Takahiko Yamaki

Post-infarct treatment with an erythropoietin-gelatin hydrogel drug delivery system for cardiac repair.

AIMS We investigated the effect of an erythropoietin (EPO)-gelatin hydrogel drug delivery system (DDS) applied to the heart on myocardial infarct (MI) size, left ventricular (LV) remodelling and function. METHODS AND RESULTS Experiments were performed in a rabbit model of MI. The infarct size was reduced, and LV remodelling and function were improved 14 days and 2 months after MI but not at 2 days after MI in the EPO-DDS group. The number of cluster of differentiation 31(CD31)-positive microvessels and the expression of erythropoietin receptor (EPO-R), phosphorylated-Akt (p-Akt), phosphorylated glycogen synthase kinase 3beta (p-GSK-3beta), phosphorylated extracellular signal-regulated protein kinase (p-ERK), phosphorylated signal transducer and activator of transcription 3 (p-Stat3), vascular endothelial growth factor (VEGF), and matrix metalloproteinase-1 (MMP-1) were significantly increased in the myocardium of the EPO-DDS group. CONCLUSION Post-MI treatment with an EPO-DDS improves LV remodelling and function by activating prosurvival signalling, antifibrosis, and angiogenesis without causing any side effect.

Antidiabetic drug pioglitazone protects the heart via activation of PPAR-γ receptors, PI3-kinase, Akt, and eNOS pathway in a rabbit model of myocardial infarction

The insulin-sensitizing drug pioglitazone has been reported to be protective against myocardial infarction. However, its precise mechanism is unclear. Rabbits underwent 30 min of coronary occlusion followed by 48 h of reperfusion. Rabbits were assigned randomly to nine groups (n = 10 in each): the control group (fed a normal diet), pioglitazone group (fed diets containing 1 mg.kg(-1).day(-1) pioglitazone), pioglitazone + 5-hydroxydecanoic acid (HD) group [fed the pioglitazone diet + 5 mg/kg iv 5-HD, a mitochondrial ATP-sensitive K(+) (K(ATP)) channel blocker], pioglitazone + GW9662 group [fed the pioglitazone diet + 2 mg/kg iv GW9662, a peroxisome proliferator activated receptor (PPAR)-gamma antagonist], GW9662 group (fed a normal diet + iv GW9662), pioglitazone + wortmannin group [fed the pioglitazone diet + 0.6 mg/kg iv wortmannin, a phosphatidylinositol (PI)3-kinase inhibitor], wortmannin group (fed a normal diet + iv wortmannin), pioglitazone + nitro-l-arginine methyl ester (l-NAME) group [fed the pioglitazone diet + 10 mg/kg iv l-NAME, a nitric oxide synthase (NOS) inhibitor], and l-NAME group (fed a normal diet + iv l-NAME). All groups were fed the diets for 7 days. The risk area and nonrisk area of the left ventricle (LV) were separated by Evans blue dye, and the infarct area was determined by triphenyltetrazolium chloride staining. The infarct size was calculated as a percentage of the LV risk area. Western blotting was performed to assess levels of Akt and phospho-Akt and phospho-endothelial NOS (eNOS) in the myocardium following reperfusion. The infarct size was significantly smaller in the pioglitazone group (21 +/- 2%) than in the control group (43 +/- 3%). This effect was abolished by GW9662 (42 +/- 3%), wortmannin (40 +/- 3%), or l-NAME (42 +/- 7%) but not by 5-HD (24 +/- 5%). Western blotting showed higher levels of phospho-Akt and phospho-eNOS in the pioglitazone group. Pioglitazone reduces the myocardial infarct size via activation of PPAR-gamma, PI3-kinase, Akt, and eNOS pathways, but not via opening the mitochondrial K(ATP) channel. Pioglitazone may be a novel strategy for the treatment of diabetes mellitus with coronary artery disease.

Postinfarct treatment with oxytocin improves cardiac function and remodeling via activating cell-survival signals and angiogenesis.

