In situ localization of interleukin-1 in normal and psoriatic skin

Interleukin-1 (IL-1) is a family of polypeptides that mediates a wide range of inflammatory and immune responses. In human skin, unstimulated keratinocytes produce a large amount of such cytokines. Although the precise role of IL-1 in the skin is unknown, there is experimental evidence supporting involvement of IL-1 in the pathogenesis of inflammatory skin diseases. In this study, we investigated in situ localization of IL-1 alpha and IL-1 beta in normal and psoriatic skin. Using polyclonal antibodies and the avidin-biotin peroxidase complex, we demonstrated the presence of both IL-1 alpha and IL-1 beta in normal and psoriatic formalin-fixed paraffin-embedded tissues. In both cases, IL-1 alpha was more prominent. However, the distribution of IL-1 alpha differed between normal and psoriatic skin. In normal skin, IL-1 alpha distribution was predominantly intercellular, whereas IL-1 alpha distribution was predominantly within the cytoplasm in psoriatic skin. These studies confirm that IL-1 alpha is the predominant form of IL-1 in the skin and provide further support for the hypothesis that IL-1 participates in the pathogenesis of psoriasis.     

Expression of transferrin receptor in normal human skin, psoriatic skin and various skin tumors

The distribution of transferrin receptor in normal human skin and its expression in psoriatic skin and various skin tumors have been investigated. Immuno-peroxidase staining was performed on biopsy specimens using monoclonal OKT 9 antibody, which reacts with transferrin receptor. Normal human skin showed positive staining with OKT 9 in eccrine glands and outer root sheaths of the hair. Sebaceous glands were also strongly positive. The basal layer stained very weakly. Psoriatic skin expressed OKT 9 strongly in the epidermis, especially in the area of the rete ridge. In squamous cell carcinoma, Bowen's disease, and malignant melanoma, a widespread and strong labelling reaction was found. Basal cell epithelioma and genital Paget's disease were partially and moderately positive in their staining pattern. No such positive staining pattern could be found in either nevus cell nevi or seborrhoic keratosis. These findings indicate that, in normal skin, transferrin receptor exists in eccrine glands, sebaceous glands, and outer root sheaths of the hair in greater amounts. High amounts of expression of this receptor in psoriatic epidermis and malignant tumors suggests that immunohistochemical demonstration of transferrin receptor parallels the proliferating activity of the tissue or tumor of the skin and may provide an useful aid for detecting such conditions.     

Immunohistochemical localization of lipocortins in normal and psoriatic human skin

The distribution of lipocortin I, a steroid-induced inhibitory protein of phospholipase A₂, was examined in normal and psoriatic human skin. Using immunoblotting analysis with specific antibody against human lipocortin I purified from human placenta, lipocortin I was detected as a 37 kDa protein in cultured epidermal cells, whole skin and epidermis. In the dermis and stratum corneum, lipocortin I was only weakly detectable by Western blotting. In contrast to normal skin, much less lipocortin I was detected by Western blotting analysis in psoriatic skin. Using immunoperoxidase immunohistochemical analysis, lipocortin I was demonstrated in the cytoplasm of keratinocytes in the upper and middle layers of the epidermis and in some infiltrating cells in the dermis in normal skin. In involved psoriatic skin, by contrast, lipocortin I was almost undetectable in the epidermis, although it was demonstrated in some infiltrating cells in the dermis. No immunostaining of lipocortin I was observed in the stratum corneum of normal or psoriatic skin. These results, together with the finding that phospholipase A₂ activity is higher in psoriatic epidermis than in normal epidermis, suggest that lipocortin I plays an important role in the regulation of differentiation and proliferation of epidermal keratinocytes.     

Thrombomodulin expression on dermal cells in normal and psoriatic skin

Abstract The various subsets of dermal cells with a dendritic appearance can be identified by phenotypic differences in cell markers. We report on the morphology and tissue distribution of dermal cells detected with a monoclonal antibody against thrombomodulin in histological sections of normal arm and scalp skin and psoriatic skin. Double staining with antibodies to factor XIIIa, CD34 and CD68 was also employed in scalp biopsies to elucidate the relationship between thrombomodulin⁺ dermal cells and dermal dendrocytes and macrophages described by others. Thrombomodulin⁺ dermal cells in normal arm skin had little cytoplasm with fine branched dendrites and tended to be localized just beneath the epidermis. In scalp skin these cells had longer, more numerous dendrites and were distributed in the papillae and perivascular adventitial dermis primarily in the upper and central reticular dermis. In psoriatic skin, thrombomodulin⁺ dermal cells had an increased cytoplasmic volume with stout, less branched dendrites and appeared in the papillae and among inflammatory cells. Dermal cells detectable by thrombomodulin expression were factor XIIIa^–, CD34^– and CD68^–, and seemed to represent a distinct subset of dermal cells which may function in tissue repair. However, thrombomodulin⁺ dermal cells and factor XIIIa⁺ dendrocytes were frequently seen close together and could act cooperatively to regulate extravascular thrombin homeostasis in both normal and pathological dermal environments. Received: 26 May 1997     

