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

Abstract

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.

Keywords

• Neointimal hyperplasia
• Superoxide
• Nitric oxide
• Vascular
• Sex differences