scholarly journals FGF23-Mediated Activation of Local RAAS Promotes Cardiac Hypertrophy and Fibrosis

2019 ◽  
Vol 20 (18) ◽  
pp. 4634 ◽  
Author(s):  
Ineke Böckmann ◽  
Jonas Lischka ◽  
Beatrice Richter ◽  
Jennifer Deppe ◽  
Anja Rahn ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Target Genes ◽  
Cardiac Fibrosis ◽  
Fibroblast Growth Factor 23 ◽  
Serum Levels ◽  
Receptor Activation ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Hypertrophic Growth

Patients with chronic kidney disease (CKD) are prone to developing cardiac hypertrophy and fibrosis, which is associated with increased fibroblast growth factor 23 (FGF23) serum levels. Elevated circulating FGF23 was shown to induce left ventricular hypertrophy (LVH) via the calcineurin/NFAT pathway and contributed to cardiac fibrosis by stimulation of profibrotic factors. We hypothesized that FGF23 may also stimulate the local renin–angiotensin–aldosterone system (RAAS) in the heart, thereby further promoting the progression of FGF23-mediated cardiac pathologies. We evaluated LVH and fibrosis in association with cardiac FGF23 and activation of RAAS in heart tissue of 5/6 nephrectomized (5/6Nx) rats compared to sham-operated animals followed by in vitro studies with isolated neonatal rat ventricular myocytes and fibroblast (NRVM, NRCF), respectively. Uremic rats showed enhanced cardiomyocyte size and cardiac fibrosis compared with sham. The cardiac expression of Fgf23 and RAAS genes were increased in 5/6Nx rats and correlated with the degree of cardiac fibrosis. In NRVM and NRCF, FGF23 stimulated the expression of RAAS genes and induced Ngal indicating mineralocorticoid receptor activation. The FGF23-mediated hypertrophic growth of NRVM and induction of NFAT target genes were attenuated by cyclosporine A, losartan and spironolactone. In NRCF, FGF23 induced Tgfb and Ctgf, which were suppressed by losartan and spironolactone, only. Our data suggest that FGF23-mediated activation of local RAAS in the heart promotes cardiac hypertrophy and fibrosis.

Activation of SIRT1 by Resveratrol Alleviates Pressure Overload-Induced Cardiac Hypertrophy via Suppression of TGF-β1 Signaling

Pharmacology ◽  
2021 ◽  
pp. 1-15
Author(s):  
Yong Chen ◽  
Ting He ◽  
Zhongjun Zhang ◽  
Junzhi Zhang
Keyword(s):  
Cardiac Hypertrophy ◽  
Protective Effect ◽  
Signaling Pathway ◽  
Cardiac Fibrosis ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Ang Ii ◽  
Tgf Β1

<b><i>Introduction:</i></b> Silent information regulator 1 (SIRT1) has been extensively investigated in the cardiovascular system and has been shown to play a pivotal role in mediating cell death/survival, energy production, and oxidative stress. However, the functional role of SIRT1 in pressure overload-induced cardiac hypertrophy and dysfunction remains unclear. Resveratrol (Rsv), a widely used activator of SIRT1, has been reported to protect against cardiovascular disease. We here examine whether activation of SIRT1 by Rsv attenuate pressure overload-induced cardiac hypertrophy and to identify the underlying molecular mechanisms. <b><i>Methods:</i></b> In vivo, rat model of pressure overload-induced myocardial hypertrophy was established by abdominal aorta constriction (AAC) procedure. In vitro, Angiotensin II (Ang II) was applied to induce hypertrophy in cultured neonatal rat cardiomyocytes (NCMs). Hemodynamics and histological analyses of the heart were evaluated. The expression of SIRT1, transforming growth factor-β1 (TGF-β1)/phosphorylated (p)-small mother against decapentaplegic (Smad)3 and hypertrophic markers were determined by immunofluorescence, real-time PCR, and Western blotting techniques. <b><i>Results:</i></b> In the current study, Rsv treatment improved left ventricular function and reduced left ventricular hypertrophy and cardiac fibrosis significantly in the pressure overload rats. The expression of SIRT1 was significantly reduced, while the expression of TGF-β1/p-Smad3 was significantly enhanced in AAC afflicted rat heart. Strikingly, treatment with Rsv restored the expressions of SIRT1 and TGF-β1/p-Smad3 under AAC influence. However, SIRT1 inhibitor Sirtinol (Snl) markedly prevented the effects of Rsv, which suggest that SIRT1 signaling pathway was involved in the cardiac protective effect of Rsv. In vitro studies performed in Ang II-induced hypertrophy in NCMs confirmed the cardiac protective effect of Rsv. Furthermore, the study presented that SIRT1 negatively correlated with the cardiac hypertrophy, cardiac fibrosis, and the TGF-β1/p-Smad3 expression. <b><i>Conclusions:</i></b> Taken together, these results indicated that activation of SIRT1 by Rsv attenuates cardiac hypertrophy, cardiac fibrosis, and improves cardiac function possibly via regulation of the TGF-β1/p-Smad3 signaling pathway. Our study may provide a potential therapeutic strategy for cardiac hypertrophy.

