Medium-dose ultraviolet A1 phototherapy and mRNA expression of TSLP, TARC, IL-5, and IL-13 in acute skin lesions in atopic dermatitis.

BACKGROUND

The mechanisms responsible for the efficacy of ultraviolet A1 (UVA1) in the treatment of atopic dermatitis (AD) are not fully understood.

OBJECTIVES

This study was designed to investigate mRNA expression of thymic stromal lymphopoietin (TSLP), thymus- and activation-regulated chemokine (TARC), interleukin-5 (IL-5), and IL-13 in AD before and after UVA1 therapy, to determine correlations among them, and to examine whether UVA1 influences their expression and whether it is associated with UVA1 efficacy.

METHODS

Twenty-five patients with AD underwent medium-dose UVA1 phototherapy. Before and after UVA1, biopsies from acute skin lesions were studied using reverse transcription and real-time polymerase chain reaction.

RESULTS

Levels of mRNA TSLP correlated with those of TARC, IL-5, and IL-13, and levels of TARC correlated with those of IL-5 and IL-13, both before and after UVA1. Expression of IL-5 correlated with that of IL-13 only before UVA1. SCORAD (SCORing of Atopic Dermatitis) indices correlated with levels of TARC and IL-5 before irradiation. After UVA1, no mRNA level correlated with the SCORAD index. Phototherapy with UVA1 improved SCORAD values (P < 0.001) and increased expression of TARC (P < 0.05) but did not affect mRNA expression of TSLP, IL-5, or IL-13.

CONCLUSIONS

Expression levels of the mediators TSLP, TARC, IL-5, and IL-13 in AD are interrelated. Phototherapy with UVA1 improves SCORAD indices and increases expression of TARC but has no direct effects on the expression of other molecules. It is likely that UVA1 also interferes with or acts via intermediators on the link between IL-5 and IL-13.