The fas and fas ligand pathways in liver allograft tolerance

Scutellaria baicalensis Induces Cell Apoptosis and Elicits Mesenchymal-Epithelial Transition to Alleviate Metastatic Hepatocellular Carcinoma via Modulating HSP90β

Hepatocellular carcinoma is one of the most common malignant tumors in the world and shows strong metastatic potential. Current medicine for hepatocellular carcinoma therapy is invalid, while Scutellaria baicalensis Georgi exhibits the pharmaceutical potential to treat liver diseases and liver cancer. Herein, we verified the inhibitory properties and the pivotal molecules regimented by Scutellaria baicalensis on advanced hepatocellular carcinoma. At first, the viability of SK-Hep-1 cells was significantly reduced under treatment of Scutellaria baicalensis extract in a dose-dependent manner without affecting the growth of normal hepatocyte. Scutellaria baicalensis extract application could remarkably cause apoptosis of SK-Hep-1 cells through p53/cytochrome C/poly-ADP ribose polymerase cascades and arrest the cell cycle at the G1/S phase by downregulating cyclin-dependent kinases. Meanwhile, administration of Scutellaria baicalensis extract remarkably attenuated the migration capability as well as suppressed matrix metalloproteinase activity of advanced hepatocellular carcinoma cells. The proteome profiles and network analysis particularly implied that exposure to Scutellaria baicalensis extract downregulated the expression of HSP90β, and the clinical stage of hepatocellular carcinoma is also positively correlated with the HSP90β level. Combined treatment of Scutellaria baicalensis extract and HSP90β siRNAs could markedly enhance the ubiquitination activity and the degradation of vimentin to subsequently inhibit the metastatic property of SK-Hep-1 cells. Moreover, application of Scutellaria baicalensis extract and HSP90β siRNAs depleted phosphorylation of AKT, which stimulated the expression of p53 and consecutively triggered cell apoptosis. These findings suggest that HSP90β may be a prospective target for the effective therapy of advanced hepatocellular carcinoma via accelerating apoptosis of hepatocellular carcinoma cells and eliciting mesenchymal-epithelial transition with the administration of Scutellaria baicalensis extract.

Role of Kupffer cells in tolerance induction after liver transplantation

Currently, liver transplantation has reached a level of maturity where it is considered an effective treatment for end-stage liver disease and can significantly prolong the survival time of patients. However, acute and chronic rejection remain major obstacles to its efficacy. Although long-term use of immunosuppressants can prevent rejection, it is associated with serious side effects and significant economic burden for patients. Therefore, the investigation of induced immune tolerance holds crucial theoretical significance and socio-economic value. In fact, the establishment of immune tolerance in liver transplantation is intricately linked to the unique innate immune system of the liver. Kupffer cells, as a crucial component of this system, play a pivotal role in maintaining the delicate balance between inflammatory response and immune tolerance following liver transplantation. The important roles of different functions of Kupffer cells, such as phagocytosis, cell polarization, antigen presentation and cell membrane proteins, in the establishment of immune tolerance after transplantation is comprehensively summarized in this paper. Providing theoretical basis for further study and clinical application of Kupffer cells in liver transplantation.

Characterization of Fibrinogen as a Key Modulator in Patients with Wilson's Diseases with Functional Proteomic Tools

Wilson’s disease (WD) is an autosomal recessive disorder of copper metabolism caused by defects in the ATPase gene (ATP7B). The various clinical features result from the massive accumulation of copper in the liver, cornea and basal ganglia. Although WD can be effectively treated with proper medicine, this disease is difficult to clearly diagnose due to its indefinite symptoms. In the current study, we achieved a positive correlation between clinical symptoms and the enzymatic activity of ceruloplasmin in WD patients. Furthermore, proteome profiles of plasma as well as network analysis demonstrated that fibrinogen is a critical indicator which is significantly unregulated in WD subjects in comparison to healthy donors and closely linked to pathogenesis of WD. Here, we applied 2DE-immunoblots and immunohistochemistry to verify the protein level and localization in situ. The enhanced expression of fibrinogen in the plasma of WD subjects with respect to that of healthy controls and patients with distinct disorders was also confirmed by utilizing clinical samples. As expected, application of high dose of copper induced expression of fibrinogen, while knockdown of ceruloplasmin also resulted in upregulation of fibrinogen as well as elimination of superoxide dismutase (SOD), leading to increased oxidative stress in cells. In summary, the liver injury or oxidative stress induced by the progression of WD may account for the obvious increase of fibrinogen, which in turn triggers inflammatory responses and interferes coagulation cascades; this finding sheds light on the early detection and diagnosis of WD.

Integrated Proteome and Cytokine Profiles Reveal Ceruloplasmin Eliciting Liver Allograft Tolerance via Antioxidant Cascades

Acute rejection (AR) and spontaneous tolerance may occur after allograft orthotopic liver transplants (OLT) performed in certain combinations of donor and recipient rat strains, yet the underlying molecular cascades involved in these conditions remain poorly understood. Comprehensive analysis with proteomic tools revealed that ceruloplasmin was highly expressed during the tolerant period on day 63 post-OLT (POD 63) compared to the rejected samples on POD 14. Meanwhile, cytokine expression profiles implied that the inflammation was significantly stimulated in the AR subjects. Again, protein carbonylation was dramatically upregulated in the rejected subject within the tolerant group. Knockdown of ceruloplasmin would elicit more severe ROS damage, leading to cell death in the presence of H₂O₂, which induced Nrf2 cascade and the recovery of ceruloplasmin to mediate spontaneous tolerance. In summary, ceruloplasmin may contribute to amending the oxidative stress that eventually causes cell apoptosis and to maintaining the survival of hepatocytes in a drug-free tolerance OLT model.

Expression Pattern of Tumor Necrosis Factor-α-Induced Protein 8-Like 2 in Acute Rejection of Cardiac Allograft

BACKGROUND

Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) is a negative regulator of innate immunity and cellular immunity, yet the expression pattern of TIPE2 in acute rejection of cardiac allograft remain enigmatic.

METHODS

We developed cardiac transplantation models and divided into 3 groups: a naive group, a syngeneic group, and an allogeneic group. Then, we detected the messenger RNA and protein of TIPE2 in cardiac allografts. Real-time polymerase chain reaction showed expression of CD4 and CD8 in the donor heart, and immunofluorescence assay revealed the association between T cells and TIPE2.

RESULTS

In our study, we first found that the expression of TIPE2 in cardiac allografts is upregulated compared with the syngeneic control, and increases in a time-dependent manner. The immunocytochemistry of heart grafts revealed a strong expression of TIPE2 in the inflammatory cells, but not in the cardiomyocytes. Finally, we proved that CD4⁺ and CD8⁺ T cells infiltrated cardiac allografts abundantly, which express ample TIPE2.

CONCLUSIONS

The upregulated expression of TIPE2 in cardiac allografts, mainly came from T cells, which infiltrated the donor heart. This finding indicates that there may be an association between TIPE2 and acute cardiac allograft rejection.

Adult human hepatocytes promote CD4(+) T-cell hyporesponsiveness via interleukin-10-producing allogeneic dendritic cells

