Transgenic mouse model of ethanol as a cofactor in HIV disease

Oxidative Stress in HIV Infection and Alcohol Use: Role of Redox Signals in Modulation of Lipid Rafts and ATP-Binding Cassette Transporters

AIMS

Human immunodeficiency virus (HIV) infection induces oxidative stress and alcohol use accelerates disease progression, subsequently causing immune dysfunction. However, HIV and alcohol impact on lipid rafts-mediated immune dysfunction remains unknown. In this study, we investigate the modulation by which oxidative stress induces reactive oxygen species (ROS) affecting redox expression, lipid rafts caveiloin-1, ATP-binding cassette (ABC) transporters, and transcriptional sterol regulatory element-binding protein (SREBP) gene and protein modification and how these mechanisms are associated with arachidonic acid (AA) metabolites in HIV positive alcohol users, and how they escalate immune dysfunction.

RESULTS

In both alcohol using HIV-positive human subjects and in vitro studies of alcohol with HIV-1 gp120 protein in peripheral blood mononuclear cells, increased ROS production significantly affected redox expression in glutathione synthetase (GSS), super oxide dismutase (SOD), and glutathione peroxidase (GPx), and subsequently impacted lipid rafts Cav-1, ABC transporters ABCA1, ABCG1, ABCB1, and ABCG4, and SREBP transcription. The increased level of rate-limiting enzyme 3-hydroxy-3-methylglutaryl HMG-CoA reductase (HMGCR), subsequently, inhibited 7-dehydrocholesterol reductase (DHCR-7). Moreover, the expression of cyclooxygenase-2 (COX-2) and lipoxygenase-5 (5-LOX) mRNA and protein modification tentatively increased the levels of prostaglandin E2 synthases (PGE₂) in plasma when compared with either HIV or alcohol alone.

INNOVATION

This article suggests for the first time that the redox inhibition affects lipid rafts, ABC-transporter, and SREBP transcription and modulates AA metabolites, serving as an important intermediate signaling network during immune cell dysfunction in HIV-positive alcohol users.

CONCLUSION

These findings indicate that HIV infection induces oxidative stress and redox inhibition, affecting lipid rafts and ABC transports, subsequently upregulating AA metabolites and leading to immune toxicity, and further exacerbation with alcohol use. Antioxid. Redox Signal. 28, 324-337.

Interaction between Tat and Drugs of Abuse during HIV-1 Infection and Central Nervous System Disease

In many individuals, drug abuse is intimately linked with HIV-1 infection. In addition to being associated with one-third of all HIV-1 infections in the United States, drug abuse also plays a role in disease progression and severity in HIV-1-infected patients, including adverse effects on the central nervous system (CNS). Specific systems within the brain are known to be damaged in HIV-1-infected individuals and this damage is similar to that observed in drug abuse. Even in the era of anti-retroviral therapy (ART), CNS pathogenesis occurs with HIV-1 infection, with a broad range of cognitive impairment observed, collectively referred to as HIV-1-associated neurocognitive disorders (HAND). A number of HIV-1 proteins (Tat, gp120, Nef, Vpr) have been implicated in the etiology of pathogenesis and disease as a result of the biologic activity of the extracellular form of each of the proteins in a number of tissues, including the CNS, even in ART-suppressed patients. In this review, we have made Tat the center of attention for a number of reasons. First, it has been shown to be synthesized and secreted by HIV-1-infected cells in the CNS, despite the most effective suppression therapies available to date. Second, Tat has been shown to alter the functions of several host factors, disrupting the molecular and biochemical balance of numerous pathways contributing to cellular toxicity, dysfunction, and death. In addition, the advantages and disadvantages of ART suppression with regard to controlling the genesis and progression of neurocognitive impairment are currently under debate in the field and are yet to be fully determined. In this review, we discuss the individual and concerted contributions of HIV-1 Tat, drug abuse, and ART with respect to damage in the CNS, and how these factors contribute to the development of HAND in HIV-1-infected patients.

