Paclitaxel interrupts TGF-beta1 signaling between gallbladder epithelial cells and myofibroblasts.
BACKGROUND
The cellular and molecular mechanisms of fibrogenesis in the extrahepatic biliary epithelium are not known. Transforming growth factor-beta1 (TGF-beta1) is a cytokine implicated in signaling pathways that mediate collagen formation. An observation that paclitaxel (PT), applied topically into the rat common bile duct, inhibited stricture formation led us to hypothesize that PT's effects might be due to interruption of TGF-beta1 signaling between biliary epithelial cells and subepithelial myofibroblasts.


METHODS
We tested this hypothesis using an in vitro cell-culture model in which murine gallbladder epithelial cells (GBEC) are cultured separately or cocultured with human gallbladder myofibroblasts (GBMF).


RESULTS
Exposure to Escherichia coli lipopolysaccharide (LPS) enhanced TGF-beta1 mRNA expression and stimulated TGF-beta1 protein secretion into both apical and basolateral compartments in GBEC. This effect was more prominent with basolateral secretion and was also more pronounced in the coculture system. In GBMF, collagen I mRNA expression and protein secretion were stimulated by treatment with LPS or TGF-beta1. GBMF also expressed TGF-beta1 mRNA, whose levels were enhanced by exposure to either LPS or exogenous TGF-beta1. PT inhibited LPS-induced TGF-beta1 mRNA expression and protein secretion in GBEC in both culture systems. Tumor necrosis factor-alpha mRNA expression and protein secretion were not affected by PT in GBEC, demonstrating that the effects were specific for TGF-beta1. PT also inhibited LPS- and TGF-beta1-induced collagen I mRNA expression and protein secretion in GBMF.


CONCLUSIONS
These findings support a model in which GBEC communicate with subepithelial GBMF via TGF-beta1, leading to collagen deposition and fibrosis, and in which GBMF possess autocrine mechanisms involving TGF-beta1 that could regulate collagen production. PT inhibits these fibrogenic pathways.
Choi
Ho-Soon
HS
Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington. 98195, USA.
Savard
Christopher E
CE
Choi
Jae-Woon
JW
Kuver
Rahul
R
Lee
Sum P
SP
D000818:Animals; D002450:Cell Communication / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics; D004847:Epithelial Cells / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology*; D005355:Fibrosis; D005704:Gallbladder / Q000473:pathology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D017239:Paclitaxel / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D024042:Collagen Type I; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D007770:L-Lactate Dehydrogenase; D017239:Paclitaxel