Paraquat-induced inflammatory response of microglia through HSP60/TLR4 signaling.

Previous studies showed that paraquat (PQ) caused the apoptosis of dopaminergic neurons by inducing the generation of oxygen radical. The purpose of this study is to explore PQ-induced microglial inflammatory response and its underlying molecular mechanisms. The murine microglia BV2 cell line was used. After stimulation with PQ and lipopolysaccharides (positive control), the concentrations of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6) in the culture supernatant and mRNA expression of TNF-α and IL-1β were determined by ELISA and quantitative real-time Polymerase Chain Reaction (PCR), respectively. The protein expression of heat shock protein 60 (HSP60) and toll-like receptor 4 (TLR4), along with the mRNA expression of transcription factors of nuclear factor κB-p65 (NF-κB-p65) and activated protein 1 (AP1, c-fos, and c-jun dimer) were evaluated with western blot and quantitative real-time PCR, respectively. The results showed that PQ activated microglia, which was characterized by increasing the generation and upregulated mRNA expression of pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6. In addition, PQ significantly enhanced the expressions of HSP60 and TLR4 proteins in BV2 cells, as well as NF-κB-p65, c-fos, and c-jun mRNA. These findings suggest that PQ can activate microglia and enhance the expression and secretion of pro-inflammatory cytokines in a HSP60/TLR4 signaling, leading to the inflammatory response.