Hiroyasu Uzui

Rationale for the role of osteoclast-like cells in arterial calcification

Atherosclerotic arteries frequently become calcified, and these calcium deposits are associated with a high risk of adverse clinical events. Descriptive studies suggest calcification is an organized and regulated process with many similarities to osteogenesis, yet the mechanism and its relationship to atherosclerosis remain largely unknown. In bone development and homeostasis, mineral deposition by osteoblasts and mineral resorption by osteoclasts are delicately balanced such that there is no overall gain or loss in bone mass. We hypothesize that there exists in arteries a mechanism that similarly balances mineral deposition with resorption. We propose that the cellular mediators of arterial mineral resorption are osteoclast‐like cells (OLCs) derived from hematopoietic precursors of the mononuclear phagocytic lineage. In arterial microenvironments, mononuclear precursors are induced to differentiate toward OLCs by macrophage‐colony stimulating factor and receptor activator of NF‐κB ligand, both of which are necessary and sufficient for osteoclastogenesis and mineral resorption in bone. OLCs may participate in normal mineral homeostasis within the arterial wall or, alternatively, may be recruited to specific sites within developing plaque. Net calcium deposition occurs as a result of focal perturbation of the balance between the activity of osteoblast‐like cells and OLCs. Our proposed mechanism thus views arterial mineral deposition not so much as an active pathological process, but as a localized failure of protective mechanisms that actively oppose mineral deposition within the disordered metabolic milieu of developing atherosclerotic plaque.—Doherty, T. M., Uzui, H., Fitzpatrick, L. A., Tripathi, P. V., Dunstan, C. R., Asotra, K., Rajavashisth, T. B. Rationale for the role of osteoclast‐like cells in arterial calcification. FASEB J. 16, 577–582 (2002)

The role of protein-tyrosine phosphorylation and gelatinase production in the migration and proliferation of smooth muscle cells.

BACKGROUND It has been reported that matrix metalloproteinase (MMP) was expressed in coronary arterial atherosclerotic lesions. However, not much is known about the relationship between the production of MMP and the progression of atherosclerosis. PURPOSE AND METHOD To demonstrate the association between the protein-tyrosine phosphorylation (PTP) and the activation of extracellular MMP in the proliferation and migration of vascular smooth muscle cells (VSMCs), the effect of platelet-derived growth factor (PDGF) and vanadate (an inhibitor of protein-tyrosine phosphatase and an activator of certain protein-tyrosine kinases) on mitogenesis ([3H]thymidine incorporation after 24 hours), migration, PTP (Western blot analysis using anti-phosphotyrosine antibodies), and production of MMP (gelatin zymography) was examined in cultured VSMCs. RESULTS Both vanadate (1-5 micromol/l) and PDGF (1-10 ng/ml) caused a dose-dependent increase in thymidine incorporation and migration and produced 72-kDa type IV gelatinase (MMP-2) in VSMCs. The combination of vanadate and PDGF resulted in a dose-dependent synergistic effect on thymidine incorporation and MMP-2 production. Western blot analysis revealed that PDGF caused an increase in PTP, extracellular signal-regulated kinases (ERK1, ERK2) and PDGF receptor in VSMCs. Vanadate given together with PDGF induced a marked increase in the intensity of tyrosine phosphorylation in these proteins. Tyrosine kinase inhibitors (genistein and herbimycin A) and a synthetic inhibitor of MMP (1,10-phenanthroline) and an anti-MMP-2 neutralizing antibody inhibited the mitogenic effect induced by vanadate and/or PDGF. CONCLUSIONS The data suggest that the proliferation and migration of cultured VSMCs was closely related to the stimulation of MMP-2 production that was induced through activation of PTK.

Circulating matrix metalloproteinase-2 is elevated in patients with congestive heart failure.

It has been reported that matrix metalloproteinase (MMP) protein concentration and activity are upregulated in the failing human heart. However, there are few reports describing the role of elevated level of circulating MMPs in congestive heart failure (CHF) patients. This study examined whether circulating matrix metalloproteinases (MMPs) are also related to the pathogenesis of CHF.

