[PS 01-18] MECHANISM OF HYPERTENSIVE CARDIAC HYPERTROPHY IN CULTURED NEONATAL RAT VENTRICULAR CARDIAC MYOCYTES

2016 ◽  
Vol 34 (Supplement 1) ◽  
pp. e101
Author(s):  
Gang Sun ◽  
Hui Yu ◽  
Zhanli Wang ◽  
Xiaomin Yang ◽  
Jianwei Yue ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Neonatal Rat

The AMPK γ1 R70Q mutant regulates multiple metabolic and growth pathways in neonatal cardiac myocytes

2007 ◽  
Vol 293 (6) ◽  
pp. H3456-H3464 ◽  
Author(s):  
Karalyn D. Folmes ◽  
Lee A. Witters ◽  
Michael F. Allard ◽  
Martin E. Young ◽  
Jason R. B. Dyck
Keyword(s):  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Glycogen Synthase ◽  
Neonatal Rat ◽  
Mrna Levels ◽  
Glycogen Accumulation ◽  
Regulatory Pathways ◽  
Γ Subunit ◽  
Gsk 3Β ◽  
Glycogen Synthase Activity

Although mutations in the γ-subunit of AMP-activated protein kinase (AMPK) can result in excessive glycogen accumulation and cardiac hypertrophy, the mechanisms by which this occurs have not been well defined. Because >65% of cardiac AMPK activity is associated with the γ1-subunit of AMPK, we investigated the effects of expression of an AMPK-activating γ1-subunit mutant (γ1 R70Q) on regulatory pathways controlling glycogen accumulation and cardiac hypertrophy in neonatal rat cardiac myocytes. Whereas expression of γ1 R70Q displayed the expected increase in palmitate oxidation rates, rates of glycolysis were significantly depressed. In addition, glycogen synthase activity was increased in cardiac myocytes expressing γ1 R70Q, due to both increased expression and decreased phosphorylation of glycogen synthase. The inhibition of glycolysis and increased glycogen synthase activity were correlated with elevated glycogen levels in γ1 R70Q-expressing myocytes. In association with the reduced phosphorylation of glycogen synthase, glycogen synthase kinase (GSK)-3β protein and mRNA levels were profoundly decreased in the γ1 R70Q-expressing myocytes. Consistent with GSK-3β negatively regulating hypertrophy via inhibition of nuclear factor of activated T cells (NFAT), the dramatic downregulation of GSK-3β was associated with increased nuclear activity of NFAT. Together, these data provide important new information about the mechanisms by which a mutation in the γ-subunit of AMPK causes altered AMPK signaling and identify multiple pathways involved in regulating both cardiac myocyte metabolism and growth that may contribute to the development of the γ mutant-associated cardiomyopathy.

Expression of an active LKB1 complex in cardiac myocytes results in decreased protein synthesis associated with phenylephrine-induced hypertrophy

2007 ◽  
Vol 292 (3) ◽  
pp. H1460-H1469 ◽  
Author(s):  
Anna A. Noga ◽  
Carrie-Lynn M. Soltys ◽  
Amy J. Barr ◽  
Suzanne Kovacic ◽  
Gary D. Lopaschuk ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Cardiac Myocyte ◽  
Adaptor Protein ◽  
Neonatal Rat ◽  
Hypertrophic Growth ◽  
Pathological Cardiac Hypertrophy ◽  
Neonatal Rat Cardiac Myocytes ◽  
Rat Cardiac Myocytes

