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Serum mannose receptor promotes pro-inflammatory macrophage activation and obesity-associated metaflammation

ABSTRACT: Elevated serum concentrations of the soluble mannose receptor (sMR) have been reported to correlate with the severity of various inflammatory diseases. A physiological role of sMR, however, remains unclear. Here, we show that sMR binds CD45 on macrophages, both in vitro and in vivo, leading to cellular reprogramming towards an inflammatory phenotype by inhibition of CD45 phosphatase activity, which induces Src/Akt/NF-κB-mediated signaling. Remarkably, increased serum sMR levels correlate with obesity in both mice and humans. In addition, MR deficiency lowers the high-fat diet-induced increase in pro-inflammatory macrophages in metabolic tissues and protects against hepatic steatosis and whole-body metabolic dysfunctions. Conversely, administration of sMR induces serum pro-inflammatory cytokines and pro-inflammatory macrophages in the liver and promote insulin resistance. Altogether, our results reveal sMR as novel regulator of pro-inflammatory macrophage activation and could constitute a novel therapeutic target for hyperinflammatory diseases.

ORGANISM(S): Mus musculus

PROVIDER: GSE145369 | GEO | 2021/07/16

REPOSITORIES: GEO

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Project description:Interferon (IFN)γ and interleukin (IL)-4 are central regulators of T helper 1 (Th1) and T helper 2 (Th2) immune responses, respectively. Both cytokines have a major impact on macrophage phenotypes: IFNγ–priming and subsequent TLR4 activation induces so called classically activated macrophages that are characterized by pronounced pro-inflammatory responses, whereas IL-4–treated macrophages, commonly called alternatively activated, are known to develop enhanced capacity for endocytosis, antigen presentation, and tissue repair and are generally considered anti-inflammatory. Considering IL-4 as priming rather than activating stimulus, we now compared the TLR4–dependent global gene activation program in IFNγ– versus IL-4–pretreated mouse macrophages, which has rarely been studied so far. Although both cytokines frequently induced opposing effects on gene transcription, the subsequent activation of bone marrow-derived macrophages by lipopolysaccharide (LPS) produced a strong, priming dependent pro-inflammatory response in both macrophage types. For example, the production of key pro-inflammatory cytokines IL-6 and IL-12 was significantly higher in IL-4– versus IFNγ–primed macrophages and several cytokine genes, including Il19, Ccl17, Ccl22, Ccl24 and Cxcl5, were preferentially induced in alternatively primed and LPS activated mouse macrophages. In a subset of genes, including IL12a, IFNγ priming was actually found to suppress LPS–induced gene expression in a Stat1–dependent manner. Our data suggest that IL-4–priming is not per se anti-inflammatory but generates a macrophage that is “tissue protective” but still capable of mounting a strong inflammatory response after TLR4–dependent activation. Keywords: Gene expression profiling Gene expression was investigated in mouse bone marrow-derived macrophages (BMM). On day 7, BMM were stimulated with either IL-4 or IFNγ overnight (18h in total). LPS treatment was performed in primed and unprimed macrophages 4 h prior to harvesting. At least three independent experiments were performed for each condition.

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Serum mannose receptor promotes pro-inflammatory macrophage activation and obesity-associated metaflammation

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