title: Enhanced cell-volume regulation in cyclosporin A cardioprotection.
abstract: OBJECTIVE
  Cyclosporin A (CsA) has been shown to protect against ischaemia/reperfusion injury presumably by its inhibition of mitochondrial permeability transition pore opening through cyclophilin D inhibition. We examine if CsA cardioprotection involves a cell-volume regulatory mechanism.
  
  
  RESULTS
  To address this issue, cultured rabbit cardiomyocytes were subjected to the following protocols: (i) cardiomyocytes were treated with 200 nM CsA either given for 10 min followed by 10 min of washout prior to 30 min hypo-osmotic stress (200 mOsm) or administered throughout 75 min simulated ischaemia/60 min simulated reperfusion. Cell necrosis and cell swelling were determined by trypan blue staining and cell-volume measurements, respectively; (ii) SPQ(6-methoxy-N-(3-sulfopropyl)quinolinium) dye loaded cardiomyocytes were treated with 200 nM CsA for 10 min followed by 10 min washout and intracellular Cl(-) concentration measured (Cl(-) efflux); (iii) 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimi-dazolylcarbocyanine iodide(JC-1) loaded cardiomyocytes were treated with 200 nM CsA to inhibit mitochondrial membrane potential (ΔΨm) dissipation (an index of mitochondria permeability transition pore opening) by either valinomycin (2 μM) or ischaemia/reperfusion injury. Cl(-) channels were blocked by indanyloxyacetic acid 94 (IAA-94, 50 μM). CsA not only significantly (P < 0.001) reduced the % of dead cells following simulated ischaemia/reperfusion but it also triggered an efflux of Cl(-), hence enhancing cardiomyocyte cell-volume regulatory response. CsA protection against cell necrosis and its effect on Cl(-) transport/volume regulation were all blocked by IAA-94. IAA-94 had no effect on ΔΨm.
  
  
  CONCLUSIONS
  These data indicate that CsA protects against cell necrosis at least in part by enhancing cardiomyocyte volume regulation, and not simply by inhibiting MPTP opening.
authors.affiliation: Division of Cell Biology, Research Institute, McMaster Bldg, Room 7019C, 555 University Ave, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Diaz
authors.forename: Kelly
authors.initials: K
authors.lastname: Fernandes
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Lytvyn
authors.forename: Krista
authors.initials: K
authors.lastname: Hawrylyshyn
authors.forename: Kordan
authors.initials: K
authors.lastname: Harvey
authors.forename: Taneya
authors.initials: T
authors.lastname: Hossain
authors.forename: Alina
authors.initials: A
authors.lastname: Hinek
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Wilson
mesh_terms: D000818:Animals; D048429:Cell Size / Q000187:drug effects*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D019610:Cytoprotection; D017136:Ion Transport; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D009997:Osmotic Pressure / Q000187:drug effects; D020011:Protective Agents / Q000494:pharmacology*; D011817:Rabbits; D013997:Time Factors
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D020011:Protective Agents; D016572:Cyclosporine
keywords: Cardiomyocytes; Cell volume regulation; Chloride channels; Cyclosporine A; Mitochondrial permeability transition pore