Figure 1.

Systemic inflammation causes sustained claudin-5 disruption after MCAo. Systemic inflammation was induced by intraperitoneal IL-1β injection, and the effects on the BBB tight junction proteins, claudin-5 and occludin, were assessed in cortical tissue ipsilateral to MCAo by immunoblot and immunofluorescence at indicated times after MCAo. A, MCAo induced a 50% reduction in claudin-5 levels in both vehicle (veh)- and IL-1β-treated mice compared with sham-operated mice after 4 h reperfusion. This disruption to claudin-5 resolved in vehicle-treated mice by 8 h after MCAo and was maintained at 24 h in which claudin-5 levels were similar to sham-operated mice. There was a sustained disruption to claudin-5 in IL-1β-treated mice 8 and 24 h after MCAo resulting in a 70% reduction compared with sham-operated mice at 24 h. The sustained loss of claudin-5 in IL-1β-challenged mice resulted in a significant reduction compared with vehicle-treated mice 8 and 24 h after MCAo. B, Claudin-5 immunofluorescence (green channel) with DAPI counterstain (blue channel) demonstrated dense networks of cerebrovascular immunoreactivity in sham-operated mice. Marked reductions in immunoreactivity were evident 4 h after MCAO in vehicle-treated mice and 4, 8, and 24 h after MCAo in IL-1β-challenged mice, consistent with the immunoblot data. C, Confocal immunofluorescence revealed the disruption by systemic inflammation to the highly organized arrangement of claudin-5 in the interendothelial tight junctions of cortical blood vessels in the ipsilateral hemisphere 24 h after MCAo. D, There were no significant effects of systemic inflammation or MCAo on occludin levels. All immunofluorescence images are from the cortex ipsilateral to MCAo. *p < 0.05 versus vehicle; Student's t test. Scale bars: B, 100 μm; C, 10 μm.