IFNβ suppresses tPA-enhanced MMP3 and MMP9 expression in the ischemic brain. Mice were subjected to 3-hour MCAO followed by vehicle, tPA, or tPA plus IFNβ administration. (A) At 9 hours postinjury, the ischemic brains were harvested and separated into the contralateral and ipsilateral hemispheres followed by western blot analysis. The representative results of MMP9 and MMP3 expression in the contralateral (Con) and ipsilateral (Ipsi) hemispheres of vehicle-, tPA-, and tPA plus IFNβ-treated MCAO mice are shown. (B) At 9 hours postinjury, MMP3 and MMP9 expression in the ipsilateral hemisphere of vehicle-, tPA-, and tPA plus IFNβ-treated MCAO mice (n = 3 per group) was measured by western blots. Statistical analysis was based on the comparison between vehicle and tPA or tPA and tPA plus IFNβ. (C) At 20 hours postinjury, the ipsilateral hemisphere of vehicle-, tPA-, and tPA plus IFNβ-treated MCAO mice was harvested and subjected to western blot analysis for MMP3 and MMP9 expression. The representative results of MMP9 and MMP3 expression in the ipsilateral hemisphere of vehicle-, tPA-, and tPA plus IFNβ-treated MCAO mice are shown (n = 3 per group), and the level of MMP9 and MMP3 expression was also quantified (n = 8 per group). *P < .05 by Kruskal-Wallis test (B) or 1-way ANOVA (C), **P < .01, ***P < .001 by 1-way ANOVA. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.