The proinflammatory myeloid cell receptor TREM-1 controls Kupffer cell activation and development of hepatocellular carcinoma

Biological impact and therapeutic implication of tumor-associated macrophages in hepatocellular carcinoma

The tumor microenvironment is a complex space comprised of normal, cancer and immune cells. The macrophages are considered as the most abundant immune cells in tumor microenvironment and their function in tumorigenesis is interesting. Macrophages can be present as M1 and M2 polarization that show anti-cancer and oncogenic activities, respectively. Tumor-associated macrophages (TAMs) mainly have M2 polarization and they increase tumorigenesis due to secretion of factors, cytokines and affecting molecular pathways. Hepatocellular carcinoma (HCC) is among predominant tumors of liver that in spite of understanding its pathogenesis, the role of tumor microenvironment in its progression still requires more attention. The presence of TAMs in HCC causes an increase in growth and invasion of HCC cells and one of the reasons is induction of glycolysis that such metabolic reprogramming makes HCC distinct from normal cells and promotes its malignancy. Since M2 polarization of TAMs stimulates tumorigenesis in HCC, molecular networks regulating M2 to M1 conversion have been highlighted and moreover, drugs and compounds with the ability of targeting TAMs and suppressing their M2 phenotypes or at least their tumorigenesis activity have been utilized. TAMs increase aggressive behavior and biological functions of HCC cells that can result in development of therapy resistance. Macrophages can provide cell-cell communication in HCC by secreting exosomes having various types of biomolecules that transfer among cells and change their activity. Finally, non-coding RNA transcripts can mainly affect polarization of TAMs in HCC.

Who is who within the universe of TREM-like transcripts (TREML)?

The Triggering Receptor Expressed on Myeloid Cells (TREM) family of receptors plays a crucial role in the immune response across various species. Particularly, TREM-1 and TREM-2 have been extensively studied, both in terms of their applications and their expression sites and signaling pathways. However, the same is not observed for the other family members collectively known as TREM-like-transcripts (TREML). The TREML family consists of eight receptors, with TREML1-5 identified in humans and mice, TREML-6 exclusive found in mice, TREML-7 in dogs and horses, and TREML-8 in rabbits and opossums. Despite the limited data available on the TREML members, they have been implicated in different immune and non-immune activities, which have been proposed to display both pro and anti-inflammatory activities, and to influence fundamental biological processes such as coagulation, bone and neurological development. In this review, we have compiled available information regarding the already discovered members of the family and provided foundational framework for understanding the function, localization, and therapeutic potential of all TREML members. Additionally, we hope that this review may shed light on this family of receptors, whose underlying mechanisms are still awaiting elucidation, while emphasizing the need for future studies to explore their functions and potential therapeutic application.

Triggering Receptor Expression on Myeloid Cells-1 (TREM1) Promoter Hypomethylation and Its Overexpression Associated With Poor Survival of Cancer Patients: A Pan-Cancer Analysis

Background Triggering receptor expression on myeloid cells-1 (TREM1) belongs to the immunoglobulin superfamily and is implicated in various conditions, including infectious and non-infectious diseases, autoimmune disorders, and cancer. Notably, TREM1 is significantly dysregulated in numerous cancer types. However, the underlying mechanism driving TREM1 mRNA expression in cancers remains unclear.  Objective This study aims to analyze the promoter methylation level of TREM1 and its overexpression with cancer. Methods  This study utilized The Cancer Genome Atlas (TCGA) cohort to analyze the methylation and expression levels of TREM1 in cancers. The University of ALabama at Birmingham CANcer (UALCAN) database facilitated data analysis from the TCGA dataset. Additionally, survival analysis was conducted using the TCGA dataset via Kaplan-Meier (KM) plots to identify significant associations with prognosis. Results Promoter methylation analysis revealed that TREM1 is hypomethylated in cancers, resulting in significantly overexpressed mRNA across various cancer types. This methylation and expression showed a negative correlation. Furthermore, high TREM1 mRNA expression was linked to poor prognosis in several cancers. Conclusion TREM1 gene expression negatively correlates with promotor DNA methylation and is associated with poor survival. It may serve as a prognostic marker and biomarker for various cancers. Future research should focus on further validation and antitumor immunity to elucidate its oncogenic role in cancers.

TREM1: Activation, signaling, cancer and therapy

Triggering receptor expressed on myeloid cells 1 (TREM1) is a cell surface receptor expressed on neutrophils, monocytes and some tissue macrophages, where it functions as an immunoregulator that controls myeloid cell responses. The activation of TREM1 is suggested to be an upregulation-based, ligands-induced and structural multimerization-mediated process, in which damage- and pathogen-associated molecular patterns play important roles. Activated TREM1 initiates an array of downstream signaling pathways that ultimately result in the production of pro-inflammatory cytokines and chemokines, whereby it functions as an amplifier of inflammation and is implicated in the pathogenesis of many inflammation-associated diseases. Over the past decade, there has been growing evidence for the involvement of TREM1 overactivation in tumor stroma inflammation and cancer progression. Indeed, it was shown that TREM1 promotes tumor progression, immunosuppression, and resistance to therapy by activating tumor-infiltrating myeloid cells. TREM1-deficiency or blockade provide protection against tumors and reverse the resistance to anti-PD-1/PD-L1 therapy and arginine-deprivation therapy in preclinical models. Here, we first review the structure, activation modes and signaling pathways of TREM1 and emphasize the role of soluble TREM1 as a biomarker of infection and cancer. We then focus on the role of TREM1 in cancer and systematically summarize its expression patterns, upregulation mechanisms and functions in tumor development and progression. Lastly, we discuss the therapeutic prospects of TREM1 inhibition, via effective pharmacological inhibitors, in treating cancer and other diseases.

Triggering receptor expressed in myeloid cells 1 (TREM1) as a potential prognostic biomarker and association with immune infiltration in oral squamous cell carcinoma

OBJECTIVE

The objective of this study is to investigate the significance and impact of Triggering Receptor Expression on Myeloid Cells-1 (TREM-1) in the context of oral squamous cell carcinoma (OSCC).

METHODS

This study involved 51 OSCC patients, 21 oral epithelial dysplasia patients (OED), and the TCGA-HNSCC dataset. TREM1 expression was analyzed using quantitative reverse transcription PCR (RT-qPCR), and Western blot. Furthermore, we assessed TREM1 expression for clinicopathological, prognosis, and immune infiltration correlations utilizing publicly available TCGA-HNSCC datasets through UALCAN, Protein Atlas, Kaplan-Meier plot, TIMER2.0, and TISIDB. We also conducted bioinformatic analyses for functional enrichment employing publicly accessible datasets.

RESULTS

TREM1 was significantly upregulated in OSCC and OED when compared to normal tissues, confirmed through multiple methods. Analysis of clinicopathological features showed associations with disease stage, grade, nodal metastasis, HPV status, and TP53 mutation. High TREM1 expression correlated with poorer patient survival. TREM1 was linked to immune cell infiltration and immune-related pathways.

CONCLUSION

TREM1 is significantly upregulated in OSCC and is associated with poor clinicopathological features and survival. It may hold promise as a therapeutic target and prognostic marker in OSCC. Further research is needed to understand its functional role in OSCC.

