The Preliminary Mechanism Study Of Oriental Lacquer-induced Itch

The oriental lacquer is widely applied in the fields of industry, agriculture, national defense, and science research, because it has obvious advantages as a coating, so be called the king of coating. However, it’s limited in practical application, because it is easy to cause the body irritation. Many researches have proved that the sensitization activity of oriental lacquer is caused by its urushiol compounds. Unbearable itching in affected area is one of the pathological reaction in oriental lacquer allergic patients. To explore the mechanism of itch caused by oriental lacquer is the aim of this study. A series of work was conducted as following.We isolated a triene urushiol monomer compounds [3-（8’Z,11’E,13’Zpentadecatrienyl） catechol] from oriental lacquer using petroleum ether extraction, preliminary separation by silica gel column chromatography. The structure of monomer compounds was determined by ¹H-NMR, ¹³C-NMR, high resolution mass spectrometry. The purity of this product reached to 95% calculated from peak area normalization method, which was determined using HPLC purity characterization.According to the results of clinical observation of people allergic to oriental lacquer, we use the method of mouse one time to spread the urushiol to send the acute dermatitis, groped through the skin swelling degree dose finalized urushiol coated method: the purified triene urushiol with anhydrous ethanol diluted 10 times, skin of mice with 10μL（about 1 mg）. After the mouse back pate skin spreads the urushiol 5h later swelling degree maximizing, 24 h later appears inflamed, seeps out, the fester and so on the obvious inflammation symptom. HE staining of the dermatitis skin in mice that shows urushiol-induced dermatitis resulted in accumulation of inflammatory cells in the skin, followed by edema, ulcers, scabs, slough symptoms, skin rehabilitation after 7-8 days. Using Elisa detection inflammatory cytokines in serum and skin before and after coating of urushiol, found after building content of inflammatory cytokines in serum had no significant change, but in skin the TNF-α, IL-1β expression ascension, this means that urushiol allergy is local inflammation of the skin. Behavior experimental results show that urushiol can cause acute dermatitis in mice both have severe itching reaction and severe pain reaction, and itch sensation of dermatitis appears before and after dermatitis appears scratching behavior of two phase.Using the calcium imaging, fluorescent quantitative real-time PCR and enzymelinked immunosorbent assay（ELISA） methol, we found that TRPA1（transient receptor potential A1） was involved in urushiol-induced itch behavior in mice. After 24 h urushiol treatment, the expression of trpa1 gene in dorsal root ganglion（DRG） neurons was significantly decreased in the urushiol-treated mice compared with ethanol-treated mice. Consistently, scratching behavior of trpa1^-/- mice was obviously enhanced in relative to trpa1^+/+ mice. The substance P in the dermatitis skin was also examined, which might participate of the generation of itch and pain sensation. We found that the concentration of substance p was significantly decreased after urushiol treatment.Taken together, we established the essential research method for investigating the oriental lacquer induced acute dermatitis in mice. Our study also preliminary suggested that TRPA1 was involved in the oriental lacquer induced itch behavior in mice.