During last funding period, we have found that reactive nitrogen species such as peroxynitrite (ONOO-) uncouples endothelial nitric oxide synthase (eNOS) {generates superoxide anions (O2.-) or ONOO- instead of nitric oxide (NO)} and that eNOS uncoupling in diabetes causes accelerated atherosclerosis. Further, we found that tetrahydrobiopterin (BH4) deficiency, an essential cofactor for eNOS, is the key in the development of eNOS uncoupling in diabetes. Finally, we report that BH4 deficiency is due to rapid degradation of GTP cyclohydrolase I (GTPCH1;E.C., the rate-limiting enzyme in BH4 de novo synthesis, by ubiquitin-proteasome system (UPS) in endothelial cells. However, why GTPCH1 is affected by diabetes hasn't been addressed. Thus, this project will test the hypothesis that oxidation of the zinc-binding structures of GTPCH1 inactivates the enzyme resulting in BH4 deficiency with consequent eNOS uncoupling in diabetes.
Aim 1 is establish the essential role of zinc in maintaining GTPCH1 activity and stability and if oxidative disruption of the zinc-cysteine- histidine complexation in GTPCH1 enhances ubiquitination and consequent proteasomal degradation.
Aim 2 is to investigate the molecular mechanisms by which hyperglycemia inhibits GTPCH1 in endothelial cells.
Aim 3 is to determine the contributions of ONOO--induced GTPCH1 inhibition and ubiquitination in diabetes-enhanced atherosclerosis in mouse models of atherosclerosis in vivo. We believe that the proposed studies will provide novel information as to how the metabolic stress associated with diabetes causes damage to the endothelium and how the endothelial cell attempts to protect itself against these stresses and whether scavenging ONOO- is an effective therapy for diabetes.

Public Health Relevance

Published data and preliminary data included in this competitive renewal application demonstrate that eNOS uncoupling causes accelerated atherosclerosis in type 1 diabetes. How diabetes uncouples eNOS is unknown. GTPCH1 is the rate-limiting enzyme for the synthesis of tetrahydrobiopterin, an essential co-factor for eNOS. The goal of this competitive renewal application is to determine 1) how diabetes inhibits GTPCH1;and 2) to determine the contribution of GTPCH1 inhibition in diabetes-enhanced atherosclerosis in mouse models of atherosclerosis in vivo.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-VH-B (03))
Program Officer
Liu, Lijuan
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Oklahoma Health Sciences Center
Internal Medicine/Medicine
Schools of Medicine
Oklahoma City
United States
Zip Code
Song, Ping; Zou, Ming-Hui (2014) Redox regulation of endothelial cell fate. Cell Mol Life Sci 71:3219-39
Li, Hongliang; Min, Qing; Ouyang, Changhan et al. (2014) AMPK activation prevents excess nutrient-induced hepatic lipid accumulation by inhibiting mTORC1 signaling and endoplasmic reticulum stress response. Biochim Biophys Acta 1842:1844-54
Zhang, Wencheng; Wang, Qilong; Wu, Yue et al. (2014) Endothelial cell-specific liver kinase B1 deletion causes endothelial dysfunction and hypertension in mice in vivo. Circulation 129:1428-39
Okon, Imoh S; Coughlan, Kathleen A; Zou, Ming-Hui (2014) Liver kinase B1 expression promotes phosphatase activity and abrogation of receptor tyrosine kinase phosphorylation in human cancer cells. J Biol Chem 289:1639-48
Shirwany, Najeeb A; Zou, Ming-Hui (2014) AMPK: a cellular metabolic and redox sensor. A minireview. Front Biosci (Landmark Ed) 19:447-74
Li, Hongliang; Lee, Jiyeon; He, Chaoyong et al. (2014) Suppression of the mTORC1/STAT3/Notch1 pathway by activated AMPK prevents hepatic insulin resistance induced by excess amino acids. Am J Physiol Endocrinol Metab 306:E197-209
Zhu, Huaiping; Foretz, Marc; Xie, Zhonglin et al. (2014) PRKAA1/AMPK?1 is required for autophagy-dependent mitochondrial clearance during erythrocyte maturation. Autophagy 10:1522-34
Wang, Qiongxin; Zhang, Miao; Ding, Ye et al. (2014) Activation of NAD(P)H oxidase by tryptophan-derived 3-hydroxykynurenine accelerates endothelial apoptosis and dysfunction in vivo. Circ Res 114:480-92
Okon, Imoh S; Coughlan, Kathleen A; Zhang, Cheng et al. (2014) Protein kinase LKB1 promotes RAB7-mediated neuropilin-1 degradation to inhibit angiogenesis. J Clin Invest 124:4590-602
He, Jinlong; Zhou, Yanhong; Xing, Junjie et al. (2013) Liver kinase B1 is required for thromboxane receptor-dependent nuclear factor-*B activation and inflammatory responses. Arterioscler Thromb Vasc Biol 33:1297-305

Showing the most recent 10 out of 66 publications