scholarly journals Low‐intensity Pulsed Ultrasound Ameliorates Angiotension Ii-induced Cardiac Fibrosisbyalleviating Inflammation via a Caveolin-1-dependent Pathway

2020 ◽  
Author(s):  
Kun Zhao ◽  
Jing Zhang ◽  
Tianhua Xu ◽  
Chuanxi Yang ◽  
Liqing Weng ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Cardiac Fibrosis ◽  
Ventricular Remodeling ◽  
Left Ventricular Remodeling ◽  
Left Ventricular ◽  
Pulsed Ultrasound ◽  
Caveolin 1 ◽  
Low Intensity Pulsed Ultrasound

Abstract Background: Cardiac hypertrophy and fibrosis are major pathological manifestations observed in left ventricular remodeling induced by Angiotensin II (AngII). Concerning the fact that low‐intensity pulsed ultrasound (LIPUS) has been reported to improve cardiac dysfunction and myocardial fibrosis in myocardial infarction (MI) through mechanotransductionanditsdownstream pathways, we aimed to investigate whether LIPUS could also exert a protective effect on ameliorating AngII-induced cardiac hypertrophy and fibrosis andand if so, to further elucidate the underlying molecular mechanisms.Methods: In our study, we used AngII to mimic the animal and cell culture models of cardiac hypertrophy and fibrosis, where LIPUS irradiation (0.5MHz, 77.20mW/cm2) was applied for 20 minutes every 2 days from 1 week before surgery to 4 weeks after surgery in vivo, and every 6 hours for a total of 2 times in vitro. Following that, the levels of cardiac hypertrophy and fibrosis were evaluated by echocardiographic, histopathological, and molecular biological methods. Results: Our results showed that LIPUS irradiation could ameliorate left ventricular remodeling in vivo and cardiac fibrosis in vitro by reducing AngII-inducedrelease of inflammatory cytokines, while the protective effects were limited on cardiac hypertrophy in vitro. Given that LIPUS irradiation increased the expression of caveolin-1 related to mechanical stimulation, we inhibited caveolin-1 activity with pyrazolopyrimidine 2 (pp2) in vitro, by which LIPUS-induced downregulation of inflammation was reversed and the anti-fibrosis effects of LIPUS irradiation were absent. Conclusions: Taken together, these results indicate that LIPUS irradiation could ameliorate AngII-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway, providing new insights for the development of novel therapeuticapparatus in clinical practice.

scholarly journals Cardiac Fibroblast Growth Factor 23 Excess Does Not Induce Left Ventricular Hypertrophy in Healthy Mice

2021 ◽  
Vol 9 ◽  
Author(s):  
Maren Leifheit-Nestler ◽  
Miriam A. Wagner ◽  
Beatrice Richter ◽  
Corinna Piepert ◽  
Fiona Eitner ◽  
...  
Keyword(s):  
Growth Factor ◽  
Left Ventricular Hypertrophy ◽  
Fibroblast Growth Factor ◽  
Ventricular Hypertrophy ◽  
Fibroblast Growth Factor 23 ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Fibroblast Growth ◽  
Hypertrophic Growth ◽  
Per Se

Fibroblast growth factor (FGF) 23 is elevated in chronic kidney disease (CKD) to maintain phosphate homeostasis. FGF23 is associated with left ventricular hypertrophy (LVH) in CKD and induces LVH via klotho-independent FGFR4-mediated activation of calcineurin/nuclear factor of activated T cells (NFAT) signaling in animal models, displaying systemic alterations possibly contributing to heart injury. Whether elevated FGF23 per se causes LVH in healthy animals is unknown. By generating a mouse model with high intra-cardiac Fgf23 synthesis using an adeno-associated virus (AAV) expressing murine Fgf23 (AAV-Fgf23) under the control of the cardiac troponin T promoter, we investigated how cardiac Fgf23 affects cardiac remodeling and function in C57BL/6 wild-type mice. We report that AAV-Fgf23 mice showed increased cardiac-specific Fgf23 mRNA expression and synthesis of full-length intact Fgf23 (iFgf23) protein. Circulating total and iFgf23 levels were significantly elevated in AAV-Fgf23 mice compared to controls with no difference in bone Fgf23 expression, suggesting a cardiac origin. Serum of AAV-Fgf23 mice stimulated hypertrophic growth of neonatal rat ventricular myocytes (NRVM) and induced pro-hypertrophic NFAT target genes in klotho-free culture conditions in vitro. Further analysis revealed that renal Fgfr1/klotho/extracellular signal-regulated kinases 1/2 signaling was activated in AAV-Fgf23 mice, resulting in downregulation of sodium-phosphate cotransporter NaPi2a and NaPi2c and suppression of Cyp27b1, further supporting the bioactivity of cardiac-derived iFgf23. Of interest, no LVH, LV fibrosis, or impaired cardiac function was observed in klotho sufficient AAV-Fgf23 mice. Verified in NRVM, we show that co-stimulation with soluble klotho prevented Fgf23-induced cellular hypertrophy, supporting the hypothesis that high cardiac Fgf23 does not act cardiotoxic in the presence of its physiological cofactor klotho. In conclusion, chronic exposure to elevated cardiac iFgf23 does not induce LVH in healthy mice, suggesting that Fgf23 excess per se does not tackle the heart.

Abstract 470: Raf Kinase Inhibitors Activate ERK1/2 in Cardiomyocytes, Promoting Cardiac Hypertrophy in vitro and, in the Context of Angiotensin II-Induced Hypertension in Mice, in vivo

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Daniel N Meijles ◽  
Michelle A Hardyman ◽  
Stephen J Fuller ◽  
Kerry A Rostron ◽  
Sam J Leonard ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Kinase Inhibitors ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Internal Diameter ◽  
Dividing Cells ◽  
Lv Volume

Introduction: ERK1/2 promote hypertrophy and are protective in the heart, but cause cancer in dividing cells. Raf kinases lie upstream of ERK1/2 and Raf inhibitors (e.g. SB590885 (SB), dabrafenib (Dab)) are in development/use for cancer. Paradoxically, in cancer cells, low concentrations of SB/Dab stimulate (rather than inhibit) ERK1/2. Hypothesis: Our hypothesis is that the heart is primed for Raf paradox signaling. Raf inhibitors have potential to activate ERK1/2 in cardiomyocytes and promote cardiac hypertrophy. Methods: Neonatal rat ventricular cardiomyocytes (NRVMs) were exposed to inhibitors. Dab or SB (3 or 0.5 mg/kg/d) were studied in 12 wk male C57Bl6 mice in vivo in the presence of angiotensin II (AngII, 0.8 mg/kg/d) (n=6-11) using osmotic minipumps. Effects were compared with vehicle controls. Echocardiography was performed (Vevo2100). M-mode images (short axis view) were analyzed; data for each mouse were normalized to the mean of 2 baseline controls. Kinase activities were assessed by immunoblotting or in vitro kinase assays. Results: SB (0.1 μM) or Dab (1 μM) activated ERK1/2 (2.3±0.1 fold; n=4) in NRVMs consistent with Raf paradox signaling. An explanation is that Raf kinases dimerise and submaximal inhibitor concentrations bind one Raf protomer, locking it in an active conformation but activating the partner. In accord with this, 0.1 μM SB increased Raf activities. High SB concentrations (1-10 μM) initially inhibited ERK1/2 in NRVMs, but ERK1/2 were then activated (1 - 24 h) and promoted hypertrophy. In vivo (24 h), Dab and SB activated the ERK1/2 cascade, increasing ANF (17.3 ± 3.1 fold) and BNP (4.5 ± 0.8 fold) mRNA (n=4/5). Over 3 d, Dab and SB increased fractional shortening in the presence of AngII (1.22±0.06; 1.17±0.08), relative to AngII alone (0.95±0.04), increased systolic left ventricular (LV) wall thickness, and reduced systolic LV volume and internal diameter (0.83±0.03 cf 0.97±0.02 for AngII alone). Conclusions: The heart is primed for Raf paradox signaling and Raf inhibitors activate ERK1/2 in cardiomyocytes, promoting hypertrophy. In vivo, Raf inhibitors enhance ERK1/2 signaling and hypertrophy in the context of hypertension, and cardiac hypertrophy may be increased in hypertensive cancer patients receiving Raf inhibitors.

scholarly journals The proarrhythmic features of pathological cardiac hypertrophy in neonatal rat ventricular cardiomyocyte cultures

2020 ◽  
Vol 128 (3) ◽  
pp. 545-553
Author(s):  
Zeinab Neshati ◽  
Martin J. Schalij ◽  
Antoine A. F. de Vries
Keyword(s):  
Action Potential ◽  
Cardiac Hypertrophy ◽  
Action Potential Duration ◽  
In Vitro Model ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Control Group ◽  
Pathological Cardiac Hypertrophy ◽  
Vitro Model

Different factors may trigger arrhythmias in diseased hearts, including fibrosis, cardiomyocyte hypertrophy, hypoxia, and inflammation. This makes it difficult to establish the relative contribution of each of them to the occurrence of arrhythmias. Accordingly, in this study, we used an in vitro model of pathological cardiac hypertrophy (PCH) to investigate its proarrhythmic features and the underlying mechanisms independent of fibrosis or other PCH-related processes. Neonatal rat ventricular cardiomyocyte (nr-vCMC) monolayers were treated with phorbol 12-myristate 13-acetate (PMA) to create an in vitro model of PCH. The electrophysiological properties of PMA-treated and control monolayers were analyzed by optical mapping at day 9 of culture. PMA treatment led to a significant increase in cell size and total protein content. It also caused a reduction in sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 level (32%) and an increase in natriuretic peptide A (42%) and α1-skeletal muscle actin (34%) levels, indicating that the hypertrophic response induced by PMA was, indeed, pathological in nature. PMA-treated monolayers showed increases in action potential duration (APD) and APD dispersion, and a decrease in conduction velocity (CV; APD30 of 306 ± 39 vs. 148 ± 18 ms, APD30 dispersion of 85 ± 19 vs. 22 ± 7 and CV of 10 ± 4 vs. 21 ± 2 cm/s in controls). Upon local 1-Hz stimulation, 53.6% of the PMA-treated cultures showed focal tachyarrhythmias based on triggered activity ( n = 82), while the control group showed 4.3% tachyarrhythmias ( n = 70). PMA-treated nr-vCMC cultures may, thus, represent a well-controllable in vitro model for testing new therapeutic interventions targeting specific aspects of hypertrophy-associated arrhythmias. NEW & NOTEWORTHY Phorbol 12-myristate 13-acetate (PMA) treatment of neonatal rat ventricular cardiomyocytes (nr-vCMCs) led to induction of many significant features of pathological cardiac hypertrophy (PCH), including action potential duration prolongation and dispersion, which provided enough time and depolarizing force for formation of early afterdepolarization (EAD)-induced focal tachyarrhythmias. PMA-treated nr-vCMCs represent a well-controllable in vitro model, which mostly resembles to moderate left ventricular hypertrophy (LVH) rather than severe LVH, in which generation of a reentry is the putative mechanism of its arrhythmias.

