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The emergence of immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, but these drugs can also cause severe immune-related adverse effects (irAEs), including myocarditis. Researchers have become interested in exploring ways to mitigate this side effect, and one promising avenue is the use of baricitinib, a Janus kinase inhibitor known to have anti-inflammatory properties. This study aimed to examine the potential mechanism by which baricitinib in ICIs-related myocarditis. To establish an ICIs-related myocarditis model, BALB/c mice were administered murine cardiac troponin I (cTnI) peptide and anti-mouse programmed death 1 (PD-1) antibodies. Subsequently, baricitinib was administered to the mice via intragastric administration. Echocardiography, HE staining, and Masson staining were performed to evaluate myocardial functions, inflammation, and fibrosis. Immunofluorescence was used to detect macrophages in the cardiac tissue of the mice.In vitro experiments utilized raw264.7 cells to induce macrophage polarization using anti-PD-1 antibodies. Different concentrations of baricitinib were applied to assess cell viability, and the release of pro-inflammatory cytokines was measured. The activation of the JAK1/STAT3 signaling pathway was evaluated through western blot analysis. Baricitinib demonstrated its ability to improve cardiac function and reduce cardiac inflammation, as well as fibrosis induced by ICIs. Mechanistically, baricitinib treatment promoted the polarization of macrophages towards the M2 phenotype. In vitro and in vivo experiments showed that anti-PD-1 promoted the release of inflammatory factors. However, treatment with baricitinib significantly inhibited the phosphorylation of JAK1 and STAT3. Additionally, the use of RO8191 reversed the effects of baricitinib, further confirming our findings. Baricitinib demonstrated its potential as a protective agent against ICIs-related myocarditis by modulating macrophage polarization. These findings provide a solid theoretical foundation for the development of future treatments for ICIs-related myocarditis. [ABSTRACT FROM AUTHOR]

• Myocarditis, a long-term complication of coronavirus disease 2019 (COVID-19) is an inflammatory condition involving the myocardium of the heart. The interplay among long COVID, immune cells, and autoimmunity in the pathogenesis of myocarditis is still not clear. However, the pathogenesis of long COVID myocarditis involving ACE2 receptor and COVID-19 spike protein is widely accepted. • A comprehensive understanding of the biomarkers involved is necessary for the development of pathogenesis-based therapies and the repurposing of the already available therapies. Various biomarkers including troponin, lactate dehydrogenase (LDH), C-reactive protein (CRP), procalcitonin, galectin-3 (GAL-3), growth differentiation factor 15 (GDF-15), presepsin, soluble suppression of tumorigenicity (sST2), copeptin, and interleukins, are helpful in the diagnosis and prognosis of long COVID myocarditis. • Invasive techniques like endomyocardial biopsy (EMB) and non-invasive techniques like transthoracic echocardiography (TTE), cardiac magnetic resonance imaging (MRI) are also beneficial in the management. • The current available treatments include glucocorticoids, intravenous immunoglobins (IVIG), interleukin antagonists, rituximab, colchicine, and aldose reductase inhibitor AT001, along with inotropes and oxygen support. Despite these therapies, reports of mortality in several studies despite treatment with these drugs, imply the importance of discovering new treatment strategies. Hence, it is recommended that further research must be carried out in patients with myocarditis. Infectious diseases are a cause of major concern in this twenty-first century. There have been reports of various outbreaks like severe acute respiratory syndrome (SARS) in 2003, swine flu in 2009, Zika virus disease in 2015, and Middle East Respiratory Syndrome (MERS) in 2012, since the start of this millennium. In addition to these outbreaks, the latest infectious disease to result in an outbreak is the SARS-CoV-2 infection. A viral infection recognized as a respiratory illness at the time of emergence, SARS-CoV-2 has wreaked havoc worldwide because of its long-lasting implications like heart failure, sepsis, organ failure, etc., and its significant impact on the global economy. Besides the acute illness, it also leads to symptoms months later which is called long COVID or post-COVID-19 condition. Due to its ever-increasing prevalence, it has been a significant challenge to treat the affected individuals and manage the complications as well. Myocarditis, a long-term complication of coronavirus disease 2019 (COVID-19) is an inflammatory condition involving the myocardium of the heart, which could even be fatal in the long term in cases of progression to ventricular dysfunction and heart failure. Thus, it is imperative to diagnose early and treat this condition in the affected individuals. At present, there are numerous studies which are in progress, investigating patients with COVID-19-related myocarditis and the treatment strategies. This review focuses primarily on myocarditis, a life-threatening complication of COVID-19 illness, and endeavors to elucidate the pathogenesis, biomarkers, and management of long COVID myocarditis along with pipeline drugs in detail. [ABSTRACT FROM AUTHOR]

Abstract Background Adiponectin is a hormone that together with its receptors modulates a number of metabolic processes including gluconeogenesis and lipid catabolism. It belongs to the C1QTNF (complement C1q tumor necrosis factor-related protein) family, which has a variety of members with high amino acid sequence homology and overlapping functions. Concentration of adiponectin in blood is inversely correlated with body fat percentage and cardiac risk factors like blood pressure and CRP (C-reactive protein) level. Studies have identified the existence of a cardiac adiponectin system. However, little is known about the role of this system in the pathogenesis of autoimmune myocarditis. Thus, we have studied the involvement of adiponectin in the development of this autoimmune disorder in a mouse model of experimental autoimmune myocarditis (EAM). Methods Adiponectin knockout (ko) and wild type (wt) mice were immunized with cardiac troponin I (cTnI) to induce an EAM. To determine the severity of myocardial damage, inflammation and fibrosis were scored after HE and Afog staining and high sensitivity troponin T (hsTnT) level was measured. To detect if changes in specific inflammatory cell numbers could be observed between the genotypes, we performed immunohistochemical staining to detect T lymphocytes, B lymphocytes and macrophages. The level of the humoral immune response was determined through the measurement of cTnI-specific serum IgG autoantibodies. Relative mRNA expression of different cytokines, C1QTNF family members and adiponectin receptors in the heart tissue was analyzed with qPCR. Results Animals immunized with cTnI developed autoimmune myocarditis with a significant deterioration of cardiac parameters compared to the corresponding control group. The adiponectin ko group immunized with cTnI showed a tendency towards increased inflammation, fibrosis, heart-to-body-weight ratio, infiltration pattern of T lymphocytes, B lymphocytes and macrophages, hsTnT concentration, humoral immune response and mRNA expression of interleukin 6 in the heart tissue and decreased weight gain compared to the wt group immunized with cTnI. However, the difference to the wt group treated with cTnI was not significant. The analysis of cardiac mRNA expression of adiponectin receptors and four C1QTNF family members, most suitable for fulfilling the functions of adiponectin in adiponectin ko mice, did not show any significant differences between adiponectin ko and wt group at all. Conclusion Our study reveals that the absence of adiponectin did not lead to a significantly increased impairment of cardiac function and was also unlikely to be compensated by its receptors or other C1QTNF family members in the murine model of EAM. Here, other synergistic or redundant effects might play a role and must be investigated in further studies to understand the role and function of adiponectin in autoimmune myocarditis. [ABSTRACT FROM AUTHOR]

