ABSTRACT
INTRODUCTION Several serine proteases have been shown to be present in the epidermis and especially in the stratum corneum (SC). These enzymes have a wide spectrum of specificities and functions and play important roles in numerous physiological and pathological reactions in cells and tissues (1). In skin they are involved in epidermal proliferation, differentiation, lipid barrier homeostasis, and tissue remodeling. Most importantly, kallikreins, together with other enzymes, are involved in the proteolysis of corneodesmosomes, a crucial event prior to desquamation (2). Impaired corneodesmolysis is known to occur in winter and soap-induced xerosis (3,4). In this respect, reduced activity of stratum corneum chymotryptic-like enzyme [SCCE; now called kallikrein 7 (KLK7)] (5) and stratum corneum tryptic-like enzyme (SCTE or KLK5) (6) has been observed in the outer layers of the SC in dry skin. However, increase in their activities in total SC has been reported after inflammatory challenges to skin, for instance following ultraviolet radiation or treatment with surfactants (7,8). Moreover, an increased epidermal expression of KLK7 has been reported in psoriasis and atopic dermatitis, two major chronic inflammatory diseases (9).
