Publications (6)7.37 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: The presence of hypertension and hyperlipidemia accelerates atherosclerosis and increases the risk of ocular disease. Since there were few rat models for atherosclerosis, spontaneously hypertensive rats (SHRs) and spontaneously hyperlipidemic rats (HLRs) were crossbred to obtain a new model: the spontaneously hypertensive hyperlipidemic rat (SHHR). Matrix metalloproteinases (MMPs) play an important role in ocular degeneration. The purpose of this study is to investigate changes in the MMP activities in vitreous and plasma as well as MMP expression in the retinas of SHHRs, which served as a model of vascular degeneration. We used 8-month-old Wistar-Kyoto (WKY) rats and Sprague-Dawley (SD) rats, SHRs, HLRs, and SHHRs. The MMP-2 and MMP-9 activities in plasma and vitreous were examined by zymography. The mRNA expression of MMP-2, MMP-9, and tissue inhibitor of metalloproteinases-3 (TIMP-3) in retina was examined by quantitative PCR. The localized expression of MMP-9 in the retinas was examined by immunostaining. The MMP-9 activity increased significantly in SHHRs compared with all other rats. MMP-9 was observed mainly at the superficial layer of the retina on immunostaining. The MMP-2, MMP-9, and TIMP-3 mRNA in retina was not significantly different in SHHRs as compared with all other rats. Increased MMP-9 activity in vitreous was influenced more intensely from plasma than retina because there was no change in MMP-9 expression in retina, and MMP-9 immunostaining was observed mainly at the surface of the retina, where blood vessels are present. In this study, the complications of hypertension and hyperlipidemia induced increased MMP-9 activity in vitreous and plasma. It is therefore suggested that MMP-9 may be involved in causing this result and in the development of retinal disease.
- [Show abstract] [Hide abstract] ABSTRACT: Atherosclerosis is accelerated when it occurs concomitantly with hypertension and hyperlpidemia. We derived a spontaneously hypertensive hyperlipidemic rat (SHHR) by cross-breeding. SHHR represents a good model of vascular degeneration, particularly when the rats are fed a high-fat diet supplemented with a sucrose solution (SHHR-HFDS) . Matrix metalloproteinases (MMPs) and the tissue inhibitor of metalloproteinases (TIMPs) play important roles in atherosclerosis. Peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists (thiazolidinediones), such as pioglitazone, decrease plasma MMP-9 expression in type 2 diabetic patients. However, the effects of pioglitazone on MMP-9 and TIMP-1 in atherosclerosis without diabetes are not clear. We investigated the effects of pioglitazone on the activities of MMP-9 and TIMP-1 in the plasma of SHHR-HFDS. Male SHHRs were fed a normal diet for 4 months, and then administered NG-nitro-L-arginine methyl ester (L-NAME) for 1 month, followed by a high-fat diet (2% cholesterol, 1% cholic acid, 5% coconut oil) and a 15% sucrose solution ad libitum for an additional 2 months. Pioglitazone (3 or 10 mg/kg/day subcutaneously) was co-administered with HFDS for 2 months. Aortic lipid deposition increased clearly in the SHHR-HFDS group at 7 months of age. Pioglitazone decreased aortic lipid deposition and plasma MMP-9 activity, but increased plasma TIMP-1 activity in the SHHR-HFDS group, as compared with the non-treated SHHR-HFDS group. These results suggest that pioglitazone decreases lipid deposition partly by modulating MMP-9 and TIMP-1 activities.
- [Show abstract] [Hide abstract] ABSTRACT: The 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) are considered first-line therapeutic agents for the prevention of coronary heart disease and atherosclerotic disorders related to hypercholesterolemia. Statins inhibit lipid deposition in the aortic endothelium. Although it has been accepted that the statins are potent inhibitors of cholesterol biosynthesis in the liver and that they lower circulating cholesterol levels, several cholesterol-independent (pleiotropic) effects have been reported. The cholesterol-independent effects of statins involve normalization of the nitric oxide (NO)-NO synthase system, anti-inflammatory effects through the inhibition of cytokine/chemokine production, inhibition of vascular smooth muscle cell proliferation and migration, and inhibition of platelet thrombus formation/reduction of the thrombotic response. Some pleiotropic effects of statins may depend on the inhibition of the biosynthesis of farnesyl- and geranylgeranyl-nonsterol compounds from mevalonate in the cells. The Rho/Rho kinase pathway and the phospatidylinositol-3 kinase/Akt pathway mediate the pleiotropic effects of statins. As variations occur in absorption, metabolism, and excretion mechanisms due to the characteristics of specific statins including their hydrophilicity and lipophilicity, there are differences in the transfer mechanisms of statins into tissues. However, the pleiotropic effects occur regardless of statin hydrophilicity and lipophilicity. This review summarizes the pleiotropic effects of statins on lipid deposition in blood vessels.
- [Show abstract] [Hide abstract] ABSTRACT: Since the rat is an atherosclerosis-resistant species, the study of atherosclerosis using rats is limited. The present study was undertaken to develop an atherosclerotic model in rats, to investigate the effect of nitric oxide (NO) inactivation and hyperlipidemia, and to evaluate the effect of pitavastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) inhibitor, on NO inactivation and on hyperlipidemia-induced changes in the cardiovascular system. Four-month-old male spontaneously hypertensive hyperlipidemic rats (SHHR) and Sprague-Dawley (SD) rats were used to study 1) the effect of the period of treatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/L) on high fat diet (HFD)-treated SHHR and SD rats, and 2) the effect of pitavastatin (Pit, 0.3 mg/kg/day) on the changes in the aorta of L-NAME- and HFD-treated SHHR and SD rats. L-NAME administration for 1 month then HFD feeding for 2 months markedly increased the deposition of lipids and the thickness of the endothelium in SHHR. Continuous L-NAME treatment with HFD produced severe injury and stripped of endothelium in both strains. The plasma total cholesterol of L-NAME + HFD-treated and L-NAME + HFD + Pit-treated SHHR was significantly higher than that of control SHHR. Lipid deposition, however, was comparatively less in the aorta of L-NAME + HFD + Pit-treated SHHR. The concentration of cholesterol in the aorta of control SHHR was significantly lower than that in the aorta of L-NAME + HFD-treated SHHR, whereas that of L-NAME + HFD + Pit-treated SHHR was the same as that in control SHHR. These data indicated that Pit blocked lipid deposition in the aorta of L-NAME + HFD treated SHHR without changing plasma lipid profiles. In conclusion, NO inactivation and HFD induce lipid deposition in the endothelium, and the HMG-CoA reductase inhibitor blocks the deposition in SHHR.
- [Show abstract] [Hide abstract] ABSTRACT: 1. To develop and characterize a new animal model of hypertension and hyperlipidaemia, we cross-bred spontaneously hypertensive rats (SHR) with spontaneously hyperlipidaemic rats (HLR). 2. A new strain of spontaneously hypertensive hyperlipidaemic rats (SHHR) was established at generation 10 through selective mating of brothers and sisters (systolic blood pressure > 150 mmHg, plasma cholesterol > 150 mg/dL). Cross-bred Wistar-Kyoto (WKY) rats and Sprague-Dawley (SD) rats (SDWKY rats) were used as a control. 3. Adrenaline and noradrenaline levels in the plasma and adrenal medulla of male SHHR were significantly higher than those of male SDWKY rats. The tyrosine hydroxylase activity in the adrenal medulla of male SHHR was significantly higher than that of male SDWKY rats. Low-density lipoprotein expression was found in the plasma of male and female SHHR and HLR. Cholesterol 7α-hydroxylase mRNA expression in the liver of male SHHR was lower than that of male SDWKY rats. Endothelium lesions and lipid deposition under the endothelium were observed in the aorta of 24-month-old SHHR, especially female SHHR, but not in age-matched HLR and SDWKY rats. 4. The hypertension of this new animal model of hypertension and hyperlipidaemia may be related to increased catecholamine activity and the hyperlipidaemia may be related to changes in the expression of cholesterol 7α-hydroxylase mRNA and lipoprotein profiles. The SHHR may be valuable in the study of mechanisms of atherosclerosis and the evaluation of anti-atherosclerosis drugs as a new strain of cardiovascular disease.
St. Marianna University School of Medicine
Kawasaki Si, Kanagawa, Japan
- Department of Pathology