Delta(12)-prostaglandin J(2) is a potent inhibitor of influenza A virus replication

Rationale for 1068 nm Photobiomodulation Therapy (PBMT) as a Novel, Non-Invasive Treatment for COVID-19 and Other Coronaviruses: Roles of NO and Hsp70

Researchers from across the world are seeking to develop effective treatments for the ongoing coronavirus disease 2019 (COVID-19) outbreak, which arose as a major public health issue in 2019, and was declared a pandemic in early 2020. The pro-inflammatory cytokine storm, acute respiratory distress syndrome (ARDS), multiple-organ failure, neurological problems, and thrombosis have all been linked to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) fatalities. The purpose of this review is to explore the rationale for using photobiomodulation therapy (PBMT) of the particular wavelength 1068 nm as a therapy for COVID-19, investigating the cellular and molecular mechanisms involved. Our findings illustrate the efficacy of PBMT 1068 nm for cytoprotection, nitric oxide (NO) release, inflammation changes, improved blood flow, and the regulation of heat shock proteins (Hsp70). We propose, therefore, that PBMT 1068 is a potentially effective and innovative approach for avoiding severe and critical illness in COVID-19 patients, although further clinical evidence is required.

Cyclopentenone Prostaglandins: Biologically Active Lipid Mediators Targeting Inflammation

Cyclopentenone prostaglandins (cyPGs) are biologically active lipid mediators, including PGA2, PGA1, PGJ2, and its metabolites. cyPGs are essential regulators of inflammation, cell proliferation, apoptosis, angiogenesis, cell migration, and stem cell activity. cyPGs biologically act on multiple cellular targets, including transcription factors and signal transduction pathways. cyPGs regulate the inflammatory response by interfering with NF-κB, AP-1, MAPK, and JAK/STAT signaling pathways via both a group of nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-γ) dependent and PPAR-γ independent mechanisms. cyPGs promote the resolution of chronic inflammation associated with cancers and pathogen (bacterial, viral, and parasitic) infection. cyPGs exhibit potent effects on viral infections by repressing viral protein synthesis, altering viral protein glycosylation, inhibiting virus transmission, and reducing virus-induced inflammation. We summarize their anti-proliferative, pro-apoptotic, cytoprotective, antioxidant, anti-angiogenic, anti-inflammatory, pro-resolution, and anti-metastatic potential. These properties render them unique therapeutic value, especially in resolving inflammation and could be used in adjunct with other existing therapies. We also discuss other α, β -unsaturated carbonyl lipids and cyPGs like isoprostanes (IsoPs) compounds.

Immuno-pathogenesis of nCOVID-19 and a possible host-directed therapy including anti-inflammatory and anti-viral prostaglandin (PG J2) for effective treatment and reduction in the death toll

Coronaviruses including severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, also known as 2019-nCoV especially in China) replicate and divide in host cells. During this they are partly hidden from the innate immune responses although inflammatory consequences of viral replication still occur. We propose that anti-inflammatory antiviral prostaglandins may not only restrict viral replication but also prevent inflammatory responses in the lungs and other vital organs that are known to be part of the immuno-pathogenesis of coronavirus disease-19 (COVID-19). The combination of anti-inflammatory antiviral prostaglandins with interferons may lead to the clearance of viruses inside growth-restricted infected cells. However, further experimental studies and clinical trials should be conducted to evaluate the safety and efficacy of these possible therapies.

15d-Prostaglandin J2 induced reactive oxygen species-mediated apoptosis during experimental visceral leishmaniasis

15-Deoxy-delta (12,14)-prostaglandin J2 (15d-PgJ2) is a potent bioactive lipid mediator, known to possess several roles in cell regulation and differentiation along with antimicrobial efficacy against different bacterial and viral infections. In the present study, we investigated the therapeutic efficacy and mechanism of action of 15d-PgJ2 in vitro in Leishmania donovani promastigotes and infected J774 macrophages, and in vivo in Balb/c mice/golden hamster model of experimental visceral leishmaniasis. 15d-PgJ2 effectively killed L. donovani promastigotes and amastigotes in vitro with IC50 of 104.6 and 80.09 nM, respectively. At 2 mg/kg (mice) and 4 mg/kg (hamster) doses, 15d-PgJ2 decreased >90 % spleen and liver parasite burden. It significantly reduced interleukin (IL)-10 and transforming growth factor (TGF)-β synthesis in infected macrophages and splenocytes. 15d-PgJ2 induced reactive oxygen species (ROS)-dependent apoptosis of promastigotes by triggering phosphatidyl serine externalization, mitochondrial membrane damage and inducing caspase-like activity. In vitro drug interaction studies revealed an indifference to the synergistic association of 15d-PgJ2 with Miltefosine and Amphotericin-B (Amp-B). Moreover, when combined with sub-curative doses of Miltefosine and Amphotericin-B, 15d-PgJ2 resulted in >95 % parasite removal. Our results suggested that 15d-PgJ2 induces mitochondria-dependent apoptosis of L. donovani and is a good therapeutic candidate for adjunct therapy against experimental visceral leishmaniasis.

KEY MESSAGE

15d-PgJ2 effectively eliminated both promastigotes and amastigotes form of L. donovani. 15d-PgJ2 decreased parasite burden from infected mice and hamsters with reduced Th2 cytokines. 15d-PgJ2 induced ROS-mediated mitochondrial apoptosis of L. donovani promastigotes. 15d-PgJ2 is a good therapeutic candidate for adjunct therapy with Miltefosine and Amp-B.

Identification of novel membrane-associated prostaglandin E synthase-1 (mPGES-1) inhibitors with anti-influenza activities in vitro

Influenza A virus (IAV) is a major public health concern that leads to high morbidity and mortality worldwide. Despite various vaccination programs and development of drugs targeting essential viral proteins, the emergence of drug-resistant variants has been frequently reported and the therapeutic options are limited. Because exaggerated inflammation is considered as an important factor in disease pathogenesis, immunomodulatory agents that effectively suppress cytokine responses are needed for the treatment of IAV infection. Membrane-associated prostaglandin E synthase-1 (mPGES-1) is an enzyme responsible for the production of prostaglandin E2 (PGE2) that is the best-characterized immune modulatory lipid in vitro and in vivo models of inflammation. In the present study, we tested the anti-influenza activities of mPGES-1 inhibitors, using a phenotype-based assay involving image analyses. Seven primary hits among 49 compounds targeting mPGES-1 exhibited anti-influenza activities against A/Puerto Rico/8/1934 (H1N1) in a dose-dependent manner. The most effective hit, MPO-0047, suppressed influenza-induced p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK) activation. We also showed that mRNA levels of TNF-α, IL-8, CCL5/RANTES, and CXCL10/IP-10 were significantly reduced by the treatment of influenza-infected cells with MPO-0047. Exogenous PGE2 reversed the inhibitory effects of MPO-0047. Our results showed that this selective mPGES-1 inhibitor has anti-influenza effects by inhibiting PGE2 production, which suppresses the induction of pro-inflammatory genes. Taken together our data revealed that mPGES-1 inhibitor has the potential for further development as an influenza therapeutic agent.

Synergistic effect of nitazoxanide with neuraminidase inhibitors against influenza A viruses in vitro

The emergence of drug-resistant influenza A virus (IAV) strains represents a serious threat to global human health and underscores the need for novel approaches to anti-influenza chemotherapy. Combination therapy with drugs affecting different IAV targets represents an attractive option for influenza treatment. We have previously shown that the thiazolide anti-infective nitazoxanide (NTZ) inhibits H1N1 IAV replication by selectively blocking viral hemagglutinin maturation. Herein we investigate the anti-influenza activity of NTZ against a wide range of human and avian IAVs (H1N1, H3N2, H5N9, H7N1), including amantadine-resistant and oseltamivir-resistant strains, in vitro. We also investigate whether therapy with NTZ in combination with the neuraminidase inhibitors oseltamivir and zanamivir exerts synergistic, additive, or antagonistic antiviral effects against influenza viruses. NTZ was effective against all IAVs tested, with 50% inhibitory concentrations (IC50s) ranging from 0.9 to 3.2 μM, and selectivity indexes (SIs) ranging from >50 to >160, depending on the strain and the multiplicity of infection (MOI). Combination therapy studies were performed in cell culture-based assays using A/Puerto Rico/8/1934 (H1N1), A/WSN/1933 (H1N1), or avian A/chicken/Italy/9097/1997 (H5N9) IAVs; dose-effect analysis and synergism/antagonism quantification were performed using isobologram analysis according to the Chou-Talalay method. Combination index (CI) analysis indicated that NTZ and oseltamivir combination treatment was synergistic against A/Puerto Rico/8/1934 (H1N1) and A/WSN/1933 (H1N1) IAVs, with CI values ranging between 0.39 and 0.63, independently of the MOI used. Similar results were obtained when NTZ was administered in combination with zanamivir (CI=0.3 to 0.48). NTZ-oseltamivir combination treatment was synergistic also against the avian A/chicken/Italy/9097/1997 (H5N9) IAV (CI=0.18 to 0.31). Taken together, the results suggest that regimens that combine neuraminidase inhibitors and nitazoxanide exert synergistic anti-influenza effects.

