Effects of intraoperative blood flow on the early patency of radiocephalic fistulas

The purpose of this study was to find the correlation between intraoperative blood flow and early patency of the radiocephalic fistula. Between March 1998 and March 1999, 50 radiocephalic arteriovenous fistulas were constructed in 41 patients. Intraoperative blood flow measurements were made 10 min after completion of the vascular anastomoses with 3-4 mm handheld flow probes. Patients were followed until failure of fistula or 3 months after the first hemodialysis with these fistulas. Intraoperative blood flow as well as age, gender, presence of diabetes, size of cephalic vein, thrill on the fistula, and flow of radial artery were correlated with early patency. The mean intraoperative blood flow was 174.7 +/- 13.2 mL/min and ranged from 50 to 500 mL/min; it was the only significant parameter that determined early patency of the radiocephalic fistula. Fistulas with flow <160 mL/min (10 of 25) had a higher failure rate than those with flow >160 mL/min (4 of 25), which was statistically significant (p < 0.01). All of the patients with flow <70 mL/min (5 of 5) failed to maintain patency within a month. However, the other variables were not correlated with early patency. We conclude that intraoperative blood flow is a reliable parameter that determines the early patency of radiocephalic fistulas.

Endothelial thrombomodulin downregulation caused by hypoxia contributes to severe infiltration and coagulopathy in COVID-19 patient lungs

BACKGROUND

Thromboembolism is a life-threatening manifestation of coronavirus disease 2019 (COVID-19). We investigated a dysfunctional phenotype of vascular endothelial cells in the lungs during COVID-19.

METHODS

We obtained the lung specimens from the patients who died of COVID-19. The phenotype of endothelial cells and immune cells was examined by flow cytometry and immunohistochemistry (IHC) analysis. We tested the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the endothelium using IHC and electron microscopy.

FINDINGS

The autopsy lungs of COVID-19 patients exhibited severe coagulation abnormalities, immune cell infiltration, and platelet activation. Pulmonary endothelial cells of COVID-19 patients showed increased expression of procoagulant von Willebrand factor (VWF) and decreased expression of anticoagulants thrombomodulin and endothelial protein C receptor (EPCR). In the autopsy lungs of COVID-19 patients, the number of macrophages, monocytes, and T cells was increased, showing an activated phenotype. Despite increased immune cells, adhesion molecules such as ICAM-1, VCAM-1, E-selectin, and P-selectin were downregulated in pulmonary endothelial cells of COVID-19 patients. Notably, decreased thrombomodulin expression in endothelial cells was associated with increased immune cell infiltration in the COVID-19 patient lungs. There were no SARS-CoV-2 particles detected in the lung endothelium of COVID-19 patients despite their dysfunctional phenotype. Meanwhile, the autopsy lungs of COVID-19 patients showed SARS-CoV-2 virions in damaged alveolar epithelium and evidence of hypoxic injury.

INTERPRETATION

Pulmonary endothelial cells become dysfunctional during COVID-19, showing a loss of thrombomodulin expression related to severe thrombosis and infiltration, and endothelial cell dysfunction might be caused by a pathologic condition in COVID-19 patient lungs rather than a direct infection with SARS-CoV-2.

FUNDING

This work was supported by the Johns Hopkins University, the American Heart Association, and the National Institutes of Health.

The Cardiac Microenvironment Instructs Divergent Monocyte Fates and Functions in Myocarditis

Two types of monocytes, Ly6C^hi and Ly6C^lo, infiltrate the heart in murine experimental autoimmune myocarditis (EAM). We discovered a role for cardiac fibroblasts in facilitating monocyte-to-macrophage differentiation of both Ly6C^hi and Ly6C^lo cells, allowing these macrophages to perform divergent functions in myocarditis progression. During the acute phase of EAM, IL-17A is highly abundant. It signals through cardiac fibroblasts to attenuate efferocytosis of Ly6C^hi monocyte-derived macrophages (MDMs) and simultaneously prevents Ly6C^lo monocyte-to-macrophage differentiation. We demonstrated an inverse clinical correlation between heart IL-17A levels and efferocytic receptor expressions in humans with heart failure (HF). In the absence of IL-17A signaling, Ly6C^hi MDMs act as robust phagocytes and are less proinflammatory, whereas Ly6C^lo monocytes resume their differentiation into MHCII⁺ macrophages. We propose that MHCII⁺Ly6C^lo MDMs are associated with the reduction of cardiac fibrosis and prevention of the myocarditis sequalae.

