| Immunohistological staining of nitrotyrosine (Ntyr) has been observed in a number of inflammatory pathologies with a prominent immune response, including transplantation. We hypothesized that the generation of nitrated protein epitopes following peroxynitrite (ONOO-) release increases antigen-dependent inflammation as modified self-proteins become novel epitopes and generate "nitroimmunity." This dissertation addresses the implications of protein nitration for the immune response in the pathobiology of chronic renal allograft rejection.;Tubular damage and loss with severe interstitial inflammation and fibrosis may be the most important determinant of chronic renal allograft dysfunction. Biochemical analysis confirmed an increased expression of inducible nitric oxide synthase, progressive nitration and inactivation of manganese superoxide dismutase, and a 90% decrease in reduced glutathione, indicating an altered oxidant environment in the rejecting graft. Time- and dose-dependent necrotic cell death was replicated in vitro following exposure of human renal proximal tubular epithelial cells to ONOO- or SIN-1.;The role of oxidant injury was further examined in a rodent model of chronic allograft nephropathy (CAN). Animals on a high-salt diet demonstrated elevated expression of nitric oxide synthase (NOS) and increased Ntyr in both tissue and urine. High dietary salt also accelerated the onset and progression of glomerular and tubular dysfunction and enhanced fibrotic changes characteristic of CAN. The increased levels of ONOO- released secondary to dietary salt induction of NOS synthase may facilitate molecular reactions that alter metabolic function and structural elements of the kidney.;Antibodies against nitrated epitopes, detected in both human and rat allografts, correlated with disease progression and severity. These antibodies were primarily selective for Ntyr versus L-tyrosine, amino-tyrosine, dinitrophenol, or tryptophan. Nitrated epitopes persisted at levels sufficient to induce isotype switching, predominantly to the IgG2 subtype in humans. One target of these nitrospecific antibodies in rats and humans is ONOO- -treated acidic fibroblast growth factor, a potent mitogen implicated in the characteristic sclerosis in CAN.;It was concluded that injury secondary to reactive nitrogen species creates novel immunoepitopes against which immunological effector mechanisms are generated. A greater understanding of nitroimmunity will generate novel interventional therapy for allograft survival and may have implications for other chronic inflammatory conditions. |