Morphine modulation of toll-like receptors in microglial cells potentiates neuropathogenesis in a HIV-1 model of coinfection with pneumococcal pneumoniae

Chronic drug users account for a third of all cases of AIDS in the United States and the progression to AIDS dementia is accelerated in opiate drug abusers. Clinically, microglial activation better correlates with HIV-associated neurocognitive disorders (HAND) than productive HIV-1 infection in the CNS. Moreover, pneumococcal pneumonia is the most common opportunistic infection in individuals with HAND. We show that coinfection with Streptococcus pneumoniae may be a contributing factor in the increased prevalence of HAND in the opioid-dependent population. To date, there have been no studies published implicating the Toll-like receptors (TLR) in the neurocognitive disorders associated with NeuroAIDS in the context of opportunistic infection. Our studies show for the first time, in a morphine-dependent model, synergistic increase and activation of TLR expression in the presence of HIV-1 protein TAT and S. pneumoniae with a significant increase in proinflammatory cytokines (IL-6, TNF-α) levels. Furthermore, concurrent increases in reactive oxygen species and nitric oxide production leading to increased caspase 3 activation are also observed in both murine and human microglial cells. These effects are recapitulated with TLR 2, 4, and 9 cognate ligands (Pam3CSK4, LPS, and CpG) and significantly attenuated in TLR 2 and 4 knock-out mice and TLR2/4 double knock-out mice. Therefor, our findings clearly suggest for the first time that activation of TLRs on microglia cells by morphine and TAT in the context of S. pneumoniae infection may be a potential mechanism for the increased prevalence of HAND in HIV-infected opioid-dependent patients.

Alcoholism: A Systems Approach From Molecular Physiology to Addictive Behavior

Alcohol consumption is an integral part of daily life in many societies. The benefits associated with the production, sale, and use of alcoholic beverages come at an enormous cost to these societies. The World Health Organization ranks alcohol as one of the primary causes of the global burden of disease in industrialized countries. Alcohol-related diseases, especially alcoholism, are the result of cumulative responses to alcohol exposure, the genetic make-up of an individual, and the environmental perturbations over time. This complex gene × environment interaction, which has to be seen in a life-span perspective, leads to a large heterogeneity among alcohol-dependent patients, in terms of both the symptom dimensions and the severity of this disorder. Therefore, a reductionistic approach is not very practical if a better understanding of the pathological processes leading to an addictive behavior is to be achieved. Instead, a systems-oriented perspective in which the interactions and dynamics of all endogenous and environmental factors involved are centrally integrated, will lead to further progress in alcohol research. This review adheres to a systems biology perspective such that the interaction of alcohol with primary and secondary targets within the brain is described in relation to the behavioral consequences. As a result of the interaction of alcohol with these targets, alterations in gene expression and synaptic plasticity take place that lead to long-lasting alteration in neuronal network activity. As a subsequent consequence, alcohol-seeking responses ensue that can finally lead via complex environmental interactions to an addictive behavior.

Effects of chronic alcohol drinking on receptor-binding, internalization, and degradation of human immunodeficiency virus 1 envelope protein gp120 in hepatocytes

Although alcohol drinking increases susceptibility to human immunodeficiency virus (HIV) infection, possible mechanisms underlying the effects of alcohol are not yet known. Since the HIV envelope protein gp120 plays a key role in progression of HIV infection, the aim of the present study was to evaluate the toxicity and degradation of gp120 in hepatocytes isolated from liver of alcohol-preferring rats drinking either 15% ethanol in water or pure water for 70 days. The hypothesis was that alcohol drinking augmented the toxicity, but suppressed degradation of gp120. Hepatocytes from water-drinking rats (C-cells) or ethanol-drinking rats (Et-cells) were treated with laptacystin, anti-CD4 antibodies, CCR5 antagonist, or mannose, followed by [(125)I]gp120 or native gp120. At predetermined intervals, control (C) and ethanol exposed (Et) cells were analyzed for toxicity and degradation of gp120. In C-cells, [(125)I]gp120 binding and internalization peaked within 5-45 min and remained elevated for up to 10h and then decreased gradually. In Et-cells, [(125)I]gp120 binding peaked comparably to C-cells, but the binding remained to the peak level throughout the experimental period. C-cells exhibited the lysosomal/ubiquitin-mediated degradation of intracellular gp120, resulting in released gp120 fragments into the incubation medium that suppressed gp120-CD4 binding, improved cell viability, and inhibited gp120-induced apoptosis. Ethanol drinking suppressed gp120 degradation in and release of gp120 fragments from hepatocytes. The incubation medium of Et-cells did not suppress gp120-CD4 binding or the gp120-mediated apoptosis in hepatocytes. Thus, chronic alcohol drinking augmented the adverse effects of gp120 possibly by suppressing its degradation in hepatocytes. The present observation also suggests that a number of CCR5 or ubiquitin-based therapeutic drugs may not be effective in suppressing HIV infection in alcohol-drinking subjects.

