Ischemia-reperfusion-induced changes in sarcolemmal Na super(+)/K super(+)-ATPase are due to the activation of calpain in the heart

• Published in: Canadian journal of physiology and pharmacology Vol. 88; no. 3; pp. 388 - 397
• Main Authors: Singh, Raja B, Dhalla, Naranjan S
• Format: Journal Article
• Language: English
• Published: 01.03.2010
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/Y10-012

Depression in cardiac performance due to ischemia-reperfusion (I/R) injury is associated with the development of oxidative stress and decreased sarcolemmal (SL) Na super(+)/K super(+)-ATPase activity. Since both I/R and oxidative stress have been reported to promote the occurrence of intracellular Ca super(2+) overload and activate proteases such as calpain, this study was undertaken to investigate whether the activation of calpain in I/R hearts is associated with alterations in the SL Na super(+)/K super(+)-ATPase activity and its isoform content. For this purpose, isolated rat hearts treated with and without 2 different calpain inhibitors (leupeptin and MDL28170) were subjected to 30 min ischemia followed by 60 min of reperfusion, and the cardiac function, SL Na super(+)/K super(+)-ATPase activity, Na super(+)/K super(+)-ATPase isoform protein content, and calpain activity were measured. The I/R-induced depressions in cardiac function, Na super(+)/K super(+)-ATPase activity, and protein content of Na super(+)/K super(+)-ATPase isoforms were associated with an increase in calpain activity , but were prevented by treatment of hearts with leupeptin. Incubation of SL membranes with calpain decreased the Na super(+)/K super(+)-ATPase activity and protein content of its isoforms; these changes were also attenuated by leupeptin. The I/R-induced alterations in cardiac function and the activity of SL Na super(+)/K super(+)-ATPase and calpain were Ca super(2+)-dependent and were prevented by MDL28170, a specific inhibitor of calpain. The I/R-induced translocation of calpain isoforms (I and II) from the cytosol to SL and the changes in distribution of calpastatin were also attenuated by treatment with calpain inhibitors. These results suggest that the depression in cardiac function and SL Na super(+)/K super(+)-ATPase activity in I/R hearts may be due to changes in the activity and translocation of calpain.Original Abstract: Des etudes ont demontre que la diminution de performance cardiaque causee par une lesion d'ischemie-reperfusion (I/R) est associee au developpement de stress oxydatif et a une diminution de l'activite Na super(+)/K super(+)-ATPase sarcolemmique (SL). Etant donne que l'I/R et le stress oxydatif favorisent l'apparition d'une surcharge de Ca super(2+) intracellulaire et activent des proteases telles que la calpaiene, la presente etude a eu pour but d'examiner si l'activation de la calpaiene dans les c[oeligurs I/R est liee a des modifications de l'activite de la Na super(+)/K super(+)-ATPase SL et de sa teneur en isoformes. Pour ce faire, on a soumis des c[oeligurs isoles de rats, traites ou non traites avec deux inhibiteurs de calpaiene (leupeptine et MDL28170), a 30 min d'ischemie, puis a 60 min de reperfusion, et on a mesure la fonction cardiaque, l'activite de la Na super(+)/K super(+)-ATPase SL, la teneur en proteines des isoformes de la Na super(+)/K super(+)-ATPase , et l'activite de la calpaiene. Les diminutions causees par l'I/R de la fonction cardiaque, de l'activite de la Na super(+)/K super(+)-ATPase SL et de la teneur en proteines des isoformes de la Na super(+)/K super(+)-ATPase ont ete associees a une augmentation de l'activite de la calpaiene; toutefois, ces diminutions ont ete prevenues par un traitement a la leupeptine. L'incubation des membranes SL avec la calpaiene a diminue l'activite de la Na super(+)/K super(+)-ATPase et la teneur en proteines de ses isoformes; ces modifications ont aussi ete attenuees par la leupeptine. Les modifications par l'l/R de la fonction cardiaque, de la Na super(+)/K super(+)-ATPase SL et de l'activite de la calpaiene ont ete dependantes du Ca super(2+) et ont ete prevenues par MDL28170, un inhibiteur specifique de la calpaiene. La translocation induite par l'I/R des isoformes (I et II) de la calpaiene du cytosol vers le sarcolemme et les modifications de la distribution de calpastatine ont aussi ete attenuees par un traitement avec les inhibiteurs de la calpaiene. Ces resultats laissent supposer que la diminution de la fonction cardiaque et de l'activite de la Na super(+)/K super(+)-ATPase SL dans les c[oeligurs I/R pourrait etre due a des modifications de l'activite et de la translocation de la calpaiene.