FGL2 knockdown improves heart function through regulation of TLR9 signaling in the experimental autoimmune myocarditis rats

FGL2 promotes tumour growth and attenuates infiltration of activated immune cells in melanoma and ovarian cancer models

The tumour microenvironment is infiltrated by immunosuppressive cells, such as regulatory T cells (Tregs), which contribute to tumour escape and impede immunotherapy outcomes. Soluble fibrinogen-like protein 2 (sFGL2), a Treg effector protein, inhibits immune cell populations, via receptors FcγRIIB and FcγRIII, leading to downregulation of CD86 in antigen presenting cells and limiting T cell activation. Increased FGL2 expression is associated with tumour progression and poor survival in several different cancers, such as glioblastoma multiforme, lung, renal, liver, colorectal, and prostate cancer. Querying scRNA-seq human cancer data shows FGL2 is produced by cells in the tumour microenvironment (TME), particularly monocytes and macrophages as well as T cells and dendritic cells (DCs), while cancer cells have minimal expression of FGL2. We studied the role of FGL2 exclusively produced by cells in the TME, by leveraging Fgl2 knockout mice. We tested two murine models of cancer in which the role of FGL2 has not been previously studied: epithelial ovarian cancer and melanoma. We show that absence of FGL2 leads to a more activated TME, including activated DCs (CD86+, CD40+) and T cells (CD25+, TIGIT+), as well as demonstrating for the first time that the absence of FGL2 leads to more activated natural killer cells (DNAM-1+, NKG2D+) in the TME. Furthermore, the absence of FGL2 leads to prolonged survival in the B16F10 melanoma model, while the absence of FGL2 synergizes with oncolytic virus to prolong survival in the ID8-p53-/-Brca2-/- ovarian cancer model. In conclusion, targeting FGL2 is a promising cancer treatment strategy alone and in combination immunotherapies.

Role of CCRL2 in the Pathogenesis of Experimental Autoimmune Myocarditis via P21-Activated Kinase 1/NOD-Like Receptor Protein 3 Pathway

Myocarditis, a severe inflammatory disease, is becoming a worldwide public health concern. This study aims to elucidate the effect of Chemokine (C C motif) receptor-like 2 (CCRL2) in experimental autoimmune myocarditis (EAM) occurrence and its potential regulatory mechanisms.EAM was simulated in a mouse model injected with α-myosin-heavy chain. The changes on EAM were assessed through histological staining of heart tissues, including measuring cardiac troponin I (cTnI), proinflammatory cytokines, transferase-mediated dUTP nick end labeling (TUNEL) assay, and cardiac function. Then, the heart tissues from the EAM mouse model and control groups were analyzed through transcriptome sequencing to identify the differential expressed genes (DEGs) and hub genes related to pyroptosis. Downregulation of CCRL2 further verified the function of CCRL2 on EAM and p21-activated kinase 1/NOD-like receptor protein 3 (PAK/NLRP3) signaling pathways in vivo.The EAM model was constructed successfully, with the heart weight/body weight ratio, serum level of cTnI, and concentrations of proinflammatory cytokines elevation. Moreover, cell apoptosis was also significantly increased. Transcriptome sequencing revealed 696 and 120 upregulated and downregulated DEGs, respectively. After functional enrichment, CCRL2 was selected as a potential target. Then, we verified that CCRL2 knockdown improved cardiac function, alleviated EAM occurrence, and reduced PAK/NLRP3 protein expression.CCRL2 may act as a novel potential treatment target in EAM by regulating the PAK1/NLRP3 pathway.

Beyond the Rhythm: In Silico Identification of Key Genes and Therapeutic Targets in Atrial Fibrillation

Atrial fibrillation (AF) is a prevalent cardiac arrhythmia worldwide and is characterized by a high risk of thromboembolism, ischemic stroke, and fatality. The precise molecular mechanisms of AF pathogenesis remain unclear. The purpose of this study was to use bioinformatics tools to identify novel key genes in AF, provide deeper insights into the molecular pathogenesis of AF, and uncover potential therapeutic targets. Four publicly available raw RNA-Seq datasets obtained through the ENA Browser, as well as proteomic analysis results, both derived from atrial tissues, were used in this analysis. Differential gene expression analysis was performed and cross-validated with proteomics results to identify common genes/proteins between them. A functional enrichment pathway analysis was performed. Cross-validation analysis revealed five differentially expressed genes, namely FGL2, IGFBP5, NNMT, PLA2G2A, and TNC, in patients with AF compared with those with sinus rhythm (SR). These genes play crucial roles in various cardiovascular functions and may be part of the molecular signature of AF. Furthermore, functional enrichment analysis revealed several pathways related to the extracellular matrix, inflammation, and structural remodeling. This study highlighted five key genes that constitute promising candidates for further experimental exploration as biomarkers as well as therapeutic targets for AF.

