Immunopathogenesis of dilated cardiomyopathy. Evidence for the role of TH2-type CD4+T lymphocytes and association with myocardial HLA-DR expression

Pathophysiological Effects of Various Interleukins on Primary Cell Types in Common Heart Disease

Myocardial infarction (MI), heart failure, cardiomyopathy, myocarditis, and myocardial ischemia-reperfusion injury (I/R) are the most common heart diseases, yet there is currently no effective therapy due to their complex pathogenesis. Cardiomyocytes (CMs), fibroblasts (FBs), endothelial cells (ECs), and immune cells are the primary cell types involved in heart disorders, and, thus, targeting a specific cell type for the treatment of heart disease may be more effective. The same interleukin may have various effects on different kinds of cell types in heart disease, yet the exact role of interleukins and their pathophysiological pathways on primary cell types remain largely unexplored. This review will focus on the pathophysiological effects of various interleukins including the IL-1 family (IL-1, IL-18, IL-33, IL-37), IL-2, IL-4, the IL-6 family (IL-6 and IL-11), IL-8, IL-10, IL-17 on primary cell types in common heart disease, which may contribute to the more precise and effective treatment of heart disease.

Role of cytokines and inflammation in heart function during health and disease

By virtue of their actions on NF-κB, an inflammatory nuclear transcription factor, various cytokines have been documented to play important regulatory roles in determining cardiac function under both physiological and pathophysiological conditions. Several cytokines including TNF-α, TGF-β, and different interleukins such as IL-1 IL-4, IL-6, IL-8, and IL-18 are involved in the development of various inflammatory cardiac pathologies, namely ischemic heart disease, myocardial infarction, heart failure, and cardiomyopathies. In ischemia-related pathologies, most of the cytokines are released into the circulation and serve as biological markers of inflammation. Furthermore, there is an evidence of their direct role in the pathogenesis of ischemic injury, suggesting cytokines as potential targets for the development of some anti-ischemic therapies. On the other hand, certain cytokines such as IL-2, IL-4, IL-6, IL-8, and IL-10 are involved in the post-ischemic tissue repair and thus are considered to exert beneficial effects on cardiac function. Conflicting reports regarding the role of some cytokines in inducing cardiac dysfunction in heart failure and different types of cardiomyopathies seem to be due to differences in the nature, duration, and degree of heart disease as well as the concentrations of some cytokines in the circulation. In spite of extensive research work in this field of investigation, no satisfactory anti-cytokine therapy for improving cardiac function in any type of heart disease is available in the literature.

TLR3 deficiency induces chronic inflammatory cardiomyopathy in resistant mice following coxsackievirus B3 infection: role for IL-4

Recent findings indicate that TLR3 polymorphisms increase susceptibility to enteroviral myocarditis and inflammatory dilated cardiomyopathy (iDCM) in patients. TLR3 signaling has been found to inhibit coxsackievirus B3 (CVB3) replication and acute myocarditis in mouse models, but its role in the progression from myocarditis to iDCM has not been previously investigated. In this study we found that TLR3 deficiency increased acute (P = 5.9 × 10(-9)) and chronic (P = 6.0 × 10(-7)) myocarditis compared with WT B6.129, a mouse strain that is resistant to chronic myocarditis and iDCM. Using left ventricular in vivo hemodynamic assessment, we found that TLR3-deficient mice developed progressively worse chronic cardiomyopathy. TLR3 deficiency significantly increased viral replication in the heart during acute myocarditis from day 3 through day 12 after infection, but infectious virus was not detected in the heart during chronic disease. TLR3 deficiency increased cytokines associated with a T helper (Th)2 response, including IL-4 (P = 0.03), IL-10 (P = 0.008), IL-13 (P = 0.002), and TGF-β(1) (P = 0.005), and induced a shift to an immunoregulatory phenotype in the heart. However, IL-4-deficient mice had improved heart function during acute CVB3 myocarditis by echocardiography and in vivo hemodynamic assessment compared with wild-type mice, indicating that IL-4 impairs cardiac function during myocarditis. IL-4 deficiency increased regulatory T-cell and macrophage populations, including FoxP3(+) T cells (P = 0.005) and Tim-3(+) macrophages (P = 0.004). Thus, TLR3 prevents the progression from myocarditis to iDCM following CVB3 infection by reducing acute viral replication and IL-4 levels in the heart.

