Electroacupuncture alleviates intestinal inflammation via a distinct neuro-immune signal pathway in the treatment of postoperative ileus

BACKGROUND: The induction of intestinal inflammation as a result of abdominal surgery is an essential factor in postoperative ileus (POI) development. Electroacupuncture (EA) at ST36 has been demonstrated to relieve intestinal inflammation and restore gastrointestinal dysmotility in POI. This study aims to elucidate the neuroimmune pathway involved in the anti-inflammatory properties of EA in POI. METHODS: After intestinal manipulation (IM) was performed to induce POI, intestinal inflammation and motility were assessed 24 h post-IM, by evaluating gastrointestinal transit (GIT), cytokines expression, and leukocyte infiltration. Experimental surgery, pharmacological intervention, and genetic knockout mice were used to elucidate the neuroimmune mechanisms of EA. RESULTS: EA at ST36 significantly improved GIT and reduced the expression of pro-inflammatory cytokines and leukocyte infiltration in the intestinal muscularis following IM in mice. The anti-inflammatory effectiveness of EA treatment was abolished by sub-diaphragmatic vagotomy, whereas splenectomy did not hinder the anti-inflammatory benefits of EA treatment. The hexamethonium chloride (HEX) administration contributes to a notable reduction in the EA capacity to suppress inflammation and enhance motility dysfunction, and EA is ineffective in α7 nicotinic acetylcholine receptor (α7nAChR) knockout mice. CONCLUSIONS: EA at ST36 prevents intestinal inflammation and dysmotility through a neural circuit that requires vagal innervation but is independent of the spleen. Further findings revealed that the process involves enteric neurons mediating the vagal signal and requires the presence of α7nAChR. These findings suggest that utilizing EA at ST36 may represent a possible therapeutic approach for POI and other immune-related gastrointestinal diseases.