GPR183 Regulates Interferons, Autophagy, and Bacterial Growth During Mycobacterium tuberculosis Infection and Is Associated With TB Disease Severity

The Association between Dyslipidemia and Pulmonary Diseases

Dyslipidemia is one of the most common diseases worldwide. As a component of metabolic syndrome, the prevalence and mechanism by which dyslipidemia promotes cardiovascular diseases has been well studied, although the relationship between pulmonary diseases is not well understood. Because the lung is a respiratory organ with a large surface area and is exposed to the environment outside the body, it continuously inhales various substances. As a result, pulmonary diseases have a vast diversity, including chronic inflammatory diseases, allergic diseases, cancers, and infectious diseases. Recently, growing evidence has suggested that dyslipidemia plays a role in the pathogenesis and prognosis of various pulmonary diseases. We herein review the current understanding of the relationship between dyslipidemia and pulmonary diseases, including chronic obstructive pulmonary diseases, asthma, and lung cancer, and infectious pulmonary diseases, including community-acquired pneumonia, tuberculosis, nontuberculous mycobacterial pulmonary disease, and COVID-19. In addition, we focus on recent evidence of the utility of statins, specifically 3-hydroxy-3-methylglutaryl-coA reductase inhibitors, in the prevention and treatment of the various pulmonary diseases described above.

Functional Analysis of Genes in Mycobacterium tuberculosis Action Against Autophagosome-Lysosome Fusion

Tuberculosis is a lethal disease that is one of the world's top ten death-associated infections in humans; Mycobacterium tuberculosis causes tuberculosis, and this bacterium is linked to the lysis of autophagolysosomal fusion action, a self-defense mechanism of its own. Thus, Cytoplasmic bacilli are sequestered by autophagy and transported to lysosomes to be inactivated to destroy intracellular bacteria. Besides this, a macrophage can limit intracellular Mycobacterium by using a type of autophagy, selective autophagy, a cell that marks undesirable ubiquitin existence in cytosolic cargo, acting as a "eat me" sensor in conjunction with cellular homeostasis. Mycobacterium tuberculosis genes of the PE_PGRS protein family inhibit autophagy, increase mycobacterial survival, and lead to latent tuberculosis infection associated with miRNAs. In addition, the family of autophagy-regulated (ATG) gene members are involved in autophagy and controls the initiation, expansion, maturation, and fusion of autophagosomes with lysosomes, among other signaling events that control autophagy flux and reduce inflammatory responses and forward to promote cellular proliferation. In line with the formation of caseous necrosis in macrophages by Mycobacterium tuberculosis and their action on the lysis of autophagosome fusion, it leads to latent tuberculosis infection. Therefore, we aimed to comprehensively analyses the autophagy and self-defense mechanism of Mycobacterium tuberculosis, which is to be gratified future research on novel therapeutic tools and diagnostic markers against tuberculosis.

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.

The role of cholesterol and its oxidation products in tuberculosis pathogenesis

Mycobacterium tuberculosis causes tuberculosis (TB), one of the world's most deadly infections. Lipids play an important role in M. tuberculosis pathogenesis. M. tuberculosis grows intracellularly within lipid-laden macrophages and extracellularly within the cholesterol-rich caseum of necrotic granulomas and pulmonary cavities. Evolved from soil saprophytes that are able to metabolize cholesterol from organic matter in the environment, M. tuberculosis inherited an extensive and highly conserved machinery to metabolize cholesterol. M. tuberculosis uses this machinery to degrade host cholesterol; the products of cholesterol degradation are incorporated into central carbon metabolism and used to generate cell envelope lipids, which play important roles in virulence. The host also modifies cholesterol by enzymatically oxidizing it to a variety of derivatives, collectively called oxysterols, which modulate cholesterol homeostasis and the immune response. Recently, we found that M. tuberculosis converts host cholesterol to an oxidized metabolite, cholestenone, that accumulates in the lungs of individuals with TB. M. tuberculosis encodes cholesterol-modifying enzymes, including a hydroxysteroid dehydrogenase, a putative cholesterol oxidase, and numerous cytochrome P450 monooxygenases. Here, we review what is known about cholesterol and its oxidation products in the pathogenesis of TB. We consider the possibility that the biological function of cholesterol metabolism by M. tuberculosis extends beyond a nutritional role.

