Tryptophan metabolites suppress the Wnt pathway and promote adverse limb events in chronic kidney disease
Nkiruka V. Arinze, … , Nader Rahimi, Vipul C. Chitalia
Nkiruka V. Arinze, … , Nader Rahimi, Vipul C. Chitalia
Published November 9, 2021
Citation Information: J Clin Invest. 2022;132(1):e142260. https://doi.org/10.1172/JCI142260.
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Research Article Nephrology Vascular biology

Tryptophan metabolites suppress the Wnt pathway and promote adverse limb events in chronic kidney disease

Abstract

Chronic kidney disease (CKD) imposes a strong and independent risk for peripheral artery disease (PAD). While solutes retained in CKD patients (uremic solutes) inflict vascular damage, their role in PAD remains elusive. Here, we show that the dietary tryptophan-derived uremic solutes including indoxyl sulfate (IS) and kynurenine (Kyn) at concentrations corresponding to those in CKD patients suppress β-catenin in several cell types, including microvascular endothelial cells (ECs), inhibiting Wnt activity and proangiogenic Wnt targets in ECs. Mechanistic probing revealed that these uremic solutes downregulated β-catenin in a manner dependent on serine 33 in its degron motif and through the aryl hydrocarbon receptor (AHR). Hindlimb ischemia in adenine-induced CKD and IS solute–specific mouse models showed diminished β-catenin and VEGF-A in the capillaries and reduced capillary density, which correlated inversely with blood levels of IS and Kyn and AHR activity in ECs. An AHR inhibitor treatment normalized postischemic angiogenic response in CKD mice to a non-CKD level. In a prospective cohort of PAD patients, plasma levels of tryptophan metabolites and plasma’s AHR-inducing activity in ECs significantly increased the risk of future adverse limb events. This work uncovers the tryptophan metabolite/AHR/β-catenin axis as a mediator of microvascular rarefaction in CKD patients and demonstrates its targetability for PAD in CKD models.

Authors

Nkiruka V. Arinze, Wenqing Yin, Saran Lotfollahzadeh, Marc Arthur Napoleon, Sean Richards, Joshua A. Walker, Mostafa Belghasem, Jonathan D. Ravid, Mohamed Hassan Kamel, Stephen A. Whelan, Norman Lee, Jeffrey J. Siracuse, Stephan Anderson, Alik Farber, David Sherr, Jean Francis, Naomi M. Hamburg, Nader Rahimi, Vipul C. Chitalia

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Figure 9

AHR inhibition normalizes postischemic angiogenesis in CKD mice to a non-CKD level.

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AHR inhibition normalizes postischemic angiogenesis in CKD mice to a non...
(A) A group of C57BL/6 female mice on a 0.2% adenine diet (n = 16) or the control diet (n = 16) for 7 days underwent HLI. The mice were randomized to 2 groups (n = 8/group) and initiated on DMSO or CH223191 for 5 days on and 2 days off for 2 weeks. (B) Average perfusion ratios. n = 8 mice/group. Error bars show SD. Independent Student’s t tests were applied at each time point. The dotted line in this graph and subsequent figures corresponds to the respective values of mice on normal diet. **P = 0.04 for day 14; ***P = 0.001 for day 21. (C) Representative stained images from 3 random images per mouse (n = 8 mice/group) of the posterior calf muscles from ligated limbs of mice. Insets represent myocytes. White arrowhead is directed at α-actin expression. Scale bar: 25 μm. Original magnification ×400. (D) Integrated density of CD31 normalized to α-actin described in Figure 7C. Line represents median value. Student’s t test was performed. ***P < 0.001. (E) Representative stained images from 3 random images per mouse (n = 8 mice/group) of the posterior calf muscles from ligated limbs of mice. Insets show a representative myocyte stained with β-catenin along with surrounding capillaries. Blue dotted lines represent ROI of a myocyte and capillaries; and white dotted lines represent ROI of a myocyte. White asterisks correspond to β-catenin in a myocyte. White arrowheads are directed to β-catenin in the capillary. Scale bars: 25 μm. Original magnification ×400. (F) The integrated densities of normalized β-catenin in muscles and capillaries from 8 mice per group. Lines represent median. Student’s t test was performed. For capillary ###P = 0.002 and skeletal muscle ***P = 0.007.