Effects of combination of irbesartan and perindopril on calcineurin expression and sarcoplasmic reticulum Ca^(2+)-ATPase activity in rat cardiac pressure-overload hypertrophy

Aim： To observe effects of angiotensin （Ang） II receptor antagonist （ATI） irbesartan and angiotensin-converting enzyme （ACE） inhibitor perindopril on rat myocardium calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity in the model of pressure-overload cardiac hypertrophy. Methods： Forty male adult Sprague Dawley rats were divided into 5 groups One group was treated by sham operation; four groups were myocardium hypertrophy cases caused by banding aortic above renal artery. Drugs were given one week after operation. Group 1： sham group, rats （n=8） were gavaged with normal saline 2 ml/（kg·d） （ig）; Group 2： control group, rats （n=8） were treated with normal saline 2 ml/（kg·d） （ig）; Group 3： rats （n=8） were given perindopril 2 mg/（kg·d） （ig）; Group 4： rats （n=8） were treated with irbesartan 20 mg/（kg·d） （ig）; Group 5： rats （n=8） were given irbesartan 20 mg/（kg·d） plus perindopril 2 mg/（kg·d） （ig）. Morphometric determination, calcineurin expression and sarcoplasmic reticulum Ca^2＋-ATPase activity were done at the end of 6 week of drug intervention. Expression of calcineurin in myocardium was detected by immunohistochemistry. Results： Left ventricular mass index （LVMI）, transverse diameter of myocardial cell （TDM）, calcineurin activity were remarkably decreased after drug intervention and this decrease was most remarkable in the combination drug therapy group. Sarcoplasmic reticulum Ca^2＋-ATPase activity was increased after drug intervention, especially in the combined drug therapy group. Calcineurin expression in myocardium was remarkably decreased after drug intervention. LVMI was positively correlated with TDM and calcineurin, negatively correlated with sarcoplasmic reticulum Ca^2＋-ATPase. Conclusion： These data suggest that irbesartan and perindopril inhibit cardiac hypertrophy through the increased activity of sarcoplasmic reticulum Ca^2＋-ATPase and decreased expression of calcineurin. Their combination had better effects on regressing of ventricular hypertrophy.

Shen-Fu Injection(参附注射液)Alleviates Post-resuscitation Myocardial Dysfunction by Up-regulating Expression of Sarcoplasmic Reticulum Ca2+-ATPase

Objective： To compare the effect of Shen-Fu Injection （SFI） and epinephrine on the expression of sarcoplasmic reticulum Ca2. ATPase 2a （SERCA2a） in a pig model with post-resuscitation myocardial dysfunction. Methods： Ventricular fibrillation （VF） was electrically induced in Wu-zhi-shan miniature pigs. After 8 min of untreated VF and 2 min of cardiopulmonary resuscitation （CPR）, all animals were randomly administered a bolus injection of saline placebo （SA group, n=10）, SFI （0.8 mg/kg, SFI group, n=10） or epinephrine （20 t~ g/kg, EPI group, n=10）. After 4 min of CPR, a 100-J shock was delivered. If the defibrillation attempt failed to attain restoration of spontaneous circulation （ROSC）, manual chest compressions were rapidly resumed for a further 2 rain followed by a second defibrillation attempt. Hemodynamic variables were recorded, and plasma concentrations of catecholamines were measured. Adenylate cyclase （AC）, cyclic adenosine monophosphate （cAMP） and the expressions of 13 1-adrenoceptor （AR） and SERCA 2a were determined. Results： Cardiac output, left ventricular dp/dtr,~x and negative dp/dtm^x were significantly higher in the SFI group than in the SA and EPI groups at 4 and 6 h after ROSC. The expression of 13 1-AR and SERCA2a at 24 h after ROSC were significantly higher in the SFI group than in the SA and EPI groups （P〈0.05 or P〈0.01）. Conclusions： The administration of epinephrine during CPR decreased the expression of SERCA2a and aggravated postresuscitation myocardial function （P〈0.01）. SFI attenuated post-resuscitation myocardial dysfunction, and the mechanism might be related to the up-regulation of SERCA2a expression.

