Protein Expression Of Phospholamban Research Articles

Abstract 13287: Sex Differences in the Impact of Parental Obesity on Offspring Cardiac SIRT3 Expression, Mitochondrial Efficiency and Diastolic Function Early in Life

Introduction: Previous studies suggest that the perinatal environment can profoundly impact long-term metabolic health of the offspring. Hypothesis: We tested the hypothesis that parental (paternal + maternal) obesity impairs cardiac function in the offspring early in life. Methods: Within 1-3 days after weaning, offspring from obese rats fed a high fat diet (HFD-Offs) and age-matched offspring from lean rats (ND-Offs) were submitted to echocardiography and cardiac catheterization for assessment of pressure-volume relationships. Then, hearts were digested and isolated cardiomyocytes were used to determine contractile function, calcium transients, proteins related to calcium signaling, and mitochondrial bioenergetics. Results: Female and male HFD-Offs were heavier (72±2 and 61±4 vs 57±2 and 49 ±1 g), hyperglycemic (112±8 and 115±12 vs 92±10 and 96±8 mg/dL), with higher plasma insulin and leptin concentrations compared to female and male ND-Offs respectively. Compared to male ND-Offs controls, male HFD-Offs exhibited similar systolic function but impaired diastolic function as indicated by increased isovolumetric relaxation time (IVRT, 22±1 vs. 17±1 ms), the ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity (E’) (E/E’ ratio, 29±2 vs. 23±1) and Tau (5.7±0.2 vs. 4.8±0.2 ms). The impaired diastolic function was associated with reduced resting free Ca 2+ levels and phospholamban protein expression, increased activated matrix metalloproteinase 2 and reduced sirtuin 3 (SIRT3) protein expression, mitochondrial ATP reserve and ATP-linked respiration. We found no differences in diastolic function or SIRT3 expression levels in female HFD-Offs and ND-Offs. Conclusions: These results indicate that male and female offspring from obese parents have metabolic abnormalities early in life (1-3 days after weaning) and that male, but not female, Offs from obese parents have impaired diastolic dysfunction and reductions in cardiac SIRT3, resting free Ca +2 levels and mitochondrial bioenergetics. (R01 DK121411, NHLBI-PO1HL51971, NIGMS P20GM104357 and U54GM115428)

Preliminary study on mechanism of electroacupuncture with the involvement of SERCA2a/PLB on the synergistic and attenuated effect of aconitine in treatment of heart failure

To investigate the mechanism of electroacupuncture (EA) with the involvement of sarcoplasmic reticulum Ca2+-ATPase2a (SERCA2a)/phospholamban (PLB) on the synergistic and attenuated effect of aconitine for heart failure. Thirty SPF-ranked SD rats were randomly divided into a control group, a model group, an EA group, an aconitine group and an EA plus aconitine group, with 6 rats in each group. The rat model of acute heart failure was established by infusion of high-dose propranolol hydrochloride solution into the right femoral vein. After stabilized for 10 min in the modeled rats, EA was exerted at "Neiguan" (PC 6), with disperse-dense wave, 2 Hz/15 Hz in frequency, 3 mA in intensity, for 30 min in the EA group and the EA plus aconitine group; aconitine solution (10 μg/kg) was injected from the left femoral veins in the rats in the aconitine group and the EA plus aconitine group. Hemodynamic indexes such as the left ventricular systolic pressure (LVSP) and the maximum rate of increase/decrease of left ventricular pressure (±dp/dtmax) were detected and arrhythmia types were observed and scored. SERCA2a protein and PLB protein expressions in left ventricular myocardial tissue of rats were detected by multiplex fluorescence Western blot. Compared with the control group, LVSP and ±dp/dtmax all were decreased after modeling and at each time point after intervention in the model group (P<0.01). Compared with the model group, ±dp/dtmax was increased in the aconitine group and the EA group at 1 min after intervention (P<0.01, P<0.05), +dp/dtmax was increased at 10 to 60 min after intervention in the aconitine group and at 20 to 60 min after intervention in the EA group (P<0.01, P<0.05), LVSP was increased at 1 min after intervention in the EA group (P<0.01), while LVSP and ±dp/dtmax were all increased at 1 to 60 min after intervention in the EA plus aconitine group (P<0.01, P<0.05). Compared with the aconitine group, LVSP and +dp/dtmax were increased at 1 min after intervention in the EA group (P<0.01, P<0.05), LVSP and ±dp/dtmax at 1 min after intervention while +dp/dtmax at 20 to 60 min after intervention were all increased in the EA plus aconitine group (P<0.01, P<0.05). Compared with the EA group, +dp/dtmax was higher at 10 to 60 min after intervention in the EA plus aconitine group (P<0.01). Compared with the model group, arrhythmia score was higher in the aconitine group (P<0.01). Compared with the aconitine group, arrhythmia score was lower in the EA group and the EA plus aconitine group (P<0.01). As compared with the control group, the expression of SERCA2a protein in the left ventricular cardiomyocytes was decreased (P<0.01), while the expression of PLB protein was increased in the model group (P<0.01). Compared with the model group, the expression of SERCA2a protein was increased in both the EA group and the EA plus aconitine group (P<0.05, P<0.01), and PLB protein expression was decreased in each intervention group respectively (P<0.01, P<0.05). As compared with the EA group and the aconitine group, the expression of SERCA2a protein was increased and the expression of PLB protein was decreased in the EA plus aconitine group separately (P<0.05, P<0.01). The intervention with electroacupuncture achieves the synergism/ attenuation effect of aconitine for the improvements in heart failure probably by up-regulating the expression of SERCA2a and down-regulating the expression of PLB in myocardial tissue.

