Abstract 15016: Critical Role of Aryl Hydrocarbon Receptor in Uremic Toxin-induced Vascular Inflammation in vivo and in vitro
Background: Aryl hydrocarbon receptor (AhR) is a ligand-inducible transcription factor mediating toxic effects of dioxins and uremic toxins. However, AhR has recently emerged as a pathophysiological regulator of immune-inflammatory conditions including atherosclerosis and vascular inflammation. Moreover, uremic toxin such as indoxyl sulfate is associated with cardiovascular disease in patients with chronic kidney disease (CKD). Here, we investigated a potential role of AhR in indoxyl sulfate-induced leukocyte-endothelial interactions.
Results: Endothelial cell specific AhR knockout (eAhR KO) mice were generated by crossing AhR floxed mice to Tie2 Cre mice. 200 mg/kg/day of indoxyl sulfate was administrated subcutaneously by osmotic pump for 2 weeks, followed by intraperitoneal injection of 2 μg of tumor necrosis factor-α (TNF-α). Intravital microscopic analysis in femoral artery revealed that indoxyl sulfate dramatically enhanced TNF-α-induced leukocyte recruitment to vascular wall, however in eAhR KO mice, indoxyl sulfate did not increase the adherent leukocytes. To elucidate the underlying mechanisms, human umbilical vein endothelial cells (HUVEC) were transfected with siRNA of AhR (siAhR) and treated with indoxyl sulfate for 20 hours, followed by stimulation with TNF-α. siAhR significantly decreased indoxyl sulfate-enhanced leukocyte adhesion as well as E-selectin expression. Although indoxyl sulfate induced ROS production, JNK phosphorylation and NF-κB activation, siAhR did not affect their activity. Luciferase assay in HUVEC revealed that the promoter region of E-selectin, corresponding to -153 to -146 bps, was responsible for indoxyl sulfate action through AhR. Further mutational analysis of this promoter region identified that activator protein-1 (AP-1), but not cAMP response element-binding protein, mediated transcriptional activity is involved in indoxyl sulfate-triggered E-selectin expression via AhR.
Conclusion: AhR mediates uremic toxin-enhanced leukocyte-endothelial interactions presumably via AP-1 transcriptional activity. These results provide a novel mechanistic insight into the CKD-related vascular inflammation.
Author Disclosures: S. Ito: Employment; Significant; KUREHA CORPORATION. M. Osaka: None. N. Sawada: None. T. Edamatsu: Employment; Significant; KUREHA CORPORATION. Y. Itoh: Employment; Significant; KUREHA CORPORATION. M. Yoshida: Research Grant; Modest; Mitsubishi Tanabe Pharma, Novartis Pharmaceuticals, MSD, Kowa pharmaceuticals, Astellas pharma Inc..
- © 2014 by American Heart Association, Inc.