β-catenin/LEF1/IGF-IIR Signaling Axis Galvanizes the Angiotensin-II- induced Cardiac Hypertrophy

Accumulated β-catenin is associated with human atrial fibrosis and atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is associated with increased risk of stroke and mortality. It has been reported that the process of atrial fibrosis was regulated by β-catenin in rats with AF. However, pathophysiological mechanisms of this process in human with AF remain unclear. This study aims to investigate the possible mechanisms of β-catenin in participating in the atrial fibrosis using human right atrial appendage (hRAA) tissues .

METHODS

We compared the difference of β-catenin expression in hRAA tissues between the patients with AF and sinus rhythm (SR). The possible function of β-catenin in the development of AF was also explored in mice and primary cells.

RESULTS

Firstly, the space between the membrane of the gap junctions of cardiomyocytes was wider in the AF group. Secondly, the expression of the gap junction function related proteins, Connexin40 and Connexin43, was decreased, while the expression of β-catenin and its binding partner E-cadherin was increased in hRAA and cardiomyocytes of the AF group. Thirdly, β-catenin colocalized with E-cadherin on the plasma membrane of cardiomyocytes in the SR group, while they were dissociated and accumulated intracellularly in the AF group. Furthermore, the expression of glycogen synthase kinase 3β (GSK-3β) and Adenomatous Polyposis Coli (APC), which participated in the degradation of β-catenin, was decreased in hRAA tissues and cardiomyocytes of the AF group. Finally, the development of atrial fibrosis and AF were proved to be prevented after inhibiting β-catenin expression in the AF model mice.

CONCLUSIONS

Based on human atrial pathological and molecular analyses, our findings provided evidence that β-catenin was associated with atrial fibrosis and AF progression.

Sesamin suppresses angiotensin-II-enhanced oxidative stress and hypertrophic markers in H9c2 cells

Myocardial hypertrophy plays a crucial role in cardiovascular disease (CVD) development. Myocardial hypertrophy is an adaptive response by myocardial cells to stress after cardiac injury to maintain cardiac output and function. Angiotensin II (Ang-II) regulates CVD through the renin-angiotensin-aldosterone system, and its signaling in cardiac myocytes leads to excessive reactive oxygen species (ROS) production, oxidative stress, and inflammation. Sesamin (SA), a natural compound in sesame seeds, has anti-inflammatory and anti-apoptotic effects. This study investigated whether SA could attenuate hypertrophic damage and oxidative injuries in H9c2 cells under Ang-II stimulation. We found that SA decreased the cell surface area. Furthermore, Ang-II treatment reduced Ang-II-increased ANP, BNP, and β-MHC expression. Ang-II enhanced NADPH oxidase activity, ROS formation, and decreased Superoxide Dismutase (SOD) activity. SA treatment reduces Ang-II-caused oxidative injuries. We also found that SA mitigates Ang-II-induced apoptosis and pro-inflammatory responses. In conclusion, SA could attenuate Ang-II-induced cardiac hypertrophic injuries by inhibiting oxidative stress, apoptosis, and inflammation in H9c2 cells. Therefore, SA might be a potential supplement for CVD management.

WNT/β-catenin pathway is a key regulator of cardiac function and energetic metabolism

The WNT/β-catenin pathway is a master regulator of cardiac development and growth, and its activity is low in healthy adult hearts. However, even this low activity is essential for maintaining normal heart function. Acute activation of the WNT/β-catenin signaling cascade is considered to be cardioprotective after infarction through the upregulation of prosurvival genes and reprogramming of metabolism. Chronically high WNT/β-catenin pathway activity causes profibrotic and hypertrophic effects in the adult heart. New data suggest more complex functions of β-catenin in metabolic maturation of the perinatal heart, establishing an adult pattern of glucose and fatty acid utilization. Additionally, low basal activity of the WNT/β-catenin cascade maintains oxidative metabolism in the adult heart, and this pathway is reactivated by physiological or pathological stimuli to meet the higher energy needs of the heart. This review summarizes the current state of knowledge of the organization of canonical WNT signaling and its function in cardiogenesis, heart maturation, adult heart function, and remodeling. We also discuss the role of the WNT/β-catenin pathway in cardiac glucose, lipid metabolism, and mitochondrial physiology.

