MFGE8 attenuates Ang-II-induced atrial fibrosis and vulnerability to atrial fibrillation through inhibition of TGF-β1/Smad2/3 pathway

SIRT3 sulfhydration using hydrogen sulfide inhibited angiotensin II-induced atrial fibrosis and vulnerability to atrial fibrillation via suppression of the TGF-β1/smad2/3 signalling pathway

Atrial fibrosis is associated with the occurrence of atrial fibrillation (AF) and regulated by the transforming growth factor-β1 (TGF-β1)/Smad2/3 signalling pathway. Unfortunately, the mechanisms of regulation of TGF-β1/Smad2/3-induced atrial fibrosis and vulnerability to AF remain still unknown. Previous studies have shown that sirtuin3 (SIRT3) sulfhydration has strong anti-fibrotic effects. We hypothesised that SIRT3 sulfhydration inhibits angiotensin II (Ang-II)-induced atrial fibrosis via blocking the TGF-β1/Smad2/3 signalling pathway. In this study, we found that SIRT3 expression was decreased in the left atrium of patients with AF compared to that in those with sinus rhythm (SR). In vitro, SIRT3 knockdown by small interfering RNA significantly expanded Ang-II-induced atrial fibrosis and TGF-β1/Smad2/3 signalling pathway activation, whereas supplementation with Sodium Hydrosulfide (NaHS, exogenous hydrogen sulfide donor and sulfhydration agonist) and SIRT3 overexpression using adenovirus ameliorated Ang-II-induced atrial fibrosis. Moreover, we observed suppression of the TGF-β1/Smad2/3 pathway when Ang-II was combined with NaHS treatment, and the effect of this co-treatment was consistent with that of Ang-II combined with LY3200882 (Smad pathway inhibitor) on reducing atrial fibroblast proliferation and cell migration in vitro. Supplementation with dithiothreitol (DTT, a sulfhydration inhibitor) and adenovirus SIRT3 shRNA blocked the ameliorating effect of NaHS and AngII co-treatment on atrial fibrosis in vitro. Finally, continued treatment with NaHS in rats ameliorated atrial fibrosis and remodelling, and further improved AF vulnerability induced by Ang-II, which was reversed by DTT and adenovirus SIRT3 shRNA, suggesting that SIRT3 sulfhydration might be a potential therapeutic target in atrial fibrosis and AF.

Epigallocatechin-3-Gallate Inhibits Atrial Fibrosis and Reduces the Occurrence and Maintenance of Atrial Fibrillation and its Possible Mechanisms

BACKGROUND

Atrial fibrosis is one of the main causes of the onset and recurrence of atrial fibrillation (AF), for which there is no effective treatment. The aim of this study was to investigate the effect and mechanism of epigallocatechin-3-gallate (EGCG) on AF in rats.

METHODS

The rat model of AF was established by rapid pacing induction after angiotensin-II (Ang-II) induced atrial fibrosis to verify the relationship between atrial fibrosis and the AF. The expression levels of TGF-β/Smad3 pathway molecules and lysyl oxidase (LOX) in AF were detected. Subsequently, EGCG was used to intervene Ang-II-induced atrial fibrosis to explore the role of EGCG in the treatment of AF and its inhibitory mechanism on fibrosis. It was further verified that EGCG inhibited the production of collagen and the expression of LOX through the TGF-β/Smad3 pathway at the cellular level.

RESULTS

The results showed that the induction rate and maintenance time of AF in rats increased with the increase of the degree of atrial fibrosis. Meanwhile, the expressions of Col I, Col III, molecules related to TGF-β/Smad3 pathway, and LOX increased significantly in the atrial tissues of rats in the Ang-II induced group. EGCG could reduce the occurrence and maintenance time of AF by inhibiting the degree of Ang-induced rat atrial fibrosis. Cell experiments confirmed that EGCG could reduce the synthesis of collagen and the expression of LOX in cardiac fibroblast induced by Ang-II. The possible mechanism is to down-regulate the expression of genes and proteins related to the TGF-β/Smad3 pathway.

CONCLUSION

EGCG could downregulate the expression levels of collagen and LOX by inhibiting the TGF-β/Smad3 signaling pathway, alleviating Ang-II-induced atrial fibrosis, which in turn inhibited the occurrence and curtailed the duration of AF.

Milk fat globule-epidermal growth factor 8 (MFGE8) prevents intestinal fibrosis

OBJECTIVE

Intestinal fibrosis is considered an inevitable consequence of chronic IBD, leading to stricture formation and need for surgery. During the process of fibrogenesis, extracellular matrix (ECM) components critically regulate the function of mesenchymal cells. We characterised the composition and function of ECM in fibrostenosing Crohn's disease (CD) and control tissues.

DESIGN

Decellularised full-thickness intestinal tissue platforms were tested using three different protocols, and ECM composition in different tissue phenotypes was explored by proteomics and validated by quantitative PCR (qPCR) and immunohistochemistry. Primary human intestinal myofibroblasts (HIMFs) treated with milk fat globule-epidermal growth factor 8 (MFGE8) were evaluated regarding the mechanism of their antifibrotic response, and the action of MFGE8 was tested in two experimental intestinal fibrosis models.

RESULTS

We established and validated an optimal decellularisation protocol for intestinal IBD tissues. Matrisome analysis revealed elevated MFGE8 expression in CD strictured (CDs) tissue, which was confirmed at the mRNA and protein levels. Treatment with MFGE8 inhibited ECM production in normal control HIMF but not CDs HIMF. Next-generation sequencing uncovered functionally relevant integrin-mediated signalling pathways, and blockade of integrin αvβ5 and focal adhesion kinase rendered HIMF non-responsive to MFGE8. MFGE8 prevented and reversed experimental intestinal fibrosis in vitro and in vivo.

CONCLUSION

MFGE8 displays antifibrotic effects, and its administration may represent a future approach for prevention of IBD-induced intestinal strictures.

