Biomedical subjects

Akihiko Yoshimura

Publications and source records attributed to Akihiko Yoshimura.

At least 19 recordsLinked to original sources

PubMed2007

Socs 3 modulates the activity of the transcription factor Stat3 in mammary tissue and controls alveolar homeostasis.

Signal transducer and activator of transcription 5 and 3 (Stat5 and Stat3) control pregnancy-mediated mammary development and involution-dependent remodeling, respectively. Suppressor of cytokine signaling 3 (Socs3) has been implicated in the modulation of both Stat3 and Stat5 activity. To explore the biology of Socs3 in mammary tissue, the gene was deleted using Cre-mediated recombination. Deletion of the Socs3 gene from mammary stem or early progenitor cells did not grossly alter pregnancy-mediated mammary development but resulted in impaired lactation due to attenuated proliferation. Loss of Socs3 from differentiated luminal cells did not interfere with glandular function during lactation, but resulted in accelerated tissue remodeling upon weaning. Loss of Socs3 led to enhanced and precocious Stat3 activation. Thus, Socs3 serves as a modulator of Stat3 activity to ensure controlled proliferation and apoptosis in pregnancy and involution, respectively.

Animals↗

PubMed2006

Sprouty2 and Sprouty4 are essential for embryonic morphogenesis and regulation of FGF signaling.

Sprouty genes encode cytoplasmic membrane-associated proteins that inhibit receptor tyrosine kinase signaling. Four orthologs of Drosophila Sprouty (dSpry) (Sprouty1-4) have been identified in mammals. Physiological function of Sprouty1 and Sprouty2 has been investigated using gene targeting approaches, however to date detailed examination of Sprouty4 knockout (KO) mice has not been reported. In this study, Sprouty4 KO mice were generated and characterized. Although a significant fraction of Sprouty4 KO mice died shortly after birth due to mandible defects, the remainder were viable and fertile. Growth retardation was observed for most Sprouty4-deficient mice, with nearly all Sprouty4 KO mice having polysyndactyly. ERK activation was sustained in Sprouty4 KO mouse embryonic fibroblasts (MEFs) in response to FGF, but not to EGF. Sprouty2 and Sprouty4 double KO (DKO) mice were embryonic lethal and showed severe defects in craniofacial, limb, and lung morphogenesis. These findings suggest both redundant and non-redundant functions for Sprouty2 and Sprouty4 on embryonic development and FGF signaling.

Adaptor Proteins, Signal Transducing↗

PubMed2006

SOCS3 is required to temporally fine-tune photoreceptor cell differentiation.

Suppressor of cytokine signaling 3 (SOCS3) is an intracellular, ligand-induced negative feedback modulator of STAT3 activation that acts during inflammation. Here, we demonstrate that SOCS3 expression is important for normal retinal development in the perinatal period. STAT3 is highly activated in the late-embryonic retina, then downregulated at postnatal day 0 (P0), presumably by the depletion of upstream ligands. We found that SOCS3 was required after P0 to shut down the residual STAT3 activation; this loss of activated STAT3 leads to Rhodopsin expression and rod photoreceptor cell differentiation. SOCS3 deficiency failed to terminate STAT3 activation, thereby delaying expression of Rhodopsin and its upstream transcription factor, crx. Development subsequently continued, but its course was temporally erratic, probably because of faulty compensation. Interestingly, SOCS3 protein expression was first detected postnatally, after STAT3 activation was mostly downregulated. It initially appeared in some of the presumptive photoreceptor cells and gradually spread. SOCS3 mRNA level was constant from the late-embryonic to early-postnatal period. Post-transcriptional inhibition of SOCS3 protein expression maintains a high STAT3 activation during late embryogenesis, and after P0, releasing from the inhibition promptly terminates STAT3 activation. Thus, SOCS3 can act as a temporal fine-tuner of STAT3 activation during photoreceptor cell differentiation.

Animals↗

PubMed2006

Innate defense mechanism against virus infection within the cardiac myocyte requiring gp130-STAT3 signaling.

BACKGROUND: Little is known about innate immune mechanisms within the cardiac myocyte that determine susceptibility to enterovirus infection, an important cause of myocarditis and subsequent heart failure. Although interferon (IFN) generally plays a key role in innate immunity, ablation of IFN receptors has little or no effect on acute coxsackievirus B3 infection in the heart. Interestingly, gp130-cytokine-mediated stimulation of neonatal ventricular myocytes has a cytoprotective effect against virus infection in culture that can be inhibited by suppressors of cytokine signaling (SOCS)-3, a physiological inhibitor of gp130 signaling that does not affect IFN signaling. Therefore, we hypothesized that inhibition of gp130 signaling by SOCS3 would change cardiac myocyte susceptibility to virus infection without affecting IFN signaling. METHODS AND RESULTS: We generated cardiac-specific SOCS3 transgenic mice. Despite an intact IFN-mediated antiviral response in adult transgenic myocytes, there was a marked increase in susceptibility to viral infection in the SOCS3 transgenic mouse hearts. This indicated the presence of IFN-independent innate defense mechanisms within the cardiac myocyte. Subsequently, we demonstrated that cardiac-specific gp130-knockout mice also had increased susceptibility to viral infection. Furthermore, we demonstrated that the gp130-mediated increase in survival of infected myocytes occurred through a signal transducers and activators of transcription-3-dependent mechanism that did not affect viral replication. This was accompanied by a persistent expression of full-length dystrophin after coxsackievirus B3 infection. In addition, we found that both SOCS3 transgenic and gp130-deficient mice had a decrease in alpha-sarcoglycan. CONCLUSIONS: SOCS3-mediated regulation of gp130 signaling can affect susceptibility to viral infection in the heart. Increased cardiac cell survival through gp130-signal transducers and activators of transcription-3 signaling appears to play an important role in preserving nondividing cardiac myocytes until specific immune responses begin to clear the virus.

Animals↗

PubMed2006

Two-sided roles of IL-27: induction of Th1 differentiation on naive CD4+ T cells versus suppression of proinflammatory cytokine production including IL-23-induced IL-17 on activated CD4+ T cells partially through STAT3-dependent mechanism.

Recent lines of evidence have demonstrated that IL-27, a newly identified IL-12-related cytokine, has two apparently conflicting roles in immune responses: one as an initiator of Th1 responses and the other as an attenuator of inflammatory cytokine production. Although the IL-27-mediated Th1 initiation mechanism has been elucidated, little is known about the molecular basis for the suppression of cytokine production. In the present study, we demonstrated that IL-27 suppressed the production of various proinflammatory cytokines by fully activated CD4+ T cells while it had no effect on the cytokine production by CD4+ T cells at early phases of activation. IL-27 also suppressed IL-17 production by activated CD4+ T cells, thereby counteracting IL-23, another IL-12-related cytokine with proinflammatory effects. In fully activated CD4+ T cells, STAT3 was preferentially activated by IL-27 stimulation, whereas both STAT1 and 3 were activated by IL-27 in early activated CD4+ T cells. Lack of STAT3 in fully activated cells impaired the suppressive effects of IL-27. These data indicated that the preferential activation of STAT3 in fully activated CD4+ T cells plays an important role in the cytokine suppression by IL-27/WSX-1.

Animals↗

PubMed2006

Loss of SOCS3 gene expression converts STAT3 function from anti-apoptotic to pro-apoptotic.

The transcription factor STAT3 is activated by interleukin-6-related cytokines and has been implicated as an oncogene; it promotes cell proliferation and is anti-apoptotic. However, in some cases, STAT3 has been shown to be pro-apoptotic, especially in mammary epithelial cells. In this report, we generated SOCS3-deficient murine embryonic fibroblasts (MEFs), in which STAT3 activation is extremely enhanced and prolonged. We found that LIF induces caspase-3 activation and apoptosis of SOCS3(-/-) MEFs. Exogenous expression of the dominant negative form of STAT3 but not STAT1 suppressed LIF-induced apoptosis of SOCS3(-/-) MEFs, indicating that STAT3 plays a critical role in apoptosis induction. As shown in mammary gland epithelial cells, expression of the phosphatidylinositol 3-kinase regulatory subunits p50alpha and p55alpha was induced in response to LIF in SOCS3(-/-) MEFs but not in wild-type MEFs, and Akt/protein kinase B activity was substantially reduced in SOCS3(-/-) MEFs. Furthermore, we found that some of the STAT3 target genes related to apoptosis and proliferation, such as Bcl-2 and cyclin D1, were repressed upon LIF treatment in SOCS3(-/-) cells. Not only the up-regulation of p50alpha and p55alpha but also the repression of cyclin D1 and Bcl-2 in SOCS3(-/-) MEFs was inhibited by dominant negative STAT3. These data suggest that prolonged activation of STAT3 could induce apoptosis/growth arrest rather than anti-apoptosis and proliferation in certain cases, and SOCS3 is a critical regulator of this balance.