Association of DNA methylation and transcriptome reveals epigenetic etiology of heart failure

Epigenetic modifications viz. DNA methylation, histone modifications, and RNA-based alterations play a crucial role in the development of cardiovascular diseases. In this study, we investigated DNA methylation with an aim to reveal the epigenetic etiology of heart failure. Sprague-Dawley rats surviving myocardial infarction developed acute heart failure in 1 week. Genomic DNA methylation changes were profiled by bisulfite sequencing, and gene expression levels were analyzed by RNA-seq in failing and sham-operation hearts. A total of 3480 differentially methylated genes in the promoter regions including transcriptional start site and 1934 transcriptome-altered genes were identified in the defected hearts. Common differential genes were enriched by the gene ontology, Kyoto Encyclopedia of Genes and Genomes pathway, and protein-protein interaction for HF phenotypes. Among these, Mettl11b, HDAC3, HDAC11, ubiquitination-related genes, and snoRNAs are new epigenetic classifiers that had not been reported yet, which may be important regulators in HF.

Angiotensin II receptor blocker irbesartan attenuates sleep apnea-induced cardiac apoptosis and enhances cardiac survival and Sirtuin 1 upregulation

BACKGROUND

The purpose of this study was to investigate whether or not angiotensin II type 1 receptor blocker irbesartan (ARB) with a partial agonist of PPAR-γ could protect against chronic nocturnal intermittent hypoxia (CIH)-induced cardiac Fas/FasL-mediated to mitochondria-mediated apoptosis.

METHODS

Sprague-Dawley rats were in a normoxic control group (CON-G), or rats were in a chronic nocturnal intermittent hypoxia group (HP-G, from 3 to 7% oxygen versus 21% oxygen per forty seconds cycle, nocturnally 8 h per day for 1 month), or rats were in a chronic nocturnal intermittent hypoxia group pretreated with ARB (50 mg/kg/day, S.C.) (ARB-HP-G). Echocardiography, H&E staining, TUNEL staining, and Western blotting were measured in the left ventricle.

RESULTS

Hypoxia-induced SIRT1 degradation, Fas receptors, FADD, active caspase-8 and caspase-3 (Fas/FasL apoptotic pathway) and Bax, tBid, active caspase-9 and -3 (mitochondrial apoptotic pathway) and TUNEL-positive apoptosis were reduced in ARB-HP-G when compared with HP-G. IGF-I, IGF1 receptor, p-PI3k, p-Akt, Bcl2, and Bcl-XL (IGF1/PI3K/AKT pro-survival pathway) were increased in ARB-HP-G compared to HP-G.

CONCLUSIONS

Our findings suggest that the ARB may prevent cardiac Fas/FasL to mitochondrial apoptotic pathways and enhance cardiac IGF1/PI3K/AKT pro-survival pathway in the sleep apnea model associated with JNK de-activation and SIRT1 upregulation. ARB prevents chronic sleep apnea-enhanced cardiac apoptosis via enhancing survival pathways.

Potential molecular mechanism of cardiac hypertrophy in mice induced by exposure to ambient PM2.5

