title: Adverse effects of simulated hyper- and hypo-phosphatemia on endothelial cell function and viability.
abstract: BACKGROUND
  Dysregulation of phosphate homeostasis as occurs in chronic kidney disease is associated with cardiovascular complications. It has been suggested that both hyperphosphatemia and hypophosphatemia can cause cardiovascular disease. The molecular mechanisms by which high or low serum phosphate levels adversely affect cardiovascular function are poorly understood. The purpose of this study was to explore the mechanisms of endothelial dysfunction in the presence of non-physiologic phosphate levels.
  
  
  RESULTS
  We studied the effects of simulated hyper- and hypophosphatemia in human umbilical vein endothelial cells in vitro. We found both simulated hyperphosphatemia and hypophosphatemia decrease eNOS expression and NO production. This was associated with reduced intracellular calcium, increased protein kinase C β2 (PKCβ2), reduced cell viability, and increased apoptosis. While simulated hyperphosphatemia was associated with decreased Akt/p-Akt, Bcl-xl/Bax ratios, NFkB-p65 and p-Erk abundance, simulated hypophosphatemia was associated with increased Akt/p-Akt and Bcl-xl/Bax ratios and p-Mek, p38, and p-p38 abundance.
  
  
  CONCLUSIONS
  This is the first demonstration of endothelial dysfunction with hypophosphatemia. Our data suggests that both hyperphosphatemia and hypophosphatemia decrease eNOS activity via reduced intracellular calcium and increased PKCβ2. Hyperphosphatemia also appears to reduce eNOS transcription via reduced signaling through PI3K/Akt/NF-kB and MAPK/NF-kB pathways. On the other hand, hypophosphatemia appears to activate these pathways. Our data provides the basis for further studies to elucidate the relationship between altered phosphate homeostasis and cardiovascular disease. As a corollary, our data suggests that the level of phosphate in the culture media, if not in the physiologic range, may inadvertently affect experimental results.
authors.affiliation: Department of Nephrology, Shanghai Tenth People's Hospital of Tongji University, Shanghai, China.
authors.forename: Ai
authors.initials: A
authors.lastname: Peng
authors.forename: Tianfu
authors.initials: T
authors.lastname: Wu
authors.forename: Caihong
authors.initials: C
authors.lastname: Zeng
authors.forename: Dinesh
authors.initials: D
authors.lastname: Rakheja
authors.forename: Jiankun
authors.initials: J
authors.lastname: Zhu
authors.forename: Ting
authors.initials: T
authors.lastname: Ye
authors.forename: Jack
authors.initials: J
authors.lastname: Hutcheson
authors.forename: Nosratola D
authors.initials: ND
authors.lastname: Vaziri
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Liu
authors.forename: Chandra
authors.initials: C
authors.lastname: Mohan
authors.forename: Xin J
authors.initials: XJ
authors.lastname: Zhou
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D054559:Hyperphosphatemia / Q000503:physiopathology; D017674:Hypophosphatemia / Q000503:physiopathology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein
chemical_list: C494811:BCL2L1 protein, human; D016328:NF-kappa B; D010710:Phosphates; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C579054:PRKCB protein, human; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium