Oxysterols induce cyclooxygenase-2 expression in... : Hepatology (original) (raw)

Original Articles

Oxysterols induce cyclooxygenase-2 expression in cholangiocytes: Implications for biliary tract carcinogenesis

Yoon, Jung-Hwan1; Canbay, Ali E.2; Werneburg, Nathan W.2; Lee, Sum P.3; Gores, Gregory J. Professor of Medicine*,2,†

1 Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, Seoul, Korea

2 Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic, and Foundation, Rochester, MN

3 Department of Medicine, VA Medical Center and University of Washington School of Medicine, Seattle, WA

E-mail:[email protected]

*Address reprint requests to: Mayo Medical School, Clinic, and Foundation, 200 First Street SW, Rochester, MN 55905

†fax: 507-284-0762

Received August 04, 2003; accepted December 12, 2003; previously published online February 27, 2004

Abstract

Cyclooxygenase-2 (COX-2), which is expressed by cholangiocytes in biliary tract disorders, has recently been implicated in biliary tract carcinogenesis. The mechanisms responsible for this COX-2 expression remain unclear. In human diseases, bile contains oxygenated derivatives of cholesterol (oxysterols) which possess diverse biological properties. Therefore, we determined if oxysterols modulate COX-2 expression. The effect of an oxysterol (22(R)-hydroxycholesterol, 22-HC) on COX-2 expression in KMBC cells, a human cholangiocarcinoma cell line, was examined. 22-HC enhanced COX-2 protein expression. This oxysterol activated p42/44 and p38 MAPK, but not JNK 1/2. A p42/44 MAPK inhibitor did not block COX-2 induction, while p38 MAPK inhibitor effectively attenuated COX-2 induction. Although COX-2 mRNA levels were increased by 22-HC, this increase was not transcriptionally regulated, as 22-OH did not increase activity in a COX-2 promoter gene assay. In contrast, COX-2 mRNA stability was augmented by 22-HC treatment, and this effect was reversed by a p38 MAPK inhibitor. In conclusion, the results demonstrate that the oxysterol 22-HC stabilizes COX-2 mRNA via a p38 MAPK-dependent mechanism. This enhanced COX-2 protein expression by oxysterols may participate in the genesis and progression of cholangiocarcinoma. (Hepatology 2004;39:732-738.)