TLR4-NOX2 axis regulates the phagocytosis and killing of Mycobacterium tuberculosis by macrophages

Immunohistochemical expression of TLR1, TLR2, TLR4, and TLR9 in the different types of lesions associated with bovine paratuberculosis

The factors that determine the appearance of the different pathologic forms associated with bovine paratuberculosis are not fully understood, but new research suggests a critical role of innate immunity. Toll-like receptors (TLRs) trigger the recognition of invading pathogens by innate immune cells and the onset of specific immune responses. The aim of this work was to assess, immunohistochemically, the expression of TLR1, TLR2, TLR4, and TLR9 in intestinal samples of 20 cows showing different types of paratuberculous lesions: uninfected controls, focal lesions, paucibacillary, and multibacillary diffuse forms. The majority of labeled cells were morphologically consistent with macrophages. A differential cell count was performed in the intestinal lamina propria, gut-associated lymphoid tissue, and mesenteric lymph node. TLR9 immunolabeling between the different types of lesions was compared using a complete H-score. Focal and diffuse paucibacillary forms contained significantly increased TLR2-expressing macrophages outside of the lesions compared with the controls and diffuse multibacillary forms, and moderate TLR9 immunolabeling within granulomas. In the multibacillary granulomatous lesions, the expression of TLR1 and TLR4 was observed as well as increased TLR9 expression compared with the rest of the groups. Differences in the predominance of one type or another of TLR allows us to elucidate the importance of the innate immune response and its possible role in the development of the different types of paratuberculosis lesions.

Early secretory antigen target of 6-kDa of Mycobacterium tuberculosis inhibits macrophage apoptosis and host defense via TLR2

Mycobacterium tuberculosis (M. tb) is an intracellular pathogen adept at evading the human immune system through a variety of mechanisms. During infection, M. tb secretes numerous virulence factors, including the 6 kDa early secretory antigen target (ESAT-6), which is produced by the ESX-1 secretion system. ESAT-6 plays a crucial role in host-pathogen interactions, either independently or in association with culture filtrate protein 10 (CFP-10). While some research has investigated the role of ESAT-6 in M. tb pathogenicity and vaccine development, its precise contribution to immune evasion and the cellular mechanisms involved remain poorly understood. To address this, we used cultured THP-1(A) macrophages to characterize the effects of secreted ESAT-6 on cellular host defenses and apoptosis. We found that ESAT-6 (5 μg/ml) inhibited M. tb-induced apoptosis in THP-1(A) macrophages by suppressing Toll-like receptor 2 (TLR2) through the Caspase-9/Caspase-3 pathway. Additionally, ESAT-6 reduced phagocytosis of M. tb by THP-1(A) macrophages by downregulating the production of interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), and interleukin-12 (IL-12). Furthermore, ESAT-6 diminished the bactericidal activity of macrophages by inducing reactive oxygen species (ROS) production. In parallel, our in silico analysis of differentially expressed genes in dendritic cells (DCs) infected with Bacille Calmette-Guérin (BCG) strains, with or without the region of difference-1 (RD1) gene, strongly suggests that ESAT-6, located within the RD1 region, modulates host defense functions and apoptosis in DCs during BCG infection. Collectively, these findings indicate that ESAT-6 plays a pivotal role in modulating the innate immune response of macrophages against M. tb by regulating macrophage recognition, phagocytosis, bactericidal activity, and apoptosis. Our study provides valuable insights into potential molecular targets for the development of innovative vaccines and therapeutic strategies against M. tb.

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.

Polyethylene microplastics promote nucleus pulposus cell senescence by inducing oxidative stress via TLR4/NOX2 axis

This study aimed to detect and characterize microplastics in intervertebral disc and investigate their effects and molecular mechanism on intervertebral disc degeneration. We collected intervertebral disc tissues from cervical, lumbar, and thoracolumbar segments and used Raman spectroscopy to identify and characterize microplastics. Among 80 samples, 47 contained microplastics, with polyethylene being the most prevalent type. To explore the effects of polyethylene microplastics (PE-MPs), we established a mouse model and a nucleus pulposus cell model. Reactive oxygen species (ROS) levels were assessed via immunofluorescence staining, cell viability was measured using the CCK-8 assay, and protein expression related to the Toll-like receptor 4 (TLR4)/NADPH oxidase 2 (NOX2) axis, oxidative stress, and nucleus pulposus degeneration were evaluated through western blotting and immunofluorescence staining. Results showed that PE-MPs exposure led to intervertebral disc degeneration by inducing oxidative stress and activating the TLR4 / NOX2 axis, which increased the senescence of nucleus pulposus cells. These effects were mitigated by TLR4 and NOX2 inhibitors. This research highlights the existence of microplastics in human intervertebral disc tissue and unveils a novel mechanism of nucleus pulposus cell senescence induced by PE-MPs, offering new avenues for clinical treatment of microplastic-related disc degeneration.

YY1 Contributes to the Inflammatory Responses of Mycobacterium tuberculosis-Infected Macrophages Through Transcription Activation-Mediated Upregulation TLR4

Tuberculosis (TB) is a chronic respiratory infectious disease and is induced by Mycobacterium tuberculosis (M.tb) infection. Macrophages serve as the cellular home in immunoreaction against M.tb infection, which is tightly regulated through Toll-like receptor 4 (TLR4) expression. Therefore, this study is designed to explore the role and mechanism of TLR4 in mycobacterial injury in human macrophages (THP-1 cells) after M.tb infection. Cell proliferation and apoptosis were assessed using MTT, EdU, and flow cytometry assays. ELISA kits were utilized to assess the levels of Interleukin-6 (IL-6), IL-1β, and tumor necrosis factor α (TNF-α). The binding between Yin-Yang-1 (YY1) and TLR4 promoter was predicted by JASPAR and verified using Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays. M.tb infection might repress THP-1 cell proliferation, and induce cell apoptosis and inflammatory response in a multiplicity of infection (MOI)-dependent manner. Moreover, M.tb infection increased the expression of TLR4 in HTP-1 cells in an MOI-dependent way, and its downregulation might overturn M.tb infection-mediated HTP-1 cell damage and inflammatory response. At the molecular level, YY1 was a transcription factor of TLR4 and promoted TLR4 transcription via binding to its promoter region. Besides, YY1 might activate the NF-kB signaling pathway via regulating TLR4. Meanwhile, TLR4 inhibitor BAY11-7082 might overturn the repression effect of TLR4 on M.tb-infected HTP-1 cell damage. YY1-activated TLR4 might aggravate mycobacterial injury in human macrophages after M.tb infection by the NF-kB pathway, providing a promising therapeutic target for TB treatment.

Proton pump inhibitor effect on macrophage and neutrophil function: a systematic review

Background

Proton pump inhibitors (PPIs) are one of the most used drugs worldwide. While generally considered safe, the usage of PPIs is associated with several adverse outcomes including acute infectious diseases. PPIs influence macrophage and neutrophil function although a systematic review has never been undertaken. The purpose of this systematic review was to determine the potential mechanisms of how PPI-induced inhibition of macrophage and neutrophil function may increase infection risk in susceptible hosts.

Methods

A database search using Scopus and PubMed was performed to identify studies that investigated the effects of PPIs on neutrophils or macrophage function.

Results

The final screening yielded 21 English-language research articles that focused on the impacts of PPIs on the function of macrophages and neutrophils. PPI mechanistic effects included cytotoxic effects on polymorphonuclear neutrophils, inhibition of reactive oxygen species (ROS) and reactive nitrogen species, phagocytosis and phagosomal degradation, inhibition of chemotaxis and migration, altering Toll-like receptor signaling and p38 protein phosphorylation in immune cells, and altering neutrophil and macrophage gene expression.

Discussion

The impact of PPIs on MΦs and neutrophils regarding their role in the immune response to bacterial pathogens was summarized. PPI effects on macrophages and neutrophils occurred due to the therapeutic mechanism of PPIs, the protonation of sulfhydryl groups and the subsequent formation of a disulfide bond, and other pleiotropic manners. Given the common use of PPIs, these results highlight the necessity to optimize PPI use and stewardship to curtail unnecessary drug use.

