Upregulation Of IFN-β Research Articles

CD40 Stimulates a “Feed-Forward” NF-κB–Driven Molecular Pathway That Regulates IFN-β Expression in Carcinoma Cells

IFN-β and the CD40L (CD154) share important roles in the antiviral and antitumor immune responses. In this study, we show that CD40 receptor occupancy results in IFN-β upregulation through an unconventional "feed-forward" mechanism, which is orchestrated by canonical NF-κB and involves the sequential de novo synthesis of IFN regulatory factor (IRF)1 and Viperin (RSAD2), an IRF1 target. RelA (p65) NF-κB, IRF1, and Viperin-dependent IRF7 binding to the IFN-β promoter largely controls its activity. However, full activation of IFN-β also requires the parallel engagement of noncanonical NF-κB2 signaling leading to p52 recruitment to the IFN-β promoter. These data define a novel link between CD40 signaling and IFN-β expression and provide a telling example of how signal propagation can be exploited to ensure efficient regulation of gene expression.

IRF7-dependent IFNβ production in response to RANK facilitates medullary thymic epithelial cell development. (60.3)

Abstract The signal transducer and activator of transcription 1 (STAT1) is an essential part of signaling cascades induced by type I and II interferons. Deficiency of STAT1 results in heightened susceptibility to infections and autoimmunity in mouse and humans. While the role of IFNγ in T cell development is well known, the role of type I interferons in thymic development has largely remained unexplored. Here we show that STAT1 and IFNAR-deficient mice harbor a defect in medullary compartment characterized by a significant reduction in self-antigen presenting, AIRE expressing medullary thymic epithelial cells. Using a novel reporter mouse we demonstrate that constitutive IFNAR signaling is taking place in the thymic medulla in the absence of any infection or inflammatory signals. In addition, we found that RANK stimulation in thymic stromal cells results in the upregulation of IFNβ which in turn is inhibits RANK signaling thereby facilitating AIRE expression. Finally, we show that IRF7 is required for the induction of IFNβ by RANKL, and that IRF7-, but not IRF3-deficient mice display a defect in thymic architecture and medullary thymic epithelial cell differentiation similar to that observed in IFNAR- or STAT1-deficient animals. These results illustrate that a spatially and temporally coordinated crosstalk between the RANKL/RANK signaling pathway and the IRF7/IFNβ/IFNAR/STAT1 axis is essential for the differentiation of AIRE-expressing medullary thymic epithelial cells.

Uterine Epithelial Cells Specifically Induce Interferon-Stimulated Genes in Response to Polyinosinic-Polycytidylic Acid Independently of Estradiol

Interferon β (IFNβ) is an antiviral cytokine secreted in response to pathogenic exposure that creates a restrictive intracellular environment through the action of downstream interferon-stimulated genes (ISG). The objective of this study was to examine the expression of IFNβ and ISG in both human uterine epithelial cells (UEC) and the ECC-1 uterine epithelial cell line and determine if expression changes with TLR stimulation and hormone exposure. Stimulation of primary uterine epithelial cells and ECC-1 cells with the TLR3 agonist poly (I∶C) induced the mRNA expression of IFNβ, MxA, OAS2 and PKR. Other TLR agonists including imiquimod and CpG had no effect on either IFNβ or ISG expression. In contrast to ECC-1 cell responses which were slower, maximal IFNβ upregulation in UEC occurred 3 hours post-stimulation and preceded the ISG response which peaked approximately 12 hours after poly (I∶C) exposure. Unexpectedly, estradiol, either alone or prior to treatment with poly (I∶C), had no effect on IFNβ or ISG expression. Blockade of the IFN receptor abrogated the upregulation of MxA, OAS2 and PKR. Furthermore, neutralizing antibodies against IFNβ partially inhibited the upregulation of all three ISG. Estradiol, directly and in the presence of poly (I∶C) had no effect on IFNβ and ISG expression. These results indicate that uterine epithelial cells are important sentinels of the innate immune system and demonstrate that uterine epithelial cells are capable of mounting a rapid IFN-mediated antiviral response that is independent of estradiol and is therefore potentially sustained throughout the menstrual cycle to aid in the defense of the uterus against potential pathogens.

Molecular Cloning and Functional Characterization of Tibetan Porcine STING

Tibetan pig is well known for its strong disease resistance. However, little is known about the molecular basis of its strong resistance to disease. Stimulator of interferon (IFN) genes (STING), also known as MPYS/MITA/ERIS/TMEM173, is an adaptor that functions downstream of RIG-I and MAVS and upstream of TBK1 and plays a critical role in type I IFN induction. Here we report the first cloning and characterization of STING gene from Tibetan pig. The entire open reading frame (ORF) of the Tibetan porcine STING is 1137 bp, with a higher degree of sequence similarity with Landrace pig (98%) and cattle (88%) than with chimpanzee (84%), human (83%) or mouse (77%). The predicted protein is composed of 378 amino acids and has 4 putative transmembrane domains. Real-time quantitative PCR analysis indicated that Tibetan pig STING mRNA was most abundant in the lung and heart. Overexpression of Tibetan porcine STING led to upregulation of IFN-β and IFN-stimulated gene 15 (ISG15) in porcine jejunal epithelial cell line IPEC-J2 cells. This is the first study investigating the biological role of STING in intestinal epithelial cells, which lays a foundation for the further study of STING in intestinal innate immunity.

Activation of the innate immune response against DENV in normal non-transformed human fibroblasts.

BackgroundWhen mosquitoes infected with DENV are feeding, the proboscis must traverse the epidermis several times (“probing”) before reaching a blood vessel in the dermis. During this process, the salivary glands release the virus, which is likely to interact first with cells of the various epidermal and dermal layers, cells which could be physiologically relevant to DENV infection and replication in humans. However, important questions are whether more abundant non-hematopoietic cells such as fibroblasts become infected, and whether they play any role in antiviral innate immunity in the very early stages of infection, or even if they might be used by DENV as primary replication cells.Methodology/Principal FindingsFibroblasts freshly released from healthy skin and infected 12 hours after their isolation show a positive signal for DENV. In addition, when primary skin fibroblast cultures were established and subsequently infected, we showed DENV-2 antigen-positive intracellular signal at 24 hours and 48 hours post-infection. Moreover, the fibroblasts showed productive infection in a conventional plaque assay. The skin fibroblasts infected with DENV-2 underwent potent signaling through both TLR3 and RIG- 1, but not Mda5, triggering up-regulation of IFNβ, TNFα, defensin 5 (HB5) and β defensin 2 (HβD2). In addition, DENV infected fibroblasts showed increased nuclear translocation of interferon (IFN) regulatory factor 3 (IRF3), but not interferon regulatory factor 7 (IRF7), when compared with mock-infected fibroblasts.Conclusions/SignificanceIn this work, we demonstrated the high susceptibility to DENV infection by primary fibroblasts from normal human skin, both in situ and in vitro. Our results suggest that these cells may contribute to the pro-inflammatory and anti-viral microenvironment in the early stages of interaction with DENV-2. Furthermore, the data suggest that fibroblast may also be used as a primary site of DENV replication and provide viral particles that may contribute to subsequent viral dissemination.

Optimized Protocol for Efficient Transfection of Dendritic Cells without Cell Maturation

Dendritic cells (DCs) can be considered sentinels of the immune system which play a critical role in its initiation and response to infection. Detection of pathogenic antigen by naïve DCs is through pattern recognition receptors (PRRs) which are able to recognize specific conserved structures referred to as pathogen-associated molecular patterns (PAMPS). Detection of PAMPs by DCs triggers an intracellular signaling cascade resulting in their activation and transformation to mature DCs. This process is typically characterized by production of type 1 interferon along with other proinflammatory cytokines, upregulation of cell surface markers such as MHCII and CD86 and migration of the mature DC to draining lymph nodes, where interaction with T cells initiates the adaptive immune response. Thus, DCs link the innate and adaptive immune systems. The ability to dissect the molecular networks underlying DC response to various pathogens is crucial to a better understanding of the regulation of these signaling pathways and their induced genes. It should also help facilitate the development of DC-based vaccines against infectious diseases and tumors. However, this line of research has been severely impeded by the difficulty of transfecting primary DCs. Virus transduction methods, such as the lentiviral system, are typically used, but carry many limitations such as complexity and bio-hazardous risk (with the associated costs). Additionally, the delivery of viral gene products increases the immunogenicity of those transduced DCs. Electroporation has been used with mixed results, but we are the first to report the use of a high-throughput transfection protocol and conclusively demonstrate its utility. In this report we summarize an optimized commercial protocol for high-throughput transfection of human primary DCs, with limited cell toxicity and an absence of DC maturation. Transfection efficiency (of GFP plasmid) and cell viability were more than 50% and 70% respectively. FACS analysis established the absence of increase in expression of the maturation markers CD86 and MHCII in transfected cells, while qRT-PCR demonstrated no upregulation of IFNβ. Using this electroporation protocol, we provide evidence for successful transfection of DCs with siRNA and effective knock down of targeted gene RIG-I, a key viral recognition receptor, at both the mRNA and protein levels.

Optimized Protocol for Efficient Transfection of Dendritic Cells without Cell Maturation

Dendritic cells (DCs) can be considered sentinels of the immune system which play a critical role in its initiation and response to infection1. Detection of pathogenic antigen by naïve DCs is through pattern recognition receptors (PRRs) which are able to recognize specific conserved structures referred to as pathogen-associated molecular patterns (PAMPS). Detection of PAMPs by DCs triggers an intracellular signaling cascade resulting in their activation and transformation to mature DCs. This process is typically characterized by production of type 1 interferon along with other proinflammatory cytokines, upregulation of cell surface markers such as MHCII and CD86 and migration of the mature DC to draining lymph nodes, where interaction with T cells initiates the adaptive immune response2,3. Thus, DCs link the innate and adaptive immune systems. The ability to dissect the molecular networks underlying DC response to various pathogens is crucial to a better understanding of the regulation of these signaling pathways and their induced genes. It should also help facilitate the development of DC-based vaccines against infectious diseases and tumors. However, this line of research has been severely impeded by the difficulty of transfecting primary DCs4. Virus transduction methods, such as the lentiviral system, are typically used, but carry many limitations such as complexity and bio-hazardous risk (with the associated costs)5,6,7,8. Additionally, the delivery of viral gene products increases the immunogenicity of those transduced DCs9,10,11,12. Electroporation has been used with mixed results13,14,15, but we are the first to report the use of a high-throughput transfection protocol and conclusively demonstrate its utility. In this report we summarize an optimized commercial protocol for high-throughput transfection of human primary DCs, with limited cell toxicity and an absence of DC maturation16. Transfection efficiency (of GFP plasmid) and cell viability were more than 50% and 70% respectively. FACS analysis established the absence of increase in expression of the maturation markers CD86 and MHCII in transfected cells, while qRT-PCR demonstrated no upregulation of IFNβ. Using this electroporation protocol, we provide evidence for successful transfection of DCs with siRNA and effective knock down of targeted gene RIG-I, a key viral recognition receptor16,17, at both the mRNA and protein levels.

MicroRNA-148/152 Impair Innate Response and Antigen Presentation of TLR-Triggered Dendritic Cells by Targeting CaMKIIα

MicroRNAs (miRNAs) are involved in the regulation of immunity, including the lymphocyte development and differentiation, and inflammatory cytokine production. Dendritic cells (DCs) play important roles in linking innate and adaptive immune responses. However, few miRNAs have been found to regulate the innate response and APC function of DCs to date. Calcium/calmodulin-dependent protein kinase II (CaMKII), a major downstream effector of calcium (Ca(2+)), has been shown to be an important regulator of the maturation and function of DCs. Our previous study showed that CaMKIIα could promote TLR-triggered production of proinflammatory cytokines and type I IFN. Inspired by the observations that dicer mutant Drosophila display defect in endogenous miRNA generation and higher CaMKII expression, we wondered whether miRNAs can regulate the innate response and APC function of DCs by targeting CaMKIIα. By predicting with software and confirming with functional experiments, we demonstrate that three members of the miRNA (miR)-148 family, miR-148a, miR-148b, and miR-152, are negative regulators of the innate response and Ag-presenting capacity of DCs. miR-148/152 expression was upregulated, whereas CaMKIIα expression was downregulated in DCs on maturation and activation induced by TLR3, TLR4, and TLR9 agonists. We showed that miR-148/152 in turn inhibited the production of cytokines including IL-12, IL-6, TNF-α, and IFN-β upregulation of MHC class II expression and DC-initiated Ag-specific T cell proliferation by targeting CaMKIIα. Therefore, miRNA-148/152 can act as fine-tuner in regulating the innate response and Ag-presenting capacity of DCs, which may contribute to the immune homeostasis and immune regulation.

Lactobacillus acidophilus induces virus immune defence genes in murine dendritic cells by a Toll‐like receptor‐2‐dependent mechanism

Lactobacilli are probiotics that, among other health-promoting effects, have been ascribed immunostimulating and virus-preventive properties. Certain Lactobacillus spp. have been shown to possess strong interleukin-12 (IL-12) -inducing properties. As IL-12 production depends on the up-regulation of type I interferons (IFNs), we hypothesized that the strong IL-12-inducing capacity of Lactobacillus acidophilus NCFM in murine bone-marrow-derived dendritic cells (DCs) is caused by an up-regulation of IFN-β, which subsequently induces IL-12 and the double-stranded RNA binding Toll-like receptor-3 (TLR-3). The expression of the genes encoding IFN-β, TLR-3, IL-12 and IL-10 in DCs upon stimulation with L. acidophilus NCFM was determined. Lactobacillus acidophilus NCFM induced a much stronger expression of Ifn-β, Il-12 and Il-10 compared with the synthetic double-stranded RNA ligand Poly I:C, whereas the levels of expressed Tlr-3 were similar. Whole genome microarray gene expression analysis revealed that other genes related to viral defence were significantly up-regulated and among the strongest induced genes in DCs stimulated with L. acidophilus NCFM. The ability to induce IFN-β was also detected in another L. acidophilus strain (X37), but was not a property of other probiotic strains tested, i.e. Bifidobacterium bifidum Z9 and Escherichia coli Nissle 1917. The IFN-β expression was markedly reduced in TLR-2(-/-) DCs, dependent on endocytosis, and the major cause of the induction of Il-12 and Tlr-3 in DCs stimulated with L. acidophilus NCFM. Collectively, our results reveal that certain lactobacilli trigger the expression of viral defence genes in DCs in a TLR-2 manner dependent on IFN-β.

Systemic Lipopolysaccharide Protects the Brain from Ischemic Injury by Reprogramming the Response of the Brain to Stroke: A Critical Role for IRF3

Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury through activation of its receptor, Toll-like receptor 4 (TLR4). Paradoxically, TLR activation by endogenous ligands after ischemia worsens stroke damage. Here, we define a novel, protective role for TLRs after ischemia in the context of LPS preconditioning. Microarray analysis of brains collected 24 h after stroke revealed a unique set of upregulated genes in LPS-pretreated animals. Promoter analysis of the unique gene set identified an overrepresentation of type I interferon (IFN)-associated transcriptional regulatory elements. This finding suggested the presence of type I IFNs or interferon regulatory factors (IRFs), which upregulate interferon-stimulated genes. Upregulation of IFNbeta was confirmed by real-time reverse transcription-PCR. Direct administration of IFNbeta intracerebroventricularly at the time of stroke was sufficient for neuroprotection. TLR4 can induce both IFNbeta and interferon-stimulated genes through its adapter molecule Toll/interleukin receptor domain-containing adaptor-inducing IFNbeta (TRIF) and the IRF3 transcription factor. We show in oxygen glucose deprivation of cortical neurons, an in vitro model of stroke, that activation of TRIF after stroke reduces neuronal death. Furthermore, mice lacking IRF3 were not protected by LPS preconditioning in our in vivo model. Our studies constitute the first demonstration of the neuroprotective capacity of TRIF/IRF3 signaling and suggest that interferon-stimulated genes, whether induced by IFNbeta or by enhanced TLR signaling to IRF3, are a potent means of protecting the brain against ischemic damage.

The Major Outer Membrane Protein of a Periodontopathogen Induces IFN-β and IFN-Stimulated Genes in Monocytes via Lipid Raft and TANK-Binding Kinase 1/IFN Regulatory Factor-3

Surface molecules of pathogens play an important role in stimulating host immune responses. Elucidation of the signaling pathways activated by critical surface molecules in host cells provides insight into the molecular pathogenesis resulting from bacteria-host interactions. MspTL is the most abundant outer membrane protein of Treponema lecithinolyticum, which is associated with periodontitis, and induces expression of a variety of proinflammatory factors. Although bacteria and bacterial components like LPS and flagellin are known to induce IFN-beta, induction by bacterial surface proteins has not been reported. In the present study, we investigated MspTL-mediated activation of signaling pathways stimulating up-regulation of IFN-beta and IFN-stimulated genes in a human monocytic cell line, THP-1 cells, and primary cultured human gingival fibroblasts. MspTL treatment of the cells induced IFN-beta and the IFN-stimulated genes IFN-gamma-inducible protein-10 (IP-10) and RANTES. A neutralizing anti-IFN-beta Ab significantly reduced the expression of IP-10 and RANTES, as well as STAT-1 activation, which was also induced by MspTL. Experiments using specific small interfering RNA showed that MspTL activated TANK-binding kinase 1 (TBK1), but not inducible IkappaB kinase (IKKi). MspTL also induced dimerization of IFN regulatory factor-3 (IRF-3) and translocation into the nucleus. The lipid rapid-disrupting agents methyl-beta-cyclodextrin, nystatin, and filipin inhibited the MspTL internalization and cellular responses, demonstrating that lipid raft activation was a prerequisite for MspTL cellular signaling. Our results demonstrate that MspTL, the major outer protein of T. lecithinolyticum, induced IFN-beta expression and subsequent up-regulation of IP-10 and RANTES via TBK1/IRF-3/STAT-1 signaling secondary to lipid raft activation.

