Publications (17)126.42 Total impact
-
Article: Vitamin D Receptor in Osteoblasts Is a Negative Regulator of Bone Mass Control.
[show abstract] [hide abstract]
ABSTRACT: The physiological and beneficial actions of vitamin D in bone health have been experimentally and clinically proven in mammals. The active form of vitamin D [1α,25(OH)(2)D(3)] binds and activates its specific nuclear receptor, the vitamin D receptor (VDR). Activated VDR prevents the release of calcium from its storage in bone to serum by stimulating intestinal calcium absorption and renal reabsorption. However, the direct action of VDR in bone tissue is poorly understood because serum Ca(2+) homeostasis is maintained through tightly regulated ion transport by the kidney, intestine, and bone. In addition, conventional genetic approaches using VDR knockout (VDR-KO, VDR(-/-)) mice could not identify VDR action in bone because of the animals' systemic defects in calcium metabolism. In this study, we report that systemic VDR heterozygous KO (VDR(+/L-)) mice generated with the Cre/loxP system as well as conventional VDR heterozygotes (VDR(+/-)) showed increased bone mass in radiological assessments. Because mineral metabolism parameters were unaltered in both types of mice, these bone phenotypes imply that skeletal VDR plays a role in bone mass regulation. To confirm this assumption, osteoblast-specific VDR-KO (VDR(ΔOb/ΔOb)) mice were generated with 2.3 kb α1(I)-collagen promoter-Cre transgenic mice. They showed a bone mass increase without any dysregulation of mineral metabolism. Although bone formation parameters were not affected in bone histomorphometry, bone resorption was obviously reduced in VDR(ΔOb/ΔOb) mice because of decreased expression of receptor activator of nuclear factor kappa-B ligand (an essential molecule in osteoclastogenesis) in VDR(ΔOb/ΔOb) osteoblasts. These findings establish that VDR in osteoblasts is a negative regulator of bone mass control.Endocrinology 02/2013; · 4.46 Impact Factor -
Article: Inhibition of Stabilin-2 elevates circulating hyaluronic acid levels and prevents tumor metastasis.
[show abstract] [hide abstract]
ABSTRACT: Hyaluronic acid (HA) has been implicated in the proliferation and metastasis of tumor cells. However, most previous studies were conducted on extracellular matrix or pericellular HA, and the role of circulating HA in vivo has not been studied. HA is rapidly cleared from the bloodstream. The scavenger receptor Stabilin-2 (Stab2) is considered a major clearance receptor for HA. Here we report a dramatic elevation in circulating HA levels in Stab2-deficient mice without any overt phenotype. Surprisingly, the metastasis of B16F10 melanoma cells to the lungs was markedly suppressed in the Stab2-deficient mice, whereas cell proliferation was not affected. Furthermore, administration of an anti-Stab2 antibody in Stab2(+) mice elevated serum HA levels and prevented the metastasis of melanoma to the lung, and also suppressed spontaneous metastasis of mammary tumor and human breast tumor cells inoculated in the mammary gland. Administration of the antibody or high-dose HA in mice blocked the lodging of melanoma cells to the lungs. Furthermore, HA at high concentrations inhibited the rolling/tethering of B16 cells to lung endothelial cells. These results suggest that blocking Stab2 function prevents tumor metastasis by elevating circulating HA levels. Stab2 may be a potential target in antitumor therapy.Proceedings of the National Academy of Sciences 02/2012; 109(11):4263-8. · 9.68 Impact Factor -
Article: Y-box binding protein-1 down-regulates expression of carbamoyl phosphate synthetase-I by suppressing CCAAT enhancer-binding protein-alpha function in mice.