Polyphenols have unique cellular effects that are distinct from antioxidant function in Toll-like receptor 4-mediated inflammation in RAW264.7 macrophage-like cells

Plant polyphenols are bioactive compounds touted for their antioxidant effects, and this is often the primary attribute used to explain their health benefits. However, we hypothesize that polyphenols have molecular properties independent of antioxidant function. The objective of this study was to investigate whether polyphenols had distinct molecular effects compared to pure antioxidants. RAW 264.7 macrophages were pretreated with either TEMPOL, a superoxide scavenger, N-acetyl cysteine, a hydroxyl radical and hydrogen peroxide scavenger, or polyphenol extracts from blackberry, blueberry, raspberry, strawberry, kale, and baru nut. After 1 hour of pretreatment, cells were treated with lipopolysaccharides (100 ng/mL) for an additional 6 hour. Antioxidants and polyphenol extracts elicited antioxidant effects in vitro; however, polyphenols regulated redox proteins in a distinct, protective manner, whereas antioxidants, TEMPOL, and N-acetyl cysteine, did not. Additionally, distinct effects were observed in downstream Toll-like receptor 4 signaling and transcriptional activity of inflammatory proteins. We conclude that polyphenols have unique molecular effects that are independent of just their free radical scavenging capacity. This work advances our molecular understanding of how polyphenols act to target inflammation.

2-(3-(Chloromethyl)benzoyloxy)benzoic Acid reduces prostaglandin E-2 concentration, NOX2 and NFKB expression, ROS production, and COX-2 expression in lipopolysaccharide-induced mice

INTRODUCTION

Inflammation is a fundamental response to various insults, including microbial invasion and tissue injury. While aspirin (ASA) has been widely used for its anti-inflammatory properties, its adverse effects and limitations highlight the need for novel therapeutic alternatives. Recently, a novel salicylic acid derivative, 2-((3-(chloromethyl)benzoyl)oxy)benzoic acid (3-CH2Cl), has emerged as a potential substitute for ASA, offering a simpler, environmentally friendly synthesis and a promising safety profile.

AIM OF THE STUDY

This research aims to evaluate the anti-inflammatory mechanism of 3-CH2Cl in a lipopolysaccharide (LPS)-induced mouse model, focusing on its effects on prostaglandin E-2 (PGE-2) concentration, NOX2 and NFkB expression, ROS production, and COX-2 expression.

MATERIAL AND METHODS

Utilizing BALB/C mice subjected to LPS-induced inflammation, we investigated the therapeutic potential of 3-CH2Cl. The study included synthesis and tablet preparation, experimental design, peripheral blood plasma PGE-2 measurement, splenocyte isolation and COX-2 expression analysis, nitric oxide and ROS measurement, and immunohistochemical analysis of NOX2 and NFkB expression.

RESULTS

3-CH2Cl significantly reduced PGE-2 levels (p = 0.005), NO concentration in liver homogenates (p = 0.005) and plasma (p = 0.0011), and expression of NOX2 and NFkB in liver (p < 0.0001) and splenocytes (p = 0.0036), demonstrating superior anti-inflammatory activity compared to ASA. Additionally, it showed potential in decreasing COX-2 expression in splenocytes.

CONCLUSION

3-CH2Cl exhibits potent anti-inflammatory properties, outperforming ASA in several key inflammatory markers in an LPS-induced inflammation model. The reduction of COX-2 expression, alongside the reduction of pro-inflammatory cytokines and oxidative stress markers, suggest it as a promising therapeutic agent for various inflammatory conditions.

Exploring host-pathogen interactions in the Dictyostelium discoideum-Mycobacterium marinum infection model of tuberculosis

Mycobacterium tuberculosis is a pathogenic mycobacterium that causes tuberculosis. Tuberculosis is a significant global health concern that poses numerous clinical challenges, particularly in terms of finding effective treatments for patients. Throughout evolution, host immune cells have developed cell-autonomous defence strategies to restrain and eliminate mycobacteria. Concurrently, mycobacteria have evolved an array of virulence factors to counteract these host defences, resulting in a dynamic interaction between host and pathogen. Here, we review recent findings, including those arising from the use of the amoeba Dictyostelium discoideum as a model to investigate key mycobacterial infection pathways. D. discoideum serves as a scalable and genetically tractable model for human phagocytes, providing valuable insights into the intricate mechanisms of host-pathogen interactions. We also highlight certain similarities between M. tuberculosis and Mycobacterium marinum, and the use of M. marinum to more safely investigate mycobacteria in D. discoideum.

RHBDL4-triggered downregulation of COPII adaptor protein TMED7 suppresses TLR4-mediated inflammatory signaling

The toll-like receptor 4 (TLR4) is a central regulator of innate immunity that primarily recognizes bacterial lipopolysaccharide cell wall constituents to trigger cytokine secretion. We identify the intramembrane protease RHBDL4 as a negative regulator of TLR4 signaling. We show that RHBDL4 triggers degradation of TLR4's trafficking factor TMED7. This counteracts TLR4 transport to the cell surface. Notably, TLR4 activation mediates transcriptional upregulation of RHBDL4 thereby inducing a negative feedback loop to reduce TLR4 trafficking to the plasma membrane. This secretory cargo tuning mechanism prevents the over-activation of TLR4-dependent signaling in an in vitro Mycobacterium tuberculosis macrophage infection model and consequently alleviates septic shock in a mouse model. A hypomorphic RHBDL4 mutation linked to Kawasaki syndrome, an ill-defined inflammatory disorder in children, further supports the pathophysiological relevance of our findings. In this work, we identify an RHBDL4-mediated axis that acts as a rheostat to prevent over-activation of the TLR4 pathway.

The reproductive and transgenerational toxicity of microplastics and nanoplastics: A threat to mammalian fertility in both sexes

Microplastics (MPs) and nanoplastics (NPs) are extensively distributed in the environment. However, a comprehensive review and in-depth discussion on the effects of MPs and NPs to reproductive capacity and transgenerational toxicity on mammals, especially on humans, is lacked. It is suggested that microplastics and nanoplastics could accumulate in mammalian reproductive organs and exert toxic effects on the reproductive system for both sexes. For males, the damage of microplastics consists of abnormal testicular and sperm structure, decreased sperm vitality, and endocrine disruption, which were caused by oxidative stress, inflammation, apoptosis of testicular cells, autophagy, abnormal cytoskeleton, and abnormal hypothalamic-pituitary-testicular axis. For females, the damage of microplastics includes abnormal ovary and uterus structure and endocrine disruption, which were caused by oxidative stress, inflammation, granulosa cell apoptosis, hypothalamic-pituitary-ovary axis abnormalities, and tissue fibrosis. For transgenerational toxicity, premature mortality existed in the rodent offspring after maternal exposure to microplastics. Among the surviving offspring, metabolic disorders, reproductive dysfunction, immune, neurodevelopmental, and cognitive disorders were detected, and these events directly correlated with transgenerational translocation of MPs and NPs. Studies on human-derived cells or organoids demonstrated that transgenerational toxicity studies for both sexes are yet in the phase of exploring suitable experimental models, and more detailed research on the threat of MPs and NPs to human fertility is still urgently needed. Further studies will help assess the MPs and NPs threat to public fertility and reproductive health risks.

BCG revaccination in adults enhances pro-inflammatory markers of trained immunity along with anti-inflammatory pathways

This study characterized mechanisms of Bacille Calmette-Guérin (BCG) revaccination-induced trained immunity (TI) in India. Adults, BCG vaccinated at birth, were sampled longitudinally before and after a second BCG dose. BCG revaccination significantly elevated tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 in HLA-DR+CD16-CD14hi monocytes, demonstrating induction of TI. Mycobacteria-specific CD4+ T cell interferon (IFN) γ, IL-2, and TNF-α were significantly higher in re-vaccinees and correlated positively with HLA-DR+CD16-CD14hi TI responses. This, however, did not translate into increased mycobacterial growth control, measured by mycobacterial growth inhibition assay (MGIA). Post revaccination, elevated secreted TNF-α, IL-1β, and IL-6 to "heterologous" fungal, bacterial, and enhanced CXCL-10 and IFNα to viral stimuli were also observed concomitant with increased anti-inflammatory cytokine, IL-1RA. RNA sequencing after revaccination highlighted a BCG and LPS induced signature which included upregulated IL17 and TNF pathway genes and downregulated key inflammatory genes: CXCL11, CCL24, HLADRA, CTSS, CTSC. Our data highlight a balanced immune response comprising pro- and anti-inflammatory mediators to be a feature of BCG revaccination-induced immunity.

