Efficacy of Novel Carbon Nanoparticle Antioxidant Therapy in a Severe Model of Reversible Middle Cerebral Artery Stroke in Acutely Hyperglycemic Rats.

INTRODUCTION: While 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. METHODS: PEG-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. RESULTS: PEG-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. CONCLUSION: This 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 worsens outcome after rt-PA primarily in the large-vessel occlusive stroke subtype.

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.

A Pilot Trial of Low-Dose Intravenous Abciximab and Unfractionated Heparin for Acute Ischemic Stroke: Translating GP IIb/IIIa Receptor Inhibition to Clinical Practice.

Thrombolysis remains a mainstay in the treatment of ischemic stroke. While not usually considered in the spectrum of clot lysis, experimental data show that inhibition of the platelet glycoprotein (GP) IIb/IIIa receptor can reduce as well as reverse thrombus formation and improve microvascular flow in stroke models. However, a recent clinical trial of GP IIb/IIIa inhibition in stroke did not demonstrate clinical benefit and was associated with increased hemorrhage. Based on an understanding of the relationship between GP IIb/IIIa receptor inhibition, efficacy and hemorrhage, we hypothesized that a lower dose of abciximab would achieve a favorable range of platelet inhibition and potentially good clinical outcomes. Forty-four patients with suspected large vessel occlusion, who were not eligible for rt-PA were offered treatment with approximately 30% lower total dose of intravenous abciximab if within 6 h for anterior circulation or 24 h for posterior circulation stroke (later modified to 12 h). Concomitant anticoagulation, usually with unfractionated heparin was employed. The extent of platelet inhibition was measured in 21 patients. Hemorrhage rate and 90-day functional outcomes and mortality were obtained. A matching algorithm involving finding the nearest neighbor from individual subjects in the control arm of the NINDS rt-PA database was used to compare outcomes at similar baseline characteristics and gender. Mean platelet inhibition was 92.1 ± 6.7% vs inhibition reported with percutaneous coronary intervention (PCI) of 96 ± 10; p = 0.08. Successful matching to NINDS controls was accomplished: after outlier elimination, median and mean NIHSS of the abciximab subjects compared to NINDS controls was 16.5 vs 15.5 (p = 0.92) and 16.3 vs 16.0 (p = 0.86). Mean age was 67.2 vs 67.1 (p = 0.97). Mean glucose was 141 vs 142 (p = 0.92). There was one symptomatic hemorrhage; minor hemorrhages occurred in 9%. The percent of patients who achieved an mRS 0-2 or died in the treated vs matched NINDS control patients was 63 vs 38 (p = .02) and 23 vs 23 (p = 1.0). Our pilot results indicated that a lower dose of abciximab results in platelet inhibition similar to that achieved in the coronary vascular bed during PCI. Comparison to matched historical controls suggests that this lower dose in combination therapy may be safe and effective therapy for thrombotic stroke and a randomized trial is warranted.