Facilitated ethanol metabolism promotes cardiomyocyte contractile dysfunction through autophagy in murine hearts

Abstract

Abbreviations: 3-MA, 3-methyladenine; ± dL/dt, maximal velocity of shortening/relengthening; ADH, alcohol dehydrogenase; ANF, atrial natriuretic factor; CaMKII, Ca 2+ -calmodulin-dependent protein kinase; ER, endoplasmic reticulum; FVB, friendly virus-B type; H&E, hematoxylin and eosin; mTOR, mammalian target of rapamycin; PtdIns3K, phosphatidylinositol-3-kinase; PS, peak shortening; SERCA, sarco(endo)plasmic reticulum Ca 2+ -ATPase; TPS, time-to-90% peak shortening; TR 90 , time-to-90% relengtheningChronic drinking leads to myocardial contractile dysfunction where ethanol metabolism plays an essential role. Acetaldehyde, the main ethanol metabolite, mediates alcohol-induced cell injury although the underlying mechanism is still elusive. This study was designed to examine the mechanism involved in accelerated ethanol metabolism-induced cardiac defect with a focus on autophagy. Wild-type FVB and cardiac-specific overexpression of alcohol dehydrogenase mice were placed on a 4% nutrition-balanced alcohol diet for 8 weeks. Myocardial histology, immunohistochemistry, autophagy markers and signal molecules were examined. Expression of micro RNA miR-30a, a potential target of Beclin 1, was evaluated by real-time PCR. Chronic alcohol intake led to cardiac acetaldehyde accumulation, hypertrophy and overt autophagosome accumulation (LC3-II and Atg7), the effect of which was accentuated by ADH. Signaling molecules governing autophagy initiation including class III PtdIns3K, phosphorylation of mTOR and p70S6K were enhanced and dampened, respectively, following alcohol intake. These alcohol-induced signaling responses were augmented by ADH. ADH accentuated or unmasked alcohol-induced downregulation of Bcl-2, Bcl-xL and MiR-30a. Interestingly, ADH aggravated alcohol-induced p62 accumulation. Autophagy inhibition using 3-MA abolished alcohol-induced cardiomyocyte contractile anomalies. Moreover, acetaldehyde led to cardiomyocyte contractile dysfunction and autophagy induction, which was ablated by 3-MA. Ethanol or acetaldehyde increased GFP-LC3 puncta in H9c2 cells, the effect of which was ablated by 3-MA but unaffected by lysosomal inhibition using bafilomycin A 1 , E64D and pepstatin A. In summary, these data suggested that facilitated acetaldehyde production via ADH following alcohol intake triggered cardiac autophagosome formation along with impaired lysosomal degradation, en route to myocardial defect.

Heavy metal scavenger metallothionein mitigates deep hypothermia-induced myocardial contractile anomalies: role of autophagy

“…Nuclei were counterstained with DAPI. Cardiac sections were visualized, and the ratio between LC3B-stained cell and nucleus was calculated on a digital microscope (ϫ400) using the Image J (version 1.34S) and Photoshop software (13).…”

Chronic alcohol consumption disrupts myocardial protein balance and function in aged, but not adult, female F344 rats

“…Although this pathway was not investigated in depth, several key regulators of autophagy, such as LC3B-I and -II, Agt7, and Agt12, were increased in hearts from alcohol-fed aged rats. Increased cardiac autophagy has also been reported in alcohol-fed mice (22). The induction of the UPP and autophagy is tightly controlled by a host of regulators and of these the Akt-FoxO signaling pathway is arguably the most important (7,68,81).…”

Activation of a7 Nicotinic Acetylcholine Receptor Protects Against Oxidant Stress Damage Through Reducing Vascular Peroxidase-1 in a JNK Signaling-Dependent Manner in Endothelial Cells

“…Immunofluorescence was performed as described previously [23,24]. HUVECs were seeded in confocal dishes approximately 24 h prior to imaging to ensure proper cell attachment.…”