Human cell-expressed tag-free rhMFG-E8 as an effective radiation mitigator

Human milk fat globule epidermal growth factor-factor VIII (MFG-E8) functions as a bridging molecule to promote the removal of dying cells by professional phagocytes. E. coli-expressed histidine-tagged recombinant human MFG-E8 (rhMFG-E8) is protective in various disease conditions. However, due to improper recombinant protein glycosylation, misfolding and the possibility of antigenicity, E. coli-expressed histidine-tagged rhMFG-E8 is unsuitable for human therapy. Therefore, we hypothesize that human cell-expressed, tag-free rhMFG-E8 will have suitable structural and functional properties to be developed as a safe and effective novel biologic to treat inflammatory diseases including radiation injury. We produced a new tag-free rhMFG-E8 protein by cloning the human MFG-E8 full-length coding sequence without any fusion tag into a mammalian vector and expressed it in HEK293-derived cells. The construct includes the leader sequence of cystatin S to maximize secretion of rhMFG-E8 into the culture medium. After purification and confirmation of the protein identity, we first evaluated its biological activity in vitro. We then determined its efficacy in vivo utilizing an experimental rodent model of radiation injury, i.e., partial body irradiation (PBI). HEK293 cell supernatant containing tag-free rhMFG-E8 protein was concentrated, purified, and rhMFG-E8 was verified by SDS-PAGE with the standard human MFG-E8 loaded as control and, mass spectrometry followed by analysis using MASCOT for peptide mass fingerprint. The biological activity of human cell-expressed tag-free rhMFG-E8 was superior to that of E. coli-expressed His-tagged rhMFG-E8. Toxicity, stability, and pharmacokinetic studies indicate that tag-free rhMFG-E8 is safe, highly stable after lyophilization and long-term storage, and with a terminal elimination half-life in circulation of at least 1.45 h. In the 15 Gy PBI model, a dose-dependent improvement of the 30-day survival rate was observed after tag-free rhMFG-E8 treatment with a 30-day survival of 89%, which was significantly higher than the 25% survival in the vehicle group. The dose modification factor (DMF) of tag-free rhMFG-E8 calculated using probit analysis was 1.058. Tag-free rhMFG-E8 also attenuated gastrointestinal damage after PBI suggesting it as a potential therapeutic candidate for a medical countermeasure for radiation injury. Our new human cell-expressed tag-free rhMFG-E8 has proper structural and functional properties to be further developed as a safe and effective therapy to treat victims of severe acute radiation injury.

[mRNA Expression Profile Changes in Angiotensin-Ⅱ-Induced Atrial Myocardial Fibrosis in Rats]

Objective

To study the differences between the mRNA expression profile in angiotensin Ⅱ (Ang Ⅱ)-induced fibrotic cardiomyocytes and that of normal cardiomyocytes and the relevant signaling pathways.

Methods

Six 8-week-old male Sprague-Dawley (SD) rats were randomly assigned to a control group and an Ang Ⅱ group, with 3 rats in each group. Rats in the control group were injected via caudal vein with 0.9% normal saline at 2 mg/kg per day, while rats in the Ang Ⅱ group were injected with Ang Ⅱ via caudal vein at 2 mg/kg per day. The medications were continuously administered in the two groups for 14 days. The degree of myocardial fibrosis was determined by Masson's Trichrome staining and the content of collagen Ⅰ was determined by immunohistochemistry. High throughput sequencing was performed to measure the mRNA expression of rat cardiomyocytes in the two groups and to screen for differentially-expressed mRNAs. The differentially-expressed mRNAs were analyzed by Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Results

Compared with those of the control group, the degree of myocardial fibrosis and the content of collagen Ⅰ in Ang Ⅱ group were significantly higher ( P<0.05). Through sequencing, 313 differentially-expressed mRNAs were identified, with 201 being up-regulated and 112 being down-regulated. Go and KEGG analyses showed that these differentially-expressed mRNA were involved in a variety of biological regulatory functions and pathways of myocardial fibrosis.

Conclusion

Ang Ⅱ can cause myocardial fibrosis in rats. There are significant differences in mRNA expression between fibrotic cardiomyocytes and normal cardiomyocytes. The differentially expressed mRNAs may play an important role in biological processes, including immune response, cell remodeling, and extracellular matrix deposition.

Effects and mechanism of Compound Qidan Formula on rats with HFpEF induced by hypertension and diabetes mellitus based on Ang Ⅱ/TGF-β1/Smads signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Compound Qidan Formula is composed of traditional Chinese herbs and has a good curative effect in the clinical application of cardiovascular diseases such as heart failure. However, its potential molecular mechanisms of action remain highly unknown.

AIM OF THE STUDY

To observe the effect of Compound Qidan Formula on cardiac function in rats with HFpEF induced by hypertension and diabetes mellitus, and to explore its mechanism from Ang Ⅱ/TGF-β1/Smads signaling pathway.

MATERIALS AND METHODS

A total of 50 SPF-grade spontaneously hypertensive rats (SHR) aged 14 weeks, fed with a high-fat and high-sucrose diet for 16 weeks, and after 2 weeks of a high-fat and high-sucrose diet, 1% streptozotocin (25 mg/kg body weight)was injected intraperitoneally to establish a rat model of HFpEF induced by hypertension and diabetes mellitus. After 8 weeks of intragastric administration, the changes in cardiac morphology and function were evaluated by echocardiography after anesthesia; the heart tissue was taken and embedded in paraffin for Masson staining, and the pathomorphological changes of left atrial tissue were observed under the optical microscope; the mRNA transcription levels of Ang Ⅱ, AT1R, TGF-β1, Smad2, Smad3, MMP-9 and TIMP-1in left atrial tissue of rats were detected by RT-PCR; and the protein expressions were detected by Western blot.

RESULTS

Compared with the SHR-DM group, the QD-Low and QD-High groups significantly decreased the left atrial (LA) anteroposterior diameter and interventricular septal thickness (IVST) and improved the peak velocity of mitral valve blood flow in early diastolic period (E), maximum mitral valve blood flow in systolic period (A), mitral ring myocardial movement velocity in early diastolic period (e') and E/e' ratio; the QD-High group significantly improved the E/A ratio, left atrial ejection fraction (LAEF) and left ventricular ejection fraction(LVEF). Masson staining showed that compared with the WKY group, the SHR-DM group had obvious myocardial histomorphological lesions. Compared with the SHR-DM group, the Compound Qidan Formula groups significantly improved cardiomyocyte hypertrophy and disordered arrangement and inhibited myocardial fibrosis; the mRNA expression levels of Ang Ⅱ, AT1R, TGF-β1, Smad2, Smad3, and MMP-9 in myocardial tissue of Compound Qidan Formula groups were significantly decreased, and the mRNA expression level of TIMP-1 was significantly increased. The protein expression levels of Ang Ⅱ, TGF-β1, P-Smad2/3, and MMP-9 were significantly decreased.

CONCLUSION

Compound Qidan Formula, composed of traditional Chinese herbs, can significantly improve cardiac function, improve atrial and ventricular remodeling, and prevent myocardial fibrosis and hypertrophy in rats with HFpEF induced by hypertension and diabetes mellitus. The mechanism may be related to regulating the Ang Ⅱ/TGF-β1/Smad2/3 signaling pathway.

SGLT2i alleviates epicardial adipose tissue inflammation by modulating ketone body-glyceraldehyde-3-phosphate dehydrogenase malonylation pathway

AIMS

Inflammation in the epicardial adipose tissue (EAT) is a contributor to atrial fibrillation. Studies have reported that sodium glucose co-transporter 2 inhibitor (SGLT2i) can alleviate EAT inflammation. However, the mechanism remains elusive. This study aims to investigate the molecular mechanism of SGLT2i in reducing EAT inflammation and to explore the effects of SGLT2i on atrial fibrosis in atrial fibrillation.

