Assuntos
Proteínas de Ligação a DNA/metabolismo , Endotélio Vascular/imunologia , Proteínas de Homeodomínio , NF-kappa B/genética , Proteínas Nucleares , Proteínas/fisiologia , Proteínas Proto-Oncogênicas/fisiologia , Proteínas Repressoras , Proteínas de Saccharomyces cerevisiae , Fatores de Transcrição/metabolismo , Animais , Bovinos , Proteínas de Ligação a DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Endotélio Vascular/citologia , Regulação da Expressão Gênica , Luciferases/genética , Luciferases/metabolismo , Antígenos de Histocompatibilidade Menor , NF-kappa B/efeitos dos fármacos , Fatores de Transcrição NFATC , Proteínas/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/fisiologia , Proteína de Replicação C , Fatores de Transcrição/efeitos dos fármacos , Fatores de Transcrição/genética , Transfecção , Proteína bcl-XRESUMO
A1 is an anti-apoptotic bcl gene that is expressed in endothelial cells (EC) in response to pro-inflammatory stimuli. We show that in addition to protecting EC from apoptosis, A1 inhibits EC activation and its associated expression of pro-inflammatory proteins by inhibiting the transcription factor nuclear factor (NF)-kappaB. This new anti-inflammatory function gives a broader dimension to the protective role of A1 in EC. We also show that activation of NF-kappaB is essential for the expression of A1. Taken together, our data suggest that A1 downregulates not only the pro-apoptotic and pro-inflammatory response, but also its own expression, thus restoring a quiescent phenotype to EC.
Assuntos
Proteínas de Ligação a DNA/genética , Endotélio Vascular/fisiologia , Regulação da Expressão Gênica , Proteínas de Homeodomínio , NF-kappa B/genética , Proteínas Proto-Oncogênicas c-bcl-2 , Proteínas Repressoras , Proteínas de Saccharomyces cerevisiae , Apoptose/fisiologia , Células Cultivadas , Humanos , Inflamação , Antígenos de Histocompatibilidade Menor , Proteína de Replicação CAssuntos
Proteínas I-kappa B , Músculo Liso Vascular/fisiologia , Proteínas/fisiologia , Animais , Aorta , Células Cultivadas , Cricetinae , Citocinas/farmacologia , Proteínas de Ligação a DNA/fisiologia , Transplante de Coração/imunologia , Transplante de Coração/fisiologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Músculo Liso Vascular/citologia , Inibidor de NF-kappaB alfa , NF-kappa B/antagonistas & inibidores , Proteínas Nucleares , Proteínas/genética , Ratos , Proteínas Recombinantes/biossíntese , Transfecção , Transplante Heterólogo/imunologia , Transplante Heterólogo/fisiologia , Proteína 3 Induzida por Fator de Necrose Tumoral alfa , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
To maintain the integrity of the vascular barrier, endothelial cells (EC) are resistant to cell death. The molecular basis of this resistance may be explained by the function of antiapoptotic genes such as bcl family members. Overexpression of Bcl-2 or Bcl-XL protects EC from tumor necrosis factor (TNF)-mediated apoptosis. In addition, Bcl-2 or Bcl-XL inhibits activation of NF-kappaB and thus upregulation of proinflammatory genes. Bcl-2-mediated inhibition of NF-kappaB in EC occurs upstream of IkappaBalpha degradation without affecting p65-mediated transactivation. Overexpression of bcl genes in EC does not affect other transcription factors. Using deletion mutants of Bcl-2, the NF-kappaB inhibitory function of Bcl-2 was mapped to bcl homology domains BH2 and BH4, whereas all BH domains were required for the antiapoptotic function. These data suggest that Bcl-2 and Bcl-XL belong to a cytoprotective response that counteracts proapoptotic and proinflammatory insults and restores the physiological anti-inflammatory phenotype to the EC. By inhibiting NF-kappaB without sensitizing the cells (as with IkappaBalpha) to TNF-mediated apoptosis, Bcl-2 and Bcl-XL are prime candidates for genetic engineering of EC in pathological conditions where EC loss and unfettered activation are undesirable.
Assuntos
Apoptose , Proteínas I-kappa B , NF-kappa B/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/biossíntese , Animais , Linhagem Celular Transformada , Células Cultivadas , Cicloeximida/farmacologia , Proteínas de Ligação a DNA/metabolismo , Endotélio Vascular/citologia , Humanos , Camundongos , Inibidor de NF-kappaB alfa , Proteínas Proto-Oncogênicas c-bcl-2/genética , Fator de Transcrição Sp1/metabolismo , Fator de Transcrição RelA , Ativação Transcricional , Fator de Necrose Tumoral alfa/farmacologia , Proteína bcl-XRESUMO
Expression of the NF-kappaB-dependent gene A20 in endothelial cells (EC) inhibits tumor necrosis factor (TNF)-mediated apoptosis in the presence of cycloheximide and acts upstream of IkappaBalpha degradation to block activation of NF-kappaB. Although inhibition of NF-kappaB by IkappaBalpha renders cells susceptible to TNF-induced apoptosis, we show that when A20 and IkappaBalpha are coexpressed, the effect of A20 predominates in that EC are rescued from TNF-mediated apoptosis. These findings place A20 in the category of "protective" genes that are induced in response to inflammatory stimuli to protect EC from unfettered activation and from undergoing apoptosis even when NF-kappaB is blocked. From a therapeutic perspective, genetic engineering of EC to express an NF-kappaB inhibitor such as A20 offers the mean of achieving an anti-inflammatory effect without sensitizing the cells to TNF-mediated apoptosis.
