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β-Carotene Uptake and Bioconversion to Retinol Differ Between Human Melanocytes and Keratinocytes
Linköping University, Department of Biomedicine and Surgery, Dermatology. Linköping University, Faculty of Health Sciences.
Section of Dermatology and Venereology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
Linköping University, Department of Biomedicine and Surgery, Dermatology. Linköping University, Faculty of Health Sciences.
2001 (English)In: Nutrition and Cancer, ISSN 0163-5581, E-ISSN 1532-7914, Vol. 39, no 2, 300-306 p.Article in journal (Refereed) Published
Abstract [en]

β-Carotene is one of the carotenoids that has been considered to play a role in the natural defense against ultraviolet-induced skin cancer. It is not known whether epidermal cells are able to accumulate β-carotene and, subsequently, convert it to vitamin A. We used normal cultured human keratinocytes and melanocytes to study the uptake, and possible bioconversion to retinol, of authentic or [14C]β-carotene. The uptake was much higher in melanocytes than in keratinocytes, corresponding to a fivefold difference in the intracellular fraction after two days of incubation. An increased level of cellular retinol was noted after one day of β-carotene incubation. The conversion of [C]β-carotene to [14C]retinol peaked at 24 hours of incubation in keratinocytes and melanocytes. The results suggest that β-carotene can function as a local supply of vitamin A in the skin and that melanocytes are especially likely to store β-carotene.

Place, publisher, year, edition, pages
2001. Vol. 39, no 2, 300-306 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-49078DOI: 10.1207/S15327914nc392_21OAI: oai:DiVA.org:liu-49078DiVA: diva2:269974
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Vitamin A and ß-carotene metabolism and effects of UV irradiation in human keratinocytes and melanocytes
Open this publication in new window or tab >>Vitamin A and ß-carotene metabolism and effects of UV irradiation in human keratinocytes and melanocytes
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Retinoids (vitamin A and its derivatives) are modulators of proliferation and differentiation. Both retinol (ROH) and its metabolite 3,4-didehydroretinol (ddROH) can be converted to retinoic acid (RA) and 3,4-didehydroretinoic acid (ddRA), ligands for the nuclear receptors, which induce gene transcriptions. A perturbed ROH metabolism is observed in several dermatoses and iu non-melanoma skin cancer. Dietary ß-carotene has been considered to play a critical role in the natural defence against cancer. Whether ß-carotene is converted to ROH in the skin has been debated.

We have investigated ß-carotene and retinoid metabolism, retinoid binding proteins and retinoid receptors in human keratinocytes (KCs) and melanocytes (MCs) in vitro. Similar studies of vitamin A have been done in human malignant epithelial cells (HeLa) and malignant melanoma cells. The influence of ultraviolet radiation (UVR) on retinoid metabolism and receptor expression was specially focused upon this thesis. KCs and MCs contained high concentrations of ROH, ddROH, while HeLa- and melanoma cells contained lower levels. KCs contained the highest level of the retinoid-binding proteins CRBP I and CRABP II compared to MCs, HeLa and melanoma cells. High CRABP II levels showed a correlation with the ability to accumulate ddROH. In MCs, CRABP I was highly expressed, but in melanoma cells CRABP II dominated. The difference between MCs and melanoma cells in receptor levels was most pronounced for RARß, which was highly expressed in melanoma cells. Such dissimilarities between benign and malignant MCs might play a role in differentiation and growth regulation. The uptake of [3H]ROH, [3H]RA and ß-carotene was significantly higher in MCs than in KCs. We were able to demonstrate that [14C]ß-carotene was converted to [14C]ROH in both these cell types. This suggests that this local storage of ß-carotene might serve as au alternative supply for vitamin A in the skin.

A moderate dose of UVR reduced the concentration of ROH, ddROH and [3H]RA in KCs and MCs by 20-50%. The concentration returned to starting levels in 1-2 days, and could be explained by a retarded metabolism of RA, the biologically most active metabolite. When KCs and MCs were exposed to UVR, the mRNA and protein levels of the three nuclear retinoid receptors (RARα, RARγ and RXRα) decreased rapidly. In MCs these levels were close to normal 3 days postirradiation. In KCs only the RARα mRNA and protein levels returned to baseline within 3 days. This thesis has increased our knowledge of the effects of UVR on retinoid metabolism and retinoid receptors in human cells. Further studies are needed to understand the role of ß-carotene and retinoid signaling in UV induced skin cancer.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 66 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 725
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25546 (URN)9993 (Local ID)91-7373-169-2 (ISBN)9993 (Archive number)9993 (OAI)
Public defence
2002-07-01, Berzeliussalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-09-14Bibliographically approved

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Andersson, EvaRosdahl, Inger

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