Alterations of sarcoplasmic reticulum-mediated Ca2+ uptake in a model of premature ventricular contraction (PVC)-induced cardiomyopathy

Abstract

Premature ventricular contractions (PVCs) are the most frequent ventricular arrhythmias in the overall population. PVCs are known to acutely enhance contractility by the post-extrasystolic potentiation phenomenon, but over time persistent PVCs promote PVC-induced cardiomyopathy (PVC-CM), characterized by a reduction of the left ventricular (LV) ejection fraction. Ca 2+ cycling in myocytes commands muscle contraction and in this process, SERCA2 leads the Ca 2+ reuptake into the sarcoplasmic reticulum (SR) shaping cytosolic Ca 2+ signal decay and muscle relaxation. Altered Ca 2+ reuptake can contribute to the contractile dysfunction observed in PVC-CM. To better understand Ca 2+ handling using our PVC-CM model (canines with 50% PVC burden for 12 weeks), SR-Ca 2+ reuptake was investigated by measuring Ca 2+ dynamics and analyzing protein expression. Kinetic analysis of Ca 2+ reuptake in electrically paced myocytes showed a ~ 21 ms delay in PVC-CM compared to Sham in intact isolated myocytes, along with a ~ 13% reduction in SERCA2 activity assessed in permeabilized myocytes. Although these trends were not statistically significant between groups using hierarchical statistics, relaxation of myocytes following contraction was significantly slower in PVC-CM vs Sham myocytes. Western blot analyses indicate a 22% reduction in SERCA2 expression, a 23% increase in phospholamban (PLN) expression, and a 50% reduction in PLN phosphorylation in PVC-CM samples vs Sham. Computational analysis simulating a 20% decrease in SR-Ca 2+ reuptake resulted in a ~ 22 ms delay in Ca 2+ signal decay, consistent with the experimental result described above. In conclusion, SERCA2 and PLB alterations described above have a modest contribution to functional adaptations observed in PVC-CM.

Mechanisms of adaptive hypertrophic cardiac remodeling in a large animal model of premature ventricular contraction‐induced cardiomyopathy

“…In contrast to tachycardia‐induced cardiomyopathy, apoptotic markers are not elevated in PVC‐CM 5 suggesting that the reduced LVEF is not linked to myocyte loss. While both L‐type Ca 2+ channel expression and activity are reduced in PVC‐CM, 29,56 RyR2 and Na + /Ca 2+ exchanger expression are unaltered, 56 and SERCA2 activity is mostly preserved despite the reduction in its expression, 4,28 indicating that Ca 2+ overload in myocytes is not the main trigger of the hypertrophic response observed in this PVC‐CM model. Altogether these data suggest that although this hypertrophic response has some pathological characteristics, it is likely an adaptive response.…”

“…LVEDV: time x PVC: F (1, 21) = 19.18, p = .0003; time: F (1, 21) = 21.40, p = .0001; PVC: F (1, 21) = 4.359, p = .0492; subject: F (21) = 4.709, p = .0004. LVESV: time × PVC: F (1, 21) = 62.33, p < .0001; time: F (1, 21) = 66.50, p < .0001; PVC: F (1, 21) = 25.20, p < .0001; subject: F (21) = 2.894, p = .0093. n = 12 (9 previously reported 28 ) for Sham and n = 11 (7 previously reported 28 ) for PVC‐CM groups. Šídák's multiple comparisons test **** p < .0001 Sham at 12‐weeks versus PVC at 12 weeks; ** p < .0011 Sham at 12‐weeks versus PVC at 12 weeks.…”

“…Postoperatively, buprenorphine 0.1–0.2 mg/kg IM twice daily for 3 days was administered for pain control. Bigeminal PVCs (50% burden) with a 200–220 ms coupling interval were delivered in half of the animals (PVC‐CM group, n = 11; 7 were previously reported in Reference 28) during at least 12 weeks. PVCs were not enabled in the remaining animals as part of the Sham group ( n = 12, 9 were previously reported in Reference 28).…”

“…Bigeminal PVCs (50% burden) with a 200–220 ms coupling interval were delivered in half of the animals (PVC‐CM group, n = 11; 7 were previously reported in Reference 28) during at least 12 weeks. PVCs were not enabled in the remaining animals as part of the Sham group ( n = 12, 9 were previously reported in Reference 28). Echocardiographic parameters were measured in awake animals at baseline and at 12 weeks of chronic PVCs to evaluate the development of cardiomyopathy.…”

Premature Ventricular Contraction-Induced Cardiomyopathy: Contemporary Evidence from Risk Stratification, Pathophysiology, and Management

“…Previous in vivo studies in a canine model with pacing ventricular bigeminy reported a decreased L-type calcium current (I CaL ) based on a patch-clamp study and a decrease in junctophilin 2 expression, a dyad protein that interacts with calcium-handing proteins and ion channels, at 12 weeks [38]. Furthermore, there was an upregulation of phospholamban (PLN), downregulation of sarcoplasmic/endoplasmic reticulum Ca 2+ ATPase-2a (SERCA2a) expression, and PLN phosphorylation [39]. Another study in a swine model with pacing ventricular bigeminy reported upregulated Ca 2+ /calmodulindependent protein kinase II (CaMKII-α), phosphorylated ryanodine receptor 2 (pRyR2) at the Ser 2814 CaMKII-α binding site, and downregulated SERCA2a [32].…”