RESUMEN
Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) exerts a potent cytotoxic activity especially against many tumor cell types such as transformed keratinocytes. The specific role of the different TRAIL receptors in this process, however, is unknown. In this report we examine the role the TRAIL receptors play in both the apoptotic and nonapoptotic responses of HaCaT keratinocytes to leucine zipper TRAIL (LZ-TRAIL). By employing receptor-specific blocking antibodies we demonstrate that TRAIL receptor 1 plays the primary role in mediating caspase activation and apoptosis in HaCaT cells. Furthermore, we show that this receptor mainly mediates nuclear factor kappaB activation and expression of the pro-inflammatory cytokine interleukin-8 and that nuclear factor kappaB activation is critically required for the induction of pro-inflammatory cytokines in response to LZ-TRAIL. Taken together, our data suggest that beside its potent pro-apoptotic role, LZ-TRAIL leads to pro-inflammatory responses that are mainly mediated by TRAIL receptor 1 in HaCaT keratinocytes.
Asunto(s)
Apoptosis/inmunología , Queratinocitos/citología , Glicoproteínas de Membrana/metabolismo , Receptores del Factor de Necrosis Tumoral/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Proteínas Reguladoras de la Apoptosis , Línea Celular Transformada , Quimiotaxis/fisiología , Dermatitis/inmunología , Dermatitis/metabolismo , Dermatitis/fisiopatología , Regulación de la Expresión Génica , Humanos , Proteína Antagonista del Receptor de Interleucina 1 , Interleucina-8/genética , Interleucina-8/metabolismo , Queratinocitos/inmunología , Queratinocitos/metabolismo , Leucina Zippers/fisiología , Glicoproteínas de Membrana/genética , FN-kappa B/metabolismo , Receptores del Ligando Inductor de Apoptosis Relacionado con TNF , Sialoglicoproteínas/genética , Transducción de Señal/fisiología , Ligando Inductor de Apoptosis Relacionado con TNF , Activación Transcripcional , Factor de Necrosis Tumoral alfa/genéticaRESUMEN
Tumor necrosis factor (TNF)-alpha-induced phosphorylation of the IkappaB proteins by the IkappaB kinase (IKK) complex containing IKK-2 and subsequent degradation of the IkappaB proteins are prerequisites for NF-kappaB activation, resulting in the stimulation of a variety of pro-inflammatory target genes. The C-C chemokine eotaxin-1 is a potent chemoattractant for eosinophils and Th2 lymphocytes, may play an important role in the pathogenesis of atopic dermatitis, and acts via binding to its receptor CCR3. To investigate the role of NF-kappaB signaling in the regulation of these genes, we stably expressed a transdominant mutant of IkappaBalpha and a constitutively active mutant of IKK-2 in mouse NIH3T3 fibroblasts. The transdominant IkappaBalpha mutant completely inhibited TNF-alpha-mediated induction of both eotaxin-1 and CCR3, whereas expression of constitutively active IKK-2 was sufficient to drive almost full expression of these two genes in the absence of TNF-alpha. Moreover, we observed elevated expression levels of CCR3 and eotaxin-1 protein levels in the skin of IkappaBalpha-deficient mice characterized by a widespread dermatitis. Finally, using dermal fibroblasts derived from IkappaBalpha-deficient mice, we observed elevated basal expression, enhanced inducibility by TNF-alpha, and attenuated down-regulation upon TNF-alpha withdrawal of both CCR3 and eotaxin-1 mRNA levels. These results demonstrate that the IKK-2/IkappaBalpha/NF-kappaB pathway plays a critical role for CCR3 and eotaxin-1 expression in fibroblasts and suggests a critical link to the pathogenesis of atopic dermatitis.