• AP1 recruits Src1 and PCG1α to transactivate TAC1 in EMCV-induced myocarditis. • In vitro overexpression of the Src1-PCG1α-AP1 members also caused the induction of TAC1 , an increase in SP concentration, initiation of apoptosis, and elevation of proinflammatory cytokine concentrations. • Injection of Src1 inhibitor Gossypol and a PCG1α inhibitor SR1892 in EMCV-infected mice could attenuate myocarditis. Substance P (SP), a neuropeptide consisting of 11 amino acid residues, is involved in the pathogenesis of encephalomyocarditis virus (EMCV)-induced myocarditis by stimulating the production of proinflammatory cytokines. However, the underlying mechanism that regulates SP production is still unknown. In this study, we report the transcriptional regulation of the Tachykinin Precursor 1 (TAC1) gene that encodes SP by a transcriptional complex composed of Steroid Receptor Coactivator 1 (Src1), Peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC1α), and Activator Protein 1 (AP1) transcription factor. Infection of mice with EMCV induced the accumulation of PGC1α and increased TAC1 expression, thereby promoting the secretion of SP, initiating apoptosis, and elevating proinflammatory cytokine levels. In vitro overexpression of the Src1-PGC1α-AP1 members also induced TAC1 expression, increased the SP concentration, initiated apoptosis, and elevated proinflammatory cytokine concentrations. Depletion or inhibition of the Src1-PGC1α-AP1 complex reversed these effects. The administration of gossypol, an Src1 inhibitor, or SR1892, a PGC1α inhibitor, to EMCV-infected mice attenuated myocarditis. Taken together, our results reveal that the upregulation of TAC1 and the secretion of SP in EMCV-induced myocarditis are dependent on the Src1-PGC1α-AP1 complex. Targeting the Src1-PGC1α-AP1 complex may represent a new therapeutic strategy for myocarditis. [ABSTRACT FROM AUTHOR]

The present study aimed to explore the pathogenesis of autoimmune myocarditis induced by PD-1 inhibitors and their potential therapeutic targets. Mouse models of autoimmune myocarditis induced by PD-1 inhibitor in mouse models of polymyositis were established. The expression level of PD-1 and regulatory T cells (Tregs), CD4, CD8 + T cells, inflammation, apoptosis and autophagy-related factors, including IL-6, TGF-β, AMA-M2, Fas/FasL, LC3 and p62 were detected in peripheral blood , muscle or myocardium of mice in each group, using ELISA, RT-PCR, Western Blot and immunofluorescence. In addition, HE and TUNEL staining and ultrastructural scanning were performed on the myocardium of mice in each group. Results showed that the expression level of PD-1 in the two myositis groups was significantly lower than that in the control group, and the level of PD-1 was lower in the myocarditis group than that in the polymyositis group. In the myocardium, TGF-β, p62, and Tregs proportion showed the same expression level trend as PD-1, while CD8, IL-6, IL-10 and LC3 showed the opposite trend. Levels of Fas/FasL were significantly higher in both myositis groups, but were slightly lower in the myocarditis group, as was AMA-M2. Inflammation, apoptosis, and autophagy were observed in both myositis groups, but were more severe in the myocarditis group. In summary, the decreased expression level of PD-1 leads to decreased Tregs level in the myocardium, aggravated inflammatory response, apoptosis and autophagy, which may be the pathological mechanism of myocarditis induced by PD-1 inhibitors. [ABSTRACT FROM AUTHOR]

IL6 is a pleiotropic cytokine that is made in response to perturbations in homeostasis. IL6 becomes elevated in the acute response to host injury and can activate immune cells, direct immune cell trafficking, signal protective responses in local tissue, initial the acute phase response or initiate wound healing. In the short term this proinflammatory response is protective and limits host damage. It is when this acute response remains chronically activated that IL6 becomes pathogenic to the host. Chronically elevated IL6 levels lead to chronic inflammation and fibrotic disorders. The heart is a tissue where this temporal regulation of IL6 is very apparent. Studies from myocardial infarction show how short-term IL6 signaling can protect and preserve the heart tissue in response to acute damage, where long term IL6 signaling or an over-production of IL6R protein plays a causal role in cardiovascular disease. Thus, IL6 can be both protective and pathogenic, depending on the kinetics of the host response. [ABSTRACT FROM AUTHOR]

