title: Sirolimus increases transforming growth factor-beta1 expression and potentiates chronic cyclosporine nephrotoxicity.
abstract: BACKGROUND
  Sirolimus (SRL) is increasingly being used to decrease cyclosporine (CsA) exposure. SRL is not known to be nephrotoxic and has a mechanism of action distinct from CsA. We investigated the effect of combining CsA and SRL on renal structure and function and on transforming growth factor-beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in a model of chronic CsA nephrotoxicity.
  
  
  METHODS
  Rats treated with vehicle, SRL 0.3 mg/kg/day, CsA 5 or 10 mg/kg/day, or CsA5+SRL were sacrificed at 7 or 28 days. Physiologic and histologic changes were studied in addition to TGF-beta1 mRNA and protein expressions, and mRNA expression of plasminogen activator inhibitor-1 (PAI-1) and ECM proteins biglycan and types I and IV collagen.
  
  
  RESULTS
  While SRL alone did not alter renal function and structure, it potentiated the nephrotoxic actions of CsA when used in combination with low-dose CsA5 and resulted in significant changes similar to high-dose CsA10. In addition, SRL alone increased TGF-beta1 by 44% to 49% (P < 0.05 vs. VH). When used in combination with low-dose CsA5, SRL potentiated TGF-beta1 mRNA and protein by 121% and 176%, respectively (P < 0.05 vs. VH and CsA5), to levels achieved with high-dose CsA10. The expression of the ECM proteins followed that of TGF-beta1; a similar effect was observed with PAI-1, suggesting a decrease in ECM degradation.
  
  
  CONCLUSIONS
  Because SRL augments nephrotoxicity, caution should be exercised when it is used in combination with CsA. More studies are needed to determine the long-term clinical impact of SRL on nephrotoxicity and allograft function.
authors.affiliation: Division of Nephrology, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA. Fuad.Shihab@hsc.utah.edu
authors.forename: Fuad S
authors.initials: FS
authors.lastname: Shihab
authors.forename: William M
authors.initials: WM
authors.lastname: Bennett
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.forename: Seung-Ok
authors.initials: SO
authors.lastname: Choi
authors.forename: Takeshi F
authors.initials: TF
authors.lastname: Andoh
mesh_terms: D000818:Animals; D002908:Chronic Disease; D016572:Cyclosporine / Q000493:pharmacokinetics / Q000506:poisoning*; D004357:Drug Synergism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D008297:Male; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020123:Sirolimus / Q000493:pharmacokinetics / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
chemical_list: D016326:Extracellular Matrix Proteins; D007166:Immunosuppressive Agents; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016572:Cyclosporine; D020123:Sirolimus