title: Peptidoglycan increases firm adhesion of monocytes under flow conditions and primes monocyte chemotaxis.
abstract: The Toll-like receptor (TLR) 2/nucleotide-binding oligomerization domain ligand peptidoglycan (PG) has been shown to be present in macrophage-rich regions within atherosclerotic lesions, and stimulation of TLR2 promotes atherosclerotic plaque and intima formation in in vivo mouse models. We determined the effect of a PG preparation and Pam(3)Cys-SK(4), a synthetic TLR2 activator, on (1) adhesion molecule expression by flow cytometry; (2) monocyte adhesion under flow conditions, and (3) monocyte migration. The total adhesion (rolling and firm adhesion) of the PG-preparation-stimulated monocytes to L cells, constitutively expressing ICAM-1 (intercellular adhesion molecule-1) and E-selectin, was decreased. This was most likely due to the L-selectin shedding, since monocyte incubation with a blocking L-selectin antibody resulted in a comparable number of adherent monocytes as PG-stimulated cells. The PG preparation induced an increased percentage of firmly adherent, polarized cells and a beta(2)-integrin-dependent binding to ICAM-1-coated beads. Interestingly, the PG preparation induced a priming of the monocytes for increased migration towards the chemoattractant C5a which was TLR2 and beta(2)-integrin dependent. Pam(3)Cys-SK(4) gave comparable results to the PG preparation in all assays tested. This study demonstrates that PG activation of monocytes results in an increase in adhesive and migratory capacities of these cells. This might be a mechanism by which PG promotes atherosclerotic disease in vivo.
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Manon M Oude
authors.initials: MM
authors.lastname: Nijhuis
authors.forename: Gerard
authors.initials: G
authors.lastname: Pasterkamp
authors.forename: Nienke I
authors.initials: NI
authors.lastname: Sluis
authors.forename: Dominique P V
authors.initials: DP
authors.lastname: de Kleijn
authors.forename: Jon D
authors.initials: JD
authors.lastname: Laman
authors.forename: Laurien H
authors.initials: LH
authors.lastname: Ulfman
mesh_terms: D000818:Animals; D050197:Atherosclerosis / Q000378:metabolism; D018821:CD18 Antigens / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D016764:Cell Polarity; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D015936:Complement C5a / Q000378:metabolism; D019040:E-Selectin / Q000235:genetics / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D007739:L Cells; D036904:Leukocyte Rolling; D055666:Lipopeptides; D008297:Male; D051379:Mice; D018715:Microscopy, Video; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D010457:Peptidoglycan / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D011673:Pulsatile Flow; D013211:Staphylococcus aureus / Q000737:chemistry; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000378:metabolism*; D014162:Transfection
chemical_list: D018821:CD18 Antigens; D019040:E-Selectin; D055666:Lipopeptides; C508075:Pam(3)CSK(4) peptide; D010455:Peptides; D010457:Peptidoglycan; D051195:Toll-Like Receptor 2; D018799:Intercellular Adhesion Molecule-1; D015936:Complement C5a