Fibrinogen-like protein 2 in inflammatory diseases: A future therapeutic target

Fibrinogen-like protein 2 (FGL2), a member of the fibrinogen family, exists as a membrane-bound protein with immune-associated coagulation activity and a soluble form possessing immunosuppressive functions. The immunomodulatory role of FGL2 is evident in fibrin deposition-associated inflammatory diseases and cancer, suggesting that FGL2 expression could be exploited as a disease biomarker and a therapeutic target. Recently, in vitro studies and knockout and transgenic animal FGL2 models have been used by us and others to reveal the involvement of FGL2 in the pathogenesis of various inflammatory diseases. This review summarizes our current knowledge of the immunomodulatory role of FGL2 in inflammatory diseases and examines the role of FGL2 as a potential therapeutic target.

Expression of fibrinogen-like protein 2 (Fgl2) on Toll-like receptor 9 (TLR9) expression in autoimmune myelitis

Toll-like receptor 9 (TLR9) can participate in the signal transduction of activated immune cells and induce myelitis and other autoimmune diseases. The effector molecule fibrin-like protein 2 (Fgl2) plays a role in regulating the body's autoimmune signaling pathway. They both have the conditions for the treatment of this disease target. The objective of this work was to investigate the effect of Fgl2 on the expression of DNA receptor TLR9 in autoimmune myelitis. 140 rats were randomly divided into a normal control group, an autoimmune myelitis group, a low-dose Fgl2 group, a middle-dose Fgl2 group, a higher-dose Fgl2 group, a high-dose Fgl2 group, and a methylprednisolone group. Different injection methods were used in each group. The changes of rat behavior and disease were recorded, and brain and spinal cord tissue slices were made for observation. The results showed that in the high dose Fgl2 group, the incidence of disease was 15 %, the nerve injury score was 1.0 ± 0.15, the body weight change was -5.8 ± 1.24 g, the number of spinal cord tissue injury was 1.82 ± 0.44, the number of TLR9 positive cells in the brain tissue was 7.53 ± 1.84, and the number of TLR9 positive cells in spinal cord tissue was 5.02 ± 1.81. These indexes were lower than those in other Fgl2 groups and significantly lower than those in autoimmune myelitis group (P < 0.05). The average incubation period of the disease was 13.66 ± 0.41 days, which was significantly higher than that of the autoimmune myelitis group (P < 0.05). It can be observed that TLR9 signaling pathway played an important role in the occurrence and development of autoimmune myelitis. With the increase of Fgl2 dose, the number of TLR9 positive cells decreased gradually. Fgl2 treatment can reduce the expression of inflammatory factors and the severity of dysfunction in autoimmune myelitis, inhibit the expression of TLR9, and improve the condition of autoimmune myelitis.

MAPK-mediated upregulation of fibrinogen-like protein 2 promotes proliferation, migration, and invasion of colorectal cancer cells

Fibrinogen-like protein 2 (FGL2) has been reported to play a key role in the development of human cancers. However, it is still unmasked whether FGL2 plays a potential role in colorectal carcinogenesis. In this study, the messenger RNA and protein expression levels were measured by quantitative real-time polymerase chain reaction and western blot. Cell counting kit-8 assay, transwell migration, and invasion assay were carried out to evaluate the proliferation, migration, and invasion of LOVO and SW620 cells. FGL2 was upregulated in colorectal cancer (CRC) tissues, as well as cell lines. Mitogen-activated protein kinase (MAPK) signaling was activated in CRC tissues and cell lines. FGL2 was confirmed to be downregulated by MAPK signaling inhibitor U0126. Further, we determined that knockdown of FGL2 caused a reduction of proliferation, migration, and invasion in LOVO and SW620 cells. Consistently, treatment of LOVO and SW620 cells with U0126 led to a decrease in cell proliferation, migration, and invasion. However, these changes initiated by U0126 were abolished by FGL2 overexpression. To conclude, MAPK-mediated upregulation of FGL2 promotes the proliferation, migration, and invasion of CRC cells.