Clinical manifestations and immune response to tuberculosis

Tuberculosis is a far-reaching, high-impact disease. It is among the top ten causes of death worldwide caused by a single infectious agent; 1.6 million tuberculosis-related deaths were reported in 2021 and it has been estimated that a third of the world's population are carriers of the tuberculosis bacillus but do not develop active disease. Several authors have attributed this to hosts' differential immune response in which cellular and humoral components are involved, along with cytokines and chemokines. Ascertaining the relationship between TB development's clinical manifestations and an immune response should increase understanding of tuberculosis pathophysiological and immunological mechanisms and correlating such material with protection against Mycobacterium tuberculosis. Tuberculosis continues to be a major public health problem globally. Mortality rates have not decreased significantly; rather, they are increasing. This review has thus been aimed at deepening knowledge regarding tuberculosis by examining published material related to an immune response against Mycobacterium tuberculosis, mycobacterial evasion mechanisms regarding such response and the relationship between pulmonary and extrapulmonary clinical manifestations induced by this bacterium which are related to inflammation associated with tuberculosis dissemination through different routes.

Inhibition of NADPH Oxidase (NOX) 2 Mitigates Colitis in Mice with Impaired Macrophage AMPK Function

Macrophage adenosine monophosphate-activated protein kinase (AMPK) limits the development of experimental colitis. AMPK activation inhibits NADPH oxidase (NOX) 2 expression, reactive oxygen species (ROS) generation, and pro-inflammatory cytokine secretion in macrophages during inflammation, while increased NOX2 expression is reported in experimental models of colitis and inflammatory bowel disease (IBD) patients. Although there are reductions in AMPK activity in IBD, it remains unclear whether targeted inhibition of NOX2 in the presence of defective AMPK can reduce the severity of colitis. Here, we investigate whether the inhibition of NOX2 ameliorates colitis in mice independent of AMPK activation. Our study identified that VAS2870 (a pan-Nox inhibitor) alleviated dextran sodium sulfate (DSS)-induced colitis in macrophage-specific AMPKβ1-deficient (AMPKβ1^LysM) mice. Additionally, VAS2870 blocked LPS-induced TLR-4 and NOX2 expression, ROS production, nuclear translocation of NF-κB, and pro-inflammatory cytokine secretion in bone marrow-derived macrophages (BMDMs) from AMPKβ1^LysM mice, whereas sodium salicylate (SS; AMPK β1 activator) did not. Both VAS2870 and SS inhibited LPS-induced NOX2 expression, ROS production, and pro-inflammatory cytokine secretions in bone marrow-derived macrophages (BMDMs) from wildtype (AMPKβ1^fl/fl) mice but only VAS2870 inhibited these effects of LPSs in AMPKβ1^LysM BMDMs. Furthermore, in macrophage cells (RAW 264.7), both SS and VAS2870 inhibited ROS production and the secretion of pro-inflammatory cytokines and reversed the impaired autophagy induced by LPSs. These data suggest that inhibiting NOX2 can reduce inflammation independent of AMPK in colitis.

IL-27 inhibits anti- Mycobacterium tuberculosis innate immune activity of primary human macrophages

Mycobacterium tuberculosis (M. tuberculosis) is an intracellular pathogen that primarily infects macrophages. Despite a robust anti-mycobacterial response, many times macrophages are unable to control M. tuberculosis. The purpose of this study was to investigate the mechanism by which the immunoregulatory cytokine IL-27 inhibits the anti-mycobacterial activity of primary human macrophages. We found concerted production of IL-27 and anti-mycobacterial cytokines by M. tuberculosis-infected macrophages in a toll-like receptor (TLR) dependent manner. Notably, IL-27 suppressed the production of anti-mycobacterial cytokines TNFα, IL-6, IL-1β, and IL-15 by M. tuberculosis-infected macrophages. IL-27 limits the anti-mycobacterial activity of macrophages by reducing Cyp27B, cathelicidin (LL-37), LC3B lipidation, and increasing IL-10 production. Furthermore, neutralizing both IL-27 and IL-10 increased the expression of proteins involved in LC3-associated phagocytosis (LAP) pathway for bacterial clearance, namely vacuolar-ATPase, NOX2, and RUN-domain containing protein RUBCN. These results implicate IL-27 is a prominent cytokine that impedes M. tuberculosis clearance.

The MerR-family regulator NmlR is involved in the defense against oxidative stress in Streptococcus pneumoniae

Streptococcus pneumoniae has to cope with the strong oxidant hypochlorous acid (HOCl), during host-pathogen interactions. Thus, we analyzed the global gene expression profile of S. pneumoniae D39 towards HOCl stress. In the RNA-seq transcriptome, the NmlR, SifR, CtsR, HrcA, SczA and CopY regulons and the etrx1-ccdA1-msrAB2 operon were most strongly induced under HOCl stress, which participate in the oxidative, electrophile and metal stress response in S. pneumoniae. The MerR-family regulator NmlR harbors a conserved Cys52 and controls the alcohol dehydrogenase-encoding adhC gene under carbonyl and NO stress. We demonstrated that NmlR senses also HOCl stress to activate transcription of the nmlR-adhC operon. HOCl-induced transcription of adhC required Cys52 of NmlR in vivo. Using mass spectrometry, NmlR was shown to be oxidized to intersubunit disulfides or S-glutathionylated under oxidative stress in vitro. A broccoli-FLAP-based assay further showed that both NmlR disulfides significantly increased transcription initiation at the nmlR promoter by RNAP in vitro, which depends on Cys52. Phenotype analyses revealed that NmlR functions in the defense against oxidative stress and promotes survival of S. pneumoniae during macrophage infections. In conclusion, NmlR was characterized as HOCl-sensing transcriptional regulator, which activates transcription of adhC under oxidative stress by thiol switches in S. pneumoniae.

Hsa_circ_0001204 modulates inflammatory response of macrophages infected by Mycobacterium tuberculosis via TLR4/NF-κB signalling pathway

Circular RNAs (circRNAs) play a vital role in the regulation of Mycobacterium tuberculosis (M.tb) by macrophages. In this project, the potential role of hsa_circ_0001204 in M.tb-infected macrophages is explored. Hsa_circ_0001204 was determined in the patients with tuberculosis (TB) and M.tb-infected macrophages. Its effect on the survival of M.tb and the apoptosis and inflammation of M.tb-infected macrophages was evaluated. Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) signalling was detected by western blotting and immunofluorescence. TB patients and M.tb-infected THP-1 cells showed the significant downregulation of hsa_circ_0001204. Upregulating hsa_circ_0001204 reduced M.tb survival and suppressed the apoptosis and inflammatory response of THP-1 cells. The TLR4/NF-κB signalling pathway could be inhibited by hsa_circ_0001204 overexpression, which was activated by M.tb-infection. Hsa_circ_0001204 confers protective effects in M.tb-infected THP-1 cells, at least partly via the inhibition of TLR4/NF-κB signalling pathway.

Modulating macrophage function to reinforce host innate resistance against Mycobacterium avium complex infection

Mycobacterium avium complex (MAC) is the main causative agent of infectious diseases in humans among nontuberculous mycobacteria (NTM) that are ubiquitous organisms found in environmental media such as soil as well as in domestic and natural waters. MAC is a primary causative agent of NTM-lung disease that threaten immunocompromised or structural lung disease patients. The incidence and the prevalence of M. tuberculosis infection have been reduced, while MAC infections and mortality rates have increased, making it a cause of global health concern. The emergence of drug resistance and the side effects of long-term drug use have led to a poor outcome of treatment regimens against MAC infections. Therefore, the development of host-directed therapy (HDT) has recently gained interest, aiming to accelerate mycobacterial clearance and reversing lung damage by employing the immune system using a novel adjuvant strategy to improve the clinical outcome of MAC infection. Therefore, in this review, we discuss the innate immune responses that contribute to MAC infection focusing on macrophages, chief innate immune cells, and host susceptibility factors in patients. We also discuss potential HDTs that can act on the signaling pathway of macrophages, thereby contributing to antimycobacterial activity as a part of the innate immune response during MAC infection. Furthermore, this review provides new insights into MAC infection control that modulates and enhances macrophage function, promoting host antimicrobial activity in response to potential HDTs and thus presenting a deeper understanding of the interactions between macrophages and MACs during infection.

Mycobacterium tuberculosis sRNA MTS2823 regulates the growth of the multidrug-resistant strain in macrophages

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a serious contagious disease. MTB-encoded small regulatory RNA (sRNA) MTS2823 was reported to be upregulated in the plasma of TB patients. Nevertheless, whether MTS2823 is implicated in MTB drug resistance is unclear. Human macrophage cell line THP-1 was infected with the drug-susceptible strain H37Rv or the multidrug-resistant (MDR) strain 8462. Colony-forming unit assay was implemented for evaluating intracellular growth of the MTB strains. Enzyme-linked immunosorbent assay was used for measurement of inflammatory cytokines. Real-time quantitative polymerase chain reaction was utilized to assess MTS2823 and recombinase A (recA) expression in strains 8462 and H37Rv. Nitric oxide (NO) production in the MDR strain-infected THP-1 cells was measured. In this study, MTS2823 was found to display a low level in the MDR strain. Overexpressing MTS2823 promoted intracellular growth of the MDR strain and inhibited inflammatory cytokine and NO production in infected THP-1 cells. RecA might be a target of MTS2823 in the MDR strain. Overall, MTB-encoded sRNA MTS2823 displays a low level and regulates the growth of the MDR strain in THP-1 cells by modulating recA.

