Репозиторий Университета

© ISUCT Publishing. Macrolide antibiotics represent a valuable class of broad-spectrum, high active natural compounds with polyketide structure. A well-known FOF1 ATP-synthase inhibitor,[1] namely oligomycin A (1), is a 26-membered α,β-unsaturatedpolyketide lactone with conjugated diene, fused to spiroketal moiety. Oligomycin A possesses strong antifungal, antiactinomycotic and cytotoxic activity, but lacks antibacterial activity. According to recent investigations, the development of anti-cancer drugs based on oligomycin A is quite perspective due to its high cytotoxic activity toward tumor cells, ability to inhibit a multidrug resistance protein p-gp and to prevent an activation of oncogenic K-Ras by inhibition of its localization at the plasma membrane.[2-4] However, high toxicity for mammalian cells and low water solubility are significant limitations of oligomycin A, making it unacceptable for clinical application. Chemical modification is a promising way to improve pharmacological properties of natural compounds. Recently we have found that site-selective modifications of oligomycin A afforded semi-synthetic derivatives with high antiproliferative activity against tumor cell lines[5-7] or selective antifungal activity against Candida spp.[8] and, at the same time, with lower toxicity toward mammalian cells. Also, semi-synthetic oligomycin A derivatives are useful tools for molecular genetic studies of additional targets for this family of antibiotics.[9,10] Previously Ramirez F. et al. have described the reaction of oligomycins with sodium borohydride resulting in mixture of diastereomeric 7-dihydro-and 7,11-tetrahydro derivatives without further separation and characterization of individual products.[11] Also, there is no data on biological activity of these reduced oligomycins against fungal/actinomycetes strains and tumor cell lines in article mentioned above. Thus, in this paper we report regio-and stereoselective methods for borohydride reduction of oligomycin A, structure determination of obtained derivatives and investigation of theirs antiproliferative, antifungal and antiactinomycotic properties. The feasibility of regio-and stereoselective reduction of C7-carbonyl group in a core structure of oligomycin A was proposed due to the presence of haptophilic hydroxyl groups[12] at C5 and C9 positions and sterical hindrance of C-11 carbonyl group. Actually, treatment of oligomycin A with bulky sodium triacetoxyborohydride in acetic acid according to the method[13] led to (7S)-dihydrooligomycin A (2) in a good yield. The second carbonyl group (C-11) reduced in more harsh conditions: only the extended treatment of (7S)-dihydrooligomycin A with sodium borohydride in ethanol give (7S,11R)-7,11-tetrahydrooligomycin A (3) as major product. Reaction proceeds with acceptable stere-oselectivity and gives tetrahydro derivative 3, but in low yield (35 %), which associated with low stability of oligomycins in basic conditions.[14] Structure of compounds 2 and 3 was confirmed by high resolution mass spectrometry (HRMS ESI) and NMR spectroscopy. Absolute configurations at C7 and C11 positions of obtained derivatives were unambiguously confirmed by observed interactions between neighboring protons in corresponding1H-1H ROESY spectra. Testing of antimicrobial properties of oligomycins 2 and 3 against Candida spp., filamentous fungi and S. fradiae (strain, extremely sensitive to oligomycins) that of the parent antibiotic in comparison with starting oligomycin A revealed that reduction of carbonyl groups led to decreasing of activity (except strain M. canis). Also, reduced derivatives 2, 3 were less potent against human colon carcinoma cell line HCT116 and its doxorubicin-resistant subline HCT116(-/-), while activity against leukemia cell line K562 and doxorubicin-resistant subline K562/4 retained at the same level as for 1. It might be pointed that biological properties of (7S)-dihydrooligomycin A and (7S,11R)-7,11-tetrahydrooligomycin A are quite similar, consequently C7-carbonyl group has a greater influence on biological activity of oligomycin A than C-11 carbonyl group.

