TY - JOUR
T1 - Recombinant Hep G2 cells that express alcohol dehydrogenase and cytochrome P450 2E1 as a model of ethanol-elicited cytotoxicity
AU - Donohue, Terrence M.
AU - Osna, Natalia A.
AU - Clemens, Dahn L.
N1 - Funding Information:
This investigation was supported by Medical Research funds from the Department of Veterans Affairs, and, in part, by Grant No. AA09384 (to T.M.D.) and by Grant No. AA11291 (to D.L.C) from the National Institute on Alcohol Abuse and Alcoholism. We are pleased to acknowledge the valuable and excellent technical assistance of Veronique Pileri, Daniel Witkin, Jimmie Nelson and Sandra Todero in this work. We thank Dr. Geoffrey Thiele, for providing liver cytosol fractions from C57Bl/6 female mice.
PY - 2006/1
Y1 - 2006/1
N2 - HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the intial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100 mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1+) and VA-13 (ADH+) cells. Exposure to 100 mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.
AB - HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the intial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100 mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1+) and VA-13 (ADH+) cells. Exposure to 100 mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.
KW - Acetaldehyde
KW - Ethanol
KW - Hep G2 cells
KW - Proteasome
KW - Toxicity
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U2 - 10.1016/j.biocel.2005.07.010
DO - 10.1016/j.biocel.2005.07.010
M3 - Article
C2 - 16181800
AN - SCOPUS:27544457323
VL - 38
SP - 92
EP - 101
JO - International Journal of Biochemistry
JF - International Journal of Biochemistry
SN - 1357-2725
IS - 1
ER -