• IL-17 could upregulate the expression of MCP-1 in experimental autoimmune myocarditis. • The mechanism of IL-17 regulation for MCP-1 is dependent on the activation of Act1/TRAF6/TAK1 signaling pathway. • Blocking Act1/TRAF6/TAK1 could attenuate inflammatory cell infiltration during experimental autoimmune myocarditis. Myocarditis is a kind of myocardial inflammatory infiltration disease. Many interventions are not effective in the treatment of myocarditis because the mechanism of myocarditis has not been elucidated. Previous studies have found that interleukin-17 (IL-17) could stimulate the expression of monocyte chemokine protein 1 (MCP-1) and mediate myocardial inflammatory infiltration. This study aimed to explore the role of Act1/TRAF6/TAK1 cascade in IL-17-induced MCP-1 expression based on a well-designed experimental autoimmune myocarditis (EAM) model. It was found that IL-17 could stimulate the expression of MCP-1 by activating Act1/TRAF6/TAK1 cascade in EAM. The expression of Act1, TRAF6 and TAK1 followed downregulation by the application of IL-17 antibody. Additionally, myocardial inflammatory cell infiltration was observably alleviated by interfering TAK1 with TAK1 siRNA, and both MCP-1 mRNA and protein expression followed downregulation. This study suggested that IL-17 could activate the Act1/TRAF6/TAK1 pathway to upregulate MCP-1 expression in the EAM, and will offer a new perspective for the study on the mechanism of myocarditis. [ABSTRACT FROM AUTHOR]

Abstract: Identification of early determinants of dengue disease progression, which could potentially enable individualized patient care are needed at present times. Soluble ST2 (sST2) has been recently reported to be elevated in the serum of children older than 2years old and adults with dengue infection and it was correlated with secondary infections as well as with severe presentations of the disease. The mechanism by which secreted ST2 is linked to severe dengue and plasma leakage remains unclear. One possibility is that IL-33 ligand may be elevated, contributing to membrane bound ST2 as part of the immune activation in dengue infection. We determined plasma levels of sST2 and the ligand IL-33 in 66 children with acute secondary dengue infections clinically classified using the guidelines of the World Health Organization, 2009. Dengue infection showed significant increases in cytokines IL-12p70, IL-10, IL-8, IL-6, IL-1β and TNFα measured by flow cytometry based assay compared to uninfected individuals. In contrast, IL-33 levels remained unchanged between infected and uninfected individuals. The levels of sST2 positively correlated with values of IL-6 and IL-8 and inversely correlated with number of median value of platelet levels. In addition to circulating cytokine positive correlations we found that sST2 and isoenzyme creatine kinase-MB (CK-MB), a marker of myocardial muscle damage present in severe dengue cases were associated. Our pediatric study concluded that in dengue infections sST2 elevation does not involve concomitant changes of IL-33 ligand. We propose a study to assess its value as a predictor factor of disease severity. [Copyright &y& Elsevier]

• Myocardial inflammation is initially protective but often leads to heart failure. • Main infiltrating cells are macrophages and T cells but B cells are rarely present. • Surprisingly, macrophages but not T cells are the major IL-7Rα expressing population. • The IL-7Rα cascade is activated and might regulate trafficking of macrophages. • Consumption of IL-7 by macrophages might reduce the number of cardiac T and B cells. Myocarditis is characterized by infiltration and activation of cytokine as well as chemokine receptors frequently producing heart failure. Causes are often infections triggering inflammatory and immune responses but these initial lines of defense might be finally disastrous. To identify mediators we screened various receptors by confocal microscopy and identified cardiac interleukin-7 (IL-7) receptor-α (IL-7Rα) expressing cells in patients with myocarditis. IL-7Rα + cells were analyzed by markers for leukocytes (CD45), B cells (CD19), T cells (CD3, CD4, CD8) and macrophages (CD68, CD163, CD206). Immune cells were hardly detected in controls. In patients with myocarditis main inflammatory populations consisted of macrophages and T cells. B cells were hardly present. 90% of CD68+ macrophages but less than 20% of CD3 + T cells were IL-7Rα +. This was surprising since T and B lymphocytes are generally regarded as the major IL-7Rα + cells. Since IL-7 acts as a chemokine, the expression of its receptor might orchestrate cardiac macrophage infiltration. In contrast, consumption of IL-7 by IL-7Rα + cardiac macrophages might potentially prevent a certain overshooting immune reaction and sepsis by reducing proliferation and survival of lymphocytes. Our data suggest a participation of IL-7Rα + macrophages in the development of myocarditis and heart failure. [ABSTRACT FROM AUTHOR]