Abstract P482: Elucidating And Characterizing The Molecular Mechanistic Role Of Phospholamban L39 Stop In The Pathophysiology Of Cardiomyopathy Using Patient-derived Human Induced Pluripotent Stem Cells And Humanized Knock-in Mouse Model Systems

Background: Heart failure (HF) is a complex clinical condition associated with substantial morbidity and mortality worldwide. The contractile dysfunction and arrhythmogenesis related to HF has been linked to the remodelling of calcium (Ca ++ ) handling. Phospholamban (PLN) has emerged as a key regulator of intracellular Ca ++ concentration. Of the PLN mutations, L39X is intriguing as it has not been fully characterized. This mutation is believed to be functionally equivalent to PLN null (KO) but contrary to PLN KO mice, L39X carriers develop a lethal cardiomyopathy (CMP). Our study aims at using induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) from homozygous L39X carriers to elucidate the role of L39X in human pathophysiology. Our plan also involves the characterization of humanized L39X knock-in mice (KM), which we hypothesize will develop a CMP from mis-localization of PLN and disruption of Ca ++ signalling. Methodology and Results: Mononuclear cells from Hom L39X carriers were obtained to generate 11 integration-free patient-specific iPSC clones. The iPSC-CMs were derived using established protocols. Compared to the WT iPSC-CMs, the Hom L39X derived-CMs PLN had an abnormal cytoplasmic distribution and formed intracellular aggregates, with the loss of perinuclear localization. There was also a 70% and 50% reduction of mRNA and protein expression of PLN respectively in L39X compared to WT iPSC-CMs. These findings indicated that L39X PLN is both under-expressed and mis-localized within the cell. To validate this observation in-vivo, we genetically modified FVB mice to harbour the human L39X. Following electroporation, positively transfected mouse embryonic stem cells were injected into host blastocysts to make humanized KM that were subsequently used to generate either a protamine-Cre (endogenous PLN driven expression) or a cardiac TNT mouse (i.e., CMP specific). Conclusion: Our data confirm an abnormal intracellular distribution of PLN, with the loss of perinuclear accumulation and mis-localization, suggestive of ineffective targeting to or retention of L39X. The mouse model will be critically important to validate the in-vitro observations and provides an ideal platform for future studies centred on the development of novel therapeutic strategies including virally delivered CRISPR/Cas9 for in-vivo gene editing and testing of biochemical signalling pathways.

Sex differences in the impact of parental obesity on offspring cardiac SIRT3 expression, mitochondrial efficiency, and diastolic function early in life.

Previous studies suggest that parental obesity may adversely impact long-term metabolic health of the offspring. We tested the hypothesis that parental (paternal + maternal) obesity impairs cardiac function in the offspring early in life. Within 1-3 days after weaning, offspring from obese rats fed a high-fat diet (HFD-Offs) and age-matched offspring from lean rats (ND-Offs) were submitted to echocardiography and cardiac catheterization for assessment of pressure-volume relationships. Then, hearts were digested and isolated cardiomyocytes were used to determine contractile function, calcium transients, proteins related to calcium signaling, and mitochondrial bioenergetics. Female and male HFD-Offs were heavier (72 ± 2 and 61 ± 4 g vs. 57 ± 2 and 49 ± 1 g), hyperglycemic (112 ± 8 and 115 ± 12 mg/dL vs. 92 ± 10 and 96 ± 8 mg/dL) with higher plasma insulin and leptin concentrations compared with female and male ND-Offs. When compared with male controls, male HFD-Offs exhibited similar systolic function but impaired diastolic function as indicated by increased IVRT (22 ± 1 vs. 17 ± 1 ms), E/E' ratio (29 ± 2 vs. 23 ± 1), and tau (5.7 ± 0.2 vs. 4.8 ± 0.2). The impaired diastolic function was associated with reduced resting free Ca2+ levels and phospholamban protein expression, increased activated matrix metalloproteinase 2, and reduced SIRT3 protein expression, mitochondrial ATP reserve, and ATP-linked respiration. These results indicate that male and female Offs from obese parents have multiple metabolic abnormalities early in life (1-3 days after weaning) and that male, but not female, Offs have impaired diastolic function as well as reductions in cardiac SIRT3, resting free Ca2+ levels, and mitochondrial biogenesis.NEW & NOTEWORTHY Parental obesity contributes to diastolic dysfunction in young offspring (1-3 days after weaning) in a sex-dependent manner, as well as reduced cardiac SIRT3 expression and altered mitochondrial bioenergetics, resting Ca2+ levels, and reduced phospholamban protein levels.

