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

Identification of 5' upstream sequence involved in HSPBP1 gene transcription and its downregulation during HIV-1 infection

The Human Immunodeficiency Virus-1 (HIV-1) is known to modulate the host environment for successful replication and propagation like other viruses. The virus utilises its proteins to interact with or modulate host factors and host signalling pathways that may otherwise restrict the virus. A previous study from our lab has shown that the host heat shock protein 70 (HSP70) binding protein (HSPBP1) is a co-chaperone that inhibits viral replication. We have also shown that the virus downregulates HSPBP1 during infection. However, the mechanism of downregulation remains to be elucidated. In the present study, we hypothesized that the HSPBP1 promoter may be repressed during infection leading to its downmodulation at the RNA and protein levels. The 5' upstream region of the HSPBP1 gene was first mapped and it was identified that a fragment comprising of a ∼600 bp upstream region of the transcription start site show the highest promoter-like activity. Further, the Sp1 transcription factor was shown to be essential for normal promoter activation. Our results further demonstrate that HIV-1 downregulates the activity of the identified promoter. It was seen that the viral transactivator protein, Tat, was responsible for the downmodulation of the HSPBP1 promoter. HIV-1 Tat is known to bind and regulate several cellular promoters during infection, thereby making the environment conducive for establishment of the virus. Our results further show that Tat is recruited to the HSPBP1 promoter and in the presence of Tat, recruitment of Sp1 on HSPBP1 promoter was decreased, which explains the suppression of HSPBP1 during HIV-1 infection. Therefore, this study further adds to the list of cellular promoters that are modulated by Tat during HIV-1 infection either directly or indirectly.

Impact of physical activity on pain perception in an animal model of endometriosis

BACKGROUND

Symptoms of endometriosis, such as pain and infertility, are considered significant sources of stress. In many chronic conditions, exercise can act as a stress buffer and influence pain perception. We tested the impact of swimming exercise on pain perception and pain receptors in an animal model of endometriosis.

METHODS

Endometriosis (Endo) was induced in female rats by suturing uterine horn tissue next to the intestinal mesentery. Sham rats received sutures only. Rats were exposed to swimming exercise for 7 consecutive days, while no-exercise rats were left in the home cage. Fecal pellets were counted after swimming as an index of anxiety, and serum corticosterone levels measured. Pain perception was assessed using the hot plate test for hyperalgesia and Von Frey test for allodynia. Mu-opioid receptor (MOR) and neurokinin-1 receptor expression in the spinal cord was measured by immunofluorescence.

RESULTS

Fecal pellet counts were higher in those animals that swam (p<0.05), but no significant difference in corticosterone was found. Although Endo-exercise rats had higher colonic damage (p<0.05) with more cellular infiltration, the lesions were smaller than in Endo-no exercise rats (p<0.05). Exercise did not ameliorate the hyperalgesia, whereas it improved allodynia in both groups. MOR expression was significantly higher in Endo-exercise vs. Endo-no exercise rats (p<0.01), similar to Sham-no exercise levels.

CONCLUSIONS

Our results point toward beneficial effects of swimming exercise during endometriosis progression. Physical interventions might be investigated further for their ability to reduce perceived stress and improve outcomes in endometriosis.

Alpha fetoprotein mediates HBx induced carcinogenesis in the hepatocyte cytoplasm

Although tumor-associated fetal protein AFP has demonstrated utility as a clinical tumor marker, the significance of intracellular AFP is still unclear. The aim of this study was to explore the role of cytoplasmic AFP during HBx induced carcinogenesis, which had not previously been recognized; 614 HCC patients were analyzed for correlation of HBV infection with AFP level, and much higher AFP levels were found in HBsAg positive patients. Tumor tissue specimens from 20 HCC patients were used for analysis of AFP and GADD45α. Analysis of HCC specimens showed that upregulation of cytoplasmic AFP is associated with down-regulation of GADD45α in neoplastic tissue. Transfected HBx promotes transcription of AFP by acting on the elements in the AFP gene regulatory region. HBx itself did not directly impact transcription of GADD45α. However, the obstruction of RAR signaling by HBx induced elevation of AFP, which led to down-regulation of GADD45α. Cytoplasmic AFP was able to interact with RAR, disrupting its entrance into the nucleus and binding to the elements in the regulatory region of the GADD45α gene. Knockdown of AFP in siRNA-transfected AFP positive cell lines was synchronously associated with an incremental increase of RAR binding to DNA, as well as upregulation of GADD45α and it was contrary in AFP gene-transfected AFP negative cell lines. These results indicate cytoplasmic AFP is not only a histochemical tumor biomarker for human hepatoma but is also an intracellular signal molecule and potential participant in HBx induced hepatocarcinogenesis.

