Anti-tuberculosis Therapies Research Articles

VIRTUAL DESIGN OF NOVEL OF ORALLY BIOAVAILABLE PIPERAZINE INHIBITORS OF ENOYL-ACYL CARRIER PROTEIN REDUCTASE OF MYCOBACTERIUM TUBERCULOSIS WITH FAVORABLE PHARMACOKINETIC PROFILES

Background: During the previous decade, Anti-tuberculosis therapies were confronted with drug-resistant strains. We report here virtual design and evaluation of novel piperazine (PPZ) as inhibitors of InhA-Mt endowed with favorable predicted pharmacokinetic profiles. Method: Three-dimensional (3D) models of InhA-PPZx complexes were prepared by in situ modifications of the crystal structure of InhA-PPZ1 (Protein Data Bank (PDB) entry code: 1P44), the reference compound of a training set of 12 PPZs with known experimental inhibitory potencies (IC50exp). First, in the search for active conformation of the PPZ 1-12, we built a gas phase quantitative structure-activity relationships (QSAR) model, linearly correlating the computed enthalpy of the InhA-PPZ complex formation and the pIC50exp. Finally, the VCL filtered by Lipinski’s rule-of-five was screened by the PH4 model and the potencies of the new PPZ analogs obtained were evaluated with the initial QSAR and their pharmacokinetic profile was evaluated. Results: The VCL of 310,500 PPZs s was filtered down to 19,044 analogs by the Lipinski’s rule. The five-point PH4 screening retained 50 new potent PPZs with predicted inhibitory potencies IC50pre up to 100-times better than that of PPZ1 (IC50exp=160 nM). Predicted pharmacokinetic profile of the new analogs showed enhanced cell membrane permeability, side effect and high human oral absorption compared to current anti-tuberculosis candidates Conclusions: Combining molecular modeling and PH4 in virtual screening of the VL resulted in the proposed novel potent antituberculotic agent candidates with favorable pharmacokinetic profiles. Peer Review History: Received 21 July 2024; Reviewed 13 September 2024; Accepted 20 October; Available online 15 November 2024 Academic Editor: Dr. Asia Selman Abdullah, Pharmacy institute, University of Basrah, Iraq, asia_abdullah65@yahoo.com Average Peer review marks at initial stage: 6.0/10 Average Peer review marks at publication stage: 7.5/10 Reviewers: Antonio José de Jesus Evangelista, Federal University of Ceará, UFC, Brazil, tony_biomed@hotmail.com Asmaa Ahmed Mohamed Ahmed Khalifa, Pharos University, Alexandria, Egypt, asmaa.khalifa@pua.edu.eg

Modulating ferroptosis and mycobactericidal activity in lung epithelial cells via YY1/iNOS pathway

BackgroundMycobacterium tuberculosis infection triggers various forms of host cell death, including ferroptosis in lung epithelial cells; YY1, a critical transcription factor, plays a pivotal role in regulating ferroptosis, however, the underlying mechanisms are not fully understood. MethodsTo investigate Mycobacterium marinum (M.marinum) infection in lung epithelial cells A549 and H1299, we utilized flow cytometry to evaluate cell death and measure reactive oxygen species (ROS). Colony-forming unit (CFU) assays determined the intracellular bacterial load. Ferroptosis was analyzed using a specific detection kit to measure malondialdehyde (MDA) and glutathione (GSH) levels. The interaction between the transcription factor YY1 and the iNOS promoter was assessed through a dual-luciferase reporter assay. ResultsM.marinum induced ferroptosis in lung epithelial cells through invasion. This effect is most pronounced at 8 h of infection and decreases over time but increased with a higher multiplicity of infection (MOI). YY1 knockdown decreases the expression of SLC7A11 and GPX4, attenuates cellular ferroptosis, while YY1 overexpression has the opposite phenomenon, enhancing the expression of bactericidal molecules such as iNOS and MPEG1, thereby markedly reducing the intracellular bacterial load. We identified substantial binding of YY1 to the iNOS promoter region (−655 to −1018 bp), enhancing mycobactericidal activity in YY1-overexpressing cells. ConclusionsOur study demonstrates that YY1 inhibits ferroptosis induced by Mycobacterium marinum infection and reduces intracellular bacterial proliferation in lung epithelial cells. These findings provide a crucial basis for developing anti-tuberculosis therapies that target YY1 modulation, potentially offering new clinical avenues for the treatment of tuberculosis.

