CX3CR1 knockout aggravates Coxsackievirus B3-induced myocarditis

Myocarditis and Inflammatory Cardiomyopathy in Dilated Heart Failure

Inflammatory cardiomyopathy is a condition that is characterised by the presence of inflammatory cells in the myocardium, which can lead to a significant deterioration in cardiac function. The etiology of this condition involves multiple factors, both infectious and non-infectious causes. While it is primarily associated with viral infections, other potential causes include bacterial, protozoal, or fungal infections, as well as a wide variety of toxic substances and drugs, and systemic immune-mediated pathological conditions. In spite of comprehensive investigation, the presence of inflammatory cardiomyopathy accompanied by left ventricular dysfunction, heart failure or arrhythmia is indicative of an unfavourable outcome. The reasons for the occurrence of either favourable outcomes, characterised by the absence of residual myocardial injury, or unfavourable outcomes, marked by the development of dilated cardiomyopathy, in patients afflicted by the condition remain to be elucidated. The relative contributions of pathogenic agents, genomic profiles of the host, and environmental factors in disease progression and resolution remain subjects of ongoing discourse. This includes the determination of which viruses function as active inducers and which merely play a bystander role. It remains unknown which changes in the host immune profile are critical in determining the outcome of myocarditis caused by various viruses, including coxsackievirus B3 (CVB3), adenoviruses, parvoviruses B19 and SARS-CoV-2. The objective of this review is unambiguous: to provide a concise summary and comprehensive assessment of the extant evidence on the pathogenesis, diagnosis and treatment of myocarditis and inflammatory cardiomyopathy. Its focus is exclusively on virus-induced and virus-associated myocarditis. In addition, the extant lacunae of knowledge in this field are identified and the extant experimental models are evaluated, with the aim of proposing future directions for the research domain. This includes differential gene expression that regulates iron and lipid and metabolic remodelling. Furthermore, the current state of knowledge regarding the cardiovascular implications of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is also discussed, along with the open questions that remain to be addressed.

CX3C chemokine: Hallmarks of fibrosis and ageing

Fibrosis refers to the progressive tissue lesion process characterized by excessive secretion and deposition of extracellular matrix (ECM). Abnormal fibrous tissue deposition distorts tissue architecture and leads to the progressive loss of organ function. Notably, fibrosis is one of the primary pathological appearances of many end stage illnesses, and is considered as a lethal threat to human health, especially in the elderly with ageing-related diseases. CX3C ligand 1 (CX3CL1) is the only member of chemokine CX3C and binds specifically to CX3C receptor 1 (CX3CR1). Different from other chemokines, CX3CL1 possesses both chemotactic and adhesive activity. CX3CL1/CX3CR1 axis involves in various physiological and pathological processes, and exerts a critical role in cells from the immune system, vascular system, and nervous system etc. Notably, increasing evidence has demonstrated that CX3CL1/CX3CR1 signaling pathway is closely related to the pathological process of fibrosis in multiple tissue and organs. We reviewed the crucial role of CX3CL1/CX3CR1 axis in fibrosis and ageing and systematically summarized the underlying mechanism, which offers prospective strategies of targeting CX3C for the therapy of fibrosis and ageing-related diseases.

Clinical Characteristics and Mechanisms of Acute Myocarditis

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05335928.

Alterations in CX3CL1 Levels and Its Role in Viral Pathogenesis

CX3CL1, also named fractalkine or neurotactin, is the only known member of the CX3C chemokine family that can chemoattract several immune cells. CX3CL1 exists in both membrane-anchored and soluble forms, with each mediating distinct biological activities. CX3CL1 signals are transmitted through its unique receptor, CX3CR1, primarily expressed in the microglia of the central nervous system (CNS). In the CNS, CX3CL1 acts as a regulator of microglia activation in response to brain disorders or inflammation. Recently, there has been a growing interest in the role of CX3CL1 in regulating cell adhesion, chemotaxis, and host immune response in viral infection. Here, we provide a comprehensive review of the changes and function of CX3CL1 in various viral infections, such as human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus, and cytomegalovirus (CMV) infection, to highlight the emerging roles of CX3CL1 in viral infection and associated diseases.

Multitargeted Immunomodulatory Therapy for Viral Myocarditis by Engineered Extracellular Vesicles

Immune regulation therapies are considered promising for treating classically activated macrophage (M1)-driven viral myocarditis (VM). Alternatively, activated macrophage (M2)-derived extracellular vesicles (M2 EVs) have great immunomodulatory potential owing to their ability to reprogram macrophages, but their therapeutic efficacy is hampered by insufficient targeting capacity in vivo. Therefore, we developed cardiac-targeting peptide (CTP) and platelet membrane (PM)-engineered M2 EVs enriched with viral macrophage inflammatory protein-II (vMIP-II), termed CTP/PM-M2 EVsvMIP-II-Lamp2b, to improve the delivery of EVs "cargo" to the heart tissues. In a mouse model of VM, the intravenously injected CTP/PM-M2 EVsvMIP-II-Lamp2b could be carried into the myocardium via CTP, PM, and vMIP-II. In the inflammatory microenvironment, macrophages differentiated from circulating monocytes and macrophages residing in the heart showed enhanced endocytosis rates for CTP/PM-M2 EVsvMIP-II-Lamp2b. Subsequently, CTP/PM-M2 EVsvMIP-II-Lamp2b successfully released functional M2 EVsvMIP-II-Lamp2b into the cytosol, which facilitated the reprogramming of inflammatory M1 macrophages to reparative M2 macrophages. vMIP-II not only helps to increase the targeting ability of M2 EVs but also collaborates with M2 EVs to regulate M1 macrophages in the inflammatory microenvironment and downregulate the levels of multiple chemokine receptors. Finally, the cardiac immune microenvironment was protectively regulated to achieve cardiac repair. Taken together, our findings suggest that CTP-and-PM-engineered M2 EVsvMIP-II-Lamp2b represent an effective means for treating VM and show promise for clinical applications.