The success of liver cell therapy remains closely dependent on how well the infused cells can be accepted after transplantation and is directly related to their degree of immunogenicity. In this study, we investigated the in vitro immunogenic properties of isolated human hepatocytes (hHeps) and adult-derived human liver progenitor cells (ADHLPCs), an alternative cell candidate for liver cell transplantation (LCT). The constitutive expression of immune markers was first analyzed on these liver-derived cells by flow cytometry. Human liver-derived cells were then cocultured with allogeneic human adult peripheral blood mononuclear cells (PBMCs), and the resulting activation and proliferation of PBMCs was evaluated, as well as the cytokine levels in the coculture supernatant. The effect of liver-derived cells on monocyte-derived dendritic cell (MoDC) properties was further analyzed in a secondary coculture with naive CD4(+) T-cells. We report that hHeps and ADHLPCs expressed human leukocyte antigen (HLA) class I and Fas but did not express HLA-DR, Fas ligand, and costimulatory molecules. hHeps and ADHLPCs did not induce T-cell activation or proliferation. Moreover, hHeps induced a cell contact-dependent production of interleukin (IL)-10 that was not observed with ADHLPCs. The IL-10 was produced by a myeloid DC subset characterized by an incomplete mature state. Furthermore, hHep-primed MoDCs induced an antigen-independent hyporesponsiveness of naive CD4(+) T lymphocytes that was partially reversed by blocking IL-10, whereas nonprimed MoDCs (i.e., those cultured alone) did not. hHeps and ADHLPCs present a low immunogenic phenotype in vitro. Allogeneic hHeps, but not ADHLPCs, promote a cell contact-dependent production of IL-10 by myeloid DCs, which induces naive CD4(+) T-cells antigen-independent hyporesponsiveness.

Hepatic stellate cells promote immunotolerance following orthotopic liver transplantation in rats via induction of T cell apoptosis and regulation of Th2/Th3-like cell cytokine production

Hepatic stellate cells (HSCs) have been demonstrated to have immunoinhibitory activity. The aim of this study was to investigate the role of HSCs in the development of immunotolerance following liver transplantation. A rat liver transplantation tolerance model [donor Lewis into recipient Dark Agouti (DA)] and rejection (donor DA into recipient Lewis) was established. On the 7th day following transplantation, the HSCs and T cells were isolated from the rats of either the tolerance or rejection group and cultured together. The apoptosis rate of the T cells was determined 24 h later by flow cytometry following staining with anti-CD3 mAb and Annexin V-FITC/PI. Additionally, the FasL expression of HSCs was determined by flow cytometry following staining with anti-FasL mAb. The protein levels of IL-2, TNF-α, TGF-β and IL-10 in the supernatant collected from mixed lymphocyte reaction cultures of HSCs and T cells for 5 days were measured using ELISA assays. HSCs isolated from the tolerance group had a higher T-cell apoptosis induction activity compared with those of the rejection group. The activity of the HSCs was partially reversed by FasL blocking mAb. Accordingly, the FasL expression level of HSCs in the tolerance group was revealed to be higher than that of the rejection group. Moreover, HSCs stimulated IL-10 and TGF-β production in the tolerance group. This study suggests that HSCs are involved in liver transplantation immune tolerance via the induction of T-cell apoptosis partially mediated by the Fas/FasL pathway and the activation of Th2/Th3-like cell cytokine production.

Transfusion of endothelial cells with lentivirus-mediated expression of fas ligand prolonged survival of rat liver allograft

BACKGROUND

Immunologically privileged sites have been shown to express Fas ligand (FasL) and may protect themselves by inducing apoptosis of infiltrating inflammatory cells. We asked whether the Fas/FasL interaction could be used to protect liver allograft from acute rejection. We proposed that endothelial cells that are resistant to Fas-mediated killing could be considered as a vehicle for expression of recombinant FasL.

METHODS

Based on the lenti-rFasl/puro expression system, constructs were designed that allowed endothelial cell-specific and continual expression of FasL. Endothelial cells with expression of FasL or viruses recombinant with FasL gene were transfused into portal vein of recipient rats during liver transplant surgery. Comparing groups of rats after liver transplant surgery using regular dose of FK506 and with no other treatment, we observed the aspartate aminotransferase and BIL value and survival of four groups of rat recipients.

RESULTS

Values of AST and BIL in the cell and virus transfusion groups were between FK506 and contrast groups. The survival of cell and virus transfusion groups were longer than contrast group and shorter than FK506 group.

CONCLUSION

This in vitro model shows that endothelial cells with expression of FasL or viruses recombinant with FasL gene transfusion can preserve liver function and prolong the survival time of liver allografts.

