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ABSTRACT: One goal of diabetic regenerative medicine is to instructively convert mature pancreatic exocrine cells into insulin-producing cells. We recently reported that ligand-bound thyroid hormone receptor α (TRα) plays a critical role in expansion of the β-cell mass during postnatal development. Herein, we used adenovirus vector that expresses TRα driven by the amylase 2 promoter (AdAmy2TRα) to induce the reprogramming of pancreatic acinar cells into insulin-producing cells. Treatment with L-3,5,3-triiodothyronine increases the association of TRα with the p85α subunit of PI3K, leading to the phosphorylation and activation of Akt and the expression of Pdx1, Ngn3 and MafA in purified acinar cells. Analyses performed with the lectin-associated cell lineage tracing system and the Cre/loxP-based direct cell lineage tracing system indicate that newly synthesized insulin-producing cells originate from elastase-expressing pancreatic acinar cells. Insulin-containing secretory granules were identified in these cells by electron microscopy. The inhibition of p85α expression by siRNA or the inhibition of PI3K by LY294002 prevents the expression of Pdx1, Ngn3 and MafA and the reprogramming to insulin-producing cells. In immunodeficient mice with streptozotocin-induced hyperglycemia, treatment with AdAmy2TRα leads to the reprogramming of pancreatic acinar cells to insulin-producing cells in vivo. Our findings suggest that ligand-bound TRα plays a critical role in β-cell regeneration during postnatal development via activation of PI3K signaling.
Journal of Biological Chemistry 04/2013; · 4.77 Impact Factor
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Hiroki Shimura,
Katsuhiko Itoh,
Atsushi Sugiyama,
Sayaka Ichijo,
Masashi Ichijo, Fumihiko Furuya,
Yuji Nakamura,
Ken Kitahara,
Kazuhiko Kobayashi,
Yasuhiro Yukawa,
Tetsuro Kobayashi
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ABSTRACT: Large quantities of radionuclides have leaked from the Fukushima Daiichi Nuclear Power Plant into the surrounding environment. Effective prevention of health hazards resulting from radiation exposure will require the development of efficient and economical methods for decontaminating radioactive wastewater and aquatic ecosystems. Here we describe the accumulation of water-soluble radionuclides released by nuclear reactors by a novel strain of alga. The newly discovered green microalgae, Parachlorella sp. binos (Binos) has a thick alginate-containing extracellular matrix and abundant chloroplasts. When this strain was cultured with radioiodine, a light-dependent uptake of radioiodine was observed. In dark conditions, radioiodine uptake was induced by addition of hydrogen superoxide. High-resolution secondary ion mass spectrometry (SIMS) showed a localization of accumulated iodine in the cytosol. This alga also exhibited highly efficient incorporation of the radioactive isotopes strontium and cesium in a light-independent manner. SIMS analysis showed that strontium was distributed in the extracellular matrix of Binos. Finally we also showed the ability of this strain to accumulate radioactive nuclides from water and soil samples collected from a heavily contaminated area in Fukushima. Our results demonstrate that Binos could be applied to the decontamination of iodine, strontium and cesium radioisotopes, which are most commonly encountered after nuclear reactor accidents.
PLoS ONE 01/2012; 7(9):e44200. · 4.09 Impact Factor
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Kaoru Aida,
Yoriko Nishida,
Shoichiro Tanaka,
Taro Maruyama,
Akira Shimada,
Takuya Awata,
Masako Suzuki,
Hiroki Shimura,
Soichi Takizawa,
Masashi Ichijo,
Daiichiro Akiyama, Fumihiko Furuya,
Akio Kawaguchi,
Masahiro Kaneshige,
Jun Itakura,
Hideki Fujii,
Toyoshi Endo,
Tetsuro Kobayashi
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ABSTRACT: The contribution of innate immunity responsible for aggressive β-cell destruction in human fulminant type 1 diabetes is unclear.
Islet cell expression of Toll-like receptors (TLRs), cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors, downstream innate immune markers, adaptive immune mediators, and apoptotic markers was studied in three autopsied pancreata obtained 2 to 5 days after onset of fulminant type 1 diabetes.
