CD73 on T Cells Orchestrates Cardiac Wound Healing After Myocardial Infarction by Purinergic Metabolic Reprogramming

Myocardial Inflammation in Heart Failure With Reduced and Preserved Ejection Fraction

Heart failure (HF) is characterized by a progressive decline in cardiac function and represents one of the largest health burdens worldwide. Clinically, 2 major types of HF are distinguished based on the left ventricular ejection fraction (EF): HF with reduced EF and HF with preserved EF. While both types share several risk factors and features of adverse cardiac remodeling, unique hallmarks beyond ejection fraction that distinguish these etiologies also exist. These differences may explain the fact that approved therapies for HF with reduced EF are largely ineffective in patients suffering from HF with preserved EF. Improving our understanding of the distinct cellular and molecular mechanisms is crucial for the development of better treatment strategies. This article reviews the knowledge of the immunologic mechanisms underlying HF with reduced and preserved EF and discusses how the different immune profiles elicited may identify attractive therapeutic targets for these conditions. We review the literature on the reported mechanisms of adverse cardiac remodeling in HF with reduced and preserved EF, as well as the immune mechanisms involved. We discuss how the knowledge gained from preclinical models of the complex syndrome of HF as well as from clinical data obtained from patients may translate to a better understanding of HF and result in specific treatments for these conditions in humans.

CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing hemodialysis

BACKGROUND

T cell dysfunction observed in patients undergoing hemodialysis (HD) has been linked to an extremely high morbidity of cardiovascular events (CVEs) and infections. The cell-surface 5'-nucleotidase CD73 sets the balance between pro-inflammatory nucleotides and anti-inflammatory adenosine.

METHODS

A total of 395 patients who had been receiving HD for at least six months were evaluated for proportions of CD73+ cells in both the CD4+ T cell and CD8+ T cell compartment and followed for one year to document CVEs and infections. Differences in the proportions of CD73-expressingT cells between healthy controls and patients undergoing HD were compared. The relationship between CD73+ T cells and clinical outcomes was analyzed using the Kaplan-Meier curve and Cox regression.

RESULTS

HD was significantly related to a lower fraction of CD4+CD73+ T cells. In patients on HD, lower proportions of CD4+ CD73+T cells and CD8+ CD73+T cells were both associated with systemic inflammation and T cell terminal differentiation. More importantly, a lower CD4+CD73+T cell ratio independently predicted CVEs and infection in these patients.

CONCLUSION

We identified CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing HD, which provides a potential target in future studies of uremia-related immune dysfunction.

The Purinergic Nature of Pseudoxanthoma Elasticum

Pseudoxanthoma Elasticum (PXE) is an inherited disease characterized by elastic fiber calcification in the eyes, the skin and the cardiovascular system. PXE results from mutations in ABCC6 that encodes an ABC transporter primarily expressed in the liver and kidneys. It took nearly 15 years after identifying the gene to better understand the etiology of PXE. ABCC6 function facilitates the efflux of ATP, which is sequentially hydrolyzed by the ectonucleotidases ENPP1 and CD73 into pyrophosphate (PPi) and adenosine, both inhibitors of calcification. PXE, together with General Arterial Calcification of Infancy (GACI caused by ENPP1 mutations) as well as Calcification of Joints and Arteries (CALJA caused by NT5E/CD73 mutations), forms a disease continuum with overlapping phenotypes and shares steps of the same molecular pathway. The explanation of these phenotypes place ABCC6 as an upstream regulator of a purinergic pathway (ABCC6 → ENPP1 → CD73 → TNAP) that notably inhibits mineralization by maintaining a physiological Pi/PPi ratio in connective tissues. Based on a review of the literature and our recent experimental data, we suggest that PXE (and GACI/CALJA) be considered as an authentic "purinergic disease". In this article, we recapitulate the pathobiology of PXE and review molecular and physiological data showing that, beyond PPi deficiency and ectopic calcification, PXE is associated with wide and complex alterations of purinergic systems. Finally, we speculate on the future prospects regarding purinergic signaling and other aspects of this disease.

The protective role of CD73 in periodontitis: preventing hyper-inflammatory fibroblasts and driving osteoclast energy metabolism

Introduction

Periodontitis is an immune-mediated inflammatory disease affecting almost half of the adult population and is the leading cause of tooth loss in the United States. The role of extracellular nucleotide signaling including nucleotide metabolizing enzyme CD73 adds an important layer of interaction of purine mediators capable of orchestrating inflammatory outcomes. CD73 is able to catabolize 5'-adenosine monophosphate into adenosine at the extracellular level, playing a critical role in regulating many processes under physiological and pathological conditions. Here, we explored the role of CD73 in ligature-induced periodontitis in vivo comparing wild-type C57Bl/6J and CD73-deficient mice.

Methods

We assessed gingival levels of inflammatory cytokines in vivo and in murine gingival fibroblasts in vitro, as well as bone loss, and RANKL-induced osteoclastogenesis. We have also analyzed CD73 mRNA in samples derived from patients diagnosed with severe periodontitis.

Results

Our results in mice show that lack of CD73 resulted in increased inflammatory cytokines and chemokines such as IL-1β, IL-17, Cxcl1 and Cxcl2 in diseased gingiva relative to the healthy-controls and in comparison with the wild type. CD73-deficient gingival fibroblasts also manifested a defective healing response with higher MMP-13 levels. CD73-deficient animals also showed increased osteoclastogenesis in vitro with increased mitochondrial metabolism typified by excessive activation of oxidative phosphorylation, increased mitochondrial membrane potential and accumulation of hydrogen peroxide. Micro-CT analysis revealed that lack of CD73 resulted in decreased bone mineral density, decreased trabecular bone volume and thickness as well as decreased bone volume in long bones. CD73 deficiency also resulted in increased alveolar bone loss in experimental periodontitis. Correlative studies of gingival samples from severe (Grade C) periodontitis showed decreased levels of CD73 compared to healthy controls, further supporting the relevance of our murine results.

Conclusion

In conclusion, CD73 appears to play a protective role in the gingival periodontal tissue and bone homeostasis, regulating hyper-inflammatory state of stromal fibroblasts and osteoclast energy metabolism and being an important candidate for future target therapies to prevent or control immune-mediated inflammatory and osteolytic diseases.

CD73 deficiency does not aggravate angiotensin II-induced aortic inflammation in mice

Vascular inflammation plays a key role in the development of aortic diseases. A potential novel target for treatment might be CD73, an ecto-5'-nucleotidase that generates anti-inflammatory adenosine in the extracellular space. Here, we investigated whether a lack of CD73 results in enhanced aortic inflammation. To this end, angiotensin II was infused into wildtype and CD73-/- mice over 10 days. Before and after infusion, mice were analyzed using magnetic resonance imaging, ultrasound, flow cytometry, and histology. The impact of age and gender was investigated using female and male mice of three and six months of age, respectively. Angiotensin II infusion led to increased immune cell infiltration in both genotypes' aortae, but depletion of CD73 had no impact on immune cell recruitment. These findings were not modified by age or sex. No substantial difference in morphological or functional characteristics could be detected between wildtype and CD73-/- mice. Interestingly, the expression of CD73 on neutrophils decreased significantly in wildtype mice during treatment. In summary, we have found no evidence that CD73 deficiency affects the onset of aortic inflammation. However, as CD73 expression decreased during disease induction, an increase in CD73 by pharmaceutical intervention might result in lower vascular inflammation and less vascular disease.

Gut-derived short-chain fatty acids bridge cardiac and systemic metabolism and immunity in heart failure

Heart failure (HF) represents a group of complex clinical syndromes with high morbidity and mortality and has a significant global health burden. Inflammation and metabolic disorders are closely related to the development of HF, which are complex and depend on the severity and type of HF and common metabolic comorbidities such as obesity and diabetes. An increasing body of evidence indicates the importance of short-chain fatty acids (SCFAs) in regulating cardiac function. In addition, SCFAs represent a unique class of metabolites and play a distinct role in shaping systemic immunity and metabolism. In this review, we reveal the role of SCFAs as a link between metabolism and immunity, which regulate cardiac and systemic immune and metabolic systems by acting as energy substrates, inhibiting the expression of histone deacetylase (HDAC) regulated genes and activating G protein-coupled receptors (GPCRs) signaling. Ultimately cardiac efficiency is improved, cardiac inflammation alleviated and cardiac function in failing hearts enhanced. In conclusion, SCFAs represent a new therapeutic approach for HF.

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.

Noninvasive assessment of metabolic turnover during inflammation by in vivo deuterium magnetic resonance spectroscopy

Background

Inflammation and metabolism exhibit a complex interplay, where inflammation influences metabolic pathways, and in turn, metabolism shapes the quality of immune responses. Here, glucose turnover is of special interest, as proinflammatory immune cells mainly utilize glycolysis to meet their energy needs. Noninvasive approaches to monitor both processes would help elucidate this interwoven relationship to identify new therapeutic targets and diagnostic opportunities.

