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Monocytic MKP-1 is a Sensor of the Metabolic Environment and Regulates Function and Phenotypic Fate of Monocyte-Derived Macrophages in Atherosclerosis

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ABSTRACT

Diabetes promotes the S-glutathionylation, inactivation and subsequent degradation of mitogen-activated protein kinase phosphatase 1 (MKP-1) in blood monocytes, and hematopoietic MKP-1-deficiency in atherosclerosis-prone mice accelerates atherosclerotic lesion formation, but the underlying mechanisms were not known. Our aim was to determine the mechanisms through which MKP-1 deficiency in monocytes and macrophages promotes atherogenesis. Transplantation of MKP-1-deficient bone marrow into LDL-R−/− (MKP-1LeuKO) mice accelerated high-fat diet (HFD)-induced atherosclerotic lesion formation. After 12 weeks of HFD feeding, MKP-1LeuKO mice showed increased lesion size in both the aortic root (1.2-fold) and the aorta (1.6-fold), despite reduced plasma cholesterol levels. Macrophage content was increased in lesions of MKP-1LeuKO mice compared to mice that received wildtype bone marrow. After only 6 weeks on a HFD, in vivo chemotactic activity of monocytes was already significantly increased in MKP-1LeuKO mice. MKP-1 deficiency in monocytes and macrophages promotes and accelerates atherosclerotic lesion formation by hyper-sensitizing monocytes to chemokine-induced recruitment, predisposing macrophages to M1 polarization, decreased autophagy and oxysterol-induced cell death whereas overexpression of MKP-1 protects macrophages against metabolic stress-induced dysfunction. MKP-1 serves as a master-regulator of macrophage phenotype and function and its dysregulation by metabolic stress may be a major contributor to atherogenesis and the progression of atherosclerotic plaques.

No MeSH data available.


Both MKP-1-deficient and metabolically primed macrophages are sensitized to oxysterol-induced apoptosis.Apoptosis was assessed in peritoneal macrophages treated with vehicle or 7-KC for 24 h. Cell death was measured by trypan blue dye exclusion and caspase 3/7 activation in peritoneal macrophages isolated from wildtype (WT) and MKP-1−/− (KO) mice (A+B), and in unprimed (Control) and metabolically primed (LDL + HG) peritoneal macrophages from C57/BL6 mice (C+D). Results are shown as mean ± SE (n = 3–4). Cell death in the atherosclerotic aortic roots of mice that received either wildtype or MKP-1−/− bone marrow and were fed a high-fat diet for 12 wk was assessed by TUNEL-positive cells relative to the atherosclerotic lesion area (E+F). Experiments were performed using 5–8 mice per experimental group (MKP-1+/+ → LDL-R−/−: n = 5; MKP-1−/− → LDL-R−/−: n = 8). Results are shown as mean ± SE.
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f4: Both MKP-1-deficient and metabolically primed macrophages are sensitized to oxysterol-induced apoptosis.Apoptosis was assessed in peritoneal macrophages treated with vehicle or 7-KC for 24 h. Cell death was measured by trypan blue dye exclusion and caspase 3/7 activation in peritoneal macrophages isolated from wildtype (WT) and MKP-1−/− (KO) mice (A+B), and in unprimed (Control) and metabolically primed (LDL + HG) peritoneal macrophages from C57/BL6 mice (C+D). Results are shown as mean ± SE (n = 3–4). Cell death in the atherosclerotic aortic roots of mice that received either wildtype or MKP-1−/− bone marrow and were fed a high-fat diet for 12 wk was assessed by TUNEL-positive cells relative to the atherosclerotic lesion area (E+F). Experiments were performed using 5–8 mice per experimental group (MKP-1+/+ → LDL-R−/−: n = 5; MKP-1−/− → LDL-R−/−: n = 8). Results are shown as mean ± SE.

Mentions: Both p38 and JNK MAP kinases play key roles in macrophage apoptosis82728. It is well established that the sustained induction of apoptosis in macrophages within advanced plaques results in a significant increase in lesion size29. We therefore examined whether MKP-1 deficiency sensitizes macrophages to apoptosis induced by oxysterols. Since 7-ketocholesterol (7-KC), a major oxidation product of cholesterol found in human atherosclerotic plaque30, is cytotoxic to macrophages31, we treated peritoneal macrophages isolated from wildtype and MKP-1−/− mice for 24 h with either vehicle or 7-KC to induce apoptosis. Cell death was determined by trypan blue dye exclusion (Suppl. Fig. 6) and by measuring caspase 3/7 activation (Suppl. Fig. 7). Cell death and caspase 3/7 activities in response to 7-KC were markedly increased in MKP-1-deficient macrophages compared to macrophages from wildtype mice (Fig. 4A+B), indicating that MKP-1 protects macrophages against oxysterol-induced cell death. Since metabolic stress results in the loss of MKP-1 activity4, we explored whether metabolic stress is sufficient to predispose peritoneal macrophages to oxysterol-induced apoptosis. As expected, metabolic stress had a very similar sensitizing effect on 7-KC-induced cell death as genetic MKP-1 deficiency (Fig. 4C+D).


