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

To elucidate the action of vitamin C on pathogenic human retroviruses, we investigated and compared the effects of noncytoxic concentrations of ascorbic acid (AA), its calcium salt (Ca-ascorbate), and two thiol-based reducing agents [glutathione (GSH) and N-acetyl-L-cysteine (NAC)] against human immunodeficiency virus (HIV)-1 replication in chronically infected T lymphocytes. Ca-ascorbate reduced extracellular HIV reverse transcriptase (RT) activity by about the same magnitude as the equivalent dose of AA. Long-term experiments showed that continuous presence of ascorbate was necessary for HIV suppression. NAC (10 mmol/L) caused less than twofold inhibition of HIV RT and conferred a synergistic effect (approximately eightfold inhibition) when tested simultaneously with AA (0.426 mmol/L). In contrast, nonesterified GSH (less than or equal to 1.838 mmol/L) had no effect on RT concentrations and did not potentiate the anti-HIV effect of AA. These results further support the potent antiviral activity of ascorbate and suggest its therapeutic value in controlling HIV infection in combination with thiols.
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PMID:Comparative study of the anti-HIV activities of ascorbate and thiol-containing reducing agents in chronically HIV-infected cells. 172 May 98

Modifications of the glutathione (GSH) intracellular level have been implicated in the regulation of human immunodeficiency virus (HIV) transcription and expression. In regard to this hypothesis, we have investigated the effects of valproic acid (VPA) on HIV replication. Indeed, it has been recently reported that VPA inhibits the human red blood cell glutathione reductase. In the supernatant of a CEM-SS T-lymphocytic cell line infected with the LAI strain of HIV-1, we observed an increase, in a dose-dependent fashion, of the reverse transcriptase activity after treatment of cells with VPA. VPA also induced HIV expression in the chronically infected monocytic U1 cell line which constitutively expresses low levels of virus, enhanced the HIV-long terminal repeat (LTR)-directed expression of beta-galactosidase in transiently transfected Jurkat T-cells, and potentiated the PMA effect on the LTR transactivation. GSH assays showed that VPA treatment led to a decrease in the intracellular level of this thiol compound in U937 (U1 parent-cell line) and in Jurkat T-cells. Work to understand the molecular mechanism of VPA-induced HIV transcription and expression are now in progress. VPA seems to be an adequate molecule to study the implications of a GSH decrease in the stimulation of HIV replication. However, a modification of the intracellular balance between reduced and oxidized glutathione, rather than a simple reduction of the intracellular glutathione level, could be of importance in the regulation of HIV replication and we are now testing this hypothesis. Finally, these findings already suggest that VPA, which is an anticonvulsive drug frequently prescribed for the management of various seizure disorders, should not be recommended for treatment of epilepsy or other related illnesses in HIV-positive individuals.
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PMID:Valproic acid reduces the intracellular level of glutathione and stimulates human immunodeficiency virus. 751 59

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 investigated the effects of glutathione (GSH), the major naturally occurring thiol, and a pharmacologic thiol precursor of GSH, N-acetyl cysteine (NAC), on the expression of human immunodeficiency type 1 (HIV-1) in primary cord blood and adult donor monocyte-derived macrophages (MDM). HIV-1 infection of cord blood and adult MDM was accomplished after incubating 10-15-d-old cultures for 4 h with a monocyte-tropic strain of HIV-1 (Bal). After 1 wk in culture cell supernatants were tested for reverse transcriptase (RT) activity. MDM were exposed to 5, 10 and 20 mM concentrations of both GSH and NAC before infection, during infection, and after infection was established. GSH and NAC suppressed the replication of HIV-1 in both primary cord blood and adult donor MDM in a concentration dependent fashion. These suppressive effects were more pronounced in cord-derived cells than in adult-derived cells. In cells treated with GSH or NAC before infection, there was no significant rise in RT activity as compared with controls. Similarly, when cells were treated with GSH and NAC and simultaneously infected, there was also no significant rise in RT activity after 1 wk in culture. In cells treated after infection was established, RT values were suppressed 80-90% that of untreated controls. This effect persisted for 1-2 wk after exposure to GSH and NAC. Untreated controls demonstrated syncytium formation and lost characteristics of spreading and elongation 2 wk after HIV-1 infection, whereas most of the treated cells remained free of syncytium and retained cytoplasmic spreading, adherence, and elongation. These data are consistent with other studies of thiol suppression of HIV-1 replication and demonstrate a similar observation for primary cultured cord MDM. These results may offer new approaches toward cellular protection after infection with HIV-1.
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PMID:Thiol suppression of human immunodeficiency virus type 1 replication in primary cord blood monocyte-derived macrophages in vitro. 767 9

