|
KMID : 1156220040300030230
|
|
Journal of Environmental Health Sciences
2004 Volume.30 No. 3 p.230 ~ p.238
|
|
|
Effect of Continuous Exposure to Reactive Oxygen Species on γ-Glutamyltranspeptidase Expression and Activity in HepG2 Cells
|
|
Kim Young-Hwan
Choi Dal-Woong
|
|
|
Abstract
|
|
|
|
The adverse health effects of a number of environment pollutions are related to the formation of free radicals. Induction of antioxidant defensive system in the response to an oxidative attack is an essential element of the cell to survive. CYP2E1 is easily induced by organic solvents and induces continuous formation of reactive oxygen species (ROS). γ-Glutamyltranspeptidase (γGT) plays an important role in glutathione metabolism and xenobiotic detoxification. To evaluate the characteristic of oxidative stress which induces GGT expression and to understand human antioxidant defensive response against oxidative stress induced by CYP2E1, we studied regulation of γGT enzyme expression in response to various oxidative stresses in human HepG2 cells. The γGT activity was not modified after exposure of acute oxidative stress inducing agents (ferric nitrilotriacetate, cumene hydroperoxide, ADP-Fe, O-tetradecanoylphorbol-13-acetate, tumor necrosis factor-alpha). To induce continuous exposure of cells to ROS, HepG2 cells were transfected by human CYP2E1 gene transiently. The CYP2E1 activity was verified with chlorzoxazone hydroxylation. Transfection of CYP2E1 showed continuous 60% increase in intracellular ROS and 240 % increase in microsomal ROS. CYP2E1 overexpressing cells showed increased γGT activity (2.5-fold). The observed enhancement of γGT activity correlated with a significant increase of γGT mRNA (2.1-fold). Treatment with antioxidant strongly prevented the increase in γGT activity. The CYP2E1 overexpression did not modify toxicity index and increased glutathione levels. These results show that continuous exposure of cells to ROS produced by CYP2E1 up-regulates γGT; This may be one of the adaptive antioxidant responses of cells to oxidative insult. Present study also suggests that the induction of γGT could be used as a marker of oxidative stress induced by exposure to organic solvents.
|
|
|
KEYWORD
|
|
|
γ-Glutamyltranspeptidase, Reactive oxygen species, mRNA, organic solvent
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|