Nitrite reduces the effects of HOCl on unsaturated phosphatidylcholines--a MALDI-TOF MS study

The concentration of nitrite (NO2-) increases under inflammatory conditions. However, the physiological role of nitrite is so far controversial discussed: it was reported that effects of HOCl (an important inflammation mediator) on phospholipids (PL) may be enhanced but also reduced in the presence of nitrite. In this paper a simple model system was used: unsaturated phosphatidylcholine (PC) vesicles were treated with HOCl in the presence of varying NaNO2 concentrations and the yield of reaction products was determined by MALDI-TOF MS: the extent of chlorohydrin generation was significantly reduced in the presence of NaNO2 because HOCl is consumed by the oxidation of NO2- to NO3-. Similar results were obtained when HOCl was generated by the myeloperoxidase (MPO)/H2O2/Cl- system or the experiments were carried out in the presence of a simple peptide. It is concluded that the transient products of the reaction between HOCl and NO2- do not have a sufficient reactivity to modify PL.