Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease
SUMMARY 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 n...
Main Authors: | , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
The Company of Biologists
2013-09-01
|
Series: | Disease Models & Mechanisms |
Online Access: | http://dmm.biologists.org/content/6/5/1213 |
id |
doaj-756f7463a544432b9611015f93364b4d |
---|---|
record_format |
Article |
spelling |
doaj-756f7463a544432b9611015f93364b4d2020-11-25T00:57:27ZengThe Company of BiologistsDisease Models & Mechanisms1754-84031754-84112013-09-01651213122610.1242/dmm.012195012195Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver diseaseOrkhontuya TsedensodnomAna M. VacaruDeanna L. HowarthChunyue YinKirsten C. SadlerSUMMARY 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.http://dmm.biologists.org/content/6/5/1213 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Orkhontuya Tsedensodnom Ana M. Vacaru Deanna L. Howarth Chunyue Yin Kirsten C. Sadler |
spellingShingle |
Orkhontuya Tsedensodnom Ana M. Vacaru Deanna L. Howarth Chunyue Yin Kirsten C. Sadler Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease Disease Models & Mechanisms |
author_facet |
Orkhontuya Tsedensodnom Ana M. Vacaru Deanna L. Howarth Chunyue Yin Kirsten C. Sadler |
author_sort |
Orkhontuya Tsedensodnom |
title |
Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
title_short |
Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
title_full |
Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
title_fullStr |
Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
title_full_unstemmed |
Ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
title_sort |
ethanol metabolism and oxidative stress are required for unfolded protein response activation and steatosis in zebrafish with alcoholic liver disease |
publisher |
The Company of Biologists |
series |
Disease Models & Mechanisms |
issn |
1754-8403 1754-8411 |
publishDate |
2013-09-01 |
description |
SUMMARY
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. |
url |
http://dmm.biologists.org/content/6/5/1213 |
work_keys_str_mv |
AT orkhontuyatsedensodnom ethanolmetabolismandoxidativestressarerequiredforunfoldedproteinresponseactivationandsteatosisinzebrafishwithalcoholicliverdisease AT anamvacaru ethanolmetabolismandoxidativestressarerequiredforunfoldedproteinresponseactivationandsteatosisinzebrafishwithalcoholicliverdisease AT deannalhowarth ethanolmetabolismandoxidativestressarerequiredforunfoldedproteinresponseactivationandsteatosisinzebrafishwithalcoholicliverdisease AT chunyueyin ethanolmetabolismandoxidativestressarerequiredforunfoldedproteinresponseactivationandsteatosisinzebrafishwithalcoholicliverdisease AT kirstencsadler ethanolmetabolismandoxidativestressarerequiredforunfoldedproteinresponseactivationandsteatosisinzebrafishwithalcoholicliverdisease |
_version_ |
1725224120066506752 |