Neutralizing anti-4-1BBL treatment improves cardiac function in viral myocarditis

Immune checkpoints in cardiac physiology and pathology: therapeutic targets for heart failure

Immune checkpoint molecules are physiological regulators of the adaptive immune response. Immune checkpoint inhibitors (ICIs), such as monoclonal antibodies targeting programmed cell death protein 1 or cytotoxic T lymphocyte-associated protein 4, have revolutionized cancer treatment and their clinical use is increasing. However, ICIs can cause various immune-related adverse events, including acute and chronic cardiotoxicity. Of these cardiovascular complications, ICI-induced acute fulminant myocarditis is the most studied, although emerging clinical and preclinical data are uncovering the importance of other ICI-related chronic cardiovascular complications, such as accelerated atherosclerosis and non-myocarditis-related heart failure. These complications could be more difficult to diagnose, given that they might only be present alongside other comorbidities. The occurrence of these complications suggests a potential role of immune checkpoint molecules in maintaining cardiovascular homeostasis, and disruption of physiological immune checkpoint signalling might thus lead to cardiac pathologies, including heart failure. Although inflammation is a long-known contributor to the development of heart failure, the therapeutic targeting of pro-inflammatory pathways has not been successful thus far. The increasingly recognized role of immune checkpoint molecules in the failing heart highlights their potential use as immunotherapeutic targets for heart failure. In this Review, we summarize the available data on ICI-induced cardiac dysfunction and heart failure, and discuss how immune checkpoint signalling is altered in the failing heart. Furthermore, we describe how pharmacological targeting of immune checkpoints could be used to treat heart failure.

4-1BBL Regulates the Polarization of Macrophages, and Inhibition of 4-1BBL Signaling Alleviates Imiquimod-Induced Psoriasis

4-1BBL, a member of the TNF superfamily, regulates the sustained production of inflammatory cytokines in macrophages triggered by TLR signaling. In this study, we have investigated the role of 4-1BBL in macrophage metabolism and polarization and in skin inflammation using a model of imiquimod-induced psoriasis in mice. Genetic ablation or blocking of 4-1BBL signaling by Ab or 4-1BB-Fc alleviated the pathology of psoriasis by regulating the expression of inflammatory cytokines associated with macrophage activation and regulated the polarization of macrophages in vitro. We further linked this result with macrophage by finding that 4-1BBL expression during the immediate TLR response was dependent on glycolysis, mitochondrial oxidative phosphorylation, and fatty acid metabolism, whereas the late-phase 4-1BBL-mediated sustained inflammatory response was dependent on glycolysis and fatty acid synthesis. Correlating with this, administration of a fatty acid synthase inhibitor, cerulenin, also alleviated the pathology of psoriasis. We further found that 4-1BBL-mediated psoriasis development is independent of its receptor 4-1BB, as a deficiency of 4-1BB augmented the severity of psoriasis linked to a reduced regulatory T cell population and increased IL-17A expression in γδ T cells. Additionally, coblocking of 4-1BBL signaling and IL-17A activity additively ameliorated psoriasis. Taken together, 4-1BBL signaling regulates macrophage polarization and contributes to imiquimod-induced psoriasis by sustaining inflammation, providing a possible avenue for psoriasis treatment in patients.

4-1BB Signaling Promotes Alveolar Macrophages-Mediated Pro-Fibrotic Responses and Crystalline Silica-Induced Pulmonary Fibrosis in Mice

Silicosis is caused by exposure to crystalline silica (CS). We have previously shown that blocking 4-1BB signaling attenuated CS-induced inflammation and pulmonary fibrosis. However, the cells that express 4-1BB, which plays a vital role in promoting fibrosis, are still unknown. In this study, we demonstrated that the expression of 4-1BB is elevated in alveolar macrophages (AMs) in the lungs of CS-injured mice. CS exposure also markedly enhanced the expression of 4-1BB in macrophage-like, MH-S cells. In these cells, activation of the 4-1BB signaling with an agonist antibody led to upregulated secretion of pro-fibrotic mediators. Consistently, blocking 4-1BB downstream signaling or genetic deletion of 4-1BB alleviated pro-fibrotic responses in vitro, while treatment with a 4-1BB fusion protein promoted pro-fibrotic responses. In vivo experiments showed that blocking 4-1BB signaling decreased the expressions of pro-fibrotic mediators and fibrosis. These data suggest that 4-1BB signaling plays an important role in promoting AMs-mediated pro-fibrotic responses and pulmonary fibrosis. Our findings may provide a potential molecular target to reduce CS-induced fibrotic responses in occupational lung disease.

