Search PubMed⌕ Search

Biomedical subjects

Kiyoshi Takeda

Publications and source records attributed to Kiyoshi Takeda.

At least 73 records · Page 4Linked to original sources
PubMed2004

Interferon-gamma production and host protective response against Mycobacterium tuberculosis in mice lacking both IL-12p40 and IL-18.

Interferon (IFN)-gamma plays an essential role in host defense against infection with Mycobacterium tuberculosis, and its synthesis is critically regulated by interleukin (IL)-12, IL-18 and the recently identified IL-23. The present study was designed to determine the roles of these cytokines in IFN-gamma-mediated host defenses against M. tuberculosis. For this purpose, we compared host protective responses in IL-12p40 and IL-18 double-knockout (DKO) mice (which lacked both IL-12/IL-18 and also IL-23) and IFN-gamma gene-disrupted (GKO) mice. DKO mice were more resistant to the infection than GKO mice, as indicated by their extended survival and reduced live colony numbers in spleen, liver and lung. IFN-gamma was detected by ELISA in liver and lung homogenates, but not in spleen and serum, and in all organs by RT-PCR in DKO mice at comparable or reduced levels to those in wild-type mice. IFN-gamma production was reduced by depletion of CD4+ T cells, but not of natural killer (NK), NKT, gammadeltaT and dendritic cells. Neutralization of IFN-gamma or TNF-alpha by specific monoclonal antibodies (mAbs) significantly shortened the survival time of the infected DKO mice. Furthermore, anti-TNF-alpha mAb partially attenuated IFN-gamma synthesis in the liver of these mice. Finally, the expression level of inducible nitric oxide synthase (iNOS) mRNA in the spleen, liver and lung was considerable in DKO mice but only marginal or undetected in GKO mice. Our results indicate the presence of IL-12-, IL-18- and IL-23-independent host protective responses against mycobacterial infection mediated by IFN-gamma, which was secreted from helper T cells.

Animals↗
PubMed2004

TIR domain-containing adaptors define the specificity of TLR signaling.

The concept that Toll-like receptors (TLRs) recognize specific molecular patterns in various pathogens has been established. In signal transduction via TLRs, MyD88, which harbors a Toll/IL-1 receptor (TIR)-domain and a death domain, has been shown to link between TLRs and MyD88-dependent downstream events leading to proinflammatory cytokine production and splenocyte proliferation. However, recent studies using MyD88-deficient mice have revealed that some TLRs possess a MyD88-independent pathway, which is represented by interferon (IFN)-beta production induced by LPS stimulation. This indicates that additional signaling molecules other than MyD88 exist in the TLR signaling pathway. Indeed, two additional TIR domain-containing adaptors, TIRAP/Mal and TRIF, have recently been identified. Both define the specific biological responses of each TLR.

Adaptor Proteins, Signal Transducing↗
PubMed2004

TLR signaling pathways.

Toll-like receptors (TLRs) have been established to play an essential role in the activation of innate immunity by recognizing specific patterns of microbial components. TLR signaling pathways arise from intracytoplasmic TIR domains, which are conserved among all TLRs. Recent accumulating evidence has demonstrated that TIR domain-containing adaptors, such as MyD88, TIRAP, and TRIF, modulate TLR signaling pathways. MyD88 is essential for the induction of inflammatory cytokines triggered by all TLRs. TIRAP is specifically involved in the MyD88-dependent pathway via TLR2 and TLR4, whereas TRIF is implicated in the TLR3- and TLR4-mediated MyD88-independent pathway. Thus, TIR domain-containing adaptors provide specificity of TLR signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Expression of Toll-like receptors 2 and 4 is downregulated after operation.

