EXTENSIVE TYROSINE NITRATION IN HUMAN MYOCARDIAL INFLAMMATION - EVIDENCE FOR THE PRESENCE OF PEROXYNITRITE

Objectives: Production of nitric oxide via the cytokine-mediated activ ation of myocardial inducible nitric oxide synthase decreases myocardi al contractility, Whether myocardial dysfunction is mediated directly by nitric oxide or indirectly through the formation of secondary react ion products, such as peroxynitrite, has not been established, Peroxyn itrite, but not nitric oxide, reacts with the phenolic ring of tyrosin e to form the stable product 3-nitro-L-tyrosine. Demonstration of tiss ue nitrotyrosine residues, therefore, infers the presence of peroxynit rite or related nitrogen-centered oxidants. Design: Retrospective anal ysis of human autopsy specimens. Setting: University pathology and bas ic science laboratories. Patients: Formalin fixed, paraffin-embedded m yocardial tissue samples were obtained from 11 patients with a diagnos is of sepsis, seven patients with a diagnosis of viral myocarditis, an d five control patients without clinical or pathologic cardiac disease . Interventions: None. Measurements and Main Results: Specific antibod ies to nitrotyrosine were utilized to detect nitrotyrosine residues in human autopsy specimens, Cardiac tissue obtained from patients with m yocarditis or sepsis demonstrated intense nitrotyrosine immunoreactivi ty in the endocardium, myocardium, and coronary vascular endothelium a nd smooth muscle, In contrast, connective tissue elements were without appreciable immunohistochemical staining, Nitrotyrosine antibody bind ing was blocked by coincubation with nitrotyrosine or nitrated bovine serum albumin, but not by aminotyrosine, phosphotyrosine, or bovine se rum albumin, In situ reduction of tissue nitrotyrosine to aminotyrosin e by sodium hydrosulfite also blocked antibody binding, Densitometric analysis of nitrotyrosine immunoreactivity demonstrated significantly higher values for specimens from myocarditis and sepsis patients when compared with control tissue specimens. Conclusion: These results demo nstrate the formation of peroxynitrite within the myocardium during in flammatory disease states, suggesting a role for peroxynitrite in infl ammation-associated myocardial dysfunction.