Blood levels of nitric oxide and DNA breaks assayed in whole blood and isolated peripheral blood mononucleated cells in patients with multiple sclerosis.

Oxidative stress, especially overproduction of nitric oxide (NO), is considered to be one of the crucial factors in the pathogenesis of multifactorial multiple sclerosis (MS). DNA breaks could be one of the consequences of oxidative stress; however, data on DNA breakage in MS are very few and contradictory. There are no data on direct measurements of NO production in the blood of MS patients. The goal of this study was to determine the level of single-stranded DNA breaks in whole blood or isolated peripheral blood mononuclear cells (PBMNCs) by means of alkaline single cell gel electrophoresis (comet assay) and to evaluate production of NO in the human blood by applying electron paramagnetic resonance (EPR) spectroscopy. Groups of healthy subjects and MS patients were enrolled in the study. Blood samples were obtained by vein puncture and divided in aliquots for the analysis of the whole blood and isolated PBMNC with comet assay. Alkaline single cell gel electrophoresis was performed on whole blood and isolated PBMNC samples of 28 patients and 15 controls. A separate blood sample was mixed with a spin-trap, frozen in liquid nitrogen and used for NO detection by EPR; 22 MS patients and 22 controls were tested. A statistically significant increase in the level of DNA breakage was observed in specimens taken from MS patients compared to healthy persons. The level of DNA damage in whole blood and PBMNCs of the same group was similar. NO production was significantly higher in the blood of MS patients.