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Jamshidi N, Nigam KB, Nigam SK. Loss of the Kidney Urate Transporter, Urat1, Leads to Disrupted Redox Homeostasis in Mice. Antioxidants (Basel) 2023; 12:antiox12030780. [PMID: 36979028 PMCID: PMC10045411 DOI: 10.3390/antiox12030780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 02/28/2023] [Accepted: 03/15/2023] [Indexed: 03/29/2023] Open
Abstract
High uric acid is associated with gout, hypertension, metabolic syndrome, cardiovascular disease, and kidney disease. URAT1 (SLC22A12), originally discovered in mice as Rst, is generally considered a very selective uric acid transporter compared to other closely-related kidney uric acid transporters such as OAT1 (SLC22A6, NKT) and OAT3 (SLC22A8). While the role of URAT1 in regulating human uric acid is well-established, in recent studies the gene has been linked to redox regulation in flies as well as progression of renal cell carcinoma. We have now identified over twenty metabolites in the Urat1 knockout that are generally distinct from metabolites accumulating in the Oat1 and Oat3 knockout mice, with distinct molecular properties as revealed by chemoinformatics and machine learning analysis. These metabolites are involved in seemingly disparate aspects of cellular metabolism, including pyrimidine, fatty acid, and amino acid metabolism. However, through integrative systems metabolic analysis of the transcriptomic and metabolomic data using a human metabolic reconstruction to build metabolic genome-scale models (GEMs), the cellular response to loss of Urat1/Rst revealed compensatory processes related to reactive oxygen species handling and maintaining redox state balances via Vitamin C metabolism and cofactor charging reactions. These observations are consistent with the increasingly appreciated role of the antioxidant properties of uric acid. Collectively, the results highlight the role of Urat1/Rst as a transporter strongly tied to maintaining redox homeostasis, with implications for metabolic side effects from drugs that block its function.
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Affiliation(s)
- Neema Jamshidi
- Department of Radiological Sciences, University of California, Los Angeles, CA 90095, USA
- Institute of Engineering in Medicine, University of California, San Diego, La Jolla, CA 92093, USA;
- Correspondence:
| | - Kabir B. Nigam
- Department of Psychiatry, Brigham and Women’s Hospital, Boston, MA 02130, USA
- Department of Psychiatry, Harvard Medical School, Boston, MA 02130, USA
| | - Sanjay K. Nigam
- Institute of Engineering in Medicine, University of California, San Diego, La Jolla, CA 92093, USA;
- Departments of Pediatrics and Medicine (Nephrology), University of California, San Diego, La Jolla, CA 92093, USA
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Jamshidi N, Nigam SK. Drug transporters OAT1 and OAT3 have specific effects on multiple organs and gut microbiome as revealed by contextualized metabolic network reconstructions. Sci Rep 2022; 12:18308. [PMID: 36316339 PMCID: PMC9622871 DOI: 10.1038/s41598-022-21091-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 09/22/2022] [Indexed: 11/07/2022] Open
Abstract
In vitro and in vivo studies have established the organic anion transporters OAT1 (SLC22A6, NKT) and OAT3 (SLC22A8) among the main multi-specific "drug" transporters. They also transport numerous endogenous metabolites, raising the possibility of drug-metabolite interactions (DMI). To help understand the role of these drug transporters on metabolism across scales ranging from organ systems to organelles, a formal multi-scale analysis was performed. Metabolic network reconstructions of the omics-alterations resulting from Oat1 and Oat3 gene knockouts revealed links between the microbiome and human metabolism including reactions involving small organic molecules such as dihydroxyacetone, alanine, xanthine, and p-cresol-key metabolites in independent pathways. Interestingly, pairwise organ-organ interactions were also disrupted in the two Oat knockouts, with altered liver, intestine, microbiome, and skin-related metabolism. Compared to older models focused on the "one transporter-one organ" concept, these more sophisticated reconstructions, combined with integration of a multi-microbial model and more comprehensive metabolomics data for the two transporters, provide a considerably more complex picture of how renal "drug" transporters regulate metabolism across the organelle (e.g. endoplasmic reticulum, Golgi, peroxisome), cellular, organ, inter-organ, and inter-organismal scales. The results suggest that drugs interacting with OAT1 and OAT3 can have far reaching consequences on metabolism in organs (e.g. skin) beyond the kidney. Consistent with the Remote Sensing and Signaling Theory (RSST), the analysis demonstrates how transporter-dependent metabolic signals mediate organ crosstalk (e.g., gut-liver-kidney) and inter-organismal communication (e.g., gut microbiome-host).
