Carotid artery intima-media thickness and reactive oxygen species formation by monocytes in hypertensive patients

Carotid artery intima-media thickness (IMT) is a widely accepted index for assessing atherosclerosis, and is known to be a risk indicator for cardiovascular and cerebrovascular events. Oxidative stress and inflammation are also known to play critical roles in the pathogenesis of vascular events. We studied the association between IMT and inflammatory markers, such as oxidative stress in polymorphonuclear leukocytes (PMNs) and mononuclear cells (MNCs) in 156 patients with essential hypertension. Reactive oxygen species (ROS) formation by PMNs and MNCs was measured by gated flow cytometry. CRP and traditional risk factors, such as age, gender, body mass index, hemoglobin A(1c), and total cholesterol were also measured. The subjects were divided into a plaque group (max-IMT>or=1.1 mm, n=40), and a nonplaque group (max-IMT<1.1 mm, n=116). ROS formation by MNCs was significantly increased in the plaque group when compared with the nonplaque group (P<0.0001). Multiple regression analysis revealed a significant correlation between IMT and ROS formation by MNCs (r=0.407, P<0.0001), or CRP (r=0.216, P=0.0029) or hemoglobinA1c (r=0.158, P=0.0270) or age (r=0.157, P=0.0447). No significant correlation was observed between IMT and ROS formation by PMNs. These results suggest that carotid artery IMT may be affected by increased ROS formation by MNCs, and that increased ROS formation by MNCs may be related to the development of atherosclerosis. We propose that ROS formation by MNCs is a marker for prediction of carotid atherosclerosis.

Left ventricular hypertrophy and angiotensin II receptor blocking agents

Angiotensin II plays a significant role in cell growth and proliferation in model systems and in humans. Numerous studies have shown that left ventricular hypertrophy (LVH) increases the risk of coronary heart disease, congestive heart failure, stroke or transient ischemic attack; all-cause deaths, and sudden death. The use of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) has provided beneficial effects on LVH regression and on cardiac remodeling in the presence of hypertension and heart failure. The new class of ARBs appears to provide cardioprotective effects that are similar to those of the ACE inhibitors. Most of the beneficial effects provided by these agents appear to be related to a more complete blockade of the angiotensin II type 1 (AT1) receptor. However, costimulation of the angiotensin II type 2 (AT2) receptor appears to increase nitric oxide and thus causes some bradykinin-like effects. Evidence for the role of angiotensin II in promoting LVH as well as abnormal regulation of the angiotensin II signal transduction pathways in model systems and in humans has been reviewed. Secondly, the mechanisms for the beneficial effects of angiotensin II receptor blockers studied in model systems and in humans, including possible involvement in the formation of reactive oxygen species by mononuclear cells, are presented. Finally, results from large-scale interventions such as the Losartan Intervention For Endpoint reduction (LIFE) study, as well as an overview of the Valsartan Antihypertensive Long-term Use Evaluation (VALUE) trial involving the use of ARB in high-risk patients, are presented.

HMG-CoA reductase inhibitors prevent migration of human coronary smooth muscle cells through suppression of increase in oxidative stress

In vitro and in vivo evidence of a decrease in vascular smooth muscle cell (SMC) migration induced by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has been reported. When added to SMC cultures for 6 hours, the HMG-CoA reductase inhibitors fluvastatin, simvastatin, and pravastatin at 1 micromol/L resulted in a 48%, 50%, and 16% suppression, respectively, of human coronary SMC migration; these reductions mirrored the suppression in oxidative stress induced by 1 micromol/L lysophosphatidylcholine (lyso-PC) of 50%, 53% and 19%, respectively. The hydroxylated metabolites of fluvastatin, M(2) and M(3), at 1 micromol/L also suppressed the enhancement of SMC migration by 58% and 45% and the increase in oxidative stress induced by lyso-PC of 58% and 49%, respectively. Lyso-PC activated phospholipase D and protein kinase C (PKC), and this activation was also suppressed by HMG-CoA reductase inhibitors. The inhibition of phospholipase D and PKC was reversed by 100 micromol/L mevalonate, its isoprenoid derivative, farnesol, and geranylgeraniol but not by 10 micromol/L squalene. Antisense oligodeoxynucleotides at 5 micromol/L to PKC-alpha, but not those to the PKC-beta isoform, suppressed the lyso-PC-mediated increases in SMC migration and oxidative stress. These findings suggest that HMG-CoA reductase inhibitors have direct antimigratory effects on the vascular wall beyond their effects on plasma lipids and that they might exert such antimigratory effects via suppression of the phospholipase D- and PKC (possibly PKC-alpha)-induced increase in oxidative stress, which might in turn prevent significant coronary artery disease.

