Stephan Winnik

Abnormal High-Density Lipoprotein Induces Endothelial Dysfunction via Activation of Toll-like Receptor-2

Endothelial injury and dysfunction (ED) represent a link between cardiovascular risk factors promoting hypertension and atherosclerosis, the leading cause of death in Western populations. High-density lipoprotein (HDL) is considered antiatherogenic and known to prevent ED. Using HDL from children and adults with chronic kidney dysfunction (HDL(CKD)), a population with high cardiovascular risk, we have demonstrated that HDL(CKD) in contrast to HDL(Healthy) promoted endothelial superoxide production, substantially reduced nitric oxide (NO) bioavailability, and subsequently increased arterial blood pressure (ABP). We have identified symmetric dimethylarginine (SDMA) in HDL(CKD) that causes transformation from physiological HDL into an abnormal lipoprotein inducing ED. Furthermore, we report that HDL(CKD) reduced endothelial NO availability via toll-like receptor-2 (TLR-2), leading to impaired endothelial repair, increased proinflammatory activation, and ABP. These data demonstrate how SDMA can modify the HDL particle to mimic a damage-associated molecular pattern that activates TLR-2 via a TLR-1- or TLR-6-coreceptor-independent pathway, linking abnormal HDL to innate immunity, ED, and hypertension.

Protective effects of sirtuins in cardiovascular diseases: from bench to bedside.

Sirtuins (Sirt1–Sirt7) comprise a family of nicotinamide adenine dinucleotide (NAD+)-dependent enzymes. While deacetylation reflects their main task, some of them have deacylase, adenosine diphosphate-ribosylase, demalonylase, glutarylase, and desuccinylase properties. Activated upon caloric restriction and exercise, they control critical cellular processes in the nucleus, cytoplasm, and mitochondria to maintain metabolic homeostasis, reduce cellular damage and dampen inflammation—all of which serve to protect against a variety of age-related diseases, including cardiovascular pathologies. This review focuses on the cardiovascular effects of Sirt1, Sirt3, Sirt6, and Sirt7. Most is known about Sirt1. This deacetylase protects from endothelial dysfunction, atherothrombosis, diet-induced obesity, type 2 diabetes, liver steatosis, and myocardial infarction. Sirt3 provides beneficial effects in the context of left ventricular hypertrophy, cardiomyopathy, oxidative stress, metabolic homeostasis, and dyslipidaemia. Sirt6 is implicated in ameliorating dyslipidaemia, cellular senescence, and left ventricular hypertrophy. Sirt7 plays a role in lipid metabolism and cardiomyopathies. Most of these data were derived from experimental findings in genetically modified mice, where NFκB, Pcsk9, low-density lipoprotein-receptor, PPARγ, superoxide dismutase 2, poly[adenosine diphosphate-ribose] polymerase 1, and endothelial nitric oxide synthase were identified among others as crucial molecular targets and/or partners of sirtuins. Of note, there is translational evidence for a role of sirtuins in patients with endothelial dysfunction, type 1 or type 2 diabetes and longevity. Given the availability of specific Sirt1 activators or pan-sirtuin activators that boost levels of the sirtuin cofactor NAD+, we anticipate that this field will move quickly from bench to bedside.

Endothelial mineralocorticoid receptor activation mediates endothelial dysfunction in diet-induced obesity.

Received 22 July 2012; revised 29 January 2013; accepted 4 March 2013 Aims Aldosterone plays a crucial role in cardiovascular disease. ‘Systemic’ inhibition of its mineralocorticoid receptor (MR) decreases atherosclerosis by reducing inflammation and oxidative stress. Obesity, an important cardiovascular risk factor, is an inflammatory disease associated with increased plasma aldosterone levels. We have investigated the role of the ‘endothelial’ MR in obesity-induced endothelial dysfunction, the earliest stage in atherogenesis. Methods and results C57BL/6 mice were exposed to a normal chow diet (ND) or a high-fat diet (HFD) alone or in combination with the MR antagonist eplerenone (200 mg/kg/day) for 14 weeks. Diet-induced obesity impaired endothelium-dependent relaxation in response to acetylcholine, whereas eplerenone treatment of obese mice prevented this. Expression analyses in aortic endothelial cells isolated from these mice revealed that eplerenone attenuated expression of pro-oxidative NADPH oxidase (subunits p22phox, p40phox) and increased expression of antioxidative genes (glutathione peroxidase-1, superoxide dismutase-1 and -3) in obesity. Eplerenone did not affect obesity-induced upregulation of cyclooxygenase (COX)-1 or prostacyclin synthase. Endothelial-specific MR deletion prevented endothelial dysfunction in obese (exhibiting high ‘endogenous’ aldosterone) and in ‘exogenous’ aldosterone-infused lean mice. Pre-incubation of aortic rings from aldosterone-treated animals with the COX-inhibitor indomethacin restored endothelial function. Exogenous aldosterone administration induced endothelial expression of p22phox in the presence, but not in the absence of the endothelial MR. Conclusion Obesity-induced endothelial dysfunction depends on the ‘endothelial’ MR and is mediated by an imbalance of oxidative stress-modulating mechanisms. Therefore, MR antagonists may represent an attractive therapeutic strategy in the increasing population of obese patients to decrease vascular dysfunction and subsequent atherosclerotic complications.

Fibroblast activation protein is induced by inflammation and degrades type I collagen in thin-cap fibroatheromata

Aims Collagen degradation in atherosclerotic plaques with thin fibrous caps renders them more prone to rupture. Fibroblast activation protein (FAP) plays a role in arthritis and tumour formation through its collagenase activity. However, the significance of FAP in thin-cap human fibroatheromata remains unknown. Methods and results We detected enhanced FAP expression in type IV–V human aortic atheromata (n = 12), compared with type II–III lesions (n = 9; P < 0.01) and healthy aortae (n = 8; P < 0.01) by immunostaining and western blot analyses. Fibroblast activation protein was also increased in thin-cap (<65 µm) vs. thick-cap (≥65 µm) human coronary fibroatheromata (n = 12; P < 0.01). Fibroblast activation protein was expressed by human aortic smooth muscle cells (HASMC) as shown by colocalization on immunofluorescent aortic plaque stainings (n = 10; P < 0.01) and by flow cytometry in cell culture. Although macrophages did not express FAP, macrophage burden in human aortic plaques correlated with FAP expression (n = 12; R2= 0.763; P < 0.05). Enzyme-linked immunosorbent assays showed a time- and dose-dependent up-regulation of FAP in response to human tumour necrosis factor α (TNFα) in HASMC (n = 6; P < 0.01). Moreover, supernatants from peripheral blood-derived macrophages induced FAP expression in cultured HASMC (n = 6; P < 0.01), an effect abolished by blocking TNFα (n = 6; P < 0.01). Fibroblast activation protein associated with collagen-poor regions in human coronary fibrous caps and digested type I collagen and gelatin in vitro (n = 6; P < 0.01). Zymography revealed that FAP-mediated collagenase activity was neutralized by an antibody directed against the FAP catalytic domain both in HASMC (n = 6; P < 0.01) and in fibrous caps of atherosclerotic plaques (n = 10; P < 0.01). Conclusion Fibroblast activation protein expression in HASMC is induced by macrophage-derived TNFα. Fibroblast activation protein associates with thin-cap human coronary fibroatheromata and contributes to type I collagen breakdown in fibrous caps.

Effects of Pycnogenol on endothelial function in patients with stable coronary artery disease: a double-blind, randomized, placebo-controlled, cross-over study

AIMS Extracts from pine tree bark containing a variety of flavonoids have been used in traditional medicine. Pycnogenol is a proprietary bark extract of the French maritime pine tree (Pinus pinaster ssp. atlantica) that exerts antioxidative, anti-inflammatory, and anti-platelet effects. However, the effects of Pycnogenol on endothelial dysfunction, a precursor of atherosclerosis and cardiovascular events, remain still elusive. METHODS AND RESULTS Twenty-three patients with coronary artery disease (CAD) completed this randomized, double-blind, placebo-controlled cross-over study. Patients received Pycnogenol (200 mg/day) for 8 weeks followed by placebo or vice versa on top of standard cardiovascular therapy. Between the two treatment periods, a 2-week washout period was scheduled. At baseline and after each treatment period, endothelial function, non-invasively assessed by flow-mediated dilatation (FMD) of the brachial artery using high-resolution ultrasound, biomarkers of oxidative stress and inflammation, platelet adhesion, and 24 h blood pressure monitoring were evaluated. In CAD patients, Pycnogenol treatment was associated with an improvement of FMD from 5.3 ± 2.6 to 7.0 ± 3.1 (P < 0.0001), while no change was observed with placebo (5.4 ± 2.4 to 4.7 ± 2.0; P = 0.051). This difference between study groups was significant [estimated treatment effect 2.75; 95% confidence interval (CI): 1.75, 3.75, P < 0.0001]. 15-F(2t)-Isoprostane, an index of oxidative stress, significantly decreased from 0.71 ± 0.09 to 0.66 ± 0.13 after Pycnogenol treatment, while no change was observed in the placebo group (mean difference 0.06 pg/mL with an associated 95% CI (0.01, 0.11), P = 0.012]. Inflammation markers, platelet adhesion, and blood pressure did not change after treatment with Pycnogenol or placebo. CONCLUSION This study provides the first evidence that the antioxidant Pycnogenol improves endothelial function in patients with CAD by reducing oxidative stress.

