Cytokine expression in psoriatic skin lesions during PUVA therapy

To determine whether an improvement in skin lesions as a result of PUVA therapy may be correlated with changes in cytokine patterns, RT-PCR amplification was used to compare the levels of IL-2, IL-6, IL-8, IL-10, TNF-alpha and IFN-gamma cytokine mRNA expression in serial biopsies from three chronic plaque psoriatic patients. In each case, 3-mm punch biopsies were taken from lesional skin before and during 2-28 days of treatment with PUVA. Total mRNA was extracted from each biopsy, cDNA synthesized, and then amplified by 35 cycles of PCR using cytokine-specific primers. The specificity of the PCR products was confirmed by the Southern blot technique. Substantial levels of specific mRNA for each of the cytokines studied was present in the lesions prior to treatment. In two of the three patients who responded well to PUVA, a reduction in all the cytokines including IL-10 was observed compared with baseline levels. In contrast, PUVA proved to be ineffective in clearing the psoriasis of the third patient whose skin lesions worsened during the course of treatment. This was accompanied by an increase in IFN-gamma but not of the other cytokines investigated, above the pretreatment level. This study showed an association between PUVA-induced resolution and decreases in the levels of various cytokines highly expressed in psoriatic lesions.