Angiotensinogen gene polymorphism as a risk factor for ischemic stroke.

While gene polymorphism for angiotensinogen (AGT) is reported to contribute to the regulation of blood pressure and salt sensitivity, its effect on the risk of ischemic stroke remains controversial. We hypothesized that polymorphism of the AGT gene could be a risk factor for ischemic stroke. Major clinical risk factors and the AGT gene M235T polymorphism were examined in 147 consecutive stroke patients and 133 healthy age-matched controls. All patients were categorized into four stroke types (single lacuna, multiple lacunae, large-artery atherosclerosis and branch atheromatous disease in brainstem) and two vascular groups (large and perforating arterial lesions). The AGT gene M allele significantly increased the risk of single lacuna, multiple lacunae and small arterial lesions, in male patients (p=0.029, 0.031 and 0.026, respectively). Synergistic effects of the AGT gene polymorphism and clinical risks were not observed. In conclusion, AGT M allele may present a risk of lacunar infarctions in Japanese men, independent of hypertension.

Low frequency regular exercise improves flow-mediated dilatation of subjects with mild hypertension.

Although exercise is recommended for the primary prevention of hypertension, and although it is generally known to have a beneficial effect on endothelial function, working individuals often find it difficult to maintain a consistent exercise regimen. In the present study, therefore, we examined the effects of infrequently performed exercise on flow-mediated dilatation (FMD), which is an index of endothelial function, in 15 subjects with hypertension (mild hypertensives) and 10 normotensive subjects (normotensives). All subjects performed mild bicycle exercise twice a week for 12 weeks. To assess the FMD, the diameter of the brachial artery was measured using ultrasound at baseline, during reactive hyperemia, and following sublingual administration of nitroglycerin. Measurement of these parameters was performed twice, at the beginning and the end of the exercise program. At the baseline, FMD was significantly lower in the mild hypertensives than in the normotensives. Nitroglycerin-mediated dilatation (NTG-D) was similar in the two groups. The exercise decreased blood pressure in the mild hypertensives, and increased high-density lipoprotein (HDL) cholesterol in both groups. The exercise improved FMD without altering NTG-D in the mild hypertensives, but did not result in any change in the normotensives. Multiple regression analysis revealed that the elevation in FMD was positively associated with changes in HDL cholesterol, and negatively associated with changes in plasma norepinephrine and systolic blood pressure. These findings suggest that regular exercise at a low frequency improves FMD, and thereby endothelial function, and lowers blood pressure in mild hypertensives.

HMG-CoA reductase inhibitor enhances inducible nitric oxide synthase expression in rat vascular smooth muscle cells; involvement of the Rho/Rho kinase pathway.

Little is known about the mechanism by which HMG-CoA reductase inhibitors affect inducible nitric oxide synthase (iNOS) expression. We investigated the effect of HMG-CoA reductase inhibitor cerivastatin on iNOS expression in cultured rat vascular smooth muscle cells (VSMCs). Quiescent VSMCs were incubated with or without various concentrations of drugs as follows: cerivastatin, C3 exoenzyme or Y-27632. Then, pretreated VSMCs were stimulated by a vehicle or interleukin (IL)-1beta (10 ng/ml). Treatment of VSMCs with cerivastatin (10(-7)-10(-5) mol/l), which inhibits isoprenylation of Rho and other small G proteins, significantly increased nitrite/nitrate (NOx) production and upregulated the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. This effect of cerivastatin was abolished by cotreatment with mevalonate (2x10(-4) mol/l) or geranylgeranyl-pyrophosphate (GGPP) (10(-5) mol/l), but not by farnesyl-pyrophosphate (10(-5) mol/l). Furthermore, C3 exoenzyme (50 microg/ml), an inactivator of Rho protein, and Rho kinase inhibitor Y-27632 (10(-5) mol/l) also enhanced NOx production and the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. Immunocytochemical study revealed that cerivastatin, C3 exoenzyme and Y-27632 did not affect the nuclear translocation of nuclear factor-kappaB in IL-1beta-stimulated VSMCs. Our study suggests that cerivastatin stimulates iNOS expression in IL-1beta treated VSMCs by its inhibitory effect on Rho/Rho kinase pathway. In addition, this effect of cerivastatin, by enhancing iNOS expression, may contribute to the prevention of restenosis after percutaneous coronary intervention and protect against atherothrombosis.

Effects of atorvastatin on oxidized low-density lipoprotein, low-density lipoprotein subfraction distribution, and remnant lipoprotein in patients with mixed hyperlipoproteinemia.

