Exposure to four typical heavy metals induced telomere shortening of peripheral blood mononuclear cells in relevant with declined urinary aMT6s in rats

Environmental heavy metals pollution have seriously threatened the health of human beings. An increasing number of researches have demonstrated that environmental heavy metals can influence the telomere length of Peripheral Blood Mononuclear Cells (PBMCs), which implicate biological aging as well as predicts diseases. Our previous study has shown that methylmercury (MeHg)-induced telomere shortening in rat brain tissue was associated with urinary melatonin metabolite 6-sulfatoxymelatonin (aMT6s) levels. Here, we aimed to further elucidate the impact of 4 typical heavy metals (As, Hg, Cd and Pb) on telomere length of PBMCs and their association with urinary aMT6s in rats. In this study, eighty-eight male Sprague-Dawley rats were randomized grouped into eleven groups. Among them, forty 3-month-old (young) and forty 12-month-old (middle-aged) rats were divided into young or middle-aged control groups as well as typical heavy metals exposed groups, respectively. Eight 24-month-old rats (old) was divided into aging control group. The results showed that MeHg exposure in young rats while sodium arsenite (iAs), MeHg, cadmium chloride (CdCl2), lead acetate (PbAc) exposure in middle-aged rats for 3 months significantly reduced the levels of and urinary aMT6s, as well as telomere length of PBMCs. In addition, they also induced abnormalities in serum oxidative stress (SOD, MDA and GPx) and inflammatory (IL-1β, IL-6 and TNF-α) indicators. Notably, there was a significant positive correlation between declined level of urinary aMT6s and the shortening of telomere length in PBMCs in rats exposed to 4 typical heavy metals. These results suggested that 4 typical heavy metals exposure could accelerate the reduction of telomere length of PBMCs partially by inducing oxidative stress and inflammatory in rats, while ageing may be an important synergistic factor. Urinary aMT6s detection may be a alternative method to reflect telomere toxic effects induced by heavy metal exposure.

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.

Alterations in leukocyte telomere length and mitochondrial DNA copy number in benzene poisoning patients

OBJECTIVE

The aim of this study is to examine and evaluate the impact of benzene poisoning on the relative content of the mitochondrial MT-ND1 gene and telomere length in individuals with occupational chronic benzene poisoning (CBP) compared to a control group. The study will analyze and gather data on the mitochondrial gene content and telomere length in cases of benzene poisoning, and investigate the relationship with blood routine parameters in order to contribute scientific experimental data for the prevention and treatment of CBP.

METHOD

The case group comprised 30 individuals diagnosed with occupational chronic benzene poisoning, whereas the control group consisted of 60 healthy individuals who underwent physical examinations at our hospital concurrently. Blood routine indicators were detected and analyzed, and the PCR method was employed to measure changes in mitochondrial MT-ND1 content and telomere length. Subsequently, a comparison and analysis of the aforementioned indicators was conducted.

RESULT

The case group exhibited a higher mitochondrial gene content (median 366.2, IQR 90.0 rate) compared to the control group (median 101.5, IQR 12.0 rate), with a statistically significant difference between the two groups (P < 0.05). Additionally, the case group demonstrated lower white blood cell levels (3.78 ± 1.387 × 109/L) compared to the control group (5.74 ± 1.41 × 109/L), with a significant difference between the two groups (P < 0.05). Furthermore, the case group displayed lower red blood cell levels (3.86 ± 0.65 × 1012/L) compared to the control group (4.89 ± 0.65 × 1012/L), with a significant difference between the two groups (P < 0.05). The hemoglobin level in the case group (113.33 ± 16.34 g/L) was lower than that in the control group (138.22 ± 13.22 g/L). There was a significant difference between the two groups (P < 0.05). Platelet levels in the case group (153.80 ± 58.31 × 109/L) is smaller than the control group (244.92 ± 51.99 × 109/L), there was a significant difference between the two groups (P < 0.05). The average telomere length of the normal control group was 1.451 ± 0.475 (rate); The mean telomere length of individuals in the case group diagnosed with benzene poisoning was determined to be 1.237 ± 0.457 (rate). No significant correlation was observed between telomere length and three blood routine parameters, namely white blood cells (WBC), hemoglobin (HB), and platelets (PLT). However, a significant correlation was found between telomere length and red blood cell count (RBC). Additionally, a negative correlation was observed between mitochondrial gene content and white blood cell count (r = - 0.314, P = 0.026), as well as between mitochondrial gene content and red blood cell count (r = - 0.226, P = 0.032). Furthermore, a negative correlation was identified between mitochondrial gene content and hemoglobin (r = - 0.314, P = 0.028), and platelets (r = - 0.445, P = 0.001).

CONCLUSION

Individuals diagnosed with occupational chronic benzene poisoning exhibit a reduction in telomere length and an elevation in the relative content of the mitochondrial MT-ND1 gene. Moreover, a negative correlation is observed between the content of the mitochondrial MT-ND1 gene and four blood routine parameters, namely white blood cells (WBC), red blood cells (RBC), hemoglobin (HB), and platelets (PLT). Consequently, benzene exposure may potentially contribute to the onset of premature aging.

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.

Absolute telomere length in peripheral blood lymphocytes of workers exposed to construction environment

Construction environment is composed of various substances classified as carcinogens. Thus, workers exposed in this environment can be susceptible to genomic instability that can be evaluated by absolute telomere length (TL). In this work, we evaluated TL in construction workers compared to a non-exposed group performed by qPCR assay. The TL was evaluated in 59 men exposed to the construction environment (10 years of exposure) and 49 men non-exposed. Our data showed that individuals exposed to the construction environment exhibited a significantly lower TL in relation to non-exposed group (p = 0.009). Also, on the multiple linear regression model, we observed that TL was significantly influenced by the construction environment exposure (p ≤ 0.001). Additionally, the arsenic exposure is associated to a shortening telomere (p ≤ 0.001), and the lead exposure caused an increase in TL (p ≤ 0.001). Thus, our findings suggest a modulation in TL by construction environment exposure, mainly by arsenic and lead exposure.

Associations of meditation with telomere dynamics: a case-control study in healthy adults

Introduction

Telomeres are protective end caps of chromosomes which naturally shorten with each cell division and thus with age. Short telomeres have been associated with many age-related diseases. Meditation has come to the fore as a mind-body practice which could influence the telomere dynamics underlying these phenomena. We previously reported meditation to be associated with higher telomerase levels, mindfulness and quality of life. Here, reporting on the same study population, we describe associations between long-term meditation and telomere length (TL), expression of hTERT and hTR genes and methylation of the promoter region of hTERT gene.

Methods

Thirty healthy meditators and matched non-meditators were recruited. TL was measured using quantitative PCR, gene expression was assessed using reverse transcriptase PCR, and methylation level was quantified by bisulfite-specific PCR followed by Sanger sequencing. Comparisons between meditators and controls were carried out using t-tests, while Pearson correlation was used to identify correlations, and regression was used to identify predictors.

Results

Males comprised 63.4% of each group with an average age of 43 years. On average, they had meditated daily for 5.82 h (±3.45) for 6.8 years (±3.27). Meditators had longer relative TLs (p = 0.020), and TL decreased with age (p < 0.001) but was not associated with other socio-demographic variables. Regression analysis showed that age (p < 0.001) and duration of meditation (p = 0.003) significantly predicted TL. The meditators showed higher relative expression of hTERT (p = 0.020) and hTR (p = 0.029) genes while the methylation level of the promoter region of hTERT gene was significantly lower when compared to non-meditators (p < 0.001). Negative correlations were identified between the methylation level of the promoter region of hTERT gene and the expression of the hTERT gene (p = 0.001) and duration of meditation (p = 0.001).

Conclusion

The findings suggest that meditation as a lifestyle practice has multi-level beneficial effects on telomere dynamics with potential to promote healthy aging.

Cadmium exposure and DNA damage (genotoxicity): a systematic review and meta-analysis

Existing literature suggests an association between chronic cadmium (Cd) exposure and the induction of DNA damage and genotoxicity. However, observations from individual studies are inconsistent and conflicting. Therefore current systematic review aimed to pool evidence from existing literature to synthesize quantitative and qualitative corroboration on the association between markers of genotoxicity and occupational Cd exposed population. Studies that evaluated markers of DNA damage among occupationally Cd-exposed and unexposed workers were selected after a systematic literature search. The DNA damage markers included were chromosomal aberrations (chromosomal, chromatid, sister chromatid exchange), Micronucleus (MN) frequency in mono and binucleated cells (MN with condensed chromatin, lobed nucleus, nuclear buds, mitotic index, nucleoplasmatic bridges, pyknosis, and karyorrhexis), comet assay (tail intensity, tail length, tail moment, and olive tail moment), and oxidative DNA damage (8-hydroxy-deoxyguanosine). Mean differences or standardized mean differences were pooled using a random-effects model. The Cochran-Q test and I² statistic were used to monitor heterogeneity among included studies. Twenty-nine studies with 3080 occupationally Cd-exposed and 1807 unexposed workers were included in the review. Cd among the exposed group was higher in blood [4.77 μg/L (-4.94-14.48)] and urine samples [standardized mean difference 0.47 (0.10-0.85)] than in the exposed group. The Cd exposure is positively associated with higher levels of DNA damage characterized by increased frequency of MN [7.35 (-0.32-15.02)], sister chromatid exchange [20.30 (4.34-36.26)], chromosomal aberrations, and oxidative DNA damage (comet assay and 8OHdG [0.41 (0.20-0.63)]) compared to the unexposed. However, with considerable between-study heterogeneity. Chronic Cd exposure is associated with augmented DNA damage. However, more extensive longitudinal studies with adequate sample sizes are necessary to assist the current observations and promote comprehension of the Cd's role in inducing DNA damage.Prospero Registration ID: CRD42022348874.

Association between cadmium exposure and pulmonary function reduction: Potential mediating role of telomere attrition in chronic obstructive pulmonary disease patients

BACKGROUND

Environmental cadmium (Cd) exposure is linked to pulmonary function injury in the general population. But, the association between blood Cd concentration and pulmonary function has not been investigated thoroughly in chronic obstructive pulmonary disease (COPD) patients, and the potential mechanisms are unclear.

METHODS

All eligible 789 COPD patients were enrolled from Anhui COPD cohort. Blood specimens and clinical information were collected. Pulmonary function test was conducted. The subunit of telomerase, telomerase reverse transcriptase (TERT), was determined through enzyme linked immunosorbent assay (ELISA). Blood Cd was measured via inductively coupled-mass spectrometer (ICP-MS).

RESULTS

Blood Cd was negatively and dose-dependently associated with pulmonary function. Each 1-unit increase of blood Cd was associated with 0.861 L decline in FVC, 0.648 L decline in FEV1, 5.938 % decline in FEV1/FVC %, and 22.098 % decline in FEV1 % among COPD patients, respectively. Age, current-smoking, self-cooking and higher smoking amount aggravated Cd-evoked pulmonary function decrease. Additionally, there was an inversely dose-response association between Cd concentration and TERT in COPD patients. Elevated TERT obviously mediated 29.53 %, 37.50 % and 19.48 % of Cd-evoked FVC, FEV1, and FEV1 % declines in COPD patients, respectively.

CONCLUSION

Blood Cd concentration is strongly associated with the decline of pulmonary function and telomerase activity among COPD patients. Telomere attrition partially mediates Cd-induced pulmonary function decline, suggesting an underlying mechanistic role of telomere attrition in pulmonary function decline from Cd exposure in COPD patients.

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.

Prenatal lead exposure, telomere length in cord blood, and DNA methylation age in the PROGRESS prenatal cohort

BACKGROUND

Lead is a ubiquitous pollutant with deleterious effects on human health and remains a major current public health concern in developing countries. This heavy metal may interfere with nucleic acids via oxidative stress or epigenetic changes that affect biological markers of aging, e.g., telomere length and DNA methylation (DNAm). Telomere shortening associates with biological age in newborns, and DNA methylation at specific CpG sites can be used to calculate "epigenetic clocks".

