Effects of triiodo-thyronine on angiotensin-induced cardiomyocyte hypertrophy: reversal of increased β-myosin heavy chain gene expression

2006 ◽  
Vol 84 (8-9) ◽  
pp. 935-941 ◽  
Author(s):  
Baohua Wang ◽  
Jingping Ouyang ◽  
Zhengyuan Xia
Keyword(s):  
Gene Expression ◽  
Angiotensin Ii ◽  
Thyroid Hormone ◽  
Cardiac Hypertrophy ◽  
Atpase Activity ◽  
Mrna Expression ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Ang Ii ◽  
Hypertrophic Growth

Thyroid hormone-induced cardiac hypertrophy is similar to that observed in physiological hypertrophy, which is associated with high cardiac contractility and increased α-myosin heavy chain (α-MHC, the high ATPase activity isoform) expression. In contrast, angiotensin II (Ang II) induces an increase in myocardial mass with a compromised contractility accompanied by a shift from α-MHC to the fetal isoform β-MHC (the low ATPase activity isoform), which is considered as a pathological hypertrophy and inevitably leads to the development of heart failure. The present study is designed to assess the effect of thyroid hormone on angiotensin II-induced hypertrophic growth of cardiomyocytes in vitro. Cardiomyocytes were prepared from hearts of neonatal Wistar rats. The effects of Ang II and 3,3′,5-triiodo-thyronine (T3) on incorporations of [3H]-thymine and [3H]-leucine, MHC isoform mRNA expression, PKC activity, and PKC isoform protein expression were studied. Ang II enhanced [3H]-leucine incorporation, β-MHC mRNA expression, PKC activity, and PKCε expression and inhibited α-MHC mRNA expression in cardiomyocytes. T3 treatment prevented Ang II-induced increases in PKC activity, PKCε, and β-MHC mRNA overexpression and favored α-MHC mRNA expression. Thyroid hormone appears to be able to reprogram gene expression in Ang II-induced cardiac hypertrophy, and a PKC signal pathway may be involved in such remodeling process.

Abstract 189: Natriuretic Peptide Receptor-A Regulates Angiotensin-II Mediated NF-κB Via Mkp-1 Dependent Pathway

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Gopi Venkatachalam ◽  
Umadevi Subramanian ◽  
Parthasarathy Arumugam ◽  
Elangovan Vellaichamy
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Natriuretic Peptide ◽  
Nuclear Translocation ◽  
Heart Tissue ◽  
Male Rats ◽  
Natriuretic Peptide Receptor ◽  
Ang Ii ◽  
Hypertrophic Growth ◽  
Peptide Receptor

Atrial natriuretic peptide (ANP) exerts local anti-hypertrophic activity in heart tissue by binding to natriuretic peptide receptor (NPR)-A. However, patients with cardiac hypertrophy and congestive heart failure have elevated plasma and tissue levels of ANP and brain natriuretic peptide (BNP) along with Angiotensin II (Ang II). However, the rationale behind the impaired action of ANP in diseased state is not well understood. In this study, we sought to examine the signaling mechanism by which Ang II modulates local anti-hypertrophic effect through inhibition of Npr1 gene, which codes for NPR-A, in the heart. Hence, in vivo , Wistar male rats (n=8/group) were administered suppressor dose of Ang II (50ng/kg/min) for 14 days through implanted mini-osmotic pumps. Also, in vitro , H9C2 (2-1) cardio myofibroblast cells were exposed to Ang II (10 -7 M) for 20 hours. Upon treatment with Ang II, the mRNA and protein expression of Npr1 (p<0.01) was decreased with significant increase in expression of AT1R (p<0.01) in the heart tissues. In addition, a concomitant decrease in cGMP activity and production in isolated heart tissue membrane preparation was found in Ang II infused rats. Moreover, Ang II infusion causes a suppression of MKP-1 phosphatase; while enhancing the phosphorylation of ERK1/2 (p<0.01) and NF-κB (p<0.01) proteins. Similarly, H9C2 cells exhibited the hypertrophic growth with increased expression of AT1R and activation of ERK1/2 proteins on stimulation with Ang II. Furthermore, gene silencing using siRNA-NPR-A prior to Ang II treatment augmented the translocation of NF-κB and activation of ERK1/2 (3-fold). Whereas, pre-treatment with losartan or cGMP analog 8-Br-cGMP, an activator of cGMP-dependent protein kinases, abolished the stimulatory effects of Ang II on AT1R, NF-κB nuclear translocation and phosphorylation of MAPK, but activated the MKP-1 phosphatase. These results suggest that NPRA-cGMP signaling exerts inhibitory effects on Ang II by antagonizing the upstream signaling pathways and by activation of MKP-1 to counter-regulate NF-κB and MAPKs through cGMP dependent mechanism; thereby mediate local anti-hypertrophic activity in cardiac hypertrophy.