Animals↗

PubMed2006

ER stress-induced apoptosis and caspase-12 activation occurs downstream of mitochondrial apoptosis involving Apaf-1.

Accumulation of unfolded proteins induces endoplasmic reticulum (ER) stress. Excessive and prolonged stresses lead cells to apoptosis. However, the precise molecular mechanisms of ER stress-induced apoptosis have not been fully elucidated. We investigated the involvement of the apoptosome in ER stress-induced cell death pathway using mouse embryonic fibroblasts (MEFs) and mice deficient for Apaf-1. Apaf-1-deficient MEFs showed more resistance to ER stress-inducing reagents as compared with wild type cells. Despite comparable induction of ER stress in both wild type and Apaf-1-deficient cells, activation of caspase-3 was only observed in wild type, but not Apaf-1-deficient, MEFs. Under ER stress conditions, BAX translocated to mitochondria and cytochrome c was released from mitochondria. We also demonstrated that caspase-12 was processed downstream of Apaf-1 and caspase-3, and neither overexpression nor knockdown of caspase-12 affected susceptibility of the cells to ER stress-induced cell death. Furthermore, in the kidneys of Apaf-1-deficient mice, apoptosis induced by in vivo administration of tunicamycin was remarkably suppressed as compared with wild type mice. These data collectively demonstrated that Apaf-1 and the mitochondrial pathway of apoptosis play significant roles in ER stress-induced apoptosis.

Animals↗

PubMed2006

Interleukin 27 negatively regulates the development of interleukin 17-producing T helper cells during chronic inflammation of the central nervous system.

Studies have focused on the events that influence the development of interleukin 17 (IL-17)-producing T helper cells (T(H)-17 cells) associated with autoimmunity, such as experimental autoimmune encephalitis, but relatively little is known about the cytokines that antagonize T(H)-17 cell effector responses. Here we show that IL-27 receptor-deficient mice chronically infected with Toxoplasma gondii developed severe neuroinflammation that was CD4+ T cell dependent and was associated with a prominent IL-17 response. In vitro, treatment of naive primary T cells with IL-27 suppressed the development T(H)-17 cells induced by IL-6 and transforming growth factor-beta, which was dependent on the intracellular signaling molecule STAT1 but was independent of inhibition of IL-6 signaling mediated by the suppressor protein SOCS3. Thus IL-27, a potent inhibitor of T(H)-17 cell development, may be a useful target for treating inflammatory diseases mediated by these cells.

Animals↗

PubMed2006

Conditional ablation of Stat3 or Socs3 discloses a dual role for reactive astrocytes after spinal cord injury.

In the injured central nervous system (CNS), reactive astrocytes form a glial scar and are considered to be detrimental for axonal regeneration, but their function remains elusive. Here we show that reactive astrocytes have a crucial role in wound healing and functional recovery by using mice with a selective deletion of the protein signal transducer and activator of transcription 3 (Stat3) or the protein suppressor of cytokine signaling 3 (Socs3) under the control of the Nes promoter-enhancer (Nes-Stat3(-/-), Nes-Socs3(-/-)). Reactive astrocytes in Nes-Stat3(-/-) mice showed limited migration and resulted in markedly widespread infiltration of inflammatory cells, neural disruption and demyelination with severe motor deficits after contusive spinal cord injury (SCI). On the contrary, we observed rapid migration of reactive astrocytes to seclude inflammatory cells, enhanced contraction of lesion area and notable improvement in functional recovery in Nes-Socs3(-/-) mice. These results suggest that Stat3 is a key regulator of reactive astrocytes in the healing process after SCI, providing a potential target for intervention in the treatment of CNS injury.

