Defective interleukin-1 receptor antagonist production is associated with resistance of acute liver graft rejection to steroid therapy

Cytokines in Liver Transplantation

Cytokines, soluble mediators of the immune system, play a critical role in the pathogenesis of autoimmune, allergic and infectious diseases. They are also implicated in the initiation and development of allograft rejection. During recent years, there have been considerable advances in generating novel anti-cytokine agents with promoted efficacy and safety, which could be administrated for managing dysregulated cytokine secretion; besides, gene therapy for overexpression of immunomodulatory cytokines has shown substantial improvements. Liver transplantation has been established as a life-saving treatment for end-stage hepatic diseases but the growing number of recipients urge for improved post-transplant care including tolerance induction, infection control and resolving immunosuppressant drugs adverse effects. Cytokines with a wide range of proinflammatory and regulatory properties might be considered as potential therapeutic targets for selective suppression or enhancement of the immune responses in recipients. In the present review, we aimed to summarize the positive and negative effects of cytokines on liver allograft in addition to their prognostic and therapeutic values.

Significant association between FOXP3 gene polymorphism and steroid-resistant acute rejection in living donor liver transplantation

Previous studies have found that preferential accumulation of regulatory T (Treg) cells in liver allografts during acute cellular rejection (ACR) is associated with less severe rejection, suggesting a role of Treg cells in preventing excessive progress of ACR. We investigated the impact of single nucleotide polymorphisms (SNPs) in the Forkhead box P3 (FOXP3) gene, a master regulator gene of Treg cells, on ACR severity in liver transplant (LT) recipients. In total, 102 living donor LT patients were enrolled in this study and categorized into no rejection (n = 86), steroid-sensitive acute rejection (SSAR; n = 11), and steroid-resistant acute rejection (SRAR; n = 5). FOXP3 SNPs -3499 A/G (rs3761547), -3279 A/C (rs3761548), and -924 A/G (rs2232365) were genotyped using the polymerase chain reaction restriction fragment length polymorphism technique. T-cell responses to allostimulation were evaluated by the mixed lymphocyte reaction assay. We found no statistical association between the FOXP3 SNP genotype frequencies and ACR incidence. However, significantly higher incidence of SRAR was observed in LT patients with the FOXP3 rs3761548 A/C+A/A genotype than in those with the C/C genotype (A/C+A/A versus C/C; no rejection, SSAR, SRAR, 85.71%, 0%, 14.29% versus 83.58%, 16.42%, 0%, respectively; P =  0.0005). The mixed lymphocyte reaction assay performed at the time of ACR diagnosis showed higher anti-donor CD4+ T-cell responses in patients carrying rs3761548 A/C+A/A than in those with the C/C genotype (P =  0.019). No significant association was observed between the incidence of SRAR and either rs3761547A/G or rs2232365 A/G. Infectious complications and overall survival were not related to FOXP3 SNPs. Conclusion: Our findings indicate that FOXP3 SNP rs3761548 A/C might be a predisposing factor for SRAR after liver transplantation. (Hepatology Communications 2017;1:406-420).

Protective effect of recombinant human IL-1Ra on CCl4-induced acute liver injury in mice

AIM: To evaluate the effects of positive regulation of recombinant human interleukin 1 receptor antagonist (rhIL-1Ra) on hepatic tissue recovery in acute liver injury in mice induced by carbon tetrachloride (CCl₄).

METHODS: Acute liver damage was induced by injecting 8-wk-old mice with CCl₄ 1 mL/kg (1:3 dilution in corn oil) intraperitoneally (ip). Survival after liver failure was assessed by injecting 8-wk-old mice with a lethal dose of CCl₄ 2.6 mL/kg (1:1 dilution in corn oil) ip. Mice were subcutaneously injected with 1 mg/kg recombinant human IL-1Ra twice a day after CCl₄ treatment for 5 d. Serum alanine amino transferase (ALT) and aspartate aminotransferase (AST) levels were determined with a commercial assay kit. Serum IL-1β, IL-1Ra levels were measured by enzyme-linked immunosorbent assay kit. Quantitative real-time polymerase chain reaction was used to determine liver IL-1β, IL-1Ra and IL-6 expression during CCl₄-induced acute liver injury. Liver sections were stained with hematoxylin-eosin. A histology-injury grading system was used to evaluate the degree of necrosis after acute liver injury. Proliferating cell nuclear antigen (PCNA) staining was used to evaluate the role of rhIL-1Ra in promoting hepatocyte proliferation.

RESULTS: Quantitative analysis showed a higher level of IL-6 mRNA expression and reduced serum AST and ALT levels in the livers of the rhIL-1Ra-treated group at the early phase of CCl₄-induced acute liver injury. Histological examination indicated a decrease in centrilobular necrotic areas in mice treated with rhIL-1Ra, and a novel role of rhIL-1Ra in promoting hepatocyte proliferation was also supported by an increase of PCNA staining. All these results, accompanied by a strong survival benefit in rhIL-1Ra-treated vs PBS-treated groups, demonstrated that rhIL-1Ra administration ameliorated the histological damage and accelerated the regeneration and recovery process of the liver.

CONCLUSION: rhIL-1Ra could be further developed as a novel therapeutic agent for the treatment of acute liver injury because of its ability to reduce hepatocellular damage and facilitate liver regeneration.

