Endothelial NO and O2− production rates differentially regulate oxidative, nitroxidative, and nitrosative stress in the microcirculation

• Published in: Free radical biology & medicine Vol. 63; pp. 161 - 174
• Main Authors: Kar, Saptarshi, Kavdia, Mahendra
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-10-2013
• Subjects: Biotransport; Computational model; Computer Simulation; Endothelial Cells - cytology; Endothelial Cells - metabolism; Endothelial dysfunction; Endothelium, Vascular - cytology; Endothelium, Vascular - metabolism; Flux; Free radicals; Humans; inducible nitric oxide synthase; Microcirculation; nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II - metabolism; Oxidation-Reduction; Oxidative Stress; Oxygen - metabolism; Peroxynitrite; Peroxynitrous Acid - metabolism; Production rate; proteins; Superoxide; superoxide anion; Superoxide dismutase; Superoxide Dismutase - metabolism; Superoxides - metabolism; toxicity; tyrosine; Tyrosine - metabolism; NO; Microcirculation; Peroxynitrite; Production rate; Free radicals; Biotransport; Flux; Endothelial dysfunction; Superoxide dismutase; Superoxide; Computational model
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2013.04.024

Endothelial dysfunction causes an imbalance in endothelial NO and O2− production rates and increased peroxynitrite formation. Peroxynitrite and its decomposition products cause multiple deleterious effects including tyrosine nitration of proteins, superoxide dismutase (SOD) inactivation, and tissue damage. Studies have shown that peroxynitrite formation during endothelial dysfunction is strongly dependent on the NO and O2− production rates. Previous experimental and modeling studies examining the role of NO and O2− production imbalance on peroxynitrite formation showed different results in biological and synthetic systems. However, there is a lack of quantitative information about the formation and biological relevance of peroxynitrite under oxidative, nitroxidative, and nitrosative stress conditions in the microcirculation. We developed a computational biotransport model to examine the role of endothelial NO and O2− production on the complex biochemical NO and O2− interactions in the microcirculation. We also modeled the effect of variability in SOD expression and activity during oxidative stress. The results showed that peroxynitrite concentration increased with increase in either O2− to NO or NO to O2− production rate ratio (QO2−/QNO or QNO/QO2−, respectively). The peroxynitrite concentrations were similar for both production rate ratios, indicating that peroxynitrite-related nitroxidative and nitrosative stresses may be similar in endothelial dysfunction or inducible NO synthase (iNOS)-induced NO production. The endothelial peroxynitrite concentration increased with increase in both QO2−/QNO and QNO/QO2− ratios at SOD concentrations of 0.1–100μM. The absence of SOD may not mitigate the extent of peroxynitrite-mediated toxicity, as we predicted an insignificant increase in peroxynitrite levels beyond QO2−/QNO and QNO/QO2− ratios of 1. The results support the experimental observations of biological systems and show that peroxynitrite formation increases with increase in either NO or O2− production, and excess NO production from iNOS or from NO donors during oxidative stress conditions does not reduce the extent of peroxynitrite mediated toxicity.
•We present a microcirculation computational model of peroxynitrite response to NO/O2− production.•The effect of SOD on microvascular peroxynitrite formation was studied.•Endothelial peroxynitrite concentration increases with increase in both QO2−/QNO and QNO/QO2− ratios.•Peroxynitrite does not increase beyond a production rate ratio of 1 without SOD.•Excess NO production in oxidative stress may not reduce peroxynitrite toxicity.