The NADPH oxidase 1 (Nox1) is a gp91phox homologue preferentially expressed in the colon. We have established primary cultures of guinea pig large intestinal epithelial cells giving 90% purity of surface mucous cells. These cells spontaneously released superoxide anion (O 2-) of 160 nmol/mg protein/h and expressed the Nox1, p22phox, p67phox, and Rac1 mRNAs, but not the gp91 phox, Nox4, p47phox, p40phox, and Rac2 mRNAs. They also expressed novel homologues of p47phox and p67 phox (p41nox and p51nox, respectively). Human colon cancer cell lines (T84 and Caco2 cells) expressed the Nox1, p22 phox, p51nox, and Rac1 mRNAs, but not the other NADPH component mRNAs, and secreted only small amounts of O2- (<2 nmol/mg protein/h). Cotransfection of p41nox and p51 nox cDNAs in T84 cells enhanced PMA-stimulated O2 - release 5-fold. Treatment of the transfected T84 cells with recombinant flagellin (rFliC) from Salmonella enteritidis further augmented the O2- release in association with the induction of Nox1 protein. The enhanced O2- production by cotransfection of p41nox and p51nox vectors further augmented the rFliC-stimulated IL-8 release from T84 cells. T84 cells expressed the Toll-like receptor 5, and rFliC rapidly phosphorylated TGF-β-activated kinase 1 and TGF-β-activated kinase 1-binding protein 1. A potent inhibitor for NF-κB (pyrrolidine dithiocarbamate) significantly blocked the rFliC-primed increase in O2- production and induction of Nox1 protein. These results suggest that p41nox and p51 nox are involved in the Nox1 activation in surface mucous cells of the colon, and besides that, epithelial cells discern pathogenicities among bacteria to appropriately operate Nox1 for the host defense.
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