Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heme oxygenase 1 (HO-1), a stress response protein, is highly induced in response to various agents causing oxidative stress including ultraviolet irradiation, sodium arsenite, hyperoxia, and glutathione depletors. We recently characterized the induction of HO-1 gene expression by nitric oxide (NO) and postulated that the addition of an antioxidant, such as pyrrolidine dithiocarbamate (PDTC), would attenuate HO-1 induction in response to NO. Surprisingly, PDTC was a very potent inducer of HO-1 gene expression, causing increases in the steady-state level of HO-1 mRNA in rat aortic vascular smooth muscle (aVSM) cells in a time- and concentration-dependent manner. PDTC-induced HO-1 gene expression correlated with a rise in protein levels and was dependent on both increased gene transcription and mRNA stability. Deletional analyses of the proximal promoter and the entire 5' distal upstream region of the HO-1 gene (11 kbp) were performed including the two 5' distal enhancers, SX2 and AB1, located 4 kbp and 10 kbp upstream of the transcription site, respectively. Plasmid vectors containing various fragments of this region were linked to a chloramphenicol acetyl transferase (CAT) reporter gene, stably transfected into RAW 264.7 cells, and transfectants were assayed for CAT activity after treatment with PDTC. We show that the AB1 distal enhancer plays an important role in mediating PDTC-induced HO-1 gene transcription. Mutational analyses of this enhancer showed that the activator protein 1 (AP-1) regulatory element is crucial for PDTC-induced HO-1 gene transcription. Electrophoretic mobility shift assays supported this data, demonstrating increased AP-1 DNA binding activity after PDTC treatment. Taken together, our data demonstrate that the antioxidant PDTC enhances HO-1 gene transcription and that the induction appears to be mediated by AP-1 activation of regulatory elements specific to the distal enhancer AB1.
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PMID:Transcriptional regulation of the heme oxygenase 1 gene by pyrrolidine dithiocarbamate. 983 57

Rat fetal lung cells (RFL-6) were transiently transfected with a full-length rat heme oxygenase (HO)-1 cDNA construct and then exposed to hyperoxia (95% O2-5% CO2) for 48 h. Total HO activity and HO-1 protein were measured as well as cell viability, lactate dehydrogenase (LDH) release, protein oxidation, lipid peroxidation, and total glutathione to measure oxidative injury. HO-1 overexpression resulted in increased total HO activity (2-fold), increased HO-1 protein (1.5-fold), and increased cell proliferation. Immunohistochemistry revealed perinuclear HO-1 localization, followed by migration to the nucleus by day 3. Decreased cell death, protein oxidation, and lipid peroxidation but increased LDH release and glutathione depletion were seen with HO-1 overexpression. Reactive iron content could not explain the apparent loss of cell membrane integrity. With the addition of tin mesoporphyrin, total HO activity was decreased and all changes in injury parameters were normalized to control values. We conclude that moderate overexpression of HO-1 is protective against oxidative injury, but we speculate that there is a beneficial threshold of HO-1 expression.
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PMID:Protective effects of transient HO-1 overexpression on susceptibility to oxygen toxicity in lung cells. 1007 Jan 8

The endothelium of the lung is sensitive to the toxic effects of oxygen, and early evidence of toxicity is characterized by protein leak and extravasation of red blood cells. The overproduction of oxygen free radicals plays a critical role in the pathophysiology of a hyperoxic lung injury. Recently, heme oxygenase 1 (HO-1), the rate-limiting enzyme in the metabolism of heme, has been found to have a protective role in oxidant injury. Our laboratory and others have identified HO-1 as a hyperoxia-inducible protein. In this study, we characterized HO-1 expression and evaluated its regulation in human pulmonary endothelial cells. Hyperoxia results in a relatively small increase in HO-1 expression; however, this induction is potentiated by heme and dramatically potentiated in the presence of free iron. This is probably more reflective of the in vivo situation in which there is extravasation of heme and iron products. We also found that HO-1 expression depended on chelatable iron. The iron chelator desferrioxamine not only inhibited the iron- dependent potentiation of HO-1 in response to hyperoxia but also inhibited both hyperoxia and basal expression. On the basis of inhibitor studies and nuclear run-on assays, we demonstrated that this induction is transcriptionally dependent. We also evaluated 4.5 kb of the human HO-1 promoter region and demonstrated that this region has promoter activity to the stimulus heme; however, there was no evidence of promoter activity to either iron or hyperoxia. This diversity of promoter activity to heme, heavy metals, and hyperoxia is unique to the human HO-1 gene.
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PMID:Iron regulates hyperoxia-dependent human heme oxygenase 1 gene expression in pulmonary endothelial cells. 1010 Oct 13