METHODS

Sprague-Dawley rats were injected with angiotensin II to induce atrial fibrillation and randomly assigned to receive SGLT2i ( n  = 6) or vehicle ( n  = 6). Macrophages (RAW264.7) were treated with ketone bodies; ACC1 knockdown/overexpression and malonyl-CoA overexpression were performed in vitro . The levels of inflammatory cytokines, ACC1, and malonyl-CoA were examined by ELISA. GAPDH malonylation was measured by co-immunoprecipitation.

RESULTS

In atrial fibrillation rats, SGLT2i increased the ketone body levels and decreased the expression of ACC1 and alleviated EAT inflammation and atrial fibrosis. In RAW264.7 cells, ketone bodies decreased the levels of ACC1, malonyl-CoA, and GAPDH malonylation, accompanied by reduced inflammatory cytokines. ACC1 knockdown decreased the expression of malonyl-CoA and GAPDH malonylation and alleviated lipopolysaccharide (LPS)-induced macrophage inflammation; these effects were inhibited by malonyl-CoA overexpression. Furthermore, the protective effects of ketone bodies on macrophage inflammation were abrogated by ACC1 overexpression.

CONCLUSION

SGLT2i alleviates EAT inflammation by reducing GAPDH malonylation via downregulating the expression of ACC1 through increasing ketone bodies, thus attenuating atrial fibrosis.

Human Keratinocyte-Derived Exosomal MALAT1 Promotes Diabetic Wound Healing by Upregulating MFGE8 via microRNA-1914-3p

Purpose

Diabetic wound is a highly prevalent and refractory disease. Extensive studies have confirmed that keratinocytes and macrophages play an important role in the process of wound healing. Additionally, exosomes are regarded as a vital intercellular communication tool. This study aimed to investigate the role of human keratinocyte-derived exosomal MALAT1 in the treatment of diabetic wound by influencing the biological function of macrophages.

Methods

We mainly assessed the function of MALAT1 on the biological changes of macrophages, and the expression of MALAT1 in the keratinocyte-exosomes analyzed by quantitative real-time polymerase chain reaction (RT-qPCR). The downstream interaction between RNAs or proteins was assessed by mechanistic experiments. Besides, we evaluated the effects of human keratinocyte-derived exosomal MALAT1 on diabetic wound healing in vivo to verify in vitro results.

Results

We demonstrated that human keratinocyte-derived exosomal MALAT1 enhanced the biological functions of high glucose-injured macrophages, including phagocytosis, converting to a pro-healing phenotype and reducing apoptosis. Mechanistically, MALAT1 accelerated the expression of MFGE8 by competitively binding to miR-1914-3p, thereby affecting the function of macrophages and the signal axis of TGFB1/SMAD3, and finally promoting the healing of diabetic wounds. Human keratinocyte-derived exosomal MALAT1 might promote collagen deposition, ECM remodeling, and expression of MFGE8, VEGF, and CD31 but reduce the expression of TGFB and SMAD3 in an in vivo model of diabetic mice wounds, which accelerated diabetic wound healing and restored its function.

Conclusion

The current study revealed that human keratinocyte-derived exosomal MALAT1 would suppress miR-1914-3p to activate MFGE8 and eventually promote wound healing by enhancing macrophage phagocytosis, converting to a pro-healing phenotype and reducing apoptosis. It proposed that keratinocyte-derived exosomes might have the capacity to serve as a new method for the clinical treatment of diabetic wound.

Vaspin Attenuates Atrial Abnormalities by Promoting ULK1/FUNDC1-Mediated Mitophagy

The worldwide incidence and prevalence of atrial fibrillation (AF) are increasing, making it a life-threatening condition due to the higher numbers of people suffering from obesity. Vaspin, an adipokine derived from epicardial adipose tissue, has been reported to reduce inflammation, inhibit apoptosis, and induce autophagy; however, its role in the pathogenesis of AF is not known. In this study, we investigated the role of vaspin in patients with AF and explored the molecular mechanisms using atrial myocytes in vitro. Our data showed that vaspin levels were significantly reduced in the plasma of patients with AF. Lower plasma levels of vaspin were also associated with a higher risk of AF in patients with obesity. Vaspin treatment in vitro alleviated cardiomyocyte injury, atrial fibrosis, atrial myocyte apoptosis, and mitochondrial injury in atrial myocytes following Ang-II stress. Moreover, our results demonstrated that vaspin protected against Ang-II-induced atrial myocyte dysfunction by inducing mitophagy. We also observed that vaspin treatment enhanced the phosphorylation of Fun14 domain-containing protein 1 (FUNDC1) at Ser17 by unc-51 like autophagy activating kinase 1 (ULK1), resulting in the induction of mitophagy. These positive effects of vaspin were reversed by ULK1 silencing in Ang-II-stimulated HL-1 cells. Our study is the first to propose that vaspin plays a vital role in AF pathogenesis via ULK1/FUNDC1-regulated mitophagy and could be a novel therapeutic target for AF.

MFG-E8 Exerts Neuroprotection in Neural Stem Cells Induced by Anesthetic Sevoflurane via Regulating the PI3K/AKT Pathways

MFG-E8 has shown tissue protection effects in various models of organ injury. In this study, the function of MFG-E8 in SEV-induced neural stem cells (NSCs) was studied. The cell viability and apoptosis affected by rhMFG-E8 were tested by MTT and flow cytometry analysis, respectively. Then, the mRNA expression of MFG-E8 was detected by qRT-PCR. The expression of SOD, GSF-Px, and MDA was assessed using ELISA assay. Western blot analysis was applied for assessing the expression of MFG-E8, BCL2, BAX, cleaved caspase-3, GRP-78, XBP-1, ATF-6, ATF-4, CHOP, p-PI3K, PI3K, p-AKT, and AKT. The pharmacological experiments suggested that both mRNA and protein expression of MFG-E8 were significantly decreased after 24 h, 48 h, and 72 h treatment with SEV, and the Western blot results displayed that 50 and 100 μg/ml rhMFG-E8 could evidently promote the expression of MFG-E8 in NSCs induced by SEV. Next, rhMFG-E8 reduced the apoptosis of NSCs induced by SEV through upregulating Bcl-2 and cleaved caspase-3 and downregulating Bax. Moreover, rhMFG-E8 alleviated the endoplasmic reticulum pressure of NSCs induced by SEV through decreasing the expression of GRP-78, XBP-1, ATF-6, ATF-4, and CHOP. In addition, the rhMFG-E8 could promote the expression of SOD and GSH-Px and inhibit the expression of MDA and LDH detected by the ELISA assay and LDH kit. Moreover, rhMFG-E8 elevated the expression of p-PI3K/PI3K and p-AKT/AKT, which were inhibited by SEV in NSCs. The results of this project supported that rhMFG-E8 protects neural activity in neural stem cells induced by anesthetic sevoflurane via regulating the PI3K/AKT pathways.

