ObjectiveTo 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.MethodsTransepidermal water loss (TEWL)and water content of skin were detected by a muhi-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 lesioual 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.ResultsThere 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).ConclusionsThe 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.