Lead-induced neurodevelopmental lesion and epigenetic landscape: Implication in neurological disorders

Hippocampal MEF2C phosphorylation mediates synaptic plasticity in lead-induced learning and memory impairments

Lead (Pb), an ancient metallic environmental pollutant, has received widespread attention and has been strictly controlled, but current findings have found the hazards of Pb to be much higher than previously estimated. Pb exposure can lead to memory impairment. However, the underlying molecular mechanisms have not been fully elucidated. Dynamic changes in dendritic spines form the structural basis of memory, and MEF2C, a key regulator of dendritic plasticity, plays an important role in hippocampus-dependent learning and memory. This study focused on the role of ERK-induced MEF2C phosphorylation in Pb-induced learning and memory impairments. A rat model of Pb exposure from the embryo to adolescence and the model of Pb exposure in PC12 cells were established. The results showed that Pb exposure reduced the phosphorylation level of MEF2C in the rat hippocampus by affecting the expression of ERK5. In addition, it reduced the expression of MEF2C at the translation stage, which affected its transcriptional ability and led to abnormal expression of the downstream factor ARC, causing alterations in neuronal dendritic plasticity and affecting its memory ability. Further experiments showed that regulating the phosphorylation level of MEF2C could affect neurite growth in PC12 cells exposed to Pb. Our findings demonstrate that Pb exposure may contribute to memory impairment by affecting MEF2C and its phosphorylation levels, resulting in altered dendritic plasticity.

Documentation of lead exposure-associated comorbidity among 4538 workers in China

BACKGROUND

Systematic documentation of morbidity with exposure assessment in a large group of lead (Pb)-exposed workers in China.

METHODS

Using the cluster sampling method, Pb-exposed workers were recruited from a factory in the Henan Province, China. The morbidity information and blood lead concentration (BLC) from each worker were collected. Relationships between the two sets of data were analyzed using the logistic regression and restricted cubic spline (RCS) models.

RESULTS

Among the 4538 recruited workers, there were 2780 males and 1758 females, with a median age of 34 years old, and BLC ranging from 7.70 to 722.70 μg/l. Among them, 1247 (27.4%) had multiple morbidities (comorbidity). Those with the highest BLC showed a 1.79-fold (significant) increase in comorbidities compared to those with the lowest BLC (95% confidence interval = 1.43, 2.25; p < 0.001). In addition, the comorbidities exhibited a BLC dose-response relationship (p < 0.001), after adjusting for potential confounding factors. The RCS curve analysis revealed a nonlinear relationship between BLC and risk of comorbidity (p-overall < 0.001, and p-nonlinear < 0.001). Sensitivity analysis further confirmed the dose-response relationship between BLC and the risk of developing comorbidities. Additionally, the data indicate that female workers were more susceptible to comorbidities.

CONCLUSION

Our study demonstrates that comorbidity was prevalent and was dose-dependent among lead exposed workers.

Normative implications of postgenomic deterministic narratives: the case study of epigenetic harm

What do we mean when we talk about epigenetic harm? This paper presents a multidimensional view of epigenetic harm. It is a plea to take a step back from discussions of epigenetic responsibility distributions prevalent in ELSA literature on epigenetics. Instead, it urges researchers to take a closer look at the normative role played by the concept of epigenetic harm. It starts out by showing that the ways in which the object of epigenetic responsibility has already been conceptualized are all related to 'epigenetic harm': something negative that happens in which epigenetic mechanisms play a role, or rather something that needs to be avoided. Epigenetic harm is then characterized as a bridging concept between relatively neutral findings on epigenetics on the one side, and potential ethical and societal implications of those findings, primarily in terms of responsibility ascriptions and distributions, on the other. The paper proposes that a sufficiently nuanced account of epigenetic harm should include at least three dimensions. The dimension of causation alone leads to an overly narrow understanding of harm, and a wrong understanding of this dimension might prompt researchers to support an excessively simplistic epigenetic determinism. It is argued that a multidimensional analysis of epigenetic harm is less vulnerable to this threat and more reflective of the various kinds of harm that may be experienced by the subjects of epigenetic alterations. The paper applies insights from disability studies and feminist philosophy to draw attention to two other dimensions of epigenetic harm, namely lived experiences and relationality. The paper concludes by exploring what a shift towards a multidimensional approach to epigenetic harm might mean for epigenetic research and responsibility ascriptions by formulating some concrete implications.

Effects of organic and inorganic contaminants and their mixtures on metabolic health and gene expression in developmentally exposed zebrafish

Organic and inorganic chemicals co-occur in household dust, and these chemicals have been determined to have endocrine and metabolic disrupting effects. While there is increasing study of chemical mixtures, the effects of complex mixtures mimicking household dust and other environmental matrices have not been well studied and their potential metabolism disrupting effects are thus poorly understood. Previous research has demonstrated high potency adipogenic effects of residential household dust extracts using in vitro adipogenesis assays. More recent research simplified this to a mixture relevant to household dust and comprised of common co-occurring organic and inorganic contaminants, finding that these complex combinations often exhibited additive or even synergistic effects in cell models. This study aimed to translate our previous in vitro observation to an in vivo model, the developing zebrafish, to evaluate the metabolic effects of early exposure to organic and inorganic chemicals, individually and in mixtures. Zebrafish embryos were exposed from 1 day post fertilization (dpf) to 6 dpf, then metabolic energy expenditure, swimming behavior and gene expression were measured. Globally, we observed that most mixtures did not reflect the effects of individual chemicals; the BFR mixture produced a less potent effect when compared to the individual chemicals, while the PFAS and the inorganic mixtures seemed to have a more potent effect than the individual chemicals. Finally, the environmental mixture, mimicking household dust proportions, was less potent than the inorganic chemical mix alone. Additional work is necessary to better understand the mixture effect of inorganic and organic chemicals combined.

