IFNβ inhibits MMP9 production in MG and attenuates TJP degradation in brain endothelial cells. (A) Mice were subjected to 3-hour MCAO followed by vehicle, tPA, or tPA plus IFNβ administration. At 20 hours postinjury, the ischemic brains were harvested and subjected to IHC analysis for MMP9 and Iba1 expression (n = 5 per group). The representative confocal images of the cortex and striatum of ipsilateral hemisphere of vehicle-, tPA-, and tPA plus IFNβ-treated MCAO mice are shown. Scale bar, 20μm (5 μm in magnified boxes). (B) Primary MG were treated with 20 ng/mL of TNFα plus 10⁻⁶ M PGE₂ or TNFα plus PGE₂ plus tPA (10 µg/mL) in the presence or absence of IFNβ (1000 U/mL) for 24 hours. Cells were then collected and subjected to western blots to measure MMP9 expression (n = 5 per group). (C) Supernatants were collected and subjected to gelatin zymography to determine MMP9 activity (n = 5 per group). (D-E) bEnd.3 cells were treated with TNFα (50 ng/mL in panel D and 100 ng/mL in panel E) or TNFα plus tPA (10 µg/mL) in the presence or absence of IFNβ (1000 U/mL). 24 hours later, cells were subjected to immunocytochemistry for ZO-1 and occludin expression. The representative confocal images are shown, and the fluorescence intensity of ZO-1 and occludin was also quantified (n = 5). Scale bars, 20 μm. *P < .05, **P < .01, ***P < .001 by 1-way ANOVA. N.S., no significant difference by 1-way ANOVA.