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Activation of growth hormone releasing hormone (GHRH) receptor stimulates cardiac reverse remodeling after myocardial infarction (MI).

ABSTRACT: Both cardiac myocytes and cardiac stem cells (CSCs) express the receptor of growth hormone releasing hormone (GHRH), activation of which improves injury responses after myocardial infarction (MI). Here we show that a GHRH-agonist (GHRH-A; JI-38) reverses ventricular remodeling and enhances functional recovery in the setting of chronic MI. This response is mediated entirely by activation of GHRH receptor (GHRHR), as demonstrated by the use of a highly selective GHRH antagonist (MIA-602). One month after MI, animals were randomly assigned to receive: placebo, GHRH-A (JI-38), rat recombinant GH, MIA-602, or a combination of GHRH-A and MIA-602, for a 4-wk period. We assessed cardiac performance and hemodynamics by using echocardiography and micromanometry derived pressure-volume loops. Morphometric measurements were carried out to determine MI size and capillary density, and the expression of GHRHR was assessed by immunofluorescence and quantitative RT-PCR. GHRH-A markedly improved cardiac function as shown by echocardiographic and hemodynamic parameters. MI size was substantially reduced, whereas myocyte and nonmyocyte mitosis was markedly increased by GHRH-A. These effects occurred without increases in circulating levels of growth hormone and insulin-like growth factor I and were, at least partially, nullified by GHRH antagonism, confirming a receptor-mediated mechanism. GHRH-A stimulated CSCs proliferation ex vivo, in a manner offset by MIA-602. Collectively, our findings reveal the importance of the GHRH signaling pathway within the heart. Therapy with GHRH-A although initiated 1 mo after MI substantially improved cardiac performance and reduced infarct size, suggesting a regenerative process. Therefore, activation of GHRHR provides a unique therapeutic approach to reverse remodeling after MI.

SUBMITTER: Kanashiro-Takeuchi RM

PROVIDER: S-EPMC3258609 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Activation of growth hormone releasing hormone (GHRH) receptor stimulates cardiac reverse remodeling after myocardial infarction (MI).

Kanashiro-Takeuchi Rosemeire M RM Takeuchi Lauro M LM Rick Ferenc G FG Dulce Raul R Treuer Adriana V AV Florea Victoria V Rodrigues Claudia O CO Paulino Ellena C EC Hatzistergos Konstantinos E KE Selem Sarah M SM Gonzalez Daniel R DR Block Norman L NL Schally Andrew V AV Hare Joshua M JM

Proceedings of the National Academy of Sciences of the United States of America 20111227 2

Both cardiac myocytes and cardiac stem cells (CSCs) express the receptor of growth hormone releasing hormone (GHRH), activation of which improves injury responses after myocardial infarction (MI). Here we show that a GHRH-agonist (GHRH-A; JI-38) reverses ventricular remodeling and enhances functional recovery in the setting of chronic MI. This response is mediated entirely by activation of GHRH receptor (GHRHR), as demonstrated by the use of a highly selective GHRH antagonist (MIA-602). One mont ...[more]

PMID: 22203988

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Project description:AimsRetinoic acid receptor-related orphan nuclear receptor ?t (ROR?t) is a transcriptional factor responsible for IL-17-producing T-cell differentiation. Although it was demonstrated that ROR?t plays essential roles in the onset of autoimmune myocarditis, pathophysiological significance of ROR?t in cardiac remodeling after myocardial infarction (MI) remains to be fully elucidated.Methods and resultsMI was generated by ligating coronary artery. The expression of ROR?t and IL-17A transcripts increased in murine hearts after MI. Additionally, immunohistochemical staining revealed that ROR?t-expressing cells infiltrated in the border zone after MI. Flow cytometric analysis showed that ROR?t-expressing cells were released from the spleen at day 1 after MI. Though ROR?t-expressing cells in spleen expressed ??TCR or CD4, ??TCR+ cells were major population of ROR?t-expressing cells that infiltrated into post-infarct myocardium. To address the biological functions of ROR?t-expressing cells in infarcted hearts, we used mice with enhanced GFP gene heterozygously knocked-in at ROR?t locus (ROR?t+/- mice), which physiologically showed reduced expression of ROR?t mRNA in thymus. Kaplan-Meier analysis showed that MI-induced mortality was higher in ROR?t+/- mice than wild-type (WT) mice. Masson's trichrome staining demonstrated that cardiac injury was exacerbated in ROR?t+/- mice 7 days after MI (Injured area: ROR?t+/-; 42.1±6.5%, WT; 34.0±3.7%, circumference of injured myocardium: ROR?t+/-; 61.8±4.8%, WT; 49.6±5.1%), accompanied by exacerbation of cardiac function (fractional shortening: ROR?t+/-; 32.9±2.9%, WT; 38.3±3.6%). Moreover, immunohistochemical analyses revealed that capillary density in border zone was significantly reduced in ROR?t+/- mice after MI, compared with WT mice, associated with the reduced expression of angiopoietin 2. Finally, the mRNA expression of ROR?t, IL-17A, IL-17F and IL-23 receptor (IL-23R) mRNA and protein expression of IL-10 were decreased in ROR?t+/- hearts.ConclusionsHeterozygous deletion of ROR?t gene resulted in aggravated cardiac remodeling, accompanied by reduced capillary density, after MI, suggesting that ROR?t-expressing cells contribute to tissue repair in infarcted myocardium.

Dataset Information

Activation of growth hormone releasing hormone (GHRH) receptor stimulates cardiac reverse remodeling after myocardial infarction (MI).

Publications

Activation of growth hormone releasing hormone (GHRH) receptor stimulates cardiac reverse remodeling after myocardial infarction (MI).

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