Role of immune cells in the pathogenesis of myocarditis

Myocarditis is an inflammatory heart disease that mostly affects young people. Myocarditis involves a complex immune network; however, its detailed pathogenesis is currently unclear. The diversity and plasticity of immune cells, either in the peripheral blood or in the heart, have been partially revealed in a number of previous studies involving patients and several kinds of animal models with myocarditis. It is the complexity of immune cells, rather than one cell type that is the culprit. Thus, recognizing the individual intricacies within immune cells in the context of myocarditis pathogenesis and finding the key intersection of the immune network may help in the diagnosis and treatment of this condition. With the vast amount of cell data gained on myocarditis and the recent application of single-cell sequencing, we summarize the multiple functions of currently recognized key immune cells in the pathogenesis of myocarditis to provide an immune background for subsequent investigations.

GPR15-mediated T cell recruitment during acute viral myocarditis facilitated virus elimination and improved outcome

Viral myocarditis is characterized by infiltration of mononuclear cells essential for virus elimination. GPR15 has been identified as a homing receptor for regulatory T cells in inflammatory intestine diseases, but its role in inflammatory heart diseases is still elusive. Here we show that GPR15 deficiency impairs coxsackievirus B3 elimination, leading to adverse cardiac remodeling and dysfunction. Delayed recruitment of regulatory T cells in GPR15-deficient mice was accompanied by prolonged persistence of cytotoxic and regulatory T cells. In addition, RNA sequencing revealed prolonged inflammatory response and altered chemotaxis in knockout mice. In line, we identified GPR15 and its ligand GPR15L as an important chemokine receptor-ligand pair for the recruitment of regulatory and cytotoxic T cells. In summary, the insufficient virus elimination might be caused by a delayed recruitment of T cells as well as delayed interferon-γ expression, resulting in a prolonged inflammatory response and an adverse outcome in GPR15-deficient mice.

Immune Responses in Checkpoint Myocarditis Across Heart, Blood, and Tumor

Immune checkpoint inhibitors (ICIs) are widely used anti-cancer therapies that can cause morbid and potentially fatal immune-related adverse events (irAEs). ICI-related myocarditis (irMyocarditis) is uncommon but has the highest mortality of any irAE. The pathogenesis of irMyocarditis and its relationship to anti-tumor immunity remain poorly understood. We sought to define immune responses in heart, tumor, and blood during irMyocarditis and identify biomarkers of clinical severity by leveraging single-cell (sc)RNA-seq coupled with T cell receptor (TCR) sequencing, microscopy, and proteomics analysis of 28 irMyocarditis patients and 23 controls. Our analysis of 284,360 cells from heart and blood specimens identified cytotoxic T cells, inflammatory macrophages, conventional dendritic cells (cDCs), and fibroblasts enriched in irMyocarditis heart tissue. Additionally, potentially targetable, pro-inflammatory transcriptional programs were upregulated across multiple cell types. TCR clones enriched in heart and paired tumor tissue were largely non-overlapping, suggesting distinct T cell responses within these tissues. We also identify the presence of cardiac-expanded TCRs in a circulating, cycling CD8 T cell population as a novel peripheral biomarker of fatality. Collectively, these findings highlight critical biology driving irMyocarditis and putative biomarkers for therapeutic intervention.

Sex- and age-related differences in the inflammatory properties of cardiac fibroblasts: impact on the cardiosplenic axis and cardiac fibrosis

Background

Age and sex are prominent risk factors for heart failure and determinants of structural and functional changes of the heart. Cardiac fibroblasts (cFB) are beyond their task as extracellular matrix-producing cells further recognized as inflammation-supporting cells. The present study aimed to evaluate the impact of sex and age on the inflammatory potential of cFB and its impact on the cardiosplenic axis and cardiac fibrosis.

Materials

Left ventricles (LV) of 3- and 12-months old male and female C57BL/6J mice were harvested for immunohistochemistry, immunofluorescence and cFB outgrowth culture and the spleen for flow cytometry. LV-derived cFB and respective supernatants were characterized.

Results

LV-derived cFB from 3-months old male mice exhibited a higher inflammatory capacity, as indicated by a higher gene expression of CC-chemokine ligand (CCL) 2, and CCL7 compared to cFB derived from 3-months old female mice. The resulting higher CCL2/chemokine C-X3-C motif ligand (Cx3CL1) and CCL7/Cx3CL1 protein ratio in cell culture supernatants of 3-months old male vs. female cFB was reflected by a higher migration of Ly6Chigh monocytes towards supernatant from 3-months old male vs. female cFB. In vivo a lower ratio of splenic pro-inflammatory Ly6Chigh to anti-inflammatory Ly6Clow monocytes was found in 3-months old male vs. female mice, suggesting a higher attraction of Ly6Chigh compared to Ly6Clow monocytes towards the heart in male vs. female mice. In agreement, the percentage of pro-inflammatory CD68+ CD206- macrophages was higher in the LV of male vs. female mice at this age, whereas the percentage of anti-inflammatory CD68+ CD206+ macrophages was higher in the LV of 3-months old female mice compared to age-matched male animals. In parallel, the percentage of splenic TGF-β+ cells was higher in both 3- and 12-months old female vs. male mice, as further reflected by the higher pro-fibrotic potential of female vs. male splenocytes at both ages. In addition, female mice displayed a higher total LV collagen content compared to age-matched male mice, whereby collagen content of female cFB was higher compared to male cFB at the age of 12-months.

