CX3CR1 is a prerequisite for the development of cardiac hypertrophy and left ventricular dysfunction in mice upon transverse aortic constriction

The CX3CL1/CX3CR1 axis mediates recruitment and extravasation of CX3CR1-expressing subsets of leukocytes and plays a pivotal role in the inflammation-driven pathology of cardiovascular disease. The cardiac immune response differs depending on the underlying causes. This suggests that for the development of successful immunomodulatory therapy in heart failure due to chronic pressure overload induced left ventricular (LV) hypertrophy, the underlying immune patterns must be examined. Here, the authors demonstrate that Fraktalkine-receptor CX3CR1 is a prerequisite for the development of cardiac hypertrophy and left ventricular dysfunction in a mouse model of transverse aortic constriction (TAC). The comparison of C57BL/6 mice with CX3CR1 deficient mice displayed reduced LV hypertrophy and preserved cardiac function in response to pressure overload in mice lacking CX3CR1. Moreover, the normal immune response following TAC induced pressure overload which is dominated by Ly6C^low macrophages changed to an early pro-inflammatory immune response driven by neutrophils, Ly6C^high macrophages and altered cytokine expression pattern in CX3CR1 deficient mice. In this early inflammatory phase of LV hypertrophy Ly6C^high monocytes infiltrated the heart in response to a C-C chemokine ligand 2 burst. CX3CR1 expression impacts the immune response in the development of LV hypertrophy and its absence has clear cardioprotective effects. Hence, suppression of CX3CR1 may be an important immunomodulatory therapeutic target to ameliorate pressure-overload induced heart failure.

Podoplanin neutralization improves cardiac remodeling and function after acute myocardial infarction

Podoplanin, a small mucine-type transmembrane glycoprotein, has been recently shown to be expressed by lymphangiogenic, fibrogenic and mesenchymal progenitor cells in the acutely and chronically infarcted myocardium. Podoplanin binds to CLEC-2, a C-type lectin-like receptor 2 highly expressed by CD11bhigh cells following inflammatory stimuli. Why podoplanin expression appears only after organ injury is currently unknown. Here, we characterize the role of podoplanin in different stages of myocardial repair after infarction and propose a podoplanin-mediated mechanism in the resolution of post-MI inflammatory response and cardiac repair. Neutralization of podoplanin led to significant improvements in the left ventricular functions and scar composition in animals treated with podoplanin neutralizing antibody. The inhibition of the interaction between podoplanin and CLEC-2 expressing immune cells in the heart enhances the cardiac performance, regeneration and angiogenesis post MI. Our data indicates that modulating the interaction between podoplanin positive cells with the immune cells after myocardial infarction positively affects immune cell recruitment and may represent a novel therapeutic target to augment post-MI cardiac repair, regeneration and function.

Full Expression of Cardiomyopathy Is Partly Dependent on B-Cells: A Pathway That Involves Cytokine Activation, Immunoglobulin Deposition, and Activation of Apoptosis

BACKGROUND

Limited information exists on the role of B-cell-dependent mechanisms in the progression of heart failure (HF). However, in failing human myocardium, there is evidence of deposition of activated complement components as well as anticardiac antibodies. We aimed to determine the contribution of B-cells in HF progression using a nonsurgical mouse model of nonischemic cardiomyopathy (CMP).

METHODS AND RESULTS

CMP protocol involved the use of l-NAME and NaCl in the drinking water and angiotensin-II infusion for 35 days. At day 35, mice were analyzed by cardiac magnetic resonance imaging, gene expression, and histology. Mice (12 weeks old) were divided into 4 groups, all in C57BL/6 background: wild-type (WT) CMP; severe combined immunodeficiency (SCID) CMP (T- and B-cell deficient); CD22(-) CMP (B-cell depleted); and Nude CMP (T-cell deficient), with their respective controls. We performed B-cell depletion and reconstitution protocols. The protective effect of B-cell depletion was demonstrated by a significant reduction of cell hypertrophy and collagen deposition and a preserved ejection fraction in the CD22(-) CMP group compared to WT CMP. Once SCID mice underwent B-cell reconstitution with isolated CMP B-cells, the CMP phenotype was restored. Furthermore, deposition of IgG3 and apoptosis in the myocardium follows the development of CMP; in addition, in vitro studies demonstrated that activated B-cells stimulate collagen production by cardiac fibroblasts.

CONCLUSIONS

The absence of B-cells in this model of HF resulted in less hypertrophy and collagen deposition, preservation of left ventricular function, and, in association with these changes, a reduction in expression of proinflammatory cytokines, immunoglobulin G deposition, and apoptosis in the myocardium. Taken together, these data suggest that B-cells play a contributory role in an angiotensin-II-induced HF model.

Olmesartan medoxomil reverses left ventricle hypertrophy and reduces inflammatory cytokine IL-6 in the renovascular hypertensive rats

AIM

To investigate the effects of Olmesartan Medoxomil (OM) on left ventricle hypertrophy (LVH) and inflammatory cytokines IL-6 and IL-10 levels in renovascular hypertensive rats.

MATERIALS AND METHODS

Qualified 30 male Wistar rats were randomly divided into three groups: sham-operation group (SO, n=10), model control group (MC, n=10), and Olmesartan Medoxomil group (OM, n=10). Renovascular hypertension was induced by ligating the abdominal aorta and 10 mg/kg OM was administered daily to the OM group by gastric perfusion for 7 weeks. The ratio of left ventricle mass to body weight (LVM/BW) was calculated as the index of cardiac hypertrophy, and the inflammatory cytokines IL-6 and IL-10 in serum and cardiac tissue were measured by ELISA assays.

RESULTS

The LVM/BW ratios in the MC group were about 50% higher than that in the SO group (p < 0.001). The OM group showed much reduced LVM/BW ratios compared with the MC group (p < 0.001) and were similar to that in the SO group (p > 0.05), indicating a complete reversal of the left ventricular hypertrophy caused by aorta ligation. The IL-6 and IL-10 levels in both the serum and cardiac tissue increased following aorta ligation (MC vs. SO, p < 0.001). While OM treatment significantly reduced IL-6 levels in the aorta-ligated rats (OM vs. MC, p < 0.001), IL-10 levels were not affected (OM vs. MC, p > 0.05).

CONCLUSIONS

OM completely reversed left ventricle hypertrophy and reduced IL-6 levels in renovascular hypertensive rats. Its effect on IL-10 levels in this animal model was not statistically significant.

[The immunologic disorders and dysfunction of endothelium as predictors of development of hypertrophy of left ventricle of heart in patients with hypertension disease]

The sampling included 231 patient with hypertension disease of stage I-II. The hypertrophy of left ventricle of heart was established in 97 patients (group I) and 134 patients had no hypertrophy of left ventricle of heart (group II). The control group consisted of 25 healthy persons. The increase of tumor necrosis factor alpha and interleukin beta was established in group I as compared with group II and control group. In patients of group I the expressed dysfunction of endothelium was observed. The increase of endothelin I and number of desquamated endotheliocytes as compared with group II and healthy persons was established. The direct relationship between increase of concentration of analyzed cytokines and presence of hypertrophy of left ventricle of heart is revealed.

[Effects of sapindus saponins on inflammatory response mediated by Ang II/p38MAPK pathway and cardiac hypertrophy in spontaneously hypertensive rats]

OBJECTIVE

To investigate the effects of sapindus saponins on myocardial inflammation mediated by Ang II/ p38MAPK signal pathway and cardiac hypertrophy in spontaneously hypertensive rats. And also to explore the correlation of cardiac hypertrophy and inflammation.

METHOD

Thirty-two 16-week-old spontaneously hypertensive rats (SHR) were randomly divided into four groups, one with placebo as model group, one with captopril tablets (27 mg x kg(-1)) as positive control, one with low-dose sapindus saponins (27 mg x kg(-1)), one with high-dose (108 mg x kg(-1)). And another eight healthy Wistar-Kyoto strain (WKY) rats were used as the normal group. The animals were treated for eight weeks, and the indicators detected were as follows: (1) left ventricular mass index (LVMI); (2) the content of Ang II and hs-CRP in plasma were determined by ELISA; (3) the protein expression of AT1R and VEGF were determined by immunohistochemical method; (4) the protein expression of p-p38MAPK in myocardial cells was determined by Western blot.

RESULT

Sapindus saponins reduced LVMI, and blocked the expression level of Ang II, AT1R, p-p38MAPK, VEGF and hs-CRP in myocardial tissue. Vs the SHR model group, there were significant differences (P < 0.05 or P < 0.01).

CONCLUSION

Our findings suggested that sapindus saponins could inhibited cardiac hypertrophy, the possible mechanisms may be related to the inhibition on inflammatory response mediated by Ang II/p38MAPK pathway.

The chemokine decoy receptor D6 prevents excessive inflammation and adverse ventricular remodeling after myocardial infarction

OBJECTIVE

Leukocyte infiltration in ischemic areas is a hallmark of myocardial infarction, and overwhelming infiltration of innate immune cells has been shown to promote adverse remodeling and cardiac rupture. Recruitment of inflammatory cells in the ischemic heart depends highly on the family of CC-chemokines and their receptors. Here, we hypothesized that the chemokine decoy receptor D6, which specifically binds and scavenges inflammatory CC-chemokines, might limit inflammation and adverse cardiac remodeling after infarction.

