Chronic ethanol consumption alters the glutathione/glutathione peroxidase-1 system and protein oxidation status in rat liver.
BACKGROUND
Alcohol-induced liver damage is associated with oxidative stress, which might be linked to disturbances in liver antioxidant defense mechanisms. The effect of chronic ethanol consumption on the mitochondrial and cytosolic glutathione/glutathione peroxidase-1 (GSHPx-1) system and oxidative modification of proteins was therefore studied in the rat.


METHODS
Male Sprague-Dawley rats were fed liquid diets that provided 36% total calories as ethanol for at least 31 days. Pair-fed controls received isocaloric diets with ethanol calories substituted with maltose-dextrins. Mitochondrial and cytosolic fractions were prepared from livers and assayed for GSHPx-1 and glutathione reductase activities and total and oxidized concentrations of glutathione. Catalase activity was measured in the postmitochondrial supernatant. Levels of GSHPx-1, lactate dehydrogenase, and the beta subunit of the F1 portion of the ATP synthase protein were determined by western blot analysis. Concentrations of mitochondrial and cytosolic protein carbonyls were measured to assess ethanol-induced oxidation of proteins.


RESULTS
Chronic ethanol consumption significantly decreased cytosolic and mitochondrial GSHPx-1 activities by 40% and 30%, respectively. Levels of GSHPx-1 protein in cytosol were unaffected by ethanol feeding, whereas there was a small decrease in GSHPx-1 protein levels in mitochondria isolated from ethanol-fed rats. Glutathione reductase activities were increased in both intracellular compartments and catalase activity was increased as a consequence of ethanol exposure. Cytosolic total glutathione was mildly decreased, whereas ethanol feeding increased mitochondrial levels of total glutathione. Chronic ethanol feeding significantly increased both cytosolic and mitochondrial concentrations of protein carbonyls by 30% and 60%, respectively.


CONCLUSIONS
This study demonstrates that chronic ethanol-induced alterations in the glutathione/GSHPx-1 antioxidant system might promote oxidative modification of liver proteins, namely those of the mitochondrion, which could contribute to the adverse effects of ethanol on the liver.
Bailey
S M
SM
Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1016, USA. sbailey@wfubmc.edu
Patel
V B
VB
Young
T A
TA
Asayama
K
K
Cunningham
C C
CC
D000437:Alcoholism / Q000378:metabolism; D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D005978:Glutathione / Q000187:drug effects* / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010659:Phenylhydrazines / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
D002492:Central Nervous System Depressants; D010659:Phenylhydrazines; D017382:Reactive Oxygen Species; C004787:2,4-dinitrophenylhydrazine; D000431:Ethanol; D005979:Glutathione Peroxidase; D005978:Glutathione