Zufeng Ding1, Shijie Liu2, Xiaoyan Deng3, Yubo Fan3, Xianwei Wang4, Jawahar L Mehta5. 1. Central Arkansas Veterans Healthcare System, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China; School of Food and Biological Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, PR China. 2. Central Arkansas Veterans Healthcare System, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA. Electronic address: SLiu2@uams.edu. 3. Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, PR China. 4. Central Arkansas Veterans Healthcare System, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA. 5. Central Arkansas Veterans Healthcare System, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA. Electronic address: MehtaJL@uams.edu.
Abstract
OBJECTIVES: Shear stress, autophagy and LOX-1 are important players in atherogenesis. Direct impact of shear stress on autophagy development in endothelial cells and role of LOX-1 therein are undelineated. METHODS AND RESULTS: A parallel-plate flow chamber was used to vary shear stress (3 to 30 dyn/cm(2)), and determine autophagy in endothelial cells. We observed that low shear stress (3 dyn/cm(2)) enhanced autophagy (expression of LC3-II) 2-3 fold, and increasing shear stress (15 to 30 dyn/cm(2)) resulted in a gradual decline. Autophagy increased when cells were treated with an inflammatory stimulus lipopolysaccharide (LPS). LOX-1 expression paralleled autophagy development. The in vitro observations were confirmed in the in vivo setting by studying autophagy (LC3-II and Beclin-1) and LOX-1 expression in wild-type mice given LPS. Expression of both autophagy and LOX-1 was most pronounced in aorto-iliac bifurcation region where shear stress is lower compared with aortic arch, thoracic aorta and iliac artery. To define the role of LOX-1 in the development of autophagy, we studied LOX-1 knockout mice. These mice despite LPS administration exhibited less autophagy (vs. wild-type mice). Role of LOX-1 in the regulation of autophagy was further established with LOX-1 inhibition (siRNA transfection and use of antibody) or overexpression (cDNA transfection), which showed that LOX-1 knockdown reduced while LOX-1 overexpression enhanced LC3-II expression in endothelial cells. CONCLUSIONS: These observations suggest that low shear stress is a powerful regulator on autophagy, particularly in state of inflammation, and LOX-1 plays an important role in shear stress induced autophagy. Published by Elsevier Ireland Ltd.
OBJECTIVES: Shear stress, autophagy and LOX-1 are important players in atherogenesis. Direct impact of shear stress on autophagy development in endothelial cells and role of LOX-1 therein are undelineated. METHODS AND RESULTS: A parallel-plate flow chamber was used to vary shear stress (3 to 30 dyn/cm(2)), and determine autophagy in endothelial cells. We observed that low shear stress (3 dyn/cm(2)) enhanced autophagy (expression of LC3-II) 2-3 fold, and increasing shear stress (15 to 30 dyn/cm(2)) resulted in a gradual decline. Autophagy increased when cells were treated with an inflammatory stimulus lipopolysaccharide (LPS). LOX-1 expression paralleled autophagy development. The in vitro observations were confirmed in the in vivo setting by studying autophagy (LC3-II and Beclin-1) and LOX-1 expression in wild-type mice given LPS. Expression of both autophagy and LOX-1 was most pronounced in aorto-iliac bifurcation region where shear stress is lower compared with aortic arch, thoracic aorta and iliac artery. To define the role of LOX-1 in the development of autophagy, we studied LOX-1 knockout mice. These mice despite LPS administration exhibited less autophagy (vs. wild-type mice). Role of LOX-1 in the regulation of autophagy was further established with LOX-1 inhibition (siRNA transfection and use of antibody) or overexpression (cDNA transfection), which showed that LOX-1 knockdown reduced while LOX-1 overexpression enhanced LC3-II expression in endothelial cells. CONCLUSIONS: These observations suggest that low shear stress is a powerful regulator on autophagy, particularly in state of inflammation, and LOX-1 plays an important role in shear stress induced autophagy. Published by Elsevier Ireland Ltd.