Lipopolysaccharide as trigger of platelet aggregation via eicosanoid over-production

Summary

The effect of lipopolysaccharide (LPS) on platelet aggregation is still controversial. We performed in vitro and ex vivo studies in controls and in patients with community-acquired pneumonia (CAP) to assess the effect of LPS on platelet activation (PA). LPS (15–100 pg/ml) significantly increased PA only if combined with sub-threshold concentrations (STC) of collagen or ADP; this effect was associated with increased platelet H₂O₂ production, Nox2 activation, PLA2 phosphorylation, thromboxane (Tx)A₂ and 8-iso-PGF2α-III, and was inhibited by aspirin, TxA2 receptor antagonist or by Toll-like receptor 4 blocking peptide (TLR4bp). Analysis of up-stream signalling potentially responsible for Nox2 and PLA2 activation demonstrated that LPS-mediated PA was associated with phosphorylation of AKT, p38 and p47phox translocation. In 10 consecutive CAP patients serum endotoxins were significantly higher compared to 10 controls (145 [115–187] vs 18 [6–21] pg/ml; p<0.01). Ex vivo study showed that agonist-stimulated platelets were associated with enhanced PA (p<0.01), Toll-like receptor 4 (TLR4) expression (p<0.05), TxA₂ (p<0.01) and 8-iso-PGF2α-III (p<0.01) production in CAP patients compared to controls. The study provides evidence that LPS amplifies the platelet response to common agonists via TLR4-mediated eicosanoid production and suggests LPS as a potential trigger for PA in CAP.

Supplementary Material to this article is available online at www.thrombosis-online.com

