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Nitric oxide (NO) is produced from endothelial cells and cardiomyocytes composing the myocardium and benefits cardiac function through both vascular-dependent and—independent effects. This study was purposed to investigate the possible adverse effect of NO focusing on the voltage-gated Na+ channel in cardiomyocytes. We carried out patch-clamp experiments on rat neonatal cardiomyocytes demonstrating that NOC-18, an NO donor, significantly reduced Na+ channel current in a dose-dependent manner by a long-term application for 24 h, accompanied by a reduction of Nav1.5-mRNA and the protein, and an increase of a transcription factor forkhead box protein O1 (FOXO1) in the nucleus. The effect of NOC-18 on the Na+ channel was blocked by an inhibitor of thiol oxidation N-ethylmaleimide, a disulfide reducing agent disulfide 1,4-Dithioerythritol, or a FOXO1 activator paclitaxel, suggesting that NO is a negative regulator of the voltage-gated Na+ channel through thiols in regulatory protein(s) for the channel transcription.

Background Subclinical hypothyroidism (SCH) is reportedly associated with an increased risk of adverse events in patients undergoing percutaneous coronary intervention (PCI). The prognostic significance of SCH in the elderly was poorly defined. The purpose of this study was to evaluate the association between SCH and long-term outcomes in older patients undergoing PCI. Methods Three thousand one hundred sixty-eight patients aged 65 years or older who underwent PCI from January 2012 to October 2014 were included. Patients were divided into SCH group (n = 320) and euthyroidism (ET) group (n = 2848) based on thyroid function test. Cox proportional hazard regression analyses were used to estimate the relative risks (RRs) of all-cause death and cardiac death for patients with SCH during a 4-year follow-up period. Results There were 227 deaths during the follow-up period including 124 deaths caused by cardiac events. There was no significant difference in mortality rate between the SCH group and the ET group (p > 0.05). After adjustment for covariates, compared with patients with ET, the RRs of death from all-cause and cardiac in patients with SCH were 1.261 (95%CI: 0.802–1.982, p = 0.315) and 1.231 (95%CI: 0.650–2.334, p = 0.524), respectively. When SCH was stratified by age, gender, and degree of thyroid-stimulating hormone elevation, no significant associations were also found in any stratum. Conclusion Our investigation revealed that SCH was negatively associated with the outcome of PCI in older patients.

SCN5A gene encodes the voltage-gated sodium channel NaV1.5 which is composed of a pore-forming α subunit of the channel. Asparagine (N)-linked glycosylation is one of the common post-translational modifications in proteins. The aim of this study was to investigate impact of N-linked glycosylation disruption on the Na+ channel, and the mechanism by which glycosylation regulates the current density and gating properties of the Na+ channel. The NaV1.5-Na+ channel isoform (α submit) derived from human was stably expressed in human embryonic kidney (HEK)-293 cells (Nav1.5-HEK cell). We applied the whole-cell patch-clamp technique to study the impact of N-linked glycosylation disruption in Nav1.5-HEK cell. Inhibition of the N-glycosylation with tunicamycin caused a significant increase of NaV1.5 channel current (INa) when applied for 24 h. Tunicamycin shifted the steady-state inactivation curve to the hyperpolarization direction, whereas the activation curve was unaffected. Recovery from inactivation was prolonged, while the fast phase (τfast) and the slow phase (τslow) of the current decay was unaffected by tunicamycin. INa was unaffected by tunicamycin in the present of a proteasome inhibitor MG132 [N-[(phenylmethoxy)carbonyl]-l-leucy-N-[(1S)-1-formyl-3-methylbutyl]-l-leucinamide], while it was significantly increased by tunicamycin in the presence of a lysosome inhibitor butyl methacrylate (BMA). These findings suggest that N-glycosylation disruption rescues the NaV1.5 channel possibly through the alteration of ubiquitin–proteasome activity, and changes gating properties of the NaV1.5 channel by modulating glycan milieu of the channel protein.

This investigation was aimed to identify gene profiles in human atrial myocardium in response to chronic mechanical stretch. Right atrial appendages from 21 patients were divided into 2 groups based on the size of right atrial volume. The microarray DATA analyses differentially identified 335 genes (> 2.0-fold, corrected P

BACKGROUND: The association between binge alcohol ingestion and atrial fibrillation (AF), often termed "holiday heart syndrome", has long been recognized. However, the underlying cellular and molecular mechanisms are unknown.Methods and Results:An experimental model of binge alcohol-induced AF was developed to elucidate the mechanisms linking acute ethanol exposure to changes in ion channel transcription and AF susceptibility. AF-susceptibility during transesophageal electrical stimulation was enhanced 8 h after, but not immediately or 24 h after, acute alcohol intake. T-type calcium channel (TCC) blockade and calcineurin inhibition diminished the AF-promoting effect of ethanol. Long-term (8-24 h) exposure to ethanol augmented TCC isoform-expression (Cav3.1 and Cav3.2) and currents in cardiomyocytes, accompanied by upregulation of the transcription factors, Csx/Nkx2.5 and nuclear factor of activated T-cells (NFAT), in the nucleus, and of phospho-glycogen synthesis kinase 3s (GSK3s) in the cytosol. Inhibition of protein kinase C (PKC) during the 7- to 8-h period following ethanol exposure attenuated susceptibility to AF, whereas acute exposure did not. GSK3s inhibition itself upregulated TCC expression and increased AF susceptibility. CONCLUSIONS: The present study results suggest a crucial role for TCC upregulation in the AF substrate following binge alcohol-drinking, resulting from ethanol-induced PKC-activation that hyperphosphorylates GSK3s to cause enhanced calcineurin-NFAT-Csx/Nkx2.5 signaling. These observations elucidate for the first time the potential mechanisms underlying the clinically well-recognized, but mechanistically enigmatic, "holiday heart syndrome".

G-protein-coupled ER (GPR30) plays an important role in cardioprotection. Recent studies have shown that the GPR30-specific agonist G-1 reduces the degree of myocardial fibrosis in rats with myocardial infarction, reduces the morbidity associated with atrial fibrillation, and inhibits the proliferation of cardiac fibroblasts in animal experiments. Nevertheless, the underlying mechanism of myocardial fibrosis and atrial fibrillation remains unclear. In this study, we explored the mechanism underlying the effect of GPR30 on atrial fibrosis and atrial fibrillation in OVX mice.We established an animal model of atrial fibrillation induced by Ang II (derived from OVX C57BL/6 female mice) and observed the role of G-1 in cardiac function by echocardiography, hemodynamics, morphology and fibrosis-related and apoptosis-related protein expression by Masson's trichrome, immunofluorescence, western blotting and TUNEL staining.Echocardiography and body surface ECG showed that G-1 combined with Ang II significantly reduced atrial fibrosis and atrial fibrillation compared to Ang II alone. The G-1 treatment group exhibited changes in the mRNA and protein expression of apoptosis-related genes. Moreover, G-1 treatment also altered the levels of inflammation-related proteins and mRNAs. In primary cultured cardiac fibroblasts (CFSs), proliferation was significantly increased in response to Ang II, and G-1 inhibited cell proliferation and apoptosis.GPR30 is a potential therapeutic target for alleviating atrial fibrosis in OVX mice by upregulating Smad7 expression to inhibit the TGF-β/Smad pathway.

Gemcitabine is an antineoplastic drug commonly used in the treatment of several types of cancers including pancreatic cancer and non–small cell lung cancer. Although gemcitabine-induced cardiotoxicity is widely recognized, the exact mechanism of cardiac dysfunction causing arrhythmias remains unclear. The objective of this study was to electrophysiologically evaluate the proarrhythmic cardiotoxicity of gemcitabine focusing on the human rapid delayed rectifier potassium channel, hERG channel. In heterologous hERG expressing HEK293 cells (hERG-HEK cells), hERG channel current (IhERG) was reduced by gemcitabine when applied for 24 h but not immediately after the application. Gemcitabine modified the activation gating properties of the hERG channel toward the hyperpolarization direction, while inactivation, deactivation or reactivation gating properties were unaffected by gemcitabine. When gemcitabine was applied to hERG-HEK cells in combined with tunicamycin, an inhibitor of N-acetylglucosamine phosphotransferase, gemcitabine was unable to reduce IhERG or shift the activation properties toward the hyperpolarization direction. While a mannosidase I inhibitor kifunensine alone reduced IhERG and the reduction was even larger in combined with gemcitabine, kifunensine was without effect on IhERG when hERG-HEK cells were pretreated with gemcitabine for 24 h. In addition, gemcitabine down-regulated fluorescence intensity for hERG potassium channel protein in rat neonatal cardiomyocyte, although hERG mRNA was unchanged. Our results suggest the possible mechanism of arrhythmias caused by gemcitabine revealing a down-regulation of IhERG through the post-translational glycosylation disruption possibly at the early phase of hERG channel glycosylation in the endoplasmic reticulum that alters the electrical excitability of cells.

Brain-derived neurotrophic factor (BDNF) has recently been recognized as a cardiovascular regulator particularly in the diseased condition, including coronary artery disease, heart failure, cardiomyopathy, and hypertension. Here, we investigate the role of BDNF on the T-type Ca2+ channel, Cav3.1 and Cav3.2, in rat neonatal cardiomyocytes exposed to normoxia (21% O2) and acute hypoxia (1% O2) in vitro for up to 3 h. The exposure of cardiomyocytes to hypoxia (1 h, 3 h) caused a significant upregulation of the mRNAs for hypoxia-inducible factor 1α (Hif1α), Cav3.1, Cav3.2 and Bdnf, but not tropomyosin-related kinase receptor B (TrkB). The upregulation of Cav3.1 and Cav3.2 caused by hypoxia was completely halted by small interfering RNA (siRNA) targeting Hif1a (Hif1a-siRNA) or Bdnf (Bdnf-siRNA). Immunocytochemical staining data revealed a distinct upregulation of Cav3.1- and Cav3.2-proteins caused by hypoxia in cardiomyocytes, which was markedly suppressed by Bdnf-siRNA. These results unveiled a novel regulatory action of BDNF on the T-type Ca2+ channels expression through the HIF-1α-dependent pathway in cardiomyocytes.

T-type calcium (Ca2+) channels play important physiological functions in excitable cells including cardiomyocyte. Phosphatidylinositol-4,5-bisphosphate (PIP2) has recently been reported to modulate various ion channels' function. However the actions of PIP2 on the T-type Ca2+ channel remain unclear. To elucidate possible effects of PIP2 on the T-type Ca2+ channel, we applied patch clamp method to investigate recombinant CaV3.1- and CaV3.2-T-type Ca2+ channels expressed in mammalian cell lines with PIP2 in acute- and long-term potentiation. Short- and long-term potentiation of PIP2 shifted the activation and the steady-state inactivation curve toward the hyperpolarization direction of CaV3.1-ICa.T without affecting the maximum inward current density. Short- and long-term potentiation of PIP2 also shifted the activation curve toward the hyperpolarization direction of CaV3.2-ICa.T without affecting the maximum inward current density. Conversely, long-term but not short-term potentiation of PIP2 shifted the steady-state inactivation curve toward the hyperpolarization direction of CaV3.2-ICa.T. Long-term but not short-term potentiation of PIP2 blunted the voltage-dependency of current decay CaV3.1-ICa.T. PIP2 modulates CaV3.1- and CaV3.2-ICa.T not by their current density but by their channel gating properties possibly through its membrane-delimited actions.

The most common cardiac feature of Kearns-Sayre syndrome (KSS) is atrioventricular block (AVB), and pacemaker implantations (PMIs) are recommended for KSS patients with advanced AVB. However, some KSS patients develop fatal arrhythmias such as polymorphic ventricular tachycardia (PMVT) and ventricular fibrillation (VF) and die suddenly even after PMIs. We report a patient with KSS who developed PMVT, VF, and QT prolongation, and was treated with mexiletine and successfully managed with an implantable cardioverter defibrillator (ICD). We reviewed the literature on arrhythmias in KSS published from 1975 to 2018. There were 112 patients with arrhythmia-associated KSS, 10 died, and 6 died suddenly after the PMI. The first manifestation of an arrhythmia was bundle branch block, then it progressed to AVB, and developed into complete AVB (CAVB) in about half the KSS patients. Ventricular arrhythmias were documented in 12 patients, and 8 were implanted with defibrillators afterwards. One patient after the implantation of a cardiac resynchronization therapy defibrillator (CRT-D) was treated for VF by an appropriate shock. This fact suggested that VF occurred even under proper pacing, and that defibrillators were effective. Pacemakers may suppress early afterdepolarizations (EADs) associated with a QT prolongation due to bradycardia. Similarly, mexiletine may suppress EADs by blocking the late sodium and Ca currents. Ventricular arrhythmias observed under suppression of EADs may be caused by delayed afterdepolarization (DADs) via an increasing intracellular Ca concentration due to mitochondrial dysfunction. Therefore, a PMI alone may not be sufficient to prevent sudden death, and an ICD implantation should be necessary.

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, statins, are widely used for preventing cardiovascular and cerebrovascular diseases by controlling blood cholesterol level. Additionally, previous studies revealed the scavenging effects of statins on free radicals. We assessed direct scavenging activities of two water-soluble statins, fluvastatin and pravastatin, on multiple free radicals using electron spin resonance spectrometry with spin trapping method. We estimated reaction rate constants (kfv for fluvastatin, and kpv for pravastatin). Superoxide anion was scavenged by fluvastatin and pravastatin with kfv and kpv of 4.82 M-1s-1 and 49.0 M-1s-1, respectively. Scavenging effects of fluvastatin and pravastatin on hydroxyl radical were comparable; both kfv and kpv were >109 M-1s-1. Fluvastatin also eliminated tert-butyl peroxyl radical with relative kfv of 2.63 to that of CYPMPO, whereas pravastatin did not affect tert-butyl peroxyl radical. Nitric oxide was scavenged by fluvastatin and pravastatin with kfv and kpv of 68.6 M-1s-1 and 701 M-1s-1, respectively. Both fluvastatin and pravastatin had scavenging effects on superoxide anion, hydroxyl radical and nitric oxide radical. On the other hand, tert-butyl peroxyl radical was scavenged only by fluvastatin, suggesting that fluvastatin might have more potential effect than pravastatin to prevent atherosclerosis and ischemia/reperfusion injury via inhibiting oxidation of lipids.

We tested the hypothesis that angiotensin II (Ang II)-induced cardiovascular complications are distinguished from what catecholamine-induced by their serum circulating biomarkers in rats. Infusion of Ang II (1.68 mg/kg/day) significantly increased systolic and diastolic blood pressure assessed at week one or later, accompanied by an increase of heart/body weight ratio. Noradrenaline infusion (5.40 mg/kg/day) produced a similar degree of hypertension, but did not increase heart weight. Ang II-, but not noradrenaline-induced hypertension was associated with a drastic upregulation of serum microRNA-30d (miR-30d) by hundreds of times, accompanied by an increase of miR-30d levels in the atrium but not in the ventricle. Ang II, but not noradrenaline, significantly increased mRNA of brain natriuretic peptide (BNP) in the atrium. Studies using rat neonatal cardiomyocytes in vitro demonstrated that BNP caused an increase of miR-30d when applied for 6 h or longer in the culture medium. In vitro application of Ang II increased the cell size, although BNP and miR-30d were unable to mimic the effect of Ang II. We conclude that serum circulating microRNA-30d is a sensitive biomarker for Ang II-induced cardiovascular complications. It is also postulated that Ang II-induced cardiomyocyte hypertrophy could be independent of miR-30d/BNP signaling pathways.

Nitric oxide (NO) is produced from endothelial cells and cardiomyocytes composing the myocardium and benefits cardiac function through both vascular-dependent and -independent effects. This study was purposed to investigate the possible adverse effect of NO focusing on the voltage-gated Na+ channel in cardiomyocytes. We carried out patch-clamp experiments on rat neonatal cardiomyocytes demonstrating that NOC-18, an NO donor, significantly reduced Na+ channel current in a dose-dependent manner by a long-term application for 24 h, accompanied by a reduction of Nav1.5-mRNA and the protein, and an increase of a transcription factor forkhead box protein O1 (FOXO1) in the nucleus. The effect of NOC-18 on the Na+ channel was blocked by an inhibitor of thiol oxidation N-ethylmaleimide or a disulfide reducing agent disulfide 1,4-Dithioerythritol, suggesting that NO is a negative regulator of the voltage-gated Na+ channel through thiols in regulatory protein(s) for the channel transcription.

microRNAs (miRNAs) have drawn more attention to the progression of atherosclerosis (AS), due to their noticeable inflammation function in cardiovascular disease. Macrophages play a crucial role in disrupting atherosclerotic plaque, thereby we explored the involvement of miR-223-3p in the inflammatory response in macrophages.RT-qPCR was used to analyze the miR-223-3p levels in carotid arteries and serum of AS patients. ROC curve was used to assess the diagnostic value of miR-223-3p. Movat staining was applied to evaluate the morphological differences. FISH was used to identify the expression of miR-223-3p in macrophages of atherosclerotic lesions. Bioinformatic analysis was performed. Double-immunofluorescence and western blot were performed to assess the inflammatory cytokine secretion and p-ERK1/2. C16-PAF was injected into the culture medium of the miR-223-3p mimic/NC-transfected macrophages with ox-LDL.MiR-223-3p was up-regulated in AS patients and was associated with a higher overall survival rate. MiR-223-3p was co-localized with CD68+ macrophages in vulnerable atherosclerotic lesions. MiR-223-3p mimics decreased atherosclerotic lesions, macrophages numbers whereas increased SMCs numbers in the lesions. The TNF-a immune-positive areas were reduced by miR-223-3p mimics. MAP2K1 was negatively associated with miR-223-3p. MiR-223-3p mimics reduced the inflammation and the MEK1/ERK1/2 signaling pathwayMiR-223-3p negatively regulates inflammatory responses by the MEK1/ERK1/2 signaling pathway. Our study provides new insight into how miR-223-3p protects against atherosclerosis, representing a broader therapeutic prospect for treating atherosclerosis by miR-223-3p.

The association between binge alcohol ingestion and atrial fibrillation (AF), often termed "holiday heart syndrome", has long been recognized. However, the underlying cellular and molecular mechanisms are unknown.Methods and Results:An experimental model of binge alcohol-induced AF was developed to elucidate the mechanisms linking acute ethanol exposure to changes in ion channel transcription and AF susceptibility. AF-susceptibility during transesophageal electrical stimulation was enhanced 8 h after, but not immediately or 24 h after, acute alcohol intake. T-type calcium channel (TCC) blockade and calcineurin inhibition diminished the AF-promoting effect of ethanol. Long-term (8-24 h) exposure to ethanol augmented TCC isoform-expression (CaThe present study results suggest a crucial role for TCC upregulation in the AF substrate following binge alcohol-drinking, resulting from ethanol-induced PKC-activation that hyperphosphorylates GSK3β to cause enhanced calcineurin-NFAT-Csx/Nkx2.5 signaling. These observations elucidate for the first time the potential mechanisms underlying the clinically well-recognized, but mechanistically enigmatic, "holiday heart syndrome".

SCN5A gene encodes the voltage-gated sodium channel Na

Signal regulators during early cardiogenetic differentiation for the cellular automaticity are largely unknown. Our investigations were designed to clarify the role of transcription factors and their modulators in P19-derived cardiomyocytes to the expression of cardiac pacemaker ion channels. Transcription factors Csx/Nkx2.5 and GATA4 but not MEF2C were markedly inhibited by p38 MAP kinase inhibition in a distinct manner; expression but not phosphorylation of GATA4 was reduced by inhibition of p38 MAP kinase actions. In the presence of an ERK1/2,5 inhibitor PD98059 or a JNK MAP kinase inhibitor SP600125, P19 cells successfully differentiated into cardiomyocytes displaying spontaneous beatings with expression of three types of pacemaker ion channels. We demonstrate that acquisition of cellular automaticity and the expression of pacemaker ion channels are regulated by the transcription factors, Csx/Nkx2.5 and GATA4, through intracellular signals including p38 MAP kinase in the process of P19-derived pluripotent cells differentiation into cardiomyocytes.

