SLAMF7 engagement superactivates macrophages in acute and chronic inflammation

Low-frequency and rare genetic variants associated with rheumatoid arthritis risk

Rheumatoid arthritis (RA) has an estimated heritability of nearly 50%, which is particularly high in seropositive RA. HLA alleles account for a large proportion of this heritability, in addition to many common single-nucleotide polymorphisms with smaller individual effects. Low-frequency and rare variants, such as those captured by next-generation sequencing, can also have a large role in heritability in some individuals. Rare variant discovery has informed the development of drugs such as inhibitors of PCSK9 and Janus kinases. Some 34 low-frequency and rare variants are currently associated with RA risk. One variant (19:10352442G>C in TYK2) was identified in five separate studies, and might therefore represent a promising therapeutic target. Following a set of best practices in future studies, including studying diverse populations, using large sample sizes, validating RA and serostatus, replicating findings, adjusting for other variants and performing functional assessment, could help to ensure the relevance of identified variants. Exciting opportunities are now on the horizon for genetics in RA, including larger datasets and consortia, whole-genome sequencing and direct applications of findings in the management, and especially treatment, of RA.

SLAMF7 Promotes Foam Cell Formation of Macrophage by Suppressing NR4A1 Expression During Carotid Atherosclerosis

Macrophage-derived lipid-laden foam cells from the subendothelium play a crucial role in the initiation and progression of atherosclerosis. However, the molecule mechanism that regulates the formation of foam cells is not completely understood. Here, we found that SLAMF7 was upregulated in mice bone marrow-derived macrophages and RAW264.7 cells stimulated with oxidized low-density lipoprotein (ox-LDL). SLAMF7 promoted ox-LDL-mediated macrophage lipid accumulation and M1-type polarization. SLAMF7 deficiency reduced serum lipid levels and improved the lesions area of carotid plaque and aortic arch in high-fat diet-fed ApoE-/- mice. In response to ox-LDL, SLAMF7 downregulated NR4A1 and upregulated RUNX3 through transcriptome sequencing analysis. Overexpression NR4A1 reversed SLAMF7-induced lipid uptake and M1 polarization via inhibiting RUNX3 expression. Furthermore, RUNX3 enhanced foam cell formation and M1-type polarization. Taken together, the study suggested that SLAMF7 play contributing roles in the pro-atherogenic effects by regulating NR4A1-RUNX3.

Synovial Tissue Insights into Heterogeneity of Rheumatoid Arthritis

PURPOSE OF REVIEW

Rheumatoid arthritis is one of the most common rheumatic and autoimmune diseases. While it can affect many different organ systems, RA primarily involves inflammation in the synovium, the tissue that lines joints. Patients with RA exhibit significant clinical heterogeneity in terms of presence or absence of autoantibodies, degree of permanent deformities, and most importantly, treatment response. These clinical characteristics point to heterogeneity in the cellular and molecular pathogenesis of RA, an area that several recent studies have begun to address.

RECENT FINDINGS

Single-cell RNA-sequencing initiatives and deeper focused studies have revealed several RA-associated cell populations in synovial tissues, including peripheral helper T cells, autoimmunity-associated B cells (ABCs), and NOTCH3+ sublining fibroblasts. Recent large transcriptional studies and translational clinical trials present frameworks to capture cellular and molecular heterogeneity in RA synovium. Technological developments, such as spatial transcriptomics and machine learning, promise to further elucidate the different types of RA synovitis and the biological mechanisms that characterize them, key elements of precision medicine to optimize patient care and outcomes in RA. This review recaps the findings of those recent studies and puts our current knowledge and future challenges into scientific and clinical perspective.

HERVK-mediated regulation of neighboring genes: implications for breast cancer prognosis

Human endogenous retroviruses (HERVs) are the remnants of ancient retroviral infections integrated into the human genome. Although most HERVs are silenced or rendered inactive by various regulatory mechanisms, they retain the potential to influence the nearby genes. We analyzed the regulatory map of 91 HERV-Ks on neighboring genes in human breast cancer and investigated the impact of HERV-Ks on the tumor microenvironment (TME) and prognosis of breast cancer. Nine RNA-seq datasets were obtained from GEO and NCBI SRA. Differentially expressed genes and HERV-Ks were analyzed using DESeq2. Validation of high-risk prognostic candidate genes using TCGA data. These included Overall survival (multivariate Cox regression model), immune infiltration analysis (TIMER), tumor mutation burden (maftools), and drug sensitivity analysis (GSCA). A total of 88 candidate genes related to breast cancer prognosis were screened, of which CD48, SLAMF7, SLAMF1, IGLL1, IGHA1, and LRRC8A were key genes. Functionally, these six key genes were significantly enriched in some immune function-related pathways, which may be associated with poor prognosis for breast cancer (p = 0.00016), and the expression levels of these genes were significantly correlated with the sensitivity of breast cancer treatment-related drugs. Mechanistically, they may influence breast cancer development by modulating the infiltration of various immune cells into the TME. We further experimentally validated these genes to confirm the results obtained from bioinformatics analysis. This study represents the first report on the regulatory potential of HERV-K in the neighboring breast cancer genome. We identified three key HERV-Ks and five neighboring genes that hold promise as novel targets for future interventions and treatments for breast cancer.

Targeted Proteomics Reveals Functional Targets for Early Diabetes Susceptibility in Young Adults

BACKGROUND

The circulating proteome may encode early pathways of diabetes susceptibility in young adults for surveillance and intervention. Here, we define proteomic correlates of tissue phenotypes and diabetes in young adults.

METHODS

We used penalized models and principal components analysis to generate parsimonious proteomic signatures of diabetes susceptibility based on phenotypes and on diabetes diagnosis across 184 proteins in >2000 young adults in the CARDIA (Coronary Artery Risk Development in Young Adults study; mean age, 32 years; 44% women; 43% Black; mean body mass index, 25.6±4.9 kg/m2), with validation against diabetes in >1800 individuals in the FHS (Framingham Heart Study) and WHI (Women's Health Initiative).

RESULTS

In 184 proteins in >2000 young adults in CARDIA, we identified 2 proteotypes of diabetes susceptibility-a proinflammatory fat proteotype (visceral fat, liver fat, inflammatory biomarkers) and a muscularity proteotype (muscle mass), linked to diabetes in CARDIA and WHI/FHS. These proteotypes specified broad mechanisms of early diabetes pathogenesis, including transorgan communication, hepatic and skeletal muscle stress responses, vascular inflammation and hemostasis, fibrosis, and renal injury. Using human adipose tissue single cell/nuclear RNA-seq, we demonstrate expression at transcriptional level for implicated proteins across adipocytes and nonadipocyte cell types (eg, fibroadipogenic precursors, immune and vascular cells). Using functional assays in human adipose tissue, we demonstrate the association of expression of genes encoding these implicated proteins with adipose tissue metabolism, inflammation, and insulin resistance.

CONCLUSIONS

A multifaceted discovery effort uniting proteomics, underlying clinical susceptibility phenotypes, and tissue expression patterns may uncover potentially novel functional biomarkers of early diabetes susceptibility in young adults for future mechanistic evaluation.

Identification of potential crucial genes shared in psoriasis and ulcerative colitis by machine learning and integrated bioinformatics

BACKGROUND

Mounting evidence suggest that there are an association between psoriasis and ulcerative colitis (UC), although the common pathogeneses are not fully understood. Our study aimed to find potential crucial genes in psoriasis and UC through machine learning and integrated bioinformatics.

METHODS

The overlapping differentially expressed genes (DEGs) of the datasets GSE13355 and GSE87466 were identified. Then the functional enrichment analysis was performed. The overlapping genes in LASSO, SVM-RFE and key module in WGCNA were considered as potential crucial genes. The receiver operator characteristic (ROC) curve was used to estimate their diagnostic confidence. The CIBERSORT was conducted to evaluate immune cell infiltration. Finally, the datasets GSE30999 and GSE107499 were retrieved to validate.

RESULTS

112 overlapping DEGs were identified in psoriasis and UC and the functional enrichment analysis revealed they were closely related to the inflammatory and immune response. Eight genes, including S100A9, PI3, KYNU, WNT5A, SERPINB3, CHI3L2, ARNTL2, and SLAMF7, were ultimately identified as potential crucial genes. ROC curves showed they all had high confidence in the test and validation datasets. CIBERSORT analysis indicated there was a correlation between infiltrating immune cells and potential crucial genes.

CONCLUSION

In our study, we focused on the comprehensive understanding of pathogeneses in psoriasis and UC. The identification of eight potential crucial genes may contribute to not only understanding the common mechanism, but also identifying occult UC in psoriasis patients, even serving as therapeutic targets in the future.

ALKBH5 mediates silica particles-induced pulmonary inflammation through increased m6A modification of Slamf7 and autophagy dysfunction

Silica particles are commonly encountered in natural and industrial activities. Long-term environmental exposure to silica can result in silicosis, which is characterized by chronic inflammation and abnormal tissue repair in lung. To uncover the role of m6A modification in silica-induced pulmonary inflammation, we conducted this study using established mouse and macrophage models. In this study, the aerodynamic diameter of silica particles was approximately 1-2 µm. We demonstrated that silica exposure in mice caused pulmonary inflammation and increased global m6A modification levels, the downregulation of alkB homolog 5 (ALKBH5) might contribute to this alteration. Besides, we found that F4/80, a macrophage-specific biomarker, was co-expressed with ALKBH5 through dual immunofluorescent staining. In vitro studies using MeRIP assays suggested that Slamf7 was a target gene regulated by m6A modification, and specific inhibition of ALKBH5 increased Slamf7 expression. Mechanistically, ALKBH5 promoted m6A modification of Slamf7, which decreased Slamf7 mRNA stability in an m6A-dependent manner, ultimately regulating Slamf7 expression. In addition, silica exposure activated PI3K/AKT and induced macrophage autophagy. Inhibition of Slamf7 promoted autophagy, reduced the secretion of pro-inflammatory cytokines, and improved silica-induced pulmonary inflammation. In summary, ALKBH5 can regulate silica-induced pulmonary inflammation by modulating Slamf7 m6A modification and affecting the function of macrophage autophagy.

Nicotine Potentially Alters Endothelial Inflammation and Cell Adhesion via LGALS9

BACKGROUND

The endothelial cell layer is essential for the maintenance of various blood vessel functions. Major risk factors for endothelial dysfunction that contribute to aortic pathologies such as abdominal aortic aneurysm (AAA) and aortic dissection (AD) include smoking tobacco cigarettes and hypertension. This study explores the effects of nicotine (Nic) and angiotensin II (Ang II) on human aortic endothelial cells (HAoECs) at a transcriptional level.

METHODS

HAoECs were exposed to 100 nM Nic and/or 100 nM Ang II. RNA sequencing (RNA-Seq) was performed to identify regulated genes following exposure. Results were validated applying RT-qPCR. GeneMANIA was used to perform in silico analysis aiming to identify potential downstream interacting genes in inflammatory, cell-adhesion, endothelial cell proliferation, and coagulation pathways.

RESULTS

RNA-Seq identified LGALS9 (Galectin-9) as being potentially regulated following Nic exposure, while subsequent RT-qPCR experiments confirmed the transcriptional regulation (p < 0.05). Subsequent in silico analysis identified potential candidate genes for interacting with LGALS9 in different gene sets. Of the top 100 genes potentially interacting with LGALS9, 18 were inflammatory response genes, 28 were involved in cell adhesion, 2 in cell proliferation, and 6 in coagulation.

