Autocrine adenosine signaling promotes regulatory T cell-mediated renal protection

VX-702 Ameliorates the Severity of Sepsis-Associated Acute Kidney Injury by Downregulating Inflammatory Factors in Macrophages

Purpose

Sepsis-associated acute kidney injury (S-AKI) contributes to high mortality, but it is lack of specific treatments. We aimed to investigate the underlying mechanism of S-AKI and to identify target drugs to alleviate AKI.

Methods

We establish a stable mouse model of S-AKI by Pseudomonas aeruginosa incision infection. Based on high-throughput sequencing and bioinformatics analysis, we investigated the underlying mechanism and selected the target drug (VX-702) for S-AKI. An in vitro model established by co-cultured of kidney tubular epithelial cell line (TCMK-1) cells with lipopolysaccharide (LPS)-induced leukemic monocyte/macrophage cells (RAW264.7), we explored the effect of VX-702 on S-AKI.

Results

The data showed interleukin (IL)-6 and IL-1β were the hub genes, and the mitogen-activated protein kinase (MAPK) signaling pathway was the main pathway involved in S-AKI. Administration of VX-702 by oral gavage decreased the elevated concentrations of IL-6, IL-1β, serum creatinine, and blood urea nitrogen in mice with S-AKI. Moreover, VX-702 reduced the number of apoptotic cells in damaged kidney tissues. Cell viability was decreased, and the number of apoptotic cells was increased in TCMK-1 cells co-cultured with LPS-induced RAW264.7 cells compared to LPS-induced TCMK-1 cells. VX-702 treatment reversed this effect. VX-702 treatment reduced the levels of phosphorylated p38 MAPK and proinflammatory cytokines in RAW264.7 cells and the supernatant. VX-702 could bind IL-6, IL-1β and MAPK, and affect the binding of IL-1β and its receptor, as demonstrated by molecular docking.

Conclusion

VX-702 ameliorated S-AKI by inhibiting the release of proinflammatory cytokines from macrophages, indicating its potential as a novel therapeutic for S-AKI treatment.

ADENOSINE INFLUENCES FOXP3 EXPRESSION OF T REGS VIA THE A2AR/CREB PATHWAY IN A MOUSE MODEL OF SEPSIS

ABSTRACT

The adenosine concentration and forkhead box protein (Foxp3) expression in T regulatory cells (T regs ) are increased during sepsis. However, the mechanism by which adenosine induces Foxp3 expression is incompletely understood. A cecal ligation and puncture (CLP) model was constructed using C57BL/J mice. The plasma adenosine concentration and Foxp3 expression in splenic T regs were increased consistently for 15 days after sepsis onset. Analysis of the mean fluorescence intensity of Foxp3 and adenosine concentration in the same mice revealed a linear correlation. In the CLP model, adenosine 2a receptor (A2aR) blockade inhibited Foxp3 expression in T regs . In vitro activation of A2aR promoted Foxp3 expression in T regs and facilitated secretion of extracellular vesicles. Transcriptome sequencing revealed that A2aR blockade led to changes in cyclic adenosine monophosphate response element-binding protein (CREB) transcription in T regs in our sepsis model. Use of adenosine or A2aR agonists promoted CREB expression, CREB phosphorylation at S133, T reg expression of Foxp3, and enhanced inhibition of proliferation of cluster of differentiation (CD)4+ lymphocytes. A2aR blockade or inhibition of CREB expression inhibited Foxp3 expression in T regs . In the CLP model, use of CREB inhibitors could inhibit Foxp3 expression and reduce the bacterial load. In summary, adenosine in sepsis promotes CREB phosphorylation via A2aR which, in turn, upregulates Foxp3 expression in T regs .

CD39 expression by regulatory T cells participates in CD8+ T cell suppression during experimental Trypanosoma cruzi infection

An imbalance between suppressor and effector immune responses may preclude cure in chronic parasitic diseases. In the case of Trypanosoma cruzi infection, specialized regulatory Foxp3+ T (Treg) cells suppress protective type-1 effector responses. Herein, we investigated the kinetics and underlying mechanisms behind the regulation of protective parasite-specific CD8+ T cell immunity during acute T. cruzi infection. Using the DEREG mouse model, we found that Treg cells play a role during the initial stages after T. cruzi infection, restraining the magnitude of CD8+ T cell responses and parasite control. Early Treg cell depletion increased the frequencies of polyfunctional short-lived, effector T cell subsets, without affecting memory precursor cell formation or the expression of activation, exhaustion and functional markers. In addition, Treg cell depletion during early infection minimally affected the antigen-presenting cell response but it boosted CD4+ T cell responses before the development of anti-parasite effector CD8+ T cell immunity. Crucially, the absence of CD39 expression on Treg cells significantly bolstered effector parasite-specific CD8+ T cell responses, preventing increased parasite replication in T. cruzi infected mice adoptively transferred with Treg cells. Our work underscores the crucial role of Treg cells in regulating protective anti-parasite immunity and provides evidence that CD39 expression by Treg cells represents a key immunomodulatory mechanism in this infection model.

Hypoxia-adenosine axis as therapeutic targets for acute respiratory distress syndrome

The human respiratory and circulatory systems collaborate intricately to ensure oxygen delivery to all cells, which is vital for ATP production and maintaining physiological functions and structures. During limited oxygen availability, hypoxia-inducible factors (HIFs) are stabilized and play a fundamental role in maintaining cellular processes for hypoxia adaptation. First discovered during investigations of erythropoietin production regulation, HIFs influence physiological and pathological processes, including development, inflammation, wound healing, and cancer. HIFs promote extracellular adenosine signaling by enhancing adenosine generation and receptor signaling, representing an endogenous feedback mechanism that curbs excessive inflammation, supports injury resolution, and enhances hypoxia tolerance. This is especially important for conditions that involve tissue hypoxia, such as acute respiratory distress syndrome (ARDS), which globally poses significant health challenges without specific treatment options. Consequently, pharmacological strategies to amplify HIF-mediated adenosine production and receptor signaling are of great importance.

Adenosinergic metabolism pathway: an emerging target for improving outcomes of solid organ transplantation

Extracellular nucleotides are widely recognized as crucial modulators of immune responses in peripheral tissues. Adenosine triphosphate (ATP) and adenosine are key components of extracellular nucleotides, the balance of which contributes to immune homeostasis. Under tissue injury, ATP exerts its pro-inflammatory function, while the adenosinergic pathway rapidly degrades ATP to immunosuppressive adenosine, thus inhibiting excessive and uncontrolled inflammatory responses. Previous reviews have explored the immunoregulatory role of extracellular adenosine in various pathological conditions, especially inflammation and malignancy. However, current knowledge regarding adenosine and adenosinergic metabolism in the context of solid organ transplantation remains fragmented. In this review, we summarize the latest information on adenosine metabolism and the mechanisms by which it suppresses the effector function of immune cells, as well as highlight the protective role of adenosine in all stages of solid organ transplantation, including reducing ischemia reperfusion injury during organ procurement, alleviating rejection, and promoting graft regeneration after transplantation. Finally, we discuss the potential for future clinical translation of adenosinergic pathway in solid organ transplantation.

Improving combination therapies: targeting A2B-adenosine receptor to modulate metabolic tumor microenvironment and immunosuppression

BACKGROUND

We investigated the role of A2B-adenosine receptor in regulating immunosuppressive metabolic stress in the tumor microenvironment. Novel A2B-adenosine receptor antagonist PBF-1129 was tested for antitumor activity in mice and evaluated for safety and immunologic efficacy in a phase I clinical trial of patients with non-small cell lung cancer.

METHODS

The antitumor efficacy of A2B-adenosine receptor antagonists and their impact on the metabolic and immune tumor microenvironment were evaluated in lung, melanoma, colon, breast, and epidermal growth factor receptor-inducible transgenic cancer models. Employing electron paramagnetic resonance, we assessed changes in tumor microenvironment metabolic parameters, including pO2, pH, and inorganic phosphate, during tumor growth and evaluated the immunologic effects of PBF-1129, including its pharmacokinetics, safety, and toxicity, in patients with non-small cell lung cancer.

RESULTS

Levels of metabolic stress correlated with tumor growth, metastasis, and immunosuppression. Tumor interstitial inorganic phosphate emerged as a correlative and cumulative measure of tumor microenvironment stress and immunosuppression. A2B-adenosine receptor inhibition alleviated metabolic stress, downregulated expression of adenosine-generating ectonucleotidases, increased expression of adenosine deaminase, decreased tumor growth and metastasis, increased interferon γ production, and enhanced the efficacy of antitumor therapies following combination regimens in animal models (anti-programmed cell death 1 protein vs anti-programmed cell death 1 protein plus PBF-1129 treatment hazard ratio = 11.74 [95% confidence interval = 3.35 to 41.13], n = 10, P < .001, 2-sided F test). In patients with non-small cell lung cancer, PBF-1129 was well tolerated, with no dose-limiting toxicities; demonstrated pharmacologic efficacy; modulated the adenosine generation system; and improved antitumor immunity.

CONCLUSIONS

Data identify A2B-adenosine receptor as a valuable therapeutic target to modify metabolic and immune tumor microenvironment to reduce immunosuppression, enhance the efficacy of immunotherapies, and support clinical application of PBF-1129 in combination therapies.

Molecular Mechanisms Underpinning Immunometabolic Reprogramming: How the Wind Changes during Cancer Progression

Metabolism and the immunological state are intimately intertwined, as defense responses are bioenergetically expensive. Metabolic homeostasis is a key requirement for the proper function of immune cell subsets, and the perturbation of the immune-metabolic balance is a recurrent event in many human diseases, including cancer, due to nutrient fluctuation, hypoxia and additional metabolic changes occurring in the tumor microenvironment (TME). Although much remains to be understood in the field of immunometabolism, here, we report the current knowledge on both physiological and cancer-associated metabolic profiles of immune cells, and the main molecular circuits involved in their regulation, highlighting similarities and differences, and emphasizing immune metabolic liabilities that could be exploited in cancer therapy to overcome immune resistance.

The role of regulatory T cells in the pathogenesis of acute kidney injury

The incidence of acute kidney injury (AKI) is on the rise and is associated with high mortality; however, there are currently few effective treatments. Moreover, the relationship between Tregs and other components of the immune microenvironment (IME) in the pathogenesis of AKI remains unclear. We downloaded four publicly accessible AKI datasets, GSE61739, GSE67401, GSE19130, GSE81741, GSE19288 and GSE106993 from the gene expression omnibus (GEO) database. Additionally, we gathered two kidney single-cell sequencing (scRNA-seq) samples from the Department of Organ Transplantation at Zhujiang Hospital of Southern Medical University to investigate chronic kidney transplant rejection (CKTR). Moreover, we also collected three samples of normal kidney tissue from GSE131685. By analysing the differences in immune cells between the AKI and Non-AKI groups, we discovered that the Non-AKI group contained a significantly greater number of Tregs than the AKI group. Additionally, the activation of signalling pathways, such as inflammatory molecules secretion, immune response, glycolytic metabolism, NOTCH, FGF, NF-κB and TLR4, was significantly greater in the AKI group than in the Non-AKI group. Additionally, analysis of single-cell sequencing data revealed that Tregs in patients with chronic kidney rejection and in normal kidney tissue have distinct biology, including immune activation, cytokine production, and activation fractions of signalling pathways such as NOTCH and TLR4. In this study, we found significant differences in the IME between AKI and Non-AKI, including differences in Tregs cells and activation levels of biologically significant signalling pathways. Tregs were associated with lower activity of signalling pathways such as inflammatory response, inflammatory molecule secretion, immune activation, glycolysis.

CD73 mediates the therapeutic effects of endometrial regenerative cells in concanavalin A-induced hepatitis by regulating CD4+ T cells

BACKGROUND

As a kind of mesenchymal-like stromal cells, endometrial regenerative cells (ERCs) have been demonstrated effective in the treatment of Concanavalin A (Con A)-induced hepatitis. However, the therapeutic mechanism of ERCs is not fully understood. Ecto-5`-nucleotidase (CD73), an enzyme that could convert immune-stimulative adenosine monophosphate (AMP) to immune-suppressive adenosine (ADO), was identified highly expressed on ERCs. The present study was conducted to investigate whether the expression of CD73 on ERCs is critical for its therapeutic effects in Con A-induced hepatitis.

METHODS

ERCs knocking out CD73 were generated with lentivirus-mediated CRISPR-Cas9 technology and identified by flow cytometry, western blot and AMPase activity assay. CD73-mediated immunomodulatory effects of ERCs were investigated by CD4+ T cell co-culture assay in vitro. Besides, Con A-induced hepatitis mice were randomly assigned to the phosphate-buffered saline treated (untreated), ERC-treated, negative lentiviral control ERC (NC-ERC)-treated, and CD73-knockout-ERC (CD73-KO-ERC)-treated groups, and used to assess the CD73-mediated therapeutic efficiency of ERCs. Hepatic histopathological analysis, serum transaminase concentrations, and the proportion of CD4+ T cell subsets in the liver and spleen were performed to assess the progression degree of hepatitis.

RESULTS

Expression of CD73 on ERCs could effectively metabolize AMP to ADO, thereby inhibiting the activation and function of conventional CD4+ T cells was identified in vitro. In addition, ERCs could markedly reduce levels of serum and liver transaminase and attenuate liver damage, while the deletion of CD73 on ERCs dampens these effects. Furthermore, ERC-based treatment achieved less infiltration of CD4+ T and Th1 cells in the liver and reduced the population of systemic Th1 and Th17 cells and the levels of pro-inflammatory cytokines such as IFN-γ and TNF-α, while promoting the generation of Tregs in the liver and spleen, while deletion of CD73 on ERCs significantly impaired their immunomodulatory effects locally and systemically.

CONCLUSION

Taken together, it is concluded that CD73 is critical for the therapeutic efficiency of ERCs in the treatment of Con A-induced hepatitis.

CD39 expression by regulatory T cells drives CD8+ T cell suppression during experimental Trypanosoma cruzi infection

An imbalance between suppressor and effector immune responses may preclude cure in chronic parasitic diseases. In the case of Trypanosoma cruzi infection, specialized regulatory Foxp3+ T (Treg) cells suppress protective type-1 effector responses. Herein, we investigated the kinetics and underlying mechanisms behind the regulation of protective parasite-specific CD8+ T cell immunity during acute T. cruzi infection. Using the DEREG mouse model, we found that Treg cells play a critical role during the initial stages after T. cruzi infection, subsequently influencing CD8+ T cells. Early Treg cell depletion increased the frequencies of polyfunctional short-lived, effector T cell subsets, without affecting memory precursor cell formation or the expression of activation markers. In addition, Treg cell depletion during early infection minimally affected the antigen-presenting cell response but it boosted CD4+ T cell responses before the development of anti-parasite effector CD8+ T cell responses. Crucially, the absence of CD39 expression on Treg cells significantly bolstered effector parasite-specific CD8+ T cell responses, leading to improved parasite control during T. cruzi infection. Our work underscores the crucial role of Treg cells in regulating protective anti-parasite immunity and provides evidence that CD39 expression by Treg cells represents a key immunomodulatory mechanism in this infection model.

The immune checkpoint adenosine 2A receptor is associated with aggressive clinical outcomes and reflects an immunosuppressive tumor microenvironment in human breast cancer

Background

The crosstalk between the immune system and cancer cells has aroused considerable interest over the past decades. To escape immune surveillance cancer cells evolve various strategies orchestrating tumor microenvironment. The discovery of the inhibitory immune checkpoints was a major breakthrough due to their crucial contribution to immune evasion. The A2AR receptor represents one of the most essential pathways within the TME. It is involved in several processes such as hypoxia, tumor progression, and chemoresistance. However, its clinical and immunological significance in human breast cancer remains elusive.

