Activation of AMPK inhibits cardiomyocyte hypertrophy by modulating of the FOXO1/MuRF1 signaling pathway in vitro.
OBJECTIVE
To examine the inhibitory effects of adenosine monophosphate-activated protein kinase (AMPK) activation on cardiac hypertrophy in vitro and to investigate the underlying molecular mechanisms.


METHODS
Cultured neonatal rat cardiomyocytes were treated with the specific AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the specific AMPK antagonist Compound C, and then stimulated with phenylephrine (PE). The Muscle RING finger 1 (MuRF1)-small interfering RNA (siRNA) was transfected into cardiomyocytes using Lipofectamine 2000. The surface area of cultured cardiomyocytes was measured using planimetry. The protein degradation was determined using high performance liquid chromatography (HPLC). The expression of beta-myosin heavy chain (beta-MHC) and MuRF1, as well as the phosphorylation levels of AMPK and Forkhead box O 1 (FOXO1), were separately measured using Western blot or real-time polymerase chain reaction.


RESULTS
Activation of AMPK by AICAR 0.5 mmol/L inhibited PE-induced increase in cardiomyocyte area and beta-MHC protein expression and PE-induced decrease in protein degradation. Furthermore, AMPK activation increased the activity of transcription factor FOXO1 and up-regulated downstream atrogene MuRF1 mRNA and protein expression. Treatment of hypertrophied cardiomyocytes with Compound C 1 micromol/L blunted the effects of AMPK on cardiomyocyte hypertrophy and changes to the FOXO1/MuRF1 pathway. The effects of AICAR on cardiomyocyte hypertrophy were also blocked after MuRF1 was silenced by transfection of cardiomyocytes with MuRF1-siRNA.


CONCLUSIONS
The present study demonstrates that AMPK activation attenuates cardiomyocyte hypertrophy by modulating the atrophy-related FOXO1/MuRF1 signaling pathway in vitro.
Chen
Bao-lin
BL
Department of Cardiology, the First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China.
Ma
Yue-dong
YD
Meng
Rong-sen
RS
Xiong
Zhao-jun
ZJ
Wang
Hai-ning
HN
Zeng
Jun-yi
JY
Liu
Chen
C
Dong
Yu-gang
YG
D055372:AMP-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D006332:Cardiomegaly / Q000188:drug therapy / Q000201:enzymology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D020868:Gene Silencing; D009124:Muscle Proteins / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D012265:Ribonucleotides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000071161:Forkhead Box Protein O1
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide; D051858:Forkhead Transcription Factors; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D010656:Phenylephrine; D011720:Pyrazoles; D011743:Pyrimidines; D034741:RNA, Small Interfering; D012265:Ribonucleotides; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases; C516138:dorsomorphin; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1; C499086:Trim63 protein, rat; C031143:AICA ribonucleotide