Ethanol increases hepatic mitophagy driven by unknown mechanisms. Type 1 mitophagy sequesters polarized mitochondria for nutrient recovery and cytoplasmic remodeling. In Type 2, mitochondrial depolarization (mtDepo) initiates mitophagy to remove the damaged organelles. Previously, we showed that acute ethanol administration produces reversible hepatic mtDepo. Here, we tested the hypothesis that ethanol-induced mtDepo initiates Type 2 mitophagy. GFP-LC3 transgenic mice were gavaged with ethanol (2–6 g/kg) with and without pre-treatment with agents that decrease or increase mtDepo–Alda-1, tacrolimus, or disulfiram. Without ethanol, virtually all hepatocytes contained polarized mitochondria with infrequent autophagic GFP-LC3 puncta visualized by intravital microscopy. At ~4 h after ethanol treatment, mtDepo occurred in an all-or-none fashion within individual hepatocytes, which increased dose dependently. GFP-LC3 puncta increased in parallel, predominantly in hepatocytes with mtDepo. Mitochondrial PINK1 and PRKN/parkin also increased. After covalent labeling of mitochondria with MitoTracker Red (MTR), GFP-LC3 puncta encircled MTR-labeled mitochondria after ethanol treatment, directly demonstrating mitophagy. GFP-LC3 puncta did not associate with fat droplets visualized with BODIPY558/568, indicating that increased autophagy was not due to lipophagy. Before ethanol administration, rhodamine-dextran (RhDex)-labeled lysosomes showed little association with GFP-LC3. After ethanol treatment, TFEB (transcription factor EB) translocated to nuclei, and lysosomal mass increased. Many GFP-LC3 puncta merged with RhDex-labeled lysosomes, showing autophagosomal processing into lysosomes. After ethanol treatment, disulfiram increased, whereas Alda-1 and tacrolimus decreased mtDepo, and mitophagy changed proportionately. In conclusion, mtDepo after acute ethanol treatment induces mitophagic sequestration and subsequent lysosomal processing. Abbreviations : AcAld, acetaldehyde; ADH, alcohol dehydrogenase; ALDH, aldehyde dehydrogenase; ALD, alcoholic liver disease; Alda-1, N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFP, green fluorescent protein; LAMP1, lysosomal-associated membrane protein 1; LMNB1, lamin B1; MAA, malondialdehyde-acetaldehyde adducts; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MPT, mitochondrial permeability transition; mtDAMPS, mitochondrial damage-associated molecular patterns; mtDepo, mitochondrial depolarization; mtDNA, mitochondrial DNA; MTR, MitoTracker Red; PI, propidium iodide; PINK1, PTEN induced putative kinase 1; PRKN, parkin; RhDex, rhodamine dextran; TFEB, transcription factor EB; Tg, transgenic; TMRM, tetramethylrhodamine methylester; TOMM20, translocase of outer mitochondrial membrane 20; VDAC, voltage-dependent anion channel

Chronic binge drinking is common among patients with alcohol-associated steatohepatitis. Therefore, we tested the hypothesis that chronic binge ethanol exposure disrupts mitophagic processing and stimulates release of mitochondrial damage-associated molecular patterns (mtDAMPs), thereby promoting hepatic inflammation and fibrosis after chronic binge ethanol (CBE) exposure in mice using the National Institute of Alcohol Abuse and Alcoholism model. After CBE, hepatic steatosis, liver injury, inflammation, and hepatic stellate cell (HSC) activation occurred. Alda-1, an aldehyde dehydrogenase-2 activator, attenuated these changes. After CBE, mitochondrial depolarization (mtDepo) occurred in ~85% hepatocytes, and mitophagy-associated proteins increased, which Alda-1 blunted. By contrast, transcription factor-EB (master regulator of lysosomal biogenesis) and lysosomal markers decreased, indicating disrupted lysosomal processing. After mitophagy, mitochondrial biogenesis (MB) restores mitochondrial mass and function. After CBE, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (MB regulator), mitochondrial transcription factor-A, oxidative phosphorylation proteins, and fatty acid oxidation all decreased, which Alda-1 largely restored. After CBE, serum mtDAMPs (mitochondrial DNA and cytochrome c) increased 3- to 10-fold. In vitro, mitochondrial DNA stimulated macrophage and HSC activation, which was prevented by toll-like receptor-9 inhibition. In conclusion, CBE increases mtDepo in an acetaldehyde-dependent fashion, leading to mitophagic overburden, disruption of mitochondrial homeostasis, mtDAMP release, and ultimately development of liver inflammation and injury.