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Differential effects of UV irradiation on the nuclear retinoid receptor levels of cultured keratinocytes and melanocytes
Linköping University, Department of Biomedicine and Surgery, Dermatology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Biomedicine and Surgery, Dermatology. Linköping University, Faculty of Health Sciences.
Department of Medical Sciences, Section of Dermatology and Venereology, Uppsala University, Uppsala.
Department of Medical Sciences, Section of Dermatology and Venereology, Uppsala University, Uppsala.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Skin cancer is the most common malignancy in man. A major risk factor is UV irradiation, which not only damages DNA but may also perturb cellular signaling, e.g. via the retinoid receptor system believed to be important for cancer protection. We used cultured normal human keratinocytes and melanocytes to study the effects of UV radiation on the expression of the retinoid receptors RARα, RARβ, RARγ and RXRα. By real-time PCR and Western blot technique, the mRNA and protein levels were monitored, before and up to 4 days following 50 mJ/cm2 UVB. In keratinocytes, UVB caused a rapid drop in all four mRNA levels (minus 50-70% the first 8 h) and protein levels dropped by 30-40% followed by a gradual increase, but full normalization was ouly reached for RARα within the study period. ln melanocytes, UVB caused a quick drop both in the receptor mRNA and protein levels (minus 50-60% after 4 h), followed by normalization of the protein levels for all receptors within 2-3 days. The UV-induced depletion of vitamin A and retinoid receptors might abrogate the retinoid signaling, which subsequently might promote tumor development.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-81447OAI: oai:DiVA.org:liu-81447DiVA: diva2:552518
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2012-09-14Bibliographically 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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