Abstract
Neuropathic pain (NP) is a common and disabling condition characterized by microglial polarization-evoked neuroinflammation. Pedunculoside has been implicated in several inflammation-related diseases and exerts the neuroprotective effects However, its role in NP remains unclear. In this study, pedunculoside dose-dependently suppressed LPS-induced activation of BV2 microglial cells by reducing expression of the microglial marker IBA-1, but without obvious cytotoxicity. Immunofluorescence assay further confirmed that pedunculoside decreased % of CD32(+) M1 microglia and increased % of CD206(+) M2 microglia in LPS-stimulated microglia, accompanied by reduced expression of M1 microglial marker CD32 and iNOS and increased expression of M2-like microglial marker CD206 and Arg-1, indicating that pedunculoside could reverse LPS-induced microglial polarization from M1 phenotype towards M2 phenotype. Moreover, pedunculoside also attenuated inflammatory response in LPS-treated microglia by lowering pro-inflammatory cytokine levels (IL-1β, TNF-α, and IL-4) and increasing anti-inflammatory IL-10 levels. Mechanistically, the activation of the TLR4-NF-κB pathway in LPS-treated microglia was suppressed by pedunculoside. Furthermore, reactivating this signaling by TLR4 overexpression abrogated pedunculoside-mediated effects on microglial polarization towards M2 and inflammation. In vivo, administration of pedunculoside alleviated pain sensitivity and modulated microglial polarization from M1 to M2 in chronic constrictive injury (CCI)-induced NP mice. Additionally, pedunculoside also alleviated neuroinflammation and suppressed activation of the TLR4-NF-κB pathway in NP mice. Collectively, these findings indicate that pedunculoside may ameliorate the progression of NP by affecting microglial polarization from M1 towards M2 phenotype through inhibition of the TLR4-NF-κB pathway, supporting its potential as a promising therapeutic agent for NP.