Nuclear GAPDH in cortical microglia mediates cellular stress-induced cognitive inflexibility.

We report a mechanism that underlies stress-induced cognitive inflexibility at the molecular level. In a mouse model under subacute cellular stress in which deficits in rule shifting tasks were elicited, the nuclear glyceraldehyde dehydrogenase (N-GAPDH) cascade was activated specifically in microglia in the prelimbic cortex. The cognitive deficits were normalized with a pharmacological intervention with a compound (the RR compound) that selectively blocked the initiation of N-GAPDH cascade without affecting glycolytic activity. The normalization was also observed with a microglia-specific genetic intervention targeting the N-GAPDH cascade. At the mechanistic levels, the microglial secretion of High-Mobility Group Box (HMGB), which is known to bind with and regulate the NMDA-type glutamate receptors, was elevated. Consequently, the hyperactivation of the prelimbic layer 5 excitatory neurons, a neural substrate for cognitive inflexibility, was also observed. The upregulation of the microglial HMGB signaling and neuronal hyperactivation were normalized by the pharmacological and microglia-specific genetic interventions. Taken together, we show a pivotal role of cortical microglia and microglia-neuron interaction in stress-induced cognitive inflexibility. We underscore the N-GAPDH cascade in microglia, which causally mediates stress-induced cognitive alteration.

NLRP3 Inflammasome Activation Through Heart-Brain Interaction Initiates Cardiac Inflammation and Hypertrophy During Pressure Overload.

BACKGROUND: Mechanical stress on the heart, such as high blood pressure, initiates inflammation and causes hypertrophic heart disease. However, the regulatory mechanism of inflammation and its role in the stressed heart remain unclear. IL-1ß (interleukin-1ß) is a proinflammatory cytokine that causes cardiac hypertrophy and heart failure. Here, we show that neural signals activate the NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing 3) inflammasome for IL-1ß production to induce adaptive hypertrophy in the stressed heart. METHODS: C57BL/6 mice, knockout mouse strains for NLRP3 and P2RX7 (P2X purinoceptor 7), and adrenergic neuron-specific knockout mice for SLC17A9, a secretory vesicle protein responsible for the storage and release of ATP, were used for analysis. Pressure overload was induced by transverse aortic constriction. Various animal models were used, including pharmacological treatment with apyrase, lipopolysaccharide, 2'(3')-O-(4-benzoylbenzoyl)-ATP, MCC950, anti-IL-1ß antibodies, clonidine, pseudoephedrine, isoproterenol, and bisoprolol, left stellate ganglionectomy, and ablation of cardiac afferent nerves with capsaicin. Cardiac function and morphology, gene expression, myocardial IL-1ß and caspase-1 activity, and extracellular ATP level were assessed. In vitro experiments were performed using primary cardiomyocytes and fibroblasts from rat neonates and human microvascular endothelial cell line. Cell surface area and proliferation were assessed. RESULTS: Genetic disruption of NLRP3 resulted in significant loss of IL-1ß production, cardiac hypertrophy, and contractile function during pressure overload. A bone marrow transplantation experiment revealed an essential role of NLRP3 in cardiac nonimmune cells in myocardial IL-1ß production and cardiac phenotype. Pharmacological depletion of extracellular ATP or genetic disruption of the P2X7 receptor suppressed myocardial NLRP3 inflammasome activity during pressure overload, indicating an important role of ATP/P2X7 axis in cardiac inflammation and hypertrophy. Extracellular ATP induced hypertrophic changes of cardiac cells in an NLRP3- and IL-1ß-dependent manner in vitro. Manipulation of the sympathetic nervous system suggested sympathetic efferent nerves as the main source of extracellular ATP. Depletion of ATP release from sympathetic efferent nerves, ablation of cardiac afferent nerves, or a lipophilic ß-blocker reduced cardiac extracellular ATP level, and inhibited NLRP3 inflammasome activation, IL-1ß production, and adaptive cardiac hypertrophy during pressure overload. CONCLUSIONS: Cardiac inflammation and hypertrophy are regulated by heart-brain interaction. Controlling neural signals might be important for the treatment of hypertensive heart disease.