Cholesterol-depleting statin drugs protect postmitotically differentiated human neurons against ethanol- and human immunodeficiency virus type 1-induced oxidative stress in vitro

The majority of human immunodeficiency virus type 1 (HIV-1)-infected individuals are either alcoholics or prone to alcoholism. Upon ingestion, alcohol is easily distributed into the various compartments of the body, particularly the brain, by crossing through the blood-brain barrier. Both HIV-1 and alcohol induce oxidative stress, which is considered a precursor for cytotoxic responses. Several reports have suggested that statins exert antioxidant as well as anti-inflammatory pleiotropic effects, besides their inherent cholesterol-depleting potentials. In our studies, postmitotically differentiated neurons were cocultured with HIV-1-infected monocytes, T cells, or their cellular supernatants in the presence of physiological concentrations of alcohol for 72 h. Parallel cultures were pretreated with statins (atorvastatin and simvastatin) with the appropriate controls, i.e., postmitotically differentiated neurons cocultured with uninfected cells and similar cultures treated with alcohol. The oxidative stress responses in the presence/absence of alcohol in these cultures were determined by the production of the well-characterized oxidative stress markers, 8-isoprostane-F2-alpha, total nitrates as an indicator for various isoforms of nitric oxide synthase activity, and heat shock protein 70 (Hsp70). An in vitro culture of postmitotically differentiated neurons with HIV-1-infected monocytes or T cells as well as supernatants from these cells enhanced the release of 8-isoprostane-F2-alpha in the conditioned medium six- to sevenfold (monocytes) and four- to fivefold (T cells). It was also observed that coculturing of HIV-1-infected primary monocytes over a time period of 72 h significantly elevated the release of Hsp70 compared with that of uninfected controls. Cellular supernatants of HIV-1-infected monocytes or T cells slightly increased Hsp70 levels compared to neurons cultured with uninfected monocytes or T-cell supernatants (controls). Ethanol (EtOH) presence further elevated Hsp70 in both infected and uninfected cultures. The amount of total nitrates was significantly elevated in the coculture system when both infected cells and EtOH were present. Surprisingly, pretreatment of postmitotic neurons with clinically available inhibitors of HMG-coenzyme A reductase (statins) inhibited HIV-1-induced release of stress/toxicity-associated parameters, i.e., Hsp70, isoprostanes, and total nitrates from HIV-1-infected cells. The results of this study provide new insights into HIV-1 neuropathogenesis aimed at the development of future HIV-1 therapeutics to eradicate viral reservoirs from the brain.

Transgenic expression of the deoxynucleotide carrier causes mitochondrial damage that is enhanced by NRTIs for AIDS

Nucleoside reverse transcriptase inhibitors (NRTIs) are antiretrovirals for AIDS with limiting mitochondrial side effects. The mitochondrial deoxynucleotide carrier (DNC) transports phosphorylated nucleosides for mitochondrial DNA replication and can transport phosphorylated NRTIs into mitochondria. Transgenic mice (TG) that exclusively overexpress DNC in the heart tested DNC's role in mitochondrial dysfunction from NRTIs. Two TG lines were created that overexpressed the human DNC gene in murine myocardium. Cardiac and mitochondrial structure and function were examined by magnetic resonance imaging, echocardiography, electrocardiography, transmission electron microscopy, and plasma lactate. Antiretroviral combinations (HAART) that contained NRTIs (stavudine (2', 3'-didehydro-2', 3'-deoxythymidine or d4T)/lamivudine/indinavir; or zidovudine (3' azido-3'-deoxythymidine or AZT)/lamivudine/indinavir; 35 days) were administered to simulate AIDS therapy. In parallel, a HAART combination without NRTIs (nevirapine/efavirenz/indinavir; 35 days) served as an NRTI-sparing, control regimen. Untreated DNC TGs exhibited normal cardiac function but abnormal mitochondrial ultrastructure. HAART that contained NRTIs caused cardiomyopathy in TGs with increased left ventricle mass and volume, heart rate variability, and worse mitochondrial ultrastructural defects. In contrast, treatment with an NRTI-sparing HAART regimen caused no cardiac changes. Data suggest the DNC is integral to mitochondrial homeostasis in vivo and may relate mechanistically to mitochondrial dysfunction in patients treated with HAART regimens that contain NRTIs.

