Signaling pathway involved in methionine enkephalin-promoted survival of lymphocytes infected by simian immunodeficiency virus in the early stage in vitro

The mechanism involved in the repression of the μ opioid receptor gene expression in CEM ×174 cells infected by simian immunodeficiency virus

Morphine can promote the pathogenesis of human acquired immunodeficiency syndrome through binding to the μ opioid receptor (MOR) in immune cells. Previous investigation has suggested that expression of the MOR gene in lymphocytes is triggered by cooperative interaction between transcription factors, specificity protein 1 (Sp1) and Ying Yang 1 (YY1), in the promoter region. However, the specific molecular mechanism by which immunodeficiency virus infection impacts regulation of the MOR gene expression in lymphocytes is still unclear. In this study, it was demonstrated that SIV (SIVmac239) infection may result in gradual reduction of the MOR gene expression and Sp1 during a period of 48 h postinfection by analysis of quantitative real-time RT-PCR and Western blotting. The results of methylation-specific PCR showed that two of 14 CpG islands adjacent to the Sp1 and YY1 elements in the promoter region were methylated, which together with reduced Sp1, contributed to the failure of interaction of Sp1 with YY1 and their binding to the elements, as determined by coimmunoprecipitation, chromatin immunoprecipitation-real-time PCR, and EMSAs. The repression of the MOR gene secondary to SIVmac239 infection could be abolished by the demethylating agent 5-aza-2′-deoxycytidine. Transfection with Sp1-expressing vector (PN3-Sp1) was also able to enhance the activity of the promoter in SIVmac239-infected cells. We therefore concluded that aberrant methylation of the promoter and reduction of Sp1 resulting from SIVmac239 infection led to the silencing of the MOR gene. This finding will be helpful in understanding the synergistic mechanism of HIV infection and morphine addiction in the pathogenesis of AIDS.

Pyrimidone derivative inhibits simian immunodeficiency virus-induced apoptosis of CEM x174 cells

The biochemical effects of 2-(ethoxymethylthio)-9-phenyl-cyclohepta[d]pyrimidone (EPCP), a novel non-nucleoside reverse transcriptase inhibitor, have been investigated. Treatment with EPCP (EC(50) of 0.88 nM in CEM x174 cells) significantly inhibited the activity of SIV reverse transcriptase and elevated the percentage of viable cells in an SIV-infected sample in a dose-dependent manner. The percentage of cells accumulated in G1 phase increased significantly from 34.5 to 62.4%, with a concomitant reduction in S-phase from 50.7% in the control to 22.6% in the infected group. This cell cycle profile was restored by treatment with EPCP. SIV upregulated the levels of the caspase-3, p53 and bax proteins, and downregulated the level of bcl-2 in infected cells. The apoptotic effect of SIV was also blocked by treatment with EPCP. The pharmacological effects of EPCP paralleled those of AZT, suggesting the possibility that EPCP might be a novel antiviral agent for SIV.

Signal transduction induced by opioids in immune cells: a review

New data regarding signal transduction triggered by opioid ligands in immune cells are reviewed, and the signal transduction in neuronal cells is documented. Similar signaling pathways are induced by opioids in immune as well as neuronal cells. Opioids altered second messenger cAMP, intracellular calcium, and second messenger-induced kinases in immune cells. Met-enkephalin, preferentially delta-opioid, was bimodally regulated, while kappa-opioids inhibited these second messengers. delta-, kappa- and micro-opioids altered nitric oxide secretion, inducing cGMP as the second messenger in immune cells. Coupling of opioid agonists to opioid receptors activated mitogen-activated protein/extracellular signal-regulated protein kinases and various transcription factors in immune cells. Activator protein 1 (AP-1), c-fos, and nuclear factor-kappaB (NF-kappaB) are transcription factors shared by neuronal and immune cells. Delta-opioids activated AP-1, c-fos, activating transcription factor 2, Ikaros-1 and Ikaros-2 transcription factors in immune cells. Induction of kappa-opioid receptor gene by retinoic acid resulted in increased binding of Sp1 transcription factor to the promoter of the kappa-opioid receptor. Micro-opioids inhibited synthesis of common transcription factors AP-1, c-fos, NF-kappaB, and nuclear factor of activated T cells in activated or stimulated immune cells, whereas micro-opioids activated NF-kappaB, GATA-3, and Kruppel-like factor 7 transcription factors in non-stimulated immune cells.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

The peptide molecular links between the central nervous and the immune systems

The central nervous system (CNS) and the immune system were for many years considered as two autonomous systems. Now, the reciprocal connections between them are generally recognized and very well documented. The links are realized mainly by various immuno- and neuropeptides. In the review the influence of the following immunopeptides on CNS is presented: tuftsin, thymulin, thymopoietin and thymopentin, thymosins, and thymic humoral factor. On the other side, the activity in the immune system of such neuropeptides as substance P, neurotensin, some neurokinins, enkephalins, and endorphins is discussed.

Morphine aggravates the apoptosis of simian immunodeficiency virus infected CEM x174 cells in the prolonged culture in vitro

This study was designed to assess the in vitro effects of morphine on the lymphocytes infected with SIV. CEM x174 cells were cotreated with morphine and simian immunodeficiency virus (SIVmac239). Cells were cultured for 96 h and the effects of morphine on the viability of infected cells were determined. At the concentration of 1 micromol/l, morphine could inhibit the proliferation of CEM x174 cells at the culture of 72 h. The stronger effect was observed in the case of viral infection. During 72 h SIV loading, the cells were accumulated in S phase in all SIV infected groups. The S arrest was observed in every experimental group and statistically different from normal groups (P<0.05). The results from annexin V binding assay showed that SIV infection resulted in a lower proportion of vital cells and higher mortality compared with corresponding control (P<0.01). Morphine failed to induce detectable alteration in the cell cycle profile of viral infected cells. Western blotting showed that the synthesis of intracellular p53 and bax protein was gradually up-regulated in the virus-loading period of 72 h. Naloxone had an apparent additive rather than antagonistic effect on the morphine-associated enhancement of bax expression. The ratio of bax/bcl-2 proteins appeared to tilt the balance toward apoptosis. At 72 h of infection, 1 micromol/l of morphine significantly elevated the level of caspase-3. These results indicated that the alteration in the balance of intracellular apoptotic and anti-apoptotic elements is one of the reasons of accelerated progression of acquired immunodeficiency syndrome (AIDS) by opioids abuse.