Bioinformatic Identification of Potential RNA Alterations on the Atrial Fibrillation Remodeling from Human Pulmonary Veins.

Atrial fibrillation (AF) is the most frequent persistent arrhythmia. Many genes have been reported as a genetic background for AF. However, most transcriptome analyses of AF are limited to the atrial samples and have not been evaluated by multiple cardiac regions. In this study, we analyzed the expression levels of protein-coding and long noncoding RNAs (lncRNAs) in six cardiac regions by RNA-seq. Samples were donated from six subjects with or without persistent AF for left atria, left atrial appendages, right atria, sinoatrial nodes, left ventricles, right ventricles, and pulmonary veins (PVs), and additional four right atrial appendages samples were collected from patients undergoing mitral valve replacement. In total, 23 AF samples were compared to 23 non-AF samples. Surprisingly, the most influenced heart region in gene expression by AF was the PV, not the atria. The ion channel-related gene set was significantly enriched upon analysis of these significant genes. In addition, some significant genes are cancer-related lncRNAs in PV in AF. A co-expression network analysis could detect the functional gene clusters. In particular, the cancer-related lncRNA, such as SAMMSON and FOXCUT, belong to the gene network with the cancer-related transcription factor FOXC1. Thus, they may also play an aggravating role in the pathogenesis of AF, similar to carcinogenesis. In the least, this study suggests that (1) RNA alteration is most intense in PVs and (2) post-transcriptional gene regulation by lncRNA may contribute to the progression of AF. Through the screening analysis across the six cardiac regions, the possibility that the PV region can play a role other than paroxysmal triggering in the pathogenesis of AF was demonstrated for the first time. Future research with an increase in the number of PV samples will lead to a novel understanding of the pathophysiology of AF.

Small-volume vitrification and rapid warming yield high survivals of one-cell rat embryos in cryotubes†.

To cryopreserve cells, it is essential to avoid intracellular ice formation during cooling and warming. One way to achieve this is to convert the water inside the cells into a non-crystalline glass. It is currently believed that to accomplish this vitrification, the cells must be suspended in a very high concentration (20-40%) of a glass-inducing solute, and subsequently cooled very rapidly. Herein, we report that this belief is erroneous with respect to the vitrification of one-cell rat embryos. In the present study, one-cell rat embryos were vitrified with 5 µL of EFS10 (a mixture of 10% ethylene glycol (EG), 27% Ficoll, and 0.45 M sucrose) in cryotubes at a moderate cooling rate, and warmed at various rates. Survival was assessed according to the ability of the cells to develop into blastocysts and to develop to term. When embryos were vitrified at a 2613 °C/min cooling rate and thawed by adding 1 mL of sucrose solution (0.3 M, 50 °C) at a warming rate of 18 467 °C/min, 58.1 ± 3.5% of the EFS10-vitrified embryos developed into blastocysts, and 50.0 ± 4.7% developed to term. These rates were similar to those of non-treated intact embryos. Using a conventional cryotube, we achieved developmental capabilities in one-cell rat embryos by rapid warming that were comparable to those of intact embryos, even using low concentrations (10%) of cell-permeating cryoprotectant and at low cooling rates.

Requirement of the Ca2+ channel ß2 subunit for sympathetic PKA phosphorylation.

Facilitation of cardiac function in response to signals from the sympathetic nervous system is initiated by the phosphorylation of L-type voltage-dependent Ca2+ channels (VDCCs) by protein kinase A (PKA), which in turn is activated by ß-adrenoceptors. Among the five subunits (α1, ß, α2/δ, and γ) of VDCCs, the α1 subunit and the family of ß subunits are substrates for PKA-catalyzed phosphorylation; however, the subunit responsible for ß-adrenergic augmentation of Ca2+ channel function has yet to be specifically identified. Here we show that the VDCC ß2 subunit is required for PKA phosphorylation upon sympathetic acceleration. In mice with ß2 subunit-null mutations, cardiac muscle contraction in response to isoproterenol was reduced and there was no significant increase in Ca2+ channel currents upon PKA-dependent phosphorylation. These findings indicate that within the sympathetic nervous system the ß2 subunit of VDCCs is required for physiological PKA-dependent channel phosphorylation.