Inflammatory Role of Milk Fat Globule-Epidermal Growth Factor VIII in Age-Associated Arterial Remodeling

Background Age-associated aortic remodeling includes a marked increase in intimal medial thickness (IMT), associated with signs of inflammation. Although aortic wall milk fat globule-epidermal growth factor VIII (MFG-E8) increases with age, and is associated with aortic inflammation, it is not known whether MFG-E8 is required for the age-associated increase in aortic IMT. Here, we tested whether MFG-E8 is required for the age-associated increase in aortic IMT. Methods and Results To determine the role of MFG-E8 in the age-associated increase of IMT, we compared aortic remodeling in adult (20-week) and aged (96-week) MFG-E8 (-/-) knockout and age matched wild-type (WT) littermate mice. The average aortic IMT increased with age in the WT from 50±10 to 70±20 μm (P<0.0001) but did not significantly increase with age in MFG-E8 knockout mice. Because angiotensin II signaling is implicated as a driver of age-associated increase in IMT, we infused 30-week-old MFG-E8 knockout and age-matched littermate WT mice with angiotensin II or saline via osmotic mini-pumps to determine whether MFG-E8 is required for angiotensin II-induced aortic remodeling. (1) In WT mice, angiotensin II infusion substantially increased IMT, elastic lamina degradation, collagen deposition, and the proliferation of vascular smooth muscle cells; in contrast, these effects were significantly reduced in MFG-E8 KO mice; (2) On a molecular level, angiotensin II treatment significantly increased the activation and expression of matrix metalloproteinase type 2, transforming growth factor beta 1, and its downstream signaling molecule phosphorylated mother against decapentaplegic homolog 2, and collagen type I production in WT mice; however, in the MFG-E8 knockout mice, these molecular effects were significantly reduced; and (3) in WT mice, angiotensin II increased levels of aortic inflammatory markers phosphorylated nuclear factor-kappa beta p65, monocyte chemoattractant protein 1, tumor necrosis factor alpha, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 molecular expression, while in contrast, these inflammatory markers did not change in knockout mice. Conclusions Thus, MFG-E8 is required for both age-associated proinflammatory aortic remodeling and also for the angiotensin II-dependent induction in younger mice of an aortic inflammatory phenotype observed in advanced age. Targeting MFG-E8 would be a novel molecular approach to curb adverse arterial remodeling.

Downregulation of lncRNA Miat contributes to the protective effect of electroacupuncture against myocardial fibrosis

Background

Myocardial fibrosis changes the structure of myocardium, leads to cardiac dysfunction and induces arrhythmia and cardiac ischemia, threatening patients’ lives. Electroacupuncture at PC6 (Neiguan) was previously found to inhibit myocardial fibrosis. Long non-coding RNAs (lncRNAs) play a variety of regulatory functions in myocardial fibrosis, but whether electroacupuncture can inhibit myocardial fibrosis by regulating lncRNA has rarely been reported.

Methods

In this study, we constructed myocardial fibrosis rat models using isoproterenol (ISO) and treated rats with electroacupuncture at PC6 point and non-point as control. Hematoxylin–eosin, Masson and Sirius Red staining were performed to assess the pathological changes and collagen deposition. The expression of fibrosis-related markers in rat myocardial tissue were detected by RT-qPCR and Western blot. Miat, an important long non-coding RNA, was selected to study the regulation of myocardial fibrosis by electroacupuncture at the transcriptional and post-transcriptional levels. In post-transcriptional level, we explored the myocardial fibrosis regulation effect of Miat on the sponge effect of miR-133a-3p. At the transcriptional level, we studied the formation of heterodimer PPARG–RXRA complex and promotion of the TGF-β1 transcription.

Results

Miat was overexpressed by ISO injection in rats. We found that Miat can play a dual regulatory role in myocardial fibrosis. Miat can sponge miR-133a-3p in an Ago2-dependent manner, reduce the binding of miR-133a-3p target to the 3ʹUTR region of CTGF mRNA and improve the protein expression level of CTGF. In addition, it can also directly bind with PPARG protein, inhibit the formation of heterodimer PPARG–RXRA complex and then promote the transcription of TGF-β1. Electroacupuncture at PC6 point, but not at non-points, can reduce the expression of Miat, thus inhibiting the expression of CTGF and TGF-β1 and inhibiting myocardial fibrosis.

Conclusion

We revealed that electroacupuncture at PC6 point can inhibit the process of myocardial fibrosis by reducing the expression of lncRNA Miat, which is a potential therapeutic method for myocardial fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00615-6.

OTUD7B (Cezanne) ameliorates fibrosis after myocardial infarction via FAK-ERK/P38 MAPK signaling pathway

Fibrosis is one of the crucial reasons for cardiac dysfunction after myocardial infarction (MI). Understanding the underlying molecular mechanism that causes fibrosis is crucial to developing effective therapy. Recently, OUT domain-containing 7B (OTUD7B), also called Cezanne, a multifunctional deubiquitylate, has been found to play various roles in cancer and vascular diseases and control many important signaling pathways, including inflammation, proliferation, and so on. However, whether OTUD7B plays a role in fibrosis caused by MI remains unclear. Our study aimed to explore the function of OTUD7B in cardiac fibrosis and investigate the underlying mechanism. We found that the expression of OTUD7B was downregulated in the MI rat model and cultured cardiac fibroblasts (CFs) in hypoxic conditions and after TGF-β1 treatment. In vitro, silencing OTUD7B using small interfering RNA (siRNA) increased α-SMA (smooth muscle actin α) and collagen Ⅰ levels in CFs, whereas the overexpression of OTUD7B using adenovirus decreased their expression. Mechanistically, OTUD7B could regulate the phosphorylation of focal adhesion kinase (FAK), a non-receptor tyrosine kinase that has been proved to act as a potential mediator of fibrosis, and ERK/P38 MAPK was involved in this regulation process. In vitro, overexpression of OTUD7B downregulated the phosphorylation level of FAK and then inhibited ERK/P38 phosphorylation, thus leading to decreased α-SMA and collagen Ⅰ expressions, while OTUD7B knockdown showed an opposite result. These findings suggest that OTUD7B could become a potentially effective therapeutic strategy against fibrosis after MI.

Epicardial adipose tissue, obesity and the occurrence of atrial fibrillation: an overview of pathophysiology and treatment methods

INTRODUCTION

Obesity is a chronic disease, which has significant health consequences and is a staggering burden to health care systems. Obesity can have harmful effects on the cardiovascular system, including heart failure, hypertension, coronary heart disease, and atrial fibrillation (AF). One of the possible substrates might be epicardial adipose tissue (EAT), which can be the link between AF and obesity. EAT is a fat deposit located between the myocardium and the visceral pericardium. Numerous studies have demonstrated that EAT plays a pivotal role in this relationship regarding atrial fibrillation.

AREAS COVERED

This review will focus on the role of obesity and the occurrence of atrial fibrillation (AF) and examine the connection between these and epicardial adipose tissue (EAT). The first part of this review will explain the pathophysiology of EAT and its association with the occurrence of AF. Secondly, we will review bariatric and metabolic surgery and its effects on EAT and AF.

