Beneficial Effect Of Rosuvastatin On Heart Failure Is Associated With Alterations Of Calcium-regulatory Proteins

Part 1 Beneficial effect of rosuvastatin on heart failure is associated with alterations of calcium-regulatory proteinsBackground:The release of Ca²⁺ from sarcoplasmic reticulum(SR) and sarcoplasmic Ca²⁺ reuptake mainly involve in the regulation of intracellular Ca²⁺ homeostasis and its pathophysiological change.Sarcoplasmic reticulum Ca²⁺ ATPase(SERCA) and SERCA regulatory protein phospholamban(PLB) are the key proteins responsible for maintaining Ca²⁺ homeostasis throughout the excitation-contraction coupling cycle in cardiomyocyte.Interfering with the abnormal expression of SERCA and PLB may be a promising method in the clinical treatment of HF patients.Recent clinical and experimental studies indicated that statins(3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) can attenuate ventricular remodeling and improve ventricular function after myocardial infarction(MI).But there are few data exploring whether statins exhibit special effect in improving left ventricular(LV) remodeling and function through influence on calcium-regulatory proteins. Aim:We undertook our research to investigate effect of rosuvastatin on LV remodeling and cardiac function in a rat model of HF induced by MI.In addition,tissue levels of SERCA2a,SERCA activity,PLB and pSerl6-PLB as well as interleukin(IL)-6 and IL-10 in myocardium of rats with MI were detected to explore the molecular mechanism.Methods:Adult male Sprague-Dawley rats were anesthetized and the left coronary artery was ligated 2 to 3 mm from its origin to induce MI.For sham-operated animals,the suture was placed but not ligated(S group).MI rats were randomized to receive gavage with either 1 ml·day-1 distilled water(MI group) or 10 mg·kg-1·day-1 rosuvastatin dissolved in 1 ml distilled water for 10 weeks(MI+R group).Normal control(NC group) and normal control plus rosuvastatin treatment rats(NC+R group) were randomly selected.Rats were evaluated by echocardiography 2,4,6,8 and 10 weeks after operation.Left ventricle(LV) internal diameter at end-diastolic phase(LVIDd),LV internal diameter at end-systolic phase(LVIDs),LV posterior wall thickness at diastolic phase(LVPWd),LV shortening fraction(FS) and ejection fraction(EF) were measured. Infarct size was also detected by echocardiography 2 and 10 weeks after MI.10 weeks after MI,rats were anesthetized,and hemodynamic variables were measured.After rats were sacrificed,LV relative weight(LVRW) and right ventricular relative weight (RVRW) were obtained,when the LV actual weight(LVAW) and right ventricular actual weight(RVAW) were corrected for body weight.Serum total cholesterol,triglycerides, and low- and high-density lipoprotein cholesterol were measured using enzymatic colorimetric assays.SR was prepared from LV tissue for Determination of SERCA activity.The protein expression of SERCA2a,PLB and phospho-PLB at serine-16 (pSer16-PLB) were detected by western blot.IL-6 and IL-10 levels were assessed by enzyme-linked immunosorbent assay.Results:After rosuvastatin treatment,LV remodeling and dysfunction were attenuated. Rosuvastatin partially restored the low expression of SERCA2a and pSerl6-PLB, increased SERCA activity,but showed no effect on PLB expression.Furthermore, rosuvastatin reduced the increased IL-6 level and further elevated IL-10 level in the peri-infarct and remote zones of MI.Serum lipid levels and infarct size remained unchanged.Conlusions:Rosuvastatin is effective in reducing LV remodeling and dysfunction in the failing heart.The molecular mechanism may be related to normalization of SERCA2a expression,SERCA activity,and pSerl6-PLB levels,as well as through cytokine alterations independent of its effect of lipid-lowering or MI size reduction. Part 2 Cardioprotection and mechanisms of polysaccharide sulfate against ischemia/reperfusion injury in isolated rat heartsBackground:Polysaccharide sulfate(PSS) is a new type heparinoid extracted from Phylum Phaeophyta.By chemically introducing sulfuryl and propylene glycol residues in the hydroxyl and carboxyl group of alginic acid sodium,PSS obtained is a diester sodium. Basic and clinical research showed PSS have the effect of anticoagulation,lowering blood viscosity,decreasing TC and TG,increasing HDL-C,depressing platelet release, stimulating PGI2 synthesis and improving microcirculation.Clinically,there is a sort of myocardial injury,which occurs with transient ischemia followed by re-establishment of flow,and results in prolonged postischemic contractile dysfunction of myocardium. Although PSS is successfully applied in ischemic cardio-cerebrovascular disease,its effect on cardiac function after ischemia/reperfusion(I/R) injury has not been investigated previously.Aim:The aim of the present study was to investigate whether acute application of PSS can protect the heart from I/R injury in a model of myocardial I/R of the isolated rat hearts.In addition,the present study is designed to explore whether the cardioprotective effect of PSS is based on the alterations of tumor necrosis factor-a(TNF-α) expression and mitogen-activated protein kinase(MAPK) signal transduction pathway.Methods:Isolated rat hearts were perfused(Langendorff) and subjected to 20 min global ischemia followed by 60 min reperfusion with Kreb's Henseleit solution or different concentrations of PSS(0.3～100 mg/L).Myocardial contractile and diastolic function (including left ventricular developed pressure,LVDP;left ventricular end diastolic pressure,LVEDP;maximum rate of intraventricular pressure development and relaxation,+dp/dt max and -dp/dt max) was continuously recorded.Heart rate and the coronary flow were measured.Creatinine kinase(CK) and lactate dehydrogenase(LDH) leakage were measured.Tumor necrosis factor-α(TNF-α) expression by cardiomyocytes was investigated.Western blot analysis for extracellular regulated kinases(ERKs),c-jun amino-terminal kinase(JNKs) and p38 mitogen-activated protein kinase(MAPK) activity were performed.Results:PSS administration at concentrations of 1-30 mg/L improved cardiac contractility, reduced CK and LDH releasing and inhibited TNF-αproduction.Phosphorylated-p38MAPK(p-p38MAPK) and p-p54/p46-JNK increased in I/R rat hearts but diminished in PSS(1～30 mg/L) treated hearts.0.3 mg/L PSS had no effect on cardiac contractility,CK and LDH releasing,TNF-αproduction as well as p-p38MAPK and p-p54/p46-JNK expression.In contrast,high concentration of PSS(100 mg/L) had adverse effects that caused worsening of heart function.P-p44/p42-ERK level was unchanged after 0.3～100 mg/L PSS treatment.Conlusions:PSS has cardioprotective effect against I/R injury on the rat heart dose-dependently. The beneficial pharmacological effect including improving cardiac performance, increasing coronary flow but not affecting heart rate and lowering cardiocyte injury may be mediated through normalization of p38 MAPK and JNK pathways as well as TNF-αexpression.