title: Ischemia-reperfusion-induced calpain activation and SERCA2a degradation are attenuated by exercise training and calpain inhibition.
abstract: The Ca2+-activated protease calpain has been shown to play a deleterious role in the heart during ischemia-reperfusion (I/R). We tested the hypothesis that exercise training would minimize I/R-induced calpain activation and provide cardioprotection against I/R-induced injury. Hearts from adult male rats were isolated in a working heart preparation, and myocardial injury was induced with 25 min of global ischemia followed by 45 min of reperfusion. In sedentary control rats, I/R significantly increased calpain activity and impaired cardiac performance (cardiac work during reperfusion = 24% of baseline). Compared with sedentary animals, exercise training prevented the I/R-induced rise in calpain activity and improved cardiac work (recovery = 80% of baseline). Similar to exercise, pharmacological inhibition of calpain activity resulted in comparable cardioprotection against I/R injury (recovery = 86% of baseline). The exercise-induced protection against I/R-induced calpain activation was not due to altered myocardial protein levels of calpain or calpastatin. However, exercise training was associated with increased myocardial antioxidant enzyme activity (Mn-SOD, catalase) and a reduction in oxidative stress. Importantly, exercise training also prevented the I/R-induced degradation of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2a. These findings suggest that increases in endogenous antioxidants may diminish the free radical-mediated damage and/or degradation of Ca2+ handling proteins (such as SERCA2a) typically observed after I/R. In conclusion, these results support the concept that calpain activation is an important component of I/R-induced injury and that exercise training provides cardioprotection against I/R injury, at least in part, by attenuating I/R-induced calpain activation.
authors.affiliation: Dept. of Applied Physiology and Kinesiology, Center for Exercise Science, Univ. of Florida, Gainesville, FL 32611, USA.
authors.forename: Joel P
authors.initials: JP
authors.lastname: French
authors.forename: John C
authors.initials: JC
authors.lastname: Quindry
authors.forename: Darin J
authors.initials: DJ
authors.lastname: Falk
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Staib
authors.forename: Youngil
authors.initials: Y
authors.lastname: Lee
authors.forename: Kevin K W
authors.initials: KK
authors.lastname: Wang
authors.forename: Scott K
authors.initials: SK
authors.lastname: Powers
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D004789:Enzyme Activation; D006334:Heart Function Tests; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000201:enzymology* / Q000628:therapy; D009206:Myocardium / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D002154:Calpain; D007770:L-Lactate Dehydrogenase; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C033668:calpastatin