EXPERT COMMENTARY

In this review, the epidemiology, pathophysiology, and treatments methods of AF are explained. Secondly the effects on EAT were elucidated. Due to the complex pathophysiological link between EAT, AF, and obesity, it is still uncertain which treatment strategy is superior.

Lactadherin: From a Well-Known Breast Tumor Marker to a Possible Player in Extracellular Vesicle-Mediated Cancer Progression

Lactadherin is a secreted glycoprotein associated with the milk fat globule membrane, which is highly present in the blood and in the mammary tissue of lactating women. Several biological functions have been associated with this protein, mainly attributable to its immunomodulatory role promoting phagocyte-mediated clearance of apoptotic cells. It has been shown that lactadherin also plays important roles in cell adhesion, the promotion of angiogenesis, and tissue regeneration. On the other hand, this protein has been used as a marker of breast cancer and tumor progression. Recently, high levels of lactadherin has been associated with poor prognosis and decreased survival, not only in breast cancer, but also in melanoma, ovarian, colorectal, and other types of cancer. Although the mechanisms responsible for the tumor-promoting effects attributed to lactadherin have not been fully elucidated, a growing body of literature indicates that lactadherin could be a promising therapeutic target and/or biomarker for breast and other tumors. Moreover, recent studies have shown its presence in extracellular vesicles derived from cancer cell lines and cancer patients, which was associated with cancer aggressiveness and worse prognosis. Thus, this review will focus on the link between lactadherin and cancer development and progression, its possible use as a cancer biomarker and/or therapeutic target, concluding with a possible role of this protein in cellular communication mediated by extracellular vesicles.

Comparison of the Mid-Term Outcomes of Robotic Magnetic Navigation-Guided Radiofrequency Ablation versus Cryoballoon Ablation for Persistent Atrial Fibrillation

Introduction: Currently, numerous ablation techniques are available for atrial fibrillation (AF), in addition to manual radio frequency ablation. The aim of this prospective, non-randomized concurrent controlled trial was to compare the mid-term efficacy and procedural outcomes of persistent AF (PerAF) using cryoballoon (CB) and robotic magnetic navigation (RMN). Methods: Two hundred PerAF patients were assigned, in a 1:1 ratio, to undergo catheter ablation using RMN (RMN group) or CB (CB group). The primary endpoint was freedom from AF recurrence following a 3-month period after the index ablation. The secondary endpoint was peri-procedural outcomes, including the total procedure time, left atrial procedure time, fluoroscopy time, and fluoroscopy dose. The Two-step cluster analysis was used to determine the efficacy of RMN and CB between the different groups. The Cox proportional hazard model and restricted cubic spline were used to determine predictors for AF recurrence. Results: At the mean follow-up of 28.1 ± 9.7 months, the primary endpoint was achieved in 71 PerAF patients in the RMN group and in 62 PerAF patients in the CB group (71% vs. 62%, p = 0.158). Compared with CB, RMN-guided ablation led to a longer procedure time (p < 0.001), but with less radiation (p < 0.001). Cluster analysis returned two clusters of patients and RMN was favorable for one cluster (p = 0.037), in which more patients presented with diabetes mellitus and smaller left atria. Conclusions: For patients with PerAF, CB is generally equivalent to RMN-guided ablation with regard to overall efficacy. RMN-guided ablation could be favorable in specific patient populations presenting with diabetes mellitus and smaller left atria.

Cordyceps cicadae Ameliorates Renal Hypertensive Injury and Fibrosis Through the Regulation of SIRT1-Mediated Autophagy

Hypertensive renal injury is a complication of hypertension. Cordyceps cicadae (C. cicadae) is a traditional Chinese medicine used to treat chronic kidney diseases especially renal fibrosis. Autophagy is described as a cell self-renewal process that requires lysosomal degradation and is utilized for the maintenance of cellular energy homeostasis. The present study explores the mechanism underlying C. cicadae’s renoprotection on hypertensive nephropathy (HN). First, HN rat models were established on spontaneously hypertensive rats (SHRs). The expression of fibrosis-related protein and autophagy-associated protein was detected in vivo. NRK-52E cells exposed to AngII were chosen to observe the potential health benefits of C. cicadae on renal damage. The level of extracellular matrix accumulation was detected using capillary electrophoresis immunoquantification and immunohistochemistry. After treatment with lysosomal inhibitors (chloroquine) or an autophagy activator (rapamycin), the expression of Beclin-1, LC3II, and SQSTM1/p62 was further investigated. The study also investigated the change in sirtuin1 (SIRT1), fork head box O3a (FOXO3a), and peroxidation (superoxide dismutase (SOD) and malondialdehyde (MDA)) expression when intervened by resveratrol. The changes in SIRT1 and FOXO3a were measured in patients and the SHRs. Here, we observed that C. cicadae significantly decreased damage to renal tubular epithelial cells and TGFβ1, α-smooth muscle actin (α-SMA), collagen I (Col-1), and fibronectin expression. Meanwhile, autophagy defects were observed both in vivo and in vitro. C. cicadae intervention significantly downregulated Beclin-1 and LC3II and decreased SQSTM1/p62, showing an inhibition of autophagic vesicles and the alleviation of autophagy stress. These functions were suppressed by rapamycin, and the results were just as effective as the resveratrol treatment. HN patients and the SHRs exhibited decreased levels of SIRT1 and FOXO3a. We also observed a positive correlation between SIRT1/FOXO3a and antifibrotic effects. Similar to the resveratrol group, the expression of SIRT1/FOXO3a and oxidative stress were elevated by C. cicadae in vivo. Taken together, our findings show that C. cicadae ameliorates tubulointerstitial fibrosis and delays HN progression. Renoprotection was likely attributable to the regulation of autophagic stress mediated by the SIRT1 pathway and achieved by regulating FOXO3a and oxidative stress.

ADAMTS8 Promotes Cardiac Fibrosis Partly Through Activating EGFR Dependent Pathway

Myocardial infarction or pressure overload leads to cardiac fibrosis, the leading cause of heart failure. ADAMTS8 (A disintegrin and metalloproteinase with thrombospondin motifs 8) has been reported to be involved in many fibrosis-related diseases. However, the specific role of ADAMTS8 in cardiac fibrosis caused by myocardial infarction or pressure overload is yet unclear. The present study aimed to explore the function of ADAMTS8 in cardiac fibrosis and its underlying mechanism. ADAMTS8 expression was significantly increased in patients with dilated cardiomyopathy; its expression myocardial infarction and TAC rat models was also increased, accompanied by increased expression of α-SMA and Collagen1. Adenovirus-mediated overexpression of ADAMTS8 through cardiac in situ injection aggravated cardiac fibrosis and impaired cardiac function in the myocardial infarction rat model. Furthermore, in vitro studies revealed that ADAMTS8 promoted the activation of cardiac fibroblasts; ADAMTS8 acted as a paracrine mediator allowing for cardiomyocytes and fibroblasts to communicate indirectly. Our findings showed that ADAMTS8 could damage the mitochondrial function of cardiac fibroblasts and then activate the PI3K-Akt pathway and MAPK pathways, promoting up-regulation of YAP expression, with EGFR upstream of this pathway. This study systematically revealed the pro-fibrosis effect of ADAMTS8 in cardiac fibrosis and explored its potential role as a therapeutic target for the treatment of cardiac fibrosis and heart failure.

