Effects of 5-aminolevulinic acid photodynamic therapy on TLRs in acne lesions and keratinocytes co-cultured with P. acnes.

OBJECTIVE: To investigate the effect of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) on the expression of Toll like receptors (TLRs) in human keratinocytes and its role in acne treatment.

METHODS: TLR2 and TLR4 expression in acne lesions before and after ALA-PDT were examined by immunohistochemical assay. Primary keratinocytes were obtained from acne lesions, co-cultured with P. acnes and then treated with ALA-PDT using red or blue LED. Cytokines production were examined by ELISA, TLR2 and TLR4 gene expression by real-time PCR, and TLR2 and TLR4 protein expression by Western-blot assay.

RESULTS: The overexpression of TLR2 and TLR4 in acne lesion were detected, which became negative or weaker after ALA-PDT. The infection of P. acnes in keratinocytes could significantly increase the levels of early inflammatory cytokines (e.g. IL-1α, TNF-α and IL-8) (P<0.05). Such responses could be inhibited by ALA-PDT. P. acnes infection could also significantly increase TLR2 and TLR4 expressions in keratinocytes (P<0.05), which could be down-regulated by ALA-PDT.

CONCLUSIONS: ALA-PDT could inhibit innate immune responses in keratinocytes treated with P. acnes via TLRs pathways.