Microbiota-driven changes in colitis susceptibility in CGD mice are associated with alterations in intestinal epithelial reactive oxygen species production and NADPH oxidase subunit gene expression

Chronic granulomatous disease (CGD) is an inborn error of immunity caused by defects in any one of the 6 subunits (gp91phox, p47phox, p22phox, p67phox, p40phox or chaperone EROS) forming the nicotinamide adenine dinucleotide phosphate oxidase (NADPH) complex 2 (NOX2) resulting in defective phagocyte-derived reactive oxygen species (ROS) production. Almost 50% of patients with CGD suffer from inflammatory bowel disease (IBD). While ROS plays an important role in intestinal homeostasis, the impact of NOX2 defects on intestinal barrier ROS levels is unknown. We previously demonstrated that the intestinal microbiome is a critical driver of colitis susceptibility in mice with CGD. Given the importance of ROS at the intestinal barrier, we hypothesize that the microbiota drives intestinal inflammation by modulating NOX-derived intestinal epithelial ROS production. To determine whether microbiota-driven changes in colitis susceptibility in mice with CGD are associated with alterations in intestinal epithelial ROS production and NOX gene expression. Susceptibility to dextran sodium sulfate (DSS) colitis was evaluated in CGD mice with distinct microbiota: 1) gp91phox-/- -mice from NIH (non-colitogenic microbiota), 2) gp91phox-/- -mice from IRCM (colitogenic microbiota), 3) p47phox-/- -mice from NIH and IRCM (colitogenic microbiota) and wild type (WT) mice cross-fostered with p47phox-/- -mice (i.e. WT mice colonized with the colitogenic p47phox-/-microbiota). ROS production and NOX (i.e. NOX1, NOX4, NOX2, DUOX2) gene expression was measured in colon epithelial cells isolated from mice used in the aforementioned colitis experiments. NIH gp91phox-/- -mice did not have increased colitis susceptibility compared to WT mice whereas IRCM gp91phox-/- -mice, p47phox-/- -mice from both facilities and cross-fostered WT mice had increased susceptibility to DSS colitis. Intestinal epithelial cells sorted from mice with increased colitis susceptibility produced more ROS and were associated with distinct patterns of NOX subunit gene expression. Our data suggest the microbiota may drive intestinal inflammation in mice with CGD by increasing NOX-derived ROS production in the intestinal epithelium. These findings bring forward a possible mechanism by which the microbiota contributes to the pathogenesis of CGD-associated IBD.