Small caliber arterial endothelial cells calcium signals elicited by PAR2 are preserved from endothelial dysfunction

Endothelial cell (EC)‐dependent vasodilation by proteinase‐activated receptor 2 (PAR2) is preserved in small caliber arteries in disease states where vasodilation by muscarinic receptors is decreased. In this study, we identified and characterized the PAR2‐mediated intracellular calcium (Ca²⁺)‐release mechanisms in EC from small caliber arteries in healthy and diseased states. Mesenteric arterial EC were isolated from PAR2 wild‐type (WT) and null mice, after saline (controls) or angiotensin II (AngII) infusion, for imaging intracellular calcium and characterizing the calcium‐release system by immunofluorescence. EC Ca²⁺ signals comprised two forms of Ca²⁺‐release events that had distinct spatial‐temporal properties and occurred near either the plasmalemma (peripheral) or center of EC. In healthy EC, PAR2‐dependent increases in the densities and firing rates of both forms of Ca²⁺‐release were abolished by inositol 1,4,5‐ trisphosphate receptor (IP₃R) inhibitor, but partially reduced by transient potential vanilloid channels inhibitor ruthenium red (RR). Acetylcholine (ACh)‐induced less overall Ca²⁺‐release than PAR2 activation, but enhanced selectively the incidence of central events. PAR2‐dependent Ca²⁺‐activity, inhibitors sensitivities, IP₃R, small‐ and intermediate‐conductance Ca²⁺‐activated potassium channels expressions were unchanged in EC from AngII WT. However, the same cells exhibited decreases in ACh‐induced Ca²⁺‐release, RR sensitivity, and endothelial nitric oxide synthase expression, indicating AngII‐induced dysfunction was differentiated by receptor, Ca²⁺‐release, and downstream targets of EC activation. We conclude that PAR2 and muscarinic receptors selectively elicit two elementary Ca²⁺ signals in single EC. PAR2‐selective IP₃R‐dependent peripheral Ca²⁺‐release mechanisms are identical between healthy and diseased states. Further study of PAR2‐selective Ca²⁺‐release for eliciting pathological and/or normal EC functions is warranted.

DOI: 10.1002/prp2.112

View this article

• Full article (html)
• Enhanced article (html)
• PDF
• References