Decreased production of neuronal NOS-derived hydrogen peroxide contributes to endothelial dysfunction in atherosclerosis

Sympathetic and angiotensinergic activity in spontaneously hypertensive rats treated with 3-amino-1,2,4-triazole

Previous studies from our laboratory have shown that the pressor response to intracerebroventricular (icv) administered ANG II in normotensive rats or spontaneously hypertensive rats (SHRs) is attenuated by increased central H2O2 concentration, produced either by direct H2O2 icv injection or by increased endogenous H2O2 centrally in response to local catalase inhibition with 3-amino-1,2,4-triazole (ATZ). In the present study, we evaluated the effects of ATZ administered peripherally on arterial pressure and sympathetic and angiotensinergic activity in SHRs. Male SHRs weighing 280-330 g were used. Mean arterial pressure (MAP) and heart rate (HR) were recorded in conscious freely moving SHRs. Acute intravenous injection of ATZ (300 mg/kg of body weight) did not modify MAP and HR during the next 4 h, however, the treatment with ATZ (300 mg/kg of body weight twice per day) for 3 days reduced MAP (144 ± 6, vs. saline, 183 ± 13 mmHg), without changing HR. Intravenous hexamethonium (ganglionic blocker) produced a smaller decrease in MAP 4 h after ATZ (-25 ± 3, vs saline -38 ± 4 mmHg). Losartan (angiotensinergic AT1 receptor blocker) produced a significant depressor response 4 h after ATZ (-22 ± 4, vs. saline: -2 ± 4 mmHg) and in 3-day ATZ treated SHRs (-25 ± 5, vs. saline: -9 ± 4 mmHg). The results suggest that the treatment with ATZ reduces sympathetic activity in SHRs and simultaneously increases angiotensinergic activity.

Butyrate inhibits LPC-induced endothelial dysfunction by regulating nNOS-produced NO and ROS production

Lipids oxidation is a key risk factor for cardiovascular diseases. Lysophosphatidylcholine (LPC), the major component of oxidized LDL, is an important triggering agent for endothelial dysfunction and atherogenesis. Sodium butyrate, a short-chain fatty acid, has demonstrated atheroprotective properties. So, we evaluate the role of butyrate in LPC-induced endothelial dysfunction. Vascular response to phenylephrine (Phe) and acetylcholine (Ach) was performed in aortic rings from male mice (C57BL/6J). The aortic rings were incubated with LPC (10 μM) and butyrate (0.01 or 0.1 Mm), with or without TRIM (an nNOS inhibitor). Endothelial cells (EA.hy296) were incubated with LPC and butyrate to evaluate nitric oxide (NO) and reactive oxygen species (ROS) production, calcium influx, and the expression of total and phosphorylated nNOS and ERK½. We found that butyrate inhibited LPC-induced endothelial dysfunction by improving nNOS activity in aortic rings. In endothelial cells, butyrate reduced ROS production and increased nNOS-related NO release, by improving nNOS activation (phosphorylation at Ser1412). Additionally, butyrate prevented the increase in cytosolic calcium and inhibited ERk½ activation by LPC. In conclusion, butyrate inhibited LPC-induced vascular dysfunction by increasing nNOS-derived NO and reducing ROS production. Butyrate restored nNOS activation, which was associated with calcium handling normalization and reduction of ERK½ activation.

Gluten worsens non-alcoholic fatty liver disease by affecting lipogenesis and fatty acid oxidation in diet-induced obese apolipoprotein E-deficient mice

Obesity is closely associated with non-alcoholic fatty liver disease (NAFLD), characterized by hepatic fat accumulation and hepatocyte injury. Preclinical studies have shown exacerbated weight gain associated with an obesogenic gluten-containing diet. However, whether gluten affects obesity-induced hepatic lipid accumulation still remains unclear. We hypothesized that gluten intake could affect fatty liver development in high-fat diet (HFD)-induced obese mice. Thus, we aimed to investigate the impact of gluten intake on NAFLD in HFD-induced obese mice. Male apolipoprotein E-deficient (Apoe-/-) mice were fed with a HFD containing (GD) or not (GFD) vital wheat gluten (4.5%) for 10 weeks. Blood and liver were collected for further analysis. We found that gluten exacerbated weight gain, hepatic fat deposition, and hyperglycemia without affecting the serum lipid profile. Livers of the GD group showed a larger area of fibrosis, associated with the expression of collagen and MMP9, and higher expression of apoptosis-related factors, p53, p21, and caspase-3. The expression of lipogenic factors, such as PPARγ and Acc1, was more elevated and factors related to beta-oxidation, such as PPARα and Cpt1, were lower in the GD group compared to the GFD. Further, gluten intake induced a more significant expression of Cd36, suggesting higher uptake of free fatty acids. Finally, we found lower protein expression of PGC1α followed by lower activation of AMPK. Our data show that gluten-containing high-fat diet exacerbated NAFLD by affecting lipogenesis and fatty acid oxidation in obese Apoe-/- mice through a mechanism involving lower activation of AMPK.

Chronic administration of catalase inhibitor attenuates hypertension in renovascular hypertensive rats

AIMS

Reactive oxygen species like hydrogen peroxide (H₂O₂) are produced endogenously and may participate in intra- and extracellular signaling, including modulation of angiotensin II responses. In the present study, we investigated the effects of chronic subcutaneous (sc) administration of the catalase inhibitor 3-amino-1,2,4-triazole (ATZ) on arterial pressure, autonomic modulation of arterial pressure, hypothalamic expression of AT1 receptors and neuroinflammatory markers and fluid balance in 2-kidney, 1clip (2K1C) renovascular hypertensive rats.

MATERIALS AND METHODS

Male Holtzman rats with a clip occluding partially the left renal artery and chronic sc injections of ATZ were used.

KEY FINDINGS

Subcutaneous injections of ATZ (600 mg/kg of body weight/day) for 9 days in 2K1C rats reduced arterial pressure (137 ± 8, vs. saline: 182 ± 8 mmHg). ATZ also reduced the sympathetic modulation and enhanced the parasympathetic modulation of pulse interval, reducing the sympatho-vagal balance. Additionally, ATZ reduced mRNA expression for interleukins 6 and IL-1β, tumor necrosis factor-α, AT1 receptor (0.77 ± 0.06, vs. saline: 1.47 ± 0.26 fold change), NOX 2 (0.85 ± 0.13, vs. saline: 1.75 ± 0.15 fold change) and the marker of microglial activation, CD 11 (0.47 ± 0.07, vs. saline, 1.34 ± 0.15 fold change) in the hypothalamus of 2K1C rats. Daily water and food intake and renal excretion were only slightly modified by ATZ.

SIGNIFICANCE

The results suggest that the increase of endogenous H₂O₂ availability with chronic treatment with ATZ had an anti-hypertensive effect in 2K1C hypertensive rats. This effect depends on decreased activity of sympathetic pressor mechanisms and mRNA expression of AT1 receptors and neuroinflammatory markers possibly due to reduced angiotensin II action.

Dietary gluten worsens hepatic steatosis by increasing inflammation and oxidative stress in ApoE-/- mice fed a high-fat diet

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disorder in the world. We have seen that gluten intake exacerbated obesity and atherosclerosis in apolipoprotein E knockout (ApoE-/-) mice. In this study, we investigated the effect of gluten consumption on inflammation and oxidative stress in the liver of mice with NAFLD. Male ApoE-/- mice were fed a gluten-free (GF-HFD) or gluten-containing (G-HFD) high-fat diet for 10 weeks. Blood, liver, and spleen were collected to perform the analyses. The animals of the gluten group had increased hepatic steatosis, followed by increased serum AST and ALT. Gluten intake increased hepatic infiltration of neutrophils, macrophages, and eosinophils, as well as the levels of chemotaxis-related factors CCL2, Cxcl2, and Cxcr3. The production of the TNF, IL-1β, IFNγ, and IL-4 cytokines in the liver was also increased by gluten intake. Furthermore, gluten exacerbated the hepatic lipid peroxidation and nitrotyrosine deposition, which were associated with increased production of ROS and nitric oxide. These effects were related to increased expression of NADPH oxidase and iNOS, as well as decreased activity of superoxide dismutase and catalase enzymes. There was an increased hepatic expression of the NF-κB and AP1 transcription factors, corroborating the worsening effect of gluten on inflammation and oxidative stress. Finally, we found an increased frequency of CD4+FOXP3+ lymphocytes in the spleen and increased gene expression of Foxp3 in the livers of the G-HFD group. In conclusion, dietary gluten aggravates NAFLD, exacerbating hepatic inflammation and oxidative stress in obese ApoE-deficient mice.

Natural flavonoids derived from herbal medicines are potential anti-atherogenic agents by inhibiting oxidative stress in endothelial cells

As the common pathological basis of various cardiovascular diseases, the morbidity and mortality of atherosclerosis (AS) have increased in recent years. Unfortunately, there are still many problems in the treatment of AS, and the prevention and treatment of the disease is not ideal. Up to now, the occurrence and development of AS can roughly include endothelial cell dysfunction, vascular smooth muscle cell proliferation, inflammation, foam cell production, and neoangiogenesis. Among them, endothelial dysfunction, as an early event of AS, plays a particularly important role in promoting the development of AS. In addition, oxidative stress occurs throughout the causes of endothelial dysfunction. Some previous studies have shown that flavonoids derived from herbal medicines are typical secondary metabolites. Due to its structural presence of multiple active hydroxyl groups, it is able to exert antioxidant activity in diseases. Therefore, in this review, we will search PubMed, Web of Science, Elesvier, Wliey, Springer for relevant literature, focusing on flavonoids extracted from herbal medicines, and summarizing how they can prevent endothelial dysfunction by inhibiting oxidative stress. Meanwhile, in our study, we found that flavonoid represented by quercetin and naringenin showed superior protective effects both in vivo and in vitro, suggesting the potential of flavonoid compounds in the treatment of AS.

Dual effect of amitriptyline in the control of vascular tone: Direct blockade of calcium channel in smooth muscle cells and reduction of TLR4-dependent NO production in endothelial cells

BACKGROUND AND PURPOSE

Amitriptyline (AM) is a classical and typical tricyclic antidepressant drug. Despite its well-known effects on the nervous system, it has been described to work as a TLR4 antagonist and several clinical works suggested some unexpected cardiovascular effects. The role of amitriptyline on vascular tone is not clear, thus we hypothesized that amitriptyline has a double effect on vascular tone by both endothelial TLR4-dependent nitric oxide down-regulation and calcium channel blockade in smooth muscle cells.

EXPERIMENTAL APPROACH

Changes in isometric tension were recorded on a wire myograph. NO production was evaluated by fluorescence microscopy and flow cytometry in the mouse aorta and EAhy926 cells using DAF fluorescence intensity. Calcium influx was evaluated in A7r5 cells by flow cytometry. Western blot was used to analyze eNOS and nNOS phosphorylation.

KEY RESULTS

AM reduced PE-induced contraction by calcium influx diminution in smooth muscle cells (F/F₀ = 225.6 ± 15.9 and 118.6 ± 17.6 to CT and AM, respectively). AM impaired Ach-dependent vasodilation (Emax = 95.8 ± 1.4; 78.1 ± 1.8; 60.4 ± 2.9 and -7.4 ± 1.0 for CT, 0.01, 0,1 and 1 μmol/L AM, respectively) through reduction of calcium influx and NO availability and TLR4 antagonism in a concentration-dependent manner. AM or TLR4 gene deletion significantly reduced NO production (Fluorescence = 9503 ± 871.7, 2561 ± 282, 4771 ± 728 and 1029 ± 103 to CT, AM, TLR4^-/- and AM + TLR4^-/-, respectively) by an increase in nNOS^ser852 and reduction in eNOS^ser1177 phosphorylation in endothelial cells.

CONCLUSIONS AND IMPLICATIONS

Our data show that amitriptyline impaired vascular function through two different mechanisms: blockade of TLR4 in endothelial cells and consequent decrease in NO production and calcium influx reduction in smooth muscle and endothelial cells. We also suggest, for the first time, nNOS activity reduction by AM in non-neuronal cells.

Targeting Reactive Oxygen Species in Atherosclerosis via Chinese Herbal Medicines

Cardio-cerebrovascular disease (CCVD) has become the leading cause of human mortality with the coming acceleration of global population aging. Atherosclerosis is among the most common pathological changes in CCVDs. It is also a multifactorial disorder; oxidative stress caused by excessive production of reactive oxygen species (ROS) has become an important mechanism of atherosclerosis. Chinese herbal medicine (CHM) is a major type of natural medicine that has made great contributions to human health. CHMs are increasingly used in the auxiliary clinical treatment of atherosclerosis. Although their mechanism of action is unclear, CHMs can exert a variety of antiatherosclerosis effects by regulating intracellular ROS. In this review, we discussed the mechanism of ROS regulation in atherosclerosis and analyzed the role of CHMs in the treatment of atherosclerosis via ROS.

The expanding roles of neuronal nitric oxide synthase (NOS1)

The nitric oxide synthases (NOS; EC 1.14.13.39) use L-arginine as a substrate to produce nitric oxide (NO) as a by-product in the tissue microenvironment. NOS1 represents the predominant NO-producing enzyme highly enriched in the brain and known to mediate multiple functions, ranging from learning and memory development to maintaining synaptic plasticity and neuronal development, Alzheimer's disease (AD), psychiatric disorders and behavioral deficits. However, accumulating evidence indicate both canonical and non-canonical roles of NOS1-derived NO in several other tissues and chronic diseases. A better understanding of NOS1-derived NO signaling, and identification and characterization of NO-metabolites in non-neuronal tissues could become useful in diagnosis and prognosis of diseases associated with NOS1 expression. Continued investigation on the roles of NOS1, therefore, will synthesize new knowledge and aid in the discovery of small molecules which could be used to titrate the activities of NOS1-derived NO signaling and NO-metabolites. Here, we address the significance of NOS1 and its byproduct NO in modifying pathophysiological events, which could be beneficial in understanding both the disease mechanisms and therapeutics.

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.

The protective role of neuronal nitric oxide synthase in endothelial vasodilation in chronic β-adrenoceptor overstimulation

AIMS

Nitric oxide synthases (NOSs) are key enzymes regulating vascular function. Previously, we reported that β-adrenergic (β-AR) overstimulation, a common feature of cardiovascular diseases, did not impair endothelium-dependent vasodilation, although it resulted in endothelial NOS (eNOS) uncoupling and reduced NO bioavailability. In addition to NO, neuronal NOS (nNOS) produces H₂O₂, which contributes to vasodilation. However, there is limited information regarding vascular β-AR signaling and nNOS. In the present study, we assessed the possible role of nNOS-derived H₂O₂ and caveolins on endothelial vasodilation function following β-AR overstimulation.

MAIN METHODS

Male C57BL/6 wild-type and nNOS knockout mice (nNOS^-/-) were treated with the β-AR agonist isoproterenol (ISO, 15 mg·kg^-1·day^-1, s.c.) or vehicle (VHE) for seven days. Relaxation responses of aortic rings were evaluated using wire myograph and H₂O₂ by Amplex Red.

KEY FINDINGS

Acetylcholine- or calcium ionophore A23187-induced endothelium-dependent relaxation was similar in aortic rings from VHE and ISO. However, this relaxation was significantly reduced in aortas from ISO compared to VHE when (1) caveolae were disrupted, (2) nNOS was pharmacologically inhibited or genetically suppressed and (3) H₂O₂ was scavenged. NOS-derived H₂O₂ production was higher in the aortas of ISO mice than in those of VHE mice. Aortas from ISO-treated mice showed increased expression of caveolin-1, nNOS and catalase, while caveolin-3 expression did not change.

SIGNIFICANCE

The results suggest a role of caveolin-1 and the nNOS/H₂O₂ vasodilatory pathway in endothelium-dependent relaxation following β-AR overstimulation and reinforce the protective role of nNOS in cardiovascular diseases associated with high adrenergic tone.

