Protease-activated receptor-2 regulates the innate immune response to viral infection in a coxsackievirus B3-induced myocarditis

Discovery of a novel ROS-based signature for predicting prognosis and immunosuppressive tumor microenvironment in lung adenocarcinoma

The role of reactive oxygen species (ROS) is critical in the emergence and progression of lung adenocarcinoma (LUAD), affecting cell survival, proliferation, angiogenesis, and metastasis. Further investigations are needed to elucidate these effects' precise pathways and devise therapeutic approaches targeting ROS. Moreover, the expression pattern and clinical significance of the ROS-related genes in LUAD remain elusive. Through comprehensive analysis incorporating 1494 LUAD cases from The Cancer Genome Atlas, six Gene Expression Omnibus series, and a Chinese LUAD cohort, we identified a ROS-related signature with substantial predictive value in various LUAD patient cohorts. The ROS-related signature has demonstrated a significant negative relationship with antitumor immunity and dendritic cell maturation and activation. Moreover, The ROS-related signature showed predictive value on immunotherapy outcomes across multiple types of solid tumors, including LUAD. These findings reinforce the ROS-related signature as a predictive tool for LUAD and provide new insights into its link with antitumor immunity and immunotherapy efficacy. These results have implications for refining clinical assessments and tailoring immunotherapeutic strategies for patients with LUAD.

New insight into the agonism of protease-activated receptors as an immunotherapeutic strategy

The activation and mobilization of immune cells play a crucial role in immunotherapy. Existing therapeutic interventions, such as cytokines administration, aim to enhance immune cell activity. However, these approaches usually result in modest effectiveness and toxic side effects, thereby restricting their clinical application. Protease-activated receptors (PARs), a subfamily of G protein-coupled receptors, actively participate in the immune system by directly activating immune cells. The activation of PARs by proteases or synthetic ligands can modulate immune cell behavior, signaling, and responses to treat immune-related diseases, suggesting the significance of PARs agonism in immunotherapy. However, the agonism of PARs in therapeutical applications remains rarely discussed, since it has been traditionally considered that PARs activation facilitates disease progressions. This review aims to comprehensively summarize the activation, rather than inhibition, of PARs in immune-related physiological responses and diseases. Additionally, we will discuss the emerging immunotherapeutic potential of PARs agonism, providing a new strategic direction for PARs-mediated immunotherapy.

Immune mechanisms of group B coxsackievirus induced viral myocarditis

Viral myocarditis is known to be a primary cause of dilated cardiomyopathy (DCM) that can lead to heart failure and sudden cardiac death and is invariably caused by myocardial viral infection following active inflammatory destruction of the myocardium. Although acute viral myocarditis frequently recovers on its own, current chronic myocarditis therapies are unsatisfactory, where the persistence of viral or immunological insults to the heart may play a role. Cellular and mouse experimental models that utilized the most prevalent Coxsackievirus group B type 3 (CVB3) virus infection causing myocarditis have illustrated the pathophysiology of viral myocarditis. In this review, immunological insights into the different stages of development of viral myocarditis were discussed, concentrating on the mechanisms of innate and adaptive immunity in the development of CVB3-induced myocarditis.

Ruxolitinib ameliorated coxsackievirus B3-induced acute viral myocarditis by suppressing the JAK-STAT pathway

BACKGROUND

Accumulating evidences have demonstrated that overwhelming inflammation occurs in the process of Coxsackievirus B3 (CVB3)-induced acute viral myocarditis (AVM). No specific therapy is available. More than an effective Janus-associated kinase (JAK) inhibiter, ruxolitinib exerts a critical role in the inflammatory diseases. In this study, we investigated the potential effect of ruxolitinib on CVB3-induced acute viral myocarditis.

METHOD

In vivo, BALB/c mice were intraperitoneally injected of CVB3, treated of a successive gavage of ruxolitinib for seven days, and subjected to a series of analysis. In vitro, primary bone marrow-derived macrophages (BMDMs) and cardiac fibroblasts were isolated, cultured, treated, harvested and finally detected.

RESULTS

In vivo, acute viral myocarditis was successfully induced by the injection of CVB3 characterized by impaired cardiac function, predominant infiltration of inflammatory cells, necroptosis of myocardium, great increase of cardiac troponin I (cTnI) and cytokine levels, replication of CVB3, and excessive activation of JAK-STAT pathways. Oral administration of ruxolitinib suppressed the activation of JAK-STAT pathway in a dosage-dependent way, lessened the infiltration of inflammatory cells and necroptosis of myocardium, reduced the levels of cTnI and cytokines, and finally alleviated CVB3-induced cardiac dysfunction, with the reduced production of type I interferon and no promising effect on the replication of CVB3. In vitro, the treatment of ruxolitinib inhibited the activation of JAK-STAT pathway and increase of multiple cytokines mRNA levels in BMDMs and had no protective effect against CVB3 replication in cardiac fibroblasts.

CONCLUSIONS

Our study suggested that ruxolitinib ameliorated CVB3-induced AVM by inhibiting the activation of JAK-STAT pathway, infiltration of inflammatory cells and necroptosis of myocardium, which may provide a novel strategy for AVM therapy.

Cytoplasm Hydrogelation-Mediated Cardiomyocyte Sponge Alleviated Coxsackievirus B3 Infection

Viral myocarditis (VMC), commonly caused by coxsackievirus B3 (CVB3) infection, lacks specific treatments and leads to serious heart conditions. Current treatments, such as IFNα and ribavirin, show limited effectiveness. Herein, rather than inhibiting virus replication, this study introduces a novel cardiomyocyte sponge, intracellular gelated cardiomyocytes (GCs), to trap and neutralize CVB3 via a receptor-ligand interaction, such as CAR and CD55. By maintaining cellular morphology, GCs serve as sponges for CVB3, inhibiting infection. In vitro results revealed that GCs could inhibit CVB3 infection on HeLa cells. In vivo, GCs exhibited a strong immune escape ability and effectively inhibited CVB3-induced viral myocarditis with a high safety profile. The most significant implication of this study is to develop a universal antivirus infection strategy via intracellular gelation of the host cell, which can be employed not only for treating defined pathogenic viruses but also for a rapid response to infection outbreaks caused by mutable and unknown viruses.

Toll-like Receptors as Pro-Thrombotic Drivers in Viral Infections: A Narrative Review

Toll-like receptors (TLRs) have a critical role in the pathogenesis and disease course of viral infections. The induced pro-inflammatory responses result in the disturbance of the endovascular surface layer and impair vascular homeostasis. The injury of the vessel wall further promotes pro-thrombotic and pro-coagulatory processes, eventually leading to micro-vessel plugging and tissue necrosis. Moreover, TLRs have a direct role in the sensing of viruses and platelet activation. TLR-mediated upregulation of von Willebrand factor release and neutrophil, as well as macrophage extra-cellular trap formation, further contribute to (micro-) thrombotic processes during inflammation. The following review focuses on TLR signaling pathways of TLRs expressed in humans provoking pro-thrombotic responses, which determine patient outcome during viral infections, especially in those with cardiovascular diseases.

Role of Coxsackievirus B3-Induced Immune Responses in the Transition from Myocarditis to Dilated Cardiomyopathy and Heart Failure

Dilated cardiomyopathy (DCM) is a cardiac disease marked by the stretching and thinning of the heart muscle and impaired left ventricular contractile function. While most patients do not develop significant cardiac diseases from myocarditis, disparate immune responses can affect pathological outcomes, including DCM progression. These altered immune responses, which may be caused by genetic variance, can prolong cytotoxicity, induce direct cleavage of host protein, or encourage atypical wound healing responses that result in tissue scarring and impaired mechanical and electrical heart function. However, it is unclear which alterations within host immune profiles are crucial to dictating the outcomes of myocarditis. Coxsackievirus B3 (CVB3) is a well-studied virus that has been identified as a causal agent of myocarditis in various models, along with other viruses such as adenovirus, parvovirus B19, and SARS-CoV-2. This paper takes CVB3 as a pathogenic example to review the recent advances in understanding virus-induced immune responses and differential gene expression that regulates iron, lipid, and glucose metabolic remodeling, the severity of cardiac tissue damage, and the development of DCM and heart failure.

