of nanomaterial-facilitated NF membranes and to incite progress in this area. Finally, future perspectives and future trends are highlighted.

Telomere length, arsenic exposure and risk of basal cell carcinoma of skin

Telomere length per se a heritable trait has been reported to be associated with different diseases including cancers. In this study, based on arsenic-exposed 528 cases with basal cell carcinoma (BCC) of skin and 533 healthy controls, we investigated effect of telomere length, measured by real-time PCR, on the disease risk. We observed a statistically significant association between decreased telomere length and increased BCC risk [odds ratio (OR) = 5.92, 95% confidence interval (CI) = 3.92 to 9.01, P < 0.0001]. Due to confounder effect of arsenic exposure, in a two-sample Mendelian randomization (MR), telomere length associated single-nucleotide polymorphisms as instrument variables violated valid assumptions; however, one-sample MR adjusted for arsenic exposure indicated an increased risk of BCC with short telomeres. The interaction between arsenic exposure and telomere length on BCC risk was statistically significant (P = 0.02). Within each tertile based on arsenic exposure, the individuals with shorter telomeres were at an increased risk of BCC, with highest risk being in the highest exposed group (OR = 16.13, 95% CI = 6.71 to 40.00, P < 0.0001), followed by those in medium exposure group and low exposure group. The combined effect of highest arsenic exposure and shortest telomeres on BCC risk (OR = 10.56, 95% CI = 5.14 to 21.70) showed a statistically significant departure from additivity (interaction contrast ratio 6.56, P = 0.03). Our results show that in the presence of arsenic exposure, decreased telomere length predisposes individuals to increased risk of BCC, with the effect being synergistic in individuals with highest arsenic exposure and shortest telomeres.

Study of baseline echocardiography and treatment endpoint in patients with acute lymphoblastic leukemia

Introduction:

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Anthracyclines are among the most common and effective drugs for the treatment of children ALL. However, long-term consumption and higher doses of these drugs may lead to toxic effects on the heart of children. For this purpose, in the present study, the baseline and posttreatment echocardiography status was evaluated in children with ALL during 7 years.

Materials and Methods:

This retrospective cross-sectional study was performed on 53 children with ALL who were under the age of 18 years. Different factors including risk groups, age, gender, white blood cells, dosage, and duration of treatment, as well as baseline and posttreatment echocardiography findings including EF, E/E^/, E^//A^/, MVE/A were evaluated in all patients.

Results:

All enrolled patients had not any abnormalities in the baseline echocardiography preventing the beginning of chemotherapy. The results of this study did not show a significant difference in mean baseline echocardiography parameters after treatment including EF̨E/E/˛E//A/˛, MVE/A. In addition, there was no significant difference in mean EF, E^//A^/˛, MVE/A, and ˛E/E^/ before and after treatment among SR, IR, and HR groups. Although there was no significant difference in the mean EF, E^//A^/, and MVE/A before and after treatment between male and female sex, the mean E/E^/ after chemotherapy in girls (8.5 ± 0.7) was significantly higher than the mean before treatment (6.85 ± 1.5) (P < 0.001). It was also higher than the mean in boys (7.04 ± 0.99) (P = 0.019). Although there was no significant relationship between the duration of chemotherapy and the mean of EF̨E/E^/˛E^//A^/˛, MVE/A after treatment, high dose of the drug was found to be significantly associated with a gradual decrease of EF or systolic function of the heart (P < 0.001). There was no significant relationship between drug dose and other parameters of echocardiography including E^/ A^/, MVE/A, and E/E^/ after treatment.

Conclusion:

It appears that chemotherapy should not be delayed by echocardiography. Based on the findings presented herein, increasing the dose of anthracycline can be considered as an effective factor in reducing the systolic function of the heart (EF reduction). On the other hand, chemotherapy in the period of 1 to 5.3 years does not seem to have a significant effect on the mean parameters of EF, E/E^/, E^//, and MVE/A although another study with higher sample size and follow-up is needed to confirm these results.

