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Analysis of the Fas system and Bcl-2 in rat liver allograft rejection
S Hiroyasu1, M Shiraishi, T Koji
1The First Department of Surgery, University of the Ryukyus, School of Medicine, Okinawa, 903-0125, Japan.
Background:
Apoptosis is involved in the mechanism of cell death observed in liver allograft rejection. The liver cells are sensitive to Fas-mediated apoptosis; however, little is known about the involvement of the Fas system in liver allograft rejection. We used rat models to investigate the expression of Fas/Fas ligand and apoptosis-related proteins during liver allograft rejection.
Materials And Methods:
DA rats to Lewis, and Lewis to Lewis orthotopic liver transplantation were performed; liver samples were collected on days 1, 3, 5, 7, and 9 postoperatively (each n = 3). Apoptosis was monitored by TUNEL and electron microscopy. The expression of Fas, FasL, bcl-2, and bax was examined at the mRNA level and by means of immunohistochemistry.
Results:
The TUNEL index in the allografts and isografts on day 7 was 20.1 +/- 1.5 and 7.7 +/- 2.6/1000 cells, respectively. Fas and bax mRNA were constitutively expressed in both of the groups. The expression of Fas ligand mRNA in the allografts which rose on day 5 was 10 times stronger compared to that in the isografts. On the other hand, bcl-2 mRNA was generally expressed in the isografts while it decreased in the allografts. The immunohistochemical analysis also showed an increased reactivity of Fas ligand on day 5 in the allograft, which was observed both in parenchymal and nonparenchymal cells.
Conclusions:
These results strongly suggest that Fas/Fas ligand interaction mediates the liver injury during allograft rejection. In addition, other regulatory factors of apoptosis, such as bcl-2, might also be involved in this pathogenesis.
Insights
Fas/Fas ligand interaction significantly contributes to liver injury during allograft rejection. Apoptosis-related proteins like bcl-2 also play a role in this process.
Area of Science:
- Immunology
- Cell Biology
- Transplantation Medicine
Background:
- Apoptosis is a key mechanism in liver allograft rejection.
- Liver cells are susceptible to Fas-mediated apoptosis.
- The role of the Fas system in liver allograft rejection requires further investigation.
Purpose of the Study:
- To investigate the expression of Fas/Fas ligand and apoptosis-related proteins during rat liver allograft rejection.
- To elucidate the involvement of the Fas system in liver allograft rejection pathogenesis.
Main Methods:
- Orthotopic liver transplantation in rat models (DA to Lewis, Lewis to Lewis).
- Apoptosis assessment using TUNEL assay and electron microscopy.
- Analysis of Fas, FasL, bcl-2, and bax expression via mRNA and immunohistochemistry.
Main Results:
- Increased Fas ligand mRNA and protein expression observed in allografts by day 5 post-transplantation.
- Decreased bcl-2 mRNA expression in allografts compared to isografts.
- Higher TUNEL index in allografts indicating greater apoptosis.
Conclusions:
- Fas/Fas ligand interaction is a likely mediator of liver injury in allograft rejection.
- Other apoptosis regulatory factors, including bcl-2, may also contribute to the pathogenesis of liver allograft rejection.