Background
EP4 prostanoid receptor (EP4R) contributes to the intestinal epithelial barrier function, and inhibition of prostaglandin E (PGE) production by non-steroidal anti-inflammatory drugs (NSAIDs) plays a central role in NSAID-induced enteropathy. However, given that M3 muscarinic acetylcholine receptor (M3R)-selective agents are unavailable, how M3R regulates the intestinal epithelial barrier function remains unclear. The present study explored how M3R is involved in the regulation of the intestinal epithelial barrier function and its pathophysiological role in NSAID-induced enteropathy.
Methods
Using the novel highly-selective M3 positive allosteric modulator PAM-369 that we recently developed, we evaluated the role of M3R in the intestinal epithelial barrier function ex vivo by measuring the short circuit current (Isc) of intestinal epithelium with a Ussing chamber system and examined whether or not M3R protects against small intestinal injury in indomethacin-treated mice.
Results
Both the PGE1 derivative misoprostol and carbachol similarly increased the Isc in a concentration-dependent manner. The Isc increases were abolished either by receptor antagonists (an EP4R antagonist and a M3R antagonist, respectively) or by removal of extracellular Cl−. PAM-369 increased the Isc by potentiating M3R, which could contribute to enhanced intestinal epithelial barrier function. Treatment with PAM-369 ameliorated small intestinal injury in indomethacin-treated mice. Importantly, the M3R expression was significantly up-regulated, and PAM-369 potentiation of M3R was augmented in indomethacin-treated mice compared to untreated mice.
Conclusions
These findings show that M3R plays a role in maintaining the intestinal epithelial barrier function. M3R is a promising target for treating or preventing NSAID-induced enteropathy.