Gene therapy for liver transplantation using adenoviral vectors: CD40-CD154 blockade by gene transfer of CD40Ig protects rat livers from cold ischemia and reperfusion injury

The role and function of CD4+ T cells in hepatic ischemia-reperfusion injury

INTRODUCTION

Hepatic ischemia-reperfusion injury (IRI) is a severe complication frequently encountered in liver surgery, seriously affecting the therapeutic effects, tissue function. Various immune cells are involved in hepatic IRI, including macrophages, NKT cells, DCs, CD4 + T cells, and CD8 + T cells, among which CD4 + T cells play a critical role in this process. This article aims to summarize the functions and changes in various CD4 + T cell type counts and related cytokine levels in hepatic IRI and to review the possible mechanisms of mutual conversion between T cell types.

AREAS COVERED

We have covered the functions and changes that occur in Th1, Th17, and Treg cells in liver IRI, as well as the pathways and factors associated with them. We also discuss the prospects of clinical application and future directions for therapeutic advances.

EXPERT OPINION

This section explores the current clinical trials involving CD4 + T cells, especially Tregs, explains the limitations of their application, and summarizes the future development trends of cell engineering and their combination with the CAT technology. We also provide new ideas and therapeutic targets for alleviating liver IRI or other liver inflammatory diseases.

Effect of heme oxygenase-1 on the protection of ischemia reperfusion injury of bile duct in rats after liver transplantation

OBJECTIVE

To investigate the effect of heme oxygenase-1 (HO-1) on the ischemic reperfusion injury (IRI) of bile duct in rat models after liver transplantation.

METHODS

320 SD rats were equally and randomly divided into 5 groups, which were group A receiving injection of 3×10⁸/pfu/ml adenovirus (adv), group B with donor receiving Adv-HO-1 and recipient receiving Adv-HO-1-siRNA, group C with donor and recipient both receiving Adv-HO-1, group D with donor receiving Adv-HO-1-siRNA and recipient receiving Adv-HO-1, and group E with donor and recipient both receiving Adv-HO-1-siRNA at 24h before liver transplantation. Donor liver was stored in UW liquid at 4°C followed by measuring HO-1 level by western blot before transplantation. On d1, d3, d7 and d14, serum and liver was isolated for analysis of liver function, inflammatory cell infiltration by H&E staining, ultrastructure of liver by transmission electron microscopy as well as the expression of HO-1, Bsep, Mrp2 and Ntcp by western blot.

RESULTS

Compared with group D and E, group B and C displayed improved liver function as demonstrated by lower level of ALT, AST, LDH, TBIL, ALP and GGT, increased secretion of TBA and PL as well as expression of transporter proteins (Bsep, Mrp2 and Ntcp), reduced inflammatory cells infiltration and liver injury.

CONCLUSION

Our study demonstrated that overexpression of HO-1 in donor liver can ameliorate the damage to bile duct and liver, and improved liver function, suggesting HO-1 might be a new therapeutic target in the treatment of IRI after liver transplantation.

CD154-CD40 T-cell co-stimulation pathway is a key mechanism in kidney ischemia-reperfusion injury

Ischemia-reperfusion occurs in a great many clinical settings and contributes to organ failure or dysfunction. CD154-CD40 signaling in leukocyte–endothelial cell interactions or T-cell activation facilitates tissue inflammation and injury. Here we tested a siRNA anti-CD40 in rodent warm and cold ischemia models to check the therapeutic efficacy and anti-inflammatory outcome of in vivo gene silencing. In the warm ischemia model different doses were used, resulting in clear renal function improvement and a structural renoprotective effect. Renal ischemia activated the CD40 gene and protein expression, which was inhibited by intravenous siRNA administration. CD40 gene silencing improved renal inflammatory status, as seen by the reduction of CD68 and CD3 T-cell infiltrates, attenuated pro-inflammatory, and enhanced anti-inflammatory mediators. Furthermore, siRNA administration decreased a spleen pro-inflammatory monocyte subset and reduced TNFα secretion by splenic T cells. In the cold ischemia model with syngeneic and allogeneic renal transplantation, the most effective dose induced similar functional and structural renoprotective effects. Our data show the efficacy of our siRNA in modulating both the local and the systemic inflammatory milieu after an ischemic insult. Thus, CD40 silencing could emerge as a novel therapeutic strategy in solid organ transplantation.

Targeting TIM-1 on CD4 T cells depresses macrophage activation and overcomes ischemia-reperfusion injury in mouse orthotopic liver transplantation

Hepatic injury due to cold storage followed by reperfusion remains a major cause of morbidity and mortality after orthotopic liver transplantation (OLT). CD4 T cell TIM-1 signaling costimulates a variety of immune responses in allograft recipients. This study analyzes mechanisms by which TIM-1 affects liver ischemia-reperfusion injury (IRI) in a murine model of prolonged cold storage followed by OLT. Livers from C57BL/6 mice, preserved at 4°C in the UW solution for 20 h, were transplanted to syngeneic recipients. There was an early (1 h) increased accumulation of TIM-1+ activated CD4 T cells in the ischemic OLTs. Disruption of TIM-1 signaling with a blocking mAb (RMT1-10) ameliorated liver damage, evidenced by reduced sALT levels and well-preserved architecture. Unlike in controls, TIM-1 blockade diminished OLT expression of Tbet/IFN-γ, but amplified IL-4/IL-10/IL-22; abolished neutrophil and macrophage infiltration/activation and inhibited NF-κB while enhancing Bcl-2/Bcl-xl. Although adoptive transfer of CD4 T cells triggered liver damage in otherwise IR-resistant RAG(-/-) mice, adjunctive TIM-1 blockade reduced Tbet transcription and abolished macrophage activation, restoring homeostasis in IR-stressed livers. Further, transfer of TIM-1(Hi) CD4+, but not TIM-1(Lo) CD4+ T cells, recreated liver IRI in RAG(-/-) mice. Thus, TIM-1 expressing CD4 T cells are required in the mechanism of innate immune-mediated hepatic IRI in OLTs.

Programmed death-1/B7-H1 negative costimulation protects mouse liver against ischemia and reperfusion injury

Programmed death-1 (PD-1)/B7-H1 costimulation acts as a negative regulator of host alloimmune responses. Although CD4 T cells mediate innate immunity-dominated ischemia and reperfusion injury (IRI) in the liver, the underlying mechanisms remain to be elucidated. This study focused on the role of PD-1/B7-H1 negative signaling in liver IRI. We used an established mouse model of partial liver warm ischemia (90 minutes) followed by reperfusion (6 hours). Although disruption of PD-1 signaling after anti-B7-H1 monoclonal antibody treatment augmented hepatocellular damage, its stimulation following B7-H1 immunoglobulin (B7-H1Ig) fusion protected livers from IRI, as evidenced by low serum alanine aminotransferase levels and well-preserved liver architecture. The therapeutic potential of B7-H1 engagement was evident by diminished intrahepatic T lymphocyte, neutrophil, and macrophage infiltration/activation; reduced cell necrosis/apoptosis but enhanced anti-necrotic/apoptotic Bcl-2/Bcl-xl; and decreased proinflammatory chemokine/cytokine gene expression in parallel with selectively increased interleukin (IL)-10. Neutralization of IL-10 re-created liver IRI and rendered B7-H1Ig-treated hosts susceptible to IRI. These findings were confirmed in T cell-macrophage in vitro coculture in which B7-H1Ig diminished tumor necrosis factor-α/IL-6 levels in an IL-10-dependent manner. Our novel findings document the essential role of the PD-1/B7-H1 pathway in liver IRI.

CONCLUSION

This study is the first to demonstrate that stimulating PD-1 signals ameliorated liver IRI by inhibiting T cell activation and Kupffer cell/macrophage function. Harnessing mechanisms of negative costimulation by PD-1 upon T cell-Kupffer cell cross-talk may be instrumental in the maintenance of hepatic homeostasis by minimizing organ damage and promoting IL-10-dependent cytoprotection.

