ULK1 plays a critical role in AMPK-mediated myocardial autophagy and contractile dysfunction following acute alcohol challenge

Curr Pharm Des. 2013;19(27):4874-87. doi: 10.2174/1381612811319270010.

Abstract

This study was designed to evaluate the role of ULK1 in AMPK-mediated myocardial autophagy and contractile dysfunction following acute alcohol challenge. Wild-type and AMPK knockout mice were challenged with ethanol (3 g/kg/d, i.p.) for 3 days. Myocardial function was evaluated using echocardiography and edge-detection. Western blot analysis was employed to evaluate the levels of AMPK, Raptor, mTOR, the AMPK downstream signal ULK1 and autophagy markers Beclin-1 and LC3-II. siRNA was used to knockdown ULK1 in H9C2 myoblasts. GFP-LC3 puncta was used to evaluate autophagosome formation. Alcohol challenge compromised cardiac function as evidenced by decreased fractional shortening, peak shortening and intracellular Ca²⁺ rise, prolonged relengthening and intracellular Ca²⁺ decay in WT mice, the effects of which were mitigated by AMPK knockout. Ethanol exposure facilitated myocardial autophagy as evidenced by enhanced LC3-II level, as well as phosphorylation of AMPK, Raptor, and dephosphorylation of mTOR and ULKI in WT hearts, which were alleviated by AMPK knockout. Pharmacological inhibition of AMPK using compound C attenuated ethanol-induced autophagosome formation, AMPK phosphorylation, ULK1 dephosphorylation and apoptosis. Ethanol exposure-induced cardiomyocyte contractile defects and autophagosome accumulation were reversed by the autophagy inhibitor 3-MA. Similarly, knockdown of ULK1 using siRNA in H9C2 cells ablated ethanol-induced autophagosome accumulation, LC3-II expression and cell death. Lysosomal inhibition using bafilomycin, E64-D and pepstatin A potentiated ethanol-induced increase in autophagosome formation. Taken together, our results suggest that ULK1 may play a critical role in AMPK-mediated myocardial autophagy, apoptosis and contractile dysfunction following acute alcohol challenge.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism*
  • Animals
  • Autophagy* / drug effects
  • Autophagy-Related Protein-1 Homolog
  • Calcium Signaling
  • Cardiomyopathy, Alcoholic / metabolism*
  • Cardiomyopathy, Alcoholic / pathology
  • Cardiomyopathy, Alcoholic / physiopathology
  • Cell Line
  • Disease Models, Animal*
  • Gene Silencing
  • Heart / physiopathology
  • Humans
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Male
  • Mice
  • Mice, Knockout
  • Myoblasts, Cardiac / enzymology
  • Myoblasts, Cardiac / metabolism
  • Myoblasts, Cardiac / pathology
  • Myocardial Contraction
  • Myocardium / metabolism*
  • Myocardium / pathology
  • Phagosomes / metabolism
  • Phagosomes / pathology
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • RNA, Small Interfering
  • Rats

Substances

  • Intracellular Signaling Peptides and Proteins
  • RNA, Small Interfering
  • Autophagy-Related Protein-1 Homolog
  • Protein Serine-Threonine Kinases
  • ULK1 protein, rat
  • Ulk1 protein, mouse
  • AMP-Activated Protein Kinases