Pivotal Role of Serum- and Glucocorticoid-Inducible Kinase 1 in Vascular Inflammation and Atherogenesis
Objective—Atherosclerosis, an inflammatory disease of arterial vessel walls, requires migration and matrix metalloproteinase (MMP)-9–dependent invasion of monocytes/macrophages into the vascular wall. MMP-9 expression is stimulated by transcription factor nuclear factor-κB, which is regulated by inhibitor κB and thus inhibitor κB-kinase IκB kinase. Regulators of nuclear factor-κB include serum- and glucocorticoid-inducible kinase 1 (SGK1). The present study explored involvement of SGK1 in vascular inflammation and atherogenesis.
Approach and Results—Gene-targeted apolipoprotein E (ApoE)–deficient mice without (apoe−/−sgk1+/+) or with (apoe−/−sgk1−/−) additional SGK1 knockout received 16-week cholesterol-rich diet. According to immunohistochemistry atherosclerotic lesions in aorta and carotid artery, vascular CD45+ leukocyte infiltration, Mac-3+ macrophage infiltration, vascular smooth muscle cell content, MMP-2, and MMP-9 positive areas in atherosclerotic tissue were significantly less in apoe−/−sgk1−/−mice than in apoe−/−sgk1+/+mice. As determined by Boyden chamber, thioglycollate-induced peritonitis and air pouch model, migration of SGK1-deficient CD11b+F4/80+ macrophages was significantly diminished in vitro and in vivo. Zymographic MMP-2 and MMP-9 production, MMP-9 activity and invasion through matrigel in vitro were significantly less in sgk1−/− than in sgk1+/+macrophages and in control plasmid–transfected or inactive K127NSGK1-transfected than in constitutively active S422DSGK1-transfected THP-1 cells. Confocal microscopy revealed reduced macrophage number and macrophage MMP-9 content in plaques of apoe−/−sgk1−/− mice. In THP-1 cells, MMP-inhibitor GM6001 (25 μmol/L) abrogated S422DSGK1-induced MMP-9 production and invasion. According to reverse transcription polymerase chain reaction, MMP-9 transcript levels were significantly reduced in sgk1−/−macrophages and strongly upregulated in S422DSGK1-transfected THP-1 cells compared with control plasmid–transfected or K127NSGK1-transfected THP-1 cells. According to immunoblotting and confocal microscopy, phosphorylation of IκB kinase and inhibitor κB and nuclear translocation of p50 were significantly lower in sgk1−/−macrophages than in sgk1+/+macrophages and significantly higher in S422DSGK1-transfected THP-1 cells than in control plasmid–transfected or K127NSGK1-transfected THP-1 cells. Treatment of S422DSGK1-transfected THP-1 cells with IκB kinase-inhibitor BMS-345541 (10 μmol/L) abolished S422DSGK1-induced increase of MMP-9 transcription and gelatinase activity.
Conclusions—SGK1 plays a pivotal role in vascular inflammation during atherogenesis. SGK1 participates in the regulation of monocyte/macrophage migration and MMP-9 transcription via regulation of nuclear factor-κB.
- Received February 21, 2014.
- Accepted January 5, 2015.
- © 2015 American Heart Association, Inc.