Overexpression of HSP25 reduces the level of TNFα-induced oxidative DNA damage biomarker, 8-hydroxy-2′-deoxyguanosine, in L929 cells
✍ Scribed by Young-Mee Park; Mi-Young Han; Robert V. Blackburn; Yong J. Lee
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 229 KB
- Volume
- 174
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Previously we and others have demonstrated that oxidative stress involving generation of reactive oxygen species (ROS) is responsible for the cytotoxic action of TNFa. Protective effect of small heat shock proteins (HSP) against diverse oxidative stress conditions has been suggested. Although overexpression of small HSP was shown to provide an enhanced survival of TNFa-sensitive cells when challenged with TNFa, neither the nature of TNFa-induced cytotoxicity nor the protective mechanism of small HSP has been completely understood. In this study, we have attempted to determine whether TNFa induces oxidative DNA damage in TNFa-sensitive L929 cells. We chose to measure the level of 8-hydroxy-2deoxyguanosine (8 ohdG), which has been increasingly recognized as one of the most sensitive markers of oxidative DNA damage. Our results clearly demonstrated that the level of 8 ohdG increased in L929 cells in a TNFa dose-dependent manner. Subsequently, we asked whether small HSP has a protective effect on TNFa-induced oxidative DNA damage. To accomplish this goal, we have stably transfected into L929 cells, which are devoid of endogenous small HSP, with the mouse small hsp cDNA (hsp25). We found that TNFa-induced 8 ohdG was decreased in cells overexpressing exogenous small HSP25. We also found that the cell-killing activity of TNFa was decreased in these cells as measured by clonogenic survival. Taken together, results from the current study show that a cytotoxic mechanism of TNFa involves oxidative damage of DNA, and that overexpression of the small HSP25 reduces this oxidative damage. We suggest that the reduction of oxidative DNA damage is an important protective mechanisms of small HSP against TNFa.