Activation of Nrf2 modulates protective immunity against Mycobacterium tuberculosis infection in THP1-derived macrophages

Tuberculosis (TB), caused by mycobacterium tuberculosis (M. tuberculosis) infection, is one of the leading causes of death globally and poses a threat to public health. During infection, M. tuberculosis causes redox imbalance and dysfunctions of protective immunity. Transcription factor nuclear factor erythroid 2 (NF-E2)-related factor (Nrf2) is a major modulator of cellular redox homeostasis via transcriptional induction of cytoprotective genes to protect cell against the damage from insults. Thus, we hypothesize that Nrf2 may regulate protective immunity against M. tuberculosis. RNA-seq and immunoblotting results suggested that the expression of Nrf2 protein increased after M. tuberculosis infection, and decreased upon long-term M. tuberculosis infection, while Keap1 protein maintained a low expression level during M. tuberculosis infection. Furthermore, Nrf2 activator sulforaphane (SFN) decreased proinflammatory cytokines production, phagocytosis and host cell apoptosis, while increasing ROS levels and promoting autophagy in THP1 macrophages infected with M. tuberculosis. In addition, SFN-activated Nrf2 augmented bacterial killing by macrophages, which might be due to the regulation of protective immunity via Nrf2. Combined, our results extend the understanding of the complex innate immunity regulation by Nrf2 against mycobacterial infection. Also, these findings suggested that the regulation of Nrf2 signaling cascade could be used as a therapeutic target for the treatment of TB patients and the development of better anti-TB vaccines.

Combination of G-CSF and a TLR4 inhibitor reduce inflammation and promote regeneration in a mouse model of ACLF

BACKGROUND & AIMS

Acute-on-chronic liver failure (ACLF) is characterised by high short-term mortality, systemic inflammation, and failure of hepatic regeneration. Its treatment is a major unmet medical need. This study was conducted to explore whether combining TAK-242, a Toll-like receptor-4 (TLR4) antagonist, with granulocyte-colony stimulating factor (G-CSF), could reduce inflammation whilst enhancing liver regeneration.

METHODS

Two mouse models of ACLF were investigated. Chronic liver injury was induced by carbon tetrachloride; lipopolysaccharide (LPS) or galactosamine (GalN) were then administered as extrahepatic or hepatic insults, respectively. G-CSF and/or TAK-242 were administered daily. Treatment durations were 24 hours and 5 days in the LPS model and 48 hours in the GalN model.

RESULTS

In a mouse model of LPS-induced ACLF, treatment with G-CSF was associated with significant mortality (66% after 48 hours vs. 0% without G-CSF). Addition of TAK-242 to G-CSF abrogated mortality (0%) and significantly reduced liver cell death, macrophage infiltration and inflammation. In the GalN model, both G-CSF and TAK-242, when used individually, reduced liver injury but their combination was significantly more effective. G-CSF treatment, with or without TAK-242, was associated with activation of the pro-regenerative and anti-apoptotic STAT3 pathway. LPS-driven ACLF was characterised by p21 overexpression, which is indicative of hepatic senescence and inhibition of hepatocyte regeneration. While TAK-242 treatment mitigated the effect on senescence, G-CSF, when co-administered with TAK-242, resulted in a significant increase in markers of hepatocyte regeneration.

CONCLUSION

The combination of TAK-242 and G-CSF inhibits inflammation, promotes hepatic regeneration and prevents mortality in models of ACLF; thus, this combination could be a potential treatment option for ACLF.

LAY SUMMARY

Acute-on-chronic liver failure is associated with severe liver inflammation and poor short-term survival. Therefore, effective treatments are urgently needed. Herein, we have shown, using mouse models, that the combination of granulocyte-colony stimulating factor (which can promote liver regeneration) and TAK-242 (which inhibits a receptor that plays a key role in inflammation) could be effective for the treatment of acute-on-chronic liver failure.

microRNAs associated with the pathogenesis and their role in regulating various signaling pathways during Mycobacterium tuberculosis infection

Despite more than a decade of active study, tuberculosis (TB) remains a serious health concern across the world, and it is still the biggest cause of mortality in the human population. Pathogenic bacteria recognize host-induced responses and adapt to those hostile circumstances. This high level of adaptability necessitates a strong regulation of bacterial metabolic characteristics. Furthermore, the immune reponse of the host virulence factors such as host invasion, colonization, and survival must be properly coordinated by the pathogen. This can only be accomplished by close synchronization of gene expression. Understanding the molecular characteristics of mycobacterial pathogenesis in order to discover therapies that prevent or resolve illness relies on the bacterial capacity to adjust its metabolism and replication in response to various environmental cues as necessary. An extensive literature details the transcriptional alterations of host in response to in vitro environmental stressors, macrophage infection, and human illness. Various studies have recently revealed the finding of several microRNAs (miRNAs) that are believed to play an important role in the regulatory networks responsible for adaptability and virulence in Mycobacterium tuberculosis. We highlighted the growing data on the existence and quantity of several forms of miRNAs in the pathogenesis of M. tuberculosis, considered their possible relevance to disease etiology, and discussed how the miRNA-based signaling pathways regulate bacterial virulence factors.

Oxidative stress mediated by the TLR4/NOX2 signalling axis is involved in polystyrene microplastic-induced uterine fibrosis in mice

Microplastics (MPs), as a new environmental pollutant, have received widespread attention worldwide. Uterine fibrosis is one of the main factors of female reproductive disorders. However, it is unclear whether the female reproductive disorders caused by MPs are related to uterine fibrosis. Therefore, in this study, we constructed female mouse models exposed to polystyrene microplastics (PS-MPs). We found that PS-MP exposure resulted in endometrial thinning and severe collagen fibre deposition in female mice. Further mechanistic studies found that PS-MP exposure increased the expression of high mobility group Box 1 (HMGB1) and acetyl-HMGB1, further activating the Toll-like receptor 4/NADPH oxidase 2 (TLR4/NOX2) signalling axis and eventually causing oxidative stress. Afterwards, oxidative stress elicited the activation of Notch and the transforming growth factor β (TGF-β) signalling pathway, leading to increased levels of fibrotic proteins and collagen. Correspondingly, PS-MP treatment upregulated the expression of TLR4 and NOX2 and the level of reactive oxygen species (ROS) and increased the levels of fibrotic protein and collagen in mouse endometrial epithelial cells cultured in vitro. Conversely, inhibition of the TLR4/NOX2 signalling pathway effectively reduced the level of ROS in cells, weakened the upregulation of Notch and TGF-β signalling by PS-MPs, and efficiently reduced the expression of fibrotic and collagen genes. In summary, we demonstrated a new mechanism by which MPs induce uterine fibrosis in mice, that is, by inducing oxidative stress to activate the Notch and TGF-β signalling pathways by triggering the TLR4/NOX2 signalling axis. Targeting TLR4/NOX2 signalling may consequently prove to be an innovative therapeutic option that is effective in alleviating the reproductive toxicity of PS-MPs. Our study sheds new light on the reproductive toxicity of MPs and provides suggestions and references for comparative medicine and clinical medicine.

Toll-like receptor-mediated innate immune responses by recognition of the recombinant dormancy-associated Mycobacterium tuberculosis proteins Rv2659c and Rv1738

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) poses a major threat to the global public health. Importantly, latent tuberculosis infection (LTBI) still impedes the elimination of TB incidence since it has a substantial risk to develop active disease. A multi-stage subunit vaccine comprising active and latency antigens of Mtb has been raised as the promising vaccine to trigger immune protection against all stages of TB. Therefore, the discovery of new antigens that could trigger broad immune response is essential. While current development of TB vaccine mainly focuses on protective immunity mediated by adaptive immune response, the knowledge on triggering the innate immune response by antigens is still limited. We showed that recombinant dormancy-associated Mtb proteins Rv2659c and Rv1738 were recognized by human innate immune recognition molecules, Toll-like receptors (TLRs) 2 and 4 by using HEK-Blue™ hTLR2/hTLR4 systems. We further demonstrated that these two proteins activated phosphorylated NF-κB p65 (Ser536) in the human CD14+ blood cells. We also investigated that these two proteins significantly induced level of pro- and anti-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10 and TNF-α) which were mediated through TLR2 and TLR4 pathways in human peripheral blood mononuclear cells (hPBMCs). These findings suggest that proteins Rv2659c and Rv1738 stimulated innate immune response targeting TLR2 and TLR4 to produce inflammatory cytokines, and their benefits would be valuable for the development of an effective prophylactic tuberculosis vaccine.

