Ligustilide inhibits microglia-mediated proinflammatory cytokines production and inflammatory pain

Ligustilide is the main component of Danggui essential oil, and recently reported to have anti-inflammatory and neuroprotective effect. Increasing evidence suggests that glia-mediated neuroinflammation in the spinal cord plays a vital role in the pathogenesis of chronic pain. In the present study, we investigated the anti-inflammatory and anti-nociceptive effect of ligustilide both in vitro and in vivo. In microglial cell line BV2 cells, lipopolysaccharide (LPS) time-dependently increased the mRNA expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6), which was decreased by pretreatment with ligustilide in a dose-dependent manner. Ligustilide also decreased LPS-induced proinflammatory cytokines production in primary cultured microglia. In vivo, intrathecal injection of LPS induced mechanical allodynia in mice. Intravenous injection of ligustilide prevented LPS-induced mechanical allodynia, and decreased LPS-induced TNF-α, IL-1β, and IL-6 up-regulation in the spinal cord. In addition, repetitive intravenous injection of ligustilide attenuated intraplantar injection of complete Freund's adjuvant (CFA)-induced mechanical allodynia and thermal hyperalgesia. The same treatment of ligustilide also inhibited CFA-induced TNF-α, IL-1β, and IL-6 up-regulation and microglial activation in the spinal cord. Taken together, our data suggest that ligustilide can alleviate inflammatory pain partly through inhibition of microglial activation and proinflammatory cytokines production, which indicates a possible benefit from the use of ligustilide in the treatment of inflammatory pain and neuroinflammation-associated disorders.