Downregulation of interleukin 36 and its cleaver cathepsin G following treatment with narrow-band ultraviolet B phototherapy in psoriasis vulgaris

Background Growing evidence suggests the important role of IL-36 in the pathogenesis of psoriasis. Cathepsin G is a neutrophil-derived protease that can activate IL-36 gamma. Objective To assess the expression of IL-36 gamma and cathepsin G in psoriasis and to quantify the impact of treatment with narrow-band ultraviolet B phototherapy (NB-UVB) on their levels. Methods This case-control study involved 26 patients with moderate-severe psoriasis and 25 healthy volunteers. Psoriasis patients eligible for phototherapy received 24 NB-UVB sessions. Punch skin biopsies were obtained from all participants at recruitment and after phototherapy from patients. Real-time PCR was utilized for quantitative assessment of IL-36 gamma and cathepsin G expression in tissue samples. Results The expression of IL-36 gamma and cathepsin G was significantly higher in psoriasis before NB-UVB therapy compared to controls (p < .001). Both proteins decreased significantly with clinical improvement following NB-UVB therapy compared to baseline (p < .001). However, their expression after treatment was still higher than controls (p < .001). Conclusion IL-36 gamma and cathepsin G expression is upregulated in psoriatic lesions, supporting their role as mediators of inflammation in psoriasis. Downregulation of IL-36 gamma and cathepsin G is a possible mechanism for psoriasis improvement after NB-UVB therapy. IL-36 and cathepsin G can be considered as therapeutic targets for psoriasis.