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

Research progress on the regulatory mechanism of cell senescence in arsenic toxicity: a systematic review

As an element with metalloid properties, arsenic is pervasively present in the environment and is recognized as a potent carcinogen. Consequently, the issue of human arsenic exposure has become a significant concern within the global public health sector. Numerous studies have indicated that arsenic induces cellular senescence through various mechanisms, including triggering epigenetic alterations, inducing the senescence-associated secretory phenotype (SASP), promoting telomere shortening, and causing mitochondrial dysfunction. This article collates and summarizes the latest research advancements on the involvement of cellular senescence in arsenic toxicity and explores the mechanisms of arsenic-induced toxicity. This study aims to provide new perspectives and directions for future research on arsenic toxicity and the development of prevention and treatment strategies.

Telomere dynamics and oxidative stress in Arabidopsis grown in lunar regolith simulant

NASA envisions a future where humans establish a thriving colony on the Moon by 2050. Plants will be essential for this endeavor, but little is known about their adaptation to extraterrestrial bodies. The capacity to grow plants in lunar regolith would represent a major step towards this goal by minimizing the reliance on resources transported from Earth. Recent studies reveal that Arabidopsis thaliana can germinate and grow on genuine lunar regolith as well as on lunar regolith simulant. However, plants arrest in vegetative development and activate a variety of stress response pathways, most notably the oxidative stress response. Telomeres are hotspots for oxidative damage in the genome and a marker of fitness in many organisms. Here we examine A. thaliana growth on a lunar regolith simulant and the impact of this resource on plant physiology and on telomere dynamics, telomerase enzyme activity and genome oxidation. We report that plants successfully set seed and generate a viable second plant generation if the lunar regolith simulant is pre-washed with an antioxidant cocktail. However, plants sustain a higher degree of genome oxidation and decreased biomass relative to conventional Earth soil cultivation. Moreover, telomerase activity substantially declines and telomeres shorten in plants grown in lunar regolith simulant, implying that genome integrity may not be sustainable over the long-term. Overcoming these challenges will be an important goal in ensuring success on the lunar frontier.

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.

Associations between prenatal multiple plasma metal exposure and newborn telomere length: Effect modification by maternal age and infant sex

Exposure to metals during pregnancy may affect maternal and infant health. However, studies on the combined effects of metals on the telomere length (TL) of newborns are limited. A prospective cohort study was conducted among 1313 mother-newborn pairs in the Guangxi Zhuang Birth Cohort. The concentrations of metals in maternal plasma during the first trimester were measured using inductively coupled plasma-mass spectrometry. We explored the associations between nine plasma metals and newborn TL using generalized linear models (GLMs), principal component analysis (PCA), quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR). The GLMs revealed the inverse association between plasma arsenic (percent change, -5.56%; 95% CI: -7.69%, -3.38%) and barium concentrations (-9.84%; 95% CI: -13.81%, -5.68%) and newborn TL. Lead levels were related to significant decreases in newborn TL only in females. The PCA revealed a negative association between the PC3 and newborn TL (-4.52%; 95% CI: -6.34%, -2.68%). In the BKMR, the joint effect of metals was negatively associated with newborn TL. Qgcomp indicated that each one-tertile increase in metal mixture levels was associated with shorter newborn TL (-9.39%; 95% CI: -14.32%, -4.18%). The single and joint effects of multiple metals were more pronounced among pregnant women carrying female fetuses and among pregnant women <28 years of age. The finding suggests that prenatal exposure to arsenic, barium, antimony, and lead and mixed metals may shorten newborn TLs. The relationship between metal exposures and newborn TL may exhibit heterogeneities according to infant sex and maternal age.

Exposure study on susceptible people - SPES: An integrative biomonitoring approach

BACKGROUND

The evaluation of environmental exposure risk requires a global analysis of pollution phenomena, including biological effects and potentially correlated clinical outcomes in susceptible populations. Although human biomonitoring plays a fundamental role in assessing the degree of contamination, it is not effective alone in identifying a direct link between exposure, biomolecular effects and outcomes on target organisms. While toxicogenomics and epidemiology are mainly focused on the investigation of molecular reactions and clinical outcomes, the monitoring of environmental matrices works independently to characterize the territorial distribution of toxic compounds, without proving any correlated health risk for residents.

