25-hydroxyvitamin D3 is an active hormone in human primary prostatic stromal cells.
According to the present paradigm, 1alpha,25-dihydroxyvitamin D3 [1alpha,25-(OH)2D3] is a biologically active hormone; whereas 25-hydroxyvitamin D3 (25OHD3) is regarded as a prohormone activated through the action of 25-hydroxyvitamin D3 1alpha-hydroxylase (1alpha-hydroxylase). Although the role of vitamin D3 in the regulation of growth and differentiation of prostatic epithelial cells has been well studied, its action and metabolism in prostatic stroma are still largely unknown. We investigated the effects of 25OHD3 and 1alpha,25-(OH)2D3 on two human stromal primary cultures termed P29SN and P32S. In a cell proliferation assay, 25OHD3 was found at physiological concentrations of 100-250 nM to inhibit the growth of both primary cultures, whereas 1alpha,25-(OH)2D3 at a pharmacological concentration of 10 nM exhibited the growth-inhibitory effects on P29SN cells but not on P32S cells. Quantitative real-time RT-PCR analysis revealed that both 25OHD3 and 1alpha,25-(OH)2D3 induced 25-hydroxyvitamin D3 24-hydroxylase (24-hydroxylase) mRNA in a dose- and time-dependent manner. By inhibiting 1alpha-hydroxylase and/or 24-hydroxylase enzyme activities, the induction of 24-hydroxylase mRNA by 250 nM 25OHD3 was clearly enhanced, suggesting that 1alpha-hydroxylation is not a prerequisite for the hormonal activity of 25OHD3. Altogether our results suggest that 25OHD3 at a high but physiological concentration acts as an active hormone with respect to vitamin D3 responsive gene regulation and suppression of cell proliferation.
Lou
Yan-Ru
YR
Department of Anatomy, Medical School, FIN 33014, University of Tampere, Finland. loyalo@uta.fi
Laaksi
Ilkka
I
Syvälä
Heimo
H
Bläuer
Merja
M
Tammela
Teuvo L J
TL
Ylikomi
Timo
T
Tuohimaa
Pentti
P
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D002112:Calcifediol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D006728:Hormones / Q000494:pharmacology; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D008297:Male; D011467:Prostate / Q000166:cytology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D013997:Time Factors; D065668:Vitamin D3 24-Hydroxylase
D065607:Cytochrome P-450 Enzyme Inhibitors; D006728:Hormones; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002112:Calcifediol