METHODS AND RESULTS

D6 was expressed in human and murine infarcted myocardium. In a murine model of myocardial infarction, D6 deficiency led to increased chemokine (C-C motif) ligand 2 and chemokine (C-C motif) ligand 3 levels in the ischemic heart. D6-deficient (D6(-/-)) infarcts displayed increased infiltration of pathogenic neutrophils and Ly6Chi monocytes, associated with strong matrix metalloproteinase-9 and matrix metalloproteinase-2 activities in the ischemic heart. D6(-/-) mice were cardiac rupture prone after myocardial infarction, and functional analysis revealed that D6(-/-) hearts had features of adverse remodeling with left ventricle dilation and reduced ejection fraction. Bone marrow chimera experiments showed that leukocyte-borne D6 had no role in this setting, and that leukocyte-specific chemokine (C-C motif) receptor 2 deficiency rescued the adverse phenotype observed in D6(-/-) mice.

CONCLUSIONS

We show for the first time that the chemokine decoy receptor D6 limits CC-chemokine-dependent pathogenic inflammation and is required for adequate cardiac remodeling after myocardial infarction.

Is left ventricular hypertrophy a low-level inflammatory state? A population-based cohort study

BACKGROUND AND AIMS

Cross-sectional studies have shown that chronic sub-clinical inflammation is associated with left ventricular hypertrophy (LVH), but results are conflicting. We investigated the association between baseline LVH and high-sensitivity C-reactive protein (CRP) values, both cross-sectionally and after a six-year-follow-up, in a population-based cohort (n = 1564) and a subgroup from this cohort (n = 515), without obesity, diabetes, metabolic syndrome or any drugs.

METHODS AND RESULTS

ECG tracings at baseline were interpreted according to the Cornell voltage-duration product criteria: 166/1564 subjects (10.6%) showed LVH. Patients with baseline LVH showed increased BMI, waist circumference, blood pressure, and a worse metabolic pattern. Their CRP values both at baseline and at follow-up were almost two-fold higher than in patients without LVH. Similar results were found in the healthier sub-sample. In a multiple regression model, CRP at follow-up was directly associated with baseline LVH (expressed as Cornell voltage-duration product) in the whole cohort (β = 0.0003; 95%CI 0.0002-0.0006; p < 0.001) and in the sub-sample (β = 0.0003; 0.0002-0.0004; p < 0.001), after adjusting for age, sex, BMI, waist circumference, smoking, exercise levels, blood pressure and baseline CRP values.

CONCLUSION

Baseline LVH, which is associated with systemic inflammation, predicts increased CRP values at follow-up, independently of cardiovascular and metabolic risk factors, both in a population-based cohort and a healthier sub-sample. The inflammatory consequences of LVH might be an intriguing subject for further researches.

[Positive rate of autoantibodies against adrenergic receptors beta1 and angiotensin II type 1 receptors in the type 2 diabetes mellitus with or without hypertension]

OBJECTIVE

To observe the positive rates of autoantibodies against beta1 adrenergic receptors (beta1-receptor) and angiotensin II type 1 receptors (AT(1)-receptor) in type 2 diabetes patients with or without hypertension.

METHODS

The epitopes of the second extracellular loop of beta1-receptor (197 - 222) and AT(1) receptor (165 - 191) were synthesized and serum autoantibodies were determined in type 2 diabetes patients with hypertension (n = 171) or without hypertension (n = 106). Left ventricular dimension was determined by echocardiography. The 24-hour urinary protein was measured by ELISA. The risk factors for enlarged left ventricle were analyzed by multiple logistic regressions.

RESULTS

The positive rates of the autoantibodies against beta1-receptors (45.0%) and AT(1)-receptor (46.2%) in patients with type 2 diabetes with hypertension were significantly higher than those in patients with type 2 diabetes without hypertension (16.0% and 10.4%, respectively, all P < 0.01). In type 2 diabetes patients with hypertension and enlarged left ventricle, the positive rates of the autoantibodies against beta1-receptor 61.4% (35/57) and against AT(1)-receptor 64.9% (37/57)were significantly higher than those in type 2 diabetes patients with normal left ventricular dimension (36.8%, 42/114 and 36.8%, 42/114, respectively, all P < 0.01). Regression analysis demonstrated that course of disease, systolic pressure, serum autoantibodies against beta1 adrenergic receptor and angiotensin II type 1 receptors sera autoantibodies were independent risk factors for left ventricular enlargement (all P < 0.05).

CONCLUSION

The serum beta1 and AT(1)-receptor autoantibodies are related to enlarged left ventricle in type 2 diabetes patients with hypertension and suggest that autoantibodies against beta1 and AT(1)-receptor might play important roles in the pathogenesis of type 2 diabetes patients with hypertension and enlarged left ventricle.

