Differential effects of platelets and platelet inhibition by ticagrelor on TLR2- and TLR4-mediated inflammatory responses

Summary

Platelets and platelet-monocyte interaction play an important role in inflammation. Both pro- and anti-inflammatory effects of platelet inhibition have been reported in animal models. This study aimed to investigate the effect of platelets and platelet inhibition by the new P2Y₁₂ receptor antagonist ticagrelor on monocyte function, as assessed by cytokine responses to Toll-like Receptor (TLR) ligands. In a set of in vitro experiments, peripheral blood mononuclear cells (PBMC) incubated with the TLR2 ligand Pam3CSK4 produced less cytokines in the presence of platelets, whereas platelets increased the production of cytokines when PBMC were exposed to TLR4 ligand lipopolysaccharide (LPS). These effects of platelets were dependent on direct platelet-leukocyte aggregation and for the Pam3CSK4-induced response, on phagocytosis of platelets by monocytes. In a double blind, placebo-controlled crossover trial in healthy volunteers, a single oral dosage of 180 mg ticagrelor reduced platelet-monocyte complex (PMC) formation. This was associated with an increase in pro-inflammatory cytokines in blood exposed to Pam3CSK4, but a decrease in these cytokines in blood exposed to LPS. These findings show that platelets differentially modulate TLR2- and TLR4-mediated cytokine responses of PBMC. Through inhibition of platelet-leukocyte interaction, P2Y₁₂ receptor antagonists may either exert a pro- or anti-inflammatory effect during infections depending on the TLR primarily involved.

Keywords

Platelets - ticagrelor - inflammation - Toll-like receptor - platelet-monocyte complex

