Epidemiological evidence for the effect of environmental heavy metal exposure on the immune system in children

Heavy metals exist widely in daily life, and exposure to heavy metals caused by environmental pollution has become a serious public health problem worldwide. Due to children's age-specific behavioral characteristics and imperfect physical function, the adverse health effects of heavy metals on children are much higher than in adults. Studies have found that heavy metal exposure is associated with low immune function in children. Although there are reviews describing the evidence for the adverse effects of heavy metal exposure on the immune system in children, the summary of evidence from epidemiological studies involving the level of immune molecules is not comprehensive. Therefore, this review summarizes the current epidemiological study on the effect of heavy metal exposure on childhood immune function from multiple perspectives, emphasizing its risks to the health of children's immune systems. It focuses on the effects of six heavy metals (lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), nickel (Ni), and manganese (Mn)) on children's innate immune cells, lymphocytes and their subpopulations, cytokines, total and specific immunoglobulins, and explores the immunotoxicological effects of heavy metals. The review finds that exposure to heavy metals, particularly Pb, Cd, As, and Hg, not only reduced lymphocyte numbers and suppressed adaptive immune responses in children, but also altered the innate immune response to impair the body's ability to fight pathogens. Epidemiological evidence suggests that heavy metal exposure alters cytokine levels and is associated with the development of inflammatory responses in children. Pb, As, and Hg exposure was associated with vaccination failure and decreased antibody titers, and increased risk of immune-related diseases in children by altering specific immunoglobulin levels. Cd, Ni and Mn showed activation effects on the immune response to childhood vaccination. Exposure age, sex, nutritional status, and co-exposure may influence the effects of heavy metals on immune function in children.

Chronic exposure to di(2-ethylhexyl) phthalate (DEHP) weakens innate immunity and leads to immunosenescence in C. elegans

Di(2-ethylhexyl) phthalate (DEHP), a widespread contaminant, has numerous adverse impacts on human health and ecosystems. Chronic DEHP exposure has been found to accelerate aging; however, its potential threat to age-dependent innate immune decline remains unknown. This study aims to evaluate the effects of chronic DEHP exposure on innate immunosenescence in Caenorhabditis elegans. We show that the length of the exposure period significantly impacts DEHP-induced age-related declines, which is linked to immunosenescence and oxidative stress. We found that the DEHP-caused immunosenescence is accompanied with downregulation of an antimicrobial gene lys-7 as well as an enhancement of the nuclear translocation of HLH-30, an orthologue of mammalian transcription factor EB (TFEB). Moreover, DEHP exposure increases the expression of riok-1, a human RIO kinase homolog, which is associated with DEHP-induced HLH-30/TFEB translocation. Our findings suggest that early-life and chronic exposure to DEHP, mostly due to parent compound rather than its metabolite mono(2-ethylhexyl) phthalate (MEHP), may weaken the innate immunity in C. elegans and may enhance susceptibility to infections or promote immunosenescence in aged populations.

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.

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.

Environmental pollutants exposure: A potential contributor for aging and age-related diseases

Telomeres are "protective messengers" at the ends of eukaryotic chromosomes that protect them from degradation, end to end fusion and recombination. Admittedly, telomeres progressively shorten with age that can also be significantly accelerated by pathological conditions, which are often considered as potential contributors for cellular senescence. It is commonly believed that constant accumulation of senescent cells may lead to dysfunctional tissues and organs, thereby accelerating aging process and subsequent occurrence of age-related diseases. In particular, epidemiological data has indicated a significant association between environmental pollutants exposure and a high incidence of age-related diseases. Moreover, there is growing evidence that environmental toxicity has a detrimental impact on telomere length. Overall, a consensus is emerging that environmental pollutants exposure could lead to accelerated telomere erosion and further induce premature senescence, which may be responsible for the acceleration of aging and the high morbidity and mortality rates of age-related diseases.

A longitudinal study of rural Bangladeshi children with long-term arsenic and cadmium exposures and biomarkers of cardiometabolic diseases