Dynamics of Matricellular Protein Levels in Blood Predict Recovery in Patients with Human Immunodeficiency Virus-Tuberculosis Coinfection.

Chronic immune activation in tuberculosis (TB) associated with human immunodeficiency virus (HIV) infection (HIV/TB) modifies their clinical course. We prospectively measured osteopontin (OPN), full-length galectin-9 (FL-Gal9), and total-Gal9 (T-Gal9) levels in 32 patients with HIV/TB coinfection treated with anti-tuberculosis and antiretroviral therapies over 6-18 months to determine the amelioration of inflammatory conditions in response to the therapies. We observed a significant time-dependent decrease in FL-Gal9 in both pulmonary TB (PTB, n = 20) and extrapulmonary TB (EPTB, n = 12) patients. The levels of T-Gal9, OPN, and CRP decreased significantly after treatment in only PTB patients. We calculated the inflammatory score (INS) indicating immunologic recovery based on the decline in OPN, FL-Gal9, T-Gal9, and CRP levels. Baseline levels of T-Gal9 and OPN positively correlated with INS in all TB and only PTB patients, respectively, indicating that their levels predict better recovery. In contrast, FL-Gal9 levels at the second visit negatively correlated with INS in EPTB patients. The decrease rate in OPN levels at the second visit also correlated positively with INS in PTB patients. Women showed a higher INS and lower levels of FL-Gal9 than men. The patients with moderate grade severity on chest X-ray had higher CD4 cell numbers than those with limited grade severity. Monitoring these markers will help to predict and assess the response to therapy as well as to devise strategies to reduce the complications caused by chronic immune activation in patients with HIV/TB coinfection.

Unlocking translational machinery for antitubercular drug development

Targeting translational factor proteins presents significant promise for the development of innovative antitubercular drugs. Previous insights from antibiotic binding mechanisms and recently solved 3D crystal structures of Mycobacterium tuberculosis (Mtb) elongation factor thermo unstable–GDP (EF-Tu–GDP), elongation factor thermo stable–EF-Tu (EF-Ts–EF-Tu), and elongation factor G–GDP (EF-G–GDP) have opened up new avenues for the design and development of potent antituberculosis (anti-TB) therapies.

Discovery and Mechanistic Study of Novel Mycobacterium tuberculosis ClpP1P2 Inhibitors.

Caseinolytic protease P (ClpP) responsible for the proteolysis of damaged or misfolded proteins plays a critical role in proteome homeostasis. MtbClpP1P2, a ClpP enzyme complex, is required for survival in Mycobacterium tuberculosis, and it is therefore considered as a promising target for the development of antituberculosis drugs. Here, we discovered that cediranib and some of its derivatives are potent MtbClpP1P2 inhibitors and suppress M. tuberculosis growth. Protein pull-down and loss-of-function assays validated the in situ targeting of MtbClpP1P2 by cediranib and its active derivatives. Structural and mutational studies revealed that cediranib binds to MtbClpP1P2 by binding to an allosteric pocket at the equatorial handle domain of the MtbClpP1 subunit, which represents a unique binding mode compared to other known ClpP modulators. These findings provide us insights for rational drug design of antituberculosis therapies and implications for our understanding of the biological activity of MtbClpP1P2.

Mycobacterial FtsZ and inhibitors: a promising target for the anti-tubercular drug development.

The emergence of multidrug-resistant tuberculosis (MDR-TB) strains has rendered many anti-TB drugs ineffective. Consequently, there is an urgent need to identify new drug targets against Mycobacterium tuberculosis (Mtb). Filament Forming Temperature Sensitive Gene Z (FtsZ), a member of the cytoskeletal protein family, plays a vital role in cell division by forming a cytokinetic ring at the cell's center and coordinating the division machinery. When FtsZ is depleted, cells are unable to divide and instead elongate into filamentous structures that eventually undergo lysis. Since the inactivation of FtsZ or alterations in its assembly impede the formation of the Z-ring and septum, FtsZ shows promise as a target for the development of anti-mycobacterial drugs. This review not only discusses the potential role of FtsZ as a promising pharmacological target for anti-tuberculosis therapies but also explores the structural and functional aspects of the mycobacterial protein FtsZ in cell division. Additionally, it reviews various inhibitors of Mtb FtsZ. By understanding the importance of FtsZ in cell division, researchers can explore strategies to disrupt its function, impeding the growth and proliferation of Mtb. Furthermore, the investigation of different inhibitors that target Mtb FtsZ expands the potential for developing effective treatments against tuberculosis.