AMP-activated protein kinase (AMPK) is a major metabolic regulator in the cardiac myocyte. Recently, LKB1 was identified as a kinase that regulates AMPK. Using immunoblot analysis, we confirmed high expression of LKB1 in isolated rat cardiac myocytes but show that, under basal conditions, LKB1 is primarily localized to the nucleus, where it is inactive. We examined the role of LKB1 in cardiac myocytes, using adenoviruses that express LKB1, and its binding partners Ste20-related adaptor protein (STRADα) and MO25α. Infection of neonatal rat cardiac myocytes with all three adenoviruses substantially increased LKB1/STRADα/MO25α expression, LKB1 activity, and AMPKα phosphorylation at its activating phosphorylation site (threonine-172). Since activation of AMPK can inhibit hypertrophic growth and since LKB1 is upstream of AMPK, we hypothesized that expression of an active LKB1 complex would also inhibit protein synthesis associated with hypertrophic growth. Expression of the LKB1/STRADα/MO25α complex in neonatal rat cardiac myocytes inhibited the increase in protein synthesis observed in cells treated with phenylephrine (measured via [3H]phenylalanine incorporation). This was associated with a decreased phosphorylation of p70S6 kinase and its substrate S6 ribosomal protein, key regulators of protein synthesis. In addition, we show that the pathological cardiac hypertrophy in transgenic mice with cardiac-specific expression of activated calcineurin is associated with a significant decrease in LKB1 expression. Together, our data show that increased LKB1 activity in the cardiac myocyte can decrease hypertrophy-induced protein synthesis and suggest that LKB1 activation may be a method for the prevention of pathological cardiac hypertrophy.

scholarly journals Effects of IGF-1 onIKandIK1Channels via PI3K/Akt Signaling in Neonatal Cardiac Myocytes

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Richard M. Millis ◽  
Zikiar V. Alvin ◽  
Aiqiu Zhao ◽  
Georges E. Haddad
Keyword(s):  
Signal Transduction ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Potassium Currents ◽  
Akt Signaling ◽  
Inward Rectifier ◽  
Neonatal Rat ◽  
Rat Cardiomyocytes ◽  
Inward Rectifier Potassium Channels ◽  
Transduction Mechanisms

Previous studies suggest that sarcolemmal potassium currents play important roles in cardiac hypertrophy. IGF-1 contributes to cardiac hypertrophy via activation of PI3K/Akt signaling. However, the relationships between IGF-1, PI3K/Akt signaling and sarcolemmal potassium currents remain unknown. Therefore, we tested the hypothesis that IGF-1 and PI3K/Akt signaling, independently, decrease sarcolemmal potassium currents in cardiac myocytes of neonatal rats. We compared the delayed outward rectifier (IK) and the inward rectifier (IK) current densities resulting from IGF-1 treatments to those resulting from simulation of PI3K/Akt signaling using adenoviral (Ad) BD110 and wild-type Akt and to those resulting from inhibition of PI3K signaling by LY294002. Ad.BD110 and Ad.Akt decreasedIKand these decrements were attenuated by LY 294002. The IGF-1 treatments decreased bothIKandIK1but only theIKdecrement was attenuated by LY294002. These findings demonstrate that IGF-1 may contribute to cardiac hypertrophy by PI3K/Akt signal transduction mechanisms in neonatal rat cardiomyocytes. Failure of LY294002 to effectively antagonize IGF-1 induced decrements inIK1suggests that a signal pathway adjunct to PI3K/Akt contributes to IGF-1 protection against arrhythmogenesis in these myocytes. Our findings imply that sarcolemmal outward and inward rectifier potassium channels are substrates for IGF-1/PI3K/Akt signal transduction molecules.

Abstract 537: Sildenafil Suppresses Cardiac Hypertrophy through Inhibition of Canonical Transient Receptor Potential Cation Channel 6 Expression in Cardiac Myocytes

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Norimichi Koitabashi ◽  
Manling Zhang ◽  
Eiki Takimoto ◽  
Takahiro Nagayama ◽  
David A Kass
Keyword(s):  
Gene Expression ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Cation Channel ◽  
Neonatal Rat ◽  
Mouse Heart ◽  
Canonical Transient Receptor Potential ◽  
Transient Receptor

