Objective：To establish a model of 2，4-dinitrochlorobenzene（DNCB）-induced atopic dermatitis（AD） in wild-type and TRPA1-knockout C57BL/6 mice，and to investigate the role of TRPA1 in this model. Methods：Wild-type male C57BL/6 mice were randomly divided into experimental group and control group，with 6 mice in each group. A model of AD was established. In the sensitization stage，the mice were given external applica－tion of 2% DNCB and acetone-olive oil solution（3∶1） on the back and acetone-olive oil solution alone on the ears on day 1，and in the challenge stage，the mice were given external application of 0.5% DNCB on the back and acetone-olive oil solution alone on the ears on days 5，8，11，14，17，and 20，with 6 times of treatment in total. HE staining was performed for skin lesions to identify whether an AD model was established successfully. Western blot and qRT-PCR were used to measure the protein and mRNA expression of TRPA1，and immunohistochemistry was used to identify the location of TRPA1 and measure its protein expression. A total of 6 TRPA1+/+（wild-type） mice were randomly selected as model group Ⅰ，6 TRPA1-/-（knockout genotype） mice were selected as model group Ⅱ，and 6 TRPA1+/+ mice were selected as control group. An AD model was established according to the method above. After modeling，serum samples and skin lesions at the ears and the back were collected to measure related pathophys－iological indices. Results：Skin lesions and HE staining showed that an AD model was successfully established in wild-type mice. As for the experimental group，the results of qRT-PCR showed a significant increase in the relative mRNA expression of TRPA1 in the back lesions（t=4.93，P=0.008）；Western blot showed a significant increase in the protein expression of TRPA1 in the back lesions，with a significant change in mean optical density（t=34.32，P=0.000）；immunohistochemistry showed varying degrees of increases in the expression of TRPA1 in the epidermis and the dermis. The AD model established in TRPA1-knockout mice showed that compared with the control group，the model groups Ⅰ and Ⅱ had marked inflammatory skin lesions on the back and marked ear swelling. Pathological examination showed hyperkeratosis and/or parakeratosis，thickening of the prickle cell layer，inflammatory cell infiltration dominated by lymphocytes in the dermis，and increased infiltration of mast cells in the model groups Ⅰ and Ⅱ. There was an in－crease in total serum IgE level and there was a significant difference between the control group and the model groups Ⅰ/Ⅱ[（1.27±0.10） μg/mL vs. （14.82±0.26） μg/mL，t=19.27，P=0.000；（1.27±0.10） μg/mL vs. （8.63±0.28） μg/mL，t=25.07，P=0.000]. There were increases in the relative expression of the TH2 cytokines interleukin-4 and interleukin-13，and there were significant differences between groups（P<0.05）. Compared with the model group Ⅰ，the model group Ⅱ had significant reductions in the severity of inflam－matory skin lesions，the degree of ear swelling，the thickening of the prickle cell layer，the degree of inflammatory cell infiltration，and the total serum IgE level[（14.82±0.26） μg/mL vs. （8.63±0.28） μg/mL，t=16.34，P=0.000]，as well as significant reductions in the relative expression of TH2 cytokines. Conclusion：A model of DNCB-induced AD has been successfully established in wild-type and TRPA1-knockout C57BL/6 mice. Upregulation of TRPA1 expression and TRPA1 knockout inhibit DNCB-induced inflammation in AD，suggesting that TRPA1 may play an important role in DNCB-induced AD，but further studies are needed to clarify the specific mechanism.
