Journal of Leukocyte Biology最新文献

Mycobacterium tuberculosis (M. tb), the causative agent of tuberculosis (TB), is responsible for extreme mortality and morbidity across the globe. The bacteria have evolved multiple strategies for their successful prevalence. The emergence of multidrug-resistant TB (MDR-TB) has established the importance of eliciting host-pathogen interactions at cellular and molecular levels. Various pattern recognition receptors play determinant roles when encountering M. tb infection. Here, we investigated the regulation of key defense responses from Dectin-1 and Mincle during mycobacterial infection in THP-1-derived macrophages, the long-term hosts for mycobacteria. Our data indicate that infection of THP-1 macrophages with either M. bovis Bacillus Calmette-Guérin (BCG) or M. tb H37Rv increases the surface expression of Dectin-1 and Mincle. This increase translated directly to increased intracellular bacterial survival within macrophages. Likewise, M. bovis BCG infection of human peripheral blood mononuclear cell-derived macrophages also led to an increased expression of Dectin-1 and Mincle. Stimulation of Dectin-1 or Mincle along with BCG infection induces suppressor responses such as an attenuated oxidative burst and mitochondrial membrane potential intactness. In addition, decreased apoptosis and autophagy induction was also observed following stimulation of Dectin-1 and Mincle. Conversely, RNA interference-mediated knockdown of Dectin-1 or Mincle reversed the previous responses, resulting in higher oxidative burst, mitochondrial membrane potential disruption, increased mitochondrial reactive oxygen species production, and increased apoptosis. This results in a significant decrease in intracellular mycobacterial survival. These results point toward a well-orchestrated strategy of fine-tuning the host's defense machinery of Dectin-1 and Mincle adopted by mycobacteria to suppress protective responses mounted against it and prepare the macrophages for prolonged persistent infection.

Toll-like receptor (TLR) signaling is vital for antimicrobial macrophage function, and its dysregulation is associated with diseases such as lupus, multiple sclerosis, pulmonary fibrosis, and cancer. The Src-family kinase Lyn may have net activating or inhibitory effects on TLR signaling, yet distinct functions of the Lyn splice variants LynA and LynB in TLR signaling have not been investigated. We used isoform-specific Lyn knockout mice (LynAKO and LynBKO) to interrogate the contribution of each isoform to TLR signaling in bone-marrow-derived macrophages. Bulk RNA sequencing and cytokine analyses revealed that complete Lyn deficiency (LynKO) dampened TLR4- and TLR7-induced inflammatory gene expression and production of tumor necrosis factor but enhanced the expression of genes responsible for synthesizing the extracellular matrix and promoting proliferation. Despite reduced expression of total Lyn in single-isoform-knockout bone-marrow-derived macrophages, expression of either LynA or LynB alone was sufficient to preserve a wild-type-like transcriptome at steady state and after treatment with the TLR7 agonist R848. However, LynAKO and LynBKO macrophages did have impaired production of tumor necrosis factor in response to the TLR4 agonist lipopolysaccharide. Additionally, LynAKO and LynBKO macrophages were as hyperproliferative as LynKO cells. These data suggest that Lyn promotes macrophage activation in response to TLR signaling and restrains aberrant proliferation and matrix deposition in a dose-dependent rather than isoform-specific manner.

Neutrophils are central to immune responses in health and disease, and their ability to deform correlates with their functional responses. In health, reorganisation of the neutrophil cytoskeleton allows neutrophils to carry out their effector mechanisms. However, in the disease state, dysregulation of neutrophil cytoskeletal properties results in disruption of neutrophil structural integrity, in turn altering their immune response capabilities. We outline how actin and actin polymerisation are essential for cell processes, the role of actin in neutrophil function, and how disruption of actin can lead and contribute to a range of disease pathogeneses.

