Efficacy of red or infrared light-emitting diodes in a mouse model of Propionibacterium acnes-induced inflammation

Background: Laser/light-based devices may provide an alternative to conventional acne therapeutics in some patients with nonresponsive acne. Objective: We investigated the efficacy of red or infrared light-emitting diode (LED) devices in a mouse model of Propionibacterium acnes-induced inflammation through clinical examination and histopathological and immunohistochemical studies. Methods: A human-derived Propionibacterium acnes suspension (10⁹ colony-forming units /μl) was injected into the back of an HR-1 mouse. Then, a 28.9 J/cm² 650-nm red LED or 9.3 J/cm² 830-nm infrared LED was applied to the mouse with P. acnes-induced inflammation once daily for 2 weeks. Two weeks after treatment, histological findings with hematoxylin and eosin staining and expression levels of inflammatory biomarkers (integrin α6, neutrophils, interleukin [IL]-1β, and matrix metalloproteinase [MMP]-2/9) were evaluated in tissue specimens using immunohistochemical staining. Results: Mice treated with red and infrared LED showed clinical improvement in inflammatory nodules compared to mice in the control group. Red LED was much more effective than infrared LED. Epidermal hyperplasia, comedone-like cysts, and integrin α6 expression improved to a similar extent in the red and infrared LED treatment groups and control group. Neutrophil, IL-1β, MMP-2, and MMP-9 expression after treatment with red and infrared LED decreased considerably compared to expression in the control group. Conclusion: In a mouse model of P. acnes-induced inflammatory nodules, red and infrared LED devices may be an alternative to conventional acne therapies. In addition, a mouse model of P. acnes-induced inflammatory nodules is helpful for laboratory research of acne.