Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutathione (GSH), its derivatives and N-acetylcysteine (NAC) inhibit the induction of HIV-1 expression in a chronically HIV-1-infected promonocytic cell line (U1/HIV) and peripheral blood mononuclear cells (PBMC). We have examined the effects of GSH and NAC on HIV-1 replication in human primary monocyte/macrophages cultured in vitro. Ficoll-gradient purified human monocytes were cultivated in vitro for 7-10 days and then infected with HIV-1 (Bal and Ada-M). Infection was blocked or substantially reduced by GSH or NAC (5-20 mM). Significant reduction (greater than or equal to 90%) in the amount of virus released, as determined by measuring supernatant reverse transcriptase activity and secreted p24 protein, was obtained when the cells were treated for 4 h with greater than or equal to 10 mM of GSH or NAC. The inhibitory effects of GSH and NAC were concentration dependent. This anti-HIV-1 effect persisted in these cultures for at least 35 days without evidence of significant increase in HIV-1 expression. Thus, a single pulse exposure of HIV-1-infected monocyte/macrophages with GSH or NAC led to a sustained, concentration-dependent decrease in HIV-1 p24 antigen levels, as well as, reverse transcriptase activity without producing detectable cellular toxicity in monocyte/macrophages.
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PMID:Glutathione and N-acetylcysteine suppression of human immunodeficiency virus replication in human monocyte/macrophages in vitro. 152 May 37

Reducing agents such as glutathione (GSH), glutathione ester (GSE), and N-acetylcysteine (NAC) have been shown to suppress the induction of HIV expression in chronically infected cells stimulated by cytokines. We present data which show the effects of the organic thiophosphate WR-151327 on the expression of latent HIV in U1 cells. The chronically infected promonocytic cell line U1 constitutively expresses low levels of HIV that can be increased by 13-phorbol 12-myristate acetate (PMA), tumor necrosis factor alpha (TNF-alpha), and granulocyte/monocyte colony-stimulating factor (GM-CSF). WR-151327 suppressed, in dose-dependent fashion, the reverse transcriptase (RT) activity induced by TNF-alpha, GM-CSF, and PMA. The maximal decrease in RT activity was 70, 80, and 50%, respectively. Pretreatment with WR-151327 also suppressed the induction of total HIV protein synthesis, as shown by Western blot analysis. In addition, WR-151327 suppressed HIV-LTR-CAT activity in transfected human rhabdomyosarcoma cells (RD). Suppression of HIV expression by WR-151327 was observed in the absence of a cytotoxic or cytostatic effect. Incubation of WR-151327 with human recombinant TNF-alpha for 6 hr at 37 degrees C did not alter the capacity of TNF-alpha to induce the expression of HIV. Our observations further support the hypothesis that reducing agents are important in the control of HIV replication and that the clinical evaluation of WR-151327 may be indicated.
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PMID:Organic thiophosphate WR-151327 suppresses expression of HIV in chronically infected cells. 752 Nov 93