Hou et al. show that cardiac fibroblasts facilitate infiltrating Ly6C^hi and Ly6C^lo monocytes to become macrophages. IL-17A trans-signaling through cardiac fibroblasts increases MerTK shedding and promotes a pro-inflammatory and pro-tissue remodeling gene expression profile in Ly6C^hi monocyte-derived macrophages. Paradoxically, IL-17A signaling through cardiac fibroblasts can substantially inhibit Ly6C^lo monocyte-to-macrophage differentiation.

Cardiac myosin-specific autoimmune T cells contribute to immune-checkpoint-inhibitor-associated myocarditis

Immune checkpoint inhibitors (ICIs) are an effective therapy for various cancers; however, they can induce immune-related adverse events (irAEs) as a side effect. Myocarditis is an uncommon, but fatal, irAE caused after ICI treatments. Currently, the mechanism of ICI-associated myocarditis is unclear. Here, we show the development of myocarditis in A/J mice induced by anti-PD-1 monoclonal antibody (mAb) administration alone without tumor cell inoculation, immunization, or viral infection. Mice with myocarditis have increased cardiac infiltration, elevated cardiac troponin levels, and arrhythmia. Anti-PD-1 mAb treatment also causes irAEs in other organs. Autoimmune T cells recognizing cardiac myosin are activated and increased in mice with myocarditis. Notably, cardiac myosin-specific T cells are present in naive mice, showing a phenotype of antigen-experienced T cells. Collectively, we establish a clinically relevant mouse model for ICI-associated myocarditis and find a contribution of cardiac myosin-specific T cells to ICI-associated myocarditis development and pathogenesis.

Characterization of CD45RO+ memory T lymphocytes in keloid disease

BACKGROUND

Memory T cells, a highly effective subset of T lymphocytes, have been reported to be involved in many inflammatory skin disorders. However, the potential role of memory T cells in keloid disease (KD) remains unclear.

OBJECTIVES

Due to their important role in regulating inflammation, we investigated the characteristics of CD45RO⁺ memory T cells in KD.

METHODS

Primary cutaneous cells were isolated from keloid scars and normal skin by enzymic digestion. Peripheral blood mononuclear cells were isolated from a related blood sample, and flow cytometry was applied to identify the phenotypic and functional abnormalities of memory T cells in KD.

RESULTS

We observed that the majority of T lymphocytes in keloid scars had the memory phenotype, and a greater number of the CD8⁺ memory T cells in keloid scars produced lower levels of tumour necrosis factor (TNF)-α. This abnormal cytokine production was even more distinct in Forkhead box (FOX)P3^-  CD8^- memory T cells, with lower TNF-α production and enhanced interferon-γ production. Furthermore, FOXP3⁺  CD8^- memory T cells in keloid scars were abnormal, including showing reduced CD25 and cytotoxic T-lymphocyte-associated antigen 4 expression and interleukin-10 production. In addition, a significant decrease in the number of CD4⁺  CD25^high  FOXP3⁺ regulatory T cells was identified in patients with multiple keloid scars. We also found that there was significantly increased infiltration of CD103⁺  CD8⁺ memory T cells in keloid scars.

CONCLUSIONS

Our findings preliminarily elucidate the abnormalities of CD45RO⁺ memory T cells in keloid scars and provide early evidence that a disrupted T-cell response contributes to the progression of KD.