Anti-inflammation role for mesenchymal stem cells transplantation in myocardial infarction

The aim of the present study was to investigate the role of anti-inflammation for MSCs transplantation in rat models of myocardial infarction. Rats with AMI induced by occlusion of the left coronary artery were randomized to MSCs transplantation group, MI group and sham operated group. The effects of MSCs transplantation on cardiac inflammation and left ventricular remodeling in non-infarcted zone were observed after 4 weeks of MI. We found that MSC transplantation (1) decreased protein production and gene expression of inflammation cytokines TNF-alpha, IL-1beta and IL-6, (2) inhibited deposition of type I and III collagen, as well as gene and protein expression of MMP-1 and TIMP-1, (3) attenuated LV cavitary dilation and transmural infarct thinning, thus prevent myocardial remodeling after myocardial infarction, and (4) increased EF, FS, LVESP and dp/dtmax (P < 0.01), decreased LVDd, LVEDV, LVEDP (P < 0.05). Anti-inflammation role for MSCs transplantation might partly account for the cardiac protective effect in ischemic heart disease.

Histopathological study of time course changes in inter-renal aortic banding-induced left ventricular hypertrophy of mice

The left ventricular hypertrophy (LVH) in response to pressure overload is an important risk factor in cardiac morbidity and mortality. To investigate the time course of histopathological alterations in the LVH in response to pressure overload, histopathological and immunohistochemical examination was performed using the aortic banding-induced mouse LVH model. Five-week-old male CD-1 mice were subjected to the inter-renal aortic banding. Major organs were sampled on 3, 10, 14, 21, 28 or 42 days after banding. Haematoxylin and eosin (H&E) staining, Masson's trichrome staining and immunohistochemistry for proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (aSMA), ICAM-1, type I collagen and CD31 was performed and microscopically examined. Three days after aortic banding, acute inflammatory changes, such as macrophages/neutrophil infiltration and vascular wall injury were observed on/around the coronary arteries/arterioles of both ventricles. Intense ICAM-1 immunostaining was observed on the endothelium of the coronary arteries/arterioles. After day 10, vascular wall thickening and perivascular fibrosis was induced on the coronary arteries/arterioles. Immunohistochemistry for aSMA and PCNA demonstrated the proliferation of vascular smooth muscle cells in the media. After day 28, minimal cardiomyocyte hypertrophy was observed at the light microscope level. In the inter-renal aortic banding LVH model, histopathological alterations in early phase were mainly observed on coronary arteries/arterioles. These early phase alterations were thought to be hypertension-related changes in the coronary vasculatures. The cardiomyocyte hypertrophy observed in later phase was minimal at the light microscope level. These evidences would facilitate the understanding of pathophysiology of pressure overload LVH.

Tumor necrosis factor-alpha mediates cardiac remodeling and ventricular dysfunction after pressure overload state

BACKGROUND

Pressure overload is accompanied by cardiac myocyte apoptosis, hypertrophy, and inflammatory/fibrogenic responses that lead to ventricular remodeling and heart failure. Despite incomplete understanding of how this process is regulated, the upregulation of tumor necrosis factor (TNF)-alpha after aortic banding in the myocardium is known. In the present study, we tested our hypothesis that TNF-alpha regulates the cardiac inflammatory response, extracellular matrix homeostasis, and ventricular hypertrophy in response to mechanical overload and contributes to ventricular dysfunction.

METHODS AND RESULTS

C57/BL wild-type mice and TNF-knockout (TNF-/-) mice underwent descending aortic banding or sham operation. Compared with sham-operated mice, wild-type mice with aortic banding showed a significant increase in cardiac TNF-alpha levels, which coincided with myocyte apoptosis, inflammatory response, and cardiac hypertrophy in week 2 and a significant elevation in matrix metalloproteinase-9 activity and impaired cardiac function in weeks 2 and 6. Compared with wild-type mice with aortic banding, TNF-/- mice with aortic banding showed attenuated cardiac apoptosis, hypertrophy, inflammatory response, and reparative fibrosis. These mice also showed reduced cardiac matrix metalloproteinase-9 activity and improved cardiac function.

CONCLUSIONS

Findings from the present study have suggested that TNF-alpha contributes to adverse left ventricular remodeling during pressure overload through regulation of cardiac repair and remodeling, leading to ventricular dysfunction.

Antigen-specific effects of autoantibodies against sarcolemmal Na–K-ATPase pump in immunized cardiomyopathic rabbits

OBJECTIVES

We examine antigen-specific actions of autoantibodies directed against sarcolemmal Na-K-ATPase.

BACKGROUND

Autoantibodies against some receptors or pumps were detected in patients with dilated cardiomyopathy. Although immunoglobulin adsorption therapy improved cardiac function in such patients, direct pathogenic effects of autoantibodies remain to be proven.

