Increased native chemiluminescence in granulocytes isolated from synovial fluid and peripheral blood of patients with rheumatoid arthritis

Differences in the reactivity of phthalic hydrazide and luminol with hydroxyl radicals

The reactivity of 5-amino-2,3-dihydro-phthalazine-1,4-dione (luminol) and phthalic hydrazide with hydroxyl radicals was studied. HO*-radicals were generated by the Fenton reaction as well as by water radiolysis. Both luminol and phthalic hydrazide react with hydroxyl radicals under intense chemiluminescence (CL) emission. However, exclusively the CL arising from phthalic hydrazide oxidation can be quenched by competition (e.g. by the addition of carbohydrates), whereas luminol CL is enhanced. The reactivities of both compounds with HO*-radicals were further studied by time-resolved spectroscopy (pulse radiolysis), competition methods, NMR spectroscopy and mass spectrometry. Whereas only slight differences were detectable by pulse radiolysis, the analysis of competition kinetics in the presence of p-nitroso-dimethylaniline (NDMA) gave a two-fold-enhanced reactivity for luminol (4.8 x 10(9) l mol(-1) s(-1)) in comparison to phthalic hydrazide (2.0 x 10(9) l mol(-1) s(-1)). NMR and mass spectrometric analyses revealed significant differences in the reactivity of HO*-radicals: whereas in luminol solutions hydroxylation of the aromatic ring system predominated, hydroxylated products were not detectable upon irradiation of phthalic hydrazide. A hypothetical mechanism is proposed which may explain the observed differences.

Peroxidation of egg yolk phosphatidylcholine liposomes by hypochlorous acid

The powerful neutrophil-derived oxidant hypochlorous acid HOCl/OCl- is assumed to contribute to tissue injury in a number of pathological states accompanied by massive accumulation of neutrophils. The production of malondialdehyde to indicate lipid peroxidation was studied in egg yolk phosphatidylcholine liposomes upon treatment with NaOCl as a source for hypochlorous acid. Its accumulation was inhibited by alpha-tocopherol and butylated hydroxytoluene. Singlet oxygen, hydroxyl radicals or superoxide anion radicals derived from direct reactions of hypochlorous acid seem not to be involved in initiation of lipid peroxidation because the malondialdehyde accumulation was unaffected by hydrogen peroxide, catalase, superoxide dismutase, ferrous sulphate or ferric chloride. Double bonds of fatty acid residues seem to be the primary target for NaOCl. Their number is continuously diminished in liposomes (2 mg lipids/ml) after incubation with increasing amounts of NaOCl at 37 degrees C for 40 min as detected by two independent methods (iodine bromide reduction and 1H-NMR spectroscopy). A 1:1 molar ratio between the loss of double bonds and NaOCl added was found only at low NaOCl concentrations. Then double bonds are decreased with a lower efficiency. A continuous increase of lipid peroxidation products was only observed up to 0.5-0.7 mmol/l NaOCl. The yield of lipid hydroperoxides kept constant at higher NaOCl concentrations. However, diene conjugates and malondialdehyde exhibit a maximum at 0.7-1 mmol/l or 0.5 mmol/l NaOCl, respectively, while the concentration of these products decreases at higher doses of NaOCl. The decrease of malondialdehyde was more pronounced than for diene conjugates. These results were discussed from the background that at minimum two (diene conjugates) or three (malondialdehyde) double bonds in a fatty acid residue are necessary for formation of lipid peroxidation products.