Effect of sulfur amino acids on stimulus-induced superoxide generation and translocation of p47 phox and p67 phox to cell membrane in human neutrophils and the scavenging of free radical

Abstract

Background Various cystathionine metabolites are in the urine of the patients with cystathioninuria. Among these metabolites, cystathionine ketimine significantly enhanced N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced superoxide generation in parallel with tyrosyl phosphorylation of 45 kDa protein in human neutrophils. Methods We investigated the effect of various sulfur amino acids on fMLP-, phorbol-12-myristate-13-acetate (PMA)- and arachidonic acid (AA)-induced superoxide generation in human neutrophils. In addition, the effects of these sulfur amino acids on the membrane translocation of cytosolic compounds p47 phox and p67 phox and on the scavenging of superoxide anions were investigated. Results When the cells were preincubated with various sulfur amino acids, fMLP-induced superoxide generation was enhanced by d,l-homocysteine and d,l-homocysteine-thiolactone but was inhibited by other sulfur amino acids in a concentration-dependent manner. The AA-induced superoxide was enhanced by l-cysteine, N-acetyl- l-cysteine and d,l-homocysteine. The strength of enhancing effect was: l-cysteine≫ N-acetyl- l-cysteine> d,l-homocysteine. On the other hand, the superoxide generation was weakly inhibited by l-cystathionine. The superoxide generation induced by PMA was weakly inhibited by l-cysteine, N-acetyl- l-cysteine and l-cystathionine. Homocysteine and d,l-homocysteine-thiolactone had no effect. In addition, d,l-homocysteine also enhanced translocation to the cell membrane of cytosolic compounds p47 phox and p67 phox. Conversely, l-cystathionine and N-acetyl- l-cysteine inhibited the translocation to membrane of p47 phox and p67 phox in a concentration-dependent manner. N-acetyl- l-cysteine and l-cysteine revealed scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The sulfur amino acids tested also indicated radical scavenging activity on superoxide anion generated by phenazine methoxysulfate (PMS)–NADH system. Conclusion d,l-homocysteine and d,l-homocysteine-thiolactone enhanced fMLP-induced superoxide generation by the increment of translocation to membrane of p47 phox and p67 phox. l-cystathionine and N-acetyl- l-cysteine suppressed fMLP- and PMA-induced superoxide generation by the inhibition of translocation to membrane of p47 phox and p67 phox. N-acetyl- l-cysteine also had scavenging activity against DPPH radicals and superoxide anion.