Molecular mechanisms of lead neurotoxicity

Lead exerts a depression of neurotransmitter release through a blockade of voltage dependent calcium channels in chromaffin cells

The present work, using chromaffin cells of bovine adrenal medullae (BCCs), aims to describe what type of ionic current alterations induced by lead (Pb2+) underlies its effects reported on synaptic transmission. We observed that the acute application of Pb2+ lead to a drastic depression of neurotransmitters release in a concentration-dependent manner when the cells were stimulated with both K+ or acetylcholine, with an IC50 of 119,57 μM and of 5,19 μM, respectively. This effect was fully recovered after washout. Pb2+ also blocked calcium channels of BCCs in a time- and concentration-dependent manner with an IC50 of 6,87 μM. This blockade was partially reversed upon washout. This compound inhibited the calcium current at all test potentials and shows a shift of the I-V curve to more negative values of about 8 mV. The sodium current was not blocked by acute application of high Pb2+ concentrations. Voltage-dependent potassium current was also shortly affected by high Pb2+. Nevertheless, the calcium- and voltage-dependent potassium current was drastically depressed in a dose-dependent manner, with an IC50 of 24,49 μM. This blockade was related to the prevention of Ca2+ influx through voltage-dependent calcium channels coupled to Ca2+-activated K+-channels (BK) instead a direct linking to these channels. Under current-clamp conditions, BCCs exhibit a resting potential of -52.7 mV, firing spontaneous APs (1-2 spikes/s) generated by the opening of Na+ and Ca2+-channels, and terminated by the activation of K+ channels. In spite of the effect on ionic channels exerted by Pb2+, we found that Pb2+ didn't alter cellular excitability, no modification of the membrane potential, and no effect on action potential firing. Taken together, these results point to a neurotoxic action evoked by Pb2+ that is associated with changes in neurotransmitter release by blocking the ionic currents responsible for the calcium influx.

Influence of lead-induced toxicity on the inflammatory cytokines

Lead (Pb2+) is a hazardous heavy metal that is pervasive in the human environment as a result of anthropogenic activity, and poses serious health risks, particularly in children. Due to its innumerable unique physical and chemical properties, it has various applications; therefore, it has become a common environmental pollutant. Lead may cause oxidative stress, and accumulating evidence indicates that oxidative stress influences the pathophysiology of lead poisoning, also called plumbism. The immune system is continually exposed to various environmental pathogens and xenobiotics, including heavy metals such as lead, and appears to be one of the most vulnerable targets. After being exposed to lead, cells are subjected to oxidative stress as a result of reactive oxygen species (ROS) production. When the generation and consumption of ROS are out of equilibrium, various cell structures, particularly phospholipids are disrupted leading to lipid peroxidation. Various inflammatory signalling pathways are activated as a consequence, along with reduced disease resistance, inflammation, autoimmunity, sensitization and disruption of the cell-mediated and humoral immune systems. Lead negatively affects the metabolism of cytokines, including the interleukins IL-2, IL-1b, IL-6, IL-4, IL-8, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN), as well as the expression and functioning of inflammatory enzymes such as cyclooxygenases. However, the cause of toxicity depends on the kind of lead, dosage, route of entry, exposure period, age, host and genetic predisposition.

In vivo and in silico approach in revealing the influence of lead (Pb) on thyroid gland function

The purpose of this study was to examine the impact of low doses of lead (Pb) on levels of thyroid hormones (T3, T4, FT3, and FT4) and thyroid-related antibodies (anti-Tg and anti-TPO) in the rat model, as well as genes that are related to Pb and thyroid function, relationships between genes, biological processes, molecular processes, and pathways using an in silico approach. Male rats were randomized into seven groups (n = 42), one control group and six groups that received a range of Pb doses: 0.1, 0.5, 1, 3, 7, and 15 mg Pb/kg body weight (b.w.). Dose-response modelling was performed by PROAST software using model averaging method. The Comparative Toxicogenomics Database, GeneMANIA server, and ToppGene Suite portal were used as the main bioinformatic tools in this analysis. The results of our study have shown that low Pb doses induced elevation of thyroid hormones (T4, FT4, and TSH) in rats after subacute exposure, while had no impact on T3, FT3, anti-TPO, and anti-Tg, indicating hyperthyroidism. Dose-dependent effects were increases in T4 and FT4, with the lowest benchmark dose derived for FT4 levels. In silico toxicogenomic data analysis showed that the main molecular pathways/process related to Pb-induced hyperthyroidism are connected with 14 genes involved in antioxidant defense and Se-dependent processes. The results presented here may be useful in further investigation of the health impacts of low-level Pb exposure on thyroid function and endocrine disruption effects.

Determination of heavy metals and risk assessment in nail cosmetics sold in Seoul, Korea

OBJECTIVE

The objective of this study was to evaluate some toxic levels of nail cosmetics marketed in Seoul, Korea and health risk assessment on humans.

METHODS

We collected 45 random nail cosmetics and analysed for lead, cadmium, arsenic and antimony by inductively coupled plasma-optical emission spectrometry (ICP-OES).

RESULTS

Four metals concentrations were Pb 0.037 ± 0.083 (

DISCUSSION AND CONCLUSION

Six nail cosmetics had high antimony concentrations which were higher than the current legal limit in Korea. Because of 6 high antimony concentrations, MoS, HQ and HI were outside the acceptable range. LCR value for Pb, As and Cd was below 1 0 -6 which was lower than the permissible limit and nail cosmetics may not possess lifetime cancer risk. Our results suggested that metals were present in nail cosmetics at diverse concentrations and some nail cosmetics appeared to pose a harmful impact on health.

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Key Words

• ICP-OES
• Nail cosmetics
• Seoul
• health risk assessment
• heavy metals

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MESH Headings

• Humans
• Cadmium/toxicity
• Cadmium/analysis
• Antimony/analysis
• Seoul
• Lead/toxicity
• Metals, Heavy/toxicity
• Metals, Heavy/analysis
• Cosmetics/analysis
• Risk Assessment

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Affiliation(s)

Suun Kim Food & Drug Division, Seoul Metropolitan Government Research Institute of Public Health and Environment, Seoul, Korea
Chaeman Choi Food & Drug Division, Seoul Metropolitan Government Research Institute of Public Health and Environment, Seoul, Korea
Myeongsook Lee Food & Drug Division, Seoul Metropolitan Government Research Institute of Public Health and Environment, Seoul, Korea
Insook Hwang Food & Drug Division, Seoul Metropolitan Government Research Institute of Public Health and Environment, Seoul, Korea

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Ionic displacement of Ca2+ by Pb2+ in calmodulin is affected by arrhythmia-associated mutations

Lead is a highly toxic metal that severely perturbs physiological processes even at sub-micromolar levels, often by disrupting the Ca²⁺ signaling pathways. Recently, Pb²⁺-associated cardiac toxicity has emerged, with potential involvement of both the ubiquitous Ca²⁺ sensor protein calmodulin (CaM) and ryanodine receptors. In this work, we explored the hypothesis that Pb²⁺ contributes to the pathological phenotype of CaM variants associated with congenital arrhythmias. We performed a thorough spectroscopic and computational characterization of CaM conformational switches in the co-presence of Pb²⁺ and four missense mutations associated with congenital arrhythmias, namely N53I, N97S, E104A and F141L, and analyzed their effects on the recognition of a target peptide of RyR2. When bound to any of the CaM variants, Pb²⁺ is difficult to displace even under equimolar Ca²⁺ concentrations, thus locking all CaM variants in a specific conformation, which exhibits characteristics of coiled-coil assemblies. All arrhythmia-associated variants appear to be more susceptible to Pb²⁺ than WT CaM, as the conformational transition towards the coiled-coil conformation occurs at lower Pb²⁺, regardless of the presence of Ca²⁺, with altered cooperativity. The presence of arrhythmia-associated mutations specifically alters the cation coordination of CaM variants, in some cases involving allosteric communication between the EF-hands in the two domains. Finally, while wild type CaM increases the affinity for the RyR2 target in the presence of Pb²⁺, no specific pattern could be detected for all other variants, ruling out a synergistic effect of Pb²⁺ and mutations in the recognition process.

