Duygu Onat

Inflammation, Oxidative Stress, and Repair Capacity of the Vascular Endothelium in Obstructive Sleep Apnea

Background— Indirect evidence implicates endothelial dysfunction in the pathogenesis of vascular diseases associated with obstructive sleep apnea (OSA). We investigated directly whether dysfunction and inflammation occur in vivo in the vascular endothelium of patients with OSA. The effects of continuous positive airway pressure (CPAP) therapy on endothelial function and repair capacity were assessed. Methods and Results— Thirty-two patients with newly diagnosed OSA and 15 control subjects were studied. Proteins that regulate basal endothelial nitric oxide (NO) production (endothelial NO synthase [eNOS] and phosphorylated eNOS) and inflammation (cyclooxygenase-2 and inducible NOS) and markers of oxidative stress (nitrotyrosine) were quantified by immunofluorescence in freshly harvested venous endothelial cells before and after 4 weeks of CPAP therapy. Vascular reactivity was measured by flow-mediated dilation. Circulating endothelial progenitor cell levels were quantified to assess endothelial repair capacity. Baseline endothelial expression of eNOS and phosphorylated eNOS was reduced by 59% and 94%, respectively, in patients with OSA compared with control subjects. Expression of both nitrotyrosine and cyclooxygenase-2 was 5-fold greater in patients with OSA than in control subjects, whereas inducible NOS expression was 56% greater. Expression of eNOS and phosphorylated eNOS significantly increased, whereas expression of nitrotyrosine, cyclooxygenase-2, and inducible NOS significantly decreased in patients who adhered to CPAP ≥4 hours daily. Baseline flow-mediated dilation and endothelial progenitor cell levels were lower in patients than in control subjects, and both significantly increased in patients who adhered to CPAP ≥4 hours daily. Conclusions— OSA directly affects the vascular endothelium by promoting inflammation and oxidative stress while decreasing NO availability and repair capacity. Effective CPAP therapy is associated with the reversal of these alterations.

Inflammatory activation: cardiac, renal, and cardio-renal interactions in patients with the cardiorenal syndrome

Although inflammation is a physiologic response designed to protect us from infection, when unchecked and ongoing it may cause substantial harm. Both chronic heart failure (CHF) and chronic kidney disease (CKD) are known to cause elaboration of several pro-inflammatory mediators that can be detected at high concentrations in the tissues and blood stream. The biologic sources driving this chronic inflammatory state in CHF and CKD are not fully established. Traditional sources of inflammation include the heart and the kidneys which produce a wide range of pro-inflammatory cytokines in response to neurohormones and sympathetic activation. However, growing evidence suggests that non-traditional biomechanical mechanisms such as venous and tissue congestion due to volume overload are also important as they stimulate endotoxin absorption from the bowel and peripheral synthesis and release of pro-inflammatory mediators. Both during the chronic phase and, more rapidly, during acute exacerbations of CHF and CKD, inflammation and congestion appear to amplify each other resulting in a downward spiral of worsening cardiac, vascular, and renal functions that may negatively impact patients’ outcome. Anti-inflammatory treatment strategies aimed at attenuating end organ damage and improving clinical prognosis in the cardiorenal syndrome have been disappointing to date. A new therapeutic paradigm may be needed, which involves different anti-inflammatory strategies for individual etiologies and stages of CHF and CKD. It may also include specific (short-term) anti-inflammatory treatments that counteract inflammation during the unsettled phases of clinical decompensation. Finally, it will require greater focus on volume overload as an increasingly significant source of systemic inflammation in the cardiorenal syndrome.

Human Vascular Endothelial Cells: A Model System for Studying Vascular Inflammation in Diabetes and Atherosclerosis

The vascular endothelium is the inner lining of blood vessels serving as autocrine and paracrine organ that regulates vascular wall function. Endothelial dysfunction is recognized as initial step in the atherosclerotic process and is well advanced in diabetes, even before the manifestation of end-organ damage. Strategies capable of assessing changes in vascular endothelium at the preclinical stage hold potential to refine cardiovascular risk. In vitro cell culture is useful in understanding the interaction of endothelial cells with various mediators; however, it is often criticized due to the uncertain relevance of results to humans. Although circulating endothelial cells, endothelial microparticles, and progenitor cells opened the way for ex vivo studies, a recently described method for obtaining primary endothelial cells through endovascular biopsy allows direct characterization of endothelial phenotype in humans. In this article, we appraise the use of endothelial cell-based methodologies to study vascular inflammation in diabetes and atherosclerosis.

