Vascular Nitric Oxide Production Research Articles

Arsenic Exposure-Related Hypertension in Bangladesh and Reduced Circulating Nitric Oxide Bioavailability.

Hypertension is a major cause of death worldwide. Although arsenic exposure has been associated with the risk of hypertension, this association appears nonuniform due to inconsistent results from studies conducted in different populations. Moreover, hypertension is a complex condition with multiple underlying mechanisms and factors. One factor is impaired production and bioavailability of vascular nitric oxide (NO). However, the implications of the effects of arsenic exposure on circulating NO and its association with hypertension in humans are largely unknown. We investigated the dose-response relationship between arsenic exposure and hypertension with vascular NO levels as a potential mediator of arsenic-related hypertension in individuals exposed to a broad range of arsenic. A total of 828 participants were recruited from low- and high-arsenic exposure areas in Bangladesh. Participants' drinking water, hair, and nail arsenic concentrations were measured by inductively coupled plasma mass spectroscopy. Hypertension was defined as a systolic blood pressure (SBP) value of and a diastolic (DBP) value of . Serum NO levels reflected by total serum nitrite concentrations were measured by immunoassay. A formal causal mediation analysis was used to assess NO as a mediator of the association between arsenic level and hypertension. Increasing concentrations of arsenic measured in drinking water, hair, and nails were associated with the increasing levels of SBP and DBP. The odds of hypertension were dose-dependently increased by arsenic even in participants exposed to relatively low to moderate levels () of water arsenic [odds ratios (ORs) and 95% confidence intervals (CIs): 2.87 (95% CI: 1.28, 6.44), 2.67 (95% CI: 1.27, 5.60), and 5.04 (95% CI: 2.71, 9.35) for the , , and groups, respectively]. Causal mediation analysis showed a significant mediating effect of NO on arsenic-related SBP, DBP, and hypertension. Increasing exposure to arsenic was associated with increasing odds of hypertension. The association was mediated through the reduction of vascular NO bioavailability, suggesting that impaired NO bioavailability was a plausible underlying mechanism of arsenic-induced hypertension in this Bangladeshi population. https://doi.org/10.1289/EHP13018.

Cardiac nitric oxide scavenging: role of myoglobin and mitochondria.

Vascular production of nitric oxide (NO) regulates vascular tone. However, highly permeable NO entering the cardiomyocyte would profoundly impact metabolism and signalling without scavenging mechanisms. The purpose of this study was to establish mechanisms of cardiac NO scavenging. Quantitative optical studies of normoxic working hearts demonstrated that micromolar NO concentrations did not alter mitochondria redox state or respiration despite detecting NO oxidation of oxymyoglobin to metmyoglobin. These data are consistent with proposals that the myoglobin/myoglobin reductase (Mb/MbR) system is the major NO scavenging site. However, kinetic studies in intact hearts reveal a minor role (∼9%) for the Mb/MbR system in NO scavenging. In vitro, oxygenated mitochondria studies confirm that micromolar concentrations of NO bind cytochrome oxidase (COX) and inhibit respiration. Mitochondria had a very high capacity for NO scavenging, importantly, independent of NO binding to COX. NO is also known to quickly react with reactive oxygen species (ROS) in vitro. Stimulation of NO scavenging with antimycin and its inhibition by substrate depletion are consistent with NO interacting with ROS generated in Complex I or III under aerobic conditions. Extrapolating these in vitro data to the intact heart supports the hypothesis that mitochondria are a major site of cardiac NO scavenging. KEY POINTS: Cardiomyocyte scavenging of vascular nitric oxide (NO) is critical in maintaining normal cardiac function. Myoglobin redox cycling via myoglobin reductase has been proposed as a major NO scavenging site in the heart. Non-invasive optical spectroscopy was used to monitor the effect of NO on mitochondria and myoglobin redox state in intact beating heart and isolated mitochondria. These non-invasive studies reveal myoglobin/myoglobin reductase plays a minor role in cardiac NO scavenging. A high capacity for NO scavenging by heart mitochondria was demonstrated, independent of cytochrome oxidase binding but dependent on oxygen and high redox potentials consistent with generation of reactive oxygen species.

2-Nucleobase-substituted 4,6-Diaminotriazine Analogs: Synthesis and Anti-cancer Activity in 5-Fluorouracil-sensitive and Resistant Colorectal Cancer Cells.