An Emerging Role for Type I Interferons as Critical Regulators of Blood Coagulation

Type I interferons (IFNs) are central mediators of anti-viral and anti-bacterial host defence. Detection of microbes by innate immune cells via pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and cGAS-STING, induces the expression of type I IFN-stimulated genes. Primarily comprising the cytokines IFN-α and IFN-β, type I IFNs act via the type I IFN receptor in an autocrine or exocrine manner to orchestrate rapid and diverse innate immune responses. Growing evidence pinpoints type I IFN signalling as a fulcrum that not only induces blood coagulation as a core feature of the inflammatory response but is also activated by components of the coagulation cascade. In this review, we describe in detail recent studies identifying the type I IFN pathway as a modulator of vascular function and thrombosis. In addition, we profile discoveries showing that thrombin signalling via protease-activated receptors (PARs), which can synergize with TLRs, regulates the host response to infection via induction of type I IFN signalling. Thus, type I IFNs can have both protective (via maintenance of haemostasis) and pathological (facilitating thrombosis) effects on inflammation and coagulation signalling. These can manifest as an increased risk of thrombotic complications in infection and in type I interferonopathies such as systemic lupus erythematosus (SLE) and STING-associated vasculopathy with onset in infancy (SAVI). We also consider the effects on coagulation of recombinant type I IFN therapies in the clinic and discuss pharmacological regulation of type I IFN signalling as a potential mechanism by which aberrant coagulation and thrombosis may be treated therapeutically.

Cytotoxic CD8+ T Cells Are Involved in the Thrombo-Inflammatory Response during First-Diagnosed Atrial Fibrillation

BACKGROUND

Atrial myopathy and atrial fibrillation (AF) accompany thrombo-inflammation. This facilitates disease progression and promotes major adverse cardiovascular events (MACEs). Thrombin receptor (protease-activated receptor 1, PAR1) signalling is central in mediating thrombo-inflammation. We hypothesised that PAR1 signalling links coagulation and inflammation through cytotoxic CD8⁺ T lymphocytes in patients presenting with first-diagnosed AF (FDAF).

METHODS

A total of 210 patients were studied. We included data and blood samples from patients presenting with FDAF (n = 160), cardiac tissue from patients with paroxysmal AF (n = 32) and 20 controls.

RESULTS

During early AF, a pro-inflammatory and cytotoxic subset of T lymphocytes (CD8⁺) circulated more frequently when compared to patients with chronic cardiovascular disease but without AF, accompanied by elevated plasma levels of CD8⁺ effector molecules, which corresponded to biomarkers of adverse cardiac remodelling and atrial dysfunction. Activation of tissue factor (TF) and PAR1 was associated with pro-inflammatory and cytotoxic effector functions. PAR1-related CD8⁺ cell activation was more frequent in FDAF patients that experienced a MACE.

CONCLUSIONS

In patients with FDAF, the TF-factor Xa-factor IIa-axis contributes to thrombo-inflammation via PAR1 in CD8⁺ T cells. Intervening in this cascade might be a promising synergistic approach to reducing disease progression and the vascular complications of AF.

Leveraging big data of immune checkpoint blockade response identifies novel potential targets

BACKGROUND

The development of immune checkpoint blockade (ICB) has changed the way we treat various cancers. While ICB produces durable survival benefits in a number of malignancies, a large proportion of treated patients do not derive clinical benefit. Recent clinical profiling studies have shed light on molecular features and mechanisms that modulate response to ICB. Nevertheless, none of these identified molecular features were investigated in large enough cohorts to be of clinical value.

MATERIALS AND METHODS

Literature review was carried out to identify relevant studies including clinical dataset of patients treated with ICB [anti-programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1), anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4) or the combination] and available sequencing data. Tumor mutational burden (TMB) and 37 previously reported gene expression (GE) signatures were computed with respect to the original publication. Biomarker association with ICB response (IR) and survival (progression-free survival/overall survival) was investigated separately within each study and combined together for meta-analysis.

RESULTS

We carried out a comparative meta-analysis of genomic and transcriptomic biomarkers of IRs in over 3600 patients across 12 tumor types and implemented an open-source web application (predictIO.ca) for exploration. TMB and 21/37 gene signatures were predictive of IRs across tumor types. We next developed a de novo GE signature (PredictIO) from our pan-cancer analysis and demonstrated its superior predictive value over other biomarkers. To identify novel targets, we computed the T-cell dysfunction score for each gene within PredictIO and their ability to predict dual PD-1/CTLA-4 blockade in mice. Two genes, F2RL1 (encoding protease-activated receptor-2) and RBFOX2 (encoding RNA-binding motif protein 9), were concurrently associated with worse ICB clinical outcomes, T-cell dysfunction in ICB-naive patients and resistance to dual PD-1/CTLA-4 blockade in preclinical models.

CONCLUSION

Our study highlights the potential of large-scale meta-analyses in identifying novel biomarkers and potential therapeutic targets for cancer immunotherapy.

Inhibition of Protease Activated Receptor 2 Attenuates HBx-Induced Inflammation and Mitochondria Oxidative Stress

BACKGROUND

Hepatitis B virus (HBV) infection is one of the global public problems. Among the known infection cases, HBV X protein (HBx) is one of the key inducements of viral replication and host infection. This study was aimed to uncover the role of protease activated receptor 2 (PAR2) on HBx-induced liver injury.

METHODS

A PAR2-KO mouse model expressing HBx was constructed using hydrodynamics-based in vivo gene transfection method. In addition, pcDNA3.1-HBx was used to over-express HBx in LO2 cells. The effects of HBx overexpression on inflammation and mitochondria oxidative stress were evaluated.

RESULTS

We found that PAR2 protein level was increased by HBx overexpression. The enforced HBx inhibited LO2 cells apoptosis. Meanwhile, HBx induced inflammation reactions through promoting the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and CXCL-2. Overexpressed HBx also resulted in mitochondria oxidative stress by upregulation of ROS level and downregulation of MMP and ATP. However, in FSLLRY-NH2 (PAR2 antagonist) treated LO2 cells or PAR2-KO mice, PAR2 blockade reversed the above adverse effects of HBx on liver cells or tissues.

CONCLUSION

Inhibition of PAR2 may suppress inflammation and mitochondria oxidative stress caused by HBx, pointing out the potential application values of PAR2 antagonist on the treatment of HBV infection in clinic.

Pleiotropic Effects of the Protease-Activated Receptor 1 (PAR1) Inhibitor, Vorapaxar, on Atherosclerosis and Vascular Inflammation

BACKGROUND

Protease-activated receptor 1 (PAR1) and toll-like receptors (TLRs) are inflammatory mediators contributing to atherogenesis and atherothrombosis. Vorapaxar, which selectively antagonizes PAR1-signaling, is an approved, add-on antiplatelet therapy for secondary prevention. The non-hemostatic, platelet-independent, pleiotropic effects of vorapaxar have not yet been studied.

METHODS AND RESULTS

Cellular targets of PAR1 signaling in the vasculature were identified in three patient cohorts with atherosclerotic disease. Evaluation of plasma biomarkers (n = 190) and gene expression in endomyocardial biopsies (EMBs) (n = 12) revealed that PAR1 expression correlated with endothelial activation and vascular inflammation. PAR1 colocalized with TLR2/4 in human carotid plaques and was associated with TLR2/4 gene transcription in EMBs. In addition, vorapaxar reduced atherosclerotic lesion size in apolipoprotein E-knock out (ApoEko) mice. This reduction was associated with reduced expression of vascular adhesion molecules and TLR2/4 presence, both in isolated murine endothelial cells and the aorta. Thrombin-induced uptake of oxLDL was augmented by additional TLR2/4 stimulation and abrogated by vorapaxar. Plaque-infiltrating pro-inflammatory cells were reduced in vorapaxar-treated ApoEko mice. A shift toward M2 macrophages paralleled a decreased transcription of pro-inflammatory cytokines and chemokines.

CONCLUSIONS

PAR1 inhibition with vorapaxar may be effective in reducing residual thrombo-inflammatory event risk in patients with atherosclerosis independent of its effect on platelets.