In silico structural and mechanical insights into bedaquiline resistance associated with high-grade non-synonymous mutations in atpE, mmpR5, and pepQ

Clinical resistance against bedaquiline (BDQ) remains intractable to anti-tuberculosis therapies since its introduction to the market over a decade ago. Herein, we investigated the structural and mechanical aspects of BDQ resistance in AtpE, MmpR5, and PepQ. The known target-specific resistant single non-synonymous mutations were refined to high-grade candidates. Thus, 7 (AtpE), 5 (MmpR5), and 1 (PepQ) single nucleotide polymorphisms (SNPs) and one insertion frameshift mutation in MmpR5 were recreated at the molecular level, and these phenotypic models were then directed to stringent dynamics to define time-scaled changes. The AtpE variants destabilized the structure; mainly, L59V, E61D, and I66M were detrimental to the complex fitness, while L74V and L114P boosted the BDQ binding to MmpR5. The first three and last two alterations gave rise to loss- and gain-of-function to AtpE and MmpR5, respectively. Hence, these five mutants are functionally relevant and therapeutically targetable hotspots of BDQ resistance. There were no noticeable changes in PepQ data analysis. The present study revealed that MmpR5 mutations confer BDQ resistance, whereas AtpE and PepQ SNPs display low susceptibility. These results were tallied with the published findings, which testified to the pursued method’s reliability and accuracy. We hope these data and inferences could be helpful for the futuristic design of novel TB drugs. Communicated by Ramaswamy H. Sarma

The Endogenous Retinoic Acid Receptor Pathway Is Exploited by Mycobacterium tuberculosis during Infection, Both InVitro and InVivo.

Retinoic acid (RA) is a fundamental vitamin A metabolite involved in regulating immune responses through the nuclear RA receptor (RAR) and retinoid X receptor. While performing experiments using THP-1 cells as a model for Mycobacterium tuberculosis infection, we observed that serum-supplemented cultures displayed high levels of baseline RAR activation in the presence of live, but not heat-killed, bacteria, suggesting that M. tuberculosis robustly induces the endogenous RAR pathway. Using invitro and invivo models, we have further explored the role of endogenous RAR activity in M. tuberculosis infection through pharmacological inhibition of RARs. We found that M. tuberculosis induces classical RA response element genes such as CD38 and DHRS3 in both THP-1 cells and human primary CD14+ monocytes via a RAR-dependent pathway. M. tuberculosis-stimulated RAR activation was observed with conditioned media and required nonproteinaceous factor(s) present in FBS. Importantly, RAR blockade by (4-[(E)-2-[5,5-dimethyl-8-(2-phenylethynyl)-6H-naphthalen-2-yl]ethenyl]benzoic acid), a specific pan-RAR inverse agonist, in a low-dose murine model of tuberculosis significantly reduced SIGLEC-F+CD64+CD11c+high alveolar macrophages in the lungs, which correlated with 2× reduction in tissue mycobacterial burden. These results suggest that the endogenous RAR activation axis contributes to M. tuberculosis infection both invitro and invivo and reveal an opportunity for further investigation of new antituberculosis therapies.

Coordination of the Uptake and Metabolism of Amino Acids in Mycobacterium tuberculosis-Infected Macrophages.

