Interleukin-8 gene regulation in intestinal epithelial cells infected with rotavirus: role of viral-induced IkappaB kinase activation

The Diagnostic and Prognostic Role of Interleukin 6 and Interleukin 8 in Childhood Acute Gastroenteritis-A Review of the Literature

Acute gastroenteritis in pediatric patients represents a major cause of morbidity and mortality in children. Interleukins 6 (IL-6) and 8 (IL-8) have been intensely studied in relation to various inflammatory conditions, including acute gastroenteritis, as they are activated in response to infection. This review aims to evaluate the ability of IL-6 and IL-8 to distinguish between bacterial and viral etiologies of acute gastroenteritis in children and to assess whether their levels correlate with the severity of this condition in light of currently available data. A scientific database search was performed to identify studies that investigated the role of IL-6 and IL-8 in acute gastroenteritis in the pediatric population. We identified nine studies that matched the review's objective. Both cytokines show increased values in acute gastroenteritis, but IL-6 levels are significantly higher in cases of bacterial infections. IL-8 levels do not present an increase to the same extent in cases of bacterial diarrhea in children but seem to be associated with the severity of the disease. The lack of sufficient research focusing on IL-6 and -8 as diagnostic, prognostic and severity biomarkers of acute gastroenteritis in children leaves room for further research on this topic, which must include larger cohort studies.

Synergistic Inhibitory Effect of Lactobacillus Cell Lysates and Butyrate on Poly I:C-Induced IL-8 Production in Human Intestinal Epithelial Cells

Postbiotics include cell lysates (CLs), enzymes, cell wall fragments, and heat-killed bacteria derived from probiotics. Although postbiotics are increasingly being considered for their potential health-promoting properties, the effects of postbiotics on virus-mediated inflammatory responses in the intestine have not been elucidated. Hence, the present study aimed to examine whether CLs of Lactipantibacillus plantarum (LP CL) and Lacticaseibacillus rhamnosus GG (LR CL) could inhibit virus-mediated inflammatory responses in the human intestinal epithelial cell line HT-29 in vitro. Pretreatment with LP CL and LR CL significantly inhibited interleukin (IL)-8 production, which was induced by poly I:C, a synthetic analog of double-stranded RNA (dsRNA) viruses, at the mRNA and protein levels in HT-29 cells. However, peptidoglycans and heat-killed L. plantarum and L. rhamnosus GG did not effectively inhibit IL-8 production. LP CL and LR CL attenuated the poly I:C-induced phosphorylation of ERK and JNK and the activation of NF-κB, suggesting that these CLs could inhibit poly I:C-induced IL-8 production by regulating intracellular signaling pathways in HT-29 cells. Furthermore, among the short-chain fatty acids, butyrate enhanced the inhibitory effect of CLs on poly I:C-induced IL-8 production at the mRNA and protein levels in HT-29 cells, while acetate and propionate did not. Taken together, these results suggest that both LP CL and LR CL could act as potent effector molecules that can inhibit virus-mediated inflammatory responses and confer synergistic inhibitory effects with butyrate in human intestinal epithelial cells.

Re-Examining Rotavirus Innate Immune Evasion: Potential Applications of the Reverse Genetics System

Rotaviruses represent one of the most successful pathogens in the world, with high infectivity and efficient transmission between the young of many animal species, including humans. To overcome host defenses, rotaviruses have evolved a plethora of strategies to effectively evade the innate immune response, establish initial infection in the small intestine, produce progeny, and shed into the environment. Previously, studying the roles and relative contributions of specific rotaviral factors in innate immune evasion had been challenging without a plasmid-only reverse genetics system. Although still in its infancy, current reverse genetics technology will help address important research questions regarding rotavirus innate immune evasion, host range restriction, and viral pathogenesis. In this review, we summarize the current knowledge about the antiviral host innate immune defense mechanisms, countermeasures of rotavirus-encoded factors, and strategies to better understand these interactions using the rotavirus reverse genetics system.

Baicalin Is Curative Against Rotavirus Damp Heat Diarrhea by Tuning Colonic Mucosal Barrier and Lung Immune Function

BACKGROUND

Previous studies have indicated that rotavirus (RV) is a causative factor for diarrhea and gastroenteritis in pediatric and neonatal settings. Baicalin has many functions, including antibacterial, antiinflammatory, and antihypertensive activities. However, the immunological mechanism of RV-induced diarrhea with heat-dampness syndrome (RV-DH) remains unclear.

AIMS

The aim of this study is to explore the role of baicalin in RV-DH diarrhea and its underlying mechanism.

METHODS

A mouse model of pediatric RV-DH diarrhea was established and treated with baicalin. The concentrations of cytokines were detected by enzyme-linked immunosorbent assay. Messenger RNA (mRNA) expression levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR), while protein expression levels were determined by Western blotting and immunohistochemistry. Flow cytometry was used to detect the frequency of lymphocytes.

RESULTS

The concentrations of interleukin-1β (IL-1β), IL-2, IL-6, IL-8, RVvb, and secretory immunoglobulin A (SIgA) in bronchoalveolar lavage fluid (BALF) and colonic mucosa were significantly increased in the RV-DH group. Decreased expression of occludin, claudin-1, and zonula occludens-1 (ZO-1) indicated loss of tight junction function and disturbances in intestinal mucosal permeability in the RV-DH group. Flow cytometry analysis showed a high rate of CD8⁺ lymphocytes and low amount of CD4⁺ lymphocytes in the RV-DH group. Treatment of RV-DH mice with baicalin significantly reduced the duration of diarrhea and ameliorated the symptoms and pathological and immunological changes. Furthermore, baicalin inhibited STAT1 and activated STAT3 signaling pathways.

CONCLUSIONS

These findings indicate the curative and immunoregulatory properties of baicalin and have direct practical and clinical relevance for the treatment of RV-DH enteritis in humans.

DACH1 antagonizes CXCL8 to repress tumorigenesis of lung adenocarcinoma and improve prognosis

BACKGROUND

C-X-C motif ligand 8 (CXCL8), known as a proinflammatory chemokine, exerts multiple effects on the proliferation, invasion, and migration of tumor cells via the autocrine or paracrine manner. Conversely, the human Dachshund homologue 1 (DACH1) is recognized as a tumor suppressor which retards the progression of various cancers. In prostate cancer, it has been demonstrated that DACH1 was negatively correlated with the expression of CXCL8 and able to antagonize the effects of CXCL8 on cellular migration. Herein, we explored the mechanisms by which DACH1 regulated the CXCL8 in non-small cell lung cancer (NSCLC).

METHODS

Public microarray and Kaplan-Meier plotter datasets were analyzed. Blood serum samples from lung adenocarcinoma (ADC) patients were collected for enzyme-linked immunosorbent assay (ELISA) analysis. Immunohistochemical staining was conducted on tissue microarray. Cell lines with stable expression of DACH1 were established, and relative gene expression was measured by Western blot, ELISA, real-time PCR, and human cytokine array. Correspondingly, cell lines transfected with shDACH1 were established, and relative gene expression was measured by real-time PCR and immunofluorescence array. Functional studies were performed by transwell and xenograft mice models. Luciferase reporter gene assay was applied to measure the regulation of DACH1 on CXCL8.

RESULTS

Our study indicated that CXCL8 both at the mRNA and protein level was associated with the high tumor burden of ADC. Correlational analyses in ADC cell lines and ADC tissues showed that DACH1 was inversely correlated with CXCL8. Meanwhile, patients with high DACH1 expression and low CXCL8 expression had prolonged time to death and recurrence. Moreover, we verified the inhibitory effects of DACH1 on CXCL8 both in vitro and in vivo. Mechanism studies proved that DACH1 transcriptionally repressed CXCL8 promoter activity through activator protein-1 (AP-1) and nuclear transcription factor-kappa B (NF-κB) sites.