Intrinsically Disordered Hs Associated Protein X-1 (HAX-1) Alters the Structure of the SERCA2A - Phospholamban Regulatory Complex

The anti-apoptotic protein HAX-1 has been proposed to modulate cardiac calcium handling by interacting with the sarcoendoplasmic reticulum calcium ATPase (SERCA) and its regulatory partner, phospholamban (PLB). HAX-1 is thought to enhance the inhibitory regulation of SERCA by phospholamban, but the mechanism of this functional effect is unknown. Here we used fluorescence resonance energy transfer (FRET) microscopy to quantify the effects of HAX-1 on the structure and affinity of the SERCA-PLB regulatory complex. In parallel experiments, HAX-1 was either coexpressed with Cer-SERCA and YFP-PLB in HEK cells, or recombinant HAX-1 was applied to saponin-permeabilized cells expressing Cer-SERCA and YFP-PLB. We observed that coexpression of HAX-1 significantly increased SERCA and PLB protein expression in HEK cells, consistent with its role as an anti-apoptotic factor. Despite this, we observed a modest decrease in FRET from SERCA to PLB, consistent with a small change in the quaternary structure of the regulatory complex. This effect was dose-dependent, with increasing expression of HAX-1 further decreasing intrinsic FRET efficiency from 31% toward a minimum of 26%. We did not observe a change in the binding affinity of PLB for SERCA, since HAX-1 did not significantly change the apparent dissociation constant (KD) of the regulatory complex. Overall, the data are consistent with previous NMR studies that suggested HAX-1 binds to the PLB cytoplasmic domain and increases its association with the surface of the bilayer membrane.

Alterations of protein expression of phospholamban, ZASP and plakoglobin in human atria in subgroups of seniors

The mature mammalian myocardium contains composite junctions (areae compositae) that comprise proteins of adherens junctions as well as desmosomes. Mutations or deficiency of many of these proteins are linked to heart failure and/or arrhythmogenic cardiomyopathy in patients. We firstly wanted to address the question whether the expression of these proteins shows an age-dependent alteration in the atrium of the human heart. Right atrial biopsies, obtained from patients undergoing routine bypass surgery for coronary heart disease were subjected to immunohistology and/or western blotting for the plaque proteins plakoglobin (γ-catenin) and plakophilin 2. Moreover, the Z-band protein cypher 1 (Cypher/ZASP) and calcium handling proteins of the sarcoplasmic reticulum (SR) like phospholamban, SERCA and calsequestrin were analyzed. We noted expression of plakoglobin, plakophilin 2 and Cypher/ZASP in these atrial preparations on western blotting and/or immunohistochemistry. There was an increase of Cypher/ZASP expression with age. The present data extend our knowledge on the expression of anchoring proteins and SR regulatory proteins in the atrium of the human heart and indicate an age-dependent variation in protein expression. It is tempting to speculate that increased expression of Cypher/ZASP may contribute to mechanical changes in the aging human myocardium.

Endurance training restores spatially distinct cardiac mitochondrial function and myocardial contractility in ovariectomized rats

We previously demonstrated that the loss of female hormones induces cardiac and mitochondrial dysfunction in the female heart. Here, we show the impact of endurance training for twelve weeks, a nonpharmacological therapy against cardiovascular disease caused by ovariectomy and its contribution to cardiac contractility, mitochondrial quality control, bioenergetics and oxidative damage. We found that ovariectomy induced cardiac hypertrophy and dysfunction by decreasing SERCA2 and increasing phospholamban protein expression. Endurance training restored myocardial contractility, SERCA2 levels, increased calcium transient in ovariectomized rats but did not change phospholamban protein expression or cardiac hypertrophy. Additionally, ovariectomy decreased the amount of intermyofibrillar mitochondria and induced mitochondrial fragmentation that were accompanied by decreased levels of mitofusin 1, PGC-1α, NRF-1, total AMPK-α and mitochondrial Tfam. Endurance training prevented all these features except for mitofusin 1. Ovariectomy reduced O2 consumption, elevated O2.- release and increased Ca2+-induced mitochondrial permeability transition pore opening in both mitochondrial subpopulations. Ovariectomy also increased NOX-4 protein expression in the heart, reduced mitochondrial Mn-SOD, catalase protein expression and increased protein carbonylation in both mitochondrial subpopulations, which were prevented by endurance training. Taken together, our findings show that endurance training prevented cardiac contractile dysfunction and mitochondrial quality control in ovariectomized rats.