Apoptosis: A target for potentiation of UV-induced IL-1Ra synthesis by IVIg

IL-1Ra prevents IL-1 induced inflammatory signalling, a mechanism potentially important for several pathological conditions characterized by inflammation. When administered as a drug in the recombinant form, it displays a protective effect towards them. We postulated that this action could also be achieved by pharmacological activation of endogenous IL-1Ra production. We previously showed that photochemotherapy and UV-light increased monocyte/macrophages IL-1Ra secretion. A similar effect has been shown for IVIg. The aim of this study was to define optimal in vitro conditions for induction of IL-1Ra secretion. As both agents induce lymphocytes apoptosis, we focused our analysis on the influence of IVIg on UV-induced-IL-1Ra production on this mechanism. After overnight preincubation at 37 degrees C, UV-irradiated PBL mixed with two IVIg concentrations (1 and 25 mg/ml) were cocultured with autologous PBMC. Apoptosis was measured by annexin V/PI. IL-1Ra secretion was evaluated by RT-PCR and Luminex microbead array assay. A significant additive dose-dependent influence of IVIg (+85%; p=0.0005) on UV-induced IL-1Ra secretion, involved both Fc-receptor activation at a low dose (1 mg/ml) and a potent apoptotic action on PBL reinforcing the UV effect at high concentrations (25 mg/ml). We conclude that lymphocyte apoptosis represents an important pathway contributing to enhancement of UV-induced monocyte/macrophages IL-1Ra production by IVIg and that these findings should be considered when evaluating in vivo protocols for photochemotherapy and IVIg treatment, in hope of improving efficacy.

From pharmacokinetics to pharmacogenomics: a new approach to tailor immunosuppressive therapy

One of the main tasks in the management of organ transplantation is the optimization of immunosuppressive therapy, in order to provide therapeutic efficacy limiting drug-related toxicity. In the past years major efforts have been carried out to define therapeutic windows based on blood/plasma levels of each immunosuppressant relating those concentrations to drug dosing and clinical events. Although this traditional approach is able to identify environmental and nongenetic factors that can influence drug exposure during the course of treatment, it presents limitations. Therefore, complementary strategies are advocated. The advent of the genomic era gives birth to pharmacogenomics, a science that studies how the genome as a whole, including single genes as well as gene-to-gene interactions, may affect the action of a drug. This science is of particular importance for drugs characterized by a narrow therapeutic index, such as the immunosuppressants. Preliminary studies focused on polymorphisms of genes encoding for enzymes actively involved in drug metabolism, drug transport and pharmacological target. Pharmacogenomics holds promise for improvement in the ability to individualize immunosuppressive therapy based on the patient's genetic profile, and can be viewed as a support to traditional therapeutic drug monitoring. However, the clinical applicability of this approach is still to be proven.

GM-CSF restores innate, but not adaptive, immune responses in glucocorticoid-immunosuppressed human blood in vitro

Infection remains the major complication of immunosuppressive therapy in organ transplantation. Therefore, reconstitution of the innate immunity against infections, without activation of the adaptive immune responses, to prevent graft rejection is a clinically desirable status in transplant recipients. We found that GM-CSF restored TNF mRNA and protein expression without inducing IL-2 production and T cell proliferation in glucocorticoid-immunosuppressed blood from either healthy donors or liver transplant patients. Gene array experiments indicated that GM-CSF selectively restored a variety of dexamethasone-suppressed, LPS-inducible genes relevant for innate immunity. A possible explanation for the lack of GM-CSF to restore T cell proliferation is its enhancement of the release of IL-1betaR antagonist, rather than of IL-1beta itself, since exogenously added IL-1beta induced an IL-2-independent Con A-stimulated proliferation of glucocorticoid-immunosuppressed lymphocytes. Finally, to test the in vivo relevance of our findings, we showed that GM-CSF restored the survival of dexamethasone- or cyclosporine A-immunosuppressed mice from an otherwise lethal infection with Salmonella typhimurium. In addition to this increased resistance to infection, GM-CSF did not induce graft rejection of a skin allotransplant in cyclosporine A-immunosuppressed mice. The selective restoration potential of GM-CSF suggests its therapeutic use in improving the resistance against infections upon organ transplantation.

The balance between IL-1 and IL-1Ra in disease

IL-1 is an important mediator of inflammation and tissue damage in multiple organs, both in experimental animal models of disease and in human diseases. The IL-1 family consists of two agonists, IL-1alpha and IL-1beta, two receptors, biologically active IL-1RI and inert IL-1RII, and a specific receptor antagonist, IL-1Ra. The balance between IL-1 and IL-1Ra in local tissues plays an important role in the susceptibility to and severity of many diseases. An allelic polymorphism in the IL-1Ra gene has been associated with a variety of human diseases primarily of epithelial and endothelial cell origin. This association may be secondary to an imbalance in the IL-1 system with enhanced production of IL-1beta and reduced production of the major intracellular isoform of IL-1Ra. Treatment of RA with daily subcutaneous injections of recombinant IL-1Ra protein has been shown to be efficacious. Gene therapy approaches with IL-1Ra are being evaluated for the treatment of RA and other human diseases.

The role of cytokine polymorphisms in rejection after solid organ transplantation

The importance of cytokines to the immune response is irrefutable. Their role in the biology of solid organ transplantation per se is also assured. Thus it is likely that subtle differences in cytokine composition, particularly at the initiation of an immune response, may have a major effect on the outcome of that response. This may be particularly relevant in solid organ transplantation, where it is possible that genetic polymorphisms which influence cytokine production may determine the outcome of a transplant. Indeed, it has been suggested that immunosuppression may be individualised on the basis of recipient or donor genotype. However, much of the early data regarding the importance of specific cytokine polymorphisms has not been reproduced, and the significance of this field remains controversial. Nonetheless, with the experience gained from earlier studies, some clear patterns for future studies are emerging.