Cilostazol ameliorates warfarin-induced hemorrhagic transformation after cerebral ischemia in mice.

BACKGROUND AND PURPOSE Although long-term treatment with the oral anticoagulant warfarin is widely used to prevent cardioembolic ischemic stroke, it has been reported that warfarin can exacerbate hemorrhagic transformation (HT) after cerebral ischemia. We investigated whether cilostazol, a phosphodiesterase-III inhibitor, suppressed the warfarin-induced HT after cerebral ischemia in mice. METHODS Male ddY mice were treated with oral warfarin before 3-hour middle cerebral artery occlusion followed by 21-hour reperfusion to induce HT. The duration of warfarin pretreatment was determined by measurement of prothrombin time-international normalized ratio value. Cilostazol or vehicle was administered by intraperitoneal injection immediately after reperfusion. The infarct volume, brain swelling, and brain hemoglobin content were evaluated at 24 hours after middle cerebral artery occlusion. We also evaluated the survival rate of each treated group for 7 days after surgery. To investigate the mechanism underlying cilostazol's effects, the proteins involved in vascular endothelial integrity were investigated using Western blotting. RESULTS HT volume was exacerbated by warfarin treatment, and cilostazol (3 mg/kg, i.p.) suppressed this exacerbation (sham, mean±SD, 29.2±13.4 mg/dL; vehicle, 33.3±11.9 mg/dL; warfarin, 379.4±428.9 mg/dL; warfarin+cilostazol 1 mg/kg, 167.5±114.2 mg/dL; warfarin+cilostazol 3 mg/kg, 116.9±152.3 mg/dL). Furthermore, cilostazol improved survival rate and upregulated the expression of tight junction proteins and vascular endothelial cadherin. CONCLUSIONS Cilostazol reduced the warfarin-related risk of HT after ischemia by protecting the vascular endothelial cells. This result suggested that cilostazol administration in patients with acute ischemic stroke might reduce HT.