The FDA-approved drug nitazoxanide is a potent inhibitor of human seasonal coronaviruses acting at postentry level: effect on the viral spike glycoprotein

Coronaviridae is recognized as one of the most rapidly evolving virus family as a consequence of the high genomic nucleotide substitution rates and recombination. The family comprises a large number of enveloped, positive-sense single-stranded RNA viruses, causing an array of diseases of varying severity in animals and humans. To date, seven human coronaviruses (HCoV) have been identified, namely HCoV-229E, HCoV-NL63, HCoV-OC43 and HCoV-HKU1, which are globally circulating in the human population (seasonal HCoV, sHCoV), and the highly pathogenic SARS-CoV, MERS-CoV and SARS-CoV-2. Seasonal HCoV are estimated to contribute to 15-30% of common cold cases in humans; although diseases are generally self-limiting, sHCoV can sometimes cause severe lower respiratory infections and life-threatening diseases in a subset of patients. No specific treatment is presently available for sHCoV infections. Herein we show that the anti-infective drug nitazoxanide has a potent antiviral activity against three human endemic coronaviruses, the Alpha-coronaviruses HCoV-229E and HCoV-NL63, and the Beta-coronavirus HCoV-OC43 in cell culture with IC50 ranging between 0.05 and 0.15 μg/mL and high selectivity indexes. We found that nitazoxanide does not affect HCoV adsorption, entry or uncoating, but acts at postentry level and interferes with the spike glycoprotein maturation, hampering its terminal glycosylation at an endoglycosidase H-sensitive stage. Altogether the results indicate that nitazoxanide, due to its broad-spectrum anti-coronavirus activity, may represent a readily available useful tool in the treatment of seasonal coronavirus infections.

Thiazolide Prodrug Esters and Derived Peptides: Synthesis and Activity

Amino acid ester prodrugs of the thiazolides, introduced to improve the pharmacokinetic parameters of the parent drugs, proved to be stable as their salts but were unstable at pH > 5. Although some of the instability was due to simple hydrolysis, we have found that the main end products of the degradation were peptides formed by rearrangement. These peptides were stable solids: they maintained significant antiviral activity, and in general, they showed improved pharmacokinetics (better solubility and reduced clearance) compared to the parent thiazolides. We describe the preparation and evaluation of these peptides.

Spike mutation resilient scFv76 antibody counteracts SARS-CoV-2 lung damage upon aerosol delivery

The uneven worldwide vaccination coverage against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and emergence of variants escaping immunity call for broadly effective and easily deployable therapeutic agents. We have previously described the human single-chain scFv76 antibody, which recognizes SARS-CoV-2 Alpha, Beta, Gamma and Delta variants. We now show that scFv76 also neutralizes the infectivity and fusogenic activity of the Omicron BA.1 and BA.2 variants. Cryoelectron microscopy (cryo-EM) analysis reveals that scFv76 binds to a well-conserved SARS-CoV-2 spike epitope, providing the structural basis for its broad-spectrum activity. We demonstrate that nebulized scFv76 has therapeutic efficacy in a severe hACE2 transgenic mouse model of coronavirus disease 2019 (COVID-19) pneumonia, as shown by body weight and pulmonary viral load data. Counteraction of infection correlates with inhibition of lung inflammation, as observed by histopathology and expression of inflammatory cytokines and chemokines. Biomarkers of pulmonary endothelial damage were also significantly reduced in scFv76-treated mice. The results support use of nebulized scFv76 for COVID-19 induced by any SARS-CoV-2 variants that have emerged so far.

Impairment of SARS-CoV-2 spike glycoprotein maturation and fusion activity by nitazoxanide: an effect independent of spike variants emergence

SARS-CoV-2, the causative agent of COVID-19, has caused an unprecedented global health crisis. The SARS-CoV-2 spike, a surface-anchored trimeric class-I fusion glycoprotein essential for viral entry, represents a key target for developing vaccines and therapeutics capable of blocking virus invasion. The emergence of SARS-CoV-2 spike variants that facilitate virus spread and may affect vaccine efficacy highlights the need to identify novel antiviral strategies for COVID-19 therapy. Here, we demonstrate that nitazoxanide, an antiprotozoal agent with recognized broad-spectrum antiviral activity, interferes with SARS-CoV-2 spike maturation, hampering its terminal glycosylation at an endoglycosidase H-sensitive stage. Engineering multiple SARS-CoV-2 variant-pseudoviruses and utilizing quantitative cell–cell fusion assays, we show that nitazoxanide-induced spike modifications hinder progeny virion infectivity as well as spike-driven pulmonary cell–cell fusion, a critical feature of COVID-19 pathology. Nitazoxanide, being equally effective against the ancestral SARS-CoV-2 Wuhan-spike and different emerging variants, including the Delta variant of concern, may represent a useful tool in the fight against COVID-19 infections.

The biogenesis of SARS-CoV-2 spike glycoprotein: multiple targets for host-directed antiviral therapy

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19 (coronavirus disease-19), represents a far more serious threat to public health than SARS and MERS coronaviruses, due to its ability to spread more efficiently than its predecessors. Currently, there is no worldwide-approved effective treatment for COVID-19, urging the scientific community to intense efforts to accelerate the discovery and development of prophylactic and therapeutic solutions against SARS-CoV-2 infection. In particular, effective antiviral drugs are urgently needed. With few exceptions, therapeutic approaches to combat viral infections have traditionally focused on targeting unique viral components or enzymes; however, it has now become evident that this strategy often fails due to the rapid emergence of drug-resistant viruses. Targeting host factors that are essential for the virus life cycle, but are dispensable for the host, has recently received increasing attention. The spike glycoprotein, a component of the viral envelope that decorates the virion surface as a distinctive crown ("corona") and is essential for SARS-CoV-2 entry into host cells, represents a key target for developing therapeutics capable of blocking virus invasion. This review highlights aspects of the SARS-CoV-2 spike biogenesis that may be amenable to host-directed antiviral targeting.