BACKGROUND: Toll-like receptors (TLR) that recognize microbial pathogens play a critical role in innate immunity; however, their expression and function after surgery remain unknown. The aim of this study was to examine TLR2 and TLR4 expression on monocytes and their responses to each agonist after surgical insults. METHODS: Blood samples were obtained from 83 patients who underwent gastrointestinal surgery. TLR2, TLR4, and inducible nitric oxide synthase expressions on peripheral blood mononuclear cells (PBMCs) were analyzed by flow cytometry. Macrophage-activating lipopeptide-2 or lipopolysaccharide-induced tumor necrosis factor-alpha and interleukin-6 production was measured by enzyme-linked immunosorbent assay. RESULTS: TLR2 and TLR4 decreased and showed the lowest values on the postoperative days 3 and 1, respectively. Macrophage-activating lipopeptide-2-stimulated tumor necrosis factor-alpha and interleukin-6 production was decreased immediately after the operation (P<.05), increased to a maximum value on postoperative day 1, and then decreased gradually. Lipopolysaccharide-stimulated tumor necrosis factor-alpha production was also suppressed immediately (P<.05) after operation then showed a gradual increase to maximum values on postoperative day 3. Inducible nitric oxide synthase in cultured PBMC that was obtained immediately after operation was upregulated (P<.05). CONCLUSION: Expressions of TLR2 and TLR4 were downregulated by operation, and agonist-induced cytokine production was suppressed transiently and soon increased through the activation of PBMC. The present study may offer new insights for postoperative modulation of innate immunity under surgical stress.

Aged↗
PubMed2004

Stimulation of human Toll-like receptor (TLR) 2 and TLR6 with membrane lipoproteins of Mycoplasma fermentans induces apoptotic cell death after NF-kappa B activation.

Mycoplasmal membrane diacylated lipoproteins not only initiate proinflammatory responses through Toll-like receptor (TLR) 2 and TLR6 via the activation of the transcriptional factor NF-kappaB, but also initiate apoptotic responses. The aim of this study was to clarify the apoptotic machineries. Mycoplasma fermentans lipoproteins and a synthetic lipopeptide, MALP-2, showed cytocidal activity towards HEK293 cells transfected with a TLR2-encoding plasmid. The activity was synergically augmented by co-expression of TLR6, but not by co-expression of other TLRs. Under the condition of co-expression of TLR2 and TLR6, the lipoproteins could induce maximum NF-kappa B activation and apoptotic cell death in the cells 6 h and 24 h after stimulation respectively. Dominant-negative forms of MyD88 and FADD, but not IRAK-4, reduced the cytocidal activity of the lipoproteins. In addition, both dominant-negative forms also downregulated the activation of both NF-kappa B and caspase-8 in the cells. Additionally, the cytocidal activity was sufficiently attenuated by a selective inhibitor of p38 MAPK. These findings suggest that mycoplasmal lipoproteins can trigger TLR2- and TLR6-mediated sequential bifurcate responses: NF-kappa B activation as an early event, which is partially mediated by MyD88 and FADD; and apoptosis as a later event, which is regulated by p38 MAPK as well as by MyD88 and FADD.

Apoptosis↗
PubMed2004

Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis.

BACKGROUND & AIMS: We tested whether the attenuation of experimental colitis by live probiotic bacteria is due to their immunostimulatory DNA, whether toll-like receptor (TLR) signaling is required, and whether nonviable probiotics are effective. METHODS: Methylated and unmethylated genomic DNA isolated from probiotics (VSL-3), DNAse-treated probiotics and Escherichia coli (DH5 alpha) genomic DNA were administered intragastrically (i.g.) or subcutaneously (s.c.) to mice prior to the induction of colitis. Viable or gamma-irradiated probiotics were administered i.g. to wild-type mice and mice deficient in different TLR or in the adaptor protein MyD88, 10 days prior to administration of dextran sodium sulfate (DSS) to their drinking water and for 7 days thereafter. RESULTS: Intragastric and s.c. administration of probiotic and E. coli DNA ameliorated the severity of DSS-induced colitis, whereas methylated probiotic DNA, calf thymus DNA, and DNase-treated probiotics had no effect. The colitis severity was attenuated to the same extent by i.g. delivery of nonviable gamma-irradiated or viable probiotics. Mice deficient in MyD88 did not respond to gamma-irradiated probiotics. The severity of DSS-induced colitis in TLR2 and TLR4 deficient mice was significantly decreased by i.g. administration of gamma-irradiated probiotics, whereas, in TLR9-deficient mice, gamma-irradiated probiotics had no effect. CONCLUSIONS: The protective effects of probiotics are mediated by their own DNA rather than by their metabolites or ability to colonize the colon. TLR9 signaling is essential in mediating the anti-inflammatory effect of probiotics, and live microorganisms are not required to attenuate experimental colitis because nonviable probiotics are equally effective.