Adverse Childhood Experiences (ACEs) and Environmental Exposures on Neurocognitive Outcomes in Children: Empirical Evidence, Potential Mechanisms, and Implications

The purpose of this article is to examine the current literature regarding the relationship between adverse childhood experiences (ACEs) and environmental exposures. Specifically, the paper will focus on how this relationship between ACEs and physical environmental factors impacts the neurocognitive development of children. With a comprehensive literary search focusing on ACEs, inclusive of socioeconomic status (SES), and environmental toxins common in urban environments, the paper explores how these factors contribute to cognitive outcomes that are associated with the environment and childhood nurturing. The relationship between ACEs and environmental exposures reveals adverse outcomes in children's neurocognitive development. These cognitive outcomes include learning disabilities, lowered IQ, memory and attention problems, and overall poor educational outcomes. Additionally, potential mechanisms of environmental exposures and children's neurocognitive outcomes are explored, referencing data from animal studies and evidence from brain imaging studies. This study further analyzes the current gaps in the literature, such as the lack of data focusing on exposure to environmental toxicants resulting from experiencing ACEs and discusses the research and social policy implications of ACEs and environmental exposure in the neurocognitive development of children.

Occupational lead exposure and survival with amyotrophic lateral sclerosis

Objective: Lead exposure has been hypothesized to increase the risk of ALS, but only two studies have examined the association with ALS survival, and with inconsistent results. The use of occupational history to assess lead exposure can avoid reverse causation that may occur in epidemiologic analyses that use biomarkers of lead exposure collected after ALS onset.Methods: We evaluated the relationship of occupational lead exposure to ALS survival among 135 cases from an international ALS cohort that included deep phenotyping, careful follow-up, and questionnaires to quantify participants' occupation history. ALS patients were recruited in 2015-2019. We determined occupational lead exposure using a job-exposure matrix. We estimated hazard ratios (HR) and 95% confidence intervals (CI) for survival using Cox proportional hazard analysis with adjustment for covariates.Results: A total of 135 ALS patients completed the environmental questionnaires, among whom 38 reached a survival endpoint (death or permanent assisted ventilation). The median survival was 48.3 months (25th-75th percentile, 30.9-74.1). Older patients and those with initial symptom other than limb onset had shorter survival time. There were 36 ALS cases with occupational lead exposure. After adjusting for age, sex, site of onset, smoking, and military service, lead exposure was associated with an HR of 3.26 (95%CI 1.28-8.28). Results with adjustment for subsets of these covariates were similar.Conclusions: These results suggest that lead exposure prior to onset of ALS is associated with shorter survival following onset of ALS, and this association is independent of other prognostic factors.

Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential Metals

Since hundreds of years ago, metals have been recognized as impacting our body's physiology. As a result, they have been studied as a potential cure for many ailments as well as a cause of acute or chronic poisoning. However, the link between aberrant metal levels and neuropsychiatric illnesses such as schizophrenia and neurodevelopmental disorders, such as autism spectrum disorders (ASDs), is a relatively new finding, despite some evident ASD-related consequences of shortage or excess of specific metals. In this review, we will summarize past and current results explaining the pathomechanisms of toxic metals at the cellular and molecular levels that are still not fully understood. While toxic metals may interfere with dozens of physiological processes concurrently, we will focus on ASD-relevant activity such as inflammation/immune activation, mitochondrial malfunction, increased oxidative stress, impairment of axonal myelination, and synapse formation and function. In particular, we will highlight the competition with essential metals that may explain why both the presence of certain toxic metals and the absence of certain essential metals have emerged as risk factors for ASD. Although often investigated separately, through the agonistic and antagonistic effects of metals, a common metal imbalance may result in relation to ASD.

Effects of Long-Term Lead Exposure on Antioxidant Enzyme Defense System in Organs of Brown Hare (Lepus europaeus Pallas) as a Bioindicator of Environmental Pollution in Croatia

In Croatia, Podravina is a well-known lead-polluted region due to the intensive exploitation of natural gas, a highly developed agricultural industry, and a traffic hub with several heavily traveled roads. It represents a natural environment with a great variety of wildlife, especially hares (Lepus europaeus Pallas), which may serve as an indicator for environmental quality assessment. This study was conducted to estimate the bioaccumulation of lead in hare liver, kidney, muscle, and brain during long-term exposure and its impact on the oxidative status of the organism and to investigate a possible lead exchange ionic mechanism in the brain. In the organs of two hare groups (experimental from polluted area and control from the island of Krk), Ca, Fe, Mg, Na, lead concentrations, and antioxidant enzyme defense system were analyzed. The accumulation of lead was highest in the brain (3.7-fold higher compared to the control group) and lowest in the liver (1.6-fold higher compared to the control group). Kendall-Tau and multiple regression analysis showed that the increased lead content caused a stronger exchange of Ca and Na ions in the brain. We proposed that lead either mobilizes intracellular cation stores or causes competitive displacement of Ca from the binding site in intoxicated cells. A linear predictive model for cell intoxication by lead was proposed, where GPx and SOD were predominantly influenced by long-term lead exposure. The presented results showed that long-term lead exposure in hares negatively affected their oxidative status and caused the strongest toxicity in the brain and muscles, making their survival and/or population vulnerable.

Impact of Environmental Pollutants on Gut Microbiome and Mental Health via the Gut–Brain Axis

Over the last few years, the microbiome has emerged as a high-priority research area to discover missing links between brain health and gut dysbiosis. Emerging evidence suggests that the commensal gut microbiome is an important regulator of the gut–brain axis and plays a critical role in brain physiology. Engaging microbiome-generated metabolites such as short-chain fatty acids, the immune system, the enteric nervous system, the endocrine system (including the HPA axis), tryptophan metabolism or the vagus nerve plays a crucial role in communication between the gut microbes and the brain. Humans are exposed to a wide range of pollutants in everyday life that impact our intestinal microbiota and manipulate the bidirectional communication between the gut and the brain, resulting in predisposition to psychiatric or neurological disorders. However, the interaction between xenobiotics, microbiota and neurotoxicity has yet to be completely investigated. Although research into the precise processes of the microbiota–gut–brain axis is growing rapidly, comprehending the implications of environmental contaminants remains challenging. In these milieus, we herein discuss how various environmental pollutants such as phthalates, heavy metals, Bisphenol A and particulate matter may alter the intricate microbiota–gut–brain axis thereby impacting our neurological and overall mental health.

