title: Alanyl-glutamine dipeptide restores the cytoprotective stress proteome of mesothelial cells exposed to peritoneal dialysis fluids.
abstract: BACKGROUND
  Exposure of mesothelial cells to peritoneal dialysis fluids (PDF) results in cytoprotective cellular stress responses (CSR) that counteract PDF-induced damage. In this study, we tested the hypothesis that the CSR may be inadequate in relevant models of peritoneal dialysis (PD) due to insufficient levels of glutamine, resulting in increased vulnerability against PDF cytotoxicity. We particularly investigated the role of alanyl-glutamine (Ala-Gln) dipeptide on the cytoprotective PDF stress proteome.
  
  
  METHODS
  Adequacy of CSR was investigated in two human in vitro models (immortalized cell line MeT-5A and mesothelial cells derived from peritoneal effluent of uraemic patients) following exposure to heat-sterilized glucose-based PDF (PD4-Dianeal, Baxter) diluted with medium and, in a comparative proteomics approach, at different levels of glutamine ranging from depletion (0 mM) via physiological (0.7 mM) to pharmacological levels (8 mM administered as Ala-Gln).
  
  
  RESULTS
  Despite severe cellular injury, expression of cytoprotective proteins was dampened upon PDF exposure at physiological glutamine levels, indicating an inadequate CSR. Depletion of glutamine aggravated cell injury and further reduced the CSR, whereas addition of Ala-Gln at pharmacological level restored an adequate CSR, decreasing cellular damage in both PDF exposure systems. Ala-Gln specifically stimulated chaperoning activity, and cytoprotective processes were markedly enhanced in the PDF stress proteome.
  
  
  CONCLUSIONS
  Taken together, this study demonstrates an inadequate CSR of mesothelial cells following PDF exposure associated with low and physiological levels of glutamine, indicating a new and potentially relevant pathomechanism. Supplementation of PDF with pharmacological doses of Ala-Gln restored the cytoprotective stress proteome, resulting in improved resistance of mesothelial cells to exposure to PDF. Future work will study the clinical relevance of CSR-mediated cytoprotection.
authors.affiliation: Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Kratochwill
authors.forename: Michael
authors.initials: M
authors.lastname: Boehm
authors.forename: Rebecca
authors.initials: R
authors.lastname: Herzog
authors.forename: Anton Michael
authors.initials: AM
authors.lastname: Lichtenauer
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Salzer
authors.forename: Michael
authors.initials: M
authors.lastname: Lechner
authors.forename: Lilian
authors.initials: L
authors.lastname: Kuster
authors.forename: Konstantin
authors.initials: K
authors.lastname: Bergmeister
authors.forename: Andreas
authors.initials: A
authors.lastname: Rizzi
authors.forename: Bernd
authors.initials: B
authors.lastname: Mayer
authors.forename: Christoph
authors.initials: C
authors.lastname: Aufricht
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D019610:Cytoprotection / Q000187:drug effects; D015314:Dialysis Solutions / Q000009:adverse effects*; D004151:Dipeptides / Q000494:pharmacology*; D015180:Electrophoresis, Gel, Two-Dimensional; D004848:Epithelium / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007223:Infant; D008297:Male; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D020543:Proteome / Q000032:analysis* / Q000187:drug effects*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D015415:Biomarkers; D015314:Dialysis Solutions; D004151:Dipeptides; D020543:Proteome; C054122:alanylglutamine