Remdesivir: From Ebola to COVID-19

Human coronaviruses (HCoV) were discovered in the 1960s and were originally thought to cause only mild upper respiratory tract diseases in immunocompetent hosts. This view changed since the beginning of this century, with the 2002 SARS (severe acute respiratory syndrome) epidemic and the 2012 MERS (Middle East respiratory syndrome) outbreak, two zoonotic infections that resulted in mortality rates of approximately 10% and 35%, respectively. Despite the importance of these pathogens, no approved antiviral drugs for the treatment of human coronavirus infections became available. However, remdesivir, a nucleotide analogue prodrug originally developed for the treatment of Ebola virus, was found to inhibit the replication of a wide range of human and animal coronaviruses in vitro and in preclinical studies. It is therefore not surprising that when the highly pathogenic SARS-CoV-2 coronavirus emerged in late 2019 in China, causing global health concern due to the virus strong human-to-human transmission ability, remdesivir was one of the first clinical candidates that received attention. After in vitro studies had shown its antiviral activity against SARS-CoV-2, and a first patient was successfully treated with the drug in the USA, a number of trials on remdesivir were initiated. Several had encouraging results, particularly the ACTT-1 double blind, randomized, and placebo controlled trial that has shown shortening of the time to recovery in hospitalized patients treated with remdesivir. The results of other trials were instead negative. Here, we provide an overview of remdesivir discovery, molecular mechanism of action, and initial and current clinical studies on its efficacy.

Coronaviruses and stress: from cellular to global

Near the end of 2019, SARS-CoV-2, a novel highly contagious coronavirus phylogenetically related to the SARS virus, entered the human population with lethal consequences. This special issue devoted to the resulting disease COVID-19 was not planned but instead the articles accumulated organically as researchers in the cell stress response field noticed similarities among the pathophysiology of COVID-19 infections and the responses that they studied in contexts unrelated to viral infection. We preface the issue with an introductory article which begins with a brief review of the structure and biology of SARS-CoV-2. As we collected and compared the COVID-19 articles, several shared themes emerged. In the second part of the introduction, each article is summarized briefly and the common themes that link each into a spontaneously arising chain of ideas and hypotheses are emphasized. These themes include growing evidence of molecular mimicry among the viral proteins and the proteins of patients. The realization that much of the consequences of such immune mimicry may play out on the plasma membrane of vascular endothelial cells raised the specter of autoimmune-induced vascular endothelial damage in multiple organs. Proposals of new therapeutic approaches have coalesced around the theme of inducing protection of the vascular endothelium. New chemical treatments that are proposed include stannous chloride, inducers of the gasotransmitter hydrogen sulfide such as sodium thiosulfate and inducers of the cytoprotective stress protein heme oxygenase. Oxygen delivered by ventilators is already in extensive use to provide life support for patients with severe COVID-19. Two articles propose to advance the use of oxygen to the level of a therapeutic treatment early in the detection of the virus in infected patients by delivering oxygen under elevated pressure in hyperbaric chambers. At elevated blood plasma concentrations, hyperbaric oxygen is capable of achieving results far beyond the capability of ventilators as it promotes the activation of transcription factors that control the establishment of inducible cellular defense systems.

The proteostasis guardian HSF1 directs the transcription of its paralog and interactor HSF2 during proteasome dysfunction

Protein homeostasis is essential for life in eukaryotes. Organisms respond to proteotoxic stress by activating heat shock transcription factors (HSFs), which play important roles in cytoprotection, longevity and development. Of six human HSFs, HSF1 acts as a proteostasis guardian regulating stress-induced transcriptional responses, whereas HSF2 has a critical role in development, in particular of brain and reproductive organs. Unlike HSF1, that is a stable protein constitutively expressed, HSF2 is a labile protein and its expression varies in different tissues; however, the mechanisms regulating HSF2 expression remain poorly understood. Herein we demonstrate that the proteasome inhibitor anticancer drug bortezomib (Velcade), at clinically relevant concentrations, triggers de novo HSF2 mRNA transcription in different types of cancers via HSF1 activation. Similar results were obtained with next-generation proteasome inhibitors ixazomib and carfilzomib, indicating that induction of HSF2 expression is a general response to proteasome dysfunction. HSF2-promoter analysis, electrophoretic mobility shift assays, and chromatin immunoprecipitation studies unexpectedly revealed that HSF1 is recruited to a heat shock element located at 1.397 bp upstream from the transcription start site in the HSF2-promoter. More importantly, we found that HSF1 is critical for HSF2 gene transcription during proteasome dysfunction, representing an interesting example of transcription factor involved in controlling the expression of members of the same family. Moreover, bortezomib-induced HSF2 was found to localize in the nucleus, interact with HSF1, and participate in bortezomib-mediated control of cancer cell migration. The results shed light on HSF2-expression regulation, revealing a novel level of HSF1/HSF2 interplay that may lead to advances in pharmacological modulation of these fundamental transcription factors.

The second-generation thiazolide haloxanide is a potent inhibitor of avian influenza virus replication

The emergence of new avian influenza virus (AIV) strains able to infect humans represents a serious threat to global human health. In addition to surveillance and vaccine development, antiviral therapy remains crucial for AIV control; however, the increase in drug-resistant AIV strains underscores the need for novel approaches to anti-influenza chemotherapy. We have previously shown that the thiazolide anti-infective nitazoxanide (NTZ) inhibits influenza A/PuertoRico/8/1934(H1N1) virus replication, and this effect was associated with inhibition of viral hemagglutinin (HA) maturation. Herein we investigated the activity of the second-generation thiazolide haloxanide (HLN) against H5N9, H7N1 and H1N1 AIV infection in vitro, and explored the mechanism of the antiviral action. Using the A/chicken/Italy/9097/1997(H5N9) AIV as a model, we show that HLN and its precursor p-haloxanide are more effective than NTZ against AIV, with IC₅₀ ranging from 0.03 to 0.1 μg/ml, and SI ranging from 200 to >700, depending on the multiplicity of infection. Haloxanide did not affect AIV entry into target cells and did not cause a general inhibition of viral protein expression, whereas it acted at post-translational level by inhibiting HA maturation at a stage preceding resistance to endoglycosidase-H digestion. Importantly, this effect was independent of the AIV-HA subtype and the host cell. Immunomicroscopy and receptor-binding studies confirmed that HLN-induced alterations impair AIV-HA trafficking to the host cell plasma membrane, a key step for viral morphogenesis. The results indicate that haloxanide could provide a new tool for treatment of avian influenza virus infections.

