Biomedical subjects

Masafumi Kitakaze

Publications and source records attributed to Masafumi Kitakaze.

At least 73 records · Page 4Linked to original sources

PubMed2004

Optimal windows of statin use for immediate infarct limitation: 5'-nucleotidase as another downstream molecule of phosphatidylinositol 3-kinase.

BACKGROUND: Although statins are reported to have a cardioprotective effect, their immediate direct influence on ischemia-reperfusion injury and the underlying mechanisms remain obscure. We investigated these issues an in vivo canine model. METHODS AND RESULTS: Dogs were subjected to coronary occlusion (90 minutes) and reperfusion (6 hours) immediately after injection of pravastatin (0.2, 2, or 10 mg/kg), pitavastatin (0.01, 0.1, or 0.5 mg/kg), or cerivastatin (0.5, 5, or 50 microg/kg). Then myocardial phosphatidylinositol 3-kinase (PI3-K) and 5'-nucleotidase activities were measured, as well as infarct size. After 15 minutes of reperfusion, pravastatin caused dose-dependent activation of Akt and ecto-5'-nucleotidase in the ischemic zone, and the effect was significant at higher doses. Pitavastatin also significantly increased these activities, and its optimal dose was within the clinical range, whereas cerivastatin caused activation at the lowest dose tested. In all cases, both Akt and ecto-5'-nucleotidase showed activation in parallel, and this activation was completely abolished by wortmannin, a PI3-K inhibitor. The magnitude of the infarct-limiting effect paralleled the increase in Akt and ecto-5'-nucleotidase activity and was blunted by administration of wortmannin, alpha,beta-methyleneadenosine-5'-diphosphate, or 8-sulfophenyltheophylline during reperfusion. Both collateral flow and the area at risk were comparable for all groups. CONCLUSIONS: Activation of ecto-5'-nucleotidase after ischemia by PI3-K activation may be crucial for immediate infarct-size limitation by statins. There seems to be an optimal dose for each statin that is independent of its clinical cholesterol-lowering effect.

5'-Nucleotidase↗

PubMed2004

Prolonged endoplasmic reticulum stress in hypertrophic and failing heart after aortic constriction: possible contribution of endoplasmic reticulum stress to cardiac myocyte apoptosis.

BACKGROUND: The endoplasmic reticulum (ER) is recognized as an organelle that participates in folding secretory and membrane proteins. The ER responds to stress by upregulating ER chaperones, but prolonged and/or excess ER stress leads to apoptosis. However, the potential role of ER stress in pathophysiological hearts remains unclear. METHODS AND RESULTS: Mice were subjected to transverse aortic constriction (TAC) or sham operation. Echocardiographic analysis demonstrated that mice 1 and 4 weeks after TAC had cardiac hypertrophy and failure, respectively. Cardiac expression of ER chaperones was significantly increased 1 and 4 weeks after TAC, indicating that pressure overload by TAC induced prolonged ER stress. In addition, the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells increased, and caspase-3 was cleaved in failing hearts. The antagonism of angiotensin II type 1 receptor prevented upregulation of ER chaperones and apoptosis in failing hearts. On the other hand, angiotensin II upregulated ER chaperones and induced apoptosis in cultured adult rat cardiac myocytes. We also investigated possible signaling pathways for ER-initiated apoptosis. The CHOP- (a transcription factor induced by ER stress), but not JNK- or caspase-12-, dependent pathway was activated in failing hearts by TAC. Pharmacological ER stress inducers upregulated ER chaperones and induced apoptosis in cultured cardiac myocytes. Finally, mRNA levels of ER chaperones were markedly increased in failing hearts of patients with elevated brain natriuretic peptide levels. CONCLUSIONS: These findings suggest that pressure overload by TAC induces prolonged ER stress, which may contribute to cardiac myocyte apoptosis during progression from cardiac hypertrophy to failure.

Angiotensin II↗

PubMed2004

Treatment of dilated cardiomyopathy with electroporation of hepatocyte growth factor gene into skeletal muscle.

Hepatocyte growth factor (HGF) is a potent angiogenic and antifibrotic factor. Cardioprotective effects of HGF for idiopathic dilated cardiomyopathy were examined in hamsters with electroporation of plasmid DNA into skeletal muscle. We used hamster skeletal muscle as a protein producer of HGF gene. A plasmid vector encoding HGF (HGF group, n=12) or empty plasmid (placebo group, n=12) was transferred with in vivo electroporation into tibialis anterior muscles of hamsters with inherited dilated cardiomyopathy (TO-2 strain). The HGF group had greater serum HGF levels (21.6+/-2.2 versus 0.11+/-0.07 ng/mL, P<0.05), higher left ventricular ejection fraction (47.9+/-9.4% versus 28.8+/-11.2%, P<0.05), and greater wall thickening (31.6+/-6.3% versus 19.7+/-6.1%, P<0.05) when compared with the placebo group. The HGF group had smaller areas of ventricular fibrosis (11.8+/-3.4% versus 17.1+/-3.5%, P<0.05) and lower hydroxyproline content (3.7+/-0.7 versus 5.1+/-0.9 micromol/g, P<0.05) than did the placebo group. The HGF group also had higher capillary density (1885+/-232 versus 1447+/-182 vessel/mm(2), P<0.05) and higher matrix metalloprotease-1 activity (13.1+/-3.5 versus 8.1+/-3.6 microg/collagen degraded per hour per gram tissue, P<0.05) than did the placebo group. Exogenous HGF might improve the deleterious changes in myocardial function and structure in the hamster with dilated cardiomyopathy. Systemic delivery of gene products with in vivo electroporation into skeletal muscle seemed to be an alternative means of direct gene delivery.

Animals↗

PubMed2004

Celiprolol, a vasodilatory beta-blocker, inhibits pressure overload-induced cardiac hypertrophy and prevents the transition to heart failure via nitric oxide-dependent mechanisms in mice.

BACKGROUND: The blockade of beta-adrenergic receptors reduces both mortality and morbidity in patients with chronic heart failure, but the cellular mechanism remains unclear. Celiprolol, a selective beta(1)-blocker, was reported to stimulate the expression of endothelial NO synthase (eNOS) in the heart, and NO levels have been demonstrated to be related to myocardial hypertrophy and heart failure. Thus, we aimed to clarify whether celiprolol attenuates both myocardial hypertrophy and heart failure via the NO-signal pathway. METHODS AND RESULTS: In rat neonatal cardiac myocytes, celiprolol inhibited protein synthesis stimulated by either isoproterenol or phenylephrine, which was partially suppressed by N(G)-nitro-L-arginine methyl ester (L-NAME). Four weeks after transverse aortic constriction (TAC) in C57BL/6 male mice, the ratio of heart weight to body weight (mg/g) (8.70+/-0.42 in TAC, 6.61+/-0.44 with celiprolol 100 mg x kg(-1) x d(-1) PO, P<0.01) and the ratio of lung weight to body weight (mg/g) (10.27+/-1.08 in TAC, 7.11+/-0.70 with celiprolol 100 mg x kg(-1) x d(-1) PO, P<0.05) were lower and LV fractional shortening was higher in the celiprolol-treated groups than in the TAC group. All of these improvements were blunted by L-NAME. Celiprolol treatment significantly increased myocardial eNOS and activated phosphorylation of eNOS. Myocardial mRNA levels of natriuretic peptide precursor type B and protein inhibitor of NO synthase, which were increased in the TAC mice, were decreased in the celiprolol-treated mice. CONCLUSIONS: These findings indicated that celiprolol attenuates cardiac myocyte hypertrophy both in vitro and in vivo and halts the process leading from hypertrophy to heart failure. These effects are mediated by a selective beta1-adrenergic receptor blockade and NO-dependent pathway.

Adrenergic beta-1 Receptor Antagonists↗

PubMed2004

Protein kinase A as another mediator of ischemic preconditioning independent of protein kinase C.

