title: Functional genomic analysis identifies indoxyl sulfate as a major, poorly dialyzable uremic toxin in end-stage renal disease.
abstract: BACKGROUND
  Chronic renal failure is characterized by progressive renal scarring and accelerated arteriosclerotic cardiovascular disease despite what is considered to be adequate hemodialysis or peritoneal dialysis. In rodents with reduced renal mass, renal scarring has been attributed to poorly filtered, small protein-bound molecules. The best studied of these is indoxyl sulfate (IS).
  
  
  METHODS
  We have attempted to establish whether there are uremic toxins that are not effectively removed by hemodialysis. We examined plasma from patients undergoing hemodialysis, employing global gene expression in normal human renal cortical cells incubated in pre- and post- dialysis plasma as a reporter system. Responses in cells incubated with pre- and post-dialysis uremic plasma (n = 10) were compared with responses elicited by plasma from control subjects (n = 5). The effects of adding IS to control plasma and of adding probenecid to uremic plasma were examined. Plasma concentrations of IS were measured by HPLC (high pressure liquid chromatography).
  
  
  RESULTS
  Gene expression in our reporter system revealed dysregulation of 1912 genes in cells incubated with pre-dialysis uremic plasma. In cells incubated in post-dialysis plasma, the expression of 537 of those genes returned to baseline but the majority of them (1375) remained dysregulated. IS concentration was markedly elevated in pre- and post-dialysis plasma. Addition of IS to control plasma simulated more than 80% of the effects of uremic plasma on gene expression; the addition of probenecid, an organic anion transport (OAT) inhibitor, to uremic plasma reversed the changes in gene expression.
  
  
  CONCLUSIONS
  These findings provide evidence that hemodialysis fails to effectively clear one or more solutes that effect gene expression, in our reporter system, from the plasma of patients with uremia. The finding that gene dysregulation was simulated by the addition of IS to control plasma and inhibited by addition of an OAT inhibitor to uremic plasma identifies IS as a major, poorly dialyzable, uremic toxin. The signaling pathways initiated by IS and possibly other solutes not effectively removed by dialysis may participate in the pathogenesis of renal scarring and uremic vasculopathy.
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Sachin
authors: S
authors: Jhawar
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Prabhjot
authors: P
authors: Singh
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Daniel
authors: D
authors: Torres
authors: Department of Dermatology, University of California San Francisco, San Francisco, CA, United States of America.
authors: Francisco
authors: F
authors: Ramirez-Valle
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Hania
authors: H
authors: Kassem
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Trina
authors: T
authors: Banerjee
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Igor
authors: I
authors: Dolgalev
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America; Department of Pathology and Center for Health Informatics and Bioinformatics, New York University Langone Medical Center, New York, NY, United States of America.
authors: Adriana
authors: A
authors: Heguy
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America; Department of Pathology and Center for Health Informatics and Bioinformatics, New York University Langone Medical Center, New York, NY, United States of America.
authors: Jiri
authors: J
authors: Zavadil
authors: Department of Medicine New York University Langone Medical Center, New York, NY, United States of America.
authors: Jerome
authors: J
authors: Lowenstein
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007200:Indican / Q000097:blood*; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D010949:Plasma / Q000737:chemistry / Q000378:metabolism; D011339:Probenecid / Q000494:pharmacology; D006435:Renal Dialysis; D013552:Swine; D014511:Uremia / Q000209:etiology*
chemical_list: D003470:Culture Media; D007200:Indican; D011339:Probenecid