We have investigated the involvement of the MAPK signaling pathway in increased androgen biosynthesis and CYP17 gene expression in women with polycystic ovary syndrome (PCOS). A comparison of MAPK kinase (MEK1/2) and ERK1/2 phosphorylation in propagated normal and PCOS theca cells, revealed that MEK1/2 phosphorylation was decreased more than 70%, and ERK1/2 phosphorylation was reduced 50% in PCOS cells as compared with normal cells. Infection with dominant-negative MEK1 increased CYP17 mRNA and dehydroepiandrosterone (DHEA) abundance, whereas constitutively active MEK1 reduced DHEA production and CYP17 mRNA abundance. Similarly, the MEK inhibitor, PD98059, increased CYP17 mRNA accumulation and CYP17 promoter activity to levels observed in PCOS cells. Remarkably, in theca cells maintained in the complete absence of insulin, ERK1/2 phosphorylation was decreased in PCOS theca cells as compared with normal theca cells, and CYP17 mRNA and DHEA synthesis were increased in PCOS theca cells. These studies demonstrate that in PCOS cells reduced levels of activated MEK1/2 and ERK1/2 are correlated with increased androgen production, irrespective of the insulin concentration. These findings implicate alterations in the MAPK pathway in the pathogenesis of excessive ovarian androgen production in PCOS.

In patients with epilepsy, treatment with valproate (VPA) has been reported to be associated with polycystic ovary syndrome-like symptoms including weight gain, hyperandrogenemia, and hyperinsulinemia. We examined the effect of VPA on androgen biosynthesis in ovarian theca cells isolated from follicles of normal cycling women to determine whether the hyperandrogenemia reported with VPA treatment could be a result of direct effects of VPA on the ovary. In long-term cultures of theca cells treated for 72 h with sodium valproate (30-3000 microm), we observed an increase in basal and forskolin-stimulated dehydroepiandrosterone (DHEA), androstenedione, and 17alpha-hydroxyprogesterone production compared with control values. In contrast, low doses of VPA treatment (i.e. 30-300 microm) had no effect on basal and forskolin-stimulated progesterone production, whereas higher doses of VPA (1000-3000 microm) inhibited progesterone production. The most pronounced effect of VPA on androgen biosynthesis was observed in the dose range of 300-3000 microm, which represent therapeutic levels in the treatment of epilepsy and bipolar disorder. Western analyses demonstrated that VPA treatment increased both basal and forskolin-stimulated P450c17 and P450scc protein levels, whereas the amount of steroidogenic acute regulatory protein was unaffected. In transient transfection studies, VPA was found to increase P450 17alpha-hydroxylase and P450 cholesterol side-chain cleavage promoter activity, whereas steroidogenic acute regulatory protein promoter activity was unaffected. Consistent with the ability of VPA to act as a histone deacetylase (HDAC) inhibitor in other cell systems, VPA (500 microm) treatment was observed to increase histone H3 acetylation and P450 17alpha-hydroxylase mRNA accumulation. The HDAC inhibitor butyric acid (500 microm) similarly increased histone H3 acetylation and DHEA biosynthesis, whereas the VPA derivative valpromide (500 microm), which lacks HDAC inhibitory activity, had no effect on histone acetylation or DHEA biosynthesis. These data suggest that VPA-induced ovarian androgen biosynthesis results from changes in chromatin modifications (histone acetylation) that augment transcription of steroidogenic genes. These studies provide the first biochemical evidence to support a role for VPA in the genesis of polycystic ovary syndrome-like symptoms, and establish a direct link between VPA treatment and increased ovarian androgen biosynthesis.

No abstract

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder characterized by ovarian hyperandrogenism. Theca interna cells isolated from the ovaries of women with PCOS are characterized by increased expression of cytochrome P450 17alpha-hydroxylase (CYP17) [steroid 17alpha-hydroxylase/17,20 lyase (P450c17)], a steroidogenic enzyme obligatory for the biosynthesis of androgens. Augmented expression of the gene encoding P450c17 (CYP17) in PCOS theca has been attributed, in part, to differential transcriptional regulation of the CYP17 promoter in normal and PCOS cells. The present studies examine whether CYP17 gene expression is also posttranscriptionally regulated at the level of mRNA stability in normal and PCOS theca cells maintained in long-term culture. Determination of endogenous CYP17 mRNA half-life by pharmacological inhibition of transcription demonstrated that the half-life of CYP17 mRNA increased 2-fold in PCOS theca cells, compared with normal theca cells. Forskolin treatment also prolonged CYP17 mRNA half-life in both normal and PCOS theca cells. In vitro mRNA degradation studies demonstrated that the 5'-untranslated region confers increased stability to CYP17 mRNA in PCOS theca cells and showed that the 5'-untranslated region of CYP17 also confers forskolin-stimulated stabilization of CYP17 mRNA. These studies indicate that a slower rate of CYP17 mRNA decay contributes to increased steady-state mRNA accumulation and augmented CYP17 gene expression in PCOS theca cells.