Conclusion

Age- and sex-dependent differences in cardiac fibrosis and inflammation are related to age- and sex-dependent variations in the inflammatory properties of cardiac fibroblasts.

Noninvasive ultrasound stimulation to treat myocarditis through splenic neuro-immune regulation

BACKGROUND

The cholinergic anti-inflammatory pathway (CAP) has been widely studied to modulate the immune response. Current stimulating strategies are invasive or imprecise. Noninvasive low-intensity pulsed ultrasound (LIPUS) has become increasingly appreciated for targeted neuronal modulation. However, its mechanisms and physiological role on myocarditis remain poorly defined.

METHODS

The mouse model of experimental autoimmune myocarditis was established. Low-intensity pulsed ultrasound was targeted at the spleen to stimulate the spleen nerve. Under different ultrasound parameters, histological tests and molecular biology were performed to observe inflammatory lesions and changes in immune cell subsets in the spleen and heart. In addition, we evaluated the dependence of the spleen nerve and cholinergic anti-inflammatory pathway of low-intensity pulsed ultrasound in treating autoimmune myocarditis in mice through different control groups.

RESULTS

The echocardiography and flow cytometry of splenic or heart infiltrating immune cells revealed that splenic ultrasound could alleviate the immune response, regulate the proportion and function of CD4+ Treg and macrophages by activating cholinergic anti-inflammatory pathway, and finally reduce heart inflammatory injury and improve cardiac remodeling, which is as effective as an acetylcholine receptor agonists GTS-21. Transcriptome sequencing showed significant differential expressed genes due to ultrasound modulation.

CONCLUSIONS

It is worth noting that the ultrasound therapeutic efficacy depends greatly on acoustic pressure and exposure duration, and the effective targeting organ was the spleen but not the heart. This study provides novel insight into the therapeutic potentials of LIPUS, which are essential for its future application.

CX3CL1 deficiency ameliorates inflammation, apoptosis and accelerates osteogenic differentiation, mineralization in LPS-treated MC3T3-E1 cells via its receptor CX3CR1

BACKGROUND

Osteoporosis is a devastating skeletal disease responsible for bone fragility and fracture. CX3C chemokine ligand 1 (CX3CL1) is an inflammatory chemokine which has been identified to possess increased expression in the serum of postmenopausal osteoporotic patients. This paper was to illuminate the impacts of CX3CL1 on inflammation, apoptosis and osteogenic differentiation, mineralization in LPS-treated osteoblasts and investigate the regulatory mechanism.

METHODS

The viability of MC3T3-E1 cells exposed to elevating doses of LPS was detected by CCK-8 assay. CX3CL1 and C-X3-C motif chemokine receptor 1 (CX3CR1) expression were detected by RT-qPCR and western blot. CX3CR1 expression was examined again following CX3CL1 depletion. The binding of CX3CL1 with CX3CR1 was testified through Co-IP assay. In MC3T3-E1 cells co-transduced with CX3CL1 interference and CX3CR1 overexpression plasmids following LPS exposure, cell activity and inflammation were separately estimated via CCK-8 assay and RT-qPCR. Apoptosis was measured by TUNEL assay and western blot. Osteoblast differentiation was evaluated by ALP activity assay, RT-qPCR and western blot. Osteoblast mineralization was assessed by ARS staining, RT-qPCR and western blot. Results The experimental data presented that LPS attenuated the viability and enhanced CX3CL1 and CX3CR1 expression in MC3T3-E1 cells in a dose-dependent manner. CX3CR1 interacted with CX3CL1 and was positively modulated by CX3CL1. The suppressive role of CX3CL1 absence in LPS-evoked viability decrease, inflammation and apoptosis in MC3T3-E1 cells was reversed by CX3CR1 elevation. Besides, CX3CR1 reversed the promoted osteoblast differentiation and mineralization imposed by CX3CL1 interference.

CONCLUSIONS

CX3CL1 knockdown eased inflammation, apoptosis and promoted osteogenic differentiation, mineralization in MC3T3-E1 cells upon LPS exposure through down-regulating CX3CR1.

Colchicine prevents disease progression in viral myocarditis via modulating the NLRP3 inflammasome in the cardiosplenic axis

Aim

The acute phase of a coxsackievirus 3 (CVB3)‐induced myocarditis involves direct toxic cardiac effects and the systemic activation of the immune system, including the cardiosplenic axis. Consequently, the nucleotide‐binding oligomerization domain‐like receptor pyrin domain‐containing‐3 (NLRP3) inflammasome pathway is activated, which plays a role in disease pathogenesis and progression. The anti‐inflammatory drug colchicine exerts its effects, in part, via reducing NLRP3 activity, and has been shown to improve several cardiac diseases, including acute coronary syndrome and pericarditis. The aim of the present study was to evaluate the potential of colchicine to improve experimental CVB3‐induced myocarditis.