A pacing-controlled protocol for frequency-diastolic relations distinguishes diastolic dysfunction specific to a mouse HFpEF model.

Heart failure with preserved ejection fraction (HFpEF), characterized by diastolic dysfunction and insufficient exercise capacity, is a growing health problem worldwide. One major difficulty with experimental research on HFpEF is the lack of methods to consistently detect diastolic dysfunction in mouse models. We developed a pacing-controlled pressure-volume (PV) loop protocol for the assessment of diastolic function at different heart rates in mice and tested if the protocol could detect diastolic dysfunction specific to a HFpEF model. A HFpEF model was generated by high-fat diet (HFD) feeding with concomitant NG-nitro-l-arginine methyl ester administration, and a pressure-overload hypertrophy (PO) model was produced by surgical constriction of the transverse aorta (TAC). Heart rate (HR) was slowed below 400 beats/min by intraperitoneal injection of ivabradine. PV loop data were acquired and analyzed at HR incrementing from 400 to 700 beats/min via atrial pacing using a miniature pacing catheter inserted into the esophagus, and comparisons were made among control, HFpEF, and PO mice. At baseline without pacing, no diastolic abnormalities were detected in either PO or HFpEF models. Frequency-diastolic relations, however, revealed the significant diastolic impairment specific to the HFpEF model; both relaxation time constant (Tau) and end-diastolic pressure-volume relationship (EDPVR) were worsened as heart rate increased. Peak positive first derivative of left ventricular pressure (dP/dtmax) was significantly lower in HFpEF versus controls only at a high HR of 700 beats/min. A pacing-controlled protocol would be a feasible and potent method to detect diastolic dysfunction specific to a mouse HFpEF model.NEW & NOTEWORTHY We developed a pacing-controlled PV loop protocol for the assessment of diastolic function at different heart rates in mice, which is a feasible and potent method for the characterization of diastolic dysfunction in a murine HFpEF model whose diastolic dysfunction might be difficult to be detected under resting conditions without pacing.

Endoplasmic reticulum stress-activated nuclear factor-kappa B signaling pathway induces the upregulation of cardiomyocyte dopamine D1 receptor in heart failure.

Dopamine D1 receptor (D1R), coded by the Drd1 gene, is induced in cardiomyocytes of failing hearts, triggering heart failure-associated ventricular arrhythmia, and therefore could be a potential therapeutic target for chronic heart failure. The regulation of D1R expression, however, is not fully understood. Here, we explored the molecular mechanism by which cardiomyocyte D1R is induced in failing hearts. We performed motif analysis for the promoter region of the Drd1 gene using the transcription factor affinity prediction (TRAP) method and identified nuclear factor-kappa B (NF-κB) as a candidate transcriptional factor regulating the expression of the Drd1 gene. We next employed murine models of heart failure from chronic pressure overload by transverse aortic constriction (TAC), and assessed myocardial Drd1 expression levels and NF-κB activity, as well as endoplasmic reticulum (ER) stress, which has been implicated in the pathogenesis of heart failure. Drd1 induction in TAC hearts was dependent on the severity of heart failure, and was associated with NF-κB activation and ER stress, as assessed by p65 phosphorylation and the expression of ER stress-related genes, respectively. We further tested if Drd1 was induced by ER stress via NF-κB activation in cultured neonatal rat ventricular myocytes. Tunicamycin activated NF-κB pathway in an ER stress-dependent manner and increased Drd1 expression. Importantly, inhibition of NF-κB pathway by pretreatment with Bay11-7082 completely suppressed the tunicamycin-induced upregulation of Drd1, suggesting that NF-κB activation is essential to this regulation. Our study demonstrates the pivotal role for the ER stress-induced NF-κB activation in the induction of D1R in cardiomyocytes. Intervention of this pathway might be a potential new therapeutic strategy for heart failure-associated ventricular arrhythmia.