Background: We investigated whether postinfarct treatment with oxytocin (OT) improves left ventricular (LV) function and remodeling via cardiac repair of myocardial ischemia-reperfusion injury. Methods and Results: Experiments were performed with 30 minutes of coronary occlusion and 2 or 14 days of reperfusion rabbit model of myocardial infarction. LV function and remodeling were significantly improved in the OT group. The infarct size was significantly reduced in the OT group. The number of CD31-positive microvessels was increased significantly in the OT group. There were no Ki67-positive myocytes in either group. The expression of the OT receptor, phosphorylated (p)-Akt protein kinase, p-extracellular signal-regulated protein kinase, p-enodthelial NO synthase, p-signal transducer and activator of transcription 3, vascular endothelial growth factor, B-cell lymphoma 2, and matrix metalloproteinase-1 (MMP-1) were markedly increased in the OT group days 2 and 14 post myocardial infarction. Conclusions: Postinfarct treatment with OT reduces myocardial infarct size and improves LV function and remodeling by activating OT receptors and prosurvival signals and by exerting antifibrotic and angiogenic effects through activation of MMP-1, endothelial NO synthase, and vascular endothelial growth factor. These findings provide new insight into therapeutic strategies for ischemic heart disease.

Postconditioning effect of granulocyte colony-stimulating factor is mediated through activation of risk pathway and opening of the mitochondrial KATP channels.

Granulocyte colony-stimulating factor (G-CSF) has been reported to improve cardiac function after myocardial infarction. However, whether postinfarct acute effect of G-CSF is mediated through the same signaling pathways as those of ischemic postconditioning is still unclear. We examined the postinfarct acute effect of G-CSF on myocardial infarct size and its precise molecular mechanism. Japanese white rabbits underwent 30 min of ischemia and 48 h of reperfusion. Rabbits were intravenously injected 10 μg/kg of G-CSF (G-CSF group) or saline (control group) immediately after reperfusion. The wortmannin + G-CSF, PD-98059 + G-CSF, N(ω)-nitro-L-arginine methyl ester (l-NAME) + G-CSF, and 5-hydroxydecanoic acid sodium salt (5-HD) + G-CSF groups were respectively injected with wortmannin (0.6 mg/kg), PD-98059 (0.3 mg/kg), L-NAME (10 mg/kg), and 5-HD (5 mg/kg) 5 min before G-CSF administration. Myocardial infarct size was calculated as a percentage of the risk area of the left ventricle. Western blot analysis was performed to examine the signals such as protein kinase B (Akt), extracellular signal-regulated protein kinase (ERK), eNOS, p70S6 kinase (p70S6K), and glycogen synthase kinase-3β (GSK3β) in the ischemic myocardium after 48 h of reperfusion. The infarct size was significantly smaller in the G-CSF group (26.7 ± 2.7%) than in the control group (42.3 ± 4.6%). The infarct size-reducing effect of G-CSF was completely blocked by wortmannin (44.7 ± 4.8%), PD-98059 (38.3 ± 3.9%), L-NAME (42.1 ± 4.2%), and 5-HD (42.5 ± 1.7%). Wortmannin, PD-98059, L-NAME, or 5-HD alone did not affect the infarct size. Western blotting showed higher myocardial expression of phospho-Akt, phospho-ERK, phosho-eNOS, phosho-p70S6K, and phosho-GSK3β at 10 min and 48 h after reperfusion in the G-CSF group than in the control group. In conclusion, postreperfusion G-CSF administration reduces myocardial infarct size via activation of phosphatidylinositol 3-kinase-Akt and ERK prosurvival signaling pathways and their downstream targets eNOS, p70S6 kinase, GSK3β, and mitochondrial ATP-dependent K(+) channel.

Edaravone reduces myocardial infarct size and improves cardiac function and remodelling in rabbits