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipid-laden necrotic macrophages within blood vessels walls. GATA2 is a normally hematopoietic transcription factor which in the bone marrow helps maintain the proliferative, nondifferentiated phenotype of hematopoietic progenitors. Unexpectedly, GATA2 is upregulated in macrophages within atherosclerotic plaque, where it plays an unknown role in disease progression. Although GATA2 can be expressed from 2 promoters, we determined that the atherogenic stimuli oxidized low-density lipoprotein and tumor necrosis factor α induce GATA2 expression via the internal (IG) GATA2 promoter, with GATA2 transcription initiated by the transcription factors NF-κB, STAT1, and the aryl hydrocarbon receptor. GATA2 had a divergent effect on promoter activity, with GATA2 upregulating genes associated with stem cell maintenance, hematopoiesis, proliferation, reactive oxygen species production, and migration, while downregulating genes central to macrophage function including those for cholesterol efflux, pathogen phagocytosis, and the efferocytosis of apoptotic cells. Consequentially, GATA2-expressing macrophages had a proatherogenic phenotype typified by highly motile cells exhibiting poor cholesterol efflux and impaired phagocytosis and efferocytosis. These results indicate that GATA2 upregulation induces an immature, stem cell-like phenotype in atheroma macrophages, that may promote plaque cellularity while compromising atheroprotective mechanisms such as cholesterol clearance and apoptotic cell removal.

Rheumatoid arthritis is a prevalent autoimmune disorder with an elusive pathogenesis, hindering early detection and therapeutic advancements. This study focuses on CD39+ T cells, which play a significant role in rheumatoid arthritis, to identify diagnostic and therapeutic biomarkers. We analyzed single-cell RNA sequencing data from rheumatoid arthritis patients to identify differentially expressed genes associated with CD39+ T cells. We then cross-referenced these differentially expressed genes with those from normal and rheumatoid arthritis samples to extract a CD39+ T cell gene signature. Functional enrichment analysis and machine learning algorithms identified key hub genes and assessed their diagnostic efficacy. We identified 13 genes linked to crucial biological pathways, including T cell activation, leukocyte adhesion, and ferroptosis. Four genes, including PELI1, emerged as central to these processes. PELI1 showed remarkable diagnostic value and was upregulated in rheumatoid arthritis patients. We observed distinct immune cell infiltration patterns based on PELI1 expression and mapped out an lncRNA-miRNA-PELI1 network. We also identified 41 small molecule drugs as potential therapeutic candidates for rheumatoid arthritis. PELI1 is a promising diagnostic biomarker for RA, contributing to the pool of potential biomarkers for diagnosis and therapy. Our study provides new insights into the role of CD39+ T cells in rheumatoid arthritis and highlights potential therapeutic targets for future research.

Neutrophils are key players in inflammatory responses that are modulated by cytokines/chemokines and damage associated molecular patterns (DAMPs). Exercise induces acute neutrophilia, but little is known regarding recruitment of neutrophil subsets (banded (CD16dim/CD62Lbright) and hypersegmented (CD16bright/CD62Ldim) cells) and its relation with the liberation of markers of tissue damage. The aim of this study was to investigate the neutrophil compartment in response to a single bout of high-intensity endurance exercise and the association with tissue damage, cortisol and myocardial injury. Blood samples were prospectively collected from 35 athletes participating in a long-distance trail-run (before, directly after, and 24 h after exercise) for biomedical analysis. The neutrophil compartment was directly analyzed in the field by automated, mobile, flow cytometry. Linear regression analyses were performed for neutrophil (subset) counts vs markers of tissue damage (CK, LDH, and AST), cortisol and markers of cardiac injury. Neutrophilia was present directly after exercise, with the appearance of banded and hypersegmented neutrophils. This was accompanied by increased levels of markers of tissue damage, cortisol and cardiac troponins. Increased cortisol levels showed a positive correlation with the increase in cell counts of both banded and mature neutrophils. This correlation was not found for hypersegmented neutrophils. No relations were found between the neutrophil (subsets) and markers of tissue damage or cardiac troponins. This study demonstrates the recruitment of 3 distinct neutrophil subsets following a single bout of high-intensity endurance exercise. These results indicate an association between neutrophil recruitment after exercise and cortisol levels, rather than tissue damage or cardiac injury.

Macrophages detect lipopolysaccharide (LPS) through toll-like receptor 4 (TLR-4) on the cell surface which initiates a signaling cascade, resulting in the recruitment of regulatory factors to chromatin and subsequent expression of chemokine and cytokine genes. Primary response genes, marked by poised promoters and enhancers, are rapidly expressed after LPS stimulation, and their gene products activate secondary response genes via paracrine and autocrine signaling pathways. While the signaling cascades following macrophage activation are well understood, the dynamics of nucleosome architecture in promoter regions during early and late LPS responses remain unclear. Here, we stimulated THP-1 derived macrophages with LPS and assessed nucleosome distribution and MNase sensitivity across promoters at 8 time points spanning primary and secondary responses. We found that while nucleosome distribution was static over most promoters, LPS stimulation resulted in transient remodeling of a subset of innate immune gene promoters. We also observed distinct MNase sensitivity alterations in 2 phases which aligned with early and late gene expression patterns. Notably, while most Pol II promoters showed altered chromatin sensitivity, only a subset exhibited transcriptional changes, suggesting that widespread alterations in nucleosome distribution and sensitivity occur at promoters with or without alterations in gene expression. These findings provide new temporal insights into the transient and long-term effects of immune stimulation on promoter architecture and offer a methodological framework for additional time-resolved studies of chromatin remodeling in other systems.