Detection of Pathologic Heart Murmurs Using a Piezoelectric Sensor.

This study aimed to evaluate the capability of a piezoelectric sensor to detect a heart murmur in patients with congenital heart defects. Heart sounds and murmurs were recorded using a piezoelectric sensor and an electronic stethoscope in healthy neonates (n = 9) and in neonates with systolic murmurs caused by congenital heart defects (n = 9) who were born at a hospital. Signal data were digitally filtered by high-pass filtering, and the envelope of the processed signals was calculated. The amplitudes of systolic murmurs were evaluated using the signal-to-noise ratio and compared between healthy neonates and those with congenital heart defects. In addition, the correlation between the amplitudes of systolic murmurs recorded by the piezoelectric sensor and electronic stethoscope was determined. The amplitudes of systolic murmurs detected by the piezoelectric sensor were significantly higher in neonates with congenital heart defects than in healthy neonates (p < 0.01). Systolic murmurs recorded by the piezoelectric sensor had a strong correlation with those recorded by the electronic stethoscope (ρ = 0.899 and p < 0.01, respectively). The piezoelectric sensor can detect heart murmurs objectively. Mechanical improvement and automatic analysis algorithms are expected to improve recording in the future.

Cross-sectional survey of depressive symptoms and suicide-related ideation at a Japanese national university during the COVID-19 stay-home order.

BACKGROUND: We aimed to estimate the prevalence of depressive symptoms as well as suicide-related ideation among Japanese university students during the stay-home order necessitated by the coronavirus disease 2019 pandemic in Japan, and offer evidence in support of future intervention to depression and suicide prevention strategies among college and university students. METHODS: The data for this cross-sectional study were derived from the Student Mental Health Survey conducted from May 20 to June 16, 2020 at a national university in Akita prefecture. Among the 5111 students recruited, 2712 participated in this study (response rate, 53%; mean age ± standard deviation, 20.5 ±3.5 years; men, 53.8%). Depressive symptoms were identified by using the Patient Health Questionnaire-9 (PHQ-9). RESULTS: The prevalence of moderate depressive symptoms based on a PHQ-9 score ≥10 and suicide-related ideation based on question 9 of PHQ-9 ≥1, which encompasses thoughts of both suicide and self-harm, was 11.7% and 6.7%, respectively. Multivariable logistic regression analyses showed that risk factors for depression included being a woman, smoking, alcohol consumption, and social network communication using either video or voice. For suicide-related ideation, alcohol consumption was the only risk factor. Exercise and having someone to consult about worries were associated with decreased risk of both depressive symptoms and suicide-related ideation. CONCLUSIONS: Negative lifestyles of smoking and drinking, and being a woman, may be important risk factors for depressive symptoms, whereas exercise and having someone to consult about worries may be protective factors.

Molecular identification of HSPA8 as an accessory protein of a hyperpolarization-activated chloride channel from rat pulmonary vein cardiomyocytes.

Pulmonary veins (PVs) are the major origin of atrial fibrillation. Recently, we recorded hyperpolarization-activated Cl- current (ICl, h) in rat PV cardiomyocytes. Unlike the well-known chloride channel protein 2 (CLCN2) current, the activation curve of ICl, h was hyperpolarized as the Cl- ion concentration ([Cl-] i ) increased. This current could account for spontaneous activity in PV cardiomyocytes linked to atrial fibrillation. In this study, we aimed to identify the channel underlying ICl, h Using RT-PCR amplification specific for Clcn2 or its homologs, a chloride channel was cloned from rat PV and detected in rat PV cardiomyocytes using immunocytochemistry. The gene sequence and electrophysiological functions of the protein were identical to those previously reported for Clcn2, with protein activity observed as a hyperpolarization-activated current by the patch-clamp method. However, the [Cl-] i dependence of activation was entirely different from the observed ICl, h of PV cardiomyocytes; the activation curve of the Clcn2-transfected cells shifted toward positive potential with increased [Cl-] i , whereas the ICl, h of PV and left ventricular cardiomyocytes showed a leftward shift. Therefore, we used MS to explore the possibility of additional proteins interacting with CLCN2 and identified an individual 71-kDa protein, HSPA8, that was strongly expressed in rat PV cardiomyocytes. With co-expression of HSPA8 in HEK293 and PC12 cells, the CLCN2 current showed voltage-dependent activation and shifted to negative potential with increasing [Cl-] i Molecular docking simulations further support an interaction between CLCN2 and HSPA8. These findings suggest that CLCN2 in rat heart contains HSPA8 as a unique accessory protein.