[show abstract] [hide abstract]
ABSTRACT: Carbamoyl phosphate synthetase-I (CPS1) is a key enzyme in the urea cycle and patients with defects in the function or expression of CPS1 suffer from hyperammonemia. CPS1 is expressed in the liver at neonatal and adult stages in a CCAAT enhancer-binding protein-alpha (C/EBPalpha)-dependent manner. Despite expression of C/EBPalpha, CPS1 is not expressed in fetal liver, indicating an additional factor is involved in the regulation of CPS1 expression. The aim of this study was to elucidate the mechanism of CPS1 expression. Microarray was performed to find Y-box binding protein-1 (YB-1) that was expressed in mouse fetal liver. The role of YB-1 in CPS1 expression was investigated by overexpression of YB-1 in mouse fetal liver culture and luciferase reporter assays using the CPS1 promoter. Chromatin immunoprecipitation assay was used to examine recruitment of YB-1 to the CPS1 promoter in vivo. Expression of YB-1 and CPS1 was inversely correlated in vivo, and YB-1 inhibited CPS1 expression and ammonia clearance in fetal liver culture. Although YB-1 was not expressed in adult liver, acute liver injury up-regulated YB-1 and down-regulated CPS1, accompanying an increase of the serum ammonia level. YB-1 inhibited C/EBPalpha-induced transcription from the CPS1 promoter via the Y-box near the C/EBPalpha-binding site. Chromatin immunoprecipitation assays demonstrated that YB-1 was recruited to the CPS1 promoter in fetal and injured adult liver, but not in normal adult liver. YB-1 is a key regulator of ammonia detoxification by negatively regulating CPS1 expression via suppression of C/EBPalpha function.Gastroenterology 03/2009; 137(1):330-40. · 11.68 Impact Factor -
Article: Foxo1 links insulin signaling to C/EBPalpha and regulates gluconeogenesis during liver development.
[show abstract] [hide abstract]
ABSTRACT: C/EBPalpha is a key transcription factor indispensable for the onset of gluconeogenesis in perinatal liver. However, C/EBPalpha was already expressed in fetal liver, suggesting that the expression of C/EBPalpha alone does not account for the dramatic increase of the expression of metabolic genes, and hence an additional factor(s) is expected to function cooperatively with C/EBPalpha in perinatal liver. We show here that expression of Foxo1 was sharply increased in the perinatal liver and augmented C/EBPalpha-dependent transcription. Foxo1 bound C/EBPalpha via its forkhead domain, and Foxo1 bound to the promoter of a gluconeogenic gene, phosphoenolpyruvate carboxykinase (PEPCK), in a C/EBPalpha-dependent manner in vivo. Insulin inhibited the expression of PEPCK in a culture of fetal liver cells, and also the C/EBPalpha-dependent transcription enhanced by Foxo1. These results indicate that Foxo1 regulates gluconeogenesis cooperatively with C/EBPalpha, and also links insulin signaling to C/EBPalpha during liver development.The EMBO Journal 09/2007; 26(15):3607-15. · 9.20 Impact Factor -
Article: TRB2, a mouse Tribbles ortholog, suppresses adipocyte differentiation by inhibiting AKT and C/EBPbeta.
[show abstract] [hide abstract]
ABSTRACT: Adipocyte differentiation is regulated by a complex array of extracellular signals, intracellular mediators and transcription factors. Here we describe suppression of adipocyte differentiation by TRBs, mammalian orthologs of Drosophila Tribbles. Whereas all the three TRBs were expressed in 3T3-L1 preadipocytes, TRB2 and TRB3, but not TRB1, were immediately down-regulated by differentiation stimuli. Forced expression of TRB2 and TRB3 inhibited adipocyte differentiation at an early stage. Akt activation is a key event in adipogenesis and was severely inhibited by TRB3 in 3T3-L1 cells. However, the inhibition by TRB2 was mild compared with severe inhibition by TRB3, though TRB2 suppressed adipogenesis as strongly as TRB3. Interestingly, TRB2 but not TRB3 reduced the level of C/EBPbeta, a transcription factor required for an early stage of adipogenesis, through a proteasome-dependent mechanism. Furthermore, knockdown of endogenous TRB2 by siRNA allowed 3T3-L1 cells to differentiate without full differentiation stimuli. These results suggest that inhibition of Akt activation in combination with degradation of C/EBPbeta is the basis for the strong inhibitory effect of TRB2 on adipogenesis.Journal of Biological Chemistry 09/2007; 282(33):24075-82. · 4.77 Impact Factor -
