Backgroud and Aim: Several reports have positively correlated cycooxygenase (COX-2) expression with tumor promotion and angiogenesis both in liver and skin. Furthermore, we and others have reported that bile acids accumulate not only in the liver but also in the skin in cholestatic liver diseases. We have also previously shown that dihydroxy bile acids including chenodeoxycholate (CDCA) affected cell proliferation in human dermal fibroblasts in primary culture. The present aims were to study the role of COX-2 in the CDCA-dependent regulation of cell proliferation in both human fibroblasts and stellate cells. Methods: Fibroblasts and stellate cells were isolated from skin and liver biopsies by an outgrowth method and cultured using standard conditions. The isolated human stellate cells were characterized imunohistochemically using specific antibodies against αSMA and desmin and over 95 to 98% of cells were positive for these proteins. Cell proliferation was measured by [3H]thymidine incorporation and COX-2 mRNA and protein expression by RT-PCR and Western blotting, respectively. Results: CDCA inhibited the proliferation of both human dermal fibroblast and human hepatic stellate cells in a dose-dependent manner with over 75% inhibition observed with 100 μM CDCA. Incubation of both fibroblasts and stellate cells with NS-398 (COX-2 inhibitor) almost completely abolished the action of CDCA. The effect of CDCA was mimicked by PGE1 (1μM), Forskolin (10 μM) and CPT-cAMP (1 and 10 μM), while neither 15DPGJ2 nor PGD2 had a significant effect on either fibroblast or stellate cell proliferation. Furthermore, transfection of both fibroblasts and stellate cells with a WT COX-2-containing vector potentiated the CDCA effect on cell proliferation. Under these conditions, a 20 μM concentration of CDCA that had little inhibitory effect on cell proliferation (empty vector) had a > 70% inhibitory effect in COX-2 transfected cells. In both fibroblasts and stellate cells, incubation with CDCA resulted in a significantly (p<0.05) increased COX-2 expression level. Conclusion: This study underlines a similar regulation of proliferation by both bile acid and cAMP-mediating agents in both human fibroblasts and stellate cells. This study highlights the possible association of bile acids and proliferative disorders under pathological conditions that lead to the accumulation of bile acids in the liver and a spill over into the systemic circulation.
[Proc Amer Assoc Cancer Res, Volume 47, 2006]