Mechanisms Underlying Spontaneous Action Potential Generation Induced by Catecholamine in Pulmonary Vein Cardiomyocytes: A Simulation Study.

Cardiomyocytes and myocardial sleeves dissociated from pulmonary veins (PVs) potentially generate ectopic automaticity in response to noradrenaline (NA), and thereby trigger atrial fibrillation. We developed a mathematical model of rat PV cardiomyocytes (PVC) based on experimental data that incorporates the microscopic framework of the local control theory of Ca2+ release from the sarcoplasmic reticulum (SR), which can generate rhythmic Ca2+ release (limit cycle revealed by the bifurcation analysis) when total Ca2+ within the cell increased. Ca2+ overload in SR increased resting Ca2+ efflux through the type II inositol 1,4,5-trisphosphate (IP3) receptors (InsP3R) as well as ryanodine receptors (RyRs), which finally triggered massive Ca2+ release through activation of RyRs via local Ca2+ accumulation in the vicinity of RyRs. The new PVC model exhibited a resting potential of -68 mV. Under NA effects, repetitive Ca2+ release from SR triggered spontaneous action potentials (APs) by evoking transient depolarizations (TDs) through Na+/Ca2+ exchanger (APTDs). Marked and variable latencies initiating APTDs could be explained by the time courses of the α1- and ß1-adrenergic influence on the regulation of intracellular Ca2+ content and random occurrences of spontaneous TD activating the first APTD. Positive and negative feedback relations were clarified under APTD generation.

Medaka as a model for ECG analysis and the effect of verapamil.

The heart of the medaka, a small fish native to East Asia, has electrophysiological aspects similar to mammalian hearts. We found that the heart rates of medaka were more similar to humans than mice or rats. Medaka exhibited similar electrocardiogram patterns to those of humans, suggesting a similarity in cardiac impulse formation and propagation. Their hearts also exhibited similar responsiveness to verapamil, a calcium channel antagonist; atropine, a parasympathetic nerve blocker; propranolol, a sympathetic ß-adrenergic blocker; and isoproterenol, a sympathetic ß-adrenergic agonist. We successfully analyzed action potentials and cardiac contractile forces in vivo. Verapamil affected action potential duration and reduced heart rate, suggesting the importance of voltage-dependent calcium channels in determining the heart rhythm of medaka. We also analyzed the expression of the voltage-dependent calcium channel ß2 subunit, which participates in channel formation in cardiac myocytes, and found that splice variant type-2 was the only major transcript in the heart. Our results indicate that medaka could be an appropriate animal model for studying cardiovascular pharmacology.

Modified sympathetic nerve regulation in AKAP5-null mice.

Genetic analyses have revealed an important association between A-kinase anchoring proteins (AKAPs) and the intracellular calcium modulating system. AKAP5, also known as AKAP79/150, is an anchoring protein between PKA and voltage-dependent calcium channels, ryanodine receptor-2, phospholamban and other molecules. The aim of the present study was to elucidate the physiological importance of AKAP5 in the creation of cardiac rhythm using AKAP5-null mice. ECG analysis showed a normal sinus rhythm and a decreased responsiveness to isoproterenol in AKAP5-null mice compared with wild-type mice. Analysis of heart rate variability revealed that the R-R interval was unstable in AKAP5-null mutants and that the low-frequency components had decreased, indicating that the tonus of the sympathetic nervous system was affected. Furthermore, the atrium of the AKAP5-null mice showed a decreased positive inotropic response to isoproterenol, indicating the involvement of AKAP5 in a PKA-dependent pathway. Thus, our present study revealed that AKAP5 plays a significant role in the regulation of sympathetic nerve activities.