OBJECTIVE

The aim of this study was to examine the associations of prenatal lead exposures with telomere length and DNA-methylation-based predictors of age in cord blood.

DESIGN

The study included 507 mother-child pairs from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) study, a birth cohort in Mexico City. Maternal blood (second trimester, third trimester and at delivery) and bone lead levels (one month postpartum) were measured using inductively coupled plasma-mass spectrometry and X-ray fluorescence, respectively. Cord blood leukocyte telomere length was measured using quantitative PCR and apparent age by DNA methylation biomarkers, i.e., Horvath's DNA methylation age and the Knight's predictor of gestational age.

RESULTS

Average maternal age was 28.5 ± 5.5 years, and 51.5% reported low socioeconomic status. Children's mean telomere length was 1.2 ± 1.3 relative units, and mean DNA methylation ages using the Horvath's and Knight's clocks were -2.6 ± 0.1 years and 37.9 ± 1.4 weeks (mean ± SD), respectively. No significant associations were found between maternal blood and bone lead concentrations with telomere length and DNAm age in newborns.

CONCLUSION

We found no associations of prenatal lead exposure with telomere length and DNA methylation age biomarkers.

Inorganic elements in occupational settings: A review on the effects on telomere length and biology

The past decades have shown that telomere crisis is highly affected by external factors. Effects of human exposure to xenobiotics on telomere length (TL), particularly in their workplace, have been largely studied. TL has been shown to be an efficient biomarker in occupational risk assessment. This is the first review focusing on studies about the effects on TL from occupational exposures to metals (lead [Pb] and mixtures), and particulate matter (PM) related to inorganic elements. Data from 15 studies were evaluated regarding occupational exposure to metals and PM-associated inorganic elements and impact on TL. Potential complementary analyses and subjects' background (age, length of employment and gender) were also assessed. There was limited information on the correlations between work length and TL dynamics, and that was also true for the correlation between age and TL. Results indicated that TL is affected differently across the types of occupational exposure investigated in this review, and even within the same exposure, a variety of effects can be observed. Fifty-three percent of the studies observed decreased TL in occupational exposure among welding fumes, open-cast coal mine, Pb and PM industries workers. Two studies focused particularly on the levels of metals and association with TL, and both linear and non-linear associations were found. Interestingly, TL modifications were accompanied by increase in DNA damage in 7 out of 8 studies that investigated it, measured either by Cytokinesis-block Micronucleus Assay or Comet assay. Five studies also investigated oxidative stress parameters, and 4 of them found increased levels of oxidative damage along with TL impairment. Oxidative stress is one of the main mechanisms by which telomeres are affected due to their high guanine content. Our review highlights the need of further studies accessing TL in simultaneous occupational exposure to mixtures of xenobiotics.

Telomere length and urinary 8-hydroxy-2'-deoxyguanosine and essential trace element concentrations in female Japanese university students

Telomere length is thought to be a biomarker of biological aging. This study examined whether telomere length was associated with urinary concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative stress, and antioxidative trace elements in 73 female Japanese university students (age: 19.2 ± 0.7 years). We quantified 8-OHdG and selenium in urine by liquid chromatography-mass spectrometry and inductively coupled plasma-mass spectrometry, respectively. Telomere length and urinary concentrations of other essential trace elements (molybdenum, cobalt, and chromium) that were previously measured in the same study participants, were used in this study. We used multiple linear regression analysis to examine the associations of telomere length with urinary 8-OHdG and essential trace element concentrations (covariates: urinary cotinine concentration, age, BMI, and drinking status). The geometric means (geometric standard deviation) of 8-OHdG and selenium were 3.4 (1.5) and 31 (1.3) µg/g creatinine, respectively. Telomere length was not associated with urinary 8-OHdG concentration, but was negatively associated with urinary selenium concentration. In conclusion, telomere length was not associated with urinary 8-OHdG concentration in the young women in this study. Longitudinal studies should be conducted to clarify the association between telomere shortening rate and oxidative stress level.

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.

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.