Bayesian kernel machine regression-causal mediation analysis

Greater understanding of the pathways through which an environmental mixture operates is important to design effective interventions. We present new methodology to estimate natural direct and indirect effects and controlled direct effects of a complex mixture exposure on an outcome through a mediator variable. We implement Bayesian Kernel Machine Regression (BKMR) to allow for all possible interactions and nonlinear effects of (1) the co-exposures on the mediator, (2) the co-exposures and mediator on the outcome, and (3) selected covariates on the mediator and/or outcome. From the posterior predictive distributions of the mediator and outcome, we simulate counterfactuals to obtain posterior samples, estimates, and credible intervals of the mediation effects. Our simulation study demonstrates that when the exposure-mediator and exposure-mediator-outcome relationships are complex, BKMR-Causal Mediation Analysis performs better than current mediation methods. We applied our methodology to quantify the contribution of birth length as a mediator between in utero co-exposure to arsenic, manganese, and lead, and children's neurodevelopmental scores, in a prospective birth cohort in Bangladesh. Among younger children, we found a negative (adverse) association between the metal mixture and neurodevelopment. We also found evidence that birth length mediates the effect of exposure to the metal mixture on neurodevelopment for younger children. If birth length were fixed to its 75 t h percentile value, the harmful effect of the metal mixture on neurodevelopment is attenuated, suggesting nutritional interventions to help increase fetal growth, and thus birth length, could potentially block the harmful effect of the metal mixture on neurodevelopment.

A Comparison of the Effect of Lead (Pb) on the Slow Vacuolar (SV) and Fast Vacuolar (FV) Channels in Red Beet (Beta vulgaris L.) Taproot Vacuoles

Little is known about the effect of lead on the activity of the vacuolar K+ channels. Here, the patch-clamp technique was used to compare the impact of lead (PbCl2) on the slow-activating (SV) and fast-activating (FV) vacuolar channels. It was revealed that, under symmetrical 100-mM K+, the macroscopic currents of the SV channels exhibited a typical slow activation and a strong outward rectification of the steady-state currents, while the macroscopic currents of the FV channels displayed instantaneous currents, which, at the positive potentials, were about three-fold greater compared to the one at the negative potentials. When PbCl2 was added to the bath solution at a final concentration of 100 µM, it decreased the macroscopic outward currents of both channels but did not change the inward currents. The single-channel recordings demonstrated that cytosolic lead causes this macroscopic effect by a decrease of the single-channel conductance and decreases the channel open probability. We propose that cytosolic lead reduces the current flowing through the SV and FV channels, which causes a decrease of the K+ fluxes from the cytosol to the vacuole. This finding may, at least in part, explain the mechanism by which cytosolic Pb2+ reduces the growth of plant cells.

Functional consequences of lead and mercury exposomes in the heart

Lead and mercury are heavy metals that are highly toxic to life forms. There are no known physiological processes that require them, and they do not have a particular threshold concentration to produce biologic damage. They are non-biodegradable, and they slowly accumulate in the environment in a dynamic equilibrium between air, water, soil, food, and living organisms. Their accumulation in the environment has been increasing over time, because they were not banned from use in anthropogenic industrial production. In their +2 cationic state they are powerful oxidizing agents with the ability to interfere significantly with processes that require specific divalent cations. Acute or chronic exposure to lead and mercury can produce multisystemic damage, especially in the developing nervous systems of children and fetuses, resulting in variety of neurological consequences. They can also affect the cardiovascular system and especially the heart, either directly through their action on cardiomyocytes or indirectly through their effects on innervation, humoral responses or blood vessel alterations. For example, heart function modified by these heavy metals are heart rate, contraction, excitability, and rhythm. Some cardiac molecular targets have been identified and characterized. The direct mechanisms of damage of these heavy metals on heart function are discussed. We conclude that exposome to these heavy metals, should be considered as a major relevant risk factor for cardiac diseases.

Co-exposure to manganese and lead and pediatric neurocognition in East Liverpool, Ohio

Exposure to metal mixtures may lead to health impacts greater than the effects associated with singular exposures. Two common childhood environmental exposures, manganese (Mn) and lead (Pb), are associated with similar adverse neurodevelopmental effects; however, the effects surrounding concurrent exposure to both metals remain unclear. We study the impact of joint exposure to Mn and Pb on cognitive performance in school-aged children participating in the Communities Actively Researching Exposure Study (CARES) based in East Liverpool, Ohio. Blood Pb levels were measured for each child (geometric mean (GM) = 1.13 μg/dL, range 0.30 μg/dL - 6.64 μg/dL). Mn was measured in participant blood, hair, and toenails with GMs of 10.1 μg/L, 360 ng/g, 0.974 μg/g, respectively. Trained team members administered the Wechsler Intelligence Scale for Children-IV (WISC-IV) to assess intelligence quotient (IQ). The WISC-IV provides scores for Full Scale IQ, Perceptual Reasoning, Processing Speed, Working Memory, and Verbal Comprehension. Interactions between blood Pb and all Mn biomarkers were tested in linear models adjusted for child sex, household income, and serum cotinine. Separate regression models were run for each of the Mn biomarkers. The cohort was comprised of 106 children with a mean age of 8.4 years. Interactions between blood Pb and hair Mn were significant (p < 0.05) for four out of the five IQ domains. The effect of blood Pb on IQ was more pronounced at higher levels of hair and toenail Mn. No significant associations were observed when characterizing the main effect of Mn using blood. Uncovering the health impacts associated with exposure mixtures is critical to understanding the impact of real-life conditions. Our findings suggest that joint exposure to Mn and Pb may produce heightened neurocognitive impacts even at blood Pb levels below the CDC reference concentration of 5 μg/dL.

Resveratrol Mitigates Cerebral Ischemic Injury by Altering Levels of Trace Elements, Toxic Metal, Lipid Peroxidation, and Antioxidant Activity

Cerebral ischemia causes increased oxidative stress due to the overproduction of reactive oxygen species. The polyphenol compound resveratrol exerts neuroprotective effects through its antioxidant and anti-inflammatory abilities. The trace elements magnesium (Mg), zinc (Zn), and selenium (Se) also exert antioxidant properties. This study mainly investigates whether the neuroprotective effect of resveratrol during cerebral ischemia is related to its modulation of the concentrations of trace element and toxic metal lead (Pb). Experimental rats were administered resveratrol (20 mg/kg) once daily for 10 consecutive days. Cerebral ischemia was surgically induced via ligation of the right middle cerebral artery and right common carotid artery for 1 h. Brain cortex tissues were homogenized, and the supernatants were harvested for biochemical analysis. Experimental results showed that rats pretreated with resveratrol before cerebral ischemia had significantly higher trace element concentrations of Mg, Zn, and Se and higher antioxidant activity (superoxide dismutase and catalase) in the brain cortex as compared to untreated cerebral ischemia rats. Conversely, resveratrol pretreatment markedly attenuated lipid peroxidation and concentrations of the toxic metal Pb as compared to untreated cerebral ischemic rats. Altogether, the findings of this study highlight that the mechanism underlying the neuroprotective effect of resveratrol involves modulation of the brain levels of trace elements, toxic metal lead, lipid peroxidation, and antioxidant activity.

