Huina Zhang, 1,2,3 Jian Liu, 1 Dan Qu, 1 Li Wang, 1 Jiang-Yun Luo, 1 Chi Wai Lau, 1 Pingsheng Liu, 3 Zhen Gao, 1 George L. Tipoe, 4 Hung Kay Lee, 5 Chi Fai Ng, 6 Ronald Ching Wan Ma, 7 Xiaoqiang Yao, 1 and Yu Huang 1 Inhibition of miR-200c Restores Endothelial Function in Diabetic Mice Through Suppression of COX-2 Diabetes 2016;65:1196–1207 | DOI: 10.2337/db15-1067 Endothelial dysfunction plays a crucial role in the develop- ment of diabetic vasculopathy. Our initial quantitative PCR results showed an increased miR-200c expression in arteries from diabetic mice and patients with diabetes. However, whether miR-200c is involved in diabetic endo- thelial dysfunction is unknown. Overexpression of miR- 200c impaired endothelium-dependent relaxations (EDRs) in nondiabetic mouse aortas, whereas suppression of miR- 200c by anti–miR-200c enhanced EDRs in diabetic db/db mice. miR-200c suppressed ZEB1 expression, and ZEB1 overexpression ameliorated endothelial dysfunction in- duced by miR-200c or associated with diabetes. More im- portantly, overexpression of anti–miR-200c or ZEB1 in vivo attenuated miR-200c expression and improved EDRs in db/db mice. Mechanistic study with the use of COX-2 2/2 mice revealed that COX-2 mediated miR-200c–induced en- dothelial dysfunction and that miR-200c upregulated COX-2 expression in endothelial cells through suppression of ZEB1 and increased production of prostaglandin E 2 , which also reduced EDR. This study demonstrates for the first time to our knowledge that miR-200c is a new mediator of di- abetic endothelial dysfunction and inhibition of miR-200c rescues EDRs in diabetic mice. These new findings suggest the potential usefulness of miR-200c as the target for drug intervention against diabetic vascular complications. Diabetes affects 9.5% of the adult population worldwide (1). Most patients with diabetes die of cardiovascular complications, including coronary heart disease, stroke, and nephropathy (2,3). Endothelial dysfunction associ- ated with reduced nitric oxide bioavailability is one of the important initiators of vascular pathogenesis leading to the development of diabetic cardiovascular events (4). Hyperglycemia decreases the bioavailability of endothelium- derived relaxing factors such as nitric oxide but increases the production of endothelium-derived contracting factors, thereby contributing to endothelial dysfunction (5,6). However, the molecular mechanisms for the hyperglycemia- mediated disrupted balance between endothelium-derived relaxing factors and endothelium-derived contracting factors remain largely unclear. microRNAs (miRNAs) are the small noncoding RNAs that bind to sequence-specific mRNA and consequently inhibit translation (7). Growing evidence has pinpointed miRNAs as important modulators of cardiovascular health and disease. For instance, miRNAs participate in vascular inflammation (8), arterial remodeling (9), smooth muscle plasticity (10), atherosclerosis (11), and endothelial cell apoptosis (12). Nevertheless, the role of miRNAs in the development of diabetic endothelial dysfunction is sparsely studied. The miR-200 family, which comprises miR-200c, -200a, -200b, -141, and -429, plays a role in the development of diabetes complications. Downregulation of miR-200b in- creases vascular endothelial growth factor expression, promotes angiogenesis, and ameliorates diabetic retinopa- thy (13), whereas elevated miR-200b induces inflammation by promoting the expression of cyclooxygenase-2 (COX-2) 1 Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing In- stitute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China 2 Beijing Institute of Heart, Lung and Blood Vessel Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China 3 National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Acad- emy of Sciences, Beijing, China 4 Department of Anatomy, The University of Hong Kong, Hong Kong, China 5 Department of Chemistry, The Chinese University of Hong Kong, Hong Kong, China 6 Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China 7 Department of Medicine & Therapeutics, The Chinese University of Hong Kong, Hong Kong, China Corresponding author: Yu Huang, yu-huang@cuhk.edu.hk. Received 10 August 2015 and accepted 6 January 2016. This article contains Supplementary Data online at http://diabetes .diabetesjournals.org/lookup/suppl/doi:10.2337/db15-1067/-/DC1. H.Z. and J.L. contributed equally to this work. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See accompanying article, p. 1152. 1196 Diabetes Volume 65, May 2016 SIGNAL TRANSDUCTION