Objective: To investigate the regulation of catechol O-methyltransferase (COMT) expression in granulosa cells and assess potential effects of 2-methoxyestradiol (2-ME2) and COMT inhibitors on granulosa cell steroidogenesis and proliferation.
Design and setting: Controlled experimental study in an academic research laboratory.
Intervention(s): JC410 porcine and HGL5 human granulosa cell lines were used for in vitro experiments. Effects of 2-ME2 and COMT inhibitor treatment on DNA proliferation and steroidogenesis were assessed by using Hoechst dye and p450SCC-luciferase reporter assays. Effects of dihydrotestosterone (DHT), insulin, and all-trans retinoic acid (ATRA) on COMT messenger RNA expression were investigated by using COMTP1 promoter-luciferase reporter and Northern blot.
Main outcome measure(s): Granulosa cell steroidogenesis and proliferation following COMP inhibitor and 2-ME2 treatment. Regulation of COMT expression with DHT, insulin, and ATRA.
Result(s): 2-Methoxyestradiol had a dual effect on granulosa cell proliferation and p450SCC- luciferase activity; low doses were stimulatory and high doses were inhibitory. Catechol O-methyltransferase inhibitor was associated with up to a 65% increase in JC410 cell number and a maximal 5.6-fold increase in p450SCC-luciferase activity at 20 micromol/L. Dihydrotestosterone, insulin, and ATRA all induced a dose-dependent increase in COMTP1-luciferase transactivation, as well as up-regulated COMT messenger RNA expression in granulosa cells.
Conclusion(s): Catechol O-methyltransferase expression in granulosa cells was up-regulated by insulin, DHT, and ATRA. Catechol O-methyltransferase product, 2-ME2, decreased, whereas COMT inhibitor increased granulosa cell proliferation and steroidogenesis. These data suggest that COMT overexpression with subsequent increased level of 2-ME2 may lead to ovulatory dysfunction.