Arsenic-related oxidative stress in experimentally-dosed wild great tit nestlings

Arsenic (As) is broadly distributed due to natural and anthropogenic sources, and it may cause adverse effects in birds. However, research on other elements (Pb, Hg and Cd) has been prioritized, resulting in scarce data on As exposure and related effects in wild birds. One of the mechanisms responsible for As toxicity is oxidative stress. Therefore, the aim of this study was to investigate if environmentally relevant As levels affected oxidative stress biomarkers in great tits (Parus major). This is the first field experiment studying the effects of As on oxidative stress in wild passerines. Wild great tit nestlings were orally dosed with sodium arsenite (Control: water, Low dose: 0.2 μg g^-1 d^-1 and High dose: 1 μg g^-1 d^-1; from day 3 to day 13 post-hatching). We intended to reach As concentrations similar to those at which passerines are exposed to at actual polluted areas. We compared the responses to the experimental manipulations (High, Low and Control groups) with those in an As/metal-exposed population breeding close to a Cu-Ni smelter in Finland (Smelter group). A set of antioxidants (tGSH, GSH:GSSG ratio, CAT, SOD, GST and GPx), and oxidative damage biomarkers (lipid peroxidation, protein carbonylation, 8-hydroxy-2'-deoxyguanosine formation in DNA, and telomere length) were explored in blood. Arsenic administration had no significant effect on most of the biomarkers measured: only the CAT activity was lower in the High As group and the GPx activity was enhanced in the Smelter group compared to the Control. Our results suggest that the dose and duration of the As exposure was not enough to induce oxidative damage in red cells of great tit nestlings. In spite of this, nestlings dosed with 1 μg g^-1 d^-1 of sodium arsenite showed non-significantly higher oxidative stress biomarkers than controls, suggesting that we were close to an effect level for the redox-defense system. Oxidative effects at equivalent As levels combined with other stressors cannot be dismissed.

Association of prenatal exposure to arsenic with newborn telomere length: Results from a birth cohort study

OBJECTIVES

The telomere length at birth has important implications for telomere dynamics over the lifespan; however, few studies have explored the relationship between prenatal arsenic exposure and newborn telomere length (TL). We investigated whether newborn TL is related to prenatal arsenic exposure.

METHODS

We used data from a birth cohort study of 762 mother-newborn pairs conducted between November 2013 and March 2015 in Wuhan, China. We measured relative cord blood TL using quantitative real-time polymerase chain reaction. Arsenic concentrations were measured in spot urine samples collected during three trimesters using inductively coupled plasma mass spectrometry. We applied multiple informant models to explore the relationships between prenatal urinary arsenic concentrations and cord blood TL.

RESULTS

The geometric means of urinary arsenic concentrations were 21.7 μg/g creatinine, 27.3 μg/g creatinine, and 27.1 μg/g creatinine in the first, second, and third trimesters, respectively. After adjustment for potential confounders, a doubling of maternal urinary arsenic concentration during the third trimester was related to a 5.75% (95% CI: 1.70%, 9.95%) increase in cord blood TL, particularly in female infants. Similarly, mothers in the highest quartile of urinary arsenic during the third trimester had an 11.45% (95% CI: 1.91%, 21.88%) longer cord blood TL than those in the lowest quartile. However, no significant association was found between maternal urinary arsenic concentration and cord blood TL during the first and second trimesters.

CONCLUSION

Our findings suggested that maternal arsenic exposure during the third trimester was positively associated with newborn TL. The elongation of newborn telomeres due to prenatal arsenic exposure may offer new insights into the mechanisms underlying arsenic-related disorders.

Urinary metals and leukocyte telomere length in American Indian communities: The Strong Heart and the Strong Heart Family Study

INTRODUCTION

While several mechanisms may explain metal-related health effects, the exact cellular processes are not fully understood. We evaluated the association between leukocyte telomere length (LTL) and urine arsenic (ΣAs), cadmium (Cd) and tungsten (W) exposure in the Strong Heart Study (SHS, N = 1702) and in the Strong Heart Family Study (SHFS, N = 1793).

METHODS

Urine metal concentrations were measured using ICP-MS. Arsenic exposure was assessed as the sum of inorganic arsenic, monomethylarsonate and dimethylarsinate levels (ΣAs). LTL was measured by quantitative polymerase chain reaction.

RESULTS

In the SHS, median levels were 1.09 for LTL, and 8.8, 1.01 and 0.11 μg/g creatinine for ΣAs, Cd, and W, respectively. In the SHFS, median levels were 1.01 for LTL, and 4.3, 0.44, and 0.10 μg/g creatinine. Among SHS participants, increased urine ΣAs, Cd, and W was associated with shorter LTL. The adjusted geometric mean ratio (95% confidence interval) of LTL per an increase equal to the difference between the percentiles 90th and 10th in metal distributions was 0.85 (0.79, 0.92) for ΣAs, 0.91 (0.84, 1.00) for Cd and 0.93 (0.88, 0.98) for W. We observed no significant associations among SHFS participants. The findings also suggest that the association between arsenic and LTL might be differential depending on the exposure levels or age.

