康复学报 (Dec 2023)
Mechanism of Electroacupuncture Mediated Macrophages Infiltration on Dorsal Root Ganglion to Alleviate Paclitaxel-Induced Neuropathic Pain
Abstract
ObjectiveTo observe the effects of electroacupuncture (EA) at bilateral Zusanli acupoint (ST 36) on the expressions of macrophage marker CD68, monocyte chemotactic protein-1 (MCP-1), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) in dorsal root ganglion (DRG) of mouse model with paclitaxel-induced neuropathic pain, and to explore the mechanism of EA in regulating paclitaxel-induced neuropathic pain.MethodsA total of 30 adult C57 mice were randomly divided into control group, model group and EA group, with 10 mice in each group. The model group and the EA group received intraperitoneal injection of 2 mg/kg paclitaxel on the 1st, 3rd, 5th and 7th day, respectively, while the control group was injected with the same volume of solvent. After injection (at the 9th day), the EA group received electroacupuncture at bilateral Zusanli acupoint (ST 36) with frequency of 15 Hz, intensity of 1 mA, 30 minutes a time, once a day, lasting for seven days. The "up and down" method was used to measure paw withdrawal mechanical threshold (PWMT); the hematoxylin-eosin (HE) staining was used to observe pathological characteristics of DRG tissues; immunofluorescence staining was used to detect the percentage of MCP-1 and CD68 immunopositive area in DRG tissues; Western blot method was used to detect the protein expression level of CD68, MCP-1, iNOS and IL-1β in DRG tissues, and transmission electron microscope was used to observe the ultrastructure of macrophages in DRG tissues.Results(1) PWMT: compared with the control group at the same time, PWMT in the model group decreased significantly at the 8th, 11th, 13th and 15th days (P<0.05); compared with the model group at the same time, PWMT in the EA group increased significantly at the 11th, 13th and 15th days, and the differences were statistically significant (P<0.05). (2) Histopathological features of DRG tissues: the inflammatory cells are nearly round in shape and blue-purple in color. There were a small number of inflammatory cells in the control group, the number of inflammatory cells in the aggregating and infiltrating state increased in the model group, and there were fewer inflammatory cells in the EA group. (3) The percentage of MCP-1 and CD68 immunopositive areas in DRG tissues: compared with the control group, the percentage of MCP-1 and CD68 immunopositive areas in DRG tissues in the model group increased significantly (P<0.05); compared with the model group, the percentage of MCP-1 and CD68 immunopositive areas in DRG tissues in the EA group decreased significantly (P<0.05). (4) The protein expression level of MCP-1, CD68, IL-1β and iNOS in DRG tissues: compared with the control group, the protein expression level of MCP-1, CD68, IL-1β and iNOS in DRG tissues in the model group increased significantly (P<0.05); compared with the model group, the relative protein expressions of MCP-1, CD68, IL-1β and iNOS in the DRG tissues in the EA group decreased significantly (P<0.05). (5) Ultrastructure of macrophages in DRG tissues: the shape of macrophages in DRG tissues in the control group was nearly round, with round and blunt processes; the shape of macrophages in DRG tissue in the model group was flat, cells with pseudopodia, and the cell bodies were larger than those in the control group; the shape of macrophages in DRG tissues in the EA group was nearly round, and the cell bodies were larger than those in the control group.ConclusionEA at bilateral Zusanli acupoint (ST 36) can relieve neuropathic pain induced by paclitaxel in mice, and its mechanism may be that EA plays an analgesic role by down-regulating the expression of MCP-1 in DRG, inhibiting the infiltration of macrophages in DRG tissue, and reducing the release of IL-1β, iNOS and CD68 inflammatory factors in DRG tissue.
