Mechanism of Extracellular Thiol Nitrosylation by N2O3 Produced by Activated Macrophages

• Published in: Nitric oxide 1999-12, Vol.3 (6), p.467-472
• Main Authors: Gobert, Alain P., Vincendeau, Philippe, Mossalayi, Djavad, Veyret, Bernard
• Format: Article
• Language: English
• Subjects: macrophage; nitric oxide; nitrosothiol; nitrous anhydride
• ISSN: 1089-8603; 1089-8611
• DOI: 10.1006/niox.1999.0260

Reactive nitrogen intermediates are synthesized by activated macrophages. These molecules, and nitrous anhydride (N2O3) in particular, are known to be potent nitrosylating species. We investigated the role of macrophage-derived N2O3 in extracellular nitrosylation. We used dilution experiments to demonstrate the intracellular production of N2O3 and its export into the extracellular medium, with a rate constant kex = 6.8 × 106 M s−1. The kinetics of the competition between extracellular hydrolysis of N2O3 and its reaction with added glutathione were also studied. We obtained a value of the rate constant kGSH for the latter reaction of 4.4 × 107 M−1 s−1, consistent with earlier determinations in cell-free systems. The implications of these results in human albumin nitrosylation were investigated. Nitrosylated albumin was detected in activated macrophages supernatants using an anti-NO-acetylated cysteine antibody. It was estimated that 10% of N2O3 produced by activated cells participate in extracellular nitrosylation. N2O3 thus appears to be a new effector molecule of the immune system, as an agent for the nitrosylation of albumin, the main nitric oxide carrier in vivo.