One-third of myocarditis cases progresses to dilated cardiomyopathy (DCM), but the mechanisms controlling this process are largely unknown. CD4(+) T helper (Th)17 cells have been implicated in the ...pathogenesis of autoimmune diseases, but the role of Th17-produced cytokines during inflammation-induced cardiac remodeling has not been previously studied.
We examined the importance of interleukin (IL)-17A in the progression of myocarditis to DCM using a mouse model.
Immunization of mice with myocarditogenic peptide in complete Freund's adjuvant induced the infiltration of IL-17A-producing Th17 cells into the inflamed heart. Unexpectedly, IL-17A-deficient mice developed myocarditis with similar incidence and severity compared to wild-type mice. Additionally, IL-17A deficiency did not ameliorate the severe myocarditis of interferon (IFN)gamma-deficient mice, suggesting that IL-17A plays a minimal role during acute myocarditis. In contrast, IL-17A-deficient mice were protected from postmyocarditis remodeling and did not develop DCM. Flow cytometric and cytokine analysis revealed an important role for IL-17A in heart-specific upregulation of IL-6, TNFalpha, and IL-1beta and the recruitment of CD11b(+) monocyte and Gr1(+) granulocyte populations into the heart. Furthermore, IL-17A-deficient mice had reduced interstitial myocardial fibrosis, downregulated expression of matrix metalloproteinase-2 and -9 and decreased gelatinase activity. Treatment of BALB/c mice with anti-IL-17A monoclonal antibody administered after the onset of myocarditis abrogated myocarditis-induced cardiac fibrosis and preserved ventricular function.
Our findings reveal a critical role for IL-17A in postmyocarditis cardiac remodeling and the progression to DCM. Targeting IL-17A may be an attractive therapy for patients with inflammatory dilated cardiomyopathy.
Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in children and young adults. DCMi develops in up to 30% of myocarditis patients, but the mechanisms involved in disease ...progression are poorly understood. Patients with eosinophilia frequently develop cardiomyopathies. In this study, we used the experimental autoimmune myocarditis (EAM) model to determine the role of eosinophils in myocarditis and DCMi. Eosinophils were dispensable for myocarditis induction but were required for progression to DCMi. Eosinophil-deficient ΔdblGATA1 mice, in contrast to WT mice, showed no signs of heart failure by echocardiography. Induction of EAM in hypereosinophilic IL-5Tg mice resulted in eosinophilic myocarditis with severe ventricular and atrial inflammation, which progressed to severe DCMi. This was not a direct effect of IL-5, as IL-5TgΔdblGATA1 mice were protected from DCMi, whereas IL-5
mice exhibited DCMi comparable with WT mice. Eosinophils drove progression to DCMi through their production of IL-4. Our experiments showed eosinophils were the major IL-4-expressing cell type in the heart during EAM, IL-4
mice were protected from DCMi like ΔdblGATA1 mice, and eosinophil-specific IL-4 deletion resulted in improved heart function. In conclusion, eosinophils drive progression of myocarditis to DCMi, cause severe DCMi when present in large numbers, and mediate this process through IL-4.
Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in individuals below the age of 40. We recently reported that IL-17A is required for the development of DCMi. We show a ...novel pathway connecting IL-17A, cardiac fibroblasts (CFs), GM-CSF, and heart-infiltrating myeloid cells with the pathogenesis of DCMi. Il17ra(-/-) mice were protected from DCMi, and this was associated with significantly diminished neutrophil and Ly6Chi monocyte/macrophage (MO/MΦ) cardiac infiltrates. Depletion of Ly6Chi MO/MΦ also protected mice from DCMi. Mechanistically, IL-17A stimulated CFs to produce key chemokines and cytokines that are critical downstream effectors in the recruitment and differentiation of myeloid cells. Moreover, IL-17A directs Ly6Chi MO/MΦ in trans toward a more proinflammatory phenotype via CF-derived GM-CSF. Collectively, this IL-17A-fibroblast-GM-CSF-MO/MΦ axis could provide a novel target for the treatment of DCMi and related inflammatory cardiac diseases.