Macrophage polarization to the M1-like phenotype, which is critical for the pro-inflammatory and antimicrobial responses of macrophages against intracellular pathogens, is associated with metabolic reprogramming to the Warburg effect and a high output of NO from increased expression of NOS2. However, there is limited understanding about the uptake and metabolism of other amino acids during M1 polarization. Based on functional analysis of a group of upregulated transporters and enzymes involved in the uptake and/or metabolism of amino acids in Mycobacterium tuberculosis-infected macrophages, plus studies of immune cell activation, we postulate a coherent scheme for amino acid uptake and metabolism during macrophage polarization to the M1-like phenotype. We describe potential mechanisms that the increased arginine metabolism by NOS2 is metabolically coupled with system L transporters LAT1 and LAT2 for the uptake of neutral amino acids, including those that drive mTORC1 signaling toward the M1-like phenotype. We also discuss the underappreciated pleiotropic roles of glutamine metabolism in the metabolic reprogramming of M1-like macrophages. Collectively, our analyses argue that a coordinated amino acid uptake and metabolism constitutes an integral component of the broad metabolic scheme required for macrophage polarization to M1-like phenotype against M. tuberculosis infection. This idea could stimulate future experimental efforts to elucidate the metabolic map of macrophage activation for the development of anti-tuberculosis therapies.

The Roles of Host Noncoding RNAs in Mycobacterium tuberculosis Infection.

Tuberculosis remains a major health problem. Mycobacterium tuberculosis, the causative agent of tuberculosis, can replicate and persist in host cells. Noncoding RNAs (ncRNAs) widely participate in various biological processes, including Mycobacterium tuberculosis infection, and play critical roles in gene regulation. In this review, we summarize the latest reports on ncRNAs (microRNAs, piRNAs, circRNAs and lncRNAs) that regulate the host response against Mycobacterium tuberculosis infection. In the context of host-Mycobacterium tuberculosis interactions, a broad and in-depth understanding of host ncRNA regulatory mechanisms may lead to potential clinical prospects for tuberculosis diagnosis and the development of new anti-tuberculosis therapies.

Targeting of myeloid-derived suppressor cells by all-trans retinoic acid as host-directed therapy for human tuberculosis

Conventional anti-tuberculosis (TB) therapies comprise lengthy antibiotic treatment regimens, exacerbated by multi-drug resistant and extensively drug resistant mycobacterial strains. We assessed the ability of all-trans retinoic acid (ATRA), as repurposed compound serving as host-directed therapy (HDT), to counteract the suppressive effects of myeloid-derived suppressor cells (MDSCs) obtained from active TB cases (untreated or during week one of treatment) on T-cell responsiveness. We show for the first time that MDSCs suppress non-specific T-cell activation and production of interleukin (IL)-2, IL-4, IL-13 and GM-CSF via contact-dependent mechanisms. ATRA treatment decreases MDSC frequency, but fails to mature MDSCs to non-suppressive, terminally differentiated myeloid cells and does not restore T-cell function or cytokine production in the presence of MDSCs. The impact of ATRA treatment on improved immunity, using the concentration tested here, is likely to be minimal, but further identification and development of MDSC-targeting TB host-directed therapies are warranted.

PREVALENCE OF LATENT TB AMONG US ADULTS WITH CHRONIC HEPATITIS B VIRUS: A RETROSPECTIVE STUDY OF THE NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY

SESSION TITLE: Chest Infections Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Tuberculosis (TB) and hepatitis B virus infection (HBV) are treatable, communicable diseases that can exist as chronic, asymptomatic infections with a significant global burden. Guidelines recommend screening TB patients for HBV if they have risk factors prior to initiating tuberculosis therapy. However, there are no clear general guidelines regarding TB screening among patients with chronic HBV or vice versa, and rates of co-infection with latent TB (LTBI) and HBV have not been well described. We aim to evaluate prevalence ratios of LTBI and HBV co-infection among U.S. adults using a large population-based database. METHODS: Using the National Health and Nutrition Examination Survey (NHANES), a cross-sectional, stratified, multistage probability sample of the U.S. population, we retrospectively evaluated the prevalence of LTBI and HBV co-infection among adults age 20 and older for the 1990-2000 and 2011-2012 cycles. LTBI was assessed using NHANES data reported for the tuberculin skin test (TST). Data for the QuantiFERON-TB Gold In-Tube test (QFT-GIT) was reported for the 2011-2012 cycle only. The presence/absence of HBV was analyzed using the hepatitis B surface antigen (HBsAg) test result. Observations with missing data were excluded from this study. Between-group comparisons used chi-squared testing with a statistical significance set at a two-tailed p<0.05. RESULTS: Overall prevalence of LTBI was 4.2%, HBV was 0.3% and prevalence of LTBI and HBV coinfection was low (0.03%). Prevalence of LTBI was higher among individuals with HBV compared to those without HBV (15.3% [95% CI 6.6-31.7%] vs. 4.3% [95% CI 3.5-5.2%] respectively, p=0.004). LTBI increased among those with HBV (6.8% [95% CI 1.4-27.1%] in 1999-2000 to 21.9% [95% CI 8.0-47.6%] in 2011-2012; p=0.16), while it remained stable among those without HBV (4.3% [95% CI 3.5-5.4%] in 1999-2000 to 4.2% [95% CI 3.0-5.8%] in 2012-2012; p=0.89). TB prevalence based on the QFT-GIT was 22.7% (95% CI 11.5-40.0) in 2011-2012. In NHANES, among the subset of patients with LTBI, prevalence of HBV showed a non-significant increase (0.4% [95% CI 0.1-1.7%] in 1999-2000 to 1.4% [95% CI 0.5-3.8%] in 2011-2012; p=0.12). CONCLUSIONS: This study is one of the first to describe TB and HBV co-infection prevalence rates using U.S. population-based data. In 2011-2012, prevalence of LTBI was 3.6 times higher among individuals with HBV compared to those without, which may reflect the importance of shared risk factors in affecting disease epidemiology. CLINICAL IMPLICATIONS: This study highlights the high prevalence of TB among chronic HBV patients, which may help guide screening practices and may suggest a potential role for co-screening for TB and HBV among these high-risk patients with shared risk factors. This is particularly important given the potential impact of HBV co-infection on the risk of drug-induced liver injury related to anti-tuberculosis therapies. DISCLOSURES: No relevant relationships by Amit Chitnis, source=Web Response No relevant relationships by Grishma Hirode, source=Web Response No relevant relationships by Ashley Hubbard, source=Web Response No relevant relationships by Robert Wong, source=Web Response

Targeting MmpL3 for anti-tuberculosis drug development.

The unique architecture of the mycobacterial cell envelope plays an important role in Mycobacterium tuberculosis (Mtb) pathogenesis. A critical protein in cell envelope biogenesis in mycobacteria, required for transport of precursors, trehalose monomycolates (TMMs), is the Mycobacterial membrane protein large 3 (MmpL3). Due to its central role in TMM transport, MmpL3 has been an attractive therapeutic target and a key target for several preclinical agents. In 2019, the first crystal structures of the MmpL3 transporter and its complexes with lipids and inhibitors were reported. These structures revealed several unique structural features of MmpL3 and provided invaluable information on the mechanism of TMM transport. This review aims to highlight the recent advances made in the function of MmpL3 and summarises structural findings. The overall goal is to provide a mechanistic perspective of MmpL3-mediated lipid transport and inhibition, and to highlight the prospects for potential antituberculosis therapies.

Intracellular Mycobacterium tuberculosis Exploits Multiple Host Nitrogen Sources during Growth in Human Macrophages

SummaryNitrogen metabolism of Mycobacterium tuberculosis (Mtb) is crucial for the survival of this important pathogen in its primary human host cell, the macrophage, but little is known about the source(s) and their assimilation within this intracellular niche. Here, we have developed 15N-flux spectral ratio analysis (15N-FSRA) to explore Mtb’s nitrogen metabolism; we demonstrate that intracellular Mtb has access to multiple amino acids in the macrophage, including glutamate, glutamine, aspartate, alanine, glycine, and valine; and we identify glutamine as the predominant nitrogen donor. Each nitrogen source is uniquely assimilated into specific amino acid pools, indicating compartmentalized metabolism during intracellular growth. We have discovered that serine is not available to intracellular Mtb, and we show that a serine auxotroph is attenuated in macrophages. This work provides a systems-based tool for exploring the nitrogen metabolism of intracellular pathogens and highlights the enzyme phosphoserine transaminase as an attractive target for the development of novel anti-tuberculosis therapies.

