Effects of Phenylacetylglutamine on the Susceptibility of Atrial Fibrillation in Overpressure-Induced HF Mice.

Phenylacetylglutamine (PAGln), a gut metabolite is substantially elevated in heart failure (HF). The increase of PAGln in plasma is associated with atrial fibrillation (AF), and contributes to AF pathogenesis. However, the role of PAGln in AF with HF remains uncertain. Therefore, this study aimed to determine the effect of PAGln on AF after HF. Thoracic aortic coarctation (TAC) created overpressure-induced HF mice for 4 weeks. Histopathology, biochemical, echocardiographic for assessment of cardiac function, and electrophysiological examination of several electrophysiological indexes (ERP, SNRT, and the occurrence rate of AF) were performed at the end of the HF mice model. We found that plasma PAGln levels were significantly elevated in PAGln-treated HF mice and that PAGln aggravated maladaptive structural remodeling and electrical remodeling, which aggravated the vulnerability of AF, shortened the ERP duration, prolonged the SNRT, increased the occurrence rate of AF in HF mice. Mechanistically, PAGln exacerbated ROS accumulation and increased the levels of phosphorylated PLB and CAMK II. Overall, PAGln played a vital role in promoting the occurrence of AF in HF mice by activating the CAMK II signaling pathway.

Leukocyte Ig-like receptor B4 (Lilrb4a) alleviates cardiac dysfunction and isoproterenol-induced arrhythmogenic remodeling associated with cardiac fibrosis and inflammation.

BACKGROUND: Heart failure is usually accompanied by activation of the sympathetic nerve, and excessive activation of the sympathetic nerve promotes cardiac remodeling and cardiac dysfunction. In the isoproterenol (ISO)-induced animal model, it is often accompanied by myocardial hypertrophy, fibrosis, and inflammation. Leukocyte immunoglobulin-like receptor B4a (Lilrb4a), an immunosuppressive regulatory receptor, plays a vital role in cardiovascular disease. However, the effect of Lilrb4a on ventricular arrhythmia in an ISO-induced mouse model remains unclear. OBJECTIVE: The purpose of this study was to explore the role and molecular mechanism of Lilrb4a in ISO-induced arrhythmogenic remodeling. METHODS: Lilrb4a knockout mice and Lilrb4a overexpression mice were infused with ISO (15 mg/kg per 24 hours, 4 weeks). Echocardiography and histology evaluations of myocardial hypertrophy and cardiac structural remodeling were conducted. Surface electrocardiography and electrophysiologic examination were used to evaluate cardiac electrical remodeling and susceptibility to ventricular arrhythmias. Quantitative reverse transcriptase-polymerase chain reaction analysis and Western blotting were used to detect the expression levels of ion channel proteins and signal pathway proteins. RESULTS: The results discovered that ISO induced cardiac hypertrophy, fibrosis, and inflammation and led to electrical remodeling and the occurrence of ventricular arrhythmias. Lilrb4a alleviated cardiac structural and electrical remodeling and protected against the occurrence of ventricular arrhythmias in ISO-induced mice by gain-of-function or loss-of-function approaches. The mechanism is that Lilrb4a inhibited NF-κB signaling and MAPK signaling activation mediated by transforming growth factor kinase 1. CONCLUSION: Lilrb4a alleviates cardiac dysfunction and ISO-induced arrhythmogenic remodeling associated with cardiac fibrosis and inflammation through the regulation of NF-κB signaling and MAPK signaling activation.

DL-3-n-butylphthalide attenuates doxorubicin-induced acute cardiotoxicity via Nrf2/HO-1 signaling pathway.

Doxorubicin (DOX) is a widely used chemotherapeutic drug known to cause dose-dependent myocardial toxicity, which limits its clinical potential. DL-3-n-butylphthalide (NBP), a substance extracted from celery seed species, has a number of pharmacological properties, such as antioxidant, anti-inflammatory, and anti-apoptotic actions. However, whether NBP can protect against DOX-induced acute myocardial toxicity is still unclear. Therefore, this study was designed to investigate the potential protective effects of NBP against DOX-induced acute myocardial injury and its underlying mechanism. By injecting 15 mg/kg of DOX intraperitoneally, eight-week-old male C57BL6 mice suffered an acute myocardial injury. The treatment group of mice received 80 mg/kg NBP by gavage once daily for 14 days. To mimic the cardiotoxicity of DOX, 1uM DOX was administered to H9C2 cells in vitro. In comparison to the DOX group, the results showed that NBP improved cardiac function and decreased serum levels of cTnI, LDH, and CK-MB. Additionally, HE staining demonstrated that NBP attenuated cardiac fibrillar lysis and breakage in DOX-treated mouse hearts. Western blotting assay and immunofluorescence staining suggested that NBP attenuated DOX-induced oxidative stress, apoptosis, and inflammation both in vivo and in vitro. Mechanistically, NBP significantly upregulated the Nrf2/HO-1 signaling pathway, while the Nrf2 inhibitor ML385 prevented NBP from protecting the myocardium from DOX-induced myocardial toxicity in vitro. In conclusion, Our results indicate that NBP alleviates DOX-induced myocardial toxicity by activating the Nrf2/HO-1 signaling pathway.

Variation and disparity in awareness of atrial fibrillation in China: A national cross-sectional study.

BACKGROUND: The latest information regarding the awareness of atrial fibrillation (AF) remains limited in China. OBJECTIVES: The present study aimed to understand the variation and disparity in awareness of AF in China. METHODS: The cross-sectional study used data from the 2020 nationwide epidemiology survey on AF among adults aged 18 years or older in mainland China to assess the prevalence of AF awareness. The awareness of AF diagnostic methods and outcomes was also assessed using an interviewer-administered questionnaire. RESULTS: Of the 114,039 adults responding to the survey, 1463 (age-standardized prevalence, 55.3% (95% confidence interval [CI], 47.7-62.9%) and 10,202 (8.2%, 95%CI 5.4-10.9%) were aware of AF in participants with and without AF, respectively. Of these, 36.4% (95%CI 30.0-42.9%) and 6.3% (95%CI 3.6-9.1%) considered electrocardiogram as a method of diagnosing AF, and 30.0% (95% CI 3.2-8.2%) and 5.2% (95%CI 2.7-7.6%) considered stroke as an outcome of AF. The proportion of participants who being aware of AF varied significantly across sociodemographic and cardiovascular disease subgroups, and was almost consistently lower in rural areas than those in urban areas. Overall, lack of AF awareness was associated with rural areas, geographical region, lower education levels, and without history and had no risk factors of cardiovascular disease. CONCLUSIONS: Nearly half of adults with AF, and >90% non-AF population are unaware of AF in China, with significant variation and disparity. Focused public health initiatives are needed to improve awareness and knowledge of AF among high-risk populations.

Gene and stem cell therapy for inherited cardiac arrhythmias.

Inherited cardiac arrhythmias are a group of genetic diseases predisposing to sudden cardiac arrest, mainly resulting from variants in genes encoding cardiac ion channels or proteins involved in their regulation. Currently available therapeutic options (pharmacotherapy, ablative therapy and device-based therapy) can not preclude the occurrence of arrhythmia events and/or provide complete protection. With growing understanding of the genetic background and molecular mechanisms of inherited cardiac arrhythmias, advancing insight of stem cell technology, and development of vectors and delivery strategies, gene therapy and stem cell therapy may be promising approaches for treatment of inherited cardiac arrhythmias. Recent years have witnessed impressive progress in the basic science aspects and there is a clear and urgent need to be translated into the clinical management of arrhythmic events. In this review, we present a succinct overview of gene and cell therapy strategies, and summarize the current status of gene and cell therapy. Finally, we discuss future directions for implementation of gene and cell therapy in the therapy of inherited cardiac arrhythmias.

Cadherin-5 facilitated the differentiation of human induced pluripotent stem cells into sinoatrial node-like pacemaker cells by regulating ß-catenin.

Our study was conducted to investigate whether cadherin-5 (CDH5), a vascular endothelial cell adhesion glycoprotein, could facilitate the differentiation of human induced pluripotent stem cells (hiPSCs) into sinoatrial node-like pacemaker cells (SANLPCs), following previous findings of silk-fibroin hydrogel-induced direct conversion of quiescent cardiomyocytes into pacemaker cells in rats through the activation of CDH5. In this study, the differentiating hiPSCs were treated with CDH5 (40 ng/mL) between Day 5 and 7 during cardiomyocytes differentiation. The findings in the present study demonstrated that CDH5 stimulated the expression of pacemaker-specific markers while suppressing markers associated with working cardiomyocytes, resulting in an increased proportion of SANLPCs among hiPSCs-derived cardiomyocytes (hiPSC-CMs) population. Moreover, CDH5 induced typical electrophysiological characteristics resembling cardiac pacemaker cells in hiPSC-CMs. Further mechanistic investigations revealed that the enriched differentiation of hiPSCs into SANLPCs induced by CDH5 was partially reversed by iCRT14, an inhibitor of ß-catenin. Therefore, based on the aforementioned findings, it could be inferred that the regulation of ß-catenin by CDH5 played a crucial role in promoting the enriched differentiation of hiPSCs into SANLPCs, which presents a novel avenue for the construction of biological pacemakers in forthcoming research.

Macrophage colony-stimulating factor ameliorates myocardial injury in mice after myocardial infarction by regulating cardiac macrophages through the P2X7R/NLRP3/IL-1ß signal pathway.

Aims: To investigate the effects of M-CSF on myocardial injury in mice after MI by regulating different types of cardiac macrophages through the P2X7R/NLRP3/IL-1ß signal pathway. Methods: A total of 60 C57BL/6J WT mice were used, with the Sham Group subjected to ligation without ligation through the LAD, the MI model was prepared by ligation of the LAD in the MC Group and MM Group, with the M-CSF reagent (500 µg/kg/d) being given an intraperitoneal injection for the first 5 days after surgery in the MM Group. All mice were fed in a barrier environment for 1 week. After the study, myocardial tissues were collected and IL-4, IL-6, IL-10, TNF-α, MCP-1, IFN-α, ANP, BNP, ß-MHC, Collage I, Collage III, P2X7R, NLRP3, IL-1ß, Bax, Caspase 3, C-Casp 3, Bcl-2, M1/2 macrophage, the apoptosis of cardiomyocytes, and the collagen deposition were detected. Results: The inflammatory response was significantly lower in the MM Group, the cardiomyocyte apoptosis, fibrosis, and hypertrophy were inhibited compared to the MC Group, and the levels of P2X7R, NLRP3, and IL-1ß were also statistically lower in the MM Group. Additionally, the expression of M2 macrophages increased in the MM Group while the M1 macrophages statistically decreased compared to the MC Group. Conclusion: M-CSF can significantly increase the expression of M2 macrophage and reduce the level of M1 macrophage by inhibiting the levels of NLRP3/IL-1ß-related proteins, thereby inhibiting inflammation, ameliorating reducing myocardial hypertrophy, apoptosis, and fibrosis, improve myocardial injury in mice after MI.

2023 Chinese expert consensus on the impact of COVID-19 on the management of cardiovascular diseases.

The primary site of infection in COVID-19 exhibit is the respiratory system, but multiple organ systems could be affected. The virus could directly invade cardiomyocytes. Alternatively, cytokine storm could lead to myocardial injury. More importantly, the management of existing cardiovascular diseases must be re-examined in COVID-19 due to, for example, interaction between antiviral agents and with a wide variety of pharmacological agents. The Branch of Cardiovascular Physicians of Chinese Medical Doctor Association organized a panel of experts in cardiovascular and related fields to discuss this important issue, and formulated the "2023 Chinese Expert Consensus on the Impact of COVID-19 on the Management of Cardiovascular Diseases." The Consensus was drafted on the basis of systematic review of existing evidence and diagnosis and treatment experience, and covers three major aspects: myocardial injury caused by COVID-10 and COVID-19 vaccine, the impact of COVID-19 on patients with cardiovascular disease, and the impact of COVID-19 on the cardiovascular system of healthy people, and rehabilitation guidance recommendations. The Consensus involves 11 core clinical issues, including incidence, pathogenesis, clinical manifestations, treatment strategies, prognosis, and rehabilitation. It is our hope that this Consensus will provide a practical guidance to cardiologists in the management of cardiovascular diseases in the new era of COVID-19 pandemic.

Advances in basic and translational research in atrial fibrillation.

Atrial fibrillation (AF) is a very common cardiac arrhythmia with an estimated prevalence of 33.5 million patients globally. It is associated with an increased risk of death, stroke and peripheral embolism. Although genetic studies have identified a growing number of genes associated with AF, the definitive impact of these genetic findings is yet to be established. Several mechanisms, including electrical, structural and neural remodelling of atrial tissue, have been proposed to contribute to the development of AF. Despite over a century of exploration, the molecular and cellular mechanisms underlying AF have not been fully established. Current antiarrhythmic drugs are associated with a significant rate of adverse events and management of AF using ablation is not optimal, especially in cases of persistent AF. This review discusses recent advances in our understanding and management of AF, including new concepts of epidemiology, genetics and pathophysiological mechanisms. We review the current status of antiarrhythmic drug therapy for AF, new potential agents, as well as mechanism-based AF ablation. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

The method of sinus node-like pacemaker cells from human induced pluripotent stem cells by BMP and Wnt signaling.

The embryonic development of sinus nodes (SAN) is co-regulated by multiple signaling pathways. Among these, the bone morphogenetic protein (BMP) and Wnt signaling pathways are involved in the development of SAN. In this study, the effects of BMP and Wnt signaling on the differentiation of SAN-like pacemaker cells (SANLPCs) were investigated. Human induced pluripotent stem cells (hiPSCs) were divided into four groups: control, BMP4, CHIR-3, and BMP4 + CHIR (CHIR: a Wnt signaling activator). The samples were tested at day (D) 15 of differentiation. The final protocol for the activation of BMP signaling at D0-D3 and reactivation of Wnt signaling at D5-D7 in the differentiation of hiPSCs were determined. The results showed that the mRNA levels of pacemaker markers (TBX18, SHOX2, TBX3, HCN4, and HCN1) were higher in the BMP4 + CHIR group than in the control group, and working myocardial genes were downregulated. The immunofluorescence assay revealed that the expression of SHOX2 and HCN4 increased in the BMP4 + CHIR group compared to that in the other groups. In addition, the results of patch clamps revealed that a funny current of higher density and typical SAN action potentials were recorded, except in the control group, in which the L-type calcium current was higher in the BMP4 + CHIR group than in the other groups. Finally, the proportion of SANLPCs (cTnT+ NKX2.5-) was further enhanced by the combination of BMP4 and CHIR treatment. In summary, the combination of BMP and Wnt signaling promotes the differentiation of SANLPCs from hiPSCs.

Melatonin alleviates doxorubicin-induced cardiotoxicity via inhibiting oxidative stress, pyroptosis and apoptosis by activating Sirt1/Nrf2 pathway.

Melatonin confers cardioprotective effects on multiple cardiovascular diseases, including doxorubicin-induced cardiomyopathy. The effectiveness of melatonin in mitigating myocardial injuries caused by Doxorubicin through enhancement of mitochondrial function is already established, however, the role of melatonin in regulating the Sirtuin-1 (Sirt1)/Nuclear factor E2-associated factor 2 (Nrf2) pathway in lessening the onset of Doxorubicin-induced cardiomyopathy is yet to be elucidated. To address this, H9C2 cardiomyocytes and C57BL/6 mice were employed to construct in vitro and in vivo models of Dox-induced myocardial impairments, respectively. Results showed that Dox markedly evoked oxidative stress, pyroptosis and apoptosis both in vitro and in vivo, which were significantly alleviated by melatonin administration. Mechanistically, melatonin attenuated Dox-induced downregulation of Sirt1 and Nrf2, and both inhibition of Sirt1 and Nrf2 significantly reversed the cardioprotective effects of melatonin. In conclusion, our studies suggest that the activation of the Sirt1/Nrf2 pathway is the underlying mechanism behind melatonin's ability to curtail oxidative stress, pyroptosis, and apoptosis in Dox-induced cardiomyopathy. These promising results demonstrated the potential application of melatonin as a treatment for doxorubicin-induced cardiac injury.

Tubeimoside I Ameliorates Doxorubicin-Induced Cardiotoxicity by Upregulating SIRT3.