N,N'bis-(2-mercaptoethyl) isophthalamide (NBMI) exerts neuroprotection against lead-induced toxicity in U-87 MG cells

N,N'-bis(2-mercaptoethyl)isophthalamide (NBMI) is a novel lipophilic heavy metal chelator and thiol redox antioxidant. This study was designed to investigate the neuroprotective activity of NBMI in U-87 MG cells exposed to lead acetate (PbAc). Cells were pretreated with NBMI for 24 h prior to a 48 h exposure to PbAc. Cell death (55%, p < 0.0001) and reduction of intracellular GSH levels (0.70-fold, p < 0.005) induced by 250 µM Pb were successfully attenuated by NBMI pretreatment at concentrations as low as 10 µM. A similar pretreatment with the FDA-approved Pb chelator dimercaptosuccinic acid (DMSA) proved ineffective, indicating a superior PKPD profile for NBMI. Pretreatment with NBMI successfully counteracted Pb-induced neuroinflammation by reducing IL-1β (0.59-fold, p < 0.05) and GFAP expression levels. NBMI alone was also found to significantly increase ferroportin expression (1.97-fold, p < 0.05) thereby enhancing cellular ability to efflux heavy metals. While no response was observed on the apoptotic pathway, this study demonstrated for the first time that necrotic cell death induced by Pb in U-87 MG cells is successfully attenuated by NBMI. Collectively these data demonstrate NBMI to be a promising neuroprotective compound in the realm of Pb poisoning.

Pb2+ sensing by coumarin sulphonamide hybrids in aqueous medium

Metals play an important role in various metabolic activities in the human body, but above desired concentrations, a role reversal occurs that causes deadly outcomes viz., cancer. Metals cannot be cracked down and are non-biodegradable. It is the bioaccumulation of toxic metals inside the biomatrices, that further intensifies the research on different means of metal detoxification from different matrices. Among heavy toxic metals lead is a brutal carcinogen that requires pitiless sensors for its capturing. The use of heterocycles for metal sensing in supramolecular chemistry is preferred due to the strong chelation they offer to toxic metals. The C1-C3 probes were synthesized and studied for their Pb²⁺ binding ability. All the probes were prepared by treating bromoacetyl coumarin with camphor sulphonamide, 5-dimethylamino-1-naphthalene sulphonamide, and methyl-2-amino-sulphonyl benzoate at room temperature. The probes show selective binding with Pb²⁺ ions in aqueous acetonitrile among different tested metal ions viz., Cu²⁺ , Zn²⁺ , Ni²⁺ , Mn^2+, and Pb²⁺ ions as shown in ultraviolet (UV)-visible, nuclear magnetic resonance (NMR), and high-performance liquid chromatography (HPLC) studies. These sulphur-containing probes bind very well with Pb²⁺ ions by offering selectivity in binding positions that capture lead ions at their minimum possible concentration.

MOLECULAR MECHANISMS OF LEAD NEUROTOXICITY

Lead (Pb2+) is a non-essential metal with numerous industrial applications that have led to ts ubiquity in the environment. Thus, not only occupational-exposed individuals' health is compromised, but also that of the general population and in particular children. Notably, although the central nervous system is particularly susceptible to Pb2+, other systems are affected as well. The present study focuses on molecular mechanisms that underlie the effects that arise from the presence of Pb2+ in situ in the brain, and the possible toxic effects that follows. As the brain barriers represent the first target of systemic Pb2+, mechanisms of Pb2+ entry into the brain are discussed, followed by a detailed discussion on neurotoxic mechanisms, with special emphasis on theories of ion mimicry, mitochondrial dysfunction, redox imbalance, and neuroinflammation. Most importantly, the confluence and crosstalk between these events is combined into a cogent mechanism of toxicity, by intertwining recent and old evidences from humans, in vitro cell culture and experimental animals. Finally, pharmacological interventions, including chelators, antioxidants substances, anti-inflammatory drugs, or their combination are reviewed as integrated approaches to ameliorate Pb2+ harmful effects in both developing or adult organisms.

Inactivation of GAP-43 due to the depletion of cellular calcium by the Pb and amyloid peptide induced toxicity: An in vitro approach

Environmental pollutant, Lead (Pb) is known to induce neurotoxicity in human. The central nervous system is the most vulnerable to the minute levels of Pb induced toxicity. Pb has been linked to Alzheimer's disease (AD) as a probable risk factor, as it shows epigenetic and developmental link associated with Alzheimer's disease-like pathology. Beta amyloid peptides were considered as the crucial factors in the beta amyloid plaque formation in Alzheimer's disease brain. In this context, we investigated the molecular mechanism involved in the development of Pb induced Alzheimer's disease in in vitro. Previous data from our studies have reported that Pb in the presence of beta Amyloid peptide (1-40) and (25-35) induces more apoptosis than individual exposures. Here, to further evaluate the molecular mechanism underlying Pb induced Alzheimer's disease; we focussed on the involvement of calcium signalling in inducing cell death. Our experimental observations suggesting that Pb in the presence of beta amyloid peptide alters intracellular calcium levels, which leads to the increased beta-secretase activity, which further promotes the generation of beta amyloid peptides. It also showed depression in the levels of GAP-43 expression, inhibition of PKC activity and altering synaptic activity further leads to cell death.

The effect of lead during the Flint water crisis on mouse embryonic stem cells self-renewal and differentiation markers

During the Flint water crisis, the residents of Flint, Michigan experienced a significant increase in blood lead levels. For some this resulted in an increase as high as 40 μg/dL from 5 μg/dL, which is considered to be safe by the Center for Disease Control and Prevention. Since the extent of the effect of the lead exposure in early embryonic development is not greatly investigated, the aim of this study is to explore the effect of lead exposure at concentrations present in Flint, MI during the Flint water crisis in the embryonic development. The expression of pluripotency and self-renewal markers (Oct4, Sox2, Nanog and Zfp-42) coupled with morphological and alkaline phosphatase assays revealed that mouse embryonic stem cells (mESC) pluripotency and self-renewal capabilities are perturbed following exposure in a lead acetate concentration dependent manner. Moreover, mouse embryoid bodies (mEB), which provide ideal models for testing toxicity in vitro, revealed that lead acetate exposure induces fewer but larger mEBs, whereas gene expression analysis of lineage specific transcription factors showed an increased mRNA level of endodermal (Gata 4, Gata 6, Sox 7) and mesodermal markers (Eomes, Hand 1, Slug 1) while the mRNA level of ectodermal markers (Otx 2, Noggin, Sox 1) decreased. Taken all together, these results indicate that lead acetate disturbs the pluripotency of mESC and differentiation potential of mEBs by inhibiting differentiation towards ectodermal lineages and inducing it towards endodermal and mesodermal lineages.

The attention set-shifting test is sensitive for revealing sex-based impairments in executive functions following developmental lead exposure in rats

The literature on lead (Pb) exposure has focused in large part on hippocampal-based learning and memory deficits, although frontoexecutive dysfunctions are known to exist in Pb-exposed humans. This study examined the effects of perinatal (PERI) and early postnatal (EPN) developmental low-level Pb-exposures in rats on frontoexecutive functions, using the Attention Set-Shift Test (ASST). Control males and females performed the ASST similarly. Male EPN rats had difficulty with simple discrimination (SD) of odors and failed to complete the compound discrimination (CD) stage of the ASST. All other Pb-exposed rats completed the training and testing. Male PERI rats performed worse on the SD, intradimensional (ID), and intradimensional-reversal (ID-Rev) ASST stages when compared to male Control rats. Female EPN rats performed similar to Controls on the ID-Rev rats, whereas PERI rats performed better the trials-to-criterion on the ID-Rev than EPN and Control rats. Pb-exposed female rats had significant difficulty performing the ED/ED-Rev stages, with the number of trials-to-criterion double that required by Pb-exposed and Control male rats and Control female rats. Together, the ASST results showed that developmental Pb-exposure induces frontoexecutive dysfunction that persists into adulthood, with different sex-based vulnerabilities dependent upon the time-period of neurotoxicant exposure.

Neurotoxicity of low-level lead exposure: History, mechanisms of action, and behavioral effects in humans and preclinical models

Lead is a neurotoxin that produces long-term, perhaps irreversible, effects on health and well-being. This article summarizes clinical and preclinical studies that have employed a variety of research techniques to examine the neurotoxic effects of low levels of lead exposure. A historical perspective is presented, followed by an overview of studies that examined behavioral and cognitive outcomes. In addition, a short summary of potential mechanisms of action is provided with a focus on calcium-dependent processes. The current level of concern, or reference level, set by the CDC is 5 μg/dL of lead in blood and a revision to 3.5 μg/dL has been suggested. However, levels of lead below 3 μg/dL have been shown to produce diminished cognitive function and maladaptive behavior in humans and animal models. Because much of the research has focused on higher concentrations of lead, work on low concentrations is needed to better understand the neurobehavioral effects and mechanisms of action of this neurotoxic metal.

Trace Metals in the Freshwater Fish Cyprinus carpio: Effect to Serum Biochemistry and Oxidative Status Markers

Interactions between trace metals, serum biochemical parameters, and oxidative status markers were observed. Freshwater fish Cyprinuscarpio blood samples (n = 38) were collected at the beginning of May (n = 19) and at the end of July (n = 19) of 2015. The concentrations of metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr, and Zn) were analyzed in blood serum samples of fishes by inductively coupled plasma optical emission spectrometry (ICP-OES), and Hg was determined by cold-vapor atomic absorption spectroscopy (CV-AAS). The general scheme of descending concentrations of metals in blood serum samples was as follows: Zn > Fe > Cu > Sr > Cr > Ni > Mn > Pb > Se > As > Cd > Hg. Zn was the most accumulated element (4.42-119.64 mg/L) in both seasons. Overall, the trace element content was higher in spring season, except Hg, Ni, Se, and Sr. The seasonal effect was confirmed for Mn, Zn, Mg, Glu, AST, and Chol levels and for most oxidative status markers. The gender effect was confirmed for Sr, GPx, PC, Chol, and CK concentrations. Trace metals (especially Cd, Cr, Cu, Fe, Hg, Mn, Ni, Sr, Zn, As) significantly affected some blood serum chemistry parameters. The correlation analysis between oxidative status markers (ROS, TAC, MDA, SOD, GSH, UA, BHB, and Alb) and trace metal (Cd, Cu, Ni, Sr, Hg, Pb, Fe, Mn) content confirmed statistically significant interactions in both seasons. Obtained results indicate specific actions of trace metals.

High Serum Lead Levels Increase the Incidence of Cognitive Impairment of Public Fueling Station Operators

BACKGROUND:

Air pollution due to lead contained in motor vehicle fuel is inhaled for a long period causing cognitive impairment. Cognitive disorders in general fuel station operators are found in developing countries as a negative impact of environmental pollution.

AIM:

This study aims to find out that high levels of lead in the blood increase the risk of cognitive impairment in operators of Public Fuel Filling Stations.

METHODS:

This was a case-control study design to determine high lead levels in the blood increasing the risk of cognitive impairment in operators of General Fuel Filling Stations. There were 76 study subjects consisting of 38 case groups and 38 control groups.

RESULTS:

Obtained lead levels of all research subjects in normal criteria (1.1-5.58 µg/dL). We used MoCA-Ina (a validated Indonesian version of MoCA questionnaire) to evaluate the cognitive function. High lead levels in the blood in the case group were 28 subjects (66.7%) and 14 subjects (33.7%) in the control group. Factors that significantly affected the occurrence of cognitive disorders are work periods of more than 3 years, which are 4 times higher risk of experiencing cognitive impairment (p = 0.021).

CONCLUSION:

High lead levels in the blood have a 6 times greater risk of cognitive impairment than subjects with not high blood lead levels and work periods of more than 3 years have a risk of 6 times greater cognitive impairment.

Inhibitory effect of Athelia rolfsii exopolysaccharides on organ damage in lead-exposed Kunming strain mice

Herein, Athelia rolfsii exopolysaccharides (AEPS) were used to alleviate organ damage in lead-exposed mice. Analysis of the body weight growth rate and visceral index revealed that AEPS maintained the normal body weight growth rates in lead-exposed mice. Biochemical indicators (T-SOD, CAT, MDA) in serum revealed that AEPS increased the activity of T-SOD in the serum of lead-exposed mice. The lead concentrations in the brain, liver, kidneys, testis and faeces were measured by flame atomic absorption. The percent reductions in lead accumulation in these organs were 76.65% (brain), 60.42% (liver), 78.43% (kidneys) and 56.47% (testis). The data suggest that a significant portion of the lead was expelled in the faeces. The results proved that AEPS prevented lead accumulation in the organs of lead-exposed mice. A histological evaluation of the brain, liver, kidneys and testis also revealed that AEPS significantly alleviated liver and kidney damage caused by lead poisoning and protected neurons and sperm cells. We hypothesize that the ingested AEPS chelated the lead in the digestive system of the mice, leading to excretion through the faeces. Thus, AEPS represent a promising method of detoxification following lead poisoning.

