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Biomedical subjects

K Maehara

Publications and source records attributed to K Maehara.

At least 19 recordsLinked to original sources
PubMed2003

Alteration in haemodynamics and pathological changes in the cardiovascular system during the development of Type 2 diabetes mellitus in OLETF rats.

AIMS/HYPOTHESIS: The process of cardiovascular complications in Type 2 diabetes mellitus (DM) is unclear. We investigated pathophysiological changes of the heart and vessels in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat Type 2 DM model during a long time period. METHODS: Echocardiography was carried out at 22 and 62 weeks of age of OLETF ( n=10, each) and age-matched Long-Evans Tokushima Otsuka (LETO) rats ( n=10, each) as a reference. Haemodynamic measurements and histological examinations of the heart and the coronary and aortic vascular walls were done. RESULTS: The left ventricular (LV) maximal -dP/dt was reduced in OLETF rats at 62 weeks (-1085+/-35 mmHg/s) less than that at 22 weeks (-1892+/-396 mmHg/sec, p<0.05) and in LETO rats at 62 weeks (-1306+/-200 mmHg/sec, p<0.05). Wall thickening of intramyocardial coronary arteries, capillary tortuosity and thickening of basement membrane were evident in OLETF rats at 62 weeks. Intimal and medial wall thickening of the aorta were prominent in OLETF rats at 62 weeks (15+/-2.2 and 90+/-6.6 micro m, in LETO rats at 62 weeks, 2+/-0.4 and 65+/-5.2 micro m, p <0.05, and in OLETF rats at 22 weeks, 7+/-4.6 and 71+/-6.0 micro m, p<0.05, respectively). CONCLUSIONS/INTERPRETATION: In the Type 2 DM model, angiopathy, especially in coronary arteries including small vessels, as well as a LV relaxation abnormality, are induced in a late stage of DM. These are considered to be important complications in Type 2 DM.

Animals↗
PubMed2003

Functional interference between estrogen-related receptor alpha and peroxisome proliferator-activated receptor alpha/9-cis-retinoic acid receptor alpha heterodimer complex in the nuclear receptor response element-1 of the medium chain acyl-coenzyme A dehydrogenase gene.

We undertook a study of molecular interference of nuclear orphan receptors. Nuclear receptor response element-1 (NRRE-1) from the human medium-chain acyl coenzyme A dehydrogenase (MCAD) gene promoter was shown to contain three hexamer elements (site 1 through 3) that are known to interact with a number of nuclear receptors including chicken ovalbumin upstream promoter transcription factor (COUP-TF) and estrogen-related receptor alpha (ERRalpha). We demonstrated that the peroxisome proliferator-activated receptor alpha/9-cis-retinoic acid receptor alpha (PPARalpha/RXRalpha) heterodimer complex can also bind to the two hexamer repeat sequences (between site 1 and site 3) arranged as an everted imperfect repeat separated by 14 bp (ER14). Mutations of the putative core elements have shown that these three sites are differentially involved in ERRalpha and PPARalpha/RXRalpha binding. Homodimer of ERRalpha was shown to interact between site 1 and site 3 (ER14). To date, no nuclear receptor is known to bind to response elements over such long intervals. Interestingly, site 1 was shown to be essential for ERRalpha binding while site 3 supports its binding only in the presence of site 1. Furthermore, it was shown that the binding profile of ERRalpha and PPARalpha/RXRalpha are competitive rather than making a high order complex within NRRE-1. At the cellular level, transcriptional activation driven by the PPARalpha/RXRalpha complex was counteracted by the expression of ERRalpha in HeLa cells. These results suggest that ERRalpha and PPARalpha/RXRalpha could interfere with each other's function through binding to similar DNA elements, thereby finetuning the transcriptional outcome of the target gene. Our findings suggest a mechanism whereby multiple nuclear receptors can activate or repress DNA binding or transcription via a single pleiotropic regulatory element.

Acyl-CoA Dehydrogenase↗
PubMed2002

Amicrobial pustular dermatosis in two patients with immunological abnormalities.

We report two patients with severe amicrobial pustular dermatosis with immunological abnormalities: a 63-year-old woman with a 30-year-history of discoid lupus erythematosus and sicca syndrome, and a 35-year-old woman with high levels of gamma-globulinemia and positive antinuclear antibodies. Both patients presented with crusty and eroded erythematous plaques studded with aseptic pustules on the back, face, and scalp. Histological examination showed acanthosis, neutrophilic exocytosis to the epidermis, and neutrophilic and lymphocytic infiltration with nuclear dust in the dermis. These patients were diagnosed as having "amicrobial pustulosis associated with autoimmune diseases". The eruptions improved with combination treatment of oral prednisolone with cyclosporin A or diaminodiphenylsulphone. Although the pathogenesis remains unclear, amicrobial pustular dermatosis might be one of the cutaneous complications in autoimmune diseases.

Administration, Oral↗
PubMed2001

Early growth-responsive-1-dependent manganese superoxide dismutase gene transcription mediated by platelet-derived growth factor.

Manganese superoxide dismutase Mn-SOD plays a major role in protecting mitochondria from oxidative damage. Overexpression of Mn-SOD maintains cell survival under conditions that lead to apoptotic death. In addition to the antioxidative enzyme, platelet-derived growth factor (PDGF) is a principal survival factor that inhibits apoptosis and promotes proliferation by activating survival signaling pathways in various cells. Here we show that PDGF induced the expression of the Mn-SOD gene in NIH3T3 cells, and its induction was associated with early growth response-1 (Egr-1), a transcription factor. An electrophoretic mobility shift assay demonstrated that Egr-1 bound to the proximal promoter of the Mn-SOD gene in response to PDGF. The proximal promoter region of Mn-SOD was shown to be transcriptionally responsive to both basal and PDGF stimulation by transfection studies. Forced expression of Egr-1 in the cells activated Mn-SOD transcription in a dose-dependent manner. The pathway by which PDGF induced Egr-1 involved the mitogen-activated protein kinase kinase-1 (MEK1) and extracellular signal-regulated kinases 1 and 2 (ERK1/2), because the effect of PDGF on the induction of Egr-1 was blocked by U0126, a specific MEK1 inhibitor. These findings indicate that the induction of Mn-SOD is part of the anti-apoptotic properties mediated by PDGF.

3T3 Cells↗
PubMed2001

Mechanism for the reduction of telomerase expression during muscle cell differentiation.

Telomerase, the reverse transcriptase that maintains telomere DNA, is usually undetectable in adult human tissues, but is positive in embryonic tissues and in cancers. However, in rodents, several organs of normal adult animals express substantial amounts of telomerase activity. To elucidate relevant control mechanisms operating on the tissue-specific expression of telomerase in rodents, we examined the transcriptional regulation of telomerase reverse transcriptase (mTERT) gene in muscle cell differentiation. Reverse transcriptase-polymerase chain reaction analysis showed that the reduction of telomerase activity was caused by the decrease of mTERT mRNA level during myogenesis. Transfections of mTERT promoter showed that the proximal 225-base pair region is the core promoter responsible for basal transcriptional activity and also participates in the reduced transcription after muscle differentiation. Electrophoretic mobility shift assays showed that this region contained the GC-boxes, which bind to Sp1 family proteins, and the E-box, which binds to c-Myc. Furthermore, DNA binding activities of Sp1, Sp3, and c-Myc were down-regulated during myogenesis. These data suggest that Sp1, Sp3, and c-Myc have critical roles of TERT transactivation in mouse, and the lack of these transcription factors cause down-regulation of mTERT gene expression in muscle cells differentiation.

3T3 Cells↗
PubMed2001

Multiple endothelial injury in epicardial coronary artery induces downstream microvascular spasm as well as remodeling partly via thromboxane A2.

