IntroductionWhile oxidative stress can be measured during transient cerebral ischemia, antioxidant therapies for ischemic stroke have been clinically unsuccessful. Many antioxidants are limited in their range and/or capacity for quenching radicals and can generate toxic intermediates overwhelming depleted endogenous protection. We developed a new antioxidant class, 40 nm × 2 nm carbon nanoparticles, hydrophilic carbon clusters, conjugated to poly(ethylene glycol) termed PEG-HCCs. These particles are high-capacity superoxide dismutase mimics, are effective against hydroxyl radical, and restore the balance between nitric oxide and superoxide in the vasculature. Here, we report the effects of PEG-HCCs administered during reperfusion after transient middle cerebral artery occlusion (tMCAO) by suture in the rat under hyperglycemic conditions. Hyperglycemia occurs in one-third of stroke patients and worsens clinical outcome. In animal models, this worsening occurs largely by accelerating elaboration of reactive oxygen species (ROS) during reperfusion.MethodsPEG-HCCs were studied for their protective ability against hydrogen peroxide in b.End3 brain endothelial cell line and E17 primary cortical neuron cultures. In vivo, hyperglycemia was induced by streptozotocin injection 2 days before tMCAO. 58 Male Sprague-Dawley rats were analyzed. They were injected IV with PBS or PEG-HCCs (4 mg/kg 2×) at the time of recanalization after either 90- or 120-min occlusion. Rats were survived for up to 3 days, and infarct volume characteristics and neurological functional outcome (modified Bederson Score) were assessed.ResultsPEG-HCCs were protective against hydrogen peroxide in both culture models. In vivo improvement was found after PEG-HCCs with 90-min ischemia with reduction in infarct size (42%), hemisphere swelling (46%), hemorrhage score (53%), and improvement in Bederson score (70%) (p = 0.068–0.001). Early high mortality in the 2-h in the PBS control group precluded detailed analysis, but a trend was found in improvement in all factors, e.g., reduction in infarct volume (48%; p = 0.034) and a 56% improvement in Bederson score (p = 0.055) with PEG-HCCs.ConclusionThis nano-antioxidant showed some improvement in several outcome measures in a severe model of tMCAO when administered at a clinically relevant time point. Long-term studies and additional models are required to assess potential for clinical use, especially for patients hyperglycemic at the time of their stroke, as these patients have the worst outcomes.

Hyperglycemia at the time of ischemic stroke has been associated with poorer outcomes. Preclinical literature suggests that hyperglycemia is an independent prognostic factor and the vasculature is more vulnerable to reperfusion injury. We applied a method to match subjects on important baseline factors to test whether, independent of stroke severity, stroke subtype influences the effect of hyperglycemia on outcome after recombinant tissue plasminogen activator (rt-PA). We reanalyzed the NINDS rt-PA dataset with respect to matching variables baseline NIHSS, age, and investigator-determined stroke subtypes small-vessel occlusive stroke (SVS), large-vessel occlusive stroke (LVS), and cardioembolic stroke (CES), above and below a glucose threshold of 150 mg/dl. Ninety-day outcomes were compared. Post hoc baseline matching was excellent in most cases. Hyperglycemia was associated with worsened functional outcome mostly in the LVS subtype with increased mortality in the placebo arm (15.3% mortality normoglycemia vs. 30.6% hyperglycemia; p = .046), worse functional outcome in the rt-PA arm (modified Rankin Score (mRS) 0-1; 46.3 vs. 22.0%; p = .034), and no improvement in functional outcome with rt-PA compared to placebo (mRS 0-1; 25% in both groups). Among hyperglycemic subjects, CES subjects showed significant improvement following rt-PA (p = .027). After matching for baseline severity, the influence of hyperglycemia on outcome was primarily in the LVS subtype, especially after rt-PA. This finding is consistent with a deleterious effect of hyperglycemia on ischemia/reperfusion of symptomatic large arteries. If confirmed, the particular vulnerability of the LVS subtype is important in understanding the role of stroke subtype in the mechanism of worsening and potential treatment of hyperglycemic stroke patients.

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