Plasma neuropeptides and perception of pruritus in psoriasis.

The aim of this study was to evaluate the influence of selected neuropeptides on itching in psoriatic individuals. Fifty-nine patients (43 pruritic and 16 non-pruritic) with psoriasis were included in the study. The severity of psoriasis, measured using the Psoriasis Area and Severity Index scale, ranged between 2 and 43.7 points. The intensity of pruritus was evaluated using a Visual Analogue Scale. The plasma levels of substance P, vasoactive intestinal peptide, calcitonin gene-related peptide and neuropeptide Y were measured radioimmunologically. The plasma level of neuropeptide Y was significantly decreased in patients with pruritus compared with those without pruritus (21.6 +/- 39.6 pg/ml and 144.3 +/- 385.7 pg/ml, respectively; p=0.03). Levels of other neuropeptides did not differ significantly between pruritic and non-pruritic patients; however, a tendency to lower plasma levels of substance P and vasoactive intestinal peptide in patients with itching was noted. Moreover, a significant negative correlation was observed between pruritus severity and levels of substance P (r = -0.36; p=0.02), as well as between pruritus severity and plasma levels of vasoactive intestinal peptide (r = -0.34; p=0.03). The imbalance of neuropeptide activity in the sera of pruritic subjects may suggest a role for neuropeptides in perception of itching in psoriatic individuals.