The neural mobilization technique modulates the expression of endogenous opioids in the periaqueductal gray and improves muscle strength and mobility in rats with neuropathic pain

BACKGROUND

The neural mobilization (NM) technique is a noninvasive method that has been proven to be clinically effective in reducing pain; however, the molecular mechanisms involved remain poorly understood. The aim of this study was to analyze whether NM alters the expression of the mu-opioid receptor (MOR), the delta-opioid receptor (DOR) and the Kappa-opioid receptor (KOR) in the periaqueductal gray (PAG) and improves locomotion and muscle force after chronic constriction injury (CCI) in rats.

METHODS

The CCI was imposed on adult male rats followed by 10 sessions of NM every other day, starting 14 days after the CCI injury. At the end of the sessions, the PAG was analyzed using Western blot assays for opioid receptors. Locomotion was analyzed by the Sciatic functional index (SFI), and muscle force was analyzed by the BIOPAC system.

RESULTS

An improvement in locomotion was observed in animals treated with NM compared with injured animals. Animals treated with NM showed an increase in maximal tetanic force of the tibialis anterior muscle of 172% (p < 0.001) compared with the CCI group. We also observed a decrease of 53% (p < 0.001) and 23% (p < 0.05) in DOR and KOR levels, respectively, after CCI injury compared to those from naive animals and an increase of 17% (p < 0.05) in KOR expression only after NM treatment compared to naive animals. There were no significant changes in MOR expression in the PAG.

CONCLUSION

These data provide evidence that a non-pharmacological NM technique facilitates pain relief by endogenous analgesic modulation.

Epigenetics, drugs of abuse, and the retroviral promoter

Drug abuse alone has been shown to cause epigenetic changes in brain tissue that have been shown to play roles in addictive behaviors. In conjunction with HIV-1 infection, it can cause epigenetic changes at the viral promoter that can result in altered gene expression, and exacerbate disease progression overall. This review entails an in-depth look at research conducted on the epigenetic effects of three of the most widely abused drugs (cannabinoids, opioids, and cocaine), with a particular focus on the mechanisms through which these drugs interact with HIV-1 infection at the viral promoter. Here we discuss the impact of this interplay on disease progression from the point of view of the nature of gene regulation at the level of chromatin accessibility, chromatin remodeling, and nucleosome repositioning. Given the importance of chromatin remodeling and DNA methylation in controlling the retroviral promoter, and the high susceptibility of the drug abusing population of individuals to HIV infection, it would be beneficial to understand the way in which the host genome is modified and regulated by drugs of abuse.

Alpha-fetoprotein acts as a novel signal molecule and mediates transcription of Fn14 in human hepatocellular carcinoma

BACKGROUND & AIMS

The function of cytoplasmic AFP as a regulatory factor in the growth of tumor cells has been well defined. However, its precise mechanism of action and its clinical significance remain to be worked out.

METHODS

Specimens from HCC patients were analyzed by using immunohistochemistry, co-immunoprecipitation (CoIP), and chromatin immunoprecipitation (ChIP) assays to evaluate the role of AFP in RAR signaling-mediated carcinogenesis. Quantitative real-time reverse transcription PCR, Western blotting, confocal microscopy, CoIP, GST pull-down, siRNA, gene transfection, and ChIP assays were also used for analysis of cell lines.

RESULTS

RAR is able to interact with cytoplasmic AFP and binds to the element of the regulatory region of the Fn14 gene in the neoplastic tissue of HCC patients. An assay of hepatocyte cell lines of differing AFP expression showed that cytoplasmic AFP is able to block ATRA-induced nuclear translocation of RAR and expression of the Fn14 gene. Knockdown of AFP in siRNA-transfected HepG2 and Bel7402 cells led to greater binding of RAR to its response element. The expression of the Fn14 gene was therefore up regulated as reflected by increases in mRNA and protein levels. Conversely, transfection of HLE and L02 cells (AFP negative) with the afp gene resulted in apparent reduction of RAR binding to DNA and Fn14 protein.

CONCLUSIONS

Demonstration of the involvement of cytoplasmic AFP in RAR-mediated expression of the Fn14 gene strongly indicates AFP plays a signal molecule-like role in the regulation of hepatocellular carcinoma growth.