Findings in recent years strongly suggest that the stress-inducible gene heme oxygenase (HO)-1 plays an important role in protection against oxidative stress. Although the mechanism(s) by which this protection occurs is poorly understood, we hypothesized that the gaseous molecule carbon monoxide (CO), a major by-product of heme catalysis by HO-1, may provide protection against oxidative stress. We demonstrate here that animals exposed to a low concentration of CO exhibit a marked tolerance to lethal concentrations of hyperoxia in vivo. This increased survival was associated with highly significant attenuation of hyperoxia-induced lung injury as assessed by the volume of pleural effusion, protein accumulation in the airways, and histological analysis. The lungs were completely devoid of lung airway and parenchymal inflammation, fibrin deposition, and pulmonary edema in rats exposed to hyperoxia in the presence of a low concentration of CO. Furthermore, exogenous CO completely protected against hyperoxia-induced lung injury in rats in which endogenous HO enzyme activity was inhibited with tin protoporphyrin, a selective inhibitor of HO. Rats exposed to CO also exhibited a marked attenuation of hyperoxia-induced neutrophil infiltration into the airways and total lung apoptotic index. Taken together, our data demonstrate, for the first time, that CO can be therapeutic against oxidative stress such as hyperoxia and highlight possible mechanism(s) by which CO may mediate these protective effects.
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PMID:Carbon monoxide provides protection against hyperoxic lung injury. 1019 67

It is often postulated that the cytoprotective nature of heme oxygenase (HO-1) explains the inducible nature of this enzyme. However, the mechanisms by which protection occurs are not verified by systematic evaluation of the physiological effects of HO. To explain how induction of HO-1 results in protection against oxygen toxicity, hamster fibroblasts (HA-1) were stably transfected with a tetracycline response plasmid containing the full-length rat HO-1 cDNA construct to allow for regulation of gene expression by varying concentrations of doxycycline (Dox). Transfected cells were exposed to hyperoxia (95% O(2)/5% CO2) for 24 h and several markers of oxidative injury were measured. With varying concentrations of Dox, HO activity was regulated between 3- and 17-fold. Despite cytoprotection with low (less than fivefold) HO activity, high levels of HO-1 expression (greater than 15-fold) were associated with significant oxygen cytotoxicity. Levels of non-heme reactive iron correlated with cellular injury in hyperoxia whereas lower levels of heme were associated with cytoprotection. Cellular levels of cyclic GMP and bilirubin were not significantly altered by modification of HO activity, precluding a substantial role for activation of guanylate cyclase by carbon monoxide or for accumulation of bile pigments in the physiological consequences of HO-1 overexpression. Inhibition of HO activity or chelation of cellular iron prior to hyperoxic exposure decreased reactive iron levels in the samples and significantly reduced oxygen toxicity. We conclude that there is a beneficial threshold of HO-1 overexpression related to the accumulation of reactive iron released in the degradation of heme. Therefore, despite the ready induction of HO-1 in oxidant stress, accumulation of reactive iron formed makes it unlikely that exaggerated expression of HO-1 is a cytoprotective response.
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PMID:Reversal of HO-1 related cytoprotection with increased expression is due to reactive iron. 1050 83

Somatic cell gene transfer is a potentially useful strategy to alter lung function. However, achieving efficient transfer to the alveolar epithelium, especially in smaller animals, has not been demonstrated. In this study, the rat heme oxygenase-1 (HO-1) gene was delivered to the lungs of neonatal mice via transpulmonary injection. A bidirectional promoter construct coexpressing both HO-1 and a luciferase reporter gene was used so that in vivo gene expression patterns could be monitored in real time. HO-1 expression levels were also modulated with doxycycline and assessed in vivo with bioluminescent light transmitted through the tissues from the coregulated luciferase reporter. As a model of oxidative stress and HO-1-mediated protection, groups of animals were exposed to hyperoxia. After gene transfer, elevated levels of HO-1 were detected predominantly in alveolar type II cells by immunocytochemistry. With overexpression of HO-1, increased oxidative injury was observed. Furthermore, this model demonstrated a cell-specific effect of lung HO-1 overexpression in oxidative stress. Specific control of expression for therapeutic genes is possible in vivo. The transpulmonary approach may prove useful in targeting gene expression to cells of the alveolar epithelium or to circumscribed areas of the lung.
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PMID:HO-1 expression in type II pneumocytes after transpulmonary gene delivery. 1083 34

We have previously shown marked induction of the stress-inducible gene heme oxygenase-1 (HO-1) in vivo and in vitro after hyperoxia. In RAW 264.7 cells, HO-1 induction is transcriptionally regulated and dependent on cooperation between the HO-1 gene promoter and the 5' distal enhancer element SX2. In our present study, further deletional and mutational analyses demonstrate that signal transducer and activator of transcription (STAT) DNA binding sites located in the promoter of HO-1 and activator protein (AP)-1 DNA binding sites in the distal enhancer element SX2 are necessary for optimal HO-1 gene activation after hyperoxia. Interestingly, a second 5' distal enhancer element, AB1, located 10 kb upstream from the HO-1 promoter, alone is activated after hyperoxia but cannot confer maximal hyperoxia-induced HO-1 gene transcription. Mutational analysis of the AB1 enhancer shows that AP-1 is essential for AB1-mediated HO-1 gene transcription after hyperoxia. Electromobility shift assays show increased STAT1, STAT3, STAT5, and AP-1 DNA binding activity in RAW 264.7 cells after hyperoxia. Taken together, our data suggest that the 5' distal enhancer elements of the HO-1 gene in concert with the promoter regulate HO-1 gene induction and highlight the complexity of HO-1 gene transcription in response to hyperoxia.
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PMID:AP-1 and STAT mediate hyperoxia-induced gene transcription of heme oxygenase-1. 1089 16

Acute lung injury is an unfortunate consequence of oxygen therapy. Increasing evidence suggests that pulmonary dysfunction resulting from acute oxygen toxicity is at least in part due to the injury and death of lung cells. Studies using morphological and biochemical analyses revealed that hyperoxia-induced pulmonary cell death is multimodal, involving not only necrosis, but also apoptosis. A correlative relationship between the severity of hyperoxic acute lung injury and increased apoptosis has been supported by numerous studies in a variety of animal models, although future experiments are necessary to determine whether it is an actual causal relationship. Altered expression of several apoptotic regulatory proteins, such as p53 and Bcl-2, and DNA damage-induced proteins is associated with hyperoxic cell death and lung injury. Stress-responsive proteins, such as heme oxygenase (HO)-1, have been shown to protect animals against hyperoxic cell injury and death. Redox-sensitive transcription factors and mitogen-activated protein kinase signal transduction pathways may play important roles in regulating the expression of stress-responsive and apoptotic regulatory genes. A better understanding of signal transduction pathways leading to hyperoxic cell death may provide new approaches to the treatment of hyperoxia-induced lung injury.
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PMID:Signal transduction pathways in hyperoxia-induced lung cell death. 1100 28

NRF2 is a transcription factor important in the protection against carcinogenesis and oxidative stress through antioxidant response element (ARE)-mediated transcriptional activation of several phase 2 detoxifying and antioxidant enzymes. This study was designed to determine the role of NRF2 in the pathogenesis of hyperoxic lung injury by comparing pulmonary responses to 95-98% oxygen between mice with site-directed mutation of the gene for NRF2 (Nrf2-/-) and wild-type mice (Nrf2+/+). Pulmonary hyperpermeability, macrophage inflammation, and epithelial injury in Nrf2-/- mice were 7.6-fold, 47%, and 43% greater, respectively, compared with Nrf2+/+ mice after 72 h hyperoxia exposure. Hyperoxia markedly elevated the expression of NRF2 mRNA and DNA-binding activity of NRF2 in the lungs of Nrf2+/+ mice. mRNA expression for ARE- responsive lung antioxidant and phase 2 enzymes was evaluated in both genotypes of mice to identify potential downstream molecular mechanisms of NRF2 in hyperoxic lung responses. Hyperoxia-induced mRNA levels of NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione-S-transferase (GST)-Ya and -Yc subunits, UDP glycosyl transferase (UGT), glutathione peroxidase-2 (GPx2), and heme oxygenase-1 (HO-1) were significantly lower in Nrf2-/- mice compared with Nrf2+/+ mice. Consistent with differential mRNA expression, NQO1 and total GST activities were significantly lower in Nrf2-/- mice compared with Nrf2+/+ mice after hyperoxia. Results demonstrated that NRF2 has a significant protective role against pulmonary hyperoxic injury in mice, possibly through transcriptional activation of lung antioxidant defense enzymes.
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PMID:Role of NRF2 in protection against hyperoxic lung injury in mice. 1180 63

Differences in lung heme oxygenase-1 (HO-1) regulation have been demonstrated in newborn (<12 h old) and adult (>2 month old) rats after exposure to hyperoxia. Contrary to adults, neonates do not demonstrate increased lung HO-1 induction nor transcription factor activator protein-1 (AP-1) binding in hyperoxia. Because AP-1 activation can be posttranslationally modified by oxidants or reductants, we investigated whether differences in lung glutathione (GSH) content account for the maturational differences in AP-1 activation and subsequent HO-1 gene regulation after hyperoxia. Neonatal rats were injected with either 1-buthionine-[S,R] sulfoximine (BSO), diamide, or selenite during the 72-h hyperoxic exposure. Lung GSH content, glutathione disulfide (GSSG) content, AP-1 binding, and HO-1 mRNA were evaluated. The ratios of GSSG to GSH were used to reflect the GSH redox state in the lungs. Changes in lung GSSG/GSH ratio did not alter AP-1 binding but did increase HO-1 mRNA in neonates. These data suggest that the neonatal lung is relatively resistant to AP-1 activation and HO-1 induction by GSH perturbation.
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PMID:Effect of glutathione on lung activator protein-1 activation and heme oxygenase-1 induction in the immature rat. 1208 44


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