A dopamine-secreting pheochromocytoma

We describe a patient with pheochromocytoma, which secretes dopamine. He was admitted to hospital because of chronic diarrhea. After surgical resection of the tumor, dramatic cessation of the diarrhea and blood pressure elevation were observed. Decreased expression of dopamine beta-hydroxylase in the tumor was considered a possible mechanism of producing a pathophysiological concentration of dopamine. This case shows that excessive excretion of dopamine, a vasodilative hormone, may affect blood pressure.

Effects of valsartan on angiotensin II-induced migration of human coronary artery smooth muscle cells

The migration as well as proliferation of coronary artery medial smooth muscle cells (SMC) into the intima is proposed to be an important process of intimal thickening in coronary atherosclerosis. In the current study, we examined the effects of the angiotensin type 1 receptor antagonist valsartan on angiotensin II (Ang II)-induced migration of cultured human coronary artery SMC using Boyden's chamber methods. Ang II significantly stimulated human coronary artery SMC migration in a concentration-dependent manner between 10(-6) and 10(-8) mol/l when cells of passage 4 to 6 were used. However, the migration response to Ang II was moderately decreased in cells of passage 10 to 12, and was markedly decreased in cells of passage 15 to 17, compared to that of passage 4 to 6. Ang II-induced migration was blocked by the Ang II type 1 (AT1) receptor antagonist valsartan in a concentration-dependent manner. By contrast, the Ang II type 2 (AT2) receptor antagonist PD 123319 did not affect Ang II-induced migration. Ang II modestly increased the cell number of human coronary artery SMC after a 24-h incubation. This increase in cell numbers was also clearly blocked by valsartan, but not by PD 123319. These results indicate that Ang II stimulates migration as well as proliferation via AT1 receptors in human coronary artery SMC when cells of passage 4 to 6 are used. Valsartan may prevent the progression of coronary atherosclerosis through an inhibition of Ang II-induced migration and proliferation in these cells, although in vivo evidence is lacking.

Effect of angiotensin-converting enzyme inhibitor on left ventricular parameters and circulating brain natriuretic peptide in elderly hypertensives with left venticular hypertrophy

In the elderly, left ventricular hypertrophy (LVH) is a powerful risk factor for cardiovascular events and cardiovascular death. The purpose of the present study is to investigate the effect of long-term effective blood pressure control with the angiotensin-converting enzyme (ACE) inhibitor temocapril on left ventricular (LV) mass and function indices and the circulating concentration of the cardiac hormone brain natriuretic peptide (BNP) in elderly hypertensives with LVH. Temocapril treatment was administered for 1 year to 11 elderly hypertensives (mean age, 72 years) with LVH. Cardiac dimensions and circulating concentrations of BNP were monitored before initiation of treatment and after 1 year of treatment. At entry, BNP levels were positively correlated with the LV mass index, but were not correlated with the mean blood pressure, LV ejection fraction, or E/A ratio (the ratio of peak transmitral flow velocity in early diastole, peak E, to that in late diastole, peak A). After 1 year, temocapril treatment resulted in effective control of blood pressure. The treatment did not affect the LV ejection fraction, but modestly increased the E/A ratio. Temocapril significantly reduced septal and posterior wall thickness and the LV mass index. BNP significantly declined after 1 year. Changes in BNP were significantly related to changes in the LV mass index, but were not related to changes in the mean blood pressure, LV ejection fraction, or E/A ratio. The results suggest that long-term ACE inhibitor treatment with temocapril can induce the regression of LV mass and reduce elevated plasma BNP in elderly hypertensive patients with LVH. In this study, changes in BNP reflected the magnitude of regression of LVH.

Dopamine as a novel antioxidative agent for rat vascular smooth muscle cells through dopamine D(1)-like receptors

BACKGROUND

To elucidate the roles of vascular D(1)-like receptors in atherosclerosis, the effects of the specific D(1)-like agonists on platelet-derived growth factor (PDGF)-BB-mediated oxidative stress in vascular smooth muscle cells (VSMCs) were studied.

METHODS AND RESULTS

Immunohistochemical studies demonstrated the coexistence of D(1A) and D(1B) dopamine receptors in VSMCs. Western blotting revealed a band of approximately 70 kDa for D(1A) and D(1B) dopamine receptors. VSMCs stimulated by PDGF-BB exhibited increased oxidative stress directly measured by flow cytometry. These effects were prevented by dopamine, SKF 38393, or YM 435, and this prevention was reversed by Sch 23390. These effects were blocked by a specific protein kinase A (PKA) inhibitor, N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide (H 89). The PDGF-BB-mediated increase in oxidative stress of VSMCs was significantly suppressed by the indirect phospholipase D (PLD) inhibitor suramin or the specific protein kinase C (PKC) inhibitor calphostin C. Both antisense but neither sense nor scrambled oligonucleotides to D(1A) and D(1B) receptors inhibited dopamine-induced suppression of increase in oxidative stress of VSMCs induced by PDGF-BB.

CONCLUSIONS

These findings suggest that vascular D(1)-like receptors (D(1A) and D(1B) receptors) inhibit any increase in oxidative stress of VSMCs, possibly through activation of PKA and suppression of PLD and PKC.

Suppression by eicosapentaenoic acid of oxidized low-density lipoprotein and lysophosphatidylcholine-induced migration in cultured rat vascular smooth muscle cells

The migration of medial smooth muscle cells into the intima is proposed to be an initial process of intimal thickening in atherosclerotic lesions. The present study was designed to determine whether pretreatment with the antiatherogenic agent eicosapentaenoic acid (EPA) inhibits the migration induced by oxidized low-density lipoprotein (LDL) and its major phospholipid component, lysophosphatidylcholine (lyso-PC), in cultured rat vascular smooth muscle cells (VSMCs) using Boyden's chamber method. The effects of EPA pretreatment on angiotensin II (Ang II)- and platelet-derived growth factor BB (PDGF BB)-induced migration were also examined in these cells. Oxidized LDL and lyso-PC induced migration in a concentration-dependent manner. EPA pretreatment clearly suppressed oxidized LDL (200 microg/mL)- and lyso-PC (10(-5) mol/L)-induced migration between 40 and 160 micromol/L. EPA pretreatment also suppressed Ang 11 (10(-7) mol/L)- and PDGF BB (5 ng/mL)-induced migration at a concentration of 80 and 160 micromol/L. However, in a trypan blue exclusion test, dead cells stained with trypan blue were not found 24 hours after treatment with EPA. These results suggest that EPA suppresses VSMC migration induced by oxidized LDL and lyso-PC, as well as Ang II and PDGF BB. These preliminary data concerning the effects of EPA may partly explain the antiatherosclerotic effects of this agent.

Aldose reductase inhibitor improves insulin-mediated glucose uptake and prevents migration of human coronary artery smooth muscle cells induced by high glucose

We examined involvement of the polyol pathway in high glucose-induced human coronary artery smooth muscle cell (SMC) migration using Boyden's chamber method. Chronic glucose treatment for 72 hours potentiated, in a concentration-dependent manner (5.6 to 22.2 mol/L), platelet-derived growth factor (PDGF) BB-mediated SMC migration. This potentiation was accompanied by an increase in PDGF BB binding, because of an increased number of PDGF-beta receptors, and this potentiation was blocked by the aldose reductase inhibitor epalrestat. Epalrestat at concentrations of 10 and 100 nmol/L inhibited high glucose-potentiated (22.2 mmol/L), PDGF BB-mediated migration. Epalrestat at 100 nmol/L inhibited a high glucose-induced increase in the reduced/oxidized nicotinamide adenine dinucleotide ratio and membrane-bound protein kinase C (PKC) activity in SMCs. PKC inhibitors calphostin C (100 nmol/L) and chelerythrine (1 micromol/L) each inhibited high glucose-induced, PDGF BB-mediated SMC migration. High glucose-induced suppression of insulin-mediated [(3)H]-deoxyglucose uptake, which was blocked by both calphostin C (100 nmol/L) and chelerythrine (1 micromol/L), was decreased by epalrestat (100 nmol/L). Chronic high glucose treatment for 72 hours increased intracellular oxidative stress, which was directly measured by flow cytometry using carboxydichlorofluorescein diacetate bis-acetoxymethyl ester, and this increase was significantly suppressed by epalrestat (100 nmol/L). Antisense oligonucleotide to PKC-beta isoform inhibited high glucose-mediated changes in SMC migration, insulin-mediated [(3)H]-deoxyglucose uptake, and oxidative stress. These findings suggest that high glucose concentrations potentiate SMC migration in coronary artery and that the aldose reductase inhibitor epalrestat inhibits high glucose-potentiated, PDGF BB-induced SMC migration, possibly through suppression of PKC (PKC-beta), impaired insulin-mediated glucose uptake, and oxidative stress.

