Mercaptopyridine-N-oxide, an NADH-fumarate reductase inhibitor, blocksTrypanosoma cruzigrowth in culture and in infected myoblasts

Abstract

The enzyme NADH-fumarate reductase is not found in mammalian cells but it is present in several parasitic protozoa including Trypanosoma cruzi, the parasite that causes Chagas' disease. This study shows that the drug 2-mercaptopyridine-N-oxide (MPNO) inhibits NADH-fumarate reductase purified from T. cruzi (ID50 = 35 microM). When added to intact cells, MPNO inhibited the growth of T. cruzi epimastigotes in culture (ID50 = 0.08 microM) as well as the infection of mammalian myoblasts by T. cruzi trypomastigotes (ID50 = 20 microM). At a concentration of 2.4 microM, MPNO also inhibited the growth of amastigotes (intracellular dividing forms) in cultured mammalian myoblasts. Supplementation of culture media with 5 mM succinate, the product of fumarate reductase, partially protected against the inhibition of the growth of epimastigotes by MPNO. Moreover, MPNO inhibited the accumulation of succinate in cultures of epimastigotes, as measured by high performance liquid chromatography. Although MPNO may have other intracellular targets in addition to fumarate reductase, these results support the hypothesis that compounds which inhibit the enzyme fumarate reductase may be potential chemotherapeutic agents against Chagas' disease.

Synthesis and characterization of a pyridine-2-thiol N-oxide gold(I) complex with potent antiproliferative effect against Trypanosoma cruzi and Leishmania sp. insight into its mechanism of action

“…The Au complex inhibited the growth of Dm28c T. cruzi epimastigotes at lower concentrations than those that blocked NADH fumarate reductase in vitro. A similar behaviour was previously described for Na mpo on T. cruzi Y strain [18].…”

“…It has been previously reported that mpo is an effective NADHfumarate reductase inhibitor on T. cruzi epimastigotes [18]. In addition, we have recently demonstrated that Pd(mpo) 2 and Pt(mpo) 2 complexes are also able to inhibit the enzyme activity of T. cruzi epimastigotes and that inhibition could be increased by metal complexation [19].…”

“…Fifty percent inhibitory concentration (IC 50 ) deduced from the dose-response curve was 0.09 lM. The Au(I) complex resulted significantly more active than the free ligand (Na mpo IC 50 0.190 lM) and than the reference drug Nifurtimox (IC 50 6 lM) [18,48]. A similar effect of metal complexation on bioactivity of mpo against T. cruzi epimastigotes was previously observed when using Pd(II) or Pt(II) as metal ion, i.e.…”

“…1). Mpo blocks T. cruzís growth in culture and in infected mammalian myoblasts, affecting all stages of the life cycle of the parasite without affecting mammalian cells and showing low IC 50 values [18]. Although it may have other intracellular targets, it inhibits the parasite-specific enzyme NADH-fumarate reductase, enzyme responsible of the conversion of fumarate to succinate.…”

Bisphosphonates as Inhibitors of Trypanosoma cruzi Hexokinase

“…Several hypotheses have been advanced to explain this phenomenon, among them the requirement of the combined action of glycosomal phosphoenolpyruvate carboxykinase and malate dehydrogenase to maintain the glycosome redox balance (11,12); malate is probably converted to succinate by a reversion of the Krebs cycle (11,12) and/or the activity of glycosomal and mitochondrial fumarate reductase (42)(43)(44), to generate extra reducing power. However, it has also been proposed that both glycosomal and mitochondrial phosphoenolpyruvate carboxykinases and malate dehydrogenases are involved in the decarboxylation of oxaloacetate, generated from the oxidation of amino acids through the Krebs cycle, with the production of phosphoenolpyruvate, which can re-enter the cycle to complete oxidative breakdown (10,26,28,45).…”