Comparison of human monocyte derived macrophages and THP1-like macrophages as in vitro models for M. tuberculosis infection

Dynamic changes in RNA m6A and 5 hmC influence gene expression programs during macrophage differentiation and polarisation

RNA modifications are essential for the establishment of cellular identity. Although increasing evidence indicates that RNA modifications regulate the innate immune response, their role in monocyte-to-macrophage differentiation and polarisation is unclear. While m6A has been widely studied, other RNA modifications, including 5 hmC, remain poorly characterised. We profiled m6A and 5 hmC epitranscriptomes, transcriptomes, translatomes and proteomes of monocytes and macrophages at rest and pro- and anti-inflammatory states. Transcriptome-wide mapping of m6A and 5 hmC reveals enrichment of m6A and/or 5 hmC on specific categories of transcripts essential for macrophage differentiation. Our analyses indicate that m6A and 5 hmC modifications are present in transcripts with critical functions in pro- and anti-inflammatory macrophages. Notably, we also discover the co-occurrence of m6A and 5 hmC on alternatively-spliced isoforms and/or opposing ends of the untranslated regions (UTR) of mRNAs with key roles in macrophage biology. In specific examples, RNA 5 hmC controls the decay of transcripts independently of m6A. This study provides (i) a comprehensive dataset to interrogate the role of RNA modifications in a plastic system (ii) a resource for exploring different layers of gene expression regulation in the context of human monocyte-to-macrophage differentiation and polarisation, (iii) new insights into RNA modifications as central regulators of effector cells in innate immunity.

Echinocandin persistence directly impacts the evolution of resistance and survival of the pathogenic fungus Candida glabrata

Recent epidemiological studies documented an alarming increase in the prevalence of echinocandin-resistant (ECR) Candida glabrata blood isolates. ECR isolates are known to arise from a minor subpopulation of a clonal population, termed echinocandin persisters. Although it is believed that isolates with a higher echinocandin persistence (ECP) are more likely to develop ECR, the implication of ECP needs to be better understood. Moreover, replacing laborious and time-consuming traditional approaches to determine ECP levels with rapid, convenient, and reliable tools is imperative to advance our understanding of this emerging concept in clinical practice. Herein, using extensive ex vivo and in vivo systemic infection models, we showed that high ECP isolates are less effectively cleared by micafungin treatment and exclusively give rise to ECR colonies. Additionally, we developed a flow cytometry-based tool that takes advantage of a SYTOX-based assay for the stratification of ECP levels. Once challenged with various collections of echinocandin-susceptible blood isolates, our assay reliably differentiated ECP levels in vitro and predicted ECP levels in real time under ex vivo and in vivo conditions when compared to traditional methods relying on colony-forming unit counting. Given the high and low ECP predictive values of 92.3% and 82.3%, respectively, our assay showed a high agreement with traditional approach. Collectively, our study supports the concept of ECP level determination in clinical settings and provides a robust tool scalable for high-throughput settings. Application of this tool facilitates the interrogation of mutant and drug libraries to further our understanding of persister biology and designing anti-persister therapeutics.

IMPORTANCE

Candida glabrata is a prevalent fungal pathogen able to replicate inside macrophages and rapidly develop resistance against frontline antifungal echinocandins. Multiple studies have shown that echinocandin resistance is fueled by the survival of a small subpopulation of susceptible cells surviving lethal concentrations of echinocandins. Importantly, bacterial pathogens that exhibit high antibiotic persistence also impose a high burden and generate more antibiotic-resistant colonies. Nonetheless, the implications of echinocandin persistence (ECP) among the clinical isolates of C. glabrata have not been defined. Additionally, ECP level determination relies on a laborious and time-consuming method, which is prone to high variation. By exploiting in vivo systemic infection and ex vivo models, we showed that C. glabrata isolates with a higher ECP are associated with a higher burden and more likely develop echinocandin resistance upon micafungin treatment. Additionally, we developed an assay that reliably determines ECP levels in real time. Therefore, our study identified C. glabrata isolates displaying high ECP levels as important entities and provided a reliable and convenient tool for measuring echinocandin persistence, which is extendable to other fungal and bacterial pathogens.

Therapeutic Polymer-Based Cannabidiol Formulation: Tackling Neuroinflammation Associated with Ischemic Events in the Brain

Cannabidiol (CBD) is the most relevant nonpsychostimulant phytocompound found in Cannabis sativa. CBD has been extensively studied and has been proposed as a therapeutic candidate for neuroinflammation-related conditions. However, being a highly lipophilic drug, it has several drawbacks for pharmaceutical use, including low solubility and high permeability. Synthetic polymers can be used as drug delivery systems to improve CBD's stability, half-life, and biodistribution. Here, we propose using a synthetic polymer as a nanoparticulate vehicle for CBD (NPCBD) to overcome the pharmacological drawbacks of free drugs. We tested the NPCBD-engineered system in the context of ischemic events in a relevant oxygen and glucose deprivation (OGD) model in primary cortical cells (PCC). Moreover, we have characterized the inflammatory response of relevant cell types, such as THP-1 (human monocytes), HMC3 (human microglia), and PCC, to NPCBD and observed a shift in the inflammatory state of the treated cells after the ischemic event. In addition, NPCBD exhibited a promising ability to restore mitochondrial function after OGD insult in both HMC3 and PCC cells at low doses of 1 and 0.2 μM CBD. Taken together, these results suggest the potential for preclinical use.

