Local resistance to oxidative stress by overexpression of copper-zinc superoxide dismutase limits neointimal formation after angioplasty

Inhibition of Neointima Hyperplasia, Inflammation, and Reactive Oxygen Species in Balloon-Injured Arteries by HVJ Envelope Vector-Mediated Delivery of Superoxide Dismutase Gene

Extracellular superoxide dismutase (EC-SOD) has been implicated in regulation of vascular function but its underlying molecular mechanism is largely unknown. These two-step experiments investigate whether hemagglutinating virus of Japan envelope (HVJ-E) vector-mediated EC-SOD gene delivery might protect against neointima formation, vascular inflammation, and reactive oxygen species (ROS) generation, and also explore cell growth signaling pathways. The first in-vitro experiment was performed to assess the transfection efficacy and safety of HVJ-E compared to lipofectamine®. Results revealed that HVJ-E has higher transfection efficiency and lower cytotoxicity than those of lipofectamine®. Another in-vivo study initially used balloon denudation to rat carotid artery, then delivered EC-SOD cDNA through the vector of HVJ-E. Arterial section with H&E staining from the animals 14 days after balloon injury showed a significant reduction of intima-to-media area ratio in EC-SOD transfected arteries when compared with control (empty vector-transfected arteries) (p < 0.05). Arterial tissue with EC-SOD gene delivery also exhibited lower levels of ROS, as assessed by fluorescent microphotography with dihydroethidium staining. Quantitative RT-PCR revealed that EC-SOD gene delivery significantly diminished mRNA expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β (p < 0.05 in all comparisons). An immunoblotting assay from vascular smooth muscle cell (VSMC) cultures showed that the EC-SOD transfected group attenuated the activation of MEK1/2, ERK1/2, and Akt signaling significantly. In conclusion, EC-SOD overexpression by HVJ-E vector inhibits neointima hyperplasia, inflammation, and ROS level triggered by balloon injury. The modulation of cell growth-signaling pathways by EC-SOD in VSMCs might play an important role in these inhibitory effects.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Sex-based differential regulation of oxidative stress in the vasculature by nitric oxide

Background

Nitric oxide (^•NO) is more effective at inhibiting neointimal hyperplasia following arterial injury in male versus female rodents, though the etiology is unclear. Given that superoxide (O₂^•−) regulates cellular proliferation, and ^•NO regulates superoxide dismutase-1 (SOD-1) in the vasculature, we hypothesized that ^•NO differentially regulates SOD-1 based on sex.

Materials and methods

Male and female vascular smooth muscle cells (VSMC) were harvested from the aortae of Sprague-Dawley rats. O₂^•− levels were quantified by electron paramagnetic resonance (EPR) and HPLC. sod-1 gene expression was assayed by qPCR. SOD-1, SOD-2, and catalase protein levels were detected by Western blot. SOD-1 activity was measured via colorimetric assay. The rat carotid artery injury model was performed on Sprague-Dawley rats ±^•NO treatment and SOD-1 protein levels were examined by Western blot.

Results

In vitro, male VSMC have higher O₂^•− levels and lower SOD − 1 activity at baseline compared to female VSMC (P < 0.05). ^•NO decreased O₂^•− levels and increased SOD − 1 activity in male (P<0.05) but not female VSMC. ^•NO also increased sod− 1 gene expression and SOD − 1 protein levels in male (P<0.05) but not female VSMC. In vivo, SOD-1 levels were 3.7-fold higher in female versus male carotid arteries at baseline. After injury, SOD-1 levels decreased in both sexes, but ^•NO increased SOD-1 levels 3-fold above controls in males, but returned to baseline in females.

Conclusions

Our results provide evidence that regulation of the redox environment at baseline and following exposure to ^•NO is sex-dependent in the vasculature. These data suggest that sex-based differential redox regulation may be one mechanism by which ^•NO is more effective at inhibiting neointimal hyperplasia in male versus female rodents.

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The baseline redox environment in the vascular is sex-dependent.

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Nitric oxide differentially affects the vascular redox environment between the sexes.

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Nitric oxide decreases superoxide (O₂^.) levels, by increasing SOD-1 activity, sod1 gene expression and SOD-1 protein levels in male vascular smooth muscle cells, but not in females.

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Sex-based differential redox regulation may be one mechanism by which is more effective at inhibiting neointimal hyperplasia in male versus female rodents.

