Pioglitazone Inhibits Androgen Production in NCI-H295R Cells by Regulating Gene Expression of CYP17 and HSD3B2

Abstract

Thiazolidinediones (TZDs) such as pioglitazone and rosiglitazone are widely used as insulin sensitizers in the treatment of type 2 diabetes. In diabetic women with polycystic ovary syndrome, treatment with pioglitazone or rosiglitazone improves insulin resistance and hyperandrogenism, but the mechanism by which TZDs down-regulate androgen production is unknown. Androgens are synthesized in the human gonads as well as the adrenals. We studied the regulation of androgen production by analyzing the effect of pioglitazone and rosiglitazone on steroidogenesis in human adrenal NCI-H295R cells, an established in vitro model of steroidogenesis of the human adrenal cortex. Both TZDs changed the steroid profile of the NCI-H295R cells and inhibited the activities of P450c17 and 3␤HSDII, key enzymes of androgen biosynthesis. Pioglitazone but not rosiglitazone inhibited the expression of the CYP17 and HSD3B2 genes. Likewise, pioglitazone repressed basal and 8-bromo-cAMP-stimulated activities of CYP17 and HSD3B2 promoter reporters in NCI-H295R cells. However, pioglitazone did not change the activity of a cAMP-responsive luciferase reporter, indicating that it does not influence cAMP/protein kinase A/cAMP response element-binding protein pathway signaling. Although peroxisome proliferator-activated receptor ␥ (PPAR␥) is the nuclear receptor for TZDs, suppression of PPAR␥ by small interfering RNA technique did not alter the inhibitory effect of pioglitazone on CYP17 and HSD3B2 expression, suggesting that the action of pioglitazone is independent of PPAR␥. On the other hand, treatment of NCI-H295R cells with mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) inhibitor 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one (PD98059) enhanced promoter activity and expression of CYP17. This effect was reversed by pioglitazone treatment, indicating that the MEK/ ERK signaling pathway plays a role in regulating androgen biosynthesis by pioglitazone.The gonads and the adrenals are the main sources of human androgens and express common genes for the biosynthesis of androgens. P450c17 and 3␤HSDII, encoded by the CYP17 and HSD3B2 genes, are key enzymes involved in biosynthesis of androgens. The mature adrenal cortex in humans produces androgens from cholesterol in a multistep pathway. In a first step, cholesterol is converted to pregnenolone by the P450 side-chain cleavage system. Second, pregnenolone then may be converted to 17␣-hydroxypregnenolone and to dehydroepiandrostenedione (DHEA) by the 17␣-hydroxylase and 17,20-lyase activities of P450c17. Third, DHEA is converted to androstenedione by 3␤-hydroxysteroid dehydrogenase type 2 (3␤HSDII). Although the fetal adrenals predominantly produce androgens, postnatal androgen production ceases only to resume at the age of 6 to 7 years, after the development of the zona reticularis, the third layer of the mature adrenal cortex.Thiazolidinediones (TZDs) are a class of oral insulin-sensitizing agents that are generally believed to exert their action as...

Effects of tris(2,3-dibromopropyl) isocyanurate on steroidogenesis in H295R cells

“…The decrease in CYP17 gene expression could shift direction to the production of mineralocorticoids other than androgen synthesis. Interestingly, our results correlated well with a recent study that showed a significant reduction in the basal and agonist-induced 3bHSD2 and CYP17 gene expression along with inhibited androgen biosynthesis in the H295R cells after exposure to pioglitazone (Kempná et al 2007). …”

Insulin and hyperandrogenism in women with polycystic ovary syndrome

“…PPARγ agonists have also been shown to reverse the enhanced expression of P450c17 induced by specific inhibition of MEK/ERK in human adrenal cells [107] (Fig. 3).…”

“…On the other hand, specific inhibition of MEK/ERK, another component of the MAPK insulin pathway, increases P450c17 activity [105]. Increased expression of P450c17 after inhibition of MEK/ERK was also found in human adrenal cells [107]. The attenuated MEK/ERK signal could stimulate androgen production via a reduction in c-fos expression, because c-fos was shown to inhibit P450c17 expression in a thecal cell tumor model [108].…”

Colon cancer cells produce immunoregulatory glucocorticoids

“…The luciferase reporter constructs for the genomic promoter sequences of CYP11A1, CYP17, CYP11B1, as well as the expression plasmids for b-galactosidase, have been described previously (Mueller et al, 2006(Mueller et al, , 2007Kempna et al, 2007;Atanasov et al, 2008). The reporter plasmid GRE2tk and the expression plasmid for GC receptor SVGR1 were kindly provided by Sam Okret (Karolinska Institute, Stockholm, Sweden; Pazirandeh et al, 1999).…”