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Biomedical subjects

S Akira

Publications and source records attributed to S Akira.

At least 145 records · Page 8Linked to original sources
PubMed1999

Induction of interleukin (IL)-6 by hypoxia is mediated by nuclear factor (NF)-kappa B and NF-IL6 in cardiac myocytes.

OBJECTIVES: We have previously reported that interleukin (IL)-6 is induced by hypoxic stimulation in cardiac myocytes. In the present study, we examined the induction of potent transcription factors of IL-6, nuclear factor (NF)-kappa B and NF-IL6, in cardiac myocytes subjected to hypoxia. METHODS: Five different lengths of IL-6 promoter-luciferase reporter plasmids and three mutant plasmids, in which the binding sites of NF-kappa B and/or NF-IL6 were disrupted, were transfected into neonatal rat cardiac myocytes. Luciferase activities after hypoxic stimulation were measured. Electrophoretic mobility shift assays were performed using oligonucleotides containing the binding site for NF-kappa B or NF-IL6 as a probe. RESULTS: Hypoxic stimulation for 4 h increased luciferase activity by 5.7 fold in -179/+12-luciferase reporter plasmid, whereas no significant increase was observed in -60/+12-luciferase plasmid. Decrease in luciferase activity was more prominent when the NF-kappa B binding site was disrupted rather than when the NF-IL6 binding site was disrupted. Moreover, when both sites were disrupted, luciferase activity increased only by 1.5 fold. Electrophoretic mobility shift assays demonstrated enhanced binding activity to oligonucleotides containing the NF-kappa B binding site in hypoxic cardiac myocytes, which displayed a supershift with antibody to its subunit, p50 or p65. The binding activity to the NF-IL6 probe also enhanced and displayed a supershift with antibody to NF-IL6. CONCLUSIONS: Although hypoxic stimulation induced NF-kappa B and NF-IL6 in cardiac myocytes, NF-kappa B may be the primary positive regulator of transcriptional activation of the IL-6 gene in the context of hypoxia.

Animals↗
PubMed1999

Enhanced Th1 activity and development of chronic enterocolitis in mice devoid of Stat3 in macrophages and neutrophils.

We have generated mice with a cell type-specific disruption of the Stat3 gene in macrophages and neutrophils. The mutant mice are highly susceptible to endotoxin shock with increased production of inflammatory cytokines such as TNF alpha, IL-1, IFN gamma, and IL-6. Endotoxin-induced production of inflammatory cytokines is augmented because the suppressive effects of IL-10 on inflammatory cytokine production from macrophages and neutrophils are completely abolished. The mice show a polarized immune response toward the Th1 type and develop chronic enterocolitis with age. Taken together, Stat3 plays a critical role in deactivation of macrophages and neutrophils mainly exerted by IL-10.

Animals↗
PubMed1999

Unresponsiveness of MyD88-deficient mice to endotoxin.

MyD88 is a general adaptor protein that plays an important role in the Toll/IL-1 receptor family signalings. Recently, Toll-like receptors 2 and 4 (TLR2 and TLR4) have been suggested to be the signaling receptors for lipopolysaccharide (LPS). In this study, we demonstrate that MyD88 knockout mice lack the ability to respond to LPS as measured by shock response, B cell proliferative response, and secretion of cytokines by macrophages and embryonic fibroblasts. However, activation of neither NF-kappaB nor the mitogen-activated protein (MAP) kinase family is abolished in MyD88 knockout mice. These findings demonstrate that signaling via MyD88 is essential for LPS response, but the inability of MyD88 knockout mice to induce LPS-dependent gene expression cannot simply be attributed to lack of the activation of MAP kinases and NF-kappaB.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Caspase-1-independent, Fas/Fas ligand-mediated IL-18 secretion from macrophages causes acute liver injury in mice.

IL-18, produced as a biologically inactive precursor, is processed by caspase-1 in LPS-activated macrophages. Here, we investigated caspase-1-independent processing of IL-18 in Fas ligand (FasL)-stimulated macrophages and its involvement in liver injury. Administration of Propionibacterium acnes (P. acnes) upregulated functional Fas expression on macrophages in an IFNgamma-dependent manner, and these macrophages became competent to secrete mature IL-18 upon stimulation with FasL. This was also the case for caspase-1-deficient mice. Administration of recombinant soluble FasL (rFasL) after P. acnes priming induced comparable elevation of serum IL-18 in parallel with elevated serum liver enzyme levels. However, liver injury was not induced in IL-18-deficient mice after rFasL administration. These results indicate a caspase-1-independent pathway of IL-18 secretion from FasL-stimulated macrophages and its critical involvement in FasL-induced liver injury.

Amino Acid Chloromethyl Ketones↗
PubMed1999

Differential roles of TLR2 and TLR4 in recognition of gram-negative and gram-positive bacterial cell wall components.

Toll-like receptor (TLR) 2 and TLR4 are implicated in the recognition of various bacterial cell wall components, such as lipopolysaccharide (LPS). To investigate in vivo roles of TLR2, we generated TLR2-deficient mice. In contrast to LPS unresponsiveness in TLR4-deficient mice, TLR2-deficient mice responded to LPS to the same extent as wild-type mice. TLR2-deficient macrophages were hyporesponsive to several Gram-positive bacterial cell walls as well as Staphylococcus aureus peptidoglycan. TLR4-deficient macrophages lacked the response to Gram-positive lipoteichoic acids. These results demonstrate that TLR2 and TLR4 recognize different bacterial cell wall components in vivo and TLR2 plays a major role in Gram-positive bacterial recognition.

Animals↗
PubMed1999

STAT6 deficiency in a mouse model of allergen-induced airways inflammation abolishes eosinophilia but induces infiltration of CD8+ T cells.

BACKGROUND: The TH2-type cytokines have been reported to contribute to the asthmatic response. STAT6 has an essential role in IL-4 signalling and in production of TH2 cytokines from T cells and is involved in IgE and IgG1 responses after nematode infections, indicating that STAT6 has an important role in allergic diseases. OBJECTIVE: In this study we investigated the effects of STAT6 deficiency on allergen-induced airways inflammation in mice. METHODS: Both ovalbumin (OVA)-sensitized STAT6 deficient (STAT6-/-) mice and wild-type C57BL/6 mice were challenged with aerosolized OVA. Changes in inflammatory cell infiltration and cytokine levels in lung tissue as well as serum immunoglobulin levels were analysed in OVA-challenged STAT6-/- and wild-type mice. RESULTS: The eosinophilia and lung damage normally resulting from aeroallergen challenge were not seen in STAT6-/- mice. Expression of TH2 cytokines (IL-4 and IL-5) in the lung tissue as well as IgE and IgG1 responses after OVA challenge were profoundly reduced in STAT6-/- mice, whereas expression of IFNgamma was the same in STAT6-/- mice and wild-type mice after OVA challenge. Immunocytochemical analysis of T cells showed the infiltration of CD4+ T cells but not CD8+ T cells increased into the lung of wild-type mice after OVA challenge. However, the OVA-exposed STAT6-/- mice demonstrated the infiltration of both CD4+ T cells and CD8+ T cells with a significant increase in percentage and total number of CD8+ T cells compared with OVA-exposed wild-type mice. CONCLUSION: These results indicate that factors which signal through STAT6 are important regulators of eosinophilia of allergic airway inflammation, regulating TH2-type cytokine production both in CD4+ T cells and CD8+ T cells.

Allergens↗
PubMed1999

Spatio-temporally regulated expression of receptor tyrosine kinases, mRor1, mRor2, during mouse development: implications in development and function of the nervous system.

BACKGROUND: Drosophila neurospecific receptor tyrosine kinases (RTKs), Dror and Dnrk, as well as Ror1 and Ror2 RTKs, isolated from human neuroblastoma, have been identified as a structurally related novel family of RTKs (Ror-family RTKs). Thus far, little is known about the expression and function of mammalian Ror-family RTKs. RESULTS: We have identified murine Ror-family RTKs, mRor1 and mRor2. Both mRor1 and mRor2 genes are induced upon neuronal differentiation of P19EC cells. During neuronal differentiation in vitro, the expression of mRor2 is transiently induced, although that of mRor1 increases continuously. During embryogenesis, the mRor1 gene is expressed in the developing nervous system within restricted regions and in the developing lens epithelium. The expression of mRor1 is sustained in the nervous system and is also detected in non-neuronal tissues after birth. In contrast, the expression of mRor2 is detected mainly in the developing nervous system within broader regions and declines after birth. Possible relationships of mRor1 and mRor2 genes with previously identified mutants have also been examined. CONCLUSIONS: The developmental expressions of mRor1 and mRor2, in particular in the nervous system, are differentially regulated, reflecting their expression patterns in vitro. mRor1 and mRor2 may thus play differential roles during the development of the nervous system.