Article: Foxo1 links insulin signaling to C/EBP|[alpha]| and regulates gluconeogenesis during liver development
[show abstract] [hide abstract]
ABSTRACT: C/EBP is a key transcription factor indispensable for the onset of gluconeogenesis in perinatal liver. However, C/EBP was already expressed in fetal liver, suggesting that the expression of C/EBP alone does not account for the dramatic increase of the expression of metabolic genes, and hence an additional factor(s) is expected to function cooperatively with C/EBP in perinatal liver. We show here that expression of Foxo1 was sharply increased in the perinatal liver and augmented C/EBP-dependent transcription. Foxo1 bound C/EBP via its forkhead domain, and Foxo1 bound to the promoter of a gluconeogenic gene, phosphoenolpyruvate carboxykinase (PEPCK), in a C/EBP-dependent manner in vivo. Insulin inhibited the expression of PEPCK in a culture of fetal liver cells, and also the C/EBP-dependent transcription enhanced by Foxo1. These results indicate that Foxo1 regulates gluconeogenesis cooperatively with C/EBP, and also links insulin signaling to C/EBP during liver development.The EMBO Journal 07/2007; 26(15):3607-3615. · 9.20 Impact Factor -
Article: Strain-dependent embryonic lethality and exaggerated vascular remodeling in heparin cofactor II-deficient mice.
[show abstract] [hide abstract]
ABSTRACT: Heparin cofactor II (HCII) specifically inhibits thrombin action at sites of injured arterial wall, and patients with HCII deficiency exhibit advanced atherosclerosis. However, the in vivo effects and the molecular mechanism underlying the action of HCII during vascular remodeling remain elusive. To clarify the role of HCII in vascular remodeling, we generated HCII-deficient mice by gene targeting. In contrast to a previous report, HCII(-/-) mice were embryonically lethal. In HCII(+/-) mice, prominent intimal hyperplasia with increased cellular proliferation was observed after tube cuff and wire vascular injury. The number of protease-activated receptor-1-positive (PAR-1-positive) cells was increased in the thickened vascular wall of HCII(+/-) mice, suggesting enhanced thrombin action in this region. Cuff injury also increased the expression levels of inflammatory cytokines and chemokines in the vascular wall of HCII(+/-) mice. The intimal hyperplasia in HCII(+/-) mice with vascular injury was abrogated by human HCII supplementation. Furthermore, HCII deficiency caused acceleration of aortic plaque formation with increased PAR-1 expression and oxidative stress in apoE-KO mice. These results demonstrate that HCII protects against thrombin-induced remodeling of an injured vascular wall by inhibiting thrombin action and suggest that HCII is potentially therapeutic against atherosclerosis without causing coagulatory disturbance.Journal of Clinical Investigation 07/2007; 117(6):1514-26. · 15.39 Impact Factor -
Article: Impaired flow-dependent control of vascular tone and remodeling in P2X4-deficient mice.
[show abstract] [hide abstract]
ABSTRACT: The structure and function of blood vessels adapt to environmental changes such as physical development and exercise. This phenomenon is based on the ability of the endothelial cells to sense and respond to blood flow; however, the underlying mechanisms remain unclear. Here we show that the ATP-gated P2X4 ion channel, expressed on endothelial cells and encoded by P2rx4 in mice, has a key role in the response of endothelial cells to changes in blood flow. P2rx4(-/-) mice do not have normal endothelial cell responses to flow, such as influx of Ca(2+) and subsequent production of the potent vasodilator nitric oxide (NO). Additionally, vessel dilation induced by acute increases in blood flow is markedly suppressed in P2rx4(-/-) mice. Furthermore, P2rx4(-/-) mice have higher blood pressure and excrete smaller amounts of NO products in their urine than do wild-type mice. Moreover, no adaptive vascular remodeling, that is, a decrease in vessel size in response to a chronic decrease in blood flow, was observed in P2rx4(-/-) mice. Thus, endothelial P2X4 channels are crucial to flow-sensitive mechanisms that regulate blood pressure and vascular remodeling.Nature Medicine 02/2006; 12(1):133-7. · 22.46 Impact Factor -
Article: Neuronal leucine-rich repeat protein 4 functions in hippocampus-dependent long-lasting memory.