Methods

The mRNA expression and protein analysis were performed by RT-qPCR and immunohistochemistry. The log-rank (Mantel-Cox) test was used to estimate Kaplan-Meier analysis for overall survival. Using large-scale microarray data (METABRIC), digital cytometry was conducted to estimate cell abundance. Analysis was performed using RStudio software (7.8 + 2023.03.0) with EPIC, CIBERSORT, and ImmuneCellAI algorithms. Tumor purity, stromal and immune scores were calculated using the ESTIMATE computational method. Finally, analysis of gene set enrichment (GSEA) and the TISCH2 scRNA-seq database were carried out.

Results

Gene and protein analysis showed that A2AR was overexpressed in breast tumors and was significantly associated with high grade, elevated Ki-67, aggressive molecular and histological subtypes, as well as poor survival. On tumor infiltrating immune cells, A2AR was found to correlate positively with PD-1 and negatively with CTLA-4. On the other hand, our findings disclosed more profuse infiltration of protumoral cells such as M0 and M2 macrophages, Tregs, endothelial and exhausted CD8+ T cells within A2ARhigh tumors. According to the Single-Cell database, A2AR is expressed in malignant, stromal and immune cells. Moreover, it is related to tumor purity, stromal and immune scores. Our results also revealed that CD8+T cells from A2ARhigh patients exhibited an exhausted functional profile. Finally, GSEA analysis highlighted the association of A2AR with biological mechanisms involved in tumor escape and progression.

Conclusion

The present study is the first to elucidate the clinical and immunological relevance of A2AR in breast cancer patients. In light of these findings, A2AR could be deemed a promising therapeutic target to overcome immune evasion prevailing within the TME of breast cancer patients.

The interplay between the DNA damage response and ectonucleotidases modulates tumor response to therapy

The extracellular nucleoside adenosine reduces tissue inflammation and is generated by irreversible dephosphorylation of adenosine monophosphate (AMP) mediated by the ectonucleotidase CD73. The pro-inflammatory nucleotides adenosine triphosphate, nicotinamide adenine dinucleotide, and cyclic guanosine -monophosphate-AMP (cGAMP), which are produced in the tumor microenvironment (TME) during therapy-induced immunogenic cell death and activation of innate immune signaling, can be converted into AMP by ectonucleotidases CD39, CD38, and CD203a/ENPP1. Thus, ectonucleotidases shape the TME by converting immune-activating signals into an immunosuppressive one. Ectonucleotidases also hinder the ability of therapies including radiation therapy, which enhance the release of pro-inflammatory nucleotides in the extracellular milieu, to induce immune-mediated tumor rejection. Here, we review the immunosuppressive effects of adenosine and the role of different ectonucleotidases in modulating antitumor immune responses. We discuss emerging opportunities to target adenosine generation and/or its ability to signal via adenosine receptors expressed by immune and cancer cells in the context of combination immunotherapy and radiotherapy.

Tumor intrinsic and extrinsic functions of CD73 and the adenosine pathway in lung cancer

The adenosine pathway is an exciting new target in the field of cancer immunotherapy. CD73 is the main producer of extracellular adenosine. Non-small cell lung cancer (NSCLC) has one of the highest CD73 expression signatures among all cancer types and the presence of common oncogenic drivers of NSCLC, such as mutant epidermal growth factor receptor (EGFR) and KRAS, correlate with increased CD73 expression. Current immune checkpoint blockade (ICB) therapies only benefit a subset of patients, and it has proved challenging to understand which patients might respond even with the current understanding of predictive biomarkers. The adenosine pathway is well known to disrupt cytotoxic function of T cells, which is currently the main target of most clinical agents. Data thus far suggests that combining ICB therapies already in the clinic with adenosine pathway inhibitors provides promise for the treatment of lung cancer. However, antigen loss or lack of good antigens limits efficacy of ICB; simultaneous activation of other cytotoxic immune cells such as natural killer (NK) cells can be explored in these tumors. Clinical trials harnessing both T and NK cell activating treatments are still in their early stages with results expected in the coming years. In this review we provide an overview of new literature on the adenosine pathway and specifically CD73. CD73 is thought of mainly for its role as an immune modulator, however recent studies have demonstrated the tumor cell intrinsic properties of CD73 are potentially as important as its role in immune suppression. We also highlight the current understanding of this pathway in lung cancer, outline ongoing studies examining therapies in combination with adenosine pathway targeting, and discuss future prospects.

Gal-9/Tim-3 signaling pathway activation suppresses the generation of Th17 cells and promotes the induction of Foxp3+ regulatory T cells in renal ischemia-reperfusion injury

CD4⁺ T cells mediate the pathogenesis of renal ischemia-reperfusion injury (IRI). Emerging research suggests that a Th17/regulatory T cell (Treg) imbalance plays a pivotal role in the development of renal IRI. A recently identified negative checkpoint protein, T cell immunoglobulin domain and mucin domain family 3 (Tim-3), inhibits the immune response by binding to its ligand, galectin-9 (Gal-9). However, the role of the Gal-9/Tim-3 signaling pathway in the regulation of CD4⁺ T cell subsets in renal IRI remains unclear. In this study, we investigated the effect of the Gal-9/Tim-3 signaling pathway on Th17/Treg subsets in renal IRI using a mouse model. Renal IRI induced the expression of Gal-9 in renal tubular epithelial cells and increased the proportion of Tim-3⁺ Th17 cells and Tim-3⁺ forkhead box P3 (Foxp3)⁺ Treg cells in the ischemia-reperfusion (IR) kidneys. Administration of rAAV9-Gal-9 suppressed kidney inflammation, reduced the mortality of mice with renal IRI, increased Foxp3⁺ Treg cells, and reduced Th17 cells. In contrast, the blockade of Tim-3 in vivo using an anti-Tim-3 monoclonal antibody aggravated renal inflammation, decreased Foxp3⁺ Treg cells, and promoted Th17 cells. Thus, Gal-9/Tim-3 signaling pathway activation may protect against renal IRI by inhibiting Th17 cell production and inducing Foxp3⁺ Treg cell expansion. Our study suggests that the Gal-9/Tim-3 signaling pathway may be targeted by immunotherapy in renal IRI.

Tumor-infiltrating regulatory T cells as targets of cancer immunotherapy

Regulatory T cells (Tregs) are abundant in tumor tissues, raising a question of whether immunosuppressive tumor-infiltrating Tregs (TI-Tregs) can be selectively depleted or functionally attenuated to evoke effective anti-tumor immune responses by conventional T cells (Tconvs), without perturbing Treg-dependent immune homeostasis in healthy organs and causing autoimmunity. Here, we review current cancer immunotherapy strategies, including immune checkpoint blockade (ICB) antibodies against CTLA-4 and PD-1 and discuss their effects on TI-Tregs. We also discuss approaches that exploit differentially regulated molecules on the cell surface (e.g., CTLA-4) and intracellularly (e.g., T cell receptor signaling molecules) between TI-Tregs and Tconvs as well as their dependence on cytokines (e.g., IL-2) and metabolites (e.g., lactate). We envisage that targeting TI-Tregs could be effective as a monotherapy and/or when combined with ICB antibodies.

Integrative analyses identify CD73 as a prognostic biomarker and immunotherapeutic target in intrahepatic cholangiocarcinoma

BACKGROUND

CD73 promotes progression in several malignancies and is considered as a novel immune checkpoint. However, the function of CD73 in intrahepatic cholangiocarcinoma (ICC) remains uncertain. In this study, we aim to investigate the role of CD73 in ICC.

METHODS

Multi-omics data of 262 ICC patients from the FU-iCCA cohort were analyzed. Two single-cell datasets were downloaded to examine the expression of CD73 at baseline and in response to immunotherapy. Functional experiments were performed to explore the biological functions of CD73 in ICC. The expression of CD73 and HHLA2 and infiltrations of CD8 + , Foxp3 + , CD68 + , and CD163 + immune cells were evaluated by immunohistochemistry in 259 resected ICC samples from Zhongshan Hospital. The prognostic value of CD73 was assessed by Cox regression analysis.

