Upregulation of SERCA2a following short-term ACE inhibition (by enalaprilat) alters contractile performance and arrhythmogenicity of healthy myocardium in rat

B-Type Natriuretic Peptide Inhibits the Expression and Function of SERCA2a in Heart Failure

B-type natriuretic peptide (BNP) possesses protective cardiovascular properties; however, there has not been sufficient serious consideration of the side effects of BNP. As for sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), it was once considered a new target for the treatment of heart failure (HF). Nevertheless, clinical trials of SERCA2a gene therapy in HF have finally become unsuccessful. Research has found that elevated BNP levels and decreased SERCA2a expression are two important HF characteristics, which are always negatively correlated. We hypothesize that BNP inhibits SERCA2a expression and, therefore, exerts negative effects on SERCA2a expression and function.The effects of BNP on endogenous SERCA2a expression and function were tested in mice with HF induced by transverse aortic constriction and neonatal rat cardiomyocytes (NRCM). Furthermore, to verify the effects of BNP on exogenous SERCA2a gene transduction efficacy, BNP was added to the myocardium and cardiomyocytes infected with an adenovirus overexpressing SERCA2a.In vivo, BNP levels were increased, SERCA2a expression was reduced in both the BNP intervention and HF groups, and BNP reduced the overexpressed exogenous SERCA2a protein in the myocardium. Our in vitro data showed that BNP dose-dependently inhibited the total and exogenous SERCA2a expression in NRCM by activating the cGMP-dependent protein kinase G. BNP also inhibited the effects of SERCA2a overexpression on Ca2+ transience in NRCM.The expression and function of endogenous and exogenous SERCA2a are inhibited by BNP. The opposite relationship between BNP and SERCA2a should be given serious attention in the treatment of HF via BNP or SERCA2a gene therapy.

Effect of age and sex on the incidence of ventricular arrhythmia in a rat model of acute ischemia

BACKGROUND

The impact of sex and age on the arrhythmic susceptibility within the setting of acute ischemia is masked by the fact that acute coronary events result from coronary artery disease appearing with age much earlier among men than among women.

METHODS AND RESULTS

LAD ligation or sham operations were performed in rats of both sexes at the age 3 and 24 months. An ECG was recorded continuously for 6 h after the operation. The number of early and late premature ventricular beats (PVBs), episodes of ventricular tachycardia (VT) and fibrillation (VF), heart rate, QRS, QT and Tpeak-Tend duration were analysed. Epicardial action potentials were recorded in vivo, Ca²⁺ signaling was evaluated in isolated cardiomyocytes, fibrosis and connexin-43 expression and localization were measured in the septum. PVBs, VT and VF episodes are much more common in older males than in young males and females independently from their age. Fibrosis with varying intensity in different muscle layers, hypertrophy of cardiomyocytes, reduced number of gap junctions and their appearance on the lateral myocyte membrane, QT prolongation, increase transmural dispersion of repolarisation and a decreased function of SERCA2a may increase the propensity to arrhythmia within the setting of acute ischemia.

CONCLUSION

We show that the male sex, especially in case of older individuals is a strong predictor of increased arrhythmic susceptibility within the acute ischemia setting regardless of its impact on the occurrence of cardiovascular diseases. A personalized sex-dependent prevention treatment is needed to reduce the mortality in acute phases of myocardial infarction.

Antiepileptic Drug Tiagabine Does Not Directly Target Key Cardiac Ion Channels Kv11.1, Nav1.5 and Cav1.2

Tiagabine is an antiepileptic drug used for the treatment of partial seizures in humans. Recently, this drug has been found useful in several non-epileptic conditions, including anxiety, chronic pain and sleep disorders. Since tachycardia-an impairment of cardiac rhythm due to cardiac ion channel dysfunction-is one of the most commonly reported non-neurological adverse effects of this drug, in the present paper we have undertaken pharmacological and numerical studies to assess a potential cardiovascular risk associated with the use of tiagabine. A chemical interaction of tiagabine with a model of human voltage-gated ion channels (VGICs) is described using the molecular docking method. The obtained in silico results imply that the adverse effects reported so far in the clinical cardiological of tiagabine could not be directly attributed to its interactions with VGICs. This is also confirmed by the results from the isolated organ studies (i.e., calcium entry blocking properties test) and in vivo (electrocardiogram study) assays of the present research. It was found that tachycardia and other tiagabine-induced cardiac complications are not due to a direct effect of this drug on ventricular depolarization and repolarization.

Velvet Antler Ameliorates Cardiac Function by Restoring Sarcoplasmic Reticulum Ca2+-ATPase Activity in Rats With Heart Failure After Myocardial Infarction

Objective: Velvet antler (VA; cornu cervi pantotrichum), a well-known traditional Chinese medicine, has been shown to exert cardioprotective effects. The purpose of this study was to investigate the effect of VA on heart failure (HF) caused by ischemia-reperfusion, and explore its possible mechanism from the regulation of sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase 2 alpha (SERCA2a).

