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Myeloid Kruppel-like factor 4 deficiency augments atherogenesis in ApoE-/- mice--brief report.

ABSTRACT: To investigate the role of Krüppel-like factor 4 (KLF4), an essential transcriptional regulator of macrophage polarization (M1/M2), in the pathogenesis of atherosclerosis.Despite the acknowledged importance of macrophages in atherosclerosis, the role of M1 (classically activated or proinflammatory) versus M2 (alternatively activated or anti-inflammatory) macrophages in this process remains incompletely understood. We recently identified KLF4 as a regulator of macrophage subset specification; that is, KLF4 promotes M2 and inhibits M1 phenotype. Here, we provide evidence that KLF4-deficient macrophages exhibit enhanced proinflammatory activation and foam cell formation in response to oxidized lipids. In vivo, myeloid KLF4-deficient mice (ApoE(-/-) background) develop significantly more vascular inflammation and atherosclerotic lesion formation.Our findings identify myeloid KLF4 as an essential regulator of vascular inflammation and experimental atherogenesis.

SUBMITTER: Sharma N

PROVIDER: S-EPMC3574634 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Myeloid Krüppel-like factor 4 deficiency augments atherogenesis in ApoE-/- mice--brief report.

Sharma Nikunj N Lu Yuan Y Zhou Guangjin G Liao Xudong X Kapil Parul P Anand Puneet P Mahabeleshwar Ganapati H GH Stamler Jonathan S JS Jain Mukesh K MK

Arteriosclerosis, thrombosis, and vascular biology 20121011 12

<h4>Objective</h4>To investigate the role of Krüppel-like factor 4 (KLF4), an essential transcriptional regulator of macrophage polarization (M1/M2), in the pathogenesis of atherosclerosis.<h4>Methods and results</h4>Despite the acknowledged importance of macrophages in atherosclerosis, the role of M1 (classically activated or proinflammatory) versus M2 (alternatively activated or anti-inflammatory) macrophages in this process remains incompletely understood. We recently identified KLF4 as a reg ...[more]

PMID: 23065827

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Project description:BackgroundThe endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) is a known modulator of inflammation and ligand to both, pro-inflammatory cannabinoid receptor 1 (CB1) and anti-inflammatory CB2. While the role of both receptors in atherogenesis has been studied extensively, the significance of 2-AG for atherogenesis is less well characterized.MethodsThe impact of 2-AG on atherogenesis was studied in two treatment groups of ApoE-/- mice. One group received the monoacylglycerol lipase (MAGL)-inhibitor JZL184 [5 mg/kg i.p.], which impairs 2-AG degradation and thus causes elevated 2-AG levels, the other group received vehicle for four weeks. Simultaneously, both groups were fed a high-cholesterol diet. The atherosclerotic plaque burden was assessed in frozen sections through the aortic sinus following oil red O staining and infiltrating macrophages were detected by immunofluorescence targeting CD68. In vitro, the effect of 2-AG on B6MCL macrophage migration was assessed by Boyden chamber experiments. Transcription of adhesion molecules and chemokine receptors in macrophages was assessed by qPCR.ResultsAs expected, application of the MAGL-inhibitor JZL184 resulted in a significant increase in 2-AG levels in vascular tissue (98.2 ± 16.1 nmol/g vs. 27.3 ± 4.5 nmol/g; n = 14-16; p < 0.001). ApoE-/- mice with elevated 2-AG levels displayed a significantly increased plaque burden compared to vehicle treated controls (0.44 ± 0.03 vs. 0.31 ± 0.04; n = 14; p = 0.0117). This was accompanied by a significant increase in infiltrating macrophages within the atherosclerotic vessel wall (0.33 ± 0.02 vs. 0.27 ± 0.01; n = 13-14; p = 0.0076). While there was no alteration to the white blood counts of JZL184-treated animals, 2-AG enhanced macrophage migration in vitro by 1.8 ± 0.2 -fold (n = 4-6; p = 0.0393) compared to vehicle, which was completely abolished by co-administration of either CB1- or CB2-receptor-antagonists. qPCR analyses of 2-AG-stimulated macrophages showed an enhanced transcription of the chemokine CCL5 (1.59 ± 0.23 -fold; n = 5-6; p = 0.0589) and its corresponding receptors CCR1 (2.04 ± 0.46 -fold; n = 10-11; p = 0.0472) and CCR5 (2.45 ± 0.62 -fold; n = 5-6; p = 0.0554).ConclusionTaken together, elevated 2-AG levels appear to promote atherogenesis in vivo. Our data suggest that 2-AG promotes macrophage migration, possibly by the CCL5-CCR5/CCR1 axis, and thereby contributes to vascular inflammation. Thus, decreasing vascular 2-AG levels might represent a promising therapeutic strategy in patients suffering from atherosclerosis and coronary heart disease.

Project description:The importance of immunosuppressive myeloid-derived suppressor cells (MDSCs) bearing monocyte markers in tumor metastasis has been well established. Recently, it was reported that these cells possess phenotypic plasticity and differentiate into fibrocytes, very distinct cells that are precursors of tumorigenic myofibroblasts. However, the importance of this transdifferentiation in tumor metastasis has not been explored. Here, we describe the role of MDSC-derived fibrocytes in tumor metastasis that is regulated by Kruppel-like factor 4 (KLF4), a transcription factor that is critical to monocyte differentiation and to promotion of cancer development. Using mouse metastasis models of melanoma and breast cancer, we found that KLF4 knockout was associated with significantly reduced pulmonary metastasis, which was accompanied by decreased populations of MDSCs, fibrocytes and myofibroblasts in the lung. Cause-effect studies by adoptive transfer revealed that KLF4 deficiency in MDSCs led to significantly reduced lung metastasis that was associated with fewer MDSC-derived fibrocytes and myofibroblasts. Mechanistically, KLF4 deficiency significantly compromised the generation of fibrocytes from MDSCs in vitro. During this process, KLF4 expression levels were tightly linked with those of fibroblast-specific protein-1 (FSP-1), deficiency of which resulted in no metastasis in mice as has been previously reported. In addition, KLF4 bound directly to the FSP-1 promoter as determined by chromatin immunoprecipitation and overexpression of KLF4 increased the FSP-1 promoter activities. Taken together, our results suggest that MDSCs not only execute their immunosuppressive function to promote metastatic seeding as reported before, but also boost metastatic tumor growth after they adopt a fibrocyte fate. Therefore, KLF4-mediated fibrocyte generation from MDSCs may represent a novel mechanism of MDSCs contributing to tumor metastasis and supports the feasibility of inhibiting KLF4 or FSP-1 to prevent tumor metastasis.

Dataset Information

Myeloid Kruppel-like factor 4 deficiency augments atherogenesis in ApoE-/- mice--brief report.

Publications

Myeloid Krüppel-like factor 4 deficiency augments atherogenesis in ApoE-/- mice--brief report.

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