Methods and results

C57BL6/j mice were intraperitoneally injected with 1 × 10⁵ plaque forming units of CVB3. After 24 h, mice were treated with colchicine (5 μmol/kg body weight) or phosphate‐buffered saline (PBS) via oral gavage (p.o.). Seven days post infection, cardiac function was haemodynamically characterized via conductance catheter measurements. Blood, the left ventricle (LV) and spleen were harvested for subsequent analyses. In vitro experiments on LV‐derived fibroblasts (FB) and HL‐1 cells were performed to further evaluate the anti‐(fibro)inflammatory and anti‐apoptotic effects of colchicine via gene expression analysis, Sirius Red assay, and flow cytometry. CVB3 + colchicine mice displayed improved LV function compared with CVB3 + PBS mice, paralleled by a 4.7‐fold (P < 0.01) and 1.7‐fold (P < 0.001) reduction in LV CVB3 gene expression and cardiac troponin‐I levels in the serum, respectively. Evaluation of components of the NLRP3 inflammasome revealed an increased percentage of apoptosis‐associated speck‐like protein containing a CARD domain (ASC)‐expressing, caspase‐1‐expressing, and interleukin‐1β‐expressing cells in the myocardium and in the spleen of CVB3 + PBS vs. control mice, which was reduced in CVB3 + colchicine compared with CVB3 + PBS mice. This was accompanied by 1.4‐fold (P < 0.0001), 1.7‐fold (P < 0.0001), and 1.7‐fold (P < 0.0001) lower numbers of cardiac dendritic cells, natural killer cells, and macrophages, respectively, in CVB3 + colchicine compared with CVB3 + PBS mice. A 1.9‐fold (P < 0.05) and 4.6‐fold (P < 0.001) reduced cardiac gene expression of the fibrotic markers, Col1a1 and lysyl oxidase, respectively, was detected in CVB3 + colchicine mice compared with CVB3 + PBS animals, and reflected by a 2.2‐fold (P < 0.05) decreased Collagen I/III protein ratio. Colchicine further reduced Col3a1 mRNA and collagen protein expression in CVB3‐infected FB and lowered apoptosis and viral progeny release in CVB3‐infected HL‐1 cells. In both CVB3 FB and HL‐1 cells, colchicine down‐regulated the NLRP3 inflammasome‐related components ASC, caspase‐1, and IL‐1β.

Conclusions

Colchicine improves LV function in CVB3‐induced myocarditis, involving a decrease in cardiac and splenic NLRP3 inflammasome activity, without exacerbation of CVB3 load.

Early activation of the cardiac CX3CL1/CX3CR1 axis delays β-adrenergic-induced heart failure

We recently highlighted a novel potential protective paracrine role of cardiac myeloid CD11b/c cells improving resistance of adult hypertrophied cardiomyocytes to oxidative stress and potentially delaying evolution towards heart failure (HF) in response to early β-adrenergic stimulation. Here we characterized macrophages (Mφ) in hearts early infused with isoproterenol as compared to control and failing hearts and evaluated the role of upregulated CX3CL1 in cardiac remodeling. Flow cytometry, immunohistology and Mφ-depletion experiments evidenced a transient increase in Mφ number in isoproterenol-infused hearts, proportional to early concentric hypertrophy (ECH) remodeling and limiting HF. Combining transcriptomic and secretomic approaches we characterized Mφ-enriched CD45⁺ cells from ECH hearts as CX3CL1- and TNFα-secreting cells. In-vivo experiments, using intramyocardial injection in ECH hearts of either Cx3cl1 or Cx3cr1 siRNA, or Cx3cr1^−/− knockout mice, identified the CX3CL1/CX3CR1 axis as a protective pathway delaying transition to HF. In-vitro results showed that CX3CL1 not only enhanced ECH Mφ proliferation and expansion but also supported adult cardiomyocyte hypertrophy via a synergistic action with TNFα. Our data underscore the in-vivo transient protective role of the CX3CL1/CX3CR1 axis in ECH remodeling and suggest the participation of CX3CL1-secreting Mφ and their crosstalk with CX3CR1-expressing cardiomyocytes to delay HF.

CX3CR1 Depletion Promotes the Formation of Platelet-Neutrophil Complexes and Aggravates Acute Peritonitis

BACKGROUND

Peritonitis is a life-threatening condition on intensive care units. Inflammatory cytokines and their receptors drive inflammation, cause the formation of platelet-neutrophil complexes (PNCs) and therefore the migration of polymorphonuclear neutrophils (PMNs) into the inflamed tissue. CX3CL1 and its receptor CX3CR1 are expressed in various cells, and promote inflammation. The shedding of CX3CL1 is mediated by a disintegrin and metalloprotease (ADAM) 17. The role of the CX3CL1-CX3CR1 axis in acute peritonitis remains elusive.

METHODS

In zymosan-induced peritonitis, we determined the formation of PNCs in the blood and the expression of PNC-related molecules on PNCs. PMN migration into the peritoneal lavage was evaluated in wild-type (WT) and CX3CR1-/- animals by flow cytometry. CX3CL1, ADAM17, and the expression of various inflammatory cytokines were detected. Further, we determined the inflammation-associated activation of the intracellular transcription factor extracellular signal-regulated kinase 1/2 (ERK1/2) by Western blot.

RESULTS

The PMN accumulation in the peritoneal lavage and the PNC formation in the circulation were significantly raised in CX3CR1-/- compared with WT animals. The expression of PNC-related selectins on PNCs was significantly increased in the blood of CX3CR1-/- animals, as well as cytokine levels. Further, we observed an increased activation of ERK1/2 and elevated ADAM17 expression in CX3CR1-/- during acute inflammation. Selective ERK1/2 inhibition ameliorated inflammation-related increased ADAM17 expression.

CONCLUSIONS

A CX3CR1 deficiency raised the release of inflammatory cytokines and increased the PNC formation respectively PMN migration via an elevated ERK1/2 activation during acute peritonitis. Further, we observed a link between the ERK1/2 activation and an elevated ADAM17 expression on PNC-related platelets and PMNs during inflammation. Our data thus illustrate a crucial role of CX3CR1 on the formation of PNCs and regulating inflammation in acute peritonitis.

