Protease-activated receptors (PARs) are partly pro-inflammatory and partly anti-inflammatory: Will PAR agonists or antagonists participate in future drug therapies?

Protease-activated receptors (PARs) are characterised by a unique mechanism of activation, which enables them to act as cellular sensors for protease activity. PARs are expressed throughout the cardiovascular, gastrointestinal and pulmonary systems, where they are potential drug targets for the treatment of disease. However, there are currently very few selective PAR antagonists or potent PAR agonists available as effective research tools, and moreover, there is considerable evidence to suggest that PARs can promote both pro-inflammatory and anti-inflammatory responses in a wide range of disease models. These confounding issues have, to date, prevented us from developing a clear understanding of the role of PARs in disease. Nevertheless, this review provides an overview of the distribution and function of PARs in the cardiovascular, gastrointestinal and pulmonary systems, and attempts to evaluate whether PAR agonists or antagonists have a place in future drug therapy.