THBS1+ myeloid cells expand in SLD hepatocellular carcinoma and contribute to immunosuppression and unfavorable prognosis through TREM1

Hepatocellular carcinoma (HCC) is an inflammation-associated cancer arising from viral or non-viral etiologies including steatotic liver diseases (SLDs). Expansion of immunosuppressive myeloid cells is a hallmark of inflammation and cancer, but their heterogeneity in HCC is not fully resolved and might underlie immunotherapy resistance. Here, we present a high-resolution atlas of innate immune cells from patients with HCC that unravels an SLD-associated contexture characterized by influx of inflammatory and immunosuppressive myeloid cells, including a discrete population of THBS1+ regulatory myeloid (Mreg) cells expressing monocyte- and neutrophil-affiliated genes. THBS1+ Mreg cells expand in SLD-associated HCC, populate fibrotic lesions, and are associated with poor prognosis. THBS1+ Mreg cells are CD163+ but distinguished from macrophages by high expression of triggering receptor expressed on myeloid cells 1 (TREM1), which contributes to their immunosuppressive activity and promotes HCC tumor growth in vivo. Our data support myeloid subset-targeted immunotherapies to treat HCC.

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

Triggering receptor expressed on myeloid cells-1 in sepsis, and current insights into clinical studies

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor and plays a critical role in the immune response. TREM-1 activation leads to the production and release of proinflammatory cytokines, chemokines, as well as its own expression and circulating levels of the cleaved soluble extracellular portion of TREM-1 (sTREM-1). Because patients with sepsis and septic shock show elevated sTREM-1 levels, TREM-1 has attracted attention as an important contributor to the inadequate immune response in this often-deadly condition. Since 2001, when the first blockade of TREM-1 in sepsis was performed, many potential TREM-1 inhibitors have been established in animal models. However, only one of them, nangibotide, has entered clinical trials, which have yielded promising data for future treatment of sepsis, septic shock, and other inflammatory disease such as COVID-19. This review discusses the TREM-1 pathway and important ligands, and highlights the development of novel inhibitors as well as their clinical potential for targeted treatment of various inflammatory conditions.

The Interaction of HMGB1 with the Proinflammatory TREM-1 Receptor Generates Cytotoxic Lymphocytes Active against HLA-Negative Tumor Cells

High mobility group protein (HMGB1) is secreted by myeloid cells and cells of damaged tissues during inflammation, causing inflammatory reactions through various receptors, including TLRS and RAGE. TREM-1 is considered to be one of the potential HMGB1 receptors. In this work, we have shown that the HMGB1 protein is able to bind to the TREM-1 receptor at high affinity both in solution and on the cell surface. This binding causes lymphocytes to release cytokines IL-2, IL-1b, IL-6, TNF and Ifny into the medium, which leads to the appearance of cytotoxic lymphocytes in PBMC capable of lysing HLA-negative tumor cells. Expanding the spectra of proinflammatory receptor ligands and understanding the mechanisms of their action is essential for the creation of new immunotherapy pathways.

The Role of microRNAs in Hepatocellular Cancer: A Narrative Review Focused on Tumor Microenvironment and Drug Resistance

Globally, hepatic cancer ranks fourth in terms of cancer-related mortality and is the sixth most frequent kind of cancer. Around 80% of liver cancers are hepatocellular carcinomas (HCC), which are the leading cause of cancer death. It is well known that HCC may develop resistance to the available chemotherapy treatments very fast. One of the biggest obstacles in providing cancer patients with appropriate care is drug resistance. According to reports, more than 90% of cancer-specific fatalities are caused by treatment resistance. By binding to the 3'-untranslated region of target messenger RNAs (mRNAs), microRNAs (miRNAs), a group of noncoding RNAs which are around 17 to 25 nucleotides long, regulate target gene expression. Moreover, they play role in the control of signaling pathways, cell proliferation, and cell death. As a result, miRNAs play an important role in the microenvironment of HCC by changing immune phenotypes, hypoxic conditions, and acidification, as well as angiogenesis and extracellular matrix components. Moreover, changes in miRNA levels in HCC can effectively resist cancer cells to chemotherapy by affecting various cellular processes such as autophagy, apoptosis, and membrane transporter activity. In the current work, we narratively reviewed the role of miRNAs in HCC, with a special focus on tumor microenvironment and drug resistance.

Role of Immunological Cells in Hepatocellular Carcinoma Disease and Associated Pathways

Hepatocellular carcinoma (HCC) remains one of the predominant causes of cancer-related mortality across the globe. It is attributed to obesity, excessive alcohol consumption, smoking, and infection by the hepatitis virus. Early diagnosis of HCC is essential, and local treatments such as surgical excision and percutaneous ablation are effective. Palliative systemic therapy, primarily with the tyrosine kinase inhibitor Sorafenib, is used in advanced cases. However, the prognosis for advanced HCC remains poor. This Review additionally describes the pathophysiological mechanisms of HCC, which include aberrant molecular signaling, genomic instability, persistent inflammation, and the paradoxical position of the immune system in promoting and suppressing HCC. The paper concludes by discussing the growing body of research on the relationship between mitochondria and HCC, suggesting that mitochondrial dysfunction may contribute to the progression of HCC. This Review focuses on immunological interactions between different mechanisms of HCC progression, including obesity, viral infection, and alcohol consumption.

Mechanisms of Resistance to Immunotherapy in Hepatocellular Carcinoma

Systemic treatment for advanced hepatocellular carcinoma (HCC) has been revolutionized over the last few years following the approval of immune checkpoint inhibitors (ICI). Despite the promising survival extension seen with ICI combination regimens, responses are not universally seen and the optimal partner for programmed cell death 1 pathway inhibitors remains to be identified. Even fewer encouraging results have been demonstrated with ICI used for monotherapy. Several mechanisms of resistance have been described so far, involving characteristics of cancer cells (intrinsic mechanisms) and of the surrounding tumor microenvironment (extrinsic mechanisms). Factors related to therapy may also contribute to the development of resistance. Increasing research efforts are being dedicated to the discovery of novel approaches and targets to overcome resistance, some of which may be introduced into clinic in the future. Herein we describe a selection of resistance mechanisms that have been involved in impairing response to ICI and propose potential therapeutic approaches to overcome resistance.

Targeting TREM1 augments antitumor T cell immunity by inhibiting myeloid-derived suppressor cells and restraining anti-PD-1 resistance

The triggering receptor expressed on myeloid cell 1 (TREM1) plays a critical role in development of chronic inflammatory disorders and the inflamed tumor microenvironment (TME) associated with most solid tumors. We examined whether loss of TREM1 signaling can abrogate the immunosuppressive TME and enhance cancer immunity. To investigate the therapeutic potential of TREM1 in cancer, we used mice deficient in Trem1 and developed a novel small molecule TREM1 inhibitor, VJDT. We demonstrated that genetic or pharmacological TREM1 silencing significantly delayed tumor growth in murine melanoma (B16F10) and fibrosarcoma (MCA205) models. Single-cell RNA-Seq combined with functional assays during TREM1 deficiency revealed decreased immunosuppressive capacity of myeloid-derived suppressor cells (MDSCs) accompanied by expansion in cytotoxic CD8+ T cells and increased PD-1 expression. Furthermore, TREM1 inhibition enhanced the antitumorigenic effect of anti-PD-1 treatment, in part, by limiting MDSC frequency and abrogating T cell exhaustion. In patient-derived melanoma xenograft tumors, treatment with VJDT downregulated key oncogenic signaling pathways involved in cell proliferation, migration, and survival. Our work highlights the role of TREM1 in cancer progression, both intrinsically expressed in cancer cells and extrinsically in the TME. Thus, targeting TREM1 to modify an immunosuppressive TME and improve efficacy of immune checkpoint therapy represents what we believe to be a promising therapeutic approach to cancer.

