Journal of Leukocyte Biology最新文献

Eosinophils (EOS), named after the Greek dawn goddess Eos, are multifunctional granulocytes with roles surpassing their well-established involvement in allergic diseases and parasitic infections. Herein, we highlighted the recent advancements in understanding the cellular structure, lineage development, surface receptors, and diverse phenotypes of EOS. In particular, we focused on their emerging roles in the tumor microenvironment and type 1 inflammatory responses. Additionally, we explored the cytokine signaling and transcription factor networks governing the differentiation of EOS, emphasizing the interplay among IL-5, IL-33, and GM-CSF. Notably, EOS exhibit phenotypic plasticity, with the ability to polarize into type 1 (E1) and type 2 (E2) subsets under different inflammatory conditions. This suggests their dual roles in antitumor and protumor activities. Our review underscores the potential of targeting EOS-specific receptors, including IL-5Rα and Siglec-8, for therapeutic interventions in EOS-related diseases. By combining recent findings on the metabolic milieu and interactions of EOS within complex tissue environments, we provide a comprehensive perspective on their physiological and pathological functions, paving the way for novel therapeutic strategies.

Tumor-associated macrophages (TAM) exert both pro- and anti-tumoral functions that influence cancer progression and patient prognosis. However, single-cell RNA sequencing (scRNA-seq) studies have revealed that TAM heterogeneity remains incompletely characterized. By performing an unbiased, integrated in silico analyses of publicly available scRNA-seq datasets, comprising samples from blood, tumor, and non-tumoral mammary tissue (NTMT) from both breast cancer (BRCA) patients and healthy individuals, we identified seven transcriptional signatures corresponding to distinct TAM subsets, exhibiting unique functional profiles, including heightened interferon responses, scavenging, and matrix remodeling, the latter two being characteristic of tissue repair. Notably, none of these subsets aligned with the M1/M2 classification of macrophage (Mφ) polarization. Interferon-associated genes were predominantly enriched in blood monocytes, whereas tissue-repair-associated-signatures were more abundant in tissue resident Mφ, suggesting that TAMs bearing these signatures resemble monocyte-derived or tissue-resident Mφs, respectively. Importantly, TAM subsets expressing interferon-associated genes were associated with improved survival compared to tissue-repairing TAMs in a BRCA cohort from The Cancer Genome Atlas (TCGA). Additionally, one signature was heightened in peripheral monocytes from BRCA patients compared with healthy individuals, which was experimentally validated in a pilot study of Mexican BRCA patients. We concluded that these signatures are a closer description of TAM heterogeneity in BRCA.

Extracellular vesicles (EVs) are essential components for intercellular communication, bioactive cargo trafficking, and homeostasis maintenance. The knowledge regarding the diverse functions and applications of EVs has continually expanded over the recent decade. The classification of eukaryotic EVs based on their biophysical or biochemical properties has failed to adequately capture the variety of biological effects attributed to these micro- and nano-vesicles. In this review, we specifically discuss the functional definition of EVs which possess decoying capabilities, including consequential biological interactions with toxins, pathogen- and damage- associated molecular patterns, and nutrients. We focus on the reported studies that highlight recent discoveries involving decoy EVs that intercept host immunity, further focusing on microbial pathogeneses as well as chronic illnesses. Lastly, we evaluate biomedical methodologies to suitably address research questions and uncover distinct decoying properties of these decoy EVs across various health and disease experimental settings.

Gamma-aminobutyric acid (GABA), a non-protein component amino acid, functions as an inhibitory neurotransmitter. Here, we showed that GABA levels are significantly elevated in the bone marrow (BM) liquid of patients with multiple myeloma (MM) compared to healthy donors (HDs). Moreover, BM GABA levels correlated with key clinical parameters, including plasma cell percentage, International Staging System (ISS) stage, and immunoglobulin subtype, highlighting its association with disease severity. Mechanistically, we identified glutamic acid decarboxylase 1 (GAD1) as a critical enzyme driving intracellular GABA production in MM cells, which promotes the survival and proliferation of MM cells. Additionally, GAD1-dependent GABA production supported MM progression by activating the GABA-B receptor, as demonstrated in vitro and in vivo, underscoring the pivotal role of this receptor axis. Further mechanistic investigations revealed that the GABA-B receptor axis enhances extracellular regulated kinases1/2 (ERK1/2) activity via cAMP downregulation, facilitating MM cell survival and proliferation. Taken together, our findings establish the GABA-B receptor-ERK1/2 axis as a central regulator of MM progression and propose it as a promising target for MM therapy.

