Disruption of TIM-4 in dendritic cell ameliorates hepatic warm IR injury through the induction of regulatory T cells

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Updates on the Immune Cell Basis of Hepatic Ischemia-Reperfusion Injury

Liver ischemia-reperfusion injury (IRI) is the main cause of organ dysfunction and failure after liver surgeries including organ transplantation. The mechanism of liver IRI is complex and numerous signals are involved but cellular metabolic disturbances, oxidative stress, and inflammation are considered the major contributors to liver IRI. In addition, the activation of inflammatory signals exacerbates liver IRI by recruiting macrophages, dendritic cells, and neutrophils, and activating NK cells, NKT cells, and cytotoxic T cells. Technological advances enable us to understand the role of specific immune cells during liver IRI. Accordingly, therapeutic strategies to prevent or treat liver IRI have been proposed but no definitive and effective therapies exist yet. This review summarizes the current update on the immune cell functions and discusses therapeutic potentials in liver IRI. A better understanding of this complex and highly dynamic process may allow for the development of innovative therapeutic approaches and optimize patient outcomes.

Function and characteristics of TIM‑4 in immune regulation and disease (Review)

T‑cell/transmembrane immunoglobulin and mucin domain containing 4 (TIM‑4) is a phosphatidylserine receptor that is mainly expressed on antigen‑presenting cells and is involved in the recognition and efferocytosis of apoptotic cells. TIM‑4 has been found to be expressed in immune cells such as natural killer T, B and mast cells and to participate in multiple aspects of immune regulation, suggesting that TIM‑4 may be involved in a variety of immune‑related diseases. Recent studies have confirmed that TIM‑4 is also abnormally expressed in a variety of malignant tumor cells and is closely associated with the occurrence and development of tumors and the tumor immune microenvironment. The present study aimed to describe the expression and functional characteristics of TIM‑4 in detail and to comprehensively discuss its role in pathophysiological processes such as infection, allergy, metabolism, autoimmunity and tumor immunity. The current review provided a comprehensive understanding of the functions and characteristics of TIM‑4, as well as novel ideas for the diagnosis and treatment of diseases.

T-Cell Immunoglobulin and Mucin Domain-Containing Protein-4 Is Critical for Kupffer Cell Homeostatic Function in the Activation and Resolution of Liver Ischemia Reperfusion Injury

BACKGROUND AND AIMS

Liver ischemia reperfusion injury (IRI) remains an unresolved clinical problem. This study dissected roles of liver-resident macrophage Kupffer cells (KCs), with a functional focus on efferocytosis receptor T-cell immunoglobulin and mucin domain-containing protein-4 (TIM-4), in both the activation and resolution of IRI in a murine liver partial warm ischemia model.

APPROACH AND RESULTS

Fluorescence-activated cell sorting results showed that TIM-4 was expressed exclusively by KCs, but not infiltrating macrophages (iMФs), in IR livers. Anti-TIM-4 antibody depleted TIM-4⁺ macrophages in vivo, resulting in either alleviation or deterioration of liver IRI, which was determined by the repopulation kinetics of the KC niche with CD11b⁺ macrophages. To determine the KC-specific function of TIM-4, we reconstituted clodronate-liposome-treated mice with exogenous wild-type or TIM-4-deficient KCs at either 0 hour or 24 hours postreperfusion. TIM-4 deficiency in KCs resulted in not only increases in the severity of liver IRI (at 6 hours postreperfusion), but also impairment of the inflammation resolution (at 7 days postreperfusion). In vitro analysis revealed that TIM-4 promoted KC efferocytosis to regulate their Toll-like receptor response by up-regulating IL-10 and down-regulating TNF-α productions.

CONCLUSIONS

TIM-4 is critical for KC homeostatic function in both the activation and resolution of liver IRI by efferocytosis.