Inhibition of viral protein translation by indomethacin in vesicular stomatitis virus infection: role of eIF2α kinase PKR

Indomethacin, a cyclooxygenase‐1 and ‐2 inhibitor widely used in the clinic for its potent anti‐inflammatory/analgesic properties, possesses antiviral activity against several viral pathogens; however, the mechanism of antiviral action remains elusive. We have recently shown that indomethacin activates the double‐stranded RNA (dsRNA)‐dependent protein kinase R (PKR) in human colon cancer cells. Because of the important role of PKR in the cellular defence response against viral infection, herein we investigated the effect of indomethacin on PKR activity during infection with the prototype rhabdovirus vesicular stomatitis virus. Indomethacin was found to activate PKR in an interferon‐ and dsRNA‐independent manner, causing rapid (< 5 min) phosphorylation of eukaryotic initiation factor‐2 α‐subunit (eIF2α). These events resulted in shutting off viral protein translation and blocking viral replication (IC₅₀ = 2 μM) while protecting host cells from virus‐induced damage. Indomethacin did not affect eIF2α kinases PKR‐like endoplasmic reticulum‐resident protein kinase (PERK) and general control non‐derepressible‐2 (GCN2) kinase, and was unable to trigger eIF2α phosphorylation in the presence of PKR inhibitor 2‐aminopurine. In addition, small‐interfering RNA‐mediated PKR gene silencing dampened the antiviral effect in indomethacin‐treated cells. The results identify PKR as a critical target for the antiviral activity of indomethacin and indicate that eIF2α phosphorylation could be a key element in the broad spectrum antiviral activity of the drug.

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.

The life and times of Ferruccio Ritossa

Ferruccio Ritossa wrote these lines only a few months before he died, as a preface to a book he wanted to write and that, unfortunately, we will never be able to read. It was to be the story of his life, an amazing story indeed. With this article, we want to take a picture of Ferruccio's life, a mosaic of events, facts, ideas, hopes, and memories linked in a way that they will not go away, even after "a stroll in our brain."

The proteasome inhibitor bortezomib is a potent inducer of zinc finger AN1-type domain 2a gene expression: role of heat shock factor 1 (HSF1)-heat shock factor 2 (HSF2) heterocomplexes

The zinc finger AN1-type domain 2a gene, also known as arsenite-inducible RNA-associated protein (AIRAP), was recently identified as a novel human canonical heat shock gene strictly controlled by heat shock factor (HSF) 1. Little is known about AIRAP gene regulation in human cells. Here we report that bortezomib, a proteasome inhibitor with anticancer and antiangiogenic properties used in the clinic for treatment of multiple myeloma, is a potent inducer of AIRAP expression in human cells. Using endothelial cells as a model, we unraveled the molecular mechanism regulating AIRAP expression during proteasome inhibition. Bortezomib induces AIRAP expression at the transcriptional level early after treatment, concomitantly with polyubiquitinated protein accumulation and HSF activation. AIRAP protein is detected at high levels for at least 48 h after bortezomib exposure, together with the accumulation of HSF2, a factor implicated in differentiation and development regulation. Different from heat-mediated induction, in bortezomib-treated cells, HSF1 and HSF2 interact directly, forming HSF1-HSF2 heterotrimeric complexes recruited to a specific heat shock element in the AIRAP promoter. Interestingly, whereas HSF1 has been confirmed to be critical for AIRAP gene transcription, HSF2 was found to negatively regulate AIRAP expression after bortezomib treatment, further emphasizing an important modulatory role of this transcription factor under stress conditions. AIRAP function is still not defined. However, the fact that AIRAP is expressed abundantly in primary human cells at bortezomib concentrations comparable with plasma levels in treated patients suggests that AIRAP may participate in the regulatory network controlling proteotoxic stress during bortezomib treatment.

Thiazolides, a new class of antiviral agents effective against rotavirus infection, target viral morphogenesis, inhibiting viroplasm formation

Rotaviruses, nonenveloped viruses presenting a distinctive triple-layered particle architecture enclosing a segmented double-stranded RNA genome, exhibit a unique morphogenetic pathway requiring the formation of cytoplasmic inclusion bodies called viroplasms in a process involving the nonstructural viral proteins NSP5 and NSP2. In these structures the concerted packaging and replication of the 11 positive-polarity single-stranded RNAs take place to generate the viral double-stranded RNA (dsRNA) genomic segments. Rotavirus infection is a leading cause of gastroenteritis-associated severe morbidity and mortality in young children, but no effective antiviral therapy exists. Herein we investigate the antirotaviral activity of the thiazolide anti-infective nitazoxanide and reveal a novel mechanism by which thiazolides act against rotaviruses. Nitazoxanide and its active circulating metabolite, tizoxanide, inhibit simian A/SA11-G3P[2] and human Wa-G1P[8] rotavirus replication in different types of cells with 50% effective concentrations (EC50s) ranging from 0.3 to 2 μg/ml and 50% cytotoxic concentrations (CC50s) higher than 50 μg/ml. Thiazolides do not affect virus infectivity, binding, or entry into target cells and do not cause a general inhibition of viral protein expression, whereas they reduce the size and alter the architecture of viroplasms, decreasing rotavirus dsRNA formation. As revealed by protein/protein interaction analysis, confocal immunofluorescence microscopy, and viroplasm-like structure formation analysis, thiazolides act by hindering the interaction between the nonstructural proteins NSP5 and NSP2. Altogether the results indicate that thiazolides inhibit rotavirus replication by interfering with viral morphogenesis and may represent a novel class of antiviral drugs effective against rotavirus gastroenteritis.

Ferruccio Ritossa's scientific legacy 50 years after his discovery of the heat shock response: a new view of biology, a new society, and a new journal

The pioneering discovery of the heat shock response by the Italian scientist Ferruccio Ritossa reached maturity this year, 2012. It was 50 years ago that Professor Ritossa, through an extraordinary combination of serendipity, curiosity, knowledge and inspiration, published the first observation that cells could mount very strong transcriptional activity when exposed to elevated temperatures, which was coined the heat shock response. This discovery led to the identification of heat shock proteins, which impact many areas of current biology and medicine, and has created a new avenue for more exciting discoveries. In recognition of the discovery of the heat shock response, Cell Stress Society International (CSSI) awarded Professor Ritossa with the CSSI medallion in October 2010 in Dozza, Italy. This article is based on a session of the Fifth CSSI Congress held in Québec commemorating Professor Ritossa and his discovery.