Therapeutic developments in matrix metalloproteinase inhibition

A family of zinc-dependent endopeptidases called matrix metalloproteinases (MMPs) have the capacity to degrade all elements of the extracellular matrix (ECM) and are required for homeostatic maintenance of the ECM. However, interest in MMPs predominantly arises from the accumulating evidence implicating that dysregulated MMP expression plays a role in mediating or accompanying a diverse array of pathologies. These include tumour invasion and metastasis and inflammatory diseases characterised by excessive tissue destruction, such as arthritis, periodontal disease, atherosclerosis, plaque rupture, arterial aneurysms, postmyocardial infarction, ventricular remodelling and cardiac rupture. Several patents representing therapeutic drugs and strategies to treat the associated conditions have been claimed, some resulting in clinical drug trials. This review will: i) summarise the current status of our understanding of MMPs and how they participate in normal and functional ECM degradation; ii) review therapeutic efforts to favourably alter the balance between MMP proteolysis and ECM sythesis; and iii) critically evaluate recent studies that have importantly advanced our understanding of the complexities of MMP function and propose areas where future efforts to develop therapeutic strategies might be most beneficial and productive.

Outcomes of everolimus-eluting stent incomplete stent apposition: a serial optical coherence tomography analysis.

AIM The aim of the present study was to evaluate the natural course of acute incomplete stent apposition (ISA) after second-generation everolimus-eluting stent (EES) when compared with first-generation sirolimus-eluting stent (SES) by using optical coherence tomography (OCT). METHODS AND RESULTS From the OCT substudy of the RESET trial, we identified 77 patients (EES = 38 and SES = 39) who successfully underwent serial OCT examination at post-stenting and 8-12-month follow-up. The presence of ISA was assessed in the OCT images, and ISA distance was measured from the centre of the strut blooming to the adjacent lumen border. Incomplete stent apposition was observed in all EES and SES at post-stenting, and it was persistent in 26% of EES and 38% of SES at 8-12-month follow-up. Maximum ISA distance was significantly decreased during the follow-up period in both EES (315 ± 94-110 ± 165 μm, P < 0.001) and SES (308 ± 119-143 ± 195 μm, P < 0.001). Receiver-operating curve analysis identified that the best cut-off value of OCT-estimated ISA distance at post-stenting for predicting late-persistent ISA at 8-12-month follow-up in EES and SES was >355 and >285 μm, respectively. CONCLUSIONS The second-generation EES showed better healing of acute ISA in comparison with the first-generation SES. Optical coherence tomography can predict late-persistent ISA after DES implantation and provide useful information to optimize PCI.

Different effects of calcium channel blockers on matrix metalloproteinase-2 expression in cultured rat cardiac fibroblasts.

The cardiac effects of calcium channel blockers (CCBs) related to cardiac remodeling are inconsistent. Matrix metalloproteinases (MMPs) contribute to tissue remodeling. Cardiac fibroblasts play an important role in the regulation of collagen degradation by MMPs. Using gelatin zymography, Western blotting, Griess reagent, and a calcium kit-fluo 3, we investigated the effects of nifedipine, verapamil, diltiazem, and amlodipine on MMP-2 expression and further elucidate the mechanisms in cultured rat cardiac fibroblasts. Nifedipine increased and amlodipine decreased the expression of MMP-2; however, neither verapamil nor diltiazem altered MMP-2 expression. Nifedipine also increased nitrite production, and this increase was blunted by a nitric oxide (NO) synthases inhibitor (L-NAME). Nifedipine-induced MMP-2 expression was also blunted by L-NAME. An NO donor (sodium nitroprusside) induced MMP-2 expression. Data indicated that nifedipine might increase MMP-2 expression through a possible NO-dependent pathway. Amlodipine had no influence on nitrite production. The amlodipine-induced decrease of MMP-2 expression was abolished by two protein tyrosine kinase inhibitors, genistein and herbimycin A, indicating that amlodipine might decrease MMP-2 expression through a possible protein tyrosine kinase pathway. None of the four CCBs could alter the fluoscence intensity of fluo 3, indicating that the effects of CCBs on MMP-2 expression were independent of the variation in intracellular Ca2+ concentration. Our findings revealed that different CCBs exerted different effects on MMP-2 expression in cardiac fibroblasts.