There is growing interest in understanding the contribution of environmental toxicant exposure in early life to development of cardiometabolic diseases (CMD) in adulthood. We aimed to assess associations of early life exposure to arsenic and cadmium with biomarkers of CMD in children in rural Bangladesh. From a longitudinal mother-child cohort in Matlab, Bangladesh, we followed up 540 pairs. Exposure to arsenic (U-As) and cadmium (U-Cd) was assessed by concentrations in urine from mothers at gestational week 8 (GW8) and children at ages 4.5 and 9 years. Blood pressure and anthropometric indices were measured at 4.5 and 9 years. Metabolic markers (lipids, glucose, hemoglobin A1c, adipokines, estimated glomerular filtration rate (eGFR) were determined in plasma/blood of 9 years old children. In linear regression models, adjusted for child sex, age, height-for-age z score (HAZ), BMI-for-age z score (BAZ), socioeconomic status (SES) and maternal education, each doubling of maternal and early childhood U-Cd was associated with 0.73 and 0.82 mmHg increase in systolic blood pressure (SBP) respectively. Both early and concurrent childhood U-Cd was associated with diastolic (D)BP (β = 0.80 at 4.5 years; β = 0.75 at 9 years). Each doubling of U-Cd at 9 years was associated with decrements of 4.98 mg/dL of total cholesterol (TC), 1.75 mg/dL high-density lipoprotein (HDL), 3.85 mg/dL low-density lipoprotein (LDL), 0.43 mg/dL glucose and 4.29 units eGFR. Each doubling of maternal U-Cd was associated with a decrement of 1.23 mg/dL HDL. Both maternal and childhood U-As were associated with decrement in TC and HDL. Multiple comparisons were checked with family-wise error rate Bonferroni-type-approach. The negative associations of arsenic and cadmium with biomarkers of CMD in preadolescent children indicated influence of both metal(loid)s on fat and carbohydrate metabolism, while cadmium additionally influenced kidney function and BP. Thus, fewer outcomes were associated with U-As compared to U-Cd at preadolescence.

Arsenic induces mTOR-dependent autophagy, whereas it impairs the autophagy-lysosome pathway and the potential role of TFEB in cultured dendritic cells

Arsenic is a toxic metalloid, which also compromises immunity and causes various immunological disorders. Exposure to arsenic exerts the immunosuppressive properties of dendritic cells (DCs). Autophagy is a self-renewal process of cells, which degrades damaged macromolecules and organelles through the lysosomal pathway. Thus, herein, we attempt to clarify the impacts of autophagy and the autophagy-lysosome pathway on arsenic-exposed DCs. Bone marrow-derived dendritic cells (BMDCs) were exposed to different concentrations of arsenic (0.25, 0.5 and 1 μM) with or without LPS stimulation. Initially, we observed that arsenic induced autophagosome accumulation, significantly enhanced the LC3 II and p62 expressions and down-regulated the p-mTOR protein levels. We also determined that arsenic-induced autophagy occurred via an mTOR pathway. The results further revealed that arsenic inhibited autophagic flux in LPS-stimulated BMDCs using the autophagy inhibitor chloroquine (CQ). Meanwhile, arsenic significantly decreased the number of lysosomes, protein expression of lysosomal-specific markers LAMP1 and LAMP2, and the protein levels of lysosomal cysteine cathepsins (CTSD and CTSL). Moreover, the overexpression of transcription factor EB (TFEB), the master transcriptional regulator of autophagy and lysosome biogenesis, partially relieved arsenic-inhibited lysosomal CTSD and CTSL expressions, recovered the disorder of autophagic flux, promoted the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-12, and reduced anti-inflammatory cytokine IL-10 secretion. In summary, our results support the idea that arsenic induces autophagy through an mTOR-dependent pathway in cultured BMDCs. Meanwhile, arsenic weakens the process of autophagic flux, which may be partially due to lysosomal dysfunction. Furthermore, we also suggest that TFEB can positively act on the autophagy-lysosome pathway and influence the expression of immunocytokines in DCs.

Periconceptional environment predicts leukocyte telomere length in a cross-sectional study of 7-9 year old rural Gambian children

Early life exposures are important predictors of adult disease risk. Although the underlying mechanisms are largely unknown, telomere maintenance may be involved. This study investigated the relationship between seasonal differences in parental exposures at time of conception and leukocyte telomere length (LTL) in their offspring. LTL was measured in two cohorts of children aged 2 yrs (N = 487) and 7–9 yrs (N = 218). The association between date of conception and LTL was examined using Fourier regression models, adjusted for age, sex, leukocyte cell composition, and other potential confounders. We observed an effect of season in the older children in all models [likelihood ratio test (LRT) χ²₂ = 7.1, p = 0.03; fully adjusted model]. LTL was greatest in children conceived in September (in the rainy season), and smallest in those conceived in March (in the dry season), with an effect size (LTL peak–nadir) of 0.60 z-scores. No effect of season was evident in the younger children (LRT χ²₂ = 0.87, p = 0.65). The different results obtained for the two cohorts may reflect a delayed effect of season of conception on postnatal telomere maintenance. Alternatively, they may be explained by unmeasured differences in early life exposures, or the increased telomere attrition rate during infancy.

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.