Abstract In the broad field of autoimmunity and clinical immunology, experimental evidence over the past few years have demonstrated several connections between the immune system and the nervous ...system, both central and peripheral, leading to the definition of neuroimmunology and of an immune-brain axis. Indeed, the central nervous system as an immune-privileged site, thanks to the blood-brain barrier, is no longer a dogma as the barrier may be altered during chronic inflammation with disruptive changes of endothelial cells and tight junctions, largely mediated by adenosine receptors and the expression of CD39/CD73. The diseases that encompass the neuroimmunology field vary from primary nervous diseases such as multiple sclerosis to systemic conditions with neuropsychiatric complications, such as systemic lupus erythematosus or vasculitidies. Despite potentially similar clinical manifestations, the pathogenesis of each condition is different, but the interaction between the ultra-specialized structure that is the nervous system and inflammation mediators are crucial. Two examples come from anti-dsDNA cross-reacting with anti- N -Methyl- d -Aspartate receptor (NMDAR) antibodies in neuropsychiatric lupus or the new family of antibody-associated neuronal autoimmune diseases including classic paraneoplastic syndromes with antibodies directed to intracellular antigens (Hu, Yo, Ri) and autoimmune encephalitis. In the case of multiple sclerosis, the T cell paradigm is now complicated by the growing evidence of a B cell involvement, particularly via aquaporin antibodies, and their influence on Th1 and Th17 lineages. Inspired by a productive AARDA-sponsored colloquium among experts we provide a critical review of the literature on the pathogenesis of different immune-mediated diseases with neurologic manifestations and we discuss the basic immunology of the central nervous system and the interaction between immune cells and the peripheral nervous system.
Two types of monocytes, Ly6Chi and Ly6Clo, infiltrate the heart in murine experimental autoimmune myocarditis (EAM). We discovered a role for cardiac fibroblasts in facilitating ...monocyte-to-macrophage differentiation of both Ly6Chi and Ly6Clo cells, allowing these macrophages to perform divergent functions in myocarditis progression. During the acute phase of EAM, IL-17A is highly abundant. It signals through cardiac fibroblasts to attenuate efferocytosis of Ly6Chi monocyte-derived macrophages (MDMs) and simultaneously prevents Ly6Clo monocyte-to-macrophage differentiation. We demonstrated an inverse clinical correlation between heart IL-17A levels and efferocytic receptor expressions in humans with heart failure (HF). In the absence of IL-17A signaling, Ly6Chi MDMs act as robust phagocytes and are less pro-inflammatory, whereas Ly6Clo monocytes resume their differentiation into MHCII+ macrophages. We propose that MHCII+Ly6Clo MDMs are associated with the reduction of cardiac fibrosis and prevention of the myocarditis sequalae.
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•Cardiac fibroblasts facilitate differentiation of Ly6Chi and Ly6Clo monocytes•IL-17A trans-signaling inhibits Ly6Clo monocyte-to-macrophage differentiation•IL-17A trans-signaling increases MerTK shedding on monocyte-derived macrophages•IL-17A trans-signaling promotes monocyte-derived macrophages to be proinflammatory
Hou et al. show that cardiac fibroblasts facilitate infiltrating Ly6Chi and Ly6Clo monocytes to become macrophages. IL-17A trans-signaling through cardiac fibroblasts increases MerTK shedding and promotes a pro-inflammatory and pro-tissue remodeling gene expression profile in Ly6Chi monocyte-derived macrophages. Paradoxically, IL-17A signaling through cardiac fibroblasts can substantially inhibit Ly6Clo monocyte-to-macrophage differentiation.
This review focuses on autoimmune myocarditis and its sequela, inflammatory dilated cardiomyopathy (DCMI), and the inflammatory and immune mechanisms underlying the pathogenesis of these diseases. ...Several mouse models of myocarditis and DCMI have improved our knowledge of the pathogenesis of these diseases, informing more general problems of cardiac remodeling and heart failure. CD4+ T cells are critical in driving the pathogenesis of myocarditis. We discuss in detail the role of T helper cell subtypes in the pathogenesis of myocarditis, the biology of T cell–derived effector cytokines, and the participation of other leukocytic effectors in mediating disease pathophysiology. We discuss interactions between these subsets in both suppressive and collaborative fashions. These findings indicate that cardiac inflammatory disease, and autoimmunity in general, may be more diverse in divergent effector mechanisms than has previously been appreciated.
The involvement of macrophages (MΦs) in Th17‐cell responses is still poorly understood. While neutrophils are thought to be the predominant effector of Th17‐cell responses, IL‐17 is also known to ...induce myelotropic chemokines and growth factors. Other T‐cell‐derived cytokines induce non‐classical functions, suggesting that IL‐17 sigxnaling may similarly elicit unique MΦ functions. Here, we characterized the expression of subunits of the IL‐17 receptor on primary murine MΦs from different anatomical compartments. The greatest expression of IL‐17 receptors was observed on mucosal Ly6Chi "inflammatory" MΦs. We further observed upregulation of IL‐17 receptors in vitro on bone marrow‐derived macrophages (BMMΦs) in response to peptidoglycan or CpG oligonucleotide stimuli, and in vivo, upon CFA administration. Macrophages expressing IL‐17 receptors were observed infiltrating the hearts of mice with myocarditis, and genetic ablation of IL‐17RA altered MΦ recruitment. Treating primary MΦs from a wide variety of different anatomic sources (as well as cell lines) with IL‐17A induced the production of unique profiles of cytokines and chemokines, including GM‐CSF, IL‐3, IL‐9, CCL4/MIP‐1β and CCL5/RANTES. IL‐17A also induced production of IL‐12p70; IL‐17‐signaling‐deficient MΦs elicited diminished IFN‐γ production by responding DO11.10 CD4+ T cells when used as APCs. These data indicate that MΦs from different anatomic locations direct IL‐17‐mediated responses.
