Abstract: Objective To detect levels of aryl hydrocarbon receptor（AhR） and its downstream molecules in peripheral blood mononuclear cells（PBMCs） and sera from patients with atopic dermatitis（AD）, and to analyze the correlation of their expression with serum cytokines and the severity of AD. Methods Real-time quantitative PCR（RT-PCR） was performed to analyze mRNA expression of AhR, cytochrome P4501A （CYP1A1）, AhR repressor （AHRR）, AhR nuclear translocator （ARNT） in PBMCs from 29 AD patients and 17 healthy controls, enzyme -linked immunosorbent assay （ELISA） to detect serum levels of interleukin （IL）-1β, IL-6, tumor necrosis factor （TNF）-α, IL-4, IL-22 and AhR in the AD patients, and immunohistochemical study to determine AhR expression in skin lesions of the AD patients and normal skin tissues of 21 patients with pigmented nevus. Measurement data were compared by using unpaired Student′s t test, enumeration data were compared by using chi-square test, and correlations between indices were analyzed by using Pearson correlation analysis. Results The serum level of AhR was significantly higher in the AD group （41.26 ± 4.52 pmol/L） than in the healthy control group （33.73 ± 2.49 pmol/L, t = 6.507, P＜0.001）. Compared with the healthy control group, the AD group showed significantly increased mRNA expression of AhR （1.572 ± 0.392 vs. 1.000 ± 0.173, t = 6.819, P = 0.007）, AHRR （2.402 ± 1.716 vs. 1.000 ± 0.788, t = 3.722, P = 0.039）, CYP1A1（2.258 ± 1.598 vs. 1.000 ± 0.796, t = 3.400, P = 0.002） and ARNT （1.383 ± 0.842 vs. 1.000 ± 0.586, t = 1.653, P = 0.105） in PBMCs. The AhR expression in skin lesions in the AD group was significantly higher than that in normal skin tissues in the control group（0.191 ± 0.041 vs. 0.087 ± 0.017, t = 10.036, P＜0.001）. In the AD group, the mRNA expression of AhR in PBMCs was positively correlated with eczema area and severity index score （r = 0.448, P = 0.019） and the serum IL-6 level （r = 0.377, P = 0.046）, and the AHRR mRNA expression was positively correlated with the serum IL-1β level （r = 0.467, P = 0.021）. Conclusion AhR and its downstream molecules were highly expressed in the AD patients compared with healthy controls, and the AhR expression was positively correlated with the serum IL-6 level and AD severity in AD patients, suggesting that the AhR signaling pathway may play a certain role in pathogenesis of AD and AhR may serve as an efficient index for evaluating AD severity.

Key words: Dermatitis, atopic, Hydrocarbons, aromatic, Cytochrome P-450 enzyme system, Interleukin-6, Aryl hydrocarbon receptor