Evolution of soluble forms of CD86, CD95 and CD95L molecules in liver transplant recipients

Co-stimulatory factors such as CD86 and apoptotic molecules such as CD95 and CD95L required to start and to turn off the allogenic immune response may also be present as soluble proteins. To determine the role of the soluble forms of CD86 (sCD86), CD95 (sCD95) and CD95L (sCD95L) in the outcome of liver transplants, we analyzed the circulating levels of these molecules in patients subjected to liver transplantation in the pre-operative period and during the first month post-transplantation. Serum samples were obtained from sixty-nine first orthotopic liver transplants (OLT). The patients were classified into acute rejection (AR=24) and not acute rejection (NAR=45), or considering the presence of chronic active hepatitis B or C (VP=30) or other primary liver diseases (VN=39). The levels of sCD86, sCD95 and sCD95L were analyzed by solid phase sandwich enzyme-linked immunoabsorbent assays. Our results first showed that the pre-transplantation serum levels of sCD86 in the AR group were significantly higher than in the NAR group (1007±82U/mL vs. 739±46U/mL, p=0.006), and in the post-transplantation period these levels decreased sharply. Second, the levels of sCD95L and sCD95 in the pre-transplantation period did not point to statistically significant differences between the AR and NAR groups. Considering primary liver disease, the pre-transplantation levels of sCD86 and sCD95L in the VP group were significantly higher than those of the VN group (VP, 977±69U/mL vs. VN, 722±51U/mL, p<0.002, and VP, 482±78pg/mL vs. VN, 221±31pg/mL, p=0.002, respectively). Multivariate analysis revealed that only the pre-transplantation levels of sCD86 were independently associated with the development of episodes of acute rejection (p=0.005, OR=2.1, IC 95%=1.27-3.47). In conclusion, the present work shows that primary liver disease could influence the pre-transplantation levels of sCD86 and sCD95L. High pre-transplantation serum levels of sCD86 could favor the development of episodes of acute rejection.

Operational tolerance: past lessons and future prospects

Every liver transplant (LT) center has had patients who either self-discontinue immunosuppressive (IS) therapy or are deliberately withdrawn due to a research protocol or clinical concern (ie, lymphoproliferative disorder [LPD], overwhelming infection). This is understandable because maintenance IS therapy, particularly calcineurin inhibitors (CNI), is associated with significant cost, side effects, and considerable long-term morbidity and mortality. Detrimental effects of IS therapy include increased risk of cardiovascular disease, metabolic syndrome, bone loss, opportunistic and community-acquired infections, and malignancy. In fact, LT recipients have among the highest rates of chronic kidney disease and associated mortality among all nonkidney solid organ recipients. This mortality is only ameliorated by undergoing a curative kidney transplant, usurping costs and valuable organ resources. The search for improved treatment algorithms includes trial and error CNI dose minimization, the use of alternative IS agents (antimetabolites, mammalian target of rapamycin [mTOR] inhibitors), or even complete CNI withdrawal. Yet those who are successful in achieving such operational tolerance (no immunosuppression and normal allograft function) are considered lucky. The vast majority of recipients will fail this approach, develop acute rejection or immune-mediated hepatitis, and require resumption of IS therapy. As such, withdrawal of IS following LT is not standard-of-care, leaving clinicians to currently maintain transplant patients on IS therapy for life. Nonetheless, the long-term complications of all IS therapies highlight the need for strategies to promote immunologic or operational tolerance. Clinically applicable biomarker assays signifying the potential for tolerance as well as tolerogenic IS conditioning are invariably needed if systematic, controlled rather than "hit or miss" approaches to withdrawal are considered. This review will provide an overview of the basic mechanisms of tolerance, particularly in relation to LT, data from previous IS withdrawal protocols and biomarker studies in tolerant recipients, and a discussion on the prospect of increasing the clinical feasibility and success of withdrawal.