RESULTS

CD73 correlated with poor prognosis in two ICC cohorts. Single-cell atlas of ICC indicated high expression of CD73 on malignant cells. TP53 and KRAS gene mutations were more frequent in patients with high CD73 expression. CD73 promoted ICC proliferation, migration, invasion, and epithelial-mesenchymal transition. High CD73 expression was associated with a higher ratio of Foxp3 + /CD8 + tumor-infiltrating lymphocytes (TILs) and CD163 + /CD68 + tumor-associated macrophages (TAMs). A positive correlation between CD73 and CD44 was observed, and patients with high CD73 expression showed elevated expression of HHLA2. CD73 expression in malignant cells was significantly upregulated in response to immunotherapy.

CONCLUSIONS

High expression of CD73 is associated with poor prognosis and a suppressive tumor immune microenvironment in ICC. CD73 could potentially be a novel biomarker for prognosis and immunotherapy in ICC.

eATP and autoimmune diabetes

PURPOSE OF REVIEW

The purine nucleotide adenosine triphosphate (ATP) is released into extracellular spaces as extracellular ATP (eATP) as a consequence of cell injury or death and activates the purinergic receptors. Once released, eATP may facilitate T-lymphocyte activation and differentiation. The purpose of this review is to elucidate the role of ATP-mediated signaling in the immunological events related to type 1 diabetes (T1D).

RECENT FINDINGS

T lymphocytes mediate immune response during the onset of T1D and promote pancreatic islet or whole pancreas rejection in transplantation. Recent data suggest a potential role for eATP in early steps of T1D onset and of allograft rejection. In different preclinical experimental models and clinical trials, several drugs targeting purinergic signaling have been employed to abrogate lymphocyte activation and differentiation, thus representing an achievable treatment to prevent/revert T1D or to induce long-term islet allograft function.

SUMMARY

In preclinical and clinical settings, eATP-signaling inhibition induces immune tolerance in autoimmune disease and in allotransplantation. In this view, the purinergic system may represent a novel therapeutic target for auto- and allo-immunity.

Tolerance to 2,4-Dinitrofluorobenzene‒Induced Contact Hypersensitivity Is Mediated by CD73-Expressing Tissue-homing Regulatory T Cells

Regulatory T cells (Tregs) express CD73, an ectonucleotidase that converts adenosine (Ado) monophosphate to Ado, which has been shown to suppress immune reactions. To investigate the role(s) of CD73⁺ Tregs during the induction of tolerance, we used a 2,4-dinitrofluorobenzene‒driven contact hypersensitivity model, in which tolerance can be induced by pretreating wild type mice with 2,4-dinitrothiocyanobenzene. CD73-deficient mice were unable to acquire tolerance. Likewise, transfer of CD73^‒/‒ Tregs failed to suppress 2,4-dinitrofluorobenzene‒induced ear swelling in wild type mice, whereas transfer of wild type‒derived Tregs into CD73^‒/‒ mice re-established tolerance. This indicates a crucial role of CD73⁺ Tregs for skin-induced tolerance. Furthermore, we found that 2,4-dinitrothiocyanobenzene induces more activated CD73⁺ tissue-homing Tregs (marked by Ki-67, CTLA4, CCR4, CD103, CCR6, and CD49b expression) in draining lymph nodes and blood, eventually accumulating in the skin. The application of anti-CD73 antibodies that block CD73-derived Ado production as well as the injection of Ado deaminase, which degrades Ado in tissues, abrogated tolerance induction. Thus, our data indicate that CD73⁺ Ado-producing Tregs are crucial for the regulation of contact hypersensitivity reactions and tolerance induction in the skin and that manipulating the function(s) of CD73 in tissues may offer a tool to influence autoimmunity and inflammation in vivo.

Burnstock oration - purinergic signalling in kidney transplantation

Kidney transplantation is the preferred treatment for individuals with kidney failure offering improved quality and quantity of life. Despite significant advancements in short term graft survival, longer term survival rates have not improved greatly mediated in large by chronic antibody mediated rejection. Strategies to reduce the donor kidney antigenic load may translate to improved transplant survival. CD39 on the vascular endothelium and on circulating cells, in particular regulatory T cells (Treg), is upregulated in response to hypoxic stimuli and plays a critical role in regulating the immune response removing proinflammatory ATP and generating anti-inflammatory adenosine. Herein, the role of CD39 in reducing ischaemia-reperfusion injury (IRI) and on Treg within the context of kidney transplantation is reviewed.

Divergent roles of PD-L1 in immune regulation during ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a type of pathological injury that commonly arises in various diseases. Various forms of immune response are involved in the process of I/R injury. As a member of the B7 costimulatory molecule family, programmed death 1-ligand 1 (PD-L1) is an important target for immune regulation. Therefore, PD-L1 may be implicated in the regulation of I/R injury. This review briefly describes the immune response during I/R injury and how PD-L1 is involved in its regulation by focusing on findings from various I/R models. Despite the limited number of studies in this field of research, PD-L1 has shown sufficient potential as a clinical therapeutic target.

M2c Macrophages Protect Mice from Adriamycin-Induced Nephropathy by Upregulating CD62L in Tregs

Regulatory T cells (Tregs) and M2c macrophages have been shown to exert potentially synergistic therapeutic effects in animals with adriamycin-induced nephropathy (AN), a model chronic proteinuric renal disease. M2c macrophages may protect against renal injury by promoting an increase in the number of Tregs in the renal draining lymph nodes of AN mice, but how they do so is unclear. In this study, we used an AN mouse model to analyze how M2c macrophages induce the migration of Tregs. Using flow cytometry, we found that M2c macrophages promoted the migration of Tregs from the peripheral blood to the spleen, thymus, kidney, and renal draining lymph nodes. At the same time, M2c macrophages significantly upregulated chemokine receptors and adhesion molecule in Tregs, including CCR4, CCR5, CCR7, CXCR5, and CD62L. Treating AN mice with monoclonal anti-CD62L antibody inhibited the migration of M2c macrophages and Tregs to the spleen, thymus, kidney, and renal draining lymph nodes. Taken together, our results suggest that M2c macrophages upregulate CD62L in Tregs and thereby promote their migration to inflammatory sites, where they exert renoprotective effects. These insights may aid the development of treatments against chronic kidney disease.

CD73-Adenosinergic Axis Mediates the Protective Effect of Extracellular Vesicles Derived from Mesenchymal Stromal Cells on Ischemic Renal Damage in a Rat Model of Donation after Circulatory Death

We propose a new organ-conditioning strategy based on mesenchymal stromal cell (MSCs)/extracellular vesicle (EVs) delivery during hypothermic perfusion. MSCs/EVs marker CD73 is present on renal proximal tubular cells, and it protects against renal ischemia-reperfusion injury by converting adenosine monophosphate into adenosine (ADO). In this study, after checking if CD73-silenced EVs (EVsi) would impact in vitro tubular-cell proliferation, we perfused kidneys of a rat model of donation after circulatory death, with Belzer solution (BS) alone, BS supplemented with MSCs, EVs, or EVsi. The ADO and ATP levels were measured in the effluents and tissues. Global renal ischemic damage score (GRS), and tubular cell proliferation index (IPT) were evaluated in the tissue. EVsi did not induce cell proliferation in vitro. Ex vivo kidneys perfused with BS or BS + EVsi showed the worst GRS and higher effluent ADO levels than the MSC- and EV-perfused kidneys. In the EV-perfused kidneys, the tissue and effluent ATP levels and IPT were the highest, but not if CD73 was silenced. Tissue ATP content was positively correlated with tissue ADO content and negatively correlated with effluent ADO level in all groups. In conclusion, kidney conditioning with EVs protects against ischemic damage by activating the CD73/ADO system.

