Deficiency in Fpr2 results in reduced numbers of Lin-cKit+Sca1+ myeloid progenitor cells

Cancer stem cells release interleukin-33 within large oncosomes to promote immunosuppressive differentiation of macrophage precursors

In squamous cell carcinoma (SCC), macrophages responding to interleukin (IL)-33 create a TGF-β-rich stromal niche that maintains cancer stem cells (CSCs), which evade chemotherapy-induced apoptosis in part via activation of the NRF2 antioxidant program. Here, we examined how IL-33 derived from CSCs facilitates the development of an immunosuppressive microenvironment. CSCs with high NRF2 activity redistributed nuclear IL-33 to the cytoplasm and released IL-33 as cargo of large oncosomes (LOs). Mechanistically, NRF2 increased the expression of the lipid scramblase ATG9B, which exposed an "eat me" signal on the LO surface, leading to annexin A1 (ANXA1) loading. These LOs promoted the differentiation of AXNA1 receptor+ myeloid precursors into immunosuppressive macrophages. Blocking ATG9B's scramblase activity or depleting ANXA1 decreased niche macrophages and hindered tumor progression. Thus, IL-33 is released from live CSCs via LOs to promote the differentiation of alternatively activated macrophage, with potential relevance to other settings of inflammation and tissue repair.

Developmental and homeostatic signaling transmitted by the G-protein coupled receptor FPR2

Formyl peptide receptor 2 (FPR2) and its mouse counterpart Fpr2 are the members of the G protein-coupled receptor (GPCR) family. FPR2 is the only member of the FPRs that interacts with ligands from different sources. FPR2 is expressed in myeloid cells as well as epithelial cells, endothelial cells, neurons, and hepatocytes. During the past years, some unusual properties of FPR2 have attracted intense attention because FPR2 appears to possess dual functions by activating or inhibiting intracellular signal pathways based on the nature, concentration of the ligands, and the temporal and spatial settings of the microenvironment in vivo, the cell types it interacts with. Therefore, FPR2 controls an abundant array of developmental and homeostatic signaling cascades, in addition to its "classical" capacity to mediate the migration of hematopoietic and non-hematopoietic cells including malignant cells. In this review, we summarize recent development in FPR2 research, particularly in its role in diseases, therefore helping to establish FPR2 as a potential target for therapeutic intervention.

Inflammation-related mRNA expression in patients with multiple myeloma undergoing hematopoietic stem cell mobilization

Mobilization of CD34+ cells is a key element in the therapy of patients with multiple myeloma undergoing autologous stem cell transplantation. The use of chemotherapy and the granulocyte colony-stimulating factor can significantly affect the expression of inflammation-related proteins and the migration of hematopoietic stem cells. We assessed the mRNA expression of selected proteins involved in the inflammatory landscape in MM patients (n=71). The aim of the study was to evaluate C-C motif chemokine ligand 3, 4, 5 (CCL3, CCL4, CCL5), leukocyte cell-derived chemotaxin 2 (LECT2), tumor necrosis factor (TNF), and formyl peptide receptor 2 (FPR2) levels in the course of mobilization and their role in the CD34+ collection efficacy. mRNA expression from peripheral blood plasma was evaluated by RT-PCR. We observed a deep decline in CCL3, CCL4, LECT2, and TNF mRNA expression on the day of the first apheresis (day A) as compared to baseline. A negative correlation was observed between CCL3, FPR2, LECT2, TNF level, and the CD34+ cells count in peripheral blood on day A, and the number of CD34+ cells obtained at first apheresis . Our results indicate that the investigated mRNAs significantly alter and may regulate the migration of CD34+ cells during mobilization. Moreover, in case of FPR2 and LECT2, the results obtained in patients differ from the murine models.

Identification of crucial genes that induce coronary atherosclerosis through endothelial cell dysfunction in AMI-identifying hub genes by WGCNA

OBJECTIVE

To identify the most relevant genes of cardiovascular disease in acute myocardial infarction patients using weighted gene co-expression network analysis (WGCNA).

METHODS

The microarray dataset of GSE66360 was downloaded from the Gene Expression Omnibus (GEO) website. The differential genes with adjusted P < 0.05 and |log2 fold change (FC)| > 0.5 were included in the analysis. The weighed gene co-expression network analysis (WGCNA) was used to build a gene co-expression network and identify the most significant module. Cytoscape was used to filter the hub genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed for the hub genes. The key genes were defined as having high statistical and biological significance.

