Indoleamine 2,3-dioxygenase-1, a Novel Therapeutic Target for Post-Vascular Injury Thrombosis in CKD

Significance Statement Patients with CKD are at a markedly higher risk of thrombosis after vascular procedures. Uremic solutes, such as indoxyl sulfate and kynurenine, are important contributors to this complication through tissue factor (TF), a trigger of the extrinsic coagulation cascade. This study examines the role of indoleamine 2,3-dioxygenase-1 (IDO-1), a key enzyme in kynurenine biogenesis, in thrombotic complications in CKD. Using genomic and pharmacological approaches, this study demonstrates that IDO-1 is a critical regulator of TF and thrombosis after vascular injury in CKD mice. Indoxyl sulfate upregulates IDO-1, creating a feedback-forward loop. IDO-1 activity was higher in patients with CKD, who developed thrombosis after vascular interventions. This study identifies IDO-1 as a therapeutic target and uncovers crosstalk between uremic solutes, perpetuating their toxic effect. Background CKD, characterized by retained uremic solutes, is a strong and independent risk factor for thrombosis after vascular procedures . Urem ic solutes such as indoxyl sulfate (IS) and kynurenine (Kyn) mediate prothrombotic effect through tissue factor (TF). IS and Kyn biogenesis depends on multiple enzymes, with therapeutic implications unexplored. We examined the role of indoleamine 2,3-dioxygenase-1 (IDO-1), a rate-limiting enzyme of kynurenine biogenesis, in CKD-associated thrombosis after vascular injury. Methods IDO-1 expression in mice and human vessels was examined. IDO-1 −/− mice, IDO-1 inhibitors, an adenine-induced CKD, and carotid artery injury models were used. Results Both global IDO-1 −/− CKD mice and IDO-1 inhibitor in wild-type CKD mice showed reduced blood Kyn levels, TF expression in their arteries, and thrombogenicity compared with respective controls. Several advanced IDO-1 inhibitors downregulated TF expression in primary human aortic vascular smooth muscle cells specifically in response to uremic serum. Further mechanistic probing of arteries from an IS-specific mouse model, and CKD mice, showed upregulation of IDO-1 protein, which was due to inhibition of its polyubiquitination and degradation by IS in vascular smooth muscle cells. In two cohorts of patients with advanced CKD, blood IDO-1 activity was significantly higher in sera of study participants who subsequently developed thrombosis after endovascular interventions or vascular surgery. Conclusion Leveraging genetic and pharmacologic manipulation in experimental models and data from human studies implicate IS as an inducer of IDO-1 and a perpetuator of the thrombotic milieu and supports IDO-1 as an antithrombotic target in CKD.