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Akihiro Yasoda

Publications and source records attributed to Akihiro Yasoda.

16 recordsLinked to original sources
PubMed2006

Antithyroid drugs inhibit thyroid hormone receptor-mediated transcription.

CONTEXT: Methimazole (MMI) and propylthiouracil (PTU) are widely used as antithyroid drugs (ATDs) for the treatment of Graves' disease. Both MMI and PTU reduce thyroid hormone levels by several mechanisms, including inhibition of thyroid hormone synthesis and secretion. In addition, PTU decreases 5'-deiodination of T(4) in peripheral tissues. ATDs may also interfere with T(3) binding to nuclear thyroid hormone receptors (TRs). However, the effect of ATDs on the transcriptional activities of T(3) mediated by TRs has not been studied. OBJECTIVE: The present study was undertaken to determine whether ATDs have an effect on the gene transcription regulated by T(3) and TRs in vitro. METHODS: Transient gene expression experiments and GH secretion assays were performed. To elucidate possible mechanisms of the antagonistic action of ATDs, the interaction between TR and nuclear cofactors was examined. RESULTS: In the transient gene expression experiments, both MMI and PTU significantly suppressed transcriptional activities mediated by the TR and T(3) in a dose-dependent manner. In mammalian two-hybrid assays, both drugs recruited one of the nuclear corepressors, nuclear receptor corepressor, to the TR in the absence of T(3). In addition, PTU dissociated nuclear coactivators, such as steroid receptor coactivator-1 and glucocorticoid receptor interacting protein-1, from the TR in the presence of T(3). Finally, MMI decreased the GH release that was stimulated by T(3). CONCLUSIONS: ATDs inhibit T(3) action by recruitment of transcriptional corepressors and/or dissociation of coactivators. This is the first report to show that ATDs can modulate T(3) action at the transcriptional level.

Antithyroid Agents↗
PubMed2005

Expression of the adrenomedullin gene in adipose tissue.

Adrenomedullin (AM) is a potent vasodilating peptide originally isolated from human pheochromocytoma cells. This report concerns the expression and secretion of AM from adipose tissue. Northern blot analysis demonstrated marked expression of AM mRNA in mouse adipose tissue. Expression levels in adipose tissues were 2.5-3.2 times higher than in the kidney. AM mRNA level in mature adipocytes was 7.3 times higher than in the stroma-vascular fraction of adipose tissue. In mature adipocyte culture, time-dependent increase of AM peptide concentration in the culture medium was detected. AM expression was also detected in human subcutaneous adipose tissue. Adipose AM expression significantly increased in obesity mouse model, high-fat diet fed mice and ob/ob mice. These results suggest that adipose tissue, especially mature adipocytes, is major source of AM in the body, and that adipocyte-derived AM plays a pathophysiological role in obesity.

Adipocytes↗
PubMed2005

High-dose glucocorticoid treatment induces rapid loss of trabecular bone mineral density and lean body mass.

A recent large-scale study revealed that glucocorticoid treatment increased fracture risk, which occurred at a far smaller dose and by a shorter duration than previously thought. To study the underlying mechanism for the increased risk of fracture, we studied the early changes in bone mineral density (BMD) and body composition by dual energy X-ray absorptiometry (DXA) after initiating high-dose glucocorticoid treatment. High-dose glucocorticoid treatment was arbitrarily defined as daily doses of >or=40 mg of a predonisolone equivalent. The 33 patients enrolled in this study had not received glucocorticoid treatment before. Only 2 months of treatment resulted in substantial BMD loss, most markedly in the lumbar spine, followed by the femoral neck and total body, which suggests the preferential trabecular bone loss. Body composition was also greatly affected. Thus, 2-month treatment with glucocorticoid significantly reduced bone mineral content (BMC), lean body mass (LBM) and increased fat mass (FAT). Our results are likely to have some clinical relevance. First, BMD loss occurs quite rapidly after starting glucocorticoid treatment, and patients receiving glucocorticoid treatment should be more carefully monitored for their BMD. Second, LBM, which mainly represents muscle volume, decreases rapidly after initiating glucocorticoid treatment. Decreased LBM might be also responsible for the increased risk of fracture, since falling is a well-known risk factor for fracture, and patients receiving glucocorticoid treatment should also be evaluated for their body composition.

Absorptiometry, Photon↗
PubMed2005

Complementary antagonistic actions between C-type natriuretic peptide and the MAPK pathway through FGFR-3 in ATDC5 cells.

