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Chronic exposure to arsenic causes health problems, including peripheral neuropathy. Oxidative stress is one of the mechanisms underlying arsenic-induced neurotoxicity. For this report, we studied the protective effect of N-acetylcysteine (NAC) on arsenic-induced oxidative injury in dorsal root ganglion (DRG) explants. After 24-h incubation, NAC concentration-dependently attenuated arsenite-induced depletion in glutathione (GSH) content and increases in the ratio of oxidized GSH/reduced GSH (GSSG/GSH ratio) in DRG explants. Furthermore, NAC inhibited arsenite-induced elevation in the expression of stress proteins, such as heat shock protein 70 and heme oxygenase 1, as well as arsenite-induced phosphorylation of p38 mitogen-activated protein kinase. Incubation with NAC ameliorated arsenite-induced apoptosis by abolishing both mitochondrial and endoplasmic reticulum (ER) pathways. In the mitochondrial pathway, NAC attenuated arsenite-induced elevation in Bcl-2 level and cytosolic cytochrome c, as well as arsenite-induced reduction in procaspase-3 levels. In the ER pathway, NAC suppressed arsenite-induced increases in activating transcription factor 6 and C/EBP homologous protein in the nuclear fraction. Furthermore, arsenite-induced reductions in procaspase-12 and elevation in BIP and caspase-12, an ER-specific enzyme, were prevented after NAC incubation. Taken together, our results demonstrate that NAC is neuroprotective against arsenite-induced oxidative injury in DRG explants. Furthermore, NAC inhibits arsenite-induced toxicity by inhibiting ER and mitochondrion activation. Our data indicate that NAC is potentially therapeutic for arsenite-induced peripheral neuropathy.

Sodium arsenite (arsenite)-induced neurotoxicity and its interaction with ferrous citrate (iron) was investigated in rat brain. In vitro data showed that arsenite (1-10 micromol/L) concentration dependently increased lipid peroxidation and the potency of arsenite was less than that of iron. The oxidative activity of arsenite, sodium arsenate (arsenate), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were evaluated by inducing lipid peroxidation in cortical homogenates, and the potency for this effect was as follows: arsenite > arsenate > MMA and DMA. Several well-known antioxidants, including glutathione, melatonin, and beta-estradiol inhibited arsenite-induced lipid peroxidation in a concentration-dependent manner. Our in vivo study employed intranigral infusion of arsenite (5 nmol) in the substantia nigra (SN) of anesthetized rats. Four hours to 7 days after infusion, lipid peroxidation was elevated while glutathione was depleted in the infused SN. The dopamine content in the striatum ipsilateral to arsenite-infused SN was first elevated 24 h and then decreased 7 days after intranigral infusion of arsenite. Using pretreatment of l-buthionine-[S,R]-sulfoximine (l-BSO, i.c.v.) to reduce glutathione content in rat brain, arsenite-induced oxidative injury was augmented. Low doses of arsenite (1.5 nmol) and iron (3 nmol) alone induced minimal oxidative injury; however, co-infusion of arsenite and iron augmented neurotoxicity, including elevated lipid peroxidation and reduced striatal dopamine content. Moreover, expression of heme oxygenase-1, alpha-synuclein aggregation, and DNA fragmentation were significantly enhanced in SN co-infused with low doses of arsenite and iron. Taken together, our study demonstrates that arsenite was less potent than iron in inducing oxidative stress. Furthermore, concomitant arsenite and iron potentiated oxidative injury in the nigrostriatal dopaminergic system, indicating that interaction of metals plays a more clinically-relevant role in pathophysiology of central nervous system neurodegeneration.