Abstract: Abstract: Objective To investigate the effects of paeonol on the expressions of substance P (SP) and neurokinin 1 receptor (NK1R) and mast cell activation in eczema model mice. Methods One hundred healthy and clean grade C57BL mice were selected, and 2,4-dinitrochlorobenzene (DNCB) was applied to the insides of both ears of the mice to sensitize to establish an eczema model. After successful modeling, a random number table method was used to divide model mice into eczema model group, paeonol low (25 mg/kg), medium (50 mg/kg) and high (100 mg/kg) dose groups and positive drug (dexamethasone 0.65 mg/kg) group, 20 mice in each group. The another 20 mice were used as control group (apply the same amount of normal saline on the inner sides of both ears). Each group began to administer the drug after successful modeling.The paeonol low, medium and high dose groups and the positive drug group were intraperitoneally injected with the corresponding dose of drugs, once per day for 14 days. Control group and eczema model group were injected with the same amount of normal saline. The skin damage of eczema was observed and scored with naked eyes in ears of mice. Hematoxylin eosin staining (HE) was used to detect the pathological changes in ears of mice in each group. SP secretion was detected by ELISA method. The expressions of NK1R and Tryptase, a marker of mast cell activity in ear lesions, were detected by immunohistochemistry. Results Compared with the control group, the mice in eczema model group showed redness, keratosis scab, exudation and other damages, hyperkeratosis of epidermis, inflammatory cell infiltration of dermis and other pathological damages. The skin damage degree score, SP content, NK1R and Tryptase expression levels were increased (P＜0.05). Compared with eczema model group, mice of the paeonol low, medium and high dose groups and positive drug group showed a reduced pathological damage such as redness, keratinization, inflammatory infiltration in ears, the reduced degree of skin lesion score, SP content, NK1R and Tryptase expression levels (P＜0.05). Moreover, each dose group of paeonol was dose-dependent, and there was no significant difference between the high dose paeonol group and the positive drug group (P＞0.05). Conclusion Paeonol may inhibit the activation of mast cells and alleviate the symptoms of eczema inflammatory damage by inhibiting the expressions of SP and NK1R in ear lesions of eczema model mice.

Key words: Key words: substance P, receptors, neurokinin-1, eczema, mast cells, tryptases, paeonol