Is Indoleamine 2,3-Dioxygenase Important for Graft Acceptance in Highly Sensitized Patients After Combined Auxiliary Liver-Kidney Transplantation?

Combined Organ Transplantation in Patients with Advanced Liver Disease

Transplantation of the liver in combination with other organs is an increasingly performed procedure. Over the years, continuous improvement in survival could be realized through careful patient selection and refined organ preservation techniques, in spite of the challenges posed by aging recipients and donors, as well as the increased use of steatotic liver grafts. Herein, we revisit the epidemiology, allocation policies in different transplant zones, indications, and outcomes with regard to simultaneous organ transplants involving the liver, that is combined heart-liver, liver-lung, liver-kidney, and multivisceral transplantation. We address challenges surrounding combined organ transplantation such as equity, utility, and logistics of dual organ implantation, but also advantages that come along with combined transplantation, thereby focusing on molecular mechanisms underlying immunoprotection provided by the liver to the other allografts. In addition, the current standing and knowledge of machine perfusion in combined organ transplantation, mostly based on center experience, will be reviewed. Notwithstanding all the technical advances, shortage of organs, and the lack of universal eligibility criteria for certain multi-organ combinations are hurdles that need to be tackled in the future.

Emerging Roles on Immunological Effect of Indoleamine 2,3-Dioxygenase in Liver Injuries

Indoleamine 2,3-dioxygenase (IDO) is one of the initial rate-limiting enzymes of the kynurenine pathway (KP), which causes immune suppression and induction of T cell anergy. It is associated with the imbalance of immune homeostasis in numerous diseases including cancer, chronic viral infection, allergy, and autoimmune diseases. Recently, IDO has extended its role to liver field. In this review, we summarize the dysregulation and potentials of IDO in the emerging field of liver injuries, as well as current challenges for IDO targets. In particular, we discuss unexpected conclusions against previous work published. IDO is induced by pro-inflammatory cytokines in liver dysfunction and exerts an immunosuppressive effect, whereas the improvement of liver injury may require consideration of multiple factors besides IDO.

Immutol regulates CD4+Tregs, CD8+Tregs and pDCs via IDO signaling pathway to induce immune tolerance in rat heart allograft transplant

Indoleamine 2,3-dioxygenase (IDO) can promote tryptophan metabolism to kynurenine and modulate regulatory T cells (Tregs), thereby maintains lower efficiency to induce tolerance. Our aim is to investigate the mechanism of tolerance induction by a IDO metabolite named Immutol.

METHODS

We established rat heterotopic heart transplantation models and treated them with Immutol, cyclosporine A (CsA) and 1-methyl-DL-tryptophan (1-MT) in vivo. The drugs were administered via gavage to all but the control group one day before surgery. CsA was gavaged continually for 20 days and Immutol for 60 days; after withdrawal of the drugs, the recipients were observed for at least 10 months. Immune cells were analyzed by flow cytometry. The IDO signaling pathway was evaluated by Western blotting, RT-PCR and immunochemical staining. Enzyme-linked immunosorbent assays (ELISAs) were used to detect changes in cytokines.

RESULTS

CsA or Immutol alone prolonged survival but did not induce tolerance after withdrawal. Immutol+CsA inhibited acute rejection, and the grafts survived more than 400 d, with tolerance detected in most rats (13/15). Increased protein IDO and kynurenine could regulate the accumulation of CD4⁺Tregs, CD8⁺Tregs and pDC to induce immune tolerance. I-MT specifically blocked IDO, weakened the expression of IDO and kynurenine, and produced grafts rejection. Additionally, Tregs could down-regulate immune responses through production of the immunosuppressive cytokines IL-10 and TGF-beta, thus induce immune tolerance. CD8⁺ Tregs produce IFN-γ, and tolerance is dependent on both IFN-γ and IDO.

CONCLUSION

Immutol combined with CsA can control acute rejection and induce tolerance in rats with cardiac allografts after withdrawal. Immutol may become a novel drug for future clinical use.

Tryptophan Metabolism via Kynurenine Pathway: Role in Solid Organ Transplantation

Solid organ transplantation is a gold standard treatment for patients suffering from an end-stage organ disease. Patient and graft survival have vastly improved during the last couple of decades; however, the field of transplantation still encounters several unique challenges, such as a shortage of transplantable organs and increasing pool of extended criteria donor (ECD) organs, which are extremely prone to ischemia-reperfusion injury (IRI), risk of graft rejection and challenges in immune regulation. Moreover, accurate and specific biomarkers, which can timely predict allograft dysfunction and/or rejection, are lacking. The essential amino acid tryptophan and, especially, its metabolites via the kynurenine pathway has been widely studied as a contributor and a therapeutic target in various diseases, such as neuropsychiatric, autoimmune disorders, allergies, infections and malignancies. The tryptophan-kynurenine pathway has also gained interest in solid organ transplantation and a variety of experimental studies investigating its role both in IRI and immune regulation after allograft implantation was first published. In this review, the current evidence regarding the role of tryptophan and its metabolites in solid organ transplantation is presented, giving insights into molecular mechanisms and into therapeutic and diagnostic/prognostic possibilities.