RIG-I was strongly expressed in β-cells in all three pancreata infected with enterovirus. Melanoma differentiation-associated gene-5 was hyperexpressed in islet cells, including β- and α-cells. TLR3 and TLR4 were expressed in mononuclear cells that infiltrated islets. Interferon (IFN)-α and IFN-β were strongly expressed in islet cells. Major histocompatibility complex (MHC)-class I, IFN-γ, interleukin-18, and CXC motif ligand 10 were expressed and colocalized in affected islets. CD11c+ MHC-class II+ dendritic cells and macrophage subsets infiltrated most islets and showed remarkable features of phagocytosis of islet cell debris. CD4+ forkhead box P3+ regulatory T cells were not observed in and around the affected islets. Mononuclear cells expressed the Fas ligand and infiltrated most Fas-expressing islets. Retinoic acid-receptor responder 3 and activated caspases 8, 9, and 3 were preferentially expressed in β-cells. Serum levels of IFN-γ were markedly increased in patients with fulminant type 1 diabetes.
These findings demonstrate the presence of specific innate immune responses to enterovirus infection connected with enhanced adoptive immune pathways responsible for aggressive β-cell toxicity in fulminant type 1 diabetes.
Diabetes 02/2011; 60(3):884-9. · 8.29 Impact Factor
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ABSTRACT: Failure of the functional pancreatic beta-cell mass to expand in response to increased metabolic demand is a hallmark of type 2 diabetes. Lineage tracing studies indicate that replication of existing beta-cells is important for beta-cell proliferation in adult animals. In rat pancreatic beta-cell lines (RIN5F), treatment with 100 nM thyroid hormone (triiodothyronine, T(3)) enhances cell proliferation. This result suggests that T(3) is required for beta-cell proliferation or replication. To identify the role of thyroid hormone receptor alpha (TR(alpha)) in the processes of beta-cell growth and cell cycle regulation, we constructed a recombinant adenovirus vector, AdTR(alpha). Infection with AdTR(alpha) to RIN5F cells increased the expression of cyclin D1 mRNA and protein. Overexpression of the cyclin D1 protein in AdTR(alpha)-infected cells led to activation of the cyclin D1/cyclin-dependent kinase/retinoblastoma protein/E2F pathway, along with cell cycle progression and cell proliferation following treatment with 100 nM T(3). Conversely, lowering cellular cyclin D1 by small interfering RNA knockdown in AdTR(alpha)-infected cells led to down-regulation of the cyclin D1/CDK/Rb/E2F pathway and inhibited cell proliferation. Furthermore, in immunodeficient mice with streptozotocin-induced diabetes, intrapancreatic injection of AdTR(alpha) led to the restoration of islet function and to an increase in the beta-cell mass. These results support the hypothesis that liganded TR(alpha) plays a critical role in beta-cell replication and in expansion of the beta-cell mass during postnatal development. Thus, liganded TR(alpha) may be a target for therapeutic strategies that can induce the expansion and regeneration of beta-cells.
Journal of Biological Chemistry 08/2010; 285(32):24477-86. · 4.77 Impact Factor
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Shoichiro Tanaka,
Yoriko Nishida,
Kaoru Aida,
Taro Maruyama,
Akira Shimada,
Masako Suzuki,
Hiroki Shimura,
Soichi Takizawa,
Masashi Takahashi,
Daiichiro Akiyama,
Sayaka Arai-Yamashita, Fumihiko Furuya,
Akio Kawaguchi,
Masahiro Kaneshige,
Ryohei Katoh,
Toyoshi Endo,
Tetsuro Kobayashi
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ABSTRACT: Fulminant type 1 diabetes is characterized by the rapid onset of severe hyperglycemia and ketoacidosis, with subsequent poor prognosis of diabetes complications. Causative mechanisms for accelerated beta-cell failure are unclear.
Subjects comprised three autopsied patients who died from diabetic ketoacidosis within 2-5 days after onset of fulminant type 1 diabetes. We examined islet cell status, including the presence of enterovirus and chemokine/cytokine/major histocompatibility complex (MHC) expressions in the pancreata using immunohistochemical analyses and RT-PCR.
Immunohistochemical analysis revealed the presence of enterovirus-capsid protein in all three affected pancreata. Extensive infiltration of CXCR3 receptor-bearing T-cells and macrophages into islets was observed. Dendritic cells were stained in and around the islets. Specifically, interferon-gamma and CXC chemokine ligand 10 (CXCL10) were strongly coexpressed in all subtypes of islet cells, including beta-cells and alpha-cells. No CXCL10 was expressed in exocrine pancreas. Serum levels of CXCL10 were increased. Expression of MHC class II and hyperexpression of MHC class I was observed in some islet cells.
