Yasuhiko Sakata

SNPs in BRAP associated with risk of myocardial infarction in Asian populations

Myocardial infarction is a common disease and among the leading causes of death in the world. We previously reported association of variants in LGALS2, encoding galectin-2, with myocardial infarction susceptibility in a case-control association study in a Japanese population. Here we identify BRAP (BRCA1-associated protein) as a galectin-2–binding protein. We report an association of SNPs in BRAP with myocardial infarction risk in a large Japanese cohort (P = 3.0 × 10−18, OR = 1.48, 2,475 cases and 2,778 controls), with replication in additional Japanese and Taiwanese cohorts (P = 4.4 × 10−6, 862 cases and 1,113 controls and P = 4.7 × 10−3, 349 cases and 994 controls, respectively). BRAP expression was observed in smooth muscle cells (SMCs) and macrophages in human atherosclerotic lesions. BRAP knockdown by siRNA using cultured coronary endothelial cells suppressed activation of NF-κB, a central mediator of inflammation.

Nifedipine-Induced Coronary Vasodilation in Ischemic Hearts Is Attributable to Bradykinin- and NO-Dependent Mechanisms in Dogs

BACKGROUNDnDihydropyridine calcium channel blockers protect endothelial cells against ischemia and reperfusion injury, suggesting that nifedipine may increase the in vivo cardiac NO level and thus coronary blood flow (CBF) in ischemic hearts. We tested this hypothesis.nnnMETHODS AND RESULTSnIn open-chest dogs, coronary perfusion pressure (CPP) was reduced in the left anterior descending coronary artery so that CBF decreased to one third of the control level, and thereafter CPP was maintained constant (103+/-8 to 43+/-3 mm Hg, n=9). We obtained fractional shortening (FS) and lactate extraction ratio (LER) as indices of regional myocardial contraction and metabolism. Both FS (26.4+/-2.1% to 6.7+/-2.0%, n=9, P<0.001) and LER (32+/-6% to -37+/-5%, n=9, P<0.001) showed a decrease when CPP was reduced. After intracoronary infusion of nifedipine (4 microgram. kg(-1). min(-1)), CBF increased from 30+/-1 to 48+/-4 mL. 100 g(-1). min(-1) (P<0.01) without a change of CPP (n=9). Both FS (14.0+/-1.9%, n=9) and LER (-9+/-7%, n=9) also increased (P<0.01). Nifedipine increased the difference in the level of metabolites of NO (nitrate+nitrite; 9+/-3 to 25+/-5 nmol/mL, n=9, P<0.01) and bradykinin (22+/-5 to 58+/-4 pmol/mL, n=9, P<0.01) between coronary venous and arterial blood. L-NAME (an NO synthase inhibitor) or HOE-140 (a bradykinin receptor antagonist) attenuated (P<0.05) the increase in CBF (29+/-3 and 35+/-2 mL. 100 g(-1). min(-1), n=5 each), FS (4.8+/-0.6% and 6.9+/-1.7%, n=5 each), LER (-47+/-8% and -35+/-9%, n=5 each), and nitrate+nitrite (3+/-2 and 8+/-4 nmol/mL, n=5 each) due to nifedipine infusion.nnnCONCLUSIONSnThese results indicate that the calcium channel blocker nifedipine mediates coronary vasodilation and improves myocardial ischemia through both bradykinin/NO-dependent and -independent mechanisms.

Differential subcellular actions of ACE inhibitors and AT(1) receptor antagonists on cardiac remodeling induced by chronic inhibition of NO synthesis in rats

