N-acetylcysteine: a new approach to anti-HIV therapy

Stimulation of glutathione peroxidase activity decreases HIV type 1 activation after oxidative stress

Am important aspect of human immunodeficiency virus (HIV-1) infection is the regulation of its expression by nuclear factor kappa B (NF-kappa B) by redox-controlled signal transduction pathways. In this study, we demonstrate that selenium supplementation can effectively increase glutathione peroxidase (GPx) activity in latently infected T lymphocytes. The Se-supplemented cells exhibited an important protection against the cytotoxic and reactivating effects of hydrogen peroxide (H2O2). Concomitantly, NF-kappa B activation by H2O2 was also decreased in Se-supplemented cells. Selenium stimulation of GPx activity also induces a protective effect against cell activation by tumor necrosis factor alpha (TNF-alpha) but less significantly by phorbol esters such as PMA. These Se-mediated effects were specific because they were not found when AP-1 DNA-binding activity was studied after H2O2-induced stress. Hyperthermia was also studied because it could promote intracellular electron leakage in electron transport chains. Elevating the temperature to 42 degrees C did not induce NF-kappa B directly. Rather, it sensitized infected cells to subsequent oxidative stress by H2O2, demonstrating the importance of hyperthermia, often associated with opportunistic infections in the development of immunodeficiency. In this case, Se induced partial protection against the sensitizing effect of hyperthermia.

Comparison of cellular accumulation, tissue distribution, and anti-HIV activity of free and liposomal 2',3'-dideoxycytidine

We have investigated the cellular accumulation, tissue distribution, and antihuman immunodeficiency virus activity of free dideoxycytidine (ddC) and liposomal ddC (L-ddC). We have found that L-ddC was more efficiently taken up than its free form by RAW 264.7 cells (a monocyte-macrophage cell line) (p < 0.01) while a comparable uptake was seen in U937 cells (a promonocytic cell line). In the rat, L-ddC accumulated preferentially in liver and spleen when injected intravenously (p < 0.01), and mostly in spleen when given intraperitoneally (p < 0.01). In contrast, free ddC was rapidly eliminated out of the body. Liposomal ddC showed a similar anti-HIV activity in comparison with free ddC in U937 cells. Given the fact that encapsulation of ddC in liposomes does not affect its anti-HIV activity but enhances its in vitro cellular accumulation and its in vivo distribution in reticuloendothelial system (RES) tissues, we conclude that ddC in liposomal formulation is a promising anti-HIV agent with a targeted action on the RES, which is considered a reservoir for dissemination of virus to other cells, tissues, and organs.

Opposing regulatory effects of thioredoxin and eosinophil cytotoxicity-enhancing factor on the development of human immunodeficiency virus 1

Exogenous recombinant human thioredoxin (rTRX, > or = 500 nM), a dithiol reductase enzyme, inhibited the expression of human immunodeficiency virus (HIV) 1BaL in human macrophages (M phi) by 71% (range, 26-100%), as evaluated by p24 antigen production and the integration of provirus at 14 d after infection. The stoichiometric reducing agent N-acetylcysteine (NAC) also inhibited HIV production, but to a lesser degree, and only at 30,000-fold higher concentrations. Exogenous rTRX is cleaved by M phi to generate the inflammatory cytokine, eosinophil cytotoxicity-enhancing factor (ECEF). In contrast to rTRX, rECEF (concentrations from 50 pM to 2 microM) enhanced the production of HIV by 67% (range, 33-92%). Thus, whereas TRX is a potent inhibitor of the expression of HIV in human M phi, cleavage of TRX to ECEF creates a mediator with the opposite effect. TRX also inhibited the expression of integrated provirus in the chronically infected OM 10.1 cell line, showing that it can act at a step subsequent to viral infection and integration.

Organic thiophosphate WR-151327 suppresses expression of HIV in chronically infected cells

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.

