Stimulation of free radical formation by aminoglycoside antibiotics

We have previously shown gentamicin to form a redox-active iron chelate. Th is study investigates whether other aminoglycosides can likewise stimulate the generation of reactive oxygen species (free radicals). Kanamycin, neomy cin and streptomycin were compared to gentamicin in intact cells and in cel l-free in vitro assays using luminescence detection with lucigenin or lumin ol. Neutrophils and Epstein-Barr virus-transformed lymphoblastoid cells ser ved as cell models in which a respiratory burst of superoxide was induced b y phorbol ester. The addition of millimolar amounts of any of the aminoglyc osides increased the luminescence significantly. The drugs also increased t he formation of free radicals in an enzymatic (hypoxanthine-xanthine oxidas e) and a non-enzymatic (phenazine methosulfate-NADH) superoxide-generating system. Half-maximal stimulation was reached with 0.4 mM gentamicin, and th ere was an absolute requirement for an electron donor, arachidonic acid. In both intact cells and cell-free systems, gentamicin-enhanced luminosity wa s suppressed by iron chelators. These results demonstrate that different am inoglycoside antibiotics can stimulate the formation of free radicals in bi ological and in cell-free systems. Luminescence detection is a convenient a ssay method to investigate the redox properties of these drugs. (C) 1999 El sevier Science B.V. All rights reserved.