Abstract W P369: Inhibitory Effect of FTY720 on Neuroinflammation in Cerebral Ischemia-reperfusion

Background: Neuroinflammation is a key contributor to brain injury in cerebral ischemia-reperfusion (CIR). FTY720 has been shown to be neuroprotective in animal stroke models. In most studies, FTY720 treatment was initiated either before or shortly after the cerebral insult. The goal of this study is to investigate the effect of FTY720 on CIR-associated neuroinflammation and outcome using a therapeutic window similar to the one utilized in clinical practice. Methods: We used the rat middle cerebral artery (MCA) occlusion model for CIR. The right MCA was occluded for 1h followed by reperfusion. Animals were treated with vehicle or 0.5 mg/kg FTY720 intraperitoneally at 3h post-reperfusion. Neurobehavioral test battery (scale from 0 to 21 points with lower scores representing increased neurological deficits), grid-walking test, infarct volume, and brain water content were determined 24h post CIR. A cranial window was established at 24h post occlusion and leukocyte trafficking behavior was monitored by direct microscopic observation of surface venules. Pial venular leukocyte adhesion was expressed as the % of vascular area occupied by adherent rhodamine-6G-labeled leukocytes. Statistical analysis was performed by t test. Results: Compared to the vehicle group (n=10), FTY720 animals (n=10) had improved neurological score (8.6±1.9 vs. 13.7±1.9; p<0.001) and better motor performance throughout all subsections of the grid test (p<0.001). FTY720 treatment also decreased infarct volume (vehicle: 342±182; FTY720: 122±138 mm 3 ; p=0.04) and ipsilateral brain edema, measured as water content (vehicle: 84.5±1.05%; FTY720: 79.4±0.87%, p=0.003). Leukocyte trafficking study showed a significant increase in vascular leukocyte adhesion 24 h post reperfusion in the vehicle group which was markedly decreased by FTY720 treatment (sham: 3.0±0.6%; vehicle: 11.4±2.6%; FTY720: 5.2±1.4%; p<0.001). Conclusion: FTY720 given at 3h post reperfusion reduces infarct volume, brain edema, neurological disability, and vascular leukocyte adhesion. These results support the beneficial effect of FTY720 when used in a clinically relevant timeframe and provides direct evidence of the anti-inflammatory effect of FTY720 on CIR.