FasL expression in hepatic antigen-presenting cells and phagocytosis of apoptotic T cells by FasL+ Kupffer cells are indicators of rejection activity in human liver allografts

Fas-Fas ligand (FasL) interaction and apoptosis are important in the mechanism of allograft rejection. However, the interaction between donor and recipient cells, specifically focusing on antigen-presenting cells (APCs), under various conditions is poorly understood in human liver allografts. FasL expression on APCs, its association with apoptosis, and the origin of apoptotic lymphocytes in human liver allografts were assessed by immunohistochemistry and in situ hybridization. We found increased expression of FasL on Kupffer cells (KCs) and endothelium in acute cellular rejection (n = 20) and to lesser extent in chronic rejection (n = 6) and septic cholangitis (n = 5) compared with stable grafts and normal controls. In addition, the graft specificity of infiltrating T cells was confirmed by polymerase chain reaction examination of T-cell receptor-gamma loci. T-cell apoptosis occurred at a higher rate in acute cellular rejection than in chronic rejection or septic cholangitis. The number of apoptotic bodies derived from recipient lymphocytes correlated with the severity of rejection and was reversed by treatment. FasL(+) KCs phagocytosed CD4(+) interferon-gamma(+) T cells, rather than CD4(+) interleukin-4(+) T cells, suggesting a role of KCs in regulating CD4(+) T-cell subset differentiation. In conclusion, our data suggest that FasL expression on APCs and phagocytosis of apoptotic T cells by FasL(+) KCs are indicators of rejection activity in human liver allografts.

Immune-privileged embryonic Swiss mouse STO and STO cell-derived progenitor cells: major histocompatibility complex and cell differentiation antigen expression patterns resemble those of human embryonic stem cell lines

Embryonic mouse STO (S, SIM; T, 6-thioguanine resistant; O, ouabain resistant) and 3(8)21-enhanced green fluorescent protein (EGFP) cell lines exhibit long-term survival and hepatic progenitor cell behaviour after xenogeneic engraftment in non-immunosuppressed inbred rats, and were previously designated major histocompatibility complex (MHC) class I- and class II-negative lines. To determine the molecular basis for undetectable MHC determinants, the expression and haplotype of H-2K, H-2D, H-2L and I-A proteins were reassessed by reverse transcriptase-polymerase chain reaction (RT-PCR), cDNA sequencing, RNA hybridization, immunoblotting, quantitative RT-PCR (QPCR), immunocytochemistry and flow cytometry. To detect cell differentiation (CD) surface antigens characteristic of stem cells, apoptotic regulation or adaptive immunity that might facilitate progenitor cell status or immune privilege, flow cytometry was also used to screen untreated and cytokine [interferon (IFN)-gamma]-treated cultures. Despite prior PCR genotyping analyses suggestive of H-2q haplotypes in STO, 3(8)21-EGFP and parental 3(8)21 cells, all three lines expressed H-2K cDNA sequences identical to those of d-haplotype BALB/c mice, as well as constitutive and cytokine-inducible H-2K(d) determinants. In contrast, apart from H-2L(d[LOW]) display in 3(8)21 cells, H-2Dd, H-2Ld and I-Ad determinants were undetectable. All three lines expressed constitutive and cytokine-inducible CD34; however, except for inducible CD117([LOW]) expression in 3(8)21 cells, no expression of CD45, CD117, CD62L, CD80, CD86, CD90.1 or CD95L/CD178 was observed. Constitutive and cytokine-inducible CD95([LOW]) expression was detected in STO and 3(8)21 cells, but not in 3(8)21-EGFP cells. MHC (class I(+[LOW])/class II-) and CD (CD34+/CD80-/CD86-/CD95L-) expression patterns in STO and STO cell-derived progenitor cells resemble patterns reported for human embryonic stem cell lines. Whether these patterns reflect associations with mechanisms that are regulatory of immune privilege or functional tissue-specific plasticity is unknown.

