Emerging roles of epigenetics in lead-induced neurotoxicity

Effect of legacy and emerging pollutants on genome-wide methylation patterns in black hake (Merluccius polli) natural populations

Exposure to pollutants such as non-essential metals and microplastics can have harmful consequences for marine organisms. Detecting the impact of pollutants in wild populations can be especially challenging. Such environmental disturbances might prompt rapid responses in the affected organisms, generating changes in their gene expression mediated by epigenetic regulation. Here we use an epiRADseq approach to determine the effect of four non-essential metals (As, Cd, Hg, Pb) and microplastics (MP) on the methylation pattern of Benguela hake, Merluccius polli, captured in the FAO fishing area 34, along the coasts of Mauritania and Senegal. We analysed 49 hake specimens and generated 44,201 epigenetic loci. Despite moderate levels of pollution identified from tissue analysis, we found significant differentially methylated loci associated with the level of the five pollutants analysed (119 significant loci for As, 134 for Cd, 92 for Hg, 119 for Pb, and 159 for microplastics). Elevated Pb was significantly associated with a reduction in hake condition factor. Differentially methylated loci were associated with diverse pathways associated to responses for all pollutants (e.g. immune response, gene expression regulation), pointing to signs of stress within the population. It is worth noting that all pollutants were differentially methylated for a locus in NLRC3, previously associated with innate immune response in fishes. Overall, we found evidence of the effects of moderate concentration of pollutants in the methylation pattern in wild populations of M. polli.

Developmental lead exposure and aggression in male rats: Influences of maternal care and environmental enrichment

Developmental lead (Pb) exposure results in a variety of cognitive deficits and behavioral issues including increased antisocial behavior and aggression. This study investigated the effect of developmental Pb exposure on aggression and violent behavior in male rats and the potential modulatory influences of quality of maternal care and enriched/non-enriched housing conditions. Long-Evans male rats with or without Pb exposure (perinatal or early postnatal) from low or high maternal care mothers (based on amounts of licking/grooming and arched-back nursing) were randomly assigned to live in enriched or non-enriched environments at weaning. At postnatal day 120-190, offensive aggression was assessed using a resident intruder test. Clinch attack (CAK) frequency and latency, and occurrence of biting events were observed to determine violent behavior. Both perinatal and postnatal Pb-exposed rats were significantly more aggressive and showed more violent behavior, compared to non-Pb-exposed animals, regardless of level of maternal care and environmental enrichment. High maternal care significantly lowered the proportion of animals with short CAK latencies and enriched housing significantly lowered the occurrence of biting events. These results suggest that high maternal care and enriched housing may potentially modify expression of violent aggressive behavior in rats with early life Pb exposure.

Effects of Lead Exposure on 1573 Male Workers' Sex Hormones in China

Lead (Pb) is recognized as an environmental pollutant with male reproductive toxicity, but its effects on sex hormones remain unclear. This study investigated the relationship between male blood lead levels (BLLs) and the sex hormones of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL), as well as testosterone (T), estrogen (E2), and progesterone (PROG). Observational and experimental data from 1573 Pb-exposed workers (712 had also been surveyed in the previous year) and 35 Pb-poisoned patients (before and after Pb chelation therapy) were analyzed. Results from a cross-sectional study showed a nonlinear relationship between BLLs and LH/FSH, and a linear relationship between BLLs and serum T. After Pb chelation therapy, the BLLs in patients decreased from 61.7 to 36.3 (μg/dL), serum T and FSH decreased significantly (p < 0.001), and serum LH also decreased but without a significant change, while PRL and PROG increased significantly (p < 0.01). The data indicate that Pb may disturb male sex hormones by including LH, T, and FSH, and this needs further research.