MDA5 RNA-sensing pathway activation by Mycobacterium tuberculosis promotes innate immune subversion and pathogen survival

Host cytosolic sensing of Mycobacterium tuberculosis (M. tuberculosis) RNA by the RIG-I-like receptor (RLR) family perturbs innate immune control within macrophages; however, a distinct role of MDA5, a member of the RLR family, in M. tuberculosis pathogenesis has yet to be fully elucidated. To further define the role of MDA5 in M. tuberculosis pathogenesis, we evaluated M. tuberculosis intracellular growth and innate immune responses in WT and Mda5-/- macrophages. Transfection of M. tuberculosis RNA strongly induced proinflammatory cytokine production in WT macrophages, which was abrogated in Mda5-/- macrophages. M. tuberculosis infection in macrophages induced MDA5 protein expression, accompanied by an increase in MDA5 activation as assessed by multimer formation. IFN-γ-primed Mda5-/- macrophages effectively contained intracellular M. tuberculosis proliferation to a markedly greater degree than WT macrophages. Further comparisons of WT versus Mda5-/- macrophages revealed that during M. tuberculosis infection MDA5 contributed to IL-1β production and inflammasome activation and that loss of MDA5 led to a substantial increase in autophagy. In the mouse TB model, loss of MDA5 conferred host survival benefits with a concomitant reduction in M. tuberculosis bacillary burden. These data reveal that loss of MDA5 is host protective during M. tuberculosis infection in vitro and in vivo, suggesting that M. tuberculosis exploits MDA5 to subvert immune containment.

Benzene Amide Ether Scaffold is Active against Non-replicating and Intracellular Mycobacterium tuberculosis

New drugs to treat tuberculosis which target intractable bacterial populations are required to develop shorter and more effective treatment regimens. The benzene amide ether scaffold has activity against intracellular Mycobacterium tuberculosis, but low activity against extracellular, actively replicating M. tuberculosis. We determined that these molecules have bactericidal activity against non-replicating M. tuberculosis but not actively replicating bacteria. Exposure to compounds depleted ATP levels in non-replicating bacteria and increased the oxygen consumption rate; a subset of molecules led to the accumulation of intrabacterial reactive oxygen species. A comprehensive screen of M. tuberculosis strains identified a number of under-expressing strains as more sensitive to compounds under replicating conditions including QcrA and QcrB hypomorphs. We determined the global gene expression profile after compound treatment for both replicating and nutrient-starved M. tuberculosis. We saw compound-dependent changes in the expression of genes involved in energy metabolism under both conditions. Taken together, our data suggest that the scaffold targets respiration in M. tuberculosis.

Optimizing THP-1 Macrophage Culture for an Immune-Responsive Human Intestinal Model

Previously established immune-responsive co-culture models with macrophages have limitations due to the dedifferentiation of macrophages in long-term cultures. This study is the first report of a long-term (21-day) triple co-culture of THP-1 macrophages (THP-1m) with Caco-2 intestinal epithelial cells and HT-29-methotrexate (MTX) goblet cells. We demonstrated that high-density seeded THP-1 cells treated with 100 ng/mL phorbol 12-myristate 13-acetate for 48 h differentiated stably and could be cultured for up to 21 days. THP-1m were identified by their adherent morphology and lysosome expansion. In the triple co-culture immune-responsive model, cytokine secretions during lipopolysaccharide-induced inflammation were confirmed. Tumor necrosis factor-alpha and interleukin 6 levels were elevated in the inflamed state, reaching 824.7 ± 130.0 pg/mL and 609.7 ± 139.5 pg/mL, respectively. Intestinal membrane integrity was maintained with a transepithelial electrical resistance value of 336.4 ± 18.0 Ω·cm². Overall, our findings suggest that THP-1m can be effectively employed in models of long-term immune responses in both normal and chronic inflammatory states of the intestinal epithelium, making them a valuable tool for future research on the association between the immune system and gut health.

Mycobacterium vaccae NCTC 11659, a Soil-Derived Bacterium with Stress Resilience Properties, Modulates the Proinflammatory Effects of LPS in Macrophages

Inflammatory conditions, including allergic asthma and conditions in which chronic low-grade inflammation is a risk factor, such as stress-related psychiatric disorders, are prevalent and are a significant cause of disability worldwide. Novel approaches for the prevention and treatment of these disorders are needed. One approach is the use of immunoregulatory microorganisms, such as Mycobacterium vaccae NCTC 11659, which have anti-inflammatory, immunoregulatory, and stress-resilience properties. However, little is known about how M. vaccae NCTC 11659 affects specific immune cell targets, including monocytes, which can traffic to peripheral organs and the central nervous system and differentiate into monocyte-derived macrophages that, in turn, can drive inflammation and neuroinflammation. In this study, we investigated the effects of M. vaccae NCTC 11659 and subsequent lipopolysaccharide (LPS) challenge on gene expression in human monocyte-derived macrophages. THP-1 monocytes were differentiated into macrophages, exposed to M. vaccae NCTC 11659 (0, 10, 30, 100, 300 µg/mL), then, 24 h later, challenged with LPS (0, 0.5, 2.5, 250 ng/mL), and assessed for gene expression 24 h following challenge with LPS. Exposure to M. vaccae NCTC 11659 prior to challenge with higher concentrations of LPS (250 ng/mL) polarized human monocyte-derived macrophages with decreased IL12A, IL12B, and IL23A expression relative to IL10 and TGFB1 mRNA expression. These data identify human monocyte-derived macrophages as a direct target of M. vaccae NCTC 11659 and support the development of M. vaccae NCTC 11659 as a potential intervention to prevent stress-induced inflammation and neuroinflammation implicated in the etiology and pathophysiology of inflammatory conditions and stress-related psychiatric disorders.

Adaptation to the intracellular environment of primary human macrophages influences drug susceptibility of Mycobacterium tuberculosis

As a facultative intracellular pathogen, M. tuberculosis (Mtb) is highly adapted to evading antibacterial mechanisms in phagocytic cells. Both the macrophage and pathogen experience transcriptional and metabolic changes from the onset of phagocytosis. To account for this interaction in the assessment of intracellular drug susceptibility, we allowed a 3-day preadaptation phase post-macrophage infection prior to drug treatment. We found that intracellular Mtb in human monocyte-derived macrophages (MDM) presents dramatic alterations in susceptibility to isoniazid, sutezolid, rifampicin and rifapentine when compared to axenic culture. Infected MDM gradually accumulate lipid bodies, adopting a characteristic appearance reminiscent of foamy macrophages in granulomas. Furthermore, TB granulomas in vivo develop hypoxic cores with decreasing oxygen tension gradients across their radii. Accordingly, we evaluated the effects of hypoxia on preadapted intracellular Mtb in our MDM model. We observed that hypoxia induced greater lipid body formation and no additional shifts in drug tolerance, suggesting that the adaptation of intracellular Mtb to baseline host cell conditions under normoxia dominates changes to intracellular drug susceptibility. Using unbound plasma concentrations in patients as surrogates for free drug concentrations in lung interstitial fluid, we estimate that intramacrophage Mtb in granulomas are exposed to bacteriostatic concentrations of most study drugs.

Early suppression of antiviral host response and protocadherins by SARS-CoV-2 Spike protein in THP-1-derived macrophage-like cells

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease-19 (COVID-19). The spike protein (S) of SARS-CoV-2 plays a crucial role in mediating viral infectivity; hence, in an extensive effort to curb the pandemic, many urgently approved vaccines rely on the expression of the S protein, aiming to induce a humoral and cellular response to protect against the infection. Given the very limited information about the effects of intracellular expression of the S protein in host cells, we aimed to characterize the early cellular transcriptomic changes induced by expression of the S protein in THP-1-derived macrophage-like cells. Results showed that a wide variety of genes were differentially expressed, products of which are mainly involved in cell adhesion, homeostasis, and most notably, antiviral and immune responses, depicted by significant downregulation of protocadherins and type I alpha interferons (IFNAs). While initially, the levels of IFNAs were higher in the medium of S protein expressing cells, the downregulation observed on the transcriptomic level might have been reflected by no further increase of IFNA cytokines beyond the 5 h time-point, compared to the mock control. Our study highlights the intrinsic pathogenic role of the S protein and sheds some light on the potential drawbacks of its utilization in the context of vaccination strategies.

THP-1 cell line model for tuberculosis: A platform for in vitro macrophage manipulation

Macrophages are large mononuclear phagocytic cells that play a vital role in the immune response. They are present in all body tissues with extremely heterogeneous and plastic phenotypes that adapt to the organs and tissues in which they live and respond in the first-line against invading microorganisms. Tuberculosis (TB) is caused by the pathogenic bacteria Mycobacterium tuberculosis (Mtb), which is among the top 10 global infectious agents and the leading cause of mortality, ranking above human immunodeficiency virus (HIV), as a single infectious agent. Macrophages, upon Mtb infection, not only phagocytose the bacteria and present the antigens to T-cells, but also react rapidly by developing antimycobacterial immune response depending highly on the production of cytokines. However, Mtb is also capable of intracellular survival in instances of sub-optimal activation of macrophages. Hence, several systems have been established to evaluate the Mtb-macrophage interaction, where the THP-1 monocytes have been developed as an attractive model for in vitro polarized monocyte-derived macrophages. This model is extensively used for Mtb as well as other intracellular bacterial studies. Herein, we have summarized the updated implications of the THP-1 model for TB-related studies and discussed the pros and cons compared to other cell models of TB.

TREM2 Promotes Immune Evasion by Mycobacterium tuberculosis in Human Macrophages

Macrophage surface receptors are critical for pathogen defense, as they are the gatekeepers for pathogen entry and sensing, which trigger robust immune responses. TREM2 (triggering receptor expressed on myeloid cells 2) is a transmembrane surface receptor that mediates anti-inflammatory immune signaling. A recent study showed that TREM2 is a receptor for mycolic acids in the mycobacterial cell wall and inhibits macrophage activation. However, the underlying functional mechanism of how TREM2 regulates the macrophage antimycobacterial response remains unclear. Here, we show that Mycobacterium tuberculosis, the causative agent for tuberculosis, specifically binds to human TREM2 to disable the macrophage antibacterial response. Live but not killed mycobacteria specifically trigger the upregulation of TREM2 during macrophage infection through a mechanism dependent on STING (the stimulator of interferon genes). TREM2 facilitated uptake of M. tuberculosis into macrophages and is responsible for blocking the production of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and reactive oxygen species (ROS), while enhancing the production of interferon-β (IFN-β) and IL-10. TREM2-mediated blockade of ROS production promoted the survival of M. tuberculosis within infected macrophages. Consistent with this, genetic deletion or antibody-mediated neutralization of TREM2 reduced the intracellular survival of M. tuberculosis through enhanced production of ROS. Importantly, inhibition of type I IFN signaling in TREM2-overexpressing macrophages restored the ability of these cells to produce inflammatory cytokines and ROS, resulting in normal levels of intracellular bacteria killing. Collectively, our study identifies TREM2 as an attractive host receptor for host-directed antimycobacterial therapeutics. IMPORTANCE Mycobacterium tuberculosis is one of the most ancient bacterial pathogens and remains the leading cause of death from a single bacterial agent. The success of M. tuberculosis relies greatly on its ability to parasitize and disable its host macrophages. Previous studies have found that M. tuberculosis uses its unique cell wall lipids to manipulate the immune response by binding to specific surface receptors on macrophages. Our study reveals that M. tuberculosis binds to TREM2, an immunomodulatory receptor expressed on macrophages, to facilitate a "silent" mode of entry. Increased levels of TREM2 triggered by intracellular sensing of M. tuberculosis promoted the intracellular survival of M. tuberculosis through type I IFN-driven inhibition of reactive oxygen species (ROS) and proinflammatory cytokine production. Importantly, deletion of TREM2 reversed the effects of "silent" entry and resulted in increased production of inflammatory cytokines, generation of ROS, and cell death. As such, antibody-mediated or pharmacological targeting of TREM2 could be a promising strategy for novel treatments against M. tuberculosis infection.