First report on chemometrics-driven multilayered lead prioritization in addressing oxysterol-mediated overexpression of G protein-coupled receptor 183

Contemporary research has convincingly demonstrated that upregulation of G protein-coupled receptor 183 (GPR183), orchestrated by its endogenous agonist, 7α,25-dihydroxyxcholesterol (7α,25-OHC), leads to the development of cancer, diabetes, multiple sclerosis, infectious, and inflammatory diseases. A recent study unveiled the cryo-EM structure of 7α,25-OHC bound GPR183 complex, presenting an untapped opportunity for computational exploration of potential GPR183 inhibitors, which served as our inspiration for the current work. A predictive and validated two-dimensional QSAR model using genetic algorithm (GA) and multiple linear regression (MLR) on experimental GPR183 inhibition data was developed. QSAR study highlighted that structural features like dissimilar electronegative atoms, quaternary carbon atoms, and CH2RX fragment (X: heteroatoms) influence positively, while the existence of oxygen atoms with a topological separation of 3, negatively affects GPR183 inhibitory activity. Post assessment of true external set prediction capability, the MLR model was deployed to screen 12,449 DrugBank compounds, followed by a screening pipeline involving molecular docking, druglikeness, ADMET, protein-ligand stability assessment using deep learning algorithm, molecular dynamics, and molecular mechanics. The current findings strongly evidenced DB05790 as a potential lead for prospective interference of oxysterol-mediated GPR183 overexpression, warranting further in vitro and in vivo validation.

Host-directed therapy against mycobacterium tuberculosis infections with diabetes mellitus

Tuberculosis (TB) is caused by the bacterial pathogen Mycobacterium tuberculosis (MTB) and is one of the principal reasons for mortality and morbidity worldwide. Currently, recommended anti-tuberculosis drugs include isoniazid, rifampicin, ethambutol, and pyrazinamide. TB treatment is lengthy and inflicted with severe side-effects, including reduced patient compliance with treatment and promotion of drug-resistant strains. TB is also prone to other concomitant diseases such as diabetes and HIV. These drug-resistant and complex co-morbid characteristics increase the complexity of treating MTB. Host-directed therapy (HDT), which effectively eliminates MTB and minimizes inflammatory tissue damage, primarily by targeting the immune system, is currently an attractive complementary approach. The drugs used for HDT are repositioned drugs in actual clinical practice with relative safety and efficacy assurance. HDT is a potentially effective therapeutic intervention for the treatment of MTB and diabetic MTB, and can compensate for the shortcomings of current TB therapies, including the reduction of drug resistance and modulation of immune response. Here, we summarize the state-of-the-art roles and mechanisms of HDT in immune modulation and treatment of MTB, with a special focus on the role of HDT in diabetic MTB, to emphasize the potential of HDT in controlling MTB infection.

Oxysterols in Infectious Diseases

Oxysterols have emerged as important bioactive lipids in the immune response to infectious diseases. This chapter discusses our current knowledge of oxysterols and their receptors in bacterial and viral infections of the respiratory and gastrointestinal tracts. Oxysterols are produced in response to infections and have multiple roles including chemotaxis of immune cells to the site of infection and regulation of inflammation. Some oxysterols have been shown to possess antiviral or antibacterial activity.Lastly, we delve into the emerging mechanisms of action of oxysterols. Oxysterols can enhance host cell resistance via reduction of membrane accessible cholesterol, modulate membrane immune signalling, and impact inflammasome activation and efferocytosis.

Cholesterol-autoxidation metabolites in host defense against infectious diseases

Cholesterol plays essential roles in biological processes, including cell membrane stability and myelin formation. Cholesterol can be metabolized to oxysterols by enzymatic or nonenzymatic ways. Nonenzymatic cholesterol metabolites, also called cholesterol-autoxidation metabolites, are formed dependent on the oxidation of reactive oxygen species (ROS) such as OH• or reactive nitrogen species, such as ONOO- . Cholesterol-autoxidation metabolites are abundantly produced in diseases such as inflammatory bowel disease and atherosclerosis, which are associated with oxidative stress. Recent studies have shown that cholesterol-autoxidation metabolites can further regulate the immune system. Here, we review the literature and summarize how cholesterol-autoxidation metabolites, such as 25-hydroxycholesterol (25-OHC), 7α/β-OHC, and 7-ketocholesterol, deal with the occurrence and development of infectious diseases through pattern recognition receptors, inflammasomes, ROS production, nuclear receptors, G-protein-coupled receptor 183, and lipid availability. In addition, we include the research regarding the roles of these metabolites in COVID-19 infection and discuss our viewpoints on the future research directions.