Regulation of cyclooxygenase-2 expression by heat: a novel aspect of heat shock factor 1 function in human cells

The heat-shock response, a fundamental defense mechanism against proteotoxic stress, is regulated by a family of heat-shock transcription factors (HSF). In humans HSF1 is considered the central regulator of heat-induced transcriptional responses. The main targets for HSF1 are specific promoter elements (HSE) located upstream of heat-shock genes encoding cytoprotective heat-shock proteins (HSP) with chaperone function. In addition to its cytoprotective function, HSF1 was recently hypothesized to play a more complex role, regulating the expression of non-HSP genes; however, the non-canonical role of HSF1 is still poorly understood. Herein we report that heat-stress promotes the expression of cyclooxygenase-2 (COX-2), a key regulator of inflammation controlling prostanoid and thromboxane synthesis, resulting in the production of high levels of prostaglandin-E(2) in human cells. We show that heat-induced COX-2 expression is regulated at the transcriptional level via HSF1-mediated signaling and identify, by in-vitro reporter gene activity assay and deletion-mutant constructs analysis, the COX-2 heat-responsive promoter region and a new distal cis-acting HSE located at position -2495 from the transcription start site. As shown by ChIP analysis, HSF1 is recruited to the COX-2 promoter rapidly after heat treatment; by using shRNA-mediated HSF1 suppression and HSE-deletion from the COX-2 promoter, we demonstrate that HSF1 plays a central role in the transcriptional control of COX-2 by heat. Finally, COX-2 transcription is also induced at febrile temperatures in endothelial cells, suggesting that HSF1-dependent COX-2 expression could contribute to increasing blood prostaglandin levels during fever. The results identify COX-2 as a human non-classical heat-responsive gene, unveiling a new aspect of HSF1 function.

AIRAP, a new human heat shock gene regulated by heat shock factor 1

Heat shock factor-1 (HSF1) is the central regulator of heat-induced transcriptional responses leading to rapid expression of molecular chaperones that protect mammalian cells against proteotoxic stress. The main targets for HSF1 are specific promoter elements (HSE) located upstream of heat shock genes encoding a variety of heat shock proteins, including HSP70, HSP90, HSP27, and other proteins of the network. Herein we report that the zinc finger AN1-type domain-2a gene, also known as AIRAP, behaves as a canonical heat shock gene, whose expression is temperature-dependent and strictly controlled by HSF1. Transcription is triggered at temperatures above 40 degrees C in different types of human cancer and primary cells, including peripheral blood monocytes. As shown by ChIP analysis, HSF1 is recruited to the AIRAP promoter rapidly after heat treatment, with a kinetics that parallels HSP70 promoter HSF1-recruitment. In transfection experiments HSF1-silencing abolished heat-induced AIRAP promoter-driven transcription, which could be rescued by exogenous Flag-HSF1 expression. The HSF1 binding HSE sequence in the AIRAP promoter critical for heat-induced transcription was identified. Because its expression is induced at febrile temperatures in human cells, AIRAP may represent a new potential component of the protective response during fever in humans.

Role of Heat Shock Proteins in Viral Infection

One of the most intriguing and less known aspects of the interaction between viruses and their host is the impact of the viral infection on the heat shock response (HSR). While both a positive and a negative role of different heat shock proteins (HSP) in the control of virus replication has been hypothesized, HSP function during the virus replication cycle is still not well understood. This chapter describes different aspects of the interactions between viruses and heat shock proteins during infection of mammalian cells: the first part focuses on the modulation of the heat shock response by human viral pathogens; the second describes the interactions of HSP and other chaperones with viral components, and their function during different steps of the virus replication cycle; the last part summarizes our knowledge on the effect of hyperthermia and HSR modulators on virus replication.

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.

Human herpesvirus 8 acute infection of endothelial cells induces monocyte chemoattractant protein 1-dependent capillary-like structure formation: role of the IKK/NF-kappaB pathway

Human herpesvirus 8 (HHV-8) is considered the causative agent of Kaposi sarcoma, a highly vascularized neoplasm characterized by spindle-shaped cells of endothelial origin and inflammatory cell infiltration. The cell transforming ability of HHV-8 has been associated with the activation of NF-kappaB, a nuclear factor playing a pivotal role in promoting inflammation and cell proliferation; however, little is known about NF-kappaB activation during acute HHV-8 infection. In the present study, we used a recently established in vitro model of HHV-8 acute productive infection in endothelial cells to investigate the effect of HHV-8 on NF-kappaB activity and function. HHV-8 rapidly and potently induced NF-kappaB activity in endothelial cells via stimulation of the IkappaB kinase (IKK). Following IKK activation, HHV-8 selectively triggered the production of high levels of monocyte chemoattractant protein 1 (MCP-1), whereas it did not affect the expression of other NF-kappaB-dependent proinflammatory proteins, including TNF-alpha, IL-8, and RANTES. Deletion of NF-kappaB-binding sites in the MCP-1 enhancer resulted in significant inhibition of HHV-8-induced transcription. Furthermore, MCP-1 production was accompanied by virus-induced capillary-like structure formation at early stages of infection. The results suggest that HHV-8-induced MCP-1 may play an important role in promoting inflammation and pathogenic angiogenesis typical of HHV-8-associated lesions.

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.

Indomethacin Has a Potent Antiviral Activity against Sars Coronavirus

Severe acute respiratory syndrome (SARS) is a newly emerging, highly transmissible and fatal disease caused by a previously unknown coronavirus (SARS-CoV). Existing in non-identified animal reservoirs, SARS-CoV continues to represent a threat to humans because there is no effective specific antiviral therapy for coronavirus infections.

Objectives

Starting from the observation that cyclopentenone cyclooxygenase (COX) metabolites are active against several RNA viruses, we investigated the effect of the COX inhibitor indomethacin on coronavirus replication.

Methods

Work involving infectious SARS-CoV was performed in biosafety level 3 facilities. SARS-CoV was grown in monkey VERO cells and human lung epithelial A549 cells, while canine coronavirus (CCoV) was grown in A72 canine cells. Antiviral activity was analysed by determining infective virus titres by TCID50, viral RNA synthesis by Northern blot analysis and real-time RT-PCR, and viral protein synthesis by SDS-PAGE analysis after 35S-methio-nine-labelling. Antiviral efficacy in vivo was determined by evaluating virus titres in CCoV-infected dogs treated orally with 1 mg/kg body weight indomethacin (INDO).