Takotsubo Syndrome Occurring after mRNA COVID-19 Vaccination in a Patient with Graves' Disease.

Cardiovascular events such as myocarditis following mRNA COVID-19 vaccination are increasing. We present a 67-year-old postmenopausal woman with Takotsubo Syndrome and Graves' disease after mRNA COVID-19 vaccination. She developed chest pain and shortness of breath one week after vaccination. An electrocardiogram revealed ST elevation in the precordial leads. Coronary angiography revealed the absence of obstructive coronary artery disease, and the left ventriculography showed a typical feature with apical ballooning. Laboratory workup showed the elevation of free T4 and thyrotropin receptor antibodies. It was presumed that Takotsubo Syndrome and Graves' disease were probably related to the COVID-19 mRNA vaccination. The patient was treated with low-dose bisoprolol, diuretics, carbimazole, and steroid and discharged uneventfully. The mRNA COVID-19 vaccination is still safe and effective to defend against COVID-19 pandemic. However, clinicians should be aware of the possible cardiovascular adverse events other than myocarditis following vaccination.

Phosphodiesterase 9A controls nitric-oxide-independent cGMP and hypertrophic heart disease.

Cyclic guanosine monophosphate (cGMP) is a second messenger molecule that transduces nitric-oxide- and natriuretic-peptide-coupled signalling, stimulating phosphorylation changes by protein kinase G. Enhancing cGMP synthesis or blocking its degradation by phosphodiesterase type 5A (PDE5A) protects against cardiovascular disease. However, cGMP stimulation alone is limited by counter-adaptions including PDE upregulation. Furthermore, although PDE5A regulates nitric-oxide-generated cGMP, nitric oxide signalling is often depressed by heart disease. PDEs controlling natriuretic-peptide-coupled cGMP remain uncertain. Here we show that cGMP-selective PDE9A (refs 7, 8) is expressed in the mammalian heart, including humans, and is upregulated by hypertrophy and cardiac failure. PDE9A regulates natriuretic-peptide- rather than nitric-oxide-stimulated cGMP in heart myocytes and muscle, and its genetic or selective pharmacological inhibition protects against pathological responses to neurohormones, and sustained pressure-overload stress. PDE9A inhibition reverses pre-established heart disease independent of nitric oxide synthase (NOS) activity, whereas PDE5A inhibition requires active NOS. Transcription factor activation and phosphoproteome analyses of myocytes with each PDE selectively inhibited reveals substantial differential targeting, with phosphorylation changes from PDE5A inhibition being more sensitive to NOS activation. Thus, unlike PDE5A, PDE9A can regulate cGMP signalling independent of the nitric oxide pathway, and its role in stress-induced heart disease suggests potential as a therapeutic target.

Novel Balloon Pulmonary Angioplasty Technique for Chronic Thromboembolic Pulmonary Hypertension.

This study aimed to clarify the usefulness of the Ikari-curve left (IL) guiding catheter for balloon pulmonary angioplasty (BPA).The current BPA strategy for chronic thromboembolic pulmonary hypertension is dilation of as many branches as possible to normalize hemodynamics and oxygenation. The shape of the guiding catheter is a major factor in achieving this. However, conventional guiding catheters are difficult to introduce into particular branches. The IL guiding catheter may be suitable; however, its utility remains unclear.We retrospectively analyzed 202 consecutive BPA sessions of 40 patients from November 2016 to October 2019 and divided these sessions into two groups: the IL group where the IL guiding catheter was used and the non-IL group where other catheters were utilized. The occurrence of lung injury was determined by the presence of bloody sputum. We compared the rates of successful introduction into target vessels and assessed for the occurrence of lung injury.The average age of enrolled patients was 60.3 ± 14.4 years, with females comprising 65%. There were 99 sessions in the IL group. The median treated branches per session differed between the 2 groups (IL group: 15 versus non-IL group: 10, P < 0.05). The occurrence of lung injury was lower in the IL group (4.0% versus 11.7%, P = 0.07). The IL group had more successful vessel insertions than the non-IL group (78.8% versus 42.7%, P < 0.01).The IL guiding catheter may be introduced into branches that cannot be accessed by conventional guiding catheters.

