Pyruvate Dehydrogenase Kinase Inhibitor Dichloroacetate Improves Host Control of Salmonella enterica Serovar Typhimurium Infection in Human Macrophages

Phenothiazines boost host control of Mycobacterium avium infection in primary human macrophages

Mycobacterium avium (Mav) complex is the leading cause of pulmonary diseases associated with non-tuberculous mycobacterial (NTM) infections worldwide. The inherent and increasing acquired antibiotic resistance of Mav hampers the treatment of Mav infections and emphasizes the urgent need for alternative treatment strategies. A promising approach is host-directed therapy (HDT), which aims to boost the host's immune defenses to combat infections. In this study, we show that phenothiazines, particularly trifluoperazine (TFP) and chlorproethazine (CPE), restricted Mav survival in primary human macrophages. Notably, TFP and CPE did not directly inhibit mycobacterial growth at used concentrations, confirming these drugs function through host-dependent mechanisms. TFP and CPE induced a mild, albeit not statistically significant, increase in autophagic flux along with the nuclear intensity of transcription factor EB (TFEB), the master transcriptional regulator of autophagy. Inhibition of autophagic flux with bafilomycin, however, did not impair the improved host infection control by TFP and CPE, suggesting that the host (auto)phagolysosomal pathway is not causally involved in the mechanism of action of TFP and CPE. Additionally, TFP and CPE increased the production of both cellular and mitochondrial reactive oxygen species (ROS). Scavenging mitochondrial ROS did not impact, whereas inhibition of NADPH oxidase (NOX)-mediated ROS production partially impaired the HDT activity of TFP and CPE, indicating that oxidative burst may play a limited role in the improved host control of Mav infection by these drugs. Overall, our study demonstrates that phenothiazines are promising HDT candidates that enhance the antimicrobial response of macrophages against Mav, through mechanism(s) that were partially elucidated.

Antitumoral Activity and Metabolic Signatures of Dichloroacetate, 6-Aminonicotinamide and Etomoxir in Breast-Tumor-Educated Macrophages

Pharmacological targeting of metabolic pathways represents an appealing strategy to selectively kill cancer cells while promoting antitumor functions of stromal cells. In this study, we assessed the effectiveness of 13 metabolic drugs (MDs) in steering in vitro generated breast tumor-educated macrophages (TEMs) toward an antitumoral phenotype. For that, the production of vascular endothelial growth factor (VEGF) and tumor necrosis factor α (TNF-α), two important regulators of tumor progression, was evaluated. Notably, dichloroacetate (DCA), 6-aminonicotinamide (6-AN), and etomoxir decreased VEGF production and enhanced TNF-α release. Hence, we further clarified their impact on TEM metabolism using an untargeted NMR-based metabolomics approach. DCA downregulated glycolysis and enhanced the utilization of extracellular substrates like lactate while reconfiguring lipid metabolism. Several DCA-induced changes significantly correlated with heightened TNF-α production in response to pro-inflammatory stimulation. The inhibition of the pentose phosphate pathway by 6-AN was accompanied by enhanced glutaminolysis, which correlated with a decreased level of VEGF production. In etomoxir-treated TEM, inhibition of fatty acid oxidation was compensated through upregulation of glycolysis, catabolism of intracellular amino acids, and consumption of extracellular branched chain alpha-ketoacids (BCKA) and citrate. Overall, our results offer a comprehensive view of the metabolic signature of each MD in breast TEM and highlight putative correlations with phenotypic effects.

The role of PI3K-Akt-mTOR axis in Warburg effect and its modification by specific protein kinase inhibitors in human and rat inflammatory macrophages