Angiotensin II increases cardiac protein synthesis in adult rat heart

1993 ◽  
Vol 265 (1) ◽  
pp. H238-H243 ◽  
Author(s):  
D. L. Geenen ◽  
A. Malhotra ◽  
J. Scheuer
Keyword(s):  
Heart Rate ◽  
Protein Synthesis ◽  
Angiotensin Ii ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Rat Heart ◽  
Left Ventricular ◽  
Ang Ii ◽  
Adult Rat ◽  
Transplanted Hearts

This study examined the direct effect of angiotensin II (ANG II) on cardiac muscle atrophy previously observed in the denervated rat heart. Rats with transplanted hearts were infused with normal saline (1 microliter/h) or a subpressor dose of ANG II dissolved in saline (3 micrograms.kg-1.h-1) for 1 wk. Left ventricular (LV) mass of transplanted hearts decreased by 29 and 18% in the saline-infused and ANG II-infused groups, respectively (P < 0.05). Total LV protein synthesis of the transplanted heart was 1.4 +/- 0.1 mg.LV-1.day-1 in the saline compared with 2.2 +/- 0.2 mg.LV-1.day-1 in the ANG II (P < 0.05) group. Heart rate and carotid systolic arterial pressures were not affected by ANG II infusion, and the decrease in alpha-myosin heavy chain normally observed in this model was unchanged between the two groups (61 +/- 3 and 66 +/- 1%, saline vs. ANG II). These data demonstrate that ANG II increases total cardiac protein synthesis in the adult heart, leading to an attenuation in cardiac atrophy. The failure of ANG II to prevent the shift from alpha- to beta-myosin heavy chain may be related to its lack of an effect on heart rate, since other interventions that affect myosin isoenzyme distribution also increase heart rate.

Abstract 833: MicroRNA-206 Controls Cardiac Myosin Heavy Chain Gene Expression By Targeting RXR-α

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Hitoo Nishi ◽  
Koh Ono ◽  
Yoshitaka Iwanaga ◽  
Takahiro Horie ◽  
Minako Kinoshita ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mrna Expression ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Cardiac Contractility ◽  
Neonatal Rat ◽  
Systemic Hypertension ◽  
Expression Ratio ◽  
Rat Cardiomyocytes ◽  
Neonatal Rat Cardiomyocytes

MicroRNA (miRNA) is a small noncoding RNA that modulates posttranscriptional translation. Growing evidence indicates that miRNA is involved in basic cell functions and oncogenesis. In order to find a possible functional role of miRNA in the heart, we first suppressed the expression of Dicer and Ago2, which are required for miRNA biogenesis and function, by lenti-virus-mediated siRNA in neonatal rat cardiomyocytes. Knockdown of Dicer and Ago2 expression significantly increased their beating rate; therefore, we hypothesized that miRNA may regulate the expression of cardiomyocyte contractile protein since cardiac contractility depends on the expression of two myosin heavy chain (MHC) genes, α and β, which are regulated in an antithetical manner by developmental, physiological, and pathological signals. As siRNA against Dicer, which results in the loss of all miRNA function, upregulated α-MHC and downregulated β-MHC mRNA expression, we tried to identify functional miRNAs which have an opposite effect against Dicer siRNA on α/β-MHC expression in the heart. We first performed miRNA microarray analysis in the heart of Dahl salt-sensitive rats in which systemic hypertension caused compensated concentric left ventricular hypertrophy (LVH) at the age of 11 weeks, followed by congestive heart failure (CHF) at the age of 17 weeks. In this model, decreased α/β-MHC ratio is observed at LVH and CHF stages. Next we overexpressed miRNAs which are upregulated in LVH and CHF stages in neonatal rat cardiomyocytes by lenti-virus. After screening these miRNAs, miR-206 was found to decrease the α/β-MHC mRNA expression ratio. The computational miRNA target prediction algorithm showed one of the targets of miR-206 is RXR-α, which regulates α/β-MHC transcription. Forced expression of miR-206 reduced the translation of RXR-α. Moreover, when the expression of RXR-α was downregulated by siRNA, the α/β-MHC mRNA expression ratio decreased in the same manner as miR-206. In conclusion, miR-206 controls the gene expression of MHC isoforms by targeting RXR-α, and these results suggest that miR-206 regulates cardiac contractility.

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