Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.99.3 (heme oxygenase)
 4,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This article provides an overview of the mechanisms by which cancer chemopreventive blocking agents increase the expression of detoxication and antioxidant genes. These agents all appear capable of transcriptionally activating a gene battery that includes NAD(P)H:quinone oxidoreductase, aldo-keto reductases, glutathione S-transferases, gamma-glutamylcysteine synthetase, glutathione synthetase and heme oxygenase. Gene induction occurs through the antioxidant responsive element (ARE), a process that is dependent on the Nuclear Factor-Erythroid 2p45-related factors, Nrf1 and Nrf2. Under basal conditions, these basic region leucine zipper (bZIP) transcription factors are located in the cytoplasm of the cell bound to Keap1, and upon challenge with inducing agents, they are released from Keap1 and translocate to the nucleus. Within the nucleus, Nrf1 and Nrf2 are recruited to the ARE as heterodimers with either small Maf proteins, FosB, c-Jun, JunD, activating transcription factor 2 (ATF2) or ATF4. The role of protein kinases in transducing chemical stress signals to the bZIP factors that affect gene induction through the ARE is discussed.
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PMID:Molecular basis for the contribution of the antioxidant responsive element to cancer chemoprevention. 1168 85

Many drugs and xenobiotics induce signal transduction events leading to gene expression of either pharmacologically beneficial effects, or unwanted side effects such as cytotoxicity which can compromise drug therapy. Using dietary chemopreventive compounds (isothiocyanates and green tea polyphenols), which are effective against various chemically-induced carcinogenesis models in animals studies, we studied the signal transduction events and gene expression profiles. These compounds have typically generated cellular "oxidative stress" and modulated gene expression including phase II detoxifying enzymes GST and QR as well as cellular defensive enzymes, heme oxygenase 1 (HO-1) and GST via the antioxidant/electrophile response element (ARE/EpRE). Members of the bZIP transcription factor, Nrf2 which heterodimerizes with Maf G/K, were found to bind to ARE, and transcriptionally activate ARE. Additionally the mitogen-activated protein kinases (MAPK; ERK, JNK and p38) were differentially activated by these compounds, and involved in the transcriptional activation of ARE-mediated reporter gene. Transfection studies with various cDNA encoding for wild-type of MAPK and Nrf2 showed synergistic response during co-transfection and to these agents. However, by increasing the concentrations of these xenobiotics, caspase activities and apoptosis were observed which were preceded by mitochondria damage and cytochrome c mitochondria release. Further, increased concentrations led to rapid cell necrosis. [corrected] Thus, we have proposed a model, that at low concentrations, these compounds activate MAPK pathway leading to activation of Nrf2 and ARE with subsequent induction of phase II and other defensive genes which protect cells against toxic insults thereby enhancing cell survival, a beneficial homeostatic response. At higher concentrations, these agents activate the caspase pathways, leading to apoptosis, a potential cytotoxic effect if it occurred in normal cells. The studies of these signaling pathways may yield important insights into the pharmacodynamic and toxicodynamic effects of drugs and xenobiotics during pharmaceutical drug discovery and development.
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PMID:Antioxidants and oxidants regulated signal transduction pathways. 1221 68

The transcription factor Nrf2, which normally exists in an inactive state as a consequence of binding to a cytoskeleton-associated protein Keap1, can be activated by redox-dependent stimuli. Alteration of the Nrf2-Keap1 interaction enables Nrf2 to translocate to the nucleus, bind to the antioxidant-responsive element (ARE) and initiate the transcription of genes coding for detoxifying enzymes and cytoprotective proteins. This response is also triggered by a class of electrophilic compounds including polyphenols and plant-derived constituents. Recently, the natural antioxidants curcumin and caffeic acid phenethyl ester (CAPE) have been identified as potent inducers of haem oxygenase-1 (HO-1), a redox-sensitive inducible protein that provides protection against various forms of stress. Here, we show that in renal epithelial cells both curcumin and CAPE stimulate the expression of Nrf2 in a concentration- and time-dependent manner. This effect was associated with a significant increase in HO-1 protein expression and haem oxygenase activity. From several lines of investigation we also report that curcumin (and, by inference, CAPE) stimulates ho-1 gene activity by promoting inactivation of the Nrf2-Keap1 complex, leading to increased Nrf2 binding to the resident ho-1 AREs. Moreover, using antibodies and specific inhibitors of the mitogen-activated protein kinase (MAPK) pathways, we provide data implicating p38 MAPK in curcumin-mediated ho-1 induction. Taken together, these results demonstrate that induction of HO-1 by curcumin and CAPE requires the activation of the Nrf2/ARE pathway.
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PMID:Curcumin activates the haem oxygenase-1 gene via regulation of Nrf2 and the antioxidant-responsive element. 1257 Aug 74

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, the expression of which is highly sensitive to induction by pro-oxidant stimuli including the substrate heme and reactive oxygen species. Conceptually, the perception that HO-1 plays a key role in response to oxidative damage is paralleled by evidence showing high expression of HO-1 in a variety of cell systems challenged with nitric oxide (NO) or NO-derivatives, thus revealing a potential biological function for HO-1 against nitrosative stress. In this study, we report that exposure of cardiac cells to hemin (5-20 microM) in combination with compounds that liberate nitroxyl (HNO/NO-) or release NO significantly potentiates HO-1 mRNA and protein expression leading to a remarkable increase in heme oxygenase activity under both normoxic and hypoxic conditions. The amplification of the heme oxygenase pathway appears to involve a direct interaction between heme and the NO groups, as the ability of both NO(-)- and NO-releasing agents to induce HO-1 is totally lost by their pre-incubation for 1 hr in complete medium prior to cell treatment but is highly preserved by addition of hemin during the preincubation step. In addition, we show that the redox-sensitive transcription factor Nrf2 is highly expressed in the nuclear fraction of cells exposed to the NO- generator and that this effect is totally abolished by the presence of N-acetyl-L-cysteine. Interestingly, the expression of Nrf2 is gradually intensified by treating cells with a combination of the NO- releaser and increasing concentrations of hemin. Thus, a strict parallelism exists between the extent of HO-1 induction and expression of Nrf2 elicited by the heme-NO interaction. We propose that modification of the iron protoporphyrin centers by NO groups to modulate HO-1 expression might be regarded as a molecular switch to maximize heme oxygenase enzymatic activity and consequently mitigate the redox imbalance imposed by oxidative and nitrosative stress.
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PMID:Interaction of heme with nitroxyl or nitric oxide amplifies heme oxygenase-1 induction: involvement of the transcription factor Nrf2. 1269 47

The export of certain nuclear proteins is involved in the regulation of various nuclear functions, including transcription. In some cases, the export of target proteins is induced upon environmental or cellular cues, resulting in conditional gene expression. The small Maf proteins appear to be critical regulators of heme oxygenase (HO)-1, an anti-oxidant defense enzyme that degrades heme into iron, carbon monoxide, and biliverdin. Although ho-1 is repressed by Bach1/small Maf heterodimers, it is activated by Nrf2/small Maf heterodimers, indicating that Bach1 and Nrf2 compete with each other. We anticipated that the nuclear concentration of Bach1 might be regulated to ensure that the entire system effectively responds to various stimuli. We carried out detailed domain analysis of Bach1 in an effort to understand how various inducers of HO-1 inactivate Bach1. We show here that cadmium, a strong inducer of HO-1, activates the nuclear export of Bach1. This cadmium-induced export of Bach1 was mediated in trans by its C-terminal region that is conserved between Bach1 and Bach2. The nuclear export of Bach2 was also induced by cadmium, indicating that the cadmium responsibility is shared between Bach1 and Bach2. The nuclear export of Bach1 was dependent on Crm1/Exportin-1 as well as the extracellular signal-regulated kinase-1/2 (ERK1/2) activity. These results indicate that the nuclear export of Bach1 constitutes an important regulatory mechanism to relieve the Bach1-mediated repression of genes such as ho-1.
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PMID:Cadmium induces nuclear export of Bach1, a transcriptional repressor of heme oxygenase-1 gene. 1450 88