Results

Unexpectedly, we found that INDO has a potent direct antiviral activity against the coronaviruses SARS-CoV and CCoV. INDO does not affect coronavirus binding or entry into host cells, but acts by blocking viral RNA synthesis at cytoprotective doses. This effect is independent of cyclooxygenase inhibition. INDO's potent antiviral activity (>1,000-fold reduction in virus yield) was confirmed in vivo in CCoV-infected dogs.

Conclusions

The results identify INDO as a potent inhibitor of coronavirus replication and suggest that, having both anti-inflammatory and antiviral activity, INDO could be beneficial in SARS therapy.

Targeting the heat shock factor 1 by RNA interference: a potent tool to enhance hyperthermochemotherapy efficacy in cervical cancer

Carcinoma of the uterine cervix is one of the highest causes of mortality in female cancer patients worldwide, and improved treatment options for this type of malignancy are highly needed. Local hyperthermia has been successfully used in combination with systemic administration of cisplatin-based chemotherapy in phase I/II clinical studies. Heat-induced expression of cytoprotective and antiapoptotic heat shock proteins (HSP) is a known complication of hyperthermia, resulting in thermotolerance and chemoresistance and hindering the efficacy of the combination therapy. Heat shock transcription factor 1 (HSF1) is the master regulator of heat-induced HSP expression. In the present report, we used small interfering RNA (siRNA) to silence HSF1 and to examine the effect of HSF1 loss of function on the response to hyperthermia and cisplatin-based chemotherapy in HeLa cervical carcinoma. We have identified the 322-nucleotide to 340-nucleotide HSF1 sequence as an ideal target for siRNA-mediated HSF1 silencing, have created a pSUPER-HSF1 vector able to potently suppress the HSF1 gene, and have generated for the first time human cancer cell lines with stable loss of HSF1 function. We report that, although it surprisingly does not affect cancer cell sensitivity to cisplatin or elevated temperatures up to 43 degrees C when administered separately, loss of HSF1 function causes a dramatic increase in sensitivity to hyperthermochemotherapy, leading to massive (>95%) apoptosis of cancer cells. These findings indicate that disruption of HSF1-induced cytoprotection during hyperthermochemotherapy may represent a powerful strategy to selectively amplify the damage in cancer cells and identify HSF1 as a promising therapeutic target in cervical carcinoma.

Induction of apoptosis in estrogen receptor-negative breast cancer cells by natural and synthetic cyclopentenones: role of the IkappaB kinase/nuclear factor-kappaB pathway

Nuclear factor-kappaB (NF-kappaB), a transcription factor with a critical role in promoting inflammation and cell survival, is constitutively activated in estrogen-receptor (ER)-negative breast cancer and is considered a potential therapeutic target for this type of neoplasia. We have previously demonstrated that cyclopentenone prostaglandins are potent inhibitors of NF-kappaB activation by inflammatory cytokines, mitogens, and viral infection, via direct binding and modification of the beta subunit of the IkappaB kinase complex (IKK). Herein, we describe the NF-kappaB-dependent anticancer activity of natural and synthetic cyclopentenone IKK inhibitors. We demonstrate that the natural cyclopentenone 15-deoxy-Delta(12,14)prostaglandin J(2) (15d-PGJ(2)) is a potent inhibitor of constitutive IkappaB-kinase and NF-kappaB activities in chemotherapy-resistant ER-negative breast cancer cells. 15d-PGJ(2)-induced inhibition of NF-kappaB function is rapidly followed by down-regulation of NF-kappaB-dependent antiapoptotic proteins cIAPs 1/2, Bcl-X(L), and cellular FLICE-inhibitory protein, leading to caspase activation and induction of apoptosis in breast cancer cells resistant to treatment with paclitaxel and doxorubicin. We then demonstrate that the cyclopentenone ring structure is responsible for these activities, and we identify a new synthetic cyclopentenone derivative, 3-tert-butyldimethylsilyloxy-5-(E)-iso-propylmethylenecyclopent-2-enone (CTC-35), as a potent NF-kappaB inhibitor with proapoptotic activity in ER-negative breast cancer cells. The results open new perspectives in the search for novel proapoptotic molecules effective in the treatment of cancers presenting aberrant NF-kappaB regulation.

Effect of nitazoxanide for treatment of severe rotavirus diarrhoea: randomised double-blind placebo-controlled trial

BACKGROUND

Rotavirus is a leading cause of morbidity and mortality in children younger than 5 years, but there is no effective treatment. We assessed the activity of nitazoxanide, a broad-spectrum anti-infective drug, against rotavirus in cell culture and in a clinical trial in paediatric patients hospitalised with severe rotavirus diarrhoea.

METHODS

We did a randomised double-blind placebo-controlled trial in 50 children admitted to the Cairo University Children's Hospital between June 15 and Aug 23, 2005, with severe rotavirus diarrhoea. 38 children aged 5 months to 7 years (median age 11 months) with rotavirus as the sole identified cause of gastroenteritis were enrolled in the clinical study. Patients were randomly assigned either 7.5 mg/kg nitazoxanide as an oral suspension or placebo twice a day for 3 days, and all remained in hospital for 7 days after start of treatment. The primary endpoint was time from first dose to resolution of illness, and analysis was by modified intention-to-treat. This study is registered with ClinicalTrials.gov, number NCT00302640.

FINDINGS

Survival analysis showed that the median time to resolution of illness was 31 h (IQR 22-73) for the nitazoxanide-treated group compared with 75 h (51-124) for the placebo group (p=0.0137). No significant adverse events were reported.

INTERPRETATION

A 3-day course of nitazoxanide significantly reduced the duration of rotavirus disease in hospitalised paediatric patients. These results are encouraging, and might lead us to think about new approaches to managing rotavirus disease in children.