CONCLUSIONS

Additional research is needed to confirm the association between metal exposures and telomere length.

Arsenic‑induced BRCA1 CpG promoter methylation is associated with the downregulation of ERα and resistance to tamoxifen in MCF7 breast cancer cells and mouse mammary tumor xenografts

A significant percentage (~30%) of estrogen receptor-α (ERα)-positive tumors become refractory to endocrine therapies; however, the mechanisms responsible for this resistance remain largely unknown. Chronic exposure to arsenic through foods and contaminated water has been linked to an increased incidence of several tumors and long-term health complications. Preclinical and population studies have indicated that arsenic exposure may interfere with endocrine regulation and increase the risk of breast tumorigenesis. In this study, we examined the effects of sodium arsenite (NaAs^III) exposure in ERα-positive breast cancer cells in vitro and in mammary tumor xenografts. The results revealed that acute (within 4 days) and long-term (10 days to 7 weeks) in vitro exposure to environmentally relevant doses reduced breast cancer 1 (BRCA1) and ERα expression associated with the gain of cyclin D1 (CCND1) and folate receptor 1 (FOLR1), and the loss of methylenetetrahydrofolate reductase (MTHFR) expression. Furthermore, long-term exposure to NaAs^III induced the proliferation and compromised the response of MCF7 cells to tamoxifen (TAM). The in vitro exposure to NaAs^III induced BRCA1 CpG methylation associated with the increased recruitment of DNA methyltransferase 1 (DNMT1) and the loss of RNA polymerase II (PolII) at the BRCA1 gene. Xenografts of NaAs^III-preconditioned MCF7 cells (MCF7NaAs^III) into the mammary fat pads of nude mice produced a larger tumor volume compared to tumors from control MCF7 cells and were more refractory to TAM in association with the reduced expression of BRCA1 and ERα, CpG hypermethylation of estrogen receptor 1 (ESR1) and BRCA1, and the increased expression of FOLR1. These cumulative data support the hypothesis that exposure to As^III may contribute to reducing the efficacy of endocrine therapy against ERα-positive breast tumors by hampering the expression of ERα and BRCA1 via CpG methylation, respectively of ESR1 and BRCA1.

Changes of RNA N6-methyladenosine in the hormesis effect induced by arsenite on human keratinocyte cells

Arsenite exposure can induce a biphasic response called "hormesis", and oxidative stress has been proposed to play critical roles in the hormesis effect. However, the precise mechanisms underlying the hormesis effect induced by arsenite is largely unknown. Recently, N⁶-methyladenosine (m⁶A) modification has been implicated to play an important role in the biological processes of cells. Nevertheless, whether and how m⁶A is involved in the hormesis of cell growth and death caused by arsenite via oxidative stress have remained a mystery. Here, oxidative stress and m⁶A as well as its methyltransferases/demethylase of human keratinocyte cells after low/high doses of arsenite exposure were simultaneously evaluated. Our results demonstrated that the treatment of human HaCaT cells with low levels of arsenite up-regulated m⁶A modification as well as its methyltransferases (METTL3/METTL14/WTAP) and inactivated the demethylase (FTO), exerting "protective response" against oxidative stress and promoting HaCaT cells survival. On the contrary, high doses of arsenite induced down-regulation of m⁶A level and enhanced oxidative stress, showing "inhibitive effects" on cell viability in HaCaT cells. Our results suggest that the reversible m⁶A modification is associated with the arsenite-driven hormesis on cytotoxicity.

Telomere length analysis in residents of a community exposed to arsenic

Differentiated cells telomere length is an indicator of senescence or lifespan; however, in peripheral blood leukocytes the relative shortening of the telomere has been considered as a biological marker of aging, and lengthening telomere as an associated risk to cancer. Individual's age, type of tissue, lifestyle, and environmental factors make telomere length variable. The presence of environmental carcinogens such as arsenic (As) influence as causal agents of these alterations, the main modes of action for As described are oxidative stress, reduction in DNA repair capacity, overexpression of genes, alteration of telomerase activity, and damage to telomeres. The telomeres of leukocytes resulting a finite capacity of replication due to the low or no activity of the telomerase enzyme, therefore, elongation telomere in this kind of cells is a potential biological marker associated with the development of chronic diseases and carcinogenesis.

A study of telomere length, arsenic exposure, and arsenic toxicity in a Bangladeshi cohort

BACKGROUND

Chronic arsenic exposure is associated with increased risk for arsenical skin lesions, cancer, and other adverse health outcomes. One potential mechanism of arsenic toxicity is telomere dysfunction. However, prior epidemiological studies of arsenic exposure, telomere length (TL), and skin lesion are small and cross-sectional. We investigated the associations between arsenic exposure and TL and between baseline TL and incident skin lesion risk among individuals participating in the Health Effects of Arsenic Longitudinal Study in Bangladesh (2000-2009).