Myeloid Protease-Activated Receptor-2 Contributes to Influenza A Virus Pathology in Mice

Background

Innate immune responses to influenza A virus (IAV) infection are initiated in part by toll-like receptor 3 (TLR3). TLR3-dependent signaling induces an antiviral immune response and an NFκB-dependent inflammatory response. Protease-activated receptor 2 (PAR2) inhibits the antiviral response and enhances the inflammatory response. PAR2 deficiency protected mice during IAV infection. However, the PAR2 expressing cell-types contributing to IAV pathology in mice and the mechanism by which PAR2 contributes to IAV infection is unknown.

Methods

IAV infection was analyzed in global (Par2-/-), myeloid (Par2fl/fl;LysMCre+) and lung epithelial cell (EpC) Par2 deficient (Par2fl/fl;SPCCre+) mice and their respective controls (Par2+/+ and Par2fl/fl). In addition, the effect of PAR2 activation on polyinosinic-polycytidylic acid (poly I:C) activation of TLR3 was analyzed in bone marrow-derived macrophages (BMDM). Lastly, we determined the effect of PAR2 inhibition in wild-type (WT) mice.

Results

After IAV infection, Par2-/- and mice with myeloid Par2 deficiency exhibited increased survival compared to infected controls. The improved survival was associated with reduced proinflammatory mediators and reduced cellular infiltration in bronchoalveolar lavage fluid (BALF) of Par2-/- and Par2fl/fl;LysMCre+ 3 days post infection (dpi) compared to infected control mice. Interestingly, Par2fl/fl;SPCCre+ mice showed no survival benefit compared to Par2fl/fl. In vitro studies showed that Par2-/- BMDM produced less IL6 and IL12p40 than Par2+/+ BMDM after poly I:C stimulation. In addition, activation of PAR2 on Par2+/+ BMDM increased poly I:C induction of IL6 and IL12p40 compared to poly I:C stimulation alone. Importantly, PAR2 inhibition prior to IAV infection protect WT mice.

Conclusion

Global Par2 or myeloid cell but not lung EpC Par2 deficiency was associated with reduced BALF inflammatory markers and reduced IAV-induced mortality. Our study suggests that PAR2 may be a therapeutic target to reduce IAV pathology.

Hypoxia-inducible transcription factor-1α inhibition by topotecan protects against lipopolysaccharide-induced inflammation and apoptosis of cardiomyocytes

Background

Myocarditis, an inflammatory disease of the myocardium, is a serious hazard to human life due to the expansion of inflammatory lesions in the myocardium. The aim of this study was to investigate the role of hypoxia-inducible transcription factor (HIF)-1α and its inhibitor topotecan in the pathogenesis of myocarditis.

Methods

H9c2 cardiomyoblasts was stimulated with lipopolysaccharide (LPS) to simulate myocarditis model in vitro. The levels of myocardial damage markers were determined using commercially available kits. Western blotting was used to evaluate HIF-1α expression after LPS challenge. Then, after HIF-1α silencing, the contents of inflammatory factors were determined with enzyme-linked immunosorbent assay (ELISA). Cell viability was tested by means of a cell counting kit-8 (CCK-8) assay. Cell apoptosis was assessed by flow cytometry, and the expression of apoptotic proteins was examined using western blot analysis. Subsequently, HIF-1α was overexpressed and topotecan was employed to treat H9c2 cells under LPS exposure condition. The biological functions were detected again.

Results

LPS significantly elevated the levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) and cardiac troponin-I (cTn-I) in supernatant of H9c2 cell lysates. Additionally, LPS led to the notably upregulated expression of HIF-1α. HIF-1α-knockdown markedly decreased the concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 compared with the LPS-induced group. Moreover, the cell viability was conspicuously enhanced and cell apoptotic ratio was remarkably reduced, accompanied by downregulated expression of Bax, Bim, caspase 3 and caspase 9 after HIF-1α silencing. Consistently, HIF-1α gain-of-function significantly promoted the production of inflammatory cytokines and cell apoptosis, which was partially counteracted by topotecan administration.

Conclusion

To conclude, these findings demonstrated that HIF-1α inhibition by topotecan ameliorates LPS-induced myocarditis in vitro, providing a new approach in the treatment of myocarditis.

Cell type-specific roles of PAR1 in Coxsackievirus B3 infection

Protease-activated receptor 1 (PAR1) is widely expressed in humans and mice, and is activated by a variety of proteases, including thrombin. Recently, we showed that PAR1 contributes to the innate immune response to viral infection. Mice with a global deficiency of PAR1 expressed lower levels of CXCL10 and had increased Coxsackievirus B3 (CVB3)-induced myocarditis compared with control mice. In this study, we determined the effect of cell type-specific deletion of PAR1 in cardiac myocytes (CMs) and cardiac fibroblasts (CFs) on CVB3-induced myocarditis. Mice lacking PAR1 in either CMs or CFs exhibited increased CVB3 genomes, inflammatory infiltrates, macrophages and inflammatory mediators in the heart and increased CVB3-induced myocarditis compared with wild-type controls. Interestingly, PAR1 enhanced poly I:C induction of CXCL10 in rat CFs but not in rat neonatal CMs. Importantly, activation of PAR1 reduced CVB3 replication in murine embryonic fibroblasts and murine embryonic cardiac myocytes. In addition, we showed that PAR1 reduced autophagy in murine embryonic fibroblasts and rat H9c2 cells, which may explain how PAR1 reduces CVB3 replication. These data suggest that PAR1 on CFs protects against CVB3-induced myocarditis by enhancing the anti-viral response whereas PAR1 on both CMs and fibroblasts inhibits viral replication.

Advocacy of targeting protease-activated receptors in severe coronavirus disease 2019

Identifying drug targets mitigating vascular dysfunction, thrombo-inflammation and thromboembolic complications in COVID-19 is essential. COVID-19 coagulopathy differs from sepsis coagulopathy. Factors that drive severe lung pathology and coagulation abnormalities in COVID-19 are not understood. Protein-protein interaction studies indicate that the tagged viral bait protein ORF9c directly interacts with PAR2, which modulates host cell IFN and inflammatory cytokines. In addition to direct interaction of SARS-CoV-2 viral protein with PARs, we speculate that activation of PAR by proteases plays a role in COVID-19-induced hyperinflammation. In COVID-19-associated coagulopathy elevated levels of activated coagulation proteases may cleave PARs in association with TMPRSS2. PARs activation enhances the release of cytokines, chemokines and tissue factor expression to propagate IFN-dependent inflammation, leukocyte-endothelial interaction, vascular permeability and coagulation responses. This hypothesis, corroborated by in vitro findings and emerging clinical evidence, will focus targeted studies of PAR1/2 blockers as adjuvant drugs against cytokine release syndrome and COVID-19-associated coagulopathy.

Toll-Like Receptors: Are They Taking a Toll on the Heart in Viral Myocarditis?

Myocarditis is an inflammatory disease of the heart with viral infections being the most common aetiology. Its complex biology remains poorly understood and its clinical management is one of the most challenging in the field of cardiology. Toll-like receptors (TLRs), a family of evolutionarily conserved pattern recognition receptors, are increasingly known to be implicated in the pathophysiology of viral myocarditis. Their central role in innate and adaptive immune responses, and in the inflammatory reaction that ensues, indeed makes them prime candidates to profoundly affect every stage of the disease process. This review describes the pathogenesis and pathophysiology of viral myocarditis, and scrutinises the role of TLRs in every phase. We conclude with directions for future research in this field.

PAR2 Promoter Hypomethylation Regulates PAR2 Gene Expression and Promotes Lung Adenocarcinoma Cell Progression

Objective

Protease-activated receptor-2 (PAR2) also known as F2RL1 is a G protein-coupled receptor that intimately correlates with cancer occurrence. DNA methylation turns out a vital mechanism regulating gene expression, while PAR2 promoter methylation is proven to be involved in cancer development. Hence, this study attempted to clarify the molecular mechanism by which PAR2 mediates lung adenocarcinoma (LUAD) progression, via identifying the effect of PAR2 promoter methylation on LUAD cell progression.