Chronic inhibition of NO synthesis induces cardiac hypertrophy independent of systemic blood pressure (SBP) by increasing protein synthesis in vivo. We examined whether ACE inhibitors (ACEIs) enalapril and temocapril and angiotensin II type-I receptor antagonists (angiotensin receptor blockers [ARBs]) losartan and CS-866 can block cardiac hypertrophy and whether changes in activation of 70-kDa S6 kinase (p70S6K) or extracellular signal–regulated protein kinase (ERK) are involved. The following 13 groups were studied: untreated Wistar-Kyoto rats and rats treated with NO synthase inhibitor N&ohgr;-nitro-l-arginine methyl ester (L-NAME), D-NAME (the inactive isomer of L-NAME), L-NAME plus hydralazine, L-NAME plus enalapril (3 mg · kg−1 · d−1) or temocapril (1 or 10 mg · kg−1 · d−1), L-NAME plus losartan (10 mg · kg−1 · d−1) or CS-866 (1 or 10 mg · kg−1 · d−1), L-NAME plus temocapril-CS866 in combination (1 or 10 mg · kg−1 · d−1), and L-NAME plus rapamycin (0.5 mg · kg−1 · d−1). After 8 weeks of each experiment, ratios of coronary wall to lumen (wall/lumen) and left ventricular weight to body weight (LVW/BW) were quantified. L-NAME increased SBP, wall/lumen, and LVW/BW compared with that of control. ACEIs, ARBs, and hydralazine equally canceled the increase in SBP induced by L-NAME. However, ACEIs and ARBs equally (but not hydralazine) attenuated increase in wall/lumen and LVW/BW induced by L-NAME. The L-NAME group showed both p70S6K and ERK activation in myocardium (2.2-fold and 1.8-fold versus control, respectively). ACEIs inactivated p70S6K and ARBs inactivated ERK in myocardium, but hydralazine did not change activation of either kinase. Thus, ACEIs and ARBs modulate different intracellular signaling pathways, inhibiting p70S6K or ERK, respectively, to elicit equal reduction of cardiac hypertrophy induced by chronic inhibition of NO synthesis in vivo.

SNPs on chromosome 5p15.3 associated with myocardial infarction in Japanese population

Myocardial infarction (MI) occurs as the result of complex interactions of multiple genetic and environmental factors. By conducting a genome wide association study in a Japanese population using 210u2009785 single nucleotide polymorphism (SNP) markers, we identified a novel susceptible locus for MI on chromosome 5p15.3. An SNP (rs11748327) in this locus showed significant association in several independent cohorts (combined P=5.3 × 10−13, odds ratio=0.80, comparison of allele frequency). Association study using tag SNPs in the same linkage disequilibrium block revealed that two additional SNPs (rs490556 and rs521660) conferred risk of MI. These findings indicate that the SNPs on chromosome 5p15.3 are novel protective genetic factors against MI.

Comparison of myocardial contrast echocardiography and coronary angiography for assessing the acute protective effects of collateral recruitment during occlusion of the left anterior descending coronary artery at the time of elective angioplasty

To assess the immediate change in collateral flow distribution within the occluded myocardium and the acute protective effects on myocardial ischemia after coronary occlusion, myocardial contrast echocardiography (MCE) was performed in 15 patients with normal left ventricular function undergoing elective coronary angioplasty of the left anterior descending artery, and the results were compared with those obtained from coronary angiography (CA). The sonicated or nonsonicated contrast material was injected into the right coronary artery before and during coronary occlusion and collaterals were graded on a 4-point scale (none = 0 to good = 3). Development of subjective anginal symptoms, ST-segment shift and wall motion abnormality during coronary occlusion were graded on a 4-point scale (none = 0 to severe = 3). Both MCE and CA detected a significant development in collateral flow during coronary occlusion. There was no significant correlation between MCE and CA collateral grades before or during coronary occlusion. The collateral flow assessed with MCE was inversely but significantly correlated with development of subjective anginal symptoms (r(s) = -0.70, p <0.01), ST-segment shift (r(s) = -0.78, p < 0.005) or wall motion abnormality (r(s) = -0.91, p < 0.001) during coronary occlusion. In contrast, the angiographic collateral flow was not correlated with development of anginal symptoms (r(s) = -0.46, p = 0.10), ST-segment shift (r(s) = -0.41, p = 0.14), or wall motion abnormality (r(s) = -0.26, p = 0.35). The present study suggested that the acute protective effects of coronary collaterals during coronary occlusion were closely associated with myocardial perfusion rather than the angiographic epicardial collateral vessel filling, and thus MCE was useful in assessing the acute protective effects of coronary collaterals during coronary occlusion.

Nifedipine limits infarct size via NO-dependent mechanisms in dogs.