Atorvastatin (10 to 20 mg/day) was administered for 3 months to 15 outpatients (average age 58 +/- 4 years) with hypercholesterolemia accompanied by hypertriglyceridemia without hypolipemic treatment. Changes in lipid profile, particularly oxidized low-density lipoprotein (LDL) (malondialdehyde LDL), subfractions of LDL, and remnant lipoprotein (RLP) cholesterol, were examined before and after administration. In addition, the influence of atorvastatin on lipoprotein(a) (known to be an independent risk factor for atherosclerosis), asymmetric dimethylarginine (known to be an endogenous inhibitor of nitric oxide synthase), and homocysteine (methionine metabolite) was also investigated. Administration of atorvastatin significantly decreased serum total cholesterol, LDL cholesterol, and triglycerides. Conversely, a significant increase in high-density lipoprotein cholesterol was shown. In LDL subfractions, large, buoyant LDL fractions were not influenced by treatment with atorvastatin (before administration, 99 +/- 14 mg/dl; after administration, 91 +/- 6 mg/dl, shown as a cholesterol content in each subfraction), but a marked decrease in small, dense LDL fractions (p <0.001) (before administration, 119 +/- 17 mg/dl; after administration, 43 +/- 10 mg/dl) was shown. Moreover, oxidized LDL was significantly decreased (p < 0.01) (before administration, 169 +/- 13 U/L; after administration, 119 +/- 10 U/L) and RLP cholesterol also was significantly decreased (p <0.01) (before administration, 11.9 +/- 2.0 mg/dl; after administration, 6.0 +/- 0.9 mg/dl) with atorvastatin treatment. No significant change was observed in fasting plasma glucose, hemoglobin A1c, lipoprotein(a), asymmetric dimethylarginine, homocysteine, and so on. These data suggest that administration of relatively low doses of atorvastatin to patients with hypercholesterolemia accompanied with hypertriglyceridemia results in a decrease not only in LDL cholesterol and triglycerides, but also in oxidized LDL and RLP cholesterol, with an increase in high-density lipoprotein cholesterol. Furthermore, small, dense LDL decreased with a shift in LDL subfractions to large, buoyant fractions, and these changes are considered to be involved in the inhibition of the onset and progression of atherosclerosis.

Comparative effects of candesartan and enalapril on augmented vasoconstrictive responses to endothelin-1 in coronary vessels of spontaneously hypertensive rats.

BACKGROUND: The aim of this study was to compare the effect of angiotensin type-1 receptor blockade (ARB) on augmented vasoconstrictive response to endothelin-1 (ET-1) in coronary vessels of hypertensive hearts with angiotensin converting enzyme (ACE) inhibitor, candesartan cilexetil (CAN) or enalapril was administered for 3 weeks in spontaneously hypertensive rats (SHR). METHODS: We used SHR (9 to 12 weeks old, n = 18) and Wistar-Kyoto (WKY) rats (n = 6). Systolic blood pressure was measured once a week. Spontaneously hypertensive rats were divided into three groups. Enalapril malate (10 mg/day) or CAN (10 mg/day) was administered orally in each of six SHR in each group receiving treatment for 3 weeks. The control group (n = 6) received no treatment. At the end of this experiment, the hearts were isolated. Isolated hearts mounted on a Langendorff apparatus after weighing were then perfused with modified Krebs-Henseleit buffer at constant pressure (75 mm Hg). The coronary perfusion pressure and coronary flow were measured during perfusion of isolated hearts. Coronary vascular resistance (CVR; mm Hg/mL/min/100 g) was calculated. RESULTS: The ET-1 elicited increases in CVR dose-dependently in both normotensive and hypertensive rat hearts. However, the responses were significantly greater in SHR than in WKY rat. Chronic treatment with enalapril or candesartan inhibited the development of hypertension and cardiac hypertrophy equally in SHR. Augmented vasoconstrictive responses to ET-1 were significantly reduced in treated SHR. There was no difference in these effects between enalapril and candesartan. CONCLUSION: These findings suggest that both ACE inhibitors and ARB can equally inhibit augmented coronary vascular response to ET-1 in hypertensive hearts.

Effects of angiotensin II type 1 receptor antagonist on pressor responses to pulsatile compression of the rostral ventrolateral medulla in rats.

The rostral ventrolateral medulla (RVLM) is known to be a major center regulating sympathetic and cardiovascular activities. A possible association between neurovascular compression of the RVLM and essential hypertension has been indicated. The present study was performed to determine the role of angiotensin II (AngII) in the pressor and sympathetic responses to pulsatile compression of the RVLM. To determine the role of glutamate and AngII in the RVLM, L-glutamate (Glu) 2 nmol or AngII 100 pmol was injected into the RVLM with or without RVLM pretreatment of kynurenate (Glu receptor antagonist) 3nmol, candesartan (AngII type 1 (AT1) receptor antagonist) 2 nmol, or PD123319 (AngII type 2 (AT2) receptor antagonist) 1 nmol in anesthetized Wistar rats. In addition, to determine the role of glutamate and AngII in the pressor and sympathetic effects to the RVLM compression, kynurenate, candesartan, or PD123319 was locally injected before pulsatile compression of the RVLM. Finally, to determine the effects of peripherally administered AngII antagonists in these pressor and sympathetic excitatory responses, candesartan 0.25 micromol or PD123319 0.05 micromol was intravenously injected before pulsatile compression of the RVLM. Glu injected into the RVLM significantly increased mean arterial pressure (MAP) and splanchnic sympathetic nerve activity (SNA), and these effects were reduced by RVLM pretreatment with kynurenate, but were unaffected by candesartan or PD123319. AngII injected into the RVLM and pulsatile compression of the RVLM also increased MAP and SNA. However, in contrast with Glu injections, these effects were reduced by RVLM pretreatment with candesartan or kynurenate, but were unaffected by PD123319. Pressor and sympathetic excitatory responses to RVLM compression were reduced by intravenous pretreatment with candesartan but not with PD123319. These results indicate that, upon pulsatile compression of the RVLM, AngII may activate RVLM neurons via AT1 receptors and stimulate Glu release to thereby elicit sympathetic activation and pressor effects. Candesartan may exert its hypotensive effect at least in part by affecting the RVLM neurons to reduce sympathetic outflow induced by pulsatile compression of the RVLM.

Lowering of blood pressure improves endothelial dysfunction by increase of nitric oxide production in hypertensive rats.

To investigate the effects of angiotensin converting enzyme inhibitor (ACE-I) and other antihypertensive agents on the nitric oxide (NO) release during hypertension, seven- and fourteen-week-old SHR and deoxycorticosterone acetate (DOCA)-salt rats were treated with hydralazine, manidipine (Ca antagonist) or quinapril (ACE-I) for 3 weeks to lower blood pressure. Systolic blood pressure (SBP) was measured by the tail cuff method once each week. Endothelial cells (ECs) derived from the descending aorta of the treated rats were cultured and NOx levels in culture media were measured with an NO analyzer based on the Griess reaction. In both SHR and DOCA-salt rats, antihypertensive therapy lowered SBP to levels similar to those of control rats. The only exception was quinapril treatment of DOCA-salt rats. Although NOx release by ECs derived from hypertensive rats was improved by antihypertensive therapy, the effect was most pronounced in SHR treated with quinapril. In addition, restoration of NOx release was much more remarkable in younger SHR. NOx release was significantly higher in DOCA-salt rats treated with quinapril than in control rats without reduction of SBP. These results suggest that lowering blood pressure improves release of NO by ECs during hypertension and that the time at which antihypertensive therapy is started is also important to preserve endothelial function. Furthermore, ACE-I is suggested to protect endothelial function by increasing NO production in addition to lowering blood pressure.

Contrasting effects of angiotensin type 1 and 2 receptors on nitric oxide release under pressure.

This study was designed to test the hypothesis that increased pressure itself could cause endothelial dysfunction and lead to decreased nitric oxide (NO) release, partly through effects on the tissue renin angiotensin system in hypertension. Cultured endothelial cells (ECs) isolated from the aortas of WKY rats were continuously exposed to a pressure of 150 mmHg in a CO2 incubator for 72 h using a pressure system, and the NOx (NO2 and NO3) and angiotensin II (Ang II) concentrations in the supernatant were measured. An Ang II type 1 receptor (AT1R) antagonist (losartan) and an Ang II type 2 receptor (AT2R) antagonist (PD123319) were added to the medium. The expression of AT1R and AT2R mRNAs was also examined. Pressure loading significantly decreased the NO release from ECs. Concomitant administration of losartan restored NO release to the level before the application of pressure (p<0.001). This effect of losartan was blocked by simultaneous administration of PD123319, bradykinin type 2 receptor antagonist, and NO synthase inhibitor (p<0.05). The Ang II concentration was increased by pressure and was further increased by losartan. The gene expression of AT1R was not changed by pressure, but AT2R mRNA was increased almost 2-fold. These results indicate that high pressure itself attenuates NO release from ECs, and that losartan improves NO release by activating the bradykinin system via AT2R stimulation. In addition, the increase of AT2R gene expression in ECs during exposure to pressure may compensate for the reduction of NO.

[Intravascular ultrasound imaging of the renal artery in patients with renovascular hypertension caused by neurofibromatosis 1].

A 26-year-old woman with neurofibromatosis 1 was admitted to our hospital for investigation of prolonged hypertension after toxemia of pregnancy. Plasma renin activity was elevated. From the renogram, stenosis of right renal artery was suspected and we performed renal arteriography, which revealed proximal right renal artery stenosis. The intravascular ultrasound (IVUS) image showed concentric stenosis with intimal and medial hypertrophy, which was iso-echoic and partly high echoic. Percutaneous transluminal renal angioplasty was performed and the lesion was well dilated. After angioplasty, blood pressure normalized in a week. From the clinical course and the IVUS image, we suspected that renal artery stenosis was due to neurofibromatosis 1.

[Pulse wave velocity(PWV)].

Brachial-ankle pulse wave velocity(baPWV) is a noninvasive and simple method of measuring arterial stiffness and an independent predictor of cardiovascular mortality in some lifestyle-related diseases. We evaluated that baPWV is well correlated with many atherosclerotic risk factors including abdominal visceral obesity and HOMA, and that the accumulation of these risk factors increases baPWV. The promotion of exercise and nutrition education for metabolic syndrome patients improves not only each risk factor but also baPWV. Multiple linear regression analysis demonstrated that baPWV is improved by decreases in SBP and BMI through several lifestyle modifications. Reversibility of baPWV suggests that vessel damage is not so serious and may be only endothelial dysfunction. Therefore baPWV should be monitored and ameliorated in treating metabolic syndrome.

Evaluation of factors associated with elevated levels of platelet-derived microparticles in the acute phase of cerebral infarction.

BACKGROUND: Platelet-derived microparticles (PDMPs) have attracted attention as blood coagulation-promoting, endothelial cell-activating factors. The objective of this study was to determine the parameters associated with elevated PDMP levels and examine their relationship with atherosclerotic lesions of main intracranial and extracranial arteries. PARTICIPANTS AND METHODS: Participants included a control group (C) of 61 patients with no apparent cerebral vascular lesions and 110 patients with acute-phase cerebral infarction, consisting of a small-vessel occlusion group (S) of 34 patients, a large-artery atherosclerosis group (L) of 41 patients, a cardioembolism group (CE) of 20 patients, and a stroke of undetermined etiology group (U) of 15 patients. Platelet-derived microparticle levels were measured using enzyme-linked immunosorbent assay (ELISA) at the time of admission, and the patients were reclassified into group CP (control level PDMPs), consisting of 70 patients with control PDMP levels, and group HP (high PDMPs), consisting of 40 patients with elevated PDMP levels. All patients underwent cranial magnetic resonance (MR) and carotid ultrasound examinations. RESULTS: Platelet-derived microparticle levels were significantly higher in groups S and L than in group C (P < .01). Concomitant intima-media thickness (IMT; odds ratio [OR] = 1.29, P < .05) and concomitant intracranial stenosis (OR = 3.95, P < .01) were significantly correlated with elevated PDMP levels. Fibrinogen and high-sensitivity CRP levels were significantly higher in group HP than in group CP. CONCLUSION: Alterations in PDMP levels correlated with the presence of atherothrombotic lesions, and PDMP levels are expected to be useful as a clinical indicator, reflecting the presence of intracranial atherosclerotic lesions in the acute phase of cerebral infarction.

Predictive markers of blood cytokine and chemokine in recurrent brain infarction.

The mechanism of the inflammatory response in the vascular wall in atherothrombosis and during the progression of atherosclerosis has attracted attention. We focused on the potential usefulness of inflammatory markers in chronic recurrent brain infarction, and analyzed the role of inflammatory markers in atherosclerosis of the intracranial artery. The subjects were 2 groups of patients treated between 2004 and 2006: a group of outpatients with recurrent infarction (group RI), who developed atherothrombotic brain infarction twice; another group of outpatients with brain infarction without recurrence (group BI), who developed brain infarction once and remained free of recurrence for >1 year; and a group of control subjects with normal brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) (group C). Plasma samples were collected from each group of patients for the simultaneous measurement of 17 kinds of candidate inflammatory markers, using a fluorescent microbead array system, and the results were compared with head MRA findings. The levels of high-sensitivity C-reactive protein (hsCRP) and monocyte chemoattractant protein-1 (MCP-1) were significantly higher in group RI patients than in groups C and BI. Subjects with a hsCRP level > or =0.3 and a MCP-1 level > or =200 in the serum have, respectively, a 1.92 and 2.98 relative risk to have a potential recurrent infarction. Regarding the relation of inflammatory marker levels with MRA findings, group RI showed significantly higher levels of hsCRP at M1 lesions and MCP-1 at A1 and M1 lesions than group BI (P < 0.05). In conclusion, the MCP-1 level as well as hsCRP in the blood can be a potential predictive marker of recurrent thrombotic brain infarction, and may reflect inflammation that promotes intracranial large-artery atherosclerosis.