Mycobacterium tuberculosis cell-wall and antimicrobial peptides: a mission impossible?

Depletion of essential mycobacterial gene glmM reduces pathogen survival and induces host-protective immune responses against tuberculosis

The limitations of TB treatment are the long duration and immune-dampening effects of anti-tuberculosis therapy. The Cell wall plays a crucial role in survival and virulence; hence, enzymes involved in its biosynthesis are good therapeutic targets. Here, we identify Mycobacterium tuberculosis (Mtb) GlmM, (GlmMMtb) engaged in the UDP-GlcNAc synthesis pathway as an essential enzyme. We generated a conditional knockdown strain, Rv-glmMkD using the CRISPR interference-mediated gene silencing approach. Depletion of GlmMMtb affects the morphology and thickness of the cell wall. The Rv-glmMkD strain attenuated Mtb survival in vitro, in the host macrophages (ex vivo), and in a murine mice infection model (in vivo). Results suggest that the depletion of GlmMMtb induces M1 macrophage polarization, prompting a pro-inflammatory cytokine response, apparent from the upregulation of activation markers, including IFNɣ and IL-17 that resists the growth of Mtb. These observations provide a rationale for exploring GlmMMtb as a potential therapeutic target.

Unveiling the Significance of LysE in Survival and Virulence of Mycobacterium tuberculosis: A Review Reveals It as a Potential Drug Target, Diagnostic Marker, and a Vaccine Candidate

Tuberculosis (TB) remains a global health threat, necessitating innovative strategies for control and prevention. This comprehensive review explores the Mycobacterium tuberculosis Lysine Exporter (LysE) gene, unveiling its multifaceted roles and potential uses in controlling and preventing tuberculosis (TB). As a pivotal player in eliminating excess L-lysine and L-arginine, LysE contributes to the survival and virulence of M. tuberculosis. This review synthesizes findings from different electronic databases and includes 13 studies focused on the LysE of M. tuberculosis. The research unveils that LysE can be a potential drug target, a diagnostic marker for TB, and a promising candidate for vaccine development. The absence of LysE in the widely used BCG vaccine underscores its uniqueness and positions it as a novel area for TB prevention. In conclusion, this review underscores the significance of LysE in TB pathogenesis and its potential as a drug target, diagnostic marker, and vaccine candidate. The multifaceted nature of LysE positions it at the forefront of innovative approaches to combat TB, calling for sustained research efforts to harness its full potential in the global fight against this infectious disease.

Modulators targeting protein-protein interactions in Mycobacterium tuberculosis

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), mainly transmitted through droplets to infect the lungs, and seriously affecting patients' health and quality of life. Clinically, anti-TB drugs often entail side effects and lack efficacy against resistant strains. Thus, the exploration and development of novel targeted anti-TB medications are imperative. Currently, protein-protein interactions (PPIs) offer novel avenues for anti-TB drug development, and the study of targeted modulators of PPIs in M. tuberculosis has become a prominent research focus. Furthermore, a comprehensive PPI network has been constructed using computational methods and bioinformatics tools. This network allows for a more in-depth analysis of the structural biology of PPIs and furnishes essential insights for the development of targeted small-molecule modulators. Furthermore, this article provides a detailed overview of the research progress and regulatory mechanisms of PPI modulators in M. tuberculosis, the causative agent of TB. Additionally, it summarizes potential targets for anti-TB drugs and discusses the prospects of existing PPI modulators.

Searching for Chemical Agents Suppressing Substrate Microbiota in White-Rot Fungi Large-Scale Cultivation

Edible fungi are a valuable resource in the search for sustainable solutions to environmental pollution. Their ability to degrade organic pollutants, extract heavy metals, and restore ecological balance has a huge potential for bioremediation. They are also sustainable food resources. Edible fungi (basidiomycetes or fungi from other divisions) represent an underutilized resource in the field of bioremediation. By maximizing their unique capabilities, it is possible to develop innovative approaches for addressing environmental contamination. The aim of the present study was to find selective chemical agents suppressing the growth of microfungi and bacteria, but not suppressing white-rot fungi, in order to perform large-scale cultivation of white-rot fungi in natural unsterile substrates and use it for different purposes. One application could be the preparation of a matrix composed of wooden sleeper (contaminated with PAHs) and soil for further hazardous waste bioremediation using white-rot fungi. In vitro microbiological methods were applied, such as, firstly, compatibility tests between bacteria and white-rot fungi or microfungi, allowing us to evaluate the interaction between different organisms, and secondly, the addition of chemicals on the surface of a Petri dish with a test strain of microorganisms of white-rot fungi, allowing us to determine the impact of chemicals on the growth of organisms. This study shows that white-rot fungi are not compatible to grow with several rhizobacteria or bacteria isolated from soil and bioremediated waste. Therefore, the impact of several inorganic materials, such as lime (hydrated form), charcoal, dolomite powder, ash, gypsum, phosphogypsum, hydrogen peroxide, potassium permanganate, and sodium hydroxide, was evaluated on the growth of microfungi (sixteen strains), white-rot fungi (three strains), and bacteria (nine strains) in vitro. Charcoal, dolomite powder, gypsum, and phosphogypsum did not suppress the growth either of microfungi or of bacteria in the tested substrate, and even acted as promoters of their growth. The effects of the other agents tested were strain dependent. Potassium permanganate could be used for bacteria and Candida spp. growth suppression, but not for other microfungi. Lime showed promising results by suppressing the growth of microfungi and bacteria, but it also suppressed the growth of white-rot fungi. Hydrogen peroxide showed strong suppression of microfungi, and even had a bactericidal effect on some bacteria, but did not have an impact on white-rot fungi. The study highlights the practical utility of using hydrogen peroxide up to 3% as an effective biota-suppressing chemical agent prior to inoculating white-rot fungi in the large-scale bioremediation of polluted substrates, or in the large-scale cultivation for mushroom production as a foodstuff.

