Role of dual-site phospholamban phosphorylation in intermittent hypoxia-induced cardioprotection against ischemia-reperfusion injury

Abstract

. Role of dual-site phospholamban phosphorylation in intermittent hypoxia-induced cardioprotection against ischemia-reperfusion injury. Am J Physiol Heart Circ Physiol 288: H2594 -H2602, 2005. First published January 6, 2005; doi:10.1152/ajpheart.00926.2004.-Cardioprotection by intermittent high-altitude (IHA) hypoxia against ischemia-reperfusion (I/R) injury is associated with Ca 2ϩ overload reduction. Phospholamban (PLB) phosphorylation relieves cardiac sarcoplasmic reticulum (SR) Ca 2ϩ -pump ATPase, a critical regulator in intracellular Ca 2ϩ cycling, from inhibition. To test the hypothesis that IHA hypoxia increases PLB phosphorylation and that such an effect plays a role in cardioprotection, we compared the time-dependent changes in the PLB phosphorylation at Ser 16 (PKA site) and Thr 17 (CaMKII site) in perfused normoxic rat hearts with those in IHA hypoxic rat hearts submitted to 30-min ischemia (I30) followed by 30-min reperfusion (R30). IHA hypoxia improved postischemic contractile recovery, reduced the maximum extent of ischemic contracture, and attenuated I/R-induced depression in Ca 2ϩ -pump ATPase activity. Although the PLB protein levels remained constant during I/R in both groups, Ser 16 phosphorylation increased at I30 and 1 min of reperfusion (R1) but decreased at R30 in normoxic hearts. IHA hypoxia upregulated the increase further at I30 and R1. Thr 17 phosphorylation decreased at I30, R1, and R30 in normoxic hearts, but IHA hypoxia attenuated the depression at R1 and R30. Moreover, PKA inhibitor H89 abolished IHA hypoxiainduced increase in Ser 16 phosphorylation, Ca 2ϩ -pump ATPase activity, and the recovery of cardiac performance after ischemia. CaMKII inhibitor KN-93 also abolished the beneficial effects of IHA hypoxia on Thr 17 phosphorylation, Ca 2ϩ -pump ATPase activity, and the postischemic contractile recovery. These findings indicate that IHA hypoxia mitigates I/R-induced depression in SR Ca 2ϩ -pump ATPase activity by upregulating dual-site PLB phosphorylation, which may consequently contribute to IHA hypoxia-induced cardioprotection against I/R injury. phospholamban phosphorylation residues; cardiac sarcoplasmic reticulum Ca 2ϩ -pump ATPase; cardiac contractile function ADAPTATION TO INTERMITTENT HIGH-ALTITUDE (IHA) hypoxia increases cardiac tolerance to subsequent severe hypoxic or ischemic injury in animal models (1,17,24,26,37). Some clinical and epidemiological observations also have shown that the cardiac tolerance to acute oxygen deprivation is increased and that the incidence of myocardial infarction and mortality from coronary heart disease is reduced in people living at high altitude (8). In addition, this form of protection persists longer in comparison with the temporal character of classic preconditioning (2, 36) and has fewer side effects such as right ventricular hypertrophy compared with the adaptation to continuously chronic hypoxia (1,25,35). Therefore, obtaining a better understanding of the mechanisms underlying such longterm protection might be of clinical import...

Hypoxia. 4. Hypoxia and ion channel function

“…Preischemic IH adaptation for several weeks increased phospholamban phosphorylation at both sites and ameliorated SERCA dysfunction, resulting in beneficial effects on cardiac contractility and I Ca (36, 256). The loss of IH-induced protection after blockade of PKA or CaMK activity (256) suggests that these kinases are critical for the IH-induced phosphorylation of phospholamban in this model. Consistent with this possibility, a rapid increase in PKA activity following hypoxia/reoxygenation was also documented in other cell types (26, 271).…”

“…Ischemia and reperfusion decrease phospholamban phosphorylation, which contributes to diminished SERCA activity and increased [Ca 2ϩ ] i (256). Preischemic IH adaptation for several weeks increased phospholamban phosphorylation at both sites and ameliorated SERCA dysfunction, resulting in beneficial effects on cardiac contractility and I Ca (36, 256).…”

“…PKA and CaMK, which contribute to cardioprotection by IH preconditioning (256), have also been implicated in HIF-1 activation (221). Whether HIF-1 exerts its effects via modulation of ion channel expression and whether HIF-1 is involved in the protection adaption afforded by long-term IH remain to be determined.…”

Proteomic analysis of mitochondrial proteins in cardiomyocytes from rats subjected to intermittent hypoxia

“…Our group and others have reported that long-term IH adaptation enhances the resistance to subsequent severe hypoxia/ischemia and has fewer side effects such as right ventricular hypertrophy, compared to chronic hypoxia (Ding et al 2004;Neckar et al 2002;Xie et al 2005;Zhang et al 2000a;Zhu et al 2003). Moreover, the cardiac protective effects are maintained for several weeks (Zhang et al 2000b).…”

“…85-23, Revised 1996), and all procedures were approved by the Institutional Review Board of Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. For IH studies, rats were exposed to a hypobaric chamber and were maintained at the equivalent of 5,000 m altitude (P B = 404 mmHg, P O2 = 84 mmHg) in daylight for one 6-h period each day for 42 days (Ding et al 2004;Dong et al 2003;Xie et al 2005;Zhu et al 2003Zhu et al , 2006. Age-matched control (normoxic) animals were kept under normoxic environments for a corresponding period.…”