title: Androgen receptor-dependent transactivation of growth arrest-specific gene 6 mediates inhibitory effects of testosterone on vascular calcification.
abstract: Recent epidemiological studies have found that androgen deficiency is associated with a higher incidence of cardiovascular disease in men. However, little is known about the mechanism underlying the cardioprotective effects of androgens. Here we show the inhibitory effects of testosterone on vascular calcification and a critical role of androgen receptor (AR)-dependent transactivation of growth arrest-specific gene 6 (Gas6), a key regulator of inorganic phosphate (P(i))-induced calcification of vascular smooth muscle cells (VSMC). Testosterone and nonaromatizable androgen dihydrotestosterone inhibited P(i)-induced calcification of human aortic VSMC in a concentration-dependent manner. Androgen inhibited P(i)-induced VSMC apoptosis, an essential process for VSMC calcification. The effects on VSMC calcification were mediated by restoration of P(i)-induced down-regulation of Gas6 expression and a subsequent reduction of Akt phosphorylation. These effects of androgen were blocked by an AR antagonist, flutamide, but not by an estrogen receptor antagonist, ICI 182,780. We then explored the mechanistic role of the AR in Gas6 expression and found an abundant expression of AR predominantly in the nucleus of VSMC and two consensus ARE sequences in the Gas6 promoter region. Dihydrotestosterone stimulated Gas6 promoter activity, and this effect was abrogated by flutamide and by AR siRNA. Site-specific mutation revealed that the proximal ARE was essential for androgen-dependent transactivation of Gas6. Furthermore, chromatin immunoprecipitation assays demonstrated ligand-dependent binding of the AR to the proximal ARE of Gas6. These results indicate that AR signaling directly regulates Gas6 transcription, which leads to inhibition of vascular calcification, and provides a mechanistic insight into the cardioprotective action of androgens.
authors.affiliation: Department of Geriatric Medicine, the Graduate School of Medicine, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Bo-Kyung
authors.initials: BK
authors.lastname: Son
authors.forename: Masahiro
authors.initials: M
authors.lastname: Akishita
authors.forename: Katsuya
authors.initials: K
authors.lastname: Iijima
authors.forename: Sumito
authors.initials: S
authors.lastname: Ogawa
authors.forename: Koji
authors.initials: K
authors.lastname: Maemura
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.forename: Kenichi
authors.initials: K
authors.lastname: Takeyama
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kato
authors.forename: Masato
authors.initials: M
authors.lastname: Eto
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Ouchi
mesh_terms: D000328:Adult; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002114:Calcinosis / Q000188:drug therapy* / Q000473:pathology; D002470:Cell Survival; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology / Q000627:therapeutic use; D015533:Transcriptional Activation; D014652:Vascular Diseases / Q000188:drug therapy* / Q000473:pathology; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D011944:Receptors, Androgen; D013739:Testosterone; D000099255:Growth Arrest-Specific Protein 6