Cardiac hypertrophy could be induced by ambient fine particulate matter (PM2.5) exposure. Since cardiac hypertrophy represents an early event leading to heart dysfunction, it is necessary to explore the molecular mechanisms, which are largely unknown. In the present study, an ambient particulate matter exposure mice model was established to explore its adverse effects related to the heart and the potential mechanisms. Forty-eight male C57BL/6 mice were randomly subjected to three groups: filtered air group, unfiltered air group and concentrated air group, and were exposed for 8 and 16 weeks, 6 h/day, respectively. In vitro experiments, the cardiac muscle cell line (HL-1) was treated with PM2.5 (0, 25, 50 and 100 μg/mL) for 24 h. In the present study, cardiac hypertrophy was occurred in vivo and vitro after exposure to PM2.5. Mechanistically, circ_0001859 could sponge miR-29b-3p, which could interact with 3'UTRs of Ctnnb1 (gene name of β-catenin). And Ctnnb1 expression was transcriptionally inhibited by si-circ_0001859 or miR-29b-3p mimic in HL-1 cells. Additionally, miR-29b-3p inhibitor could also make a reversion about the inhibition effect of circ_0001859 silencing on Ctnnb1 mRNA level in HL-1 cells. Functionally, knockout of circ_0001859 or overexpression of miR-29b-3p could inhibit LEF1/IGF-2R pathway and alleviate the progress of hypertrophy induced by PM2.5 in HL-1 cells. And miR-29b-3p inhibitor could reverse the inhibition effect of circ_0001859 silencing on hypertrophic response induced by PM2.5 in HL-1 cells. Consequently, the data demonstrated that circRNA_0001859 promoted the process of cardiac hypertrophy through suppressing miR-29b-3p leading to enhance Ctnnb1 level, and activated downstream pathway molecules LEF1/IGF-2R.

Leech extract: A candidate cardioprotective against hypertension-induced cardiac hypertrophy and fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence of cardiovascular diseases (CVDs) has been increasing worldwide. Despite significant improvements in therapeutics and on-going developments of novel targeted-treatment regimens, cardiac diseases lack effective preventive and curative therapies with minimal side effects. Therefore, there is an urgent need to identify and propagate alternative and complementary therapies against cardiovascular diseases. Some traditional Chinese medicines can contribute to the prevention and treatment of CVDs and other chronic diseases, with few side effects. Hirudo, a medicinal leech, has been acclaimed for improving blood circulation and overcoming blood stagnation; however, the precise molecular mechanisms of leech extract treatment against pathological cardiac remodeling remain elusive. In this study, we aimed to delineate the molecular mechanisms of medicinal leech extract in the treatment of cardiac hypertrophy and fibrosis, using both in vitro and in vivo assessments.

MATERIALS AND METHODS

We conducted in vitro and in vivo animal experiments, including cell-viability assays, fluorescence microscopy, immunoblotting, immunohistochemistry, and Masson's trichrome staining.

RESULTS

Pre-treatment with leech extract conferred a survival benefit to spontaneously-hypertensive rats (SHRs) and significantly reduced angiotensin II (ANG II)-induced cardiac hypertrophy and fibrosis. ANG II-stimulated cardiac hypertrophy markers were attenuated by leech extract treatment, versus controls. Translational expression of stress-associated mitogen-activated protein kinases (MAPKs) was also repressed. In vivo, leech extract treatment significantly ameliorated the cardiac hypertrophy phenotype in SHRs and diminished interstitial fibrosis, accompanied with reduced fibrosis markers.

CONCLUSION

Leech extract treatment under a hypertensive condition exerted significant cardio-protective benefits by reducing the expression of cardiac hypertrophy-related transcription factors, stress-associated MAPKs, and fibrosis mediators. Our findings imply that medicinal leach extract may be effective against hypertension-induced cardiac hypertrophy and fibrosis.

β-Catenin Regulates Cardiac Energy Metabolism in Sedentary and Trained Mice

The role of canonical Wnt signaling in metabolic regulation and development of physiological cardiac hypertrophy remains largely unknown. To explore the function of β-catenin in the regulation of cardiac metabolism and physiological cardiac hypertrophy development, we used mice heterozygous for cardiac-specific β-catenin knockout that were subjected to a swimming training model. β-Catenin haploinsufficient mice subjected to endurance training displayed a decreased β-catenin transcriptional activity, attenuated cardiomyocytes hypertrophic growth, and enhanced activation of AMP-activated protein kinase (AMPK), phosphoinositide-3-kinase-Akt (Pi3K-Akt), and mitogen-activated protein kinase/extracellular signal-regulated kinases 1/2 (MAPK/Erk1/2) signaling pathways compared to trained wild type mice. We further observed an increased level of proteins involved in glucose aerobic metabolism and β-oxidation along with perturbed activity of mitochondrial oxidative phosphorylation complexes (OXPHOS) in trained β-catenin haploinsufficient mice. Taken together, Wnt/β-catenin signaling appears to govern metabolic regulatory programs, sustaining metabolic plasticity in adult hearts during the adaptation to endurance training.