β-hydroxybutyrate impairs monocyte function via the ROS-NLR family pyrin domain-containing three inflammasome (NLRP3) pathway in ketotic cows

Cows with ketosis display severe metabolic stress and immune dysfunction which renders them more susceptible to infections. Monocytes, one of the major subtypes of white blood cells, play an important role in innate immune defense against infections. Thus, the aim of this study was to investigate alterations in immune function, reactive oxygen species (ROS) production and activity of the NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway in monocytes (CD14+) of cows with clinical ketosis (CK). Twelve healthy multiparous Holstein cows [blood β-hydroxybutyrate (BHB) concentration &lt; 1.2 mM] and 12 cows with CK (BHB &gt; 3.0 mM) at 3 to 14 days in milk were used for blood sample collection. To determine effects of BHB on phagocytosis, ROS and protein abundance of the NLRP3 inflammasome pathway in vitro, monocytes isolated from healthy cows were treated with 3.0 mM BHB for 0, 6, 12 or 24 h. Dry matter intake (22.7 vs. 19.0 kg) was lower in cows with CK. Serum concentrations of fatty acids (0.30 vs. 0.88 mM) and BHB (0.52 vs. 3.78 mM) were greater in cows with CK, whereas concentration of glucose was lower (4.09 vs. 2.23 mM). The adhesion, migration and phagocytosis of monocytes were lower in cows with CK, but apoptosis and ROS content were greater. Protein abundance of NLRP3, cysteinyl aspartate specific proteinase 1 (caspase 1) and interleukin-1B p17 (IL1B p17) were greater in monocytes of cows with CK, while abundance of NADPH oxidase isoform 2 (NOX2) was lower. Compared with 0 h BHB, ROS content and apoptosis were greater in the monocytes challenged for 6, 12 or 24 h BHB. Compared with 0 h BHB, protein abundance of NLRP3, caspase 1, IL1B p17 and concentration of IL1B in medium were greater in the monocytes challenged for 6, 12 or 24 h BHB. However, compared with 0 h BHB, protein abundance of NOX2 and phagocytosis of monocytes were lower in the monocytes challenged for 6, 12 or 24 h BHB. Overall, the data suggested that exogenous BHB activated the ROS-NLRP3 pathway, which might be partly responsible for immune dysfunction of dairy cows with CK.

Role of TLR4 signaling on Porphyromonas gingivalis LPS-induced cardiac dysfunction in mice

Oral infections, particularly periodontitis, are a well-established risk factor for cardiovascular diseases, although the molecular mechanisms involved remain elusive. The aims of the present study were to investigate the effects of lipopolysaccharide derived from Porphyromonas gingivalis (PG-LPS) on cardiac function in mice, and to elucidate the underlying mechanisms. Mice (C57BL/6) were injected with PG-LPS (0.8 mg/kg/day) with or without an inhibitor of Toll-like receptor 4 (TLR4) signaling (TAK-242, 0.8 mg/kg/day) for 4 weeks. Left ventricular ejection function was significantly decreased at 1 week (from 67 ± 0.5 to 58 ± 1.2%) and remained low at 4 weeks (57 ± 1.0%). The number of apoptotic myocytes was increased (approximately 7.4-fold), the area of fibrosis was increased (approximately 3.3-fold) and the number of 8-hydroxydeoxyguanosine-positive myocytes, a sensitive indicator of oxidative DNA damage, was increased (approximately 7.6-fold) at 4 weeks in the heart of PG-LPS treated mice. However, levels of various serum pro-inflammatory cytokines in PG-LPS-treated mice were similar to those in control mice. The impairment of cardiac function in PG-LPS-treated mice appears to involve activation of TLR4-NADPH oxidase (NOX) 4 signaling, leading to abundant production of reactive oxygen species and Ca²⁺ leakage from sarcoplastic reticulumn induced by calmodulin kinase II (CaMKII)-mediated phosphorylation of phospholamban (at Thr-17) and ryanodine receptor 2 (at Ser-2448). Pharmacological inhibition of TLR4 with TAK-242 attenuated the changes in cardiac function in PG-LPS-treated mice. Our results indicate that TLR4-NOX4 signaling may be a new therapeutic target for treatment of cardiovascular diseases in patients with periodontitis.

Hyperphosphorylated tau self-assembles into amorphous aggregates eliciting TLR4-dependent responses

Soluble aggregates of the microtubule-associated protein tau have been challenging to assemble and characterize, despite their important role in the development of tauopathies. We found that sequential hyperphosphorylation by protein kinase A in conjugation with either glycogen synthase kinase 3β or stress activated protein kinase 4 enabled recombinant wild-type tau of isoform 0N4R to spontaneously polymerize into small amorphous aggregates in vitro. We employed tandem mass spectrometry to determine the phosphorylation sites, high-resolution native mass spectrometry to measure the degree of phosphorylation, and super-resolution microscopy and electron microscopy to characterize the morphology of aggregates formed. Functionally, compared with the unmodified aggregates, which require heparin induction to assemble, these self-assembled hyperphosphorylated tau aggregates more efficiently disrupt membrane bilayers and induce Toll-like receptor 4-dependent responses in human macrophages. Together, our results demonstrate that hyperphosphorylated tau aggregates are potentially damaging to cells, suggesting a mechanism for how hyperphosphorylation could drive neuroinflammation in tauopathies.

Strongylocentrotus nudus Eggs Polysaccharide Enhances Macrophage Phagocytosis Against E.coli Infection by TLR4/STAT3 Axis

Antibiotics resistance is one of the most significant public health threats globally. Strategies that strengthen host defenses to control pathogen infection has become a hot research field. Macrophages are part of early host defense mechanisms, and are activated via host pattern recognition receptors (PRRs), such as Toll-like receptor 4 (TLR4), which then facilitates phagocytosis and elimination of invading pathogens. However, few activators of PRRs have been approved for clinical use because of their toxic effects. This study aimed to investigate whether Strongylocentrotus nudus eggs polysaccharide (SEP), a non-toxic extract from seafood, contributes to host defense against bacterial infection. Results showed that SEP promoted bacterial clearance by enhancing phagocytosis by macrophages during E. coli infection in vitro, but was inhibited by TLR4 specific inhibitor TAK-242, STAT3 inhibitor Stattic or blockade of CD64. In addition, SEP protected mice from E. coli induced mortality, reduced pulmonary inflammation and inhibited dissemination of bacteria to organs, while TAK-242 retarded the protection of SEP. Overall, SEP strengthened innate host defense and improved the outcome in bacterial infection, suggesting that SEP could be used as a potential immunomodulator in host-directed therapies.

MIR337-3p Enhances Mycobacterial Pathogenicity Involving TLR4/MYD88 and STAT3 Signals, Impairing VDR Antimicrobial Response and Fast-Acting Immunity

Active form of vitamin D (VitD) enhances human innate immunity against Mycobacterium tuberculosis (Mtb) infection. Our previous studies showed that MIR337-3p was highly expressed in lymphocytes of tuberculosis (TB) patients. Here, we identified the mechanism of MIR337-3p in the regulation of fast-acting anti-TB immunity by inhibiting VitD-dependent antimicrobial response pathways. While high-level MIR337-3p expression was induced by mycobacterial infection in cellular models and mice, TB patients exhibited significantly increased MIR337-3p in CD14⁺ monocytes/macrophages, innate-like Vγ2⁺ T cells, and CD8⁺ lymphocytes containing natural killer (NK)/innate lymphoid cells. MIR337-3p promoted the mycobacterial entry/infection and replication/growth in host target cells: macrophages and lung epithelial cells. Such MIR337-3p-enhanced pathogenicity coincided with the MIR337-3p depression of VitD-dependent antimicrobial response of cytochrome P450, family 27, subfamily b, polypeptide 1 (CYP27B1)/Beta-defensin 4 (DEFB4A)/ cathelicidin antimicrobial peptide CAMP pathways. Surprisingly, single MIR337-3p species could specifically target both the Toll-like receptor 4 (TLR4) and signal transducer and activator of transcription 3 (STAT3) 3′-untranslated regions (UTRs) to depress the TLR4/MYD88 and STAT3 signals and impair either of the two signals inhibiting the VitD-dependent antimicrobial pathways in macrophages. Concurrently, human peripheral blood mononuclear cells (PBMCs) expressing high-level MIR337-3p exhibited a reduced ability of innate cell populations to mount fast-acting cellular immunity against intracellular mycobacterial infection. Furthermore, a higher expression of Mir337-3p after mycobacterial infection of mice coincided with much greater colony-forming unit (CFU) counts in lungs and even the death of infected animals, whereas Mir337-3p inhibitor treatment of infected mice reduced Mir337-3p levels and reversed Mir337-3p-mediated increases in CFU counts. Thus, TB-driven single MIR337-3p species could specifically target/impair both TLR4/MYD88 and STAT3 activation signals, inhibiting VitD-dependent antimicrobial response and fast-acting anti-TB immunity, leading to enhanced pathogenicity.