OBJECTIVES

We propose a new biomonitoring model based on a whole systemic analytical evaluation of environmental context. The paradigm of the method consists of identifying the sources of pollution, the migration pathways of those pollutants and their effects on target organisms. By means of this innovative, holistic epidemiological approach, we included healthy human subjects in a cohort to identify potential risks of exposure and predict possible correlated clinical outcomes. 4205 residents of the Campania region were enrolled in the "SPES" biomonitoring study, which especially focused on the areas dubbed "Land of Fires" in the recent decades.

DISCUSSION

The analysis of environmental exposure risk suffers the lack of data integration from various science fields, and this comes down to a limited point of view and a limited knowledge of phenomena. In implementing our model, we first constructed an analytical picture of the Real-world situation. We next conducted a comparative risk assessment, in order to identify possible correlations between pollution and health within a holistic view.

CONCLUSION

This type of research activities aims to support the implementation of public health interventions and to become a reference model in the evaluation of the risk of exposure to environmental pollutants.

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.

Recent Advances in Arsenic Research: Significance of Differential Susceptibility and Sustainable Strategies for Mitigation

Arsenic contamination in drinking water and associated adverse outcomes are one of the major health issues in more than 50 countries worldwide. The scenario is getting even more detrimental with increasing number of affected people and newer sites reported from all over the world. Apart from drinking water, the presence of arsenic has been found in various other dietary sources. Chronic arsenic toxicity affects multiple physiological systems and may cause malignancies leading to death. Exposed individuals, residing in the same area, developed differential dermatological lesion phenotypes and varied susceptibility toward various other arsenic-induced disease risk, even after consuming equivalent amount of arsenic from the similar source, over the same duration of time. Researches so far indicate that differential susceptibility plays an important role in arsenic-induced disease manifestation. In this comprehensive review, we have identified major population-based studies of the last 20 years, indicating possible causes of differential susceptibility emphasizing arsenic methylation capacity, variation in host genome (single nucleotide polymorphism), and individual epigenetic pattern (DNA methylation, histone modification, and miRNA expression). Holistic multidisciplinary strategies need to be implemented with few sustainable yet cost-effective solutions like alternative water source, treatment of arsenic-contaminated water, new adaptations in irrigation system, simple modifications in cooking strategy, and dietary supplementations to combat this menace. Our review focuses on the present perspectives of arsenic research with special emphasis on the probable causes of differential susceptibility toward chronic arsenic toxicity and sustainable remediation strategies.

Co-exposure to multiple metals, TERT-CLPTM1L variants, and their joint influence on leukocyte telomere length

OBJECTIVE

Telomere is required for maintaining chromosome stability and genome integrity, while telomere length is sensitive to environmental stressors. We aimed to identify the effects of multiple metals co-exposure as well as their joint effects with TERT-CLPTM1L variants on leukocyte telomere length (LTL).

METHODS

This study included 842 workers from a coke-oven plant, of whom plasma concentrations of 23 metals and LTL were determined. Genetic variations in TERT-CLPTM1L were genotyped by using the Global Screening Array. Multipollutant-based statistical methods, including the Bonferroni-correction, backward elimination procedure, and LASSO penalized regression analysis, were used to select the LTL-associated metals. Generalized linear regression models were used to evaluate the joint effects of TERT-CLPTM1L variants with positive metal on LTL.

RESULTS

Each 1% increase in plasma concentration of manganese (Mn) was significantly associated with a 0.153% increase in LTL [β(95%CI) = 0.153(0.075, 0.230), P < 0.001] in single-metal models after Bonferroni-correction. The multiple-metal models and the LASSO penalized regression analysis both indicated Mn as the sole significant predictor for LTL. Furthermore, 5 tagSNPs (rs33954691, rs6554759, rs465498, rs2455393, and rs31489) in TERT-CLPTM1L with high plasma Mn (>4.21 μg/L) showed joint effects on increasing LTL.

CONCLUSIONS

Our study revealed the independent and positive association between plasma Mn and LTL when accounting for co-exposure to other metals. This effect can be further enhanced by TERT-CLPTM1L variants. These results may advance our understanding of the complex interplay between genetic and environmental factors on telomere length. Further experimental studies are warranted to elucidate the underlying mechanisms.

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.

