The effect of Xiaobi decoction on minimal erythema dose of irradiation with 308 nm excimer lamp in guinea pigs.

Background: Psoriasis is a chronic autoimmune-mediated inflammatory skin disease. The main clinical manifestation of this complex condition is scaly erythema. Excimer 308-nm light can be used to selectively and safely treat skin lesions. In clinical practice, the combination of Xiaobi decoction combined with 308-nm excimer light therapy has been found to have a beneficial effect on advanced psoriasis vulgaris. However, the effect of Xiaobi decoction on light sensitivity in psoriasis patients has not been explored. Therefore, this study aimed to observe the effect of Xiaobi decoction on the minimal erythema dose (MED) value in guinea pigs.

Methods: Eighty guinea pigs were divided into a Xiaobi decoction group and a control group according to the serial number: guinea pigs with odd numbers were assigned into the Xiaobi decoction group, and those with even numbers were assigned into the control group. The Xiaobi decoction group was administrated Xiaobi decoction by gastric lavage, while the control group was given distilled water by gastric lavage. The back skin of the guinea pigs in the two groups was irradiated with a 308-nm excimer lamp before gavaging, and after 10, 20, and 30 days of gavaging. The MED values 24 hours after irradiation were recorded.

Results: The average MED in the Xiaobi decoction group was (800±126.5) mJ/cm2, compared with (780±107.7) mJ/cm2 in the control group, and the difference was not significant (P>0.05). After 10 days, 20 days, and 30 days of gavaging, the MED values of the guinea pigs in the Xiaobi decoction group were significantly lower than those of the control group (P<0.05). Blood tests showed that the levels of vascular endothelial growth factor (164.5±25.7 vs. 145.3±27.4, P=0.002) and interleukin-23 (1.8±0.7 vs. 1.5±0.5, P=0.030) were significantly lower in the Xiaobi decoction group than in the control group.

Conclusions: Xiaobi decoction can reduce the MED value of guinea pigs, and increase the sensitivity of skin lesions to 308-nm excimer light and the amount of light absorbed by skin lesions. These results may represent the mechanisms of action of Xiaobi decoction in the treatment of psoriasis.