Patients who survive sepsis experience a prolonged period of immunosuppression. This period is accompanied by the expansion of monocytic myeloid-derived suppressor cells (M-MDSCs), a subset of suppressive myeloid cells; however, the impact of M-MDSCs on the innate immune response to infection is not well understood. Here we investigate the effect of MDSCs on neutrophils, a critical component of the innate immune response, during bacterial infection. We found that M-MDSCs, differentiated from monocytes in vitro, impaired neutrophil chemotaxis to IL-8 in a simple microfluidic chemotactic device. We then integrated M-MDSCs and neutrophils into our 3D infection-on-a-chip device that incorporates key features of an infectious environment including an endothelial lumen, a collagen extracellular matrix, and a source of Pseudomonas aeruginosa. When M-MDSCs were present in the matrix during simulated infection with Pseudomonas aeruginosa, significantly fewer neutrophils extravasated from the lumen, and those that left traveled a shorter distance from the lumen edge. We found IL-10 secretion increased during infections in the presence of M-MDSCs and blocking IL-10 restored neutrophil extravasation, indicating IL-10 secretion reduces neutrophil extravasation in the presence of M-MDSCs. In summary, we demonstrated impaired neutrophil chemotaxis, extravasation, and migration in the presence of M-MDSCs during bacterial infection and found increased levels of IL-10 contribute to reduced extravasation, indicating that MDSCs play a role in regulating the immune environment, leading to a reduced neutrophil response to infection.

Monocytes play a fundamental role in the inflammatory response to diverse stimuli. A critical early step in the initiation of this response is the recruitment of monocytes from the bloodstream to sites of tissue injury. This migration is tightly regulated at the molecular level through interactions between vascular selectins and sialyl Lewis X (sLeX)-bearing glycoproteins on the surface of monocytes. Galectin-3, a β-galactoside-binding lectin with diverse immunological functions, has been linked to enhanced monocyte recruitment through mechanisms that are still being elucidated. Here, using a combination of genetic and pharmacological inhibition approaches, we show that galectin-3 enhances sLeX epitope biosynthesis in both mouse and human monocytes. This effect is mediated by transcriptional upregulation of α(1,3)-fucosyltransferase 7 (FUT7), a rate-limiting enzyme in sLeX synthesis. Furthermore, we demonstrate that restoring FUT7 activity in galectin-3-deficient monocytes rescues cell surface expression of sLeX. These findings reveal a previously unrecognized role for galectin-3 in regulating monocyte adhesion by directly influencing selectin ligand biosynthesis.

The Ets family transcription factor PU.1 plays multiple roles in hematopoiesis. PU.1 acts in a graded manner to regulate myeloid and lymphoid development with high expression levels promoting monopoiesis and low expression levels instructing B cell fate. It remains incompletely understood how PU.1 promotes monocyte development. In this study, we show that PU.1 activation upregulated, whereas PU.1 knockdown downregulated, the expression of c-Fos, Egr-1, and Egr-2, which are the immediate early response genes of the Erk1/2 pathway and have been shown to promote monopoiesis. A PU.1 mutant defective in c-Jun interaction was unable to upregulate the expression of c-Fos, Egr-1, and Egr-2, indicating that interaction with c-Jun is required for PU.1-mediated upregulation of c-Fos, Egr-1, and Egr-2. We further demonstrate that PU.1 bound to and transcriptionally activated the promoters of c-Fos, Egr-1, and Egr-2. Knockdown of c-Fos or Egr-1 favored neutrophil over monocyte development in response to PU.1 activation, which was associated with increased Gfi1 expression. Notably, PU.1-mediated upregulation of c-Fos, Egr-1, and Egr-2 was blocked upon inhibition of Erk1/2 signaling, which was also associated with an increase in Gfi1 expression and a shift toward neutrophil development at the expense of monopoiesis. Together, these results reveal a novel mechanism by which PU.1 acts to promote monopoiesis and a critical role of the Erk1/2 downstream targets c-Fos, Egr-1 and Egr-2 in PU.1-driven monocyte development.