Abstract 97: Induction of Hexosamine Biosynthetic Pathway Promotes Cardiac Hypertrophy through Activation of O-GlcNAcylation

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Diem H Tran ◽  
Jianping Li ◽  
Xiaoding Wang ◽  
Herman I May ◽  
Gabriele G Schiattarella ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Biosynthetic Pathway ◽  
Heart Diseases ◽  
Pressure Overload ◽  
Neonatal Rat ◽  
Mice Model ◽  
Hexosamine Biosynthetic Pathway ◽  
Hypertrophic Growth

Background & significance: Heart failure affects approximately 6 million Americans, with 5-year survival of 50%, which is responsible for a huge burden on the US economy and healthcare system. The relevance and significance of the metabolic alteration to the pathogenesis of pressure overload-induced cardiac hypertrophy and heart failure are largely unknown. The hexosamine biosynthetic pathway (HBP) that is linked to metabolism of glucose, fatty acids and amino acids, has been implicated in the pathophysiology of heart diseases. Methods & results: Thoracic aortic constriction (TAC) was performed to induce heart failure by pressure overload in mice. At the in vitro levels, treatment of phenylephrine (PE, 50 μM) was used to induce cellular hypertrophy in neonatal rat ventricular myocytes (NRVM). Our data revealed that all the enzymes of the HBP were upregulated while induction of hypertrophy at both in vivo and in vitro levels. Consistently, the intermediate product of the HBP was elevated in heart by afterload stress, as measured by metabolomics analyses. In the transgenic mice model for Gfat1, the rate-limiting enzyme of the HBP, we found more profound cardiac hypertrophy and cardiac remodeling in response to pressure overload. The increase of O-GlcNAc was also observed. In addition, the regulation of O-GlcNAcylation by specific targeting of two enzymes of the HBP (1 mM Alloxan, an inhibitor of OGT and 10 μM PUGNAc, an inhibitor of OGA) in NRVM suggested an involvement of the mTOR signaling in the activation of O-GlcNAc levels and the hypertrophy response. Targeting of the HBP by either specific siRNA or Gfat1 inhibitor (Azaserine, 5 μM) led to decrease in cellular hypertrophic response. Conclusions: Together, our data strongly suggest that the HBP participates in cardiac hypertrophic growth and pharmacologic targeting of the HBP may represent a novel approach to ameliorate pathological remodeling.

Abstract 107: MicroRNA-31: A Novel Therapeutic Target for Ischemic Heart Disease

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Eliana C Martinez ◽  
Shera Lilyanna ◽  
Leah A Vardy ◽  
Arunmozhiarasi Armugam ◽  
Kandiah Jeyaseelan ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Target Genes ◽  
Subcutaneous Administration ◽  
Left Ventricular ◽  
Ischemic Heart ◽  
Neonatal Rat ◽  
Rat Cardiomyocytes ◽  
Repressive Effect

MicroRNAs (miRNA), small sequences of non-coding RNA which interact with complementary sequences on the 3’untranslated region of target messenger RNAs to modulate translation, have a pivotal role in the development of the heart and its response to injury. Myocardial infarction (MI) triggers a dynamic miRNA response with the potential of yielding therapeutic targets. Following miRNA array profiling in rat hearts 2, 7 and 14 days after MI induced by coronary ligation, we identified a progressive time-dependent up-regulation of miR-31 compared to sham rats. Increase of miR-31 in heart tissue in the acute and subacute phases after MI (up to 90-fold) was also detected by Real-Time PCR (P=0.02 at day 2; P<0.0001 at days 7 and 14, vs. sham). We found that miR-31 has a repressive effect on tissue mRNA expression of cardiac troponin-T (TNNT2), E2F transcription factor 6 (E2F6) and mineralocorticoid receptor (NR3C2). Reporter gene assays showed that miR-31 targets the 3′UTR of these genes, with a marked repressive effect on TNNT2. In vitro, exposure to hypoxia significantly induced the expression of miR-31 in neonatal rat cardiomyocytes (nRCM), rat cardiac fibroblasts (nRCF) and cardiomyoblasts (H9C2) and suppressed the expression of TNNT2, E2F6 and NR3C2 in nRCM and H9C2 cells, and of E2F6 and NR3C2 in nRCF. LNA-based oligonucleotide inhibition of miR-31(miR-31i) in vitro reversed its repressive effect on translation from target genes. Therapeutic modulation of miR-31 expression in vivo after MI via subcutaneous administration of miR-31i (25mg/Kg/q2w) in rats, led to cardiac repression of miR-31 and subsequent enhanced expression of target genes. Also, miR-31i led to preservation of cardiac function and structure by day 14 after treatment. An absolute 10% improvement in left ventricular (LV) ejection fraction (EF) was observed in miR-31i-treated rats from day 2 to 16 after MI, while control rats that received scrambled LNA inhibitor or placebo displayed 23% deterioration in EF (n=6-8/group, P<0.0001). We conclude that miR-31 induction after MI is deleterious to cardiac function and plays an important role in adverse remodeling, while its therapeutic inhibition in vivo ameliorates cardiac dysfunction and prevents the development of post-ischemic heart failure.

