Cantharidin-induced acantholysis: adhesion molecules, proteases, and related proteins.

Acantholysis is a feature of disorders such as Hailey-Hailey disease and Darier's disease. Immunocytochemical studies have shown internalization of desmosomal components after acantholysis. Basal cytokeratins show suprabasal expression in lesional Darier's disease. The exact mechanisms of acantholysis are still unclear. Cantharidin induces blistering, with suprabasal keratinocyte acantholysis, possibly by protease activation. Plasmin has been implicated in the pathogenesis of acantholysis in Darier's disease and Hailey-Hailey disease. We examined the distribution of desmosomal components, proteases and cytokeratins in cantharidin blisters, to compare them with those previously found in Darier's disease and Hailey-Hailey disease. Two drops of cantharidin collodion were applied to the skin of five normal volunteers. A 4-mm punch biopsy of the blister was taken, and snap frozen. Sections were stained with antibodies to desmosomal proteins (dp) 1/2, dp 3, desmosomal glycoproteins (dg) 1, 2/3, extracellular carbohydrate residues, using the lectins peanut agglutinin (PNA) and soybean agglutinin (SBA), proteases and cytokeratins. Acantholytic cells were stained diffusely with dp1/2; there was markedly reduced or absent peripheral staining for dp3, dg1, dg2/3, PNA and SBA. There was no clumping of stain. Plasminogen, fibrinogen and urokinase were expressed in some acantholytic cells. Basal keratin markers were expressed suprabasally in acantholytic cells. These results are similar to those previously obtained in Darier's disease, but different from the staining obtained in Hailey-Hailey disease. Extracellular glycosylated portions of adhesion molecules may be lost after acantholysis, perhaps as a result of conformational changes, internalization of extracellular domains, or proteolysis. The changes in the expression of plasminogen, fibrinogen, urokinase and cytokeratins in acantholytic cells in cantharidin-induced blisters are, as in Darier's disease and Hailey-Hailey disease, probably secondary to acantholysis, and changes in the shape of cells. We conclude that cantharidin blisters may be a useful model for the study of acantholysis in Darier's disease.