• References

• 1 Semple JW, Italiano JE, Jr. Freedman J. Platelets and the immune continuum. Nat Rev Immunol 2011; 11: 264-274.
• 2 Rondina MT, Weyrich AS, Zimmerman GA. Platelets as cellular effectors of inflammation in vascular diseases. Circ Res 2013; 112: 1506-1519.
• 3 Weyrich AS, Elstad MR, McEver RP. et al. Activated platelets signal chaemokine synthesis by human monocytes. J Clin Invest 1996; 97: 1525-1534.
• 4 Weyrich AS, McIntyre TM, McEver RP. et al. Monocyte tethering by P-selectin regulates monocyte chaemotactic protein-1 and tumor necrosis factor-alpha secretion. Signal integration and NF-kappa B translocation. J Clin Invest 1995; 95: 2297-2303.
• 5 McIntyre TM, Prescott SM, Weyrich AS. et al. Cell-cell interactions: leukocyteendothelial interactions. Curr Opin Hematol 2003; 10: 150-158.
• 6 May AE, Langer H, Seizer P. et al. Platelet-leukocyte interactions in inflammation and atherothrombosis. Semin Thromb Haemost 2007; 33: 123-127.
• 7 Suzuki J, Hamada E, Shodai T. et al. Cytokine secretion from human monocytes potentiated by P-selectin-mediated cell adhesion. Int Arch Allergy Immunol 2013; 160: 152-160.
• 8 Klinkhardt U, Bauersachs R, Adams J. et al. Clopidogrel but not aspirin reduces P-selectin expression and formation of platelet-leukocyte aggregates in patients with atherosclerotic vascular disease. Clin Pharmacol Therap 2003; 73: 232-241.
• 9 Xiao Z, Théroux P. Clopidogrel inhibits platelet-leukocyte interactions and thrombin receptor agonist peptide-induced platelet activation in patients with an acute coronary syndrome. J Am Coll Cardiol 2004; 43: 1982-1988.
• 10 Storey RF, James SK, Siegbahn A. et al. Lower mortality following pulmonary adverse events and sepsis with ticagrelor compared to clopidogrel in the PLATO study. Platelets 2014; 25: 517-525.
• 11 Hagiwara S, Iwasaka H, Hasegawa A. et al. Adenosine diphosphate receptor antagonist clopidogrel sulfate attenuates LPS-induced systemic inflammation in a rat model. Shock 2011; 35: 289-292.
• 12 Winning J, Baranyai J, Claus R. et al. Beneficial effects of antiplatelet drugs in patients with community-acquired pneumonia and in endotoxin shock in mice. Critical Care 2007; 11 (Suppl. 02) 27.
• 13 Winning J, Reichel J, Eisenhut Y. et al. Anti-platelet drugs and outcome in severe infection: clinical impact and underlying mechanisms. Platelets 2009; 20: 50-57.
• 14 Garcia AE, Mada SR, Rico MC. et al. Clopidogrel, a P2Y12 receptor antagonist, potentiates the inflammatory response in a rat model of peptidoglycan polysaccharide- induced arthritis. PloS one 2011; 06: e26035.
• 15 Hirschfeld M, Weis JJ, Toshchakov V. et al. Signaling by toll-like receptor 2 and 4 agonists results in differential gene expression in murine macrophages. Infection Immun 2001; 69: 1477-1482.
• 16 Tunjungputri RN, Van Der Ven AJ, Schonsberg A. et al. Reduced platelet hyperreactivity and platelet-monocyte aggregation in HIV-infected individuals receiving a raltegravir-based regimen. AIDS 2014; 28: 2091-2096.
• 17 van Bladel ER, Laarhoven AG, van der Heijden LB. et al. Functional platelet defects in children with severe chronic ITP as tested with two novel assays applicable for low platelet counts. Blood. 2014. Epub ahead of print.
• 18 Risitano A, Beaulieu LM, Vitseva O. et al. Platelets and platelet-like particles mediate intercellular RNA transfer. Blood 2012; 119: 6288-6295.
• 19 Kirkpatrick JP, McIntire LV, Moake JL. et al. Differential effects of cytochalasin B on platelet release, aggregation and contractility: evidence against a contractile mechanism for the release of platelet granular contents. Thromb Haemost 1980; 42: 1483-1489.
• 20 Blasco-Colmenares E, Perl TM, Guallar E. et al. Aspirin plus clopidogrel and risk of infection after coronary artery bypass surgery. Arch Intern Med 2009; 169: 788-796.
• 21 Gross AK, Dunn SP, Feola DJ. et al. Clopidogrel treatment and the incidence and severity of community acquired pneumonia in a cohort study and metaanalysis of antiplatelet therapy in pneumonia and critical illness. J Thromb Thrombol 2013; 35: 147-154.
• 22 Dixon DA, Tolley ND, Bemis-Standoli K. et al. Expression of COX-2 in plateletmonocyte interactions occurs via combinatorial regulation involving adhesion and cytokine signaling. J Clin Invest 2006; 116: 2727-2738.
• 23 van Gils JM, Zwaginga JJ, Hordijk PL. Molecular and functional interactions among monocytes, platelets, and endothelial cells and their relevance for cardiovascular diseases. J Leukoc Biol 2009; 85: 195-204.
• 24 Ple H, Landry P, Benham A. et al. The repertoire and features of human platelet microRNAs. PloS one 2012; 07: e50746.
• 25 Chai LY, Kullberg BJ, Vonk AG. et al. Modulation of Toll-like receptor 2 (TLR2) and TLR4 responses by Aspergillus fumigatus. Infection Immun 2009; 77: 2184-2192.
• 26 Gudbrandsdottir S, Hasselbalch HC, Nielsen CH. Activated Platelets Enhance IL-10 Secretion and Reduce TNF-α Secretion by Monocytes. J Immunol 2013; 191: 4059-4067.
• 27 Aslam R, Speck ER, Kim M. et al. Platelet Toll-like receptor expression modulates lipopolysaccharide-induced thrombocytopenia and tumor necrosis factoralpha production in vivo. Blood 2006; 107: 637-641.
• 28 Nylander S, Femia EA, Scavone M. et al. Ticagrelor inhibits human platelet aggregation via adenosine in addition to P2Y12 antagonism. J Thromb Haemost 2013; 11: 1867-1876.
• 29 Eltzschig HK, Sitkovsky MV, Robson SC. Purinergic signaling during inflammation. N Engl J Med 2013; 368: 1260.
• 30 Gremmel T, Eslam RB, Koppensteiner R. et al. Prasugrel reduces agonists’ inducible platelet activation and leukocyte-platelet interaction more efficiently than clopidogrel. Cardiovasc Therap 2013; 31: e40-e45.