Botulinum toxin type A inhibits chronic post-thoracotomy pain through the HMGB1-mediated TLR4/NF-κB signaling pathway

Objective: To elucidate the analgesic role and underlying mechanism of botulinum toxin type A (BTX-A) in chronic post-thoracotomy pain (CPTP).Methods: Postoperative wound scar tissues were collected from patients with and without CPTP.Histopathologic changes were evaluated using hematoxylin-eosin (H&E) staining, and the expression levels of high mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α) were assessed.Spinal microglia were cultured in vitro to establish a cell model of CPTP.The activated microglial cells were then treated with BTX-A to evaluate its effects on substance P (SP)-induced microglia activation, HMGB1 expression, TLR4/NF-κB pathway, and inflammatory cytokine (TNF-α and IL-10) secretion.Additionally, microglia were transfected with an HMGB1 lentiviral vector to assess the regulatory role of HMGB1 on TLR4/NF-κB signaling, microglial activation, cytokine release, and the inhibitory effects of BTX-A.Results: H&E staining showed strong inflammatory cell infiltration and upregulated expression of HMGB1, TLR4, IL-10, and TNF-α in tissues from the CPTP group (P < 0.05).Transfection with HMGB1 lentiviral vector significantly increased the expression levels of TLR4, p-P65, and p-IκB-α in microglial cells, enhanced cell proliferation, and promoted IL-10 and TNF-α secretion.TLR4/NF-κB pathway activation positively regulated microglial activation and TNF-α and IL-10 expression.Moreover, HMGB1 overexpression attenuated the inhibitory effects of BTX-A on microglial activation.Conclusions: BTX-A may alleviate post-thoracotomy pain by downregulating the HMGB1/TLR4/NF-κB pathway, thereby reducing the secretion of inflammatory factors and inhibiting microglial activation.