Interleukin-18 expression and the response to treatment in patients with psoriasis

Rasmy, Hanaa; Mikhael, Nancy; Ismail, Somaia

In the present study the IL-18 expression in patients receiving topical steroids was significantly lower in non-lesional skin than lesional skin before and after treatment. After 2 months of treatment, IL-18 expression levels returned back to low values but not significantly lower than the lesional skin levels of expression before treatment. In patients receiving methotrexate non-lesional skin expression was significantly lower than lesional skin before treatment. Also the expression levels decreased after treatment but still not statistically significantly when compared to lesional skin before treatment. Otkjaer et al. [22] determined IL-19 and IL-20 in nonlesional and lesional psoriatic skin after 28 days of treatment using topical calcipotriol ointment for mild cases and oral cyclosporine for moderate and severe cases. They found that in patients treated with calcipotriol, IL-19 and IL-20 mRNA expression levels in lesional psoriatic skin were reduced after 14 days, but the reduction became statistically significant only after 28 days. So the timing for mRNA expression analysis could affect the degree of significance. This is further supported by studies demonstrating a decrease of IL-18 levels after narrowband UVB therapy together with other parameters characteristic of the T helper 1 (Th1) response [23] . Apart from stimulating the Th1 response, IL-18 can regulate the Th2 response depending on the local cytokine network. Interleukin-12 enhances IFN-γ production induced by IL-18, whereas IL-18 alone induces IL-4 and IL-13 production [24] . Classic systemic treatments for psoriasis have not fully met the needs of patients for permanent improvement. Antibody-based or fusion proteinbased selective targeting of key mediators of inflammation has been added to the treatment approaches for psoriasis. Kong et al. and Smeltz [25, 26] studied IL-18 receptor blocking by using 1,25-dihydroxyvitamin D in mouse keratinocytes. They observed that the IL-18 expression level was decreased synchronously with treatment. Tak et al. [27] investigated IL-18 binding protein (IL-18 BP) in psoriatic patients and demonstrated that IL-18 BP neutralizes the activity of IL-18.