Keywords

LPS - platelet activation - oxidative stress - community-acquired pneumonia

• References

• 1 Shahian DM, Liu X, Meyer GS. et al. Hospital teaching intensity and mortality for acute myocardial infarction, heart failure, and pneumonia. Med Care 2014; 52: 38-46.
• 2 Cangemi R, Calvieri C, Falcone M. et al. Relation of Cardiac Complications in the Early Phase of Community-Acquired Pneumonia to Long-Term Mortality Cardiovascular Events. Am J Cardiol 2015; 116: 647-651.
• 3 Cangemi R, Casciaro M, Rossi E. et al. Platelet activation is associated with myocardial infarction in patients with pneumonia. J Am Coll Cardiol 2014; 64: 1917-1919.
• 4 Kritselis I, Tzanetakou V, Adamis G. et al. The level of endotoxemia in sepsis varies in relation to the underlying infection: Impact on final outcome. Immunol Lett 2013; 152: 167-172.
• 5 Lopes-Pires ME, Casarin AL, Pereira-Cunha FG. et al. Lipopolysaccharide treatment reduces rat platelet aggregation independent of intracellular reactive-oxygen species generation. Platelets 2012; 23: 195-201.
• 6 Morganti RP, Cardoso MH, Pereira FG. et al. Mechanisms underlying the inhibitory effects of lipopolysaccharide on human platelet adhesion. Platelets 2010; 21: 260-269.
• 7 Zhang G, Han J, Welch EJ. et al. Lipopolysaccharide stimulates platelet secretion and potentiates platelet aggregation via TLR4/MyD88 and the cGMP-dependent protein kinase pathway. J Immunol 2009; 182: 7997-8004.
• 8 Wiedermann CJ, Kiechl S, Dunzendorfer S. et al. Association of endotoxemia with carotid atherosclerosis and cardiovascular disease: prospective results from the Bruneck study. J Am Coll Cardiol 1999; 34: 1975-1981.
• 9 Pignatelli P, Carnevale R, Di Santo S. et al. Inherited human gp91phox deficiency is associated with impaired isoprostane formation and platelet dysfunction. Arterioscler Thromb Vasc Biol 2011; 31: 423-434.
• 10 Cifuentes-Pagano E, Csanyi G, Pagano PJ. NADPH oxidase inhibitors: a decade of discovery from Nox2ds to HTS. Cell Mol Life Sci 2012; 69: 2315-2325.
• 11 El Benna J, Han J, Park JW. et al. Activation of p38 in stimulated human neutrophils: phosphorylation of the oxidase component p47phox by p38 and ERK but not by JNK. Arch Biochem Biophys 1996; 334: 395-400.
• 12 Leoncini G, Bruzzese D, Signorello MG. Activation of p38 MAPKinase/cPLA2 pathway in homocysteine-treated platelets. J Thromb Haemost 2006; 04: 209-216.
• 13 Pignatelli P, Carnevale R, Cangemi R. et al. Atorvastatin inhibits gp91phox circulating levels in patients with hypercholesterolemia. Arterioscler Thromb Vasc Biol 2010; 30: 360-367.
• 14 Pulcinelli FM, Riondino S, Celestini A. et al. Persistent production of platelet thromboxane A2 in patients chronically treated with aspirin. J Thromb Haemost 2005; 03: 2784-2789.
• 15 Fortuño A, Bidegain J, Robador PA. et al. Losartan metabolite EXP3179 blocks NADPH oxidase-mediated superoxide production by inhibiting protein kinase C: potential clinical implications in hypertension. Hypertension 2009; 54: 744-750.
• 16 Hai J, Lin Q, Lu Y. et al. Induction of apoptosis in rat C6 glioma cells by panaxydol. Cell Biol Int 2007; 31: 711-715.
• 17 Loffredo L, Cangemi R, Perri L. et al. Impaired flow-mediated dilation in hospitalized patients with community-acquired pneumonia. Eur J Intern Med 2016; 36: 74-80.
• 18 Chen Q, Powell DW, Rane MJ. et al. Akt phosphorylates p47phox and mediates respiratory burst activity in human neutrophils. J Immunol 2003; 170: 5302-5308.
• 19 Li Z, Delaney MK, O’Brien KA. et al. Signaling during platelet adhesion and activation. Arterioscler Thromb Vasc Biol 2010; 30: 2341-2349.
• 20 Harizi H, Corcuff JB, Gualde N. Arachidonic-acid-derived eicosanoids: roles in biology and immunopathology. Trends Mol Med 2008; 14: 461-469.
• 21 Morrow JD, Hill KE, Burk RF. et al. A series of prostaglandin F2-like compounds are produced in vivo in humans by a non-cyclooxygenase, free radical-catalyzed mechanism. Proc Natl Acad Sci USA 1990; 87: 9383-9387.
• 22 Loscalzo J. Nitric oxide insufficiency, platelet activation, and arterial thrombosis. Circ Res 2001; 88: 756-762.
• 23 Rivera J, Lozano ML, Navarro-Núñez L. et al. Platelet receptors and signaling in the dynamics of thrombus formation. Haematologica 2009; 94: 700-711.
• 24 Pignatelli P, Sanguigni V, Lenti L. et al. gp91phox-dependent expression of platelet CD40 ligand. Circulation 2004; 110: 1326-1329.
• 25 Gijón MA, Leslie CC. Regulation of arachidonic acid release and cytosolic phospholipase A2 activation. J Leukoc Biol 1999; 65: 330-336.
• 26 Pignatelli P, Sanguigni V, Lenti L. et al. Sepsis, thrombosis and organ dysfunction. Thrombosis Res 2012; 129: 290-295.
• 27 Mirsaeidi M, Peyrani P, Aliberti S. et al. Thrombocytopenia and thrombocytosis at time of hospitalization predict mortality in patients with community-acquired pneumonia. Chest 2010; 137: 416-420.
• 28 Kreutz RP, Bliden KP, Tantry US. et al. Viral respiratory tract infections increase platelet reactivity and activation: an explanation for the higher rates of myocardial infarction and stroke during viral illness. J Thromb Haemost 2005; 03: 2108-2109.
• 29 Lee B, Robinson KM, McHugh KJ. et al. Influenza-induced type I interferon enhances susceptibility to gram-negative and gram-positive bacterial pneumonia in mice. Am J Physiol Lung Cell Mol Physiol 2015; 309: L158-167.