Effect and Mechanisms of Electroacupuncture on Mucosal Healing in Ulcerative Colitis Mice via Non-neuroronal Cholinergic System.

Objective: To explore the effect of electroacupuncture (EA) on enhancing local acetylcholine (ACh) synthesis through activation of the nonneuronal cholinergic system (NNCS) and its action on the muscarinic ACh receptor (mAChR)-mediated signalling pathway for repair of mucosal barrier in ulcerative colitis (UC) mice.

Methods: Twenty-four wild-type male C57BL/6 mice were randomly divided into 4 groups using a random number table method, including control, model, EA, and sham EA (SEA) groups, 6 mice in each group. The UC model mice were induced by 2.5% dextran sodium sulfate (DSS) in free drinking water for 1 week. EA was administered by electrical stimulation (parameters: 2/15 Hz, 0.8 mA, 30 min/d) at the bilateral Zusanli (ST 36) for 7 consecutive days. SEA was performed at the same acupoints without electrical stimulation. The disease activity index (DAI) was determined and colonic permeability were analysed by fluorescein isothiocyanate dextran. The mucosal barrier and tight junctions (TJs) were observed by transmission electron microscopy. Zonula occludens-1 (ZO-1) and colocalization of choline acetyltransferase (ChAT) with organic cation transporters (OCT) and vesicular ACh transporter (VAChT) were tested by immunofluorescence analysis. The protein expressions of myosin light chain (MLC), phosphorylation MLC (pMLC), phospholipase C (PLC), ChAT, nuclear factor kappa-B p65 (NF-κ Bp65), mAChR, OCT and VAChT were measured by Western blot.

Results: Compared with the model group, DAI score, colonic permeability, as well as the protein expressions of pMLC, NF-κ Bp65 and VAChT were decreased in the EA group, and the mucosal barrier and TJs were repaired by EA treatment (P<0.05 or P<0.01). The expressions of ZO-1, mAChR and ChAT in the EA group were increased (P<0.05). The fluorescence intensities of ChAT relative to OCT and the ratio of the colocalization of ChAT with OCT and VAChT were increased as well (P<0.05 or P<0.01).

Conclusion: EA at bilateral ST 36 may activate the NNCS, promote ACh release by OCT, activate mAChR-related signaling by inhibiting pMLC expression, upregulate ZO-1, reduce colonic permeability and repair TJs to achieve mucosal barrier repair in UC.