Cancer continues to be the second leading cause of death worldwide, with colorectal cancer (CRC) being the third most common type. Despite significant advances in cancer therapies, the current treatment of CRC remains suboptimal. In addition, the effectiveness of available chemotherapeutic drugs such as 5-Fluorouracil (5-FU) is limited by CRC-acquired resistance. In this study, we provide innovative approaches employed in synthesizing four novel nucleobase analogs. Equally, we describe the effects of these compounds on proliferation, migration, aggregation, and adhesion of 5-FU-sensitive (HCT116) and -resistant (5-FU-R-HCT116) human CRC cells. In either cell type, our synthesized novel analogs significantly inhibited cell viability in a concentration- and time-dependent manner. This highlights the higher potency of these novel analogs. In addition, these compounds attenuated migration and adhesion of both cell types while they promoted homotypic cell-cell interaction. These changes were reflected by the downregulation of matrix metalloproteases (MMP-2 and MMP-9). Furthermore, our analogs exhibited potent anti-angiogenic activity in vivo. These novel nucleobase analogs reduced the level of secreted vascular endothelial growth factor (VEGF) and nitric oxide (NO) production in both 5-FU-sensitive and -resistant CRC cells. Taken together, our data highlight the potential chemotherapeutic properties of our novel analogs against CRC, including the 5-FU-resistant form.

Effects of physical exercise associated with a diet enriched with natural antioxidants on cerebral hypoperfusion and reperfusion injury in spontaneously hypertensive rats.

Oxidative stress is implicated in the pathogenesis of arterial hypertension. The reduction in the bioavailability of nitric oxide (NO) causes endothelial dysfunction, altering the functions of cerebral blood vessels. Physical exercise and intake of antioxidants improve the redox state, increasing the vascular NO production and/or the decrease in NO scavenging by reactive oxygen species (ROS). The present study was aimed at assessing the effects of physical exercise associated with a diet enriched with antioxidants from the Annurca apple in preventing the microvascular damage due to cerebral hypoperfusion and reperfusion injury in spontaneously hypertensive rats (SHRs). The rat pial microcirculation was investigated by intravital fluorescence microscopy through a parietal closed cranial window. As expected, SHRs subjected to physical exercise or an antioxidants-enriched diet showed a reduction of microvascular permeability, ROS formation, and leukocyte adhesion to venular walls, with a major effect of the antioxidants-enriched diet, when compared to untreated SHRs. Moreover, capillary perfusion was preserved by both treatments in comparison with untreated SHRs. Unexpectedly, the combined treatments did not induce higher effects than the single treatment. In conclusion, our results support the efficacy of physical activity or antioxidant supplement in reducing the microvascular alterations due to hypertension and ascribe to an antioxidants-enriched diet effective microvascular protection in SHRs.

The loading of C-type natriuretic peptides improved hemocompatibility and vascular regeneration of electrospun poly(ε-caprolactone) grafts

As a result of thrombosis or intimal hyperplasia, synthetic artificial vascular grafts had a low success rate when they were used to replace small-diameter arteries (inner diameter < 6 mm). C-type natriuretic peptides (CNP) have anti-thrombotic effects, and can promote endothelial cell (EC) proliferation and inhibit vascular smooth muscle cell (SMC) over-growth. In this study, poly(ε-caprolactone) (PCL) vascular grafts loaded with CNP (PCL-CNP) were constructed by electrospinning. The PCL-CNP grafts were able to continuously release CNP at least 25 days in vitro. The results of scanning electron microscopy (SEM) and mechanical testing showed that the loading of CNP did not change the microstructure and mechanical properties of the PCL grafts. In vitro blood compatibility analysis displayed that PCL-CNP grafts could inhibit thrombin activity and reduce platelet adhesion and activation. In vitro cell experiments demonstrated that PCL-CNP grafts activated ERK1/2 and Akt signaling in human umbilical vein endothelial cells (HUVECs), as well as increased cyclin D1 expression, enhanced proliferation and migration, and increased vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production. The rabbit arteriovenous (AV)-shunt ex vitro indicated that CNP loading significantly improved the antithrombogenicity of PCL grafts. The assessment of vascular grafts in rat abdominal aorta implantation model displayed that PCL-CNP grafts promoted the regeneration of ECs and contractile SMCs, modulated macrophage polarization toward M2 phenotype, and enhanced extracellular matrix remodeling. These findings confirmed for the first time that loading CNP is an effective approach to improve the hemocompatibility and vascular regeneration of synthetic vascular grafts. Statement of significanceSmall-diameter (< 6 mm) vascular grafts (SDVGs) have not been made clinically available due to their prevalence of thrombosis, limited endothelial regeneration and intimal hyperplasia. The incorporation of bioactive molecules into SDVGs serves as an effective solution to improve hemocompatibility and endothelialization. In this study, for the first time, we loaded C-type natriuretic peptides (CNP) into PCL grafts by electrospunning and confirmed the effectiveness of loading CNP on improving the hemocompatibility and vascular regeneration of artificial vascular grafts. Regenerative advantages included enhancement of endothelialization, modulation of macrophage polarization toward M2 phenotypes, and improved contractile smooth muscle cell regeneration. Our investigation brings attention to CNP as a valuable bioactive molecule for modifying cardiovascular biomaterial.

Biocompatible silane adhesion layer on titanium implants improves angiogenesis and osteogenesis.

Silane adhesion layer strategy has been widely used to covalently graft biomolecules to the titanium implant surface, thereby conferring the implant bioactivity to ameliorate osseointegration. However, few researchers pay attention to the effects of silanization parameters on biocompatibility and biofunctionality of the silane adhesion layers. Accordingly, the present study successfully fabricated the silane adhesion layers with different thickness, intactness, and surface morphologies by introducing 3-aminopropyltriethoxysilane on the alkali-treated titanium surface in time-varied processing of silanization. The regulatory effects of the silane adhesion layers on angiogenesis and osteogenesis were assessed in vitro. Results showed that the prolonged silanization processing time increased the thickness and intactness of the silane adhesion layer and significantly improved its biocompatibility. Notably, the silane adhesion layer prepared after 12h of silanization exhibited a brain-like surface morphology and benefited the adhesion and proliferation of endothelial cells (ECs) and osteoblasts (OBs). Moreover, the layer promoted angiogenesis via stimulating vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production of ECs. Simultaneously, it improved osteogenesis by enhancing alkaline phosphatase (ALP) activity, collagen secretion, and extracellular matrix mineralization of OBs. This work systematically investigated the biocompatibility and biofunctionality of the modified silane adhesion layers, thus providing valuable references for their application in covalently grafting biomolecules on the titanium implant surface.

The effects of bathing in neutral bicarbonate ion water

Percutaneously absorbed carbon dioxide enhances blood flow. The mechanism by which it does so is unclear, but we hypothesized that it involves bicarbonate ions. BALB/c mice were bathed in neutral bicarbonate ionized water (NBIW) and showed increased blood bicarbonate levels and blood flow via phosphorylation of peripheral vascular endothelial nitric oxide synthase (eNOS) and production of nitric oxide (NO). Phosphorylation of eNOS and NO production were also increased in human umbilical vein endothelial cells cultured in medium containing NBIW, and NBIW showed reactive oxygen species scavenging activity. In a double-blind, randomized study in men and women aged 30 to 59 years with subjective cold intolerance, bathing in NBIW elevated body temperature faster than bathing in a control solution and improved chills and sleep quality. Taken together, our results show that percutaneously absorbed carbon dioxide changes to bicarbonate ions, which act directly on endothelial cells to increase NO production by phosphorylation of eNOS and thus improve blood flow.

Perivascular adipose tissue and microvascular endothelial dysfunction in obese mice: Beneficial effects of aerobic exercise in adiponectin receptor (AdipoR1) and peNOSSer1177.

In the present study, we aim to investigate the effects of aerobic physical training on perivascular adipose tissue (PVAT)-induced microvascular dysfunction of the femoral artery in obese mice. Microvascular reactivity was evaluated in control sedentary (c-SD), obese sedentary (o-SD) and obese trained (o-TR) male mice (C57BL6/JUnib), in the absence (PVAT-) or the presence (PVAT+) of femoral artery PVAT. We also analyzed protein expression, vascular nitric oxide (NO) production and reactive oxygen species (ROS) generation in PVAT. The blood glucose, triglycerides and total cholesterol levels were increased in the o-SD group, when compared with the c-SD group. The maximal responses and the potency to acetylcholine (ACh) were decreased in PVAT+ compared with PVAT- rings in the o-SD group, accompanied by a decrease in vascular protein expression of peNOSSer1177 , Cu/Zn-SOD, leptin receptor (Ob-R) and adiponectin receptor (AdipoR1). The protein expression of leptin increased and that of adiponectin decreased in PVAT. Additionally, vascular NO production was reduced and ROS generation was enhanced in PVAT in the o-SD group. Aerobic exercise training was effective for normalizing ACh relaxation response, vascular NO production and ROS generation in the o-TR group. It partially re-established the vascular protein expression of peNOSSer1177 and the PVAT leptin; normalized the vascular Cu/Zn-SOD and AdipoR1 protein expressions. In obese sedentary mice, the presence of PVAT is involved in the process of microvascular dysfunction of the femoral artery in a pathway associated with increased inflammation and ROS generation. The aerobic exercise training normalized the vascular response, the NO production and/or bioavailability and oxidative stress, with improved vascular expressions of Cu/Zn-SOD, peNOSser1177 , and AdipoR1.

Deacetylation mimetic of mitochondrial cyclophilin D CypD‐K166R mutant mice are protected from inflammation, oxidative stress, endothelial dysfunction and hypertension

Despite treatment with multiple drugs, a third of hypertensive patients remain hypertensive, therefore, new treatments may improve treatment of hypertension. Hypertension is a multifactorial disorder associated with inflammation, mitochondrial oxidative stress and vascular dysfunction. We have previously reported that depletion or inhibition of Cyclophilin D (CypD), a regulatory subunit of mitochondrial permeability transition pore, improves vascular function and attenuates hypertension. Analysis of human arterioles showed 3-fold increase in CypD acetylation in hypertensive subjects. We hypothesized that hyperacetylation of CypD promotes vascular oxidative stress and hypertension, and deacetylation mimetic CypD-K166R mutation prevents vascular oxidative stress and attenuates hypertension. To test this hypothesis, we used CypD-K166R mutant mice developed in our lab, angiotensin II model of hypertension and ex vivo treatment of aortic tissue with inflammatory cytokines. It was found that angiotensin II-induced hypertension was substantially attenuated in CypD-K166R mice (144 mmHg) compared with wild-type C57B/6J mice (161 mmHg). Furthermore, MitoSOX/HPLC analysis of mitochondrial superoxide in aortas isolated from angiotensin II-infused mice showed 2-fold increase in wild-type mice which was abrogated in CypD-K166R mice. Angiotensin II infusion in wild-type mice significantly impaired endothelial dependent relaxation and reduced the level of endothelial nitric oxide measured by electron spin resonance and NO spin trap. Meanwhile, endothelial dependent relaxation and vascular nitric oxide production were preserved in angiotensin II-infused CypD-K166R mice. Hypertension is linked to inflammation, increased levels of TNFα and IL-17A which promote vascular oxidative stress and end-organ damage. We have tested if CypD-K166R mice are protected from cytokine-induced oxidative stress. Indeed, ex vivo incubation of aorta with the mixture of angiotensin II, TNFα and IL-17A (24 hours) increased mitochondrial superoxide by 2-fold in wild-type tissue which was abolished in CypD-K166R mice. To define molecular mechanisms of mitochondrial protection in CypD-K166R mice we have investigated respiration and calcium-induced swelling in isolated kidney mitochondria. It was found that mitochondria isolated from deacetylation mimetic CypD-K166R mice have improved respiration and diminished swelling with pyruvate and palmitoyl-carnitine as a substrates which promote CypD acetylation in wild-type animals. These data support the pathophysiological role of CypD acetylation in inflammation, oxidative stress and hypertensive end-organ damage. We conclude that targeting CypD acetylation may have therapeutic potential in treatment of vascular dysfunction and hypertension.

Effect of iron oxide nanoparticles on vascular function and nitric oxide production in acute stress-exposed rats.

We investigated whether polyethylene glycol-coated Fe3O4 nanoparticles (IONs), acute stress and their combination modifies vascular functions, nitric oxide synthase (NOS) activity, mean arterial pressure (MAP) as well as hepcidin and ferritin H gene expressions in Wistar-Kyoto rats. Rats were divided into control, ION-treated rats (1 mg Fe/kg i.v.), repeated acute air-jet stress-exposed rats and IONs-and-stress co-exposed rats. Maximal acetylcholine (ACh)-induced and sodium nitroprusside (SNP)-induced relaxations in the femoral arteries did not differ among the groups. IONs alone significantly elevated the N?-nitro-L-arginine methyl ester (L-NAME)-sensitive component of ACh-induced relaxation and reduced the sensitivity of vascular smooth muscle cells to SNP. IONs alone also elevated NOS activity in the brainstem and hypothalamus, reduced NOS activity in the kidneys and had no effect in the liver. Acute stress alone failed to affect vascular function and NOS activities in all the tissues investigated but it elevated ferritin H expression in the liver. In the ION-and-stress group, NOS activity was elevated in the kidneys and liver, but reduced in the brainstem and hypothalamus vs. IONs alone. IONs also accentuated air-jet stress-induced MAP responses vs. stress alone. Interestingly, stress reduced ION-originated iron content in blood and liver while it was elevated in the kidneys. In conclusion, the results showed that 1) acute administration of IONs altered vascular function, increased L-NAME-sensitive component of ACh-induced relaxation and had tissue-dependent effects on NOS activity, 2) ION effects were considerably reduced by co-exposure to repeated acute stress, likely related to decrease of ION-originated iron in blood due to elevated decomposition and/or excretion.

Effect of β3-adrenergic receptor modulation on endothelial function

Understanding endothelial dysfunction is at the heart of current concerns due to its involvement in many cardiovascular diseases such as heart failure (HF). The β3-adrenergic receptor (β3-AR) could be at the origin of this endothelial dysfunction. Indeed, it is expressed at the level of the endothelial cell and induces vasorelaxation by the release of nitric oxide (NO), a central actor in endothelial dysfunction. Our objective was therefore to study the overexpression of the receptor in endothelial cells to understand its involvement in endothelial dysfunction. We used the Tgβ3 rat at 45 weeks of age, which overexpresses the human β3-AR gene in the endothelium. Endothelium-dependent aortic relaxation versus isoproterenol was measured with or without L-VNIO an inhibitor of nNOS at 10 μM. The protein expression of NOS was evaluated by Western-Blot and the production of NO and O2- was evaluated by EPR on aorta. Vascular reactivity was significantly reduced in response to isoproterenol in Tgβ3 aorta (−10% P < 0.05 vs. WT) indicating an alteration of endothelial function without alteration in systemic arterial pressure. With L-VNIO vasorelaxation was significantly reduce in Tgβ3 rat indicating a major implication of nNOS in vascular reactivity. nNOS expression was increased in aorta (+ 56% P < 0.05 vs. WT). Vascular production of NO was increased in Tgβ3 rats (+ 53% P < 0.05 vs. WT), possibly link to nNOS increase. This production was associated with an elevation of O2- and ONOO- in Tgβ3 rats (+ 340%, respectively P < 0.05 vs. WT). The increase in β3-AR expression induces endothelial dysfunction with a key role of eNOS and nNOS. Further studies will be conducted to understand the causal links between endothelial dysfunction and the alteration of the cardiac function.

Elevated circulating amyloid concentrations in obesity and diabetes promote vascular dysfunction.

Diabetes, obesity, and Alzheimer’s disease (AD) are associated with vascular complications and impaired nitric oxide (NO) production. Furthermore, increased β-site amyloid precursor protein–cleaving (APP-cleaving) enzyme 1 (BACE1), APP, and β-amyloid (Aβ) are linked with vascular disease development and increased BACE1 and Aβ accompany hyperglycemia and hyperlipidemia. However, the causal relationship between obesity and diabetes, increased Aβ, and vascular dysfunction is unclear. We report that diet-induced obesity (DIO) in mice increased plasma and vascular Aβ42 that correlated with decreased NO bioavailability, endothelial dysfunction, and increased blood pressure. Genetic or pharmacological reduction of BACE1 activity and Aβ42 prevented and reversed, respectively, these outcomes. In contrast, expression of human mutant APP in mice or Aβ42 infusion into control diet–fed mice to mimic obese levels impaired NO production, vascular relaxation, and raised blood pressure. In humans, increased plasma Aβ42 correlated with diabetes and endothelial dysfunction. Mechanistically, higher Aβ42 reduced endothelial NO synthase (eNOS), cyclic GMP (cGMP), and protein kinase G (PKG) activity independently of diet, whereas endothelin-1 was increased by diet and Aβ42. Lowering Aβ42 reversed the DIO deficit in the eNOS/cGMP/PKG pathway and decreased endothelin-1. Our findings suggest that BACE1 inhibitors may have therapeutic value in the treatment of vascular disease associated with diabetes.

Effect of the double bond conjugation on the vascular physiology and nitric oxide production of isomers of eicosapentaenoic and docosahexaenoic acids prepared from shark oil.

A collection of evidence suggests that conjugation of double bonds of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, omega-3 polyunsaturated fatty acids (n-3 PUFAs), increases their anticarcinogenic activity; however, the effect of such conjugation on vascular tone activity remains unknown. We propose that the mixture of conjugated PUFAs exerts higher vasorelaxation activity than the corresponding mixture of nonconjugated PUFAs. The vascular response to different concentrations of conjugated and nonconjugated isomers of EPA and DHA, among other fatty acids (FAs) naturally present in shark oil, and the role of nitric oxide (NO) as a vasorelaxant agent were investigated. Both conjugated EPA (CEPA) and conjugated DHA (CDHA) were prepared by alkaline isomerization of all PUFAs contained in shark oil. Different concentrations of conjugated and nonconjugated PUFAs were placed in contact with precontracted aortic rings of Wistar rats to assess their effect on vascular tone. All tested samples exerted a vasorelaxant effect. Compared to nonconjugated PUFAs, conjugated isomers exhibited an increase in the dilatation of the aortic rings (P<0.001) in a dose-dependent manner (P<0.001). In addition, nonconjugated PUFAs produced nitric oxide (NO) in a dose-dependent manner, while conjugated PUFAs did not, suggesting that their dilatation mechanism is not totally dependent on NO.

Aerobic Exercise Training Prevents Perivascular Adipose Tissue-Induced Endothelial Dysfunction in Thoracic Aorta of Obese Mice.

Background: The mechanisms underlying the perivascular adipose tissue (PVAT) dysfunction in obesity are closely related to inflammation and oxidative stress. The present study aimed to investigate the effects of aerobic exercise training on PVAT-induced endothelial dysfunction of thoracic aorta of obese mice.Methods: Male mice C57BL6/JUnib (6–7 weeks) were divided into: sedentary (c-SD), trained (c-TR), obese sedentary (o-SD), and obese trained (o-TR). Obesity was induced by 16 weeks of high-fat diet and exercise training of moderate intensity started after 8 weeks of protocol and was performed on a treadmill, 5 days/week, for more 8 weeks, 60 min per session. The vascular responsiveness was performed in thoracic aorta in the absence (PVAT−) or in the presence (PVAT+) of PVAT. We analyzed circulatory parameters, protein expression, vascular nitric oxide (NO) production, and reactive oxygen species (ROS) in PVAT.Results: The maximal responses to acetylcholine (ACh) were reduced in PVAT+ compared with PVAT− rings in the o-SD group, accompanied by an increase in circulating glucose, insulin, resistin, leptin, and TNF-α. Additionally, the protein expression of iNOS and generation of ROS were increased in PVAT and production of vascular NO was reduced in the o-SD group compared with c-SD. In the o-TR group, the relaxation response to ACh was completely restored and the circulatory TNF-α, iNOS protein expression, and ROS were normalized with increased expression of Mn-SOD in PVAT, resulting in enhanced vascular NO production.Conclusion: The PVAT-induced endothelial dysfunction in thoracic aorta of obese mice, associated with circulatory inflammation and oxidative stress. Aerobic exercise training upregulated the anti-oxidant expression and decreased PVAT oxidative stress with beneficial impact on endothelium-dependent relaxation.

1933-P: Acute Hyperglycemia + Hyperinsulinemia Increases Carotid-Femoral Arterial Stiffness and Perfusion of Skeletal Muscle in Healthy Subjects

Introduction: Chronic hyperglycemia injures both micro-and microvasculature. Conversely, insulin stimulates vascular nitric oxide production and acts as a vasodilator. Whether acute hyperglycemia (AH) inhibits insulin’s vasodilator action in healthy vasculature is unknown. Here we tested whether AH interfered with insulin’s action to recruit microvasculature, enhance endothelial function, or diminish vascular stiffness. Methods: Nine healthy, fasting subjects (ages 18-35 years; BMI 18-25 kg/m2) twice received a 1 mU/kg/minute 2-hour insulin clamp. On one occasion, subjects were euglycemic (EH); and on the second, were hyperglycemic (∼200 mg/dL) (HH) for 2 hours before and throughout the clamp. Octreotide infusion blocked endogenous insulin in both studies. We assessed endothelial function by flow-mediated dilation (FMD) and arterial stiffness with pulse wave velocity (PWV) and augmentation index (AI). We used contrast-enhanced ultrasound to measure insulin-mediated capillary recruitment in skeletal and cardiac muscle. Linear mixed model was used for statistical analysis, with Bonferroni correction for comparison between studies. Results: Insulin increased carotid-femoral PWV (p=0.02 for Δ PWV) but decreased AI (p= 0.02) during HH, with AI significantly reduced in HH compared to EH (p=0.04). Insulin recruited microvasculature (p&amp;lt;0.05) with either EH or HH, and microvascular blood volume (p=0.03) and blood flow (p=0.04) significantly increased in skeletal muscle after HH. No changes were observed in FMD or cardiac microvascular perfusion with either condition. Discussion: This study provides evidence that 4 hours of AH evokes insulin-induced increases of carotid-femoral arterial stiffness in healthy subjects. Insulin’s ability to recruit microvasculature is preserved during AH. Disclosure W.B. Horton: None. L. Jahn: None. L. Hartline: None. J.T. Patrie: None. E. Barrett: Research Support; Self; AstraZeneca. Funding National Institutes of Health (F32HL142304-01)

