Antimycobacterial Drugs and the Production of Reactive Oxidants by Polymorphonuclear Leucocytes in vitro

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Abstract
The effect of five antimycobacterial drugs isoniazid, rifampicin, streptomycin, pyrazinamide and ethambutol on the generation of reactive oxidants by polymorphonuclear leucocytes was investigated in vitro, using N-formyl-L-methionyl-L-leucyl-phenylalanine (FMLP) activated and spontaneous luminol-enhanced chemiluminescence and myeloperoxidase-mediated iodination. Streptomycin, pyrazinamide and ethambutol had no effect on the assays at the concentrations investigated. Isoniazid at concentrations of 1.25 and 5 μg/ml and rifampicin at 100 μg/ml significantly inhibited iodination. Rifampicin also caused dose-dependent inhibition of chemiluminescence, which was partly due to its light-absorbing activities. It is concluded that isoniazid, and to a lesser extent, rifampicin at therapeutic concentrations possess anti-oxidative properties.