Stepwise increase of angiopoietin-2 serum levels is related to haemodynamic and functional impairment in stable chronic heart failure.

BACKGROUND: A reciprocal link between inflammation, oxidative/nitrosative stress, and endothelial dysfunction has been postulated in chronic heart failure (CHF). The endothelial repair mechanisms involved remain to be determined. Our aim was to investigate whether there are detectable signs of ongoing angiogenesis in serum of CHF patients and to evaluate the correlation with indexes of haemodynamic and functional impairment. METHODS AND RESULTS: Enzyme-linked immunosorbent assay tests were used to quantify angiogenin, angiopoietin-1, angiopoietin-2, vascular endothelial growth factor, Tie-2, and brain natriuretic peptide in serum of 87 patients with CHF of increasing severity according to New York Heart Association (NYHA; class I, n = 8; II, n = 45; and III, n = 34) and in 14 healthy subjects matched for age and sex. Angiogenin, angiopoietin-2, and Tie-2 were significantly increased in CHF of increasing severity (Kruskal-Wallis: p = 0.0004, p < 0.0001, and p = 0.017, respectively). Angiopoietin-2 was inversely correlated with the 6-min walking test (r = -0.65, p < 0.0001), peak oxygen consumption (VO(2max); r = -0.57, p = 0.0002), and deceleration time (r = -0.61, p < 0.0001). Multiple regression analysis showed that angiopoietin-2 was mainly associated with VO(2max) (p = 0.018). The angiopoietin-2 area under the receiver operating characteristic curve for CHF diagnosis was 0.94 (95% CI 0.88-0.99; p < 0.001). CONCLUSIONS: These data demonstrate that angiopoietin-2 and selected serum markers of angiogenesis progressively increase with haemodynamic and functional decline in CHF.

Oxidative stress induces myeloperoxidase expression in endocardial endothelial cells from patients with chronic heart failure.

Increased oxidative stress has been implicated in the pathogenesis of a number of cardiovascular diseases. Recent findings suggest that myeloperoxidase (MPO) may play a key role in the initiation and maintenance of chronic heart failure (CHF) by contributing to the depletion of the intracellular reservoir of nitric oxide (NO). NO consumption through MPO activity may lead to protein chlorination or nitration, leading to tissue damage. Primary cultures of human endocardial endothelial cells (EEC) obtained at heart transplantation of patients with CHF and human umbilical vein endothelial cells (HUVEC) were subjected to oxidative stress by incubation with hydrogen peroxide at non lethal (60 microM) dose for different exposure times (3 and 6 h). Treated and control cells were tested by immunohistochemistry and RT-PCR for MPO and 3-chlorotyrosine expression. Both endothelial cell types expressed myeloperoxidase following oxidative stress, with higher levels in EEC. Moreover, 3-chlorotyrosine accumulation in treated cells alone indicated the presence of MPO-derived hypochlorous acid. Immunohistochemistry on sections from post-infarcted heart confirmed in vivo the endothelial positivity to MPO, 3-chlorotyrosine and, to a minor extent, nitrotyrosine. Immunohistochemical observations were confirmed by detection of MPO mRNA in both stimulated EEC and HUVEC cells. This study demonstrates for the first time that EEC can express MPO after oxidative stress, both in vitro and in vivo, followed by accumulation of 3-chlorotyrosine, an end product of oxidative stress. Deregulation of endothelial functions may contribute to the development of a number of cardiovascular diseases, including CHF. The results also highlight the notion that endothelium is not only a target but also a key player in oxidative-driven cardiovascular stress.

Role of oxidative and nitrosative stress biomarkers in chronic heart failure.

In this review, we present recent insights on chronic heart failure (CHF) and the potential role of tumor necrosis factor (TNF)-alpha, interleukins, myeloperoxidase (MPO), and nitrosative stress in the progression of this disease process. Reactive oxygen species (ROS) are produced as a consequence of aerobic metabolism. Under physiologic conditions, their unfavourable effect in causing oxidative damage is counteracted by antioxidants. An imbalance in favour of oxidants leads to oxidative stress, and contributes to myocyte apoptosis, direct negative inotropic effects, and reduced bioavailability of nitric oxide (NO). Together, these effects lead to impaired vasodilatation of the coronary, pulmonary and peripheral vascular beds. In patients with moderate to severe forms of CHF, TNF-alpha leads to the formation of nitrotyrosine and consumption of nitric oxide by virtue of activation of myeloperoxidase. Further studies are required to better elucidate the complex interaction of oxidative stress, endothelial dysfunction and inflammatory activation in CHF. Such insights would likely lead to development of better strategies for the assessment of the disease severity by monitoring of new bio-humoral indices and better treatment approaches.

Increased nitrotyrosine plasma levels in relation to systemic markers of inflammation and myeloperoxidase in chronic heart failure.

The presence of a reciprocal link between inflammation and oxidative/nitrosative stress has been postulated in chronic heart failure (CHF). We aimed to determine signs of nitrosative stress in serum/plasma of CHF patients. ELISA tests were used for quantification of serum/plasma levels of Nitrotyrosine (NT), H(2)O(2), total NO, nitrite (NO(2)(-)), myeloperoxidase (MPO), Tumor Necrosis Factor-alpha (TNFalpha) and pro-Brain Natriuretic Peptide (proBNP) in 66 CHF patients (9 in NYHA I, 34 NYHA II, 23 NYHA III) and in 14 age-matched healthy subjects. NT levels were higher in NYHA III CHF patients compared to NYHA II (p<0.05), NYHA I (p<0.03) and controls (p<0.02), whereas NO(2)(-) and total NO were higher in NYHA III compared to I (p<0.05 and p<0.04, respectively) and controls (p<0.004 and 0.002) and in NYHA II compared to controls (p<0.04 and p<0.009). NT levels correlated significantly with MPO (r=0.37, p<0.003), TNFalpha (r=0.32, p<0.01) and proBNP (r=0.32, p<0.01). These data demonstrate an increased NT plasma level in patients with moderate/severe CHF which is associated to increased levels of markers of systemic inflammation.

Role of endothelial cell stress in the pathogenesis of chronic heart failure.

Endothelial cells are key modulators of diverse physiological processes, and their impaired function is a cause of numerous cardiovascular diseases. Under physiologic condition, the reactive oxygen and nitrogen mediators in endothelia lead to the signal propagation of the initial stimulus, by forming molecules with a longer half-life like hydrogen peroxide. Hydrogen peroxide is the focus of growing attention in endothelial biology, and consequently the enzymes involved in its generation and clearance are viewed as novel mediators of great importance. In particular, among peroxidases, myeloperoxidase is recognized as a key enzyme, capable of impairing intracellular NO reservoirs as well as producing oxidized amino acids such as 3-chlorotyrosine or 3-nitrotyrosine. This process switches the functional pathways from normal signalling to a condition characterized by oxidative and/or nitrosative stress. Understanding the molecular mechanisms involved in these stress responses in endothelium will lead to better therapeutic strategies for oxidative stress-driven cardiovascular diseases.