Inflammation In Autoimmune Myocarditis Research Articles

IL-23 promotes T-cell mediated cardiac inflammation but protects the heart from fibrosis

Abstract Introduction Cardiac inflammation varies widely and, in some cases, triggers autoimmune myocarditis and further inflammatory dilated cardiomyopathy (iDCM) and heart failure. In children, myocarditis leads to cardiomyopathy in almost half of affected individuals and up to 20% of sudden death cases in young adults have been reported to be due to myocarditis. IL-12 and IL-23 belong to the same family of cytokines known to mediate inflammatory conditions. Both regulate the differentiation of T cells: IL-12 promotes towards IFN-gamma-producing Th-1 cells, while IL-23 induces IL-17-producing Th-17 cells. Heart-reactive CD4+Th17 cells play a leading role in the development of myocarditis, however, literature reports excessiveness of IL-23 in Th17-derived IL-17 production. Therapeutic strategies blocking IL-23 were suggested as a promising approach, though the specific role of IL-23 in pathogenesis is unclear and the long-term perspectives stay elusive. Purpose We aim to explore the role IL-23 compared to IL-12 in the manifestation of cardiac autoimmune myocarditis. Methodology We use dendritic cell (DC) model of experimental autoimmune myocarditis in IL-12 and IL-23-deficient mice. Mice were injected with bone marrow-derived in vitro activated and loaded with cardiac-specific peptide DCs. This model mimics natural processes taking place during heart inflammation and provides a unique method to address the role of DCs-derived cytokines. Cardiac inflammation, as well as remodeling and heart function, were analysed at the acute and chronic stages of the disease. Results Surprisingly, all mice developed acute myocarditis, though wt receiving IL-23−/−bmDCs showed a twofold decrease in heart-infiltrating T cells and lower numbers of Th17 population. Further decrease of heart-infiltrating T cells appeared upon total systemic IL-23 deficiency. In comparison to IL-12, directly inducing differentiation of IFN-gamma–producing Th1, IL-23 cannot induce Th17 differentiation. None of the two cytokines affect proliferation, though, IL-23 activates T cell migratory potential and increases T cell migration by twofold. At the same time, deficiency of IL-23-production by bmDCs leads to lower migration of T cells. We also show an involvement of RhoA, and the other Rho GTPases, in the mechanism of migration as blocking revoke the IL-23 effect on T cells. Moreover, we further observed more fibrosis and worse heart functioning in IL-23−/−, but not IL-12−/− mice at the chronic stage what underlines the importance of IL-23-dependent T cell trafficking in the resolution of the acute stage of autoimmune myocarditis. Conclusion Our observations underline IL-23 as an important cytokine responsible for T cell trafficking and resolution of the inflammation in autoimmune myocarditis. Therapeutic approaches involving inflammatory cytokine targeting are a promising clinical perspective though IL-23 deficiency might lead to increased cardiac remodeling and iDCM progression. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): The Swiss National Science Foundation

Non-invasive contrast enhanced ultrasound molecular imaging of inflammation in autoimmune myocarditis for prediction of left ventricular fibrosis and remodeling.

BackgroundMyocarditis can lead to myocyte loss and myocardial fibrosis resulting in dilated cardiomyopathy (DCMP). Currently employed methods for assessing the risk for development of DCMP are inaccurate or rely on invasive myocardial biopsies. We hypothesized that molecular imaging of tissue inflammation with contrast enhanced ultrasound during peak inflammation in myocarditis could predict development of fibrosis and impaired left ventricular function.Methods and resultsExperimental autoimmune myocarditis (EAM) was induced in Balbc mice by injection of the α-myosin heavy chain peptide. Contrast enhanced ultrasound (CEU) using microbubbles targeted to leukocytes (MBLc), to CD4+ lymphocytes (MBCD4), and to the endothelial cell adhesion molecule P-selectin (MBPSel) was performed during the expected EAM peak inflammatory activity 21 days after induction. High resolution ultrasound, invasive hemodynamic measurements and fibrosis quantification were done 63 days after EAM assessment. All tested microbubbles correlated to fibrosis (MBLc spearman r 0.28, p 0.047, MBCD4 r 0.44, p 0.01, MBPSel r 0.73, p 0.02), however, correlations were weak overall and the spread of data was considerable. Also, targeted CEU data on day 21 did not correlate to hemodynamic and functional data on day 63.ConclusionsUltrasound molecular imaging using targeted microbubbles during the peak inflammatory activity of myocarditis correlates weakly with later development of fibrosis but not with hemodynamic or left ventricular functional parameters.

