Quantitative proteomics reveals the neurotoxicity of trimethyltin chloride on mitochondria in the hippocampus of mice

Abstract

Trimethyltin chloride (TMT) is a potent neurotoxin widely used as a constituent of polyvinyl chloride plastic in the industrial and agricultural fields. However, the underlying mechanisms by which TMT leads to neurotoxicity remain elusive. In the present study, we constructed a dose and time dependent neurotoxic mouse model of TMT exposure to explore the molecular mechanisms involved in TMT-induced neurological damage. Based on this model, the cognitive ability of TMT exposed mice was assessed by the Morris water maze test and a passive avoidance task. The ultrastructure of hippocampus was analyzed by the transmission electron microscope. Subsequently, proteomics integrated with bioinformatics and experimental verification were employed to reveal potential mechanisms of TMT-induced neurotoxicity. Gene ontology (GO) and pathway enrichment analysis were done by using Metascape and GeneCards database respectively. Our results demonstrated that TMT-exposed mice exhibited cognitive disorder, and mitochondrial respiratory chain abnormality of the hippocampus. Proteomics data showed that a total of 7303 proteins were identified in hippocampus of mice of which 224 ones displayed a 1.5-fold increase or decrease in TMT exposed mice compared with controls. Further analysis indicated that these proteins were mainly involved in tricarboxylic acid (TCA) cycle and respiratory electron transport, proteasome degradation, and multiple metabolic pathways as well as inflammatory signaling pathways. Some proteins, including succinate-CoA ligase subunit (Suclg1), NADH dehydrogenase subunit 5 (Nd5), NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 4-like 2 (Ndufa4l2) and cytochrome c oxidase assembly factor 7 (Coa7), which were closely related to mitochondrial respiratory electron transport, showed TMT dose and time dependent changes in the hippocampus of mice. Moreover, apoptotic molecules Bax and cleaved caspase-3 were up-regulated, while anti-apoptotic Bcl-2 was down-regulated compared with controls. In conclusion, our findings suggest that impairment of mitochondrial respiratory chain transport and promotion of apoptosis are the potential mechanisms of TMT induced hippocampus toxicity in mice.

Keywords: Apoptosis; Hippocampus; Mitochondria; Trimethyltin chloride.