Opiate effects on in vitro human retroviral infection

Accelerated evolution of SIV env within the cerebral compartment in the setting of morphine-dependent rapid disease progression

Human immunodeficiency virus-1 (HIV-1) and simian immunodeficiency virus (SIV) have been shown to compartmentalize within various tissues, including the brain. However, the evolution of viral quasispecies in the setting of drug abuse has not been characterized. The goal of this study was to examine viral evolution in the cerebral compartment of morphine-dependent and control macaques to determine its role in rapid disease progression. To address this issue, we analyzed the envelope (env) gene from proviral DNA in our SIV/SHIV macaque model of morphine dependence and AIDS. Analyses of proviral DNA revealed a direct correlation between total genetic changes and survival time. However, the rate of evolution during disease progression was higher in morphine-dependent and rapid-progressor macaques than was the rate of evolution in the control animals. This study provides additional insight into SIV envelope variation in the CNS of morphine-dependent macaques and genotypes that may have evolved in the brain and contributed to disease progression.

CCL5/RANTES gene deletion attenuates opioid-induced increases in glial CCL2/MCP-1 immunoreactivity and activation in HIV-1 Tat-exposed mice

To assess the role of CC-chemokine ligand 5 (CCL5)/RANTES in opiate drug abuse and human immunodeficiency virus type 1 (HIV-1) comorbidity, the effects of systemic morphine and intrastriatal HIV-1 Tat on macrophage/microglial and astroglial activation were assessed in wild-type and CCL5 knockout mice. Mice were injected intrastriatally with vehicle or Tat and assessed after 7 days. Morphine was administered to some Tat-injected mice via time-release implant (5 mg/day, s.c. for 5 days) starting at 2 days post injection. Glial activation was significantly reduced in CCL5(-/-) compared to wild-type mice at 7 days following combined Tat and morphine exposure. Moreover, the percentage of 3-nitrotyrosine immunopositive macrophages/microglia was markedly reduced in CCL5(-/-) mice injected with Tat +/- morphine compared to wild-type counterparts, suggesting that CCL5 contributes to nitrosative stress in HIV-1 encephalitis. In CCL5(-/-) mice, the reductions in Tat +/- morphine-induced gliosis coincided with significant declines in the proportion of CCL2/MCP-1-immunoreactive astrocytes and macrophages/microglia compared to wild-type counterparts. In knockout mice, neither Tat alone nor in combination with morphine increased the proportion of CCL2-immunoreactive astrocytes above percentages seen in vehicle-injected controls. Macrophages/microglia differed showing modest, albeit significant, increases in the proportion of CCL2-positive cells with combined Tat and morphine exposure, suggesting that CCL5 preferentially affects CCL2 expression by astroglia. Thus, CCL5 mediates glial activation caused by Tat and morphine, thereby aggravating HIV-1 neuropathogenesis in opiate abusers and non-abusers. CCL5 is implicated as mediating the cytokine-driven amplification of CCL2 production by astrocytes and resultant macrophage/microglial recruitment and activation.

Drugs of abuse, immune modulation, and AIDS

Illicit drugs such as amphetamines, cocaine, marijuana, and opiates alter immune function and decrease host resistance to microbes in vitro and in experimental animal models. Effects on the immune system may be mediated indirectly as a result of drug interactions in the central nervous system (CNS) or directly through activation of cognate receptors on various immune cell types. For marijuana and opioids, seven-transmembranal G protein-coupled receptors have been identified in the CNS and in the immune system that may play a functionally relevant role in immune modulation. There is accumulating evidence that sigma(1) receptors play a comparable role in cocaine-mediated alteration of immune responses. A mode by which these exogenously introduced substances affects immunity and host resistance may be by perturbing the balance of Th(1) proinflammatory versus Th(2) anti-inflammatory cytokines and lipid bioeffectors. However, while illicit drugs have been documented to alter immune functions in vitro and in animal models, there is a paucity of controlled longitudinal epidemiological studies that definitively correlate immunosuppressive effects with increased incidence of infections or immune disorders in humans, including infection with the human immunodeficiency virus (HIV) or disease progression to AIDS.

The opioid ligand binding of human μ-opioid receptor is modulated by novel splice variants of the receptor

The pharmacological actions of morphine and morphine-like drugs, such as heroin, mediate primarily through the mu-opioid receptor (MOR). It has been proposed that the functional diversity of MOR may be related to alternative splicing of the MOR gene. Although a number of MOR mRNA splice variants have been reported, their biological function has been controversial. In this study, two novel splice variants of the human MOR gene were discovered. Splice variants 1 and 2 (here called the SV1 and SV2) retain different portions of intron I. In vitro translation of SV1 and SV2 produced proteins with the predicted molecular weights. The splice variant proteins were identical to the wild-type MOR-1 up to the first transmembrane domains, but were different after the first intracellular loop domains. SV1 and SV2 of hMOR were present in human neuroblastoma NMB cells and human whole brain confirmed by RT-PCR. In a receptor binding assay, cells expressing the SV1 and SV2 do not exhibit binding to [(3)H]diprenorphine. The formations of MOR.SV1 and MOR.SV2 heterodimers were demonstrated by co-immunoprecipitation and bioluminescence resonance energy transfer between MOR and splice variants. Co-transfection of MOR-GFP and SV-DsRed gene showed that MOR and SV protein co-localized at the cytoplasmic membrane. In NMB cells expressing human MOR gene, transfection of SV1 or SV2 reduced binding activity of the endogenous MOR. These data support a potential role of SV1 and SV2 proteins as possible biological modulator of human mu-opioid receptor.