Trapidil improves hemodynamic, echocardiographic and redox state parameters of right ventricle in monocrotaline-induced pulmonary arterial hypertension model

BackgroundPulmonary arterial hypertension is a disease characterized by increased pulmonary vascular resistance and redox imbalance, leading to failure of right ventricle. Trapidil has been described to improve the redox balance and cardiac conditions. HypothesisTrapidil can improve the redox balance and contribute to functional improvements of the RV in PAH. Methods and ResultsMale, 5week-old Wistar rats were divided into four groups: Control, Control + Trapidil, Monocrotaline and Monocrotaline + Trapidil. PAH was induced by an intraperitoneal injection of monocrotaline 60 mg/kg at day 0. Treatment started at day 7 (5 or 8 mg/kg/day) until day 14, when animals were euthanized after echocardiography and catheterism. Right ventricular systolic pressure and pressure/time derivatives were increased in monocrotaline animals. The increased right ventricular diameters in monocrotaline groups were reduced with trapidil. Monocrotaline groups showed higher lipid peroxidation and glutathione peroxidase activity. Trapidil reduced NADPH oxidases activities and increased the reduced glutathiones/total glutathiones ratio. Protein expression of phospholamban in RV was diminished in monocrotaline groups, whereas expression of RyR and SERCA was enhanced in the groups treated with trapidil. ConclusionOur data suggest that trapidil induces an improvement in RV remodeling in PAH model, mitigating the progression of the disease.

Phenotyping of Mice with Heart Specific Overexpression of A2A-Adenosine Receptors: Evidence for Cardioprotective Effects of A2A-Adenosine Receptors.

Background: Adenosine can be produced in the heart and acts on cardiac adenosine receptors. One of these receptors is the A2A-adenosine receptor (A2A-AR).Methods and Results: To better understand its role in cardiac function, we generated and characterized mice (A2A-TG) which overexpress the human A2A-AR in cardiomyocytes. In isolated atrial preparations from A2A-TG but not from WT, CGS 21680, an A2A-AR agonist, exerted positive inotropic and chronotropic effects. In ventricular preparations from A2A-TG but not WT, CGS 21680 increased the cAMP content and the phosphorylation state of phospholamban and of the inhibitory subunit of troponin in A2A-TG but not WT. Protein expression of phospholamban, SERCA, triadin, and junctin was unchanged in A2A-TG compared to WT. Protein expression of the α-subunit of the stimulatory G-protein was lower in A2A-TG than in WT but expression of the α-subunit of the inhibitory G-protein was higher in A2A-TG than in WT. While basal hemodynamic parameters like left intraventricular pressure and echocardiographic parameters like the systolic diameter of the interventricular septum were higher in A2A-TG than in WT, after β-adrenergic stimulation these differences disappeared. Interestingly, A2A-TG hearts sustained global ischemia better than WT.Conclusion: We have successfully generated transgenic mice with cardiospecific overexpression of a functional A2A-AR. This receptor is able to increase cardiac function per se and after receptor stimulation. It is speculated that this receptor may be useful to sustain contractility in failing human hearts and upon ischemia and reperfusion.

Heart Failure Re-Distributes Phospholamban between Nuclear Membranes and Sarcoplasmic Reticulum in Cardiomyocytes

We recently documented that phospholamban (PLB), a sarcoplasmic reticulum (SR) resident protein regulator of cardiac SR Ca-ATPase (SERCA2a), is localized to the nuclear envelope (NE) of cardiomyocytes (CMs). It is well-known that heart failure (HF) remodeling involves altered protein expression of PLB and SERCA2a; however, with the demonstrated compartmentalization of PLB accumulation, we asked whether HF alters trafficking between ER/SR subcompartments affecting steady-state intracellular distribution of PLB and SERCA. In this study, we examined heart tissue from non-failing and pacing-induced HF dogs with the monoclonal PLB (2D12 or 1F1) and SERCA (2A7-A1) antibodies. Confocal immunofluorescence microscopy was used to compare subcellular concentration of PLB and SERCA. At least 3 regions from NE and SR in 10 CMs were analyzed for each dog, n = 4 dogs). Both PLB and SERCA antibodies stained SR and NE in these CMs. Fluorescence intensity ratios between NE and SR for PLB was 2.05±0.82 (mean ± SD) in control dog CMs, consistent with results just reported. In HF CMs we found a highly decreased ratio of PLB between NE and SR to 1.26 ± 0.34 (n = 8 dogs). In contrast to re-distribution of PLB, intensity ratios for SERCA in NE and SR remained unchanged (1.01±0.14 in Control, and 0.98±0.26 in HF). Furthermore, while there was only minor levels of phosphoPLB in Control CMs, we found that phosphoPLB (S16) were very significantly higher in NE of failed CMs. The decreased PLB relative to SERCA in the NE of CMs suggests that retention and accumulation of PLB in the NE is decreased in HF, leading to a smaller, possibly hyper-phosphorylated steady-state of PLB concentration in the NE.