CONCLUSIONS

Our study proved that CXCL8 acted as an unfavorable factor promoting to tumor progression and poor prognosis of ADC, while DACH1 antagonized CXCL8 to provide a favorable survival of ADC patients. Double detection of DACH1 and CXCL8 may provide a precise information for further evaluating the prognosis of ADC patients.

Immunobiotic Bifidobacteria Strains Modulate Rotavirus Immune Response in Porcine Intestinal Epitheliocytes via Pattern Recognition Receptor Signaling

In this work, we aimed to characterize the antiviral response of an originally established porcine intestinal epithelial cell line (PIE cells) by evaluating the molecular innate immune response to rotavirus (RVs). In addition, we aimed to select immunomodulatory bacteria with antiviral capabilities. PIE cells were inoculated with RVs isolated from different host species and the infective titers and the molecular innate immune response were evaluated. In addition, the protection against RVs infection and the modulation of immune response by different lactic acid bacteria (LAB) strains was studied. The RVs strains OSU (porcine) and UK (bovine) effectively infected PIE cells. Our results also showed that RVs infection in PIE cells triggered TLR3-, RIG-I- and MDA-5-mediated immune responses with activation of IRF3 and NF-κB, induction of IFN-β and up-regulation of the interferon stimulated genes MxA and RNase L. Among the LAB strains tested, Bifidobacterium infantis MCC12 and B. breve MCC1274 significantly reduced RVs titers in infected PIE cells. The beneficial effects of both bifidobacteria were associated with reduction of A20 expression, and improvements of IRF-3 activation, IFN-β production, and MxA and RNase L expressions. These results indicate the value of PIE cells for studying RVs molecular innate immune response in pigs and for the selection of beneficial bacteria with antiviral capabilities.

Antiviral effects of cyclosporine A in neonatal mice with rotavirus-induced diarrhea

OBJECTIVES

Because rotavirus gastroenteritis is associated with high morbidity and mortality especially in developing countries, it is necessary to develop antirotavirus drugs for the treatment of rotavirus infection. Previous studies have demonstrated that cyclosporin A (CsA) has antiviral properties against rotavirus. Its effect has not yet been evaluated against rotavirus diarrheal disease. The aim of this study was to assess the anti-rotavirus efficacy of CsA in neonatal mice after induction of rotavirus diarrhea.

METHODS

Suckling mice were inoculated with murine rotavirus. On the onset of diarrhea, mice were given different concentrations of CsA. To evaluate the effects of CsA on reduction of rotavirus diarrhea, diarrhea score, fecal virus shedding, and pathological lesion change in the small intestine, messenger RNA (mRNA) expression levels in the small intestine and spleen of mice were measured for type I interferon (IFN-α and IFN-β), inflammation-related cytokines (interleukin [IL]-8, IL-10, IFN-γ, and tumor necrosis factor-α), and inflammatory signaling pathways (p38, c-Jun N-terminal kinase, activator protein-1, and nuclear factor-kappa B).

RESULTS

Among virus-inoculated and CsA-treated groups, a dose of 5 mg · kg⁻¹ · day⁻¹ of CsA inhibited diarrhea and improved fecal virus shedding and intestinal lesion changes. IFN-β mRNA expression was significantly increased in rotavirus-induced diarrhea mice treated with 5 mg · kg⁻¹ · day⁻¹ of CsA, whereas the mRNA expression levels of inflammation-related cytokines (IL-8, IL-10, IFN-γ, and tumor necrosis factor-α) and inflammatory signaling pathways (p38, c-Jun N-terminal kinase, activator protein-1, and nuclear factor-kappa B) were markedly decreased. Antiviral effects of CsA were dose dependent.

CONCLUSIONS

CsA can inhibit rotavirus infection in neonatal mice through its antiviral properties. The mechanism for this may be through CsA suppression of inflammation by viral inhibition in animal models.

Inhibition of rotavirus ECwt infection in ICR suckling mice by N-acetylcysteine, peroxisome proliferator-activated receptor gamma agonists and cyclooxygenase-2 inhibitors

Live attenuated vaccines have recently been introduced for preventing rotavirus disease in children. However, alternative strategies for prevention and treatment of rotavirus infection are needed mainly in developing countries where low vaccine coverage occurs. In the present work, N-acetylcysteine (NAC), ascorbic acid (AA), some nonsteroidal anti-inflammatory drugs (NSAIDs) and peroxisome proliferator-activated receptor gamma (PPARγ) agonists were tested for their ability to interfere with rotavirus ECwt infectivity as detected by the percentage of viral antigen-positive cells of small intestinal villi isolated from ECwt-infected ICR mice. Administration of 6 mg NAC/kg every 8 h for three days following the first diarrhoeal episode reduced viral infectivity by about 90%. Administration of AA, ibuprofen, diclofenac, pioglitazone or rosiglitazone decreased viral infectivity by about 55%, 90%, 35%, 32% and 25%, respectively. ECwt infection of mice increased expression of cyclooxygenase-2, ERp57, Hsc70, NF-κB, Hsp70, protein disulphide isomerase (PDI) and PPARγ in intestinal villus cells. NAC treatment of ECwt-infected mice reduced Hsc70 and PDI expression to levels similar to those observed in villi from uninfected control mice. The present results suggest that the drugs tested in the present work could be assayed in preventing or treating rotaviral diarrhoea in children and young animals.

Benign convulsion with mild gastroenteritis

Benign convulsion with mild gastroenteritis (CwG) is a type of afebrile seizure that occurs in children. CwG is defined as a convulsion in a previously healthy child with no known central nervous system infection or encephalopathy, accompanying mild diarrhea without fever, electrolyte imbalance, or moderate to severe dehydration. Convulsions in CwG are characterized by multiple brief episodes of generalized or focal seizures. Although the etiology and pathophysiology have yet to be fully explained, many pathogenic mechanisms have been proposed including the possibility of direct invasion of the central nervous system by a gastrointestinal virus such as rotavirus or the possibility of indirect influence by the production and effects of certain mediators. The electroencephalogram findings are benign and long-term antiepileptic treatment is typically not required. Long-term prognosis has been favorable with normal psychomotor development. This review provides a general overview of CwG with the goal of allowing physicians practicing in the field of pediatrics to better recognize this unique entity and, ultimately, to minimize unnecessary evaluation and treatment.

Innate cellular responses to rotavirus infection

Rotavirus is a leading cause of severe dehydrating diarrhoea in infants and young children. Following rotavirus infection in the intestine an innate immune response is rapidly triggered. This response leads to the induction of type I and type III interferons (IFNs) and other cytokines, resulting in a reduction in viral replication. Here we review the current literature describing the detection of rotavirus infection by pattern recognition receptors within host cells, the subsequent molecular mechanisms leading to IFN and cytokine production, and the processes leading to reduced rotavirus replication and the development of protective immunity. Rotavirus countermeasures against innate responses, and their roles in modulating rotavirus replication in mice, also are discussed. By linking these different aspects of innate immunity, we provide a comprehensive overview of the host’s first line of defence against rotavirus infection. Understanding these processes is expected to be of benefit in improving strategies to combat rotavirus disease.

Anti-rotaviral effects of Glycyrrhiza uralensis extract in piglets with rotavirus diarrhea

Background

Since rotavirus is one of the leading pathogens that cause severe gastroenteritis and represents a serious threat to human and animal health, researchers have been searching for cheap, safe, and effective anti-rotaviral drugs. There is a widespread of interest in using natural products as antiviral agents, and among them, licorice derived from Glycyrrhiza spp. has exerted antiviral properties against several viruses. In this study, anti-rotaviral efficacy of Glycyrrhiza uralensis extract (GUE) as an effective and cheaper remedy without side-effects was evaluated in colostrums-deprived piglets after induction of rotavirus diarrhea.