IRGM proteins are associated with increased susceptibility to Crohn's disease, mycobacterial infections, sepsis, and other inflammatory diseases, but the cells in which they function in vivo have not been delineated. To address this, mice with conditional deletions of Irgm1 were created and challenged with model pathogens. Irgm1fl/flLyz2-Cre+ mice (a myeloid deletion) displayed marked susceptibility to infections with Salmonella typhimurium, Listeria monocytogenes, and Toxoplasma gondii, paralleling those of global Irgm1-/- mice. However, infections of Irgm1fl/flLyz2-Cre+ mice with Citrobacter rodentium showed no increase in susceptibility, contrasting with marked increases in Irgm1fl/flVav-Cre+ mice (a hematopoietic deletion). Macrophages from Irgm1fl/flLyz2-Cre+ mice displayed pathologies present in macrophages from global Irgm1-/- mice, validating the conditional deletion in myeloid cells. These results suggest that Irgm1 functioning in myeloid cells is critical for immune resistance to intracellular pathogens, while Irgm1 functioning in additional hematopoietic population(s) is required for resistance to extracellular pathogens in the intestinal lumen.

Host defense functions of neutrophils during infection critically depend on microbicidal and proteolytic proteins stored in primary, secondary, and tertiary granules that are released into the phagosome or into the extracellular space upon degranulation. Granules are generated during granulopoiesis, and impaired granule production or granule protein sorting has been linked to inefficient pathogen clearance resulting in recurrent bacterial and fungal infections. Here, we studied the role of secretory carrier associated membrane protein 3 (SCAMP3) for neutrophil defense functions. We generated Scamp3 knockout (KO) Hoxb8 cells and found that killing of Escherichia coli by Scamp3 KO Hoxb8 cell-derived neutrophils (dHoxb8 cells) was compromised as compared with control dHoxb8 cells in vitro. Mass spectrometric and Western blot analyses revealed a significant reduction of primary, secondary, and tertiary granule proteins in the genetic absence of Scamp3, resulting in a reduced overall granularity of these cells. Accordingly, degranulation was reduced in Scamp3 KO dHoxb8 cells compared with control dHoxb8 cells. Similarly, Scamp3 deficiency in zebrafish resulted in reduced neutrophil granularity in comparison with wild-type animals. However, neutrophil migration toward sites of E. coli infection was unaffected in scamp3 KO zebrafish larvae. In summary, SCAMP3 represents an important novel player in granule equipment and degranulation, with key functions in neutrophil defense mechanisms during host-pathogen interactions in vitro.

Evolutionarily conserved HOXA9 is a well-known player of hematopoiesis and leukemogenesis. However, the involvement of this transcription factor in CD4+ T cell development is largely unexplored. Th2 cells play a critical role in the pathogenesis of numerous autoimmune disorders. The development of this heterogenic subpopulation of cells is orchestrated by a consortium of factors including GATA3 and PU.1, among others. Here, we recognized the molecular regulation bestowed by HOXA9 in Th2 cell development. We found that overexpression of HOXA9 in Th2 cell leads to increased secretion of IL-10 while suppressing IL-4 and IL-13. Through promoter activity analysis, we determined the crucial role played by the structural domains of HOXA9 on Th2-specific cytokines. These findings further indicated the presence of other cofactors that contribute to the functional activity of HOXA9. Our findings demonstrated that HOXA9 can engage in physical interactions with PU.1 and PBX1, but not with GATA3, and exhibits direct binding to PU.1-specific chromosomal loci within Th2 cells. PBX1 overexpression stimulates the secretion of IL-4, IL-13, and IL-10. In contrast, the combined overexpression of HOXA9 and PBX1 suppresses IL-4 and IL-13 secretion but boosts IL-10 production. Taken together, the data suggest that PBX1 acts specifically as a coregulator for HOXA9 in the context of Th2 cell function. The contribution of HOXA9 and PBX1 is significantly more pronounced in the proximal promoter region of the Il10 gene. This study has significantly advanced our understanding of Th2 cell differentiation and cytokine production, regulated by HOXA9-PBX1 axis through interactions with other key transcription factors.