Function and biomedical implications of exosomal microRNAs delivered by parenchymal and nonparenchymal cells in hepatocellular carcinoma

Small extracellular vesicles (exosomes) are important components of the tumor microenvironment. They are small membrane-bound vesicles derived from almost all cell types and play an important role in intercellular communication. Exosomes transmit biological molecules obtained from parent cells, such as proteins, lipids, and nucleic acids, and are involved in cancer development. MicroRNAs (miRNAs), the most abundant contents in exosomes, are selectively packaged into exosomes to carry out their biological functions. Recent studies have revealed that exosome-delivered miRNAs play crucial roles in the tumorigenesis, progression, and drug resistance of hepatocellular carcinoma (HCC). In addition, exosomes have great industrial prospects in the diagnosis, treatment, and prognosis of patients with HCC. This review summarized the composition and function of exosomal miRNAs of different cell origins in HCC and highlighted the association between exosomal miRNAs from stromal cells and immune cells in the tumor microenvironment and the progression of HCC. Finally, we described the potential applicability of exosomal miRNAs derived from mesenchymal stem cells in the treatment of HCC.

Immune landscape and immunotherapy of hepatocellular carcinoma: focus on innate and adaptive immune cells

Hepatocellular carcinoma (HCC) is responsible for roughly 90% of all cases of primary liver cancer, and the cases are on the rise. The treatment of advanced HCC is a serious challenge. Immune checkpoint inhibitor (ICI) therapy has marked a watershed moment in the history of HCC systemic treatment. Atezolizumab in combination with bevacizumab has been approved as a first-line treatment for advanced HCC since 2020; however, the combination therapy is only effective in a limited percentage of patients. Considering that the tumor immune microenvironment (TIME) has a great impact on immunotherapies for HCC, an in-depth understanding of the immune landscape in tumors and the current immunotherapeutic approaches is extremely necessary. We elaborate on the features, functions, and cross talk of the innate and adaptive immune cells in HCC and highlight the benefits and drawbacks of various immunotherapies for advanced HCC, as well as future projections. HCC consists of a heterogeneous group of cancers with distinct etiologies and immune microenvironments. Almost all the components of innate and adaptive immune cells in HCC have altered, showing a decreasing trend in the number of tumor suppressor cells and an increasing trend in the pro-cancer cells, and there is also cross talk between various cell types. Various immunotherapies for HCC have also shown promising efficacy and application prospect. There are multilayered interwoven webs among various immune cell types in HCC, and emerging evidence demonstrates the promising prospect of immunotherapeutic approaches for HCC.

The biology of TREM receptors

Triggering receptors expressed on myeloid cells (TREMs) encompass a family of cell-surface receptors chiefly expressed by granulocytes, monocytes and tissue macrophages. These receptors have been implicated in inflammation, neurodegenerative diseases, bone remodelling, metabolic syndrome, atherosclerosis and cancer. Here, I review the structure, ligands, signalling modes and functions of TREMs in humans and mice and discuss the challenges that remain in understanding TREM biology.

TREM1 activation of myeloid cells promotes antitumor immunity

Myeloid cells in the tumor microenvironment (TME) can exist in immunosuppressive and immunostimulatory states that impede or promote antitumor immunity, respectively. Blocking suppressive myeloid cells or increasing stimulatory cells to enhance antitumor immune responses is an area of interest for therapeutic intervention. Triggering receptor expressed on myeloid cells-1 (TREM1) is a proinflammatory receptor that amplifies immune responses. TREM1 is expressed on neutrophils, subsets of monocytes and tissue macrophages, and suppressive myeloid populations in the TME, including tumor-associated neutrophils, monocytes, and tumor-associated macrophages. Depletion or inhibition of immunosuppressive myeloid cells, or stimulation by TREM1-mediated inflammatory signaling, could be used to promote an immunostimulatory TME. We developed PY159, an afucosylated humanized anti-TREM1 monoclonal antibody with enhanced FcγR binding. PY159 is a TREM1 agonist that induces signaling, leading to up-regulation of costimulatory molecules on monocytes and macrophages, production of proinflammatory cytokines and chemokines, and enhancement of T cell activation in vitro. An antibody against mouse TREM1, PY159m, promoted antitumor efficacy in syngeneic mouse tumor models. These results suggest that PY159-mediated agonism of TREM1 on tumoral myeloid cells can promote a proinflammatory TME and offer a promising strategy for immunotherapy.

Advances in radiotherapy and immunity in hepatocellular carcinoma

Primary liver cancer is one of the most common malignant tumours worldwide; it caused approximately 830,000 deaths in 2020. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, accounting for over 80% of all cases. Various methods, including surgery, chemotherapy, radiotherapy, and radiofrequency ablation, have been widely used in the treatment of HCC. With the advancement of technology, radiotherapy has become increasingly important in the comprehensive treatment of HCC. However, due to the insufficient sensitivity of tumour cells to radiation, there are still multiple limitation in clinical application of radiotherapy. In recent years, the role of immunotherapy in cancer has been increasingly revealed, and more researchers have turned their attention to the combined application of immunotherapy and radiotherapy in the hope of achieving better treatment outcomes. This article reviews the progress on radiation therapy in HCC and the current status of its combined application with immunotherapy, and discusses the prospects and value of radioimmunotherapy in HCC.

Impact of TREM1 Variants on the Risk and Prognosis of Glioma in the Chinese Han Population

Background

Glioma is the main pathological subtype of brain tumors with high mortality.

Objective

This study aimed to elucidate the correlation between TREM1 variants and glioma risk in the Chinese Han population.

Methods

Genotyping of six variants of TREM1 was completed by Agena MassARRAY platform in 1061 subjects (503 controls and 558 glioma patients). The relationship between TREM1 polymorphisms and glioma risk was calculated using the logistic regression model, with odds ratio (OR) and 95% confidence intervals (CIs). A multifactor dimensionality reduction (MDR) method was performed to assess SNP-SNP interactions to predict glioma risk.

Results

In this research, overall analysis illustrated an association between TREM1 rs9369269 and an increased risk of glioma. Rs9369269 was also related to the risk of glioma in patients aged ≤40 years and females. Subjects with rs9369269 AC genotype were likely to obtain glioma compared to people with CC genotype (patients with astroglioma vs healthy people). Compared to TT genotype carriers, carriers with AT genotype of rs1351835 were significantly associated with overall survival (OS).

Conclusion

Taken together, the study identified the association between TREM1 variants and glioma risk and TREM1 variants were significantly associated with the prognosis of glioma. In the future, larger samples are needed to verify the results.

HMGB1: a potential new target for tendinopathy treatment

Tendinopathy describes a complex pathology of the tendon characterized by abnormalities in the microstructure, composition, and cellularity of the tendon, leading to pain, limitation of activity and reduced function. Nevertheless, the mechanism of tendinopathy has not been fully elucidated, and the treatment of tendinopathy remains a challenge. High mobility group box 1 (HMGB1), a highly conserved and multifaceted nuclear protein, exerts multiple roles and high functional variability and is involved in many biological and pathological processes. In recent years, several studies have suggested that HMGB1 is associated with tendinopathy and may play a key role in the pathogenesis of tendinopathy. Therefore, this review summarizes the expression and distribution of HMGB1 in tendinopathy, focuses on the roles of HMGB1 and HMGB1-based potential mechanisms involved in tendinopathy, and finally summarizes the findings on HMGB1-based therapeutic approaches in tendinopathy, probably providing new insight into the mechanism and further potential therapeutic targets of tendinopathy.