Myocardial expression profiles of candidate molecules in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia compared to those with dilated cardiomyopathy and healthy controls

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is mainly an autosomal dominant disease characterized by fibrofatty infiltration of the right ventricle, leading to ventricular arrhythmias. Mutations in desmosomal proteins can be identified in about half of the patients. The pathogenic mechanisms leading to disease expression remain unclear. The purpose of this study was to investigate myocardial expression profiles of candidate molecules involved in the pathogenesis of ARVC/D. Myocardial messenger RNA (mRNA) expression of 62 junctional molecules, 5 cardiac ion channel molecules, 8 structural molecules, 4 apoptotic molecules, and 6 adipogenic molecules was studied. The averaged expression of candidate mRNAs was compared between ARVC/D samples (n = 10), nonfamilial dilated cardiomyopathy (DCM) samples (n = 10), and healthy control samples (n = 8). Immunohistochemistry and quantitative protein expression analysis were performed. Genetic analysis using next generation sequencing was performed in all patients with ARVC/D. Following mRNA levels were significantly increased in patients with ARVC/D compared to those with DCM and healthy controls: phospholamban (P ≤ .001 vs DCM; P ≤ .001 vs controls), healthy tumor protein 53 apoptosis effector (P = .001 vs DCM; P ≤ .001 vs controls), and carnitine palmitoyltransferase 1β (P ≤ .001 vs DCM; P = 0.008 vs controls). Plakophillin-2 (PKP-2) mRNA was downregulated in patients with ARVC/D with PKP-2 mutations compared with patients with ARVC/D without PKP-2 mutations (P = .04). Immunohistochemistry revealed significantly increased protein expression of phospholamban, tumor protein 53 apoptosis effector, and carnitine palmitoyltransferase 1β in patients with ARVC/D and decreased PKP-2 expression in patients with ARVC/D carrying a PKP-2 mutation. Changes in the expression profiles of sarcolemmal calcium channel regulation, apoptosis, and adipogenesis suggest that these molecular pathways may play a critical role in the pathogenesis of ARVC/D, independent of the underlying genetic mutations.

Sex Hormones Promote Opposite Effects on ACE and ACE2 Activity, Hypertrophy and Cardiac Contractility in Spontaneously Hypertensive Rats.

BackgroundThere is growing interest in sex differences and RAS components. However, whether gender influences cardiac angiotensin I-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) activity is still unknown. In the present work, we determined the relationship between ACE and ACE2 activity, left ventricular function and gender in spontaneously hypertensive rats (SHRs).Methodology / Principal FindingsTwelve-week-old female (F) and male (M) SHRs were divided into 2 experimental groups (n = 7 in each group): sham (S) and gonadectomized (G). Fifty days after gonadectomy, we measured positive and negative first derivatives (dP/dt maximum left ventricle (LV) and dP/dt minimum LV, respectively), hypertrophy (morphometric analysis) and ACE and ACE2 catalytic activity (fluorimetrically). Expression of calcium handling proteins was measured by western blot. Male rats exhibited higher cardiac ACE and ACE2 activity as well as hypertrophy compared to female rats. Orchiectomy decreased the activity of these enzymes and hypertrophy, while ovariectomy increased hypertrophy and ACE2, but did not change ACE activity. For cardiac function, the male sham group had a lower +dP/dt than the female sham group. After gonadectomy, the +dP/dt increased in males and reduced in females. The male sham group had a lower -dP/dt than the female group. After gonadectomy, the -dP/dt increased in the male and decreased in the female groups when compared to the sham group. No difference was observed among the groups in SERCA2a protein expression. Gonadectomy increased protein expression of PLB (phospholamban) and the PLB to SERCA2a ratio in female rats, but did not change in male rats.ConclusionOvariectomy leads to increased cardiac hypertrophy, ACE2 activity, PLB expression and PLB to SERCA2a ratio, and worsening of hemodynamic variables, whereas in males the removal of testosterone has the opposite effects on RAS components.

Effects of adiponectin on calcium-handling proteins in heart failure with preserved ejection fraction.

