Topical vitamin E inhibition of immunosuppression and tumorigenesis induced by ultraviolet irradiation.
Ultraviolet (UV) irradiation of C3H/HeN mice induces skin cancer and an immunosuppression that prevents the host from rejecting antigenic UV-induced tumors. The capacity of topical vitamin E (dl-alpha-tocopherol) to prevent photocarcinogenesis or the immunosuppression induced by UV irradiation were assessed. Skin cancer incidence in UV-irradiated mice was 81% at 33 weeks after the first UV exposure; application to mice of 25 mg vitamin E three times per week for three weeks before UV irradiation, and throughout the experiment, reduced this incidence to 42% (p = 0.0065, log rank test). Immunoenhancement by vitamin E was assessed by comparing levels of immunosuppression by splenocytes from normal or UV-irradiated mice, with and without topical vitamin E treatment. Transfer of splenocytes from UV-irradiated mice to naive mice prevented the recipients from rejecting a UV-induced tumor challenge, whereas splenocytes from UV-irradiated mice treated with vitamin E did not prevent recipients from rejecting a similar tumor challenge. Phenotypic analysis of splenocytes used in the passive transfer assay, conducted with a biotin-avidin-immunoperoxidase technique, revealed that vitamin E treatment of mice undergoing UV irradiation prevented the UV-induced down regulation of Ia expression in splenocytes and increased the proportion of Lyt-2+ and L3T4+ splenocytes. Therefore, chronically applied vitamin E can effectively reduce cancer formation and immunosuppression induced by UV irradiation. Prevention of UV-induced down regulation of Ia expression may have contributed to this immunomodulation.
Gensler
H L
HL
Department of Radiation Oncology, University of Arizona, Tucson 85724.
Magdaleno
M
M
D000287:Administration, Topical; D000818:Animals; D001835:Body Weight; D005260:Female; D007108:Immune Tolerance / Q000187:drug effects*; D007116:Immunization, Passive; D051379:Mice; D008809:Mice, Inbred C3H; D011833:Radiation Injuries, Experimental; D012044:Regression Analysis; D012878:Skin Neoplasms / Q000209:etiology / Q000517:prevention & control*; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology*
D014810:Vitamin E