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Tetsuro Ago

Publications and source records attributed to Tetsuro Ago.

15 recordsLinked to original sources
PubMed2006

Thioredoxin and ventricular remodeling.

Increasing bodies of evidence indicate that reactive oxygen species (ROS) produced by mitochondria and other sources play an essential role in mediating ventricular remodeling after myocardial infarction and the development of heart failure. Antioxidants scavenge ROS, thereby maintaining the reduced environment of cells and inhibiting ventricular remodeling in the heart. Thioredoxin not only functions as a major antioxidant in the heart but also interacts with important signaling molecules and transcription factors, thereby modulating various cellular functions. The activity of thioredoxin is regulated by a variety of mechanisms, such as transcription, localization, protein-protein interaction, and post-translational modification. In this review, we will summarize the cardiac effects of thioredoxin and the mechanisms by which thioredoxin mediates inhibition of ventricular remodeling.

Animals↗
PubMed2006

Valsartan improves the lower limit of cerebral autoregulation in rats.

The effects of angiotensin II type 1 receptor blockers (ARBs) on cerebral blood flow (CBF) autoregulation have not been fully clarified. Thus, we examined the acute effect of valsartan, the most selective ARB, on CBF autoregulation in spontaneously hypertensive rats. Intravenous administration of valsartan (0.3 mg/kg) reduced the mean arterial pressure (MAP) from 184+/-5 (mean+/-SEM) to 174+/-5 mmHg (p<0.001) without affecting CBF as measured by laser-Doppler flowmetry. The lower limit of CBF autoregulation (the MAP at which the CBF was 80% of the baseline value) in the valsartan-treated group (122+/-3 mmHg) was significantly lower than that in the control group (135+/-4 mmHg, p<0.05). Reverse transcribed-polymerase chain reaction and immunohistochemical staining demonstrated that both angiotensin II type 2 receptors and angiotensin II type 1 receptors (AT1Rs) were expressed in endothelial and smooth muscle cells of the rat cerebral arteries. These results suggest that specific inhibition of AT1Rs in the cerebral circulation causes the leftward shift of the lower limit of autoregulation.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

NAD(P)H oxidases in rat basilar arterial endothelial cells.

BACKGROUND AND PURPOSE: Reactive oxygen species (ROS) may play a critical role in the regulation of vascular tone and development of vascular diseases, such as stroke. NAD(P)H oxidase is a major source of ROS in vascular cells, including endothelial cells. It has been considered that Nox2 and Nox4 are exclusively expressed among Nox homologues in the endothelial cells of noncerebral blood vessels. However, the precise molecular identity of the NAD(P)H oxidase in the endothelial cells of the cerebral arteries is not fully understood. We examined the expression of Nox homologues and their activation mechanism in the endothelial cells of the cerebral arteries. METHODS: We isolated and cultured basilar artery endothelial cells (BAECs) of Sprague-Dawley rats. Expression of NAD(P)H oxidase was examined by reverse-transcription-polymerase chain reaction (RT-PCR) and immunohistological staining. RESULTS: RT-PCR disclosed abundant expression of Nox4 with marginal Nox2 in BAEC. In addition, Nox1 was expressed highly both at mRNA and protein levels in BAECs. Immunohistological staining also showed the prominent expression of Nox1 in the endothelial cells of the basilar artery. With respect to the cytosolic components of NAD(P)H oxidases, BAECs expressed p67phox and, to a lesser extent, p47phox, Noxo1, and Noxa1. Both NADH and NADPH induced superoxide production of the BAEC membranes. The phagocyte-type cytosolic components, p47phox and p67phox, significantly enhanced the NADH-induced superoxide production of the BAEC membranes, whereas the components failed to increase the NADPH-induced superoxide production. CONCLUSIONS: Nox1 is highly expressed in the endothelial cells of the cerebral arteries along with Nox2 and Nox4, and the endothelial NAD(P)H oxidase of the cerebral arteries may have a unique activation mechanism by the phagocyte-type cytosolic components.

Animals↗
PubMed2005

Postischemic gene transfer of interleukin-10 protects against both focal and global brain ischemia.

BACKGROUND: Gene therapy may be a promising approach for treatment of brain ischemia, although the efficiency of postischemic gene therapy is not established. Our goal in this study was to examine the effects of gene transfer of interleukin-10 (IL-10), an antiinflammatory cytokine, after induction of brain ischemia. METHODS AND RESULTS: Brain ischemia was produced by either photochemical occlusion of distal middle cerebral artery for focal ischemia or bilateral carotid occlusion for global ischemia in spontaneously hypertensive rats. Adenoviral vectors encoding human IL-10 (AdIL10) or beta-galactosidase (control) were injected into the lateral ventricle 90 or 60 minutes after focal or global ischemia. Five days after ischemia, IL-10, IL-1beta, or tissue necrosis factor-alpha in the cerebrospinal fluid, infarct volume, infiltrations of leukocytes/macrophages in the infarct area, or hippocampal neuronal damages were determined. The transduced IL-10 was released to the cerebrospinal fluid from the ventricular wall and increased to 7623+/-2965 pg/mL 5 days after AdIL10 transfection. Cerebral blood flow during ischemia was not different between treatments in either focal or global ischemia. Brain infarction of the AdIL10 group was significantly smaller and infiltrations of leukocytes and macrophages were fewer in the IL-10 treatment than control. Hippocampal neurons after global ischemia were more preserved, and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling-positive cells were diminished by the IL-10 gene transfer with attenuated IL-1beta and augmented tissue necrosis factor-alpha. CONCLUSIONS: Postischemic gene transfer of IL-10 into the lateral ventricle attenuated brain infarction and hippocampal damages, suggesting the promise for treatment of brain ischemia.

Animals↗
PubMed2004

Calcium influx pathways in rat CNS pericytes.

In central nervous system (CNS), pericytes have been proposed to play a role in broad functional activities including blood-brain barrier, microcirculation, and macrophage activity. However, contractile responses and Ca2+ signaling in CNS pericytes have not been elucidated. The aim of the present study is to investigate contractility and Ca2+ influx pathway in CNS pericytes. CNS pericytes were cultured from rat brain. Contraction of the pericytes in response to various stimuli was evaluated by the change in surface area measured by a light microscope with a digital camera. Reverse transcription and polymerase chain reaction (RT-PCR) was performed to examine the expression of mRNA of alpha-smooth muscle actin. Intracellular Ca2+ was measured using fura-2 fluorescence spectroscopy. A23187 (Ca2+ ionophore), high external K+ (4 x 10(-2) mol/l), endothelin-1, and serotonin induced contraction of CNS pericytes. RT-PCR analysis revealed the expression of alpha-smooth muscle actin in CNS pericytes. Cytosolic Ca2+ ([Ca2+]i) increased after application of high concentration of external K+, tetraethylammonium, and charybdotoxin, which was inhibited by nicardipine and removal of external Ca2+. Angiotensin-II, serotonin, acetylcholine, ATP, and endothelin-1 caused biphasic response in [Ca2+]i. In response to these agents, [Ca2+]i rapidly increased and then decayed to a relatively constant Ca2+ plateau. The Ca2+ plateau was partially inhibited by nicardipine and completely abolished by omission of external Ca2+. After intracellular Ca2+ store was depleted by the removal of external Ca2+ and addition of thapsigargin, reapplication of external Ca2+ evoked increases in [Ca2+]i. These results indicate that CNS pericytes express mRNA of alpha-smooth muscle actin and possess contractile ability. In CNS pericytes, resting membrane potential is regulated by large conductance Ca2+-activated K+ channels and Ca2+ enters into the cells via L-type voltage-dependent Ca2+ channels, agonist-activated Ca2+ permeable channels, and capacitative Ca2+ entry pathways.

Acetylcholine↗
PubMed2004

Nox4 as the major catalytic component of an endothelial NAD(P)H oxidase.