Absorption↗
PubMed2004

Deletion of the kinase domain in death-associated protein kinase attenuates tubular cell apoptosis in renal ischemia-reperfusion injury.

Death-associated protein kinase (DAPK) is a calcium/calmodulin-dependent serine/threonine kinase localized to renal tubular epithelial cells. To elucidate the contribution of DAPK activity to apoptosis in renal ischemia-reperfusion (IR) injury, wild-type (WT) mice and DAPK-mutant mice, which express a DAPK deletion mutant that lacks a portion of the kinase domain, were subjected to renal pedicle clamping and reperfusion. After IR, DAPK activity was elevated in WT kidneys but not in mutant kidneys (1785.7 +/- 54.1 pmol/min/mg versus 160.7 +/- 60.6 pmol/min/mg). Furthermore, there were more TUNEL-positive nuclei and activated caspase 3-positive cells in WT kidneys than in mutant kidneys after IR (24.0 +/- 5.9 nuclei or 9.4 +/- 0.6 cells per high-power field [HPF] versus 6.3 +/- 2.2 nuclei or 4.4 +/- 0.7 cells/HPF at 40 h after ischemia). In addition, the increase in p53-positive tubule cells after IR was greater in WT kidney than in mutant kidneys (9.9 +/- 1.4 cells/HPF versus 0.8 +/- 0.4 cells/HPF), which is consistent with the theory that DAPK activity stabilizes p53 protein. Finally, serum creatinine levels after IR were higher in WT mice than in mutant mice (2.54 +/- 0.34 mg/dl versus 0.87 +/- 0.24 mg/dl at 40 h after ischemia). Thus, these results indicate that deletion of the kinase domain from DAPK molecule can attenuate tubular cell apoptosis and renal dysfunction after IR injury.

Animals↗
PubMed2004

Interleukin-18 improves the early defence system against influenza virus infection by augmenting natural killer cell-mediated cytotoxicity.

The role of interleukin (IL)-18 in the development of the host defence system against influenza virus infection was investigated. IL-18-deficient (IL-18(-/-)) C57BL/6 mice that were inoculated intranasally with the mouse-adapted strain of human influenza A/PR/8/34 (H1N1) virus showed an increased mortality with the occurrence of pathogenic changes in the lung for the first 3 days of infection, which included pronounced virus growth with massive infiltration of inflammatory cells and elevated nitric oxide production. The interferon-gamma (IFN-gamma) level induced in the respiratory tract of IL-18(-/-) mice in the first few days after virus infection was significantly lower but, in contrast, the IL-12 level was slightly higher than the corresponding levels in wild-type C57BL/6 mice. Natural killer (NK) cell-mediated cytotoxicity in the lung of IL-18(-/-) mice was poorly activated. Local immune responses in the lung such as specific cytotoxic T lymphocyte and antibody production were induced upon influenza virus infection equally well in both strains of mice. These results indicate that IL-18 is involved in controlling influenza virus replication in the lung, especially at an early stage of infection, through activation of the innate immune mechanisms such as IFN and NK cells.

Animals↗
PubMed2004

Limited role for interleukin-18 in the host protection response to pulmonary infection with Pseudomonas aeruginosa in mice.

We report that clearance of Pseudomonas aeruginosa, accumulation of neutrophils, and synthesis of tumor necrosis factor alpha and macrophage inflammatory protein 2 in the infected lung were not largely different in interleukin-18 (IL-18) knockout or transgenic mice compared with control mice. Our results suggest a limited role for IL-18 in the host defense against P. aeruginosa.

Animals↗
PubMed2004

Papillomavirus-like particles stimulate murine bone marrow-derived dendritic cells to produce alpha interferon and Th1 immune responses via MyD88.

Dendritic cells (DCs) link innate and adaptive immunity by sensing pathogens or vaccinogens and signaling a variety of defense responses. Since human papillomavirus type 16 L1 virus-like particles (HPV16 VLPs) induce a potent, protective immune response after vaccination, we examined their recognition by DCs. HPV16 VLPs cause phenotypic maturation of murine bone marrow-derived DCs (BMDCs), and immunization of mice with HPV16 VLP-loaded BMDCs or HPV16 VLPs alone induced T helper 1 (Th1)-biased immune responses. Analysis of transcriptional responses of murine BMDCs by microarray suggested that alpha/beta interferon (IFN-alpha/beta) transcripts and numerous proinflammatory cytokines and chemokines are up regulated in response to HPV16 VLPs. Indeed, the induction of IFN-alpha, IFN-gamma, and interleukin-12 (IL-12) production by BMDCs after stimulation with HPV16 VLPs was demonstrated by quantitative enzyme-linked immunosorbent assay. Many microbial products that induce proinflammatory responses are recognized via Toll-like receptor (TLR) signaling through the key adaptor protein MyD88 and activation of NF-kappaB, nuclear factor of activated T cells (NF-AT), and activating protein 1 (AP-1). Reporter assays indicated that HPV16 VLPs activated NF-kappaB-, NF-AT-, and AP-1-dependent transcription in the RAW264.7 macrophage cell line. Knockdown of MyD88 transcripts by small interfering RNA in the RAW264.7 macrophage cell line inhibited the activation of NF-kappaB-, NF-AT- and AP-1-dependent transcription by HPV16 VLP. Furthermore, MyD88(-/-) BMDCs failed to up regulate IL-12 and IFN-alpha and -gamma in response to HPV16 VLPs. Finally, Th1-biased immune responses to HPV16 VLPs are dramatically impaired in MyD88 and IFN-alpha/beta receptor-deficient mice. This implicates TLR recognition as central to immune recognition of HPV16 L1 VLPs.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Stat-3 is required for pulmonary homeostasis during hyperoxia.

Acute lung injury syndromes remain common causes of morbidity and mortality in adults and children. Cellular and physiologic mechanisms maintaining pulmonary homeostasis during lung injury remain poorly understood. In the present study, the Stat-3 gene was selectively deleted in respiratory epithelial cells by conditional expression of Cre-recombinase under control of the surfactant protein C gene promoter. Cell-selective deletion of Stat-3 in respiratory epithelial cells did not alter prenatal lung morphogenesis or postnatal lung function. However, exposure of adult Stat-3-deleted mice to 95% oxygen caused a more rapidly progressive lung injury associated with alveolar capillary leak and acute respiratory distress. Epithelial cell injury and inflammatory responses were increased in the Stat-3-deleted mice. Surfactant proteins and lipids were decreased or absent in alveolar lavage material. Intratracheal treatment with exogenous surfactant protein B improved survival and lung histology in Stat-3-deleted mice during hyperoxia. Expression of Stat-3 in respiratory epithelial cells is not required for lung formation, but plays a critical role in maintenance of surfactant homeostasis and lung function during oxygen injury.

Adult↗
PubMed2004

Deletion of the kinase domain in death-associated protein kinase attenuates renal tubular cell apoptosis in chronic obstructive uropathy.

