Eicosapentaenoic acid (EPA) reduces pulmonary endothelial dysfunction and inflammation due to changes in protein expression during exposure to particulate matter air pollution

AIMS

Inhalation of air pollution small particle matter (PM) is a leading cause of cardiovascular (CV) disease. Exposure to PMs causes endothelial cell (EC) dysfunction as evidenced by nitric oxide (NO) synthase uncoupling, vasoconstriction and inflammation. Eicosapentaenoic acid (EPA) has been shown to mitigate PM-induced adverse cardiac changes in patients receiving omega-3 fatty acid supplementation. We set out to determine the pro-inflammatory effects of multiple PMs (urban and fine) on pulmonary EC NO bioavailability and protein expression, and whether EPA restores EC function under these conditions.

METHODS AND RESULTS

We pretreated pulmonary ECs with EPA and then exposed them to urban or fine air pollution PMs. LC/MS-based proteomic analysis to assess relative expression levels. Expression of adhesion molecules was measured by immunochemistry. The ratio of NO to peroxynitrite (ONOO-) release, an indication of eNOS coupling, was measured using porphyrinic nanosensors following calcium stimulation. Urban/fine PMs also modulated 9/12 and 13/36 proteins, respectively, linked to platelet and neutrophil degranulation pathways and caused > 50% (p < 0.001) decrease in the stimulated NO/ONOO- release ratio. EPA treatment altered expression of proteins involved in these inflammatory pathways, including a decrease in peroxiredoxin-5 and an increase in superoxide dismutase-1. EPA also increased expression of heme oxygenase-1 (HMOX1), a cytoprotective protein, by 2.1-fold (p = 0.024). EPA reduced elevations in sICAM-1 levels by 22% (p < 0.01) and improved the NO/ONOO- release ratio by > 35% (p < 0.05).

CONCLUSION

These cellular changes may contribute to anti-inflammatory, cytoprotective and lipid changes associated with EPA treatment during air pollution exposure.

Abstract WP229: Eicosapentaenoic Acid (EPA) Modulates Expression Of Thrombotic And Metabolic Proteins In Brain Endothelium Following Cytokine Challenge

Background: During inflammation, vascular endothelial cells (ECs) release vasoconstrictive and thrombotic factors that promote abnormal blood flow and atherothrombosis. The omega-3 fatty acid (n3FA) eicosapentaenoic acid (EPA) reduced first and total ischemic strokes each by 36% in patients with elevated cardiovascular risk (REDUCE-IT) when administered as icosapent ethyl. We measured the effects of EPA on expression of proteins involved in cytoprotection, thrombosis, and fatty acid metabolism in human brain ECs subjected to inflammation.

Methods: Human brain microvascular ECs (HBECs) were first challenged with IL-6 at 12 ng/ml for 2 hr and then treated with EPA (40 μM) for 24 hr. Global proteomic analysis was performed using LC/MS to measure relative expression levels of >1,000 proteins simultaneously. Only significant (p<0.05) changes in expression between treatment groups >1-fold were analyzed.

Results: EPA treatment significantly modulated the expression of 504 proteins (212 increased expression, 292 decreased expression) in HBECs compared with IL-6 alone. EPA treatment increased expression of the cytoprotective enzyme heme oxygenase-1 by 1.5-fold (p = 4.7 х 10 -16 ) relative to IL-6 alone. Additionally, IL-6 increased expression of prothrombin (clotting factor II) 1.3-fold relative to control (p = 1.41 х 10 -20 ), and EPA decreased expression of prothrombin by 1.3-fold relative to IL-6 (p = 2.10 х 10 -24 ). EPA also reduced expression of fatty acid desaturase 1 & 2 by 1.4-fold and 2.6-fold, respectively, which may lead to changes in intracellular fatty acid levels.

Conclusions: EPA significantly modulated expression of cytoprotective, thrombotic, and metabolic proteins in brain ECs under conditions of inflammation with IL-6. These effects of EPA on inflammation have implications for ischemic disease, including stoke, as demonstrated in large outcome trials.

Abstract WP210: Eicosapentaenoic Acid (EPA) Decreases Cytokine Release And Inflammatory Proteins In Brain Vascular Endothelium During Inflammation

Background: Brain vascular endothelial cell (EC) dysfunction is characterized by release of pro-inflammatory mediators that contribute to atherosclerosis and ischemic stroke. Treatment with icosapent ethyl (IPE), the ethyl ester of the omega-3 fatty acid, eicosapentaenoic acid (EPA), reduced first and total ischemic strokes each by 36%, without increasing hemorrhagic stroke, in statin-treated patients with elevated cardiovascular risk (REDUCE-IT). We tested the effects of EPA on cytokine release and expression of inflammatory proteins from brain microvascular ECs during inflammation.

Methods: Human brain microvascular endothelial cells (HBECs) were pretreated with the cytokine IL-6 at 12 ng/ml for 2 h before treatment with EPA (40 μM) for 24 h. Proteomic analysis was performed using LC/MS to capture relative expression levels. Only significant changes in protein expression between treatment groups >1-fold were analyzed. Gene set enrichment analysis was also performed on all significantly regulated proteins to identify groups of proteins (pathways) that were affected. Levels of soluble intercellular adhesion molecule-1 (sICAM-1) and tumor necrosis factor-α (TNF-α) were measured by immunochemistry (ELISA).

Results: IL-6 exposure produced increased levels of sICAM-1 and TNF-α by 102% and 147% (p<0.001), respectively, in brain ECs compared with vehicle. EPA treatment reduced release of sICAM-1 by 43% (p<0.001) and TNF-α by 52% (p<0.001) compared to IL-6 alone. EPA also downregulated 43 proteins involved in the “neutrophil degranulation” pathway in brain ECs (p-adjusted = 2.63 х 10 -12 ), including heat shock protein 90-alpha and beta by 1.1-fold each relative to IL-6 alone.

Conclusions: In brain vascular ECs, EPA significantly reduced expression of pro-inflammatory mediators and proteins associated with neutrophil degranulation under inflammatory conditions. The ability of EPA to reverse brain EC dysfunction during inflammatory may contribute to reductions in stroke risk.

Omega-3 fatty acids differentially alter the expression of detoxification enzymes and nitric oxide bioavailability in endothelial cells during IL-6 exposure

Background

Atherosclerotic plaques can elaborate reactive oxygen species (ROS) that reduce nitric oxide (NO) bioavailability. Cellular detoxification enzymes including various peroxiredoxin (PRDX) and superoxide dismutase (SOD) isoforms can inactivate ROS. The omega-3 fatty acid (n3-FA) eicosapentaenoic acid (EPA) reduced cardiovascular (CV) events in high-risk patients (REDUCE-IT), a benefit not observed with mixed n3-FAs containing docosahexaenoic acid (DHA).

Purpose

The purpose of this study was to compare the effects of EPA and DHA on NO bioavailability and expression of detoxification enzymes in the vascular endothelium in vitro.

Methods

Human umbilical vein endothelial cells (HUVECs) were pretreated with EPA or DHA at equimolar levels (10 μM) for 2 h, then challenged with IL-6 at 12 ng/ml for 24 h. Proteomic analysis was performed using LC/MS to measure relative protein expression. Only significant (p&lt;0.05) changes between treatment groups &gt;1-fold were analyzed. Cells were stimulated with calcium ionophore to measure NO and peroxynitrite (ONOO-) release using a porphyrinic nanosensor.

Results

EPA, but not DHA, augmented PRDX-2 and SOD1 expression in HUVECs relative to IL-6 alone (1.2-fold and 1.6-fold, respectively, p=0.03). EPA also significantly lowered other isoforms unlike DHA. Either EPA or DHA increased thioredoxin expression by 1.5-fold (p=0.001) and 1.3-fold (p=0.02), respectively and decreased SOD2 expression by 1.5-fold (p=8.75E-11) and 1.6-fold (p=6.03E-9), respectively. IL-6 alone only increased expression of 6 detoxification enzymes by at least 1.2-fold, relative to vehicle. Unlike DHA, EPA also increased the NO to ONOO- release ratio by 36% (p&lt;0.05) relative to IL-6 alone, without changes in NO synthase (eNOS) expression.

Conclusions

n3-FAs differentially influenced NO bioavailability and expression of ROS detoxification proteins, including peroxiredoxin and SOD isoforms. The net benefits of EPA on eNOS function and ROS detoxification may contribute to reduced atherothrombotic risk compared to DHA.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Amarin Pharma Inc., Elucida Research

Eicosapentaenoic acid inhibits lipopolysaccharide (LPS)-induced nitrite production and cytokine release from J774 macrophages

Background

Eicosapentaenoic acid (EPA), an omega-3 (ω-3) fatty acid, reduced cardiovascular (CV) events in high-risk patients (REDUCE-IT) but the mechanism is not fully understood. Activated macrophages, characterized by cytokine release and increased inducible nitric oxide synthase (iNOS) activity, contribute to atherosclerosis. As both a substrate for and potential inhibitor of cyclooxygenase (COX), EPA may reduce iNOS activity.

Purpose

The purpose of this study was to evaluate the dose-dependent effects of EPA on nitrite and cytokine release from lipopolysaccharide (LPS)-activated macrophages.

Methods

Murine J774 macrophages were pretreated with vehicle or EPA at 10, 20 and 40 μM for 2 h, then challenged with LPS at 1.0 μg/ml. After 24 hr, iNOS activity was measured by nitrite production using the Griess assay. EPA was compared to the COX inhibitor diclofenac at 1.0 μg/ml. Levels of interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) in cell supernatant were measured by immunochemistry using colchicine as a positive control.

Results

Activated macrophages caused a &gt;4-fold increase in nitrite production (p&lt;0.001) that was reduced by EPA in a dose-dependent manner. EPA decreased nitrite levels by 40, 62 and 77% at 10, 20 and 40 μM, respectively (p&lt;0.01). Diclofenac separately reduced nitrite levels by 40% (p&lt;0.01). EPA also reduced expression of IL-1β and TNF-α by 40% and 31%, respectively (p&lt;0.01), in a manner similar to equimolar colchicine (10 μM). The reductions in IL-1β and TNF-α with EPA were dose-dependent.

Conclusions

EPA reduced macrophage activation as evidenced by decreased nitrite production and cytokine release similar to other anti-inflammatory agents. These findings indicate a novel effect of EPA on mechanisms of inflammation associated with vascular disease.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Amarin Pharma Inc., Elucida Research

Omega-3 fatty acids differentially reduced expression of neutrophil degranulation-associated proteins in endothelial cells during IL-6 exposure

Background

Neutrophil degranulation contributes to atherogenesis and tissue injury. Mixed omega-3 fatty acid (n3-FA) formulations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have failed to reduce CV events compared to EPA only (REDUCE-IT), but the mechanisms are not understood.

Purpose

The purpose of this study was to compare the effects of EPA and DHA on expression of proteins linked to neutrophil degranulation in the vascular endothelium in vitro.

Methods

Human umbilical vein endothelial cells (HUVECs) were pretreated with EPA or DHA at equimolar levels (10 μM) for 2 h, then challenged with IL-6 at 12 ng/ml for 24 h. Proteomic analysis was performed using LC/MS to measure relative protein expression. Only significant (p&lt;0.05) changes between treatment groups &gt;1-fold were analyzed.

