Human tissue kallikrein expression in the stratum corneum and serum of atopic dermatitis patients

Human tissue kallikreins are a family of 15 trypsin- or chymotrypsin-like secreted serine proteases (KLK1-KLK15). Many KLKs have been identified in normal stratum corneum (SC) and sweat, and are candidate desquamation-related proteases. We report quantification by enzyme-linked immunosorbent assay (ELISA) of KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13 and KLK14 in the SC and serum of atopic dermatitis (AD) patients by ELISA, and examine their variation with clinical phenotype, correlation with blood levels of eosinophils, lactate dehydrogenase (LDH) and immunoglobulin E. The overall SC serine protease activities were also measured. In the SC of AD, all KLKs, except KLK11, were significantly elevated. The elevation of chymotrypsin-like KLK7 was predominant, compared with trypsin-like KLKs. The SC overall plasmin- and furin-like activities were significantly elevated, while trypsin- and chymotrypsin-like activities did not differ significantly. In the serum of AD patients, KLK8 was significantly elevated and KLK5 and KLK11 were significantly decreased. However, their serum levels were not modified by corticosteroid topical agents. The alterations of KLK levels in the SC of AD were more pronounced than those in the serum. KLK7 in the serum was significantly correlated with eosinophil counts in the blood of AD patients, while KLK5, KLK8 and KLK11 were significantly correlated with LDH in the serum. In conclusion, we report abnormal kallikrein levels in the SC and the serum of AD patients. KLKs might be involved in skin manifestation and/or focal/systemic inflammatory reactions in AD. Our data may contribute to a better understanding of the pathogenesis of AD.