NF-kappaB: a stress-regulated switch for cell survival

Nuclear factor-kappaB (NF-kappaB), a stress-regulated transcription factor belonging to the Rel family, has a pivotal role in the control of the inflammatory and the innate immune responses. Its activation rapidly induces the transcription of a variety of genes encoding cell adhesion molecules, inflammatory and chemotactic cytokines, cytokine receptors, and enzymes that produce inflammatory mediators. More recently, NF-kappaB activation has been connected with multiple aspects of oncogenesis, including the control of cell proliferation, migration, cell cycle progression, and apoptosis. Interestingly, NF-kappaB is constitutively activated in several types of cancer cells, including hematological and epithelial malignancies. In addition, activation of NF-kappaB in cancer cells by chemotherapy or radiation therapy has been associated with the acquisition of resistance to apoptosis, which has emerged as a significant impediment to effective cancer treatment. Selective cyclopentenone inhibitors of the IkappaB kinase, the key enzyme controlling NF-kappaB activation, were recently shown to be potent inducers of apoptosis in chemoresistant lymphoid malignancies. Increasing evidence, summarized in this review, indicates that the development of selective NF-kappaB inhibitors may represent a promising therapeutic tool to sensitize tumor cells to apoptosis and increase the efficacy of conventional anticancer drugs in a wide spectrum of malignancies.

Herpes simplex virus disrupts NF-kappaB regulation by blocking its recruitment on the IkappaBalpha promoter and directing the factor on viral genes

Herpes simplex viruses (HSVs) are able to hijack the host-cell IkappaB kinase (IKK)/NF-kappaB pathway, which regulates critical cell functions from apoptosis to inflammatory responses; however, the molecular mechanisms involved and the outcome of the signaling dysregulation on the host-virus interaction are mostly unknown. Here we show that in human keratinocytes HSV-1 attains a sophisticated control of the IKK/NF-kappaB pathway, inducing two distinct temporally controlled waves of IKK activity and disrupting the NF-kappaB autoregulatory mechanism. Using chromatin immunoprecipitation we demonstrate that dysregulation of the NF-kappaB-response is mediated by a virus-induced block of NF-kappaB recruitment to the promoter of the IkappaBalpha gene, encoding the main NF-kappaB-inhibitor. We also show that HSV-1 redirects NF-kappaB recruitment to the promoter of ICP0, an immediate-early viral gene with a key role in promoting virus replication. The results reveal a new level of control of cellular functions by invading viruses and suggest that persistent NF-kappaB activation in HSV-1-infected cells, rather than being a host response to the virus, may play a positive role in promoting efficient viral replication.

Indomethacin has a potent antiviral activity against SARS coronavirus

Severe acute respiratory syndrome (SARS) is a newly emerging, highly transmissible and fatal disease caused by a previously unknown coronavirus (SARS-CoV). Existing in non-identified animal reservoirs, SARS-CoV continues to represent a threat to humans because there is no effective specific antiviral therapy for coronavirus infections.

OBJECTIVES

Starting from the observation that cyclopentenone cyclooxygenase (COX) metabolites are active against several RNA viruses, we investigated the effect of the COX inhibitor indomethacin on coronavirus replication.

METHODS

Work involving infectious SARS-CoV was performed in biosafety level 3 facilities. SARS-CoV was grown in monkey VERO cells and human lung epithelial A549 cells, while canine coronavirus (CCoV) was grown in A72 canine cells. Antiviral activity was analysed by determining infective virus titres by TCID50, viral RNA synthesis by Northern blot analysis and real-time RT-PCR, and viral protein synthesis by SDS-PAGE analysis after 35S-methionine-labelling. Antiviral efficacy in vivo was determined by evaluating virus titres in CCoV-infected dogs treated orally with 1 mg/kg body weight indomethacin (INDO).

RESULTS

Unexpectedly, we found that INDO has a potent direct antiviral activity against the coronaviruses SARS-CoV and CCoV. INDO does not affect coronavirus binding or entry into host cells, but acts by blocking viral RNA synthesis at cytoprotective doses. This effect is independent of cyclooxygenase inhibition. INDO's potent antiviral activity (>1,000-fold reduction in virus yield) was confirmed in vivo in CCoV-infected dogs.

CONCLUSIONS

The results identify INDO as a potent inhibitor of coronavirus replication and suggest that, having both anti-inflammatory and antiviral activity, INDO could be beneficial in SARS therapy.

Antiviral activity of proteasome inhibitors in herpes simplex virus-1 infection: role of nuclear factor-kappaB

BACKGROUND

Herpes simplex virus type 1 (HSV-1) is a potent inducer of nuclear factor-KB (NF-kappaB), 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-kappaB is actively recruited to KB-binding sites in the HSV-1 infected-cell protein 0 (ICPO) promoter enhancing viral transcription and replication, we investigated the effect of proteasome inhibitors MG132, MG115 and epoxomicin, which block NF-kappaB function by preventing the degradation of the inhibitory proteins IkappaBalpha, on HSV-1-induced NF-kappaB 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. ICPO transcription was studied in transient transfection experiments using the ICPO promoter-luciferase IE1-Luc construct. IkappaBalpha degradation and NF-kappaB activity were determined by immunoblot analysis and EMSA, respectively.

RESULTS

Proteasome inhibitors were found to prevent HSV-1-induced NF-kappaB activation in the early phase of infection. Block of virus-induced NF-kappaB activation resulted in inhibiting HSV-1 ICPO 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-kappaB activation, and appeared to be independent of the HSV-1-induced activation of the JNK pathway.

CONCLUSIONS

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

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.

15-Deoxy-Δ12,14-prostaglandin J2 induces apoptosis in human malignant B cells: an effect associated with inhibition of NF-κB activity and down-regulation of antiapoptotic proteins

Cyclopentenone prostaglandins are potent inhibitors of nuclear factor-κB (NF-κB), a transcription factor with a critical role in promoting inflammation and connected with multiple aspects of oncogenesis and cancer cell survival. In the present report, we investigated the role of NF-κB in the antineoplastic activity of the cyclopentenone prostaglandin 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2) in multiple myeloma (MM) and Burkitt lymphoma (BL) cells expressing constitutively active NF-κB. 15d-PGJ2 was found to suppress constitutive NF-κB activity and potently induce apoptosis in both types of B-cell malignancies. 15d-PGJ2-induced apoptosis occurs through multiple caspase activation pathways involving caspase-8 and caspase-9, and is prevented by pretreatment with the pan-caspase inhibitor ZVAD (z-Val-Ala-Asp). NF-κB inhibition is accompanied by rapid down-regulation of NF-κB-dependent antiapoptotic gene products, including cellular inhibitor-of-apoptosis protein 1 (cIAP-1), cIAP-2, X-chromosome-linked inhibitor-of-apoptosis protein (XIAP), and FLICE-inhibitory protein (cFLIP). These effects were mimicked by the proteasome inhibitor MG-132, but not by the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist troglitazone, suggesting that 15d-PGJ2-induced apoptosis is independent of PPAR-γ. Knockdown of the NF-κB p65-subunit by lentiviral-mediated shRNA interference also resulted in apoptosis induction in malignant B cells with constitutively active NF-κB. The results indicate that inhibition of NF-κB plays a major role in the proapoptotic activity of 15d-PGJ2 in aggressive B-cell malignancies characterized by aberrant regulation of NF-κB. (Blood. 2005;105:1750-1758)

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.