Coxsackievirus B3 replication and pathogenesis

ABSTRACT 

Viruses such as coxsackievirus B3 (CVB3) are entirely host cell-dependent parasites. Indeed, they must cleverly exploit various compartments of host cells to complete their life cycle, and consequently launch disease. Evolution has equipped this pico-rna-virus, CVB3, to use different strategies, including CVB3-induced direct damage to host cells followed by a host inflammatory response to CVB3 infection, and cell death to super-additively promote target organ tissue injury, and dysfunction. In this update, the patho-stratagems of CVB3 are explored from molecular, and systems-level approaches. In summarizing recent developments in this field, we focus particularly on mechanisms by which CVB3 can harness different host cell processes including kinases, host cell-killing and cell-eating machineries, matrix metalloproteinases and miRNAs to promote disease.

Inhibition of 4-1BBL-regulated TLR response in macrophages ameliorates endotoxin-induced sepsis in mice

Activation of Toll-like receptor (TLR) signaling rapidly induces the expression of inflammatory genes, which is persistent for a defined period of time. However, uncontrolled and excessive inflammation may lead to the development of diseases. 4-1BB ligand (4-1BBL) plays an essential role in sustaining the expression of inflammatory cytokines by interacting with TLRs during macrophage activation. Here, we show that inhibition of 4-1BBL signaling reduced the inflammatory responses in macrophages and ameliorated endotoxin-induced sepsis in mice. A 4-1BB-Fc fusion protein significantly reduced TNF production in macrophages by blocking the oligomerization of TLR4 and 4-1BBL. Administration of 4-1BB-Fc suppressed LPS-induced sepsis by reducing TNF production, and the coadministration of anti-TNF and 4-1BB-Fc provided better protection against LPS-induced sepsis. Taken together, these observations suggest that inhibition of the TLR/4-1BBL complex formation may be highly efficient in protecting against continued inflammation, and that 4-1BB-Fc could be a potential therapeutic target for the treatment of inflammatory diseases.

Intricacies of cardiac damage in coxsackievirus B3 infection: implications for therapy

Heart disease is the leading cause of death in humans, and myocarditis is one predominant cause of heart failure in young adults. Patients affected with myocarditis can develop dilated cardiomyopathy (DCM), a common reason for heart transplantation, which to date is the only viable option for combatting DCM. Myocarditis/DCM patients show antibodies to coxsackievirus B (CVB)3 and cardiac antigens, suggesting a role for CVB-mediated autoimmunity in the disease pathogenesis; however, a direct causal link remains to be determined clinically. Experimentally, myocarditis can be induced in susceptible strains of mice using the human isolates of CVB3, and the disease pathogenesis of postinfectious myocarditis resembles that of human disease, making the observations made in animals relevant to humans. In this review, we discuss the complex nature of CVB3-induced myocarditis as it relates to the damage caused by both the virus and the host's response to infection. Based on recent data we obtained in the mouse model of CVB3 infection, we provide evidence to suggest that CVB3 infection accompanies the generation of cardiac myosin-specific CD4 T cells that can transfer the disease to naïve recipients. The therapeutic implications of these observations are also discussed.

Targeting matrix metalloproteinase activity and expression for the treatment of viral myocarditis

Infectious agents including viruses can infect the heart muscle, resulting in the development of heart inflammation called myocarditis. Chronic myocarditis can lead to dilated cardiomyopathy (DCM). DCM develops from the extensive extracellular matrix (ECM) remodeling caused by myocarditis and may result in heart failure. Epidemiological data for viral myocarditis has long suggested a worse pathology in males, with more recent data demonstrating sex-dependent pathogenesis in DCM as well. Matrix metalloproteinases (MMPs), long known modulators of the extracellular matrix, have important roles in mediating heart inflammation and remodeling during disease and in convalescence. This ability of MMPs to control both the inflammatory response and ECM remodeling during myocarditis makes them potential drug targets. In this review, we analyze the role of MMPs in mediating myocarditis/DCM disease progression, their sex-dependent expression, and their potential as drug targets during viral myocarditis and DCM.