Liraglutide directly protects cardiomyocytes against reperfusion injury possibly via modulation of intracellular calcium homeostasis

Background Liraglutide is glucagon-like peptide-1 receptor agonist for treating patients with type 2 diabetes mellitus. Our previous studies have demonstrated that liraglutide protects cardiac function through improving endothelial function in patients with acute myocardial infarction undergoing percutaneous coronary intervention. The present study will investigate whether liraglntide can perform direct protective effects on cardiomyocytes against reperfusion injury. Methods In vitro experiments were performed using H9C2 cells and neonatal rat ventricular cadiomyocytes undergoing simulative hypoxia/reoxygenation （H/R） induction. Cardiomyocytes apoptosis was detected by fluorescence TUNEL. Mitochondrial membrane potential （AWm） and intracellular reactive oxygen species （ROS） was assessed by JC-1 and DHE, respectively. Fura-2/AM was used to measure intracellular Ca2＋ concentration and calcium transient. Immtmofluorescence staining was used to assess the expression level of sarcoplasmic reticulum Ca2＋-ATPase （SERCA2a）. In vivo experiments, myocardial apoptosis and expression of SERCA2a were detected by colorimetric TUNEL and by immunofluorescence staining, respectively. Results In vitro liraglutide inhibited cardiomyotes apoptosis against H/R. △mψ of cardiomyocytes was higher in liraglntide group than H/R group. H/R increased ROS production in H9C2 cells which was attenuated by liraglutide. Liraglutide significantly lowered Ca2＋ overload and improved calcium transient compared with H/R group, lmmunofluorescence staining results showed liraglutide promoted SERCA2a expression which was decreased in H/R group. In ischemia/reperfusion rat hearts, apoptosis was significantly attenuated and SERCA2a expression was increased by liraglutide compared with H/R group. Conclusions Liraglutide can directly protect cardiomyocytes against reperfusion injury which is possibly through modulation of intracellular calcium homeostasis.

Effects of two medicinal plants Psidium guajava L. (Myrtaceae) and Diospyros mespiliformis L. (Ebenaceae) leaf extracts on rat skeletal muscle cells in primary culture

Crude decoction, aqueous and ethanolic extracts of two medicinal plants （Psidiura guajava and Diospyros raespiliformis）, widely used in the central plateau of Burkina Faso to treat many diseases were evaluated for their antagonistic effects on caffeine induced calcium release from sarcoplasmic reticulum of rat skeletal muscle cells. These different extracts showed a decrease of caffeine induced calcium release in a dose dependent manner. Comparison of the results showed that Psidiura guajava leaf extracts are more active than extracts of Diospyros mespiliformis and that crude decoctions show better inhibitory activity. The observed results could explaine their use as antihypertensive and antidiarrhoeal agents in traditional medicine, by inhibiting intracellular calcium release.

Phospholamban Antisense RNA Improves SR Ca^(2+)-ATPase Activity and Left Ventricular Function in STZ-induced Diabetic Rats

Objective To study the effect of phospholamban antisense RNA （asPLB） on sarcoplasmic reticulum Ca2＋-ATPase activity and cardiac function in rats with diabetes mellitus （DM） mediated by recombinant adeno-associated virus （rAAV） vector. Methods Six weeks after the induction of DM by streptozotocin injected intraperitoneally, the rats were divided into three groups, namely： DM-rAAV-asPLB group, DM-saline group and DM group （control group）. The rats in the DM-rAAV-asPLB group were intramyocardially injected with rAAV-asPLB, the rats in the DM-saline group were injected with saline, and those in the control group did not receive any treatment. Six weeks after gene transfer, the expressions of PLB protein and PLB phosphorylation were detected by Western-blot, while the activity of sarcoplasmic reticulum （SR） Ca2＋-ATPase and left ventricular function were measured. Results The PLB protein expression level was significantly higher whereas the PLB phosphorylation, SR Ca2＋-ATPase activity and left ventricular function were significantly lower in the DM-saline group than in the control group. No significant difference was found in PLB protein expression level, PLB phosphorylation or SR Ca2＋-ATPase activity between the DM-rAAV-asPLB group and the control group. The left ventricular function in the DM-rAAV-asPLB group was poorer than in the control group and was better than in the DM-saline group. Conclusion rAAV-asPLB can down-regulate PLB protein expression and up-regulate phosphorylation and SR Ca2＋-ATPase activity, thus contributing to the improvement of in vivo ventricutar function. PLB left

Switching-on of serotonergic calcium signaling in activated hepatic stellate cells

AIM:To investigate serotonergic Ca 2+ signaling and the expression of 5-hydroxytryptamine(5-HT) receptors,as well as Ca 2+ transporting proteins,in hepatic stellate cells(HSCs) . METHODS:The intracellular Ca 2+ concentration([Ca 2+ ]i) of isolated rat HSCs was measured with a fluorescence microscopic imaging system.Quantitative PCR was per-formed to determine the transcriptional levels of 5-HT receptors and endoplasmic reticulum(ER) proteins involved in Ca 2+ storage and release in cultured rat HSCs. RESULTS:Distinct from quiescent cells,activated HSCs exhibited[Ca 2+ ]i transients following treatment with 5-HT,which was abolished by U-73122,a phospholipase C inhibitor.Upregulation of 5-HT2A and 5-HT2B receptors,but not 5-HT3,was prominent during trans-differentiation of HSCs.Pretreatment with ritanserin,a 5-HT2 antagonist,inhibited[Ca 2+ ]i changes upon application of 5-HT.Expression of type 1 inositol-5'-triphosphate receptor and type 2 sarcoplasmic/endoplasmic reticulum Ca 2+ ATPase were also increased during activation of HSCs and serve as the major isotypes for ER Ca 2+ storage and release in activated HSCs.Ca 2+ binding chaperone proteins of the ER,including calreticulin,calnexin and calsequestrin,were up-regulated following activation of HSCs. CONCLUSION:The appearance of 5-HT-induced[Ca 2+ ]i response accompanied by upregulation of metabotropic 5-HT2 receptors and Ca 2+ transporting/chaperone ER proteins may participate in the activating process of HSCs.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury

Background:Sarcoplasmic reticulum calcium ATPase 2a(SERCA2a)is a key protein that maintains myocardial Ca2+homeostasis.The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation(small ubiquitinlike modifier)process after ischemia/reperfusion injury(I/RI)in vitro and in vivo.Methods:Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout(KO)and wildtype mice with I/RI were compared.SUMO-relevant protein expression and localization were detected by quantitative real-time PCR(RT-qPCR),Western blotting,and immunofluorescence in vitro and in vivo.Serca2a-SUMOylation,infarct size,and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes,were detected by immunoprecipitation,triphenyltetrazolium chloride(TTC)-Evans blue staining,and echocardiography respectively.Results:The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO+I/RI groups.Senp1 and Senp2 messenger ribose nucleic acid(mRNA)and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI.However,the highest levels in HL-1 cells were recorded at 12 h.Senp2 expression increased in the cytoplasm,unlike that of Senp1.Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline,reduced the infarction area,and improved cardiac function,while inhibition of Senp1 protein could not restore the above indicators.Conclusion:I/RI activated Senp1 and Senp2 protein expression,which promoted Serca2a-deSUMOylation,while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

Effect of tetrandrine on cellular electrophysiology and calcium uptake of myocardium in guinea pigs and dogs

Objective To study the effects of tetrandrine, a Chinese herbal medicine, on the action potential (AP),contraction as well as sarcoplasmic reticulum (SR) calcium uptake of myocardium in guinea-pigs and dogs.Methods Changes in AP, dV/dt, peak tension (PT) and dT/dt of myocardial cells were studied using the technique of glass electrode. Changes of the calcium uptake rate by sarcoplasmic reticulum and release of inorganic phosphate from sarcoplasmic reticulum were assessed with biochemical techniques.Results Tetrandrine exerts a concentration-dependent and frequency-dependent negative inotropic effect and shortens action potential duration. Tetrandrine depresses both dT(E)/dt and dT(L)/dt as well as the tension of myocardium, and reduces dV/dt and amplitude only in the slow action potential, thus implying that tetrandrine blocks the slow calcium channel. In addition, compared with thapsigargin, a specific inhibitor of Ca2+-ATPase on SR, tetrandrine more apparently suppresses the contraction of the myocardium.Conclusions Tetrandrine is a wide-range calcium antagonist of plant origin. Not only it blocks the voltageoperated calcium channels as other authors reported, but also may play an important role in affecting the function of Ca2+ -ATPase and calcium release channels on SR. From this study, we also suggest that the calcium channel appears to be more critical than SR for the contraction of my ocardium.

Arrhythmogenic mechanisms in ryanodine receptor channelopathies

Ryanodine receptors(Ry Rs) are the calcium release channels of sarcoplasmic reticulum(SR) that provide the majority of calcium ions(Ca2+) necessary to induce contraction of cardiac and skeletal muscle cells.In their intracellular environment,Ry R channels are regulated by a variety of cytosolic and luminal factors so that their output signal(Ca2+) induces finely-graded cell contraction without igniting cellular processes that may lead to aberrant electrical activity(ventricular arrhythmias) or cellular remodeling.The importance of Ry R dysfunction has been recently highlighted with the demonstration that point mutations in RYR2,the gene encoding for the cardiac isoform of the Ry R(Ry R2),are associated with catecholaminergic polymorphic ventricular tachycardia(CPVT),an arrhythmogenic syndrome characterized by the development of adrenergically-mediated ventricular tachycardia in individuals with an apparently normal heart.Here we summarize the state of the field in regards to the main arrhythmogenic mechanisms triggered by Ry R2 channels harboring mutations linked to CPVT.Most CPVT mutations characterized to date endow Ry R2 channels with a gain of function,resulting in hyperactive channels that release Ca2+ spontaneously,especially during diastole.The spontaneous Ca2+ release is extruded by the electrogenic Na+/Ca2+ exchanger,which depolarizes the external membrane(delayed afterdepolarization or DAD) and may trigger untimely action potentials.However,a rare set of CPVT mutations yield Ry R2 channels that are intrinsically hypo-active and hypo-responsive to stimuli,and it is unclear whether these channels release Ca2+ spontaneously during diastole.We discuss novel cellular mechanisms that appear more suitable to explain ventricular arrhythmias due to Ry R2 loss-of-function mutations.

Effect of n-butanol Extract from Potentilla anserina on Hypoxia-induced Calcium Overload and SERCA2 Expression of Rat Cardiomyocytes

Objective To investigate the effect of n-butanol extract from Potentilla anserina(NP)intervention on hypoxia-induced Ca 2+ overload and SERCA2 expression of rat cardiomyocytes.Methods Primary cultured myocardial cell from SD neonatal rat(1-3 d)was used in the establishment of hypoxia model.After hypoxia for 3 h,the Ca 2+ concentration of myocardial cells was measured with fura-2/AM fluorescent probe,and the biochemical indicator intracellular Ca 2+ -ATPase was examined and the mRNA and its protective protein levels of the sarcoplasmic reticulum(SR)Ca 2+ -ATPases(SERCA2)were assayed with RT-PCR,Western-blotting,and immune-cytochemical staining in each group.Results The results showed that NP decreased Ca 2+ concentration, increased the activity of Ca 2+ -ATPase,and improved the mRNA and protein expression of SERCA2 in hypoxia-injured myocardial cells as compared with the model group.Conclusion These results indicate that NP could attenuate the Ca 2+ overload.The mechanism might be explained as that NP could elevate the SERCA2 level, increase the activity of myocardium in rats,and further enhance the capacity of SR Ca 2+ re-uptake.

The Involvement of Ca^2＋ Signal Pathways in Distal Colonic Myocytes in a Rat Model of Dextran Sulfate Sodium-induced Colitis

Background： Disrupted Ca2＋ homeostasis contributes to the development of colonic dysmotility in ulcerative colitis （UC）, but the underlying mechanisms are unknown. This study aimed to examine the alteration of colonic smooth muscle （SM） Ca2＋ signaling and Ca2＋ handling proteins in a rat model of dextran sulfate sodium （DSS）-induced UC. Methods： Male Sprague-Dawley rats were randomly divided into control （n = 18） and DSS （n = 17） groups. Acute colitis was induced by 5% DSS in the drinking water for 7 days. Contractility of colonic SM strips （controls, n = 8 and DSS, n = 7） was measured in an organ bath. Cytosolic resting Ca2＋ levels （n = 3 in each group） and Ca2＋ transients （n = 3 in each group） were measured in single colonic SM cells. Ca2＋ handling protein expression was determined by Western blotting （n = 4 in each group）. Differences between control and DSS groups were analyzed by a two-sample independent t-test. Results： Average tension and amplitude of spontaneous contractions of colonic muscle strips were significantly enhanced in DSS-treated rats compared with controls （1.25 ± 0.08 g vs. 0.96 - 0.05 g, P = 0.007; and 2.67 - 0.62 g vs. 0.52 ±0.10 g, P= 0.013）. Average tensions of carbachol-evoked contractions were much weaker in the DSS group （1.08 ±0.10 g vs. 1.80 ±0.19 g, P = 0.006）. Spontaneous Ca2＋ transients were observed in more SM cells from DSS-treated rats （15/30 cells） than from controls （5/36 cells）. Peak caffeine-induced intracellular Ca2＋ release was lower in SM cells of DSS-treated rats than controls （0.413 ±0.046 vs. 0.548 ±0.041, P = 0.033）. Finally, several Ca2＋ handling proteins in colonic SM were altered by DSS treatment, including sarcoplasmic reticulum calcium-transporting ATPase 2a downregulation and phospholamban and inositol 1,4,5-trisphosphate receptor 1 upregulation. Conclusions： Impaired intracellular Ca2＋ signaling of colonic SM, caused by alteration of Ca2＋ handing proteins, contribute to colonic dysmotility in DSS-induced UC.

Cardiac contraction and calcium transport function after severe burn injury in rats

Objective: To examine the function change of myocardial calcium transports and determined what role the change plays in cardiac dysfunction after severe burn injury in rats. Methods: The contraction and relaxation properties of the left ventricle (LV) were studied in the isolated hearts preparations of Wistar rats at 3, 8, and 24 h after a 30% TBSA (total body surface area) full thickness burn. The calcium transport function of the sarcoplasmic reticulum (SR) was measured by the millipore filtration technique. Results: The maximal rate of LV pressure (±dp/dtmax) of the burn group was significantly lower than that of the control group (P< 0.01 ). In addition, the calcium dependent ATPase activity and the coupling ratio of SR were also markedly depressed. Conclusions: It indicates that the decrease in the SR calcium transport function is one of the important mechanisms for the cardiac contractile dysfunction after severe burn injury.

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.