It is known that activated MEK1/2 specifically catalyzes the phosphorylation of ERK1/2, and thus U0126 can block the activation of ERK. that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Abstract Background Alcohol insult triggers complex events in the liver, promoting fibrogenic/inflammatory signals and in more advanced cases, aberrant matrix deposition. It is well accepted that the regenerative capacity of the adult liver is impaired during alcohol injury. The liver progenitor/stem cells have been shown to play an important role in liver regeneration -in response to various chronic injuries; however, the effects of alcohol on stem cell differentiation in the liver are not well understood. Methods We employed hepatic progenitor cells derived from hESCs to study the impact of ethanol on hepatocyte differentiation by exposure of these progenitor cells to ethanol during hepatocyte differentiation. Results We found that ethanol negatively regulated hepatic differentiation of hESC-derived hepatic progenitor cells in a dose-dependent manner. There was also a moderate cell cycle arrest at G1/S checkpoint in the ethanol treated cells, which is associated with a reduced level of cyclin D1 in these cells. Ethanol treatment specifically inhibited the activation of the ERK but not JNK nor the p38 MAP signaling pathway. At the same time, the WNT signaling pathway was also reduced in the cells exposed to ethanol. Upon evaluating the CORO1A effects of the inhibitors of these two signaling pathways, we determined that the Erk inhibitor replicated the effects of ethanol on the hepatocyte differentiation and attenuated the WNT/-catenin signaling, however, inhibitors of WNT only partially replicated the effects of ethanol on the hepatocyte differentiation. Conclusion Our results demonstrated that ethanol negatively regulated hepatic differentiation of hESC-derived hepatic progenitors through inhibiting the MAPK/ERK signaling pathway, and subsequently attenuating the WNT signaling pathway. Thus, our finding provides a novel insight into the mechanism by which alcohol regulates cell fate selection of hESC-derived hepatic progenitor cells, and the identified pathways may provide therapeutic targets aimed at promoting liver repair and regeneration during alcoholic injury. Introduction The liver is the Pardoprunox HCl (SLV-308) major location for the metabolism of ethanol, and Pardoprunox HCl (SLV-308) alcoholic hepatitis and other forms of alcoholic liver disease (ALD) are major complications of chronic excessive ethanol intake [1], [2]. At an early stage in the course of alcohol-induced liver injury, damaged hepatocytes can be replaced Pardoprunox HCl (SLV-308) by the proliferation of adult hepatocytes. However, with the course of more progressive and chronic injury, hepatocyte proliferation becomes less successful in the re-establishment of an adequate hepatocyte mass for the restoration of liver function. At that stage, the differentiation of hepatic stem/progenitor cells becomes critical in hepatocyte regeneration and in the other elements of the repair process, including fibrogenesis. Although the types and nomenclature of liver stem/progenitor cells are in some dispute, and differ in rodents and humans, there Pardoprunox HCl (SLV-308) is some consensus that they evolve from bipotent stem cells that resides within the Canal of the Hering between the hepatocyte plate and bile duct. These liver stem/progenitor cells are shown to give rise to both hepatocytes and cholangiocytes in response to various chronic injuries [3], [4]. The effects of alcohol injury of adult liver cells have been studied extensively. Alcohol injures hepatocytes and activates stellate cells as well as Kupffer cells, leading to a loss of hepatic function, aberrant deposition of ECM proteins and production of inflammatory and profibrogenic signals [5], [6], [7], [8]. However, relatively little is known about the human liver stem cell response to this toxicant [9]. While the isolation of human hepatic progenitor cells has been reported in the literature [10], [11], [12], the scarcity of human livers and small numbers of progenitor/stem cells Pardoprunox HCl (SLV-308) in the liver make it impractical to conduct mechanistic studies of alcoholic injury on liver progenitor/stem cells model to evaluate the impact of alcohol on liver progenitor/stem cells. Hepatic derivatives from human embryonic stem cells (hESCs) provide promising resources to acquire knowledge of the cellular and molecular bases underlying human liver development and pathological.