title: Thrombin-induced expression of endothelial CX3CL1 potentiates monocyte CCL2 production and transendothelial migration.
abstract: CX3CL1 (fractalkine, neurotactin) is the sole CX3C chemokine. It induces monocyte locomotion in its cleaved form, but in its membrane-anchored form, it also acts as an adhesion molecule. The expression of CX3CL1 is up-regulated in endothelial cells by proinflammatory cytokines such as IL-1 or TNF-alpha. Here, we studied the effect of the serine protease thrombin on endothelial CX3CL1 induction and its putative relevance for monocyte function. In HUVEC, thrombin triggered a time- and concentration-dependent expression of CX3CL1 at the mRNA and the protein level as shown by RT-PCR, Western immunoblotting, and flow cytometric analysis. Thrombin induced CX3CL1 by activating protease-activated receptor 1 (PAR1) as demonstrated by the use of PAR1-activating peptide and the PAR1-specific antagonist SCH 79797. The thrombin-induced CX3CL1 expression was NF-kappaB-dependent, as shown by EMSA, ELISA, and by inhibition of the NF-kappaB signaling pathway by the IkappaB kinase inhibitor acety-11-keto-beta-boswellic acid or by transient overexpression of a transdominant-negative form of IkappaBalpha. Upon cocultivation of human monocytes with HUVEC, the thrombin-dependent induction of membrane-anchored CX3CL1 in HUVEC triggered monocyte adhesion and an enhanced release of the MCP-1/CCL2 by monocytes and potentiated the monocyte transendothelial migration. Accordingly, the recombinant extracellular domain of CX3CL1 induced CCL2 release by monocytes. Thus, the thrombin-induced monocyte/endothelial cell cross-talk mediated by increased CX3CL1 expression potentiates the CCL2 chemokine generation that might contribute to the recruitment of monocytes into inflamed areas.
authors.affiliation: Institute of Pharmacology of Natural Products and Clinical Pharmacology, Ulm University, Helmholtzstr. 20, D-89081 Ulm, Germany.
authors.forename: Milan
authors.initials: M
authors.lastname: Popovic
authors.forename: Yves
authors.initials: Y
authors.lastname: Laumonnier
authors.forename: Ladislav
authors.initials: L
authors.lastname: Burysek
authors.forename: Tatiana
authors.initials: T
authors.lastname: Syrovets
authors.forename: Thomas
authors.initials: T
authors.lastname: Simmet
mesh_terms: D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects*; D018932:Chemokine CCL2 / Q000378:metabolism*; D054428:Chemokine CX3CL1 / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis / Q000187:drug effects; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D014471:Umbilical Veins / Q000166:cytology
chemical_list: C111835:CCL2 protein, human; C515538:CX3CL1 protein, human; D018932:Chemokine CCL2; D054428:Chemokine CX3CL1; D016328:NF-kappa B; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D013917:Thrombin