METHODS

Japanese white rabbits were immunized once a month with purified Na-K-ATPase (NKA rabbits, n=10) or a synthetic peptide corresponding to the second extracellular loop of beta1-adrenergic receptors (beta rabbits, n=10), respectively. Control rabbits (n=10) received vehicle in the same manner.

RESULTS

At 6 months, cardiac hypertrophy along with increased left ventricular end-diastolic pressure was observed in both NKA and beta rabbits, and inhibitory G protein level increased in both NKA and beta rabbits. Histological findings showed similar myocyte hypertrophy and interstitial fibrosis in both rabbits. Enzymatic activities of Na-K-ATPase were lower in NKA rabbits than in other groups. Immunoblotting showed that alpha3-isoform of Na-K-ATPase was selectively reduced in myocardium from NKA rabbits.

CONCLUSIONS

Our present findings suggested that isoform-specific alterations of myocardial Na-K-ATPase activity were induced by immunizing rabbits. This was not secondary change due to cardiac hypertrophy. Thus, autoantibodies against sarcolemmal Na-K-ATPase have antigen-specific effect on the heart in vivo.

[Impact of chronic Chlamydia pneumoniae infection on left ventricular remodeling after myocardial infarction]

BACKGROUND

Postmyocardial infarction left ventricular remodeling is modified by inflammatory processes and structural changes in the myocardium. Chlamydia pneumoniae (Chp) causes chronic myocyte infection, affects apoptosis and TNF-alpha production, and may induce cross reactivity with alpha myosin. This is the way in which this intracellular pathogen may modulate remodeling on the cellular and organ level.

MATERIAL AND METHODS

The study was conducted in 101 patients with a first myocardial infarction in whom we evaluated the serological features of Chp infection using the ELISA method and echocardiographic left ventricular volume at 10 days and 10 weeks after the infarction.

RESULTS

Patients with chronic Chp infection had a tendency toward higher end-diastolic volume at 10 weeks after the infarction (123 +/- 32.9 ml vs. 134 +/- 34.7 ml, p = 0.09). In order to better define this relationship we used ROC analysis and measured levels of antibodies: IgG = 117 EIU and IgA = 15.6 EIU by which we divided the patients into two subgroups. Those with IgG > or = 117 EIU and IgA > or = 15.6 EIU belong to the subgroup with chronic and active Chp infection. These patients had larger left ventricular end-diastolic volumes (155.8 vs. 123.1 ml, p = 0.0005) and end-systolic volumes (77.4 vs. 59.5 ml, p = 0.006) at 10 weeks after the infarction. Both subgroups were similar with respect to age, gender, history of arterial hypertension, systolic and diastolic blood pressure values, infarct site, reperfusion, infarct size, left ventricular ejection fraction and left ventricular contractility index. Type of reperfusion therapy and pharmacological treatment at 10 days and at 10 weeks did not differ, either.

CONCLUSIONS

Chronic Chlamydia pneumonie infection modifies the course of left ventricular remodeling.

Hypertensive left ventricular hypertrophy: relation to beta-adrenergic receptor kinase-1 (betaARK1) in peripheral lymphocytes

BACKGROUND

Left ventricular hypertrophy (LVH) is associated with increased cardiovascular risk and altered sympathetic regulation in hypertension.

OBJECTIVES

To determine whether the level of beta-adrenergic receptor kinase-1 (betaARK1) in lymphocytes is related to LVH in patients with hypertension.

METHODS

Forty-nine patients with untreated essential hypertension were recruited to the study and classified into two groups: left ventricular hypertrophy (LVH: left ventricular mass index > or =134 g/m in men and > or =110 g/m in women; ages 52.4 +/- 12.8 years, n = 25) and non-LVH (NLVH: left ventricular mass index < 134 g/m in men and < 110 g/m in women; ages 50.8 +/- 13.1 years, n = 24). Lymphocytes were isolated from patients and quantitative-competitive reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were used to estimate the expression of betaARK1 in the lymphocytes. G-protein-coupled receptor kinase activity was assessed by rhodopsin phosphorylation assay.

RESULTS

The expression of betaARK1 in lymphocytes was greater in the LVH group than in the NLVH group (0.0069 +/- 0.002 ng compared with 0.0048 +/- 0.0017 ng, P < 0.01) and correlated well with left ventricular mass index (r = 0.527, P < 0.001) and relative wall thickness (r = 0.627, P < 0.001). The concentration of betaARK1 protein in lymphocytes from individuals with LVH was increased two-fold compared with that in the NLVH group (both n = 7). Lymphocyte G-protein-coupled receptor kinase activity from LVH was enhanced 1.7-fold compared with NLVH (1.03 +/- 2.16 and 1.79 +/- 1.87 pmol phosphate/min per mg protein, respectively; P < 0.05, n = 7 for each group).