Prostaglandin A1 inhibits avian influenza virus replication at a postentry level: Effect on virus protein synthesis and NF-κB activity

Influenza A viruses (IAV) have the potential to cause devastating pandemics. In recent years, the emergence of new avian strains able to infect humans represents a serious threat to global human health. The increase in drug-resistant IAV strains underscores the need for novel approaches to anti-influenza chemotherapy. Herein we show that prostaglandin-A1 (PGA1) possesses antiviral activity against avian IAV, including H5N9, H7N1 and H1N1 strains, acting at a level different from the currently available anti-influenza drugs. PGA1 acts at postentry level, causing dysregulation of viral protein synthesis and preventing virus-induced disassembly of host microtubular network and activation of pro-inflammatory factor NF-κB. The antiviral activity is dependent on the presence of a cyclopentenone ring structure and is associated with activation of a cytoprotective heat shock response in infected cells. The results suggest that cyclopentenone prostanoids or prostanoids-derived molecules may represent a new tool to combat avian influenza virus infection.

Inhibition of influenza virus-induced NF-kappaB and Raf/MEK/ERK activation can reduce both virus titers and cytokine expression simultaneously in vitro and in vivo

Influenza virus (IV) infection can cause severe pneumonia and death. Therapeutic actions are limited to vaccines and a few anti-viral drugs. These target viral functions thereby selecting resistant variants. During replication IV activates the Raf/MEK/ERK-cascade and the transcription factor NF-kappaB. Both result in virus supportive and anti-viral effects by promoting viral genome transport for virus assembly and by inducing expression of pro-inflammatory host factors. Apart from tissue damage caused by the virus lytic replication, an imbalanced overproduction of anti-viral cytokines can cause severe lung damage as observed in human H5-type IV infections. Recently we showed that inhibition of NF-kappaB activity reduces the virus titer in vitro and in vivo. We have now analyzed whether inhibition of these pathways, allows simultaneous reduction of virus titers and virus-induced cytokines. The results show that inhibition of either pathway indeed leads to decreased virus titers and cytokine expression. This was not only true for infected permanent cells or primary mouse alveolar epithelial cells, but also in infected mice. Hereby we demonstrate for the first time in vitro and in vivo that virus titers and pro-inflammatory cytokine expression can be modulated simultaneously. This could provide a new rationale of future therapeutic strategies to treat IV pneumonia.

Heat shock protein 70 inhibits the activity of Influenza A virus ribonucleoprotein and blocks the replication of virus in vitro and in vivo

Background

Heat shock protein 70 (Hsp70) was identified as a cellular interaction partner of the influenza virus ribonucleoprotein (RNP) complex. The biological significance of the interaction between Hsp70 and RNP has not been fully investigated.

Principal Findings

Here we demonstrated that Hsp70 was involved in the regulation of influenza A viral transcription and replication. It was found that Hsp70 was associated with viral RNP by directly interacting with the PB1 and PB2 subunits, and the ATPase domain of Hsp70 was required for the association. Immunofluorescence analysis showed that Hsp70 was translocated from the cytoplasm into the nucleus in infected cells. Then we found that Hsp70 negatively regulated the expression of viral proteins in infected cells. Real-time PCR analysis revealed that the transcription and replication of all eight viral segments were significantly reduced in Hsp70 overexpressed cells and greatly increased as Hsp70 was knocked down by RNA interference. Luciferase assay showed that overexpression of Hsp70 could inhibit the viral RNP activity on both vRNA and cRNA promoters. Biochemical analysis demonstrated that Hsp70 interfered with the integrity of RNP. Furthermore, delivered Hsp70 could inhibit the replication of influenza A virus in mice.

Significance

Our study indicated that Hsp70 interacted with PB1 and PB2 of RNP and could interfere with the integrity of RNP and block the virus replication in vitro and in vivo possibly through disrupting the binding of viral polymerase with viral RNA.