Blockade of 4-1BB and 4-1BBL interaction reduces obesity-induced skeletal muscle inflammation

Obesity-induced skeletal muscle inflammation is characterized by increased macrophage infiltration and inflammatory cytokine production. In this study, we investigated whether 4-1BB, a member of the TNF receptor superfamily (TNFRSF9) that provides inflammatory signals, participates in obesity-induced skeletal muscle inflammation. Expression of the 4-1BB gene, accompanied by increased levels of inflammatory cytokines, was markedly upregulated in the skeletal muscle of obese mice fed a high-fat diet, in muscle cells treated with obesity factors, and in cocultured muscle cells/macrophages. In vitro stimulation of 4-1BB with agonistic antibody increased inflammatory cytokine levels in TNFα-pretreated muscle cells, and this effect was absent in cells derived from 4-1BB-deficient mice. Conversely, disruption of the interaction between 4-1BB and its ligand (4-1BBL) with blocking antibody decreased the release of inflammatory cytokines from cocultured muscle cells/macrophages. Moreover, deficiency of 4-1BB markedly reduced macrophage infiltration and inflammatory cytokine production in the skeletal muscle of mice fed a high-fat diet. These findings indicate that 4-1BB mediates the inflammatory responses in obese skeletal muscle by interacting with its ligand 4-1BBL on macrophages. Therefore, 4-1BB and 4-1BBL may be useful targets for prevention of obesity-induced inflammation in skeletal muscle.

Regulation of Inflammation by Bidirectional Signaling through CD137 and Its Ligand

Although the majority of research on CD137 has been directed to T cells, it is becoming clear that this molecule has distinct functions in other lineages of cells, including non-hematopoietic cells. In particular, emerging evidence suggests that the CD137-its ligand (CD137L) network involving immune cells and non-immune cells, directly or indirectly regulates inflammation in both positive and negative manners. Bidirectional signaling through both CD137 and CD137L is critical in the evolution of inflammation: 1) CD137L signaling plays an indispensible role in the activation and recruitment of neutrophils by inducing the production of proinflammatory cytokines and chemokines in hematopoietic and non-hematopoietic cells such as macrophages, endothelial cells and epithelial cells; 2) CD137 signaling in NK cells and T cells is required for their activation and can influence other cells participating in inflammation via either their production of proinflammatory cytokines or engagement of CD137L by their cell surface CD137: 3) CD137 signaling can suppress inflammation by controlling regulatory activities of dendritic cells and regulatory T cells. As recognition grows of the role of dysregulated CD137 or CD137L stimulation in inflammatory diseases, significant efforts will be needed to develop antagonists to CD137 or CD137L.

The role of costimulatory receptors of the tumour necrosis factor receptor family in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.

Deficiency for costimulatory receptor 4-1BB protects against obesity-induced inflammation and metabolic disorders

OBJECTIVE

Inflammation is an important factor in the development of insulin resistance, type 2 diabetes, and fatty liver disease. As a member of the tumor necrosis factor receptor superfamily (TNFRSF9) expressed on immune cells, 4-1BB/CD137 provides a bidirectional inflammatory signal through binding to its ligand 4-1BBL. Both 4-1BB and 4-1BBL have been shown to play an important role in the pathogenesis of various inflammatory diseases.

RESEARCH DESIGN AND METHODS

Eight-week-old male 4-1BB-deficient and wild-type (WT) mice were fed a high-fat diet (HFD) or a regular diet for 9 weeks.

RESULTS

We demonstrate that 4-1BB deficiency protects against HFD-induced obesity, glucose intolerance, and fatty liver disease. The 4-1BB-deficient mice fed an HFD showed less body weight gain, adiposity, adipose infiltration of macrophages/T cells, and tissue levels of inflammatory cytokines (e.g., TNF-α, interleukin-6, and monocyte chemoattractant protein-1 [MCP-1]) compared with HFD-fed control mice. HFD-induced glucose intolerance/insulin resistance and fatty liver were also markedly attenuated in the 4-1BB-deficient mice.

CONCLUSIONS

These findings suggest that 4-1BB and 4-1BBL may be useful therapeutic targets for combating obesity-induced inflammation and metabolic disorders.

Matrix metalloproteinases in the pathogenesis of viral heart disease

Matrix metalloproteinases (MMPs) are enzymes that digest the extracellular matrix and regulate the immune response by cleavage of chemokines and cytokines into products with altered activities. Matrix metalloproteinase expression in viral heart disease has been linked to the onset of myocarditis and the long-term sequelae associated with this illness. However, MMPs are also expressed as a functional part of the immune response, and it was recently shown that MMP-9 is a beneficial part of the antiviral immune response in viral myocarditis. In this review, we will attempt to reconcile the studies that claim MMPs inflict damage in viral myocarditis with those studies that report a protective role for MMPs in this cardiac disease.

