title: Pentoxifylline modulates intracellular signalling of TGF-beta in cultured human peritoneal mesothelial cells: implications for prevention of encapsulating peritoneal sclerosis.
abstract: BACKGROUND
  Peritoneal matrix accumulation is a major characteristic of encapsulating peritoneal sclerosis (EPS), which is a serious complication in long-term peritoneal dialysis (PD) patients. We reported previously that TGF-beta stimulates collagen gene expression in cultured HPMC, and is attenuated by pentoxifylline (PTX). The SMAD family and the mitogen-activated protein kinase (MAPK) (ERK1/2, JNK and p38(HOG)) pathways have been shown to participate in TGF-beta signalling. However, how PTX modulates the intracellular signalling downstream to TGF-beta remains undetermined in HPMC. In this study, we explored these signalling pathways in HPMC, and investigated the molecular mechanisms involved in the inhibitory effects of PTX on TGF-beta-induced collagen gene expression in HPMC.
  
  
  METHODS
  HPMC was cultured from human omentum by an enzyme digestion method. The expression of collagen alpha1(I) mRNA was determined by northern blotting, while the SMAD proteins and the MAPK kinase activity were determined by western blotting.
  
  
  RESULTS
  TGF-beta-stimulated collagen alpha1(I) mRNA expression of HPMC was inhibited by PTX. The Smad2, ERK1/2 and p38(HOG) pathways were activated in response to TGF-beta. However, TGF-beta displayed no activation of the JNK pathway in HPMC. The addition of PD98059 and SB203580, which blocked the activation of ERK1/2 and p38(HOG), respectively, suppressed the TGF-beta-induced collagen alpha1(I) mRNA expression. At a concentration (300 micro g/ml) that inhibited the collagen gene expression, PTX suppressed the ERK1/2 and p38(HOG) activation by TGF-beta. In contrast, PTX had no effect on the TGF-beta-induced activation of Smad2, under the same concentration.
  
  
  CONCLUSIONS
  PTX inhibits the TGF-beta-induced collagen gene expression in HPMC through modulating the ERK1/2 and p38(HOG) pathways. Our study of PTX may provide the therapeutic basis for clinical applications in the prevention of EPS.
authors.affiliation: Department of Internal Medicine, Far-Eastern Memorial Hospital, Pan-Chiao, Taiwan, ROC.
authors.forename: Kuan-Yu
authors.initials: KY
authors.lastname: Hung
authors.forename: Jenq-Wen
authors.initials: JW
authors.lastname: Huang
authors.forename: Chin-Tin
authors.initials: CT
authors.lastname: Chen
authors.forename: Po-Huang
authors.initials: PH
authors.lastname: Lee
authors.forename: Tun-Jun
authors.initials: TJ
authors.lastname: Tsai
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D004847:Epithelial Cells; D006801:Humans; D010431:Pentoxifylline / Q000494:pharmacology*; D010529:Peritoneal Cavity / Q000166:cytology; D010532:Peritoneal Diseases / Q000473:pathology* / Q000517:prevention & control*; D010537:Peritoneum / Q000166:cytology / Q000378:metabolism; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D012598:Sclerosis / Q000473:pathology; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000187:drug effects*; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000187:drug effects* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D010431:Pentoxifylline