The role of glutathione (GSH) in tumor cell resistance to alkylating agents and platinum compounds is suggested by a body of laboratory and clinical studies. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS), the expression of which is proportional both to GSH content and to the level of resistance in ovarian cancer cell lines. The role of this enzyme in regulating GSH levels is unclear, however. Reversal of resistance is achieved in vitro and in vivo with the use of buthionine sulfoximine (BSO), a potent inhibitor of gamma-GCS. In the course of a Phase I clinical trial of BSO and melphalan, we have measured GSH and expression of gamma-GCS mRNA in peripheral mononuclear cells before and at intervals after the initiation of treatment with BSO. Mean baseline GSH content was 6.89 nmol/mg protein. Treatment with BSO (10.5 to 17 g/m2 i.v. every 12 h for six doses) resulted in a mean nadir GSH decline to 19% of control values, most commonly on day 3. Baseline expression of gamma-GCS mRNA was measured by a reverse transcriptase polymerase chain reaction-based method. When described relative to that of beta-actin, the expression of gamma-GCS varied over 3-fold among individuals. Following GSH depletion by BSO, the level of gamma-GCS mRNA rose successively on days 3 and 5 to reach a mean increase of 2-fold on day 8. Differences were observed among patients in their capacity to respond to GSH depletion by increasing gamma-GCS steady-state mRNA levels (1.4- to 3.1-fold). These results show that the expression of gamma-GCS is variable in the population and suggest that the cellular content of GSH may be involved in the regulation of its expression.
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PMID:Variable baseline gamma-glutamylcysteine synthetase messenger RNA expression in peripheral mononuclear cells of cancer patients, and its induction by buthionine sulfoximine treatment. 810 66

Glutathione (GSH) levels are markedly depleted in patients infected with human immunodeficiency virus type 1 (HIV-1) and supplementation of media with high concentrations (5-20 mM) of low-molecular weight thiols prevents HIV-1 replication in cultured cells. We were intrigued whether chemopreventive enzyme inducers might represent a more pharmacologically feasible method to inhibit HIV-1 replication since these compounds elevate intracellular concentrations of GSH at nontoxic doses in vivo. After establishing that all inducers surveyed were able to elevate GSH levels in human T-cell and monocytoid cell lines, we were surprised to find that oltipraz (5-pyrazinyl-4-methyl-1,2-dithiole-3-thione) was uniquely able to inhibit HIV-1 replication (IC50 = 5-15 microM). Oltipraz and other antiviral 1,2-dithiole-3-thiones (DTTs) appear to inhibit acute HIV-1 replication by inactivating reverse transcriptase (RT). However, among DTTs that inhibit HIV-1 replication in acutely infected cells, only oltipraz was able to inhibit HIV-1 replication in a chronic infection model. Thus, in addition to inactivating RT, oltipraz appears to have an additional antiviral mechanism distal to viral integration. Our laboratories are attempting to determine the mechanism by which oltipraz inhibits HIV-1 replication in chronically infected cells; we are also attempting to determine the bioorganic mechanism for the inactivation of RT. Since the covalent modification of schistosomal proteins and transcription factor(s) are thought to be responsible for the antiparasitic and chemopreventive activities of DTTs, respectively, our studies should be relevant to understanding the diverse medicinal properties of DTTs. Oltipraz, an antischistosomal drug undergoing clinical evaluation as an anticarcinogen, inhibits HIV-1 replication at concentrations achievable in human serum. It is intriguing to consider oltipraz as a therapeutic agent not only for its antiretroviral activity, but also for the prevention of HIV-1 associated neoplasms.
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PMID:Oltipraz, a novel inhibitor of human immunodeficiency virus type 1 (HIV-1) replication. 853 88