Background: We have shown that a phosphodiesterase 5A (PDE5A) inhibitor, sildenafil blocks cardiac pathological hypertrophy through inhibition of Gαq mediated signaling and calcineurin (Cn) signaling. However, the precise molecular mechanism is still unknown. Recently canonical transient receptor potential cation channel 6 (TRPC6) and its up-regulation have been shown to play a critical role for Gαq-mediated Cn activation in pathogenesis of cardiac hypertrophy. Therefore, we hypothesized that PDE5A inhibition blocks TRPC6 gene induction in cardiac myocytes and thus prevents cardiac hypertrophy. Methods and Results: We examined TRPC6 expression levels using real-time RT-PCR in hypertrophied mouse heart created by transverse aortic constriction (TAC). TRPC6 mRNA expression was significantly increased after TAC. Sildenafil effectively attenuated TAC-induced hypertrophy, Cn protein level and upregulation of TRPC6 mRNA. To investigate role of TRPC6 in sildenafil’s anti-hypertrophic effects, we studied cultured adult mouse cardiac myocytes (AMCM) and neonatal rat cardiac myocytes (NRCM). Stimulation with Endothelin 1 (ET1) or angiotensin II (AngII) increased cell surface area, leucine uptake, Cn protein expression and TRPC6 gene expression. Sildenafil dose-dependently blocked these increases. 8-bromo cGMP also blocked TRPC6 induction by ET1 and AngII. In addition, 8-bromo cGMP stimulation following adenovirus-mediated overexpression of cGMP-dependent protein kinase I-α (PKG) showed a marked decrease in TRPC6 expression. These results suggest that PKG activation regulates TRPC6 gene in cardiac myocytes. Using adenovirus-based expression of artificial PDE5A-gene silencing miRNA, PDE5 protein was effectively knocked down both in NRCM and AMCM. Importantly, PDE5-miRNA completely blocked ET1-mediated increase of Cn and TRPC6 same as sildenafil. Conclusion: Sildenafil effectively blocks TRPC6 induction both in vivo and in vitro . TRPC6 gene regulation is PKG and PDE5A dependent in cardiac myocytes. Given that TRPC6 induction triggers Gαq-mediated maladaptive signaling, especially Cn, these data show that the inhibition of TRPC6 gene expression contributes to the Gαq-coupled anti-hypertrophic mechanism of sildenafil.

Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
V Montiel ◽  
R Bella ◽  
L Michel ◽  
E Robinson ◽  
J.C Jonas ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Cardiac Remodeling ◽  
Cardiac Myocyte ◽  
Water Channel ◽  
Transmembrane Transport ◽  
Funding Source ◽  
Water Pore

Abstract Background Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown. Purpose We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy. Methods We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis. Results RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis. Conclusion We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio

scholarly journals Qiliqiangxin Attenuates Phenylephrine-Induced Cardiac Hypertrophy through Downregulation of MiR-199a-5p

2016 ◽  
Vol 38 (5) ◽  
pp. 1743-1751 ◽  
Author(s):  
Haifeng Zhang ◽  
Shanshan Li ◽  
Qiulian Zhou ◽  
Qi Sun ◽  
Shutong Shen ◽  
...  
Keyword(s):  
Cell Surface ◽  
Cardiac Hypertrophy ◽  
Natriuretic Peptide ◽  
Neonatal Rat ◽  
Immunofluorescent Staining ◽  
Mouse Heart ◽  
Mrna Levels ◽  
Elevated Protein ◽  
Ischemic Stress