OBJECTIVES: The study was undertaken to develop a coronary microvascular spasm model in pigs by repeated epicardial coronary artery endothelial injury. BACKGROUND: The pathophysiologic mechanisms responsible for coronary microvascular spasm remain unclear, in large part because a suitable animal model has yet to be found. METHODS: Balloon endothelial denudation was done just distal to the site of an implanted Doppler flowmeter in the left anterior descending coronary artery (LAD) every two weeks for a total of four times. Changes in LAD blood flow by intracoronary administration of vasoactive agents were assessed before each denudation. RESULTS: In the epicardial LAD endothelial denudation pigs, decreases in LAD blood flow caused by acetylcholine were augmented. Before denudation, it was - 15 +/- 4%, and at week 8 (i.e., two weeks after the fourth denudation) it was -100% (i.e., zero flow [p < 0.01]). The LAD flow changes in response to 5-hydroxytryptamine (5-HT) changed from an increase to a decrease, accompanied by medial thickening of microvessels in the LAD perfusion area. These flow responses were observed without significant changes in LAD diameter. In contrast, the LAD blood flow responses to acetylcholine and 5-HT did not change throughout the experiment in pigs given aspirin and a thromboxane A2 (TXA2) synthase inhibitor orally. CONCLUSIONS: This microvascular spasm model indicates that hypersensitivity to vasoactive substances in the microvascular beds as well as microvascular remodeling are brought about partly through TXA2. This model should be useful for examining the pathophysiology and treatment of microvascular angina.

Animals↗
PubMed2001

Attenuation of angiotensin II-mediated coronary vasoconstriction and vasodilatory action of angiotensin-converting enzyme inhibitor in pacing-induced heart failure in dogs.

OBJECTIVES: We investigated the changes in coronary vascular resistance caused by angiotensin II, angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 or 2 receptor (AT(1)R and AT(2)R, respectively) antagonists in chronic heart failure (CHF). BACKGROUND: Angiotensin II is an intense vasoconstrictor, and increased angiotensin II in CHF might exert significant vasoconstriction. METHODS: Eleven dogs were studied. Before and after three and five weeks of rapid pacing, coronary flow dynamics were evaluated by the coronary pressure-flow relationship (PFR) in long diastole, before and after intracoronary injection of angiotensin II, the ACE inhibitor enalaprilat, the AT(1)R antagonist L158,809 or the AT(2)R antagonist PD123319. RESULTS: Before rapid pacing, angiotensin II reduced the slope of PFR (1.16 +/- 0.08 to 0.81 +/- 0.07 ml/min/100 g left ventricular mass per mm Hg; p < 0.01) and increased the perfusion pressure at which coronary flow ceased (zero-flow pressure [P(f) = 0]), whereas enalaprilat did not change either of them. After rapid pacing, angiotensin II did not change the slope or P(f) = 0. In contrast, enalaprilat increased the slope (three weeks: 1.20 +/- 0.05 to 1.50 +/- 0.03; five weeks: 1.25 +/- 0.19 to 1.37 +/- 0.08; both p < 0.05) and decreased P(f) = 0 after three weeks of pacing, but not after five weeks. Pretreatment with the bradykinin antagonist HOE-140 attenuated the enalaprilat-induced increase in coronary blood flow. L158,809 and PD123319 had no effect both before and after rapid pacing. CONCLUSIONS: This suggests that the coronary vasoconstrictive effect of angiotensin II would disappear and the vasodilatory effect of the ACE inhibitor, partly through bradykinin, would be enhanced in the early stage of CHF.

Angiotensin II↗
PubMed2001

Increased plasminogen activator inhibitor-1 and apolipoprotein (a) in coronary atherectomy specimens in acute coronary syndromes.

