Microarray analysis of the chelerythrine-induced transcriptome of Mycobacterium tuberculosis

The significance of persisters in tuberculosis drug discovery: Exploring the potential of targeting the glyoxylate shunt pathway

The significant challenge in confronting TB eradication is the discursive treatment that results in the disease reactivation, patient non compliance and drug resistance. The presently available drug regimen for TB largely targets the active bacilli and thus remains inadequate against the dormant or persistent subpopulation of Mtb that results in latent TB affecting a quarter of the global population. The crucial pathways that are particularly essential for the survival of dormant Mtb demand better apprehension. Novel drugs are needed to specifically address these persisters in order to enhance treatment effectiveness. Among such pathways, the glyoxylate bypass plays a critical role in the persistence and latent infection of Mtb, making it a promising target for drug development in recent years. In this review, we have compiled the attributes of bacterial subpopulations liable for latent TB and the pathways indispensable for their survival. Specifically, we delve into the glyoxylate shunt pathway and its key enzymes as potential drug targets.

Pharmacokinetics of Chelerythrine and Its Metabolite after Oral and Intramuscular Administrations in Pigs

The objective of this study was to investigate the single- and multiple-dose pharmacokinetics of chelerythrine (CHE) and its metabolite, dihydrochelerythrine (DHCHE), after oral and IM administrations in pigs.Six crossbreed (Landrace × Large White) female pigs (7 to 8 weeks old; 24.1 ± 2.6 kg bw) administered oral and IM CHE at a dose of 0.1 mg/kg orally and intramuscularly in a cross-over design. Multiple oral administration was performed at 0.1 mg/kg a time, three times a day at 8-h intervals for three consecutive days. Blood samples were collected from the anterior vena cava and placed into heparinized centrifuge tubes before dosing (time 0 h) and at different times after oral oral and IM administrations. Pretreatment plasma was analyzed by high-performance liquid chromatography tandem mass spectrometry.After IM administration, CHE and DHCHE rapidly reached peak concentrations (C_max, 69.79 ± 15.41 and 3.47 ± 1.23 ng/ml) at 0.42 ± 0.13 and 0.33 ± 0.13 h, respectively. After single oral administration, CHE and DHCHE rapidly increased to reach C_max of 5.04 ± 1.00 and 1.21 ± 0.35 ng/ml at 1.83 ± 0.26 and 1.67 ± 0.26 h, respectively. The half-life (T_1/2) was 2.03 ± 0.26 and 2.56 ± 1.00 h for CHE and DHCHE, respectively. After multiple oral administration, the average steady-state concentrations (C_ss) of CHE and DHCHE were 2.51 ± 0.40 and 0.6 ± 0.06 ng/ml, respectively.CHE is metabolized rapidly after a single oral administration, multiple daily doses and long-term use of CHE are recommended.

Restoration of the Antibiotic Susceptibility of Methicillin-Resistant Staphylococcus aureus and Extended-Spectrum β-Lactamases Escherichia coli Through Combination with Chelerythrine

Multidrug resistance poses a severe threat to public health and urgently requires new solutions. The natural product chelerythrine (CHE) is a benzophenanthridine alkaloid with antimicrobial potential. In this study, CHE was effective against seven gram-positive bacterial strains, and the minimum inhibitory concentrations (MICs) ranged from 2 to 4 μg/mL. By contrast, CHE showed inferior antibacterial activities against 11 gram-negative strains, and the MICs varied from 16 to 256 μg/mL. We also determined the synergistic/additive effects of combining CHE with nine currently used antibiotics. CHE restored the antibacterial efficacy of the antibiotics against methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamases producing Escherichia coli. This study suggests that the combination of CHE with conventional antibiotics may be a promising strategy to combat infections caused by multidrug-resistant organisms.

Multi-Omics Technologies Applied to Tuberculosis Drug Discovery

Multi-omics strategies are indispensable tools in the search for new anti-tuberculosis drugs. Omics methodologies, where the ensemble of a class of biological molecules are measured and evaluated together, enable drug discovery programs to answer two fundamental questions. Firstly, in a discovery biology approach, to find new targets in druggable pathways for target-based investigation, advancing from target to lead compound. Secondly, in a discovery chemistry approach, to identify the mode of action of lead compounds derived from high-throughput screens, progressing from compound to target. The advantage of multi-omics methodologies in both of these settings is that omics approaches are unsupervised and unbiased to a priori hypotheses, making omics useful tools to confirm drug action, reveal new insights into compound activity, and discover new avenues for inquiry. This review summarizes the application of Mycobacterium tuberculosis omics technologies to the early stages of tuberculosis antimicrobial drug discovery.

