Mycobacterial antigens accumulation in foamy macrophages in murine pulmonary tuberculosis lesions: Association with necrosis and making of cavities

The impact of Mycobacterium tuberculosis on the macrophage cholesterol metabolism pathway

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen capable of adapting and surviving within macrophages, utilizing host nutrients for its growth and replication. Cholesterol is the main carbon source during the infection process of Mtb. Cholesterol metabolism in macrophages is tightly associated with cell functions such as phagocytosis of pathogens, antigen presentation, inflammatory responses, and tissue repair. Research has shown that Mtb infection increases the uptake of low-density lipoprotein (LDL) and cholesterol by macrophages, and enhances de novo cholesterol synthesis in macrophages. Excessive cholesterol is converted into cholesterol esters, while the degradation of cholesterol esters in macrophages is inhibited by Mtb. Furthermore, Mtb infection suppresses the expression of ATP-binding cassette (ABC) transporters in macrophages, impeding cholesterol efflux. These alterations result in the massive accumulation of cholesterol in macrophages, promoting the formation of lipid droplets and foam cells, which ultimately facilitates the persistent survival of Mtb and the progression of tuberculosis (TB), including granuloma formation, tissue cavitation, and systemic dissemination. Mtb infection may also promote the conversion of cholesterol into oxidized cholesterol within macrophages, with the oxidized cholesterol exhibiting anti-Mtb activity. Recent drug development has discovered that reducing cholesterol levels in macrophages can inhibit the invasion of Mtb into macrophages and increase the permeability of anti-tuberculosis drugs. The development of drugs targeting cholesterol metabolic pathways in macrophages, as well as the modification of existing drugs, holds promise for the development of more efficient anti-tuberculosis medications.

Novel Insights into the Pathogenesis of Human Post-Primary Tuberculosis from Archival Material of the Pre-Antibiotic Era, 1931-1947

OBJECTIVES

Primary and post-primary tuberculosis (TB) are distinct entities. The aim of this study was to study the histopathology of primary and post-primary TB by using the unique human autopsy material from the pre-antibiotic era, 1931-1947.

MATERIAL AND METHODS

Autopsy data were collected from the autopsy journals, and the human tissue was collected from the pathology archives at the Department of Pathology, the Gades Institute.

RESULTS

Histological presentations of TB lesions showed great diversity within a single lung. Post-primary TB starts as a pneumonia forming early lesions, characterized by the infiltration of foamy macrophages containing mycobacterial antigens within alveoli, and progressing to necrotic pneumonias with an increasing density of mycobacterial antigens in the lesions. These necrotic pneumonic lesions appeared to either resolve as fibrocaseous lesions or lead to cavitation. The typical granulomatous inflammation, the hallmark of TB lesions, appeared later in the post-primary TB and surrounded the pneumonic lesions. These post-primary granulomas contained lesser mycobacterial antigens as compared to necrotic pneumonia.

CONCLUSIONS

Immunopathogenesis of post-primary TB is different from primary TB and starts as pneumonia. The early lesions of post-primary TB may progress or regress, holding the key to understanding how a host can develop the disease despite an effective TB immunity.

Virulence Factors of Mycobacterium tuberculosis as Modulators of Cell Death Mechanisms

Mycobacterium tuberculosis (Mtb) modulates diverse cell death pathways to escape the host immune responses and favor its dissemination, a complex process of interest in pathogenesis-related studies. The main virulence factors of Mtb that alter cell death pathways are classified according to their origin as either non-protein (for instance, lipomannan) or protein (such as the PE family and ESX secretion system). The 38 kDa lipoprotein, ESAT-6 (early antigen-secreted protein 6 kDa), and another secreted protein, tuberculosis necrotizing toxin (TNT), induces necroptosis, thereby allowing mycobacteria to survive inside the cell. The inhibition of pyroptosis by blocking inflammasome activation by Zmp1 and PknF is another pathway that aids the intracellular replication of Mtb. Autophagy inhibition is another mechanism that allows Mtb to escape the immune response. The enhanced intracellular survival (Eis) protein, other proteins, such as ESX-1, SecA2, SapM, PE6, and certain microRNAs, also facilitate Mtb host immune escape process. In summary, Mtb affects the microenvironment of cell death to avoid an effective immune response and facilitate its spread. A thorough study of these pathways would help identify therapeutic targets to prevent the survival of mycobacteria in the host.

