Cell surface carbohydrates in psoriasis. Defective cytoplasmic transport by glycoconjugates carrying fucose residues suggested by lectin staining

The antiproliferative effect of lectin from the edible mushroom (Agaricus bisporus) on human keratinocytes: preliminary studies on its use in psoriasis

Lectins or agglutinins are proteins with affinity for specific sugar residues. Peanut agglutinin (PNA) and the lectin from the edible mushroom (Agaricus bisporus, ABL) both bind to the disaccharide galactosyl beta-1,3-N-acetyl galactosamine alpha-. This is expressed in keratinocytes as an O-linked chain on CD44, a polymorphic membrane glycoprotein. Many lectins are mitogens and PNA is a mitogen for colonic epithelial cells. However, ABL reversibly inhibits proliferation of colonic cancer cell lines without cytotoxicity and thus has therapeutic potential in situations such as psoriasis where proliferation is increased. We have therefore investigated the effect of ABL on the growth of normal human cultured keratinocytes and a human papilloma virus (HPV)-transformed cell line. In a 5-day dose-response study, keratinocyte growth was greatly reduced by 1.0 microg/mL ABL and completely inhibited by 3.0 microg/mL ABL (ANOVA, P < 0.0001). Exposure to 1.0 microg/mL ABL for only 8 h gave the same growth inhibition as did continued exposure for 3 days. No cytotoxic or morphological changes were observed. An HPV-immortalized cell line was relatively resistant to ABL: in a 5-day dose-response study, exposure to 30 microg/mL was required to inhibit cell growth completely. Topical application of ABL 0.01% or 0.1% to normal human skin caused no change in skin erythema, blood flow or thickness compared with vehicle or baseline (n = 6). ABL 0. 1% in white soft paraffin was compared with vehicle in 11 psoriatic patients, using comparative contralateral plaques. Twice daily application for 2 weeks showed no significant difference from vehicle-treated sites, although the skin thickness of plaques fell from 5.3 +/- 0.4 (n = 11, mean +/- SEM) to 4.1 +/- 0.3 mm. In view of the in vitro results further studies are warranted, particularly if means can be found to improve the epidermal penetration of the relatively large ABL molecule (60 kDa).

Human epidermal keratinocyte expression of sialyl-Lewis X

Cell-surface oligosaccharides can function as ligands for intercellular adhesion receptors, matrix proteins, and growth factors. We report that human neonatal and adult epidermal keratinocytes (KC) express sialyl Lewis X [s-Le(x); SA alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3R], a ligand for endothelial and platelet selectins. Freshly isolated or cultured KC bind FH6 monoclonal antibody (MoAb), which is specific for s-Le(x)-containing oligosaccharides. The relevant epitope is bona fide s-Le(x), because sialidase treatment of KC suspensions abrogates FH6 binding while generating de novo KC reactivity with anti-Le(x). KC stained in ice-cold suspension display a knobby membrane distribution of s-Le(x) detectable by immunofluorescence microscopy. As others have reported, FH6 appeared not to bind KC in perpendicular skin sections. However, basal KC in intact epidermal sheets exhibited obvious "honeycomb" reactivity with FH6 when stained and viewed en face, suggesting that s-Le(x) in intact epidermis may occur in bands that parallel the major tissue axis. FH6 specifically immunoprecipitated proteins of Mr 34 kd, 44 kd, and 56 kd from [35S]-labeled KC, and anti-Le(x) precipitated similar proteins from sialidase-treated KC. The enzymatic basis for KC s-Le(x) expression was studied by analyzing acceptor specificities and other properties of KC fucosyltransferases. Results indicate that KC express both Lewis- and myeloid-type alpha 1-3fucosyltransferases. KC s-Le(x) could be an important element of the epithelial milieu, because both epithelial cells and immune cells that home to epithelia express s-Le(x) and related structures, and because KC s-Le(x) is well positioned for selectin-mediated platelet binding after trans-cutaneous wounding. The apparent distributions of s-Le(x) in epidermis and on isolated KC are compatible with a functional role for s-Le(x) in these intercellular interactions.