[show abstract] [hide abstract]
ABSTRACT: Neuronal leucine-rich repeat proteins (NLRRs) are type I transmembrane proteins and expressed in neuronal tissues, but their function remains unknown. Here, we describe the identification and characterization of a new member of the NLRR family, NLRR4, and its potential role in long-lasting memory. We generated NLRR4-deficient (NLRR4(-/-)) mice and found that they showed impaired memory retention. In hippocampus-dependent learning tasks, NLRR4(-/-) mice were able to learn and maintain the memories for one day but unable to retain the memories for four days after learning. In contrast, in a hippocampus-independent task, NLRR4(-/-) mice were able to retain the memory normally for at least seven days. These results suggest that NLRR4 plays a key role in hippocampus-dependent long-lasting memory.Molecular and Cellular Biology 06/2005; 25(10):4166-75. · 5.53 Impact Factor -
Article: SRC-1 is necessary for skeletal responses to sex hormones in both males and females.
[show abstract] [hide abstract]
ABSTRACT: We created SRC-1(-/-) mice by mating floxed SRC-1 mice with CMV-Cre transgenic mice. The SRC-1(-/-) mice showed high turnover osteopenia under physiological conditions and hardly responded to osteoanabolic actions of exogenous androgen and estrogen in males and females, respectively, after gonadectomies, indicating that SRC-1 is essential for the maintenance of bone mass by sex hormones. Steroid receptor coactivator-1 (SRC-1) is the first identified coactivator of nuclear receptors. This study investigated the role of SRC-1 in skeletal tissues of males and females using the deficient (SRC-1(-/-)) mice. SRC-1(-/-) mice were generated by mating our original floxed SRC-1 mice with CMV-Cre transgenic mice. Bone metabolism between 24-week-old SRC-1(-/-) and wildtype (WT) littermates under physiological conditions was compared in males and females by radiological, histological, and biochemical analyses. Difference of skeletal responses to steroid hormones was examined by gonadectomies and exogenous administration experiments with the hormones. Statistical analysis was performed by ANOVA determined by posthoc testing using Bonferroni's method. Although SRC-1(-/-) mice showed no abnormality in growth or major organs, both males and females showed osteopenia with high bone turnover in the trabecular bones, but not in the cortical bones, compared with WT littermates. Their serum levels of sex hormones were upregulated, suggesting a compensatory reaction for the insensitivity to these hormones. Gonadectomies caused decreases in BMDs of SRC-1(-/-) and WT mice to the same levels; however, replacement with 5 alpha-dihydrotestosterone and 17 beta-estradiol in males and females, respectively, failed to restore the bone loss in SRC-1(-/-), whereas the WT bone volume was increased to the sham-operated levels. In contrast, bone loss by administered prednisolone was similarly seen in SRC-1(-/-) and WT mice. We conclude that SRC-1 is essential for the maintenance of bone mass by sex hormones, but not for the catabolic action of glucocorticoid, under both physiological and pathological conditions.Journal of Bone and Mineral Research 10/2004; 19(9):1452-61. · 6.37 Impact Factor -
Article: SRC‐1 Is Necessary for Skeletal Responses to Sex Hormones in Both Males and Females
[show abstract] [hide abstract]