These results strongly suggest the presence of a circuit for the destruction of beta-cells in fulminant type 1 diabetes. Enterovirus infection of the pancreas initiates coexpression of interferon-gamma and CXCL10 in beta-cells. CXCL10 secreted from beta-cells activates and attracts autoreactive T-cells and macrophages to the islets via CXCR3. These infiltrating autoreactive T-cells and macrophages release inflammatory cytokines including interferon-gamma in the islets, not only damaging beta-cells but also accelerating CXCL10 generation in residual beta-cells and thus further activating cell-mediated autoimmunity until all beta-cells have been destroyed.
Diabetes 08/2009; 58(10):2285-91. · 8.29 Impact Factor
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ABSTRACT: TSH-secreting pituitary tumors (TSHomas) are pituitary tumors that constitutively secrete TSH. Molecular mechanisms underlying this abnormality are largely undefined. We recently created a knock-in mutant mouse harboring a mutation (denoted as PV) in the thyroid hormone receptor-beta gene (TRbeta(PV/PV) mouse). As these mice age, they spontaneously develop TSHomas. Using this mouse model, we investigated the role of the phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway in the pathogenesis of TSHomas. Concurrent with aberrant growth of pituitaries, AKT and its downstream effectors, mammalian target rapamycin and p70(S6K), were activated to contribute to increased cell proliferation and pituitary growth. In addition, activation of AKT led to decreased apoptosis by inhibiting proapoptotic activity of Bcl-2-associated death promoter, further contributing to the aberrant cell proliferation. These results suggest an activated PI3K-AKT pathway could underscore tumorigenesis, raising the possibility that this pathway could be a potential therapeutic target in TSHomas. Indeed, TRbeta(PV/PV) mice treated with a PI3K-specific inhibitor, LY294002, showed a significant decrease in pituitary growth. The progrowth signaling via AKT-mammalian target rapamycin-p70(S6K) and cyclin D1/cyclin-dependent kinase were inhibited, and proapoptotic activity of Bcl-2-associated death promoter was increased by LY294002 treatment. Thus, activation of the PI3K-AKT pathway mediates, at least in part, the aberrant pituitary growth, and the intervention of this signaling pathway presents a novel therapeutic opportunity for TSHomas.
Endocrinology 08/2008; 149(7):3339-45. · 4.46 Impact Factor
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ABSTRACT: Aberrant activation of the phosphatidylinositol 3-kinase (PI3K)-AKT/protein kinase B-signaling pathway has been associated with multiple human cancers, including thyroid cancer. Recently, we showed that, similar to human thyroid cancer, the PI3K-AKT pathway is overactivated in both the thyroid and metastatic lesions of a mouse model of follicular thyroid carcinoma (TRbeta(PV/PV) mice). This TRbeta(PV/PV) mouse harbors a knockin mutant thyroid hormone receptor beta gene (TRbetaPV mutant) that spontaneously develops thyroid cancer and distant metastasis similar to human follicular thyroid cancer. That the activation of the PI3K-AKT signaling contributes to thyroid carcinogenesis raised the possibility that this pathway could be a potential therapeutic target in follicular thyroid carcinoma. The present study tested this possibility by treating TRbeta(PV/PV) mice with LY294002 (LY), a potent and specific PI3K inhibitor, and evaluating the effect of LY on the spontaneous development of thyroid cancer. LY treatment inhibited the AKT-mammalian target of rapamycin (mTOR)-p70(S6K) signaling, and it decreased cyclin D1 and increased p27(Kip1) expression to inhibit thyroid tumor growth and reduce tumor cell proliferation. LY treatment increased caspase 3 and decreased phosphorylated-BAD to induce apoptosis. In addition, LY treatment reduced the AKT-matrix metalloproteinase 2 signaling to decrease cell motility to block metastatic spread of thyroid tumors. Thus, these altered signaling pathways converged effectively to prolong survival of TRbeta(PV/PV) mice treated with LY. No significant adverse effects were observed for wild-type mice treated similarly with LY. The present study provides the first preclinical evidence for the in vivo efficacy for LY in the treatment of follicular thyroid cancer.
