Interleukin‐8 and melanoma growth‐stimulating activity (GRO) are induced by ultraviolet B radiation in human keratinocyte cell lines

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Abstract
Ultraviolet radiation can induce the transcription and release of cytokines From keratinocytes (KC's). These cytokines have the potential to modulate local and systemic immunologic responses. In this paper we report that northern blotting showed that human KC and KC lines expressed a 1.2‐1.4 kb transcript for the chemokine and melanoma growth‐stimulatory protein, GRO‐α and that ultraviolet B radiation (UVB) could upregulate the expression of GRO‐α mRNA and protein in the KC line A431. The GRO‐α gene response to UVB was maximal at 48h post‐irradiation with 70 J/m2. Reverse transcription‐polymerase chain reaction (RT‐PCR) revealed a 4.5‐fold increase in GRO‐α mRNA over basal levels (p<0.001). GRO‐α protein was measured in the culture media by enzyme‐linked immunosorbent assay (ELISA). Media from unirradiated cultures contained 1166±83 pg/ml GRO‐α protein. After UVB, a time‐dependent increase in GRO‐α protein was seen in the culture media from 6‐48h. At 48h post‐irradiation the GRO‐α protein content was 27583±678 pg/ml, or 23 times the basal level. This protein release could be inhibited by 70% when the cells were pre‐incubated with 10 μg/ml interleukin‐1 receptor antagonist (IL‐1RA). We also show that another potent leukocyte chemoattractant, Interleukin‐8 (IL‐8), was induced in A431 cells by UVB. The induction of IL‐8 mRNA began as early as 3h post‐irradiation, when it reached twice basal levels (p<0.05) and reached 4.5‐fold basal levels at 48h post‐irradiation (p<0.005). Analysis of the conditioned media from the irradiated cells by ELISA revealed that IL‐8 protein accumulation was increased from 162± 16 pg/ml (unirradiated cultures) to 993± 120 pg/ml 24h post‐irradiation. The accumulation increased to 1383± 178 pg/ml, or 9‐fold the basal level by 48h post‐irradiation. Thus keratinocytes are capable of generating chemoattractant factors which enhance melanoma growth after UVB irradiation, which may contribute to the inflammatory infiltrate found in the dermis of sunburned skin.

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