Relationship among coronary plaque compliance, coronary risk factors and tissue characteristics evaluated by integrated backscatter intravascular ultrasound

BACKGROUND

The purpose of the present study was to evaluate the mechanical properties of coronary plaques and plaque behavior, and to elucidate the relationship among tissue characteristics of coronary plaques, mechanical properties and coronary risk factors using integrated backscatter intravascular ultrasound (IB-IVUS).

METHODS

Non-targeted plaques with moderate stenosis (plaque burden at the minimal lumen site: 50-70%) located proximal to the site of the percutaneous coronary intervention target lesions were evaluated by IB-IVUS. Thirty-six plaques (less calcified group: an arc of calcification ≤10°) in 36 patients and 22 plaques (moderately calcified group: 10° < an arc of calcification ≤60°) in 22 patients were evaluated. External elastic membrane volume (EEMV) compliance, lumen volume (LV) compliance, plaque volume (PV) response (difference between PV in systole and diastole), EEM area stiffness index were measured at the minimal lumen site. Relative lipid volume (lipid volume/internal elastic membrane volume) was calculated by IB-IVUS.

RESULTS

In the less calcified group, there was a significant correlation between EEMV compliance and the relative lipid volume (r = 0.456, p = 0.005). There was a significant inverse correlation between EEM area stiffness index and the relative lipid volume (p = 0.032, r = -0.358). The LV compliance and EEM area stiffness index were significantly different in the diabetes mellitus (DM) group than in the non-DM group (1.32 ± 1.49 vs. 2.47 ± 1.79%/10 mmHg, p =0.014 and 28.3 ± 26.0 vs. 15.7 ± 17.2, p =0.020). The EEMV compliance and EEM area stiffness index were significantly different in the hypertension (HTN) group than in the non-HTN group (0.77 ± 0.68 vs. 1.57 ± 0.95%/10 mmHg, p =0.012 and 26.5 ± 24.3 vs. 13.0 ± 16.7, p =0.020). These relationships were not seen in the moderately calcified group.

CONCLUSION

The present study provided new findings that there was a significant correlation between mechanical properties and tissue characteristics of coronary arteries. In addition, our results suggested that the EEMV compliance and the LV compliance were independent and the compliance was significantly impaired in the patients with DM and/or HTN. Assessment of coronary mechanical properties during PCI may provide us with useful information regarding the risk stratification of patients with coronary heart disease.

Tetomilast attenuates elastase-induced pulmonary emphysema through inhibition of oxidative stress in rabbits

Tetomilast was originally identified as a potent inhibitor of superoxide production in human neutrophils, and is of interest because it may relieve oxidative stress related to chronic obstructive pulmonary disease (COPD). Our objective was to determine whether tetomilast effectively protects against the development of porcine pancreatic elastase (PPE)-induced emphysema in rabbits. Rabbits were divided into three groups (sham n=19, PPE n=19, PPE/Tetomilast n=18). The rabbits were once daily orally administered vehicle solution or tetomilast 5 d/week for 4 weeks before the PPE instillation. We compared pulmonary function, inflammatory cell infiltration, oxidative stress, and the incidences of apoptosis among the three groups. Tetomilast suppressed PPE-induced increases in the incidence of apoptosis and the production of 8-hydroxy-deoxyguanosine (8-OHdG) in lung tissues. PPE-instilled rabbits treated with tetomilast showed significantly less mean linear intercept and significantly better pulmonary function than rabbits administered PPE alone. Tetomilast may inhibit the development of emphysema by attenuating pulmonary inflammation and apoptosis caused by PPE-induced oxidative stress.

Left atrial pathological degeneration assessed by integrated backscatter transesophageal echocardiography as a predictor of progression to persistent atrial fibrillation: results from a prospective study of three-years follow-up

Background

It is recognized that one of the causes of atrial fibrillation (AF) is pathological degeneration of the left atrium (LA). However, prospective study that elucidated the relationship between the incidence of persistent AF and pathological degeneration has not been performed. The purpose of this study was to elucidate the usefulness of integrated backscatter (IBS) values for the prediction of progression from paroxysmal AF (PAF) to persistent AF.

Methods

We measured IBS values of the entire LA wall at 5 mm intervals (except the posterior wall) in 27 patients with paroxysmal AF and evaluated progression to persistent AF for three years. IBS values were acquired with transesophageal echocardiography (TEE) using a 4–7 MHz transducer. IBS values were calculated as the average power of the backscattered signal from regions of interest (ROI). Each IBS value was color-coded to construct three dimensional maps.

Results

Average IBS values of total voxels in color-coded maps in the persistent AF group were significantly greater than those in the non-persistent AF group (25.8 ± 5.0 dB vs. 17.4 ± 10.2 dB, p = 0.047), whereas there was no significant difference in LA diameter between the persistent AF and the non-persistent AF group. There was significant difference in persistent AF-free survival after the baseline measurements in the subjects stratified by IBS value (<20 dB versus ≥20 dB) (univariate Cox regression analysis: hazard ratio: 8.74, p =0.046).

Conclusion

Using IBS values measured by TEE, we can identify an increase in atrial degeneration that may predict the occurrence of persistent AF before LA dilation.

Treatment with Lindera strychnifolia Reduces Blood Pressure by Decreasing Sympathetic Nerve Activity in Spontaneously Hypertensive Rats

Lindera strychnifolia (Tendai-Uyaku), a medicinal plant, has long been used for the treatment of cardiac, renal and rheumatic diseases in Japan. We investigated the effect of Lindera strychnifolia on systolic blood pressure, cardiac function, and plasma noradrenaline levels in rats. Spontaneously hypertensive rats (SHR) were given free access to water or extract solution of Lindera strychnifolia, which was extracted with a ratio of 10 g Lindera strychnifolia roots/20 ml water. Systolic blood pressure was measured by using a tail-cuf sphygmomanometer twice a week from 10 to 30 weeks of age, and compared to the age-matched Wistar Kyoto rats (WKY) as a control group. At 30 weeks of age, heart function was measured by echocardiography and blood samples were taken for detection of plasma noradrenaline levels, and rats were then sacrificed. Systolic blood pressure gradually increased from 10 to 30 weeks of age in the SHR group, while it did not change in the WKY group. In the Lindera-treated SHR group, the increase in systolic blood pressure was significantly attenuated from 21 to 30 weeks of age. Echocardiography showed a significant increase in ejection fraction in the Lindera-treated SHR group (60.4 ± 7.8%) as compared to the SHR group (39.7 ± 23.4%). Plasma noradrenaline levels were significantly decreased in Lindera-treated SHR group compared to the SHR group. These results suggest that Lindera strychnifolia has an anti-hypertensive effect and improves cardiac function in spontaneous hypertensive rats. These effects may be related to the decrease in plasma noradrenaline levels by Lindera strychnifolia.

Extracts from the Roots of Lindera strychifolia Induces Apoptosis in Lung Cancer Cells and Prolongs Survival of Tumor-bearing Mice

Lindera strychifolia, a scandent shrub Lauraceous medicinal plant, has been used in Chinese traditional medicine as a palliative and an anti-spasmodic. It also shows cytotoxic effects against several tumor cell lines and inhibits marcromolecule biosynthesis. This study investigated the anti-tumor effects of L. strychifolia extract against lung cancer cells using in vitro and in vivo models. Two human lung cancer cell lines A549 (adenocarcinoma) and SBC-3 (small cell carcinoma), and a non-tumor cell line 3T3-L1 (mice fibroblasts) were subjected to L. strychifolia extract treatment. On lung cancer cells, L. strychifolia induced cell growth inhibition in a dose-dependent manner. Conversely, the extract did not show any significant cytotoxic effect on 3T3-L1 cells. Therefore, the extract is specific for tumor cells. Tumor cells treated with L. strychifolia extract showed typical morphological appearance of apoptosis including nuclei fragmentation and cell condensation. The in vivo effects of L. strychifolia extract were investigated in C57BL/6 mice transplanted with Lewis lung cancer (LL-2) cells, and in BALB/c nude mice transplanted with A549 or SBC-3 human lung cancer cells. Oral administration of L. strychifolia extract prolonged survival time and inhibited tumor growth in a dose-dependent manner by inducing apoptosis in the LL-2 cell mice model. Furthermore, in A549 or SBC-3 cell nude mice models, oral administration of L. strychifolia extract also significantly inhibited tumor growth at the 5.0 mg/ml concentration. These findings suggested that the components of L. strychifolia have anticancer activity and may contribute to clinical applications in the prevention and treatment of lung cancer.

Lindera strychnifolia is Protective Against Post-ischemic Myocardial Dysfunction Through Scavenging Hydroxyl Radicals and Opening the Mitochondrial KATP Channels in Isolated Rat Hearts

Lindera strychnifolia (Tendai-Uyaku), a medicinal plant, has long been used for the treatment of cardiac, renal and rheumatic diseases in Japan. We aim to clarify (1) whether L. strychnifolia is protective against post-ischemic myocardial dysfunction, and (2) whether its effect is related to scavenging hydroxyl radicals and opening the mitochondrial K ATP channels in isolated rat hearts. Male Sprague-Dawley rats were orally given 1 ml/day of L. strychnifolia, which was extracted from 0.75 and 1.5 g/kg of roots of L. strychnifolia for 4 days. The rat hearts were excised and perfused on a Langendorff apparatus with Krebs-Henseleit solution with a gas mixture of 95% O 2 and 5% CO 2. The hearts were paced at 320 beats/min except during ischemia. Left ventricular developed pressure (LVDP, mmHg), ± dP/dt (mmHg/sec) and coronary flow (ml/min) were continuously monitored. All hearts were perfused for a total of 120 minutes consisting of a 30-minute pre-ischemic period followed by 30 minutes of global ischemia and 60 minutes of reperfusion with or without 5-HD, a mitochondrial K ATP channel blocker. The levels of lactate, LDH and 2,5-DHBA, an indicator of hydroxyl radicals, in the perfusate during reperfusion period were also measured. Treatment with L. strychnifolia significantly improved LVDP and ± dP/dt without altering coronary flow during reperfusion. The 100 μM of 5-HD in Krebs-Henseleit solution was perfused during the 10 minutes of pre-ischemic periods. Pretreatment with 5-HD abolished the improvement of LVDP and ± dP/dt by L. strychnifolia. L. strychnifolia significantly attenuated the levels of lactate, LDH and 2,5-DHBA during reperfusion, and which were restored by pretreatment with 5-HD. In conclusion, L. strychnifolia is protective against post-ischemic left ventricular dysfunction through scavenging hydroxyl radicals and opening the K ATP channels in the isolated rat heart.

Guidelines for the use and interpretation of assays for monitoring autophagy

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.

Asialoerythropoietin, a nonerythropoietic derivative of erythropoietin, displays broad anti-heart failure activity

BACKGROUND

We investigated the effects of asialoerythropoietin (asialoEPO), a nonerythrogenic erythropoietin derivative, on 3 murine models of heart failure with different etiologies.

METHODS AND RESULTS

Doxorubicin (15 mg/kg) induced heart failure within 2 weeks (toxic cardiomyopathy). Treatment with asialoEPO (6.9 μg/kg) for 2 weeks thereafter attenuated the associated left ventricular dysfunction and dilatation. In addition, the asialoEPO-treated heart showed less myocardial fibrosis, inflammation, and oxidative damage, and diminished atrophic cardiomyocyte degeneration, which was accompanied by restored expression of GATA-4 and sarcomeric proteins. Mice with large 6-week-old myocardial infarctions exhibited marked left ventricular dysfunction with adverse remodeling (ischemic cardiomyopathy). AsialoEPO treatment for 4 weeks significantly mitigated progression of the dysfunction and remodeling and reduced myocardial fibrosis, inflammation, and oxidative damage. Finally, 25-week-old δ-sarcoglycan-deficient mice (genetic cardiomyopathy) were treated with asialoEPO for 5 weeks. AsialoEPO mitigated the progressive cardiac remodeling and dysfunction through cardiomyocyte hypertrophy, and upregulated expression of GATA-4 and sarcomeric proteins. AsialoEPO appears to act by altering the activity of the downstream erythropoietin receptor signals extracellular signal-regulated protein kinase, Akt, signal transducer, and activator of transcription 3 and 5 in a model-specific manner.

CONCLUSIONS

The findings suggest that asialoEPO exerts broad cardioprotective effects through distinct mechanisms depending on the model, which are independent of the erythrogenic action. This compound may be promising for the treatment of heart failure of various etiologies.

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.

EXPERIMENTAL APPROACH

The effects of p.o. and i.v. administration of miglitol on myocardial infarct size were compared in a rabbit model of ischaemia induced by 30 min of coronary occlusion and 48 h of reperfusion. The levels of phospho(p)-PI3kinase and p-Akt were measured in cardiac tissue by use of Western blot analysis.

RESULTS

Both p.o. and i.v. administration of miglitol reduced the infarct size, and this effect was greater after p.o. than after i.v. administration under similar plasma miglitol concentrations. The reduction in infarct size induced by p.o. miglitol but not that induced by i.v. miglitol was partially inhibited by treatment with exendin(9-39), a GLP-1 receptor blocker. Both p.o. and i.v. miglitol improved ejection fraction and ±dP/dt after myocardial infarction. Miglitol administered p.o. but not i.v. up-regulated the myocardial expression of phospho(p)-PI3kinase and p-Akt following myocardial infarction; an effect that was inhibited by exendin(9-39).

CONCLUSIONS AND IMPLICATIONS

Administration of miglitol p.o. reduces myocardial infarct size through stimulation of GLP-1 receptors and activation of PI3kinase-Akt pathway in addition to the inhibition of glycogenolysis. These findings may have clinical implications for the p.o. administration of miglitol for the treatment of patients with diabetes mellitus combined with coronary artery disease.

Cilostazol protects the heart against ischaemia reperfusion injury in a rabbit model of myocardial infarction: focus on adenosine, nitric oxide and mitochondrial ATP-sensitive potassium channels

1. The present study examined whether or not cilostazol reduces the myocardial infarct size, and investigated its mechanism in a rabbit model of myocardial infarction. 2. Japanese white rabbits underwent 30 min of coronary occlusion, followed by 48 h of reperfusion. Cilostazol (1 and 5 mg/kg) or vehicle was given intravenously 5 min before ischaemia. 8-p-sulfophenyl theophylline (8SPT; an adenosine receptor blocker, 7.5 mg/kg), Nω-nitro-L-arginine methylester (l-NAME; an NOS inhibitor, 10 mg/kg) or 5-hydroxydecanoic acid sodium salt (5-HD; a mitochondrial ATP-sensitive potassium (KATP) channel blocker, 5 mg/kg) was given intravenously 5 min before cilostazol injection. Infarct size was determined as a percentage of the risk area. 3. The myocardial interstitial levels of adenosine and nitrogen oxide (NOx) during ischaemia and reperfusion, and the intensity of myocardial dihydroethidium staining were determined. 4. Infarct size was significantly reduced in the cilostazol 1 mg/kg (38.4% (2.9%)) and cilostazol 5 mg/kg (30.7% (4.7%)) groups compared with that in the control group (46.5% (4.2%)). The infarct size-reducing effect of cilostazol was completely abolished by 8SPT (46.6% (3.5%)), L-NAME (49.0% (5.5%)), or 5HD (48.5% (5.1%)). 8SPT, L-NAME or 5HD alone did not affect the infarct size. Cilostazol treatment significantly increased myocardial levels of adenosine and NOx during ischaemia, and attenuated the intensity of dihydroethidium staining during reperfusion. 5. These findings show that cilostazol reduces the myocardial infarct size by increasing adenosine and NOx levels, attenuating superoxide production and opening the mitochondrial KATP channels. Cilostazol might provide a new strategy for the treatment of coronary heart disease.

Left atrial global and regional function in patients with paroxysmal atrial fibrillation has already been impaired before enlargement of left atrium: velocity vector imaging echocardiography study

AIMS

Left atrial volume (LAV) has been proposed as a predictor of atrial fibrillation (AF) and LA function has been investigated by velocity vector imaging (VVI) echocardiography. The aim of this study was to determine whether LA function was associated with the existence of AF.

METHODS AND RESULTS

We examined emptying function (EF) as a global function and strain rate (SR) as a regional function of LA function during three phases of the cardiac cycle (reservoir, conduit, and booster pump phase). The parameters were measured (apical four-chamber view) by VVI in 302 subjects [126 sinus rhythm, 91 paroxysmal AF (PAF), and 85 chronic AF]. Global and regional LA function were significantly lower in PAF patients during sinus rhythm (LA total EF: 35 ± 8%; SR at atrial contraction: -0.8 ± 0.3s(-1)) and much lower in chronic AF patients (LA total EF 22 ± 8%) than in subjects with sinus rhythm (LA total EF: 47 ± 7%; SR at atrial contraction: -1.4 ± 0.4s(-1)). In multivariate logistic regression analysis, LA active EF and SR at atrial contraction were independent features of PAF.

CONCLUSION

LA function, particularly LA active relaxation and contraction, was lower in PAF patients than in subjects with sinus rhythm, regardless of LA size and age. LA functional impairment was observed regardless of hypertension before LA enlargement in patients with PAF. Reduced LA function, as assessed by VVI, is an important feature of AF as well as LA structure.

Abstract P307: A Novel Protective Effect of the Antidiabetic Drug Voglibose via GLP-1 Receptor in the Infarcted Heart

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 via 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 following 30 min of coronary occlusion and 48 h 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, L-NAME or 5-HD, which inhibit GLP-1 receptors, PI3K, NOS and K ATP channels, respectively. Western blot analysis showed that treatment with voglibose upregulated myocardial expression of phospho-Akt, phospho-eNOS, phospho-ERK and HSP27 following myocardial infarction. The upregulation of phospho-Akt was inhibited by exendin(9–39) and wortmannin, while the upregulation of phospho-ERK and HSP27 was inhibited by wortmannin but not by exendin(9–39). These findings suggest that voglibose reduces myocardial infarct size through stimulation of GLP-1 receptors, activation of PI3K-Akt-eNOS and ERK pathways, and the opening of mitochondrial K ATP channels. These findings may provide new insight into therapeutic strategies for the treatment of diabetic patients with coronary artery disease.

Left atrial function assessed by speckle tracking echocardiography as a predictor of new-onset non-valvular atrial fibrillation: results from a prospective study in 580 adults

AIMS

The aim of this prospective study was to evaluate left atrial (LA) function for the prediction of increased risk of new-onset non-valvular atrial fibrillation (AF). Risk stratification for new-onset AF based on LA remodelling may have a major public health impact. Although left atrial volume (LAV) or LA dimension have been proposed as predictors of AF, other predictive parameters of LA function have not yet been fully examined.

METHODS AND RESULTS

LA emptying function (EF), strain rate (SR), and LAV were evaluated in the apical four-chamber view by speckle tracking echocardiography in 580 consecutive adults (age 64 ± 17, 303 men) without a history of atrial arrhythmias. During a follow-up period of 28 months, 32 subjects (age 73 ± 9, 18 men) developed electrocardiographically confirmed AF. Subjects with new-onset AF had lower LA active EF (16 ± 5 vs. 28 ± 8%, P< 0.001) and lower LA SR at atrial contraction (-0.9 ± 0.2 vs. -1.4 ± 0.5 S(-1), P< 0.001), but larger maximum LAV index (59 ± 12 vs. 46 ± 16 mL/m(2), P< 0.001) compared with non-AF subjects at baseline. In multivariate logistic regression analysis, LA active EF was the only independent predictor of new-onset AF. Using an LA active EF cut-off of ≤20%, the sensitivity and specificity for new-onset AF based on receiver operator characteristic curve analysis were 88 and 81%, respectively (area under the curve: 0.92).

CONCLUSION

Reduced LA active EF (booster pump function) assessed by speckle tracking echocardiography independently predicts the risk of new-onset AF, suggesting a stronger association between LA functional remodelling and AF than between LA size and AF.

Constitutive SIRT1 overexpression impairs mitochondria and reduces cardiac function in mice

Heart failure is associated with a change in cardiac energy metabolism. SIRT1 is a NAD(+)-dependent protein deacetylase, and important in the regulation of cellular energy metabolism. To examine the role of SIRT1 in cardiac energy metabolism, we created transgenic mice overexpressing SIRT1 in a cardiac-specific manner, and investigated cardiac functional reserve, energy reserve, substrate uptake, and markers of mitochondrial function. High overexpression of SIRT1 caused dilated cardiomyopathy. Moderate overexpression of SIRT1 impaired cardiac diastolic function, but did not cause heart failure. Fatty acid uptake was decreased and the number of degenerated mitochondria was increased dependent on SIRT1 gene dosage. Markers of reactive oxygen species were decreased. Changes in morphology and reactive oxygen species were associated with the reduced expression of genes related to mitochondrial function and autophagy. In addition, the respiration of isolated mitochondria was decreased. Cardiac function was normal in transgenic mice expressing a low level of SIRT1 at baseline, but the mice developed cardiac dysfunction upon pressure overload. In summary, the constitutive overexpression of SIRT1 reduced cardiac function associated with impaired mitochondria in mice.

Autophagy limits acute myocardial infarction induced by permanent coronary artery occlusion

Ischemia is known to potently stimulate autophagy in the heart, which may contribute to cardiomyocyte survival. In vitro, transfection with small interfering RNAs targeting Atg5 or Lamp-2 (an autophagy-related gene necessary, respectively, for the initiation and digestion step of autophagy), which specifically inhibited autophagy, diminished survival among cultured cardiomyocytes subjected to anoxia and significantly reduced their ATP content, confirming an autophagy-mediated protective effect against anoxia. We next examined the dynamics of cardiomyocyte autophagy and the effects of manipulating autophagy during acute myocardial infarction in vivo. Myocardial infarction was induced by permanent ligation of the left coronary artery in green fluorescent protein-microtubule-associated protein 1 light chain 3 (GFP-LC3) transgenic mice in which GFP-LC3 aggregates to be visible in the cytoplasm when autophagy is activated. Autophagy was rapidly (within 30 min after coronary ligation) activated in cardiomyocytes, and autophagic activity was particularly strong in salvaged cardiomyocytes bordering the infarcted area. Treatment with bafilomycin A1, an autophagy inhibitor, significantly increased infarct size (31% expansion) 24 h postinfarction. Interestingly, acute infarct size was significantly reduced (23% reduction) in starved mice showing prominent autophagy before infarction. Treatment with bafilomycin A1 reduced postinfarction myocardial ATP content, whereas starvation increased myocardial levels of amino acids and ATP, and the combined effects of bafilomycin A1 and starvation on acute infarct size offset one another. The present findings suggest that autophagy is an innate and potent process that protects cardiomyocytes from ischemic death during acute myocardial infarction.

The role of autophagy emerging in postinfarction cardiac remodelling

AIMS

Autophagy is activated in cardiomyocytes in ischaemic heart disease, but its dynamics and functional roles remain unclear after myocardial infarction. We observed the dynamics of cardiomyocyte autophagy and examined its role during postinfarction cardiac remodelling.

METHODS AND RESULTS

Myocardial infarction was induced in mice by ligating the left coronary artery. During both the subacute and chronic stages (1 and 3 weeks postinfarction, respectively), autophagy was found to be activated in surviving cardiomyocytes, as demonstrated by the up-regulated expression of microtubule-associated protein-1 light chain 3-II (LC3-II), p62 and cathepsin D, and by electron microscopic findings. Activation of autophagy, specifically the digestion step, was prominent in cardiomyocytes 1 week postinfarction, especially in those bordering the infarct area, while the formation of autophagosomes was prominent 3 weeks postinfarction. Bafilomycin A1 (an autophagy inhibitor) significantly aggravated postinfarction cardiac dysfunction and remodelling. Cardiac hypertrophy was exacerbated in this group and was accompanied by augmented ventricular expression of atrial natriuretic peptide. In these hearts, autophagic findings (i.e. expression of LC3-II and the presence of autophagosomes) were diminished, and activation of AMP-activated protein kinase was enhanced. Treatment with rapamycin (an autophagy enhancer) brought about opposite outcomes, including mitigation of cardiac dysfunction and adverse remodelling. A combined treatment with bafilomycin A1 and rapamycin offset each effect on cardiomyocyte autophagy and cardiac remodelling in the postinfarction heart.

CONCLUSION

These findings suggest that cardiomyocyte autophagy is an innate mechanism that protects against progression of postinfarction cardiac remodelling, implying that augmenting autophagy could be a therapeutic strategy.

Tissue characterization of coronary plaques and assessment of thickness of fibrous cap using integrated backscatter intravascular ultrasound. Comparison with histology and optical coherence tomography

BACKGROUND

The purpose of this study was to develop a new online integrated backscatter intravascular ultrasound (IB-IVUS) system and to validate its ability to measure fibrous cap thickness by comparing IB-IVUS images with those from optical coherence tomography (OCT).

METHODS AND RESULTS

Images were acquired from 125 segments of 26 coronary arteries obtained at autopsy from 11 cadavers. In the training study (n=30), 242 regions-of-interest on color-coded maps were compared with histology. In the validation study, 95 cross-sections were diagnosed by IB-IVUS and histology. In 24 patients with stable angina, 28 arterial cross-sections were imaged by IB-IVUS and OCT in vivo. In the training study, cutoff values of 39 decibels (dB) and 17dB were the optimal predictors of lipid pool/fibrosis and fibrosis/calcification, respectively, with 38-MHz mode; 42dB and 20dB, respectively, with 43-MHz mode. In the validation study, IB classified the fibrous, lipid-rich and fibrocalcific components with an accuracy of 92%, 91% and 95%, respectively. Agreement between the histological and IB-IVUS diagnoses was excellent (Cohen's κ=0.83). There was a correlation between the fibrous cap thickness measured by IB-IVUS and OCT (r=0.74, P<0.001).

CONCLUSIONS

The IB-IVUS system with improved resolution provides high diagnostic accuracy for the analysis of the tissue characteristics of coronary plaques, and enables estimation of the thickness of the fibrous cap in the clinical setting.

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.

Repeated phlebotomy augments angiogenesis to improve blood flow in murine ischemic legs

Anemia may accelerate angiogenesis in ischemic organs through its ability to augment tissue hypoxia-induced generation of several known angiogenic factors and to increase erythropoietin levels, which are also potently angiogenic. We examined the effect of controlled phlebotomy (bloodletting) on blood flow in a mouse ischemic leg model. We ligated the right femoral artery of BALB/c mice. In the phlebotomy group, 200 microl of blood were drawn from the tail vein once a week. After 4 wk, blood flow in the ischemic leg was significantly better in the phlebotomy group (flow ratio of the ischemic to nonischemic leg, 0.87 + or - 0.04) than the control group (0.59 + or - 0.05, P < 0.05), and capillary density was significantly higher. Repeated phlebotomy increased serum erythropoietin levels as well as the expression of hypoxia-inducible transcription factor-1alpha and vascular endothelial growth factor and both the expression and activity of Akt and endothelial nitric oxide synthase (eNOS) in ischemic legs. Treatment with wortmannin or N(omega)-nitro-l-arginine methyl ester significantly attenuated the phlebotomy-induced improvement of blood flow. In addition, fluorescence-activated cell sorting analysis revealed an increase in circulating peripheral endothelial progenitor cells in the phlebotomy group, and treatment with AMD3100, a specific inhibitor of the chemokine receptor CXCR4, blocked the beneficial effect of phlebotomy. These findings suggest that repeated phlebotomy improves blood flow in ischemic legs through an angiogenic action that involves the Akt/eNOS pathway, endothelial progenitor cell mobilization, and their complicated cross talk. An adequately controlled phlebotomy might be one method by which to induce therapeutic angiogenesis.

Sleep apnoea induces cardiac electrical instability assessed by T-wave alternans in patients with congestive heart failure

AIMS

To assess the involvement of sleep apnoea in nocturnal sudden cardiac death (SCD) by evaluating cardiac electrical instability using T-wave alternans (TWA), a risk marker for lethal cardiac arrhythmias, and severity of sleep apnoea in congestive heart failure (CHF) patients.

METHODS AND RESULTS

A total of 40 CHF patients simultaneously underwent overnight simplified respiratory polygraphy and 24 h continuous electrocardiography. Peak TWA during both daytime and nighttime were calculated by the modified moving average method. The patients were divided into two groups; 30 patients with daytime predominant TWA (whose peak TWA was higher during daytime than during nighttime) and 10 with nighttime predominant. Apnoea-hypopnoea index (AHI) was significantly higher in patients with nighttime predominant TWA than in those with daytime predominant (35.9 +/- 8.1 vs. 23.9 +/- 14.4 events/h, P = 0.02), and was an independent predictor of nighttime predominant TWA (odds ratio, 1.08; 95% confidence interval, 1.01-1.16; P = 0.03). Moreover, peak TWA during the night was correlated positively with AHI (P < 0.001), and AHI was an independent determinant of nocturnal TWA value (r(2) = 0.27, P = 0.009).

CONCLUSION

In CHF patients, sleep apnoea induces cardiac electrical instability manifested as TWA, reflecting increased risk of nocturnal SCD. Moreover, some CHF patients with sleep apnoea exhibit nighttime predominant TWA. Therefore, TWA should also be evaluated during the night.

Anti-Fas gene therapy prevents doxorubicin-induced acute cardiotoxicity through mechanisms independent of apoptosis

Activation of Fas signaling is a key mediator of doxorubicin cardiotoxicity, which involves both cardiomyocyte apoptosis and myocardial inflammation. In this study, acute cardiotoxicity was induced in mice by doxorubicin, and some mice simultaneously received an intramuscular injection of adenoviral vector encoding mouse soluble Fas (sFas) gene (Ad.CAG-sFas), an inhibitor of Fas/Fas ligand interaction. Two weeks later, left ventricular dilatation and dysfunction were apparent in the LacZ-treated control group, but both were significantly mitigated in the sFas-treated group. The in situ nick-end labeling-positive rate were similar in the two groups, and although electron microscopy revealed cardiomyocyte degeneration, no apoptotic structural features and no activation of caspases were detected, suggesting an insignificant role of apoptosis in this model. Instead, sFas treatment reversed doxorubicin-induced down-regulation of GATA-4 and attenuated ubiquitination of myosin heavy chain and troponin I to preserve these sarcomeric proteins. In addition, doxorubicin-induced significant leukocyte infiltration, fibrosis, and oxidative damage to the myocardium, all of which were largely reversed by sFas treatment. sFas treatment also suppressed doxorubicin-induced p53 overexpression, phosphorylation of c-Jun N-terminal kinase, c-Jun, and inhibitor of nuclear factor-kappaB, as well as production of cyclooxygenase-2 and monocyte chemoattractant protein-1, and it restored extracellular signal-regulated kinase activation. Therefore, sFas gene therapy prevents the progression of doxorubicin-induced acute cardiotoxicity, with accompanying attenuation of the cardiomyocyte degeneration, inflammation, fibrosis, and oxidative damage caused by Fas signaling.

MicroRNA-15b modulates cellular ATP levels and degenerates mitochondria via Arl2 in neonatal rat cardiac myocytes

MicroRNAs (miRNAs or miRs) are small, non-coding RNAs that modulate mRNA stability and post-transcriptional translation. A growing body of evidence indicates that specific miRNAs can affect the cellular function of cardiomyocytes. In the present study, miRNAs that are highly expressed in the heart were overexpressed in neonatal rat ventricular myocytes, and cellular ATP levels were assessed. As a result, miR-15b, -16, -195, and -424, which have the same seed sequence, the most critical determinant of miRNA targeting, decreased cellular ATP levels. These results suggest that these miRNAs could specifically down-regulate the same target genes and consequently decrease cellular ATP levels. Through a bioinformatics approach, ADP-ribosylation factor-like 2 (Arl2) was identified as a potential target of miR-15b. It has already been shown that Arl2 localizes to adenine nucleotide transporter 1, the exchanger of ADP/ATP in mitochondria. Overexpression of miR-15b, -16, -195, and -424 suppressed the activity of a luciferase reporter construct fused with the 3'-untranslated region of Arl2. In addition, miR-15b overexpression decreased Arl2 mRNA and protein expression levels. The effects of Arl2 siRNA on cellular ATP levels were the same as those of miR-15b, and the expression of Arl2 could restore ATP levels reduced by miR-15b. A loss-of-function study of miR-15b resulted in increased Arl2 protein and cellular ATP levels. Electron microscopic analysis revealed that mitochondria became degenerated in cardiomyocytes that had been transduced with miR-15b and Arl2 siRNA. The present results suggest that miR-15b may decrease mitochondrial integrity by targeting Arl2 in the heart.

Autophagy maintains cardiac function in the starved adult

To examine the functional significance and detailed morphological characteristics of starvation-induced autophagy in the adult heart, we starved green fluorescent protein (GFP)-microtubule-associated protein 1 light chain 3 (LC3) transgenic mice for up to 3 days. Electron microscopy revealed that, after as little as 12 hours of starvation, round and homogenously electron-dense lipid droplet-like vacuoles appeared in cardiomyocytes. These were determined to be lysosomes based on cathepsin D immunopositivity and acid phosphatase activity. The number of these lysosomes increased with starvation time, and typical autolysosomes with intracellular organelles destined for degradation appeared and increased in number at later times during the starvation period. Myocardial expression of the autophagy-related proteins LC3-II, cathepsin D and ubiquitin increased, while myocardial ATP content decreased, as the starvation interval proceeded. Treatment with bafilomycin A(1), an autophagy inhibitor, did not affect cardiac function in normally fed mice, but it significantly depressed cardiac function and caused significant left ventricular dilatation in the mice starved for 3 days. Cardiomyocytes from starved mice treated with bafilomycin A(1) showed marked accumulation of lysosomes, and the myocardial amino acid content, which increased during starvation in normally fed mice, as well as the myocardial ATP content, were severely reduced, which likely contributed to the cardiac dysfunction. The present findings suggest autophagy plays a critical role in the maintenance of cardiac function during starvation in the adult.

Postinfarction gene therapy with adenoviral vector expressing decorin mitigates cardiac remodeling and dysfunction

The small leucine-rich proteoglycan decorin is a natural inhibitor of transforming growth factor-beta (TGF-beta) and exerts antifibrotic effects in heart and to stimulate skeletal muscle regeneration. We investigated decorin's chronic effects on postinfarction cardiac remodeling and dysfunction. Myocardial infarction (MI) was induced in mice by left coronary artery ligation. An adenoviral vector encoding human decorin (Ad. CAG-decorin) was then injected into the hindlimbs on day 3 post-MI (control, Ad.CAG-LacZ). Four weeks post-MI, the decorin-treated mice showed significant mitigation of the left ventricular dilatation and dysfunction seen in control mice. Although infarct size did not differ between the two groups, the infarcted wall thickness was greater and the segmental length of the infarct was smaller in decorin-treated mice. In addition, cellular components, including myofibroblasts and blood vessels, were more abundant within the infarcted area in decorin-treated mice, and fibrosis was significantly reduced in both the infarcted and noninfarcted areas of the left ventricular wall. Ten days post-MI, there was greater cell proliferation and less apoptosis among granulation tissue cells in the infarcted areas of decorin-treated mice. The treatment, however, did not affect proliferation and apoptosis of salvaged cardiomyocytes. Although decorin gene therapy did not affect TGF-beta1 expression in the infarcted heart, it inhibited Smad2/3 activation (downstream mediators of TGF-beta signaling). In summary, postinfarction decorin gene therapy mitigated cardiac remodeling and dysfunction by altering infarct tissue noncardiomyocyte dynamics and preventing cardiac fibrosis, accompanying inhibition of Smad2/3 activation.

THE FAS/FAS-LIGAND PATHWAY DOES NOT MEDIATE THE APOPTOSIS IN ELASTASE-INDUCED EMPHYSEMA IN MICE

Porcine pancreatic elastase (PPE), which induces emphysema via apoptosis, was administered to wild-type and Fas-deficient (lpr) mice. On days 3 and 28 after administration, the mean linear intercepts within lung tissues were significantly higher in PPE-treated wild-type and lpr mice than in control mice, though there were no significant differences between the PPE-treated groups. Likewise, the numbers of TUNEL-positive cells were increased in the lungs of PPE-treated wild-type and lpr mice, and again the effect was similar in the two PPE-treated groups. These findings suggest that apoptosis associated with PPE-induced emphysema is not mediated via the Fas/Fas-ligand pathway.