Amino Acid Sequence↗
PubMed1999

IL-18-deficient mice are resistant to endotoxin-induced liver injury but highly susceptible to endotoxin shock.

IL-18 is an IL-1-related cytokine which shares biological functions with IL-12. These include the activation of NK cells, induction of IFN-gamma production and Th1 cell differentiation. In this study we analyzed the effect of IL-18 deficiency on lipopolysaccharide (LPS)-induced liver injury and endotoxin shock in Propionibacterium acnes-primed mice. P. acnes-primed IL-18-deficient (IL-18KO) mice showed resistance to LPS-induced liver injury. Unexpectedly, P. acnes-primed IL-18KO mice were highly susceptible to LPS-induced endotoxin shock. Serum level of tumor necrosis factor (TNF)-alpha were markedly elevated (approximately 10-fold higher) within 1.5 h after LPS challenge in IL-18KO mice as compared with wild-type mice. Anti-TNF-alpha antibody administration to IL-18KO mice was significantly protective against endotoxin-induced lethality. P. acnes-primed IL-18KO macrophages produced approximately 6-fold more TNF-alpha protein than did P. acnes-primed wild-type control macrophages. Taken together, these findings demonstrate that IL-18 is responsible for the progression of endotoxin-induced liver injury as well as down-regulation of endotoxin-induced TNF-alpha production in P. acnes-primed mice.

Animals↗
PubMed1999

IKK-i, a novel lipopolysaccharide-inducible kinase that is related to IkappaB kinases.

Using the suppression subtractive hybridization technique, we isolated a novel kinase, IKK-i, whose message is drastically induced by lipopolysaccharide (LPS) in the mouse macrophage cell line RAW264. 7. The predicted protein contains the kinase domain in its N-terminus, which shares 30% identity to that of IKK-alpha or IKK-beta. The C-terminal portion contains a leucine zipper and a potential helix-loop-helix domain, as in the case of IKK-alpha and IKK-beta. IKK-i is expressed mainly in immune cells, and is induced in response to proinflammatory cytokines such as tumor necrosis factor-alpha, IL-1 and IL-6, in addition to LPS. Overexpression of wild-type IKK-i phosphorylated serine residues Ser32 and Ser36 of IkappaB-alpha (preferentially Ser36), and significantly stimulated NF-kappaB activation. These results suggest that IKK-i is an inducible IkappaB kinase which may play a special role in the immune response.

Amino Acid Sequence↗
PubMed1999

Role of interleukin-18 (IL-18) in mycobacterial infection in IL-18-gene-disrupted mice.

Immunity to mycobacterial infection is closely linked to the emergence of T cells that secrete cytokines, gamma interferon (IFN-gamma), interleukin-12 (IL-12), and tumor necrosis factor alpha (TNF-alpha), resulting in macrophage activation and recruitment of circulating monocytes to initiate chronic granuloma formation. The cytokine that mediates macrophage activation is IFN-gamma, and, like IL-12, IL-18 was shown to activate Th1 cells and induce IFN-gamma production by these cells. In order to investigate the role of IL-18 in mycobacterial infection, IL-18-deficient mice were infected with Mycobacterium tuberculosis and Mycobacterium bovis BCG Pasteur, and their capacities to control bacterial growth, granuloma formation, cytokine secretion, and NO production were examined. These mice developed marked granulomatous, but not necrotic, lesions in their lungs and spleens. Compared with the levels in wild-type mice, the splenic IFN-gamma levels were low but the IL-12 levels were normal in IL-18-deficient mice. The reduced IFN-gamma production was not secondary to reduced induction of IL-12 production. The levels of NO production by peritoneal macrophages of IL-18-deficient and wild-type mice did not differ significantly. Granulomatous lesion development by IL-18-deficient mice was inhibited significantly by treatment with exogenous recombinant IL-18. Therefore, IL-18 is important for the generation of protective immunity to mycobacteria, and its main function is the induction of IFN-gamma expression.

Animals↗
PubMed1999

[Bacteria killing by macrophages via NF-IL6 gene dependent mechanism: the susceptibility to Mycobacterium leprae in NF-IL6 knockout mice].

