Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease

Orkhontuya Tsedensodnom, Ana M. Vacaru, Deanna L. Howarth, Chunyue Yin, Kirsten Sadler Edepli

    Research output: Contribution to journalArticle

    Abstract

    Secretory pathway dysfunction and lipid accumulation (steatosis) are the two most common responses of hepatocytes to ethanol exposure and are major factors in the pathophysiology of alcoholic liver disease (ALD). However, the mechanisms by which ethanol elicits these cellular responses are not fully understood. Recent data indicates that activation of the unfolded protein response (UPR) in response to secretory pathway dysfunction can cause steatosis. Here, we examined the relationship between alcohol metabolism, oxidative stress, secretory pathway stress and steatosis using zebrafish larvae. We found that ethanol was immediately internalized and metabolized by larvae, such that the internal ethanol concentration in 4-day-old larvae equilibrated to 160 mM after 1 hour of exposure to 350 mM ethanol, with an average ethanol metabolism rate of 56 μmol/larva/hour over 32 hours. Blocking alcohol dehydrogenase 1 (Adh1) and cytochrome P450 2E1 (Cyp2e1), the major enzymes that metabolize ethanol, prevented alcohol-induced steatosis and reduced induction of the UPR in the liver. Thus, we conclude that ethanol metabolism causes ALD in zebrafish. Oxidative stress generated by Cyp2e1-mediated ethanol metabolism is proposed to be a major culprit in ALD pathology. We found that production of reactive oxygen species (ROS) increased in larvae exposed to ethanol, whereas inhibition of the zebrafish CYP2E1 homolog or administration of antioxidants reduced ROS levels. Importantly, these treatments also blocked ethanol-induced steatosis and reduced UPR activation, whereas hydrogen peroxide (H2O2) acted as a pro-oxidant that synergized with low doses of ethanol to induce the UPR. Collectively, these data demonstrate that ethanol metabolism and oxidative stress are conserved mechanisms required for the development of steatosis and hepatic dysfunction in ALD, and that these processes contribute to ethanol-induced UPR activation and secretory pathway stress in hepatocytes.

    Original languageEnglish (US)
    Pages (from-to)1213-1226
    Number of pages14
    JournalDMM Disease Models and Mechanisms
    Volume6
    Issue number5
    DOIs
    StatePublished - Sep 1 2013

    Fingerprint

    Unfolded Protein Response
    Alcoholic Liver Diseases
    Oxidative stress
    Zebrafish
    Metabolism
    Liver
    Oxidative Stress
    Ethanol
    Chemical activation
    Proteins
    Secretory Pathway
    Larva
    Cytochrome P-450 CYP2E1
    Reactive Oxygen Species
    Hepatocytes
    Alcohols
    Alcohol Dehydrogenase
    Pathology
    Hydrogen Peroxide

    ASJC Scopus subject areas

    • Neuroscience (miscellaneous)
    • Medicine (miscellaneous)
    • Immunology and Microbiology (miscellaneous)
    • Biochemistry, Genetics and Molecular Biology(all)

    Cite this

    Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease. / Tsedensodnom, Orkhontuya; Vacaru, Ana M.; Howarth, Deanna L.; Yin, Chunyue; Sadler Edepli, Kirsten.

    In: DMM Disease Models and Mechanisms, Vol. 6, No. 5, 01.09.2013, p. 1213-1226.

    Research output: Contribution to journalArticle

    Tsedensodnom, Orkhontuya ; Vacaru, Ana M. ; Howarth, Deanna L. ; Yin, Chunyue ; Sadler Edepli, Kirsten. / Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease. In: DMM Disease Models and Mechanisms. 2013 ; Vol. 6, No. 5. pp. 1213-1226.
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