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)

Reactive oxygen species like hydrogen peroxide (H2O2) have been shown to serve as messengers in the induction of NF-kappa B and then in the activation and replication of HIV-1 in human cells. Because singlet oxygen (1O2) is another very important reactive oxygen species whose action in transcription factor activation is totally undetermined, we started to investigate its role in both NF-kappa B and HIV-1 activation. For provoking unbalanced redox conditions, 1O2 was generated by photosensitization using methylene blue as photosensitizer. Lymphocytes or monocytes (ACH-2 or U1 respectively) latently infected with HIV-1 were treated by photosensitization mediated by methylene blue and the production of reactive oxygen species was monitored through their cytotoxic effect in infected cells. The generation of 1O2 by methylene blue turns out to be very efficient in inducing NF-kappa B as a heterodimer composed of the p50 and p65 subunits. This induction appears specific since other transcription factors like AP-1 are only weakly activated by this treatment. In comparison with other inducing treatments such as phorbol esters or tumor necrosis factor alpha (TNF-alpha), the methylene-blue-mediated activation of NF-kappa B is slow, becoming optimal 180 min after treatment. These kinetic data were obtained by following, on the same samples, both the emergence of NF-kappa B in the nucleus and the disappearance of I kappa B-alpha in the cytoplasmic extracts. Conjugated with the induction of this transcription factor, HIV-1 reactivation from these latently infected cells was also observed by the measurement of reverse transcriptase activity in the cell supernatants. These data allow us to postulate that 1O2 is a biologically important reactive oxygen species which could play a role in the establishment of oxidative stress conditions leading to HIV-1 activation via the presence of NF-kappa B in the nucleus of infected cells.
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PMID:NF-kappa B transcription factor and human immunodeficiency virus type 1 (HIV-1) activation by methylene blue photosensitization. 770 61

A single dose of coumarin derivatives, warfarin, 4-hydroxycoumarin and umbelliferone, added at the time of inoculation either by free virus or by contact with U1 monocytes exhibited a dose-dependent inhibitory effect on viral replication in target MOLT-4 lymphocytes observable even at 5 days post infection. In addition, marked decrease of HIV-1 gap p24 release and reduction in reverse transcriptase activity was observed when chronically HIV-infected ACH-2 lymphocytes were treated with coumarins (ED50% range 10(-6)-10(-9) mol/l). However, the intracellular composition of HIV-1 core proteins in drug-exposed cells was not modified. Results suggest that although no complete inhibition of viral production has been observed in vitro this class of drugs may present potential interest as antiviral agents.
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PMID:Inhibitory effect of coumarins on HIV-1 replication and cell-mediated or cell-free viral transmission. 790 38

An in vitro model of placental infection by human immunodeficiency virus type 1 (HIV-1) was established using human choriocarcinoma-derived trophoblast lines exposed to free HIV-1 or HIV-1-infected lymphocytic and monocytic cells. Virus infectivity was evaluated by measuring both the levels of p24 HIV-1 antigen and reverse transcriptase activity either from indicator MT-4 lymphocytes after co-cultivation with infected trophoblasts or directly from trophoblast cultures. None of the tested trophoblast lines were permissive, in a detectable manner, to infection by cell-free virus. Furthermore, there were no signs of infection when trophoblasts were exposed to HIV-1-carrying ACH-2 and U1 cells with impaired adhesion capacity. However, the exposure to MOLT-4/IIIB lymphocytes or U937/YH5 monocytes that adhere to substrate cells resulted invariably in productive infection. The ultrastructure of the trophoblasts suggests endocytosis of HIV-1. It appears that the infection of the host cell results from the escape of virions from degradation in lysosomes. Alternatively, HIV-1 may enter by budding directly from the lymphocyte surface into the cytoplasm of trophoblasts. These results confirm previous studies and suggest that CD4-negative placental trophoblasts--the only foetal cells in direct contact with maternal blood--can be susceptible to HIV-1 infection.
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PMID:Human immunodeficiency virus type 1 infection of choriocarcinoma-derived trophoblasts. 810 49

An important aspect of human immunodeficiency virus (HIV-1) infection is the regulation of its expression by nuclear factor kappa B (NF-kappa B) through redox-controlled signal transduction pathways. In this study, we demonstrate that iron chelation by deferoxamine (DFO) protects against the cytotoxic and reactivating effects of hydrogen peroxide (H2O2). These protective effects were observed both in lymphocytic (ACH-2) and promonocytic (U1) cells latently infected by HIV-1. Concomitantly, NF-kappa B activation by H2O2, when followed by gel retardation assay, was decreased in the DFO-treated U1 and ACH-2 cells. This latter DFO-mediated effect was specific, as DFO did not clearly affect AP-1 DNA-binding activity when studied after H2O2-induced stress. More importantly, DFO protected against the H2O2-induced activation of HIV-1 as evidenced by reverse transcriptase activity in the supernatant. DFO also protected against PMA-induced NF-kappa B activation as well as TNF-alpha-induced HIV-1 activation. Furthermore, DFO attenuated the p24 response in PBMC infected with HIV-1 and stimulated with IL-2. These different effects of DFO were obtained at DFO concentrations lower than 5 microM. Other chemically unrelated iron chelators also provided protection against cytotoxicity, NF-kappa B activation, and HIV-1 activation in U1 cells challenged with H2O2.
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PMID:Iron chelation decreases NF-kappa B and HIV type 1 activation due to oxidative stress. 855 2

The ACH-2 cell clone derived from a human T-cell line and chronically infected with human immunodeficiency virus 1 (HIV-1) and the U1 cell clone derived from a human promonocyte cell line and also chronically infected with HIV-1 produce HIV-1 in a response to stimulation with monokine-enriched supernatants prepared from highly purified populations of peripheral blood-derived human monocytes. Monokine-mediated expression of HIV-1 in these cell lines resulted in augmented virus production reflected by increases in reverse transcriptase (RT) activity, production of p24 antigen, and synthesis of major viral proteins. Examination of the cells by electron microscopy revealed numerous HIV-1 virions in the cells treated with the supernatants. This stimulation of virus production by monokine-enriched supernatants resulted in approximately 100-fold increases in RT activity and p24 antigen expression in comparison with those in untreated U1 and ACH-2 cells. Absorption of monokine-enriched supernatants with rabbit anti-tumor necrosis factor alpha antibody removed most, but not all, of the induced HIV-1 RT activity and p24 antigen expression in U1 and ACH-2 cell lines, suggesting that tumor necrosis factor alpha in the monokine-enriched supernatants is a major factor in the induction of HIV-1 expression in these cells.
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PMID:Monokine-mediated increase in human immunodeficiency virus type 1 expression in chronically infected promonocyte- and T-cell-derived lines. 855 95

The interaction between a chronically human immunodeficiency virus type 1 (HIV-1)-infected promonocytic line (U1) and a normal human embryonic lung fibroblast line (MRC-5) on HIV-1 expression was investigated. Coculture of U1 cells with MRC-5 cells induced HIV-1 reverse transcriptase (RT) activities 40- to 50-fold higher than those of parallel control cultures of U1 cells. Culture of U1 cells in the presence of media conditioned by MRC-5 cell culture supernatants resulted in a 30- to 40-fold greater HIV-1 RT activity over a 6-day period. HIV-1 RT activity, however, was not increased in the chronically infected T lymphocyte cell line (ACH-2) by either coculture with MRC-5 cells or when cultured in the MRC-5 cell culture supernatant-conditioned media. A polyclonal antibody against interleukin-6 (IL-6) blocked HIV-1 induction in the U1 cells by MRC-5 culture supernatants, indicating that IL-6 plays an important role in the HIV-1 induction. The magnitude of HIV-1 induction by the MRC-5 cell culture supernatant-conditioned media was proportional to the concentration of IL-6. In addition, the supernatants from three other normal human lung fibroblast (HLF) cell lines induced HIV-1 RT expression in U1 cells. Thus, normal unstimulated HLFs stimulate HIV-1 expression in chronically infected promonocytic cells by secreting IL-6, suggesting that the interaction of HLFs and macrophages may play an important role in the development of HIV-1 infection in the lungs.
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PMID:Induction of HIV-1 expression in chronically infected promonocytic cells cocultured with human lung fibroblasts. 876 62

Acute HIV-1 infection of H9 and C8166 cultures has been shown to be suppressed by certain flavonoids, and evidence for inhibition of HIV-1 protease, integrase, and reverse transcriptase by flavonoids also exists. The present aim was to determine whether flavonoids inhibit HIV-1 activation in models of latent infection. By screening flavonoids from six different classes, three structurally related compounds (chrysin, acacetin, and apigenin) were identified that inhibited HIV expression in TNF-alpha-treated OM-10.1 cultures. The three compounds had favorable potencies against HIV activation in relation to their growth inhibitory effects (therapeutic index 5-10). Chrysin also inhibited HIV expression in response to PMA in OM-10.1 cells, in ACH-2 cells stimulated with either TNF-alpha or PMA, and in 8E5 cultures. Furthermore, return to viral latency in OM-10.1 cells previously exposed to TNF-alpha occurred over a shorter time interval when chrysin was added. The inhibition of HIV activation was not dependent on preincubation with flavonoids relative to TNF, and was characterized by a lack of HIV RNA accumulation by Northern analysis. Gel-shift experiments revealed that NF-kappa B activation after TNF-alpha treatment was not inhibited by these agents, suggesting that some other critical factor(s) needed for viral transcription was being affected. These findings indicate that flavonoids inhibit HIV-1 activation via a novel mechanism, and that these agents are potential candidates for therapeutic strategies aimed at maintaining a cellular state of HIV-1 latency.
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PMID:Inhibition of HIV activation in latently infected cells by flavonoid compounds. 882 17

