The central hypothesis of the proposed investigation is that ethanol consumption inhibits hepatic proteolysis by affecting the lysosomal and extralysosomal proteolytic pathways in the liver. An ethanol-elicited inhibition of protein degradation is one of the principal factors responsible for ethanol-induced protein accumulation in the liver, a phenomenon which contributes to hepatomegaly resulting from chronic drinking.
Our aim i n these investigations is to examine two key hepatic proteolytic systems in rat liver and to determine to what degree they are affected by acute and,/or chronic ethanol administration. The systems to be analyzed are the hepatic autophagic/lysosomal system and the ubiquitin proteolytic pathway. These pathways are responsible for the complete degradation of most intracellular proteins. Disruption of their intracellular function(s) may lead to other disturbances in liver cell function. The specific objectives of this proposal are to examine the effects of acute and/or chronic ethanol consumption on 1) The formation and maturation of hepatic autophagic vacuoles, 2) endogenous proteolytic activities as well as HSP-70-mediated proteolytic activities of liver lysosomes 3) the content of hepatic ubiquitin as well as ubiquitin dependent conjugation and proteolytic activities in rat liver extracts, and 4) the activities of these proteolytic systems in different zones of the hepatic lobule. The latter objective will be important in determining whether any relationship exists between the ethanol-induced reduction in hepatic proteolysis and ethanol-elicited specific cell injury. Our investigation will utilize recently updated techniques for the enrichment and isolation of autophagic vacuoles from the livers of control and ethanol-fed rats. We will analyze these vacuoles morphologically and biochemically in order to determine whether ethanol ingestion affects the formation, maturation and proteolytic capacities of these organelles. We will then assess the effects of ethanol consumption, as well as that of ethanol's initial oxidation product acetaldehyde, on the formation and the degradation of ubiquitin-protein conjugates. Finally, we will analyze the protein content, the rates of protein catabolism, as well as the aforementioned proteolytic systems in isolated perivenous and periportal hepatocytes from control and ethanol-fed rats. Since the liver is responsible for the regulation of serum protein, amino acid, lipid and glucose levels, it is important to understand the effects of ethanol toxicity or hepatic protein metabolism.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
5R01AA009384-02
Application #
3113468
Study Section
Biochemistry, Physiology and Medicine Subcommittee (ALCB)
Project Start
1992-08-01
Project End
1996-07-31
Budget Start
1993-08-01
Budget End
1994-07-31
Support Year
2
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Nebraska Medical Center
Department
Type
Schools of Medicine
DUNS #
City
Omaha
State
NE
Country
United States
Zip Code
68198
Curry-McCoy, Tiana V; Osna, Natalia A; Nanji, Amin A et al. (2010) Chronic ethanol consumption results in atypical liver injury in copper/zinc superoxide dismutase deficient mice. Alcohol Clin Exp Res 34:251-61
Curry-McCoy, Tiana V; Osna, Natalia A; Donohue Jr, Terrence M (2009) Modulation of lysozyme function and degradation after nitration with peroxynitrite. Biochim Biophys Acta 1790:778-86
Osna, Natalia A; White, Ronda L; Krutik, Viatcheslav M et al. (2008) Proteasome activation by hepatitis C core protein is reversed by ethanol-induced oxidative stress. Gastroenterology 134:2144-52
Donohue, Terrence M; Curry-McCoy, Tiana V; Nanji, Amin A et al. (2007) Lysosomal leakage and lack of adaptation of hepatoprotective enzyme contribute to enhanced susceptibility to ethanol-induced liver injury in female rats. Alcohol Clin Exp Res 31:1944-52
Donohue Jr, Terrence M; Curry-McCoy, Tiana V; Todero, Sandra L et al. (2007) L-Buthionine (S,R) sulfoximine depletes hepatic glutathione but protects against ethanol-induced liver injury. Alcohol Clin Exp Res 31:1053-60
Osna, Natalia A; Clemens, Dahn L; Donohue Jr, Terrence M (2005) Ethanol metabolism alters interferon gamma signaling in recombinant HepG2 cells. Hepatology 42:1109-17
Donohue Jr, Terrence M; Kharbanda, Kusum K; Casey, Carol A et al. (2004) Decreased proteasome activity is associated with increased severity of liver pathology and oxidative stress in experimental alcoholic liver disease. Alcohol Clin Exp Res 28:1257-63
Osna, Natalia A; Haorah, James; Krutik, Viatcheslav M et al. (2004) Peroxynitrite alters the catalytic activity of rodent liver proteasome in vitro and in vivo. Hepatology 40:574-82
Donohue Jr, Terrence M; Osna, Natalia A (2003) Intracellular proteolytic systems in alcohol-induced tissue injury. Alcohol Res Health 27:317-24
Haorah, James; MacDonald, Richard G; Stoner, Julie A et al. (2003) Ethanol consumption decreases the synthesis of the mannose 6-phosphate/insulin-like growth factor II receptor but does not decrease its messenger RNA. Biochem Pharmacol 65:637-48

Showing the most recent 10 out of 19 publications