Nobukiyo Tanaka

Glucocorticoid Receptor Regulates ATP-Binding Cassette Transporter-A1 Expression and Apolipoprotein-Mediated Cholesterol Efflux from Macrophages

Objective—The ATP-binding cassette transporter-A1 (ABCA1) regulates cholesterol efflux from cells and is involved in high-density lipoprotein metabolism and atherogenesis. The objective of this study was to investigate the effect of dexamethasone (Dex) and other glucocorticoid receptor (GR) ligands on apolipoprotein AI–mediated cholesterol efflux from macrophages and ABCA1 expression in them. Methods and Results—Dex, a GR agonist, decreased ABCA1 mRNA levels in a dose- and time-dependent fashion, and RU486, a GR antagonist, reversed the inhibitory effect of Dex. The effects of Dex and RU486 on ABCA1 protein levels and apolipoprotein AI–mediated cholesterol efflux from the macrophages were consistent with these changes in mRNA levels. Transfected RAW264.7, together with a human ABCA1 promoter–luciferase construct, inhibited transcriptional activity by Dex and overexpression of human GR. Transrepression by GR was not mediated by liver X receptor (LXR), because there were no differences in the effects of the GR ligands on promoter activity between a reporter construct with mutations at the LXR binding site and one without the mutations, and no changes were brought about in ABCG1 and ABCG4 expression by GR ligands. Conclusions—Our results showed that GR ligands affected ABCA1 expression and cholesterol efflux from macrophages, which are regulated by GR through a LXR-independent mechanism.

High plasma levels of matrix metalloproteinase-8 in patients with unstable angina

Matrix metalloproteinases (MMPs) play a role in collagen breakdown, leading to plaque instability. High levels of MMPs mRNA and proteins, especially MMP-1, MMP-2, MMP-8, MMP-9, and MMP-13, were shown in human atherosclerotic plaques. However, among various MMPs, only MMP-1, MMP-8 and MMP-13, so-called interstitial collagenases, can initiate collagen breakdown. To elucidate whether MMP-1, MMP-8 and MMP-13 levels in blood were high in patients with unstable angina (UAP), we measured serum MMP-1 and plasma MMP-8 and MMP-13 levels in 45 patients with UAP, 175 with stable coronary artery disease (CAD), and 45 controls. Plasma C-reactive protein levels tended to be higher in patients with UAP than in those with stable CAD and controls (median 0.94 vs. 0.69 and 0.51mg/l). Regarding blood levels of MMPs, MMP-13 levels were above the lower detection limit in only one patient with UAP (2%), one with stable CAD (1%), and none in controls. MMP-1 levels did not differ among patients with UAP, stable CAD, and controls (median 4.8, 5.3, and 5.4ng/ml). Notably, MMP-8 levels were higher in patients with stable CAD than in controls (median 3.5ng/ml vs. 2.8ng/ml, P<0.005), however, MMP-8 levels in patients with UAP were much higher than those in stable CAD (3.9ng/ml vs. 3.5ng/ml, P<0.05). In multivariate analysis, MMP-8 level was an independent factor for UAP. Thus, plasma MMP-8 levels were found to be high in patients with UAP, suggesting that MMP-8 levels in UAP may reflect coronary plaque instability and that MMP-8 is a promising biomarker for UAP.

ATP-Binding Cassette Transporter A1 Gene Transcription Is Downregulated by Activator Protein 2α Doxazosin Inhibits Activator Protein 2α and Increases High-Density Lipoprotein Biogenesis Independent of α1-Adrenoceptor Blockade

ATP-binding cassette transporter A1 (ABCA1) is a rate-limiting factor for high-density lipoprotein (HDL) biogenesis. The ABCA1 gene expression is known to be upregulated by various transcriptional factors. However, negative regulation factors would be better targets for pharmacological modulation of HDL biogenesis. Doxazosin, an &agr;1-adrenoceptor blocker, increased ABCA1 mRNA, its protein, and apolipoprotein A-I–mediated HDL biogenesis in THP-1 macrophages and CHO-K1 cells, independent of &agr;1-adrenoceptor blockade. Analysis of the human ABCA1 promoter indicated that the region between the positions −368 and −147 that contains an activator protein (AP)2-binding site responsible for the effects of doxazosin. Overexpression of AP2&agr; inhibited ABCA1 transcription in a dose-dependent fashion. Mutation in the AP2-binding site caused increase of the basal promoter activity and canceling both the transactivation by doxazosin and the trans-repression by AP2&agr;. Doxazosin had no effect on ABCA1 mRNA level in HepG2 cells, which lack endogenous AP2&agr;, and it reversed the inhibitory effect of AP2&agr; expression in this type of cells. Chromatin immunoprecipitation and gel shift assays revealed that doxazosin reduced specific binding of AP2&agr; to the ABCA1 promoter, as it suppressed phosphorylation of AP2&agr;. Finally, doxazosin increased ABCA1 expression and plasma HDL in mice. We thus concluded that AP2&agr; negatively regulates the ABCA1 gene transcription. Doxazosin inhibits AP2&agr; activity independent of &agr;1-adrenoceptor blockade and increases the ABCA1 expression and HDL biogenesis. AP2&agr; is a potent pharmacological target for the increase of HDL.