We have previously reported that carbon tetrachloride (CCI4) stimulates c-fos, c-jun, and Ca(2+)-activated neutral protease gene expression in rat hepatic tissue (Zawaski et al., Biochem. Biophys. Res. Comm. 197, 585-590, 1993). The proteins c-Fos and c-Jun constitute inducible transcription factors in signal transduction and regulate the transcriptional activation of a battery of genes involved in cell growth and division. The present study was initiated to characterize the role of cytochrome P450 expression and metabolic activation on the magnitude of immediate-early (i.e. c-fos and c-jun) gene expression. Animals were treated either with diallyl sulfide, N-acetylcysteine, pyridine, or phenobarbital before treatment with CCI4. Total and poly(A)+ RNA were isolated, and c-fos and c-jun mRNA levels were analyzed by Northern blot and reverse transcriptase-polymerase chain reaction analyses. Treatment of animals with CCI4 increased c-fos and c-jun mRNA levels from below the limit of detection in control tissue to intense bands within 30 min of treatment, with maximal expression monitored at 1 and 2 hr posttreatment. Treatment of animals with diallyl sulfide alone also elevated c-fos and c-jun mRNA expression to detectable levels. However, pretreatment of animals with diallyl sulfide before treatment with CCI4 produced a 76-92% decrease in c-fos and c-jun mRNA levels, relative to that monitored for CCI4-treated animals. Pretreatment with N-acetylcysteine did not affect c-fos or c-jun mRNA levels and diminished CCI4-stimulated c-fos and c-jun gene expression by 44 and 55%, respectively, relative to the immediate-early gene mRNA levels monitored in the hepatic tissue of CCI4-treated animals. Pretreatment of animals with the CYP2E1 inducer pyridine for 24 hr had only a marginal effect on c-fos mRNA levels, but increased CCI4-stimulated c-fos and c-jun mRNA levels by an additional approximately 2- to approximately 4-fold over those monitored in the uninduced hepatic tissue of CCI4-treated animals. Whereas phenobarbital treatment alone enhanced c-fos expression only marginally, CCI4 treatment of phenobarbital-pretreated animals increased c-fos expression by up to an additional approximately 8-fold and c-jun mRNA levels by up to an additional approximately 5-fold over the respective levels monitored in the hepatic tissue of CCI4-treated animals. Enhanced CYP2E1 or CYP2B1/2B2 levels after treatment with pyridine or phenobarbital elevated c-fos mRNA over untreated controls. This increase was marginal, however, and detectable only with reverse transcriptase-polymerase chain reaction. Examination of nuclear levels of the heterodimeric c-Fos and c-Jun AP-1 transcription factor complex revealed a time-dependent increase in AP-1 levels. AP-1 transcription factor binding was confirmed using competitor consensus sequences and antibody supershifts. Nuclear levels of NF-kappa B, a transcription factor complex implicated in hepatocyte proliferation and apoptotic or programmed cell death, were also examined. NF-kappa B, which consists of the p50 and p65/Rel A polypeptides, was increased in hepatic nuclear extracts at 2 and 24 hr after CCI4 administration, with a concomitant decrease in the p50 polypeptide. Thus, the magnitude of CCI4 stimulation of the immediate-early genes c-fos and c-jun is dependent on metabolic activation by the P450s, and the magnitude of the effect is dependent on the levels and isozyme composition of P450s in the tissue. Furthermore, nuclear transcription factor levels of AP-1 and NF-kappa B are elevated in response to this toxicant.
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PMID:Cytochrome P4502E1- and cytochrome P4502B1/2B2-catalyzed carbon tetrachloride metabolism: effects on signal transduction as demonstrated by altered immediate-early (c-Fos and c-Jun) gene expression and nuclear AP-1 and NF-kappa B transcription factor levels. 882 85

In AIDS patients, chronic inflammation and elevated levels of cytokines seem to be associated with reduced levels of glutathione (GSH). GSH has been proposed to inhibit the activation of NF-kB, which results in the inhibition of HIV-1 replication. Here, we show the evidence that GSH and N-acetylcysteine, but not L-cysteine or dithiothreitol, could inhibit the reverse transcriptase (RT) process of HIV-1. Such inhibition was not observed with the RT of murine leukemia virus.
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PMID:Intracellular glutathione as a possible direct blocker of HIV type 1 reverse transcription. 894 99

The role of antioxidants in preventing apoptosis and viral activation in HIV is well documented. N-acetylcysteine, glutathione, and alpha-lipoic acid have been shown to interrupt the process of viral activation and CD4 cell death. L-glutamine has been shown to improve glutathione levels and significantly increase lean body mass in HIV infection. The literature on the use of L-carnitine and acetyl-L-carnitine in treating mitochondrial toxicity, both in muscle and nerve pathologies is relevant in nutritional treatment of HIV, given the mitochondrial toxicity of nucleoside analog reverse transcriptase inhibitor therapy. The current use of highly active antiviral therapies, their toxicity, and significant failure rates have created the need for a more conservative reassessment of HIV treatment. The adjunctive use of nutrient therapy in the treatment of HIV is reviewed here.
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PMID:Nutrients and HIV: part three - N-acetylcysteine, alpha-lipoic acid, L-glutamine, and L-carnitine. 1095 77

Evidence is rapidly accumulating that low-activity-reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidases homologous to that in phagocytic cells generate reactive oxygen species as signaling intermediates in both endothelium and vascular smooth muscle. We therefore explored the possibility of such an oxidase regulating growth of airway smooth muscle (AWSM). Proliferation of human AWSM cells in culture was inhibited by the antioxidants catalase and N-acetylcysteine, and by the flavoprotein inhibitor diphenylene iodonium (DPI). Membranes prepared from human AWSM cells generated superoxide anion (O) measured by superoxide dismutase-inhibitable lucigenin chemiluminescence, with a distinct preference for NADPH instead of reduced nicotinamide adenine dinucleotide as substrate. Chemiluminescence was also inhibited by DPI, suggesting the presence of a flavoprotein containing oxidase generating O as a signaling molecule for cell growth. Examination of human AWSM cells by reverse transcriptase-polymerase chain reaction consistently demonstrated transcripts with sequences identical to those reported for p22(phox). Transfection with p22(phox) antisense oligonucleotides reduced human AWSM proliferation. Inhibition of NADPH oxidase activity with DPI prevented serum-induced activation of nuclear factor-kappaB (NF-kappaB), and overexpression of a superrepressor form of the NF-kappaB inhibitor IkappaBalpha significantly reduced human AWSM growth. These findings suggest that an NADPH oxidase containing p22(phox) regulates growth-factor responsive human AWSM proliferation, and that the oxidase signals in part through activation of the prototypical redox-regulated transcription factor NF-kappaB.
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PMID:NADPH oxidase promotes NF-kappaB activation and proliferation in human airway smooth muscle. 1188 Mar 5

The present work aims to determine the relevance of an astrocytoma cell line U373 MG, for assessing the role of some astroglial cytochrome P450 in neurotoxicity and neuroprotection. CYP1B1, CYP2C8, CYP2C9, CYP2D6, CYP2J2, CYP2E1 and CYP4A11 mRNA were detected by reverse transcriptase-polymerase chain reaction in control U373 MG cell cultures. Among them we focused on CYP1B1 expression. After 48 h treatment with a range of concentrations of interleukin-1beta (1, 5, 10 ng/ml) used to simulate stress conditions, CYP1B1 mRNA expression was enhanced in a dose-dependent way. This increased expression was followed 24 h later by an increase in protein level, determined by Western-blot. N-acetylcysteine (NAC) partially inhibited this effect both on the mRNA and protein levels. As CYP1B1 activates procarcinogenic compounds to reactive metabolites, an increase in this P450 isoform will participate to toxic consequences of an inflammatory/oxidative stress. NAC will prevent this deleterious effect.
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PMID:Astroglial CYP1B1 up-regulation in inflammatory/oxidative toxic conditions: IL-1beta effect and protection by N-acetylcysteine. 1256 1

The Nuclear Factor Kappa B (NF-kappaB) is a lymphoid-specific transcription factor, which is sequestered in the cytoplasm by the protein IkappaB. NF-kappaB plays a major role in the regulation of HIV-1 gene expression. Upon activation, NF-kappaB is released from IkappaB, moves to the nucleus, and binds to its sites on the HIV long terminal repeat to start transcription of integrated HIV genome. The present review focuses on the NF-kappaB as a potential target for the development of chemotherapy against HIV-1. Beginning from the viral-binding to reverse transcription, integration, and gene expression, to the virion maturation, the life cycle of HIV presents drug-targets at all the stages. As a result, many drugs have been developed and have entered clinical trials. Some of the most important of these are reverse transcriptase and protease inhibitors, which have been used mostly in clinical studies in the form of combined therapy. But, this combined therapy has presented the problem of resistance, due to mutations in the virus. However, targeting NF-kappaB for the suppression of virus does not present the problem of resistance, as NF-kappaB is a normal part of the human T-4 cell, and is not subject to mutations, as is the virus. An overview of the NF-kappaB system and its role in HIV-1 is presented, followed by a critical review of its current and potential synthetic inhibitors. The drugs studied against NF-kappaB fall mainly into three categories: (1) Antioxidants, against oxidative stress conditions, which aid in NF-kappaB activation, (2) IkappaB phosphorylation and degradation inhibitors (the phosphorylation and degradation of IkappaB is necessary to make NF-kappaB free and move to the nucleus), and (3) NF-kappaB DNA binding inhibitors. The antioxidants include N-Acetyl-L-cysteine (NAC), alpha-Lipoic acid, glutathione monoester, pyrrolidine dithiocarbamate, and tepoxalin, of which NAC is the best studied. The IkappaB phosphorylation and degradation inhibitors, which have been studied in the context of HIV-1 include the salicylates (sodium salicylate, and acetylsalicylic acid (aspirin)). Finally, the NF-kappaB DNA binding inhibitors, which have received attention only recently, are reviewed. These include the most potential, aurine tricarboxylic acid (ATA), a chelating agent, which has been found to inhibit NF-kappaB DNA binding at a low concentration of 30 micro M. The probable mechanism of action of these drugs is discussed alongwith relevant suggestions and conclusions.
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PMID:Nuclear factor kappa B: a potential target for anti-HIV chemotherapy. 1287 Nov 31

