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Kazuo Chihara

Publications and source records attributed to Kazuo Chihara.

At least 37 records · Page 2Linked to original sources
PubMed2005

Low-dose parathyroid hormone and estrogen reverse alkaline phosphatase activity suppressed by dexamethasone in mouse osteoblastic cells.

Glucocorticoid (GC)-induced osteoporosis (GIO) is frequently seen in patients with excessive GC. Numerous questions remain to be clarified about the pathogenesis and treatment of GIO, and the mechanism of GC-inhibited bone formation is not well known. Several studies suggest that parathyroid hormone (PTH) and hormone replacement therapy are effective for GIO. We therefore investigated whether PTH and estrogen would affect cell proliferation and alkaline phosphatase (ALP) activity inhibited by dexamethasone (Dex) in mouse osteoblastic cell-line MC3T3-E1 cells. Low-dose (10(-11) M) PTH as well as 10(-8) M 17-beta-estradiol (17beta-E2) significantly attenuated Dex-inhibited ALP activity, although 10(-8) M PTH did not affect it. ICI 182780 (10(-8) M) antagonized the effects of 17beta-E(2) on Dex-suppressed ALP activity. Neutralizing anti-IGF-I antibody (3 microg/ml) blocked the reverse effects of 17beta-E2 on ALP activity suppressed by Dex. PTH (10(-11) M), but not 17beta-E2, significantly attenuated [3H]thymidine incorporation inhibited by Dex. On the other hand, PTH and estrogen did not affect the level of 11-beta-hydrosteroid dehydrogenase type I mRNA increased by Dex. In conclusion, the present study demonstrated that low-dose PTH and estrogen reversed Dex-inhibited ALP activity in the mouse osteoblastic cell-line.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2005

Activation of the precuneus is related to reduced reaction time in serial reaction time tasks.

Multiple brain areas are activated during serial reaction time (RT) tasks (SRTTs), but the part of the brain that facilitates reductions in RT remains unclear. The present study attempted to determine the brain region contributing most to improved RTs during explicit SRTTs. Subjects comprised 18 healthy volunteers who were instructed to press one of four buttons corresponding to visual stimuli as quickly as possible and with minimal errors during functional MRI. Stimuli were presented either in random order (control condition) or in a repeated six-item sequence (learning condition). Conventional analysis contrasting learning and control conditions revealed activation in the prefrontal-parietal area, which shifted to motor area. Subjects with high RT reduction showed more prominent activation in the precuneus than subjects with low RT reduction. Intra-subject correlation analysis revealed that time course of precuneus activation was unrelated to time-course of RT reduction. However, inter-subject correlation analysis revealed that RT changes correlate only with precuneus activation, meaning that subjects showing more prominent RT reduction revealed more prominent activation of the precuneus, which is known to play critical roles in controlling finger movements with reference to buffered memory.

Adult↗
PubMed2005

The role of transcriptional coactivator TRAP220 in myelomonocytic differentiation.

The TRAP220 subunit of the thyroid hormone receptor-associated polypeptide transcription coactivator complex (TRAP/Mediator complex), mammalian counterpart of the yeast Mediator complex, is proposed to act on a variety of major and specific biological events through physical interactions with nuclear receptors. The vitamin D receptor (VDR) and retinoic acid receptor (RAR), coupled with retinoid X receptor (RXR), are nuclear receptors which have important roles for monopoiesis and granulopoiesis, respectively. In this study, we present the functional role of TRAP220 in nuclear receptor-mediated monopoiesis and granulopoiesis. The mouse Trap220(-/-) yolk sac hematopoietic progenitor cells were resistant to 1,25-dihydroxyvitamin D(3)-stimulated differentiation into monocytes/macrophages. Furthermore, flow cytometric analyses showed that HL-60 cells, human promyelocytic leukemia cell line, wherein TRAP220 was down-regulated, did not differentiate efficiently into monocytes and granulocytes by stimulation with 1,25-dihydroxyvitamin D(3) and all-trans retinoic acid, correspondingly. The expression of direct target genes of VDR or RAR, as well as the differentiation marker genes, was low in the knockdown cells. These results indicated a crucial role of TRAP220 in the optimal VDR- and RAR-mediated myelomonocytic differentiation processes in mammalian hematopoiesis.