Animals↗

PubMed2006

IFNgamma-dependent, spontaneous development of colorectal carcinomas in SOCS1-deficient mice.

Approximately 20% of human cancers are estimated to develop from chronic inflammation. Recently, the NF-kappaB pathway was shown to play an essential role in promoting inflammation-associated cancer, but the role of the JAK/STAT pathway, another important signaling pathway of proinflammatory cytokines, remains to be investigated. Suppressor of cytokine signaling-1 (SOCS1) acts as an important physiological regulator of cytokine responses, and silencing of the SOCS1 gene by DNA methylation has been found in several human cancers. Here, we demonstrated that SOCS1-deficient mice (SOCS1-/- Tg mice), in which SOCS1 expression was restored in T and B cells on a SOCS1-/- background, spontaneously developed colorectal carcinomas carrying nuclear beta-catenin accumulation and p53 mutations at 6 months of age. However, interferon (IFN)gamma-/- SOCS1-/- mice and SOCS1-/- Tg mice treated with anti-IFNgamma antibody did not develop such tumors. STAT3 and NF-kappaB activation was evident in SOCS1-/- Tg mice, but these were not sufficient for tumor development because these are also activated in IFNgamma-/- SOCS1-/- mice. However, colons of SOCS1-/- Tg mice, but not IFNgamma-/- SOCS1-/- mice, showed hyperactivation of STAT1, which resulted in the induction of carcinogenesis-related enzymes, cyclooxygenase-2 and inducible nitric oxide synthase. These data strongly suggest that SOCS1 is a unique antioncogene which prevents chronic inflammation-mediated carcinogenesis by regulation of the IFNgamma/STAT1 pathways.

Animals↗

PubMed2006

Pigment epithelium-derived factor inhibits advanced glycation end product-induced retinal vascular hyperpermeability by blocking reactive oxygen species-mediated vascular endothelial growth factor expression.

Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis, suggesting that loss of PEDF contributes to proliferative diabetic retinopathy. However, the role of PEDF against retinal vascular hyperpermeability remains to be elucidated. We investigated here whether and how PEDF could inhibit the advanced glycation end product (AGE) signaling to vascular hyperpermeability. Intravenous administration of AGEs to normal rats not only increased retinal vascular permeability by stimulating vascular endothelial growth factor (VEGF) expression but also decreased retinal PEDF levels. Simultaneous treatments with PEDF inhibited the AGE-elicited VEGF-mediated permeability by down-regulating mRNA levels of p22(phox) and gp91(phox), membrane components of NADPH oxidase, and subsequently decreasing retinal levels of an oxidative stress marker, 8-hydroxydeoxyguanosine. PEDF also inhibited the AGE-induced vascular hyperpermeability evaluated by transendothelial electrical resistance by suppressing VEGF expression. Furthermore, PEDF decreased reactive oxygen species (ROS) generation in AGE-exposed endothelial cells by suppressing NADPH oxidase activity via down-regulation of mRNA levels of p22(PHOX) and gp91(PHOX). This led to blockade of the AGE-elicited Ras activation and NF-kappaB-dependent VEGF gene induction in endothelial cells. These results indicate that the central mechanism for PEDF inhibition of the AGE signaling to vascular permeability is by suppression of NADPH oxidase-mediated ROS generation and subsequent VEGF expression. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy.

Adult↗

PubMed2006

Selective regulatory function of Socs3 in the formation of IL-17-secreting T cells.

Suppressor of cytokine signaling (Socs) 3 is a cytokine-inducible inhibitor with critical but selective cell-specific effects. We show that deficiency of Socs3 in T cells had minimal effects on differentiation of T cells to the T helper (Th) 1 or Th2 subsets; accordingly, Socs3 had no effect on IL-12-dependent signal transducer and activator of transcription (Stat) 4 phosphorylation or IL-4-dependent Stat6 phosphorylation. By contrast, Socs3 was found to be a major regulator of IL-23-mediated Stat3 phosphorylation and Th17 generation, and Stat3 directly binds to the IL-17A and IL-17F promoters. We conclude that Socs3 is an essential negative regulator of IL-23 signaling, inhibition of which constrains the generation of Th17 differentiation.

Animals↗

PubMed2006

SOCS1-negative feedback of STAT1 activation is a key pathway in the dsRNA-induced innate immune response of human keratinocytes.

Toll-like receptor (TLR)3 is a receptor for virus-associated double-stranded RNA, and triggers antiviral immune responses during viral infection. Epidermal keratinocytes express TLR3 and provide an innate immune defense against viral infection. Since the intracellular regulatory mechanism is unknown, we hypothesized that the signal transducers and activators of transcription (STAT)-suppressors of cytokine signaling (SOCS) system regulates the innate immune response of keratinocytes. Treatment with polyinosinic-polycytidylic acid (poly(I:C)) resulted in the rapid translocation of IFN regulatory factor (IRF)-3 into the nucleus, followed by phosphorylation of STAT1 and STAT3. The activation of STATs by poly(I:C) probably occurs in an indirect fashion, through poly(I:C)-induced IFN. We infected cells with the dominant-negative forms of STAT1 (STAT1F), STAT3 (STAT3F), and SOCS1 using adenovirus vectors. Infection with STAT1F suppressed the induction of macrophage inflammatory protein (MIP)-1alpha by poly(I:C), whereas STAT3F had a minimal effect, which indicates that STAT1 mediates MIP-1alpha induction. SOCS1, which is a negative feedback regulator of STAT1 signaling, was induced by treatment with poly(I:C). SOCS1 infection inhibited the phosphorylation of STAT1 and significantly reduced poly(I:C)-induced MIP-1alpha production. Furthermore, STAT1-SOCS1 regulated poly(I:C)-induced TLR3 and IRF-7 expression. However, SOCS1 did not affect NF-kappaB signaling. Thus, the STAT1-SOCS1 pathway regulates the innate immune response via TLR3 signaling in epidermal keratinocytes.

Adenoviruses, Human↗

PubMed2006

A novel Zinc finger protein, ZCCHC11, interacts with TIFA and modulates TLR signaling.

Toll-like receptors (TLRs) play an important role as a sensor of microbial pathogens in the innate immune response. TLRs transmit signals through the recruitment of adaptor proteins including tumor necrosis factor-associated factor 6 (TRAF6), which mediates the activation of IkappaB kinase (IKK). TIFA (TRAF-interacting protein with a forkhead-associated (FHA) domain) has been shown to bind to TRAF6 and activate IKK by promoting the oligomerization and ubiquitin-ligase activity of TRAF6. FHA domains preferentially bind to phospho-threonine residues in their targets. Here, we identified a novel zinc finger protein, ZCCHC11, that interacts with TIFA from phosphoproteins of a macrophage cell line, RAW 264.7, by using affinity purification with GST-TIFA and mass spectrometric analysis. By a search of the EST database, we found a 200kDa full-length form (ZCCHC11L). ZCCHC11L was mostly located to the nucleus, but translocated into the cytoplasm in response to LPS and bound to TIFA. Overexpression and knockdown by siRNA indicated that ZCCHC11 functions as a negative regulator of TLR-mediated NF-kappaB activation. The N-terminal region (ZCCHC11S) including C2H2-type [corrected] Zn-finger motif was sufficient for suppression of NF-kappaB. We propose that ZCCHC11 is a unique TLR signal regulator, which interacts with TIFA after LPS treatment and suppresses the TRAF6-dependent activation of NF-kappaB.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Loss of SOCS3 in T helper cells resulted in reduced immune responses and hyperproduction of interleukin 10 and transforming growth factor-beta 1.

Suppressor of cytokine signaling (SOCS)3 is a major negative feedback regulator of signal transducer and activator of transcription (STAT)3-activating cytokines. Transgenic mouse studies indicate that high levels of SOCS3 in T cells result in type 2 T helper cell (Th2) skewing and lead to hypersensitivity to allergic diseases. To define the physiological roles of SOCS3 in T cells, we generated T cell-specific SOCS3 conditional knockout mice. We found that the mice lacking SOCS3 in T cells showed reduced immune responses not only to ovalbumin-induced airway hyperresponsiveness but also to Leishmania major infection. In vitro, SOCS3-deficient CD4+ T cells produced more transforming growth factor (TGF)-beta1 and interleukin (IL)-10, but less IL-4 than control T cells, suggesting preferential Th3-like differentiation. We found that STAT3 positively regulates TGF-beta1 promoter activity depending on the potential STAT3 binding sites. Furthermore, chromatin immunoprecipitation assay revealed that more STAT3 was recruited to the TGF-beta1 promoter in SOCS3-deficient T cells than in control T cells. The activated STAT3 enhanced TGF-beta1 and IL-10 expression in T cells, whereas the dominant-negative form of STAT3 suppressed these. From these findings, we propose that SOCS3 regulates the production of the immunoregulatory cytokines TGF-beta1 and IL-10 through modulating STAT3 activation.