Methods: A rat model of HF was established by ligating the left anterior descending coronary artery of male Sprague–Dawley rats (n = 88). One week after surgery, VA (200, 400, or 800 mg/[kg day⁻¹]) or enalapril (1 mg/[kg day⁻¹]) was administered daily for the next 4 weeks. Heart function was detected by echocardiography and histopathological analysis. The serum BNP level was measured by ELISA, and the expression of SERCA2a, PLB, PLB-Ser¹⁶, and PKA was determined by western blotting. SERCA2a and PLB mRNA levels were determined by real-time quantitative PCR.

Results: Compared with the sham group, cardiac function in the HF group, including the serum BNP level, heart mass index, myocardial collagen deposition, and left ventricular ejection fraction, was markedly reduced; however, these changes could be reversed by VA treatment. In addition, VA (200 mg/[kg·d⁻¹]) inhibited the decrease of SERCA2a and PLB mRNA levels and SERCA2a, PLB, PLB-Ser¹⁶, and PKA protein expression and restored the activity of SERCA2a and PKA. Enalapril affected only PLB protein expression.

Conclusion: VA can improve myocardial fibrosis and ventricular remodeling in rats, thereby helping to restore cardiac function. The underlying mechanism may be related to the upregulation of the expression and activation of PKA and PLB and the restoration of the expression and activity of SERCA2a.

miR-125a, miR-139 and miR-324 contribute to Urocortin protection against myocardial ischemia-reperfusion injury

Urocortin 1 and 2 (Ucn-1 and Ucn-2) have established protective actions against myocardial ischemia-reperfusion (I/R) injuries. However, little is known about their role in posttranscriptional regulation in the process of cardioprotection. Herein, we investigated whether microRNAs play a role in urocortin-induced cardioprotection. Administration of Ucn-1 and Ucn-2 at the beginning of reperfusion significantly restored cardiac function, as evidenced ex vivo in Langendorff-perfused rat hearts and in vivo in rat subjected to I/R. Experiments using microarray and qRT-PCR determined that the addition of Ucn-1 at reperfusion modulated the expression of several miRNAs with unknown role in cardiac protection. Ucn-1 enhanced the expression of miR-125a-3p, miR-324-3p; meanwhile it decreased miR-139-3p. Similarly, intravenous infusion of Ucn-2 in rat model of I/R mimicked the effect of Ucn-1 on miR-324-3p and miR-139-3p. The effect of Ucn-1 involves the activation of corticotropin-releasing factor receptor-2, Epac2 and ERK1/2. Moreover, the overexpression of miR-125a-3p, miR-324-3p and miR-139-3p promoted dysregulation of genes expression involved in cell death and apoptosis (BRCA1, BIM, STAT2), in cAMP and Ca²⁺ signaling (PDE4a, CASQ1), in cell stress (NFAT5, XBP1, MAP3K12) and in metabolism (CPT2, FoxO1, MTRF1, TAZ). Altogether, these data unveil a novel role of urocortin in myocardial protection, involving posttranscriptional regulation with miRNAs.

The Impact of Sevoflurane on Coupling of the Left Ventricular-to-Systemic Vasculature in Rats With Chronic Pulmonary Hypertension

OBJECTIVES

The relationship between left ventricular function and afterload has not been investigated as much as the right ventricular function under chronic pulmonary hypertension (PH) during anesthesia. This study was designed to investigate effects of sevoflurane on the intrinsic coupling relationship between the left ventricle and systemic vasculature in the presence of PH.

DESIGN

A randomized, controlled study.

SETTING

University hospital.

PARTICIPANTS

Sprague-Dawley rats.

INTERVENTIONS

Monocrotaline (MCT) was injected intraperitoneally to induce a PH model.

MEASUREMENTS AND MAIN RESULTS

Four weeks later, rats with MCT injection demonstrated significantly increased pulmonary arterial pressure and right/left ventricular systolic ratio of ventricular pressure (p < 0.001). Rats were treated with 1.5% sevoflurane inhalation. The PV catheters were inserted and left ventricular pressure-volume loops were measured at baseline, 30, 60, and 90 minutes during sevoflurane treatment. Preload recruitable stroke work and end-systolic elastance were decreased markedly in rats with MCT injection (p < 0.05). However, arterial elastance decreased similarly in both groups. Sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a) level was decreased and the expression of phospholamban (PLB) was increased in the PH group and after sevoflurane treatment. PH rats suffered further SERCA2/PLB ratio decrease from their already low baseline. The left ventricular contractility and ventricular-vascular coupling were decreased in rats with PH after sevoflurane inhalation.

CONCLUSIONS

Sevoflurane reduced SERCA2a expression and increased PLB expression in PH rats. This partially could explain why the LV contractility and ventricular-to-vasculature coupling of PH rats were attenuated after sevoflurane treatment.

Electrocardiography in rats: a comparison to human

Electrocardiography (ECG) in rats is a widely applied experimental method in basic cardiovascular research. The technique of ECG recordings is simple; however, the interpretation of electrocardiographic parameters is challenging. This is because the analysis may be biased by experimental settings, such as the type of anesthesia, the strain or age of animals. Here, we aimed to review electrocardiographic parameters in rats, their normal range, as well as the effect of experimental settings on the parameters variation. Furthermore, differences and similarities between rat and human ECG are discussed in the context of translational cardiovascular research.