Methods

Associations of PAR2 promoter methylation with PAR2 gene expression and prognosis of LUAD patients were analyzed via bioinformatics analysis. PAR2 promoter methylation and gene expression at the cellular level were measured using methylation-specific PCR, qRT-PCR, and Western blot assays. DNA methyltransferase inhibitor 5-AzadC was used to treat cells to assess PAR2 gene expression alteration. Cell biological behaviors upon PAR2 overexpression were characterized via MTT, wound healing assay, and Transwell assay.

Results

Bioinformatics analysis revealed that PAR2 promoter methylation was negatively related to PAR2 gene expression, while PAR2 promoter hypermethylation and low gene expression indicated favorable LUAD prognosis. Besides, it turned out that PAR2 presented upregulated expression and hypomethylated promoter in LUAD cells. Moreover, PAR2 gene expression was elevated in cells treated with 5-AzadC, and the proliferative, migratory, and invasive capabilities of cells with 5-AzadC or high PAR2 gene expression were all enhanced.

Conclusion

In sum, PAR2 promoter hypomethylation potentiates LUAD cell progression, in turn affecting the prognosis of LUAD patients.

PAR1 regulation of CXCL1 expression and neutrophil recruitment to the lung in mice infected with influenza A virus

BACKGROUND

Protease-activated receptor 1 (PAR1) is expressed in various immune cells and in the lung. We showed that PAR1 plays a role in Coxsackievirus B3 infection by enhancing toll-like receptor 3-dependent interferon- β expression in cardiac fibroblasts.

OBJECTIVES

We investigated the role of PAR1 in a mouse model of influenza A virus (IAV) infection.

METHODS

We used mice with either a global deficiency of PAR1, cell type-specific deficiencies of PAR1, or mutation of PAR1 at the R41 or R46 cleavage sites.

RESULTS

PAR1-deficient mice had increased CXCL1 expression in the lung, increased neutrophil recruitment, increased protein levels in the bronchoalveolar lavage fluid, and increased mortality after IAV infection compared with control mice infected with IAV. Results from mice with cell type-specific deletion of PAR1 indicated that PAR1 expression by hematopoietic cells suppressed CXCL1 expression, whereas PAR1 expression by endothelial cells enhanced CXCL1 expression in response to IAV infection. PAR1 activation also enhanced polyinosinic:polycytodylic acid induction of interleukin-8 in a human endothelial cell line. Mutation of the R46 cleavage site of PAR1 was associated with increased CXCL1 expression in the lung in response to IAV infection, which suggested that R46 signaling suppresses CXCL1 expression.

CONCLUSIONS

These results indicate that PAR1 expression by different cell types and activation by different proteases modulates the immune response during IAV infection.

Protease-activated receptor 2 deficiency mediates cardiac fibrosis and diastolic dysfunction

AIMS

Heart failure with preserved ejection fraction (HFpEF) and pathological cardiac aging share a complex pathophysiology, including extracellular matrix remodelling (EMR). Protease-activated receptor 2 (PAR2) deficiency is associated with EMR. The roles of PAR1 and PAR2 have not been studied in HFpEF, age-dependent cardiac fibrosis, or diastolic dysfunction (DD).

METHODS AND RESULTS

Evaluation of endomyocardial biopsies from patients with HFpEF (n = 14) revealed that a reduced cardiac PAR2 expression was associated with aggravated DD and increased myocardial fibrosis (r = -0.7336, P = 0.0028). In line, 1-year-old PAR2-knockout (PAR2ko) mice suffered from DD with preserved systolic function, associated with an increased age-dependent α-smooth muscle actin expression, collagen deposition (1.7-fold increase, P = 0.0003), lysyl oxidase activity, collagen cross-linking (2.2-fold increase, P = 0.0008), endothelial activation, and inflammation. In the absence of PAR2, the receptor-regulating protein caveolin-1 was down-regulated, contributing to an augmented profibrotic PAR1 and transforming growth factor beta (TGF-β)-dependent signalling. This enhanced TGF-β/PAR1 signalling caused N-proteinase (ADAMTS3) and C-proteinase (BMP1)-related increased collagen I production from cardiac fibroblasts (CFs). PAR2 overexpression in PAR2ko CFs reversed these effects. The treatment with the PAR1 antagonist, vorapaxar, reduced cardiac fibrosis by 44% (P = 0.03) and reduced inflammation in a metabolic disease model (apolipoprotein E-ko mice). Patients with HFpEF with upstream PAR inhibition via FXa inhibitors (n = 40) also exhibited reduced circulating markers of fibrosis and DD compared with patients treated with vitamin K antagonists (n = 20).

CONCLUSIONS

Protease-activated receptor 2 is an important regulator of profibrotic PAR1 and TGF-β signalling in the heart. Modulation of the FXa/FIIa-PAR1/PAR2/TGF-β-axis might be a promising therapeutic approach to reduce HFpEF.

The pro-apoptosis and pro-inflammation role of LncRNA HIF1A-AS1 in Coxsackievirus B3-induced myocarditis via targeting miR-138

Background

Cardiomyocyte apoptosis and inflammation induced by Coxsackievirus B3 (CVB3) are key pathogenetic mechanisms in viral myocarditis. Alterations in microRNAs and lncRNAs are associated with cardiac remodeling. However, whether the microRNA and lncRNA interact to regulate cardiomyocyte apoptosis and inflammation is unknown.

Methods

BALB/c mice were infected with CVB3 to generate acute viral myocarditis model. The expression levels of lncRNA HIF1A-AS1 and miR-138 were examined in mouse myocardium and primary cardiomyocytes with CVB3 infection. We then knocked down HIF1A-AS1 by siRNA and upregulated miR-138 by microRNA mimics in cardiomyocytes.

Results

The expression of lncRNA HIF1A-AS1was significantly increased in CVB3-induced myocardium and cardiomyocytes. As documented by flow cytometry, silencing of HIF1A-AS1 alleviated late apoptosis (5.1%±2.8% vs. 17.2%±4.2%, P<0.01) and ROS production (68.73%±2.78% vs. 90.40%±2.86%, P<0.01) compared to their levels in cardiomyocytes transfected with control siRNA. The content of proinflammatory cytokines was substantially decreased by HIF1A-AS1 siRNA. Furthermore, we identified that HIF1A-AS1 bound to miR-138 and significantly suppressed miR-138 expression. Blocking HIF1A-AS1 attenuated IκBα phosphorylation and NF-κB activity, while cotransfection with miR-138 mimics markedly reversed its effect.

Conclusions

In conclusion, lncRNA HIF1A-AS1 promotes NF-κB signaling and subsequently aggravates cardiomyocyte apoptosis and inflammation via targeting miR-138.

An overview of the immune mechanisms of viral myocarditis

Viral myocarditis has been identified as a major cause of dilated cardiomyopathy (DCM) that can lead to heart failure. Historically, Coxsackieviruses and adenoviruses have been commonly suspected in myocarditis/DCM patients in North America and Europe. However, this notion is changing as other viruses such as Parvovirus B19 and human herpesvirus-6 are increasingly reported as causes of myocarditis in the United States, with the most recent example being the severe acute respiratory syndrome coronavirus 2, causing the Coronavirus Disease-19. The mouse model of Coxsackievirus B3 (CVB3)-induced myocarditis, which may involve mediation of autoimmunity, is routinely used in the study of immune pathogenesis of viral infections as triggers of DCM. In this review, we discuss the immune mechanisms underlying the development of viral myocarditis with an emphasis on autoimmunity in the development of post-infectious myocarditis induced with CVB3.

Protease-activated receptor 2 deficiency in hematopoietic lineage protects against myocardial infarction through attenuated inflammatory response and fibrosis

Ischaemic heart disease is one of the leading causes of death. Protease-activated receptor 2 (PAR2) is widely expressed within the cardiovascular system and is known to mediate inflammatory processes in various immunocytes, such as macrophages, mastocytes and neutrophils. Here, we investigated whether activating macrophage PAR2 modulates cardiac remodelling in a murine model of myocardial infarction. Myocardial infarction was produced by the permanent ligation of the left anterior descending coronary artery (LAD) in C57BL/6J background wild-type (WT) mice transplanted with bone marrow from WT or PAR2 knockout (PAR2 KO) mice. Hematopoietic deficiency of PAR2 had improvement of left ventricular systolic dysfunction and dilatation and decreased fibrosis deposition in remote zone at 1 week after LAD ligation. Inactivation of PAR2 also led to less recruitment of macrophages in myocardium, which was accompanied by decreased expression of pro-inflammatory cytokines. Furthermore, cultured cardiac fibroblasts (CFs) were activated and showed a fibrotic phenotype after being co-cultured in medium containing PAR2-activating macrophage, which enhances interferon-beta (INF-β) expression. The beneficial effects of macrophages with INF-β neutralisation or PAR2-deletion ameliorates the JAK/STAT3 pathway in CFs, which might be attributed to CF activation. These data suggest that macrophage-derived IFN-β plays a crucial role in adverse cardiac remodelling after myocardial infarction, at least in part, through a PAR2-dependent mechanism.