Carcinogenesis 01/2008; 28(12):2451-8. · 5.70 Impact Factor
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ABSTRACT: The nuclear receptor corepressor (NCoR) regulates the activities of DNA-binding transcription factors. Recent observations of its distribution in the extranuclear compartment raised the possibility that it could have other cellular functions in addition to transcription repression. We previously showed that phosphatidylinositol 3-kinase (PI3K) signaling is aberrantly activated by a mutant thyroid hormone beta receptor (TRbetaPV, hereafter referred to as PV) via physical interaction with p85alpha, thus contributing to thyroid carcinogenesis in a mouse model of follicular thyroid carcinoma (TRbetaPV/PV mouse). Since NCoR is known to modulate the actions of TRbeta mutants in vivo and in vitro, we asked whether NCoR regulates PV-activated PI3K signaling. Remarkably, we found that NCoR physically interacted with and competed with PV for binding to the C-terminal SH2 (Src homology 2) domain of p85alpha, the regulatory subunit of PI3K. Confocal fluorescence microscopy showed that both NCoR and p85alpha were localized in the nuclear as well as in the cytoplasmic compartments. Overexpression of NCoR in thyroid tumor cells of TRbetaPV/PV mouse reduced PI3K signaling, as indicated by the decrease in the phosphorylation of its immediate downstream effector, p-AKT. Conversely, lowering cellular NCoR by siRNA knockdown in tumor cells led to overactivated p-AKT and increased cell proliferation and motility. Furthermore, NCoR protein levels were significantly lower in thyroid tumor cells than in wild-type thyrocytes, allowing more effective binding of PV to p85alpha to activate PI3K signaling and thus contributing to tumor progression. Taken together, these results indicate that NCoR, via protein-protein interaction, is a novel regulator of PI3K signaling and could serve to modulate thyroid tumor progression.
Molecular and Cellular Biology 10/2007; 27(17):6116-26. · 5.53 Impact Factor
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ABSTRACT: Thyroid hormone (T3) is critical for growth, differentiation, and maintenance of metabolic homeostasis. Mice with a knock-in mutation in the thyroid hormone receptor alpha gene (TRalpha1PV) were created previously to explore the roles of mutated TRalpha1 in vivo. TRalpha1PV is a dominant negative mutant with a frameshift mutation in the carboxyl-terminal 14 amino acids that results in the loss of T3 binding and transcription capacity. Homozygous knock-in TRalpha1(PV/PV) mice are embryonic lethal, and heterozygous TRalpha1(PV/+) mice display the striking phenotype of dwarfism. These mutant mice provide a valuable tool for identifying the defects that contribute to dwarfism. Here we show that white adipose tissue (WAT) mass was markedly reduced in TRalpha1(PV/+) mice. The expression of peroxisome proliferator-activated receptor gamma (PPARgamma), the key regulator of adipogenesis, was repressed at both mRNA and protein levels in WAT of TRalpha1(PV/+) mice. Moreover, TRalpha1PV acted to inhibit the transcription activity of PPARgamma by competition with PPARgamma for binding to PPARgamma response elements and for heterodimerization with the retinoid X receptors. The expression of TRalpha1PV blocked the T3-dependent adipogenesis of 3T3-L1 cells and repressed the expression of PPARgamma. Thus, mutations of TRalpha1 severely affect adipogenesis via cross talk with PPARgamma signaling. The present study suggests that defects in adipogenesis could contribute to the phenotypic manifestation of reduced body weight in TRalpha1(PV/+) mice.
Molecular and Cellular Biology 04/2007; 27(6):2359-71. · 5.53 Impact Factor
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ABSTRACT: Follicular thyroid cancer (FTC) is known to metastasize to distant sites via hematogenous spread; however, the underlying pathways that contribute to metastasis remain unknown. Recent creation of a knockin mutant mouse that expresses a mutant thyroid hormone receptor-beta (TRbeta(PV/PV) mouse) that spontaneously develops thyroid cancer with metastasis similar to humans has provided new opportunities to study contributors to FTC metastasis. This study evaluates the role of gelsolin, an actin-regulatory protein, in modulating the metastatic potential of FTC. Gelsolin was previously found by cDNA microarray analysis to be down-regulated in TRbeta(PV/PV) mice as compared with wild-type mice. This study found an age-dependent reduction of gelsolin protein abundance in TRbeta(PV/PV) mice as tumorigenesis progressed. Knockdown of gelsolin by small interfering RNA resulted in increased tumor cell motility and increased gelsolin expression by histone deacetylase inhibitor (trichostatin A) led to decreased cell motility. Additional biochemical analyses demonstrated that gelsolin physically interacted with TRbeta1 or PV in vivo and in vitro. The interaction regions were mapped to the C terminus of gelsolin and the DNA binding domain of TR. The physical interaction of gelsolin with PV reduced its binding to actin, leading to disarrayed cytoskeletal architectures. These results suggest that PV-induced alteration of the actin/gelsolin cytoskeleton contributes to increased cell motility. Thus, the present study uncovered a novel PV-mediated oncogenic pathway that could contribute to the local tumor progression and metastatic potential of thyroid carcinogenesis.
