Effects of urocanic acid on primary human keratinocytes

Urocanic acid (UCA) is a major epidermal chromophore that undergoes trans to cis photoisomerisation following exposure to solar ultraviolet radiation (UVR). Although there is considerable evidence that cis-UCA suppresses cell-mediated immune response in mouse skin, the molecular events are not fully understood. In this study, we examined involvement of gene transcription in the immunomodulatory effects of cis-UCA on primary human keratinocytes. The results showed that about 400 genes were induced by UVR, 16 of which also up-regulated by cis-UCA. In contrast, trans-UCA had no effect on gene expression. The genes up-regulated by both cis-UCA and UVR were associated with apoptosis, cell growth arrest, cytokines and oxidative stress. Keywords: Agent response RNA was extracted from primary human keratinocytes treated with trans-, cis-UCA (10ug/ml) or solar simulated UVR (12J/cm2 ~ 2-3 minimal erythema doses for fair skin), or untreated. At 24hr, the transcriptional profiles were assessed by Affymetrix HG-U133A microarray.