PEROXYNITRITE AUGMENTS FMLP-STIMULATED CHEMILUMINESCENCE BY NEUTROPHILS IN HUMAN WHOLE-BLOOD

The neutrophil respiratory burst was examined by the technique of lumi nol-dependent chemiluminescence (LDCL) triggered by submaximal concent rations of N-formyl-methionyl-leucyl-phenylalanine (fMLP) in diluted w hole blood, We sought to identify the chemical species responsible for LDCL in whole blood, to examine the role of leukotriene B-4 (LTB(4)) and other arachidonic acid metabolites as mediators of the fMLP signal ing pathway, and to investigate the effect of peroxynitrite on this re sponse, Both sodium azide and taurine significantly inhibited LDCL (93 % inhibition with 100 mu M azide, 52% inhibition with 10 mM taurine), More modest inhibition was seen with superoxide dismutase (SOD), catal ase, the nitric oxide synthase inhibitor monomethyl-L-arginine (L-NMMA ), and with inhibitors of the cyclooxygenase (indomethacin), lipoxygen ase (AA-861; no effect), and cytochrome P-450 (SKF 525-A) pathways of arachidonic acid metabolism, The nitric oxide donor SIN-1 (1-100 mu M) and peroxynitrite (10-300 mu M) also augmented fMLP-induced LDCL. The augmentation seen with peroxynitrite and SIN-1 was attenuated by SOD. Despite the increase in LDCL, peroxynitrite caused a dose-related inh ibition of fMLP-stimulated LTB(4) release, In summary, our results ind icate that (1) LDCL elicited by fMLP in diluted whole blood appears pr imarily mediated by hypochlorous acid derived from myeloperoxidase; (2 ) pretreatment with the nitric oxide donor SIN-1 or with peroxynitrite augments LDCL; and (3) LTB(4) release does not contribute to fMLP-sti mulated LDCL or in the modulation of LDCL by SIN-1 or peroxynitrite.