Chemokines in cardiac fibrosis

Several members of the chemokine family are involved in regulation of fibrosis. This review manuscript discusses the role of the chemokines in the pathogenesis of myocardial fibrosis. The CC chemokine CCL2 exerts fibrogenic actions through recruitment and activation of monocytes and macrophages expressing its receptor, CCR2. Other CC chemokines may also contribute to fibrotic remodeling by recruiting subsets of fibrogenic macrophages. CXC chemokines containing the ELR motif may exert pro-fibrotic actions, through recruitment of activated neutrophils and subsequent formation of neutrophil extracellular traps (NETs), or via activation of fibrogenic monocytes. CXCL12 has also been suggested to exert fibrogenic actions through effects on fibroblasts and immune cells. In contrast, the CXCR3 ligand CXCL10 was found to reduce cardiac fibrosis, inhibiting fibroblast migration. Chemokines are critical links between inflammation and fibrosis in myocardial disease and may be promising therapeutic targets for patients with heart failure accompanied by prominent inflammation and fibrosis.

Opioid-Induced Immunomodulation: Consequences for the Experimental Coxsackievirus B3-Induced Myocarditis Model

Simple Summary

Myocarditis is an inflammatory disorder of the heart mainly caused by viruses. To investigate viral myocarditis, the Coxsackievirus B3 (CVB3)-induced myocarditis model is the experimental model used since more than sixty years. In the pathogeneses of viral myocarditis, the subtle balance between pro-and anti-inflammatory immune responses is of great importance for disease manifestation. Parallel to the infection of the heart, experimental CVB3-induced myocarditis results in an infection of the pancreas, causing a severe burden for the challenged animals. In frame of animal welfare, application of analgesics is mandatory. So far, positive as well as negative effects of opioids on the immune system have been described. However, the impact of opioid application on the pathogenesis of experimental CVB3-induced myocarditis has not been investigated yet. Since examinations on disease pathways and new treatment options rely on established models to generate reproducible data, applicability of opioids in experimental CVB3-induced myocarditis needs to be carefully evaluated. For this purpose, we summarized published studies for 13 different opioids and discussed their potential impact on the CVB3-induced myocarditis model.

Abstract

Myocarditis is an inflammatory disorder of the heart predominantly caused by infectious agents. Since more than sixty years, the Coxsackievirus B3 (CVB3)-induced myocarditis mouse model is the experimental model used to investigate viral myocarditis. The pathogenesis of viral myocarditis is conceptually a multiphase process, initiated by the infection of cardiomyocytes, followed by activation of the immune system, and resulting in myocardial fibrosis and left ventricular dysfunction. In parallel to the direct infection of the heart, CVB3 replicates in lymphatic organs such as the pancreas. Due to infection of the pancreas, the model of experimental CVB3-induced myocarditis is estimated as a severe burden for the challenged animals. Application of analgesics in frame of the animal welfare act (European directive 2010/63/EU) is more and more becoming a matter of debate. For this purpose, we summarized published studies for 13 different opioids and discussed their potential impact on CVB3-induced myocarditis. In addition, with this summary we also want to provide guidance for researchers beyond the myocarditis field to estimate the impact of opioids on the immune system for their specific model. In the literature, both immunosuppressive as well as immune-activating effects of opioids have been described, but examinations in experimental CVB3-induced myocarditis have still not been reported so far. Based on the existing publications, administration of opioids in experimental CVB3-induced myocarditis might result in more severe disease progression, including higher mortality, or a less pronounced myocarditis model, failing to be used for the establishment of new treatment options. Taken together, the applicability of opioids in experimental CVB3-induced myocarditis and in inflammatory models in general needs to be carefully evaluated and further investigated.

Myocarditis and inflammatory cardiomyopathy: current evidence and future directions

Inflammatory cardiomyopathy, characterized by inflammatory cell infiltration into the myocardium and a high risk of deteriorating cardiac function, has a heterogeneous aetiology. Inflammatory cardiomyopathy is predominantly mediated by viral infection, but can also be induced by bacterial, protozoal or fungal infections as well as a wide variety of toxic substances and drugs and systemic immune-mediated diseases. Despite extensive research, inflammatory cardiomyopathy complicated by left ventricular dysfunction, heart failure or arrhythmia is associated with a poor prognosis. At present, the reason why some patients recover without residual myocardial injury whereas others develop dilated cardiomyopathy is unclear. The relative roles of the pathogen, host genomics and environmental factors in disease progression and healing are still under discussion, including which viruses are active inducers and which are only bystanders. As a consequence, treatment strategies are not well established. In this Review, we summarize and evaluate the available evidence on the pathogenesis, diagnosis and treatment of myocarditis and inflammatory cardiomyopathy, with a special focus on virus-induced and virus-associated myocarditis. Furthermore, we identify knowledge gaps, appraise the available experimental models and propose future directions for the field. The current knowledge and open questions regarding the cardiovascular effects associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are also discussed. This Review is the result of scientific cooperation of members of the Heart Failure Association of the ESC, the Heart Failure Society of America and the Japanese Heart Failure Society.

Advancement of Mechanisms of Coxsackie Virus B3-Induced Myocarditis Pathogenesis and the Potential Therapeutic Targets

Viral myocarditis is a cardiac disease caused by Group B Coxsackie virus of Enterovirus genus in the Picorna viridae family. It causes heart failure in children, young and adults. Ten Percent (10%) of acute heart failure and 12% of sudden deaths in young and adults who are less than 40 years is due to this viral myocarditis. If treatment action is not taken earlier, the viral disease can develop into chronic myocarditis and Dilated Cardiomyopathy which lead to congestive heart failure. And these eventually result in a reduced cardiac function which finally brings the victim to death. The only treatment option of the disease is heart transplantation once the acute stage of disease develops to chronic and Dilated Cardiomyopathy. Currently, there is a limitation in daily clinical treatments and even some available treatment options are ineffective. Therefore, focusing on search for treatment options through investigation is imperative. Recent studies have reported that biological molecules show a promising role. But their mechanism of pathogenesis is still unclear. A detailed study on identifying the role of biological molecules involved in Coxsackie B3 virus induced myocarditis and their mechanisms of pathogenesis; compiling and disseminating the findings of the investigation to the scientific communities contribute one step forward to the solution. Therefore, this review is aimed at compiling information from findings of current studies on the potential therapeutic role of micro RNA, cytokines and chemokines on the mechanism of pathogenesis of Coxsackie virus B3- induced myocarditis to give brief information for scholars to conduct a detailed study in the area.

