Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Incubating human cells in diethylmaleate (DEM) depletes the intracellular pool of reduced glutathione (GSH) and increases the concentration of oxidative free radicals. We found that DEM-induced oxidative stress reduced the ability of p53 to bind its consensus recognition sequence and to activate transcription of a p53-specific reporter gene. Nevertheless, DEM treatment induced expression of WAF1/CIP1 but not GADD45 mRNA. The fact that N-acetylcysteine, a precursor of GSH that blocks oxidative stress, prevented WAF1/CIP1 induction by DEM suggests that WAF1/CIP1 induction probably was a consequence of the ability of DEM to reduce intracellular GSH levels. DEM induced WAF1/CIP1 expression in Saos-2 and T98G cells, both of which lack functional p53 protein. DEM treatment did not produce an increase in membrane-associated protein kinase C, but ERK2, a mitogen-activated protein kinase, was phosphorylated in a manner consistent with ERK2 activation. DEM treatment also produced a dose-dependent delay in cell cycle progression, which at low concentrations (0.25 mM) consisted of a G2/M arrest and at higher concentrations (1 mM) also involved G1 and S phase delays. Our results indicate that oxidative stress induces WAF1/CIP1 expression and arrests cell cycle progression through a mechanism that is independent of p53. This mechanism may provide for cell cycle checkpoint control under conditions that inactivate p53.
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PMID:A p53-independent pathway for activation of WAF1/CIP1 expression following oxidative stress. 749 74

Oxidative DNA damage by NAD(P)H in the presence of metal ions has been characterized by using 32P 5' end-labeled DNA fragments obtained from human p53 tumor suppressor gene and c-Ha-ras-1 protooncogene. NADH, as well as other endogenous reductants, induced DNA damage in the presence of Cu(II). The order of inducing effect on Cu(II)-dependent DNA damage was ascorbate > reduced glutathione (GSH) > NADH > NADPH. Although NADH caused no or little DNA damage in the presence of Fe(III)-EDTA, the addition of H2O2 induced the DNA damage. The Cu(II)-mediated DNA damage induced by NADH was inhibited by catalase and bathocuproine, a Cu(I)-specific chelator; but not by scavengers of hydroxyl free radical (.OH), suggesting the involvement of active species derived from hydrogen peroxide (H2O2) and Cu(I) rather than .OH. The predominant cleavage sites were thymine residues located 5' and/or 3' to guanine. The cleavage pattern was similar to that induced by Cu(II) plus GSH, Cu(II) plus ascorbate, or Cu(I) plus H2O2. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine by NADH increased with its concentration in the presence of Cu(II). UV-visible spectroscopy indicated the facilitation of reduction of Cu(II) by NADH under some conditions. ESR spin-trapping experiments and mass spectrometry showed that the carbon-centered radical was formed during the reaction of NADH with Cu(II). These results suggest that optimal molar ratios of DNA/metal ion yield copper with a high redox potential which catalyzes NADH autoxidation to NAD. being further oxidized to NAD+ with generation of superoxide radical and that H2O2 reacts with Cu(I) to form active oxygen species such as copper(I)-peroxide complex causing DNA damage.
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PMID:Site-specific DNA damage induced by NADH in the presence of copper(II): role of active oxygen species. 860 9

Previous studies have shown that reduced glutathione (GSH) inhibits experimental oral carcinogenesis in the hamster buccal pouch model. To gain further understanding of molecular mechanisms in the anticancer effect of GSH, these studies examined levels of p53 protein expression. 7,12-Dimethylbenz[a]anthracene (DMBA) was applied to the buccal pouches of 20 Syrian Golden hamsters (Mesocricetus auratus) in a 0.5% solution in mineral oil thrice weekly for 14 weeks. In 10 animals, 10 mg/kg reduced glutathione (GSH) in 0.5 ml of mineral oil was administered by mouth thrice weekly on days alternate to the DMBA painting. An additional 20 animals served as DMBA-untreated and GSH controls. At the termination of the experimental period, there were fewer tumors in the DMBA-GSH than in the DMBA tumor control group, and the tumors were smaller (tumor burden 315 vs. 3,040 mm3). Histologically, the DMBA-GSH group showed a marked reduction in dysplasia, carcinoma in situ, and invasive epidermoid carcinoma sites. Immunohistochemically, by use of monoclonal antibodies for wild-type p53 (PAb 246), changes were observed in protein expression levels at dysplastic sites and within the malignant tumors. Staining for p53 protein was slightly increased in dysplasia and squamous cell carcinoma in the tumor control animals (painted with DMBA) compared with the untreated controls that were free of tumors. In the GSH and DMBA treatment group, p53 protein expression levels were strongly increased in dysplastic and tumor sites. The significant inhibition of oral carcinogenesis associated with the administration of GSH was correlated with the increased levels of the wild-type p53 tumor suppressor gene, suggesting its possible use as a biomarker for GSH chemoprevention. The inhibition of oral carcinogenesis by reduced GSH was also related to a very significant inhibition of tumor angiogenesis, defined by factor VIII staining. Thus angiogenesis inhibition may be an additional mechanism for antioxidant chemoprevention, and this suggests another possible biomarker for antioxidant chemoprevention.
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PMID:Glutathione inhibits experimental oral carcinogenesis, p53 expression, and angiogenesis. 887 60

