Proteinase-activated receptor 2 is a G protein-coupled receptor that regulates vascular tone and inflammatory signalling in the circulatory system. The roles of PAR2 appear complex and sometimes opposing. Studies using PAR2 deficient mice provide a framework to define these effects at the system level. This review examines cardiovascular phenotypes associated with PAR2 deficiency in basal conditions and in disease. PAR2 deficiency produces modest increases in arterial blood pressure and vascular stiffness while preserving endothelial vasodilator function. Cardiac function remains normal in young PAR2 deficient animals but changes with age. Older PAR2 deficient mice develop diastolic dysfunction and cardiac fibrosis. In disease models, PAR2 deficiency promotes fibrosis in cardiac and vascular tissues but reduces vascular inflammation in atherosclerosis. PAR2 deficiency limits plaque progression and promotes stable lesion structure. PAR2 deficiency also reduces myocardial injury and adverse remodelling after ischemia. The effects of PAR2 deficiency on inflammatory signalling vary with context and tissue. These findings show that PAR2 functions depend on physiological and pathological context. Future studies should define cell-specific mechanisms to guide therapeutic targetting of PAR2.

Proteinase-activated receptor-2 (PAR2) regulates cardiac pressure and vascular function through context-dependent mechanisms that integrate G protein-coupled receptor signalling. We investigated the baseline cardiovascular phenotype of PAR2-deficient (PAR2^−/−) mice and the acute in vivo effects of the PAR2 agonist trans-cinnamoyl-Leu-Ile-Gly-Arg-Leu-Orn-amide (tcLIGRLO). Left ventricular pressure–volume (PV) analysis revealed that PAR2^−/− mice had elevated systolic and diastolic pressures with reduced end-diastolic volumes and increased ejection fraction while maintaining stroke volume and cardiac output. Thus, PAR2 deficiency produces a pressure-dominant cardiovascular state with increased mechanical work and preserved global function. In WT mice, tcLIGRLO dose-dependently reduced cardiac pressure generation, contractility, relaxation kinetics, and stroke work, whereas these effects were absent in PAR2^−/− mice, indicating PAR2-dependent cardiac regulation. Despite these changes, global cardiac output remained largely preserved despite modest reductions in heart rate. In contrast, tcLIGRLO elicited strain-dependent vascular responses, including altered effective aortic elastance and reduced carotid blood flow in PAR2^−/− mice. Ex vivo experiments showed that tcLIGRLO-induced contraction in PAR2^−/− arteries required Gq-dependent signalling in this experimental context. These findings identify PAR2 as a context-dependent regulator of cardiac pressure and vascular tone, in which PAR2-dependent cardiac effects and PAR2-independent, Gq-mediated vascular responses reflect distinct but interacting signalling mechanisms.

Proteinase-activated receptor 2 is a G protein-coupled receptor that regulates vascular tone and inflammatory signalling in the circulatory system. The roles of PAR2 appear complex and sometimes opposing. Studies using PAR2-deficient mice provide a framework to define these effects at the system level. This review examines cardiovascular phenotypes associated with PAR2 deficiency in basal conditions and in disease. PAR2 deficiency produces modest increases in arterial blood pressure and vascular stiffness while preserving endothelial vasodilator function. Cardiac function remains largely normal in young PAR2-deficient animals but changes with age. Older PAR2-deficient mice develop diastolic dysfunction and cardiac fibrosis. In disease models, PAR2 deficiency has been associated with increased fibrosis in cardiac and vascular tissues and reduced vascular inflammation in atherosclerosis. PAR2 deficiency is also associated with reduced plaque progression and features of plaque stabilisation. In myocardial ischaemia models, PAR2 deficiency has been associated with reduced cardiac injury and adverse remodelling. The effects of PAR2 deficiency on inflammatory signalling vary according to tissue and disease context. Together, these findings suggest that the cardiovascular consequences of PAR2 deficiency depend on physiological and pathological context. Future studies should define cell-specific mechanisms to guide therapeutic targeting of PAR2.