Counter Regulatory Effects of PKC βII and PKC δ on Coronary Endothelial Permeability

Abstract

Objective— The aim of this study was to examine the endothelial distribution and activity of selected PKC isoforms in coronary vessels with respect to their functional impact on endothelial permeability under the experimental conditions relevant to diabetes. Methods and Results— En face immunohistochemistry demonstrated a significant increase of PKC _βΙΙ and decrease of PKCδ expression in coronary arterial endothelium of Zucker diabetic rats. To test whether changes in PKC expression alter endothelial barrier properties, we measured the transcellular electric resistance in human coronary microvascular endothelial monolayers and found that either PKC _βΙΙ overexpression or PKCδ inhibition disrupted the cell–cell adhesive barrier. Three-dimensional fluorescence microscopy revealed that hyperpermeability was caused by altered PKC activity in association with distinct translocation of PKC _βΙΙ to the cell–cell junction and PKCδ localization to the cytosol. Further analyses in fractionated endothelial lysates confirmed the differential redistribution of these isozymes. Additionally, FRET analysis of PKC subcellular dynamics demonstrated a high PKC _βΙΙ activity at the cell surface and junction, whereas PKCδ activity is concentrated in intracellular membrane organelles. Conclusion— Taken together, these data suggest that PKC _βΙΙ and PKCδ counter-regulate coronary endothelial barrier properties by targeting distinctive subcellular sites. Imbalanced PKC _βΙΙ /PKCδ expression and activity may contribute to endothelial hyperpermeability and coronary dysfunction in diabetes.