Nitric oxide inhibits neointimal hyperplasia following vascular injury via differential, cell-specific modulation of SOD-1 in the arterial wall

Superoxide (O2(•-)) promotes neointimal hyperplasia following arterial injury. Conversely, nitric oxide ((•)NO) inhibits neointimal hyperplasia through various cell-specific mechanisms, including redox regulation. What remains unclear is whether (•)NO exerts cell-specific regulation of the vascular redox environment following arterial injury to inhibit neointimal hyperplasia. Therefore, the aim of the present study was to assess whether (•)NO exerts cell-specific, differential modulation of O2(•-) levels throughout the arterial wall, establish the mechanism of such modulation, and determine if it regulates (•)NO-dependent inhibition of neointimal hyperplasia. In vivo, (•)NO increased superoxide dismutase-1 (SOD-1) levels following carotid artery balloon injury in a rat model. In vitro, (•)NO increased SOD-1 levels in vascular smooth muscle cells (VSMC), but had no effect on SOD-1 in endothelial cells or adventitial fibroblasts. This SOD-1 increase was associated with an increase in sod1 gene expression, increase in SOD-1 activity, and decrease in O2(•-) levels. Lastly, to determine the role of SOD-1 in (•)NO-mediated inhibition of neointimal hyperplasia, we performed the femoral artery wire injury model in wild type and SOD-1 knockout (KO) mice, with and without (•)NO. Interestingly, (•)NO inhibited neointimal hyperplasia only in wild type mice, with no effect in SOD-1 KO mice. In conclusion, these data show the cell-specific modulation of O2(•-) by (•)NO through regulation of SOD-1 in the vasculature, highlighting its importance on the inhibition of neointimal hyperplasia. These results also shed light into the mechanism of (•)NO-dependent redox balance, and suggest a novel VSMC redox target to prevent neointimal hyperplasia.

Deficiency of CuZn superoxide dismutase promotes inflammation and alters medial structure following vascular injury

AIM

The anti-oxidant enzyme copper/zinc superoxide dismutase (CuZnSOD) metabolizes superoxide anion (O(2)(-)) in vascular cells. However, the role of CuZnSOD in vascular injury remains poorly understood.

METHODS

Using CuZnSOD-deficient (CuZnSOD(-/-)) mice and wild-type (WT) mice, we investigated morphometric changes and the role of O(2)(-) in vascular remodeling after femoral artery injury induced by an external vascular cuff model.

RESULTS

Three days post-injury, inflammatory cell infiltration increased significantly. Moreover, the percent positive area of tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in media were higher in CuZnSOD(-/-) mice than in WT mice (TNF-α: 34.8±8.4% versus 18.8±5.6%, p < 0.05, ICAM-1: 29.6±6.5% versus 11.0±2.8%, p < 0.05, VCAM-1: 23.5±7.5% versus 3.7±1.1%, p < 0.05). mRNA expression of iNOS was markedly increased in CuZnSOD(-/-) mice with cuff injury. Dihydroethidine staining revealed increased levels of vascular O(2)(-) in media from CuZnSOD(-/-) mice. Although neointimal formation remained unchanged, 14 days postinjury, we observed degeneration of the media, and the media/vessel wall ratio increased in CuZnSOD(-/-) mice (40.4±2.1% versus 26.8±1.4%, p < 0.05). Furthermore, SMemb/MHC-B-stained lesions increased markedly in CuZnSOD(-/-) mice.

CONCLUSIONS

CuZnSOD-deficiency promoted inflammation, expressed adhesion molecules, and altered the structure of the media post-injury. Our results suggest that O(2)(-) participates importantly in the progression of early stage vascular inflammation, resulting in vascular remodeling in media but not neointimal formation, post-injury.

Superoxide dismutases: role in redox signaling, vascular function, and diseases

Excessive reactive oxygen species Revised abstract, especially superoxide anion (O₂•-), play important roles in the pathogenesis of many cardiovascular diseases, including hypertension and atherosclerosis. Superoxide dismutases (SODs) are the major antioxidant defense systems against (O₂•-), which consist of three isoforms of SOD in mammals: the cytoplasmic Cu/ZnSOD (SOD1), the mitochondrial MnSOD (SOD2), and the extracellular Cu/ZnSOD (SOD3), all of which require catalytic metal (Cu or Mn) for their activation. Recent evidence suggests that in each subcellular location, SODs catalyze the conversion of (O₂•-), H2O2, which may participate in cell signaling. In addition, SODs play a critical role in inhibiting oxidative inactivation of nitric oxide, thereby preventing peroxynitrite formation and endothelial and mitochondrial dysfunction. The importance of each SOD isoform is further illustrated by studies from the use of genetically altered mice and viral-mediated gene transfer. Given the essential role of SODs in cardiovascular disease, the concept of antioxidant therapies, that is, reinforcement of endogenous antioxidant defenses to more effectively protect against oxidative stress, is of substantial interest. However, the clinical evidence remains controversial. In this review, we will update the role of each SOD in vascular biologies, physiologies, and pathophysiologies such as atherosclerosis, hypertension, and angiogenesis. Because of the importance of metal cofactors in the activity of SODs, we will also discuss how each SOD obtains catalytic metal in the active sites. Finally, we will discuss the development of future SOD-dependent therapeutic strategies.