Role of Nox family NADPH oxidases in host defense.
The phagocytic NADPH oxidase is recognized as a critical component of innate immunity, responsible for generation of microbicidal reactive oxygen species (ROS). This enzyme is one representative of the Nox family of oxidases (Nox1-Nox5, Duox1, and Duox2) that exhibit diverse expression patterns and appear to serve a variety of functions related to ROS generation. Mounting evidence now suggests that several of these novel oxidases also serve in host defense, particularly those showing high expression along epithelial surfaces exposed to the external environment. Within these sites, Nox enzymes tend to be located on apical cell surfaces and release ROS into extracellular environments, where they can be used by known antimicrobial peroxidases. Moreover, microbial factors were shown in several cases to cause higher ROS production, either by direct oxidase activation or by inducing higher oxidase expression. Several oxidases are also induced by immune cytokines, including interferon-gamma, interleukin (IL)-4, and IL-13. Although most of the evidence supporting host defense roles for mammalian nonphagocytic oxidases remains circumstantial, recent evidence indicates that Drosophila Duox plays a role in host resistance to infection. Finally, oxidative defense against invading pathogens appears to be an ancient protective mechanism, because related oxidases are known to participate in disease resistance in plants.
Leto
Thomas L
TL
Molecular Defenses Section, Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852, USA. tleto@nih.gov
Geiszt
Miklos
M
D000818:Animals; D000074623:Dual Oxidases; D005420:Flavoproteins / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D008954:Models, Biological; D000074624:NADPH Oxidase 1; D000074664:NADPH Oxidase 5; D019255:NADPH Oxidases / Q000378:metabolism* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism
D005420:Flavoproteins; D007527:Isoenzymes; D008565:Membrane Proteins; D017382:Reactive Oxygen Species; D000074623:Dual Oxidases; D000074624:NADPH Oxidase 1; D000074664:NADPH Oxidase 5; D019255:NADPH Oxidases; C402799:NOX1 protein, human; C431571:NOX5 protein, human; C431513:DUOX1 protein, human