Prostaglandin E2 Up-regulates HIV-1 long terminal repeat-driven gene activity in T cells via NF-kappaB-dependent and -independent signaling pathways

A Canadian Survey of Research on HIV-1 Latency-Where Are We Now and Where Are We Heading?

Worldwide, almost 40 million people are currently living with HIV-1. The implementation of cART inhibits HIV-1 replication and reduces viremia but fails to eliminate HIV-1 from latently infected cells. These cells are considered viral reservoirs from which HIV-1 rebounds if cART is interrupted. Several efforts have been made to identify these cells and their niches. There has been little success in diminishing the pool of latently infected cells, underscoring the urgency to continue efforts to fully understand how HIV-1 establishes and maintains a latent state. Reactivating HIV-1 expression in these cells using latency-reversing agents (LRAs) has been successful, but only in vitro. This review aims to provide a broad view of HIV-1 latency, highlighting Canadian contributions toward these aims. We will summarize the research efforts conducted in Canadian labs to understand the establishment of latently infected cells and how this informs curative strategies, by reviewing how HIV latency is established, which cells are latently infected, what methodologies have been developed to characterize them, how new compounds are discovered and evaluated as potential LRAs, and what clinical trials aim to reverse latency in people living with HIV (PLWH).

Rotavirus-Mediated Prostaglandin E2 Production in MA104 Cells Promotes Virus Attachment and Internalisation, Resulting in an Increased Viral Load

Rotaviruses are one of the leading causes of severe dehydrating diarrhoea in infants and children under the age of five. Despite the introduction of vaccines, disease burden remains high in sub-Saharan Africa, with no known anti-viral treatments available. During early infection rotavirus attaches to several cellular receptors and enters the cells by either clathrin-dependent or -independent endocytosis. Prostaglandin E_2, an abundant eicosanoid, is produced from arachidonic acid during rotavirus infection and inhibition of prostaglandin E₂ formation have a deleterious effect on rotavirus infection. In this study, MA104 cells were supplemented with γ-linolenic acid (GLA), a precursor of arachidonic acid. Infection of supplemented cells with rotavirus SA11 led to a depletion in the relative percentages of GLA and arachidonic acid which coincided with an increased production of prostaglandin E₂ as monitored by ELISA. Confocal microscopy demonstrated that prostaglandin E₂ co-localises with the viroplasm-forming proteins, NSP5 and NSP2. Due to the known association of viroplasms with lipid droplets and the fact that lipid droplets are sites for prostaglandin E₂ production, our results indicate a possible role for viroplasms in the production of rotavirus-induced prostaglandin E₂. Replication kinetics showed that inhibitors, targeting the biosynthesis of prostaglandin E₂, had negative effects on rotavirus yield, especially during the early stages of infection. Using flow cytometry and prostaglandin E₂ addback experiments, we show that prostaglandin E₂ enhances the attachment and internalisation of rotavirus in MA104 cells indicating a possible role for prostaglandin E₂ during clathrin-mediated rotavirus entry. The production of prostaglandin E₂ during rotavirus infection could serve as a possible target for anti-viral treatment.

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

Prostaglandin E2 Induction Suppresses the Th1 Immune Responses in Cattle with Johne's Disease

Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis, is a bovine chronic infection that is endemic in Japan and many other countries. The expression of immunoinhibitory molecules is upregulated in cattle with Johne's disease, but the mechanism of immunosuppression is poorly understood. Prostaglandin E₂ (PGE₂) is immunosuppressive in humans, but few veterinary data are available. In this study, functional and kinetic analyses of PGE₂ were performed to investigate the immunosuppressive effect of PGE₂ during Johne's disease. In vitro PGE₂ treatment decreased T-cell proliferation and Th1 cytokine production and upregulated the expression of immunoinhibitory molecules such as interleukin-10 and programmed death ligand 1 (PD-L1) in peripheral blood mononuclear cells (PBMCs) from healthy cattle. PGE₂ was upregulated in sera and intestinal lesions of cattle with Johne's disease. In vitro stimulation with Johnin purified protein derivative (J-PPD) induced cyclooxygenase-2 (COX-2) transcription, PGE₂ production, and upregulation of PD-L1 and immunoinhibitory receptors in PBMCs from cattle infected with M. avium subsp. paratuberculosis Therefore, Johnin-specific Th1 responses could be limited by the PGE₂ pathway in cattle. In contrast, downregulation of PGE₂ with a COX-2 inhibitor promoted J-PPD-stimulated CD8⁺ T-cell proliferation and Th1 cytokine production in PBMCs from the experimentally infected cattle. PD-L1 blockade induced J-PPD-stimulated CD8⁺ T-cell proliferation and interferon gamma production in vitro Combined treatment with a COX-2 inhibitor and anti-PD-L1 antibodies enhanced J-PPD-stimulated CD8⁺ T-cell proliferation in vitro, suggesting that the blockade of both pathways is a potential therapeutic strategy to control Johne's disease. The effects of COX-2 inhibition warrant further study as a novel treatment of Johne's disease.

Prostaglandin E2 As a Modulator of Viral Infections

Viral infections are a major cause of infectious diseases worldwide. Inflammation and the immune system are the major host defenses against these viral infection. Prostaglandin E2 (PGE2), an eicosanoid generated by cyclooxygenases, has been shown to modulate inflammation and the immune system by regulating the expression/concentration of cytokines. The effect of PGE2 on viral infection and replication is cell type- and virus-family-dependent. The host immune system can be modulated by PGE2, with regards to immunosuppression, inhibition of nitrogen oxide (NO) production, inhibition of interferon (IFN) and apoptotic pathways, and inhibition of viral receptor expression. Furthermore, PGE2 can play a role in viral infection directly by increasing the production and release of virions, inhibiting viral binding and replication, and/or stimulating viral gene expression. PGE2 may also have a regulatory role in the induction of autoimmunity and in signaling via Toll-like receptors. In this review the known effects of PGE2 on the pathogenesis of various infections caused by herpes simplex virus, rotavirus, influenza A virus and human immunodeficiency virus as well the therapeutic potential of PGE2 are discussed.

Gene Expression Profiling of Human Vaginal Cells In Vitro Discriminates Compounds with Pro-Inflammatory and Mucosa-Altering Properties: Novel Biomarkers for Preclinical Testing of HIV Microbicide Candidates

BACKGROUND

Inflammation and immune activation of the cervicovaginal mucosa are considered factors that increase susceptibility to HIV infection. Therefore, it is essential to screen candidate anti-HIV microbicides for potential mucosal immunomodulatory/inflammatory effects prior to further clinical development. The goal of this study was to develop an in vitro method for preclinical evaluation of the inflammatory potential of new candidate microbicides using a microarray gene expression profiling strategy.

METHODS

To this end, we compared transcriptomes of human vaginal cells (Vk2/E6E7) treated with well-characterized pro-inflammatory (PIC) and non-inflammatory (NIC) compounds. PICs included compounds with different mechanisms of action. Gene expression was analyzed using Affymetrix U133 Plus 2 arrays. Data processing was performed using GeneSpring 11.5 (Agilent Technologies, Santa Clara, CA).

RESULTS

Microarraray comparative analysis allowed us to generate a panel of 20 genes that were consistently deregulated by PICs compared to NICs, thus distinguishing between these two groups. Functional analysis mapped 14 of these genes to immune and inflammatory responses. This was confirmed by the fact that PICs induced NFkB pathway activation in Vk2 cells. By testing microbicide candidates previously characterized in clinical trials we demonstrated that the selected PIC-associated genes properly identified compounds with mucosa-altering effects. The discriminatory power of these genes was further demonstrated after culturing vaginal cells with vaginal bacteria. Prevotella bivia, prevalent bacteria in the disturbed microbiota of bacterial vaginosis, induced strong upregulation of seven selected PIC-associated genes, while a commensal Lactobacillus gasseri associated to vaginal health did not cause any changes.