Protective role of selenium in the shortening of telomere length in newborns induced by in utero heavy metal exposure

The effects of toxic heavy metals, such as arsenic (As), cadmium (Cd), and lead (Pb), on telomere length (TL) have been reported previously. Although selenium (Se) is considered as an anti-oxidant which may detoxify the effects, there are no data on whether Se could protect against the TL-shortening effects of heavy metals. Thus, the aim of this study was to evaluate the protective role of Se against heavy metal-induced TL shortening. A birth cohort study was conducted in Myanmar in 2016, including 408 mother-infant pairs. First, pregnant women in the third trimester were interviewed concerning their socioeconomic, and pregnancy and birth characteristics using a pre-validated questionnaire. Maternal spot urine samples were collected after the interview. During the follow-up period (1-3 months), blood samples were collected from the umbilical cord at birth by local health workers. Metal concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). TL was measured by quantitative real-time polymerase chain reaction (PCR). Relative TL was calculated as the ratio of telomere genes to single-copy genes. To evaluate the effect of Se on TL shortening, molar ratios were calculated. Linear regression analyses were performed to examine the associations between heavy metals and TL, individually and after adjustment for Se level. The effects of As, Cd, and Pb exposure on TL were smaller after adjustment for the Se level, especially for Pb (unadjusted β = -0.10; 95% CI: 0.18, -0.01; adjusted β = -0.03; 95% CI: 0.13, 0.05). On stratifying the data by Se concentration, there was no significant association between Cd or Pb exposure and TL in the high-Se group. Our study indicated a protective effect of Se against the TL shortening induced by heavy metal exposure, where the effect sizes were smaller after adjusting for the Se level, compared to individual metal exposure.

Telomeres and Telomere Length: A General Overview

Telomeres are highly conserved tandem nucleotide repeats that include proximal double-stranded and distal single-stranded regions that in complex with shelterin proteins afford protection at chromosomal ends to maintain genomic integrity. Due to the inherent limitations of DNA replication and telomerase suppression in most somatic cells, telomeres undergo age-dependent incremental attrition. Short or dysfunctional telomeres are recognized as DNA double-stranded breaks, triggering cells to undergo replicative senescence. Telomere shortening, therefore, acts as a counting mechanism that drives replicative senescence by limiting the mitotic potential of cells. Telomere length, a complex hereditary trait, is associated with aging and age-related diseases. Epidemiological data, in general, support an association with varying magnitudes between constitutive telomere length and several disorders, including cancers. Telomere attrition is also influenced by oxidative damage and replicative stress caused by genetic, epigenetic, and environmental factors. Several single nucleotide polymorphisms at different loci, identified through genome-wide association studies, influence inter-individual variation in telomere length. In addition to genetic factors, environmental factors also influence telomere length during growth and development. Telomeres hold potential as biomarkers that reflect the genetic predisposition together with the impact of environmental conditions and as targets for anti-cancer therapies.

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

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

Exposure to arsenic and lead in children from Salamanca México, effects on telomeric lengthening and mitochondrial DNA

Levels of urinary arsenic and levels of lead in blood were measured in children attending elementary schools located in an industrial zone in Salamanca, México. Its possible effects using telomere length and mitochondrial DNA copy number as biomarkers of genomic disequilibrium by oxidative stress were studied. Eighty-eight children (6-15 years old) were included and urine samples were collected for quantification of arsenic, while lead was measured in blood samples using inductively coupled plasma mass spectrometry (ICP-MS). DNA was isolated from peripheral blood and relative telomere length and the mitochondrial DNA copy number were determined by real-time PCR. The geometric mean of urinary arsenic was 54.16 μg/L (11.7-141.1 μg/L). Ninety-eight percent of the children were above 15 μg/L (biomonitoring equivalent value). With respect to the concentration of lead in blood, the mean was 3.78 μg/dL (LOD-22.61), where 24.5% of the participants had equal or above the reference value (5 μg/dL; Mexican Official Norm NOM-199-SSA1-2000, 2017). A positive association between urinary arsenic and telomere length was found (β = 0.161; 95% CI: 0.12; 0.301; P = 0.034), while lead blood concentrations were negatively associated with mitochondrial DNA copy number (β = - 0.198; 95% CI: - 2.81; - 0.17; P = 0.019), after adjusting by age, sex, and total white blood cell count. Differences in the mitochondrial DNA content were observed in children with lead blood levels from 2.5 μg/dL, (P ≤ 0.001), suggesting an effect at lead exposure levels considered acceptable (< 5 μg/dL). In conclusion, children living in an industrial area in Salamanca showed an exposure to arsenic and lead and an impact on telomere length and mitochondrial DNA content associated with arsenic and lead exposure, respectively.