BACKGROUND: We and others have reported that transient accumulation of cyclic AMP (cAMP) in the myocardium during ischemic preconditioning (IP) limits infarct size independent of protein kinase C (PKC). Accumulation of cAMP activates protein kinase A (PKA), which has been demonstrated to cause reversible inhibition of RhoA and Rho-kinase. We investigated the involvement of PKA and Rho-kinase in the infarct limitation by IP. METHODS AND RESULTS: Dogs were subjected to 90-minute ischemia and 6-hour reperfusion. We examined the effect on Rho-kinase activity during sustained ischemia and infarct size of (1) preischemic transient coronary occlusion (IP), (2) preischemic activation of PKA/PKC, (3) inhibition of PKA/PKC during IP, and (4) inhibition of Rho-kinase or actin cytoskeletal deactivation during myocardial ischemia. Either IP or dibutyryl-cAMP treatment activated PKA, which was dose-dependently inhibited by 2 PKA inhibitors (H89 and Rp-cAMP). IP and preischemic PKA activation substantially reduced infarct size, which was blunted by preischemic PKA inhibition. IP and preischemic PKA activation, but not PKC activation, caused a substantial decrease of Rho-kinase activation during sustained ischemia. These changes were cancelled by preischemic inhibition of PKA but not PKC. Furthermore, either Rho-kinase inhibition (hydroxyfasudil or Y27632) or actin cytoskeletal deactivation (cytochalasin-D) during sustained ischemia achieved the same infarct limitation as preischemic PKA activation without affecting systemic hemodynamic parameters, the area at risk, or collateral blood flow. CONCLUSIONS: Transient preischemic activation of PKA reduces infarct size through Rho-kinase inhibition and actin cytoskeletal deactivation during sustained ischemia, implicating a novel mechanism for cardioprotection by ischemic preconditioning independent of PKC and a potential new therapeutic target.

Animals↗

PubMed2004

Beta-adrenoceptor blocker carvedilol provides cardioprotection via an adenosine-dependent mechanism in ischemic canine hearts.

BACKGROUND: Carvedilol is a beta-adrenoceptor blocker with a vasodilatory action that is more effective for the treatment of congestive heart failure than other beta-blockers. Recently, carvedilol has been reported to reduce oxidative stress, which may consequently reduce the deactivation of adenosine-producing enzymes and increase cardiac adenosine levels. Therefore, carvedilol may also have a protective effect on ischemia and reperfusion injury, because adenosine mediates cardioprotection in ischemic hearts. METHODS AND RESULTS: In anesthetized dogs, the left anterior descending coronary artery was occluded for 90 minutes, followed by reperfusion for 6 hours. Carvedilol reduced the infarct size (15.0+/-2.8% versus 40.9+/-4.2% in controls), and this effect was completely reversed by the nonselective adenosine receptor antagonist 8-sulfophenyltheophylline (45.2+/-5.4%) or by an inhibitor of ecto-5'-nucleotidase (44.4+/-3.6%). There were no differences of either area at risk or collateral flow among the various groups. When the coronary perfusion pressure was reduced in other dogs so that coronary blood flow was decreased to 50% of the nonischemic level, carvedilol increased coronary blood flow (49.4+/-5.6 to 73.5+/-7.5 mL x 100 g(-1) x min(-1); P<0.05) and adenosine release (112.3+/-22.2 to 240.6+/-57.1 nmol/L; P<0.05) during coronary hypoperfusion. This increase of coronary blood flow was attenuated by either 8-sulfophenyltheophylline or superoxide dismutase. In human umbilical vein endothelial cells cultured with or without xanthine and xanthine oxidase, carvedilol caused an increase of ecto-5'-nucleotidase activity. CONCLUSIONS: Carvedilol shows a cardioprotective effect against ischemia and/or reperfusion injury via adenosine-dependent mechanisms.

5'-Nucleotidase↗

PubMed2004

The role of a common TNNT2 polymorphism in cardiac hypertrophy.

We found a five-basepair insertion/deletion polymorphism in intron 3 of TNNT2, one of the genes responsible for hypertrophic cardiomyopathy. These five bases may be part of an intronic polypyrimidine tract sequence that may affect splicing. The purpose of the study was to examine the association of the polymorphism with cardiac hypertrophy. The study population consisted of 151 subjects with prominent concentric left ventricular hypertrophy, and 987 healthy subjects recruited from medical checkups (control population). The deletion/deletion genotype tended to be associated with a larger left ventricular mass/height ratio in the HCM population ( p<0.0001). Multiple regression analyses indicated that the left ventricular mass/height ratio was determined ( p<0.0001, R=0.738) by the TNNT2 genotype. Moreover, the frequency of the deletion allele was significantly higher in the hypertrophy population than in the control population ( p<0.0001). In vitro expression study revealed the deletion allele significantly affected the mRNA expression pattern by skipping exon 4 during splicing. In conclusion, TNNT2 deletion allele could be associated with a predisposition to prominent left ventricular hypertrophy.

Aged↗

PubMed2004

Lamr1 functional retroposon causes right ventricular dysplasia in mice.

Arrhythmogenic right ventricular dysplasia (ARVD) is a hereditary cardiomyopathy that causes sudden death in the young. We found a line of mice with inherited right ventricular dysplasia (RVD) caused by a mutation of the gene laminin receptor 1 (Lamr1). This locus contained an intron-processed retroposon that was transcribed in the mice with RVD. Introduction of a mutated Lamr1 gene into normal mice by breeding or by direct injection caused susceptibility to RVD, which was similar to that seen in the RVD mice. An in vitro study of cardiomyocytes expressing the product of mutated Lamr1 showed early cell death accompanied by alteration of the chromatin architecture. We found that heterochromatin protein 1 (HP1) bound specifically to mutant LAMR1. HP1 is a dynamic regulator of heterochromatin sites, suggesting that mutant LAMR1 impairs a crucial process of transcriptional regulation. Indeed, mutant LAMR1 caused specific changes to gene expression in cardiomyocytes, as detected by gene chip analysis. Thus, we concluded that products of the Lamr1 retroposon interact with HP1 to cause degeneration of cardiomyocytes. This mechanism may also contribute to the etiology of human ARVD.

Animals↗

PubMed2004

Haplotypes of CYP3A4 and their close linkage with CYP3A5 haplotypes in a Japanese population.

In order to identify single nucleotide polymorphisms (SNPs) and haplotype frequencies of CYP3A4 in a Japanese population, the distal enhancer and proximal promoter regions, all exons, and the surrounding introns were sequenced from genomic DNA of 416 Japanese subjects. We found 24 SNPs, including 17 novel ones: two in the distal enhancer, four in the proximal promoter, one in the 5'-untranslated region (UTR), seven in the introns, and three in the 3'-UTR. The most common SNP was c.1026+12G>A (IVS10+12G>A), with a 0.249 frequency. Four non-synonymous SNPs, c.554C>G (p.T185S, CYP3A4(*)16), c.830_831insA (p.E277fsX8, (*)6), c.878T>C (p.L293P, (*)18), and c.1088 C>T (p.T363M, (*)11) were found with frequencies of 0.014, 0.001, 0.028, and 0.002, respectively. No SNP was found in the known nuclear transcriptional factor-binding sites in the enhancer and promoter regions. Using these 24 SNPs, 16 haplotypes were unambiguously identified, and nine haplotypes were inferred by aid of an expectation-maximization-based program. In addition, using data from 186 subjects enabled a close linkage to be found between CYP3A4 and CYP3A5 SNPs, especially among the SNPs at c.1026+12 in CYP3A4 and c.219-237 (IVS3-237, a key SNP site for CYP3A5(*)3), c.865+77 (IVS9+77) and c.1523 in CYP3A5. This result suggested that CYP3A4 and CYP3A5 are within the same gene block. Haplotype analysis between CYP3A4 and CYP3A5 revealed several major haplotype combinations in the CYP3A4-CYP3A5 block. Our findings provide fundamental and useful information for genotyping CYP3A4 (and CYP3A5) in the Japanese, and probably Asian populations.