CONCLUSIONS

In vitro evaluation of the immunoinflammatory potential of microbicides using the PIC-associated genes defined in this study could help in the initial screening of candidates prior to entering clinical trials. Additional characterization of these genes can provide further insight into the cervicovaginal immunoinflammatory and mucosal-altering processes that facilitate or limit HIV transmission with implications for the design of prevention strategies.

Prostaglandin E2 reduces the release and infectivity of new cell-free virions and cell-to-cell HIV-1 transfer

Background

The course of human immunodeficiency virus type-1 (HIV-1) infection is influenced by a complex interplay between viral and host factors. HIV infection stimulates several proinflammatory genes, such as cyclooxigense-2 (COX-2), which leads to an increase in prostaglandin (PG) levels in the plasma of HIV-1-infected patients. These genes play an indeterminate role in HIV replication and pathogenesis. The effect of prostaglandin E₂ (PGE₂) on HIV infection is quite controversial and even contradictory, so we sought to determine the role of PGE₂ and the signal transduction pathways involved in HIV infection to elucidate possible new targets for antiretrovirals.

Results

Our results suggest that PGE₂ post-infection treatment acts in the late stages of the viral cycle to reduce HIV replication. Interestingly, viral protein synthesis was not affected, but a loss of progeny virus production was observed. No modulation of CD4 CXCR4 and CCR5 receptor expression, cell proliferation, or activation after PGE₂ treatment was detected. Moreover, PGE₂ induced an increase in intracellular cAMP (cyclic AMP) levels through the EP2/EP4 receptors. PGE₂ effects were mimicked by dbcAMP and by a specific Epac (exchange protein directly activated by cyclic AMP) agonist, 8-Cpt-cAMP. Treatment with PGE₂ increased Rap1 activity, decreased RhoA activity and subsequently reduced the polymerization of actin by approximately 30% compared with untreated cells. In connection with this finding, polarized viral assembly platforms enriched in Gag were disrupted, altering HIV cell-to-cell transfer and the infectivity of new virions.

Conclusions

Our results demonstrate that PGE₂, through Epac and Rap activation, alters the transport of newly synthesized HIV-1 components to the assembly site, reducing the release and infectivity of new cell-free virions and cell-to-cell HIV-1 transfer.

Seminal plasma induces prostaglandin-endoperoxide synthase (PTGS) 2 expression in immortalized human vaginal cells: involvement of semen prostaglandin E2 in PTGS2 upregulation

Inflammation of the cervicovaginal mucosa is considered a risk factor for HIV infection in heterosexual transmission. In this context, seminal plasma (SP) may play an important role that is not limited to being the main carrier for the virions. It is known that SP induces an inflammatory reaction in the cervix called postcoital leukocytic reaction, which has been associated with promotion of fertility. The mechanisms by which SP triggers this reaction, however, have not been clearly established. Previously we reported the expression of prostaglandin-endoperoxide synthase 2 (PTGS2), also known as cyclooxygenase 2 (COX-2), in human vaginal cells in response to toll-like receptor (TLR) ligands and other proinflammatory stimuli. In this study, we demonstrate that SP induces transcriptional and translational increase of COX-2 expression in human vaginal cells and cervicovaginal tissue explants. Furthermore, SP potentiates vaginal PTGS2 expression induced by other proinflammatory stimulants, such as TLR ligands and a vaginal mucosal irritant (nonoxynol-9) in a synergistic manner. SP-induced PTGS2 expression is mediated by intracellular signaling pathways involving MAPKs and NF-κB. Using fractionation and functional analysis, seminal prostaglandin (PG)-E(2) was identified as a one of the major factors in PTGS2 induction. Given the critical role of this PG-producing enzyme in mucosal inflammatory processes, the finding that SP induces and potentiates the expression of PTGS2 in cervicovaginal cells and tissues has mechanistic implications for the role of SP in fertility-associated mucosal leukocytic reaction and its potential HIV infection-enhancing effect.

Interactions between prostaglandins, leukotrienes and HIV-1: possible implications for the central nervous system

In HIV-1-infected individuals, there is often discordance between viremia in peripheral blood and viral load found in the central nervous system (CNS). Although the viral burden is often lower in the CNS compartment than in the plasma, neuroinflammation is present in most infected individuals, albeit attenuated by the current combined antiretroviral therapy. The HIV-1-associated neurological complications are thought to result not only from direct viral replication, but also from the subsequent neuroinflammatory processes. The eicosanoids - prostanoids and leukotrienes - are known as potent inflammatory lipid mediators. They are often present in neuroinflammatory diseases, notably HIV-1 infection. Their exact modulatory role in HIV-1 infection is, however, still poorly understood, especially in the CNS compartment. Nonetheless, a handful of studies have provided evidence as to how these lipid mediators can modulate HIV-1 infection. This review summarizes findings indicating how eicosanoids may influence the progression of neuroAIDS.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

The therapeutic potential of adenosine triphosphate as an immune modulator in the treatment of HIV/AIDS: a combination approach with HAART

Extracellular adenosine triphosphate (eATP) is a potent molecule that has the capacity to modulate various aspects of cell functions including gene expression. This element of modulation is essential to the role of ATP as a therapeutic agent. The hypothesis presented is that ATP can have an important impact on the treatment of HIV infection. This is supported in part by published research, although a much greater role for ATP is suggested than prior authors ever thought possible. ATP has the ability to enhance the immune system and could thus improve the host's own defense mechanisms to eradicate the virus-infected cells and restore normal immune function. This could provide effective therapy when used in conjunction with highly active antiretroviral therapies (HAART) to eliminate the latently infected cells. The key lies in applying ATP through the methodology described. This article presents a strategy for using ATP therapeutically along with background evidence to substantiate the importance of using ATP in the treatment of HIV infection.

Enterovirus 71 modulates a COX-2/PGE2/cAMP-dependent viral replication in human neuroblastoma cells: role of the c-Src/EGFR/p42/p44 MAPK/CREB signaling pathway

Enterovirus 71 (EV71) has been shown to induce cyclooxygenase‐2 (COX‐2) expression in human neuroblastoma SK‐N‐SH cells through the action of MAPKs, NF‐κB, and AP‐1. On the other hand, the transcription factor CREB has also been implicated in the expression of COX‐2 in other cell lines. Here, we report that EV71‐induced COX‐2 expression and PGE₂ production were both inhibited by pretreatment with the PKA inhibitor H89 or by transfection with CREB siRNA. In addition, EV71‐induced COX‐2 expression and c‐Src/EGFR phosphorylation were both attenuated by transfection with c‐Src siRNA or pretreatment with the inhibitors of c‐Src (PP1) or EGF receptor (EGFR) (AG1478 and EGFR‐neutralizing antibody). We also observed that EV71‐induced p42/p44 MAPK phosphorylation was decreased following pretreatment with AG1478. Moreover, EV71‐induced COX‐2 expression was blocked by pretreatment with the p300 inhibitor GR343 or by transfection with p300 siRNA. Using immunoprecipitation and chromatin immunoprecipitation assays, we observed that EV71 stimulated the association of CREB and p300 with the COX‐2 promoter region. Notably, we also demonstrated that EV71‐induced COX‐2 expression and PGE₂ production promoted viral replication via cAMP signaling. In summary, this study demonstrates that EV71 activates the c‐Src/EGFR/p42/p44 MAPK pathway in human SK‐N‐SH cell, which leads to the activation of CREB/p300, and stimulates COX‐2 expression and PGE₂ release. J. Cell. Biochem. 112: 559–570, 2011. © 2010 Wiley‐Liss, Inc.

