PubMed Health⌕ Search

Biomedical subjects

Masakazu Kohno

Publications and source records attributed to Masakazu Kohno.

At least 19 recordsLinked to original sources
PubMed2007

Differential impact of atorvastatin vs pravastatin on progressive insulin resistance and left ventricular diastolic dysfunction in a rat model of type II diabetes.

BACKGROUND: Controversy exists regarding the effects of statin therapy on progressive insulin resistance (IR) and its consequences, in the present study a rat model of spontaneously developing type II diabetes mellitus (DM) was used to examine the impact of atorvastatin (AS) vs pravastatin (PS). METHODS AND RESULTS: The Otsuka Long-Evans Tokushima Fatty rats were either untreated or treated with 100 mg/kg per day of AS or PS from 6 weeks of age for 24 weeks. AS achieved much greater lipid lowering than PS. Serial oral glucose tolerance tests revealed new-onset diabetes was delayed by PS only. The untreated rats exhibited a progressive decrease in plasma adiponectin, increases in plasma leptin and tumor necrosis factor-alpha, and reduction of plasma nitric oxide (NO), which were limited more by PS than AS. PS, but not AS, enhanced adiponectin mRNA expression in white adipose tissue at 30 weeks. Cardiac endothelial NO synthase expression was upregulated, and overexpression of both transforming growth factor-beta1 and monocyte chemoattractant protein-1 mRNA was limited more by PS than AS. Coronary perivascular fibrosis at 30 weeks was suppressed only by PS, which was accompanied by preserved left ventricular diastolic function assessed with Doppler echocardiography. CONCLUSIONS: The moderate lipid lowering by PS, but not the intensive lipid lowering by AS, prevented new-onset DM and diastolic dysfunction in a rat model of IR, and this was associated with preferable adipocytokine profiles and cardiac redox states.

Adiponectin↗
PubMed2006

Involvements of Rho-kinase and TGF-beta pathways in aldosterone-induced renal injury.

Recent studies have suggested a role for aldosterone in the pathogenesis of renal injury. This study investigated the potential contributions of Rho-kinase and TGF-beta pathways to aldosterone-induced renal injury. Rats were uninephrectomized and then treated for 5 wk with 1% NaCl in a drinking solution and one of the following: Vehicle (2% ethanol, subcutaneously; n = 9); aldosterone (0.75 microg/h, subcutaneously; n = 9); or aldosterone + fasudil, a specific Rho-kinase inhibitor (10 mg/kg per d, subcutaneously; n = 8). Phosphorylation of myosin phosphate target subunit-1 (MYPT1) and Smad2/3 in renal cortical tissue was measured by Western blotting with anti-phospho MYPT1 and Smad2/3 antibodies, respectively. Rats that received aldosterone infusion exhibited hypertension and severe renal injury characterized by proteinuria, glomerular sclerosis, and tubulointerstitial fibrosis with increases in alpha-smooth muscle actin staining and numbers of monocytes/macrophages in the interstitium. Renal cortical mRNA levels of types I and III collagen, TGF-beta, connective tissue growth factor, and monocyte chemoattractant protein-1 as well as Smad2/3 phosphorylation were significantly increased in rats that received aldosterone infusion. All of these changes were associated with an increase in renal tissue MYPT1 phosphorylation. Treatment with fasudil did not alter BP but significantly ameliorated proteinuria and renal injury in rats that received aldosterone infusion. Furthermore, fasudil prevented MYPT1 phosphorylation and markedly decreased alpha-smooth muscle actin staining, numbers of monocytes/macrophages, mRNA levels of types I and III collagen, TGF-beta, connective tissue growth factor and monocyte chemoattractant protein-1, and Smad2/3 activity in renal cortical tissues. These results provide evidence, for the first time, that Rho-kinase is substantially involved in aldosterone-induced renal injury through activation of a TGF-beta-dependent pathway.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2006

Effects of adrenomedullin on cardiac oxidative stress and collagen accumulation in aldosterone-dependent malignant hypertensive rats.