Phage display sequencing reveals that genetic, environmental, and intrinsic factors influence variation of human antibody epitope repertoire

Phage-displayed immunoprecipitation sequencing (PhIP-seq) has enabled high-throughput profiling of human antibody repertoires. However, a comprehensive overview of environmental and genetic determinants shaping human adaptive immunity is lacking. In this study, we investigated the effects of genetic, environmental, and intrinsic factors on the variation in human antibody repertoires. We characterized serological antibody repertoires against 344,000 peptides using PhIP-seq libraries from a wide range of microbial and environmental antigens in 1,443 participants from a population cohort. We detected individual-specificity, temporal consistency, and co-housing similarities in antibody repertoires. Genetic analyses showed the involvement of the HLA, IGHV, and FUT2 gene regions in antibody-bound peptide reactivity. Furthermore, we uncovered associations between phenotypic factors (including age, cell counts, sex, smoking behavior, and allergies, among others) and particular antibody-bound peptides. Our results indicate that human antibody epitope repertoires are shaped by both genetics and environmental exposures and highlight specific signatures of distinct phenotypes and genotypes.

Migration mediated by the oxysterol receptor GPR183 depends on arrestin coupling but not receptor internalization

The chemotactic G protein-coupled receptor GPR183 and its most potent endogenous oxysterol ligand 7α,25-dihydroxycholesterol (7α,25-OHC) are important for immune cell positioning in secondary lymphoid tissues. This receptor-ligand pair is associated with various diseases, in some cases contributing favorably and in other cases adversely, making GPR183 an attractive target for therapeutic intervention. We investigated the mechanisms underlying GPR183 internalization and the role of internalization in the main biological function of the receptor, chemotaxis. We found that the C terminus of the receptor was important for ligand-induced internalization but less so for constitutive (ligand-independent) internalization. β-arrestin potentiated ligand-induced internalization but was not required for ligand-induced or constitutive internalization. Caveolin and dynamin were the main mediators of both constitutive and ligand-induced receptor internalization in a mechanism independent of G protein activation. Clathrin-mediated endocytosis also contributed to constitutive GPR183 internalization in a β-arrestin-independent manner, suggesting the existence of different pools of surface-localized GPR183. Chemotaxis mediated by GPR183 depended on receptor desensitization by β-arrestins but could be uncoupled from internalization, highlighting an important biological role for the recruitment of β-arrestin to GPR183. The role of distinct pathways in internalization and chemotaxis may aid in the development of GPR183-targeting drugs for specific disease contexts.

GPR183 antagonism reduces macrophage infiltration in influenza and SARS-CoV-2 infection

RATIONALE

Severe viral respiratory infections are often characterised by extensive myeloid cell infiltration and activation and persistent lung tissue injury. However, the immunological mechanisms driving excessive inflammation in the lung remain poorly understood.

OBJECTIVES

To identify the mechanisms that drive immune cell recruitment in the lung during viral respiratory infections and identify novel drug targets to reduce inflammation and disease severity.

METHODS

Preclinical murine models of influenza A virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

RESULTS

Oxidised cholesterols and the oxysterol-sensing receptor GPR183 were identified as drivers of monocyte/macrophage infiltration to the lung during influenza A virus (IAV) and SARS-CoV-2 infection. Both IAV and SARS-CoV-2 infection upregulated the enzymes cholesterol 25-hydroxylase (CH25H) and cytochrome P450 family 7 subfamily member B1 (CYP7B1) in the lung, resulting in local production of the oxidised cholesterols 25-hydroxycholesterol (25-OHC) and 7α,25-dihydroxycholesterol (7α,25-OHC). Loss-of-function mutation of Gpr183 or treatment with a GPR183 antagonist reduced macrophage infiltration and inflammatory cytokine production in the lungs of IAV- or SARS-CoV-2-infected mice. The GPR183 antagonist significantly attenuated the severity of SARS-CoV-2 infection and viral loads. Analysis of single-cell RNA-sequencing data on bronchoalveolar lavage samples from healthy controls and COVID-19 patients with moderate and severe disease revealed that CH25H, CYP7B1 and GPR183 are significantly upregulated in macrophages during COVID-19.

CONCLUSION

This study demonstrates that oxysterols drive inflammation in the lung via GPR183 and provides the first preclinical evidence for the therapeutic benefit of targeting GPR183 during severe viral respiratory infections.

