Effect of the alkyl-lysophospholipids on the proliferation and differentiation of Trypanosoma cruzi

Alkyl-lysophospholipids (ALPs), designed as potential immunomodulators, hav e been shown to be cytotoxic for a variety of tumour cells and are under cl inical studies for cancer chemotherapy. ET-18-OCH3, hexadecylphosphocholine and ilmofosine were assayed against the three forms of Trypanosoma cruzi. Incubation with bloodstream trypomastigotes resulted, under different exper imental conditions, in higher activity of the compounds in comparison with crystal violet. The ED50/24 h values were 13.4 +/- 2.8 mu M and 11.7 +/- 0. 6 mu M for amastigotes and epimastigotes, respectively. ET-18-OCH3 (0.3 and 0.6 mu M) inhibited the differentiation of epimastigotes to trypomastigote s (Dm28C clone) in the range 40-57%. This drug (3.75-15 mu M) also caused a time- and dose-dependent inhibition of the intracellular proliferation of amastigotes in heart muscle cells with ED50 values of 14.3 +/- 4.2, 8.9 +/- 1.9 and 6.8 +/- 0.4 mu M, after 1, 2 and 3 days of treatment. Pre-treatmen t of the parasite with this drug inhibited its interiorization into the hos t cell. Interestingly, the intracellular differentiation of amastigotes to trypomastigotes was not hampered by the drug. The present results demonstra te the lytic effect of ALPs on the three forms of T. cruzi, as well as the inhibition of both the differentiation to the infective form and the prolif eration of parasites interiorized in heart cells. Ultrastructural analysis of epimastigotes treated with the three ALPs showed extensive blebing of th e flagellar membrane. As described in tumour cells, the membrane seems to b e a primary target of the drugs. (C) 2000 Published by Elsevier Science B.V . All rights reserved.