Hexarelin protects rat cardiomyocytes from angiotensin II-induced apoptosis in vitro.
Loss of cardiomyocytes by apoptosis is proposed to cause heart failure. Angiotensin II (ANG II), an important neurohormonal factor during heart failure, can induce cardiomyocyte apoptosis. Inasmuch as hexarelin has been reported to have protective effects in this process, we examined whether hexarelin can prevent cardiomyocytes from ANG II-induced cell death. Cultured cardiomyocytes from neonatal rats were stimulated with ANG II. Apoptosis was evaluated using fluorescence microscopy, TdT-mediated dUTP nick-end labeling (TUNEL) method, flow cytometry, DNA laddering, and analysis of cell viability by (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). It was found that incubation with 0.1 micromol/l ANG II for 48 h increased cardiomyocyte apoptosis. Administration of 0.1 micromol/l hexarelin significantly decreased this ANG II-induced apoptosis and DNA fragmentation and increased myocyte viability. To further investigate the underlying mechanisms, caspase-3 activity assay and mRNA expression of Bax, Bcl-2, and growth hormone secretagogue receptor (GHS-R; the supposed hexarelin binding site) were examined. GHS-R mRNA was abundantly expressed in cardiomyocytes and was upregulated after administration of hexarelin. These results suggest that hexarelin abates cardiomyocytes from ANG II-induced apoptosis possibly via inhibiting the increased caspase-3 activity and Bax expression induced by ANG II and by increasing the expression of Bcl-2, which is depressed by ANG II. Whether the upregulated expression of GHS-R induced by hexarelin is associated with this antiapoptotic effect deserves further investigation.
Pang
Jin-Jiang
JJ
Prince Henry's Institute of Medical Research, PO Box 5152, Clayton, Victoria 3168, Australia.
Xu
Rong-Kun
RK
Xu
Xiang-Bin
XB
Cao
Ji-Min
JM
Ni
Chao
C
Zhu
Wen-Ling
WL
Asotra
Kamlesh
K
Chen
Meng-Chin
MC
Chen
Chen
C
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004396:Coloring Agents; D004305:Dose-Response Relationship, Drug; D004587:Electrophoresis, Agar Gel; D005434:Flow Cytometry; D006133:Growth Substances / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D004396:Coloring Agents; D006133:Growth Substances; D009842:Oligopeptides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013778:Tetrazolium Salts; D013844:Thiazoles; D014662:Vasoconstrictor Agents; D051028:bcl-2-Associated X Protein; C086184:hexarelin; D000804:Angiotensin II; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue