Pharmacological Inhibition of NAD(P)H Oxidase with the Peptide gp91ds‐tat During Ischemic Stroke Reduces Infarct Volume and Improves Vascular Reactivity in Obese Zucker Rats

Abstract

Production of reactive oxygen species (ROS) during ischemic stroke and subsequent reperfusion has been linked to increased infarct size and poor outcomes in multiple rodent models. NAD(P)H) oxidase (NOX) has been identified as a principal source of ROS generation during ischemia/reperfusion, and inhibition of NOX during ischemic stroke results in decreased infarct size and improved outcomes in preclinical models, although underlying mechanisms are unclear. Elevated blood glucose increases ROS production by NOX during ischemia/reperfusion, and vascular dysfunction can impair collateral flow; a stroke model that incorporates hyperglycemia and vascular dysfunction may therefore amplify ROS production and lead to larger infarcts and worsened outcomes. As such, the aim of this study was to determine the effects of gp91ds‐tat, a peptide inhibitor of NOX‐2, on infarct size and vascular reactivity in both the ipsilateral (IL) and contralateral (CL) middle cerebral arteries (MCAs) of lean and obese Zucker rats (LZR, OZR) two weeks after ischemic stroke. Strokes were induced in 17 week old rats for 60 min by transient MCA occlusion (tMCAO); 30 minutes into tMCAO, OZR received either gp91ds‐tat (10mg/kg body weight) or vehicle. Changes in cerebral blood flow were monitored by laser Doppler. 15 days after tMCAO, animals were sacrificed and the IL and CL MCAs were isolated and cannulated in an ex vivo microvessel preparation; MCA reactivity was assessed in response to acetylcholine (ACh). Infarct size was measured by TTC stain. Infarct size and mortality rates were increased at 15 days post‐tMCAO in control treated OZR vs. LZR. Vascular dysfunction was worsened in both CL and IL MCA; ACh‐induced vasodilation was reduced 35% in CL‐MCA compared to non‐stroke OZR MCA, while in IL‐MCA, dilation was completely ablated, likely due to reperfusion injury. In contrast, OZR treated with gp91ds‐tat demonstrated reduced infarct size and mortality, as well as improved recovery of cerebral blood flow after reperfusion vs. control OZR. Vascular reactivity improved significantly, as ACh‐induced dilation in CL‐MCA and IL‐MCA increased 12% and 67% respectively vs. control treated OZR, indicating gp91ds‐tat acutely reduced damage from reperfusion injury. Our findings suggest that preexisting metabolic syndrome can worsen neurological and cerebrovascular outcomes following ischemic stroke though a mechanism at least partially mediated by NOX. Targeted inhibition of NOX during ischemia/reperfusion may improve stroke outcomes, especially in patients with history of metabolic syndrome, and warrants further consideration as a treatment avenue for ischemic stroke.Support or Funding InformationNIH COBRE GrantAHA Predoctoral Fellowship