title: The chemorepellent Slit3 promotes monocyte migration.
abstract: Directional migration is an essential step for monocytes to infiltrate sites of inflammation, a process primarily regulated by chemoattractants. Slits are large matrix proteins that are secreted by endothelial cells; they were reported to inhibit the chemoattractant-induced migration of different cell types, including leukocytes. The aim of this study was to determine the effect of Slit3 on primary monocyte migration and to address the underlying mechanisms. We show that Roundabout (Robo)1, one of the Robo receptors that recognize Slit3, is the only Robo homolog expressed by CD14(+) monocytes. Interestingly, we found that stimulation with Slit3 increased the spontaneous and chemoattractant-induced migration of primary monocytes in vitro and increased the myeloid cell recruitment during peritoneal inflammation in vivo. In addition, Slit3 did not seem to act as a chemoattractant itself; it promoted directed migration triggered by chemoattractants, such as CXCL12, by inducing a chemokinetic effect. We further show that Slit3 prevented monocyte spreading and induced rounding of spread monocytes without affecting monocyte adhesion. Stimulation with Slit3 was not associated with changes in the levels of phosphorylated p38, p42/p44, or Src, known regulators of monocyte migration, but it directly acts on molecular pathways involved in basal leukocyte migration by activating RhoA. These findings show an unexpected response of monocytes to Slit3 and add insights into the possible role of Slit proteins during inflammatory cell recruitment.
authors.affiliation: Department of Molecular Cell Biology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Sacha B
authors.initials: SB
authors.lastname: Geutskens
authors.forename: Peter L
authors.initials: PL
authors.lastname: Hordijk
authors.forename: Paula B
authors.initials: PB
authors.lastname: van Hennik
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000276:immunology*; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000276:immunology / Q000378:metabolism; D042783:Endothelial Cells / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D018950:Lipopolysaccharide Receptors; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000276:immunology / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism; D011971:Receptors, Immunologic / Q000276:immunology / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000276:immunology / Q000378:metabolism; D000097905:Roundabout Proteins
chemical_list: D054377:Chemokine CXCL12; D018950:Lipopolysaccharide Receptors; D008565:Membrane Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D000097905:Roundabout Proteins; C515255:CXCL12 protein, human; C515256:Cxcl12 protein, mouse; C498990:SLIT3 protein, human; C432251:Slit3 protein, mouse; C066737:RHOA protein, human; C526380:RhoA protein, mouse