P2Y1 RECEPTOR SIGNALING INFLUENCES EPITHELIAL RESPONSE TO INTESTINAL INFLAMMATION

Abstract Purines are among the most influential and ancient biochemical molecules in evolutionary history. In recent years, several studies have identified that nucleotides are released from cells during infection and tissue injury and serve as paracrine signaling molecules that help coordinate host defense and repair responses. These important extracellular signaling molecules activate purinergic receptors, of which there are 19 different purinergic receptor subtypes, which are classified into P1 and P2 receptors. Several studies have revealed crucial roles for P2 purinergic receptors during inflammatory and infectious diseases; however, these studies have largely examined purinergic signaling in immune cells and the enteric nervous system. Yet, while epithelial cells serve as the first barrier against infection and inflammation, the role of purinergic signaling within the gastrointestinal tract remains largely unknown. Our group recently discovered a novel and prominent role for P2Y1 in mediating host responses during rotavirus infection. To extend these studies, we sought to elucidate the P2 purinergic receptor repertoire expressed within gut epithelium and assess their functional role during insult. Using the Human Protein Atlas, we queried single-cell RNA sequencing data for P2 purinergic receptor expression in small intestine, colon, and rectum. In silico analysis revealed high expression of P2Y1, P2Y2, P2Y11 and P2X4 among the purinergic receptors throughout the gastrointestinal tract. Interestingly, P2Y1 showed highest expression in intestinal enterocytes and goblet cells. Further, we compared P2 receptor expression between commonly used, cancer-derived intestinal cell lines (T84, HT29 and Caco2) and crypt-derived human intestinal organoids (HIOs). Both HIOs and T84 and Caco2 cell lines had similar mRNA expressions of P2Y1, P2Y2, P2Y11 and P2X4. However, live calcium imaging studies showed robust responses to P2Y receptor-specific agonists in HIOs, particularly P2Y1 and P2Y2 agonists, but the cancer-derived cell lines failed to respond to these agonists, suggesting these cell lines have defects in P2Y signaling. Functionally, blocking P2Y1, but not P2Y2, significantly delayed wound healing in epithelial scratch assays, indicating a potential role in epithelial injury repair. To delineate the role of epithelial P2Y1 in vivo, we generated VillinCre P2Y1flex/flox mice. At baseline, the knockout animals did not exhibit any overt intestinal defects; however, in the DSS-induced colitis model, the epithelial P2Y1 KO mice had significantly greater weight loss and epithelial damage than their wildtype littermates. These findings confirm that the gastrointestinal tract express P2Y1, P2Y2, P2Y11 and P2X4 purinergic receptors and P2Y1 signaling plays important functional roles in both gastrointestinal epithelial homeostasis and repair of injury.