Despite the increasing prevalence of heart failure with preserved ejection fraction (HFpEF) in humans, there remains no therapeutic options for HFpEF. Adiponectin, an adipocyte-derived cytokine, exerts cardioprotective actions, and its deficiency is implicated in the development of hypertension and HF with reduced ejection fraction. Similarly, adiponectin deficiency in HFpEF exacerbates left ventricular hypertrophy, diastolic dysfunction, and HF. However, the therapeutic effects of adiponectin in HFpEF remain unknown. We sought to test the hypothesis that chronic adiponectin overexpression protects against the progression of HF in a murine model of HFpEF. Adiponectin transgenic and wild-type mice underwent uninephrectomy, a continuous saline or d-aldosterone infusion and given 1.0% sodium chloride drinking water for 4 weeks. Aldosterone-infused wild-type mice developed HFpEF with hypertension, left ventricular hypertrophy, and diastolic dysfunction. Aldosterone infusion increased myocardial oxidative stress and decreased sarcoplasmic reticulum Ca(2+)-ATPase protein expression in HFpEF. Although total phospholamban protein expression was unchanged, there was a decreased expression of protein kinase A-dependent phospholamban phosphorylation at Ser16 and CaMKII (Ca(2+)/calmodulin-dependent protein kinase II)-dependent phospholamban phosphorylation at Thr17. Adiponectin overexpression in aldosterone-infused mice ameliorated left ventricular hypertrophy, diastolic dysfunction, lung congestion, and myocardial oxidative stress without affecting blood pressure and left ventricular EF. This improvement in diastolic dysfunction parameters in aldosterone-infused adiponectin transgenic mice was accompanied by the preserved protein expression of protein kinase A-dependent phosphorylation of phospholamban at Ser16. Adiponectin replacement prevented the progression of aldosterone-induced HFpEF, independent of blood pressure, by improving diastolic dysfunction and by modulating cardiac hypertrophy. These findings suggest that adiponectin may have therapeutic effects in patients with HFpEF.

Losartan and Carvedilol prevent ventricular dysfunction induced by ovariectomy in female rats

Ovarian sex hormones (OSHs) modulates myocardial contractility due to a mechanism involving the intracellular calcium handling. We evaluated the possibility that, at long-term, OSHs could modulates the ventricular contractility dependent on the renin-angiotensin system (RAS) and the noradrenergic receptors. Female Wistar rats were divided into: control (Sham); ooforectomy (OVX); OVX plus Losartan (15 mg/Kg/day i.m., OVX-LOS); OVX plus Carvedilol (20 mg/Kg/dia v.o., OVX-CAR) and OVX plus estrogen (1 mg/Kg i.m., once a week). After 60 days the inotropic responses to Ca2+ and to isoproterenol were assessed using isolated left ventricle papillary muscle. The cardiac protein expression of SERCA2a and phospholamban was determined. The body weight gain in the OVX group was reverted by estrogen and losartan treatment (Sham: 257±5; OVX:305±9*; OVX-LOS:277±3#; OVX-CAR:295±4; OVX-E2:251±9# g *#p<0.05). The reduced positive inotropic response to Ca2+ and Isoproterenol was restored by estrogen, losartan and carvedilol replacement (Ca2+=3.75 mM: Sham:650±42; OVX:388±35*; OVX-LOS:636±61#; OVX-CAR:591±51#; OVX-E2:593±76# g/g, *#p<0.05 and Isoproterenol=10-3 M:Sham:598±41; OVX:311±32*; OVX-LOS:586±57#; OVX-CAR:545±66#; OVX-OVX-Estrogen:574±45# g/g, *#p<0.05). The reduction in SERCA2a and the increase in phospholamban protein expression in the OVX group were restored by all treatment.

Cardioprotective effects of Astragali Radix against isoproterenol‐induced myocardial injury in rats and its possible mechanism

The purpose of the present study was to investigate the effects of the Chinese medical herb Astragali Radix on myocardial injury in vivo and its possible mechanisms. Myocardial injury in rats was induced by the subcutaneous injection of a high dose of isoproterenol for 10 days, and the therapeutic effects of Astragali Radix were observed. Cardiac hemodynamics, heart coefficient and marker enzymes in serum showed that Astragali Radix prevented isoproterenol-induced myocardial damage. Astragali Radix also improved the antioxidant status by decreasing the lipid peroxidative product malondialdehyde and increasing the activity of the antioxidant enzyme superoxide dismutase. The observed depressions in sarcoplasmic reticulum Ca2+-ATPase mRNA and protein expression as well as Ser(16)-phosphorylated phospholamban protein expression in isoproterenol-treated rats were attenuated by Astragali Radix treatment. Moreover, treatment with Astragali Radix showed higher myocardial cAMP content compared with the isoproterenol-alone group. These results suggest that the antioxidant property and partial prevention of changes in protein and gene expression of cardiac sarcoplasmic reticulum Ca2+ regulatory proteins which may be mediated through the cAMP pathway could help to explain the beneficial effects of Astragali Radix on myocardial injury in vivo.

