RESUMO
OBJECTIVE: Endothelial cell activation by tumor necrosis factor (TNF) and associated leukocyte infiltration are hallmarks of vasculitis. The aim of this study was to investigate the potential role of the cellular stress-associated endothelial X-box binding protein 1 (XBP-1) transcription factor in TNF-induced endothelial cell inflammation and vasculitis. METHODS: Mice with an endothelial cell-specific XBP-1 deficiency were used in a modified local Shwartzman reaction (LSR) model of TNF-induced small vessel vasculitis. To address the contribution of XBP-1 to the TNF-mediated inflammatory response in endothelial cells, we examined the activation of XBP-1 expression by TNF as well as the effect of XBP-1 knockdown in endothelial cells on TNF-induced signaling, proinflammatory gene expression, and leukocyte-endothelial cell adhesion. RESULTS: The active spliced form of XBP-1 in endothelial cells was triggered by TNF. In addition, endothelial XBP-1 contributed to the sustained TNF-triggered NF-κB-dependent transcriptional activation of proinflammatory molecules, which was associated with leukocyte-endothelial cell adhesion. In the LSR model, endothelial cell-specific XBP-1-deficient mice displayed significantly less vascular damage, accompanied by reduced perivascular neutrophil infiltration, as compared with wild-type mice. CONCLUSION: Endothelial XBP-1 is activated by TNF and regulates leukocyte-endothelial cell adhesion in vitro as well as neutrophil infiltration and vascular damage in murine vasculitis.
Assuntos
Adesão Celular/genética , Proteínas de Ligação a DNA/genética , Células Endoteliais/metabolismo , NF-kappa B/metabolismo , Infiltração de Neutrófilos/genética , Fenômeno de Shwartzman/genética , Fatores de Transcrição/genética , Vasculite/genética , Animais , Adesão Celular/efeitos dos fármacos , Adesão Celular/imunologia , Proteínas de Ligação a DNA/imunologia , Modelos Animais de Doenças , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/imunologia , Leucócitos/efeitos dos fármacos , Leucócitos/imunologia , Leucócitos/metabolismo , Camundongos , Camundongos Knockout , NF-kappa B/efeitos dos fármacos , NF-kappa B/imunologia , Infiltração de Neutrófilos/efeitos dos fármacos , Infiltração de Neutrófilos/imunologia , Fatores de Transcrição de Fator Regulador X , Fenômeno de Shwartzman/imunologia , Fatores de Transcrição/imunologia , Fator de Necrose Tumoral alfa/farmacologia , Vasculite/imunologia , Proteína 1 de Ligação a X-BoxRESUMO
The signals linking neutrophil opsonic receptors, FcgammaRs and complement receptor 3 (Mac-1) to cellular cytotoxic responses are poorly understood. Furthermore, because a deficiency in activating FcgammaRs reduces both IgG-mediated neutrophil recruitment and tissue injury, the role of FcgammaRs specifically in mediating neutrophil cytotoxicity in vivo remains unclear. In this study, we demonstrate that neutrophil Vav 1 and 3, guanine exchange factors for Rac GTPases, are required for IgG/FcgammaR-mediated hemorrhage and edema in the reverse passive Arthus in the lung and skin. Rac GTPases are also required for development of the reverse passive Arthus reaction. A deficiency in Vav 1 and 3 does not affect neutrophil accumulation at the site of immune complex deposition, thus uncoupling neutrophil recruitment and tissue injury. Surprisingly, Vav and Rac proteins are dispensable for the development of the local Shwartzman reaction in vivo and phagocytosis of complement-opsonized RBC in vitro, processes strictly dependent on Mac-1 and complement C3. Thus, FcgammaR signaling through the Vav and Rac proteins in neutrophils is critical for stimulating immune complex disease while Vav- and Rac-independent pathways promote Mac-1/complement C3-dependent functions.
Assuntos
Complemento C3/imunologia , Imunoglobulina G/imunologia , Infiltração de Neutrófilos/imunologia , Neutrófilos/imunologia , Proteínas Proto-Oncogênicas c-vav/imunologia , Transdução de Sinais/imunologia , Animais , Complexo Antígeno-Anticorpo/imunologia , Reação de Arthus/genética , Reação de Arthus/imunologia , Complemento C3/genética , Edema/genética , Edema/imunologia , Hemorragia/genética , Hemorragia/imunologia , Imunoglobulina G/genética , Pulmão/imunologia , Antígeno de Macrófago 1/genética , Antígeno de Macrófago 1/imunologia , Camundongos , Camundongos Knockout , Infiltração de Neutrófilos/genética , Fagocitose/imunologia , Proteínas Proto-Oncogênicas c-vav/genética , Receptores de IgG/genética , Receptores de IgG/imunologia , Fenômeno de Shwartzman/genética , Fenômeno de Shwartzman/imunologia , Pele/imunologia , Proteínas rac de Ligação ao GTP/genética , Proteínas rac de Ligação ao GTP/imunologiaRESUMO
Mouse soluble CD14 truncated at amino acid 71 (N71) contains the lipopolysaccharide (LPS)-binding sequence. Transgenic mice carrying alpha1-antitrypsin (AT) promoter-N71 fusion genes, designated AT363-1 and AT363-2, were produced. These mice constitutively produced elevated levels of N71. The concentration of LPS in sera after intraperitoneal LPS injection was lower in AT363-1 mice than in nontransgenic mice. The expression of N71 mRNA was enhanced by subcutaneous turpentine oil injection. The levels of serum LPS and tumor necrosis factor-alpha (TNF-alpha) after intraperitoneal LPS injections were lower in AT363-1 mice than in nontransgenic mice. Cell surface TNF-alpha and CD14 expression in exudate peritoneal macrophages prepared by intraperitoneal injection of proteose peptone and then LPS were higher in AT363-1 mice than in nontransgenic mice. Neutrophil infiltration in the liver after induction of the generalized Shwartzman reaction was lower in AT363-1 mice than in nontransgenic mice. Lethality of the Shwartzman reaction was significantly lower in AT363-1 than in nontransgenic mice. These findings suggest that the endotoxin-binding protein (N71) from CD14 prevents endotoxin-mediated toxic shock.