Methods

Colostrums-deprived piglets were inoculated with porcine rotavirus K85 (G5P[7]) strain. On the onset of diarrhea, piglets were treated with different concentration of GUE. To evaluate the antiviral efficacy of GUE, fecal consistency score, fecal virus shedding and histological changes of the small intestine, mRNA expression levels of inflammation-related cytokines (IL8, IL10, IFN-β, IFN-γ and TNF-α), signaling molecules (p38 and JNK), and transcription factor (NFκB) in the small intestine and spleen were determined.

Results

Among the dosages (100-400 mg/ml) administrated to animals, 400 mg/ml of GUE cured diarrhea, and markedly improved small intestinal lesion score and fecal virus shedding. mRNA expression levels of inflammation-related cytokines (IL8, IL10, IFN-β, IFN-γ and TNF-α), signaling molecules (p38 and JNK), and transcription factor (NFκB) in the small intestine and spleen were markedly increased in animals with RVA-induced diarrhea, but dose- dependently decreased in GUE treated animals after RVA-induced diarrhea.

Conclusions

GUE cures rotaviral enteritis by coordinating antiviral and anti-inflammatory effects. Therapy of this herbal medicine can be a viable medication for curing rotaviral enteritis in animals and humans.

P2Y6 receptor contributes to neutrophil recruitment to inflamed intestinal mucosa by increasing CXC chemokine ligand 8 expression in an AP-1-dependent manner in epithelial cells

BACKGROUND

Inflammatory bowel diseases are characterized by the presence of CXCL8 at the site of lesions resulting in neutrophil recruitment and loss of tissue functions. We report that P2Y(6) receptor activation stimulates CXCL8 expression and release by intestinal epithelial cells (IECs). In this context, we investigated if uridine 5'-diphosphate (UDP) enemas stimulate neutrophil recruitment to the mucosa of mice suffering from colitis-like disease and we characterized the signaling events linking P2Y(6) to CXCL8 expression in IEC.

METHODS

Neutrophil recruitment was monitored by immunofluorescence and FACS analysis. Expression of Cxcl1, a mouse functional homolog of CXCL8, was determined by quantitative real-time polymerase chain reaction (qPCR). Pharmacological inhibitors and interfering RNAs were used to characterize the signaling pathway. The outcomes of these treatments on protein phosphorylation and on CXCL8 expression were characterized by western blots, qPCR, luciferase, and chromatin immunoprecipitation (ChIP) assays.

RESULTS

Mutation of the AP-1 site in the CXCL8 core promoter abolished the UDP-stimulating effect. The c-fos/c-jun dimer was identified as the AP-1 complex regulating CXCL8 in response to UDP stimulation. Regulation of CXCL8 expression by P2Y(6) required PKCδ activation upstream of the signaling pathway composed of MEK1/2-ERK1/2 and c-fos. UDP administration to mice suffering from colitis-like disease increased the number of neutrophil infiltrating the mucosa, correlating with Cxcl1 increased expression in IEC and the severity of inflammation.

CONCLUSIONS

This study not only describes the P2Y(6) signaling mechanism regulating CXCL8 expression in IEC, but it also illustrates the potential of targeting P2Y(6) to reduce intestinal inflammation.

Inhibition of rotavirus infection in cultured cells by N-acetyl-cysteine, PPARγ agonists and NSAIDs

Although the current rotavirus vaccines have shown good tolerance and significant efficacy, it would be useful to develop alternative or complementary strategies aimed at preventing or treating acute diarrhoeal disease caused by this viral agent. A variety of antiviral strategies other than vaccines have been assayed for rotavirus infection management. The recently demonstrated sensitivity of rotavirus infectivity to thiol/disulfide reagents prompted assays for screening drugs that potentially affect cellular redox reactions. MA104 or Caco-2 cells were inoculated with the rotavirus strains RRV, Wa, Wi or M69 and then incubated with different concentrations of drugs belonging to a selected group of 60 drugs that are currently used in humans for purposes other than rotavirus infection treatment. Eighteen of these drugs were able to inhibit rotavirus infectivity to different extents. A more systematic evaluation was performed with drugs that could be used in children such as N-acetylcysteine and ascorbic acid, in addition to ibuprofen, pioglitazone and rosiglitazone, all of which affecting cellular pathways potentially needed by the rotavirus infection process. Evidence is provided here that rotavirus infectivity is significantly inhibited by NAC in different cell-culture systems. These findings suggest that NAC has the potential to be used as a therapeutic tool for treatment and prevention of rotavirus disease in children.

Antigenemia and cytokine expression in rotavirus gastroenteritis in children

BACKGROUND

Antigenemia is commonly found in children with rotavirus infection, although its clinical significance is undetermined. The aim of this study was to evaluate the association of antigenemia with clinical manifestations and cytokine profiles in children infected by rotavirus.

METHODS

In total, 68 children hospitalized with rotavirus gastroenteritis were enrolled. Serum samples were collected for detection of antigenemia and viremia. Clinical, laboratory and demographic data were analyzed. Proinflammatory, Th1 and Th2 cytokines were evaluated by bead-based flow cytometry.

RESULTS

Antigenemia and viremia were found in 45.6% (n = 31) and 5.9% (n = 4) of the 68 rotavirus-infected children, respectively. The mean age of the antigenemia group was significantly greater than that of the non-antigenemia group (43.5 vs. 27.3 months; p = 0.034). The antigenemia group had a significantly shorter length of hospitalization (4.8 vs. 5.8 days; p = 0.0354) in comparison with the non-antigenemia group, and antigenemia was inversely associated with the length of hospitalization (β = 0.31, p = 0.021). A significantly higher tumor necrosis factor (TNF)-β level was found in the patients with antigenemia than those without (236.7 vs. 29.2 pg/mL, p = 0.026). The severity of disease and the rate of extra-intestinal manifestations did not differ between the groups. Viremia was associated with a higher fever (p = 0.012).

CONCLUSIONS

Antigenemia was positively correlated with shorter hospital stay in children with rotavirus infection. Enhanced innate and T-cell-mediated immunity evidenced by up-regulation of TNF-β was found in patients with antigenemia.

Viral interference with innate immunity by preventing NF-κB activity

Viruses are the most abundant and diverse pathogens challenging the host immune system, and as such are a severe threat to human health. To this end, viruses have evolved multiple strategies to evade and subvert the host immune response. Host-pathogen interactions are usually initiated via recognition of pathogen-associated molecular patterns (PAMPs) by host sensors known as pattern recognition receptors (PRRs), which include, Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), NOD-like receptors (NLRs) and DNA receptors. Effective sensing of PAMPs rapidly triggers host immune responses, via activation of complex signalling pathways that culminates in the induction of inflammatory responses and the eradication of pathogens. Activation of the nuclear factor-κB (NF-κB) transcription pathway is crucial for the immediate early step of immune activation. This review discusses the recent evidence describing a variety of viral effectors that have been shown to prevent NF-κB signalling. Most of these viral effectors can be broadly classified into three categories based on the site of inhibition within the NF-κB pathway, that is, at the (i) TLRs, (ii) IKK complex or (iii) the transcriptional level.

TAK1 regulates NF-ΚB and AP-1 activation in airway epithelial cells following RSV infection

Respiratory syncytial virus (RSV) is the most common cause of epidemic respiratory diseases in infants and young children. RSV infection of airway epithelial cells induces the expression of immune/inflammatory genes through the activation of a subset of transcription factors, including Nuclear Factor-κB (NF-κB) and AP-1. In this study, we have investigated the signaling pathway leading to activation of these two transcription factors in response to RSV infection. Our results show that IKKβ plays a key role in viral-induced NF-κB activation, while JNK regulates AP-1-dependent gene transcription, as demonstrated by using kinase inactive proteins and chemical inhibitors of the two kinases. Inhibition of TAK1 activation, by overexpression of kinase inactive TAK1 or using cells lacking TAK1 expression, significantly reduced RSV-induced NF-κB and AP-1 nuclear translocation and DNA-binding activity, as well as NF-κB-dependent gene expression, identifying TAK1 as an important upstream signaling molecule regulating RSV-induced NF-κB and AP-1 activation.

Rotavirus infection activates the UPR but modulates its activity

Background

Rotaviruses are known to modulate the innate antiviral defense response driven by IFN. The purpose of this study was to identify changes in the cellular proteome in response to rotavirus infection in the context of the IFN response. We also sought to identify proteins outside the IFN induction and signaling pathway that were modulated by rotavirus infection.

Methods

2D-DIGE and image analysis were used to identify cellular proteins that changed in levels of expression in response to rotavirus infection, IFN treatment, or IFN treatment prior to infection. Immunofluorescence microscopy was used to determine the subcellular localization of proteins associated with the unfolded protein response (UPR).

Results

The data show changes in the levels of multiple proteins associated with cellular stress in infected cells, including levels of ER chaperones GRP78 and GRP94. Further investigations showed that GRP78, GRP94 and other proteins with roles in the ER-initiated UPR including PERK, CHOP and GADD34, were localized to viroplasms in infected cells.

Conclusions

Together the results suggest rotavirus infection activates the UPR, but modulates its effects by sequestering sensor, transcription factor, and effector proteins in viroplasms. The data consequently also suggest that viroplasms may directly or indirectly play a fundamental role in regulating signaling pathways associated with cellular defense responses.

Rotavirus antagonism of the innate immune response

Rotavirus is a primary cause of severe dehydrating gastroenteritis in infants and young children. The virus is sensitive to the antiviral effects triggered by the interferon (IFN)-signaling pathway, an important component of the host cell innate immune response. To counteract these effects, rotavirus encodes a nonstructural protein (NSP1) that induces the degradation of proteins involved in regulating IFN expression, such as members of the IFN regulatory factor (IRF) family. In some instances, NSP1 also subverts IFN expression by causing the degradation of a component of the E3 ubiquitin ligase complex responsible for activating NF-κB. By antagonizing multiple components of the IFN-induction pathway, NSP1 aids viral spread and contributes to rotavirus pathogenesis.

Regulation of inflammatory cytokine expression in pulmonary epithelial cells by pre-B-cell colony-enhancing factor via a nonenzymatic and AP-1-dependent mechanism

Although our previous studies found Pre-B-cell colony-enhancing factor (PBEF) as a highly up-regulated gene in acute lung injury that could stimulate expressions of other inflammatory cytokines, the underlying molecular mechanisms remain to be fully elucidated. Growing evidence indicates that PBEF is a nicotinamide phosphoribosyltransferase involved in the mammalian salvage pathway of NAD synthesis. This study was designed to determine whether the effect of PBEF to stimulate expressions of inflammatory cytokines depends on its enzymatic activity. We prepared two human PBEF mutant (H247E and H247A) recombinant proteins and overexpressing constructs for their overexpressions in A549 cells and confirmed that enzymatic activities of both mutants were nearly or completely abolished. Two mutants stimulated interleukin-8 (IL-8) expression at both the mRNA level and protein level just as equally effective as the wild-type PBEF did. These effects were due to the increased transcription, not the mRNA stability, of the IL-8 gene. Reporter gene assays and gel shift experiments indicated that AP-1 transcription factor is required to mediate these effects. SB203580, a p38 MAPK pathway inhibitor, and JNK inhibitor 1 can attenuate these effects. Both PBEF mutants similarly stimulated the expression of two other inflammatory cytokines: IL-16 and CCR3. These results indicate that PBEF stimulated expression of IL-8, IL-16, and CCR3 via its non-enzymatic activity. This effect is AP-1-dependent, in part via the p38 MAPK pathway and the JNK pathway. This finding reveals a new insight, which may manifest a novel role of PBEF in the pathogenesis of acute lung injury and other inflammatory disorders.

Tumor necrosis factor (TNF)-alpha-induced IL-8 expression in gastric epithelial cells: role of reactive oxygen species and AP endonuclease-1/redox factor (Ref)-1

TNF-alpha contributes to oxidative stress via induction of reactive oxygen species (ROS) and pro-inflammatory cytokines. The molecular basis of this is not well understood but it is partly mediated through the inducible expression of IL-8. As redox factor-1 (Ref-1), is an important mediator of redox-regulated gene expression we investigated whether ROS and Ref-1 modulate TNF-alpha-induced IL-8 expression in human gastric epithelial cells. We found that TNF-alpha treatment of AGS cells enhanced nuclear expression of Ref-1 and potently induced IL-8 expression. Overexpression of Ref-1 enhanced IL-8 gene transcription at baseline and after TNF-alpha treatment whereas Ref-1 suppression and antioxidant treatment inhibited TNF-alpha-stimulated IL-8 expression. TNF-alpha-mediated enhancement of other pro-inflammatory chemokines like MIP-3 alpha and Gro-alpha was also regulated by Ref-1. Although TNF-alpha increased DNA binding activity of Ref-1-regulated transcription factors, AP-1 and NF-kappaB, to the IL-8 promoter, promoter activity was mainly mediated by NF-kappaB binding. Silencing of Ref-1 in AGS cells inhibited basal and TNF-alpha-induced AP-1 and NF-kappaB DNA binding activity, but not their nuclear accumulation. Collectively, we provide the first mechanistic evidence of Ref-1 involvement in TNF-alpha-mediated, redox-sensitive induction of IL-8 and other chemokines in human gastric mucosa. This has implications for understanding the pathogenesis of gastrointestinal inflammatory disorders.

Rotavirus antagonizes cellular antiviral responses by inhibiting the nuclear accumulation of STAT1, STAT2, and NF-kappaB

A vital arm of the innate immune response to viral infection is the induction and subsequent antiviral effects of interferon (IFN). Rotavirus reduces type I IFN induction in infected cells by the degradation of IFN regulatory factors. Here, we show that the monkey rotavirus RRV and human rotavirus Wa also block gene expression induced by type I and II IFNs through a mechanism allowing signal transducer and activator of transcription 1 (STAT1) and STAT2 activation but preventing their nuclear accumulation. In infected cells, this may allow rotavirus to block the antiviral actions of IFN produced early in infection or by activated immune cells. As the intracellular expression of rotavirus nonstructural proteins NSP1, NSP3, and NSP4 individually did not inhibit IFN-stimulated gene expression, their involvement in this process is unlikely. RRV and Wa rotaviruses also prevented the tumor necrosis factor alpha-stimulated nuclear accumulation of NF-kappaB and NF-kappaB-driven gene expression. In addition, NF-kappaB was activated by rotavirus infection, confirming earlier findings by others. As NF-kappaB is important for the induction of IFN and other cytokines during viral infection, this suggests that rotavirus prevents cellular transcription as a means to evade host responses. To our knowledge, this is the first report of the use of this strategy by a double-stranded RNA virus.