Transcription factor, NF-IL6 recognizes the same nucleotide sequences as C/EBP, and it is predominantly expressed in macrophages. Tanaka et al. reported that NF-IL6 knockout mice are highly susceptible to Listeria monocytogenes and Salmonella typhimurium due to impairment of bacteria killing by activated macrophages. We have tried to see the susceptibility for Mycobacterium leprae infection with intraperitoneal(i.p.) or both hind foot pad (BHF) in the NF-IL6 knockout mice with wild control mice. Although we examined the cytokine genes expression and induction of such as IL-1 alpha, IL-6, IL-12, IL-18/IGIF, NO2. and TNF alpha in the peritoneal macrophages on 1 month after inoculation, also IL-2 and IL-10 by splenocytes on 1 and 8 months after infection. Following the inoculation of M. leprae with i.p. or BHF, the mice were sacrificed from 1 to 12 months after inoculation in order to confirm the multiplication and the dissemination of the infection. Many leprosy bacilli was found in the peritoneal macrophages of NF-IL6 knockout mice on 1 month after inoculation while that of the wild control mice was showing disappear. In the case of the intraperitoneal infection, NF-IL6 knockout mice shows predominantly multiplication of M. leprae on the abdemino-organs such as omentum and also scrotum with male. Although NF-IL6 knockout mice with BHF inoculation did not show any swelling at the site of inoculated foot, however the foot pad on 12 month after inoculation was processed for Fite-Faraco's stain and microscopy shows many leprosy bacilli in the intermuscular layer or around the blood vessels/sciatic nerve in the subcutaneous tissue and then the multiplication extended to the toes. Besides the induction of cytokines such as IL-1 alpha, TNF alpha and IL-12 production were observed stronger in culture supernatant of peritoneal macrophages of NF-IL6 knockout mice than that of the wild control mice. IL-2 production was also observed strong in culture supernatant in splenocytes of NF-IL6 knockout mice while that of IL-10 production never induced at anytime. This is doubtless the results of impairment of bacteria killing by macrophages via NF-IL6 gene dependent mechanism not to antigen specific immune system.

Animals↗
PubMed1998

Expressions of CCAAT/Enhancer-binding proteins beta and delta and their activities are intensified by cAMP signaling as well as Ca2+/calmodulin kinases activation in hippocampal neurons.

The transcription factor, Aplysia CCAAT enhancer-binding protein (ApC/EBP), plays a crucial role in long term facilitation, a synaptic mechanism of long term memory in Aplysia. To gain a clue to whether the mammalian C/EBP family of transcription factors are also involved in long term memory, we examined how C/EBP activities in hippocampal neurons can be modulated in response to cAMP and Ca2+, crucial inductive signals for memory formation. As a result, stimulation of either cAMP or Ca2+ signals in hippocampal neurons was found to enhance mRNA expressions and DNA binding activities of C/EBPbeta and C/EBPdelta. Furthermore, it is indicated that CaM kinases have essential roles for increasing the expression and DNA binding activities of C/EBPbeta in hippocampal neurons activated by membrane depolarization. Overexpression of constitutively active calcium/calmodulin-dependent kinase IV was found to directly stimulate either C/EBPbeta-dependent or C/EBPdelta-dependent transcription, reinforcing the evidence that C/EBP family members contribute to Ca2+-dependent transcription. Thus, these results suggest that C/EBPbeta and C/EBPdelta may be involved in the transcription-dependent phase of memory formation by increasing the expression of both the DNA binding and the transcriptional activities under the direction of cAMP and/or Ca2+ signaling in hippocampal neurons.

Animals↗
PubMed1998

Stat3 activation is responsible for IL-6-dependent T cell proliferation through preventing apoptosis: generation and characterization of T cell-specific Stat3-deficient mice.

Stat3, a member of STAT, is activated by a variety of cytokines such as IL-6 family of cytokines, granulocyte CSF, epidermal growth factor, and leptin. A recent study with mice genetically deficient in the Stat3 gene has revealed its important role in the early embryogenesis. To assess the function of Stat3 in adult tissues, we disrupted the Stat3 gene specifically in T cells by conditional gene targeting using Cre-loxP system. In Stat3-deficient T cells, IL-6-induced proliferation was severely impaired. IL-6 did not enhance cell cycle progression, but prevented apoptosis of normal T cells. In contrast, IL-6 did not prevent apoptosis of Stat3-deficient T cells. Antiapoptotic protein, Bcl-2, was normally up-regulated in response to IL-6 even in Stat3-deficient T cells. These results demonstrate that Stat3 activation is involved in IL-6-dependent T cell proliferation through prevention of apoptosis independently of Bcl-2.

