| 1. |
- Andersson, Eva, et al.
(författare)
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The metabolism of vitamin A to 3,4-didehydroretinol can be demonstrated in human keratinocytes, melanoma cells and HeLa cells, and is correlated to cellular retinoid-binding protein expression
- 1994
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - : Elsevier BV. - 0167-4889 .- 1879-2596. ; 1224:3, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of retinol to 3,4-didehydroretinol is probably a rate-limiting step in the formation of 3,4-didehydroretinoic acid, a candidate ligand for nuclear retinoid receptors in human epidermal keratinocytes. To investigate whether this metabolic pathway also exists in other cell systems, we compared the retinoid concentrations and the bioconversion of [3H]retinol to [3H]3,4-didehydroretinol in human primary keratinocytes, human cervical carcinoma (HeLa) cells, human melanoma (JKM86-4) cells, monkey kidney epithelium (CV-1) cells, and murine teratocarcinoma (F9) cells. The cellular retinol concentration ranged from 2.33 to 99.1 pmol/mg protein with the highest values observed in keratinocytes. 3,4-Didehydroretinol was only detected in cells of human origin and its concentration ranged from 0.24 pmol/mg in HeLa to 34.6 pmol/mg in the keratinocytes. Incubation with [3H]retinol for 1–24 h resulted in a rapid appearance of [3H]3,4-didehydroretinol in human keratinocytes, and to a lesser extent in HeLa and melanoma cells, but not in the other cells. Analysis of cellular retinol- and retinoic acid-binding protein concentrations showed a correlation to the cells' ability to accumulate 3,4-didehydroretinol, suggesting a role for these proteins in the 3,4-didehydro metabolic pathway. The combined results suggest that although 3,4-didehydroretinol is most typical for human keratinocytes, studies of its metabolism are also feasible in HeLa cells which contain low levels of retinoid-binding proteins.
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| 2. |
- Andersson, Eva, 1946-, et al.
(författare)
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Ultraviolet irradiation depletes cellular retinol and alters the metabolism of retinoic acid in cultured human keratinocytes and melanocytes
- 1999
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Ingår i: Melanoma research. - 0960-8931 .- 1473-5636. ; 9:4, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- Vitamin A is an intrinsic modulator of proliferation and differentiation in human epidermis, and may be destroyed by ultraviolet radiation (UVR) impinging on the skin. To identify the deleterious effects of a perturbed cellular vitamin A status, we investigated the endogenous retinoid concentrations and the metabolism of [3H]retinol and all-trans [3H]retinoic acid in cultured human keratinocytes and melanocytes exposed to UVR, using high performance liquid chromatography. Before UVR the retinoid content was similar in keratinocytes and melanocytes, but the uptake of [3H]retinol was three-fold higher and the uptake of [3H]retinoic acid was 10-fold higher in the melanocytes. In both cell types, UVR (UVA 360 mJ/cm2 plus UVB 140 mJ/cm2) instantaneously reduced the concentration of retinol by about 50% and that of 3,4-didehydroretinol by about 20%. The retinoid concentrations returned to normal within 1-2 days post-irradiation, despite there being no overt increase in the uptake of [3H]retinol or the biosynthesis of 3,4-didehydroretinol. However, in both types of irradiated cells, the accumulation of the biologically most active metabolite, all-trans [3H]retinoic acid, was about 60% higher than in control cells. Furthermore, the metabolism of authentically supplied [3H]retinoic acid was reduced, especially in irradiated keratinocytes, which probably contributed to the restoration of retinoid levels after UV exposure.
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| 3. |
- Busch, Christer, et al.
