Nitric oxide evokes an adaptive response to oxidative stress by arresting respiration.
Aerobic metabolism generates biologically challenging reactive oxygen species (ROS) by the endogenous autooxidation of components of the electron transport chain (ETC). Basal levels of oxidative stress can dramatically rise upon activation of the NADPH oxidase-dependent respiratory burst. To minimize ROS toxicity, prokaryotic and eukaryotic organisms express a battery of low-molecular-weight thiol scavengers, a legion of detoxifying catalases, peroxidases, and superoxide dismutases, as well as a variety of repair systems. We present herein blockage of bacterial respiration as a novel strategy that helps the intracellular pathogen Salmonella survive extreme oxidative stress conditions. A Salmonella strain bearing mutations in complex I NADH dehydrogenases is refractory to the early NADPH oxidase-dependent antimicrobial activity of IFNgamma-activated macrophages. The ability of NADH-rich, complex I-deficient Salmonella to survive oxidative stress is associated with resistance to peroxynitrite (ONOO(-)) and hydrogen peroxide (H(2)O(2)). Inhibition of respiration with nitric oxide (NO) also triggered a protective adaptive response against oxidative stress. Expression of the NDH-II dehydrogenase decreases NADH levels, thereby abrogating resistance of NO-adapted Salmonella to H(2)O(2). NADH antagonizes the hydroxyl radical (OH(.)) generated in classical Fenton chemistry or spontaneous decomposition of peroxynitrous acid (ONOOH), while fueling AhpCF alkylhydroperoxidase. Together, these findings identify the accumulation of NADH following the NO-mediated inhibition of Salmonella's ETC as a novel antioxidant strategy. NO-dependent respiratory arrest may help mitochondria and a plethora of organisms cope with oxidative stress engendered in situations as diverse as aerobic respiration, ischemia reperfusion, and inflammation.
Husain
Maroof
M
Department of Microbiology, University of Colorado Health Sciences Center at Fitzsimons, Aurora, Colorado 80045, USA.
Bourret
Travis J
TJ
McCollister
Bruce D
BD
Jones-Carson
Jessica
J
Laughlin
James
J
Vázquez-Torres
Andrés
A
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial / Q000235:genetics; D045222:Electron Transport Chain Complex Proteins / Q000235:genetics / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000201:enzymology* / Q000382:microbiology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000235:genetics; D054464:Peroxiredoxins / Q000235:genetics / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016897:Respiratory Burst / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000201:enzymology* / Q000235:genetics; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D045222:Electron Transport Chain Complex Proteins; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D007371:Interferon-gamma; D054464:Peroxiredoxins; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D009252:NADPH Dehydrogenase