• TRAF6 is strongly induced after CVB3 infection in vitro and in vivo. • TRAF6 induction is stronger in mice that are susceptible to CVB3-induced myocarditis. • Knockdown of TRAF6 expression does not block CVB3-induced NFκB activation in vitro. Coxsackievirus B3 (CVB3) is an important inducer of myocarditis, which, in susceptible individuals, can chronify and eventually lead to the development of dilated cardiomyopathy and heart failure. The respective mechanisms are not completely understood. Here, we analyzed expression of the TRAF6 gene, encoding TNF receptor-associated factor 6 (TRAF6), a signal transduction scaffold protein that acts downstream of cytokine receptors, in heart tissue of susceptible and non-susceptible mouse strains. We found that after infection, TRAF6 expression was upregulated in both non-susceptible C57BL/6 wildtype and susceptible A.BY/SnJ and C57BL/6-TLR3 (−/−) mice, however, to different degrees. In infected HeLa cells, we also found moderately elevated TRAF6 levels after infection, in addition, activity of the transcription factor nuclear factor kappa B (NFκB), which can be activated downstream of TRAF6, was strongly enhanced in infected cells. To functionally analyze the role of TRAF6 with regard to infection progression, TRAF6 expression was knocked down in cultured HeLa cells using specific siRNAs. We found that reduction of TRAF6 expression had no effect on NFκB activation in response to infection. Taken together, our data suggest that CVB3 infection enhances TRAF6 levels, however, this induction might not be necessary for infection-induced NFκB activation. [ABSTRACT FROM AUTHOR]

We have recently reported that IL17A−/− animals are protected from progression of experimental autoimmune myocarditis (EAM) to dilated cardiomyopathy (DCM) as determined by echocardiography on day 54. IL17A−/− mice had lower IL6 levels in their heart compared with wildtype (WT) BALB/c animals. This was the only cytokine found to differ significantly between the two groups at both days 14 and 21. To investigate the IL6 requirement for DCM development we used two experimental approaches. First, we over-expressed IL6 in WT and IL17A−/− animals through hydrodynamic gene delivery (HGD) on days −1 or 7 of EAM. Mice over-expressing IL6 showed worsening of heart function compared to controls. Second, we blocked IL6R signaling using an anti-IL6R monoclonal antibody (mAb) in WT mice with EAM. Mice administered the anti-IL6R mAb on days 7 and 14 or 14 and 21 of EAM were protected from heart failure and DCM development by day 54 of disease. At day 14 of EAM there was reduced STAT3 phosphorylation in the heart after anti-IL6R mAb administration and increased STAT3 phosphorylation following HGD of IL6. In the mice receiving anti-IL6R mAb there was a significant decrease in the total number of CD45+ cells infiltrating the heart as measured by flow cytometry with similar composition in controls. Mice over-expressing IL6, both WT and IL17A−/− genotypes, had more CD11b+F4/80+ macrophages as well as CD11b+Ly6G+ neutrophils in the heart. IL6R mAb treated mice had lower circulating complement C3 levels where over-expressing mice had higher C3 levels than controls. Our data suggest that in EAM IL6 promotes the development of DCM during early events around day 7. [ABSTRACT FROM AUTHOR]