Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitric oxide (NO) is produced from amino acid L-arginine via the catalytic action of NO synthases, which use dioxygen and NADH or NADPH as cofactor. This simple molecule acts at nanomolar concentrations and demonstrates a wide spectrum of physiological effects, a primary of which is vasodilatation. The production of NO in endothelium cells is induced by mechanical action (increased blood-vessels wall tension) and chemical agents (catecholamines, acetylcholine, bradykinin, histamine). The endothelium-released NO easily diffuses to the underlying smooth muscles and triggers their relaxation by increasing cyclic guanosine monophosphate level and subsequent opening of endothelial potassium channels (K(ATP), K(Ca)). NO on the endothelium surface inhibits adhesion and aggregation of platelets, regulates the main functions of myocardium, modulates the permeability of endothelium, and weakens the interaction of endothelium cells and leukocytes by reducing the expression of adhesion-stimulating proteins. Direct evidence suggests that free radicals and related reactive oxygen species mostly as O2-, HO-, ONOO-, ROO- are associated with an endothelium dysfunction, which manifests itself as an impairment of endothelium-dependent vasorelaxation. Though reactive oxygen species in a small amount are produced constantly, the decreased metabolic turnover of homocysteine, poor performance of antioxidants or high level of angiotensin II alters the balance between production of free radicals and their neutralization. Such events decrease NO bioavailability and thus condition the development of various diseases like arteriosclerosis, hypertension, diabetes, heart and renal failure. Agents increasing NO bioavailability and depressing the endothelial dysfunction would be the most useful for the treatment above-mentioned pathologies.
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PMID:[The main determinants of endothelial dysfunction]. 1677 63

NADPH oxidase is critically involved in increased blood pressure, vascular hypertrophy, inflammation and endothelial dysfunction in experimental and clinical hypertension. We hypothesized that NADPH oxidase might also play a role in the development of spontaneous aortic tone in spontaneously hypertensive rats (SHR). Wistar Kyoto rats (WKY) were used as normotensive controls. Tone was recorded under isometric conditions. NADPH oxidase activity was measured by both lucigenin luminescence and dihydroethidium fluorescence. p47phox protein was localized by immunohistochemistry. SHR (but not WKY rat) aortae showed spontaneous tone in the absence of exogenous vasoconstrictors as evidenced by a stronger relaxant effect of Ca2+-free sodium nitroprusside solution. This tone was enhanced in endothelium-denuded arteries and was inhibited by superoxide dismutase, apocynin, diphenylene iodonium and quercetin. Aortic NADPH oxidase activity, measured by both lucigenin luminescence and dihydroethidium fluorescence, was increased in SHR compared with WKY rats. Immunohistochemical analysis revealed a strong increase in p47phox expression in the medial layer in SHR. Taken together, the present results indicate that enhanced NADPH oxidase activity and, hence, NADPH driven O2- production, is involved in the spontaneous aortic tone in SHR. This was associated with an increased expression of p47phox in the medial layer of the aorta.
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PMID:Increased NADPH oxidase activity mediates spontaneous aortic tone in genetically hypertensive rats. 1684 72

Sleep disorders are a form of stress associated with increased sympathetic activity, and they are a risk factor for the occurrence of cardiovascular disease. Given that nitric oxide (NO) may play an inhibitory role in the regulation of sympathetic tone, this study set out to determine the NO synthase (NOS) reactivity in the primary cardiovascular afferent neurons (i.e. nodose neurons) following total sleep deprivation (TSD). TSD was performed by the disc-on-water method. Following 5 days of TSD, all experimental animals were investigated for quantitative nicotinamine adenine dinucleotide phosphate-diaphorase (NADPH-d, a co-factor of NOS) histochemistry, neuronal NOS immunohistochemistry and neuronal NOS activity assay. In order to evaluate the endogenous metabolic activity of nodose neurons, cytochrome oxidase (COX) reactivity was further tested. All the above-mentioned reactivities were objectively assessed by computerized image analysis. The clinical significance of the reported changes was demonstrated by alterations of mean arterial blood pressure (MAP). The results indicated that in normal untreated rats, numerous NADPH-d/NOS- and COX-reactive neurons were found in the nodose ganglion (NG). Following TSD, however, both the labelling and staining intensity of NADPH-d/NOS as well as COX reactivity were drastically reduced in the NG compared with normal untreated ganglions. MAP was significantly higher in TSD rats (136+/-4 mmHg) than in normal untreated rats (123+/-2 mmHg). NO may serve as an important sympathoinhibition messenger released by the NG neurons, and decrease of NOS immunoexpression following TSD may account for the decrease in NOS content. In association with the reduction of NOS activity, a defect in NOS expression in the primary cardiovascular afferent neurons would enhance clinical hypertension, which might serve as a potential risk factor in the development of TSD-relevant cardiovascular disturbances.
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PMID:Total sleep deprivation inhibits the neuronal nitric oxide synthase and cytochrome oxidase reactivities in the nodose ganglion of adult rats. 1687 2

Nitric oxide is a diatomic gaseous molecule with unpaired electron in the molecule. Physical properties such as solubility, diffusibility and half-life decide the chemical reactivity of nitric oxide. Nitric oxide is the unstable free radical in vessels, immune system and central nervous system. The reactivity of nitric oxide under physiological and pathological conditions depends upon its concentration and site of production. Nitric oxide is thought to play a role in many pathological situations: septic shock, cardiovascular diseases, arthritis, diabetes, multiple sclerosis, asthma, and hypertension. Nitric oxide synthase is a self-sufficient flavohemoprotein capable of producing nitric oxide from L-arginine by two successive monooxygenation steps. Although the N-terminal heme domain functionally resembles cytochromes P450, no structural similarities exist between cytochrome P450 and nitric oxide synthases heme domains. The C-terminal domain of nitric oxide synthases containing flavin adenine dinucleotide and flavin mononucleotide as cofactors exhibits a high degree of sequence similarity with NADPH-cytocrome P450 reductase. The reductase domains serve as an intermediary for the transfer of electrons from NADPH for the catalytic reaction. The connecting domain between the oxygenase and the reductase domains of nitric oxide synthase isoforms binds calmodulin in the presence of calcium. The binding of calmodulin to all nitric oxide synthase isoforms is obligatory for the production of nitric oxide. At the same time, the presence of one or more phosphorylation sites in nitric oxide synthase puts them among the kinase-mediated signaling pathways. This also means that nitric oxide synthases are regulated indirectly by the events that regulate kinases. This field of research of nitric oxide synthase regulation has become one of the most actively pursued and much has been learned from basic biochemical mechanisms to physiological processes and to medical applications, but many more questions still remain to be answered.
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PMID:[Nitric oxide synthase, typical flavohemoproteins and their complicated enzymology]. 1692 79

Men have higher blood pressure than women, and androgens and oxidative stress have been implicated as playing roles in this sexual dimorphism. The spontaneously hypertensive rat (SHR) is an animal model of both androgen- and oxidative stress-mediated hypertension. Therefore, the present studies were performed to test the hypothesis that androgens cause hypertension in SHR in part by stimulating superoxide production via NADPH oxidase. Castration of male SHR reduced blood pressure by 15% and attenuated both basal and NADPH-stimulated superoxide production in kidney cortical homogenates. Expression of p47(phox) and gp91(phox) but not p22(phox) subunits of NADPH oxidase were significantly lower in kidney cortex from castrated males compared with intact males. Moreover, inhibition of NADPH oxidase with apocynin caused approximately 15 mmHg reduction in blood pressure and reduced basal and NADPH-stimulated superoxide production in intact male SHR, but had no effect on blood pressure or superoxide production in castrated males. These data support the hypothesis that androgens cause oxidative stress and thereby increase blood pressure in male SHR via an NADPH oxidase-dependent mechanism.
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PMID:Impact of androgen-induced oxidative stress on hypertension in male SHR. 1697 73

NADPH oxidases have a distinct cellular localization in the kidney. Reactive oxygen species (ROS) are produced in the kidney by fibroblasts, endothelial cells (EC), vascular smooth muscle cells (VSMC), mesangial cells (MCs), tubular cells, and podocyte cells. All components of the phagocytic NADPH oxidase, as well as the Nox-1 and -4, are expressed in the kidney, with a prominent expression in renal vessels, glomeruli, and podocytes, and cells of the thick ascending limb of the loop of Henle (TAL), macula densa, distal tubules, collecting ducts, and cortical interstitial fibroblasts. NADPH oxidase activity is upregulated by prolonged infusion of angiotensin II (Ang II) or a high salt diet. Since these are major factors underlying the development of hypertension, renal NADPH oxidase may have an important pathophysiological role. Indeed, recent studies with small interference RNAs (siRNAs) targeted to p22( phox ) implicate p22( phox ) in Ang II-induced activation of renal NADPH oxidase and the development of oxidative stress and hypertension, while studies with apocynin implicate activation of p47( phox ) in the development of nephropathy in a rat model of type 1 diabetes mellitus (DM). Experimental studies of the distribution, signaling, and function of NADPH oxidases in the kidney are described.
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PMID:NADPH oxidases in the kidney. 1698 14

Obesity is independently associated with increased cardiovascular risk. However, since established obesity clusters with various cardiovascular risk factors, configuring the metabolic syndrome, the early effects of obesity on vascular function are still poorly understood. The current study was designed to evaluate the effect of early obesity on coronary endothelial function in a new animal model of swine obesity. As to method, juvenile domestic crossbred pigs were randomized to either high-fat/high-calorie diet (HF) or normal chow diet for 12 wk. Coronary microvascular permeability and abdominal wall fat were determined by using electron beam computerized tomography. Epicardial endothelial function and oxidative stress were measured in vitro. Systemic oxidative stress, renin-angiotensin activity, leptin levels, and parameters of insulin sensitivity were evaluated. As a result, HF pigs were characterized by abdominal obesity, hypertension, and elevated plasma lysophosphatidylcholine and leptin in the presence of increased insulin sensitivity. Coronary endothelium-dependent vasorelaxation was reduced in HF pigs and myocardial microvascular permeability increased compared with those values in normal pigs. Systemic redox status in HF pigs was similar to that in normal pigs, whereas the coronary endothelium demonstrated higher content of superoxide anions, nitrotyrosine, and NADPH-oxidase subunits, indicating increased tissue oxidative stress. In conclusion, the current study shows that early obesity is characterized by increased vascular oxidative stress and endothelial dysfunction in association with increased levels of leptin and before the development of insulin resistance and systemic oxidative stress. Vascular dysfunction is therefore an early manifestation of obesity and might contribute to the increased cardiovascular risk, independently of insulin resistance.
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PMID:Early experimental obesity is associated with coronary endothelial dysfunction and oxidative stress. 1701 56

The thioredoxin (TRX) system (TRX, TRX reductase, and NADPH) is a ubiquitous thiol oxidoreductase system that regulates cellular reduction/oxidation (redox) status. The impairment of cell redox state alters multiple cell pathways, which may contribute to the pathogenesis of cardiovascular disorders including hypertension, atherosclerosis, and heart failure. In this manuscript, we review the essential roles that TRX plays by limiting oxidative stress directly via antioxidant effects and indirectly by protein-protein interactions with key signaling molecules such as thioredoxin interacting protein (TXNIP). TRX and its endogenous regulators may represent important future targets to develop clinical therapies for diseases associated with oxidative stress.
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PMID:Thioredoxin in the cardiovascular system. 1702 8

Endothelial NO synthase (eNOS) is the predominant enzyme responsible for vascular NO synthesis. A functional eNOS transfers electrons from NADPH to its heme center, where L-arginine is oxidized to L-citrulline and NO. Common conditions predisposing to atherosclerosis, such as hypertension, hypercholesterolemia, diabetes mellitus and smoking, are associated with enhanced production of reactive oxygen species (ROS) and reduced amounts of bioactive NO in the vessel wall. NADPH oxidases represent major sources of ROS in cardiovascular pathophysiology. NADPH oxidase-derived superoxide avidly interacts with eNOS-derived NO to form peroxynitrite (ONOO(-)), which oxidizes the essential NOS cofactor (6R-)5,6,7,8-tetrahydrobiopterin (BH(4)). As a consequence, oxygen reduction uncouples from NO synthesis, thereby rendering NOS to a superoxide-producing pro-atherosclerotic enzyme. Supplementation with BH(4) corrects eNOS dysfunction in several animal models and in patients. Administration of high local doses of the antioxidant L-ascorbic acid (vitamin C) improves endothelial function, whereas large-scale clinical trials do not support a strong role for oral vitamin C and/or E in reducing cardiovascular disease. Statins, angiotensin-converting enzyme inhibitors and AT1 receptor blockers have the potential of reducing vascular oxidative stress. Finally, novel approaches are being tested to block pathways leading to oxidative stress (e.g. protein kinase C) or to upregulate antioxidant enzymes.
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PMID:Janus-faced role of endothelial NO synthase in vascular disease: uncoupling of oxygen reduction from NO synthesis and its pharmacological reversal. 1713 97

Superoxide anion is produced in human platelets predominantly by Nox2-dependent NADPH oxidases. In vitro experiments have shown that it might play a role in modulating platelet functions. The relationship between platelet superoxide production and aggregation remains poorly defined. Accordingly, we aimed to study superoxide production and aggregation in platelets from subjects with significant cardiovascular risk factors (hypertension, hypercholesterolemia, smoking and diabetes mellitus) and from control individuals. Moreover, we studied the effects of novel polyphenol-rich extracts of Aronia melanocarpa (chokeberry) berries on platelet function in vitro. Superoxide production was significantly increased in patients with cardiovascular risk profile when compared to controls, while platelet aggregation in response to either collagen or thrombin were borderline higher, and did not reach statistical significance. Interestingly, no relationship was observed between platelet aggregation ex vivo and platelet superoxide production in either of studied groups. No correlation was found between endothelial function (measured by FMD) and platelet aggregation ex vivo either. Polyphenol-rich extracts of A. melanocarpa berries caused a significant concentration dependent decrease in superoxide production only in patients with cardiovascular risk factors, while no effect was observed in the control group. A. melanocarpa extracts abolished the difference in superoxide production between risk factor patients and controls. A. melanocarpa extracts exerted significant concentration dependent anti-aggregatory effects in both studied groups, which indicated that these effects may be independent of it's ability to modulate superoxide production. The anti-aggregatory effects of chokeberry extracts were similar irrespective of aggregation inducing agent (collagen or thrombin). Moreover, they appear to be independent of platelet NO release as NOS inhibition by L-NAME did not lead to their abrogation.
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PMID:Effects of novel plant antioxidants on platelet superoxide production and aggregation in atherosclerosis. 1722 85


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