Hydrogen Sulfide Ameliorates Angiotensin II-Induced Atrial Fibrosis Progression to Atrial Fibrillation Through Inhibition of the Warburg Effect and Endoplasmic Reticulum Stress

Atrial fibrosis is the basis for the occurrence and development of atrial fibrillation (AF) and is closely related to the Warburg effect, endoplasmic reticulum stress (ERS) and mitochondrion dysfunctions-induced cardiomyocyte apoptosis. Hydrogen sulfide (H₂S) is a gaseous signalling molecule with cardioprotective, anti-myocardial fibrosis and improved energy metabolism effects. Nevertheless, the specific mechanism by which H₂S improves the progression of atrial fibrosis to AF remains unclear. A case-control study of patients with and without AF was designed to assess changes in H₂S, the Warburg effect, and ERS in AF. The results showed that AF can significantly reduce cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate thiotransferase (3-MST) expression and the H₂S level, induce cystathionine-β-synthase (CBS) expression; increase the Warburg effect, ERS and atrial fibrosis; and promote left atrial dysfunction. In addition, AngII-treated SD rats had an increased Warburg effect and ERS levels and enhanced atrial fibrosis progression to AF compared to wild-type SD rats, and these conditions were reversed by sodium hydrosulfide (NaHS), dichloroacetic acid (DCA) or 4-phenylbutyric acid (4-PBA) supplementation. Finally, low CSE levels in AngII-induced HL-1 cells were concentration- and time-dependent and associated with mitochondrial dysfunction, apoptosis, the Warburg effect and ERS, and these effects were reversed by NaHS, DCA or 4-PBA supplementation. Our research indicates that H₂S can regulate the AngII-induced Warburg effect and ERS and might be a potential therapeutic drug to inhibit atrial fibrosis progression to AF.

Updates on epicardial adipose tissue mechanisms on atrial fibrillation

Obesity is a well-known risk factor for atrial fibrillation (AF). Local epi-myocardial or intra-myocardial adiposity caused by aging, obesity, or cardiovascular disease (CVD) is considered to be a better predictor of the risk of AF than general adiposity. Some of the described mechanisms suggest that epicardial adipose tissue (EAT) participates in structural remodeling owing to its endocrine activity or its infiltration between cardiomyocytes. Epicardial fat also wraps up the ganglionated plexi that reach the myocardium. Although the increment of volume/thickness and activity of EAT might modify autonomic activity, autonomic system dysfunction might also change the endocrine activity of epicardial fat in a feedback response. As a result, new preventive therapeutic strategies are focused on reducing adiposity and weight loss before AF ablation or inhibiting autonomic neurotransmitter secretion on fat pads during open-heart surgery to reduce the recurrence or postoperative risk of AF. In this manuscript, we review some of the novel findings regarding the pathophysiology and associated risk factors of AF, with special emphasis on the role of EAT in the electrical, structural, and molecular mechanisms of AF initiation and maintenance. In addition, we have included a brief note provided on epicardial fat preclinical models that could be useful for identifying new therapeutic targets.

Molecular Insights in Atrial Fibrillation Pathogenesis and Therapeutics: A Narrative Review

The prevalence of atrial fibrillation (AF) is bound to increase globally in the following years, affecting the quality of life of millions of people, increasing mortality and morbidity, and beleaguering health care systems. Increasingly effective therapeutic options against AF are the constantly evolving electroanatomic substrate mapping systems of the left atrium (LA) and ablation catheter technologies. Yet, a prerequisite for better long-term success rates is the understanding of AF pathogenesis and maintenance. LA electrical and anatomical remodeling remains in the epicenter of current research for novel diagnostic and treatment modalities. On a molecular level, electrical remodeling lies on impaired calcium handling, enhanced inwardly rectifying potassium currents, and gap junction perturbations. In addition, a wide array of profibrotic stimuli activates fibroblast to an increased extracellular matrix turnover via various intermediaries. Concomitant dysregulation of the autonomic nervous system and the humoral function of increased epicardial adipose tissue (EAT) are established mediators in the pathophysiology of AF. Local atrial lymphomononuclear cells infiltrate and increased inflammasome activity accelerate and perpetuate arrhythmia substrate. Finally, impaired intracellular protein metabolism, excessive oxidative stress, and mitochondrial dysfunction deplete atrial cardiomyocyte ATP and promote arrhythmogenesis. These overlapping cellular and molecular alterations hinder us from distinguishing the cause from the effect in AF pathogenesis. Yet, a plethora of therapeutic modalities target these molecular perturbations and hold promise in combating the AF burden. Namely, atrial selective ion channel inhibitors, AF gene therapy, anti-fibrotic agents, AF drug repurposing, immunomodulators, and indirect cardiac neuromodulation are discussed here.

Rare Coding Variants Associated With Electrocardiographic Intervals Identify Monogenic Arrhythmia Susceptibility Genes: A Multi-Ancestry Analysis

BACKGROUND

Alterations in electrocardiographic (ECG) intervals are well-known markers for arrhythmia and sudden cardiac death (SCD) risk. While the genetics of arrhythmia syndromes have been studied, relations between electrocardiographic intervals and rare genetic variation at a population level are poorly understood.

METHODS

Using a discovery sample of 29 000 individuals with whole-genome sequencing from Trans-Omics in Precision Medicine and replication in nearly 100 000 with whole-exome sequencing from the UK Biobank and MyCode, we examined associations between low-frequency and rare coding variants with 5 routinely measured electrocardiographic traits (RR, P-wave, PR, and QRS intervals and corrected QT interval).

RESULTS

We found that rare variants associated with population-based electrocardiographic intervals identify established monogenic SCD genes (KCNQ1, KCNH2, and SCN5A), a controversial monogenic SCD gene (KCNE1), and novel genes (PAM and MFGE8) involved in cardiac conduction. Loss-of-function and pathogenic SCN5A variants, carried by 0.1% of individuals, were associated with a nearly 6-fold increased odds of the first-degree atrioventricular block (P=8.4×10^-5). Similar variants in KCNQ1 and KCNH2 (0.2% of individuals) were associated with a 23-fold increased odds of marked corrected QT interval prolongation (P=4×10^-25), a marker of SCD risk. Incomplete penetrance of such deleterious variation was common as over 70% of carriers had normal electrocardiographic intervals.

CONCLUSIONS

Our findings indicate that large-scale high-depth sequence data and electrocardiographic analysis identifies monogenic arrhythmia susceptibility genes and rare variants with large effects. Known pathogenic variation in conventional arrhythmia and SCD genes exhibited incomplete penetrance and accounted for only a small fraction of marked electrocardiographic interval prolongation.

