Abstract WP312: Rosiglitazone Ameliorates Tissue Plasminogen Activator-Induced Hemorrhagic Transformation After Stroke via Promoting Phagocytic Activity of Microglia

Abstract

Objective: Delayed thrombolytic treatment with recombinant tissue plasminogen activator (tPA) may lead to lethal hemorrhagic transformation (HT) after ischemic stroke. Rosiglitazone(RSG) is one of the PPAR-γ agonists and has been reported to protect against cerebral ischemia. However, whether RSG can alleviate HT after tPA treatment still remains unknown. In this study, we sort to examine the role of RSG on tPA-induced HT. Methods and results: We used the murine suture middle cerebral artery occlusion (MCAO) models of stroke to investigate the therapeutic potential of RSG against tPA-induced HT. Delayed administration of tPA (10mg/kg, 2 hours after reperfusion) resulted in HT in the ischemic territory 1 day after ischemia. When RSG(6mg/kg) were intraperitoneally administered 1 hour before MCAO , HT was significantly decreased. In addition, we found the BBB disruption and tight junction damage in tPA-treated MCAO mice can be mitigated after RSG treatment. Using flow cytometry and immunostaining, we confirmed that the expression of CD206 was significantly upregulated while the expression of iNOS was down-regulated in microglia of the tPA and RSG treated MCAO mice. Simultaneously, the expression of arg-1, CD36, CD68 and TREM2 were upregulated in tPA and RSG treated stroke mice. To further address our hypothesis that RSG could exert protection against the BBB disruption via phenotypic change into enhanced phagocytosis activity, we intend to use the two-photon live imaging to elucidate that CX3CR1-GFP + microglia could phagocytose more exogenously injected rhodamine-dextran while treated with RSG and tPA compared with those treated with tPA alone. In addition, we plan to inject pH-sensitive beads through the lateral ventricle to demonstrate an increased engulfment of pH-sensitive beads after co-treatment with RSG and tPA. In vitro, phagocytic efficiency in primary microglia and BV2 cells will be verified through adding latex beads after co-administrating RSG and tPA. Conclusions: In conclusion, our data demonstrates that RSG treatment ameliorates HT in delayed tPA-treated stroke mice. Enhanced phagocytic activity of microglia may be responsible for the RSG afforded protection against the BBB disruption in the tPA-induced HT after stroke.