Low Doses of Arsenic in a Mouse Model of Human Exposure and in Neuronal Culture Lead to S-Nitrosylation of Synaptic Proteins and Apoptosis via Nitric Oxide.

Accumulating public health and epidemiological literature support the hypothesis that arsenic in drinking water or food affects the brain adversely. Experiments on the consequences of nitric oxide (NO) formation in neuronal cell culture and mouse brain were conducted to probe the mechanistic pathways of nitrosative damage following arsenic exposure. After exposure of mouse embryonic neuronal cells to low doses of sodium arsenite (SA), we found that Ca2+ was released leading to the formation of large amounts of NO and apoptosis. Inhibition of NO synthase prevented neuronal apoptosis. Further, SA led to concerted S-nitrosylation of proteins significantly associated with synaptic vesicle recycling and acetyl-CoA homeostasis. Our findings show that low-dose chronic exposure (0.1-1 ppm) to SA in the drinking water of mice led to S-nitrosylation of proteomic cysteines. Subsequent removal of arsenic from the drinking water reversed the biochemical alterations. This work develops a mechanistic understanding of the role of NO in arsenic-mediated toxicity in the brain, incorporating Ca2+ release and S-nitrosylation as important modifiers of neuronal protein function.