Alternatively Activated (M2) Macrophage Phenotype Is Inducible by Endothelin-1 in Cultured Human Macrophages

Abstract

BackgroundAlternatively activated (M2) macrophages are phenotypically characterized by the expression of specific markers, mainly macrophage scavenger receptors (CD204 and CD163) and mannose receptor-1 (CD206), and participate in the fibrotic process by over-producing pro-fibrotic molecules, such as transforming growth factor-beta1 (TGFbeta1) and metalloproteinase (MMP)-9. Endothelin-1 (ET-1) is implicated in the fibrotic process, exerting its pro-fibrotic effects through the interaction with its receptors (ETA and ETB). The study investigated the possible role of ET-1 in inducing the transition from cultured human macrophages into M2 cells.MethodsCultured human monocytes (THP-1 cell line) were activated into macrophages (M0 macrophages) with phorbol myristate acetate and subsequently maintained in growth medium (M0-controls) or treated with either ET-1 (100nM) or interleukin-4 (IL-4, 10ng/mL, M2 inducer) for 72 hours. Similarly, primary cultures of human peripheral blood monocyte (PBM)-derived macrophages obtained from healthy subjects, were maintained in growth medium (untreated cells) or treated with ET-1 or IL-4 for 6 days. Both M0 and PBM-derived macrophages were pre-treated with ET receptor antagonist (ETA/BRA, bosentan 10-5M) for 1 hour before ET-1 stimulation. Protein and gene expression of CD204, CD206, CD163, TGFbeta1 were analysed by immunocytochemistry, Western blotting and quantitative real time polymerase chain reaction (qRT-PCR). Gene expression of interleukin(IL)-10 and macrophage derived chemokine (CCL-22) was evaluated by qRT-PCR. MMP-9 production was investigated by gel zymography.ResultsET-1 significantly increased the expression of M2 phenotype markers CD204, CD206, CD163, IL-10 and CCL-22, and the production of MMP-9 in both cultures of M0 and PBM-derived macrophages compared to M0-controls and untreated cells. In cultured PBM-derived macrophages, ET-1 increased TGFbeta1 protein and gene expression compared to untreated cells. The ET-1-mediated effects were contrasted by ETA/BRA treatment in both cultured cell types.ConclusionET-1 seems to induce the M2 phenotype in cultured human macrophages, a process apparently contrasted by the action of the ETA/BRA, suggesting possible clinical implications in those fibrotic diseases characterized by increased ET-1 concentrations, such as systemic sclerosis but also type 2 diabetes.

Transcriptome Profiling of Bovine Macrophages Infected by Mycobacterium avium spp. paratuberculosis Depicts Foam Cell and Innate Immune Tolerance Phenotypes

“…An example is Mtb using KLF4 to tilt macrophage response toward the production of arginase and the inhibition of autophagy. KLF4 inhibits M1 and activates M2 polarization (91) while the EDN1 factor mainly exerts a pro-fibrotic effect (92). In MAP-infected JD(-) macrophages, KLF4 and EDN1 were found strikingly induced.…”

Corilagin controls post-parasiticide schistosome egg-induced liver fibrosis by inhibiting Stat6 signalling pathway

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“…M2 macrophages are activated by Th2 cytokines, such as IL-13 and IL-4, which are abundant in chronic infectious. Excessive M2 activation contributes to chronic liver fibrosis by secreting pro-fibrotic cytokines (45, 60). In our cellular model, the M2 macrophage pathway was activated by IL-4/IL-13 cytokines.…”

Hepatitis C virus–induced tumor‐initiating cancer stem–like cells activate stromal fibroblasts in a xenograft tumor model

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“…TGF-b from polarized M2 macrophages also plays a role in fibrotic processes. (16,17) In this study, we examined how HCV infection activates HSCs to promote desmoplasia. Implantation of HCV-associated TISCs was examined for enhancement of tumor-associated fibroblasts (TAFs) in a xenograft model.…”