Exploring the mechanism of wrist-ankle acupuncture in treating chemotherapy-induced neuropathic pain in mice by regulating neuroinflammatory responses through α7 nicotinic acetylcholine receptor in the spinal dorsal horn

To investigate the effect of wrist-ankle acupuncture on the α7 nicotinic acetylcholine receptor (α7nAChR) /Janus kinase 2 (JAK2) /signal transducer and activator of transcription 3 (STAT3) signaling pathway in the spinal dorsal horn of mice with chemotherapy-induced neuropathic pain (CINP), and to explore the mechanisms by which low-intensity wrist-ankle electroacupuncture alleviates pain hypersensitivity in CINP mice.

C57BL/6 mice were randomly divided into a blank group, a model group, a wrist-ankle acupuncture group, and a wrist-ankle acupuncture + antagonist group, with 8 mice in each group. A CINP model was established by intraperitoneal injection of paclitaxel (2 mg/kg). The wrist-ankle acupuncture group received electroacupuncture at the “Lower 4” and “Lower 5” points in the wrist-ankle region for 30 min per session, once every other day, for a total of 7 sessions. The wrist-ankle acupuncture + antagonist group received intrathecal injections of the α 7nAChR antagonist α-BGT (0.5 μg/kg) on day 1, 7, and 13, in addition to acupuncture. The mechanical and thermal pain thresholds were assessed using Von Frey filaments and hot plate tests. The expression level of α7nAChR protein in the spinal dorsal horn (L4-L6) was determined by Western blot. Immunofluorescence staining was used to detect the expression of ionized calcium-binding adapter molecule 1 (Iba-1) in the spinal dorsal horn. ELISA was used to measure the relative levels of phosphorylated (p) -JAK2 and p-STAT3 in the spinal dorsal horn. Quantitative PCR was used to detect the relative mRNA expression levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6).

Compared with the blank group, the model group exhibited decreased mechanical and thermal pain thresholds (P＜0.001), reduced α7nAChR protein expression (P＜0.05), increased Iba-1 expression (P＜0.05), elevated relative contents of p-JAK2 and p-STAT3 (P＜0.05), and increased mRNA expression levels of TNF-α, IL-1β, and IL-6 (P＜0.05). Compared with the model group, the wrist-ankle acupuncture group showed increased mechanical and thermal pain thresholds (P＜0.05), elevated α7nAChR protein expression (P＜0.05), decreased Iba-1 expression (P＜0.05), reduced relative contents of p-JAK2 and p-STAT3 (P＜0.05), and decreased mRNA expression levels of TNF-α, IL-1β, and IL-6 (P＜0.05). Compared with the wrist-ankle acupuncture group, the wrist-ankle acupuncture + antagonist group showed decreased mechanical and thermal pain thresholds (P＜0.05), lower α7nAChR protein expression (P＜0.05), increased Iba-1 expression (P＜0.05), higher relative contents of p-JAK2 and p-STAT3 (P＜0.05), and elevated mRNA expression levels of TNF-α, IL-1β, and IL-6 (P＜0.05).

Wrist-ankle acupuncture may alleviate pain hypersensitivity in CINP mice by regulating the α7nAChR/JAK2/STAT3 signaling pathway in the spinal dorsal horn, inhibiting microglial activation, and reducing neuroinflammation.