Modulatory role of nitric oxide on superoxide-dependent luminol chemiluminescence

Reactive oxygen species are involved in luminol chemiexcitation induced in biological systems, but the contribution of nitrogen-derived oxidants in the process still remains unclear. Herein, we report that luminol chemiluminescence (LCL) induced by a superoxide (O-2(.-))- and hydrogen peroxide (H2O2)-generating system (2-25 mU/ml xanthine oxidase plus acetaldehyde and oxygen) was markedly inhibited by nitric oxide ((NO)-N-.) added either as bolus (0-10 mu M) Or a continuous flow (0-10 mu M/min). However, the inhibition of LCL was followed by an overshoot in light emission after most (NO)-N-. was consumed or the infusion stopped and was due to reactions of remaining peroxynitrite, the product of the reaction between O-2(.-) and (NO)-N-., with luminol. Nitric oxide also inhibited peroxynitrite- and glucose oxidase-induced LCL, but no overshoot was observed. On the other hand, a continuous flux of pure peroxynitrite, at 2 to 10 mu M/min, induced LCL with quantum yields close to those obtained by identical micromolar fluxes of O-2(.-), while peroxynitrite formed from the decomposition of the sydnonimine SIN-1 yielded 76% of the chemiluminescence obtained with authentic peroxynitrite. Peroxynitrite-induced LCL was 80 and 55% inhibitable by SOD and catalase, respectively, showing that there were O-2(.-) and H2O2-dependent routes of chemiexcitation. The hydroxyl radical scavengers dimethyl sulfoxide, mannitol, and ethanol and the metal chelator diethylenetriaminepentaacetic acid did not inhibit peroxynitrite-induced LCL while desferrioxamine was an efficient inhibitor of Light emission by reaction with an activated state of peroxynitrous acid which is responsible of performing the initial one-electron oxidation of luminol, Our results are consistent with a dual role of (NO)-N-. in O-2(.-)-induced LCL: (I) formation of peroxynitrite which in turn promotes the cal intermediates directing the system toward a dark pathway. These considerations are of critical importance when analyzing cell- and tissue-derived LCL in (NO)-N-.-, O-2(.-), and peroxynitrite-producing systems. (C) 1996 Academic Press, Inc.