Death-associated protein kinase (DAPK) is a Ca2+/calmodulin-dependent serine/threonine kinase that has been implicated as a positive mediator of apoptosis. However, little is known about the involvement of DAPK in the apoptosis associated with several pathological states, except for cancer. Here, DAPK-mutant mice were used in order to examine the role of DAPK in renal cell apoptosis in chronic obstructive uropathy (COU) created by unilateral ureteral ligation. These mice express mutant DAPK with a deletion of 74 amino acids from the catalytic kinase domain. Obstructed kidneys in wild-type and mutant mice were examined for both DAPK protein levels and renal cell apoptosis during the course of COU. Obstructed kidneys in wild-type and mutant mice showed a marked increase in the DAPK and mutant DAPK protein levels, respectively, at day 14 after ureteric ligation. The obstructed kidneys in DAPK-mutant mice displayed a significant attenuation of tubular cell apoptosis, compared with wild-type mice. In contrast, no significant difference in interstitial cell apoptosis was observed between the obstructed kidneys from wild-type and mutant mice. Thus, these results indicate that the part of the kinase domain deleted by the gene targeting is crucial for the execution of tubular cell apoptosis, but is not essential for interstitial cell apoptosis in a COU model in mice.

Animals↗
PubMed2003

IL-1R-associated kinase 4 is required for lipopolysaccharide-induced activation of APC.

The bacterial product LPS is a critical stimulus for the host immune system in the response against the corresponding bacterial infection. LPS provides an activation stimulus for macrophages and a maturation signal for dendritic cells to set up innate and adaptive immune responses, respectively. The signaling cascade of myeloid differentiation factor 88-->IL-1R-associated kinase (IRAK)-->TNFR-associated factor 6 has been implicated in mediating LPS signaling. In this report, we studied the function of IRAK-4 in various LPS-induced signals. We found that IRAK-4-deficient cells were severely impaired in producing some IFN-regulated genes as well as inflammatory cytokines in response to LPS. Among the critical downstream signaling pathways induced by LPS, NF-kappaB activation but not IFN regulatory factor 3 or STAT1 activation was defective in cells lacking IRAK-4. IRAK-4 was also required for the proper maturation of dendritic cells by LPS stimulation, particularly in terms of cytokine production and the ability to stimulate Th cell differentiation. Our results demonstrate that IRAK-4 is critical for the LPS-induced activations of APCs.

Animals↗
PubMed2003

Toll-like receptor 2 pathway drives streptococcal cell wall-induced joint inflammation: critical role of myeloid differentiation factor 88.

The IL-1R/Toll-like receptor (TLR) superfamily of receptors has a key role in innate immunity and inflammation. In this study, we report that streptococcal cell wall (SCW)-induced joint inflammation is predominantly dependent on TLR-2 signaling, since TLR-2-deficient mice were unable to develop either joint swelling or inhibition of cartilage matrix synthesis. Myeloid differentiation factor 88 (MyD88) is a Toll/IL-1R domain containing adaptor molecule known to have a central role in both IL-1R/IL-18R and TLR signaling. Mice deficient for MyD88 did not develop SCW-induced arthritis; both joint swelling and disturbance of cartilage chondrocyte anabolic function was completely abolished. Local levels of proinflammatory cytokines and chemokines in synovial tissue washouts were strongly reduced in MyD88-deficient mice. Histology confirmed the pivotal role of MyD88 in acute joint inflammation. TLR-2-deficient mice still allow influx of inflammatory cells into the joint cavity, although the number of cells was markedly reduced. No influx of inflammatory cells was seen in joints of MyD88-deficient mice. In addition, cartilage matrix proteoglycan loss was completely absent in MyD88 knockout mice. These findings clearly demonstrated that MyD88 is a key component in SCW-induced joint inflammation. Since agonists of the Toll-like pathway are abundantly involved in both septic and rheumatoid arthritis, targeting of MyD88 may be a novel therapy in inflammatory joint diseases.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Aberrant inflammation and lethality to septic peritonitis in mice lacking STAT3 in macrophages and neutrophils.