METHODS

Quantitative PCR was used to measure the average TL of peripheral blood DNA collected at baseline. The association between baseline arsenic exposure (well water and urine) and TL was estimated in a randomly-selected subcohort (n = 1469). A nested case-control study (466 cases and 464 age- and sex-matched controls) was used to estimate the association between baseline TL and incident skin lesion risk (diagnosed < 8 years after baseline).

RESULTS

No association was observed between arsenic exposure (water or urine) and TL. Among incident skin lesion cases and matched controls, we observed higher skin lesion risk among individuals with shorter TL (P_trend = 1.5 × 10^-5) with odds ratios of 2.60, 1.59, and 1.10 for the first (shortest), second, and third TL quartiles compared to the fourth (longest).

CONCLUSIONS

Arsenic exposure was not associated with TL among Bangladeshi adults, suggesting that leukocyte TL may not reflect a primary mode of action for arsenic's toxicity. However, short TL was associated with increased skin lesion risk, and may be a biomarker of arsenic susceptibility modifying arsenic's effect on skin lesion risk.

Arjunolic Acid Improves the Serum Level of Vitamin B12 and Folate in the Process of the Attenuation of Arsenic Induced Uterine Oxidative Stress

Continuation of prolonged treatment against arsenicosis with conventional chelating therapy is a global challenge. The present study was intended to evaluate the defensive effect of arjunolic acid against arsenic-induced oxidative stress and female reproductive dysfunction. Wistar strain adult female rats were given sodium arsenite (10 mg/kg body weight) in combination with arjunolic acid (10 mg/kg body weight) orally for two estrous cycles. Electrozymographic analysis explored that arjunolic acid co-treatment counteracted As³⁺-induced ROS production in uterine tissue by stimulating the activities of endogenous enzymatic antioxidants. Arjunolic acid was able to enhance the protection against mutagenic uterine DNA breakage, necrosis, and ovarian-uterine tissue damages in arsenicated rats by improving the ovarian steroidogenesis. The mechanisms might be coupled with the augmentation of antioxidant defense system, partly through the elimination of arsenic with the involvement of S-adenosyl methionine pool where circulating levels of vitamin B₁₂, folic acid, and homocysteine play critical roles as evidenced from our present investigation.

Epigenetics of breast cancer: Modifying role of environmental and bioactive food compounds

SCOPE

Reduced expression of tumor suppressor genes (TSG) increases the susceptibility to breast cancer. However, only a small percentage of breast tumors is related to family history and mutational inactivation of TSG. Epigenetics refers to non-mutational events that alter gene expression. Endocrine disruptors found in foods and drinking water may disrupt epigenetically hormonal regulation and increase breast cancer risk. This review centers on the working hypothesis that agonists of the aromatic hydrocarbon receptor (AHR), bisphenol A (BPA), and arsenic compounds, induce in TSG epigenetic signatures that mirror those often seen in sporadic breast tumors. Conversely, it is hypothesized that bioactive food components that target epigenetic mechanisms protect against sporadic breast cancer induced by these disruptors.

METHODS AND RESULTS

This review highlights (i) overlaps between epigenetic signatures placed in TSG by AHR-ligands, BPA, and arsenic with epigenetic alterations associated with sporadic breast tumorigenesis; and (ii) potential opportunities for the prevention of sporadic breast cancer with food components that target the epigenetic machinery.

CONCLUSIONS

Characterizing the overlap between epigenetic signatures elicited in TSG by endocrine disruptors with those observed in sporadic breast tumors may afford new strategies for breast cancer prevention with specific bioactive food components or diet.

Arsenite Effects on Mitochondrial Bioenergetics in Human and Mouse Primary Hepatocytes Follow a Nonlinear Dose Response

Arsenite is a known carcinogen and its exposure has been implicated in a variety of noncarcinogenic health concerns. Increased oxidative stress is thought to be the primary cause of arsenite toxicity and the toxic effect is thought to be linear with detrimental effects reported at all concentrations of arsenite. But the paradigm of linear dose response in arsenite toxicity is shifting. In the present study we demonstrate that arsenite effects on mitochondrial respiration in primary hepatocytes follow a nonlinear dose response. In vitro exposure of primary hepatocytes to an environmentally relevant, moderate level of arsenite results in increased oxidant production that appears to arise from changes in the expression and activity of respiratory Complex I of the mitochondrial proton circuit. In primary hepatocytes the excess oxidant production appears to elicit adaptive responses that promote resistance to oxidative stress and a propensity to increased proliferation. Taken together, these results suggest a nonlinear dose-response characteristic of arsenite with low-dose arsenite promoting adaptive responses in a process known as mitohormesis, with transient increase in ROS levels acting as transducers of arsenite-induced mitohormesis.

