Novel action of 3,4-DAA ameliorating acute liver allograft injury

Tranilast Reduces Intestinal Ischemia Reperfusion Injury in Rats Through the Upregulation of Heme-Oxygenase (HO)-1

Background: Intestinal ischemia reperfusion injury (IRI) is a harmful process that occurs during intestinal infarction and intestinal transplantation (ITx). It is characterized by severe inflammation which disrupts the mucosal barrier, causing bacterial translocation and sepsis. Tranilast (N-[3,4-dimethoxycinnamoyl]-anthranilic acid) (TL) is a synthetic compound with powerful anti-inflammatory properties. Objective: To investigate the effect of pretreatment with TL in a validated rat model of intestinal IRI (60 min of ischemia). Methods: TL (650 mg/kg) was administered by oral gavage 24 and 2 h before the onset of ischemia. Experiment 1 examined 7-day survival in 3 study groups (sham, vehicle+IRI and TL+IRI, n = 10/group). In Experiment 2, the effects on the intestinal wall integrity and inflammation were studied after 60 min of reperfusion using 3 groups (sham, IRI and TL+IRI, n = 6/group). The following end-points were studied: L-lactate, intestinal fatty acid-binding protein (I-FABP), histology, intestinal permeability, endotoxin translocation, pro- and anti-inflammatory cytokines and heme oxygenase-1 (HO-1) levels. Experiment 3 examined the role of HO-1 upregulation in TL pretreatment, by blocking its expression using Zinc protoporphyrin (ZnPP) at 20 mg/kg vs. placebo (n = 6/group). Results: Intestinal IRI resulted in severe damage of the intestinal wall and a 10% 7-day survival. These alterations led to endotoxin translocation and upregulation of pro-inflammatory cytokines. TL pretreatment improved survival up to 50%, significantly reduced inflammation and protected the intestinal barrier. The HO-1 inhibitor ZnPP, abolished the protective effect of TL. Conclusions: TL pretreatment improves survival by protecting the intestinal barrier function, decreasing inflammation and endotoxin translocation, through upregulation of HO-1.This rat study of severe intestinal ischemia reperfusion injury demonstrates a novel role for Tranilast as a potential therapy. Administration of Tranilast led to a marked reduction in mortality, inflammation and intestinal permeability and damage. The study proved that Tranilast functions through upregulation of heme oxygenase-1.

TDO2 Deficiency Exacerbates the Immune Rejection Response in Rat Liver Transplantation via the Kyn-AHR Axis

BACKGROUND

The role of tryptophan 2,3-dioxygenase2 (TDO2), a key enzyme in the L-tryptophan (Trp)-kynurenine (Kyn) pathway, in liver transplant immunity is unclear. This study aims to explore the role of TDO2 in liver transplant rejection.

METHODS

We used clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 to construct a TDO2 knockout rat model for liver transplant rejection. We validated the effects of TDO2 on acute rejection and survival, assessed TDO2 expression, and measured Trp and Kyn levels. We studied how TDO2 deficiency affects inflammatory cytokines, analyzed immune cell subtypes and their spatial distribution, and examined programmed death 1 and programmed cell death-ligand 1 (PDL1) spatial distribution and expression using multiplex immunohistochemistry. We also validated the regulatory mechanism of TDO2 on transplant-related immune cells in vivo and in vitro.

RESULTS

TDO2 deficiency in the allograft liver worsens acute rejection and reduces survival rates. During transplant rejection, TDO2 expression increases, enhancing Trp metabolism and elevating serum Kyn levels. TDO2 knockout mitigates this process. The TDO2-Kyn-aryl hydrocarbon receptor pathway regulates acute rejection. TDO2 knockout reprograms immune cell distribution, decreasing regulatory T cells and M2 macrophages in the intermediate region while increasing CD8+ T cells and M1 macrophages in the portal area, leading to M1 polarization. Additionally, TDO2 deficiency raises programmed death 1 and programmed cell death-ligand 1 expression, varying with the spatial distribution and quantity of immune cells. TDO2 can regulate the proliferation and differentiation of various immune cells through the Kyn-aryl hydrocarbon receptor pathway.

CONCLUSIONS

Collectively, we elucidated the mechanism of TDO2 in liver transplant immune rejection and used spatial immunity to reveal the impact of TDO2 on liver transplantation.

Activation of the Aryl Hydrocarbon Receptor Ameliorates Acute Rejection of Rat Liver Transplantation by Regulating Treg Proliferation and PD-1 Expression

BACKGROUND

Aryl hydrocarbon receptor (AhR) plays important roles in modulating immune responses. However, the role of AhR in rat liver transplantation (LT) has not been explored.

METHODS

Safety and side effects of N -(3,4-dimethoxycinnamonyl) anthranilic acid (3,4-DAA) and 2-methyl-2H-pyrazole-3-carboxylic acid amide (CH223191) were evaluated. We used optimal doses of 2 drugs, 3,4-DAA, a drug used for mediating AhR activation, and CH223191, antagonist of AhR (3,4-DAA, CH223191, and 3,4-DAA + CH223191), intraperitoneally administered to recipients daily to investigate the role of AhR in the rat LT model. The recipient livers were used to observe the pathological changes, the cells infiltrating the graft, and changes of AhR and programmed death-1 (PD-1) by Western blot, real-time polymerase chain reaction, and immunofluorescence assays. The contents of Foxp3 + and PD-1 + T cells in the recipient spleen and peripheral blood mononuclear cells were evaluated by flow cytometry. In vitro, after isolating CD4 + T cells, they were treated with different AhR ligands to observe the differentiation direction and PD-1 expression level.

RESULTS

The activation of AhR by 3,4-DAA prolonged survival time and ameliorated graft rejection, which were associated with increased expression of AhR and PD-1 in the livers and increased Foxp3 + T cells and PD-1 + T cells in recipient spleens, livers, and peripheral blood mononuclear cells. In vitro, primary T cells incubated with 3,4-DAA mediated increased proportion of Treg and PD-1 + T cells. However, the suppression of AhR with CH223191 reverses these effects, both in the LT model and in vitro.

CONCLUSIONS

Our results indicated that AhR activation might reduce the occurrence of rat acute rejection by increasing the proportion of Treg and the expression of PD-1.

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.

Local gene therapy with indoleamine 2,3-dioxygenase protects against development of transplant vasculopathy in chronic kidney transplant dysfunction

Chronic transplant dysfunction (CTD) is the primary cause of late allograft loss in kidney transplantation. Indoleamine 2,3-dioxygenase (IDO) is involved in fetomaternal tolerance and IDO gene therapy inhibits acute rejection following kidney transplantation. The aim of this study is to investigate whether gene therapy with IDO is able to attenuate CTD. Transplantation was performed in a rat Dark-Agouti to Wistar-Furth CTD model. Donor kidneys were incubated either with an adenovirus carrying IDO gene, a control adenovirus or saline. During the first 10 days recipients received low-dose cyclosporine. Body weight, blood pressure, serum creatinine and proteinuria were measured every 2 weeks. Rats were killed after 12 weeks. IDO had a striking beneficial effect on transplant vasculopathy at week 12. It also significantly improved body weight gain; it reduced blood pressure and decreased proteinuria during the follow-up. However, it did not affect the kidney function. In addition, IDO therapy significantly decreased the number of graft-infiltrating macrophages at week 12. The messenger RNA levels of forkhead box p3 and transforming grow factor-β were elevated in the IDO treated group at week 12. Here we show for first time a clear beneficial effect of local IDO gene therapy especially on transplant vasculopathy in a rat model of renal CTD.

Tranilast: a review of its therapeutic applications

Tranilast (N-[3',4'-dimethoxycinnamoyl]-anthranilic acid) is an analog of a tryptophan metabolite. Initially, tranilast was identified as an anti-allergic agent, and used in the treatment of inflammatory diseases, such as bronchial asthma, atypical dermatitis, allergic conjunctivitis, keloids and hypertrophic scars. Subsequently, the results showed that it could be also effective in the management of a wide range of conditions. The beneficial effects of tranilast have also been seen in a variety of disease states, such as fibrosis, proliferative disorders, cancer, cardiovascular problems, autoimmune disorders, ocular diseases, diabetes and renal diseases. Moreover, several trials have shown that it has very low adverse effects and it is generally well tolerated by patients. In this review, we have attempted to accurately summarize previously published studies relating to the use of tranilast for a range of disorders and discuss the drug's possible mode of action. The major mode of the drug's efficacy appears to be the suppression of the expression and/or action of the TGF-β pathway, but the drug affects other factors as well. The findings presented in this review demonstrate the potential of tranilast for the control of a vast array of pathological situations, furthermore, it is a prescribed drug without severe side effects.

Adenovirus-mediated dual gene expression of human interleukin-10 and hepatic growth factor exerts protective effect against CCl4-induced hepatocyte injury in rats

BACKGROUND

Hepatocyte injury is a common pathological cause of various liver diseases. Due to a lack of an effective preventive treatment, gene therapy has become an interesting approach to prevent and alleviate liver injury.

AIMS

A protective effect of adenovirus-mediated dual gene expression of human interleukin-10 (hIL-10) and human hepatocyte growth factor (hHGF) was investigated against tetrachloromethane (CCl(4))-induced hepatocyte injury in rats.

METHODS

An adenoviral vector carrying the hIL-10 and hHGF genes was constructed, and its protective effect against rat hepatocyte injury was investigated both in vivo and in vitro.

RESULTS

In the in vitro CCl(4)-induced cell injury model, simultaneous transfection of hIL-10 and hHGF genes via an adenoviral vector resulted in production of anti-hepatocyte biological factors by an autocrine mechanism, then significantly improved hepatocyte viability. In the in vivo rat model, synergistic effects of these two gene products protected hepatocytes from damage by reducing the CC1(4)-induced hepatocyte degeneration, hepatic fibrosis, and intrahepatic inflammatory cell infiltration, thereby preserving liver function.

CONCLUSION

Adenovirus-mediated dual gene expression of hIL-10 and hHGF effectively protected against liver damage by likely regulating immune responses to reduce hepatocyte injury and by promoting hepatocyte regeneration. The hIL-10 and hHGF dual gene expression vector has significant potential in the field of liver disease therapeutics and constitutes one of the most promising current strategies for gene therapy.