Activation of Epac/Rap1 attenuates VE‐cadherin redistribution in response to PAF in vivo

Abstract

Intracellular cAMP inhibits microvascular hyperpermeability induced by inflammatory mediators such as platelet activating factor (PAF). In cultured endothelium activation of the small GTPase Rap1 via a PKA-independent pathway involving Epac, the cAMP dependent guanine nucleotide exchange factor for Rap1, promotes distribution of tight junction and adherens junction (AJ) components to cell-cell junctions. The cAMP analog 8-pCPT-2′-O-Methyl-cAMP (O-Me) is specific for the Epac/Rap1 pathway. We previously showed that O-Me significantly attenuates PAF-induced hyperpermeability, measured as increased hydraulic conductivity in single perfused post-capillary microvessels of rat mesentery. Here we tested the hypothesis that O-Me (100 μM, 30 min pretreatment) would prevent the PAF-induced rearrangement of the AJ component, VE-cadherin (VE). After PAF (10 nM, 5 min) induced increased permeability, there was rearrangement of immuno-fluorescently labeled VE; numerous lateral spikes and frequent short breaks appeared in the peripheral label. In control vessels, VE formed a continuous peripheral ribbon. Then, after O-Me attenuated PAF induced hyperpermeability, there were fewer gaps in the peripheral VE ribbon. These results suggest that cAMP acts in part by activation of Rap1 to stabilize key components of the inter-endothelial junction as well as attenuating hyperpermeability. NIH HL28607