Rose Bengal acetate-mediated photodynamic therapy alleviates Cutibacterium acnes-induced acne-like lesions in a mouse model.

Acne vulgaris is a wordwide distressing skin condition which is often treated by topical antibiotics or retinoids, and in severe cases with oral medications. It is generated by a series of factors including excess sebum production clogging sebaceous glands and infection with Cutibacterium acnes producing inflammation. Photodynamic therapy (PDT) with topical aminolevulanic acid or its methyl ester plus red light has shown good results, especially for inflammatory lesions. The present study investigated the use of a new photosensitzer Rose Bengal acetate (RBAc) for acne PDT treatment. RBAc plus green light killed 6 logs of C. acnes bacteria in vitro at <1 μM. Three daily intradermal injections of C. acnes bacteria into the back of Balb/c mice produced acne-like lesions. A hyaluronic-acid gel containing RBAc (0-600 μM) was topically applied to the lesions followed after 1 h by 20 J/cm2 of 540 nm light. RBAc at a concentration of 200 μM gave the most pronounced reduction in lesion area at days 1-4 post-PDT. Histology, immunohistochemistry, TUNEL staining and Western blotting at 10 days showed that RBAc-PDT reduced the inflammatory response and promoted apoptosis in the lesion tissue. These findings support RBAc-PDT as a promising and well-tolerated topical candidate for further preclinical and clinical evaluation in acne management.