Publications

Abstract Dendritic cells (DCs) are key regulators of the immune system; they capture antigens and then can either stimulate an immune response or induce tolerance. Our aim was to activate individual DC signaling pathways to regulate the immune response. We therefore expressed constitutive activators of mitogen-activated protein kinase (MAPK) pathways or the interferon pathway, together with tumor antigens, using lentivectors. Triggering of p38 activated DCs substantially enhanced the antitumor immune response and prolonged survival of tumor-bearing mice. Activation of extracellular signal–regulated kinase (ERK) increased TGF-β expression while expression of a constitutively activated interferon regulatory factor-3 (IRF3) stimulated IL-10 secretion by DCs. ERK and IRF3 suppressed the immune response and stimulated expansion of regulatory T cells. These results provide a toolkit to regulate immune responses to viral vector or DC immunization; vaccine responses to foreign or tumor antigens can be enhanced and harmful responses to self-antigens or introduced transgenes can be reduced.

Backgrounds A mouse receptor tyrosine kinase (RTK), mRor2, which belongs to the Ror‐family of RTKs consisting of at least two structurally related members, is primarily expressed in the heart and nervous system during mouse development. To elucidate the function of mRor2, we generated mice with a mutated mRor2 locus. Results Mice with a homozygous mutation in mRor2 died just after birth, exhibiting dwarfism, severe cyanosis, and short limbs and tails. Whole‐mount in situ hybridization analysis showed that mRor2 was expressed in the branchial arches, heart and limb/tailbuds, in addition to the developing nervous system. The mutants had cardiac septal defects, mainly a ventricular septal defect. In addition, an examination of the skeletal systems revealed that the mutants had shorter limbs, vertebrae and facial structure, with a particular defect in their distal portions, and that almost no calcification was observed in their distal limbs. Histological examination showed abnormalities in the chondrocytes. Conclusions Our findings suggest that mRor2 plays essential roles in the development of the heart and in limb/tail formation, in particular cardiac septal formation and ossification of distal portions of limbs and tails.

5,6-Dimethylxanthenone-4-acetic acid (DMXAA), a potent type I interferon (IFN) inducer, was evaluated as a chemotherapeutic agent in mouse cancer models and proved to be well tolerated in human cancer clinical trials. Despite its multiple biological functions, DMXAA has not been fully characterized for the potential application as a vaccine adjuvant. In this report, we show that DMXAA does act as an adjuvant due to its unique property as a soluble innate immune activator. Using OVA as a model antigen, DMXAA was demonstrated to improve on the antigen specific immune responses and induce a preferential Th2 (Type-2) response. The adjuvant effect was directly dependent on the IRF3-mediated production of type-I-interferon, but not IL-33. DMXAA could also enhance the immunogenicity of influenza split vaccine which led to significant increase in protective responses against live influenza virus challenge in mice compared to split vaccine alone. We propose that DMXAA can be used as an adjuvant that targets a specific innate immune signaling pathway via IRF3 for potential applications including vaccines against influenza which requires a high safety profile.

Transcription factors known as CCAAT enhancer binding proteins (C/EBPs) are involved in hematopoietic differentiation, including myelopoiesis and granulopoiesis. C/EBPβ-deficient mice develop normally; however, they exhibit defective macrophage function, resulting in increased susceptibility to infection. Little is known about the role of C/EBPβ in granulopoiesis; therefore, we examined granulopoiesis in C/EBPβ-deficient mice. Morphology, the number of peripheral blood and bone marrow cells, and the expression of genes specific for the myeloid lineage were normal in C/EBPβ-deficient mice. Interestingly, the hematopoietic progenitor cells of C/EBPβ-deficient mice did not respond normally to granulocyte/macrophage-colony stimulating factor and granulocyte colony stimulating factor. In addition, C/EBPβ-deficient neutrophils displayed enhanced apoptosis compared with wild-type neutrophils. Our present results indicate that C/EBPβ helps regulate survival of neutrophils, downstream of the granulocyte colony stimulating factor receptor.

No abstract is provided for this article.

