Proteinase-activated Receptor 2 (PAR2): a challenging new target for treatment of vascular diseases

Proteinase-activated Receptor 2 (PAR2) is a potential target for the design of drug treatments for vascular diseases. Its unique mechanism of activation by serine proteinases, questions regarding the identities of endogenous agonists and its apparent multiple activities in the vasculature contribute to complex pharmacology. The progress of the pursuit to understand the function of PAR2 relies on the design of short specific peptides as selective agonists for PAR2 in receptor-selective cultured cell expression systems and is limited by the lack of any PAR2 antagonists. Fortunately, the utilization of transgenic PAR2-deficient mice enables the identification of the actions of selective PAR2-derived activating peptides attributed to activation solely of PAR2 in more physiologically complex systems. Of multiple pharmacological responses, PAR2-derived peptide agonists reduce vascular tone, and therefore increase blood flow, via nitric oxide-dependent and -independent paracrine actions of the endothelium upon the underlying vascular smooth muscle cells of blood vessels. PAR2-mediated endothelial-dependent relaxation and hyperpolarization of vascular smooth muscle in select arterial vascular beds via a nitric oxide/cyclooxygenases-independent mechanism suggests a strategy for correction of endothelium-based vascular dysfunction. Vascular tissues respond to progression of vascular diseases such as atherosclerosis or to injury with variable changes of PAR2 expression. With further research and drug development, PAR2 agonists and antagonists may become a basis for a new class of therapeutic agents for treatment of vascular diseases.