Enterovirus 71 induces COX-2 expression via MAPKs, NF-kappaB, and AP-1 in SK-N-SH cells: Role of PGE(2) in viral replication

The enterovirus 71 (EV71) causes severe neurological diseases that were mediated through cyclooxygenase-2 (COX-2) expression in brain. However, the mechanisms underlying EV71-initiated intracellular signaling pathways leading to COX-2 expression remain unknown in neurons. Here we report that exposure of SK-N-SH cells to EV71 increased COX-2 expression and PGE(2) generation in a time- and virus titer-dependent manner, revealed by Western blot, real-time PCR, and PGE(2) analyses. These EV71-induced responses were mediated through activation of p42/p44 MAPK, p38 MAPK, JNK, NF-kappaB, and AP-1, revealed by using selective pharmacological inhibitors or transfection with respective siRNAs. Consistently, EV71-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaBalpha in the cytosol was blocked by pretreatment with the selective inhibitors of MEK1/2 (U0126) and NF-kappaB (Bay11-7085), respectively, suggesting that MEK1/2-p42/p44 MAPK cascade linking to NF-kappaB was involved in COX-2 expression. In addition, EV71-induced AP-1 subunits (c-jun and c-fos mRNA) expression was also attenuated by pretreatment with a selective JNK inhibitor SP600125, suggesting that JNK cascade linking to AP-1 was involved in COX-2 expression induced by EV71. These findings suggested that up-regulation of COX-2 associated with the release of PGE(2) from EV71-infected SK-N-SH cells which was mediated through activation of p38 MAPK, JNK, p42/p44 MAPK, NF-kappaB, and AP-1 pathways.

Oral infectious diseases: a potential risk factor for HIV virus recrudescence?

As the highly active antiretroviral therapy (HAART) has transitioned human immunodeficiency virus (HIV) infection into a 'chronic disease' management strategy, there is growing evidence that infection with non-HIV pathogens in HIV+ patients may have important public health implications in undermining HAART success and acquired immunodeficiency syndrome progression. Several bacterial and host cell products during infections with non-HIV pathogens have shown the capacity to regulate HIV replication in latently infected cells. A high prevalence of oral infections caused by bacteria, viruses and fungi has been described in HIV+ patients, including periodontal disease. The oral cavity appears to be a site of HIV pathogenesis and potential reservoir for the disease as HIV RNA and DNA forms are present in saliva as well as in gingival crevicular fluid, and oral epithelial cells are susceptible to either cell free or cell-associated HIV infection. The clinical and biological bases of potential associations between chronic oral inflammatory disorders, such as periodontal disease, and exacerbation of HIV viraemia have received little attention. This review attempts to evaluate the current understanding of HIV reactivation as a result of co-infection and/or inflammation induced by non-HIV pathogens in HIV-infected patients, and presents a hypothetic model about the potential role of periodontitis as a global oral infection that potentially contributes to HIV recrudescence.

Inflammation and apoptosis in Clostridium difficile enteritis is mediated by PGE2 up-regulation of Fas ligand

BACKGROUND & AIMS

Clostridium difficile toxin A causes acute inflammation and fluid secretion in experimental animals and patients with C difficile infection. We previously reported that toxin A increased cyclooxygenase-2/prostaglandin E(2) (PGE(2)) expression and apoptosis in human colonocytes. Here, we assessed the role of secreted PGE(2) in inflammation and enterocyte apoptosis in toxin A enteritis.

METHODS

Effects of PGE(2) and PGE(2) blockade on toxin A-induced apoptosis of human colonocytes (NCM460) and of PGE(2) or toxin A on the Fas ligand (FasL) induction were analyzed by flow cytometry and Western blot. Functional activity of elevated FasL on colonocytes was assessed by coculture of colonocytes with Fas bearing Jurkat T cells. The involvement of PGE(2)-dependent Fas/FasL activation in toxin A enteritis was further assessed in either scid or FasL and Fas deficient mice.

RESULTS

Inhibition of cyclooxygenase-2 by NS-398 and of PGE(2) using a blocking antibody markedly attenuated apoptosis in colonocytes exposed to toxin A. Enhanced expression and release of FasL followed PGE(2) or toxin A exposure in vivo and in vitro and also was significantly attenuated by treatment with NS-398 and PGE(2) blocking antibody. PGE(2) acting through an EP1 receptor activated nuclear factor-kappaB, which induced transcription of FasL. Toxin A enteritis was accompanied by increased cellular infiltration, fluid secretion, and mucosal damage in control mice, but this response was markedly reduced in both Fas(-/-) and FasL(-/-) mice.

CONCLUSIONS

Toxin A enteritis involves release of PGE(2), which activates the Fas/FasL system, causing enterocyte apoptosis and inflammation.

Additive effect of ethanol and HCV subgenomic replicon expression on COX-2 protein levels and activity

The mechanisms by which alcohol exacerbates liver injury in patients with hepatitis C are unknown. We used the hepatitis C virus (HCV) subgenomic replicon cell system to evaluate the effect of ethanol on HCV replication and viral protein synthesis. Our results demonstrate that alcohol stimulates HCV replicon expression at both HCV-RNA and protein levels. Furthermore, we observed that ethanol treatment showed an additive effect in cyclooxygenase-2 (COX-2) protein expression and activity already induced by HCV viral proteins, and in turn increased HCV viral expression. Our results suggest that COX-2 activity is involved in ethanol-induced HCV-RNA and NS5A protein expression, because acetylsalicylic acid (ASA), a COX-1/2 inhibitor, blocked this induction and downregulated COX-2 protein expression and activity. Therefore, we suggest that ethanol increases HCV replication expression, at least in part, by upregulating a key cellular regulator of oxidative stress pathway known as COX-2 or its products.

Bovine herpesvirus 4 is tropic for bovine endometrial cells and modulates endocrine function

Bovine postpartum uterine disease, metritis, affects about 40% of animals and is widely considered to have a bacterial aetiology. Although the gamma-herpesvirus bovine herpesvirus 4 (BoHV-4) has been isolated from several outbreaks of metritis or abortion, the role of viruses in endometrial pathology and the mechanisms of viral infection of uterine cells are often ignored. The objectives of the present study were to explore the interaction, tropism and outcomes of BoHV-4 challenge of endometrial stromal and epithelial cells. Endometrial stromal and epithelial cells were purified and infected with a recombinant BoHV-4 carrying an enhanced green fluorescent protein (EGFP) expression cassette to monitor the establishment of infection. BoHV-4 efficiently infected both stromal and epithelial cells, causing a strong non-apoptotic cytopathic effect, associated with robust viral replication. The crucial step for the BoHV-4 endometriotropism appeared to be after viral entry as there was enhanced transactivation of the BoHV-4 immediate early 2 gene promoter following transient transfection into the endometrial cells. Infection with BoHV-4 increased cyclooxygenase 2 protein expression and prostaglandin estradiol secretion in endometrial stromal cells, but not epithelial cells. Bovine macrophages are persistently infected with BoHV-4, and co-culture with endometrial stromal cells reactivated BoHV-4 replication in the persistently infected macrophages, suggesting a symbiotic relationship between the cells and virus. In conclusion, the present study provides evidence of cellular and molecular mechanisms, supporting the concept that BoHV-4 is a pathogen associated with uterine disease.

Cyclooxygenase activity is important for efficient replication of mouse hepatitis virus at an early stage of infection

Cyclooxygenases (COXs) play a significant role in many different viral infections with respect to replication and pathogenesis. Here we investigated the role of COXs in the mouse hepatitis coronavirus (MHV) infection cycle. Blocking COX activity by different inhibitors or by RNA interference affected MHV infection in different cells. The COX inhibitors reduced MHV infection at a post-binding step, but early in the replication cycle. Both viral RNA and viral protein synthesis were affected with subsequent loss of progeny virus production. Thus, COX activity appears to be required for efficient MHV replication, providing a potential target for anti-coronaviral therapy.

Lithium and antidepressants: Stimulating immune function and preventing and reversing infection

The ability to safely and economically stimulate immune function would transform the humanitarian and economic landscapes of nosocomial, surgical and antibiotic-resistant infections, as well as reduce the burden of epidemics, pandemics and bioterrorism. Such stimulation is widely held to be beyond our reach, an unfortunate misconception. As early as the mid 1980s sufficient evidence had accumulated to be able to state with conviction that lithium and antidepressants have these properties. Excessive production of prostaglandin E2 activates microorganisms and suppresses immune function, and lithium and antidepressants oppose prostaglandin E2. Immunostimulation is non-specific, possibly relevant to all infections, pertinent to one, two, or more concurrent infections, and highly cost/effective. In controlled studies an antidepressant would be relevant to that agent and only that agent, rendering such studies worthless. Over the past twenty years 22 drug companies have declined interest in developing antidepressants as antiinfectives. It would be unethical to deny the infected these well documented benefits.

Cyclooxygenase 2 induced by Kaposi's sarcoma-associated herpesvirus early during in vitro infection of target cells plays a role in the maintenance of latent viral gene expression

Infection of human dermal microvascular endothelial (HMVEC-d) cells and human foreskin fibroblast (HFF) cells in vitro by Kaposi's sarcoma-associated herpesvirus (KSHV) provides an excellent in vitro model system to study viral latency. KSHV infection is characterized by the induction of preexisting host signal cascades; sustained expression of the latency-associated open reading frame 73 (ORF73) (LANA-1), ORF72, and K13 genes; transient expression of a limited number of lytic genes, including the lytic cycle switch ORF50 (replication and transcription activator) gene; and reprogramming of host transcriptional machinery regulating a variety of cellular processes, including several proinflammatory responses. The cyclooxygenase 2 (COX-2) gene was one of the host cell genes that was highly up-regulated at 2 and 4 h postinfection (p.i.) of HMVEC-d and HFF cells (P. P. Naranatt, H. H. Krishnan, S. R. Svojanovsky, C. Bloomer, S. Mathur, and B. Chandran, Cancer Res. 64:72-84, 2004). Since COX-2 is an important mediator of inflammatory and angiogenic responses, here, using real-time PCR, Western blot, and immunofluorescence assays, we characterized the COX-2 stimulation and its role in KSHV infection. KSHV induced a robust COX-2 expression, which reached a maximum at 2 h p.i. in HMVEC-d cells and at 8 h p.i. in HFF cells, and significantly higher levels were continuously detected for up to 72 h p.i. Constitutive COX-1 protein levels were not modulated by KSHV infection. Moderate levels of COX-2 were also induced by UV-irradiated KSHV and by envelope glycoproteins gB and gpK8.1A; however, viral gene expression appears to be essential for the increased COX-2 induction. High levels of prostaglandin E(2) (PGE(2)), a COX-2 product, were released in the culture supernatant medium of infected cells. PGE(2) synthase, catalyzing the biosynthesis of PGE(2), also increased upon infection and inhibition of COX-2 by NS-398, and indomethacin drastically reduced the levels of PGE(2) and PGE(2) synthase. COX-2 inhibition did not affect KSHV binding, internalization of virus, or the trafficking to the infected cell nuclei. However, latent ORF73 gene expression and ORF73 promoter activity were significantly reduced by COX-2 inhibitors, and this inhibition was relieved by exogenous supplementation with PGE(2). In contrast, lytic ORF50 gene expression and ORF50 promoter activity were unaffected. These studies demonstrate that COX-2 and PGE(2) play roles in facilitating latent viral gene expression and the establishment and maintenance of latency and suggest that KSHV has evolved to utilize the inflammatory responses induced during infection of endothelial cells for the maintenance of viral latent gene expression.

Interaction of macrophages with apoptotic cells enhances HIV Type 1 replication through PGE2, PAF, and vitronectin receptor

Phagocytosis of apoptotic cells by macrophages increases secretion of soluble mediators and generates an antiinflammatory environment. We previously reported that phagocytosis of apoptotic cells by HIV-1-infected macrophages enhances viral replication, with the participation of the cytokine transforming growth factor- beta1 and an integrin receptor. Now, we describe the role of prostaglandin E2 (PGE2), platelet-activating factor (PAF), and the integrin alphaVbeta3 (vitronectin receptor, VnR) in this phenomenon. Exacerbation of HIV-1 growth induced by phagocytosis of apoptotic cells was inhibited when HIV-1-infected macrophages were treated with a cyclooxygenase 2 inhibitor, or with a PAF receptor antagonist (BN 52021) immediately after macrophage interaction with apoptotic cells. Treatment of HIV-1-infected macrophages with BN 52021 decreased viral replication, whereas addition of PGE2 or PAF to these cells enhanced viral replication. Monoclonal antibodies (MAbs) to VnR reduced the macrophage uptake of apoptotic cells, prevented the enhancement of HIV-1 growth upon the engulfment of apoptotic cells, and potently augmented viral replication in HIV-1-infected macrophages in the absence of apoptotic cells. In conclusion, PGE2 and PAF, and ligation of VnR as well, contribute to amplify viral growth in HIV-1-infected macrophages upon uptake of apoptotic cells.

Human cytomegalovirus induced cyclooxygenase-2 in human retinal pigment epithelial cells augments viral replication through a prostaglandin pathway

Cytomegalovirus (CMV) retinitis is characterized by alterations in retinal cell function and host responses to virus replication. The goal of this study was to evaluate the induction of cyclooxygenase-2 (COX-2) and prostaglandin (PGE) in CMV infected human retinal pigment epithelial (RPE) cells and to determine their effect on virus replication. CMV immediate early (IE) protein and COX-2 proteins were identified in RPE cells in retinal tissue sections from patients with CMV retinitis. COX-2 mRNA and protein were induced after CMV infection of human RPE cell cultures. CMV infection of RPE cells induced translocation of NF-kappaB from the cytoplasm to the nucleus. PGE1 and PGE2 were significantly (p<0.001) increased in human RPE cell cultures infected with CMV. Inhibition of CMV IE gene by antisense oligonucleotides abrogated induction of mRNA for COX-2 and protein synthesis of COX-2 and PGE2. PGE enhanced CMV plaque formation and real time PCR analysis revealed that PGE treatment significantly increased CMV DNA copy numbers. These studies demonstrate that when CMV replicates within human RPE cells, COX-2 induction augments virus replication via the PGE pathway. The induction of COX-2 and PGE during retinal CMV infection may augment virus replication and alter a variety of retinal physiological responses.

Inhibition of cyclooxygenase-2 gene expression by the heat shock response in J774 murine macrophages

The heat shock response is a highly conserved mechanism of protection elicited in the cell by various kinds of stimuli, such as heat, sodium arsenite, oxidants and inflammation. Among the mechanisms potentially involved in mediating the protective effects of hsp, one of the most investigated is the inhibition of pro-inflammatory gene expression such as inducible nitric oxide synthase (iNOS) and inflammatory cytokines. Nevertheless, data about the effects of heat shock response on cyclooxygenase-2 expression in activated macrophages are so far not available in literature. The aim of this study was to investigate the changes in cyclooxygenase-2 expression following lipopolysaccharide stimulation of heat shocked J774 murine macrophages. We found, by Western blotting analysis and reverse transcription-polymerase chain reaction analysis (RT-PCR), that the lipopolysaccharide-induced cyclooxygenase-2 gene expression was reduced in heat shocked cells. Such a reduction was associated to activation of heat shock factor, increased levels of heat shock protein 72 and inhibition of lipopolysaccharide-induced nuclear factor-kappaB binding activity. These data suggest that the heat shock response inhibits cyclooxygenase-2 gene expression at transcriptional level, i.e. by preventing the activation of nuclear factor-kappaB, and provide additional information about mechanism(s) underlying the anti-inflammatory effect of the heat shock proteins.

