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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxidative stress occurs when the production of reactive oxygen species (ROS) exceeds the capacity of the cell to detoxify these potentially injurious oxidants using endogenous antioxidant defense systems. Conditions associated with oxidative stress include ischemia/reperfusion, hypercholesterolemia, diabetes, and hypertension. The adhesion of circulating blood cells (leukocytes, platelets) to vascular endothelium is a key element of the pro-inflammatory and prothrombogenic phenotype assumed by the vasculature in these and other disease states that are associated with an oxidative stress. There is a growing body of evidence that links the blood cell endothelial cell interactions in these conditions to the enhanced production of ROS. Potential enzymatic sources of ROS within the microcirculation include xanthine oxidase, NAD(P)H oxidase, and nitric oxide synthase. ROS can promote a pro-inflammatory/prothrombogenic phenotype within the microvasculature by a variety of mechanisms, including the inactivation of nitric oxide, the activation of redox-sensitive transcription factors (e.g., nuclear factor-kappaB) that govern the expression of endothelial cell adhesion molecules (e.g., P-selectin), and the activation of enzymes (e.g., phospholipase A(2)) that produce leukocyte-stimulating inflammatory mediators (e.g., platelet-activating factor). The extensively documented ability of different oxidant-ablating interventions to attenuate blood cell endothelial cell interactions underscores the importance of ROS in mediating the dysfunctional microvascular responses to oxidative stress.
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PMID:Oxidative stress promotes blood cell-endothelial cell interactions in the microcirculation. 1266 63

Recently, the binding of renin and prorenin to cellular receptors with the subsequent generation of second messengers and the production of physiological effects has been demonstrated. In addition, the internalization of prorenin by target cells has been associated with increased cellular synthesis of angiotensin and cardiac pathology. Also, a renin transcript lacking the sequences encoding a secretory signal has been reported, and this transcript appears to produce a renin that acts in the cell that synthesized it. Some years ago, we coined the term intracrine for a peptide hormone or factor that acts in the intracellular space either after internalization or retention in its cell of synthesis. Thus defined, a wide variety of peptides display intracrine functionality, including hormones, growth factors, transcription factors, and enzymes. For example, considerable evidence indicates that angiotensin II is an intracrine. Also, general principles of intracrine functionality have been developed. Thus, recent evidence demonstrates that the prorenin/renin molecule is an intracrine enzyme. Here, the actions of intracrine enzymes (angiogenin, phosphoglucose isomerase, phospholipase A2, granzyme A and B, thioredoxin, platelet-derived endothelial growth factor, and serine protease inhibitors) are reviewed. The relation of prorenin/renin to other intracrine enzymes, and to intracrines in general, is discussed.
Hypertension 2003 Aug
PMID:Intracellular renin and the nature of intracrine enzymes. 1286 Aug 32

Traditional risk factors for atherosclerosis are well known and their control decreases importantly the appearance of the disease. These factors are the genetic charge, dyslipidemia, smoking, systemic arterial hypertension, diabetes, obesity, gender, age, stress, estrogen levels in women, and life style. However, in the last decade, new risk factors have been identified especially for coronary and cerebrovascular atherosclerosis. Among these factors, the inflammatory process has been pointed out in which acute stage reactants participate, such as C-reactive protein, leukocyte count, globular sedimentation, multiple cytokines, alpha tumor necrosis factor, vascular and cellular adhesion molecules, some metalloproteinases, pregnancy-associated plasma protein A, lipoprotein-associated phospholipase A2, angiotensin II, and very probably infection. This article discusses the mechanism by which these markers participate in the atherosclerotic process and their value as predictors of future coronary events, as well as to what extent current therapeutics can contribute to decrease these events and to improve patient care.
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PMID:[Inflammation in atherosclerosis]. 1296 66

Markers of inflammation are predictive of cardiovascular events but their association with atherosclerotic burden remains poorly defined. We hypothesized that markers of inflammation, including C-reactive protein (CRP), white blood cell (WBC) count, and lipoprotein-associated phospholipase A2 (Lp-PLA2), would be associated with the ankle-brachial index (ABI), a marker of atherosclerotic burden. Subjects were 247 patients referred for lower extremity arterial evaluation to the non-invasive vascular laboratory excluding those with active infection or lower extremity revascularization within the previous year. ABI was measured at two sites in both legs and the lowest of four measurements was used in the analyses. CRP was measured by a high-sensitivity immunoturbidimetric assay and Lp-PLA2 was measured by ELISA. The mean patient age was 68+/-11 years, and 54% were men. Mean ABI was 0.84+/-0.31 and 49% had an ABI < 0.9. Age, hypertension, fasting plasma glucose, and 'ever' smoking were independently associated with the ABI. Spearman correlation coefficients of inflammatory markers with the ABI were: CRP (r = -0.15, p= 0.02), WBC count (r = -0.27, p = 0.001), and Lp-PLA2 (r = -0.09, p = 0.21). In a multiple regression model that included conventional risk factors and statin use, CRP and WBC count were no longer significantly associated with ABI, whereas Lp-PLA2 was a borderline-significant predictor of lower ABI (p = 0.05). These data indicate that CRP and WBC count are not independently associated with ABI, a marker of atherosclerotic burden in subjects referred for non-invasive lower extremity arterial evaluation. The association of Lp-PLA2 with ABI merits further study.
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PMID:Relation of markers of inflammation (C-reactive protein, white blood cell count, and lipoprotein-associated phospholipase A2) to the ankle-brachial index. 1567 80

Radiation-induced renal injury is characterized by proteinuria, hypertension, and progressive decline in renal function. We have previously shown that in vivo or in vitro irradiation of glomeruli with a single dose of radiation (9.5 Gy) increases glomerular albumin permeability (P(alb)) within 1 hr. The current studies tested the hypothesis that this early radiation-induced increase in P(alb) is caused by the release of arachidonic acid and by the generation of specific arachidonic acid metabolites. Glomeruli obtained from WAG/Rij/MCW rats and cultured rat glomerular epithelial and mesangial cells were studied after irradiation (9.5 Gy, single dose). Arachidonic acid release and eicosanoid synthesis by glomeruli or cultured glomerular cells were measured after irradiation, and the effect of inhibitors of phospholipase A2 (PLA2) and cyclooxygenase (COX) on the irradiation-induced increase in P(alb) was assessed. Arachidonic acid release was demonstrated within 10 mins of irradiation of isolated glomeruli and monolayer cultures of glomerular epithelial and mesangial cells. Prostaglandin F(2alpha) (PGF(2alpha)) and PGE2 release was increased after irradiation of isolated glomeruli. Blocking arachidonic acid release or COX activity before irradiation completely prevented the increase in P(alb). COX inhibition immediately after irradiation also diminished the radiation-induced increase in P(alb). We conclude that arachidonic acid and its COX metabolites play an essential role in the early cellular changes that lead to the radiation-induced increase in P(alb). Understanding of the early epigenetic effects of irradiation may lead to new intervention strategies against radiation-induced injury of normal tissues.
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PMID:Arachidonic acid metabolites mediate the radiation-induced increase in glomerular albumin permeability. 1638 Jun 50

The development of fibrosis in the chronically hypertensive heart is associated with infiltration of inflammatory cells and cardiac hypertrophy. In this study, an inhibitor of the proinflammatory enzyme, group IIA human secretory phospholipase A2 (sPLA2-IIA), has been found to prevent collagen deposition as an important component of cardiovascular remodeling in a rat model of developing chronic hypertension. Daily treatment of young male spontaneously hypertensive rats (SHR) with an sPLA2-IIA inhibitor (KH064, 5-(4-benzyloxyphenyl)-4S-(phenyl-heptanoylamino)-pentanoic acid, 5 mg/kg/day p.o.) prevented increases in the content of perivascular (SHR 20.6 +/- 0.9%, n = 5; SHR+KH064 14.0 +/- 1.2%, n = 5) and interstitial (SHR 7.9 +/- 0.3%, n = 6; SHR+KH064 5.4 +/- 0.7%, n = 6) collagen in the left ventricle of rat hearts, but did not affect numbers of infiltrating monocytes/macrophages, left ventricular hypertrophy (SHR 2.88 +/- 0.08, n = 12; SHR+KH064 3.09 +/- 0.08 mg/g body weight, n = 9), increased systolic blood pressure, or thoracic aortic responses. This selective antifibrotic activity suggests that sPLA2-IIA may have an important but specific role in cardiac fibrosis, and that its inhibitors could be useful in dissecting molecular pathways leading to fibrotic conditions.
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PMID:Antifibrotic activity of an inhibitor of group IIA secretory phospholipase A2 in young spontaneously hypertensive rats. 1670 61

Rgs2 (regulator of G-protein signaling-2)-deficient mice exhibit severe hypertension, and genetic variations of RGS2 occur in hypertensive patients. RGS2 mRNA up-regulation by angiotensin II (Ang II) in vascular smooth muscle cells (VSMC) is a potentially important negative feedback mechanism in blood pressure homeostasis, but how it occurs is unknown. Here we demonstrate that group VIA phospholipase A2 (iPLA2beta) plays a pivotal role in Ang II-induced RGS2 mRNA up-regulation in VSMC by three independent approaches, including pharmacologic inhibition with a bromoenol lactone suicide substrate, suppression of iPLA2beta expression with antisense oligonucleotides, and genetic deletion in iPLA2beta-null mice. Selective inhibition of iPLA2beta by each of these approaches abolishes Ang II-induced RGS2 mRNA up-regulation. Furthermore, using adenovirus-mediated gene transfer, we demonstrate that restoration of iPLA2beta-expression in iPLA2beta-null VSMC reconstitutes the ability of Ang II to up-regulate RGS2 mRNA expression. In contrast, Ang II-induced vasodilator-stimulated phosphoprotein phosphorylation and Ang II receptor expression are unaffected. Moreover, in wild-type but not iPLA2beta-null VSMC, Ang II stimulates iPLA2 enzymatic activity significantly. Both arachidonic acid and lysophosphatidylcholine, products of iPLA2beta action, induce RGS2 mRNA up-regulation. Inhibition of lipoxygenases, particularly 15-lipoxygenase, and cyclooxygenases, but not cytochrome P450-dependent epoxygenases inhibits Ang II- or AA-induced RGS2 mRNA expression. Moreover, RGS2 protein expression is also up-regulated by Ang II, and this is attenuated by bromoenol lactone. Disruption of the Ang II/iPLA2beta/RGS2 feedback pathway in iPLA2beta-null cells potentiates Ang II-induced vasodilator-stimulated phosphoprotein and Akt phosphorylation in a time-dependent manner. Collectively, our results demonstrate that iPLA2beta participates in Ang II-induced transcriptional up-regulation of RGS2 in VSMC.
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PMID:Group VIA phospholipase A2 (iPLA2beta) participates in angiotensin II-induced transcriptional up-regulation of regulator of g-protein signaling-2 in vascular smooth muscle cells. 1761 34

Few studies have investigated the role of elevated lipoprotein-associated phospholipase A2 (Lp-PLA(2)) with stroke risk, and those that have are based on small numbers of strokes. No study has evaluated the effect of hormone therapy use on the association of Lp-PLA(2) and stroke. We assessed the relationship between Lp-PLA(2) and the risk of incident ischemic stroke in 929 stroke patients and 935 control subjects in the Hormones and Biomarkers Predicting Stroke Study, a nested case-control study from the Women's Health Initiative Observational Study. Mean (SD) levels of Lp-PLA(2) were significantly higher among case subjects (309.0 [97.1]) than control subjects (296.3 [87.3]; P<0.01). Odds ratio for ischemic stroke for the highest quartile of Lp-PLA(2), compared with lowest, controlling for multiple covariates, was 1.08 (95% CI: 0.75 to 1.55). However, among 1137 nonusers of hormone therapy at baseline, the corresponding odds ratio was 1.55 (95% CI: 1.05 to 2.28),whereas there was no significant association among 737 hormone users (odds ratio: 0.70; 95% CI: 0.42 to 1.17; P for interaction=0.055). Moreover, among nonhormone users, women with high C-reactive protein and high Lp-PLA2 had more than twice the risk of stroke (odds ratio: 2.26; 95% CI: 1.55 to 3.35) compared with women low levels in both biomarkers. Furthermore, different stroke cases were identified as high risk by Lp-PLA(2) rather than by C-reactive protein. Lp-PLA(2) was associated with incident ischemic stroke independently of C-reactive protein and traditional cardiovascular risk factors among nonusers of hormone therapy with highest risk in those who had both high C-reactive protein and high Lp-PLA(2).
Hypertension 2008 Apr
PMID:Lipoprotein-associated phospholipase A2, hormone use, and the risk of ischemic stroke in postmenopausal women. 1825 35

Causal relationship between sodium and hypertension has been proposed and various changes in Na+,K+-ATPase (sodium pump) activity have been described in established primary hypertension. A number of direct vascular effects of estradiol have been reported, including its impact on the regulation of sodium pump activity and vasomotor tone. The effects of estradiol involve the activation of multiple signaling cascades, including phosphatydil inositol-3 kinase (PI3K) and p42/44 mitogen-activated protein kinase (p42/44(MAPK)). In addition, some of the effects of estradiol have been linked to activity of cytosolic phospholipase A(2) (cPLA(2)). One possible cardioprotective mechanism of estradiol involves of the interaction between estradiol and the rennin-angiotensin system (RAS). Elevated circulating and tissue levels of angiotensin II (Ang II) have been implicated in the development of hypertension and heart failure. The aim of our investigation was to elucidate the signaling mechanisms employed by estradiol and Ang II in mediating sodium pump, in vascular smooth muscle cells (VSMC). The aim of our investigation was to elucidate the signaling mechanisms employed by estradiol and Ang II in mediating sodium pump activity/expression in VSMC, with particular emphasis on PI3K/cPLA(2)/p42/44(MAPK) signaling pathways. Our primary hypothesis is that estradiol stimulates sodium pump activity/expression in VSMC via PI3K/cPLA(2)/p42/44(MAPK) dependent mechanism and, that impaired estradiol-stimulated sodium pump activity/expression in hypertensive rodent models (i.e. SHR), Ang II-mediated vascular impairment of estradiol is related to a decrease ability of estradiol to stimulate the PI3K/cPLA(2)/p42/44(MAPK) signaling pathways. An important corollary to this hypothesis is that in hypertensive state (i.e. SHR rats) the decreasing in ACE enzyme activity and/or AT1 receptor expression caused by administration of estradiol is accompanying with abrogated ability of Ang II to decrease IRS-1/PI3K association, and consequent PI3K/cPLA(2)/p42/44(MAPK) activity and associated sodium pump activity/expression. A clear characterization of how Ang II attenuates estradiol signaling may lead to a better understanding of the molecular mechanism(s) underlying pathophysiological conditions such as hypertension and to understanding how certain pathophysiological situations affect sodium pump activity/expression in VSMC.
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PMID:Hypothetical mechanism of sodium pump regulation by estradiol under primary hypertension. 1830 83

In recent years, atherosclerosis has become recognized as an inflammatory disease whose activity can be assessed by circulating biomarkers. Along with C-reactive protein (CRP), lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) may now be considered as a biomarker with sufficient accumulated evidence to support its application in clinical practice. Lp-PLA(2) is especially appealing because of its vascular specificity, which directly derives from its role in plaque pathophysiology. This article reviews the highlights of the >25 prospective epidemiologic studies now published on Lp-PLA(2) as a risk marker in primary or secondary prevention. These trials demonstrate generally consistent correlations between elevated Lp-PLA(2) levels and the increased risk for cardiovascular events, even after multivariable adjustment for traditional risk factors, with roughly a doubling of risk associated with upper quantile levels. Furthermore, Lp-PLA(2) as a risk predictor has been shown to be independent of and complementary to high-sensitivity CRP. These study results combined with recommendations from the American Heart Association/Centers for Disease Control (AHA/CDC) and the National Cholesterol Education Program III (NCEP III) suggest that Lp-PLA(2) might best be used in current clinical practice to refine risk prediction in those at intermediate cardiovascular risk. An increasingly prevalent group at intermediate risk shown to benefit from Lp-PLA(2) risk modification is the population with the cardiovascular metabolic syndrome, clinically identified as overweight patients with features of mixed dyslipidemia, dysglycemia, and hypertension. An additional application supported by these studies is further risk stratification of high- (often secondary-) risk patients into a group at very high risk, for whom a more aggressive target for low-density lipoprotein of <70 mg/dL (1 mg/dL = 0.02586 mmol/L) is now recommended as a reasonable therapeutic goal.
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PMID:Lipoprotein-associated phospholipase A2: an independent predictor of coronary artery disease events in primary and secondary prevention. 1854 68


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