MicroRNA‑502‑3p promotes Mycobacterium tuberculosis survival in macrophages by modulating the inflammatory response by targeting ROCK1

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (M. tuberculosis) infection and has the highest mortality rate of any single infectious disease worldwide. The aim of the present study was to investigate the function of microRNA (miR)-502-3p in M. tuberculosis-infected macrophages. The Gene Expression Omnibus database was used to analyze miR-502-3p expression in patients with TB and healthy individuals. THP-1 and RAW 264.7 cells were transfected with miR-502-3p mimic, miR-502-3p inhibitor, pcDNA3.1-ROCK1 or their negative controls. The expression levels of miR-502-3p and inflammatory cytokines were evaluated using reverse transcription-quantitative PCR. The colony-forming unit assay was performed to assess the survival of M. tuberculosis in macrophages, and Toll-like receptor (TLR)4/NF-κB signaling pathway-associated protein expression levels were detected by western blotting. The nuclear translocation of NF-κB p65 was detected via immunocytochemistry. TargetScan was used to predict the binding sites between miR-502-3p and ROCK1. The interaction between miR-502-3p and Rho-associated coiled-coil-forming protein kinase 1 (ROCK1) was confirmed using a dual-luciferase reporter assay; ROCK1 was demonstrated to be a direct target gene of miR-502-3p. Results from the present study demonstrated that miR-502-3p expression was significantly increased during M. tuberculosis infection in macrophages. Upregulation of miR-502-3p expression levels significantly enhanced the survival of intracellular M. tuberculosis. IL-6, TNF-α, and IL-1β mRNA expression levels were significantly upregulated during M. tuberculosis infection but were downregulated by miR-502-3p overexpression. Moreover, miR-502-3p mimics transfection significantly downregulated TLR4/NF-κB signaling pathway-associated protein expression and significantly reduced nuclear transcription of NF-κB in M. tuberculosis-infected macrophages. ROCK1 overexpression reversed the miR-502-3p inhibitory effect on cytokine production in M. tuberculosis-infected macrophages. In conclusion, miR-502-3p/ROCK1 may serve an anti-inflammatory role and may improve the survival of M. tuberculosis within macrophages, which may provide a promising therapeutic target for TB.

Roles of PRR-Mediated Signaling Pathways in the Regulation of Oxidative Stress and Inflammatory Diseases

Oxidative stress is a major contributor to the pathogenesis of various inflammatory diseases. Accumulating evidence has shown that oxidative stress is characterized by the overproduction of reactive oxygen species (ROS). Previous reviews have highlighted inflammatory signaling pathways, biomarkers, molecular targets, and pathogenetic functions mediated by oxidative stress in various diseases. The inflammatory signaling cascades are initiated through the recognition of host cell-derived damage associated molecular patterns (DAMPs) and microorganism-derived pathogen associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs). In this review, the effects of PRRs from the Toll-like (TLRs), the retinoic acid-induced gene I (RIG-I)-like receptors (RLRs) and the NOD-like (NLRs) families, and the activation of these signaling pathways in regulating the production of ROS and/or oxidative stress are summarized. Furthermore, important directions for future studies, especially for pathogen-induced signaling pathways through oxidative stress are also reviewed. The present review will highlight potential therapeutic strategies relevant to inflammatory diseases based on the correlations between ROS regulation and PRRs-mediated signaling pathways.

TARM-1 Is Critical for Macrophage Activation and Th1 Response in Mycobacterium tuberculosis Infection

T cell-interacting activating receptor on myeloid cells 1 (TARM-1) is a novel leukocyte receptor expressed in neutrophils and macrophages. It plays an important role in proinflammatory response in acute bacterial infection, but its immunomodulatory effects on chronic Mycobacterium tuberculosis infections remain unclear. TARM-1 expression was significantly upregulated on CD14^high monocytes from patients with active pulmonary tuberculosis (TB) as compared that on cells from patients with latent TB or from healthy control subjects. Small interfering RNA knockdown of TARM-1 reduced expression levels of proinflammatory cytokines IL-12, IL-18, IL-1β, and IL-8 in M. tuberculosis-infected macrophages, as well as that of HLA-DR and costimulatory molecules CD83, CD86, and CD40. Moreover, TARM-1 enhanced phagocytosis and intracellular killing of M. tuberculosis through upregulating reactive oxygen species. In an in vitro monocyte and T cell coculture system, blockade of TARM-1 activity by TARM-1 blocking peptide suppressed CD4⁺ T cell activation and proliferation. Finally, administration of TARM-1 blocking peptide in a mouse model of M. tuberculosis infection increased bacterial load and lung pathology, which was associated with decreased macrophage activation and IFN-γ production by T cell. Taken together, these results, to our knowledge, demonstrate a novel immune protective role of TARM-1 in M. tuberculosis infection and provide a potential therapeutic target for TB disease.

Trained immunity contributes to the prevention of Mycobacterium tuberculosis infection, a novel role of autophagy

Mycobacterium tuberculosis (M. tuberculosis) is the pathogen which causes tuberculosis (TB), a significant human public health threat. Co-infection of M. tuberculosis and the human immunodeficiency virus (HIV), emergence of drug resistant M. tuberculosis, and failure to develop highly effective TB vaccines have limited control of the TB epidemic. Trained immunity is an enhanced innate immune response which functions independently of the adaptive/acquired immune system and responds non-specifically to reinfection with invading agents. Recently, several studies have found trained immunity has the capability to control and eliminate M. tuberculosis infection. Over the past decades, however, the consensus was adaptive immunity is the only protective mechanism by which hosts inhibit M. tuberculosis growth. Furthermore, autophagy plays an essential role in the development of trained immunity. Further investigation of trained immunity, M. tuberculosis infection, and the role of autophagy in this process provide new possibilities for vaccine development. In this review, we present the general characteristics of trained immunity and autophagy. We additionally summarize several examples where initiation of trained immunity contributes to the prevention of M. tuberculosis infection and propose future directions for research in this area.

Interaction of TLR4 and TLR8 in the Innate Immune Response against Mycobacterium Tuberculosis

The interaction and crosstalk of Toll-like receptors (TLRs) is an established pathway in which the innate immune system recognises and fights pathogens. In a single nucleotide polymorphisms (SNP) analysis of an Indian cohort, we found evidence for both TLR4-399T and TRL8-1A conveying increased susceptibility towards tuberculosis (TB) in an interdependent manner, even though there is no established TLR4 ligand present in Mycobacterium tuberculosis (Mtb), which is the causative pathogen of TB. Docking studies revealed that TLR4 and TLR8 can build a heterodimer, allowing interaction with TLR8 ligands. The conformational change of TLR4-399T might impair this interaction. With immunoprecipitation and mass spectrometry, we precipitated TLR4 with TLR8-targeted antibodies, indicating heterodimerisation. Confocal microscopy confirmed a high co-localisation frequency of TLR4 and TLR8 that further increased upon TLR8 stimulation. The heterodimerisation of TLR4 and TLR8 led to an induction of IL12p40, NF-κB, and IRF3. TLR4-399T in interaction with TLR8 induced an increased NF-κB response as compared to TLR4-399C, which was potentially caused by an alteration of subsequent immunological pathways involving type I IFNs. In summary, we present evidence that the heterodimerisation of TLR4 and TLR8 at the endosome is involved in Mtb recognition via TLR8 ligands, such as microbial RNA, which induces a Th1 response. These findings may lead to novel targets for therapeutic interventions and vaccine development regarding TB.

Lipopolysaccharide induces platelet activation in HIV patients: the role of different viral load patterns

OBJECTIVES

This study aimed to assess whether gut-derived lipopolysaccharide (LPS) could affect platelet function in HIV-1 patients with residual viral load.

