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Phenylephrine-Induced Cardiomyocyte Injury Is Triggered by Superoxide Generation through Uncoupled Endothelial Nitric-Oxide Synthase and Ameliorated by 3-[2-[4-(3-Chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxyinda zole (DY-9836), a Novel Calmodulin Antagonist

Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Molecular pharmacology (Impact Factor: 4.12). 10/2008; 75(1):101-12. DOI: 10.1124/mol.108.050716
Source: PubMed

ABSTRACT The pathophysiological relevance of endothelial nitric-oxide synthase (eNOS)-induced superoxide production in cardiomyocyte injury after prolonged phenylephrine (PE) exposure remains unclear. The aims of this study were to define the mechanism of O2(*) production by uncoupled eNOS and evaluate the therapeutic potential of a novel calmodulin antagonist 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxyindazole (DY-9836) to rescue hypertrophied cardiomyocytes from PE-induced injury. In cultured rat cardiomyocytes, prolonged exposure for 96 h to PE led to translocation from membrane to cytosol of eNOS and breakdown of caveolin-3 and dystrophin. When NO and O2(*) production were monitored in PE-treated cells by 4-amino-5-methylamino-2',7'-difluorofluorescein and dihydroethidium, respectively, Ca(2+)-induced NO production elevated by 5.7-fold (p < 0.01) after 48-h PE treatment, and the basal NO concentration markedly elevated (16-fold; p < 0.01) after 96-h PE treatment. On the other hand, the O2(*) generation at 96 h was closely associated with an increased uncoupled eNOS level. Coincubation with DY-9836 (3 microM) during the last 48 h inhibited the aberrant O2(*) generation nearly completely and NO production by 72% (p < 0.01) after 96 h of PE treatment and inhibited the breakdown of caveolin-3/dystrophin in cardiomyocytes. PE-induced apoptosis assessed by TdT-mediated dUTP nick-end labeling staining was also attenuated by DY-9836 treatment. These results suggest that O2(*) generation by uncoupled eNOS probably triggers PE-induced cardiomyocyte injury. Inhibition of abnormal O2(*) and NO generation by DY-9836 treatment represents an attractive therapeutic strategy for PE/hypertrophy-induced cardiomyocyte injury.

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    • "It has been shown that oxidative inhibition of cystathionine β-synthase occurs, leading to accumulation of intracellular homocysteine [37]. Previous studies have demonstrated the production and accumulation of reactive oxygen species PE in cardiomyocytes [38]. Therefore, it is possible that PE-induced increase of homocysteine concentrations may result from the oxidative inhibition of the cystathionine β-synthase, which will be determined in our future studies. "
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    ABSTRACT: Cardiomyocyte hypertrophy induced by phenylephrine (PE) is accompanied by suppression of cytochrome c oxidase (CCO) activity, and copper (Cu) supplementation restores CCO activity and reverses the hypertrophy. The present study was aimed to understand the mechanism of PE-induced decrease in CCO activity. Primary cultures of neonatal rat cardiomyocytes were treated with PE at a final concentration of l00 µM in cultures for 72 h to induce cell hypertrophy. The CCO activity was determined by enzymatic assay and changes in CCO subunit COX-IV as well as copper chaperones for CCO (COX17, SCO2, and COX11) were determined by Western blotting. PE treatment increased both intracellular and extracellular homocysteine concentrations and decreased intracellular Cu concentrations. Studies in vitro found that homocysteine and Cu form complexes. Inhibition of the intracellular homocysteine synthesis in the PE-treated cardiomyocytes prevented the increase in the extracellular homocysteine concentration, retained the intracellular Cu concentration, and preserved the CCO activity. PE treatment decreased protein concentrations of the COX-IV, and the Cu chaperones COX17, COX11, and SCO2. These PE effects were prevented by either inhibition of the intracellular homocysteine synthesis or Cu supplementation. Therefore, PE-induced elevation of homocysteine restricts Cu availability through its interaction with Cu and suppression of Cu chaperones, leading to the decrease in CCO enzyme activity.
    PLoS ONE 06/2013; 8(6):e67549. DOI:10.1371/journal.pone.0067549 · 3.23 Impact Factor
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    • "In situ DNA fragmentation was assessed using a TUNEL assay as previously described [20]. Images were recorded after counterstaining with TO-PRO3 (nuclei marker), and cardiac myocytes were identified by staining with anti-sarcomeric actinin (green). "
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    PLoS ONE 09/2011; 6(9):e24724. DOI:10.1371/journal.pone.0024724 · 3.23 Impact Factor
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