Vascular miR-181b controls tissue factor-dependent thrombogenicity and inflammation in type 2 diabetes

BACKGROUND

Diabetes mellitus is characterized by chronic vascular inflammation leading to pathological expression of the thrombogenic full length (fl) tissue factor (TF) and its isoform alternatively-spliced (as) TF. Blood-borne TF promotes factor (F) Xa generation resulting in a pro-thrombotic state and cardiovascular complications. MicroRNA (miR)s impact gene expression on the post-transcriptional level and contribute to vascular homeostasis. Their distinct role in the control of the diabetes-related procoagulant state remains poorly understood.

METHODS

In a cohort of patients with poorly controlled type 2 diabetes (n = 46) plasma levels of miR-181b were correlated with TF pathway activity and markers for vascular inflammation. In vitro, human microvascular endothelial cells (HMEC)-1 and human monocytes (THP-1) were transfected with miR-181b or anti-miR-181b and exposed to tumor necrosis factor (TNF) α or lipopolysaccharides (LPS). Expression of TF isoforms, vascular adhesion molecule (VCAM) 1 and nuclear factor (NF) κB nuclear translocation was assessed. Moreover, aortas, spleen, plasma, and bone marrow-derived macrophage (BMDM)s of mice carrying a deletion of the first miR-181b locus were analyzed with respect to TF expression and activity.

RESULTS

In patients with type 2 diabetes, plasma miR-181b negatively correlated with the procoagulant state as evidenced by TF protein, TF activity, D-dimer levels as well as markers for vascular inflammation. In HMEC-1, miR-181b abrogated TNFα-induced expression of flTF, asTF, and VCAM1. These results were validated using the anti-miR-181b. Mechanistically, we confirmed a miR-181b-mediated inhibition of importin-α3 (KPNA4) leading to reduced nuclear translocation of the TF transcription factor NFκB. In THP-1, miR-181b reduced both TF isoforms and FXa generation in response to LPS due to targeting phosphatase and tensin homolog (PTEN), a principal inducer for TF in monocytes. Moreover, in miR-181-/- animals, we found that reduced levels of miR-181b were accompanied by increased TF, VCAM1, and KPNA4 expression in aortic tissue as well as increased TF and PTEN expression in spleen. Finally, BMDMs of miR-181-/- mice showed increased TF expression and FXa generation upon stimulation with LPS.

CONCLUSIONS

miR-181b epigenetically controls the procoagulant state in diabetes. Reduced miR-181b levels contribute to increased thrombogenicity and may help to identify individuals at particular risk for thrombosis.

Roles of Coagulation Proteases and PARs (Protease-Activated Receptors) in Mouse Models of Inflammatory Diseases

Activation of the blood coagulation cascade leads to fibrin deposition and platelet activation that are required for hemostasis. However, aberrant activation of coagulation can lead to thrombosis. Thrombi can cause tissue ischemia, and fibrin degradation products and activated platelets can enhance inflammation. In addition, coagulation proteases activate cells by cleavage of PARs (protease-activated receptors), including PAR1 and PAR2. Direct oral anticoagulants have recently been developed to specifically inhibit the coagulation proteases FXa (factor Xa) and thrombin. Administration of these inhibitors to wild-type mice can be used to determine the roles of FXa and thrombin in different inflammatory diseases. These results can be compared with the phenotypes of mice with deficiencies of either Par1 (F2r) or Par2 (F2rl1). However, inhibition of coagulation proteases will have effects beyond reducing PAR signaling, and a deficiency of PARs will abolish signaling from all proteases that activate these receptors. We will summarize studies that examine the roles of coagulation proteases, particularly FXa and thrombin, and PARs in different mouse models of inflammatory disease. Targeting FXa and thrombin or PARs may reduce inflammatory diseases in humans.

Targeting coagulation in heart failure with preserved ejection fraction and cardiac fibrosis

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Triggering of protease-activated receptors (PARs) induces alternative M2 macrophage polarization with impaired plasticity

Protease-activated receptors (PARs) have been described in a wide diversity of vertebrate cells, including human immune cells. Macrophages are pivotal cells in the host-pathogen interaction and their polarization in M1 or M2 cells has been described as a new central paradigm in the immune response to pathogens. In this context, we explored the involvement of PAR activation by serine proteases on M1/M2 macrophage differentiation and their impact on the Th1/Th2 cytokine profile in response to Mycobacterium tuberculosis antigen. Our results demonstrate that the serine proteases, thrombin and trypsin, induce interleukin (IL)-4 release from human monocytes, together with upregulation of the macrophage mannose receptor (CD206) in the same way that alternative M2a differentiated cells with M-CSF/IL-4. Protease stimulation of monocytes in the presence of PAR-1 (SCH-79797) or PAR-2 (FSLLRY-NH2) antagonists abolished IL-4 release from monocytes, whereas the use of the peptide agonist for PAR-1 (SFLLRNPNDKYEPF-NH2) or PAR-2 (SLIGKV-NH2) induced the secretion of IL-4 at a level comparable to thrombin or trypsin. When these protease-induced M2 macrophages from healthy human PPD + donors were co-cultured with autologous lymphocyte population in the presence of Mycobacterium tuberculosis antigen, we found a consistent inhibition of IFN-γ/IL-12 release together with persistent IL-4 expression, in contrast to the expected Th1 profile obtained with M2a macrophages. To our knowledge, this is the first observation that proteolytic activation of PAR1/2 receptors in monocytes induces M2-like macrophages with impaired plasticity and their implication in the driving of the Th1/Th2 cytokine profile.

Protease-activated receptor 4 protects mice from Coxsackievirus B3 and H1N1 influenza A virus infection

PAR4 is expressed by a variety of cells, including platelets, cardiac, lung and immune cells. We investigated the contribution of PAR4 to viral infections of the heart and lung. Toll-like receptor (TLR) 3-dependent immune responses were analyzed after co-stimulation of PAR4 in murine bone-marrow derived macrophages, embryonic fibroblasts and embryonic cardiomyocytes. In addition, we analyzed Coxsackievirus B3 (CVB3) or H1N1 influenza A virus (H1N1 IAV) infection of PAR4^-/- (ΔPAR4) and wild-type (WT) mice. Lastly, we investigated the effect of platelet inhibition on H1N1 IAV infection. In vitro experiments revealed that PAR4 stimulation enhances the expression of TLR3-dependent CXCL10 expression and decreases TLR3-dependent NFκB-mediated proinflammatory gene expression. Furthermore, CVB3-infected ΔPAR4 mice exhibited a decreased anti-viral response and increased viral genomes in the heart leading to more pronounced CVB3 myocarditis compared to WT mice. Similarly, H1N1 IAV-infected ΔPAR4 mice had increased immune cell numbers and inflammatory mediators in the lung, and increased mortality compared with infected WT controls. The study showed that PAR4 protects mice from viral infections of the heart and lung.

Myocarditis evolving in cardiomyopathy: when genetics and offending causes work together

Myocarditis is an infectious–inflammatory disease often superimposed to individual genetic background which could favour or inhibit its progression into a chronic heart muscle disorder (most often dilated cardiomyopathy, rarely arrhythmogenic, or right-sided cardiomyopathy). Post-myocarditis cardiomyopathy is likely caused by a complex interaction between the viral infection and an individual predisposition. Some viruses are able to highlight a clinical phenotype replicating a model similar to the genetically determined conditions, while other can affect the resolution or the progressive remodelling of the left ventricle after the infectious process. The identification of specific individual genetic backgrounds, or genes favouring the progression of the disease, are important future research goals for precision medicine aiming at a specific and individualized treatment for patients affected with myocarditis.