Modulation of caspase-3 gene expression and protective effects of garlic and spirulina against CNS neurotoxicity induced by lead exposure in male rats

Lead (Pb) is a ubiquitous environmental and industrial pollutant with worldwide health problems. The present study was designed to investigate the neurotoxic effects of Pb in albino rats and to evaluate the ameliorative role of garlic as well as Spirulina maxima against such toxic effects. Forty adult male rats were used in this investigation (10 rats/group). Group I: served as control, Group II: rats received lead acetate (100 mg/kg), Group III: rats received both lead acetate (100 mg/kg) and garlic (600 mg/kg) and Group IV: rats received both lead acetate (100 mg/kg) and spirulina (500 mg/kg) daily by oral gavage for one month. Exposure to Pb acetate adversely affected the measured acetyl cholinesterase enzyme activity, oxidative stress and lipid peroxidation parameters as well as caspase-3 gene expression in brain tissue (cerebrum and cerebellum). Light and electron microscopical examination of the cerebrum and cerebellum showed various lesions after exposure to Pb which were confirmed by immunohistochemistry. On the other hand, administration of garlic and spirulina concomitantly with lead acetate ameliorated most of the undesirable effects. It could be concluded that, the adverse effects induced by lead acetate, were markedly ameliorated by co-treatment with S. maxima more than garlic.

Carnosine and Histidine Supplementation Blunt Lead-Induced Reproductive Toxicity through Antioxidative and Mitochondria-Dependent Mechanisms

Lead (Pb)-induced reproductive toxicity is a well-characterized adverse effect associated with this heavy metal. It has been found that Pb exposure is associated with altered spermatogenesis, increased testicular degeneration, and pathological sperm alterations. On the other hand, it has been reported that Pb-induced reproductive toxicity is associated with increased reactive oxygen species (ROS) formation and diminished antioxidant capacity in the reproductive system. Hence, administration of antioxidants as protective agents might be of value against Pb-induced reproductive toxicity. This study was designed to investigate whether carnosine (CAR) and histidine (HIS) supplementation would mitigate the Pb-induced reproductive toxicity in male rats. Animals received Pb (20 mg/kg/day, oral, 14 consecutive days) alone or in combination with CAR (250 and 500 mg/kg/day, oral, 14 consecutive days) or HIS (250 and 500 mg/kg/day, oral, 14 consecutive days). Pb toxicity was evident in the reproductive system by a significant increase in tissue markers of oxidative stress along with severe histopathological changes, seminal tubule damage, tubular desquamation, low spermatogenesis index, poor sperm parameters, and impaired sperm mitochondrial function. It was found that CAR and HIS supplementation blunted the Pb-induced oxidative stress and mitochondrial dysfunction in the rat reproductive system. Thereby, antioxidative and mitochondria-protective properties serve as primary mechanisms for CAR and HIS against Pb-induced reproductive toxicity.

Effects of combined arsenic and lead exposure on the brain monoaminergic system and behavioral functions in rats: Reversal effect of MiADMSA

In this study, we evaluated the therapeutic efficacy of monoisoamyldimercaptosuccinic acid (MiADMSA) against individual and combined effects of arsenic (As) and lead (Pb) on the monoaminergic system and behavioral functions in rats. Pregnant rats were exposed to sodium metaarsenite (50 ppm) and lead acetate (0.2%) individually and in combination (As = 25 ppm + Pb = 0.1%) via drinking water from gestation day (GD) 6 to postnatal day (PND) 21. MiADMSA (50 mg/kg body weight) was given orally through gavage for 3 consecutive days to pups from PND 18 to PND 20. The results showed increases in synaptosomal epinephrine, dopamine, and norepinephrine levels with individual metal exposures and decreases with combined exposure to As and Pb in the cortex, cerebellum, and hippocampus in PND 21, PND 28, and 3 months age-group rats. We found decreased activity of mitochondrial monoamine oxidase in the selected brain regions following individual and combined exposures to Pb and As. In addition, rats treated with Pb and As alone or in combination showed significant deficits in open-field behavior, grip strength, locomotor activity, and exploratory behavior at PND 28 and 3 months of age. However, MiADMSA administration showed reversal effects against the As- and/or Pb-induced impairments in the monoaminergic system as well as in behavioral functions of rats. Our data demonstrated that the mixture of Pb and As induced synergistic toxicity to developing brain leading to impairments in neurobehavioral functions and also suggest therapeutic efficacy of MiADMSA against Pb- and/or As-induced developmental neurotoxicity.

Latent consequences of early-life lead (Pb) exposure and the future: Addressing the Pb crisis

BACKGROUND

The lead (Pb) exposure crisis in Flint, Michigan has passed from well-publicized event to a footnote, while its biological and social impact will linger for lifetimes. Interest in the "water crisis" has dropped to pre-event levels, which is neither appropriate nor safe. Flint's exposure was severe, but it was not unique. Problematic Pb levels have also been found in schools and daycares in 42 states in the USA. The enormity of Pb exposure via municipal water systems requires multiple responses. Herein, we focus on addressing a possible answer to long-term sequelae of Pb exposure. We propose "4R's" (remediation, renovation, reallocation, and research) against the Pb crisis that goes beyond a short-term fix. Remediation for affected individuals must continue to provide clean water and deal with both short and long-term effects of Pb exposure. Renovation of current water delivery systems, at both system-wide and individual site levels, is necessary. Reallocation of resources is needed to ensure these two responses occur and to get communities ready for potential sequelae of Pb exposure. Finally, properly focused research can track exposed individuals and illuminate latent (presumably epigenetic) results of Pb exposure and inform further resource reallocation.

CONCLUSION

Motivation to act by not only the general public but also by scientific and medical leaders must be maintained beyond initial news cycle spikes and an annual follow-up story. Environmental impact of Pb contamination of drinking water goes beyond one exposure incident in an impoverished and forgotten Michigan city. Population effects must be addressed long-term and nationwide.

Lead: Tiny but Mighty Poison

The documentation of lead toxicity (plumbism) dates back to the times when man learnt its various applications. This versatile heavy metal is non-degradable and its ability to get accumulated in the body that goes undiagnosed, makes it a serious environmental health hazard. Lead is now known to affect almost every organ/tissue of the human body. With irreversible effects on neurobiological development of young children and foetus, its toxicity has lasting implications on the human life. Outlining the symptoms, diagnosis and treatment therapy for lead poisoning, the present review elaborates the pathophysiological effects of lead on various organs. This will be of immense help to the health professionals so as to inculcate a better understanding of the lead poisoning which otherwise is asymptomatic. With chelation therapy being the classic path of treatment, new strategies are being explored as additive/adjunct therapy. It is now understood that lead toxicity is completely preventable. In this regard significant efforts are in place in the developed countries whereas much needs to be done in the developing countries. Spreading the awareness amongst the masses by educating them and reducing the usage of lead following stricter industry norms appears to be the only roadmap to prevent lead poisoning. Efforts being undertaken by the Government of India and other organisations are also mentioned.

Exploiting the unique phenotypes of the earthworm Eudrilus eugeniae to evaluate the toxicity of chemical substances

Both the evaluation and the determination of toxicity of chemical substances present in the environment have implications in human health. In this present study, the natural phenomenon named autotomy, a self-defense mechanism employed by several animals against the toxic chemical contaminants, was considered to assess the toxicity of different chemical substances. We investigated the effects of glucose, sodium chloride, kanamycin, mercuric chloride, arsenic trioxide, and lead oxide on the phenotypes of earthworm Eudrilus eugeniae. Depending on the concentration of different chemicals, worms exhibit unique phenotypes. These phenotypes can be used to identify the toxicity as well as the toxic concentration of the chemicals. Upon exposure to toxic chemicals, worms use different mechanical forces at the site of cleavage furrow to detach its segments. During the detachment, there is no apparent blood loss at both the ends of the worm. Our results show that the mercuric chloride is toxic at the concentration above 5 μg when compared to other chemicals. Based on our findings, the toxic effects of a chemical and the toxic concentration of a chemical can be evaluated in both cost and time-efficient manner; in addition, these chemicals can be classified into the following categories: (1) mercuric chloride is extreme-toxic, (2) arsenic trioxide and lead oxide is toxic, (3) kanamycin and sodium chloride is low-toxic, and (4) glucose is non-toxic.

