Papaverine inhibits lipopolysaccharide-induced microglial activation by suppressing NF-κB signaling pathway

Objective: To investigate the effects of papaverine (PAP) on lipopolysaccharide (LPS)-induced microglial activation and its possible mechanisms. Materials and methods: BV2 microglial cells were first pretreated with PAP (0, 0.4, 2, 10, and 50 mu g/mL) and then received LPS stimulation. Transcription and production of proinflammatory factors (IL1 beta, TNF alpha, iNOS, and COX-2) were used to evaluate microglial activation. The transcriptional changes undergone by M1/M2a/M2b markers were used to evaluate phenotype transformation of BV2 cells. Immunofluorescent staining and Western blot were used to detect the location and expression of P65 and p-IKK in the presence or absence of PAP pretreatment. Results: Pretreatment with PAP significantly inhibited the expression of IL1 beta and TNF alpha, and suppressed the transcription of M1/M2b markers Il1rn, Socs3, Nos2 and Ptgs2, but upregulated the transcription of M2a markers (Arg1 and Mrc1) in a dose-dependent manner. In addition, PAP pretreatment significantly decreased the expression of p-IKK and inhibited the nuclear translocation of P65 after LPS stimulation. Conclusion: PAP not only suppressed the LPS-induced microglial activity by inhibiting transcription/production of proinflammatory factors, but also promoted the transformation of activated BV2 cells from cytotoxic phenotypes (M1/M2b) to a neuroprotective phenotype (M2a). These effects were probably mediated by NF-kappa B signaling pathway. Thus, it would be a promising candidate for the treatment of neurodegenerative diseases.