Modulation of the acute defence reaction by eplerenone prevents cardiac disease progression in viral myocarditis

Aims

Left ventricular (LV) dysfunction in viral myocarditis is attributed to myocardial inflammation and fibrosis, inducing acute and long‐time cardiac damage. Interventions are not established. On the basis of the link between inflammation, fibrosis, aldosterone, and extracellular matrix regulation, we aimed to investigate the effect of an early intervention with the mineralocorticoid receptor antagonist (MRA) eplerenone on cardiac remodelling in a murine model of persistent coxsackievirus B3 (CVB3)‐induced myocarditis.

Methods and results

SWR/J mice were infected with 5 × 10⁴ plaque‐forming units of CVB3 (Nancy strain) and daily treated either with eplerenone (200 mg/kg body weight) or with placebo starting from Day 1. At Day 8 or 28 post infection, mice were haemodynamically characterized and subsequently sacrificed for immunohistological and molecular biology analyses. Eplerenone did not influence CVB3 load. Already at Day 8, 1.8‐fold (P < 0.05), 1.4‐fold (P < 0.05), 3.2‐fold (P < 0.01), and 2.1‐fold (P < 0.001) reduction in LV intercellular adhesion molecule 1 expression, presence of monocytes/macrophages, oxidative stress, and apoptosis, respectively, was observed in eplerenone‐treated vs. untreated CVB3‐infected mice. In vitro, eplerenone led to 1.4‐fold (P < 0.01) and 1.2‐fold (P < 0.01) less CVB3‐induced cardiomyocyte oxidative stress and apoptosis. Furthermore, collagen production was 1.1‐fold (P < 0.05) decreased in cardiac fibroblasts cultured with medium of eplerenone‐treated vs. untreated CVB3‐infected HL‐1 cardiomyocytes. These ameliorations were in vivo translated into prevention of cardiac fibrosis, as shown by 1.4‐fold (P < 0.01) and 2.1‐fold (P < 0.001) lower collagen content in the LV of eplerenone‐treated vs. untreated CVB3‐infected mice at Days 8 and 28, respectively. This resulted in an early and long‐lasting improvement of LV dimension and function, as indicated by reduced LV end‐systolic volume and end‐diastolic volume, and an increase in LV contractility (dP/dt_max) and LV relaxation (dP/dt_min), respectively (P < 0.05).

Conclusions

Early intervention with the MRA eplerenone modulates the acute host and defence reaction and prevents cardiac disease progression in experimental CVB3‐induced myocarditis without aggravation of viral load. The findings advocate for an initiation of therapy of viral myocarditis as early as possible, even before the onset of inflammation‐induced myocardial dysfunction. This may also have implications for coronavirus disease‐19 therapy.

A Toolbox of Potential Immune-Related Therapies for Inflammatory Cardiomyopathy

Myocarditis is a multifactorial disorder, characterized by an inflammatory reaction in the myocardium, predominantly triggered by infectious agents, but also by antigen mimicry or autoimmunity in susceptible individuals. Unless spontaneously resolved, a chronic inflammatory course concludes with cardiac muscle dysfunction portrayed by ventricular dilatation, clinically termed inflammatory cardiomyopathy (Infl-CM). Treatment strategies aim to resolve chronic inflammation and preserve cardiac function. Beside standard heart failure treatments, which only play a supportive role in this condition, systemic immunosuppressants are used to diminish inflammatory cell function at the cost of noxious side effects. To date, the treatment protocols are expert-based without large clinical evidence. This review describes concept and contemporary strategies to alleviate myocardial inflammation and sheds light on potential inflammatory targets in an evidence-based order.

Stimulating pro-reparative immune responses to prevent adverse cardiac remodelling: consensus document from the joint 2019 meeting of the ESC Working Groups of cellular biology of the heart and myocardial function

Cardiac injury may have multiple causes, including ischaemic, non-ischaemic, autoimmune, and infectious triggers. Independent of the underlying pathophysiology, cardiac tissue damage induces an inflammatory response to initiate repair processes. Immune cells are recruited to the heart to remove dead cardiomyocytes, which is essential for cardiac healing. Insufficient clearance of dying cardiomyocytes after myocardial infarction (MI) has been shown to promote unfavourable cardiac remodelling, which may result in heart failure (HF). Although immune cells are integral key players of cardiac healing, an unbalanced or unresolved immune reaction aggravates tissue damage that triggers maladaptive remodelling and HF. Neutrophils and macrophages are involved in both, inflammatory as well as reparative processes. Stimulating the resolution of cardiac inflammation seems to be an attractive therapeutic strategy to prevent adverse remodelling. Along with numerous experimental studies, the promising outcomes from recent clinical trials testing canakinumab or colchicine in patients with MI are boosting the interest in novel therapies targeting inflammation in cardiovascular disease patients. The aim of this review is to discuss recent experimental studies that provide new insights into the signalling pathways and local regulators within the cardiac microenvironment promoting the resolution of inflammation and tissue regeneration. We will cover ischaemia- and non-ischaemic-induced as well as infection-related cardiac remodelling and address potential targets to prevent adverse cardiac remodelling.

Picornavirus Cellular Remodeling: Doubling Down in Response to Viral-Induced Inflammation

Purpose of Review

To highlight recent findings on how picornavirus infections of the airways and cardiac tissues impact cellular inflammation and remodeling events.

Recent Findings

Recent published work has revealed that although many picornavirus infections appear to be initially asymptomatic, there are significant disease sequelae that result from chronic or persistent infections and the long-term, pathogenic effects on host tissues.

Summary

Because many acute picornavirus infections are asymptomatic, it is difficult to diagnose these pathologies at the early stages of disease. As a result, we must rely on preventative measures (i.e., vaccination) or discover novel treatments to reverse tissue damage and remodeling in affected individuals. Both of these strategies will require a comprehensive knowledge of virus-and cell-specific replication determinants and how these processes induce pathogenic effects in infected cells and tissues.

Management of Myocarditis-Related Cardiomyopathy in Adults

Myocarditis is generally a mild and self-limited consequence of systemic infection of cardiotropic viruses. However, patients can develop a temporary or permanent impairment of cardiac function including acute cardiomyopathy with hemodynamic compromise or severe arrhythmias. In this setting, specific causes of inflammation are associated with variable risks of death and transplantation. Recent translational studies suggest that treatments tailored to specific causes of myocarditis may impact clinical outcomes when added to guideline-directed medical care. This review summarizes recent advances in translational research that influence the utility of endomyocardial biopsy for the management of inflammatory cardiomyopathies. Emerging therapies for myocarditis based on these mechanistic hypotheses are entering clinical trials and may add to the benefits of established heart failure treatment.

The Macrophage in Cardiac Homeostasis and Disease: JACC Macrophage in CVD Series (Part 4)

Macrophages are integral components of cardiac tissue and exert profound effects on the healthy and diseased heart. Paradigm shifting studies using advanced molecular techniques have revealed significant complexity within these macrophage populations that reside in the heart. In this final of a 4-part review series covering the macrophage in cardiovascular disease, the authors review the origins, dynamics, cell surface markers, and respective functions of each cardiac macrophage subset identified to date, including in the specific scenarios of myocarditis and after myocardial infarction. Looking ahead, a deeper understanding of the diverse and often dichotomous functions of cardiac macrophages will be essential for the development of targeted therapies to mitigate injury and orchestrate recovery of the diseased heart. Moreover, as macrophages are critical for cardiac healing, they are an emerging focus for therapeutic strategies aimed at minimizing cardiomyocyte death, ameliorating pathological cardiac remodeling, and for treating heart failure and after myocardial infarction.

Viral myocarditis: a prime example for endomyocardial biopsy-guided diagnosis and therapy

Purpose of review

Myocarditis is an inflammatory disease of the cardiac muscle mainly caused by viral infection. Due to the diverse clinical presentation of myocarditis, accurate diagnosis demands simultaneous histologic, immunohistochemical and molecular biological workup of endomyocardial biopsies (EMBs) as defined by the position statement of the Working Group on Myocardial and Pericardial Diseases of the European Society of Cardiology on myocarditis.

Recent findings

Endomyocardial biopsy-based analysis of viral transcriptional activity, mRNA expression, epigenetics and region-specific protein expression analysis via imaging mass spectrometry have led to the identification of novel potential diagnostic criteria, markers with prognostic value and therapeutic targets for the treatment of viral myocarditis, opening new avenues for novel therapies, including cell therapies, as well as the use of established treatment options, be it from other indications.

Summary

Under certain clinical scenarios EMB-based analysis is required to come to a tailored individualized therapy that improves symptoms and prognosis of patients with acute and chronic viral-driven cardiac inflammation.

Posttranslational modifications of titin from cardiac muscle: how, where, and what for?

Titin is a giant elastic protein expressed in the contractile units of striated muscle cells, including the sarcomeres of cardiomyocytes. The last decade has seen enormous progress in our understanding of how titin molecular elasticity is modulated in a dynamic manner to help cardiac sarcomeres adjust to the varying hemodynamic demands on the heart. Crucial events mediating the rapid modulation of cardiac titin stiffness are post‐translational modifications (PTMs) of titin. In this review, we first recollect what is known from earlier and recent work on the molecular mechanisms of titin extensibility and force generation. The main goal then is to provide a comprehensive overview of current insight into the relationship between titin PTMs and cardiomyocyte stiffness, notably the effect of oxidation and phosphorylation of titin spring segments on titin stiffness. A synopsis is given of which type of oxidative titin modification can cause which effect on titin stiffness. A large part of the review then covers the mechanically relevant phosphorylation sites in titin, their location along the elastic segment, and the protein kinases and phosphatases known to target these sites. We also include a detailed coverage of the complex changes in phosphorylation at specific titin residues, which have been reported in both animal models of heart disease and in human heart failure, and their correlation with titin‐based stiffness alterations. Knowledge of the relationship between titin PTMs and titin elasticity can be exploited in the search for therapeutic approaches aimed at softening the pathologically stiffened myocardium in heart failure patients.

Mechanical Unloading by Fulminant Myocarditis: LV-IMPELLA, ECMELLA, BI-PELLA, and PROPELLA Concepts

Mechanical circulatory support (MCS) is often required to stabilize patients with acute fulminant myocarditis with cardiogenic shock. This review gives an overview of the successful use of left-sided Impella in the setting of fulminant myocarditis and cardiogenic shock as the sole means of MCS as well as in combination with right ventricular (RV) support devices including extracorporeal life support (ECLS) (ECMELLA) or an Impella RP (BI-PELLA). It further provides evidence from endomyocardial biopsies that in addition to giving adequate support, LV unloading by Impella exhibits disease-modifying effects important for myocardial recovery (i.e., bridge-to-recovery) achieved by this newly termed “prolonged Impella” (PROPELLA) concept in which LV-IMPELLA 5.0, implanted via an axillary approach, provides support in awake, mobilized patients for several weeks. Finally, this review addresses the question of how to define the appropriate time point for weaning strategies and for changing or discontinuing unloading in fulminant myocarditis.

Immunomodulation by adoptive regulatory T-cell transfer improves Coxsackievirus B3-induced myocarditis

Regulatory T (Treg) cells offer new therapeutic options for controlling undesired systemic and local immune responses. The aim of the current study was to determine the impact of therapeutic Treg administration on systemic and cardiac inflammation and remodeling in coxsackievirus B3 (CVB3) -induced myocarditis. Therefore, syngeneic Treg cells were applied intravenously in CVB3-infected mice 3 d after infection. Compared with CVB3 + PBS mice, CVB3 + Treg mice exhibited lower left ventricular (LV) chemokine expression, accompanied by reduced cardiac presence of proinflammatory Ly6ChighCCR2highCx3Cr1low monocytes and higher retention of proinflammatory Ly6CmidCCR2highCx3Cr1low monocytes in the spleen. In addition, splenic myelopoiesis was reduced in CVB3 + Treg compared with CVB3 + PBS mice. Coculture of Treg cells with splenocytes isolated from mice 3 d post-CVB3 infection further demonstrated the ability of Treg cells to modulate monocyte differentiation in favor of the anti-inflammatory Ly6ClowCCR2lowCx3Cr1high subset. Treg-mediated immunomodulation was paralleled by lower collagen 1 protein expression and decreased levels of soluble and insoluble collagen in LV of CVB3 + Treg compared with CVB3 + PBS mice. In agreement with these findings, LV systolic and diastolic function was improved in CVB3 + Treg mice compared with CVB3 + PBS mice. In summary, adoptive Treg transfer in the inflammatory phase of viral-induced myocarditis protects the heart against inflammatory damage and fibrosis via modulation of monocyte subsets.-Pappritz, K., Savvatis, K., Miteva, K., Kerim, B., Dong, F., Fechner, H., Müller, I., Brandt, C., Lopez, B., González, A., Ravassa, S., Klingel, K., Diez, J., Reinke, P., Volk, H.-D., Van Linthout, S., Tschöpe, C. Immunomodulation by adoptive regulatory T-cell transfer improves Coxsackievirus B3-induced myocarditis.

Cardiac (myo)fibroblasts modulate the migration of monocyte subsets

Cardiac fibroblasts play an important role in the regulation of the extracellular matrix and are newly recognized as inflammatory supporter cells. Interferon (IFN)-γ is known to counteract transforming growth factor (TGF)-ß1-induced myofibroblast differentiation. This study aims at investigating in vitro how IFN-γ affects TGF-ß1-induced monocyte attraction. Therefore, C4 fibroblasts and fibroblasts obtained by outgrowth culture from the left ventricle (LV) of male C57BL6/j mice were stimulated with TGF-β1, IFN-γ and TGF-β1 + IFN-γ. Confirming previous studies, IFN-γ decreased the TGF-ß1-induced myofibroblast differentiation, as obviated by lower collagen I, III, α-smooth muscle actin (α-SMA), lysyl oxidase (Lox)-1 and lysyl oxidase-like (LoxL)-2 levels in TGF-β1 + IFN-γ- versus TGF-ß1-stimulated cardiac fibroblasts. TGF-β1 + IFN-γ-stimulated C4 and cardiac fibroblasts displayed a higher CC-chemokine ligand (CCL) 2, CCL7 and chemokine C-X3-C motif ligand (Cx3CL1) release versus sole TGF-ß1-stimulated fibroblasts. Analysis of migrated monocyte subsets towards the different conditioned media further revealed that sole TGF-β1- and IFN-γ-conditioned media particularly attracted Ly6C^low and Ly6C^high monocytes, respectively, as compared to control media. In line with theses findings, TGF-β1 + IFN-γ-conditioned media led to a lower Ly6C^low/Ly6C^high monocyte migration ratio compared to sole TGF-ß1 treatment. These differences in monocyte migration reflect the complex interplay of pro-inflammatory cytokines and pro-fibrotic factors in cardiac remodelling and inflammation.

Pathogenic Role of the Damage-Associated Molecular Patterns S100A8 and S100A9 in Coxsackievirus B3-Induced Myocarditis

BACKGROUND

The alarmins S100A8 and S100A9 are damage-associated molecular patterns, which play a pivotal role in cardiovascular diseases, inflammation, and viral infections. We aimed to investigate their role in Coxsackievirus B3 (CVB3)-induced myocarditis.

METHODS AND RESULTS

S100A8 and S100A9 mRNA expression was 13.0-fold (P=0.012) and 5.1-fold (P=0.038) higher in endomyocardial biopsies from patients with CVB3-positive myocarditis compared with controls, respectively. Elimination of CVB3 led to a downregulation of these alarmins. CVB3-infected mice developed an impaired left ventricular function and displayed an increased left ventricular S100A8 and S100A9 protein expression versus controls. In contrast, CVB3-infected S100A9 knockout mice, which are also a complete knockout for S100A8 on protein level, showed an improved left ventricular function, which was associated with a reduced cardiac inflammatory and oxidative response, and lower CVB3 copy number compared with wild-type CVB3 mice. Exogenous application of S100A8 to S100A9 knockout CVB3 mice induced a severe myocarditis similar to wild-type CVB3 mice. In CVB3-infected HL-1 cells, S100A8 and S100A9 enhanced oxidative stress and CVB3 copy number compared with unstimulated infected cells. In CVB3-infected RAW macrophages, both alarmins increased MIP-2 (macrophage inflammatory protein-2) chemokine expression, which was reduced in CVB3 S100A8 knockdown versus scrambled siRNA CVB3 cells.

CONCLUSIONS

S100A8 and S100A9 aggravate CVB3-induced myocarditis and might serve as therapeutic targets in inflammatory cardiomyopathies.