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries but the clinical presentation and rate of disease progression are highly variable. When treatment is required the most commonly used therapy is the nitrogen mustard alkylating agent, chlorambucil (CLB), with or without prednisone. Although CLB has been used in the treatment of CLL for forty years the exact mechanism of action of this agent in CLL is still unclear. Studies in proliferating model tumor systems have demonstrated that CLB can bind to a variety of cellular structures such as membranes, RNA, proteins and DNA; however, DNA crosslinking appears to be most important for antitumor activity in these systems. In addition, a number of different mechanisms can contribute to CLB resistance in these tumor models including increased drug metabolism, DNA repair and CLB detoxification resulting from elevated levels of glutathione (GSH) and glutathione S-transferase (GST) activity. However, unlike tumor models in vitro, CLL cells are generally not proliferating and studies in CLL cells have raised questions about the hypothesis that DNA crosslinking is the major mechanism of antitumor action for CLB in this disease. CLB induces apoptosis in CLL cells and this appears to correlate with the clinical effects of this agent. Thus, alkylation of cellular targets other than DNA, which can also induce apoptosis, may contribute to the activity of CLB. Alterations in genes such as p53, mdm-2, bcl-2 and bax which control entry into apoptosis may cause drug resistance. Loss of wild-type p53 by mutation or deletion occurs in 10 to 15% of CLL patients and appears to correlate strongly with poor clinical response to CLB. The induction of apoptosis by CLB is paralleled by an increase in P53 and Mdm-2 but this increase in not observed in patients with p53 mutations indicating that with high drug concentrations CLB can produce cell death through P53 independent pathways. The level of Mdm-2 mRNA in the CLL cells is not a useful predictor of drug sensitivity. In addition, although Bax and Bcl-2 are important regulators of apoptosis and the levels of these proteins are elevated in CLL cells compared with normal B cells, the levels of Bax and Bcl-2, or the Bax:Bcl-2 ratio, are not important determinants of drug sensitivity in this leukemia. Finally, whereas CLB and nucleoside analogs may produce cell death in CLL by a P53 dependent pathway other agents, such as dexamethasone or vincristine, may act through P53-independent pathways.
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PMID:Chlorambucil in chronic lymphocytic leukemia: mechanism of action. 903 Oct 99

Glutathione (GSH) conjugate formation with tetrachlorohydroquione (TCHQ) and the GSH content in vivo were measured by capillary zone electrophoresis. A more than 60% depletion of GSH content was found in liver tissue of mice treated with TCHQ. In addition, p53 protein accumulation and DNA fragmentation was induced by TCHQ. A two-stage model of chemical transformation of mouse embryonic fibroblasts was used to elucidate the transformation activity of TCHQ in vitro, and a 33% foci formation efficiency was found at the concentration of 5 microM. GSH depletion caused by TCHQ could abolish the protective ability of the cell against reactive oxygen species provided by GSH. When DNA was damaged, p53 protein accumulated in the nucleus and, in the case of severe damage, initiated apoptosis. TCHQ's ability to cause GSH depletion and DNA damage may play a role in the cytotoxic and genotoxic properties of its metabolic precursor, PCP.
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PMID:Induction of glutathione depletion, p53 protein accumulation and cellular transformation by tetrachlorohydroquinone, a toxic metabolite of pentachlorophenol. 923 72

Peroxynitrite (0.5-50 microM) induced dose-dependent cytotoxic effects in rat pancreatic acinar AR4-2J cells. Glutathione (2 mM) and ebselen (10 microM) partially reduced the cytotoxicity caused by 1-10 microM concentrations of peroxynitrite. Higher concentrations (10-50 microM) of peroxynitrite induced DNA smear suggestive of necrosis, while lower concentrations (2-5 microM) induced DNA fragmentations suggestive of apoptosis. The effects of peroxynitrite on [Ca2+]i showed a similar dose dependency. Peroxynitrite concentrations > 10 microM rapidly increased [Ca2+]i in a dose-dependent manner, while concentrations < 5 microM did not affect [Ca2+]i. In contrast, the presentation of wild-type P53 was accelerated at lower concentrations of peroxynitrite (< or = 10 microM) but not at higher concentrations (50 microM). The present study suggests that peroxynitrite at lower concentrations (2-5 microM) induces wildtype P53 and apoptosis, which is potentially a protective response toward the DNA damage caused by peroxynitrite. On the other hand, higher concentrations of peroxynitrite (10-50 microM) rapidly increase [Ca2+]i and eventually induce necrosis.
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PMID:Cytotoxicity of peroxynitrite in rat pancreatic acinar AR4-2J cells. 933 92

This study evaluated the action of menadione on cell proliferation and integrity of the rat pancreatic acinar cell line, AR4-2J. Menadione at 1-20 microM dose- and time-dependently inhibited cell proliferation of AR4-2J cells. In contrast, a high concentration of menadione (100 microM) caused rapid cell death (> 90% of cells took up trypan blue within 4-h). While the high concentration of menadione (100 microM) induced DNA smear in electrophoresis indicative of necrosis, lower concentrations (10-20 microM) induced a DNA ladder indicative of apoptosis. Similar results were obtained using a DNA fragmentation ELISA. Glutathione (1 mM), the calcium chelator EGTA (500 microM), and the cysteine protease inhibitor NCO-700 (5 mM) partly inhibited the effect of 1-10 microM menadione on cell proliferation and DNA fragmentation. Menadione at 1-20 microM induced wild-type P53, whereas the 100 microM menadione had a minor effect on wild-type P53. It is concluded that menadione induced necrosis at high concentrations and apoptosis at low concentrations in AR4-2J cells. Apoptosis induced by lower concentrations of menadione may be mediated by wild-type P53, intracellular calcium, and mechanisms which decrease the intracellular concentration of reduced glutathione.
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PMID:Menadione induces both necrosis and apoptosis in rat pancreatic acinar AR4-2J cells. 937 63

The objective of the study was to analyze the intracellular antioxidative response of macrophages (Mphi) exposed to increased levels of low density lipoprotein (LDL). We studied manganese superoxide dismutase (MnSOD) and, in part, GSH in cultured human and rabbit Mphi, and in atheromatous arterial tissue of humans and heritable hyperlipidemic (HHL) rabbits. Incubation of human Mphi with oxidized-LDL (ox-LDL) resulted in an induction of MnSOD mRNA production as shown by RT-PCR. MnSOD immunoreactivity (IR) was found to be located in the mitochondria of Mphi. In HHL rabbits, MnSOD activity and GSH concentration were significantly increased in atherosclerotic intima compared to the media of the aorta, but significantly decreased (P<0.01) in larger plaques compared with smaller ones, resulting in a significant inverse correlation of MnSOD activity (r=-0.67, P<0.001) and GSH concentration (r=-0.57, P<0.01) with plaque size. Immunohistology of the atherosclerotic intima revealed MnSOD-IR in Mac-1 (CD 11b/CD 18)-immunoreactive (ir) Mphi of human arteries and, similarly, in RAM-11-ir Mphi of rabbit ones. The relation of MnSOD-ir Mphi decreased with plaque advancement, which is consistent with biochemical findings. Most MnSOD-ir Mphi in atherosclerotic plaques revealed TUNEL-positive nuclei, indicating DNA strand breaks, and p53-IR. We conclude that mitochondrial antioxidants such as MnSOD are induced in Mphi in vitro and in atherosclerotic arteries as a reply to increased mitochondrial oxidation. As normal consequences of an increased oxidative stress due to the exposure to ox-LDL nuclear DNA strand breaks occur, which are suggested to be a signal to increase p53 protein levels. Reactive oxygen species-mediated mitochondrial-dependent pathways are suggested as major contributing pathomechanisms to nuclear damage, which eventually may result in apoptosis. A common response to increased oxidative stress due to modified LDL is presumed in rabbit and human atherosclerotic plaques.
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PMID:Induction of mitochondrial manganese superoxide dismutase in macrophages by oxidized LDL: its relevance in atherosclerosis of humans and heritable hyperlipidemic rabbits. 940 51