Protease-activated receptors (PARs): mechanisms of action and potential therapeutic modulators in PAR-driven inflammatory diseases

Inflammatory diseases have become increasingly prevalent with industrialization. To address this, numerous anti-inflammatory agents and molecular targets have been considered in clinical trials. Among molecular targets, protease-activated receptors (PARs) are abundantly recognized for their roles in the development of chronic inflammatory diseases. In particular, several inflammatory effects are directly mediated by the sensing of proteolytic activity by PARs.

PARs belong to the seven transmembrane domain G protein-coupled receptor family, but are unique in their lack of physiologically soluble ligands. In contrast with classical receptors, PARs are activated by N-terminal proteolytic cleavage. Upon removal of specific N-terminal peptides, the resulting N-termini serve as tethered activation ligands that interact with the extracellular loop 2 domain and initiate receptor signaling. In the classical pathway, activated receptors mediate signaling by recruiting G proteins. However, activation of PARs alternatively lead to the transactivation of and signaling through receptors such as co-localized PARs, ion channels, and toll-like receptors.

In this review we consider PARs and their modulators as potential therapeutic agents, and summarize the current understanding of PAR functions from clinical and in vitro studies of PAR-related inflammation.

Infectious myocarditis: the role of the cardiac vasculature

Infectious myocarditis is the result of an immune response to a microbial infection of the heart. The blood vessels of the heart, both the intramyocardial microvasculature and the large epicardial coronary arteries, play an important role in the pathogenesis of infectious myocarditis. First of all, in addition to cardiomyocytes, endothelial cells of the cardiac (micro)vasculature are direct targets for infection. Moreover, through the expression of adhesion molecules and antigen presenting Major Histocompatibility Complex molecules, the blood vessels assist in shaping the cellular immune response in infectious myocarditis. In addition, damage and dysfunction of the cardiac (micro)vasculature are associated with thrombus formation as well as aberrant regulation of vascular tone including coronary vasospasm. These in turn can cause cardiac perfusion abnormalities and even myocardial infarction. In this review, we will discuss the role of the cardiac (micro)vasculature in the pathogenesis of infectious myocarditis.

Astragalus polysaccharide from Astragalus Melittin ameliorates inflammation via suppressing the activation of TLR-4/NF-κB p65 signal pathway and protects mice from CVB3-induced virus myocarditis

Inflammation plays a crucial role in regulating cardiomyopathy and injuries of coxsackievirus B3 (CVB3)-induced viral myocarditis (VM). It has been reported that Astragalus polysaccharide (AP) from Astragalus Melittin could inhabit inflammatory gene expression under a variety of pathological conditions. However, the functional roles of AP in CVB3-induced VM still remain unknown. Here, we found that AP significantly enhanced survival for CVB3-induced mice. AP protected the mice against CVB3-induced myocardial injuries characterized by the increased body weight and depressed serum level of creatine kinase-MB (CK-MB), aspartate transaminases (AST) and lactate dehydrogenase (LDH), enhanced left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS). At the pathological level, AP ameliorated the mice against CVB3-induced myocardial damage, dilated cardiomyopathy and chronic myocardial fibrosis. We subsequently found that AP significantly suppressed CVB3-induced expression of inflammation marker (IL-1β, IL-6, TNF-α, INF-γ and MCP-1) in heart. Furthermore, we confirmed that AP suppressed the CVB3-induced expression of TLR-4 and phosphorylated NF-κB p65 in heart. Taken together, the data suggest that AP protects against CVB3-induced myocardial damage and inflammation, which may partly attribute to the regulation of TLR-4/NF-κB p65 signal pathway, moreover, suppressive effect of AP on CVB3-induced activation of TLR-4/NF-κB p65 signal was TNF-α-independent.

The coagulation system in host defense

The blood coagulation system and immune system of higher organisms are thought to have a common ancestral origin. During infections, the blood coagulation system is activated and components of the hemostatic system are directly involved in the immune response and immune system modulations. The current view is that the activation of coagulation is beneficial for infections with bacteria and viruses. It limits pathogen dissemination and supports pathogen killing and tissue repair. On the other hand, over-activation can lead to thrombosis with subsequent depletion of hemostatic factors and secondary bleeding. This review will summarize the current knowledge on blood coagulation and pathogen infection with focus on most recent studies of the role of the different parts of the blood coagulation system in selected bacterial and viral infections.

Advances in Clinical and Basic Science of Coagulation: Illustrated abstracts of the 9th Chapel Hill Symposium on Hemostasis

This 9th Symposium on Hemostasis is an international scientific meeting held biannually in Chapel Hill, North Carolina. The meeting is in large measure the result of the close friendship between the late Dr. Harold R. Roberts of UNC Chapel Hill and Dr. Ulla Hedner of Novo Nordisk. When Novo Nordisk was developing the hemophilia therapy that would become NovoSeven, they sponsored a series of meetings to understand the basic biology and clinical applications of factor VIIa. The first meeting in Chapel Hill was held April 4-6, 2002 with Dr. Roberts as the organizer. Over the years, the conference emphasis has expanded from discussions of factor VIIa and tissue factor to additional topics in hemostasis and thrombosis. This year's meeting includes presentations by internationally renowned speakers that discuss the state-of-the-art on an array of important topics, including von Willebrand factor, engineering advances, coagulation and disease, tissue factor biology, therapeutic advances, and basic clotting factor biology. Included in this review article are illustrated abstracts provided by our speakers, which highlight the main conclusions of each invited talk. This will be the first meeting without Dr. Roberts in attendance, yet his commitment to excellent science and his focus on turning science to patient care are pervasively reflected in the presentations by our speakers.

Proteinase-activated receptor 2 promotes tumor cell proliferation and metastasis by inducing epithelial-mesenchymal transition and predicts poor prognosis in hepatocellular carcinoma

AIM

To clarify the role of proteinase-activated receptor 2 (PAR2) in hepatocellular carcinoma, especially in the process of metastasis.

METHODS

PAR2 expression levels were assessed by qRT-PCR and immunohistochemistry (IHC) in patient tissues and in hepatocellular carcinoma cell lines SMMC-7721 and HepG2. Cell proliferation and metastasis were assessed both in vitro and in vitro. Immunoblotting was carried out to monitor the levels of mitogen-activated protein kinase (MAPK) and epithelial-mesenchymal transition markers.

RESULTS

The prognosis was significantly poorer in patients with high PAR2 levels than in those with low PAR2 levels. Patients with high PAR2 levels had advanced tumor stage (P = 0.001, chi-square test), larger tumor size (P = 0.032, chi-square test), and high microvascular invasion rate (P = 0.037, chi-square test). The proliferation and metastasis ability of SMMC-7721 and HepG2 cells was increased after PAR2 overexpression, while knockdown of PAR2 decreased the proliferation and metastasis ability of SMMC-7721 and HepG2 cells. Knockdown of PAR2 also inhibited hepatocellular carcinoma tumor cell growth and liver metastasis in nude mice. Mechanistically, PAR2 increased the proliferation ability of SMMC-7721 and HepG2 cells via ERK activation. Activated ERK further promoted the epithelial-mesenchymal transition of these cells, which endowed them with enhanced migration and invasion ability.

CONCLUSION

These data suggest that PAR2 plays an important role in the proliferation and metastasis of hepatocellular carcinoma. Therefore, targeting PAR2 may present a favorable target for treatment of this malignancy.

MicroRNA-19a contributes to the epigenetic regulation of tissue factor in diabetes

Background

Diabetes mellitus is characterized by chronic vascular disorder and presents a main risk factor for cardiovascular mortality. In particular, hyperglycaemia and inflammatory cytokines induce vascular circulating tissue factor (TF) that promotes pro-thrombotic conditions in diabetes. It has recently become evident that alterations of the post-transcriptional regulation of TF via specific microRNA(miR)s, such as miR-126, contribute to the pathogenesis of diabetes and its complications. The endothelial miR-19a is involved in vascular homeostasis and atheroprotection. However, its role in diabetes-related thrombogenicity is unknown. Understanding miR-networks regulating procoagulability in diabetes may help to develop new treatment options preventing vascular complications.

