Inflammation drives thrombosis after Salmonella infection via CLEC-2 on platelets
Jessica R. Hitchcock, … , Steve P. Watson, Adam F. Cunningham
Jessica R. Hitchcock, … , Steve P. Watson, Adam F. Cunningham
Published November 16, 2015
Citation Information: J Clin Invest. 2015;125(12):4429-4446. https://doi.org/10.1172/JCI79070.
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Research Article Hematology

Inflammation drives thrombosis after Salmonella infection via CLEC-2 on platelets

Abstract

Thrombosis is a common, life-threatening consequence of systemic infection; however, the underlying mechanisms that drive the formation of infection-associated thrombi are poorly understood. Here, using a mouse model of systemic Salmonella Typhimurium infection, we determined that inflammation in tissues triggers thrombosis within vessels via ligation of C-type lectin–like receptor-2 (CLEC-2) on platelets by podoplanin exposed to the vasculature following breaching of the vessel wall. During infection, mice developed thrombi that persisted for weeks within the liver. Bacteria triggered but did not maintain this process, as thrombosis peaked at times when bacteremia was absent and bacteria in tissues were reduced by more than 90% from their peak levels. Thrombus development was triggered by an innate, TLR4-dependent inflammatory cascade that was independent of classical glycoprotein VI–mediated (GPVI-mediated) platelet activation. After infection, IFN-γ release enhanced the number of podoplanin-expressing monocytes and Kupffer cells in the hepatic parenchyma and perivascular sites and absence of TLR4, IFN-γ, or depletion of monocytic-lineage cells or CLEC-2 on platelets markedly inhibited the process. Together, our data indicate that infection-driven thrombosis follows local inflammation and upregulation of podoplanin and platelet activation. The identification of this pathway offers potential therapeutic opportunities to control the devastating consequences of infection-driven thrombosis without increasing the risk of bleeding.

Authors

Jessica R. Hitchcock, Charlotte N. Cook, Saeeda Bobat, Ewan A. Ross, Adriana Flores-Langarica, Kate L. Lowe, Mahmood Khan, C. Coral Dominguez-Medina, Sian Lax, Manuela Carvalho-Gaspar, Stefan Hubscher, G. Ed Rainger, Mark Cobbold, Christopher D. Buckley, Tim J. Mitchell, Andrea Mitchell, Nick D. Jones, N. Van Rooijen, Daniel Kirchhofer, Ian R. Henderson, David H. Adams, Steve P. Watson, Adam F. Cunningham

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Figure 3

Infection is associated with altered platelet homeostasis.

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Infection is associated with altered platelet homeostasis. WT mice were ...
WT mice were infected i.p. as above. (A) Photomicrographs of noninfected and day 7–infected frozen liver tissue. (B) Fluorescent confocal microscopy on frozen liver sections of noninfected and day 7–infected mice: CD41 (green), Hoechst (gray). Scale bars: 200 μm. (C) Vessel occlusion was quantified by point counting of large vessels per tissue section. Statistical significance of thrombosis resolution was determined relative to day 7 after infection. (D) Bacterial colonization of the blood was enumerated at the indicated time points after infection. (E) Platelet numbers and (F) mean platelet volume (MPV) in the blood throughout infection. (G) Megakaryocytes (indicated by circles) in the spleen; H&E staining of frozen spleen sections at days 0 and 7 after infection. F, follicle. Scale bar: 100 μm. (H) Megakaryocytes per mm2 spleen. (I) Thrombopoietin concentration in the serum at the indicated time points after infection. Graphs show mean + SD. In all cases, data shown are representative of a minimum of 3 experiments, where n ≥ 4 mice in each group. Statistical significance was determined relative to day 7 after infection or to noninfected mice (D–F, H, and I). *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001, 1-way ANOVA with Dunnett’s test (C–F and I) or Mann-Whitney sum of ranks test (H).