Nano NiO induced liver toxicity via activating the NF-κB signaling pathway in rats

Studies have demonstrated that nano NiO could induce liver toxicity in rats, but its mechanism remains unclear. This study aimed to explore the role of the NF-κB signaling pathway in rat liver toxicity after nano NiO exposure. Male Wistar rats were exposed to nano NiO (0.015, 0.06 and 0.24 mg per kg b.w.) and micro NiO (0.24 mg per kg b.w.) by intratracheal instillation twice a week for 6 weeks. To investigate the liver toxicity induced by nano NiO, the indicators of liver function and inflammatory response were detected, and the histopathological changes were observed. The levels of NF-κB signaling pathway related gene and protein expression were examined using RT-qPCR and western blot techniques in the liver tissue. The results showed that the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyltranspeptidase (GGT) increased after nano NiO exposure. Cellular edema, hepatic sinus disappearance, and neutrophil and lymphocyte infiltration were observed. Nano NiO increased the concentrations of pro-inflammatory cytokines (IL-1β and IL-6), but decreased the levels of anti-inflammatory cytokines (IL-4 and IL-10). It also induced the upregulation of TNF-α, NF-κB-inducible kinase (NIK), IκB kinase alpha (IKK-α) and NF-κB mRNA, while inducing the downregulation of the inhibitor kappa B (IκB) alpha. In addition, we found that the protein content of NIK, IKK-α, p-IKK-α, p-IκB-α and NF-κB was elevated, whereas that of IκB-α was reduced. The results indicated that the NF-κB signaling pathway played an important role in rat liver toxicity induced by nano NiO.