In vivo quantification of microvessels in clinically uninvolved psoriatic skin and in normal skin

BACKGROUND: Microvascular abnormalities (capillary elongation, widening and tortuosity) are a characteristic feature of psoriasis and form one of the pathological diagnostic criteria. However, it is still not entirely clear when these microcirculatory changes appear in the skin of psoriatic subjects. Some studies suggest that capillary dilatation and elongation are present in the clinically uninvolved skin of psoriatic patients even at sites at which psoriatic plaques rarely occur. OBJECTIVES: To determine, using noninvasive techniques in vivo, the nature of any microvascular changes in the clinically uninvolved skin of psoriatic subjects and to quantify the dermal microvasculature in the clinically uninvolved skin of psoriatic subjects, in vivo. METHODS: Dermal microvessels in both the clinically uninvolved skin of psoriatic subjects and in the skin of normal volunteers (i.e. individuals without any clinical evidence of psoriasis or other inflammatory dermatoses) were directly visualized by native video-capillaroscopy, in vivo. Images were analysed using a combination of nonstereological and stereological measurements. The findings in each group were then compared to determine if there were any differences in microvascular parameters. RESULTS: Quantitative analysis of capillaroscopic images showed that there were no significant differences in microvessel density (P = 0.9), image area fraction (P = 0.6), microvessel length density (P = 0.7) and vessel image width (P = 1.0) in the clinically uninvolved skin of psoriatic subjects and the normal skin of healthy volunteers, when extensor forearm skin was examined. CONCLUSIONS: These findings indicate that prior to the development of clinical lesions there are no significant morphological differences between the dermal microvessels in the clinically uninvolved skin of psoriatic subjects and the dermal microvessels in the normal skin of healthy volunteers. However, during plaque formation, the superficial papillary microvessels in plaque skin undergo a striking, characteristic change, i.e. elongation, widening and tortuosity. These blood vessels must therefore, at least in part, play an important, necessary, but probably secondary role in the pathogenesis of clinical lesions in psoriasis.     

Differential expression of a human endogenous retrovirus E transmembrane envelope glycoprotein in normal, psoriatic and atopic dermatitis human skin

BACKGROUND: Psoriasis is a common inflammatory skin disease characterized by uncontrolled proliferation of keratinocytes and recruitment of T lymphocytes into the skin. The possible role of human endogenous retroviruses (HERVs) in the induction of psoriasis has been suggested, based upon the previous observations of retrovirus-like particles in psoriasis from skin lesional plaques, urine and stimulated lymphocytes. OBJECTIVES: To investigate the expression of HERV-E transmembrane envelope glycoprotein (HERV-E env) in normal, psoriatic and atopic human skin, and to examine the influence of ultraviolet (UV) B irradiation on HERV-E env expression in normal human epidermal keratinocytes. METHODS: The analysis was performed on both skin biopsies and organotypic skin cultures using immunofluorescence and Western immunoblotting. UVB irradiation (312 nm) of cultured normal human keratinocytes was performed using a dose of 30 mJ cm(-2). RESULTS: Positive staining was observed in most of the psoriatic and atopic skin samples, whereas only 15% of the normal skin samples were faintly positive. In addition, the pattern of expression of HERV-E env differed markedly in psoriasis vs. atopy. By Western blotting analysis, two main proteins of 54 and 57 kDa were detected in extracts of normal skin, normal keratinocyte cultures and reconstructed epidermis from psoriatic and normal punch biopsies. An increased level of expression of these proteins was noted in extracts from psoriatic vs. normal reconstructed epidermis. The overexpression of the 57-kDa protein in normal human cultured keratinocytes was dramatically reduced by UVB irradiation. CONCLUSIONS: These data suggest for the first time that HERV-E env is expressed in normal and pathological human skin. Further studies are now required to elucidate the role of such viral proteins in the pathogenesis of psoriasis.     

