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 7

Adenine-induced CKD model shows compromised angiogenesis and β-catenin expression in the ligated limb of mice.

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Adenine-induced CKD model shows compromised angiogenesis and β-catenin e...
(A) A group of 8- to 12-week-old C57BL/6 female mice on a 0.2% adenine diet (n = 10) or the control diet (n = 10) underwent HLI and mice were harvested at the end of 21 days. (B) Representative laser doppler images of mouse hind paws. n = 10 mice/per group. (C) Average perfusion ratios. Error bars show SD. Independent Student’s t tests were applied to compare 2 groups at each time point. *P = 0.05; ***P < 0.001; #P = 0.002. (D) Three random images from stained posterior calf muscles of the ligated limbs of each mouse (n = 10 mice/group). Insets represent myocytes, where white arrowheads are directed at α-actin expression. Scale bars: 25 μm. Original magnification ×400. (E) Averages of the normalized integrated density of CD3 to α-actin per image described in Figure 6D are shown. Lines represent median. Student’s t test was performed. ***P < 0.001. (F) Three random images of stained posterior calf muscles of the ligated limb per mouse (n = 10 mice/group). Insets show a myocyte stained with β-catenin with surrounding capillaries. Blue dotted lines represent ROI of a myocyte and capillaries; 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 a capillary. Scale bars: 25 μm. Original magnification ×400. (G) Normalized integrated densities of β-catenin of muscles and capillaries obtained from 30 random images per group (n = 10 mice/group). Lines represent median. Student’s t test was performed. For capillary ***P < 0.001 and for muscle ***P = 0.001.