Investigation of Host-Microbe-Parasite Interactions in an In Vitro 3D Model of the Vertebrate Gut

In vitro models of the gut-microbiome axis are in high demand. Conventionally, intestinal monolayers grown on Transwell setups are used to test the effects of commensals/pathogens on the barrier integrity, both under homeostatic and pathophysiological conditions. While such models remain valuable for deepening the understanding of host-microbe interactions, often, they lack key biological components that mediate this intricate crosstalk. Here, a 3D in vitro model of the vertebrate intestinal epithelium, interfaced with immune cells surviving in culture for over 3 weeks, is developed and applied to proof-of-concept studies of host-microbe interactions. More specifically, the establishment of stable host-microbe cocultures is described and functional and morphological changes in the intestinal barrier induced by the presence of commensal bacteria are shown. Finally, evidence is provided that the 3D vertebrate gut models can be used as platforms to test host-microbe-parasite interactions. Exposure of gut-immune-bacteria cocultures to helminth "excretory/secretory products" induces in vivo-like up-/down-regulation of certain cytokines. These findings support the robustness of the modular in vitro cell systems for investigating the dynamics of host-microbe crosstalk and pave the way toward new approaches for systems biology studies of pathogens that cannot be maintained in vitro, including parasitic helminths.

Increased Interferon-Induced Protein With Tetracopeptides (IFITs) Reduces Mycobacterial Growth

Objectives

The host immune response towards Mycobacterium tuberculosis (M. tb) is known to vary with the virulence of mycobacterial species. While the majority of M. tb-exposed individuals develop latent TB infection (LTBI), a small proportion develops active TB disease. The milieu of understudied immune factors is believed to play an important role against host immune response towards mycobacteria. Here, we investigate the role of antiviral factors of the interferon-induced proteins with tetracopeptides (IFITs) family, which, in our previous research, have shown to be upregulated in response to pathogenic M. tb, but as yet have no established role in host response to bacterial infections.

Methods

We performed vector-driven overexpression and siRNA-mediated downregulation of IFITs in THP-1 cells infected with different mycobacterial species. Also, we investigated the mRNA levels of IFITs in the LTBI and active-TB cases.

Results

Overexpression of IFITs reduces CFUs by ~32% (30%–43%) [Median (IQR)] across three different mycobacterial strains, while knock-down increases CFUs by ~57% (41%–78%). Compared to IFN-γ, treatment of infected THP-1 cells with IFN-β significantly increases the expression of IFITs, while the overexpression of IFITs had higher mRNA expression of IFN-β than IFN-γ. Cytokines like IDO-1, IL-6, IL-23, and IFN- γ are observed to play key roles in mycobacterial survival upon IFITs intervention. mRNA expression levels of IFITs were higher in LTBI cases as compared to active TB.

Conclusion

Higher expression levels of IFITs reduce in vitro survival of different drug-susceptible and drug-resistant mycobacteria and correlates with latent TB infection in infected individuals, hence emerging as an immuno-therapeutic target against M. tb.

Versatile-in-All-Trades: Multifunctional Boron-Doped Calcium-Deficient Hydroxyapatite Directs Immunomodulation and Regeneration

Osseointegration of implants depends on several intertwined factors: osteogenesis, angiogenesis, and immunomodulation. Lately, novel reinforcements allowing faster bonding with osseous tissue have been explored intensively. In this study, we hypothesized the use of boron as a major multifunctional ion to confer versatility to calcium-deficient hydroxyapatite (cHA) synthesized by a wet precipitation/microwave reflux method. By synthesis of boron-doped calcium-deficient hydroxyapatite (BcHA), we expected to obtain an osteoimmunomodulatory and regenerative nanoreinforcement. BcHA was found to possess a pure HA phase, a greater surface area (66.41 m²/g, p = 0.028), and cumulative concentrations of Ca (207.87 ± 6.90 mg/mL, p < 0.001) and B (112.70 ± 11.79 mg/mL, p < 0.001) released in comparison to cHA. Osteogenic potential of BcHA was analyzed using human fetal osteoblasts. BcHA resulted in a drastic increase in the ALP activity (1.11 ± 0.11 mmol/gDNA·min, p < 0.001), biomineralization rate, and osteogenic gene expressions compared to cHA. BcHA angiogenic potential was investigated using human umbilical cord vein endothelial cells. Significantly, the highest VEGF-A release (1111.14 ± 87.82 in 4 h, p = 0.009) and angiogenic gene expressions were obtained for BcHA-treated samples. These samples were also observed to induce a more prominent and highly branched tube network. Finally, inflammatory and inflammasome responses toward BcHA were elucidated using human monocyte-derived macrophages differentiated from THP-1s. BcHA exhibited lower CAS-1 release (50.18 ± 5.52 μg/g_DNA μg/gDNA) and higher IL-10 release (126.97 ± 15.05 μg/g_DNA) than cHA. In addition, BcHA treatment led to increased expression of regenerative genes such as VEGF-A, RANKL, and BMP-2. In vitro results demonstrated that BcHA has tremendous osteogenic, angiogenic, and immunomodulatory potential to be employed as a "versatile-in-all-trades" modality in various bone tissue engineering applications.

Differential susceptibility to lipopolysaccharide affects the activation of toll-like-receptor 4 signaling in THP-1 cells and PMA-differentiated THP-1 cells

Monocytes and macrophages that originate from common myeloid progenitors perform various crucial roles in the innate immune system. Stimulation with LPS combined with TLR4 drives the production of pro-inflammatory cytokines through MAPKs and NF-κB pathway in different cells. However, the difference in LPS susceptibility between monocytes and macrophages is poorly understood. In this study, we found that pro-inflammatory cytokines-IL-1β, IL-6 and TNFα showed greater induction in phorbol-12-myristate-13-acetate (PMA)-differentiated THP-1 cells than in THP-1 cells. To determine the difference in cytokine expression, the surface proteins such as TLR4-related proteins and intracellular adaptor proteins were more preserved in PMA-differentiated THP-1 cells than in THP-1 cells. MyD88 is a key molecule responsible for the difference in LPS susceptibility. Moreover, MAPKs and NF-κB pathway-related molecules showed higher levels of phosphorylation in PMA-differentiated THP-1 cells than in THP-1 cells. Upon MyD88 depletion, there was no difference in the phosphorylation of MAPK pathway-related molecules. Therefore, these results demonstrate that the difference in LPS susceptibility between THP-1 cells and PMA-differentiated THP-1 cells occur as a result of gap between the activated MAPKs and NF-κB pathways via changes in the expression of LPS-related receptors and MyD88.

Understanding immune-modulatory efficacy in vitro

Boosting or suppressing our immune system represents an attractive adjunct in the treatment of infections including SARS-CoV-2, cancer, AIDS, malnutrition, age related problems and some inflammatory disorders. Thus, there has been a growing interest in exploring and developing novel drugs, natural or synthetic, that can manipulate our defence mechanism. Many of such studies, reported till date, have been designed to explore effect of the therapeutic on function of macrophages, being a key component in innate immune system. Indeed, RAW264.7, J774A.1, THP-1 and U937 cell lines act as ideal model systems for preliminary investigation and selection of dose for in vivo studies. Several bioassays have been standardized so far where many techniques require high throughput instruments, cost effective reagents and technical assistance that may hinder many scholars to perform a method demanding compilation of available protocols. In this review, we have taken an attempt for the first time to congregate commonly used in vitro immune-modulating techniques explaining their principles. The study detected that among about 40 different assays and more than 150 sets of primers, the methods of cell proliferation by MTT, phagocytosis by neutral red, NO detection by Griess reaction and estimation of expression of TLRs, COX-2, iNOS, TNF-α, IL-6 and IL-1β by PCR have been the most widely used to screen the therapeutics under investigation.

Intracellular Accumulation of Novel and Clinically Used TB Drugs Potentiates Intracellular Synergy

The therapeutic repertoire for tuberculosis (TB) remains limited despite the existence of many TB drugs that are highly active in in vitro models and possess clinical utility. Underlying the lack of efficacy in vivo is the inability of TB drugs to penetrate microenvironments inhabited by the causative agent, Mycobacterium tuberculosis, including host alveolar macrophages. Here, we determined the ability of the phenoxazine PhX1 previously shown to be active against M. tuberculosis in vitro to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. We also investigated the extent of permeation into uninfected and M. tuberculosis-infected human macrophage-like Tamm-Horsfall protein 1 (THP-1) cells directly and by comparing to results obtained in vitro in synergy assays. Our data indicate that PhX1 (4,750 ± 127.2 ng/ml) penetrates more effectively into THP-1 cells than do the clinically used anti-TB agents, rifampin (3,050 ± 62.9 ng/ml), moxifloxacin (3,374 ± 48.7 ng/ml), bedaquiline (4,410 ± 190.9 ng/ml), and linezolid (770 ± 14.1 ng/ml). Compound efficacy in infected cells correlated with intracellular accumulation, reinforcing the perceived importance of intracellular penetration as a key drug property. Moreover, we detected synergies deriving from redox-stimulatory combinations of PhX1 or clofazimine with the novel prenylated amino-artemisinin WHN296. Finally, we used compound synergies to elucidate the relationship between compound intracellular accumulation and efficacy, with PhX1/WHN296 synergy levels shown to predict drug efficacy. Collectively, our data support the utility of the applied assays in identifying in vitro active compounds with the potential for clinical development. IMPORTANCE This study addresses the development of novel therapeutic compounds for the eventual treatment of drug-resistant tuberculosis. Tuberculosis continues to progress, with cases of Mycobacterium tuberculosis (M. tuberculosis) resistance to first-line medications increasing. We assess new combinations of drugs with both oxidant and redox properties coupled with a third partner drug, with the focus here being on the potentiation of M. tuberculosis-active combinations of compounds in the intracellular macrophage environment. Thus, we determined the ability of the phenoxazine PhX1, previously shown to be active against M. tuberculosis in vitro, to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. In addition, the extent of permeation into human macrophage-like THP-1 cells and H37Rv-infected THP-1 cells was measured via mass spectrometry and compared to in vitro two-dimensional synergy and subsequent intracellular efficacy. Collectively, our data indicate that development of new drugs will be facilitated using the methods described herein.

Comparative transcriptomic analysis of THP-1-derived macrophages infected with Mycobacterium tuberculosis H37Rv, H37Ra and BCG

Tuberculosis (TB) remains a worldwide healthcare concern, and the exploration of the host‐pathogen interaction is essential to develop therapeutic modalities and strategies to control Mycobacterium tuberculosis (M.tb). In this study, RNA sequencing (transcriptome sequencing) was employed to investigate the global transcriptome changes in the macrophages during the different strains of M.tb infection. THP‐1 cells derived from macrophages were exposed to the virulent M.tb strain H37Rv (Rv) or the avirulent M.tb strain H37Ra (Ra), and the M.tb BCG vaccine strain was used as a control. The cDNA libraries were prepared from M.tb‐infected macrophages and then sequenced. To assess the transcriptional differences between the expressed genes, the bioinformatics analysis was performed using a standard pipeline of quality control, reference mapping, differential expression analysis, protein‐protein interaction (PPI) networks, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Q‐PCR and Western blot assays were also performed to validate the data. Our findings indicated that, when compared to BCG or M.tb H37Ra infection, the transcriptome analysis identified 66 differentially expressed genes in the M.tb H37Rv‐infected macrophages, out of which 36 genes were up‐regulated, and 30 genes were down‐regulated. The up‐regulated genes were associated with immune response regulation, chemokine secretion, and leucocyte chemotaxis. In contrast, the down‐regulated genes were associated with amino acid biosynthetic and energy metabolism, connective tissue development and extracellular matrix organization. The Q‐PCR and Western blot assays confirmed increased expression of pro‐inflammatory factors, altered energy metabolic processes, enhanced activation of pro‐inflammatory signalling pathways and increased pyroptosis in H37Rv‐infected macrophage. Overall, our RNA sequencing‐based transcriptome study successfully identified a comprehensive, in‐depth gene expression/regulation profile in M.tb‐infected macrophages. The results demonstrated that virulent M.tb strain H37Rv infection triggers a more severe inflammatory immune response associated with increased tissue damage, which helps in understanding the host‐pathogen interaction dynamics and pathogenesis features in different strains of M.tb infection.