Reactions of some cyclopentenones with selected cysteine derivatives and biological activities of the product thioethers

The conjugate addition reaction between glutathione, N-Boc-cysteine methyl ester, N-acetyl cysteine methyl ester and N-acetyl cysteine and several substituted cyclopentenones is described. The reversibility of this process was demonstrated by thio-adduct metathesis on treatment of the adduct with a different cysteinyl derivative. The levels at which these compounds inhibit the function of nuclear factor kappa B (NF-kappaB) and potentiate heat shock factor (HSF) are reported and the possible relevance of these studies concerning the antiviral and anti-inflammatory activities of the cyclopentenone prostanoids is discussed.

Anti-inflammatory activity of 15-deoxy-delta12,14-PGJ2 and 2-cyclopenten-1-one: role of the heat shock response

The transcription factor heat shock factor 1 (HSF1) plays a key role in the expression of several genes, such as heat shock protein (hsp) genes, which are cytoprotective against several pathological conditions, including inflammation. Cyclopentenone prostaglandins (cyPG) are able to activate HSF1 and induce the synthesis of the 70-kDa hsp (hsp70) in mammalian cells. These molecules are characterized by the presence of a reactive alpha,beta-unsatured carbonyl group in the cyclopentane ring (cyclopentenone) which is the key structure for triggering HSF1 activation. In the present study, we investigated, in carrageenin hind-paw edema, an acute model of inflammation, the effect of double-stranded oligodeoxynucleotides with consensus HSF1 sequence as transcription factor decoys to inhibit HSF1 binding to native DNA sites. We show that HSF1 activation and hsp72 expression occurs in inflamed tissue and that this effect is associated with the remission of the inflammatory reaction. Moreover, we studied the effect of prostaglandin 15-deoxy-delta12,14-prostaglandin (PG) J2, of its precursor, PGD2 and, for the first time in vivo, the effect of the cyclopentenone ring structure itself, 2-cyclopenten-1-one. Our results demonstrated that all agents used had anti-inflammatory properties and that this effect was associated with HSF1-induced hsp72 expression in vivo, suggesting that the use of cyclopentenone derivatives may represent a novel therapeutic approach to the treatment of inflammatory diseases.

NF-kappaB and virus infection: who controls whom

Among the different definitions of viruses, 'pirates of the cell' is one of the most picturesque, but also one of the most appropriate. Viruses have been known for a long time to utilize a variety of strategies to penetrate cells and, once inside, to take over the host nucleic acid and protein synthesis machinery to build up their own components and produce large amounts of viral progeny. As their genomes carry a minimal amount of information, encoding only a few structural and regulatory proteins, viruses are largely dependent on their hosts for survival; however, despite their apparent simplicity, viruses have evolved different replicative strategies that are regulated in a sophisticated manner. During the last years, the study of the elaborate relationship between viruses and their hosts has led to the understanding of how viral pathogens not only are able to alter the host metabolism via their signaling proteins, but are also able to hijack cellular signaling pathways and transcription factors, and control them to their own advantage. In particular, the nuclear factor-kappaB (NF-kappaB) pathway appears to be an attractive target for common human viral pathogens. This review summarizes what is known about the control of NF-kappaB by viruses, and discusses the possible outcome of NF-kappaB activation during viral infection, which may benefit either the host or the pathogen.

Activation of I kappa b kinase by herpes simplex virus type 1. A novel target for anti-herpetic therapy

Herpes simplex viruses (HSV) are ubiquitous pathogens causing a variety of diseases ranging from mild illness to severe life-threatening infections. HSV utilize cellular signaling pathways and transcription factors to promote their replication. Here we report that HSV type 1 (HSV-1) induces persistent activation of transcription factor NF-kappa B, a critical regulator of genes involved in inflammation, by activating the I kappa B kinase (IKK) in the early phase of infection. Activated NF-kappa B enhances HSV-1 gene expression. HSV-1-induced NF-kappa B activation is dependent on viral early protein synthesis and is not blocked by the anti-herpetic drug acyclovir. IKK inhibition by the anti-inflammatory cyclopentenone prostaglandin A(1) blocks HSV-1 gene expression and reduces virus yield by more than 3000-fold. The results identify IKK as a potential target for anti-herpetic drugs and suggest that cyclopentenone prostaglandins or their derivatives could be used in the treatment of HSV infection.

Anti-inflammatory cyclopentenone prostaglandins are direct inhibitors of IkappaB kinase

NF-kappaB is a critical activator of genes involved in inflammation and immunity. Pro-inflammatory cytokines activate the IkappaB kinase (IKK) complex that phosphorylates the NF-kappaB inhibitors, triggering their conjugation with ubiquitin and subsequent degradation. Freed NF-kappaB dimers translocate to the nucleus and induce target genes, including the one for cyclo-oxygenase 2 (COX2), which catalyses the synthesis of pro-inflammatory prostaglandins, in particular PGE. At late stages of inflammatory episodes, however, COX2 directs the synthesis of anti-inflammatory cyclopentenone prostaglandins, suggesting a role for these molecules in the resolution of inflammation. Cyclopentenone prostaglandins have been suggested to exert anti-inflammatory activity through the activation of peroxisome proliferator-activated receptor-gamma. Here we demonstrate a novel mechanism of antiinflammatory activity which is based on the direct inhibition and modification of the IKKbeta subunit of IKK. As IKKbeta is responsible for the activation of NF-kappaB by pro-inflammatory stimuli, our findings explain how cyclopentenone prostaglandins function and can be used to improve the utility of COX2 inhibitors.

