Dual Oxidases Control Release of Hydrogen Peroxide by the Gastric Epithelium to Prevent Helicobacter felis Infection and Inflammation in Mice

Abstract

Background & Aims Dual oxidases (DUOX) are conserved NADPH oxidases that produce H2O2 at the epithelial cell surface. The DUOX enzyme comprises the DUOX and DUOXA (DUOX maturation factor) subunits. Mammalian genomes encode 2 DUOX isoenzymes (DUOX1–DUOXA1 and DUOX2–DUOXA2). Expression of these genes is upregulated during bacterial infection and chronic inflammatory diseases of the luminal gastrointestinal tract. The roles of DUOX in cellular interactions with microbes have not been determined in higher vertebrates. Methods Mice with disruptions of Duoxa1 and Duoxa2 genes (Duoxa−/− mice) and control mice were infected with Helicobacter felis to create a model of Helicobacter pylori infection—the most common human chronic infection. Results Infection with H felis induced expression of Duox2 and Duoxa2 in the stomachs of wild-type mice, and DUOX protein specifically localized to the apical surface of epithelial cells. H felis colonized the mucus layer in the stomachs of Duoxa−/− mice to a greater extent than in control mice. The increased colonization persisted into the chronic phase of infection and correlated with an increased, yet ineffective, inflammatory response. H felis colonization was also increased in Duoxa+/− mice, compared with controls. We observed reduced expression of the H2O2-inducible katA gene in H felis that colonized Duoxa−/− mice, compared with that found in controls (P=.0002), indicating that Duox causes oxidative stress in these bacteria. In vitro, induction of oxidative defense by H felis failed to prevent a direct bacteriostatic effect, at sustained levels of H2O2 as low as 30 μM. Conclusions Based on studies of Duoxa−/− mice, the DUOX enzyme complex prevents gastric colonization by H felis and the inflammatory response. These findings indicate the non-redundant function of epithelial production of H2O2 in restricting microbial colonization.

The Helicobacter pylori CZB Cytoplasmic Chemoreceptor TlpD Forms an Autonomous Polar Chemotaxis Signaling Complex That Mediates a Tactic Response to Oxidative Stress

“…We furthermore determined that TlpD mediates a repellent response to compounds that generate ROS. Oxygen and ROS are ubiquitous in the stomach, where H. pylori resides, arising from both epithelial and immune cells (31,50). Our findings thus suggest a model in which TlpD is used to help H. pylori avoid regions with high ROS, as discussed below.…”

“…H. pylori is exposed to ROS produced in the stomach by both epithelial and phagocytic cells (31,50,64). The ability to survive ROS appears to be critical during H. pylori colonization, as antioxidant enzymes are highly expressed by this microbe, and mutants lacking them are attenuated in colonizing animal hosts (43,65).…”

“…Others have documented that epithelial cells of the stomach release hydrogen peroxide that exposes the related Helicobacter felis to ROS, consistent with the idea that gastric Helicobacter spp. are regularly exposed to ROS (50). Additionally, there is a recently appreciated radial oxygen gradient emanating from the tissue to the lumen of the gastrointestinal tract.…”

Aquaporin-3 mediates hydrogen peroxide-dependent responses to environmental stress in colonic epithelia

“…Studies in Drosophila, Caenorhabditis elegans, and zebrafish intestine have shown that epithelial production of H 2 O 2 is part of the host response to gut infection and is involved in microbial clearance and responses to gut symbionts and pathogens (28)(29)(30). In mammals, a similar role has been postulated based on studies of pathogen infection in stomach and airway ECs (31,32).…”

Nox/Duox Family of NADPH Oxidases: Lessons from Knockout Mouse Models

“…In non-vertebrates, such as Drosophila, zebrafish, and Caenorhabditis elegans, a growing cluster of data supports the indispensable role of Duox in gastrointestinal control of commensal, foodborne, or pathogenic microorganisms [61][62][63]. Recently, an interesting study on DuoxA double knockout mice confirmed the protective role of Duox2-derived H 2 O 2 , as it prevented the gastric colonization by Helicobacter felis and attendant inflammatory responses [64]. This study was the first in vivo genetic demonstration in a mammalian organism of how Duox can control the colonization of a noninvasive pathogen of the mucus layer.…”