B7-H4 transfection prolongs beta-cell graft survival

B7-H4, a recently discovered member of B7 family, can negatively regulate T cell responses. However, it is not clear whether B7-H4 negatively function in cell transplantation. In this study we investigated the immunosuppressive effect of B7-H4 on beta-cell transplantation. An insulinoma cell line, NIT-1, transfected with B7-H4 (B7-H4-NIT) was established, and transplanted to diabetic C57BL/6 mice by intraperitoneal injection. Proliferation assay of splenocytes in vitro showed that B7-H4-NIT suppressed alloreactive T cell activation. The proportion of IFN-gamma-producing cells in recipient spleen was significantly reduced and the number of Treg cells was upregulated in B7-H4-NIT group compared to the control, EGFP-NIT. The expression of mRNA coding IFN-gamma was lower but that of IL-4 was higher in B7-H4-NIT transplanted recipients than in the control animals. The results of ELISA also revealed the same trends. Diabetic mice reached normalglycemic quickly and gained weight after transplantation of B7-H4-NIT. More importantly, the survival time for recipients transplanted with B7-H4-NIT cells was significantly longer than that with EGFP-NIT cells. These results indicate that B7-H4 transfection prolongs beta-cell graft survival.

Molecular mediators of liver ischemia and reperfusion injury: a brief review

Ischemia and reperfusion injury is a dynamic process that involves multiple organ systems in various clinical states including transplantation, trauma, and surgery. Research into this field has identified key molecular and signaling players that mediate, modulate, or augment cellular, tissue, and organ injury during this disease process. Further elucidation of the molecular mechanisms should provide the rationale to identify much-needed novel therapeutic options to prevent or ameliorate organ damage due to ischemia and reperfusion in clinics.

Gene therapy using adenoviral vector encoding 4-1BBIg gene significantly prolonged murine cardiac allograft survival

4-1BB, a member of the tumor necrosis factor (TNF) receptor superfamily, interacts with 4-1BBL expressed on APC and delivers a costimulatory signal for T cell activation and growth. In this study, we investigated the efficacy of an adenoviral vector encoding murine 4-1BB extracellular domain and human IgG1 Fc (Ad4-1BBIg) fusion gene on murine cardiac allograft survival. Abdomen heterotopical heart graft model was performed from Balb/c to C57BL/6 mice. The adenoviral vectors, Ad4-1BBIg or an adenoviral vector containing EGFP gene (AdEGFP), were administered intravenously to recipient animals after cardiac grafting. The cardiac allograft survival was monitored by daily palpation. The serum level of 4-1BBIg and graft histology was assessed. Cytokine profiles in the grafts were detected by RT-PCR. IFN-gamma producing cells in recipient spleen were examined by flow cytometry. 4-1BBIg gene expression was achieved highly level at 72 h after vector injection. The proportion of IFN-gamma producing cells in recipient spleen was significantly reduced after administration of Ad4-1BBIg, compared to the group given AdEGFP or to the untreated control group. Unlike in controls, cardiac allograft expression of mRNA coding for IL-2 and IFN-gamma remained low in the Ad4-1BBIg group. Ad4-1BBIg therapy markedly reduced T cell infiltration into the graft and significantly prolonged recipient survival time (13.5 days), compared to the untreated group (7.5 days) and the AdEGFP-treated group (8.0 days) (P < 0.05). These results indicate that blockade of 4-1BB/4-1BB ligand interactions by Ad4-1BBIg inhibited alloreactive T-cell activation and attenuated T-cell infiltration into the graft, resulting in significant prolongation of murine cardiac allograft survival. Therefore, Ad4-1BBIg may be useful for preventing allograft rejection.

Vascular endothelial growth factor antagonist modulates leukocyte trafficking and protects mouse livers against ischemia/reperfusion injury

Although hypoxia stimulates the expression of vascular endothelial growth factor (VEGF), little is known of the role or mechanism by which VEGF functions after ischemia and reperfusion (I/R) injury. In this report, we first evaluated the expression of VEGF in a mouse model of liver warm ischemia. We found that the expression of VEGF increased after ischemia but peaked between 2 and 6 hours after reperfusion. Mice were treated with a neutralizing anti-mouse VEGF antiserum (anti-VEGF) or control serum daily from day -1 (1 day before the initiation of ischemia). Treatment with anti-VEGF significantly reduced serum glutaminic pyruvic transaminase levels and reduced histological evidence of hepatocellular damage compared with controls. Anti-VEGF also markedly decreased T-cell, macrophage, and neutrophil accumulation within livers and reduced the frequency of intrahepatic apoptotic terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive cells. Moreover, there was a reduction in the expression of pro-inflammatory cytokines (tumor necrosis factor-alpha and interferon-gamma), chemokines (interferon-inducible protein-10 and monocyte chemoattractant protein-1) and adhesion molecules (E-selectin) in parallel with enhanced expression of anti-apoptotic genes (Bcl-2/Bcl-xl and heme oxygenase-1) in anti-VEGF-treated animals. In conclusion, hypoxia-inducible VEGF expression by hepatocytes modulates leukocyte trafficking and leukocyte-induced injury in a mouse liver model of warm I/R injury, demonstrating the importance of endogenous VEGF production in the pathophysiology of hepatic I/R injury.

