Increased superoxide and endothelial NO synthase uncoupling in blood vessels of Bmal1-knockout mice
Authors: Sanjiv Kumar
Lin Yao
Ana M Merloiu
Stephen M Black
Ciprian B Anea
Shruti Sharma
Bo Cheng
R Daniel Rudic
M Irfan Ali
David W Stepp
David J R Fulton
R William Caldwell
Journal: Circulation Research (2012)
Discipline: CLINICAL MEDICINE
Keywords: circadian clock; endothelial NO synthase; reactive oxygen species; Bmal1; endothelial function
Affiliations: Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, GA 30912, USA., From the Department of Pharmacology and Toxicology (C.B.A., B.C., R.W.C., L.Y., A.M.M., R.D.R.), Vascular Biology Center (S.S., S.K., M.I.A., D.W.S., S.M.B., D.J.R.F.), and Department of Physiology (D.W.S.), Georgia Health Sciences University, Augusta, GA; and Department of Stomatology, Wuhan Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China (B.C.).

Abstract:  Rationale: Disruption of the circadian clock in mice produces vascular dysfunction as evidenced by impairments in endothelium-dependent signaling, vasomotion, and blood vessel remodeling. Although the altered function of endothelial NO synthase and the overproduction of reactive oxygen species are central to dysfunction of the endothelium, to date, the impact of the circadian clock on endothelial NO synthase coupling and vascular reactive oxygen species production is not known. Objective: The goals of the present study were to determine whether deletion of a critical component of the circadian clock, Bmal1, can influence endothelial NO synthase coupling and reactive oxygen species levels in arteries from Bmal1-knockout (KO) mice. Methods and results: Endothelial function was reduced in aortae from Bmal1-KO mice and improved by scavenging reactive oxygen species with polyethylene glycol-superoxide dismutase and nonselectively inhibiting cyclooxygenase isoforms with indomethacin. Aortae from Bmal1-KO mice exhibited enhanced superoxide levels as determined by electron paramagnetic resonance spectroscopy and dihydroethidium fluorescence, an elevation that was abrogated by administration of nitro-l-arginine methyl ester. High-performance liquid chromatography analysis revealed a reduction in tetrahydrobiopterin and an increase in dihydrobiopterin levels in the lung and aorta of Bmal1-KO mice, whereas supplementation with tetrahydrobiopterin improved endothelial function in the circadian clock KO mice. Furthermore, levels of tetrahydrobiopterin, dihydrobiopterin, and the key enzymes that regulate biopterin bioavailability, GTP cyclohydrolase and dihydrofolate reductase exhibited a circadian expression pattern. Conclusions: Having an established influence in the metabolic control of glucose and lipids, herein, we describe a novel role for the circadian clock in metabolism of biopterins, with a significant impact in the vasculature, to regulate coupling of endothelial NO synthase, production of superoxide, and maintenance of endothelial function. 

Retracted: No

PubPeer comments:
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 The above figure was from a pre-proof version of the article, not the final corrected version. The error had been raised to our attention at the time of proofing. The corrected version without this mistake is the published version (see link below). Thank you. https: www.ncbi.nlm.nih.gov pmc articles PMC3740771 , 
 #2 Thank you for correcting me. ,