Mitochondrials complex I activity is reduced in latent adriamycin-induced cardiomyopathy of rat

We previously reported on the use of enzymatic analysis to impair fatty acid metabolism followed by reduced myocardial energy content, leading to severe heart failure in adriamycin (ADR)-treated rats. The aim of this study is to investigate whether impaired myocardial energy metabolism can also be detected by other methods; i.e. measuring mitochondrial complex I activity and myocardial 125I-15-(p-iodophenyl)-3-(R,S)- methylpentadecanoic acid (BMIPP) accumulation in ADR-treated rats. Eight-week-old male Sprague-Dawley rats received 6 intraperitoneal injections of ADR (total 15 mg/kg: group ADR) or saline (control group) over 2 weeks. Left ventricular (LV) ejection fraction was assessed using echocardiography at 3- and 6-weeks after ADR injection (3 weeks and 6 weeks, respectively). Myocardial fatty acid utilization was assessed at 3 weeks and 6 weeks. The myocardial counts of BMIPP were measured after intravenous BMIPP (370 kBq) injection, and 125I counts were measured to calculate the uptake ratio. The enzymatic activity of complex I was assessed by monitoring the oxidation of nicotinamide-adenine-dinucleotide-disodium-salt (NADH). In rats treated with ADR, significant decrease in LV ejection fraction was observed only at 6 weeks compared to control (72.5 vs. 84.5%, p < 0.01rpar;. LV ejection fraction at 3 weeks was identical between group ADR and control (81.8 vs. 84.4%). However, at 3 weeks, complex I activity was already reduced significantly in group ADR as compared to control group (p = 0.03), but the reduction in BMIPP accumulation was not (p = 0.15). Our data indicated that reduced complex I activity in a phenomenon occurred in early phase of ADR-induced cardiomyopathy, and it might play an important role in the progression of ADR-induced heart failure.

Nitric Oxide Synthase Activity in Peripheral Polymorphonuclear Leukocytes in Patients With Chronic Congestive Heart Failure

Increased activity of inducible nitric oxide synthase (NOS) has been found in cardiac tissue and in skeletal muscle from patients with chronic congestive heart failure (CHF). There have been few reports investigating NOS activity in other organs or in peripheral blood cells from patients with chronic CHF. To examine whether NOS activities in peripheral polymorphonuclear leukocytes (PML) are increased in patients with chronic CHF and to determine whether a correlation exists between disease severity and NOS activity in PML of patients with chronic CHF, we assessed the levels of NOS activity in PML by measuring the capacity of isolated PML to convert 3H-L-arginine to 3H-L-citrullin in 70 Japanese patients with chronic CHF and in 24 age-matched healthy volunteers. The levels of NOS activity in PML were significantly greater in patients with chronic CHF than in healthy volunteers (18.0 +/- 0.6% vs 11.5 +/- 0.3%, p <0.01). NOS activity in PML was increased with the severity of New York Heart Association functional class. Among the various neurohumonal factors, the plasma levels of interleukin-6, atrial natriuretic peptide, and norepinephrine showed independent and significant positive relations with levels of NOS activity in PML. Thus, we demonstrated that NOS activity in PML was elevated in patients with chronic CHF in relation to the severity of heart failure, circulating proinflammatory cytokines, and neurohormonal factors.

Effects of magnesium on the production of extracellular matrix metalloproteinases in cultured rat vascular smooth muscle cells

The precise correlation between magnesium and cardiovascular disease remains to be established. Matrix metalloproteinases (MMPs) are expressed in coronary arterial atherosclerotic lesions. MMP production in vascular smooth muscle cells (VSMCs) is stimulated by growth factors such as platelet-derived growth factor (PDGF). To assess the association between magnesium and MMPs, we examined the effects of different extracellular magnesium concentrations (0-3.0 mmol/l) on MMPs production in cultured rat VSMCs under basal and PDGF-stimulated conditions using gelatin zymography and western blotting. As magnesium is called a natural calcium antagonist, we further compared the effects of magnesium with some calcium antagonists. Magnesium reduced MMP-2 production dose-dependently at basal and PDGF-stimulated conditions in VSMCs. However, neither verapamil nor nifedipine influenced MMP-2 production under any conditions examined. The effect of magnesium on the production of MMP-2 was inhibited by two tyrosine kinase inhibitors-genistein and herbimycin A. The results of this study indicate that extracellularly added magnesium decreased MMPs secretion, which appears to be associated with protein tyrosine kinase.

Acarbose treatments improve arterial stiffness in patients with type 2 diabetes mellitus.

Aims/Introduction:  Although the improvement of postprandial hyperglycemia by an alpha‐glucosidase inhibitor (α‐GI) has been associated with a risk reduction of cardiovascular events, the relationship between postprandial hyperglycemia and arterial stiffness has not been well understood. We therefore examined whether ameliorating the postprandial state by α‐GI leads to an improvement in arterial stiffness.