To distinguish the role of Mn superoxide dismutase (MnSOD) from that of cytoplasmic CuZn superoxide dismutase (CuZnSOD), the mouse MnSOD gene (Sod2) was inactivated by homologous recombination. Sod2−/− mice on a CD1 (outbred) genetic background die within the first 10 days of life (mean, 5.4 days) with a complex phenotype that includes dilated cardiomyopathy, accumulation of lipid in liver and skeletal muscle, metabolic acidosis and ketosis, and a severe reduction in succinate dehydrogenase (complex II) and aconitase (a TCA cycle enzyme) activities in the heart and, to a lesser extent, in other organs. These findings indicate that MnSOD is required to maintain the integrity of mitochondrial enzymes susceptible to direct inactivation by superoxide. On the other hand, Lebovitz et al. reported an independently derived MnSod null mouse (Sod2tmlLeb) on a mixed C57BL/6 and 129Sv background with a different phenotype. Because a difference in genetic background is the most likely explanation for the phenotypic differences, the two mutant lines were crossed into different genetic backgrounds for further analyses. To study the phenotype of Sod2tmlLeb mice CD1 background, the Sod2tmlLeb mice were crossed to CD1 for two generations before the −/+ mice were intercrossed to generate −/− mice. The life span distribution of CD1〈Sod2−/−〉Leb was shifted to the left, indicating a shortened life span on the CD1 background. Furthermore, the CD1〈Sod2−/−〉Leb mice develop metabolic acidosis at an early stage as was observed with CD1〈Sod2−/−〉Cje. When Sod2tmlCje was placed on C57BL/6J (B6) background, the −/− mice were found to die either during midgestation or within the first 4 days after birth. However, when the B6〈Sod2−/+〉Cje were crossed with DBA/2J (D2) for the generation of B6D2F2〈Sod2−/−〉Cje mice, an entirely different phenotype, similar to that described by Lebovitz et al., was observed. The F2 Sod−/− mice were able to survive up to 18 days, and the animals that lived for more than 15 days displayed neurological abnormalities including ataxia and seizures. Their hearts were not as severely affected as were those of the CD1 mice, and neurological degeneration rather than heart defect appears to be the cause of death.
"A recent study confirmed our results of sustained ROS formation till 72 h after burn, which attributed to defects in ROS defense including loss of membrane integrity and antioxidant defense in mitochondria . As SOD is one of main enzymatic antioxidants for scavenging superoxide, and thus relieve the cellular stress caused by superoxide anion and improve organ function under disease conditions , , the significant downregulation of kidney SOD activity after burn injury may contributed to the burn-mediated persistent oxidative damage to renal. "
[Show abstract][Hide abstract] ABSTRACT: Clinical evidence indicates that late acute renal failure (ARF) predicts high mortality in severely burned patients but the pathophysiology of late ARF remains undefined. This study was designed to test the hypothesis that sustained reactive oxygen species (ROS) induced late ARF in a severely burned rat model and to investigate the signaling mechanisms involved.
Rats were exposed to 100°C bath for 15 s to induce severe burn injury (40% of total body surface area). Renal function, ROS generation, tubular necrosis and apoptosis, and phosphorylation of MAPK and Akt were measured during 72 hours after burn.
Renal function as assessed by serum creatinine and blood urea nitrogen deteriorated significantly at 3 h after burn, alleviated at 6 h but worsened at 48 h and 72 h, indicating a late ARF was induced. Apoptotic cells and cleavage caspase-3 in the kidney went up slowly and turned into significant at 48 h and 72 h. Tubular cell ROS production shot up at 6 h and continuously rose during the 72-h experiment. Scavenging ROS with tempol markedly attenuated tubular apoptosis and renal dysfunction at 72 h after burn. Interestingly, renal p38 MAPK phosphorylation elevated in a time dependent manner whereas Akt phosphorylation increased during the first 24 h but decreased at 48 h after burn. The p38 MAPK specific inhibitor SB203580 alleviated whereas Akt inhibitor exacerbated burn-induced tubular apoptosis and renal dysfunction. Furthermore, tempol treatment exerted a duplex regulation through inhibiting p38 MAPK phosphorylation but further increasing Akt phosphorylation at 72 h postburn.
