Chronic Effects of Adaptive Servo-Ventilation Therapy on Mortality and the Urgent Rehospitalization Rate in Patients Experiencing Recurrent Admissions for Heart Failure - A Multicenter Prospective Observational Study (SAVIOR-L)

BACKGROUND

This study investigated whether the chronic use of adaptive servo-ventilation (ASV) reduces all-cause mortality and the rate of urgent rehospitalization in patients with heart failure (HF).Methods and Results: This multicenter prospective observational study enrolled patients hospitalized for HF in Japan between 2019 and 2020 who were treated either with or without ASV therapy. Of 845 patients, 110 (13%) received chronic ASV at hospital discharge. The primary outcome was a composite of all-cause death and urgent rehospitalization for HF, and was observed in 272 patients over a 1-year follow-up. Following 1:3 sequential propensity score matching, 384 patients were included in the subsequent analysis. The median time to the primary outcome was significantly shorter in the ASV than in non-ASV group (19.7 vs. 34.4 weeks; P=0.013). In contrast, there was no significant difference in the all-cause mortality event-free rate between the 2 groups.

CONCLUSIONS

Chronic use of ASV did not impact all-cause mortality in patients experiencing recurrent admissions for HF.

Effectiveness and safety of morphine administration for refractory dyspnoea among hospitalised patients with advanced heart failure: the Morphine-HF study

OBJECTIVES

Morphine is effective in alleviating dyspnoea in patients with cancer. We aimed to investigate the effectiveness and safety of morphine administration for refractory dyspnoea in patients with advanced heart failure (HF).

METHODS

We conducted a multicentre, prospective, observational study of hospitalised patients with advanced HF in whom morphine was administered for refractory dyspnoea. Morphine effectiveness was evaluated by dyspnoea intensity changes, assessed regularly by both a quantitative subjective scale (Visual Analogue Scale (VAS; graded from 0 to 100 mm)) and an objective scale (Support Team Assessment Schedule-Japanese (STAS-J; graded from 0 to 4 points)). Safety was assessed by vital sign changes and new-onset severe adverse events, including nausea, vomiting, constipation and delirium based on the Common Terminology Criteria for Adverse Events.

RESULTS

From 15 Japanese institutions between September 2020 and August 2022, we included 28 hospitalised patients with advanced HF in whom morphine was administered (mean age: 83.8±8.7 years, male: 15 (54%), New York Heart Association class IV: 26 (93%) and mean left ventricular ejection fraction: 38%±19%). Both VAS and STAS-J significantly improved from baseline to day 1 (VAS: 67±26 to 50±31 mm; p=0.02 and STAS-J: 3.3±0.8 to 2.6±1.1 points; p=0.006, respectively), and thereafter the improvements sustained through to day 7. After morphine administration, vital signs including blood pressure, pulse rate and oxygen saturation did not change, and no new-onset severe adverse events occurred through to day 7.

CONCLUSIONS

This study suggested acceptable effectiveness and safety for morphine administration in treating refractory dyspnoea in hospitalised patients with advanced HF.

Prognostic Predictors of Tricuspid Regurgitation Worsening after Mitral Regurgitation Surgery with Mild Tricuspid Regurgitation

We aimed to investigate the prevalence and predictors of postoperative tricuspid regurgitation (TR) worsening in patients with mitral regurgitation (MR) and concomitant ≤mild TR. A total of 620 patients underwent surgery for MR from 2013 to 2017. Of these, 260 had ≤mild preoperative TR and no concomitant tricuspid valve surgery and were enrolled in this single-center retrospective study. The primary endpoint was postoperative worsening of ≥moderate TR. The primary endpoint occurred in 28 of 260 patients (11%) during the follow-up period [median: 4.1 years (interquartile range: 2.9-6.1 years)]. In the multivariable analysis, age, female sex, and left atrial volume index (LAVI) were significant predictors of the primary outcome during intermediate-term follow-up (age: hazard ratio [HR] 1.05 per 1-year increment, 95% confidence interval [CI] 1.02-1.10, p = 0.003; female sex: HR 3.53, 95% CI 1.61-7.72, p = 0.002; LAVI: HR 1.17 per 10-mL/m² increment, 95% CI 1.07-1.26, p < 0.001). The optimal LAVI cut-off value for predicting postoperative TR worsening was 79 mL/m² (area under the curve: 0.69). A high LAVI (>79 mL/m²) was significantly associated with a low rate of freedom from postoperative TR worsening compared with a low LAVI (≤79 mL/m²) (82.6% vs. 93.9% at 5 years, respectively; log-rank p = 0.008). In patients with ≤mild preoperative TR and no concomitant tricuspid surgery, the rate of postoperative TR worsening was 11% during intermediate-term follow-up. LA enlargement in patients with MR and ≤mild preoperative TR was significantly associated with postoperative TR worsening.