A 14-Year Follow-Up of a Combined Liver-Pancreas-Kidney Transplantation: Case Report and Literature Review

Objective: To investigate the long-term effect of triple organ transplantation (liver, kidney, and pancreas) in a patient with end-stage liver disease, post chronic hepatitis B, cirrhosis, chronic renal failure, and insulin-dependent diabetes mellitus caused by chronic pancreatitis and to explore the optimal surgical procedure.

Case: A 43-year-old man with progressive emaciation and hypourocrinia for 2 months. Results indicated exocrine pancreatic insufficiency and insulin-dependent diabetes related to chronic pancreatitis (CP) after developing end-stage hepatic and renal failure. Simultaneous piggyback orthotopic liver and heterotopic pancreas-duodenum and renal transplantation was performed in 2005. Pancreatic exocrine secretions were drained enterically to the jejunum, and the donor kidney was placed in the left iliac fossa. Patient was prescribed with prednisone, tacrolimus, mycophenolate mofetil, Rabbit Anti-human Thymocyte Immunoglobulin, and simulect for immunosuppression.

Results: Satisfactory hepatic and pancreatic functional recovery was achieved within 7 days post-surgery. The kidney was not functional, and continuous renal replacement therapy was used. However, the donor kidney was removed at day 16 post-surgery due to acute rejection reaction. A new renal transplantation at the same position was performed, and satisfactory kidney function from the new graft was achieved 3 days later. In 14 years of follow-up, patient has not had any rejection reactions or other complications such as pancreatitis, thrombosis, and localized infections. The patient is insulin independent with normal liver and renal functions. FK506+Pred was used for immunosuppression, and the tac tough level maintained 3.0–4.5 ng/ml. Lamivudine was prescribed for long-term use to inhibit HBV virus duplication.

Conclusion: Simultaneous piggyback orthotopic liver and heterotopic pancreas-duodenum and renal transplantation is a good therapeutic option for patients with exocrine pancreatic insufficiency and insulin-dependent diabetes combined with hepatic and renal failure.

Donor-specific hypo-responsiveness occurs in simultaneous liver-kidney transplant recipients after the first year

Kidney allografts of patients who undergo simultaneous liver-kidney transplantation incur less immune-mediated injury, and retain better function compared to other kidney allografts. To characterize the host alloimmune responses in 28 of these patients, we measured the donor-specific alloresponsiveness and phenotypes of peripheral blood cells after the first year. These values were then compared to those of 61 similarly immunosuppressed recipients of a solitary kidney or 31 recipients of liver allografts. Four multicolor, non-overlapping flow cytometry protocols were used to assess the immunophenotypes. Mixed cell cultures with donor or third party cells were used to measure cell proliferation and interferon gamma production. Despite a significant overlap, simultaneous liver-kidney transplant recipients had a lower overall frequency of circulating CD8⁺, activated CD4⁺ and effector memory T cells, compared to solitary kidney transplant recipients. Simultaneous liver-kidney transplant recipient T cells had a significantly lower proliferative response to the donor cells compared to solitary kidney recipients (11.9 vs. 42.9%), although their response to third party cells was unaltered. The frequency of interferon gamma producing alloreactive T cells in simultaneous liver-kidney transplant recipients was significantly lower than that of solitary kidney transplant recipients. Flow cytometric analysis of the mixed cultures demonstrated that both alloreactive CD4⁺ and CD8⁺ compartments of the simultaneous liver-kidney transplant recipient circulating blood cells were smaller. Thus, the phenotypic and functional characteristics of the circulating blood cells of the simultaneous liver-kidney transplant recipients resembled those of solitary liver transplant recipients, and appear to be associated with donor-specific hypo-alloresponsiveness.

Combined Kidney Transplantation and Splenic Fossa Auxiliary Heterotopic Liver Transplantation in a Highly Sensitized Recipient: A Case Report

BACKGROUND

Combined kidney and auxiliary orthotopic liver transplantation from the same donor is used to treat highly sensitized renal transplant recipients. Auxiliary liver can protect the transplanted kidney against hyperacute rejection.

