Influence of narrow-band ultraviolet B therapy on sirtuin 1 expression in lesional skin of patients with chronic plaque psoriasis: Relation to clinical improvement and interferon-gamma expression

Background: Reduced sirtuin 1 (Sirt1) expression in psoriasis was previously reported, and its activation was associated with disease improvement. Narrow-band ultraviolet B (NB-UVB) downregulates several pro-inflammatory cytokines such as interferon-gamma (IFN-gamma) and influences keratinocyte differentiation in psoriasis. Objectives: The aim of this study was to study the in vivo influence NB-UVB treatment on Sirt1 expression in psoriatic skin in relation to disease improvement and IFN-gamma expression. Methods: Twenty-six patients with chronic plaque psoriasis were evaluated, and psoriasis area severity index (PAST) was calculated. Skin biopsies were taken from lesional skin of the patients before and after 3 months of treatment with NB-UVB and from 26 controls, where the distribution and immunohistochemistry (IHC) scores of Sirt1 and IFN-y were determined. Results: After 3 months of treatment, Sirt1 distribution and epidermal IHC score were significantly higher, whereas Sirt1 dermal IHC score and IFN-gamma distribution, epidermal and dermal IHC scores were significantly lower than the pre-treatment values. Before and after 3 months of NB-UVB therapy, PAST showed a significant negative correlation with Sirt1 distribution and epidermal IHC score; and a significant positive correlation with interferon-gamma distribution and epidermal IHC score. Moreover, Sirt1 distributions were negatively correlated with the corresponding interferon-y distributions. Conclusions The detected upregulation of epidermal Sirt1 following NB-UVB therapy possibly represents another mechanism by which NB-UVB can act in psoriasis and also highlights the role of Sirt1 upregulation in psoriasis treatment.