Clinical Outcomes of Radiologic Relapse in Patients With Cardiac Sarcoidosis Under Immunosuppressive Therapies

Although nuclear imaging can detect cardiac involvement of cardiac sarcoidosis (CS), including subclinical states, little is known about the prevalence and outcomes of radiologic relapse under prednisolone (PSL) therapy. This study aimed to investigate the clinical characteristics and outcomes in patients with radiologic relapse. A total of 80 consecutive patients with CS whose disease activity on nuclear imaging decreased at least once after initiation of immunosuppressive therapy were identified through a retrospective chart review. Radiologic relapse of CS was diagnosed using ¹⁸F-fluoro-2-deoxyglucose positron emission tomography or gallium-67 scintigraphy. Composite adverse events were defined as at least 1 of the following: all-cause death, hospitalization for heart failure, or lethal arrhythmia. During the follow-up period (median 2.9 years), radiologic relapse was observed in 31 patients (38.8% of overall patients) at 30 months (median) after immunosuppressive therapy initiation. After radiologic relapse was detected, all patients were treated with intensified immunosuppressive therapies (increasing PSL, n = 26 [83.9%], adding other immunosuppressive therapies to PSL, n = 5 [16.1%]). There were no differences in occurrences of composite adverse events in patients with and patients without radiologic relapse. Radiologic relapse under immunosuppressive therapy was observed in many patients with CS, but it was not associated with clinical outcomes under intensified immunosuppressive therapy.

Prevalence and predictive factors for clinical outcomes of isolated functional tricuspid regurgitation

BACKGROUND

A substantial number of patients have functional tricuspid regurgitation (TR). Isolated functional TR has been undertreated and may be a next target for transcatheter intervention. However, the prevalence, patient characteristics, and predictive factors for prognosis remain unclear.

METHODS

From patients in our echocardiographic database (N = 64,242), we extracted those with severe TR and examined prognosis according to etiologies of TR. Thereafter, we focused on two types of isolated functional TR; progressive TR after left-sided valve surgery (postoperative TR) and TR associated with annular dilatation (atrial TR). Composite adverse events were defined as all-cause death or hospitalization for heart failure (HF).

RESULTS

Of 1001 patients with severe TR (median age, 77 years; female, 58 %), 71 (7 %) patients were classified as postoperative TR, and 149 (15 %) as atrial TR. During the follow-up period (median, 1.6 years), 30 composite adverse events were observed (postoperative TR, n = 14; atrial TR, n = 16). Composite adverse events were less frequent in these two types of functional TR than TR of other etiologies. Multivariate analysis adjusted for age and sex showed that a history of hospitalization for HF, history of cardiac surgery >2 times, loop diuretics, estimated glomerular filtration rate, blood urea nitrogen, hemoglobin, platelet level, left ventricular ejection fraction, and right ventricular dimension were associated with clinical adverse events (p < 0.05), while B-type natriuretic peptide level was not.

CONCLUSIONS

A considerable number of patients had isolated functional TR. Extracardiac factors such as renal function, hemoglobin and platelet are important in determining clinical outcomes.