METHODS

In the current case, combined kidney and splenic fossa auxiliary heterotopic liver transplantation was performed from the same donor for a highly sensitized recipient without preoperative preconditioning. No postoperative hyperacute rejection occurred.

RESULTS

Seven days after surgery, preexisting antibody levels rose and decreased after treatment; meanwhile, the function of transplanted kidney returned to normal. During 24 months of follow-up, the grafts showed good blood perfusion and functioned well. The levels of preexisting antibodies, donor-specific antibodies (DSA) and C1q-fixing human leukocyte antigen (C1q-HLA) antibodies, all decreased.

CONCLUSIONS

Combined kidney and splenic fossa auxiliary heterotopic liver transplantation can be used in renal transplantation for highly sensitized recipients.

Hepatic stellate cells increase the immunosuppressive function of natural Foxp3+ regulatory T cells via IDO-induced AhR activation

Immunosuppressive, naturally occurring CD4⁺CD25⁺forkhead box p3⁺ (Foxp3⁺) regulatory T cells (nT_regs) offer potential for the treatment of immune-mediated inflammatory disorders. However, potential instability of ex vivo-expanded nT_regs following their adoptive transfer may be a significant limitation. LPS-stimulated hepatic stellate cells (HSCs) induce expansion and enhance the suppressive function and stability of allogeneic nT_regs We aimed to delineate mechanisms underlying HSC-induced expansion and increased potency of nT_regs HSCs and nT_regs were isolated from mouse livers and spleens, respectively. Following coculture with LPS-pretreated allogeneic HSCs (LPS/HSCs), proliferation of nT_regs was measured by CFSE dilution, and Foxp3 expression and acetylation were determined by immunoprecipitation (IP) and Western blotting analysis. Expression of various genes associated with immunologic tolerance was determined by quantitative RT-PCR (qRT-PCR). LPS stimulation increased the expression and activity of the immunoregulatory enzyme IDO1 in HSCs, and LPS/HSCs stimulated aryl hydrocarbon receptor (AhR) signaling in cocultured nT_regs Reciprocally, T_regs increased IDO1 expression in HSCs. IDO1^-/- LPS/HSCs were inferior to WT LPS/HSCs in stimulating nT_reg expansion. Pharmacologic inhibition of IDO1 in HSCs by 1-methyltryptophan (1MT) inhibited LPS/HSC-induced AhR signaling in nT_regs, which was responsible for their expansion, Foxp3 expression, and stabilization of Foxp3 by increasing acetylation of lysine residues. Finally, HSCs cryopreserved, following 2-3 passages, were as potent as primary-cultured HSCs in expanding nT_regs In conclusion, LPS/HSCs expand allogeneic nT_regs through an IDO-dependent, AhR-mediated mechanism and increase their stability through lysine-acetylation of Foxp3. nT_regs expanded by cryopreserved HSCs may have potential for clinical use.

Serum indoleamine 2,3 dioxygenase and tryptophan and kynurenine ratio using the UPLC-MS/MS method, in patients undergoing peritoneal dialysis, hemodialysis, and kidney transplantation

BACKGROUND

The level and activity of indoleamine 2,3-dioxygenase (IDO) and the concentrations of L-tryptophan and its metabolite L-kynurenine were determined in association with various renal diseases. However, there have been no data regarding these parameters in patients on peritoneal dialysis compared to those undergoing hemodialysis or kidney transplantation.

METHODS

This study investigated the level and activity of IDO and determined oxidative balance by calculating the total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI). We enrolled 60 kidney disease patients, including 20 on peritoneal dialysis (PD group), 19 on hemodialysis (HD group), and 21 with kidney transplantation (KT group), as well as 21 control group.

RESULTS

IDO levels were increased in the PD, HD, and KT groups compared to the control group. The concentration of kynurenine was significantly increased in the PD group compared to the other groups (p < 0.01). The kynurenine/tryptophan ratio was increased in the PD group compared to the other groups (all p < 0.01). TAS levels in the PD and HD groups were significantly decreased compared to the control group (both p < 0.05). TAS levels in the PD group were significantly decreased compared to the KT group. TOS levels in the PD group were higher than in the HD and KT groups.

CONCLUSION

The results showed that IDO levels were increased in peritoneal dialysis and hemodialysis patients and in renal transplant recipients, while oxidative stress was found to be related to IDO activity and was most increased in the patients on peritoneal dialysis.

IDO-competent-DCs induced by IFN-γ attenuate acute rejection in rat liver transplantation

PURPOSE

We established a stable rat model of liver transplantation using Sprague-Dawley rats and Wistar rats in order to investigate the role of the IDO gene in acute rejection after rat liver transplantation.

