Guizhen Zhao1, Yi Fu1, Zeyu Cai1, Fang Yu1, Ze Gong1, Rongbo Dai1, Yanhua Hu1, Lingfang Zeng1, Qingbo Xu1, Wei Kong2. 1. From the Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Beijing, P. R. China (G.Z., Y.F., Z.C., F.Y., Z.G., R.D., W.K.); and BHF Centre, School of Cardiovascular Medicine & Science, King's College London, United Kingdom (Y.H., L.Z., Q.X.). 2. From the Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Beijing, P. R. China (G.Z., Y.F., Z.C., F.Y., Z.G., R.D., W.K.); and BHF Centre, School of Cardiovascular Medicine & Science, King's College London, United Kingdom (Y.H., L.Z., Q.X.). kongw@bjmu.edu.cn qingbo.xu@kcl.ac.uk.
Abstract
RATIONALE: Although not fully understood, the phenotypic transition of vascular smooth muscle cells exhibits at the early onset of the pathology of aortic aneurysms. Exploring the key regulators that are responsible for maintaining the contractile phenotype of vascular smooth muscle cells (VSMCs) may confer vascular homeostasis and prevent aneurysmal disease. XBP1 (X-box binding protein 1), which exists in a transcriptionally inactive unspliced form (XBP1u) and a spliced active form (XBP1s), is a key component in response to endoplasmic reticular stress. Compared with XBP1s, little is known about the role of XBP1u in vascular homeostasis and disease. OBJECTIVE: We aim to investigate the role of XBP1u in VSMC phenotypic switching and the pathogenesis of aortic aneurysms. METHODS AND RESULTS: XBP1u, but not XBP1s, was markedly repressed in the aorta during the early onset of aortic aneurysm in both angiotensin II-infused apolipoprotein E knockout (ApoE-/-) and CaPO4 (calcium phosphate)-induced C57BL/6J murine models, in parallel with a decrease in smooth muscle cell contractile apparatus proteins. In vivo studies revealed that XBP1 deficiency in smooth muscle cells caused VSMC dedifferentiation, enhanced vascular inflammation and proteolytic activity, and significantly aggravated both thoracic and abdominal aortic aneurysms in mice. XBP1 deficiency, but not an inhibition of XBP1 splicing, induced VSMC switching from the contractile phenotype to a proinflammatory and proteolytic phenotype. Mechanically, in the cytoplasm, XBP1u directly associated with the N terminus of FoxO4 (Forkhead box protein O 4), a recognized repressor of VSMC differentiation via the interaction and inhibition of myocardin. Blocking the XBP1u-FoxO4 interaction facilitated nuclear translocation of FoxO4, repressed smooth muscle cell marker genes expression, promoted proinflammatory and proteolytic phenotypic transitioning in vitro, and stimulated aortic aneurysm formation in vivo. CONCLUSIONS: Our study revealed the pivotal role of the XBP1u-FoxO4-myocardin axis in maintaining the VSMC contractile phenotype and providing protection from aortic aneurysm formation.
RATIONALE: Although not fully understood, the phenotypic transition of vascular smooth muscle cells exhibits at the early onset of the pathology of aortic aneurysms. Exploring the key regulators that are responsible for maintaining the contractile phenotype of vascular smooth muscle cells (VSMCs) may confer vascular homeostasis and prevent aneurysmal disease. XBP1 (X-box binding protein 1), which exists in a transcriptionally inactive unspliced form (XBP1u) and a spliced active form (XBP1s), is a key component in response to endoplasmic reticular stress. Compared with XBP1s, little is known about the role of XBP1u in vascular homeostasis and disease. OBJECTIVE: We aim to investigate the role of XBP1u in VSMC phenotypic switching and the pathogenesis of aortic aneurysms. METHODS AND RESULTS: XBP1u, but not XBP1s, was markedly repressed in the aorta during the early onset of aortic aneurysm in both angiotensin II-infused apolipoprotein E knockout (ApoE-/-) and CaPO4 (calcium phosphate)-induced C57BL/6J murine models, in parallel with a decrease in smooth muscle cell contractile apparatus proteins. In vivo studies revealed that XBP1 deficiency in smooth muscle cells caused VSMC dedifferentiation, enhanced vascular inflammation and proteolytic activity, and significantly aggravated both thoracic and abdominal aortic aneurysms in mice. XBP1 deficiency, but not an inhibition of XBP1 splicing, induced VSMC switching from the contractile phenotype to a proinflammatory and proteolytic phenotype. Mechanically, in the cytoplasm, XBP1u directly associated with the N terminus of FoxO4 (Forkhead box protein O 4), a recognized repressor of VSMC differentiation via the interaction and inhibition of myocardin. Blocking the XBP1u-FoxO4 interaction facilitated nuclear translocation of FoxO4, repressed smooth muscle cell marker genes expression, promoted proinflammatory and proteolytic phenotypic transitioning in vitro, and stimulated aortic aneurysm formation in vivo. CONCLUSIONS: Our study revealed the pivotal role of the XBP1u-FoxO4-myocardin axis in maintaining the VSMC contractile phenotype and providing protection from aortic aneurysm formation.
Authors: Xiaoding Wang; Yingfeng Deng; Guangyu Zhang; Chao Li; Guanqiao Ding; Herman I May; Diem H Tran; Xiang Luo; Ding-Sheng Jiang; Dan L Li; Xiang Wei; Lin Xu; Anwarul Ferdous; Thomas G Gillette; Philipp E Scherer; Xuejun Jiang; Zhao V Wang Journal: Circulation Date: 2019-06-10 Impact factor: 29.690
Authors: Ying H Shen; Scott A LeMaire; Nancy R Webb; Lisa A Cassis; Alan Daugherty; Hong S Lu Journal: Arterioscler Thromb Vasc Biol Date: 2020-02-26 Impact factor: 8.311