Association between single and mixed exposure to potentially toxic trace metals and the risk of prostate cancer: a case-control study in Tanzania

Metal contamination is a major environmental concern in Tanzania, where it has been linked to an increased risk of prostate cancer. However, there have been no epidemiological studies addressing this association. The aim of this study was to investigate the association between urinary toxic trace metals and prostate cancer. Inductively coupled plasma atomic emission spectrophotometer (ICP-AES) was employed to measure the concentrations of Pb, As, Ni, Al, and Cd in urine samples from histologically confirmed100 prostate cancer patients (n = 100) and 80 healthy controls (n = 80). The associations between individual metals and prostate cancer were assessed using unconditional logistic regression, while Bayesian kernel machine regression (BKMR) was employed to investigate the combined effects of multiple metals with adjustments of potential covariates. Cancer patients had significantly higher mean levels of Ni, Pb, and As in their urine compared to controls. In multivariable logistic models, the findings suggested that quartiles increase of As and Cd were positively associated with prostate cancer with ORs of 5.25 (1.33, 20.72) in Q3 for As and ORs of 2.87 (1.72, 11.52) in Q4 for Cd. The BKMR results revealed that the combined effect of five urinary metals exhibited a negative association with prostate cancer risk. In conclusion, this study offers preliminary evidence suggesting that exposure to trace metals particularly Cd and As may potentially be associated with prostate cancer. Pb and Al were found to have an inverse relationship with prostate cancer and overall metal mixture had no impact on prostate cancer. Since the study was preliminary, these results remain to be confirmed by further large-scale studies.

Characteristics of lead in lung and brain reveals respiration as a direct exposure way

Lead (Pb) is known as a neurotoxicant, posing a global public health threat. Although Pb exposure is reported to be associated with brain functional impairment, there remain gaps to directly clarify their links and how the environmental lead entry into brain is rarely known. This study explored the entry pathway of atmospheric Pb to brain and lung through comprehensive profiling of Pb characteristics (distribution, nanoparticle characterization and isotope ratio) in the biological and atmospheric samples collected from a typical pollution area. The Pb distribution showed the targeted accumulation of Pb in brain and its descending trend with distances in both tissues and atmosphere indicated the direct transportation of Pb to lung due to point emission of atmospheric Pb. Then the identical characteristics of Pb-containing nanoparticles (PbNPs) in the lung (two sizes: 35 ± 6 nm and 52 ± 24 nm) and atmospheric (37 ± 6 nm and 53 ± 24 nm inside the smelter) samples, which was identified to be the mixture of PbSO4 and Pb5[PO4]3Cl particles, suggested the origination of exogenous PbNPs in lung from atmosphere through direct respiration. Finally, the highly correlation of Pb isotope ratios in brain and lung, liver and kidney, and the significant difference between the two groups (p < 0.0001) indicated Pb in brain and lung was most likely directly inhaled after exposure to particulate pollution in atmosphere, but not from the liver through circulatory system. This is the first time to apply Pb isotopic characteristics in biological organs for investigating the Pb circulations and possible entry route to brain, which would provide direct evidence and a crucial link to understand the brain diseases caused by atmospheric Pb.

Environmental pollutants and atherosclerosis: Epigenetic mechanisms linking genetic risk and disease

Over the past half-century, significant strides have been made to identify key risk factors, genetic mechanisms, and treatments for atherosclerosis. Yet, coronary artery disease (CAD) remains a leading global public health challenge. While the heritability of CAD is well-documented, there is increasing focus on the role of environmental exposures, such as smoking, air pollution, and heavy metals, on global CAD risk. Recent research has shed light on the interplay between genetic variation and environmental factors, offering insights into gene-environment (GxE) interactions. Moreover, emerging evidence suggests that environmental toxicants can profoundly impact the epigenome, altering gene regulation beyond the genetic sequence itself, revealing novel mechanisms underlying disease. Epigenetic changes - such as modifications in DNA methylation, chromatin structure, and non-coding RNA function - are now recognized as key molecular determinants of atherosclerosis. These observations have created a foundational paradigm that environment, genetics, and epigenetic mechanisms influence risk through a highly complex interaction regulating cellular phenotype, pathology, and disease progression. In this review, we explore the mechanisms by which environmental exposures influence the epigenome and contribute to the regulation of atherosclerotic disease. Additionally, we examine the transgenerational epigenetic effects of these exposures on disease risk. Advancing our understanding of these mechanisms is essential for informing public health strategies aimed at mitigating harmful environmental exposures and reducing the global burden of cardiovascular disease.