scholarly journals Kaempferol Alleviates Angiotensin II-Induced Cardiac Dysfunction and Interstitial Fibrosis in Mice

2017 ◽  
Vol 43 (6) ◽  
pp. 2253-2263 ◽  
Author(s):  
Yuan Liu ◽  
Lu Gao ◽  
Sen Guo ◽  
Yuzhou Liu ◽  
Xiaoyan Zhao ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Cardiac Dysfunction ◽  
Cardiac Fibrosis ◽  
Neonatal Rat ◽  
Cardiac Remodelling ◽  
Ang Ii ◽  
Ventricular Fibrosis

Background/Aims: Endothelial-to-mesenchymal transition (EndMT) is a mechanism that promotes cardiac fibrosis induced by Angiotensin II (AngII). Kaempferol (KAE) is a monomer component mainly derived from the rhizome of Kaempferia galanga L. It shows anti-inflammatory, anti-oxidative, anti-microbial and anti-cancer properties, which can be used in the treatment of cancer, cardiovascular diseases, infection, etc. But, its effects on the development of cardiac remodelling remain completely unknown. The aim of the present study was to determine whether KAE attenuates cardiac hypertrophy induced by angiotensin II (Ang II) in cultured neonatal rat cardiac myocytes in vitro and cardiac hypertrophy induced by AngII infusion in mice in vivo. Methods: Male wild-type mice aged 8-10 weeks with or without KAE were subjected to AngII or saline, to induce fibrosis or as a control, respectively. Morphological changes, echocardiographic parameters, histological analyses, and hypertrophic markers were also used to evaluate hypertrophy. Results: KAE prevented and reversed cardiac remodelling induced by AngII. The KAE in this model exerted no basal effects but attenuated cardiac fibrosis, hypertrophy and dysfunction induced by AngII. Both in vivo and in vitro experiments demonstrated that Ang II infusion or TGF-β induced EndMT can be reduced by KAE and the proliferation and activation of cardiac fibroblasts (CFs) can be inhibited by KAE. Conclusions: The results suggest that KAE prevents and reverses ventricular fibrosis and cardiac dysfunction, providing an experimental basis for clinical treatment on ventricular fibrosis.

Abstract 157: Alterations in Signaling Pathways During Regression of Pathological Cardiac Hypertrophy

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Deanna Langager ◽  
Leslie Leinwand
Keyword(s):  
Cardiac Hypertrophy ◽  
Signaling Pathways ◽  
Ventricular Myocytes ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Akt Pathway ◽  
Compensatory Mechanism ◽  
Akt Inhibitor ◽  
Pathological Cardiac Hypertrophy