Methods

For induction of defined inflammatory hotspots, LPS-doped Matrigel plugs were implanted into the neck of C57BL/6J mice. Subsequently, 1H/19F magnetic resonance imaging (MRI) was used to track the recruitment of 19F-loaded immune cells to the inflammatory focus and deuterium (2H) magnetic resonance spectroscopy (MRS) was used to monitor the metabolic fate of [6,6-2H2]glucose within the affected tissue. Histology and flow cytometry were used to validate the in vivo data.

Results

After plug implantation and intravenous administration of the 19F-containing contrast agent, 1H/19F MRI confirmed the infiltration of 19F-labeled immune cells into LPS-doped plugs while no 19F signal was observed in PBS-containing control plugs. Identification of the inflammatory focus was followed by i.p. bolus injection of deuterated glucose and continuous 2H MRS. Inflammation-induced alterations in metabolic fluxes could be tracked with an excellent temporal resolution of 2 min up to approximately 60 min after injection and demonstrated a more anaerobic glucose utilization in the initial phase of immune cell recruitment.

Conclusion

1H/2H/19F MRI/MRS was successfully employed for noninvasive monitoring of metabolic alterations in an inflammatory environment, paving the way for simultaneous in vivo registration of immunometabolic data in basic research and patients.

Pericardial Immune Cells and Their Evolving Role in Cardiovascular Pathophysiology

The pericardium plays several homeostatic roles to support and maintain everyday cardiac function. Recent advances in techniques and experimental models have allowed for further exploration into the cellular contents of the pericardium itself. Of particular interest are the various immune cell populations present in the space within the pericardial fluid and fat. In contrast to immune cells of the comparable pleura, peritoneum and heart, pericardial immune cells appear to be distinct in their function and phenotype. Specifically, recent work has suggested these cells play critical roles in an array of pathophysiological conditions including myocardial infarction, pericarditis, and post-cardiac surgery complications. In this review, we spotlight the pericardial immune cells currently identified in mice and humans, the pathophysiological role of these cells, and the clinical significance of the immunocardiology axis in cardiovascular health.

Immunometabolism at the Heart of Cardiovascular Disease

Immune cell function among the myocardium, now more than ever, is appreciated to regulate cardiac function and pathophysiology. This is the case for both innate immunity, which includes neutrophils, monocytes, dendritic cells, and macrophages, as well as adaptive immunity, which includes T cells and B cells. This function is fueled by cell-intrinsic shifts in metabolism, such as glycolysis and oxidative phosphorylation, as well as metabolite availability, which originates from the surrounding extracellular milieu and varies during ischemia and metabolic syndrome. Immune cell crosstalk with cardiac parenchymal cells, such as cardiomyocytes and fibroblasts, is also regulated by complex cellular metabolic circuits. Although our understanding of immunometabolism has advanced rapidly over the past decade, in part through valuable insights made in cultured cells, there remains much to learn about contributions of in vivo immunometabolism and directly within the myocardium. Insight into such fundamental cell and molecular mechanisms holds potential to inform interventions that shift the balance of immunometabolism from maladaptive to cardioprotective and potentially even regenerative. Herein, we review our current working understanding of immunometabolism, specifically in the settings of sterile ischemic cardiac injury or cardiometabolic disease, both of which contribute to the onset of heart failure. We also discuss current gaps in knowledge in this context and therapeutic implications.

Targeting myocardial equilibrative nucleoside transporter ENT1 provides cardioprotection by enhancing myeloid Adora2b signaling

Previous studies implicate extracellular adenosine signaling in attenuating myocardial ischemia and reperfusion injury (IRI). This extracellular adenosine signaling is terminated by its uptake into cells by equilibrative nucleoside transporters (ENTs). Thus, we hypothesized that targeting ENTs would function to increase cardiac adenosine signaling and concomitant cardioprotection against IRI. Mice were exposed to myocardial ischemia and reperfusion injury. Myocardial injury was attenuated in mice treated with the nonspecific ENT inhibitor dipyridamole. A comparison of mice with global Ent1 or Ent2 deletion showed cardioprotection only in Ent1-/- mice. Moreover, studies with tissue-specific Ent deletion revealed that mice with myocyte-specific Ent1 deletion (Ent1loxP/loxP Myosin Cre+ mice) experienced smaller infarct sizes. Measurements of cardiac adenosine levels demonstrated that postischemic elevations of adenosine persisted during reperfusion after targeting ENTs. Finally, studies in mice with global or myeloid-specific deletion of the Adora2b adenosine receptor (Adora2bloxP/loxP LysM Cre+ mice) implied that Adora2b signaling on myeloid-inflammatory cells in cardioprotection provided by ENT inhibition. These studies reveal a previously unrecognized role for myocyte-specific ENT1 in cardioprotection by enhancing myeloid-dependent Adora2b signaling during reperfusion. Extension of these findings implicates adenosine transporter inhibitors in cardioprotection against ischemia and reperfusion injury.

Hilaire C, Reddy A, Kim J, Pinsky DJ, Murthy VL, Sutton NR. Circulating Ectonucleotidases Signal Impaired Myocardial Perfusion at Rest and Stress

Background Ectonucleotidases maintain vascular homeostasis by metabolizing extracellular nucleotides, modulating inflammation and thrombosis, and potentially, myocardial flow through adenosine generation. Evidence implicates dysfunction or deficiency of ectonucleotidases CD39 or CD73 in human disease; the utility of measuring levels of circulating ectonucleotidases as plasma biomarkers of coronary artery dysfunction or disease has not been previously reported. Methods and Results A total of 529 individuals undergoing clinically indicated positron emission tomography stress testing between 2015 and 2019 were enrolled in this single-center retrospective analysis. Baseline demographics, clinical data, nuclear stress test, and coronary artery calcium score variables were collected, as well as a blood sample. CD39 and CD73 levels were assessed as binary (detectable, undetectable) or continuous variables using ELISAs. Plasma CD39 was detectable in 24% of White and 8% of Black study participants (P=0.02). Of the clinical history variables examined, ectonucleotidase levels were most strongly associated with underlying liver disease and not other traditional coronary artery disease risk factors. Intriguingly, detection of circulating ectonucleotidase was inversely associated with stress myocardial blood flow (2.3±0.8 mL/min per g versus 2.7 mL/min per g±1.1 for detectable versus undetectable CD39 levels, P<0.001) and global myocardial flow reserve (Pearson correlation between myocardial flow reserve and log(CD73) -0.19, P<0.001). A subanalysis showed these differences held true independent of liver disease. Conclusions Vasodilatory adenosine is the expected product of local ectonucleotidase activity, yet these data support an inverse relationship between plasma ectonucleotidases, stress myocardial blood flow (CD39), and myocardial flow reserve (CD73). These findings support the conclusion that plasma levels of ectonucleotidases, which may be shed from the endothelial surface, contribute to reduced stress myocardial blood flow and myocardial flow reserve.

CD73 mediated host purinergic metabolism in intestine contributes to the therapeutic efficacy of a novel mesenchymal-like endometrial regenerative cells against experimental colitis

Background

The disruption of intestinal barrier functions and the dysregulation of mucosal immune responses, mediated by aberrant purinergic metabolism, are involved in the pathogenesis of inflammatory bowel diseases (IBD). A novel mesenchymal-like endometrial regenerative cells (ERCs) has demonstrated a significant therapeutic effect on colitis. As a phenotypic marker of ERCs, CD73 has been largely neglected for its immunosuppressive function in regulating purinergic metabolism. Here, we have investigated whether CD73 expression on ERCs is a potential molecular exerting its therapeutic effect against colitis.

Methods

ERCs either unmodified or with CD73 knockout (CD73-/-ERCs), were intraperitoneally administered to dextran sulfate sodium (DSS)-induced colitis mice. Histopathological analysis, colon barrier function, the proportion of T cells, and maturation of dendritic cells (DCs) were investigated. The immunomodulatory effect of CD73-expressing ERCs was evaluated by co-culture with bone marrow-derived DCs under LPS stimulation. FACS determined DCs maturation. The function of DCs was detected by ELISA and CD4+ cell proliferation assays. Furthermore, the role of the STAT3 pathway in CD73-expressing ERCs-induced DC inhibition was also elucidated.

Results

Compared with untreated and CD73-/-ERCs-treated groups, CD73-expressing ERCs effectively attenuated body weight loss, bloody stool, shortening of colon length, and pathological damage characterized by epithelial hyperplasia, goblet cell depletion, the focal loss of crypts and ulceration, and the infiltration of inflammatory cells. Knockout of CD73 impaired ERCs-mediated colon protection. Surprisingly, CD73-expressing ERCs significantly decreased the populations of Th1 and Th17 cells but increased the proportions of Tregs in mouse mesenteric lymph nodes. Furthermore, CD73-expressing ERCs markedly reduced the levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α) and increased anti-inflammatory factors (IL-10) levels in the colon. CD73-expressing ERCs inhibited the antigen presentation and stimulatory function of DCs associated with the STAT-3 pathway, which exerted a potent therapeutic effect against colitis.

Conclusions

The knockout of CD73 dramatically abrogates the therapeutic ability of ERCs for intestinal barrier dysfunctions and the dysregulation of mucosal immune responses. This study highlights the significance of CD73 mediates purinergic metabolism contributing to the therapeutic effects of human ERCs against colitis in mice.

Purinergic signaling in myocardial ischemia-reperfusion injury

Purines and their derivatives, extensively distributed in the body, act as a class of extracellular signaling molecules via a rich array of receptors, also known as purinoceptors (P1, P2X, and P2Y). They mediate multiple intracellular signal transduction pathways and participate in various physiological and pathological cell behaviors. Since the function in myocardial ischemia-reperfusion injury (MIRI), this review summarized the involvement of purinergic signal transduction in diversified pathological processes, including energy metabolism disorder, oxidative stress injury, calcium overload, inflammatory immune response, platelet aggregation, coronary vascular dysfunction, and cell necrosis and apoptosis. Moreover, increasing evidence suggests that purinergic signaling also mediates the prevention and treatment of MIRI, such as ischemic conditioning, pharmacological intervention, and some other therapies. In conclusion, this review exhibited that purinergic signaling mediates the complex processes of MIRI which shows its promising application and prospecting in the future.

Hydrogel delivery of purinergic enzymes improves cardiac ischemia/reperfusion injury

RATIONALE

The innate immune response contributes to cardiac injury in myocardial ischemia/reperfusion (MI/R). Neutrophils are an important early part of the innate immune response to MI/R. Adenosine, an endogenous purine, is a known innate immune modulator and inhibitor of neutrophil activation. However, its delivery to the heart is limited by its short half-life (<30 s) and off-target side effects. CD39 and CD73 are anti-inflammatory homeostatic enzymes that can generate adenosine from phosphorylated adenosine substrate such as ATP released from injured tissue.

OBJECTIVE

We hypothesize that hydrogel-delivered CD39 and CD73 target the local early innate immune response, reduce neutrophil activation, and preserve cardiac function in MI/R injury.

METHODS AND RESULTS

We engineered a poly(ethylene) glycol (PEG) hydrogel loaded with the adenosine-generating enzymes CD39 and CD73. We incubated the hydrogels with neutrophils in vitro and showed a reduction in hydrogen peroxide production using Amplex Red. We demonstrated availability of substrate for the enzymes in the myocardium in MI/R by LC/MS, and tested release kinetics from the hydrogel. On echocardiography, global longitudinal strain (GLS) was preserved in MI/R hearts treated with the loaded hydrogel. Delivery of purinergic enzymes via this synthetic hydrogel resulted in lower innate immune infiltration into the myocardium post-MI/R, decreased markers of macrophage and neutrophil activation (NETosis), and decreased leukocyte-platelet complexes in circulation.

CONCLUSIONS

In a rat model of MI/R injury, CD39 and CD73 delivered via a hydrogel preserve cardiac function by modulating the innate immune response.

Impact of Reperfusion on Temporal Immune Cell Dynamics After Myocardial Infarction

Excessive inflammation and impaired healing of cardiac tissue following a myocardial infarction (MI) can drive the development of heart failure. Cardiac repair begins immediately after the onset of MI and continues for months. The repair process can be divided into the following 3 overlapping phases, each having distinct functions and sequelae: the inflammatory phase, the proliferative phase, and the maturation phase. Macrophages, neutrophils, and lymphocytes are present in the myocardium throughout the repair process and govern the duration and function of each of these phases. However, changes in the functions of these cell types across each phase are poorly characterized. Numerous immunomodulatory therapies that specifically target inflammation have been developed for promoting cardiac repair and preventing heart failure after MI. However, these treatments have been largely unsuccessful in large-scale clinical randomized controlled trials. A potential explanation for this failure is the lack of a thorough understanding of the time-dependent evolution of the functions of immune cells after a major cardiovascular event. Failure to account for this temporal plasticity in cell function may reduce the efficacy of immunomodulatory approaches that target cardiac repair. This review is concerned with how the functions of different immune cells change with time following an MI. Improved understanding of the temporal changes in immune cell function is important for the future development of effective and targeted treatments for preventing heart failure after MI.

Cardiac injection of USSC boosts remuscularization of the infarcted heart by shaping the T-cell response

Regenerating the injured heart remains one of the most vexing challenges in cardiovascular medicine. Cell therapy has shown potential for treatment of myocardial infarction, but low cell retention so far has limited its success. Here we show that intramyocardial injection of highly apoptosis-resistant unrestricted somatic stem cells (USSC) into infarcted rat hearts resulted in an unprecedented thickening of the left ventricular wall with cTnT⁺/BrdU⁺ cardiomyocytes that was paralleled by progressively restored ejection fraction. USSC induced significant T-cell enrichment in ischemic tissue with enhanced expression of T-cell related cytokines. Inhibition of T-cell activation by anti-CD28 monoclonal antibody, fully abolished the regenerative response which was restored by adoptive T-cell transfer. Secretome analysis of USSC and lineage tracing studies suggest that USSC secrete paracrine factors over an extended period of time which boosts a T-cell driven endogenous regenerative response mainly from adult cardiomyocytes.

Cardiac repair after myocardial infarction: A two-sided role of inflammation-mediated

Myocardial infarction is the leading cause of death and disability worldwide, and the development of new treatments can help reduce the size of myocardial infarction and prevent adverse cardiovascular events. Cardiac repair after myocardial infarction can effectively remove necrotic tissue, induce neovascularization, and ultimately replace granulation tissue. Cardiac inflammation is the primary determinant of whether beneficial cardiac repair occurs after myocardial infarction. Immune cells mediate inflammatory responses and play a dual role in injury and protection during cardiac repair. After myocardial infarction, genetic ablation or blocking of anti-inflammatory pathways is often harmful. However, enhancing endogenous anti-inflammatory pathways or blocking endogenous pro-inflammatory pathways may improve cardiac repair after myocardial infarction. A deficiency of neutrophils or monocytes does not improve overall cardiac function after myocardial infarction but worsens it and aggravates cardiac fibrosis. Several factors are critical in regulating inflammatory genes and immune cells' phenotypes, including DNA methylation, histone modifications, and non-coding RNAs. Therefore, strict control and timely suppression of the inflammatory response, finding a balance between inflammatory cells, preventing excessive tissue degradation, and avoiding infarct expansion can effectively reduce the occurrence of adverse cardiovascular events after myocardial infarction. This article reviews the involvement of neutrophils, monocytes, macrophages, and regulatory T cells in cardiac repair after myocardial infarction. After myocardial infarction, neutrophils are the first to be recruited to the damaged site to engulf necrotic cell debris and secrete chemokines that enhance monocyte recruitment. Monocytes then infiltrate the infarct site and differentiate into macrophages and they release proteases and cytokines that are harmful to surviving myocardial cells in the pre-infarct period. As time progresses, apoptotic neutrophils are cleared, the recruitment of anti-inflammatory monocyte subsets, the polarization of macrophages toward the repair phenotype, and infiltration of regulatory T cells, which secrete anti-inflammatory factors that stimulate angiogenesis and granulation tissue formation for cardiac repair. We also explored how epigenetic modifications regulate the phenotype of inflammatory genes and immune cells to promote cardiac repair after myocardial infarction. This paper also elucidates the roles of alarmin S100A8/A9, secreted frizzled-related protein 1, and podoplanin in the inflammatory response and cardiac repair after myocardial infarction.

Alterations of long noncoding RNAs and mRNAs in extracellular vesicles derived from the murine heart post-ischemia-reperfusion injury

Extracellular vesicles (EVs) play important roles in cardiovascular diseases by delivering their RNA cargos. However, the features and possible role of the lncRNAs and mRNAs in cardiac EVs during ischemia-reperfusion (IR) remain unclear. Therefore, we performed RNA sequencing analysis to profile the features of lncRNAs and mRNAs and predicted their potential functions. Here, we demonstrated that the severity of IR injury was significantly correlated with cardiac EV production. RNA sequencing identified 73 significantly differentially expressed (DE) lncRNAs (39 upregulated and 34 downregulated) and 720 DE-mRNAs (317 upregulated and 403 downregulated). Gene Ontology (GO) and pathway analysis were performed to predict the potential functions of the DE-lncRNAs and mRNAs. The lncRNA-miRNA-mRNA ceRNA network showed the possible functions of DE-lncRNAs with DE-mRNAs which are enriched in the pathways of T cell receptor signalling pathway and cell adhesion molecules. Moreover, the expressions of ENSMUST00000146010 and ENSMUST00000180630 were negatively correlated with the severity of IR injury. A significant positive correlation was revealed between TCONS_00010866 expression and the severity of the cardiac injury. These findings revealed the lncRNA and mRNA profiles in the heart derived EVs and provided potential targets and pathways involved in cardiac IR injury.