(författare)
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Expression of Cellular Retinoid-Binding Proteins During Normal and Abnormal Epidermal Differentiation
- 1992
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Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 0022-202X .- 1523-1747. ; 99:6, s. 795-802
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Tidskriftsartikel (refereegranskat)abstract
- Retinoids have important roles in growth and differentiation of epidermal cells. We have analyzed the expression of two intracellular retinoid-binding proteins, the cellular retinol-binding protein type I and the cellular retinoic acid - binding protein type I, during normal and abnormal epidermal differentiation. Both proteins were found to be expressed in normal epidermis with increasing expression from basal layer towards superficial layers. In psoriatic lesions, a hyperproliferative condition of the skin, the epidermal expression of cellular retinol-binding protein I was induced, whereas expression of cellular retinoic acid-binding protein I was sharply down-regulated. This and other features of psoriatic lesions indicate that down-regulation of cellular retinoic acid - binding protein I expression might cause aberrant retinoid-regulated gene expression in skin. In basal and squamous cell carcinomas, cellular retinoic acid - binding protein I expression was down-regulated, whereas cellular retinol-binding protein I was expressed. Apart from epidermal cells, a mesenchymal, dendritic cell-type, strongly expressing cellular retinoic acid-binding protein I, was identified in the dermis. In several hyperproliferative conditions of the skin, including psoriasis, and squamous and basal cell carcinomas, this cell type was abundant. These results have implications for the role of retinoids in normal and abnormal epidermal differentiation and suggest that part of the phenotype of psoriasis is due to inappropriate metabolism of retinoic acid in skin.
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| 4. |
- Danielsson, Carina, et al.
(författare)
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Positive and negative interaction of 1,25-dihydroxyvitamin D3 and the retinoid CD437 on the induction of apoptosis of human melanoma cells
- 1999
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Ingår i: International Journal of Cancer. - 0020-7136 .- 1097-0215. ; 81:3, s. 467-470
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Tidskriftsartikel (refereegranskat)abstract
- The natural ligands of the nuclear receptors vitamin D receptor (VDR) and retinoic acid receptor (RAR), i.e., 1alpha,25-dihydroxyvitamin D3 (VD) and all-trans retinoic acid, have important effects on the proliferation, differentiation and apoptosis of a variety of malignant cells, including melanoma. The therapeutic potential of the 2 nuclear hormones can be enhanced by the use of synthetic analogues. In this study, the 2 human melanoma cell lines WM1341 and MeWo were compared for the combined effect of VD and synthetic retinoids. Both cell lines expressed reasonable amounts of VDR, RARgamma and retinoid X receptor alpha and differed only in the relative expression of RARalpha and beta. From 9 functional variants of retinoids, only the RARgamma-selective retinoid CD437 showed, in both cell lines, a significant anti-proliferative effect. In MeWo cells, but not in WM1341 cells, VD induced growth arrest but showed no synergistic interaction with the effects of CD437. In contrast, VD induced apoptosis in WM1341, but not in MeWo, cells. CD437 was a strong inducer of apoptosis in both melanoma cell lines. Parallel treatment with CD437 and VD resulted in synergistic enhancement of apoptosis in WM1341 cells, whereas a clear decrease in induction of apoptosis in MeWo cells occurred. Our results indicate that a combined treatment of melanoma with VD and selected retinoids is promising but should be adapted to individual types of tumor.
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| 5. |
- Stenström, E., et al.
(författare)
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Retinoids Can Be Classified according to Their Effects on Vitamin A Metabolism in HeLa Cells
- 1996
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Ingår i: Skin pharmacology : the official journal of the Skin Pharmacology Society. - 1011-0283. ; 9:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- Although retinoids may exert their action via binding to nuclear retinoic acid receptors (RARs), other mechanisms of action are not excluded. For example, the anti-acne drug, isotretinoin, lacks affinity for the receptors, but is a very potent inhibitor of endogenous vitamin A metabolism in human epidermal cells. To further extend this observation, we studied the effect of 12 different retinoids on the metabolism of [3H]retinol ([3H]ROH) in HeLa cells, previously shown to produce constant levels of 3,4-didehydroretinol (ddROH). The cells were cultured in the presence of the unlabeled retiniods for 20 h, followed by 4 h incubation with [3H]ROH. The accumulation of [3H]ROH and [3H]ddROH in cellular extracts was analysed by HPLC. Addition of 10(-10) to 10(-5) M of four naturally occurring isomers of retinoic acid caused a 4- to 6-fold increase in [3H]ROH accumulation and an 80% decrease in [3H]ddROH. Addition of synthetic retinoids with a terminal carboxyl (CD270, CD271, CD367 and Ro 13-7410) decreased the [3H]ddROH accumulation with about 70%, but hardly at all affected the accumulation of [3H]ROH. We conclude that cultured HeLa cells appear to be useful for screening retinoids for their effects on vitamin A metabolism showing that a terminal carboxylic acid is a prerequisite for any major effects on metabolism to occur. Whether this effect is due to interaction with RARs or to competitive inhibition of vitamin-A-metabolizing enzymes demands to be studied.
