The Expression of Elafin and Its Implication in the Inflammatory and Keratinizing Disorders of the Skin

Kim, Chong Hyeok; Kim, Soo Nam; Song, Hae Jun

Abstract

BACKGROUND: Elafin is a serine proteinase inhibitor first discovered in keratinocytes from psoriatic epidermis. The molecular structure of elafin contains two different functional domains; one for the proteinase inhibitor, which is directed against elastase and proteinase-3, and the other for transglutaminase substrate. As this unique structural characteristic implies, elafin would be expected to have two distinct biologic functions in tissues. But, the roles and biological features of elafin have not been extensively studied in the skin. OBJECTIVES: This study was designed to demonstrate the immunohistochemical localization of elafin in inflammatory and keratinizing skin disorders, and to elucidate its biological functions. MATERIALS AND METHODS: The pre-elafin sequence was amplified by PCR using a human epidermal cDNA library and expression construct which was ligated into an expression vector. Then, the expressed proelafin sequence was purified and injected intradermally into rabbits to raise a polyclonal antibody. The skin biopsy samples of various skin diseases and normal controls were used for immunohistochemical staining to detect elafin expression. RESULTS: 1)Expression of elafin was observed in infected epidermis, and is believed to be involved in the defense mechanism of the skin. 2)In dermal and subcutaneous inflammatory diseases, epidermal elafin expression was influenced by the location of the inflammation. 3)Elafin was expressed in bullous dermatoses accompanied by acantholysis or spongiosis of epidermal cells. 4)Expression of elafin was upregulated in papulosquamous skin diseases which was characterized by epidermal hyperplasia and abnormal differentiation. 5)Elafin was expressed in keratinizing skin diseases that was accompanied by abnormal differentiation of epidermal cells. 6)Expression of elafin was demonstrated in skin tumors that showed proliferation of suprabasal cells. The intensity of expression is not related to the degree of malignancy, but to the degree of differentiation of tumor cells. CONCLUSION: Induction of elafin expression may play an important role in protecting the skin components against tissue damage. Elafin expression is related to the abnormal proliferation and differentiation of suprabasal cells. This means that elafin may be used as a marker of these conditions.