Agomir miRNA-150-5p alleviates pristane-induced lupus by suppressing myeloid dendritic cells activation and inflammation via TREM-1 axis

OBJECTIVE

Triggering receptors expressed on myeloid cells-1 (TREM-1) has been shown to participate in inflammatory autoimmune diseases. Nevertheless, the detailed underlying mechanisms and therapeutic benefits by targeting TREM-1 remain elusive, especially in myeloid dendritic cells (mDCs) and systemic lupus erythematosus (SLE). Disorders of epigenetic processes including non-coding RNAs give rise to SLE, resulting in complicated syndromes. Here, we aim to address this issue and explore the miRNA to inhibit the activation of mDCs and alleviate the progress of SLE by targeting TREM-1 signal axis.

METHODS

Bioinformatics methods were used to analyze the differentially expressed genes (DEGs) between patients with SLE and healthy individuals by four mRNA microarray datasets from Gene Expression Omnibus (GEO). Then we identified the expression of TREM-1 and its soluble form (sTREM-1) in clinical samples by ELISA, quantitative real-time PCR and Western blot. Phenotypic and functional changes of mDCs elicited by TREM-1 agonist were determined. Three databases of miRNAs target prediction and a dual-luciferase reporter assay were used to screen and verify miRNAs that can directly inhibit TREM-1 expression in vitro. Moreover, pristane-induced lupus mice were injected with miR-150-5p agomir to evaluate the effects of miR-150-5p on mDCs in lymphatic organs and disease activity in vivo.

RESULTS

We screened TREM-1 as one of the hub genes closely correlated with the progression of SLE and identified sTREM-1 in serum as a valuable diagnostic biomarker for SLE. Moreover, activation of TREM-1 by its agonist promoted activation and chemotaxis of mDCs and increased the production of inflammatory cytokines and chemokines, showing higher expression of IL-6, TNF-α, and MCP-1. We showed that lupus mice displayed a unique miRNA signature in spleen, among which miR-150 was the most significantly expressed miRNA that targeting TREM-1 compared with wild type group. Transfection of miRNA-150-5p mimics directly suppressed the expression of TREM-1 by binding to its 3' UTR. Our in vivo experiments first indicated that administration of miR-150-5p agomir effectively ameliorated lupus symptoms. Intriguingly, miR-150 inhibited the over activation of mDCs through TREM-1 signal pathway in lymphatic organs and renal tissues.

CONCLUSIONS

TREM-1 represents a potentially novel therapeutic target and we identify miR-150-5p as one of the mechanisms to alleviate lupus disease, which is attributable for inhibiting mDCs activation through TREM-1 signaling pathway.

TREM-1 as a potential prognostic biomarker associated with immune infiltration in clear cell renal cell carcinoma

BACKGROUND

The tumor immune microenvironment plays a crucial role in the efficacy of various therapeutics. However, their correlation is not yet completely understood in Clear cell renal cell carcinoma (ccRCC). This study aimed to investigate the potential of TREM-1 as a potential novel biomarker for ccRCC.

METHODS

We constructed a ccRCC immune prognostic signature. The clinical characteristics, the status of the tumor microenvironment, and immune infiltration were analyzed through the ESTIMATE and CIBERSORT algorithms for the hub gene, while the Gene Set Enrichment Analysis and PPI analysis were performed to predict the function of the hub gene. Immunohistochemical staining was used to detect the expression of TREM-1 in renal clear cell carcinoma tissues.

RESULTS

The CIBERSORT and ESTIMATE algorithms revealed that TREM-1 was correlated with the infiltration of 12 types of immune cells. Therefore, it was determined that TREM-1 was involved in numerous classical pathways in the immune response via GSEA analysis. In Immunohistochemical staining, we found that the expression of TREM-1 was significantly upregulated with increasing tumor grade in renal clear cell carcinoma, and elevated TREM-1 expression was associated with poor prognosis.

CONCLUSIONS

The results suggest that TREM-1 may act as an implicit novel prognostic biomarker in ccRCC that could be utilized to facilitate immunotherapeutic strategy.

Dengue Virus Increases the Expression of TREM-1 and CD10 on Human Neutrophils

Every year, dengue is responsible for 400 million infections worldwide. Inflammation is related to the development of severe forms of dengue. Neutrophils are a heterogeneous cell population with a key role in the immune response. During viral infection, neutrophils are mainly recruited to the infection site; however, their excessive activation is linked to deleterious results. During dengue infection, neutrophils are involved in the pathogenesis through neutrophils extracellular traps production, tumor necrosis factor-alpha, and interleukin-8 secretion. However, other molecules regulate the neutrophil role during viral infection. TREM-1 is expressed on neutrophils and its activation is related to increased production of inflammatory mediators. CD10 is expressed on mature neutrophils and has been associated with the regulation of neutrophil migration and immunosuppression. However, the role of both molecules during viral infection is limited, particularly during dengue infection. Here, we report for the first time that DENV-2 can significantly increase TREM-1 and CD10 expression as well as sTREM-1 production in cultured human neutrophils. Furthermore, we observed that treatment with granulocyte-macrophage colony stimulating factor, a molecule mostly produced in severe cases of dengue, is capable of inducing the overexpression of TREM-1 and CD10 on human neutrophils. These results suggest the participation of neutrophil CD10 and TREM-1 in the pathogenesis of dengue infection.

The CDR3 region as the major driver of TREM-1 interaction with its ligands, an in silico characterization

The triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor heavily investigated in infectious and non-infectious diseases. Because of its role in amplifying inflammation, TREM-1 has been explored as a diagnostic/prognostic biomarker. Further, as the receptor has been implicated in the pathophysiology of several diseases, therapies aiming at modulating its activity represent a promising strategy to constrain uncontrolled inflammatory or infectious diseases. Despite this, several aspects concerning its interaction with ligands and activation process, remain unclear. Although many molecules have been suggested as TREM-1 ligands, only five have been confirmed to interact with the receptor: actin, eCIRP, HMGB1, Hsp70 and PGLYRP1. However, the domains involved in the interaction between the receptor and these proteins are not clarified yet. Therefore, here we used in silico approaches to investigate the putative binding domains in the receptor, using hot spots analysis, molecular docking and molecular dynamics simulations between TREM-1 and its five known ligands. Our results indicated the complementarity-determining regions (CDRs) of the receptor as the main mediators of antigen recognition, especially the CDR3 loop. We believe that our study could be used as structural basis for the elucidation of TREM-1's recognition process, and may be useful for prospective in silico and biological investigations exploring the receptor in different contexts.

The role of triggering receptor expressed on myeloid cells-1 (TREM-1) in central nervous system diseases

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a member of the immunoglobulin superfamily and is mainly expressed on the surface of myeloid cells such as monocytes, macrophages, and neutrophils. It plays an important role in the triggering and amplification of inflammatory responses, and it is involved in the development of various infectious and non-infectious diseases, autoimmune diseases, and cancers. In recent years, TREM-1 has also been found to participate in the pathological processes of several central nervous system (CNS) diseases. Targeting TREM-1 may be a promising strategy for treating these diseases. This paper aims to characterize TREM-1 in terms of its structure, signaling pathway, expression, regulation, ligands and pathophysiological role in CNS diseases.

Hepatic macrophage mediated immune response in liver steatosis driven carcinogenesis

Obesity confers an independent risk for carcinogenesis. Classically viewed as a genetic disease, owing to the discovery of tumor suppressors and oncogenes, genetic events alone are not sufficient to explain the progression and development of cancers. Tumor development is often associated with metabolic and immunological changes. In particular, obesity is found to significantly increase the mortality rate of liver cancer. As its role is not defined, a fundamental question is whether and how metabolic changes drive the development of cancer. In this review, we will dissect the current literature demonstrating that liver lipid dysfunction is a critical component driving the progression of cancer. We will discuss the involvement of inflammation in lipid dysfunction driven liver cancer development with a focus on the involvement of liver macrophages. We will first discuss the association of steatosis with liver cancer. This will be followed with a literature summary demonstrating the importance of inflammation and particularly macrophages in the progression of liver steatosis and highlighting the evidence that macrophages and macrophage produced inflammatory mediators are critical for liver cancer development. We will then discuss the specific inflammatory mediators and their roles in steatosis driven liver cancer development. Finally, we will summarize the molecular pattern (PAMP and DAMP) as well as lipid particle signals that are involved in the activation, infiltration and reprogramming of liver macrophages. We will also discuss some of the therapies that may interfere with lipid metabolism and also affect liver cancer development.