Sacubitril/Valsartan Decreases Atrial Fibrillation Susceptibility by Inhibiting Angiotensin II-Induced Atrial Fibrosis Through p-Smad2/3, p-JNK, and p-p38 Signaling Pathways

Sacubitril/valsartan (SAC/VAL) prevents angiotensin II (AngII) from binding AT1-R and blocks degradation of natriuretic peptides. Despite its efficacy in reducing ventricular fibrosis and preserving cardiac functions, which has been extensively demonstrated in myocardial infarction or pressure overload models, few studies have been conducted to determine whether SAC/VAL could attenuate atrial fibrosis and decrease atrial fibrillation (AF) susceptibility. Our study provided evidence for the inhibition of atrial fibrosis and reduced susceptibility to AF by SAC/VAL. After 28 days of AngII continuous subcutaneous stimulation, rats in SAC/VAL group exhibited reduced extent of atrial fibrosis, inhibited proliferation, migration, and differentiation of atrial fibroblasts, and decreased susceptibility to AF. We further found that inhibition of p-Smad2/3, p-JNK, and p-p38MAPK pathways is involved in the role of SAC/VAL on AngII-induced atrial fibrosis in vivo. These results emphasize the importance of SAC/VAL in the prevention of AngII-induced atrial fibrosis and may help to enrich the options for AF pharmacotherapy.

Hypoxia-induced retinal pigment epithelium cell-derived bFGF promotes the migration and angiogenesis of HUVECs through regulating TGF-β1/smad2/3 pathway

Hypoxia promotes the secretion of basic fibroblast growth factor (bFGF) in retinal pigment epithelium (RPE), which plays an important part in retinopathy of prematurity (ROP). This study preliminarily explored the effect of hypoxia-induced RPE-derived bFGF on the biological functions of human umbilical vein endothelial cells (HUVECs). After cell culture in hypoxia conditions, the cell viability, apoptosis, and the expressions of bFGF and vascular endothelial growth factor A (VEGFA) in human RPEs were detected by 3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), flow cytometry, western blot, RT-qPCR, or ELISA. The HUVECs were transfected with siRNA for bFGF (sibFGF) or transforming growth factor-β1 (TGF-β1) (siTGF-β1) and grown in the supernatant RPE under normoxia conditions or hypoxia conditions to further determine the cell viability, migration, angiogenesis, and the expressions of TGF-β1, p-smad2/3, and smad2/3 in the cells by performing MTT, transwell, tube formation, Western blot, or RT-qPCR. Hypoxia culture decreased the cell viability and promoted the apoptosis as well as the expressions of bFGF and VEGFA in RPEs. In both normoxia and hypoxia conditions, RPE-derived bFGF increased the cell viability, migration, angiogenesis, and the expressions of TGF-β1 and p-smad2/3 in the HUVECs, with hypoxia-induced RPE-derived bFGF showing a stronger effect than bFGF induced by normoxia. However, sibFGF reversed the effects caused by RPE-derived bFGF. Moreover, siTGF-β1 decreased the high cell viability, migration and angiogenesis of HUVECs, and downregulated the expressions of TGF-β1 and phosphorylated (p)-smad2/3 upregulated by hypoxia-induced RPE-derived bFGF. Hypoxia-induced RPE-derived bFGF could promote the migration and angiogenesis of HUVECs through regulating TGF-β1/smad2/3 pathway.

Fus knockdown inhibits the profibrogenic effect of cardiac fibroblasts induced by angiotensin II through targeting Pax3 thereby regulating TGF-β1/Smad pathway

The Angiotensin II/transforming growth factor-β1 (AngII/TGF-β1) signal axis is an important regulatory pathway for atrial fibrosis, which can contribute to atrial fibrillation (AF). Fused in sarcoma (FUS) was recently found to regulate cardiac diseases. This study aimed to investigate whether FUS could regulate AngII induced fibrosis and uncover the possible mechanisms. The expression of FUS in AF patients and AngII-induced cardiac fibroblasts was measured by RT-qPCR and western blot assays. Fus was silenced in cells using short hairpin RNA (shRNA), then cell proliferation, migration, collagen synthesis and TGF-β1/Smad signaling were detected by CCK-8, wound healing and western blot assays, respectively. The possible target for Fus was predicted by searching Starbase database and verified by RNA-binding protein immunoprecipitation (RIP) and RNA pull down. Cells were overexpressed with Pax3 in the presence of Fus silence and AngII stimulation, then the above cellular processes were further evaluated. Results showed that FUS was upregulated in AF patients and AngII-induced cardiac fibroblasts. Fus knockdown inhibited AngII-enhanced cell proliferation, migration, collagen synthesis and TGF-β1/Smad signaling activation. Furthermore, Fus functions as an RNA-binding protein to bind to Pax3 mRNA and positively regulate its expression. Further studies demonstrated that Pax3 overexpression canceled the above effects of Fus knockdown on cell proliferation, migration, collagen synthesis, and TGF-β1/Smad signaling activation in AngII-induced cells. In conclusion, Fus could target Pax3 to increase the pro-fibrotic effect of AngII in cardiac fibroblasts via activating TGF-β1/Smad signaling. Knockdown of Fus/Pax3 axis may provide a potential therapy for relieving AF.

C1q/TNF-Related Protein 9 Inhibits Coxsackievirus B3-Induced Injury in Cardiomyocytes through NF-κB and TGF-β1/Smad2/3 by Modulating THBS1

C1q/TNF-related protein 9 (CTRP9) is implicated in diverse cardiovascular diseases, but its role in viral myocarditis (VMC) is not well explored. This study is aimed at investigating the role and potential mechanism of CTRP9 in VMC. Herein, we found that the peripheral blood collected from children with VMC had lower CTRP9 levels than that from children who had recovered from VMC. H9c2 cardiomyocytes treated with coxsackievirus B3 (CVB3) were applied to establish a VMC model in vitro, and the expression of CTRP9 was significantly decreased in CVB3-induced H9c2 cells. The overexpression of CTRP9 attenuated CVB3-induced apoptosis, inflammation, and fibrosis reactions in H9c2 cells by promoting cell proliferation, reducing the cell apoptosis rate, and inhibiting inflammatory cytokine levels and fibrosis-related gene expression. Moreover, we found that thrombospondin 1 (THBS1) levels were increased in children with VMC, and CTRP9 negatively regulated THBS1 expression by interacting with THBS1. The downregulation of THBS1 inhibited CVB3-induced apoptosis, inflammation, and fibrosis in H9c2 cells. In addition, our mechanistic investigation indicated that the overexpression of THBS1 impaired the inhibitory effect of CTRP9 on CVB3-induced H9c2 cells. The results further revealed that the CVB3-induced NF-κB and TGF-β1/Smad2/3 signaling pathways of H9c2 cells were blocked by CTRP9 yet activated by THBS1. In conclusion, CTRP9 protected H9c2 cells from CVB3-induced injury via the NF-κB and TGF-β1/Smad2/3 signaling pathways by modulating THBS1.