Modulation of TLR4 signaling by TLR2 in the macrophage response to Mycoplasma pneumoniae (135.10)

Abstract Several clinical reports suggest that Mycoplasma pneumoniae (Mp) can contribute importantly to asthma pathogenesis. As a foundation for understanding interactions between Mp and asthma, we are first studying the mechanisms by which the host normally eliminates Mp. We showed previously that macrophages are critical for elimination of Mp from the lungs of mice, and that MyD88-NFκB signaling is needed for this response. Here, we focus on the role of TLR signaling in the macrophage response to this microbe. Several mycoplasma lipoproteins have been shown to activate macrophages via TLR2, the majority through the TLR2/6 heterodimer. Interestingly, we found enhanced clearance of Mp from TLR2-/- mice, but reduced clearance of Mp from TLR1-/- or TLR6-/- mice. The enhanced clearance in TLR2-/- mice is dependent on both TLR4 signaling and the presence of macrophages. These data suggest interactions between TLR2 and TLR4 in the anti-Mp response. We extended these studies in vitro by infecting bone marrow-derived macrophages (BMM) with Mp. After infection with Mp, TLR2-/- BMM showed increased phosphorylation of IRF3 and NFκB, and up-regulation of IFN-β and IL-6 mRNA expression, compared to Mp-infected wild type BMM. These effects were TLR4-dependent. Altogether, TLR2 plays an inhibitory role in the regulation of TLR4 signaling in the macrophage response to Mp. Supported by NHLBI HL073907.

Signal regulatory protein α negatively regulates both TLR3 and cytoplasmic pathways in type I interferon induction

Recognition of double-stranded RNA (dsRNA) activates interferon-regulatory factor 3 (IRF3)-dependent expression of anti-viral factors. The innate immune system recognizes viral dsRNA through two distinct pathways. First, the Toll-like receptor 3 (TLR3) detects dsRNA phagocytosed in endosomes. In addition, the helicases retinoic acid induced protein I (RIG-I)/melanoma differentiation associated gene 5 (MDA5) binds cytoplasmic dsRNA generated during viral replication. Both RIG-I/MDA5 and TLR3 can bind polyriboinosinic:polyribocytidylic acid (poly(I:C)), the synthetic analog of viral dsRNA, and mediate type I IFN production. Here we show that signal regulatory protein (SIRP) α negatively regulates both TLR3- and RIG-1/MDA5-dependent anti-viral pathways. Suppression of SIRPα expression by RNA interference results in enhanced activation of IRF3 and MAPK pathways after poly(I:C) treatment, coupled with the up-regulation of IFN-β and IFN-β-inducible gene transcriptional activation. The requirement of phosphoinositide 3-kinase (PI3K) activity for the induction of IFN-β and IFN-β-inducible genes by dsRNA is supported by the observation that a PI3K inhibitor failed to activate IFN-β and IFN-β-inducible gene expression. PI3K, whose activity is essential for activation of IRF3, is recruited to the phosphorylated tyrosine residues of SIRPα upon poly(I:C) stimulation, which lead to a reduction in the activity of the downstream kinase AKT. Thus SIRPα may accomplish its inhibitory function in type I IFN induction, in part, through its association and sequestration of the signal transducer PI3K.

Evidence for Evolving Toll-IL-1 Receptor-Containing Adaptor Molecule Function in Vertebrates

