title: Melatonin counteracts BMP-6 regulation of steroidogenesis by rat granulosa cells.
abstract: The ovarian bone morphogenetic protein (BMP) system is a physiological inhibitor of luteinization in growing ovarian follicles. BMP-6, which is expressed in oocytes and granulosa cells of healthy follicles, specifically inhibits FSH actions by suppressing adenylate cyclase activity. In the present study, we studied the role of melatonin in ovarian steroidogenesis using rat primary granulosa cells of immature female rat ovaries by focusing on the interaction with BMP-6 activity. Treatment with melatonin had no direct effect on FSH-induced progesterone or estradiol production by granulosa cells, and the results were not affected by the presence of co-cultured oocytes. In addition, synthesis of cAMP by granulosa cells was not significantly altered by melatonin treatment. To elucidate the interaction between activities of melatonin and BMPs, the effect of melatonin treatment on suppression of progesterone synthesis by BMP-6 was investigated. Interestingly, the inhibitory effect of BMP-6 on FSH-induced progesterone production was impaired by co-treatment with melatonin. Granulosa cells express higher levels of MT1 than MT2, and BMP-6 had no significant effect on MT1 expression in granulosa cells. However, BMP-6-induced Smad1/5/8 phosphorylation and Id-1 transcription were suppressed by melatonin, suggesting that melatonin has an inhibitory effect on BMP receptor signaling in granulosa cells. Although the expression levels of ALK-2, -6, ActRII and BMPRII were not affected by melatonin, inhibitory Smad6, but not Smad7, expression was upregulated by melatonin. Thus, melatonin plays a role in the regulation of BMP-6 signal intensity for controlling progesterone production in the ovary. These findings suggest that the effect of melatonin on maintenance of ovarian function is, at least in part, due to the regulation of endogenous BMP activity in granulosa cells.
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Nakamura
authors.affiliation: Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan. Electronic address: fumiotsu@md.okayama-u.ac.jp.
authors.forename: Fumio
authors.initials: F
authors.lastname: Otsuka
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan; Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Terasaka
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Inagaki
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hosoya
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Tsukamoto-Yamauchi
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Kishio
authors.initials: K
authors.lastname: Toma
authors.affiliation: Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Makino
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D015153:Blotting, Western; D055418:Bone Morphogenetic Protein 6 / Q000378:metabolism*; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008550:Melatonin / Q000494:pharmacology*; D011374:Progesterone / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000975:Antioxidants; D055418:Bone Morphogenetic Protein 6; D012333:RNA, Messenger; D011374:Progesterone; D004958:Estradiol; C498218:BMPR2 protein, human; D052006:Bone Morphogenetic Protein Receptors, Type II; D008550:Melatonin
keywords: Bone morphogenetic protein (BMP); Follicle-stimulating hormone (FSH); Granulosa cells; Melatonin; Oocyte; Steroidogenesis