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Articles by K. Nakao
Total Records ( 9 ) for K. Nakao
  T Kake , H Kitamura , Y Adachi , T Yoshioka , T Watanabe , H Matsushita , T Fujii , E Kondo , T Tachibe , Y Kawase , K. i Jishage , A Yasoda , M Mukoyama and K. Nakao

C-type natriuretic peptide (CNP) plays a critical role in endochondral ossification through guanylyl cyclase-B (GC-B), a natriuretic peptide receptor subtype. Cartilage-specific overexpression of CNP enhances skeletal growth and rescues the dwarfism in a transgenic achondroplasia model with constitutive active mutation of fibroblast growth factor receptor-3. For future clinical application, the efficacy of CNP administration on skeletal growth must be evaluated. Due to the high clearance of CNP, maintaining a high concentration is technically difficult. However, to model high blood CNP concentration, we established a liver-targeted CNP-overexpressing transgenic mouse (SAP-CNP tgm). SAP-CNP tgm exhibited skeletal overgrowth in proportion to the blood CNP concentration and revealed phenotypes of systemic stimulation of cartilage bones, including limbs, paws, costal bones, spine, and skull. Furthermore, in SAP-CNP tgm, the size of the foramen magnum, the insufficient formation of which results in cervico-medullary compression in achondroplasia, also showed significant increase. CNP primarily activates GC-B, but under high concentrations it cross-reacts with guanylyl cyclase-A (GC-A), a natriuretic peptide receptor subtype of atrial natriuretic peptides (ANP) and brain natriuretic peptides (BNP). Although activation of GC-A could alter cardiovascular homeostasis, leading to hypotension and heart weight reduction, the skeletal overgrowth phenotype in the line of SAP-CNP tgm with mild overexpression of CNP did not accompany decrease of systolic blood pressure or heart weight. These results suggest that CNP administration stimulates skeletal growth without adverse cardiovascular effect, and thus CNP could be a promising remedy targeting achondroplasia.

  T Ishii Yonemoto , H Masuzaki , S Yasue , S Okada , C Kozuka , T Tanaka , M Noguchi , T Tomita , J Fujikura , Y Yamamoto , K Ebihara , K Hosoda and K. Nakao

Increased expression and activity of the intracellular glucocorticoid-reactivating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) contribute to dysfunction of adipose tissue. Although the pathophysiological role of 11β-HSD1 in mature adipocytes has long been investigated, its potential role in preadipocytes still remains obscure. The present study demonstrates that the expression of 11β-HSD1 in preadipocyte-rich stromal vascular fraction (SVF) cells in fat depots from ob/ob and diet-induced obese mice was markedly elevated compared with lean control. In 3T3-L1 preadipocytes, the level of mRNA and reductase activity of 11β-HSD1 was augmented by TNF-, IL-1β, and LPS, with a concomitant increase in inducible nitric oxide synthase (iNOS), monocyte chemoattractant protein-1 (MCP-1), or IL-6 secretion. Pharmacological inhibition of 11β-HSD1 and RNA interference against 11β-HSD1 reduced the mRNA and protein levels of iNOS, MCP-1, and IL-6. In contrast, overexpression of 11β-HSD1 further augmented TNF--induced iNOS, IL-6, and MCP-1 expression. Moreover, 11β-HSD1 inhibitors attenuated TNF--induced phosphorylation of NF-B p65 and p38-, JNK-, and ERK1/2-MAPK. Collectively, the present study provides novel evidence that inflammatory stimuli-induced 11β-HSD1 in activated preadipocytes intensifies NF-B and MAPK signaling pathways and results in further induction of proinflammatory molecules. Not limited to 3T3-L1 preadipocytes, we also demonstrated that the notion was reproducible in the primary SVF cells from obese mice. These findings highlight an unexpected, proinflammatory role of reamplified glucocorticoids within preadipocytes in obese adipose tissue.

  S Yasuno , S Usami , K Kuwahara , M Nakanishi , Y Arai , H Kinoshita , Y Nakagawa , M Fujiwara , M Murakami , K Ueshima , M Harada and K. Nakao

Ventricular myocytes are known to show increased expression of the cardiac hormones atrial and brain natriuretic peptide (ANP and BNP, respectively) in response to pathological stress on the heart, but their function during the progression of nonischemic dilated cardiomyopathy remains unclear. In this study, we crossed a mouse model of dilated cardiomyopathy and sudden death, which we generated by cardioselectively overexpressing a dominant-negative form of the transcriptional repressor neuron-restrictive silencer factor (dnNRSF Tg mice), with mice lacking guanylyl cyclase-A (GC-A), a common receptor for ANP and BNP, to assess the effects of endogenously expressed natriuretic peptides during progression of the cardiomyopathy seen in dnNRSF Tg mice. We found that dnNRSF Tg;GC-A–/– mice were born normally, but then most died within 4 wk. The survival rates among dnNRSF Tg;GC-A+/– and dnNRSF Tg mice were comparable, but dnNRSF Tg;GC-A+/– mice showed greater systolic dysfunction and a more severe cardiomyopathic phenotype than dnNRSF Tg mice. Collectively, our findings suggest that endogenous ANP/BNP protects the heart against the death and progression of pathological remodeling in a mouse model of dilated cardiomyopathy and sudden death.

  D Taura , M Sone , K Homma , N Oyamada , K Takahashi , N Tamura , S Yamanaka and K. Nakao

Objective— Induced pluripotent stem (iPS) cells are a novel stem cell population derived from human adult somatic cells through reprogramming using a defined set of transcription factors. Our aim was to determine the features of the directed differentiation of human iPS cells into vascular endothelial cells (ECs) and mural cells (MCs), and to compare that process with human embryonic stem (hES) cells.

Methods and Results— We previously established a system for differentiating hES cells into vascular cells. We applied this system to human iPS cells and examined their directed differentiation. After differentiation, TRA1–60 Flk1+ cells emerged and divided into VE-cadherin-positive and -negative populations. The former were also positive for CD34, CD31, and eNOS and were consistent with ECs. The latter differentiated into MCs, which expressed smooth muscle -actin and calponin after further differentiation. The efficiency of the differentiation was comparable to that of human ES cells.

Conclusions— We succeeded in inducing and isolating human vascular cells from iPS cells and indicate that the properties of human iPS cell differentiation into vascular cells are nearly identical to those of hES cells. This work will contribute to our understanding of human vascular differentiation/development and to the development of vascular regenerative medicine.

  H Kinoshita , K Kuwahara , M Takano , Y Arai , Y Kuwabara , S Yasuno , Y Nakagawa , M Nakanishi , M Harada , M Fujiwara , M Murakami , K Ueshima and K. Nakao

Background— Pharmacological interventions for prevention of sudden arrhythmic death in patients with chronic heart failure remain limited. Accumulating evidence suggests increased ventricular expression of T-type Ca2+ channels contributes to the progression of heart failure. The ability of T-type Ca2+ channel blockade to prevent lethal arrhythmias associated with heart failure has never been tested, however.

Methods and Results— We compared the effects of efonidipine and mibefradil, dual T- and L-type Ca2+ channel blockers, with those of nitrendipine, a selective L-type Ca2+ channel blocker, on survival and arrhythmogenicity in a cardiac-specific, dominant-negative form of neuron-restrictive silencer factor transgenic mice (dnNRSF-Tg), which is a useful mouse model of dilated cardiomyopathy leading to sudden death. Efonidipine, but not nitrendipine, substantially improved survival among dnNRSF-Tg mice. Arrhythmogenicity was dramatically reduced in dnNRSF-Tg mice treated with efonidipine or mibefradil. Efonidipine acted by reversing depolarization of the resting membrane potential otherwise seen in ventricular myocytes from dnNRSF-Tg mice and by correcting cardiac autonomic nervous system imbalance. Moreover, the R(–)-isomer of efonidipine, a recently identified, highly selective T-type Ca2+ channel blocker, similarly improved survival among dnNRSF-Tg mice. Efonidipine also reduced the incidence of sudden death and arrhythmogenicity in mice with acute myocardial infarction.

Conclusions— T-type Ca2+ channel blockade reduced arrhythmias in a mouse model of dilated cardiomyopathy by repolarizing the resting membrane potential and improving cardiac autonomic nervous system imbalance. T-type Ca2+ channel blockade also prevented sudden death in mice with myocardial infarction. Our findings suggest T-type Ca2+ channel blockade is a potentially useful approach to preventing sudden death in patients with heart failure.

  A Yasoda , H Kitamura , T Fujii , E Kondo , N Murao , M Miura , N Kanamoto , Y Komatsu , H Arai and K. Nakao

Skeletal dysplasias are a group of genetic disorders characterized by severe impairment of bone growth. Various forms of them add to produce a significant morbidity and mortality, yet no efficient drug therapy has been developed to date. We previously demonstrated that C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, is a potent stimulator of endochondral bone growth. Furthermore, we exhibited that targeted overexpression of a CNP transgene in the growth plate rescued the impaired bone growth observed in a mouse model of achondroplasia (Ach), the most frequent form of human skeletal dysplasias, leading us to propose that CNP may prove to be an effective treatment for this disorder. In the present study, to elucidate whether or not the systemic administration of CNP is a novel drug therapy for skeletal dysplasias, we have investigated the effects of plasma CNP on impaired bone growth in Ach mice that specifically overexpress CNP in the liver under the control of human serum amyloid P component promoter or in those treated with a continuous CNP infusion system. Our results demonstrated that increased plasma CNP from the liver or by iv administration of synthetic CNP-22 rescued the impaired bone growth phenotype of Ach mice without significant adverse effects. These results indicate that treatment with systemic CNP is a potential therapeutic strategy for skeletal dysplasias, including Ach, in humans.

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