Distinct transcriptional signatures in purified circulating immune cells drive heterogeneity in disease location in IBD

OBJECTIVE

To infer potential mechanisms driving disease subtypes among patients with inflammatory bowel disease (IBD), we profiled the transcriptome of purified circulating monocytes and CD4 T-cells.

DESIGN

RNA extracted from purified monocytes and CD4 T-cells derived from the peripheral blood of 125 endoscopically active patients with IBD was sequenced using Illumina HiSeq 4000NGS. We used complementary supervised and unsupervised analytical methods to infer gene expression signatures associated with demographic/clinical features. Expression differences and specificity were validated by comparison with publicly available single cell datasets, tissue-specific expression and meta-analyses. Drug target information, druggability and adverse reaction records were used to prioritise disease subtype-specific therapeutic targets.

RESULTS

Unsupervised/supervised methods identified significant differences in the expression profiles of CD4 T-cells between patients with ileal Crohn's disease (CD) and ulcerative colitis (UC). Following a pathway-based classification (Area Under Receiver Operating Characteristic - AUROC=86%) between ileal-CD and UC patients, we identified MAPK and FOXO pathways to be downregulated in UC. Coexpression module/regulatory network analysis using systems-biology approaches revealed mediatory core transcription factors. We independently confirmed that a subset of the disease location-associated signature is characterised by T-cell-specific and location-specific expression. Integration of drug-target information resulted in the discovery of several new (BCL6, GPR183, TNFAIP3) and repurposable drug targets (TUBB2A, PRKCQ) for ileal CD as well as novel targets (NAPEPLD, SLC35A1) for UC.

CONCLUSIONS

Transcriptomic profiling of circulating CD4 T-cells in patients with IBD demonstrated marked molecular differences between the IBD-spectrum extremities (UC and predominantly ileal CD, sandwiching colonic CD), which could help in prioritising particular drug targets for IBD subtypes.

Role of Interferons in Mycobacterium tuberculosis Infection

Considerable measures have been implemented in healthcare institutions to screen for and treat tuberculosis (TB) in developed countries; however, in low- and middle-income countries, many individuals still suffer from TB’s deleterious effects. TB is caused by an infection from the Mycobacterium tuberculosis (M. tb) bacteria. Symptoms of TB may range from an asymptomatic latent-phase affecting the pulmonary tract to a devastating active and disseminated stage that can cause central nervous system demise, musculoskeletal impairments, and genitourinary compromise. Following M. tb infection, cytokines such as interferons (IFNs) are released as part of the host immune response. Three main classes of IFNs prevalent during the immune defense include: type I IFN (α and β), type II IFN (IFN-γ), and type III IFN (IFN-λ). The current literature reports that type I IFN plays a role in diminishing the host defense against M. tb by attenuating T-cell activation. In opposition, T-cell activation drives type II IFN release, which is the primary cytokine mediating protection from M. tb by stimulating macrophages and their oxidative defense mechanisms. Type III IFN has a subsidiary part in improving the Th1 response for host cell protection against M. tb. Based on the current evidence available, our group aims to summarize the role that each IFN serves in TB within this literature review.

GPR183 Regulates 7α,25-Dihydroxycholesterol-Induced Oxiapoptophagy in L929 Mouse Fibroblast Cell

7α,25-dihydroxycholesterol (7α,25-DHC) is an oxysterol synthesized from 25-hydroxycholesterol by cytochrome P450 family 7 subfamily B member 1 (CYP7B1) and is a monooxygenase (oxysterol-7α-hydroxylase) expressed under inflammatory conditions in various cell types. In this study, we verified that 7α,25-DHC-induced oxiapoptophagy is mediated by apoptosis, oxidative stress, and autophagy in L929 mouse fibroblasts. MTT assays and live/dead cell staining revealed that cytotoxicity was increased by 7α,25-DHC in L929 cells. Consequentially, cells with condensed chromatin and altered morphology were enhanced in L929 cells incubated with 7α,25-DHC for 48 h. Furthermore, apoptotic population was increased by 7α,25-DHC exposure through the cascade activation of caspase-9, caspase-3, and poly (ADP-ribose) polymerase in the intrinsic pathway of apoptosis in these cells. 7α,25-DHC upregulated reactive oxygen species (ROS) in L929 cells. Expression of autophagy biomarkers, including beclin-1 and LC3, was significantly increased by 7α,25-DHC treatment in L929 cells. 7α,25-DHC inhibits the phosphorylation of Akt associated with autophagy and increases p53 expression in L929 cells. In addition, inhibition of G-protein-coupled receptor 183 (GPR183), a receptor of 7α,25-DHC, using GPR183 specific antagonist NIBR189 suppressed 7α,25-DHC-induced apoptosis, ROS production, and autophagy in L929 cells. Collectively, GPR183 regulates 7α,25-DHC-induced oxiapoptophagy in L929 cells.