In vitro effect of nicorandil on the carbachol-induced contraction of the lower esophageal sphincter of the rat.

The lower esophageal sphincter (LES) is a specialized region of the esophageal smooth muscle that allows the passage of a swallowed bolus into the stomach. Nitric oxide (NO) plays a major role in LES relaxation. Nicorandil possesses dual properties of a NO donor and an ATP-sensitive potassium channel (KATP channel) agonist, and is expected to reduce LES tone. This study investigated the mechanisms underlying the effects of nicorandil on the LES. Rat LES tissues were placed in an organ bath, and activities were recorded using an isometric force transducer. Carbachol-induced LES contraction was significantly inhibited by KATP channel agonists in a concentration-dependent manner; pinacidil >> nicorandil ≈ diazoxide. Nicorandil-induced relaxation of the LES was prevented by pretreatment with glibenclamide, whereas N(G)-nitro-l-arginine methyl ester (l-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and iberiotoxin were ineffective at preventing nicorandil-induced LES relaxation. Furthermore, nicorandil did not affect high K(+)-induced LES contraction. Reverse-transcription polymerase chain reaction analysis and immunohistochemistry revealed expression of KCNJ8 (Kir6.1), KCNJ11 (Kir6.2), ABCC8 (SUR1) and ABCC9 (SUR2) subunits of the KATP channel in the rat lower esophagus. These findings indicate that nicorandil causes LES relaxation chiefly by activating the KATP channel, and that it may provide an additional pharmacological tool for the treatment of spastic esophageal motility disorders.

Age-related effects of dexmedetomidine on myocardial contraction and coronary circulation in isolated guinea pig hearts.

Dexmedetomidine is a selective α2 adrenergic agonist. Although dexmedetomidine is widely used for sedation and analgesia, it frequently produces hypotension and bradycardia. The present study aimed to evaluate the effects of dexmedetomidine on cardiac function and coronary circulation using Langendorff-perfused guinea pig hearts. Coronary perfusion pressure (CPP) and left ventricular pressure (LVP) were continuously monitored, and electric field stimulation (EFS) was applied to stimulate sympathetic nerve terminals. Dexmedetomidine almost completely inhibited the EFS-induced increase in LVP at all ages. The effect of dexmedetomidine on coronary artery resistance varied according to postnatal age, i.e., dexmedetomidine had little effect on CPP in young hearts (<4 weeks) but increased CPP by 10 mmHg at 4-8 weeks and by 15 mmHg at >8 weeks. The increase in CPP in adult hearts was inhibited by imiloxan, an α2B antagonist, and prazosin, an α1 antagonist. The results suggest that dexmedetomidine acts on α2 adrenergic receptors at sympathetic nerve terminals to suppress the release of norepinephrine. In addition, the findings suggest that dexmedetomidine directly affects α1 adrenoceptors and/or α2B adrenoceptors on coronary smooth muscles to increase CPP. The age-related changes in α adrenoceptor subtypes may be linked to the cardiodepressant effects of dexmedetomidine.

Modified autonomic regulation in mice mutated in the ß4 subunit of the lh/lh calcium channel.

