RESUMO
BACKGROUND: Tumor necrosis factor-alpha (TNF-α) is a pro-inflammatory cytokine today identified as a key mediator of several chronic inflammatory diseases. TNF-α, initially synthesized as a membrane-anchored precursor (pro-TNF-α), is processed by proteolytic cleavage to generate the secreted mature form. TNF-α converting enzyme (TACE) is currently the first and single protease described as responsible for the inducible release of soluble TNF-α. METHODOLOGY/PRINCIPAL FINDINGS: Here, we demonstrated the presence on THP-1 cells as on human monocytes of a constitutive proteolytical activity able to cleave pro-TNF-α. Revelation of the cell surface TACE protein expression confirmed that the observed catalytic activity is due to TACE. However, further studies using effective and innovative TNF-α inhibitors, as well as a highly selective TACE inhibitor, support the presence of a catalytically different sheddase activity on LPS activated THP-1 cells. It appears that this catalytically different TACE protease activity might have a significant contribution to TNF-α release in LPS activated THP-1 cells, by contrast to human monocytes where the TACE activity remains catalytically unchanged even after LPS activation. CONCLUSIONS/SIGNIFICANCE: On the surface of LPS activated THP-1 cells we identified a releasing TNF-α activity, catalytically different from the sheddase activity observed on human monocytes from healthy donors. This catalytically-modified TACE activity is different from the constitutive shedding activity and appears only upon stimulation by LPS.
Assuntos
Proteínas ADAM/metabolismo , Lipopolissacarídeos/metabolismo , Monócitos/citologia , Fator de Necrose Tumoral alfa/metabolismo , Proteína ADAM17 , Animais , Benzoquinonas/farmacologia , Linhagem Celular , Membrana Celular/metabolismo , Doença Crônica , Ensaio de Imunoadsorção Enzimática/métodos , Citometria de Fluxo/métodos , Humanos , Ácidos Hidroxâmicos/farmacologia , Inflamação , Concentração Inibidora 50 , Camundongos , Microscopia Confocal/métodos , Triterpenos Pentacíclicos , Peptídeo Hidrolases/metabolismo , Proteínas Recombinantes/metabolismo , Sulfonamidas/farmacologia , Triterpenos/farmacologiaRESUMO
We synthesized 3-O-methylviridicatin and several analogues of this fungal metabolite. We showed that replacement of the methoxy moiety by a thiomethyl enhanced dramatically its ability to inhibit TNF-alpha secretion. These results strongly suggest that 4-phenyl-3-methylthioquinolinone may provide the basis for the development of new anti-inflammatory agents.
