Synergistic effects of acitretin and narrow-band ultraviolet-B in inducing retinoic acid receptor gamma mRNA expression in normal human keratinocytes

OBJECTIVE: To investigate the changes in cell proliferation and retinoic acid receptor gamma (RARgamma) mRNA expression in normal human keratinocytes after acitretin treatment and/or narrow-band ultraviolet-B irradiation. METHODS: Normal human keratinocytes were exposed to irradiation with 100 mJ/cm square NB-UVB and/or subsequent 12-hour incubation with 1x10(-6) mol/L acitretin, and the expression of RARgamma mRNA in the cells was examined using RT-PCR and real-time quantitative RT-PCR. RESULTS: A 0.9- and a 2.3-fold increase in RARgamma mRNA expression was induced in the cells by exposure to 100 mJ/cm square NB-UVB and 10(-6) mol/L acitretin, respectively, and the expression was synergistically enhanced by 2.8-fold after their combined treatment. CONCLUSION: Upregulated expression of RARgamma mRNA can be associated with keratinocyte growth inhibition after treatment with acitretin and NB-UVB irradiation.