Mitochondria and Cancer Recurrence after Liver Transplantation—What Is the Benefit of Machine Perfusion?

Tumor recurrence after liver transplantation has been linked to multiple factors, including the recipient’s tumor burden, donor factors, and ischemia-reperfusion injury (IRI). The increasing number of livers accepted from extended criteria donors has forced the transplant community to push the development of dynamic perfusion strategies. The reason behind this progress is the urgent need to reduce the clinical consequences of IRI. Two concepts appear most beneficial and include either the avoidance of ischemia, e.g., the replacement of cold storage by machine perfusion, or secondly, an endischemic organ improvement through perfusion in the recipient center prior to implantation. While several concepts, including normothermic perfusion, were found to reduce recipient transaminase levels and early allograft dysfunction, hypothermic oxygenated perfusion also reduced IRI-associated post-transplant complications and costs. With the impact on mitochondrial injury and subsequent less IRI-inflammation, this endischemic perfusion was also found to reduce the recurrence of hepatocellular carcinoma after liver transplantation. Firstly, this article highlights the contributing factors to tumor recurrence, including the surgical and medical tissue trauma and underlying mechanisms of IRI-associated inflammation. Secondly, it focuses on the role of mitochondria and associated interventions to reduce cancer recurrence. Finally, the role of machine perfusion technology as a delivery tool and as an individual treatment is discussed together with the currently available clinical studies.

The complex role of tumor-infiltrating macrophages

Long recognized as an evolutionarily ancient cell type involved in tissue homeostasis and immune defense against pathogens, macrophages are being re-discovered as regulators of several diseases, including cancer. Tumor-associated macrophages (TAMs) represent the most abundant innate immune population in the tumor microenvironment (TME). Macrophages are professional phagocytic cells of the hematopoietic system specializing in the detection, phagocytosis and destruction of bacteria and other harmful micro-organisms, apoptotic cells and metabolic byproducts. In contrast to these healthy macrophage functions, TAMs support cancer cell growth and metastasis and mediate immunosuppressive effects on the adaptive immune cells of the TME. Cancer is one of the most potent insults on macrophage physiology, inducing changes that are intimately linked with disease progression. In this Review, we outline hallmarks of TAMs and discuss the emerging mechanisms that contribute to their pathophysiological adaptations and the vulnerabilities that provide attractive targets for therapeutic exploitation in cancer.

Non-alcoholic fatty liver disease-related hepatocellular carcinoma: Is there a role for immunotherapy?

Hepatocellular carcinoma (HCC) is among the most common cancers and it is a major cause of cancer-related deaths. Non-alcoholic fatty liver disease (NAFLD) affects approximately one fourth of individuals worldwide and it is becoming one of the most important causes of HCC. The pathogenic mechanisms leading to NAFLD-related HCC are complex and not completely understood. However, metabolic, fibrogenic, oncogenic, inflammatory and immunological pathways seem to be involved. First-line therapy of advanced HCC has recently undergone major changes, since the combination of atezolizumab and bevacizumab was proven to increase survival when compared to sorafenib. Other immune-oncology drugs are also demonstrating promising results in patients with advanced HCC when compared to traditional systemic therapy. However, initial studies raised concerns that the advantages of immunotherapy might depend on the underlying liver disease, which seems to be particularly important in NAFLD-related HCC, as these tumors might not benefit from it. This article will review the mechanisms of NAFLD-related hepatocarcinogenesis, with an emphasis on its immune aspects, the efficacy of traditional systemic therapy for advanced NAFLD-related HCC, and the most recent data on the role of immunotherapy for this specific group of patients, showing that the management of this condition should be individualized and that a general recommendation cannot be made at this time.

TREM-1 Modulation Strategies for Sepsis

The triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor, which can be upregulated in inflammatory diseases as an amplifier of immune responses. Once activated, TREM-1 induces the production and release of pro-inflammatory cytokines and chemokines, in addition to increasing its own expression and circulating levels of the cleaved soluble extracellular portion of TREM-1 (sTREM-1). This amplification of the inflammatory response by TREM-1 has now been considered as a critical contributor to the dysregulated immune responses in sepsis. Studies have shown that in septic patients there is an elevated expression of TREM-1 on immune cells and increased circulating levels of sTREM-1, associated with increased mortality. As a result, a considerable effort has been made towards identifying endogenous ligands of TREM-1 and developing TREM-1 inhibitory peptides to attenuate the exacerbated inflammatory response in sepsis. TREM-1 modulation has proven a promising strategy for the development of therapeutic agents to treat sepsis. Therefore, this review encompasses the ligands investigated as activators of TREM-1 thus far and highlights the development and efficacy of novel inhibitors for the treatment of sepsis and septic shock.

The Fatal Circle of NETs and NET-Associated DAMPs Contributing to Organ Dysfunction

The innate immune system is the first line of defense against invading pathogens or sterile injuries. Pattern recognition receptors (PRR) sense molecules released from inflamed or damaged cells, or foreign molecules resulting from invading pathogens. PRRs can in turn induce inflammatory responses, comprising the generation of cytokines or chemokines, which further induce immune cell recruitment. Neutrophils represent an essential factor in the early immune response and fulfill numerous tasks to fight infection or heal injuries. The release of neutrophil extracellular traps (NETs) is part of it and was originally attributed to the capture and elimination of pathogens. In the last decade studies revealed a detrimental role of NETs during several diseases, often correlated with an exaggerated immune response. Overwhelming inflammation in single organs can induce remote organ damage, thereby further perpetuating release of inflammatory molecules. Here, we review recent findings regarding damage-associated molecular patterns (DAMPs) which are able to induce NET formation, as well as NET components known to act as DAMPs, generating a putative fatal circle of inflammation contributing to organ damage and sequentially occurring remote organ injury.

HMGB1 signaling pathway in diabetes-related dementia: Blood-brain barrier breakdown, brain insulin resistance, and Aβ accumulation

Diabetes contributes to the onset of various diseases, including cancer and cardiovascular and neurodegenerative diseases. Recent studies have highlighted the similarities and relationship between diabetes and dementia as an important issue for treating diabetes-related cognitive deficits. Diabetes-related dementia exhibits several features, including blood-brain barrier disruption, brain insulin resistance, and Aβ over-accumulation. High-mobility group box1 (HMGB1) is a protein known to regulate gene transcription and cellular mechanisms by binding to DNA or chromatin via receptor for advanced glycation end-products (RAGE) and toll-like receptor 4 (TLR4). Recent studies have demonstrated that the interplay between HMGB1, RAGE, and TLR4 can impact both neuropathology and diabetic alterations. Herein, we review the recent research regarding the roles of HMGB1-RAGE-TLR4 axis in diabetes-related dementia from several perspectives and emphasize the importance of the influence of HMGB1 in diabetes-related dementia.

