Calcium/calmodulin-dependent protein kinase II mediates cardioprotection of intermittent hypoxia against ischemic-reperfusion-induced cardiac dysfunction

Abstract

Intermittent high-altitude (IHA) hypoxia-induced cardioprotection against ischemia-reperfusion (I/R) injury is associated with the preservation of sarcoplasmic reticulum (SR) function. Although Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) and phosphatase are known to modulate the function of cardiac SR under physiological conditions, the status of SR CaMKII and phosphatase during I/R in the hearts from IHA hypoxic rats is unknown. In the present study, we determined SR and cytosolic CaMKII activity during preischemia and I/R (30 min/30 min) in perfused hearts from normoxic and IHA hypoxic rats. The left ventricular contractile recovery, SR CaMKII activity as well as phosphorylation of phospholamban at Thr(17), and Ca(2+)/CaM-dependent SR Ca(2+)-uptake activity were depressed in the I/R hearts from normoxic rats, whereas these changes were prevented in the hearts from IHA hypoxic rats. Such beneficial effects of IHA hypoxia were lost by treating the hearts with a specific CaMKII inhibitor, KN-93. I/R also depressed cytosolic CaMKII and SR phosphatase activity, but these alterations remained unchanged in IHA hypoxic group. Furthermore, we found that the autophosphorylation at Thr(287), which confers Ca(2+)/CaM-independent activity, was not altered by I/R in both groups. These findings indicate that preservation of SR CaMKII activity plays an important role in the IHA hypoxia-induced cardioprotection against I/R injury via maintaining SR Ca(2+)-uptake activity.

ROS generated during early reperfusion contribute to intermittent hypobaric hypoxia-afforded cardioprotection against postischemia-induced Ca2+ overload and contractile dysfunction via the JAK2/STAT3 pathway

“…Taken together, these observations support the view that Bcl-2 acts as the downstream target of ROS/JAK2/STAT3 pathways and contributes to the IHH-maintained Ca 2+ homeostasis through binding to the SERCA2 and preserving the SERCA2 activity during reperfusion. The cardioprotection of IHH on the postischemic SERCA2 expression and activity is consistent with the previous reports [12,16,19]. IHH attenuates the I/R-induced Ca 2+ overload and cell contraction dysfunction via the improvement of SERCA2 expression and activity, and the latter effect is at least in part mediated by the ROS production at the early reperfusion and the subsequent activation of STAT3.…”

“…IHH attenuates the I/R-induced Ca 2+ overload and cell contraction dysfunction via the improvement of SERCA2 expression and activity, and the latter effect is at least in part mediated by the ROS production at the early reperfusion and the subsequent activation of STAT3. Of note, IHH may preserve postischemic SERCA2 activity through at least two additional mechanisms: (i) the maintenance of the protein level of SERCA2 during reperfusion, though the mechanisms need to be elucidated; (ii) the removal of PLB inhibition to SERCA2 by upregulating dual-site PLB phosphorylation at Ser 16 and Thr 17 via the activation of cAMPdependent protein kinase (PKA) and Ca 2+ -calmodulin-dependent protein kinase II [16,19].…”

“…Since the SR is a major source and sink of cytosolic Ca 2+ and SERCA2 is a key target for protection of I/R injury [12,16,29], we investigated the influence of ROS/JAK2/STAT3 pathways on the expression and activity of SERCA2 during early reperfusion. The total PLB was used as an internal control of SERCA2 expression as its level is not altered by I/R and IHH as previously reported [16,19] nor 2-MPG and AG490 (Suppl. Fig.…”

“…This form of cardioprotection mimics the physiological adaptation by triggering intrinsic adaptive responses against I/R-induced intracellular Ca 2+ overload and proteolysis, resulting in the improvement of postischemic recovery of contractile function, reduction of the incidence and severity of arrhythmias, and limit of the infarct size [4,[12][13][14][16][17][18][19][20][21][22]. In this study, using the I/R and IHH preconditioning models, combining with the ROS scavenger and JAK2 inhibitor given during the early reperfusion or the specific short hairpin RNA (shRNA), we examined (i) the effect of ROS in IHH-preserved Ca 2+ homeostasis and cardiac contraction during reperfusion; (ii) the activation and the effect of STAT3 in the IHH-protected postischemic Ca 2+ homeostasis and cardiac contraction and its relationship with the ROS; and (iii) the target of ROS/JAK2/STAT3 pathways in the IHH-protected postischemic Ca 2+ homeostasis.…”

In vitro studies of early cardiac remodeling impact on contraction and calcium handling

“…The ser16 sites seems to be the most vital phosphorylation site with many studies highlighting its necessity to induce any effect on Serca activation (65). However, thr17 has become a target of interest specifically in studies looking at compensatory effects during ischemia reperfusion injury and coronary artery occlusion (66). It has been shown that CaMKII phosphorylation of PLB may play a role in frequencydependent acceleration of relaxation which is altered in failure (67), although recent evidence argues against a prominent role in this regulation (68).…”