Increased Interleukin 18-Dependent Immune Responses Are Associated With Myopericarditis After COVID-19 mRNA Vaccination

Myocarditis and myopericarditis may occur after COVID-19 vaccination with an incidence of two to twenty cases per 100,000 individuals, but underlying mechanisms related to disease onset and progression remain unclear. Here, we report a case of myopericarditis following the first dose of the mRNA-1273 COVID-19 vaccine in a young man who had a history of mild COVID-19 three months before vaccination. The patient presented with chest pain, elevated troponin I level, and electrocardiogram abnormality. His endomyocardial biopsy revealed diffuse CD68⁺ cell infiltration. We characterized the immune profile of the patient using multiplex cytokine assay and flow cytometry analysis. Sex-matched vaccinated individuals and healthy individuals were used as controls. IL-18 and IL-27, Th1-type cytokines, were highly increased in the patient with COVID-19 vaccine-related myopericarditis compared with vaccinated controls who experienced no cardiac complications. In the patient, circulating NK cells and T cells showed an activated phenotype and mRNA profile, and monocytes expressed increased levels of IL-18 and its upstream NLRP3 inflammasome. We found that recombinant IL-18 administration into mice caused mild cardiac dysfunction and activation of NK cells and T cells in the hearts, similar to the findings in the patient with myopericarditis after COVID-19 mRNA vaccination. Collectively, myopericarditis following COVID-19 mRNA vaccination may be associated with increased IL-18-mediated immune responses and cardiotoxicity.

Nonspecific induction of immunoglobulin M antibodies to periodontal disease-associated microorganisms after polyclonal human B-lymphocyte activation by Fusobacterium nucleatum

The production of antibodies to oral bacteria was determined in lymphocyte cultures stimulated with sonicated Fusobacterium nucleatum, a potent inducer of polyclonal B-cell activation. After 9 days the cultures were examined by a microenzyme-linked immunosorbent assay for immunoglobulin M (IgM) antibodies to F. nucleatum, Bacteroides gingivalis, Actinomyces viscosus, and Streptococcus sanguis. Antibodies to these four bacteria were detected in cultures stimulated with polyclonal B-cell activation-inducing concentrations of F. nucleatum. However, significant concentrations of antibodies to F. nucleatum, but not to the other three microorganisms, were produced in cultures that received suboptimal polyclonal B-cell activation-inducing doses of F. nucleatum. Absorption studies indicated the specificity of the antibodies to each of the bacteria tested. IgM antibody production induced by F. nucleatum was enhanced by the addition of T cells. The production of IgM antibodies to the bacteria was reproducible in cultures from a single person tested on 3 consecutive days. The concentration of antibodies in replicate cultures, however, fluctuated greatly. To obtain consistent responses on successive days, multiple replicate cultures were required. These results suggest that F. nucleatum, which is frequently present in subgingival plaque, could induce the production of antibodies not only to F. nucleatum, but also to other microorganisms associated with periodontal diseases.

Cutting Edge: Check Your Mice-A Point Mutation in the Ncr1 Locus Identified in CD45.1 Congenic Mice with Consequences in Mouse Susceptibility to Infection

B6.SJL-Ptprc^a Pepc^b /Boy (CD45.1) mice have been used in hundreds of congenic competitive transplants, with the presumption that they differ from C57BL/6 mice only at the CD45 locus. In this study, we describe a point mutation in the natural cytotoxicity receptor 1 (Ncr1) locus fortuitously identified in the CD45.1 strain. This point mutation was mapped at the 40th nucleotide of the Ncr1 locus causing a single amino acid mutation from cysteine to arginine at position 14 from the start codon, resulting in loss of NCR1 expression. We found that these mice were more resistant to CMV due to a hyper innate IFN-γ response in the absence of NCR1. In contrast, loss of NCR1 increased susceptibility to influenza virus, a result that is consistent with the role of NCR1 in the recognition of influenza Ag, hemagglutinin. This work sheds light on potential confounding experimental interpretation when this congenic strain is used as a tool for tracking lymphocyte development.

