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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phagocyte-mediated oxidant damage to vascular endothelium is likely involved in various vasculopathies including atherosclerosis and pulmonary leak syndromes such as adult respiratory distress syndrome. We have shown that heme, a hydrophobic iron chelate, is rapidly incorporated into endothelial cells where, after as little as 1 h, it markedly aggravates cytotoxicity engendered by polymorphonuclear leukocyte oxidants or hydrogen peroxide (H2O2). In contrast, however, if cultured endothelial cells are briefly pulsed with heme and then allowed to incubate for a prolonged period (16 h), the cells become highly resistant to oxidant-mediated injury and to the accumulation of endothelial lipid peroxidation products. This protection is associated with the induction within 4 h of mRNAs for both heme oxygenase and ferritin. After 16 h heme oxygenase and ferritin have increased approximately 50-fold and 10-fold, respectively. Differential induction of these proteins determined that ferritin is probably the ultimate cytoprotectant. Ferritin inhibits oxidant-mediated cytolysis in direct relation to its intracellular concentration. Apoferritin, when added to cultured endothelial cells, is taken up in a dose-responsive manner and appears as cytoplasmic granules by immunofluorescence; in a similar dose-responsive manner, added apoferritin protects endothelial cells from oxidant-mediated cytolysis. Conversely, a site-directed mutant of ferritin (heavy chain Glu62----Lys; His65----Gly) which lacks ferroxidase activity and is deficient in iron sequestering capacity, is completely ineffectual as a cytoprotectant. We conclude that endothelium and perhaps other cell types may be protected from oxidant damage through the iron sequestrant, ferritin.
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PMID:Ferritin: a cytoprotective antioxidant strategem of endothelium. 151 45

Iron-derived reactive oxygen species play an important role in the pathogenesis of various vascular disorders including vasculitis, atherosclerosis, and capillary leak syndromes such as the adult respiratory distress syndrome (ARDS). We have suggested that acute incorporation of the heme moiety of hemoglobin released from red blood cells into endothelium could provide catalytically active iron to the vasculature. Adaptation to chronic heme stress involves the induction of heme oxygenase and ferritin; the latter provides cytoprotection against free radicals in vitro. The present studies examine the bioavailability of heme, derived from hemoglobin, to induce heme oxygenase and ferritin in rat lungs in vivo. Intravenous injection of methemoglobin, but not oxyhemoglobin, increases total lung heme oxygenase mRNA approximately fivefold after 16 h. Accompanying this mRNA induction, expression of total lung heme oxygenase enzyme activity is also markedly enhanced. In situ hybridization for heme oxygenase reveals mRNA accumulation in the lung microvascular endothelium, implying incorporation of heme into endothelial cells. Similarly, methemoglobin significantly increases the ferritin protein content of rat lungs and in parallel, ferritin light-chain mRNA increases approximately 1.6-fold, whereas heavy-chain mRNA is upregulated by approximately 1.9-fold. Immunoreactive ferritin is present in lung microvascular endothelium after methemoglobin treatment, suggesting incorporation of heme iron into pulmonary vasculature. Subcutaneous injection of Sn-protoporphyrin IX, a competitive inhibitor of heme oxygenase, does not affect methemoglobin-induced ferritin synthesis in lungs. We speculate that methemoglobin, which might be generated by activated leukocytes in ARDS associated with disseminated interavascular coagulation, can provide heme iron to lung microvascular endothelium to induce heme oxygenase and ferritin.
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PMID:Endothelial cell heme oxygenase and ferritin induction in rat lung by hemoglobin in vivo. 786 52

Heme proteins transport oxygen and facilitate redox reactions. Heme, however, may be dangerous, especially when free in biologic systems. For example, iron released from hemoglobin-derived heme can catalyze oxidative injury to neuronal cell membranes and may be a factor in post-traumatic damage to the central nervous system. We have shown that heme catalyzes the oxidation of low density lipoproteins which can damage vascular endothelial cells. The endothelium is susceptible to damage by oxidants generated by activated phagocytes, and this has been invoked as an important mechanism in a number of pathologies including the Adulte Respiratory Distress Syndrome (ARDS), acute tubular necrosis, reperfusion injury and atherosclerosis. Because of its highly hydrophobic nature, heme readily intercalates into endothelial membranes and potentiates oxidant-mediated damage. This injury is dependent on the iron content of heme and is completely blocked when concomitant hemopexin is added. Ferrohemoglobin, when added to cultured endothelial cells, is without deleterious effects, but if oxidized to ferrihemoglobin (methemoglobin), it greatly amplifies oxidant damage. Methemoglobin, but not ferrohemoglobin, releases its hemes which can then be incorporated into endothelial cells. Cultured endothelial cells, when exposed to methemoglobin but not ferrohemoglobin, cytochrome c or metmyoglobin, potentiate this oxidant injury. Stabilization of the methemoglobin by cyanide, haptoglobin or capture of the heme by hemopexin abrogates this effect. Paradoxically, more prolonged exposure of endothelium to heme or methemoglobin renders them remarkably resistant to oxidant challenge. Endothelium defends itself from heme by induction of the heme degrading enzyme heme oxygenase and the concomitant production of large amounts of the iron binding protein ferritin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Heme and the vasculature: an oxidative hazard that induces antioxidant defenses in the endothelium. 808 43

Iron-derived reactive oxygen species are implicated in the pathogenesis of various vascular disorders including atherosclerosis, vasculitis, and reperfusion injury. The present studies examine whether heme, when liganded to physiologically relevant proteins as in hemoglobin, can provide potentially damaging iron to intact endothelium. We demonstrate that reduced ferrohemoglobin, while relatively innocuous to cultured endothelial cells, when oxidized to ferrihemoglobin (methemoglobin), greatly amplifies oxidant (H2O2)-mediated endothelial-cell injury. Drawing upon our previous observation that free heme similarly primes endothelium for oxidant damage, we posited that methemoglobin, but not ferrohemoglobin, releases its hemes that can then be incorporated into endothelial cells. In support, cultured endothelial cells exposed to methemoglobin--in contrast to exposure to ferrohemoglobin, cytochrome c, or metmyoglobin--rapidly increased their heme oxygenase mRNA and enzyme activity, thereby supporting heme uptake; ferritin production was also markedly increased after such exposure, thus attesting to eventual incorporation of Fe. These cellular methemoglobin effects were inhibited by the heme-scavenging protein hemopexin and by haptoglobin or cyanide, agents that strengthen the liganding between heme and globin. If the endothelium is exposed to methemoglobin for a more prolonged period (16 hr), it accumulates large amounts of ferritin; concomitantly, and presumably associated with iron sequestration by this protein, the endothelium converts from hypersusceptible to hyperresistant to oxidative damage. We conclude that when oxidation of hemoglobin facilitates release of its heme groups, catalytically active iron is provided to neighboring tissue environments. The effect of this relinquished heme on the vasculature is determined both by extracellular factors--i.e., plasma proteins, such as haptoglobin and hemopexin--as well as intracellular factors, including heme oxygenase and ferritin. Acutely, if both extra- and intracellular defenses are overwhelmed, cellular toxicity arises; chronically, when ferritin is induced, resistance to oxidative injury may supervene.
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PMID:Endothelial-cell heme uptake from heme proteins: induction of sensitization and desensitization to oxidant damage. 841 93

Hypoxia has profound effects on blood vessel tone. Acute hypoxia causes pulmonary vasoconstriction and chronic hypoxia causes smooth muscle cell replication and extracellular matrix accumulation resulting in vessel wall remodeling. The cellular responses to hypoxia involve complex cell-cell interactions mediated by the release of growth factors, cytokines and biological messengers. We have reported that hypoxia increases the expression of a number of genes encoding vascular cell mitogens produced by endothelial cells: platelet-derived growth factor B (PDGF-B); endothelin-1 (ET-1); and vascular endothelial growth factor (VEGF). A 28-bp enhancer in the 5' upstream region of the VEGF gene mediates the expression of VEGF by endothelial cells under conditions of hypoxia. Hypoxia, however, has opposite effects on the vasodilator nitric oxide (NO); hypoxia suppresses both the transcriptional rate of the endothelial nitric oxide synthase gene and the stability of its mRNA. These endothelial-dependent processes would lead to vessel wall remodeling characteristic of a number of diseases from atherosclerosis to pulmonary hypertension. The smooth muscle cell also responds to hypoxia. It increases the transcriptional rate of the heme oxygenase gene-1 responsible for the breakdown of heme to carbon monoxide (CO) and biliverdin. CO is a vasodilator with properties similar to the well-studied molecule NO. CO suppresses the production of ET-1 and PDGF-B by endothelial cells. The regulated production of NO and CO under hypoxia, therefore, results in complex feedback loop interactions leading to altered smooth muscle cell growth in an autocrine and paracrine manner.
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PMID:Mechanisms by which oxygen regulates gene expression and cell-cell interaction in the vasculature. 902 18