To develop a rapid and sensitive means of detecting cell-associated human immunodeficiency virus (HIV), donor cells from HIV seropositive patients were treated with the potent viral activator sodium-n-butyrate (NaB) and subsequently assayed by both in situ RNA hybridization and a reverse transcriptase polymerase chain reaction (RT-PCR). The sensitivity of RT-PCR was estimated to be equivalent to 1 x 10(-16) grams (0.1 fg) or approximately 64 copies of the input standard viral RNA per reaction. The present study takes advantage of the ability of NaB to introduce changes in chromatin structure of latently infected cells, leading to increased HIV gene expression. Human ACH-2 and U1 cell lines were used as representatives of T-lymphocytic and monocytoid cells harboring latent inducible proviruses. HIV gene expression was readily detected when these cells were treated with NaB. Viral gag RNA was detected by both in situ and RT-PCR assays. When peripheral blood mononuclear cells (PBMCs) from acquired immunodeficiency syndrome (AIDS) patients, who were all negative for in situ hybridization and serum/plasma p24 assays, were used for detection of viral gene expression, four categories with distinct patterns of induction were observed. The first set of patients showed HIV-positive PBMCs by RT-PCR without any added NaB, and suppression by added NaB or PHA. The second set of samples showed induction of viral RNA by NaB alone. The third set could be induced with PHA, but not NaB, and the fourth set required both NaB and PHA for induction of HIV gene expression. Our results suggest that direct treatment of the cells with HIV activators may be useful in increasing sensitivity of the RT-PCR intended to be used for detection of cell-associated viral RNAs. This approach may be used to confirm true status of the HIV infection when p24 results are negative or HIV RNAs in serum/plasma are below the threshold of detection. Moreover, this method may identify the presence of latent proviral genomes possibly reflecting the true rate of cell-associated viral load in vivo and without possible mutations brought about by long-term co-cultivation assays with cells from seronegative donors.
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PMID:Rapid and sensitive detection of cell-associated HIV-1 in latently infected cell lines and in patient cells using sodium-n-butyrate induction and RT-PCR. 917 66

We investigated a strategy for gene therapy, intracellular expression of anti-HIV-1 Rev single-chain variable fragments (SFvs), in promonocytic (U1) and T (ACH-2) cell lines latently infected with HIV-1. The cellular and molecular mechanisms leading to activation of latent integrated HIV-1 provirus in U1 and ACH-2 cells have been well delineated. These cells produce HIV-1 in response to stimulation with certain cytokines. U1 and ACH-2 cells were transduced with a murine retroviral shuttle vector that expresses anti-Rev SFv (pLXSN-D8SFv-Rev) or with a control murine leukemia virus (MLV) vector (pLXSN). Tumor necrosis factor alpha (TFNalpha)-, interleukin 6 (IL-6)-, and phorbol myristate acid (PMA)-induced HIV-1 expression, as determined by reverse transcriptase (RT) assay, was significantly inhibited in cells transduced with pLXSN-D8SFv-Rev, compared with cells transduced with pLXSN. In addition, pLXSN-D8SFv-Rev-transduced cells, when incubated with monokine-enriched supernatants of human peripheral blood monocyte cultures, produced significantly less HIV-1 than did cells transduced with pLXSN. This resistance to cytokine-induced HIV-1 expression was demonstrated in SFv-transduced U1 and ACH-2 cells maintained in G418-free medium for 2 months. These data suggest that feasibility of utilizing various anti-HIV-1 SFvs to block activation of HIV-1 infection in vivo.
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PMID:Inhibition of HIV type 1 replication in chronically infected monocytes and lymphocytes by retrovirus-mediated gene transfer of anti-Rev single-chain variable fragments. 984 Feb 90

Several groups, including ours, have reported that chloroquine (CQ) or its analog hydroxychloroquine has anti-HIV-1 activity both in vitro and in vivo. We studied in vitro whether the addition of CQ to the combination of hydroxyurea (HU) plus didanosine (ddI) had an additive effect in inhibiting the replication of HIV-1. Therefore both the H-9 T lymphocytic cell line and the U-937 promonocytic cell line as well as primary T cells and monocytes were infected with HIV-1 and then treated with HU at 0.2 mM and ddI at 1 microM and varying concentrations of CQ. Addition of CQ resulted in an additional inhibition of HIV-1 replication, as assessed by reverse transcriptase (RT) activity, with a CQ EC50 of 0.4-0.9 microM for the cell lines and of 0.2-0.9 microM for the primary cells. Similarly, addition of CQ further inhibited HIV-1 replication in U-1 cells stimulated either with LPS or H2O2 and in ACH-2 cells stimulated either with PMA or H2O2, with CQ EC50 values of 0.1 and 1 microM, respectively. Under the experimental conditions used, CQ induced neither toxicity nor apoptosis in the H-9 and U-937 cells. This in vitro additive anti-HIV-1 activity of CQ, in combination with HU + ddI, supports the idea that this triple regimen should be studied in clinical trials. It may become of particular interest to HIV-1-infected individuals from the developing world, in view of the low cost of both CQ and HU.
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PMID:Chloroquine exerts an additive in vitro anti-HIV type 1 effect when associated with didanosine and hydroxyurea. 1050 72


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