IL-34 deficiency impairs FOXP3+ Treg function in a model of autoimmune colitis and decreases immune tolerance homeostasis

Bromodomain-Containing 4 Is a Positive Regulator of Interleukin-34 Production in the Gut

Experimental evidence suggests that, in the inflamed gut of inflammatory bowel disease (IBD) patients, interleukin-34 (IL-34) triggers detrimental signaling pathways. Factors/mechanisms regulating IL-34 production in IBD remain poorly characterized. Bromodomain-containing 4 (BRD4), a transcriptional and epigenetic regulator, is over-expressed in IBD, and studies in cancer cells suggest that BRD4 might positively control IL-34 expression. This study aimed to assess whether, in IBD, BRD4 regulates IL-34 expression. In IBD, there was an up-regulation of both IL-34 and BRD4 compared to the controls, and the two proteins co-localized in both lamina propria mononuclear cells (LPMCs) and epithelial cells. Flow cytometry analysis of CD45+ LPMCs confirmed that the percentages of IL-34- and BRD4-co-expressing cells were significantly higher in IBD than in the controls and showed that more than 80% of the IL-34-positive CD45-LPMCs expressed BRD4. IL-34 and BRD4 were mainly expressed by T cells and macrophages. IL-34 expression was reduced in IBD LPMCs transfected with BRD4 antisense oligonucleotide and in the colons of mice with dextran sulfate sodium-induced colitis treated with JQ1, a pharmacological inhibitor of BRD4. These data indicate that BRD4 is a positive regulator of IL-34 in IBD, further supporting the pathogenic role of BRD4 in IBD-associated mucosal inflammation.

CRISPR-Cas9 applications in T cells and adoptive T cell therapies

T cell immunity is central to contemporary cancer and autoimmune therapies, encompassing immune checkpoint blockade and adoptive T cell therapies. Their diverse characteristics can be reprogrammed by different immune challenges dependent on antigen stimulation levels, metabolic conditions, and the degree of inflammation. T cell-based therapeutic strategies are gaining widespread adoption in oncology and treating inflammatory conditions. Emerging researches reveal that clustered regularly interspaced palindromic repeats-associated protein 9 (CRISPR-Cas9) genome editing has enabled T cells to be more adaptable to specific microenvironments, opening the door to advanced T cell therapies in preclinical and clinical trials. CRISPR-Cas9 can edit both primary T cells and engineered T cells, including CAR-T and TCR-T, in vivo and in vitro to regulate T cell differentiation and activation states. This review first provides a comprehensive summary of the role of CRISPR-Cas9 in T cells and its applications in preclinical and clinical studies for T cell-based therapies. We also explore the application of CRISPR screen high-throughput technology in editing T cells and anticipate the current limitations of CRISPR-Cas9, including off-target effects and delivery challenges, and envisioned improvements in related technologies for disease screening, diagnosis, and treatment.

T Cell Subsets and Immune Homeostasis

T cells are a heterogeneous group of cells that can be classified into different subtypes according to different classification methods. The body's immune system has a highly complex and effective regulatory network that allows for the relative stability of immune system function. Maintaining proper T cell homeostasis is essential for promoting protective immunity and limiting autoimmunity and tumor formation. Among the T cell family members, more and more T cell subsets have gradually been characterized. In this chapter, we summarize the functions of some key T cell subsets and their impact on immune homeostasis.