Treatment for 48 h of murine Hepa 1c1c7 cells in culture with the cancer chemopreventive oltipraz (1) followed by addition of CD(3)I and immediate cell lysis yields, by LC/MS analysis, three isotopomers of the methylated pyrrolopyrazine (2), a known human metabolite of oltipraz. The major isotopomer (58%) is the one containing two CD(3)- groups attached to the pendant sulfur atoms of the pyrrolopyrazine ring, the others containing one CD(3)- and one CH(3)- group or two CH(3)- groups. It is concluded from this that the unmethylated pyrrolopyrazine (4) is the major metabolite of oltipraz. Prodrugs 5 and 6, which have been shown to rapidly generate 4 in the presence of GSH at physiological pH, induce the phase 2 enzyme NQO1 in Hepa 1c1c7 cells with potencies on par with oltipraz itself: CD(NQO1) = 14.4 +/- 1.3, 20.1 +/- 4.6, and 23.6 +/- 1.6 microM for oltipraz, 5, and 6, respectively. Pretreatment of oltipraz, 5, and 6 in cell culture media with 1 mM GSH, which is shown to immediately convert 5 and 6 to 4, followed by incubation with Hepa 1c1c7 cells shows similar potencies for oltipraz and the (decomposed) produrgs, with CD(NQO1) = 18.0 +/- 4.4 microM for 5, 17.8 +/- 0.2 microM for 6, and 13.5 +/- 1.4 microM for oltipraz. Treatment with compound 6 of murine hepatoma cells containing a luciferase gene under the control of the antioxidant response element (ARE) from the mouse heme oxygenase (ho-1) gene elicits induction of luciferase activity, CD = 35.8 +/- 2.8 microM, somewhat greater than the potency than oltipraz itself. Western blots of nuclear proteins isolated from Hepa 1c1c7 cells and probed with anti-Nrf2 indicate that as compared to vehicle DMSO, compound 6 stimulates nuclear translocation of Nrf2 from the cytosol. From this study, it is concluded that the major metabolite of the cancer chemopreventive oltipraz is a phase 2 enzyme inducer of comparable potency that activates the ARE and initiates nuclear translocation of transcription factor Nrf 2.
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PMID:Phase 2 enzyme induction by the major metabolite of oltipraz. 1461 73

Activated macrophages express high levels of Nrf2, a transcription factor that positively regulates the gene expression of antioxidant and detoxication enzymes. In this study, we examined how Nrf2 contributes to the anti-inflammatory process. As a model system of acute inflammation, we administered carrageenan to induce pleurisy and found that in Nrf2-deficient mice, tissue invasion by neutrophils persisted during inflammation and the recruitment of macrophages was delayed. Using an antibody against 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), it was observed that macrophages from pleural lavage accumulate 15d-PGJ(2). We show that in mouse peritoneal macrophages 15d-PGJ(2) can activate Nrf2 by forming adducts with Keap1, resulting in an Nrf2-dependent induction of heme oxygenase 1 and peroxiredoxin I (PrxI) gene expression. Administration of the cyclooxygenase 2 inhibitor NS-398 to mice with carrageenan-induced pleurisy caused persistence of neutrophil recruitment and, in macrophages, attenuated the 15d-PGJ(2) accumulation and PrxI expression. Administration of 15d-PGJ(2) into the pleural space of NS-398-treated wild-type mice largely counteracted both the decrease in PrxI and persistence of neutrophil recruitment. In contrast, these changes did not occur in the Nrf2-deficient mice. These results demonstrate that Nrf2 regulates the inflammation process downstream of 15d-PGJ(2) by orchestrating the recruitment of inflammatory cells and regulating the gene expression within those cells.
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PMID:Transcription factor Nrf2 regulates inflammation by mediating the effect of 15-deoxy-Delta(12,14)-prostaglandin j(2). 1467 41