Bacterial Engulfment Mechanism Is Strongly Conserved in Evolution Between Earthworm and Human Immune Cells

Invertebrates, including earthworms, are applied to study the evolutionarily conserved cellular immune processes. Earthworm immunocytes (so-called coelomocytes) are functionally similar to vertebrate myeloid cells and form the first line of defense against invading pathogens. Hereby, we compared the engulfment mechanisms of THP-1 human monocytic cells, differentiated THP-1 (macrophage-like) cells, and Eisenia andrei coelomocytes towards Escherichia coli and Staphylococcus aureus bacteria applying various endocytosis inhibitors [amantadine, 5-(N-ethyl-N-isopropyl) amiloride, colchicine, cytochalasin B, cytochalasin D, methyl-ß-cyclodextrin, and nystatin]. Subsequently, we investigated the messenger RNA (mRNA) expressions of immune receptor-related molecules (TLR, MyD88, BPI) and the colocalization of lysosomes with engulfed bacteria following uptake inhibition in every cell type. Actin depolymerization by cytochalasin B and D has strongly inhibited the endocytosis of both bacterial strains in the studied cell types, suggesting the conserved role of actin-dependent phagocytosis. Decreased numbers of colocalized lysosomes/bacteria supported these findings. In THP-1 cells TLR expression was increased upon cytochalasin D pretreatment, while this inhibitor caused a dropped LBP/BPI expression in differentiated THP-1 cells and coelomocytes. The obtained data reveal further insights into the evolution of phagocytes in eukaryotes. Earthworm and human phagocytes possess analogous mechanisms for bacterial internalization.

Standard therapy of Mycobacterium avium complex pulmonary disease shows limited efficacy in an open source hollow fibre system that simulates human plasma and epithelial lining fluid pharmacokinetics

OBJECTIVES

Mycobacterium avium complex (MAC) bacteria can cause chronic pulmonary disease (PD). Current treatment regimens of azithromycin, ethambutol and rifampicin have culture conversion rates of around 65%. Dynamic, preclinical models to assess the efficacy of treatment regimens are important to guide clinical trial development. The hollow fibre system (HFS) has been applied but reports lack experimental details.

METHODS

We simulated the human pharmacokinetics of azithromycin, ethambutol and rifampicin both in plasma and epithelial lining fluid (ELF) in a HFS, exposing THP-1 cells infected with M. avium to the triple-drug regimen for 3 weeks. We accounted for drug-drug interactions and protein-binding and provide all laboratory protocols. We differentiated the effects on the intracellular and extracellular mycobacterial population.

RESULTS

The antibiotic concentrations in the HFS accurately reflected the time to peak concentration (T_max), the peak concentration (C_max) and half-life of azithromycin, rifampicin and ethambutol in plasma and ELF reported in literature. We find that plasma drug concentrations fail to hold the MAC bacterial load static (ΔLog10 CFU/mL_{Control:Regimen} = 0.66 ± 0.76 and 0.45 ± 0.28 at 3 and 21 days); ELF concentrations do hold the bacterial load static for 3 days and inhibit bacterial growth for the duration of the experiment (ΔLog10 CFU/mL_{Control:Regimen} = 1.1 ± 0.1 and 1.64 ± 0.59 at 3 and 21 days).

DISCUSSION

In our model, the current therapy against MAC is ineffective, even when accounting for antibiotic accumulation at the site of infection and intracellularly. New treatment regimens need to be developed and be compared with currently recommended regimens in dynamic models prior to clinical evaluation. With the publication of all protocols we aim to open this technology to new users.

Integrative Analysis of Human Macrophage Inflammatory Response Related to Mycobacterium tuberculosis Virulence

Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis, kills 1.5 to 1.7 million people every year. Macrophages are Mtb's main host cells and their inflammatory response is an essential component of the host defense against Mtb. However, Mtb is able to circumvent the macrophages' defenses by triggering an inappropriate inflammatory response. The ability of Mtb to hinder phagolysosome maturation and acidification, and to escape the phagosome into the cytosol, is closely linked to its virulence. The modulation of the host inflammatory response relies on Mtb virulence factors, but remains poorly studied. Understanding macrophage interactions with Mtb is crucial to develop strategies to control tuberculosis. The present study aims to determine the inflammatory response transcriptome and miRNome of human macrophages infected with the virulent H37Rv Mtb strain, to identify macrophage genetic networks specifically modulated by Mtb virulence. Using human macrophages infected with two different live strains of mycobacteria (live or heat-inactivated Mtb H37Rv and M. marinum), we quantified and analyzed 184 inflammatory mRNAs and 765 micro(mi)RNAs. Transcripts and miRNAs differently modulated by H37Rv in comparison with the two other conditions were analyzed using in silico approaches. We identified 30 host inflammatory response genes and 37 miRNAs specific for H37Rv virulence, and highlight evidence suggesting that Mtb intracellular-linked virulence depends on the inhibition of IL-1β-dependent pro-inflammatory response, the repression of apoptosis and the delay of the recruitment and activation of adaptive immune cells. Our findings provide new potential targets for the development of macrophage-based therapeutic strategies against TB.

