title: The Blockade of Transmembrane Cl⁻ Flux Mitigates I/R-Induced Heart Injury via the Inhibition of Calpain Activity.
abstract: OBJECTIVE
  The aim of this study was to determine whether calpain is involved in Cl(-)-induced myocardial ischemia/reperfusion (I/R) injury.
  
  
  METHODS
  Isolated rat hearts were subjected to either 45 min of global no-flow ischemia followed by reperfusion or successive perfusion with Ca(2+)-free KH solution for 3 min and normal KH solution for 30 min, also known as Ca(2+) paradox.
  
  
  RESULTS
  The hearts in the I/R group exhibited increases in myocardial injury area, LDH release, caspase 3 activity and apoptotic indices and a marked decline in cardiac performance. As was the case regarding the effects of MDL 28170, an inhibitor of calpain, treatment with 5 µM NPPB, 5 µM DIDS and low Cl(-) significantly attenuated cardiac injury. Moreover, each of the treatments significantly protected against Ca(2+) overload-induced injury in the setting of Ca(2+) paradox. The Western blot and immunofluorescence data revealed that there was an increase in the percentages of calpain membrane-positive cells and the numbers of fragments resulting from the calpain-mediated proteolysis of α-fodrin in both the I/R and the Ca(2+) paradox, indicating that the activation of calpain occurred. More importantly, these effects were mitigated by the blockade of transmembrane Cl(-) flux, as was accomplished via MDL 28170.
  
  
  CONCLUSIONS
  Our results provide evidence that the blockade of transmembrane Cl(-) flux mitigates I/R-induced cardiac injury via the inhibition of calpain activity. They also indicate that intracellular Ca(2+) overload regulates calpain activation in the setting of Cl(-)-induced injury.
authors.affiliation: Department of Physiology, The Fourth Military Medical University, Xi'an, China.
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: Wu
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Gu
authors.forename: Zhen-Xiao
authors.initials: ZX
authors.lastname: Jin
authors.forename: Ling-Heng
authors.initials: LH
authors.lastname: Kong
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jing-Jun
authors.initials: JJ
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors*; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002712:Chlorides / Q000009:adverse effects* / Q000037:antagonists & inhibitors*; D004151:Dipeptides / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006335:Heart Injuries / Q000139:chemically induced* / Q000188:drug therapy; D008297:Male; D008840:Microfilament Proteins / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000139:chemically induced* / Q000188:drug therapy / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013049:Spectrin
chemical_list: D002118:Calcium; D002154:Calpain; D002352:Carrier Proteins; D053148:Caspase 3; D002712:Chlorides; D004151:Dipeptides; D008840:Microfilament Proteins; D013049:Spectrin; C058076:calpain inhibitor III