Stat3 is a transcription factor mediating anti-inflammatory properties of IL-10. In the present study, we demonstrate a pivotal role of Stat3 expressed in innate immune cells during septic peritonitis induced by cecal ligation and puncture (CLP). Mice with targeted disruption of Stat3 in macrophages and neutrophils were succumbed to septic peritonitis induced by CLP. The mice displayed an excessive local and systemic inflammation relative to the control mice, an event that was accompanied by substantial increases in the level of multiple cytokines. Hepatic and renal injury was significantly exacerbated in mice with Stat3 deficiency. Despite enhanced inflammatory responses, the mice failed to facilitate bacterial clearance as compared with the control mice. In addition, the mice exhibited an increased lethality after i.p. inoculation of live bacteria recovered from CLP-mice. In vitro, resident peritoneal macrophages from mice with Stat3 deficiency impaired bactericidal activity relative to the control whereas productions of inflammatory cytokines were significantly augmented when cells were stimulated with a synthetic lipopeptide, macrophage-activating lipopeptide-2 and LPS. Elicited macrophages and neutrophils with Stat3 deficiency also impaired bactericidal activity as compared with those with Stat3. Lysosomal enzyme release, an effector molecule for bacterial clearance, was significantly decreased in elicited leukocytes with Stat3 deficiency while increasing the production of inflammatory cytokines. Altogether, these results suggest that macrophage/neutrophil-specific STAT3 is crucial in not only modulating multiple organ failure associated with systemic inflammation but also intensifying the bactericidal activity, which highlight the significance of cell-specific Stat3 in the protective immunity during sepsis.

Animals↗
PubMed2003

Toll/IL-1 receptor domain-containing adaptor inducing IFN-beta (TRIF) associates with TNF receptor-associated factor 6 and TANK-binding kinase 1, and activates two distinct transcription factors, NF-kappa B and IFN-regulatory factor-3, in the Toll-like receptor signaling.

We previously reported a new Toll/IL-1R (TIR)-containing molecule, named TIR domain-containing adaptor inducing IFN-beta (TRIF). Although initial study indicated that TRIF possesses the ability to activate not only the NF-kappaB-dependent but also the IFN-beta promoters, the molecular mechanisms of TRIF-induced signaling are poorly understood. In this study, we investigated the signaling cascades through TRIF. TNF receptor-associated factor (TRAF)6 interacted with TRIF through the TRAF domain of TRAF6 and TRAF6-binding motifs found in the N-terminal portion of TRIF. Disruption of TRAF6-binding motifs of TRIF disabled it from associating with TRAF6, and resulted in a reduction in the TRIF-induced activation of the NF-kappaB-dependent but not IFN-beta promoter. TANK-binding kinase (TBK)-1, which was recently reported to be a kinase of IFN regulatory factor-3, which is an essential transcription factor for IFN-beta expression, also associated with the N-terminal region of TRIF. Moreover, the association between TRIF and TBK1 appeared to require the kinase activity of TBK1, as well as phosphorylation of TRIF. Because TRAF6 and TBK1 bind close the region of TRIF, it seems that TRAF6 physically prevents the association between TRIF and TBK1. Taken together, these results demonstrate that TRIF associates with TRAF6 and TBK1 independently, and activates two distinct transcription factors, NF-kappaB and IFN regulatory factor-3, respectively.

Adaptor Proteins, Vesicular Transport↗
PubMed2003

TRAM is specifically involved in the Toll-like receptor 4-mediated MyD88-independent signaling pathway.

Recognition of pathogens by Toll-like receptors (TLRs) triggers innate immune responses through signaling pathways mediated by Toll-interleukin 1 receptor (TIR) domain-containing adaptors such as MyD88, TIRAP and TRIF. MyD88 is a common adaptor that is essential for proinflammatory cytokine production, whereas TRIF mediates the MyD88-independent pathway from TLR3 and TLR4. Here we have identified a fourth TIR domain-containing adaptor, TRIF-related adaptor molecule (TRAM), and analyzed its physiological function by gene targeting. TRAM-deficient mice showed defects in cytokine production in response to the TLR4 ligand, but not to other TLR ligands. TLR4- but not TLR3-mediated MyD88-independent interferon-beta production and activation of signaling cascades were abolished in TRAM-deficient cells. Thus, TRAM provides specificity for the MyD88-independent component of TLR4 signaling.

Adaptor Proteins, Signal Transducing↗