Toshio Imanishi

Impact of Heterogeneity of Human Peripheral Blood Monocyte Subsets on Myocardial Salvage in Patients With Primary Acute Myocardial Infarction

OBJECTIVES We examined whether distinct monocyte subsets contribute in specific ways to myocardial salvage in patients with acute myocardial infarction (AMI). BACKGROUND Recent studies have shown that monocytes in human peripheral blood are heterogeneous. METHODS We studied 36 patients with primary AMI. Peripheral blood sampling was performed 1, 2, 3, 4, 5, 8, and 12 days after AMI onset. Two monocyte subsets (CD14(+)CD16(-) and CD14(+)CD16(+)) were measured by flow cytometry. The extent of myocardial salvage 7 days after AMI was evaluated by cardiovascular magnetic resonance imaging as the difference between myocardium at risk (T2-weighted hyperintense lesion) and myocardial necrosis (delayed gadolinium enhancement). Cardiovascular magnetic resonance imaging was also performed 6 months after AMI. RESULTS Circulating CD14(+)CD16(-) and CD14(+)CD16(+) monocytes increased in AMI patients, peaking on days 3 and 5 after onset, respectively. Importantly, the peak levels of CD14(+)CD16(-) monocytes, but not those of CD14(+)CD16(+) monocytes, were significantly negatively associated with the extent of myocardial salvage. We also found that the peak levels of CD14(+)CD16(-) monocytes, but not those of CD14(+)CD16(+) monocytes, were negatively correlated with recovery of left ventricular ejection fraction 6 months after infarction. CONCLUSIONS The peak levels of CD14(+)CD16(-) monocytes affect both the extent of myocardial salvage and the recovery of left ventricular function after AMI, indicating that the manipulation of monocyte heterogeneity could be a novel therapeutic target for salvaging ischemic damage.

Angiotensin II accelerates endothelial progenitor cell senescence through induction of oxidative stress.

Objectives Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cell (EPC). We investigated the effect of angiotensin II (Ang II) on EPC senescence, leading to the impairment of proliferative activity. Methods and results EPCs were isolated from peripheral blood and characterized. Both reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting were used to assess gp91phox expression. Immunofluorescence of nitrotyrosine provided evidence of peroxynitrite formation. Our data indicate that Ang II increased the expression of gp91phox mRNA in a dose-dependent manner, which was attenuated by Ang II type 1 (AT1) receptor antagonist valsartan. Similarly, Western blotting revealed that Ang II stimulated an increase in gp91phox, whereas pre-treatment with Valsartan reduced the Ang II-induced expression of gp91phox protein. Valsartan as well as superoxide dismutase (SOD) also inhibited Ang II-induced peroxynitrite formation. The exposure of cultured EPC to Ang II (100 nmol/l) significantly accelerated the rate of senescence compared to a control during 14 days in culture as determined by acidic β-galactosidase staining. Ang II-induced EPC senescence was significantly inhibited by pre-treatment of either valsartan or SOD (P < 0.01). Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity by using PCR-enzyme-linked immunosorbent-based assay. Ang II significantly diminished telomerase activity, although the effect was significantly reduced by pre-treatment with either valsartan or SOD (P < 0.01). We examined whether Ang II-induced EPC senescence translates into an impairment of EPC proliferation. MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetrazolium] assay disclosed an inhibitory effect of Ang II on EPC proliferation. Conclusions Ang II increases gp91phox expression in EPC, which may contribute to oxidative stress, as evidenced by peroxynitrite formation. Ang II accelerates the onset of EPC senescence via increased oxidative stress, which may be related to telomerase inactivation. In addition, Ang II-induced EPC senescence leads to the impairment of proliferative activity.

