RESUMO
A combination of 8-methoxypsoralen (8-MOP) and ultraviolet-A (UVA) radiation (320-400 nm) (PUVA) is widely used in the treatment of psoriasis and other skin diseases. PUVA is highly effective in eliminating hyperproliferative cells in the epidermis, but its mechanism of action has not been fully elucidated. In this study, we used immortalized JB6 mouse epidermal cells, p53(-/-), and Fas ligand deficient (gld) mice to investigate the molecular mechanism by which PUVA induces cell death. The results indicate that PUVA treatment induces apoptosis in JB6 cells. In addition, PUVA treatment of JB6 cells results in p53 stabilization, phosphorylation, and nuclear localization as well as induction of p21(Waf/Cip1) and caspase-3 activity. In vivo studies reveal that PUVA treatment induces significantly less apoptosis in the epidermis of p53(-/-) mice compared to p53(+/+) mice. Furthermore, FasL-deficient (gld) mice are completely resistant to PUVA-induced apoptosis compared to wild-type mice. These results indicate that PUVA treatment induces apoptosis in mouse epidermal cells in vitro and in vivo and that p53 and Fas/Fas ligand interactions are required for this process, at least in vivo. This implies that similar mechanisms may be involved in the elimination of psoriatic keratinocytes from human skin following PUVA therapy.
Assuntos
Apoptose/fisiologia , Epiderme/efeitos da radiação , Glicoproteínas de Membrana/metabolismo , Metoxaleno/farmacologia , Proteína Supressora de Tumor p53/metabolismo , Raios Ultravioleta , Transporte Ativo do Núcleo Celular/efeitos dos fármacos , Transporte Ativo do Núcleo Celular/efeitos da radiação , Animais , Animais Geneticamente Modificados , Caspase 3 , Caspases/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Células Cultivadas , Inibidor de Quinase Dependente de Ciclina p21 , Ciclinas/biossíntese , Ativação Enzimática , Epiderme/efeitos dos fármacos , Epiderme/fisiologia , Proteína Ligante Fas , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos BALB C , Receptor fas/genética , Receptor fas/metabolismoRESUMO
The ultraviolet radiation present in sunlight is the primary cause of nonmelanoma skin cancer and has been implicated in the development of cutaneous malignant melanoma. In addition, ultraviolet is immune suppressive and the suppression induced by ultraviolet radiation has been identified as a risk factor for skin cancer induction. Ultraviolet also suppresses the immune response to infectious agents. In most experimental models, ultraviolet is applied to immunologically naive animals prior to immunization. Of equal concern, however, is the ability of sunlight to suppress established immune reactions, such as the recall reaction in humans, which protects against microbial infections. Here we demonstrate that solar-simulated ultraviolet radiation, applied after immunization, suppresses immunologic memory and the elicitation of delayed-type hypersensitivity. Further, we found that wavelengths in the ultraviolet A region of the solar spectrum were critical for inducing immune suppression. Ultraviolet A (320-400 nm) radiation was as effective as solar-simulated ultraviolet A + B (290-400 nm) in suppressing the elicitation of an established immune response. Irradiation with ultraviolet AI (340-400 nm) had no effect. Supporting a critical role for ultraviolet A in ultraviolet-induced immune suppression was the observation that applying a sunscreen that contained an ultraviolet B only filter had no protective effect, whereas, a sunscreen containing both ultraviolet A and ultraviolet B filters totally blocked ultraviolet-induced immune suppression. These data suggest that sunlight may depress the protective effect of prior vaccination. In addition, the observation that ultraviolet A is immunosuppressive indicates the need for ultraviolet A protection when designing sun protection strategies.
