1.
Ellfolk, Maria, et al.
(författare)
Regulation of human vitamin D(3) 25-hydroxylases in dermal fibroblasts and prostate cancer LNCaP cells
2009
Ingår i: Molecular Pharmacology. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0026-895X .- 1521-0111. ; 75:6, s. 1392-1399
Tidskriftsartikel (refereegranskat) abstract
In this study, we examined whether 1alpha,25-dihydroxyvitamin D(3) (calcitriol), phenobarbital, and the antiretroviral drug efavirenz, drugs used by patient groups with high incidence of low bone mineral density, could affect the 25-hydroxylase activity or expression of human 25-hydroxylases in dermal fibroblasts and prostate cancer LNCaP cells. Fibroblasts express the 25-hydroxylating enzymes CYP2R1 and CYP27A1. LNCaP cells were found to express two potential vitamin D 25-hydroxylases-CYP2R1 and CYP2J2. The presence in different cells of nuclear receptors vitamin D receptor (VDR), pregnane X receptor (PXR), and constitutive androstane receptor (CAR) was also determined. Phenobarbital suppressed the expression of CYP2R1 in fibroblasts and CYP2J2 in LNCaP cells. Efavirenz suppressed the expression of CYP2R1 in fibroblasts but not in LNCaP cells. CYP2J2 was slightly suppressed by efavirenz, whereas CYP27A1 was not affected by any of the two drugs. Calcitriol suppressed the expression of CYP2R1 in both fibroblasts and LNCaP cells but had no clear effect on the expression of either CYP2J2 or CYP27A1. The vitamin D(3) 25-hydroxylase activity in fibroblasts was suppressed by both calcitriol and efavirenz. In LNCaP cells, consumption of substrate (1alpha-hydroxyvitamin D(3)) was used as indicator of metabolism because no 1alpha,25-dihydroxyvitamin D(3) product could be determined. The amount of 1alpha-hydroxyvitamin D(3) remaining in cells treated with calcitriol was significantly increased. Taken together, 25-hydroxylation of vitamin D(3) was suppressed by calcitriol and drugs. The present study provides new information indicating that 25-hydroxylation of vitamin D(3) may be regulated. In addition, the current results may offer a possible explanation for the impaired bone health after treatment with certain drugs.
2.
3.
Pettersson, Hanna, et al.
(författare)
CYP7B1-mediated metabolism of 5 alfa-androstane-3 alfa,17 beta-diol (3 alfa-Adiol) : A novel pathway for potential regulation of the cellular levels of androgens and neurosteroids
2009
Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1791:12, s. 1206-1215
Tidskriftsartikel (refereegranskat) abstract
The current study presents data indicating that 5alfa-androstane-3alfa,17beta-diol (3alfa-Adiol) undergoes a previously unknown metabolism into hydroxymetabolites, catalyzed by CYP7B1. 3alfa-Adiol is an androgenic steroid which serves as a source for the potent androgen dihydrotestosterone and also can modulate gamma-amino butyric acid A (GABAA) receptor function in the brain. The steroid hydroxylase CYP7B1 is known to metabolize cholesterol derivatives, sex hormone precursors and certain estrogens, but has previously not been thought to act on androgens or 3a-hydroxylated steroids. 3alfa-Adiol was found to undergo NADPH-dependent metabolism into 6- and 7-hydroxymetabolites in incubations with porcine microsomes and human kidney-derived HEK293 cells, which are high in CYP7B1 content. This metabolism was suppressed by addition of steroids known to be metabolized by CYP7B1. Also, recombinant expression of human CYP7B1 in HEK293 cells significantly increased the rate of 3alfa-Adiol hydroxylation. In addition, 3alfa-Adiol significantly suppressed CYP7B1-mediated catalytic reactions, in a way as would be expected for substrates that compete for the same enzyme. The present results indicate that CYP7B1-mediated catalysis may play a role for control of the cellular levels of androgens, not only of estrogens. These findings suggest a previously unknown mechanism for metabolic elimination of 3alfa-Adiol which may impact intracellular levels of dihydrotestosterone and GABAA-modulating steroids.
4.
Pettersson, Hanna, 1968-
(författare)
Steroid-Metabolizing Cytochrome P450 (CYP) Enzymes in the Maintenance of Cholesterol and Sex Hormone Levels
2009
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The enzymes CYP27A1 and CYP7B1 are widely expressed in various human tissues and perform catalytic reactions in cholesterol homeostasis and endocrine signaling. We have investigated the metabolism of a synthetic oxysterol. In this study, we show that CYP27A1 is the enzyme responsible for a 28-hydroxylation of this oxysterol and that the rate of CYP27A1-mediated metabolism is relatively slow. This may give an explanation for the prolonged inhibitory effects on cholesterol biosynthesis that have been shown for this oxysterol. The current study contributes to the knowledge of synthetically produced oxysterols and their potential use as cholesterol lowering drugs. In two studies we investigated CYP7B1-mediated metabolism of different sex hormones. Our data indicate that CYP7B1 may carry out a previously unknown catalytic reaction involving an androgen. Taken together the data suggest that varying steroid concentrations in cells and tissues may be important for CYP7B1-dependent metabolism of sex hormones and sex hormone precursors. CYP7B1-mediated hydroxylation of sex hormones may influence the cellular levels of these steroids and may be a potential pathway for elimination of the steroids from the cell. Some known CYP7B1 substrates are agonists for ERα and ERβ but the reported role(s) of CYP7B1 for ER action are not fully understood. In the last study we investigated the role(s) of CYP7B1-mediated metabolism for ER-mediated action. Our data indicate that CYP7B1-mediated conversion of steroids that affect ER-mediated response into their 7α-hydroxymetabolites will result in loss of action. This indicates that CYP7B1 may have an important role for regulation of ER-mediated processes in the body. In summary, results from this thesis contribute to the knowledge on the metabolism of synthetic oxysterols of potential use as cholesterol lowering drugs and the role(s) of CYP7B1-mediated metabolism for processes related to the functions of sex hormones.
5.
Wikvall, Kjell, et al.
(författare)
Regulation of CYP enzymes in steroidogenesis with particular focus on cholesterol metabolism and vitamin D-related processes
2009
Ingår i: Proceedings of the 16th International Conference on Cytochrome P450, Nago, Okinawa, Japan, June 21-25. - Bologna : Medimond. - 9788875875244 ; , s. 177-182
Konferensbidrag (refereegranskat) abstract
CYP27A1 is an enzyme essential for cholesterol homeostasis and is considered an anti-atherogenic enzyme. CYP27A1 is required in bile acid biosynthesis and participates in oxysterol formation, cholesterol transport and cholesterol elimination (Fig 1). Considering these important functions, mechanisms for regulation of the human CYP27A1 gene are of great interest (1). CYP27A1 is also a vitamin D 25-hydroxylase, catalyzing the first step in the bioactivation of vitamin D into the multifunctional hormone 1,25-dihydroxyvitamin D. Fig 2 shows the bioactivation of vitamin D. Multiple vitamin D 25-hydroxylases exist in humans. In addition to CYP27A1, other known vitamin D 25-hydroxylases are CYP2R1, CYP2J2 and CYP3A4 (2). The active 1,25-dihydroxyvitamin D is a calcium-regulating hormone. Newly discovered functions of this hormone are regulation of cell growth, regulation of immune function and regulation of blood pressure and insulin production. In the current presentation, we focus on our recent studies on the regulation of CYP27A1 and the CYP enzymes catalyzing the first step in the bioactivation of vitamin D.