Diagnosis and treatment of pancreatic tuberculosis: experiences of 10 cases

Objectives: To study the clinical characteristics of pancreatic tuberculosis, and therefore to improve the diagnosis and treatment of this disease. Methods: The clinical data of 10 patients with pancreatic tuberculosis form 1990 to 2017 were reviewed, including clinical characteristics, laboratory tests and imaging features. Results: The ten patients aged 28 to 71 (median 56) years. All of them presented varying degrees of abdominal pain and weight loss (3 to 8 kg). Hypo-echoic pancreatic masses were shown by abdominal ultra-sound in 7 cases, and cystic-solid masses with thick wall was shown by abdominal CT scan in 4 cases, but dilatation of the pancreatic duct was found in none of the 10 cases. Hemoglobin levels lower than 12 g/L were found in 6 cases, and ESR more than 20 mm/1 h was present in 7 cases. Four cases received PPD test, but only one was positive. CA19-9 was found to be higher than normal (27 IU/ml) in 3 cases (39.2 IU/ml, 125.7 IU/ml, 88.9 IU/ml respectively). Three cases received T-spot.TB tests, and all the results were positive. Seven cases received laparotomy, and the other 3 received endoscopic ultrasound-guided biopsy. Caseous necrosis and Langerhans cells were found in all the 10 cases. Nine patients were treated by 6 to 12 months' anti-tuberculosis therapies, and at 1-5 years' follow-up, 8 were cured and 1 improved. Conclusions: The manifestations of pancreatic tuberculosis were easy to be confused with other diseases, and therefore a comprehensive understanding of history and careful examinations were important for a correct diagnosis. Once the diagnosis was made, prompt standard anti-tuberculosis therapy could lead to a favorable outcome.

Simultaneous amplification and testing method for Mycobacterium tuberculosis rRNA to differentiate sputum-negative tuberculosis from sarcoidosis.

We use the simultaneous application and testing method to detect Mycobacterium tuberculosis rRNA (SAT-TB) with the endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) biopsy specimens to differentiate sputum-negative tuberculosis from sarcoidosis. In the first part, we validated the SAT-TB on the bronchial or EBUS-TBNA biopsy specimens from sputum smear-positive pulmonary tuberculosis. In the second part, all EBUS-TBNA specimens for sputum smear-negative intrathoracic tuberculous lymphadenopathies or sarcoidosis were tested with the SAT-TB, acid-fast bacilli smear, and culture. In the 16 sputum-positive tuberculosis cases, 5 showed negative SAT (2 nontuberculous mycobacteria and 3 had anti-tuberculosis therapies previously); the remaining 11 were positive. Of the 41 sputum-negative tuberculosis cases in the second part, five other diseases were negative. In the remaining 36 cases, 27 sarcoidosis cases were negative; 7 in 9 with sputum-negative tuberculosis were positive (77.78%). In these 36 patients, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the SAT method were 77.78, 100, 100, 93.10, and 94.44%, respectively. The SAT distinguished sputum-negative tuberculosis from sarcoidosis significantly ( P < 0.0001) and identified cases with active M. tuberculosis as accurately as the conventional methods (κ = 0.912, P < 0.0001). We conclude that the SAT-TB may be an effective method for using biopsy specimens to differentiate sputum-negative tuberculosis from sarcoidosis.

Tuberculous Meningitis in Children and Adults: New Insights for an Ancient Foe.

Tuberculous meningitis is the most devastating manifestation of infection with Mycobacterium tuberculosis and represents a medical emergency. Approximately one half of tuberculous meningitis patients die or suffer severe neurologic disability. The goal of this review will be to review the pathogenic, clinical, and radiologic features of tuberculous meningitis and to highlight recent advancements in translational and clinical science. Pharmacologic therapy includes combination anti-tuberculosis drug regimens and adjunctive corticosteroids. It is becoming clear that a successful treatment outcome depends on an immune response that is neither too weak nor overly robust, and genetic determinants of this immune response may identify which patients will benefit from adjunctive corticosteroids. Recent clinical trials of intensified anti-tuberculosis treatment regimens conducted in Indonesia and Vietnam, motivated by the pharmacologic challenges of treating M. tuberculosis infections of the central nervous system, have yielded conflicting results regarding the survival benefit of intensified treatment regimens. More consistent findings have been observed regarding the relationship between initial anti-tuberculosis drug resistance and mortality among tuberculous meningitis patients. Prompt initiation of anti-tuberculosis treatment for all suspected cases remains a key aspect of management. Priorities for research include the improvement of diagnostic testing strategies and the optimization of host-directed and anti-tuberculosis therapies.