Endothelial Stromal PD-L1 (Programmed Death Ligand 1) Modulates CD8+ T-Cell Infiltration After Heart Transplantation

BACKGROUND

The role of checkpoint axes in transplantation has been partially addressed in animal models but not in humans. Occurrence of fulminant myocarditis with allorejection-like immunologic features in patients under anti-PD1 (programmed death cell protein 1) treatment suggests a key role of the PD1/PD-L1 (programmed death ligand 1) axis in cardiac immune homeostasis.

METHODS

We cross-sectionally studied 23 heart transplant patients undergoing surveillance endomyocardial biopsy. Endomyocardial tissue and peripheral blood mononuclear cells were analyzed by flow cytometry. Multivariate logistic regression analyses including demographic, clinical, and hemodynamic parameters were performed. Murine models were used to evaluate the impact of PD-L1 endothelial graft expression in allorejection.

RESULTS

We found that myeloid cells dominate the composition of the graft leukocyte compartment in most patients, with variable T-cell frequencies. The CD (cluster of differentiation) 4:CD8 T-cell ratios were between 0 and 1.5. The proportion of PD-L1 expressing cells in graft endothelial cells, fibroblasts, and myeloid leukocytes ranged from negligible up to 60%. We found a significant inverse logarithmic correlation between the proportion of PD-L1+HLA (human leukocyte antigen)-DR+ endothelial cells and CD8+ T cells (slope, -18.3 [95% CI, -35.3 to -1.3]; P=0.030). PD-L1 expression and leukocyte patterns were independent of demographic, clinical, and hemodynamic parameters. We confirmed the importance of endothelial PD-L1 expression in a murine allogeneic heart transplantation model, in which Tie2Crepdl1fl/fl grafts lacking PD-L1 in endothelial cells were rejected significantly faster than controls.

CONCLUSIONS

Loss of graft endothelial PD-L1 expression may play a role in regulating CD8+ T-cell infiltration in human heart transplantation. Murine model results suggest that loss of graft endothelial PD-L1 may facilitate alloresponses and rejection.

Monocyte suppression of Fusobacterium nucleatum-induced human polyclonal B-lymphocyte activation

Previous studies reported that Fusobacterium nucleatum induced polyclonal B-lymphocyte activation (PBA) as determined by immunoglobulin M production in cultures of human peripheral blood mononuclear cells. However, the PBA response was greatly enhanced when the cells were depleted of esterase-positive, adherent cells (i.e., monocytes). The purpose of this study was to confirm and further examine the suppression of F. nucleatum-induced PBA (F. nucleatum-PBA) by blood monocytes. For comparison, PBA induced by pokeweed mitogen (PWM-PBA), which is enhanced by monocytes, was assessed in some experiments. We found the removal of monocytes from unfractionated cells by (i) Sephadex G-10, (ii) anti-monocyte specific OM-1 monoclonal antibody plus complement, or (iii) L-leucine methyl ester, a compound which selectively kills lysosome-rich cells, resulted in a population of cells responsive to F. nucleatum-PBA and unresponsive to PWM-PBA. The addition of double adherence-purified monocytes (greater than 85% esterase-positive cells), particularly in concentrations of greater than 10%, to lymphocytes depleted of monocytes by G-10, OM-1, or L-leucine methyl ester treatments, suppressed F. nucleatum-PBA and enhanced PWM-PBA. Monocytes also suppressed a mixture of isolated T and B cells combined in a T/B cell ratio of 3:1, which is an optimal ratio for F. nucleatum-PBA. Allogeneic monocytes suppressed F. nucleatum-PBA, although at low numbers these cells were not as suppressive as autologous monocytes. Heating at 56 degrees C for 15 min, sonicating, or freeze-thawing the monocyte preparations resulted in an abrogation of monocyte-induced suppression of F. nucleatum-PBA. Kinetic studies in which fresh monocytes were added daily to lymphocytes stimulated with F. nucleatum or PWM showed that the monocytes must be added within the first 2 days of culture to suppress F. nucleatum-PBA or enhance PWM-PBA. Monocytes incubated with F. nucleatum for 48 h released into the culture medium a soluble factor that suppressed F. nucleatum-PBA. The results from this study demonstrate a potent mechanism by which the host might prevent exaggerated nonspecific immunoglobulin responses when exposed to PBA-inducing concentrations of F. nucleatum. On the other hand, the induction of suppressive monocytes (or monocyte-mediated suppressive factors) by interaction with F. nucleatum might result in the inhibition of host protective immune reactions.

Effects of basic fibroblast growth factor on early revascularization and epithelial regeneration in rabbit tracheal orthotopic transplantation

OBJECTIVES

Donor airway ischemia is a significant problem after tracheal replacement with homograft or lung transplantation. Omentopexy is the usual countermeasure to prevent or overcome the ischemia of the airway but this is frequently not sufficient. This study was designed to investigate whether basic fibroblast growth factor (bFGF) can augment tracheal revascularization and its epithelial regeneration in rabbit tracheal autograft.

METHODS

About half the length (44-45%) of the trachea of New Zealand white rabbit were autotransplanted in the original position immediately after harvest. In group I (n=15, control group), cervical tracheal autotransplantation was done only. In group II (n=15, omentopexy group), the cervical tracheal autograft was wrapped with subcutaneously advanced omentum. In group III (n=15, bFGF group), 1 microg of bFGF was applied evenly on the graft after the completion of anastomosis. Five animals in each group were examined on the 3rd, 7th and 14th postoperative days. Three rings of trachea were taken at the mid portion of the graft and the supra-carinal untouched normal trachea in each. The effect of revascularization was assessed by measuring the uptake of human serum albumin labeled with 99m technetium, which was injected into the left atrium just before sacrifice. The epithelial regeneration was assessed by means of light microscopic examination.

RESULTS

The proportion of perfusion of the graft to normal trachea was much higher in group III (P<0.05) on day 3 (25.4, 27.8 and 54.7% in groups I, II and III, respectively), but there was no difference on the 7th and 14th days. The epithelial regeneration was better in group III (P<0.05) than in the other groups on day 3, and was better in groups II and III than group I on day 7.

CONCLUSION

we concluded that bFGF enhances the revascularization and epithelial regeneration of the tracheal autograft, especially during their early phases.

Autoimmune Myocarditis, Old Dogs and New Tricks

Autoimmunity significantly contributes to the pathogenesis of myocarditis, underscored by its increased frequency in autoimmune diseases such as systemic lupus erythematosus and polymyositis. Even in cases of myocarditis caused by viral infections, dysregulated immune responses contribute to pathogenesis. However, whether triggered by existing autoimmune conditions or viral infections, the precise antigens and immunologic pathways driving myocarditis remain incompletely understood. The emergence of myocarditis associated with immune checkpoint inhibitor therapy, commonly used for treating cancer, has afforded an opportunity to understand autoimmune mechanisms in myocarditis, with autoreactive T cells specific for cardiac myosin playing a pivotal role. Despite their self-antigen recognition, cardiac myosin-specific T cells can be present in healthy individuals due to bypassing the thymic selection stage. In recent studies, novel modalities in suppressing the activity of pathogenic T cells including cardiac myosin-specific T cells have proven effective in treating autoimmune myocarditis. This review offers an overview of the current understanding of heart antigens, autoantibodies, and immune cells as the autoimmune mechanisms underlying various forms of myocarditis, along with the latest updates on clinical management and prospects for future research.

Programmed Death Ligand 1-Expressing Macrophages and Their Protective Role in the Joint During Arthritis

OBJECTIVE

Arthritis associated with immune checkpoint inhibitor therapies highlights the importance of immune checkpoint expression for joint homeostasis. We investigated the role of programmed death ligand (PD-L) 1 in the synovium using a collagen-induced arthritis (CIA) mouse model.