METHODS

IDO gene expression and IDO enzyme activity were quantified in liver syngeneic grafts and allografts using microdialysis-HPLC. Liver allografts were evaluated for IDO expression by histopathology. We measured liver function-related biomarkers in liver allografts which were re-infused with untreated or IFN-γ-treated dendritic cells (DCs).

RESULTS

We found a significant increase in IDO gene expression and IDO enzyme activity in liver allografts compared the sham and syngeneic graft groups. There was a significant correlation between the number of IDO-positive cells and severity of acute rejection. IDO gene expression and enzyme activity was upregulated in the IFN-γ-treated DC group within 7 days after transplantation compared to the untreated DC group and survival rates were significantly improved.

CONCLUSIONS

Our results suggested that IDO gene expression correlates with the severity of acute rejection and that IFN-γ-induced IDO-positive DCs may attenuate acute rejection and catalyze local tryptophan metabolism via IDO enzyme expression, leading to immune tolerance after liver transplantation.

Auxiliary liver transplantation in children

PURPOSE OF REVIEW

Auxiliary liver transplantation (ALT) has developed as a technique for treating patients with acute liver failure. The surgical techniques of ALT have been refined and current patient survival appears to be similar to that observed with conventional liver replacement for acute liver failure.

RECENT FINDINGS

Our understanding of liver regeneration has improved with experience and it is possible to identify patient and disease groups that are more likely to regenerate and wean off immunosuppression after ALT. Withdrawal of immunosuppression is possible in at least two thirds of survivors up to 4 years post transplant. Young patients have most to gain in the long term from immunosuppression withdrawal. Documentation of liver regeneration should be performed by liver histology, nuclear medicine scanning and CT volumetry. Weaning should be gradual to allow for graft atrophy to avoid complications. ALT has also been utilised for the management of inborn errors of metabolism based in the liver and for other rare problems and these will be briefly addressed in the review.

SUMMARY

Auxiliary liver transplantation should be considered for the treatment of children with acute liver failure satisfying current criteria for liver transplantation.

Postischemic inflammatory response in an auxiliary liver graft predicts renal graft outcome in sensitized patients

BACKGROUND

The liver is considered a tolerogenic organ that favors the induction of peripheral tolerance and protects other organs from the same donor from rejection. This has been exploited in combined auxiliary liver-kidney transplantation, where a renal graft is transplanted against a positive crossmatch under the protection of a liver transplanted from the same donor.

METHODS

To elucidate mechanisms behind the liver protective effect, we studied early transcriptional changes of inflammatory mediators in the grafts during combined auxiliary liver-kidney transplantation using microarrays and real-time polymerase chain reaction. The results were correlated to clinical data.

RESULTS

Liver and kidney grafts both exhibited an upregulation of the leukocyte-recruiting chemokines CCL2, CCL3, and CCL4. Notably, liver grafts strongly upregulated CCL20, a dendritic cell, and T-cell recruiting chemokine. By comparing the gene expression in liver grafts with the clinical outcome, we found that 14 of 45 investigated inflammatory genes were expressed significantly higher in patients without early rejection when compared with those with early rejections. This included the above-mentioned chemokines and the T-cell-recruiting CX3CL1, NFKB1, and the tolerance-inducing gene indoleamine 2,3-dioxygenase.

CONCLUSIONS

In this study, the protective role of the liver was associated with a proinflammatory reaction within this organ after ischemia-reperfusion. In particular, we found an increased expression of leukocyte-recruiting chemokines in patients without rejection, indicating a protective role of host inflammatory cells infiltrating the auxiliary liver graft in presensitized patients. Second, gene expression profiling of transplant biopsies shortly after reperfusion predicted the risk of early rejection in these patients.

The potential role of indoleamine 2,3 dioxygenase (IDO) as a predictive and therapeutic target for diabetes treatment: a mythical truth

Type 1 diabetes (T1D) is an autoimmune disease in which a T-cell-mediated reaction demolishes insulin-producing cells of pancreatic islets. Inadequacy of insulin therapy has motivated research focused on mechanisms by which autoimmune reactions can be suppressed. In recent years, the role of indoleamine 2,3 dioxygenase (IDO) in regulation of immune system has been extensively investigated. Initially, IDO was recognized as a host defense mechanism. However, recent studies have suggested an immunomodulatory role for IDO which may contribute to the induction of immune tolerance. In this review, we concentrate on the role of IDO in several pathologic conditions with a focus on T1D to rationalize our hypothesis regarding the potential for inclusion of IDO in certain therapeutic strategies aimed at early detection, treatment or ideally cure of chronic and autoimmune diseases such as T1D.