CONCLUSION

Nic exposure of HAoECs causes a significant increase in LGALS9 at a transcriptional level. LGALS9 itself may serve as key regulator for essential endothelial cell processes via interfering with various signaling pathways and may thus represent a potentially novel target in the pathogenesis of aortic pathologies.

Bexmarilimab-induced macrophage activation leads to treatment benefit in solid tumors: The phase I/II first-in-human MATINS trial

Macrophage Clever-1 contributes to impaired antigen presentation and suppression of anti-tumor immunity. This first-in-human trial investigates the safety and tolerability of Clever-1 blockade with bexmarilimab in patients with treatment-refractory solid tumors and assesses preliminary anti-tumor efficacy, pharmacodynamics, and immunologic correlates. Bexmarilimab shows no dose-limiting toxicities in part I (n = 30) and no additional safety signals in part II (n = 108). Disease control (DC) rates of 25%-40% are observed in cutaneous melanoma, gastric, hepatocellular, estrogen receptor-positive breast, and biliary tract cancers. DC associates with improved survival in a landmark analysis and correlates with high pre-treatment intratumoral Clever-1 positivity and increasing on-treatment serum interferon γ (IFNγ) levels. Spatial transcriptomics profiling of DC and non-DC tumors demonstrates bexmarilimab-induced macrophage activation and stimulation of IFNγ and T cell receptor signaling selectively in DC patients. These data suggest that bexmarilimab therapy is well tolerated and show that macrophage targeting can promote immune activation and tumor control in late-stage cancer.

Role of signaling lymphocytic activation molecule family of receptors in the pathogenesis of rheumatoid arthritis: insights and application

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and joint damage. The signaling lymphocytic activation molecule (SLAMF) family of receptors are expressed on various hematopoietic and non-hematopoietic cells and can regulate both immune cell activation and cytokine production. Altered expression of certain SLAMF receptors contributes to aberrant immune responses in RA. In RA, SLAMF1 is upregulated on T cells and may promote inflammation by participating in immune cell-mediated responses. SLAMF2 and SLAMF4 are involved in regulating monocyte tumor necrosis factor production and promoting inflammation. SLAMF7 activates multiple inflammatory pathways in macrophages to drive inflammatory gene expression. SLAMF8 inhibition can reduce inflammation in RA by blocking ERK/MMPs signaling. Of note, there are differences in SLAMF receptor (SFR) expression between normal and arthritic joint tissues, suggesting a role as potential diagnostic biomarkers. This review summarizes recent advances on the roles of SLAMF receptors 1, 2, 4, 7, and 8 in RA pathogenesis. However, further research is needed to elucidate the mechanisms of SLAMF regulation of immune cells in RA. Understanding interactions between SLAMF receptors and immune cells will help identify selective strategies for targeting SLAMF signaling without compromising normal immunity. Overall, the SLAMF gene family holds promise as a target for precision medicine in RA, but additional investigation of the underlying immunological mechanisms is needed. Targeting SLAMF receptors presents opportunities for new diagnostic and therapeutic approaches to dampen damaging immune-mediated inflammation in RA.

Deconstruction of rheumatoid arthritis synovium defines inflammatory subtypes

Rheumatoid arthritis is a prototypical autoimmune disease that causes joint inflammation and destruction1. There is currently no cure for rheumatoid arthritis, and the effectiveness of treatments varies across patients, suggesting an undefined pathogenic diversity1,2. Here, to deconstruct the cell states and pathways that characterize this pathogenic heterogeneity, we profiled the full spectrum of cells in inflamed synovium from patients with rheumatoid arthritis. We used multi-modal single-cell RNA-sequencing and surface protein data coupled with histology of synovial tissue from 79 donors to build single-cell atlas of rheumatoid arthritis synovial tissue that includes more than 314,000 cells. We stratified tissues into six groups, referred to as cell-type abundance phenotypes (CTAPs), each characterized by selectively enriched cell states. These CTAPs demonstrate the diversity of synovial inflammation in rheumatoid arthritis, ranging from samples enriched for T and B cells to those largely lacking lymphocytes. Disease-relevant cell states, cytokines, risk genes, histology and serology metrics are associated with particular CTAPs. CTAPs are dynamic and can predict treatment response, highlighting the clinical utility of classifying rheumatoid arthritis synovial phenotypes. This comprehensive atlas and molecular, tissue-based stratification of rheumatoid arthritis synovial tissue reveal new insights into rheumatoid arthritis pathology and heterogeneity that could inform novel targeted treatments.