TLRs can activate two distinct branches of downstream signaling pathways. MyD88 and Toll/IL-1R domain-containing adaptor inducing IFN-β (TRIF) pathways lead to the expression of proinflammatory cytokines and type I IFN genes, respectively. Numerous reports have demonstrated that resveratrol, a phytoalexin with anti-inflammatory effects, inhibits NF-κB activation and other downstream signaling pathways leading to the suppression of target gene expression. However, the direct targets of resveratrol have not been identified. In this study, we attempted to identify the molecular target for resveratrol in TLR-mediated signaling pathways. Resveratrol suppressed NF-κB activation and cyclooxygenase-2 expression in RAW264.7 cells following TLR3 and TLR4 stimulation, but not TLR2 or TLR9. Further, resveratrol inhibited NF-κB activation induced by TRIF, but not by MyD88. The activation of IFN regulatory factor 3 and the expression of IFN-β induced by LPS, poly(I:C), or TRIF were also suppressed by resveratrol. The suppressive effect of resveratrol on LPS-induced NF-κB activation was abolished in TRIF-deficient mouse embryonic fibroblasts, whereas LPS-induced degradation of IκBα and expression of cyclooxygenase-2 and inducible NO synthase were still inhibited in MyD88-deficient macrophages. Furthermore, resveratrol inhibited the kinase activity of TANK-binding kinase 1 and the NF-κB activation induced by RIP1 in RAW264.7 cells. Together, these results demonstrate that resveratrol specifically inhibits TRIF signaling in the TLR3 and TLR4 pathway by targeting TANK-binding kinase 1 and RIP1 in TRIF complex. The results raise the possibility that certain dietary phytochemicals can modulate TLR-derived signaling and inflammatory target gene expression and can alter susceptibility to microbial infection and chronic inflammatory diseases.

The role of the Toll-like receptor (TLR)-2 in the generation of protective immunity to Mycobacterium avium was evaluated using gene-disrupted mice. TLR-2-/- mice were more susceptible than wild-type C57Bl/6 mice to M. avium strains that were able to proliferate in vivo before the development of protective immunity and mycobacteriostasis. In contrast, the elimination of non-virulent strains was not affected by the mutation. The generation of interferon-gamma (IFN-gamma)-producing T cells and the expression of the interleukin-12 p40 gene were reduced in TLR-2-deficient mice as compared to C57Bl/6 mice early during infection with M. avium strain 2447. The generation of protective CD4+ T cells was also compromised in the mutated mice as compared with the controls. Our data show that TLR-2 is required for optimal immunity against certain virulent M. avium strains.

Group 2 innate lymphoid cells (ILC2s) are a critical innate source of type 2 cytokines in allergic inflammation. Although ILC2s are recognized as a critical cell population in the allergic inflammation, the regulatory mechanism(s) of ILC2s are less well understood. Here, we show that Regnase-1, an immune regulatory RNAse that degrades inflammatory mRNAs, negatively regulates ILC2 function and that IκB kinase (IKK) complex–mediated Regnase-1 degradation is essential for IL-33– and IL-25–induced ILC2 activation. ILC2s from Regnase-1AA/AA mice expressing a Regnase-1 S435A/S439A mutant resistant to IKK complex–mediated degradation accumulated Regnase-1 protein in response to IL-33 and IL-25. IL-33– and IL-25–stimulated Regnase-1AA/AA ILC2s showed reduced cell proliferation and type 2 cytokine (IL-5, IL-9, and IL-13) production and increased cell death. In addition, Il2ra and Il1rl1, but not Il5, Il9, or Il13, mRNAs were destabilized in IL-33–stimulated Regnase-1AA/AA ILC2s. In vivo, Regnase-1AA/AA mice showed attenuated acute type 2 pulmonary inflammation induced by the instillation of IL-33, IL-25, or papain. Furthermore, the expulsion of Nippostrongylus brasiliensis was significantly delayed in Regnase-1AA/AA mice. These results demonstrate that IKK complex–mediated Regnase-1 degradation is essential for ILC2-mediated type 2 responses both in vitro and in vivo. Therefore, controlling Regnase-1 degradation is a potential therapeutic target for ILC2-contributed allergic disorders.

The ocular surface epithelium is part of the mucosal defense system. Because transcription factor NF-kappa B in mucosal epithelial cells plays a central role in regulating the genes that govern the onset of mucosal inflammatory responses, we examined the role of a regulator of NF-kappa B, I kappa B zeta, in murine ocular surface inflammation.The eyes of I kappa B zeta(-/-) mice were analyzed biomicroscopically and histologically. I kappa B zeta expression in normal mouse cornea and conjunctiva was examined by RT-PCR. The results were compared with those obtained in other tissues by real-time PCR. I kappa B zeta mRNA on the ocular surface and in other mucosal tissues was localized by in situ hybridization.I kappa B zeta(-/-) mice manifested chronic inflammation, specifically in the ocular surface, but not in other tissues. In normal mice, I kappa B zeta was expressed in a variety of mucosal tissues. The I kappa B zeta transcript was predominantly distributed in the epithelia of these tissues. As inflammatory symptoms progressed on the ocular surface of I kappa B zeta(-/-) mice, inflammatory cells, mainly CD45R/B220(+) and CD4(+) cells, intensely infiltrated the submucosa of the conjunctival epithelia. This infiltration was accompanied by an almost complete loss of goblet cells in the conjunctival epithelia.The authors postulate that I kappa B zeta in the ocular surface epithelia negatively regulates the pathologic progression of ocular surface inflammation.