The ability of arsenic metabolism affected the expression of lncRNA PANDAR, DNA damage, or DNA methylation in peripheral blood lymphocytes of laborers

Arsenic has been associated with significant effects on human health. Exposure to inorganic arsenic has been associated with the changes in gene expression. Promoter of CDKN1A antisense DNA damage activated RNA (PANDAR) expression is induced by p53 protein and DNA damage response. Here, we investigated whether the ability of arsenic metabolism in individuals affected the expression of PANDAR, DNA damage, and DNA methylation. Levels of gene expression and DNA damage were examined by the quantitative polymerase chain reaction and DNA methylation was measured by the methylation-sensitive high-resolution melting curve. In our study, we demonstrated that arsenic exposure increased PANDAR expression and DNA damage among arsenic smelting plant laborers. The PANDAR expression and DNA damage were positively linked to monomethylarsonic acid % ( R = 0.25, p < 0.05 and R = 0.32, p < 0.01) and negatively linked to dimethylarsinic acid % ( R = −0.21, p < 0.05 and R = −0.31, p < 0.01). Subjects with low primary methylation index had increased levels of DNA damage (51.62 ± 2.96 vs. 60.93 ± 3.10, p < 0.05) and methylation (17.14 (15.88–18.51) vs. 15.83 (14.82–18.00), p < 0.05). Subjects with low secondary methylation index had increased levels of PANDAR expression (4.88 ± 0.29 vs. 4.07 ± 0.23, p < 0.01) and DNA damage (17.38 (15.88–19.29) vs. 15.83 (14.82–17.26), p < 0.01). DNA methylation of PANDAR gene was linked to the regulation of its expression in peripheral blood lymphocytes among laborers ( Y = −2.08 × X + 5.64, p < 0.05). These findings suggested arsenic metabolism ability and exposure affected the expression of PANDAR, DNA damage, and DNA methylation.

Children's environmental health based on birth cohort studies of Asia (2) - air pollution, pesticides, and heavy metals

The life style and child raising environment in Asia are quite different compared with Western countries. Besides, the children's environmental threats and difficulties in conducting studies could be different. To address children's environmental health in Asia area, the Birth Cohort Consortium of Asia (BiCCA) was co-established in 2011. We reviewed the mercury, polychlorinated biphenyls, perfluoroalkyl substances, phthalates, and environmental tobacco smoke in pervious based on birth cohort studies in Asia. The aim of this study was to summarize the traditional environmental pollution and the target subjects were also based on the birth cohort in Asia area. Environmental pollutants included air pollutants, pesticides focusing on organochlorine pesticides, diakylphosphates, and pyrethroid, and heavy metals including lead, arsenic, cadmium, manganese, vanadium, and thallium. Fetal growth and pregnancy outcomes, childhood growth and obesity, neurodevelopment and behavioral problems, and allergic disease and immune function were classified to elucidate the children's health effects. In total, 106 studies were selected in this study. The evidences showed air pollution or pesticides may affect growth during infancy or childhood, and associated with neurodevelopmental or behavioral problems. Prenatal exposure to lead or manganese was associated with neurodevelopmental or behavioral problems, while exposure to arsenic or cadmium may influence fetal growth. In addition to the harmonization and international collaboration of birth cohorts in Asia; however, understand the whole picture of exposure scenario and consider more discipline in the research are necessary.

Cadmium Exposure and Blood Telomere Length in Female University Students in Japan

Cadmium is a toxic metal found ubiquitously throughout the world. Our study evaluated whether cadmium exposure was associated with telomere length in 73 female university students. Determination of telomere length was performed by quantitative polymerase chain reaction using DNA in blood. Urinary cadmium concentration was measured by inductively coupled plasma mass spectrometry. The students' physiological attributes and lifestyle were surveyed by means of a self-administered questionnaire. The geometric mean of urinary cadmium concentration was 0.312 μg/g creatinine, which was lower than the levels previously reported for Japan. Urinary cadmium concentration was not significantly associated with telomere length, though the exposure level of the present subjects was similar to that of previous study subjects which found significantly negative associations. It is possible that other factors affected telomere length in this study population.

Exposure to low-dose arsenic in early life alters innate immune function in children