Emerging Trends in Immunotherapy for Cancer

Recent advances in cancer immunology have enabled the discovery of promising immunotherapies for various malignancies that have shifted the cancer treatment paradigm. The innovative research and clinical advancements of immunotherapy approaches have prolonged the survival of patients with relapsed or refractory metastatic cancers. Since the U.S. FDA approved the first immune checkpoint inhibitor in 2011, the field of cancer immunotherapy has grown exponentially. Multiple therapeutic approaches or agents to manipulate different aspects of the immune system are currently in development. These include cancer vaccines, adoptive cell therapies (such as CAR-T or NK cell therapy), monoclonal antibodies, cytokine therapies, oncolytic viruses, and inhibitors targeting immune checkpoints that have demonstrated promising clinical efficacy. Multiple immunotherapeutic approaches have been approved for specific cancer treatments, while others are currently in preclinical and clinical trial stages. Given the success of immunotherapy, there has been a tremendous thrust to improve the clinical efficacy of various agents and strategies implemented so far. Here, we present a comprehensive overview of the development and clinical implementation of various immunotherapy approaches currently being used to treat cancer. We also highlight the latest developments, emerging trends, limitations, and future promises of cancer immunotherapy.

Myocardial-Treg Crosstalk: How to Tame a Wolf

The immune system plays a vital role in maintaining tissue integrity and organismal homeostasis. The sudden stress caused by myocardial infarction (MI) poses a significant challenge for the immune system: it must quickly substitute dead myocardial with fibrotic tissue while controlling overt inflammatory responses. In this review, we will discuss the central role of myocardial regulatory T-cells (Tregs) in orchestrating tissue repair processes and controlling local inflammation in the context of MI. We herein compile recent advances enabled by the use of transgenic mouse models with defined cardiac antigen specificity, explore whole-heart imaging techniques, outline clinical studies and summarize deep-phenotyping conducted by independent labs using single-cell transcriptomics and T-cell repertoire analysis. Furthermore, we point to multiple mechanisms and cell types targeted by Tregs in the infarcted heart, ranging from pro-fibrotic responses in mesenchymal cells to local immune modulation in myeloid and lymphoid lineages. We also discuss how both cardiac-specific and polyclonal Tregs participate in MI repair. In addition, we consider intriguing novel evidence on how the myocardial milieu takes control of potentially auto-aggressive local immune reactions by shaping myosin-specific T-cell development towards a regulatory phenotype. Finally, we examine the potential use of Treg manipulating drugs in the clinic after MI.

Adenosine A2a Receptor Regulates Autophagy Flux and Apoptosis to Alleviate Ischemia-Reperfusion Injury via the cAMP/PKA Signaling Pathway

Exploring effective methods to lessen myocardial ischemia-reperfusion injury still has positive significance. The adenosine A2a receptor (A2aR) has played a crucial part in cardiac ischemia-reperfusion injury. Previous studies revealed that the adenosine A2a receptor regulated autophagy, but the specific mechanism in myocardial ischemia-reperfusion injury was still unclear. We established an ischemia-reperfusion model (30 min of ischemia and 2 h of reperfusion) in vivo and a model with oxygen-glucose deprivation for 6 h and reoxygenation for 18 h (OGDR) in vitro. The ischemia-reperfusion injury resulted in prolonged QTc interval, left ventricular systolic dysfunction, and myocardial infarction. In vitro model, we found that the OGDR-induced autophagosomes and apoptosis caused myocardial cell death, as evidenced by a significant increase in the generation of lactate dehydrogenase and creatine kinase-MB. Furthermore, overactivated autophagy with rapamycin showed an anti-apoptotic effect. The interaction between autophagy and apoptosis in myocardial ischemia-reperfusion injury was complex and variable. We discovered that the activation of adenosine A2a receptor could promote the expression of Bcl-2 to inhibit the levels of Beclin-1 and LC3II. The number of autophagosomes exceeded that of autolysosomes under OGDR, but the result reversed after A2aR activation. Activated A2aR with its agonist CGS21680 before reperfusion saved cellular survival through anti-apoptosis and anti-autophagy effect, thus improving ventricular contraction disorders, and visibly reducing myocardial infarction size. The myocardial protection of adenosine A2a receptor after ischemia may involve the cAMP-PKA signaling pathway and the interaction of Bcl-2-Beclin-1.

Sevoflurane Dampens Acute Pulmonary Inflammation via the Adenosine Receptor A2B and Heme Oxygenase-1

Acute respiratory distress syndrome is a life-threatening disease associated with high mortality. The adenosine receptor A2B (Adora2b) provides anti-inflammatory effects, which are also associated with the intracellular enzyme heme oxygenase-1 (HO-1). Our study determined the mechanism of sevoflurane’s protective properties and investigated the link between sevoflurane and the impact of a functional Adora2b via HO-1 modulation during lipopolysaccharide (LPS)-induced lung injury. We examined the LPS-induced infiltration of polymorphonuclear neutrophils (PMNs) into the lung tissue and protein extravasation in wild-type and Adora2b−/− animals. We generated chimeric animals, to identify the impact of sevoflurane on Adora2b of hematopoietic and non-hematopoietic cells. Sevoflurane decreased the LPS-induced PMN-infiltration and diminished the edema formation in wild-type mice. Reduced PMN counts after sevoflurane treatment were detected only in chimeric mice, which expressed Adora2b exclusively on leukocytes. The Adora2b on hematopoietic and non-hematopoietic cells was required to improve the permeability after sevoflurane inhalation. Further, sevoflurane increased the protective effects of HO-1 modulation on PMN migration and microvascular permeability. These protective effects were abrogated by specific HO-1 inhibition. In conclusion, our data revealed new insights into the protective mechanisms of sevoflurane application during acute pulmonary inflammation and the link between sevoflurane and Adora2b, and HO-1 signaling, respectively.

Immunometabolic Mechanisms of Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is increasing in prevalence worldwide, already accounting for at least half of all heart failure (HF). As most patients with HFpEF are obese with metabolic syndrome, metabolic stress has been implicated in syndrome pathogenesis. Recently, compelling evidence for bidirectional crosstalk between metabolic stress and chronic inflammation has emerged, and alterations in systemic and cardiac immune responses are held to participate in HFpEF pathophysiology. Indeed, based on both preclinical and clinical evidence, comorbidity-driven systemic inflammation, coupled with metabolic stress, have been implicated together in HFpEF pathogenesis. As metabolic alterations impact immune function(s) in HFpEF, major changes in immune cell metabolism are also recognized in HFpEF and in HFpEF-predisposing conditions. Both arms of immunity - innate and adaptive - are implicated in the cardiomyocyte response in HFpEF. Indeed, we submit that crosstalk among adipose tissue, the immune system, and the heart represents a critical component of HFpEF pathobiology. Here, we review recent evidence in support of immunometabolic mechanisms as drivers of HFpEF pathogenesis, discuss pivotal biological mechanisms underlying the syndrome, and highlight questions requiring additional inquiry.

If these myocytes could talk, they would speak the language of metabolites

Cardiac wound healing following ischemic injury requires a well-described spatiotemporal progression of events involving multiple cell types and cell-cell interactions. While cellular crosstalk among immune cell, endothelial cell, and fibroblast populations is known to regulate these progressive phases, the role of cardiac myocytes in controlling the wound-healing program is unclear. In this issue of the JCI, Li et al. describe a mechanism of cellular crosstalk between cardiac myocytes and fibroblasts that disrupts nonmyocyte cell function and worsens wound healing outcomes following myocardial infarction (MI). This tour de force study used an arsenal of multidisciplinary approaches to identify a central role for the ectonucleotidase ENPP1 in this process. These findings have clear therapeutic implications, as the authors identified a small molecular inhibitor of ENPP1 that improved post-MI outcomes in mice. These exciting data provide impactful mechanistic information that advance the field’s understanding of cardiac repair and remodeling.

