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E-cadherin expression in macrophages dampens their inflammatory responsiveness in vitro, but does not modulate M2-regulated pathologies in vivo.

ABSTRACT: IL-4/IL-13-induced alternatively activated macrophages (M(IL-4/IL-13), AAMs or M2) are known to express E-cadherin, enabling them to engage in heterotypic cellular interactions and IL-4-driven macrophage fusion in vitro. Here we show that E-cadherin overexpression in Raw 264.7 macrophages inhibits their inflammatory response to LPS stimulation, as demonstrated by a reduced secretion of inflammatory mediators like interleukin (IL)-6, tumor necrosis factor (TNF) and nitric oxide (NO). To study the function of E-cadherin in M(IL-4/IL-13) macrophages in vivo, we generated macrophage-specific E-cadherin-deficient C57BL/6 mice. Using this new tool, we analyzed immunological parameters during two typical AAM-associated Th2-driven diseases and assessed Th2-associated granuloma formation. Although E-cadherin is strongly induced in AAMs during Taenia crassiceps helminth infections and allergic airway inflammation, its deletion in macrophages does not affect the course of both Th2 cytokine-driven diseases. Moreover, macrophage E-cadherin expression is largely redundant for granuloma formation around Schistosoma mansoni ova. Overall, we conclude that E-cadherin is a valuable AAM marker which suppresses the inflammatory response when overexpressed. Yet E-cadherin deletion in macrophages does not affect M(LPS+IFN?) and M(IL-4) polarization in vitro, nor in vivo macrophage function, at least in the conditions tested.

SUBMITTER: Van den Bossche J

PROVIDER: S-EPMC4521155 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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E-cadherin expression in macrophages dampens their inflammatory responsiveness in vitro, but does not modulate M2-regulated pathologies in vivo.

Van den Bossche Jan J Laoui Damya D Naessens Thomas T Smits Hermelijn H HH Hokke Cornelis H CH Stijlemans Benoît B Grooten Johan J De Baetselier Patrick P Van Ginderachter Jo A JA

Scientific reports 20150731

IL-4/IL-13-induced alternatively activated macrophages (M(IL-4/IL-13), AAMs or M2) are known to express E-cadherin, enabling them to engage in heterotypic cellular interactions and IL-4-driven macrophage fusion in vitro. Here we show that E-cadherin overexpression in Raw 264.7 macrophages inhibits their inflammatory response to LPS stimulation, as demonstrated by a reduced secretion of inflammatory mediators like interleukin (IL)-6, tumor necrosis factor (TNF) and nitric oxide (NO). To study the ...[more]

PMID: 26226941

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Project description:BackgroundToll-like receptors (TLRs) and macrophages play an important role in rheumatoid arthritis (RA). Currently, it is not clear whether inflammatory M1 or anti-inflammatory M2 predominate among the resident macrophages in the synovium. In the present study, we set out to investigate the impact of TLR stimulation on monocyte-derived M1 and M2 macrophage function and phenotype by mimicking the exposure to abundant TLR agonists as occurs in the context of RA. The response of macrophage subsets to TLR2 and TLR4 activation was evaluated on cluster of differentiation (CD) marker profile; cytokine secretion; gene expression; and NF-?B, interferon regulatory factors 3 and 7 (IRF3/7), and mitogen-activated protein kinase (MAPK) activation.MethodsHuman monocytes were isolated from peripheral blood of healthy individuals and patients with RA and differentiated into M1-like and M2-like macrophages by granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF), respectively. Cells were either (1) stimulated with TLR ligands Pam3 or lipopolysaccharide (LPS) or (2) classically activated via interferon (IFN)-?/LPS. Cytokine production was measured by enzyme-linked immunosorbent assay, and gene expression was measured by qPCR. Cells were stained for CD markers and analyzed by fluorescence-activated cell sorting. NF-?B, IRF3/7, and MAPKs were detected by Western blotting.ResultsMonocyte-derived macrophages of healthy donors (HD) or patients with RA displayed comparable subset-specific phenotypes upon exposure to TLR agonists. CD14 and CD163 marker expression on M2 macrophages did not change upon TLR2 and TLR4 engagement. By contrast, M2 gene markers HMOX1, FOLR2, and SLC40A1 were decreased. Importantly, M2 macrophages derived from HD or patients with RA showed both a decreased ratio of interleukin (IL)-10/IL-6 and IL-10/IL-8 upon stimulation with TLR2 ligand Pam3 compared with TLR4 ligand LPS. Gene expression of TLR2 was increased, whereas TLR4 expression was decreased, by TLR ligand stimulation. MAPKs p38, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase were activated more strongly in M2 than in M1 macrophages by Pam3 or LPS.ConclusionsWe show that the anti-inflammatory activity of M2 macrophages is reduced in the presence of abundant TLR2 ligands without significant changes in cell surface markers. Thus, the classical M1/M2 paradigm based on cellular markers does not apply to macrophage functions in inflammatory conditions such as RA.

Project description:BackgroundAlpha-momorcharin (α-MMC) is a natural medicine derived from bitter melon and has been found to exert immunomodulatory effects. Our previous study indicated that α-MMC can regulate cytokine release from monocytes, but it remains unknown about its regulatory effect on different types of cytokines, such as inflammatory cytokines or anti-inflammatory cytokines.MethodsLPS-induced M1-type macrophages model and IL-4-induced M2-type macrophages model were established, and the expression of proinflammatory cytokines and anti-inflammatory cytokines were assessed by ELISA after α-MMC was administered. Then, a LPS-induced acute pneumonia mouse model was established, the proinflammatory cytokines levels and inflammatory lesions in lung tissues were examined by ELISA or H&E staining. Furthermore, omics screening analysis and Western blotting verification were performed on TLR4 and JAK1-STAT6 signalling pathway-related proteins to elucidate the regulatory mechanism of α-MMC in those M1 macrophages and M2 macrophages.ResultsAt a noncytotoxic dose of 0.3 μg/mL, α-MMC significantly inhibited the LPS-induced expression of inflammatory cytokines, such as TNF-α, IL-1β, IL-6, IL-8, MIP-1α and MCP-1, by M1 macrophages in a time-dependent manner, but α-MMC did not inhibit the IL-4-induced synthesis of anti-inflammatory cytokines, such as IL-10, IL-1RA, EGF, VEGF, TGF-β and CCL22, by M2 macrophages. Moreover, α-MMC also inhibited inflammatory cytokine expression in an LPS-induced acute pneumonia mouse model and alleviated inflammation in lung tissues. Furthermore, omics screening and Western blotting analysis confirmed that α-MMC inhibited TAK1/p-TAK1 and subsequently blocked the downstream MAPK and NF-κB pathways, thus inhibiting the LPS-induced inflammatory cytokine expression.ConclusionOur results reveal that α-MMC inhibits proinflammatory cytokine expression by M1 macrophages but not anti-inflammatory cytokine expression by M2 macrophages. The efficacy of α-MMC in selectively inhibiting proinflammatory cytokine expression renders it particularly suitable for the treatment of severe inflammation and autoimmune diseases characterized by cytokine storms.

Dataset Information

E-cadherin expression in macrophages dampens their inflammatory responsiveness in vitro, but does not modulate M2-regulated pathologies in vivo.

Publications

E-cadherin expression in macrophages dampens their inflammatory responsiveness in vitro, but does not modulate M2-regulated pathologies in vivo.

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