Marein ameliorates Ang II/hypoxia-induced abnormal glucolipid metabolism by modulating the HIF-1α/PPARα/γ pathway in H9c2 cells

The objectives of this study were to investigate the effects of marein, a major bioactive compound in functional food Coreopsis tinctoria, in hypertrophic H9c2 cells. Treating angiotensin II/hypoxia-stimulated H9c2 cells with marein led to decreasing cell surface area, intracellular total protein, atrial natriuretic peptide, and free fatty acids levels, but increasing glucose level. Marein treatment decreased hypoxia inducible factor-1α (HIF-1α), peroxisome proliferator activated receptor γ (PPARγ), medium chain acyl-coenzyme A dehydrogenase, glucose transporter-4, and glycerol-3-phosphate acyltransferase protein expressions, and increased PPARα, fatty acid transport protein-1, carnitine palmitoyltransferase-1, and pyruvate dehydrogenase kinase-4 protein expressions. Similar results were observed in HIF-1α-overexpressing H9c2 cells, whereas these effects were abolished in siRNA-HIF-1α-transfected H9c2 cells. It was concluded that marein could ameliorate abnormal glucolipid metabolism in hypertrophic H9c2 cells, and the effects could be attributable to reduction of HIF-1α expression and subsequent regulation PPARα/γ-mediated lipogenic gene expressions.

Endogenous CCN5 Participates in Angiotensin II/TGF-β1 Networking of Cardiac Fibrosis in High Angiotensin II-Induced Hypertensive Heart Failure

Aberrant activation of angiotensin II (Ang II) accelerates hypertensive heart failure (HF); this has drawn worldwide attention. The complex Ang II/transforming growth factor (TGF)-β₁ networking consists of central mechanisms underlying pro-fibrotic effects; however, this networking still remains unclear. Cellular communication network 5 (CCN5), known as secreted matricellular protein, mediates anti-fibrotic activity by inhibiting fibroblast-to-myofibroblast transition and the TGF-β₁ signaling pathway. We hypothesized that endogenous CCN5 plays an essential role in TGF-β₁/Ang II networking-induced cardiac fibrosis (CF), which accelerates the development of hypertensive HF. This study aimed to investigate the potential role of CCN5 in TGF-β₁/Ang II networking-induced CF. Our clinical retrospective study demonstrated that serum CCN5 decreased in hypertensive patients, but significantly increased in hypertensive patients taking oral angiotensin-converting enzyme inhibitor (ACEI). A negative association was observed between CCN5 and Ang II in grade 2and 3 hypertensive patients receiving ACEI treatment. We further created an experimental model of high Ang II-induced hypertensive HF. CCN5 was downregulated in the spontaneously hypertensive rats (SHRs) and increased via the inhibition of Ang II production by ACEI. This CCN5 downregulation may activate the TGF-β₁ signaling pathway, which promotes direct deposition of the extracellular matrix (ECM) and fibroblast-to-myofibroblast transition via activated Smad-3. Double immunofluorescence staining of CCN5 and cell markers of cardiac tissue cell types suggested that CCN5 was mainly expressed in the cardiac fibroblasts. Isolated cardiac fibroblasts were exposed to Ang II and transfected with small interfering RNA targeting CCN5. The expression of TGF-β₁ together with Col Ia and Col IIIa was further promoted, and alpha-smooth muscle actin (α-SMA) was strongly expressed in the cardiac fibroblasts stimulated with Ang II and siRNA. In our study, we confirmed the anti-fibrotic ability of endogenous CCN5 in high Ang II-induced hypertensive HF. Elevated Ang II levels may decrease CCN5 expression, which subsequently activates TGF-β₁ and finally promotes the direct deposition of the ECM and fibroblast-to-myofibroblast transition via Smad-3 activation. CCN5 may serve as a potential biomarker for estimating CF in hypertensive patients. A novel therapeutic target should be developed for stimulating endogenous CCN5 production.