The expression of serine protease inhibitors in epidermal keratinocytes is increased by calcium, but not 1,25(OH)2 vitamin D3 or retinoic acid

Summary

Background

In the human skin, the serine proteases kallikrein-related peptidases (KLK) 5 and KLK7 degrade corneodesmosome proteins, which leads to desquamation. The serine protease activity of the skin is tightly regulated by the interplay between such proteases and serine protease inhibitors, which include lympho-epithelial Kazal-type related inhibitor (LEKTI) encoded by SPINK5, secretory leukocyte peptidase inhibitor (SLPI), and elafin. The expression of KLK5 and KLK7 is controlled and up-regulated by stimulants such as calcium, 1,25(OH)₂ vitamin D₃ (1,25(OH)₂VD₃), and retinoic acid (RA).

Objectives

To understand the effect of calcium, 1,25(OH)₂VD₃, and RA on the expression of serine protease inhibitors in epidermal keratinocytes.

Methods

We stimulated normal human epidermal keratinocytes (NHEKs) with high calcium, 1,25(OH)₂VD₃, or RA and then analysed the expression of serine protease inhibitors using quantitative real-time-PCR, ELISA, and immunocytofluorescence. We also analysed trypsin- and chymotrypsin-like serine protease activities in stimulated NHEKs.

Results

High calcium, but not 1,25(OH)₂VD₃ or RA, significantly induced the expression of LEKTI, SLPI, and elafin at both transcript and protein levels in NHEKs. These inductions were time- and dose-dependent. The activities of trypsin- and chymotrypsin-like serine proteases were significantly up- and down-regulated by high calcium, respectively, in NHEKs.

Conclusions

High calcium, but not 1,25(OH)₂VD₃ or RA, increases the expression of serine protease inhibitors in epidermal keratinocytes. Our findings contribute to the understanding of the mechanisms by which serine protease activities are regulated by serine proteases and related inhibitors in epidermal keratinocytes.

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