L-arginine alleviates doxorubicin-induced endothelium-dependent dysfunction by promoting nitric oxide generation and inhibiting apoptosis

Background/aimsPatients with doxorubicin (Dox) treatment have a high risk of developing vascular toxicity with an unknown mechanism. l-arginine is a substrate for nitric oxide (NO). The decreased level of arginine-NO metabolite in Dox-treated cancer patients was associated with increased level of vascular damage, which promoted us to investigate the mechanism of Dox-induced vascular dysfunction and verify whether l-arginine supplement could alleviate this vasculotoxic effect. MethodWithin a mouse model of Dox injection (5 mg/kg i.p., 2 or 4 weeks), we measured vascular relaxation, blood pressure, vascular NO generation, apoptosis, and oxidative stress. We tested the efficacy of l-arginine (1.5 mg/g/day, 4 weeks) on Dox-induced vascular relaxation, blood pressure, vascular NO generation, apoptosis, as well as oxidative stress. ResultsDox induced endothelium-dependent vascular dysfunction, which was associated with increased reactive oxidative stress (ROS) production and reduced NO generation in the vessel. ROS was required for Dox-induced apoptosis of both smooth muscle cells and endothelial cells. Dox treatment in mice increased blood pressure, but had no effect on vascular inflammation and fibrosis. L-aringine restored Dox-induced vascular dysfunction via enhancing vascular NO production and alleviating ROS-mediated apoptosis. ConclusionWe for the first time demonstrated l-arginine was effectively in suppressing Dox-induced vascular dysfunction, by attenuating vascular NO release and apoptosis. Our results provide a therapeutic target or a circulating marker for assessing vascular dysfunction which response to Dox treatment, and advance our understanding of the mechanisms of Dox-induced vascular dysfunction.

A Molecular Model of the Alpha Globin/eNOS Complex

Nitric oxide (NO) signaling is a primary mechanism of vasodilation that has therapeutic potential for hypertensive pathologies. A key regulator of vascular wall nitric oxide production is the expression of alpha globin in the endothelium. We have previously shown that a small peptide mimicking alpha globin binds directly to the oxygenase domain of endothelial NO synthase (eNOS), competes with the full‐length protein, and thereby decreases NO scavenging by alpha globin. A molecular model of this interaction informs the mechanism of NO signaling inhibition by alpha globin and provides a framework for continued development of anti‐hypertensive therapies.The residues on alpha globin that determine its interaction with eNOS are known, but the binding site on eNOS is yet undescribed. To determine the motif on eNOS that interacts with alpha globin, a map of the interface is described via crosslinking mass spectrometry with proteolytic cleavage. Differential cleavage patterns after orthogonal protease treatments show eNOS peptides that are modified by alpha globin crosslinking. The sequence of proteolysis products modified by crosslinking are identified by high‐resolution LC‐MS, and the interaction model is reconstructed in silico. Using disulfide trapping, we can validate the orientation of the molecular model with full‐length proteins in an overexpression culture system using mammalian and primary cell lines. Overall, the molecular understanding of this complex informs the mechanism of alpha globin inhibition of NO signaling in the endothelium.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Magnesium lithospermate B ameliorates microcirculation perfusion in rats by promoting vascular NO production via activating the PI3K/AKT pathway.

