Neuronal NOS-mediated nitration and inactivation of manganese superoxide dismutase in brain after experimental and human brain injury.
Manganese superoxide dismutase (MnSOD) provides the first line of defense against superoxide generated in mitochondria. SOD competes with nitric oxide for reaction with superoxide and prevents generation of peroxynitrite, a potent oxidant that can modify proteins to form 3-nitrotyrosine. Thus, sufficient amounts of catalytically competent MnSOD are required to prevent mitochondrial damage. Increased nitrotyrosine immunoreactivity has been reported after traumatic brain injury (TBI); however, the specific protein targets containing modified tyrosine residues and functional consequence of this modification have not been identified. In this study, we show that MnSOD is a target of tyrosine nitration that is associated with a decrease in its enzymatic activity after TBI in mice. Similar findings were obtained in temporal lobe cortical samples obtained from TBI cases versus control patients who died of causes not related to CNS trauma. Increased nitrotyrosine immunoreactivity was detected at 2 h and 24 h versus 72 h after experimental TBI and co-localized with the neuronal marker NeuN. Inhibition and/or genetic deficiency of neuronal nitric oxide synthase (nNOS) but not endothelial nitric oxide synthase (eNOS) attenuated MnSOD nitration after TBI. At 24 h after TBI, there was predominantly polymorphonuclear leukocytes accumulation in mouse brain whereas macrophages were the predominant inflammatory cell type at 72 h after injury. However, a selective inhibitor or genetic deficiency of inducible nitric oxide synthase (iNOS) failed to affect MnSOD nitration. Nitration of MnSOD is a likely consequence of peroxynitrite within the intracellular milieu of neurons after TBI. Nitration and inactivation of MnSOD could lead to self-amplification of oxidative stress in the brain progressively enhancing peroxynitrite production and secondary damage.
Bayir
Hülya
H
Safar Center for Resuscitation Research, Pittsburgh, Pennsylvania 15260, USA. bayihx@ccm.upmc.edu
Kagan
Valerian E
VE
Clark
Robert S B
RS
Janesko-Feldman
Keri
K
Rafikov
Ruslan
R
Huang
Zhentai
Z
Zhang
Xiaojing
X
Vagni
Vincent
V
Billiar
Timothy R
TR
Kochanek
Patrick M
PM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000503:physiopathology; D001930:Brain Injuries / Q000201:enzymology* / Q000503:physiopathology; D002634:Chemotaxis, Leukocyte; D004660:Encephalitis / Q000201:enzymology* / Q000209:etiology / Q000503:physiopathology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008875:Middle Aged; D009410:Nerve Degeneration / Q000201:enzymology* / Q000503:physiopathology; D009566:Nitrates / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000096:biosynthesis
D004791:Enzyme Inhibitors; D009566:Nitrates; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D052248:Nitric Oxide Synthase Type I; D013482:Superoxide Dismutase