The Sirt1 activator SRT3025 provides atheroprotection in Apoe−/− mice by reducing hepatic Pcsk9 secretion and enhancing Ldlr expression

Aims The deacetylase sirtuin 1 (Sirt1) exerts beneficial effects on lipid metabolism, but its roles in plasma LDL-cholesterol regulation and atherosclerosis are controversial. Thus, we applied the pharmacological Sirt1 activator SRT3025 in a mouse model of atherosclerosis and in hepatocyte culture. Methods and results Apolipoprotein E-deficient (Apoe−/−) mice were fed a high-cholesterol diet (1.25% w/w) supplemented with SRT3025 (3.18 g kg−1 diet) for 12 weeks. In vitro, the drug activated wild-type Sirt1 protein, but not the activation-resistant Sirt1 mutant; in vivo, it increased deacetylation of hepatic p65 and skeletal muscle Foxo1. SRT3025 treatment decreased plasma levels of LDL-cholesterol and total cholesterol and reduced atherosclerosis. Drug treatment did not change mRNA expression of hepatic LDL receptor (Ldlr) and proprotein convertase subtilisin/kexin type 9 (Pcsk9), but increased their protein expression indicating post-translational effects. Consistent with hepatocyte Ldlr and Pcsk9 accumulation, we found reduced plasma levels of Pcsk9 after pharmacological Sirt1 activation. In vitro administration of SRT3025 to cultured AML12 hepatocytes attenuated Pcsk9 secretion and its binding to Ldlr, thereby reducing Pcsk9-mediated Ldlr degradation and increasing Ldlr expression and LDL uptake. Co-administration of exogenous Pcsk9 with SRT3025 blunted these effects. Sirt1 activation with SRT3025 in Ldlr−/− mice reduced neither plasma Pcsk9, nor LDL-cholesterol levels, nor atherosclerosis. Conclusion We identify reduction in Pcsk9 secretion as a novel effect of Sirt1 activity and uncover Ldlr as a prerequisite for Sirt1-mediated atheroprotection in mice. Pharmacological activation of Sirt1 appears promising to be tested in patients for its effects on plasma Pcsk9, LDL-cholesterol, and atherosclerosis.

Systemic VEGF inhibition accelerates experimental atherosclerosis and disrupts endothelial homeostasis – implications for cardiovascular safety

OBJECTIVES This study sought to examine the effects and underlying mechanisms of systemic VEGF inhibition in experimental atherosclerosis and aortic endothelial cells. BACKGROUND Pharmacological inhibition of vascular endothelial growth factor (VEGF), a major mediator of angiogenesis, has become a widely applied treatment of certain cancers and multiple ocular diseases including age-related macular degeneration. However, recent clinical trials raise concern for systemic vascular adverse effects, prompting the Food and Drug Administration to revoke the approval of bevacizumab for metastatic breast cancer. METHODS Eight-week old apolipoprotein E knockout mice received a high-cholesterol diet (1.25% cholesterol) for 24 weeks and were exposed to a systemic pan-VEGF receptor inhibitor (PTK787/ZK222584, 50mg/kg/d) or placebo (gavage) for the last 10 weeks. Atherosclerotic lesions were characterized in thoraco-abdominal aortae and aortic arches. Mechanistic analyses were performed in cultured human aortic endothelial cells. RESULTS Systemic VEGF inhibition increased atherosclerotic lesions by 33% whereas features of plaque vulnerability (i.e. necrotic core size, fibrous cap thickness) remained unchanged compared with controls. Aortic eNOS expression was decreased (trend). In human endothelial cells VEGF inhibition induced a dose-dependent increase in mitochondrial superoxide generation with an uncoupling of eNOS, resulting in reduced NO availability and decreased proliferation. CONCLUSION Systemic VEGF inhibition disrupts endothelial homeostasis and accelerates atherogenesis, suggesting that these events contribute to the clinical cardiovascular adverse events of VEGF-inhibiting therapies. Cardiovascular safety profiles of currently applied anti-angiogenic regimens should be determined to improve patient selection for therapy and allow close monitoring of patients at increased cardiovascular risk.

From abstract to impact in cardiovascular research: factors predicting publication and citation

Aims Through a 4-year follow-up of the abstracts submitted to the European Society of Cardiology Congress in 2006, we aimed at identifying factors predicting high-quality research, appraising the quality of the peer review and editorial processes, and thereby revealing potential ways to improve future research, peer review, and editorial work. Methods and results All abstracts submitted in 2006 were assessed for acceptance, presentation format, and average reviewer rating. Accepted and rejected studies were followed for 4 years. Multivariate regression analyses of a representative selection of 10% of all abstracts (n= 1002) were performed to identify factors predicting acceptance, subsequent publication, and citation. A total of 10 020 abstracts were submitted, 3104 (31%) were accepted for poster, and 701 (7%) for oral presentation. At Congress level, basic research, a patient number ≥ 100, and prospective study design were identified as independent predictors of acceptance. These factors differed from those predicting full-text publication, which included academic affiliation. The single parameter predicting frequent citation was study design with randomized controlled trials reaching the highest citation rates. The publication rate of accepted studies was 38%, whereas only 24% of rejected studies were published. Among published studies, those accepted at the Congress received higher citation rates than rejected ones. Conclusions Research of high quality was determined by study design and largely identified at Congress level through blinded peer review. The scientometric follow-up revealed a marked disparity between predictors of full-text publication and those predicting citation or acceptance at the Congress.

SIRT1 – An Anti-Inflammatory Pathway at the Crossroads Between Metabolic Disease and Atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is based on the interaction between inflammatory cell subsets and specific cells in the arterial wall. SIRT1 deacetylates histone and non-histone proteins and has been implicated in protective effects of caloric restriction on lifespan and metabolic pathways in yeast, nematodes, and mice. In the vasculature of rodents, SIRT1 mediates vasodilatation through the release of endothelial nitric oxide synthase-derived nitric oxide and scavenges reactive oxygen species. Using a genetic loss-of-function approach, SIRT1 has been shown to interfere with crucial steps of endothelial activation and atherogenesis by suppressing NFκB signaling: Partial SIRT1 deletion in ApoE-/- mice prevented expression of endothelial adhesion molecules thereby hampering the extravasation of circulating monocytes. In monocyte-derived macrophages SIRT1 deletion reduced the expression of the scavenger receptor lectin-like oxidized low-density lipoprotein receptor 1 (Lox-1) resulting in reduced foam cell formation and atherosclerosis. Moreover, it was reported that SIRT1 regulates the activity of liver X-receptor, thereby promoting ABCA1-driven reverse cholesterol transport in plaque-resident macrophages slowing foam cell formation. Finally, SIRT1 suppressed the expression of endothelial tissue factor, and thus exerted anti-thrombotic properties during induced carotid thrombosis in mice. These findings indicate protective effects of SIRT1 in atherogenesis and thrombosis at an experimental level and highlight the opportunity to translate this concept from bench to bedside. Indeed, SIRT1 activators are available and have been shown to exert beneficial effects at the preclinical level in obesity and type 2 diabetes mellitus (T2DM). SIRT1 activators are currently being evaluated in phase II clinical trials in patients with T2DM. The concept of SIRT1 activation appears a promising strategy for novel therapeutic approaches in patients with atherothrombosis.

Multimodal Imaging in Rats Reveals Impaired Neurovascular Coupling in Sustained Hypertension

Background and Purpose— Arterial hypertension is an important risk factor for cerebrovascular diseases, such as transient ischemic attacks or stroke, and represents a major global health issue. The effects of hypertension on cerebral blood flow, particularly at the microvascular level, remain unknown. Methods— Using the spontaneously hypertensive rat (SHR) model, we examined cortical hemodynamic responses on whisker stimulation applying a multimodal imaging approach (multiwavelength spectroscopy, laser speckle imaging, and 2-photon microscopy). We assessed the effects of hypertension in 10-, 20-, and 40-week-old male SHRs and age-matched male Wistar Kyoto rats (CTRL) on hemodynamic responses, histology, and biochemical parameters. In 40-week-old animals, losartan or verapamil was administered for 10 weeks to test the reversibility of hypertension-induced impairments. Results— Increased arterial blood pressure was associated with a progressive impairment in functional hyperemia in 20- and 40-week-old SHRs; baseline capillary red blood cell velocity was increased in 40-week-old SHRs compared with age-matched CTRLs. Antihypertensive treatment reduced baseline capillary cerebral blood flow almost to CTRL values, whereas functional hyperemic signals did not improve after 10 weeks of drug therapy. Structural analyses of the microvascular network revealed no differences between normo- and hypertensive animals, whereas expression analyses of cerebral lysates showed signs of increased oxidative stress and signs of impaired endothelial homeostasis upon early hypertension. Conclusions— Impaired neurovascular coupling in the SHR evolves upon sustained hypertension. Antihypertensive monotherapy using verapamil or losartan is not sufficient to abolish this functional impairment. These deficits in neurovascular coupling in response to sustained hypertension might contribute to accelerate progression of neurodegenerative diseases in chronic hypertension.