DOWN-REGULATION OF LANGERHANS CELL PROTEIN-KINASE C-BETA ISOENZYME EXPRESSION IN INFLAMMATORY AND HYPERPLASTIC DERMATOSES

The family of protein kinase C (PKC) isoenzymes plays a fundamental part in signal transduction, and thereby regulates important cellular functions, including growth, differentiation, cytokine production and adhesion molecule expression, In lesional psoriatic skin, Ca2+-dependent PKC activity, PKC-beta protein and epidermal Langerhans cell (LC) PKC-beta immunostaining are significantly decreased, indicating activation and subsequent down-regulation of PKC, Whether these changes occur in other inflammatory/hyperplastic dermatoses is, however, unknown. We examined PKC-alpha and PKC-beta expression in normal skin, psoriasis, cutaneous T-cell lymphoma (CTCL), lamellar ichthyosis, non-bullous ichthyosiform erythroderma, atopic dermatitis, urushiol-induced allergic contact dermatitis, and sodium lauryl sulphate (SLS)-induced irritant contact dermatitis, Cryostat sections were stained for PKC-alpha and PKC-beta, and the LC marker CD1a, using an immunoperoxidase technique and specific monoclonal antibodies. Double-labelling studies, in normal skin, revealed co-expression of PKC-beta and CD1a by epidermal LCs, Analysis of the number of PKC-beta(+) and CD1a(+) epidermal LCs, in diseased compared with normal skin, revealed three categories: (i) in psoriasis and CTCL, the PKC-beta(+) epidermal LC number was significantly reduced, whereas the CD1a(+) epidermal LC number was unchanged; (ii) in allergic and irritant contact dermatitis, both PKC-beta(+) and CD1a(+) epidermal LCs were significantly reduced in number; and (iii) in atopic dermatitis, the PKC-beta(+) epidermal LC number was normal, and CD1a(+) epidermal LCs were significantly increased in number, Moreover, the ratio of epidermal LC PKC+/CD1a(+) was reduced in all the dermatoses studied, suggesting activation of PKC-beta, with subsequent down-regulation. Within the dermis, increased PKC-beta staining of infiltrating cells was observed in all the conditions' studied except lamellar ichthyosis and non-bullous ichthyosiform erythroderma. These data indicate that: (i) downregulation of LC PKC-beta occurs in a variety of inflammatory and hyperplastic skin disorders, and is not unique to psoriasis, and (ii) the pattern of epidermal LC PKC-beta and CD1a expression varies among the diseases studied, In mice, PKC activation induces LC migration, Thus, downregulation of epidermal LC PKC-beta associated with reduced CD1a(+) epidermal LCs in allergic and irritant contact dermatitis suggests that PKC-beta may transduce the signal for migration of LCs from human epidermis.