SUC-VAL-PRO-PHE-PNA

Tryptase-containing mast cells have recently been found to be increased in the upper dermis of psoriatic lesions. In the present study, the distribution of chymase- and tryptase-containing mast cells was morphometrically analysed at different dermal levels of lesional and non-lesional psoriatic skin (12 patients) as well as normal human skin. Mast cell tryptase was identified enzyme-histochemically, using Z-Gly-Pro-Arg-MNA as the substrate. For demonstrating mast cell chymase, a simple and specific enzyme-histochemical staining method was developed, using Suc-Val-Pro-Phe-MNA as the substrate. All mast cells positive for chymase were also positive for tryptase and Giemsa stain. Although the number of tryptase-positive mast cells was slightly increased throughout the dermis of lesional psoriatic skin, this increase was most pronounced in the upper dermis immediately beneath, and in close contact with, the epidermis. In contrast, the number of chymase-positive mast cells was clearly decreased in the upper dermis of psoriatic lesions, but not in the deeper dermis, as compared with non-lesional psoriatic skin. In addition, all chymase-positive mast cells observed in the upper dermis were very weakly stained when compared with those in the deeper dermis. No differences were found between non-lesional psoriatic skin and normal skin in which the number of mast cells containing chymase was 72-73% of the number containing tryptase. The present results suggest that T mast cells particularly, containing tryptase but no chymase, proliferate in psoriatic lesions, and that the increase in tryptase activity and the decrease in chymase activity in the upper dermis may lead to an imbalance in the biochemical regulatory systems.

The number and distribution of mast cells in non-lesional and lesional skin samples from 13 psoriatic patients were analyzed enzyme- and immunohistochemically. Mast cell tryptase was stained with the sensitive substrate Z-Gly-Pro-Arg-4-methoxy-2-naphthylamide, and chymase with Suc-Val-Pro-Phe-MNA and monoclonal B7 anti-chymase antibody. In addition, healthy-looking skin from 27 psoriatic patients was tape-stripped resulting in induction of the Köbner response in 9 patients. Sequential biopsies were taken before and after (7, 14 and 21 days) tape-stripping, and both tryptase and chymase were stained enzyme-histochemically. In non-lesional psoriatic skin, 70 +/- 24% (mean +/- SD) of the mast cells contained chymase enzyme activity, and 78 +/- 18% chymase immunoreactivity. About 10% of the chymase-immunoreactive cells lacked chymase activity. In lesional psoriatic skin, tryptase-positive cells were increased in number throughout the dermis but especially beneath the epidermis. Chymase immunoreactivity paralleled the tryptase activity, whereas chymase activity was strongly diminished both in terms of mast cell numbers and in staining intensity in the papillary dermis. The apparent inactivation of chymase may be due to the action of the chymase inhibitors, alpha 1-antitrypsin and alpha 1-antichymotrypsin, localized immunohistochemically in mast cells of lesional and non-lesional psoriatic skin. In the developing psoriatic lesion, mast cells displaying chymase activity were already 27-38% decreased in number in the upper dermis on day 7 after tape-stripping, along with the first clinical signs of psoriasis.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution of mast cells (MCs) containing tryptase (T) and chymase (C) was studied in the non-lesional and lesional skin of 26 patients with atopic dermatitis (AD) and 23 patients with non-atopic nummular eczema (NE), and in the skin of eight healthy controls. T and C activities were demonstrated enzymehistochemically using Z-Gly-Pro-Arg-MNA and Suc-Val-Pro-Phe-MNA as substrates, respectively. The T- and C-containing MCs were counted separately in the epidermis, in contact with the basement membrane, in the papillary dermis and in different dermal levels (0.2 mm each). Also, the C protein was determined immunohistochemically. T-positive MCs were similarly distributed in non-lesional and lesional skin of both AD and NE. The MC number was relatively high in the upper dermis (papillary dermis and levels I and II) of non-lesional and lesional skin of AD. In the upper dermis of non-lesional AD and NE skin and in normal skin, about 50% of T-positive MCs displayed C activity, whereas the percentage in lesional AD and NE skin was only about 30%. In this respect, the non-lesional and lesional samples differed significantly from each other in both dermatoses (in AD p = 0.003; in NE p = 0.002, Students' t-test). In all samples the MC number decreased in the deeper dermal levels, although numerous T-containing MCs were still counted in the deeper dermis (dermal levels IV-VII) of lesional AD and NE skin, differing significantly from the MC number in normal skin (In AD p = 0.005, In NE p = 0.041). In the deeper dermis, the percentage of MCs containing active C was about 70% in non-lesional and lesional AD and NE, and about 90% in normal healthy skin. However, in the upper dermis of non-lesional and lesional skin of both AD and NE, about 80% of all MCs contained the C protein, which differed significantly from the value of 100% in normal skin (p < 0.05). In conclusion, the increased number of T-positive MCs in the upper dermis of non-lesional and lesional AD contributes to promoting inflammation. C apparently loses its activity in the upper dermis of lesional AD and especially in NE. Thus, the enzyme partially lacks its capability to suppress inflammation, such as degradation of neuropeptides and proteins. The dysregulation of these proteinases exists already in non-lesional skin of AD and NE.