Markers of autophagy are downregulated in failing human heart after mechanical unloading.
BACKGROUND
Autophagy is a molecular process that breaks down damaged cellular organelles and yields amino acids for de novo protein synthesis or energy provision. Mechanical unloading with a left ventricular assist device (LVAD) decreases the energy demand of the failing human heart. We tested the hypothesis that LVAD support reverses activation of autophagy.


RESULTS
Paired biopsy samples of left ventricular myocardium were obtained from 9 patients with idiopathic dilated cardiomyopathy (mean duration of LVAD support, 214 days) at the time of implantation and explantation of the LVAD. Transcript and protein levels of markers and mediators of autophagy and apoptosis were measured by quantitative reverse-transcription polymerase chain reaction and Western blotting. TUNEL assays, C9 immunohistochemistry, and 20S proteasome activity assays were also performed. Mechanical unloading significantly decreased mRNA transcript levels of Beclin-1, autophagy-related gene 5 (Atg5), and microtubule-associated protein-1 light chain-3 (MAP1-LC3 or LC3; P<0.02). Protein levels of Beclin-1, Atg5-Atg12 conjugate, and LC3-II were also significantly reduced after LVAD support (P<0.05). A significant increase in 20S proteasome activity was observed with unloading, in parallel to the decrease in autophagic markers. Although BNIP3 and the ratio of activated caspase 3 to procaspase 3 increased after LVAD support, Bcl-2 and TUNEL-positive nuclei were not significantly different between samples.


CONCLUSIONS
Mechanical unloading of the failing human heart decreases markers of autophagy. These findings suggest that autophagy may be an adaptive mechanism in the failing heart, and this phenomenon is attenuated by LVAD support.
Kassiotis
Christos
C
The University of Texas Medical School at Houston, 77030, USA.
Ballal
Kalpana
K
Wellnitz
Kari
K
Vela
Deborah
D
Gong
Mei
M
Salazar
Rebecca
R
Frazier
O Howard
OH
Taegtmeyer
Heinrich
H
D000328:Adult; D017209:Apoptosis; D001343:Autophagy; D015415:Biomarkers; D015536:Down-Regulation; D005260:Female; D006333:Heart Failure / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D006353:Heart-Assist Devices; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000502:physiology; D008875:Middle Aged; D032383:Myocytes, Cardiac / Q000473:pathology; D009336:Necrosis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism
C090121:BNIP3 protein, human; D015415:Biomarkers; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex