Stefan Chlopicki

Aim Protein disulfide isomerases (PDIs) are involved in platelet aggregation and intravascular thrombosis, but their role in regulating endothelial function is unclear. Here, we characterized the involvement of vascular PDIA1 in angiotensin II (Ang II)‐induced endothelial dysfunction in mice. Methods Endothelial dysfunction was induced in C57BL/6JCmd male mice via Ang II subcutaneous infusion, and PDIA1 was inhibited with bepristat. Endothelial function was assessed in vivo with magnetic resonance imaging and ex vivo with a myography, while arterial stiffness was measured as pulse wave velocity. Nitric oxide (NO) bioavailability was measured in the aorta (spin‐trapping electron paramagnetic resonance) and plasma (NO 2 − and NO 3 − levels). Oxidative stress, eNOS uncoupling (DHE‐based aorta staining), and thrombin activity (thrombin–antithrombin complex; calibrated automated thrombography) were evaluated. Results The inhibition of PDIA1 by bepristat in Ang II‐treated mice prevented the impairment of NO‐dependent vasodilation in the aorta as evidenced by the response to acetylcholine in vivo, increased systemic NO bioavailability and the aortic NO production, and decreased vascular stiffness. Bepristat's effect on NO‐dependent function was recapitulated ex vivo in Ang II‐induced endothelial dysfunction in isolated aorta. Furthermore, bepristat diminished the Ang II‐induced eNOS uncoupling and overproduction of ROS without affecting thrombin activity. Conclusion In Ang II‐treated mice, the inhibition of PDIA1 normalized the NO‐ROS balance, prevented endothelial eNOS uncoupling, and, thereby, improved vascular function. These results indicate the importance of vascular PDIA1 in regulating endothelial function, but further studies are needed to elucidate the details of the mechanisms involved.