Diagnosing Heart Failure from Chest X-Ray Images Using Deep Learning.

The development of deep learning technology has enabled machines to achieve high-level accuracy in interpreting medical images. While many previous studies have examined the detection of pulmonary nodules in chest X-rays using deep learning, the application of this technology to heart failure remains rare. In this paper, we investigated the performance of a deep learning algorithm in terms of diagnosing heart failure using images obtained from chest X-rays. We used 952 chest X-ray images from a labeled database published by the National Institutes of Health. Two cardiologists verified and relabeled a total of 260 "normal" and 378 "heart failure" images, with the remainder being discarded because they had been incorrectly labeled. Data augmentation and transfer learning were used to obtain an accuracy of 82% in diagnosing heart failure using the chest X-ray images. Furthermore, heatmap imaging allowed us to visualize decisions made by the machine. Deep learning can thus help support the diagnosis of heart failure using chest X-ray images.

Erratum: Diagnosing Heart Failure from Chest X-Ray Images Using Deep Learning.

An error appeared in the article entitled "Diagnosing Heart Failure from Chest X-Ray Images Using Deep Learning" by Takuya Matsumoto, Satoshi Kodera, Hiroki Shinohara, Hirotaka Ieki, Toshihiro Yamaguchi, Yasutomi Higashikuni, Arihiro Kiyosue, Kaoru Ito, Jiro Ando, Eiki Takimoto, Hiroshi Akazawa, Hiroyuki Morita, Issei Komuro (Vol. 61, No. 4, 781-786, 2020). The Figure 5on page 784 should be replaced by the following figure.

Sex Differences in the Mortality Risk of Elderly Patients with Systolic Heart Failure in Taiwan.

BACKGROUND: Sex differences in heart failure mortality might be affected by age, race, and treatment response. Many large studies in Western countries have shown conflicting results, however few studies have been conducted in Asian patients. OBJECTIVES: We prospectively investigated the mortality risk in a multicenter cohort of 1,093 male and 416 female heart failure patients with reduced ejection fraction (HFrEF) hospitalized for worsening symptoms in Taiwan between 2013 and 2015. METHODS: Kaplan-Meier curve and Cox proportional regression analyses were used to determine the one-year mortality risk by sex. RESULTS: There were no significant differences in major adverse cardiovascular events, re-admission rate, and mortality between sexes in the overall cohort and the young subgroup during one-year of follow-up. In the elderly subgroup, the overall and cardiac mortality rate of the male patients were higher than those of the female patients (p = 0.035, p = 0.049, respectively). We found that the prognostic effect of old age on overall mortality rate appeared to be stronger in the male patients (p < 0.0001) than in the female patients (p = 0.69) in Cox regression analysis and Kaplan-Meier survival curves. Male sex was a risk factor for all-cause mortality in the elderly (hazard ratio: 1.50, 95% confidence interval 1.02-2.25) independently of systolic blood pressure, diabetes mellitus, hemoglobin concentration, kidney function, and medications. CONCLUSIONS: In the Taiwan HFrEF registry, the highest mortality risk was observed in male patients aged 65 years or more. Clinicians need to pay more attention to these patients.

High-throughput single-molecule RNA imaging analysis reveals heterogeneous responses of cardiomyocytes to hemodynamic overload.

