Quantification of Human Tissue Kallikreins in the Stratum Corneum: Dependence on Age and Gender

Abstract

Human tissue kallikreins are a family of 15 trypsin or chymotrypsin-like secreted serine proteases (hK1-hK15). hK5, hK6, hK7, hK8, and hK13 have been identified in the stratum corneum (SC), stratum granulosum, and skin appendages. It has been reported that hK5 and hK7 degrade desmosomes/corneodesmosomes, suggesting that kallikreins are responsible for desquamation. We report the quantification of hK5, hK6, hK7, hK8, hK10, hK11, hK13, and hK14 in the SC by ELISA and their variation among age groups. The total SC trypsin and chymotrypsin-like activities were also measured. The amount of hK7, hK8, and hK11 (ng per mg dry weight) were high, and varied from 6 to 14, hK5 (2.0-4.0) was present at intermediate levels, and hK10 (0.65-1.0), hK14 (0.1-0.3), hK6 (0.1-0.3), and hK13 (0.02-0.1) were present at lower levels. hK6 and hK14 were significantly lower in females between 20 and 59 y. hK5, hK7, hK10, hK11, and hK14 were not significantly different across the age groups. hK8 was lowest at extremes of age (highest at 30-39 y), hK6 was lower at >30 y, and hK13 was lower at >20 y. Overall trypsin-like activity did not differ across age groups but was higher in subjects <11 y. Overall chymotrypsin-like activity was not related to age. In conclusion, we found multiple kallikreins in the SC and suggest that these enzymes may be responsible for desquamation through an enzymatic cascade pathway.

Kallikrein 8 Is Involved in Skin Desquamation in Cooperation with Other Kallikreins

“…Up-regulation of hK8 has been reported in human psoriatic lesions (12,13). TPA, an activator of protein kinase C, induces epidermal hyperplasia similar to psoriatic lesion.…”

“…4). Previous reports suggested that both hK6 and hK7 are involved in the pathogenesis of psoriasis (10,13). Cascade reactions of KLKs have been suggested to play a critical role in skin desquamation (7,8).…”

“…hK5 also has a potential to directly cleave DSG1 and CDSN. In addition, at least eight kallikreins, including hK5, hK6, hK7, and hK8, are thought to be involved in desquamation cascade of the human skin (13).…”

“…Protease Activity Assays in the Epidermis after TPA Application-To investigate the difference of protease activity between WT and Klk8 Ϫ/Ϫ mice, we measured proteolytic activity of epidermal extraction toward VPR-MCA and FSR-MCA, both of which were shown to be good substrates of mK8 and mK6 (11,24), and toward RPY-pNA, a substrate of mK7 (13). Protease activity to VPR-MCA of WT epidermis gradually increased upon TPA treatment peaking at 72 h, whereas the activity to FSR-MCA increased, peaking at 48 h. The proteolytic activities to VPR-MCA and FSR-MCA of the untreated Klk8 Ϫ/Ϫ epidermis were comparable with that of WT epidermis.…”

“…In human and mouse skin, hK8 and mK8 are localized from the upper stratum spinosum to the stratum corneum. Increases in KLK8 transcripts and protein were observed in human skin diseases, such as psoriasis vulgaris, lichen planus, and atopic dermatitis (12,13). These results led to the hypothesis that hK8 is involved in the pathogenesis of inflammatory skin diseases.…”