Genetic analyses have revealed an important association between P/Q-type calcium channel activities and hereditary neurological disorders. The P/Q-type channels are composed principally of heterologous multimeric subunits including CaV2.1 and CaVß4. Of these, the ß4 subunit is thought to play a significant role in channel physiology, because a mouse line mutant in that subunit (the lethargic mouse: lh) exhibits a severe ataxic phenotype. The aim of the present study was to elucidate the physiological importance of the ß4 subunit. ECG analysis showed that the T wave was high in 8-week-old lh mutants; this may be associated with hyperkalemia. Upon pharmacological ECG analysis, 2-3-week-old lh mutants exhibited reduced responses to a ß-blocker and a muscarinic receptor antagonist. Analysis of heart rate variability revealed that the R-R interval was unstable in lh mutants and that both the low- and high-frequency components had increased in extent, indicating that the tonus of both the sympathetic and parasympathetic nervous systems was modified. Thus, our present study revealed that the ß4 subunit played a significant role in regulation of sympathetic and parasympathetic nerve activities.

Involvement of the orexin system in sympathetic nerve regulation.

Orexin, also known as hypocretin, is a secreted neuropeptide implicated in the regulation of sleep and food intake. In the present study, we examined the importance of orexin in regulation of the sympathetic nervous system using an orexin/ataxin-3 transgenic (OXTg) rat, which has a minimal number of orexin neurons. RT-PCR analysis identified expression of prepro-orexin and orexin receptor-1 (OX1R) in the superior cervical ganglion (SCG), and expression of another receptor (OX2R) was marginal in the wild-type rat. The orexin/ataxin-3 transgenic rat showed increased expression of OX1R and OX2R, whereas expression of prepro-orexin was undetectable, suggesting a compensatory increase in both receptors. In the ECG recording (R-R interval), orexin/ataxin-3 transgenic rats showed decreased responsiveness to the ß-adrenergic blocker propranolol. Furthermore, OXTg rats had deteriorated R-R interval regulation, indicating involvement of the orexin system in sympathetic nerve regulation. This was accompanied by decreased baroreflex and responsiveness to ß-adrenergic blocker in blood pressure recording, also suggesting involvement of the orexin system in sympathetic nerve regulation. Histological examination revealed hypotrophic changes in the transgenic heart, suggesting involvement of the orexin system in cardiac development. Taken together, our present results indicate involvement of the orexin system in sympathetic nerve control.

Pathological impact of hyperpolarization-activated chloride current peculiar to rat pulmonary vein cardiomyocytes.

Pulmonary veins (PVs) are believed to be a crucial origin of atrial fibrillation. We recently reported that rat PV cardiomyocytes exhibit arrhythmogenic automaticity in response to norepinephrine. Herein, we further characterized the electrophysiological properties underlying the potential arrhythmogenicity of PV cardiomyocytes. Patch clamping studies revealed a time dependent hyperpolarization-activated inward current in rat PV cardiomyocytes, but not in left atrial (LA) myocytes. The current was Cs(+) resistant, and was not affected by removal of external Na(+) or K(+). The current was inhibited with Cd(2+), and the reversal potential was sensitive to changes in [Cl(-)] on either side of the membrane in a manner consistent with a Cl(-) selective channel. Cl(-) channel blockers attenuated the current, and slowed or completely inhibited the norepinephrine-induced automaticity. The biophysical properties of the hyperpolarization-activated Cl(-) current in rat PVs were different from those of ClC-2 currents previously reported: (i) the voltage-dependent activation of the Cl(-) current in rat PVs was shifted to negative potentials as [Cl(-)]i increased, (ii) the Cl(-) current was enhanced by extracellular acidification, and (iii) extracellular hyper-osmotic stress increased the current, whereas hypo-osmotic cell swelling suppressed the current. qPCR analysis revealed negligible ClC-2 mRNA expression in the rat PV. These findings suggest that rat PV cardiomyocytes possess a peculiar voltage-dependent Cl(-) channel, and that the channel may play a functional role in norepinephrine-induced automaticity.

Effects of propofol on electrocardiogram measures in mice.