BACKGROUND: The heart responds to hemodynamic overload through cardiac hypertrophy and activation of the fetal gene program. However, these changes have not been thoroughly examined in individual cardiomyocytes, and the relation between cardiomyocyte size and fetal gene expression remains elusive. We established a method of high-throughput single-molecule RNA imaging analysis of in vivo cardiomyocytes and determined spatial and temporal changes during the development of heart failure. METHODS AND RESULTS: We applied three novel single-cell analysis methods, namely, single-cell quantitative PCR (sc-qPCR), single-cell RNA sequencing (scRNA-seq), and single-molecule fluorescence in situ hybridization (smFISH). Isolated cardiomyocytes and cross sections from pressure overloaded murine hearts after transverse aortic constriction (TAC) were analyzed at an early hypertrophy stage (2 weeks, TAC2W) and at a late heart failure stage (8 weeks, TAC8W). Expression of myosin heavy chain ß (Myh7), a representative fetal gene, was induced in some cardiomyocytes in TAC2W hearts and in more cardiomyocytes in TAC8W hearts. Expression levels of Myh7 varied considerably among cardiomyocytes. Myh7-expressing cardiomyocytes were significantly more abundant in the middle layer, compared with the inner or outer layers of TAC2W hearts, while such spatial differences were not observed in TAC8W hearts. Expression levels of Myh7 were inversely correlated with cardiomyocyte size and expression levels of mitochondria-related genes. CONCLUSIONS: We developed a new image-analysis pipeline to allow automated and unbiased quantification of gene expression at the single-cell level and determined the spatial and temporal regulation of heterogenous Myh7 expression in cardiomyocytes after pressure overload.

Overview of the 83rd Annual Scientific Meeting of the Japanese Circulation Society　- Renaissance of Cardiology for the Creation of Future Medicine.

The 83rdAnnual Scientific Meeting of the Japanese Circulation Society was held in Yokohama, Japan, on March 29-31, 2019, just as the cherry blossoms came into full bloom. Because the environment around cardiovascular healthcare is rapidly changing, it becomes highly important to make a breakthrough at the dawn of a new era. The main theme of this meeting was "Renaissance of Cardiology for the Creation of Future Medicine". The meeting benefited from the participation of 18,825 people, and there were in-depth and extensive discussions at every session, focusing on topics covering clinical and basic research, medical care provision system, human resource development, and public awareness in cardiovascular medicine. The meeting was completed with great success, and we greatly appreciate the tremendous cooperation and support from all affiliates.

Analysis of Oxygenation in Chronic Thromboembolic Pulmonary Hypertension Using Dead Space Ratio and Intrapulmonary Shunt Ratio.

Current therapeutic methods for chronic thromboembolic pulmonary hypertension (CTEPH) can improve hemodynamic status and are expected to improve prognoses. However, some patients experience dyspnea during effort and continue supplemental oxygenation despite their hemodynamic status being fully improved. Considering the pathogenesis of CTEPH, the dead space and intrapulmonary shunt are assumed to be responsible for hypoxia in CTEPH, but their contributions are unclear. It is also unclear whether they are improved after treatment. The aim of this study was to investigate the implications of the dead space ratio (DSR) and the intrapulmonary shunt ratio (ISR) for hypoxia in CTEPH and treatment for CTEPH.We retrospectively measured the DSR and ISR of 23 consecutive patients with CTEPH. For 11 of these 23 (10 were treated by balloon pulmonary angioplasty, one with riociguat), we also measured these parameters before and after CTEPH treatments. Overall, the DSR and ISR were abnormally elevated (DSR: 0.63 ± 0.06; ISR: 0.20 ± 0.05). After treatment, mean pulmonary artery pressure was improved (from 40.3 ± 8.1 to 25.5 ± 2.7 mmHg). Although atrial oxygen saturation (SaO2), DSR and ISR were improved (SaO2: from 90.2 ± 3.2 to 93.7 ± 1.8%; DSR: from 0.64 ± 0.06 to 0.58 ± 0.05; ISR: from 0.20 ± 0.04 to 0.18 ± 0.02), these improvements were slight compared with that of mean pulmonary artery pressure.The DSR and ISR were abnormally elevated in patients with CTEPH and their improvement by treatment was limited. Only DSR can be a useful marker for normalization of hypoxia in CTEPH.

Murine Model of Pulmonary Artery Overflow Vasculopathy Revealed Macrophage Accumulation in the Lung.

