RESUMO
The receptor for advanced glycation end products (RAGE) contributes to the inflammatory response in many acute and chronic diseases. In this context, RAGE has been identified as a ligand for the beta(2)-integrin Mac-1 under static in vitro conditions. Because intercellular adhesion molecule (ICAM)-1 also binds beta(2)-integrins, we studied RAGE(-/-), Icam1(-/-), and RAGE(-/-) Icam1(-/-) mice to define the relative contribution of each ligand for leukocyte adhesion in vivo. We show that trauma-induced leukocyte adhesion in cremaster muscle venules is strongly dependent on RAGE and ICAM-1 acting together in an overlapping fashion. Additional in vivo experiments in chimeric mice lacking endothelium-expressed RAGE and ICAM-1 located the adhesion defect to the endothelial compartment. Using microflow chambers coated with P-selectin, CXCL1, and soluble RAGE (sRAGE) demonstrated that sRAGE supports leukocyte adhesion under flow conditions in a Mac-1- but not LFA-1-dependent fashion. A static adhesion assay revealed that wild-type and RAGE(-/-) neutrophil adhesion and spreading were similar on immobilized sRAGE or fibrinogen. These observations indicate a crucial role of endothelium-expressed RAGE as Mac-1 ligand and uncover RAGE and ICAM-1 as a new set of functionally linked adhesion molecules, which closely cooperate in mediating leukocyte adhesion during the acute trauma-induced inflammatory response in vivo.
Assuntos
Quimiotaxia de Leucócito/fisiologia , Endotélio Vascular/metabolismo , Molécula 1 de Adesão Intercelular/fisiologia , Proteínas Quinases Ativadas por Mitógeno/fisiologia , Músculo Esquelético/irrigação sanguínea , Vasculite/imunologia , Doença Aguda , Animais , Adesão Celular , Forma Celular , Quimiotaxia de Leucócito/efeitos dos fármacos , Humanos , Leucotrieno B4/farmacologia , Ligantes , Antígeno de Macrófago 1/metabolismo , Camundongos , Camundongos Knockout , Proteínas Quinases Ativadas por Mitógeno/deficiência , Músculo Esquelético/lesões , Músculo Esquelético/patologia , Neutrófilos/patologia , Quimera por Radiação , Proteínas Recombinantes de Fusão/fisiologia , Fator de Necrose Tumoral alfa/farmacologia , Vasculite/etiologia , Vênulas/patologiaRESUMO
BACKGROUND: The receptor for advanced glycation endproducts, RAGE, is involved in the pathogenesis of many inflammatory conditions, which is mostly related to its strong activation of NF-κB but also due to its function as ligand for the ß2-integrin Mac-1. To further dissect the stimulus-dependent role of RAGE on leukocyte recruitment during inflammation, we investigated ß2-integrin-dependent leukocyte adhesion in RAGE-/- and Icam1-/- mice in different cremaster muscle models of inflammation using intravital microscopy. RESULTS: We demonstrate that RAGE, but not ICAM-1 substantially contributes to N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced leukocyte adhesion in TNF-α-pretreated cremaster muscle venules in a Mac-1-dependent manner. In contrast, fMLP-stimulated leukocyte adhesion in unstimulated cremaster muscle venules is independent of RAGE, but dependent on ICAM-1 and its interaction with LFA-1. Furthermore, chemokine CXCL1-stimulated leukocyte adhesion in surgically prepared cremaster muscle venules was independent of RAGE but strongly dependent on ICAM-1 and LFA-1 suggesting a differential and stimulus-dependent regulation of leukocyte adhesion during inflammation in vivo. CONCLUSION: Our results demonstrate that RAGE and ICAM-1 differentially regulate leukocyte adhesion in vivo in a stimulus-dependent manner.