The Warburg effect occurs both in cancer cells and in inflammatory macrophages. The aim of our work was to demonstrate the role of PI3K-Akt-mTOR axis in the Warburg effect in HL-60 derived, rat peritoneal and human blood macrophages and to investigate the potential of selected inhibitors of this pathway to antagonize it. M1 polarization in HL-60-derived and human blood monocyte-derived macrophages was supported by the increased expression of NOS2 and inflammatory cytokines. All M1 polarized and inflammatory macrophages investigated expressed higher levels of HIF-1α and NOS2, which were reduced by selected kinase inhibitors, supporting the role of PI3K-Akt-mTOR axis. Using Seahorse XF plates, we found that in HL-60-derived and human blood-derived macrophages, glucose loading reduced oxygen consumption (OCR) and increased glycolysis (ECAR) in M1 polarization, which was antagonized by selected kinase inhibitors and by dichloroacetate. In rat peritoneal macrophages, the changes in oxidative and glycolytic metabolism were less marked and the NOS2 inhibitor decreased OCR and increased ECAR. Non-mitochondrial oxygen consumption and ROS production were likely due to NADPH oxidase, expressed in each macrophage type, independently of PI3K-Akt-mTOR axis. Our results suggest that inflammation changed the metabolism in each macrophage model, but a clear relationship between polarization and Warburg effect was confirmed only after glucose loading in HL-60 and human blood derived macrophages. The effect of kinase inhibitors on Warburg effect was variable in different cell types, whereas dichloroacetate caused a shift toward oxidative metabolism. Our findings suggest that these originally anti-cancer inhibitors may also be candidates for anti-inflammatory therapy.

Integrative bioinformatics analysis for identifying the mitochondrial-related gene signature associated with immune infiltration in premature ovarian insufficiency

BACKGROUND

Premature ovarian insufficiency (POI) is a reproductive disorder characterized by the cessation of ovarian function before the age of 40. Although mitochondrial dysfunction and immune disorders are believed to contribute to ovarian damage in POI, the interplay between these factors remains understudied.

METHODS

In this research, transcriptomic data related to POI were obtained from the NCBI GEO database. Hub biomarkers were identified through the construction of a protein‒protein interaction (PPI) network and further validated using RT‒qPCR and Western blot. Moreover, their expression across various cell types was elucidated via single-cell RNA sequencing analysis. A comprehensive investigation of the mitochondrial and immune profiles of POI was carried out through correlation analysis. Furthermore, potential therapeutic agents were predicted utilizing the cMap database.

RESULTS

A total of 119 mitochondria-related differentially expressed genes (MitoDEGs) were identified and shown to be significantly enriched in metabolic pathways. Among these genes, Hadhb, Cpt1a, Mrpl12, and Mrps7 were confirmed both in a POI model and in human granulosa cells (GCs), where they were found to accumulate in GCs and theca cells. Immune analysis revealed variations in macrophages, monocytes, and 15 other immune cell types between the POI and control groups. Notably, strong correlations were observed between seven hub-MitoDEGs (Hadhb, Cpt1a, Cpt2, Mrpl12, Mrps7, Mrpl51, and Eci1) and various functions, such as mitochondrial respiratory complexes, dynamics, mitophagy, mitochondrial metabolism, immune-related genes, and immunocytes. Additionally, nine potential drugs (calyculin, amodiaquine, eudesmic acid, cefotaxime, BX-912, prostratin, SCH-79797, HU-211, and pizotifen) targeting key genes were identified.

CONCLUSIONS

Our results highlight the crosstalk between mitochondrial function and the immune response in the development of POI. The identification of MitoDEGs could lead to reliable biomarkers for the early diagnosis, monitoring, and personalized treatment of POI.

Host-directed therapy with amiodarone in preclinical models restricts mycobacterial infection and enhances autophagy

Mycobacterium tuberculosis (Mtb) as well as nontuberculous mycobacteria are intracellular pathogens whose treatment is extensive and increasingly impaired due to the rise of mycobacterial drug resistance. The loss of antibiotic efficacy has raised interest in the identification of host-directed therapeutics (HDT) to develop novel treatment strategies for mycobacterial infections. In this study, we identified amiodarone as a potential HDT candidate that inhibited both intracellular Mtb and Mycobacterium avium in primary human macrophages without directly impairing bacterial growth, thereby confirming that amiodarone acts in a host-mediated manner. Moreover, amiodarone induced the formation of (auto)phagosomes and enhanced autophagic targeting of mycobacteria in macrophages. The induction of autophagy by amiodarone is likely due to enhanced transcriptional regulation, as the nuclear intensity of the transcription factor EB, the master regulator of autophagy and lysosomal biogenesis, was strongly increased. Furthermore, blocking lysosomal degradation with bafilomycin impaired the host-beneficial effect of amiodarone. Finally, amiodarone induced autophagy and reduced bacterial burden in a zebrafish embryo model of tuberculosis, thereby confirming the HDT activity of amiodarone in vivo. In conclusion, we have identified amiodarone as an autophagy-inducing antimycobacterial HDT that improves host control of mycobacterial infections.