NRSF-GNAO1 Pathway Contributes to the Regulation of Cardiac Ca2+ Homeostasis

BACKGROUND

During the development of heart failure, a fetal cardiac gene program is reactivated and accelerates pathological cardiac remodeling. We previously reported that a transcriptional repressor, NRSF (neuron restrictive silencer factor), suppresses the fetal cardiac gene program, thereby maintaining cardiac integrity. The underlying molecular mechanisms remain to be determined, however.

METHODS

We aim to elucidate molecular mechanisms by which NRSF maintains normal cardiac function. We generated cardiac-specific NRSF knockout mice and analyzed cardiac gene expression profiles in those mice and mice cardiac-specifically expressing a dominant-negative NRSF mutant.

RESULTS

We found that cardiac expression of Gαo, an inhibitory G protein encoded in humans by GNAO1, is transcriptionally regulated by NRSF and is increased in the ventricles of several mouse models of heart failure. Genetic knockdown of Gnao1 ameliorated the cardiac dysfunction and prolonged survival rates in these mouse heart failure models. Conversely, cardiac-specific overexpression of GNAO1 in mice was sufficient to induce cardiac dysfunction. Mechanistically, we observed that increasing Gαo expression increased surface sarcolemmal L-type Ca2+ channel activity, activated CaMKII (calcium/calmodulin-dependent kinase-II) signaling, and impaired Ca2+ handling in ventricular myocytes, which led to cardiac dysfunction.

CONCLUSIONS

These findings shed light on a novel function of Gαo in the regulation of cardiac Ca2+ homeostasis and systolic function and suggest Gαo may be an effective therapeutic target for the treatment of heart failure.

Left Ventricular Dysfunction Caused by IgG4-related Small Intramural Coronary Periarteritis

IgG4-related disease (IgG4-RD) is a systemic autoimmune disorder known to affect multiple organs. However, IgG4-RD rarely affects the myocardium. We herein report a case of left ventricular dysfunction due to cardiac involvement of IgG4-RD.

Clinical trajectory of a patient with filaminopathy who developed arrhythmogenic cardiomyopathy, myofibrillar myopathy, and multiorgan tumors

We report a case of a patient presenting with arrhythmogenic cardiomyopathy, myofibrillar myopathy, and multiorgan tumors. A 41-year-old woman with a history of hypertrophic cardiomyopathy, diagnosed at 6 years of age, developed scoliosis after puberty. Following spinal surgery to address the scoliosis, she developed recurrent severe arrhythmia and heart failure. She developed hypoventilation at age 29 years. Proximal dominant weakness and mild elevation of serum creatine kinase indicated possible myopathy. Myofibrillar myopathy was diagnosed by muscle biopsy at age 30 year. Acute abdomen was repeatedly reported from age 33 years, eventually leading to a diagnosis of gastric polyp and erosive ulcer. A urinary bladder tumor was found at age 35 years, and breast cancer was diagnosed at age 40 years. Whole exome sequencing detected a heterozygous missense mutation in Filamin C. Recent evidences suggest that filamins are associated with tumors, and this case further highlights the clinical spectrum of filaminopathy.

Diagnostic value of vena contracta area measurement using three-dimensional transesophageal echocardiography in assessing the severity of aortic regurgitation

PURPOSE

Transthoracic echocardiography (TTE) provides noninvasively quantitative assessment of aortic regurgitation (AR) severity, but its diagnostic accuracy depends on image quality. Two-dimensional transesophageal echocardiography (TEE) is a semi-invasive procedure that is excellent in evaluating AR mechanism. However, quantitative assessment may be challenging due to restrictions in probe manipulation. This study aimed to investigate the diagnostic value of three-dimensional TEE to measure the vena contracta area (3DVCA) of AR.

METHODS

The subjects comprised 62 patients (age, 65 ± 16 years) whose AR was evaluated using TEE. The 3DVCA and semi-quantitative TEE parameters, such as the ratio of AR jet width to left ventricular outflow tract (jet/LVOT) and the vena contracta width (VCW) of AR jet, were compared using angiography grade and quantitative TTE measurements including regurgitant volume (RVol) and effective regurgitant orifice area (EROA). The diagnostic accuracy was determined using receiver operating characteristic (ROC) analysis, and the reproducibility of 3DVCA was also evaluated.

