Study On The Mechanism Of DNA Strand Breakage Induced By Peroxynitrite And The Suppression Function Of Some Antioxidants

Peroxynitrie, which is produced in vivo by the reaction of nitric oxide and superoxide, is a powerful oxidant. It may be the crucial step in the pathological and physiological damage induced by nitric oxide. At present, it has been found that peroxynitrite is involved in some diseases, such as shock, atherosclerosis, ischemic infusion. It has an important academic signification to develop the study on its properity and its pathological and physiological function, which can provide a new way to treat with some illnesses.In this paper, we mostly study the mechanism of DNA damage induced by peroxynitrite, the effect of carbon dioxide on the reaction of peroxynitrite with DNA and the inhibition effect of several antioxidants on the DNA damage. The results are as follwed:1. It has been demonstrated that peroxynitrite can induce pBR322 single-stranded breakage obviously under near physiological condition. The ability of peroxynitrite breaking DNA is related with pH, which is mostly strongest in the acid solution. At the same time, through the TBA reavealing color reaction, we find ·OH produced when peroxynitrite reacts with DNA. The amount of ·OH is more in the acid solution than in the neutral solution. Those suggest that the reaction of peroxynitrite with DNA is a free radical mechanism: peroxynitrite reacts in the form of its acid, which cleaves into ·NO2 and ·OH to damage DNA.2. Because the concentration of CO2 is considerable high in vivo, it is necessary to evaluate the effect of CO2 on the reaction of peroxynitrite with DNA. In present study, the results show that CO2 can change the reaction route of peroxynitrite so that it can affect the DNA damage induced by peroxynitrite. CO2 decreases the DNA single-stranded breakages induced by peroxynitrite obviously, but it also can increases the amount of 8-NO2 guanine induced by peroxynitrite. The effect of CO2 on the DNA damage induced by peroxynitrite demonstrates the free radical mechanism that peroxynitrite reacts with DNA further. 3. Some antioxidants including Na2SeO3, GSH, ascorbic acid and Ebselen to suppress DNA damage induced by peroxynitrite are investigated. In which, Ebselen reducing DNA damage is the best. Na2SeO3 and GSH are secondary during some concentrations in this study. Interestingly, ascorbic acid is a good antioxidant to inhibit peroxynitrite-induced DNA damage in lower concentration, but plays contrary role in higher content.