IMPORTANCE

Due to the global rise in antibiotic resistance, there is a strong need for alternative treatment strategies against intracellular bacterial infections, including Mycobacterium tuberculosis (Mtb) and non-tuberculous mycobacteria. Stimulating host defense mechanisms by host-directed therapy (HDT) is a promising approach for treating mycobacterial infections. This study identified amiodarone, an antiarrhythmic agent, as a potential HDT candidate that inhibits the survival of Mtb and Mycobacterium avium in primary human macrophages. The antimycobacterial effect of amiodarone was confirmed in an in vivo tuberculosis model based on Mycobacterium marinum infection of zebrafish embryos. Furthermore, amiodarone induced autophagy and inhibition of the autophagic flux effectively impaired the host-protective effect of amiodarone, supporting that activation of the host (auto)phagolysosomal pathway is essential for the mechanism of action of amiodarone. In conclusion, we have identified amiodarone as an autophagy-inducing HDT that improves host control of a wide range of mycobacteria.

Identification of kinase inhibitors as potential host-directed therapies for intracellular bacteria

The emergence of antimicrobial resistance has created an urgent need for alternative treatments against bacterial pathogens. Here, we investigated kinase inhibitors as potential host-directed therapies (HDTs) against intracellular bacteria, specifically Salmonella Typhimurium (Stm) and Mycobacterium tuberculosis (Mtb). We screened 827 ATP-competitive kinase inhibitors with known target profiles from two Published Kinase Inhibitor Sets (PKIS1 and PKIS2) using intracellular infection models for Stm and Mtb, based on human cell lines and primary macrophages. Additionally, the in vivo safety and efficacy of the compounds were assessed using zebrafish embryo infection models. Our screen identified 11 hit compounds for Stm and 17 hit compounds for Mtb that were effective against intracellular bacteria and non-toxic for host cells. Further experiments were conducted to prioritize Stm hit compounds that were able to clear the intracellular infection in primary human macrophages. From these, two structurally related Stm hit compounds, GSK1379738A and GSK1379760A, exhibited significant activity against Stm in infected zebrafish embryos. In addition, we identified compounds that were active against intracellular Mtb, including morpholino-imidazo/triazolo-pyrimidinones that target PIK3CB, as well as 2-aminobenzimidazoles targeting ABL1. Overall, this study provided insights into kinase targets acting at the host-pathogen interface and identified several kinase inhibitors as potential HDTs.

HBV suppresses macrophage immune responses by impairing the TCA cycle through the induction of CS/PDHC hyperacetylation

BACKGROUND

It is now understood that HBV can induce innate and adaptive immune response disorders by affecting immunosuppressive macrophages, resulting in chronic HBV infection. However, the underlying mechanism is not fully understood. Dysregulated protein acetylation can reportedly influence the differentiation and functions of innate immune cells by coordinating metabolic signaling. This study aims to assess whether HBV suppresses macrophage-mediated innate immune responses by affecting protein acetylation and to elucidate the underlying mechanisms of HBV immune escape.

METHODS

We investigated the effect of HBV on the acetylation levels of human THP-1 macrophages and identified potential targets of acetylation that play a role in glucose metabolism. Metabolic and immune phenotypes of macrophages were analyzed using metabolomic and flow cytometry techniques. Western blot, immunoprecipitation, and immunofluorescence were performed to measure the interactions between deacetylase and acetylated targets. Chronic HBV persistent infected mice were established to evaluate the role of activating the tricarboxylic acid (TCA) cycle in macrophages for HBV clearance.