Heat shock factors and the control of the stress response

Living cells are continually challenged by conditions which cause acute and chronic stress. To adapt to environmental changes and survive different types of injuries, eukaryotic cells have evolved networks of different responses which detect and control diverse forms of stress. One of these responses, known as the heat shock response, has attracted a great deal of attention as a universal fundamental mechanism necessary for cell survival under a variety of unfavorable conditions. In mammalian cells, the induction of the heat shock response requires the activation and translocation to the nucleus of one or more heat shock transcription factors which control the expression of a specific set of genes encoding cytoprotective heat shock proteins. The discovery that the heat shock response is turned on under several pathological conditions and contributes to establish a cytoprotective state in a variety of human diseases, including ischemia, inflammation, and infection, has opened new perspectives in medicine and pharmacology, as molecules activating this defense mechanism appear as possible candidates for novel cytoprotective drugs. This article focuses on the regulation and function of the heat shock response in mammalian cells and discusses the molecular mechanisms involved in its activation by stress and bioactive cyclopentenone prostanoids, as well as its interaction with nuclear factor kappaB, a stress-regulated transcription factor with a pivotal role in inflammation and immunity.

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

9-Deoxy-Delta(9),Delta(12)-13,14-dihydro-prostaglandin D(2) (Delta(12)-PGJ(2)), a natural cyclopentenone metabolite of prostaglandin D(2), is shown to possess therapeutic efficacy against influenza A virus A/PR8/34 (H1N1) infection in vitro and in vivo. The results indicate that the antiviral activity is associated with induction of cytoprotective heat shock proteins and suggest novel strategies for treatment of influenza virus infection.

Induction of ferritin and heat shock proteins by prostaglandin A1 in human monocytes. Evidence for transcriptional and post-transcriptional regulation

Prostaglandins of the A type (PGA) exert a cytoprotective activity during hyperthermia and virus infection. This effect is associated with induction of heat shock proteins (HSP) in mammalian cells. We now report that, in human monocytes, PGA1 is able to induce the synthesis of the iron-binding, redox-regulated protein ferritin. L-chain ferritin induction is consequent to a substantial increase in the accumulation of L-chain ferritin transcripts in PGA1-treated cells, whereas H-chain ferritin is regulated post-transcriptionally, consequently to reduction of iron-regulatory protein binding to iron-responsive elements in ferritin mRNA. Ferritin induction is specific for cyclopentenone prostaglandins (PGA1, PGA2, PGJ2, Delta12-PGJ2), whereas other arachidonic acid (AA) metabolites have no effect. In human monocytes, PGA1 also induces heat shock gene transcription via heat shock factor activation, as well as the synthesis of the oxidative-stress protein heme oxygenase (HOS). Differently from HSP, the induction of ferritin by PGA1 is specific for monocytes. Monocytes/macrophages play a pivotal role in inflammation, controlling iron metabolism and releasing a variety of mediators, including proinflammatory reactive oxygen species (ROS), cytokines and AA metabolites. As ferritin, together with hsp70 and HO, plays a key role in protection from oxidant damage, these results suggest that PGA1 may have cytoprotective activity also during oxidative injury.

Antiviral effect of hyperthermic treatment in rhinovirus infection

Human rhinoviruses (HRV) are recognized as the major etiologic agents for the common cold. Starting from the observation that local hyperthermic treatment is beneficial in patients with natural and experimental common colds, we have studied the effect of brief hyperthermic treatment (HT) on HRV replication in HeLa cells. We report that a 20-min HT at 45 degrees C is effective in suppressing HRV multiplication by more than 90% when applied at specific stages of the virus replication cycle. Synthesis of virus proteins is not affected by HT, indicating that the target for treatment is a posttranslational event. The antiviral effect is a transient cell-mediated event and is associated with the synthesis of the 70-kDa heat shock protein hsp70. Unlike poliovirus, rhinovirus infection does not inhibit the expression of hsp70 induced by heat. The possibility that hsp70 could play a role in the control of rhinovirus replication is suggested by the fact that a different class of HSP inducers, the cyclopentenone prostaglandins PGA1 and delta 12-PGJ2, were also effective in inhibiting HRV replication in HeLa cells. Inhibition of hsp70 expression by actinomycin D prevented the antiviral activity of prostaglandins in HRV-infected cells. These results indicate that the beneficial effect of respiratory hyperthermia may be mediated by the induction of a cytoprotective heat shock response in rhinovirus-infected cells.

Induction of the heat-shock response by antiviral prostaglandins in human cells infected with human immunodeficiency virus type 1

Cyclopentenone prostaglandins inhibit the replication of several DNA and RNA viruses, including retroviruses. The antiviral activity has been associated with the induction of a 70-kDa heat-shock protein (HSP70), via activation of the heat-shock transcription factor (HSF) in infected cells. In the present study we investigated the effect of prostaglandin A1 (PGA1) on the regulation of HSP70 gene expression as well as on viral RNA and protein synthesis in CEM-SS cells during acute infection with human immunodeficiency virus type 1 (HIV-1). We report that HIV-1 infection does not alter HSF activation by PGA1, whereas it causes an increase in intracellular HSP70 mRNA levels, as a result of enhanced HSP70 mRNA stability. We also show that, as reported in studies of different virus/host cell models, PGA1 inhibits HIV-1 replication by acting at multiple levels during HIV-1 infection. In addition to the previously reported block of HIV-1 mRNA transcription, PGA1 was also found to inhibit viral protein synthesis. These results, together with the fact that prostaglandins are used clinically in the treatment of several diseases, open new perspectives in the search for novel antiretroviral drugs.

Stress-inducible responses and heat shock proteins: new pharmacologic targets for cytoprotection

Molecular chaperones protect proteins against environmental and physiologic stress and from the deleterious consequences of an imbalance in protein homeostasis. Many of these stresses, if prolonged, result in defective development and pathologies associated with a diverse array of diseases due to tissue injury and repair including stroke, myocardial reperfusion damage, ischemia, cancer, amyloidosis, and other neurodegenerative diseases. We discuss the molecular nature of the stress signals, the mechanisms that underlie activation of the heat shock response, the role of heat shock proteins as cytoprotective molecules, and strategies for pharmacologically active molecules as regulators of the heat shock response.