The potential of plant systems to break the HIV-TB link

Tuberculosis (TB) and human immunodeficiency virus (HIV) can place a major burden on healthcare systems and constitute the main challenges of diagnostic and therapeutic programmes. Infection with HIV is the most common cause of Mycobacterium tuberculosis (Mtb), which can accelerate the risk of latent TB reactivation by 20-fold. Similarly, TB is considered the most relevant factor predisposing individuals to HIV infection. Thus, both pathogens can augment one another in a synergetic manner, accelerating the failure of immunological functions and resulting in subsequent death in the absence of treatment. Synergistic approaches involving the treatment of HIV as a tool to combat TB and vice versa are thus required in regions with a high burden of HIV and TB infection. In this context, plant systems are considered a promising approach for combatting HIV and TB in a resource-limited setting because plant-made drugs can be produced efficiently and inexpensively in developing countries and could be shared by the available agricultural infrastructure without the expensive requirement needed for cold chain storage and transportation. Moreover, the use of natural products from medicinal plants can eliminate the concerns associated with antiretroviral therapy (ART) and anti-TB therapy (ATT), including drug interactions, drug-related toxicity and multidrug resistance. In this review, we highlight the potential of plant system as a promising approach for the production of relevant pharmaceuticals for HIV and TB treatment. However, in the cases of HIV and TB, none of the plant-made pharmaceuticals have been approved for clinical use. Limitations in reaching these goals are discussed.

Genome-Wide Transcriptional Responses of Mycobacterium to Antibiotics

Antibiotics can stimulate or depress gene expression in bacteria. The analysis of transcriptional responses of Mycobacterium to antimycobacterial compounds has improved our understanding of the mode of action of various drug classes and the efficacy and effect of such compounds on the global metabolism of Mycobacterium. This approach can provide new insights for known antibiotics, for example those currently used for tuberculosis treatment, as well as help to identify the mode of action and predict the targets of new compounds identified by whole-cell screening assays. In addition, changes in gene expression profiles after antimycobacterial treatment can provide information about the adaptive ability of bacteria to escape the effects of antibiotics and allow monitoring of the physiology of the bacteria during treatment. Genome-wide expression profiling also makes it possible to pinpoint genes differentially expressed between drug sensitive Mycobacterium and multidrug-resistant clinical isolates. Finally, genes involved in adaptive responses and drug tolerance could become new targets for improving the efficacy of existing antibiotics.

Plants in our combating strategies against Mycobacterium tuberculosis: progress made and obstacles met

CONTEXT

Traditionally used plants for treating chest-related problems/tuberculosis (TB) have not been evaluated in detail and hence a thorough study is needed in this regard. This knowledge may find application in developing new anti-TB drugs.

OBJECTIVE

This article elaborates on studying the activity of medicinal plants against different forms of Mycobacterium tuberculosis (Mtb) using different model strains, in vitro and ex vivo assays for studying the tuberculocidal activity and discusses the results from different studies on the activity against different forms of Mtb and human immunodeficiency virus-tuberculosis (HIV-TB) co-infection.

METHODS

Scientific databases such as PubMed, Elsevier, Scopus, Google scholar, were used to retrieve the information from 86 research articles (published from 1994 to 2016) related to the topic of this review.

RESULTS

Twenty-three plant species have been reported to possess active molecules against multi-drug resistant (MDR) isolates of Mtb. Seven plants were found to be active against intracellular Mtb and six against dormant bacilli. Seven plants were synergistically effective when combined with anti-TB drugs. Six studies suggest that the beneficial effects of plant extracts are due to their wide array of immuno-modulatory effects manifested by the higher expression of cytokines. Some studies have also shown the dual activity (anti-HIV and anti-TB) of plants.

CONCLUSION

We emphasize on identifying plants based on traditional uses and testing their extracts/phytomolecules against MDR strains, intracellular Mtb as well as against dormant Mtb. This will help in future to shorten the current therapeutic regimens for TB and also for treating HIV-TB co-infection.

Application of Omics Technologies for Evaluation of Antibacterial Mechanisms of Action of Plant-Derived Products

In the face of increasing bacterial resistance to antibiotics currently in use, the search for new antimicrobial agents has received a boost in recent years, with natural products playing an important role in this field. In fact, several methods have been proposed to investigate the antibacterial activities of natural products. However, given that the ultimate aim is future therapeutic use as novel drugs, it is extremely necessary to elucidate their modes of action, stating the molecular effects in detail, and identifying their targets in the bacterial cell. This review analyzes the application of “omics technologies” to understand the antibacterial mechanisms of bioactive natural products, to stimulate research interest in this area and promote scientific collaborations. Some studies have been specifically highlighted herein by examining their procedures and results (targeted proteins and metabolic pathways). These approaches have the potential to provide new insights into our comprehension of antimicrobial resistance/susceptibility, creating new perspectives for the struggle against bacteria, and leading to the development of novel products in the future.