1 In the present study, we investigated the effect of 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one (edaravone), a free radical scavenger, on myocardial infarct (MI) size and cardiac function in an in vivo model of MI in rabbits. We further investigated the contribution of hydroxyl radicals, superoxide and nitric oxide (NO) to its effects. 2 Anaesthetized open‐chest Japanese white male rabbits were subjected to 30 min coronary occlusion and 48 h reperfusion. The control group (n = 10) was injected with saline 10 min before reperfusion. The edaravone group (n = 10) was injected with a bolus of 3 mg/kg edaravone 10 min before reperfusion. The edaravone + NG‐nitro‐l‐arginine methyl ester (l‐NAME) group (n = 5) was given 10 mg/kg, i.v., l‐NAME 10 min before the administration of 3 mg/kg edaravone. The l‐NAME group (n = 5) was given 10 mg/kg, i.v., l‐NAME 20 min before reperfusion. Infarct size was measured using the triphenyl tetrazolium chloride method and is expressed as a percentage of area at risk. Cardiac function was assessed by echocardiography 14 days after infarction. 3 In another series of experiments, rabbits were subjected to 30 min coronary occlusion and 30 min reperfusion and myocardial interstitial 2,3‐dihydroxybenzoic acid (DHBA) and 2,5‐DHBA levels, indicators of hydroxyl radical, were measured using a microdialysis technique. 4 Infarct size in the edaravone group was significantly reduced compared with that in the control group (27.4 ± 6.8 vs 43.4 ± 6.8%, respectively; P < 0.05). The edaravone‐induced reduction of infarct size was abolished by pretreatment with l‐NAME. Myocardial interstitial levels of 2,3‐DHBA and 2,5‐DHBA increased 20 and 30 min after ischaemia and peaked at 10 min reperfusion in the control group. Edaravone significantly inhibited the increase in 2,3‐DHBA and 2,5‐DHBA levels seen during reperfusion. Dihydroethidium staining showing in situ detectoion of superoxide was less intense in ischaemic myocardium in the edaravone‐treated group compared with the control group. Edaravone improved cardiac function and left ventricular remodelling 14 days after infarction. 5 In conclusion, edaravone significantly reduces MI size and improves cardiac function and LV remodelling by decreasing hydroxyl radicals and superoxide in the myocardium and increasing the production of NO during reperfusion in rabbits.

Both stimulation of GLP‐1 receptors and inhibition of glycogenolysis additively contribute to a protective effect of oral miglitol against ischaemia‐reperfusion injury in rabbits

BACKGROUND AND PURPOSE We previously reported that pre‐ischaemic i.v. miglitol reduces myocardial infarct size through the inhibition of glycogenolysis during ischaemia. Oral administration of miglitol has been reported to produce glucagon‐like peptide 1 (GLP‐1). We hypothesized that p.o. administration of miglitol, an absorbable antidiabetic drug, reduces myocardial infarct size by stimulating GLP‐1 receptors and inhibiting glycogenolysis in the myocardium.

Antidiabetic drug voglibose is protective against ischemia-reperfusion injury through glucagon-like peptide 1 receptors and the phosphoinositide 3-kinase-Akt-endothelial nitric oxide synthase pathway in rabbits.

Glucagon-like peptide 1 (GLP-1) reportedly exerts a protective effect against cardiac ischemia. We hypothesized that the α-glucosidase inhibitor voglibose, an unabsorbable antidiabetic drug with cardioprotective effects, may act through stimulation of GLP-1 receptors. The results of the present study suggest oral administration of voglibose reduces myocardial infarct size and mitigates cardiac dysfunction in rabbits after 30 minutes of coronary occlusion and 48 hours of reperfusion. Voglibose increased basal and postprandial plasma GLP-1 levels and reduced postprandial plasma glucose levels. The infarct size-reducing effect of voglibose was abolished by treatment with exendin(9-39), wortmannin, Nω-nitro-l-arginine methylester, or 5-hydroxydecanoate), which inhibit GLP-1 receptors, phosphoinositide 3-kinase, nitric oxide synthase, and KATP channels, respectively. Western blot analysis showed that treatment with voglibose upregulated myocardial levels of phospho-Akt, phospho-endothelial nitric oxide synthase after myocardial infarction. The upregulation of phospho-Akt was inhibited by exendin(9-39) and wortmannin. These findings suggest that voglibose reduces myocardial infarct size through stimulation of GLP-1 receptors, activation of the phosphoinositide 3-kinase-Akt-endothelial nitric oxide synthase pathways, and the opening of mitochondrial KATP channels. These findings may provide new insight into therapeutic strategies for the treatment of patients with coronary artery disease.

