The Commensal Microbiota Enhances ADP-Triggered Integrin αIIbβ3 Activation and von Willebrand Factor-Mediated Platelet Deposition to Type I Collagen.

Klytaimnistra Kiouptsi,Eivor Wilms,Jana Winterstein,Kerstin Jurk,Sven Jäckel,Giulia Pontarollo,Christoph Reinhardt,Cornelia Karwot,Kathrin Groß

doi:10.3390/ijms21197171

Abstract

The commensal microbiota is a recognized enhancer of arterial thrombus growth. While several studies have demonstrated the prothrombotic role of the gut microbiota, the molecular mechanisms promoting arterial thrombus growth are still under debate. Here, we demonstrate that germ-free (GF) mice, which from birth lack colonization with a gut microbiota, show diminished static deposition of washed platelets to type I collagen compared with their conventionally raised (CONV-R) counterparts. Flow cytometry experiments revealed that platelets from GF mice show diminished activation of the integrin αIIbβ3 (glycoprotein IIbIIIa) when activated by the platelet agonist adenosine diphosphate (ADP). Furthermore, washed platelets from Toll-like receptor-2 (Tlr2)-deficient mice likewise showed impaired static deposition to the subendothelial matrix component type I collagen compared with wild-type (WT) controls, a process that was unaffected by GPIbα-blockade but influenced by von Willebrand factor (VWF) plasma levels. Collectively, our results indicate that microbiota-triggered steady-state activation of innate immune pathways via TLR2 enhances platelet deposition to subendothelial matrix molecules. Our results link host colonization status with the ADP-triggered activation of integrin αIIbβ3, a pathway promoting platelet deposition to the growing thrombus.

Highlights

While genetic predisposition to arterial thrombosis is increasingly understood [1], the knowledge of environmental modifiers contributing to cardiovascular disease (CVD) progression and arterial thrombosis remains elusive [2]
We demonstrated in the hyperlipidemic low-density lipoprotein-receptor (Ldlr)-deficient mouse model that the platelets of GF Ldlr-deficient mice, which were kept on an autoclaved standard laboratory diet, had reduced activation of the integrin αIIbβ3 when adhering to a collagen type III matrix relative to conventionally raised (CONV-R) Ldlr-deficient controls
Our results identified the gut microbiota as an actuating variable of integrin αIIbβ3 activation, which in our experimental conditions was triggered by adenosine diphosphate (ADP)

Summary

Introduction

While genetic predisposition to arterial thrombosis is increasingly understood [1], the knowledge of environmental modifiers contributing to cardiovascular disease (CVD) progression and arterial thrombosis remains elusive [2]. In addition to signaling-active microbiota-derived metabolites that are largely determined by the availability of nutrients, the microbiota provides a broad variety of microbial-associated molecular patterns (MAMPs) that steadily trigger the basal activation of pattern recognition receptors, such as Toll-like receptors (TLRs) [13,14]. These pro-inflammatory signals are not restricted to the surface of the intestinal epithelium, but remain active and can be detected at varying levels in the bloodstream, dependent on gut barrier function [15,16,17]. Remote signaling of microbial patterns is mediated by TLRs and nucleotide-binding oligomerization domain (NOD)-like receptors [15,21], impacting on hematopoiesis and affecting the development of vascular disease states such as atherosclerosis, ischemia-reperfusion injury, and arterial thrombosis [22,23,24]

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Results

Conclusion