Abstract: FR-PO182
Metabolomics Screen in Cilia-Deficient Cells Identifies Tryptophan Metabolism as a Possible Mechanism for Cilia-Dependent Cyst Growth
Session Information
- AKI: Mechanisms - II
November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
Authors
- Lerner, Kasey, Medical University of South Carolina, Charleston, South Carolina, United States
- Winkler, Brennan, Medical University of South Carolina, Charleston, South Carolina, United States
- Zuo, Xiaofeng, Medical University of South Carolina, Charleston, South Carolina, United States
- Misare, Kelly R., Medical University of South Carolina, Charleston, South Carolina, United States
- Hartman, Jessica H., Medical University of South Carolina, Charleston, South Carolina, United States
- Lipschutz, Joshua H., Medical University of South Carolina, Charleston, South Carolina, United States
Background
Primary cilia and mitochondria are involved in polycystic kidney disease (PKD). We showed that knockdown (KD) or ciliary targeting sequence mutation (cts-mut) of Exoc5, a central exocyst complex component, resulted in cilia loss while Exoc5 overexpression (OE) resulted in longer cilia. Ift88 knockout (KO) also resulted in cilia loss which was reversed by Ift88 rescue.
Methods
Seahorse assays and metabolic profiling were performed on canine (MDCK control, Exoc5 cts-mut, KD, OE) and murine (Ift88 KO, rescue) kidney cells.
Results
Seahorse assays showed lower basal respiration (BR), maximal respiration (MR), and spare respiratory capacity (SRC) in Exoc5 KD and Exoc5 cts-mut compared to control MDCK cells. Conversely, Exoc5 OE cells had higher BR, MR, and SRC. MR and SRC were also lower in Ift88 KO than rescue cells. A metabolomics screen showed tryptophan increased in Exoc5 KD and Exoc5 cts-mut cells by 58- and 113-fold compared to control. In Exoc5 OE cells, tryptophan decreased 59%. Similarly, tryptophan increased by 21% in Ift88 KO cells. Kynurenine is directly downstream of tryptophan and decreased by 83% and 20% in Exoc5 KD and cts-mut cells, and increased by 25% in Exoc5 OE cells. In Ift88 KO cells kynurenine decreased by 49%.
Conclusion
Kynurenine drives oxidative stress and mitochondrial dysfunction and was higher in MDRD Study participants with ADPKD compared to other CKD, and patients with ADPKD had higher plasma levels compared to healthy individuals which increased with disease progression. Nguyen et al (2022, JCI Insight) found decreased tryptophan and increased kynurenine in Pkd1 RC/RC mice. This is the opposite of what we found following cilia loss. IDO1 converts tryptophan to kynurenine. When Nguyen et al pharmacologically inhibited or genetically knocked out IDO1, cystogenesis decreased. In 2013 Ma et al (2013, Nature Genet) showed that cilia loss suppresses cyst growth in ADPKD mouse models. Shao et al (2020, Kidney Int) showed that Ift88 KO slowed cyst growth in a PKD1 mouse model. Therefore, we hypothesize that cilia loss inhibits cystogenesis by increasing tryptophan and decreasing kynurenine. These findings highlight a link between cilia and mitochondrial function and suggest that tryptophan metabolism via IDO1 could be a novel target for ADPKD treatment.
Funding
- Other NIH Support