A novel model of acute liver injury in mice induced by T cell-mediated immune response to lactosylated bovine serum albumin

The present study aimed to establish a murine liver injury model with T cell-mediated immune response to mimic the cellular immunological pathogenesis of hepatitis. Bovine serum albumin was conjugated with lactose by redox to prepare lactosylated bovine serum albumin (LacBSA). The liver injury was induced in C57BL/6 mice by a T cell-mediated immune response to LacBSA. After a systemic injection of LacBSA, which elicited immune response in mice sensitized twice with LacBSA, liver injury was observed with obvious increase of aminotransferase levels in serum and hepatocelluar damage in liver histology. However, the splenectomy before the elicitation significantly alleviated the liver injury. Direct contact between spleen T cells/nonparenchymal cells and hepatocytes was proved to be essential to induce the release of alanine aminotransferase in the culture supernatant. In addition, both levels of Fas mRNA in liver tissues and Fas Ligand in spleen cells were up-regulated at 6 h after the elicitation. The Fas mRNA expression was maintained in a relatively high level at 18 h while Fas Ligand began to decrease after 12 h. These results demonstrated that the T cell immune response to LacBSA could be successfully localized in the liver to induce an immunological liver injury in mice. The pathogenesis of the liver injury might involve the interaction between the liver-infiltrating lymphocytes and hepatocytes through Fas/FasL pathway.

Study of Fas (CD95) and FasL (CD178) polymorphisms in liver transplant recipients

The Fas receptor is capable of transducing apoptotic cell death upon interaction with their ligand (FasL). Recent studies suggest that the Fas/FasL system is involved both in graft rejection and in transplantation tolerance. In this study, we analyzed the effect of Fas and FasL polymorphisms in liver allograft outcome. Fas and FasL polymorphisms were analyzed in 151 primary liver graft recipients. The Fas (-670 A/G) and the FasL (IVS2nt -124 A/G and IVS3nt 169 T/delT) polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Fas -1377 G/A polymorphism was determined by allele-specific amplification. Fas and FasL polymorphisms were not associated with acute and chronic rejection in liver transplant. In contrast, those recipients bearing the AA -670 Fas genotype showed significantly lower graft survival rate (S = 40%) than those bearing the GA genotype (S = 63.1%). These differences were detected from the first year post-transplant. Multivariate analysis confirmed that the AA genotype increased the risk of liver graft loss. This work suggests for the first time a possible harmful effect of Fas -670 AA genotype on liver graft survival, whereas the Fas and FasL polymorphisms are not associated with acute or chronic rejection in liver graft recipients.

Expression, by functional proteomics, of spontaneous tolerance in rat orthotopic liver transplantation

Orthotopic liver transplants (OLT) performed in certain combinations of donor and recipient rat strains, such as DA (RT1a) to PVG (RT1c), without immunosuppressive drugs could completely overcome major histocompatibility complex barriers. Although other organs transplanted in a similar fashion within the same combination have been promptly rejected, 60 day post-OLT serum (POD 60) has been proven competent in rapidly reversing the established rejection in animal models. In order to understand the functional role of tolerogenic serum proteins and their involvement with immune response regulation, a comprehensive analysis surveying global changes in complex OLT systems by proteomic techniques was applied. The results display the varying protein expressions in sera extracted from naïve and transplanted animals on POD 60 with regard to immunosuppression. Among these proteins, haptoglobin (Hp) which is related to inhibition of T-cell proliferation was found to be up-regulated following OLT. In addition, the transcriptional expression level and intracellular localization of Hp correlated with the immune events. Hp also exhibited a strong in vitro immunosuppressive effect on the mixed lymphocyte reaction. In conclusion, the presence of Hp may play an important role in modulating the spontaneous tolerance of liver transplantation. Furthermore, the serum proteome map could provide guidance with respect to discovering potential protein targets in OLT tolerance and eventually prolong hepatic allograft survival in the future.

