Fumitaka Ohsuzu

Osteopontin Plays an Important Role in the Development of Medial Thickening and Neointimal Formation

Osteopontin (OPN) is a soluble secreted phosphoprotein that binds with high affinity to several integrins and it has been found at the site of atherosclerotic lesions. However, the role of OPN expression in vivo is still poorly understood. To investigate the physiological role of OPN in detail, we generated transgenic mice (Tg) overexpressing the OPN gene under control of the cytomegalovirus enhancer/chicken &bgr;-actin promoter. We detected OPN mRNAs in almost all tissues of 3 lines of Tg mice by Northern blotting. The serum levels of OPN were significantly higher in Tg than in non-Tg mice (782±107 versus 182±44 ng/mL;P <0.001). Compared with non-Tg mice, a 73% (88±6 versus 51±7 &mgr;m;P <0.001) and 94% (126±15 versus 73±11 &mgr;m;P <0.0001) increase in the medial thickness of the aorta was determined in Tg mice at 16 and 32 weeks after birth. However, we found no evidence of inflammatory cells adhering to endothelial cells, intimal hyperplasia, or calcification in any region of Tg mice without artery injury. We then investigated the effect of cuff-induced injury to the femoral artery. The intimal thickening in Tg mice increased 2.9-fold more than that in non-Tg mice (4.9±1.9 versus 1.7±0.4 &mgr;m;P =0.022). The expression of OPN induces both medial thickening without injury and neointimal formation after injury, thus suggesting that OPN plays a role in the development of atherosclerosis, vascular remodeling, and restenosis after angioplasty in vivo.

Suppression of NF-kappaB-dependent gene expression by a hexamethylene bisacetamide-inducible protein HEXIM1 in human vascular smooth muscle cells.

Background: Neointima formation is a characteristic feature of atherosclerosis and post‐angioplasty restenosis, in which various soluble factors and mechanical injury stimulate signalling pathways in vascular smooth muscle cells (VSMC), promoting their migration and proliferation, and the eventual formation of the neointima. The transcription factor NF‐κB has been shown to play a pivotal role in this process. Hexamethylene bisacetamide, an inhibitor of VSMC proliferation, induces the mRNA expression of HEXIM1 (hexamethylene bisacetamide‐inducible protein 1). However, the protein expression and function of HEXIM1 remain unknown.

Impaired Endothelium-Dependent Vasodilation in the Brachial Artery in Variant Angina Pectoris and the Effect of Intravenous Administration of Vitamin C

UNLABELLED Endothelial dysfunction in the coronary artery contributes to the pathogenesis of variant angina, and endothelial dysfunction in variant angina may be associated with increased oxidant stress in the systemic arteries. We investigated whether endothelial dysfunction exists in the peripheral artery in patients with variant angina, and also examined the effect of vitamin C, an antioxidant, on endothelium-dependent vasodilation. Using high-resolution ultrasound, both the flow-mediated vasodilation (FMD, endothelium-dependent vasodilation) and sublingual nitroglycerin-induced vasodilation (NTG-D, endothelium-independent vasodilation) in the brachial artery were measured in 28 patients with variant angina and 24 control subjects who had normal coronary arteries. FMD was significantly impaired in patients with variant angina compared with control subjects (1.8 +/- 2.2% vs 6.4 +/- 4.9%, p <0.001). FMD and NTG-D before and after intravenous administration of either vitamin C or placebo were measured in 17 patients with variant angina. FMD significantly improved after the administration of vitamin C (from 2.2 +/- 2.4% to 4.5 +/- 1.6%, p <0.01), but not after administration of the placebo (from 2.0 +/- 2.6% to 1.7 +/- 1.9%). The improved FMD due to vitamin C in patients with variant angina, however, was not significantly different from that in the control subjects. NTG-D was not significantly different between patients with variant angina and control subjects (14.0 +/- 7.8% vs 13.6 +/- 5.0%) and it was also not affected by vitamin C. IN CONCLUSION (1) FMD in the brachial artery is impaired in patients with variant angina, and (2) the acute administration of the antioxidant, vitamin C, was observed to reverse this endothelial dysfunction. These findings support the theory that the systemic inactivation of nitric oxide due to oxidative stress might exist in patients with variant angina.

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.

Involvement of Tumor Necrosis Factor-α in the Development of T Cell–Dependent Aortitis in Interleukin-1 Receptor Antagonist–Deficient Mice

Background—Interleukin-1 receptor antagonist–deficient (IL-1Ra−/−) mice on the BALB/c background spontaneously develop inflammatory arthropathy that resembles rheumatoid arthritis in humans. These mice also frequently develop aortitis at the root of the aorta, but the mechanism underlying the development of this disease has not been completely elucidated. Methods and Results—Using IL-1Ra−/− mice (backcrossed 8 generations to the BALB/c background) and wild-type mice, we studied the histopathology and examined the immunologic mechanisms involved in the development of aortic inflammation by cell transplantation experiments. Half of the IL-1Ra−/− mice developed aortitis at the root of the aorta, with massive infiltration of macrophages and monocytes and loss of elastic lamellae in the aortic media. Left ventricular hypertrophy and mild aortic stenosis were also shown by transthoracic echocardiography. Transplantation of T cells from IL-1Ra−/− mice induced aortitis in recipient nu/nu mice. Bone marrow cell transplants from IL-1Ra−/− mice also induced aortitis in irradiated wild-type recipient mice. Furthermore, tumor necrosis factor (TNF)-&agr; deficiency completely suppressed the development of aortitis in IL-1Ra−/− mice, whereas IL-6 deficiency did not affect pathology. Conclusions—These observations suggest that IL-1Ra deficiency in T cells activates them excessively, resulting in the development of aortitis in IL-1Ra−/− mice in a TNF-&agr;–dependent manner.

Relation of segmental wall motion to global left ventricular function in acute myocardial infarction

The relation of left ventricular regional wall motion to global ventricular function was evaluated by radionuclide ventriculography in 127 patients within 18 hours of acute myocardial infarction. No patient had evidence of previous myocardial infarction. The following parameters were measured: (1) wall motion index; (2) percent of abnormally contracting segment; (3) ejection fraction (EF); (4) end-diastolic volume (EDV) and end-systolic volume (ESV); and (5) peak systolic cuff pressure/end-systolic volume ratio (PSP/ESV). The measurements of global function correlated well with wall motion index (r = 0.83, p less than 0.001 for EF; r = -0.69, p less than 0.001 for ESV; and r = 0.061, p less than 0.001 for PSP/ESV), but EDV correlated less well (r = -0.35, p less than 0.001). Multiple linear regression analysis revealed that EF correlated best with wall motion index, and no other parameters of global left ventricular function added significantly to the regression. The correlation of motion in each segment with EF was determined by multiple linear regression analysis. Ejection fraction correlated best with motion in the anterobasal, then in order of correlation, in the apical-septal, inferoapical, anterolateral, and superlateral walls. The relation of EDV, ESV, and degree of percent abnormally contracting segments was as follows: EDV did not increase with a mild regional wall motion abnormality; however, ESV did increase and reduced stroke volume. As percent abnormally contracting segments worsened, enlargement of both EDV and ESV was seen and was associated with further reduction in systolic volume. These data suggest that EF is the best global left ventricular function correlate of the severity of the regional wall motion abnormality, and that abnormal motion in the territory of the left anterior descending coronary best predicts reduction in global left ventricular function. Radionuclide ventriculography is useful in characterizing global and regional left ventricular function in the early hours of acute myocardial infarction.

Interleukin-1 and Occlusive Arterial Diseases

Interleukin (IL)-1 is a pro-inflammatory cytokine and a central mediator in the cytokine network, and is known to control important functions both in the immune system and inflammation. The activity of IL-1 is counter-regulated by its endogenous inhibitor, IL-1 receptor antagonist (IL-1Ra). IL-1 and IL-1Ra are produced and secreted by a variety of cells including those responsible for controlling immunity. A recent study indicated that IL-1 and IL-1Ra transcripts were expressed in the vessel wall, suggesting that these cytokines contribute to the development and progression of vascular diseases. In this review, we will discuss the recent advances in our understanding of the mechanism of action of IL-1 in occlusive arterial diseases such as neointimal hyperplasia and atherosclerosis, specifically in a mouse model.