Red blood cell transfusion induces abnormal HIF-1α response to cytokine storm after adult cardiac surgery

Patients undergoing cardiac surgery develop a marked postoperative systemic inflammatory response. Blood transfusion may contribute to disruption of homeostasis in these patients. We sought to evaluate the impact of blood transfusion on serum interleukin-6 (IL-6), hypoxia induced factor-1 alpha (HIF-1α) levels as well as adverse outcomes in patients undergoing adult cardiac surgery. We prospectively enrolled 282 patients undergoing adult cardiac surgery. Serum IL-6 and HIF-1α levels were measured preoperatively and on the first postoperative day. Packed red blood cells were transfused in 26.3% of patients (mean 2.93 ± 3.05 units) by the time of postoperative sampling. Postoperative IL-6 levels increased over 30-fold and were similar in both groups (p = 0.115), whilst HIF-1α levels (0.377 pg/mL vs. 0.784 pg/mL, p = 0.002) decreased significantly in patients who received red blood cell transfusion. Moreover, greater decrease in HIF-1α levels predicted worse in-hospital and 3mo adverse outcome. Red blood cell transfusion was associated with higher risk of major adverse outcomes (stroke, pneumonia, all-cause mortality) during the index hospitalization. Red blood cell transfusion induces blunting of postoperative HIF-1 α response and is associated with higher risk of adverse thrombotic and pulmonary adverse events after cardiac surgery.

Clinical Trial Registration ClinicalTrials.gov Identifier: NCT03444259.

Normoxic induction of HIF-1α by adenosine-A2B R signaling in epicardial stromal cells formed after myocardial infarction

Myocardial infarction (MI) activates the epicardium to form epicardial stromal cells (EpiSC) that reside in the epicardial hypoxic microenvironment. Paracrine factors secreted by EpiSC were shown to modulate the injury response of the post-MI heart and improve cardiac function. We have previously reported that the expression of the angiogenic cytokines vascular endothelial growth factor A (VEGFA) and IL-6 is strongly upregulated in EpiSC by adenosine acting via the A_2B receptor (A_2B R). Since tissue hypoxia is well known to be a potent stimulus for the generation of extracellular adenosine, the present study explored the crosstalk of A_2B R activation and hypoxia-hypoxia-inducible factor 1 alpha (HIF-1α) signaling in cultured EpiSC, isolated from rat hearts 5 days after MI. We found substantial nuclear accumulation of HIF-1α after A_2B R activation even in the absence of hypoxia. This normoxic HIF-1α induction was PKC-dependent and involved upregulation of HIF-1α mRNA expression. While the influence of hypoxia on adenosine generation and A_2B R signaling was only minor, hypoxia and A_2B R activation cumulatively increased VEGFA expression. Normoxic A_2B R activation triggered an HIF-1α-associated cell-protective metabolic switch and reduced oxygen consumption. HIF-1α targets and negative regulators PHD2 and PHD3 were only weakly induced by A_2B R signaling, which may result in a sustained HIF-1α activity. The A_2B R-mediated normoxic HIF-1α induction was also observed in cardiac fibroblasts from healthy mouse hearts, suggesting that this mechanism is also functional in other A_2B R-expressing cell types. Altogether, we identified A_2B R-mediated HIF-1α induction as novel aspect in the HIF-1α-adenosine crosstalk, which modulates EpiSC activity and can amplify HIF-1α-mediated cardioprotection.

Sevoflurane Exerts Protective Effects in Murine Peritonitis-induced Sepsis via Hypoxia-inducible Factor 1α/Adenosine A2B Receptor Signaling

BACKGROUND

Sepsis is one of the leading causes of mortality in intensive care units, and sedation in the intensive care unit during sepsis is usually performed intravenously. The inhalative anesthetic sevoflurane has been shown to elicit protective effects in various inflammatory studies, but its role in peritonitis-induced sepsis remains elusive. The hypothesis was that sevoflurane controls the neutrophil infiltration by stabilization of hypoxia-inducible factor 1α and elevated adenosine A2B receptor expression.

METHODS

In mouse models of zymosan- and fecal-induced peritonitis, male mice were anesthetized with sevoflurane (2 volume percent, 30 min) after the onset of inflammation. Control animals received the solvent saline. The neutrophil counts and adhesion molecules on neutrophils in the peritoneal lavage of wild-type, adenosine A2B receptor -/-, and chimeric animals were determined by flow cytometry 4 h after stimulation. Cytokines and protein release were determined in the lavage. Further, the adenosine A2B receptor and its transcription factor hypoxia-inducible factor 1α were evaluated by real-time polymerase chain reaction and Western blot analysis 4 h after stimulation.

RESULTS

Sevoflurane reduced the neutrophil counts in the peritoneal lavage (mean ± SD, 25 ± 17 × 105vs. 12 ± 7 × 105 neutrophils; P = 0.004; n = 19/17) by lower expression of various adhesion molecules on neutrophils of wild-type animals but not of adenosine A2B receptor -/- animals. The cytokines concentration (means ± SD, tumor necrosis factor α [pg/ml], 523 ± 227 vs. 281 ± 101; P = 0.002; n = 9/9) and protein extravasation (mean ± SD [mg/ml], 1.4 ± 0.3 vs. 0.8 ± 0.4; P = 0.002; n = 12/11) were also lower after sevoflurane only in the wild-type mice. Chimeric mice showed the required expression of the adenosine A2B receptor on the hematopoietic and nonhematopoietic compartments for the protective effects of the anesthetic. Sevoflurane induced the expression of hypoxia-inducible factor 1α and adenosine A2B receptor in the intestine, liver, and lung.

CONCLUSIONS

Sevoflurane exerts various protective effects in two murine peritonitis-induced sepsis models. These protective effects were linked with a functional adenosine A2B receptor.

EDITOR’S PERSPECTIVE

BAY 60-6583 Enhances the Antitumor Function of Chimeric Antigen Receptor-Modified T Cells Independent of the Adenosine A2b Receptor

Chimeric antigen receptor (CAR) T cells are powerful in eradicating hematological malignancies, but their efficacy is limited in treating solid tumors. One of the barriers is the immunosuppressive response induced by immunomodulatory signaling pathways. Pharmacological targeting of these immunosuppressive pathways may be a simple way to improve the efficacy of CAR T cells. In this study, anti-CD133 and anti-HER2 CAR T cells were generated from healthy donors, and combination therapy using CAR T cells and small molecules targeting adenosine receptors was performed in vitro and in vivo with the goal of probing for potential synergistic antitumor activities. The adenosine A2b receptor agonist, BAY 60-6583, was found to significantly increase cytokine secretion of CD133-or HER2-specific CAR T cells when co-cultured with the respective target tumor cells. The in vitro cytotoxicity and proliferation of CAR T cells were also enhanced when supplied with BAY 60-6583. Furthermore, the combination with this small molecule facilitated the anti-HER2 CAR T cell-mediated elimination of tumor cells in a xenograft mouse model. However, the enhanced antitumor activities could not be suppressed by knockout of the adenosine A2b receptor in CAR T cells. Furthermore, mass spectrometry and computational methods were used to predict several potential alternative targets. Four potential targets (pyruvate kinase M (PKM), Talin-1, Plastin-2, and lamina-associated polypeptide 2) were captured by a photo-affinity probe, of which PKM and Talin-1 were predicted to interact with BAY 60-6583. Overall, our data suggest that BAY 60-6583 upregulates T cell functions through a mechanism independent of the adenosine A2b receptor.

A venous-specific purinergic signaling cascade initiated by Pannexin 1 regulates TNFα-induced increases in endothelial permeability

The endothelial cell barrier regulates the passage of fluid between the bloodstream and underlying tissues, and barrier function impairment exacerbates the severity of inflammatory insults. To understand how inflammation alters vessel permeability, we studied the effects of the proinflammatory cytokine TNFα on transendothelial permeability and electrophysiology in ex vivo murine veins and arteries. We found that TNFα specifically decreased the barrier function of venous endothelium without affecting that of arterial endothelium. On the basis of RNA expression profiling and protein analysis, we found that claudin-11 (CLDN11) was the predominant claudin in venous endothelial cells and that there was little, if any, CLDN11 in arterial endothelial cells. Consistent with a difference in claudin composition, TNFα increased the permselectivity of Cl^- over Na⁺ in venous but not arterial endothelium. The vein-specific effects of TNFα also required the activation of Pannexin 1 (Panx1) channels and the CD39-mediated hydrolysis of ATP to adenosine, which subsequently stimulated A_2A adenosine receptors. Moreover, the increase in vein permeability required the activation of the Ca²⁺ channel TRPV4 downstream of Panx1 activation. Panx1-deficient mice resisted the pathologic effects of sepsis induced by cecal ligation and puncture on life span and lung vascular permeability. These data provide a targetable pathway with the potential to promote vein barrier function and prevent the deleterious effects of vascular leak in response to inflammation.