Antiviral properties, metabolism, and pharmacokinetics of a novel azolo-1,2,4-triazine-derived inhibitor of influenza A and B virus replication

Influenza viruses of types A and B cause periodic pandemics in the human population. The antiviral drugs approved to combat influenza virus infections are currently limited. We have investigated an effective novel inhibitor of human influenza A and B viruses, triazavirine [2-methylthio-6-nitro-1,2,4-triazolo[5,1-c]-1,2,4-triazine-7(4I)-one] (TZV). TZV suppressed the replication of influenza virus in cell culture and in chicken chorioallantoic membranes, and it protected mice from death caused by type A and B influenza viruses. TZV was also effective against a rimantadine-resistant influenza virus strain and against avian influenza A virus H5N1 strains. The pharmacokinetic parameters and bioavailability of TZV were calculated after the administration of TZV to rabbits. The TZV metabolite AMTZV [2-methylthio-6-amino-1,2,4-triazolo[5,1-s]-1,2,4-triazin(e)-7(4I)-one] was discovered in IAK 293T and Huh7 cell cultures, a liver homogenate, and rabbit blood after intragastric administration of TZV. AMTZV was nontoxic and inactive as an inhibitor of influenza virus in cell culture. Most likely, this metabolite is a product of TZV elimination.

Thiazolides, a new class of anti-influenza molecules targeting viral hemagglutinin at the post-translational level

The emergence of highly contagious influenza A virus strains, such as the new H1N1 swine influenza, represents a serious threat to global human health. Efforts to control emerging influenza strains focus on surveillance and early diagnosis, as well as development of effective vaccines and novel antiviral drugs. Herein we document the anti-influenza activity of the anti-infective drug nitazoxanide and its active circulating-metabolite tizoxanide and describe a class of second generation thiazolides effective against influenza A virus. Thiazolides inhibit the replication of H1N1 and different other strains of influenza A virus by a novel mechanism: they act at post-translational level by selectively blocking the maturation of the viral hemagglutinin at a stage preceding resistance to endoglycosidase H digestion, thus impairing hemagglutinin intracellular trafficking and insertion into the host plasma membrane, a key step for correct assembly and exit of the virus from the host cell. Targeting the maturation of the viral glycoprotein offers the opportunity to disrupt the production of infectious viral particles attacking the pathogen at a level different from the currently available anti-influenza drugs. The results indicate that thiazolides may represent a new class of antiviral drugs effective against influenza A infection.

Bcl-2 expression and p38MAPK activity in cells infected with influenza A virus: impact on virally induced apoptosis and viral replication

Previous reports have shown that various steps in the influenza A virus life cycle are impaired in cells expressing the antiapoptotic protein Bcl-2 (Bcl-2(+) cells). We demonstrated a direct link between Bcl-2 and the reduced nuclear export of viral ribonucleoprotein (vRNP) complexes in these cells. However, despite its negative impact on viral replication, Bcl-2 did not prevent host cells from undergoing virally triggered apoptosis. The protein's reduced antiapoptotic capacity was related to phosphorylation of its threonine 56 and serine 87 residues by virally activated p38MAPK. In infected Bcl-2(+) cells, activated p38MAPK was found predominantly in the cytoplasm, colocalized with Bcl-2, and both Bcl-2 phosphorylation and virally induced apoptosis were diminished by specific inhibition of p38MAPK activity. In contrast, in Bcl-2-negative (Bcl-2(-)) cells, which are fully permissive to viral infection, p38MAPK activity was predominantly nuclear, and its inhibition decreased vRNP traffic, phosphorylation of viral nucleoprotein, and virus titers in cell supernatants, suggesting that this kinase also contributes to the regulation of vRNP export and viral replication. This could explain why in Bcl-2(+) cells, where p38MAPK is active in the cytoplasm, phosphorylating Bcl-2, influenza viral replication is substantially reduced, whereas apoptosis proceeds at rates similar to those observed in Bcl-2(-) cells. Our findings suggest that the impact of p38MAPK on the influenza virus life cycle and the apoptotic response of host cells to infection depends on whether or not the cells express Bcl-2, highlighting the possibility that the pathological effects of the virus are partly determined by the cell type it targets.

Study of protein targets for covalent modification by the antitumoral and anti-inflammatory prostaglandin PGA1: focus on vimentin

Prostaglandins with cyclopentenone structure (cyPG) display potent antiproliferative actions that have elicited their study as potential anticancer agents. Several natural and synthetic analogs of the cyPG prostaglandin A(1) (PGA(1)) have proven antitumoral efficacy in cancer cell lines and animal models. In addition, PGA(1) has been used as an inhibitor of transcription factor NF-kappaB-mediated processes, including inflammatory gene expression and viral replication. An important determinant for these effects is the ability of cyPG to form Michael adducts with free thiol groups. The chemical nature of this interaction implies that PGA(1) could covalently modify cysteine residues in a large number of cellular proteins potentially involved in its beneficial effects. However, only a few targets of PGA(1) have been identified. In previous work, we have observed that a biotinylated analog of PGA(1) that retains the cyclopentenone moiety (PGA(1)-B) binds to multiple targets in fibroblasts. Here, we have addressed the identification of these targets through a proteomic approach. Cell fractionation followed by avidin affinity chromatography yielded a fraction enriched in proteins modified by PGA(1)-B. Analysis of this fraction by SDS-PAGE and LC-MS/MS allowed the identification of the chaperone Hsp90, elongation and initiation factors for protein synthesis and cytoskeletal proteins including actin, tubulin and vimentin. Furthermore, we have characterized the modification of vimentin both in vitro and in intact cells. Our observations indicate that cysteine 328 is the main site for PGA(1) addition. These results may contribute to a better understanding of the mechanism of action of PGA(1) and the potential of cyPG-based therapeutic strategies.

Eicosanoid biosynthesis inhibitors increase the susceptibility of Lymantria dispar to nucleopolyhedrovirus LdMNPV

Eighteen pharmaceutical inhibitors of eicosanoid biosynthesis were tested for their effects on gypsy moth, Lymantria dispar and its susceptibility to the nucleopoly-hedrovirus LdMNPV. None of the inhibitors tested had any detrimental effects upon larval growth and development. Treatment with nine inhibitor/NPV combinations (e.g., bromophenacylbromide, clotrimazole, dexamethasone, esculetin, flufenamic acid, indomethacin, nimesulide, sulindac, tolfenamic acid) resulted in 3.5- to 6.6-fold reductions in LC(50)s. Larvae treated with several other COX inhibitors did not yield significant LC(50) reductions. We infer that eicosanoids act in insect defense responses to viral infection. Eicosanoids may act at three levels of insect immune reactions to viral infection, organismal (febrile response), cellular (hemocytic microaggregation, nodulation and plasmatocytes spreading reactions) and intracellular level (mechanisms responsible for insect permissiveness to viral replication).

Antiviral Activity of Proteasome Inhibitors in Herpes Simplex Virus-1 Infection: Role of Nuclear Factor-κB

Background

Herpes simplex virus type 1 (HSV-1) is a potent inducer of nuclear factor-κB (NF-κB), a cellular transcription factor with a crucial role in promoting inflammation and controlling cell proliferation and survival.

Objectives

On the basis of the recent demonstration that HSV-1-induced NF-κB is actively recruited to κB-binding sites in the HSV-1 infected-cell protein 0 (ICP0) promoter enhancing viral transcription and replication, we investigated the effect of proteasome inhibitors MG132, MG115 and epoxomicin, which block NF-κB function by preventing the degradation of the inhibitory proteins IκBα, on HSV-1-induced NF-κB activation and viral replication.

Methods

Antiviral activity of proteasome inhibitors was analysed in HSV-1-infected HEp2 cells by determining infective virus titres by CPE50%, viral RNA synthesis by RT-PCR, and viral protein synthesis by immunoblot analysis or immunofluorescence. ICP0 transcription was studied in transient transfection experiments using the ICP0 promoter-luciferase IE1-Luc construct. IκBα degradation and NF-κB activity were determined by immunoblot analysis and EMSA, respectively.

Results

Proteasome inhibitors were found to prevent HSV-1-induced NF-κB activation in the early phase of infection. Block of virus-induced NF-κB activation resulted in inhibiting HSV-1 ICP0 gene expression, in decreasing the level of immediate-early and late viral proteins, and ultimately in greatly suppressing viral replication. The antiviral effect was lost if treatment was started after NF-κB activation, and appeared to be independent of the HSV-1-induced activation of the JNK pathway.

Conclusions

Proteasome inhibitors possess NF-κB-dependent antiherpetic activity. The results described further identify the IKK/NF-κB pathway as a suitable target for novel antiherpetic drugs.