Results

In the Reactome “neutrophil degranulation” pathway, EPA and DHA downregulated 27 and 14 proteins, respectively, (p=9.97E-9 and 5.30E-4, respectively) relative to IL-6 alone. There were 12 protein changes common to both n3-FAs, including heme oxygenase-2 and ferritin light chain. EPA downregulated 15 proteins unlike DHA, including peroxiredoxin-6 and mitogen-activated protein kinase-1 (MAPK1). A combined 21 proteins downregulated by EPA and DHA versus IL-6 were upregulated by IL-6 alone relative to vehicle. EPA also increased expression of Rho-associated protein kinase-1 (ROCK-1), a protein downregulated by IL-6 alone and unaffected by DHA.

Conclusions

EPA and DHA differentially modulated expression of proteins linked to neutrophil degranulation. The distinct effects of EPA on protein expression may contribute to reduced inflammation in vascular injury compared to DHA.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Amarin Pharma Inc., Elucida Research

Omega-3 and omega-6 fatty acids have distinct effects on endothelial fatty acid content and nitric oxide bioavailability

Treatment with high dose icosapent ethyl (IPE), an ethyl ester of the omega-3 fatty acid eicosapentaenoic acid (EPA), significantly reduced ischemic events in patients with either cardiovascular disease (CV) or diabetes plus other risk factors (REDUCE-IT) but the mechanism is not well understood.  We compared the effects of EPA, docosahexaenoic acid (DHA), and the omega-6 fatty acid arachidonic acid (AA) on bioavailability of nitric oxide (NO) and fatty acid composition. Human umbilical vein endothelial cells (HUVECs) were pretreated with EPA, DHA, or AA (10 µM). Cells were stimulated with calcium ionophore and NO and peroxynitrite (ONOO^-) were measured using porphyrinic nanosensors. Levels of EPA, DHA, AA and other fatty acids were measured by gas chromatography (GC). EPA treatment caused the greatest NO release (18%, p < 0.001) and reduction in ONOO^- (13%, p < 0.05) compared to control; the [NO]/[ ONOO^-] ratio increased by 35% (p < 0.001). DHA treatment increased NO levels by 12% (p < 0.01) but had no effect on ONOO^- release. AA did not affect either NO or ONOO^- release.  Fatty acid treatments increased their respective levels in endothelial cells.  EPA levels increased 10-fold to 4.59 mg/g protein (p < 0.001) with EPA treatment and the EPA/AA ratio increased by 10-fold (p < 0.001) compared to vehicle.  Only EPA increased docosapentaenoic acid (DPA, omega-3) levels by 2-fold (p < 0.001). AA alone decreased the EPA/AA ratio 4-fold (p<0.001). These findings support a preferential benefit of EPA on endothelial function and omega-3 fatty acid content.

Abstract 318: Eicosapentaenoic Acid Improved Nitric Oxide Bioavailability and Reduced Nitroxidative Stress in Human Endothelial Cells in Contrast to Arachidonic Acid In Vitro

Treatment with prescription, high dose, stable icosapent ethyl (IPE), which is eicosapentaenoic acid (EPA), an omega-3 fatty acid (O3FA), significantly reduced clinical events in high-risk patients with diabetes and other risk factors or cardiovascular disease (REDUCE-IT). Previous studies suggest that the benefits of EPA correlate positively with its levels and ratio to arachidonic acid (AA) in circulation. Unlike EPA, AA is an omega-6 fatty acid (O6FA) that, along with its metabolites, contributes to inflammation and diabetes. One mechanism of benefit of an increased EPA to AA ratio may be improved endothelial cell (EC) function, as evidenced by increased nitric oxide (NO) release and decreased nitroxidative (ONOO – ) stress. In this study, human umbilical vein endothelial cells (HUVECs) were pretreated with EPA or AA at equimolar levels (10 μM) at various time points (4-24 hr) in 5% FBS. Following treatment, the cells were stimulated with calcium ionophore and assayed for the ratio of NO and ONOO – release, an indicator of eNOS coupling, using tandem porphyrinic nanosensors. ECs treated with EPA had significantly greater NO release following stimulation compared with vehicle at all time points, including 17% and 21% at 4 and 24 hr, respectively (p<0.05 and p<0.01) without changes in eNOS expression. By contrast, AA did not significantly improve NO production. ECs treated with EPA also showed a non-significant reduction in ONOO - release by 10% at 4 hr and 14% at 24 hr. EPA, but not AA, increased NO/ONOO - release ratio by 42% (4.03 ± 0.06 vs 2.83 ± 0.05; p <0.01) by 24 hr. Thus, EPA increased NO bioavailability in human ECs, unlike AA, due to improved eNOS coupling and reduced oxidative stress. These findings support a preferential benefit of EPA on endothelial function as compared to AA and supports further investigation.

A prospective study of contrast preservation using ultra-low contrast delivery technique versus standard automated contrast injector system in coronary procedures

Background

We aimed to assess the decrease in contrast media volume (CMV) with ultra-low contrast delivery technique (ULCD) developed at our institution versus the usual automated contrast injector system (ACIS) contrast delivery in coronary procedures.

Methods

We analyzed the amount of contrast given in the consecutive 204 patients of the operators who use ULCD technique versus consecutive 200 patients of the other operators who use ACIS without ULCD technique for coronary angiograms and/or percutaneous coronary interventions (PCIs) from May 2017 to July 2018 at our center. We calculated the mean CMV between these groups.

Results

We observed a significant reduction in mean CMV with ULCD technique versus standard ACIS, respectively: angiogram 24.8 ± 15.8 mL (n = 194) vs 42.3 ± 25.1 mL (n = 200) (p < 0.0001); PCI 23.5 ± 19.7 mL (n = 52) vs 48.2 ± 30.8 mL (n = 16) (p < 0.0070); angiogram with ad hoc PCI 53.4 ± 32.1 mL (n = 23) vs 89.7 ± 35.6 mL (n = 16) (p < 0.0024); and overall angiogram and PCI 27.4 ± 20.5 mL (n = 204) vs 44.9 ± 28.0 mL (n = 181) (p < 0.0001).

