ToxSci Advance Access published online on May 13, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn096
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17 beta Estradiol and Hydroxyestradiols Interact Via the NF-Kappa B Pathway To Elevate Cyclo-oxygenase 2 Expression and Prostaglandin E2 Secretion in Human Bronchial Epithelial Cells.




,1
* Institute of NanoEngineering and Microsystems, National Tsing Hua University
Department of Chemistry, National Tsing Hua University
Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Taiwan, ROC
1 All correspondence should be addressed to Dr. Pinpin Lin, Division of Environmental Health and Occupational Medicine, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 350, Taiwan, ROC.Tel: +886-37-246-166, ext. 36508, Fax: +886-37-587-406, E-mail: pplin{at}nhri.org.tw
Received February 1, 2008; revision received April 2, 2008; accepted May 8, 2008
| Abstract |
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Some epidemiological studies suggest women may be at greater risk for lung cancer than men. Hydroxyestradiols (OHE2) are genotoxic and considered as carcinogenic metabolites of estrogens. In this study, we demonstrate that treatment with 0.1 or 1 nM 2-/4- OHE2 significantly increased intracellular oxidative stress, NF-
B activity, and cyclooxygenase-2 (COX-2) expression within 24 h in human bronchial epithelial cells BEAS-2B. Co-treatment with the NF-
B inhibitor, Bay 117085, prevented OHE2-induced COX-2 mRNA accumulation, suggesting that OHE2 induced COX-2 expression via the NF-
B dependent pathway. Furthermore, co-treatment with 10 nM 17 beta estradiol (E2) significantly enhanced OHE2-increased intracellular oxidative stress and significantly increased not only NF-
B activity but also COX-2 levels. As COX-2 participates in biosynthesis of prostaglandin E2 (PGE2), PGE2 secretion was enhanced by the co-treatment of 1 nM OHE2 and 10 nM E2. To understand the enhancement mechanism between OHE2 and E2, cells were co-treated with an antioxidant, N-acetylcysteine (NAC), or NF-kB inhibitor, Bay 117085. Both NAC and Bay 117085 prevented the enhancement in COX-2 expression and PGE2 secretion by the co-treatment of E2 and OHE2 in BEAS-2B cells. Similarly, Bay 117085 prevented PGE2 secretion induced by the co-treatment of E2 and OHE2 in rat lung slice cultures. These results suggest that E2 enhanced OHE2-increased intracellular oxidative stress which increased NF-
B activity, COX-2 expression, and PGE2 secretion. Elevated COX-2 expression and PGE2 secretion has been shown to increase the risk of cancer development. Our present data suggest a pathway that contributes an epigenetic mechanism to the overall mechanism of carcinogenesis.
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