© 2018 Ruslania. All rights reserved. The frequency of resistance of pathogens to antimicrobial drugs is on continued rise with a threat of returning to the "pre-antibiotic" era. This has led to the appearance of bacterial infections which are essentially untreatable by the current spectrum of available modem preparations. The presence of cross-group resistance inspires the search of new targets for antibacterial drugs both in the pathogen body and in the human body. This review considers potential strategies for the search of the new generation of antimicrobial agents for treating drug-resistant pathogens.

© ISUCT Publishing. The macrolide antibiotic oligomycin A (1), produced by actinomycetes Streptomyces,[1] is a well-known inhibitor of FO F1 ATP-synthase, which is regarded as a molecular target for new drugs in the treatment of tumors and infections. Oligomycin A (1) exhibits antifungal and cytotoxic activities, but Gram-negative and Gram-positive bacteria are resistant to 1 except actinobacteria.[2] In micromolar concentrations, oligomycin binds to FO c-subunit, blocks proton translocation and disrupts bioenergetic metabolism.[3] However, a clinical application of oligomycin A is limited by high cytotoxicity for mammalian cells. The searches of new derivatives of oligomycin A with more selective pharmacological activity and low toxicity for normal cells are of great interest. New semi-synthetic oligomycins also would be valuable for SAR studies and depicting the mechanism of FO F1 ATP-synthase inhibition. The complicity of oligomycin structure and its lability in basic conditions[4] significantly impede modifications and an applicability of this antibiotic. However, previously we have managed this challenge and developed some modifications of the side chain and chemical transformations of the lactone moiety of 1.[4-9] In this paper, throughout our research we describe synthesis and biological investigation of novel oligomycin A derivatives, namely 16,33-O,O-diformyl-16,17-dihydro-16(S),17(R)-dihydroxyoligomycin A (3) and 33-O-formyloligomycin A (4). First, we have studied Prilezhaev epoxidation of double bonds in core structure of oligomycin A. It was found that treatment 1 with m-CPBA at -17oC in dichloromethane led to 16,17-epoxyoligomycin (2). Unfortunately, all attempts for isolation of product 2 were failed due to its instability on silica gel, and, consequently, we were unable to determine the structure of 2 by direct physicochemical and spectral methods. The presence of epoxide at C16-C19 positions was confirmed by tandem mass spectrometry, but its exact localization was still elusive. We assumed that it might be at C16-C17 positions, because C18-C19 double bond is hindered by ethyl side chain at C20. In order to obtain a stable oligomycin A derivative we performed an epoxide ring-opening reaction by the treatment of the crude epoxyoligomycin 2 with formic acid. This acid-catalyzed opening of the epoxide accompanied with acylation of 33-OH group and led to16,33-O,O-diformyl-16,17-dihydro-16(S),17(R)-dihydroxyoligomycin A (3). The structure of 3 was confirmed by NMR spectroscopy and high resolution mass spectrometry. Configurations at C16 and C17 positions were determined by detecting correlations in1H-1H ROESY spectrum. Obtained results allowed to confirm an assumption about localization of the epoxide ring and establish the structure of 2 as (R,R)-16,17-epoxyoligomycin A, since inversion of configuration has taken place at the attacked carbon atom.[23] It is known that O-acyl derivatives of pharmacologically active agents are widely used as prodrugs.[24] Acylation of 2-hydroxypropyl side chain in 2 prompts us to examine the reaction of oligomycin A (1) with formic acid. Thus, stirring the solution of 1 in HCOOH (98 %) for 2 h at room temperature afforded 33-O-formyloligomycin A (4) in a good yield. The structure of 4 was confirmed by NMR-spectroscopy and high resolution mass spectrometry. Also, biological data of new derivatives were evaluated. The modification of C16-C17 positions of the macrocycle as well as acylation of C33 hydroxyl group led to the decreasing of activity against S. fradiae, Candida spp. and filamentous fungi. Obtained results were in agreement with docking studies. A simulation of an interaction of 1, 3 and 4 with the FO subunit of the ATP-synthase (PDB: 4f4s) revealed that these modifications led to a significant change in the solvation energy and an increase in the conformational capacity of the ligands during the binding with the target. This resulted in decrease of the binding affinity for derivatives 2, 3. However, 33-O-formyloligomycin A (4) showed similar antiproliferative activity against tumor cell lines (HCT-116 colon carcinoma, К562 myeloid leukemia cell lines and MDR K562/4 subline) as for 1, but less cytotoxic for non-malignant human cells.