Effect of lipid-lowering therapy with atorvastatin on atherosclerotic aortic plaques: a 2-year follow-up by noninvasive MRI

Background Using MRI, we reported plaque regression in thoracic aorta and retardation of plaque progression in abdominal aorta by 1-year atorvastatin. However, association between serial plaque changes and LDL-cholesterol levels was not fully elucidated. Design A prospective, randomized, open-label trial. Methods We investigated the long-term effect of 20 versus 5-mg atorvastatin on thoracic and abdominal plaques and the association between plaque progression and on-treatment LDL-cholesterol levels in 36 hypercholesterolemia patients. MRI was performed at baseline and 1 and 2 years of treatment. Vessel wall area change was evaluated. Results The 20-mg dose markedly reduced LDL-cholesterol levels (−47%) versus 5-mg (−35%) dose. After 2 years of treatment, regression of thoracic plaques was found in the 20-mg group (−15% vessel wall area reduction), but not in the 5-mg group (+7%). Although the 20-mg dose induced plaque regression (−14%) from baseline to 1 year, no further regression was seen from 1 to 2 years of treatment (−1%). Regarding abdominal plaques, progression was found in the 5-mg group (+10%), but not in the 20-mg group (+2%). Plaque progression in the 5-mg group was found from baseline to 1 year (+8%), but not from 1 to 2 years (+2%). The degree of thoracic plaque regression correlated with LDL-cholesterol reduction (r = 0.61), whereas thoracic plaque change from 1 to 2 years correlated with on-treatment LDL-cholesterol levels (r = 0.64). Conclusion Twenty milligrams of atorvastatin regressed thoracic plaques. However, maintaining low LDL-cholesterol levels was needed to prevent plaque progression. In abdominal aorta, only retardation of plaque progression was found after 2 years of 20-mg treatment. Eur J Cardiovasc Prev Rehabil 16:222-228

A Possible Association Between Coronary Plaque Instability and Complex Plaques in Abdominal Aorta

Objective—Coronary plaque instability causes myocardial infarction (MI). Angiographic lesions with such instability are complex lesions. Complex carotid plaques were reported to be prevalent in unstable angina. We investigated associations between coronary plaque instability, such as MI and angiographic complex coronary lesions, and aortic plaques. Methods and Results—Aortic MRI was performed in 146 patients undergoing coronary angiography, of whom 108 had coronary artery disease (CAD) and 44 also had MI. Prevalence of plaques in thoracic and abdominal aortas was higher in patients with than without CAD (73% and 94% versus 32% and 79%), but it was similar in CAD patients with and without MI. Notably, complex plaques in abdominal aorta were more prevalent in CAD patients with than without MI (36% versus 14%; P<0.025). In multivariate analysis, abdominal complex plaques were associated with MI (odds ratio [OR], 4.5; 95% CI, 1.5 to 13.8). Among patients without MI, thoracic and abdominal complex plaques were more prevalent in patients with than without complex coronary lesions (22% and 33% versus 2% and 7%; P<0.05). Abdominal complex plaques were also associated with complex coronary lesions (OR, 9.8; 95% CI, 1.1 to 85.9). Conclusion—Complex plaques in abdominal aorta were associated with MI and complex coronary lesions, suggesting a link between coronary and aortic plaque instability.

Associations between serum lipoprotein(a) levels and the severity of coronary and aortic atherosclerosis

To elucidate the associations between Lp(a) levels and coronary and aortic atherosclerosis, we performed aortic MRI in 143 patients undergoing coronary angiography. Severity of aortic atherosclerosis was represented as plaque scores. Of the 143 patients, 104 had coronary artery disease (CAD). Thoracic and abdominal aortic plaques were found in 89 and 131 patients. Lp(a) levels increased stepwise with the number of stenotic coronary vessels: 15.7 (CAD(-)), 21.2 (1-vessel), 21.4 (2-vessel), and 22.9 mg/dl (3-vessel) (P<0.05). For aortic atherosclerosis, 143 patients were divided into quartiles by plaque scores. Lp(a) did not differ among quartiles of thoracic plaques: 17.1, 19.0, 23.5, and 21.2 mg/dl (P=NS), whereas Lp(a) increased stepwise with quartiles of abdominal plaques: 17.1, 19.2, 19.1, and 24.0 mg/dl (P<0.05). Lp(a) was an independent factor for CAD and abdominal aortic plaques, but not thoracic plaques. Thus, Lp(a) levels were associated with aortic atherosclerosis, especially in abdominal aorta, as well as coronary atherosclerosis.

