title: Toll like receptor 2/1 mediated platelet adhesion and activation on bacterial mimetic surfaces is dependent on src/Syk-signaling and purinergic receptor P2X1 and P2Y12 activation.
abstract: Platelets are considered to have important functions in inflammatory processes as key players in innate immunity. Toll like receptors (TLRs), expressed on platelets, recognize pathogen associated molecular patterns and trigger immune responses. Pathogens are able to adhere to human tissues and form biofilms which cause a continuous activation of the immune system. The authors aimed to investigate how immobilized Pam3CSK4 (a synthetic TLR2/1 agonist) and IgG, respectively, resembling a bacterial focus, affects adhesion and activation of platelets including release of two cytokines, regulated on activation normal T-cell expressed and secreted (RANTES) and macrophage migration inhibitory factor (MIF). The authors also aim to clarify the signaling downstream of TLR2/1 and FcγRII (IgG receptor) and the role of adenine nucleotides in this process. Biolayers of Pam3CSK4 and IgG, respectively, were confirmed by null-ellipsometry and contact angle measurements. Platelets were preincubated with signaling inhibitors for scr and Syk and antagonists for P2X1 or P2Y1 [adenosine triphosphate (ATP), adenosine diphosphate (ADP) receptors] prior to addition to the surfaces. The authors show that platelets adhere and spread on both Pam3CSK4- and IgG-coated surfaces and that this process is antagonized by scr and Syc inhibitors as well as P2X1 and P2Y antagonists. This suggests that Pam3CSK4 activated platelets utilize the same pathway as FcγRII. Moreover, the authors show that ATP-ligation of P2X1 is of importance for further platelet activation after TLR2/1-activation, and that P2Y12 is the prominent ADP-receptor involved in adhesion and spreading. RANTES and MIF were secreted over time from platelets adhering to the coated surfaces, but no MIF was released upon stimulation with soluble Pam3CSK4. These results clarify the importance of TLR2/1 and FcγRII in platelet adhesion and activation, and strengthen the role of platelets as an active player in sensing bacterial infections.
authors.affiliation: Department of Biomedicine, School of Health and Medical Sciences, Örebro University, Örebro SE-70182, Sweden.
authors.forename: Kristin
authors.initials: K
authors.lastname: Klarström Engström
authors.affiliation: Department of Physics, Chemistry and Biology, Division of Molecular Surface Physics and Nanoscience, Linköping University, Linköping SE-58183, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Brommesson
authors.affiliation: Department of Clinical Pathology and Clinical Genetics, Linköping University Hospital, Linköping SE-58191, Sweden and Department of Clinical and Experimental Medicine, Linköping University, Linköping SE-58191, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Kälvegren
authors.affiliation: Department of Biomedicine, School of Health and Medical Sciences, Örebro University, Örebro SE-70182, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Bengtsson
mesh_terms: D032701:Biomimetics; D001792:Blood Platelets / Q000502:physiology*; D002448:Cell Adhesion; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D015539:Platelet Activation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism*; D058474:Receptors, Purinergic P2X1 / Q000378:metabolism*; D058925:Receptors, Purinergic P2Y12 / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D051194:Toll-Like Receptor 1 / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D016207:Cytokines; D007074:Immunoglobulin G; D047908:Intracellular Signaling Peptides and Proteins; C548576:P2RY12 protein, human; D017452:Receptors, IgG; D058474:Receptors, Purinergic P2X1; D058925:Receptors, Purinergic P2Y12; C495342:TLR2 protein, human; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D019061:src-Family Kinases