ALB, HP, OAF and RBP4 as novel protein biomarkers for identifying cured patients with pulmonary tuberculosis by DIA

BACKGROUND

Pulmonary tuberculosis (TB) is a serious infectious disease that lacks robust blood-based biomarkers to identify cured TB. Some discharged patients are not fully cured and may relapse or even develop multidrug-resistant TB. This study is committed to finding proteomic-based plasma biomarkers to support establishing laboratory standards for clinical TB cure.

METHODS

Data-independent acquisition (DIA) was used to obtain the plasma protein expression profiles of TB patients at different treatment stages compared with healthy controls. Multivariate statistical methods and bioinformatics were used to analyze the data.

RESULTS

Bioinformatic analysis suggests coagulation dysfunction and vitamin and lipid metabolism disturbances in TB. Albumin (ALB), haptoglobin (HP), out at first protein homolog (OAF), and retinol-binding protein 4 (RBP4) can be used to establish a diagnostic model for the efficacy evaluation of TB with an area under the curve of 0.963, which could effectively distinguish untreated TB patients from cured patients.

CONCLUSIONS

Our research demonstrated that ALB, HP, OAF and RBP4 can be potential biomarkers for evaluating the efficacy of TB. These findings may provide experimental data for establishing the laboratory indicators of clinical TB cure and providing clinicians with new targets for exploring the underlying mechanisms of TB pathogenesis.

High levels of plasma S100A9 at admission indicate an increased risk of death in severe tuberculosis patients

Objective

This study aims to evaluate plasma S100A9 levels in tuberculosis (TB) patients with admission to the ICU as a marker to predict the risk of death for pulmonary severe TB.

Methods

This study enrolled 256 severe TB patients admitted to Beijing Chest Hospital from Jan to Dec 2019. The S100A9 levels were measured by ELISA. Standard clinical parameters were collected. The non-parametric Mann-Whitney test, t-test, and chi-square test were applied to statistical comparison. A multivariable analysis was performed to identify risk factors for death.

Results

The plasma S100A9 levels were higher in non-survivors (25.88, 16.77-44.64) compared to survivors (15.51, 13.67-19.94). S100A9 performed better than Acute Physiology and Chronic Health Evaluation (APACHE II) score in predicting death, with AUC of 0.725, sensitivity of 65.5%, and specificity of 80.3%. By combining APACHE II score together with the S100A9 levels we got an AUC of 0.754 (95% CI 0.68 to 0.82) in predicting death. Lastly, S100A9 levels were significantly higher in patients with APACHE II score >17.5, sputum smear-positive, early death, and high cavitary lesions numbers, all of which were related to TB progression.

Conclusion

Measurement and monitoring levels of plasma S100A9 in severe TB patients could facilitate the evaluation of patients with high risk at the early stage, which may help to improve the treatment outcome for TB patients.

LncRNA FENDRR in Carcinoma-Associated Fibroblasts Regulates the Angiogenesis of Oral Squamous Cell Carcinoma Through the PI3K/AKT Pathway

Angiogenesis is essential for the development of tumors. Studies have shown that carcinoma-associated fibroblasts (CAFs) are involved in regulating tumor angiogenesis, but the mechanism remains unclear. Recently, long noncoding RNAs (lncRNAs) have been proved to play an important role in the angiogenesis of various tumors. However, there is currently no research involving the regulation of CAFs on the angiogenesis of oral squamous cell carcinoma (OSCC) mediated by lncRNAs. By analyzing microarray data, we identified that the expression of lncRNA FOXF1 adjacent noncoding developmental regulatory RNA (FENDRR) in OSCC patients is downregulated, compared to that in normal tissues. Quantitative polymerase chain reaction (qPCR) results demonstrated that FENDRR expression is lower in CAFs compared to normal fibroblasts (NFs) of OSCC patients. KEGG pathway analysis revealed that some genes differentially expressed between CAFs and NFs of HNSCC patients are enriched to the PI3K/AKT pathway. Further experiments confirmed that the downregulation of FENDRR can activate the PI3K/AKT pathway in NFs and enhances the expression of matrix metalloproteinase 9 (MMP9). The overexpression of FENDRR had the opposite effect. Besides, we co-cultured human umbilical vein endothelial cells (HUVECs) with CAFs, and the tube-forming ability of HUVECs co-cultured with CAFs overexpressing FENDRR decreased significantly. However, activation of the AKT pathway of CAFs overexpressing FENDRR can weaken the inhibitory effect of FENDRR on angiogenesis. In summary, our experiments are focused on the influence of lncRNAs in CAFs on OSCC angiogenesis for the first time and prove that FENDRR mediates CAFs’ regulation of OSCC angiogenesis through the PI3K/AKT pathway.

