title: Dipyridamole inhibits TGF-beta-induced collagen gene expression in human peritoneal mesothelial cells.
abstract: BACKGROUND
  Peritoneal matrix accumulation is characteristic of peritoneal fibrosis (PF). Continuous ambulatory peritoneal dialysis (CAPD) patients who had persistent transforming growth factor-beta (TGF-beta) in their drained effluent had an increased risk of PF. We previously reported that TGF-beta stimulates the expression of types I and III collagen mRNA in cultured human peritoneal mesangial cells (HPMCs), which may predispose them to develop PF. Pharmacological interventions to attenuate TGF-beta-stimulated matrix accumulation in HPMC may have therapeutic potential for the treatment of PF. The SMAD family and the extracellular signal-regulated protein kinase (ERK1/2, p44/p42) pathways have been shown to participate in TGF-beta signaling. Our current study identified these signal pathways in HPMCs and investigated the molecular mechanisms involved in the inhibitory effects of dipyridamole on TGF-beta-induced collagen gene expression in HPMCs.
  
  
  METHODS
  HPMCs were cultured from human omentum by an enzyme digestion
  
  
  METHODS
  Expression of collagen alpha1(I) mRNA was determined by Northern blotting. The SMAD proteins and the ERK1/2 activity were determined by Western blotting.
  
  
  RESULTS
  TGF-beta-stimulated collagen alpha1(I) mRNA expression of HPMC was inhibited by dipyridamole in a dose-dependent manner. Smad2 and ERK1/2 were activated in response to TGF-beta; however, TGF-beta had little effect on the protein expression of Smad4. The addition of PD98059, which blocked activation of ERK1/2, suppressed TGF-beta-induced collagen alpha1(I) mRNA expression in a dose-dependent manner. At a concentration that inhibited collagen gene expression (17 microg/mL), dipyridamole suppressed ERK1/2 activation by TGF-beta. In contrast, the same concentration of dipyridamole had no effect on TGF-beta-induced activation of Smad2.
  
  
  CONCLUSIONS
  Dipyridamole inhibits TGF-beta-induced collagen gene expression in HPMC through modulation of the ERK pathway. Our study of dipyridamole may provide therapeutic basis for clinical applications in the prevention of PF.
authors.affiliation: Department of Internal Medicine, Center for Optoelectronic Biomedicine and Surgery, College of Medicine, National Taiwan University, and Far Eastern Memorial Hospital, Taipei, Taiwan, ROC.
authors.forename: K Y
authors.initials: KY
authors.lastname: Hung
authors.forename: C T
authors.initials: CT
authors.lastname: Chen
authors.forename: J W
authors.initials: JW
authors.lastname: Huang
authors.forename: P H
authors.initials: PH
authors.lastname: Lee
authors.forename: T J
authors.initials: TJ
authors.lastname: Tsai
authors.forename: B S
authors.initials: BS
authors.lastname: Hsieh
mesh_terms: D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics*; D024042:Collagen Type I / Q000235:genetics; D024061:Collagen Type III / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D004176:Dipyridamole / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010529:Peritoneal Cavity / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497782:SMAD2 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D004176:Dipyridamole; D003094:Collagen; D020928:Mitogen-Activated Protein Kinases