Rotavirus NSP1 inhibits NFkappaB activation by inducing proteasome-dependent degradation of beta-TrCP: a novel mechanism of IFN antagonism

Mechanisms by which viruses counter innate host defense responses generally involve inhibition of one or more components of the interferon (IFN) system. Multiple steps in the induction and amplification of IFN signaling are targeted for inhibition by viral proteins, and many of the IFN antagonists have direct or indirect effects on activation of latent cytoplasmic transcription factors. Rotavirus nonstructural protein NSP1 blocks transcription of type I IFNalpha/beta by inducing proteasome-dependent degradation of IFN-regulatory factors 3 (IRF3), IRF5, and IRF7. In this study, we show that rotavirus NSP1 also inhibits activation of NFkappaB and does so by a novel mechanism. Proteasome-mediated degradation of inhibitor of kappaB (IkappaBalpha) is required for NFkappaB activation. Phosphorylated IkappaBalpha is a substrate for polyubiquitination by a multisubunit E3 ubiquitin ligase complex, Skp1/Cul1/F-box, in which the F-box substrate recognition protein is beta-transducin repeat containing protein (beta-TrCP). The data presented show that phosphorylated IkappaBalpha is stable in rotavirus-infected cells because infection induces proteasome-dependent degradation of beta-TrCP. NSP1 expressed in isolation in transiently transfected cells is sufficient to induce this effect. Targeted degradation of an F-box protein of an E3 ligase complex with a prominent role in modulation of innate immune signaling and cell proliferation pathways is a unique mechanism of IFN antagonism and defines a second strategy of immune evasion used by rotaviruses.

Broad early immune response of porcine epithelial jejunal IPI-2I cells to Entamoeba histolytica

Amoebiasis caused by Entamoebahistolytica triggers an acute inflammatory response at early stages of intestinal infection. The patho-physiological study of intestinal amoebiasis requires the development of powerful animal models. Swine provide robust model for human diseases and they could be used to study intestinal amoebiasis. Here, we introduce an in vitro model of swine intestinal epithelial cell (IPI-2I) co-cultured with E. histolytica. Intestinal epithelial cells (IECs) have crucial roles in sensing pathogens and initiating innate immune response, which qualitatively influence adaptive immune response against them. The contact between the two cells induces marked macroscopic lesions of IEC monolayer and striking alteration of the IPI-2I cell phenotype including blebbing, such as loss of attachment before to be phagocyte by the trophozoite. Increase in Lactate Dehydrogenase (LDH) levels in the culture supernatant of IECs was observed when ameba is present and could reflect the cellular cytotoxicity exerted by the parasite. Using quantitative real-time PCR, we identified the up-regulation of cytokines/chemokines implicated in neutrophil chemoattraction and inflammation, such as CCL2, CCL20, CXCL2, CXCL3, GM-CSF, IL1 alpha, IL6 and IL8, in response to the parasite that can further regulate the immunoregulatory functions of the immune cells of the host. The study points a cardinal role of these pro-inflammatory compounds as central mediators in the interaction IECs/ameba and suggests mechanisms by which they coordinate intestinal immune response. This will focus future efforts on delineating the molecular and cellular mechanisms of other cell partners by the way of in vivo infection of swine.

Analysis of rotavirus antigenemia and extraintestinal manifestations in children with rotavirus gastroenteritis

OBJECTIVE

This study was conducted to examine the association between rotavirus antigenemia and clinical features, particularly extraintestinal manifestations, and the association between serum cytokine levels and rotavirus antigen quantity.

METHODS

Sixty hospitalized children who received a diagnosis of acute rotavirus gastroenteritis were enrolled in this study. Paired serum samples were collected from the 60 children when admitted to and discharged from the hospital. Associations among viral antigen levels and fever, elevated transaminase levels, and seizures were evaluated to determine whether antigenemia correlated with disease severity. Viral antigen was measured by using an in-house enzyme-linked immunosorbent assay that detected VP6 antigen. A flow-cytometric bead array was used to measure serum cytokine levels.

RESULTS

Rotavirus antigen levels were significantly higher in serum collected at the time of hospital admission than at the time of discharge. Serum rotavirus antigen levels peaked on day 2 of the illness (2.02 +/- 0.73), followed by a gradual decrease in antigen levels to nearly undetectable levels by day 6. The quantity of rotavirus antigen was significantly higher in serum collected from patients with fever than those without fever. The presence or absence of elevated transaminase levels and seizures was not associated with serum rotavirus antigen levels. A weak but significantly positive association was observed between interleukin 8 levels and antigenemia. A weak but significantly negative association was observed between interleukin 10 levels and antigenemia.

CONCLUSIONS

Rotavirus antigenemia is frequently observed in a patient's serum during the acute phase, and viral antigen levels change dramatically during the acute phase of the illness. Because patients with fever had higher rotavirus antigen levels, antigenemia severity might contribute to fever. The host immune response plays an important role in controlling antigenemia levels.

Dachshund inhibits oncogene-induced breast cancer cellular migration and invasion through suppression of interleukin-8

Oncogene-mediated signaling to the host environment induces a subset of cytokines and chemokines. The Drosophila Dac gene promotes migration of the morphogenetic furrow during eye development. Expression of the cell-fate determination factor Dachshund (DACH1) was lost in poor prognosis invasive breast cancer. Mouse embryo fibroblasts derived from Dach1(-/-) mice demonstrated endogenous Dach1 constitutively represses cellular migration. DACH1 inhibited cellular migration and invasion of oncogene (Ras, Myc, ErbB2, c-Raf)-transformed human breast epithelial cells. An unbiased proteomic analysis identified and immunoneutralizing antibody and reconstitution experiments demonstrated IL-8 is a critical target of DACH1 mediating breast cancer cellular migration and metastasis in vivo. DACH1 bound the endogenous IL-8 promoter in ChIP assays and repressed the IL-8 promoter through the AP-1 and NF-kappaB binding sites. Collectively, our data identify a pathway by which an endogenous cell-fate determination factor blocks oncogene-dependent tumor metastasis via a key heterotypic mediator.

Intestinal inflammation increases the expression of the P2Y6 receptor on epithelial cells and the release of CXC chemokine ligand 8 by UDP

Epithelial cells participate in the immune response of the intestinal mucosa. Extracellular nucleotides have been recognized as inflammatory molecules. We investigated the role of extracellular nucleotides and their associated P2Y receptors in the secretion of cytokines by epithelial cells. The effect of intestinal inflammation on P2Y(6) receptor expression was determined by PCR in the mouse, rat, and human. Localization of the P2Y(6) receptor was determined by immunofluorescence microscopy in the colon of normal and dextran sulfate sodium-treated mice. The effect of P2Y(6) activation by UDP on cytokine expression and release by epithelial cells was determined using a combination of Western blots, luciferase assays, RT-PCR, cytokine Ab arrays, and ELISA. Inflammation up-regulates P2Y(2) as well as P2Y(6) receptor expression in the mucosa of the colon of colitic mice. In vitro, we demonstrated that UDP could be released by Caco-2/15 cells. We have confirmed the increased expression of P2Y(6) by challenging intestinal epithelial cell-6 and Caco-2/15 cells with TNF-alpha and IFN-gamma and showing that stimulation of epithelial cells by UDP results in an increased expression and release of CXCL8 by an ERK1/2-dependent mechanism. The increase in CXCL8 expression was associated with a transcriptional activation by the P2Y(6) receptor. This study is the first report demonstrating the implication of P2Y receptors in the inflammatory response of intestinal epithelial cells. We show for the first time that P2Y(6), as well as P2Y(2), expression is increased by the stress associated with intestinal inflammation. These results demonstrate the emergence of extracellular nucleotide signaling in the orchestration of intestinal inflammation.

