Analysis of human DNA-arginine photoadduct modified with peroxynitrite

Amino acid arginine and adducts: autoimmune activity

Arginine is derived from dietary intake, body protein breakdown, or endogenous de novo arginine production. Arginine methylation of non-histone proteins is used in transcriptional regulation. Protein-arginine methylation is used for regulation of transcriptional and various physiological pathological processes. Protein methylation may affect protein-protein, protein-DNA, or protein-RNA interaction. Arginine has an effect on the DNA-binding activity of NF-κB, a dominant transcriptional factor in inflammation. Adduct formation results in increased secretion of messenger molecules such as cytokines and chemokines that mediate communication among cells and promote inflammation. Arginine and lysine amino acid-rich histones in nucleosomes on modification by environmental agents form histone-DNA adducts, making it immunogenic. Alteration of DNA resulting from photomodification could lead to the development of antibodies or mutations to modified DNA. Lysine and arginine-rich histones in nucleosomes on modification by environmental agents form histone-DNA adducts, making it immunogenic. Alteration of DNA resulting from photomodification could lead to the development of antibodies or mutations to modified DNA. Therefore, the DNA-arginine photoadduct and modified photoadduct could have important implications in various pathophysiological conditions such as toxicology, carcinogenesis, and autoimmune phenomena. Abbreviations: Arg: Arginine; SLE: systemic lupus erythematosus; UV: ultraviolet; Tm: thermal melting temperature; NO: nitric oxide; O₂.^-: superoxide anion.

Genotoxic effect and antigen binding characteristics of SLE auto-antibodies to peroxynitrite-modified human DNA

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease characterized by auto-antibodies against native deoxyribonucleic acid after modification and is one of the reasons for the development of SLE. Here, we have evaluated the structural perturbations in human placental DNA by peroxynitrite using spectroscopy, thermal denaturation and high-performance liquid chromatography (HPLC). Peroxynitrite is a powerful potent bi-functional oxidative/nitrative agent that is produced both endogenously and exogenously. In experimental animals, the peroxynitrite-modified DNA was found to be highly immunogenic. The induced antibodies showed cross-reactions with different types of DNA and nitrogen bases that were modified with peroxynitrite by inhibition ELISA. The antibody activity was inhibited by approximately 89% with its immunogen as the inhibitor. The antigen-antibodies interaction between induced antibodies with peroxynitrite-modified DNA showed retarded mobility as compared to the native form. Furthermore, significantly increased binding was also observed in SLE autoantibodies with peroxynitrite-modified DNA than native form. Moreover, DNA isolated from lymphocyte of SLE patients revealed significant recognition of anti-peroxynitrite-modified DNA immunoglobulin G (IgG). Our data indicates that DNA modified with peroxynitrite presents unique antigenic determinants that may induce autoantibody response in SLE.