Evaluation of Left Atrial Degeneration for the Prediction of Atrial Fibrillation Usefulness of Integrated Backscatter Transesophageal Echocardiography

OBJECTIVES The purpose of this study was to elucidate the usefulness of integrated backscatter (IBS) transesophageal echocardiography (TEE) for the evaluation of atrial degeneration and clarify whether atrial degeneration predicts the occurrence of atrial fibrillation (AF). BACKGROUND One of the causes of AF is pathological degeneration of the left atrium (LA). However, there is no appropriate method to evaluate degeneration of the LA in the clinical setting. METHODS The IBS images were acquired with TEE with a 4- to 7-MHz transducer. The IBS values were calculated as the average power of the backscattered signal from regions of interest (ROI). In the pathological study, we measured IBS values of 21 left atrial specimens obtained from 10 autopsied hearts. Relative interstitial area in the ROI was automatically calculated by a personal computer. In the clinical study, we measured IBS values of the entire LA wall at 5-mm intervals (except the posterior wall) in 42 patients (18 non-AF patients, 14 paroxysmal AF patients, and 10 chronic AF patients). Each IBS value was color-coded to construct 3-dimensional maps. RESULTS There was a weak correlation between the relative interstitial area and IBS values (r = 0.45, p = 0.038). Average corrected IBS values of total voxels in color-coded maps in the AF group (24.4 +/- 6.4 dB) and the paroxysmal AF group (23.9 +/- 9.6 dB) were significantly greater than those in the non-AF group (15.6 +/- 7.4 dB, p = 0.007), whereas there was no significant difference in LA diameter between the paroxysmal AF group (39.4 +/- 6.5 mm) and the non-AF group (36.7 +/- 5.5 mm). CONCLUSIONS With IBS-TEE, we can identify an increase in atrial degeneration that might predict the occurrence of AF before LA dilation.

Transcatheter embolization by autologous blood clot is useful management for small side branch perforation due to percutaneous coronary intervention guide wire

A 75-year-old man underwent PCI for a bifurcation lesion with 90% stenosis in segment 6 and 75% proximal stenosis in segment 9 of the left coronary artery. We implanted a Duraflex coronary stent into segment 6 and kissing balloon inflation for segments 6 and 9. Although these 2 lesions were adequately dilated, we noticed coronary perforation caused by the guide wire in a small branch of segment 9. We tried to repair the perforation using a small balloon and long inflation, but unfortunately the perforation was not improved. We attempted to occlude the small branch including the perforation site with an autologous blood clot via a wire microcatheter inserted into the small branch. The autologous blood clot was suspended in contrast media and saline. Using this procedure, the small branch of segment 9 was occluded completely and the perforated site was repaired. After the procedure, no significant CPK elevation was detected, and 6 months later, we confirmed that small branch embolization was improved and coronary flow was good. Autologous blood clot is useful to occlude and repair perforations in small side branches of the coronary artery without myocardial damage.

Simvastatin reduces myocardial infarct size via increased nitric oxide production in normocholesterolemic rabbits

OBJECTIVE Statins have been reported to be protective against myocardial infarction (MI). Moreover, statin drugs upregulate nitric oxide (NO) in coronary artery independent of lipid-lowering effects. However their precise mechanism for MI-protection is unclear. We investigated the effect of lipophilic statin administration in a normocholesterolemic rabbit MI model. METHODS Nω-nitro-L-arginine methylester (L-NAME, 10 mg/kg) or vehicle alone was intravenously administered 20 min before inducing ischemia, followed by intravenous administration of simvastatin (5 mg/kg) or saline 10 min before ischemia. Rabbits then underwent 30 min of coronary occlusion followed by 48 h of reperfusion. The at-risk and infarct areas were calculated as a percentage of the total left ventricular slice area. RESULTS Determination of infarct size revealed that pre-ischemic treatment with simvastatin reduced infarct size (30.5 ± 4%) in comparison to controls (45.0 ± 3%) (P < 0.05). This infarct size-reducing effect of simvastatin could be completely abrogated by pretreatment with L-NAME (42.0 ± 4%). CONCLUSIONS Pre-ischemic treatment with simvastatin reduces MI size via NO production. Simvastatin could be a useful drug for coronary artery disease patients without dyslipidemia as it has direct protective effects.