Recent research suggests higher circulating lymphocyte counts may protect against colorectal cancer (CRC). However, the role of specific lymphocyte subtypes and activation states remain unclear. CD4+ T cells-a highly dynamic lymphocyte subtype-undergo gene expression changes upon activation that are critical to their effector function. Previous studies using bulk tissue have limited our understanding of their role in CRC risk to static associations. We applied Mendelian randomization (MR) and genetic colocalisation to evaluate causal relationships of gene expression on CRC risk across multiple CD4+ T cell subtypes and activation states. Genetic proxies were obtained from single-cell transcriptomic data, allowing us to investigate the causal effect of expression of 1,805 genes across CD4+ T cell activation states on CRC risk (78,473 cases; 107,143 controls). Analyses were stratified by CRC anatomical subsites and sex, with sensitivity analyses assessing whether the observed effect estimates were likely to be CD4+ T cell-specific. We identified 6 genes-FADS2, FHL3, HLA-DRB1, HLA-DRB5, RPL28, and TMEM258-with strong evidence for a causal role in CRC development (FDR-P < 0.05; colocalisation H4 > 0.8). Causal estimates varied by CD4+ T cell subtype, activation state, CRC subsite and sex. However, many of genetic proxies used to instrument gene expression in CD4+ T cells also act as eQTLs in other tissues, highlighting the challenges of using genetic proxies to instrument tissue-specific expression changes. We demonstrate the importance of capturing the dynamic nature of CD4+ T cells in understanding CRC risk, and prioritize genes for further investigation in cancer prevention.

The immune response to Trypanosoma cruzi infection relies on robust inflammatory activation of macrophages and proper CD8+ T cells function to control parasite replication. However, an exacerbated respiratory burst from macrophages can damage tissues where parasites reside, such as the heart and liver. Subsequent fibrotic repair in the heart contributes to cardiomyopathy in patients with chronic Chagas disease and in mouse models. Additionally, respiratory burst metabolites are implicated in the impairment of CD8+ T cell responses. While excessive reactive oxygen species production is associated with increased differentiation of Foxp3+ regulatory T cells, T cell receptor nitration occurs in the presence of high extracellular nitric oxide (NO) levels. Both mechanisms contribute to CD8+ T cell suppression during T. cruzi infection. In this study, we use metformin (Metf) to balance parasite control and immune-mediated tissue damage by modulating macrophage activation. We found that Metf ex vivo treatment in peritoneal macrophages (PEMs) from acutely infected mice led to reduced inducible NO synthase expression, decreased NO production, and lowered secretion of interleukin-1β, tumor necrosis factor, and IL-6. However, IL-12 levels increased and CD8+ T cells cocultured with these PEMs showed enhanced proliferation and interferon γ production. In vivo, Metf-treated infected mice exhibited lower parasitemia and improved CD8+ T cell functionality, potentially linked to reduced T cell receptor nitration and decreased regulatory T cell frequencies in the peritoneum, as well as reduced cardiac inflammation. These findings provide new insights into the inflammatory modulation exerted by Metf and its potential impact on CD8+ T cell response and Chagas disease outcome.

Metabolic remodeling is involved in multiple diseases, including tumors, acute and chronic inflammations, but our understanding of the molecular pathways remains limited. Neutrophils, as pivotal effector cells of the innate immune system, exhibit significant functional heterogeneity influenced by the hypoxic microenvironment, a prevalent pathological feature of diseases. Emerging evidence reveals that disease progression is tightly linked to this regulatory mechanism. This review focuses on the functional remodeling of neutrophils under hypoxic stress, systematically elucidates the mechanisms by which neutrophils monitor and respond to hypoxia, the metabolic and functional changes that occur in neutrophils under hypoxic conditions, and the impact of these changes on the progression of associated diseases. Furthermore, it provides several potential intervention targets and may offer insights for the treatment of disorders with hypoxic microenvironments.