The homeobox-containing gene Csx/Nkx2.5 codes several cardiac transcription factors and plays a critical role in early cardiogenesis. We investigated the effect of Csx/Nkx2.5 on the expression of cardiac ion channels using P19-derived cardiomyocytes. P19CL6 cells and P19CL6 cells with Csx/Nkx2.5 overexpression (P19CL6-Csx cells) were induced to differentiate into cardiomyocytes by treatment with dimethyl sulfoxide. Action potentials and membrane currents were measured by whole cell patch clamp at different differentiation stage: the early stage (1–5 days after beating had begun) and the late stage (10–15 days after beating). Expression of Csx/Nkx2.5 mRNA was increased as the differentiation stages advanced in both P19CL6 and P19CL6-Csx cells. In action potential configuration, maximal diastolic potentials in P19CL6-Csx cells exhibited more hyperpolarized potential (‒ 64.2 mV) than those in P19CL6 cells (‒ 54.8 mV,p +channels expressed during the early stage, the transient-outward K+channel was most predominant. By overexpression of Csx/Nkx2.5, developmental decrease in the transient-outward K+channel was suppressed. Homeobox-containing gene Csx/Nkx2.5 modifies the amount of distinct ionic channels, during differentiation periods, predominantly changing the expression of the transient-outward K+channel.

Men have shorter rate-corrected QT intervals (QTc) than women, especially at the period of adolescence or later. The aim of this study was to elucidate the long-term effects of testosterone on cardiac excitability parameters including electrocardiogram (ECG) and potassium channel current. Testosterone shortened QT intervals in ECG in castrated male rats, not immediately after, but on day 2 or later. Expression of Kv7.1 (KCNQ1) mRNA was significantly upregulated by testosterone in cardiomyocytes of male and female rats. Short-term application of testosterone was without effect on delayed rectifier potassium channel current (IKs), whereas IKs was significantly increased in cardiomyocytes treated with dihydrotestosterone for 24 h, which was mimicked by isoproterenol (24 h). Gene-selective inhibitors of a transcription factor SP1, mithramycin, abolished the effects of testosterone on Kv7.1. Testosterone increases Kv7.1-IKs possibly through a pathway related to a transcription factor SP1, suggesting a genomic effect of testosterone as an active factor for cardiac excitability.

Background Atrial fibrillation (AF) begets AF in part due to atrial remodeling, the molecular mechanisms of which have not been completely elucidated. This study was conducted to identify microRNA(s) responsible for electrical remodeling in AF. Methods and results The expression profiles of 1205 microRNAs, in cardiomyocytes from patients with persistent AF and from age-, gender-, and cardiac function-matched control patients with normal sinus rhythm, were examined by use of a microRNA microarray platform. Thirty-nine microRNAs differentially expressed in AF patients' atria were identified, including miR-30d, as a candidate responsible for ion channel remodeling by in silico analysis. MiR-30d was significantly upregulated in cardiomyocytes from AF patients, whereas the mRNA and protein levels ofCACNA1C/Cav1.2 andKCNJ3/Kir3.1, postulated targets of miR-30d, were markedly reduced.KCNJ3/Kir3.1 expression was downregulated by transfection of the miR-30 precursor, concomitant with a reduction of the acetylcholine-sensitive inward-rectifier K(+)current (IK.ACh).KCNJ3/Kir3.1 (but notCACNA1C/Cav1.2) expression was enhanced by the knockdown of miR-30d. The Ca(2+)ionophore, A23187, induced a dose-dependent upregulation of miR-30d, followed by the suppression ofKCNJ3mRNA expression. Blockade of protein kinase C signaling blunted the [Ca(2+)]i-dependent downregulation of Kir3.1 via miR-30d. Conclusions The downward remodeling ofIK.AChis attributed, at least in part, to deranged Ca(2+)handling, leading to the upregulation of miR-30d in human AF, revealing a novel post-transcriptional regulation ofIK.ACh. (Circ J 2016; 80: 1346-1355).