METHODS

We blocked PD-L1 using blocking antibodies during CIA and assessed the arthritis severity by clinical and histologic scoring. PD-L1 expression and the origin of synovial macrophages were investigated using flow cytometry and parabiosis. We used Cre-Lox mice to ascertain the protective role of PD-L1-expressing macrophages in arthritis. The immune profile of human and murine synovial PD-L1+ macrophages was determined by reverse transcriptase-polymerase chain reaction, flow cytometry, and single-cell RNA sequencing.

RESULTS

Anti-PD-L1 antibody treatment during CIA worsened arthritis with increased immune cell infiltration compared with isotype control, supporting the regulatory role of PD-L1 in the joint. The main cells expressing PD-L1 in the synovium were macrophages. Using parabiosis, we showed that synovial PD-L1+ macrophages were both locally proliferating and partially replaced by the circulation. PD-L1+ macrophages had increased levels of MER proto-oncogene tyrosine kinase (MerTK) and interleukin (IL)-10 expression during acute CIA. Genetic depletion of PD-L1 on macrophages in LyzcrePD-L1fl/fl mice resulted in worsened CIA compared with controls. We found that human PD-L1+ macrophages in the synovium of healthy individuals and patients with rheumatoid arthritis express MerTK and IL-10.

CONCLUSION

PD-L1+ macrophages with efferocytotic and anti-inflammatory characteristics protect the synovium from severe arthritis in the CIA mouse model. Tissue-protective, PD-L1-expressing macrophages are also present in the human synovium at homeostasis and during rheumatoid arthritis.

Autoimmunity against Cardiac Self-Antigen Drives Immune Checkpoint Inhibitor-Associated Myocarditis Development

Immune checkpoint inhibitor (ICI) blocking PD-1 has been approved by the Food and Drug Administration for treatment of several types of cancers. However, fulminant myocarditis has occurred in the ICI-treated cancer patients, with low incidence but with 50 percent mortality. In this study, we investigated if PD-1 blockade can induce myocarditis in the mouse mimicking ICI-associated myocarditis in the human. We found that anti-PD-1 mAb treatment caused myocarditis development in A/J mice exhibiting enlarged heart and increased cardiac infiltration. In the cardiac infiltration, CD8+ T cells, CD4+ T cells, monocytes and macrophages were increased in the PD-1 blockade group compared to isotype control. Cardiac damage was confirmed by elevated serum level of cardiac troponin I and anti-myosin IgG. In addition, PD-1 blockade caused arrhythmia, right bundle branch block, while controls showed a normal ECG trace. The A/J mice with PD-1 blockade also developed systemic autoimmune responses such as colitis, sialadenitis, pneumonitis and myositis like immune-related adverse events in the human, supporting the immunotoxicity of PD-1 blockade. Next, using myosin-MHC tetramer staining, we found the increase of autoreactive T cells specific for cardiac myosin in the mouse heart with ICI-associated myocarditis compared to control. In the naïve heart, we were able to detect myosin-specific T cells, which number was very few but expressed a high level of PD-1. Collectively, we have developed the mouse model for human ICI-associated myocarditis and showed that the pathogenesis of this disease is an autoimmune reaction against heart-specific antigens.

Injury-induced myosin-specific tissue-resident memory T cells drive immune checkpoint inhibitor myocarditis

Cardiac myosin-specific (MyHC) T cells drive the disease pathogenesis of immune checkpoint inhibitor-associated myocarditis (ICI-myocarditis). To determine whether MyHC T cells are tissue-resident memory T (TRM) cells, we characterized cardiac TRM cells in naive mice and established that they have a distinct phenotypic and transcriptional profile that can be defined by their upregulation of CD69, PD-1, and CXCR6. We then investigated the effects of cardiac injury through a modified experimental autoimmune myocarditis mouse model and an ischemia-reperfusion injury mouse model and determined that cardiac inflammation induces the recruitment of autoreactive MyHC TRM cells, which coexpress PD-1 and CD69. To investigate whether the recruited MyHC TRM cells could increase susceptibility to ICI-myocarditis, we developed a two-hit ICI-myocarditis mouse model where cardiac injury was induced, mice were allowed to recover, and then were treated with anti-PD-1 antibodies. We determined that mice who recover from cardiac injury are more susceptible to ICI-myocarditis development. We found that murine and human TRM cells share a similar location in the heart and aggregate along the perimyocardium. We phenotyped cells obtained from pericardial fluid from patients diagnosed with dilated cardiomyopathy and ischemic cardiomyopathy and established that pericardial T cells are predominantly CD69+ TRM cells that up-regulate PD-1. Finally, we determined that human pericardial macrophages produce IL-15, which supports and maintains pericardial TRM cells.

