AMP-activated protein kinase is a key regulator of acute neurovascular permeability.

Many neuronal and retinal disorders are associated with pathological hyperpermeability of the microvasculature. We have used explants of rodent retinae to study acute neurovascular permeability and signal transduction and the role of AMP-activated protein kinase (AMPK). Following stimulation with either vascular endothelial growth factor (VEGF-A) or bradykinin (BK), AMPK was rapidly and strongly phosphorylated and acted as a key mediator of permeability downstream of Ca2+ Accordingly, AMPK agonists potently induced acute retinal vascular leakage. AMPK activation led to phosphorylation of endothelial nitric oxide synthase (eNOS), which in turn increased VE-cadherin phosphorylation on Y685. In parallel, AMPK also mediated phosphorylation of p38 MAP kinase and HSP27, indicating that it regulated paracellular junctions and cellular contractility, both previously associated with endothelial permeability. Endothelial AMPK provided a missing link in neurovascular permeability, connecting Ca2+ transients to the activation of eNOS and p38, irrespective of the permeability-inducing factor used. Collectively, we find that, due to its compatibility with small molecule antagonists/agonists and siRNA, the ex-vivo retina model constitutes a reliable tool to identify and study regulators and mechanism of acute neurovascular permeability.