A distinct stratum corneum antigen in psoriasis and its reactions with stratum corneum autoantibodies

Stratum corneum antibodies are ubiquitous and can be detected by various immunological methods. Of these, the ones detected by hemagglutination undergo changes in antibody titers and have been implicated in psoriasis. The purpose of our study was to examine if differences exist in the activities of the antigens isolated from psoriatic scales in comparison to normal callus. Stratum corneum antigens were prepared by trypsin-phenol-water extraction. The water phase, which contains the stratum corneum antigen, was used to sensitize the red blood cells in the hemagglutination assay. The antibody activity in human sera was determined before and after absorption with antigens isolated from callus, psoriatic scales, and cell envelopes. We found notable differences in the antigens obtained from callus and psoriatic scales. These include higher antibody titers to the antigens of the scales, the presence of unique antigenic determinants on psoriatic scales and the localization of the antigen on cell envelopes. These immunological differences were corroborated by the marked biochemical differences of certain amino acids, most notably glycine and proline, and these differences were unique to psoriatic scales as they were not shared with other hyperproliferative disorders.

Isolation of plasma membranes from keratinocytes: A newly developed method allows the sensitive detection of the membrane antigen pattern in normal and psoriatic skin

Distinct differences of proteins in the plasma membranes have been described in psoriatic keratinocytes as compared with normal epidermis. These changes are presumably involved in the pathogenesis of psoriasis. To identify and distinguish glycosylated proteins of the plasma membranes of keratinocytes, a method for mild preparation was developed that avoids the use of degrading or digestive enzymes. After cell lysis, three steps of centrifugation were performed, including the use of a sucrose step gradient. A fine-vesicular membrane fraction was obtained. Using marker enzymes for cell compartments, no contamination of cell nuclei or mitochondria and only 0.4% of endoplasmic reticulum was detectable in the final membrane fraction. Based on this preparation, disc-polyacrylamide-gel electrophoresis, followed by Western blotting, were performed. Staining with five different lectins to visualize glycosylated proteins allowed 75 different membrane glycoproteins to be distinguished. The patterns of normal, transformed (HaCaT), foreskin and psoriatic keratinocytes after cell culture with one passage were compared. Up to six proteins per lectin staining were expressed differently in psoriatic as compared to normal keratinocytes. Psoriatic cells shared similarities with highly proliferative foreskin cells, but not with transformed HaCaT cells. Main alterations of glycosylation were detected in the fucose content. In conclusion, the method developed for isolation of plasma membranes allows selective and sensitive examination of plasma membranes of normal and pathological keratinocytes. The glycosylation patterns observed suggest that distinct membrane proteins may be involved in the pathogenesis of psoriasis.

Ultrastructural localization of lectin binding sites in human melanocytes

The ultrastructural localization of carbohydrate residues in human melanocytes of normal epidermis and of one compound naevus was studied. The following lectins were used in a post-embedding technique: 1. peanut agglutinin (PNA), which reacts specifically with N-acetylgalactosamine; 2. Concanavalia ensiformis (Con A) indicating alpha-D-glucose and alpha-D-mannose binding sites; 3. Ulex europaeus agglutinin (UEA I) specific for alpha-L-fucose; 4. Wheat germ agglutinin (WGA), reacting specifically with N-acetyl-glucosamine and neuraminic acid (sialic acid); and 5. Limax flavus agglutinin (LFA), also specific for sialic acid (Neu5Ac-alpha-2,3-Gal and Neu5Ac-alpha-2,6-Gal). When incubated with WGA, Con A and LFA strong labelling was seen within the cytoplasm and in the plasma membrane of melanocytes, whereas incubations with PNA and UEA I revealed an occasional gold particle only. The determination of the distribution of carbohydrate residues in normal melanocytes is a prerequisite for future studies of abnormal melanocytes.

Ultrastructural localization of lectin-binding sites in normal skin

The distribution of carbohydrate residues in keratinocytes of normal epidermis was studied. Normal skin was embedded in Lowicryl. Thin sections were incubated with concanavalin A (Con A), peanut agglutinin (PNA), wheat germ agglutinin (WGA), Ulex europaeus agglutinin I (UEA I), dolichos biflorus agglutinin (DBA), and soybean agglutinin (SBA). A positive reaction in the dermis, in the basal lamina (lamina densa, lamina lucida), intracellularly and within the plasma membrane including the desmosomes was obtained after incubation with Con A and WGA. PNA binding sites were found predominantly in the plasma membrane between the desmosomes. The labeling with Con A, WGA, and PNA was most pronounced in the upper stratum spinosum and granulosum. Incubation with UEA revealed heavy labeling of the keratohyalin granules and the cytoplasm of the corneocytes. Incubation with DBA and SBA revealed weak labeling of the keratinocytes. The study of the distribution of carbohydrate residues in normal epidermis is important, since alterations in this distribution might be linked to autoimmunity or malignant transformation.