Inhibition of pro-inflammatory signaling in human primary macrophages by enhancing arginase-2 via target site blockers

The modulation of macrophage phenotype from a pro-inflammatory to an anti-inflammatory state holds therapeutic potential in the treatment of inflammatory disease. We have previously shown that arginase-2 (Arg2), a mitochondrial enzyme, is a key regulator of the macrophage anti-inflammatory response. Here, we investigate the therapeutic potential of Arg2 enhancement via target site blockers (TSBs) in human macrophages. TSBs are locked nucleic acid antisense oligonucleotides that were specifically designed to protect specific microRNA recognition elements (MREs) in human ARG2 3' UTR mRNA. TSBs targeting miR-155 (TSB-155) and miR-3202 (TSB-3202) MREs increased ARG2 expression in human monocyte-derived macrophages. This resulted in decreased gene expression and cytokine production of TNF-α and CCL2 and, for TSB-3202, in an increase in the anti-inflammatory macrophage marker, CD206. Proteomic analysis demonstrated that a network of pro-inflammatory responsive proteins was modulated by TSBs. In silico bioinformatic analysis predicted that TSB-3202 suppressed upstream pro-inflammatory regulators including STAT-1 while enhancing anti-inflammatory associated proteins. Proteomic data were validated by confirming increased levels of sequestosome-1 and decreased levels of phosphorylated STAT-1 and STAT-1 upon TSB treatment. In conclusion, upregulation of Arg2 by TSBs inhibits pro-inflammatory signaling and is a promising novel therapeutic strategy to modulate inflammatory signaling in human macrophages.

SLAMF7 as a Promising Immunotherapeutic Target in Multiple Myeloma Treatments

Multiple myeloma (MM) is a common hematological malignancy that has fostered several new therapeutic approaches to combat newly diagnosed or relapsed MM. While the field has advanced over the past 2 decades, the majority of patients will develop resistance to these treatments, causing the need for new therapeutic targets. SLAMF7 is an attractive therapeutic target in multiple myeloma, and a monoclonal antibody that targets SLAMF7 has shown consistent beneficial outcomes in clinical trials to date. In this review, we will focus on the structure and regulation of SLAMF7 and its mechanism of action. The most recent clinical trials will be reviewed to further understand the clinical implications and improve the prognosis of MM. Furthermore, the efficacy of anti-SLAMF7 monoclonal antibodies combined with standard therapies and possible resistance mechanisms will be discussed. This review aimed to provide a detailed summary of the role of SLAMF7 in the pathogenesis of patients with MM and the rationale for further investigation into SLAMF7-mediated molecular pathways associated with MM development.

Identification and elucidation of cross talk between SLAM Family Member 7 (SLAMF7) and Toll-like receptor (TLR) pathways in monocytes and macrophages

