Lidocaine attenuates lipopolysaccharide-induced inflammatory responses in microglia.

Lidocaine has been used as a local anesthetic with anti-inflammatory properties, but its effects on neuroinflammation have not been well defined. In the present study, we investigated the prophylactic effects of lidocaine on lipopolysaccharide (LPS)-activated microglia and explored the underlying mechanisms. Microglial cells were incubated with or without 1 μg/mL LPS in the presence or absence of lidocaine, a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (SB203580), a nuclear factor-kappa B (NF-κB) inhibitor (pyrrolidine dithiocarbamate), or small interfering RNA. The protein and expression levels of inflammatory mediators, such as monocyte chemotactic protein 1, nitric oxide, prostaglandin E2, interleukin 1β, and tumor necrosis factor α were measured using enzyme-linked immunosorbent assays and real-time polymerase chain reaction. The effect of lidocaine on NF-κB and p38 MAPK activation was evaluated using enzyme-linked immunosorbent assays, Western blot analysis, and electrophoretic mobility shift assay. Lidocaine (≥2 μg/mL) significantly inhibited the release and expression of nitric oxide, monocyte chemotactic protein 1, prostaglandin E2, interleukin 1β, and tumor necrosis factor α in LPS-activated microglia. Treatment with lidocaine also significantly inhibited the phosphorylation of p38 MAPK and the nuclear translocation of NF-κB p50/p65, increased the protein levels of inhibitor kappa B-α. Furthermore, our study shows that the LPS-induced release of inflammatory mediators was suppressed by SB203580, pyrrolidine dithiocarbamate, and small interfering RNA. Prophylactic treatment with lidocaine inhibits LPS-induced release of inflammatory mediators from microglia, and these effects may be mediated by blockade of p38 MAPK and NF-κB signaling pathways.