Activation of Notch signalling by soluble Dll4 decreases permeability via a cAMP/PKA‐dependent pathway

Abstract

The Notch ligand Delta like ligand 4 (Dll4), which is upregulated by VEGF during angiogenesis, is a key regulator of vessel morphogenesis, maturation and function. It has been widely described as a regulator of tip and stalk cell selection during sprouting angiogenesis. Inhibition of Dll4 results in hyper‐sprouting, non‐functional and poorly perfused vessels, which suggests a role for Dll4 in the formation of mature, reactive, functional vessels, that have low permeability and are able to restrict fluid and solute exchange across vessel walls. We therefore tested the hypothesis that Dll4 plays a role in controlling transvascular fluid exchange. Using a recombinant protein expressing only the extracellular portion of Dll4 (soluble Dll4: sDll4), we were able to induce Notch signalling in endothelial cells (EC), resulting in an increased expression of VE‐Cadherin at intercellular junctions. sDll4 decreased permeability of FITC labelled albumin across EC monolayers and this effect was abrogated by co‐culture with DAPT. One of the known molecular effectors responsible for strengthening EC‐EC contacts is the cyclic AMP dependent protein kinase PKA, so we tested the effect of modulation of PKA on sDll4‐mediated reduction of permeability. Inhibition of PKA reversed the sDll4‐mediated reduction in permeability and reduced Hey‐1 expression. We showed that sDll4 caused a significant decrease in the hydraulic conductivity of rat mesenteric microvessels in vivo. This reduction was abolished upon co‐perfusion with the PKA inhibitor H89 dihydrochloride. These results indicate that Dll4 signalling, through Notch activation, acts upon intercellular adherens junctions through a cAMP/PKA pathway, to regulate endothelial barrier function.Support or Funding InformationSupported the British Heart FoundationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.