Angiotensin II-induced dilated cardiomyopathy in Balb/c but not C57BL/6J mice

Balb/c mice, which are T-helper lymphocyte 2 (Th2) responders, are highly susceptible to infectious and non-infectious heart diseases, whereas C57BL/6 mice (Th1 responders) are not. Angiotensin II (Ang II) is not only a vasopressor but also a pro-inflammatory factor that leads to cardiac hypertrophy, fibrosis and dysfunction. We hypothesized that Ang II exacerbates cardiac damage in Balb/c but not in C57BL/6 mice even though both strains have a similar level of hypertension. Twelve-week-old male C57BL/6J and Balb/c mice received either vehicle or Ang II (1.4 mg kg(-1) day(-1), s.c. via osmotic minipump) for 8 weeks. At baseline, Balb/c mice exhibited the following: (1) a lower heart rate; (2) an enlarged left ventricular chamber; (3) a lower ejection fraction and shortening fraction; and (4) twice the left ventricular collagen deposition of age-matched C57BL/6J mice. Angiotensin II raised systolic blood pressure (to ∼150 mmHg) and induced cardiomyocyte hypertrophy in a similar manner in both strains. While C57BL/6J mice developed compensatory concentric hypertrophy and fibrosis in response to Ang II, Balb/c mice demonstrated severe left ventricular chamber dilatation, wall thinning and fibrosis, leading to congestive heart failure as evidenced by dramatically decreased ejection fraction and lung congestion (significant increase in lung weight), which are both characteristic of dilated cardiomyopathy. Our study suggests that the Th phenotype plays an active role in cardiac remodelling and function both in basal conditions and in hypertension. Angiotensin II-induced dilated cardiomyopathy in Balb/c mice is an ideal animal model for studying the impact of the adaptive immune system on cardiac remodelling and function and for testing strategies to prevent or treat hypertension-associated heart failure.

Increases in circulating T lymphocytes expressing HLA-DR and CD40 ligand in patients with dilated cardiomyopathy

Inflammatory and immunological mechanisms are implicated in the development of idiopathic dilated cardiomyopathy (DCM). Since activated T lymphocytes express surface HLA-DR antigens, an increased level of these cells in the circulation could indicated an ongoing immune response. While the role of activated T lymphocytes in experimental myocarditis has been elucidated, the contribution of T lymphocyte activation in clinical DCM remains unclear. We therefore examined the role of T-cell activation in peripheral blood samples obtained from 10 patients with DCM (mean age, 49 +/- 12 years) and from 10 age-matched healthy controls. Citrated whole blood was mixed with fluorescein isothiocyanate- or phycoerythrin-conjugated specific monoclonal antibodies and analyzed using a fluorescence-activated cell sorter (FACS). The ratio (%) of histocompatibility leukocyte antigen (HLA)-DR positive cells in the FACS gated lymphocyte population was significantly higher in DCM patients than in controls (7.9% +/- 5.3% vs 2.0% +/- 0.9%; P < 0.01). The expression of CD40L on T cells determined as mean fluorescence intensity (MFI) was also significantly higher in DCM patients than in controls (3.6 +/- 2.1 vs 1.8 +/- 0.4 MFI; P < 0.05). Furthermore, the ratios of T cells expressing HLA-DR and serum brain natriuretic peptide (BNP) levels closely correlated (P = 0.0008). We showed that HLA-DR on peripheral T cells significantly correlated with serum BNP levels and that high CD40L expression on T cells was concomitant with increased BNP levels (P < 0.05). Therefore the magnitude of T-cell expression, such as increased expression of HLA-DR and CD40L, contributes to myocardial dysfunction in DCM.

Cardiac-related hospitalization and/or death associated with immune dysregulation and symptoms of depression in heart failure patients

OBJECTIVE

Congestive heart failure (CHF) patients with depressive symptoms have a greater risk of morbidity and mortality. Immune activity such as inflammation is increasingly implicated as underlying this relationship. However, it is unknown whether there is a broader spectrum of immune dysregulation beyond inflammatory activity. This study examined in CHF patients the relationship of depressive symptoms with cellular immune activity measured by Th1/Th2 ratios and cardiac rehospitalization and/or death.

METHOD

Eighteen patients with CHF (mean age = 62, NYHA classes II-IV) were enrolled and depressive symptoms were measured with interviewer ratings using the Hamilton Rating Scale-Depression. For the determination of Th1/Th2 ratios, intracellular cytokine expression of interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) CD4+ T cells were measured by flow cytometry. Plasma interleukin-6 levels were measured to ascertain circulating inflammatory cytokine activity. Patient records were examined for cardiac related rehospitalization or cardiac related death over a two-year period after baseline depression and immune measures were taken.

RESULTS

Higher depression scores were associated with a prospective increase in incidence of cardiac related hospitalizations and/or death (p = .037). Lesser IFN-gamma/IL-10 expressing CD4+ T cell ratios were related to higher depressive symptom scores at baseline (p = .005) and a prospective increased incidence of cardiac related hospitalization or death over a two-year period (p = .05).

CONCLUSIONS

A shift in the Th1/Th2 ratio may play a role in the association between depressive symptoms and morbidity and mortality in CHF patients, suggesting broader immune dysregulation than previously considered.