Epigenetics of µ-opioid receptors: intersection with HIV-1 infection of the central nervous system

The abuse of intravenous drugs, such as heroin, has become a major public health concern due to the increased risk of HIV-1 infection. Opioids such as heroin were originally identified and subsequently abused for their analgesic effects. However, many investigations have found additional effects of opioids, including regulation of the immune system. As such, chronic opioid abuse has been shown to promote HIV-1 pathogenesis and facilitate HIV-1-associated neurocognitive dysfunction. Clinical opioids, such as morphine and methadone, as well as illicit opioids, such as heroin, exert their effects primarily through interactions with the µ-opioid receptor (MOR). However, the mechanisms by which opioids enhance neurocognitive dysfunction through MOR-mediated signaling pathways are not completely understood. New findings in the regulation of MOR expression, particularly epigenetic and transcriptional regulation as well as alternative splicing, sheds new insights into possible mechanisms of HIV-1 and opiate synergy. In this review, we identify mechanisms regulating MOR expression and propose novel mechanisms by which opioids and HIV-1 may modulate this regulation. Additionally, we suggest that differential regulation of newly identified MOR isoforms by opioids and HIV-1 has functional consequence in enhancing HIV-1 neurocognitive dysfunction.

KLF6/Sp1 initiates transcription of the tmsg-1 gene in human prostate carcinoma cells: an exon involved mechanism

The tumor metastasis suppressor gene-1 (tmsg-1) was first cloned as a new tumor suppressor gene in our laboratory several years ago. Since then, however, despite the substantial progression that has been made in investigation of the biologic roles played by this gene, the manner in which it exerts its regulatory influence is still unknown. With transfection of various deletion or mutation constructs, we identified a potential enhancer and three potential silencers in the 5'-flanking region. However, it was particularly interesting to find that a region (+59 to +123 bp) of exon 1 exhibited a strong role in initiation of tmsg-1 gene transcription. Deletion of this region led to essentially complete loss of driving activity of exon-1 sequence on luciferase. Further analysis showed that transcription factors KLF6 and Sp1 are able to interact with each other and bind to their elements in this region. Co-transfection of pGL3-114/+123 with KLF6- and/or Sp1-expressing plasmids resulted in an elevation of luciferase activity and transcription level of tmsg-1, which was abolished by knockdown of KLF6 or Sp1. Analysis of metastatic capacity showed that cells with high metastatic capability exhibited a lower level of KLF6/TMSG-1 proteins with higher invasive capability and vice versa. Thus, we concluded that interaction of KLF6 and Sp1, together with their binding of elements in exon 1 are critical events in initiation of transcription of the tmsg-1 gene. These results reveal a hitherto unreported mechanism for initiation of transcription of the tmsg-1 gene.

Association of polymorphisms of the mu opioid receptor gene with the severity of HIV infection and response to HIV treatment

BACKGROUND

Mu opioid receptor (OPRM1) ligands may alter expression of chemokines and chemokine receptors involved in penetration of human immunodeficiency virus (HIV) type 1 into the cell. We suggest that OPRM1 variants may affect the pathophysiology of HIV infection.

METHODS

DNA samples from 1031 eligible African Americans, Hispanics, and whites from the Women's Interagency HIV Study (WIHS) who were alive as of April 2006 were analyzed. We performed regression analysis of association of 18 OPRM1 variants with a change of viral load and CD4 cell count during 2 periods: between admission to WIHS and the start of highly active antiretroviral therapy (HAART) (interval X) and between the start of HAART and the most recent WIHS visit (interval Y), and examined the association of these variants with HIV status.

RESULTS

Regardless of genotype, a significant decrease in viral load during interval X was found for each ethnicity. Whites with allele G of the functional polymorphism 118A > G (reference sequence rs1799971) showed a smaller decrease in viral load; those bearing minor alleles IVS1 + 1050A, IVS1 + 14123A, and IVS2 + 31A showed a larger decrease in viral load over interval X (0.01 < P < .05). Hispanics with the same alleles showed a greater increase in CD4 cell count over interval Y (0.01 < P < .05). We found an association between OPRM1 variants and HIV status in African Americans and whites.

CONCLUSIONS

OPRM1 polymorphisms may alter the severity of HIV infection before and after HAART.

Cannabinoid CB2 receptors contribute to upregulation of β-endorphin in inflamed skin tissues by electroacupuncture

BACKGROUND

Electroacupuncture (EA) can produce analgesia by increasing the β-endorphin level and activation of peripheral μ-opioid receptors in inflamed tissues. Endogenous cannabinoids and peripheral cannabinoid CB2 receptors (CB2Rs) are also involved in the antinociceptive effect of EA on inflammatory pain. However, little is known about how peripheral CB2Rs interact with the endogenous opioid system at the inflammatory site and how this interaction contributes to the antinociceptive effect of EA on inflammatory pain. In this study, we determined the role of peripheral CB2Rs in the effects of EA on the expression of β-endorphin in inflamed skin tissues and inflammatory pain.