Application of BactTiter-Glo ATP bioluminescence assay for Mycobacterium tuberculosis detection

BACKGROUND

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains a global health threat, necessitating faster and more accessible diagnostic methods. This study investigates critical parameters in the application of a commercial ATP bioluminescence assay for the detection of MTB.

METHOD

Our objective was to optimize the ATP bioluminescence protocol using BacTiter-Glo™ for MTB, investigating the impact of varying volumes of MTB suspension and reagent on assay sensitivity, evaluating ATP extraction methods, establishing calibration curves, and elucidating strain-specific responses to antimicrobial agents.

RESULTS

ATP extraction methods showed no significant improvement over controls. Calibration curves revealed a linear correlation between relative light units (RLU) and colony-forming units (CFU/mL), establishing low detection limits. Antimicrobial testing demonstrated strain-specific responses aligning with susceptibility and resistance patterns.

CONCLUSION

Our findings contribute to refining ATP bioluminescence protocols for enhanced MTB detection and susceptibility testing. Further refinements and validation efforts are warranted, holding promise for more efficient diagnostic platforms in the future.

Promising Ursolic Acid as a Novel Antituberculosis Agent: Current Progress and Challenges

Tuberculosis (TB) stands as the second most prevalent cause of global human mortality from infectious diseases. In 2022, the World Health Organization documented an estimated number of global TB cases reaching 7.5 million, which causes death for 1.13 million patients. The continuous growth of drug-resistant TB cases due to various mutations in the Mycobacterium tuberculosis (MTB) strain, raises the urgency of the exploration of novel anti-TB treatments. Ursolic acid (UA) is a natural pentacyclic triterpene found in various plants that has shown potential as a novel anti-TB agent. This review aims to provide an overview of the therapeutic prospects of UA against MTB, with a particular emphasis on in silico, in vitro, and in vivo studies. Various mechanisms of action of UA against MTB are briefly recapped from in silico studies, such as enoyl acyl carrier protein reductase inhibitors, FadA5 (Acetyl-CoA acetyltransferase) inhibitors, tuberculosinyl adenosine transferase inhibitors, and small heat shock protein 16.3 inhibitor. The potential of UA to overcome drug resistance and its synergistic effects with existing antituberculosis drugs are briefly explained from in vitro studies using a variety of methods, such as Microplate Alamar Blue Assay, Mycobacteria Growth Indicator Tube 960 and Resazurin Assays, morphological change evaluation using transmission electron microscopy, and in vivo studies using BALB/C infected with multi drug resistant clinical isolates. Besides its promising mechanism as an antituberculosis drug, its complex chemical composition, limited availability and supply, and lack of intellectual property are also reviewed as those are the most frequently occurring challenges that need to be addressed for the successful development of UA as novel anti-TB agent.

ERK1/2-CEBPB Axis-Regulated hBD1 Enhances Anti-Tuberculosis Capacity in Alveolar Type II Epithelial Cells

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), remains a global health crisis with substantial morbidity and mortality rates. Type II alveolar epithelial cells (AEC-II) play a critical role in the pulmonary immune response against Mtb infection by secreting effector molecules such as antimicrobial peptides (AMPs). Here, human β-defensin 1 (hBD1), an important AMP produced by AEC-II, has been demonstrated to exert potent anti-tuberculosis activity. HBD1 overexpression effectively inhibited Mtb proliferation in AEC-II, while mice lacking hBD1 exhibited susceptibility to Mtb and increased lung tissue inflammation. Mechanistically, in A549 cells infected with Mtb, STAT1 negatively regulated hBD1 transcription, while CEBPB was the primary transcription factor upregulating hBD1 expression. Furthermore, we revealed that the ERK1/2 signaling pathway activated by Mtb infection led to CEBPB phosphorylation and nuclear translocation, which subsequently promoted hBD1 expression. Our findings suggest that the ERK1/2-CEBPB-hBD1 regulatory axis can be a potential therapeutic target for anti-tuberculosis therapy aimed at enhancing the immune response of AEC-II cells.