Methods and results

Plasma of 44 patients with known diabetes was assessed for the expression of miR-19a, TF protein, TF activity, and markers for vascular inflammation. High miR-19a expression was associated with reduced TF protein, TF-mediated procoagulability, and vascular inflammation based on expression of vascular adhesion molecule-1 and leukocyte count. We found plasma expression of miR-19a to strongly correlate with miR-126. miR-19a reduced the TF expression on mRNA and protein level in human microvascular endothelial cells (HMEC) as well as TF activity in human monocytes (THP-1), while anti-miR-19a increased the TF expression. Interestingly, miR-19a induced VCAM expression in HMEC. However, miR-19a and miR-126 co-transfection reduced total endothelial VCAM expression and exhibited additive inhibition of a luciferase reporter construct containing the F3 3′UTR.

Conclusions

While both miRs have differential functions on endothelial VCAM expression, miR-19a and miR-126 cooperate to exhibit anti-thrombotic properties via regulating vascular TF expression. Modulating the post-transcriptional control of TF in diabetes may provide a future anti-thrombotic and anti-inflammatory therapy.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0678-z) contains supplementary material, which is available to authorized users.

Cardiac Function Remains Impaired Despite Reversible Cardiac Remodeling after Acute Experimental Viral Myocarditis

Background. Infection with Coxsackievirus B3 induces myocarditis. We aimed to compare the acute and chronic phases of viral myocarditis to identify the immediate effects of cardiac inflammation as well as the long-term effects after resolved inflammation on cardiac fibrosis and consequently on cardiac function. Material and Methods. We infected C57BL/6J mice with Coxsackievirus B3 and determined the hemodynamic function 7 as well as 28 days after infection. Subsequently, we analyzed viral burden and viral replication in the cardiac tissue as well as the expression of cytokines and matrix proteins. Furthermore, cardiac fibroblasts were infected with virus to investigate if viral infection alone induces profibrotic signaling. Results. Severe cardiac inflammation was determined and cardiac fibrosis was consistently colocalized with inflammation during the acute phase of myocarditis. Declined cardiac inflammation but no significantly improved hemodynamic function was observed 28 days after infection. Interestingly, cardiac fibrosis declined to basal levels as well. Both cardiac inflammation and fibrosis were reversible, whereas the hemodynamic function remains impaired after healed viral myocarditis in C57BL/6J mice.

MicroRNA-20b suppresses the expression of ZFP-148 in viral myocarditis

Viral myocarditis is a common cardiovascular disease, which seriously endangers the health of people and even leads to sudden unexpected death. MicroRNAs play very important roles in various physical and pathological processes including cardiogenesis and heart diseases. In recent years, miR-20b has been implicated in various diseases such as breast cancer, gastric cancer, hepatocellular carcinoma, cardiovascular diseases. However, the function of miR-20b in the pathological progress of viral myocarditis has not been reported. In this study, we found that miR-20b was up-regulated in mouse heart tissues post Coxsackievirus B3 (CVB3) infection. Bioinformatics analysis identified ZFP-148, a transcription factor that plays essential roles in the regulation of virus replication, is one of the predicted targets of miR-20b. MiR-20b expression was found to be up-regulated and ZFP-148 protein level was markedly repressed during viral myocarditis. Further studies demonstrated that miR-20b directly binds to the 3'-UTR of ZFP-148 and suppresses its translation. Moreover, aberrant expression of miR-20b promoted the expression of anti-apoptosis proteins Bcl-2 and Bcl-xL, suggesting that altered gene expression might promote cardiomyocytes survival in viral myocarditis. Our findings indicated that miR-20b might be a potential therapeutic target for CVB3-induced viral myocarditis and a useful marker for the diagnosis of viral myocarditis.

The Quest for New Approaches in Myocarditis and Inflammatory Cardiomyopathy

Myocarditis is a diverse group of heart-specific immune processes classified by clinical and histopathological manifestations. Up to 40% of dilated cardiomyopathy is associated with inflammation or viral infection. Recent experimental studies revealed complex regulatory roles for several microribonucleic acids and T-cell and macrophage subtypes. Although the prevalence of myocarditis remained stable between 1990 and 2013 at about 22 per 100,000 people, overall mortality from cardiomyopathy and myocarditis has decreased since 2005. The diagnostic and prognostic value of cardiac magnetic resonance has increased with new, higher-sensitivity sequences. Positron emission tomography has emerged as a useful tool for diagnosis of cardiac sarcoidosis. The sensitivity of endomyocardial biopsy may be increased, especially in suspected sarcoidosis, by the use of electrogram guidance to target regions of abnormal signal. Investigational treatments on the basis of mechanistic advances are entering clinical trials. Revised management recommendations regarding athletic participation after acute myocarditis have heightened the importance of early diagnosis.

Protease-Activated Receptor 1 Enhances Poly I:C Induction of the Antiviral Response in Macrophages and Mice

The coagulation cascade is activated during viral infections as part of the host defense system. Coagulation proteases activate cells by cleavage of protease-activated receptors (PARs). Recently, we reported that the activation of PAR-1 enhanced interferon (IFN)β and CXCL10 expression in cardiac fibroblasts and in the hearts of mice infected with Coxsackievirus B3. In this study, we used the double-stranded RNA mimetic polyinosinic:polycytidylic acid (poly I:C) to induce an antiviral response in macrophages and mice. Activation of PAR-1 enhanced poly I:C induction of IFNβ and CXCL10 expression in the murine macrophage cell line RAW264.7, bone-marrow derived mouse macrophages (BMM) and mouse splenocytes. Next, poly I:C was used to induce a type I IFN innate immune response in the spleen and plasma of wild-type (WT) and PAR-1-/- mice. We found that poly I:C treated PAR-1-/- mice and WT mice given the thrombin inhibitor dabigatran etexilate exhibited significantly less IFNβ and CXCL10 expression in the spleen and plasma than WT mice. These studies suggest that thrombin activation of PAR-1 contributes to the antiviral response in mice.

Coxsackievirus B3 Induces Autophagic Response in Cardiac Myocytes in vivo

Viral myocarditis is a common disease that contributes to dilated cardiomyopathy or heart failure. Coxsackievirus B (CVB) is one of the major causative pathogens of viral myocarditis. Previous studies have shown that autophagy is exploited to promote CVB replication in cell lines. To study whether cardiac myocytes respond to CVB infection in a similar way, viral myocarditis was established by the inoculation of 3-week-old BALB/c mice with CVB3. Electron microscopic observation showed that autophagosome-like vesicles were induced in the cardiac myocytes of mice infected by CVB3 at 3, 5, and 7 days after viral infection. The lipidated microtubule-associated protein 1 light chain 3 (LC3), LC3-II, was also significantly increased in both myocardium and the cardiac myocytes extracted from the ventricles of mice infected with CVB3. The increased LC3-II coincided with high level of viral RNA and proteins in both myocardium and isolated cardiac myocytes. Moreover, viral protein synthesis was significantly decreased in primary cardiac myocytes by the treatment with 3-methyladenine, an inhibitor of autophagy. The expression and the phosphorylation of extracellular signal regulated kinase (ERK) were also increased in both myocardium and in the isolated cardiac myocytes of the virus-infected mice, while the interplay of ERK with autophagic response remains to be studied. This study demonstrated that cardiac myocytes respond to CVB3 infection by increased formation of autophagosomes in vivo, which might be exploited for viral replication.

Platelets and coagulation in infection

Disseminated intravascular coagulation (DIC) is a frequent complication in sepsis that is associated with worse outcomes and higher mortality in patients. In addition to the uncontrolled generation of thrombi throughout the patient's vasculature, DIC often consumes large quantities of clotting factors leaving the patient susceptible to hemorrhaging. Owing to these complications, patients often receive anticoagulants to treat the uncontrolled clotting, often with mixed outcomes. This lack of success with the current array of anticoagulants can be partly explained by the fact that during sepsis clotting is often initiated by the immune system. Systemic inflammation has the capacity to activate and amplify coagulation and, as such, potential therapies for the treatment of sepsis-associated DIC need to address the interaction between inflammation and coagulation. Recent studies have suggested that platelets and neutrophil extracellular traps (NETs) are the key mediators of infection-induced coagulation. This review explores current anticoagulant therapies and discusses the development of future therapies to target platelet and NET-mediated coagulation.

Nicotinamide phosphoribosyltransferase/pre-B-cell colony enhancing factor/visfatin plasma levels and clinical outcome in patients with dilated cardiomyopathy

BACKGROUND

Nicotinamide phosphoribosyltransferase (Nampt) is an enzyme involved in nicotinamide adenine dinucleotide biosynthesis. Nampt functions as gatekeeper of energy status and survival in cardiac myocytes in animal models of ischemia-reperfusion and might regulate inflammatory processes. Therefore, we performed for the 1st time a clinical study to determine the effects of Nampt on cardiac function in patients with nonischemic dilated (DCM) and inflammatory (DCMi) cardiomyopathy.

METHODS AND RESULTS

A total of 113 patients were enrolled in the study and classified into control (n = 25), DCM (n = 38), and DCMi (n = 50) groups. Cardiac functional and inflammatory parameters as well as plasma Nampt and cardiac mRNA and protein Nampt expression were determined at baseline and follow-up after 6 months. Patients with DCM (1.04 ± 0.8 ng/mL; P < .001) and DCMi (1.07 ± 0.7 ng/mL; P < .001) showed significantly increased Nampt plasma concentrations at baseline compared with the control group (0.57 ± 0.5 ng/mL). Patients with higher Nampt concentrations in both heart failure groups showed significant better improvement of cardiac functional parameters (correlation between Nampt plasma levels and the change of left ventricular ejection fraction after 6 months: DCM: r = 0.698, P < .001; DCMi: r = 0.503, P < .001). Moreover, cardiac inflammation did not influence Nampt expression, and Nampt concentrations did not modulate cardiac inflammation in DCMi. A multivariate linear regression model revealed high plasma Nampt expression to contribute to better improvement of cardiac function in patients of both heart failure groups. Moreover, heart failure patients with high plasma Nampt levels showed suppressed cardiac TNF-α and IL-6 mRNA expression after 6 months' follow-up as well as lower B-type natriuretic peptide levels compared with heart failure patients with low Nampt plasma concentrations.

CONCLUSIONS

High Nampt expression in patients with nonischemic DCM and DCMi is associated with a favorable outcome and improvement in functional status.

Inhibition of coagulation factor Xa improves myocardial function during CVB3-induced myocarditis

INTRODUCTION

Myocarditis is induced by coxsackievirus B3 (CVB3). Myocardial inflammation is tied to the activation of coagulation. Coagulation factor (F) Xa, a central player in coagulation, activates matrix metalloproteinases (MMP), which modulate the remodeling.

AIMS

In this study, we investigated the effects of pharmacological FXa inhibition on myocardial function, inflammation, and remodeling during a CVB3-induced myocarditis.

METHODS AND RESULTS

Immune cells and matrix proteins were detected by immunohistochemistry. The expression of cytokines was measured by real-time PCR and the activity of MMP-2 by zymography. Left ventricular function was analyzed using microconductance pressure catheter. Treatment with the FXa inhibitor fondaparinux led to an improved left ventricular function in CVB3-induced mice compared to saline-treated controls (dPdtmax: fondaparinux 4632 ± 499.6 vs. saline 3131 ± 374.0 [mmHg/s], P = 0.0503; SV: fondaparinux 33.19 ± 4.893 vs. saline 19.32 ± 2.236 [μL], P < 0.118; CO: fondaparinux 15124 ± 2183 vs. saline 8088 ± 1035 [μL/min], P < 0.05). Therapy with fondaparinux reduced the activity of MMP-2 (fondaparinux 1.208 ± 0.1247 vs. saline 1.565 ± 0.05476, P < 0.05). The collagen type I/III ratio as well as the expression of TIMP-1 was comparable in both infection groups postinfectionem (p.i.), despite an increased infiltration of macrophages into the hearts of mice treated with fondaparinux 8 days p.i. (CD68+: fondaparinux 494.2 ± 64.73 vs. saline 306.9 ± 43.73 [cells/mm(2) ], P < 0.05). Anti-inflammatory CD206-positive M2-type macrophages were increased in the infected hearts after fondaparinux treatment (CD206+: fondaparinux 182.1 ± 18.18 vs. saline 111.6 ± 21.07 [cells/mm(2) ], P < 0.05), whereas CD80-positive M1-type macrophages were comparable in both groups.

CONCLUSION

In conclusion, selective inhibition of FXa improves the left ventricular function during CVB3-induced myocarditis and seems to be associated with an improved myocardial remodeling.

Roles of PAR1 and PAR2 in viral myocarditis

Viral myocarditis is estimated to cause ~20% of sudden death in people under the age of 40. A variety of viruses have been found to cause myocarditis including coxsackievirus B3 (CVB3). Many studies have been performed with CVB3 because there is a mouse model of CVB3-induced myocarditis. Studies have shown that the TLR3-IFNβ pathway plays a central role in the innate immune response to CVB3 infection. Our laboratory studies the role of protease activated receptors (PAR) in different biological responses including viral infection. We examined the effect of a deficiency in either PAR1 or PAR2 on CVB3-induced myocarditis. Interestingly, we found that PAR1 knockout mice had increased cardiac injury whereas PAR2 knockout mice had decreased cardiac injury. Our studies support the notion that PARs modulate the innate immune response and can have both positive and negative effects on TLR-dependent responses.

Cardiac fibroblasts aggravate viral myocarditis: cell specific coxsackievirus B3 replication

Myocarditis is an inflammatory disease caused by viral infection. Different subpopulations of leukocytes enter the cardiac tissue and lead to severe cardiac inflammation associated with myocyte loss and remodeling. Here, we study possible cell sources for viral replication using three compartments of the heart: fibroblasts, cardiomyocytes, and macrophages. We infected C57BL/6j mice with Coxsackievirus B3 (CVB3) and detected increased gene expression of anti-inflammatory and antiviral cytokines in the heart. Subsequently, we infected cardiac fibroblasts, cardiomyocytes, and macrophages with CVB3. Due to viral infection, the expression of TNF-α, IL-6, MCP-1, and IFN-β was significantly increased in cardiac fibroblasts compared to cardiomyocytes or macrophages. We found that in addition to cardiomyocytes cardiac fibroblasts were infected by CVB3 and displayed a higher virus replication (132-fold increase) compared to cardiomyocytes (14-fold increase) between 6 and 24 hours after infection. At higher virus concentrations, macrophages are able to reduce the viral copy number. At low virus concentration a persistent virus infection was determined. Therefore, we suggest that cardiac fibroblasts play an important role in the pathology of CVB3-induced myocarditis and are another important contributor of virus replication aggravating myocarditis.

NK-derived IFN-γ/IL-4 triggers the sexually disparate polarization of macrophages in CVB3-induced myocarditis

Coxsackievirus B3 (CVB3) is a common etiology of myocarditis with an increased morbidity and mortality in males. We previously reported that differential polarization of macrophages contributed to sexually dimorphic susceptibility of mice to CVB3-induced myocarditis. However, the underlying kinetics, impetus as well as the molecular mechanism remain unclear. Here, we demonstrated that myocardial macrophages started to polarize at as early as day 5 post CVB3 infection in both genders of BALB/c mice, with M1 phenotype detected in males and M2a phenotype in females, and this trend was further amplified at day 7 when myocarditis reached peak. In addition, we identified that prevailed IFN-γ in males and dominant IL-4 in females were critical myocardial cytokines for the disparate macrophage polarization, which respectively activated JAK1-STAT1 and JAK3-STAT6 pathways. Strikingly, we found that the main source of IFN-γ and IL-4 cytokines in both genders were myocardial infiltrating NK cells, which differentially secreted cytokines in various microenvironments manifested synergistically by sex hormones and CVB3 infection. Consistently, depletion of NK cells significantly impeded the myocardial macrophage polarization in both genders of CVB3-infected mice. Collectively, these data indicated that myocardial NK-derived IFN-γ/IL-4 was critical for the differential polarization of macrophages in CVB3-induced myocarditis via activating JAK1-STAT1 and JAK3-STAT6 pathways respectively. Our study may help understand the mechanism of sexually differential polarization of macrophages and provide clues for the gender bias in CVB3-induced myocarditis.