Uremic Solute-Aryl Hydrocarbon Receptor-Tissue Factor Axis Associates with Thrombosis after Vascular Injury in Humans

Abstract

Individuals with CKD are particularly predisposed to thrombosis after vascular injury. Using mouse models, we recently described indoxyl sulfate, a tryptophan metabolite retained in CKD and an activator of tissue factor (TF) through aryl hydrocarbon receptor (AHR) signaling, as an inducer of thrombosis across the CKD spectrum. However, the translation of findings from animal models to humans is often challenging. Here, we investigated the uremic solute-AHR-TF thrombosis axis in two human cohorts, using a targeted metabolomics approach to probe a set of tryptophan products and high-throughput assays to measure AHR and TF activity. Analysis of baseline serum samples was performed from 473 participants with advanced CKD from the Dialysis Access Consortium Clopidogrel Prevention of Early AV Fistula Thrombosis trial. Participants with subsequent arteriovenous thrombosis had significantly higher levels of indoxyl sulfate and kynurenine, another uremic solute, and greater activity of AHR and TF, than those without thrombosis. Pattern recognition analysis using the components of the thrombosis axis facilitated clustering of the thrombotic and nonthrombotic groups. We further validated these findings using 377 baseline samples from participants in the Thrombolysis in Myocardial Infarction II trial, many of whom had CKD stage 2-3. Mechanistic probing revealed that kynurenine enhances thrombosis after vascular injury in an animal model and regulates thrombosis in an AHR-dependent manner. This human validation of the solute-AHR-TF axis supports further studies probing its utility in risk stratification of patients with CKD and exploring its role in other diseases with heightened risk of thrombosis.

Indoxyl Sulfate, a Uremic Endotheliotoxin

“…This meta-analysis included five studies with heterogeneity in dialysis modalities (peritoneal dialysis or hemodialysis) and in the follow-up of patients. IS levels were correlated with an increased risk of arteriovenous fistula thrombosis after angioplasty in two studies [47,48]. These observational studies were limited by potential confounders between IS plasma levels and nutritional intake.…”

“…Moreover, the number of endothelial progenitor cells is inversely correlated with IS plasma levels [54,55]. This mechanism could impair neovascularization [48][49][50][51]. The endotheliotoxicity of IS was demonstrated in living kidney donors with an eGFR greater than 60 mL/mn/1.73 m 2 and increased IS plasma levels.…”

“…In patients with CKD, IS plasma levels are correlated with circulating tissue factor and its procoagulant activity (determined by measuring the generation of factor Xa) [26,90,91]. Recently, Kolachalama et al [48] showed a Toxins 2020, 12, 229 8 of 14 correlation between plasma tissue factor activity and arteriovenous fistula thrombosis in hemodialysis patients. In vitro, IS increases endothelial expression of tissue factor and its procoagulant activity secondary to activation of the aryl hydrocarbon receptor (AhR) [91].…”

“…AhR-AP levels are inversely correlated to eGFR [93] and correlated with IS plasma levels and cardiovascular events [93]. Kolachalama el al [48] reported that arteriovenous fistula thrombosis in CKD patient is associated with higher serum AhR-AP. Furthermore, IS plasma concentration, serum AhR-AP and tissue factor activity were correlated in a cohort of 20 hemodialysis patients [90].…”

Oral Charcoal Adsorbents Attenuate Neointima Formation of Arteriovenous Fistulas

“…Particularly, indolic solutes produced by tryptophan metabolism, such as IS, could increase tissue factor expression through aryl hydrocarbon receptor (AHR) signaling. The relevance of the uremic solute-AHR-thrombosis pathway on thrombosis was observed in human studies as well [29,30]. Using fibrin stain, we demonstrated that the luminal loss of AV fistula was in part secondary to thrombus formation in the vessel wall.…”