Cardiotoxicity linked to doxorubicin (DOX) is primarily caused by inflammation, oxidative stress, and apoptosis. The role of tubeimoside I (TBM) in DOX-induced cardiotoxicity remains ambiguous, despite growing evidence that it could reduce inflammation, oxidative stress, and apoptosis in various diseases. This study was designed to investigate the role of TBM in DOX-induced cardiotoxicity and uncover the underlying mechanisms. H9c2 cell line and C57BL/6 mice were used to construct an in vitro and in vivo model of DOX-induced myocardial injury, respectively. We observed that DOX treatment provoked inflammation, oxidative stress, and cardiomyocyte apoptosis, which were significantly alleviated by TBM administration. Mechanistically, TBM attenuated DOX-induced downregulation of sirtuin 3 (SIRT3), and SIRT3 inhibition abrogated the beneficial effects of TBM both in vitro and in vivo. In conclusion, TBM eased inflammation, oxidative stress, and apoptosis in DOX-induced cardiotoxicity by increasing the expression of SIRT3, suggesting that it holds great promise for treating DOX-induced cardiac injury.

Ginsenoside Rh2 attenuates myocardial ischaemia­reperfusion injury by regulating the Nrf2/HO­1/NLRP3 signalling pathway.

Ginsenoside Rh2 (GRh2) is a monomer isolated from red ginseng that has extensive pharmacological effects. However, whether GRh2 has a protective effect on ischaemia/reperfusion (I/R) in the myocardium has yet to be elucidated. The present study aimed to identify the anti-inflammatory and antioxidant effects of GRh2 on I/R in the myocardium and its underlying mechanism. A rat model of myocardial I/R injury was constructed by ligating the left anterior descending coronary artery, which was subsequently treated with GRh2. A total of 40 male Sprague-Dawley rats were divided into the following four groups: The sham group, the I/R group, the I/R+GRh2 (10 mg/kg) group and the I/R+GRh2 (20 mg/kg) group. Neonatal rat cardiomyocytes were also used to evaluate the protective effect of GRh2 on hypoxia/reoxygenation (H/R)-induced myocardial injury in vitro. The GRh2 pre-treatment reduced the I/R- or H/R-induced release of myocardial enzymes and the production of IL-1ß, IL-18 and TNF-α. GRh2 reduced the area of myocardial infarction and the histological changes in the myocardium and improved cardiac functions. In addition, GRh2 reduced the expression levels of NOD-like receptor family pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein, caspase-1, malondialdehyde and reactive oxygen species and increased the expression levels of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), glutathione peroxidase and superoxide dismutase. In conclusion, the present study confirmed that GRh2 could reduce oxidative stress and inflammation in cardiomyocytes after reperfusion, and its mechanism of action may be related to its regulation of the Nrf2/HO-1/NLRP3 signalling pathway.

The paired-related homeobox protein 1 promotes cardiac fibrosis via the Twist1-Prrx1-tenascin-C loop.

Cardiac fibrosis is a common pathology in the advanced stage of cardiovascular diseases, which leads to cardiac systolic and diastolic dysfunction. It is important to prevent cardiac fibrosis during myocardial injury. The transcription factor Prrx1 is involved in cancer-associated fibrosis and other organ fibrosis. However, the role and mechanism of Prrx1 in cardiac fibrosis deserves further exploration. We identified that overexpressed Prrx1 promoted the proliferation and migration of cardiac fibroblasts, and transform cardiac fibroblasts to myofibroblasts in vitro. We demonstrated that the expression of Prrx1 is upregulated in TGF-ß1-treated fibroblasts. And silencing Prrx1 could attenuate cardiac fibrosis induced by TGF-ß1 in vitro. In addition, a Twist1-paired-related homeobox 1 (Prrx1)-tenascin-C (TNC) positive feedback loop (PFL) combined with Twist1, Prrx1, and TNC activated fibroblasts, which was the mechanism the Prrx1 in cardiac fibrosis. In conclusion, our findings showed that the deficiency of Prrx1 attenuated cardiac fibrosis in vitro and reveal a novel Twist1-Prrx1-TNC PFL in the regulation of cardiac fibrosis.

Inhibition of intermittent calcium-activated potassium channel (SK4) attenuates Ang II-induced hypertrophy of human-induced stem cell-derived cardiomyocytes via targeting Ras-Raf-MEK1/2-ERK1/2 and CN-NFAT signaling pathways.