Animals↗
PubMed2005

Effects of age, grip strength and smoking on forearm volumetric bone mineral density and bone geometry by peripheral quantitative computed tomography: comparisons between female and male.

Peripheral quantitative computed tomography (pQCT) is useful to measure volumetric bone mineral density (vBMD) distinguishing trabecular from cortical bones as well as quantity of bone geometry. In the present study, we examined the effects of age, grip strength and smoking on vBMD, bone geometry and bone strength index (polar strength strain index (SSIp)), and then compared with the differences between female and male by employing pQCT in Japanese 252 female and 230 male subjects. Age was negatively correlated with vBMD, cortical area (Ct.Ar) and cortical thickness (Ct.Th) as well as SSIp in both sexes, and the correlation coefficients were higher in female, compared with those in male. Although age was correlated with endocortical circumferences (En.Le) in both sexes, periosteal circumferences (Ex.Le) were correlated with age only in male. Volumetric BMD, Ct.Ar, Ct.Th and SSIp were significantly lower in the group with vertebral fractures, although En.Le and Ex.Le were similar between subjects with and without vertebral fractures. Grip strength was positively correlated with vBMD, Ct.Ar, Ct.Th as well as SSIp. The extent of correlation was much higher in female, compared with that in male. Ct.vBMD, Ct.Ar, Ct.Th and SSIp, but not trabecular vBMD, were significantly lower in the group with high Brinkman index (number of cigarettes smoked per day) x (duration of smoking (years)) in female. These parameters were not significantly different between groups with high and low Brinkman index in male. In conclusion, the present study demonstrated that age, grip strength and smoking affected forearm vBMD, bone geometry and bone strength index by pQCT. These effects were greater in female, compared with those in male.

Absorptiometry, Photon↗
PubMed2005

An individualized GH dose regimen for long-term GH treatment in Japanese patients with adult GH deficiency.

OBJECTIVES: To investigate the effects of growth hormone (GH) treatment, using a dose-adjustment regimen based on serum insulin-like growth factor (IGF)-I concentrations, in adult Japanese hypopituitary patients with GH deficiency. STUDY DESIGN: Japanese patients who had initially been administered GH (n = 31) or placebo (n = 28) in a 24-week double-blind study received individualized GH treatment in an open-label study for 48 weeks. Body composition from dual-energy X-ray absorptiometry (DXA) and serum IGF-I, IGF-binding protein 3 (IGFBP-3) and lipid levels were determined centrally. RESULTS: Significant increases in lean body mass (4.5%) and decreases in fat mass (-10.5%) were observed in the group that received individualized GH doses in the present open-label study following placebo in the double-blind study. This was comparable with the changes observed in these parameters (4.7 and -9.2%, respectively) with fixed-dose GH treatment in the double-blind study; this latter group maintained these improvements throughout the open-label study. Individualized dose adjustment allowed for more moderate dose increases than the fixed-dose titration method. Individualized dosing also resulted in a lower mean dose for adult-onset compared with childhood-onset GH-deficient patients (0.032+/-0.019 versus 0.061+/-0.023 mg/kg per week for patients treated with GH for 48 weeks in the open-label study following placebo in the double-blind study). Dosing patterns in the two groups were paralleled by the changes in IGF-I and IGFBP-3. The incidence of oedema and cases with high IGF-I level were less frequent under the IGF-I controlled regimen compared with those during the fixed-dose titration method. CONCLUSION: Individualized GH administration based on IGF-I levels was safe and effective. This regimen demonstrated differences in dose requirements between adult- and childhood-onset patients. An individualized dose regimen is recommended in adult Japanese GH-deficient patients.

Adult↗
PubMed2005

The threshold of bone mineral density for vertebral fractures in female patients with primary hyperparathyroidism.

BACKGROUND AND OBJECTIVE: Primary hyperparathyroidism (pHPT) is one of the causal diseases that induce secondary osteoporosis. Although patients with pHPT have reduced bone mineral density (BMD) especially at the cortical bone, there have been controversies about risk of fracture. Moreover, no reports have been available about the threshold of BMD for fractures in pHPT patients. METHODS: BMD values were measured by dual-energy x-ray absorptiometry at lumbar spine, femoral neck and distal one third of radius. Various indices were compared in 116 female pHPT patients and 716 control subjects. Moreover, we analyzed relationship between the cut-off values of BMD and the prevalence of vertebral fractures in pHPT and control subjects. RESULTS: The prevalence of subjects with vertebral fractures was lower in pHPT patients, compared with that of control subjects. Age and body height were significantly higher and lower in pHPT women with vertebral fractures, respectively. Lumbar spine BMD was significantly lower in pHPT women with vertebral fractures, presumably due to their increased age. There were no differences in femoral neck and radius BMD or in bone metabolic indices between pHPT women with and without vertebral fractures. On the other hand, age-matched BMD was not significantly different between both groups at any measured site. Cut-off values of BMD at lumbar spine and femoral neck were lower in postmenopausal pHPT patients, compared with those of the postmenopausal control group. Moreover, cut-off values of BMD at radius was much lower in postmenopausal pHPT patients, compared with those of the postmenopausal control group (pHPT vs control (g/cm(2)): 0.670 vs 0.706 at lumbar spine; 0.549 vs 0.570 at femoral; 0.394 vs 0.474 at radius). Sensitivity and specificity of vertebral fractures was lower in pHPT patients, compared with those in control group. CONCLUSIONS: The present cross-sectional study demonstrated that thresholds of BMD for vertebral fractures were lower especially at radial bone in female patients with pHPT, compared with those in the control group.

Absorptiometry, Photon↗
PubMed2005

Dexamethasone suppresses Smad3 pathway in osteoblastic cells.

Central in the pathogenesis of glucocorticoid (GC)-induced osteoporosis is the effects of GC on bone formation. However, the mechanism of GC-inhibited bone formation is not well known. Transforming growth factor (TGF)-beta is most abundant in bone matrix compared with other tissues, and we have recently proposed that Smad3, a TGF-beta signaling molecule, is important for promoting bone formation. However, no reports have been available about the effects of GC on Smad3 in osteoblasts. In the present study, we investigated whether dexamethasone (Dex), an active GC analog, would affect the expression and activity of Smad3 in mouse osteoblastic MC3T3-E1 and rat osteoblastic UMR-106 cells. Dex significantly suppressed Smad3-stimulated alkaline phosphatase (ALP) activity, although it did not affect TGF-beta-inhibited ALP activity in MC3T3-E1 cells. Moreover, pretreatment with Dex suppressed TGF-beta-enhanced expression of type I collagen in MC3T3-E1 and UMR-106 cells. In the luciferase assay using p3TP-Lux with a Smad3-specific response element, Dex significantly suppressed the transcriptional activity induced by TGF-beta as well as Smad3. However, Dex did not affect the expression of Smad3 in these cells at both mRNA and protein levels. In conclusion, the present study indicates that Dex inhibits ALP activity and type I collagen expression, presumably by suppressing Smad3-induced transcriptional activity but not by modulating Smad3 expression in osteoblastic cells.

Alkaline Phosphatase↗
PubMed2005

Heat shock protein 90 is required for increased DNA binding activity of activator protein-1, a heterodimer of Fos/JunD, in rheumatoid synovial cells under inflammatory stimuli.

We have studied the DNA binding profiles of activator protein-1 (AP-1) involved in synovial overgrowth and osteoporosis in rheumatoid arthritis (RA) in relation to the molecular chaperon heat shock protein 90 (HSP90). The AP-1 binding activity of the nuclear extracts of rheumatoid synovial cells was basically increased as compared with osteoarthritic synovial cells. Upon stimulation with inflammatory cytokines IL-1beta or TNFalpha, the AP-1 binding activity was further increased in rheumatoid synovial cells, and increased AP-1 protein was composed as heterodimers of Fos and JunD which was not known before as a major component of AP-1 in rheumatoid synovial cells. The increase of AP-1 binding activity as induced by inflammatory cytokines was specifically inhibited by geldanamycin, radicicol or herbimycin A, specific inhibitors of HSP90, while AP-1 protein was not decreased by geldanamycin. Further, HSP90 protein was not decreased by the inhibitors. The findings indicate that HSP90 is required for increased AP-1 binding activity of rheumatoid synovial cells under inflammatory stimuli and that AP-1 binding activity is inhibited by functionally inactivating HSP90 with the inhibitors.