CONCLUSIONS

The concentration of betaARK1 in lymphocytes is greater in hypertensive individuals with LVH than in those without LVH and parallels the degree of hypertrophy. Generalized alterations in beta-adrenergic signalling, including betaARK1, could be a major contributory factor in the development of LVH in hypertension, and the concentration of betaARK1 in lymphocytes can reflect the development of LVH in a patient with hypertension.

[Expression of cytokines and their receptors in left ventricular hypertrophy in TGR(mRen2)27 rats]

Variations in the expression of cytokines from the interleukin-6 (IL-6) family: ciliary neurotrophic factor (CNTF), leukaemia inhibitory factor (LIF), and cardiotrophin 1 (CT-1) were studied during cardiac remodelling leading to left ventricular hypertrophy (LVH) in TGR(mRen2)27 rats at the age of 8 and 20 weeks. The cytokines mRNA levels within the free wall of the left ventricle were measured by semi-quantitative RT-PCR standardised with 18S. They were compared between heterozygous rats for the mRen2 transgene (TG+/-) and control rats (TG-/-). No significant difference was observed between results obtained at 8 and 20 weeks of age. At 20 weeks of age, TGR(mRen2)27 rats showed higher levels of mRNA LIF and IL-6 respectively by 52 and 55% compared to the control rats [LIF TG+/-: 3.17 +/- 0.21, TG-/-: 2.09 +/- 0.03; p < 0.001; n = 5; and IL-6 TG+/-: 1.53 +/- 0.13; TG-/-: 0.99 +/- 0.17; p < 0.05; n = 5]. By contrast, no variation of mRNAs levels of CT-1 and gp 130 genes was observed between control and transgenic rats. Concerning the cytokine receptors, the levels of mRNA for IL-6R did not vary while those of receptor subunits LIFR and CNTFR were decreased respectively by 48 and 42% in transgenic rats vs controls [LIFR TG+/-: 0.48 +/- 0.01; TG-/-: 0.92 +/- 0.08 p < 0.001; n = 5; and CNTFR TG+/-: 1.07 +/- 0.08; TG-/-: 1.85 +/- 0.18; p < 0.01; n = 5]. Therefore, these results show a specific pattern of activation of the cytokines pathway in the LVH of the TGR(mRen2)27 rat.

Inflammation, arteriosclerosis, and cardiovascular therapy in hemodialysis patients

BACKGROUND

Aortic stiffness and left ventricular hypertrophy (LVH) are predictors of mortality in hemodialysis (HD) patients. Attenuation of arterial stiffness and regression of LVH had a favorable effect on survival in these patients, but this favorable effect was observed in less than 50% of patients, the rest being resistant to therapeutical interventions. The aim of this study was to analyze the factors associated with this resistance to treatment.

METHODS

138 patients on HD were studied during a follow-up survey. From entry until the end of follow up, the changes of aortic pulse wave velocity (PWV) and of LV mass were measured in response to treatment with antihypertensive drugs and erythropoietin, together with measurements of blood chemistry, including high-sensitive C-reactive protein (CRP). Patients with decreased aortic PWV were considered to be responders (N = 68), the others to be nonresponders (N = 70).

RESULTS

Nonresponders were older (P < 0.05) and had persistently higher systolic blood pressure (BP) and pulse pressure. Responders were treated more frequently with an ACE inhibitor (P < 0.001), and had lower serum CRP (P < 0.01). The baseline PWV, as well as the changes of PWV and LV mass during the follow-up were significantly and independently correlated with serum CRP level (P < 0.001). According to logistic regression after adjustment for age, gender, diabetes, history of CVD, and the nonspecific cardiovascular risk factors, the improvement of aortic stiffness and LV hypertrophy was positively associated with prescription of ACE inhibitor (P < 0.0001), and negatively with the serum CRP level (P < 0.01).

CONCLUSION

These results indicate that in HD patients, the presence of low-grade inflammation decreases the efficiency of cardiovascular therapeutic interventions and participates in the persistence of cardiovascular hemodynamic overload.

Systemic immunosuppression fails to suppress cardiac cytokine induction in pressure overload hypertrophy in rats

BACKGROUND

Activation of cytokines such as interleukin-6 (IL-6) has been implicated in the pathogenesis of left ventricular dysfunction and hypertrophy since they have been shown to mediate cell proliferation, negative inotropic effects and myocardial hypertrophy. However, the effects of immunosuppressive therapy on cytokines in the treatment of heart failure and hypertrophy are unclear.

