Objective: To determine whether UV-A irradiation induces synthesis of inflammatory cytokines in the skin.
Methods: Human keratinocytes and dermal fibroblasts were cultured and exposed to various doses of UV-A radiation. The cellular distribution of IL-6 and TNF alpha was determined by indirect immunofluorescence and by flow cytometry with monoclonal anti-IL-6 and anti-TNF alpha antibodies. Cytokine production was measured in the supernatants using an ELISA. IL-6 and TNF alpha transcription induced by UV-A was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) amplification.
Results: IL-6 and TNF alpha were detected in small amounts in nonUV-A-irradiated cell. UV-A exposure was followed by significant increases in IL-6 and TNF alpha expression and by small increases in IL-6 and TNF alpha levels in culture supernatants. RT-PCR demonstrated a UV-A-mediated increase in the transcription of IL-6 and TNF alpha genes.
Conclusion: Synthesis of IL-6 and TNF alpha can be induced by UV-A irradiation. This effect of UV-A may contribute to the inflammatory skin changes seen during lupus flare-ups after sun exposure.