Peroxynitrite and vascular endothelial dysfunction in diabetes mellitus

Area of Science:

• Biochemistry
• Vascular Biology
• Diabetes Mellitus Research

Background:

• Macro and microvascular complications are leading causes of death in diabetes.
• Reactive nitrogen species (RNS), including peroxynitrite (ONOO-), are implicated in diabetes-related vascular dysfunction.
• The precise mechanisms linking diabetes, RNS, and vascular damage remain unclear.

Purpose of the Study:

• To elucidate the mechanisms by which RNS, specifically peroxynitrite, contribute to vascular disease in diabetes.
• To investigate the impact of peroxynitrite on endothelial nitric oxide synthase (eNOS) and prostacyclin synthase (PGIS).
• To understand the interdependency of these oxidative modifications in diabetic vascular pathology.

Main Methods:

• Investigated the effect of peroxynitrite on the zinc thiolate center of eNOS in vitro.
• Assessed the impact of peroxynitrite on prostacyclin synthase (PGIS) activity and modification.
• Examined eNOS uncoupling and PGIS nitration in diabetic animal models (mice and rats).

Main Results:

• Peroxynitrite oxidizes and disrupts the zinc thiolate center of eNOS, leading to eNOS uncoupling (reduced NO bioavailability, increased superoxide production).
• Peroxynitrite selectively nitrates and inactivates PGIS, diminishing prostacyclin production and increasing vasoconstrictor release.
• Diabetic mice and rats exhibit eNOS uncoupling and increased tyrosine nitration of PGIS, confirming in vivo relevance.

Conclusions:

• Diabetes-induced RNS lead to oxidative inactivation of key vasodilatory enzymes, eNOS and PGIS, through distinct yet interdependent mechanisms.
• eNOS uncoupling and PGIS inactivation by peroxynitrite contribute significantly to the vascular pathophysiology of diabetes.
• These findings highlight novel therapeutic targets for mitigating diabetes-associated vascular complications.