Asymmetric Structure of the Dimerization Domain of PhoR, a Sensor Kinase Important for the Virulence of Mycobacterium tuberculosis.

The PhoP–PhoR two-component system is essential for the virulence of Mycobacterium tuberculosis (Mtb) and therefore represents a potential target for developing novel antituberculosis therapies. However, little is known about the mechanism by which this two-component system regulates the virulence. In this study, we demonstrated that a phoR mutant Mtb strain has phenotypes similar to those of a phoP mutant, suggesting that PhoP and PhoR work in the same pathway to regulate Mtb virulence. We determined the structure of the dimerization and histidine phosphotransfer (DHp) domain of PhoR to a 1.9 Å resolution. The structure revealed that the DHp domain is a dimer. Each subunit consists of two antiparallel α helices connected by a loop of five residues. The two subunits of the dimer fold into a four-helical bundle with a continuous hydrophobic core. The topology of the four-helical bundle is identical to the histidine kinases that are known to have a cis-autophosphorylation mechanism, suggesting that PhoR is likely to autophosphorylate in cis. The dimer is asymmetric, with one subunit having a greater bending angle than the other at the highly conserved proline residue five-residues downstream of the phosphorylation site histidine. This structural asymmetry of the dimer suggests the flexibility of the PhoR DHp domain, which is likely to be important for the signal transduction mechanism in controlling the autophosphorylation and phosphotransfer reactions and communicating with the upstream structure.

Mechanism Investigation of Rifampicin-Induced Liver Injury Using Comparative Toxicoproteomics in Mice.

Tuberculosis is one of the top causes of death among curable infectious diseases; it is an airborne infectious disease that killed 1.1 million people worldwide in 2010. Anti-tuberculosis drug-induced liver injury is the primary cause of drug-induced liver injury (DILI). Rifampicin is one of the most common anti-tuberculosis therapies and has well-known hepatotoxicity. To understand the mechanism of rifampicin-induced liver injury, we performed a global proteomic analysis of liver proteins by LC-MS/MS in a mouse model after the oral administration of 177 and 442.5 mg/kg rifampicin (LD10 and LD25) for 14 days. Based on the biochemical parameters in the plasma after rifampicin treatment, the hepatotoxic effect of rifampicin in the mouse liver was defined as a mixed liver injury. In the present study, we identified 1101 proteins and quantified 1038 proteins. A total of 29 and 40 proteins were up-regulated and 27 and 118 proteins were down-regulated in response to 177 and 442.5 mg/kg rifampicin, respectively. Furthermore, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to characterize the mechanism of rifampicin-induced hepatotoxicity. In the molecular function category, glutathione transferase activity was up-regulated and proteins related to arachidonic acid metabolism were down-regulated. In the KEGG pathway enrichment-based clustering analysis, the peroxisome proliferator-activated receptor-γ (PPARγ) signaling pathway, cytochrome P450, glutathione metabolism, chemical carcinogenesis, and related proteins increased dose-dependently in rifampicin-treated livers. Taken together, this study showed in-depth molecular mechanism of rifampicin-induced liver injury by comparative toxicoproteomics approach.

Microbiology: Diversity breeds tolerance.

A gene has been identified that underpins the capacity of mycobacterial cells to divide to produce physiologically different daughter cells. This finding has implications for drug treatment of tuberculosis. See Letter p.153 Here the authors report the discovery of a new protein (LamA) that functions as part of the 'divisome' in mycobacteria. The authors report that LamA functions as an inhibitor of cell wall synthesis at the nascent cell pole, contributing to asymmetry in polar growth. Asymmetric growth and division increases population heterogeneity, which has been linked to antibiotic tolerance and persistent infection. Here they show that removal of LamA leads to a more uniform cell population that is more effectively killed by antibiotics. Thus, LamA represents a much-needed new target for the development of anti-tuberculosis therapies.