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.

Lead induced cerebellar toxicology of developmental Japanese quail (Coturnix japonica) via oxidative stress-based Nrf2/Keap1 pathway inhibition and glutathione-mediated apoptosis signaling activation

Lead (Pb) is a heavy metal that has been recognized as a neurotoxin, meaning it can cause harmful effects on the nervous system. However, the neurotoxicology of Pb to birds still needs further study. In this study, we examined the neurotoxic effects of Pb exposure on avian cerebellum by using an animal model-Japanese quail (Coturnix japonica). The one-week old male chicks were exposed to 50, 200 and 500 mg/kg Pb of environmental relevance in the feed for five weeks. The results showed Pb caused cerebellar microstructural damages charactered by deformation of neuroglia cells, granule cells and Purkinje cells with Nissl body changes. Moreover, cerebellar neurotransmission was disturbed by Pb with increasing acetylcholine (ACh) and decreasing acetylcholinesterase (AChE), dopamine (DA), γ-Aminobutyric Acid (GABA) and Na+/K+ ATPase. Meanwhile, cerebellar oxidative stress was caused by Pb exposure represented by increasing reactive oxygen species (ROS) and malondialdehyde (MDA) as well as decreasing catalase (CAT), glutathione peroxidase (GPX), glutathione (GSH) and superoxide dismutase (SOD). Moreover, RNA-Seq analysis showed that molecular signaling pathways in the cerebellum were disrupted by Pb exposure. In particular, the disruption of nuclear factor erythroid-2-related factor 2 (Nfr2)/kelch-like ECH-associated protein 1 (Keap1) pathway and glutathione metabolism pathway indicated increasing cell apoptosis and functional disorder in the cerebellum. The present study revealed that Pb induced cerebellar toxicology through structural injury, oxidative stress, neurotransmission interference and abnormal apoptosis.

Dynamic alterations of locomotor activity and the microbiota in zebrafish larvae with low concentrations of lead exposure

Lead (Pb) is a ubiquitous heavy metal associated with developmental and behavioral disorders. The establishment of pioneer microbiota overlaps with the development of the brain during early life, and Pb-induced developmental neurotoxicity may be partially caused by early-life microbiota dysbiosis. This study investigated the locomotor activity and the microbiota in developing zebrafish at multiple developmental time points (five days post fertilization [5 dpf], 6 dpf, and 7 dpf) under exposure to low concentrations of lead (0.05 mg/L). Time-dependent reductions in the number of activities and the average movement distance of larvae compared to the control were observed following Pb exposure. Furthermore, Pb exposure significantly altered the composition of the gut microbiota of zebrafish larvae. At the phylum level, the abundance of Proteobacteria decreased from 5 to 7 dpf, while that of Actinobacteria increased in the control groups. At the class level, the proportion of Alphaproteobacteria decreased, while that of Actinobacteria increased in the control groups. Notably, all showed the opposite trend in Pb groups. A correlation analysis between indices of locomotor activity and microbial communities revealed genus-level features that were clearly linked to the neurobehavioral performance of zebrafish. Seven genera were significantly correlated with the two performance indicators of the locomotion analysis, namely Rhodococcus, Deinococcus, Bacillus, Bosea, Bradyrhizobium, Staphylococcus, and Rhizobium. Rhizobium was dominant in zebrafish and increased in the Pb groups in a time-dependent manner. In addition, the expression levels of bdnf, trkb1, trkb2, and p75ntr changed in zebrafish from 5 to 7 dpf under Pb exposure. Collectively, these results suggest that Pb-induced neurotoxicity could potentially be treated by targeting the gut microbiota.

Emerging roles of epigenetics in lead-induced neurotoxicity

Lead is a common environmental heavy metal contaminant. Humans are highly susceptible to lead accumulation in the body, which causes nervous system damage and leads to a variety of nervous system diseases, such as Alzheimer's disease, Parkinson's disease, and autism spectrum disorder. Recent research has focused on the mechanisms of lead-induced neurotoxicity at multiple levels, including DNA methylation, histone modifications, and non-coding RNAs, which are involved in various lead-induced nervous system diseases. We reviewed the latest articles and summarised the emerging roles of DNA methylation, histone modification, and non-coding RNAs in lead-induced neurotoxicity. Our summary provides a theoretical basis and directions for future research on the prevention, diagnosis, and treatment of lead-induced neurological diseases.

Pollution Profiles, Source Identification and Health Risk Assessment of Heavy Metals in Soil near a Non-Ferrous Metal Smelting Plant

Heavy metal pollution related to non-ferrous metal smelting may pose a significant threat to human health. This study analyzed 58 surface soils collected from a representative non-ferrous metal smelting area to screen potentially hazardous heavy metals and evaluate their health risk in the studied area. The findings demonstrated that human activity had contributed to the pollution degrees of Cu, Cd, As, Zn, and Pb in the surrounding area of a non-ferrous metal smelting plant (NMSP). Cu, Cd, As, Zn, Pb, Ni, and Co pollution within the NMSP was serious. Combining the spatial distribution and Spearman correlations with principal component analysis (PCA), the primary sources of Cd, As, Pb, and Zn in surrounding areas were related to non-ferrous metal smelting and transportation activities. High non-cancer (THI = 4.76) and cancer risks (TCR = 2.99 × 10^-4) were found for adults in the NMSP. Moreover, heavy metals in the surrounding areas posed a potential cancer risk to children (TCR = 3.62 × 10^-6) and adults (TCR = 1.27 × 10^-5). The significant contributions of As, Pb, and Cd to health risks requires special attention. The construction of a heavy metal pollution management system will benefit from the current study for the non-ferrous metal smelting industry.