To further elucidate the expression, regulation and function of Signaling Lymphocytic Activation Molecule Family (SLAMF) protein members in human monocytes and macrophages. Un-differentiated monocytic THP-1 cell (u-THP-1) and differentiated THP-1 macrophage (d-THP-1) were used as culture models in the study. Responses of cells to the differentiation agents phorbol ester (25 ng/ml) and TLR (Toll-like receptor) ligands were assessed. RT-PCR and Western blot analysis were used to determine mRNA and protein level. Pro-inflammatory cytokine mRNA expression levels and phagocytosis were used as functional markers. Data analyzed using t-test, one-way or two-way ANOVA followed by post hoc test. SLAMFs were differentially expressed in THP-1 cells. Differentiation of u-THP-1 to d-THP-1 led to significantly higher SLAMF7 mRNA and protein levels than other SLAMF. In addition, TLR stimuli increased SLAMF7 mRNA expression but not protein expression. Importantly, SLAMF7 agonist antibody and TLR ligands synergistically increased the mRNA expression levels of IL-1β, IL-6 and TNF-α, but had no effect on phagocytosis. SLAMF7 knocked-down in d-THP-1 significantly lowered TLR-induced mRNA expressions of pro-inflammatory markers. SLAM family proteins are differentially regulated by differentiation and TLRs. SLAMF7 enhanced TLR-mediated induction of pro-inflammatory cytokines in monocytes and macrophages but not phagocytosis.

Emerging synovial cell states in rheumatoid arthritis as potential therapeutic targets

PURPOSE OF REVIEW

To summarize recently discovered novel cell states in rheumatoid arthritis (RA) synovium that could have important implications for disease treatment.

RECENT FINDINGS

The use of multiomic technologies, including single-cell and spatial transcriptomics and mass cytometry, has led to the discovery of several novel cell states, which could have important implications for the treatment of RA. These cells can be found in patient blood, synovial fluid, or synovial tissue and span several immune cell subsets as well as stromal cell types. These diverse cell states may represent the targets of current or future therapeutics, while their fluctuations may inform the ideal timing for therapy. Future efforts are needed to implicate how each cell state functions in the pathophysiologic network within affected joints and how medications perturb each cell state and ultimately the tissue.

SUMMARY

Multiomic molecular technologies have afforded the discovery of numerous novel cellular states in RA synovium; the next challenge will be to link these states to pathophysiology and treatment response.

Advanced methods and novel biomarkers in autoimmune diseases ‑ a review of the recent years progress in systemic lupus erythematosus

There are several autoimmune and rheumatic diseases affecting different organs of the human body. Multiple sclerosis (MS) mainly affects brain, rheumatoid arthritis (RA) mainly affects joints, Type 1 diabetes (T1D) mainly affects pancreas, Sjogren's syndrome (SS) mainly affects salivary glands, while systemic lupus erythematosus (SLE) affects almost every organ of the body. Autoimmune diseases are characterized by production of autoantibodies, activation of immune cells, increased expression of pro-inflammatory cytokines, and activation of type I interferons. Despite improvements in treatments and diagnostic tools, the time it takes for the patients to be diagnosed is too long, and the main treatment for these diseases is still non-specific anti-inflammatory drugs. Thus, there is an urgent need for better biomarkers, as well as tailored, personalized treatment. This review focus on SLE and the organs affected in this disease. We have used the results from various rheumatic and autoimmune diseases and the organs involved with an aim to identify advanced methods and possible biomarkers to be utilized in the diagnosis of SLE, disease monitoring, and response to treatment.

SLAMF8, a potential new immune checkpoint molecule, is associated with the prognosis of colorectal cancer

Recently, immune checkpoint inhibitors (ICIs), such as programmed cell death 1 (PD-1) monoclonal antibodies (mAbs), have revolutionized the treatment of malignant tumors. Therefore, the number of studies aiming to screen and identify new immune checkpoint molecules for antitumor immunotherapy is increasing. Signaling lymphocytic activation molecule (SLAM) family members are mainly expressed by and regulate the functions of immune cells. Recent studies have shown that several SLAM family members are involved in the regulation of the tumor immune microenvironment and are promising targets for antitumor immunotherapy. Signaling lymphocytic activation molecule family member 8 (SLAMF8) is a type I cell surface glycoprotein and is encoded on chromosome 1q21. To further illustrate the clinical value of SLAMF8 in colorectal cancer (CRC), we retrospectively analyzed the relationship between SLAMF8 expression and the prognosis of CRC patients and the associations between SLAMF8 expression and the expression levels of other SLAM family members and other classic immune checkpoint molecules using The Cancer Genome Atlas (TCGA) data, RNA sequencing data, tissue immunohistochemistry staining, and systematic follow-up analysis. Here, high SLAMF8 expression was associated with poor overall survival (OS) in CRC. The mRNA expression level of SLAMF8 was positively correlated with the expression levels of multiple classic immune checkpoints and other SLAM family members. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that the pathways enriched in CRC tissues with high SLAMF8 expression were associated with the regulation of the tumor immune microenvironment.