The teratogenicity of many xenobiotics is thought to depend at least in part upon their bioactivation by embryonic cytochromes P450, prostaglandin H synthase (PHS) and lipoxygenases (LPOs) to electrophilic and/or free radical reactive intermediates that covalently bind to or oxidize cellular macromolecules such as DNA, protein and lipid, resulting in in utero death or teratogenesis. Using as models the tobacco carcinogens benzo[a]pyrene (B[a]P) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the anticonvulsant drug phenytoin, structurally related anticonvulsants (e.g. mephenytoin, nirvanol, trimethadione, dimethadione) and the sedative drug thalidomide, we have examined the potential teratologic relevance of free radical-initiated, reactive oxygen species (ROS)-mediated oxidative molecular target damage, genotoxicity (micronucleus formation) and DNA repair in mouse and rabbit models in vivo and in embryo culture, and in vitro using purified enzymes or cultured rat skin fibroblasts. These teratogens were bioactivated by PHS and LPOs to free radical reactive intermediary metabolites, characterized by electron spin resonance spectrometry, that initiated ROS formation, including hydroxyl radicals, which were characterized by salicylate hydroxylation. ROS-initiated oxidation of DNA (8-hydroxy-2'-deoxyguanosine formation), protein (carbonyl formation), glutathione (GSH) and lipid (peroxidation), and embryotoxicity were shown for phenytoin, its major hydroxylated metabolite 5-(p-hydroxyphenyl)-5-phenylhydantoin [HPPH], thalidomide, B[a]P and NNK in vivo and/or in embryo culture, the latter indicating a teratologically critical role for embryonic, as distinct from maternal, processes. DNA oxidation and teratogenicity of phenytoin and thalidomide were reduced by PHS inhibitors. Oxidative macromolecular lesions and teratogenicity also were reduced by the free radical trapping agent phenylbutylnitrone (PBN), and the antioxidants caffeic acid and vitamin E. In embryo culture, addition of superoxide dismutase (SOD) to the medium enhanced embryonic SOD activity, and SOD or catalase blocked the oxidative lesions and embryotoxicity initiated by phenytoin and B[a]P, suggesting a major contribution of ROS, as distinct from covalent binding, to the teratologic mechanism. In in vivo studies, other antioxidative enzymes like GSH peroxidase, GSH reductase and glucose-6-phosphate dehydrogenase (G6PD) were similarly protective. Even untreated G6PD-deficient mice had enhanced embryopathies, indicating a teratological role for endogenous oxidative stress. In cultured fibroblasts, B[a]P, NNK, phenytoin and HPPH initiated DNA oxidation and micronucleus formation, which were inhibited by SOD. Oxidation of DNA may be particularly critical, since transgenic mice with +/- or -/- deficiencies in the p53 tumor suppressor gene, which facilitates DNA repair, are more susceptible to phenytoin and B[a]P teratogenicity. Even p53-deficient mice treated only with normal saline showed enhanced embryopathies, suggesting the teratological importance of endogenous oxidative stress, as observed with G6PD deficiency. These results suggest that oxidative macromolecular damage may play a role in the teratologic mechanism of xenobiotics that are bioactivated to a reactive intermediate, as well in the mechanism of embryopathies occurring in the absence of xenobiotic exposure.
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PMID:Oxidative damage in chemical teratogenesis. 943 60

Median survival of human malignant glioma patients is less than one year even with cytoreductive surgery and postoperative radiotherapy. Adjuvant chemotherapy has been rather ineffective. Here, we studied the potentiation by L-buthionine-[S,R]-sulfoximine (BSO), a glutathione-depleting agent, of anticancer drug actions on two human malignant glioma cell lines, LN-229 and T98G. LN-229 has wild-type p53 status, T98G is mutant for p53. Glutathione levels were depleted by BSO with similar kinetics in both cell lines. Only LN-229 cells were growth-inhibited by BSO. BSO had minor effects on the toxicity of doxorubicin, ACNU (1-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-3-(2-chloroethyl)-3-nitrosou rea, nimustine) and vincristine. BSO failed to alter teniposide or cytarabine toxicity. BSO induced prominent sensitization to the alkylating agent, treosulfan, in both cell lines, as assessed by viability assays, in situ DNA end labeling and quantitative DNA fragmentation. Treosulfan is thought to mediate toxicity via formation of reactive epoxides. In the absence of BSO, treosulfan had little acute cytotoxic and moderate antiproliferative effects. Synergistic glioma cell cytotoxicity induced by treosulfan and BSO was not associated with reactive oxygen species formation. Ectopic expression of bcl-2 did not alter basal glutathione levels but attenuated glutathione depletion induced by BSO. Bcl-2 provided only moderate protection from synergistic induction of glioma cell death by treosulfan and BSO. Glutathione depletion may play a role in BSO-mediated chemosensitization, but other mechanisms are probably involved as well. BSO may be a useful agent for glioma cell sensitization to specific chemotherapeutic drugs such as treosulfan.
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PMID:Potentiation of treosulfan toxicity by the glutathione-depleting agent buthionine sulfoximine in human malignant glioma cells: the role of bcl-2. 948 2


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