Conclusion

Our study showed a highly significant reduction in CMV using ULCD technique compared to standard ACIS contrast delivery in coronary invasive procedures. Even in the standard ACIS arm, CMV was significantly lower than values reported in literature, possibly due to operators' bias toward contrast preservation.

Variable Effects Of LDL Subclasses Of Cholesterol On Endothelial Nitric Oxide/Peroxynitrite Balance - The Risks And Clinical Implications For Cardiovascular Disease

Background

Elevated levels of low density lipoprotein (LDL), “bad cholesterol”, is not an accurate indicator of coronary disease. About 75% of patients with heart attacks have cholesterol levels that do not indicate a high risk for a cardiovascular event. LDL is comprised of three subclasses, with particles of different size and density. We used nanomedical systems to elucidate the noxious effects of LDL subclasses on endothelium.

Experimental

Nanosensors were employed to measure the concentrations of nitric oxide (NO) and peroxynitrite (ONOO⁻) stimulated by LDL subclasses in HUVECs. N-LDL and ox-LDL (subclass A: 1.016–1.019 g/mL, subclass I: 1.024–1.029 g/mL, and subclass B: 1.034–1.053 g/mL) stimulated NO and ONOO⁻ release. The concentrations ratio of (NO)/(ONOO⁻) was used to evaluate the noxious effects of the subclasses on endothelium.

Results

In HUVECs, the (NO)/(ONOO⁻) ratio for normal endothelium is about 5, but shifts to 2.7±0.4, 0.5±0.1, and 0.9±0.1 for subclasses A, B, and I, respectively. Ratios below 1.0 indicate an imbalance between NO and ONOO⁻, affecting endothelial function. LDL of 50% B and 50% I produced the most severe imbalance (0.45±0.04), whereas LDL of 60% A, 20% B, and 20% I had the most favorable balance of 5.66±0.69. Subclass B significantly elevated the adhesion of molecules and monocytes. The noxious effect was significantly higher for ox-LDL than n-LDL.

Conclusion

Subclass B of “bad cholesterol” is the most damaging to endothelial function and can contribute to the development of atherosclerosis. Contrary to the current national guidelines, this study suggests that it’s not the total LDL, rather it is the concentration of subclass B in relation to subclasses A and/or I, that should be used for diagnosis of atherosclerosis and the risk of heart attack. By utilizing specific pharmacological therapy to address the concentration of subclass B, there is a potential to significantly reduce the risk of heart attack and atherosclerosis.

Eicosapentaenoic acid improves endothelial function and nitric oxide bioavailability in a manner that is enhanced in combination with a statin

The endothelium exerts many vasoprotective effects that are largely mediated by release of nitric oxide (NO). Endothelial dysfunction represents an early but reversible step in atherosclerosis and is characterized by a reduction in the bioavailability of NO. Previous studies have shown that eicosapentaenoic acid (EPA), an omega-3 fatty acid (O3FA), and statins individually improve endothelial cell function, but their effects in combination have not been tested. Through a series of in vitro experiments, this study evaluated the effects of a combined treatment of EPA and the active metabolite of atorvastatin (ATM) on endothelial cell function under conditions of oxidative stress. Specifically, the comparative and time-dependent effects of these agents on endothelial dysfunction were examined by measuring the levels of NO and peroxynitrite (ONOO^-) released from human umbilical vein endothelial cells (HUVECs). The data suggest that combined treatment with EPA and ATM is beneficial to endothelial function and was unique to EPA and ATM since similar improvements could not be recapitulated by substituting another O3FA docosahexaenoic acid (DHA) or other TG-lowering agents such as fenofibrate, niacin, or gemfibrozil. Comparable beneficial effects were observed when HUVECs were pretreated with EPA and ATM before exposure to oxidative stress. Interestingly, the kinetics of EPA-based protection of endothelial function in response to oxidation were found to be significantly different than those of DHA. Lastly, the beneficial effects on endothelial function generated by combined treatment of EPA and ATM were reproduced when this study was expanded to an ex vivo model utilizing rat glomerular endothelial cells. Taken together, these findings suggest that a combined treatment of EPA and ATM can inhibit endothelial dysfunction that occurs in response to conditions such as hyperglycemia, oxidative stress, and dyslipidemia.

Nanomedical studies of the restoration of nitric oxide/peroxynitrite balance in dysfunctional endothelium by 1,25-dihydroxy vitamin D3 - clinical implications for cardiovascular diseases

Background

Clinical studies indicate that vitamin D₃ improves circulation and may have beneficial effects in hypertension. This study uses nanomedical systems to investigate the role of 1,25-dihydroxy vitamin D₃ in the preservation/restoration of endothelial function in an angiotensin II (Ang II) cellular model of hypertension.

Methods

1,25-dihydroxy vitamin D₃-stimulated nitric oxide (NO) and peroxynitrite (ONOO⁻) concentrations were measured in situ with nanosensors (200–300 mm diameter with a detection limit of 1 nM) in human umbilical vein endothelial cells of African American (AA) and Caucasian American (CA) donors exposed to Ang II. The balance/imbalance between NO and ONOO⁻ concentrations ([NO]/[ONOO⁻]) was simultaneously monitored and used as an indicator of endothelial nitric oxide synthase (eNOS) uncoupling and endothelial dysfunction.

Results

[NO]/[ONOO⁻] imbalance in Ang II-stimulated dysfunctional endothelium was 0.20±0.16 for CAs and 0.11±0.09 for AAs. Uncoupled eNOS and overexpression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase contributed to high production of ONOO⁻. Vitamin D₃ treatment reversed [NO]/[ONOO⁻] to 3.0±0.1 in CAs and 2.1±0.1 in AAs – exceeding that observed in normal endothelium. Vitamin D₃ restored uncoupled eNOS and endothelial function by increasing cytoprotective NO and decreasing the cytotoxic ONOO⁻. The beneficial effect of vitamin D₃ is associated with a favorable rate of NO and ONOO⁻ release, restoration of the [NO]/[ONOO⁻] and the overall decrease in the overexpression of eNOS, inducible nitric oxide synthase and NADPH oxidase. This effect of vitamin D₃ may prove to be beneficial in the treatment of hypertension and other cardiovascular diseases, including heart failure, myocardial infarction, vasculopathy, stroke and diabetes.

Metformin treatment decreases nitroxidative stress, restores nitric oxide bioavailability and endothelial function beyond glucose control

Reduction of nitric oxide (NO), a potent vasodilator, and an increase in cytotoxic peroxynitrite (ONOO^-) may be associated with the uncoupling of NO synthase (eNOS) and endothelial cell (EC) dysfunction. In addition to its effect on glucose control, metformin, may also directly benefit in the restoration of the function of eNOS and EC. Obese Zucker rats were administered vehicle or 300 mg/kg/day metformin for 4 weeks. NO concentration [NO] and ONOO^- concentration [ONOO^-] were measured in aortic and glomerular endothelial cells from Zucker rats in vitro. Compared with controls, aortic and glomerular endothelial [NO] was reduced by 32% and 41%, while [ONOO^-] release increased 79% and 69%, respectively. Metformin treatment increased aortic and glomerular endothelial [NO] by 37% and 57%, respectively, while decreasing [ONOO^-] by 32% and 34%, compared with vehicle-treated animals. Treatment with metformin significantly restored the balance in the [NO]/[ONOO^-] ratio with 101% and 138% increase for aortic and glomerular endothelial cells, respectively. Fasting glucose levels were not significantly changed. These findings indicate that metformin therapy has a direct and beneficial effect on arterial and renal EC function in obese rats, including enhanced NO release and reduced nitroxidative stress, beyond any effects on fasting glucose levels.

The intravenous and oral pharmacokinetics of afoxolaner and milbemycin oxime when used as a combination chewable parasiticide for dogs

The pharmacokinetics of afoxolaner and milbemycin oxime (A3 and A4 forms) in dogs were evaluated following the oral administration of NexGard Spectra^® (Merial), a fixed combination chewable formulation of these two active pharmaceutical ingredients. Absorption of actives was rapid at levels that provide the minimum effective doses of 2.5 mg/kg and 0.5 mg/kg of afoxolaner and milbemycin oxime, respectively. The time to maximum afoxolaner plasma concentrations (t_max ) was 2-4 h. The milbemycin t_max was 1-2 h. The terminal plasma half-life (t_1/2 ) and the oral bioavailability were 14 ± 3 days and 88.3% for afoxolaner, 1.6 ± 0.4 days and 80.5% for milbemycin oxime A3 and 3.3 ± 1.4 days and 65.1% for milbemycin oxime A4. The volume of distribution (V_d ) and systemic clearance (Cls) were determined following an IV dose of afoxolaner or milbemycin oxime. The V_d was 2.6 ± 0.6, 2.7 ± 0.4 and 2.6 ± 0.6 L/kg for afoxolaner, milbemycin oxime A3 and milbemycin oxime A4, respectively. The Cls was 5.0 ± 1.2, 75 ± 22 and 41 ± 12 mL/h/kg for afoxolaner, milbemycin oxime A3 and milbemycin oxime A4, respectively. The pharmacokinetic profile for the combination of afoxolaner and milbemycin oxime supports the rapid onset and a sustained efficacy for afoxolaner against ectoparasites and the known endoparasitic activity of milbemycin oxime.

Effect of chronic treatment with the vasopeptidase inhibitor AVE 7688 and ramipril on endothelial function in atherogenic diet rabbits

Cardiovascular disease is the major cause of death in Western nations, although improved possibilities regarding diagnosis and therapy now exist. Endothelial dysfunction is triggered by cardiovascular risk factors such as hypercholesterolaemia, hypertension, adiposity and smoking, contributing to the common endpoint of atherosclerosis.

This study examined the pharmacological effects of angiotensin-converting enzyme (ACE) and combined ACE-neutral endopeptidase (NEP) (vasopeptidase) inhibitors on endothelial dysfunction in the model of hyperlipidaemic rabbits. The focus of the study was to assess endothelial function after treatment with the ACE-NEP inhibitor AVE 7688 (30 mg/kg/day) in comparison to the ACE inhibitor (ACE-I) ramipril (1 mg/kg/day). Different parameters, such as endothelial function, blood pressure (BP), expansion of plaques, endothelial nitric oxide (NO) and superoxide (O2 ) release and plasma levels of various lipidaemic parameters were analysed. Control groups consisted of one group fed only with normal diet, one group fed only with atherogenic diet and the direct control group fed with varied diets (six weeks atherogenic diet followed by 12 weeks normal diet). Since for the treatment of atherosclerosis, a change in feeding is absolutely necessary, in the present study, at the start of the treatments with AVE 7688 and ramipril, the rabbits food was changed to a normal diet.

At the end of the study, mean arterial blood pressure (MAP) was measured in the anaesthetised animals. The values in standard, atherogenic and varied diet-fed rabbits were around 73±2 mmHg. Angiotensin I (Ang I) given intravenous (i.v.) induced a strong increase in MAP of about 20%. In both the treated groups Ang I-induced BP increase was inhibited. In contrast, i.v. bradykinin led to a strong reduction in MAP in both the treated groups of around 50%.

Six weeks' feeding with an atherogenic diet in the rabbits induced an enduring endothelial dysfunction despite the food subsequently being changed to a normal chow. All measured parameters indicated a significant favourable effect on endothelial dysfunction as a result of the two treatment regimens. Endothelial function measured in the organ chamber showed somewhat greater improvement in the ACE-NEP treated group than in the ACE-I treated group. The treatment with ramipril, as well as with AVE 7688, restored endothelial function by increasing the ratio of NO to O2- concentration and bioavailability of NO. In this study, a similar protective effect on endothelial function was shown by ACE-NEP inhibition as already seen with ACE inhibitors in an animal model of atherosclerosis.

Ramipril improves nitric oxide availability in hypertensive rats with failing hearts after myocardial infarction

A markedly decreased aortic nitric oxide (NO) availability, probably due to impaired endothelial nitric oxide synthase activity with enhanced O2- and peroxynitrite production, seems to be attributable to endothelial dysfunction in spontaneously hypertensive rats (SHR) with severe congestive heart failure (CHF). In this study, we investigated the chronic effect of the angiotensin-converting enzyme inhibitor, ramipril (RA) and the loop diuretic, frusemide (FU), as well as the combination of both on endothelial NO, O2- and peroxynitrite production in aortae from SHR with failing hearts after myocardial infarction (MI).

Heart failure was induced by permanent occlusion of the left coronary artery. SHR were randomised to receive either placebo, RA, (1 mg/kg/day), FU (4 mg/kg/day) or RA+FU (1 and 4 mg/kg/day, respectively). Treatments were started two weeks following MI and continued for six weeks. Reduced aortic and coronary flow indices in the working heart, which can be considered as markers for endothelial function, were significantly normalised and improved, respectively, by RA, FU or RA+FU-treatment. Similarly, all three treatment regimens significantly enhanced the reduced calcium ionophore (CaI)-induced NO-release (assessed by a NO-sensitive microsensor) from aortic endothelial cells of placebo- treated animals with CHF. Concomitantly, the increased CaI-stimulated O 2production (assessed by an electrochemical sensor) in aortic endothelial cells of placebo-treated animals with CHF was significantly reduced by RA and RA+FUtreatment. Treatment with RA and RA+FU also attenuated the dramatic increase in endothelial peroxynitrite concentration (chemiluminescence method), which was observed in placebo-treated rats with CHF. FU did not counteract improved haemo- and cardiodynamic parameters by RA.

Thus, RA and FU act synergistically to enhance bioavailability of endothelium-derived NO, and this may contribute to the clinical usefulness of the combination of these drugs in treatment of heart failure.

Development of novel FP-based probes for live-cell imaging of nitric oxide dynamics

Nitric oxide () is a free radical with a wide range of biological effects, but practically impossible to visualize in single cells. Here we report the development of novel multicoloured fluorescent quenching-based probes by fusing a bacteria-derived -binding domain close to distinct fluorescent protein variants. These genetically encoded probes, referred to as geNOps, provide a selective, specific and real-time read-out of cellular dynamics and, hence, open a new era of bioimaging. The combination of geNOps with a Ca(2+) sensor allowed us to visualize and Ca(2+) signals simultaneously in single endothelial cells. Moreover, targeting of the probes was used to detect signals within mitochondria. The geNOps are useful new tools to further investigate and understand the complex patterns of signalling on the single (sub)cellular level.

The Abdominal Aortic Aneurysm and Intraluminal Thrombus: Current Concepts of Development and Treatment

The pathogenesis of the abdominal aortic aneurysm (AAA) shows several hallmarks of atherosclerotic and atherothrombotic disease, but comprises an additional, predominant feature of proteolysis resulting in the degradation and destabilization of the aortic wall. This review aims to summarize the current knowledge on AAA development, involving the accumulation of neutrophils in the intraluminal thrombus and their central role in creating an oxidative and proteolytic environment. Particular focus is placed on the controversial role of heme oxygenase 1/carbon monoxide and nitric oxide synthase/peroxynitrite, which may exert both protective and damaging effects in the development of the aneurysm. Treatment indications as well as surgical and pharmacological options for AAA therapy are discussed in light of recent reports.

Atorvastatin enhanced nitric oxide release and reduced blood pressure, nitroxidative stress and rantes levels in hypertensive rats with diabetes

Clinical trials have shown that atorvastatin benefits patients with diabetes even with normal baseline LDL levels. We hypothesized that atorvastatin improves endothelial cell (EC) function and reduces inflammation in hypertensive rats with diabetes. Non-diabetic and streptozotocin-induced type 2 diabetic male spontaneously hypertensive rats (SHR) were treated with atorvastatin at 20 mg/kg/day. After five weeks, nitric oxide (NO) and peroxynitrite (ONOO(-)) were measured in aortic and glomerular endothelial cells. A tandem of nanosensors was used to simultaneously measure NO and ONOO(-) concentration and their ratio [NO]/[ONOO(-)] was monitored with a time resolution better than 10 μs and detection limit 1 nM. [NO]/[ONOO(-)] was applied as a marker of endothelial NO synthase (eNOS) uncoupling, endothelial dysfunction and nitroxidative stress. Glucose, cholesterol, blood pressure (BP), and the cytokine RANTES were also measured. Diabetic SHR rats had elevated glucose (355 ± 38 mg/dL), mean BP (172 ± 15 mmHg), and plasma RANTES (38.4 ± 2.7 ng/mL), low endothelial NO bioavailability and high ONOO(-). Maximal NO release measured 267 ± 29 nM in aortic endothelium of SHR rats and 214 ± 20 nM for diabetic SHR rats; [NO]/[ONOO(-)] was 0.88 ± 12 and 0.61 ± 0.08, respectively. [NO]/[ONOO(-)] ratios below one indicate a high uncoupling of eNOS, endothelial dysfunction and high nitroxidative stress. Atorvastatin treatment partially restored endothelial function by increasing NO level by 98%, reducing ONOO(-) by 40% and favorably elevating [NO]/[ONOO(-)] to 1.1 ± 0.2 for diabetic SHR rats and 1.6 ± 0.3 for SHR rats. The effects of atorvastatin were similar in glomerular endothelial cells and were partially reproduced by modulators of eNOS or NADPH oxidase. Atorvastatin had no significant effect on fasting glucose or total cholesterol levels but reduced mean BP by 21% and 11% in diabetic and non-diabetic animals, respectively. Atorvastatin also reduced RANTES levels by 50%. Atorvastatin favorably increased the [NO]/[ONOO(-)] balance, enhanced endothelial cytoprotective NO, decreased cytotoxic ONOO(-) and reduced BP, inflammation and RANTES levels in diabetic, hypertensive rats without altering cholesterol levels. These findings provide insights into mechanisms of restoration of endothelial function and vascular protection by atorvastatin in diabetes and hypertension.

Using nanosensors for in situ monitoring and measurement of nitric oxide and peroxynitrite in a single cell

The cytotoxic peroxynitrite (ONOO(-)) is an oxidation product of the cytoprotective nitric oxide (NO). Our studies support the hypothesis that the concentration ratio of NO and ONOO(-), [NO]/[ONOO(-)] can be a marker of nitroxidative imbalance, which subsequently correlates well with endothelial dysfunction and dysfunction of the cardiovascular system. Nanosensors, described here, have been used for simultaneous monitoring and measurement of NO and ONOO(-) release from a single endothelial cell. These nanosensors, with a diameter of 200-300 nm, can be positioned accurately in close proximity of 5-10 μm from the endothelial cell membrane. The response time of the sensors is better than a millisecond and the detection limit is 10(-9) M, with a linear concentration response of up to about 2 μM. The application of these sensors for the measurement of the balance and imbalance of [NO]/[ONOO(-)] in normal and dysfunctional endothelium is demonstrated.

Abstract 648: Nebivolol and Valsartan Increase Nitric Oxide Release from Human Endothelial Cells in a Synergistic Fashion

Introduction: Nebivolol is a β1-adrenergic receptor antagonist that stimulates endothelial nitric oxide (NO) release through β3-adrenergic receptor activation, ATP-mediated stimulation of purinergic P2Y receptors, and inhibition of membrane lipid oxidation. Valsartan is an angiotensin II receptor blocker (ARB) that selectively inhibits angiotensin II type 1 (AT1) receptors, thereby exerting no direct effect at type 2 (AT2) receptors, which have been shown to stimulate NO synthase activity through a bradykinin-mediated pathway. As NO is a key regulator of blood pressure and these two antihypertensive agents promote NO release through distinct mechanisms, we compared their individual and combined effects on NO release from human endothelial cells.

Methods: Human umbilical vein endothelial cells (HUVECs) were incubated for 1 hr with vehicle, nebivolol or valsartan alone (each at 1.0 μM), or nebivolol (1.0 μM) and valsartan (0.5-5.0 μM) combined. The comparative effects of these agents on maximal NO release were measured in individual cells using porphyrinic nanosensors following stimulation with calcium ionophore (1.0 μM).

Results: Nebivolol treatment increased HUVEC NO release by 49% (509 ± 18 nM, mean ± SD) as compared to vehicle treatment alone (342 ± 26 nM; p<0.001). Valsartan had a more modest effect, increasing NO release by 13% (385 ± 19 nM) as compared to vehicle-treated controls (p<0.01). Treatment with both agents at 1.0 μM increased HUVEC NO release by 91% (655 ± 19 nM) as compared to vehicle alone (p<0.001) and was 29% (p<0.001) and 70% (p<0.001) greater than the separate effects observed for nebivolol and valsartan, respectively. The additive effect of valsartan was dose-dependent and was also observed at 0.5 and 5.0 μM in combination with nebivolol.

Conclusions: These data suggest that nebivolol and valsartan, when applied in combination, increase the ability of endothelial cells to release NO in a synergistic manner. The exact mechanism of this process remains unclear but, considering the importance of NO in regulating blood pressure, merits further study.

Amlodipine increased endothelial nitric oxide and decreased nitroxidative stress disproportionately to blood pressure changes

BACKGROUND

Clinical trials have shown that amlodipine reduces cardiovascular events at a rate that is not predicted by changes in brachial arterial pressure alone. These findings may be explained, in part, by the pleiotropic effects of amlodipine on endothelial cell (EC) function. In this study, we elucidated the effect of amlodipine on nitric oxide (NO) bioavailability and cytotoxic peroxynitrite (ONOO(-)) and blood pressure (BP).

METHODS

Spontaneously hypertensive rats (SHRs) were treated with vehicle or amlodipine (5 mg/kg/day) for 8 weeks and compared with untreated, baseline rats. NO and ONOO(-) release from aortic and glomerular ECs were measured ex vivo using amperometric nanosensors following maximal stimulation with calcium ionophore. BP was measured using the tail-cuff method.

RESULTS

As compared with baseline, vehicle treatment had reduced aortic endothelial NO release from 157 ± 11 nM to 55 ± 6 nM and increased ONOO(-) from 69 ± 7 nM to 156 ± 19 nM. The NO/ONOO(-) ratio, a comprehensive measurement of eNOS function, decreased from 2.3 ± 0.3 to 0.3 ± 0.1. Compared with vehicle, amlodipine treatment restored NO to 101 ± 3 nM, decreased ONOO(-) to 50 ± 4 nM, and increased the NO/ONOO(-) ratio to 2.0 ± 0.2, a level similar to baseline. Similar changes were observed for glomerular ECs. Mean arterial blood pressure increased from 149 ± 3 mm Hg (baseline) to 174 ± 1 mm Hg (vehicle). Amlodipine slightly, but significantly, decreased mean arterial blood pressure to 167 ± 3 mm Hg vs. vehicle treatment.

CONCLUSIONS

Amlodipine increased NO bioavailability and decreased nitroxidative stress in SHRs with EC dysfunction disproportionately to BP changes. These direct, vascular effects of amlodipine on EC function may contribute to reduced risk for atherothrombotic events as observed in clinical trials.