Imbalance between oxidants and antioxidants in the lungs of HIV-seropositive individuals

Following the initial infection with HIV, there is evidence of immune dysfunction despite an apparent normal clinical state. In the context that the lung is a major site affected by opportunistic infection, and that some components of the immune system are activated during early HIV infection, we hypothesized that there may be activation of alveolar macrophages (AM), a key component of the pulmonary host defense system. Compared to cells from normal individuals, AM of asymptomatic HIV-seropositive (HIV+) individuals (CDC-stage II) spontaneously released significantly more superoxide anion (O2-.) (P < 0.002). The O2-. release by AM of HIV-infected individuals was comparable to the spontaneous O2-.-release by AM of cigarette smokers (P > 0.6), a condition often associated with chronic damage of respiratory tissues. The destructive effects of oxidants are normally suppressed by antioxidant defense systems. Evaluation of the concentrations of glutathione, a major component of the pulmonary antioxidant protective screen, demonstrated that the HIV+ state is also characterized by a significant glutathione deficiency in lung epithelial lining fluid (P < 0.001) and in venous plasma (P < 0.001). This suggests that the alveolar structures of HIV+ individuals are continuously exposed to increased amounts of toxic oxygen radicals without adequate protection, i.e. the reactive oxygen metabolites may cause sufficient tissue damage culminating in interstitial lung disease. Further, since many immune functions are susceptible to injury by extracellular oxidants, the consequences of an unsuppressed oxidant burden in the lung may amplify the extent of local immunocompromise. In addition, since glutathione plays an important role in modulating lymphocyte activation and effector functions independent of its antioxidant activity, the systemic glutathione deficiency may contribute to the progressive global immune dysfunction that characterizes HIV infection.

Valproic acid reduces the intracellular level of glutathione and stimulates human immunodeficiency virus

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.

Correction of glutathione deficiency in the lower respiratory tract of HIV seropositive individuals by glutathione aerosol treatment

BACKGROUND

Concentrations of glutathione, a ubiquitous tripeptide with immune enhancing and antioxidant properties, are decreased in the blood and lung epithelial lining fluid of human immunodeficiency virus (HIV) seropositive individuals. Since the lung is the most common site of infection in those who progress to AIDS it is rational to consider whether it is possible to safely augment glutathione levels in the epithelial lining fluid of HIV seropositive individuals, thus potentially improving local host defence.

METHODS

Purified reduced glutathione was delivered by aerosol to HIV seropositive individuals (n = 14) and the glutathione levels in lung epithelial lining fluid were compared before and at one, two, and three hours after aerosol administration.

RESULTS

Before treatment total glutathione concentrations in the epithelial lining fluid were approximately 60% of controls. After three days of twice daily doses each of 600 mg reduced glutathione, total glutathione levels in the epithelial lining fluid increased and remained in the normal range for at least three hours after treatment. Strikingly, even though > 95% of the glutathione in the aerosol was in its reduced form, the percentage of oxidised glutathione in epithelial lining fluid increased from 5% before treatment to about 40% three hours after treatment, probably reflecting the use of glutathione as an antioxidant in vivo. No adverse effects were observed.

CONCLUSIONS

It is feasible and safe to use aerosolised reduced glutathione to augment the deficient glutathione levels of the lower respiratory tract of HIV seropositive individuals. It is rational to evaluate further the efficacy of this tripeptide in improving host defence in HIV seropositive individuals.

Immunobiological aspects of HIV treatment

Recent information on the efficacy of anti-retroviral therapy and vaccination strategies has been disappointing as well as confusing. The recently announced Concorde study suggested that there is no advantage to early treatment of asymptomatic HIV infection with azidothymidine alone, even though the levels of CD4+ cells in the treated group were consistently higher than in the untreated group. This will lead to increasing attention being paid to the mechanisms whereby HIV causes AIDS, which have sadly been sidelined in the rush to produce classically based therapies and vaccines. Over the last year many different theories on how HIV kills CD4+ cells and leads to AIDS have been discussed and tentatively explored.

Malnutrition in AIDS

Malnutrition, weight loss, and chronic diarrhea are common findings in patients infected with human immunodeficiency virus (HIV), and many traditional and nontraditional dietary approaches have been suggested. This article examines the mechanisms and pathophysiology of wasting in HIV, and the evidence for malnutrition of protein, energy, and micronutrients in patients with the acquired immunodeficiency syndrome (AIDS). The article concludes with a review of dietary therapy in AIDS patients.