AIMS

To test the hypothesis that systemic immunosuppresion may influence serum and myocardial IL-6 and, thereby, may affect progression of myocardial hypertrophy. We studied the effects of chronic treatment with methotrexate (MTx) and with the ACE inhibitor ramipril on IL-6 in rats with pressure overload left ventricular hypertrophy (LVH) due to aortic banding.

METHODS

Animals were treated with either vehicle (n = 6) or methotrexate (MTx 1: 0.3 mg/kg BW/week; MTx 2: 0.9 mg/kg BW/week; i.p.; n = 6 each group) once a week during weeks 4-12 after aortic banding; sham-operated rats served as controls (CTRL; n = 8). During the development of LVH, serum IL-6 was determined by rat-specific ELISA and 12 weeks after aortic banding myocardial IL-6 was measured using a tissue superfusion technique or determining of protein concentration.

RESULTS

Aortic banding significantly lowered blood pressure, increased left ventricular weight and resulted in elevated serum IL-6 levels (27.6 +/- 5.1 vs 19.1 +/- 2.3 pg/ml, p < 0.05) compared to CTRL. MTx treatment normalised the initially elevated serum IL-6 levels after 8 weeks of treatment. The significant increase in IL-6 concentration in the superfusate of all aortic banding groups compared to CTRL (< 30%, p < 0.05) was not altered by prior MTx therapy. Accordingly, both doses of MTx failed to prevent LVH progression (1.67 +/- 0.23 g vs. 2.32 +/- 0.31 g, p < 0.05). In contrast, chronic inhibition of the RAAS not only prevents LVH but also reduces myocardial IL-6 concentration (6898 +/- 355 vs. 3073 +/- 366 pg/mg protein, p < 0.05).

CONCLUSION

Pressure overload LVH in rats is characterized by an increase in serum levels of IL-6 as well as myocardial IL-6. Chronic immunosuppressive therapy normalized systemic IL-6 levels, but failed to reduce cardiac IL-6 expression and the progression of LVH, while ACE inhibition is sufficient to modify LVH and thereby normalises myocardial IL-6 expression.

Active immunization of combined beta1-adrenoceptor and M2-muscarinic receptor peptides induces cardiac hypertrophy in rabbits

BACKGROUND

The high prevalence of patients with dilated cardiomyopathy (DCM) with anti-beta1-adrenoceptor and/or anti-M2-muscarinic receptor autoantibodies in their sera has been observed. However, the pathophysiological role of these autoantibodies in the development of cardiomyopathy is unknown. We previously reported an experimental model of early-stage DCM-like cardiomyopathy induced by immunizing rabbits for 1 year with synthetic peptides corresponding to the sequence of the second extracellular loop of either beta1-adrenoceptor or M2-muscarinic receptor. Because approximately half the sera of patients with DCM that recognize one of the two receptor sequences also recognize the second sequence, a model was created in rabbits simultaneously immunized with the synthetic peptides corresponding to the second extracellular loop of the beta1-adrenoceptor and M2-muscarinic receptor.

METHODS AND RESULTS

All rabbits (n = 8) immunized with both peptides had a high titer of both anti-beta1-adrenoceptor and anti-M2-muscarinic receptor autoantibodies in their sera, whereas none of the sera from control rabbits injected with saline (n = 9) was positive. No significant cross-reaction with peptides other than those used for immunization was found. The weight of the hearts of immunized rabbits increased significantly. The hearts of immunized rabbits showed marked concentric left ventricular hypertrophy with mild inflammatory cell infiltration. In these rabbits, mild or moderate interstitial fibrosis was also observed. In electron micrographs, immunized rabbits showed focal myofibrillar lysis, loss of myofilament, and a marked increase in the number of mitochondria and deposition of dense granules in both sarcoplasm and myofibrils. Conversely, one of the control rabbits showed scant mononuclear cell infiltration. However, in this control rabbit, no significant alteration was found by electron microscopy.

CONCLUSION

Our results showed the coexistence of both anti-beta1-adrenoceptor and anti-M2-muscarinic receptor autoantibodies in the sera has pathophysiological importance, shown by their ability to induce cardiac hypertrophy in rabbits.

