Electroacupuncture improves intestinal motility and visceral sensitivity in mice with functional constipation via up-regulating Piezo1/2 channel activity

To investigate the effect of electroacupuncture (EA) on intestinal motility and visceral sensitivity in functional constipation (FC) mice and its regulatory mechanism on Piezo1/2 channels in enterochromaffin (EC) cell.

Twenty-four male C57BL/6J mice were randomly divided into normal control, model, and EA groups (n=8 in each group). The FC model was established by gavage of loperamide hydrochloride. EA (1 mA, 3 Hz/15 Hz) was applied to unilateral “Tianshu” (ST25) and “Shangjuxu” (ST37) for 20 min per session, once daily for 5 consecutive days per week, two weeks altogether. Fecal parameters (number of stool particles in 6 h, characters, and fecal water content), intestinal motility (the time of the first blue stool excretion after gavage of Evans blue solution and small intestinal transit rate), and visceral sensitivity (assessed by abdominal withdrawal reflex [AWR] in responding to colorectal dilation) were observed. A transmission electron microscopy (TEM) was used to observe EC cells' ultrastructure. Triple immunofluorescence, Western blot and real-time qPCR were used to detect the expressions of Piezo1/2 in the EC cells and colon, and ELISA was employed to detect the contents of serum and colonic 5-HT and colonic Ca²⁺.

Compared with the normal group, the model group showed a significant reduction in the number of stool particles, fecal character score, and fecal water content, small intestinal transit rate, AWR scores at 0.25 mL, 0.35 mL and 0.65 mL, contents of serum and colonic 5-HT and colonic Ca²⁺, expression levels of colonic Piezol1 and Piezol 2 proteins and mRNAs, and the positive areas of Piezol1 and Piezol2, EC, Piezol1/EC and Piezol2/EC (P<0.01, P<0.001,P<0.05), and an evident increase in the time of the first blue stool particle excretion (decrease of intestinal propulsion) and AWR 3-points threshold (P<0.01). Following EA treatment, both the decrease and increase of the indexes mentioned above were reversed completely (P<0.05, P<0.001, P<0.01). TEM showed mitochondrial swelling and a reduction in the secretory granules of EC cells in the model group, which was partially restored following EA treatment.

EA of ST25 and ST37 can alleviate FC-related intestinal dysmotility and visceral hypersensitivity in FC mice, which may be associated with its functions in up-regulating Piezo1/2 channels of EC cell, promoting Ca²⁺ influx and 5-HT secretion.