Cardiac hypertrophy caused by angiotensin II (Ang II) is essential for the pathological process of heart failure. The intermediate calcium-activated potassium channel (SK4) has been shown to be involved in the process of the inflammatory response, cell proliferation, and apoptosis. However, the role of SK4 in cardiac hypertrophy has not been elucidated. Cardiac hypertrophy in human-induced pluripotent stem cells-derived cardiomyocytes (HiPSC-CMs) was induced by Ang II. Cells were transfected with SK4 adenovirus or treated with SK4 inhibitor (TRAM-34). TUNEL staining was used to assess the levels of apoptosis. Real-time polymerase chain reaction and Western blot analysis were used to measure messenger RNA (mRNA) and protein levels, respectively. The present results showed that SK4 expression was upregulated in HiPSC-CMs stimulated by Ang II. The downregulation of SK4 by a specific inhibitor TRAM-34 markedly ameliorated cardiac hypertrophy (reflected by the mRNA levels of atrial natriuretic peptide, brain natriuretic peptide, and ß-myosin heavy chain) and apoptosis (reflected by the level of Caspase 3, Bax, and Bcl-2) induced by Ang II treatment. The action of SK4 in cardiac hypertrophy was mediated by Ras-Raf-mitogen-activated protein kinases 1/2 (MEK1/2)-extracellular-regulated protein kinases 1/2 (ERK1/2) and calcineurin (CN)-nuclear factors of activated T cells (NFAT) activation. Our studies demonstrated that inhibition of SK4 significantly alleviated cardiac hypertrophy induced by Ang II in hiPSC-CMs by targeting Ras-Raf-MEK1/2-ERK1/2 signaling and CN-NFAT signaling pathway. Our studies suggest that SK4 may serve as a potential therapeutic target that could delay hypertrophy.

Blockade of SK4 channels suppresses atrial fibrillation by attenuating atrial fibrosis in canines with prolonged atrial pacing.

Background: We previously found that intermediate conductance Ca2+-activated K+ channel (SK4) might be an important target in atrial fibrillation (AF). Objective: To investigate the role of SK4 in AF maintenance. Methods: Twenty beagles were randomly assigned to the sham group (n=6), pacing group (n=7), and pacing+TRAM-34 group (n=7). Rapid atrial pacing continued for 7 days in the pacing and TRAM-34 groups. During the pacing, the TRAM-34 group received TRAM-34 intravenous injection (10 mg/Kg) 3 times per day. Atrial fibroblasts isolated from canines were treated with angiotensin II or adenovirus carrying the SK4 gene (Ad-SK4) to overexpress SK4 channels. Results: TRAM-34 treatment significantly suppressed the increased intra-atrial conducting time (CT) and AF duration in canines after rapid atrial pacing (P<0.05). Compared with the sham group, the expression of SK4 in atria was higher in the pacing group, which was associated with an increased number of myofibroblasts and levels of extracellular matrix in atrium (all P<0.05), and this effect was reversed by TRAM-34 treatment (all P<0.05). In atrial fibroblasts, the increased expression of SK4 induced by angiotensin II stimulation or Ad-SK4 transfection contributed to higher levels of P38, ERK1/2 and their downstream factors c-Jun and c-Fos, leading to the increased expression of α-SMA (all P<0.05), and all these increases were markedly reduced by TRAM-34 treatment. Conclusion: SK4 blockade suppressed AF by attenuating cardiac fibroblast activity and atrial fibrosis, which was realized through not only a decrease in fibrogenic factors but also inhibition of fibrotic signaling pathways.

Maresin1 ameliorates ventricular remodelling and arrhythmia in mice models of myocardial infarction via NRF2/HO-1 and TLR4/NF-kB signalling.

Ventricular remodelling and arrhythmias are the main factors that affect the quality of life of patients with myocardial infarction (MI). Maresin 1 (Mar1) is associated with antioxidative and anti-inflammatory effects. However, the mechanisms underlying the effects of Mar1 in MI remain unclear. In this study, we aimed to explore the role and potential mechanisms of Mar1 in a mouse model of MI. The mice were divided into four groups: Sham, Sham + Mar1, MI, and MI + Mar1. In the MI groups, the left anterior descending coronary artery of the mice was ligated for 28 days, while this ligation was not conducted in the Sham groups. Mar1 was injected into mice in the Sham + Mar1 and MI + Mar1 groups. H9c2 cells were cultured in vitro under hypoxic conditions for MI models, and then Mar1 was added to the medium for 24 h. Our data demonstrated that Mar1 activated NRF2/HO-1 signalling and inhibited TLR4/NF-kB signalling in MI. These activities lead to inhibition of the release of inflammatory cytokines, reduction of myocardial apoptosis and interstitial fibrosis, decreased susceptibility to ventricular arrhythmias, and improved cardiac function. Similarly, our in vitro analyses showed that Mar1 inhibited inflammatory signalling by enhancing the antioxidative function of NRF2/HO-1 signalling. Furthermore, Mar1 inhibited hypoxia-activated apoptosis in cardiomyocytes. Taken together, our data demonstrate that Mar1 ameliorates ventricular remodelling and arrhythmias in mice post-MI via the activation of NRF2/HO-1 signalling and inhibition of the TLR4/NF-kB signalling pathways.