METHODS

In 23 HIV-1 patients on effective antiretroviral treatment, 10 treatment-naïve HIV-1 subjects and 20 healthy subjects (HS), LPS, zonulin, markers of platelet activation and oxidative stress were evaluated. In vitro, platelets from HS were exposed to plasma from HIV-1-infected treated and untreated patients.

RESULTS

Compared with HS, LPS was higher in treated and treatment-naïve subjects with HIV-1 (7.7 ± 2.9, 80.9 ± 13.7 and 75.3 ± 22.6 pg/mL, P < 0.001 vs. HS) as well as serum zonulin (1.3 ± 0.5, 6.1 ± 1.5 and 5.3 ± 1.7 ng/mL, P < 0.001 vs. HS). LPS and zonulin were correlated in HIV patients (Spearman correlation coefficient (rS) = 0.73, P < 0.0001). Levels of soluble CD40 ligand (sCD40L), soluble P-selectin (sP-selectin) and thromboxane B₂ (TxB₂ ) were higher in HIV-1-treated and treatment-naïve subjects compared with HS as well as NADPH oxidase 2 (NOX2) activation and hydrogen peroxide (H₂ O₂ ) production. In vitro, sCD40L, sP-selectin and TxB₂ production, NOX2 activation and p47^phox phosphorylation were higher in platelets exposed to plasma from HIV-1 patients with different viral load compared with the exposure to plasma from HS. This effect was blunted in platelets pre-treated with TLR4 or TLR7 inhibitors.

CONCLUSIONS

Low-grade endotoxaemia and persistent viraemia increase platelet function with a mechanism mediated by NOX2 in patients with HIV-1 infection.

Innate Immune Pattern Recognition Receptors of Mycobacterium tuberculosis: Nature and Consequences for Pathogenesis of Tuberculosis

Innate immunity against Mycobacterium tuberculosis is a critical early response to prevent the establishment of the infection. Despite recent advances in understanding the host-pathogen dialogue in the early stages of tuberculosis (TB), much has yet to be learnt. The nature and consequences of this dialogue ultimately determine the path of infection: namely, either early clearance of M. tuberculosis, or establishment of M. tuberculosis infection leading to active TB disease and/or latent TB infection. On the frontline in innate immunity are pattern recognition receptors (PRRs), with soluble factors (e.g. collectins and complement) and cell surface factors (e.g. Toll-like receptors and other C-type lectin receptors (Dectin 1/2, Nod-like receptors, DC-SIGN, Mincle, mannose receptor, and MCL) that play a central role in recognising M. tuberculosis and facilitating its clearance. However, in a 'double-edged sword' scenario, these factors can also be involved in enhancement of pathogenesis as well. Furthermore, innate immunity is also a critical bridge in establishing the subsequent adaptive immune response, which is also responsible for granuloma formation that cordons off M. tuberculosis infection, establishing latency and acting as a reservoir for bacterial persistence and dissemination of future disease. This chapter discusses the current understanding of pattern recognition of M. tuberculosis by innate immunity and the role this plays in the pathogenesis and protection against TB.

Melatonin Ameliorates Inflammation and Oxidative Stress by Suppressing the p38MAPK Signaling Pathway in LPS-Induced Sheep Orchitis

Gram-negative bacterial infections of the testis can lead to infectious orchitis, which negatively influences steroid hormone synthesis and spermatogenesis. Lipopolysaccharide (LPS), a major component of the Gram-negative bacterial cell wall, acts via toll like receptors 4 (TLR4) to trigger innate immune responses and activate nuclear factor kappa B signaling. The protective mechanisms of melatonin on LPS-induced infectious orchitis have not been reported. Herein, we developed an LPS-induced sheep infectious orchitis model. In this model, the phagocytic activity of testicular macrophages (TM) was enhanced after melatonin treatment. Moreover, we found that melatonin suppressed secretion of TM pro-inflammatory factors by suppressing the p38MAPK pathway and promoting Leydig cell testosterone secretion. Expressions of GTP cyclohydrolase-I and NADPH oxidase-2 were reduced by melatonin while heme oxygenase-1 expression was up-regulated. Thus, melatonin reduced the severity of LPS-induced orchitis by stimulating antioxidant activity. The results of this study provide a reference for the treatment of acute infectious orchitis.

Paeonol promotes the phagocytic ability of macrophages through confining HMGB1 to the nucleus

Phagocytosis is a basic immune response to the pathogens invading. Immunosuppression may occur in diseases like sepsis and cancer, and cause a low phagocytic ability of phagocytes. High mobility group protein B1 (HMGB1) is a DNA chaperone which is closely related to the phagocytosis. Nonetheless, its influence on phagocytosis is still controversial. We found that paeonol could inhibit the translocation of HMGB1 from the nucleus to the cytoplasm, it may have an impact on phagocytosis. In the present study, we performed in vivo and in vitro experiments to investigate the influence of paeonol on phagocytosis. Zymosan was used to test the phagocytic function of macrophages. Our results showed that paeonol promotes the phagocytosis of macrophages through confining HMGB1 to the nucleus. Through interacting with P53, the nuclear HMGB1 keep it in the nucleus and decrease the negative influence of P53 on the phosphorylation of Focal Adhesion Kinase (FAK). The increasing of phosphorylated FAK promotes the formation of pseudopod and enhances the phagocytic ability of macrophages.

The TLR4-MyD88 Signaling Axis Regulates Lung Monocyte Differentiation Pathways in Response to Streptococcus pneumoniae

Streptococcus pneumoniae is the main cause of bacterial pneumonia, a condition that currently produces significant global morbidity and mortality. The initial immune response to this bacterium occurs when the innate system recognizes common motifs expressed by many pathogens, events driven by pattern recognition receptors like the Toll-like family receptors (TLRs). In this study, lung myeloid-cell populations responsible for the innate immune response (IIR) against S. pneumoniae, and their dependence on the TLR4-signaling axis, were analyzed in TLR4-/- and Myeloid-Differentiation factor-88 deficient (MyD88-/-) mice. Neutrophils and monocyte-derived cells were recruited in infected mice 3-days post-infection. Compared to wild-type mice, there was an increased bacterial load in both these deficient mouse strains and an altered IIR, although TLR4-/- mice were more susceptible to bacterial infection. These mice also developed fewer alveolar macrophages, weaker neutrophil infiltration, less Ly6Chigh monocyte differentiation and a disrupted classical and non-classical monocyte profile. The pro-inflammatory cytokine profile (CXCL1, TNF-α, IL-6, and IL-1β) was also severely affected by the lack of TLR4 and no induction of Th1 was observed in these mice. The respiratory burst (ROS production) after infection was profoundly dampened in TLR4-/- and MyD88-/- mice. These data demonstrate the complex dynamics of myeloid populations and a key role of the TLR4-signaling axis in the IIR to S. pneumoniae, which involves both the MyD88 and TRIF (Toll/IL-1R domain-containing adaptor-inducing IFN-β) dependent pathways.

Epigenetic regulation of apoptosis via the PARK7 interactome in peripheral blood mononuclear cells donated by tuberculosis patients vs. healthy controls and the response to treatment: A systems biology approach

AIMS

The aims of our study were to determine for the first time differentially expressed genes (DEGs) and enriched molecular pathways involving the PARK7 interactome in PBMCs donated from tuberculosis patients.

METHODS

Data on a previously reconstructed PARK7 interactome (Vavougios et al., 2017) from datasets GDS4966 (Case-Control) and GDS4781 (Treatment Series) were retrieved from the Gene Expression Omnibus (GEO) repository. Gene Enrichment analysis was performed via the STRING algorithm and the GeneTrail2 software.

RESULTS

17 and 22 PARK7 interactores were determined as DEGs in the active TB vs HD and Treatment Series subset analyses, correspondingly, associated with significantly enriched pathways (FDR <0.05) involving p53 and PTEN mediated, stress responsive apoptosis regulation pathways. The treatment subset was characterized by the emergence of an additional layer of transcriptional regulation mediated by polycomb proteins among others, as well as TLR-mediated and cytokine survival signaling. Finally, the enrichment of a Parkinson's disease signature including PARK7 interactors was determined by its differential regulation both in the exploratory analyses (FDR = 0.024), as well as the confirmatory analyses (FDR = 1.81e^-243).

CONCLUSIONS

Our in silico analysis revealed for the first time the role of PARK7's interactome in regulating the epigenetics of the PBMC lifecycle and Mtb symbiosis.