RESULTS

Citrate synthase/pyruvate dehydrogenase complex hyperacetylation in macrophages after HBV stimulation inhibited their enzymatic activities and was associated with impaired TCA cycle and M2-like polarization. HBV downregulated Sirtuin 3 (SIRT3) expression in macrophages by means of the toll-like receptor 2 (TLR2)-NF-κB- peroxisome proliferatoractivated receptor γ coactivator 1α (PGC-1α) axis, resulting in citrate synthase/pyruvate dehydrogenase complex hyperacetylation. In vivo administration of the TCA cycle agonist dichloroacetate inhibited macrophage M2-like polarization and effectively reduced the number of serum HBV DNA copies.

CONCLUSIONS

HBV-induced citrate synthase/pyruvate dehydrogenase complex hyperacetylation negatively modulates the innate immune response by impairing the TCA cycle of macrophages. This mechanism represents a potential therapeutic target for controlling HBV infection.

Tumor-associated macrophages: new insights on their metabolic regulation and their influence in cancer immunotherapy

Tumor-associated macrophages (TAMs) are a dynamic and heterogeneous cell population of the tumor microenvironment (TME) that plays an essential role in tumor formation and progression. Cancer cells have a high metabolic demand for their rapid proliferation, survival, and progression. A comprehensive interpretation of pro-tumoral and antitumoral metabolic changes in TAMs is crucial for comprehending immune evasion mechanisms in cancer. The metabolic reprogramming of TAMs is a novel method for enhancing their antitumor effects. In this review, we provide an overview of the recent research on metabolic alterations of TAMs caused by TME, focusing primarily on glucose, amino acid, and fatty acid metabolism. In addition, this review discusses antitumor immunotherapies that influence the activity of TAMs by limiting their recruitment, triggering their depletion, and re-educate them, as well as metabolic profiles leading to an antitumoral phenotype. We highlighted the metabolic modulational roles of TAMs and their potential to enhance immunotherapy for cancer.

The Biological Significance of Pyruvate Sensing and Uptake in Salmonella enterica Serovar Typhimurium

Pyruvate (CH₃COCOOH) is the simplest of the alpha-keto acids and is at the interface of several metabolic pathways both in prokaryotes and eukaryotes. In an amino acid-rich environment, fast-growing bacteria excrete pyruvate instead of completely metabolizing it. The role of pyruvate uptake in pathological conditions is still unclear. In this study, we identified two pyruvate-specific transporters, BtsT and CstA, in Salmonella enterica serovar Typhimurium (S. Typhimurium). Expression of btsT is induced by the histidine kinase/response regulator system BtsS/BtsR upon sensing extracellular pyruvate, whereas expression of cstA is maximal in the stationary phase. Both pyruvate transporters were found to be important for the uptake of this compound, but also for chemotaxis to pyruvate, survival under oxidative and nitrosative stress, and persistence of S. Typhimurium in response to gentamicin. Compared with the wild-type cells, the ΔbtsTΔcstA mutant has disadvantages in antibiotic persistence in macrophages, as well as in colonization and systemic infection in gnotobiotic mice. These data demonstrate the surprising complexity of the two pyruvate uptake systems in S. Typhimurium.

Progressive Host-Directed Strategies to Potentiate BCG Vaccination Against Tuberculosis

The pursuit to improve the TB control program comprising one approved vaccine, M. bovis Bacille Calmette-Guerin (BCG) has directed researchers to explore progressive approaches to halt the eternal TB pandemic. Mycobacterium tuberculosis (M.tb) was first identified as the causative agent of TB in 1882 by Dr. Robert Koch. However, TB has plagued living beings since ancient times and continues to endure as an eternal scourge ravaging even with existing chemoprophylaxis and preventive therapy. We have scientifically come a long way since then, but despite accessibility to the standard antimycobacterial antibiotics and prophylactic vaccine, almost one-fourth of humankind is infected latently with M.tb. Existing therapeutics fail to control TB, due to the upsurge of drug-resistant strains and increasing incidents of co-infections in immune-compromised individuals. Unresponsiveness to established antibiotics leaves patients with no therapeutic possibilities. Hence the search for an efficacious TB immunization strategy is a global health priority. Researchers are paving the course for efficient vaccination strategies with the radically advanced operation of core principles of protective immune responses against M.tb. In this review; we have reassessed the progression of the TB vaccination program comprising BCG immunization in children and potential stratagems to reinforce BCG-induced protection in adults.