Association of cadmium and lead exposure with mortality in cancer survivors: A prospective cohort study

Lead and cadmium are well-documented for their carcinogenic properties and their potential to induce cellular malignancy. Nevertheless, there is a paucity of research examining the correlation between blood cadmium and lead levels and the prognostic outcomes of cancer survivors. This study aims to investigate the relationship between blood concentrations of these heavy metals and both overall and site-specific cancer mortality risks among cancer survivors. We identified mortality rates and specific causes of death among cancer survivors by using National Health and Nutrition Examination Survey mortality data. To assess mortality outcomes, we employed multivariable Cox regression analyses, generating hazard ratios (HR) and 95 % confidence intervals (CI). We used Kaplan-Meier survival curves and restricted cubic spline models to further examine these associations. We conducted subgroup analyses to observe the prognostic risks associated with high concentrations of these metals across various tumor categories. This study revealed a significant positive correlation between whole blood cadmium concentration and all-cause mortality in cancer survivors, yielding a hazard ratio (HR) of 1.73 (95 % CI: 1.39-2.16). Elevated blood cadmium levels were significantly linked to increased cancer-specific mortality, with an HR of 2.72 (95 % CI: 1.73-4.26). A notable positive association was found between blood lead and cancer-specific mortality (HR = 1.83, 95 % CI: 1.13-2.97). Subgroup analyses indicated that elevated blood cadmium levels were significantly correlated with increased mortality risk in patients with skin and soft tissue cancers, whereas high blood lead levels were significantly associated with greater mortality risk in patients with reproductive system cancers. Additionally, elevated levels of both blood lead and cadmium were significantly related to a marked increase in mortality risk among patients with lung and mediastinal malignancies. In conclusion, our study indicates a positive correlation between increased whole blood cadmium concentrations and both all-cause and cancer-specific mortality among cancer survivors.

Combined effects of global DNA methylation, blood lead and total urinary arsenic levels on developmental delay in preschool children

DNA methylation is a critical step in brain development, 5-Methyl-2'-deoxycytidine (5mdC) is one of the global DNA methylation markers. Arsenic and lead exposures have been associated with neurotoxicity, which may be linked to epigenetic changes. Our research sought to investigate the correlation between 5mdC and developmental delay (DD) among preschoolers. Additionally, we assessed whether 5mdC modified the impacts of blood lead and total urinary arsenic levels on DD. We analyzed the concentrations of 5mdC, blood cadmium and lead, and total urinary arsenic in 174 children with DD and 88 healthy children. Global DNA methylation levels are expressed as the ratio 5mdC/2'-dexyguanosine (dG), called 5mdC (%). In our findings, elevated levels of blood lead and total urinary arsenic were significantly associated with DD risk among preschoolers. Furthermore, high 5mdC (%) was related with reduced risk of DD, with an odds ratio (OR) and 95% confidence interval (CI) of 0.14 (0.06 - 0.32). A notable multiplicative interaction was observed between low 5mdC (%) and elevated blood lead levels to increase OR of DD, with OR and 95% CI was 9.51 (4.18 - 21.64). The findings provide evidence of the combined effects of reduced 5mdC (%) and high blood lead concentrations, increasing the OR of DD.

Rutin alleviates Pb-induced oxidative stress, inflammation and cell death via activating Nrf2/ARE system in SH-SY5Y cells

Lead (Pb) is harmful to almost all organs, particularly the developmental neural system, and previous studies revealed oxidative stress played an important role in Pb neurotoxicity. Rutin, a type of flavonoid glycoside found in various plants and fruits, is widely used as a dietary supplement due to its antioxidant and anti-inflammatory properties, but whether rutin could protect against Pb neurotoxicity is unclear. In this study, we found rutin treatment significantly alleviated Pb-induced cell death, oxidative stress, and inflammation, resulting in cell survival. Moreover, rutin treatment promoted nuclear factor erythroid 2-related factor 2 (Nrf2) translocation from cytoplasm to nucleus and subsequently activated antioxidant and detoxifying enzymes expression including HO-1. Knocking down Nrf2 by siRNA transfection abolished this protection of rutin against Pb. Overall, rutin could alleviate Pb-induced oxidative stress, inflammation, and cell death by activating the Nrf2/antioxidant response elements (ARE) system.