Telomeres in toxicology: Occupational health

The ends of chromosomes shorten at each round of cell division, and this process is thought to be affected by occupational exposures. Occupational hazards may alter telomere length homeostasis resulting in DNA damage, chromosome aberration, mutations, epigenetic alterations and inflammation. Therefore, for the protection of genetic material, nature has provided a unique nucleoprotein structure known as a telomere. Telomeres provide protection by averting an inappropriate activation of the DNA damage response (DDR) at chromosomal ends and preventing recognition of single and double strand DNA (ssDNA and dsDNA) breaks or chromosomal end-to-end fusion. Telomeres and their interacting six shelterin complex proteins in coordination act as inhibitors of DNA damage machinery by blocking DDR activation at chromosomes, thereby preventing the occurrence of genome instability, perturbed cell cycle, cellular senescence and apoptosis. However, inappropriate DNA repair may result in the inadequate distribution of genetic material during cell division, resulting in the eventual development of tumorigenesis and other pathologies. This article reviews the current literature on the association of changes in telomere length and its interacting proteins with different occupational exposures and the potential application of telomere length or changes in the regulatory proteins as potential biomarkers for exposure and health response, including recent findings and future perspectives.

Development of a benchmark dose for lead-exposure based on its induction of micronuclei, telomere length changes and hematological toxicity

BACKGROUND

Excessive lead exposure is associated with adverse health effects. However, there is a lack of systematic investigation using large populations to ascertain acceptable exposure limits.

OBJECTIVES

Our study was aimed to identify human exposure-response relationships between lead exposure and health-related outcomes, and to determine a benchmark dose (BMD).

METHODS

A total of 1896 participants from a lead-acid battery plant were recruited. Blood lead levels (BLLs) were detected for all participants. Hematological parameters (n = 1896), micronuclei (MN) frequencies (n = 934), and relative telomere length (rTL) (n = 757) were also determined. Multivariate linear/Poisson regression analyses were performed to examine associations between BLLs and these health outcomes. Restricted cubic splines were used to identify dose-response relationships. Three BMD approaches were used to calculate BMD and its 95% lower confidence limit (BMDL).

RESULTS

Among all participants, BLLs show a right-skewed distribution (median, 185.40 μg/L; 25th - 75th percentile, 104.63-271.70 μg/L). There existed significant differences for red blood cell (RBC), hemoglobin (Hb), MN and rTL among different BLL dose groups. After adjusting for possible confounders, all indicators were significantly associated with BLLs. Restricted cubic splines show that there were linear dose-response relationships for RBC and Hb with BLLs, while non-linear for MN and rTL. Results from the three BMD approaches indicate that the dichotomous models were better than continuous models to calculate BMD and BMDL of BLLs. The conservative BMDL obtained from RBC data was 135 for total, 104 for male and 175 μg/L for female. The corresponding BMDL obtained from Hb data was 105 for total, 116 for male and 70 μg/L for female. As for MN data, the BMDL estimate was 66 for total, 69 for male and 64 μg/L for female. Finally, the BMDL from rTL data was 35 for total, 32 for male and 43 μg/L for female.

CONCLUSIONS

Our data show significant dose-response relationships between lead exposure and expressions of hematological toxicity and genotoxicity. The new BMDLs of 135 and 105 μg/L based on RBC and Hb, and even more strict level of 66 and 35 μg/L based on MN and rTL are lower than current exposure limits in China. Therefore, the four values can be considered as novel exposure limits. In addition, sex effect should be taken into account when setting occupational health standard. Considering that different biomarkers have different sensitivities, better understanding their relationships will certainly improve the current emphasis on precision health risk assessment.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) μg/dl in 2016 to 18.5 (10.5, 27.2) μg/dl in 2017, and to 20.8 (11.3, 31.0) μg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.

Prenatal toxic metal mixture exposure and newborn telomere length: Modification by maternal antioxidant intake

BACKGROUND

Telomere length (TL) predicts the onset of cellular senescence and correlates with longevity and age-related disease risk. While telomeres erode throughout life, adults display fixed ranking and tracking of TL, supporting the importance of the early environment in determining inter-individual variability across the life course. Given their guanine-rich structure, telomeres are highly susceptible to oxidative stress (OS). We examined maternal metal exposure, which can induce OS, in relation to newborn TL. We also considered the modifying role of maternal antioxidant intake.

