Expression of caspase-14 in skin lesions of patients with chronic actinic dermatitis and effect of ultraviolet B radiation on its mRNA and protein expression in HaCaT cells

Abstract

Objective To determine the expression of caspase-14 in skin lesions of patients with chronic actinic dermatitis (CAD) , and to explore the effect of ultraviolet B (UVB) radiation on its mRNA and protein expression in HaCaT cells. Methods In 2016, skin samples were collected from lesions of 10 patients with CAD (test group), 10 patients with eczema (positive control group) and from normal skin of 10 healthy controls after cosmetic surgery (negative control group) in the Department of Dermatology, First Affiliated Hospital of Kunming Medical University. Immunohistochemical staining was performed to determine the expression of caspase-14 in the normal skin, CAD and eczema lesions. Cultured HaCaT cells were divided into several groups: UVB groups irradiated with 0, 30, 60, 90 mJ/cm2 UVB separately, and 5-AzaC groups irradiated with 0, 30, 60, 90 mJ/cm2 UVB separately followed by the treatment with the methylase inhibitor 5-AzaC for 24 hours. Then, the cells were collected, and real-time fluorescence-based quantitative PCR (RT-PCR) and Western blot analysis were conducted to determine the mRNA and protein expression of caspase-14 respectively in HaCaT cells in the UVB groups and 5-AzaC groups. Statistical analysis was carried out with SPSS22.0 software by using chi-square test for the comparison of rates, and t test and two-factor analysis of variance for the comparison of means. Results In the CAD and eczema lesions, caspase-14 was mainly expressed in the spinous and granular layers, but not in the stratum corneum. However, caspase-14 was markedly expressed in the stratum corneum of the normal skin tissues. Of the 10 CAD samples, 5 were positive for caspase-14, and 9 of 10 normal skin samples were positive for caspase-14. The positive rate of caspase-14 significantly differed between the two above groups (χ2=7.30, P < 0.05) . RT-PCR and Western blot analysis showed significant changes in the mRNA and protein expression of caspase-14 in HaCaT cells after irradiation with different doses of UVB (F=87.54, 23.46, both P < 0.05) , which showed a decreasing trend along with the increase in the dose of UVB. After exposure to 0, 30, 60 and 90 mJ/cm2 UVB, the mRNA and protein expression of caspase-14 was significantly higher in the 5-AzaC groups than in the UVB groups (all P < 0.05) . Conclusions In CAD lesions, the expression of caspase-14 markedly decreased, and was absent in the stratum corneum. UVB radiation can down-regulate the mRNA and protein expression of caspase-14 in HaCaT cells. Key words: Photosensitivity disorders; Eczema; Ultraviolet rays; Caspase 14; Keratinocytes; Chronic actinic dermatitis