Genetically encoded fluorescent sensors for measuring transition and heavy metals in biological systems

Great progress has been made in expanding the repertoire of genetically encoded fluorescent sensors for monitoring intracellular transition metals (TMs). This powerful toolkit permits dynamic and non-invasive detection of TMs with high spatial-temporal resolution, which enables us to better understand the roles of TM homeostasis in both physiological and pathological settings. Here we summarize the recent development of genetically encoded fluorescent sensors for intracellular detection of TMs such as zinc and copper, as well as heavy metals including lead, cadmium, mercury, and arsenic.

Lead poisoning: acute exposure of the heart to lead ions promotes changes in cardiac function and Cav1.2 ion channels

Lead ions (Pb²⁺) possess characteristics similar to Ca²⁺. Because of this and its redox capabilities, lead causes different toxic effects. The neurotoxic effects have been well documented; however, the toxic effects on cardiac tissues remain allusive. We utilized isolated guinea pig hearts and measured the effects of Pb²⁺ on their contractility and excitability. Acute exposure to extracellular Pb²⁺ had a negative inotropic effect and increased diastolic tension. The speed of contraction and relaxation were affected, though the effects were more dramatic on the speed of contraction. Excitability was also altered. Heart beat frequency increased and later diminished after lead ion exposure. Pro-arrhytmic events, such as early after-depolarization and a reduction of the action potential plateau, were also observed. In isolated cardiomyocytes and tsA 201 cells, extracellular lead blocked currents through Cav1.2 channels, diminished their activation, and enhanced their fast inactivation, negatively affecting their gating currents. Thus, Pb²⁺ was cardiotoxic and reduced cardiac contractility, making the heart prone to arrhythmias. This was due, in part, to Pb²⁺ effects on the Cav1.2 channels; however, other channels, transporters or pathways may also be involved. Acute cardiotoxic effects were observed at Pb²⁺ concentrations achievable during acute lead poisoning. The results suggest how Cav1.2 gating can be affected by divalent cations, such as Pb², and also suggest a more thorough evaluation of heart function in individuals affected by lead poisoning.

Genome-wide gene by lead exposure interaction analysis identifies UNC5D as a candidate gene for neurodevelopment

BACKGROUND

Neurodevelopment is a complex process involving both genetic and environmental factors. Prenatal exposure to lead (Pb) has been associated with lower performance on neurodevelopmental tests. Adverse neurodevelopmental outcomes are more frequent and/or more severe when toxic exposures interact with genetic susceptibility.

METHODS

To explore possible loci associated with increased susceptibility to prenatal Pb exposure, we performed a genome-wide gene-environment interaction study (GWIS) in young children from Mexico (n = 390) and Bangladesh (n = 497). Prenatal Pb exposure was estimated by cord blood Pb concentration. Neurodevelopment was assessed using the Bayley Scales of Infant Development.

RESULTS

We identified a locus on chromosome 8, containing UNC5D, and demonstrated evidence of its genome-wide significance with mental composite scores (rs9642758, p _meta = 4.35 × 10^-6). Within this locus, the joint effects of two independent single nucleotide polymorphisms (SNPs, rs9642758 and rs10503970) had a p-value of 4.38 × 10^-9 for mental composite scores. Correlating GWIS results with in vitro transcriptomic profiles identified one common gene, SLC1A5, which is involved in synaptic function, neuronal development, and excitotoxicity. Further analysis revealed interconnected interactions that formed a large network of 52 genes enriched with oxidative stress genes and neurodevelopmental genes.

CONCLUSIONS

Our findings suggest that certain genetic polymorphisms within/near genes relevant to neurodevelopment might modify the toxic effects of Pb exposure via oxidative stress.

The Joint Effect of Prenatal Exposure to Metal Mixtures on Neurodevelopmental Outcomes at 20-40 Months of Age: Evidence from Rural Bangladesh

BACKGROUND

Exposure to chemical mixtures is recognized as the real-life scenario in all populations, needing new statistical methods that can assess their complex effects.

OBJECTIVES

We aimed to assess the joint effect of in utero exposure to arsenic, manganese, and lead on children's neurodevelopment.

METHODS

We employed a novel statistical approach, Bayesian kernel machine regression (BKMR), to study the joint effect of coexposure to arsenic, manganese, and lead on neurodevelopment using an adapted Bayley Scale of Infant and Toddler Development™. Third Edition, in 825 mother-child pairs recruited into a prospective birth cohort from two clinics in the Pabna and Sirajdikhan districts of Bangladesh. Metals were measured in cord blood using inductively coupled plasma-mass spectrometry.

RESULTS

Analyses were stratified by clinic due to differences in exposure profiles. In the Pabna district, which displayed high manganese levels [interquartile range (IQR): 4.8, 18 μg/dl], we found a statistically significant negative effect of the mixture of arsenic, lead, and manganese on cognitive score when cord blood metals concentrations were all above the 60th percentile (As≥0.7 μg/dl, Mn≥6.6 μg/dl, Pb≥4.2 μg/dl) compared to the median (As=0.5 μg/dl, Mn=5.8 μg/dl, Pb=3.1 μg/dl). Evidence of a nonlinear effect of manganese was found. A change in log manganese from the 25th to the 75th percentile when arsenic and manganese were at the median was associated with a decrease in cognitive score of −0.3 (−0.5, −0.1) standard deviations. Our study suggests that arsenic might be a potentiator of manganese toxicity.

CONCLUSIONS

Employing a novel statistical method for the study of the health effects of chemical mixtures, we found evidence of neurotoxicity of the mixture, as well as potential synergism between arsenic and manganese. https://doi.org/10.1289/EHP614.

Low-Level Environmental Lead Exposure and Dysglycemia in Adult Individuals: Results from the Canadian Health and Measure Survey 2007-2011

We aimed to evaluate the association of exposure to lead with glycated hemoglobin (HbA1c), fasting glucose levels (FGLs), and the likelihood for dysglycemia. We accessed data from Canada Health and Measures Survey. General linear models were used to estimate the association between blood lead concentrations (BPb) and both HbA1c and FGLs, while controlling for confounders. Multivariate logistic regression was used for assessing the relation between BPb and the likelihood for dysglycemia. FGLs in participants with moderate BPb (2.5-5.0 μg/dL) were 1.03 (95 % CI 1.00-1.06) times higher compared with participants with BPb < 2.5 μg/dL. Equivalent figures for those with BPb ≥ 5.0 μg/dL were 1.10 (95 % CI 1.01-1.20) times, relative to the lowest stratum. This association was attenuated using HbA1c to define dysglycemia. Lead exposure was associated with the likelihood for neither FGLs ≥ 1.10 g/L nor HbA1c ≥ 5.7 %. The association between lead exposure and dysglycemia, if any, is likely to be very modest, at least at the population level.

