Effect of ultrapure lipopolysaccharides derived from diverse bacterial species on the modulation of platelet activation

Thomas M Vallance,Dina A I Albadawi,Rajendran Vaiyapuri,Ketan Patel,Sakthivel Vaiyapuri,Philip Dash,Darius Widera,Divyashree Ravishankar,Jonathan Sheard,Harry Layfield

doi:10.1038/s41598-019-54617-w

Thomas M Vallance, Dina A I Albadawi + Show 8 more

Open Access

https://doi.org/10.1038/s41598-019-54617-w

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Journal: Scientific Reports	Publication Date: Dec 1, 2019
Citations: 14	License type: open-access

Affiliation: University of Reading

Abstract

Platelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting. However, they also play critical roles in the regulation of innate immune responses. Inflammatory receptors, specifically Toll-like receptor (TLR)-4, have been reported to modify platelet reactivity. A plethora of studies have reported controversial functions of TLR4 in the modulation of platelet function using various chemotypes and preparations of its ligand, lipopolysaccharide (LPS). The method of preparation of LPS may explain these discrepancies however this is not fully understood. Hence, to determine the impact of LPS on platelet activation, we used ultrapure preparations of LPS from Escherichia coli (LPSEC), Salmonella minnesota (LPSSM), and Rhodobacter sphaeroides (LPSRS) and examined their actions under diverse experimental conditions in human platelets. LPSEC did not affect platelet activation markers such as inside-out signalling to integrin αIIbβ3 or P-selectin exposure upon agonist-induced activation in platelet-rich plasma or whole blood whereas LPSSM and LPSRS inhibited platelet activation under specific conditions at supraphysiological concentrations. Overall, our data demonstrate that platelet activation is not largely influenced by any of the ultrapure LPS chemotypes used in this study on their own except under certain conditions.

Highlights

Platelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting
In order to confirm whether the ultrapure LPS chemotypes used in this study are functionally active and selective to TLR4, they were individually tested in U251-NF-κB-GFP-Luc cells, a reporter cell line for NF-κB signalling selectively via TLR424
No significant increase in NF-κB activity induced by LPS from Escherichia coli (LPSEC) or LPS [obtained from Salmonella minnesota (LPSSM) was seen in the presence of LPSRS

Summary

Introduction

Platelets are small circulating blood cells that play essential roles in the maintenance of haemostasis via blood clotting. To determine the impact of LPS on platelet activation, we used ultrapure preparations of LPS from Escherichia coli (LPSEC), Salmonella minnesota (LPSSM), and Rhodobacter sphaeroides (LPSRS) and examined their actions under diverse experimental conditions in human platelets. The presence of signalling molecules involved in both pathways suggests the potential binding of TLR4 with different LPS chemotypes to trigger either MyD88-dependent or -independent signalling[10]. In order to determine the impact of LPS chemotypes obtained from various bacterial species on the modulation of platelet activation under different experimental settings, we used ultrapure LPSEC, LPSSM, and Rhodobacter sphaeroides (LPSRS, which is a TLR4 antagonist13,22,23) and analysed their effects in platelets.

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