title: Oxalate impairs aminophospholipid translocase activity in renal epithelial cells via oxidative stress: implications for calcium oxalate urolithiasis.
abstract: OBJECTIVE
  We evaluated the possible involvement of phospholipid transporters and reactive oxygen species in the oxalate induced redistribution of renal epithelial cell phosphatidylserine.
  
  
  METHODS
  Madin-Darby canine kidney cells were labeled with the fluorescent phospholipid NBD-PS in the inner or outer leaflet of the plasma membrane and then exposed to oxalate in the presence or absence of antioxidant. This probe was tracked using a fluorescent quenching assay to assess the bidirectional transmembrane movement of phosphatidylserine. Surface expressed phosphatidylserine was detected by annexin V binding assay. The cell permeable fluorogenic probe DCFH-DA was used to measure the intracellular reactive oxygen species level.
  
  
  RESULTS
  Oxalate produced a time and concentration dependent increase in phosphatidylserine, which may have resulted from impaired aminophospholipid translocase mediated, inward directed phosphatidylserine transport and from enhanced phosphatidylserine outward transport. Adding the antioxidant N-acetyl-L-cysteine significantly attenuated phosphatidylserine externalization by effectively rescuing aminophospholipid translocase activity.
  
  
  CONCLUSIONS
  To our knowledge our findings are the first to show that oxalate induced increased reactive oxygen species generation impairs aminophospholipid translocase activity and decreased aminophospholipid translocase activity has a role in hyperoxaluria promoted calcium oxalate urolithiasis by facilitating phosphatidylserine redistribution in renal epithelial cells.
authors.affiliation: Department of Urology, First Affiliated Hospital of Harbin Medical University, and Tumor Prevention and Cure Research Laboratory, Harbin Medical University, Harbin, People's Republic of China.
authors.forename: Shi-Liang
authors.initials: SL
authors.lastname: Yu
authors.forename: Xiu-Guo
authors.initials: XG
authors.lastname: Gan
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Huang
authors.forename: Yan
authors.initials: Y
authors.lastname: Cao
authors.forename: Yong-Quan
authors.initials: YQ
authors.lastname: Wang
authors.forename: Shang-Ha
authors.initials: SH
authors.lastname: Pan
authors.forename: Li-Yan
authors.initials: LY
authors.lastname: Ma
authors.forename: Yue-Qiu
authors.initials: YQ
authors.lastname: Teng
authors.forename: Rui-Hua
authors.initials: RH
authors.lastname: An
mesh_terms: D000818:Animals; D002129:Calcium Oxalate / Q000378:metabolism*; D002478:Cells, Cultured; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D007668:Kidney / Q000166:cytology*; D018384:Oxidative Stress; D049294:Phospholipid Transfer Proteins / Q000378:metabolism*; D052878:Urolithiasis / Q000209:etiology*
chemical_list: D049294:Phospholipid Transfer Proteins; D002129:Calcium Oxalate