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Deletion of sphingosine 1-phosphate receptor 1 in myeloid cells reduces hepatic inflammatory macrophages and attenuates MASH

ABSTRACT: Background: Immune cell-driven inflammation is a key mediator of metabolic dysfunction-associated steatohepatitis (MASH) progression. We have previously demonstrated that pharmacological sphingosine 1-phosphate (S1P) receptor modulation ameliorates MASH and is associated with attenuated accumulation of intrahepatic macrophage and T cell subsets. Although S1P receptors are expressed on several immune cell types, given the prominent role of monocyte-derived recruited macrophages in the sterile inflammation of MASH, we hypothesized that deletion of S1P receptor 1 (S1P1) on myeloid cells may ameliorate MASH by reducing the accumulation of proinflammatory monocyte-derived macrophages into the liver. Methods: The LyzMCre approach was used to generate myeloid cell-specific knockout mice, termed S1pr1MKO. Littermate S1pr1loxp/loxp mice were used as wild-type (WT) controls. MASH was established by feeding mice a high-fat, fructose, and -cholesterol (FFC) diet for 24 weeks which leads to the development of steatohepatitis and MASH-defining cardiometabolic risk factors. Liver injury and inflammation were determined by histological and gene expression analyses. Intrahepatic leukocyte populations were analyzed by mass cytometry and immunohistochemistry. Results: Histological examination demonstrated a reduction in liver inflammatory infiltrates and fibrosis in FFC-fed S1pr1MKO compared to WT. There was a corresponding reduction in alanine aminotransferase, a sensitive marker for liver injury. As determined by mass cytometry, a significant decrease in recruited macrophages was noted in the livers of FFC-fed S1pr1MKO mice compared to WT. Gene ontology pathway analysis revealed a significant suppression of the peroxisome proliferator-activated receptor gamma (PPARγ) and mitogen activated protein kinase (MAPK) pathways in S1pr1MKO consistent with attenuated MASH in mice. Conclusion: Deletion of S1P1 in myeloid cells is sufficient to attenuate intrahepatic accumulation of monocyte-derived macrophages and ameliorate murine MASH.

ORGANISM(S): Mus musculus

PROVIDER: GSE288368 | GEO | 2025/03/01

REPOSITORIES: GEO

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Project description:Metabolic Dysfunction Associated Steatohepatitis (MASH) is characterized by excess circulating toxic lipids, hepatic steatosis, and liver inflammation. Monocyte adhesion to the liver sinusoidal endothelial cells (LSEC) and transendothelial migration (TEM) are crucial in the inflammatory process. LSEC under lipotoxic stress develops a pro-inflammatory phenotype known as endotheliopathy. However, the mediators of endotheliopathy remain obscure. Primary mouse LSEC isolated from C57BL/6J mice on chow or MASH-inducing diets rich in fat, fructose, and cholesterol (FFC) were subjected to multi-omics profiling. Mice with established MASH, due to a choline-deficient high-fat diet (CDHFD) or FFC diet, were treated with two structurally distinct GSK3 inhibitors [LY2090314, elraglusib (9-ING-41)]. Integrated pathway analysis of mouse LSEC proteome and transcriptome indicates that leukocyte TEM and focal adhesion are major pathways altered in MASH. Kinome profiling of the LSEC phospho-proteome identified GSK3β as the major kinase hub in MASH. GSK3β activating phosphorylation was increased in primary human LSEC treated with the toxic lipid palmitate and in human MASH. Palmitate upregulated the expression of C-X-C motif chemokine ligand 2, intracellular adhesion molecule 1, and phosphorylated focal adhesion kinase, via a GSK3-dependant mechanism. Congruently, the adhesive and transendothelial migratory capacities of primary human neutrophils and THP-1 monocytes through LSEC monolayer under lipotoxic stress were reduced by GSK3 inhibition. Treatment with the GSK3 inhibitors LY2090314 and elraglusib ameliorated liver inflammation, injury, and fibrosis in FFC and CDHFD-fed mice, respectively. Immunophenotyping of intrahepatic leukocytes from CDHFD-fed mice treated with elraglusib using cytometry by the time of flight showed reduced proinflammatory monocyte-derived macrophages and monocyte-derived dendritic cells infiltration.GSK3 inhibition attenuates lipotoxicity-induced LSEC endotheliopathy and may serve as a potential therapeutic strategy in human MASH.

Project description:Sphingosine 1-phosphate (S1P) influences T cell migration into and out of secondary lymphoid organs; however, its mechanism of action remains uncertain. Our previous research shows that agonism of the S1P receptor S1P1 inhibits the egress of T lymphocytes from the peripheral tissues into afferent lymphatics. To better define the mechanism of inhibition, we developed an in vitro model to characterize T cell transendothelial migration across lymphatics. Two commercially available endothelial cell lines (MS-1 and SVEC4-10) were characterized by flow cytometry, real time RT-PCR, and Affymetrix Gene Array. These cell lines were grown to confluent monolayers in transwell systems, on either the upper or lower surface of the transwell insert. T cells were isolated from the spleens of (C57BL/6 x C3H/HeJ)F1, S1P1 KO, or S1P1 KO littermate controls, and either treated with the S1P receptor modulator FTY720 or left untreated. Cells were migrated to chemokines (CCL19 or CCL21) for 4 hours, and migration quantified. Flow cytometry, RT-PCR, and array results identified MS-1 as a blood vascular endothelial cell line, expressing high levels of CD31, CD34, and ICAM-1 as well as other endothelial cell markers; while SVEC4-10 closely resemble a lymphatic phenotype, expressing LYVE-1, VEGFR-3, and podoplanin. T cells efficiently migrate across MS-1, whether grown on the upper or lower surface; whereas migration across SVEC4-10 only occurs when cells are grown on the lower surface of the transwell (iSVEC), recapitulating basal (abluminal) to apical (luminal) migration that occurs in vivo. FTY720 inhibits T cell migration across iSVEC, but not across MS-1. Inhibition is due to drug effects only on T cells but not endothelial cells. S1P1 KO T cells treated with FTY720 are not inhibited in their migration across the iSVEC line, showing that S1P1 stimulation is required for migration inhibition. The in vitro model developed here is the first to use endothelial cell lines to analyze the regulation of T cell migration across lymphatic endothelium. The results show there is directional control of T cell migration across lymphatic cells, such that T cells only migrate from a basal to apical direction. Agonism of S1P1 specifically inhibits migration, while absence of the receptor does not. These findings have important implications for the use of S1P1 agonists in transplantation, as inhibition of cell entry into afferent lymphatics and lymph nodes could impede the development of graft rejection. We used microarrays to detail the global gene expression of these two cell lines in order to beter determine their phenotype as blood vascular or lymphatic endothelial cell line for use in our newly-developed in vitro model. Experiment Overall Design: MS-1 or SVEC4-10 endothelial cell lines were grown in culture flasks for 3-5 days in standard culture medium (see protocol below) until reaching confluence. Cells were then gently dissociated from flask and cells were placed in Trizol reagent for RNA isolation.

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Deletion of sphingosine 1-phosphate receptor 1 in myeloid cells reduces hepatic inflammatory macrophages and attenuates MASH

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