The Multifaceted Actions of CD73 During Development and Suppressive Actions of Regulatory T Cells

Adenosine (Ado) has been shown to have immunosuppressive effects in a variety of diseases. It can either be released directly into the extracellular environment by cells, or it can be produced by degradation of ATP within the extracellular spaces. This extracellular pathway is facilitated by the concerted actions of the ectoenzymes CD39 and CD73. In a first step CD39 dephosphorylates ATP to ADP and AMP, respectively, and in a second step CD73 converts AMP to Ado. Thus, activity of CD73 on the cell surface of cells is the rate limiting step in the generation of extracellular Ado. Among T cells, CD73 is most abundantly expressed by regulatory T cells (Tregs) and is even upregulated after their activation. Functionally, the generation of Ado by CD73+ Tregs has been shown to play a role in immune suppression of dendritic cells, monocytes and T cells, and the defined expression of CD73 by Tregs in immunosuppressive environments, such as tumors, made CD73 a novel checkpoint inhibitor. Therefore, therapeutical intervention by anti-CD73 antibodies or by chemical inhibitors of the enzymatic function is currently under investigation in some preclinical animal models. In the following we summarize the expression pattern and the possible functions of CD73 in T cells and Tregs, and exemplify novel ways to manipulate CD73 functions in Tregs to stimulate anti-tumor immunity.

Role of T cells in ischemic acute kidney injury and repair

Ischemic acute kidney injury (AKI) is a common medical problem with significant mortality and morbidity, affecting a large number of patients globally. Ischemic AKI is associated with intrarenal inflammation as well as systemic inflammation; thus, the innate and adaptive immune systems are implicated in the pathogenesis of ischemic AKI. Among various intrarenal immune cells, T cells play major roles in the injury process and in the repair mechanism affecting AKI to chronic kidney disease transition. Importantly, T cells also participate in distant organ crosstalk during AKI, which affects the overall outcomes. Therefore, targeting T cell-mediated pathways and T cell-based therapies have therapeutic promise for ischemic AKI. Here, we review the major populations of kidney T cells and their roles in ischemic AKI.

Targeting nucleotide metabolism: a promising approach to enhance cancer immunotherapy

Targeting nucleotide metabolism can not only inhibit tumor initiation and progression but also exert serious side effects. With in-depth studies of nucleotide metabolism, our understanding of nucleotide metabolism in tumors has revealed their non-proliferative effects on immune escape, indicating the potential effectiveness of nucleotide antimetabolites for enhancing immunotherapy. A growing body of evidence now supports the concept that targeting nucleotide metabolism can increase the antitumor immune response by (1) activating host immune systems via maintaining the concentrations of several important metabolites, such as adenosine and ATP, (2) promoting immunogenicity caused by increased mutability and genomic instability by disrupting the purine and pyrimidine pool, and (3) releasing nucleoside analogs via microbes to regulate immunity. Therapeutic approaches targeting nucleotide metabolism combined with immunotherapy have achieved exciting success in preclinical animal models. Here, we review how dysregulated nucleotide metabolism can promote tumor growth and interact with the host immune system, and we provide future insights into targeting nucleotide metabolism for immunotherapeutic treatment of various malignancies.

Soluble Programmed Cell Death Protein 1 and Its Ligand: Potential Biomarkers to Predict Acute Kidney Injury After Surgery in Critically Ill Patients

Purpose

Programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) have been detected in injury kidney. However, their expressions are unclear in mice kidneys under renal ischemia-reperfusion injury (IRI). In this study, we would observe the expressions of PD-1 and PD-L1 in kidney tissues and analyze the association between the concentrations of PD-1 and PD-L1 in mouse kidney homogenate and the corresponding concentrations of soluble PD-1 (sPD-1) and soluble PD-L1 (sPD-L1) in plasma after renal IRI. Further, we explored the predictive value of sPD-1 and sPD-L1 for acute kidney injury (AKI) in high-risk patients after surgery.

Methods

This study established an AKI model induced by IRI in mice. Plasma, kidney samples, and homogenate were collected 0h, 24h, and 48h after surgery for immunohistochemistry and enzyme-linked immunosorbent assay. Then, we continuously enrolled 88 AKI high-risk patients who underwent noncardiac surgery. The biomarkers, including sPD-1, sPD-L1, and urine neutrophil gelatinase-associated lipocalin (NGAL), tissue inhibitor of metalloproteinase-2 (TIMP-2), insulin-like growth factor-binding protein 7 (IGFBP7), were detected immediately after surgery.

Results

Our data revealed the concentrations of PD-1 and PD-L1 in kidney homogenate, and sPD-1 and sPD-L1 in plasma significantly increased at 0h, 24h, and 48h after IRI. A positive association was found between PD-1 and sPD-1 (r = 0.774, p < 0.001), and between PD-L1 and sPD-L1 (r = 0.881, p < 0.001). Compared to NGAL, [TIMP-2]*[IGFBP7], sPD-1 and sPD-L1 showed better predictive abilities for AKI with an area under the ROC curve of 0.856 (95% confidence interval [CI]: 0.825-0.958, p < 0.001) and 0.906 (95% CI: 0.764-0.921, p < 0.001).

Conclusion

The increased expressions of PD-1 and PD-L1 in kidneys under IRI suggested they may play essential roles in AKI development. sPD-1 and sPD-L1 can indirectly reflect the expressions of PD-1 and PD-L1 in kidneys, respectively. sPD-1 and sPD-L1 showed excellent predictive ability for AKI in high-risk patients.

A DNA Nanoraft-Based Cytokine Delivery Platform for Alleviation of Acute Kidney Injury

Cytokine immunotherapy represents an attractive strategy to stimulate robust immune responses for renal injury repair in ischemic acute kidney injury (AKI). However, its clinical application is hindered by its nonspecificity to kidney, short circulation half-life, and severe side effects. An ideal cytokine immunotherapy for AKI requires preferential delivery of cytokines with accurate dosage to the kidney and sustained-release of cytokines to stimulate the immune responses. Herein, we developed a DNA nanoraft cytokine by precisely arranging interleukin-33 (IL-33) nanoarray on rectangle DNA origami, through which IL-33 can be preferentially delivered to the kidney for alleviation of AKI. A nanoraft carrying precisely quantified IL-33 predominantly accumulated in the kidney for up to 48 h. Long-term sustained-release of IL-33 from nanoraft induced rapid expansion of type 2 innate lymphoid cells (ILC 2s) and regulatory T cells (Tregs) and achieved better treatment efficiency compared to free IL-33 treatment. Thus, our study demonstrates that a nanoraft can serve as a structurally well-defined delivery platform for cytokine immunotherapy in ischemic AKI and other renal diseases.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments.

Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis.

Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

The role of PD-L1 in the immune dysfunction that mediates hypoxia-induced multiple organ injury

Hypoxia is a pathological condition common to many diseases, although multiple organ injuries induced by hypoxia are often overlooked. There is increasing evidence to suggest that the hypoxic environment may activate innate immune cells and suppress adaptive immunity, further stimulating inflammation and inhibiting immunosurveillance. We found that dysfunctional immune regulation may aggravate hypoxia-induced tissue damage and contribute to secondary injury. Among the diverse mechanisms of hypoxia-induced immune dysfunction identified to date, the role of programmed death-ligand 1 (PD-L1) has recently attracted much attention. Besides leading to tumour immune evasion, PD-L1 has also been found to participate in the progression of the immune dysfunction which mediates hypoxia-induced multiple organ injury. In this review, we aimed to summarise the role of immune dysfunction in hypoxia-induced multiple organ injury, the effects of hypoxia on the cellular expression of PD-L1, and the effects of upregulated PD-L1 expression on immune regulation. Furthermore, we summarise the latest information pertaining to the involvement, diagnostic value, and therapeutic potential of immunosuppression induced by PD-L1 in various types of hypoxia-related diseases, including cancers, ischemic stroke, acute kidney injury, and obstructive sleep apnoea. Video Abstract.

Regulation of immune responses through CD39 and CD73 in cancer: Novel checkpoints

The immunosuppressive tumor microenvironment has been implicated in attenuating anti-tumoral immune responses and tumor growth in various cancers. Inhibitory immune checkpoints have been introduced as the primary culprits for developing the immunosuppressive tumor microenvironment. Therefore, a better understanding of the cross-talk between inhibitory immune checkpoints in the tumor microenvironment can pave the way for introducing novel approaches for treating affected patients. Growing evidence indicates that CD39 and CD73, as novel checkpoints, can transform adenosine triphosphate (ATP)-mediated pro-inflammatory tumor microenvironment into an adenosine-mediated immunosuppressive one via the purinergic signaling pathway. Indeed, enzymatic processes of CD39 and CD73 have crucial roles in adjusting the extent, intensity, and chemical properties of purinergic signals. This study aims to review the biological function of CD39 and CD73 and shed light on their significance in regulating anti-tumoral immune responses in various cancers.

