Pulmonary endothelium as a site of synthesis and storage of interleukin-6 in experimental congestive heart failure

Pathophysiologic Processes and Novel Biomarkers Associated With Congestion in Heart Failure

BACKGROUND

Congestion is the main driver behind symptoms of heart failure (HF), but pathophysiology related to congestion remains poorly understood.

OBJECTIVES

Using pathway and differential expression analyses, the authors aim to identify biological processes and biomarkers associated with congestion in HF.

METHODS

A congestion score (sum of jugular venous pressure, orthopnea, and peripheral edema) was calculated in 1,245 BIOSTAT-CHF patients with acute or worsening HF. Patients with a score ranking in the bottom or top categories of congestion were deemed noncongested (n = 408) and severely congested (n = 142), respectively. Plasma concentrations of 363 unique proteins (Olink Proteomics Multiplex CVD-II, CVD-III, Immune Response and Oncology II panels) were compared between noncongested and severely congested patients. Results were validated in an independent validation cohort of 1,342 HF patients (436 noncongested and 232 severely congested).

RESULTS

Differential protein expression analysis showed 107/363 up-regulated and 6/363 down-regulated proteins in patients with congestion compared with those without. FGF-23, FGF-21, CA-125, soluble ST2, GDF-15, FABP4, IL-6, and BNP were the strongest up-regulated proteins (fold change [FC] >1.30, false discovery rate [FDR], P < 0.05). KITLG, EGF, and PON3 were the strongest down-regulated proteins (FC <-1.30, FDR P < 0.05). Pathways most prominently involved in congestion were related to inflammation, endothelial activation, and response to mechanical stimulus. The validation cohort yielded similar findings.

CONCLUSIONS

Severe congestion in HF is mainly associated with inflammation, endothelial activation, and mechanical stress. Whether these pathways play a causal role in the onset or progression of congestion remains to be established. The identified biomarkers may become useful for diagnosing and monitoring congestion status.

Pulmonary haemodynamic effects of interatrial shunt in heart failure with preserved ejection fraction: a preclinical study

AIMS

The aim of this study was to evaluate the effect of the creation of a left-to-right interatrial shunt on pulmonary haemodynamics in rats with heart failure with preserved ejection fraction (HFPEF).

METHODS AND RESULTS

An interatrial communication (IAC) was created in 11 healthy rats (Lewis rats) and 11 rats which developed HFPEF (36-week-old spontaneously hypertensive rats [SHR]). Effects of the interatrial shunt were compared to 11 sham-operated Lewis and 11 sham-operated SHR. At 45 days post shunt, strain effect was observed in diastolic function (E/A ratio, p<0.001; isovolumetric relaxation time, p<0.001), left atrial volume (p=0.005) and pulmonary wall shear rate (WSR) (p=0.02) measured by Doppler echo. At sacrifice of the animals (60 days), a strain effect was also noted in elastin density (p=0.003) and eNOS protein expression (p=0.001). Interatrial shunt creation resulted in (i) an increase in pulmonary WSR (p=0.04) and a decrease in left atrial volume (p<0.001), (ii) an increase in elastin density (p<0.005), and (iii) an increase in eNOS protein expression (p=0.03).

CONCLUSIONS

Creation of a left-to-right atrial shunt in rats with HFPEF was effective in improving pulmonary haemodynamics. In addition, this study provides preliminary evidence of the potential risk of right volume overload and pulmonary hypertension due to atrial shunting.

Heart failure epicardial fat increases atrial arrhythmogenesis

BACKGROUND

Obesity is an important risk factor for atrial fibrillation (AF) and heart failure (HF). The effects of epicardial fat on atrial electrophysiology were not clear. This study was to evaluate whether HF may modulate the effects of epicardial fat on atrial electrophysiology.

METHODS

Conventional microelectrodes recording was used to record the action potential in left (LA) and right (RA) atria of healthy (control) rabbits before and after application of epicardial fat from control or HF (ventricular pacing of 360-400 bpm for 4 weeks) rabbits. Adipokine profiles were checked in epicardial fat of control and HF rabbits.