Effects on recovery during acidosis in cardiac myocytes overexpressing CaMKII

Recovery of intracellular Ca transients and fractional shortening during late phase acidosis are suggested to be associated with CaMKII-dependent processes of which phospholamban (PLB) phosphorylation may play an important role. To test whether increased expression levels of CaMKII may further enhance recovery, we investigated myocytes from CaMKIIδ C transgenic (TG) mice (cytosolic localized CaMKII) having heart failure vs. wild-type littermates (WT). Furthermore, mouse and rabbit myocytes overexpressing CaMKIIδ C using adenovirus-mediated gene transfer (vs. LacZ control) were investigated. Fractional shortening (% vs. resting cell length, % RCL) was assessed during control conditions (pH 7.4) and during acidosis (pH 6.5). Ca transients were measured using fluo-3 (Δ F/ F 0, 10 μM). In WT mouse myocytes, fractional shortening clearly recovered by 90% from 4.6 ± 0.6 to 7.2 ± 0.7% RCL during late acidosis. In parallel, Ca transients increased from 2.01 ± 0.11 to 2.33 ± 0.15 Δ F/ F 0. When blocking CaMKII (KN-93, 1 μM), recovery of Ca transients and shortening could be completely abolished. In contrast, in CaMKIIδ C TG mouse myocytes shortening recovered only by 32% from 3.4 ± 0.6 to 4.4 ± 0.5% RCL ( P < 0.05 vs. WT using ANOVA). In parallel, Ca transients increased only slightly from 1.75 ± 0.15 to 1.84 ± 0.13 Δ F/ F 0 ( P < 0.05 vs. WT using ANOVA). In accordance, SR Ca content (measured by caffeine contractures, 10 mM) in WT significantly increased during late acidosis but not in CaMKIIδ C TG mice. In contrast, in mouse and rabbit myocytes overexpressing CaMKIIδ C by means of adenovirus-mediated gene transfer, recovery of fractional shortening and Ca transients was not impaired during late acidosis but even slightly improved vs. LacZ control ( P < 0.05 vs. CaMKIIδ C using ANOVA for mouse and rabbit myocytes). This was associated with significantly increased SR Ca content during late acidosis in CaMKIIδ C as compared to LacZ. CaMKII-dependent PLB Thr-17 phosphorylation, contributing to increased SR Ca uptake, was significantly increased in CaMKIIδ C transfected rabbit myocytes vs. LacZ in the light of unchanged SR Ca ATPase and PLB protein expression. CaMKII inhibition completely prevented recovery of all parameters in both CaMKIIδ C and LacZ. In summary and in contrast to our initial hypothesis, we showed for the first time that TG CaMKIIδ C overexpression (i.e., chronic overexpression) in mice with heart failure clearly resulted in impaired recovery associated with impaired SR Ca loading during late acidosis vs. WT. This may be due to decreased SR Ca ATPase and PLB expression as reported previously. In contrast, adenovirus-mediated gene transfer of CaMKIIδ C in mouse and rabbit myocytes (i.e., acute overexpression) did not result in impaired but even slightly improved recovery associated with increased SR Ca load during late acidosis as compared to LacZ. This most likely was due to higher PLB Thr-17 phosphorylation in CaMKIIδ C myocytes. In conclusion, possible beneficial effects by therapeutical CaMKIIδ C stimulation on the ability to recover from acidosis may be challenged by altered expression levels of its target proteins and should be carefully considered.

Modification of alterations in cardiac function and sarcoplasmic reticulum by astragaloside IV in myocardial injury in vivo

Astragaloside IV, the primary pure saponin isolated from Astragalus membranaceus has been found to have potent cardioprotective effects. In this study, we aim to investigate if the beneficial effects of astragaloside IV on cardiac function are associated with improvement in sarcoplasmic reticulum Ca 2+-pump function in myocardial injury in vivo. Myocardial injury in rats was induced by subcutaneous injection of a high dose of isoproterenol, and the therapeutic effect of astragaloside IV was observed. Isoproterenol-treated rats showed widespread subendocardial necrosis, a rise in serum lactate dehydrogenase and creatine kinase, formation of lipid oxide product malondialdehyde and inhibition of left ventricular diastolic and systolic function, which suggested severe myocardial injury and acute heart failure. Moreover, sarcoplasmic reticulum Ca 2+-uptake ability and Ca 2+-ATPase (SERCA2a) activity were significantly reduced. And the level of SERCA2a mRNA and protein expression was also markedly decreased, associated with a decrease in Ser 16-phosphorylated phospholamban protein expression, while total phospholamban level was unchanged in the isoproterenol-treated group compared with controls. However, these biochemical and hemodynamic changes in the acute failing hearts were prevented by treatment of isoproterenol-induced rats with astragaloside IV. Likewise, the observed reductions in sarcoplasmic reticulum Ca 2+-pump function as well as in SERCA2a mRNA and protein levels and the phosphorylation level of phospholamban in the injured hearts were attenuated by astragaloside IV treatment. These results suggest that the beneficial effect of astragaloside IV on isoproterenol-induced myocardial injury may be due to its ability to prevent changes of SERCA2a and Ser 16-phosphorylated phospholamban protein expression and, thus, may prevent the depression in sarcoplasmic reticulum Ca 2+ transport and improve cardiac function.

Improvement of Cardiac Sarcoplasmic Reticulum Calcium Cycling in Dogs with Heart Failure Following Long-Term Therapy with the Acorn Cardiac Support Device

Abnormal Ca(2+)-homeostasis is a hall-marked characteristic of the failing heart. In the normal myocardium, the sarcoplasmic reticulum (SR) is a principal organelle that controls intracellular Ca(2+) concentration during the cardiac cycle. The SR consists of longitudinal and terminal cisternea regions. The former contains the Ca(2+)-ATPase pump or SERCA-2a whose function is to transport cytosolic Ca(2+) into the lumen of the SR during diastole and whose activity is regulated by reversible phosphorylation of the endogenously SR-bound phospholamban (PLB). The SR's terminal cisternea region contains ryanodine-sensitive Ca(2+)-release channels (RR), the activity of which is regulated by direct and indirect reversible phosphorylation. These channels release the SR-stored Ca(2+) during contraction. We have shown that in left ventricular (LV) myocardium from dogs with coronary microembolization-induced heart failure, ability of the SR to sequester and release Ca(2+) during the cardiac cycles is impaired. This abnormality was associated with reduced expression (protein and mRNA) levels of Ca(2+)-ATPase, PLB, and reduced PLB phosphorylation. Long-term therapy with the Acorn Cardiac Support Device (CSD) is associated with restoration of the ability of the SR to sequester Ca(2+). This improvement in SR function following chronic CSD therapy was due primarily to increased affinity of the SERCA-2a for calcium. The later was associated with (1) increased phosphorylation of PLB at serine 16 and threonine 17, (2) unchanged protein expression of PLB and (3) unchanged protein expression of SERCA-2a in LV myocardium of CSD-treated dogs compared to controls. This review summarizes our current understanding of the role of the CSD in modulating SR calcium cycling in an experimental canine model of chronic heart failure produced by multiple sequential intracoronary microembolizations.

Adenovirus-Mediated Overexpression of O -GlcNAcase Improves Contractile Function in the Diabetic Heart

To examine whether excessive protein O-GlcNAcylation plays a role in the dysfunction of the diabetic heart, we delivered adenovirus expressing O-GlcNAcase (Adv-GCA) into the myocardium of STZ-induced diabetic mice. Our results indicated that excessive cellular O-GlcNAcylation exists in the diabetic heart, and that in vivo GCA overexpression reduces overall cellular O-GlcNAcylation. Myocytes isolated from diabetic hearts receiving Adv-GCA exhibited improved calcium transients with a significantly shortened T(decay) (P<0.01) and increased sarcoplasmic reticulum Ca2+ load (P<0.01). These myocytes also demonstrated improved contractility including a significant increase in +dL/dt and -dL/dt and greater fractional shortening as measured by edge detection (P<0.01). In isolated perfused hearts, developed pressure and -dP/dt were significantly improved in diabetic hearts receiving Adv-GCA (P<0.05). These hearts also exhibited a 40% increase in SERCA2a expression. Phospholamban protein expression was reduced 50%, but the phosphorylated form was increased 2-fold in the diabetic hearts receiving Adv-GCA. We conclude that excess O-GlcNAcylation in the diabetic heart contributes to cardiac dysfunction, and reducing this excess cellular O-GlcNAcylation has beneficial effects on calcium handling and diabetic cardiac function.

Daily exercise-induced cardioprotection is associated with changes in calcium regulatory proteins in hypertensive rats.

Epidemiological data document that regular exercise protects against the morbidity and mortality associated with ischemic heart disease. Therefore, we tested the hypothesis that daily exercise (DE) increases the ventricular arrhythmia threshold (VAT) induced by coronary artery occlusion and alters the expression of calcium regulatory proteins. The VAT was defined as the time from coronary occlusion to sustained ventricular tachycardia resulting in a reduction in arterial pressure. To test this hypothesis, we recorded the VAT in conscious sedentary normotensive, sedentary hypertensive, and DE hypertensive rats, and we associated these thresholds with the protein expression of the L-type calcium channel, Na+/Ca2+ exchanger, phospholamban, and sarco(endo)plasmic reticulum Ca(2+)-ATPase. Results document a significantly reduced time to ventricular arrhythmias (sedentary hypertensive, 3.7 +/- 0.3 min vs. sedentary normotensive, 4.8 +/- 0.3 min), an increased Na+/Ca2+ exchanger protein expression (47%), and a decreased phospholamban protein expression (-34%) in conscious hypertensive rats. DE increased the VAT (5.9 +/- 0.2 min), decreased the protein expression of the Na+/Ca2+ exchanger, and normalized the protein expression of phospholamban in the hypertensive rats. Thus DE may be a primary prevention approach for reducing the incidence of arrhythmias by altering calcium regulatory proteins in hypertensive rats.