Abstract 12156: Loss of Thiol on C674 SERCA2 Leads to Ca2 ⁺ Mishandling With Hypertrophy in Right Ventricular Exposed to Hypoxia

Abstract

Introduction: Right ventricular (RV) dysfunction is the strongest predictor of mortality in pulmonary artery hypertension (PAH). Reactive oxygen species in heart failure cause irreversible oxidation of sarcoplasmic reticulum (SR) Ca 2+ -ATPase2 (SERCA2) C674, which results in SERCA2 dysfunction and intracellular Ca 2+ overload. However, the contribution of the loss of the thiol on C674 SERCA2 and RV failure in PAH remains unclear. Hypothesis: The loss of the thiol on C674 SERCA2 contributes to the RV dysfunction in PAH. Methods & Results: We employed the SERCA2 C674S heterozygote knock-in (SKI) mice, in which C674 is replaced by serine, mimics oxidative modification of SERCA2 by loss of the specific thiol. Wild-type mice (WT) and SKI were exposed to either normoxia (Nx) or chronic hypoxia (Hx) for four weeks. Hypoxia elevated RV systolic pressure (WT-Nx: 21.4mmHg vs. WT-Hx: 37.0mmHg, P<0.0001) and represented pulmonary vascular remodeling similarly both in WT and SKI. In histology, SKI-Hx showed the markedly increased Fulton's Index with higher levels of the mRNA expression of atrial natriuretic peptide and B-type natriuretic peptide than WT-Hx. In the exercise test, exercise duration was shorter and peak oxygen consumption was decreased in SKI-Hx than WT Hx. The mRNA levels of SERCA2 were not changed among the four groups. In Ca 2+ transient measurement of isolated myocytes with Fluo-4, SKI prolonged the time to 50% of cytosolic Ca 2+ extrusion (T50) and lower the peak Ca 2+ transient amplitude (F/F0) than WT under Nx. Prolonged T50 and lowered peak F/F0 were observed in WT-Hx, both of which additionally progressed in SKI-Hx. Conclusions: Hypoxia impaired SR Ca 2+ homeostasis in RV. SKI additionally impaired SR Ca 2+ homeostasis with the progression of RV hypertrophy. The loss of the thiol on C674 SERCA2 contributed to the pathogenesis of RV failure in PAH.