RESULTS

The LA 90% of AP duration was prolonged by control epicardial fat (from 77 ± 6 to 87 ± 7 ms, p<0.05, n=7), and by HF epicardial fat (from 78 ± 3 to 98 ± 4 ms, p<0.001, n=9). However, control or HF epicardial fat did not change the AP morphology in RA. HF epicardial fat increased the contractility in LA (61 ± 11 vs. 35 ± 6 mg, p=0.001), but not in RA. Control fat did not change the LA or RA contractility. Moreover, control and HF epicardial fat induced early and delayed afterdepolarizations in LA and RA, but only HF epicardial fat provoked spontaneous activity and burst firing in LA (n=3/9, 33.3% vs. n=0/7, 0%, n=0/9, 0%, p<0.05). Compared to control fat, HF epicardial fat, had lower resistin, C-reactive protein and serum amyloid A, but similar interleukin-6, leptin, monocyte chemotactic protein-1, adiponectin and adipsin.

CONCLUSIONS

HF epicardial fat increases atrial arrhythmogenesis, which may contribute to the higher atrial arrhythmia in obesity.

Systemic inflammation in heart failure--the whys and wherefores

Patients with chronic heart failure (HF) are characterized by systemic inflammation, as evident by raised circulating levels of several inflammatory cytokines with increasing levels according to the degree of disease severity. In addition to the myocardium itself, several tissues and cells can contribute to this inflammation, including leukocytes, platelets, tissue macrophages and endothelial cells. Although the mechanisms for the systemic inflammation is unknown, both infectious (e.g., endotoxins) and non-infectious (e.g., oxidative stress and hemodynamic overload) events could be operating, also including activation of Toll-like receptors as well as interaction with the neurohormone system. A growing body of evidence suggests that this systemic inflammation in chronic HF may play a role in the development and progression of this disorder, not only by promoting myocardial dysfunction, but also by inducing pathogenic consequences in other organs and tissues, thereby contributing to additional aspects of the HF syndrome such as cachexia, endothelial dysfunction and anemia. Although this inappropriate immune activation and inflammation could represent a new target for therapy in patients with chronic HF, the anti-tumor necrosis factor trials have been disappointing, and future research in this area will have to more precisely identify the most important mechanisms and actors in the immunopathogenesis of chronic HF in order to develop better immunomodulating agents for this disorder.

Myocardial Ischemia Induces Interleukin-6 and Tissue Factor Production in Patients With Coronary Artery Disease

BACKGROUND

Interleukin-6 (IL-6) and macrophage colony stimulating factor plasma levels are elevated in acute coronary syndromes. IL-6 has an inherent negative inotropic action and, with tissue factor (TF), mediates the ischemia-reperfusion myocardial injury. We hypothesized that inducible ischemia leads to cytokine production, TF expression, and consequently persistent left ventricular dysfunction after dobutamine stress echocardiography (DSE) in coronary artery disease patients.

METHODS AND RESULTS

DSE was performed in 103 patients with angiographically documented coronary artery disease. Blood samples were obtained at rest, at peak stress, and 30 minutes after cessation of dobutamine infusion for measurement of macrophage colony stimulating factor, IL-6, and TF. New or worsening wall motion abnormalities at peak stress and their duration into recovery were noted. Median IL-6 and TF levels were increased at peak stress and at 30 minutes into recovery compared with rest (2.7 and 2.4 versus 2.1 pg/mL for IL-6, 310 and 385 versus 266 pg/mL for TF [P<0.01] in patients with an ischemic response; n=55). Compared with rest, a greater release of IL-6 at peak stress and recovery was observed in patients with increasing number of ischemic segments at peak DSE (2 versus 3 to 4 versus 5 to 6 versus 7 to 8 segments; P=0.03). The time to recovery of wall motion abnormalities was also associated with IL-6 levels at peak stress and recovery (r=0.51 and r=0.39, P<0.05). Macrophage colony stimulating factor levels remained unchanged throughout DSE.

CONCLUSIONS

Reversible ischemia induced during DSE increases IL-6 and TF plasma levels. IL-6 is related to the extent of left ventricular dysfunction at peak stress and to persistent LV dysfunction during recovery.