BACKGROUND: Recent evidence has suggested that reactive oxygen species are important signaling molecules in vascular cells and play a pivotal role in the development of vascular diseases. The activity of NAD(P)H oxidase has been identified as the major source of reactive oxygen species in vascular endothelial cells. However, the precise molecular structure and the mechanism of activation of the oxidase have remained poorly understood. METHODS AND RESULTS: Here, we investigated the molecular identities and the superoxide-producing activity of endothelial NAD(P)H oxidase. We found that Nox4, a homologue of gp91phox/Nox2, was abundantly expressed in endothelial cells. The expression of Nox4 in endothelial cells markedly exceeded that of other Nox proteins, including gp91phox/Nox2, and was affected by cell growth. Using electron spin resonance and chemiluminescence, we measured the superoxide production and found that the endothelial membranes had an NAD(P)H-dependent superoxide-producing activity comparable to that of the neutrophil membranes, whereas the activity was not enhanced by the 2 recombinant proteins p47phox and p67phox, in contrast to that of the neutrophil membranes. Downregulation of Nox4 by an antisense oligonucleotide reduced superoxide production in endothelial cells in vivo and in vitro. CONCLUSIONS: These findings suggest that Nox4 may function as the major catalytic component of an endothelial NAD(P)H oxidase.

Animals↗
PubMed2004

PPARgamma ligands attenuate mesangial contractile dysfunction in high glucose.

BACKGROUND: To elucidate the regulation of peroxisome proliferator-activated receptor gamma (PPARgamma) and its roles in mesangial cells, we examined the expression of PPARgamma1 and effects of its ligands on cell phenotypes and angiotensin II-induced contractile response in cultured rat mesangial cells under a high (20 mmol/L) glucose condition. METHODS: The effects of tumor necrosis factor alpha (TNFalpha), protein kinase C (PKC) activation, antisense DNA for PPARgamma1, PPARgamma ligands and PD98059 were examined in mesangial cells cultured in either 5 mmol/L or 20 mmol/L glucose. The expressions of PPARgamma1 protein and alpha-smooth muscle actin (alphaSMA) as a marker of phenotype of cells were determined by Western blot. The expression of PPARgamma1 mRNA was determined by a reverse transcription-polymerase chain reaction method. The reduction of cell surface area in response to angiotensin II was measured by microscope to determine cellular contraction. RESULTS: PKC activation, TNFalpha, and 20 mmol/L glucose decreased PPARgamma1 at both protein and mRNA levels, which was inhibited by PD98059, a specific inhibitor of mitogen-activated protein kinase (MAPK). Decreases of PPARgamma1 protein and contractile response and an increase of alphaSMA occurred simultaneously in the cells treated with 20 mmol/L glucose after 5 days, which were attenuated to the normal levels by PPARgamma ligands. The antisense DNA also induced the decrease of PPARgamma1 protein, contractile dysfunction, and increase of alphaSMA. CONCLUSION: MAPK suppresses PPARgamma1 at the transcriptional level, and the reduction of PPARgamma1 in cultured rat mesangial cells under the high glucose condition induces phenotypic change and loss of contractile function. PPARgamma ligands recover both reductions of PPARgamma 1 protein and contractile response.

Actins↗
PubMed2003

ATP-sensitive potassium channels mediate dilatation of basilar artery in response to intracellular acidification in vivo.

BACKGROUND AND PURPOSE: During cerebral ischemia, both hypoxia and hypercapnia appear to produce marked dilatation of the cerebral arteries. Hypercapnia and hypoxia may be accompanied by extracellular and intracellular acidosis, which is another potent dilator of cerebral arteries. However, the precise mechanism by which acidosis produces dilatation of the cerebral arteries is not fully understood. The objective of the present study was to examine the mechanisms by which intracellular acidosis produces dilatation of the basilar artery in vivo. METHODS: Using a cranial window in anesthetized rats, we examined responses of the basilar artery to sodium propionate, which was used to cause intracellular acidosis specifically. Expression of subunits of potassium channels was determined by reverse transcription and polymerase chain reaction (RT-PCR). RESULTS: Topical application of propionate increased diameter of the basilar artery in a concentration-related manner. Propionate-induced dilatation of the artery was attenuated by glibenclamide, an inhibitor of ATP-sensitive potassium channels. However, inhibitors of nitric oxide synthase (N(G)-nitro-L-arginine), large-conductance calcium-activated potassium channels (iberiotoxin), and cyclooxygenase (indomethacin) did not affect the vasodilatation. Expression of mRNA for SUR2B and Kir6.1 was detected, with the use of RT-PCR, in the cultured basilar arterial muscle cells. CONCLUSIONS: The findings suggest that intracellular acidification may produce dilatation of the basilar artery through activation of ATP-sensitive potassium channels in vivo. Kir6.1/SUR2B may be the major potassium channels that mediate propionate-induced dilatation of the artery.

ATP-Binding Cassette Transporters↗
PubMed2003

Phosphorylation of p47phox directs phox homology domain from SH3 domain toward phosphoinositides, leading to phagocyte NADPH oxidase activation.

Protein-phosphoinositide interaction participates in targeting proteins to membranes where they function correctly and is often modulated by phosphorylation of lipids. Here we show that protein phosphorylation of p47(phox), a cytoplasmic activator of the microbicidal phagocyte oxidase (phox), elicits interaction of p47(phox) with phosphoinositides. Although the isolated phox homology (PX) domain of p47(phox) can interact directly with phosphoinositides, the lipid-binding activity of this protein is normally suppressed by intramolecular interaction of the PX domain with the C-terminal Src homology 3 (SH3) domain, and hence the wild-type full-length p47(phox) is incapable of binding to the lipids. The W263R substitution in this SH3 domain, abrogating the interaction with the PX domain, leads to a binding of p47(phox) to phosphoinositides. The findings indicate that disruption of the intramolecular interaction renders the PX domain accessible to the lipids. This conformational change is likely induced by phosphorylation of p47(phox), because protein kinase C treatment of the wild-type p47(phox) but not of a mutant protein with the S303304328A substitution culminates in an interaction with phosphoinositides. Furthermore, although the wild-type p47(phox) translocates upon cell stimulation to membranes to activate the oxidase, neither the kinase-insensitive p47(phox) nor lipid-binding-defective proteins, one lacking the PX domain and the other carrying the R90K substitution in this domain, migrates. Thus the protein phosphorylation-driven conformational change of p47(phox) enables its PX domain to bind to phosphoinositides, the interaction of which plays a crucial role in recruitment of p47(phox) from the cytoplasm to membranes and subsequent activation of the phagocyte oxidase.

Amino Acid Substitution↗
PubMed2002

Increased activity of calcium channels and Rho-associated kinase in the basilar artery during chronic hypertension in vivo.

OBJECTIVES: Several factors mediating vascular responses appear to play an important role in the increased resistance of cerebral blood vessels during hypertension. The objective of this study was to elucidate the mechanisms by which hypertension increases the basal tone of the basilar artery in vivo. METHODS: Using a cranial window, we examined effects of inhibitors of L-type voltage-dependent calcium channels (nicardipine) and Rho-associated kinase (Y-27632) on the baseline diameter of the basilar artery in spontaneously hypertensive rats (SHR) and compared to the responses in normotensive Wistar-Kyoto (WKY) rats. RESULTS: Topical application of nicardipine (10(-8), 10(-7) and 10(-6) mol/l) produced dilatation of the basilar artery. Nicardipine-induced vasodilatation was enhanced in SHR compared to WKY rats. Nicardipine (10-6 mol/l) dilated the artery in WKY rats and SHR by 9 +/- 2 and 24 +/- 4%, respectively. Topical application of Y-27632 (10(-7), 10(-6) and 10(-5) mol/l) produced dilatation of the basilar artery in WKY rats in a concentration-related manner. The vasodilatation produced by Y-27632 was markedly enhanced in SHR compared to WKY rats. Y-27632 (10(-5) mol/l) dilated the artery in WKY rats and SHR by 14 +/- 2 and 45 +/- 6%, respectively. We also tested the effects of inhibitors of nitric oxide synthase (NG-nitro-l-arginine methyl ester, l-NAME), ATP-sensitive potassium channels (glibenclamide) and large-conductance calcium-activated potassium channels (tetraetyhlammonium, TEA). l-NAME and, to a lesser extent, glibenclamide produced similar constriction of the basilar artery in both strains. TEA did not affect the baseline diameter of the basilar artery in WKY rats and produced small but significant vasoconstriction in SHR. CONCLUSIONS: These results suggest that the activity of L-type calcium channels and Rho-associated kinase is enhanced in the basilar artery during hypertensionin vivo. The enhanced contractility may contribute to the increased resistance of the basilar artery during chronic hypertension in vivo.

Acetylcholine↗
PubMed2002

Chronic administration of a tyrosine kinase inhibitor restores functional and morphological changes of the basilar artery during chronic hypertension.

OBJECTIVE: Activation of tyrosine kinase appears to play an important role in pathogenesis of cardiovascular disease during chronic hypertension. In the present study, we tested the hypothesis that long-term treatment with an inhibitor of tyrosine kinase would have beneficial effects on hypertension-induced morphological and functional changes of the cerebral artery. METHODS: Male spontaneously hypertensive rats (SHR; 4 months old) were fed normal rat chow, or that containing an inhibitor of tyrosine kinase, genistein (1 mg/kg chow). Normotensive Wistar-Kyoto (WKY) rats were also fed either of the chows. After feeding the rats for 2 months, we measured wall thickness, diameter of the basilar artery and its dilator responses to acetylcholine (ACh); Y-26763, an opener of ATP-sensitive potassium channels; and Y-27632, an inhibitor of Rho-associated kinase. RESULTS: Treatment with genistein did not cause significant changes in physiological variables, including mean arterial pressure in either strain. In control SHR, the wall thickness of the basilar artery was greater than that of WKY rats. Genistein treatment reduced the wall thickness significantly in SHR. Vasodilator responses induced by ACh and Y-26763 were markedly attenuated in SHR compared to WKY rats, and treatment of SHR with genistein significantly improved the vasodilatation. Dilatation of the artery in response to Y-27632 was enhanced in SHR compared to WKY rats and treatment of SHR with genistein did not affect the enhanced vasodilator responses to Y-27632. CONCLUSIONS: Chronic treatment with genistein may be a novel approach to prevent cerebrovascular disorders.

Acetylcholine↗
PubMedDate not supplied

Thioredoxin1 upregulates mitochondrial proteins related to oxidative phosphorylation and TCA cycle in the heart.

Thioredoxin1 (Trx1) inhibits hypertrophy and exhibits protective functions in the heart. To elucidate further the cardiac functions of Trx1, we used a DNA microarray analysis, with hearts from transgenic mice with cardiac- specific overexpression of Trx1 (Tg-Trx1, n = 4) and nontransgenic controls (n = 4). Expression of a large number of genes is regulated in Tg-Trx1, with a greater number of genes downregulated, versus upregulated, at high-fold changes. The peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1gamma) gene was among the top 50 significantly upregulated genes. By pathway analyses, we found that genes involved in both mitochondrial oxidative phosphorylation and the TCA cycle were upregulated in Tg-Trx1. We confirmed upregulation of cytochrome c oxidase (COX) components and mitochondrial transcription factor A in Tg-Trx1. The activity of citrate synthase and COX and the cardiac ATP content were significantly higher in Tg-Trx1. A transcription factor binding-site analysis showed that upregulated genes frequently contained binding sites for nuclear respiratory factor 1 (NRF1). Expression of NRF1 and PGC-1gamma was upregulated in Tg-Trx1, and Trx1 stimulated the transcriptional activity of NRF1 and NRF2 in cardiac myocytes. These results suggest that, in cardiac myocytes, Trx1 upregulates mitochondrial proteins and enhances mitochondrial functions, possibly through PGC-1alpha and NRFs.

Adenosine Triphosphate↗