Molecular targets of opiate drug abuse in neuroAIDS

Opiate drug abuse, through selective actions at mu-opioid receptors (MOR), exacerbates the pathogenesis of human immunodeficiency virus-1 (HIV-1) in the CNS by disrupting glial homeostasis, increasing inflammation, and decreasing the threshold for pro-apoptotic events in neurons. Neurons are affected directly and indirectly by opiate-HIV interactions. Although most opiates drugs have some affinity for kappa (KOR) and/or delta (DOR) opioid receptors, their neurotoxic effects are largely mediated through MOR. Besides direct actions on the neurons themselves, opiates directly affect MOR-expressing astrocytes and microglia. Because of their broad-reaching actions in glia, opiate abuse causes widespread metabolic derangement, inflammation, and the disruption of neuron-glial relationships, which likely contribute to neuronal dysfunction, death, and HIV encephalitis. In addition to direct actions on neural cells, opioids modulate inflammation and disrupt normal intercellular interactions among immunocytes (macrophages and lymphocytes), which on balance further promote neuronal dysfunction and death. The neural pathways involved in opiate enhancement of HIV-induced inflammation and cell death, appear to involve MOR activation with downstream effects through PI3-kinase/Akt and/or MAPK signaling, which suggests possible targets for therapeutic intervention in neuroAIDS.

Transcriptional regulation of mouse mu opioid receptor gene: Sp3 isoforms (M1, M2) function as repressors in neuronal cells to regulate the mu opioid receptor gene

The 5'-flanking region of the mouse mu opioid receptor (MOR) gene has two promoters, referred to as distal and proximal. MOR mRNA is predominantly initiated by the proximal promoter. Previously, several important cis-elements and trans-factors have been shown to play a functional role in the proximal promoter of the MOR gene. In this study, we defined another functional, negative regulatory element located in the -219- to -189-base pair (translational start site designed as +1) region of the proximal promoter. It is designated as the Sp binding sequence for its sequence homology to the consensus Sp binding element. Mutation of the Sp binding element led to a 100% increase of MOR promoter activity in MOR-positive cells (NMB cells), confirming the negative role of the Sp binding sequence. Surprisingly, electrophoretic mobility shift analysis and chromatin immunoprecipitation assays revealed that Sp3 and its isoforms (M1 and M2) were specifically bound to the Sp binding sequence. In cotransfection assays of Drosophila melanogaster SL2 cells using cDNA encoding Sp1, Sp3, and the M1 and M2 isoforms of Sp3, the M1 and M2 isoforms trans-repressed the MOR promoter, whereas Sp1 and Sp3 trans-activated the MOR promoter. Significantly, ectopic expression of the M1 and M2 isoforms of Sp3 led to repression of the endogenous MOR gene transcripts in NMB cells. These results suggest that the binding of the M1 and M2 isoforms of the Sp3 transcription factor to the Sp binding sequence may play a role in mouse MOR gene expression.

Transcriptional Regulation of Mouse μ Opioid Receptor Gene by PU.1

We previously reported that the 34-bp cis-acting element of the mouse micro opioid receptor (MOR) gene represses transcription of the MOR gene from the distal promoter. Using a yeast one-hybrid screen to identify potential transcription factors of the MOR promoter, we have identified PU.1 as one of the candidate genes. PU.1 is a member of the ets family of transcription factors, expressed predominantly in hematopoietic cells and microglia of brain. PU.1 plays an essential role in the development of both lymphoid and myeloid lineages. Opioids exert neuromodulatory as well as immunomodulatory effects, which are transduced by MOR. Moreover, MOR-deficient mice exhibit increased proliferation of hematopoietic cells, suggesting a possible link between the opioid system and hematopoietic development. The PU.1 protein binds to the 34-bp element of the MOR gene in a sequence-specific manner confirmed by electrophoretic mobility shift assay and supershift assays. We have also determined endogenous PU.1 interactions with the 34-bp element of MOR promoter by chromatin immunoprecipitation assays. In co-transfection studies PU.1 represses MOR promoter reporter constructs through its PU.1 binding site. When the PU.1 gene is disrupted as in PU.1 knock-out mice and using small interfering RNA-based strategy in RAW264.7 cells, the transcription of the endogenous target MOR gene is increased significantly. This increase is probably mediated through modification of the chromatin structure, as suggested by the reversal of the PU.1-mediated repression of MOR promoter activity after trichostatin A treatment in neuroblastoma NMB cells. Our results suggest that PU.1 may be an important regulator of the MOR gene, particularly in brain and immune cells.

