Browse
Submit Data
Databases
API
Help

Dataset Information

30 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Molecular mechanism of the synergistic activity of ethambutol and isoniazid against Mycobacterium tuberculosis.

ABSTRACT: Isoniazid (INH) and ethambutol (EMB) are two major first-line drugs for managing tuberculosis (TB), caused by the microbe Mycobacterium tuberculosis Although co-use of these two drugs is common in clinical practice, the mechanism for the potential synergistic interplay between them remains unclear. Here, we present first evidence that INH and EMB act synergistically through a transcriptional repressor of the inhA gene, the target gene of INH encoding an enoyl-acyl carrier protein reductase of the fatty acid synthase type II system required for bacterial cell wall integrity. We report that EMB binds a hypothetical transcription factor encoded by the Rv0273c gene, designated here as EtbR. Using DNA footprinting, we found that EtbR specifically recognizes a motif sequence in the upstream region of the inhA gene. Using isothermal titration calorimetry and surface plasmon resonance assays, we observed that EMB binds EtbR in a 1:1 ratio and thereby stimulates its DNA-binding activity. When a nonlethal dose of EMB was delivered in combination with INH, EMB increased the INH susceptibility of cultured M. tuberculosis cells. In summary, EMB induces EtbR-mediated repression of inhA and thereby enhances the mycobactericidal effect of INH. Our findings uncover a molecular mechanism for the synergistic activity of two important anti-TB drugs.

SUBMITTER: Zhu C

PROVIDER: S-EPMC6204910 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Molecular Dynamics Assisted Mechanistic Study of Isoniazid-Resistance against Mycobacterium tuberculosis InhA.

Project description:Examination of InhA mutants I16T, I21V, I47T, S94A, and I95P showed that direct and water mediated H-bond interactions between NADH and binding site residues reduced drastically. It allowed conformational flexibility to NADH, particularly at the pyrophosphate region, leading to weakening of its binding at dinucleotide binding site. The highly scattered distribution of pyrophosphate dihedral angles and chi1 side chain dihedral angles of corresponding active site residues therein confirmed weak bonding between InhA and NADH. The average direct and water mediated bridged H-bond interactions between NADH and mutants were observed weaker as compared to wild type. Further, estimated NADH binding free energy in mutants supported the observed weakening of InhA-NADH interactions. Similarly, per residue contribution to NADH binding was also found little less as compared to corresponding residues in wild type. This investigation clearly depicted and supported the effect of mutations on NADH binding and can be accounted for isoniazid resistance as suggested by previous biochemical and mutagenic studies. Further, structural analysis of InhA provided the crucial points to enhance the NADH binding affinity towards InhA mutants in the presence of direct InhA inhibitors to combat isoniazid drug resistance. This combination could be a potential alternative for treatment of drug resistant tuberculosis.

| S-EPMC4682841 | biostudies-literature

Acetylation of Isoniazid Is a Novel Mechanism of Isoniazid Resistance in Mycobacterium tuberculosis.

Project description:Isoniazid (INH), one of the first-line drugs used for the treatment of tuberculosis, is a prodrug which is activated by the intracellular KatG enzyme of Mycobacterium tuberculosis The activated drug hinders cell wall biosynthesis by inhibiting the InhA protein. INH-resistant strains of M. tuberculosis usually have mutations in katG, inhA, ahpC, kasA, and ndh genes. However, INH-resistant strains which do not have mutations in any of these genes are reported, suggesting that these strains may adopt some other mechanism to become resistant to INH. In the present study, we characterized Rv2170, a putative acetyltransferase in M. tuberculosis, to elucidate its role in inactivating isoniazid. The purified recombinant protein was able to catalyze the transfer of the acetyl group to INH from acetyl coenzyme A (acetyl-CoA). High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses showed that following acetylation by Rv2170, INH is broken down into isonicotinic acid and acetylhydrazine. A drug susceptibility assay and confocal analysis showed that Mycobacterium smegmatis, which is susceptible to INH, is not inhibited by INH acetylated with Rv2170. Mutant proteins of Rv2170 failed to acetylate INH. Recombinant M. smegmatis and M. tuberculosis H37Ra overexpressing Rv2170 were found to be resistant to INH at MICs that inhibited wild-type strains. Besides, intracellular M. tuberculosis H37Ra overexpressing Rv2170 survived better in macrophages when treated with INH. Our results strongly indicate that Rv2170 acetylates INH, and this could be one of the strategies adopted by at least some M. tuberculosis strains to overcome INH toxicity, although this needs to be tested in INH-resistant clinical strains.

| S-EPMC7927840 | biostudies-literature

Synergy between Circular Bacteriocin AS-48 and Ethambutol against Mycobacterium tuberculosis.

