Early transcriptional changes after UVB treatment in atopic dermatitis includes inverse regulation of IL‐36γ and IL‐37

Phototherapy with narrow‐band Ultraviolet B (nb‐UVB) is a major therapeutic option in atopic dermatitis (AD), yet knowledge of the early molecular responses to this treatment is lacking. The objective of this study was to map the early transcriptional changes in AD skin in response to nb‐UVB treatment. Adult patients (n = 16) with AD were included in the study and scored with validated scoring tools. AD skin was irradiated with local nb‐UVB on day 0, 2 and 4. Skin biopsies were taken before and after treatment (day 0 and 7) and analysed for genome‐wide modulation of transcription. When examining the early response after three local UVB treatments, gene expression analysis revealed 77 significantly modulated transcripts (30 down‐ and 47 upregulated). Among them were transcripts related to the inflammatory response, melanin synthesis, keratinization and epidermal structure. Interestingly, the pro‐inflammatory cytokine IL‐36γ was reduced after treatment, while the anti‐inflammatory cytokine IL‐37 increased after treatment with nb‐UVB. There was also a modulation of several other mediators involved in inflammation, among them defensins and S100 proteins. This is the first study of early transcriptomic changes in AD skin in response to nb‐UVB. We reveal robust modulation of a small group of inflammatory and anti‐inflammatory targets, including the IL‐1 family members IL36γ and IL‐37, which is evident before any detectable changes in skin morphology or immune cell infiltrates. These findings provide important clues to the molecular mechanisms behind the treatment response and shed light on new potential treatment targets.