Peroxynitrite Decomposition Catalyst Reduces Delayed Thrombolysis-induced Hemorrhagic Transformation in Ischemia-reperfused Rat Brains

Aim: Hemorrhagic transformation (HT) is a major complication of delayed tissue plasminogen activator (t-PA) treatment in ischemic stroke. We aimed to explore whether peroxynitrite decomposition catalyst (PDC) could prevent such complication. Methods: Male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion (MCAO) with t-PA (10 mg/kg) or t-PA plus FeTMPyP (3 mg/kg, a representative PDC) at MCAO for 2 or 5 h and reperfusion for 22 or 19 h, respectively. HT was assessed with hemoglobin assay. Neurological deficit was evaluated with Modified Neurological Severity Score (mNSS). Peroxynitrite formation was examined by detecting 3-nitrotyrosine (3-NT) formation. The expression and activity of MMP-9/MMP-2 were assessed by Western blotting and gelatin zymography. Results: t-PA treatment at 2 h of MCAO did not induce HT but attenuated neurological deficit, whereas treatment at 5 h significantly induced HT and worsened the neurological outcome. Such complications were prevented by FeTMPyP cotreatment. Early t-PA treatment inhibited 3-NT and MMP-9/MMP-2 expression, whereas delayed treatment induced 3-NT and MMP-9/MMP-2 expression and activity. FeTMPyP cotreatment downregulated 3-NT and inhibited MMP-9/MMP-2 in both time points. Conclusion: Peroxynitrite decomposition catalyst could prevent hemorrhagic transformation and improve neurological outcome ischemic rat brains with delayed t-PA treatment via inhibiting peroxynitritemediated MMP activation.