Acetylcholinesterase inhibitors are widely used for a variety of medical, agricultural and public health purposes. Consequently, exposure is highly possible during lifetime. However, their systematic use raises concerns for the potential impact on the fetus and newborn since these substances may affect angiogenesis, the neonatal and maternal intensive care, neuroimmune function and response, mammary growth/lactation via cholinergic/non-cholinergic central and peripheral neuroendocrine pathways. New methodologies, neuroscientific technologies and research studies are needed to harness existing knowledge along with the proper management, availability for new acetylcholinesterase inhibitors, with stable pharmacodynamics and clinical outcomes.

Sequential courses of anticancer target therapy lead to selection of drug-resistant cells, which results in continuous decrease of clinical response. Here we present a new approach for predicting effective combinations of target drugs, which act in a synergistic manner. Synergistic combinations of drugs may prevent or postpone acquired resistance, thus increasing treatment efficiency. We cultured human ovarian carcinoma SKOV-3 and neuroblastoma NGP-127 cancer cell lines in the presence of Tyrosine Kinase Inhibitors (Pazopanib, Sorafenib, and Sunitinib) and Rapalogues (Temsirolimus and Everolimus) for four months and obtained cell lines demonstrating increased drug resistance. We investigated gene expression profiles of intact and resistant cells by microarrays and analyzed alterations in 378 cancer-related signaling pathways using the bioinformatical platform Oncobox. This revealed numerous pathways linked with development of drug resistant phenotypes. Our approach is based on targeting proteins involved in as many as possible signaling pathways upregulated in resistant cells. We tested 13 combinations of drugs and/or selective inhibitors predicted by Oncobox and 10 random combinations. Synergy scores for Oncobox predictions were significantly higher than for randomly selected drug combinations. Thus, the proposed approach significantly outperforms random selection of drugs and can be adopted to enhance discovery of new synergistic combinations of anticancer target drugs. View Full-Text

Acetylcholinesterase inhibitors are widely used for a variety of medical, agricultural and public health purposes. Consequently, exposure is highly possible during lifetime. However, their systematic use raises concerns for the potential impact on the fetus and newborn since these substances may affect angiogenesis, the neonatal and maternal intensive care, neuroimmune function and response, mammary growth/lactation via cholinergic/non-cholinergic central and peripheral neuroendocrine pathways. New methodologies, neuroscientific technologies and research studies are needed to harness existing knowledge along with the proper management, availability for new acetylcholinesterase inhibitors, with stable pharmacodynamics and clinical outcomes.

Sequential courses of anticancer target therapy lead to selection of drug-resistant cells, which results in continuous decrease of clinical response. Here we present a new approach for predicting effective combinations of target drugs, which act in a synergistic manner. Synergistic combinations of drugs may prevent or postpone acquired resistance, thus increasing treatment efficiency. We cultured human ovarian carcinoma SKOV-3 and neuroblastoma NGP-127 cancer cell lines in the presence of Tyrosine Kinase Inhibitors (Pazopanib, Sorafenib, and Sunitinib) and Rapalogues (Temsirolimus and Everolimus) for four months and obtained cell lines demonstrating increased drug resistance. We investigated gene expression profiles of intact and resistant cells by microarrays and analyzed alterations in 378 cancer-related signaling pathways using the bioinformatical platform Oncobox. This revealed numerous pathways linked with development of drug resistant phenotypes. Our approach is based on targeting proteins involved in as many as possible signaling pathways upregulated in resistant cells. We tested 13 combinations of drugs and/or selective inhibitors predicted by Oncobox and 10 random combinations. Synergy scores for Oncobox predictions were significantly higher than for randomly selected drug combinations. Thus, the proposed approach significantly outperforms random selection of drugs and can be adopted to enhance discovery of new synergistic combinations of anticancer target drugs. View Full-Text