Oltipraz, an inhibitor of human immunodeficiency virus type 1 replication

Glutathione depletion may play a pivotal role in the pathogenesis of human immunodeficiency virus type-1 (HIV-1) infection. Since certain compounds prevent experimental carcinogenesis by elevating the levels of glutathione and phase II detoxication enzymes, we compared the potencies of several inducers with their ability to inhibit basal levels of HIV-1 replication in H9 cutaneous T-cell lymphoma cells. All monofunctional inducers tested elevated the levels of glutathione and quinone reductase, a marker for phase II enzyme induction. However, only oltipraz [4-methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione] was effective at inhibiting HIV-1 replication (IC50 = 14.8 +/- 3.1 microM). The antiviral effect of oltipraz was potentiated by 3'-azido-3'-deoxythymidine. Thus, 1,2-dithiole-3-thiones represent a hitherto unrecognized class of anti-HIV-1 agents. Oltipraz behaves kinetically as an irreversible inhibitor of HIV-1 reverse transcriptase in the template-primer binding domain. Oltipraz has been used to treat schistosomiasis in humans and is undergoing clinical evaluation as an anticarcinogen. Thus, oltipraz (and other 1,2-dithiole-3-thiones) may have therapeutic utility in HIV-1-infected individuals, not only because of their antiretroviral activity, but also by preventing the development of HIV-1-associated neoplasms.

Antioxidants inhibit stimulation of HIV transcription

In studies presented here, we demonstrate that antioxidants regulate NF-kappa B activation and signal transduction pathways leading to HIV expression. We show (1) that N-acetyl-L-cysteine (NAC), an antioxidant and an efficient glutathione (GSH) precursor, inhibits NF-kappa B activation and HIV expression under conditions in which GSH is depleted and NAC cannot be converted to GSH, (2) that the D-stereoisomer of NAC and a wide variety of chemically unrelated antioxidants also inhibit NF-kappa B activation and/or transcription directed by the HIV LTR, and (3) that depletion of GSH, the principal intracellular antioxidant, augments HIV production in an acute infection model. Taken together, these findings suggest direct antioxidant action as the mechanism for inhibition of HIV transcription by NAC. They also confirm that GSH, acting in its capacity as an antioxidant, regulates HIV expression and that exogenous antioxidants can potentiate this regulation.

Reactive oxygen intermediates and human immunodeficiency virus (HIV) infection

HIV infection affects various parts of the immune system, including the CD4+ lymphocytes and mononuclear phagocytes, and causes a progressive immunodeficiency. This renders the patient susceptible to various opportunistic infections and neoplasms. Reactive oxygen intermediates (ROI) are important for the intracellular killing of microorganisms by mononuclear phagocytes and neutrophils. Although data are discrepant, several studies suggest that the generation of ROI is impaired in mononuclear phagocytes, and possibly also in neutrophils, from HIV-infected individuals. This may lead to deficient killing of intracellular microorganisms predisposing the HIV-infected patient to certain opportunistic infections. Recently, in vitro studies have shown that ROI activate the intracellular transcription factor nuclear factor kappa B (NF-kappa B) which stimulates HIV replication. Intracellular antioxidant systems, such as the glutathione system, seem to be of importance for the regulation of ROI levels and thus probably for HIV replication in vitro. However, the role of ROI in regulation of HIV replication in vivo is unknown at present. The role of ROI in HIV infection is thus difficult to assess, both at the cellular and clinical level. Reduced intracellular concentrations of ROI may lead to impaired phagocyte microbicidal functions, thus predisposing HIV-infected patients to various opportunistic infections. On the other hand, increased ROI levels may be associated with a stimulation of HIV replication leading to clinical deterioration.

The inhibitory ankyrin and activator Rel proteins

The gene families encoding the proteins NF-kappa B, c-Rel and Dorsal, in conjunction with their respective inhibitors l kappa B, pp40, and Cactus, achieve specificity in gene regulation by means of common principles. The related activities of NF-kappa B and Dorsal are mediated by heterodimeric or homodimeric complexes of proteins containing the conserved dimerization and DNA-binding domain termed Rel. The l kappa Bs and Cactus, which share a core series of structural repeats termed ankyrin, inhibit cognate activators through differential interactions with the Rel-homology domain. Together, the inhibitory ankyrin proteins and their cognate Rel dimers probably define specific signalling pathways able to activate specific gene expression. Both gene families include proto-oncogenes, thus broadly implicating Rel/l kappa B in the control of both normal gene expression and the aberrant gene expression that makes cells cancerous.