Macrophage pyroptosis promotes synovial fibrosis through the HMGB1/TGF- β1 axis: an in vivo and in vitro study

Macrophages and fibroblasts are the main effector cells in synovial tissue in the knee joint. Our previous studies showed that there was synovial macrophage pyroptosis in knee osteoarthritis (KOA) and that inhibiting this pyroptosis could alleviate synovial fibrosis. In the present study, we aimed to elucidate the mechanism by which macrophage pyroptosis affects synovial fibrosis. We established an LPS/ATP-induced model in macrophages that mimicked the inflammatory environment of KOA and induced macrophage pyroptosis. The TGF-β1, SMAD3, and P-SMAD3, and the synovial fibrosis markers (Collagen I, TIMP1, Vimentin, and TGF-β1) were significantly decreased after fibroblasts were cultured with RAGE inhibitors and SMAD3 inhibitors. Moreover, ELISA and immunofluorescence analysis showed that macrophage pyroptosis induced the release of IL-1β, IL-18, and HMGB1 and caused the translocation of HMGB1 from the fibroblast nucleus to the cell membrane, where it could bind with RAGE. Subsequently, in the synovial tissue of KOA model rats, we observed that inhibiting HMGB1, RAGE, and SMAD3 could alleviate the expression of synovial fibrosis markers (Collagen I, TIMP1, Vimentin, and TGF-β1) at both the mRNA and protein levels. Besides, HE and Sirius Red staining were used to observe the transverse diameter of the right knee. In conclusion, macrophage pyroptosis induced IL-1β, IL-18, and HMGB1, which could be caused HMGB1 to translocate from the fibroblast nucleus and bind with RAGE, activating the TGF-β1/SMAD3 signaling pathway and affecting synovial fibrosis.

Inhibition of autophagy in macrophage promotes IL-1β-mediated hepatocellular carcinoma progression via inflammasome accumulation and self-recruitment

Hepatocellular carcinoma (HCC) has a complex and changeable tumor microenvironment. Despite emerging evidence focusing on autophagy process within immune cells, the function and regulatory mechanism of macrophage autophagy in tumor progression remains unclear. Our results of multiplex-immunohistochemistry and RNA-sequencing identified the reduced levels of autophagy in tumor macrophages in the HCC microenvironment, associated with a poor prognosis and increased microvascular metastasis in HCC patients. Specifically, HCC suppressed the macrophage autophagy initiation through the up-regulation of mTOR and ULK1 phosphorylation at Ser757. Knockdown of autophagy-related proteins to further inhibit autophagy significantly boosted the metastatic potential of HCC. Mechanistically, the accumulation of NLRP3 inflammasome mediated by autophagy inhibition promoted the cleavage, maturation, and release of IL-1β, which facilitated the HCC progression, eventually accelerating HCC metastasis via the epithelial-mesenchymal transition. Autophagy inhibition provoked macrophage self-recruitment through the CCL20-CCR6 signaling was also a crucial account of HCC progression. Recruited macrophages mediated the cascade amplification of IL-1β and CCL20 to form a novel pro-metastatic positive feedback loop through promoting HCC metastasis and increased macrophage recruitment, respectively. Notably, targeting IL-1β/IL-1 receptor signaling impaired lung metastasis induced by macrophage autophagy inhibition in a mice HCC lung metastasis model. In summary, this study highlighted that inhibition of tumor macrophage autophagy facilitated HCC progression by increasing IL-1β secretion via NLRP3 inflammasome accumulation and by macrophage self-recruitment through the CCL20 signaling pathway. Interruption of this metastasis-promoting loop by IL-1β blockade may provide a promising therapeutic strategy for HCC patients.

