Contrasting effects of an ultraviolet B and an ultraviolet A tanning lamp on interleukin-6, tumour necrosis factor-alpha and intercellular adhesion molecule-1 expression

Background Recent studies have demonstrated that a tanning lamp emitting pr edominantly ultraviolet (UV) A induces significant yields of the type of po tentially mutagenic DNA damage that are associated with the onset of skin c ancer (i.e. cyclobutane pyrimidine dimers). UV-induced immunosuppression is also an important event leading to skin cancer. Objectives To the modulation of key immunological molecules following expos ure to a broad-spectrum UVB lamp and a predominantly UVA-emitting tanning l amp using model in vitro systems. Methods We compared secretion and mRNA expression of interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha in normal human epidermal keratinocytes , and interferon (IFN)-gamma -induced intracellular adhesion molecule (ICAM )-1 in normal human fibroblasts irradiated in vitro with a broad-spectrum U VB lamp or with a Philips 'Performance' tanning lamp. Results With broad-spectrum UVB irradiation, upregulation of IL-6 and TNF-a lpha mRNA was detected 6 h after irradiation, and a dose-dependent increase of cytokines in the supernatants of irradiated cells was found 24 h after irradiation. In contrast, there was no cytokine secretion and little eviden ce for mRNA upregulation following exposure to a tanning lamp. When cells w ere exposed first to broad-spectrum UVB, then the tanning lamp, UVB-induced cytokine secretion was inhibited, although mRNA levels were upregulated to a level close to that observed with UVB alone. By using a Schott WG 320 nm filter to attenuate the level of UVB relative to UVA emitted by the tannin g lamp, the inhibition of cytokine secretion was shown to be associated wit h UVA exposure. Both UV sources inhibited IFN-gamma -induced ICAM-1 mRNA ex pression in a dose-dependent fashion. By using a Schott WG 335 nm filter, i nhibition of ICAM-1 mRNA expression by the tanning lamp was shown to be ass ociated with UVB exposure. Conclusions These results suggest that UV sources emitting different levels of UVA and UVB have differential effects on the modulation of different im munoregulatory molecules, and indicate that there are potential interaction s between these wavelengths.