Associations between plasma osteopontin levels and the severities of coronary and aortic atherosclerosis

High levels of osteopontin (OPN) mRNA and proteins were reported in atherosclerotic plaques [1–3]. OPN-overexpressing transgenic mice developed marked atherosclerotic lesions [4]. These suggest that OPN plays an important role in atherosclerosis. Regarding blood OPN levels, we reported plasma OPN levels to be higher in patients with coronary artery disease (CAD) than without CAD [5]. However, some overlap in OPN levels was found between patients with and without CAD. Since atherosclerotic process is a generalized process that may involve the entire vasculature, we hypothesized that plasma OPN levels may reflect not only coronary atherosclerosis but also atherosclerosis in other vascular beds.

Effect of Atorvastatin on Plasma Osteopontin Levels in Patients With Hypercholesterolemia

To the Editor High levels of osteopontin (OPN) mRNA and proteins were reported in atherosclerotic plaques.1,2 OPN-transgenic mice developed marked atherosclerosis.3 We reported plasma OPN levels to be high in patients with coronary artery disease (CAD) and to correlate with the severity of CAD.4 We also reported high plasma levels of OPN in patients with restenosis.5 These suggest that OPN plays a role in the development of atherosclerosis. In vitro, Takemoto et al6 demonstrated statins to reduce OPN mRNA in cultured aortic smooth muscle cells and upregulated OPN mRNA in aorta of diabetic rats. We investigated the effects of 20 mg/d versus 5 mg/d atorvastatin on plasma OPN levels in 40 hypercholesterolemic patients without any history of cardiovascular disease. Our study was approved by institutional ethics committee. If patients were taking statins, these were discontinued. After 4-week washout period, fasting blood samples were taken after informed consent was obtained. If LDL-cholesterol >150 mg/dL, patients …

The LDL-cholesterol to HDL-cholesterol ratio and the severity of coronary and aortic atherosclerosis

The LDL-cholesterol to HDL-cholesterol (LDL/HDL-cholesterol) atio is recognized as a stronger risk predictor of cardiovascuar diseases than LDL-cholesterol and HDL-cholesterol levels [1,2]. he close correlation between the LDL/HDL-cholesterol ratio and he severity of coronary artery stenosis is also reported [3]. Howver, the association between the LDL/HDL-cholesterol ratio and ortic atherosclerosis has not been elucidated yet. Magnetic resoance imaging (MRI) is a useful tool for non-invasively evaluating therosclerotic plaques in both the thoracic and abdominal aorta 4–7]. Regarding this MRI method, we [8] and others [9] showed ood correlations for the aortic plaque extent between the in vivo nd ex vivo MRI findings and histopathology in animal models. In umans, we reported that MRI evaluations of the thoracic aorta losely correlated with TEE findings [6]. To elucidate the associations between thoracic and abdomnal aortic atherosclerosis and the LDL/HDL-cholesterol ratio as ell as LDLand HDL-cholesterol levels, we performed aortic MRI n 159 patients undergoing coronary angiography for suspected r known coronary artery disease (CAD). Since 64 patients who ere taking lipid-lowering drugs were excluded, our study patients onsist of 95 patients not taking lipid-lowering drugs. Our study as approved by the institutional ethics committee. After writen informed consent was obtained, fasting blood samples were aken from all patients. Plasma LDL-cholesterol levels were meaured by the direct enzymatic method (Cholestest LDL, Daiichi Pure hemicals). Aortic MRI was performed on the Signa 1.5T Cvi scanner (GE edical Systems). The transverse proton density-weighted and T2eighted images of the thoracic descending and abdominal aorta ere obtained using a double-inversion-recovery FSE sequence: R = 2 RR intervals, TE = 10 ms (PDW) and 60 ms (T2W), 20-cm FOV, -mm slice thickness, and 8-mm inter-slice gap. As in our previous tudies [4,5], 9 slices of the thoracic aorta and 9 slices of the abdomnal aorta were obtained at 12-mm intervals, which each covered bout a 10-cm portion of the thoracic aorta and a 10-cm portion of he abdominal aorta. The extent of plaque in each slice was scored as –4 points by the percentage of luminal surface involved by plaque. he severity of aortic atherosclerosis was represented as the sum f scores. The plaque extents were all evaluated by two observers, nd any discrepancy was resolved by consensus. The intra-observer nd inter-observer agreement for the assessment of plaque extents as 98% and 92% of slices, respectively [4]. On coronary angiogram, he degree of stenosis was evaluated by 5 grades (≤25%, 26–50%,

1038 Magnetic resonance evaluation of the associations of thoracic and abdominal aortic plaques with the presense and extent of coronary artery stenosis

The association between coronary artery disease (CAD) and thoracic aortic plaques has often been reported using transesophageal echocardiography. However, studies showing the association between CAD and abdominal aortic plaques are scarce. CMR can visualize plaques in both the thoracic and abdominal aortas. Using CMR, we investigated the associations of thoracic and abdominal aortic plaques with the presence and extent of coronary artery stenosis in 146 patients undergoing coronary angiography, of whom 108 had CAD. The prevalence of thoracic and abdominal aortic plaques was higher in patients with CAD than in those without CAD (73% and 94% vs. 32% and 79%, p 50% and > 25% stenotic coronary segments (rs = 0.30 and 0.41). Plaque extent in the abdominal aorta also correlated with ...