title: Selective inhibition of the reverse mode of Na(+)/Ca(2+) exchanger attenuates contrast-induced cell injury.
abstract: BACKGROUND
  The precise mechanisms underlying radiocontrast nephropathy (RCN) are not well understood. Intracellular Ca(2+) overload is considered to be a key factor in RCN. The Na(+)/Ca(2+) exchanger (NCX) system is one of the main pathways of intracellular Ca(2+) overload. We investigated whether intracellular Ca(2+) overload via the NCX system was involved in contrast-induced renal tubular cytotoxicity.
  
  
  METHODS
  NRK-52E cells were exposed to ioversol (100 mg iodine/ml) for 4 h. KB-R7943 (inhibitor of reverse mode of NCX, 4 × 10(-5), 4 × 10(-6)M) was added 1 h before incubation with ioversol. Cell viability and permeability were determined by 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase assay. Apoptosis was determined by flow cytometry. Intracellular Ca(2+) concentration ([Ca(2+)](i)] and reactive oxygen species (ROS) were detected by confocal microscopy. The expression of NCX1 mRNA and caspase-3 protein was evaluated by reverse transcription-polymerase chain reaction and Western blot, respectively.
  
  
  RESULTS
  Ioversol exposure induced significantly increased lactate dehydrogenase release and decreased 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide conversion in NRK-52E cells. Significantly increased apoptosis and caspase-3 protein expression were observed in the NRK-52E cells exposed to ioversol for 4 h. Ioversol treatment induced a significant increase in [Ca(2+)](i) and intracellular ROS. KB-R7943 dose-dependently and significantly suppressed the increase in [Ca(2+)](i), intracellular ROS and caspase-3 overexpression induced by ioversol and attenuated the contrast-induced NRK-52E cell apoptosis. No significant changes in NCX1 mRNA expression were observed following contrast exposure.
  
  
  CONCLUSIONS
  Intracellular Ca(2+) overload via the reverse mode of NCX, followed by ROS overproduction and caspase-3 overexpression played an important role in the contrast-induced renal tubular cytotoxicity. The reverse mode of the NCX inhibitor KB-R7943 attenuated contrast-induced renal tubular cytotoxicity.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Renmin Hospital of Wuhan University, Wuhan, China. dxyang007@yahoo.com.cn
authors.forename: Dingping
authors.initials: D
authors.lastname: Yang
authors.forename: Dingwei
authors.initials: D
authors.lastname: Yang
authors.forename: Ruhan
authors.initials: R
authors.lastname: Jia
authors.forename: Guohua
authors.initials: G
authors.lastname: Ding
mesh_terms: D058186:Acute Kidney Injury; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003287:Contrast Media / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D007684:Kidney Tubules / Q000166:cytology* / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014283:Triiodobenzoic Acids / Q000494:pharmacology
chemical_list: C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D003287:Contrast Media; D017382:Reactive Oxygen Species; D019831:Sodium-Calcium Exchanger; D014283:Triiodobenzoic Acids; C110374:sodium-calcium exchanger 1; D013890:Thiourea; C054871:ioversol; D002118:Calcium