Objective    To study the effect of 420 nm intense pulse light on animal acne model and its possible mechanism.     Methods    A rat model of auricular acne was established by intradermal injection with propionibac-terium and irradiated with 420 nm intense pulse light. Inflammatory skin damage was observed before and after irradiation. Expression of TNF-α

MMP-2 and other factors was detected by dermatopathology

immunohistochemistry and real-time PCR

respectively.     Results    Acne-like lesions were observed in acne model group 5 days after injection of propionibac-terium. The inflammatory reaction level was significantly lower

the folliculus pili cuticular layer was notably thinner

the number of dermal inflammatory cells was obviously less

and the sebiferous gland was remarkably smaller in irradiation group than in control group. Immunohistochemistry showed positive expression of TNF-α and MMP-2 in model group

which was influenced by irradiation. Real-time PCR showed over-expression of TNF-α and MMP-2 in model group

which was reduced after irradiation (P＜0.05).     Conclusion    420 nm intense pulse light has good therapeutic effects on ance

which may be related with the expression of TNF-α

MMP-2 and other factors.