RESULTS

Inflammatory pain was induced by injection of complete Freund's adjuvant into the left hindpaw of rats. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified using von Frey filaments. The mRNA level of POMC and protein level of β-endorphin were quantified by real-time PCR and Western blotting, respectively. The β-endorphin-containing keratinocytes and immune cells in the inflamed skin tissues were detected by double-immunofluorescence labeling. The CB2R agonist AM1241 or EA significantly reduced thermal hyperalgesia and mechanical allodynia, whereas the selective μ-opioid receptor antagonist β-funaltrexamine significantly attenuated the antinociceptive effect produced by them. AM1241 or EA significantly increased the mRNA level of POMC and the protein level of β-endorphin in inflamed skin tissues, and these effects were significantly attenuated by pretreatment with the CB2R antagonist AM630. AM1241 or EA also significantly increased the percentage of β-endorphin-immunoreactive keratinocytes, macrophages, and T-lymphocytes in inflamed skin tissues, and these effects were blocked by AM630.

CONCLUSIONS

EA and CB2R stimulation reduce inflammatory pain through activation of μ-opioid receptors. EA increases endogenous opioid expression in keratinocytes and infiltrating immune cells at the inflammatory site through CB2R activation.

Impact of intracellular alpha fetoprotein on retinoic acid receptors-mediated expression of GADD153 in human hepatoma cell lines

The aim of our study was to gain a better understanding of the molecular mechanism underlying the previously unrecognized role of cytoplasmic alpha fetoprotein (AFP) in retinoic acid receptors (RAR) mediated expression and biological effects of GADD153. Using microarray analysis, the expression of the GADD153 gene showed the greatest fold change among apoptosis/growth related genes in response to ATRA. AFP was able to interact with RAR in HepG2 cells, which was undetectable in HLE cells owing to absence of AFP. ATRA promoted nuclei entrance of RAR, expression of GADD153 and apoptosis, and these changes were reversed after transfection with the afp gene or addition of AGN193109. The level of GADD153 was gradually elevated as the effect of AFP was counteracted by increasing dose or prolonging treatment time with ATRA in HepG2 cells. Knockdown of AFP in siRNA-transfected HepG2 cells or over-expression of AFP in afp gene-transfected HLE cells was synchronously associated with up-regulation or down-regulation, respectively, of GADD153 expression. Both ATRA administration and AFP knockdown were each able to promote greater binding of RAR to its response element with consequent elevation of the proportion of apoptotic cells. Conversely, transfection of HLE cells with pcDNA3.1-afp resulted in apparent reduction of RAR binding to DNA and change of biological effect. These data taken together demonstrate the involvement of AFP in RAR-mediated expression and biological effects of GADD153. These findings provide a novel insight into the mechanism underlying the impact of AFP on the RAR signal network.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Mechanisms involved in phosphatidylinositol 3-kinase pathway mediated up-regulation of the mu opioid receptor in lymphocytes

Despite the substantial progress made in understanding initiation expression of the MOR gene in lymphocytes, the signal pathway associated with MOR gene transcription remains to be better defined. As the phosphatidylinositol 3-kinase (PI3K)/AKT pathway can mediate diverse biological responses and is crucial for optimal immune responses and lymphocyte development, this study was undertaken to delineate the role of PI3K/AKT signaling in expression of the MOR gene in CEM x174 cells. The data show that morphine treatment enhanced the level of phosphorylated, rather than un-phosphorylated, PI3K and AKT, which were synchronously recruited to membrane. The levels of PTEN and p53 which are negative regulators of these signal molecules were reduced, and as a result, the interaction between PTEN and p53 was completely interrupted. With morphine treatment, the levels of both cytoplasmic and nuclear E2F1 which is the downstream effecter of AKT were elevated and the interaction of E2F1 with YY1, rather than Sp1, was also increased. Subsequently, E2F1 triggered the transcription of the MOR gene through its enhanced ability to bind the element in promoter region of the MOR gene. All responses to morphine were abolished by naloxone, which is an antagonist of MOR, or by LY294002, an inhibitor of PI3K, implying specific involvement of PI3K/AKT. These results strongly suggest that the PI3K/AKT pathway plays a critical role in the transfer of signal from morphine stimuli to the machinery by which MOR gene transcription is initiated.