Abstract:

Objective To study the roles of aquaporin 3 （AQP3）, Caspase 14 and bleomycin hydrolase （BH） in skin barrier in patients with chronic eczema and to tackle the mechanisms underlying the therapeutic effect of narrow-band ultraviolet B （NB-UVB） on eczema. Methods Transepidermal water loss （TEWL）and water content of skin were detected by a multi-functional skin tester in lesions and non-lesional skin of 30 patients with chronic eczema. The protein expressions of AQP3, Caspase 14 and BH were detected by immunohistochemistry in tissue specimens from lesional and non-lesional skin of these patients. Cultured keratinocytes were irradiated with 3 different doses （400, 800, 1200 mJ/cm2） of UVB, and Western blot was performed to quantify the protein expressions of AQP3, Caspase 14 and BH at 24 hours after the irradiation. Results There was a significant decrease in water content of skin （11.32 ± 5.25 vs. 49.68 ± 8.62） but an increase in TEWL （86.28 ± 16.35 vs. 14.62 ± 6.68） in lesional skin compared with non-lesional skin from the patients with chronic eczema （both P < 0.05）. The protein expression levels of AQP3, Caspase 14 and BH in lesional skin were 5.3 times, 4.2 times and one-third of, those in non-lesional skin from the patients, respectively, and significant differences existed between the lesional and non-lesional skin in the 3 parameters （all P < 0.05）. After irradiation with NB-UVB at 400, 800 and 1200 mJ/cm2, the expression level of AQP3 in keratinocytes was decreased by 52%, 77% and 84%, respectively, and that of Caspase 14 was decreased by 18%, 22% and 78%, respectively, compared with unirradiated keratinocytes （all P < 0.05）. A marked decrease （by 66%） was also observed in the expression of Caspase 14 in keratinocytes after irradiation with NB-UVB at 1200 mJ/cm2 （P < 0.05） . Conclusions The impairment of skin barrier function in chronic eczema may be related to the downregulated expression of BH and upregulated expression of Caspase 14 and AQP3. The therapeutic effect of NB-UVB on chronic eczema may be partly attributed to the diminished expression of AQP3, Caspase 14 and BH.

Key words: bleomycin hydrolase