title: Unconjugated bilirubin mediates heme oxygenase-1-induced vascular benefits in diabetic mice.
abstract: Heme oxygenase-1 (HO-1) exerts vasoprotective effects. Such benefit in diabetic vasculopathy, however, remains unclear. We hypothesize that bilirubin mediates HO-1-induced vascular benefits in diabetes. Diabetic db/db mice were treated with hemin (HO-1 inducer) for 2 weeks, and aortas were isolated for functional and molecular assays. Nitric oxide (NO) production was measured in cultured endothelial cells. Hemin treatment augmented endothelium-dependent relaxations (EDRs) and elevated Akt and endothelial NO synthase (eNOS) phosphorylation in db/db mouse aortas, which were reversed by the HO-1 inhibitor SnMP or HO-1 silencing virus. Hemin treatment increased serum bilirubin, and ex vivo bilirubin treatment improved relaxations in diabetic mouse aortas, which was reversed by the Akt inhibitor. Biliverdin reductase silencing virus attenuated the effect of hemin. Chronic bilirubin treatment improved EDRs in db/db mouse aortas. Hemin and bilirubin reversed high glucose-induced reductions in Akt and eNOS phosphorylation and NO production. The effect of hemin but not bilirubin was inhibited by biliverdin reductase silencing virus. Furthermore, bilirubin augmented EDRs in renal arteries from diabetic patients. In summary, HO-1-induced restoration of endothelial function in diabetic mice is most likely mediated by bilirubin, which preserves NO bioavailability through the Akt/eNOS/NO cascade, suggesting bilirubin as a potential therapeutic target for clinical intervention of diabetic vasculopathy.
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Xiao Yu
authors.initials: XY
authors.lastname: Tian
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX.
authors.forename: Wing Tak
authors.initials: WT
authors.lastname: Wong
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Quan-Bin
authors.initials: QB
authors.lastname: Han
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Hing-Man
authors.initials: HM
authors.lastname: Ho
authors.affiliation: Institute of Cardiovascular Science, Peking University, Beijing, China.
authors.forename: Nanping
authors.initials: N
authors.lastname: Wang
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Siu Ling
authors.initials: SL
authors.lastname: Wong
authors.affiliation: School of Life Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Zhen-Yu
authors.initials: ZY
authors.lastname: Chen
authors.affiliation: Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Surgery, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Chi-Fai
authors.initials: CF
authors.lastname: Ng
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yao
authors.affiliation: Institute of Vascular Medicine, Shenzhen Research Institute, and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China yu-huang@cuhk.edu.hk.
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
mesh_terms: D000109:Acetylcholine; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001663:Bilirubin / Q000378:metabolism* / Q000494:pharmacology*; D002478:Cells, Cultured; D003920:Diabetes Mellitus / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D009573:Nitrites; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D012077:Renal Artery / Q000187:drug effects; D046509:Tissue Culture Techniques
chemical_list: D009573:Nitrites; D017382:Reactive Oxygen Species; D006427:Hemin; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D051547:Heme Oxygenase-1; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D000109:Acetylcholine; D001663:Bilirubin