Dendritic Cell-Mediated Regulation of Liver Ischemia-Reperfusion Injury and Liver Transplant Rejection

Liver allograft recipients are more likely to develop transplantation tolerance than those that receive other types of organ graft. Experimental studies suggest that immune cells and other non-parenchymal cells in the unique liver microenvironment play critical roles in promoting liver tolerogenicity. Of these, liver interstitial dendritic cells (DCs) are heterogeneous, innate immune cells that appear to play pivotal roles in the instigation, integration and regulation of inflammatory responses after liver transplantation. Interstitial liver DCs (recruited in situ or derived from circulating precursors) have been implicated in regulation of both ischemia/reperfusion injury (IRI) and anti-donor immunity. Thus, livers transplanted from mice constitutively lacking DCs into syngeneic, wild-type recipients, display increased tissue injury, indicating a protective role of liver-resident donor DCs against transplant IRI. Also, donor DC depletion before transplant prevents mouse spontaneous liver allograft tolerance across major histocompatibility complex (MHC) barriers. On the other hand, mouse liver graft-infiltrating host DCs that acquire donor MHC antigen via "cross-dressing", regulate anti-donor T cell reactivity in association with exhaustion of graft-infiltrating T cells and promote allograft tolerance. In an early phase clinical trial, infusion of donor-derived regulatory DCs (DCreg) before living donor liver transplantation can induce alterations in host T cell populations that may be conducive to attenuation of anti-donor immune reactivity. We discuss the role of DCs in regulation of warm and liver transplant IRI and the induction of liver allograft tolerance. We also address design of cell therapies using DCreg to reduce the immunosuppressive drug burden and promote clinical liver allograft tolerance.

Tim-4 expressing monocytes as a novel indicator to assess disease activity and severity of ulcerative colitis

AIMS

The dysregulation of the immune response has been shown to be involved in ulcerative colitis (UC) pathogenesis. Tim-4 is a potential regulator of the immune system which plays key roles in multiple autoimmune diseases. However, whether it is involved in UC remains unclear. The aim of this research was to determine the expression of Tim-4 on circulating monocytes and its clinical significance in UC patients.

MAIN METHODS

In total, 36 UC patients and 34 healthy controls (HCs) were enrolled in this study. The frequencies of CD14⁺Tim-4⁺ cells, regulatory T cells (Treg) and CD14⁺HLA-DR^-/low myeloid-derived suppressor cells (MDSCs) in the peripheral blood were determined by flow cytometry. Serum IL-6 levels were determined by chemiluminescence immunoassay.

KEY FINDINGS

The percentage of CD14⁺Tim-4⁺ cells was higher in UC patients than in HCs. The frequency of Treg cells was significantly decreased, while that of MDSCs was significantly increased in UC patients. The frequency of CD14⁺Tim-4⁺ cells was significantly elevated in subjects with high severity, high number of defecations per day, high UC disease activity index Mayo score, high IgG, and high levels of inflammatory markers. And the percentages of Tim-4-expressing monocytes were significantly decreased in UC patients that received a 3-week treatment with mesalazine. Furthermore, the frequency of CD14⁺Tim-4⁺ cells was also positively correlated with MDSCs and negatively correlated with Treg cells.

SIGNIFICANCE

CD14⁺Tim-4⁺ cells was elevated in UC patients and could be a novel indicator to assess disease severity and activity of UC.

Tim-4 in Health and Disease: Friend or Foe?

T-cell immunoglobulin and mucin domain containing 4 (Tim-4) is a phosphatidylserine receptor and is selectively expressed on antigen presenting cells. Recently, Tim-4 was reported to be expressed on iNKT cells, B1 cells, and tumor cells, suggesting it has multiple biological functions. In this review, we mainly summarize the expression and regulation of Tim-4 in immune cells including T cells, macrophages, dendritic cells, NKT cells, B cells, and mast cells. The expression of Tim-4 in these cells implies that Tim-4 might participate in immune related diseases. Emerging evidence emphasizes a substantial role for Tim-4 in maintaining homeostasis by regulating various immune responses, including viral infection, allergy, autoimmunity, and tumor immunity. Here, we collectively evaluated the role of Tim-4 in health and diseases. This summary will be extremely useful to fully understand the function of Tim-4 in the pathogenesis of immune related diseases, which would provide novel clues for the diagnosis and treatment of diseases.

Association of Tim-4 expression in monocyte subtypes with clinical course and prognosis in acute ischemic stroke patients

Background: It has been proven that T cell immunoglobin and mucin domain (Tim)-4 and monocytes (Mo) are involved in regulation of immunity, which is important for the recovery of acute ischemic stroke (AIS).Methods: In this study, the expression of Tim-4 in both circulating Mo subtypes and plasma in 32 consecutive AIS patients and 32 control patients was assessed to determine their correlation with the clinical course and prognosis of AIS.Results: It was found that, compared to the control patients, the percentage of Tim-4 expression in overall Mo, classical Mo and non-classical Mo was significantly elevated after 2 and 5 days of stroke (p < 0.05), while it was promoted from 0 to 10 days of stoke in intermediate Mo (p < 0.05). Furthermore, Tim-4 expressions in non-classical Mo and intermediate Mo were obviously correlated with National Institutes of Health Stroke Scale (NIHSS) scores at 2 days of stroke (r = 0.351, p = 0.048; r = 0.358, p = 0.044, respectively). In poor outcome (PO) patients, the expression of Tim-4 in non-classical Mo was remarkably promoted at 2 days of stroke in comparison with non-PO patients (p < 0.05). More importantly, our results revealed a positive correlation between Tim-4 expression in non-classical Mo and interleukin (IL)-6 plasma levels in AIS patients without infection.Conclusion: In summary, our findings proved that Tim-4 expression in non-classical Mo could be an appropriate target for the prediction of the clinical course and prognosis in AIS patients.

Developments in the field of allergy in 2017 through the eyes of Clinical and Experimental Allergy

In this article, we described the development in the field of allergy as described by Clinical and Experimental Allergy in 2017. Experimental models of allergic disease, basic mechanisms, clinical mechanisms, allergens, asthma and rhinitis and clinical allergy are all covered.

RETRACTED: Tim-4 promotes the growth of colorectal cancer by activating angiogenesis and recruiting tumor-associated macrophages via the PI3K/AKT/mTOR signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors. After publication, the authors noted unreliable data in the experimental validations. Specifically, representative images of IHC staining for CD31 and α-SMA in CT26-Vector and CT26-Tim-4 tumors in Fig. 2C and the expression of MMP9, VEGF and LOX in CT26-Tim-4 and CT26-Vector tumors was assessed by immunohistochemistry in Fig. 2E; incorrect photos were provided due to file placement confusion. All authors “agree with this retraction and deeply regret these errors and apologize to the editorial board and readers for any inconvenience caused.” Additionally, after publication, the journal was made aware of comments in relation to this article (https://pubpeer.com/publications/D191AE022DDD7B810564039CB16395). The authors have not responded to the journal request to respond to these comments.

Ketamine ameliorates ischemia-reperfusion injury after liver autotransplantation by suppressing activation of Kupffer cells in rats

This study aimed to investigate the protective effects of ketamine against hepatic ischemia-reperfusion (I/R) injury by suppressing activation of Kupffer cells (KCs) in rat liver autotransplantation. Male Sprague-Dawley rats were randomized into 3 groups (n = 10 each). Group I, the sham group, received saline. Group II received saline and underwent orthotopic liver autotransplantation (OLAT). Group III received 10 mg/kg ketamine and underwent OLAT. Blood samples were obtained at 3, 6, 12, and 24 h after I/R, and following ALT, AST, LDH, IL-6, TNF-α, IL-1β, and IL-10 in serum were detected. Model rats were sacrificed at the indicated time points and the graft liver tissues were evaluated histologically. KCs were isolated from rat liver tissues, and inflammatory products and proteins of NF-κB signaling pathway were detected using quantitative RT-PCR and Western blotting. Our results showed that ketamine significantly decreased ALT, AST, LDH, IL-6, TNF-α, and IL-1β levels and increased IL-10 level. Furthermore, ketamine alleviated the histopathology changes, by less KC infiltration and lower hepatocyte apoptosis. Moreover, activity of NF-κB signaling pathway in KCs was suppressed. In addition, production of pro- and anti-inflammatory factors is consistent with the results in tissues. Ketamine ameliorated I/R injury after liver transplantation by suppressing activation of KCs in rats.

Diverse roles of TIM4 in immune activation: implications for alloimmunity

PURPOSE OF REVIEW

T-cell immunoglobulin and mucin domain-containing molecule (TIM)4 is a costimulatory molecule and phosphatidylserine receptor. Its dominant function varies according to the expressing cell and site of activation. In recent years, studies have identified its role in diverse disease processes and increasingly in alloimmunity. Herein, we will comprehensively review the literature on TIM4 and outline its function in shaping the alloimmune response.

RECENT FINDINGS

TIM4 expression on dendritic cells increases following transplantation. Blockade of TIM4 in vivo leads to increased differentiation of regulatory T cells and improved allograft survival. TIM4 binds phosphatidylserine-expressing apoptotic cells. Previously thought of as a tethering molecule, recent studies have demonstrated that TIM4 interacts with integrins to mediate uptake of apoptotic cells. TIM4 B cells have recently been identified, which produce high levels of IFNγ and promote allograft rejection. Targeting these B cells improved allograft survival and promoted the development of TIM1 regulatory B cells.

SUMMARY

TIM4 is expressed in niche compartments and has many immunological effects. However, inhibition of TIM4 has been demonstrated to prolong allograft survival, through varied mechanisms. A unifying explanation for the role of TIM4 in alloimmunity remains to be found, but this pathway appears to hold considerable promise in transplantation.

TIM4-TIM1 interaction modulates Th2 pattern inflammation through enhancing SIRT1 expression

Skewed T helper 2 (Th2)-cell polarization plays a critical role in the pathogenesis of allergic inflammations; however, the underlying mechanisms require further elucidation. The aim of the present study was to investigate the mechanisms through which the interaction between T-cell immunoglobulin and mucin domain (TIM)4 and TIM1 regulates the expression of silent information regulator 1 (SIRT1) in Th2 cells, and the role of SIRT1 in Th2-cell polarization during nasal allergic inflammation. The results demonstrated that TIM4 expression by splenic dendritic cells was increased in mice with allergic rhinitis, and the TIM4̸TIM1 interaction promoted CD4⁺ T cells to express SIRT1 during allergic inflammation via enhancing phosphoinositide 3-kinase/Akt phosphorylation. SIRT1 then facilitated CD4⁺ T-cell proliferation through downregulating the expression of Fas ligand, caspase-3 and p53 in mice with nasal allergic inflammation. In conclusion, the interaction of TIM4̸TIM1 was found to promote Th2-cell proliferation through enhancing SIRT1 expression in mice with nasal allergic rhinitis.

Forkhead box protein-3 (Foxp3)-producing dendritic cells suppress allergic response

BACKGROUND

The generation of the tolerogenic dendritic cells (DC) is not fully understood yet. Forkhead box protein-3 (Foxp3) is an important molecule in the immune tolerance. This study tests a hypothesis that DCs express Foxp3, which can be upregulated by Staphylococcal enterotoxin B (SEB).

METHODS

The expression of Foxp3 by DCs was evaluated by real-time RT-PCR, Western blotting, flow cytometry, and chromatin immunoprecipitation assay.

RESULTS

We observed that mice treated with SEB at 0.25-0.5 μg/mouse showed high frequencies of transforming growth factor (TGF)-β-producing CD4⁺ T cells and TGF-β-producing DCs in the intestine, while the IL-4⁺ CD4⁺ T cells and TIM4⁺ DCs were dominated in the intestine in mice treated with SEB at 1-10 μg/mouse. Treating DCs with SEB in the culture induced high levels of Foxp3 at the TGF-β promoter locus. The function of Foxp3 was blocked by STAT6 (signal transducer and activator transcription-6); the latter was induced by exposing DCs to SEB in the culture at doses of 100-400 ng/ml. Treating allergic mice with specific immunotherapy (SIT) together with SEB significantly promoted the therapeutic effects on the allergic responses than treating with SIT alone.

CONCLUSION

Dendritic cells have the capacity to express Foxp3, which can be upregulated by exposure to SEB.

Nobiletin ameliorates ischemia-reperfusion injury by suppressing the function of Kupffer cells after liver transplantation in rats

This study aims to explore the protective effects of nobiletin against hepatic ischemia-reperfusion (IR) injury after liver transplantation. Kupffer cells (KCs) were activated and co-cultured with different concentration of nobiletin for 24h in vitro, inflammatory products and activity of TLR4/NF-κB signaling pathway were detected. Sprague-Dawley rats were selected and underwent orthotopic liver transplantation. Donors were injected intravenously with nobiletin (50mg/kg) or saline solution, once a day for 1 week before the surgery. Recipients were randomly paired and sacrificed at the indicated time points (3, 6, and 24h after the surgery), the graft liver tissues and blood samples were collected for analysis. Hepatic function, inflammatory mediators, apoptosis of hepatocytes, histological changes, KCs and CD4+ T-lymphocyte infiltration were assessed. Results showed nobiletin dose-dependently suppressed the expression of inflammatory mediators and the activity of TLR4/NF-κB signaling pathway in activated KCs. Furthermore, nobiletin alleviated liver damage induced by IR in vivo, significantly decreased the serum levels of alanine aminotransferase, aspartate transaminase, inflammatory cytokines and alleviated the histopathology changes. Moreover, liver in the nobiletin treated group exhibited less KCs and CD4+ lymphocyte infiltration and lower hepatocyte apoptosis after operation. In addition, activity of TLR4/NF-κB signaling pathway in KCs was also suppressed, consistent with the results in vitro. Collectively, Nobiletin can ameliorate IR injury after liver transplantation and may be a promising new strategy to protect against liver IR injury.

Dust mite allergen, glutathione S-transferase, induces T cell immunoglobulin mucin domain-4 in dendritic cells to facilitate initiation of airway allergy

BACKGROUND

Allergens from dust mites play a critical role in the pathogenesis of airway allergy. The mechanism by which dust mite allergens induce allergic diseases is not fully understood yet.

OBJECTIVE

This study tests a hypothesis that the eighth subtypes of Dermatophagoides farina allergen (Derf8) play an important role in the induction of airway allergy.

METHODS

The protein of Derf8 was synthesized via molecular cloning approach. Dendritic cells (DC) were stimulated with Derf8 in the culture, and then, the expression of T cell immunoglobulin mucin domain 4 (TIM4) in dendritic cells (DC) was analysed. The role of Derf8 in the induction of airway allergy was evaluated with a mouse model.

RESULTS

Exposure to Derf8 markedly induced the TIM4 expression in DCs by modulating the chromatin at the TIM4 promoter locus. Derf8 played a critical role in the expansion of the T helper 2 response in the mouse airway via inducing DCs to produce TIM4. Administration with Derf8-depleted dust mite extracts (DME) inhibited the allergic inflammation and induced regulatory T cells in mice with airway allergy.

CONCLUSION

Derf8 plays an important role in the initiation of dust mite allergy. Vaccination with Derf8-deficient DME is more efficient to inhibit the dust mite allergic inflammation than using wild DME.