Antiinflammatory therapy in myocarditis

Inflammation and cardiac remodeling during viral myocarditis

Acute viral myocarditis is the main cause of cardiac failure in young patients and accounts for up to 60% of "idiopathic" dilated cardiomyopathy. The clinical course of viral myocarditis is mostly insidious with limited cardiac inflammation and dysfunction. However, overwhelming inflammation may occur in a subset of patients, leading to fulminant cardiac injury, whereas others develop chronic heart failure due to autoimmune myocarditis. Today, little effective treatment exists for patients, apart from general supportive therapy and antifailure regimens. Urokinase-type plasminogen activator (u-PA) and matrix metalloproteinases (MMP) have been implicated in cardiac inflammation, matrix remodeling, and wound healing after cardiac injury. The present review will assess the mechanism by which these proteinases mediate cardiac dilatation, fibrosis, and dysfunction after cardiac stress or injury, in order to understand how inhibition of proteinases may provide a novel therapeutic tool to prevent cardiac dilatation and failure during viral myocarditis.

Inhibition of Urokinase-Type Plasminogen Activator or Matrix Metalloproteinases Prevents Cardiac Injury and Dysfunction During Viral Myocarditis

Background— Acute viral myocarditis is an important cause of cardiac failure in young adults for which there is no effective treatment apart from general heart failure therapy. The present study tested the hypothesis that increased expression of the proteinases urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs) is implicated in cardiac inflammation, injury, and subsequent failure during Coxsackievirus-B3 (CVB3)–induced myocarditis.

Methods and Results— First, we showed increased expression and activity of uPA and MMP-9 in wild-type mice at 7 days of CVB3-induced myocarditis. Targeted deletion of uPA, which resulted in reduced MMP activity and cytokine expression or inhibition of MMPs by adenoviral gene overexpression of tissue inhibitor of metalloproteinases-1, decreased cardiac inflammation and reduced myocardial necrosis at 7 days and decreased cardiac fibrosis at 35 days after CVB3 infection. Importantly, loss of uPA or MMP activity prevented CVB3-induced cardiac dilatation and dysfunction, as determined by serial echocardiography.

Conclusions— Loss of uPA or MMP activity reduces the cardiac inflammatory response after CVB3 infection, thereby protecting against cardiac injury, dilatation, and failure during CVB3-induced myocarditis.

Outcome of acute fulminant myocarditis in children

OBJECTIVES

To highlight clinical features and outcome of acute fulminant myocarditis (AFM) in children.

METHODS

Diagnostic criteria were (1) the presence of severe and acute heart failure; (2) left ventricular dysfunction on echocardiography; (3) recent history of viral illness; and (4) no history of cardiomyopathy.

RESULTS

Eleven children were included between 1998 and 2003, at a median age of 1 (0 to 9) year. Their mean left ventricular ejection fraction (LVEF) was 22 (SD 9)% at presentation. A virus was identified in five patients: human parvovirus B19 (n = 2), Epstein-Barr (n = 1), varicella zoster (n = 1), and coxsackie (n = 1). The median intensive care unit course was 13 (2-34) days. Intravenous inotropic support was required by nine patients and eight were mechanically ventilated. All patients received corticosteroid, associated with intravenous immunoglobulin in seven. Five patients experienced cardiocirculatory arrest that was successfully resuscitated in four. At a median follow up of 58.7 (33.8-83.1) months, the 10 survivors are asymptomatic with normalised LVEF.

CONCLUSION

Despite a severe presentation, the outcome of AFM is favourable. Aggressive symptomatic management is warranted and heart transplantation should be considered only when maximal supportive therapy does not lead to improvement.

Molecular determinants of crosstalk between nuclear receptors and toll-like receptors

Nuclear receptors (NRs) repress transcriptional responses to diverse signaling pathways as an essential aspect of their biological activities, but mechanisms determining the specificity and functional consequences of transrepression remain poorly understood. Here, we report signal- and gene-specific repression of transcriptional responses initiated by engagement of toll-like receptors (TLR) 3, 4, and 9 in macrophages. The glucocorticoid receptor (GR) represses a large set of functionally related inflammatory response genes by disrupting p65/interferon regulatory factor (IRF) complexes required for TLR4- or TLR9-dependent, but not TLR3-dependent, transcriptional activation. This mechanism requires signaling through MyD88 and enables the GR to differentially regulate pathogen-specific programs of gene expression. PPARgamma and LXRs repress overlapping transcriptional targets by p65/IRF3-independent mechanisms and cooperate with the GR to synergistically transrepress distinct subsets of TLR-responsive genes. These findings reveal combinatorial control of homeostasis and immune responses by nuclear receptors and suggest new approaches for treatment of inflammatory diseases.