Intracellular glutathione levels in T cell subsets decrease in HIV-infected individuals

Redox regulation of signal transduction: tyrosine phosphorylation and calcium influx

Studies presented here show that altering the intracellular redox balance by decreasing glutathione levels profoundly affects early signal transduction events in human T cells. In a T-cell receptor (TCR) signaling model, short-term pretreatment with buthionine sulfoximine, which specifically decreases intracellular glutathione, essentially abrogates the stimulation of calcium influx by anti-CD3 antibodies without significantly impairing other aspects of TCR-initiated signal transduction, such as overall levels of TCR-stimulated tyrosine phosphorylation. In an inflammatory-cytokine signaling model, the failure of tumor necrosis factor alpha to stimulate more than minimal tyrosine phosphorylation in lymphocytes is overcome by buthionine sulfoximine pretreatment--i.e., tumor necrosis factor alpha stimulates extensive tyrosine phosphorylation in glutathione-depleted lymphocytes. These redox-dependent changes in T-cell responsiveness suggest that the glutathione deficiency that we and others have demonstrated in human immunodeficiency virus-infected individuals may contribute significantly to the immunodeficiency and the increased inflammatory reactions in these individuals.

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.

Glutathione inhibits replication and expression of viral proteins in cultured cells infected with Sendai virus

Addition of reduced glutathione inhibited the production of Sendai virus in African green monkey kidney (AGMK) cells. This result could be accounted for by a direct action of GSH on viral replication. The inhibitory action was associated to an increase of the GSH intracellular level, while the host cell metabolism was unaffected. The antiviral effect was related to decrease and inactivation of the hemagglutinin-neuraminidase (HN) virus glycoprotein.

Dysregulation of adult T-cell leukemia-derived factor (ADF)/thioredoxin in HIV infection: loss of ADF high-producer cells in lymphoid tissues of AIDS patients

Adult T-cell leukemia (ATL)-derived factor (ADF) is a multifunctional protein homologous to thioredoxin (TRX) with co-cytokine and thiol-dependent reducing activities. ADF/thioredoxin production is enhanced in T cells transformed by HTLV-I. We have examined the effect of HIV-1 infection on ADF/TRX expression using specific antibody against ADF/TRX. Lymph nodes from 5 AIDS and 1 AIDS-related complex (ARC) patients were examined. As a control, 8 HIV noninfected lymph nodes, including 3 cases with hyperplasia, were also examined. Immunohistopathological studies using normal HIV noninfected lymph nodes showed that ADF/TRX high-producer (ADFh) cells were macrophages and cells with dendritic morphology in the paracortical area. Abundant ADFh cells were observed in HIV noninfected hyperplastic lymph nodes. The number of ADFh cells was low in hyperplastic lymph nodes from an ARC patient. All of the lymph nodes of 5 AIDS cases were atrophic and the number of ADFh cells were extremely low. To verify these histochemical studies, we examined the effect of in vitro HIV infection on ADF/TRX expression in HTLV-I (+) T-cell lines. Western blot analysis showed that a reduction of ADF/TRX in HIV-1-infected SKT-1B and MT-2 cells, and the reduction inversely correlated with p24 antigen level. On the basis of the above in vivo and in vitro findings, we imply that the levels of ADF/TRX were down-regulated by HIV-1 infection and that the down-regulation may play a role for pathophysiology of HIV-infected individuals.