Arthritis, Rheumatoid↗
PubMed2005

Successful treatment with defibrotide for sinusoidal obstruction syndrome after hematopoietic stem cell transplantation.

Sinusoidal obstruction syndrome (SOS) (formerly known as hepatic veno-occlusive disease (VOD)) is a life-threatening complication subsequent to hematopoietic stem cell transplantation. However, no completely satisfactory strategies for the treatment of SOS have been established yet. Defibrotide is a single-stranded polydeoxyribonucleotide with anti-thrombotic, anti-ischemic, anti-inflammatory and thrombolytic properties, but without systemic anticoagulant effects, and some encouraging results have been reported in western countries. We treated four patients with defibrotide for SOS, since there seemed to be no possibility to cure the patients with conventionally available treatments in Japan. All patients showed evidence of multiple organ failure at the start of the treatment. Defibrotide was administered intravenously in normal saline in four divided doses for 14 to 27 days. Three patients (75%) responded to the therapy, while one died of SOS and cytomegalovirus infection despite intensive therapy. None of the patients suffered from significant adverse effects such as severe hemorrhage. This is the first report dealing with the treatment with defibrotide of Japanese patients with SOS. Because defibrotide is considered to be promising for the treatment of SOS, it is important to start a phase II study as soon as possible.

Adult↗
PubMed2004

HLA typing in focal myositis.

It is still controversial if idiopathic focal myositis is a part of systemic polymyositis. We present here four patients, including identical twins, with focal myositis accompanied by the same HLA typings. Gradually developing unilateral calf muscle pain was an initial symptom in all patients. Neither muscular weakness nor creatine kinase (CK) elevation was observed, while minimal inflammatory findings such as erythrocyte sedimentation rate (ESR) increase appeared in serum. Magnetic resonance imaging (MRI) revealed localized abnormalities of calf muscles. Biopsy specimen was characterized by perimysial and endomysial inflammatory infiltration consisted of T cells and macrophages and rare necrotic fibers. Corticosteroid administrations ameliorated their symptoms and signs, though recurrence occurred along with decreasing doses. HLA typings common to all patients were A2, B62, Cw3, and DQ3, whereas HLA-D DNA typings were DQB1 *0303 for two patients, and DQB1*0302 for three patients. These findings suggest that at least some focal myositis may be a new disease unit, with a common genetic background but not a part of systemic polymyositis.

Adult↗
PubMed2004

Menin suppresses osteoblast differentiation by antagonizing the AP-1 factor, JunD.

Mice null for menin, the product of the multiple endocrine neoplasia type 1 (MEN1) gene, exhibit cranial and facial hypoplasia suggesting a role for menin in bone formation. We have shown previously that menin is required for the commitment of multipotential mesenchymal stem cells into the osteoblast lineage in part by interacting with the bone morphogenetic protein (BMP)-2 signaling molecules Smad1/5, and the key osteoblast transcriptional regulator, Runx2 (Sowa H., Kaji, H., Hendy, G. N., Canaff, L., Komori, T., Sugimoto, T., and Chihara, K. (2004) J. Biol. Chem. 279, 40267-40275). However, menin inhibits the later differentiation of committed osteoblasts. The activator protein-1 (AP-1) transcription factor, JunD, is expressed in osteoblasts and has been shown to interact with menin in other cell types. Here, we examined the consequences of menin-JunD interaction on osteoblast differentiation in mouse osteoblastic MC3T3-E1 cells. JunD expression, assessed by immunoblot, gradually increased during osteoblast differentiation. Stable expression of JunD enhanced expression of the differentiation markers, Runx2, type 1 collagen (COL1), and osteocalcin (OCN) and alkaline phosphatase (ALP) activity and mineralization. Hence, JunD promotes osteoblast differentiation. In MC3T3-E1 cells in which menin expression was reduced by stable menin antisense DNA transfection, JunD levels were increased. When JunD and menin were co-transfected in MC3T3-E1 cells, they co-immunoprecipitated. JunD overexpression increased the transcriptional activity of an AP-1 luciferase reporter construct, and this activity was reduced by co-transfection of menin. Therefore, JunD and menin interact both physically and functionally in osteoblasts. Furthermore, menin overexpression inhibited the ALP activity induced by JunD. In conclusion, the data suggest that menin suppresses osteoblast maturation, in part, by inhibiting the differentiation actions of JunD.