Bacterial iron-oxide nanowires from biofilm waste as a new adsorbent for the removal of arsenic from water

Biofilm waste material generated by the bacteria in the groundwater pipelines was found is composed of amorphous twisted iron-oxide nanowires which are shown to have considerable adsorption properties for removal As(iii) and As(v) ions from waters.

Association of cadmium and arsenic exposure with salivary telomere length in adolescents in Terai, Nepal

BACKGROUND

Cadmium and arsenic are ubiquitous metals commonly found in the environment which can harm human health. A growing body of research shows telomere length as a potential biomarker of future disease risk. Few studies have examined the effects of metals on telomere length and none have focused on adolescents.

OBJECTIVES

In this study, the impact of cadmium and arsenic on salivary telomere length was studied in adolescents in Terai, Nepal.

METHODS

Adolescents aged 12-16 years old (n=351)were recruited where questionnaire interviews and both saliva and urine collection took place. Telomere length was determined by quantitative polymerase chain reaction using DNA extracted from saliva. Urinary cadmium and arsenic concentration were measured by inductively coupled plasma mass spectrometry. Multivariable linear regression was used to examine associations between urinary metals and salivary telomere length.

RESULTS

The geometric means and standard deviations of cadmium and arsenic were 0.33±0.33μg/g creatinine and 196.0±301.1μg/g creatinine, respectively. Urinary cadmium concentration was negatively associated with salivary telomere length after adjustment for confounders (β=-0.24, 95% CI -0.42,-0.07). Arsenic showed positive associations with telomere length but did not reach statistical significance.

CONCLUSIONS

This is the first study to demonstrate that cadmium may shorten adolescent telomeres, even at exposure levels that may be considered low. These results agree with prior experimental and adult epidemiological studies, and also help identify the mechanism of DNA damage by cadmium. This study expanded current evidence on the harmful effects of cadmium exposure on telomere length even to adolescents.

Arsenic exposure, genetic susceptibility and leukocyte telomere length in an Italian young adult population

Arsenic-induced health effects may be associated with critically shortened telomeres. However, few data are available on the effects of arsenic exposure on telomere length. The aim of this study was to investigate the effects of chronic arsenic exposure on leukocyte telomere length (LTL) as well as the contribution of common polymorphisms in genes implicated in arsenic metabolism (GSTT1 and GSTM1) and DNA repair (hOGG1 and XRCC1). A group of 241 healthy subjects was enrolled from four areas of Italy known to be affected by natural or anthropogenic arsenic pollution. Urine samples were tested for inorganic As (iAs), monomethylarsinic (MMA) and dimethylarsinic acid (DMA). LTL was evaluated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Genotyping was carried out by PCR-RFLP on leukocyte DNA. In multiple linear regression analysis, LTL was significantly and inversely correlated with age (β = -0.231, P = 0.006) and showed a certain trend toward significance with iAs urinary concentration (log10 iAs, β = -0.106, P = 0.08). The genotype distribution showed significant associations between GSTT1 and the As concentration (log10 iAs, P = 0.01) and metabolite patterns (log10 DMA, P = 0.05) in the urine. However, GST genes did not interact with arsenic exposure in the modulation of LTL. Conversely, the combined presence of a higher level of iAs + MMA + DMA ≥ 19.3 μg/l (F = 6.0, P interaction = 0.01), Asi ≥ 3.86 (F = 3.9, P interaction = 0.04) μg/l, iAs + MMA + DMA ≥ 15 μg/l (F = 4.2, P interaction = 0.04) and hOGG1 Cys allele was associated with a significantly lower LTL. An interaction between XRCC1 Arg399Gln and arsenic exposure was also observed (all P interaction = 0.04). These findings suggest that telomere shortening may represent a mechanism that contributes to arsenic-related disease. The interaction of hOGG1 and XRCC1 DNA repair polymorphisms and exposure enhances telomeric DNA damage. Future studies are warranted to understand better the epidemiologic impact of arsenic on telomere function as well as to identify the subgroups of exposed subjects who need better health surveillance.

