Synergistic Effect of an Endothelin Type A Receptor Antagonist, S-0139, With rtPA on the Neuroprotection After Embolic Stroke

Abstract

Using a model of embolic stroke, the present study tested the hypothesis that blockage of endothelin-1 with S-0139, a specific endothelin type A receptor (ET(A)) antagonist, enhances the neuroprotective effect of recombinant tissue plasminogen activator (rtPA) by suppressing molecules that mediate thrombosis and blood brain barrier (BBB) disruption induced by ischemia and rtPA. Rats (n=104) subjected to embolic middle cerebral artery (MCA) occlusion were randomly divided into 1 of 4 infusion groups with 26 rats per group: (1) the control group in which rats were administered saline, (2) the monotherapy rtPA group in which rtPA was intravenously administered at a dose of 10 mg/kg 4 hours after MCA occlusion, (3) the monotherapy S-0139 group in which S-0139 was intravenously given 2 hours after MCA occlusion, and (4) the combination of rtPA +S-0139 group in which S-0139 and rtPA were given 2 and 4 hours after MCA occlusion, respectively. Measurements of infarct volume and parenchymal hemorrhage, behavioral outcome, and immunostaining were performed on rats euthanized 1 and 7 days after stroke. The combination therapy of S-0139 and rtPA significantly (P<0.01) reduced infarct volume (24.8+/-0.9% versus 33.8+/-1.5% in control) and hemorrhagic area (7.1+/-6.1 microm(2) versus 36.5+/-19.2 microm(2) in control) and improved functional recovery compared with control saline-treated animals. Immunostaining analysis revealed that the combination therapy had the synergistically suppressed ischemia- and rtPA-induced ICAM-1, protease-activated receptor 1 (PAR-1), as well as accumulation of platelets in cerebral microvessels. Furthermore, the combination treatment synergistically reduced loss of laminin, ZO1, and occludin in cerebral vessels. These data suggest that S-0139 provides the neuroprotection by suppressing ischemia- and rtPA-triggered molecules that evoke thrombosis and BBB disruption.