Dismutase Knockout Mice Research Articles

Gender differences in myogenic tone in superoxide dismutase knockout mouse: animal model of oxidative stress

Oxidative stress mediated by prooxidants has been implicated in the pathogenesis of vascular disorders. However, the effect of prooxidants on myogenic regulation of vascular function and the differential influence of gender is not known. SOD, an intracellular enzyme, restricts excess prooxidant levels and may limit vascular dysfunction. We therefore tested the effects of Cu,Zn SOD deficiency on vascular tone in both male and female SOD knockout (SOD-/-) mice. We hypothesized that myogenic tone would be enhanced in SOD-/- mice by excess prooxidants compared with wild-type control mice. Indeed, resistance-sized mesenteric arteries from SOD-/- mice exhibited enhanced myogenic tone compared with control mice. Myogenic tone was lower in female than male control mice. Interestingly, this gender effect was absent in SOD-/- mice, such that myogenic tone of mesenteric arteries from females was equated to that of arteries from males. Furthermore, the pathways that modulate myogenic tone were diverse. In both male and female control mice, inhibition of prostaglandin H synthase (PGHS) and nitric oxide synthase (NOS) pathways enhanced myogenic tone. In female SOD-/- mice, inhibition of PGHS and NOS pathways enhanced myogenic tone to a greater extent compared with control mice. Conversely, in male SOD-/- mice, NOS and PGHS inhibition did not alter tone and only inhibition of gap junctions enhanced myogenic tone. In conclusion, this study revealed enhanced myogenic tone in SOD-/- mice compared with control mice. Furthermore, Cu,Zn SOD deficiency particularly enhanced myogenic tone in female mice such that their vascular tone attained the level of male SOD-/- mice, possibly mediated by prooxidants.

Endothelial-dependent vasodilation is reduced in mesenteric arteries from superoxide dismutase knockout mice.

Oxidative stress has increasingly been implicated in the development and progression of many vascular diseases. Previous work from our laboratory indicated that peroxynitrite alters vasoactive pathways in endothelial cells, which could potentially reduce vascular relaxation. To test this hypothesis in vivo, we utilized an animal model of endogenous oxidative stress, the CuZn superoxide dismutase (SOD) knockout mouse, to assess vascular function. Vascular reactivity of mouse mesenteric arteries was assessed in the presence or absence of inhibitors to nitric oxide synthase (NOS) and/or prostaglandin H synthase (PGHS). Endothelial-dependent function was also measured after the addition of exogenous SOD. Peroxynitrite formation was detected by nitrotyrosine immunofluorescence in mesenteric arteries. Our data indicate that endothelial-dependent relaxation responses to methacholine are highly reduced in SOD-/- mice (P<0.01, ANOVA). In only the wild-type mice, NOS or PGHS inhibition significantly blunted relaxation, suggesting that vasodilators from these pathways are present only in the controls and not in SOD-/- mice. A combination of NOS and PGHS inhibitors reduced methacholine relaxation in both wild type and SOD-/- mice. This residual EDHF-like relaxation was not different between groups. After incubation with exogenous SOD, endothelial-dependent relaxation could be partially restored in SOD-/- mice, due to increased NOS-mediated vasodilation. In addition, peroxynitrite formation was significantly elevated in mesenteric arteries from SOD-/- mice. Our data suggest that in a novel animal model of oxidative stress, vessel function is compromised due to alterations in NOS and PGHS-dependent relaxation responses.

The effect of hyperoxia and N-acetylcysteine on the lungs of neonatal manganese superoxide dismutase knockout mice: [formula omitted], Ting-Ting Huang 2, Hannu Sariola 3, Anna-Liisa Levonen 1, Elaine Carlson 2, Risto Lapatto 1, Charles J. Epstein 2, Kari O. Raivio 1. 1Hospital for Children and Adolescents, Univ. of Helsinki, Helsinki, Finland; 2Department of Pediatrics, Univ. of California, San Francisco, USA;

The effect of hyperoxia and N-acetylcysteine on the lungs of neonatal manganese superoxide dismutase knockout mice: [formula omitted], Ting-Ting Huang 2, Hannu Sariola 3, Anna-Liisa Levonen 1, Elaine Carlson 2, Risto Lapatto 1, Charles J. Epstein 2, Kari O. Raivio 1. 1Hospital for Children and Adolescents, Univ. of Helsinki, Helsinki, Finland; 2Department of Pediatrics, Univ. of California, San Francisco, USA;

Increased Oxidative Damage Is Correlated to Altered Mitochondrial Function in Heterozygous Manganese Superoxide Dismutase Knockout Mice

This study characterizes mitochondria isolated from livers of Sod2(-/+) and Sod2(+/+) mice. A 50% decrease in manganese superoxide dismutase (MnSOD) activity was observed in mitochondria isolated from Sod2(-/+) mice compared with Sod2(+/+) mice, with no change in the activities of either glutathione peroxidase or copper/zinc superoxide dismutase. However, the level of total glutathione was 30% less in liver mitochondria of the Sod2(-/+) mice. The reduction in MnSOD activity in Sod2(-/+) mice was correlated to an increase in oxidative damage to mitochondria: decreased activities of the Fe-S proteins (aconitase and NADH oxidoreductase), increased carbonyl groups in proteins, and increased levels of 8-hydroxydeoxyguanosine in mitochondrial DNA. In contrast, there were no significant changes in oxidative damage in the cytosolic proteins or nuclear DNA. The increase in oxidative damage in mitochondria was correlated to altered mitochondrial function. A significant decrease in the respiratory control ratio was observed in mitochondria isolated from Sod2(-/+) mice compared with Sod2(+/+) mice for substrates metabolized by complexes I, II, and III. In addition, mitochondria isolated from Sod2(-/+) mice showed an increased rate of induction of the permeability transition. Therefore, this study provides direct evidence correlating reduced MnSOD activity in vivo to increased oxidative damage in mitochondria and alterations in mitochondrial function.