ligustilide and Pain

Ligustilide is a major component of Radix Angelica Sinensis and reported to have anti-inflammatory and anti-nociceptive effects. Toll-like receptor 4 (TLR4) has been shown to be expressed in the spinal cord and be involved in inflammatory pain and neuropathic pain. Whether ligustilide can inhibit spinal TLR4 expression in inflammatory pain is still unknown. In the present study, we intravenously injected ligustilide daily for 4 days, with the first injection given at 1 h before complete Freund's adjuvant (CFA) injection. We tested the analgesic effect of ligustilide by behavioral test and checked the expression and distribution of TLR4 in the spinal cord by real-time quantitative PCR, Western blot, and immunofluorescence. Our data showed that repeated daily intravenous treatment with ligustilide alleviated CFA-induced heat hyperalgesia and mechanical allodynia. The same treatment also inhibited CFA-induced TLR4 mRNA and protein increase in the spinal cord. Immunofluorescence double staining showed that TLR4 was predominantly expressed in spinal astrocytes. In primary cultured astrocytes, ligustilide dose-dependently reduced lipopolysaccharide-induced upregulation of TLR4 mRNA expression. These data indicate that ligustilide treatment reduces TLR4 expression in spinal astrocytes and is an effective therapy for inflammatory pain.

Topics: 4-Butyrolactone; Animals; Astrocytes; Cells, Cultured; Freund's Adjuvant; Hot Temperature; Hyperalgesia; Inflammation; Male; Mice, Inbred ICR; Pain; RNA, Messenger; Spinal Cord; Toll-Like Receptor 4; Up-Regulation

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.

Topics: 4-Butyrolactone; Animals; Anti-Inflammatory Agents; Calcium-Binding Proteins; Cell Line, Transformed; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; Freund's Adjuvant; Inflammation; Lipopolysaccharides; Male; Mice; Microfilament Proteins; Microglia; Pain; Pain Measurement; Pain Threshold; RNA, Messenger; Spinal Cord; Time Factors

Danggui is a popular traditional Chinese medicinal (TCM) herb, which has long been used clinically to treat primary dysmenorrhoea. In a recent study, we demonstrated that ligustilide (LIG), one of the main compounds of Danggui essential oil, has multiple effects on uterine smooth muscles and possesses a non-specific antispasmodic function, which suggests that LIG might play a major role in the therapeutic activity of Danggui in primary dysmenorrhoea. Since pain is the main syndrome of dysmenorrhea, the present investigation was carried out to evaluate the analgesic activity of LIG in vivo. LIG was intra-gastrically administered to animals. We demonstrated for the first time that LIG could cause a significant dose-related reduction of acetic acid-induced writhing response and formalin-induced licking time in both the early and late phases. These results showed that LIG possessed antinociceptive and anti-inflammatory activities. These findings plus the data we reported recently implied that LIG not only has an active dilatory effect on myometrium but also an effective role in reducing the neurogenic and inflammatory pain, thus having the potential to be developed into an effective drug for the treatment of various pain syndromes including primary dysmenorrhoea.

Topics: 4-Butyrolactone; Acetic Acid; Analgesics; Animals; Drugs, Chinese Herbal; Female; Formaldehyde; Medicine, Chinese Traditional; Mice; Mice, Inbred ICR; Pain; Pain Measurement