The protective role of GATA6+ pericardial macrophages in pericardial inflammation

Prior research has suggested that GATA6+ pericardial macrophages may traffic to the myocardium to prevent interstitial fibrosis after myocardial infarction (MI), while subsequent literature claims that they do not. We demonstrate that GATA6+ pericardial macrophages are critical for preventing IL-33 induced pericarditis and attenuate trafficking of inflammatory monocytes and granulocytes to the pericardial cavity after MI. However, absence of GATA6+ macrophages did not affect myocardial inflammation due to MI or coxsackievirus-B3 induced myocarditis, or late-stage cardiac fibrosis and cardiac function post MI. GATA6+ macrophages are significantly less transcriptionally active following stimulation in vitro compared to bone marrow-derived macrophages and do not induce upregulation of inflammatory markers in fibroblasts. This suggests that GATA6+ pericardial macrophages attenuate inflammation through their interactions with surrounding cells. We therefore conclude that GATA6+ pericardial macrophages are critical in modulating pericardial inflammation, but do not play a significant role in controlling myocardial inflammation or fibrosis.

Hypereosinophilia causes progressive cardiac pathologies in mice

Hypereosinophilic syndrome is a progressive disease with extensive eosinophilia that results in organ damage. Cardiac pathologies are the main reason for its high mortality rate. A better understanding of the mechanisms of eosinophil-mediated tissue damage would benefit therapeutic development. Here, we describe the cardiac pathologies that developed in a mouse model of hypereosinophilic syndrome. These IL-5 transgenic mice exhibited decreased left ventricular function at a young age which worsened with age. Mechanistically, we demonstrated infiltration of activated eosinophils into the heart tissue that led to an inflammatory environment. Gene expression signatures showed tissue damage as well as repair and remodeling processes. Cardiomyocytes from IL-5Tg mice exhibited significantly reduced contractility relative to wild type (WT) controls. This impairment may result from the inflammatory stress experienced by the cardiomyocytes and suggest that dysregulation of contractility and Ca2+ reuptake in cardiomyocytes contributes to cardiac dysfunction at the whole organ level in hypereosinophilic mice.

Immune checkpoint inhibitors associated cardiovascular immune-related adverse events

Immune checkpoint inhibitors (ICIs) are specialized monoclonal antibodies (mAbs) that target immune checkpoints and their ligands, counteracting cancer cell-induced T-cell suppression. Approved ICIs like cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), its ligand PD-L1, and lymphocyte activation gene-3 (LAG-3) have improved cancer patient outcomes by enhancing anti-tumor responses. However, some patients are unresponsive, and others experience immune-related adverse events (irAEs), affecting organs like the lung, liver, intestine, skin and now the cardiovascular system. These cardiac irAEs include conditions like myocarditis, atherosclerosis, pericarditis, arrhythmias, and cardiomyopathy. Ongoing clinical trials investigate promising alternative co-inhibitory receptor targets, including T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) and T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT). This review delves into the mechanisms of approved ICIs (CTLA-4, PD-1, PD-L1, and LAG-3) and upcoming options like Tim-3 and TIGIT. It explores the use of ICIs in cancer treatment, supported by both preclinical and clinical data. Additionally, it examines the mechanisms behind cardiac toxic irAEs, focusing on ICI-associated myocarditis and atherosclerosis. These insights are vital as ICIs continue to revolutionize cancer therapy, offering hope to patients, while also necessitating careful monitoring and management of potential side effects, including emerging cardiac complications.