Tissue inhibitor of metalloproteinases-3 and matrix metalloproteinase-3 regulate neuronal sensitivity to doxorubicin-induced apoptosis

Metalloproteinase activity at the cell surface influences cellular sensitivity to extrinsic death vs. survival signals in a variety of cell types, through proteolytic shedding of cell surface signalling molecules. Tissue inhibitor of metalloproteinases-3 (TIMP-3) is a unique natural metalloproteinase inhibitor that plays a pro-apoptotic role through its ability to inhibit metalloproteinases that proteolytically cleave death receptors and their ligands from the cell surface. To study the convergence of metalloproteinase activity and death receptor signalling in neurons, we established an in vitro model of neuronal apoptosis utilizing the chemotherapeutic drug, doxorubicin (Dox). Primary cultures established from embryonic rat cerebral cortices displayed robust and selective neuronal apoptosis in response to Dox, an effect that was dependent on the activation of the death receptor, Fas. We demonstrate that both TIMP-3 and matrix metalloproteinase-3 (MMP-3) are constitutively expressed by primary cortical neurons in culture, and selectively modulated Fas-mediated neuronal apoptosis induced by Dox. Metalloproteinase inhibition by TIMP-3 was found to be necessary for Dox-induced neuronal death, whereas addition of active MMP-3 markedly attenuated apoptosis and diminished Fas-Fas ligand interaction at the cell surface. These observations implicate a physiological role for the balance of TIMP-3 and MMP-3 activity at the neuronal surface in regulating death receptor sensitivity. The convergence of metalloproteinase activity and death receptor signalling at the cell surface may influence neuronal cell death vs. survival decisions.

Crucial Fas-Fas ligand interaction in spontaneous acceptance of hepatic allografts in mice

The Fas/Fas ligand (FasL) system plays important roles in the immune system, including host immunoregulation and cytotoxicity. In this study, we investigated the involvement of Fas-FasL interactions in spontaneous acceptance of hepatic allografts in murine orthotopic liver transplantation. Liver transplantation between the C57BL/6 (B6, H-2b) donor and the MRL/Mp (MRL, H-2k) recipient was performed in various combinations of donor and recipient mice with wild type (+/+), Fas-mutant (lpr) or FasL-mutant (gld) genotypes. The prolongation and spontaneous acceptance of the fully allogeneic grafts in recipients was not observed in either MRL-lpr recipients with B6+/+ livers or MRL+/+ recipients with B6-gld livers. Moreover, the serum alanine aminotransferase (ALT) levels and the degree of cell infiltration into hepatic allografts on day 7 after transplantation were inversely correlated with the recipient survival time (in days). The donor-specific cytotoxic T-lymphocyte (CTL) activities of the graft-infiltrating cells (GICs) from MRL-gld recipients with B6+/+ livers were much lower than those from MRL+/+ or -lpr recipients on days 5 and 10 after transplantation. However, the CTL activities of the GICs from MRL+/+ and -gld recipients predominantly disappeared by day 15 after transplantation. Furthermore, the anti-donor CTL activities induced in MRL+/+ recipients were ascribed to CD8+ cells, and were not mediated by Fas-FasL interactions. These results strongly suggest that the Fas/FasL system plays a critical role for recipient immunoregulation, enabling recipients in accepting hepatic allografts by deletion of the donor-specific T cells, but not for CTL/target cell interaction in MRL+/+ recipients.

Blocking CTL-based cytotoxic pathways reduces apoptosis of transplanted hepatocytes

BACKGROUND

A major obstacle in allogenic hepatocyte transplantation is increased apoptosis of grafted cells due to CTL-based cytotoxicity. However, whether blockade of Fas- and granzyme-mediated pathways of CTL-based cytotoxicity may provide immune protection to transplanted hepatocytes is poorly defined. Our study aimed to reduce apoptosis of allogenic transplanted hepatocytes by inhibiting granzyme B (GraB) activity and blocking Fas-FasL interaction.

MATERIALS AND METHODS

Hepatocyte transplantation was performed by inoculating isolated liver cells from ACI rats (allogenic) or Lewis rats (syngenic) into the spleens of Lewis rats. Recipients were treated with FLIM58, an inhibitory anti-FasL mAb, and GraB inhibitor I alone or a combination of the two drugs for 5 days after transplantation, and were sacrificed at Day 7. Apoptosis of transplanted hepatocytes was detected in situ by TUNEL assay and M30 immunostaining. Glutamate dehydrogenase (GLDH) activity in recipient spleens was examined to evaluate survival of transplanted cells. Recipient spleens were assayed for FasL level with Western blotting and for GraB activity by hydrolysis of GraB substrate.

