Macrophages peroxynitrite production

It has been shown that lung macrophages from patients with systemic sclerosis (SS) produced the elevated levels of nitric oxide, superoxide, and peroxynitrite and expressed the enhanced level of iNOS [281], NAC administration reduced peroxynitrite production and might be possibly recommended for the treatment SS patients. Solans et al. [282] found the significant enhancement of lipid peroxidation in erythrocytes from SS patients. Cracowski et al. [283] showed that in vivo lipid peroxidation was enhanced in scleroderma spectrum disorders including SS and undifferentiated connective tissue disease. 

FIGURE 7.9 (See color insert) Peroxynitrite production by activated macrophages. Cells isolated from control (CTL) and toxicant (TOX)-treated animals were cultured overnight in the presence of IFNa + LPS. Phorbol myristate acetate was then added. Thirty minutes later, the cells were loaded with DHR 123. After 5 minutes incubation, the cells were rinsed and analyzed for fluorescence associated with peroxynitrite production by confocal microscopy. 

FIGURE 7.9 Peroxynitrite production by activated macrophages. For description, see page 115. 

We have used the nitration of a tyrosine analog with superoxide dismutase to measure the peroxynitrite production from activated rat alveolar macrophages (Fig. 38). The estimated rate of peroxynitrite synthesis was estimated to be 0.1 nmol/10 cells/min (Ischiropoulos et al., 1992a). The rate of nitration was the same whether native Cu,Zn-superoxide dismutase or the phenylglyoxyl-H202 modified superoxide dismutase (which is >99% inhibited with respect to its superoxide scavenging activity) was used (Fig. 39). Three other independent but indirect estimates of peroxynitrite formation were consistent with the superoxide... 

High antioxidative activity carvedilol has been shown in isolated rat heart mitochondria [297] and in the protection against myocardial injury in postischemic rat hearts [281]. Carvedilol also preserved tissue GSL content and diminished peroxynitrite-induced tissue injury in hypercholesterolemic rabbits [298]. Habon et al. [299] showed that carvedilol significantly decreased the ischemia-reperfusion-stimulated free radical formation and lipid peroxidation in rat hearts. Very small I50 values have been obtained for the metabolite of carvedilol SB 211475 in the iron-ascorbate-initiated lipid peroxidation of brain homogenate (0.28 pmol D1), mouse macrophage-stimulated LDL oxidation (0.043 pmol I 1), the hydroxyl-initiated lipid peroxidation of bovine pulmonary artery endothelial cells (0.15 pmol U1), the cell damage measured by LDL release (0.16 pmol l-1), and the promotion of cell survival (0.13 pmol l-1) [300]. SB 211475 also inhibited superoxide production by PMA-stimulated human neutrophils. 

NO generated in the immune system does not operate through GC. Instead, NO appears to act directly as a cytotoxic molecule or as some other reactive product such as ONOO (peroxynitrite). During the immune oxidative burst in macrophage cells, reactive oxygen intermediates. 

Generation of peroxynitrite in the vascular compartment as the result of ischemia/reperfusion. The introduction of oxygen following ischemia will initiate the simultaneous production of superoxide and nitric oxide. Neutrophils and macrophages may also generate nitric oxide and peroxynitrite directly. The rate of forming peroxynitrite will increase as the pnxluct of nitric oxide and superoxide concentration, and thus will increase rapidly under conditions when both are produced simultaneously. 

NOS products of neurons, epithelial cells and other cells in the lung have both bronchodilator and inflammatory properties (Gaston etal., 1994b) the specific nature of this bioactivity depends on the chemical characteristics of the functional products in the specific microenvironment under consideration. For example, NO is capable of complexing with and affecting the activity of a variety of metalloproteins and enzymes, such as guanylyl cyclase and ribonucleotide reductase (Nathan, 1992 Stamler et al., 1992). NO can also complex with superoxide anion to form peroxynitrite, which has a cytotoxic immune effector role (Radi etal., 1991 Stamler etal., 1992). Furthermore, NO can form iron nitrosyl complexes, which are the putative intracellular macrophage products of iNOS responsible for lysis of intracellular parasites (Hibbs... 

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