Dapagliflozin reduces the vulnerability of rats with pulmonary arterial hypertension-induced right heart failure to ventricular arrhythmia by restoring calcium handling.

BACKGROUND: Malignant ventricular arrhythmia (VA) is a major contributor to sudden cardiac death (SCD) in patients with pulmonary arterial hypertension (PAH)-induced right heart failure (RHF). Recently, dapagliflozin (DAPA), a sodium/glucose cotransporter-2 inhibitor (SGLT2i), has been found to exhibit cardioprotective effects in patients with left ventricular systolic dysfunction. In this study, we examined the effects of DAPA on VA vulnerability in a rat model of PAH-induced RHF. METHODS: Rats randomly received monocrotaline (MCT, 60 mg/kg) or vehicle via a single intraperitoneal injection. A day later, MCT-injected rats were randomly treated with placebo, low-dose DAPA (1 mg/kg/day), or high-dose (3 mg/kg/day) DAPA orally for 35 days. Echocardiographic analysis, haemodynamic experiments, and histological assessments were subsequently performed to confirm the presence of PAH-induced RHF. Right ventricle (RV) expression of calcium (Ca2+) handling proteins were detected via Western blotting. RV expression of connexin 43 (Cx43) was determined via immunohistochemical staining. An optical mapping study was performed to assess the electrophysiological characteristics in isolated hearts. Cellular Ca2+ imaging from RV cardiomyocytes (RVCMs) was recorded using Fura-2 AM or Fluo-4 AM. RESULTS: High-dose DAPA treatment attenuated RV structural remodelling, improved RV function, alleviated Cx43 remodelling, increased the conduction velocity, restored the expression of key Ca2+ handling proteins, increased the threshold for Ca2+ and action potential duration (APD) alternans, decreased susceptibility to spatially discordant APD alternans and spontaneous Ca2+ events, promoted cellular Ca2+ handling, and reduced VA vulnerability in PAH-induced RHF rats. Low-dose DAPA treatment also showed antiarrhythmic effects in hearts with PAH-induced RHF, although with a lower level of efficacy. CONCLUSION: DAPA administration reduced VA vulnerability in rats with PAH-induced RHF by improving RVCM Ca2+ handling.

RA signaling pathway combined with Wnt signaling pathway regulates human-induced pluripotent stem cells (hiPSCs) differentiation to sinus node-like cells.

BACKGROUND: The source of SAN is debated among researchers. Many studies have shown that RA and Wnt signaling are involved in heart development. In this study, we investigated the role of retinoic acid (RA) and Wnt signaling in the induction of sinus node-like cells. METHODS: The experimental samples were divided into four groups: control group (CHIR = 0), CHIR = 3, RA + CHIR = 0 andRA + CHIR = 3. After 20 days of differentiation, Western blot, RT-qPCR, immunofluorescence and flow cytometry were performed to identify sinus node-like cells. Finally, whole-cell patch clamp technique was used to record pacing funny current and action potential (AP) in four groups. RESULTS: The best intervention method used in our experiment was RA = 0.25 µmol/L D5-D9 + CHIR = 3 µmol/L D5-D7. Results showed that CHIR can increase the expression of ISL-1 and TBX3, while RA mainly elevated Shox2. Immunofluorescence assay and flow cytometry further illustrated that combining RA with CHIR can induce sinus node-like cells (CTNT+Shox2+Nkx2.5-). Moreover, CHIR might reduce the frequency of cell beats, but in conjunction with RA could partly compensate for this side effect. Whole cell patch clamps were able to record funny current and the typical sinus node AP in the experimental group, which did not appear in the control group. CONCLUSIONS: Combining RA with Wnt signaling within a specific period can induce sinus node-like cells.