Animals↗

PubMed2006

The neuropeptide neuromedin U promotes IL-6 production from macrophages and endotoxin shock.

Neuromedin U (NMU) is a neuropeptide involved in appetite, circadian rhythm, and pronociception. However, the NMU receptor NMU-R1 has been shown to be expressed in immune cells and NMU promotes mast cell-dependent inflammation. In this study, we demonstrated that NMU plays an important role in IL-6 production in macrophages. NMU-deficient mice were resistant against cecal ligation puncture- as well as LPS-induced septic shock. IL-6 but not TNF-alpha levels were markedly reduced in LPS-treated NMU-deficient mice compared with wild type mice. Both NMU and NMU-R1 were expressed in wild type peritoneal macrophages, and treatment with LPS resulted in up-regulation of NMU but down-regulation of NMU-R1 expression, however, no down-regulation of NMU-R1 was observed in NMU-deficient macrophages where LPS-induced IL-6 production was severely reduced. These data suggest that LPS-induced IL-6 expression is partly dependent on autocrine/paracrine activation of the NMU-NMU-R1 signals in macrophages.

Animals↗

PubMed2006

Suppression of IL-6 production and proliferation by blocking STAT3 activation in malignant soft tissue tumor cells.

There is no established optimum treatment for malignant fibrous histiocytoma (MFH) at present, and few MFH cell lines are established. In the present study, we established new MFH cell lines, KHZ-MFH and SFT85-03, and investigated the JAK/STAT (Janus kinase/signal transducer and activator of transcription) signaling pathway. We found that MFH cells secreted high levels of IL-6 and that STAT3 was constitutively activated in these cells. The JAK2 kinase inhibitor, tyrphostin AG490, suppressed the growth of MFH cells and inhibited the secretion of IL-6. Furthermore, blockade of activated STAT3 by forced expression of a cytokine signaling repressor, SOCS3 gene as well as a dominant-negative STAT3 in these cells significantly suppressed their growth. These results indicated that an autocrine mechanism of the JAK/STAT3 signaling pathway could promote the growth of MFH cells and that this pathway could be a therapeutic target of MFH.

Aged↗

PubMed2006

Computer simulation of the role of SOCS family protein in helper T cell differentiation.

The Th1/Th2 balance determines the nature of an immune response, and particular cytokines, IL-4 and IL-12, determine the direction at the initial stage of activation through TCRs. To investigate how cytokine networks and related signaling pathways impact upon the Th1/Th2 balance, we have developed a computer model for the simulation of Th differentiation. The model includes the IL-4, IL-12 and IFN-gamma signal transduction pathways, a positive and negative feedback mechanism for cytokine signaling and cytokine-induced negative regulators such as suppressors of cytokine signaling (SOCS)1, SOCS3 and SOCS5. In the present study, we propose a 'Th0 model', in which naive T cells differentiate neither into Th1 nor into Th2 states in unskewed cytokine conditions. The model was found to be consistent with experimental results in BALB/c mice. The results of in silico analysis in the condition with SOCS- and signal transducer and activator of transcription (STAT) family-deficient and transgenic states were well fitted to ex vivo experimental results for Th1 and Th2 differentiation profiles in the deficient and transgenic mice. The Th0 model suggested the possibility that dominant Th1 differentiation in STAT4/STAT6 double-deficient mice may be due to a positive feedback effect of initial IFN-gamma production from T cells. The in silico assessment of beneficial effects of inhibitory drugs by simulation analysis with our Th0 model indicated that Janus kinase 3-specific inhibitors might be suitable candidates for the modification of Th2-dominant immune responses. Our results demonstrate that models for the simulation of signaling network, such as our Th0 model, are useful tools for the in silico evaluation of novel drug candidates.

Animals↗