Lead exposure and its association with neurological damage: systematic review and meta-analysis

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.

Associations between plasma metabolites and heavy metal exposure in residents of environmentally polluted areas

Heavy metals are commonly released into the environment through industrial processes such as mining and refining. The rapid industrialization that occurred in South Korea during the 1960s and 1970s contributed significantly to the economy of the country; however, the associated mining and refining led to considerable environmental pollution, and although mining is now in decline in South Korea, the detrimental effects on residents inhabiting the surrounding areas remain. The bioaccumulation of toxic heavy metals leads to metabolic alterations in human homeostasis, with disruptions in this balance leading to various health issues. This study used metabolomics to explore metabolomic alterations in the plasma samples of residents living in mining and refining areas. The results showed significant increases in metabolites involved in glycolysis and the surrounding metabolic pathways, such as glucose-6-phosphate, phosphoenolpyruvate, lactate, and inosine monophosphate, in those inhabiting polluted areas. An investigation of the associations between metabolites and blood clinical parameters through meet-in-the-middle analysis indicated that female residents were more affected by heavy metal exposure, resulting in more metabolomic alterations. For women, inhabiting the abandoned mine area, metabolites in the glycolysis and pentose phosphate pathways, such as ribose-5-phosphate and 3-phosphoglycerate, have shown a negative correlation with albumin and calcium. Finally, Mendelian randomization(MR) was used to determine the causal effects of these heavy metal exposure-related metabolites on heavy metal exposure-related clinical parameters. Metabolite biomarkers could provide insights into altered metabolic pathways related to exposure to toxic heavy metals and improve our understanding of the molecular mechanisms underlying the health effects of toxic heavy metal exposure.

Trends in elemental Pb concentrations within atmospheric PM2.5 and associated risk to human health in major cities of China

High concentrations of elemental lead (Pb) in the atmosphere pose a serious threat to human health. This study presents and summarizes data obtained from relevant literature on Pb concentrations within fine particulate matter (PM_2.5) recorded in major cities in China from 2008 to 2019. An environmental health risk assessment model was then used to evaluate the health hazards of inhaling Pb among adults and children in China. Owing to the promulgation and implementation of a series of air pollution control measures, the Pb concentrations within PM_2.5 measured in major cities in China showed a downward trend after peaking in 2013. The concentrations were higher in winter than in summer, and higher in northern cities than in southern cities. Although the Pb concentrations in most cities did not exceed the limit (500 ng/m³) set by China, they remained much higher than concentrations recorded in developed countries. The results of the environmental health risk analysis showed that the non-carcinogenic risk from atmospheric Pb exposure was higher in children than in adults (adult females > adult males), while the carcinogenic risk was higher in adults than in children. This study shows that even if the health risk of Pb in PM_2.5 does not exceed the acceptable limit, stricter Pb pollution control measures are required to safeguard population health due to the dangers of Pb.

Lead suppresses interferon γ to induce splenomegaly via modification on splenic endothelial cells and lymphoid tissue organizer cells in mice

Splenomegaly is a symptom characterized by the presence of an enlarged spleen. The impact of environmental factors on splenomegaly is largely unknown. In this study, C57BL/6 mice were treated with 125 ppm or 1250 ppm lead (Pb) via drinking water for 8 wk, and the process of splenomegaly was evaluated. Treatment with 1250 ppm Pb, but not 125 ppm Pb, caused splenomegaly, which was associated with increased capacity for erythrocyte clearance. Intriguingly, Pb-caused splenomegaly was independent of lymphoid tissue inducer (LTi) cells, which produce lymphotoxins α and β (LTα/β) to activate endothelial cells and LT organizer (LTo) cells and drive the development of spleen physiologically. A direct action of Pb on endothelial cells and LTo cells did not impact their proliferation. On the other hand, during steady state, a tonic level of interferon (IFN)γ acted on endothelial cells and LTo cells to suppress splenomegaly, as IFNγ receptor (IFNγR)-deficient mice had enlarged spleens relative to wild-type mice; during Pb exposure, splenic IFNγ production was suppressed, thus leading to a loss of the inhibitory effect of IFNγ on splenomegaly. Mechanically, Pb acted on splenic CD4⁺ T cells to suppress IFNγ production, which impaired the Janus kinase (Jak)1/ signal transducer and activator of transcription (STAT)1 signaling in endothelial cells and LTo cells; the weakened Jak1/STAT1 signaling resulted in the enhanced nuclear factor-κB (NF-κB) signaling in endothelial cells and LTo cells, which drove their proliferation and caused splenomegaly. The present study reveals a previously unrecognized mechanism for the immunotoxicity of Pb, which may extend our current understanding for Pb toxicology.

Global Trends in Mortality and Burden of Stroke Attributable to Lead Exposure From 1990 to 2019

Background

Lead exposure is an important risk factor for stroke. However, the latest global spatiotemporal patterns of lead exposure-related stroke burden were unclear. In this study, we assessed this topic.

Methods

The data were obtained from the Global Burden of Disease Study (2019). The estimated annual percentage change (EAPC) was estimated to evaluate the temporal trends of the age-standardized mortality and disability-adjusted life years (DALYs) rates (ASMR and ASDR) of stroke attributable to lead exposure.