Rotavirus replication in intestinal cells differentially regulates integrin expression by a phosphatidylinositol 3-kinase-dependent pathway, resulting in increased cell adhesion and virus yield

Changes in the interactions between intestinal cells and their surrounding environment during virus infection have not been well documented. The growth and survival of intestinal epithelial cells, the main targets of rotavirus infection, are largely dependent on the interaction of cell surface integrins with the extracellular matrix. In this study, we detected alterations in cellular integrin expression following rotavirus infection, identified the signaling components required, and analyzed the subsequent effects on cell binding to the matrix component collagen. After rotavirus infection of intestinal cells, expression of alpha2beta1 and beta2 integrins was up-regulated, whereas that of alphaVbeta3, alphaVbeta5, and alpha5beta1 integrins, if present, was down-regulated. This differential regulation of integrins was reflected at the transcriptional level. It was unrelated to the use of integrins as rotavirus receptors, as both integrin-using and integrin-independent viruses induced integrin regulation. Using pharmacological agents that inhibit kinase activity, integrin regulation was shown to be dependent on phosphatidylinositol 3-kinase (PI3K) but independent of the activities of the mitogen-activated protein kinases p38 and ERK1/2, and cyclooxygenase-2. Replication-dependent activation of the PI3K/Akt pathway was observed following infection of intestinal and nonintestinal cell lines. Rotavirus activation of PI3K was important for regulation of alpha2beta1 expression. Blockade of integrin regulation by PI3K inhibition led to decreased adherence of infected intestinal cells to collagen and a concomitant decrease in virus titer. These findings indicate that rotavirus-induced PI3K activation causes regulation of integrin expression in intestinal cells, leading to prolonged adherence of infected cells to collagen and increased virus production.

Transcriptional regulation of deoxynivalenol-induced IL-8 expression in human monocytes

The trichothecene mycotoxin deoxynivalenol (DON), commonly present in contaminated grains worldwide, induces expression of the chemokine interleukin (IL)-8 in human monocytes. The purpose of this study was to test the hypothesis that DON modulates transcriptional and posttranscriptional regulation of IL-8 expression in the U937 human monocyte model. When U937 cells were transfected with a wild-type IL-8 promoter luciferase construct (-162/+44 IL-8 LUC) and incubated with DON (1 mug/ml) or the positive control, lipopolysaccharide (LPS) (1 mug/ml), there was a significant increase in luciferase expression. Mutation of the nuclear factor-kappaB (NF-kappaB) binding site significantly impaired both DON- and LPS-induced luciferase expression. In contrast, mutating the activator protein-1 binding site resulted in significantly increased DON- and LPS-induced luciferase expression. CCAAT/enhancer-binding protein beta, octamer-1, or NF-kappaB repressing factor binding site mutations did not affect DON-induced luciferase activity. Consistent with reporter studies, the NF-kappaB inhibitor caffeic acid phenethyl ester completely ablated both DON-induced IL-8 mRNA and protein expression. When NF-kappaB subunit binding to a specific IL-8 promoter probe was evaluated by enzyme-linked immunosorbent assay (ELISA), DON was observed to increase p65 binding by 21-fold, have no effect on p50 binding and decrease p52 binding. DON was not found to stabilize IL-8 mRNA in U937 cells. Taken together, these data suggest that DON-induced IL-8 expression is likely to be mediated at the transcriptional level by NF-kappaB, specifically p65, but does not appear to involve mRNA stabilization.

Rotavirus activates JNK and p38 signaling pathways in intestinal cells, leading to AP-1-driven transcriptional responses and enhanced virus replication

Rotavirus infection is known to regulate transcriptional changes in many cellular genes. The transcription factors NF-kappaB and AP-1 are activated by rotavirus infection, but the upstream processes leading to these events are largely unidentified. We therefore studied the activation state during rotavirus infection of c-Jun NH2-terminal kinase (JNK) and p38, which are kinases known to activate AP-1. As assessed by Western blotting using phospho-specific antibodies, infection with rhesus rotavirus (RRV) or exposure to UV-psoralen-inactivated RRV (I-RRV) resulted in the activation of JNK in HT-29, Caco-2, and MA104 cells. Activation of p38 during RRV infection was observed in Caco-2 and MA104 cells but not in HT-29 cells, whereas exposure to I-RRV did not lead to p38 activation in these cell lines. Rotavirus strains SA11, CRW-8, Wa, and UK also activated JNK and p38. Consistent with the activation of JNK, a corresponding increase in the phosphorylation of the AP-1 component c-Jun was shown. The interleukin-8 (IL-8) and c-jun promoters contain AP-1 binding sequences, and these genes have been shown previously to be transcriptionally up-regulated during rotavirus infection. Using specific inhibitors of JNK (SP600125) and p38 (SB203580) and real-time PCR, we showed that maximal RRV-induced IL-8 and c-jun transcription required JNK and p38 activity. This highlights the importance of JNK and p38 in RRV-induced, AP-1-driven gene expression. Significantly, inhibition of p38 or JNK in Caco-2 cells reduced RRV growth but not viral structural antigen expression, demonstrating the potential importance of JNK and p38 activation for optimal rotavirus replication.

H. influenzae potentiates airway epithelial cell responses to rhinovirus by increasing ICAM-1 and TLR3 expression

Rhinovirus (RV) is an important trigger of chronic obstructive pulmonary disease (COPD) exacerbations. In addition, respiratory viruses are more likely to be isolated in patients with a history of frequent exacerbations, suggesting that these patients are more susceptible to viral infection. To examine potential mechanisms for cooperative effects between bacterial and viral infection in COPD, we studied the responses of cultured human airway epithelial cells to nontypeable Hemophilus influenzae and RV. In both 16HBE14o- and primary mucociliary-differentiated cells, preincubation with H. influenzae enhanced RV serotype 39-induced protein expression of interleukin (IL)-8, epithelial-derived neutrophil attractant-78, and growth-related oncogene-alpha. H. influenzae infection also increased the binding of RV39 to cultured cells, as well as expression of intercellular adhesion molecule (ICAM)-1 and Toll-like receptor (TLR)-3, receptors for RV and dsRNA, respectively. Neutralizing antibody against tumor necrosis factor-alpha inhibited IL-8 expression induced by H. influenzae and RV39. Finally, siRNA against TLR3 attenuated RV-induced IL-8 expression. We conclude that H. influenzae infection increases airway epithelial cell ICAM-1 and TLR3 expression, leading to enhanced binding of RV and a potentiation of RV-induced chemokine release. These data provide a cellular mechanism by which H. influenzae infection may increase the susceptibility of COPD patients to RV-induced exacerbations.

Cannabinoid signalling in TNF-α induced IL-8 release

The molecular events mediating the immunomodulatory properties of cannabinoids have remained largely unresolved. We have therefore investigated the molecular mechanism(s) through which R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl] pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-napthanlenyl) methanone (WIN55212-2) modulate production of interleukin-8 (IL-8) in HT-29 cells. Release of IL-8 induced by tumor necrosis factor-alpha (TNF-alpha) was determined by enzyme-linked immunosorbent assay (ELISA). Changes in expression of inhibitory kappa B (IkappaB) were monitored by Western blotting and activation of nuclear factor-kappa B (NF-kappaB) was determined in electrophoretic mobility shift assay (EMSAs). TNF-alpha induced release of IL-8 was inhibited by WIN55212-2 which also blocked the degradation of IkappaB-alpha and activation of NF-kappaB induced by TNF-alpha. These data provide strong evidence that WIN55212-2 may modulate IL-8 release by negatively regulating the signaling cascade leading to the activation of NF-kappaB. These findings highlight a potential mechanism for the immunomodulatory properties of cannabinoids and contribute towards acquiring a clear understanding of the role of cannabinoids in inflammation.