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Affiliation(s)
- Neema Jamshidi
- grid.19006.3e0000 0000 9632 6718Department of Radiological Sciences, University of California, Los Angeles, Los Angeles, CA USA ,grid.266100.30000 0001 2107 4242Institute of Engineering in Medicine, University of California, San Diego, La Jolla, CA USA
| | - Sanjay K. Nigam
- grid.266100.30000 0001 2107 4242Departments of Pediatrics and Medicine (Nephrology), University of California, San Diego, La Jolla, CA USA
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Ganguly S, Finkelstein D, Shaw TI, Michalek RD, Zorn KM, Ekins S, Yasuda K, Fukuda Y, Schuetz JD, Mukherjee K, Schuetz EG. Metabolomic and transcriptomic analysis reveals endogenous substrates and metabolic adaptation in rats lacking Abcg2 and Abcb1a transporters. PLoS One 2021; 16:e0253852. [PMID: 34255797 PMCID: PMC8277073 DOI: 10.1371/journal.pone.0253852] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 06/14/2021] [Indexed: 12/21/2022] Open
Abstract
Abcg2/Bcrp and Abcb1a/Pgp are xenobiotic efflux transporters limiting substrate permeability in the gastrointestinal system and brain, and increasing renal and hepatic drug clearance. The systemic impact of Bcrp and Pgp ablation on metabolic homeostasis of endogenous substrates is incompletely understood. We performed untargeted metabolomics of cerebrospinal fluid (CSF) and plasma, transcriptomics of brain, liver and kidney from male Sprague Dawley rats (WT) and Bcrp/Pgp double knock-out (dKO) rats, and integrated metabolomic/transcriptomic analysis to identify putative substrates and perturbations in canonical metabolic pathways. A predictive Bayesian machine learning model was used to predict in silico those metabolites with greater substrate-like features for either transporters. The CSF and plasma levels of 169 metabolites, nutrients, signaling molecules, antioxidants and lipids were significantly altered in dKO rats, compared to WT rats. These metabolite changes suggested alterations in histidine, branched chain amino acid, purine and pyrimidine metabolism in the dKO rats. Levels of methylated and sulfated metabolites and some primary bile acids were increased in dKO CSF or plasma. Elevated uric acid levels appeared to be a primary driver of changes in purine and pyrimidine biosynthesis. Alterations in Bcrp/Pgp dKO CSF levels of antioxidants, precursors of neurotransmitters, and uric acid suggests the transporters may contribute to the regulation of a healthy central nervous system in rats. Microbiome-generated metabolites were found to be elevated in dKO rat plasma and CSF. The altered dKO metabolome appeared to cause compensatory transcriptional change in urate biosynthesis and response to lipopolysaccharide in brain, oxidation-reduction processes and response to oxidative stress and porphyrin biosynthesis in kidney, and circadian rhythm genes in liver. These findings present insight into endogenous functions of Bcrp and Pgp, the impact that transporter substrates, inhibitors or polymorphisms may have on metabolism, how transporter inhibition could rewire drug sensitivity indirectly through metabolic changes, and identify functional Bcrp biomarkers.