N-Terminal Peptide of PGLYRP1/Tag7 Is a Novel Ligand for TREM-1 Receptor

An investigation of innate immunity receptors sheds light on the mechanisms of inflammation and associated immune reactions. One of the key immune regulators is the TREM-1 receptor, which is involved in both inflammation and antitumor immune response. In this article, we have obtained a new ligand for the TREM-1 receptor. The peptide, named N3, is a part of the innate immune protein PGLYRP1/Tag7. It is responsible for activating the TREM-1 signaling pathway. Here, we have demonstrated that the N3 peptide acts like other TREM-1 receptor ligands: its binding results in a mild inflammation response and appearance of cytotoxic lymphocytes. We have shown that cytotoxic populations of lymphocytes in N3 peptide-treated PBMCs are similar to those treated with Tag7 or Hsp70. We also determined the part of the N3 peptide responsible for binding to TREM-1. The resulting peptide (N9) consists of nine amino acids and can be considered as a potential peptide that blocks TREM-1 signaling.

Endothelial Dysfunction Induced by Extracellular Neutrophil Traps Plays Important Role in the Occurrence and Treatment of Extracellular Neutrophil Traps-Related Disease

Many articles have demonstrated that extracellular neutrophil traps (NETs) are often described as part of the antibacterial function. However, since the components of NETs are non-specific, excessive NETs usually cause inflammation and tissue damage. Endothelial dysfunction (ED) caused by NETs is the major focus of tissue damage, which is highly related to many inflammatory diseases. Therefore, this review summarizes the latest advances in the primary and secondary mechanisms between NETs and ED regarding inflammation as a mediator. Moreover, the detailed molecular mechanisms with emphasis on the disadvantages from NETs are elaborated: NETs can use its own enzymes, release particles as damage-associated molecular patterns (DAMPs) and activate the complement system to interact with endothelial cells (ECs), drive ECs damage and eventually aggravate inflammation. In view of the role of NETs-induced ED in different diseases, we also discussed possible molecular mechanisms and the treatments of NETs-related diseases.

Mechanistic contributions of Kupffer cells and liver sinusoidal endothelial cells in nanoparticle-induced antigen-specific immune tolerance

The intravenous delivery of disease-relevant antigens (Ag) by polymeric nanoparticles (NP-Ags) has demonstrated Ag-specific immune tolerance in autoimmune and allergic disorders as well as allogeneic transplant rejection. NP-Ags are observed to distribute to the spleen, which has an established role in the induction of immune tolerance. However, studies have shown that the spleen is dispensable for NP-Ag-induced tolerance, suggesting significant contributions from other immunological sites. Here, we investigated the tolerogenic contributions of Kupffer cells (KCs) and liver sinusoidal endothelial cells (LSECs) to NP-Ag-induced tolerance in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Intravenously delivered Ag-conjugated poly(lactide-co-glycolide) NPs (PLG-Ag) distributed largely to the liver, where they associated with both KCs and LSECs. This distribution was accompanied by CD4 T cell accumulation, clonal deletion, and PD-L1 expression by KCs and LSECs. Ex vivo co-cultures of PLG-Ag-treated KCs or LSECs with Ag-specific CD4 T cells resulted in PGE2 and IL-10 or PGE2 secretion, respectively. KC depletion and adoptive transfer experiments demonstrated that KCs were sufficient, but not necessary, to mediate PLG-Ag-induced tolerance in EAE. The durability of PLG-Ag-induced tolerance in the absence of KCs may be attributed to the distribution of PLG-Ags to LSECs, which demonstrated similar levels of PD-L1, PGE2, and T cell stimulatory ability. Collectively, these studies provide mechanistic support for the role of liver KCs and LSECs in Ag-specific tolerance for a biomaterial platform that is currently being evaluated in clinical trials.

Clinical relevance of tumour-associated macrophages

In the past decade, substantial advances have been made in understanding the biology of tumour-associated macrophages (TAMs), and their clinical relevance is emerging. A particular aspect that is becoming increasingly clear is that the interaction of TAMs with cancer cells and stromal cells in the tumour microenvironment enables and sustains most of the hallmarks of cancer. Therefore, manipulation of TAMs could enable improved disease control in a substantial fraction of patients across a large number of cancer types. In this Review, we examine the diversity of TAMs in various cancer indications and how this heterogeneity is being revisited with the advent of single-cell technologies, and then explore the current knowledge on the functional roles of different TAM states and the prognostic and predictive value of TAM-related signatures. We also review agents targeting TAMs that are currently being or will soon be tested in clinical trials, and how manipulations of TAMs can improve existing anticancer treatments. Finally, we discuss how TAM-targeting approaches could be further integrated into routine clinical practice, considering a precision oncology approach and viewing TAMs as a dynamic population that can evolve under treatment pressure.

A novel eCIRP/TREM-1 pathway inhibitor attenuates acute kidney injury

BACKGROUND

Extracellular cold-inducible RNA-binding protein aggravates acute kidney injury after renal ischemia/reperfusion. Although extracellular cold-inducible RNA-binding protein activates triggering receptor expressed on myeloid cells-1, how this receptor and its antagonism with a novel peptide M3 affects acute kidney injury is poorly understood. We, therefore, hypothesize that inhibiting the extracellular cold-inducible RNA-binding protein/triggering receptor expressed on myeloid cells-1 pathway with M3 attenuates acute kidney injury.

METHODS

Wild-type and triggering receptor expressed on myeloid cells-1^-/- mice were subjected to bilateral 30-minute renal hilum clamping followed by reperfusion or sham. After 4 hours, wild-type mice received M3 (10 mg/kg BW) or normal saline intraperitoneally. After 24 hours, renal tissue and serum were collected for analysis. Additionally, wild-type mice were subjected to bilateral renal ischemia for 34 minutes and treated with M3 at 10 mg/kg BW or vehicle at the time of reperfusion. Survival was monitored for 10 days.

RESULTS

After renal ischemia/reperfusion, triggering receptor expressed on myeloid cells-1 messenger ribonucleic acid expression increased by 9-fold in wild-type mice compared to sham mice. Wild-type mice also demonstrated significant increases in serum blood urea nitrogen, creatinine, and interleukin-6 and renal tissue levels of interleukin-6 and neutrophil gelatinase-associated lipocalin after renal ischemia/reperfusion compared to sham mice. Triggering receptor expressed on myeloid cells-1^-/- mice demonstrated significant reductions in serum blood urea nitrogen, creatinine, and interleukin-6 compared to wild-type mice after renal ischemia/reperfusion. Levels of renal interleukin-6 and neutrophil gelatinase-associated lipocalin were also significantly decreased in the kidneys of triggering receptor expressed on myeloid cells-1^-/- mice. Furthermore, treatment with M3 in wild-type mice significantly decreased serum and renal levels of interleukin-6 after renal ischemia/reperfusion. M3 treatment demonstrated significant reductions in renal messenger ribonucleic acid and protein levels of neutrophil gelatinase-associated lipocalin, serum blood urea nitrogen and creatinine, and histologic structural damage as well as apoptosis. Treatment with M3 also increased survival from 35% to 65% in mice with acute kidney injury.

CONCLUSION

Triggering receptor expressed on myeloid cells-1 mediates the deleterious effects of extracellular cold-inducible RNA-binding protein in acute kidney injury after renal ischemia/reperfusion. The novel extracellular cold-inducible RNA-binding protein/triggering receptor expressed on myeloid cells-1 pathway antagonist, M3, attenuates acute kidney injury and has the potential to be developed as a therapeutic agent for acute kidney injury.

Inhibition of the Interaction of TREM-1 and eCIRP Attenuates Inflammation and Improves Survival in Hepatic Ischemia/Reperfusion

INTRODUCTION

Triggering receptor expressed on myeloid cells-1 (TREM-1) has important implications in sepsis and inflammation and is a novel receptor for extracellular cold-inducible RNA-binding protein (eCIRP). We hypothesize that the inhibition of TREM-1 via its interaction with eCIRP by novel peptide inhibitor M3 or knockout gene will attenuate the inflammation and injury associated with severe hepatic ischemia/reperfusion (I/R).