Temperature-Induced Restructuring of Mycolic Acid Bilayers Modeling the Mycobacterium tuberculosis Outer Membrane: A Molecular Dynamics Study

The emergence of new drug-resistant strains of the tuberculosis pathogen Mycobacterium tuberculosis (Mtb) is a new challenge for modern medicine. Its resistance capacity is closely related to the properties of the outer membrane of the Mtb cell wall, which is a bilayer membrane formed by mycolic acids (MAs) and their derivatives. To date, the molecular mechanisms of the response of the Mtb outer membrane to external factors and, in particular, elevated temperatures have not been sufficiently studied. In this work, we consider the temperature-induced changes in the structure, ordering, and molecular mobility of bilayer MA membranes of various chemical and conformational compositions. Using all-atom long-term molecular dynamics simulations of various MA membranes, we report the kinetic parameters of temperature-dependent changes in the MA self-diffusion coefficients and conformational compositions, including the apparent activation energies of these processes, as well as the characteristic times of ordering changes and the features of phase transitions occurring over a wide range of elevated temperatures. Understanding these effects could be useful for the prevention of drug resistance and the development of membrane-targeting pharmaceuticals, as well as in the design of membrane-based materials.

Defensins: A novel weapon against Mycobacterium tuberculosis?

Tuberculosis (TB) is a serious airborne communicable disease caused by organisms of the Mycobacterium tuberculosis (Mtb) complex. Although the standard treatment antimicrobials, including isoniazid, rifampicin, pyrazinamide, and ethambutol, have made great progress in the treatment of TB, problems including the rising incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), the severe toxicity and side effects of antimicrobials, and the low immunity of TB patients have become the bottlenecks of the current TB treatments. Therefore, both safe and effective new strategies to prevent and treat TB have become a top priority. As a subfamily of cationic antimicrobial peptides, defensins are rich in cysteine and play a vital role in resisting the invasion of microorganisms and regulating the immune response. Inspired by studies on the roles of defensins in host defence, we describe their research history and then review their structural features and antimicrobial mechanisms, specifically for fighting Mtb in detail. Finally, we discuss the clinical relevance, therapeutic potential, and potential challenges of defensins in anti-TB therapy. We further debate the possible solutions of the current application of defensins to provide new insights for eliminating Mtb.

In silico Screening of Food and Drug Administration-approved Compounds against Trehalose 2-sulfotransferase (Rv0295c) in Mycobacterium tuberculosis: Insights from Molecular Docking and Dynamics Simulations

BACKGROUND

Tuberculosis (TB) remains a prominent global health challenge, distinguished by substantial occurrences of infection and death. The upsurge of drug-resistant TB strains underscores the urgency to identify novel therapeutic targets and repurpose existing compounds. Rv0295c is a potentially druggable enzyme involved in cell wall biosynthesis and virulence. We evaluated the inhibitory activity of Food and Drug Administration (FDA)-approved compounds against Rv0295c of Mycobacterium tuberculosis, employing molecular docking, ADME evaluation, and dynamics simulations.

METHODS

The study screened 1800 FDA-approved compounds and selected the top five compounds with the highest docking scores. Following this, we subjected the initially screened ligands to ADME analysis based on their dock scores. In addition, the compound exhibited the highest binding affinity chosen for molecular dynamics (MD) simulation to investigate the dynamic behavior of the ligand-receptor complex.

RESULTS

Dihydroergotamine (CHEMBL1732) exhibited the highest binding affinity (-12.8 kcal/mol) for Rv0295c within this set of compounds. We evaluated the stability and binding modes of the complex over extended simulation trajectories.

CONCLUSION

Our in silico analysis demonstrates that FDA-approved drugs can serve as potential Rv0295c inhibitors through repurposing. The combination of molecular docking and MD simulation offers a comprehensive understanding of the interactions between ligands and the protein target, providing valuable guidance for further experimental validation. Identifying Rv0295c inhibitors may contribute to new anti-TB drugs.

Mycobacterium tuberculosis and its clever approaches to escape the deadly macrophage

Mycobacterium tuberculosis (Mt.b), a deadly disease causer, is a facultative parasite. This microorganism has developed several methods to defend itself, once internalized within specialised vacuoles in the macrophages. A wide array of receptors like the complement receptor mannose receptors, scavenger receptor assists the entry of the microbe within the phagocytic macrophages. However, Mt.b is clever enough to protect itself from the hostile environment of the macrophage thereby prevailing within it. The microbe can efficiently inhibit processes like phagosome-lysosome fusion, acidification of phagosomes, release of proinflammatory cytokines and stop crucial events like apoptosis. Additionally, it also adopts resistance to killing by reactive oxygen intermediates and reactive nitrogen intermediates. There are multiple genes both in host and the pathogen which are involved in this successful survival of Mt.b. The regulation of phagolysosome fusion is mediated by proteins such as Coronin, TlyA, SapM, PnkG, EsxH. The microbe has certain mechanisms to even acquire iron from the host cell, to withstand iron deprivation as a mode of host's defence mechanism. This review focuses on the various defensive adaptations acquired by Mt.b for fighting against the deprived conditions existing within the macrophages and their capability of proliferating successfully within it, thereby resulting in a diseased condition.