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Affiliation(s)
- Samit Ganguly
- Cancer & Developmental Biology Track, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - David Finkelstein
- Department of Computational Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Timothy I. Shaw
- Department of Computational Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | | | - Kimberly M. Zorn
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina, United States of America
| | - Sean Ekins
- Collaborations Pharmaceuticals, Inc., Raleigh, North Carolina, United States of America
| | - Kazuto Yasuda
- Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Yu Fukuda
- Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - John D. Schuetz
- Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Kamalika Mukherjee
- Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Erin G. Schuetz
- Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
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Xu J, Liu Y, Liu J, Shou Y, Xiong Z, Xiong H, Xu T, Wang Q, Liu D, Liang H, Yang H, Yang X, Zhang X. Low Expression Levels of SLC22A12 Indicates a Poor Prognosis and Progresses Clear Cell Renal Cell Carcinoma. Front Oncol 2021; 11:659208. [PMID: 34249694 PMCID: PMC8262335 DOI: 10.3389/fonc.2021.659208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 04/07/2021] [Indexed: 01/07/2023] Open
Abstract
Clear cell renal cell carcinoma (ccRCC) accounts for approximately 4/5 of all kidney cancers. Accumulation of minor changes in the cellular homeostasis may be one cause of ccRCC. Therefore, we downloaded the RNA sequencing and survival data of the kidney renal cell carcinoma (KIRC) cohort from the Cancer Genome Atlas (TCGA) database. After the univariate and multivariate Cox regression analyses, 19 kidney-specific differentially expressed genes (DEGs) were found. Solute Carrier Family 22 Member 12 (SLC22A12) resulted in an independent prognostic predictor for both overall survival (OS) and disease-free survival (DFS). SLC22A12 expression was lower in tumoral tissue compared to normal tissue. Moreover, patients in the SLC22A12 low expression group had a higher pathological stage and worse survival than the high expression group. Additionally, qRT-PCR assay, immunoblotting test (IBT), and immunohistochemical (IHC) analyses of cancer tissues/cells and the corresponding normal controls verified that SLC22A12 is downregulated in ccRCC. Receiver operator characteristic (ROC) curves showed that the low expression level of SLC22A12 could be a good diagnostic marker for ccRCC (AUC=0.7258; p <0.0001). Gene set enrichment analysis (GSEA) showed that SLC22A12 expression levels are related to metabolism, cell cycle, and tumor-related signaling pathways. GO and KEGG analyses revealed that SLC22A12 transports multiple organic compounds, ions, and hormones and participates in the extracellular structure organization. Furthermore, SLC22A12 over-expression in vitro inhibited the proliferation, migration, and invasion of renal cancer cells by regulating PI3K/Akt pathways. Such effects were reversed when knocking out SLC22A12. In summary, as a transporter for many vital metabolites, SLC22A12 may affect tumor cell survival through its impacts on the mentioned metabolites. In conclusion, this study uncovered that SLC22A12 is a promising prognostic and diagnostic biomarker for ccRCC.
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Affiliation(s)
- Jiaju Xu
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuenan Liu
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingchong Liu
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yi Shou
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhiyong Xiong
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hairong Xiong
- Department of Pathogenic Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
| | - Tianbo Xu
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qi Wang
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Di Liu
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Huageng Liang
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hongmei Yang
- Department of Pathogenic Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
| | - Xiong Yang
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiaoping Zhang
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen, China
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Torres AM, Dnyanmote AV, Granados JC, Nigam SK. Renal and non-renal response of ABC and SLC transporters in chronic kidney disease. Expert Opin Drug Metab Toxicol 2021; 17:515-542. [PMID: 33749483 DOI: 10.1080/17425255.2021.1899159] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION The solute carrier (SLC) and the ATP-binding cassette (ABC) transporter superfamilies play essential roles in the disposition of small molecules (endogenous metabolites, uremic toxins, drugs) in the blood, kidney, liver, intestine, and other organs. In chronic kidney disease (CKD), the loss of renal function is associated with altered function of remote organs. As renal function declines, many molecules accumulate in the plasma. Many studies now support the view that ABC and SLC transporters as well as drug metabolizing enzymes (DMEs) in renal and non-renal tissues are directly or indirectly affected by the presence of various types of uremic toxins, including those derived from the gut microbiome; this can lead to aberrant inter-organ communication. AREAS COVERED Here, the expression, localization and/or function of various SLC and ABC transporters as well as DMEs in the kidney and other organs are discussed in the context of CKD and systemic pathophysiology. EXPERT OPINION According to the Remote Sensing and Signaling Theory (RSST), a transporter and DME-centric network that optimizes local and systemic metabolism maintains homeostasis in the steady state and resets homeostasis following perturbations due to renal dysfunction. The implications of this view for pharmacotherapy of CKD are also discussed.