How transforming growth factor contributes to atrial fibrillation?

Atrial fibrillation (AF) is the most common clinically significant arrhythmia. There are four fundamental pathophysiological mechanisms of AF including: electrical remodeling, structural remodeling, autonomic nervous system changes, and Ca2+ handling abnormalities. The transforming growth factor-β (TGF-β) superfamily are cytokines that have the ability to regulate numerous cell functions including proliferation, differentiation, apoptosis, epithelial-mesenchymal transition, and production of extracellular matrix. During the last decade numerous studies have demonstrated that TGF-β affects the architecture of the heart. TGF-β1 has been shown to be involved in the development and propagation of atrial fibrillation (AF). Investigators have studied TGF-β signaling in AF with the aim of discovering potential therapeutic agents. In this review we discuss the role of TGF-β in atrial fibrillation and specifically its role in atrial structural and electrical remodeling.

LncRNA NRON promotes M2 macrophage polarization and alleviates atrial fibrosis through suppressing exosomal miR-23a derived from atrial myocytes

BACKGROUND/PURPOSE

miR-23a is a pro-hypertrophic miRNA that inhibits M2 macrophage polarization. A previous study demonstrated that lncRNA NRON alleviated atrial fibrosis through suppression of M1 macrophages activated by atrial myocytes. This study aimed to determine whether NRON promotes M2 macrophage polarization and alleviates atrial fibrosis through suppressing exosomal miR-23a derived from atrial myocytes.

METHODS

Mouse atrial myocytes were transfected with the NRON overexpression vector or empty vector, followed by Ang II treatment. Exosomes were isolated from the treated atrial myocytes and then co-cultured with RAW264.7 macrophages. The culture medium from RAW264.7 macrophages treated as described above was added to mouse atrial fibroblasts for incubation.

RESULTS

We found that exosomes derived from Ang II-treated atrial myocytes inhibited M2 macrophage polarization by transferring miR-23a. NFATc3 could directly bind to the miR-23a promoter. Overexpression of NRON inhibited the expression of miR-23a by inhibiting NFATc3 nuclear transport in Ang II-treated atrial myocytes, resulting in a decrease in the level of miR-23a in atrial myocyte-derived exosomes. Meanwhile, exosomes derived from NRON-overexpressing atrial myocytes promoted M2 macrophage polarization and inhibited expression of fibrosis markers in atrial fibroblasts.

CONCLUSION

NRON promotes M2 macrophage polarization and alleviates atrial fibrosis through suppressing exosomal miR-23a derived from atrial myocytes.

MFGE8 is down-regulated in cardiac fibrosis and attenuates endothelial-mesenchymal transition through Smad2/3-Snail signalling pathway

Endothelial‐mesenchymal transition (EndMT) is a major source of transformed cardiac fibroblasts, which is reported to play a key role in cardiac fibrosis (CF), a pathogenesis of cardiovascular diseases such as heart failure, myocardial infarction and atrial fibrillation. Nonetheless, the specific mechanism underlying the progression of EndMT to CF is still largely unknown. In this study, we aimed to investigate the role of milk fat globule‐EGF factor 8 (MFGE8), a kind of soluble glycoprotein, in TGF‐β1‐induced EndMT. In animal experiments, the expression of MFGE8 was found down‐regulated in the left ventricle and aorta of rats after transverse aortic constriction (TAC) compared with the sham group, especially in endothelial cells (ECs). In in vitro cultured ECs, silencing MFGE8 with small interfering RNA (siRNA) was found to promote the process of TGF‐β1‐induced EndMT, whereas administration of recombinant human MFGE8 (rh‐MFGE8) attenuated the process. Moreover, activated Smad2/3 signalling pathway after TGF‐β1 treatment and EndMT‐related transcription factors, such as Snail, Twist and Slug, was potentiated by MFGE8 knock‐down but inhibited by rh‐MFGE8. In conclusion, our experiments indicate that MFGE8 might play a protective role in TGF‐β1‐induced EndMT and might be a potential therapeutic target for cardiac fibrosis.

NLRC5 deficiency ameliorates cardiac fibrosis in diabetic cardiomyopathy by regulating EndMT through Smad2/3 signaling pathway

Diabetic cardiomyopathy (DCM) is one of the main causes of heart failure in patients with diabetes. Cardiac fibrosis caused by endothelial mesenchymal transformation (EndMT) plays an important role in the pathogenesis of DCM. NLRC5 is a recently discovered immune and inflammatory regulatory molecule in the NOD-like receptor family, and is involved in organ fibrosis. In this study, we found that the expression of NLRC5 was up-regulated in endothelial cells (ECs) and cardiac fibroblasts (CFs) in diabetes models both in vivo and in vitro. NLRC5 knockdown significantly inhibited high glucose-induced EndMT. In addition, NLRC5 deficiency inhibited the expression of phosphorylated Smad2/3 and the activation of EndMT-related transcription factors in ECs induced by high glucose. However, the effect of NLRC5 deficiency on CFs was not obvious. In summary, our results suggest that NLRC5 deficiency ameliorates cardiac fibrosis in DCM by inhibiting EndMT through Smad2/3 signaling pathway and related transcription factors. NLRC5 is likely to be a biomarker and therapeutic target of cardiac fibrosis in diabetic cardiomyopathy.

Delphinidin attenuates pathological cardiac hypertrophy via the AMPK/NOX/MAPK signaling pathway

Reactive oxygen species (ROS) play a pivotal role in the development of pathological cardiac hypertrophy. Delphinidin, a natural flavonoid, was reported to exert marked antioxidative effects. Therefore, we investigated whether delphinidin ameliorates pathological cardiac hypertrophy via inhibiting oxidative stress. In this study, male C57BL/6 mice were treated with DMSO or delphinidin after surgery. Neonatal rat cardiomyocytes (NRCMs) were treated with angiotensin II (Ang II) and delphinidin in vitro. Eighteen-month-old mice were administered delphinidin to investigate the effect of delphinidin on aging-related cardiac hypertrophy. Through analyses of hypertrophic cardiomyocyte growth, fibrosis and cardiac function, delphinidin was demonstrated to confer resistance to aging- and transverse aortic constriction (TAC)-induced cardiac hypertrophy in vivo and attenuate Ang II-induced cardiomyocyte hypertrophy in vitro by significantly suppressing hypertrophic growth and the deposition of fibrosis. Mechanistically, delphinidin reduced ROS accumulation upon Ang II stimulation through the direct activation of AMP-activated protein kinase (AMPK) and subsequent inhibition of the activity of Rac1 and expression of p47^phox. In addition, excessive levels of ERK1/2, P38 and JNK1/2 phosphorylation induced by oxidative stress were abrogated by delphinidin. Delphinidin was conclusively shown to repress pathological cardiac hypertrophy by modulating oxidative stress through the AMPK/NADPH oxidase (NOX)/mitogen-activated protein kinase (MAPK) signaling pathway.