RESULTS

In 3DVCA, less overlap between angiography grades were observed. Correlation with RVol or EROA was better in 3DVCA than in Jet/LVOT or VCW. The area under the ROC curve was .737 for jet/LVOT, .773 for VCW, and .849 for 3DVCA, respectively. The optimal cutoff value of 3DVCA was ≥.31 cm² for grading severe AR. Inter- and intra-observer reproducibility of 3DVCA were .92 and .97, respectively.

CONCLUSIONS

The 3DVCA method using TEE showed high diagnostic accuracy and reproducibility. 3DVCA deserves use in accurately assessing AR severity, especially in patients who present difficulty in quantitative Doppler assessment using TTE.

Improvements of predictive power of B-type natriuretic peptide on admission by mathematically estimating its discharge levels in hospitalised patients with acute heart failure

BACKGROUNDS

Earlier studies showed that in patients with heart failure (HF), circulating levels of B-type natriuretic peptide (BNP) at hospital discharge (BNP_dis) are more predictive of prognosis than BNP levels on admission (BNP_ad). However, the mechanism underlying that difference has not been fully elucidated. We examined the association between confounding factors during hospitalisation and BNP_dis in patients with HF.

METHODS

We identified patients admitted to our hospital for HF (BNP_ad ≥100 pg/mL). Estimated left ventricular end-diastolic pressure (eLVEDP) was calculated using echocardiographic data. To identify the factors associated with the relation between BNP_ad and BNP_dis, we performed a stepwise regression analysis of retrospective data. To validate that analysis, we performed a prospective study.

RESULTS

Through stepwise regression of the patient data (n=688, New York Heart Association 3-4, 88%), we found age, blood urea nitrogen and eLVEDP to be significantly (p<0.05) associated with BNP_dis. Through multivariate analysis after accounting for these factors, we created a formula for predicting BNP levels at discharge (predicted-BNP_dis) from BNP_ad and other parameters measured at admission (p<0.05). By statistically adjusting for these factors, the prognostic power of BNP_ad was significantly improved (p<0.001). The prospective study also confirmed the strong correlation between predicted-BNP_dis and BNP_dis (n=104, r=0.625, p<0.05).

CONCLUSION

This study showed that statistically accounting for confounding factors affecting BNP levels improves the predictive power of BNP levels measured at the time of hospital admission, suggesting that these confounding factors are associated with lowering predictive power of BNP on admission.

TRIAL REGISTRATION NUMBER

UMIN 000034409, 00035428.

Prognostic comparison of atrial and ventricular functional mitral regurgitation

Objective

Atrial functional mitral regurgitation (A-FMR) has been suggested as a new aetiology of functional MR (MR); however, its prognosis and prognostic predictors are not fully elucidated. Aim of this study was to investigate the prognosis and prognostic predictors of A-FMR in comparison with ventricular functional MR (V-FMR).

Methods

Three hundred and seventy-eight consecutive patients with moderate-to-severe or severe functional MR were studied. Functional MR was classified into V-FMR (N=288) and A-FMR (N=90) depending on the alterations of left ventricle (LV) or left atrium (LA) along with clinical context and diagnosis of ischaemic heart disease or cardiomyopathy.

Results

During a median follow-up of 4.1 (2.0–6.7) years, all-cause mortality, cardiovascular mortality and heart failure (HF) hospitalisation occurred in 98 (26%), 81 (21%) and 177 (47%) patients, respectively, and rates of these events and the composite end point of all-cause mortality and HF hospitalisation were consistently higher in V-FMR than A-FMR (unadjusted HR 1.762 (95% CI 1.250 to 2.438), p<0.001; adjusted HR 1.654 (95% CI 1.027 to 2.664), p=0.038, for the composite end point). Further analysis showed different prognostic predictors between V-FMR and A-FMR; while age and LA volume index were independent prognostic predictors of both V-FMR and A-FMR, systolic blood pressure and B-type natriuretic peptide were also those of V-FMR, and estimated glomerular filtration rate, LV end-systolic dimension and tricuspid regurgitation were also those of A-FMR.