Endothelial progenitor cell senescence is accelerated in both experimental hypertensive rats and patients with essential hypertension

Objectives Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cells (EPCs). Although hypertension is an important coronary risk factor, the influence to the EPCs is not fully understood. We investigated the effect of hypertension on EPC senescence. Methods Experimental study We investigated the number and senescence of EPCs in spontaneously hypertensive rats (SHR/Izm) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. EPCs were isolated from peripheral blood of rats and were characterized. EPC senescence was detected by acidic β-galactosidase staining. In addition, we measured the telomerase activity using polymerase chain reaction-enzyme-linked immunosorbent assay. Clinical study EPCs were isolated from peripheral blood samples in 37 patients with essential hypertension. After ex-vivo cultivation, we detected senescence and measured the telomerase activity. The total severity index of hypertension-induced organ damage was calculated by the summation of each severity index in the classification of hypertension severity by Tokyo University (1984). Results Experimental study The EPC senescence in SHR/Izm and DOCA-salt hypertensive rats was significantly increased compared with that of control rats. The telomerase activities in SHR/Izm and DOCA-salt hypertensive sensitive rats were also significantly lowered compared with those of control rats. Clinical study Compared with the control group, EPCs from hypertensive patients showed accelerated senescence and also showed reduced telomerase activity. In hypertensive patients, the degree of hypertension-induced organ damage was negatively correlated with telomerase activity, and was positively correlated with EPC senescence. Conclusions EPC senescence is accelerated in both experimental hypertensive rats and patients with essential hypertension, which may be related to telomerase inactivation. The hypertension-induced EPC senescence may affect the process of vascular remodeling.

OXIDIZED LOW-DENSITY LIPOPROTEIN INDUCES ENDOTHELIAL PROGENITOR CELL SENESCENCE, LEADING TO CELLULAR DYSFUNCTION

1. Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow‐derived endothelial progenitor cells (EPC). We investigated the effect of oxidized low‐density lipoprotein (ox‐LDL) on the senescence of EPC, leading to cellular dysfunction.

Effect of statin therapy on coronary fibrous-cap thickness in patients with acute coronary syndrome: assessment by optical coherence tomography study.

BACKGROUND The thickness of coronary fibrous caps is a major determinant of vulnerable plaques. Several clinical trials have suggested that statin therapy could stabilize vulnerable plaques. Recently, optical coherence tomography (OCT) has been proposed as an effective histology-resolution imaging modality for assessing such micro-structural changes. METHODS Forty AMI patients with hyperlipidemia were enrolled and underwent percutaneous coronary intervention (PCI). They were divided into two groups; statin treatment group (n=23) or control group (n=17). Serial OCT analyses were performed at baseline and 9-month follow-up for a non-PCI lipid-rich plaque lesion. RESULTS The LDL-cholesterol level in the statin group was significantly lower than that in the control group at follow-up. Although the fibrous-cap thickness was significantly increased in both the statin treatment group (151+/-110 to 280+/-120 microm, p<0.01) and the control group (153+/-116 to 179+/-124 microm, p<0.01) during follow-up period, the degree of increase was significantly greater in the statin treatment group than in the control group (188+/-64% vs. 117+/-39%, p<0.01). Furthermore, when the patients in the statin treatment group were divided into two subgroups (fibrous-cap thickness or=median), the thin fibrous-cap group (or=median). CONCLUSION The lipid-lowering therapy with statin for 9 months after the onset of acute myocardial infarction significantly increased the fibrous-cap thickness in patients with hyperlipidemia.

Morphology of Exertion-Triggered Plaque Rupture in Patients With Acute Coronary Syndrome An Optical Coherence Tomography Study

Background— Plaque rupture and secondary thrombus formation play key roles in the onset of acute coronary syndrome (ACS). One pathological study suggested that the morphologies of plaque rupture differed between rest-onset and exertion-triggered rupture in men who experienced sudden death. The aim of the present study was to use optical coherence tomography to investigate the relationship in patients with ACS between the morphology of a ruptured plaque and the patients activity at the onset of ACS. Methods and Results— The study population was drawn from 43 consecutive ACS patients (with or without ST-segment elevation) who underwent optical coherence tomography and presented with a ruptured plaque at the culprit site. Patients were divided into a rest group and an exertion group on the basis of their activities at the onset of ACS. The thickness of the broken fibrous cap correlated positively with activity at the onset of ACS. The culprit plaque ruptured at the shoulder more frequently in the exertion group than in the rest group (rest 57% versus exertion 93%, P=0.014). The thickness of the broken fibrous cap in the exertion group was significantly higher than in the rest-onset group (rest onset: 50 &mgr;m [interquartile median 15 &mgr;m]; exertion: 90 &mgr;m [interquartile median 65 &mgr;m], P<0.01). Conclusions— The morphologies of exertion-triggered and rest-onset ruptured plaques differ in ACS patients. Our data suggest that a thin-cap fibroatheroma is a lesion predisposed to rupture both at rest and during the patients day-to day activity, and some plaque rupture may occur in thick fibrous caps depending on exertion levels.

Advantage of next-generation frequency-domain optical coherence tomography compared with conventional time-domain system in the assessment of coronary lesion.

Background: Intracoronary optical coherence tomography (OCT) is a high‐resolution imaging modality used for evaluation of coronary lesion morphology. However, current time‐domain OCT (TD‐OCT) have a number of limitations with regard to both procedural usage and safety in the clinical setting. The next‐generation frequency‐domain OCT (FD‐OCT), which has a much faster frame rate and pullback speed than TD‐OCT, is expected to overcome these limitations. The aim of this study was to evaluate the feasibility and usability of next generation FD‐OCT in the assessment of coronary lesions. Methods: A comparison study was performed between FD‐OCT and TD‐OCT from the aspect of usability (set‐up time), qualitatively (rate of clear image segment), and safety (adverse event) in 14 ischemic heart disease patients with 20 previously implanted coronary stents. Results: The mean time of the OCT procedure in this study from setup to completion of image acquisition was 3.2 ± 0.8 min for FD‐OCT and 11.2 ± 2.5 min for TD‐OCT (P < 0.01). In qualitative image assessment, FD‐OCT has the potential to yield a higher rate of clear image segments (CIS) than TD‐OCT (99.4% vs. 80.8%, respectively; P < 0.01). In addition to these improved characteristics, there were no ischemic ECG changes or arrhythmia associated with FD‐OCT. Conclusions: The next‐generation intracoronary FD‐OCT has better performance in the clinical setting and the potential to overcome several limitations of conventional TD‐OCT systems.

Renin Inhibitor Aliskiren Improves Impaired Nitric Oxide Bioavailability and Protects Against Atherosclerotic Changes

We investigated whether aliskiren, a direct renin inhibitor, improves NO bioavailability and protects against spontaneous atherosclerotic changes. We also examined the effects of cotreatment with aliskiren and valsartan, an angiotensin II receptor blocker, on the above-mentioned outcomes. Watanabe heritable hyperlipidemic rabbits were treated with vehicle (control), aliskiren, valsartan, or aliskiren plus valsartan for 8 weeks. Then, acetylcholine-induced NO production was measured as a surrogate index of endothelium protective function, and both superoxide and vascular peroxynitrite were measured. Tetrahydrobiopterin in aortic segments was assessed by high-performance liquid chromatography with fluorescence detection. Plaque area was quantified by histology. Increase in plasma NO concentration in response to intra-aortic acetylcholine infusion was significantly greater in all of the test groups than in controls. Aliskiren+valsartan cotreatment increased acetylcholine-induced NO by 6.2 nmol/L, which was significantly higher than that with either aliskiren or valsartan alone. Vascular superoxide and peroxynitrite levels were both significantly higher in controls and significantly lower in the aliskiren+valsartan group than in the aliskiren or valsartan group. The highest tetrahydrobiopterin levels were observed after aliskiren+valsartan cotreatment. Histology of the thoracic aorta revealed that the plaque area was significantly decreased with combination therapy compared with monotherapy. Treatment with a direct renin inhibitor has protective effects on endothelial function and atherosclerotic changes. Furthermore, cotreatment with a direct renin inhibitor and an angiotensin II receptor blocker has additive protective effects on both.

Difference of Culprit Lesion Morphologies Between ST-Segment Elevation Myocardial Infarction and Non–ST-Segment Elevation Acute Coronary Syndrome : An Optical Coherence Tomography Study

OBJECTIVES The aim of this study was to investigate the difference of culprit lesion morphologies assessed by optical coherence tomography (OCT) between ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation acute coronary syndrome (NSTEACS). BACKGROUND Autopsy studies have reported that rupture of a thin-cap fibroatheroma and subsequent thrombus formation is the most important mechanism leading to acute coronary syndrome (ACS). Optical coherence tomography is a high-resolution imaging modality that is capable of investigating detailed coronary plaque morphology in vivo. METHODS We examined the culprit lesion morphologies by OCT in 89 consecutive patients with acute coronary syndrome (STEMI = 40; NSTEACS = 49). RESULTS The incidence of plaque rupture, thin-cap fibroatheroma, and red thrombus was significantly higher in STEMI compared with NSTEACS (70% vs. 47%, p = 0.033, 78% vs. 49%, p = 0.008, and 78% vs. 27%, p < 0.001, respectively). Although the lumen area at the site of plaque rupture was similar in the both groups (2.44 ± 1.34 mm(2) vs. 2.96 ± 1.91 mm(2), p = 0.250), the area of ruptured cavity was significantly larger in STEMI compared with NSTEACS (2.52 ± 1.36 mm(2) vs. 1.67 ± 1.37 mm(2), p = 0.034). Furthermore, the ruptured plaque of which aperture was open-wide against the direction of coronary flow was more often seen in STEMI compared with NSTEACS (46% vs. 17%, p = 0.036). CONCLUSIONS The present OCT study demonstrated the differences of the culprit lesion morphologies between STEMI and NSTEACS. The morphological feature of plaque rupture and the intracoronary thrombus could relate to the clinical presentation in patients with acute coronary disease.

Lipid-rich plaque and myocardial perfusion after successful stenting in patients with non-ST-segment elevation acute coronary syndrome: an optical coherence tomography study

AIMS Although some recent guidelines recommend an early invasive strategy for non-ST-segment elevation acute coronary syndrome (NSTEACS), several studies have failed to identify any benefit for very early intervention for NSTEACS. The no-reflow phenomenon may inhibit the expected benefit from very early recanalization for NSTEACS subjects. The aim of this study was to investigate whether optical coherence tomography (OCT) could predict no-reflow in patients with NSTEACS. METHODS AND RESULTS This study comprised 83 consecutive patients with NSTEACS who underwent OCT and successful emergent primary stenting. On the basis of post-stent TIMI flow, patients were divided into two groups: no-reflow group (n = 14) and reflow group (n = 69). Thin-cap fibroatheroma (TCFA) was defined as a plaque presenting lipid content for >90 degrees , and with thinnest part of the fibrous cap measuring <70 microm. Thin-cap fibroatheroma were more frequently observed in the no-reflow group than in the reflow group (50% vs. 16%, P = 0.005). The frequency of the no-reflow phenomenon increases according to the size of the lipid arc in the culprit plaque. Final TIMI blush grade also deteriorated according to the increase in the lipid arc. A multivariable logistic regression model revealed that lipid arc alone was an independent predictor of no-reflow (odds ratio 1.018; CI 1.004-1.033; P = 0.01). CONCLUSION Optical coherence tomography can predict no-reflow after percutaneous coronary intervention (PCI) in NSTEACS. The lipid contents of a culprit plaque may play a key role in damage to the microcirculation after PCI for NSTEACS. From our results, it is found that OCT is useful tool for stratifying risk for PCI for NSTEACS.