ABSTRACT: We created SRC-1−/− mice by mating floxed SRC-1 mice with CMV-Cre transgenic mice. The SRC-1−/− mice showed high turnover osteopenia under physiological conditions and hardly responded to osteoanabolic actions of exogenous androgen and estrogen in males and females, respectively, after gonadectomies, indicating that SRC-1 is essential for the maintenance of bone mass by sex hormones.Introduction: Steroid receptor coactivator-1 (SRC-1) is the first identified coactivator of nuclear receptors. This study investigated the role of SRC-1 in skeletal tissues of males and females using the deficient (SRC-1−/−) mice.Materials and Methods:SRC-1−/− mice were generated by mating our original floxed SRC-1 mice with CMV-Cre transgenic mice. Bone metabolism between 24-week-old SRC-1−/− and wildtype (WT) littermates under physiological conditions was compared in males and females by radiological, histological, and biochemical analyses. Difference of skeletal responses to steroid hormones was examined by gonadectomies and exogenous administration experiments with the hormones. Statistical analysis was performed by ANOVA determined by posthoc testing using Bonferroni's method.Results and Conclusions: Although SRC-1−/− mice showed no abnormality in growth or major organs, both males and females showed osteopenia with high bone turnover in the trabecular bones, but not in the cortical bones, compared with WT littermates. Their serum levels of sex hormones were upregulated, suggesting a compensatory reaction for the insensitivity to these hormones. Gonadectomies caused decreases in BMDs of SRC-1−/− and WT mice to the same levels; however, replacement with 5α-dihydrotestosterone and 17β-estradiol in males and females, respectively, failed to restore the bone loss in SRC-1−/−, whereas the WT bone volume was increased to the sham-operated levels. In contrast, bone loss by administered prednisolone was similarly seen in SRC-1−/− and WT mice. We conclude that SRC-1 is essential for the maintenance of bone mass by sex hormones, but not for the catabolic action of glucocorticoid, under both physiological and pathological conditions.Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 06/2004; 19(9):1452 - 1461. · 6.04 Impact Factor -
Article: Brain masculinization requires androgen receptor function.
[show abstract] [hide abstract]
ABSTRACT: Testicular testosterone produced during a critical perinatal period is thought to masculinize and defeminize the male brain from the inherent feminization program and induce male-typical behaviors in the adult. These actions of testosterone appear to be exerted not through its androgenic activity, but rather through its conversion by brain aromatase into estrogen, with the consequent activation of estrogen receptor (ER)-mediated signaling. Thus, the role of androgen receptor (AR) in perinatal brain masculinization underlying the expression of male-typical behaviors remains unclear because of the conversion of testosterone into estrogen in the brain. Here, we report a null AR mutation in mice generated by the Cre-loxP system. The AR-null mutation in males (AR(L-/Y)) resulted in the ablation of male-typical sexual and aggressive behaviors, whereas female AR-null homozygote (AR(L-/L-)) mice exhibited normal female sexual behaviors. Treatment with nonaromatizable androgen (5alpha-dihydrotestosterone, DHT) was ineffective in restoring the impaired male sexual behaviors, but it partially rescued impaired male aggressive behaviors in AR(L-/Y) mice. Impaired male-typical behaviors in ERalpha(-/-) mice were restored on DHT treatment. The role of AR function in brain masculinization at a limited perinatal stage was studied in AR(L-/L-) mice. Perinatal DHT treatment of females led to adult females sensitive to both 17beta-estradiol and DHT in the induction of male-typical behaviors. However, this female brain masculinization was abolished by AR inactivation. Our results suggested that perinatal brain masculinization requires AR function and that expression of male-typical behaviors in adults is mediated by both AR-dependent and -independent androgen signaling.Proceedings of the National Academy of Sciences 03/2004; 101(6):1673-8. · 9.68 Impact Factor -
Article: [STAT: transcriptional regulator of cytokine signaling].
Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 01/2004; 48(16):2241-6. -
Article: Suppressive function of androgen receptor in bone resorption.
