Cardioprotective Effects of Qishen Granule(芪参颗粒)on Sarcoplasmic Reticulum Ca^2＋ Handling in Heart Failure Rats

Objective：To assess the effects of Qishen Granule（芪参颗粒, QSG） on sarcoplasmic reticulum（SR） Ca^2＋ handling in heart failure（HF） model of rats and to explore the underlying molecular mechanisms. Methods：HF rat models were induced by left anterior descending coronary artery ligation surgery and high-fat diet feeding. Rats were randomly divided into sham（n=10）, model（n=10）, QSG（n=12, 2.2 g/kg daily） and metoprolol groups（n=12, 10.5 mg/kg daily）. The therapeutic effects of QSG were evaluated by echocardiography and blood lipid testing. Intracellular Ca^2＋ concentration and sarco-endoplasmic reticulum ATPase 2a（SERCA2a） activity were detected by specific assay kits. Expressions of the critical regulators in SR Ca^2＋ handling were evaluated by Western blot and real-time quantitative polymerase chain reaction. Results：HF model of rats developed ventricular remodeling accompanied with calcium overload and defective Ca^2＋ releaseuptake cycling in cardiomyocytes. Treatment with QSG improved contractive function, attenuated ventricular remodeling and reduced the basal intracellular Ca^2＋ level. QSG prevented defective Ca^2＋ leak by attenuating hyperphosphorylation of ryanodine receptor 2, inhibiting expression of protein kinase A and up-regulating transcriptional expression of protein phosphatase 1. QSG also restored Ca^2＋ uptake by up-regulating expression and activity of SERCA2 a and promoting phosphorylation of phospholamban. Conclusion：QSG restored SR Ca^2＋cycling in HF rats and served as an ideal alternative drug for treating HF.

The substitution of SERCA2 redox cysteine 674 promotes pulmonary vascular remodeling by activating IRE1α/XBP1s pathway

Pulmonary hypertension(PH) is a life-threatening disease characterized by pulmonary vascular remodeling, in which hyperproliferation of pulmonary artery smooth muscle cells(PASMCs)plays an important role. The cysteine 674(C674) in the sarcoplasmic/endoplasmic reticulum Ca^(2+)ATPase 2(SERCA2) is the critical redox regulatory cysteine to regulate SERCA2 activity. Heterozygous SERCA2 C674 S knock-in mice(SKI), where one copy of C674 was substituted by serine to represent partial C674 oxidative inactivation, developed significant pulmonary vascular remodeling resembling human PH, and their right ventricular systolic pressure modestly increased with age. In PASMCs, substitution of C674 activated inositol requiring enzyme 1 alpha(IRE1 a) and spliced X-box binding protein 1(XBP1 s) pathway, accelerated cell cycle and cell proliferation, which reversed by IRE1 a/XBP1 s pathway inhibitor 4μ8 C. In addition, suppressing the IRE1 a/XBP1 s pathway prevented pulmonary vascular remodeling caused by substitution of C674. Similar to SERCA2 a, SERCA2 b is also important to restrict the proliferation of PASMCs. Our study articulates the causal effect of C674 oxidative inactivation on the development of pulmonary vascular remodeling and PH, emphasizing the importance of C674 in restricting PASMC proliferation to maintain pulmonary vascular homeostasis. Moreover, the IRE1 a/XBP1 s pathway and SERCA2 might be potential targets for PH therapy.