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

High-altitude cerebral edema (HACE) has been tentatively attributed to either cellular ion pump failure from ATP depletion or high cerebral blood flow inducing high capillary pressure. These hypotheses are inadequate because 1) ATP decrease occurs only after anoxia has silenced neuronal activity and 2) prolonged hypercapnic hyperemia generates only minor transcapillary protein leakage localized to the less hyperemic brain regions. In connection with this review of HACE and its causes, three other hypothetical mechanisms that might contribute are presented. 1) Osmotic cell swelling: cellular and mitochondrial osmotic pressure may rise 30 mosmol in ischemia or anoxia (potentially a 7-10% expansion). Smaller rises caused by hypoxia may be significant in the closed calvarium. 2) Focal ischemia: this may result from intracranial hypertension from hyperemia and osmotic swelling. 3) Angiogenesis: cellular hypoxia initially attracts and activates macrophages that express vascular endothelial growth factor and other cytokines, dissolving capillary basement membranes and degrading extracellular matrix, resulting in capillary leakage. In HACE, petechial hemorrhages are seen in the nerve cell layers of the retina, and similar changes have been described throughout the brain. Evidence linking HACE to angiogenesis is that dexamethasone, an effective inhibitor of angiogenesis, has demonstrated unique success in preventing and treating HACE.
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PMID:Hypothetical roles of angiogenesis, osmotic swelling, and ischemia in high-altitude cerebral edema. 759 90

The vascular system undergoes remodeling throughout life, first as primitive vessels form and reorganize, then as the circulation accommodates changing tissue perfusion requirements. Recent investigations that have targeted receptor tyrosine kinases have elucidated fundamental mechanisms that are involved in early formation and restructuring of blood vessels. Distinct receptors for vascular endothelial growth factor, and other receptor tyrosine kinases, appear to regulate very different aspects of early vessel formation including endothelial cell differentiation, tube formation and differentiation of blood vessels into microvasculature versus large vessels. In later development and in the adult circulation, remodeling adapts arteries to chronic changes in hemodynamic function. Furthermore, novel findings of how vascular cells transduce the hemodynamic forces to which they respond have been reported. Force-sensitive gene transcription occurs by previously characterized transcription factors that bind to both established and novel responsive elements in promoter regions of relevant genes. There now is evidence that more than one of these factors can regulate gene expression in response to a single physical force (shear stress). Recent studies have emphasized the role of matrix degradation and cell death, in addition to matrix synthesis and cell proliferation, in arterial remodeling. The importance of cell death and matrix degradation has also been emphasized in the pathogenesis of vascular pathologies. As a result of these and other findings, the role tissue remodeling is being examined closely as a primary factor in the pathogenesis of atherosclerosis, hypertension and restenosis after angioplasty.
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PMID:Cellular and molecular biology of vascular remodeling. 874 2

Endothelial cells are known to secrete various antiproliferative and vasodilating factors, such as nitric oxide and natriuretic peptides. The presence of endothelial dysfunction, well known in hypertensive individuals, potentially results in the development and progression of atherosclerosis. Therefore, it is important to know the factors that might influence endothelial cell growth. We examined the mitogenic actions of hepatocyte growth factor (HGF) on human endothelial and vascular smooth muscle cells. Exogenously added human recombinant HGF stimulated endothelial but not vascular smooth muscle cell growth in a dose-dependent manner. We also compared the mitogenic action of HGF with that of basic fibroblast growth factor and vascular endothelial growth factor. Interestingly, the mitogenic action of HGF on endothelial cells was greater than the actions of basic fibroblast growth factor and vascular endothelial growth factor, whereas basic fibroblast growth factor but not HGF and vascular endothelial growth factor stimulated vascular smooth muscle cell growth. Given the characteristics of HGF as an endothelium-specific growth factor, we evaluated the relationship of circulating HGF and blood pressure in normotensive and hypertensive subjects. Serum HGF concentration has been reported to be elevated in response to organ damage, such as in hepatitis and nephritis, and recent findings show that HGF may play an important role in tissue regeneration. We hypothesized that HGF might contribute to the protection or repair of vascular endothelial cells. If so, serum HGF level might be elevated in response to endothelial cell damage induced by hypertension. To test this hypothesis, we measured serum levels of HGF, lipoprotein(a), plasminogen activator inhibitor-1, tissue plasminogen activator, total cholesterol, and blood pressure in 41 normotensive and hypertensive subjects without liver, kidney, or lung damage. Serum HGF concentration was significantly correlated with systolic pressure (P < .01, r = .43) but not diastolic pressure. Serum HGF concentration in hypertensive subjects was significantly higher than in normotensive subjects. None of the other factors showed any correlation with blood pressure. We have demonstrated that HGF is an endothelium-specific growth factor whose serum concentration is significantly associated with systolic pressure. These results suggest that HGF secretion might be elevated in response to high blood pressure as a counterregulatory system against endothelial dysfunction.
Hypertension 1996 Sep
PMID:A vascular modulator, hepatocyte growth factor, is associated with systolic pressure. 879 25