Amino Acid Sequence↗
PubMed1998

DRAKs, novel serine/threonine kinases related to death-associated protein kinase that trigger apoptosis.

The present study describes the cloning of two novel serine/threonine kinases termed DRAK1 and DRAK2, whose catalytic domains are related to that of death-associated protein kinase, a serine/threonine kinase involved in apoptosis. Both DRAKs are composed of the N-terminal catalytic domain and the C-terminal domain that is responsible for regulation of kinase activity. DRAK1 and DRAK2 show 59.7% identity and display ubiquitous expression. An in vitro kinase assay revealed that both DRAKs are autophosphorylated and phosphorylate myosin light chain as an exogenous substrate, although the kinase activity of DRAK2 is significantly lower than that of DRAK1. Both DRAKs are exclusively localized to the nucleus. Furthermore, overexpression of both DRAKs induces the morphological changes of apoptosis in NIH 3T3 cells, suggesting the role of DRAKs in apoptotic signaling.

3T3 Cells↗
PubMed1998

IL-12 up-regulates IL-18 receptor expression on T cells, Th1 cells, and B cells: synergism with IL-18 for IFN-gamma production.

IL-18 is a product of macrophages and with IL-12 strikingly induces IFN-gamma production from T, B, and NK cells. Furthermore, IL-18 and 1L-12 synergize for IFN-gamma production from Th1 cells, although this combination fails to affect Th2 cells. In this study, we show that IL-12 and IL-18 promptly and synergistically induce T and B cells to develop into IFN-gamma-producing cells without engaging their Ag receptors. We also studied the mechanism underlying differences in IL-18 responsiveness between Th1 and Th2 cells. Pretreatment of T or B cells with IL-12 rendered them responsive to IL-18, which induces cell proliferation and IFN-gamma production. These IL-12-stimulated cells had both high and low affinity IL-18R and an increased IL-18R mRNA expression. In particular, IL-12-stimulated T cells strongly and continuously expressed IL-18R mRNA. However, when T cells developed into Th1 cells after stimulation with anti-CD3 and IL-12, they lowered this IL-12-induced-IL-18R mRNA expression. Then, such T cells showed a dominant response to anti-CD3 by IFN-gamma production when they were subsequently stimulated with anti-CD3 and IL-18. In contrast, Th2 cells did not express IL-18R mRNA and failed to produce IFN-gamma in response to anti-CD3 and IL-18, although they produced a substantial amount of IFN-gamma in response to anti-CD3 and IL-12. However, when Th1 and Th2 cells were stimulated with anti-CD3, IL-12, and IL-18, only the Th1 cells markedly augmented IFN-gamma production in response to IL-18, suggesting that IL-18 responsiveness between Th1 and Th2 cells resulted from their differential expression of IL-18R.

Animals↗
PubMed1998

Abrogation of bronchial eosinophilic inflammation and airway hyperreactivity in signal transducers and activators of transcription (STAT)6-deficient mice.

Signal transducers and activators of transcription 6 (STAT6) is essential for interleukin 4-mediated responses, including class switching to IgE and induction of type 2 T helper cells. To investigate the role of STAT6 in allergic asthma in vivo, we developed a murine model of allergen-induced airway inflammation. Repeated exposure of actively immunized C57BL/6 mice to ovalbumin (OVA) aerosol increased the level of serum IgE, the number of eosinophils in bronchoalveolar lavage (BAL) fluid, and airway reactivity. Histological analysis revealed peribronchial inflammation with pulmonary eosinophilia in OVA-treated mice. In STAT6-deficient (STAT6-/-) C57BL/6 mice treated in the same fashion, there were no eosinophilia in BAL and significantly less peribronchial inflammation than in wild-type mice. Moreover STAT6-/- mice had much less airway reactivity than wild-type mice. These findings suggest that STAT6 plays a crucial role in the pathogenesis of allergen-induced airway inflammation.

Animals↗