Role of Purinergic Signalling in Endothelial Dysfunction and Thrombo-Inflammation in Ischaemic Stroke and Cerebral Small Vessel Disease

The cerebral endothelium is an active interface between blood and the central nervous system. In addition to being a physical barrier between the blood and the brain, the endothelium also actively regulates metabolic homeostasis, vascular tone and permeability, coagulation, and movement of immune cells. Being part of the blood–brain barrier, endothelial cells of the brain have specialized morphology, physiology, and phenotypes due to their unique microenvironment. Known cardiovascular risk factors facilitate cerebral endothelial dysfunction, leading to impaired vasodilation, an aggravated inflammatory response, as well as increased oxidative stress and vascular proliferation. This culminates in the thrombo-inflammatory response, an underlying cause of ischemic stroke and cerebral small vessel disease (CSVD). These events are further exacerbated when blood flow is returned to the brain after a period of ischemia, a phenomenon termed ischemia-reperfusion injury. Purinergic signaling is an endogenous molecular pathway in which the enzymes CD39 and CD73 catabolize extracellular adenosine triphosphate (eATP) to adenosine. After ischemia and CSVD, eATP is released from dying neurons as a damage molecule, triggering thrombosis and inflammation. In contrast, adenosine is anti-thrombotic, protects against oxidative stress, and suppresses the immune response. Evidently, therapies that promote adenosine generation or boost CD39 activity at the site of endothelial injury have promising benefits in the context of atherothrombotic stroke and can be extended to current CSVD known pathomechanisms. Here, we have reviewed the rationale and benefits of CD39 and CD39 therapies to treat endothelial dysfunction in the brain.

The role of regulatory T cells in the pathogenesis and treatment of prostate cancer

Despite developments in the treatment of various cancers, prostate cancer is one of the deadliest diseases known to men. Systemic therapies such as androgen deprivation, chemotherapy, and radiation therapy have not been very successful in treating this disease. Numerous studies have shown that there is a direct relationship between cancer progression and inhibition of anti-tumor immune responses that can lead to progression of various malignancies, including prostate cancer. Interestingly, CD4⁺CD25⁺FoxP3⁺ regulatory T cells significantly accumulate and increase in draining lymph nodes and PBMCs of patients with prostate cancer and other solid tumors. In vivo and in vitro studies have shown that Tregs can suppress anti-tumor responses, which is directly related to the increased risk of cancer recurrence. Tregs are essential for preserving self-tolerance and inhibiting extra immune responses harmful to the host. Since the tumor-related antigens are mainly self-antigens, Tregs could play a major role in tumor progression. Accordingly, it has discovered that prostate cancer patients with higher Tregs have poor prognosis and low survival rates. However, anti-tumor responses can be reinforced by suppression of Tregs with using monoclonal antibodies against CD25 and CTLA-4. Therefore, depleting Tregs or suppressing their functions could be one of the effective ways for prostate cancer immunotherapy. The purpose of this review is to investigate the role of Treg cells in the progression of prostate cancer and to evaluate effective strategies for the treatment of prostate cancer by regulating Treg cells.

Immune regulation in renal inflammation

Renal inflammation, induced by autoantigen recognition or toxic drugs, leads to renal tissue injury and decline in kidney function. Recent studies have demonstrated the crucial role for regulatory T cells in suppressing pathogenic adaptive but also innate immune responses in the inflamed kidney. However, there is also evidence for other immune cell populations with immunosuppressive function in renal inflammation. This review summarizes mechanisms of immune cell regulation in immune-mediated glomerulonephritis and acute and chronic nephrotoxicity.

PD-L1/PD-1 Axis in Multiple Myeloma Microenvironment and a Possible Link with CD38-Mediated Immune-Suppression

The emerging role of the PD-1/PD-L1 axis in MM immune-microenvironment has been highlighted by several studies. However, discordant data have been reported on PD-1/PD-L1 distribution within the bone marrow (BM) microenvironment of patients with monoclonal gammopathies. In addition, the efficacy of PD-1/PD-L1 blockade as a therapeutic strategy to reverse myeloma immune suppression and inhibit myeloma cell survival still remains unknown. Recent data suggest that, among the potential mechanisms behind the lack of responsiveness or resistance to anti-PD-L1/PD-1 antibodies, the CD38 metabolic pathways involving the immune-suppressive factor, adenosine, could play an important role. This review summarizes the available data on PD-1/PD-L1 expression in patients with MM, reporting the main mechanisms of regulation of PD-1/PD-L1 axis. The possible link between the CD38 and PD-1/PD-L1 pathways is also reported, highlighting the rationale for the potential use of a combined therapeutic approach with CD38 blocking agents and anti-PD-1/PD-L1 antibodies in order to improve their anti-tumoral effect in MM patients.

CD73 contributes to anti-inflammatory properties of afferent lymphatic endothelial cells in humans and mice

CD73 is an important ectoenzyme responsible for the production of extracellular adenosine. It is involved in regulating inflammatory responses and cell migration and is overexpressed in various cancers. The functions of CD73 in blood endothelial cells are understood in detail, but its role on afferent lymphatics remains unknown. Moreover, anti-CD73 antibodies are now used in multiple clinical cancer trials, but their effects on different endothelial cell types have not been studied. This study reveals that a previously unknown role of CD73 on afferent lymphatics is to dampen immune responses. Knocking it out or suppressing it by siRNA leads to the upregulation of inflammation-associated genes on lymphatic endothelial cells and a more pro-inflammatory phenotype of interacting dendritic cells in vitro and in vivo. In striking contrast, anti-CD73 antibodies had only negligible effects on the gene expression of lymphatic- and blood-endothelial cells. Our data thus reveal new functions of lymphatic CD73 and indicate a low likelihood of endothelial cell-related adverse effects by CD73 targeting therapeutic antibodies.

Hyper-Progressive Disease: The Potential Role and Consequences of T-Regulatory Cells Foiling Anti-PD-1 Cancer Immunotherapy

Antibody-mediated disruption of the programmed cell death protein 1 (PD-1) pathway has brought much success to the fight against cancer. Nevertheless, a significant proportion of patients respond poorly to anti-PD-1 treatment. Cases of accelerated and more aggressive forms of cancer following therapy have also been reported. Termed hyper-progressive disease (HPD), this phenomenon often results in fatality, thus requires urgent attention. Among possible causes of HPD, regulatory T-cells (Tregs) are of suspect due to their high expression of PD-1, which modulates Treg activity. Tregs are a subset of CD4⁺ T-cells that play a non-redundant role in the prevention of autoimmunity and is functionally dependent on the X chromosome-linked transcription factor FoxP3. In cancer, CD4⁺FoxP3⁺ Tregs migrate to tumors to suppress anti-tumor immune responses, allowing cancer cells to persist. Hence, Treg accumulation in tumors is associated with poor prognosis. In mice, the anti-tumor efficacy of anti-PD-1 can be enhanced by depleting Tregs. This suggests Tregs pose resistance to anti-PD-1 therapy. In this article, we review the relevant Treg functions that suppress tumor immunity and the potential effects anti-PD-1 could have on Tregs which are counter-productive to the treatment of cancer, occasionally causing HPD.