METHODS

Wild-type (WT) C57BL/6 and TREM-1-/- mice underwent 60 min of 70% hepatic ischemia, with 24 h of reperfusion. Additionally, WT mice underwent hepatic I/R and were treated with M3 (10 mg/kg body weight) or vehicle (normal saline) at the start of reperfusion. Blood and ischemic liver tissues were collected, and analysis was performed using enzymatic assays, enzyme-linked immunosorbent assay, reverse-transcription quantitative polymerase chain reaction, and pathohistology techniques. For survival surgery, mice additionally underwent resection of non-ischemic lobes of the liver and survival was monitored for 10 days.

RESULTS

There was an increase in serum levels of tissue markers including aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase as well as cytokine levels (IL-6) and histological scoring of hematoxylin and eosin sections in WT I/R mice. These markers decreased substantially in TREM-1-/- mice. Additionally, neutrophil infiltration markers and markers of local inflammation (myeloperoxidase, macrophage inflammatory protein-2, cyclooxygenase-2) were attenuated in TREM-1-/- mice. Similarly, we show a significant decrease in injury and inflammation markers with M3 treatment. Additionally, we demonstrate decreased apoptosis with TREM-1 inhibition. Finally, M3 treatment improved the survival rate from 42% to 75% after hepatic I/R.

CONCLUSION

TREM-1 is an important eCIRP receptor in the inflammatory response of hepatic I/R, and deficiency of TREM-1 via knockout gene or peptide inhibition attenuated liver injury and inflammation, and improved survival. Inhibition of the TREM-1 and eCIRP interaction in hepatic I/R may have important therapeutic potential.

Non-alcoholic fatty liver disease and hepatocellular carcinoma: Clinical challenges of an intriguing link

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most common liver disorder worldwide mainly attributed to the epidemic spread of obesity and type 2 diabetes mellitus. Although it is considered a benign disease, NAFLD can progress to non-alcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma (HCC). Most data regarding the epidemiology of NAFLD-related HCC are derived from cohort and population studies and show that its incidence is increasing as well as it is likely to emerge as the leading indication for liver transplantation, especially in the Western World. Although cirrhosis constitutes the main risk factor for HCC development, in patients with NAFLD, HCC can arise in the absence of cirrhosis, indicating specific carcinogenic molecular pathways. Since NAFLD as an underlying liver disease for HCC is often underdiagnosed due to lack of sufficient surveillance in this population, NAFLD-HCC patients are at advanced HCC stage at the time of diagnosis making the management of those patients clinically challenging and affecting their prognostic outcomes. In this current review, we summarize the latest literature on the epidemiology, other than liver cirrhosis-pathogenesis, risk factors and prognosis of NAFLD-HCC patients. Finally, we emphasize the prevention of the development of NAFLD-associated HCC and we provide some insight into the open questions and issues regarding the appropriate surveillance policies for those patients.

Adult-Onset Still's Disease: Novel Biomarkers of Specific Subsets, Disease Activity, and Relapsing Forms

Adult-onset Still’s disease (AOSD) is a systemic inflammatory disease of unknown etiology. Recent studies have demonstrated that the hallmark of AOSD is a cytokine storm, which is characterized by the excessive production of interleukin (IL)-1, IL-6, IL-18, tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ), suggesting how pro-inflammatory cytokines play an important role in the pathogenesis of this disease. Actually, a certain proportion of patients (around 17–32%) with severe clinical symptoms achieves only partial remission or is resistant to both first-line corticosteroids and second-line DMARDs. These patients are defined as refractory AOSD patients, requiring higher dosage glucocorticoids, longer treatment duration, or the simultaneous introduction of immunosuppressive drugs, further leading to AOSD relapses. In this narrative review, we will analyze the latest literature data to unravel potential pathogenetic factors associated with specific patterns of AOSD disease or relapses in order to identify biomarkers that may guide clinical decisions, eventually leading to new therapeutic options.

Bulk and Single-Cell Profiling of Breast Tumors Identifies TREM-1 as a Dominant Immune Suppressive Marker Associated With Poor Outcomes

Background

Triggering receptor expressed on myeloid cells (TREM)-1 is a key mediator of innate immunity previously associated with the severity of inflammatory disorders, and more recently, the inferior survival of lung and liver cancer patients. Here, we investigated the prognostic impact and immunological correlates of TREM1 expression in breast tumors.

Methods

Breast tumor microarray and RNAseq expression profiles (n=4,364 tumors) were analyzed for associations between gene expression, tumor immune subtypes, distant metastasis-free survival (DMFS) and clinical response to neoadjuvant chemotherapy (NAC). Single-cell (sc)RNAseq was performed using the 10X Genomics platform. Statistical associations were assessed by logistic regression, Cox regression, Kaplan-Meier analysis, Spearman correlation, Student’s t-test and Chi-square test.

Results

In pre-treatment biopsies, TREM1 and known TREM-1 inducible cytokines (IL1B, IL8) were discovered by a statistical ranking procedure as top genes for which high expression was associated with reduced response to NAC, but only in the context of immunologically “hot” tumors otherwise associated with a high NAC response rate. In surgical specimens, TREM1 expression varied among tumor molecular subtypes, with highest expression in the more aggressive subtypes (Basal-like, HER2-E). High TREM1 significantly and reproducibly associated with inferior distant metastasis-free survival (DMFS), independent of conventional prognostic markers. Notably, the association between high TREM1 and inferior DMFS was most prominent in the subset of immunogenic tumors that exhibited the immunologically hot phenotype and otherwise associated with superior DMFS. Further observations from bulk and single-cell RNAseq analyses indicated that TREM1 expression was significantly enriched in polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and M2-like macrophages, and correlated with downstream transcriptional targets of TREM-1 (IL8, IL-1B, IL6, MCP-1, SPP1, IL1RN, INHBA) which have been previously associated with pro-tumorigenic and immunosuppressive functions.

Conclusions

Together, these findings indicate that increased TREM1 expression is prognostic of inferior breast cancer outcomes and may contribute to myeloid-mediated breast cancer progression and immune suppression.

Identification of Differentially Expressed Genes Reveals BGN Predicting Overall Survival and Tumor Immune Infiltration of Gastric Cancer

Gastric cancer (GC) is one of the most widely occurring malignancies worldwide. Although the diagnosis and treatment strategies of GC have been greatly improved in the past few decades, the morbidity and lethality rates of GC are still rising due to lacking early diagnosis strategies and powerful treatments. In this study, a total of 37 differentially expressed genes were identified in GC by analyzing TCGA, GSE118897, GSE19826, and GSE54129. Using the PPI database, we identified 17 hub genes in GC. By analyzing the expression of hub genes and OS, MFAP2, BGN, and TREM1 were related to the prognosis of GC. In addition, our results showed that higher levels of BGN exhibited a significant correlation with shorter OS time in GC. Nomogram analysis showed that the dysregulation of BGN could predict the prognosis of GC. Moreover, we revealed that BGN had a markedly negative correlation with B cells but had positive correlations with CD8⁺ T cells, CD4⁺ T cells, macrophages, neutrophils, and dendritic cells in GC samples. The pan-cancer analysis demonstrated that BGN was differentially expressed and related to tumor-infiltrating immune cells across human cancers. This study for the first time comprehensively revealed that BGN was a potential biomarker for the prediction of GC prognosis and tumor immune infiltration.

