TY - JOUR
T1 - Feedback Inhibition of Steroidogenic Acute Regulatory Protein Expression in Vitro and in Vivo by Androgens
AU - Houk, Christopher P.
AU - Pearson, Elliot J.
AU - Martinelle, Nina
AU - Donahoe, Patricia K.
AU - Teixeira, Jose
PY - 2004/3
Y1 - 2004/3
N2 - Müllerian-inhibiting substance (MIS) reduces testosterone synthesis in Leydig cells by inhibiting cytochrome P450C17 hydroxylase/C17-20 lyase expression. However, in mouse Leydig MA-10 cells, MIS also enhances the cAMP-induced expression of mRNA for steroidogenic acute regulatory protein (StAR), which transports cholesterol to the inner mitochondrial membrane for conversion to pregnenolone. We hypothesized that the MIS-induced StAR expression is the indirect result of reduced testosterone synthesis in Leydig cells caused by MIS. We show that, in addition to MIS, flutamide, an androgen receptor antagonist, enhanced StAR mRNA expression when added to cAMP-treated MA-10 cells, whereas dihydrotestosterone, a potent androgen receptor agonist, attenuated these responses. Progesterone, dexamethasone, and estradiol also inhibited StAR mRNA expression. Addition of MIS to cAMP-treated MA-10 cells transfected with a StAR-promoter luciferase reporter resulted in increased StAR promoter activity over cAMP alone; this effect was inhibited by dihydrotestosterone, suggesting that androgens inhibit StAR mRNA expression at the transcriptional level. Androgen-mediated inhibition of StAR expression was also observed in primary Leydig cell culture and in vivo using both hypophysectomized mice and mice treated with the GnRH antagonist, acyline. These results suggest that the induction of StAR expression by MIS occurs secondary to the MIS-mediated reduction in testosterone synthesis by relieving a hitherto uncharacterized androgen-dependent feedback inhibition on StAR expression. These findings may impact future treatment strategies aimed at reducing androgen; for example, in the treatment of prostatic cancer, antiandrogen treatment might benefit from adjuvant therapy to inhibit StAR expression.
AB - Müllerian-inhibiting substance (MIS) reduces testosterone synthesis in Leydig cells by inhibiting cytochrome P450C17 hydroxylase/C17-20 lyase expression. However, in mouse Leydig MA-10 cells, MIS also enhances the cAMP-induced expression of mRNA for steroidogenic acute regulatory protein (StAR), which transports cholesterol to the inner mitochondrial membrane for conversion to pregnenolone. We hypothesized that the MIS-induced StAR expression is the indirect result of reduced testosterone synthesis in Leydig cells caused by MIS. We show that, in addition to MIS, flutamide, an androgen receptor antagonist, enhanced StAR mRNA expression when added to cAMP-treated MA-10 cells, whereas dihydrotestosterone, a potent androgen receptor agonist, attenuated these responses. Progesterone, dexamethasone, and estradiol also inhibited StAR mRNA expression. Addition of MIS to cAMP-treated MA-10 cells transfected with a StAR-promoter luciferase reporter resulted in increased StAR promoter activity over cAMP alone; this effect was inhibited by dihydrotestosterone, suggesting that androgens inhibit StAR mRNA expression at the transcriptional level. Androgen-mediated inhibition of StAR expression was also observed in primary Leydig cell culture and in vivo using both hypophysectomized mice and mice treated with the GnRH antagonist, acyline. These results suggest that the induction of StAR expression by MIS occurs secondary to the MIS-mediated reduction in testosterone synthesis by relieving a hitherto uncharacterized androgen-dependent feedback inhibition on StAR expression. These findings may impact future treatment strategies aimed at reducing androgen; for example, in the treatment of prostatic cancer, antiandrogen treatment might benefit from adjuvant therapy to inhibit StAR expression.
UR - http://www.scopus.com/inward/record.url?scp=1442274655&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=1442274655&partnerID=8YFLogxK
U2 - 10.1210/en.2003-1046
DO - 10.1210/en.2003-1046
M3 - Article
C2 - 14630719
AN - SCOPUS:1442274655
SN - 0013-7227
VL - 145
SP - 1269
EP - 1275
JO - Endocrinology
JF - Endocrinology
IS - 3
ER -