Tadashi Kuroda

Association between hyperglycemia and the no-reflow phenomenon inpatients with acute myocardial infarction

OBJECTIVES We investigated the association between hyperglycemia and the no-reflow phenomenon in patients with acute myocardial infarction (AMI). BACKGROUND Hyperglycemia is associated with increased risks of heart failure, cardiogenic shock, and death after AMI, but its underlying mechanism remains unknown. METHODS A total of 146 consecutive patients with a first AMI were studied by intracoronary myocardial contrast echocardiography (MCE) after successful reperfusion within 24 h after symptom onset. Two-dimensional echocardiography was recorded on day 1 and three months later to determine the change in the wall motion score (DeltaWMS; sum of 16 segmental scores; dyskinesia = 4 to normokinesia = 0). RESULTS The no-reflow phenomenon was found on MCE in 49 (33.6%) of 146 patients; their glucose level on hospital admission was significantly higher than that of patients who did not exhibit this phenomenon (209 +/- 79 vs. 159 +/- 56 mg/dl; p < 0.0001). There was no difference in glycosylated hemoglobin or in the incidence of diabetes mellitus between the two subsets. The no-reflow phenomenon was more often observed in the 75 patients with hyperglycemia (>/=160 mg/dl) than in those without hyperglycemia (52.0% vs. 14.1%; p < 0.0001). Patients with hyperglycemia had a higher peak creatine kinase level (2,497 +/- 1,603 vs. 1,804 +/- 1,300 IU/l; p = 0.005) and a lower DeltaWMS (3.7 +/- 4.8 vs. 5.7 +/- 4.3; p = 0.01) than did those without hyperglycemia. The blood glucose level was an independent prognostic factor for no reflow, along with age, gender, absence of pre-infarction angina, complete occlusion of the culprit lesion, and anterior AMI. CONCLUSIONS Hyperglycemia might be associated with impaired microvascular function after AMI, resulting in a larger infarct size and worse functional recovery.

AMP-activated protein kinase protects cardiomyocytes against hypoxic injury through attenuation of endoplasmic reticulum stress

ABSTRACT Oxygen deprivation leads to the accumulation of misfolded proteins in the endoplasmic reticulum (ER), causing ER stress. Under conditions of ER stress, inhibition of protein synthesis and up-regulation of ER chaperone expression reduce the misfolded proteins in the ER. AMP-activated protein kinase (AMPK) is a key regulatory enzyme involved in energy homeostasis during hypoxia. It has been shown that AMPK activation is associated with inhibition of protein synthesis via phosphorylation of elongation factor 2 (eEF2) in cardiomyocytes. We therefore examined whether AMPK attenuates hypoxia-induced ER stress in neonatal rat cardiomyocytes. We found that hypoxia induced ER stress, as assessed by the expression of CHOP and BiP and cleavage of caspase 12. Knockdown of CHOP or caspase 12 through small interfering RNA (siRNA) resulted in decreased expression of cleaved poly(ADP-ribose) polymerase following exposure to hypoxia. We also found that hypoxia-induced CHOP expression and cleavage of caspase 12 were significantly inhibited by pretreatment with 5-aminoimidazole-4-carboxyamide-1-β-d-ribofuranoside (AICAR), a pharmacological activator of AMPK. In parallel, adenovirus expressing dominant-negative AMPK significantly attenuated the cardioprotective effects of AICAR. Knockdown of eEF2 phosphorylation using eEF2 kinase siRNA abolished these cardioprotective effects of AICAR. Taken together, these findings demonstrate that activation of AMPK contributes to protection of the heart against hypoxic injury through attenuation of ER stress and that attenuation of protein synthesis via eEF2 inactivation may be the mechanism of cardioprotection by AMPK.

Maximum carotid intima-media thickness improves the prediction ability of coronary artery stenosis in type 2 diabetic patients without history of coronary artery disease

OBJECTIVE Carotid intima-media thickness (CIMT), a marker of early atherosclerosis and vascular remodelling, is one of the independent predictors of coronary artery disease (CAD). However, it is unknown whether ultrasonic assessment of carotid atherosclerosis, including CIMT, improves the prediction ability for CAD over and above conventional coronary risk factors in the diabetic patients. METHODS Ultrasonic scanning of the common carotid artery (CCA), the carotid bulb (Bul), and the internal carotid artery (ICA) was performed. The site with the greatest IMT, including plaque lesions, was sought along the arterial walls and max-IMT (the greatest IMT in the observation-possible areas of the CCA, Bul and ICA) was measured. The association of max-IMT with coronary artery stenosis assessed by coronary computed tomography angiography and the incremental effect of adding max-IMT to the conventional risk factors for predicting coronary artery stenosis were evaluated in 241 asymptomatic type 2 diabetic patients. RESULTS Multiple logistic regression analyses showed that max-IMT was significantly associated with coronary artery stenosis even after adjustment for conventional risk factors. ROC curve analysis revealed that the AUC significantly increased after addition of max-IMT to conventional coronary risk factors [from 0.64 (95% CI; 0.57-0.71) to 0.74 (95% CI; 0.67-0.80), p = 0.020]. The addition of max-IMT to conventional coronary risk factors increased the AUC in obese patients (from 0.58 to 0.76, p = 0.012) but not in non-obese patients (from 0.68 to 0.72, NS). CONCLUSIONS In type 2 diabetic patients without apparent cardiovascular disease, the addition of max-IMT to conventional risk factors substantially improves the risk stratification for CAD.

Docking Protein Gab1 Is an Essential Component of Postnatal Angiogenesis After Ischemia via HGF/c-Met Signaling

Rationale: Grb2-associated binder (Gab) docking proteins, consisting of Gab1, Gab2, and Gab3, have crucial roles in growth factor–dependent signaling. Various proangiogenic growth factors regulate angiogenesis and endothelial function. However, the roles of Gab proteins in angiogenesis remain elusive. Objective: To elucidate the role of Gab proteins in postnatal angiogenesis. Methods and Results: Endothelium-specific Gab1 knockout (Gab1ECKO) mice were viable and showed no obvious defects in vascular development. Therefore, we analyzed a hindlimb ischemia (HLI) model of control, Gab1ECKO, or conventional Gab2 knockout (Gab2KO) mice. Intriguingly, impaired blood flow recovery and necrosis in the operated limb was observed in all of Gab1ECKO, but not in control or Gab2KO mice. Among several proangiogenic growth factors, hepatocyte growth factor (HGF) induced the most prominent tyrosine phosphorylation of Gab1 and subsequent complex formation of Gab1 with SHP2 (Src homology-2–containing protein tyrosine phosphatase 2) and phosphatidylinositol 3-kinase subunit p85 in human endothelial cells (ECs). Gab1-SHP2 complex was required for HGF-induced migration and proliferation of ECs via extracellular signal-regulated kinase (ERK)1/2 pathway and for HGF-induced stabilization of ECs via ERK5. In contrast, Gab1-p85 complex regulated activation of AKT and contributed partially to migration of ECs after HGF stimulation. Microarray analysis demonstrated that HGF upregulated angiogenesis-related genes such as KLF2 (Krüppel-like factor 2) and Egr1 (early growth response 1) via Gab1-SHP2 complex in human ECs. In Gab1ECKO mice, gene transfer of vascular endothelial growth factor, but not HGF, improved blood flow recovery and ameliorated limb necrosis after HLI. Conclusion: Gab1 is essential for postnatal angiogenesis after ischemia via HGF/c-Met signaling.

Smad1 Protects Cardiomyocytes From Ischemia-Reperfusion Injury

Background—We previously reported that bone morphogenetic protein 2 (BMP2) protected against apoptosis of serum-deprived cardiomyocytes via induction of Bcl-xL through the Smad1 pathway. To investigate whether Smad1 signaling promotes cell survival in the adult heart, we subjected transgenic mice with cardiac-specific overexpression of smad1 gene (Smad1TG) to ischemia-reperfusion (I/R) injury. Methods and Results—The effects of BMP2 or adenovirus-mediated transfection of smad1 on cardiomyocyte survival in hypoxia-reoxygenation were examined using rat neonatal cardiomyocytes. BMP2 and Smad1 each significantly promoted survival and diminished apoptotic death of cardiomyocytes during hypoxia-reoxygenation. Interestingly, Smad1 was found to be activated during I/R in normal mouse heart. To examine physiological and pathological roles of Smad1 in I/R, we generated Smad1TG using the α-myosin heavy chain gene promoter. Phosphorylation of Smad1 was found in all smad1 transgene–positive mouse hearts. To examine whether Smad1 prevents injury of cardiomyocytes in vivo, we subjected Smad1TG and age-matched wild-type mice (WT) to I/R injury induced by 1 hour of ligation of the left coronary artery and 1 hour of reperfusion. TUNEL and DNA ladder analyses showed that Smad1TG had significantly smaller myocardial infarctions and fewer apoptotic deaths of cardiomyocytes than did WT. Interestingly, increased expression of Bcl-xL and β-catenin was more remarkable whereas caspase3 was less activated in Smad1TG heart than in that of WT. Conclusions—These findings suggest that the Smad1 signaling pathway plays a role in cardioprotection against I/R injury.

Relationship Between Carotid Intima-Media Thickness and the Presence and Extent of Coronary Stenosis in Type 2 Diabetic Patients With Carotid Atherosclerosis but Without History of Coronary Artery Disease

OBJECTIVE We examined the relationship between the presence and extent of coronary stenosis and carotid intima-media thickness (CIMT) in type 2 diabetic patients without history of coronary artery disease (CAD) but with carotid atherosclerosis. RESEARCH DESIGN AND METHODS A total of 91 type 2 diabetic patients underwent multi-slice computed tomography coronary angiography. RESULTS Max-IMT in the ≥50% stenosis group by multi-slice computed tomography coronary angiography estimation was significantly greater than the 0–25 and 25–50% stenosis group (2.68 ± 0.77 vs. 1.61 ± 0.49 mm, P < 0.0005, and 2.14 ± 0.81 mm, P < 0.05, respectively), and max-IMT in the 25–50% stenosis group was significantly greater than the 0–25% stenosis group (P < 0.05) after adjustment for age, sex, duration of type 2 diabetes, hypertension, and dyslipidemia. In the analysis for trend through the categories of max-IMT, as max-IMT increased, the percentage of ≥50% stenosis increased and the percentage of 0–25% stenosis decreased. CONCLUSIONS Our data suggest that max-IMT might be closely associated with the extent of coronary stenosis in type 2 diabetic patients without history of CAD but with carotid atherosclerosis.

Detection of TIMI-3 Flow Before Mechanical Reperfusion With Ultrasonic Tissue Characterization in Patients With Anterior Wall Acute Myocardial Infarction

Background—Spontaneous coronary reperfusion with TIMI-3 flow is associated with favorable clinical outcomes in patients with acute myocardial infarction (AMI). We investigated the ability of analyzing cardiac cycle-dependent variation of myocardial integrated backscatter (IBS) for predicting spontaneous reperfusion in anterior AMI. Methods and Results—We recorded IBS images on admission in 104 patients with first anterior wall AMI and subsequently performed coronary angiography and coronary intervention. We measured the cyclic variation of IBS within the infarct zone and expressed its magnitude as phase-corrected magnitude (PCM) by giving positive and negative values when it showed synchronous and asynchronous contraction, respectively. Twenty-three patients showing TIMI-3 flow at the initial coronary angiography had smaller peak creatine kinase value than 57 patients with initial TIMI-0/1 flow (864±961 versus 2358±1757 IU/L; P =0.0002) and better percent wall thickening within risk area (36.1±15.1%) than those with TIMI-2 (16.7±12.8%, P <0.0001) or TIMI-0/1 (5.1±11.6, P <0.0001). The patients with initial TIMI-3 had higher PCM (2.7±1.3 dB) than those with TIMI-2 (−0.3±2.2 dB, P <0.0001) or those with TIMI-0/1 (−1.1±2.4 dB, P <0.0001). Using PCM=1.0 dB as the cutoff point, PCM detected TIMI-3 flow with 95.7% sensitivity and 90.1% specificity. Multivariable logistic regression analysis revealed that only PCM is an independent predictor for spontaneous reperfusion among the hemodynamic, echocardiographic, and electrocardiographic variables. Conclusions—Analysis of myocardial IBS could detect spontaneous reperfusion noninvasively in the emergent stage of anterior AMI.

SHP2 mediates gp130-dependent cardiomyocyte hypertrophy via negative regulation of skeletal alpha-actin gene

Morphological and biochemical phenotypes of cardiomyocyte hypertrophy are determined by neurohumoral factors. Stimulation of G protein-coupled receptor (GPCR) results in uniform cell enlargement in all directions with an increase in skeletal alpha-actin (alpha-SKA) gene expression, while stimulation of gp130 receptor by interleukin-6 (IL-6)-related cytokines induces longitudinal elongation with no increase in alpha-SKA gene expression. Thus, alpha-SKA is a discriminating marker for hypertrophic phenotypes; however, regulatory mechanisms of alpha-SKA gene expression remain unknown. Here, we clarified the role of SH2-containing protein tyrosine phosphatase 2 (SHP2) in alpha-SKA gene expression. In neonatal rat cardiomyocytes, endothelin-1 (ET-1), a GPCR agonist, but not leukemia inhibitory factor (LIF), an IL-6-related cytokine, induced RhoA activation and promotes alpha-SKA gene expression via RhoA. In contrast, LIF, but not ET-1, induced activation of SHP2 in cardiomyocytes, suggesting that SHP2 might negatively regulate alpha-SKA gene expression downstream of gp130. Therefore, we examined the effect of adenovirus-mediated overexpression of wild-type SHP2 (SHP2(WT)), dominant-negative SHP2 (SHP2(C/S)), or beta-galactosidase (beta-gal), on alpha-SKA gene expression. LIF did not upregulate alpha-SKA mRNA in cardiomyocytes overexpressing either beta-gal or SHP2(WT). In cardiomyocytes overexpressing SHP2(C/S), LIF induced upregulation of alpha-SKA mRNA, which was abrogated by concomitant overexpression of either C3-toxin or dominant-negative RhoA. RhoA was activated after LIF stimulation in the cardiomyocytes overexpressing SHP2(C/S), but not in myocytes overexpressing beta-gal. Furthermore, SHP2 mediates LIF-induced longitudinal elongation of cardiomyocytes via ERK5 activation. Collectively, these findings indicate that SHP2 negatively regulates alpha-SKA expression via RhoA inactivation and suggest that SHP2 implicates ERK5 in cardiomyocyte elongation downstream of gp130.

Clinical significance of plasma endothelin-1 level after bosentan administration in pulmonary arterial hypertension

BACKGROUND Endothelin (ET)-1 has been shown to play a significant pathogenic role in pulmonary arterial hypertension (PAH). However, the pathobiological significance of increased ET-1 concentration after administration of ET receptor antagonist in patients with PAH has not yet been fully examined. METHODS In 16 PAH patients, plasma ET-1 concentration was measured at 0, 1, 3, 6, and 24h after a single 62.5mg dose of bosentan, a dual ET receptor antagonist, and the peak and 24-h change in ET-1 concentration from baseline were examined. The severity of PAH was evaluated by hemodynamic parameters, 6-min walk distance, New York Heart Association (NYHA) functional class, and brain natriuretic peptide (BNP). RESULTS Plasma ET-1 concentration significantly increased from 1.93+/-0.12 to 3.36+/-0.18 pg/ml after bosentan administration in PAH patients (p<0.01). The peak-to-baseline ratio of ET-1 concentration after bosentan administration showed a significant positive correlation with baseline ET-1 concentration (p<0.05). After 4-week bosentan administration, NYHA functional class improved in 7 patients but was not changed in 9 patients. The optimal cut-off point of % change of ET-1 concentration at 24h for discriminating the two groups was 30%. According to this cut-off point, patients were divided into the higher (n=7) and the lower (n=9) groups. NYHA functional class did not change in the lower group, but significantly improved (p<0.01) in the higher group after 4-week bosentan administration. In addition, plasma BNP levels significantly decreased from baseline in the higher group compared with those in the lower group after 12-week bosentan administration (-44+/-11% vs. 7+/-20%, p<0.05). CONCLUSIONS Although the population in this study is small and heterogeneous, measurement of plasma ET-1 concentration after bosentan administration might predict the responsiveness to bosentan treatment, and be useful in the determination of effective therapy in treatment of PAH patients.

Aortic Dissection and Cardiac Dysfunction Emerged Coincidentally During the Long-Term Treatment with Angiogenesis Inhibitors for Metastatic Renal Cell Carcinoma: A Case Report of Onco-Cardiology

Angiogenesis inhibitors, such as sorafenib and axitinib, which target vascular endothelial growth factor (VEGF) signaling, are widely used for renal cell carcinoma, including metastasis. In this study, we report a case of cardiovascular adverse events of aortic dissection and cardiac dysfunction during treatment with sorafenib and axitinib for metastatic renal cell carcinoma. A 66-year-old man had been administered sorafenib for 2 years after nephrectomy due to renal cell carcinoma. To control the progression of metastatic lung tumor, axitinib was started after sorafenib for four years. During the treatment, angiotensin II type 1 receptor blockers and Ca antagonists were used to strictly control the axitinib-induced hypertension and proteinuria. Aortic dissection and cardiac dysfunction occurred coincidentally. Considering the critical role of VEGF signaling in the homeostasis of the cardiovascular system, we speculated that the long-term use of axitinib and sorafenib directly influenced the initiation of aortic dissection and cardiac dysfunction. Although the precise mechanisms underlying the aortic dissection and cardiac dysfunction induced by angiogenesis inhibition are still elusive, onco-cardiologists and oncologists should pay careful attention to cardiovascular toxicity and complications in patients with cancer, particularly patients undergoing long-term cancer treatment.