Monocytic MKP-1 is a Sensor of the Metabolic Environment and Regulates Function and Phenotypic Fate of Monocyte-Derived Macrophages in Atherosclerosis
Both MKP-1-deficient and metabolically primed macrophages are sensitized to oxysterol-induced apoptosis.Apoptosis was assessed in peritoneal macrophages treated with vehicle or 7-KC for 24 h. Cell death was measured by trypan blue dye exclusion and caspase 3/7 activation in peritoneal macrophages isolated from wildtype (WT) and MKP-1−/− (KO) mice (A+B), and in unprimed (Control) and metabolically primed (LDL + HG) peritoneal macrophages from C57/BL6 mice (C+D). Results are shown as mean ± SE (n = 3–4). Cell death in the atherosclerotic aortic roots of mice that received either wildtype or MKP-1−/− bone marrow and were fed a high-fat diet for 12 wk was assessed by TUNEL-positive cells relative to the atherosclerotic lesion area (E+F). Experiments were performed using 5–8 mice per experimental group (MKP-1+/+ → LDL-R−/−: n = 5; MKP-1−/− → LDL-R−/−: n = 8). Results are shown as mean ± SE.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f4: Both MKP-1-deficient and metabolically primed macrophages are sensitized to oxysterol-induced apoptosis.Apoptosis was assessed in peritoneal macrophages treated with vehicle or 7-KC for 24 h. Cell death was measured by trypan blue dye exclusion and caspase 3/7 activation in peritoneal macrophages isolated from wildtype (WT) and MKP-1−/− (KO) mice (A+B), and in unprimed (Control) and metabolically primed (LDL + HG) peritoneal macrophages from C57/BL6 mice (C+D). Results are shown as mean ± SE (n = 3–4). Cell death in the atherosclerotic aortic roots of mice that received either wildtype or MKP-1−/− bone marrow and were fed a high-fat diet for 12 wk was assessed by TUNEL-positive cells relative to the atherosclerotic lesion area (E+F). Experiments were performed using 5–8 mice per experimental group (MKP-1+/+ → LDL-R−/−: n = 5; MKP-1−/− → LDL-R−/−: n = 8). Results are shown as mean ± SE.
Mentions: Both p38 and JNK MAP kinases play key roles in macrophage apoptosis82728. It is well established that the sustained induction of apoptosis in macrophages within advanced plaques results in a significant increase in lesion size29. We therefore examined whether MKP-1 deficiency sensitizes macrophages to apoptosis induced by oxysterols. Since 7-ketocholesterol (7-KC), a major oxidation product of cholesterol found in human atherosclerotic plaque30, is cytotoxic to macrophages31, we treated peritoneal macrophages isolated from wildtype and MKP-1−/− mice for 24 h with either vehicle or 7-KC to induce apoptosis. Cell death was determined by trypan blue dye exclusion (Suppl. Fig. 6) and by measuring caspase 3/7 activation (Suppl. Fig. 7). Cell death and caspase 3/7 activities in response to 7-KC were markedly increased in MKP-1-deficient macrophages compared to macrophages from wildtype mice (Fig. 4A+B), indicating that MKP-1 protects macrophages against oxysterol-induced cell death. Since metabolic stress results in the loss of MKP-1 activity4, we explored whether metabolic stress is sufficient to predispose peritoneal macrophages to oxysterol-induced apoptosis. As expected, metabolic stress had a very similar sensitizing effect on 7-KC-induced cell death as genetic MKP-1 deficiency (Fig. 4C+D).

View Article: PubMed Central - PubMed

ABSTRACT

Diabetes promotes the S-glutathionylation, inactivation and subsequent degradation of mitogen-activated protein kinase phosphatase 1 (MKP-1) in blood monocytes, and hematopoietic MKP-1-deficiency in atherosclerosis-prone mice accelerates atherosclerotic lesion formation, but the underlying mechanisms were not known. Our aim was to determine the mechanisms through which MKP-1 deficiency in monocytes and macrophages promotes atherogenesis. Transplantation of MKP-1-deficient bone marrow into LDL-R−/− (MKP-1LeuKO) mice accelerated high-fat diet (HFD)-induced atherosclerotic lesion formation. After 12 weeks of HFD feeding, MKP-1LeuKO mice showed increased lesion size in both the aortic root (1.2-fold) and the aorta (1.6-fold), despite reduced plasma cholesterol levels. Macrophage content was increased in lesions of MKP-1LeuKO mice compared to mice that received wildtype bone marrow. After only 6 weeks on a HFD, in vivo chemotactic activity of monocytes was already significantly increased in MKP-1LeuKO mice. MKP-1 deficiency in monocytes and macrophages promotes and accelerates atherosclerotic lesion formation by hyper-sensitizing monocytes to chemokine-induced recruitment, predisposing macrophages to M1 polarization, decreased autophagy and oxysterol-induced cell death whereas overexpression of MKP-1 protects macrophages against metabolic stress-induced dysfunction. MKP-1 serves as a master-regulator of macrophage phenotype and function and its dysregulation by metabolic stress may be a major contributor to atherogenesis and the progression of atherosclerotic plaques.

No MeSH data available.