Damage-Associated Molecular Patterns As Double-Edged Swords in Sepsis

Significance: Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host response to infection. This leads to an uncontrolled inflammatory response at the onset of infection, followed by immunosuppression. The development of a specific treatment modality for sepsis is still challenging, reflecting our inadequate understanding of its pathophysiology. Understanding the mechanism and transition of the early hyperinflammation to late stage of immunosuppression in sepsis is critical for developing sepsis therapeutics. Recent Advances: Damage-associated molecular patterns (DAMPs) are intracellular molecules and released upon tissue injury and cell death in sepsis. DAMPs are recognized by pattern recognition receptors to initiate inflammatory cascades. DAMPs not only elicit an inflammatory response but also they subsequently induce immunosuppression, both are equally important for exacerbating sepsis. Recent advances on a new DAMP, extracellular cold-inducible RNA-binding protein for fueling inflammation and immunosuppression in sepsis, have added a new avenue into the dual functions of DAMPs in sepsis. Critical Issues: The molecular modification of DAMPs and their binding to pattern recognition receptors transit dynamically by the cellular environment in pathophysiologic conditions. Correlation between the dynamic changes of the impacts of DAMPs and the clinical outcomes in sepsis still lacks adequate understanding. Here, we focus on the impacts of DAMPs that cause inflammation as well as induce immunosuppression in sepsis. We further discuss the therapeutic potential by targeting DAMPs to attenuate inflammation and immunosuppression for mitigating sepsis. Future Directions: Uncovering pathways of the transition from inflammation to immunosuppression of DAMPs is a potential therapeutic avenue for mitigating sepsis.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

Protein PGLYRP1/Tag7 Peptides Decrease the Proinflammatory Response in Human Blood Cells and Mouse Model of Diffuse Alveolar Damage of Lung through Blockage of the TREM-1 and TNFR1 Receptors

Infection caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) in many cases is accompanied by the release of a large amount of proinflammatory cytokines in an event known as "cytokine storm", which is associated with severe coronavirus disease 2019 (COVID-19) cases and high mortality. The excessive production of proinflammatory cytokines is linked, inter alia, to the enhanced activity of receptors capable of recognizing the conservative regions of pathogens and cell debris, namely TLRs, TREM-1 and TNFR1. Here we report that peptides derived from innate immunity protein Tag7 inhibit activation of TREM-1 and TNFR1 receptors during acute inflammation. Peptides from the N-terminal fragment of Tag7 bind only to TREM-1, while peptides from the C-terminal fragment interact solely with TNFR1. Selected peptides are capable of inhibiting the production of proinflammatory cytokines both in peripheral blood mononuclear cells (PBMCs) from healthy donors and in vivo in the mouse model of acute lung injury (ALI) by diffuse alveolar damage (DAD). Treatment with peptides significantly decreases the infiltration of mononuclear cells to lungs in animals with DAD. Our findings suggest that Tag7-derived peptides might be beneficial in terms of the therapy or prevention of acute lung injury, e.g., for treating COVID-19 patients with severe pulmonary lesions.

Hepatocellular carcinoma in nonalcoholic fatty liver disease: A growing challenge

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease worldwide, and its prevalence increases continuously. As it predisposes to hepatocellular carcinoma both in the presence and in the absence of cirrhosis, it is not surprising that the incidence of NAFLD-related hepatocellular carcinoma would also rise. Some of the mechanisms involved in hepatocarcinogenesis are particular to individuals with fatty liver, and they help explain why liver cancer develops even in patients without cirrhosis. Genetic and immune-mediated mechanisms seem to play an important role in the development of hepatocellular carcinoma in this population. Currently, it is consensual that patients with NAFLD-related cirrhosis should be surveilled with ultrasonography every 6 mo (with or without alpha-fetoprotein), but it is known that they are less likely to follow this recommendation than individuals with other kinds of liver disease. Moreover, the performance of the methods of surveillance are lower in NAFLD than they are in other liver diseases. Furthermore, it is not clear which subgroups of patients without cirrhosis should undergo surveillance. Understanding the mechanisms of hepatocarcinogenesis in NAFLD could hopefully lead to the identification of biomarkers to be used in the surveillance for liver cancer in these individuals. By improving surveillance, tumors could be detected in earlier stages, amenable to curative treatments.

Increased sTREM-1 levels identify cirrhotic patients with bacterial infection and predict their 90-day mortality

BACKGROUND AND AIMS

Patients with cirrhosis are susceptible to bacterial infections (BIs) that are major causes of specific complications and mortality. However, the diagnosis of BIs can often be difficult in advanced disease stage since their symptoms may overlap with the ones of acute decompensation (AD). Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is released from monocytes/macrophages and neutrophils during activation and has been reported to correlate with activity of various inflammatory processes. We investigated its diagnostic and prognostic performance in patients with cirrhosis and BI.

METHODS

Sera of 269 patients were assayed for sTREM-1 by ELISA (172 outpatients and 97 patients with AD of whom 56 had BI). We investigated capacity of sTREM-1 to identify patients with BI and conducted a 90-day follow-up observational study to assess its possible association with short-term mortality.

RESULTS

sTREM-1 levels were significantly higher in patients with more severe liver disease, BI, and acute-on-chronic liver failure than in patients without these conditions. sTREM-1 had similar accuracy to CRP identifying BI [sTREM-1: AUROC (95%CI) 0.804 (0.711-0.897), p < 0.0001; CRP: 0.791 (0.702-0.881), p < 0.0001)] among AD patients. The combination of these two molecules and the presence of ascites into a composite score significantly increased their discriminative power (AUROC: 0.878, 95%CI: 0.812-0.944, p < 0.0001). High sTREM-1 level (>660 pg/mL) was an independent predictor of 90-day mortality in patients with BI [HR: 2.941, (95%CI: 1.009-8.573), p = 0.048] in our multivariate model.

CONCLUSIONS

Use of sTREM-1 could increase the recognition of BIs in cirrhosis and help clinicians in mortality risk assessment of these patients.

Emergence of Dengue 4 as Dominant Serotype During 2017 Outbreak in South India and Associated Cytokine Expression Profile

Dengue virus (DENV) infection is prevalent in tropical and subtropical regions of the world, which is fatal if untreated symptomatically. Emergence of new genotype within serotypes led to enhanced severity. The objective of the study is to identify the molecular characteristics of the DENV circulated during 2017 outbreak in Tamil Nadu, India, and to investigate the role of inflammatory cytokines in different “serotypes” and in “dengue severity”. A total of 135 suspected samples were tested for DENV infection using IgM, IgG, and qPCR assay; where 76 samples were positive for DENV and analyzed for 12 inflammatory cytokines using ELISA. Serotyping shows 14 DENV-1, 22 DENV-2, 7 DENV-3, and 33 DENV-4, where DENV-4 was predominant. Among 76, 42 isolates were successfully sequenced for C-prM region and grouped. A lineage shift was observed in DENV-4 genotype. Irrespective of serotypes, IFNγ was significantly elevated in all serotypes than control as well as in primary infection than secondary, indicating its role in immune response. GM-CSF and IP-10 were significantly elevated in secondary infection and could be used as prognostic biomarkers for secondary infection. Our observation shows differential cytokine expression profile varied with each serotype, indicating serotype/genotype-specific viral proteins might play a major role in dengue severity. DENV-4 as dominant serotype was reported in Tamil Nadu for the first time during an outbreak with a mixed Th1/Th17 cytokine expression profile that correlated with disease severity. We conclude it is essential to identify circulating viral genotype and their fitness by mutational analysis to correlate with disease severity and immune status, as this correlation will be helpful in diagnostics and therapeutics applications.