Early-life exposure to arsenic (As) increases risks of respiratory diseases/infections in children. However, data on the ability of the innate immune system to combat bacterial infections in the respiratory tracts of As-exposed children are scarce. To evaluate whether persistent low-dose As exposure alters innate immune function among children younger than 5 years-of-age, mothers and participating children (N = 51) that were members of the Health Effects of Arsenic Longitudinal Study (HEALS) cohort in rural Bangladesh were recruited. Household water As, past and concurrent maternal urinary As (U-As) as well as child U-As were all measured at enrollment. In addition, U-As metabolites were evaluated. Innate immune function was examined via measures of cathelicidin LL-37 in plasma, ex vivo monocyte-derived-macrophage (MDM)-mediated killing of Streptococcus pneumoniae (Spn), and serum bactericidal antibody (SBA) responses against Haemophilus influenzae type b (Hib). Cyto-/chemokines produced by isolated peripheral blood mononuclear cells (PBMC) were assayed using a Multiplex system. Multivariable linear regression analyses revealed that maternal (p < 0.01) and child (p = 0.02) U-As were positively associated with plasma LL-37 levels. Decreased MDM-mediated Spn killing (p = 0.05) and SBA responses (p = 0.02) were seen to be each associated with fractions of mono-methylarsonic acid (MMA; a U-As metabolite) in the children. In addition, U-As levels were seen to be negatively associated with PBMC formation of fractalkine and IL-7, and positively associated with that for IL-13, IL-17 and MIP-1α. These findings suggested that early-life As exposure may disrupt the innate host defense pathway in these children. It is possible that such disruptions may have health consequences later in life.

Arsenic induces human chondrocyte senescence and accelerates rat articular cartilage aging

Arsenic-contaminated drinking water is known to be a serious human health problem. A previous epidemiological study has indicated that arsenic levels in blood were higher in arthritis patients compared to age-matched control subjects. Bone is known as an important arsenic store compartment in the body. Arsenic exposure has been suggested to promote senescence in human mesenchymal stem cells that may affect the balance of adipogenic and osteogenic differentiation. The toxicological effect and mechanism of arsenic exposure on articular chondrocytes still remain unclear. Here, we investigated the arsenic-induced senescence in cultured human articular chondrocytes and long-term arsenic-exposed rat articular cartilage. Arsenic trioxide (As₂O₃; 1-5 μM) significantly induced senescence in human articular chondrocytes by increasing senescence-associated β-galactosidase (SA-β-Gal) activity and protein expression of p16, p53, and p21. Arsenic induced the phosphorylation of p38 and c-Jun N-terminal kinase (JNK) proteins. The inhibitors of p38 and JNK significantly reversed the arsenic-induced chondrocyte senescence. Arsenic could also trigger the induction of GATA4-NF-κB signaling and senescence-associated secretory phenotype (SASP) by increasing IL-1α, IL-1β, TGF-β, TNF-α, CCL2, PAI-1, and MMP13 mRNA expression. The increased cartilage senescence and abrasion were also observed in a rat model long-term treatment with arsenic (0.05 and 0.5 ppm) in drinking water for 36 weeks as compared to age-matched control rats. The phosphorylation of p38 and JNK and the induction of GATA4-NF-κB signaling and SASP were enhanced in the rat cartilages. Taken together, these findings suggest that arsenic exposure is capable of inducing chondrocyte senescence and accelerating rat articular cartilage aging and abrasion.

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.

Exploring telomere length in mother-newborn pairs in relation to exposure to multiple toxic metals and potential modifying effects by nutritional factors

BACKGROUND

The uterine environment may influence telomere length at birth, which is essential for cellular function, aging, and disease susceptibility over the lifespan. However, little is known about the impact of toxic chemicals on early-life telomeres. Therefore, we assessed the potential impact of multiple toxic metals on relative telomere length (rTL) in the maternal blood, cord blood, and placenta, as well as the potential modifying effects of pro-oxidants.

METHOD

In a mother-child cohort in northern Argentina (n = 169), we measured multiple toxic metals in the maternal blood or urine collected during late pregnancy, as well as the placenta and cord blood collected at delivery, using inductively coupled plasma mass spectrometry (ICP-MS). We assessed associations of log₂-transformed metal concentrations with rTL, measured in maternal and cord blood leukocytes and the placenta by real-time PCR, using multivariable-adjusted linear regression. Additionally, we tested for modifications by antioxidants (zinc, selenium, folate, and vitamin D₃).

RESULTS

Exposure to boron and antimony during pregnancy was associated with shorter maternal rTL, and lithium with longer maternal rTL; a doubling of exposure was associated with changes corresponding to 0.2-0.4 standard deviations (SD) of the rTL. Arsenic concentrations in the placenta (n = 98), blood, and urine were positively associated with placental rTL, about 0.2 SD by doubled arsenic. In the cord blood (n = 88), only lead was associated with rTL (inversely), particularly in boys (p for interaction 0.09). Stratifying by newborn sex showed ten times stronger association in boys (about 0.6 SD) than in girls. The studied antioxidants did not modify the associations, except that with antimony.

CONCLUSIONS

Elevated exposure to boron, lithium, arsenic, and antimony was associated with maternal or newborn rTL in a tissue-specific, for lead also sex-specific, manner. Nutritional antioxidants did not generally influence the associations.

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.