Objectives Amlodipine increases NO levels in coronary vessels and aorta via bradykinin-dependent mechanisms in vitro. We have previously reported that nifedipine increases cardiac NO levels in the ischemic canine hearts, suggesting that nifedipine may also have protective effects against ischemia and reperfusion injury, because the enhancement of NO production limits infarct size. We tested whether nifedipine limits infarct size via NO-dependent mechanisms. Methods In open chest dogs, the left anterior descending coronary artery was perfused with blood through a bypass tube and occluded for 90 min followed by 6 hours of reperfusion. Infarct size was assessed at 6 hours of reperfusion. Nifedipine of 3 or 6 μg/kg/min was infused into the bypass tube between 10 min prior to the onset of ischemia and 60 min of reperfusion. Results Neither systemic blood pressure nor heart rate changed during infusion of nifedipine. Infarct size was reduced by the administration of nifedipine (3 or 6 μg/kg/min) compared with the untreated condition (25.6 plusmn; 2.6 and 19.1 ± 3.5 vs. 43.4 ± 5.6 %, respectively), which was completely blunted by L-NAME (45.0 ± 3.6 and 45.4 ± 4.2 vs. 47.9 ± 3.9 % in the nifedipine (3 or 6 μg/kg/min) with L-NAME groups vs. the L-NAME group). Myeloperoxidase activity of the myocardium increased after 6 hours of reperfusion, which was attenuated by nifedipine. The limitation of infarct size and the attenuation in myeloperoxidase activity were completely blunted by L-NAME. There were no significant differences in collateral blood flow at 45 min of ischemia between each group. Conclusions We conclude that the Ca channel blocker, nifedipine, limits infarct size via NO-dependent mechanisms.

Benidipine, a long-acting Ca channel blocker, limits infarct size via bradykinin- and NO-dependent mechanisms in canine hearts.

Amlodipine increases NO levels in coronary vessels and aorta via bradykinin-dependent mechanisms in vitro. We have previously reported that a long-acting Ca channel blocker, benidipine, increases cardiac NO levels in ischemic canine hearts, suggesting that benidipine may also protect against ischemia and reperfusion injury via bradykinin- and NO-dependent mechanisms. We examined this possibility. In open chest dogs, the left anterior descending coronary artery was perfused with blood through a bypass tube and was occluded for 90 min followed by 6 hours of reperfusion. Infarct size was assessed by TTC staining at 6 hours of reperfusion. When benidipine doses of 50, 100, and 200 ng/kg/min were infused via the bypass tube between 10 min prior to the onset of ischemia and after 60 min of reperfusion, systemic blood pressure did not change significantly. Infarct size decreased with the administration of benidipine (50, 100, and 200 ng/kg/min) when compared to the untreated condition (24.8 ± 2.5, 17.3 ± 3.1, and 16.5 ± 2.0 vs. 43.4 ± 5.6%, respectively) associated with the increased release of NO and bradykinin in the coronary venous blood upon reperfusion. Myeloperoxidase activity of the myocardium increased after 6 hours of reperfusion, which was attenuated by benidipine. The limitation of infarct size and the increase in myeloperoxidase activity were completely blunted by either L-NAME or HOE140. There were no significant differences in collateral blood flow assessed by the microsphere method after 45 min of ischemia for any of the groups. Thus, we conclude that the Ca channel blocker, benidipine, limits infarct size via bradykinin- and NO-dependent mechanisms.

Inhibition of Nitric Oxide Synthesis Induces Coronary Vascular Remodeling and Cardiac Hypertrophy Associated with the Activation of p70 S6 Kinase in Rats

Chronic inhibition of nitric oxide (NO) synthesis is reported to induce the thickening of coronary artery walls and cardiac hypertrophy in vivo via angiotensin II receptors. Increased protein synthesis is the main feature of these structural changes. Activation of 70 kD S6 kinase (p70S6K) phosphorylates the 40S ribosomal protein S6 that regulates protein synthesis. We examined the role of p70S6K in the vascular and myocardial structural changes induced by the chronic inhibition of NO synthesis. The following 5 groups were studied: untreated Wister-Kyoto rats, those treated with an inhibitor of NO synthase, Nω-nitro-L-arginine methyl ester (L-NAME), those treated with L-NAME and an angiotensin I converting enzyme inhibitor (imidapril), those treated with L-NAME and hydralazine, and those treated with L-NAME and an inhibitor of p70S6K (rapamycin). After 8 weeks, wall-to-lumen ratio in myocardium and cardiomyocyte cross-sectional areas were quantified. L-NAME increased systolic blood pressure, wall-to-lumen ratio, and cardiomyocyte cross-sectional area compared with control animals. Imidapril or rapamycin, but not hydralazine, markedly reduced these structural changes. L-NAME increased p70S6K activity in myocardium compared with control rats. Imidapril or rapamycin prevented the activation of p70S6K activity in myocardium induced by L-NAME. These results suggest that activation of p70S6K plays an important role in coronary vascular remodeling and cardiac hypertrophy induced by the chronic inhibition of nitric oxide synthesis in vivo.

