8 results on '"Pilch DS"'
Search Results
2. Inhibition of RND-type efflux pumps confers the FtsZ-directed prodrug TXY436 with activity against Gram-negative bacteria.
- Author
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Kaul M, Zhang Y, Parhi AK, Lavoie EJ, and Pilch DS
- Subjects
- Animals, Anti-Bacterial Agents chemistry, Benzamides chemistry, Gene Expression Regulation, Bacterial drug effects, Klebsiella pneumoniae drug effects, Microbial Sensitivity Tests, Molecular Structure, Pyridines chemistry, Thiazoles chemistry, rho GTP-Binding Proteins genetics, rho GTP-Binding Proteins metabolism, Acinetobacter baumannii drug effects, Anti-Bacterial Agents pharmacology, Bacterial Proteins metabolism, Benzamides pharmacology, Cytoskeletal Proteins metabolism, Escherichia coli drug effects, Prodrugs, Pyridines pharmacology, Thiazoles pharmacology, rho GTP-Binding Proteins antagonists & inhibitors
- Abstract
Infections caused by Gram-negative bacterial pathogens are often difficult to treat, with the emergence of multidrug-resistant strains further restricting clinical treatment options. As a result, there is an acute need for the development of new therapeutic agents active against Gram-negative bacteria. The bacterial protein FtsZ has recently been demonstrated to be a viable antibacterial target for treating infections caused by the Gram-positive bacteria Staphylococcus aureus in mouse model systems. Here, we investigate whether an FtsZ-directed prodrug (TXY436) that is effective against S. aureus can also target Gram-negative bacteria, such as Escherichia coli. We find that the conversion product of TXY436 (PC190723) can bind E. coli FtsZ and inhibit its polymerization/bundling in vitro. However, PC190723 is intrinsically inactive against wild-type E. coli, with this inactivity being derived from the actions of the efflux pump AcrAB. Mutations in E. coli AcrAB render the mutant bacteria susceptible to TXY436. We further show that chemical inhibition of AcrAB in E. coli, as well as its homologs in Klebsiella pneumoniae and Acinetobacter baumannii, confers all three Gram-negative pathogens with susceptibility to TXY436. We demonstrate that the activity of TXY436 against E. coli and K. pneumoniae is bactericidal in nature. Evidence for FtsZ-targeting and inhibition of cell division in Gram-negative bacteria by TXY436 is provided by the induction of a characteristic filamentous morphology when the efflux pump has been inhibited as well as by the lack of functional Z-rings upon TXY436 treatment., (Copyright © 2014 Elsevier Inc. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
3. Pharmacokinetics and in vivo antistaphylococcal efficacy of TXY541, a 1-methylpiperidine-4-carboxamide prodrug of PC190723.
- Author
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Kaul M, Mark L, Zhang Y, Parhi AK, LaVoie EJ, and Pilch DS
- Subjects
- Animals, Anti-Bacterial Agents pharmacokinetics, Female, Heterocyclic Compounds, 2-Ring pharmacokinetics, Imides pharmacokinetics, Mice, Microbial Sensitivity Tests, Prodrugs pharmacokinetics, Pyridines pharmacokinetics, Thiazoles pharmacokinetics, Anti-Bacterial Agents pharmacology, Heterocyclic Compounds, 2-Ring pharmacology, Imides pharmacology, Prodrugs pharmacology, Pyridines pharmacology, Staphylococcus drug effects, Thiazoles pharmacology
- Abstract
The benzamide derivative PC190723 was among the first of a promising new class of FtsZ-directed antibacterial agents to be identified that exhibit potent antistaphylococcal activity. However, the compound is associated with poor drug-like properties. As part of an ongoing effort to develop FtsZ-targeting antibacterial agents with increased potential for clinical utility, we describe herein the pharmacodynamics, pharmacokinetics, in vivo antistaphylococcal efficacy, and mammalian cytotoxicity of TXY541, a novel 1-methylpiperidine-4-carboxamide prodrug of PC190723. TXY541 was found to be 143-times more soluble than PC190723 in an aqueous acidic vehicle (10mM citrate, pH 2.6) suitable for both oral and intravenous in vivo administration. In staphylococcal growth media, TXY541 converts to PC190723 with a half-life of approximately 8h. In 100% mouse serum, the TXY541-to-PC190723 conversion was much more rapid (with a half-life of approximately 3min), suggesting that the conversion of the prodrug in serum is predominantly enzyme-catalyzed. Pharmacokinetic analysis of both orally and intravenously administered TXY541 in mice yielded a half-life for the PC190723 conversion product of 0.56h and an oral bioavailability of 29.6%. Whether administered orally or intravenously, TXY541 was found to be efficacious in vivo in mouse models of systemic infection with both methicillin-sensitive and methicillin-resistant S. aureus. Toxicological assessment of TXY541 against mammalian cells revealed minimal detectable cytotoxicity. The results presented here highlight TXY541 as a potential therapeutic agent that warrants further pre-clinical development., (Copyright © 2013 Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
