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The molecular basis of the renal and vascular consequences of Uremia

ABSTRACT: Background. Chronic renal failure is characterized by progressive renal scarring and accelerated cardiovascular disease. In animal models, this is thought to be due to non-dialyzable uremic toxins – small, protein-bound molecules normally secreted via Organic Anion Transporters (OATs) in the proximal renal tubule,rather than filtered at the glomerulus. The best studied of these is indoxyl sulfate (IS). Methods. We examined global gene expression responses in cultured normal human renal tubular cells incubated with control plasma (n=5) or pre- and post-dialysis uremic plasma (n=10). Results. GeneSpring analysis of microarrays revealed significantly altered expression of 2016 genes. The expression of 537 genes “normalized” in post-dialysis plasma, suggesting removal of “low molecular weight uremic toxins” by dialysis. The expression of the majority of dysregulated genes (1479) was not normalized in post-dialysis plasma. These likely represent the effects of substances not effectively removed by dialysis (“protein-bound uremic toxins”). Addition of indoxyl sulfateto control plasma simulated most effects (81.1%) of uremic plasma, while the addition of probenecid, an OAT inhibitor, to uremic plasma reversed most changes in gene expression. Analysis of molecular programs with the Gene Set Enrichment Analysis and the DAVID database revealed patterns common to indoxyl sulfate-treated control plasma, pre-dialysis, and post-dialysis uremic plasma. These included increased cell cycle, pro-inflammatory, and pro-fibrotic molecular programs, particularly genes in the TGF-β pathway. Conclusion: These findings provide insight into the role of non-dialyzable, protein-bound uremic toxins in the pathogenesis of renal scarring and uremic vasculopathy. The GSEA patterns confirm that inflammatory and fibrotic programs are active.

ORGANISM(S): Homo sapiens

PROVIDER: GSE45709 | GEO | 2013/06/30

SECONDARY ACCESSION(S): PRJNA195913

REPOSITORIES: GEO

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Project description:Background. Chronic renal failure is characterized by progressive renal scarring and accelerated cardiovascular disease. In animal models, this is thought to be due to non-dialyzable uremic toxins M-bM-^@M-^S small, protein-bound molecules normally secreted via Organic Anion Transporters (OATs) in the proximal renal tubule,rather than filtered at the glomerulus. The best studied of these is indoxyl sulfate (IS). Methods. We examined global gene expression responses in cultured normal human renal tubular cells incubated with control plasma (n=5) or pre- and post-dialysis uremic plasma (n=10). Results. GeneSpring analysis of microarrays revealed significantly altered expression of 2016 genes. The expression of 537 genes M-bM-^@M-^\normalizedM-bM-^@M-^] in post-dialysis plasma, suggesting removal of M-bM-^@M-^\low molecular weight uremic toxinsM-bM-^@M-^] by dialysis. The expression of the majority of dysregulated genes (1479) was not normalized in post-dialysis plasma. These likely represent the effects of substances not effectively removed by dialysis (M-bM-^@M-^\protein-bound uremic toxinsM-bM-^@M-^]). Addition of indoxyl sulfateto control plasma simulated most effects (81.1%) of uremic plasma, while the addition of probenecid, an OAT inhibitor, to uremic plasma reversed most changes in gene expression. Analysis of molecular programs with the Gene Set Enrichment Analysis and the DAVID database revealed patterns common to indoxyl sulfate-treated control plasma, pre-dialysis, and post-dialysis uremic plasma. These included increased cell cycle, pro-inflammatory, and pro-fibrotic molecular programs, particularly genes in the TGF-M-NM-2 pathway. Conclusion: These findings provide insight into the role of non-dialyzable, protein-bound uremic toxins in the pathogenesis of renal scarring and uremic vasculopathy. The GSEA patterns confirm that inflammatory and fibrotic programs are active. Transcriptomic remodeling in response to external stimulus RNA from non-immortalized cultured renal cortical cells incubated with plasma samples from 5 controls, 10 uremics pre-dialysis, 10 uremics post-dialysis, 5 controls with indoxyl sulfate added, 5 uremics pre-dialysis with probenecid added, 5 uremics post-dialysis with indoxyl sulfate added

Project description:Indoxyl sulfate (IS) is a uremic toxin and ligand of the aryl-hydrocarbon receptor (Ahr), a transcriptional regulator. Elevated serum IS may contribute to the progression of kidney disease. Therefore, we assessed mouse podocyte damage mediated by IS. Ahr was predominantly localized to the podocyte nucleus in vivo and in vitro. In isolated glomeruli, IS-exposure for 2 – 24 h induced Cyp1a1 expression, the most sensitive biomarker of Ahr activation. Mice exposed to IS for 4–8 weeks exhibited microalbuminuria, and mild glomerular injury characterized by ischemic changes, partial podocyte foot process effacement, as well as vascular and tubulointerstitial damage. Chronically IS-exposed kidneys exhibited decreased mRNA, decreased protein levels, and altered staining patterns for podocin, synaptopodin, and non-muscle myosin IIA (Myh9). Immortalized podocytes, upon differentiation, exhibited Ahr nuclear translocation beginning 30 min after 1 mM IS-exposure. At 2 h, there was a dose-dependent decrease in podocyte mRNA expression of WT1, Podxl, Snypo, Myh9, Actn4, and Cd2ap. After 24 h of exposure to IS, podocytes were smaller, had fewer actin/Myh9 fibers, and decreased viability. Ahr-RNAi decreased mRNA expression of podocyte-specific proteins and inhibited Cyp1a1 induction by IS-exposure. Combinations of Ahr-RNAi and IS-exposure further decreased Myh9 expression. In immortalized human podocytes, IS treatment caused cell injury, decreased mRNA expression of podocyte-specific proteins, integrins, collagens, cytoskeletal proteins, and bone morphogenetic proteins, and increased cytokine and chemokine expression. Thus, chronic IS-exposure causes glomerular damage by activating Ahr, altering podocyte function, differentiation, and morphology, and inducing a pro-inflammatory phenotype. Podocyte cells treated with Indoxyl sulfate, a uremic toxin and aryl-hydrocarbon receptor ligand, mediates progressive glomerular disease by damaging podocytes Human podocyte cell line treated with or without 3-Indoxyl sulfate (1mM/0.1%DMSO) in three replications

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The molecular basis of the renal and vascular consequences of Uremia

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