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| 6. |
- Törmä, Hans, et al.
(författare)
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The vitamin A metabolism and expression of retinoid-binding proteins differ in HaCaT cells and normal human keratinocytes
- 1999
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Ingår i: Archives of Dermatological Research. - : Springer Science and Business Media LLC. - 0340-3696 .- 1432-069X. ; 291:6, s. 339-345
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Tidskriftsartikel (refereegranskat)abstract
- HaCaT keratinocytes differ from normal human epidermal keratinocytes (HEK) by constitutive expression of differentiation markers which are normally suppressed by vitamin A. In search of an explanation for this discrepancy we compared the vitamin A content, the expression of retinoid-binding proteins, and the vitamin A metabolism in the two cell types. The concentrations of retinol and 3,4-didehydroretinol in cultured HaCaT cells were less than one-fifth those in HEK, and the content of fatty acyl esters was even lower. Similarly, the concentrations of cellular retinol-binding protein and cellular retinoic acid-binding protein (CRBPI and CRABPII, respectively) were 10-30 times lower in HaCaT cells than in HEK corresponding to a reduced mRNA expression of these proteins. Unexpectedly, HaCaT cells expressed RARbeta in addition to RARalpha, RARgamma and RXRalpha, which are nuclear receptors normally found in HEK. Radioactive retinol added to the culture medium appeared only transiently in HaCaT cells, and pulse labeling confirmed a defective cellular retention of retinyl esters. After 24 h of incubation with [3H]retinol, cell-associated radioactivity corresponding to retinol, 3,4-didehydroretinol, all-trans-retinoic acid and 3,4-didehydroretinoic acid was found in both HaCaT cells and HEK. [3H]Retinoic acid showed a more rapid metabolism to 4-hydroxy/4-keto-retinoic acid in HaCaT cells than in HEK, which could be explained by a higher expression of cytochrome p450RAI in the former cells. In conclusion, the abnormal uptake of vitamin A and low levels of retinoid binding proteins in HaCaT cells, linked with an aberrant metabolism of retinol, may help to explain why these cells differentiate also in the presence of retinoids.
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| 7. |
- Vahlquist, Anders, et al.
(författare)
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Increased concentrations of 3,4-didehydroretinol and retinoic acid-binding protein (CRABPII) in human squamous cell carcinoma and keratoacanthoma but not in basal cell carcinoma of the skin
- 1996
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Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 0022-202X .- 1523-1747. ; 106:5, s. 1070-1074
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Tidskriftsartikel (refereegranskat)abstract
- Retinoids are biologic response modifiers that are present in normal skin and may possibly be perturbed in carcinogenesis. To examine this possibility in human skin, we analyzed vitamin A and cytosolic retinoid binding proteins (cellular retinol binding protein and cellular retinoic acid binding protein [CRABP]) in a total of 38 non-melanoma skin tumors and 25 healthy skin samples using high performance liquid chromatography, radioligand electrophoresis, and reverse transcriptase-polymerase chain reaction. The mean +/- SEM retinol concentration was normal in basal cell carcinoma (0.60 +/- 0.10 microM) and seborrheic keratosis (0.47 +/- 0.07 microM), but increased in keratoacanthoma (1.60 +/- 0.41 microM) and squamous cell carcinoma (1.17 +/- 0.28 microM) (p < 0.05 for both). Also, the concentrations of 3,4-didehydroretinol, a major vitamin A metabolite produced in human skin, were markedly elevated (6-7 times normal) in keratoacanthoma and squamous cell cancer. All types of tumors showed moderately increased levels of cellular retinol binding protein. In addition, keratoacanthoma and squamous cell cancer showed markedly increased levels (6-7 times normal) of CRABPII protein. Transcriptional activity of the CRABPII gene was demonstrated in both normal and neoplastic epidermis, but clear CRABPI mRNA expression was found only in basal cell carcinoma. The data indicate that characteristic perturbations of the vitamin A and retinoid binding protein levels occur in squamous cell-derived skin tumors, but whether these reflect intrinsic errors in retinoid metabolism or are secondary to abnormal cellular differentiation is unknown.
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