Hyper-Progressive Disease: The Potential Role and Consequences of T-Regulatory Cells Foiling Anti-PD-1 Cancer Immunotherapy

Antibody-mediated disruption of the programmed cell death protein 1 (PD-1) pathway has brought much success to the fight against cancer. Nevertheless, a significant proportion of patients respond poorly to anti-PD-1 treatment. Cases of accelerated and more aggressive forms of cancer following therapy have also been reported. Termed hyper-progressive disease (HPD), this phenomenon often results in fatality, thus requires urgent attention. Among possible causes of HPD, regulatory T-cells (Tregs) are of suspect due to their high expression of PD-1, which modulates Treg activity. Tregs are a subset of CD4⁺ T-cells that play a non-redundant role in the prevention of autoimmunity and is functionally dependent on the X chromosome-linked transcription factor FoxP3. In cancer, CD4⁺FoxP3⁺ Tregs migrate to tumors to suppress anti-tumor immune responses, allowing cancer cells to persist. Hence, Treg accumulation in tumors is associated with poor prognosis. In mice, the anti-tumor efficacy of anti-PD-1 can be enhanced by depleting Tregs. This suggests Tregs pose resistance to anti-PD-1 therapy. In this article, we review the relevant Treg functions that suppress tumor immunity and the potential effects anti-PD-1 could have on Tregs which are counter-productive to the treatment of cancer, occasionally causing HPD.

CD73 expression is critical to therapeutic effects of human endometrial regenerative cells in inhibition of cardiac allograft rejection in mice

The newly found mesenchymal‐like endometrial regenerative cells (ERCs) have been proved to induce immune tolerance in cardiac allograft transplantation. However, the therapeutic mechanism is not clear. The present study was undertaken to investigate whether ecto‐5′‐nucleotidase (CD73) expression on ERCs is critical to cardiac allograft protection. C57BL/6 mouse recipients receiving BALB/c mouse cardiac allografts were treated with unmodified ERCs or anti‐CD73 monoclonal antibodies (mAb) pretreated ERCs, respectively. It has been found that CD73 expression was critical to ERC‐induced attenuation of graft pathology. The blockage of CD73 expression on ERCs was related to the percentage decline of tolerogenic dendritic cells (Tol‐DCs), macrophages type 2 (M2), and regulatory T cells (Tregs). As compared with anti‐CD73 mAb pretreated ERCs group, CD73 expressing ERCs significantly increased the level of anti‐inflammatory cytokine IL‐10 but decreased levels of pro‐inflammatory cytokines including IFN‐γ and TNF‐α. In addition, CD73 expressing ERCs showed tissue protective function via the regulation of adenosine receptor expression which was related to the infiltration of CD4⁺ and CD8⁺ cells in the allografts. Furthermore, significant increase of A_2B receptors in the cardiac allograft was also associated with CD73 expressing ERC‐induced prolongation of cardiac allograft survival.

Implications of CD39 in immune-related diseases

Extracellular adenosine triphosphate (eATP) mediates pro-inflammatory responses by recruiting and activating inflammatory cells. CD39 can hydrolyze eATP into adenosine monophosphate (AMP), while CD73 can convert AMP into the immunosuppressive nucleoside adenosine (ADO). CD39 is a rate-limiting enzyme in this cascade, which is regarded as an immunological switch shifting the ATP-mediated pro-inflammatory environment to the ADO- mediated anti-inflammatory status. The CD39 expression can be detected in a wide spectrum of immunocytes, which is under the influence of environmental and genetic factors. It is increasingly suggested that, CD39 participates in some pathophysiological processes, like inflammatory bowel disease (IBD), sepsis, multiple sclerosis (MS), allergic diseases, ischemia-reperfusion (I/R) injury, systemic lupus erythematosus (SLE), diabetes and cancer. Here, we focus on the current understanding of CD39 in immunity, and comprehensively illustrate the diverse CD39 functions within a variety of disorders.

The Use of Immune Checkpoint Inhibitors in Oncology and the Occurrence of AKI: Where Do We Stand?

Immune checkpoint inhibitors (ICIs) are a novel class of immunotherapy drugs that have improved the treatment of a broad spectrum of cancers as metastatic melanoma, non-small lung cancer or renal cell carcinoma. These humanized monoclonal antibodies target inhibitory receptors (e.g. CTLA-4, PD-1, LAG-3, TIM-3) and ligands (PD-L1) expressed on T lymphocytes, antigen presenting cells and tumor cells and elicit an anti-tumor response by stimulating immune system. Nevertheless, the improved overall survival is complicated by the manifestation of Immune-related Adverse Effects (irAEs). During treatment with ICIs, the most common adverse kidney effect is represented by the development of acute kidney injury (AKI) with the acute tubulointerstitial nephritis as recurrent histological feature. The mechanisms involved in ICIs-induced AKI include the re-activation of effector T cells previously stimulated by nephrotoxic drugs (i.e. by antibiotics), the loss of tolerance versus self-renal antigens, the increased PD-L1 expression by tubular cells or the establishment of a pro-inflammatory milieu with the release of self-reactive antibodies. For renal transplant recipient treated with ICIs, the increased incidence of rejection is a serious concern. Therefore, the combination of ICIs with mTOR inhibitors represents an emerging strategy. Finally, it is relevant to anticipate which patients under ICIs would experience severe irAEs and from a kidney perspective, to predict patients with higher risk of AKI. Here, we provide a detailed overview of ICIs-related nephrotoxicity and the recently described multicenter studies. Several factors have been reported as biomarkers of ICIs-irAEs, in this review we speculate on potential biomarkers for ICIs-associated AKI.

The adenosine pathway in immuno-oncology

Cancer immunotherapy based on immune-checkpoint inhibition or adoptive cell therapy has revolutionized cancer care. Nevertheless, a large proportion of patients do not benefit from such treatments. Over the past decade, remarkable progress has been made in the development of 'next-generation' therapeutics in immuno-oncology, with inhibitors of extracellular adenosine (eADO) signalling constituting an expanding class of agents. Induced by tissue hypoxia, inflammation, tissue repair and specific oncogenic pathways, the adenosinergic axis is a broadly immunosuppressive pathway that regulates both innate and adaptive immune responses. Inhibition of eADO-generating enzymes and/or eADO receptors can promote antitumour immunity through multiple mechanisms, including enhancement of T cell and natural killer cell function, suppression of the pro-tumourigenic effects of myeloid cells and other immunoregulatory cells, and promotion of antigen presentation. With several clinical trials currently evaluating inhibitors of the eADO pathway in patients with cancer, we herein review the pathophysiological function of eADO with a focus on effects on antitumour immunity. We also discuss the treatment opportunities, potential limitations and biomarker-based strategies related to adenosine-targeted therapy in oncology.

Ectonucleotidase CD73 and CD39 expression in non-small cell lung cancer relates to hypoxia and immunosuppressive pathways

AIMS

Adenosine triphosphate (ATP) is released at a high concentration in the tumor microenvironment. The overexpression of ectonucleotidases in non-small-cell lung cancer (NSCLC), metabolizing ΑΤP to the immunosuppressive adenosine, is studied.

MATERIALS AND METHODS

We examined the expression of the ectonucleotidases CD73 and CD39 in NSCLC in parallel with immunological parameters and markers of hypoxia and anaerobic metabolism. In vitro experiments with A549 and H1299 lung cancer cell lines were also conducted.

RESULTS

CD73 and CD39 were not expressed by normal bronchial and alveolar epithelium. In contrast, these were overexpressed by cancer cells, cancer-associated fibroblasts (CAFs), and tumor-infiltrating lymphocytes (TILs). High CD73 cancer cell expression was directly linked with lactate dehydrogenase LDH5 and with hypoxia-inducible factor HIF1α expression by cancer cells. The expression of CD39 by CAFs was directly linked with PD-L1 expression by cancer cells. A significant abundance of FOXP3+ and PD-1+ TILs was noted in tumors with high CD73 and CD39 stroma expression. In in vitro experiments, hypoxia and acidity induced CD73 mRNA and protein levels in cancer cell lines. Exposure of cancer cell lines to adenosine induced the expression of PD-L1 and LDHA mRNA and protein levels.

CONCLUSION

Ectonucleotidases are up-regulated in cancer cells, CAFs, and TILs in lung tumors. Such overexpression is linked with regulatory TIL-phenotype and PD-L1 up-regulation by cancer cells. Overexpression of LDH5 is up-regulated by adenosine, creating a vicious cycle, as the high amounts of ATP produced by LDH5-mediated anaerobic glycolysis promote the production of adenosine by a tumor microenvironment rich in ectonucleotidases.

