Re-canalization of cerebral vessels in
ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate
hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate
hypoxia followed by reoxygenation (MHR) on the evolution of
reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using
2',7'-dichlorodihydrofluorescein diacetate (DCF),
MitoSox and immunostaining for
nitrotyrosine.
Tight-junction protein (TJ) integrity in BEC, stainings for
nitrotyrosine and
FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy.
Diphenyleneiodonium (DPI) was used to investigate
NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ
proteins zonula occludens 1 (ZO-1) and
claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the
NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of
FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this process.