Adjuvant treatment with a glycoprotein IIb/IIIa receptor inhibitor increases the therapeutic window for low-dose tissue plasminogen activator administration in a rat model of embolic stroke.

Abstract

Platelet aggregation and fibrin deposition are key events leading to microvascular thrombosis and progressive impairment of downstream microvascular perfusion after stroke. We tested the hypothesis that inhibition of platelet function with a GP IIb/IIIa receptor antagonist would increase the efficacy and safety and increase the time window for thrombolytic therapy for stroke with full- and half-dose tissue plasminogen activator (tPA). Rats were subjected to embolic middle cerebral artery occlusion. Four hours after ischemia, rats were treated with 7E3 F(ab')2 (6 mg/kg) in combination with tPA at doses of 10 and 5 mg/kg, tPA alone at a dose of 10 or 5 mg/kg, 7E3 F(ab')2 (6 mg/kg) alone, or saline. Combination treatment with 7E3 F(ab')2 and tPA (full- or half-dose) significantly (P<0.05) reduced infarct volume and neurological deficits compared with saline-treated rats. However, treatment with 7E3 F(ab')2 or tPA (full- or half-dose) alone did not reduce infarct volume. Quantitative measurements of cerebral microvessels perfused by FITC-dextran revealed that combination treatment with 7E3 F(ab')2 and full-dose tPA significantly (P<0.05) increased the percentage of FITC-dextran-perfused vessels compared with saline and full-dose tPA-treated rats. In addition, treatment with 7E3 F(ab')2 in combination with full-dose tPA significantly (P<0.05) decreased microvascular platelet accumulation and matrix metalloproteinase 9 immunoreactivity and protected against loss of collagen IV immunoreactivity. Combination treatment with 7E3 F(ab')2 with full- and half-dose tPA at 4 hours after ischemia significantly reduces infarct volume and improves neurological outcome. Enhancement of patency and integrity of cerebral microvessels most likely contributes to the benefits observed with this combination therapy.