Temperature sensitive influenza A virus genome replication results from low thermal stability of polymerase-cRNA complexes

Background

The RNA-dependent RNA polymerase of Influenza A virus is a determinant of viral pathogenicity and host range that is responsible for transcribing and replicating the negative sense segmented viral genome (vRNA). Transcription produces capped and polyadenylated mRNAs whereas genome replication involves the synthesis of an alternative plus-sense transcript (cRNA) with unmodified termini that is copied back to vRNA. Viral mRNA transcription predominates at early stages of viral infection, while later, negative sense genome replication is favoured. However, the "switch" that regulates the transition from transcription to replication is poorly understood.

Results

We show that temperature strongly affects the balance between plus and minus-sense RNA synthesis with high temperature causing a large decrease in vRNA accumulation, a moderate decrease in cRNA levels but (depending on genome segment) either increased or unchanged levels of mRNA. We found no evidence implicating cellular heat shock protein activity in this effect despite the known association of hsp70 and hsp90 with viral polymerase components. Temperature-shift experiments indicated that polymerase synthesised at 41°C maintained transcriptional activity even though genome replication failed. Reduced polymerase association with viral RNA was seen in vivo and in confirmation of this, in vitro binding assays showed that temperature increased the rate of dissociation of polymerase from both positive and negative sense promoters. However, the interaction of polymerase with the cRNA promoter was particularly heat labile, showing rapid dissociation even at 37°C. This suggested that vRNA synthesis fails at elevated temperatures because the polymerase does not bind the promoter. In support of this hypothesis, a mutant cRNA promoter with vRNA-like sequence elements supported vRNA synthesis at higher temperatures than the wild-type promoter.

Conclusion

The differential stability of negative and positive sense polymerase-promoter complexes explains why high temperature favours transcription over replication and has implications for the control of viral RNA synthesis at physiological temperatures. Furthermore, given the different body temperatures of birds and man, these finding suggest molecular hypotheses for how polymerase function may affect host range.

Persistent borna disease virus infection confers instability of HSP70 mRNA in glial cells during heat stress

Borna disease virus (BDV) is a highly neurotropic RNA virus that causes neurological disorders in many vertebrate species. Although BDV readily establishes lasting persistence, persistently infected cells maintain an apparently normal cell phenotype in terms of morphology, viability, and proliferation. In this study, to understand the regulation of stress responses in BDV infection, we investigated the expression of heat shock proteins (HSPs) in glial cells persistently infected with BDV. Interestingly, we found that BDV persistence did not upregulate HSP70 expression even in cells treated with heat stress. Furthermore, BDV-infected glial cells exhibited rapid rounding and detachment from the culture plate under various stressful conditions. Immunofluorescence analysis demonstrated that heat stress rapidly disrupts the cell cytoskeleton only in persistently infected cells, suggesting a lack of thermotolerance. Intriguingly, we found that although persistently infected glial cells expressed HSP70 mRNA after heat stress, its expression rapidly disappeared during the recovery period. These observations indicated that persistent BDV infection may affect the stability of HSP70 mRNA. Finally, we found that the double-stranded RNA-dependent protein kinase (PKR) is expressed at a constant level in persistently infected cells with or without heat shock. Considering the interrelationship between HSP70 and PKR production, our data suggest that BDV infection disturbs the cellular stress responses to abolish antiviral activities and maintain persistence.

The IkappaB kinase is a key factor in triggering influenza A virus-induced inflammatory cytokine production in airway epithelial cells

Influenza A viruses continue to represent a severe threat worldwide, causing large epidemics and pandemics responsible for thousands of deaths every year. Excessive inflammation due to overabundant production of proinflammatory cytokines by airway epithelial cells is considered an important factor in disease pathogenesis. Here we report that influenza A virus induced IkappaB kinase (IKK) activity in human airway epithelial A549 cells, resulting in persistent activation of nuclear factor-kappaB (NF-kappaB), a critical regulator of the inflammatory response. Although lung epithelial cells are highly sensitive to stimulation of the IKK/NF-kappaB pathway by influenza virus infection, NF-kappaB was not activated in several non-pulmonary cells permissive to the virus, indicating a cell-specific response. Moreover, NF-kappaB was not essential for virus replication but triggered the expression of proinflammatory cytokines in infected lung cells and was directly responsible for production of high levels of interleukin-8, a chemokine associated with influenza-induced inflammation and airway pathology. We also report that 9-deoxy-delta9,delta12-13,14-dihydro-prostaglandin D2, a cyclopentenone prostanoid with therapeutic efficacy against influenza in preclinical studies, was a powerful inhibitor of influenza virus-induced IKK activity and interleukin-8 production by human pulmonary cells. The results identify IKK as an important factor in triggering influenza virus-induced inflammatory reactions in pulmonary epithelium, suggesting novel therapeutic approaches in the treatment of influenza.