Continuous inhibition of poly(ADP-ribose) polymerase does not reduce reperfusion injury in isolated rat heart.

Abstract: Poly(ADP-ribose) polymerase (PARP), an enzyme that is important to the regulation of nuclear function, is activated by DNA strand breakage. In massive DNA damage, PARP is overactivated, exhausting nicotinamide adenine dinucleotide and leading to cell death. Recent studies have succeeded in reducing cellular damage in ischemia/reperfusion by inhibiting PARP. However, PARP plays an important part in the DNA repair system, and its inhibition may be hazardous in certain situations. We compared the short-time inhibition of PARP against continuous inhibition during ischemia/reperfusion using isolated rat hearts. The hearts were reperfused after 21 minutes of ischemia with a bolus injection of 3-aminobenzamide (3-AB) (10 mg/kg) followed by continuous 3-AB infusion (50 &mgr;M) for the whole reperfusion period or for the first 6 minutes or without 3-AB. At the end of reperfusion, contractile function, high-energy phosphate content, nicotinamide adenine dinucleotide content, and infarcted area were significantly preserved in the 3-AB 6-minute group. In the 3-AB continuous group, these advantages were not apparent. At the end of reperfusion, PARP cleavage had significantly proceeded in the 3-AB continuous group, indicating initiation of the apoptotic cascade. Thus, continuous PARP inhibition by 3-AB does not reduce reperfusion injury in the isolated rat heart, which may be because of acceleration of apoptosis.

Primary myocardial lymphoma demonstrated by Tl-201, Tc-99m sestamibi, and Ga-67 SPECT.

A very uncommon case with primary myocardial lymphoma that was clearly depicted by Tl-201 and Tc-99m sestamibi and Ga-67 SPECT is presented. Accumulation in the lymphoma in order of intensity was Ga-67, redistribution Tl-201, stress Tl-201, and Tc-99m Sestamibi SPECT.

Whole-heart dipyridamole stress first-pass myocardial perfusion MRI for the detection of coronary artery disease with and without prior myocardial infarction

A whole-heart coverage MRI sequence, which employes a hybrid of fast gradient echo and echo planar acquisition imaging (FastCard EchoTrain), has recently been developed. Using this sequence, a first-pass myocardial perfusion MRI was shown to be a good noninvasive modality for detecting coronary artery disease (CAD) in a clinical setting. In addition, the clinical usefulness of delayed enhanced MRI has recently been reported. The objectives of this study were (1) to investigate the accuracy of dipyridamole stress first-pass myocardial perfusion MRI for diagnosing CAD (> 50% stenosis) and (2) to clarify whether additional delayed enhancement MRI has any clinical significance. We performed first-pass myocardial perfusion MRI in 102 consecutive patients (66 +/- 9 years old) suspected to have CAD or new lesions in patients with well-documented prior myocardial infarction (MI). Using a 1.5 T cardiac MR imager (GE CV/i), eight short axis MR images of the left ventricle were acquired by injecting gadolinium (0.1 mmol/kg) under dipyridamole infusion stress (0.56 mg/kg). Fifteen minutes later, aminophylline (250 mg) was injected and first-pass perfusion MRI was repeated in the resting state in order to evaluate both the presence of perfusion defect and delayed enhancement. The presence of perfusion defect and delayed enhancement was determined based on a visual qualitative analysis by the agreement of two separate readers who were blinded to any clinical information. Based on the stress and rest findings, no defect, reversible defect, or fixed defect with or without delayed enhancement was recorded in any patient. The MR findings revealed 76 CAD patients, including 24 MI patients with new lesions and 26 patients without CAD on coronary angiography. The presence of stress perfusion defect had a 93% sensitivity and an 85% specificity for diagnosing CAD. A fixed defect showed an 86% sensitivity and a 66% specificity for diagnosing a prior MI. Patients with a fixed defect with delayed enhancement had more significant stenosis in the infarct related artery than in those without any enhancement (11/26 vs 15/20, P < 0.05). Dipyridamole stress first-pass myocardial perfusion MRI using the FastCard EchoTrain was found to be a clinically useful and accurate modality for diagnosing CAD.