Treg expansion with trichostatin A ameliorates kidney ischemia/reperfusion injury in mice by suppressing the expression of costimulatory molecules

Innate immune reactions are believed to be associated with ischemia/reperfusion injury (IRI), and IRI might be treatable by expanding regulatory T cells (Tregs), which can suppress the excessive responses of the immune system. Organ IRI is known to be closely involved in the expression of costimulatory molecules. The present study aimed to assess whether Tregs endogenously expanded by the administration of trichostatin A (TsA), a histone deacetylase inhibitor, could reduce renal IRI and to clarify their association with the expression of costimulatory molecules in a murine model. In this study, the wild-type mice used for an IRI model were randomly divided into the following four treatment groups: TsA group, DMSO group (control), DMSO+PC61 group, and TsA + PC61 group. Renal injury in the early phase after IRI was ameliorated in the TsA group (increased Tregs) when compared with the other groups. After renal IRI, both the mRNA and the protein levels of anti-inflammatory cytokines, IL-10 and TGF-β in the kidney and spleen were significantly higher in the TsA group than in the other groups, whereas the IL-6 levels were significantly lower in the TsA group than in the other groups. These results were offset by the administration of PC61, supporting that the renoprotective effect of TsA in this study is Treg dependent. mRNA expression levels of CD80, CD86, and ICAM-1 were lower in the TsA group, consistent with Treg control of injury through costimulatory molecules. Our findings suggest that endogenously expanded Tregs coordinate postischemic immune responses and decrease the expression of costimulatory molecules after renal IRI, and thus, they might ameliorate renal IRI. TsA administration for expanding Tregs is a promising therapeutic strategy for renal IRI.

The Yin and Yang of Alarmins in Regulation of Acute Kidney Injury

Acute kidney injury (AKI) is a major clinical burden affecting 20 to 50% of hospitalized and intensive care patients. Irrespective of the initiating factors, the immune system plays a major role in amplifying the disease pathogenesis with certain immune cells contributing to renal damage, whereas others offer protection and facilitate recovery. Alarmins are small molecules and proteins that include granulysins, high-mobility group box 1 protein, interleukin (IL)-1α, IL-16, IL-33, heat shock proteins, the Ca++ binding S100 proteins, adenosine triphosphate, and uric acid. Alarmins are mostly intracellular molecules, and their release to the extracellular milieu signals cellular stress or damage, generally leading to the recruitment of the cells of the immune system. Early studies indicated a pro-inflammatory role for the alarmins by contributing to immune-system dysregulation and worsening of AKI. However, recent developments demonstrate anti-inflammatory mechanisms of certain alarmins or alarmin-sensing receptors, which may participate in the prevention, resolution, and repair of AKI. This dual function of alarmins is intriguing and has confounded the role of alarmins in AKI. In this study, we review the contribution of various alarmins to the pathogenesis of AKI in experimental and clinical studies. We also analyze the approaches for the therapeutic utilization of alarmins for AKI.

Rethinking the adenosine-A2AR checkpoint: implications for enhancing anti-tumor immunotherapy

Adenosine signaling through A_2AR serves as a negative regulator of the immune system. Unique to this suppressive pathway is its ability to impact numerous stromal and immune cells. Additionally, tumors exhibit elevated concentrations of adenosine further advancing the pathway's potential as a powerful target for activating anti-tumor immunity. The promise of this therapeutic strategy has been repeatedly demonstrated in mice, but has so far only yielded limited success in the clinic. Nonetheless, it is notable that many of these observed clinical responses have been in individuals resistant to prior immunotherapy. These observations suggest this pathway is indeed involved in tumor immune evasion. Thus, identifying the disparities between the translational and clinical implementation of this therapy becomes necessary. To this end, this review will revisit how and where adenosine-A_2AR signaling regulates the immune system and anti-tumor immunity so as to reveal opportunities for improving the translational success of this immunotherapy.

Regulatory T cells in ischemic cardiovascular injury and repair

Ischemic injury triggers a heightened inflammatory response that is essential for tissue repair, but excessive and chronic inflammatory responses contribute to the pathogenesis of ischemic cardiovascular disease. Regulatory T cells (Tregs), a major regulator of self-tolerance and immune suppression, control innate and adaptive immune responses, modulate specific immune cell subsets, prevent excessive inflammation, and participate in tissue repair after ischemia. Herein, we summarize the multiple potential mechanisms by which Tregs exert suppressor functions including modulation of cytokine production, alteration of cell-cell interactions, and disruption of metabolic pathways. Furthermore, we review the role of Tregs implicated in ischemic injury and repair including myocardial, limb, and cerebral ischemia. We conclude with a perspective on the therapeutic opportunities and future challenges of Treg biology in understanding the pathogenesis of ischemic cardiovascular disease states.

FoxP3+ T regulatory cells in cancer: Prognostic biomarkers and therapeutic targets

T Regulatory cells (Tregs) can have both protective and pathological roles. They maintain immune homeostasis and inhibit immune responses in various diseases, including cancer. Proportions of Tregs in the peripheral blood of some cancer patients increase by approximately two-fold, compared to those in healthy individuals. Tregs contribute to cancer development and progression by suppressing T effector cell functions, thereby compromising tumor killing and promoting tumor growth. Highly immunosuppressive Tregs express upregulated levels of the transcription factor, Forkhead box protein P3 (FoxP3). Elevated levels of FoxP3⁺ Tregs within the tumor microenvironment (TME) showed a positive correlation with poor prognosis in various cancer patients. Despite the success of immunotherapy, including the use of immune checkpoint inhibitors, a significant proportion of patients show low response rates as a result of primary or acquired resistance against therapy. Some of the mechanisms which underlie the development of therapy resistance are associated with Treg suppressive function. In this review, we describe Treg contribution to cancer development/progression, and the mechanisms of Treg-mediated immunosuppression. We discuss the prognostic significance of FoxP3⁺ Tregs in different cancers and their potential use as prognostic biomarkers. We also describe potential therapeutic strategies to target Tregs in combination with other types of immunotherapies aiming to overcome tumor resistance and improve clinical outcomes in cancer patients. Overall, understanding the prognostic significance of FoxP3⁺ Tregs in various cancers and their contribution to therapy resistance could help in the development of more effective targeted therapeutic strategies to enhance the clinical outcomes in cancer patients.

Harnessing Endogenous T-Regulatory Cells in Acute Kidney Injury

Acute kidney injury (AKI) affects 20-50% of hospitalized and intensive care patients, with a sizable proportion progressing to ESRD or death (https://www.kidney.org/atoz/content/AcuteKidneyInjury). Since inflammation contributes to the pathogenesis of AKI, studies on T-regulatory cells (Tregs), which suppress inflammation are important. Here, we highlight advances that utilize Tregs for intervention in AKI and were presented at the 25th International Conference on Advances in Critical Care Nephrology and UAB/UCSD O'Brien Center AKI &amp; CRRT 2020.

Conversion of extracellular ATP into adenosine: a master switch in renal health and disease

ATP and its ultimate degradation product adenosine are potent extracellular signalling molecules that elicit a variety of pathophysiological functions in the kidney through the activation of P2 and P1 purinergic receptors, respectively. Extracellular purines can modulate immune responses, balancing inflammatory processes and immunosuppression; indeed, alterations in extracellular nucleotide and adenosine signalling determine outcomes of inflammation and healing processes. The functional activities of ectonucleotidases such as CD39 and CD73, which hydrolyse pro-inflammatory ATP to generate immunosuppressive adenosine, are therefore pivotal in acute inflammation. Protracted inflammation may result in aberrant adenosinergic signalling, which serves to sustain inflammasome activation and worsen fibrotic reactions. Alterations in the expression of ectonucleotidases on various immune cells, such as regulatory T cells and macrophages, as well as components of the renal vasculature, control purinergic receptor-mediated effects on target tissues within the kidney. The role of CD39 as a rheostat that can have an impact on purinergic signalling in both acute and chronic inflammation is increasingly supported by the literature, as detailed in this Review. Better understanding of these purinergic processes and development of novel drugs targeting these pathways could lead to effective therapies for the management of acute and chronic kidney disease.