title: Activation of p38 mitogen-activated protein kinase promotes peritoneal fibrosis by regulating fibrocytes.
abstract: BACKGROUND
  Peritoneal fibrosis is a serious complication of long-term peritoneal dialysis, and yet the precise pathogenic mechanisms of peritoneal fibrosis remain unknown. Fibrocytes participate in tissue fibrosis and express chemokine receptors that are necessary for migration. The p38 mitogen-activated protein kinase (MAPK) pathway regulates the production of chemokines and has been demonstrated to contribute to the pathogenesis of various fibrotic conditions. Accordingly, we used an experimental mouse model of peritoneal fibrosis to examine the dependency of fibrocytes on p38MAPK signaling.
  
  
  METHODS
  Peritoneal fibrosis was induced in mice by the injection of 0.1% chlorhexidine gluconate (CG) into the abdominal cavity. Mice were treated with FR167653, a specific inhibitor of p38MAPK, and immunohistochemical studies were performed to detect fibrocytes and cells positive for phosphorylated p38MAPK. The involvement of p38MAPK in the activation of fibrocytes also was also investigated in vitro.
  
  
  RESULTS
  Fibrocytes infiltrated peritoneum in response to CG, and that response was accompanied by progressive peritoneal fibrosis. The phosphorylation of p38MAPK, as defined by CD45+ spindle-shaped cells, was detected both in peritoneal mesothelial cells and in fibrocytes. The level of peritoneal expression of CCL2, a chemoattractant for fibrocytes, was upregulated by CG injection, and treatment with FR167653 reduced the number of cells positive for phosphorylated p38MAPK, the peritoneal expression of CCL2, and the extent of peritoneal fibrosis. Pretreatment with FR167653 inhibited the expression of procollagen type I α1 induced by transforming growth factor-β1.
  
  
  CONCLUSIONS
  Our results suggest that p38MAPK signaling contributes to peritoneal fibrosis by regulating fibrocyte function.
authors: Department of Disease Control and Homeostasis, Institute of Medical, Pharmaceutical and Health Sciences, Faculty of Medicine, Kanazawa University, Kanazawa, Japan. kokkii1973@hotmail.com
authors: Satoshi
authors: S
authors: Kokubo
authors: Norihiko
authors: N
authors: Sakai
authors: Kengo
authors: K
authors: Furuichi
authors: Tadashi
authors: T
authors: Toyama
authors: Shinji
authors: S
authors: Kitajima
authors: Toshiya
authors: T
authors: Okumura
authors: Kouji
authors: K
authors: Matsushima
authors: Shuichi
authors: S
authors: Kaneko
authors: Takashi
authors: T
authors: Wada
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology*; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010530:Peritoneal Dialysis / Q000009:adverse effects; D056627:Peritoneal Fibrosis / Q000201:enzymology* / Q000473:pathology / Q000517:prevention & control; D010537:Peritoneum / Q000201:enzymology / Q000473:pathology*; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C104334:FR 167653; D006131:Growth Inhibitors; D011720:Pyrazoles; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases