title: Estradiol-mediated suppression of CYP1B1 expression in mouse MA-10 Leydig cells is independent of protein kinase A and estrogen receptor.
abstract: Estrogens have multifaceted roles in mammalian testis. In the present study, we focused on estradiol as a potential regulator of testicular cytochrome P450 1B1 (CYP1B1) expression and investigated the possible mechanisms involved in the estradiol-mediated suppression. CYP1B1 protein levels were measured in the testes of rats that were treated with 17β-estradiol benzoate (1.5 mg/kg) at different stages of development. In addition, CYP1B1 mRNA levels were measured in mouse MA-10 Leydig tumor cells treated with (a) various concentrations of 17β-estradiol benzoate, (b) 17β-estradiol benzoate in the presence of exogenous luteinizing hormone (LH), or (c) 17β-estradiol benzoate in the presence of ICI 182,780, a competitive steroidal antagonist of estrogen receptors (ERs). Treatment of neonatal, pubertal, or adult rats with 17β-estradiol benzoate was associated with a reduction of approximately 90% in testicular CYP1B1 protein content compared to age-matched controls. Treatment of MA-10 cells with 17β-estradiol benzoate (10-500 nM) produced a concentration- and time-dependent decrease in CYP1B1 mRNA levels, but had no effect on LH receptor mRNA levels or on protein kinase A (PKA) activity. However, 17β-estradiol benzoate (10-500 nM), regardless of the concentration tested, failed to attenuate the LH-elicited increase in CYP1B1 mRNA or PKA activity in MA-10 cells that were co-treated with LH and estradiol. Similarly, ICI 182,780 (10-1000 µM) did not reverse the suppressive effect of estradiol on CYP1B1 mRNA expression in MA-10 cells co-treated with estradiol and ICI 182,780. The results indicate that downregulation of testicular CYP1B1 by estradiol was independent of PKA activity and was not mediated by ERs in MA-10 cells.
authors.affiliation: The University of British Columbia, 2146 East Mall, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Subrata
authors.initials: S
authors.lastname: Deb
authors.forename: Jenny K
authors.initials: JK
authors.lastname: Tai
authors.forename: Grace S
authors.initials: GS
authors.lastname: Leung
authors.forename: Thomas K H
authors.initials: TK
authors.lastname: Chang
authors.forename: Stelvio M
authors.initials: SM
authors.lastname: Bandiera
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D000077267:Fulvestrant; D005786:Gene Expression Regulation / Q000187:drug effects; D007985:Leydig Cells / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000378:metabolism; D011974:Receptors, LH / Q000235:genetics / Q000378:metabolism; D012756:Sheep
chemical_list: D020847:Estrogen Receptor Modulators; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011974:Receptors, LH; D000077267:Fulvestrant; D004958:Estradiol; D001189:Aryl Hydrocarbon Hydroxylases; C585498:Cyp1b1 protein, mouse; C585499:Cyp1b1 protein, rat; D065633:Cytochrome P-450 CYP1B1; D017868:Cyclic AMP-Dependent Protein Kinases