RESUMEN
Irradiation causes DNA damage and induces neoplastic transformation. In response to irradiation, cells induce genes or activate proteins that protect themselves from the external insult. Nuclear factor kappaB (NFkappaB) activates transcription of target genes and plays important roles in inflammation. We studied the mechanism(s) for activation of NFkappaB by irradiation in human monocytic cells THP-1. Gel mobility shift assays showed that irradiation stimulated the NFkappaB-DNA binding activity of nuclear extracts from these cells. Western blot analysis using polyclonal antibody against phosphorylated IkappaB protein showed that irradiation increased the levels of phosphorylated IkappaB. The production of tumor necrosis factor alpha (TNFalpha) was stimulated by irradiation in these cells. Treatment with exogenously added TNFalpha also stimulated the NFkappaB binding activity with concomitant degradation of IkappaB. Further study found that the activation of NFkappaB by irradiation was inhibited by a neutralizing anti-TNFalpha antibody. Macrophages from TNFalpha-deficient mice were also defective in the irradiation-induced activation of NFkappaB. These results indicate that endogenous production of TNFalpha in macrophages/monocytes is required for NFkappaB activation by irradiation. Our data also suggest that TNFalpha in monocytes/macrophages exposed to irradiation is involved in signal transduction network initiation.
Asunto(s)
Regulación de la Expresión Génica/efectos de la radiación , Monocitos/metabolismo , Monocitos/efectos de la radiación , FN-kappa B/metabolismo , Factor de Necrosis Tumoral alfa/biosíntesis , Animales , Línea Celular Tumoral , ADN/metabolismo , Fragmentación del ADN/efectos de la radiación , Humanos , Proteínas I-kappa B/metabolismo , Ratones , Ratones Noqueados , Fosforilación , Procesamiento Proteico-Postraduccional , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factor de Necrosis Tumoral alfa/deficiencia , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
The heat shock (HS) response is a universal response activated after exposure to various stimuli. The major HS protein (HSP) is the 72 kDa HSP70 with strong homology in different eukaryotic species. We demonstrate that HS treatment of mice leads to a strong induction of HSP70 in several organs and confers significant protection against lethality induced by tumor necrosis factor (TNF). HS prevents high production of interleukin-6 and nitric oxide and reduces severe damage and apoptosis of the enterocytes in the bowel. Mice deficient in the inducible hsp70.1 gene were no longer protected by HS treatment. We show that HS can be applied successfully in an antitumor protocol based on TNF and interferon-gamma, leading to a significant inhibition of lethality but not to a reduction of antitumoral capacity.