Dichotomous effect of ultraviolet B on the expression of corneodesmosomal enzymes in human epidermal keratinocytes

BackgroundThe stratum corneum chymotryptic enzyme (SCCE) and the stratum corneum tryptic enzyme (SCTE) are serine proteases of the kallikrein family that are encoded by the KLK7 and KLK5 genes, respectively. They might play a role in desquamation by cleaving corneodesmosomal proteins. Their activities are regulated by lympho-ephithelial Kazal-type related inhibitor (LEKTI), which is encoded by the SPINK5 gene.ObjectiveTo elucidate the role of these molecules in ultraviolet B (UVB)-induced desquamation of the stratum corneum, we examined the effect of UVB irradiation on the expression of these enzymes in human epidermal keratinocytes.MethodsThe effects of UVB on SCCE (KLK7), SCTE (KLK5) and LEKTI (SPINK5) expression in keratinocytes were estimated using HaCaT cells, normal human epidermal keratinocytes and a reconstructed human epidermis model.ResultsUVB irradiation significantly reduced the expression of SPINK5 and increased the expression of KLK5 and KLK7, as assessed by real-time PCR, and reduced the expression of LEKTI and increased the expression of SCTE and SCCE by Western blotting and/or immunofluorescence analysis. Protease activity, as assessed by in situ zymography, was enhanced in the epidermis following exposure to UVB irradiation compared with sham-irradiated epidermis.ConclusionThese results suggest that reduced expression of LEKTI and increased expression of SCCE and SCTE in human epidermal keratinocytes after UVB irradiation may contribute to desquamation of the stratum corneum.