PubMed Health⌕ Search

Biomedical subjects

Kazumasa Isobe

Publications and source records attributed to Kazumasa Isobe.

At least 19 recordsLinked to original sources
PubMed2006

Effect of norepinephrine on RhoA, MAP kinase, proliferation and VEGF expression in human umbilical vein endothelial cells.

Norepinephrine is a well known major vasoconstricting factor. Recent reports suggest that norepinephrine, in addition to acting as a vasoconstricting factor, may also play several additional roles in endothelial cells. These include: 1] induction of NO release. It has been demonstrated that a small GTP-binding protein, Rho, and its downstream effecter, Rho kinase (ROCK), negatively regulate endothelial nitric oxide synthase (eNOS) production. However, it is not known whether ROCK is directly involved in norepinephrine-induced NO release. 2] Norepinephrine is reported to induce a mitogenic effect, but whether MAPKs are involved in this process is unknown. 3] Recently, we demonstrated an increase in vascular endothelial growth factor (VEGF) mRNA/protein expression in human pheochromocytoma tissue in comparison to normal adrenomedullary tissue. Thus, it is reasonable to speculate that norepinephrine may stimulate the level of VEGF mRNA. The aim of the present study was to clarify the role of norepinephrine and related endothelial adrenoceptor systems in various pathophysiological conditions, such as hypertension and in particular pheochromocytoma, using human umbilical vein endothelial cells (HUVEC). Norepinephrine-induced RhoA attenuation, through cAMP/protein kinase A (PKA) activation coupled with beta-adrenoceptors, may lead to eNOS activation in acute conditions. Norepinephrine stimulates the production of VEGF mRNA through cAMP/PKA activation coupled with beta-adrenoceptors. Norepinephrine stimulates a mitogenic effect through ERK activation coupled with the alpha(1)-adrenoceptor. In conclusion, norepinephrine stimulates eNOS activity via RhoA attenuation, VEGF mRNA synthesis and mitogenic activity in endothelial cells. We propose that an excess of norepinephrine can lead to endothelial dysfunction due to these aforementioned processes.

Blotting, Western↗
PubMed2006

Long-term exercise stimulates adenosine monophosphate-activated protein kinase activity and subunit expression in rat visceral adipose tissue and liver.

Adenosine monophosphate-activated protein kinase (AMPK) is activated in response to adenosine triphosphate depletion caused by the metabolic and nutritional state. Mammalian AMPK is a heterotrimeric enzyme composed of a catalytic alpha subunit and 2 regulatory subunits (beta and gamma). Although much attention has been focused on exercise-induced AMPK activation in skeletal muscle, little information is available on the role of AMPK in adipose tissue and liver. Acetyl-coenzyme A carboxylase (ACC) is a well-known downstream target of AMPK. The ACC contains serine residues that are phosphorylated by AMPK. The present study was undertaken to determine whether long-term exercise of medium intensity (60% of Vo2max for 12 weeks) may influence AMPK enzyme activity, gene/protein expression, and subsequent ACC phosphorylation in rat adipose tissue (visceral and subcutaneous) and liver. We initially demonstrated that long-term exercise induced a significant increase in phosphorylation of Thr172 in the AMPK alpha1 subunit and of Ser79 in ACC in visceral adipose tissue rather than subcutaneous tissue. We also demonstrated that the AMPK alpha1-,alpha2-subunit messenger RNA (mRNA) level as well as the corresponding protein levels were increased in response to long-term exercise, whereas the other subunits were not altered significantly. In contrast to that of visceral adipose tissue, long-term exercise did not induce any significant effect on any of the AMPK subunit mRNA levels or alpha1-,alpha2-subunit protein levels in subcutaneous adipose tissue. In addition to adipose tissue, we demonstrated that long-term exercise induced an increase in both AMPK/ACC phosphorylation and alpha1-,alpha2-subunit mRNA/protein expression in the liver. Although the precise physiologic relevance of AMPK activation in these tissues remains unknown, it is possible that it might play an important role in long-term exercise-induced adaptation mechanisms and may lead to an improvement in certain metabolic abnormalities in metabolic diseases.

AMP-Activated Protein Kinases↗
PubMed2006

Expression of mRNAs for succinate dehydrogenase subunits and related genes in pheochromocytoma.