Adenosine metabolism in the vascular system

The concept of extracellular purinergic signaling was first proposed by Geoffrey Burnstock in the early 1970s. Since then, extracellular ATP and its metabolites ADP and adenosine have attracted an enormous amount of attention in terms of their involvement in a wide range of immunomodulatory, thromboregulatory, angiogenic, vasoactive and other pathophysiological activities in different organs and tissues, including the vascular system. In addition to significant progress in understanding the properties of nucleotide- and adenosine-selective receptors, recent studies have begun to uncover the complexity of regulatory mechanisms governing the duration and magnitude of the purinergic signaling cascade. This knowledge has led to the development of new paradigms in understanding the entire purinome by taking into account the multitude of signaling and metabolic pathways involved in biological effects of ATP and adenosine and compartmentalization of the adenosine system. Along with the "canonical route" of ATP breakdown to adenosine via sequential ecto-nucleoside triphosphate diphosphohydrolase-1 (NTPDase1/CD39) and ecto-5'-nucleotidase/CD73 activities, it has now become clear that purine metabolism is the result of concerted effort between ATP release, its metabolism through redundant nucleotide-inactivating and counteracting ATP-regenerating ectoenzymatic pathways, as well as cellular nucleoside uptake and phosphorylation of adenosine to ATP through complex phosphotransfer reactions. In this review I provide an overview of key enzymes involved in adenosine metabolic network, with special emphasis on the emerging roles of purine-converting ectoenzymes as novel targets for cancer and vascular therapies.

Recent Advances in GPCR-Regulated Leukocyte Responses during Acute Cardiac Injury

Following acute cardiac injury such as myocardial infarction (MI), the controlled activation and recruitment of various leukocytes to the site of tissue damage significantly impacts chronic changes to cardiac structure and function, and ultimately host survival. While recent research has focused primarily on how leukocytes respond to injury, understanding how to effectively modulate their responsiveness to dampen maladaptive inflammation and promote repair processes is not yet fully understood. The complex spatio-temporal migration and activation of leukocytes are largely controlled by various chemokines and their cognate receptors, belonging to the G protein-coupled receptor (GPCR) family. Beyond chemokine receptors, leukocytes express a host of additional GPCRs that have recently been shown to regulate their responsiveness to cardiac injury. In this minireview, we will briefly discuss the impact of chemokine receptors on leukocyte behaviour, with subsequent focus on the most recent advancements in understanding the impact and therapeutic potential of other GPCR classes on leukocyte responses after acute cardiac injury.

Cardiac ECM: Its Epigenetic Regulation and Role in Heart Development and Repair

The extracellular matrix (ECM) is the non-cellular component in the cardiac microenvironment, and serves essential structural and regulatory roles in establishing and maintaining tissue architecture and cellular function. The patterns of molecular and biochemical ECM alterations in developing and adult hearts depend on the underlying injury type. In addition to exploring how the ECM regulates heart structure and function in heart development and repair, this review conducts an inclusive discussion of recent developments in the role, function, and epigenetic guidelines of the ECM. Moreover, it contributes to the development of new therapeutics for cardiovascular disease.

Novel roles of immunometabolism and nonmyocyte metabolism in cardiac remodeling and injury

Changes in cardiomyocyte metabolism have been heavily implicated in cardiac injury and heart failure (HF). However, there is emerging evidence that metabolism in nonmyocyte populations, including cardiac fibroblasts, immune cells, and endothelial cells, plays an important role in cardiac remodeling and adaptation to injury. Here, we discuss recent advances and insights into nonmyocyte metabolism in the healthy and injured heart. Metabolic switching from mitochondrial oxidative phosphorylation to glycolysis is critical for immune cell (macrophage and T lymphocyte) and fibroblast phenotypic switching in the inflamed and fibrotic heart. On the other hand, cardiac endothelial cells are heavily reliant on glycolytic metabolism, and thus impairments in glycolytic metabolism underlie endothelial cell dysfunction. Finally, we review current and ongoing metabolic therapies for HF and the potential implications for nonmyocyte metabolism.

T Cells in Fibrosis and Fibrotic Diseases

Fibrosis is the extensive deposition of fibrous connective tissue, and it is characterized by the accumulation of collagen and other extracellular matrix (ECM) components. Fibrosis is essential for wound healing and tissue repair in response to a variety of triggers, which include infection, inflammation, autoimmune disorder, degenerative disease, tumor, and injury. Fibrotic remodeling in various diseases, such as liver cirrhosis, pulmonary fibrosis, renal interstitial fibrosis, myocardial infarction, systemic sclerosis (SSc), and graft-versus-host disease (GVHD), can impair organ function, causing high morbidity and mortality. Both innate and adaptive immunity are involved in fibrogenesis. Although the roles of macrophages in fibrogenesis have been studied for many years, the underlying mechanisms concerning the manner in which T cells regulate fibrosis are not completely understood. The T cell receptor (TCR) engages the antigen and shapes the repertoire of antigen-specific T cells. Based on the divergent expression of surface molecules and cell functions, T cells are subdivided into natural killer T (NKT) cells, γδ T cells, CD8⁺ cytotoxic T lymphocytes (CTL), regulatory T (Treg) cells, T follicular regulatory (Tfr) cells, and T helper cells, including Th1, Th2, Th9, Th17, Th22, and T follicular helper (Tfh) cells. In this review, we summarize the pro-fibrotic or anti-fibrotic roles and distinct mechanisms of different T cell subsets. On reviewing the literature, we conclude that the T cell regulations are commonly disease-specific and tissue-specific. Finally, we provide perspectives on microbiota, viral infection, and metabolism, and discuss the current advancements of technologies for identifying novel targets and developing immunotherapies for intervention in fibrosis and fibrotic diseases.

HIF-1α and CD73 expression in cardiac leukocytes correlates with the severity of myocarditis in end-stage Chagas disease patients

Chronic Chagas cardiomyopathy is the main infectious myocarditis worldwide. Almost 30% of Trypanosoma cruzi infected individuals develop slow and progressive myocarditis that leads to ventricular dilation and heart failure. Heart transplantation is an established, valuable therapeutic option for end-stage Chagas disease patients. Although the pathophysiology of Chagas disease has been addressed for decades by numerous groups, the cardiac immunologic mechanisms involved in the progression of clinical manifestation are still unknown. Growing evidence demonstrates that hypoxia-inducible factor (HIF)-1α plays indispensable roles in driving immune response by triggering the expression of CD73 purinergic ecto-enzyme. Purinergic system controls the duration and magnitude of purine signals directed to modulate immune cells through the conversion of extracellular ATP (microbicide/proinflammatory) to the immunoregulatory metabolite adenosine. In the present work, we described that infiltrating leukocytes within cardiac explants from patients with end-stage Chagas cardiomyopathy up-regulated HIF-1α and CD73 expression. Moreover, the number of HIF-1α+ and CD73+ leukocytes positively correlated with the myocarditis severity and the local parasite load. Furthermore, we demonstrated a direct relationship between tissue parasite persistence and the influx of immune cells to the infected hearts, which ultimately determine the severity of the myocarditis. These findings provide evidence that CD73-dependent regulatory pathways are locally triggered in the myocardium of patients with end-stage Chagas disease.

Tripartite motif 10 regulates cardiac hypertrophy by targeting the PTEN/AKT pathway

The pathogenesis of cardiac hypertrophy is tightly associated with activation of intracellular hypertrophic signalling pathways, which leads to the synthesis of various proteins. Tripartite motif 10 (TRIM10) is an E3 ligase with important functions in protein quality control. However, its role in cardiac hypertrophy was unclear. In this study, neonatal rat cardiomyocytes (NRCMs) and TRIM10-knockout mice were subjected to phenylephrine (PE) stimulation or transverse aortic constriction (TAC) to induce cardiac hypertrophy in vitro and in vivo, respectively. Trim10 expression was significantly increased in hypertrophied murine hearts and PE-stimulated NRCMs. Knockdown of TRIM10 in NRCMs alleviated PE-induced changes in the size of cardiomyocytes and hypertrophy gene expression, whereas TRIM10 overexpression aggravated these changes. These results were further verified in TRIM10-knockout mice. Mechanistically, we found that TRIM10 knockout or knockdown decreased AKT phosphorylation. Furthermore, we found that TRIM10 knockout or knockdown increased ubiquitination of phosphatase and tensin homolog (PTEN), which negatively regulated AKT activation. The results of this study reveal the involvement of TRIM10 in pathological cardiac hypertrophy, which may occur by prompting of PTEN ubiquitination and subsequent activation of AKT signalling. Therefore, TRIM10 may be a promising target for treatment of cardiac hypertrophy.