Targeted myocardial transgenic expression of HIV Tat causes cardiomyopathy and mitochondrial damage

Cardiac effects of human immunodeficiency virus (HIV) transactivator (Tat) are unclear, but Tat decreases liver glutathione (an important mitochondrial antioxidant) when ubiquitously expressed in transgenic mice (TG). With an alpha-myosin heavy chain promoter, Tat was selectively targeted to murine cardiac myocytes. One high-expression hemizygous ((+/-)Tat(high); 12 copies) and two low-expression ((+/-)Tat(lowA,B); 2-5 copies) TG lines were created. Cardiomyopathy was documented with increased left ventricle (LV) mass, ventricular expression of atrial natriuretic factor (ANF) mRNA, mitochondrial ultrastructural defects, and myocardial depletion of glutathione. In (+/-)Tat(high) TGs, normalized LV mass (determined echocardiographically) increased 46% (90 days), 134% (240 days), and 96% (365 days) compared with wild-type littermates (WT). LV fractional shortening was decreased to 28% (90 days), 27% (240 days), and 19% (365 days). (+/-)Tat(low) LV mass was unchanged (<or=365 days). ANF in (+/-)Tat(high) ventricles (180 days) was twofold WT values. Glutathione was selectively decreased in (+/-)Tat(high) hearts (120 days). (+/-)Tat(high) hearts contained damaged mitochondria (>or=210 days); however, profound mitochondrial destruction occurred in homozygous (+/+)Tat(high) hearts (10 days) and the pups died (14 days). Tat caused cardiac dysfunction in this TG and may impact on cardiomyopathy in acquired immunodeficiency syndrome.

Ethanol enhances TNF-alpha-inducible NFkappaB activation and HIV-1-LTR transcription in CD4+ Jurkat T lymphocytes

During the latent phase of human immunodeficiency virus type 1 (HIV-1) infection, CD4+ T cells carrying replication-competent proviral HIV-1 DNA play an important role in persistence of the virus. Several cofactors can induce and or amplify HIV-1 replication and negatively affect disease progression and pathogenesis. Ethanol consumption is an important risk factor for HIV-1 infection, and it has been implicated in increased HIV-1 replication and progression of infection. Because tumor necrosis factor-alpha (TNF-alpha) is an important modulator of HIV-1 replication, in the present study we examined the possible effects of ethanol on TNF-alpha-inducible signaling associated with HIV-1 replication in human CD4+ T cells (Jurkat E6-1). We demonstrate that clinically relevant ethanol concentrations significantly potentiate TNF-alpha-inducible NFkappaB. Although ethanol effectively collaborated with TNF-alpha, by itself it did not have a direct effect on NFkappaB activation. The ethanol-dependent potentiation of TNF-alpha-inducible NFkappaB nuclear translocation was observed to involve the enhanced degradation of IkappaBalpha. Additionally, the ethanol-mediated potentiation of TNF-alpha-inducible NFkappaB activation was abrogated by the known antioxidant pyrrolidinedithiocarbamate, suggesting an important mechanistic role for reactive oxygen species in this process. In correspondence with its effect on NFkappaB, ethanol was also observed to significantly enhance HIV-1 long terminal repeat-dependent transcription induced by TNF-alpha. Overall, the data provide a molecular basis for the possible role of ethanol as a cofactor that can adversely affect HIV-1 infection and pathogenesis.