4. Macrocyclic biphenyl tetraoxazoles: synthesis, evaluation as G-quadruplex stabilizers and cytotoxic activity.
- Author
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Blankson GA, Pilch DS, Liu AA, Liu LF, Rice JE, and LaVoie EJ
- Subjects
- Antineoplastic Agents chemical synthesis, Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology, Biphenyl Compounds chemical synthesis, Biphenyl Compounds chemistry, Biphenyl Compounds pharmacology, Cell Line, Tumor, Humans, Macrocyclic Compounds chemical synthesis, Models, Molecular, Molecular Structure, Oxazoles chemical synthesis, G-Quadruplexes drug effects, Macrocyclic Compounds pharmacology, Oxazoles chemistry, Oxazoles pharmacology
- Abstract
A series of macrocyclic biphenyl tetraoxazoles was synthesized. The latter stages of the synthetic approach allowed for the addition of varied N-protected α-amino acids, which were subsequently deprotected and condensed to provide the desired macrocycles. Improved yields could be realized in the macrocyclization step of their synthesis relative to other macrocyclic G-quadruplex stabilizers. These 24-membered macrocycles were evaluated for their ability to stabilize G-quadruplex DNA and for their relative cytotoxicity against human tumor cells. These biphenyl tetraoxazoles were not strong ligands for G-quadruplex DNA relative to other macrocyclic polyoxazoles. This reduced stabilizing potential did correlate with their comparatively lower cytotoxic activity as observed in the human tumor cell lines, RPMI 8402 and KB3-1. These studies provide useful insights into the conformational requirements for the development of selective and more potent G-quadruplex ligands., (Copyright © 2013. Published by Elsevier Ltd.)
- Published
- 2013
- Full Text
- View/download PDF
5. 3-Phenyl substituted 6,7-dimethoxyisoquinoline derivatives as FtsZ-targeting antibacterial agents.
- Author
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Kelley C, Zhang Y, Parhi A, Kaul M, Pilch DS, and LaVoie EJ
- Subjects
- Anti-Bacterial Agents chemical synthesis, Anti-Bacterial Agents toxicity, Bacterial Proteins chemistry, Cytoskeletal Proteins chemistry, Enterococcus faecalis drug effects, HEK293 Cells, Humans, Isoquinolines chemical synthesis, Isoquinolines toxicity, Molecular Targeted Therapy, Staphylococcus aureus chemistry, Staphylococcus aureus drug effects, Staphylococcus aureus metabolism, Anti-Bacterial Agents chemistry, Anti-Bacterial Agents pharmacology, Bacterial Proteins metabolism, Cytoskeletal Proteins metabolism, Isoquinolines chemistry, Isoquinolines pharmacology
- Abstract
The emergence of multidrug-resistant bacteria has created an urgent need for antibiotics with a novel mechanism of action. The bacterial cell division protein FtsZ is an attractive target for the development of novel antibiotics. The benzo[c]phenanthridinium sanguinarine and the dibenzo[a,g]quinolizin-7-ium berberine are two structurally similar plant alkaloids that alter FtsZ function. The presence of a hydrophobic functionality at either the 1-position of 5-methylbenzo[c]phenanthridinium derivatives or the 2-position of dibenzo[a,g]quinolizin-7-ium derivatives is associated with significantly enhanced antibacterial activity. 3-Phenylisoquinoline represents a subunit within the ring-systems of both of these alkaloids. Several 3-phenylisoquinolines and 3-phenylisoquinolinium derivatives have been synthesized and evaluated for antibacterial activity against Staphylococcus aureus and Enterococcus faecalis, including multidrug-resistant strains of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). A number of derivatives were found to have activity against both MRSA and VRE. The binding of select compounds to S. aureus FtsZ (SaFtsZ) was demonstrated and characterized using fluorescence spectroscopy. In addition, the compounds were shown to act as stabilizers of SaFtsZ polymers and concomitant inhibitors of SaFtsZ GTPase activity. Toxicological assessment of select compounds revealed minimal cross-reaction mammalian β-tubulin as well as little or no human cytotoxicity., (Copyright © 2012 Elsevier Ltd. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
6. 2"-Substituted 5-phenylterbenzimidazoles as topoisomerase I poisons.