Leukocyte-Dependent Regulation of Cardiac Fibrosis

Cardiac fibrosis begins as an intrinsic response to injury or ageing that functions to preserve the tissue from further damage. Fibrosis results from activated cardiac myofibroblasts, which secrete extracellular matrix (ECM) proteins in an effort to replace damaged tissue; however, excessive ECM deposition leads to pathological fibrotic remodeling. At this extent, fibrosis gravely disturbs myocardial compliance, and ultimately leads to adverse outcomes like heart failure with heightened mortality. As such, understanding the complexity behind fibrotic remodeling has been a focal point of cardiac research in recent years. Resident cardiac fibroblasts and activated myofibroblasts have been proven integral to the fibrotic response; however, several findings point to additional cell types that may contribute to the development of pathological fibrosis. For one, leukocytes expand in number after injury and exhibit high plasticity, thus their distinct role(s) in cardiac fibrosis is an ongoing and controversial field of study. This review summarizes current findings, focusing on both direct and indirect leukocyte-mediated mechanisms of fibrosis, which may provide novel targeted strategies against fibrotic remodeling.

Adenosine 2A Receptor Activation Contributes to Ang II–Induced Aortic Remodeling by Promoting Macrophage Retention

The A 2A R (adenosine 2A receptor) plays a crucial role in the pathophysiological process of cardiovascular diseases, yet its effect on aortic remodeling remains unclear. We observed elevated adenosine and A 2A R levels following infusion of mice with Ang II (angiotensin II), suggesting a potential role for the adenosine-A 2A R system in macrophage accumulation and subsequent aortic remodeling. The effects and mechanisms of A 2A R on macrophage dynamics during aortic remodeling were further investigated using mice with macrophage knockout of A 2A R and by transplantation of A 2A R −/− bone marrow. We demonstrated that macrophage knockout of A 2A R inhibited macrophage accumulation and subsequent aortic remodeling by inhibiting macrophage retention. This was shown to occur via promotion of macrophage emigration to the draining lymph node. These effects correlated with restoration of the expression and surface content of CCR7 (CC chemokine receptor 7). Consistently, A 2A R −/− bone marrow transplantation relieved Ang II–induced aortic remodeling, macrophage retention, and CCR7 downregulation and internalization, all of which were rescued by A 2A R + / + bone marrow transplantation. In addition, CCR7 antibody treatment blocked all the protective effects observed in A 2A R-cKO mice, including attenuation of aortic remodeling and decreased macrophage retention. In in vitro studies, A 2A R activation induced by Ang II suppressed macrophage migration to CCL19 (CC-chemokine ligand) 19 through downregulation and internalization of CCR7. In summary, A 2A R activation contributes to Ang II–induced macrophage retention and subsequent aortic remodeling by inhibiting migration of macrophages to the draining lymph node through regulating CCR7 expression and internalization.

Deficiency of CD73 activity promotes protective cardiac immunity against Trypanosoma cruzi infection but permissive environment in visceral adipose tissue

Damaged cells release the pro-inflammatory signal ATP, which is degraded by the ectonucleotidases CD39 and CD73 to the anti-inflammatory mediator adenosine (ADO). The balance between ATP/ADO is known to determine the outcome of inflammation/infection. However, modulation of the local immune response in different tissues due to changes in the balance of purinergic metabolites has yet to be investigated. Here, we explored the contribution of CD73-derived ADO on the acute immune response against Trypanosoma cruzi parasite, which invades and proliferates within different target tissues. Deficiency of CD73 activity led to an enhanced cardiac microbicidal immune response with an augmented frequency of macrophages with inflammatory phenotype and increased CD8+ T cell effector functions. The increment of local inducible nitric oxide (NO) synthase (iNOS)⁺ macrophages and the consequent rise of myocardial NO production in association with reduced ADO levels induced protection against T. cruzi infection as observed by the diminished cardiac parasite burden compared to their wild-type (WT) counterpart. Unexpectedly, parasitemia was substantially raised in CD73KO mice in comparison with WT mice, suggesting the existence of tissue reservoir/s outside myocardium. Indeed, CD73KO liver and visceral adipose tissue (VAT) showed increased parasite burden associated with a reduced ATP/ADO ratio and the lack of substantial microbicidal immune response. These data reveal that the purinergic system has a tissue-dependent impact on the host immune response against T. cruzi infection.

Role of purines in regulation of metabolic reprogramming

Purines, among most influential molecules, are reported to have essential biological function by regulating various cell types. A large number of studies have led to the discovery of many biological functions of the purine nucleotides such as ATP, ADP, and adenosine, as signaling molecules that engage G protein-coupled or ligand-gated ion channel receptors. The role of purines in the regulation of cellular functions at the gene or protein level has been well documented. With the advances in multiomics, including those from metabolomic and bioinformatic analyses, metabolic reprogramming was identified as a key mechanism involved in the regulation of cellular function under physiological or pathological conditions. Recent studies suggest that purines or purine-derived products contribute to important regulatory functions in many fundamental biological and pathological processes related to metabolic reprogramming. Therefore, this review summarizes the role and potential mechanism of purines in the regulation of metabolic reprogramming. In particular, the molecular mechanisms of extracellular purine- and intracellular purine-mediated metabolic regulation in various cells during disease development are discussed. In summary, our review provides an extensive resource for studying the regulatory role of purines in metabolic reprogramming and sheds light on the utilization of the corresponding peptides or proteins for disease diagnosis and therapy.

Cell type- and tissue-specific functions of ecto-5'-nucleotidase (CD73)

Ecto-5'-nucleotidase [cluster of differentiation 73 (CD73)] is a ubiquitously expressed glycosylphosphatidylinositol-anchored glycoprotein that converts extracellular adenosine 5'-monophosphate to adenosine. Anti-CD73 inhibitory antibodies are currently undergoing clinical testing for cancer immunotherapy. However, many protective physiological functions of CD73 need to be taken into account for new targeted therapies. This review examines CD73 functions in multiple organ systems and cell types, with a particular focus on novel findings from the last 5 years. Missense loss-of-function mutations in the CD73-encoding gene NT5E cause the rare disease "arterial calcifications due to deficiency of CD73." Aside from direct human disease involvement, cellular and animal model studies have revealed key functions of CD73 in tissue homeostasis and pathology across multiple organ systems. In the context of the central nervous system, CD73 is antinociceptive and protects against inflammatory damage, while also contributing to age-dependent decline in cortical plasticity. CD73 preserves barrier function in multiple tissues, a role that is most evident in the respiratory system, where it inhibits endothelial permeability in an adenosine-dependent manner. CD73 has important cardioprotective functions during myocardial infarction and heart failure. Under ischemia-reperfusion injury conditions, rapid and sustained induction of CD73 confers protection in the liver and kidney. In some cases, the mechanism by which CD73 mediates tissue injury is less clear. For example, CD73 has a promoting role in liver fibrosis but is protective in lung fibrosis. Future studies that integrate CD73 regulation and function at the cellular level with physiological responses will improve its utility as a disease target.

CD73 Rather Than CD39 Is Mainly Involved in Controlling Purinergic Signaling in Calcified Aortic Valve Disease

The study aimed to compare composition of peripheral blood T-cell subsets and assess their surface expression of CD39 and CD73 ectonucleotidases in patients with severe and moderate aortic stenosis (AS) as well as to evaluate involvement of T-cell-mediated immune processes in valve calcification. The study was performed with 38 patients suffering from severe calcified aortic stenosis (SAS), 33 patients with MAS, and 30 apparently healthy volunteers (HVs). The relative distribution and percentage of T-cell subsets expressing CD39 and CD73 were evaluated by flow cytometry. T helper (Th) and cytotoxic T-cell subsets (Tcyt) were identified by using CD3, CD4, and CD8 antibodies. Regulatory T cells (Tregs) were characterized by the expression of CD3, CD4, and high IL-2R alpha chain (CD25high) levels. CD45R0 and CD62L were used to assess differentiation stage of Th, Tcyt, and Treg subsets. It was found that MAS and SAS patients differed in terms of relative distribution of Tcyt and absolute number of Treg. Moreover, the absolute number of Tcyt and terminally differentiated CD45RA-positive effector T-cells (TEMRA) subset was significantly higher in SAS vs. MAS patients and HVs. However, the absolute and relative number of naïve Th and the absolute number of Treg were significantly higher in MAS vs. SAS patients; the relative number of naïve Tregs was significantly (p < 0.01) decreased in SAS patients. It was shown that CD73 expression was significantly higher in SAS vs. MAS patients noted in all EM, CM, TEMRA, and naïve Th cell subsets. However, only the latter were significantly increased (p = 0.003) in patients compared with HVs. SAS vs. MAS patients were noted to have significantly higher percentage of CD73+ EM Tcyt (p = 0.006) and CD73+ CM Tcyt (p = 0.002). The expression of CD73 in patients significantly differed in all three Treg populations such as EM (p = 0.049), CM (p = 0.044), and naïve (p < 0.001). No significant differences in CD39 expression level was found in MAS and SAS patients compared with the HV group. Overall, the data obtained demonstrated that purinergic signaling was involved in the pathogenesis of aortic stenosis and calcification potentially acting via various cell types, wherein among enzymes, degrading extracellular ATP CD73 rather than CD39 played a prominent role.