Cytochrome P-450 CYP3A↗

PubMed2004

A novel data mining approach to the identification of effective drugs or combinations for targeted endpoints--application to chronic heart failure as a new form of evidence-based medicine.

BACKGROUND: Data mining is a technique for discovering useful information hidden in a database, which has recently been used by the chemical, financial, pharmaceutical, and insurance industries. It may enable us to detect the interesting and hidden data on useful drugs especially in the field of cardiovascular disease. METHODS AND RESULTS: We evaluated the current treatments for chronic heart failure (CHF) in our institute using a decision tree method of data mining and compared the results with those of large-scale clinical trials. We enrolled 1,100 patients with CHF (NYHA classes II-IV and EF < 40%) who were hospitalized at the National Cardiovascular Center during the past 31 months. Drugs prescribed at discharge were extracted from the clinical database. Both echocardiograms and plasma BNP level at 6-12 months after discharge were determined prospectively. It was found that beta-blockers, angiotensin converting enzyme inhibitors, and angiotensin II receptor antagonists independently improve both the plasma BNP level and %fractional shortening (FS), while oral inotropic agents increased the plasma BNP level and decreased %FS. These findings agree with evidence accumulated from several large-scale trials. Interestingly, statins, histamine receptor blockers, and alpha-glucosidase inhibitors also attenuated the severity of CHF, suggesting the possibility of new treatment of CHF. CONCLUSION: Clinical data mining using Japanese CHF patients yielded almost identical data to the results of large-scale trials, and also suggested novel and unexpected candidates for CHF therapy. Further validation of the data mining approved in the cardiovascular field is warranted.

Chronic Disease↗

PubMed2004

UGT1A1 haplotypes associated with reduced glucuronidation and increased serum bilirubin in irinotecan-administered Japanese patients with cancer.

PURPOSE: A comprehensive haplotype analysis of UGT1A1 in the Japanese population was conducted, and the effects of these haplotypes were investigated with respect to UGT1A1-related phenotypic parameters in patients with cancer who received irinotecan. METHODS: The UGT1A1 gene, including the enhancer, the promoter, and all 5 exons and their flanking regions, was sequenced from 195 Japanese subjects. The gene was divided into 2 blocks, and the haplotypes of each block were assigned. The association of these haplotypes with area under the concentration-time curve (AUC) ratios (7-ethyl-10-hydroxycamptothecin glucuronide [SN-38G]/7-ethyl-10-hydroxycamptothecin [SN-38]) and pretreatment levels of serum total bilirubin was investigated in 85 cancer patients who received irinotecan. RESULTS: Four haplotype groups (*1, *60, *28, and *6) were assigned in block 1, and 2 haplotype groups (*IA and *IB) were in block 2. The majority of the *IB haplotypes in block 2 were linked to either the *1 or the *60 haplotype but not to *28 in block 1. Highly significant associations were obtained between the *28 haplotypes and both a reduced AUC ratio (P =.0014, Jonckheere-Terpstra [JT] test) and an increased total bilirubin level (P =.0007, JT test). Increased total bilirubin levels in the *60 (P =.0048, JT test) and *IB groups (P =.0224, JT test) were also observed. The reduction in the AUC ratio by the *6 group was moderate (P =.0372, JT test) but was remarkable in combination with *60 (*6/*60) or *28 (*6/*28) as compared with the *1 group (*1/*1) (P =.049 and P =.0071, respectively; nonparametric Dunnett test). CONCLUSION: This study identified several UGT1A1 haplotypes significantly associated with the reduced AUC ratio (*28 and *6) and with the increased total bilirubin level (*28, *60, and *IB) and suggested that the novel haplotype *IB might be functionally important. These findings will be useful for further pharmacogenetic studies on adverse reactions to irinotecan.

Aged↗

PubMed2004

Ischemic preconditioning: emerging evidence, controversy, and translational trials.

