ABSTRACT
Plasmodium falciparum lactate dehydrogenase (PfLDH) is essential for ATP generation. Based on structural differences within the active site between P. falciparum and human LDH, we have identified a series of heterocyclic azole-based inhibitors that selectively bind within the PfLDH but not the human LDH (hLDH) active site and showed anti-malarial activity in vitro and in vivo. Here we expand on an azole, OXD1, from this series and found that the anti-P. falciparum activity was retained against a panel of strains independently of their anti-malarial drug sensitivity profile. Trophozoites had relatively higher PfLDH enzyme activity and PfLDH-RNA expression levels than rings and were the most susceptible stages to OXD1 exposure. This is probably linked to their increased energy requirements and consistent with glycolysis being an essential metabolic pathway for parasite survival within the erythrocyte. Further structural elaboration of these azoles could lead to the identification of compounds that target P. falciparum through such a novel mechanism and with more potent anti-malarial activity.
Subject(s)
Antimalarials/pharmacology , Carboxylic Acids/pharmacology , L-Lactate Dehydrogenase/antagonists & inhibitors , Oxadiazoles/pharmacology , Plasmodium falciparum/drug effects , Plasmodium falciparum/enzymology , Animals , Antimalarials/chemistry , Antimalarials/toxicity , Carboxylic Acids/chemistry , Carboxylic Acids/toxicity , Dose-Response Relationship, Drug , Flow Cytometry , Fluorescent Dyes/metabolism , Gene Expression Regulation, Enzymologic , L-Lactate Dehydrogenase/chemistry , L-Lactate Dehydrogenase/genetics , Microscopy, Confocal , Oxadiazoles/chemistry , Oxadiazoles/toxicity , Phenanthridines/metabolism , Plasmodium falciparum/growth & development , RNA, Protozoan/biosynthesis , Species SpecificityABSTRACT
Systemic infections caused by fungi after cytoreductive therapies are especially difficult to deal with in spite of currently available antimicrobials. However, little is known about the effects of fungi on the immune system of immunosuppressed hosts. We have addressed this by studying the in vitro T cell responses after systemic infection with Candida albicans in cyclophosphamide-treated mice. After cyclophosphamide treatment, a massive splenic colonization of the spleens, but not lymph nodes, by immature myeloid progenitor (Ly-6G(+)CD11b(+))cells is observed. These cells are able to suppress proliferation of T lymphocytes via a nitric oxide (NO)-dependent mechanism. Systemic infection with a sublethal dose of C. albicans did not cause immunosuppression per se but strongly increased NO-dependent suppression in cyclophosphamide-treated mice, by selective priming of suppressive myeloid progenitors (Ly-6G(+)CD11b(+)CD31(+)CD40(+)WGA(+)CD117(low/-)CD34(low/-)) for iNOS protein expression. The results indicate that systemic C. albicans infection can augment the effects of immunosuppressive therapies by promoting functional changes in immunosuppressive cells.
Subject(s)
Candidiasis/immunology , Cyclophosphamide/toxicity , Immune Tolerance/drug effects , Immunosuppressive Agents/toxicity , Myeloid Progenitor Cells/metabolism , Nitric Oxide Synthase/biosynthesis , Nitric Oxide/biosynthesis , Animals , Enzyme Induction , Female , Immune Tolerance/immunology , Immunocompromised Host , Lymphocyte Activation , Lymphocyte Depletion , Mice , Mice, Inbred BALB C , Myeloid Progenitor Cells/immunology , Nitric Oxide Synthase Type II , Specific Pathogen-Free Organisms , Spleen/pathology , T-Lymphocyte Subsets/immunologyABSTRACT
A number of new 2',3'-fused oxirane derivatives were synthesized for structure-activity relationship study. Many of these derivatives exhibit high potency against Candida spp. In addition, sordarin manno epoxide derivative 6 presents in vivo therapeutic effect in mice and is considered a promising antifungal lead within this series.