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Affiliation(s)
- Adriana M Torres
- Pharmacology Area, Faculty of Biochemistry and Pharmaceutical Sciences, National University of Rosario, CONICET, Suipacha 531, S2002LRK Rosario, Argentina
| | - Ankur V Dnyanmote
- Department of Pediatrics, IWK Health Centre - Dalhousie University, 5850 University Ave, Halifax, NS, B3K 6R8, Canada
| | - Jeffry C Granados
- Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0693, USA
| | - Sanjay K Nigam
- Departments of Pediatrics and Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0693, USA
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Zeng Y, Ma Y, Yang Z, Mao J, Zheng Y. Antihyperuricemic efficacy of Scopoletin-loaded Soluplus micelles in yeast extract/potassium oxonate-induced hyperuricemic mice. Drug Dev Ind Pharm 2020; 46:1550-1557. [PMID: 32811191 DOI: 10.1080/03639045.2020.1811302] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Scopoletin (Sco) has great potential for hyperuricemia therapy. However, the relatively low oral bioavailability of Sco limits its further applications. Soluplus-based Sco micelles (Sco-Ms) were successfully prepared in our previous work. The oral bioavailability of Sco-Ms was increased by 438% compared with free Sco. In this study, we aimed to compare the biodistribution and antihyperuricemic efficacy of Sco and Sco-Ms, and explore their therapeutic mechanisms as well. We studied the tissue biodistribution of Sco and Sco-Ms after they were orally administered to mice. The antihyperuricemic effect and the therapeutic mechanisms of Sco and Sco-Ms were evaluated using yeast extract/potassium oxonate-induced hyperuricemia model in mice. The Sco concentration in each tissue was significantly higher than that of Sco suspension after orally administrating Sco-Ms to mice. Oral delivery of Sco-Ms exhibited significantly stronger hypouricemic efficacy in hyperuricemic mice than Sco. Meanwhile, Sco-Ms showed a better protective effect on mice kidney injury. The hypouricemic efficacy of Sco was due to promoting the excretion of uric acid via modulating the alteration of gene expression levels of renal uric acid transporter (URAT1), glucose transporter (GLUT9), and organic anion transporter 1 (OAT1). Sco-Ms could not only restore the dysregulation of URAT1, GLUT9, and OAT1 more effectively, but also down-regulate the activity of hepatic xanthine oxidase (XOD) to inhibit the production of uric acid. In conclusion, taken together, Sco-Ms represents a potential oral strategy for the treatment of hyperuricemia.
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Affiliation(s)
- Yingchun Zeng
- School of Pharmacy, Chengdu Medical College, Chengdu, China
| | - Yu Ma
- School of Pharmacy, Chengdu Medical College, Chengdu, China
| | - Zhengyu Yang
- School of Pharmacy, Chengdu Medical College, Chengdu, China
| | - Jiamin Mao
- School of Pharmacy, Chengdu Medical College, Chengdu, China
| | - Yaxin Zheng
- School of Pharmacy, Chengdu Medical College, Chengdu, China
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Rosenthal SB, Bush KT, Nigam SK. A Network of SLC and ABC Transporter and DME Genes Involved in Remote Sensing and Signaling in the Gut-Liver-Kidney Axis. Sci Rep 2019; 9:11879. [PMID: 31417100 PMCID: PMC6695406 DOI: 10.1038/s41598-019-47798-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 07/23/2019] [Indexed: 02/07/2023] Open
Abstract
Genes central to drug absorption, distribution, metabolism and elimination (ADME) also regulate numerous endogenous molecules. The Remote Sensing and Signaling Hypothesis argues that an ADME gene-centered network-including SLC and ABC "drug" transporters, "drug" metabolizing enzymes (DMEs), and regulatory genes-is essential for inter-organ communication via metabolites, signaling molecules, antioxidants, gut microbiome products, uremic solutes, and uremic toxins. By cross-tissue co-expression network analysis, the gut, liver, and kidney (GLK) formed highly connected tissue-specific clusters of SLC transporters, ABC transporters, and DMEs. SLC22, SLC25 and SLC35 families were network hubs, having more inter-organ and intra-organ connections than other families. Analysis of the GLK network revealed key physiological pathways (e.g., involving bile acids and uric acid). A search for additional genes interacting with the network identified HNF4α, HNF1α, and PXR. Knockout gene expression data confirmed ~60-70% of predictions of ADME gene regulation by these transcription factors. Using the GLK network and known ADME genes, we built a tentative gut-liver-kidney "remote sensing and signaling network" consisting of SLC and ABC transporters, as well as DMEs and regulatory proteins. Together with protein-protein interactions to prioritize likely functional connections, this network suggests how multi-specificity combines with oligo-specificity and mono-specificity to regulate homeostasis of numerous endogenous small molecules.
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Affiliation(s)
- Sara Brin Rosenthal
- Center for Computational Biology and Bioinformatics, University of California at San Diego, La Jolla, CA, 92093-0693, USA
| | - Kevin T Bush
- Departments of Pediatrics, University of California at San Diego, La Jolla, CA, 92093-0693, USA
| | - Sanjay K Nigam
- Departments of Pediatrics, University of California at San Diego, La Jolla, CA, 92093-0693, USA.