Maternal stress modifies the effect of exposure to lead during pregnancy and 24-month old children's neurodevelopment

BACKGROUND

Lead and psychosocial stress disrupt similar but not completely overlapping mechanisms. Exposure during the prenatal period to each of these insults singularly has been found to alter normal neurodevelopment; however, longitudinal associations with stress modifying the effect of lead have not been sufficiently analyzed in epidemiologic studies.

OBJECTIVE

To evaluate prenatal stress as an effect modifier of gestational lead neurotoxicity.

METHODS

We used a structural equations modeling approach with a trivariate response to evaluate cognitive, language and motor scores of the Bayley Scales of Infant Development-III in 24month-old children (n=360). Maternal blood lead levels were measured at the 2nd and 3rd trimester and psychosocial stress during pregnancy was assessed using a negative life events (NLE) scale derived from the CRYSIS questionnaire.

RESULTS

3rd trimester lead (mean 3.9±3.0 SDμg/dL) and stress (median=3 NLE) were negatively associated with Bayley III scores. Using the model's results we generated profiles for 0, 2, 4 and 6 NLE across lead levels (up to 10μg/dL) and observed a dose-response for the developmental scores when lead levels were below 2μg/dL. Each NLE curve had a different shape across increasing lead levels. Higher stress (NLE=6) resulted in lower cognitive scores for both sexes, in lower language scores in girls but not boys. In the absence of stress we saw a negative association with lead for all scores, however for language and motor scores, higher stress seemed to mask this association.

CONCLUSIONS

Our work examined and confirmed prenatal stress exposure as a modifier of the well-known neurotoxic effects of prenatal lead. It adds to the existing evidence pointing at the importance of studying the co-exposure of chemical and non-chemical exposures, specifically of considering the emotional environment of children at early developmental stages of life.

Effect of Lead (Pb) on Inflammatory Processes in the Brain

That the nervous system is the main target of lead (Pb) has long been considered an established fact until recent evidence has linked the Pb effect on the immune system to the toxic effects of Pb on the nervous system. In this paper, we present recent literature reports on the effect of Pb on the inflammatory processes in the brain, particularly the expression of selected cytokines in the brain (interleukin 6, TGF-β1, interleukin 16, interleukin 18, and interleukin 10); expression and activity of enzymes participating in the inflammatory processes, such as cyclooxygenase 2, caspase 1, nitrogen oxide synthase (NOS 2) and proteases (carboxypeptidases, metalloproteinases and chymotrypsin); and the expression of purine receptors P2X4 and P2X7. A significant role in the development of inflammatory processes in the brain is also played by microglia (residual macrophages in the brain and the spinal cord), which act as the first line of defense in the central nervous system, and astrocytes—Whose most important function is to maintain homeostasis for the proper functioning of neurons. In this paper, we also present evidence that exposure to Pb may result in micro and astrogliosis by triggering TLR4-MyD88-NF-κB signaling cascade and the production of pro-inflammatory cytokines.

Chemical Approaches to Addressing the Instability and Toxicity of Lead-Halide Perovskite Absorbers

The impressive rise in efficiencies of solar cells employing the three-dimensional (3D) lead-iodide perovskite absorbers APbI₃ (A = monovalent cation) has generated intense excitement. Although these perovskites have remarkable properties as solar-cell absorbers, their potential commercialization now requires a greater focus on the materials' inherent shortcomings and environmental impact. This creates a challenge and an opportunity for synthetic chemists to address these issues through the design of new materials. Synthetic chemistry offers powerful tools for manipulating the magnificent flexibility of the perovskite lattice to expand the number of functional analogues to APbI₃. To highlight improvements that should be targeted in new materials, here we discuss the intrinsic instability and toxicity of 3D lead-halide perovskites. We consider possible sources of these instabilities and propose methods to overcome them through synthetic design. We also discuss new materials developed for realizing the exceptional photophysical properties of lead-halide perovskites in more environmentally benign materials. In this Forum Article, we provide a brief overview of the field with a focus on our group's contributions to identifying and addressing problems inherent to 3D lead-halide perovskites.

Serum IgE elevation correlates with blood lead levels in battery manufacturing workers

Lead (Pb), an occupational and environmental toxicant, is known to induce immunomodulatory effects resulting in lowered resistance to infectious micro-organisms and altered levels of immunoglobulins in humans. Preferential activation of type-2 helper T cells and inhibition of type-1 T-cell activation is considered a cellular mechanism for the Pb-induced immune alteration, which has not been investigated well in humans. Lead's influence on in vivo balance between type-1 and type-2 activities was assessed among workers exposed to Pb through battery manufacturing in Korea. Serum IgE levels were significantly higher in the workers with a blood Pb level (PbB) of ≤30 μg/dL than in the workers with a PbB of <30 μg/dL. Furthermore, the serum IgE concentrations significantly correlated with PbB although no significant relationship between PbB and serum interleukin-4 or interferon gamma levels was observed. The present study indicates that elevation of IgE levels may be an immunologic index for Pb-induced in vivo toxicities, potentially involved with progression of various allergic diseases in humans.

The detrimental effects of lead on human and animal health

Lead, a chemical element in the carbon group with symbol Pb (from Latin: Plumbum, meaning “the liquid silver”) and has an atomic number 82 in the periodic table. It was the first element that was characterized by its kind of toxicity. In animal systems, lead (Pb) has been incriminated in a wide spectrum of toxic effects and it is considered one of the persistent ubiquitous heavy metals. Being exposed to this metal could lead to the change of testicular functions in human beings as well as in the wildlife. The lead poising is a real threat to the public health, especially in the developing countries. Accordingly, great efforts on the part of the occupational and public health have been taken to curb the dangers of this metal. Hematopoietic, renal, reproductive, and central nervous system are among the parts of the human body and systems that are vulnerable toward the dangers following exposure to high level of Pb. In this review, we discussed the massive harmful impact that leads acetate toxicity has on the animals and the worrying fact that this harmful toxicant can be found quite easily in the environment and abundance. Highlighting its (Pb) effects on various organs in the biological systems, its economic, as well as scientific importance, with the view to educate the public/professionals who work in this area. In this study, we focus on the current studies and research related to lead toxicity in animals and also to a certain extent toward human as well.

Lead Toxicity, Antioxidant Defense and Environment

Environmental and occupational exposure to a large number of chemicals occurs at various stages throughout human life. Many of these are devoid of toxicity, but some could pose a significant health risk, i.e. the exposure to environmental xenobiotic metals as lead, mercury (Sinicropi et al. 2010a; Carocci et al. 2014), cadmium, etc. In particular, lead has long been a widespread public concern (Basha and Reddy 2010). Lead is one of the earliest heavy metals discovered by men. Due to its unique properties, as low melting point, softness, malleability, ductility, and resistance to corrosion, men have used lead for the last 5000 years in a wide range of applications.

DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO₃)₂ exposure and its associated adverse health effects.