51 L-Arginine ameliorates the progression of autoimmune myocarditis

Objectives Nitric oxide (NO) plays a dual role: it can inhibit the inflammatory process under physiological conditions, but on the other hand, a large amount of NO can be involved in inflammation in autoimmune myocarditis. We investigated the effects of N-nitro-L-arginine methyl ester (L-NAME), an inducible nitric oxide synthase (iNOS) inhibitor, in the treatment of BALB/c mice with experimental autoimmune myocarditis (EAM) and discuss the therapeutic mitochondrial mechanism induced by apoptosis. Methods Sixty male BALB/c mice aged 4–5 weeks were randomly divided into a normal control group, a model control group and an experimental group. EAM was induced in the model control group and experimental group by injection of porcine cardiac myosin subcutaneously into the groin and axilla and intraperitoneal injection of pertussis toxin on days 0 and 7, respectively. The model control group was intraperitoneally administered 5 mg/kg/day of physiological saline after injection of myosin and pertussis toxin. The experimental group was intraperitoneally given 5 mg/kg/day of L-NAME on days 1–21. At the end of the intervention, mice were euthanatized and hearts were harvested on day 21. The inflammatory score, fibrosis score, protein expression levels of caspase-3, caspase-8 and caspase-9, serum NO level, iNOS, iNOS mRNA, caspase-3, caspase-8 and caspase-9 mRNA, cardiac reactive oxygen species (ROS) production rate and mitochondrial membrane potential were measured. Mouse heart weight/body weight was calculated (HW/BW). Results The inflammatory score, cardiac interstitial fibrosis score, cardiac apoptotic index, protein expression levels of caspase-3, caspase-8 and caspase-9, HW/BW, level of NO and activity of iNOS, expression levels of iNOS mRNA, and caspase-3, caspase-8 and caspase-9 protein were all significantly higher in the model control group and experimental group than in the normal control group (p Conclusions The development of EAM is related to the NO catalyzed by iNOS. L-NAME protected cardiac myocytes through suppressing the activity of iNOS and further decreased production of NO in EAM. The mechanism may be related to inhibiting the apoptosis of cardiac myocytes mediated by the caspase family and protecting mitochondrial function. Acknowledgments This research was financially supported by the National Natural Science Foundation (Grant No. 61573139).

Silencing of CCR2 in myocarditis.

Myocarditis is characterized by inflammatory cell infiltration of the heart and subsequent deterioration of cardiac function. Monocytes are the most prominent population of accumulating leucocytes. We investigated whether in vivo administration of nanoparticle-encapsulated siRNA targeting chemokine (C-C motif) receptor 2 (CCR2)-a chemokine receptor crucial for leucocyte migration in humans and mice--reduces inflammation in autoimmune myocarditis. In myocardium of patients with myocarditis, CCL2 mRNA levels and CCR2(+) cells increased (P < 0.05), motivating us to pursue CCR2 silencing. Flow cytometric analysis showed that siRNA silencing of CCR2 (siCCR2) reduced the number of Ly6C(high) monocytes in hearts of mice with acute autoimmune myocarditis by 69% (P < 0.05), corroborated by histological assessment. The nanoparticle-delivered siRNA was not only active in monocytes but also in bone marrow haematopoietic progenitor cells. Treatment with siCCR2 reduced the migration of bone marrow granulocyte macrophage progenitors into the blood. Cellular magnetic resonance imaging (MRI) after injection of macrophage-avid magnetic nanoparticles detected myocarditis and therapeutic effects of RNAi non-invasively. Mice with acute myocarditis showed enhanced macrophage MRI contrast, which was prevented by siCCR2 (P < 0.05). Follow-up MRI volumetry revealed that siCCR2 treatment improved ejection fraction (P < 0.05 vs. control siRNA-treated mice). This study highlights the importance of CCR2 in the pathogenesis of myocarditis. In addition, we show that siCCR2 affects leucocyte progenitor trafficking. The data also point to a novel therapeutic strategy for the treatment of myocarditis.

Role of the Cholinergic Antiinflammatory Pathway in Murine Autoimmune Myocarditis

This study was performed to gain insights into novel therapeutic approaches for the treatment of autoimmune myocarditis. Chemical stimulation of the efferent arm of the vagus nerve through activation of nicotinic acetylcholine receptor subtype-7α (α7-nAChR) has been shown to be protective in several models of inflammatory diseases. In the present study, we investigated the potentially protective effect of vagus nerve stimulation on myocarditis. A/J mice were immunized with cardiac troponin I (TnI) to induce autoimmune myocarditis. Mice were exposed to drinking water that contained nicotine in different concentrations and for different time periods (for 3 days at 12.5 mg/L; 3 days at 125 mg/L; 21 days at 12.5 mg/L; and 21 days at 125 mg/L after first immunization). TnI-immunized mice with no pharmacological treatment showed extensive myocardial inflammation and fibrosis and significantly elevated levels of interleukin-6 and tumor necrosis factor-α. Furthermore, elevated levels of mRNA transcripts of proinflammatory chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and RANTES) and chemokine receptors (CCR1, CCR2, and CCR5) were found. Oral nicotine administration reduced inflammation within the myocardium, decreased the production of interleukin-6 and tumor necrosis factor-α, and downregulated the expression of monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, RANTES, CCR1, CCR2, and CCR5. In addition, nicotine treatment resulted in decreased expression of matrix metalloproteinase-14, natriuretic peptide precursor B, tissue inhibitor of metalloproteinase-1, and osteopontin, proteins that are commonly involved in heart failure. Finally, we found that nicotine reduced levels of pSTAT3 (phosphorylated signal transducer and activator of transcription 3) protein expression within the myocardium. Neostigmine treatment did not affect the progression of myocarditis. We showed that activation of the cholinergic antiinflammatory pathway with nicotine reduces inflammation in autoimmune myocarditis. Our results may open new possibilities in the therapeutic management of autoimmune myocarditis.