Conclusions

The prognosis of V-FMR was significantly worse than that of A-FMR, and prognostic predictors were different between V-FMR and A-FMR. Our study suggests the importance of discriminating A-FMR and V-FMR, and that different treatment strategies may be considered for each aetiology.

Prognostic differences between atrial functional mitral regurgitation and ventricular functional mitral regurgitation

Introduction

Atrial functional mitral regurgitation (A-FMR) has been under-recognized until recently as a cause of FMR, and the prognostic difference between A-FMR and ventricular FMR (V-FMR) has not been fully elucidated. As there has been different mechanisms of FMR suggested in A-FMR and V-FMR, we hypothesized that prognosis and prognostic predictors of A-FMR may differ from those of V-FMR.

Purpose

To investigate the prognosis and prognostic predictors of A-FMR in comparison with V-FMR.

Methods

Among 1312 consecutive patients with grade 3+ (moderate to severe) or 4+ (severe) MR, 378 consecutive FMR patients were identified by excluding patients with degenerative MR, previous cardiac surgery, or concomitant aortic valve disease and/or mitral stenosis. FMR with ejection fraction (EF) &lt;40% or FMR due to regional wall motion abnormalities with leaflet tethering were classified as V-FMR (N=288), and FMR due to left atrial (LA) and/or annular dilatation with preserved or mid-range EF (≥40%) were classified as A-FMR (N=90). All-cause death and heart failure hospitalization were analyzed as cardiovascular (CV) events in this study. Surgical or percutaneous mitral valve intervention without CV events was handled as not reaching an endpoint and these cases were censored.

Results

A-FMR were significantly older (76 [69–82] vs. 70 [58–77] years), higher rates of female (64 vs. 35%) and atrial fibrillation (88 vs. 42%), and lower B-type natriuretic peptide (BNP) values (169 [101–318] vs. 447 [213–952] pg/ml) compared to V-FMR (all P&lt;0.05). On echocardiography, LV end-diastolic and end-systolic dimensions (52 [48–57] vs. 64 [58–72] mm, 34 [31–37] vs. 55 [48–64] mm), respectively) were smaller, and EF (55 [50–60] vs. 28 [19–35] %) and LA volume (99 [73–137] vs. 73 [57–91] ml/m2) were larger in A-FMR (all P&lt;0.05). Effective regurgitant orifice area (32 [26–40] vs. 31 [24–45] mm2) and regurgitant volume (50±15 vs. 52±16 ml) were similar (both n.s.). During a median follow up of 1407 days, 206 (54%) patients developed CV events. Kaplan-Meier analysis revealed that V-FMR had a significantly higher rates of CV events compared to A-FMR (Figure) with adjusted hazard ratio (HR) of 1.762 [1.168–2.660], P=0.007 after adjusted for variables including age, sex, New York Heart Association functional class, previous heart failure hospitalization, estimated glomerular filtration rate (eGFR) and BNP. Further, stepwise multivariate analysis showed that independent prognostic predictors of A-FMR were LA volume and eGFR, while those for V-FMR were LA volume, age, and LV end-systolic dimension.

Conclusions

A-FMR had relatively better prognosis compared to V-FMR, and there were different prognostic predictors between A-FMR and V-FMR. Our results suggest that different treatment strategies need to be considered between A-FMR and V-FMR.

The Kaplan-Meier life table

Funding Acknowledgement

Type of funding source: None

Recurrences of disease activity in patients with cardiac sarcoidosis under corticosteroid therapy: prevalence, clinical background and prognosis

Background

Corticosteroid therapy (CTx) has been widely accepted as first-line therapy for cardiac sarcoidosis (CS), but there are very limited data regarding recurrence of disease activity of CS. We retrospectively investigated the prevalence, patient characteristics and prognostic significance in patients with recurrences of CS.

Methods

We identified 102 consecutive patients who were clinically diagnosed CS (admission: 2012 and 2019) and whose disease activity was diminished clinically at least once. Recurrence of CS was defined as detection of increased uptake of 18F-fluoro-2-deoxyglucose or gallium-67 in the follow-up examination. Composite adverse events (events) were defined as all-cause of death or hospitalization for heart failure. Echocardiographic and laboratory data before initiation of CTx were obtained.