Chlamydia pneumoniae antibodies in severe essential hypertension

Several studies have implied an association between Chlamydia pneumoniae (C. pneumoniae) and cardiovascular disease. Our study was designed to determine whether this organism is associated with severe essential hypertension in a multiracial British population. Antibodies to C. pneumoniae were measured by microimmunofluorescence in 123 patients with chronic severe hypertension and 123 control subjects, matched for ethnic origin, age, sex, and smoking habit, admitted to the same hospital with various noncardiovascular, nonpulmonary disorders. Previous infection was defined by IgG 64 to 256, provided that there was no detectable IgM. Multiple regression analyses of matched and unmatched data were used to investigate the influences of antibody levels and potential confounding factors (ethnic origin, age, sex, smoking habit, diabetes mellitus, and social deprivation) on hypertension. A portion of the hypertensive patients underwent echocardiography, estimation of left ventricular mass index, and measurements of fibrinogen, D-dimer, and von Willebrand factor concentrations. Thirty-five percent of hypertensive patients and 17.9% of matched control subjects had antibody titers consistent with previous C. pneumoniae infection. The hypertensive patients differed significantly from their matched control subjects in their level of previous infection, with an odds ratio of 2.5 (95% confidence interval, 1.3 to 4.7). There were no significant differences in antibody levels between patients with left ventricular hypertrophy and those without it. Fibrinogen, D-dimer, and von Willebrand factor concentrations were not significantly associated with antibody levels. These data support an association of C. pneumoniae with severe essential hypertension. They provide no evidence of a predisposition to develop left ventricular hypertrophy in hypertensive patients with C. pneumoniae infection or of associations with hypercoagulability or endothelial dysfunction.

Immunopathogenic mechanisms in hypertension

There is a growing interest in immunologically-mediated lesions in the cardiovascular system, as there has been evidence that there are antimitochondrial antibodies (AMA) in patients with hypertrophic cardiomyopathy or hypertensives with left ventricular hypertrophy (LVH). We have also very recently published findings from our laboratory that hypertensives with LVH have a considerable quantity of anticardiac antibodies (ACA) in their serum. The aim of this study was to investigate the possible involvement of autoimmune mechanisms in the pathogenesis and evolution of hypertensive disease. Three groups of subjects were included in the study. Group A comprised 37 patients (20 men, 17 women, mean age 50.5 +/- 8.5 years) with mild to moderate essential hypertension, 19 without echocardiographic evidence of LVH, and 18 with LVH. Group B comprised 10 patients (6 men, 4 women, mean age 45.1 +/- 8.7 years) with secondary hypertension. The control group (C) comprised 15 normotensive subjects (8 men, 7 women, mean age 47.7 +/- 8.7 years). Cellular immunity against arterial wall antigen was studied in all subjects by means of migration inhibitory factor (MIF) against relevant antigen preparation. Sera from Group A and C subjects were tested for the presence of autoantibodies against both specific (myocardial) and nonspecific antigens, by means of the indirect immunofluorescence technique. Eighty per cent of patients with essential hypertension showed a positive cellular response (MIF) against an arterial wall antigen compared to the patients with secondary hypertension or the control group. Moreover, patients with essential hypertension and LVH had the highest incidence of specific (anticardiac, ACA) and nonspecific autoantibodies and the highest C3c and C4 complement component levels compared to patients without LVH or the control group. Most of the ACA positive patients were also AMA positive, while the ACA negative patients were AMA negative as well. Defects in cell-mediated immunity against arterial wall antigen(s) may be the cause or the effect of hypertension. On the basis of our findings that there was no delayed type hypersensitivity response to arterial wall antigen(s) in the patients with secondary hypertension, we suggest that, in some cases of essential hypertension, delayed hypersensitivity reactions possibly contribute to the pathogenesis of hypertension. Autoimmune mechanisms are discussed on the basis of common epitopes shared between heart and arterial tissue.

A possible role for autoantibodies in left ventricular hypertrophy

The purpose of the study was to investigate the possible role of autoantibodies in the development and type of left-ventricular hypertrophy (LVH). Three groups of subjects were studied: (a) 15 patients with hypertrophic cardiomyopathy (HCM; 11 males, 4 females; mean age 50.0 +/- 16.3 years); (b) 15 patients with essential hypertension (10 males, 5 females; mean age 56.8 +/- 13.5 years) with normal renal function and serum electrolytes and (c) 15 male athletes (mean age 20.8 +/- 5.9 years). The control group consisted of 15 normal subjects with no sign of heart disease. The following indices of cardiac performance were determined by means of echocardiography: end-diastolic and end-systolic diameters, interventricular septum thickness, left-ventricular (LV) wall thickness, LV mass and LV mass index. The immunologic parameters studied included autoantibodies against (a) specific (anticardiac cell; ACA) and (b) nonspecific (antimitochondrial cell; AMA) autoantigens according to a conventional indirect immunofluorescence technique. (1) Higher values for LV mass and LV mass index were observed in HCM. (2) The incidence of specific and non-specific autoantibodies in hypertensive patients and in patients with HCM was significantly higher compared to athletes and controls. All ACA-positive individuals (5 with HCM, 3 with hypertension and 1 athlete) were AMA positive as well, while all ACA-negative individuals were also AMA negative. The ACA-positive individuals had higher C3c and C4 levels compared to the ACA-negative individuals. An autoantibody-mediated immunopathogenic role is discussed in the development and type of myocardial hypertrophy.