Results

In 2019, the numbers of global stroke deaths and DALYs attributable to lead exposure were 305.27 and 6738.78 thousand, respectively. The corresponding ASMR and ASDR were highest in males, the elderly population, low and middle-income countries, and the intracerebral hemorrhage subtype. From 1990 to 2019, the ASMR and ASDR of global stroke attributable to lead exposure decreased [ASMR: EAPC = −1.34, 95% confidence interval (CI): (−1.57, −1.10); ASDR: EAPC = −1.74, 95% CI: (−1.95, −1.52)], especially in females, the high-income countries, and the subarachnoid hemorrhage subtype.

Conclusion

This study emphasizes the importance of continued implementation of lead exposure prevention strategies and improved high-efficiency treatment and stroke acute health care, especially in low and middle-income countries.

Neurotoxicity of Chronic Co-Exposure of Lead and Ionic Liquid in Common Carp: Synergistic or Antagonistic?

Previous studies have indicated that the harmful heavy metal lead (Pb) contamination in aquatic systems has caused intelligence development disorders and nervous system function abnormalities in juveniles due to the increased permeability of the blood-brain barrier. Ionic liquids (ILs) are considered "green" organic solvents that can replace traditional organic solvents. Studies have found the presence of ILs in soil and water due to chemical applications or unintentional leakage. Therefore, what would happen if Pb interacted with ILs in a body of water? Could ILs enable Pb to more easily cross the blood-brain barrier? Therefore, we examined the combined exposure of Pb and ILs in common carp at low concentration (18.3 mg L^-1 of Pb(CH₃COO)₂•3 H₂O and 11 mg L^-1 of the IL 1-methyl-3-octylimidazolium chloride, 5% of their LC₅₀) for 28 days in the present study. The result of a neurobehavioral assay showed that chronic exposure of lead at lower concentrations significantly altered fish movement and neurobehaviors, indicating that lead exposure caused neurotoxicity in the carp. Increases in the neurotransmitter dopamine levels and injuries in the fish brain accounted for neurobehavioral abnormalities induced by lead exposure. Moreover, we also found that lead could easily cross the blood-brain barrier and caused significant bioaccumulation in the brain. Particularly, our study indicated that the ionic liquid could not synergistically promote blood-brain barrier permeability and hence failed to increase the absorption of lead in the fish brain, suggesting that the combined exposure of lead and ILs was not a synergistic effect but antagonism to the neurotoxicity. The results of this study suggested that ILs could recede the Pb induced neurotoxicity in fish.

Modification by genetic polymorphism of lead-induced IQ alteration: a systematic review

As well as a lead-related environmental factor, genetic factors could also corroborate important changes in intelligence quotient (IQ) through single-nucleotide polymorphisms. Thus, a systematic review was carried out to evaluate the possible influence of polymorphism on blood Pb levels and IQ points in pediatric patients (0-19 years old). Following the PRISMA guideline, the studies were systematically collected on PubMed, Scopus, and Embase databases. Six genes (transferrin (TF); glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A); glutamate ionotropic receptor NMDA type subunit 2B (GRIN2B); dopamine receptor D2/ankyrin repeat and kinase domain containing 1 ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1); aminolevulinate dehydratase (ALAD); vitamin D receptor (VDR)) were found in six selected articles. In these genes, 11 single-nucleotide polymorphisms were searched and six different types of variations (missense variant, intron variant, synonymous variant, stop, stop gained) were observed. Due to the few studies in the literature, there is no conclusive data to point out that there is a direct relationship between polymorphisms, Pb levels, and reduction of IQ points.

IQ alteration induced by lead in developed and underdeveloped/developing countries: A systematic review and a meta-analysis

The aim of this study was to evaluate the effects of Pb exposure on full-scale IQ score in pediatric subjects. Following PRISMA guidelines, the data from January 2010 to April 2020 were systematically searched and collected on electronic databases (PubMed, Scopus, and Embase). The eligibility criteria included cross-sectional, cohort, and case-control studies that were published in English, from 2010 to 2020, that analyzed the blood Pb levels of pediatric subjects (0-19 years) and possible changes in the full-scale IQ score. In this study, 2174 scientific papers were collected from three electronic databases. From those, 726 were duplicates and 1421 were excluded because they did not meet the eligibility criteria, resulting in a total of 27 papers, from which, seven were used to perform the meta-analysis. The 27 scientific papers systematically selected for this study were separated by the country where the study was realized in developed and underdeveloped/developing countries. In the underdeveloped/developing countries the blood Pb levels are higher and showed a greater variation (1.30-11.66 μgPb/dL of blood) than in countries with higher development index (0.57-4.80 μgPb/dL of blood). The full-scale IQ score are inversely proportional to the blood Pb values, and it is possible to see that in the underdeveloped/developing countries the full-scale IQ score showed lower values and greater variation (59.2-111) compared to the individuals from developed countries (91.9-114.5). In conclusion, it was observed that blood Pb levels alter the full-scale IQ score. Thus, policies for the prevention of environmental contamination and the reduction of Pb exposure must be taken, mainly, in underdeveloped/developing countries.