Contribution of Heptose Metabolites and the cag Pathogenicity Island to the Activation of Monocytes/Macrophages by Helicobacter pylori

The human gastric pathogen Helicobacter pylori activates human epithelial cells by a particular combination of mechanisms, including NOD1 and ALPK1-TIFA activation. These mechanisms are characterized by a strong participation of the bacterial cag pathogenicity island, which forms a type IV secretion system (CagT4SS) that enables the bacteria to transport proteins and diverse bacterial metabolites, including DNA, glycans, and cell wall components, into human host cells. Building on previous findings, we sought to determine the contribution of lipopolysaccharide inner core heptose metabolites (ADP-heptose) in the activation of human phagocytic cells by H. pylori. Using human monocyte/macrophage-like Thp-1 cells and human primary monocytes and macrophages, we were able to determine that a substantial part of early phagocytic cell activation, including NF-κB activation and IL-8 production, by live H. pylori is triggered by bacterial heptose metabolites. This effect was very pronounced in Thp-1 cells exposed to bacterial purified lysates or pure ADP-heptose, in the absence of other bacterial MAMPs, and was significantly reduced upon TIFA knock-down. Pure ADP-heptose on its own was able to strongly activate Thp-1 cells and human primary monocytes/macrophages. Comprehensive transcriptome analysis of Thp-1 cells co-incubated with live H. pylori or pure ADP-heptose confirmed a signature of ADP-heptose-dependent transcript activation in monocyte/macrophages. Bacterial enzyme-treated lysates (ETL) and pure ADP-heptose–dependent activation differentiated monocytes into macrophages of predominantly M1 type. In Thp-1 cells, the active CagT4SS was less required for the heptose-induced proinflammatory response than in epithelial cells, while active heptose biosynthesis or pure ADP-heptose was required and sufficient for their early innate response and NF-κB activation. The present data suggest that early activation and maturation of incoming and resident phagocytic cells (monocytes, macrophages) in the H. pylori–colonized stomach strongly depend on bacterial LPS inner core heptose metabolites, also with a significant contribution of an active CagT4SS.

Salmonella enterica serovar Typhi genomic regions involved in low pH resistance and in invasion and replication in human macrophages

Purpose

Salmonella enterica serovar Typhi, the etiological agent of typhoid fever, causes a systemic life-threatening disease. To carry out a successful infection process, this bacterium needs to survive alkaline and acid pH conditions presented in the mouth, stomach, small intestine, and gallbladder. Therefore, in this work, a genetic screening to identify S. Typhi genes involved in acid and circumneutral pH resistance was performed.

Methods

A collection of S. Typhi mutants deleted of fragments ranging from 6 to 80 kb were obtained by the Datsenko and Wanner method. Bacterial growth rate assays of each mutant were performed to identify S. Typhi genes involved in circumneutral and acid pH resistance. S. Typhi mutants deficient to growth at specific pH were evaluated in their capacity to invade and replicate in phagocytic cells.

Results

In this work, it is reported that S. Typhi ∆F4 (pH 4.5), S. Typhi ∆F44 (pH 4.5, 5.5, and 6.5), and S. Typhi ∆F73 (pH 4.5, 5.5, 6.5, and 7.5) were deficient to grow in the pH indicated. These three mutant strains were also affected in their ability to invade and replicate in human macrophages.

Conclusions

S. Typhi contains defined genomic regions that influence the survival at specific pH values, as well as the invasion and replication inside human cells. Thus, this genetic information probably allows the bacteria to survive in different human compartments for an efficient infection cycle.

Rutin-protected BisGMA-induced cytotoxicity, genotoxicity, and apoptosis in macrophages through the reduction of the mitochondrial apoptotic pathway and induction of antioxidant enzymes

Bisphenol-A-glycidyldimethacrylate (BisGMA) is a resin monomer frequently used in dentin restorative treatments. The leakage of BisGMA monomer from BisGMA-based polymeric resins can lead to cytotoxicity in macrophages. Rutin has various beneficial bioeffects, including antioxidation and antiinflammation. In this study, we found that pretreatment of RAW264.7 macrophages with rutin-inhibited cytotoxicity induced by BisGMA in a concentration-dependent manner. BisGMA-induced apoptosis, which was detected by levels of phosphatidylserine from the internal to the external membrane and formation of sub-G1, and genotoxicity, which was detected by cytokinesis-blocked micronucleus and single-cell gel electrophoresis assays, were inhibited by rutin in a concentration-dependent manner. Rutin suppressed the BisGMA-induced activation of caspase-3 and -9 rather than caspase-8. Rutin inhibited the activation of the mitochondrial apoptotic pathway, including cytochrome C release and mitochondria disruption, after macrophages were treated with BisGMA. Finally, BisGMA-induced reactive oxygen species (ROS) generation and antioxidant enzyme (AOE) deactivation could be reversed by rutin. Parallel trends were observed in the elevation of AOE activation and inhibition of ROS generation, caspase-3 activity, mitochondrial apoptotic pathway activation, and genotoxicity. These results suggested that rutin suppressed BisGMA-induced cytotoxicity through genotoxicity, the mitochondrial apoptotic pathway, and relatively upstream factors, including reduction of ROS generation and induction of AOE.

Cellular and Molecular Response of Macrophages THP-1 during Co-Culture with Inactive Trichophyton rubrum Conidia

Trichophyton rubrum is causing an increasing number of invasive infections, especially in immunocompromised and diabetic patients. The fungal invasive infectious process is complex and has not yet been fully elucidated. Therefore, this study aimed to understand the cellular and molecular mechanisms during the interaction of macrophages and T. rubrum. For this purpose, we used a co-culture of previously germinated and heat-inactivated T. rubrum conidia placed in contact with human macrophages cell line THP-1 for 24 h. This interaction led to a higher level of release of interleukins IL-6, IL-2, nuclear factor kappa beta (NF-κB) and an increase in reactive oxygen species (ROS) production, demonstrating the cellular defense by macrophages against dead fungal elements. Cell viability assays showed that 70% of macrophages remained viable during co-culture. Human microRNA expression is involved in fungal infection and may modulate the immune response. Thus, the macrophage expression profile of microRNAs during co-culture revealed the modulation of 83 microRNAs, with repression of 33 microRNAs and induction of 50 microRNAs. These data were analyzed using bioinformatics analysis programs and the modulation of the expression of some microRNAs was validated by qRT-PCR. In silico analysis showed that the target genes of these microRNAs are related to the inflammatory response, oxidative stress, apoptosis, drug resistance, and cell proliferation.

