Abstract WP254: The Contribution of Serpinf2 to Tissue Plasminogen Activator Therapy for Stroke: Effects on Neuronal Cell Death, Brain Swelling, Breakdown of the Blood Brain Barrier and Mortality

Abstract

For poorly understood reasons, tissue plasminogen activator (TPA) therapy for ischemic stroke is limited by a narrow therapeutic window and by toxicities including hemorrhage. In this study we investigated the contribution of serpinf2 (Sf2, a2-plasmin inhibitor, a2-antiplasmin) to the success and complications of TPA therapy. Methods: Ischemic stroke was induced by MCA thromboembolism in anesthetized mice. Infarct size, hemorrhage and swelling were examined by a blinded observer. Breakdown of the blood brain barrier, MMP-9 expression and apoptosis were determined by quantitative immunohistochemistry. Results: TPA treatment within 15 min. of ischemia significantly reduced infarction (p<0.001). However, after 1 hr TPA had no effect and after 2.5 h TPA significantly increased infarction (p<0.01). As ischemic time prolonged, TPA treatment increased brain hemorrhage (p<0.001). Increasing levels of Sf2 doubled infarct size after TPA treatment (p<0.001) and quadrupled brain swelling (p<0.001). In contrast, when mice were given a specific Sf2 inactivator (Sf2-i) in combination with TPA, there was a significant increase in the dissolution of the thromboembolus by comparison to the same dose of TPA alone (p<0.001). The combination of an Sf2-I and TPA significantly decreased stroke size (p<0.001) and markedly reduced hemorrhage by comparison to TPA alone (p<0.001). In addition, the combination of TPA and an Sf2-i significantly improved survival (p<0.05). Consistent with its effects on reducing brain swelling, the addition of sf2-i to TPA therapy markedly reduced expression of matrix metalloproteinase 9 (p<0.01) and breakdown of the blood brain barrier (p<0.01). Addition of the Sf2-i also significantly reduced apoptosis (p<0.01) assessed by TUNEL and activated caspase 3 staining. Conclusion: Sf2 reduces TPA’s efficacy and enhances toxicity by increasing stroke infarct size and brain swelling. In contrast, inactivation of Sf2 increased the therapeutic window for TPA, which in turn reduced infarction, brain swelling and hemorrhage. Sf2-i also significantly reduced break down of the blood brain barrier and apoptosis. Thus inactivation of Sf2 may increase the therapeutic value of TPA.