Beneficial Effects of Intracoronary Nicorandil on Microvascular Dysfunction After Primary Percutaneous Coronary Intervention: Demonstration of Its Superiority to Nitroglycerin in a Cross-Over Study

PurposeIn patients undergoing primary percutaneous coronary intervention (PCI) for the treatment of ST-segment elevation myocardial infarction (STEMI), coronary microvascular dysfunction is associated with poor prognosis. Coronary microvascular resistance is predominantly regulated by ATP-sensitive potassium (KATP) channels. The aim of this study wasto clarify whether nicorandil, a hybrid KATP channel opener and nitric oxide donor, may be a good candidate for improving microvascular dysfunction even when administered after primary PCI.MethodsWe compared the beneficial effects of nicorandil and nitroglycerin on microvascular function in 60 consecutive patients with STEMI. After primary PCI, all patients received single intracoronary administrations of nitroglycerin (250xa0μg) and nicorandil (2xa0mg) in a randomized order; 30 received nicorandil first, while the other 30 received nitroglycerin first. Microvascular dysfunction was evaluated with the index of microcirculatory resistance (IMR), defined as the distal coronary pressure multiplied by the hyperemic mean transit time.ResultsAs a first administration, nicorandil decreased IMR significantly more than did nitroglycerin (median [interquartile ranges]: 10.8[5.2–20.7] U vs. 2.1[1.0–6.0] U, pu2009=u20090.0002).As a second administration, nicorandil further decreased IMR, while nitroglycerin did not (median [interquartile ranges]: 6.0[1.3–12.7] U vs. −1.4[−2.6 to 1.3] U, pu2009<u20090.0001). The IMR after the second administration was significantly associated with myocardial blush grade, angiographic TIMI frame count after the procedure, and peak creatine kinase level.ConclusionIntracoronary nicorandil reduced microvascular dysfunction after primary PCI more effectively than did nitroglycerin in patients with STEMI, probably via its KATP channel-opening effect.

Protein Tyrosine Kinase Is Not Involved in the Infarct Size–Limiting Effect of Ischemic Preconditioning in Canine Hearts

Protein kinase C (PKC) plays an important role in ischemic preconditioning (IP). Because (1) tyrosine kinase is located at the downstream of PKC for IP in the rabbit hearts and (2) we have reported that ecto–5′-nucleotidase is the substrate for PKC and plays a crucial role for the infarct size–limiting effect, we tested whether tyrosine kinase activation contributes to either activation of ecto–5′-nucleotidase or the infarct size–limiting effect of the early phase of IP in the canine heart. In dogs, the IP procedure (4 cycles of 5-minute occlusion of coronary artery) and exposure to 12,13-phorbol myristate acetate (PMA) each activated myocardial ecto–5′-nucleotidase and Lck tyrosine kinase. Genistein (10, 30, and 100 &mgr;g · kg−1 · min−1 IC), an inhibitor of tyrosine kinase, attenuated the activation of Lck tyrosine kinase but did not attenuate the activation of ecto–5′-nucleotidase due to either IP or PMA. In the other canine hearts, IP attenuated infarct size (49±5 versus 11±3 or 16±3%, P <0.01) due to 90 minutes of coronary occlusion followed by 6 hours of reperfusion, which was not blunted by 3 or 2 (30 and 100 &mgr;g · kg−1 · min−1) doses of genistein (infarct sizes, 15±4, 13±4, and 13±3%, respectively, and 17±3 and 15±4%, respectively) or lavendustin A. Tyrosine kinase does not activate ecto–5′-nucleotidase or trigger the infarct size–limiting effect of the early phase of IP in canine hearts.