Increased microvascular permeability, which occurs in conditions such as the adult respiratory distress syndrome and diabetes mellitus, is related to physicochemical alterations in the microvascular barrier. We postulate that, in part, capillary pericytes affect microvascular permeability via production of a vasoactive cytokine, viz, vascular endothelial growth factor (VEGF), also known as vascular permeability factor. The goal of the present study was to evaluate the effects of phorbol myristate acetate (PMA), a substance known to produce nonhydrostatic pulmonary edema in intact animals, on VEGF gene expression in pericyte cultures. Microvascular pericytes were isolated from bovine retinas using magnetic microspheres coated with 3G5 monoclonal antibody. Pericyte identity was confirmed both morphologically and by immunostaining for alpha-smooth muscle actin and 3G5 ganglioside. The cultured pericytes were stimulated with N(omega)-nitro-L-arginine methyl ester (L-NAME, 1 x 10(-4) mmol/L), angiotensin II (1 x 10(-6) mmol/L), and PMA (5 x 10(-8) mmol/L), selected because of their ability to upregulate VEGF mRNA expressions in other cell types. Northern blot analysis was performed using [32P]dCTP labeled human VEGF cDNA (Genentech). Lane-loading differences were normalized using mouse GAPDH control cDNA probe. VEGF mRNA expression was upregulated by PMA (10(-9) to 10(-6) mol/L) in a dose-dependent manner, whereas neither L-NAME nor angiotensin II affected VEGF mRNA expression in pericytes. These results support the hypothesis that pericytes increase permeability of the endothelial barrier through increased VEGF production.
Hypertension 1998 Jan
PMID:Vascular endothelial growth factor mRNA in pericytes is upregulated by phorbol myristate acetate. 945 54

Growth factors produced by a variety of cells act as signalling peptides through specific cell surface receptor pathways. Functions such as cell proliferation, migration and differentiation have been assigned to each of them. Here, we report alterations of platelet-derived growth factor receptor alpha (PDGFR-alpha) and beta (PDGFR-beta) and vascular endothelial growth factor (VEGF) expression patterns in the progressive clinical stages of chronic venous insufficiency (CVI). A total of 30 punch biopsies were taken from patients with CVI, and VEGF and PDGFR were detected by indirect immunofluorescence and immunoperoxidase techniques. PDGFR-alpha and PDGFR-beta expression was strongly increased in endothelial cells of capillaries, pericapillary cells and connective tissue cells in the stroma of the skin of venous eczema and venous leg ulcer patients, and to a smaller extend in the dermis of those with lipodermatosclerosis. VEGF staining showed a similar expression pattern in the progressive CVI stages. However, staining of vessels in particular might simply reflect binding of VEGF, secreted by keratinocytes or fibroblasts, to its receptors. Growth factor and receptor expression in specimens from telangiectases and reticular veins, and from pigmented areas, resembled that of normal skin. We conclude that PDGFR-alpha, PDGFR-beta and VEGF play an important role in mediating inflammation and epithelial hyperproliferation in venous eczema, inducing connective tissue sclerosis in lipodermatosclerosis, and causing the reduced reepithelialization tendency in venous ulcers. We speculate that endothelial proliferation with chronic venous hypertension might be mediated by these growth factors.
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PMID:Increased expression of platelet-derived growth factor receptor alpha and beta and vascular endothelial growth factor in the skin of patients with chronic venous insufficiency. 970 59

Skin damage in the presence of chronic venous disease is partially mediated through leukocytes. The endothelium is activated and exhibits proliferation in the skin. Up-regulation of vascular endothelial growth factor (VEGF) expression in the skin of patients with chronic venous disease has been demonstrated with immunohistologic techniques. Abnormal VEGF expression can have local deleterious effects. The aim of this study was to determine whether patients with chronic venous disease have elevated plasma levels of VEGF. We conducted a prospective study with 30 patients with varicose veins of clinical, etiologic, anatomic, and pathologic class C3 (normal skin, n = 15) and C4 (trophic skin changes, n = 15) and 25 control subjects with no clinical evidence of venous or arterial disease of the lower limb. Blood samples were collected from a foot vein of each subject before and after a period of experimental venous hypertension produced by means of standing. Assay of VEGF protein was performed with a sandwich enzyme-linked immunosorbent assay. Plasma VEGF level was elevated in both groups of patients with venous disease compared with the control group. The median VEGF levels among patients were 81 pg/mL (interquartile range [IQR] 56 to 122) supine and 98 pg/mL (IQR 63 to 153) after standing for 30 minutes. Median VEGF levels among control subjects were 52 pg/mL (IQR 35 to 71) lying supine and 60 pg/mL (IQR 39 to 105) after standing for 30 minutes. Experimental venous hypertension caused a small rise in VEGF levels among the patients but not the control subjects. Further studies are required to determine whether increased VEGF expression contributes to tissue injury in chronic venous disease.
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PMID:Increased plasma vascular endothelial growth factor among patients with chronic venous disease. 973 65

The walls of pulmonary capillaries are extremely thin, and wall stress increases greatly when capillary pressure rises. Alveolar hypoxia causes pulmonary vasoconstriction and hypertension, and if this is uneven, some capillaries may be exposed to high transmural pressure and develop stress failure. There is evidence that increased wall stress causes capillary remodeling. In this study we exposed Madison strain Sprague-Dawley rats to normobaric hypoxia (10% oxygen) for 6 h or 3 d (short-term group), and for 3 d or 10 d (long-term group). Peripheral lung tissue was then collected and messenger RNA (mRNA) levels were determined for extracellular matrix (ECM) proteins and growth factors. Collagen content (hydroxyproline) was also measured. Levels of mRNA for alpha2(IV) procollagen increased sixfold after 6 h of hypoxia and sevenfold after 3 d of hypoxia, and then decreased after 10 d exposure. Levels of mRNA for platelet-derived growth factor-B (PDGF-B) doubled after 6 h of hypoxia but returned to control values after 3 d. mRNA levels for alpha1(I) and alpha1(III) procollagens and fibronectin were increased after 3 d of hypoxia (by seven- to 12-fold, 1.6- to eightfold, and 12-fold, respectively), then decreased toward control values after 10 d. In contrast, neither levels of mRNA for vascular endothelial growth factor (VEGF) nor collagen content changed. These results suggest that alveolar hypoxia causes vascular remodeling in lung parenchyma, and are consistent with capillary wall remodeling in response to increased wall stress.
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PMID:Alveolar hypoxia increases gene expression of extracellular matrix proteins and platelet-derived growth factor-B in lung parenchyma. 984 87

The increase in vascular wall stress imposed by hypertension has been strongly implicated in the pathogenesis of cardiovascular disease. Much of this chronic cyclical mechanical strain is experienced by the vascular smooth (VSM) cells of the vascular media. The cellular mechanisms whereby VSM cells sense and respond to changing mechanical forces are poorly understood. This review focuses on an emerging field of cardiovascular research in which the direct effects of mechanical strain on VSM cells and isolated blood vessels in organ culture have been characterized, in vitro. Cyclical mechanical strain profoundly influences cultured VSM cell orientation, growth and phenotype. Mechanical strain also increases the secretory function of VSM cells leading to increased extracellular matrix protein production. Vasoactive mediators such as angiotensin II potentiate these effects. Mechanical strain increases VSM cell release of platelet derived growth factor, transforming growth factor beta1, fibroblast growth factor and vascular endothelial growth factor, which act in autocrine or paracrine loops to influence VSM and endothelial cell growth and function. Mechanical strain may also activate local tissue renin-angiotensin systems and regulate expression of angiotensin II receptors within the cardiovascular system. The mechanism whereby VSM cells transduce mechanical stimuli into an intracellular signal and biological response, i.e. 'mechanotransduction', is strongly dependent on integrins. Moreover, specific matrix protein:integrin engagements lead to differential VSM cells responses via the selective activation of numerous intracellular signalling pathways including; mitogen-activated protein kinase, focal adhesion kinase and c-Src. The study of vascular mechanotransduction has begun to delineate the complex cellular basis of cardiovascular structural and functional modification in hypertension.
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PMID:Mechanical influences on vascular smooth muscle cell function. 988 78

Human essential hypertension is a complex, multifactorial, quantitative trait under a polygenic control. Several strategies have been developed over the last decade to dissect genetic determinants of hypertension. Of these, the most successful have been studies that identified rare mendelian syndromes in which a single gene mutation causes high blood pressure. The attempts to identify multiple genes, each with a small contribution to the common polygenic form of hypertension, have been less successful. Several laboratories focused their attention on rat models of genetic hypertension, which can be considered as a reductionist paradigm for human disease. Using numerous crosses between hypertensive and normotensive strains, investigators identified several quantitative trait loci (QTL) for blood pressure subphenotypes and for cardiovascular complications such as left ventricular hypertrophy, kidney failure, stroke, and insulin resistance. Furthermore, congenic strains have been produced to confirm the existence of some of these QTL and to narrow down the chromosomal regions of interest. A number of interesting strategies have been developed, including a "speed" congenic strategy perfected by our group in Glasgow. However, the limit of congenic strategy is estimated at 1 cM, which corresponds to 2x10(6) base pairs of DNA and approximately 50 candidate genes. It is envisaged that gene expression profiling with cDNA microarrays might allow a quick progression toward the gene identification within cardiovascular QTL. In parallel experimental effort, several laboratories have been developing gene transfer/therapy strategies with adenoviral or adeno-associated viral vectors used, for example, to overexpress protective vascular genes such as vascular endothelial growth factor or endothelial nitric oxide synthase. It is anticipated that further developments in positional cloning of susceptibility and severity genes in hypertension and its complications will lead to a direct transfer of these discoveries to essential hypertension in humans and will ultimately produce novel targets for local and systemic gene therapy in cardiovascular disease.
Hypertension 2000 Jan
PMID:Genes and hypertension: from gene mapping in experimental models to vascular gene transfer strategies. 1064 93

It has recently been shown that mesangial cells are subjected to multiple forms of mechanical strain (fluid shear, hydrostatic pressure, and triaxial stretch) as a result of forces exerted by the vasculature. Nevertheless, the exact nature and the relative response to these stimuli have not been clarified. Although it is now well established that cyclic stretching of mesangial cells in culture results in the overproduction of extracellular matrix, indicating how intraglomerular hypertension may lead to glomerular scar formation, the contribution of different intracellular signalling mechanisms and extracellular mediators of the response are only now being identified. Recent studies point to a role for high glucose concentrations, transforming growth factor beta and its receptors, vascular endothelial growth factor, and connective tissue growth factor as important mediators, or modifiers of the response to mechanical strain. Although evidence exists for a role for protein kinase C, recent studies also implicate the mitogen-activated protein kinases along with enhanced DNA-binding activity of AP-1 as part of the signalling cascade altering matrix synthesis and cell proliferation in response to stretch. Finally, recent studies examining the effects of oscillating hyperbaric pressure demonstrate similarities, as well as differences, in comparison to those of cyclic stretch.
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PMID:Modelling the effects of vascular stress in mesangial cells. 1065 24


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