P2Y receptors as regulators of lung endothelial barrier integrity

Endothelial cells (ECs), forming a semi-permeable barrier between the interior space of blood vessels and underlying tissues, control such diverse processes as vascular tone, homeostasis, adhesion of platelets, and leukocytes to the vascular wall and permeability of vascular wall for cells and fluids. Mechanisms which govern the highly clinically relevant process of increased EC permeability are under intense investigation. It is well known that loss of this barrier (permeability increase) results in tissue inflammation, the hall mark of inflammatory diseases such as acute lung injury and its severe form, acute respiratory distress syndrome. Little is known about processes which determine the endothelial barrier enhancement or protection against permeability increase. It is now well accepted that extracellular purines and pyrimidines are promising and physiologically relevant barrier-protective agents and their effects are mediated by interaction with cell surface P2Y receptors which belong to the superfamily of G-protein-coupled receptors. The therapeutic potential of P2Y receptors is rapidly expanding field in pharmacology and some selective agonists became recently available. Here, we present an overview of recently identified P2Y receptor agonists that enhance the pulmonary endothelial barrier and inhibit and/or reverse endothelial barrier disruption.