RESUMO
OBJECTIVE: Extracellular high mobility group box chromosomal protein 1 (HMGB-1) is a recently identified, endogenous, potent tumor necrosis factor- and interleukin-1 (IL-1)-inducing protein detectable in inflamed synovia in both human and experimental disease. In the present study, we examined clinical effects in collagen-induced arthritis (CIA) using therapeutic administration of neutralizing HMGB-1 antibodies or truncated HMGB-1-derived A-box protein, a specific, competitive antagonist of HMGB-1. METHODS: CIA was induced in DBA/1j mice or dark agouti rats, and animals were examined daily for signs of arthritis. Treatment with polyclonal anti-HMGB-1 antibodies or the A-box protein was initiated at the onset of disease and was administered intraperitoneally twice daily for 7 days. Animals were killed 8 days after initiation of therapy, and immunohistochemical analysis of synovial tissue specimens was performed. RESULTS: Systemic administration of anti-HMGB-1 antibodies or A-box protein significantly reduced the mean arthritis score, the disease-induced weight loss, and the histologic severity of arthritis. Beneficial effects were observed in both mice and rats. Immunohistochemical analysis revealed pronounced synovial IL-1beta expression and articular cartilage destruction in vehicle-treated mice. Both these features were significantly less manifested in animals treated with anti-HMGB-1 antibodies or A-box protein. CONCLUSION: Counteracting extracellular HMGB-1 with either neutralizing antibodies or a specific HMGB-1 antagonist may offer a new method for the successful treatment of arthritis. Inflammation and tissue destruction were suppressed in CIA after HMGB-1 blockade.
Assuntos
Artrite Experimental/tratamento farmacológico , Proteína HMGB1/farmacologia , Animais , Anticorpos/farmacologia , Artrite Experimental/patologia , Cartilagem Articular/patologia , Espaço Extracelular , Feminino , Proteína HMGB1/imunologia , Masculino , Camundongos , Camundongos Endogâmicos DBA , Ratos , Ratos Endogâmicos , Membrana Sinovial/patologiaRESUMO
Lipopolysaccharide (LPS) is lethal to animals because it activates cytokine release, causing septic shock and tissue injury. Early proinflammatory cytokines (e.g., tumor necrosis factor [TNF] and interleukin [IL]-1) released within the first few hours of endotoxemia stimulate mediator cascades that persist for days and can lead to death. High mobility group 1 protein (HMG-1), a ubiquitous DNA-binding protein, was recently identified as a "late" mediator of endotoxin lethality. Anti-HMG-1 antibodies neutralized the delayed increase in serum HMG-1, and protected against endotoxin lethality, even when passive immunization was delayed until after the early cytokine response. Here we examined whether HMG-1 might stimulate cytokine synthesis in human peripheral blood mononuclear cell cultures. Addition of purified recombinant HMG-1 to human monocyte cultures significantly stimulated the release of TNF, IL-1alpha, IL-1beta, IL-1RA, IL-6, IL-8, macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta; but not IL-10 or IL-12. HMG-1 concentrations that activated monocytes were within the pathological range previously observed in endotoxemic animals, and in serum obtained from septic patients. HMG-1 failed to stimulate cytokine release in lymphocytes, indicating that cellular stimulation was specific. Cytokine release after HMG-1 stimulation was delayed and biphasic compared with LPS stimulation. Computer-assisted image analysis demonstrated that peak intensity of HMG-1-induced cellular TNF staining was comparable to that observed after maximal stimulation with LPS. Administration of HMG-1 to Balb/c mice significantly increased serum TNF levels in vivo. Together, these results indicate that, like other cytokine mediators of endotoxin lethality (e.g., TNF and IL-1), extracellular HMG-1 is a regulator of monocyte proinflammatory cytokine synthesis.