Immunohistochemical characterization of hepatic malondialdehyde and 4-hydroxynonenal modified proteins during early stages of ethanol-induced liver injury.
BACKGROUND
Chronic ethanol consumption is associated with hepatic lipid peroxidation and the deposition or retention of aldehyde-adducted proteins postulated to be involved in alcohol-induced liver injury. The purpose of this study was to characterize hepatocellular formation of aldehyde-protein adducts during early stages of alcohol-induced liver injury.


METHODS
Female Sprague Dawley(R) rats were subjected to the intragastric administration of a low-carbohydrate/high-fat total enteral nutrition diet or a total enteral nutrition diet containing ethanol for a period of 36 days. Indexes of hepatic responses to ethanol were evaluated in terms of changes in plasma alanine aminotransferase activity, hepatic histopathologic analysis, and induction of cytochrome P-4502E1 (CYP2E1). Immunohistochemical methods were used to detect hepatic proteins modified with malondialdehyde (MDA) or 4-hydroxynonenal (4-HNE) for subsequent quantitative image analysis.


RESULTS
After 36 days of treatment, rats receiving the alcohol-containing diet displayed hepatic histopathologies characterized by marked micro- and macrosteatosis associated with only minor inflammation and necrosis. Alcohol administration resulted in a 3-fold elevation of plasma alanine aminotransferase activity and 3-fold increases (p < 0.01) in hepatic CYP2E1 apoprotein and activity. Quantitative immunohistochemical analysis revealed significant (p < 0.01) 5-fold increases in MDA- and 4-HNE modified proteins in liver sections prepared from rats treated with alcohol. The MDA- or 4-HNE modified proteins were contained in hepatocytes displaying intact morphology and were colocalized primarily with microvesicular deposits of lipid. Aldehyde-modified proteins were not prevalent in parenchymal or nonparenchymal cells associated with foci of necrosis or inflammation.


CONCLUSIONS
These results suggest that alcohol-induced lipid peroxidation is an early event during alcohol-mediated liver injury and may be a sensitizing event resulting in the production of bioactive aldehydes that have the potential to initiate or propagate ensuing proinflammatory or profibrogenic cellular events.
Sampey
Brante P
BP
Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, 80262, USA.
Korourian
Soheila
S
Ronis
Martin J
MJ
Badger
Thomas M
TM
Petersen
Dennis R
DR
D000447:Aldehydes / Q000032:analysis* / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000032:analysis* / Q000096:biosynthesis; D000431:Ethanol / Q000008:administration & dosage*; D005260:Female; D007150:Immunohistochemistry; D008099:Liver / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008315:Malondialdehyde / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D000447:Aldehydes; D001059:Apoproteins; D000431:Ethanol; D008315:Malondialdehyde; C027576:4-hydroxy-2-nonenal