Endocrinology 04/2007; 148(3):1306-12. · 4.46 Impact Factor
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ABSTRACT: Study of molecular actions of thyroid hormone receptor beta (TRbeta) mutants in vivo has been facilitated by creation of a mouse model (TRbetaPV mouse) that harbors a knockin mutant of TRbeta (denoted PV). PV, which was identified in a patient with resistance to thyroid hormone, has lost T3 binding activity and transcription capacity. The striking phenotype of thyroid cancer exhibited by TRbeta(PV/PV) mice has allowed the elucidation of novel oncogenic activity of a TRbeta mutant (PV) [PAS1] beyond nucleus-initiated transcription. PV was found to physically interact with the regulatory p85alpha subunit of phosphatidylinositol 3-kinase (PI3K) in both the nuclear and cytoplasmic compartments. This protein-protein interaction activates the PI3K signaling by increasing phosphorylation of AKT, mammalian target of rapamycin (mTOR), and p70(S6K). PV, via interaction with p85alpha, also activates the PI3K-integrin-linked kinase-matrix metalloproteinase-2 signaling pathway in the extra-nuclear compartment. The PV-mediated PI3K activation results in increased cell proliferation, motility, migration, and metastasis. In addition to affecting these membrane-initiated signaling events, PV affects the stability of the pituitary tumor-transforming gene (PTTG) product. PTTG (also known as securin), a critical mitotic checkpoint protein, is physically associated with TRbeta or PV in vivo. Concomitant with T3-induced degradation of TRbeta, PTTG is degraded by the proteasome machinery, but no such degradation occurs when PTTG is associated with PV. The degradation of PTTG/TRbeta is activated by the direct interaction of the T3-bound TRbeta with the steroid receptor coactivator-3 (SRC-3) that recruits a proteasome activator (PA28gamma). PV that does not bind T3 cannot interact directly with SRC-3/PA28gamma to activate proteasome degradation, and the absence of degradation results in an aberrant accumulation of PTTG. The PV-induced failure of timely degradation of PTTG results in mitotic abnormalities. PV, via novel protein-protein interaction and transcription regulation, acts to antagonize the functions of wild-type TRs and contributes to the oncogenic functions of this mutation.
Steroids 03/2007; 72(2):171-9. · 2.83 Impact Factor
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ABSTRACT: Overexpression of pituitary tumor-transforming 1 (PTTG1) is associated with thyroid cancer. We found elevated PTTG1 levels in the thyroid tumors of a mouse model of follicular thyroid carcinoma (TRbeta(PV/PV) mice). Here we examined the molecular mechanisms underlying elevated PTTG1 levels and the contribution of increased PTTG1 to thyroid carcinogenesis. We showed that PTTG1 was physically associated with thyroid hormone beta receptor (TRbeta) as well as its mutant, designated PV. Concomitant with thyroid hormone-induced (T3-induced) degradation of TRbeta, PTTG1 proteins were degraded by the proteasomal machinery, but no such degradation occurred when PTTG1 was associated with PV. The degradation of PTTG1/TRbeta was activated by the direct interaction of the liganded TRbeta with steroid receptor coactivator 3 (SRC-3), which recruits proteasome activator PA28gamma. PV, which does not bind T3, could not interact directly with SRC-3/PA28gamma to activate proteasome degradation, resulting in elevated PTTG1 levels. The accumulated PTTG1 impeded mitotic progression in cells expressing PV. Our results unveil what we believe to be a novel mechanism by which PTTG1, an oncogene, is regulated by the liganded TRbeta. The loss of this regulatory function in PV led to an aberrant accumulation of PTTG1 disrupting mitotic progression that could contribute to thyroid carcinogenesis.