These results demonstrate that sustained renal ROS overproduction induces continuous tubular cell apoptosis and thus a late ARF at 72 h after burn in severely burned rats, which may result from ROS-mediated activation of p38 MAPK but a late inhibition of Akt phosphorylation.
PLoS ONE 01/2013; 8(1):e54593. DOI:10.1371/journal.pone.0054593 · 3.23 Impact Factor
"O 2 @BULLET− is involved in both physiological and pathological processes , with O 2 @BULLET− overproduction implicated in a range of inflammatory states such as rheumatoid arthritis, osteoarthritis, arteriosclerosis, and ischemia– reperfusion . The toxicity of increased O 2 @BULLET− levels is evident in homozygous SOD2 knockout mice, which die within the first 3 weeks of age . O 2 @BULLET− can inactivate a range of enzymes in addition to causing direct molecular damage by initiating lipoperoxidation, leading to the destruction of neurotransmitters and hormones, and DNA single-strand damage . "
[Show abstract][Hide abstract] ABSTRACT: Superoxide (O(2)(•-)) is implicated in inflammatory states including arteriosclerosis and ischemia-reperfusion injury. Cobalamin (Cbl) supplementation is beneficial for treating many inflammatory diseases and also provides protection in oxidative-stress-associated pathologies. Reduced Cbl reacts with O(2)(•-) at rates approaching that of superoxide dismutase (SOD), suggesting a plausible mechanism for its anti-inflammatory properties. Elevated homocysteine (Hcy) is an independent risk factor for cardiovascular disease and endothelial dysfunction. Hcy increases O(2)(•-) levels in human aortic endothelial cells (HAEC). Here, we explore the protective effects of Cbl in HAEC exposed to various O(2)(•-) sources, including increased Hcy levels. Hcy increased O(2)(•-) levels (1.6-fold) in HAEC, concomitant with a 20% reduction in cell viability and a 1.5-fold increase in apoptotic death. Pretreatment of HAEC with physiologically relevant concentrations of cyanocobalamin (CNCbl) (10-50nM) prevented Hcy-induced increases in O(2)(•-) and cell death. CNCbl inhibited both Hcy and rotenone-induced mitochondrial O(2)(•-) production. Similarly, HAEC challenged with paraquat showed a 1.5-fold increase in O(2)(•-) levels and a 30% decrease in cell viability, both of which were prevented with CNCbl pretreatment. CNCbl also attenuated elevated O(2)(•-) levels after exposure of cells to a Cu/Zn-SOD inhibitor. Our data suggest that Cbl acts as an efficient intracellular O(2)(•-) scavenger.
Free Radical Biology and Medicine 06/2011; 51(4):876-83. DOI:10.1016/j.freeradbiomed.2011.05.034 · 5.74 Impact Factor
"SOD1 is an antioxidant isoenzyme mainly localized in the cytosol that dismutates superoxide anions to hydrogen peroxide (Fridovich 1975). SOD1 is constitutively present in all cells (Huang et al. 1999). In animals that overexpress SOD1, cytochrome c release and neuronal death were highly inhibited after FCI (Kinouchi et al. 1991; Chan 1996; Fujimura et al. 2000), tGCI (Murakami et al. 1997; Chan et al. 1998; Endo et al. 2006b), and subarachnoid hemorrhage (Endo et al. 2007). "
[Show abstract][Hide abstract] ABSTRACT: Mitochondria are the powerhouse of the cell. Their primary physiological function is to generate adenosine triphosphate through oxidative phosphorylation via the electron transport chain. Reactive oxygen species generated from mitochondria have been implicated in acute brain injuries such as stroke and neurodegeneration. Recent studies have shown that mitochondrially-formed oxidants are mediators of molecular signaling, which is implicated in the mitochondria-dependent apoptotic pathway that involves pro- and antiapoptotic protein binding, the release of cytochrome c, and transcription-independent p53 signaling, leading to neuronal death. Oxidative stress and the redox state of ischemic neurons are also implicated in the signaling pathway that involves phosphatidylinositol 3-kinase/Akt and downstream signaling, which lead to neuronal survival. Genetically modified mice or rats that over-express or are deficient in superoxide dismutase have provided strong evidence in support of the role of mitochondrial dysfunction and oxidative stress as determinants of neuronal death/survival after stroke and neurodegeneration.
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