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Effect of tumor necrosis factor alpha on intrahepatic bile duct epithelial cell of rat liver
1Third Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Abstract:
Tumor necrosis factor alpha (TNF-alpha), which is primarily produced by macrophages, is a cytokine with various biological activities. Macrophage infiltration often accompanies experimental cholangitis in rats, and chronic cholangitis in humans. The pathophysiologic significance of TNF-alpha in cholangitis is not known. We used cultured, polarized intrahepatic bile duct epithelial cells (IBDECs) from rat liver to determine whether TNF-alpha directly affects the organization of IBDEC monolayers. The addition of recombinant TNF-alpha (rTNF-alpha) to culture media at concentrations from 10 to 200 U/mL lacked cytotoxicity to the IBDECs as judged by trypan blue exclusion and lactate dehydrogenase (LDH) release. rTNF-alpha transiently reduced transepithelial electrical resistance in a dose-dependent manner. During this decrease in resistance, the cellular tight junctions became leaky, allowing horseradish peroxidase (HRP) penetration. rTNF-alpha, at concentrations up to 200 U/mL, did not detach IBDECs from Matrigel, an artificial basement membrane. Electron microscopy and immunohistochemistry for F-actin showed a well-preserved cell structure and organization of IBDECs. Results suggest that TNF-alpha is nontoxic to IBDECs, and that it increases the permeability of tight junctions. TNF-alpha may thus disturb the barrier function of the bile duct.
Insights
Tumor necrosis factor alpha (TNF-alpha) does not harm bile duct cells but increases the leakiness of their tight junctions. This cytokine may disrupt the bile duct
Area of Science:
- Cell Biology
- Immunology
- Gastroenterology
Background:
- Macrophage infiltration is common in cholangitis.
- The role of TNF-alpha in cholangitis is unclear.
Purpose of the Study:
- To investigate the direct effects of TNF-alpha on intrahepatic bile duct epithelial cells (IBDECs).
- To determine if TNF-alpha impacts IBDEC monolayer organization and barrier function.
Main Methods:
- Cultured, polarized rat IBDECs were treated with recombinant TNF-alpha (rTNF-alpha).
- Cytotoxicity was assessed via trypan blue exclusion and LDH release.
- Transepithelial electrical resistance and horseradish peroxidase (HRP) penetration were measured.
- Cell structure was analyzed using electron microscopy and F-actin immunohistochemistry.
Main Results:
- rTNF-alpha (10–200 U/mL) was not cytotoxic to IBDECs.
- rTNF-alpha caused a dose-dependent, transient decrease in transepithelial electrical resistance.
- Tight junctions became leaky, allowing HRP penetration.
- Cell structure and organization remained intact; cells did not detach from Matrigel.
Conclusions:
- TNF-alpha is nontoxic to IBDECs.
- TNF-alpha increases the permeability of IBDEC tight junctions.
- TNF-alpha may impair the barrier function of the bile duct.