Journal of Clinical Investigation 12/2006; 116(11):2972-84. · 15.39 Impact Factor
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Yukio Hiroi,
Hyung-Hwan Kim,
Hao Ying, Fumihiko Furuya,
Zhihong Huang,
Tommaso Simoncini,
Kensuke Noma,
Kojiro Ueki,
Ngoc-Ha Nguyen,
Thomas S Scanlan,
Michael A Moskowitz,
Sheue-Yann Cheng,
James K Liao
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ABSTRACT: The binding of thyroid hormone to the thyroid hormone receptor (TR) mediates important physiological effects. However, the transcriptional effects of TR mediated by the thyroid response element (TRE) cannot explain many actions of thyroid hormone. We postulate that TR can initiate rapid, non-TRE-mediated effects in the cardiovascular system through cross-coupling to the phosphatidylinositol 3-kinase (PI3-kinase)/protein kinase Akt pathway. In vascular endothelial cells, the predominant TR isoform is TRalpha1. Treatment of endothelial cells with L-3,5,3'-triiodothyronine (T3) increased the association of TRalpha1 with the p85alpha subunit of PI3-kinase, leading to the phosphorylation and activation of Akt and endothelial nitric oxide synthase (eNOS). The activation of Akt and eNOS by T3 was abolished by the PI3-kinase inhibitors, LY294002 and wortmannin, but not by the transcriptional inhibitor, actinomycin D. To determine the physiological relevance of this PI3-kinase/Akt pathway, we administered T3 to mice undergoing transient focal cerebral ischemia. Compared with vehicle, a single bolus infusion of T3 rapidly increased Akt activity in the brain, decreased mean blood pressure, reduced cerebral infarct volume, and improved neurological deficit score. These neuroprotective effects of T3 were greatly attenuated or absent in eNOS-/- and TRalpha1-/-beta-/- mice and were completely abolished in WT mice pretreated with LY294002 or a T3 antagonist, NH-3. These findings indicate that the activation of PI3-kinase/Akt pathways can mediate some of the rapid, non-TRE effects of TR and suggest that the activation of Akt and eNOS contributes to some of the acute vasodilatory and neuroprotective effects of thyroid hormone.
Proceedings of the National Academy of Sciences 10/2006; 103(38):14104-9. · 9.68 Impact Factor
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ABSTRACT: Activation of the phosphatidylinositol 3-kinase (PI3K)-AKT/protein kinase B signaling pathway has been associated with multiple human cancers. Recently we showed that AKT is activated in both the thyroid and metastatic lesions of a mouse model of follicular thyroid carcinoma [thyroid hormone beta receptor (TRbeta)(PV/PV) mice]. This TRbeta(PV/PV) mouse harbors a knock-in mutant TRbeta gene (TRbetaPV mutant) that spontaneously develops thyroid cancer and distant metastasis similar to human follicular thyroid cancer. Here we show that in thyroid tumors, PV mutant bound significantly more to the PI3K-regulatory subunit p85alpha, resulting in a greater increase in the kinase activity than did TRbeta1 in wild-type mice. By GST pull-down assays, the ligand-binding domain of TR was identified as the interaction site with p85alpha. By confocal fluorescence microscopy, p85alpha was shown to colocalize with TRbeta1 or PV mainly in the nuclear compartment of cultured tumor cells from TRbeta(PV/PV) mice, but cytoplasmic p85alpha/PV or p85alpha/TRbeta1 complexes were also detectable. Further biochemical analysis revealed that the activation of the PI3K-AKT-mammalian target of the rapamycin-p70(S6K) pathway was observed in both the cytoplasmic and nuclear compartments, whereas the activation of the PI3K-integrin-linked kinase-matrix metalloproteinase 2 pathway was detected mainly in the extranuclear compartments. These results suggest that PV, via the activation of p85alpha, could act to affect PI3K downstream signaling in both the nuclear and extranuclear compartments, thereby contributing to thyroid carcinogenesis. Importantly, the present study unveils a mechanism by which a mutant TR acts to activate PI3K activity via protein-protein interactions.
Proceedings of the National Academy of Sciences 03/2006; 103(6):1780-5. · 9.68 Impact Factor
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ABSTRACT: Atherosclerosis and its related complications are the leading causes of death in the hemodialysis (HD) population. Aortic calcification index (ACI), intima-media thickness (IMT) in common carotid arteries, and electrocardiogram (ECG) are atherosclerotic parameters that are available in usual clinical outpatient settings. Macrophage colony-stimulating factor (MCSF) and monocyte chemoattractant protein-1 (MCP-1) play important roles in atherosclerosis.
We performed a cross-sectional study of 133 outpatients on maintenance HD in a single HD outpatient center. We measured serum levels of MCSF and MCP-1, determined the ACI using computed tomography scan and the IMT using high-sensitivity ultrasound B-mode imaging, and performed ECGs.