Identification of cis- and trans-acting factors regulating gene expression remains an important problem in biology. Bioinformatics analyses of regulatory regions are hampered by several difficulties. One is that binding sites for regulatory proteins are often not significantly over-represented in the set of DNA sequences of interest, because of high levels of false positive predictions, and because of positional restrictions on functional binding sites with regard to the transcription start site.We have developed a novel method for the detection of regulatory motifs based on their local over-representation in sets of regulatory regions. The method makes use of a Parzen window-based approach for scoring local enrichment, and during evaluation of significance it takes into account GC content of sequences. We show that the accuracy of our method compares favourably to that of other methods, and that our method is capable of detecting not only generally over-represented regulatory motifs, but also locally over-represented motifs that are often missed by standard motif detection approaches. Using a number of examples we illustrate the validity of our approach and suggest applications, such as the analysis of weaker binding sites.Our approach can be used to suggest testable hypotheses for wet-lab experiments. It has potential for future analyses, such as the prediction of weaker binding sites. An online application of our approach, called LocaMo Finder (Local Motif Finder), is available at http://sysimm.ifrec.osaka-u.ac.jp/tfbs/locamo/.

Objectives The objectives of this study were to determine whether late apoptotic cell material directly induces autoantibodies characteristic of systemic lupus erythematosus (SLE) and to investigate the innate recognition pathways involved. Methods B6, B6.MyD88 –/– , B6.TLR7 –/– and B6.TLR9 –/– mice were subcutaneously injected with B6 syngeneic late apoptotic thymocytes (SLATs) without adjuvant on days 0, 10, 24 and 37. Sera were tested for IgG antibodies to histones and double-stranded DNA (dsDNA) by ELISA and Crithidia luciliae indirect immunofluorescence. IgG and C3 deposition in kidney glomeruli was assessed by immunostaining and fluorescence microscopy. Results SLAT injections induced anti-dsDNA and anti-histone antibodies of the IgG1 and IgG2b isotypes in B6 but not MyD88 –/– mice. TLR7 –/– and TLR9 –/– mice injected with SLATs produced delayed or slightly more robust responses, respectively. SLAT injections induced IgG deposits in renal glomeruli of B6, TLR7 –/– and TLR9 –/– mice that were absent in MyD88 –/– mice. Unlike B6 and TLR9 –/– animals, TLR7 –/– mice failed to exhibit IgG colocalised glomerular C3 deposits and demonstrated autoantibodies of primarily the IgG2a isotype. Conclusions Late apoptotic cell-induced anti-histone and anti-dsDNA antibodies require MyD88 but not Toll-like receptor (TLR)9. Moreover, TLR7 promotes glomerular C3 deposition, possibly through a mechanism of altered antibody isotype switching.

Toll-like receptors (TLRs) recognize a variety of microbial components and mediate downstream signal transduction pathways that culminate in the activation of nuclear factor κB (NF-κB) and mitogen-activated protein (MAP) kinases. Trib1 is reportedly involved in the regulation of NF-κB and MAP kinases, as well as gene expression in vitro. To clarify the physiological function of Trib1 in TLR-mediated responses, we generated Trib1-deficient mice by gene targeting. Microarray analysis showed that Trib1-deficient macrophages exhibited a dysregulated expression pattern of lipopolysaccharide-inducible genes, whereas TLR-mediated activation of MAP kinases and NF-κB was normal. Trib1 was found to associate with NF-IL6 (also known as CCAAT/enhancer-binding protein β). NF-IL6–deficient cells showed opposite phenotypes to those in Trib1-deficient cells in terms of TLR-mediated responses. Moreover, overexpression of Trib1 inhibited NF-IL6–dependent gene expression by down-regulating NF-IL6 protein expression. In contrast, Trib1-deficient cells exhibited augmented NF-IL6 DNA-binding activities with increased amounts of NF-IL6 proteins. These results demonstrate that Trib1 is a negative regulator of NF-IL6 protein expression and modulates NF-IL6–dependent gene expression in TLR-mediated signaling.