Low density lipoprotein receptor expression on keratinocytes in normal and psoriatic epidermis

Biochemical and morphologic studies on the interaction of low density lipoprotein (LDL) with cultured normal keratinocytes and squamous carcinoma cells have shown a negative correlation between LDL receptor activity and terminal differentiation of the epidermal cells [Ponec M et al, J Invest Dermatol 83:436-440, 1984 and Vermeer, BJ et al, J Invest Dermatol 86:195-200, 1986]. Whether such in vitro studies pertain to the epidermis in vivo is not known. To obtain information on the distribution of LDL receptors in the epidermis in situ, morphologic studies were performed using LDL-gold as an ultrastructural marker. When freshly isolated mouse and human epidermal cells were incubated with LDL-gold complexes, only keratinocytes with the morphologic characteristics of basal cells showed binding and uptake of LDL-gold. No LDL receptor activity was found on Langerhans cells, melanocytes or highly differentiated keratinocytes. Since cell separation techniques can destroy receptors, the staphylococcal epidermolytic toxin was utilized to produce intercellular and intra-epithelial splitting of the epidermis. In preparations of both normal mouse and human epidermis, LDL-gold binding was restricted to basal cells and a few suprabasal keratinocytes. In contrast, in psoriatic epidermis, and to a lesser extent, essential fatty acid-deficient mouse epidermis, cells in the stratum spinosum showed abundant LDL-gold binding. Thus LDL-gold may be a useful marker for epidermal differentiation.     

Immunolocalization of adhesion molecules in psoriatic arthritis, psoriatic and normal skin

Adhesion molecule expression in synovial membrane obtained from patients with psoriatic arthritis (PA) has previously been compared with rheumatoid arthritis (RA). Although expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) was similar in both psoriatic and rheumatoid synovium, in contrast, little or no endothelial leucocyte adhesion molecule-1 (ELAM-1) was observed in psoriatic synovium. In the present study, the expression of ICAM-1. ELAM-1 and VCAM-1 was examined in the involved and uninvolved skin from patients with PA (n= 15), patients with psoriasis (Ps) but no arthritis (n= 5) and in normal skin (n= 4). ICAM-1 was intensely expressed on endothelium and keratinocytes of involved skin from patients with Ps with or without arthritis. There was constitutive expression of ICAM-1 on endothelium only in uninvolved and normal skin. In contrast, ELAM-1 expression was restricted to endothelial cells; it was widespread and intense in involved skin, but was minimal in uninvolved and normal skin. VCAM-1 was expressed on endothelium, and also on some dendritic cells in involved psoriatic skin. There was minimal VCAM-1 staining on endothelial cells in uninvolved and normal skin. In conclusion, in involved psoriatic skin from patients with and without arthritis ICAM-1, ELAM-1 and VCAM-1 expression is up-regulated on vascular endothelium, and ICAM-1 is expressed on keratinocytes. However, ELAM-1 and VCAM-1 expression seen in dermal vessels is not found in psoriatic synovial vessels. These differences suggest a mechanism for controlling cellular traffic in Ps and in PA.     

Incorporation of 14C-linoleic acid in cerebrosides of psoriatic and normal human skin

Summary Psoriasis is marked by loss of glycocalyx. Glycocalyx is composed of glycoproteins and glycolipids such as cerebrosides. It was shown that the incorporation of ¹⁴C-linoleic acid in cerebrosides of normal and psoriatic human skin is different. In psoriatic epidermis and corium the turnover of this fatty acid is significantly elevated. It is suggested that in psoriasis the epidermal cell is not able to build up a regular carbohydrate sequences of lipids because the false carbohydrate chain activates the degradation of glycolipids and in compensating for the increased degradation raises the synthese rate of glycolipids.     

Cyclic AMP-dependent protein kinase isozymes of pig skin and human skin from normal and psoriatic subjects

Cyclic AMP-dependent protein kinase isozymes of pig and human skin (epidermis) were separated by DEAE-cellulose column chromatography after micromodification for small biopsy samples. Clear-cut separations of type I and type II isozymes, which were of about equal amounts, could be obtained only when the ischemia effect was avoided by in vivo freezing of skin and homogenization for less than 10 s. Intradermal injections of epinephrine caused dose-dependent activation of type I isozyme, but not of type II. Injections of other skin adenylate cyclase stimulators such as histamine, adenosine, and prostaglandin E2 elevated the local cyclic AMP levels to not more than 5 pmol/mg protein and also stimulated only the type I isozyme. Incubation of keratome-sliced pig skin under various conditions caused both activation by dissociation and inactivation by reassociation of the subunits, which appeared to be dependent on the cyclic AMP content. Epinephrine added to the incubation medium led to complete activation of both type I and type II isozymes (the intraepidermal cyclic AMP contents ranged from 20-50 pmol/mg protein). The isozymes of normal skin and involved skin of psoriatics showed identical peaks of type I and type II isozymes of equal amounts. The data indicate that protein kinase in the involved skin is not in an activated (by cyclic AMP) state.