Structure-activity relationship and studies on the molecular mechanism of leishmanicidal N,C-coupled arylisoquinolinium salts.
ABSTRACT Alternative drugs against leishmaniasis are desperately needed. Antimonials, the main chemotherapeutic tool, cause serious side effects and promote chemoresistance. We previously demonstrated that representatives of N,C-linked arylisoquinolines are promising leishmanicidal drug candidates. We now performed structure-activity relationship studies varying the aryl portion of our lead substrate. The new series of compounds show an enhanced selectivity against Leishmania major in comparison to their major host cell, the macrophage. Our results suggest that the arylisoquinolinium salts decrease the macrophage infection rate acting directly on the intracellular parasites. However, the activity of the 4'-i-propyl derivative might also involve the modulation of cytokine and nitric oxide production by host macrophages. Additionally, this isoquinoline acts synergistically with amphotericin B and does not interact with drug-metabolizing cytochrome P450 enzymes involved in the metabolism of antileishmanial drugs. The results demonstrate that the newly synthesized structurally simplified N,C-coupled arylisoquinolinium salts are promising candidates to be considered as leishmanicidal pharmacophores.
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ABSTRACT: Xenobiotics represent an environmental stress and as such are a source for antibiotics, including the isoquinoline (IQ) compound IQ-143. Here, we demonstrate the utility of complementary analysis of both host and pathogen datasets in assessing bacterial adaptation to IQ-143, a synthetic analog of the novel type N,C-coupled naphthyl-isoquinoline alkaloid ancisheynine. Metabolite measurements, gene expression data and functional assays were combined with metabolic modeling to assess the effects of IQ-143 on Staphylococcus aureus, Staphylococcus epidermidis and human cell lines, as a potential paradigm for novel antibiotics. Genome annotation and PCR validation identified novel enzymes in the primary metabolism of staphylococci. Gene expression response analysis and metabolic modeling demonstrated the adaptation of enzymes to IQ-143, including those not affected by significant gene expression changes. At lower concentrations, IQ-143 was bacteriostatic, and at higher concentrations bactericidal, while the analysis suggested that the mode of action was a direct interference in nucleotide and energy metabolism. Experiments in human cell lines supported the conclusions from pathway modeling and found that IQ-143 had low cytotoxicity. The data suggest that IQ-143 is a promising lead compound for antibiotic therapy against staphylococci. The combination of gene expression and metabolite analyses with in silico modeling of metabolite pathways allowed us to study metabolic adaptations in detail and can be used for the evaluation of metabolic effects of other xenobiotics.Genome biology 03/2011; 12(3):R24. · 10.30 Impact Factor
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ABSTRACT: In most laboratories the screening for leishmanicidal compounds is carried out with Leishmania promastigotes or axenic amastigotes. However, the best approach to identify leishmanicidal compounds is the use of amastigotes residing in macrophages. Reporter gene-based assays are relatively new tools in the search for drugs against eucaryotic protozoa, permitting the development of faster, more automated assays. In this paper we report on the establishment of a rapid screening assay in 96-well format. A luciferase-transgenic (Luc-tg) L. major strain was generated and applied to infect bone marrow derived macrophages (BMDM). Amastigote infected BMDM were treated with different compound concentrations. Cells were lysed with a luciferin-containing buffer and the resulting luminescence was measured to determine the half-maximal inhibitory concentration (IC50 value). To validate this new amastigote screening assay, a library of a new class of quinolinium salts were synthesized and tested for leishmanicidal activity. Some of the quinolinium salts showed very promising activities, with IC50 values against intracellular amastigotes (IC50 < 1 μg/ml) and selectivity indices (SI > 20) that match the criteria of World Health Organization (WHO) for hits. Compound 21c (IC50 = 0.03 μg/ml; SI = 358) could become a new lead structure for the development of improved chemotherapeutical drugs against L. major. In summary we describe the establishment of a new 96-well format assay with Luc-transgenic L. major for the rapid screening of compounds for leishmanicidal activity against intracellular amastigotes and its application to the identification of a new class of quinolinium salts with most promising leishmanicidal activity.Antimicrobial Agents and Chemotherapy 04/2013; · 4.57 Impact Factor
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ABSTRACT: A marine-derived fungus of the genus Stachylidium was isolated from the sponge Callyspongia cf. C. flammea. Chemical investigation of the bioactive fungal extract led to the isolation of the novel phthalimidine derivatives marilines A(1) (1a), A(2) (1b), B (2), and C (3). The absolute configurations of the enantiomeric compounds 1a and 1b were assigned by a combination of experimental circular dichroism (CD) investigations and quantum chemical CD calculations. The skeleton of marilines is most unusual, and its biosynthesis is suggested to require uncommon biochemical reactions in fungal secondary metabolism. Both enantiomers, marilines A(1) (1a) and A(2) (1b), inhibited human leukocyte elastase (HLE) with an IC(50) value of 0.86 μM.Chemistry 06/2012; 18(28):8827-34. · 5.93 Impact Factor