METHODS

Analyses included 100 mother-newborn pairs enrolled in the Boston and New York City-based PRogramming of Intergenerational Stress Mechanisms (PRISM) pregnancy cohort. We measured As, Ba, Cd, Ni, and Pb in maternal late-pregnancy urine by ICP-MS and quantified relative leukocyte TL (rLTL) in cord blood using qPCR. We used Weighted Quantile Sum (WQS) regression to estimate the metal mixture - rLTL association and conducted repeated holdout validation to improve the stability of estimates across data partitions. We examined models stratified by high (>median) versus low (≤median) maternal antioxidant intake, estimated from Block98 Food Frequency Questionnaires. We considered urinary creatinine, week of urine collection, maternal age, and race/ethnicity as covariates.

RESULTS

In adjusted models, urinary metals were inversely associated with newborn rLTL (βWQS = -0.50, 95% CI: -0.78, -0.21). The top metals contributing to the negative association included Ba (weight: 35.4%), Cd (24.5%) and Pb (26.9%). In models stratified by antioxidant intake, the significant inverse association between metals and rLTL remained only among mothers with low antioxidant intake (low: βWQS = -0.92, 95% CI: -1.53, -0.30; high: βWQS = -0.03, 95% CI: -0.58, 0.52). Results were similar in unadjusted models.

CONCLUSIONS

Relative LTL was shorter among newborns of mothers with higher exposure to metals during pregnancy. Higher maternal antioxidant intake may mitigate the negative influence of metals on newborn rLTL.

The Effects of Different Burn Dressings on Length of Telomere and Expression of Telomerase in Children With Thermal Burns

BACKGROUND

Burns are a common traumatic injury triggered by local tissue damage and a systemic response. In this study, we evaluated the effects of different burn dressings on telomere kinetics in children with thermal burn injury.

METHODS

Sixty children with thermal burn were included in this prospective study. The burn area of the patients included 20 to 50% total body surface area. Three different dressings (hydrofiber with silver [HFAg], poylactic membrane [PLM], and silver sulfadiazine [SSD]) and control groups were created. Telomere length in nucleated blood cells and telomerase expression in the skin tissue were evaluated in control and burn groups.

RESULTS

In the whole burn groups, telomere length in blood cells increased. The length of telomeres increased the most in the SSD group. The PLM group is the treatment that increases the number of squamous cell counts in the basal layer and telomerase expression in the skin. In HFAg and SSD groups, the expression of telomerase in the skin is decreased. In the HFAg group, the basal layer in the skin was also reduced in squamous cells.

CONCLUSION

In all burn groups, the telomere length of nucleated cells in the blood was higher than in the control group. SSD dressing along with autografting is the treatment method that maximizes telomere length in blood cells. The PLM has the most increased telomerase expression in the skin of burned patients. The PLM application increases the number of cells on both burned and normal skin.

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.

Investigation of the cardiotoxic effects of parenteral nutrition in rabbits

INTRODUCTION

Parenteral nutrition (PN) is used for the intravenous delivery of nutrients to patients who cannot take food orally. However, it is not clear whether PN also negatively impacts cardiac tissue. The present empirical study investigated the cardiac effects of PN in rabbits.

METHODS

The effects of PN were examined in three groups of rabbits: animals in the PN + fasting group (n = 14) had been fully fasted before receiving a full PN dose via an intravenous central catheter; the PN + oral feeding group (n = 14) received half of the daily calorie requirement as a half dose of PN via an intravenous central catheter; the third group consisted of controls (n = 14) with full enteral feeding and full enteral fluid intake with no PN and no central venous catheter. At the end of the 10-day study period, the rabbits were subjected to echocardiographic examination and euthanized. Blood and tissue samples were obtained from all groups. DNA was isolated from nucleated blood cells. Tissue samples were examined by both light and electron microscopy, relative telomere length was determined from DNA, and blood samples were analyzed biochemically.

