title: Immunosuppressive effects of photodynamic therapy by topical aminolevulinic acid.
abstract: Photodynamic therapy (PDT) has been used for inflammatory skin disorders as well as superficial skin cancers such as solar keratosis and Bowen's disease. Whether PDT with topical application of aminolevulinic acid (ALA) and exposure to visible light has a similar immunosuppressive action to ultraviolet phototherapy was investigated using a murine contact hypersensitivity (CHS) model. The number of epidermal Langerhans cells (LC) was decreased with their morphological changes 1 day after PDT with the minimal level at 5 days and gradual recovery thereafter. Conversely, the number of CD11c(+) I-A(+) cells was significantly increased in the draining lymph nodes after PDT. This suggests that LC moved from PDT-treated skin, resulting in the decrement of epidermal LC and migration to lymph nodes. CHS response to DNFB applied on the PDT-treated skin with 20% ALA and 40 J/cm(2) visible light was significantly suppressed (local immunosuppression). When mice were treated with 80 J/cm(2) of PDT, CHS response to the antigen applied on untreated distant skin was also significantly suppressed (systemic immunosuppression). The locally or systemically immunosuppressed mice by PDT were attempted to sensitize again with DNFB on non-treated skin, but elicitation responses were significantly suppressed. However, these mice were able to be sensitized with another hapten, oxasolone. Thus, a hapten-specific immunological unresponsiveness (tolerance) was induced in mice by topical ALA-PDT. These findings suggest that PDT has a potential immunological contribution to clinical efficacy for inflammatory diseases identical to ultraviolet phototherapies.
authors.affiliation: Department of Dermatology, Kansai Medical University, Moriguchi, Osaka, Japan. hayamij@takii.kmu.ac.jp
authors.forename: Junji
authors.initials: J
authors.lastname: Hayami
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okamoto
authors.forename: Akira
authors.initials: A
authors.lastname: Sugihara
authors.forename: Takeshi
authors.initials: T
authors.lastname: Horio
mesh_terms: D000287:Administration, Topical; D000622:Aminolevulinic Acid / Q000008:administration & dosage*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003877:Dermatitis, Contact / Q000517:prevention & control*; D005260:Female; D007108:Immune Tolerance / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D007801:Langerhans Cells / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage*
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid