MnSOD protects against COX1-mediated endothelial dysfunction in chronic heart failure

Integrating network pharmacology and experimental verification to explore the pharmacological mechanisms of Guanxin Shutong capsule in treating heart failure

The Guanxin Shutong capsule (GXST), a traditional Chinese medicine, is commonly used for treating cardiovascular disease, it has shown efficacy in improving symptoms and enhancing the quality of life for patients with heart failure (HF). However, the specific mechanism of action of GXST in HF remains unclear. In this study, we employed a comprehensive approach combining network pharmacology, molecular dynamics (MD) simulations, and in vitro validations to investigate the potential targets and molecular mechanisms of GXST against HF. We collected active ingredients and target genes of GXST, as well as related genes of HF, from multiple public databases. Using bioinformatics analysis, we constructed networks of ingredients-disease-targets and performed functional annotations of the core targets. MD simulations were conducted to verify the binding between the core protein-ligand complexes. In vitro evaluations, including cell proliferation, apoptosis, and protein expression in human umbilical vein endothelial cells (HUVECs) and H9C2 cells were treated with GXST, were performed for pharmacodynamics evaluation. Network analysis revealed 320 intersection genes and 74 active ingredients in the Herbs-ingredients-target genes-disease network. We identified key active ingredients and target genes that overlapped. The KEGG pathways of the intersection genes were primarily enriched in the PI3K-Akt signaling pathway and apoptosis. The protein-protein interaction network highlighted proteins such as AKT1, VEGFR2, and eNOS. MD simulations confirmed stable docking and lower binding energy between 4 identified ingredients (kaempferol, quercetin, (2R)-5,7-dihydroxy-2-(4-hydroxyphenyl) chroman-4-one, and ellagic acid) and their respective core proteins (VEGFR2, eNOS, and AKT). In vitro experiments demonstrated the protective effects of GXST against H2O2-induced apoptosis in both HUVECs and H9C2 cells. Notably, consistent with the in silico predictions, GXST effectively activates the VEGFR2/AKT/eNOS signaling pathways in HUVECs. This study provides insights into the underlying mechanism of GXST's therapeutic effects in heart failure. The involvement of the VEGFR2/AKT/eNOS signaling pathways suggests their importance in further elucidating and applying GXST in the clinical treatment of heart failure.

Vena cava presents endothelial dysfunction prior to thoracic aorta in heart failure: the pivotal role of nNOS uncoupling/oxidative stress

Arterial endothelial dysfunction has been extensively studied in heart failure (HF). However, little is known about the adjustments shown by the venous system in this condition. Considering that inferior vena cava (VC) tone could influence cardiac performance and HF prognosis, the aim of the present study was to assess the VC and thoracic aorta (TA) endothelial function of HF-post-myocardial infarction (MI) rats, comparing both endothelial responses and signaling pathways developed. Vascular reactivity of TA and VC from HF post-MI and sham operated (SO) rats was assessed with a wire myograph, 4 weeks after coronary artery occlusion surgery. Nitric oxide (NO), H2O2 production and oxidative stress were evaluated in situ with fluorescent probes, while protein expression and dimer/monomer ratio was assessed by Western blot. VC from HF rats presented endothelial dysfunction, while TA exhibited higher acetylcholine (ACh)-induced vasodilation when compared with vessels from SO rats. TA exhibited increased ACh-induced NO production due to a higher coupling of endothelial and neuronal NO synthases isoforms (eNOS, nNOS), and enhanced expression of antioxidant enzymes. These adjustments, however, were absent in VC of HF post-MI rats, which exhibited uncoupled nNOS, oxidative stress and higher H2O2 bioavailability. Altogether, the present study suggests a differential regulation of endothelial function between VC and TA of HF post-MI rats, most likely due to nNOS uncoupling and compromised antioxidant defense.

Sirtuin 6 Protects Against Oxidative Stress and Vascular Dysfunction in Mice

Objective: Sirtuin deacetylases are major regulators of organismal aging, and while depletion of sirtuin 6 (SIRT6) in mice results in a profound progeroid phenotype, the role of SIRT6 in the regulation of vasomotor function is unknown. Thus, our objective was to test the hypothesis that reductions in SIRT6 elicit endothelial dysfunction in young, genetically altered mice.

Results and Approach: We used young (3 month old), littermate-matched, SIRT6 wild-type (WT), and SIRT6 heterozygous (HET) mice. SIRT6 expression (qRT-PCR) was reduced by 50% in HET mice. Carotid vessel responses to acetylcholine, sodium nitroprusside, U46619, and serotonin were examined in isolated organ chamber baths. Relaxation in response to acetylcholine (ACH) was impaired in HET mice compared to littermate-matched WT controls (67 ± 3% versus 76 ± 3%, respectively; p < 0.05), while responses to sodium nitroprusside were unchanged. Short-term incubation of carotid rings with the NAD(P)H oxidase inhibitor, apocynin, significantly improved in vessels from HET mice but not their WT littermates. Peak tension generated in response to either U46619 or serotonin was significantly blunted in HET mice compared to their WT littermates.

Conclusion: These data suggest that SIRT6 is a key regulator of vasomotor function in conduit vessels. More specifically, we propose that SIRT6 serves as a tonic suppressor of NAD(P)H oxidase expression and activation, as inhibition of NAD(P)H oxidase improved endothelial function in SIRT6 haploinsufficient mice. Collectively, SIRT6 activation and/or histone acetyltransferase inhibition may be useful therapeutic approaches to reduce endothelial dysfunction and combat age-associated cardiovascular disease.

MnSOD protects against vascular calcification independent of changes in vascular function in hypercholesterolemic mice

BACKGROUND AND AIMS

The overall goal of this study was to determine the effects of MnSOD-deficiency on vascular structure and function in hypercholesterolemic mice. Previous work suggested that increases in mitochondrial-derived reactive oxygen species (ROS) can exacerbate vascular dysfunction and atherosclerosis. It remains unknown, however, how MnSOD-deficiency and local compensatory mechanisms impact atherosclerotic plaque composition.

METHODS AND RESULTS

We used a hypercholesterolemic mouse model (ldlr^-/-/ApoB^100/100; LA), either wild-type for MnSOD (LA-MnSOD^+/+) or MnSOD-haploinsufficient (LA-MnSOD^+/-), that was fed a western diet for either 3 or 6 months. Consistent with previous reports, reductions of MnSOD did not significantly worsen hypercholesterolemia-induced endothelial dysfunction in the aorta. Critically, dramatic impairment of vascular function with Nox2 inhibition or catalase pretreatment suggested the presence of a significant NO-independent vasodilatory mechanism in LA-MnSOD^+/- mice (e.g. H₂O₂). Despite remarkably well-preserved overall vascular relaxation, loss of mitochondrial antioxidant capacity in LA-MnSOD^+/- mice significantly increased osteogenic signalling and vascular calcification compared to the LA-MnSOD^+/+ littermates.

CONCLUSIONS

Collectively, these data are the first to suggest that loss of mitochondrial antioxidant capacity in hypercholesterolemic mice results in dramatic upregulation of NADPH oxidase-derived H₂O₂. While this appears to be adaptive in the context of preserving overall endothelium-dependent relaxation and vascular function, these increases in ROS appear to be remarkably maladaptive and deleterious in the context of vascular calcification.

Interplay Between Oxidative Stress, Cyclooxygenases, and Prostanoids in Cardiovascular Diseases

Significance: Endothelial cells lining the lumen of blood vessels play an important role in the regulation of cardiovascular functions through releasing both vasoconstricting and vasodilating factors. The production and function of vasoconstricting factors are largely elevated in hypertension, diabetes, atherosclerosis, and ischemia/reperfusion injuries. Cyclooxygenases (COXs) are the major enzymes producing five different prostanoids that act as either contracting or relaxing substances. Under conditions of increased oxidative stress, the expressions and activities of COX isoforms are altered, resulting in changes in production of various prostanoids and thus affecting vascular tone. This review briefly summarizes the relationship between oxidative stress, COXs, and prostanoids, thereby providing new insights into the pathophysiological mechanisms of cardiovascular diseases (CVDs). Recent Advances: Many new drugs targeting oxidative stress, COX-2, and prostanoids against common CVDs have been evaluated in recent years and they are summarized in this review. Critical Issues: Comprehensive understanding of the complex interplay between oxidative stress, COXs, and prostanoids in CVDs helps develop more effective measures against cardiovascular pathogenesis. Future Directions: Apart from minimizing the undesired effects of harmful prostanoids, future studies shall investigate the restoration of vasoprotective prostanoids as a means to combat CVDs. Antioxid. Redox Signal. 34, 784-799.

ALDOA protects cardiomyocytes against H/R-induced apoptosis and oxidative stress by regulating the VEGF/Notch 1/Jagged 1 pathway

Myocardial infarction (MI) is a myocardial necrosis disease caused by continuous ischemia and hypoxia. Abnormal expression of aldolase A (ALDOA) has been reported in cardiac hypertrophy, heart failure and other cardio-cerebrovascular diseases. The present study aims to explore the effects of ALDOA on hypoxia/reperfusion (H/R)-induced oxidative stress, and investigate the underlying mechanisms. ALDOA was expressed at a low level in blood samples from MI patients and H/R-induced H9C2 cardiomyocytes. Overexpression of ALDOA suppressed H/R-induced oxidative stress and apoptosis. Using co-immunoprecipitation and protein blots, we demonstrated that ALDOA modulates the Notch 1-Jagged 1 signalling pathway by upregulating VEGF. Taken together, our data reveal that ALDOA protects cardiomyocytes from H/R-induced oxidative stress through the VEGF/Notch 1/Jagged 1 axis, and should be investigated as a therapeutic target for the treatment of MI in future.

Non-hematopoietic erythropoietin-derived peptides for atheroprotection and treatment of cardiovascular diseases

Relevance: Cardiovascular diseases continue to be the leading cause of premature adult death.

Lipid profile and atherogenesis: Dislipidaemia leads to subsequent lipid accumulation and migration of immunocompetent cells into the vessel intima. Macrophages accumulate cholesterol forming foam cells – the morphological substrate of atherosclerosis in its initial stage.

Inflammation and atherogenesis: Pro-inflammatory factors provoke oxidative stress, vascular wall damage and foam cells formation.

Endothelial and mitochondrial dysfunction in the development of atherosclerosis: Endothelial mitochondria are some of the organelles most sensitive to oxidative stress. Damaged mitochondria produce excess superoxide and H2O2, which are the main factors of intracellular damage, further increasing endothelial dysfunction.

Short non-hematopoietic erythropoietin-based peptides as innovative atheroprotectors: Research in recent decades has shown that erythropoietin has a high cytoprotective activity, which is mainly associated with exposure to the mitochondrial link and has been confirmed in various experimental models. There is also a short-chain derivative, the 11-amino acid pyroglutamate helix B surface peptide (PHBSP), which selectively binds to the erythropoietin heterodymic receptor and reproduces its cytoprotective properties. This indicates the promising use of short-chain derivatives of erythropoietin for the treatment and prevention of atherosclerotic vascular injury. In the future, it is planned to study the PHBSP derivatives, the modification of which consists in adding RGD and PGP tripeptides with antiaggregant properties to the original 11-member peptide.

Switch to direct anticoagulants and improved endothelial function in patients with chronic heart failure and atrial fibrillation

BACKGROUND

Chronic heart failure (CHF) is characterized by higher rates of atrial fibrillation (AF) and endothelial dysfunction (ED). First line anticoagulant therapy in AF is represented by direct oral anticoagulants (DOACs); several patients, however, are still treated with vitamin-K inhibitors. The use of DOACs is associated in previous studies with an improved vascular function. We therefore sought to evaluate possible changes in endothelial function assessed by flow-mediated dilation (FMD) in patients with CHF and AF shifting from warfarin to DOACs.

METHODS

Forty-three consecutive outpatients were enrolled in the study. FMD was assessed at baseline and after 4 months. Patients were compared according to AC therapy.

RESULTS

After the first measurement of FMD, 18 patients "switched" to DOACs because of poor compliance to warfarin therapy or time in therapeutic range, 19 patients continued to use DOACs, 6 warfarin. "Switched" patients to DOACs therapy showed an improved FMD (19.0 ± 6.6% vs 3.8 ± 1.3%, p < 0.0001); C-reactive protein (CRP) levels decreased in "switched" patients from 1.4 ± 0.5 to 1.0 ± 0.7 mg/dl (p < 0.05). FMD and CRP changes were not significant in patients who did not changed anticoagulant therapy. In switched patients, changes in CRP levels were proportional to FMD changes (r = -0.50, p < 0.05). Shifting from warfarin to DOACs was significantly correlated to improved FMD levels even at multivariable analysis (p < 0.05).

CONCLUSIONS

Switch from warfarin to DOACs in patents with CHF and AF was associated in an observational non randomized study with an improved endothelial function. Changes in FMD values were related to changes in CRP levels.

Association of combined genetic variations in SOD3, GPX3, PON1, and GSTT1 with hypertension and severity of coronary artery disease

Oxidative stress plays a critical role in the pathophysiology of hypertension (HT) and the progression of atherosclerotic coronary artery disease (CAD). Genetic variations in superoxide dismutase (SOD), glutathione peroxidase 3 (GPX3), paraoxonase 1 (PON1) and glutathione S-transferase theta 1 (GSTT1) may modulate their gene functions, affecting protein functions. These changes could have an impact on the pathogenesis of HT and progression of CAD. The present study investigated the associations of individual and combined antioxidant-related gene polymorphisms with the incidence of HT and severity of CAD. Two study populations were enrolled. The HT-associated study comprised 735 control and 735 hypertensive subjects (mean age 59.3 ± 9.0 years), matched for age and sex. The CAD study, hospital-based subjects (mean age 62.1 ± 9.5 years), included 279 CAD patients and 165 non-CAD subjects. Gene polymorphisms were identified in genomic DNA using polymerase chain reaction (PCR)-based technique. Genetic variations were assessed for their associations with HT and severity of CAD. Antioxidant gene variants, SOD3 rs2536512-GG, GPX3 rs3828599-GG, PON1 rs705379-TT, and GSTT1^{-/- and +/-}, were independently associated with the incidence of HT. A combination of four HT-associated genotypes, as a genetic risk score (GRS), revealed an association of GRS 5 and GRS ≥ 6 with increased susceptibility to HT and CAD, and further with multivessel coronary atherosclerosis (multivessel CAD) compared with GRS 0-2 [respective ORs(95% CI) for GRS ≥ 6 = 2.37 (1.46-3.85), 3.26 (1.29-8.25), and 4.36 (1.36-14.0)]. Combined polymorphisms in these four antioxidant-related genes were associated with the incidences of HT and CAD, and with the severity of coronary atherosclerosis.

Low-Dose Aspirin Treatment Attenuates Male Rat Salt-Sensitive Hypertension via Platelet Cyclooxygenase 1 and Complement Cascade Pathway

Background The role of platelets in the development of vascular inflammation and endothelial dysfunction in the pathogenesis of hypertension is well established at this time. Aspirin is known to relieve pain, decrease fever, reduce inflammation, impair platelet aggregation, and prevent clotting, yet its effect in the context of salt-sensitive hypertension remains unclear. The present study investigated the importance of aspirin in inhibiting the abnormal activation of platelets and promoting the normal function of the vascular endothelium in a rat model of salt-sensitive hypertension. Method and Results Dahl salt-sensitive rats and salt-resistant rats were fed a normal-salt diet (4% NaCl), a high-salt diet (8% NaCl), or a high-salt diet with aspirin gavage (10 mg/kg per day) for 8 weeks. Blood pressure, platelet activation, vascular function, inflammatory response, and potential mechanism were measured. Low-dose aspirin (10 mg/kg per day) decreased the high-salt diet-induced elevation of blood pressure, platelet activation, leukocyte infiltration, and leukocyte-platelet aggregation (CD45+CD61+), as well as vascular endothelial and renal damage. These effects were related to the ability of aspirin to prevent the adhesion of leukocytes to endothelial cells via inhibition of the platelet cyclooxygenase 1 but not the cyclooxygenase 2 pathway. Aspirin also reversed the high-salt diet-induced abnormal activation of complement and coagulation cascades in platelets. Conclusions These results highlight a new property of aspirin in ameliorating vascular endothelial dysfunction induced by platelet activation, which may be beneficial in the treatment of salt-sensitive hypertension.

Comorbidities in chronic heart failure: An update from Italian Society of Cardiology (SIC) Working Group on Heart Failure

The increasing number of patients with heart failure HF and comorbidities is due to aging population and increase of life expectancy of patients with cardiovascular disease. Encouraging results derived by recent trials may suggest some comorbidities as new targets for new drugs, highlighting the need for a better understanding of the comorbidities' effects in HF patients and the need of a multidisciplinary approach for the management of chronic HF with comorbidities. We report a brief review about main cardiovascular and non-cardiovascular comorbidities in HF patients in order to update physicians and researchers engaged in the HF research or in "fight against heart failure."

Mitochondrial Quality Control in Cardiac Diseases

Disruption of mitochondrial homeostasis is a hallmark of cardiac diseases. Therefore, maintenance of mitochondrial integrity through different surveillance mechanisms is critical for cardiomyocyte survival. In this review, we discuss the most recent findings on the central role of mitochondrial quality control processes including regulation of mitochondrial redox balance, aldehyde metabolism, proteostasis, dynamics, and clearance in cardiac diseases, highlighting their potential as therapeutic targets.

Chronic senolytic treatment alleviates established vasomotor dysfunction in aged or atherosclerotic mice

While reports suggest a single dose of senolytics may improve vasomotor function, the structural and functional impact of long‐term senolytic treatment is unknown. To determine whether long‐term senolytic treatment improves vasomotor function, vascular stiffness, and intimal plaque size and composition in aged or hypercholesterolemic mice with established disease. Senolytic treatment (intermittent treatment with Dasatinib + Quercetin via oral gavage) resulted in significant reductions in senescent cell markers (TAF⁺ cells) in the medial layer of aorta from aged and hypercholesterolemic mice, but not in intimal atherosclerotic plaques. While senolytic treatment significantly improved vasomotor function (isolated organ chamber baths) in both groups of mice, this was due to increases in nitric oxide bioavailability in aged mice and increases in sensitivity to NO donors in hypercholesterolemic mice. Genetic clearance of senescent cells in aged normocholesterolemic INK‐ATTAC mice phenocopied changes elicited by D+Q. Senolytics tended to reduce aortic calcification (alizarin red) and osteogenic signaling (qRT–PCR, immunohistochemistry) in aged mice, but both were significantly reduced by senolytic treatment in hypercholesterolemic mice. Intimal plaque fibrosis (picrosirius red) was not changed appreciably by chronic senolytic treatment. This is the first study to demonstrate that chronic clearance of senescent cells improves established vascular phenotypes associated with aging and chronic hypercholesterolemia, and may be a viable therapeutic intervention to reduce morbidity and mortality from cardiovascular diseases.

Role of Mitochondria in Cerebral Vascular Function: Energy Production, Cellular Protection, and Regulation of Vascular Tone

Mitochondria not only produce energy in the form of ATP to support the activities of cells comprising the neurovascular unit, but mitochondrial events, such as depolarization and/or ROS release, also initiate signaling events which protect the endothelium and neurons against lethal stresses via pre-/postconditioning as well as promote changes in cerebral vascular tone. Mitochondrial depolarization in vascular smooth muscle (VSM), via pharmacological activation of the ATP-dependent potassium channels on the inner mitochondrial membrane (mitoKATP channels), leads to vasorelaxation through generation of calcium sparks by the sarcoplasmic reticulum and subsequent downstream signaling mechanisms. Increased release of ROS by mitochondria has similar effects. Relaxation of VSM can also be indirectly achieved via actions of nitric oxide (NO) and other vasoactive agents produced by endothelium, perivascular and parenchymal nerves, and astroglia following mitochondrial activation. Additionally, NO production following mitochondrial activation is involved in neuronal preconditioning. Cerebral arteries from female rats have greater mitochondrial mass and respiration and enhanced cerebral arterial dilation to mitochondrial activators. Preexisting chronic conditions such as insulin resistance and/or diabetes impair mitoKATP channel relaxation of cerebral arteries and preconditioning. Surprisingly, mitoKATP channel function after transient ischemia appears to be retained in the endothelium of large cerebral arteries despite generalized cerebral vascular dysfunction. Thus, mitochondrial mechanisms may represent the elusive signaling link between metabolic rate and blood flow as well as mediators of vascular change according to physiological status. Mitochondrial mechanisms are an important, but underutilized target for improving vascular function and decreasing brain injury in stroke patients. © 2016 American Physiological Society. Compr Physiol 6:1529-1548, 2016.

Effect of inflammatory factor-induced cyclo-oxygenase expression on the development of reperfusion-related no-reflow phenomenon in acute myocardial infarction

No reflow after reperfusion therapy for myocardial infarction is a strong predictor of clinical outcome. Increased levels of inflammatory factors, including C-reactive protein (CRP), in patients with acute myocardial infarction (AMI) undergoing primary percutaneous coronary intervention (PCI) may affect myocardial perfusion. However, why the no-reflow phenomenon increases in inflammation stress after PCI is not clear. The aim of the present study was to determine the effects and molecular mechanisms underlying the effects of CRP on the expression of cyclo-oxygenase (COX) on the development of the no-reflow phenomenon. There was a significant increase in plasma levels of CRP and interleukin (IL)-6 in no-reflow patients, suggesting that inflammatory factors play an important role in the development of the no-reflow phenomenon. The mechanisms involved were further evaluated after reperfusion in a rat model mimicking the no-reflow phenomenon. Compared with normal reflow rats, there were significant increases in both COX-1 and COX-2 in cardiac tissue from no-reflow rats. The COX inhibitor indomethacin (5 mg/kg, i.p.) significantly reduced the no-reflow area. In another series of experiments, human coronary artery endothelial cells (HCAEC) were treated with CRP at clinically relevant concentrations (5-25 μg/mL). C-Reactive protein significantly increased COX-1 and COX-2 levels in a time- and concentration-dependent manner. In addition, extracellular signal-regulated kinase (ERK) and Jun N-terminal kinase (JNK) were activated in CRP (5, 10, 25 μg/mL)-treated HCAEC cultures. Furthermore, the ERK inhibitor pd98059 (30 μmol/L) and the JNK inhibitor sp600125 (10 μmol/L) blocked CRP-induced COX-1 and COX-2 expression for 12 h. Together, the findings of the present study suggest that CRP can promote the development of the no-reflow phenomenon by increasing COX-1 and COX-2 expression, which is regulated, in part, via ERK and JNK activity.

Exercise training reduces insulin resistance in postmyocardial infarction rats

Myocardial infarction (MI) induces cardiac dysfunction and insulin resistance (IR). This study examines the effects of MI-related IR on vasorelaxation and its underlying mechanisms, with a specific focus on the role of exercise in reversing the impaired vasorelaxation. Adult male Sprague-Dawley rats were divided into three groups: Sham, MI, and MI+Exercise. MI+Exercise rats were subjected to 8 weeks of treadmill training. Cardiac contraction, myocardial and arterial structure, vasorelaxation, levels of inflammatory cytokines, expression of eNOS and TNF-α, and activation of PI3K/Akt/eNOS and p38 mitogen-activated protein kinase (p38 MAPK) were determined in aortas. MI significantly impaired endothelial structure and vasodilation (P < 0.05-0.01), as indicated by decreased arterial vasorelaxation to ACh and insulin. MI also attenuated the myocardial contractile response, decreased aortic PI3K/Akt/eNOS expression and phosphorylation by insulin, and increased IL-1β, IL-6, and TNF-α expression and p38 MAPK activity (P < 0.05-0.01). Exercise improved insulin sensitivity in aortas, facilitated myocardial contractile response and arterial vasorelaxation to ACh and insulin, and increased arterial PI3K/Akt/eNOS activity. Moreover, exercise markedly reversed increased p38 MAPK activity and normalized inflammatory cytokines in post-MI arteries. Inhibition of PI3K with LY-294002, and eNOS with L-NAME significantly blocked arterial vasorelaxation and PI3K/Akt/eNOS phosphorylation in response to insulin. In conclusion, these results demonstrate that endothelial dysfunction in response to insulin plays an important role in MI-related IR. The reversal of IR by exercise is most likely associated with normalizing inflammatory cytokines, increasing the activation of PI3K/Akt/eNOS, and reducing the activation of p38 MAPK.

Impact of neonatal sertraline exposure on the post-myocardial infarction outcomes of adult male mice

Neonatal exposure to a selective serotonin reuptake inhibitor (SSRI) leads to decreased left ventricular volumes and sympathetic activation in adult mice. We hypothesized this neonatal SSRI exposure-induced small left heart syndrome would increase post-myocardial infarction (MI) morbidity and mortality. C57BL/6 mice received saline or sertraline (5 mg/kg intraperitoneally) on postnatal days 1-14. At 5 months, male mice underwent coronary artery ligation and were monitored by radiotelemetry until death or 4 weeks after ligation. After ligation, SSRI-exposed mice had increased heart rates (SSRI, 516 ± 13 bpm; control, 470 ± 15 bpm; P < 0.05). SSRI-exposed mice had significant reductions in left ventricular systolic volumes both before and after coronary ligation (SSRI: baseline = 20 ± 3 μL, post-MI = 37 ± 10 μL; control: baseline = 30 ± 3 μL, post-MI = 65 ± 23 μL). Post-MI echocardiography showed significantly decreased ejection fraction in control mice (baseline = 60% ± 4%, post-MI = 41% ± 2%, P < 0.01) but not the SSRI-exposed mice (baseline = 65% ± 3%, post-MI = 53% ± 7%). Neonatal SSRI exposure did not significantly alter post-MI survival. We conclude that the preexisting SSRI-induced small left heart syndrome may provide protection from post-MI ventricular dilation.

Mitochondrial mechanisms in cerebral vascular control: shared signaling pathways with preconditioning

Mitochondrial-initiated events protect the neurovascular unit against lethal stress via a process called preconditioning, which independently promotes changes in cerebrovascular tone through shared signaling pathways. Activation of adenosine triphosphate (ATP)-dependent potassium channels on the inner mitochondrial membrane (mitoKATP channels) is a specific and dependable way to induce protection of neurons, astroglia, and cerebral vascular endothelium. Through the opening of mitoKATP channels, mitochondrial depolarization leads to activation of protein kinases and transient increases in cytosolic calcium (Ca(2+)) levels that activate terminal mechanisms that protect the neurovascular unit against lethal stress. The release of reactive oxygen species from mitochondria has similar protective effects. Signaling elements of the preconditioning pathways also are involved in the regulation of vascular tone. Activation of mitoKATP channels in cerebral arteries causes vasodilation, with cell-specific contributions from the endothelium, vascular smooth muscles, and nerves. Preexisting chronic conditions, such as insulin resistance and/or diabetes, prevent preconditioning and impair relaxation to mitochondrial-centered responses in cerebral arteries. Surprisingly, mitochondrial activation after anoxic or ischemic stress appears to protect cerebral vascular endothelium and promotes the restoration of blood flow; therefore, mitochondria may represent an important, but underutilized target in attenuating vascular dysfunction and brain injury in stroke patients.

Mitochondria, endothelial cell function, and vascular diseases

Mitochondria are perhaps the most sophisticated and dynamic responsive sensing systems in eukaryotic cells. The role of mitochondria goes beyond their capacity to create molecular fuel and includes the generation of reactive oxygen species, the regulation of calcium, and the activation of cell death. In endothelial cells, mitochondria have a profound impact on cellular function under both healthy and diseased conditions. In this review, we summarize the basic functions of mitochondria in endothelial cells and discuss the roles of mitochondria in endothelial dysfunction and vascular diseases, including atherosclerosis, diabetic vascular dysfunction, pulmonary artery hypertension, and hypertension. Finally, the potential therapeutic strategies to improve mitochondrial function in endothelial cells and vascular diseases are also discussed, with a focus on mitochondrial-targeted antioxidants and calorie restriction.

Myocardial and anti-inflammatory effects of chronic bosentan therapy in monocrotaline-induced pulmonary hypertension

INTRODUCTION AND OBJECTIVES

Endothelin-1 antagonists are increasingly used in the treatment of pulmonary hypertension despite the lack of knowledge of their myocardial and systemic effects. We assessed the right ventricular myocardial and systemic effects of endothelin-1 antagonists in monocrotaline-induced pulmonary hypertension.

METHODS

Male Wistar rats (180-200 g, n=57) randomly received 60 mg/kg monocrotaline or vehicle subcutaneously. Two days later, bosentan was randomly started (300 mg/kg/day) by oral route in a subgroup of monocrotaline-injected rats, while the other monocrotaline-injected and control rats received vehicle. At 25-30 days, invasive hemodynamic assessment was performed under anesthesia, arterial blood samples were collected for gas analysis and plasma was extracted for quantification of endothelin-1, cytokines, nitrates and 6-keto-prostaglandin F1α. Right ventricular myocardium was collected for assessment of cyclooxygenase and nitric oxide synthase activity and gene expression.

RESULTS

The monocrotaline group developed pulmonary hypertension, low cardiac output, right ventricular hypertrophy and dilation, changes in gene expression and inflammatory activation that were attenuated in the group treated with bosentan. From a functional point of view, this group had improved right ventricular function and preserved ventriculo-vascular coupling, without deterioration in arterial gas parameters or systemic hypotension. In molecular terms, they showed reduced endothelin-1 and cytokine levels, decreased right ventricular inducible nitric oxide synthase and cyclooxygenase-2 activity and increased nitrate plasma levels compared with the non-treated group.

CONCLUSIONS

In this study we demonstrate that besides attenuating pulmonary hypertension, bosentan has beneficial hemodynamic, myocardial and anti-inflammatory effects.

A novel approach to minimize false discovery rate in genome-wide data analysis

BACKGROUND

High-throughput technologies, such as DNA microarray, have significantly advanced biological and biomedical research by enabling researchers to carry out genome-wide screens. One critical task in analyzing genome-wide datasets is to control the false discovery rate (FDR) so that the proportion of false positive features among those called significant is restrained. Recently a number of FDR control methods have been proposed and widely practiced, such as the Benjamini-Hochberg approach, the Storey approach and Significant Analysis of Microarrays (SAM).

METHODS

This paper presents a straight-forward yet powerful FDR control method termed miFDR, which aims to minimize FDR when calling a fixed number of significant features. We theoretically proved that the strategy used by miFDR is able to find the optimal number of significant features when the desired FDR is fixed.

RESULTS

We compared miFDR with the BH approach, the Storey approach and SAM on both simulated datasets and public DNA microarray datasets. The results demonstrated that miFDR outperforms others by identifying more significant features under the same FDR cut-offs. Literature search showed that many genes called only by miFDR are indeed relevant to the underlying biology of interest.

CONCLUSIONS

FDR has been widely applied to analyzing high-throughput datasets allowed for rapid discoveries. Under the same FDR threshold, miFDR is capable to identify more significant features than its competitors at a compatible level of complexity. Therefore, it can potentially generate great impacts on biological and biomedical research.

AVAILABILITY

If interested, please contact the authors for getting miFDR.

Transcriptional and phenotypic changes in aorta and aortic valve with aging and MnSOD deficiency in mice

The purpose of this study was to characterize changes in antioxidant and age-related gene expression in aorta and aortic valve with aging, and test the hypothesis that increased mitochondrial oxidative stress accelerates age-related endothelial and aortic valve dysfunction. Wild-type (MnSOD(+/+)) and manganese SOD heterozygous haploinsufficient (MnSOD(+/-)) mice were studied at 3 and 18 mo of age. In aorta from wild-type mice, antioxidant expression was preserved, although there were age-associated increases in Nox2 expression. Haploinsufficiency of MnSOD did not alter antioxidant expression in aorta, but increased expression of Nox2. When compared with that of aorta, age-associated reductions in antioxidant expression were larger in aortic valves from wild-type and MnSOD haploinsufficient mice, although Nox2 expression was unchanged. Similarly, sirtuin expression was relatively well-preserved in aorta from both genotypes, whereas expression of SIRT1, SIRT2, SIRT3, SIRT4, and SIRT6 were significantly reduced in the aortic valve. Expression of p16(ink4a), a marker of cellular senescence, was profoundly increased in both aorta and aortic valve from MnSOD(+/+) and MnSOD(+/-) mice. Functionally, we observed comparable age-associated reductions in endothelial function in aorta from both MnSOD(+/+) and MnSOD(+/-) mice. Interestingly, inhibition of NAD(P)H oxidase with apocynin or gp91ds-tat improved endothelial function in MnSOD(+/+) mice but significantly impaired endothelial function in MnSOD(+/-) mice at both ages. Aortic valve function was not impaired by aging or MnSOD haploinsufficiency. Changes in antioxidant and sirtuin gene expression with aging differ dramatically between aorta and aortic valve. Furthermore, although MnSOD does not result in overt cardiovascular dysfunction with aging, compensatory transcriptional responses to MnSOD deficiency appear to be tissue specific.

Vascular function during prolonged progression and regression of atherosclerosis in mice

OBJECTIVE

Endothelial dysfunction is associated with atherosclerosis in mice, but it is difficult to reduce cholesterol levels enough to study regression of atherosclerosis in genetically modified mice. The goal of this study was to examine vascular structure and function before and after reducing elevated plasma lipid levels with a genetic switch in Reversa mice, and identify novel mechanisms contributing to structural and functional improvements in the vasculature after reduction of blood lipids.

METHODS AND RESULTS

After 6 months of hypercholesterolemia, endothelial function (maximum relaxation to acetylcholine) in aorta was impaired and responses to nitric oxide were unaffected. Further impairment in endothelial function was observed after 12 months of hypercholesterolemia and was associated with reductions in sensitivity to nitric oxide. Expression of dihydrofolate reductase was reduced at 6 and 12 months, and addition of the tetrahydrobiopterin precursor sepiapterin significantly improved endothelial function. Reducing cholesterol levels at 6 months normalized dihydrofolate reductase expression and prevented further impairment in endothelial function. Similar functional changes were observed after 12 months of hypercholesterolemia followed by 2 months of lipid lowering.

CONCLUSIONS

Our data suggest that endothelial dysfunction after prolonged hypercholesterolemia is the result of both impairment of sensitivity to nitric oxide and reduced nitric oxide synthase cofactor bioavailability. Both of these changes can be prevented by normalizing blood lipids during moderately severe or advanced atherosclerosis.

Vascular endothelial function is not related to serum uric acid in healthy adults

Background

Some experimental evidence suggests that uric acid impairs endothelial function. It is controversial if high uric acid levels and impaired endothelial function are related in healthy adults. In addition, the effect of uric acid on endothelial cells (ECs) of humans is unexplored.

Methods

Data of 107 healthy adult volunteers were analyzed. The association between serum uric acid and endothelial-dependant dilation (EDD) and endothelial-independent dilation (EID) was evaluated by linear regression models. We also examined the relations between uric acid and systemic and cellular markers of inflammation and oxidative stress in all or subsets of participants.

Results

Uric acid levels and EDD were not related in unadjusted or adjusted models. There was a significant negative correlation between uric acid and EID in the pooled sample (r = −0.34, P = 0.005). This correlation remained significant after adjusting for demographics (P = 0.04) and was attenuated after adjusting for other cardiac risk factors (P = 0.12). Higher serum uric acid levels were found to correlate significantly with C-reactive protein (CRP) (r = 0.31, P = 0.002). Serum uric acid levels were not associated with brachial artery EC nuclear factor-κB (NF-κB) p65 or NADPH oxidase p47^phox expression or with nitrotyrosine staining, but were inversely associated with EC manganese superoxide dismutase (MnSOD) expression (r = −0.5, P = 0.01, n = 25).

Conclusion

Elevated serum uric acid is not associated with endothelial dysfunction among healthy adults, but is inversely related to EID and EC MnSOD, and positively related to systemic inflammation. These findings may have implications for cardiovascular risk in healthy adults.

Mitochondria-derived superoxide and voltage-gated sodium channels in baroreceptor neurons from chronic heart-failure rats

Our previous study has shown that chronic heart failure (CHF) reduces expression and activation of voltage-gated sodium (Na(v)) channels in baroreceptor neurons, which are involved in the blunted baroreceptor neuron excitability and contribute to the impairment of baroreflex in the CHF state. The present study examined the role of mitochondria-derived superoxide in the reduced Na(v) channel function in coronary artery ligation-induced CHF rats. CHF decreased the protein expression and activity of mitochondrial complex enzymes and manganese SOD (MnSOD) and elevated the mitochondria-derived superoxide level in the nodose neurons compared with those in sham nodose neurons. Adenoviral MnSOD (Ad.MnSOD) gene transfection (50 multiplicity of infection) into the nodose neurons normalized the MnSOD expression and reduced the elevation of mitochondrial superoxide in the nodose neurons from CHF rats. Ad.MnSOD also partially reversed the reduced protein expression and current density of the Na(v) channels and the suppressed cell excitability (the number of action potential and the current threshold for inducing action potential) in aortic baroreceptor neurons from CHF rats. Data from the present study indicate that mitochondrial dysfunction, including decreased protein expression and activity of mitochondrial complex enzymes and MnSOD and elevated mitochondria-derived superoxide, contributes to the reduced Na(v) channel activation and cell excitability in the aortic baroreceptor neurons in CHF rats.

Clair DK. Manganese superoxide dismutase: guardian of the powerhouse

The mitochondrion is vital for many metabolic pathways in the cell, contributing all or important constituent enzymes for diverse functions such as β-oxidation of fatty acids, the urea cycle, the citric acid cycle, and ATP synthesis. The mitochondrion is also a major site of reactive oxygen species (ROS) production in the cell. Aberrant production of mitochondrial ROS can have dramatic effects on cellular function, in part, due to oxidative modification of key metabolic proteins localized in the mitochondrion. The cell is equipped with myriad antioxidant enzyme systems to combat deleterious ROS production in mitochondria, with the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) acting as the chief ROS scavenging enzyme in the cell. Factors that affect the expression and/or the activity of MnSOD, resulting in diminished antioxidant capacity of the cell, can have extraordinary consequences on the overall health of the cell by altering mitochondrial metabolic function, leading to the development and progression of numerous diseases. A better understanding of the mechanisms by which MnSOD protects cells from the harmful effects of overproduction of ROS, in particular, the effects of ROS on mitochondrial metabolic enzymes, may contribute to the development of novel treatments for various diseases in which ROS are an important component.

NADPH oxidase-derived reactive oxygen species: involvement in vascular physiology and pathology

Reactive oxygen species (ROS) are essential mediators of normal cell physiology. However, in the last few decades, it has become evident that ROS overproduction and/or alterations of the antioxidant system associated with inflammation and metabolic dysfunction are key pathological triggers of cardiovascular disorders. NADPH oxidases (Nox) represent a class of hetero-oligomeric enzymes whose primary function is the generation of ROS. In the vasculature, Nox-derived ROS contribute to the maintenance of vascular tone and regulate important processes such as cell growth, proliferation, differentiation, apoptosis, cytoskeletal organization, and cell migration. Under pathological conditions, excessive Nox-dependent ROS formation, which is generally associated with the up-regulation of different Nox subtypes, induces dysregulation of the redox control systems and promotes oxidative injury of the cardiovascular cells. The molecular mechanism of Nox-derived ROS generation and the means by which this class of molecule contributes to vascular damage remain debatable issues. This review focuses on the processes of ROS formation, molecular targets, and neutralization in the vasculature and provides an overview of the novel concepts regarding Nox functions, expression, and regulation in vascular health and disease. Because Nox enzymes are the most important sources of ROS in the vasculature, therapeutic perspectives to counteract Nox-dependent oxidative stress in the cardiovascular system are discussed.

Exercise improves the dilatation function of mesenteric arteries in postmyocardial infarction rats via a PI3K/Akt/eNOS pathway-mediated mechanism

Myocardial infarction (MI) has been shown to induce endothelial dysfunction in peripheral resistance arteries and thus increase peripheral resistance. This study was designed to investigate the underlying mechanisms of post-MI-related dysfunctional dilatation of peripheral resistance arteries and, furthermore, to examine whether exercise may restore dysfunctional dilatation of peripheral resistance arteries. Adult male Sprague-Dawley rats were divided into three groups: sham-operated, MI, and MI + exercise. Ultrastructure and relaxation function of the mesenteric arteries, as well as phosphatidylinositol-3 kinase (PI3K), Akt kinases (Akt), endothelial nitric oxide synthase (eNOS) activity, and phosphorylation of PI3K, Akt, and eNOS by ACh were determined. Post-MI rats exhibited pronounced ultrastructural changes in mesenteric artery endothelial cells and endothelial dysfunction. In addition, the activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh were significantly attenuated in mesenteric arteries (P < 0.05-0.01). After 8 wk of exercise, not only did endothelial cells appeared more normal in structure, but also ameliorated post-MI-associated mesenteric arterial dysfunction, which were accompanied by elevated activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh (P < 0.05-0.01). Importantly, inhibition of either PI3K or eNOS attenuated exercise-induced restoration of the dilatation function and blocked PI3K, Akt, and eNOS phosphorylation by ACh in the mesenteric arteries. These data demonstrate that MI induces dysfunctional dilation of peripheral resistance arteries by degradation of endothelial structural integrity and attenuating PI3K-Akt-eNOS signaling. Exercise may restore dilatation function of peripheral resistance arteries by protecting endothelial structural integrity and increasing PI3K-Akt-eNOS signaling cascades.