Abstract
Solar light generates inflammatory responses in exposed skin. These effects are generally attributed to UVB light. However, skin is expose d to a huge quantum of UVA photons as UVA is a predominant part of sunlight and the radiation used in tanning beds. We examined the effects of a single exposure to UVA and UVB wavebands on cytokine levels in skin and plasma, myeloperoxidase (MPO) activity, expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in skin. Hairless mice were irradiated with either UVA (10 or 20 J/cm²) or UVB (200 or 800 mJ/cm²). The effects were assessed after 4/24 h. Plasma cytokine levels were evaluated using a Bio-Plex cytokine assay. Cytokine, iNOS and COX-2 levels in skin were determined by Western blot. Skin MPO activity was monitored spectrophotometrically. UVB induced up-regulation of interleukin-1β (IL-1β) and interleukin-6 (IL-6) and decrease in interleukin-10 (IL-10) mainly after 4 h. In contrast, UVA caused increase in levels of tumor necrosis factor-alpha (TNF-α) and IL-6 after 4 h and up-regulated IL-10 and interleukin-12 (IL-12) after 24 h. The increase in MPO activity from infiltrated leucocytes was observed only in UVB irradiated animals. iNOS was up-regulated 4 h after UVA and UVB treatment. No significant effect on COX-2 expression was detected. UVA and UVB light affected several inflammatory markers. For individual waveband, changes in plasma parameters did not correlate with those in skin. Thus evaluation of plasma samples cannot simply be replaced by determination in skin specimens and vice versa.
Highlights
Human skin is normally exposed exclusively to wavelengths > 294 nm, as ozone in the stratosphere completely absorbs shorter wavelengths[1]
Rabbit polyclonal primary antibody anti-Tumor necrosis factor-alpha (TNF-α), -IL-1α, -IL-1β, -IL-6, -IL-10(p40), -IL-12, -cyclooxygenase 2 (COX-2), -inducible nitric oxide synthase (iNOS), goat polyclonal primary antibody anti-actin and goat anti-rabbit and rabbit anti-goat horseradish peroxidase (HRP) conjugated secondary antibodies were purchased from Santa Cruz Biotechnology (USA)
At 24 h following UVB treatment, the IL-6 level was significantly enhanced in both irradiated groups
Summary
Human skin is normally exposed exclusively to wavelengths > 294 nm, as ozone in the stratosphere completely absorbs shorter wavelengths[1]. Biological effects of UV radiation on skin include the inflammatory response. Biochemical changes include increase in myeloperoxidase (MPO) activity and cyclooxygenase-2 (COX-2) expression, generation of arachidonic acid products and cytokines[4,5]. All these substances very likely assist in mediating the inflammatory reaction. Solar light generates inflammatory responses in exposed skin. These effects are generally attributed to UVB light. We examined the effects of a single exposure to UVA and UVB wavebands on cytokine levels in skin and plasma, myeloperoxidase (MPO) activity, expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in skin. Evaluation of plasma samples cannot be replaced by determination in skin specimens and vice versa
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