[show abstract] [hide abstract]
ABSTRACT: As locally converted estrogen from testicular testosterone contributes to apparent androgen activity, the physiological significance of androgen receptor (AR) function in the beneficial effects of androgens on skeletal tissues has remained unclear. We show here that inactivation of AR in mice using a Cre-loxP system-mediated gene-targeting technique caused bone loss in males but not in females. Histomorphometric analyses of 8-week-old male AR knockout (ARKO) mice showed high bone turnover with increased bone resorption that resulted in reduced trabecular and cortical bone mass without affecting bone shape. Bone loss in orchidectomized male ARKO mice was only partially prevented by treatment with aromatizable testosterone. Analysis of primary osteoblasts and osteoclasts from ARKO mice revealed that AR function was required for the suppressive effects of androgens on osteoclastogenesis supporting activity of osteoblasts but not on osteoclasts. Furthermore, expression of the receptor activator of NF-kappaB ligand (RANKL) gene, which encodes a major osteoclastogenesis inducer, was found to be up-regulated in osteoblasts from AR-deficient mice. Our results indicate that AR function is indispensable for male-type bone formation and remodeling.Proceedings of the National Academy of Sciences 09/2003; 100(16):9416-21. · 9.68 Impact Factor -
Article: Molecular genetics of vitamin D receptor acting in bone
Journal of Bone and Mineral Metabolism 05/1998; 16(2):65-71. · 2.27 Impact Factor -
Article: Mice lacking the vitamin D receptor exhibit impaired bone formation, uterine hypoplasia and growth retardation after weaning
[show abstract] [hide abstract]
ABSTRACT: 1,25-Dihydroxy vitamin D3[1,25(OH)2D3] an active form of vitamin D, has roles in many biological phenomena such as calcium homeostasis and bone formation1−3, which are thought to be mediated by the 1,25(OH)2D3 receptor (VDR), a member of the nuclear hormone receptor superfamily4−6. However, the molecular basis for the actions of 1,25(OH)2D3 in bone formation, its role during development and VDR genetic polymorphisms for predicting bone mineral density7 are uncertain. To investigate the functional role of VDR, we generated mice deficient in VDR by gene targeting. We report here that in VDR null mutant mice, no defects in development and growth were observed before weaning, irrespective of reduced expression of vitamin D target genes. After weaning, however, mutants failed to thrive, with appearance of alopoecia, hypocalcaemia and infertility, and bone formation was severely impaired as a typical feature of vitamin D−dependent rickets type II (refs 8,9). Unlike humans with this disease, most of the null mutant mice died within 15 weeks after birth, and uterine hypoplasia with impaired folliculogenesis was found in female reproductive organs. These defects, such as alopoecia and uterine hypoplasia, were not observed in vitamin D−deficient animals. The findings establish a critical role for VDR in growth, bone formation and female reproduction in the post-weaning stage.Nature Genetics. 07/1997; 16(4):391-396. -
Article: In vivo function of VDR in gene expression-VDR knock-out mice
[show abstract] [hide abstract]
ABSTRACT: Vitamin D exerts many biological actions through nuclear vitamin D receptor (VDR)-mediated gene expression. The transactivation function of VDR is activated by binding 1α,25-dihydroxyvitamin D3[1α,25(OH)2D3], an active form of vitamin D. Conversion from 25(OH)D3 is finely regulated in kidney by 25(OH)D3 1α-hydroxylase[25(OH)D 1α-hydroxylase], keeping serum levels of 1α,25(OH)2D3 constant. Deficiency of vitamin D and mutations in the genes like VDR (type II genetic rickets) are known to cause rickets like lowered serum calcium, alopecia and impaired bone formation. However, the molecular basis of vitamin D–VDR system in the vitamin D action in intact animals remained to be established. In addition, the 1α-hydroxylase gene from any species had not yet been cloned, irrespective of its biological significance and putative link to the type I genetic rickets. We generated VDR-deficient mice (VDR KO mice). VDR KO mice grew up normally until weaning, but after weaning they developed abnormality like the type II rickets patients. These results demonstrated indispensability of vitamin D–VDR system in mineral and bone metabolism only in post-weaning life. Using a newly developed cloning system, we cloned the cDNA encoding a novel P450 enzyme, mouse and human 1α-hydroxylase. The study in VDR KO mice demonstrated the function of liganded VDR in the negative feed-back regulation of 1α,25(OH)2D3 production. Finally, from the analysis of type I rickets patients, we found missense genetic mutations in 1α-hydroxylase, leading to the conclusion that this gene is responsible for the type I rickets.The Journal of Steroid Biochemistry and Molecular Biology.
Top co-authors
Top Journals
Institutions
-
1998–2012
-
The University of Tokyo
- Institute of Molecular and Cellular Biosciences
Tokyo, Tokyo-to, Japan
-