The pathogenesis of rheumatoid arthritis

Significant recent progress in understanding rheumatoid arthritis (RA) pathogenesis has led to improved treatment and quality of life. The introduction of targeted-biologic and -synthetic disease modifying anti-rheumatic drugs (DMARDs) has also transformed clinical outcomes. Despite this, RA remains a life-long disease without a cure. Unmet needs include partial response and non-response to treatment in many patients, failure to achieve immune homeostasis or drug free remission, and inability to repair damaged tissues. RA is now recognized as the end of a multi-year prodromal phase in which systemic immune dysregulation, likely beginning in mucosal surfaces, is followed by a symptomatic clinical phase. Inflammation and immune reactivity are primarily localized to the synovium leading to pain and articular damage, but is also associated with a broader series of comorbidities. Here, we review recently described immunologic mechanisms that drive breach of tolerance, chronic synovitis, and remission.

Leishmania kinetoplast DNA contributes to parasite burden in infected macrophages: Critical role of the cGAS-STING-TBK1 signaling pathway in macrophage parasitemia

Leishmania parasites harbor a unique network of circular DNA known as kinetoplast DNA (kDNA). The role of kDNA in leishmania infections is poorly understood. Herein, we show that kDNA delivery to the cytosol of Leishmania major infected THP-1 macrophages provoked increased parasite loads when compared to untreated cells, hinting at the involvement of cytosolic DNA sensors in facilitating parasite evasion from the immune system. Parasite proliferation was significantly hindered in cGAS- STING- and TBK-1 knockout THP-1 macrophages when compared to wild type cells. Nanostring nCounter gene expression analysis on L. major infected wild type versus knockout cells revealed that some of the most upregulated genes including, Granulysin (GNLY), Chitotriosidase-1 (CHIT1), Sialomucin core protein 24 (CD164), SLAM Family Member 7 (SLAMF7), insulin-like growth factor receptor 2 (IGF2R) and apolipoprotein E (APOE) were identical in infected cGAS and TBK1 knockout cells, implying their involvement in parasite control. Amlexanox treatment (a TBK1 inhibitor) of L. major infected wild type cells inhibited both the percentage and the parasite load of infected THP-1 cells and delayed footpad swelling in parasite infected mice. Collectively, these results suggest that leishmania parasites might hijack the cGAS-STING-TBK1 signaling pathway to their own advantage and the TBK1 inhibitor amlexanox could be of interest as a candidate drug in treatment of cutaneous leishmaniasis.

Synovial tissue macrophages in joint homeostasis, rheumatoid arthritis and disease remission

Synovial tissue macrophages (STMs) were principally recognized as having a pro-inflammatory role in rheumatoid arthritis (RA), serving as the main producers of pathogenic tumour necrosis factor (TNF). Recent advances in single-cell omics have facilitated the discovery of distinct STM populations, providing an atlas of discrete phenotypic clusters in the context of healthy and inflamed joints. Interrogation of the functions of distinct STM populations, via ex vivo and experimental mouse models, has re-defined our understanding of STM biology, opening up new opportunities to better understand the pathology of the arthritic joint. These works have identified STM subpopulations that form a protective lining barrier within the synovial membrane and actively participate in the remission of RA. We discuss how distinct functions of STM clusters shape the synovial tissue environment in health, during inflammation and in disease remission, as well as how an increased understanding of STM heterogeneity might aid the prediction of clinical outcomes and inform novel treatments for RA.