Arsenic-Induced Antioxidant Depletion, Oxidative DNA Breakage, and Tissue Damages are Prevented by the Combined Action of Folate and Vitamin B12

Arsenic is a grade I human carcinogen. It acts by disrupting one-carbon (1C) metabolism and cellular methyl (-CH3) pool. The -CH3 group helps in arsenic disposition and detoxification of the biological systems. Vitamin B12 and folate, the key promoters of 1C metabolism were tested recently (daily 0.07 and 4.0 μg, respectively/100 g b.w. of rat for 28 days) to evaluate their combined efficacy in the protection from mutagenic DNA-breakage and tissue damages. The selected tissues like intestine (first-pass site), liver (major xenobiotic metabolizer) and lung (major arsenic accumulator) were collected from arsenic-ingested (0.6 ppm/same schedule) female rats. The hemo-toxicity and liver and kidney functions were monitored. Our earlier studies on arsenic-exposed humans can correlate carcinogenesis with DNA damage. Here, we demonstrate that the supplementation of physiological/therapeutic dose of vitamin B12 and folate protected the rodents significantly from arsenic-induced DNA damage (DNA fragmentation and comet assay) and hepatic and renal tissue degeneration (histo-architecture, HE staining). The level of arsenic-induced free-radical products (TBARS and conjugated diene) was significantly declined by the restored actions of several antioxidants viz. urate, thiol, catalase, xanthine oxidase, lactoperoxidase, and superoxide dismutase in the tissues of vitamin-supplemented group. The alkaline phosphatase, transaminases, urea and creatinine (hepatic and kidney toxicity marker), and lactate dehydrogenase (tissue degeneration marker) were significantly impaired in the arsenic-fed group. But a significant protection was evident in the vitamin-supplemented group. In conclusion, the combined action of folate and B12 results in the restitution in the 1C metabolic pathway and cellular methyl pool. The cumulative outcome from the enhanced arsenic methylation and antioxidative capacity was protective against arsenic induced mutagenic DNA breakages and tissue damages.

Prenatal arsenic exposure and drowning among children in Bangladesh

There is increasing concern regarding adverse effects of prenatal arsenic exposure on the neurodevelopment of children. We analyzed mortality data for children, who were born to 11,414 pregnant women between 2002 and 2004, with an average age of 5 years of follow-up. Individual drinking-water arsenic exposure during pregnancy was calculated using tubewell water arsenic concentration between last menstrual period and date of birth. There were 84 drowning deaths registered, with cause of death ascertained using verbal autopsy (International Classification of Diseases, 10th revision, codes X65–X70). The prenatal water arsenic exposure distribution was tertiled, and the risk of drowning mortality was estimated by Cox proportional hazard models, adjusted for potential confounders. We observed a significant association between prenatal arsenic exposure and drowning in children aged 1–5 years in the highest exposure tertile (HR=1.74, 95% CI: 1.03–2.94). This study showed that in utero arsenic exposure might be associated with excess mortality among children aged 1–5 years due to drowning.

Arsenic exposure, telomere length, and expression of telomere-related genes among Bangladeshi individuals

BACKGROUND

Inorganic arsenic is a carcinogen whose mode of action may involve telomere dysfunction. Recent epidemiological studies suggest that chronic arsenic exposure is associated with longer telomeres and altered expression of telomere-related genes in peripheral blood. In this study, we evaluated the association of urinary arsenic concentration with expression of telomere-related genes and telomere length in Bangladeshi individuals with a wide range of arsenic exposure through naturally contaminated drinking water.

METHODS

We used linear regression models to estimate associations between urinary arsenic and array-based expression measures for 69 telomere related genes using mononuclear cell RNA samples from 1799 individuals. Association between arsenic exposure and a qPCR-based telomere length measure was assessed among 167 individuals.

RESULTS

Urinary arsenic was positively associated with expression of WRN, and negatively associated with TERF2, DKC1, TERF2IP and OBFC1 (all P<0.00035, Bonferroni-corrected threshold). We detected interaction between urinary arsenic and arsenic metabolism efficiency in relation to expression of WRN (P for interaction =0.00008). In addition, we observed that very high arsenic exposure was associated with longer telomeres compared to very low exposure (P=0.02).

DISCUSSION

Our findings suggest that arsenic's carcinogenic mode of action may involve alteration of telomere maintenance and/or telomere damage. This study extends our knowledge regarding the effect of arsenic on telomere length and expression of telomere-related genes.