Stepwise multivariate regression analysis revealed that the MCSF level correlated with age-adjusted mean and maximum IMT (F = 10.811, p = 0.001, and F = 6.784, p = 0.010, respectively) as well as with the diastolic blood pressure. Age and MCSF level (F = 4.866, p = 0.029) were independently related to an increased ACI. High-sensitivity C-reactive protein (hsCRP) was not related to IMT and ACI. The hsCRP level (chi2 = 5.002, p = 0.025) correlated with ECG changes followed by MCSF (chi2 = 3.940, p = 0.047). MCP-1 was not related to the above atherosclerotic parameters.
A head-to-head comparison between MCSF and hsCRP revealed that MCSF was more closely associated with IMT and ACI in HD patients.
Nephron Clinical Practice 02/2006; 102(1):c14-20. · 2.04 Impact Factor
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ABSTRACT: Thyroid hormone (T3) and peroxisome proliferators have overlapping metabolic effects in the maintenance of lipid homeostasis. Their actions are mediated by their respective receptors: thyroid hormone receptors (TR) and peroxisome proliferator-activated receptors (PPAR). We recently found that a dominantly negative TRbeta mutant (PV) that causes a genetic disease, resistance to thyroid hormone, acts to repress the ligand (troglitazone)-mediated transcriptional activity of PPARgamma in cultured thyroid cells. This finding suggests that TRbeta mutants could crosstalk with PPARgamma-signaling pathways. The present study explored the molecular mechanisms by which PV represses the PPARgamma transcriptional activity. Gel-shift assays show that the PV, similar to wild-type TRbeta, bound to the peroxisome proliferator response element (PPRE) as homodimers and heterodimers with PPARgamma or the retinoid X receptor (RXR), thereby competing with PPARgamma for binding to PPRE and for sequestering RXR. Association of PPRE-bound PV with corepressors [e.g., nuclear receptor corepressor (NCoR)] that led to transcriptional repression was independent of T3 and troglitazone. Chromatin immunoprecipitation assay further demonstrated that, despite the presence of ligands, NCoR was recruited to PPRE-bound PV on a PPARgamma-target gene, the lipoprotein lipase, in vivo, suggesting the dominant action of PV on PPARgamma-mediated transcriptional activity. Thus, the dominant negative action of PV is not limited on the wild-type TRs. The findings that TRbeta mutants affect PPARgamma functions through dominant negative action provide insights into the molecular mechanisms by which TR regulates the PPARgamma-target genes involved in metabolic pathways, lipid homeostasis, and carcinogenesis.
Proceedings of the National Academy of Sciences 12/2005; 102(45):16251-6. · 9.68 Impact Factor
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ABSTRACT: Mutations of the thyroid hormone receptor beta (TRbeta) gene cause resistance to thyroid hormone (RTH). RTH is characterized by increased serum thyroid hormone associated with nonsuppressible thyroid-stimulating hormone (TSH) and impaired growth. It is unclear how the actions of TRbeta mutants are modulated in vivo to affect the manifestation of RTH. Using a mouse model of RTH that harbors a knockin mutation of the TRbeta gene (TRbetaPV mouse), we investigated the effect of the steroid hormone receptor coactivator 3 (SRC-3) on RTH. In TRbetaPV mice deficient in SRC-3, dysfunction of the pituitary-thyroid axis and hypercholesterolemia was lessened, but growth impairment of RTH was worsened. The lessened dysfunction of the pituitary-thyroid axis was attributed to a significant decrease in growth of the thyroid and pituitary. Serum insulin-like growth factor 1 (IGF-1) was further reduced in TRbetaPV mice deficient in SRC-3. This effect led to reduced signaling of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway that is known to mediate cell growth and proliferation. Thus, SRC-3 modulates RTH by at least two mechanisms, one via its role as a receptor coregulator and the other via its growth regulatory role through the IGF-1/PI3K/AKT/mTOR signaling.