Recent Advances in Arsenic Research: Significance of Differential Susceptibility and Sustainable Strategies for Mitigation

Arsenic contamination in drinking water and associated adverse outcomes are one of the major health issues in more than 50 countries worldwide. The scenario is getting even more detrimental with increasing number of affected people and newer sites reported from all over the world. Apart from drinking water, the presence of arsenic has been found in various other dietary sources. Chronic arsenic toxicity affects multiple physiological systems and may cause malignancies leading to death. Exposed individuals, residing in the same area, developed differential dermatological lesion phenotypes and varied susceptibility toward various other arsenic-induced disease risk, even after consuming equivalent amount of arsenic from the similar source, over the same duration of time. Researches so far indicate that differential susceptibility plays an important role in arsenic-induced disease manifestation. In this comprehensive review, we have identified major population-based studies of the last 20 years, indicating possible causes of differential susceptibility emphasizing arsenic methylation capacity, variation in host genome (single nucleotide polymorphism), and individual epigenetic pattern (DNA methylation, histone modification, and miRNA expression). Holistic multidisciplinary strategies need to be implemented with few sustainable yet cost-effective solutions like alternative water source, treatment of arsenic-contaminated water, new adaptations in irrigation system, simple modifications in cooking strategy, and dietary supplementations to combat this menace. Our review focuses on the present perspectives of arsenic research with special emphasis on the probable causes of differential susceptibility toward chronic arsenic toxicity and sustainable remediation strategies.

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.

Impact of prenatal heavy metal exposure on newborn leucocyte telomere length: A birth-cohort study

Arsenic, cadmium and lead are toxic environmental contaminants. They were shown to be associated with telomere length (TL) in adults. Although they can cross the placental barrier, the effect of prenatal exposure of these metals on newborn TL is unknown. The aim of this study was to examine whether prenatal exposure to heavy metals has an impact on newborn leucocyte TL. A birth-cohort study was conducted with 409 pregnant women and their newborns in Myanmar. During the first visit, face-to-face interviews were conducted, and maternal spot urine sampling was performed. Cord blood samples were collected during follow-up. Urinary heavy metal concentration was measured by ICP-MS and adjusted for creatinine. Relative TL was measured by quantitative real-time polymerase chain reaction. The extent of prenatal arsenic, cadmium and lead exposure and their associations with newborn leucocyte TL were assessed using multivariate linear regression. The median values of maternal urinary arsenic, cadmium, and lead concentrations were 73.9, 0.9, and 1.8 μg/g creatinine, respectively. Prenatal arsenic and cadmium exposure was significantly associated with newborn TL shortening (lowest vs highest quartile, coefficient = - 0.13, 95% CI: - 0.22, - 0.03, p = 0.002, and coefficient = - 0.17, 95% CI: - 0.27, - 0.07, p = 0.001, respectively), and the associations remained robust after adjusting for confounders. There was no significant association between prenatal lead exposure and newborn TL. The present study identified the effect of arsenic and cadmium exposure on TL shortening, even in utero exposure at a lower concentration.

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.

Association between arsenic metabolism gene polymorphisms and arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China

Individuals in a given environment contaminated with arsenic have different susceptibilities to disease, which may be related to arsenic metabolism, age, gender, genetics and other factors. This study recruited 850 subjects, including 331 cases and 519 controls, from populations exposed to high levels of arsenic in drinking water in northwest China. Genotypes were determined using a custom-by-design 48-Plex SNPscan^TM kit. The results indicated that subjects who carried at least one C allele for GSTO1 rs11191979 polymorphism, at least one A allele for GSTO1 rs2164624, at least one A allele for GSTO1 rs4925, the AG genotype for GSTO2 rs156697, the AG genotype or at least one G allele for GSTO2 rs2297235 or the GG genotype or at least one G allele for PNP rs3790064 had an increased risk of arsenic-related skin lesions. In addition, the haplotype CT between rs4925 and rs11191979 appeared to confer a high risk of arsenic-included skin lesions (OR = 1.377, 95% CI = 1.03–1.84), as did the haplotype GCG among rs156697, rs157077 and rs2297235 (OR = 2.197, 95% CI = 1.08–4.44). The results showed that the variants of GSTO1, GSTO2 and PNP render the susceptible toward developing arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China.

