Role of caveolae in shear stress-mediated endothelium-dependent dilation in coronary arteries

Aims: Caveolae are membrane microdomains where important signalling pathways are assembled and molecular effects trans-duced. In this study, we hypothesized that shear stress-mediated vasodilation (SSD) of mouse small coronary arteries (MCA) is caveolae-dependent. Methods and results: MCA (80-150 μm) isolated from wild-type (WT) and caveolin-1 null (Cav-1^-/-) mice were subjected to physiological levels of shear stress (1-25 dynes/cm ²) with and without pre-incubation of inhibitors of nitric oxide synthase (L-NAME), cyclooxygenase (indomethacin, INDO), or cytochrome P450 epoxygenase (SKF 525A). SSD was endothelium-depend-entin WT and Cav-1 ^-/- coronaries but that in Cav-1^-/- was significantly diminished compared with WT. Pre-incubation with L-NAME, INDO, or SKF 525A significantly reduced SSD in WT but not in Cav-1^-/- mice. Vessels from the soluble epoxide hydrolase null (Ephx2^-/-) mice showed enhanced SSD, which was further augmented by the presence of ara-chidonic acid. In donor-detector-coupled vessel experiments, Cav-1^-/- donor vessels produced diminished dilation in WT endothelium-denuded detector vessels compared withWTdonor vessels. Shear stress elicited arobust intracellular Ca ²⁺ increase in vascular endothelial cells isolated from WT but not those from Cav-1^-/- mice. Conclusion: Integrity of caveolae is critical for endothelium-dependent SSD in MCA. Cav-1^-/- endothelium is deficient in shear stress-mediated generation of vasodilators including NO, prostaglandins, and epoxyeicosatrienoic acids. Caveolae plays a critical role in endothelial signal transduction from shear stress to vasodilator production and release.