title: Conversion of biliverdin to bilirubin by biliverdin reductase contributes to endothelial cell protection by heme oxygenase-1-evidence for direct and indirect antioxidant actions of bilirubin.
abstract: Heme oxygenase-1 (HO-1) is highly protective in various pathophysiological states such as cardiovascular and neurodegenerative diseases. HO-1-derived bilirubin is an efficient scavenger of reactive oxygen and nitrogen species (RONS). It remains to determine whether conversion of biliverdin to bilirubin is an essential step for HO-1-conferred protection of endothelial cells. RONS scavenging activities of biliverdin versus bilirubin were assessed by different RONS generating systems and detection techniques. We also silenced the biliverdin reductase (BVR) or HO-1 gene in cultured primary human endothelial cells (HUVECs) and measured the effect on RONS formation upon stimulation with lipopolysaccharide (LPS). In addition, effects of bilirubin and biliverdin on expression of GTP-cyclohydrolase were assessed in an endothelial cell line (EA.hy 926). HO-1- and BVR-silenced cells have increased levels of oxidative stress and bilirubin but not biliverdin increased expression of the protective protein GTP-cyclohydrolase. Moreover, protection by hemin-induced HO-1 expression or biliverdin-triggered bilirubin formation was impaired upon silencing of the HO-1 or BVR gene, respectively. Since bilirubin significantly scavenged RONS but chronic treatment was even more protective our observations support direct and indirect antioxidant properties of BVR and bilirubin and an important role for BVR and bilirubin in HO-1 conferred protection of endothelial cells.
authors.affiliation: Klinikum der Johannes Gutenberg-Universität Mainz, II. Medizinische Klinik, Kardiologie, 55101 Mainz, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jansen
authors.forename: Marcus
authors.initials: M
authors.lastname: Hortmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Oelze
authors.forename: Benjamin
authors.initials: B
authors.lastname: Opitz
authors.forename: Sebastian
authors.initials: S
authors.lastname: Steven
authors.forename: Richard
authors.initials: R
authors.lastname: Schell
authors.forename: Maike
authors.initials: M
authors.lastname: Knorr
authors.forename: Susanne
authors.initials: S
authors.lastname: Karbach
authors.forename: Swenja
authors.initials: S
authors.lastname: Schuhmacher
authors.forename: Philip
authors.initials: P
authors.lastname: Wenzel
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzel
authors.forename: Andreas
authors.initials: A
authors.lastname: Daiber
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism*; D001663:Bilirubin / Q000378:metabolism*; D001664:Biliverdine / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D016166:Free Radical Scavengers / Q000378:metabolism; D055785:Gene Knockdown Techniques; D020868:Gene Silencing / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006801:Humans; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D015538:Nitrosation / Q000187:drug effects; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects; D014443:Tyrosine / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D000804:Angiotensin II; D030421:Peroxynitrous Acid; D014443:Tyrosine; D051547:Heme Oxygenase-1; D014969:Xanthine Oxidase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019789:biliverdin reductase; D001664:Biliverdine; D001663:Bilirubin