We examined the effects of adrenomedullin on cardiac oxidative stress and collagen accumulation in aldosterone-dependent malignant hypertensive rats. Spontaneously hypertensive rats (SHRs) were treated with one of the following combinations for 4 weeks: tap water and vehicle [0.5% ethanol, subcutaneously (s.c.), n = 5], 1% NaCl in drinking water and vehicle (n = 8), 1% NaCl and aldosterone (0.75 microg/h s.c., n = 8), and 1% NaCl, aldosterone, and adrenomedullin (1.3 microg/kg/h s.c., n = 8). Systolic blood pressure (SBP) and left ventricular (LV) weight were higher in aldosterone-treated SHRs than vehicle- or vehicle/1% NaCl-treated SHRs. Thiobarbituric acid reactive substances (TBARS) levels and NADPH oxidase activity in LV tissues of aldosterone-treated SHRs were also higher than those of vehicle- or vehicle/1% NaCl-treated SHRs, and these changes were associated with increases in LV mRNA levels of p22phox, gp91phox, fibronectin, collagen types I and III, as well as collagen content. Treatment with adrenomedullin did not alter SBP or LV weight but attenuated aldosterone-induced increases in TBARS levels, NADPH oxidase activity, and mRNA levels of p22phox, gp91phox, fibronectin, collagen types I and III, as well as collagen content in LV tissues. These data suggest that NADPH oxidase-mediated reactive oxygen species production is involved in the pathogenesis of cardiac collagen accumulation in aldosterone-dependent malignant hypertensive rats and that the cardioprotective effects of adrenomedullin are mediated through the suppression of this pathway.

Adrenomedullin↗
PubMed2006

An antioxidant treatment potentially protects myocardial energy metabolism by regulating uncoupling protein 2 expression in a chronic beta-adrenergic stimulation rat model.

Excessive beta-adrenergic stimulation causes cardiac toxicity, which also contributes to cardiac oxidative stress. Although uncoupling protein 2 (UCP2), a member of the mitochondrial inner membrane carrier family, can regulate energy efficiency and oxidative stress in mitochondria, little data exist regarding interactions between UCP2 expression and beta-adrenergic stimulation induced cardiac oxidative damage. We investigated whether chronic beta-adrenergic stimulation induces myocardial energy metabolism abnormality via oxidative stress, including any role of UCP2. We also examined whether 3-methyl-1-phenyl-2-pyrazolin-5-one (MIC-186; edaravone), a potent free radical scavenger, has cardioprotective effects against beta-adrenergic stimulation. Male Sprague-Dawley rats received isoproterenol (1.2 mg/kg/day) subcutaneously or/and edaravone (30 mg/kg/day) orally. Isoproterenol increased the heart/body weight ratio, accompanied by an increase in the level of myocardial thiobarbituric acid reactive substances (TBARS) and a decreased phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio. Isoproterenol also markedly increased expressions of UCP2 mRNA (1.74 fold vs. non-isoproterenol) and protein (1.93 fold vs. non-isoproterenol). Edaravone had no apparent effect in hypertrophic responses, but significantly prevented both increases in TBARS and decreases in the PCr/ATP ratio. Edaravone also prevented increases in UCP2 mRNA (0.76 fold vs. isoproterenol) and protein (0.62 fold vs. isoproterenol) expressions against isoproterenol administration. Our results suggest that chronic beta-adrenergic stimulation induces myocardial energy inefficiency via excessive oxidative stress. The antioxidant effect of edaravone has potential to improve energy metabolism abnormalities against beta-adrenergic stimulation. Adequate regulation of UCP2 expression through artificial reduction of oxidative stress may play an important role in protection of the myocardial energy metabolism.

Adrenergic beta-Agonists↗
PubMed2006

Synergistic effect of mechanical stretch and angiotensin II on superoxide production via NADPH oxidase in vascular smooth muscle cells.