Mutations in the genes encoding succinate dehydrogenase (SDH) have been associated with susceptibility to pheochromocytoma. However, few reports have examined the level of SDH mRNAs expression. In this study, we examined the level of expression of mRNAs encoding SDHB, SDHC, and SDHD in pheochromocytoma, pheochromocytoma subgroups, and normal adrenal gland, and compared the expression of these genes to the level of expression of related genes in the same tissues. The mean relative level of expression of SDHB, SDHC, SDHD and VHL mRNA was 28.7+/-6.2%, 16.6+/-4.8%, 214+/-47.5% and 25.9+/-8.2%, respectively, in pheochromocytoma tissues compared to normal adrenal gland. Furthermore, the mean relative level of the RET proto-oncogene mRNA was 707+/-149% in pheochromocytoma compared to normal adrenal gland. The level of expression of the SDH genes was highly correlated in each individual sample (P<0.0001). The level of expression of the SDH mRNAs correlated with the level of VHL mRNA (P<0.0001), but not with the level of RET mRNA. The level of SDH mRNAs expression also correlated with the expression of phenylethanolamine N-methyl transferase (PNMT), an adrenaline synthesizing enzyme (P<0.01), which may explain the correlation between SDH expression and adrenaline content (P<0.05). The level of SDH mRNAs expression correlated strongly with the expression of VEGF mRNA (P<0.0001). In multiple endocrine neoplasia (MEN) 2a, the expression of the SDH genes and VHL mRNA was significantly higher than that observed in adrenal or extra-adrenal pheochromocytoma. The expression of the corticotropin-releasing hormone (CRH) mRNA was significantly higher in extra-adrenal pheochromocytoma than in adrenal pheochromocytoma or MEN2a. Thus, tumor-specific gene expression exists in pheochromocytoma, which may explain the characteristics of the tumor.

Adolescent↗
PubMed2005

Inhibition of the RhoA/Rho kinase system attenuates catecholamine biosynthesis in PC 12 rat pheochromocytoma cells.

The small GTPase, RhoA, and its downstream effecter Rho-kinase (ROK) are reported to be involved in various cellular functions, such as myosin light chain phosphorylation during smooth muscle contraction and exocytosis. Indeed, growing evidence suggests that the RhoA/Rho-kinase pathway plays an important role in regulating exocytosis in these cells. However, it is not known whether the RhoA/Rho-kinase pathway has an effect on catecholamine synthesis. Using the rat pheochromocytoma cell line, PC12, we examined the effects of either Rho-kinase inhibitor (Y27632) or RhoA inhibitor (C3 toxin) on nicotine-induced catecholamine biosynthesis. We show that nicotine (10 microM) induces a significant, though transient, increase in RhoA activation in these cells. Treatment with either Y27632 (1 microM) or C3 toxin (10 microg/ml) significantly inhibited the nicotine-induced increase of tyrosine hydroxylase (TH) mRNA and the corresponding enzyme activity. TH catalyzes the rate-limiting step in the biosynthesis of catecholamine. Y27632 significantly inhibited nicotine-induced phosphorylation of TH at Ser40 as well as Ser19, which are known to be phosphorylated by Ca(2+)/calmodulin kinase II. Furthermore, Y27632 (10 microM) as well as C3 toxin (10 microg/ml) significantly inhibited the nicotine-induced increase of TH at the protein level. Thus, we propose that activation of RhoA, and its downstream effecter Rho-kinase, is a prerequisite for catecholamine biosynthesis in PC12 cells. At the concentrations used in our experiments, Y27632 does not affect cAMP/PKA activity or PKC activity, indicating that the inhibitory effect of Y27632 can be attributed to the inhibition of Rho-kinase activity as observed in chromaffin cells. In contrast, neither Y27632 (10 microM) nor C3 toxin (10 microg/ml) significantly altered catecholamine secretion in PC12 cells. In conclusion, we have demonstrated that inhibition of the Rho/Rho-kinase pathway in chromaffin cells lowers TH activity, probably through CaMKII inhibition. By contrast, neither Y27632 nor C3 toxin affect the secretion of catecholamine.

Amides↗
PubMed2005

Urocortin stimulates tyrosine hydroxylase activity via the cAMP/protein kinase a pathway in rat Pheochromocytoma PC12 cells.

Urocortin is a novel mammalian member of the corticotrophin releasing factor (CRF)-related peptides. We have investigated the expression, mechanism of action and second messenger for urocortin in rat pheochromocytoma PC12 cells. We initially confirmed the expression of urocortin and CRF-R2beta, which is thought to be an endogenous receptor for urocortin, in PC12 cells. We also demonstrate that urocortin (> or = 1 nM) significantly elevates the level of cAMP in these cells. Moreover, alpha-helical CRF-(9-41), a more specific antagonist of CRF-R2 than CRF-R1 and the adenylate cyclase inhibitor SQ22536, inhibited the urocortin-induced increase in the level of cAMP. Thus, urocortin may exert its physiological role in chromaffin cells via CRF-R2beta coupling to adenylate cyclase. Urocortin (> or = 1 nM) significantly increased the mRNA level and activity of tyrosine hydroxylase (TH), a rate-limiting enzyme in the biosynthesis of catecholamine. Furthermore, urocortin-induced changes in TH-mRNA and activity were inhibited by H89 (a PKA inhibitor) and SQ22536 as well as alpha-helical CRF-(9-41). However, urocortin did not affect DNA synthesis or catecholamine secretion in these cells. In conclusion, we have demonstrated that urocortin stimulates catecholamine biosynthesis via the cAMP/protein kinase A pathway in PC12 cells, where both urocortin and its receptor, CRF-R2, are expressed.

Adenine↗
PubMed2005

The relationship between non-HDL cholesterol and other lipid parameters in Japanese subjects.

Plasma non-HDL cholesterol (HDL-C) concentration that is simply estimated from plasma total cholesterol and HDL-C concentrations, without the influence of plasma triglyceride concentration, has been included as a therapeutic target for hypertriglyceridemic patients in the most recent National Cholesterol Education Program (NCEP) recommendations. In the present study, we estimated plasma non-HDL-C concentration in Japanese subjects to clarify the correlation of plasma non-HDL-C to other plasma lipid concentrations, and to evaluate the NCEP recommendation. Plasma non-HDL-C concentration has a positive correlation with low-density lipoprotein cholesterol (LDL-C) and triglyceride concentrations. From our analysis, 140 mg/dl of plasma LDL-C concentration, which is the level for the diagnosis of hyper-LDL cholesterolemia, corresponds to 169 mg/dl of non HDL-C concentration. The relationship between plasma non-HDL-C and LDL-C concentrations in Japanese subjects is quite similar to that described in the NCEP guideline. Thus, we suggest that non-HDL-C is a useful risk marker in Japan, as recommended by the NCEP.

Arteriosclerosis↗
PubMed2005

[Pheochromocytoma].

Explore the source record for details and available documents.

Adrenal Gland Neoplasms↗
PubMed2004

Expression of mRNAs for PACAP and its receptor in human neuroblastomas and their relationship to catecholamine synthesis.

PURPOSE: Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin/glucagon/vasoactive intestinal peptide family, induces the expression of catecholamine-synthesizing enzymes in adrenal medullary cells. In addition, PACAP and its receptor have been detected in human neuroblastoma tissues and cell lines, though it is not yet known whether PACAP enhances the expression of genes encoding catecholamine-synthesizing enzymes. To address this question, we analyzed PACAP, PACAP receptor and tyrosine hydroxylase (TH) mRNAs in neuroblastomas. METHODS: The levels of mRNA for PACAP and vasoactive intestinal peptide (VIP), as well as their receptors and the mRNA for TH were measured by RT-PCR or real-time PCR analysis. RESULTS: VPAC1R mRNA was detected in all of 16 tissues and 3 cell lines that were examined, while VPAC2R mRNA was detected in 5 of 16 (31%) tissue and 2 of 3 cell lines. PAC1R mRNA was detected in 6 out of 16 (38%) tissues and none of 3 cell lines. mRNA expression of PACAP and TH were detected in many tissues (10/16 and 16/16, respectively). However, neither in tissues nor cell lines did PACAP mRNA expression correlate with TH mRNA expression. CONCLUSION: Our findings suggest that PACAP is not involved in the regulation of expression of TH in neuroblastomas.

Base Sequence↗
PubMed2004

Expression of vascular endothelial growth factor (VEGF) and its cognate receptors in human pheochromocytomas.

Pheochromocytomas are well-vascularized tumors, suggesting that a potent angiogenic factor may be involved in the mechanism of their formation. As vascular endothelial growth factor (VEGF) is a potent mitogen for vascular endothelial cells, here we have investigated the mRNA and protein expression of VEGF and the mRNA expression of its two receptors (Flt-1 and Flk-1/KDR) in pheochromocytomas tissue. An increase in VEGF mRNA (mainly isoforms VEGF(121) and VEGF(165)) and in VEGF protein expression were observed by semi-quantitative RT-PCR and Western blot, respectively, compared to normal adrenomedullary tissue. Flk-1/KDR, and Flt-1 levels of mRNA were also increased markedly in tumors and correlated with levels of VEGF mRNA. Therefore, we speculate that upregulation of VEGF expression and its receptors might be important in the pathogenesis of pheochromocytomas.

Adrenal Gland Neoplasms↗
PubMed2004

Expression of the human telomerase reverse transcriptase in pheochromocytoma and neuroblastoma tissues.

In an effort to clarify the role of telomerase in the pathogenesis of pheochromocytomas and neuroblastomas, and to test whether its component could serve as a marker of malignancy, we measured telomerase reverse transcriptase (TERT) mRNA in 31 human pheochromocytoma tissue samples (5 malignant, 23 benign and 3 suspected malignant) and 16 neuroblastoma tissues (9 unfavorable and 7 favorable). All cases were classified by both the clinical course and histopathological examination. Malignancy was defined as the presence of metastasis and/or extensive local invasion. TERT mRNA was determined by nested PCR and a real-time PCR system (LightCycler). By nested PCR methods, 5 of the 5 malignant pheochromocytoma samples were positive (sensitivity = 100%), and 21 of 23 benign pheochromocytoma samples were negative (specificity = 91%) in pheochromocytomas. Four out of five malignant tumors were positive for either hTERT expression or Ki-67/MIB-1 immunoreactivity. In the neuroblastoma tissues, 9 of the 9 unfavorable samples were positive (sensitivity = 100%), and only 2 of 7 favorable samples were negative (specificity = 29%). We also determined the expression of the hTERT mRNA by real-time PCR to quantitate the mRNA. The mean values of hTERT mRNA by real time PCR in benign and malignant pheochromocytomas were 2 and 26 arbitrary units (AU), respectively. The difference was not significant by the U-test. The mean values of hTERT mRNA in favorable and unfavorable neuroblastoma were 203 and 497 AU, respectively. This difference was also not significant (U-test). N-Myc mRNA expression correlated with the expression of hTERT mRNA in the neuroblastoma samples (r = 0.534, p = 0.0317). Thus, hTERT mRNA might be a potential marker for estimating the malignancy of pheochromocytomas and neuroblastomas.

Adolescent↗
PubMed2003

Prolactin-releasing peptide stimulates catecholamine release but not proliferation in rat pheochromocytoma PC12 cells.

We examined the effect of prolactin-releasing peptide (PrRP) on catecholamine secretion and DNA synthesis in rat pheochromocytoma PC12 cells. We initially confirmed the expression of both PrRP and its receptor in PC12 cells. PrRP31 and PrRP20 (> or =10 nM) significantly increased dopamine secretion from PC12 cells. However, PrRP20-stimulated dopamine secretion was markedly weaker than that of PrRP31. Both EDTA (extracellular Ca2+ chelator) and BAPTA-AM (intracellular Ca2+ chelator) effectively suppressed PrRP31 (100 nM)-induced dopamine secretion. PrRP31and PrRP20 (> or =1 nM) significantly induced an increase in the level of cAMP. The PKA inhibitor H89 (at 10 microM) impeded PrRP31- and PrRP20-induced dopamine secretion. Finally, we confirmed that PrRP did not affect DNA synthesis. These results indicate that PrRP may regulate catecholamine secretion but not the mitogenic effects in chromaffin cells.

Animals↗
PubMed2003

Expression of mRNA for PACAP and its receptors in intra- and extra-adrenal human pheochromocytomas and their relationship to catecholamine synthesis.

PURPOSE: Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin/glucagons/vasoactive intestinal peptide family, induces the expression of catecholamine-synthesizing enzymes in adrenal medullary cells. In addition, PACAP and its receptor have been detected in human pheochromocytoma tissues, though it is not yet known whether PACAP enhances the expression of genes encoding catecholamine-synthesizing enzymes. To address this question, we analyzed PACAP, PACAP receptor, and tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT) mRNAs in pheochromocytomas. METHODS: The levels of the mRNA for PACAP and vasoactive intestinal peptide (VIP), and their receptors, and for TH and PNMT were measured by RT-PCR or real-time PCR analysis, and the concentrations of catecholamines were measured by HPLC in 24 intra-adrenal and six extra-adrenal pheochromocytomas. RESULTS: mRNA expression of PACAP and its receptor VPAC1R were detected in many pheochromocytomas (24/30 and 29/30, respectively), but mRNA expression of the PAC1R and VPAC2R receptor subtypes were detected in only one of six extra-adrenal pheochromocytomas. PACAP mRNA expression correlated with TH (p=0.0018) and PNMT (p=0.05) mRNA expression, as well as epinephrine (p=0.0342) levels in 16 intra-adrenal pheochromocytomas. CONCLUSION: Our findings support a possible role for PACAP in the regulation of expression of genes encoding catecholamine-synthesizing enzymes in intra-adrenal pheochromocytomas.

Adrenal Gland Neoplasms↗
PubMed2003

Effect of Ghrelin on catecholamine secretion in rat pheochromocytoma PC12 cells.

A novel peptide Ghrelin, found to be a ligand to growth hormone (GH) secretagogue receptor (GHS-R), exeterts to stimulates GH release from pituitary gland. Recently, it has been shown that ghrelin and its receptor are existed in a adrenal ground. At concentrations of 10 nM and over (10 nM, 100 nM, and 1 microM), ghrelin significantly inhibited basal dopamine release by 30, 32 and 34%, respectively (P < 0.05) in PC12 cells, suggesting that ghrelin may be involved in the mechanism of catecholamine regulation in chromaffin cells.

Animals↗
PubMed2002

Vascular endothelial growth factor gene expression in a retinal pigmented cell is up-regulated by glucose deprivation through 3' UTR.

Diabetic retinopathy is known to be worsened when hypoglycemia occurs, however the pathogenic mechanisms are not defined. Vascular endothelial growth factor (VEGF) is increased in ocular fluid with diabetic retinopathy and linked with development of retinopathy. In this study, we examined whether glucose deficiency could up-regulate VEGF levels in retinal pigmented cells. Exposure to glucose deprived medium induced 30% up-regulation of VEGF mRNA. In hypoxia, as one of the most well-known inducer of VEGF, its up-regulation mechanism is mainly due to increase of transcription of VEGF gene via hypoxia response element in 5'-untranslated region (5'-UTR). We examined the role of 5'-UTR and 3'-UTR of VEGF gene in glucose deprived conditions using luciferase assay system. 5'-UTR containing reporter vector did not show increase of activity in glucose deprived conditions in contrast to the result in oxygen deprived condition. Both 5'-UTR and 3'-UTR containing vector demonstrated significant increase of activity in glucose deficient conditions compared with 5'-UTR containing vector. These findings suggest 3'-UTR of VEGF gene is important for increasing mRNA level in glucose deprived condition.

3' Untranslated Regions↗
PubMed2002

Effects of orexin on cultured porcine adrenal medullary and cortex cells.

New orexigenic peptides called orexins have recently been described in the neurons of the lateral hypothalamus and perifornical area. No orexins have been found in the adipose tissues or visceral organs, including the adrenal gland. However, expression of the orexin receptor (OXR) in the rat adrenal gland has been reported. With regard to the effects of orexins on peripheral organs, we previously reported that orexins suppress catecholamine synthesis and secretion in the rat pheochromocytoma cell line PC12. To further clarify the pharmacological effects of orexins on peripheral organs, we examined the effects of orexin-A on catecholamine, cortisol, and aldosterone secretion, using cultured porcine adrenal glands. We initially confirmed the expression of the orexin receptor (OXR-1) in cultured porcine adrenal medulla and cortex. Orexin-A (1000 nM) significantly increased the release of both epinephrine (E) and norepinephrine (NE) from porcine adrenal medullary cells. Similarly, orexin-A (> or = 100 nM) significantly increased the release of both cortisol and aldosterone from porcine adrenal cortex cells. Orexin-A (100 nM) significantly inhibited basal and the PACAP-induced increase in cAMP levels in adrenal medullary cells. Conversely, orexin-A (>o = 100 nM) significantly increased the cAMP level in adrenal cortex cells. These results indicate that orexin-A induces the release of catecholamine from porcine adrenal medullary cells, and aldosterone and cortisol from the cortex cells and has opposite effects on cAMP levels in adrenal medulla and cortex.

Adrenal Cortex↗