To better understand dermal response to visible light, we used DNA microarray analysis to search genes induced by blue or near-UV light in normal human dermal fibroblasts. Of about 12 800 transcripts analyzed, near-UV light most prominently upregulated the transcript level of Mic-1, a gene encoding a TGF-β superfamily protein. Quantitative RT-PCR and immunoblot analyses revealed that mRNA and protein levels of Mic-1 were upregulated by both short-wavelength light but not by green or red light. These results suggest that the human dermis is a site for macrophage inhibitory cytokine-1 (MIC-1) production and that visible light activates a dermal transcription cascade. Considering the role of MIC-1 in immune regulation and appetite control, photic MIC-1 regulation is of physiological importance.
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