Project description:The increasing incidence of multidrug-resistant Mycobacterium tuberculosis strains and the very few drugs available for treatment are promoting the discovery and development of new molecules that could help in the control of this disease. Bacteriocin AS-48 is an antibacterial peptide produced by Enterococcus faecalis and is active against several Gram-positive bacteria. We have found that AS-48 was active against Mycobacterium tuberculosis, including H37Rv and other reference and clinical strains, and also against some nontuberculous clinical mycobacterial species. The combination of AS-48 with either lysozyme or ethambutol (commonly used in the treatment of drug-susceptible tuberculosis) increased the antituberculosis action of AS-48, showing a synergic interaction. Under these conditions, AS-48 exhibits a MIC close to some MICs of the first-line antituberculosis agents. The inhibitory activity of AS-48 and its synergistic combination with ethambutol were also observed on M. tuberculosis-infected macrophages. Finally, AS-48 did not show any cytotoxicity against THP-1, MHS, and J774.2 macrophage cell lines at concentrations close to its MIC. In summary, bacteriocin AS-48 has interesting antimycobacterial activity in vitro and low cytotoxicity, so further studies in vivo will contribute to its development as a potential additional drug for antituberculosis therapy.

| S-EPMC6125546 | biostudies-other

Transfer of embB codon 306 mutations into clinical Mycobacterium tuberculosis strains alters susceptibility to ethambutol, isoniazid, and rifampin.

Project description:Implicated as a major mechanism of ethambutol (EMB) resistance in clinical studies of Mycobacterium tuberculosis, mutations in codon 306 of the embB gene (embB306) have also been detected in EMB-susceptible clinical isolates. Other studies have found strong associations between embB306 mutations and multidrug resistance, but not EMB resistance. We performed allelic exchange studies in EMB-susceptible and EMB-resistant clinical M. tuberculosis isolates to identify the role of embB306 mutations in any type of drug resistance. Replacing wild-type embB306 ATG from EMB-susceptible clinical M. tuberculosis strain 210 with embB306 ATA, ATC, CTG, or GTG increased the EMB MIC from 2 microg/ml to 7, 7, 8.5, and 14 microg/ml, respectively. Replacing embB306 ATC or GTG from two high-level EMB-resistant clinical strains with wild-type ATG lowered EMB MICs from 20 microg/ml or 28 microg/ml, respectively, to 3 microg/ml. All parental and isogenic mutant strains had identical isoniazid (INH) and rifampin (RIF) MICs. However, embB306 CTG mutants had growth advantages compared to strain 210 at sub-MICs of INH or RIF in monocultures and at sub-MICs of INH in competition assays. CTG mutants were also more resistant to the additive or synergistic activities of INH, RIF, or EMB used in different combinations. These results demonstrate that embB306 mutations cause an increase in the EMB MIC, a variable degree of EMB resistance, and are necessary but not sufficient for high-level EMB resistance. The unusual growth property of embB306 mutants in other antibiotics suggests that they may be amplified during treatment in humans and that a single mutation may affect antibiotic susceptibility against multiple first-line antibiotics.

| S-EPMC2415778 | biostudies-literature

Novel Isoniazid-Carborane Hybrids Active in Vitro Against Mycobacterium tuberculosis.

Project description:Tuberculosis (TB) is a severe infectious disease with high mortality and morbidity. The emergence of drug-resistant TB has increased the challenge to eliminate this disease. Isoniazid (INH) remains the key and effective component in the therapeutic regimen recommended by World Health Organization (WHO). A series of isoniazid-carborane derivatives containing 1,2-dicarba-closo-dodecaborane, 1,7-dicarba-closo-dodecaborane, 1,12-dicarba-closo-dodecaborane, or 7,8-dicarba-nido-undecaborate anion were synthesized for the first time. The compounds were tested in vitro against the Mycobacterium tuberculosis (Mtb) H37Rv strain and its mutant (DkatG) defective in the synthesis of catalase-peroxidase (KatG). N'-((7,8-dicarba-nido-undecaboranyl)methylidene)isonicotinohydrazide (16) showed the highest activity against the wild-type Mtb strain. All hybrids could inhibit the growth of the ΔkatG mutant in lower concentrations than INH. N'-([(1,12-dicarba-closo-dodecaboran-1yl)ethyl)isonicotinohydrazide (25) exhibited more than 60-fold increase in activity against Mtb DkatG as compared to INH. This compound was also found to be noncytotoxic up to a concentration four times higher than the minimum inhibitory concentration 99% (MIC99) value.

| S-EPMC7765321 | biostudies-literature

Transcriptional Response of Mycobacterium tuberculosis H37Rv to Ethambutol

Project description:To understand the response of M. tuberculosis (MTB) to the first-line drug ethambutol, we performed transcriptomics on MTB bacilli exposed to the drug.