Mechanism of prostaglandin (PG)E2-induced prolactin expression in human T cells: cooperation of two PGE2 receptor subtypes, E-prostanoid (EP) 3 and EP4, via calcium- and cyclic adenosine 5'-monophosphate-mediated signaling pathways

We previously reported that prolactin gene expression in the T-leukemic cell line Jurkat is stimulated by PGE(2) and that cAMP acts synergistically with Ca(2+) or protein kinase C on the activation of the upstream prolactin promoter. Using the transcription inhibitor actinomycin D, we now show that PGE(2)-induced prolactin expression requires de novo prolactin mRNA synthesis and that PGE(2) does not influence prolactin mRNA stability. Furthermore, PGE(2)-induced prolactin expression was inhibited by protein kinase inhibitor fragment 14-22 and BAPTA-AM, which respectively, inhibit protein kinase A- and Ca(2+)-mediated signaling cascades. Using specific PGE(2) receptor agonists and antagonists, we show that PGE(2) induces prolactin expression through engagement of E-prostanoid (EP) 3 and EP4 receptors. We also found that PGE(2) induces an increase in intracellular cAMP concentration as well as intracellular calcium concentration via EP4 and EP3 receptors, respectively. In transient transfections, 3000 bp flanking the leukocyte prolactin promoter conferred a weak induction of the luciferase reporter gene by PGE(2) and cAMP, whereas cAMP in synergy with ionomycin strongly activated the promoter. Mutation of a C/EBP responsive element at -214 partially abolished the response of the leukocyte prolactin promoter to PGE(2), cAMP, and ionomycin plus cAMP.

Cyclooxygenase-1 and -2 are required for production of infectious pseudorabies virus

We have recently shown that cyclooxygenase-2 (COX-2) transcription is markedly induced after herpes simplex virus type 1 and pseudorabies virus (PRV) infections of rat embryonic fibroblast (REF) cells (N. Ray and L. W. Enquist, J. Virol. 78:3489-3501, 2004). For this study, we investigated the role of cyclooxygenase induction in the replication and growth of PRV. We demonstrate here a concordant increase in COX-2 mRNA and protein levels after the infection of REF cells. Inhibitors blocking the activity of cyclooxygenases caused a dramatic reduction in PRV growth. Viral growth could be restored if prostaglandin E(2), the final product of COX-2 activity, was added simultaneously with the COX inhibitors. Immediate-early protein IE180, major capsid protein VP5, and glycoprotein expression were slightly reduced in the presence of COX-2 inhibitors, but expression of the early protein EP0 was not affected by COX inhibition. Viral DNA replication was marginally reduced in the presence of a COX-1/2 inhibitor, but there was no defect in viral DNA cleavage. Electron microscopy analysis revealed an increased number of unusual empty capsid structures in the nuclei of cells infected with PRV in the presence of a COX-1/2 inhibitor. These capsid structures shared some characteristics with procapsids but had a novel appearance by negative staining. Our data establish a role for COX-1 and COX-2 in facilitating the efficient growth and replication of PRV in primary cells.

Inhibition of cyclooxygenase activity reduces rotavirus infection at a postbinding step

Elevated levels of prostaglandins (PGs), products of cyclooxygenases (COXs), are found in the plasma and stool of rotavirus-infected children. We sought to determine the role of COXs, PGs, and the signal transduction pathways involved in rotavirus infection to elucidate possible new targets for antiviral therapy. Human intestinal Caco-2 cells were infected with human rotavirus Wa or simian rotavirus SA-11. COX-2 mRNA expression and secreted PGE2 levels were determined at different time points postinfection, and the effect of COX inhibitors on rotavirus infection was studied by an immunofluorescence assay (IFA). To reveal the signal transduction pathways involved, the effect of MEK, protein kinase A (PKA), p38 mitogen-activated protein kinase (MAPK), and NF-kappaB inhibitors on rotavirus infection was analyzed. In infected Caco-2 cells, increased COX-2 mRNA expression and secreted PGE2 levels were detected. Indomethacin (inhibiting both COX-1 and COX-2) and specific COX-1 and COX-2 inhibitors reduced rotavirus infection by 85 and 50%, respectively, as measured by an IFA. Indomethacin reduced virus infection at a postbinding step early in the infection cycle, inhibiting virus protein synthesis. Indomethacin did not seem to affect viral RNA synthesis. Inhibitors of MEK, PKA, p38 MAPK, and NF-kappaB decreased rotavirus infection by at least 40%. PGE2 counteracted the effect of the COX and PKA inhibitors but not of the MEK, p38 MAPK, and NF-kappaB inhibitors. Conclusively, COXs and PGE2 are important mediators of rotavirus infection at a postbinding step. The ERK1/2 pathway mediated by PKA is involved in COX induction by rotavirus infection. MAPK and NF-kappaB pathways are involved in rotavirus infection but in a PGE2-independent manner. This report offers new perspectives in the search for therapeutic agents in treatment of severe rotavirus-mediated diarrhea in children.

The role and regulation of COX-2 during viral infection

Prostaglandins are lipid mediators, generated by cyclooxygenase (COX), that have been shown to participate in the regulation of virus replication and the modulation of inflammatory responses following infection. A number of studies support a role for PGE2 in the modulation of virus replication and virulence in a cell type and virus selective manner. Virus infection also stimulates the expression of a number of proinflammatory gene products, including COX-2, inducible nitric oxide synthase (iNOS) as well as proinflammatory cytokines. This review will focus on the mechanisms by which proinflammatory prostaglandin production regulates virus replication and virulence. In addition, the signaling pathways that are activated during a virus infection, and that regulate proinflammatory gene expression in macrophages will be reviewed. Specific attention will be placed on the ability of virus infection to activate multiple signaling cascades (such as PKR, MAPK, iPLA2, NF-kappaB) and how these pathways are integrated in the regulation of individual target gene expression.

COX-2 induction during murine gammaherpesvirus 68 infection leads to enhancement of viral gene expression

The murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) model provides many advantages for studying virus-host interactions involved in gammaherpesvirus replication, including the role of cellular responses to infection. We examined the effects of cellular cyclooxygenase-2 (COX-2) and its by-product prostaglandin E(2) (PGE(2)) on MHV-68 gene expression and protein production following de novo infection of cultured cells. Western blot analyses revealed an induction of COX-2 protein in MHV-68-infected cells but not in cells infected with UV-irradiated MHV-68. Luciferase reporter assays demonstrated activation of the COX-2 promoter during MHV-68 replication. Two nonsteroidal anti-inflammatory drugs, a COX-2-specific inhibitor (NS-398) and a COX-1-COX-2 inhibitor (indomethacin), substantially reduced MHV-68 protein production in infected cells. Inhibition of viral protein expression and virion production by NS-398 was reversed in the presence of exogenous PGE(2). Global gene expression analysis using an MHV-68 DNA array showed that PGE(2) increased production of multiple viral gene products, and NS-398 inhibited production of many of the same genes. These studies suggest that COX-2 activity and PGE(2) production may play significant roles during MHV-68 de novo infection.

