Fractalkine (CX3CL1) stimulated by nuclear factor kappaB (NF-kappaB)-dependent inflammatory signals induces aortic smooth muscle cell proliferation through an autocrine pathway

Biochem J. 2003 Jul 15;373(Pt 2):547-58. doi: 10.1042/BJ20030207.

Abstract

Fractalkine (also known as CX3CL1), a CX3C chemokine, activates and attracts monocytes/macrophages to the site of injury/inflammation. It binds to CX3C receptor 1 (CX3CR1), a pertussis toxin-sensitive G-protein-coupled receptor. In smooth muscle cells (SMCs), fractalkine is induced by proinflammatory cytokines [tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)], which may mediate monocyte adhesion to SMCs. However, the mechanisms underlying its induction are unknown. In addition, it is unlear whether SMCs express CX3CR1. TNF-alpha activated nuclear factor kappaB (NF-kappaB) and induced fractalkine and CX3CR1 expression in a time-dependent manner in rat aortic SMCs. Transient transfections with dominant-negative (dn) inhibitory kappaB (IkappaB)-alpha, dnIkappaB-beta, dnIkappaB kinase (IKK)-gamma, kinase-dead (kd) NF-kappaB-inducing kinase (NIK) and kdIKK-beta, or pretreatment with wortmannin, Akt inhibitor, pyrrolidinecarbodithioc acid ammonium salt ('PDTC') or MG-132, significantly attenuated TNF-alpha-induced fractalkine and CX3CR1 expression. Furthermore, expression of dn TNF-alpha-receptor-associated factor 2 (TRAF2), but not dnTRAF6, inhibited TNF-alpha signal transduction. Pretreatment with pertussis toxin or neutralizing anti-CX3CR1 antibodies attenuated TNF-alpha-induced fractalkine expression, indicating that fractalkine autoregulation plays a role in TNF-alpha-induced sustained fractalkine expression. Fractalkine induced its own expression, via pertussis toxin-sensitive G-proteins, phosphoinositide 3-kinase (PI 3-kinase), phosphoinositide-dependent kinase 1 (PDK1), Akt, NIK, IKK and NF-kappaB activation, and induced SMC cell-cell adhesion and cellular proliferation. Taken together, our results demonstrate that TNF-alpha induces the expression of fractalkine and CX3CR1 in rat aortic SMCs and that this induction is mediated by NF-kappaB activation. We also show that fractalkine induces its own expression, which is mediated by the PI 3-kinase/PDK1/Akt/NIK/IKK/NF-kappaB signalling pathway. More importantly, fractalkine increased cell-cell adhesion and aortic SMC proliferation, indicating a role in initiation and progression of atherosclerotic vascular disease.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Androstadienes / pharmacology
  • Animals
  • Antineoplastic Agents / pharmacology
  • Aorta / cytology
  • Autocrine Communication
  • CX3C Chemokine Receptor 1
  • Cell Division / drug effects
  • Cells, Cultured
  • Chemokine CX3CL1
  • Chemokines, CX3C / metabolism*
  • Electrophoretic Mobility Shift Assay
  • Enzyme Inhibitors / pharmacology
  • GTP-Binding Proteins / metabolism
  • I-kappa B Proteins / metabolism
  • Luciferases / metabolism
  • Membrane Proteins / metabolism*
  • Muscle, Smooth, Vascular / cytology*
  • Muscle, Smooth, Vascular / drug effects
  • NF-kappa B / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Proline / analogs & derivatives*
  • Proline / pharmacology
  • Protein-Serine-Threonine Kinases*
  • Proteins / metabolism
  • Proto-Oncogene Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Cytokine / metabolism
  • Receptors, HIV / metabolism
  • TNF Receptor-Associated Factor 2
  • TNF Receptor-Associated Factor 6
  • Thiocarbamates / pharmacology
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology*
  • Wortmannin

Substances

  • Androstadienes
  • Antineoplastic Agents
  • CX3C Chemokine Receptor 1
  • Chemokine CX3CL1
  • Chemokines, CX3C
  • Cx3cl1 protein, rat
  • Enzyme Inhibitors
  • I-kappa B Proteins
  • Membrane Proteins
  • NF-kappa B
  • Phosphoinositide-3 Kinase Inhibitors
  • Proteins
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Receptors, Cytokine
  • Receptors, HIV
  • TNF Receptor-Associated Factor 2
  • TNF Receptor-Associated Factor 6
  • Thiocarbamates
  • Tumor Necrosis Factor-alpha
  • prolinedithiocarbamate
  • Proline
  • Luciferases
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • GTP-Binding Proteins
  • Wortmannin