We previously reported that C-type natriuretic peptide (CNP) stimulates endochondral ossification and corrects the reduction in body length of achondroplasia model mouse with constitutive active fibroblast growth factor receptor 3 (FGFR-3). In order to examine the interaction between CNP and FGFR-3, we studied intracellular signaling by using ATDC5 cells, a mouse chondrogenic cell line, and found that FGF2 and FGF18 markedly reduced CNP-dependent intracellular cGMP production, and that these effects were attenuated by MAPK inhibitors. Western blot analysis demonstrated that the level of GC-B, a particulate guanylyl cyclase specific for CNP, was not changed by treatment with FGFs. Conversely, CNP and 8-bromo-cGMP strongly and dose-dependently inhibited the induction of ERK phosphorylation by FGF2 and FGF18 without changing the level of FGFR-3, although they did not affect the phosphorylation of STAT-1. In the organ-cultured fetal mouse tibias, CNP and FGF18 counteracted on the longitudinal bone growth, and both the size and number of hypertrophic chondrocytes. The FGF/FGFR-3 pathway is known as the negative regulator of endochondral ossification. We found that FGFs inhibited CNP-stimulated cGMP production by disrupting the signaling pathway through GC-B while CNP antagonized the activation of the MAPK cascade by FGFs. These results suggest that the CNP/GC-B pathway plays an important role in growth plate chondrocytes and constitutes the negative cross talk between FGFs and the activity of MAPK. Our results may explain one of the molecular mechanisms of the growth stimulating action of CNP and suggest that activation of the CNP/GC-B pathway may be effective as a novel therapeutic strategy for achondroplasia.

Animals↗
PubMed2003

Overexpression of CNP in chondrocytes rescues achondroplasia through a MAPK-dependent pathway.

Achondroplasia is the most common genetic form of human dwarfism, for which there is presently no effective therapy. C-type natriuretic peptide (CNP) is a newly identified molecule that regulates endochondral bone growth through GC-B, a subtype of particulate guanylyl cyclase. Here we show that targeted overexpression of CNP in chondrocytes counteracts dwarfism in a mouse model of achondroplasia with activated fibroblast growth factor receptor 3 (FGFR-3) in the cartilage. CNP prevented the shortening of achondroplastic bones by correcting the decreased extracellular matrix synthesis in the growth plate through inhibition of the MAPK pathway of FGF signaling. CNP had no effect on the STAT-1 pathway of FGF signaling that mediates the decreased proliferation and the delayed differentiation of achondroplastic chondrocytes. These results demonstrate that activation of the CNP-GC-B system in endochondral bone formation constitutes a new therapeutic strategy for human achondroplasia.

Achondroplasia↗
PubMed2003

[Not Available].

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Journal Article↗
PubMed2003

[The possible novel treatment of achondroplasia, C-type natriuretic peptide (CNP)].

C-type natiruetic peptide (CNP) showed a potent effect on the elongation of the tibial organ culture system. CNP also corrected the dwarfing phenotype of the CNP knockout mice. These results suggest that CNP is the novel promoter of the endochondral ossification, and that CNP/GC-B activation is possible target of the treatment of the achondroplasia.

English Abstract↗
PubMed2002

A novel interaction between thyroid hormones and 1,25(OH)(2)D(3) in osteoclast formation.

Thyroid hormones enhance osteoclast formation and their excess is an important cause of secondary osteoporosis. 3,5,3' -Triiodo-L-thyronine (T3) induced the mRNA expression of receptor activator of nuclear factor-kappa B ligand (RANKL), which is a key molecule in osteoclast formation, in primary osteoblastic cells (POB). This effect was amplified in the copresence of 1 alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)). Although T3 alone did not induce octeoclasts in coculture of bone marrow cells with POB, T3 enhanced 1,25(OH)(2)D(3)-induced osteoclast formation. Thyroxine (T4) also enhanced 1,25(OH)(2)D(3)-induced osteoclast formation. These data suggested that T4 was locally metabolized to T3 for its action, since T4 is a prohormone with little hormonal activity. The mRNA expression of type-2 iodothyronine deiodinase (D2), which is responsible for maintaining local T3 concentration, was induced by 1,25(OH)(2)D(3) dose- and time-dependently. Our data would facilitate our understanding of the mechanism of osteoclast formation by thyroid hormones and suggest a novel interaction between thyroid hormones and 1,25(OH)(2)D(3).

Animals↗
PubMed2002

C-type natriuretic peptide/guanylate cyclase B system in ATDC5 cells, a chondrogenic cell line.

Natriuretic peptides constitute a family of three structurally related peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). Particulate guanylate cyclases, GC-A, and GC-B, are the receptors for these peptides to mediate their action. ANP and BNP possess high affinities for GC-A, and CNP is the preferred ligand for GC-B. In this article, we report our study of the expression and possible role(s) of natriuretic peptides in ATDC5 cells, which represent a chondrogenic cell line. ATDC5 cells produced cyclic guanosine monophosphate (cGMP) in response to natriuretic peptides. CNP was far more potent than ANP in terms of cGMP production. The messages for GC-A and GC-B were demonstrated by means of Northern blot analysis, and the presence of CNP was shown by Southern blotting coupled with reverse transcription-polymerase chain reaction (RT-PCR). These results suggest that the CNP/GC-B system is preferentially expressed in ATDC5 cells. GC-B mRNA expression was higher at 14 days after confluency than that at confluency. CNP or 8-bromo cGMP reduced [3H] thymidine uptake and slightly increased the message for collagen type X, which is a marker of hypertrophic chondrocytes. These data suggest that the CNP/GC-B system is likely to be an autocrine/paracrine regulator of ATDC5 cells, thus affecting both their growth and differentiation.

Animals↗
PubMed2002

Cyclic GMP-dependent protein kinase II plays a critical role in C-type natriuretic peptide-mediated endochondral ossification.

Longitudinal bone growth is determined by endochondral ossification at the growth plate, which is located at both ends of long bones and vertebrae, and involves many systemic hormones and local regulators. C-type natriuretic peptide (CNP), a third member of the natriuretic peptide family, occurs at the growth plate and acts locally as a positive regulator of endochondral ossification through the intracellular accumulation of cyclic GMP (cGMP). The increase in cGMP concentrations is known to activate different signaling mediators, such as cyclic nucleotide phosphodiesterases, cGMP-regulated ion channels, and cGMP-dependent protein kinases (cGKs). The type II cGK (cGKII)-deficient mice (Prkg2(-/-) mice) develop dwarfism as a result of impaired endochondral ossification, suggesting that cGKII is important for the CNP-mediated endochondral ossification. However, given that Prkg2(-/-) mice differ from CNP-deficient mice (Nppc(-/-) mice) in the growth plate histology, which downstream mediator(s) of cGMP play key roles in the process is still an enigma. Here we show that targeted expression of CNP in the growth plate chondrocytes fails to rescue the skeletal defect of Prkg2(-/-) mice. Using cultured fetal mouse tibias, an in vitro model system of endochondral ossification, we also demonstrated that CNP cannot increase the longitudinal bone growth, and chondrocytic proliferation and hypertrophy, and cartilage matrix synthesis in Prkg2(-/-) mice. This study provides in vivo and in vitro genetic evidence that cGKII plays a critical role in CNP-mediated endochondral ossification.

Animals↗
PubMed2002

Thyroid hormones promote chondrocyte differentiation in mouse ATDC5 cells and stimulate endochondral ossification in fetal mouse tibias through iodothyronine deiodinases in the growth plate.

Thyroid hormones (THs), 3,3',5-triiodo-L-thyronine (T3) and L-thyroxine (T4), are important for the normal development of the growth plate (GP); congenital TH deficiency leads to severe dwarfism. In mouse chondrogenic cell line, ATDC5, T3 enhanced differentiation and increased Alizarin red staining, but did not affect Alcian blue staining. In organ-cultured mouse tibias, THs stimulated the cartilage growth, especially in the hypertrophic zone. Interestingly, T4 was as equally potent as T3 in organ-cultured tibias, which suggests that T4 is metabolized locally to T3, because T4 is a prohormone and must be converted to T3 for its activity. Two enzymes catalyze the conversion; type I deiodinase (D1) and type II deiodinase (D2). D1 has a ubiquitous distribution and D2, with a high affinity for T4, is present where the maintenance of intracellular T3 concentration is critical. Messenger RNAs (mRNAs) for D1 and D2 were detected in neonatal mouse tibias and ATDC5 cells. The enzyme activity was unaffected by the D1 inhibitor 6-propyl-2-thiouracil, suggesting that D2 mainly catalyzes the reaction. D2 mRNA was detected in differentiated ATDC5 cells. In organ-cultured mouse tibias, D2 activity was greater at later stages. In contrast, thyroid hormone receptors (TRs) were expressed in neonatal mouse tibias and ATDC5 cells, but their expression levels in ATDC5 cells were stable throughout the culture periods. Therefore, increased T3 production at later stages by D2 is likely to contribute to the preferential effects of THs in the terminal differentiation of GP. This article is the first to show that T4 is activated locally in GP and enhances the understanding of TH effects in GP.

Animals↗
PubMed2002

[Not Available].

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Journal Article↗