Canonical Wnt Pathway Maintains Blood-Brain Barrier Integrity upon Ischemic Stroke and Its Activation Ameliorates Tissue Plasminogen Activator Therapy

AbstractStroke induces blood-brain barrier (BBB) breakdown, which promotes complications like oedema and hemorrhagic transformation. Administration of recombinant tissue plasminogen activator (rtPA) within a therapeutic time window of 4.5  h after stroke onset constitutes the only existing treatment. Beyond this time window, rtPA worsens BBB breakdown. Canonical Wnt pathway induces BBB formation and maturation during ontogeny. We hypothesized that the pathway is required to maintain BBB functions after stroke; thus, its activation m ight improve rtPA therapy. Therefore, we first assessed pathway activity in the brain of mice subjected to transient middle cerebral artery occlusion (MCAo). Next, we evaluated the effect of pathway deactivation early after stroke onset on BBB functions. Finally, we assessed the impact of pathway ac tivation on BBB breakdown associated to delayed administration of rtPA. Our results show that pathway activity is induced predominately in endothelial cells early after ischemic stroke. Early deactivation of the pathway using a potent inhibitor, XAV939, aggravates BBB breakdown and increases hemorrh agic transformation incidence. On the other hand, pathway activation using a potent activator, 6-bromoindirubin-3′-oxime (6-BIO), reduces the incidence of hemorrhagic transformation associated to delayed rtPA administration by attenuating BBB breakdown via promotion of tight junction formation and repressing endothelial basal permeability independently o...
Source: Molecular Neurobiology - Category: Neurology Source Type: research