Nitrosation-modulating effect of ascorbate in a model dynamic system of coexisting nitric oxide and superoxide.

The coexistence of nitric oxide and superoxide leads to complex oxidative and nitrosative chemistry, which has been implicated in many pathophysiological conditions. The present study investigated the role of ascorbate in affecting the kinetics of nitrosative chemistry in a model dynamic snystem of coexisting nitric oxide and superoxide. SIN-1 (3-morpholinosydnonimine) was used to elicit various degrees of nitroxidative stress in a reaction buffer and DAN (2,3-diaminonaphthalene) was used as a probe for N-nitrosation reaction. The nitrosation kinetics in the absence and presence of ascorbate was followed by measuring the formation of the fluorescent product over time. Computational modelling was used to provide quantitative or semi-quantitative insights into the studied system. The results show that ascorbate effectively quenches N-nitrosation reaction, which could be partially attributed to the free radical scavenging and repairing effect of ascorbate. Computational modelling reveals an interesting temporal distribution of superoxide, nitric oxide and peroxynitrite. The model predicts that peroxynitrite is the most predominant species in the SIN-1 system. Furthermore, ascorbate might alter the system dynamics by removing superoxide and, thereby, increasing the availability of nitric oxide.