Effect of electroacupuncture on enteric neuronal autophagy in functional constipation mice.

Abstract

To explore the effect mechanism of electroacupuncture (EA) on functional constipation (FC) at the combined lower he-sea and front-mu points of large intestine based on enteric neuronal autophagy. A total of 40 SPF Kunming mice were randomly divided into 5 groups (n = 8), i.e. a control group, a model group, an acupuncture group, a 3-methyl adenine (3-MA) group, and a 3-MA + acupuncture group. Except the control group, the FC model was established by gavage with compound diphenoxylate suspension for 14 days in the other 4 groups. After successful modeling, the mice of the acupuncture group and the 3-MA + acupuncture group received EA at bilateral "Tianshu" (ST 25) and "Shangjuxu" (ST 37), stimulated for 30 min with disperse-dense wave, 2 Hz/15 Hz of frequency, 1 mA of intensity. EA was delivered once daily. One course of treatment was composed of 5 days and 2 courses were needed, with an interval of 2 days. An intraperitoneal injection of 3-MA (15 mg/kg) was administered 30 min before EA in the mice of the 3-MA group and the 3-MA + acupuncture group, once daily. Before and after intervention, the time of the first black stool defecation and defecation behaviors in 6 h were observed in each group. After intervention, in every group, the small intestine propulsion rate was calculated, the colon tissue morphology was observed using HE staining, the ultrastructure of enteric neuronal autophagy was observed under transmission electron microscope, and the expressions of microtubule-associated protein 1 light chain 3 (LC3), Beclin-1 and neuronal nuclear antigen protein (NeuN) in neurons of colonic muscularis were determined by immunohistochemistry. Before intervention, when compared with those in the control group, the time of the first black stool defecation was prolonged (P<0.01, P<0.05), and numbers (P<0.01), wet weight (P<0.01, P<0.05) and water content (P<0.05, P<0.01) of stool in 6 h were reduced in the model, acupuncture, 3-MA and 3-MA + acupuncture groups. After intervention, compared with those in the control group, the time of the first black stool defecation was longer (P<0.05), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were decreased in the model group. The time of the first black stool defecation was shortened (P<0.01), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were increased in the acupuncture group when compared with those in the model group. The time of the first black stool defecation was extended (P<0.01), and numbers (P<0.01), wet weight (P<0.01) and water content (P<0.01) of stool in 6 h were declined in the 3-MA + acupuncture group in comparison with those in the acupuncture group. All layers of colon tissue were normal and intact in each group. When compared with the control group, the small intestine propulsion rate and the average optical density (OD) values of LC3, Beclin-1 and NeuN in neurons of colonic muscularis were decreased (P<0.01), and autophagosomes were dropped in the model group. In the acupuncture group, the small intestine propulsion rate and the average OD values of NeuN, LC3 and Beclin-1 in neurons of colonic muscularis increased (P<0.01,P<0.05), and autophagosomes were elevated when compared with those in the model group. The small intestine propulsion rate and the average OD values of NeuN, LC3 and Beclin-1 in neurons of colonic muscularis were dropped (P<0.05,P<0.01) in the 3-MA + acupuncture group in comparison with those in the acupuncture group. Electroacupuncture may promote enteric neuronal autophagy and increase the number of neurons so that the intestinal motility can be improved and constipation symptoms can be relieved in FC mice.