NEUROPEPTIDES IN PSORIASIS: POSSIBLE ROLE OF BETA‐ENDORPHIN IN THE PATHOMECHANISM OF THE DISEASE

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Abstract
Background. An increased concentration of neuropeptides in psoriatic lesional skin may be responsible for alterations in the neurogenic erythematous response and transmission of stimuli through sensory nerve fibers (sensation of pruritus). Methods. Increasing doses of capsaicin from 0.125 to 4 μg/ cm2 were applied to nonlesional psoriatic skin to establish the minimal dose that induced the substance P‐mediated neurogenic response in 30 patients with psoriasis. Plasma beta‐endorphin was quantitated in 71 psoriatics by radioimmunoassay using NEN 1251‐RIA kit. Results. The mean beta‐endorphin concentration was increased about 2‐fold compared to normals, whereas doses of capsaicin needed to induce erythema were higher (1–4 μg/ cm2) in psoriatics (mainly in patients with type II psoriasis) than in healthy subjects (0.125–0.25 ug/cm2). Conclusions. The data indicate that increased beta‐endorphin in psoriatic skin might affect both substance P‐mediated neurogenic inflammation and transmission of sensory stimuli due to local antinociceptive effects of this opioid. The differences in the neurogenic response in type I and II psoriasis may be related to the degradation of substance P and beta‐endorphin by neutral proteinases in the lesional skin.