Nickel-refining fumes induce NLRP3 activation dependent on mitochondrial damage and ROS production in Beas-2B cells

Nickel (Ni) is a silver-white transition metal that is widely used in the production field due to its unique physical and chemical properties. As a toxicant, long-term exposure to Ni can cause rhinitis, pneumonia and other respiratory inflammation. In the present study, we investigated the effect of particles extracted from Ni-refining fumes on cell viability, inflammation-related proteins and mitochondrial damage in human lung epithelial Beas-2B cells. The cells were exposed to Ni-refining fume particles for 24 h at concentrations of 0, 6.25, 12.50 and 25.00 μg/mL. The expression levels of the NACHT-LRR-PYD domains-containing protein 3 (NLRP3), caspase-1, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), interleukin (IL)-1β and tumor necrosis factor (TNF)-α protein in Beas-2B cells exposed to Ni-refining fume particles increased significantly. Downregulation of NLRP3 expression by siRNA decreased the content of IL-1β. During activation of NLRP3, the mitochondrial membrane potential (MMP) decreased, the opening rate of mitochondrial permeability transition pore (MPTP) increased, and the content of reactive oxygen species (ROS) increased. Using lipopolysaccharide (LPS) intervention as the positive control group, N-acetylcysteine (NAC, an effective ROS remover) acted as an inhibitor. After NAC reduced the level of ROS, activation of the NLRP3 inflammasome was significantly inhibited. Ni-refining fumes caused significant cytotoxicity, inflammation and mitochondrial damage in Beas-2B cells. The present study thus provides experimental support for the hypothesis that Ni-refining fumes cause inflammation by inducing ROS production in Beas-2B cells.