Genetic and Immunohistochemistry Tools to Visualize Rat Macrophages In Situ

Macrophages contribute to many aspects of development and homeostasis, innate and acquired immunity, immunopathology, and tissue repair. Every tissue contains an abundant resident macrophage population. Inflammatory stimuli promote the recruitment of monocytes from the blood and their adaptation promotes the removal of the stimulus and subsequent restoration of normal tissue architecture. Dysregulation of this response leads to chronic inflammation and tissue injury. In many tissues, their differentiation and survival are dependent on the colony stimulating factor 1 receptor (CSF1R) signalling axis, which is highly conserved across all vertebrates. Complete loss of either CSF1R or its cognate ligands, colony stimulating factor 1 (CSF1), and interleukin 34 (IL-34), results in the loss of many tissue-resident macrophage populations. This provides a useful paradigm to study macrophages.There are many tools used to visualize tissue-resident macrophages and their precursors, monocytes, in mice and humans. Particularly in mice there are genetic tools available to delete, enhance and manipulate monocytes and macrophages and their gene products to gain insight into phenotype and function. The laboratory rat has many advantages as an experimental model for the understanding of human disease, but the analytical resources are currently more limited than in mice. Here, we describe available genetic models, antibodies, and immunohistochemistry (IHC) methods that may be used to visualize tissue-resident macrophages in rats.

MTHFD2 ablation in T cells protects against heart transplant rejection by perturbing IRF4/PD-1 pathway through the metabolic-epigenetic nexus

BACKGROUND

One-carbon metabolism supports the activation, proliferation, and function of multiple immune cells. However, researchers have not clearly determined whether and how one-carbon metabolic enzymes contribute to heart transplant rejection.

METHODS

We investigated the dynamic metabolic adaptation in grafts during heart transplant rejection by conducting transcriptomics, metabolomics and single-cell RNA sequencing studies of cardiac tissue from human and mouse heart transplant recipients. We also assessed the expression of the one-carbon metabolic enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) in cardiac grafts by immunofluorescence and flow cytometry assays. Then we constructed a murine heart transplant model with T cell-specific Mthfd2 knockout mice, analyzed T cells function by flow cytometry assays and enzyme-linked immunospot assays, and studied the mechanism by Cleavage Under Targets and Tagmentation assays. Finally, we studied the effect of a pharmacological inhibitor of MTHFD2 in humanized skin transplant model.

RESULTS

We revealed that the one-carbon metabolism enzyme MTHFD2 was a hallmark of alloreactive T cells and was linked to T cell proliferation and function after exposure to alloantigen. And, Mthfd2 ablation prevented murine heart transplant rejection. Mechanistically, we found Mthfd2 ablation affected the interferon regulatory factor 4/programmed death-1 pathway through a metabolic-epigenetic mechanism involving H3K4me3. Furthermore, we found that inhibiting MTHFD2 attenuated human allograft rejection in a humanized skin transplant model.

CONCLUSIONS

These data show that the one-carbon metabolic enzyme MTHFD2 serves as a metabolic checkpoint of alloreactive T cells and suggest that it may be a potential therapeutic target for heart transplant rejection.

Significance of IL-34 and SDC-1 in the pathogenesis of RA cells and preclinical models

IL-34 shares a common receptor with M-CSF, while it can bind to other distinct receptors including protein-tyrosine phosphatase zeta (PTPζ), and syndecan1 (SDC-1). In physiological conditions, IL-34 has a critical role in the maintenance and development of Langerhans and microglial cells in part through PTPζ ligation. Conversely, in autoimmune diseases such as rheumatoid arthritis (RA), SDC-1-induced phosphorylation of M-CSFR was responsible for the pathological effect of IL-34 in patient cells and/or preclinical models. Intriguingly, enrichment of IL-34 is strongly linked to rheumatoid factor (RF), disease activity score (DAS)28, erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), and radiographic progression. In parallel, IL-34-induced naïve cell reprogramming into glycolytic RA CD14+CD86+GLUT1+ macrophage was dysregulated via M-CSFR or SDC-1 antibody therapy. Moreover, the inflammatory and erosive imprints of IL-34 arthritic mice were mitigated by glucose uptake inhibition and SDC-1, or RAG deficiency through nullifying macrophage metabolic rewiring and their ability to advance Th1/Th17 cell polarization. Consistently, IL-34-/- and SDC-1-/- mice could effectively impair CIA joint inflammation, osteoclast formation, and neovascularization by restraining monocyte infiltration as well as suppressing the inflammatory macrophage and T effector cell reconfiguration via metabolic deactivation. In conclusion, targeting IL-34/SDC-1 signaling, or its interconnected metabolites can uniquely intercept the crosstalk between glycolytic RA myeloid and lymphoid cells and their ability to trigger arthritis.