Functional consequences of a close encounter between microglia and brain-infiltrating monocytes during CNS pathology and repair

Neuroinflammation is recognized as an important factor contributing to the development and progression of several central nervous system (CNS) disorders. Upon CNS trauma or disease, parenchymal microglia highly proliferate and accumulate in and around the lesion site. In addition, blood-derived monocytes can infiltrate the inflamed CNS in response to cellular damage and/or a compromised blood-brain barrier. Both microglia and infiltrating monocytes are characterized by multiple functional states and can either display highly proinflammatory properties or promote resolution of inflammation and tissue regeneration. Despite sharing some basic immunologic functions, microglia and monocytes display many distinctive features, which ultimately define their contribution to neuropathology. Understanding how the innate immune system participates to brain disease is imperative to identify novel treatment options for CNS inflammatory disorders. In this context, existing and newly developed in vitro platforms for disease modeling are fundamental tools to investigate and modulate microglia and monocyte immune functions within a specific neuropathologic context. In this review, we first briefly summarize the current knowledge on microglia and monocyte ontogenesis, as well as their complex and interconnected contributions to the development of various CNS pathologies. Following the well-recognized concept that both microglia and monocytes can either exert neuroprotective functions or exacerbate tissue damage, we provide a comprehensive overview of cellular models currently available for in vitro study of neuroinflammatory responses. In this context, we highlight how simplified single-cell models may not always correctly recapitulate in vivo biology, hence future research should move toward novel models with higher and multicellular complexity.

High-Content Screening of Eukaryotic Kinase Inhibitors Identify CHK2 Inhibitor Activity Against Mycobacterium tuberculosis

A screen of a eukaryotic kinase inhibitor library in an established intracellular infection model identified a set of drug candidates enabling intracellular killing of Mycobacterium tuberculosis (M.tb). Screen validity was confirmed internally by a Z′ = 0.5 and externally by detecting previously reported host-targeting anti-M.tb compounds. Inhibitors of the CHK kinase family, specifically checkpoint kinase 2 (CHK2), showed the highest inhibition and lowest toxicity of all kinase families. The screen identified and validated DDUG, a CHK2 inhibitor, as a novel bactericidal anti-M.tb compound. CHK2 inhibition by RNAi phenocopied the intracellular inhibitory effect of DDUG. DDUG was active intracellularly against M.tb, but not other mycobacteria. DDUG also had extracellular activity against 4 of 12 bacteria tested, including M.tb. Combined, these observations suggest DDUG acts in tandem against both host and pathogen. Importantly, DDUG’s validation highlights the screening and analysis methodology developed for this screen, which identified novel host-directed anti-M.tb compounds.

Preclinical Models of Nontuberculous Mycobacteria Infection for Early Drug Discovery and Vaccine Research

Nontuberculous mycobacteria (NTM) represent an increasingly prevalent etiology of soft tissue infections in animals and humans. NTM are widely distributed in the environment and while, for the most part, they behave as saprophytic organisms, in certain situations, they can be pathogenic, so much so that the incidence of NTM infections has surpassed that of Mycobacterium tuberculosis in developed countries. As a result, a growing body of the literature has focused attention on the critical role that drug susceptibility tests and infection models play in the design of appropriate therapeutic strategies against NTM diseases. This paper is an overview of the in vitro and in vivo models of NTM infection employed in the preclinical phase for early drug discovery and vaccine development. It summarizes alternative methods, not fully explored, for the characterization of anti-mycobacterial compounds.

Modulating Tumor-Associated Macrophage Polarization by Synthetic and Natural PPARγ Ligands as a Potential Target in Breast Cancer

Activation of peroxisome proliferator-activated receptor gamma (PPARγ) elicits anti-proliferative effects on different tumor cells, including those derived from breast cancer. PPARγ is also expressed in several cells of the breast tumor microenvironment, among which tumor associated macrophages (TAMs) play a pivotal role in tumor progression and metastasis. We explored the ability of synthetic and natural PPARγ ligands to modulate TAM polarization. The ligands included rosiglitazone (BRL-49653), and two docosahexaenoic acid (DHA) conjugates, N-docosahexaenoyl ethanolamine (DHEA) and N-docosahexaenoyl serotonin (DHA-5-HT). Human THP-1 monocytic cells were differentiated into M0, M1 and M2 macrophages that were characterized by qRT-PCR, ELISA and western blotting. A TAM-like phenotypic state was generated by adding two different breast cancer cell conditioned media (BCC-CM) to the cultures. Macrophages exposed to BCC-CM concomitantly exhibited M1 and M2 phenotypes. Interestingly, rosiglitazone, DHEA and DHA-5-HT attenuated cytokine secretion by TAMs, and this effect was reversed by the PPARγ antagonist GW9662. Given the key role played by PPARγ in the crosstalk between cancer cells and TAMs in tumor progression, its activation via endogenous or synthetic ligands may lead to novel strategies that target both epithelial neoplastic cells and the tumor microenvironment.

2'-5'-Oligoadenylate synthetase-like protein inhibits intracellular M. tuberculosis replication and promotes proinflammatory cytokine secretion

Host cytoplasmic surveillance pathways are known to elicit type I interferon (IFN) responses which are crucial to antimicrobial defense mechanisms. Oligoadenylate synthetase-like (OASL) protein has been extensively characterized as a part of the anti-viral mechanism, however a number of transcriptomic studies reveal its upregulation in response to infection with a wide variety of intracellular bacterial pathogens. To date, there is no evidence documenting the role (if any) of OASL during mycobacterium tuberculosis infection. Using two pathogenic strains differing in virulence only, as well as the non-pathogenic M. bovis BCG strain, we observed that pathogenicity and virulence strongly induced OASL expression after 24 h of infection. Further, we observed that OASL knock down led to a significant increase in M. tb CFU counts 96 h post-infection in comparison to the respective controls. Luminex revealed that OASL silencing significantly decreased IL-1β, TNF-α and MCP-1 secretion in THP-1 cells and had no effect on IL-10 secretion. We therefore postulate that OASL regulates pro-inflammatory mediators such as cytokines and chemokines which suppress intracellular mycobacterial growth and survival.