Arsenic contamination of groundwater: a review of sources, prevalence, health risks, and strategies for mitigation

Arsenic contamination of groundwater in different parts of the world is an outcome of natural and/or anthropogenic sources, leading to adverse effects on human health and ecosystem. Millions of people from different countries are heavily dependent on groundwater containing elevated level of As for drinking purposes. As contamination of groundwater, poses a serious risk to human health. Excessive and prolonged exposure of inorganic As with drinking water is causing arsenicosis, a deteriorating and disabling disease characterized by skin lesions and pigmentation of the skin, patches on palm of the hands and soles of the feet. Arsenic poisoning culminates into potentially fatal diseases like skin and internal cancers. This paper reviews sources, speciation, and mobility of As and global overview of groundwater As contamination. The paper also critically reviews the As led human health risks, its uptake, metabolism, and toxicity mechanisms. The paper provides an overview of the state-of-the-art knowledge on the alternative As free drinking water and various technologies (oxidation, coagulation flocculation, adsorption, and microbial) for mitigation of the problem of As contamination of groundwater.

Alterations in leukocyte telomere length in workers occupationally exposed to benzene

Exposure to benzene, a known leukemogen and probable lymphomagen, has been demonstrated to result in oxidative stress, which has previously been associated with altered telomere length (TL). TL specifically has been associated with several health outcomes in epidemiologic studies, including cancer risk, and has been demonstrated to be altered following exposure to a variety of chemical agents. To evaluate the association between benzene exposure and TL, we measured TL by monochrome multiplex quantitative PCR in 43 workers exposed to high levels of benzene and 43 age and sex-matched unexposed workers in Shanghai, China. Benzene exposure levels were monitored using organic vapor passive dosimetry badges before phlebotomy. The median benzene exposure level in exposed workers was 31 ppm. The mean TL in controls, workers exposed to levels of benzene below the median (≤31 ppm), and above the median (>31 ppm) was 1.26 ± 0.17, 1.25 ± 0.16, and 1.37 ± 0.23, respectively. Mean TL was significantly elevated in workers exposed to >31 ppm of benzene compared with controls (P = 0.03). Our findings provide evidence that high levels of occupational benzene exposure are associated with TL. Environ.

Bimodal responses of cells to trace elements: insights into their mechanism of action using a biospectroscopy approach

Understanding how organisms respond to trace elements is important because some are essential for normal bodily homeostasis, but can additionally be toxic at high concentrations. The inflection point for many of these elements is unknown and requires sensitive techniques capable of detecting subtle cellular changes as well as cytotoxic alterations. In this study, we treated human cells with arsenic (As), copper or selenium (Se) in a dose-response manner and used attenuated total reflection Fourier-transform infrared (ATR-FTIR) microspectroscopy combined with computational analysis to examine cellular alterations. Cell cultures were treated with As(V), Cu(2+) or Se(IV) at concentrations ranging from 0.001 mg L(-1) to 1000 mg L(-1) and their effects were spectrochemically determined. Results show that As(V) and Cu(2+) induce bimodal dose-response effects on cells; this is in line with hormesis-driven responses. Lipids and proteins seem to be the main cell targets for all the elements tested; however, each compound produced a unique fingerprint of effect. Spectral biomarkers indicate that all test agents generate reactive oxygen species (ROS), which could either stimulate repair mechanisms or induce damage in cells.

In utero arsenic exposure and fetal immune repertoire in a US pregnancy cohort

Arsenic has wide-ranging effects on human health and there is evidence that it alters the immune response by influencing CD4+/CD8+ T cell ratios, IL-2 cytokine levels, and the expression of immune-response genes. We investigated the impact of in utero environmental arsenic exposure on immune development and function in newborns participating in a pregnancy cohort in New Hampshire, U.S., where arsenic levels have exceeded the current EPA maximum contaminant level of 10 μg/L. Our results showed that maternal urinary arsenic concentrations were inversely related to absolute total CD45RA+ CD4+ cord blood CD69+ T cell counts (N=116, p=0.04) and positively associated with CD45RA+ CD69- CD294+ cell counts (p=0.01). In placental samples (N=70), higher in utero urinary arsenic concentrations were positively associated with the expression of IL1β (p=0.03). These data provide evidence that relatively low-level arsenic exposure in utero may alter the fetal immune system and lead to immune dysregulation.