Microcirculation morphologically refers to the blood flow in vessels of less than 150 μm in diameter, including arterioles, capillaries and venules, which provides nutrients and removes metabolic byproducts within tissues. Microcirculation dysfunction is involved in the pathological progress of many diseases, such as obesity, hypertension, and insulin resistance. In this study we investigated the effects of magnesium lithospermate B (MLB), an active compound of the traditional Chinese medicine Slavia miltiorrhiza, on the microcirculation dysfunction in rats and the underlying molecular mechanisms. The effects of MLB on microcirculation were assessed in vivo by measuring the hindlimb blood perfusion in dextran-induced microcirculation dysfunction rats and mesentery blood flow in anesthetized rats. We demonstrated that administration of MLB restored the impaired rat hindlimb blood flow and promoted the mesenteric micoperfusion in vivo. We further revealed in these two animal models that MLB treatment significantly increased the production of total nitrite in vascular tissues (mesentery, aorta, and heart), which was confirmed in human microvascular endothelial cells (HMEC-1) treated with MLB in vitro. Moreover, we showed that MLB treatment significantly increased the phosphorylation of endothelium nitric oxide synthase (eNOS) via inducing AKT phosphorylation in vivo and in vitro. Co-administration of the eNOS inhibitor L-NAME (20 mg/kg) abolished the protective effects of MLB against dextran-induced microcirculation dysfunction in rats, whereas pretreatment with PI3K inhibitor LY294002 (10 μM) prevented eNOS activation in MLB-treated HMEC-1 cells. Our results suggest that MLB can restore the microcirculation dysfunction via activating eNOS, and in turn enhancing the vascular nitric oxide production, which is medicated by MLB-caused activation of the PI3K/AKT pathway.

Streptococcal M1 protein induces hyporesponsiveness and cytokine release from human arteries in a fibrinogen-dependent manner: a translational study

BackgroundStreptococcus pyogenes is a Gram positive bacterial species commonly involved in sepsis. Invasive strains express virulence factors such as the M1 protein. M1 protein forms complexes with fibrinogen leading to a cytokine storm in plasma contributing to the development of septic shock and organ failure. In experimental animals M1 protein causes vascular nitric oxide production and hyporesponsiveness to pressors, but it is not known whether it affects the human vascular wall.MethodsHuman omental arteries obtained during surgery were incubated in vitro with M1 protein or lipopolysaccharide (LPS) as positive control, with or without plasma. After 48 h, contractile response to noradrenaline was measured, and levels of nitrite/nitrate and the cytokines interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α in the incubation medium were measured. A second set of arteries were incubated with or without main components of plasma (immunoglobulin G, albumin or fibrinogen), in the presence of M1 protein followed by cytokine measurement.ResultsArtery segments incubated with M1 protein and plasma contracted weaker in response to noradrenaline, and levels of IL-6 and IL-8 were significantly higher compared to after incubation with M1 protein alone. Incubation with M1 protein and fibrinogen resulted in elevated levels of IL-6 and IL-8, while incubation with M1 protein and albumin or immunoglobulin G did not affect the levels. Neither any of the other cytokines nor nitrite/nitrate was detected in the medium in any of the incubation conditions.ConclusionsThe study shows that M1 protein of Streptococcus pyogenes has a direct effect on the human vascular wall in the presence of plasma, demonstrated both as a diminished contractile response to noradrenaline and increased cytokine production. The effect of plasma was attributed to fibrinogen. The findings suggest that M1 protein contributes to the development of septic shock through impairment of the contractility of the vascular wall.

HDLs and the pathogenesis of atherosclerosis.

Plasma levels of HDL cholesterol are a biomarker of cardiovascular health but not a therapeutic target, as demonstrated by the failure of pharmacological modulation of HDL cholesterol to prevent or treat atherosclerotic cardiovascular disease. In health, HDL particles exert pleiotropic effects against atherosclerosis, including cholesterol removal from foam cells, vasodilatory effects through vascular endothelial cell nitric oxide production, decreased vascular inflammation and oxidative damage, endothelial cell proliferation and antiapoptotic effects. These functional effects of HDL are independent of the cholesterol mass and are related to the proteome and lipidome. In disease states and with the ageing process, HDL components are extensively modified and may no longer play a beneficial role but are retained in the atheroma and contribute to atherosclerosis. We have recently shown that desmocollin 1 (DSC1) acts as an apolipoprotein (apo) A-I binding protein that is highly expressed in atherosclerotic plaques and inhibits atheroprotective HDL functions by retaining apoA-I. The apoA-I retention hypothesis proposes that macrophages express DSC1 in a maladaptive process that renders apoA-I inactive and contributes to atherosclerosis. HDL loses their beneficial properties in ageing and disease states. Novel pathways may present new therapeutic avenues to restore their biological functions.