Photocytotoxicity of a 5-nitrofuran-ethenyl-quinoline antiseptic (Quinifuryl) to P388 mouse leukemia cells

Antiplasmodial Activity of Nitroaromatic Compounds: Correlation with Their Reduction Potential and Inhibitory Action on Plasmodium falciparum Glutathione Reductase

With the aim to clarify the mechanism(s) of action of nitroaromatic compounds against the malaria parasite Plasmodium falciparum, we examined the single-electron reduction by P. falciparum ferredoxin:NADP⁺ oxidoreductase (PfFNR) of a series of nitrofurans and nitrobenzenes (n = 23), and their ability to inhibit P. falciparum glutathione reductase (PfGR). The reactivity of nitroaromatics in PfFNR-catalyzed reactions increased with their single-electron reduction midpoint potential (E¹₇). Nitroaromatic compounds acted as non- or uncompetitive inhibitors towards PfGR with respect to NADPH and glutathione substrates. Using multiparameter regression analysis, we found that the in vitro activity of these compounds against P. falciparum strain FcB1 increased with their E¹₇ values, octanol/water distribution coefficients at pH 7.0 (log D), and their activity as PfGR inhibitors. Our data demonstrate that both factors, the ease of reductive activation and the inhibition of PfGR, are important in the antiplasmodial in vitro activity of nitroaromatics. To the best of our knowledge, this is the first quantitative demonstration of this kind of relationship. No correlation between antiplasmodial activity and ability to inhibit human erythrocyte GR was detected in tested nitroaromatics. Our data suggest that the efficacy of prooxidant antiparasitic agents may be achieved through their combined action, namely inhibition of antioxidant NADPH:disulfide reductases, and the rapid reduction by single-electron transferring dehydrogenases-electrontransferases.

Light induced cytotoxicity of nitrofurantoin toward murine melanoma

The cytotoxicity of nitrofurantoin (NFT) in the dark and after light exposure (UVA irradiation, λ = 385 nm) was evaluated in murine melanoma B16F10 cells. NFT induces both cell proliferation and inhibition of cell viability. The dominance of one or the other effect depends on the drug concentration, incubation time (t_inc) and irradiation dose. The uptake of NFT in these cells, as well as its photocytotoxicity, reaches saturation after 24 hours of incubation. The mechanism of cell death in the dark is associated with the enzymatic release of nitric oxide (NO). The increase of NFT cytotoxicity under light irradiation is associated with the increase of NO concentration due to photorelease. NO photorelease by NFT in solution was confirmed by chemiluminescence, while NO formation in cells was confirmed by fluorescence microscopy using DAF-2DA, a specific indicator of NO in living cells. The NFT does not enter nuclei, distributing preferentially in the cell cytoplasm, as shown by fluorescence microscopy.