Protection against ischemia by ischemic preconditioning (IP) is seen in many tissues and organs. However, the preconditioning ischemia must precede lethal ischemia for this effect to occur, and the creation of ischemia to treat heart disease does not seem to be a realistic strategy. Accordingly, the underlying mechanisms that confer cardioprotection should be identified. Early studies revealed that IP causes two windows of cardioprotection, and subsequent efforts to detect cardioprotective factors have identified various triggers, mediators, and potent effectors of IP, such as endogenous receptor agonists (adenosine, catecholamines, bradykinin, and opioids), intracellular messengers [protein kinase C (PKC), p38MAPK, PI-3K, and PKA], ion channels such as KATP channels, enzymes including heat shock proteins (HSPs), superoxide dismutase (SOD), and 5'-nucleotidase, and other factors [nitric oxide (NO), growth factors, free radicals, and products of the arachidonic acid cascade]. Some of these factors are involved in several different pathways and may have multiple roles in IP-induced cardioprotection. Recently, however, certain problems have arisen such as controversies related to increasing knowledge and the relative lack of clinical studies in contrast to the intensive performance of basic studies. To overcome these problems, the latest studies have followed three major trends: (1) investigation of mechanisms to explain the current controversies, (2) detection of other unknown potent mechanisms, and (3) promotion of clinical trials based on the evidence from experimental studies in larger animals. Here, we summarize recent investigations on IP, emphasizing on the controversial issues and emerging factors, and discuss current research on the prevention or treatment of ischemic heart disease including some relevant clinical studies.

Animals↗

PubMed2004

Opening of Ca2+-activated K+ channels is involved in ischemic preconditioning in canine hearts.

Brief periods of ischemia that precede sustained ischemia can markedly reduce infarct size (IS), a phenomenon that is known as ischemic preconditioning (IP). Several investigators have shown that elevation of the intracellular Ca(2+) level ([Ca(2+)](i)) during the antecedent brief periods of ischemia triggers the cardioprotective mechanism of IP. Since opening of Ca(2+) activated K(+) (K(Ca)) channels is reported to be cardioprotective, we hypothesized that these channels may be involved in the cardioprotective mechanism of IP. In anesthetized open-chest dogs, myocardial ischemia/reperfusion injury was created by occlusion of the left anterior descending coronary artery (LAD) for 90 min followed by 6 h of reperfusion. First, we showed that the treatment with NS1619, a K(Ca) channel opener, reduced IS (IS in NS1619 group and control group, 19.8 +/- 5.5% vs. 45.4 +/- 3.5% of the area at risk, P < 0.05). Next, four cycles coronary occlusion for 5 min and reperfusion (IP) were performed before the 90-min occlusion with or without the infusion of potent K(Ca) channel inhibitors, iberiotoxin (IbTX) and charybdotoxin (ChTX). IP markedly reduced IS (IS in the IP group was 8.2 +/- 1.8%, P < 0.01 vs. control group). Infusion of either of K(Ca) channel blockers during IP blunted the IS-limiting effect of IP (IS in the IP + IbTX and IP + ChTX groups was 30.7 +/- 7.0% and 35.5 +/- 3.7%, respectively, P < 0.05, vs. IP group). However, the cardioprotective effect of IP was not blunted by the treatment with ChTX when treated only during reperfusion (14.0 +/- 4.1%). Thus, we conclude that the opening of K(Ca) channel is involved in early trigger phase of the molecular mechanism of IP.

Animals↗

PubMed2004

Selective blockade of serotonin 5-HT2A receptor increases coronary blood flow via augmented cardiac nitric oxide release through 5-HT1B receptor in hypoperfused canine hearts.