Effect of glyceryl trinitrate on staphylococcus aureus growth and leukocyte activation during simulated extracorporeal circulation

BACKGROUND

Previously, nitric oxide has been shown to possess antimicrobial effects. In this study, we aim to test the effect of glyceryl trinitrate (GTN) on Staphylococcus aureus growth during simulated extracorporeal circulation (SECC) and also to examine the effect of S. aureus, alone and in combination with GTN, on activation markers of the innate immune system during SECC.

METHODS

In an in vitro system of SECC, we measured GTN-induced changes in markers of leukocyte activation in whole blood caused by S. aureus infestation, as well as the effect of GTN on S. aureus growth.

RESULTS

GTN had no effect on S. aureus growth after 240 minutes SECC. Staphylococcus aureus reduced the expression of granulocyte Fcγ-receptor CD32 but stimulated the expression of monocyte CD32. Staphylococcus aureus stimulated expression of some leukocyte adhesion key proteins, activation marker CD66b, lipopolysaccharide-receptor CD14, and C3b-receptor CD35. Staphylococcus aureus and GTN addition induced significant increases in monocyte CD63 (lysosomal granule protein) levels.

CONCLUSION

GTN does not affect S. aureus growth during SECC and has no effect on SECC-induced leukocyte activation.

The favorable kinetics and balance of nebivolol-stimulated nitric oxide and peroxynitrite release in human endothelial cells

Background

Nebivolol is a third-generation beta-blocker used to treat hypertension. The vasodilation properties of nebivolol have been attributed to nitric oxide (NO) release. However, the kinetics and mechanism of nebivolol-stimulated bioavailable NO are not fully understood.

Methods

Using amperometric NO and peroxynitrite (ONOO^-) nanosensors, β₃-receptor (agonist: L-755,507; antagonists: SR59230A and L-748,337), ATP efflux (the mechanosensitive ATP channel blocker, gadolinium) and P2Y-receptor (agonists: ATP and 2-MeSATP; antagonist: suramin) modulators, superoxide dismutase and a NADPH oxidase inhibitor (VAS2870), we evaluated the kinetics and balance of NO and ONOO^- stimulated by nebivolol in human umbilical vein endothelial cells (HUVECs). NO and ONOO^- were measured with nanosensors (diameter ~ 300 nm) placed 5 ± 2 μm from the cell membrane and ATP levels were determined with a bioluminescent method. The kinetics and balance of nebivolol-stimulated NO and ONOO^- were compared with those of ATP, 2-MeSATP, and L-755,507.

Results

Nebivolol stimulates endothelial NO release through β₃-receptor and ATP-dependent, P2Y-receptor activation with relatively slow kinetics (75 ± 5 nM/s) as compared to the kinetics of ATP (194 ± 10 nM/s), L-755,507 (108 ± 6 nM/s), and 2-MeSATP (105 ± 5 nM/s). The balance between cytoprotective NO and cytotoxic ONOO^- was expressed as the ratio of [NO]/[ONOO^-] concentrations. This ratio for nebivolol was 1.80 ± 0.10 and significantly higher than that for ATP (0.80 ± 0.08), L-755,507 (1.08 ± 0.08), and 2-MeSATP (1.09 ± 0.09). Nebivolol induced ATP release in a concentration-dependent manner.

Conclusion

The two major pathways (ATP efflux/P2Y receptors and β₃ receptors) and several steps of nebivolol-induced NO and ONOO^- stimulation are mainly responsible for the slow kinetics of NO release and low ONOO^-. The net effect of this slow kinetics of NO is reflected by a favorable high ratio of [NO]/[ONOO^-] which may explain the beneficial effects of nebivolol in the treatment of endothelial dysfunction, hypertension, heart failure, and angiogenesis.

Effects of angiotensin receptor blockers on endothelial nitric oxide release: the role of eNOS variants

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Angiotensin II receptor blockers improve endothelial cell-dependent vasodilation in patients with hypertension through suppression of angiotensin II type 1 receptors but may have additional and differential effects on endothelial nitric oxide synthase (eNOS) function.

WHAT THIS STUDY ADDS

• The key finding from this study is that angiotensin II receptor blockers (ARBs) differentially enhanced nitric oxide (NO) release in a manner influenced by certain genetic variants of eNOS. This finding provides new insights into the effects of ARBs on endothelial cell-dependent vasodilation and eNOS function that are of high importance in vascular medicine and clinical pharmacology. AIM Angiotensin II receptor blockers (ARBs) improve endothelial cell (EC)-dependent vasodilation in patients with hypertension through suppression of angiotensin II type 1 receptors but may have additional and differential effects on endothelial nitric oxide (NO) synthase (eNOS) function. To investigate this question, we tested the effects of various ARBs on NO release in ECs from multiple donors, including those with eNOS genetic variants linked to higher cardiovascular risk.

METHODS

The effects of ARBs (losartan, olmesartan, telmisartan, valsartan), at 1 µm, on NO release were measured with nanosensors in human umbilical vein ECs obtained from 18 donors. NO release was stimulated with calcium ionophore (1 µm) and its maximal concentration was correlated with eNOS variants. The eNOS variants were determined by a single nucleotide polymorphism in the promoter region (T-786C) and in the exon 7 (G894T), linked to changes in NO metabolism. RESULTS All of the ARBs caused an increase in NO release as compared with untreated samples (P < 0.01, n= 4-5 in all eNOS variants). However, maximal NO production was differentially influenced by eNOS genotype. Olmesartan increased maximal NO release by 30%, which was significantly greater (P < 0.01, n= 4-5 in all eNOS variants) than increases observed with other ARBs.

CONCLUSIONS

The ARBs differentially enhanced NO release in ECs in a manner influenced by eNOS single nucleotide polymorphisms. These findings provide new insights into the effects of ARBs on EC-dependent vasodilation and eNOS function.