Molecular and Cellular Biology 10/2005; 25(17):7687-95. · 5.53 Impact Factor
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ABSTRACT: Loss of thyroid-specific gene expression and functions accompanied by loss of thyroid transcription factors render them unresponsive to radioiodide therapy in poorly differentiated and anaplastic thyroid cancer. In anticipation of reactivation of thyroid functions, we investigated the effect of thyroid transcription factor-1 (TTF-1) gene transfer on thyroid cancer cells. Reexpression of thyroperoxidase (TPO) and thyroglobulin (Tg) mRNA and protein was detected in poorly differentiated human thyroid cancer cells that were infected with an adenovirus vector containing TTF-1 (AdTTF-1). Although TTF-1 gene transfer faintly induced iodide uptake, the induction of sodium/iodide symporter (NIS) mRNA was not observed in AdTTF-1-infected cells. To analyze the effect of TTF-1 on iodide metabolism, we transfected an NIS expression vector into BHP18-21v cells and cloned a cell line (N-BHP18-21v) that stably expressed NIS. The treatment of N-BHP18-21v cells with AdTTF-1 significantly increased the amount of protein-bound radioiodide and prolonged the iodide efflux. AdTTF-1 injections significantly induced iodide retention and organification in tumors formed from N-BHP18-21v cells in nude mice. These results indicate that AdTTF-1 specifically induces iodide organification and retards iodide efflux in thyroid cancer cells in vitro and in vivo.
Endocrinology 12/2004; 145(11):5397-405. · 4.46 Impact Factor
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Shoichiro Tanaka,
Toyoshi Endo,
Kaoru Aida,
Hiroki Shimura,
Norihiko Yokomori,
Masahiro Kaneshige, Fumihiko Furuya,
Shin Amemiya,
Mie Mochizuki,
Koji Nakanishi,
Tetsuro Kobayashi
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ABSTRACT: Diagnostic criteria in fulminant type 1 diabetes, a novel subtype of type 1 diabetes, remain unclear.
We analyzed basal and longitudinal changes of serum C-peptide levels during a 75-g oral glucose tolerance test (OGTT) in 125 consecutively recruited patients with type 1 diabetes including fulminant type 1 diabetes (n = 25) and acute-onset type 1 diabetes (n = 100). Discriminating criteria of fulminant type 1 diabetes were examined using receiver-operating characteristic curve analysis and multiple logistic regression analysis.
The integrated values of serum C-peptide response during OGTT (SigmaC-peptide) in fulminant type 1 diabetes at onset, 1 year, and 2 years after onset were markedly lower than those in acute-onset type 1 diabetes. None of the patients with fulminant type 1 diabetes had improvement of C-peptide response to OGTT. Fasting C-peptide values at onset in fulminant type 1 diabetes were significantly lower than those in acute-onset type 1 diabetes. We established diagnostic criteria of serum C-peptide and HbA(1c) levels at onset that discriminate fulminant type 1 diabetes from acute-onset type 1 diabetes with high sensitivity and specificity: a criterion in which the levels of both the fasting C-peptide is <or=0.033 nmol/l and HbA(1c) is <or=8.0% or a criterion in which the levels of both the SigmaC-peptide is <or=0.540 nmol/l and HbA(1c) is <or=8.0%.
Fulminant type 1 diabetes has extremely low beta-cell function at onset that rarely recovers after onset. Sensitive and specific diagnostic criteria were established for detection of fulminant type 1 diabetes based on serum C-peptide and HbA(1c) levels at onset.
Diabetes Care 08/2004; 27(8):1936-41. · 8.09 Impact Factor
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ABSTRACT: Iodide uptake by the thyroid is mediated by the sodium/iodide symporter. Upon iodide uptake, thyroperoxidase catalyzes iodination of tyrosine residues in thyroglobulin, retaining iodide within thyroid follicles. Dedifferentiation-induced loss of these functions in cancers, rendering them unresponsive to radioiodide, occurs with most poorly differentiated and anaplastic tumors. We focused on the histone deacetylase (HDAC) inhibitors (HDACI) as a way to induce differentiation of thyroid cancer cells. We assessed re-expression of thyroid-specific genes mRNA induced by HDACI using quantitative RT-PCR and immunostaining in poorly differentiated papillary and anaplastic thyroid cancer cells. HDACI induced expression of thyroid-specific gene mRNAs and proteins, and accumulation of radioiodide through iodination of generic cellular proteins were detected. HDACI-treated tumors could specifically accumulate (125)I as revealed by imaging experiments and radioiodide concentration in vivo. In an attempt to determine the mechanism by which these gene expressions occurred, we detected the inhibition of protein synthesis by cycloheximide, which up-regulated the expression of thyroperoxidase and thyroglobulin mRNA in HDACI-treated cells and down-regulated that of sodium/iodide symporter mRNA. Together, our results suggest that HDACI-induced expression of thyroid-specific genes, some of which is mediated by some protein synthesis, may contribute to development of novel strategy against thyroid cancer.
Endocrinology 07/2004; 145(6):2865-75. · 4.46 Impact Factor
