title: Phenylephrine protects neonatal rat cardiomyocytes from hypoxia and serum deprivation-induced apoptosis.
abstract: Previous studies have shown that alpha-adrenergic activation reduces myocardial damages caused by ischemia/reperfusion. However, the molecular mechanisms of how alpha-adrenergic activation protects the myocardium are not completely understood. The objective of this study was to test the hypothesis that alpha-adrenergic activation protects the myocardium by, at least in part, inhibiting apoptosis in cardiomyocytes. The current data has shown that apoptosis in neonatal rat cardiomyocytes, induced by 24 h treatment with hypoxia (95% N2 and 5% CO2) and serum deprivation, was inhibited by co-treatment with phenylephrine. Pre-treatment with phenylephrine for 24 h also protected cardiomyocytes against subsequent 24 h treatment with hypoxia and serum deprivation. Exposure of cardiomyocytes to phenylephrine for up to 9 days under normoxic conditions did not cause apoptosis. The phenylephrine-mediated cytoprotection was blocked by an alpha-adrenergic antagonist, phentolamine. beta-adrenergic activation with isoproterenol did not protect cardiomyocytes against hypoxia and serum deprivation-induced apoptosis. Under hypoxic conditions, phenylephrine prevented the down-regulation of Bcl-2 and Bcl-X mRNA/protein and induced hypertrophic growth. Phenylephrine-mediated protection was abrogated by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin and was mimicked by the caspase-9 peptidic inhibitor LEHD-fmk. These results suggest that alpha-adrenergic activation protects cardiomyocytes against hypoxia and serum deprivation-induced apoptosis through regulating the expression of mitochondrion-associated apoptosis regulatory genes, preventing activation of mitochondrial damage-induced apoptosis pathway (cytochrome C-caspase-9), and activating hypertrophic growth.
authors.affiliation: Department of Cardiovascular Biology, Rhone-Poulenc Rorer Research and Development, Collegeville, PA 19426, USA. hzhu@collateralthx.com
authors.forename: H
authors.initials: H
authors.lastname: Zhu
authors.forename: S
authors.initials: S
authors.lastname: McElwee-Witmer
authors.forename: M
authors.initials: M
authors.lastname: Perrone
authors.forename: K L
authors.initials: KL
authors.lastname: Clark
authors.forename: A
authors.initials: A
authors.lastname: Zilberstein
mesh_terms: D000185:Actinin / Q000276:immunology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000494:pharmacology; D001769:Blood; D015152:Blotting, Northern; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D015687:Cell Hypoxia; D016895:Culture Media, Serum-Free; D053938:DNA Fragmentation; D019254:Genes, bcl-2 / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D000077191:Wortmannin; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D000316:Adrenergic alpha-Agonists; D000730:Androstadienes; C494813:Bcl2l1 protein, rat; D061945:Caspase Inhibitors; D016895:Culture Media, Serum-Free; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018341:Receptors, Adrenergic, alpha-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D000185:Actinin; D010656:Phenylephrine; D012313:RNA; D009320:Atrial Natriuretic Factor; C505410:Casp3 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D000077191:Wortmannin