Chronic thromboembolic pulmonary hypertension (CTEPH) develops as a consequence of unresolved pulmonary embolism or clots in the pulmonary arteries. The obstruction not only reduces the area of the pulmonary vascular bed, but also elicits high pressure and high shear stress in the spared unobstructed arteries. Subsequent overflow of the small pulmonary arteries induces vascular remodeling, termed as overflow vasculopathy (OV). While the development of OV significantly contributes to the occurrence of pulmonary hypertension, its precise molecular mechanisms are yet to be determined.We established a novel murine pulmonary artery OV (PAOV) model, in which we resected left lung and induced redistribution of the cardiac output to the remaining pulmonary artery of the right lung. At 21 days after operation, mice showed an increase in the vascular media area, indicating the development of pulmonary arterial remodeling. In addition, right ventricular hypertrophy was detected in the PAOV model. Intriguingly, marked accumulation of F4/80-positive monocytes/macrophages was visualized in high-flow arteries, implying the role of an inflammatory process in the pathogenesis of overflow-induced vascular remodeling.

Clinically Worsening Chronic Thromboembolic Pulmonary Hypertension by Riociguat After Balloon Pulmonary Angioplasty.

Riociguat, a soluble guanylate cyclase stimulator, induces pulmonary artery dilatation through blood flow and is effective in treating chronic thromboembolic pulmonary hypertension (CTEPH). There are two types of vasculopathies in CTEPH based upon its location, in other words, proximal or distal to the thrombus-medicated obstruction. Distal vasculopathy is characterized by intrapulmonary shunts due to diminished blood flow. While other therapeutic interventions for CTEPH including pulmonary endarterectomy and balloon pulmonary angioplasty achieve reperfusion to the distal vasculopathy vessels, the effects of riociguat on distal vasculopathy vessels remain undetermined. Herein, we describe a case of a 66-year-old woman who exhibited deterioration of mean pulmonary artery pressure and exercise tolerance after a 4-month treatment with riociguat. She received balloon pulmonary angioplasty prior to riociguat administration. Her lung perfusion scintigraphy and pulmonary angiography findings did not change over the course of treatment. Notably, after the discontinuation of riociguat, her clinical values returned to their levels prior to riociguat administration. Her intrapulmonary shunt ratio followed a similar course as her hemodynamic status. We demonstrate that riociguat can deteriorate hemodynamic status, which may mediate the dilatation of intrapulmonary shunts. We should perform close monitoring of symptoms and hemodynamic status after riociguat administration, especially in patients in whom the reperfused DVs occurred due to invasive treatment.

Hypoxia-Inducible Factor 1α Is a Critical Downstream Mediator for Hypoxia-Induced Mitogenic Factor (FIZZ1/RELMα)-Induced Pulmonary Hypertension.

OBJECTIVE: Pulmonary hypertension (PH) is characterized by progressive elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. We have shown that in rodents, hypoxia-induced mitogenic factor (HIMF; also known as FIZZ1 or resistin-like molecule-ß) causes PH by initiating lung vascular inflammation. We hypothesized that hypoxia-inducible factor-1 (HIF-1) is a critical downstream signal mediator of HIMF during PH development. APPROACH AND RESULTS: In this study, we compared the degree of HIMF-induced pulmonary vascular remodeling and PH development in wild-type (HIF-1α(+/+)) and HIF-1α heterozygous null (HIF-1α(+/-)) mice. HIMF-induced PH was significantly diminished in HIF-1α(+/-) mice and was accompanied by a dysregulated vascular endothelial growth factor-A-vascular endothelial growth factor receptor 2 pathway. HIF-1α was critical for bone marrow-derived cell migration and vascular tube formation in response to HIMF. Furthermore, HIMF and its human homolog, resistin-like molecule-ß, significantly increased interleukin (IL)-6 in macrophages and lung resident cells through a mechanism dependent on HIF-1α and, at least to some extent, on nuclear factor κB. CONCLUSIONS: Our results suggest that HIF-1α is a critical downstream transcription factor for HIMF-induced pulmonary vascular remodeling and PH development. Importantly, both HIMF and human resistin-like molecule-ß significantly increased IL-6 in lung resident cells and increased perivascular accumulation of IL-6-expressing macrophages in the lungs of mice. These data suggest that HIMF can induce HIF-1, vascular endothelial growth factor-A, and interleukin-6, which are critical mediators of both hypoxic inflammation and PH pathophysiology.