BACKGROUND: Although increased tissue factor expression is known in vulnerable plaques, there is no reported study to compare plaque fibrinolysis in stable and unstable plaques. This study investigates the extent of plasminogen activator inhibitor-1 (PAI-1) and apolipoprotein (a) [apo(a)] in the plaques of different types of coronary artery disease as well as the correlation between these molecules and infiltration of macrophages to plaques. METHODS: Using immunohistochemical staining, we examined PAI-1 expression and apo(a) deposition in coronary atherosclerotic specimens obtained by directional coronary atherectomy from 19 patients with acute myocardial infarction (AMI), 12 with unstable angina pectoris (UAP), and 13 with stable angina pectoris (SAP). The percentages of the total areas of specimens stained with PAI-1 or apo(a) were estimated by an NIH image program. The proportion of macrophages as a percentage of all cells in plaques was calculated as the macrophage density. RESULTS: We found significantly higher percentages of total areas of specimens stained with PAI-1 in AMI (25.5 +/- 8.6%, P < 0.001) and UAP (22.2 +/- 10.4%, P < 0.005) than in SAP (9.5 +/- 5.0%), as well as with apo(a) (AMI; 11.7 +/- 7.1%, P < 0.005, UAP; 11.1 +/- 5.5%, P < 0.01 versus SAP; 3.9 +/- 1.5%). Linear regression analysis of all the samples showed a correlation between PAI-1 or apo(a) and macrophage density (PAI-1: r = 0.75, P < 0.001 and apo(a): r = 0.56, P < 0.001). CONCLUSIONS: Our results suggest a possible contribution of increased PAI-1 and apo(a) in plaques to the pathogenesis of acute coronary syndromes including impaired fibrinolysis.

Aged↗
PubMed2001

Continuous observation of superoxide generation in an in-situ ischemia-reperfusion rat lung model.

To investigate the time course of superoxide generation in ischemia-reperfusion in the in-vivo rat lung, the present study used an enhanced chemiluminescence method with 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1, 2-alpha]pyrazin-3-one (MCLA) as a specific probe. The right pulmonary artery was occluded for 120 min, followed by 90-min reperfusion. Chemiluminescence induced by MCLA was continuously monitored by a photomultiplier exposed to the right lung. Chemiluminescence increased gradually in 30 min of reperfusion and remained elevated throughout reperfusion. The ratio of the luminescence count during reperfusion to the preischemic value increased to 2.20+/-0.31 (mean+/-SEM) (p<0.02 vs preischemic level), 2.50+/-0.39 (p<0.005), and 2.69+/-0.44 (p<0.005), at 30, 60, and 90 min of reperfusion, respectively. Bolus administration of superoxide dismutase during the reperfusion period significantly attenuated the chemiluminescence by 45.0+/-6.7% (p<0.01). The present results suggest that increasing oxygen radical formation leading to ischemia-reperfusion lung injury may occur even after a short period of occlusion of the pulmonary artery alone in vivo.

Animals↗
PubMed2001

Complement and polymorphonuclear leukocyte activation each play a role in determining myocardial ischemia-reperfusion injury.

Cobra venom factor (CVF) transiently activates polymorphonuclear leukocytes (PMN) by complement activation, followed by rapid complement depletion and gradual reversal of PMN activation. Utilizing these sequential changes caused by CVF, the individual and combined effects of complement and PMNs on myocardial infarct size (IS) were investigated. Rats were treated with CVF, and/or anti-PMNs. Complement was depleted, but circulating PMNs were being activated at 4h after CVF administration, and at 36h after, complement was depleted, but PMNs were in a near basal condition. Under anesthesia, the rats had a 30-min coronary occlusion followed by 6h of reperfusion. The IS was assessed by tetrazolium staining. CVF, as well as anti-PMNs, reduced myeloperoxidase (MPO) activity in the risk area and the reduced MPO resulted in a reduced IS, which was also the effect of anti-PMNs, but complement depletion by CVF, during which circulating PMNs were activated, failed to reduce the IS despite low MPO activity. These results suggest that complement and the condition of PMNs each play a role in determining the IS, and ischemic reperfusion injury might be produced even by relatively low myocardial MPO activity.

Animals↗
PubMed2000

A NF-kappaB p65 subunit is indispensable for activating manganese superoxide: dismutase gene transcription mediated by tumor necrosis factor-alpha.

Expression of the manganese superoxide dismutase (Mn-SOD) is induced by tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and lipopolysaccharide (LPS). Recently, a TNF-responsive element (TNFRE) was identified within the second intron of the murine Mn-SOD gene. The 5' CCAAT/enhancer binding protein (C/EBP)-related region within the TNFRE was responsive to TNF, whereas the 3' NF-kappaB-related region alone was not. This report describes the minimal promoter region of the Mn-SOD gene and investigates the cis-acting elements and trans-acting factors responsible for TNF-alpha-induced Mn-SOD gene expression. Reporter plasmid transfection studies demonstrated that inducible transcription factors enhanced the transcriptional activity of the Mn-SOD gene through the intronic enhancer region. Electrophoretic mobility shift assays demonstrated that after TNF-alpha stimulation, p50 and p65 NF-kappaB subunits bound specifically to the newly identified NF-kappaB transcription factor-binding site, distinct from the previously described NF-kappaB site, within the intronic enhancer region. In addition, site-directed mutagenesis and cotransfection studies demonstrated that the NF-kappaB p65 subunit enhanced the transcriptional activity of the Mn-SOD gene through the newly identified NF-kappaB site. These results show that a NF-kappaB p65 subunit is mainly involved in the molecular mechanisms controlling TNF-alpha-mediated Mn-SOD gene transcription.

3T3 Cells↗
PubMed2000

Apoptosis in relevant clinical situations: contribution of apoptosis in myocardial infarction.

Myocardial infarction is associated with increased TUNEL-positivity in cardiac resident and infiltrated cells. Apoptosis of proliferated interstitial myofibroblasts and infiltrated inflammatory cells may have a role in terminating tissue repair processes after infarction. Lateral and endocardial border zones of infarction within the risk area have frequent appearance of TUNEL-positive cardiomyocytes. Although the typical ultrastructural morphology of apoptosis has rarely been detected in ischaemic cardiomyocytes, there are many reports in which the TUNEL method was used for assessment of cardiomyocyte apoptosis. It has become evident that TUNEL-positivity reflects a wide range of cellular conditions; viable cells undergoing DNA repair, apoptosis, and necrosis. Therefore, it is controversial whether TUNEL-positive cardiomyocytes in infarcted myocardium are all apoptotic. Methods which will be more specific for identifying apoptosis are required for future study. TUNEL-positivity can be attenuated by anti-apoptotic interventions such as inhibition of caspases, mitochondrial protection, free radical scavenging, and some conventional pharmacotherapies. However, it remains to be determined whether anti-apoptotic interventions result in satisfactory reduction of infarct size. The injurious impact of myocardial ischaemia comes from a mixture of pro-apoptotic and necrosis-promoting signals, and the target of both signals is mitochondria. Through a common pathway they may cause permeability transition. Interventions which act only at the post-mitochondrial stage of apoptosis may fail to reduce infarct size, whereas those acting at pre-mitochondrial and mitochondrial stages may reduce infarct size. Progress in investigating the basic mechanisms of apoptosis and recognition of the modes of cardiomyocytes death will contribute to advances in cardioprotective therapy in myocardial infarction.

Adenosine↗
PubMed2000

Prediction of embolism in atrial fibrillation: classification of left atrial thrombi by transesophageal echocardiography.

The current study was undertaken to clarify the relationship between cerebral/arterial embolism and the morphology of left atrial thrombi. Forty-one patients with atrial fibrillation and left atrial thrombi were followed for 1 year, using transesophageal echocardiography (TEE) to study how the shape, site, movability, number and maximum dimension of left atrial thrombi are related to embolism. Left atrial thrombi were classified by their shape and movability into movable ball (MB) type (n=13), fixed ball (FB) type (n=17) and mountain (MN) type (n=11). The thrombi were also classified by location into the interior section (n=3), middle section (n=8), and the entrance section (n=19) of the left atrial appendage, and the section outside of the left atrial appendage (n=11). The rate of embolism in the MB-type group was significantly higher than that in the other groups (ie, MB 76.9% vs FB 17.6% (p<0.01) vs MN 9.1%; p<0.01), which indicates that the MB-type thrombus is an important risk factor for cerebral/arterial embolism.

Adult↗
PubMed2000

Effects of unstimulated polymorphonuclear neutrophils on porcine distal coronary artery tone.

Recently, it has been demonstrated that polymorphonuclear neutrophils (PMNs) affect coronary vascular tone. We have reported that unstimulated PMNs constrict the porcine proximal coronary artery. However, the mechanism(s) of interaction between PMNs and coronary artery and the regional differences in susceptibility of the coronary arterial tree have not been fully explored. We examined changes in the isometric tension of porcine distal coronary arterial rings caused by unstimulated PMNs, in which the levels of superoxide anion detected by the cytochrome C method were slight when unstimulated and significant when stimulated with A23187. Unstimulated PMNs relaxed the distal coronary artery and the effect was suppressed by endothelial denudation, indomethacin and the prostacyclin synthetase inhibitor, tranylcypromine. During vasorelaxation, prostacyclin was produced (n=8, with without relaxation; 596 +/- 76/247 +/- 26 pg/ml, p < 0.01) and was considered, therefore, to be the vasodilatory substance responsible for the action. These results suggest that PMNs modulate coronary arterial tone via an interaction between PMNs and endothelium and the release of vasodilating prostaglandins, of which prostacyclin is considered to be one of the substances responsible. Further, the effect differed markedly depending on the site of the coronary artery. In vivo, coronary artery tone is complexly regulated, therefore, the relative contribution of the present PMN-endothelial cell interaction observed in vitro is unclear.

Animals↗
PubMed1999

Cooperative interaction of NF-kappaB and C/EBP binding sites is necessary for manganese superoxide dismutase gene transcription mediated by lipopolysaccharide and interferon-gamma.

Expression of the manganese superoxide dismutase (Mn-SOD) is induced by pro-inflammatory cytokines. We investigated the cis-acting elements within a tumor necrosis factor-responsive element (TNFRE) which was identified in the second intron of the murine Mn-SOD gene. Site-directed mutagenesis, reporter plasmid transfection studies and electrophoretic mobility shift assays demonstrated that inducible transcription factors enhanced the transcriptional activity of the Mn-SOD gene through the TNFRE. The cooperation between proteins binding to the newly identified NF-kappaB and C/EBP sites led to synergistic gene transcription. This report provides the first evidence that cooperation between two distinct cis-acting elements may be required for induction of Mn-SOD gene expression mediated by lipopolysaccharide and interferon-gamma.

3T3 Cells↗
PubMed1999

Expression of cytokine and adhesion molecule mRNA in atherectomy specimens from patients with coronary artery disease.

Coronary arteriosclerosis is an underlying condition in acute myocardial infarction (AMI), unstable angina pectoris (UAP) and stable angina pectoris (SAP), and is also related to restenosis (RS) following coronary intervention. To investigate the pathogenesis of this condition, a quantitative reverse transcriptase polymerase chain reaction was used to determine relative levels of mRNA for interleukin (IL)-1beta, IL-6, IL-8, transforming growth factor beta (TGF-beta), intercellular adhesion molecule (ICAM)-1, E-selectin and vascular cell adhesion molecule (VCAM)-1 using directional coronary atherectomy (DCA) specimens. Eleven patients with AMI, 7 with UAP, 10 with SAP and 6 with RS following a previous coronary intervention underwent DCA. The mRNA intensity for each molecule was expressed by comparing it with that of beta-actin mRNA. The AMI and UAP patients showed high frequencies of mRNA for IL-1beta, IL-8, TGF-beta, and ICAM-1 together with strong intensities of expression, whereas SAP patients showed decreased mRNA expression for these molecules. Increased IL-6 mRNA expression was observed only in AMI samples. Specimens from RS patients revealed an accumulated expression of proinflammatory cytokines, except for IL-6, as well as of TGF-beta. The study suggests that variation in mRNA expression may reflect the pathophysiology of specific types of coronary artery disease, and remodeling following vascular injury.

Aged↗