Cardiovascular diseases are major contributors to global deaths and disability-adjusted life years, with hypertension a significant risk factor for all causes of death. The endothelium that lines the inner wall of the vasculature regulates essential haemostatic functions, such as vascular tone, circulation of blood cells, inflammation and platelet activity. Endothelial dysfunction is an early predictor of atherosclerosis and future cardiovascular events. We review the prognostic value of obtaining measurements of endothelial function, the clinical techniques for its determination, the mechanisms leading to endothelial dysfunction and the therapeutic treatment of endothelial dysfunction. Since vascular oxidative stress and inflammation are major determinants of endothelial function, we have also addressed current antioxidant and anti-inflammatory therapies. In the light of recent data that dispute the prognostic value of endothelial function in healthy human cohorts, we also discuss alternative diagnostic parameters such as vascular stiffness index and intima/media thickness ratio. We also suggest that assessing vascular function, including that of smooth muscle and even perivascular adipose tissue, may be an appropriate parameter for clinical investigations.

Tobacco cigarette smoking is among the most complex and least understood health risk factors. A deeper insight into the pathophysiological actions of smoking exposure is of special importance as smoking is a major cause of chronic non-communicable diseases, in particular of cardiovascular disease as well as risk factors such as atherosclerosis and arterial hypertension. It is well known that smoking exerts its negative effects on cardiovascular health through various interdependent pathophysiological actions including hemodynamic and autonomic alterations, oxidative stress, inflammation, endothelial dysfunction, thrombosis, and hyperlipidemia. Importantly, impaired vascular endothelial function is acknowledged as an early key event in the initiation and progression of smoking-induced atherosclerosis. Increasing evidence from human studies indicates that cigarette smoke exposure associates with a pathological state of the vascular endothelium mainly characterized by reduced vascular nitric oxide bioavailability due to increased vascular superoxide production. In the present overview, we provide compact evidence on the effects of tobacco cigarette smoke exposure on vascular biology and function in humans centered on main drivers of adverse cardiovascular effects including endothelial dysfunction, inflammation, and oxidative stress.

Sepsis causes high mortality in the setting of septic shock. LEADER and other trials revealed cardioprotective and anti-inflammatory properties of glucagon-like peptide-1 (GLP-1) analogs like liraglutide (Lira). We previously demonstrated improved survival in lipopolysaccharide (LPS)-induced endotoxemia by inhibition of GLP-1 degradation. Here we investigate the effects of Lira in the polymicrobial sepsis model of cecal ligation and puncture (CLP). C57BL/6J mice were intraperitoneally injected with Lira (200 µg/kg/d; 3 days) and sepsis induced by CLP after one day of GLP-1 analog treatment. Survival and body temperature were monitored. Aortic vascular function (isometric tension recording), protein expression (immunohistochemistry and dot blot) and gene expression (qRT-PCR) were determined. Endothelium-dependent relaxation in the aorta was impaired by CLP and correlated with markers of inflammation (e.g., interleukin 6 and inducible nitric oxide synthase) and oxidative stress (e.g., 3-nitrotyrosine) was higher in septic mice, all of which was almost completely normalized by Lira therapy. We demonstrate that the GLP-1 analog Lira ameliorates sepsis-induced endothelial dysfunction by the reduction of vascular inflammation and oxidative stress. Accordingly, the findings suggest that the antioxidant and anti-inflammatory effects of GLP-1 analogs may be a valuable tool to protect the cardiovascular system from dysbalanced inflammation in polymicrobial sepsis.

Objective. Oxidative stress and endothelial dysfunction contribute to pulmonary arterial hypertension (PAH). The role of the nitrovasodilator pentaerythritol tetranitrate (PETN) on endothelial function and oxidative stress in PAH has not yet been defined. Methods and Results. PAH was induced by monocrotaline (MCT, i.v.) in Wistar rats. Low (30 mg/kg; MCT30), middle (40 mg/kg; MCT40), or high (60 mg/kg; MCT60) dose of MCT for 14, 28, and 42 d was used. MCT induced endothelial dysfunction, pulmonary vascular wall thickening, and fibrosis, as well as protein tyrosine nitration. Pulmonary arterial pressure and heart/body and lung/body weight ratio were increased in MCT40 rats (28 d) and reduced by oral PETN (10 mg/kg, 24 d) therapy. Oxidative stress in the vascular wall, in the heart, and in whole blood as well as vascular endothelin-1 signaling was increased in MCT40-treated rats and normalized by PETN therapy, likely by upregulation of heme oxygenase-1 (HO-1). PETN therapy improved endothelium-dependent relaxation in pulmonary arteries and inhibited endothelin-1-induced oxidative burst in whole blood and the expression of adhesion molecule (ICAM-1) in endothelial cells. Conclusion. MCT-induced PAH impairs endothelial function (aorta and pulmonary arteries) and increases oxidative stress whereas PETN markedly attenuates these adverse effects. Thus, PETN therapy improves pulmonary hypertension beyond its known cardiac preload reducing ability.

Atherogenic lipoproteins may impair vascular reactivity consecutively causing tissue damage in multiple organs via abnormal perfusion and excessive reactive oxygen species generation. We tested the hypothesis that chronic hypercholesterolemia causes endothelial dysfunction and cell loss in the retina.

Angiotensin II (Ang II) has been implicated in the pathophysiology of various age-dependent ocular diseases. The purpose of this study was to test the hypothesis that Ang II induces endothelial dysfunction in mouse ophthalmic arteries and to identify the underlying mechanisms. Ophthalmic arteries were exposed to Ang II in vivo and in vitro to determine vascular function by video microscopy. Moreover, the formation of reactive oxygen species (ROS) was quantified and the expression of prooxidant redox genes and proteins was determined. The endothelium-dependent artery responses were blunted after both in vivo and in vitro exposure to Ang II. The Ang II type 1 receptor (AT1R) blocker, candesartan, and the ROS scavenger, Tiron, prevented Ang II-induced endothelial dysfunction. ROS levels and NOX2 expression were increased following Ang II incubation. Remarkably, Ang II failed to induce endothelial dysfunction in ophthalmic arteries from NOX2-deficient mice. Following Ang II incubation, endothelium-dependent vasodilation was mainly mediated by cytochrome P450 oxygenase (CYP450) metabolites, while the contribution of nitric oxide synthase (NOS) and 12/15-lipoxygenase (12/15-LOX) pathways became negligible. These findings provide evidence that Ang II induces endothelial dysfunction in mouse ophthalmic arteries via AT1R activation and NOX2-dependent ROS formation. From a clinical point of view, the blockade of AT1R signaling and/or NOX2 may be helpful to retain or restore endothelial function in ocular blood vessels in certain ocular diseases.

Diabetes increases the risk of pulmonary hypertension and is associated with alterations in pulmonary vascular function. Still, it is not clear whether alterations in the phenotype of pulmonary endothelium induced by diabetes are distinct, as compared to peripheral endothelium. In the present work, we characterized differences between diabetic complications in the lung and aorta in db/db mice with advanced diabetes. Male, 20-week-old db/db mice displayed increased HbA1c and glucose concentration compatible with advanced diabetes. Diabetic lungs had signs of mild fibrosis, and pulmonary endothelium displayed significantly ultrastructural changes. In the isolated, perfused lung from db/db mice, filtration coefficient (Kf,c) and contractile response to TXA2 analogue were enhanced, while endothelial NO-dependent modulation of pulmonary response to hypoxic ventilation and cumulative production of NO2- were impaired, with no changes in immunostaining for eNOS expression. In turn, 6-keto-PGF1α release from the isolated lung from db/db mice was increased, as well as immunostaining of thrombomodulin (CD141). In contrast to the lung, NO-dependent, acetylcholine-induced vasodilation, ionophore-stimulated NO2- generation, and production of 6-keto-PGF1α were all impaired in aortic rings from db/db mice. Although eNOS immunostaining was not changed, that of CD141 was clearly lowered. Interestingly, diabetes-induced nitration of proteins in aorta was higher than that in the lungs. In summary, diabetes induced marked ultrastructural changes in pulmonary endothelium that were associated with the increased permeability of pulmonary microcirculation, impaired NO-dependent vascular function, with compensatory increase in PGI2 production, and increased CD141 expression. In contrast, endothelial dysfunction in the aorta was featured by impaired NO-, PGI2-dependent function and diminished CD141 expression.

Cardiovascular outcome trials demonstrated that GLP-1 (glucagon-like peptide-1) analogs including liraglutide reduce the risk of cardiovascular events in type 2 diabetes mellitus. Whether GLP-1 analogs reduce the risk for atherosclerosis independent of glycemic control is challenging to elucidate as the GLP-1R (GLP-1 receptor) is expressed on different cell types, including endothelial and immune cells. Approach and Results: Here, we reveal the cardio- and vasoprotective mechanism of the GLP-1 analog liraglutide at the cellular level in a murine, nondiabetic model of arterial hypertension. Wild-type (C57BL/6J), global (Glp1r-/-), as well as endothelial (Glp1rflox/floxxCdh5cre) and myeloid cell-specific knockout mice (Glp1rflox/floxxLysMcre) of the GLP-1R were studied, and arterial hypertension was induced by angiotensin II. Liraglutide treatment normalized blood pressure, cardiac hypertrophy, vascular fibrosis, endothelial dysfunction, oxidative stress, and vascular inflammation in a GLP-1R-dependent manner. Mechanistically, liraglutide reduced leukocyte rolling on the endothelium and infiltration of myeloid Ly6G-Ly6C+ and Ly6G+Ly6C+ cells into the vascular wall. As a consequence, liraglutide prevented vascular oxidative stress, reduced S-glutathionylation as a marker of eNOS (endothelial NO synthase) uncoupling, and increased NO bioavailability. Importantly, all of these beneficial cardiovascular effects of liraglutide persisted in myeloid cell GLP-1R-deficient (Glp1rflox/floxxLysMcre) mice but were abolished in global (Glp1r-/-) and endothelial cell-specific (Glp1rflox/floxxCdh5cre) GLP-1R knockout mice.

Chronic administration of nitroglycerin (NTG) induces nitrate tolerance. Among possible underlying mechanisms, increased vascular production of reactive oxygen species (ROS) has emerged as a principal mechanism. Using cell culture and animal models of nitrate tolerance, we aimed to assess the impact of nitrates on NAD(P)H oxidases and aldehyde dehydrogenase 2 (ALDH2) expression. Rats and vascular smooth muscle cells were treated with NTG. Vascular reactivity was assessed by isometric tension studies. Superoxide was detected by dihydroethidium staining. Gene expression was measured by real-time polymerase chain reaction. NAD(P)H oxidase activity was measured using lucigenin-enhanced chemiluminescence. ALDH activity was measured biochemically, and NO consumption electrochemically. Nitrate tolerance was induced in rats by treatment with NTG for 3 days, and detected as impaired endothelium-dependent and -independent relaxation of aortic segments. Although superoxide production was increased in all aortic layers, expression of nox1, nox2 and nox4 was significantly decreased. Similarly, in vascular smooth muscle cells exposed to NTG for 6-24 h, NAD(P)H oxidase activity was increased, in spite of nox1 downregulation. In addition, expression and activity of ALDH-2 was decreased in nitrate-tolerant rings. Furthermore, exogenous addition of ALDH decreased superoxide generation in vitro and attenuated NO consumption in vascular smooth muscle cell homogenates. Our data suggest that in nitrate tolerance, activation of nox enzymes more than compensates for their downregulation, resulting in a net increase in superoxide and NO consumption. Furthermore, reduced ALDH-2 activity and expression leads to decreased NTG bioconversion. Therefore, both mechanisms reduce NO availability and impair vasorelaxation.

Alcoholic cardiomyopathy (ACM) resulting from excess alcohol consumption is an important cause of heart failure (HF). Although it is assumed that the cardiotoxicity of the ethanol (EtOH)-metabolite acetaldehyde (ACA) is central for its development and progression, the exact mechanisms remain obscure. Murine cardiomyocytes (CMs) exposed to ACA or EtOH showed increased superoxide (O2(•-)) levels and decreased mitochondrial polarization, both being normalized by NADPH oxidase (NOX) inhibition. C57BL/6 mice and mice deficient for the ACA-degrading enzyme mitochondrial aldehyde dehydrogenase (ALDH-2(-/-)) were fed a 2% EtOH diet for 5 weeks creating an ACA-overload. 2% EtOH-fed ALDH-2(-/-) mice exhibited a decreased cardiac function, increased heart-to-body and lung-to-body weight ratios, increased cardiac levels of the lipid peroxidation product malondialdehyde (MDA) as well as increased NOX activity and NOX2/glycoprotein 91(phox) (NOX2/gp91(phox)) subunit expression compared to 2% EtOH-fed C57BL/6 mice. Echocardiography revealed that ALDH-2(-/-)/gp91(phox-/-) mice were protected from ACA-overload-induced HF after 5 weeks of 2% EtOH-diet, demonstrating that NOX2-derived O2(•-) contributes to the development of ACM. Translated to human pathophysiology, we found increased gp91(phox) expression in endomyocardial biopsies of ACM patients. In conclusion, ACM is promoted by ACA-driven mitochondrial dysfunction and can be improved by ablation of NOX2/gp91(phox). NOX2/gp91(phox) therefore might be a potential pharmacological target to treat ACM.