Calcipotriene is a synthetic analogue of 1,25-dihydroxyvitamin D3 established to be effective topically in the treatment of psoriasis. We investigated the early cellular and immunological events induced by calcipotriene in psoriasis. Thirty patients with moderate plaque-type psoriasis were randomly assigned to receive twice daily applications of either calcipotriene ointment 0.005% or matching vehicle for 6 weeks. Skin biopsies (6 mm) were performed from designated plaques at baseline and days 3 and 7. On these days and at weeks 2, 4 and 6, complete clinical evaluations were made in a double-blind fashion. Consistent with previous studies, significant clinical improvement (P < 0.05) in psoriasis was observed in patients receiving calcipotriene vs. those receiving vehicle by day 7 for scale and erythema, and by day 14 for thickness. No significant improvement, however, was seen on day 3. None of the immunohistological markers (CD1a, CD4, CD8, ICAM-1, VCAM-1, E-selectin, HLA-DR) semiquantitatively assessed in psoriatic plaques was significantly changed by calcipotriene treatment for 7 days. In the calcipotriene-treated group, interleukin (IL)-10 levels (pg/μg of protein) increased by 57% from baseline (0.030 ± 0.006: mean ± SEM) to day 3 (0.047 ± 0.011) (P=0.05 vs. baseline; n = 10) and remained elevated at day 7 (0.046 ± 0.012). IL-8 levels (pg/μg of protein), however, declined by 70% from baseline (0.13 ± 0.06) to day 3 (0.04 ± 0.01), and remained low at day 7 (0.03 ± 0.02) (P<0.05 vs. baseline; n = 10). Both IL-8 and IL-10 were unaffected by vehicle treatment. Calcipotriene-induced clinical improvement of psoriasis is preceded by an increase in IL-10 and a concomitant decrease in IL-8 levels. The changes in the level of these two cytokines provide further evidence for immunological changes as a significant part of the mechanism of action of calcipotriene in psoriasis.
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