Inhibiting mitochondrial Na+/Ca2+ exchange prevents sudden death in a Guinea pig model of heart failure.

RATIONALE: In cardiomyocytes from failing hearts, insufficient mitochondrial Ca(2+) accumulation secondary to cytoplasmic Na(+) overload decreases NAD(P)H/NAD(P)(+) redox potential and increases oxidative stress when workload increases. These effects are abolished by enhancing mitochondrial Ca(2+) with acute treatment with CGP-37157 (CGP), an inhibitor of the mitochondrial Na(+)/Ca(2+) exchanger. OBJECTIVE: Our aim was to determine whether chronic CGP treatment mitigates contractile dysfunction and arrhythmias in an animal model of heart failure (HF) and sudden cardiac death (SCD). METHODS AND RESULTS: Here, we describe a novel guinea pig HF/SCD model using aortic constriction combined with daily ß-adrenergic receptor stimulation (ACi) and show that chronic CGP treatment (ACi plus CGP) attenuates cardiac hypertrophic remodeling, pulmonary edema, and interstitial fibrosis and prevents cardiac dysfunction and SCD. In the ACi group 4 weeks after pressure overload, fractional shortening and the rate of left ventricular pressure development decreased by 36% and 32%, respectively, compared with sham-operated controls; in contrast, cardiac function was completely preserved in the ACi plus CGP group. CGP treatment also significantly reduced the incidence of premature ventricular beats and prevented fatal episodes of ventricular fibrillation, but did not prevent QT prolongation. Without CGP treatment, mortality was 61% in the ACi group <4 weeks of aortic constriction, whereas the death rate in the ACi plus CGP group was not different from sham-operated animals. CONCLUSIONS: The findings demonstrate the critical role played by altered mitochondrial Ca(2+) dynamics in the development of HF and HF-associated SCD; moreover, they reveal a novel strategy for treating SCD and cardiac decompensation in HF.

Regulation of Mitochondrial Dynamics by Dynamin-Related Protein-1 in Acute Cardiorenal Syndrome.

Experimental evidence has clarified distant organ dysfunctions induced by AKI. Crosstalk between the kidney and heart, which has been recognized recently as cardiorenal syndrome, appears to have an important role in clinical settings, but the mechanisms by which AKI causes cardiac injury remain poorly understood. Both the kidney and heart are highly energy-demanding organs that are rich in mitochondria. Therefore, we investigated the role of mitochondrial dynamics in kidney-heart organ crosstalk. Renal ischemia reperfusion (IR) injury was induced by bilateral renal artery clamping for 30 min in 8-week-old male C57BL/6 mice. Electron microscopy showed a significant increase of mitochondrial fragmentation in the heart at 24 h. Cardiomyocyte apoptosis and cardiac dysfunction, evaluated by echocardiography, were observed at 72 h. Among the mitochondrial dynamics regulating molecules, dynamin-related protein 1 (Drp1), which regulates fission, and mitofusin 1, mitofusin 2, and optic atrophy 1, which regulate fusion, only Drp1 was increased in the mitochondrial fraction of the heart. A Drp1 inhibitor, mdivi-1, administered before IR decreased mitochondrial fragmentation and cardiomyocyte apoptosis significantly and improved cardiac dysfunction induced by renal IR. This study showed that renal IR injury induced fragmentation of mitochondria in a fission-dominant manner with Drp1 activation and subsequent cardiomyocyte apoptosis in the heart. Furthermore, cardiac dysfunction induced by renal IR was improved by Drp1 inhibition. These data suggest that mitochondrial fragmentation by fission machinery may be a new therapeutic target in cardiac dysfunction induced by AKI.