T-cell receptor/CD28 engagement when combined with prostaglandin E2 treatment leads to potent activation of human T-cell leukemia virus type 1

Infection with human T-cell leukemia virus type 1 (HTLV-1) is characterized by long latency periods, indicating that viral gene expression is under tight control. There is presently little information available regarding the nature of extracellular stimuli that can transactivate the regulatory elements of HTLV-1 (i.e., long terminal repeat [LTR]). To gain insight into the biological importance of externally induced activation pathways in virus gene expression, primary and established T cells were transfected with HTLV-1-based reporter gene vectors and then were treated with agents that cross-linked the T-cell receptor (TCR) or the costimulatory CD28 molecule with prostaglandin E(2) (PGE(2)). We demonstrated that a potent induction of HTLV-1 LTR-driven reporter gene activity was seen only when the three agents were used in combination. Interestingly, similar observations were made when using C91/PL, a cell line that carries integrated HTLV-1 proviral DNA. This TCR-CD28-PGE(2)-mediated increase in virus transcription was dependent on protein kinase A activation and induction of the cAMP response element binding protein. Experiments with a mutated reporter construct further revealed the importance of the Tax-responsive elements in the HTLV-1 LTR in the observed up regulation of virus gene expression when TCR/CD28 engagement was combined with PGE(2) treatment. The protein tyrosine kinases p56(lck) and the transmembrane tyrosine phosphatase CD45 were all found to be involved in TCR-CD28-PGE(2)-directed increase in HTLV-1 LTR activity. This study presents new information on the possible mechanisms underlying reactivation of this retrovirus.

Distinct roles of eicosanoids in the immune response to viral encephalitis: or why you should take NSAIDS

Prostaglandins (PGs) and leukotrienes (LTs) are important proinflammatory mediators. They are both derived from arachidonic acid (AA). Cyclooxygenase (COX), the key enzyme in transforming AA into PGs, has two isoforms: COX-1 is constitutively expressed, and COX-2, is inducible. Lipoxygenase (5-LO) is the key enzyme for LT production. PGs and LTs have been intensively studied. Release of these molecules is associated with mucus secretion, redness, pain, fever and other inflammatory manifestations. Both PGs and LTs are involved in host defense against various pathogens. In addition to mediating inflammatory symptoms, PGs might suppress some innate immune factors, including nitric oxide (NO) production. PGs also suppress a TH1 response. LTs have pathologic potential, especially in asthma. LTs also have been found to have positive roles in host defense, either against virus or bacteria. Finally, PGs and LTs might regulate the production of each other, possibly at the level of substrate competition by their enzymes. Because they are clinically important molecules, a further understanding of the roles that PGs and LTs played in host defense will have great impact on therapeutic research.

HIV-1 transcription and virus production are both accentuated by the proinflammatory myeloid-related proteins in human CD4+ T lymphocytes

S100A8, S100A9, and S100A12, collectively known as myeloid-related proteins (MRPs), are highly expressed by the myeloid cell lineage and are found in the extracellular milieu during infections and inflammatory conditions. Recent data showed high levels of MRPs in the serum of HIV type 1 (HIV-1)-infected patients which correlated with disease progression and low CD4(+) counts. Therefore, we set out to investigate the effect of MRPs on HIV-1 replication. We observed a 4- to 5-fold induction of virus production in J1.1, a human T lymphoid cell line latently infected with HIV-1, following treatment with MRPs. Using luciferase-based reporter gene assays, we demonstrated that MRPs induce a dose- and time-dependent activation of the HIV-1 long terminal repeat promoter region that could be blocked by specific anti-MRP polyclonal Abs and by physical denaturation of these proteins. The MRP-mediated induction was acting through the HIV-1 enhancer sequence and was dependent upon NF-kappaB activity. These latter results were also confirmed by EMSA experiments conducted in Jurkat cells and freshly isolated PBMCs. In conclusion, we demonstrate that MRPs induce HIV-1 transcriptional activity and viral replication in infected CD4(+) T-lymphocytes at concentrations similar to those found in the serum of HIV-1-infected patients.

Activation of monocyte cyclooxygenase-2 gene expression by human herpesvirus 6. Role for cyclic AMP-responsive element-binding protein and activator protein-1

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite mainly produced by activated monocytes/macrophages (Mo/Mphi) that display broad immunomodulatory activities. Several viruses capable of infecting Mo/Mphi modulate PGE(2) synthesis in a way that favors the infection processes and the spread of virions. In the present work, we studied the effect of human herpesvirus 6 (HHV-6) infection of Mo/Mphi on PGE(2) synthesis. Our results indicate that HHV-6 induces COX-2 gene expression and PGE(2) synthesis within a few hours of infection. We mapped the different promoter elements associated with COX-2 gene activation by HHV-6 to two cis-acting elements: a cyclic AMP-responsive element and an activator protein-1 element. HHV-6 immediate-early protein 2 was identified as a modulator of COX-2 gene expression in Mo/Mphi. Finally, addition of PGE(2) to HHV-6-infected peripheral blood mononuclear cells cultures was found to increase significantly viral replication. Overall, these results further contribute to the immunomodulatory properties of HHV-6 and highlight a potential role for eicosanoids in the replication process of this virus.

Cyclooxygenases and prostaglandins: shaping up the immune response

The relevance of cyclooxygenases (COX)-1 and -2 and their products to inflammation, thrombosis and gastroprotection are well known. Their importance in the immune response was first recognized more than 25 years ago, but has only gained widespread attention recently. In this review, we attempt to integrate information on prostanoids and both the innate and acquired immune responses, including effects on leukocytes, antigen presenting cells, dendritic cells, T and B lymphocytes. Prostanoids may be relevant to immunotolerance, autoimmune disorders, transplantation, immunologic defense against tumors, acquired immunodeficiencies and viral infections. Insight into the role of prostanoids in immune function may afford novel therapeutic opportunities.

VPAC1 is a cellular neuroendocrine receptor expressed on T cells that actively facilitates productive HIV-1 infection

OBJECTIVE

A lack of productive HIV-1 infection of Kit225 compared to Jurkat T cells, despite similar levels of CD4 and HIV-1 chemokine co-receptors, was found to correlate with the expression of vasoactive intestinal peptide/pituitary adenylate cyclase activating polypeptide receptor-1 (VPAC1). We therefore examined a role for this seven-transmembrane G protein-coupled neuroendocrine receptor in modulating HIV-1 infection.

METHODS

Reverse transcription-PCR was used to show the level of VPAC1 expression in different T-cell lines. A signal-blocking antibody to VPAC1 was used to examine its inhibiting effect on HIV-1 infection. Transfection of VPAC1 cDNA in both sense and anti-sense orientation was used to assess the role of VPAC1 in HIV-1 infection. HIV-1 infection was monitored by gag p24 ELISA using HIV-1IIIB or by luciferase activity using pseudo envelope-typed HXB2-NL4-3-luciferase. Analysis of HIV-1 gag DNA and 2-LTR circles was utilized to examine a possible mechanism for the effect of VPAC1.

RESULTS

Using VPAC1 signal blocking antibody, we showed that up to 80% of productive infection with HIV-1IIIB was inhibited. We also demonstrated that HIV-1 gp120 has sequence similarity to the natural ligand for VPAC1 and postulate that it can activate this receptor directly. Transfection of VPAC1 cDNA in the anti-sense orientation resulted in a significant loss, up to 50% of productive infection. In contrast, transfection of cells with VPAC1 in the sense orientation increased the productive infection by more than 15-fold and caused a profound increase in syncytium formation. Furthermore, stimulation of VPAC1 on primary cells facilitated in vitro infection with HIV-1 HXB2-NL4-3. Analysis of HIV-1 gag DNA indicated that VPAC1 does not affect viral entry; however, cells that show negligible expression of VPAC1 may not be productively infected as indicated by a lack of 2-LTR circle formation.

CONCLUSION

We have discovered a cellular receptor, VPAC1, that is a novel and potent facilitator of HIV-1 infection and thus, is a potentially important new target for therapeutic intervention.

Phosphorylation of glycogen synthase kinase-3 and stimulation of T-cell factor signaling following activation of EP2 and EP4 prostanoid receptors by prostaglandin E2

Recently we have shown that the FP(B) prostanoid receptor, a G-protein-coupled receptor that couples to Galpha(q), activates T-cell factor (Tcf)/lymphoid enhancer factor (Lef)-mediated transcriptional activation (Fujino, H., and Regan, J. W. (2001) J. Biol. Chem. 276, 12489-12492). We now report that the EP(2) and EP(4) prostanoid receptors, which couple to Galpha(s), also activate Tcf/Lef signaling. By using a Tcf/Lef-responsive luciferase reporter gene, transcriptional activity was stimulated approximately 10-fold over basal by 1 h of treatment with prostaglandin E(2) (PGE(2)) in HEK cells that were stably transfected with the human EP(2) and EP(4) receptors. This stimulation of reporter gene activity was accompanied by a PGE(2)-dependent increase in the phosphorylation of both glycogen synthase kinase-3 (GSK-3) and Akt kinase. H-89, an inhibitor of protein kinase A (PKA), completely blocked the agonist-dependent phosphorylation of GSK-3 in both EP(2)- and EP(4)-expressing cells. However, H-89 pretreatment only blocked PGE(2)-stimulated Lef/Tcf reporter gene activity by 20% in EP(4)-expressing cells compared with 65% inhibition in EP(2)-expressing cells. On the other hand wortmannin, an inhibitor of phosphatidylinositol 3-kinase, had the opposite effect and inhibited PGE(2)-stimulated reporter gene activity to a much greater extent in EP(4)-expressing cells as compared with EP(2)-expressing cells. These findings indicate that the activation of Tcf/Lef signaling by EP(2) receptors occurs primarily through a PKA-dependent pathway, whereas EP(4) receptors activate Tcf/Lef signaling mainly through a phosphatidylinositol 3-kinase-dependent pathway. This is the first indication of a fundamental difference in the signaling potential of EP(2) and EP(4) prostanoid receptors.

Prostaglandin E(2)-mediated activation of HIV-1 long terminal repeat transcription in human T cells necessitates CCAAT/enhancer binding protein (C/EBP) binding sites in addition to cooperative interactions between C/EBPbeta and cyclic adenosine 5'-monophosphate response element binding protein

Previous work indicates that treatment of human T cells with PGE(2) results in an increase of HIV-1 long terminal repeat (LTR) transcriptional activity. The noticed PGE(2)-mediated activation of virus gene activity required the participation of specific intracellular second messengers such as calcium and two transcription factors, i.e., NF-kappaB and CREB. We report in this work that the nuclear transcription factor CCAAT/enhancer binding protein (C/EBP) is also important for PGE(2)-dependent up-regulation of HIV-1 LTR-driven gene activity. The implication of C/EBP was shown by using a trans-dominant negative inhibitor of C/EBP (i.e., liver-enriched transcriptional inhibitory protein) and several molecular constructs carrying site-directed mutations in the C/EBP binding sites located within the HIV-1 LTR. Mutated HIV-1 LTR constructs also revealed the involvement of the two most proximal C/EBP binding sites. Data from cotransfection experiments with vectors coding for dominant negative mutants and gel mobility shift assays indicated that PGE(2)-mediated induction of HIV-1 LTR activity results from a cooperative interaction between C/EBPbeta and CREB, two members of the basic leucine zipper family of transcription factors. Altogether these findings indicate that treatment of human T cells with PGE(2) induces HIV-1 LTR activity through a complex interplay between C/EBPbeta and CREB. Such a combinatorial regulation may represent a mechanism that permits a fine regulation of HIV-1 expression by PGE(2) in human T cells.

Prostaglandin E(2) inhibits replication of HIV-1 in macrophages through activation of protein kinase A

Since macrophages are a source of increased PGE(2) in AIDS, we investigated the role of PGE(2) in the replication of HIV-1 in these cells. PGE(2) inhibited HIV-1 replication measured by reverse transcriptase in human monocyte-derived macrophage (MDM). Treatment of MDM with the PGE(1) analog misoprostol, the adenylate cyclase activator forskolin, and the cyclic AMP analog dibutyryl-cyclic AMP (db-cAMP) suppressed HIV replication. The protein kinase A (PKA) activator 8-bromo-cyclic AMP also inhibited HIV-1 replication. Similar results were observed with the entry-independent, latently HIV-infected U1 cells. There was a parallel decrease in HIV-1 mRNA levels following PGE(2) treatment. Co-transfection of the HIV-1 promoter LTR.luciferase, with the vector CMV.Calpha, which expresses the PKA catalytic unit increasing PKA activity, reduced HIV-1 promoter activity. Inhibition of PKA activity with the pMT.RAB vector, a mutant regulatory unit of PKA, augmented HIV-1 promoter activity. In summary, PGE(2) inhibits HIV-1 gene expression in MDM through a PKA-dependent mechanism.

Sphingosine 1-phosphate activates nuclear factor-kappa B through Edg receptors. Activation through Edg-3 and Edg-5, but not Edg-1, in human embryonic kidney 293 cells

Sphingosine 1-phosphate (S1P) exerts a variety of actions as a second messenger or as an agonist that binds to one or more members of the Edg family of G protein-coupled receptors. By using human embryonic kidney 293 cells, we show that S1P activates nuclear factor-kappa B (NF-kappa B) in a receptor-dependent fashion. Edg-3 and Edg-5, which are coupled to G(i), G(q), and G(13), affect activation of NF-kappa B, whereas Edg-1, which is coupled to G(i) alone, does not. We find that the activation of NF-kappa B requires protein kinase C and Ca(2+), probably downstream of G(q), but that the activation of Rho alone by S1P, whether through G(q) or G(13), does not translate into the activation of NF-kappa B. G beta gamma has little effect of its own but potentiates the activation of NF-kappa B achieved through other G proteins. We conclude that the activation of NF-kappa B by S1P is a receptor-mediated process that relies primarily on the activation of a phospholipase C by G(q) and secondarily on effector regulation through other G proteins.

Positive and negative regulation of NF-kappaB by COX-2: roles of different prostaglandins

The prostaglandin H synthases (PGHS) catalyze the conversion of arachidonic acid to prostaglandin H(2), the committed step in prostanoid synthesis. Two forms of PGHS exist, PGHS-1 (COX-1) and PGHS-2 (COX-2). The gene encoding the latter form is known to be inducible by a number of stimuli including several inflammatory mediators. Recent evidence indicates that the inducible cyclooxygenase may have both pro- and anti-inflammatory properties through the generation of different prostaglandins. Previous reports indicate that the transcription factor NF-kappaB can function upstream of COX-2 to control transcription of this gene and that the cyclopentenone prostaglandins can inhibit NF-kappaB activation via the inhibition of the IkappaB kinase. Thus, it is suggested that cyclopentenones feed back to inhibit continued nuclear accumulation of NF-kappaB. In this report we demonstrate COX-2 expression inhibits nuclear translocation of NF-kappaB, and we confirm that the cyclopentenone prostaglandins inhibit NF-kappaB. In addition, we show that prostaglandin E(2) and its analogs promote the inherent transcriptional activity of the p65/RelA subunit of NF-kappaB in a manner independent of induced nuclear accumulation. Consistent with this evidence, prostaglandin E(2) strongly synergizes with the inflammatory cytokine tumor necrosis factor-alpha to promote NF-kappaB-dependent transcription and gene expression. The data provide a molecular rationale to explain both the pro- and anti-inflammatory nature of COX-2.

