Ultraviolet radiation and the slug transcription factor induce proinflammatory and immunomodulatory mediator expression in melanocytes

Abstract

Despite extensive investigation, the precise contribution of the ultraviolet radiation (UVR) component of sunlight to melanoma etiology remains unclear. UVR induces keratinocytes to secrete proinflammatory and immunomodulatory mediators that promote inflammation and skin tumor development; expression of the slug transcription factor in keratinocytes is required for maximal production of these mediators. In the present studies we examined the possibility that UVR-exposed melanocytes also produce proinflammatory mediators and that Slug is important in this process. Microarray studies revealed that both UVR exposure and Slug overexpression altered transcription of a variety of proinflammatory mediators by normal human melanocytes; some of these mediators are also known to stimulate melanocyte growth and migration. There was little overlap in the spectra of cytokines produced by the two stimuli. However IL-20 was similarly induced by both stimuli and the NFκB pathway appeared to be important in both circumstances. Further exploration of UVR-induced and Slug-dependent pathways of cytokine induction in melanocytes may reveal novel targets for melanoma therapy.

Figure 1

UVR induction of Slug 24 hours following a dose of 300 J/m² UVR. (a) Slug mRNA levels were determined by RT-QPCR in two independent assays, each performed in triplicate. Bars represent the standard error of all six values. (b) Slug protein levels were determined by Western blotting followed by densitometry in three independent assays. Bars represent the standard deviation.

Figure 2

Ingenuity Pathway Analysis of altered expression of proinflammatory genes in normal human melanocytes. Cells were harvested 24 hours following a dose of 300 J/m² UVR. mRNA expression levels were determined using the PAHS-3803 Human Inflammatory Response and Autoimmunity Cytokine Array (SA Biosciences), and genes with expression altered more than two-fold in duplicate assays were included in the Ingenuity Pathway Analysis.

Figure 3

Ingenuity Pathway Analysis of altered expression of proinflammatory genes in normal human melanocytes transduced with Ad-Slug. Expression levels were determined using the PAHS-3803 Human Inflammatory Response and Autoimmunity Cytokine Array (SA Biosciences), and genes with expression altered more than two-fold in duplicate assays were included in the Ingenuity Pathway Analysis.