RESULTS

At the end of the study, there were no statistically significant differences in weight change between the three groups. Echocardiography revealed minimally impaired diastolic function in the PN + fasting group compared to the other groups. Biochemical and histopathological analyses, relative telomere length determination, and electron micrographs showed significant cardiac damage in the PN + fasting group but not in the PN + oral feeding group or the control group. The blood biochemical analyses showed hyperglycemia and a low insulin level in the PN + fasting group but not in the other two groups.

CONCLUSIONS

A combination of PN and fasting may damage the cardiac muscle cells of rabbits via a mechanism involving hyperglycemia and oxidative stress. Additional enteral feeding may protect against the destructive effects of PN on cardiac tissue.

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.

Folic Acid Supplementation Suppresses Sleep Deprivation-Induced Telomere Dysfunction and Senescence-Associated Secretory Phenotype (SASP)

Sleep deprivation is reported to cause oxidative stress and is hypothesized to induce subsequent aging-related diseases including chronic inflammation, Alzheimer's disease, and cardiovascular disease. However, how sleep deprivation contributes to the pathogenesis of sleep deficiency disorder remains incompletely defined. Accordingly, more effective treatment methods for sleep deficiency disorder are needed. Thus, to better understand the detailed mechanism of sleep deficiency disorder, a sleep deprivation mouse model was established by the multiple platform method in our study. The accumulation of free radicals and senescence-associated secretory phenotype (SASP) was observed in the sleep-deprived mice. Moreover, our mouse and human population-based study both demonstrated that telomere shortening and the formation of telomere-specific DNA damage are dramatically increased in individuals suffering from sleeplessness. To our surprise, the secretion of senescence-associated cytokines and telomere damage are greatly improved by folic acid supplementation in mice. Individuals with high serum baseline folic acid levels have increased resistance to telomere shortening, which is induced by insomnia. Thus, we conclude that folic acid supplementation could be used to effectively counteract sleep deprivation-induced telomere dysfunction and the associated aging phenotype, which may potentially improve the prognosis of sleeplessness disorder patients.

Telomere dynamic in humans and animals: Review and perspectives in environmental toxicology

Telomeres (TLs) play major roles in stabilizing the genome and are usually shortened with ageing. The maintenance of TLs is ensured by two mechanisms involving telomerase (TA) enzyme and alternative lengthening telomeres (ALT). TL shortening and/or TA inhibition have been related to health effects on organisms (leading to reduced reproductive lifespan and survival), suggesting that they could be key processes in toxicity mechanisms (at molecular and cellular levels) and relevant as an early warning of exposure and effect of chemicals on human health and animal population dynamics. Consequently, a critical analysis of knowledge about relationships between TL dynamic and environmental pollution is essential to highlight the relevance of TL measurement in environmental toxicology. The first objective of this review is to provide a survey on the basic knowledge about TL structure, roles, maintenance mechanisms and causes of shortening in both vertebrates (including humans) and invertebrates. Overall, TL length decreases with ageing but some unexpected exceptions are reported (e.g., in species with different lifespans, such as the nematode Caenorhabditis elegans or the crustacean Homarus americanus). Inconsistent results reported in various biological groups or even between species of the same genus (e.g., the microcrustacean Daphnia sp.) indicate that the relation usually proposed between TL shortening and a decrease in TA activity cannot be generalized and depends on the species, stage of development or lifespan. Although the scientific literature provides evidence of the effect of ageing on TL shortening, much less information on the relationships between shortening, maintenance of TLs, influence of other endogenous and environmental drivers, including exposure to chemical pollutants, is available, especially in invertebrates. The second objective of this review is to connect knowledge on TL dynamic and exposure to contaminants. Most of the studies published on humans rely on correlative epidemiological approaches and few in vitro experiments. They have shown TL attrition when exposed to contaminants, such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), pesticides and metallic elements (ME). In other vertebrates, the studies we found deals mainly with birds and, overall, report a disturbance of TL dynamic consecutively to exposure to chemicals, including metals and organic compounds. In invertebrates, no data are available and the potential of TL dynamic in environmental risk assessment remains to be explored. On the basis of the main gaps identified some research perspectives (e.g., impact of endogenous and environmental drivers, dose response effects, link between TL length, TA activity, longevity and ageing) are proposed to better understand the potential of TL and TA measurements in humans and animals in environmental toxicology.