Cardiac manifestations are a major cause of morbidity and mortality in patients with eosinophil‐associated diseases. Eosinophils are thought to play a pathogenic role in myocarditis. We investigated ...the pathways that recruit eosinophils to the heart using a model of eosinophilic myocarditis, in which experimental autoimmune myocarditis (EAM) is induced in IFNγ−/−IL‐17A−/− mice. Two conditions are necessary for efficient eosinophil trafficking to the heart: high eotaxin (CCL11, CCL24) expression in the heart and expression of the eotaxin receptor CCR3 by eosinophils. We identified cardiac fibroblasts as the source of CCL11 in the heart interstitium. CCL24 is produced by F4/80+ macrophages localized at inflammatory foci in the heart. Expression of CCL11 and CCL24 is controlled by Th2 cytokines, IL‐4 and IL‐13. To determine the relevance of this pathway in humans, we analyzed endomyocardial biopsy samples from myocarditis patients. Expression of CCL11 and CCL26 was significantly increased in eosinophilic myocarditis compared to chronic lymphocytic myocarditis and positively correlated with the number of eosinophils. Thus, eosinophil trafficking to the heart is dependent on the eotaxin‐CCR3 pathway in a mouse model of EAM and associated with cardiac eotaxin expression in patients with eosinophilic myocarditis. Blocking this pathway may prevent eosinophil‐mediated cardiac damage.
We determined the pathway for eosinophil trafficking to the heart by examining a murine myocarditis model and heart biopsies from myocarditis patients. IL‐4 and IL‐13 induce production of eotaxins CCL11 and CCL24 by cardiac fibroblasts and macrophages. In response to eotaxins, eosinophils migrate to the heart via the receptor CCR3.
We report here that interleukin (IL)-13 protects BALB/c mice from myocarditis, whether induced by peptide immunization or by viral infection. In contrast to mild disease in IL-4 knockout (KO) BALB/c ...mice, IL-13 KO BALB/c mice developed severe coxsackievirus B3 (CVB3)-induced autoimmune myocarditis and myocarditogenic peptide-induced experimental autoimmune myocarditis. Such severe disease was characterized by increased cardiac inflammation, increased total intracardiac CD45+ leukocytes, elevated anti-cardiac myosin autoantibodies, and increased cardiac fibrosis. Echocardiography revealed that IL-13 KO mice developed severe dilated cardiomyopathy with impaired cardiac function and heart failure. Hearts of IL-13 KO mice had increased levels of the proinflammatory and profibrotic cytokines IL-1β, IL-18, interferon-γ, transforming growth factor-β1, and IL-4 as well as histamine. The hallmark of the disease in IL-13 KO mice was the up-regulation of T-cell responses. CD4+ T cells were increased in IL-13 KO hearts both proportionally and in absolute number. Splenic T cells from IL-13 KO mice were highly activated, and myosin stimulation additionally increased T-cell proliferation. CD4+ CD25+ Foxp3+ regulatory T-cell numbers were decreased in the spleens of IL-13 KO mice. IL-13 deficiency led to decreased levels of alternatively activated CD206+ and CD204+ macrophages and increased levels of classically activated macrophages. IL-13 KO mice had increased caspase-1 activation, leading to increased production of both IL-1β and IL-18. Therefore, IL-13 protects against myocarditis by modulating monocyte/macrophage populations and by regulating their function.
Myocarditis is a leading cause of sudden cardiac failure in young adults. Natural killer (NK) cells, a subset of the innate lymphoid cell compartment, are protective in viral myocarditis. Herein, we ...demonstrated that these protective qualities extend to suppressing autoimmune inflammation. Experimental autoimmune myocarditis (EAM) was initiated in BALB/c mice by immunization with myocarditogenic peptide. During EAM, activated cardiac NK cells secreted interferon γ, perforin, and granzyme B, and expressed CD69, tumor necrosis factor–related apoptosis-inducing ligand treatment, and CD27 on their cell surfaces. The depletion of NK cells during EAM with anti-asialo GM1 antibody significantly increased myocarditis severity, and was accompanied by elevated fibrosis and a 10-fold increase in the percentage of cardiac-infiltrating eosinophils. The resultant influx of eosinophils to the heart was directly responsible for the increased disease severity in the absence of NK cells, because treatment with polyclonal antibody asialogangloside GM-1 did not augment myocarditis severity in eosinophil-deficient ΔdoubleGATA1 mice. We demonstrate that NK cells limit eosinophilic infiltration both indirectly, through altering eosinophil-related chemokine production by cardiac fibroblasts, and directly, by inducing eosinophil apoptosis in vitro. Altogether, we define a new pathway of eosinophilic regulation through interactions with NK cells.
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