Arsenic trioxide exerts a double effect on osteoblast growth in vitro

Arsenic trioxide (ATO) is a promising antitumor agent used to treat acute promyelocytic leukemia (APL) and, recently solid tumor. The present study was designed to evaluate the effect of ATO proliferation of osteoblast that plays very important roles in maintaining the structure integrity and function of bone. Cell survives, apoptosis, collagen, and molecular targets were identified by multiple detecting techniques, including MTT assay, electron microscopy, collagen detecting kit, TUNEL kit, and western blot in hFOB1.19 human osteoblasts cell line. The results showed that low dose of ATO (0.25, 0.5, and 1μM) remarkably enhanced the viability of cultured osteoblasts in a concentration- and time-dependent manner. Intriguingly, a dual effect of high dose of ATO (5, 10, and 20μM) was also observed showing significant reduction in viability of culture osteoblasts at concentration- and time-dependent fashion. Moreover, low dose of ATO promoted secretion and synthesis of collagen, whereas high dose of ATO induced typical morphological characteristics of apoptosis in osteoblasts. Mechanically, western blot results demonstrated that low dose of ATO dramatically up-regulated TGF-β1 protein and activated p-AKT proliferative signaling. And, high dose of ATO increased Bax/Bcl-2 ratio in a time-dependent fashion and activated caspase-3 apoptotic signaling. These results demonstrate at the first time that ATO exerts a double effect on osteoblast function depending upon the concentration and provide a clue to rationally use ATO for clinicians to pay more attention to protect bone from the adverse effects of therapeutic dose of ATO during tumor therapy.

Arsenic and selenium toxicity and their interactive effects in humans

Arsenic (As) and selenium (Se) are unusual metalloids as they both induce and cure cancer. They both cause carcinogenesis, pathology, cytotoxicity, and genotoxicity in humans, with reactive oxygen species playing an important role. While As induces adverse effects by decreasing DNA methylation and affecting protein 53 expression, Se induces adverse effects by modifying thioredoxin reductase. However, they can react with glutathione and S-adenosylmethionine by forming an As-Se complex, which can be secreted extracellularly. We hypothesize that there are two types of interactions between As and Se. At low concentration, Se can decrease As toxicity via excretion of As-Se compound [(GS3)2AsSe](-), but at high concentration, excessive Se can enhance As toxicity by reacting with S-adenosylmethionine and glutathione, and modifying the structure and activity of arsenite methyltransferase. This review is to summarize their toxicity mechanisms and the interaction between As and Se toxicity, and to provide suggestions for future investigations.

Does mortality risk of cigarette smoking depend on serum concentrations of persistent organic pollutants? Prospective investigation of the vasculature in Uppsala seniors (PIVUS) study

Cigarette smoking is an important cause of preventable death globally, but associations between smoking and mortality vary substantially across country and calendar time. Although methodological biases have been discussed, it is biologically plausible that persistent organic pollutants (POPs) like polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides can affect this association. This study was performed to evaluate if associations of cigarette smoking with mortality were modified by serum concentrations of PCBs and OC pesticides. We evaluated cigarette smoking in 111 total deaths among 986 men and women aged 70 years in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) with mean follow-up for 7.7 years. The association between cigarette smoking and total mortality depended on serum concentration of PCBs and OC pesticides (P value for interaction = 0.02). Among participants in the highest tertile of the serum POPs summary score, former and current smokers had 3.7 (95% CI, 1.5-9.3) and 6.4 (95% CI, 2.3-17.7) times higher mortality hazard, respectively, than never smokers. In contrast, the association between cigarette smoking and total mortality among participants in the lowest tertile of the serum POPs summary score was much weaker and statistically non-significant. The strong smoking-mortality association observed among elderly people with high POPs was mainly driven by low risk of mortality among never smokers with high POPs. As smoking is increasing in many low-income and middle-income countries and POPs contamination is a continuing problem in these areas, the interactions between these two important health-related issues should be considered in future research.

Growth, bioluminescence and shoal behavior hormetic responses to inorganic and/or organic chemicals: a review

A biphasic dose response, termed hormesis, is characterized by beneficial effects of a chemical at a low dose and harmful effects at a high dose. This biphasic dose response phenomenon has the potential to strongly alter toxicology in a broad range. The present review focuses on the progress of research into hormetic responses in terms of growth (in plants, birds, algae and humans), bioluminescence, and shoal behavior as end points. The paper describes how both inorganic and organic chemicals at a low dose show stimulatory responses while at higher doses are inhibitory. The article highlights how factors such as symbiosis, density-dependent factors, time, and contrasting environmental factors (availability of nutrients, temperature, light, etc.) affect both the range and amplitude of hormetic responses. Furthermore, the possible underlying mechanisms are also discussed and we suggest that, for every end point, different hormetic mechanisms may exist. The occurrences of varying interacting receptor systems or receptor systems affecting the assessment of hormesis for each endpoint are discussed. The present review suggests that a hormetic model should be adopted for toxicological evaluations instead of the older threshold and linear non-threshold models.