Inhibition of herpesvirus-induced HIV-1 replication by cyclopentenone prostaglandins: role of IkappaB kinase (IKK)

OBJECTIVES

Herpes simplex virus (HSV) infections have been associated with reactivation of HIV-1 replication and increases of HIV-1-load in plasma of co-infected individuals. The present authors have previously reported that in epithelial cells HSV-1 induces the IkappaB-kinase (IKK) causing persistent activation of NF-kappaB, a critical regulator of HIV-1 replication. The present study was performed to investigate whether HSV-1-infection could induce IKK-mediated NF-kappaB activation and enhance HIV-1 expression in human T cells, and to analyze the effect of the IKK-inhibitor prostaglandin A1 (PGA1) and other prostanoids on the NF-kappaB-mediated HSV-HIV interaction.

DESIGN AND METHODS

Induction of IKK and NF-kappaB activity was determined in lymphoblastoid Jurkat cells and HIV-1 chronically-infected H9 and ACH-2 cells by kinase assay and electrophoretic mobility shift assay, respectively. The effect of HSV-1 and different prostanoids on HIV-1 expression and replication was determined in Jurkat cells transfected with HIV-1-LTR-driven reporter genes, and in H9 and ACH-2 cells by p24-antigen level evaluation. The role of NF-kappaB in HSV-1-induced HIV-1 expression was investigated by using the IkappaBalpha dominant-negative IkappaBalpha-AA in co-transfection experiments.

RESULTS

In human T lymphoblastoid cells HSV-1 potently induces IKK activity, causing a persistent induction of NF-kappaB. HSV-1-induced IKK and NF-kappaB function results in transactivation of HIV-1-LTR-regulated genes and induction of HIV-1 replication in chronically-infected T cells. The cyclopentenone PGA1 inhibits HSV-1-induced IKK and NF-kappaB activities, blocking HIV-1-LTR-driven expression and preventing HSV-1-induced HIV-1 replication in co-infected cells.

CONCLUSIONS

The results indicate that IKK is a key factor in triggering HSV-1-induced HIV-1 transcription in chronically-infected cells and identify cyclopentenone prostanoids as potent inhibitors of HSV-1-induced HIV-1 reactivation.

Transactivator protein BICP0 of bovine herpesvirus 1 (BHV-1) is blocked by prostaglandin D2 (PGD2), which points to a mechanism for PGD2-mediated inhibition of BHV-1 replication

The immediate-early protein, BICP0, of bovine herpesvirus 1 (BHV-1) transactivates a variety of viral and cellular genes. In a yeast two-hybrid cDNA library screening, we found that lipocalin-type prostaglandin D synthase, which catalyzes the production of prostaglandin D(2) (PGD(2)), is a cellular target of BICP0. We observed that, during wild-type BHV-1 infection, PGD(2) levels were increased intracellularly and decreased in the medium. These effects were absent upon infection with recombinant BHV-1 expressing beta-galactosidase instead of BICP0 (A2G2). Transient-expression assays showed that BICP0 alone caused a significant increase in PGD(2) levels in the cell. PGD(2) repressed BHV-1 replication in cultured cells. Antiviral activities of prostaglandins have been documented long ago, but their mode of action remains to be clarified. Here we provide evidence that PGD(2) impairs the transactivation ability of BICP0 that is necessary for efficient virus replication.