Addition of High Molecular Weight Hyaluronic Acid to Fibroblast-Like Stromal Cells Modulates Endogenous Hyaluronic Acid Metabolism and Enhances Proteolytic Processing and Secretion of Versican

We have examined the effect of exogenous linear chain high molecular weight hyaluronic acid (HMW HA) on endogenously synthesized hyaluronic acid (HA) and associated binding proteins in primary cultures of fibroblast-like stromal cells that were obtained by collagenase digestion of the murine peripatellar fat pad. The cultures were expanded in DMEM that was supplemented with fetal bovine serum and basic fibroblast growth factor (bFGF) then exposed to macrophage-colony-stimulating factor (MCSF) to induce macrophage properties, before activation of inflammatory pathways using E. coli lipopolysaccharide (LPS). Under all culture conditions, a significant amount of endogenously synthesized HA localized in LAMP1-positive lysosomal vesicles. However, this intracellular pool was depleted after the addition of exogenous HMW HA and was accompanied by enhanced proteolytic processing and secretion of de novo synthesized versican, much of which was associated with endosomal compartments. No changes were detected in synthesis, secretion, or proteolytic processing of aggrecan or lubricin (PRG4). The addition of HMW HA also modulated a range of LPS-affected genes in the TLR signaling and phagocytosis pathways, as well as endogenous HA metabolism genes, such as Has1, Hyal1, Hyal2, and Tmem2. However, there was no evidence for association of endogenous or exogenous HMW HA with cell surface CD44, TLR2 or TLR4 protein, suggesting that its physiochemical effects on pericelluar pH and/or ionic strength might be the primary modulators of signal transduction and vesicular trafficking by this cell type. We discuss the implications of these findings in terms of a potential in vivo effect of therapeutically applied HMW HA on the modification of osteoarthritis-related joint pathologies, such as pro-inflammatory and degradative responses of multipotent mesenchymal cells residing in the synovial membrane, the underlying adipose tissue, and the articular cartilage surface.

Thinking Outside the Box: Innate- and B Cell-Memory Responses as Novel Protective Mechanisms Against Tuberculosis

Tuberculosis (TB) is currently the deadliest infectious disease worldwide. Failure to create a highly effective vaccine has limited the control of the TB epidemic. Historically, the vaccine field has relied on the paradigm that IFN-γ-mediated CD4+ T cell memory responses are the principal correlate of protection in TB. Nonetheless, the demonstration that other cellular subsets offer protective memory responses against Mycobacterium tuberculosis (Mtb) is emerging. Among these are memory-like features of macrophages, myeloid cell precursors, natural killer (NK) cells, and innate lymphoid cells (ILCs). Additionally, the dynamics of B cell memory responses have been recently characterized at different stages of the clinical spectrum of Mtb infection, suggesting a role for B cells in human TB. A better understanding of the immune mechanisms underlying such responses is crucial to better comprehend protective immunity in TB. Furthermore, targeting immune compartments other than CD4+ T cells in TB vaccine strategies may benefit a significant proportion of patients co-infected with Mtb and the human immunodeficiency virus (HIV). Here, we summarize the memory responses of innate immune cells and B cells against Mtb and propose them as novel correlates of protection that could be harnessed in future vaccine development programs.

Extract from Coriolus versicolor fungus partially prevents endotoxin tolerance development by maintaining febrile response and increasing IL-6 generation

Endotoxin tolerance is defined as a reduced endotoxin-induced fever following repeated injections of lipopolysaccharide (LPS). Clinical examples of endotoxin tolerance include sepsis or cystic fibrosis. This state is characterized by inhibition of pro-inflammatory cytokines production and decrease in nuclear factor-kappa B (NF-κB) activation. Extract from Coriolus versicolor (CV) fungus is classified as a biological response modifier, which exhibits various biological activities, including immunopotentiating properties. The aim of study was to examine the effect of CV extract injection on body core temperature of Wistar rats during LPS-induced endotoxin tolerance. Body temperature was measured using biotelemetry. CV extract was injected intraperitoneally (100 mg kg^-1) 2 h prior to the first LPS peritoneal administration (50 μg/kg). Endotoxin tolerance was induced by three consecutive daily injections of LPS at the same dose. We also investigated the influence of CV extract pre-injection on the properties of peripheral blood mononuclear cells (PBMCs) isolated from LPS-treated rats in response to LPS stimulation ex vivo. PBMCs were isolated 2 h after the first LPS injection. After 24 h pre-incubation, the cells were stimulated with LPS (1 μg ml^-1) for 4 h. Our results revealed that CV extract partially prevents endotoxin tolerance through maintaining febrile response in rats following consecutive exposure to LPS. This state was accompanied by the ability of PBMCs isolated from rats injected with CV extract and LPS to release larger amounts of interleukin 6 and greater NF-κB activation in response to LPS stimulation ex vivo compared with the cells derived from rats injected only with LPS. Data also showed that CV extract augmented mitogenic effect of LPS on PBMCs and caused increase in reactive oxygen species generation. We concluded that CV extract, by a modifying effect on body temperature during endotoxin tolerance, can be consider as the immunostimulating agent, which prevents the non-specific refractoriness described in patients with sepsis or ischemia.

Specific function and modulation of teleost monocytes/macrophages: polarization and phagocytosis

Macrophages exist in most tissues and play a variety of functions in vertebrates. Teleost fish species are found in most aquatic environments throughout the world and are quite diverse for a group of vertebrate animals. Due to whole genome duplication and environmental adaptation, teleost monocytes/macrophages possess a variety of different functions and modulations compared with those of mammals. A deeper understanding of teleost monocytes/macrophages in the immune system will not only help develop teleost-specific methods of disease prevention but will also help improve our understanding of the various immune mechanisms in mammals. In this review, we summarize the differences in polarization and phagocytosis of teleost and mammalian macrophages to improve our understanding of the various immune mechanisms in vertebrates.

Significance of the Differential Peptidome in Multidrug-Resistant Tuberculosis

Most multidrug-resistant tuberculosis (MDR-TB) patients fail to receive a timely diagnosis and treatment. Therefore, we explored the differentially expressed peptides in MDR-TB compared with drug-susceptible tuberculosis (DS-TB) patients using LC-MS/MS and Ingenuity Pathway Analysis (IPA) to analyse the potential significance of these differentially expressed peptides. A total of 301 peptides were differentially expressed between MDR-TB and DS-TB groups. Of these, 24 and 16 peptides exhibited presented high (fold change ≥ 2.0, P < 0.05) and low (fold change ≤ −2.0, P < 0.05) levels in MDR-TB. Significant canonical pathways included the prothrombin activation system, coagulation system, and complement system. In the network of differentially expressed precursor proteins, lipopolysaccharide (LPS) regulates many precursor proteins, including four proteins correlated with organism survival. These four important differentially expressed proteins are prothrombin (F2), complement receptor type 2 (CR2), collagen alpha-2(V) chain (COL5A2), and inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4). After addition of CR2 peptide, IL-6 mRNA expression in THP-1 cells decreased significantly in dose- and time-dependent manners. Cumulatively, our study proposes potential biomarkers for MDR-TB diagnosis and enables a better understanding of the pathogenesis of MDR-TB. The functions of differentially expressed peptides, especially CR2, in MDR-TB require further investigation.

Anti-β2GPI/β2GPI induces neutrophil extracellular traps formation to promote thrombogenesis via the TLR4/MyD88/MAPKs axis activation

Antiphospholipid antibodies (aPLs) are a large group of heterogeneous antibodies that bind to anionic phospholipids alone or in combination with phospholipid binding proteins. Increasing evidence has converged to indicate that aPLs especially anti-β₂ glycoprotein I antibody (anti-β₂GPI) correlate with stroke severity and outcome. Though studies have shown that aPLs promote thrombus formation in a neutrophil-dependent way, the underlying mechanisms remain largely unknown. In the present study, we investigated the effect of anti-β₂GPI in complex with β₂GPI (anti-β₂GPI/β₂GPI) on neutrophil extracellular traps (NETs) formation and thrombus generation in vitro and in vivo. We found that anti-β₂GPI/β₂GPI immune complex induced NETs formation in a time- and concentration-dependent manner. This effect was mediated by its interaction with TLR4 and the production of ROS. We demonstrated that MyD88-IRAKs-MAPKs, an intracellular signaling pathway, was involved in anti-β₂GPI/β₂GPI-induced NETs formation. We also presented evidence that tissue factor was expressed on anti-β₂GPI/β₂GPI-induced NETs, and NETs could promote platelet aggregation in vitro. In addition, we identified that anti-β₂GPI/β₂GPI-induced NETs enhanced thrombus formation in vivo, and this effect was counteracted by using DNase I. Our data suggest that anti-β₂GPI/β₂GPI induces NETs formation to promote thrombogenesis via the TLR4/MyD88/MAPKs axis activation, and could be a potentially novel target for aPLs related ischemic stroke.