Results

During the follow-up term (median: 4.9 years), the recurrences of CS occurred in 28 patients at 30 months (median) after the initiation of CTx. In patients with recurrence, left ventricular (LV) ejection fraction before initiation of CTx was lower than in those without recurrences (median: 31% vs. 39%, p&lt;0.05). After the detection of CS recurrences, 17 patients were treated with only increases of PSL and remaining 11 patients were treated with adding other immunosuppressive therapies to CTx. The univariate analysis demonstrated that there were no parameters in echocardiographic and laboratory examinations to predict the recurrences of CS. The results of univariate analysis for event occurrences (n=12) are shown in the Table. Additionally, the Kaplan-Meier analysis showed that there were no differences in event free survival rate in the patients with and without CS recurrences (Figure).

Conclusion

This study showed that the recurrences of disease activity were observed in a substantial number of patients with CS even under the CTx. All patients received intensification of CTx or additional immunosuppressive therapy, and LV systolic function, rather than the recurrence itself, was associated with clinical outcomes in this study.

Kaplan-Meier analysis for events

Funding Acknowledgement

Type of funding source: None

NRSF-GNAO1-CaMK2 axis exacerbates cardiac remodeling and progresses heart failure by impairing Ca2+ homeostasis

Background

In the development of heart failure, pathological intracellular signaling reactivates fetal cardiac genes, which leads to maladaptive remodeling and cardiac dysfunction. We previously reported that a transcriptional repressor, neuron restrictive silencer factor (NRSF) represses fetal cardiac genes and maintains normal cardiac function under normal conditions, while hypertrophic stimuli de-repress this NRSF mediated repression via activation of CaMKII. Molecular mechanisms by which NRSF maintains cardiac systolic function remains to be determined, however.

Purpose

To elucidate how NRSF maintains normal cardiac homeostasis and identify the novel therapeutic targets for heart failure.

Methods and results

We generated cardiac-specific NRSF knockout mice (NRSF cKO), and found that these NRSF cKO showed cardiac dysfunction and premature deaths accompanied with lethal arrhythmias, as was observed in our previously reported cardiac-specific dominant-negative mutant of NRSF transgenic mice (dnNRSF-Tg).

By cDNA microarray analysis of dnNRSF-Tg and NRSF-cKO, we identified that expression of Gnao1 gene encoding Gαo, a member of inhibitory G proteins, was commonly increased in ventricles of both types of mice.

ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay identified that NRSF transcriptionally regulates Gnao1 gene expression.

Genetic Knockdown of Gαo in dnNRSF-Tg and NRSF-cKO by crossing these mice with Gnao1 knockout mice ameliorated the reduced systolic function, increased arrhythmogenicity and reduced survival rates.

Transgenic mice expressing a human GNAO1 in their hearts (GNAO1-Tg) showed progressive cardiac dysfunction with cardiac dilation. Ventricles obtained from GNAO1-Tg have increased phosphorylation level of CaMKII and increased expression level of endogenous mouse Gnao1 gene. These data suggest that increased cardiac expression of Gαo is sufficient to induce pathological Ca2+-dependent signaling and cardiac dysfunction, and that Gαo forms a positive regulatory circuit with CaMKII and NRSF.

Electrophysiological analysis in ventricular myocytes of dnNRSF-Tg revealed that impaired Ca2+ handling via alterations in localized L-type calcium channel (LTCC) activities; decreased T-tubular and increased surface sarcolemmal LTCC activities, underlies Gαo-mediated cardiac dysfunction.

Furthermore, we also identified increased expression of Gαo in ventricles of two different heart failure mice models, mice with transverse aortic constriction and mice carrying a mutant cardiac troponin T, and confirmed that genetic reduction of Gαo prevented the progression of cardiac dysfunction in both types of mice.

