RESUMO
Drugs that target tumor necrosis factor-alpha (TNF) are particularly important in the treatment of severe inflammatory progression in rheumatoid arthritis, Crohn's disease and psoriasis. Despite the central role of the TNF/TNF receptor (TNFR) in various disease states, there is a paucity of information concerning TNFR2 signaling. In this study, we have developed a simple and highly sensitive cell-death based assay system for analyzing TNFR2-mediated bioactivity that can be used to screen for TNFR2-selective drugs. Using a lentiviral vector, a chimeric receptor was engineered from the extracellular and transmembrane domain of human TNFR2 and the intracellular domain of mouse Fas and the recombinant protein was then expressed in TNFR1(-/-)R2(-/-) mouse preadipocytes. Our results demonstrate that this chimeric receptor is capable of inducing apoptosis by transmembrane- as well as soluble-TNF stimuli. Moreover, we found that our bioassay based on cell death phenotype had an approximately 80-fold higher sensitivity over existing bioassays. We believe our assay system will be an invaluable research tool for studying TNFR2 and for screening TNFR2-targeted drugs.
Assuntos
Adipócitos/metabolismo , Apoptose , Bioensaio , Avaliação Pré-Clínica de Medicamentos/métodos , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Receptor fas/metabolismo , Animais , Anti-Inflamatórios/farmacologia , Apoptose/efeitos dos fármacos , Membrana Celular/metabolismo , Sobrevivência Celular , Células Cultivadas , Proteína de Domínio de Morte Associada a Fas/metabolismo , Vetores Genéticos , Humanos , Lentivirus/genética , Camundongos , Estrutura Terciária de Proteína , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo II do Fator de Necrose Tumoral/efeitos dos fármacos , Receptores Tipo II do Fator de Necrose Tumoral/genética , Proteínas Recombinantes de Fusão/metabolismo , Transfecção , Receptor fas/genéticaRESUMO
BACKGROUND: Carbon dioxide-rich water bathing has the effect of vasodilatation, whereas it remains undetermined whether this therapy exerts an angiogenic action associated with new vessel formation. METHODS AND RESULTS: Unilateral hindlimb ischemia was induced by resecting the femoral arteries of C57BL/J mice. Lower limbs were immersed in CO2-enriched water (CO2 concentration, 1000 to 1200 mg/L) or freshwater (control) at 37 degrees C for 10 minutes once a day. Laser Doppler imaging revealed increased blood perfusion in ischemic limbs of CO2 bathing (38% increase at day 28, P<0.001), whereas N(G)-nitro-L-arginine methyl ester treatment abolished this effect. Angiography or immunohistochemistry revealed that collateral vessel formation and capillary densities were increased (4.1-fold and 3.7-fold, P<0.001, respectively). Plasma vascular endothelial growth factor (VEGF) levels were elevated at day 14 (18%, P<0.05). VEGF mRNA levels, phosphorylation of NO synthase, and cGMP accumulation in the CO2-bathed hindlimb muscles were increased (2.7-fold, 2.4-fold, and 3.4-fold, respectively) but not in forelimb muscles. The number of circulating Lin-/Flk-1+/CD34- endothelial-lineage progenitor cells was markedly increased by CO2 bathing (24-fold at day 14, P<0.001). The Lin-/Flk-1+/CD34- cells express other endothelial antigens (endoglin and VE-cadherin) and incorporated acetylated LDL. CONCLUSIONS: Our present study demonstrates that CO2 bathing of ischemic hindlimb causes the induction of local VEGF synthesis, resulting in an NO-dependent neocapillary formation associated with mobilization of endothelial progenitor cells.