RESULTS

FLIM58 or GraB inhibitor I significantly reduced the percentage of TUNEL-positive and M30-positive hepatocytes and markedly increased GLDH levels in allogenic, but not syngenic, recipient spleens. These effects were more pronounced when the two drugs were used in combination (P < 0.05). Additionally, elevation of FasL and GraB levels in allogenic recipient spleens can be significantly reduced by FLIM58 and GraB inhibitor I, respectively.

CONCLUSIONS

Inhibition of GraB activity and blockade of Fas-FasL interaction reduce the apoptosis of allogenic transplanted hepatocytes, and thus improve their survival.

Persistence of stable intragraft cell chimerism in rat liver allografts after drug-induced tolerance

BACKGROUND

Drug-induced tolerance of rat liver allografts is well documented. We analyzed cellular events during immunosuppressive therapy on day (d) 10 and in the late phase (d 100) after transplantation to assess for characteristics in the intrahepatic leukocyte (IHL) population in the phase of tolerance.

METHODS

Lewis rats served as recipients of Dark Agouti rat livers. Temporary immunosuppression with either cyclosporine (CsA) monotherapy (3 mg/kg/d) or triple therapy that consisted of a subtherapeutic CsA dosage (0.25 mg/kg/d) and monoclonal antibodies directed against the interleukin-2 receptor (IL-2R, CD25) and the intercellular adhesion molecule-1 (ICAM-1, CD54) was administered from postoperative d 0 to d 13. Cell migration and cell activation within liver grafts was assessed by standard histology and flow cytometry. IHL apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL).

RESULTS

Both CsA monotherapy and triple therapy prolonged liver allograft survival to more than 100 d and led to the induction of donor-specific tolerance. Untreated recipients rejected their allografts within 14 d. In both groups, donor-specific IHLs initially dropped to 18% to 25% on d 10, but they rebounded to as much as 40% on d 100 as a common characteristic of both groups. Within this population, donor-specific T cells were dominant. In both groups, increased numbers of activated (IL-2R+) CD8+ T lymphocytes were present on d 100. No accumulation of apoptotic IHL was observed on d 100. Their proportion was unchanged in the triple therapy group and slightly decreased in the CsA group compared to the syngeneic controls.

CONCLUSIONS

The present study reveals that tolerant liver allografts are repopulated by donor-specific T lymphocytes. This phenomenon is independent of the type of applied immunosuppression. The persistence of activated CD8+ T cells in the phase of proven donor-specific tolerance on d 100 indicates that liver tolerance is associated with the state of a permanent intragraft immune activation. It seems that the coexistence of donor cells with infiltrating recipient cells within liver grafts, termed intrahepatic cell chimerism, is characteristic for tolerated liver allografts.

Major hepatic resection may suppress the growth of tumours remaining in the residual liver

Little is known as to how hepatectomy is associated with the growth of hepatic tumours, which may reside in the remaining liver after curative resection for hepatocellular carcinoma. Using an intra-hepatic tumour implantation model in rats, the effects of hepatectomy on tumour growth in the remaining liver were investigated. On post-operative day 7, the tumour weight in the remaining liver following 30% hepatectomy was 0.321+/-0.058 g (mean +/- SD) which was significantly greater than that (0.245+/-0.040 g) in sham operations (P<0.05). However, the tumour weight (0.156+/-0.067 g) in the remaining liver following 60% hepatectomy was significantly lower than that in sham animals (P< 0.005). The number of TdT-mediated dUTP nick-end labelling (TUNEL) positive tumour cells was significantly increased in 60% hepatectomy as compared with the sham and 30% hepatectomy group. The mRNA expression of TGF-beta1, TNF-alpha and Fas in the tumour portion of 60% hepatectomy, was higher than that in 30% hepatectomy group. Plasma levels of TGF-beta1 were inversely correlated with intra-hepatic tumour weights. These results suggest that major hepatic resection may lead to an increased induction of apoptosis for the remaining hepatic tumour.