Rapid GPR183-mediated recruitment of eosinophils to the lung after Mycobacterium tuberculosis infection

Influx of eosinophils into the lungs is typically associated with type II responses during allergy and fungal and parasitic infections. However, we previously reported that eosinophils accumulate in lung lesions during type I inflammatory responses to Mycobacterium tuberculosis (Mtb) in humans, macaques, and mice, in which they support host resistance. Here we show eosinophils migrate into the lungs of macaques and mice as early as one week after Mtb exposure. In mice this influx is CCR3 independent and instead requires cell-intrinsic expression of the oxysterol receptor GPR183, which is highly expressed on human and macaque eosinophils. Murine eosinophils interact directly with bacilli-laden alveolar macrophages, which upregulate the oxysterol-synthesizing enzyme Ch25h, and eosinophil recruitment is impaired in Ch25h-deficient mice. Our findings show that eosinophils are among the earliest cells from circulation to sense and respond to Mtb infection of alveolar macrophages and reveal a role for GPR183 in the migration of eosinophils into lung tissue.

Eosinophils are usually associated with allergy or type II responses. Here, Bohrer et al. show that eosinophils are rapidly recruited to the lungs after respiratory infection with the intracellular pathogen Mycobacterium tuberculosis through the oxysterol sensor GPR183.

Characterization of lncRNA-Based ceRNA Network and Potential Prognostic Hub Genes for Sepsis

Objective

Sepsis is one of the most common reasons for hospitalization and in-hospital mortality each year. Noncoding RNAs have been reported not only as diagnostic and prognostic indicators but also as therapeutic targets of sepsis. Herein, we used an integrative computational approach to identify miRNA-mediated ceRNA crosstalk between lncRNAs and genes in sepsis based on the “ceRNA hypothesis” and investigated prognostic roles of hub genes in sepsis.

Methods

Two good-quality gene expression datasets with more than 10 patient samples, GSE89376 and GSE95233, were employed to obtain differentially expressed lncRNAs (DElncRNAs) and genes (DEGs) in sepsis. The DElncRNA-miRNA-DEG regulatory network was constructed using a combination of DElncRNA-miRNA pairs and miRNA-DEmRNA pairs. The protein-protein interaction (PPI) network was constructed by mapping DEGs into the STRING database to identify hub genes in sepsis. The clinical and prognostic significance of hub genes was validated in 89 patients with post-traumatic sepsis.

Results

The integrative computational approach identified 311 DEGs and 19 DElncRNAs between septic patients and healthy volunteers. Results yielded 122 downDElncRNA-miRNA-downDEG networks based on two lncRNAs, HCP5, and HOTAIRM1, and 36 upDElncRNA-miRNA-upDEG network based on BASP1-AS1. The PPI network identified serum/glucocorticoid regulated kinase 1 (SGK1), arrestin beta 1 (ARRB1), and G protein-coupled receptor 183 (GPR183) as located at the core of the network, and three of them were downregulated in sepsis. SGK1, ARRB1, and GPR183 were all involved in lncRNA HCP5-based ceRNA network. The quantitative real-time PCR revealed that the patients with post-traumatic sepsis exhibited reduced relative mRNA levels of SGK1, ARRB1, and GPR183 compared to the patients without sepsis. The nonsurvivor group, according to the 28-day mortality, showed lower relative mRNA levels of SGK1, ARRB1, and GPR183 than the survivor group. We also demonstrated reduced mRNA levels of SGK1, ARRB1, and GPR183 were associated with sepsis-related death after trauma.

Conclusion

Our integrative analysis and clinical validation suggest lncRNA HCP5-based ceRNA networks with SGK1, ARRB1, and GPR183 involved were associated with the occurrence and progression of sepsis.

Effects of Oxysterols on Immune Cells and Related Diseases

Oxysterols are the products of cholesterol oxidation. They have a wide range of effects on several cells, organs, and systems in the body. Oxysterols also have an influence on the physiology of the immune system, from immune cell maturation and migration to innate and humoral immune responses. In this regard, oxysterols have been involved in several diseases that have an immune component, from autoimmune and neurodegenerative diseases to inflammatory diseases, atherosclerosis, and cancer. Here, we review data on the participation of oxysterols, mainly 25-hydroxycholesterol and 7α,25-dihydroxycholesterol, in the immune system and related diseases. The effects of these oxysterols and main oxysterol receptors, LXR and EBI2, in cells of the immune system (B cells, T cells, macrophages, dendritic cells, oligodendrocytes, and astrocytes), and in immune-related diseases, such as neurodegenerative diseases, intestinal diseases, cancer, respiratory diseases, and atherosclerosis, are discussed.

A blunted GPR183/oxysterol axis during dysglycemia results in delayed recruitment of macrophages to the lung during M. tuberculosis infection

Background

We previously reported that reduced GPR183 expression in blood from tuberculosis (TB) patients with diabetes is associated with more severe TB.

Methods

To further elucidate the role of GPR183 and its oxysterol ligands in the lung, we studied dysglycemic mice infected with Mycobacterium tuberculosis (Mtb).

Results

We found upregulation of the oxysterol-producing enzymes CH25H and CYP7B1 and increased concentrations of 25-hydroxycholesterol upon Mtb infection in the lungs of mice. This was associated with increased expression of GPR183 indicative of oxysterol-mediated recruitment of GPR183-expressing immune cells to the lung. CYP7B1 was predominantly expressed by macrophages in TB granulomas. CYP7B1 expression was significantly blunted in lungs from dysglycemic animals, which coincided with delayed macrophage infiltration. GPR183-deficient mice similarly had reduced macrophage recruitment during early infection.

Conclusions

Taken together, we demonstrate a requirement of the GPR183/oxysterol axis for positioning of macrophages to the site of infection and add an explanation to more severe TB in diabetes patients.

Oxysterols in the Immune Response to Bacterial and Viral Infections

Oxidized cholesterols, the so-called oxysterols, are widely known to regulate cholesterol homeostasis. However, more recently oxysterols have emerged as important lipid mediators in the response to both bacterial and viral infections. This review summarizes our current knowledge of selected oxysterols and their receptors in the control of intracellular bacterial growth as well as viral entry into the host cell and viral replication. Lastly, we briefly discuss the potential of oxysterols and their receptors as drug targets for infectious and inflammatory diseases.

Diabetes-Associated Susceptibility to Tuberculosis: Contribution of Hyperglycemia vs. Dyslipidemia

Diabetes is a major risk factor for tuberculosis (TB). Diabetes increases the risk of the progression from latent tuberculosis infection (LTBI) to active pulmonary TB and TB patients with diabetes are at greater risk of more severe disease and adverse TB treatment outcomes compared to TB patients without co-morbidities. Diabetes is a complex disease, characterised not only by hyperglycemia but also by various forms of dyslipidemia. However, the relative contribution of these underlying metabolic factors to increased susceptibility to TB are poorly understood. This review summarises our current knowledge on the epidemiology and clinical manifestation of TB and diabetes comorbidity. We subsequently dissect the relative contributions of body mass index, hyperglycemia, elevated cholesterol and triglycerides on TB disease severity and treatment outcomes. Lastly, we discuss the impact of selected glucose and cholesterol-lowering treatments frequently used in the management of diabetes on TB treatment outcomes.

Discovery of GPR183 Agonists Based on an Antagonist Scaffold

The G protein-coupled receptor GPR183/EBI2, which is activated by oxysterols, is a therapeutic target for inflammatory and metabolic diseases where both antagonists and agonists are of potential interest. Using the piperazine diamide core of the known GPR183 antagonist (E)-3-(4-bromophenyl)-1-(4-(4-methoxybenzoyl)piperazin-1-yl)prop-2-en-1-one (NIBR189) as starting point, we identified and sourced 79 structurally related compounds that were commercially available. In vitro screening of this compound collection using a Ca2+ mobilization assay resulted in the identification of 10 compounds with agonist properties. To enable establishment of initial structure-activity relationship trends, these were supplemented with five in-house compounds, two of which were also shown to be GPR183 agonists. Taken together, our findings suggest that the agonist activity of this compound series is dictated by the substitution pattern of one of the two distal phenyl rings, which functions as a molecular efficacy-switch.