Novel therapeutic evaluation biomarkers of lipid metabolism targets in uncomplicated pulmonary tuberculosis patients

Currently, the management of pulmonary tuberculosis (TB) lacks potent medications and accurate efficacy evaluation biomarkers. In view of the fact that the host lipids are the important energy source of Mycobacterium tuberculosis (Mtb), UPLC-MS/MS based on lipid metabolism was used to monitor the plasma lipid spectrum of TB patients from the initial diagnosis to cured. The analysis showed that TB patients presented aberrant metabolism of phospholipids, glycerides, and sphingolipids. Upon the treatment, the abnormal expression of Cer (d18:1/24:0), CerP (d18:1/20:3), LPE (0:0/22:0), LPA (0:0/16:0), and LPA (0:0/18:0) in TB patients were gradually normalized, indicating that the intervention of lipid metabolism could block energy metabolism and inhibit the cell wall synthesis of Mtb. Furthermore, the increase in ceramide (Cer) levels could promote autophagosome-lysosome fusion. LPA (0:0/16:0) and LPA (0:0/18:0) had a great potential in the early diagnosis (both sensitivity and specificity were 100%) and efficacy evaluation (both sensitivity and specificity were 100%) of TB, indicating that the above lipid metabolites could be used as potential biomarkers for TB.

Identification of potential lipid biomarkers for active pulmonary tuberculosis using ultra-high-performance liquid chromatography-tandem mass spectrometry

Early diagnosis of active pulmonary tuberculosis (TB) is the key to controlling the disease. Host lipids are nutrient sources for the metabolism of Mycobacterium tuberculosis. In this research work, we used ultra-high-performance liquid chromatography-tandem mass spectrometry to screen plasma lipids in TB patients, lung cancer patients, community-acquired pneumonia patients, and normal healthy controls. Principal component analysis, orthogonal partial least squares discriminant analysis, and K-means clustering algorithm analysis were used to identify lipids with differential abundance. A total of 22 differential lipids were filtered out among all subjects. The plasma phospholipid levels were decreased, while the cholesterol ester levels were increased in patients with TB. We speculate that the infection of M. tuberculosis may regulate the lipid metabolism of TB patients and may promote host-assisted bacterial degradation of phospholipids and accumulation of cholesterol esters. This may be related to the formation of lung cavities with caseous necrosis. The results of receiver operating characteristic curve analysis revealed four lipids such as phosphatidylcholine (PC, 12:0/22:2), PC (16:0/18:2), cholesteryl ester (20:3), and sphingomyelin (d18:0/18:1) as potential biomarkers for early diagnosis of TB. The diagnostic model was fitted by using logistic regression analysis and combining the above four lipids with a sensitivity of 92.9%, a specificity of 82.4%, and the area under the curve (AUC) value of 0.934 (95% CI 0.873 - 0.971). The machine learning method (10-fold cross-validation) demonstrated that the model had good accuracy (0.908 AUC, 85.3% sensitivity, and 85.9% specificity). The lipids identified in this study may serve as novel biomarkers in TB diagnosis. Our research may pave the foundation for understanding the pathogenesis of TB.

The Pathogenesis of Tuberculosis-The Koch Phenomenon Reinstated

Research on the pathogenesis of tuberculosis (TB) has been hamstrung for half a century by the paradigm that granulomas are the hallmark of active disease. Human TB, in fact, produces two types of granulomas, neither of which is involved in the development of adult type or post-primary TB. This disease begins as the early lesion; a prolonged subclinical stockpiling of secreted mycobacterial antigens in foamy alveolar macrophages and nearby highly sensitized T cells in preparation for a massive necrotizing hypersensitivity reaction, the Koch Phenomenon, that produces caseous pneumonia that is either coughed out to form cavities or retained to become the focus of post-primary granulomas and fibrocaseous disease. Post-primary TB progresses if the antigens are continuously released and regresses when they are depleted. This revised paradigm is supported by nearly 200 years of research and suggests new approaches and animal models to investigate long standing mysteries of human TB and vaccines that inhibit the early lesion to finally end its transmission.