Background/Aims: Qiliqiangxin (QL), a traditional Chinese medicine, has long been used to treat chronic heart failure. Previous studies demonstrated that QL could prevent cardiac remodeling and hypertrophy in response to hypertensive or ischemic stress. However, little is known about whether QL could modulate cardiac hypertrophy in vitro, and (if so) whether it is through modulation of specific hypertrophy-related microRNA. Methods: The primary neonatal rat ventricular cardiomyocytes were isolated, cultured, and treated with phenylephrine (PE, 50 µmol/L, 48 h) to induce hypertrophy in vitro, in the presence or absence of pretreatment with QL (0.5 µg/ml, 48 h). The cell surface area was determined by immunofluorescent staining for α-actinin. The mRNA levels of hypertrophic markers including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (MYH7) were assayed by qRT-PCRs. The protein synthesis of cardiomyocytes was determined by the protein/DNA ratio. The miR-199a-5p expression level was quantified in PE-treated cardiomyocytes and heart samples from acute myocardial infarction (AMI) mouse model. MiR-199a-5p overexpression was used to determine its role in the anti-hypertrophic effect of QL on cardiomyocytes. Results: PE induced obvious enlargement of cell surface in cardiomyocytes, paralleling with increased ANP, BNP, and MYH7 mRNA levels and elevated protein/DNA ratio. All these changes were reversed by the treatment with QL. Meanwhile, miR-199a-5p was increased in AMI mouse heart tissues. Of note, the increase of miR-199a-5p in PE-treated cardiomyocytes was reversed by the treatment with QL. Moreover, overexpression of miR-199a-5p abolished the anti-hypertrophic effect of QL on cardiomyocytes. Conclusion: QL prevents PE-induced cardiac hypertrophy. MiR-199a-5p is increased in cardiac hypertrophy, while reduced by treatment with QL. miR-199a-5p suppression is essential for the anti-hypertrophic effect of QL on cardiomyocytes.

Abstract 191: Ras GTPase-activating Protein SH3 Domain Binding Protein 1 (G3BP1) Regulates The Induction Of Stress Granules During Cardiac Hypertrophy

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Danish Sayed
Keyword(s):  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Posttranscriptional Regulation ◽  
Binding Protein ◽  
Stress Granules ◽  
Sh3 Domain ◽  
Gtpase Activating Protein ◽  
Ras Gtpase ◽  
Mrna Binding

Stress granules (SGs) are dynamic, microscopically visible, cytoplasmic bodies that play a major role in mRNA metabolism (e.g. sorting, storage, decay) and induced in cells during stress conditions like starvation, oxidative strain or growth. With substantial role in cancer and neurodegenerative diseases, these granules have never been studied during cardiac hypertrophy, or in the heart in general. Several studies have identified independent proteins, mostly mRNA binding proteins that are part of these granules, some of which are sufficient to nucleate the assembly in quiescent cells even without stress. One such mRNA binding protein is Ras GTPase-activating protein SH3 domain binding protein 1 (G3BP1), which increases during cardiac hypertrophy via posttranscriptional regulation. Thus, we hypothesized that G3BP1 might be involved in the induction of SGs during hypertrophy and hence in regulating mRNA processing and gene expression. Our aim was to investigate, 1) if these SGs appear in hypertrophied hearts and 2) if G3BP1 is necessary and sufficient to induce them during hypertrophic stimuli. In vivo staining of TIA-1/TIAR (SG marker) in mouse hearts subjected to sham or transaortic coarctation (TAC) surgeries showed accumulation of these granules with cardiac hypertrophy. Similar induction was seen in isolated, cultured, rat neonatal cardiac myocytes with hypertrophic stimulation (Endothelin1) or overexpression of G3BP1 alone (>60% of myocytes stained for SG). Conversely, switch to growth-inhibited conditions or knockdown of G3BP1 in hypertrophying myocytes was sufficient to prevent the assembly of these structures. Co-staining with other components of these granules like TIA-1/TIAR or proteins specific to P bodies, like decapping enzyme 1 validated these structures as SGs in cardiac myocytes. Interestingly, a long non-coding RNA, Gas5 (Growth Arrest Specific 5) that is validated binding partner of G3BP1 sequestered to perinuclear focal locations in myocytes stimulated with ET1, suggesting growth-induced recruitment to SGs. While we are still in process of examining G3BP1 targets that are recruited to SGs and their role in hypertrophy development, we have concluded that G3BP1 is required for the induction of SGs during cardiac hypertrophy

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