Myocardial infarction triggers cardioprotective antigen-specific T helper cell responses

T cell autoreactivity is a hallmark of autoimmune diseases but can also benefit self-maintenance and foster tissue repair. Herein, we investigated whether heart-specific T cells exert salutary or detrimental effects in the context of myocardial infarction (MI), the leading cause of death worldwide. After screening more than 150 class-II-restricted epitopes, we found that myosin heavy chain alpha (MYHCA) was a dominant cardiac antigen triggering post-MI CD4+ T cell activation in mice. Transferred MYHCA614-629-specific CD4+ T (TCR-M) cells selectively accumulated in the myocardium and mediastinal lymph nodes (med-LN) of infarcted mice, acquired a Treg phenotype with a distinct pro-healing gene expression profile, and mediated cardioprotection. Myocardial Treg cells were also detected in autopsies from patients who suffered a MI. Noninvasive PET/CT imaging using a CXCR4 radioligand revealed enlarged med-LNs with increased cellularity in MI-patients. Notably, the med-LN alterations observed in MI patients correlated with the infarct size and cardiac function. Taken together, the results obtained in our study provide evidence showing that MI-context induces pro-healing T cell autoimmunity in mice and confirms the existence of an analogous heart/med-LN/T cell axis in MI patients.

Generation and Function of Non-cell-bound CD73 in Inflammation

Extracellular adenine nucleotides participate in cell-to-cell communication and modulate the immune response. The concerted action of ectonucleotidases CD39 and CD73 plays a major role in the local production of anti-inflammatory adenosine, but both ectonucleotidases are rarely co-expressed by human T cells. The expression of CD39 on T cells increases upon T cell activation and is high at sites of inflammation. CD73, in contrast, disappears from the cellular membrane after activation. The possibility that CD73 could act in trans would resolve the conundrum of both enzymes being co-expressed for the degradation of ATP and the generation of adenosine. An enzymatically active soluble form of CD73 has been reported, and AMPase activity has been detected in body fluids of patients with inflammation and cancer. It is not yet clear how CD73, a glycosylphosphatidylinositol (GPI)-anchored protein, is released from the cell membrane, but plausible mechanisms include cleavage by metalloproteinases and shedding mediated by cell-associated phospholipases. Importantly, like many other GPI-anchored proteins, CD73 at the cell membrane is preferentially localized in detergent-resistant domains or lipid rafts, which often contribute to extracellular vesicles (EVs). Indeed, CD73-containing vesicles of different size and origin and with immunomodulatory function have been found in the tumor microenvironment. The occurrence of CD73 as non-cell-bound molecule widens the range of action of this enzyme at sites of inflammation. In this review, we will discuss the generation of non-cell-bound CD73 and its physiological role in inflammation.

A2bR-dependent signaling alters immune cell composition and enhances IL-6 formation in the ischemic heart

Although the cardioprotective effect of adenosine is undisputed, the role of the adenosine A2breceptor (A2bR) in ischemic cardiac remodeling is not defined. In this study we aimed to unravel the role A2bR plays in modulating the immune response and the healing mechanisms after myocardial infarction. Genetic and pharmacological (PSB603) inactivation of A2bR as well as activation of A2bR with BAY60-6583 does not alter cardiac remodeling of the infarcted (50-min left anterior descending artery occlusion/reperfusion) murine heart. Flow cytometry of immune cell subsets identified a significant increase in B cells, NK cells, CD8 and CD4 T cells, as well as FoxP3-expressing regulatory T cells in the injured heart in A2bR-deficient mice. Analysis of T-cell function revealed that expression and secretion of interleukin (IL)-2, interferon (IFN)γ, and tumor necrosis factor (TNF)α by T cells is under A2bR control. In addition, we found substantial cellular heterogeneity in the response of immune cells and cardiomyocytes to A2bR deficiency: while in the absence of A2bR, expression of IL-6 was greatly reduced in cardiomyocytes and immune cells except T cells, and expression of IL-1β was strongly reduced in cardiomyocytes, granulocytes, and B cells as determined by quantitative PCR. Our findings indicate that A2bR signaling in the ischemic heart triggers substantial changes in cardiac immune cell composition of the lymphoid lineage and induces a profound cell type-specific downregulation of IL-6 and IL-1β. This suggests the presence of a targetable adenosine–A2bR–IL-6-axis triggered by adenosine formed by the ischemic heart.

NEW & NOTEWORTHY Genetic deletion and pharmacological inactivation/activation of A2bR does not alter cardiac remodeling after MI but is associated by compensatory upregulation of various pro- and anti-inflammatory immune cell subsets (B cells, NK cells, CD8 and CD4 T cells, regulatory T cells). In the inflamed heart, A2bR modulates the expression of IL-2, IFNγ, TNFα in T cells and of IL-6 in cardiomyocytes, monocytes, granulocytes and B cells. This suggests an important adenosine–IL-6 axis, which is controlled by A2bR via local adenosine.

Immune cells as targets for cardioprotection: new players and novel therapeutic opportunities

New therapies are required to reduce myocardial infarct (MI) size and prevent the onset of heart failure in patients presenting with acute myocardial infarction (AMI), one of the leading causes of death and disability globally. In this regard, the immune cell response to AMI, which comprises an initial pro-inflammatory reaction followed by an anti-inflammatory phase, contributes to final MI size and post-AMI remodelling [changes in left ventricular (LV) size and function]. The transition between these two phases is critical in this regard, with a persistent and severe pro-inflammatory reaction leading to adverse LV remodelling and increased propensity for developing heart failure. In this review article, we provide an overview of the immune cells involved in orchestrating the complex and dynamic inflammatory response to AMI-these include neutrophils, monocytes/macrophages, and emerging players such as dendritic cells, lymphocytes, pericardial lymphoid cells, endothelial cells, and cardiac fibroblasts. We discuss potential reasons for past failures of anti-inflammatory cardioprotective therapies, and highlight new treatment targets for modulating the immune cell response to AMI, as a potential therapeutic strategy to improve clinical outcomes in AMI patients. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Adenosine 2A Receptor Activation Attenuates Ischemia Reperfusion Injury During Extracorporeal Cardiopulmonary Resuscitation

OBJECTIVE

We tested the hypothesis that systemic administration of an A2AR agonist will reduce multiorgan IRI in a porcine model of ECPR.

SUMMARY BACKGROUND DATA

Advances in ECPR have decreased mortality after cardiac arrest; however, subsequent IRI contributes to late multisystem organ failure. Attenuation of IRI has been reported with the use of an A2AR agonist.

METHODS

Adult swine underwent 20 minutes of circulatory arrest, induced by ventricular fibrillation, followed by 6 hours of reperfusion with ECPR. Animals were randomized to vehicle control, low-dose A2AR agonist, or high-dose A2AR agonist. A perfusion specialist using a goal-directed resuscitation protocol managed all the animals during the reperfusion period. Hourly blood, urine, and tissue samples were collected. Biochemical and microarray analyses were performed to identify differential inflammatory markers and gene expression between groups.

RESULTS

Both the treatment groups demonstrated significantly higher percent reduction from peak lactate after reperfusion compared with vehicle controls. Control animals required significantly more fluid, epinephrine, and higher final pump flow while having lower urine output than both the treatment groups. The treatment groups had lower urine NGAL, an early marker of kidney injury (P = 0.01), lower plasma aspartate aminotransferase, and reduced rate of troponin rise (P = 0.01). Pro-inflammatory cytokines were lower while anti-inflammatory cytokines were significantly higher in the treatment groups.

CONCLUSIONS

Using a novel and clinically relevant porcine model of circulatory arrest and ECPR, we demonstrated that a selective A2AR agonist significantly attenuated systemic IRI and warrants clinical investigation.

Lymphocytic subsets play distinct roles in heart diseases

Heart diseases are one of the leading causes of death for humans in the world. Increasing evidence has shown that myocardial injury induced innate and adaptive immune responses upon early cellular damage but also during chronic phases post-injury. The immune cells can not only aggravate the injury but also play an essential role in the induction of wound healing responses, which means they play a complex role throughout the acute inflammatory response and reparative response after cardiac injury. This review will summarize the current experimental and clinical evidence of lymphocytes, one of the major types of immune cells, participate in heart diseases and try to explain the possible role of these immune cells following cardiac injury.