acid-phosphatase and diminazene-aceturate

Different classes of topoisomerase (TOP) inhibitors and antitrypanosomatid agents exhibited variable efficacies against Leishmania donovani parasites and human mononuclear cells both at the level of DNA topoisomerase I (TOPI) catalytic activity and in cytotoxicity assays. Bis-benzimidazoles and the diamidine diminazene aceturate exhibited uniformly high efficacies against parasite and host enzymes as well as against parasite and mononuclear cells, but pentamidine showed around 2 orders of magnitude greater specificity for Leishmania TOPI and amastigote cells (P<0.05). The protoberberine coralyne and the flavonoid quercetin were highly potent, but non-selective, inhibitors in vitro, although the latter showed slight selectivity for parasite TOPI. Camptothecin was selective for mononuclear cells at both levels (P<0.05) and sodium stibogluconate was selective only at the enzyme level displaying 30-fold greater potency against parasite TOPI (P<0.05). These data suggest that at least part of pentamidines' leishmanicidal activity may be mediated through TOPI inhibition, and support the feasibility of exploiting differences between Leishmania and human TOPs to develop modified compounds with improved selectivity.

Topics: Acid Phosphatase; Animals; Antimony Sodium Gluconate; Antiprotozoal Agents; Benzimidazoles; Berberine Alkaloids; Bisbenzimidazole; Camptothecin; Cell Line; Diminazene; DNA Topoisomerases, Type I; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Inhibitory Concentration 50; Leishmania donovani; Luciferases, Firefly; Luminescent Agents; Macrophages; Monocytes; Pentamidine; Quercetin; Topoisomerase I Inhibitors

The trypanosomes and Leishmania species are parasitic protozoa that afflict millions of people throughout the world. If not treated, African trypanosomiasis and visceral leishmaniasis are fatal. The available drugs are severely limited by toxicity, marginal efficacy, the requirement for parenteral administration, and spreading drug resistance. In this study, a spectrophotometric assay was developed and validated for measuring the cytotoxicity of test compounds against axenically cultured bloodstream-form Trypanosoma brucei (African trypanosomes) and promastigotes of Leishmania donovani. Enzymatic hydrolysis of p-nitrophenyl phosphate, monitored by a microtiter plate reader, is a reliable surrogate for parasite cell counts. The assay is simple, inexpensive, and highly reproducible. The coefficient of variation for EC50 values is < 10% for determinations obtained over several months. This method permits the rapid screening of candidates for much-needed new drugs against these parasites.

Topics: Acid Phosphatase; Amphotericin B; Animals; Camptothecin; Diminazene; Drug Evaluation, Preclinical; Leishmania donovani; Pentamidine; Trypanocidal Agents; Trypanosoma brucei brucei