The disposition of stavudine, a potent and orally active nucleoside reverse transcriptase inhibitor, was investigated in six healthy human subjects. Before dosing humans with [1'-(14)C]stavudine, a tissue distribution study was performed in Long-Evans rats. Results from this study showed no accumulation of radioactivity in any of the tissues studied, indicating that the position of the (14)C-label on the molecule was appropriate for the human study. After a single 80-mg (100 microCi) oral dose of [1'-(14)C]stavudine, approximately 95% of the radioactive dose was excreted in urine with an elimination half-life of 2.35 h. Fecal excretion was limited, accounting for only 3% of the dose. Unchanged stavudine was the major drug-related component in plasma (61% of area under the plasma concentration-time curve from time zero extrapolated to infinite time of the total plasma radioactivity) and urine (67% of dose). The remaining radioactivity was associated with minor metabolites, including mono- and bis-oxidized stavudine, glucuronide conjugates of stavudine and its oxidized metabolite, and an N-acetylcysteine (NAC) conjugate of the ribose (M4) after glycosidic cleavage. Formation of metabolite M4 was shown in human liver microsomes incubated with 2',3'-didehydrodideoxyribose, the sugar base of stavudine, in the presence of NAC. In addition, after similar microsomal incubations fortified with GSH, two GSH conjugates, 3'-GS-deoxyribose and 1'-keto-2',3'-dideoxy-3'-GS-ribose, were observed. This suggests that 2',3'-didehydrodideoxyribose underwent cytochrome P450-mediated oxidation leading to an epoxide intermediate, 2',3'-ribose epoxide, followed by GSH addition. In conclusion, absorption and elimination of stavudine were rapid and complete after oral dosing, with urinary excretion of unchanged drug as the predominant route of elimination in humans.
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PMID:Disposition of [1'-(14)C]stavudine after oral administration to humans. 2005 18

Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor used against the human immunodeficiency virus type-1 (HIV-1), mostly to prevent mother-to-child transmission of the virus in developing countries. However, reports of severe NVP-induced hepatotoxicity and serious adverse cutaneous effects have raised concerns about its use. NVP metabolism involves oxidation of the 4-methyl substituent to 4-hydroxymethyl-NVP (12-hydroxy-NVP) and the formation of phenolic derivatives. Further metabolism, through either oxidation to quinoid derivatives or phase II esterification, may produce electrophilic derivatives capable of reacting with bionucleophiles to yield covalent adducts. These adducts could potentially be involved in the initiation of toxic responses. To gain insight into potentially reactive sites in proteins and prepare reliable and fully characterized NVP-amino acid adduct standards for subsequent assessment as biomarkers of NVP toxicity, we have used the model electrophile, 12-mesyloxy-NVP, as a synthetic surrogate for the NVP metabolite, 12-sulfoxy-NVP. Reactions of this model ester were conducted with glutathione and the nucleophilic amino acids arginine, cysteine, histidine, and tryptophan. Moreover, because adducts through the N-terminal valine of hemoglobin are convenient biomarkers of exposure to electrophilic toxicants, we also investigated the reaction with valine. We obtained very efficient (>80%) binding through the sulfur of both glutathione and N-acetylcysteine and moderate yields (10-14%) for binding through C2 of the indole ring of tryptophan and N1 of the imidazole ring of histidine. Reaction with arginine occurred through the alpha-amino group, possibly due to the high basicity of the guanidino group in the side chain. Reaction at the alpha-amino group of valine occurred to a significant extent (33%); the resulting adduct was converted to a thiohydantoin derivative, to obtain a standard useful for prospective biomonitoring studies. All adducts were characterized by a combination of (1)H and (13)C NMR spectroscopy and mass spectrometry techniques. The NVP conjugates with glutathione and N-acetylcysteine identified in this work were previously reported to be formed in vivo, although the corresponding structures were not fully characterized. Our results support the validity of 12-mesyloxy-NVP as a surrogate for 12-sulfoxy-NVP and suggest that NVP metabolism to 12-hydroxy-NVP, and subsequent esterification, could potentially be a factor in NVP toxicity. They further imply that multiple sites in proteins may be targets for modification by 12-hydroxy-NVP-derived electrophiles in vivo. Additionally, we obtained reliable, fully characterized standards for the assessment of protein modification by NVP in vivo, which should help clarify the potential role of metabolism in NVP-induced toxicity.
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PMID:Amino acid adduct formation by the nevirapine metabolite, 12-hydroxynevirapine--a possible factor in nevirapine toxicity. 2039 79


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