Heat shock protein 70 is related to thermal inhibition of nuclear export of the influenza virus ribonucleoprotein complex

The influenza virus genome replicates and forms a viral ribonucleoprotein complex (vRNP) with nucleoprotein (NP) and RNA polymerases in the nuclei of host cells. vRNP is then exported into the cytoplasm for viral morphogenesis at the cell membrane. Matrix protein 1 (M1) and nonstructural protein 2/nuclear export protein (NS2/NEP) work in the nuclear export of vRNP by associating with it. It was previously reported that influenza virus production was inhibited in Madin-Darby canine kidney (MDCK) cells cultured at 41 degrees C because nuclear export of vRNP was blocked by the dissociation of M1 from vRNP (A. Sakaguchi, E. Hirayama, A. Hiraki, Y. Ishida, and J. Kim, Virology 306:244-253, 2003). Previous data also suggested that a certain protein(s) synthesized only at 41 degrees C inhibited the association of M1 with vRNP. The potential of heat shock protein 70 (HSP70) as a candidate obstructive protein was investigated. Induction of HSP70 by prostaglandin A1 (PGA1) at 37 degrees C caused the suppression of virus production. The nuclear export of viral proteins was inhibited by PGA1, and M1 was not associated with vRNP, indicating that HSP70 prevents M1 from binding to vRNP. An immunoprecipitation assay showed that HSP70 was bound to vRNP, suggesting that the interaction of HSP70 with vRNP is the reason for the dissociation of M1. Moreover, NS2 accumulated in the nucleoli of host cells cultured at 41 degrees C, showing that the export of NS2 was also disturbed at 41 degrees C. However, NS2 was exported normally from the nucleus, irrespective of PGA1 treatment at 37 degrees C, suggesting that HSP70 does not influence NS2.

Antiviral effects of geranylgeranylacetone: enhancement of MxA expression and phosphorylation of PKR during influenza virus infection

A cyclic polyisoprenoid compound, geranylgeranylacetone (GGA), has been used as antiulcer drug. GGA is also a potent inducer of heat shock proteins (HSPs). HSPs are considered to induce an antiviral effect; however, the detailed mechanism is unknown. To determine whether GGA might show antiviral activity and what the mechanism is, the effect of GGA against influenza virus (strain PR8) infection in vivo and in vitro was investigated. The results demonstrated that GGA treatment strongly suppressed the deleterious consequences of PR8 replication and was accompanied by an increase in HSP70 gene expression in mice. Results from in vitro analyses demonstrated that GGA significantly inhibited the synthesis of PR8-associated proteins and prominently enhanced expression of human myxovirus resistance 1 (MxA) followed by increased HSP70 transcription. Moreover, GGA augmented the expression of an interferon-inducible double-strand RNA-activated protein kinase (PKR) gene and promoted PKR autophosphorylation and concomitantly alpha subunit of eukaryotic initiation factor 2 phosphorylation during PR8 infection. It is proposed that GGA-induced HSP70 has potent antiviral activity by enhancement of antiviral factors and can clinically achieve protection from influenza virus infection.

Inhibition by prostaglandin PGA1 on the multiplication of influenza virus is a dose-dependent effect

Cyclopentenone prostaglandins (PGs), are strong inhibitors of the multiplicative cycle of a wide variety of enveloped RNA and DNA viruses. Their antiviral activity is generally associated with alterations in the synthesis or maturation of specific virus proteins. In this report, we describe the effect of cyclopentenone PGA1 on the replication of influenza A virus Ulster 73 in LLC-MK2 cells. PGA1 was found to inhibit viral replication in a dose-dependent fashion and virus particle yield was reduced at a PGA1 concentration, which did not suppress protein synthesis in mock-infected cells. The kinetic of late viral protein synthesis was delayed in PGA1-treated cells till 10 h post-infection; after that period, viral polypeptide synthesis appeared to be similar in PGA1-treated as well as untreated cells both infected by Ulster 73 virus. This finding suggests that PGA1 might interfere with one or more events in the viral multiplicative cycle such as protein synthesis and assembly, correct insertion of virus polypeptides into the cell membrane and, or maturation of Ulster 73 virion particles. In particular, inhibition of viral replication in LLC-MK2 cells by PGA1 is accompanied by the induction of a cellular polypeptide of 70K molecular weight. We identified this cell protein as a heat shock protein (HSP) related to the inducible isoform of HSP 70, a polypeptide of 72K molecular weight. Induction of this polypeptide by PGA1 was found to be dose-dependent and a substantial accumulation could be seen at a PGA1 concentration that did not inhibit cell protein synthesis in uninfected cells. HSP 70 synthesis started after the beginning of PGA1 treatment and remained at the same level for at least 10 h, leading us to hypothesize that the delay of production of late Ulster 73 proteins could be the consequence of HSP 70 synthesis. These results suggest that HSP 70 could play a role in the antiviral activity of cyclopentenone PGA1 in LLC-MK2 cells.