tempo and peroxynitric-acid

Peroxynitrite (ONOO(-)) the highly reactive coupling product of nitric oxide and superoxide, has been implicated in the pathogenesis of an increasing number of (inflammatory) diseases. At present, however, selective peroxynitrite antagonizing agents with therapeutic potential are not available. Therefore, the NADPH-oxidase inhibitor apocynin (4-hydroxy-3-methoxy-acetophenone) was tested for its ability to inhibit peroxynitrite formation in vitro The murine macrophage cell-line J774A.1, stimulated with IFNgamma/LPS, was used as a model. Conversion of 123-dihydrorhodamine (123-DHR) to its oxidation product 123-rhodamine was used to measure peroxynitrite production. Stimulated peroxynitrite formation could be completely inhibited by apocynin, by the superoxide scavenger TEMPO as well as by the nitric oxide synthase inhibitor aminoguanidine. Apocynin and aminoguanidine specifically inhibited superoxide and nitric oxide formation respectively as confirmed by measuring lucigenin enhanced chemiluminescence and nitrite accumulation. It is concluded that J774A.1 macrophages produce significant amounts of peroxynitrite, which is associated with nitric oxide production and NADPH-oxidase dependent superoxide formation. The NADPH-oxidase inhibitor apocynin proved to be a potent inhibitor of both superoxide and peroxynitrite formation by macrophages, which may be of future therapeutic significance in a wide range of inflammatory disorders.

Topics: Acetophenones; Acridines; Animals; Antioxidants; Cell Line; Cyclic N-Oxides; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanidines; Interferon-gamma; Lipopolysaccharides; Luminescent Measurements; Macrophages; Mice; Molsidomine; Nitrates; Nitric Oxide Synthase; Oxidation-Reduction; Rhodamines

The action of peroxynitrite on human erythrocytes and erythrocyte membranes was studied. Peroxynitrite (0.1-2 mM) induced a transient decrease of intracellular reduced glutathione, oxidized membrane protein -SH groups, initiated membrane lipid peroxidation and inactivated erythrocyte membrane acetylcholinesterase and ATPase activities. Membranes exposed to peroxynitrite showed aggregation and nitration of proteins and changes in protein organization detectable with a maleimide spin label.

Topics: Acetylcholinesterase; Adenosine Triphosphatases; Adult; Cholinesterase Inhibitors; Cyclic N-Oxides; Deferoxamine; Enzyme Inhibitors; Erythrocyte Membrane; Erythrocytes; Glutathione; Hemoglobins; Humans; Lipid Peroxidation; Maleimides; Membrane Lipids; Membrane Proteins; Nitrates; Oxidation-Reduction; Spin Labels; Sulfhydryl Compounds