Introduction: Cardiac hypertrophy is initially, a compensatory mechanism to maintain cardiac output when there is an increased load on the heart. However, if cardiac hypertrophy persists for an extended time, there can be maladaptive changes to the myocardium. Even when the underlying cause of hypertrophy is treated, regression is often minimal or absent. Clinical cases of cardiac regression do exist, including patients receiving bariatric surgery or a left ventricular assist device. While many of the mechanisms leading to cardiac hypertrophy are well understood, little is known about the mechanisms of reversal of hypertrophy and why it is sometimes irreversible. We hypothesized that a reversal of isoproterenol (Iso) induced cardiac hypertrophy in the mouse will be observed within 7 days following the removal of the stimulus and we will be able to identify alterations in signaling pathways. Methods: We induced pathological cardiac hypertrophy with Iso for 7 days, at which peak hypertrophy is achieved. To identify if/when regression occurs, the Iso treatment was stopped and the mice were monitored for 7 days. Heart weights were measured at peak hypertrophy, post-drug days 1, 2, 3 & 7, along with vehicle treated mice (8/group). We used left ventricle tissue for protein analysis and protein degradation activity assays. Results: Regression from cardiac hypertrophy occurs by post-drug day 7 (p=0.016) in the Iso mouse model. p-Akt is increased with Iso treatment and returns to vehicle control levels by post-drug day 7. There is a decrease in p-mTOR and an increase in LC3-II levels at post-drug day 7, indicating a possible role of autophagy in cardiac regression. In addition, there was a decrease in cell size when neonatal rat ventricular myocytes were treated with the Akt inhibitor, Wortmannin, following phenylephrine induced hypertrophy. Conclusion: Regression of Iso-induced cardiac hypertrophy occurs in the mouse after 7 days following the removal of the stimulus. The Akt pathway is activated with Iso treatment and when this pathway is inactivated during regression, autophagy is activated, which may be an important mechanism to degrade proteins and lead to a decrease in cardiac hypertrophy. Finally, when the Akt pathway is inhibited in vitro , hypertrophic cells regress.

Abstract 304: Estrogen Plays a Protective Role in Advanced Heart Failure by Suppressing Cardiac Fibrosis Associated Genes via miR129 Induction

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Salil Sharma ◽  
Andrea Iorga ◽  
Harnek Singh ◽  
Jingyaun Li ◽  
Mansoureh Eghbali
Keyword(s):  
Heart Failure ◽  
Target Genes ◽  
Cardiac Fibrosis ◽  
Cardiac Fibroblasts ◽  
Pressure Overload ◽  
Neonatal Rat ◽  
Fibroblast Proliferation ◽  
Short Term ◽  
Short Term Treatment

We have previously shown that short term treatment of estrogen(E2) can rescue advance heart failure(HF) and decreases associated fibrosis. We hypothesized that E2 can reduce fibrosis by regulating the levels of specific microRNAs including miR129-5p(miR129) through ERβ mediated mechanism. We used transaortic constriction to induce HF in male mice, and once the ejection fraction (EF) reached ~30%, one group of animals was sacrificed (HF), and the other group received 17b-estradiol via a subcutaneous pellet implant (0.012mg/pellet, n=16) (E2) for 10 days. Sham-operated mice served as CTRL. Serial echocardiography was performed to monitor cardiac structure and function. Short-term E2 treatment rescued pressure overload-induced decompensated HF in mice by restoring the EF from 33.17±1.12% to 53.05±1.29 (p <0.001, n=16). E2 decreased both interstitial and perivascular fibrosis in HF. Microarray analysis comparing HF with E2 revealed ~70 microRNAs including miR129 regulated by E2. qPCR validation revealed that E2 treatment upregulates miR129 by 2 folds compared to HF restoring it to CTRL levels. Treatment of HF with ERβ agonist (DPN), but not ERα agonist (PPT) resulted in the upregulation of miR129 indicating the E2 mediated induction of miR129 is mediated through ERβ. In vitro, angiotensin II treatment significantly downregulated miR129 expression in neonatal rat fibroblasts (NRVF) which was restored by E2 and DPN but not by E2+ERβ antagonist (PHPT) further confirming the role of ERβ in regulating miR129. In vitro, OE of miR129 in both neonatal and adult rat cardiac fibroblasts (ARVF) resulted in significant downregulation of transcripts of many in-silico predicted pro-fibrotic target genes including EGFR, RUNX, GREM1, COL2A, PDGFA, PDGFRA and the transcription factor SOX4. OE of miR129 in fibroblasts also resulted in downregulation of EGFR protein. Gain of miR129 prevented the transition of fibroblasts to myofibroblasts in both NRVF and ARVF and inhibited fibroblast proliferation in vitro. In conclusion, E2 treatment during HF induces miR129 likely through ERβ. MiR129 represses fibrosis by targeting key genes associated with cardiac fibrosis, inhibits fibroblast proliferation and fibroblast to myofibroblast transition.

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