Peroxynitrite induced structural changes result in the generation of neo-epitopes on human serum albumin

Human serum albumin (HSA), the most abundant plasma protein, is quite vulnerable to oxidizing and nitrating agents. In this study, peroxynitrite induced nitration and oxidation of HSA was assessed by various physicochemical techniques. Cross-linking of HSA was evident on polyacrylamide gel electrophoresis. The carbonyl content was markedly elevated in peroxynitrite-modified HSA as compared to the native protein. Dityrosine and 3-nitrotyrosine were present only in peroxynitrite-modified HSA. The peroxynitrite-modified HSA induced high titre antibodies in experimental animals showing high specificity towards the immunogen. Spectroscopic studies showed structural alterations in the HSA molecule upon peroxynitrite treatment which result in the generation of neo-epitopes and enhanced immunogenicity. The possible role of damaged HSA in various diseases has been suggested.