Neurotoxic activation of microglia is promoted by a nox1-dependent NADPH oxidase.
Reactive oxygen species (ROS) modulate intracellular signaling but are also responsible for neuronal damage in pathological states. Microglia, the resident CNS macrophages, are prominent sources of ROS through expression of the phagocyte oxidase which catalytic subunit Nox2 generates superoxide ion (O2(.-)). Here we show that microglia also express Nox1 and other components of nonphagocyte NADPH oxidases, including p22(phox), NOXO1, NOXA1, and Rac1/2. The subcellular distribution and functions of Nox1 were determined by blocking Nox activity with diphenylene iodonium or apocynin, and by silencing the Nox1 gene in microglia purified from wild-type (WT) or Nox2-KO mice. [Nox1-p22(phox)] dimers localized in intracellular compartments are recruited to phagosome membranes during microglial phagocytosis of zymosan, and Nox1 produces O2(.-) in zymosan-loaded phagosomes. In microglia activated with lipopolysaccharide (LPS), Nox1 produces O2(.-), which enhances cell expression of inducible nitric oxide synthase and secretion of interleukin-1beta. Comparisons of microglia purified from WT, Nox2-KO, or Nox1-KO mice indicate that both Nox1 and Nox2 are required to optimize microglial production of nitric oxide. By injecting LPS in the striatum of WT and Nox1-KO mice, we show that Nox1 also enhances microglial production of cytotoxic nitrite species and promotes loss of presynaptic proteins in striatal neurons. These results demonstrate the functional expression of Nox1 in resident CNS phagocytes, which can promote production of neurotoxic compounds during neuroinflammation. Our study also shows that Nox1- and Nox2-dependent oxidases play distinct roles in microglial activation and that Nox1 is a possible target for the treatment of neuroinflammatory states.
Chéret
Cyril
C
Inserm, Unité Mixte de Recherche (UMR) 711, Institut Fédératif de Recherche 70, 75013 Paris, France.
Gervais
Annie
A
Lelli
Aurélia
A
Colin
Catherine
C
Amar
Lahouari
L
Ravassard
Philippe
P
Mallet
Jacques
J
Cumano
Ana
A
Krause
Karl-Heinz
KH
Mallat
Michel
M
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology; D003573:Cytochrome b Group / Q000235:genetics / Q000378:metabolism; D004660:Encephalitis / Q000201:enzymology* / Q000503:physiopathology; D005260:Female; D005911:Gliosis / Q000201:enzymology* / Q000503:physiopathology; D018836:Inflammation Mediators / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015054:Zymosan / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein
D048868:Adaptor Proteins, Signal Transducing; D003573:Cytochrome b Group; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D009479:Neuropeptides; D009498:Neurotoxins; D009573:Nitrites; C472286:Noxa1 protein, mouse; C472287:Noxo1 protein, mouse; D011506:Proteins; C484602:Rac1 protein, mouse; D017382:Reactive Oxygen Species; D015054:Zymosan; D009247:NADH, NADPH Oxidoreductases; C488842:Cybb protein, mouse; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C000614711:NOX1 protein, mouse; C515614:Cyba protein, mouse; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein