Dexamethasone Prolongs Cardiac Allograft Survival in a Murine Model Through Myeloid-derived Suppressor Cells

Macrophage membrane coated nanoscale coordination polymers promote graft survival in allogeneic transplantation

Organ transplantation is a crucial life-saving procedure for patients suffering from end-stage organ failure, yet it faces a global shortage. This scarcity not only impacts individual patients but also places strain on healthcare systems worldwide. However, the risk of rejection adds another layer of difficulty to this already intricate medical procedure. Herein, we present the design and synthesis of graft-targeting macrophage membrane coated nanoscale coordination polymers (dNCPs@MM), in which dexamethasone sodium phosphate (DEXp) serves as an effective immunosuppressive drug, Fe3+ acts as bridging ligands for coordination-driven self-assembly with cargo molecules, and macrophage membranes are utilized to reduce uptake by the immune system as well as a retarder to enhance the blood circulation time. The high drug loading, responsive release behavior and targeting capability of the obtained dNCPs@MM promote their biological performance. In a murine allogeneic heart transplantation model, dNCPs@MM exhibited remarkable efficacy in attenuating acute rejection at a low dosage, with a mean survival time of 14.7 days compared to 8.6 days for DEXp and 9.3 days for dNCPs treatment. At a high dosage, dNCPs@MM exhibited the ability to control established rejection by inducing exhaustion in both CD4+ and CD8+ T cell and preventing of alloreactive T cells from acquiring effector (CD44hiCD62L-) functions. Moreover, while high doses of DEXp or dNCPs treatment led to significant adverse effects, the administration of dNCPs@MM demonstrates tolerable adverse effects even at high dosage levels. Therefore, dNCPs@MM exhibits promising potential for clinical application in addressing rejections in allografts and xenografts.

Comparative analysis of the effects of cyclophosphamide and dexamethasone on intestinal immunity and microbiota in delayed hypersensitivity mice

BACKGROUND

The T cell-mediated delayed-type hypersensitivity (DTH) response is critical for elucidating cellular immune mechanisms, especially the role of memory T cells upon antigen re-exposure. This study aimed to investigate the specific effects of the immunosuppressive drugs Cyclophosphamide (CY) and Dexamethasone (DEX) on intestinal immunity and microbiota in a DTH mouse model, contributing to a more nuanced understanding of their immunomodulatory mechanisms.

METHODS

Female BALB/c mice were sensitized to 2,4-dinitrofluorobenzene (DNFB) and randomly allocated into control, CY, and DEX groups. The impact of CY and DEX on immune function was assessed through measurement of thymus and spleen indices, lymphocyte proliferation in mesenteric lymph nodes (MLNs) using MTT assay, and flow cytometric analysis of T cell subsets and TCR expression. Intestinal secretory IgA (sIgA) was quantified by ELISA, and gut microbiota diversity was evaluated using 16S rRNA gene sequencing.

RESULTS

CY and DEX significantly reduced the immune function in DNFB-induced sensitized mice, as indicated by decreased thymus and spleen indices, MLN enlargement, intestinal sIgA content, and ear swelling degree. Flow cytometry revealed that CY increased the proportion of total CD3+ T cells but reduced CD3+CD69+ activated T cells and CD3+TCRγ/δ+ T cells, while DEX increased CD3+CD4+ helper T cells. Both drugs induced distinct changes in gut microbiota diversity and structure, with CY enhancing α diversity and DEX reducing it.

CONCLUSIONS

The study demonstrates that CY and DEX have distinct regulatory effects on the immune organ index, distribution of T cell subsets, and diversity and structure of gut microbiota on DTH-induced immune responses mice, suggesting their differential influence on intestinal mucosal immunity. These findings have implications for the development of targeted immunotherapies and understanding the interplay between immunosuppressive drugs and gut microbiota.

Aging Affects the Role of Myeloid-Derived Suppressor Cells in Alloimmunity

Myeloid-derived suppressor cells (MDSC) are defined as a group of myeloid cells with potent immunoregulatory functions that have been shown to be involved in a variety of immune-related diseases including infections, autoimmune disorders, and cancer. In organ transplantation, MDSC promote tolerance by modifying adaptive immune responses. With aging, however, substantial changes occur that affect immune functions and impact alloimmunity. Since the vast majority of transplant patients are elderly, age-specific modifications of MDSC are of relevance. Furthermore, understanding age-associated changes in MDSC may lead to improved therapeutic strategies. Here, we provide a comprehensive update on the effects of aging on MDSC and discuss potential consequences on alloimmunity.

Glucocorticoid receptor modulates myeloid-derived suppressor cell function via mitochondrial metabolism in immune thrombocytopenia

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature cells and natural inhibitors of adaptive immunity. Intracellular metabolic changes in MDSCs exert a direct immunological influence on their suppressive activity. Our previous study demonstrated that high-dose dexamethasone (HD-DXM) corrected the functional impairment of MDSCs in immune thrombocytopenia (ITP); however, the MDSC population was not restored in nonresponders, and the mechanism remained unclear. In this study, altered mitochondrial physiology and reduced mitochondrial gene transcription were detected in MDSCs from HD-DXM nonresponders, accompanied by decreased levels of carnitine palmitoyltransferase-1 (CPT-1), a rate-limiting enzyme in fatty acid oxidation (FAO). Blockade of FAO with a CPT-1 inhibitor abolished the immunosuppressive function of MDSCs in HD-DXM responders. We also report that MDSCs from ITP patients had lower expression of the glucocorticoid receptor (GR), which can translocate into mitochondria to regulate the transcription of mitochondrial DNA (mtDNA) as well as the level of oxidative phosphorylation. It was confirmed that the expression of CPT-1 and mtDNA-encoded genes was downregulated in GR-siRNA-treated murine MDSCs. Finally, by establishing murine models of active and passive ITP via adoptive transfer of DXM-modulated MDSCs, we confirmed that GR-silenced MDSCs failed to alleviate thrombocytopenia in mice with ITP. In conclusion, our study indicated that impaired aerobic metabolism in MDSCs participates in the pathogenesis of glucocorticoid resistance in ITP and that intact control of MDSC metabolism by GR contributes to the homeostatic regulation of immunosuppressive cell function.

G-CSF promotes alloregulatory function of MDSCs through a c-Kit dependent mechanism

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells that expand in inflammatory conditions including transplantation. MDSCs may be capable of controlling rejection. The critical mechanisms underlying MDSC mediated alloregulation remain unexplored. G-CSF potently stimulates MDSC expansion. We hypothesized that G-CSF-induced MDSCs use a novel mechanism to suppress T cell responses. G-CSF promoted expansion of MDSCs and enhanced their suppressive function against T cell proliferation. Gene expression analysis revealed MDSCs expanded with G-CSF upregulated immune-related genes, but downregulated proliferation-related genes when compared to naïve control MDSCs. The KIT oncogene, encoding the c-Kit (CD117) transmembrane tyrosine kinase receptor, was the most significantly increased in MDSCs expanded with G-CSF. c-Kit inhibition with both imatinib and monoclonal blocking antibody reduced expression of ARG-1, iNOS, PD-L1, and SAA3. Further, imatinib also reduced MDSC-mediated T cell suppression in vitro. Modulation of c-Kit activity may represent a therapeutic target for alloregulatory MDSCs.

The Role of Regulatory Myeloid Cell Therapy in Renal Allograft Rejection

Kidney transplantation is a primary therapy for end-stage renal disease (ESRD) all the time. But it does not mean that we have fully unraveling the mystery of kidney transplantation and confer every patient favorable prognosis. Immune rejection has always been a stumbling block when we try to increase the success rate of kidney transplantation and improve long-term outcomes. Even if the immune rejection is effectively controlled in acute phase, there is a high possibility that the immune response mediated by chronically activated antibodies will trigger chronic rejection and ultimately lead to graft failure. At present, immunosuppressive agent prepared chemically is mainly used to prevent acute or chronic rejection, but it failed to increase the long-term survival rate of allografts or reduce the incidence of chronic rejection after acute rejection, and is accompanied by many adverse reactions. Therefore, many studies have begun to use immune cells to regulate the immune response in order to control allograft rejection. This article will focus on the latest study and prospects of more popular regulatory myeloid cells in the direction of renal transplantation immunotherapy and introduce their respective progress from experimental research to clinical research.

Recent advances in myeloid-derived suppressor cell biology

In recent years, studying the role of myeloid-derived suppressor cells (MDSCs) in many pathological inflammatory conditions has become a very active research area. Although the role of MDSCs in cancer is relatively well established, their role in non-cancerous pathological conditions remains in its infancy resulting in much confusion. Our objectives in this review are to address some recent advances in MDSC research in order to minimize such confusion and to provide an insight into their function in the context of other diseases. The following topics will be specifically focused upon: (1) definition and characterization of MDSCs; (2) whether all MDSC populations consist of immature cells; (3) technical issues in MDSC isolation, estimation and characterization; (4) the origin of MDSCs and their anatomical distribution in health and disease; (5) mediators of MDSC expansion and accumulation; (6) factors that determine the expansion of one MDSC population over the other; (7) the Yin and Yang roles of MDSCs. Moreover, the functions of MDSCs will be addressed throughout the text.

Correlation between MDSC and Immune Tolerance in Transplantation: Cytokines, Pathways and Cell-cell Interaction

MDSCs play an important role in the induction of immune tolerance. Cytokines and chemokines (GM-CSF, IL-6) contributed to the expansion, accumulation of MDSCs, and MDSCs function through iNOS, arginase and PD-L1. MDSCs are recruited and regulated through JAK/STAT, mTOR and Raf/MEK/ERK signaling pathways. MDSCs' immunosuppressive functions were realized through Tregs-mediated pathways and their direct suppression of immune cells. All of the above contribute to the MDSC-related immune tolerance in transplantation. MDSCs have huge potential in prolonging graft survival and reducing rejection through different ways and many other factors worthy to be further investigated are also introduced.

Myeloid-derived suppressor cells in transplantation tolerance induction

Myeloid-derived suppressor cells (MDSCs) are a group of heterogeneous cells derived from bone marrow. These cells are developed from immature myeloid cells and have strong negative immunomodulatory effects. In the context of pathology (such as tumor, autoimmune disease, trauma, and burns), MDSCs accumulate around tumor and inflammatory tissues, where their main role is to inhibit the function of effector T cells and promote the recruitment of regulatory T cells. MDSCs can be used in organ transplantation to regulate the immune responses that participate in rejection of the transplanted organ. This effect is achieved by increasing the production of MDSCs in vivo or transfusion of MDSCs induced in vitro to establish immune tolerance and prolong the survival of the graft. In this review, we discuss the efficacy of MDSCs in a variety of transplantation studies as well as the induction of immune tolerance to prevent transplant rejection through the use of common clinical immunosuppressants combined with MDSCs.

Context-Dependent Effect of Glucocorticoids on the Proliferation, Differentiation, and Apoptosis of Regulatory T Cells: A Review of the Empirical Evidence and Clinical Applications

Glucocorticoids (GCs) are widely used to treat several diseases because of their powerful anti-inflammatory and immunomodulatory effects on immune cells and non-lymphoid tissues. The effects of GCs on T cells are the most relevant in this regard. In this review, we analyze how GCs modulate the survival, maturation, and differentiation of regulatory T (Treg) cell subsets into both murine models and humans. In this way, GCs change the Treg cell number with an impact on the mid-term and long-term efficacy of GC treatment. In vitro studies suggest that the GC-dependent expansion of Treg cells is relevant when they are activated. In agreement with this observation, the GC treatment of patients with established autoimmune, allergic, or (auto)inflammatory diseases causes an expansion of Treg cells. An exception to this appears to be the local GC treatment of psoriatic lesions. Moreover, the effects on Treg number in patients with multiple sclerosis are uncertain. The effects of GCs on Treg cell number in healthy/diseased subjects treated with or exposed to allergens/antigens appear to be context-dependent. Considering the relevance of this effect in the maturation of the immune system (tolerogenic response to antigens), the success of vaccination (including desensitization), and the tolerance to xenografts, the findings must be considered when planning GC treatment.

Myeloid-Derived Suppressor Cells as a Regulator of Immunity in Organ Transplantation

Regulation of allo-immune responses is proposed as a topic for investigation in the current field of organ transplantation. As a regulator, regulatory T cells (Tregs) have received attention due to their ability to control allograft rejection. Concurrently, however, the independent action of Tregs is not enough to achieve tolerance status in many situations. Meanwhile, as a multi-functional regulator, myeloid-derived suppressor cells (MDSCs) can suppress effector T cells as well as induce Tregs or regulatory B cells (Bregs) in certain circumstances. Furthermore, the importance of a crosstalk between MDSCs and natural killer T cells to induce tolerance has been reported. Thus, orchestration between MDSCs, myeloid regulators, T/Bregs and other lymphoid/myeloid regulators can shed light on achieving allogeneic tolerance. Here, we review the current knowledge in terms of immunological regulatory function displayed by MDSCs in the context of organ transplantation. Ideal control of MDSCs would lead to a reduction of allograft rejection and subsequent long-term allograft acceptance.