T-type channels are low-voltage-activated channels that play a role in the cardiovascular system particularly for pacemaker activity. Glycosylation is one of the most prevalent post-translational modifications in protein. Among various glycosylation types, the most common one is asparagine-linked (N-linked) glycosylation. The aim of this study was to elucidate the roles of N-linked glycosylation for the gating properties of the Ca

T-type calcium (Ca

Bepridil is an effective antiarrhythmic drug on supraventricular and ventricular arrhythmias, and inhibitor of calmodulin. Recent investigations have been elucidating that bepridil exerts antiarrhythmic effects through its acute and chronic application for patients. The aim of this study was to identify the efficacy and the potential mechanism of bepridil on the inward-rectifier potassium channel in neonatal rat cardiomyocytes in acute- and long-term conditions. Bepridil inhibited inward-rectifier potassium current (I K1) as a short-term effect with IC50 of 17 μM. Bepridil also reduced I K1 of neonatal cardiomyocytes when applied for 24 h in the culture medium with IC50 of 2.7 μM. Both a calmodulin inhibitor (W-7) and an inhibitor of calmodulin-kinase II (KN93) reduced I K1 when applied for 24 h as a long-term effect in the same fashion, suggesting that the long-term application of bepridil inhibits I K1 more potently than that of the short-term application through the inhibition of calmodulin kinase II pathway in cardiomyocytes.

Atrial fibrillation (AF) begets AF in part due to atrial remodeling, the molecular mechanisms of which have not been completely elucidated. This study was conducted to identify microRNA(s) responsible for electrical remodeling in AF.The expression profiles of 1205 microRNAs, in cardiomyocytes from patients with persistent AF and from age-, gender-, and cardiac function-matched control patients with normal sinus rhythm, were examined by use of a microRNA microarray platform. Thirty-nine microRNAs differentially expressed in AF patients' atria were identified, including miR-30d, as a candidate responsible for ion channel remodeling by in silico analysis. MiR-30d was significantly upregulated in cardiomyocytes from AF patients, whereas the mRNA and protein levels ofCACNA1C/Cav1.2 andKCNJ3/Kir3.1, postulated targets of miR-30d, were markedly reduced.KCNJ3/Kir3.1 expression was downregulated by transfection of the miR-30 precursor, concomitant with a reduction of the acetylcholine-sensitive inward-rectifier K(+)current (IK.ACh).KCNJ3/Kir3.1 (but notCACNA1C/Cav1.2) expression was enhanced by the knockdown of miR-30d. The Ca(2+)ionophore, A23187, induced a dose-dependent upregulation of miR-30d, followed by the suppression ofKCNJ3mRNA expression. Blockade of protein kinase C signaling blunted the [Ca(2+)]i-dependent downregulation of Kir3.1 via miR-30d.The downward remodeling ofIK.AChis attributed, at least in part, to deranged Ca(2+)handling, leading to the upregulation of miR-30d in human AF, revealing a novel post-transcriptional regulation ofIK.ACh. (Circ J 2016; 80: 1346-1355).

Background: Understanding of the functional and structural disturbances of cardiac autonomic nerves in ventricular hypertrophy and eventual chronic heart failure (CHF) remains unclear. Methods and results: ECG signals were obtained by a radio transmitter from male Wistar rats that received monocrotaline (MCT) via subcutaneous injection. Heart rate (HR) and HR variability (HRV) were analyzed. The RR interval, total power (TP), low frequency (LF) power, high frequency (HF) power, and LF/HF (L/H) power ratio were measured. Ultrastructural changes in cardiac autonomic nerves at the sinoatrial (SA) node region were studied using an electron microscope. TP and HF powers in MCT-induced right ventricular hypertrophy (RVH) and eventual CHF were significantly decreased, and HR was significantly increased at week 5 or later after the MCT injection. The electron microscopic findings indicated the depletion of neurotransmitter vesicles and degradation of parasympathetic but not sympathetic nerve endings in the SA node region of the heart. Conclusion: MCT-induced RVH and CHF rats showed presynaptic vagal nerve degradation prior to sympathetic nerve derangement in the heart.

Background: The neurohypophyseal hormones oxytocin (OT) and [Arg 8 ]-vasopressin (AVP) have recently been implicated in cardiac function. This study was designed to investigate actions of OT and AVP on regulation of the voltage-gated Ca 2+ channel in cardiomyocytes. Methods and Results: Cultured neonatal rat cardiomyocytes were stimulated with OT or AVP (10 -8 M to 10 -6 M) for 24-72 h, followed by real-time PCR and patch clamp studies. Although OT did not exert any modulatory effect on L-type Ca 2+ channel current, as a shortterm effect, stimulation of cardiomyocytes with OT but not AVP decreased the expression of Ca v 1.2 mRNA with a reduced L-type Ca 2+ channel current. A transcription factor CREB mRNA expression was down-regulated by OT treatment, although T-type Ca 2+ channels (Ca v 3.1, Ca v 3.2) were unaffected by OT or AVP. Conclusion: OT but not AVP down-regulates L-type Ca 2+ channel expression through the inhibition of CREB transcriptional, suggesting a novel mechanism of OT action in the cardiac electrophysiology.

The continuous usage of pyrethroids against insects has provoked the emergence of insecticide resistance that has become a major obstacle to disease vector control. The knockdown resistance (kdr) voltage-gated sodium channel gene is regarded as a key to understanding the mechanism of resistance to pyrethroids. The main purpose of this study is to identify point mutations in the sodium channel gene associated with deltamethrin resistance in Aedes aegypti. Two mutations in the IIS6 domain of the channel, S989P and V1016G, were identified as possible candidates responsible for the emergence of deltamethrin resistance in Ae. aegypti Khu Bua strain. As S989P and V1016G mutations are located within the IIS5-S6 loop and IIS6 near the ion filter and binding site, these mutations might enhance pyrethroid resistance. Allelic variation in the sodium channel gene is thought to be one of the principal molecular mechanisms regulating pyrethroid resistance in mosquitoes.

We established a new animal model called SPORTS (Spontaneously-Running Tokushima-Shikoku) rats, which show high-epinephrine (Epi) levels. Recent reports show that Epi activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) in adipocytes. Acetyl-CoA carboxylase (ACC) is the rate-limiting enzyme in fatty acid synthesis, and the enzymatic activity is suppressed when its Ser-79 is phosphorylated by AMPK. The aim of this study was to investigate the in vivo effect of Epi on ACC and abdominal visceral fat accumulation. We divided both 6-week male control and SPORTS rats into two groups, which were fed either normal diet or high fat and sucrose (HFS) diet for 16 weeks. At the end of diet treatment, retroperitoneal fat was collected for western blotting and histological analysis. Food intake was not different among the groups, but SPORTS rats showed significantly lower weight gain than control rats in both diet groups. After 10 weeks of diet treatment, glucose tolerance tests (GTTs) revealed that SPORTS rats had increased insulin sensitivity. Furthermore, SPORTS rats had lower quantities of both abdominal fat and plasma triglyceride (TG). In abdominal fat, elevated ACC Ser-79 phosphorylation was observed in SPORTS rats and suppressed by an antagonist of beta-adrenergic receptor (AR), propranolol, or an inhibitor of AMPK, Compound C. From these results, high level of Epi induced ACC phosphorylation mediated through beta-AR and AMPK signaling pathways in abdominal visceral fat of SPORTS rats, which may contribute to reduce abdominal visceral fat accumulation and increase insulin sensitivity. Our results suggest that beta-AR-regulated ACC activity would be a target for treating lifestyle-related diseases, such as obesity.