One-electron reduction of an anthracycline antibiotic carminomycin by a human erythrocyte redox chain

Antiplasmodial activity of nitroaromatic and quinoidal compounds: redox potential vs. inhibition of erythrocyte glutathione reductase

Prooxidant nitroaromatic and quinoidal compounds possess antimalarial activity, which might be attributed either to their formation of reactive oxygen species or to their inhibition of antioxidant enzyme glutathione reductase (GR, EC 1.6.4.2). We have examined the activity in vitro against Plasmodium falciparum of 24 prooxidant compounds of different structure (nitrobenzenes, nitrofurans, quinones, 1,1'-dibenzyl-4,4'-bipyridinium, and methylene blue), which possess a broad range of single-electron reduction potentials (E(1)(7)) and erythrocyte glutathione reductase inhibition constants (K(i(GR))). For a series of homologous derivatives of 2-(5'-nitrofurylvinyl)quinoline-4-carbonic acid, the relationship between compound K(i(GR)) and concentration causing 50% parasite growth inhibition (IC(50)) was absent. For all the compounds examined in this study, the dependence of IC(50) on their K(i(GR)) was insignificant. In contrast, IC(50) decreased with an increase in E(1)(7) and positive electrostatic charge of aromatic part of molecule (Z): log IC(50) (microM) = -(0.9846 +/- 0.3525) - (7.2850 +/- 1.2340) E(1)(7) (V) - (1.1034 +/- 0.1832) Z (r(2) = 0.8015). The redox cycling activity of nitroaromatic and quinoidal compounds in ferredoxin:NADP(+) reductase-catalyzed reaction and the rate of oxyhemoglobin oxidation in lysed erythrocytes increased with an increase in their E(1)(7) value. Our findings imply that the antiplasmodial activity of nitroaromatic and quinoidal compounds is mainly influenced by their ability to form reactive oxygen species, and much less significantly by the GR inhibition.

Plasma membrane as a site of redox activation of daunomycin in intact human erythrocytes. Quantitative evaluation of the hydrogen peroxide produced by the membrane with respect to the cytosol

The relative importance in human red blood cells of the plasma membrane as a site of redox activation of anthracyclines as compared to hemoglobin was evaluated by assaying the H2O2 produced upon exposure to daunomycin. The method of H2O2-dependent irreversible inhibition of catalase (EC 1.11.1.6) activity by 3-amino-1,2,4-triazole was applied to intact erythrocytes, as well as to isolated membranes with added purified catalase. The results obtained indicate a secondary role in daunomycin activation for the plasma membrane from a quantitative point of view, although membrane pathways can be more harmful than cytosolic pathways, especially towards extracellular targets, when the high efficiency of the cytosolic antioxidative defences and the external location of the membrane activation site are considered.

Effect of carminomycin on the viability of fibroblasts from patients with regular trisomy 21

The sensitivity of three human fibroblast lines, trisomic with respect to chromosome 21, to an anthracycline antibiotic carminomycin was compared with that of a normal fibroblast line using a 51Cr release assay. It was found that for an intermediate antibiotic concentration (10 microM) the sensitivity of trisomic fibroblasts, of increased content of Cu,Zn-superoxide dismutase was lower. These results suggest a role for superoxide-mediated membrane damage in the cytotoxic action of anthracycline antibiotics.