Activation of proteases and changes in Na⁺-K⁺-ATPase subunits in hearts subjected to ischemia-reperfusion

Abstract

Previous studies have shown that ischemia-reperfusion (I/R) injury is associated with cardiac dysfunction and changes in sarcolemmal Na(+)-K(+)-ATPase subunits and activity. This study was undertaken to evaluate the role of proteases in these alterations by subjecting rat hearts to different times of global ischemia, as well as reperfusion after 45 min of ischemia. Decreases in Na(+)-K(+)-ATPase activity at 30-60 min of global ischemia were accompanied by augmented activities of both calpain and matrix metalloproteinases (MMPs) and depressed protein content of β(1)- and β(2)-subunits, without changes in α(1)- and α(2)-subunits of the enzyme. Compared with control values, the activities of both calpain and MMP-2 were increased, whereas the activity and protein content for all subunits of Na(+)-K(+)-ATPase were decreased upon reperfusion for 5-40 min, except that α(1)- and α(2)-subunit content was not depressed in 5 min I/R hearts. MDL28170, a calpain inhibitor, was more effective in attenuating the I/R-induced alterations in cardiac contracture, Na(+)-K(+)-ATPase activity, and α(2)-subunit than doxycycline, an MMP inhibitor. Incubation of control sarcolemma preparation with calpain, unlike MMP-2, depressed Na(+)-K(+)-ATPase activity and decreased α(1)-, α(2)-, and β(2)-subunits, without changes in the β(1)-subunit. These results support the view that activation of both calpain and MMP-2 are involved in depressing Na(+)-K(+)-ATPase activity and degradation of its subunits directly or indirectly in hearts subjected to I/R injury.

Total Saponins of Aralia Elata (Miq) Seem Alleviate Calcium Homeostasis Imbalance and Endoplasmic Reticulum Stress-Related Apoptosis Induced by Myocardial Ischemia/Reperfusion Injury

“…Therefore, we detected some ATPase activities associated with calcium to determine their relationship. Na + -K + -ATPase is an integral membrane protein and an important system of cell energy conversion [34]. Our study showed Na + -K + -ATPase activity is decreased significantly after MIR.…”

Role of intracellular Ca2+ overload in inducing changes in cardiac gene expression

“…Varying degrees of alterations in functional and biochemical activities of SL, SR and MF activities have also been shown to occur in CP hearts as a consequence of intracellular Ca 2+ overload (13)(14)(15)17,(21)(22)(23). Although elevated levels of intracellular Ca 2+ have been observed to activate proteases, such as calpains, directly the observed increase in mRNA levels for both calpain-1 and -2 proteins may also contribute to increased calpain activity in hearts under different pathological conditions associated with the occurrence of intracellular Ca 2+ overload (27)(28)(29)(30)(31). Thus, it appears that the observed depressions in SL, SR and MF gene expression, as well as the increased gene expression for calpains due to intracellular Ca 2+ overload, may account for remodelling of subcellular organelles observed in the hearts subjected to CP.…”

“…It appears that a critical level of LVEDP needs to be achieved for the occurrence of intracellular Ca 2+ overload for inducing depression in cardiac gene expression in hearts subjected to CP. It should be emphasized that there are varying degrees of depression in SL, SR and MF gene expression, protein content and functional activities in hearts subjected to ischemia-reperfusion and these alterations have been attributed to the occurrence of intracellular Ca 2+ overload (7)(8)(9)(31)(32)(33)(34)(35)(36)38). Furthermore, intracellular Ca 2+ overload has been suggested to play a critical role in the development of alterations in SL, SR and MF gene expression, protein content and functional activities in hearts failing due to myocardial infarction (1)(2)(3)(4)(5)(6).…”

“…In the present study, we examined whether hearts perfused with Ca 2+ -free medium followed by reperfusion with medium containing different concentrations of Ca 2+ exhibit alterations in gene expression for SL Na + -K + ATPase and Na + -Ca 2+ exchanger, SR Ca 2+ -pump ATPase, Ca 2+ -release channel and phospholamban (PLB), as well as MF α-and β-myosin heavy chain proteins. Because subcellular remodelling in the failing heart is dependent on the balance between changes in gene expression and activities of proteolytic enzymes, such as calpain (27)(28)(29)(30)(31)(32)(33), messenger RNA (mRNA) levels for both calpain-1 and calpain-2 were measured in CP hearts. It may be noted that subcellular remodelling in failing hearts has also been suggested to be the result of activation of different proteolytic enzymes (27,28).…”

Organ Preservation in Liver Transplantation

“…20 The lack of ATP leads to failure of the ATP-dependent sodium/potassium plasma membrane pump (Na þ /K þ adenosinetriphosphatase [ATPase]), with subsequent intracellular Na þ accumulation, edema, and swelling. 21 Kupffer and sinusoidal cell swelling, combined with an increase in the vasoconstrictors endothelin/thromboxane A2 and a decrease in the vasodilator nitric oxide, leads to sinusoidal narrowing, further reducing the delivery of oxygen and substrates to the liver graft. The calcium ATPase-dependent transport mechanisms very soon become dysfunctional too, and the "calcium overload" resulting from an altered Ca 2þ homeostasis is associated with the activation of various cell death pathways through necrotic, apoptotic, and autophagic mechanisms.…”