Mechanism of action of anti-proliferative lysophospholipid analogues against the protozoan parasite Trypanosoma cruzi: potentiation of in vitro activity by the sterol biosynthesis inhibitor ketoconazole

Abstract

We investigated the mechanism of action of metabolically stable lysophospholipid analogues (LPAs), with potent anti-tumour and anti-protozoal activity against Trypanosoma cruzi, the causative agent of Chagas' disease. Against the axenically grown epimastigote form of the parasite, the IC(50)s after 120 h for ET-18-OCH(3), miltefosine and ilmofosine were 3, 1 and 3 microM, respectively; at higher concentrations immediate lytic effects were observed. Eradication of the intracellular amastigote, grown inside Vero cells, was achieved at 0.1, 0.1 and 1 microM for ET-18-OCH(3), miltefosine and ilmofosine, respectively. Analysis of the lipid composition of epimastigotes exposed to LPAs at their IC(50) for 120 h showed that the ratio of phosphatidyl-choline (PC) to phosphatidylethanolamine (PE) changed from 1.5 in control cells to c. 0.67 in those treated with the analogues. A significant increase in the content of phosphatidylserine was also observed in treated cells. Intact epimastigotes efficiently incorporated radioactivity from L-[methyl-(14)C]methionine into PC, but not from [methyl-(14)C]choline. ET-18-OCH(3) inhibited the incorporation of L-[methyl-(14)C]methionine into PC with an IC(50) of 2 microM, suggesting that inhibition of the de novo synthesis through the Greenberg's pathway was a primary effect underlying the selective anti-parasitic activity of this compound. Antiproliferative synergism was observed as a consequence of combined treatment of epimastigotes with ET-18-OCH(3) and ketoconazole, a sterol biosynthesis inhibitor, probably due to the fact that a secondary effect of the latter is also a blockade of PC synthesis at the level of PE-PC-N-methyl-transferase.

Leishmania donovani Resistance to Miltefosine Involves a Defective Inward Translocation of the Drug

“…HePC (miltefosine) was from Zentaris (Frankfurt, Germany). Hexadecylphospho[1,2-ethylene- 14 C]choline ([ 14 C]HePC; 1,33 MBq/ mmol) was synthesized by Amersham Pharmacia Biotech (Little Chalfont, United Kingdom). N- amino-PS (C 6 -NBD-PS), C 6 -NBD-PC, and C 6 -NBD-PE were from Avanti Polar Lipids (Birmingham,…”

“…However, little is known about the leishmanicidal and trypanocidal mechanisms of HePC and other alkyl-lysophospholipids. Perturbation of the alkyl-lipid metabolism and the biosynthesis of alkyl-anchored glycoproteins (15), as well as damage to the flagellar membrane and phospholipid biosynthesis (14,25), have been described. The mechanisms of action of this class of drugs against tumor cell lines have been linked to (i) nonspecific ion channel formation, (ii) cell signaling inhibition through phospholipase C inactivation, and (iii) inhibition of de novo phosphatidylcholine (PC) and sphingomyelin synthesis, leading to the accumulation of ceramides and apoptosis (33).…”

Match-making for posaconazole through systems thinking

“…Glycerophospholipid biosynthesis inhibitors, such as ajoene or alkyl-lysophospholipids (ALP, e.g., miltefosine), have been shown to have antiproliferative effects on T. cruzi epimastigotes and amastigotes [20][21][22]. Growth inhibition correlated with a decrease in the phosphatidylcholine to phosphatidylethanolamine ratio (PC:PE) and, in the case of ALP, also with a marked effect on sterol composition due to inhibition of sterol 22-desaturase (Erg5), a finding that probably explains the antiproliferative synergism of these drugs with the Cyp51 inhibitor ketoconazole against both proliferative stages (epimastigotes and intracellular amastigotes) of the parasite [21,22]. Here, we propose to combine the anti-chagasic triazoles with inhibitors of sphingolipid synthesis, as suggested by systems approaches.…”

Proposta conceitual de estudo para a integração e gerenciamento do uso de marcadores bioquímicos de contaminação ambiental

“…A aplicação de algumas metodologias como o cálculo da concentração fracionária inibitória (Fractional Inhibitory Concentration -FIC) (LIRA et al, 2001) permite estudar e classificar o tipo de interação entre os poluentes. Contudo, alguns problemas dificultam a avaliação dos possíveis efeitos que as misturas possam produzir como o pequeno conhecimento relativo sobre a magnitude, duração, frequência e tempo de exposição cumulativa ambiental, bem como a compreensão insuficiente sobre os mecanismos interativos de toxicidade entre os componentes da mistura.…”