Arsenic-contaminated freshwater: assessing arsenate and arsenite toxicity and low-dose genotoxicity in Gammarus elvirae (Crustacea; Amphipoda)

Arsenic (As) contamination of freshwater is largely due to geogenic processes, but As is also released into the environment because of improper anthropic activities. The European regulatory limits in drinking water are of 10 μg L^-1 As. However, knowledge of the genotoxic effects induced by low doses of As in freshwater environments is still scanty. This study was designed to investigate arsenate (As(V)) and arsenite (As(III)) toxicity and low-dose genotoxicity in Gammarus elvirae, which has proved to be a useful organism for genotoxicity assays in freshwater. As(V) and As(III) toxicity was assessed on the basis of the median lethal concentration, LC(50), while estimates of DNA damage were based on the Comet assay. The G. elvirae LC (50-240 h) value we calculated was 1.55 mg L^-1 for As(V) and 1.72 mg L^-1 for As(III). Arsenic exposure (240 h) at 5, 10, and 50 µg L^-1 of As in assays with either arsenate or arsenite-induced DNA damage in hemocytes of G. elvirae in a concentration-dependent manner. Our study provides a basis for future genotoxic research on exposure to freshwater that contains low levels of arsenic.

Arsenic and subclinical vascular damage in a sample of Italian young adults: a cross-sectional analysis

Exposure to arsenic (As) increases cardiovascular risk. The purpose of this study was to evaluate the relationship between As and intima-media thickness (IMT) in the common carotid artery and common genetic variants in genes implicated in As metabolism (ASIIIMT Met287Thr, GSTT1+/-, and GSTM1+/-) and DNA repair (hOGG1 Ser326Cys and XRCC1 Arg399Ser). Two hundred and fourteen healthy volunteers, age 20-46, were recruited in four zones polluted by As. Urine samples were tested for total As, inorganic As (iAs), monomethylarsinic (MMA), and dimethylarsinic acid (DMA). Primary and secondary methylation index (PMI, SMI) were computed as MMA/iAs and DMA/MMA. Common carotid artery scans were obtained by high-resolution ultrasound. There was no correlation between IMT and total As, iAs, iAs + MMA + DMA, PMI, or SMI. However, the increase of IMT with age was higher than that observed in the healthy population, both in males (6.25 vs. 5.20 μm/year) and, to a lesser extent, in females (5.05 vs. 4.97 μm/year). After correction for age and gender, subjects with a high urinary As level (≥3.86 μg/L) and carriers of the GSTT1-positive (+) genotype also had higher IMT than those with a low urinary level and the GSTT1-null (-) genotype (0.56 [0.48-0.64] vs. 0.53 [0.44-0.62] mm, p = 0.010). The analysis hints at faster vascular aging as compared to the healthy population. Our findings also suggested that GSTT1 and hOGG1 gene polymorphisms might play an important role in the individual risk of As-induced carotid atherosclerosis.

Repair activity of oxidatively damaged DNA and telomere length in human lung epithelial cells after exposure to multi-walled carbon nanotubes

One type of carbon nanotubes (CNTs) (MWCNT-7, from Mitsui) has been classified as probably carcinogenic to humans, however insufficient data does not warrant the same classification for other types of CNTs. Experimental data indicate that CNT exposure can result in oxidative stress and DNA damage in cultured cells, whereas these materials appear to induce low or no mutagenicity. Therefore, the present study aimed to investigate whether in vitro exposure of cultured airway epithelial cells (A549) to multi-walled CNTs (MWCNTs) could increase the DNA repair activity of oxidatively damaged DNA and drive the cells toward replicative senescence, assessed by attrition of telomeres. To investigate this, H₂O₂ and KBrO₃ were used to induce DNA damage in the cells and the effect of pre-exposure to MWCNT tested for a change in repair activity inside the cells or in the extract of treated cells. The effect of MWCNT exposure on telomere length was investigated for concentration and time response. We report a significantly increased repair activity in A549 cells exposed to MWCNTs compared to non-exposed cells, suggesting that DNA repair activity may be influenced by exposure to MWCNTs. The telomere length was decreased at times longer than 24h, but this decrease was not concentration dependent. The results suggest that the seemingly low mutagenicity of CNTs in cultured cells may be associated with an increased DNA repair activity and a replicative senescence, which may counteract the manifestation of DNA lesions to mutations.