dorsomorphin and Cardiomegaly

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.. 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.. 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.. The present study demonstrates that AMPK activation attenuates cardiomyocyte hypertrophy by modulating the atrophy-related FOXO1/MuRF1 signaling pathway in vitro.

Topics: Aminoimidazole Carboxamide; AMP-Activated Protein Kinases; Animals; Cardiomegaly; Cells, Cultured; Enzyme Activation; Forkhead Transcription Factors; Gene Silencing; Muscle Proteins; Myocytes, Cardiac; Nerve Tissue Proteins; Phenylephrine; Pyrazoles; Pyrimidines; Rats; Rats, Sprague-Dawley; Ribonucleotides; RNA, Small Interfering; Signal Transduction; Transfection; Tripartite Motif Proteins; Ubiquitin-Protein Ligases

Substrate use switches from fatty acids toward glucose in pressure overload-induced cardiac hypertrophy with an acceleration of glycolysis being characteristic. The activation of AMP-activated protein kinase (AMPK) observed in hypertrophied hearts provides one potential mechanism for the acceleration of glycolysis. Here, we directly tested the hypothesis that AMPK causes the acceleration of glycolysis in hypertrophied heart muscle cells. The H9c2 cell line, derived from the embryonic rat heart, was treated with arginine vasopressin (AVP; 1 microM) to induce a cellular model of hypertrophy. Rates of glycolysis and oxidation of glucose and palmitate were measured in nonhypertrophied and hypertrophied H9c2 cells, and the effects of inhibition of AMPK were determined. AMPK activity was inhibited by 6-[4-(2-piperidin-1- yl-ethoxy)-phenyl]-3-pyridin-4-yl-pyrrazolo-[1,5-a]pyrimidine (compound C) or by adenovirus-mediated transfer of dominant negative AMPK. Compared with nonhypertrophied cells, glycolysis was accelerated and palmitate oxidation was reduced with no significant alteration in glucose oxidation in hypertrophied cells, a metabolic profile similar to that of intact hypertrophied hearts. Inhibition of AMPK resulted in the partial reduction of glycolysis in AVP-treated hypertrophied H9c2 cells. Acute exposure of H9c2 cells to AVP also activated AMPK and accelerated glycolysis. These elevated rates of glycolysis were not altered by AMPK inhibition but were blocked by agents that interfere with Ca(2+) signaling, including extracellular EGTA, dantrolene, and 2-aminoethoxydiphenyl borate. We conclude that the acceleration of glycolysis in AVP-treated hypertrophied heart muscle cells is partially dependent on AMPK, whereas the acute glycolytic effects of AVP are AMPK independent and at least partially Ca(2+) dependent.

Topics: AMP-Activated Protein Kinases; Animals; Arginine Vasopressin; Autocrine Communication; Calcium; Cardiomegaly; Cell Line; Energy Metabolism; Glucose; Glycolysis; Myocytes, Cardiac; Paracrine Communication; Pyrazoles; Pyrimidines; Rats; Vasoconstrictor Agents