- Departments of Medicine, University of California at San Diego, La Jolla, CA, 92093-0693, USA.
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Wan Y, Wang F, Zou B, Shen Y, Li Y, Zhang A, Fu G. Molecular mechanism underlying the ability of caffeic acid to decrease uric acid levels in hyperuricemia rats. J Funct Foods 2019. [DOI: 10.1016/j.jff.2019.03.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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The systems biology of uric acid transporters: the role of remote sensing and signaling. Curr Opin Nephrol Hypertens 2019; 27:305-313. [PMID: 29847376 DOI: 10.1097/mnh.0000000000000427] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW Uric acid homeostasis in the body is mediated by a number of SLC and ABC transporters in the kidney and intestine, including several multispecific 'drug' transporters (e.g., OAT1, OAT3, and ABCG2). Optimization of uric acid levels can be viewed as a 'systems biology' problem. Here, we consider uric acid transporters from a systems physiology perspective using the framework of the 'Remote Sensing and Signaling Hypothesis.' This hypothesis explains how SLC and ABC 'drug' and other transporters mediate interorgan and interorganismal communication (e.g., gut microbiome and host) via small molecules (e.g., metabolites, antioxidants signaling molecules) through transporters expressed in tissues lining body fluid compartments (e.g., blood, urine, cerebrospinal fluid). RECENT FINDINGS The list of uric acid transporters includes: SLC2A9, ABCG2, URAT1 (SLC22A12), OAT1 (SLC22A6), OAT3 (SLC22A8), OAT4 (SLC22A11), OAT10 (SLC22A13), NPT1 (SLC17A1), NPT4 (SLC17A3), MRP2 (ABCC2), MRP4 (ABCC4). Normally, SLC2A9, - along with URAT1, OAT1 and OAT3, - appear to be the main transporters regulating renal urate handling, while ABCG2 appears to regulate intestinal transport. In chronic kidney disease (CKD), intestinal ABCG2 becomes much more important, suggesting remote organ communication between the injured kidney and the intestine. SUMMARY The remote sensing and signaling hypothesis provides a useful systems-level framework for understanding the complex interplay of uric acid transporters expressed in different tissues involved in optimizing uric acid levels under normal and diseased (e.g., CKD, gut microflora dysbiosis) conditions.
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Wu W, Bush KT, Nigam SK. Key Role for the Organic Anion Transporters, OAT1 and OAT3, in the in vivo Handling of Uremic Toxins and Solutes. Sci Rep 2017; 7:4939. [PMID: 28694431 PMCID: PMC5504054 DOI: 10.1038/s41598-017-04949-2] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/30/2017] [Indexed: 01/25/2023] Open
Abstract
In vitro data indicates that the kidney proximal tubule (PT) transporters of uremic toxins and solutes (e.g., indoxyl sulfate, p-cresol sulfate, kynurenine, creatinine, urate) include two “drug” transporters of the organic anion transporter (OAT) family: OAT1 (SLC22A6, originally NKT) and OAT3 (SLC22A8). Here, we have examined new and prior metabolomics data from the Oat1KO and Oat3KO, as well as newly obtained metabolomics data from a “chemical double” knockout (Oat3KO plus probenecid). This gives a picture of the in vivo roles of OAT1 and OAT3 in the regulation of the uremic solutes and supports the centrality of these “drug” transporters in independently and synergistically regulating uremic metabolism. We demonstrate a key in vivo role for OAT1 and/or OAT3 in the handling of over 35 uremic toxins and solutes, including those derived from the gut microbiome (e.g., CMPF, phenylsulfate, indole-3-acetic acid). Although it is not clear whether trimethylamine-N-oxide (TMAO) is directly transported, the Oat3KO had elevated plasma levels of TMAO, which is associated with cardiovascular morbidity in chronic kidney disease (CKD). As described in the Remote Sensing and Signaling (RSS) Hypothesis, many of these molecules are involved in interorgan and interorganismal communication, suggesting that uremia is, at least in part, a disorder of RSS.
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Affiliation(s)
- Wei Wu
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Kevin T Bush
- Department of Pediatrics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Sanjay K Nigam
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. .,Department of Pediatrics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. .,Departments of Medicine, Pediatrics, and Cellular and Molecular Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
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