Co-exposure to Fe, Zn, and Cu induced neuronal ferroptosis with associated lipid metabolism disorder via the ERK/cPLA2/AA pathway.

Excessive amounts of iron (Fe), zinc (Zn), and copper (Cu) can be toxic to neuronal cells, even though these are essential trace elements for animals and humans. However, the precise mechanisms underlying the neurotoxicity of exposure to mixtures of Fe, Zn, and Cu are still mostly unclear. The research aimed to investigate the influence of co-exposure to iron, zinc and copper and the related mechanisms in HT22 murine hippocampal neuronal cells. Intracellular metal content, markers of oxidative damage, and biomarkers of ferroptosis were respectively detected. Afterward, metabolomic analyses were performed to obtain a comprehensive understanding of the metal mixtures on metabolism, and the functions of key enzymes on metabolic pathways were validated. The results showed that metal co-exposure resulted in cellular iron overload and increased lipid peroxidation, accompanied by significant pathological damage and mitochondrial abnormalities in HT22 cells. Meanwhile, it was found that GSH depletion, decreased GPX4, and increased expression of the lipid metabolism gene ACSL4 play important roles in ferroptosis induced by metal mixture. Further, metabolomic analysis revealed metal co-exposure induced significant alterations in metabolite levels, especially in the glycerophospholipid metabolism pathway and the arachidonic acid metabolism pathway. The levels of cPLA2 and its metabolite, arachidonic acid, were significantly increased after metal co-exposure. Then, inhibition of cPLA2 decreased the level of arachidonic acid and attenuated ferroptosis in neuronal cells. Collectively, our findings unveiled ferroptosis induced by metal co-exposure associated with crucial molecular changes in neuronal cells, providing a novel perspective on the comprehensive toxicity risk assessment of metal mixtures.

Mechanistic investigation of the differential synergistic neurotoxicity between pesticide metam sodium and copper or zinc.

Epidemiological studies suggest neurological disorders have been associated with the co-exposure to certain pesticides and transition metals. The present study aims to investigate whether co-exposure to the widely-used pesticide metam sodium and copper (Cu2+) or zinc ion (Zn2+) is able to cause synergistic neurotoxicity in neural PC12 cells and its possible mechanism(s). We found that both metam/Cu2+ and metam/Zn2+ synergistically induced apoptosis, intracellular Cu2+/Zn2+ uptake, reactive oxygen species (ROS) accumulation, double-strand DNA breakage, mitochondrial membrane potential decrease, and nerve function disorder. In addition, metam/Cu2+ was shown to release cytochrome c and apoptosis-inducing factor (AIF) from mitochondria to cytoplasm and nucleus, respectively, and activate the caspase 9, 8, 3, 7. However, metam/Zn2+ induced caspase 7 activation and AIF translocation and mildly activated cytochrome c/caspase 9/caspase 3 pathway. Furthermore, metam/Cu2+ activated caspase 3/7 by the p38 pathway, whereas metam/Zn2+ did so via both the p38 and JNK pathways. These results demonstrated that metam/Cu2+ or metam/Zn2+ co-exposure cause synergistic neurotoxicity via different mechanisms, indicating a potential risk to human health when they environmentally co-exist.

Identification of the Differentially Expressed Genes Involved in the Synergistic Neurotoxicity of an HIV Protease Inhibitor and Methamphetamine.

BACKGROUND: The abuse of psychostimulants such as methamphetamine (METH) is common in human immunodeficiency virus (HIV)-infected individuals. Acquired immunodeficiency syndrome (AIDS) patients taking METH and antiretroviral drugs could suffer severe neurologic damage and cognitive impairment. OBJECTIVE: To reveal the underlying neuropathologic mechanisms of an HIV protease inhibitor (PI) combined with METH, growth-inhibition tests of dopaminergic cells and RNA sequencing were performed. METHODS: A combination of METH and PI caused more growth inhibition of dopaminergic cells than METH alone or a PI alone. Furthermore, we identified differentially expressed gene (DEG) patterns in the METH vs. untreated cells (1161 genes), PI vs. untreated cells (16 genes), METH-PI vs. PI (3959 genes), and METH-PI vs. METH groups (14 genes). RESULTS: The DEGs in the METH-PI co-treatment group were verified in the brains of a mouse model using quantitative polymerase chain reaction and were involved mostly in the regulatory functions of cell proliferation and inflammation. CONCLUSION: Such identification of key regulatory genes could facilitate the study of their neuroprotective potential in the users of METH and PIs.

Mechanisms of synergistic neurotoxicity induced by two high risk pesticide residues - Chlorpyrifos and Carbofuran via oxidative stress.

Multi-component pesticide residues, especially pesticide residues with synergistic toxicity, are a serious threat to food safety. With risk assessment, we found that Chlorpyrifos (CPF) and Carbofuran (CBF) are 2 pesticide residues with highest risk for Actinidia chinensis planch. The results showed CPF and CBF have a synergistic neurotoxicity on neural cell SK-N-SH. The toxicity was partly depending on oxidative stress (OS) and had effects on cell apoptosis and cell cycle arrest. Furthermore, the toxicity remained on long-term low-dose condition.

Lead, cadmium, arsenic, and mercury combined exposure disrupted synaptic homeostasis through activating the Snk-SPAR pathway.

Lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) are among the leading toxic agents detected in the environment, and they have also been detected simultaneously in blood, serum, and urine samples of the general population. Meanwhile early neurologic effects and multiple interactions of Pb, Cd, As, and Hg had been found in children from environmentally polluted area. However, the current studies of these four metals were mostly limited to the interactions between any two metals, whereas the interaction characteristics between any three and four metals were rarely studied. In our study, we firstly explored the characteristics of the neurotoxic interactions among these four elements in nerve cells with factorial designs. The results showed that Pb+Cd+As+Hg co-exposure had a synergistic neurotoxic effect that was more severe than that induced by any two or three metals, when their individual metals were at human environmental exposure (in the blood of U.S. population) relevant levels and below no observed adverse effect levels (NOAELs). Therefore, Pb+Cd+As+Hg co-exposure at human environmental exposure relevant levels were further selected to examine synaptic homeostasis as the cellular and molecular foundation of learning and memory. We reported for the first time that Pb+Cd+As+Hg co-exposure induced dose-dependent decreases of the dendritic lengths and branching, as well as spine density and mature phenotype in primary hippocampal neurons, and the stimulated neurite outgrowths in NGF-differentiated PC12 cells. And the above synaptic homeostasis disruption was associated with serum induced kinase (Snk)-spine associated Rap GTPase activating protein (SPAR) pathway. Our study suggests that human environmental Pb, Cd, As, and Hg co-exposure has the potential to evoke synergistic neurotoxicity even if their individual metals are below NOAELs, which reinforces the need to control and regulate potential sources of metal contamination.