RESULTS

A total of 4751 differentially expressed genes (DEGs) were screened from the dataset. The purple module had the highest significance in AMI. There were 47 hub genes identified from the module. The GO terms "amyloid beta protein metabolism" and "carbohydrate metabolism" and the KEGG terms "phagosome-related pathways" and "Staphylococcus aureus-associated pathways" were the pathways strongly enriched in AMI. Fatty acid translocase cluster of differentiation (CD36), formyl peptide receptor type 2 (FPR2), integrin subunit alpha M (ITGAM), and oxidized low density lipoprotein receptor 1 (OLR1) were considered key genes in AMI.

CONCLUSION

Our research suggested that the underlying mechanism was related to inflammation and lipid formation. The hub genes identified were CD36, FPR2, ITGAM, and OLR1.

The G-Protein Coupled Formyl Peptide Receptors and Their Role in the Progression of Digestive Tract Cancer

Chronic inflammation is a causative factor of many cancers, although it originally acts as a protective host response to the loss of tissue homeostasis. Many inflammatory conditions predispose susceptible cells, most of which are of epithelial origin, to neoplastic transformation. There is a close correlation between digestive tract (DT) cancer and chronic inflammation, such as esophageal adenocarcinoma associated with Barrett’s esophagus, helicobacter pylori infection as the cause of stomach cancer, hepatitis leading to liver cirrhosis and subsequent cancer, and colon cancer linking to inflammatory bowel diseases and schistosomiasis. A prominent feature of malignant transformation of DT tract epithelial cells is their adoption of somatic gene mutations resulting in abnormal expression of proteins that endow the cells with unlimited proliferation as well as increased motility and invasive capabilities. Many of these events are mediated by Gi-protein coupled chemoattractant receptors (GPCRs) including formyl peptide receptors (FPRs in human, Fprs in mice). In this article, we review the current understanding of FPRs (Fprs) and their function in DT cancer types as well as their potential as therapeutic targets.

Lack of resolution sensor drives age-related cardiometabolic and cardiorenal defects and impedes inflammation-resolution in heart failure

Objective

Recently, we observed that the specialized proresolving mediator (SPM) entity resolvin D1 activates lipoxin A₄/formyl peptide receptor 2 (ALX/FPR2), which facilitates cardiac healing and persistent inflammation is a hallmark of impaired cardiac repair in aging. Splenic leukocyte-directed SPMs are essential for the safe clearance of inflammation and cardiac repair after injury; however, the target of SPMs remains undefined in cardiac healing and repair.

Methods

To define the mechanistic basis of ALX/FPR2 as a resolvin D1 target, ALX/FPR2-null mice were examined extensively. The systolic-diastolic heart function was assessed using echocardiography, leukocytes were phenotyped using flow cytometry, and SPMs were quantitated using mass spectrometry. The presence of cardiorenal syndrome was validated using histology and renal markers.

Results

Lack of ALX/FPR2 led to the development of spontaneous obesity and diastolic dysfunction with reduced survival with aging. After cardiac injury, ALX/FPR2^−/− mice showed lower expression of lipoxygenases (−5, −12, −15) and a reduction in SPMs in the infarcted left ventricle and spleen, indicating nonresolving inflammation. Reduced SPM levels in the infarcted heart and spleen are suggestive of impaired cross-talk between the injured heart and splenic leukocytes, which are required for the resolution of inflammation. In contrast, cyclooxygenases (−1 and −2) were over amplified in the infarcted heart. Together, these results suggest interorgan signaling in which the spleen acts as both an SPM biosynthesizer and supplier in acute heart failure. ALX/FPR2 dysfunction magnified obesogenic cardiomyopathy and renal inflammation (↑NGAL, ↑TNF-α, ↑CCL2, ↑IL-1β) with elevated plasma creatinine levels in aging mice. At the cellular level, ALX/FPR2^−/− mice showed impairment of macrophage phagocytic function ex-vivo with expansion of neutrophils after myocardial infarction.

Conclusions

Lack of ALX/FPR2 induced obesity, reduced the life span, amplified leukocyte dysfunction, and facilitated profound interorgan nonresolving inflammation. Our study shows the integrative and indispensable role of ALX/FPR2 in lipid metabolism, cardiac inflammation–resolution processes, obesogenic aging, and renal homeostasis.

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Lack of resolution sensor (ALX/FPR2) led to spontaneous, age-related obesity.

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Absence of ALX/FPR2 triggered obesogenic cardiomyopathy and renal inflammation.

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Deficiency of ALX/FPR2 reduced SPMs in the infarcted heart after cardiac injury.

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ALX/FPR2 dysfunction impaired macrophage function and amplified inflammation.

The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model

Pattern recognition receptors (PRRs) are key elements in the innate immune response. Formyl peptide receptor (FPR) 2 is a PRR that, in addition to proinflammatory, pathogen-derived compounds, also recognizes the anti-inflammatory endogenous ligand annexin A1 (AnxA1). Because the contribution of this signaling axis in viral infections is undefined, we investigated AnxA1-mediated FPR2 activation on influenza A virus (IAV) infection in the murine model. AnxA1-treated mice displayed significantly attenuated pathology upon a subsequent IAV infection with significantly improved survival, impaired viral replication in the respiratory tract, and less severe lung damage. The AnxA1-mediated protection against IAV infection was not caused by priming of the type I IFN response but was associated with an increase in the number of alveolar macrophages (AMs) and enhanced pulmonary expression of the AM-regulating cytokine granulocyte-M-CSF (GM-CSF). Both AnxA1-mediated increase in AM levels and GM-CSF production were abrogated when mouse (m)FPR2 signaling was antagonized but remained up-regulated in mice genetically deleted for mFPR1, an mFPR2 isoform also serving as AnxA1 receptor. Our results indicate a novel protective function of the AnxA1-FPR2 signaling axis in IAV pathology via GM-CSF–associated maintenance of AMs, expanding knowledge on the potential use of proresolving mediators in host defense against pathogens.—Schloer, S., Hübel, N., Masemann, D., Pajonczyk, D., Brunotte, L., Ehrhardt, C., Brandenburg, L.-O., Ludwig, S., Gerke, V., Rescher, U. The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model.

Inhibition of FPR2 impaired leukocytes recruitment and elicited non-resolving inflammation in acute heart failure

Lifestyle or age-related risk factors over-activate the inflammation that triggers acute heart failure (HF)-related mortality following myocardial infarction (MI). Post-MI activated leukocytes express formyl peptide receptor 2 (FPR2) that is essential for inflammation-resolution and in cardiac healing. However, the role of FPR2 in acute HF is incomplete and remain of interest. Here, we aimed to determine whether pharmacological inhibition of FPR2 perturb leukocyte trafficking in acute HF. Male C57BL/6 (8-12 weeks) mice were subjected to acute HF (MI-d1) using permanent coronary artery ligation that develops irreversible acute and chronic heart failure. FPR2 antagonist WRW4 (1 μg/kg/day) was subcutaneously injected 3 h post-MI maintaining saline-injected MI-controls. Leukocytes were quantitated using flow cytometry, and acute decompensated HF was confirmed using echocardiography and histology. FPR2 inhibition decreased the expression of FPR2 in the LV and spleen tissues. Administration of WRW4 inhibitor to mice primed immature and inactive neutrophils infiltration Ly6G^int and intensified the Ccl2 expression compared to MI-control in the infarcted LV post-MI. Leukocyte profiling revealed an overall decrease in monocytes (23.3 ± 2%) in WRW4-injected mice compared with MI-control (49.1 ± 2%) in infarcted LV. FPR2 inhibition increased F4/80⁺/Ly6C^hi pro-inflammatory macrophages (14.8 ± 2%) compared with MI-control (10 ± 1%) with increased transcripts of pro-inflammatory markers TNF-α and IL-1β, and decreased Arg-1 expression in the infarcted LV compared to MI-controls is suggestive of the impaired acute inflammatory response. Inhibition of FPR2 using WRW4 also disturbed splenocardiac leukocytes recruitment by priming immature neutrophils leading to the onset of incomplete resolution signaling in acute decompensated HF post-MI.

Proresolving Lipid Mediators and Receptors in Stem Cell Biology: Concise Review

Accumulating evidence indicates that stem cells (SCs) possess immunomodulatory, anti‐inflammatory, and prohealing properties. The mechanisms underlying these functions are being investigated with the final goal to set a solid background for the clinical use of SCs and/or their derivatives. Specialized proresolving lipid mediators (SPMs) are small lipids formed by the enzymatic metabolism of polyunsaturated fatty acids. They represent a leading class of molecules that actively and timely regulate the resolution of inflammation and promote tissue/organ repair. SC formation of these mediators as well as expression of their receptors has been recently reported, suggesting that SPMs may be involved in the immunomodulatory, proresolving functions of SCs. In the present review, we summarize the current knowledge on SPMs in SCs, focusing on biosynthetic pathways, receptors, and bioactions, with the intent to provide an integrated view of SPM impact on SC biology. stem cells translational medicine2019;8:992–998