title: Ornithine is a key mediator in hyperphosphatemia-mediated human umbilical vein endothelial cell apoptosis: Insights gained from metabolomics.
abstract: OBJECTIVE
  Hyperphosphatemia is associated with accelerated vascular endothelial dysfunction in patients with chronic kidney disease (CKD). The purpose of this study is to investigate the molecular mechanisms underlying hyperphosphatemia-caused endothelial dysfunction.
  
  
  METHODS
  The metabolic fingerprinting of human umbilical vein endothelial cells (HUVECs) subjected to hyperphosphatemia was characterized using an integrated metabolomics approach. HUVECs cultured in physiologically simulated hyperphosphatemia with or without phosphonoformic acid, a sodium-dependent phosphate transporter inhibitor (N=6) were collected for metabolomics analysis. Multivariate principle component analysis and partial least squares discriminant analysis were applied to analyze the metabolic data. The key metabolites were confirmed by quantitative analysis using liquid chromatography coupled with tandem mass spectrometer (LC-MS/MS).
  
  
  RESULTS
  36 metabolites were significantly altered in HUVECs following the challenges of hyperphosphatemia mimic, involving several metabolic pathways (all P<0.05). Among them, ornithine increased significantly in the HUVECs mediated by hyperphosphatemia mimic, and its levels positively correlated with cell apoptosis rate (r=0.674, P=0.002), and several additional metabolites in multiple metabolic pathways. The changes in the levels of ornithine and other several metabolites were supported by subsequent quantitative analyses using LC-MS/MS. Further study demonstrated that the increase in ornithine level may result from the increased expression of arginase 2 in HUVECs, which mediates the hydrolysis of arginine to form ornithine.
  
  
  CONCLUSIONS
  This is the first study demonstrating ornithine a key molecule mediating hyperphosphatemia-induced apoptosis of ECs. Arginase 2 may be a therapeutic target for hyperphosphatemia-associated cardiovascular events.
authors.affiliation: Center for Nephrology and Clinical Metabolomics, Division of Nephrology and Rheumatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China; Department of nephrology, Tongji University School of Medicine, Shanghai, PR China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhou
authors.affiliation: Center for Nephrology and Clinical Metabolomics, Division of Nephrology and Rheumatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Kang
authors.affiliation: Center for Nephrology and Clinical Metabolomics, Division of Nephrology and Rheumatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China.
authors.forename: Bo
authors.initials: B
authors.lastname: Tang
authors.affiliation: Department of Biomedical Engineering, University of Houston, TX, USA.
authors.forename: Chandra
authors.initials: C
authors.lastname: Mohan
authors.affiliation: Department of Biomedical Engineering, University of Houston, TX, USA.
authors.forename: Tianfu
authors.initials: T
authors.lastname: Wu
authors.affiliation: Center for Nephrology and Clinical Metabolomics, Division of Nephrology and Rheumatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China. Electronic address: pengai@tongji.edu.cn.
authors.forename: Ai
authors.initials: A
authors.lastname: Peng
authors.affiliation: Center for Nephrology and Clinical Metabolomics, Division of Nephrology and Rheumatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China. Electronic address: jyliu@tongji.edu.cn.
authors.forename: Jun-Yan
authors.initials: JY
authors.lastname: Liu
mesh_terms: D017209:Apoptosis; D001119:Arginase / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D017245:Foscarnet / Q000494:pharmacology; D061307:Human Umbilical Vein Endothelial Cells / Q000473:pathology*; D006801:Humans; D054559:Hyperphosphatemia / Q000473:pathology / Q000503:physiopathology*; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D055432:Metabolomics; D009952:Ornithine / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000378:metabolism; D028061:Phosphate Transport Proteins / Q000037:antagonists & inhibitors; D010710:Phosphates / Q000378:metabolism / Q000494:pharmacology
chemical_list: D028061:Phosphate Transport Proteins; D010710:Phosphates; D017245:Foscarnet; D001120:Arginine; D009952:Ornithine; D001119:Arginase; D009955:Ornithine Decarboxylase
keywords: Arginase 2; CKD; Endothelial dysfunction; GC/MS; LC–MS/MS