Pharmacological activation of aldehyde dehydrogenase 2 by Alda-1 reverses alcohol-induced hepatic steatosis and cell death in mice Wei Zhong 1 , Wenliang Zhang 1 , Qiong Li 1 , Guoxiang Xie 3 , Qian Sun 1,2 , Xiuhua Sun 1 , Xiaobing Tan 1 , Xinguo Sun 1 , Wei Jia 3 , Zhanxiang Zhou 1,2,⇑ 1 Center for Translational Biomedical Research, University of North Carolina at Greensboro, North Carolina Research Campus, Kannapolis, NC 28081, USA; 2 Department of Nutrition, University of North Carolina at Greensboro, Greensboro, NC 27412, USA; 3 University of Hawaii Cancer Center, Honolulu, HI 96813, USA See Editorial, pages 1228–1230 Background & Aims: Effective therapies for alcoholic liver disease are currently unavailable. The present study tested the efficacy of Alda-1, a specific aldehyde dehydrogenase 2 (ALDH2) activator, in treating alcoholic liver disease. Methods: Male C57BL/6J mice were exposed to alcohol for a time-course study on aldehyde metabolism. The specificity and efficacy of Alda-1 on activating hepatic ALDH2 and aldehyde clearance were determined by acute treatments. Then, mice were fed alcohol for 8 weeks with Alda-1 administration for the last 10 days to test the therapeutic potential of Alda-1. Lastly, H4IIEC3 cells were treated with ethanol, acetaldehyde, or 4-hydroxynonenal to define the link between aldehydes and hepatotoxicity. Results: Alcohol feeding for 8 weeks induced hepatic ALDH2 dysfunction and aldehyde accumulation. One dose of Alda-1 administration elevated hepatic ALDH activity, which was blocked by the specific ALDH2 inhibitor, daidzin. Alda-1 acceler- ated acetaldehyde clearance after acute alcohol intoxication. Alda-1 treatment in the 8-week alcohol feeding model reversed liver damage along with reduction of hepatic aldehydes. Alda-1 re-activated transcription factors, upregulated fatty acid oxidation enzymes, and reversed steatosis. Alcohol-induced endoplasmic reticulum stress and apoptotic cell death were also attenuated by Alda-1. Acetaldehyde or 4-hydroxynonenal treatment to H4IIEC3 cells inactivated transcription factors and induced endoplasmic reticulum stress and apoptosis, while ethanol per se showed limited effects. Conclusions: Pharmacological activation of ALDH2 by Alda-1 reversed alcoholic steatosis and apoptosis through accelerating aldehyde clearance. This study indicates that ALDH2 is a promis- ing molecular target and Alda-1 has therapeutic potential for treating alcoholic liver disease. Ó 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Introduction Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide [1]. Although great efforts to explore poten- tial therapeutic targets for ALD have been made for decades, effective therapies for any stage of ALD are currently lacking. Ethanol is metabolized mainly in the liver through alcohol dehydrogenase (ADH), cytochrome P450 2E1 (CYP2E1), and cata- lase pathways [2], which all generate acetaldehyde. Ethanol meta- bolism also generates reactive oxygen species which, in turn, cause lipid peroxidation, leading to formation of lipid aldehydes such as 4-hydroxynonenol (4-HNE) and malondialdehyde (MDA). Acetaldehyde is known to be detoxified to acetic acid by the alde- hyde dehydrogenase (ALDH) family, of which the mitochondrial ALDH2 is the most potent isoenzyme. Furthermore, ALDH2 is also involved in lipid aldehyde detoxification [3]. The vital role of ALDH2 in aldehyde detoxification and ALD progression has been reported both in humans and experimental models. Individuals carrying ALDH2 mutant alleles showed a high blood acetaldehyde level after alcohol consumption [4], thereby being more susceptible to alcohol-induced organ injury. ALDH2 knockout mice showed an increased acetaldehyde accu- mulation in the liver after alcohol exposure [5,6] or acetaldehyde inhalation [7] along with exaggerated liver inflammation and fibrosis [6]. In contrast, ALDH2 over-expressing mice exhibited Journal of Hepatology 2015 vol. 62 j 1375–1381 Keywords: Aldehyde dehydrogenase 2; Alda-1; Alcohol; Steatosis; Apoptosis. Received 22 July 2014; received in revised form 18 November 2014; accepted 11 December 2014; available online 24 December 2014 q DOI of original article: http://dx.doi.org/10.1016/j.jhep.2015.02.011. ⇑ Corresponding author. Address: Center for Translational Biomedical Research and Department of Nutrition, University of North Carolina at Greensboro, North Carolina Research Campus, 500 Laureate Way, Suite 4226, Kannapolis, NC 28081, USA. Tel.: +1 704 250 5800; fax: +1 704 250 5809. E-mail address: z_zhou@uncg.edu (Z. Zhou). Abbreviations: ALDH2, aldehyde dehydrogenase 2; ALD, Alcoholic liver disease; ADH, alcohol dehydrogenase; 4-HNE, 4-hydroxynonenol; MDA, malondialdehyde; AF, alcohol-fed; PF, pair-fed; BW, body weight; ALT, alanine aminotransferase; AST, aspartate aminotransferase. Research Article