We investigated the anesthetic effects of propofol on the electrocardiogram (ECG) in mice. We also compared the effects of isoflurane (2%) inhalation anesthesia, intraperitoneal propofol (50 or 100 mg/kg), and pentobarbital (50 mg/kg) on ECG in mice. Isoflurane inhalation and pentobarbital anesthesia were both associated with an acceptable heart rate (HR) range (ca. 450 - 500 bpm). In contrast, high-dose propofol anesthesia significantly decreased the HR. Importantly, propofol anesthesia led to significantly reduced responses to propranolol, a ß-blocker, suggesting that it affects sympathetic tonus and is not suitable for the evaluation of cardiovascular or sympathetic function. Propofol also reduced the response to atropine, indicative of suppression of mouse parasympathetic nerve activity. Our data suggest that propofol anesthesia should not be the first choice for cardiovascular analysis in mice.

Inhalation anesthesia is preferable for recording rat cardiac function using an electrocardiogram.

The effects of inhalation anesthesia (2% isoflurane, sevoflurane, or enflurane) and intraperitoneal anesthesia with pentobarbital (65 mg/kg) were compared in rats using an electrocardiogram (ECG) and determination of blood oxygen saturation (SPO2) levels. Following inhalation anesthesia, heart rate (HR) and SPO2 were acceptable while pentobarbital anesthesia decreased HR and SPO2 significantly. This indicates that inhalation anesthesia is more preferable than pentobarbital anesthesia when evaluating cardiovascular factors. Additionally, pentobarbital significantly increased HR variability (HRV), suggesting a regulatory effect of pentobarbital on the autonomic nervous system, and resulted in a decreased response of the baro-reflex system. Propranolol or atropine had limited effects on ECG recording following pentobarbital anesthesia. Taken together, these data suggest that inhalation anesthesia is suitable for conducting hemodynamic analyses in the rat.

Sildenafil prevents the up-regulation of transient receptor potential canonical channels in the development of cardiomyocyte hypertrophy.

BACKGROUND: Transient receptor potential canonical (TRPCs) channels are up-regulated in the development of cardiac hypertrophy. Sildenafil inhibits TRPC6 activation and expression, leading to the prevention of cardiac hypertrophy. However, the effects of sildenafil on the expression of other TRPCs remain unknown. We hypothesized that in addition to its effects of TRPC6, sildenafil blocks the up-regulation of other TRPC channels to suppress cardiomyocyte hypertrophy. METHODS AND RESULTS: In cultured neonatal rat cardiomyocytes, a 48 h treatment with 10nM endothelin (ET)-1 induced hypertrophic responses characterized by nuclear factor of activated T cells activation and enhancement of brain natriuretic peptide expression and cell surface area. Co-treatment with sildenafil (1 µM, 48 h) inhibited these ET-1-induced hypertrophic responses. Although ET-1 enhanced the gene expression of TRPCs, sildenafil inhibited the enhanced gene expression of TRPC1, C3 and C6. Moreover, co-treatment with sildenafil abolished the augmentation of SOCE in the hypertrophied cardiomyocytes. CONCLUSIONS: These results suggest that sildenafil inhibits cardiomyocyte hypertrophy by suppressing the up-regulation of TRPC expression.

Cytosolic Ca2+-induced apoptosis in rat cardiomyocytes via mitochondrial NO-cGMP-protein kinase G pathway.

Previously, we showed that in adult rat cardiomyocytes, nitric oxide (NO) donors stimulate mitochondrial cGMP production, followed by cytochrome c release, independently of the mitochondrial permeable transition pore. We investigated whether mitochondrial cGMP-induced cytochrome c release from cardiac mitochondria is Ca(2+)-sensitive. Mitochondria and primary cultured cardiomyocytes were prepared from left ventricles of male Wistar rats. The cytosolic Ca(2+) concentration was adjusted with Ca(2+)-EGTA buffers. Cytochrome c released from mitochondria was measured by Western blotting. Cardiomyocyte apoptosis was assessed by Annexin V staining. Cytochrome c release from cardiac mitochondria was evoked by buffered Ca(2+) (1 µM); this was inhibited by NO-cGMP pathway inhibitors such as N(G)-monomethyl-l-arginine monoacetate (inhibitor of NO synthase), 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NO scavenger), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, NO-sensitive guanylyl cyclase inhibitor) and voltage-dependent anion channel (VDAC) inhibitor, 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, but not by cyclosporin A (mitochondrial permeable transition pore inhibitor). Furthermore, this release was significantly and dose dependently inhibited by 0.3-3 µM KT5823 (protein kinase G inhibitor). At the cellular level, intracellular perfusion of cardiomyocytes with buffered Ca(2+) (1 µM) also induced apoptosis, which was inhibited in the presence of ODQ. A membrane-permeable cGMP analog, 8-Br-cGMP, but not cGMP itself, mimicked buffered Ca(2+) actions in both cardiac mitochondria and cardiomyocytes. We further confirmed an increase in protein kinase G activity by adding cGMP in mitochondrial protein fraction. Our results suggest that mitochondrial NO-cGMP pathway-induced cytochrome c release from cardiac mitochondria, triggered by increased cytosolic Ca(2+), occurs through VDAC via the stimulation of an undiscovered mitochondrial protein kinase G.

