Duox‐a novel antimicrobial duodenal defense mechanism

Antimicrobial defense mechanisms are necessary to maintain relative foregut sterility. We hypothesized that dual oxidase (Duox), a H 2 O 2 generating system in airway, is also present in duodenum, and that Duox‐generated H 2 O 2 activates cytosolic phospholipase A2 (cPLA 2 ) in the prostaglandin (PG) synthesis. We measured duodenal HCO 3 − secretion (DBS) with pH and CO 2 electrodes in the perfused duodenum of anesthetized rats. ATP or pH 2.2 acid was luminally perfused +/− NADPH oxidase inhibitor DPI or VAS2870, P2Y receptor antagonist suramin, cPLA 2 inhibitor OBAA, or indomethacin pretreatment (IND). H 2 O 2 in the perfusate was measured with Amplex Red; ATP using bioluminescence. Duox2 and its chaperone DuoxA2 were expressed on the duodenal villous brush border. Acid exposure increased DBS with releasing ATP and H 2 O 2 . DPI or VAS2870 inhibited DBS and H 2 O 2 output without affecting ATP release. Luminal ATP increased DBS and H 2 O 2 output, both inhibited by DPI or suramin. IND or OBAA inhibited ATP‐induced DBS without affecting H 2 O 2 output. H 2 O 2 exposure stimulated DBS. Luminal acid increases ATP release, increasing intracellular Ca 2+ via P2Y receptor activation, then activates Duox2, generating H 2 O 2 . Luminal H 2 O 2 activates cPLA 2 , increasing PG production, then stimulates DBS. The ATP‐P2Y‐Duox pathway generates antimicrobial luminal H 2 O 2 while increasing acid‐neutralizing DBS. VA Merit Review, NIH R01 DK54221