Peripheral venous congestion causes inflammation, neurohormonal, and endothelial cell activation

AIMS Volume overload and venous congestion are typically viewed as a consequence of advanced and of acute heart failure (HF) and renal failure (RF) although it is possible that hypervolaemia itself might be a critical intermediate in the pathophysiology of these diseases. This study aimed at elucidating whether peripheral venous congestion is sufficient to promote changes in inflammatory, neurohormonal, and endothelial phenotype similar to those observed in HF and RF. METHODS To experimentally model peripheral venous congestion, we developed a new method (so-called venous stress test) and applied the methodology on 24 healthy subjects (14 men, age 35 ± 2 years). Venous arm pressure was increased to ∼30 mmHg above the baseline level by inflating a tourniquet cuff around the dominant arm (test arm). Blood and endothelial cells (ECs) were sampled from test and control arm (lacking an inflated cuff) before and after 75 min of venous congestion, using angiocatheters and endovascular wires. Magnetic beads coated with EC-specific antibodies were used for EC separation; amplified mRNA was analysed by Affymetrix HG-U133 Plus 2.0 Microarray. RESULTS Plasma interleukin-6 (IL-6), endothelin-1 (ET-1), angiotensin II (AII), vascular cell adhesion molecule-1 (VCAM-1), and chemokine (C-X-C motif) ligand 2 (CXCL2) were significantly increased in the congested arm. A total of 3437 mRNA probe sets were differentially expressed (P < 0.05) in venous ECs before vs. after testing, including ET-1, VCAM-1, and CXCL2. CONCLUSION Peripheral venous congestion causes release of inflammatory mediators, neurohormones, and activation of ECs. Overall, venous congestion mimicked, notable aspects of the phenotype typical of advanced and of acute HF and RF.

Acute heart failure as “acute endothelitis” — Interaction of fluid overload and endothelial dysfunction

Acute heart failure (AHF) is defined as a change in heart failure (HF) symptoms (i.e. dyspnoea, abdominal bloating, and fatigue) and signs (i.e. pulmonary crackles, jugular vein distension, and peripheral oedema) resulting in a need for urgent therapy. Symptoms and signs of HF are due to elevated left and right ventricular filling pressures with or without low cardiac output [1]. Heart failure symptoms typically worsen a few days (3±2.5 days) before hospital admission [2]. However, recent studies, based on continuous monitoring of intracardiac pressures (i.e. Chronicle, Medtronic Inc.) and of intrathoracic impedance (i.e. OptiVol, Medtronic Inc.), have substantially moved back the clock for the onset of AHF. Congestion (high filling pressures) progressively increases and intrathoracic fluid accumulates, starting 7–14 days before HF signs and symptoms worsen, eventually requiring urgent intravenous therapy [2,3]. What happens during the days that precede overt clinical decompensation? Can congestion itself cause progressive fluid overload, and, if so, is it possible to break this vicious cycle? Our hypothesis is that “systemic endothelitis”, characterized by a boost in endothelial oxidative stress and activation with induction of vasoactive and pro-inflammatory genes,

Venous congestion and endothelial cell activation in acute decompensated heart failure.

Despite accumulating clinical evidence supporting a key role for venous congestion in the development of acute decompensated heart failure (ADHF), there remain several gaps in our knowledge of the pathophysiology of ADHF. Specifically, the biomechanically driven effects of venous congestion on the vascular endothelium (the largest endocrine/paracrine organ of the body), on neurohormonal activation, and on renal and cardiac dysfunction remain largely unexplored. We propose that venous congestion is a fundamental, hemodynamic stimulus for vascular inflammation, which plays a key role in the development and possibly the resolution of ADHF through vascular, humoral, renal, and cardiac mechanisms. A better understanding of the role of venous congestion and endothelial activation in the pathophysiology of ADHF may provide a strong rationale for near-future testing of treatment strategies that target biomechanically driven inflammation. Targeting vascular and systemic inflammation before symptoms arise may prevent progression to overt clinical decompensation in the ADHF syndrome.

Activation of Endothelial Cells in Conduit Veins of Dogs With Heart Failure and Veins of Normal Dogs After Vascular Stretch by Acute Volume Loading

BACKGROUND The venous endothelium is a key regulator of central blood volume, organ perfusion, and hemostasis in heart failure (HF). We previously reported activation of the inflammatory/oxidative program in venous endothelial cells collected from decompensated HF patients. The underlying causes are unknown. We tested the hypothesis that the pro-inflammatory state of HF and vascular strain associated with congestion can activate the endothelial inflammatory/oxidative and hemostatic programs. METHODS AND RESULTS We studied 6 normal (NL) dogs (left ventricular ejection fraction [LVEF] >50%, central venous pressure [CVP] = 8 +/- 2 mm Hg) and 6 dogs with HF (LVEF approximately 30%, CVP 8 +/- 2 mm Hg) produced by intracoronary microembolizations. Normal dogs were studied at baseline and 1 hour after fluid load to a target CVP >or=20 mm Hg. Endothelial cells were scraped from jugular veins; mRNA expression was analyzed by reverse transcription polymerase chain reaction. The endothelial inflammatory/oxidative and hemostatic programs were significantly activated in HF dogs compared with NL. In NL dogs, fluid load significantly activated the endothelial inflammatory/oxidative and hemostatic programs, and, concurrently, caused a significant increase in plasma neurohumoral indices to levels that approached those of HF dogs. CONCLUSIONS The pro-inflammatory state of HF and vascular strain associated with congestion can both activate venous endothelial cells in dogs in a manner consistent with that seen in HF patients.

Venous Congestion, Endothelial and Neurohormonal Activation in Acute Decompensated Heart Failure: Cause or Effect?

Venous congestion and endothelial and neurohormonal activation are known to occur in acute decompensated heart failure (ADHF), yet the temporal role of these processes in the pathophysiology of decompensation is not fully understood. Conventional wisdom presumes congestion to be a consequence of worsening cardiovascular function; however, the biomechanically driven effects of venous congestion are biologically plausible contributors to ADHF that remain largely unexplored in vivo. Recent experimental evidence from human models suggests that fluid accumulation and venous congestion are not simply consequences of poor cardiovascular function, but rather are fundamental pro-oxidant, pro-inflammatory, and hemodynamic stimuli that contribute to acute decompensation. The latest advances in the monitoring of volume status using implantable devices allow for the detection of venous congestion before symptoms arise. This may ultimately lead to improved treatment strategies including not only diuretics, but also specific, adjuvant interventions to counteract endothelial and neurohormonal activation during early preclinical decompensation.

Soluble CD146 Is a Novel Marker of Systemic Congestion in Heart Failure Patients: An Experimental Mechanistic and Transcardiac Clinical Study.

BACKGROUND Soluble CD146 (sCD146), is an endothelial marker with similar diagnostic power as natriuretic peptides in decompensated heart failure (HF). While natriuretic peptides are released by the failing heart, sCD146 may be released by veins in response to stretch induced by systemic congestion in HF. This study investigated the source, effects of vascular stress on release and prognostic properties of sCD146 in HF. METHODS In a peripheral venous stress study, plasma concentrations of sCD146 and N-terminal probrain natriuretic-peptide (NT-proBNP) were measured in 44 HF patients at baseline and after 90 min of unilateral forearm venous congestion. In addition, sCD146 and NT-proBNP were measured in peripheral vein (PV) and coronary sinus (CS) blood samples of 137 HF patients and the transcardiac gradient was calculated. Those patients were followed for major adverse cardiovascular events (MACE) during 2 years. RESULTS The induction of venous stress was associated with a pronounced increase in circulating concentrations of sCD146 in the congested arm (+60 μg/L) compared to the control arm (+16 μg/L, P = 0.025), while no difference in NT-proBNP concentrations was seen. In contrast to positive transcardiac gradient for NT-proBNP, median sCD146 concentrations were lower in CS than in PV (396 vs 434, P < 0.001), indicating a predominantly extracardiac source of sCD146. Finally, increased PV concentrations of sCD146 were associated with higher risk of MACE at 2 years. CONCLUSIONS Soluble CD146 is released from the peripheral vasculature in response to venous stretch and may reflect systemic congestion in chronic HF patients.

Reliability of Nesiritide Infusion via Non-Primed Tubing and Heparin-Coated Catheters:

BACKGROUND: Prescribing information for nesiritide mandates priming of intravenous tubing prior to connecting to the patients intravenous access because the drug may adsorb to the line. As of this writing, no published study has quantified the binding effect of nesiritide to intravenous tubing. Objective: To investigate whether priming of peripheral intravenous tubing is necessary and whether nesiritide can be reliably delivered through central intravenous lines, including heparin-coated catheters, where priming cannot occur. METHODS: A 23.3-mL bolus of nesiritide followed by a 7-mL/h 2-hour infusion were run through (1) polyvinylchloride (PVC) peripheral intravenous tubing primed with nesiritide, (2) non-primed PVC peripheral intravenous tubing, (3) non-primed polyethylene peripheral intravenous tubing, (4) non-primed PVC peripheral intravenous tubing connected to a central intravenous polyurethane catheter, and (5) non-primed PVC peripheral intravenous tubing connected to a heparin-coated pulmonary artery PVC catheter. Nesiritide concentrations were measured in the intravenous bags and in samples collected from the 5 intravenous settings. RESULTS: Priming of intravenous tubing with nesiritide did not increase drug recovery: at least 94% of the bolus dose and 96% of the total drug were recovered from all intravenous sets. CONCLUSIONS: Infusion of nesiritide via non-primed peripheral and central intravenous tubing, including heparin-coated pulmonary catheter, is reliable. Changes in nesiritide labeling appear to be warranted.