Inflammatory responses in a new mouse model of prolonged hepatic cold ischemia followed by arterialized orthotopic liver transplantation

The current models of liver ischemia/reperfusion injury (IRI) in mice are largely limited to a warm ischemic component. To investigate the mechanism of hepatic "cold" IRI, we developed and validated a new mouse model of prolonged cold preservation followed by syngeneic orthotopic liver transplantation (OLT). Two hundred and forty-three OLTs with or without rearterialization and preservation in University of Wisconsin solution at 4 degrees C were performed in Balb/c mice. The 14-day survivals in the nonarterialized OLT groups were 92% (11/12), 82% (9/11), and 8% (1/12) after 1-hour, 6-hour and 24-hour preservation, respectively. In contrast, hepatic artery reconstruction after 1-hour, 6-hour, and 24-hour preservation improved the outcome as evidenced by 2-week survival of 100% (12/12), 100% (10/10), and 33% (4/12), respectively, and diminished hepatocellular damage (serum alanine aminotransferase /histology). Moreover, 24-hour (but not 1-h) cold preservation of rearterialized OLTs increased hepatic CD4+ T-cell infiltration and proinflammatory cytokine (tumor necrosis factor-alpha, interleukin 2, interferon-gamma) production, as well as enhanced local apoptosis, and Toll-like receptor 4/caspase 3 expression. These cardinal features of hepatic IRI validate the model. In conclusion, we have developed and validated a new mouse model of IRI in which hepatic artery reconstruction was mandatory for long-term animal survival after prolonged (24-h) OLT preservation. With the availability of genetically manipulated mouse strains, this model should provide important insights into the mechanism of antigen-independent hepatic IRI and help design much needed refined therapeutic means to combat hepatic IRI in the clinics.

The CD154-CD40 T-cell co-stimulation pathway in liver ischemia and reperfusion inflammatory responses

BACKGROUND

Ischemia-reperfusion (I/R) injury is a prime antigen-independent inflammatory factor in the dysfunction of liver transplants. The precise contribution of T cells in the mechanism of I/R injury remains to be elucidated. As the CD154-CD40 co-stimulation pathway provides essential second signal in the initiation and maintenance of T-cell-dependent immune responses, this study was designed to assess the role of CD154 signaling in the pathophysiology of liver I/R injury.

METHODS

A mouse model of partial 90-min warm hepatic ischemia followed by 6 hr of reperfusion was used. Three animal groups were studied: (1) wild-type (WT) mice treated with Ad-(-gal versus Ad-CD40 immunoglobulin; (2) untreated WT versus CD154 (MR1) monoclonal antibody-treated WT mice; and (3) untreated WT versus CD154 knockout mice.

RESULTS

The disruption of CD154 signaling in all three animal groups ameliorated otherwise fulminant liver injury, as evidenced by depressed serum glutamic oxaloacetic transaminase levels, compared with controls. These beneficial effects were accompanied by depressed hepatic T-cell sequestration, local decrease of vascular endothelial growth factor expression, inhibition of tumor necrosis factor-(and T-helper type 1 cytokine production, and induction of antiapoptotic (Bcl-2/Bcl-xl) but depression of proapoptotic (caspase-3) proteins.

CONCLUSIONS

By using in parallel a gene therapy approach, pharmacologic blockade, and genetically targeted mice, these findings document the benefits of disrupting CD154 to selectively modulate inflammatory responses in liver I/R injury. This study reinforces the key role of CD154-CD40 T-cell co-stimulation in the pathophysiology of liver I/R injury.