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Differential effects of UV irradiation on nuclear retinoid receptor levels in cultured keratinocytes and melanocytes
Author(s) -
Andersson Eva,
Rosdahl Inger,
Törmä Hans,
Vahlquist Anders
Publication year - 2003
Publication title -
experimental dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 96
eISSN - 1600-0625
pISSN - 0906-6705
DOI - 10.1034/j.1600-0625.2003.00090.x
Subject(s) - retinoid , retinoid x receptor alpha , receptor , retinoid x receptor , human skin , keratinocyte , retinoid x receptor beta , biology , apoptosis , microbiology and biotechnology , western blot , cancer research , endocrinology , chemistry , nuclear receptor , cell culture , retinoic acid , transcription factor , biochemistry , gene , genetics
A major risk factor for skin cancer is UV irradiation, which not only damages DNA and other photosensitive compounds like vitamin A, 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 examine the effects of UV irradiation on the expression of the predominant retinoid receptors in the human skin (RARα, RARγ and RXRα) and the AP‐1 protein c‐Jun; mRNA levels were studied by real‐time PCR and protein levels by Western blot. In keratinocytes, a single dose of UVB (50 mJ/cm 2 ) caused a rapid drop in the expression of all three receptors (mRNA levels minus 35–50% after 4 h; protein levels minus 20–45% after 8 h), which was followed over the next 40 h by a variable response, leading to full normalization for RARα only. In contrast, the levels of c‐Jun did not change significantly after UV exposure. In melanocytes, UVB caused a similar drop of the retinoid receptor levels as in keratinocytes but this was soon followed by an increased expression leading to a complete normalization of all receptor levels within 1–3 days. The c‐Jun levels in melanocytes increased 1 day after UV exposure and remained high (plus 50%) thereafter. In both cell types, a ∼3‐fold increase in apoptosis (measured by DNA fragmentation) was observed 8–48 h after UVB irradiation. In conclusion, a depletion of vitamin A and retinoid receptors by UV irradiation, together with unchanged or even increased c‐Jun levels, might seriously interfere with retinoid signaling and thus promote future tumor development, especially in keratinocytes.