Small Maf proteins serve as dual-function transcription factors through an exchange of their heterodimerization partners. For example, as heterodimers with hematopoietic cell-specific p45 NF-E2 or NF-E2-related factors (Nrf), they activate the beta-globin or antioxidative stress enzyme heme oxygenase 1 (HO-1) genes, respectively. In contrast, together with Bach1, they repress these same genes. However, the signals leading to this partner exchange are not known. Using chromatin immunoprecipitation assays in NIH 3T3 cells, we show that heme, an inducer of ho-1, promotes displacement of Bach1 from the MafK-occupied ho-1 enhancers, which is followed by Nrf2 binding to these elements. Whereas histone H3 at the ho-1 enhancers and promoter is hyperacetylated irrespective of gene activity, exposure of cells to heme results in de novo hyperacetylation and hypermethylation of histone H3 in the transcribed region. These data indicate that, under normal conditions, the chromatin structure of ho-1 is in a preactivation state, but transcription is repressed by Bach1. Heme induces switching of Maf dimers, resulting in ho-1 expression. Heme also promotes displacement of Bach1 from the beta-globin locus control region without affecting MafK binding in murine erythroleukemia cells. Thus, heme functions as a signaling molecule for gene expression in higher eukaryotes.
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PMID:Heme regulates the dynamic exchange of Bach1 and NF-E2-related factors in the Maf transcription factor network. 1474 57

HO-1 (haem oxygenase-1) is a stress-inducible enzyme that plays a protective role in inflammation. Pro-inflammatory mediators, including lipopolysaccharide and cytokines, induce HO-1 expression. The 5'-flanking region of the HO-1 gene contains binding sites for the transcription factors that regulate inflammation, including nuclear factor-kappaB and activator protein 1. However, these do not appear to mediate lipopolysaccharide-induced HO-1 gene expression. In response to haem and antioxidants, murine HO-1 is regulated by the transcription factor Nrf2 (NF-E2-related factor 2). This transcription factor may also be important in the regulation of HO-1 by pro-inflammatory stimuli.
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PMID:Haem oxygenase-1 in inflammation. 1550 75

A series of synthetic triterpenoid (TP) analogues of oleanolic acid are powerful inhibitors of cellular inflammatory processes such as the induction by IFN-gamma of inducible nitric oxide synthase (iNOS) and of cyclooxygenase 2 in mouse macrophages. Here, we show that these analogues are also extremely potent inducers of the phase 2 response [e.g., elevation of NAD(P)H-quinone oxidoreductase and heme oxygenase 1], which is a major protector of cells against oxidative and electrophile stress. Moreover, like previously identified phase 2 inducers, the TP analogues use the antioxidant response element-Nrf2-Keap1 signaling pathway. Thus, induction of the phase 2 response and suppression of the iNOS induction was abrogated in nrf2(-/-) and keap1(-/-) mouse embryonic fibroblasts. The high potency of TP analogues in inducing the phase 2 response and blocking inflammation depends on the presence of activated Michael reaction (enone) functions at critical positions in rings A and C. The most potent TP doubles NAD(P)H-quinone oxidoreductase in murine hepatoma cells at 0.28 nM and has an IC(50) for suppression of iNOS induction in primary mouse macrophages of 0.0035 nM. The direct interaction of this TP with thiol groups of the Keap1 sensor for inducers is demonstrated spectroscopically. The antiinflammatory and phase 2 inducer potencies of 18 TP are closely linearly correlated (r(2) = 0.91) over 6 orders of magnitude of concentration. Thus, in addition to blocking inflammation and promoting differentiation, these TP exhibit another very important protective property: the induction of the phase 2 response.
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PMID:Extremely potent triterpenoid inducers of the phase 2 response: correlations of protection against oxidant and inflammatory stress. 1576 73


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