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Vascular Semaphorin 7A Upregulation by Disturbed Flow Promotes Atherosclerosis Through Endothelial ?1 Integrin.

ABSTRACT: OBJECTIVE:Accumulating evidence suggests a role of semaphorins in vascular homeostasis. Here, we investigate the role of Sema7A (semaphorin 7A) in atherosclerosis and its underlying mechanism. APPROACH AND RESULTS:Using genetically engineered Sema7A-/-ApoE-/- mice, we showed that deletion of Sema7A attenuates atherosclerotic plaque formation primarily in the aorta of ApoE-/- mice on a high-fat diet. A higher level of Sema7A in the atheroprone lesser curvature suggests a correlation of Sema7A with disturbed flow. This notion is supported by elevated Sema7A expression in human umbilical venous endothelial cells either subjected to oscillatory shear stress or treated with the PKA (protein kinase A)/CREB (cAMP response element-binding protein) inhibitor H89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide·2HCl hydrate). Further studies using the partial carotid artery ligation model showed that disturbed flow in the left carotid artery of Sema7A+/+ApoE-/- mice promoted the expression of endothelial Sema7A and cell adhesion molecules, leukocyte adhesion, and plaque formation, whereas such changes were attenuated in Sema7A-/-ApoE-/- mice. Further studies showed that blockage of ?1 integrin, a known Sema7A receptor, or inhibition of FAK (focal adhesion kinase), MEK1/2 (mitogen-activated protein kinase kinase 1/2), or NF-?B (nuclear factor-?B) significantly reduced the expression of cell adhesion molecules and THP-1 (human acute monocytic leukemia cell line) monocyte adhesion in Sema7A-overexpressing human umbilical venous endothelial cells. Studies using chimeric mice suggest that vascular, most likely endothelial, Sema7A plays a major role in atherogenesis. CONCLUSIONS:Our findings indicate a significant role of Sema7A in atherosclerosis by mediating endothelial dysfunction in a ?1 integrin-dependent manner.

SUBMITTER: Hu S

PROVIDER: S-EPMC5785426 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Vascular Semaphorin 7A Upregulation by Disturbed Flow Promotes Atherosclerosis Through Endothelial β1 Integrin.

Hu Shuhong S Liu Yifei Y You Tao T Heath Jack J Xu Linru L Zheng Xiaowei X Wang Aili A Wang Yinyan Y Li Fengchan F Yang Fei F Cao Yiren Y Zhang Huayu H van Gils Janine M JM van Zonneveld Anton Jan AJ Jo Hanjoong H Wu Qingyu Q Zhang Yonghong Y Tang Chaojun C Zhu Li L

Arteriosclerosis, thrombosis, and vascular biology 20171221 2

<h4>Objective</h4>Accumulating evidence suggests a role of semaphorins in vascular homeostasis. Here, we investigate the role of Sema7A (semaphorin 7A) in atherosclerosis and its underlying mechanism.<h4>Approach and results</h4>Using genetically engineered <i>Sema7A</i><sup>-/-</sup><i>ApoE</i><sup>-/-</sup> mice, we showed that deletion of Sema7A attenuates atherosclerotic plaque formation primarily in the aorta of <i>ApoE</i><sup>-/-</sup> mice on a high-fat diet. A higher level of Sema7A in ...[more]

PMID: 29269512

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Project description:BackgroundNumerous genome-wide association studies revealed that SNPs (single nucleotide polymorphisms) at the PHACTR1 (phosphatase and actin regulator 1) locus strongly correlate with coronary artery disease. However, the biological function of PHACTR1 remains poorly understood. Here, we identified the proatherosclerotic effect of endothelial PHACTR1, contrary to macrophage PHACTR1.MethodsWe generated global (Phactr1-/-) and endothelial cell (EC)-specific (Phactr1ECKO) Phactr1 KO (knockout) mice and crossed these mice with apolipoprotein E-deficient (Apoe-/-) mice. Atherosclerosis was induced by feeding the high-fat/high-cholesterol diet for 12 weeks or partially ligating carotid arteries combined with a 2-week high-fat/high-cholesterol diet. PHACTR1 localization was identified by immunostaining of overexpressed PHACTR1 in human umbilical vein ECs exposed to different types of flow. The molecular function of endothelial PHACTR1 was explored by RNA sequencing using EC-enriched mRNA from global or EC-specific Phactr1 KO mice. Endothelial activation was evaluated in human umbilical vein ECs transfected with siRNA targeting PHACTR1 and in Phactr1ECKO mice after partial carotid ligation.ResultsGlobal or EC-specific Phactr1 deficiency significantly inhibited atherosclerosis in regions of disturbed flow. PHACTR1 was enriched in ECs and located in the nucleus of disturbed flow areas but shuttled to cytoplasm under laminar flow in vitro. RNA sequencing showed that endothelial Phactr1 depletion affected vascular function, and PPARγ (peroxisome proliferator-activated receptor gamma) was the top transcription factor regulating differentially expressed genes. PHACTR1 functioned as a PPARγ transcriptional corepressor by binding to PPARγ through the corepressor motifs. PPARγ activation protects against atherosclerosis by inhibiting endothelial activation. Consistently, PHACTR1 deficiency remarkably reduced endothelial activation induced by disturbed flow in vivo and in vitro. PPARγ antagonist GW9662 abolished the protective effects of Phactr1 KO on EC activation and atherosclerosis in vivo.ConclusionsOur results identified endothelial PHACTR1 as a novel PPARγ corepressor to promote atherosclerosis in disturbed flow regions. Endothelial PHACTR1 is a potential therapeutic target for atherosclerosis treatment.

Project description:Atherosclerotic lesions occur non-randomly at vascular niches in bends and bifurcations where fluid flow can be characterized as "disturbed" (low shear stress with both forward and retrograde flow). Endothelial cells (ECs) at these locations experience significantly lower average shear stress without change in the levels of pressure or strain, which affects the local balance in mechanical stresses. Common in vitro models of atherosclerosis focus primarily on shear stress without accounting for pressure and strain loading. To overcome this limitation, we used our microfluidic endothelial cell culture model (ECCM) to achieve accurate replication of pressure, strain, and shear stress waveforms associated with both normal flow seen in straight sections of arteries and disturbed flow seen in the abdominal aorta in the infrarenal segment at the wall distal to the inferior mesenteric artery (IMA), which is associated with high incidence of atherosclerotic lesion formation. Human aortic endothelial cells (HAECs) were cultured within the ECCM under both normal and disturbed flow and evaluated for cell shape, cytoskeletal alignment, endothelial barrier function, and inflammation using immunofluorescence microscopy and flow cytometry. Results clearly demonstrate quantifiable differences between cells cultured under disturbed flow conditions, which are cuboidal with short and randomly oriented actin microfilaments and show intermittent expression of β-Catenin and cells cultured under normal flow. However, in the absence of pro-inflammatory stimulation, the levels of expression of activation markers: intra cellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), platelet endothelial cell adhesion molecule-1 (PECAM-1), and vascular endothelial cell growth factor - receptor 2 (VEGF-R2) known to be involved in the initiation of plaque formation were only slightly higher in HAECs cultured under disturbed flow in comparison to cells cultured under normal flow.

Dataset Information

Vascular Semaphorin 7A Upregulation by Disturbed Flow Promotes Atherosclerosis Through Endothelial ?1 Integrin.

Publications

Vascular Semaphorin 7A Upregulation by Disturbed Flow Promotes Atherosclerosis Through Endothelial β1 Integrin.

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