OBJECTIVE: Mechanical forces and angiotensin II influence the structure and function of vascular cells, and play an important role in reactive oxygen species production. In this study, we examined the effects of mechanical stretch and angiotensin II on the expression of p22-phox and Nox-1, essential membrane components of NADPH oxidase, and superoxide production in rat vascular smooth muscle cells (VSMCs). METHODS AND RESULTS: Neither a stretch force nor angiotensin II alone altered p22-phox and Nox-1 expression in VSMCs. Combined stimulation markedly increased p22-phox and Nox-1 mRNA, however, which was associated with increased NADPH oxidase activity, superoxide production and total 8-iso-prostaglandin F2alpha concentration. The increases in p22-phox mRNA levels induced by a stretch force in combination with angiotensin II were prevented by treatment with an angiotensin type I (AT1) receptor antagonist, RNH-6270 (100 nmol/l). Protein expression of the AT1 receptor was upregulated by a stretch force. CONCLUSIONS: These data indicate that mechanical stretch and angiotensin II synergistically increase NADPH oxidase expression in VSMCs, and suggest that part of this mechanism is mediated through an upregulation of the AT1 receptor induced by mechanical stretch. The combined effects of mechanical strain and angiotensin II might promote vascular damage through the production of superoxide in a hypertensive state.

Angiotensin II↗
PubMed2006

Contribution of reactive oxygen species to the pathogenesis of left ventricular failure in Dahl salt-sensitive hypertensive rats: effects of angiotensin II blockade.

OBJECTIVE: We investigated the contribution of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) generation to the pathogenesis of diastolic heart failure (DHF) in Dahl salt-sensitive (DS) hypertensive rats, with the aim of testing our hypothesis that the cardioprotective effects of angiotensin II (Ang II) blockade are provided by the suppression of this pathway. METHODS: DS rats were maintained on high (H: 8.0% NaCl) or low (L: 0.3% NaCl) salt diets from age 7 to 17 weeks. DS/H rats were also treated with candesartan cilexetil (10 mg/kg per day, orally) or a superoxide dismutase mimetic, tempol (3 mmol/l in drinking water) from age 7 to 17 weeks. RESULTS: DS/H rats represented hypertension, left ventricular (LV) relaxation abnormality and myocardial stiffening with preserved systolic heart function. As compared with DS/L rats, DS/H rats showed higher levels of transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF), p22phox and gp91phox mRNA expression, NADPH oxidase activity and thiobarbituric acid-reactive substance (TBARS) contents in LV tissues. Gene expression of uncoupling protein-2 (UCP-2), an inner mitochondrial membrane proton transporter, was also 2.8 +/- 0.5-fold higher. In DS/H rats, treatment with candesartan did not alter blood pressure, but resulted in a marked improvement of the hemodynamic deterioration; these therapeutic effects were accompanied by decreases in myocardial NADPH oxidase activity, TBARS contents and the expression of TGF-beta, CTGF, p22phox, gp91phox and UCP-2. Similar therapeutic effects were provided by treatment with tempol in DS/H rats. CONCLUSIONS: Our data suggest that NADPH oxidase-mediated ROS production contributes to the pathogenesis of DHF in DS hypertensive rats, and that the cardioprotective effects of AngII blockade are, at least partially, mediated through the suppression of this pathway.

Angiotensin II↗
PubMed2006

Chronic pulmonary complications associated with toxic epidermal necrolysis: report of a severe case with anti-Ro/SS-A and a review of the published work.

Patients with toxic epidermal necrolysis (TEN) have been known to have various complications. Though pulmonary complications are often observed, they usually show an acute form; however, chronic complications are quite rare and little is known about either their incidences or clinical manifestations. We herein report a 33-year-old man who presented with chronic pulmonary complications after a recovery from TEN. At the onset of TEN, he had severe respiratory failure and artificial ventilation was instituted. Despite being extubated successfully, respiratory failure reappeared 1 month later. A diagnosis of chronic bronchitis with severe obstructive ventilatory impairment and bronchiectasis was made and he was treated with steroids, bronchodilators and antibiotics, however, he died 1.5 years after the onset of TEN. There have been 13 reported cases of chronic pulmonary complications with TEN or Stevens-Johnson syndrome (SJS) in the English published work. Such cases are usually classified into chronic bronchitis/bronchiolitis with obstructive change (including bronchiolitis obliterans and bronchiolitis obliterans organizing pneumonia), respiratory tract obstruction and bronchiectasis. Approximately 40% of all such patients die while the surviving continue to suffer from these complications because no curative therapy yet exists. As a result, the prognosis seems to be poor. The relationship between TEN and these chronic pulmonary complications remains to be elucidated. Interestingly, our patient was asymptomatically anti-Ro/SS-A positive at the onset of TEN. In addition, eccrine gland involvement and an extremely high level of serum salivary amylase were observed at the onset of TEN, furthermore, Sjögren-like symptoms occurred after recovery from TEN. These findings suggested that the Sjögren-like autoimmune abnormalities induced by anti-Ro/SS-A correlated with the development of chronic pulmonary complications in our patient.

Adult↗
PubMed2006

Augmentation of intrarenal angiotensin II levels in uninephrectomized aldosterone/salt-treated hypertensive rats; renoprotective effects of an ultrahigh dose of olmesartan.

Recent studies have suggested that aldosterone plays a role in the pathogenesis of renal injury. In this study, we investigated whether local angiotensin II (Ang II) activity contributes to the progression of renal injury in aldosterone/salt-induced hypertensive rats. Uninephrectomized rats were treated with 1% NaCl in a drinking solution and one of the following combinations for 6 weeks: vehicle (2% ethanol, s.c.; n=9), aldosterone (0.75 mug/h, s.c.; n=8), aldosterone+Ang II type 1 receptor blocker olmesartan (10 mg/kg/day, p.o.; n=8), or aldosterone+olmesartan (100 mg/kg/day, p.o.; n=9). Aldosterone/salt-treated hypertensive rats exhibited severe proteinuria and renal injury characterized by glomerular sclerosis and tubulointerstitial fibrosis. Aldosterone/salt-induced renal injury was associated with augmented expression of angiotensin converting enzyme and Ang II levels in the renal cortex and medullary tissues. Renal cortical and medullary mRNA expression of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) as well as the collagen contents were increased in aldosterone/salt-treated hypertensive rats. Treatment with olmesartan (10 or 100 mg/kg/day) had no effect on blood pressure but attenuated proteinuria in a dose-dependent manner. Olmesartan at 10 mg/kg/day tended to decrease renal cortical and medullary Ang II levels, TGF-beta and CTGF expression, and collagen contents; however, these changes were not significant. On the other hand, an ultrahigh dose of olmesartan (100 mg/kg/day) significantly decreased these values and ameliorated renal injury. These data suggest that augmented local Ang II activity contributes, at least partially, to the progression of aldosterone/salt-dependent renal injury.

Aldosterone↗
PubMed2005

Effects of calcium channel blockade on angiotensin II-induced peritubular ischemia in rats.

Recent studies have indicated that derangement of peritubular capillary (PTC) circulation with consequent tubulointerstitial hypoxia plays a pivotal role in the pathogenesis of renal injury. The present study was performed to determine whether azelnidipine, a new dihydropyridine calcium channel blocker, attenuates angiotensin II (AngII)-induced peritubular ischemia in anesthetized rats. The superficial PTCs were visualized directly using an intravital fluorescence videomicroscope system, and the PTC blood flow was evaluated by analyzing the velocity of fluorescein isothiocyanate-labeled erythrocytes. Intravenous infusion of AngII (50 ng/kg/min, 10 min) significantly increased mean arterial pressure (MAP) and renal vascular resistance (RVR) (by 35 +/- 3% and 110 +/- 32%, respectively), and decreased total renal blood flow (RBF) and PTC erythrocyte velocity (by -34 +/- 4 and -37 +/- 1%, respectively). Treatment with azelnidipine (5 microg/kg/min i.v., 10 min) had no effect on basal MAP, RBF, RVR, or PTC erythrocyte velocity. However, azelnidipine markedly attenuated the AngII-induced increases in MAP (7 +/- 3%) and RVR (40 +/- 4%) and decreases in RBF (-24 +/- 1%) and PTC erythrocyte velocity (-22 +/- 1%). Similar attenuation in the AngII-induced responses of MAP, RBF, RVR, and PTC erythrocyte velocity were observed in rats treated with a higher dose of azelnidipine (20 microg/kg/min i.v., 10 min), which significantly decreased basal MAP and RVR and increased RBF and PTC erythrocyte velocity. These data suggest that calcium channel blockade attenuates AngII-induced peritubular ischemia, which may be involved in its beneficial effects on renal injury.

Adenosine Triphosphate↗
PubMed2005

Treatment of ischemic limbs based on local recruitment of vascular endothelial growth factor-producing inflammatory cells with ultrasonic microbubble destruction.

OBJECTIVES: We sought to clarify the mechanism for neovascularization by ultrasonic microbubble destruction (US/MB) and its ability to improve the function of ischemic limbs. BACKGROUND: In tissue, US/MB can cause capillary rupture, leading to angiogenesis and arteriogenesis. METHODS: Seven days after removal of the femoral artery (day 0) in mice, microbubble/ultrasound treatment was performed by intermittent insonation (1.6 MHz, mechanical index 1.1) to the ischemic limbs after intravenous infusion of phospholipid-stabilized microbubbles BR14 (US/MB group). Effects were compared with those in untreated mice with ischemic limbs (control group). RESULTS: Immunostaining of the treated muscles revealed a greater leukocyte (CD45-positive cell) count in the US/MB group on days 3 and 7. These cells included F4/80-positive cells (macrophages) and CD3-positive cells (T-lymphocytes), both of which were immunoreactive to vascular endothelial growth factor (VEGF) antibody. Muscular VEGF content by Western blotting was elevated in the US/MB group on day 3, which declined but remained greater until day 21. The US/MB group showed a greater capillary density by alkaline phosphatase stain on day 7 without further increase at day 21. Surface vascularity of the muscles and blood flow were greater in the US/MB group on day 7, which further increased by day 21. Moreover, the US/MB group showed a two-fold longer treadmill time compared with the untreated control group on day 21. None of these favorable effects were observed in mice treated with ultrasound only or microbubbles only. CONCLUSIONS: Ultrasonic destruction of microbubbles delivered to the ischemic limbs can recruit inflammatory cells producing VEGF, which is followed by neovascularization and functional improvement, and thus has a therapeutic potential.

Animals↗
PubMed2005

Aldosterone stimulates reactive oxygen species production through activation of NADPH oxidase in rat mesangial cells.

It has recently been shown that glomerular mesangial injury is associated with increases in renal cortical reactive oxygen species (ROS) levels in rats treated chronically with aldosterone and salt. This study was conducted to determine the mechanisms responsible for aldosterone-induced ROS production in cultured rat mesangial cells (RMC). Oxidative fluorescent dihydroethidium was used to evaluate intracellular production of superoxide anion (O(2)(-)) in intact cells. The lucigenin-derived chemiluminescence assay was used to determine NADPH oxidase activity. The staining of dihydroethidium was increased in a dose-dependent manner by aldosterone (1 to 100 nmol/L) with a peak at 3 h in RMC. Aldosterone (100 nmol/L for 3 h) also significantly increased NADPH oxidase activity from 232 +/- 18 to 346 +/- 30 cpm/5 x 10(4) cells. Immunoblotting data showed that aldosterone (100 nmol/L for 3 h) increased p47phox and p67phox protein levels in the membrane fraction by approximately 2.1- and 2.3-fold, respectively. On the other hand, mRNA expression of NADPH oxidase membrane components, p22phox, Nox-1, and Nox-4, were not altered by aldosterone (for 3 to 12 h) in RMC. Pre-incubation with the selective mineralocorticoid receptor (MR) antagonist, eplerenone (10 micromol/L), significantly attenuated aldosterone-induced O(2)(-) production, NADPH oxidase activation and membranous translocation of p47phox and p67phox. These results suggest that aldosterone-induced ROS generation is associated with NAPDH oxidase activation through MR-mediated membranous translocation of p47phox and p67phox in RMC. These cellular actions of aldosterone may play a role in the pathogenesis of glomerular mesangial injury.

Aldosterone↗
PubMed2005

Aldosterone stimulates collagen gene expression and synthesis via activation of ERK1/2 in rat renal fibroblasts.

Recently, we demonstrated that in rats treated chronically with aldosterone and salt, severe tubulointerstitial fibrosis is associated with the activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERK1/2). Here, we investigated whether aldosterone stimulates collagen synthesis via ERK1/2-dependent pathways in cultured rat renal fibroblasts. Gene expression of mineralocorticoid receptor (MR) and types I, II, III, and IV collagen was measured by real-time polymerase chain reaction (PCR). MR protein expression and ERK1/2 activity were evaluated by Western blotting analysis with anti-MR and anti-phospho-ERK1/2 antibodies, respectively. Collagen synthesis was determined by [3H]-proline incorporation. Significant levels of MR mRNA and protein expression were observed in rat renal fibroblasts. Treatment with aldosterone (0.1 to 10 nmol/L) increased ERK1/2 phosphorylation in a concentration-dependent manner with a peak at 5 minutes. Aldosterone (10 nmol/L) also increased the mRNA levels of types I, III, and IV collagen at 36 hours but had no effect on the type II collagen mRNA level. [3H]-proline incorporation was significantly increased by aldosterone in both the medium and cell layer at 48 hours. Aldosterone-induced ERK1/2 phosphorylation was markedly attenuated by pretreatment with eplerenone (10 micromol/L), a selective MR antagonist, or PD98059 (10 micromol/L), a specific inhibitor of MAPK kinase/ERK kinase, which is the upstream activator of ERK1/2. In addition, both eplerenone and PD98059 prevented the aldosterone-induced increases in types I, III, and IV collagen mRNA and [3H]-proline incorporation. These results suggest that aldosterone stimulates collagen gene expression and synthesis via MR-mediated ERK1/2 activation in renal fibroblasts, which may contribute to the progression of aldosterone-induced tubulointerstitial fibrosis.

Aldosterone↗
PubMed2005

Calcineurin-nuclear factor of activated T cells pathway-dependent cardiac remodeling in mice deficient in guanylyl cyclase A, a receptor for atrial and brain natriuretic peptides.

BACKGROUND: Although disruption of guanylyl cyclase (GC) A, a natriuretic peptide receptor, induces cardiac hypertrophy and fibrosis, the molecular mechanism underlying these effects are not well understood. In this study, we examined the role of calcineurin, a calcium-dependent phosphatase, in cardiac remodeling in GCA-knockout (GCA-KO) mice. METHODS AND RESULTS: At 14 weeks of age, calcineurin activity, nuclear translocation of nuclear factor of activated T cells c3 (NFATc3), and modulatory calcineurin-interacting protein 1 (MCIP1) gene expressions were increased in the hearts of GCA-KO mice compared with wild-type (WT) mice. Blockade of calcineurin activation by FK506 (6 mg/kg body weight administered subcutaneously once a day from 10 to 14 weeks of age) significantly decreased the heart-to-body weight ratio, cardiomyocyte size, and collagen volume fraction in GCA-KO mice, whereas FK506 did not affect these parameters in WT mice. Overexpression of atrial and brain natriuretic peptides, collagen, and fibronectin mRNAs in GCA-KO mice was also attenuated by FK506. Electrophoretic mobility shift assays demonstrated that GATA4 DNA-binding activity was increased in GCA-KO mice, and this increase was inhibited by calcineurin blockade. In neonatal cultured cardiac myocytes, inhibition of GCA by HS142-1 (100 microg/mL) increased basal and phenylephrine (10(-6) mol/L)-stimulated calcineurin activity, nuclear translocation of NFATc3, and MCIP1 mRNA expression. In contrast, activation of GCA by atrial natriuretic peptide (10(-6) mol/L) inhibited phenylephrine (10(-6) mol/L)-stimulated nuclear translocation of NFATc3. CONCLUSIONS: These results suggest that activation of cardiac GCA by locally secreted natriuretic peptides protects the heart from excessive cardiac remodeling by inhibiting the calcineurin-NFAT pathway.

Animals↗
PubMed2005

Involvement of aldosterone and mineralocorticoid receptors in rat mesangial cell proliferation and deformability.

We demonstrated recently that chronic administration of aldosterone to rats induces glomerular mesangial injury and activates mitogen-activated protein kinases including extracellular signal-regulated kinases 1/2 (ERK1/2). We also observed that the aldosterone-induced mesangial injury and ERK1/2 activation were prevented by treatment with a selective mineralocorticoid receptor (MR) antagonist, eplerenone, suggesting that the glomerular mesangium is a potential target for injuries induced by aldosterone via activation of MR. In the present study, we investigated whether MR is expressed in cultured rat mesangial cells (RMCs) and involved in aldosterone-induced RMC injury. MR expression and localization were evaluated by Western blotting analysis and fluorolabeling methods. Cell proliferation and micromechanical properties were determined by [3H]-thymidine uptake measurements and a nanoindentation technique using an atomic force microscope cantilever, respectively. ERK1/2 activity was measured by Western blotting analysis with an anti-phospho-ERK1/2 antibody. Protein expression and immunostaining revealed that MR was abundant in the cytoplasm of RMCs. Aldosterone (1 to 100 nmol/L) dose-dependently activated ERK1/2 in RMCs with a peak at 10 minutes. Pretreatment with eplerenone (10 micromol/L) significantly attenuated aldosterone-induced ERK1/2 phosphorylation. Aldosterone (100 nmol/L) treatment for 30 hours increased [3H]-thymidine incorporation and decreased the elastic modulus, indicating cellular proliferative and deforming effects of aldosterone, respectively. These aldosterone-induced changes in cellular characteristics were prevented by pretreatment with eplerenone or an ERK (MEK) inhibitor, PD988059 (100 micromol/L). The results indicate that aldosterone directly induces RMC proliferation and deformability through MR and ERK1/2 activation, which may contribute to the pathogenesis of glomerular mesangial injury.

Aldosterone↗
PubMed2005

Temporary angiotensin II blockade at the prediabetic stage attenuates the development of renal injury in type 2 diabetic rats.

Whether temporary angiotensin II (AngII) blockade at the prediabetic stage attenuates renal injury in type 2 diabetic OLETF rats later in life was investigated. OLETF rats were treated with an AT(1) receptor antagonist (olmesartan, 0.01% in food), angiotensin-converting enzyme inhibitor (temocapril, 0.01% in food), a combination of the two, or hydralazine (25 mg/kg per d) at the prediabetic stage (4 to 11 wk of age) and then monitored without further treatment until 50 wk of age. At 11 wk of age, blood glucose levels and urinary protein excretion (U(protein)V) were similar between OLETF and control LETO rats. However, OLETF rats showed higher kidney AngII contents and type IV collagen mRNA expression than LETO rats at this age. These decreased with olmesartan, temocapril, and a combination of these but not with hydralazine. At 50 wk of age, diabetic OLETF rats showed higher BP, U(protein)V, and intrarenal AngII levels than LETO rats. Temporary AngII blockade did not affect glucose metabolism or the development of hypertension in OLETF rats but significantly suppressed proteinuria and ameliorated glomerular injury. However, no parameters were affected by temporary hydralazine treatment. The present study demonstrated that intrarenal AngII and type IV collagen expression are already augmented long before diabetes becomes apparent in OLETF rats. Furthermore, temporary AngII blockade at the prediabetic stage attenuates the progression of renal injury in these animals. These data suggest that early AngII blockade could be an effective strategy for preventing the development of type 2 diabetic renal injury later in life.

Angiotensin II↗
PubMed2005

Association of uncoupling protein-2 expression with increased reactive oxygen species in residual myocardium of the enlarged left ventricle after myocardial infarction.

Left ventricular (LV) dilatation following myocardial infarction (MI) is a major determinant of the patient's prognosis, and myocardial energy metabolism may play a key role in LV remodeling. We aimed to investigate the relative timing of LV dilatation to LV function, myocardial energy regulation by uncoupling protein (UCP)-2, and cellular damage in the noninfarct zone. Myocardial infarction was produced in Sprague-Dawley rats by ligation of the coronary artery. The LV end-diastolic dimension (mm) increased (8.9+/-0.3 vs 6.8+/-0.8 in sham-operated rats, P<0.01) in association with elevation of the LV end-diastolic pressure (mmHg) (18+/-5 vs 6+/-2 in sham-operated rats) at 1 week following the ligation. At 4 weeks, the UCP-2 expression (180% of that in sham-operated rats) and LV end-diastolic dimension increased further (11.1+/-0.5, P<0.01) but there was no change in the LV end-diastolic pressure. The mechanisms for LV dilatation were quite different between the early and late stages after MI. In the late stage, augmentation of UCP-2 expression in the noninfarct zone may be related to the LV dilatation. Further examinations regarding the possibility of the protective role of UCP-2 are needed.

Animals↗
PubMed2005

Spatial distribution of right ventricular perfusion abnormalities following acute right coronary artery occlusion: a study by myocardial contrast echocardiography and blue dye staining.

OBJECTIVE: Although echocardiography is used for diagnosing right ventricular (RV) infarction produced by right coronary artery (RCA) occlusion, there has been no data on the spatial distribution of RV perfusion abnormalities following acute RCA occlusion. We examined this distribution by myocardial contrast echocardiography (MCE) and blue dye staining in canine models. METHODS: The RCA was occluded in 10 open-chest dogs. MCE was performed with 0.27 g/min Levovist infusion by harmonic power Doppler with electrocardiogram gated intermittent triggered imaging at baseline and at 90 min after RCA occlusion. The opacification defects were assessed at the basal, middle, and apical levels of the RV free wall by short-axis view. The extent of the risk area of the occluded RCA, expressed as a percentage of the RV free wall, was measured at each level by injecting blue dye at the end of the experiments. In 10 other dogs, the left anterior descending coronary artery (LAD) was occluded by ligating the proximal portion of the LAD to examine the territory of the LAD on the same levels of the RV free wall by injecting blue dye. RESULTS: Although patchy opacification defects accompanying RV dilation were observed at the basal and middle levels during RCA occlusion, no apical defects were observed in any dogs by MCE. The risk area of the occluded RCA, as delineated by blue dye, was larger in the basal than apical level of the RV free wall in all 10 dogs (basal: 79 +/- 9%; middle: 48 +/- 14%; apical: 3 +/- 6%, p < 0.0001). The risk area of the occluded LAD (basal: 17 +/- 7%; middle: 12 +/- 6%; apical: 6 +/- 6%) was smaller than the risk area of the occluded RCA at the basal and middle levels of the RV free wall (p < 0.0001), and no significant difference was observed at the apical level. CONCLUSIONS: RV perfusion abnormalities produced by RCA occlusion are larger in the basal than apical level of the RV free wall. This finding elucidates the spatial distribution of the territory of the RCA on the RV free wall, and may help in identifying and assessing RV ischemia by echocardiography in humans. Moreover, the data in the current study indicate that RV infarction may be produced by occlusion of the coronary arteries except RCA, because the territory of the LAD on the RV free wall is clearly delineated.

Animals↗