TLR3-mediated signal induces proinflammatory cytokine and chemokine gene expression in astrocytes: differential signaling mechanisms of TLR3-induced IP-10 and IL-8 gene expression

Viral infection is one of the leading causes of brain encephalitis and meningitis. Recently, it was reported that Toll-like receptor-3 (TLR3) induces a double-stranded RNA (dsRNA)-mediated inflammatory signal in the cells of the innate immune system, and studies suggested that dsRNA may induce inflammation in the central nervous system (CNS) by activating the CNS-resident glial cells. To explore further the connection between dsRNA and inflammation in the CNS, we have studied the effects of dsRNA stimulation in astrocytes. Our results show that the injection of polyinosinic-polycytidylic acid (poly(I:C)), a synthetic dsRNA, into the striatum of the mouse brain induces the activation of astrocytes and the expression of TNF-alpha, IFN-beta, and IP-10. Stimulation with poly(I:C) also induces the expression of these proinflammatory genes in primary astrocytes and in CRT-MG, a human astrocyte cell line. Furthermore, our studies on the intracellular signaling pathways reveal that poly(I:C) stimulation activates IkappaB kinase (IKK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) in CRT-MG. Pharmacological inhibitors of nuclear factor-kappaB (NF-kappaB), JNK, ERK, glycogen synthase kinase-3beta (GSK-3beta), and dsRNA-activated protein kinase (PKR) inhibit the expression of IL-8 and IP-10 in astrocytes, indicating that the activation of these signaling molecules is required for the TLR3-mediated chemokine gene induction. Interestingly, the inhibition of PI3 kinase suppressed the expression of IP-10, but upregulated the expression of IL-8, suggesting differential roles for PI3 kinase, depending on the target genes. These data suggest that the TLR3 expressed on astrocytes may initiate an inflammatory response upon viral infection in the CNS.

Diarrhea caused by primarily non-gastrointestinal infections

Direct infections of the gastrointestinal tract cause most cases of diarrhea, but diarrhea can also be caused by systemic infections or infections that affect other organ systems. The authors of this Review discuss clinically relevant infectious diseases that do not primarily affect the gastrointestinal tract but commonly cause diarrhea, and note that they should be included in the differential diagnosis and diagnostic approach to diarrhea.

Infectious diseases that do not primarily affect the gastrointestinal tract can cause severe diarrhea. The pathogenesis of this kind of diarrhea includes cytokine action, intestinal inflammation, sequestration of red blood cells, apoptosis and increased permeability of endothelial cells in the gut microvasculature, and direct invasion of gut epithelial cells by various infectious agents. Of the travel-associated systemic infections presenting with fever, diarrhea occurs in patients with malaria, dengue fever and SARS. Diarrhea also occurs in patients with community-acquired pneumonia, when it is suggestive of legionellosis. Diarrhea can also occur in patients with systemic bacterial infections. In addition, although diarrhea is rare in patients with early Lyme borreliosis, the incidence is higher in those with other tick-borne infections, such as ehrlichiosis, tick-borne relapsing fever and Rocky Mountain spotted fever. Unfortunately, it is often not established whether diarrhea is an initial symptom or develops during the course of the disease. The real incidence of diarrhea in some infectious diseases must also be questioned because it could represent an adverse reaction to antibiotics.

Protein kinase R mediates intestinal epithelial gene remodeling in response to double-stranded RNA and live rotavirus

As sentinels of host defense, intestinal epithelial cells respond to the viral pathogen rotavirus by activating a gene expression that promotes immune cell recruitment and activation. We hypothesized that epithelial sensing of rotavirus might target dsRNA, which can be detected by TLR3 or protein kinase R (PKR). Accordingly, we observed that synthetic dsRNA, polyinosinic acid:cytidylic acid (poly(I:C)), potently induced gene remodeling in model intestinal epithelia with the specific pattern of expressed genes, including both classic proinflammatory genes (e.g., IL-8), as well as genes that are classically activated in virus-infected cells (e.g., IFN-responsive genes). Poly(I:C)-induced IL-8 was concentration dependent (2-100 mug/ml) and displayed slower kinetics compared with IL-8 induced by bacterial flagellin (ET(50) approximately 24 vs 8 h poly(I:C) vs flagellin, respectively). Although model epithelia expressed detectable TLR3 mRNA, neither TLR3-neutralizing Abs nor chloroquine, which blocks activation of intracellular TLR3, attenuated epithelial responses to poly(I:C). Conversely, poly(I:C)-induced phosphorylation of PKR and inhibitors of PKR, 2-aminopurine and adenine, ablated poly(I:C)-induced gene expression but had no effect on gene expression induced by flagellin, thus suggesting that intestinal epithelial cell detection of dsRNA relies on PKR. Consistent with poly(I:C) detection by an intracellular molecule such as PKR, we observed that both uptake of and responses to poly(I:C) were polarized to the basolateral side. Lastly, we observed that the pattern of pharmacologic inhibition of responses to poly(I:C) was identical to that seen in response to infection by live rotavirus, indicating a potentially important role for PKR in activating intestinal epithelial gene expression in rotavirus infection.

Inhibition of NF-kappa B activity and cFLIP expression contribute to viral-induced apoptosis

Virus-induced activation of nuclear factor-kappa B (NF-kappaB) is required for Type 3 (T3) reovirus-induced apoptosis. We now show that NF-kappaB is also activated by the prototypic Type 1 reovirus strain Lang (T1L), which induces significantly less apoptosis than T3 viruses, indicating that NF-kappaB activation alone is not sufficient for apoptosis in reovirus-infected cells. A second phase of virus-induced NF-kappaB regulation, where NF-kappaB activation is inhibited at later times following infection with T3 Abney (T3A), is absent in T1L-infected cells. This suggests that inhibition of NF-kappaB activation at later times post infection also contributes to reovirus-induced apoptosis. Reovirus-induced inhibition of stimulus-induced activation of NF-kappaB is significantly associated with apoptosis following infection of HEK293 cells with reassortant reoviruses and is determined by the T3 S1 gene segment, which is also the primary determinant of reovirus-induced apoptosis. Inhibition of stimulus-induced activation of NF-kappaB also occurs following infection of primary cardiac myocytes with apoptotic (8B) but not non-apoptotic (T1L) reoviruses. Expression levels of the NF-kappaB-regulated cellular FLICE inhibitory protein (cFLIP) reflect NF-kappaB activation in reovirus-infected cells. Further, inhibition of NF-kappaB activity and cFLIP expression promote T1L-induced apoptosis. These results demonstrate that inhibition of stimulus-induced activation of NF-kappaB and the resulting decrease in cFLIP expression promote reovirus-induced apoptosis.

Rotavirus-induced murine biliary atresia is mediated by nuclear factor-kappaB

BACKGROUND/PURPOSE

Intraperitoneal inoculation of rhesus rotavirus (RRV) was shown to cause atretic-appearing segments of the extrahepatic bile ducts (EHBDs) in a murine model. The factors responsible for the injury of bile ducts, however, remain unknown. In this study, the morphologic status of nuclear factor- kappa B (NF- kappa B) activation in the liver and in the EHBDs from murine model of biliary atresia induced by intraperitoneal injection of rotavirus was investigated.

METHODS

Within the first 24 hours of life, the newborn mice were infected through intraperitoneal route with a volume of 50 microL containing different titers of RRV. The pups were killed on days 5, 10, 15, 21, and 28 after inoculation and prepared under a dissecting microscope with photographic documentation. Consecutive sections of specimens were stained with H & E and used for histopathologic studies. The methods of modified Vision immunohistochemical staining was used to detect viral antigen of VP7 and active NF- kappa B. The distribution and intensity of staining were analyzed by image analysis software (GT-2 model, Huakang Co, Chengdu, China).

RESULTS

The viral antigen was detected by immunohistochemical staining in specimens from experimental groups on day 5 after infection. The occlusion of the EHBDs could be visualized after intraperitoneal injection of 10(7) plaque-forming unit (pfu) of RRV, whereas the incidence of cholestasis was reduced with an infection dosage of 10(6) pfu or less. Obliteration of the EHBDs did not occur when the injection dosage of RRV was reduced to 10(5) pfu or when inoculation of 10(7) pfu of RRV was combined with pyrolidine dithiocarbamate (PDTC), a chemical inhibitor of active NF- kappa B. The antigen of active NF- kappa B was detected by immunohistochemical staining in the liver and in the EHBDs from pups after inoculation of 10(7), 10(6), and 10(5) pfu RRV. Low or no expression of active NF- kappa B was noted in the specimens obtained from the control group. As the inflammatory reaction in the liver and in the EHBDs gradually subsided on day 28 after inoculation, the expression of active NF- kappa B also decreased. The expression of active NF- kappa B after injection of RRV combined with PDTC was similar to the expression in the control group on days 5 and 10 after infection.