- Author
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Rangarajan M, Kim JS, Jin S, Sim SP, Liu A, Pilch DS, Liu LF, and LaVoie EJ
- Subjects
- Antineoplastic Agents chemistry, Antineoplastic Agents metabolism, Antineoplastic Agents pharmacology, Benzimidazoles chemistry, Benzimidazoles metabolism, Cell Line, DNA metabolism, Enzyme Inhibitors chemistry, Enzyme Inhibitors metabolism, Humans, Molecular Structure, Spectrum Analysis, Benzimidazoles pharmacology, Enzyme Inhibitors pharmacology, Topoisomerase I Inhibitors
- Abstract
5-Phenylterbenzimidazole (1) is active as a topoisomerase I poison (topo I) and is cytotoxic to human tumor cells. No cross-resistance was observed for 1 when it was evaluated against the camptothecin-resistant cell line, CPT-K5. Derivatives of 1 substituted at the 2"-position, however, did exhibit cross-resistance to this cell line. The basis for the resistance of this cell line towards CPT is that it possesses a mutant form of topo I. These results suggest that substituents at the 2"-position may be in proximity to the wild-type enzyme. Therefore, we hypothesized that terbenzimidazoles with 2"-substituents could be capable of interacting with the enzyme and thereby influence activity within this class of topo I poisons. 5-Phenylterbenzimidazoles with a hydroxy, hydroxymethyl, mercapto, amino, N-benzoylaminomethyl, chloro, and trifluoromethyl group at the 2"-position were synthesized. In addition, several 2"-ethyl-5-phenylterbenzimidazoles were prepared containing either a methoxy, hydroxy, amino, or N-acetylamino group at the 2-position of the ethyl side-chain. These 2"-substituted 5-phenylterbenzimidazoles were evaluated as topo I poisons and for cytotoxic activity. The presence of a strong electron-withdrawing group at the 2"-position, such as a chloro or trifluoromethyl group, did enhance both topo I poisoning activity and cytotoxicity. Studies on the relative DNA binding affinity of 1 to its 2"-amino and 2"-trifluoromethyl derivatives did exhibit a correlation with their relative differences in biological activity.
- Published
- 2000
- Full Text
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7. Modulation of nucleic acid structure by ligand binding: induction of a DNA.RNA.DNA hybrid triplex by DAPI intercalation.
- Author
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Xu Z, Pilch DS, Srinivasan AR, Olson WK, Geacintov NE, and Breslauer KJ
- Subjects
- Calorimetry, Differential Scanning, Chemical Phenomena, Chemistry, Physical, DNA metabolism, Drug Stability, Fluorescent Dyes pharmacology, Heating, Ligands, Nucleic Acid Conformation, Nucleic Acid Denaturation, Oligodeoxyribonucleotides chemistry, Oligodeoxyribonucleotides metabolism, Poly A chemistry, Poly A metabolism, RNA metabolism, Spectrophotometry, Ultraviolet, DNA chemistry, DNA drug effects, Indoles pharmacology, Intercalating Agents pharmacology, Nucleic Acid Hybridization drug effects, RNA chemistry, RNA drug effects
- Abstract
The aromatic diamidine, DAPI (4',6-diamidino-2-phenylindole), is used as an important biological and cytological tool since it forms highly fluorescent complexes with nucleic acid duplexes via minor groove-directed/intercalative modes of interaction. In this study, we find that DAPI binding can induce the formation of an RNA-DNA hybrid triplex that would not otherwise form. More specifically, through application of a broad range of spectroscopic, viscometric, and molecular modeling techniques, we demonstrate that DAPI intercalation induces the formation of the poly(dT).poly(rA).poly(dT) hybrid triple helix, a structure which does not form in the absence of the ligand. Using UV mixing studies, we demonstrate that, in the presence of DAPI, the poly(rA).poly(dT) duplex and the poly(dT) single strand form a 1:1 complex (a triplex) that does not form in the absence of DAPI. Through temperature-dependent absorbance measurements, we show that the poly(dT).poly(rA).poly(dT) triplex melts via two distinct transitions: initial conversion of the triplex to the duplex state, with the DAPI remaining bound, followed by denaturation of the duplex-DAPI complex to its component single strands and free DAPI. Using optical melting profiles, we show that DAPI binding enhances the thermal stability of the poly(dT).poly(rA).poly(dT) triplex, an observation consistent with the preferential binding of the ligand to the triplex versus the duplex and single-stranded states. Our differential scanning calorimetric measurements reveal melting of the DAPI-saturated poly(dT).poly(rA).poly(dT) triplex to be associated with a lower enthalpy but greater cooperativity than melting of the corresponding DAPI-saturated poly(rA).poly(dT) duplex. Our flow linear dichroism and viscometric data are consistent with an intercalative mode of binding when DAPI interacts with both the poly(dT).poly(rA).poly(dT) triplex and the poly(rA).poly(dT) duplex. Finally, computer modeling studies suggest that a combination of both stacking and electrostatic interactions between the intercalated ligand and the host nucleic acid play important roles in the DAPI-induced stabilization of the poly(dT).poly(rA).poly(dT) triplex. In the aggregate, our results demonstrate that ligand binding can be used to induce the formation of triplex structures that do not form in the absence of the ligand. This triplex-inducing capacity has potentially important implications in the design of novel antisense, antigene, antiviral, and diagnostic strategies.
- Published
- 1997
- Full Text
- View/download PDF
8. The thermodynamics of DNA structures that contain lesions or guanine tetrads.
- Author
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Pilch DS, Plum GE, and Breslauer KJ
- Subjects
- Animals, Base Sequence, DNA Damage, Guanine, Humans, Molecular Sequence Data, Molecular Structure, Thermodynamics, DNA chemistry
- Abstract
It is becoming increasingly apparent that energetic as well as structural information is required to develop a complete appreciation of the critical interrelationships between structure, energetics, and biological function. Motivated by this recognition, we have reviewed in this article the current state of the thermodynamic databases associated with lesion-containing DNA duplexes and DNA quadruplexes, while highlighting important considerations concerning the methods used to obtain the requisite data.
- Published
- 1995
- Full Text
- View/download PDF
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