The effect of calcitonin gene-related peptide on T lymphocyte infiltration and its role in the therapeutic effects of acitretin in psoriasis vulgaris

Background: The pathogenesis of psoriatic plaque lesions is related to the overexpression of calcitonin gene-related peptide (CGRP). We investigated changes in circulating and skin CGRP content, and their impacts on T lymphocyte infiltration and acitretin therapy in psoriasis vulgaris. Methods: CGRP expression was examined through immunohistochemistry of skin biopsies, and its serum levels were determined by radioimmunity in both patients with psoriasis vulgaris and healthy volunteers. Correlation between serum CGRP levels and Psoriasis Area and Severity Index (PASI) scores was analyzed. Effects of CGRP on adhesion, migration, and IL-6 secretion of T lymphocytes of healthy subjects were assessed. After psoriasis patients were treated with acitretin, CGRP I and II mRNA expression of T lymphocytes was determined by real-time polymerase chain reaction, and the CGRP contents of serum were assayed (via radioimmunity). T lymphocytes from healthy volunteers were obtained to detect the effect of acitretin on CGRP secretion. Results: CGRP expression levels in the skin and serum were higher in psoriasis patients than in healthy subjects. CGRP levels in psoriasis patients were correlated with their PASI score. CGRP facilitated T lymphocyte adhesion, migration, and IL-6 secretion. Treatment with acitretin inhibited CGRP I and II mRNA expression in T lymphocytes and serum CGRP levels in patients with psoriasis vulgaris. Acitretin inhibited CGRP secretion in T lymphocytes of healthy volunteers. Conclusions: CGRP is involved in derma T lymphocyte infiltration of psoriasis vulgaris, and the therapeutic effects of acitretin are related to decreases in CGRP synthesis and the release of circulatory T lymphocytes.