Atherosclerotic lesions are found opposite vascular flow dividers at sites of low shear stress and oscillatory flow. Since endothelial proinflammatory genes prominent in lesions are regulated by oxidation-sensitive transcriptional control mechanisms, we examined the redox state of cultured human umbilical vein endothelial cells after either oscillatory or steady laminar fluid shear stress. Endothelial oxidative stress was assessed by measuring activity of the superoxide (O2.- )-producing NADH oxidase (a major source of reactive oxygen species in vascular cells), intracellular O2.- levels, induction of the redox-sensitive gene heme oxygenase-1 (HO-1), and abundance of Cu/Zn superoxide dismutase (Cu/Zn SOD), an antioxidant defense enzyme whose level of expression adapts to changes in oxidative stress. When cells were exposed to oscillatory shear (+/-5 dyne/cm2, 1 Hz) for 1, 5, and 24 hours, NADH oxidase activity and the amount of HO-1 progressively increased up to 174+/-16% (P<0.05) and 505+/-111% (P<0.05) versus static conditions, respectively, whereas levels of Cu/Zn SOD remained unchanged. This upregulation of HO-1 was completely blocked by the antioxidant N-acetylcysteine (NAC, 20 mmol/L). In contrast, steady laminar shear (5 dyne/cm2) induced NADH oxidase activity and NAC-sensitive HO-1 mRNA expression only at 1 and 5 hours, a transient response that returned toward baseline at 24 hours. Levels of Cu/Zn SOD mRNA and protein were increased after 24 hours of steady laminar shear. Furthermore, intracellular O2.-, as measured by dihydroethidium fluorescence, was higher in cells exposed to oscillatory than to laminar shear. These data are consistent with the hypothesis that continuous oscillatory shear causes a sustained activation of pro-oxidant processes resulting in redox-sensitive gene expression in human endothelial cells. Steady laminar shear stress initially activates these processes but appears to induce compensatory antioxidant defenses. We speculate that differences in endothelial redox state, orchestrated by different regimens of shear stress, may contribute to the focal nature of atherosclerosis.
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PMID:Oscillatory and steady laminar shear stress differentially affect human endothelial redox state: role of a superoxide-producing NADH oxidase. 962 62

Atherogenic lipoproteins such as oxidized LDL are implicated in the pathogenesis of atherosclerosis and renal disease. Fatty acid hydroperoxides and phospholipids such as linoleyl hydroperoxide (LAox or 13-HPODE) and lysophosphatidylcholine (lyso-PC), abundant components of oxidized LDL, mediate the effects of atherogenic lipids. Oxidized LDL has been shown to induce heme oxygenase-1 (HO-1), a microsomal enzyme that is involved in heme detoxification and is a major endogenous source of carbon monoxide. HO-1 is also induced by many other stimuli that shift cellular redox. To identify the constituents and molecular mechanisms of oxidized LDL-mediated HO-1 induction, human renal epithelial cells and aortic endothelial cells were exposed to LAox and lyso-PC. Exposure to LAox (25 microM) showed an approximately 16-fold induction of HO-1 mRNA, whereas exposure to lyso-PC (25 microM) showed only an approximate 2.6-fold increase. Treatment with actinomycin-D (4 microM), a transcriptional inhibitor, as well as nuclear run-on assays, demonstrated that LAox-mediated HO-1 gene induction is dependent on de novo transcription. Cycloheximide did not affect LAox-mediated HO-1 mRNA induction, suggesting that new protein synthesis is not required for transcriptional induction. Transfection of a human HO-1 promoter-reporter gene construct showed that LAox upregulation of HO-1 occurs via mechanisms different from those of known inducers, heme and cadmium. These studies are the first demonstration that LAox induces HO-1 by transcriptional mechanisms and may have implications in the pathogenesis of cell injury in atherosclerosis and progressive renal disease.
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PMID:Linoleyl hydroperoxide transcriptionally upregulates heme oxygenase-1 gene expression in human renal epithelial and aortic endothelial cells. 980 84