Alkaline Phosphatase↗
PubMed2004

Involvement of calcium-sensing receptor in osteoblastic differentiation of mouse MC3T3-E1 cells.

We have previously shown that the extracellular calcium-sensing receptor (CaR) is expressed in various bone marrow-derived cell lines and plays an important role in stimulating their proliferation and chemotaxis. It has also been reported that the CaR modulates matrix production and mineralization in chondrogenic cells. However, it remains unclear whether the CaR plays any role in regulating osteoblast differentiation. In this study, we found that mineralization of the mouse osteoblastic MC3T3-E1 cells was increased when the cells were exposed to high calcium (2.8 and 3.8 mM) or a specific CaR activator, NPS-R467 (1 and 3 microM). Next, we stably transfected MC3T3-E1 cells with either a CaR antisense vector (AS clone) or a vector containing the inactivating R185Q variant of the CaR (DN clone) that has previously been shown to exert a dominant negative action. Alkaline phosphatase activities were decreased compared with controls in both the AS and DN clones. However, the levels of type I procollagen and osteopontin mRNA in the AS clone, as detected by Northern blotting, were almost the same as in the controls. On the other hand, the expression of osteocalcin, which is expressed at a later stage of osteoblastic differentiation, was significantly reduced in both the AS and DN clones. Mineralization was also decreased in both clones. In conclusion, this study showed that the abolition of CaR function results in diminishing alkaline phosphatase activity, osteocalcin expression, and mineralization in mouse osteoblastic cells. This suggests that the CaR may be involved in osteoblastic differentiation.

3T3 Cells↗
PubMed2004

Menin is required for bone morphogenetic protein 2- and transforming growth factor beta-regulated osteoblastic differentiation through interaction with Smads and Runx2.

Menin, the product of the multiple endocrine neoplasia type 1 (MEN1) gene, is required for commitment of multipotential mesenchymal stem cells to the osteoblast lineage, however, it inhibits their later differentiation (Sowa, H., Kaji, H., Canaff, L., Hendy, G.N., Tsukamoto, T., Yamaguchi, T., Miyazono, K., Sugimoto, T., and Chihara, K. (2003) J. Biol. Chem. 278, 21058-21069). Here, we have examined the mechanism of action of menin in regulating osteoblast differentiation using the mouse bone marrow stromal ST2 and osteoblast MC3T3-E1 cell lines. In ST2 cells, reduced menin expression achieved by transfection of menin antisense DNA (AS) antagonized bone morphogenetic protein (BMP)-2-induced alkaline phosphatase activity and osteocalcin and Runx2 mRNA expression. Menin was co-immunoprecipitated with Smad1/5 in ST2 and MC3T3-E1 cells, and inactivation of menin antagonized BMP-2-induced transcriptional activity of Smad1/5 in ST2 cells, but not MC3T3-E1 cells. Menin was co-immunoprecipitated with the key osteoblast regulator, Runx2, and AS antagonized Runx2 transcriptional activity and the ability of Runx2 to stimulate alkaline phosphatase activity only in ST2 cells but not in MC3T3-E1 cells. In the osteoblast MC3T3-E1 cells, transforming growth factor-beta and its signaling molecule, Smad3, negatively regulated Runx2 transcriptional activity. Menin and Smad3 were co-immunoprecipitated, and combined menin and Smad3 overexpression antagonized, whereas menin and the dominant-negative Smad3DeltaC together enhanced BMP-2-induced transcriptional activity of Smad1/5 and Runx2. Smad3 alone had no effect. Therefore, menin interacts physically and functionally with Runx2 in uncommitted mesenchymal stem cells, but not in well differentiated osteoblasts. In osteoblasts the interaction of menin and the transforming growth factor-beta/Smad3 pathway negatively regulates the BMP-2/Smad1/5- and Runx2-induced transcriptional activities leading to inhibition of late-stage differentiation.

3T3 Cells↗
PubMed2004

Menin inactivation leads to loss of transforming growth factor beta inhibition of parathyroid cell proliferation and parathyroid hormone secretion.