Association Between History of Psychiatric Disorder and Degree of Physical Injury Among Suicide Attempters: Secondary Data Analysis in a Japanese Rural Area.

INTRODUCTION: While there may be differences in the choice of suicide methods between attempters with and those without a history of psychiatric disorders, it is not clear whether these differences predict the actual degree of physical injury. The present study aimed to investigate the association between the history of psychiatric disorder and the degree of physical injury among suicide attempters in a Japanese rural area. METHODS: We conducted a cross-sectional study analyzing secondary data of 806 suicide attempters from April 2012 to March 2022 obtained from a Japanese rural city. The exposure variable was a history of psychiatric disorders. The primary outcome was the degree of physical injury of suicide attempters: moderate and severe. We conducted a multivariate Poisson regression analysis to estimate the prevalence ratios (PRs) and 95% confidence intervals (CIs). RESULTS: Among 806 suicide attempters, a significant negative association between the history of psychiatric disorder and the degree of physical injury was observed (PR = 0.40; 95% CI, 0.28-0.59). Those with and without psychiatric disorders were more likely to choose low- and severe-lethality suicide methods such as drug or psychotropic overdoses and hanging or deep wrist injuries, respectively (P < .001). CONCLUSIONS: The present study highlights the importance of considering suicide attempters, both with and without psychiatric disorders, while formulating targeted suicide prevention strategies.

Arrhythmogenic coupling between the Na+ -Ca2+ exchanger and inositol 1,4,5-triphosphate receptor in rat pulmonary vein cardiomyocytes.

Atrial fibrillation, the most common sustained arrhythmia, is believed to be triggered by ectopic electrical activity originating in the myocardial sleeves surrounding the pulmonary veins (PVs). It has been reported that myocardial sleeves have the potential to generate automaticity in response to norepinephrine. This study investigated the cellular mechanisms underlying norepinephrine-induced automaticity in PV cardiomyocytes isolated from rats. Application of 10 µM norepinephrine to PV cardiomyocytes induced repetitive and transient increases in intracellular Ca(2+) concentrations. The Ca(2+) transient was accompanied by depolarization, and induced automatic rhythmic action potentials at approximately 4Hz in perforated patch clamp preparations in 27% of myocytes were observed. When the recording mode was switched from current-clamp to voltage-clamp mode during the continuous presence of automaticity, an oscillatory current was observed. The oscillatory current was always inward, irrespective of the membrane potential, indicating that the current was derived mainly from the Na(+)-Ca(2+) exchanger (NCX). The norepinephrine-induced automaticity was suppressed by blocking either the ß(1)- or α(1)-adrenoceptor. Additionally, this automaticity was blocked by inhibitors of phospholipase C and the inositol 1,4,5-triphosphate receptor (IP(3)R) but not by a protein kinase C inhibitor. We observed that the transverse-tubule system was enriched in cardiomyocytes in the PV, in contrast to those of the atrium, and that the NCX and IP(3)R were co-localized along transverse tubules. These findings suggest that a functional coupling between the NCX and IP(3)R causes arrhythmic excitability of the PV during the presence of combined ß(1)- and α(1)-adrenoceptor stimulation.