Neuropeptides in skin from patients with atopic dermatitis: an immunohistochemical study

Human mast cell proteases hydrolyze neurotensin, kinetensin and Leu5-enkephalin

Purified mast cell carboxypeptidase cleaved the C-terminal leucines from Leu5-enkephalin (Leu-ENK), neurotensin (NT), and kinetensin (KT), with Km values of 36, 16, and 15 microM, and kcat values of 44, 51, and 53 s-1, respectively. To better predict potential in vivo hydrolysis products generated by mast cell proteases, these peptides were incubated with released skin mast cell supernatants. Leu5-enkephalin was hydrolyzed only by carboxypeptidase. Kinetensin was cleaved by tryptase, chymase, and carboxypeptidase to yield KT(1-3), KT(1-7), KT(1-8), KT(4-7), and KT(4-8), the last two peptides by the concerted action of two of the proteases. NT(1-11) and NT(1-12) were generated from neurotensin by chymase and carboxypeptidase, respectively.

Image analysis quantification of peptide-immunoreactive nerves in the skin of patients with Raynaud's phenomenon and systemic sclerosis

Image analysis quantification was used to assess the results of immunocytochemistry for a neuronal marker and neuropeptides in digital skin biopsies from Raynaud's phenomenon (RP) and systemic sclerosis (SS) patients, to verify the possibility of a selective quantitative abnormality of immunoreactive nerves. The field area of specific immunostaining and nerve counts were evaluated on coded specimens, and the data compared by statistical analysis. Nerves immunoreactive for protein gene product 9.5 (PGP), a marker for neuronal elements, were decreased significantly in epidermal and subepidermal layers of digital skin in RP patients (P less than 0.0001). This change was paralleled by a decrease of calcitonin gene-related peptide (CGRP) immunoreactive nerves in the epidermis and around capillaries in the dermal papillae (P = 0.005). In the skin of RP patients, these changes were readily demonstrated by image analysis, although they were not always apparent on visual screening. In digital skin of SS patients, there was a generalized and very significant decrease of PGP, CGRP, and VIP immunoreactivities in all areas (P less than 0.0001). These results demonstrate that neuropeptide-containing nerves are involved in the digital pathology of RP and SS, and that image analysis quantification is an accurate and sensitive method for assessing morphological changes in pathological samples.

Skin levels of vasoactive intestinal polypeptide in atopic dermatitis

Atopic dermatitis (AD) can be exacerbated by various factors, including emotional stress, scratching and sweating. The aim of the present study was to evaluate the hypothesis that the inflammatory reaction in AD is also neurogenic. For this purpose, the levels of vasoactive intestinal polypeptide were measured radioimmunologically in whole-tissue homogenates of lesional skin of 13 patients with atopic dermatitis. Radioimmunoassay was performed using an antiserum, AH78, recognizing the carboxy-terminal fragment vasoactive intestinal polypeptide (22-28). Vasoactive intestinal polypeptide immunoreactivity was detected in relatively low amounts in control skin (0.428 +/- 0.08 pmol/g tissue), whereas a marked increase in the peptide was observed in lesional skin of patients with atopic dermatitis (5.62 +/- 1.25 pmol/g tissue). These results seem to suggest that vasoactive intestinal polypeptide could have a pathogenetic relevance in skin lesions of atopic dermatitis.