title: The effect of chronic treatment of mice with urocanic acid isomers.
abstract: Trans-urocanic acid (trans-UCA) accumulates in the upper layers of the epidermis and can be isomerized to cis-UCA by UV light irradiation. Cis-urocanic acid possesses immunosuppressive properties that have led to its consideration as one of the initiators of UV-induced immunosuppression. High quantities of cis-UCA persist in human skin for prolonged periods in the summer months. In the present study, mice were injected intradermally with trans-UCA and cis-UCA three times a week for 4 weeks in order to ascertain the long-term effects of the presence of these compounds in the skin. The weight of mice and of their spleens were unaffected by the cis- or trans-UCA treatment. A decrease in thymus weight, accompanied by an increase in lymph node weight, was detected in the cis-UCA-treated mice compared with trans-UCA-treated mice and untreated controls. A net accumulation of lymphocytes and dendritic cells (DC) in lymph nodes was evident following cis-UCA treatment but the percentage of both CD4+ and CD8+ lymphocytes as well as Ia+ DC remained constant among the different treatment groups, indicating that there was no specific migration or proliferation of a particular subset of cells. The in vitro lymphoproliferative response of lymph node cells to the mitogen concanavalin A was significantly sup pressed by cis-UCA treatment. The density of Langerhans cells in the epidermis of the ears was not altered by the chronic cis-UCA treatment. However, chronic cis-UCA treatment did suppress the mixed skin lymphocyte reaction response utilizing epidermal cells from the ears (an uninjected area of skin), indicating a systemic suppression. Compared with trans-UCA treatment, chronic cis-UCA treatment did not cause a significant reduction in the contact hypersensitivity response to oxazolone or the delayed hypersensitivity response to herpes simplex virus. Thus, chronic treatment with cis-UCA led to the suppression of some, but not all, of the immune parameters that are affected by UVB irradiation.
authors.affiliation: Department of Medical Microbiology, University of Edinburgh Medical School, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: el-Ghorr
authors.forename: M
authors.initials: M
authors.lastname: Norval
mesh_terms: D000818:Animals; D018791:CD4 Lymphocyte Count; D018414:CD8-Positive T-Lymphocytes; D002455:Cell Division / Q000187:drug effects; D003877:Dermatitis, Contact; D005260:Female; D006968:Hypersensitivity, Delayed; D007536:Isomerism; D008198:Lymph Nodes / Q000166:cytology / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D009929:Organ Size / Q000187:drug effects; D010641:Phenotype; D013950:Thymus Gland / Q000187:drug effects; D014560:Urocanic Acid / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014560:Urocanic Acid