Tanshinone IIA Downregulates HMGB1 and TLR4 Expression in a Spinal Nerve Ligation Model of Neuropathic Pain

Fifty-four Sprague-Dawley rats weighing 200~240 g were randomly divided into sham-operated group (sham group), vehicle-treated SNL group (model group), and Tan IIA-treated SNL group (Tan IIA group). Tan IIA was administered intraperitoneally to rats in the Tan IIA-treated group at a dose of 30 mg/kg daily for 14 days after SNL surgery. Paw withdrawal mechanical thresholds (PWTs) and paw withdrawal thermal latencies (PWLs) were measured. High-mobility group box 1 (HMGB1) and Toll-like Receptor 4 (TLR4) mRNA and protein expression in the spinal cord were measured. Tumour necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-10 (IL-10) in the spinal cord were measured, too. Both the mechanical and heat pain thresholds were significantly decreased. After Tan IIA treatment, HMGB1, and TLR4 mRNA and protein levels, the expression of TNF-α and IF-1β was reduced significantly. In conclusion, Tanshinone IIA reversed SNL-induced thermal hyperalgesia and mechanical allodynia and downregulated HMGB1 and TLR4 levels and inhibited the HMGB1-TLR4 pathway. Tanshinone IIA inhibited TNF-α and IL-1β expression but not IF-10 expression in the spinal cords of SNL rats. These results indicate that Tanshinone IIA inhibited SNL-induced neuropathic pain via multiple effects, and targeting the HMGB1-TLR4 pathway could serve as the basis of new antinociceptive agents.