title: S-nitrosation of calpains is associated with cardioprotection in myocardial I/R injury.
abstract: BACKGROUND
  Myocardial infarction remains the single leading cause of death worldwide. Upon reperfusion of occluded arteries, deleterious cellular mediators particularly located at the mitochondria level can be activated, thus limiting the outcome in patients. This may lead to the so-called ischemia/reperfusion (I/R) injury. Calpains are cysteine proteases and mediators of caspase-independent cell death. Recently, they have emerged as central transmitters of cellular injury in several cardiac pathologies e.g. hypertrophy and acute I/R injury.
  
  
  METHODS
  Here we investigated the role of cardiac calpains in acute I/R in relation to mitochondrial integrity and whether calpains can be effectively inhibited by posttranslational modification by S-nitrosation. Taking advantage of the a cardiomyocyte cell line (HL1), we determined S-nitrosation by the Biotin-switch approach, cell viability and intracellular calcium concentration after simulated ischemia and reoxygenation - all in dependence of supplementation with nitrite, which is known as an 'hypoxic nitric oxide (NO) donor'. Likewise, using an in vivo I/R model, calpain S-nitrosation, calpain activity and myocardial I/R injury were characterized in vivo.
  
  
  RESULTS
  Nitrite administration resulted in an increased S-nitrosation of calpains, and this was associated with an improved cell-survival. No impact was detected on calcium levels. In line with these in vitro experiments, nitrite initiated calpain S-nitrosation in vivo and caused an infarct sparing effect in an in vivo myocardial I/R model. Using electron microscopy in combination with immuno-gold labeling we determined that calpain 10 increased, while calpain 2 decreased in the course of I/R. Nitrite, in turn, prevented an I/R induced increase of calpains 10 at mitochondria and reduced levels of calpain 1.
  
  
  CONCLUSIONS
  Lethal myocardial injury remains a key aspect of myocardial I/R. We show that calpains, as key players in caspase-independent apoptosis, increasingly locate at mitochondria following I/R. Inhibitory post-translational modification by S-nitrosation of calpains reduces deleterious calpain activity in murine cardiomyocytes and in vivo.
authors.affiliation: University Hospital Essen, Medical Faculty, West German Heart and Vascular Center, Department of Cardiology and Angiology, Hufelandstr. 55, 45147 Essen, Germany. Electronic address: Matthias.totzeck@uk-essen.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Totzeck
authors.affiliation: University Hospital Essen, Medical Faculty, West German Heart and Vascular Center, Department of Cardiology and Angiology, Hufelandstr. 55, 45147 Essen, Germany. Electronic address: Sebastian.Korste@uk-essen.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Korste
authors.affiliation: Biocenter Oulu Electron Microscopy Core Facility, University of Oulu, Finland. Electronic address: Ilkka.Miinalainen@oulu.fi.
authors.forename: Ilkka
authors.initials: I
authors.lastname: Miinalainen
authors.affiliation: University Hospital Essen, Medical Faculty, West German Heart and Vascular Center, Department of Cardiology and Angiology, Hufelandstr. 55, 45147 Essen, Germany. Electronic address: Ulrike.hendgen-cotta@uk-essen.de.
authors.forename: Ulrike B
authors.initials: UB
authors.lastname: Hendgen-Cotta
authors.affiliation: University Hospital Essen, Medical Faculty, West German Heart and Vascular Center, Department of Cardiology and Angiology, Hufelandstr. 55, 45147 Essen, Germany. Electronic address: Tienush.rassaf@uk-essen.de.
authors.forename: Tienush
authors.initials: T
authors.lastname: Rassaf
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D008297:Male; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism; D017202:Myocardial Ischemia / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009566:Nitrates / Q000737:chemistry*; D009573:Nitrites / Q000008:administration & dosage; D015538:Nitrosation
chemical_list: D009566:Nitrates; D009573:Nitrites; D002154:Calpain
keywords: Calpains; Myocardial I/R injury; Nitrite; S-nitrosation