CD137-CD137 Ligand Interactions in Inflammation

The main stream of CD137 studies has been directed to the function of CD137 in CD8⁺ T-cell immunity, including its anti-tumor activity, and paradoxically the immunosuppressive activity of CD137, which proves to be of a great therapeutic potential for animal models of a variety of autoimmune and inflammatory diseases. Recent studies, however, add complexes to the biology of CD137. Accumulating is evidence supporting that there exists a bidirectional signal transduction pathway for the CD137 receptor and its ligand (CD137L). CD137/CD137L interactions are involved in the network of hematopoietic and nonhematopoietic cells in addition to the well characterized antigen-presenting cell-T cell interactions. Signaling through CD137L plays a critical role in the differentiation of myeloid cells and their cellular activities, suggesting that CD137L signals trigger and sustain inflammation. The overall consequence might be that the amplified inflammation by CD137L enhances the T-cell activity together with CD137 signals by upregulating costimulatory molecules, MHC molecules, cell adhesion molecules, cytokines, and chemokines. Solving this outstanding issue is urgent and will have an important clinical implication.

Attenuation of experimental autoimmune myocarditis by blocking T cell activation through 4-1BB pathway

4-1BB, a member of the tumor necrosis factor receptor (TNFR) family, binds the 4-1BB ligand (4-1BBL), works as a costimulatory molecule, and regulates T cell-mediated immune responses. Although inflammation is an essential pathological feature of myocarditis, the role of 4-1BB in experimental autoimmune myocarditis (EAM) remains unclear. Lewis rats were immunized on day 0 with purified porcine cardiac myosin to establish EAM. 4-1BB-immunoglobulin (4-1BBIg) was administered intraperitoneally (n=6) a total of 9 times (3 times per week). Rats were killed on day 21 to study effects of 4-1BB/4-1BBL pathway blockade. For controls, isotype-matched human IgG was administered in other EAM rats (n=6). Histologic and echocardiographic examination showed development of EAM attenuated by 4-1BBIg. Suppression of mRNA expression for IL-1alpha, IL-1beta, IL-4, IL-6, and TNF-alpha was noted in the heart tissue treated with 4-1BBIg. Treatment with 4-1BBIg reduced production of Th1-type cytokines, and inhibited T cell proliferation in vitro. In the 4-1BB signaling pathway in splenocytes, 4-1BBIg suppressed JNK, p38, and IkappaB activity but not that of ERK1/2. Blockade of T cell activation through the 4-1BB/4-1BBL pathway regulates development of EAM; therefore, 4-1BB may be an effective target for treating myocarditis.

Ablation of Matrix Metalloproteinase-9 Increases Severity of Viral Myocarditis in Mice

Background— Coxsackievirus B3 (CVB3) causes human myocarditis, which can result in cardiac damage, maladaptive remodeling, and heart failure. Matrix metalloproteinases (MMP)-8 and -9 have been identified in virus-infected myocardium, but their particular roles and underlying mechanisms of effect are unknown. For the first time, we examine the severity of CVB3-induced myocarditis in MMP-8–and MMP-9–deficient mice.

Methods and Results— CVB3-infected MMP-8 and MMP-9 knockout (KO) mice and corresponding wild-type (WT) mice were euthanized and harvested at 9 days after infection. Expression of MMP-2, -8, -12, and -13 and tissue inhibitors of MMPs was assessed by zymography or immunoblotting on harvested hearts, and in situ hybridization was performed to detect active infection. Infected MMP-9 KO mice had greater myocardial injury and foci of infection than WT mice despite similar pancreatic infection. Increased fibrosis (10.6±2.7% versus 7.1±2.6%, P =0.04), viral titer, as well as decreased cardiac output, were evident in MMP-9 KO compared with WT mice as assessed by picrosirius red staining, plaque assay, and echocardiography, respectively. Immune infiltration was also greatly increased in MMP-9 KO compared with WT mice (15.2±12.6% versus 2.0±3.0%, P <0.002). Myocardial interferon-β1, interferon-γ, interleukin-6, interleukin-10, and macrophage inflammatory protein-1α expression was elevated in MMP-9 KO mice as measured by quantitative real-time polymerase chain reaction and ELISA. In contrast, MMP-8 KO mice had the same degree of cardiac injury, fibrosis, and viral infection as their WT counterparts.

Conclusions— During acute CVB3 infection, MMP-9 appears necessary to halt virus propagation in the heart, promote proper immune infiltration and remodeling, and preserve cardiac output.