Dithranol is a potent topical treatment for psoriasis, leading to fast PASI reduction. Application of
dithranol causes inflammation, but its mechanisms of action are still largely unclear and markers of treatment response are unknown. The aim of this study was to reveal any possible association between disease activity and/or response to dithranol treatment and plasma levels of selected cytokines/chemokines. 15 psoriasis patients (mean PASI score at baseline, 13,6±10,6) were enrolled in this study. Biopsy and blood samples were taken before (day 0), during (day 4 at maximum inflammation), at the end of treatment (week 2-3) and after dithranol therapy (week 6-7).
65-Multiplex Immunoassay was used to analyze cytokine/chemokine concentrations in plasma and CD1a immunohistochemistry (IHC) was performed to quantify Langerhans cells in the epidermis. Dithranol treatment reduced PASI by a mean of 57% (range 42 to 74%) at week 2-3 and by 59% (range 3 to 81%) in the follow-up at week 6-7. Though several other cytokines correlated with disease activity and/or PASI reduction, the strongest correlation was observed in CCL22. It significantly correlated with PASI score before (r=0.91, p<0.0001), during (r=0.90, p<0.0001) and after therapy (r=0.90, p<0.0001), and pretreatment values of CCL22 inversely correlated with overall reduction in PASI. The results of IHC showed a trend of increase in cell count of CD1a positive cells in the epidermis during dithranol treatment, which further increased at the follow up visit (p=0.0253). Our results suggest that a persistent high level of CCL22 in plasma may be associated with poor response to dithranol treatment. CCL22 could be a potential biomarker to predict therapy response to dithranol in psoriasis patients.

Chemokine Ligand 22 (CCL22) plasma levels correlate with disease severity and predict response to dithranol treatment in patients with psoriasis