Metal Toxicity and Dementia Including Frontotemporal Dementia: Current State of Knowledge

Frontotemporal dementia (FTD) includes a number of neurodegenerative diseases, often with early onset (before 65 years old), characterized by progressive, irreversible deficits in behavioral, linguistic, and executive functions, which are often difficult to diagnose due to their similar phenotypic characteristics to other dementias and psychiatric disorders. The genetic contribution is of utmost importance, although environmental risk factors also play a role in its pathophysiology. In fact, some metals are known to produce free radicals, which, accumulating in the brain over time, can induce oxidative stress, inflammation, and protein misfolding, all of these being key features of FTD and similar conditions. Therefore, the present review aims to summarize the current evidence about the environmental contribution to FTD-mainly dealing with toxic metal exposure-since the identification of such potential environmental risk factors can lead to its early diagnosis and the promotion of policies and interventions. This would allow us, by reducing exposure to these pollutants, to potentially affect society at large in a positive manner, decreasing the burden of FTD and similar conditions on affected individuals and society overall. Future perspectives, including the application of Artificial Intelligence principles to the field, with related evidence found so far, are also introduced.

Bisphenol mixtures, metal mixtures and type 2 diabetes mellitus: Insights from metabolite profiling

BACKGROUND

Little is known about the combined effect of bisphenol mixtures and metal mixtures on type 2 diabetes mellitus (T2DM) risk, and the mediating roles of metabolites.

METHODS

The study included 606 pairs of T2DM cases and controls matched by age and sex, and information of participants was collected through questionnaires and laboratory tests. Serum bisphenol and plasma metal concentrations were measured using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. Widely targeted metabolomics was employed to obtain the serum metabolomic profiles. Conditional logistic regression models were used to assess the single associations of bisphenols and metals with T2DM risk after multivariable adjustment. Additionally, the joint effects of bisphenol mixtures and metal mixtures were examined using quantile-based g-computation (QG-C) models. Furthermore, differential metabolites associated with T2DM were identified, and mediation analyses were performed to explore the role of metabolites in the associations of bisphenols and metals with T2DM risk.

RESULTS

The results showed bisphenol mixtures were associated with an increased T2DM risk, with bisphenol A (BPA) identified as the primary contributor. While the association between metal mixtures and T2DM remained inconclusive, cobalt (Co), iron (Fe), and zinc (Zn) showed the highest weight indices for T2DM risk. A total of 154 differential metabolites were screened between the T2DM cases and controls. Mediation analyses indicated that 9 metabolites mediated the association between BPA and T2DM, while L-valine mediated the association between Zn and T2DM risk.

CONCLUSIONS

The study indicated that BPA, Co, Fe, and Zn were the primary contributors to increased T2DM risk, and metabolites played a mediating role in the associations of BPA and Zn with the risk of T2DM. Our findings contribute to a better understanding of the mechanisms underlying the associations of bisphenols and metals with T2DM.

Paternal exposures to endocrine-disrupting chemicals induce intergenerational epigenetic influences on offspring: A review

Endocrine-disrupting chemicals (EDCs) are ubiquitous in ecological environments and have become a great issue of public health concern since the 1990 s. There is a deep scientific understanding of the toxicity of EDCs. However, recent studies have found that the abnormal physiological functions of the parents caused by EDCs could be transmitted to their unexposed offspring, leading to intergenerational toxicity. We questioned whether sustained epigenetic changes occur through the male germline. In this review, we (1) systematically searched the available research on the intergenerational impacts of EDCs in aquatic and mammal organisms, including 42 articles, (2) summarized the intergenerational genetic effects, such as decreased offspring survival, abnormal reproductive dysfunction, metabolic disorders, and behavioral abnormalities, (3) summarized the mechanisms of intergenerational toxicity through paternal interactions, and (4) propose suggestions on future research directions to develop a deeper understanding of the ecological risk of EDCs.

Reproductive toxicity of cadmium stress in male animals

Cadmium (Cd) is a common heavy metal pollutant in the environment, and the widespread use of products containing Cd compounds in industry has led to excessive levels in the environment, which enter the animal body through the food chain, thus seriously affecting the reproductive development of animals. Related studies have reported that Cd severely affects spermatogonia development and spermatogenesis in animals. In contrast, the reproductive toxicity of Cd in males and its mechanism of action have not been clarified. Therefore, this paper reviewed the toxic effects of Cd on germ cells, spermatogonia somatic cells and hypothalamic-pituitary-gonadal axis (HPG axis) of male animals and its toxic action mechanisms of oxidative stress, apoptosis and autophagy from the perspectives of cytology, genetics and neuroendocrinology. The effects of Cd stress on epigenetic modification of reproductive development in male animals were also analyzed. We hope to provide a reference for the in-depth study of the toxicity of Cd on male animal reproduction.