CONCLUSIONS

The authors found that occlusion of the EHBDs could be noted in pups after inoculation of 10(7) pfu RRV. Meanwhile, the expression of active NF- kappa B in the liver and in the EHBDs was increased after inoculation of RRV. Simultaneous intraperitoneal injection of PDTC, however, was shown to prevent the obstruction of EHBDs secondary to inoculation of RRV. These results show that the murine biliary atresia induced by RRV is mediated by active NF- kappa B.

Reactive oxygen and nitrogen species differentially regulate Toll-like receptor 4-mediated activation of NF-kappa B and interleukin-8 expression

Toll-like receptor 4 (TLR4) has been identified as a transmembrane protein involved in the host innate immune response to gram-negative bacterial lipopolysaccharide (LPS). Upon activation by LPS recognition, the TIR domain of TLR4 signals through MyD88 to activate the nuclear factor kappa B (NF-kappa B) pathway, a critical regulator of many proinflammatory genes, including interleukin-8 (IL-8). Emerging evidence suggests that reactive oxygen species (ROS) can contribute to diverse signaling pathways, including the LPS-induced cascade. In the present study we investigated the role of ROS in TLR-mediated signaling. Purified Escherichia coli LPS, a highly specific TLR4 agonist, elicited an oxidative burst in the monocyte-like cell line THP-1 in a time- and dose-dependent manner. This oxidative burst was shown to be dependent on the presence of TLR4 through transfection studies in HEK cells, which do not normally express this protein, and with bone marrow-derived macrophages from C3H/HeJ mice, which express a mutated TLR4 protein. LPS-stimulated IL-8 expression could be blocked by the antioxidants N-acetyl-L-cysteine and dimethyl sulfoxide at both the protein and mRNA levels. These antioxidants also blocked LPS-induced IL-8 promoter transactivation as well as the nuclear translocation of NF-kappa B. These data provide evidence that ROS regulate immune signaling through TLR4 via their effects on NF-kappa B activation.

Inhibition of NF-kappa B activation and its target genes by heparin-binding epidermal growth factor-like growth factor

Many cells upon injury mount extensive, compensatory responses that increase cell survival; however, the intracellular signals that regulate these responses are not completely understood. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been implicated as a cytoprotective agent. We have previously demonstrated that pretreatment of human intestinal epithelial cells with HB-EGF significantly decreased cytokine-induced activation of inducible NO synthase mRNA expression and NO production and protected the cells from apoptosis and necrosis. However, the mechanisms by which HB-EGF exerts these effects are not known. Here we show that cytokine exposure (IL-1beta and IFN-gamma) induced NF-kappaB activation and IL-8 and NO production in DLD-1 cells. Transient expression of a dominant negative form of IkappaBalpha decreased NO production, suggesting that the cytokines stimulated NO production in part through activation of NF-kappaB. HB-EGF dramatically suppressed NF-kappaB activity and IL-8 release and decreased NO production in cells pretreated with HB-EGF. HB-EGF blocked NF-kappaB activation by inhibiting IkappaB kinase activation and IkappaB phosphorylation and degradation, thus interfering with NF-kappaB nuclear translocation, DNA-binding activity, and NF-kappaB-dependent transcriptional activity. The data demonstrate that HB-EGF decreases inflammatory cytokine and NO production by interfering with the NF-kappaB signaling pathway. Inhibition of NF-kappaB may represent one of the mechanisms by which HB-EGF exerts its potent anti-inflammatory and cytoprotective effects.

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Expression and function of chemokines during viral infections: from molecular mechanisms to in vivo function

Recruitment and activation of leukocytes are important for elimination of microbes, including viruses, from infected areas. Chemokines constitute a group of bioactive peptides that regulate leukocyte migration and also contribute to activation of these cells. Chemokines are essential mediators of inflammation and important for control of viral infections. The profile of chemokine expression contributes to shaping the immune response during viral infection, whereas viral subversion of the chemokine system allows the virus to evade antiviral activities of the host. In this review, we discuss the role of chemokines in host-defense against virus infections, and we also look deeper into the virus-cell interactions that trigger chemokine expression as well as the cellular signaling cascades involved.

Two distinct phases of virus-induced nuclear factor kappa B regulation enhance tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in virus-infected cells

Cellular transcription factors are often utilized by infecting viruses to promote viral growth and influence cell fate. We have previously shown that nuclear factor kappaB (NF-kappaB) is activated after reovirus infection and that this activation is required for virus-induced apoptosis. In this report we identify a second phase of reovirus-induced NF-kappaB regulation. We show that at later times post-infection NF-kappaB activation is blocked in reovirus-infected cells. This results in the termination of virus-induced NF-kappaB activity and the inhibition of tumor necrosis factor alpha and etoposide-induced NF-kappaB activation in infected cells. Reovirus-induced inhibition of NF-kappaB activation occurs by a mechanism that prevents IkappaBalpha degradation and that is blocked in the presence of the viral RNA synthesis inhibitor, ribavirin. Reovirus-induced apoptosis is mediated by tumor necrosis factor-related apoptosis inducing ligand (TRAIL) in a variety of epithelial cell lines. Herein we show that ribavirin inhibits reovirus-induced apoptosis in TRAIL-resistant HEK293 cells and prevents the ability of reovirus infection to sensitize TRAIL-resistant cells to TRAIL-induced apoptosis. Furthermore, TRAIL-induced apoptosis is enhanced in HEK293 cells expressing IkappaBDeltaN2, which blocks NF-kappaB activation. These results indicate that the ability of reovirus to inhibit NF-kappaB activation sensitizes HEK293 cells to TRAIL and facilitates virus-induced apoptosis in TRAIL-resistant cells. Our findings demonstrate that two distinct phases of virus-induced NF-kappaB regulation are required to efficiently activate host cell apoptotic responses to reovirus infection.

Regulation of RANTES promoter activation in alveolar epithelial cells after cytokine stimulation

Regulated on activation, normal T cell expressed, and presumably secreted (RANTES) is a member of the CC chemokine family of proteins implicated in a variety of diseases characterized by lung eosinophilia and inflammation, strongly produced by stimulated airway epithelial cells. Because such cytokines as tumor necrosis factor (TNF)-alpha and interferon-gamma (IFN-gamma) have been shown to enhance RANTES induction in airway epithelial cells and RANTES gene expression appears to be differentially regulated depending on the cell type and the stimulus applied, in this study we have elucidated mechanisms that operate to control RANTES induction on exposure to TNF-alpha and/or IFN-gamma. Our results indicate that TNF-alpha and IFN-gamma synergistically induce RANTES protein secretion and mRNA expression. RANTES transcription is activated only after stimulation with TNF-alpha, but not IFN-gamma, which affects RANTES mRNA stabilization. Promoter deletion and mutagenesis experiments indicate that the nuclear factor (NF)-kappaB site is the most important cis-regulatory element controlling TNF-induced RANTES transcription, although NF-interleukin-6 binding site, cAMP responsive element (CRE), and interferon-stimulated responsive element (ISRE) also play a significant role. TNF-alpha stimulation induces nuclear translocation of interferon regulatory factor (IRF)-3, which in viral infection binds the RANTES ISRE and is necessary for activation of RANTES transcription. However, TNF-induced IRF-3 translocation does not result in IRF-3 binding to the RANTES ISRE. Although viral infection can activate an ISRE-driven promoter, TNF cannot, indicating that RANTES gene enhancers are controlled in a stimulus-specific fashion. Identification of molecular mechanisms involved in RANTES gene expression is fundamental for developing strategies to modulate lung inflammatory responses.