Genetic Approaches to Facilitate Antibacterial Drug Development

Very few chemically novel agents have been approved for antibacterial chemotherapies during the last 50 yr. Yet new antibacterial drugs are needed to reduce the impact on global health of an increasing number of drug-resistant infections, including highly drug-resistant forms of tuberculosis. This review discusses how genetic approaches can be used to study the mechanism of action of whole-cell screening hits and facilitate target-driven strategies for antimicrobial drug development.

Potential inhibitors for isocitrate lyase of Mycobacterium tuberculosis and non-M. tuberculosis: a summary

Isocitrate lyase (ICL) is the first enzyme involved in glyoxylate cycle. Many plants and microorganisms are relying on glyoxylate cycle enzymes to survive upon downregulation of tricarboxylic acid cycle (TCA cycle), especially Mycobacterium tuberculosis (MTB). In fact, ICL is a potential drug target for MTB in dormancy. With the urge for new antitubercular drug to overcome tuberculosis treat such as multidrug resistant strain and HIV-coinfection, the pace of drug discovery has to be increased. There are many approaches to discovering potential inhibitor for MTB ICL and we hereby review the updated list of them. The potential inhibitors can be either a natural compound or synthetic compound. Moreover, these compounds are not necessary to be discovered only from MTB ICL, as it can also be discovered by a non-MTB ICL. Our review is categorized into four sections, namely, (a) MTB ICL with natural compounds; (b) MTB ICL with synthetic compounds; (c) non-MTB ICL with natural compounds; and (d) non-MTB ICL with synthetic compounds. Each of the approaches is capable of overcoming different challenges of inhibitor discovery. We hope that this paper will benefit the discovery of better inhibitor for ICL.

Genome-wide transcription analyses in Mycobacterium tuberculosis treated with lupulone

Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis, still causes higher mortality than any other bacterial pathogen until now. With the emergence and spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR-TB) strains, it becomes more important to search for alternative targets to develop new antimycobacterial drugs. Lupulone is a compound extracted from Hops (Hurnulus lupulus), which exhibits a good antimicrobial activity against M. tuberculosis with minimal inhibitory concentration (MIC) value of 10 μg/mL, but the response mechanisms of lupulone against M. tuberculosis are still poorly understood. In this study, we used a commercial oligonucleotide microarray to determine the overall transcriptional response of M. tuberculosis H37Rv triggered by exposure to MIC of lupulone. A total of 540 genes were found to be differentially regulated by lupulone. Of these, 254 genes were upregulated, and 286 genes were downregulated. A number of important genes were significantly regulated which are involved in various pathways, such as surface-exposed lipids, cytochrome P450 enzymes, PE/PPE multigene families, ABC transporters, and protein synthesis. Real-time quantitative RT-PCR was performed for choosed genes to verified the microarray results. To our knowledge, this genome-wide transcriptomics approach has produced the first insights into the response of M. tuberculosis to a lupulone challenge.

Genome-wide expression profiling of the response to linezolid in Mycobacterium tuberculosis

Tuberculosis (TB) is still one of the most common causes of death in the world. The emergence of multidrug-resistant and extensively drug-resistant (XDR-TB) Mycobacterium tuberculosis (M. tuberculosis) strains has increased the importance of searching for alternative targets to develop new antimycobacterial drugs. Linezolid, the first of oxazolidinones, is active in vitro against M. tuberculosis, but the response mechanisms of M. tuberculosis to linezolid are still poorly understood. To reveal the possible mechanism of action of linezolid against M. tuberculosis, commercial oligonucleotide microarrays were used to analyze the genome-wide transcriptional changes triggered by treatment with subinhibitory concentrations of linezolid. Quantitative real-time RT-PCR was performed for selected genes to verify the microarray results. A total of 729 genes were found to be differentially regulated by linezolid. Among these, 318 genes were upregulated, and 411 genes were downregulated. A number of important genes were significantly regulated that are involved in various pathways, such as protein synthesis, sulfite metabolism, and genes involved in the cell envelope and virulence. This genome-wide transcriptomics approach produced the first insights into the response of M. tuberculosis to a linezolid challenge.