Primary hyperparathyroidism is a common endocrine disorder caused by parathyroid gland enlargement and excessive parathyroid hormone (PTH) secretion. However, the precise mechanisms of tumorigenesis of the parathyroids are unknown. Here we have investigated the roles of transforming growth factor (TGF)-beta and menin, the product of the multiple endocrine neoplasia type 1 (Men1) gene, in the proliferation and PTH production of parathyroid cells from either patients with secondary hyperparathyroidism or Men1. TGF-beta was expressed in the parathyroid endocrine cells. Addition of TGF-beta to parathyroid cells from patients with secondary hyperparathyroidism inhibited their proliferation and PTH secretion. These responses to TGF-beta were lost when menin was specifically inactivated by antisense oligonucleotides. Moreover, TGF-beta did not affect the proliferation and PTH production of parathyroid cells from a Men1 patient. These results indicate that menin is required for TGF-beta action in the parathyroid. We conclude that TGF-beta is an important autocrine/paracrine negative regulator of parathyroid cell proliferation and PTH secretion and that loss of TGF-beta signaling due to menin inactivation contributes to parathyroid tumorigenesis.

Cell Division↗
PubMed2004

Up-regulation of mitochondrial transcription factor 1 mRNA levels by GH in VSMC.

It is well known that growth hormone (GH) is involved in the development of arteriosclerosis in which vascular smooth muscle cells (VSMC) play an important role. In this study, we attempted to specify the genes up- or down-regulated by recombinant human GH (rhGH) in VSMC using a differential display method. We found that rhGH increased cytochrome oxidase subunit II/III mRNA in VSMC. Furthermore, the mRNA for mitochondrial transcription factor 1 (mtTF1), which stimulates the expression of cytochrome oxidase subunit II/III, was found to be up-regulated by rhGH in a dose dependent manner using a quantitative PCR method. On the other hand, IGF-I alone did not change mtTF1 mRNA levels. In rat L6 myoblasts and rat H4-II-E hepatocytes, rhGH did not change mtTF1 mRNA levels. Pretreatment with a JAK2 inhibitor AG490 (10 nM) and a MEK inhibitor PD98059 (10 microM) suppressed rhGH-induced rise in mtTF1 mRNA levels of VSMC to the control levels. Pretreatment with a PI-3kinase inhibitor wortomannin (1 nM) did not suppress rhGH-induced rise in mtTF1 mRNA levels. These findings suggest that GH up-regulates mtTF1 mRNA levels through JAK2 and MEK signaling in VSMC.

Androstadienes↗
PubMed2004

Involvement of casein kinase Iepsilon in cytokine-induced granulocytic differentiation.

Two closely related casein kinase I (CKI) isoforms, CKIdelta and CKIepsilon, are ubiquitously expressed in many human tissues, but their specific biologic function remains to be clarified. Here, we provide the first evidence that CKIepsilon is involved in hematopoietic cell differentiation. CKIepsilon, but not CKIdelta, was down-regulated along with human granulocytic differentiation. The specific down-regulation was observed in granulocyte colony-stimulating factor (G-CSF)-induced cell differentiation of murine interleukin-3 (IL-3)-dependent myeloid progenitor 32D cells. Introduction of wild-type (WT)-CKIepsilon into 32D cells inhibited the G-CSF-induced cell differentiation, whereas kinase-negative (KN)-CKIepsilon promoted the differentiation. Neither WT- nor KN-CKIepsilon affected IL-3-dependent cell growth. Moreover, introduction of WT- or KN-CKIdelta did not affect the cytokine-induced cell growth and differentiation. While G-CSF-induced activation of signal transducers and activators of transcription 3 (STAT3) was sustained by KN-CKIepsilon, STAT3 activation was attenuated by WT-CKIepsilon. This may be explained by the fact that the suppressor of cytokine signaling 3 (SOCS3) was stabilized by its physical association with CKIepsilon. Such stabilization by CKIepsilon was also seen in IL-3-induced beta-catenin. The stabilization of downstream components of cytokine and Wnt signaling by CKIepsilon might be critical for integration of several intracellular signaling pathways to a cell-specific biologic response in hematopoietic cell self-renewal.

Animals↗