Conclusions

Increased expression of Gαo, induced by attenuation of NRSF-mediated repression forms a pathological circuit via activation of CaMKII. This circuit exacerbates cardiac remodeling and progresses heart failure by impairing Ca2+ homeostasis. Gαo is a potential therapeutic target for heart failure.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Grants-in –Aid for Scientific Research from the Japan Society for the Promotion of Science

Abstract MP170: Increased Ga o Expression Regulated by NRSF Plays a Key Role in the Development of Heart Failure Through the Impairment of Ca 2+ Homeostasis

Background: In the development of heart failure, pathological intracellular signaling reactivates fetal cardiac gene program, which leads to pathological cardiac remodeling. We previously reported that a transcriptional repressor, neuron restrictive silencer factor (NRSF) represses fetal cardiac gene program and maintains normal cardiac function, while pathological stimuli de-repress this NRSF mediated repression via activation of CaMKII. Molecular mechanisms by which NRSF maintains cardiac function remains to be determined, however.

Purpose: To elucidate molecular mechanisms by which NRSF maintains normal cardiac function.

Methods and Results: Newly generated cardiac-specific NRSF knockout mice (NRSF-cKO) showed cardiac dysfunction and premature deaths accompanied with lethal arrhythmias, as was observed in our previously reported cardiac-specific dominant-negative mutant of NRSF transgenic mice (dnNRSF-Tg). Expression of Gnao1 gene encoding Gα o , a member of inhibitory G proteins, was commonly increased in ventricles of dnNRSF-Tg and NRSF-cKO. ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay identified that NRSF transcriptionally regulates Gnao1 gene expression. Genetic Knockdown of Gα o in dnNRSF-Tg and NRSF-cKO ameliorated the reduced systolic function, increased arrhythmogenicity and reduced survival rates. Conversely cardiac-specific GNAO1 overexpression was sufficient to show impaired cardiac function. Mechanistically, Gα o increases current density in surface sarcolemmal L-type Ca 2 + channel and then activates CaMKII without affecting protein kinase A activity, which finally leads to impaired Ca 2+ handling and systolic dysfunction. Furthermore, expression of Gα o is also increased in ventricles of transverse aortic constriction model mice and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gα o prevented the progression of cardiac dysfunction.

Conclusions: Increased expression of Gα o , induced by attenuation of NRSF-mediated repression forms a pathological circuit via activation of CaMKII and progresses heart failure by impairing Ca 2+ homeostasis. Gα o is a potential therapeutic target for heart failure.

4968Increased Gao expression underlies cardiac dysfunction and lethal arrhythmias accompanied with abnormal Ca2+ handling

Background

We previously demonstrated that a transcriptional repressor, neuron restrictive silencer factor (NRSF), maintains normal cardiac function and electrical stability. Transgenic mice expressing a dominant-negative mutant of NRSF in their hearts (dnNRSF-Tg) exhibit systolic dysfunction with cardiac dilation and premature death due to lethal arrhythmias like human dilated cardiomyopathy (DCM). Underlining mechanisms remain to be elucidated, however.

Purpose

We studied underling mechanisms by which NRSF maintains normal cardiac function to identify novel therapeutic targets for heart failure.

Methods and results

We generated cardiac-specific NRSF knockout mice (NRSFcKO) and confirmed that cardiac phenotypes of NRSFcKO are similar to those of dnNRSF-Tg.

cDNA microarray analysis revealed that cardiac gene expression of GNAO1 that encodes Gαo, a member of inhibitory G protein Gαi family, is increased in both dnNRSF-Tg and NRSFcKO ventricles.

We confirmed that GNAO1 is a direct target of NRSF through ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay.

In dnNRSF-Tg, pharmacological inhibition of Gαo with pertussis toxin improved systolic dysfunction and knockdown of Gαo by crossing with GNAO1 knockout mice improved not only systolic function but also frequency of ventricular arrhythmias and survival rates.