SIRT1-induced deacetylation of Akt expedites platelet phagocytosis and delays HEMEC aging

Maintaining the health of the endothelium is of critical importance to prevention against cell aging. The current study was performed to clarify the role of sirtuin1 (SIRT1) in platelet phagocytosis in cell aging and identified its downstream molecular mechanism. Platelet phagocytosis by human endometrial microvascular endothelial cells (HEMECs) was characterized by transmission electron and fluorescence microscopy. Functional experiments were conducted to examine platelet phagocytosis and cell aging using the overexpression or knockdown plasmids of SIRT1 and G alpha-interacting, vesicle-associated protein (GIRDIN) as well as Akt inhibitor and activator. It was found that SIRT1 facilitated platelet phagocytosis by HEMECs, contributing to inhibition of cell aging. Akt activation facilitated platelet phagocytosis and repressed cell aging. GIRDIN overexpression accelerated platelet phagocytosis by HEMECs, leading to a delay in cell aging. GIRDIN phosphorylation at Ser1417 was induced by Akt activation, while activation of Akt was induced by SIRT1-mediated deacetylation, consequently augmenting platelet phagocytosis and delaying cell aging. Taken together, SIRT1 delayed aging of HEMECs by deacetylating Akt, phosphorylating GIRDIN, and inducing platelet phagocytosis. The study highlights a possible target for the prevention of HEMEC aging.

Amitriptyline Downregulates Chronic Inflammatory Response to Biomaterial in Mice

Recent data has signaled that in addition to its therapeutic indications as antidepressant and analgesic, amitriptyline (AM) exerts anti-inflammatory effects in humans and experimental animal models of acute inflammation. We tested the hypothesis that this compound could also modulate the chronic inflammatory process induced by synthetic matrix in mice. Polyether-polyurethane sponge disks were implanted subcutaneously in 9-week-old male C57BL/6 mice. The animals received by oral gavage 5.0 mg/kg of amitriptyline for seven consecutive days in two treatment regimens. In the first series, the treatment was initiated on the day of surgery and the implants removed at day 7 post-implantation. For the assessment of the effect of amitriptyline on chronic inflammation, the treatment was initiated 7 days post-implantation and the sponge discs removed 14 after implantation. The inflammatory markers evaluated, myeloperoxidase - MPO, nitrite content, IL-6, IFN-γ, TNF-α, CXCL1 and CCL2 levels, and NF-κB transcription factor activation were reduced in implants when the treatment began 7 days post-implantation (chronic inflammation). In contrast, only mast cell number, MPO activity and activation of NF-κB pathway decreased when the treatment began soon after implantation (sub-acute inflammation) in 7-day old implants. The anti-inflammatory effects of amitriptyline described here, extend its range of actions as a potential agent able to attenuate long-term inflammatory processes.

Role of neuronal nitric oxide synthase on cardiovascular functions in physiological and pathophysiological states

This review describes and summarizes the role of neuronal nitric oxide synthase (nNOS) on the central nervous system, particularly on brain regions such as the ventrolateral medulla (VLM) and the periaqueductal gray matter (PAG), and on blood vessels and the heart that are involved in the regulation and control of the cardiovascular system (CVS). Furthermore, we shall also review the functional aspects of nNOS during several physiological, pathophysiological, and clinical conditions such as exercise, pain, cerebral vascular accidents or stroke and hypertension. For example, during stroke, a cascade of molecular, neurochemical, and cellular changes occur that affect the nervous system as elicited by generation of free radicals and nitric oxide (NO) from vulnerable neurons, peroxide formation, superoxides, apoptosis, and the differential activation of three isoforms of nitric oxide synthases (NOSs), and can exert profound effects on the CVS. Neuronal NOS is one of the three isoforms of NOSs, the others being endothelial (eNOS) and inducible (iNOS) enzymes. Neuronal NOS is a critical homeostatic component of the CVS and plays an important role in regulation of different systems and disease process including nociception. The functional and physiological roles of NO and nNOS are described at the beginning of this review. We also elaborate the structure, gene, domain, and regulation of the nNOS protein. Both inhibitory and excitatory role of nNOS on the sympathetic autonomic nervous system (SANS) and parasympathetic autonomic nervous system (PANS) as mediated via different neurotransmitters/signal transduction processes will be explored, particularly its effects on the CVS. Because the VLM plays a crucial function in cardiovascular homeostatic mechanisms, the neuroanatomy and cardiovascular regulation of the VLM will be discussed in conjunction with the actions of nNOS. Thereafter, we shall discuss the up-to-date developments that are related to the interaction between nNOS and cardiovascular diseases such as hypertension and stroke. Finally, we shall focus on the role of nNOS, particularly within the PAG in cardiovascular regulation and neurotransmission during different types of pain stimulus. Overall, this review focuses on our current understanding of the nNOS protein, and provides further insights on how nNOS modulates, regulates, and controls cardiovascular function during both physiological activity such as exercise, and pathophysiological conditions such as stroke and hypertension.

Gluten exacerbates atherosclerotic plaque formation in ApoE-/- mice with diet-induced obesity

OBJECTIVES

Atherosclerosis is an underlying cause of cardiovascular disease, and obesity is one of the risk factors for atherogenesis. Although a gluten-free diet (GFD) has gained popularity as a strategy for weight loss, little is known about the effects of gluten on obesity. We have previously shown a negative effect of gluten on obesity in mice. However, its effects on atherogenesis are still unknown. Therefore, the aim of this study was to determine the effects of gluten on atherosclerosis progression during obesity.

METHODS

Atherosclerosis-susceptible ApoE knockout mice were subjected to an obesogenic GFD or a diet with 4.5% gluten (GD) for 10 wk.

RESULTS

Results from the study found that food intake and lipid profile were similar between the groups. However, GD promoted an increase in weight gain, adiposity, and plasma glucose. Pro-inflammatory factors such as tumor necrosis factor, interleukin-6, chemokine ligand-2, and matrix metalloproteinase-2 and -9 also were increased in the adipose tissue of gluten-fed mice. This inflammatory profile was associated with reduced phosphorylation of Akt, and consequently with the intensification of insulin resistance. The GD-enhanced vascular inflammation contributed to the worsening of atherosclerosis in the aorta and aortic root. Inflammatory cells, such as monocyte/macrophage and natural killer cells, and oxidative stress markers, such as superoxide and nitrotyrosine, were increased in atherosclerotic lesions of the GD group. Furthermore, the lesions presented higher necrotic core and lower collagen content, characterizing the less stable plaques.

CONCLUSION

The gluten-containing high-fat diet was associated with a more severe proatherogenic profile than the gluten-free high-fat diet owing to increased inflammatory and oxidative status at atherosclerotic lesions in obese mice.

Catalase blockade reduces the pressor response to central cholinergic activation

Intracerebroventricular (icv) injection of hydrogen peroxide (H₂O₂), a reactive oxygen species, or the blockade of catalase (enzyme that degrades H₂O₂ into H₂O and O₂) with icv injection of 3-amino-1,2,4-triazole (ATZ) reduces the pressor effects of angiotensin II also injected icv. In the present study, we investigated the effects of ATZ injected icv or intravenously (iv) on the pressor responses induced by icv injections of the cholinergic agonist carbachol, which similar to angiotensin II induces pressor responses that depend on sympathoexcitation and vasopressin release. In addition, the effects of H₂O₂ icv on the pressor responses to icv carbachol were also tested to compare with the effects of ATZ. Normotensive non-anesthetized male Holtzman rats (280-300 g, n = 8-9/group) with stainless steel cannulas implanted in the lateral ventricle were used. Previous injection of ATZ (5 nmol/1 μl) or H₂O₂ (5 μmol/1 μl) icv similarly reduced the pressor responses induced by carbachol (4 nmol/1 μl) injected icv (13 ± 4 and 12 ± 4 mmHg, respectively, vs. vehicle + carbachol: 30 ± 5 mmHg). ATZ (3.6 mmol/kg of body weight) injected iv also reduced icv carbachol-induced pressor responses (21 ± 2 mmHg). ATZ icv or iv and H₂O₂ icv injected alone produced no effect on baseline arterial pressure. The treatments also produced no significant change of heart rate. The results show that ATZ icv or iv reduced the pressor responses to icv carbachol, suggesting that endogenous H₂O₂ acting centrally inhibits the pressor mechanisms (sympathoactivation and/or vasopressin release) activated by central cholinergic stimulation.

Endothelial Dysfunction: Is There a Hyperglycemia-Induced Imbalance of NOX and NOS?

NADPH oxidases (NOX) are enzyme complexes that have received much attention as key molecules in the development of vascular dysfunction. NOX have the primary function of generating reactive oxygen species (ROS), and are considered the main source of ROS production in endothelial cells. The endothelium is a thin monolayer that lines the inner surface of blood vessels, acting as a secretory organ to maintain homeostasis of blood flow. The enzymatic production of nitric oxide (NO) by endothelial NO synthase (eNOS) is critical in mediating endothelial function, and oxidative stress can cause dysregulation of eNOS and endothelial dysfunction. Insulin is a stimulus for increases in blood flow and endothelium-dependent vasodilation. However, cardiovascular disease and type 2 diabetes are characterized by poor control of the endothelial cell redox environment, with a shift toward overproduction of ROS by NOX. Studies in models of type 2 diabetes demonstrate that aberrant NOX activation contributes to uncoupling of eNOS and endothelial dysfunction. It is well-established that endothelial dysfunction precedes the onset of cardiovascular disease, therefore NOX are important molecular links between type 2 diabetes and vascular complications. The aim of the current review is to describe the normal, healthy physiological mechanisms involved in endothelial function, and highlight the central role of NOX in mediating endothelial dysfunction when glucose homeostasis is impaired.

Dysregulation of stress systems and nitric oxide signaling underlies neuronal dysfunction in Alzheimer's disease

Stress is a multimodal response involving the coordination of numerous body systems in order to maximize the chance of survival. However, long term activation of the stress response results in neuronal oxidative stress via reactive oxygen and nitrogen species generation, contributing to the development of depression. Stress-induced depression shares a high comorbidity with other neurological conditions including Alzheimer's disease (AD) and dementia, often appearing as one of the earliest observable symptoms in these diseases. Furthermore, stress and/or depression appear to exacerbate cognitive impairment in the context of AD associated with dysfunctional catecholaminergic signaling. Given there are a number of homologous pathways involved in the pathophysiology of depression and AD, this article will highlight the mechanisms by which stress-induced perturbations in oxidative stress, and particularly NO signaling, contribute to neurodegeneration.

New insights into oxidative stress and inflammation during diabetes mellitus-accelerated atherosclerosis

Oxidative stress and inflammation interact in the development of diabetic atherosclerosis. Intracellular hyperglycemia promotes production of mitochondrial reactive oxygen species (ROS), increased formation of intracellular advanced glycation end-products, activation of protein kinase C, and increased polyol pathway flux. ROS directly increase the expression of inflammatory and adhesion factors, formation of oxidized-low density lipoprotein, and insulin resistance. They activate the ubiquitin pathway, inhibit the activation of AMP-protein kinase and adiponectin, decrease endothelial nitric oxide synthase activity, all of which accelerate atherosclerosis. Changes in the composition of the gut microbiota and changes in microRNA expression that influence the regulation of target genes that occur in diabetes interact with increased ROS and inflammation to promote atherosclerosis. This review highlights the consequences of the sustained increase of ROS production and inflammation that influence the acceleration of atherosclerosis by diabetes. The potential contributions of changes in the gut microbiota and microRNA expression are discussed.

Neuronal nitric oxide synthase contributes to the normalization of blood pressure in medicated hypertensive patients

Neuronal nitric oxide synthase (nNOS) is expressed in the cardiovascular system and besides NO, generates H₂O₂. nNOS has been proposed to contribute to the control of blood pressure in healthy humans. The aim of this study was to verify the hypothesis that nNOS can contribute to the control of vascular relaxation and blood pressure in hypertensive patients undergoing drug treatment. The study was conducted in resistance mesenteric arteries from 63 individuals, as follows: 1) normotensive patients; 2) controlled hypertensive patients (patients on antihypertensive treatment with blood pressure normalized); 3) uncontrolled hypertensive patients (patients on antihypertensive treatment that remained hypertensive). Only mesenteric arteries from uncontrolled hypertensive patients showed impaired endothelium-dependent vasorelaxation in response to acetylcholine (ACh). Selective nNOS blockade with inhibitor 1 and catalase, which decomposes H₂O₂, decreased vasorelaxation in the three groups. However, the inhibitory effect was greater in controlled hypertensive patients. Decreased eNOS expression was detected in both uncontrolled and controlled hypertensive groups. Interestingly nNOS expression and ACh-stimulated H₂O₂ production were greater in controlled hypertensive patients, than in the other groups. ACh-stimulated NO production was lower in controlled hypertensive when compared to normotensive patients, while uncontrolled hypertensive patients showed the lowest levels. Catalase and nNOS blockade inhibited ACh-induced H₂O₂ production. In conclusion, nNOS-derived H₂O₂ contributes to the endothelium-dependent vascular relaxation in human resistance mesenteric arteries. The endothelial dysfunction observed in uncontrolled hypertensive patients involves decreased eNOS expression and NO production. The normalization of vascular relaxation and blood pressure in controlled hypertensive patients involves increased nNOS-derived H₂O₂ and NO production.

Engulfment of platelets delays endothelial cell aging via girdin and its phosphorylation

Endothelial cells are critical in angiogenesis and maintain the homeostasis of the blood‑brain barrier (BBB). Platelets (PLTs) are essential in vascular biology, including angiogenesis. The present study aimed to investigate the effect of PLTs on the aging of endothelial cells. Human brain microvascular endothelial cells (HBMECs) and human astrocytes were co‑cultured to mimic the BBB. Transmission electron microscopy was used to observe the engulfment of PLTs. Confocal microscopy was used to observe the co‑localization of PLTs, girders of actin filament (girdin) and phosphorylated (p‑)girdin. Senescence‑associated β‑galactosidase (β‑gal) staining, 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide and flow cytometry were performed to examine the cell senescence, viability and apoptosis, respectively. Transwell assays were performed to examine cell invasion and migration. Western blot analysis was performed to detect the expression of girdin, AKT and p‑AKT. PLTs delayed senescence, and promoted the viability and resistance to apoptosis of the HBMECs. Cell invasion and migration were enhanced by PLTs. In addition, girdin and p‑girdin were essential to the engulfment of HBMECs to PLTs. Mechanically, the inhibition of AKT signals reversed the effect of PLTs on HBMECs by increasing the activity of β‑gal, decreasing the cell viability, and inhibiting the invasion and migration of the HBMECs. The engulfment of PLTs assisted in delaying the aging of endothelial cells via girdin and p‑girdin, in which the AKT signal was involved. The present study indicated a potential strategy for delaying endothelial cell aging in the treatment of central nervous system diseases.

Protective Role of Perivascular Adipose Tissue in Endothelial Dysfunction and Insulin-Induced Vasodilatation of Hypercholesterolemic LDL Receptor-Deficient Mice

Background: Endothelial dysfunction plays a pivotal role in the initiation of atherosclerosis. Vascular insulin resistance might contribute to a reduction in endothelial nitric oxide (NO) production, leading to impaired endothelium-dependent relaxation in cardiometabolic diseases. Because perivascular adipose tissue (PVAT) controls endothelial function and NO bioavailability, we hypothesized a role for this fat deposit in the vascular complications associated with the initial stages of atherosclerosis. Therefore, we investigated the potential involvement of PVAT in the early endothelial dysfunction in hypercholesterolemic LDL receptor knockout mice (LDLr-KO).

Methods: Thoracic aortas with and without PVAT were isolated from 4-month-old C57BL/6J (WT) and LDLr-KO mice. The contribution of PVAT to relaxation responses to acetylcholine, insulin, and sodium nitroprusside was investigated. Western blotting was used to examine endothelial NO synthase (eNOS) and adiponectin expression, as well the insulin signaling pathway in aortic PVAT.

Results: PVAT-free aortas of LDLr-KO mice exhibited impaired acetylcholine- and insulin-induced relaxation compared with those of WT mice. Both vasodilatory responses were restored by the presence of PVAT in LDLr-KO mice, associated with enhanced acetylcholine-induced NO levels. PVAT did not change vasodilatory responses to acetylcholine and insulin in WT mice, while vascular relaxation evoked by the NO donor sodium nitroprusside was not modified by either genotype or PVAT. The expression of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), AKT, ERK1/2, phosphorylation of AKT (Ser473) and ERK1/2 (Thr202/Tyr204), and adiponectin was similar in the PVAT of WT and LDLr-KO mice, suggesting no changes in PVAT insulin signaling. However, eNOS expression was enhanced in the PVAT of LDLr-KO mice, while eNOS expression was less abundant in PVAT-free aortas.

Conclusion: These results suggest that elevated eNOS-derived NO production in aortic PVAT might be a compensatory mechanism for the endothelial dysfunction and impaired vasodilator action of insulin in hypercholesterolemic LDLr-deficient mice. This protective effect may limit the progression of atherosclerosis in genetic hypercholesterolemia in the absence of an atherogenic diet.

Modulation of nNOSser852 phosphorylation and translocation by PKA/PP1 pathway in endothelial cells

Neuronal nitric oxide synthase (nNOS) is now considered an important player in vascular function. It has a protective role in atherosclerosis and hypertension. However, despite its importance, little is known about the mechanisms that regulate its activity in vascular cells. Here we explore the mechanisms by which nNOS is activated in endothelium. We evaluated aorta relaxation response and phosphorylation of nNOS during protein phosphatases 1 and 2 (PP1 and PP2) inhibition, in eNOS silenced mice. PP1 translocation and interaction between the nuclear inhibitor of PP1 (NIPP1) and PP1 was evaluated in endothelial EA.hy926 cells. We demonstrate here that acetylcholine (Ach)-induced relaxation is completely abolished by nNOS inhibition in eNOS silenced mice aorta which also decreased NO and H₂O₂ concentrations. ACh induced dephosphorylation of nNOS^ser852 in aorta after 20 min stimulation. Endothelial cells also showed a decrease in nNOS^ser852 phosphorylation during 20 min of ACh stimulation. PP2 inhibition had no effect on Ach-induced nNOS^Ser852 dephosphorylation in endothelial cells and did not modify Ach-induced vasodilation in aorta from eNOS silenced mice. Non-selective PP1/PP2 inhibition prevented nNOSSer852 dephosphorylation in endothelial cells and prevented Ach-induced vasodilation in eNOS silenced mice. ACh induced time-dependent PP1 and NIPP1 dissociation and PP1 translocation to cytoplasm. Protein kinase A (PKA) inhibition abolished PP1 translocation and further nNOS^ser852 dephosphorylation. In addition, 8-Br-cAMP reduced NIPP1/PP1 interaction, stimulated PP1 translocation and nNOS^ser852 dephosphorylation. Moreover, PKA Inhibition led to a decreased nNOS translocation to perinuclear region. Taken together, our results elucidate a mechanism whereby PP1 is activated by a cAMP/PKA-dependent pathway, leading to dephosphorylation of nNOS^ser852 and subsequent NO and possible H₂O₂ production resulting in endothelium-dependent vascular relaxation.

The human coronary vasodilatory response to acute mental stress is mediated by neuronal nitric oxide synthase

Acute mental stress induces vasodilation of the coronary microvasculature. Here, we show that this response involves neuronal nitric oxide synthase in the human coronary circulation.

Mental stress-induced ischemia approximately doubles the risk of cardiac events in patients with coronary artery disease, yet the mechanisms underlying changes in coronary blood flow in response to mental stress are poorly characterized. Neuronal nitric oxide synthase (nNOS) regulates basal coronary blood flow in healthy humans and mediates mental stress-induced vasodilation in the forearm. However, its possible role in mental stress-induced increases in coronary blood flow is unknown. We studied 11 patients (6 men and 5 women, mean age: 58 ± 14 yr) undergoing elective diagnostic cardiac catheterization and assessed the vasodilator response to mental stress elicited by the Stroop color-word test. Intracoronary substance P (20 pmol/min) and isosorbide dinitrate (1 mg) were used to assess endothelium-dependent and -independent vasodilation, respectively. Coronary blood flow was estimated using intracoronary Doppler recordings and quantitative coronary angiography to measure coronary artery diameter. Mental stress increased coronary flow by 34 ± 7.0% over the preceding baseline during saline infusion (P < 0.01), and this was reduced to 26 ± 7.0% in the presence of the selective nNOS inhibitor S-methyl-l-thiocitrulline (0.625 µmol/min, P < 0.001). Mental stress increased coronary artery diameter by 6.9 ± 3.7% (P = 0.02) and 0.5 ± 2.8% (P = 0.51) in the presence of S-methyl-l-thiocitrulline. The response to substance P did not predict the response to mental stress (r² = −0.22, P = 0.83). nNOS mediates the human coronary vasodilator response to mental stress, predominantly through actions at the level of coronary resistance vessels.

NEW & NOTEWORTHY Acute mental stress induces vasodilation of the coronary microvasculature. Here, we show that this response involves neuronal nitric oxide synthase in the human coronary circulation.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/nnos-and-coronary-flow-during-mental-stress/.

Nitric oxide signalling and neuronal nitric oxide synthase in the heart under stress

Nitric oxide (NO) is an imperative regulator of the cardiovascular system and is a critical mechanism in preventing the pathogenesis and progression of the diseased heart. The scenario of bioavailable NO in the myocardium is complex: 1) NO is derived from both endogenous NO synthases (endothelial, neuronal, and/or inducible NOSs [eNOS, nNOS, and/or iNOS]) and exogenous sources (entero-salivary NO pathway) and the amount of NO from exogenous sources varies significantly; 2) NOSs are located at discrete compartments of cardiac myocytes and are regulated by distinctive mechanisms under stress; 3) NO regulates diverse target proteins through different modes of post-transcriptional modification (soluble guanylate cyclase [sGC]/cyclic guanosine monophosphate [cGMP]/protein kinase G [PKG]-dependent phosphorylation, S-nitrosylation, and transnitrosylation); 4) the downstream effectors of NO are multidimensional and vary from ion channels in the plasma membrane to signalling proteins and enzymes in the mitochondria, cytosol, nucleus, and myofilament; 5) NOS produces several radicals in addition to NO (e.g. superoxide, hydrogen peroxide, peroxynitrite, and different NO-related derivatives) and triggers redox-dependent responses. However, nNOS inhibits cardiac oxidases to reduce the sources of oxidative stress in diseased hearts. Recent consensus indicates the importance of nNOS protein in cardiac protection under pathological stress. In addition, a dietary regime with high nitrate intake from fruit and vegetables together with unsaturated fatty acids is strongly associated with reduced cardiovascular events. Collectively, NO-dependent mechanisms in healthy and diseased hearts are better understood and shed light on the therapeutic prospects for NO and NOSs in clinical applications for fatal human heart diseases.

Vascular Kinin B1 and B2 Receptors Determine Endothelial Dysfunction through Neuronal Nitric Oxide Synthase

B₁- and B₂-kinin receptors are G protein-coupled receptors that play an important role in the vascular function. Therefore, the present study was designed to evaluate the participation of kinin receptors in the acetylcholine (ACh)-induced vascular relaxation, focusing on the protein-protein interaction involving kinin receptors with endothelial and neuronal nitric oxide synthases (eNOS and nNOS). Vascular reactivity, nitric oxide (NO·) and reactive oxygen species (ROS) generation, co-immunoprecipitation were assessed in thoracic aorta from male wild-type (WT), B₁- (B₁R^−/−), B₂- (B₂R^−/−) knockout mice. Some vascular reactivity experiments were also performed in a double kinin receptors knockout mice (B₁B₂R^−/−). For pharmacological studies, selective B₁- and B₂-kinin receptors antagonists, NOS inhibitors and superoxide dismutase (SOD) mimetic were used. First, we show that B₁- and B₂-kinin receptors form heteromers with nNOS and eNOS in thoracic aorta. To investigate the functionality of these protein-protein interactions, we took advantage of pharmacological tools and knockout mice. Importantly, our results show that kinin receptors regulate ACh-induced relaxation via nNOS signaling in thoracic aorta with no changes in NO· donor-induced relaxation. Interestingly, B₁B₂R^−/− presented similar level of vascular dysfunction as found in B₁R^−/− or B₂R^−/− mice. In accordance, aortic rings from B₁R^−/− or B₂R^−/− mice exhibit decreased NO· bioavailability and increased superoxide generation compared to WT mice, suggesting the involvement of excessive ROS generation in the endothelial dysfunction of B₁R^−/− and B₂R^−/− mice. Alongside, we show that impaired endothelial vasorelaxation induced by ACh in B₁R^−/− or B₂R^−/− mice was rescued by the SOD mimetic compound. Taken together, our findings show that B₁- and B₂-kinin receptors regulate the endothelium-dependent vasodilation of ACh through nNOS activity and indicate that molecular disturbance of short-range interaction between B₁- and B₂-kinin receptors with nNOS might be involved in the oxidative pathogenesis of endothelial dysfunction.

Interaction between interleukin‑6 and angiotensin II receptor 1 in the hypothalamic paraventricular nucleus contributes to progression of heart failure

The association between interleukin‑6 (IL‑6) and angiotensin II receptor 1 (AT1‑R) in modulating the progression of heart failure (HF) remains to be fully elucidated. The aim of the present study was to investigate the mechanism of IL‑6 and AT1‑R in a model of HF induced by surgery. Male Sprague‑Dawley rats were randomly divided into five groups, including sham surgery and vehicle groups. The animals were treated for 4 weeks via paraventricular nucleus infusion with either vehicle, losartan (LOS; 200 µg/day), IL‑6 (1 µg/day) or LOS and IL‑6 together (LOS+IL‑6). The rats with HF had higher levels of IL‑6, corticotropin‑releasing hormone (CRH) and norepinephrine (NE), and a lower level of neuronal nitric oxide synthase (nNOS), compared with the rats in the sham surgery group. Treatment with LOS attenuated the decrease in nNOS and the increases in IL‑6, CRH and NE; whereas treatment with IL‑6 facilitated the lower expression of nNOS and higher expression levels of IL‑6, CRH and NE. No differences in the expression levels of nNOS, CRH or NE were found between the LOS group and LOS+IL‑6 group. The results of the study demonstrated that IL‑6 contributed to the progression of HF via the AT1‑R pathway.

Neuronal nitric oxide synthase-derived hydrogen peroxide effect in grafts used in human coronary bypass surgery

Recently, H₂O₂ has been identified as the endothelium-dependent hyperpolarizing factor (EDHF), which mediates flow-induced dilation in human coronary arteries. Neuronal nitric oxide synthase (nNOS) is expressed in the cardiovascular system and, besides NO, generates H₂O₂ The role of nNOS-derived H₂O₂ in human vessels is so far unknown. The present study was aimed at investigating the relevance of nNOS/H₂O₂ signaling in the human internal mammary artery (IMA) and saphenous vein (SV), the major conduits used in coronary artery bypass grafting. In the IMA, but not in the SV, ACh (acetylcholine)-induced vasodilatation was decreased by selective nNOS inhibition with TRIM or Inhibitor 1, and by catalase, which specifically decomposes H₂O₂ Superoxide dismutase (SOD), which generates H₂O₂ from superoxide, decreased the vasodilator effect of ACh on SV. In the IMA, SOD diminished phenylephrine-induced contraction in endothelium-containing, but not in endothelium-denuded vessels. Importantly, while exogenous H₂O₂ produced vasodilatation in IMA, it constricted SV. ACh increased H₂O₂ production in both sets of vessels. In the IMA, the increase in H₂O₂ was inhibited by catalase and nNOS blockade. In SV, H₂O₂ production was abolished by catalase and reduced by nNOS inhibition. Immunofluorescence experiments showed the presence of nNOS in the vascular endothelium and smooth muscle cells of both the IMA and SV. Together, our results clearly show that H₂O₂ induced endothelium-dependent vascular relaxation in the IMA, whereas, in the SV, H₂O₂ was a vasoconstrictor. Thus, H₂O₂ produced in the coronary circulation may contribute to the susceptibility to accelerated atherosclerosis and progressive failure of the SV used as autogenous graft in coronary bypass surgery.

Optimizing the host substrate environment for cardiac angiogenesis, arteriogenesis, and myogenesis

INTRODUCTION

The diseased host milieu, such as endothelial dysfunction (ED), decreased NO bioavailability, and ischemic/inflammatory post-MI environment, hamper the clinical success of existing cardiac regenerative therapies. Area covered: In this article, current strategies including pharmacological and nonpharmacological approaches for improving the diseased host milieu are reviewed. Specifically, the authors provide focus on: i) the mechanism of ED in patients with cardiovascular diseases, ii) the current results of ED improving strategies in pre-clinical and clinical studies, and iii) the use of biomaterials as a novel modulator in damaged post-MI environment. Expert opinion: Adjunct therapies which improve host endothelial function have demonstrated promising outcomes, potentially overcoming disappointing results of cell therapy in human studies. In the future, elucidation of the interactions between the host tissue and therapeutic agents, as well as downstream signaling pathways, will be the next challenges in enhancing regenerative therapy. More careful investigations are also required to establish these agents' safety and efficacy for wide usage in humans.

Roles of Vascular Oxidative Stress and Nitric Oxide in the Pathogenesis of Atherosclerosis

Major reactive oxygen species (ROS)–producing systems in vascular wall include NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase, xanthine oxidase, the mitochondrial electron transport chain, and uncoupled endothelial nitric oxide (NO) synthase. ROS at moderate concentrations have important signaling roles under physiological conditions. Excessive or sustained ROS production, however, when exceeding the available antioxidant defense systems, leads to oxidative stress. Animal studies have provided compelling evidence demonstrating the roles of vascular oxidative stress and NO in atherosclerosis. All established cardiovascular risk factors such as hypercholesterolemia, hypertension, diabetes mellitus, and smoking enhance ROS generation and decrease endothelial NO production. Key molecular events in atherogenesis such as oxidative modification of lipoproteins and phospholipids, endothelial cell activation, and macrophage infiltration/activation are facilitated by vascular oxidative stress and inhibited by endothelial NO. Atherosclerosis develops preferentially in vascular regions with disturbed blood flow (arches, branches, and bifurcations). The fact that these sites are associated with enhanced oxidative stress and reduced endothelial NO production is a further indication for the roles of ROS and NO in atherosclerosis. Therefore, prevention of vascular oxidative stress and improvement of endothelial NO production represent reasonable therapeutic strategies in addition to the treatment of established risk factors (hypercholesterolemia, hypertension, and diabetes mellitus).

Nitric Oxide and Hydrogen Sulfide Interact When Modulating Gastric Physiological Functions in Rodents

AIM

The objective was to evaluate the effects of nitric oxide (NO) and hydrogen sulfide (H₂S) donors and possible interactions between these two systems in modulating gastric function.

METHODS

Mice received saline, sodium nitroprusside (SNP), or sodium hydrosulfite (NaHS), and after 1 h, the animals were killed for immunofluorescence analysis of CSE or eNOS expressions, respectively. Other groups received saline, SNP, NaHS, Lawesson's reagent (H₂S donor), PAG + SNP, L-NAME, L-NAME + NaHS, or L-NAME + Lawesson's reagent. Then, the gastric secretions (mucous and acid), gastric blood flow, gastric defense against ethanol, and gastric motility (gastric emptying and gastric contractility) were evaluated.

RESULTS

SNP and NaHS increased the expression of CSE or eNOS, respectively. SNP or Lawesson's reagent did not alter gastric acid secretion but increased mucus production, and these effects reverted with PAG and L-NAME treatment, respectively. SNP or NaHS increased gastric blood flow and protected the gastric mucosa against ethanol injury, and these effects reverted with PAG and L-NAME treatments, respectively. SNP delayed gastric emptying when compared with saline, and PAG partially reversed this effect. NaHS accelerate gastric emptying, and L-NAME partially reversed this effect. SNP and NaHS alone induced gastric fundus and pylorus relaxation. However, pretreatment with PAG or L-NAME reversed these relaxant effects only in the pylorus but not in the gastric fundus.

CONCLUSION

NO and H₂S interact in gastric physiological functions, and this "cross-talk" is important in the control of mucus secretion, gastric blood flow, gastric mucosal defense, and gastric motility, but not in the control of basal gastric acid secretion.

Role of ERK1/2 activation and nNOS uncoupling on endothelial dysfunction induced by lysophosphatidylcholine

BACKGROUND AND AIMS

Lysophosphatidylcholine (LPC) - a main component of oxidized LDL - is involved in endothelial dysfunction that precedes atherosclerosis, with an increased superoxide anions and a reduced NO production via endothelial NO synthase (eNOS) uncoupling. However, there is no evidence about the mechanisms involved in neuronal NOS (nNOS) uncoupling. Extracellular signal-regulated kinase (ERK) is related to the control of NO production and inflammatory gene transcription activation in atherosclerosis. Our aim was to investigate the role of nNOS/ERK1/2 pathway on endothelial dysfunction induced by LPC, in mouse aorta and human endothelial cells.

METHODS

Thoracic aorta from wild type mice was used to perform vascular reactivity studies in the presence or absence of LPC. Human endothelial cells were used to investigate the effect of LPC on expression of nNOS and his products NO and H₂O₂.

RESULTS

LPC reduced acetylcholine (ACh)-induced vasodilation in mouse aorta (Emax_CT/LPC = ∼95 ± 2/62 ± 3%, p = 0.0004) and increased phenylephrine-induced vasoconstriction (Emax_CT/LPC = ∼4 ± 0,1/6 ± 0,1 mN/mm, p = 0.0002), with a reduction in NO (fluorescence intensity_CT/LPC = 91 ± 3/62±2 × 10³, p = 0.0002) and H₂O₂ (fluorescence intensity_CT/LPC = ∼16 ± 0,8/10 ± 0,7 × 10³, p = 0.0041) production evocated by ACh. An inhibition of nNOS by TRIM (Emax_CT/CT+TRIM = ∼93 ± 1/43 ± 3%, p = 0,0048; Emax_LPC/LPC+TRIM = ∼62 ± 3/65 ± 3%) or H₂O₂ degradation by catalase (Emax_CT/CT+cat = ∼93 ± 1/46 ± 2%, p < 0,001; Emax_LPC/LPC+cat = ∼62,8 ± 3,2/60,5 ± 4,7%) reduced the relaxation in the control but not in LPC group. PD98059, an ERK1/2 inhibitor, abolished the increase in vasoconstriction in LPC-treated vessels (Emax_LPC/LPC+PD = ∼6 ± 0,1/3 ± 0,1 mN/mm, p = 0.0001). LPC also reduced the dimer/monomer proportion and increased nNOS^ser852 phosphorylation.

CONCLUSIONS

LPC induced nNOS uncoupling and nNOS^Ser852 phosphorylation, reduced NO and H₂O₂ production and improved superoxide production by modulating ERK1/2 activity in human and murine endothelial cells.

Aerobic exercise training protects against endothelial dysfunction by increasing nitric oxide and hydrogen peroxide production in LDL receptor-deficient mice

BACKGROUND

Endothelial dysfunction associated with hypercholesterolemia is an early event in atherosclerosis characterized by redox imbalance associated with high superoxide production and reduced nitric oxide (NO) and hydrogen peroxide (H2O2) production. Aerobic exercise training (AET) has been demonstrated to ameliorate atherosclerotic lesions and oxidative stress in advanced atherosclerosis. However, whether AET protects against the early mechanisms of endothelial dysfunction in familial hypercholesterolemia remains unclear. This study investigated the effects of AET on endothelial dysfunction and vascular redox status in the aortas of LDL receptor knockout mice (LDLr(-/-)), a genetic model of familial hypercholesterolemia.

METHODS

Twelve-week-old C57BL/6J (WT) and LDLr(-/-) mice were divided into sedentary and exercised (AET on a treadmill 1 h/5 × per week) groups for 4 weeks. Changes in lipid profiles, endothelial function, and aortic NO, H2O2 and superoxide production were examined.

RESULTS

Total cholesterol and triglycerides were increased in sedentary and exercised LDLr(-/-) mice. Endothelium-dependent relaxation induced by acetylcholine was impaired in aortas of sedentary LDLr(-/-) mice but not in the exercised group. Inhibition of NO synthase (NOS) activity or H2O2 decomposition by catalase abolished the differences in the acetylcholine response between the animals. No changes were noted in the relaxation response induced by NO donor sodium nitroprusside or H2O2. Neuronal NOS expression and endothelial NOS phosphorylation (Ser1177), as well as NO and H2O2 production, were reduced in aortas of sedentary LDLr(-/-) mice and restored by AET. Incubation with apocynin increased acetylcholine-induced relaxation in sedentary, but not exercised LDLr(-/-) mice, suggesting a minor participation of NADPH oxidase in the endothelium-dependent relaxation after AET. Consistent with these findings, Nox2 expression and superoxide production were reduced in the aortas of exercised compared to sedentary LDLr(-/-) mice. Furthermore, the aortas of sedentary LDLr(-/-) mice showed reduced expression of superoxide dismutase (SOD) isoforms and minor participation of Cu/Zn-dependent SODs in acetylcholine-induced, endothelium-dependent relaxation, abnormalities that were partially attenuated in exercised LDLr(-/-) mice.

CONCLUSION

The data gathered by this study suggest AET as a potential non-pharmacological therapy in the prevention of very early endothelial dysfunction and redox imbalance in familial hypercholesterolemia via increases in NO bioavailability and H2O2 production.

Neuronal Nitric Oxide Synthase in Vascular Physiology and Diseases

The family of nitric oxide synthases (NOS) has significant importance in various physiological mechanisms and is also involved in many pathological processes. Three NOS isoforms have been identified: neuronal NOS (nNOS or NOS 1), endothelial NOS (eNOS or NOS 3), and an inducible NOS (iNOS or NOS 2). Both nNOS and eNOS are constitutively expressed. Classically, eNOS is considered the main isoform involved in the control of the vascular function. However, more recent studies have shown that nNOS is present in the vascular endothelium and importantly contributes to the maintenance of the homeostasis of the cardiovascular system. In physiological conditions, besides nitric oxide (NO), nNOS also produces hydrogen peroxide (H2O2) and superoxide ([Formula: see text]) considered as key mediators in non-neuronal cells signaling. This mini-review highlights recent scientific releases on the role of nNOS in vascular homeostasis and cardiovascular disorders such as hypertension and atherosclerosis.

Oral butyrate reduces oxidative stress in atherosclerotic lesion sites by a mechanism involving NADPH oxidase down-regulation in endothelial cells

Butyrate is a 4-carbon fatty acid that has antiinflammatory and antioxidative properties. It has been demonstrated that butyrate is able to reduce atherosclerotic development in animal models by reducing inflammatory factors. However, the contribution of its antioxidative effects of butyrate on atherogenesis has not yet been studied. We investigated the influence of butyrate on oxidative status, reactive oxygen species (ROS) release and oxidative enzymes (NADPH oxidase and iNOS) in atherosclerotic lesions of ApoE(-/-) mice and in oxLDL-stimulated peritoneal macrophages and endothelial cells (EA.hy926). The lesion area in aorta was reduced while in the aortic valve, although lesion area was unaltered, superoxide production and protein nitrosylation were reduced in butyrate-supplemented mice. Peritoneal macrophages from the butyrate group presented a lower free radical release after zymosan stimulus. When endothelial cells were pretreated with butyrate before oxLDL stimulus, the CCL-2 and superoxide ion productions and NADPH oxidase subunit p22phox were reduced. In macrophage cultures, in addition to a reduction in ROS release, nitric oxide and iNOS expression were down-regulated. The data suggest that one mechanism related to the effect of butyrate on atherosclerotic development is the reduction of oxidative stress in the lesion site. The reduction of oxidative stress related to NADPH oxidase and iNOS expression levels associated to butyrate supplementation attenuates endothelium dysfunction and macrophage migration and activation in the lesion site.

Significant Modules and Biological Processes between Active Components of Salvia miltiorrhiza Depside Salt and Aspirin

The aim of this study is to examine and compare the similarities and differences between active components of S. miltiorrhiza depside salt and aspirin using perspective of pharmacological molecular networks. Active components of S. miltiorrhiza depside salt and aspirin's related genes were identified via the STITCH4.0 and GeneCards Database. A text search engine (Agilent Literature Search 2.71) and MCODE software were applied to construct network and divide modules, respectively. Finally, 32, 2, and 28 overlapping genes, modules, and pathways were identified between active components of S. miltiorrhiza depside salt and aspirin. A multidimensional framework of drug network showed that two networks reflected commonly in human aortic endothelial cells and atherosclerosis process. Aspirin plays a more important role in metabolism, such as the well-known AA metabolism pathway and other lipid or carbohydrate metabolism pathways. S. miltiorrhiza depside salt still plays a regulatory role in type II diabetes mellitus, insulin resistance, and adipocytokine signaling pathway. Therefore, this study suggests that aspirin combined with S. miltiorrhiza depside salt may be more efficient in treatment of CHD patients, especially those with diabetes mellitus or hyperlipidemia. Further clinical trials to confirm this hypothesis are still needed.

Endothelial dysfunction in DOCA-salt-hypertensive mice: role of neuronal nitric oxide synthase-derived hydrogen peroxide

Endothelial dysfunction is a common problem associated with hypertension and is considered a precursor to the development of micro- and macro-vascular complications. The present study investigated the involvement of nNOS (neuronal nitric oxide synthase) and H2O2 (hydrogen peroxide) in the impaired endothelium-dependent vasodilation of the mesenteric arteries of DOCA (deoxycorticosterone acetate)-salt-hypertensive mice. Myograph studies were used to investigate the endothelium-dependent vasodilator effect of ACh (acetylcholine). The expression and phosphorylation of nNOS and eNOS (endothelial nitric oxide synthase) were studied by Western blot analysis. Immunofluorescence was used to examine the localization of nNOS and eNOS in the endothelial layer of the mesenteric artery. The vasodilator effect of ACh is strongly impaired in mesenteric arteries of DOCA-salt-hypertensive mice. Non-selective inhibition of NOS sharply reduced the effect of ACh in both DOCA-salt-hypertensive and sham mice. Selective inhibition of nNOS and catalase led to a higher reduction in the effect of ACh in sham than in DOCA-salt-hypertensive mice. Production of H2O2 induced by ACh was significantly reduced in vessels from DOCA-salt-hypertensive mice, and it was blunted after nNOS inhibition. The expression of both eNOS and nNOS was considerably lower in DOCA-salt-hypertensive mice, whereas phosphorylation of their inhibitory sites was increased. The presence of nNOS was confirmed in the endothelial layer of mesenteric arteries from both sham and DOCA-salt-hypertensive mice. These results demonstrate that endothelial dysfunction in the mesenteric arteries of DOCA-salt-hypertensive mice is associated with reduced expression and functioning of nNOS and impaired production of nNOS-derived H2O2 Such findings offer a new perspective for the understanding of endothelial dysfunction in hypertension.

Vascular dysfunctions in the isolated aorta of double-transgenic hypertensive mice developing aortic aneurysm

Angiotensin-II and oxidative stress are involved in the genesis of aortic aneurysms, a phenomenon exacerbated by endothelial nitric oxide synthase (eNOS) deletion or uncoupling. The purpose of this work was to study the endothelial function in wild-type C57BL/6 (BL) and transgenic mice expressing the h-angiotensinogen and h-renin genes (AR) subjected to either a control, or a high-salt diet plus a treatment with a NO-synthase inhibitor, N-ω-nitro-L-arginine-methyl-ester (L-NAME; BLSL and ARSL). BLSL showed a moderate increase in blood pressure, while ARSL became severely hypertensive. Seventy-five percent of ARSL developed aortic aneurysms, characterized by major histo-morphological changes and associated with an increase in NADP(H) oxidase-2 (NOX2) expression. Contractile responses (KCl, norepinephrine, U-46619) were similar in the four groups of mice, and relaxations were not affected in BLSL and AR. However, in ARSL, endothelium-dependent relaxations (acetylcholine, UK-14304) were significantly reduced, and this dysfunction was similar in aortae without or with aneurysms. The endothelial impairment was unaffected by catalase, superoxide-dismutase mimetic, radical scavengers, cyclooxygenase inhibition, or TP-receptor blockade and could not be attributed to sGC oxidation. Thus, ARSL is a severe hypertension model developing aortic aneurysm. A vascular dysfunction, involving both endothelial (reduced role of NO) and smooth muscle cells, precedes aneurysms formation and, paradoxically, does not appear to involve oxidative stress.

Acid-sensing ion channel 1 and nitric oxide synthase are in adjacent layers in the wall of rat and human cerebral arteries

Extracellular acidification activates a family of proteins known as acid-sensing ion channels (ASICs). One ASIC subtype, ASIC type 1 (ASIC1), may play an important role in synaptic plasticity, memory, fear conditioning and ischemic brain injury. ASIC1 is found primarily in neurons, but one report showed its expression in isolated mouse cerebrovascular cells. In this study, we sought to determine if ASIC1 is present in intact rat and human major cerebral arteries. A potential physiological significance of such a finding is suggested by studies showing that nitric oxide (NO), which acts as a powerful vasodilator, may modulate proton-gated currents in cultured cells expressing ASIC1s. Because both constitutive NO synthesizing enzymes, neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS), are expressed in cerebral arteries we also studied the anatomical relationship between ASIC1 and nNOS or eNOS in both rat and human cerebral arteries. Western blot analysis demonstrated ASIC1 in cerebral arteries from both species. Immunofluorescent histochemistry and confocal microscopy also showed that ASIC1-immunoreactivity (IR), colocalized with the smooth muscle marker alpha-smooth muscle actin (SMA), was present in the anterior cerebral artery (ACA), middle cerebral artery (MCA), posterior cerebral artery (PCA) and basilar artery (BA) of rat and human. Expression of ASIC1 in cerebral arteries is consistent with a role for ASIC1 in modulating cerebrovascular tone both in rat and human. Potential interactions between smooth muscle ASIC1 and nNOS or eNOS were supported by the presence of nNOS-IR in the neighboring adventitial layer and the presence of nNOS-IR and eNOS-IR in the adjacent endothelial layer of the cerebral arteries.

Butyrate impairs atherogenesis by reducing plaque inflammation and vulnerability and decreasing NFκB activation

BACKGROUND & AIMS

Butyrate is a four-carbon fatty acid that presents anti-inflammatory, anti-oxidative and apoptotic properties in colon and several cell lines. Because atherosclerosis has important oxidative and inflammatory components, butyrate could reduce oxidation and inflammation, impairing atherogenesis. We evaluated the effects of butyrate supplementation of butyrate on atherosclerosis and its mechanisms of action.

METHODS AND RESULTS

ApoE knockout mice were fed on chow diet or 1% butyrate-supplemented chow diet (Butyrate) for 10 weeks to assess atherosclerosis lesions area and inflammatory status. Macrophage and endothelial cells were also pretreated with butyrate (0.5 mM) for 2 h before oxLDL stimulation to study oxLDL uptake and pro and anti-inflammatory cytokine production. Butyrate reduced atherosclerosis in the aorta by 50%. In the aortic valve, butyrate reduced CCL2, VCAM1 and MMP2 productions in the lesion site, resulting in a lower migration of macrophage and increased collagen depositions in the lesion and plaque stability. When EA.hy926 cells were pretreated with butyrate, oxLDL uptake, CD36, VCAM1, CCL2 TNF, IL1β and IL6 productions were reduced, whereas IL10 production was increased. These effects were accompanied by a lower activation of NFκB due to a lower nuclear translocation of the p65 subunit.

CONCLUSION

Oral butyrate is able to slow the progression of atherosclerosis by reducing adhesion and migration of macrophages and increasing plaque stability. These actions are linked to the reduction of CD36 in macrophages and endothelial cells, decreased pro-inflammatory cytokines and lower activation of NFκB all of these data support a possible role for butyrate as an atheroprotective agent.

Thiamine deficiency leads to reduced nitric oxide production and vascular dysfunction in rats

BACKGROUND AND AIMS

Thiamine deficiency is a condition that is known to cause damage to the nervous and cardiovascular systems because it interferes with cellular metabolism. It is well known that the control of vascular function is highly dependent on the production of nitric oxide (NO) by NO synthases. Studies exploring the physiological relevance of NO signaling under conditions of thiamine deficiency are scarce. The present study sought to investigate whether chronic metabolic changes would cause alterations in vascular responsiveness.

METHODS AND RESULTS

By removing thiamine from the diet, we observed a reduced acetylcholine-mediated relaxation and an increased phenylephrine-mediated vasoconstriction in the aortas containing functional endothelium. Removal of the endothelium or the pre-treatment of vessels with l-NAME restored the contractile responses to the level of controls. Conversely, indomethacin did not modify phenylephrine-mediated contractions. We also used carbon microsensors to continually measure NO production in situ while simultaneously measuring the vascular tone. The results revealed a significant decrease in NO production. Western blot analysis showed a decreased expression of the total eNOS in the thiamine-deficient aorta compared to the control. Concentration-response curves for phenylephrine indicated no difference between the control and deficient groups in the presence and absence of SOD or Tyron. The NO donor DEA-NONOate produced a concentration-dependent relaxation response in the endothelium-denuded vessels that did not differ between the control and thiamine-deficient rats.

CONCLUSION

Thiamine deficiency modulates eNOS-dependent NO production, leading to a decreased vasorelaxation and an increased contractile response in the rat aorta.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.