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

Elevation of glutathione (GSH) is widely observed in cellular resistance to platinum agents. Our previous studies have shown that sublines of human ovarian carcinoma cell line A2780, which exhibited low levels of resistance to oxaliplatin, showed elevated steady state levels of mRNA and activity of gamma-glutamyl transpeptidase (gamma-GT, EC 2.3.2.2), but not of gamma-glutamylcysteine synthetase (gamma-GCS, EC 6.3.2.2) [El-akawi et al., Cancer Lett. 105:5-14; 1966]. To understand this phenomenon better, we have studied the effect of single exposures of oxaliplatin or cisplatin on the mRNA expression of gamma-GT and gamma-GCS in A2780 cells. The mRNAs of gamma-GT and gamma-GCS were measured by reverse transcriptase PCR, with quantitation of the PCR product by HPLC; mRNA levels are expressed as ratios to beta-actin mRNA, used as an endogenous standard. GSH was measured by HPLC. The gamma-GT activity was measured by a colorimetric assay. Single exposures of cells to oxaliplatin induced a time- and concentration-dependent increase in the mRNA of gamma-GT, but not of gamma-GCS. Cisplatin also induced an elevation in gamma-GT mRNA, but to a lower degree. The gamma-GT enzyme activity increased corresponding to the elevation in mRNA expression. The gamma-GT-induced cells showed an increase in cellular GSH when incubated in medium containing GSH. The data suggest that a) single, brief exposures to pharmacologically relevant concentrations of platinum complexes induce elevation in mRNA of gamma-GT, b) elevation in gamma-GT mRNA translates into elevated gamma-GT activity and increase in GSH salvage, and c) the degree of induction of gamma-GT mRNA differs between platinum complexes.
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PMID:Induction of gamma-glutamyl transpeptidase mRNA by platinum complexes in a human ovarian carcinoma cell line. 911 34

The genomes of both bacteria and eukaryotic organisms are known to encode selenoproteins, using the UGA codon for seleno-cysteine (SeC), and a complex cotranslational mechanism for SeC incorporation into polypeptide chains, involving RNA stem-loop structures. These common features and similar codon usage strongly suggest that this is an ancient evolutionary development. However, the possibility that some viruses might also encode selenoproteins remained unexplored until recently. Based on an analysis of the genomic structure of the human immunodeficiency virus HIV-1, we demonstrated that several regions overlapping known HIV genes have the potential to encode selenoproteins (Taylor et al. [31], J. Med. Chem. 37, 2637-2654 [1994]). This is provocative in the light of overwhelming evidence of a role for oxidative stress in AIDS pathogenesis, and the fact that a number of viral diseases have been linked to selenium (Se) deficiency, either in humans or by in vitro and animal studies. These include HIV-AIDS, hepatitis B linked to liver disease and cancer, Coxsackie virus B3, Keshan disease, and the mouse mammary tumor virus (MMTV), against which Se is a potent chemoprotective agent. There are also established biochemical mechanisms whereby extreme Se deficiency can induce a proclotting or hemorrhagic effect, suggesting that hemorrhagic fever viruses should also be examined for potential virally encoded selenoproteins. In addition to the RNA stem-loop structures required for SeC insertion at UGA codons, genomic structural features that may be required for selenoprotein synthesis can also include ribosomal frameshift sites and RNA pseudoknots if the potential selenoprotein module overlaps with another gene, which may prove to be the rule rather than the exception in viruses. One such pseudoknot that we predicted in HIV-1 has now been verified experimentally; a similar structure can be demonstrated in precisely the same location in the reverse transcriptase coding region of hepatitis B virus. Significant new findings reported here include the existence of highly distinctive glutathione peroxidase (GSH-Px)-related sequences in Coxsackie B viruses, new theoretical data related to a previously proposed potential selenoprotein gene overlapping the HIV protease coding region, and further evidence in support of a novel frameshift site in the HIV nef gene associated with a well-conserved UGA codon in the 1-reading frame.
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PMID:Genomic structures of viral agents in relation to the biosynthesis of selenoproteins. 915 12


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