Serotonin (5-hydroxytryptamine [5-HT]), which induces vasoconstriction via 5-HT2A receptors in smooth muscle cells and vasodilation through activating nitric oxide (NO) synthase (NOS) via 5-HT1B receptors in endothelial cells, possesses divergent effects on regulating vascular tone. These facts lead us to consider that sarpogrelate, a 5-HT2A receptor blocker, may increase coronary blood flow (CBF) via either attenuation of vasoconstriction through 5-HT2A receptor blockade or augmentation of vasodilation by relative stimulation of NOS through 5-HT1B receptor and we tested this hypothesis in ischemic canine hearts. In open chest dogs, coronary perfusion pressure was reduced so that CBF was decreased to 33% of the baseline and kept constant. Thereafter, sarpogrelate was infused selectively into the left anterior descending artery with and without either an inhibitor of NOS (NG-nitro-L-arginine methyl ester (L-NAME)) or a 5-HT1B receptor antagonist (GR55562). An intracoronary administration of sarpogrelate increased CBF (34.0 +/- 4.0 to 44.5 +/- 4.4 ml/100 g/min, P < 0.05), along with the cardiac NOx release (3.2 +/- 0.6 to 6.8 +/- 1.2 nmol/ml, P < 0.05). The increases in both CBF and NOx by sarpogrelate were completely blunted by the co-administration of either L-NAME or GR55562. Interestingly, sarpogrelate increased the cardiac serotonin release (-4.8 +/- 3.2 vs. 22.1 +/- 1.5 ng/ml, P < 0.05, respectively) in the hypoperfused heart. Immunohistochemical analysis showed that sarpogrelate induced serotonin production in ischemic cardiac myocytes. These results suggest that sarpogrelate increases CBF via augmented cardiac NO production through 5-HT1B receptor activation along with the blockade of 5-HT2A receptors. The increase in cardiac release of serotonin may increase NO production in the ischemic heart.

Animals↗

PubMed2004

Roles of systemic nitric oxide metabolites for human coronary circulation.

Several previous studies have suggested decreased bioactivity of nitric oxide (NO) in coronary artery diseases using NO synthase inhibitors. Nitrite is delivered as bioactive NO in the forearm circulation. However, the role(s) of NO metabolites in the systemic and coronary circulation are still unknown. The aim of this study was to investigate the role(s) of systemic NO metabolites for human coronary circulation in patients with and without coronary spastic angina (CSA). Twenty-nine patients with chest symptoms were enrolled to perform the acetylcholine (Ach) provocative test. Blood was sampled from the aorta at baseline, and from the great cardiac vein at baseline and after Ach to measure plasma levels of nitrate and nitrite (NOx). The epicardial left anterior descending artery was examined by quantitative angiography. The patients were divided into the two groups according to the Ach provocative test. In the non-CSA group, the NOx uptake across the coronary circulation correlated with the endothelium-dependent vasoresponse to Ach (r = -0.61, p < 0.05) and NOx levels of the aorta also correlated (r = -0.72, p < 0.005), which suggested the compensatory increase of systemic NOx levels for impaired endothelial function. In the CSA group, the NOx uptake across the coronary circulation did not correlate with the vasoresponse to Ach (r = 0.29, p = 0.28). However, NOx levels of the aorta correlated with vasosensitivity to Ach (r = 0.61, p < 0.005). The higher systemic NOx levels correlated well with the vasodilator responsiveness to Ach. These results suggest that systemic NOx is delivered into the coronary circulation as bioactive NO to preserve endothelial function in the non-CSA patients, and to attenuate Ach-induced vasoconstriction in the CSA patients. There is a possibility that systemic NOx plays a complementary role on impaired coronary vasoregulation.

Acetylcholine↗

PubMed2004

Methotrexate and MX-68, a new derivative of methotrexate, limit infarct size via adenosine-dependent mechanisms in canine hearts.

Methotrexate, an anti-rheumatic agent, has recently been reported to show an anti-inflammatory action via ecto-5'-nucleotidase- and adenosine-dependent mechanisms. Because ecto-5'-nucleotidase contributes to the production of adenosine and adenosine has a potent cardioprotective effect against ischemia/reperfusion injury, we investigated whether methotrexate or MX-68 [N-1-((2,4-diamino-6-pteridinyl) methyl)-3,4-dihydro-2H-1,4-benzothiazine-7- carbonyl]-N-2- aminoadipic acid] could reduce infarct size via adenosine-dependent mechanisms. In beagle dogs, the left anterior descending coronary artery was perfused through a bypass tube, which was occluded for 90 minutes followed by 6 hours of reperfusion. The size of infarcts was assessed by TTC staining. MX-68 reduced infarct size compared with that in untreated dogs (13.7 +/- 1.9 versus 38.6 +/- 5.3%, P < 0.01). This effect was completely blunted by either the adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) (45.0 +/- 4.6% and 46.8 +/- 5.8% in the 8-SPT and MX-68 + 8-SPT groups, respectively) or by the ecto-5'-nucleotidase inhibitoralpha,beta-methylenadenosine 5'-diphosphate (AMP-CP) (44.0 +/- 4.5% and 46.7 +/- 5.8% in the AMP-CP and MX-68 + AMP-CP groups, respectively). Methotrexate also reduced infarct size to a level comparable with that in the MX-68 group, and its effect was also blunted by 8-SPT. There were no significant differences of collateral blood flow or risk area between the groups. We conclude that methotrexate and its derivative (MX-68) both limit infarct size via adenosine-dependent mechanisms.

2-Aminoadipic Acid↗

PubMed2004

Raloxifene improves coronary perfusion, cardiac contractility, and myocardial metabolism in the ischemic heart: role of phosphatidylinositol 3-kinase/Akt pathway.

The purpose of this study is to examine whether raloxifene, one of the selective estrogen receptor modulators, could improve myocardial ischemia and to assess the mechanisms involved. In open-chest beagle dogs anesthetized by intravenous infusion of sodium pentobarbital, the left anterior descending coronary artery (LAD) was perfused from the left carotid artery through an extracorporeal bypass tube. Raloxifene was infused into the LAD through the bypass tube under either ischemic or non-ischemic conditions. In the non-ischemic heart, raloxifene had no effect on coronary blood flow, fractional shortening, and myocardial metabolism. However, raloxifene caused an acute increase in both coronary blood flow and fractional shortening, and also improved myocardial anaerobic metabolism in the ischemic heart. These effects were partially attenuated by pretreatment with either L-NAME or wortmannin and were completely abolished by ICI182780 (an estrogen receptor antagonist) or L-NAME plus charybdotoxin (a blocker of Ca-activated K channels). Raloxifene also increased both Akt activity and the NO level, with these changes being completely abrogated by pretreatment with wortmannin. These results demonstrated that raloxifene improves coronary perfusion, cardiac contractility, and myocardial metabolism by release of NO and opening of Ca-activated K channels in the ischemic heart, and that NO production is mediated by the phosphatidylinositol 3-kinase/Akt pathway.

Animals↗

PubMed2004

Oestrogen increases myocardial blood flow in men: assessment by 13N-ammonia positron emission tomography.

OBJECTIVES: Oestrogen has been shown to increase nitric oxide-mediated vasodilatation and modulate sympathetic tone in postmenopausal women. We investigated the acute effects of oestrogen on the coronary microcirculation in men. METHODS: Myocardial blood flow was quantified using N-ammonia positron emission tomography before and 20 min after an intravenous administration of conjugated oestrogen (10 mg) in nine healthy men. RESULTS: There were no significant changes in either systemic blood pressure or heart rate before and after oestrogen infusion. However, myocardial blood flow was increased by oestrogen from 0.88 +/-0.06 to 1.05+/-0.09 ml x g x min (P<0.05). Although serum levels of nitrite/nitrate (end products of nitric oxide) were not increased, circulating norepinephrine (noradrenaline) levels were decreased after the administration of oestrogen from 401+/-114 to 346+/-112 pg x ml (P<0.01). A significant negative correlation was found between myocardial blood flow and plasma norepinephrine levels (r=-0.67, P<0.05). CONCLUSIONS: A single administration of oestrogen enhanced myocardial circulation in healthy men. The oestrogen-induced increase in myocardial blood flow may be due to direct effects on the coronary circulation or through the modulation of norepinephrine levels, rather than the production of nitric oxide.

Adult↗