2018-08-04 | GSE118084 | GEO

Mycobacterium tuberculosis transcriptional response to Isoniazid

Project description:The ability of Mycobacterium tuberculosis (Mtb) to adopt heterogeneous physiological states, underlies it’s success in evading the immune system and tolerating antibiotic killing. Drug tolerant phenotypes are a major reason why the tuberculosis (TB) mortality rate is so high, with over 1.8 million deaths annually. To develop new TB therapeutics that better treat the infection (faster and more completely), a systems-level approach is needed to reveal the complexity of network-based adaptations of Mtb. Here, we report the transcriptional response of Mtb to the drug isoniazid. We performed transcriptomic sequencing (RNA-seq) on Mtb bacilli at 4, 24, 72 h following exposure to the drug.

2021-12-15 | GSE165581 | GEO

Molecular basis for the exquisite sensitivity of Mycobacterium tuberculosis to isoniazid.

Project description:The exceptional sensitivity of Mycobacterium tuberculosis to isonicotinic acid hydrazide (INH) lacks satisfactory definition. M. tuberculosis is a natural mutant in oxyR, a central regulator of peroxide stress response. The ahpC gene, which encodes a critical subunit of alkyl hydroperoxide reductase, is one of the targets usually controlled by oxyR in bacteria. Unlike in mycobacterial species less susceptible to INH, the expression of ahpC was below detection limits at the protein level in INH-sensitive M. tuberculosis and Mycobacterium bovis strains. In contrast, AhpC was detected in several series of isogenic INH-resistant (INHr) derivatives. In a demonstration of the critical role of ahpC in sensitivity to INH, insertional inactivation of ahpC on the chromosome of Mycobacterium smegmatis, a species naturally insensitive to INH, dramatically increased its susceptibility to this compound. These findings suggest that AhpC counteracts the action of INH and that the levels of its expression may govern the intrinsic susceptibility of mycobacteria to this front-line antituberculosis drug.

| S-EPMC24072 | biostudies-literature

Nitrate reductase assay for rapid detection of isoniazid, rifampin, ethambutol, and streptomycin resistance in Mycobacterium tuberculosis: a systematic review and meta-analysis.

Project description:Colorimetric phenotypic tests recently gained interest because traditional primary drug susceptibility testing of Mycobacterium tuberculosis isolates takes a long time. We used meta-analysis techniques to review the reliability and accuracy of the nitrate reductase assay (NRA), which is one of the most popular colorimetric methods to detect resistance to first-line drugs. Medline, PubMed, ISI Web, Web of Science, and Google Scholar were used to search for studies enrolled in the meta-analysis. The analysis included 35 studies for isoniazid (INH), 38 for rifampin (RIF), and 22 for ethambutol (EMB) and streptomycin (STR). Summary receiver operating characteristic (SROC) curves were applied to summarize diagnostic accuracy. The meta-analyses were performed by the use of Meta-DiSc software (version 1.4) and were focused on sensitivity and specificity values for measurements of accuracy. The pooled sensitivities were 96% for INH, 97% for RIF, 90% for EMB, and 82% for STR. The pooled specificities for INH, RIF, EMB, and STR were 99%, 100%, 98%, and 96%, respectively. The times required to obtain results were between 5 and 28 days by the direct NRA and between 5 and 14 days by the indirect test. In conclusion, the present meta-analysis showed that the NRA is a reliable low-cost rapid colorimetric susceptibility test that can be used for the detection of multidrug-resistant (MDR) tuberculosis, including detection of EMB resistance. However, the test appears to have a relatively low sensitivity for STR and needs further improvement.

| S-EPMC3911439 | biostudies-literature

Chemical disarming of isoniazid resistance in Mycobacterium tuberculosis

Project description:This SuperSeries is composed of the SubSeries listed below.

2019-05-31 | GSE129835 | GEO