Interleukin 34 in Disease Progressions: A Comprehensive Review

IL-34, a cytokine, discovered a decade before and is known to be a colony stimulating factor CSF-1 receptor (CSF-1R) ligand. Along with CSF-1R, it also interacts with syndecan-1 receptors and protein-tyrosine phosphatase (PTP-ζ). Hence, IL-34 takes part in a number of biological activities owing to its involvement in different signaling pathways. This review was done to analyze the recent studies on the functions of IL-34 in progression of diseases. The role of IL-34 under the physiological and pathological settings is studied by reviewing current data. In the last ten years, studies suggested that the IL-34 was involved in the regulation of morbid states such as inflammatory diseases, infections, transplant rejection, autoimmune diseases, neurologic diseases, and cancer. In general, the involvement of IL-34 is observed in many serious health ailments like metabolic diseases, heart diseases, infections and even cancer. As such, IL-34 can be regarded as a therapeutic target, potential biomarker or as a therapeutic tool, which ought to be assessed in future research activities.

Interleukin-34 deficiency aggravates development of colitis and colitis-associated cancer in mice

BACKGROUND

Although expression of interleukin (IL)-34 is upregulated in active ulcerative colitis (UC), the molecular function and underlying mechanism are largely unclear.

AIM

To investigate the function of IL-34 in acute colitis, in a wound healing model and in colitis-associated cancer in IL-34-deficient mice.

METHODS

Colitis was induced by administration of dextran sodium sulfate (DSS), and carcinogenesis was induced by azoxymethane (AOM). Whether the impact of IL-34 on colitis was dependent on macrophages was validated by depletion of macrophages in a murine model. The association between IL-34 expression and epithelial proliferation was studied in patients with active UC.

RESULTS

IL-34 deficiency aggravated murine colitis in acute colitis and in wound healing phase. The effect of IL-34 on experimental colitis was not dependent on macrophage differentiation and polarization. IL-34-deficient mice developed more tumors than wild-type mice following administration of AOM and DSS. No significant difference was shown in degree of cellular differentiation in tumors between wild-type and IL-34-deficient mice. IL-34 was dramatically increased in the active UC patients as previously reported. More importantly, expression of IL-34 was positively correlated with epithelial cell proliferation in patients with UC.

CONCLUSION

IL-34 deficiency exacerbates colonic inflammation and accelerates colitis-associated carcinogenesis in mice. It might be served as a potential therapeutic target in UC.

Interleukin-34-regulated T-cell responses in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a multifaceted etiology, which primarily affects and results in the deterioration of the synovium of patients. While the exact etiology of RA is still largely unknown, there is growing interest in the cytokine interleukin-34 (IL-34) as a driver or modulator of RA pathogenesis on the grounds that IL-34 is drastically increased in the serum and synovium of RA patients. Several studies have so far revealed the relationship between IL-34 levels and RA disease progression. Nevertheless, the significance and role of IL-34 in RA have remained ambiguous, as illustrated by two most recent studies, which reported contrasting effects of genetic IL-34 deletion in RA. Of note, IL-34 is a macrophage growth factor and is increasingly perceived as a master regulator of T-cell responses in RA via macrophage-dependent as well as T cell-intrinsic mechanisms. In this regard, several studies have demonstrated that IL-34 potentiates helper T-cell (Th) responses in RA, whereas studies also suggested that IL-34 alleviates synovial inflammation, potentially by inducing regulatory T-cells (Treg). Herein, we provide an overview of the current understanding of IL-34 involvement in RA and outline IL-34-mediated mechanisms in regulating T-cell responses in RA.