Coumarins attenuate intestinal motility by inhibiting TMEM16A.

Abstract

Transmembrane 16A (TMEM16A) is highly expressed in interstitial cells of Cajal (ICC) and participates in ICC-mediated rhythmic contractile activity of intestinal smooth muscle. TMEM16A is also expressed in epithelium of intestine with a minor contributor to transepithelial fluid secretion, while other unidentified Ca²⁺ -activated Cl - channels (unCaCCs) are mainly responsible for this physiological process. TMEM16A/CaCCs dysfunction can lead to disorders of intestinal motility and transepithelial fluid secretion. TMEM16A/CaCCs regulators are important tools to identify unCaCCs and study the physiopathological functions related to TMEM16A/CaCCs. In the present study, coumarins were identified as TMEM16A inhibitors in a concentration- and time-dependent manner in TMEM16A-expressed Fischer rat thyroid (FRT) epithelial cells. Coumarins attenuated intestinal motility by inhibiting TMEM16A in vivo and ex vivo. Coumarins inhibited CaCCs-mediated Cl^- currents induced by ATP in T84 and HT-29 cells or by carbachol (CCh) in mouse colonic mucosa with reduction of ATP-induced increase of cytoplasmic Ca²⁺ concentration in HT-29 cells. Coumarins inhibited basolateral Ca²⁺ -activated K⁺ channels without affecting Na + /K + -ATPase activity in mouse colonic mucosa. Coumarins did not show inhibition of cystic fibrosis transmembrane conductance regulator (CFTR), but mild activation of CFTR-mediated Cl - currents under the low concentration forskolin (FSK) in CFTR-expressed FRT cells, while coumarins did not activate CFTR-mediated Cl- currents in mouse colonic mucosa. This study was the first to demonstrate that coumarins attenuate intestinal motility by inhibiting TMEM16A, which may provide a strategy for clinical drug intervention aimed at reducing secretory diarrhea.