Acupuncture relieves pain by inhibiting expression of Cx43 in astrocytes and release of interfe-ron-γ in neurons of trigeminal spinal nucleus in rats with migraine

Abstract

To observe the effect of acupuncture on the expression of connexin 43 (Cx43), glial fibrillary acidic protein (GFAP), interferon-γ (IFN-γ) in the trigeminal spinal nucleus (TNC) of rats with migraine, so as to explore its mechanisms underlying amelioration of migraine. A total of 44 SD rats were randomly divided into control, model, acu-puncture, and sham acupuncture groups (n=11 in each group). Acupuncture was applied to bilateral "Shuaigu"(GB8) and "Yanglingquan"(GB34) or non-acupoint Ⅰ (the spot about 10 mm superior to the iliac spine and 20 mm lateral to the post-median line) and non-acupoint Ⅱ (behind the iliac spine, the ending-spot of the posterior superior iliac spine at the muscles) on both sides for 20 min, once daily for 9 days. Paw withdrawal latency (mechanical pain threshold,PWMT) and thermal tail flick latency (TFL) were measured using a VonFrey detector and photothermal tail pain meter, respectively. The content of IFN-γ of TNC tissue was detected by ELISA. The expression levels of Cx43 and IFN-γ proteins of TNC tissue were detected by Western blot. The immunofluorescence dual labeling method was used to detect the positive expression of GFAP and Cx43, IFN-γR and NeuN in TNC tissue, for displaying the activity of Cx43 in astrocytes and IFN-γ in neurons, respectively. Compared with the control group, both PWMT and TFL at 3, 5, 7 and 9 days after modeling were significantly decreased (P<0.01), while the expression of Cx43 and IFN-γ proteins, the immunofluorescence intensity of GFAP, Cx43, IFN-γR, and the content of IFN-γ were considerably up-regulated in the model group (P<0.01). In comparison with the model group, both PWMT and TFL at 3, 5, 7 and 9 days after modeling were obviously increased (P<0.01), whereas the expression of Cx43 and IFN-γ proteins, the immunofluorescence intensity of GFAP, Cx43, IFN-γR, and the content of IFN-γ in the acupuncture group, as well as the protein expression of IFN-γR in the sham acupuncture group were also remarkably decreased (P<0.05, P<0.01). The effect of acupuncture was significantly superior to that of sham acupuncture in down-regulating the expression of Cx43 and IFN-γ proteins, and the immunofluorescence intensity of GFAP, Cx43, and IFN-γR (P<0.05, P<0.01). Immunofluorescence dual labeling outcomes showed that in the model group, a large number of GFAP and Cx43 co-expressed astrocytes were found, and the cell body and protrusion of GFAP-labelled astrocytes were evidently increased, and Cx43 was mainly expressed on the surface of astrocyte membrane and the protrusion site, and the proportion of IFN-γR and NeuN co-expressing neurons in the model group was significantly increased, suggesting an activation of astrocytes and neurons after modeling. Whereas in the acupuncture group, the bright green clustered particles on the cell membrane and protrusion of astrocytes, and the proportion of IFN-γR and NeuN co-expressing neurons were significantly reduced, suggesting a suppression of activities of Cx43, astrocytes and neurons and IFN-γ release from TNC after acupuncture intervention. Acupuncture can relieve the pain response in rats with migraine, which may be associa-ted with its functions in inhibiting the expression of Cx43 and activation of astrocytes and neurons, and reducing release of pro-inflammatory factor IFN-γ in TNC.