Human immunodeficiency virus type-1 and chemokines: beyond competition for common cellular receptors

The chemokines and their receptors have been receiving exceptional attention in recent years following the discoveries that some chemokines could specifically block human immunodeficiency virus type 1 (HIV-1) infection and that certain chemokine receptors were the long-sought coreceptors which, along with CD4, are required for the productive entry of HIV-1 and HIV-2 isolates. Several chemokine receptors or orphan chemokine receptor-like molecules can support the entry of various viral strains, but the clinical significance of the CXCR4 and CCR5 coreceptors appear to overshadow a critical role for any of the other coreceptors and all HIV-1 and HIV-2 strains best employ one or both of these coreceptors. Binding of the HIV-1 envelope glycoprotein gp120 subunit to CD4 and/or an appropriate chemokine receptor triggers conformational changes in the envelope glycoprotein oligomer that allow it to facilitate the fusion of the viral and host cell membranes. During these interactions, gp120 appears to be capable of inducing a variety of signaling events, all of which are still not defined in detail. In addition, the more recently observed dichotomous effects, of both inhibition and enhancement, that chemokines and their receptor signaling events elicit on the HIV-1 entry and replication processes has once again highlighted the intricate and complex balance of factors that govern the pathogenic process. Here, we will review and discuss these new observations summarizing the potential significance these processes may have in HIV-1 infection. Understanding the complexities and significance of the signaling processes that the chemokines and viral products induce may substantially enhance our understanding of HIV-1 pathogenesis, and perhaps facilitate the discovery of new ways for the prevention and treatment of HIV-1 disease.

Endometrial and myometrial corticotropin-releasing hormone (CRH): its regulation and possible roles

In human endometrium, both epithelial and stroma cells produce corticotropin-releasing hormone (CRH). Both types of cells also possess specific CRH-binding sites indicating a local effect of endometrial CRH. The transcription of the CRH gene in human endometrium is under the control of steroid hormones and locally produced prostanoids and interleukins. Endometrial CRH interacts with locally produced prostaglandins and interleukins. Based on these observations it can be hypothesized that CRH, prostaglandins and interleukins form a network responsible for the communication between epithelial and stromal cells, at the level of the endometrium, and between endometrial and myometrial cells at the level of uterus. The net product of these interaction is the micro-regulation of the decidualizing process and the preparation of endometrium for the implantation/nidation of the conceptus. Indeed, this network may represent the core of the intrauterine neuroendocrine-immune interactions involved in the decidualization of stroma and implantation of blastocyst. In addition, this network appears to be essential for the fine-tuning of myometrial tone.

Attachment of human immunodeficiency virus-1 (HIV-1) particles bearing host-encoded B7-2 proteins leads to nuclear factor-kappa B- and nuclear factor of activated T cells-dependent activation of HIV-1 long terminal repeat transcription

Previous studies have shown that human immunodeficiency virus type-1 (HIV-1) can incorporate several surface proteins of host origin. Recent findings indicate that host-encoded cell surface constituents retain their functionality when found embedded into the viral envelope. The primary objective of the current study was to define whether interaction between some specific virion-bound host proteins with their natural cognate ligands present on target cells could mediate intracellular signaling cascade(s). For this purpose, we have generated a whole series of isogenic virus stocks (NL4-3 backbone) bearing or not bearing on their surface foreign CD28, CD54 (ICAM-1), CD80 (B7-1) or CD86 (B7-2) proteins. Our results indicate that incubation of human T lymphoid cells with virions bearing host-derived B7-2 proteins and anti-CD3 antibody can potently activate HIV-1 long terminal repeat-driven gene expression. This up-regulating effect necessitates the involvement of nuclear factor-kappa B (NF-kappa B) and nuclear factor of activated T cells (NFAT) as revealed by the use of vectors coding for dominant negative versions of both transcription factors (i.e. I kappa B alpha S32A/36A and dnNFAT) and band shift assays. The increase of NF-kappa B activity was abolished when infection with B7-2-bearing HIV-1 particles was performed in the presence of the fusion protein CTLA-4 Ig suggesting that the interaction between virally embedded B7-2 and CD28 on the target cell is responsible for the observed NF-kappa B induction. The findings presented here provide the first demonstration that host-encoded proteins acquired by HIV-1 can mediate signal transduction events.

Reciprocal interactions between human T-lymphotropic virus type 1 and prostaglandins: implications for viral transmission

Human T-lymphotropic virus type 1 (HTLV-1), the etiologic agent of adult T-cell leukemia/lymphoma, is transmitted through breast milk and seminal fluid, which are rich in prostaglandins (PGs). We demonstrate that PGE(2) upregulates the HTLV-1 long terminal repeat promoter through the protein kinase A pathway, induces replication of HTLV-1 in peripheral blood mononuclear cells (PBMC) derived from asymptomatic carriers, and enhances transmission of HTLV-1 to cord blood mononuclear cells (CBMC). Furthermore, HTLV-1 Tax transactivates a promoter for cyclooxygenase 2, a PG synthetase, and induces PGE(2) expression in PBMC or CBMC. Thus, HTLV-1 interacts with and benefits from PGs, constituents of its own vehicle for transmission.

Potential of allospecific gene-engineered T cells in transplantation gene therapy: specific T cell activation determines transgene expression in vitro and in vivo

T lymphocytes, regardless of their specificity, are considered key targets for genetic modification in the treatment of inherited or acquired human diseases. In this study, we generated Lewis T cell lines specific for Dark Agouti rat alloantigens and tested the potential of allospecific T lymphocytes as carriers of genes encoding therapeutic proteins in transplantation gene therapy. These allospecific T lymphocytes were successfully, stably transduced with enhanced green fluorescent protein (EGFP) by an Mo-MuLV-based retrovirus vector. A novel gene delivery protocol was utilized, resulting in nearly 100% EGFP-expressing T cells. This approach enabled tracking of allospecific transduced T cells in vivo and illustrates their transgene production by fluorometric determination after ex vivo isolation. Quantitation of EGFP transgene expression was used to determine the influence of T cell receptor-specific activation on transgene regulation. A strict positive correlation between activation state and expression level was detected in vitro and in vivo. The activation-induced increase in transgene expression could be blocked by interference with T cell activation signaling pathways by cyclosporin A, anti-CD4 MAb, or CTLA4-Ig. These data provide strong evidence that direct or indirect effects caused by activation-induced transcription factors are crucial in transgene upregulation. Allospecific activation in spleens, lymph nodes, and transplanted grafts can be considered as antigen-specific targeting strategy. This activation might be useful in expressing therapeutic proteins such as TGF-beta or IL-10 specific to these sites. T lymphocyte priming and activation might be prevented or altered by modification of the local microenvironments, thereby exerting a therapeutic influence on acute and chronic graft rejection processes.

The transcription of corticotropin-releasing hormone in human endometrial cells is regulated by cytokines

Corticotropin-releasing hormone (CRH), a hypothalamic neuropeptide, is also produced in the human endometrium where it participates in local inflammatory phenomena associated with the decidualization of endometrial stroma and the implantation of the fertilized egg. The inflammatory cytokines interleukin 1 (IL-1), IL-6 and leukemia inhibitory factor (LIF) appear to be the dominant local regulators of these intrauterine inflammatory processes. In the present study we have examined the direct interactions between cytokines and CRH in the endometrium. For this purpose we have measured the effects of IL-1, IL-6 and LIF on the activity of CRH promoter inserted in human endometrial cells in culture. Homologous transient transfection experiments were conducted employing a 0.9-kb fragment of the 5' flanking region of the human CRH gene coupled to the luciferase reporter gene, using Ishikawa human endometrial cells. We have found that IL-1beta increased the activity of CRH gene promoter, in a time- and dose-dependent manner. This effect was antagonized by the IL-1 receptor antagonist IL-1ra and blocked completely by the cyclo-oxygenase inhibitor indomethacin. Similarly, IL-6 increased the activity of CRH promoter in a dose-dependent fashion, an effect partially reversed by indomethacin. LIF did not have any apparent effect. In conclusion, our data suggest that IL-1 and IL-6 exert a strong stimulatory effect on the expression of endometrial CRH. This effect is most probably mediated via prostaglandins. Based on these data we hypothesize that in the human endometrium interleukins, prostaglandins and CRH form a local network regulating the inflammatory phenomena taking place within the uterine cavity.