Arsenic Activates the NLRP3 Inflammasome and Disturbs the Th1/Th2/Th17/Treg Balance in the Hippocampus in Mice.

Abstract

Arsenic exerts neurotoxicity and immunomodulatory effects. Studies have shown that the nervous system is not considered to be an immune-privileged site. However, the effect of arsenic-induced neuroimmune toxicity has rarely been reported. We aimed to investigate the toxic effects of arsenic on the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and the Th1/Th2/Th17/Treg balance in the brain tissue of mice. Mice were exposed to NaAsO2 (0, 2.5, 5, and 10mg/kg) for 24h. Our results showed that 10mg/kg arsenic exposure significantly decreased brain and hippocampal indices (p < 0.05). The mRNA and protein levels of the blood‒brain barrier (BBB) tight junction protein occludin were decreased in the 5 and 10mg/kg arsenic-treated groups. Compared with those in the control group, NLRP3 protein levels in 10mg/kg arsenic-treated mice, caspase-1 protein levels in 2.5, 5, and 10mg/kg arsenic-treated mice, and IL-1β protein levels in 5 and 10mg/kg arsenic-treated mice were increased in the hippocampus (p < 0.05). In addition, arsenic induced a hippocampal inflammatory response by upregulating the mRNA levels of the proinflammatory factors IL-6 and TNF-α and downregulating the mRNA level of the anti-inflammatory factor IL-10. Moreover, arsenic decreased the mRNA levels of the Th1 and Th2 transcription factors T-bet and GATA3 and the cytokines IFN-γ and IL-4 and increased the mRNA levels of the Th17 transcription factor RORγt and the cytokine IL-22 (p < 0.05). Collectively, our study demonstrated that arsenic could induce immune-inflammatory responses by regulating the NLRP3 inflammasome and CD4+ T lymphocyte differentiation. These results provide a novel strategy to block the arsenic-induced impairment of neuroimmune responses.