Cell surface glycosylation patterns in psoriasis

Cell surface carbohydrates are excellent markers of cellular differentiation and maturation processes due to their great structural and antigenic diversity as well as their known biosynthetic precursor/product relationships. Using a panel of monoclonal antibodies with well-defined carbohydrate specificities we have studied the expression of biosynthetically related antigens in normal and psoriatic skin. Two "families" of carbohydrate structures were investigated. One series of structures based on N-acetyllactosamine chains (type 2 chain: N-acetyllactosamine and fucosylated derivates hereof of H, Lex, Ley and sialyl-Lex) and another based on the simple mucin type core structures (type 3 chain: Tn, T and sialylated derivates hereof as well as the fucosylated derivative, H). Previously we have found these carbohydrate structures define distinct cell layers in stratified squamous epithelia of mucosa of the cheek, esophagus and uterine cervix. In normal and uninvolved epidermis, N-acetyllactosamine and T carbohydrates were found in the spinous cell layer, whereas the fucosylated derivates, H structures, were found in the granular cell layers above. The fucosylated and sialylated derivate of N-acetyllactosamine, sialylated Lex, had the same distribution as N-acetyllactosamine and T structures. This sequential expression of carbohydrates is similar to our previous findings in mucosa. However, in contrast to mucosa, normal skin basal cells did not label. The glycosylation pattern in psoriatic epithelium was changed in two ways. 1) Some carbohydrates (types 2 and 3 chain H and T) were expressed at an earlier stage of cell maturation. 2) The biosynthetic precursors to T structures, Tn and sialyl-Tn, which are not expressed in normal skin, and are often considered cancer-associated antigens, appeared in psoriatic skin. The Tn-antigen was expressed on basal and lower spinous cells, whereas the sialyl-Tn was only found on basal cells above the dermal papillae. The findings in the present work support previous studies of changes in cell surface glycosylation in psoriatic epidermis and demonstrate the appearance of tumor-associated antigens in highly proliferative, but benign, stratified epithelium.

Concanavalin A and Lens culinaris agglutinin binding patterns in normal and neoplastic sebaceous epithelium

Formalin-fixed, paraffin-embedded tissue sections of normal skin, sebaceous hyperplasia, nevus sebaceus, sebaceous adenoma, and sebaceous carcinoma were studied by means of biotinylated and FITC conjugated concanavalin A (Con A) and Lens culinaris agglutinin (LCA). At relatively high concentrations of these lectins, all cutaneous epithelial cells were stained. As the concentration of LCA was lowered, there was a corresponding decrease in the intensity of staining of all epithelial cells. With lowered concentrations of Con A, staining of sebaceous epithelium remained strongly positive, while staining of other epithelia decreased in a manner similar to that seen for LCA. These staining patterns were seen in normal and neoplastic tissues. Both Con A and LCA are known to bind to alpha-D-mannopyranosyl and alpha-D-glucopyranosyl residues of glycoproteins and glycolipids. The difference in staining of sebaceous epithelial cells by Con A and LCA suggests that the binding of these lectins is not determined strictly by the presence of alpha-D-mannopyranosyl or alpha-D-glucopyranosyl residues, but is modified by side-chain substitution on the monosaccharides and/or by the oligosaccharide which contains the particular monosaccharide. Whichever event is operative, a saccharide moiety is present on the surface of mature sebaceous cells which has a strong affinity for Con A.

Cell surface carbohydrates in proliferative epidermal lesions. II. Masking of peanut agglutinin (PNA) binding sites in solar keratoses, Bowen's disease, and squamous cell carcinoma by neuraminic acid

Seventy-six skin biopsies of proliferative lesions were studied by using 4 different lectins and an avidin-biotin-peroxidase complex. In solar keratosis, Bowen's disease and squamous cell carcinoma, malignant-appearing keratinocytes exhibited loss of membrane staining with Concanavalia ensiformis agglutinin (Con A), but revealed cytoplasmic staining. When incubated with peanut agglutinin (PNA), the malignant keratinocytes did not stain. However, the PNA binding sites were not absent, but masked by sialic acid. Following cleavage of the sialic acid with neuraminidase, free PNA binding sites could be demonstrated in the plasma membranes. In contrast, the keratinocytes in keratoacanthomas showed membrane staining with Con A and also contained free PNA binding sites. These histochemical findings confirm and extend our earlier observations regarding cell surface carbohydrates in premalignant and malignant epidermal lesions.