Prostaglandins and leukotriene B4 are potent inhibitors of 11β-hydroxysteroid dehydrogenase type 2 activity in human choriocarcinoma JEG-3 cells

The 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) is responsible for the inactivation of glucocorticoids. This is the predominant isozyme in the human placenta, where it is proposed to protect the fetus from high levels of maternal cortisol. In the present study, we examined the effects of eicosanoids on the activity of 11 beta-HSD2 in human choriocarcinoma JEG-3 cells, a well-established model for placental trophoblasts. Treat ment of JEG-3 cells for 24 h with either prostaglandin (PG) E-2 or F-2 alpha attenuated 11 beta-HSD2 activity (similar to 40%). Paradoxically, indomethacin, an inhibitor of cyclooxygenases, inhibited (similar to 40%) rather than stimulated the activity of this enzyme. This indicated that the arachidonic acid metabolism may be diverted to other pathway(s), the products of which may inhibit 11 beta-HSD2 activity. To determine whether the lipoxygenase pathways were involved, the cells were treated with nordihydroguaretic acid (NDGA), a blocker of all three (5-, 12-, and 15-) lipoxygenases. NDGA caused a 3-fold increase in 11 beta-HSD2 activity, To further delineate which specific lipoxygenase pathway was involved, the cells were incubated with zileuton, a selective inhibitor of 5-lipoxygenase, This resulted in a similar increase in 11 beta-HSD2 activity, suggesting that the products of this pathway (e.g., leukotrienes) may be involved. Given that leukotriene B-4 (LTB4) is the most biologically active product of the 5-lipoxygenase pathway,we treated the cells with LTB4, which inhibited 11 beta-HSD2 activity in a time- and dose-dependent manner with a maximal effect (60% reduction) at 10 nM for 9 h. Semiquantitative reverse transcription-polymerase chain reaction analysis revealed that 11 beta-HSD2 mRNA levels were not altered by the addition of LTB4, PGE(2), or PGF(2 alpha), indicating an effect at the posttranscriptional level. In conclusion, these results demonstrate that prostaglandins and LTB4 are potent inhibitors of 11 beta-HSD2 activity in JEG-3 cells, suggesting that placental 11 beta-HSD2 activity is modulated by these locally produced eicosanoids. This is the first time that the products of arachidonic acid metabolism have been found to regulate the activity of 11 beta-HSD2.