In mammals, Toll-IL-1R-containing adaptor molecule 1 (TICAM1)-dependent TLR pathways induce NF-kappaB and IFN-beta responses. TICAM1 activates NF-kappaB through two different pathways involving its interactions with TNFR-associated factor 6 and receptor-interacting protein 1. It also activates IFN regulatory factor 3/7 through its interaction with TANK-binding kinase-1, leading to the robust up-regulation of IFN-beta. In this study, we describe the role of zebrafish (Danio rerio) TICAM1 in activating NF-kappaB and zebrafish type I IFN. Zebrafish IFN is unique in that it cannot be categorized as being alpha- or beta-like. Through comprehensive sequence, phylogenetic, and syntenic analyses, we fully describe the identification of a zebrafish TICAM1 ortholog. Zebrafish TICAM1 exhibits sequence divergence from its mammalian orthologs and our data demonstrate that these sequence differences have functional consequences. Zebrafish TICAM1 activates zebrafish IFN; however, it does so in an apparently IFN regulatory factor 3/7-independent manner. Furthermore, zebrafish TICAM1 does not interact with zebrafish TNFR-associated factor 6, thus NF-kappaB activation is dependent upon its interaction with receptor-interacting protein 1. Comparative genome analysis suggests that TICAM1 and TICAM2 evolved from a common vertebrate TICAM ancestor following a gene duplication event and that TICAM2 was lost in teleosts following the divergence of the rayfin and lobefin fishes 450 million years ago. These studies provide evidence, for the first time, of the evolving function of a vertebrate TLR pathway.

Protective DNA Vaccination Against MOG91‐108‐Induced Experimental Autoimmune Encephalomyelitis Involves Induction of IFNβ

DNA vaccine coding for the encephalitogenic peptide MOG91‐108 protects LEW.1AV1 from subsequent development of experimental autoimmune encephalomyelitis (EAE). Protection is associated with a type 1 immune response and is dependent on the presence of CpG DNA motifs. The mechanisms underlying the observed reduction of EAE development in protected rats have not been fully clarified. We investigated immunological characteristics of lymphocytes after DNA vaccinaton and subsequent EAE induction. We confirm that protection was not associated with suppression of T1 cells, as transcription of the novel molecule rat T‐cell immunoglobulin‐ and mucin‐domain‐containing molecule (TIM‐3), reported to be exclusively expressed on differentiated T1 cells, was not altered by DNA vaccination. We did not note any clonal deletion upon tolerization, but detected an antigen‐specific lymphocyte population upregulating IFNγ upon recall stimulation 3 weeks after protective DNA vaccination. In protected rats, we observed (1) no alterations in antigen‐specific Th2 or Th3 responses, (2) reduced MHC II expression on splenocytes early after EAE induction, (3) antigen‐specific upregulation of IFNβ upon recall stimulation and (4) reduced IL‐12Rβ2 on lymphocytes. We thus demonstrate an association of the protective effect of DNA vaccination with expression of IFNβ. We are currently investigating the cellular mechanisms behind this IFNβ‐mediated protection.

Protective DNA vaccination against experimental autoimmune encephalomyelitis is associated with induction of IFNβ

DNA vaccines encoding encephalitogenic peptides protect against subsequent development of rat experimental autoimmune encephalomyelitis (EAE) through unknown mechanisms. We investigated immune cell phenotypes at different time points after DNA vaccination with vaccine encoding myelin oligodendrocyte glycoprotein peptide 91–108 and subsequent induction of EAE. In protected rats, we observed (i) no alterations in antigen-specific Th2 or Th3 responses, (ii) reduced MHC II expression on splenocytes early after EAE induction, (iii) antigen-specific upregulation of IFNβ upon recall stimulation and (iv) reduced IL-12Rβ2 on lymphocytes. We suggest that the underlying mechanism of DNA vaccination is associated with immunomodulation exerted by induced IFNβ.

Interferon-β induction by Chlamydia pneumoniae in human smooth muscle cells

Clinical studies have suggested a causal or contributory role of Chlamydia pneumoniae infection in asthma and atherosclerosis. The activation of synthetic functions of smooth muscle cells (SMC) including the production of cytokines and growth factors plays a major role in the formation of fibrous atherosclerotic plaques as well as in structural remodelling of the airway wall in chronic asthma. In this study we demonstrated that C. pneumoniae induced the production of low levels of interferon (IFN)-β in bronchial and vascular SMC when infected cells were treated with tumour necrosis factor-α (TNF-α). IFN-β production was analysed by reverse transcription-PCR and enzyme-linked immunosorbent assay. The upregulation of IFN-β was paralleled by an increase in mRNA levels of interferon regulatory factor-1 and interferon-stimulated gene factor 3γ, two transcription factors activating the expression of the IFN-β gene. In addition, C. pneumoniae infection enhanced the mRNA level of indoleamine 2,3-dioxygenase, an IFN-inducible factor mediating the restriction of intracellular chlamydial growth, in TNF-α-stimulated SMC. C. pneumoniae-induced IFN-β production by SMC may modulate inflammation and tissue remodelling during respiratory and vascular infection.