Atherosclerosis is a major contributor to cardiovascular disease, and genetic disorders of lipoprotein metabolism are recognized risk factors in atherogenesis. The gaseous monoxides nitric oxide (NO) and carbon monoxide (CO), generated within the blood vessel wall, have been identified as important cellular messengers involved in the regulation of vascular smooth muscle tone. Microsomal heme oxygenases degrade heme to biliverdin and CO, and the cytosolic enzyme biliverdin reductase then catalyzes reduction of biliverdin to bilirubin, both powerful chain-breaking antioxidants. Two principal isozymes of heme oxygenase have been identified, a constitutive isoform HO-2 (M(r) approximately 34,000) and an inducible isoform HO-1 (M(r) approximately 32,000), which is expressed at a low basal level in vascular endothelial and smooth muscle cells and is induced by heavy metals, oxidative stress, inflammatory mediators and oxidized low density lipoproteins. Although NO and CO modulate intracellular cGMP levels, platelet aggregation and smooth muscle relaxation, CO has a much lower affinity for soluble guanylyl cyclase than NO. Decreased production or sensitivity to NO in atherosclerosis may be compensated for by an induction of HO-1, with bilirubin acting as a cellular antioxidant and CO as a vasodilator. This review examines the evidence that oxidized low density lipoproteins (LDL), hypoxia and pro-inflammatory cytokines induce HO-1 expression and activity in vascular endothelial and smooth muscle cells, and evaluates the anti-atherogenic potential of the heme oxygenase signalling pathway.
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PMID:Heme oxygenase-carbon monoxide signalling pathway in atherosclerosis: anti-atherogenic actions of bilirubin and carbon monoxide? 1034 38

Elevated levels of lipid peroxidation and increased formation of reactive oxygen species within the vascular wall in atherosclerosis can overwhelm cellular antioxidant defence mechanisms. Accumulating evidence implicates oxidatively modified low density lipoproteins (LDL) in vascular dysfunction in atherosclerosis and oxidized LDL have been localized with in atherosclerotic lesions. We here report that human oxidatively modified LDL induce expression of 'antioxidant-like' stress proteins in vascular cells, involving increases in the activity of L-cystine transport, glutathione synthesis, heme oxygenase-1 and the murine stress protein MSP23. Moreover, treatment of human arterial smooth muscle cells with the dietary antioxidant vitamin C markedly attenuates adaptive increases in endogenous antioxidant gene expression and affords protection against smooth muscle cell apoptosis induced by moderately oxidized LDL. As vascular cell death is a key feature of atherosclerotic lesions and may contribute to the plaque 'necrotic' core, cap rupture and thrombosis, our findings suggest that the cytoprotective actions of vitamin C could limit plaque instability in advanced atherosclerosis.
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PMID:Induction of antioxidant stress proteins in vascular endothelial and smooth muscle cells: protective action of vitamin C against atherogenic lipoproteins. 1051 35

Macrophages produce reactive oxygen species such as O2-, H2O2 and *OH that contribute to the pathogenesis of diseases such as inflammation and atherosclerosis. The cells have multiple defense systems against those reactive oxygen species, and we describe here such an oxidative stress-inducible defense system. Upon exposure to reactive oxygen species and electrophilic agents, murine peritoneal macrophages induce stress proteins to protect themselves. Using differential screening, we cloned two novel proteins designated MSP23 and A170 that are induced in the cells by low levels of reactive oxygen species, electrophilic agents and other oxidative stress agents. MSP23 is murine peroxiredoxin I having a thioredoxin peroxidase activity and A170 is known as an ubiquitin- and PKC xi-binding protein. In addition to these two proteins, heme oxygenase-1 (HO-1) and cystine transport activity are also induced in the cells under oxidative stress conditions. Using nrf2-deficient macrophages, we found that transcription factor Nrf2, which is known to interact with antioxidant responsive elements (AREs) in the regulatory sequences of the genes, plays an important role in the oxidative stress-inducible response in the cells.
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PMID:Oxidative stress-inducible proteins in macrophages. 1051 40


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