Electrophysiological and biochemical analysis in ventricular myocytes obtained from dnNRSF-Tg demonstrated that genetic reduction of Gαo ameliorated abnormalities in Ca2+ handling, which include increased current density in surface sarcolemmal L-type Ca2+ channel, reduced content of sarcoplasmic reticulum Ca2+ and lowered peak of Ca2+ transient. Furthermore, genetic reduction of Gαo attenuated increased phosphorylation levels of CAMKII in dnNRSF-Tg ventricles, which presumably underlies the improvement in Ca2+ handling. In addition, we identified increased Gαo expression in ventricles of heart failure model mice induced by transverse aortic constriction and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gαo ameliorated cardiac dysfunction.

Figure 1

Conclusions

We found that increased expression of Gαo, induced by attenuation of NRSF-mediated repression, plays a crucial role in the progression of cardiac dysfunction and lethal arrhythmias by evoking Ca2+ handling abnormality. These data demonstrate that Gαo is a potential therapeutic target for heart failure.

Abstract 652: Increased Gα o Expression Plays a Pivotal Role in the Progression of Heart Failure by Impairing Ca 2+ Handling

Background: A transcriptional repressor, neuron restrictive silencer factor (NRSF), maintains normal cardiac function and electrical stability. Transgenic mice expressing a dominant-negative mutant of NRSF in their hearts (dnNRSF-Tg) exhibit systolic dysfunction and premature death due to lethal arrhythmias like human dilated cardiomyopathy(DCM). Underlining mechanisms remain to be elucidated, however.

Purpose: To clarify how NRSF maintains normal cardiac homeostasis.

Methods and Results: cDNA microarray analysis of dnNRSF-Tg and newly generated cardiac-specific NRSF knockout mice (NRSFcKO), which show similar cardiac phenotypes to those of dnNRSF-Tg, revealed that cardiac gene expression of GNAO1 that encodes Gα o , a member of inhibitory G protein Gα i family, is increased in both dnNRSF-Tg and NRSFcKO ventricles.

ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay identified that GNAO1 is a direct target of NRSF.

In dnNRSF-Tg, pharmacological inhibition of Gα o by pertussis toxin improved systolic dysfunction and knockdown of Gα o by crossing with GNAO1 knockout mice improved not only systolic function but also frequency of ventricular arrhythmias and survival rates.

Electrophysiological analysis in ventricular myocytes obtained from dnNRSF-Tg demonstrated that genetic reduction of Gα o ameliorated abnormalities in Ca 2 + handling, which include increased current density in surface sarcolemmal L-type Ca 2 + channel, reduced content of sarcoplasmic reticulum Ca 2+ and lowered peak of Ca 2+ transient.

In addition, genetic reduction of Gα o attenuated increased phosphorylation levels of CAMKII and RyR2 in dnNRSF-Tg ventricles, which presumably underlies the improvement in Ca 2 + handling.

Furthermore, we identified increased Gα o expression in ventricles of heart failure model mice induced by transverse aortic constriction and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gα o ameliorated cardiac dysfunction.

Conclusions: We found that increased expression of Gα o , induced by attenuation of NRSF-mediated repression, plays a pivotal role in the progression of heart failure by evoking Ca 2+ handling abnormality. Gα o is a potential therapeutic target for heart failure.

Differences in effects of sultopride and sulpiride on dopamine turnover in rat brain

Sultopride and sulpiride are both chemically similar benzamide derivatives and selective antagonists of dopamine D2 receptors. However, these drugs differ in clinical properties. We compared the effects of sultopride and sulpiride on dopamine turnover in rats following the administration of these drugs alone or in combination with apomorphine. The administration of sultopride or sulpiride markedly accelerated dopamine turnover in the rat brain. The increase in the level of dopamine metabolites in the striatum was more marked in the sultopride-treated rats. Sulpiride affected the limbic dopamine receptors preferentially, whereas sultopride affected the striatal and the limbic dopamine receptors equally. A low dose of apomorphine induced a reduction in the concentration of dopamine metabolites in the striatum and the nucleus accumbens by approximately 55%, but not in the medial prefrontal cortex. Sultopride was more effective in preventing an apomorphine-induced reduction in dopamine metabolite levels. These results from rat experiments would model the pharmacological differences observed between sultopride and sulpiride in clinical use.