Opioid receptors on white blood cells: effect of HIV infection and methadone treatment

Opioid receptors (OR) are involved in many physiological and pathological immune functions. During recent years, the treatment of opiate addiction with methadone in HIV-positive and HIV-negative patients has become widely accepted. However, little is known on the occurrence and course of OR on lymphocytes of these individuals. The objective of the study was to detect and quantify OR on peripheral white blood cells (WBC) by fluorescence-activated cell sorting using polyclonal antibodies and reverse transcriptase polymerase chain reaction, and to assess the influence of HIV infection and methadone treatment. We compared OR levels in 80 HIV-positive homosexuals, 18 HIV-positive intravenous drug users (IVDU) treated with methadone, 18 HIV-negative IVDU receiving methadone and 25 healthy controls. HIV infection was shown to decrease the amount of OR on WBC, especially of the delta-subtype on lymphocytes and granulocytes. The decrease correlated with the duration of HIV-infection (P<0.01), and inversely with the HIV viral load (P<0.01). In contrast, chronic methadone administration led to a significant increase of OR exclusively in HIV-negative IVDU. In particular the delta-OR was increased by 31-, 62- and 42-fold on lymphocytes, monocytes and granulocytes of HIV-negative patients (each P<0.005), respectively, which was not observed in HIV-positive IVDU. Therefore, HIV seems to reduce OR particularly on lymphocytes and granulocytes regardless of the mode of HIV transmission. The quantification of OR on immune cells may help to elucidate the effects of opioid analogues in health and drug addiction.

Alteration of cytokine levels in murine retrovirus infection: modulation by combination therapy

Immunoregulatory cytokines may regulate the resistance or susceptibility of a host to retroviral infection. These cytokines may be therapeutically modulated to prevent or limit the progression of infection. The non-progression to AIDS of some HIV+ patients has been related to a strong type 1 cytokine response (IL-2, IL-12, and IFNgamma). For this reason, we investigated the ability of combination therapeutics to modulate cytokines in vivo towards a type 1 cytokine response in a murine retroviral infection using Friend leukemia virus (FLV). BALB/c mice were infected with FLV and treated with either 3'-azido-3'-deoxythymidine (AZT), the immunomodulator methionine enkephalin (MENK), or a combination of both AZT and MENK starting 3 d post infection. Splenocytes were harvested on days 1, 3, 7, 14, 21 and 28 post treatment initiation and cultured with 1 microg/ml concanavalin A (ConA) for 24 h. Supernatants were examined for IL-2, IL-4, IL-10, IL-12, and IFNgamma cytokine production using cytokine specific ELISAs. The levels of type 2 cytokines were not significantly changed by any treatment group over the course of the disease. However, although decreased in all infected animals, type 1 cytokines were partially maintained by the combination treatment through day 21. RT-PCR for cytokine specific mRNA confirmed these results, with expression of the type 1 cytokines, especially IFNgamma, being maintained through day 21. Establishment of a treatment regime that can maintain protective cytokine activities against disease progression may prove applicable to other retroviral infections.

Cocaine potentiates the switch between latency and replication of Epstein-Barr virus in Raji cells

This paper shows that cocaine amplifies Epstein-Barr virus (EBV) reactivation in Raji cells. Its effect on early viral protein synthesis was maximal when it was added with 12-O-tetradecanoyl phorbol-13-acetate (TPA) plus n-butyrate, but nil when added alone. The enhancing effect of cocaine on early replicative stages of latent EBV was associated with an increase of Ca(2+) mobilization induced by the drug and with an induction of cellular protein phosphorylation in chemicals and cocaine-treated Raji cells. Cocaine also acted synergistically with TPA and n-butyrate to induce Z Epstein-Barr replication activator (ZEBRA), a nuclear phosphoprotein responsible for the activation of early viral gene expression. These findings provide the first evidence that cocaine may represent an important co-factor in the reactivation of early stages of latent EBV infection.

Morphine effects on HTLV-I infection in the presence or absence of concurrent HIV-1 infection

Human T-cell leukemia virus type I (HTLV-I) infection is emerging as an important complication in HIV infection and AIDS in injecting drug users. HIV-1 and HTLV-I share a common host in CD4+ T lymphocytes. However, the result of HIV-1 infection is the decimation of this cell population, whereas a hallmark of HTLV-I infection is the inappropriate proliferation of infected cells. Combined epidemiologic data suggest that HTLV-I infection is enhanced during concurrent HIV-1/HTLV-I infection; however, there are currently no in vitro studies focusing on the effects of drugs of abuse on retrovirus coinfection. We have found that in an in vitro coinfection system (HIV-1 + HTLV-I), morphine treatment further enhanced the levels of HTLV-I p19. In addition, indicators of in vitro infection by cell-free HIV-1 were reduced by morphine treatment in both single and dual in vitro infection experiments. Interleukin 2 levels in the affected cultures were found to increase with combined HTLV-I infection and morphine treatment. These in vitro results indicate the need to further explore the activity of HTLV-I within opiate-treated cells, as this oncoretrovirus appears to be especially sensitive to morphine-induced alterations to its host cell environment.