Evidence for a protective role of Protein Disulfide Isomerase-A1 against aortic dissection

Preferential Secretion of Oxidation-Sensitive Proteins by Unconventional Pathways: Why is This Important for Inflammation?

Significance: Fidelity of intercellular communication depends on unambiguous interactions between protein ligands and membrane receptors. Most proteins destined to the extracellular space adopt the required three-dimensional shape as they travel through the endoplasmic reticulum (ER), Golgi complex, and other organelles of the exocytic pathway. However, some proteins, many of which are involved in inflammation, avoid this classical secretory route and follow unconventional pathways to leave the cell. Recent Advances: Stringent quality control systems operate in the ER and cis-Golgi, restricting transport to native conformers, devoid of non-native disulfides and/or reactive thiols. However, some proteins released by living cells require reduced cysteines to exert their extracellular function(s). Remarkably, these proteins lack the secretory signal sequence normally required by secretory proteins for translocation into the ER lumen. Critical Issues: Why do interleukin-1β, high mobility group box 1, and other proinflammatory proteins avoid the ER-Golgi route to reach the intercellular space? These proteins require reactive cysteines for exerting their function. Therefore, eluding thiol-mediated quality control along the exocytic pathway is likely one of the main reasons why extracellular proteins that need to be reduced utilize unconventional pathways of secretion, where a quality control aimed at oxidating native cysteines is not present. Future Directions: Particularly under stress conditions, cells release redox-active enzymes and nonprotein thiol compounds that exert an extracellular control of redox-sensitive protein activity, shaping inflammatory responses. This post-secretion, redox-dependent editing of protein messages is still largely undefined. Understanding the underlying mechanistic events will hopefully provide new tools to control inflammation. Antioxid. Redox Signal. 41, 693-705.

Vascular protein disulfide isomerase A1 mediates endothelial dysfunction induced by angiotensin II in mice

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 (NO2 - and NO3 - 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.