Molecular and epigenetic markers as promising tools to quantify the effect of occupational exposures and the risk of developing non-communicable diseases

Non-communicable diseases (NCDs) are chronic diseases that are by far the leading cause of death in the world. Many occupational hazards, together with social, economic and demographic factors, have been associated to NCDs development. Genetic susceptibility or environmental exposures alone are not usually sufficient to explain the pathogenesis of NCDs, but can be integrated in a more complex scenario that can result in pathological phenotypes. Epigenetics is a crucial component of this scenario, as its changes are related to specific exposures, therefore potentially able to display the effects of environment on the genome, filling the gap between genetic asset and environment in explaining disease development. To date, the most promising biomarkers have been assessed in occupational cohorts as well as in case/control studies and include DNA methylation, histone modifications, microRNA expression, extracellular vesicles, telomere length, and mitochondrial alterations.

Reproduction and development of Spodoptera exigua from cadmium and control strains under differentiated cadmium stress

The growth and development of living organisms is programmed in genes, but exogenous factors (e.g. cadmium) may modulate endogenous information. Heavy metals may disturb physiological functions and accumulate in the tissues. The insects under prolonged heavy metal stress show some modifications in their metabolism management. The aim of this study was to compare the reproduction and development between individuals of S. exigua from the strain, exposed over 130 generations to sublethal concentration of cadmium (44 mg Cd/kg dry weight of larval diet), and the individuals from the control strain, both additionally exposed to different concentration of cadmium (22-704 mg Cd/kg dry weight of larval diet). The exposure to various cadmium concentrations in the diet revealed survival difference between the cadmium and the control animals at the larvae stage. The differences between adults were not evident. The telomere length (responsible for the duration of a lifespan) in the cadmium strain was shorter in the females than in the males and the individuals from the control strain. TERF1 gene expression (indirectly responsible for the telomere length) was higher in the individuals from the cadmium strain 24 hrs after eclosion. The significant reduction in the larvae body mass was observed in both strains, when the metal concentration was equal to or higher than 264 mg/kg dry weight of larval diet. The EC50 values (defined as of body mass loss), calculated 48 hours after cadmium exposure of individuals from control and cadmium strains, were respectively 632 and 725 mg Cd/kg dry weight of diet. However, some difference in reproduction (the total number of eggs laid and the oviposition time) between the strains appeared only in the groups fed on the uncontaminated diet. The control females laid almost two times more eggs than those from the cadmium strain, and the control ones had more than two times longer oviposition time than the females from the cadmium strain. The fluctuation was also noted in the size of eggs and the hatching success on the following days when both strains were compared, while the hatching success was higher for the insects from the cadmium strain. In conclusion, the insects from the cadmium strain are more resistant to cadmium contamination, as it is evidenced by the EC50 parameter. However, the females from the cadmium strain start laying eggs statistically later, have shorter telomeres and slightly reduced TERF1 gene expression, but hutching success in the strain is significantly higher when compared with the control individuals.

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.

Ageing at the level of telomeres in association to residential landscape and air pollution at home and work: a review of the current evidence

Studies suggest that leukocyte telomere length is an index of systemic ageing. Here, we discuss telomere length as a marker of biological ageing in relation to residential landscape (greenness), residential air pollution and work-related exposures. Telomere lengths are memories of cumulative oxidative and inflammatory stress, and show to have inverse associations with the risk of non-communicable diseases. For this reason, telomeres are considered as markers of biological ageing. Studies at birth, in children, young adulthood, and elderly show that residential green space, lower traffic exposure and long-term lower exposure to particulate air pollution are associated with longer telomeres. Work-related exposures including exposure to toxic metals, polycyclic aromatic hydrocarbons and particulate matter are associated with shorter telomeres for a given age. In contrast to chronic exposures, evidence is present of the observation that recent exposure is associated with longer telomeres. Our overview shows that the magnitude of residential and work-related environmental factors on telomere length are often as important as many classical lifestyle factors.