Regulation of CYP19 gene expression in primary human osteoblasts: effects of vitamin D and other treatments.
OBJECTIVE
Extragonadal estrogen biosynthesis is relevant for the regulation of bone metabolism. The aims of this paper were: (i) to examine CYP19 (aromatase) gene expression in primary cultures of osteoblasts under several hormone and cytokine treatments and (ii) to study the promoter usage of CYP19 in these cells.


METHODS
Primary cultures of osteoblasts were obtained from healthy donors. The effects of vitamin D and other factors on CYP19 expression were analysed by semiquantitative RT-PCR. Furthermore, CYP19 alternative promoter usage under the different treatments was characterized by RT-PCR.


RESULTS
CYP19 transcripts were detected in cultured human osteoblasts in serum-free conditions. Vitamin D, dexamethasone, 17beta-estradiol and testosterone increased transcript levels of CYP19, whereas interleukin-1beta or tumor necrosis factor alpha decreased them. Aromatase mRNA produced under treatment with vitamin D was transcribed from promoters I.4 and I.3, while stimulation with dexamethasone or dexamethasone plus vitamin D also involved promoter I.2. Testosterone activated promoters I.2 and I.4.


CONCLUSIONS
Our results suggested that vitamin D, testosterone, estrogens and glucocorticoids regulate CYP19 gene expression in human primary osteoblasts and the main promoter used appears to be promoter I.4. Promoters pII and I.3 seem to be related to basal transcription and may mediate estrogen stimulation, while promoter I.2 seems to play a role in the effect of glucocorticoids. These findings indicate that vitamin D and several hormones regulate local estrogen synthesis in human osteoblasts mainly through usage of promoters I.4 and I.3.
URFOA-IMIM, Hospital del Mar, Universitat Autonoma de Barcelona, C/Doctor Aiguader 80, E-08003 Barcelona, Spain. aenjuanes@imim.es
Anna
A
Enjuanes
Natalia
N
Garcia-Giralt
August
A
Supervia
Xavier
X
Nogués
Leonardo
L
Mellibovsky
Jordi
J
Carbonell
Daniel
D
Grinberg
Susana
S
Balcells
Adolfo
A
Díez-Pérez
D000199:Actins / Q000235:genetics; D001141:Aromatase / Q000235:genetics*; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D012739:Gonadal Steroid Hormones / Q000494:pharmacology; D006801:Humans; D010006:Osteoblasts / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D014807:Vitamin D / Q000494:pharmacology
D000199:Actins; D016207:Cytokines; D012739:Gonadal Steroid Hormones; D012333:RNA, Messenger; D014807:Vitamin D; D003907:Dexamethasone; D001141:Aromatase