Effects of cardiac natriuretic peptides on oxidized low-density lipoprotein- and lysophosphatidylcholine-induced human mesangial cell migration

The objectives of the present study were (1) to determine whether oxidized LDL and lysophosphatidylcholine (lyso-PtdCho), a major phospholipid component of oxidized LDL, stimulate the migration of cultured human mesangial cells and (2) to investigate the possible effects on mesangial cell migration of the cardiac natriuretic peptides atrial and brain natriuretic peptide (ANP and BNP). Oxidized LDL (10 and 100 microg/mL) and lyso-PtdCho (10(-7) to 10(-5) mol/L) stimulated migration in a concentration-dependent manner. In contrast, the effects of native LDL and phosphatidylcholine were modest or nonexistent. Protein kinase C (PKC) inhibitor and downregulation of PKC activity by phorbol ester inhibited oxidized LDL- and lyso-PtdCho-induced migration. Human ANP(1-28) and human BNP-32 significantly inhibited oxidized LDL- and lyso-PtdCho-induced migration in a concentration-dependent manner. C-ANF (des-[Glu(18),Ser(19),Gly(20),Leu(21),Gly(22)]ANP(4-23)), a specific ligand for ANP clearance receptors, could not inhibit oxidized LDL- and lyso-PtdCho-induced migration. Inhibition by ANP and BNP of lyso-PtdCho-induced migration was paralleled by an increase in the cellular level of GMP. Oxidized LDL- and lyso-PtdCho-induced migrations were inhibited by 8-bromo-cGMP. The results suggest that oxidized LDL and lyso-PtdCho stimulate the migration of human mesangial cells, at least in part, through a PKC-dependent process and that ANP and BNP inhibit this stimulated migration, probably through a cGMP-dependent process.

Regulation of rat mesangial cell migration by platelet-derived growth factor, angiotensin II, and adrenomedullin

This study sought to determine whether platelet-derived growth factor (PDGF) and angiotensin II (AngII) stimulate migration of cultured rat glomerular mesangial cells. After finding that this was so, the effects of adrenomedullin (ADM) and cAMP-elevating agents on basal and stimulated mesangial cell migration were examined. Two isoforms of PDGF, AB and BB, stimulated migration in a concentration-dependent manner between 1 and 50 ng/ml, while the AA isoform lacked significant effect. AngII modestly but significantly stimulated migration in a concentration-dependent manner between 10(-7) and 10(-6) mol/L. Rat ADM significantly inhibited the PDGF BB- and AngII-stimulated migration in a concentration-dependent manner between 10(-8) and 10(-7) mol/L. Inhibition by rat ADM was accompanied by an increase in cellular cAMP. cAMP agonists or inducers such as 8-bromo cAMP, forskolin, and prostaglandin I2 also significantly reduced the stimulated migration. H 89, a protein kinase A (PKA) inhibitor, attenuated the inhibitory effect of ADM, and a calcitonin gene-related peptide (CGRP) receptor antagonist, human CGRP (8-37), abolished the inhibitory effects of rat ADM. These results suggest that PDGF AB and BB as well as AngII stimulate rat mesangial cell migration and that ADM can inhibit PDGF BB- and AngII-stimulated migration, at least in part through cAMP-dependent mechanisms likely to involve specific ADM receptors with which CGRP interacts. The adenylate cyclase/cAMP/PKA system may be involved in the migration-inhibitory effect of ADM in these cells.

Plasma levels of nitric oxide and related vasoactive factors following long-term treatment with angiotensin-converting enzyme inhibitor in patients with essential hypertension

Several mechanisms other than the inhibition of systemic and local formation of angiotensin II (Ang II) have been proposed to play a role in mediating the hypotensive effects of angiotensin-converting enzyme (ACE) inhibitors. In the present study, we measured plasma levels of nitric oxide (NO) and the related vasoactive factors bradykinin, 6-keto prostaglandin F1alpha (6-keto PGF1alpha) a stable metabolite of prostacyclin, and cyclic guanosine-3',5'-monophosphate (cGMP) before and after a 4-week treatment with the ACE inhibitor lisinopril in 17 patients with essential hypertension. Plasma NO levels were measured by the Griess method after conversion of nitrate to nitrite. Long-term lisinopril treatment significantly reduced blood pressure and increased plasma NO and 6-keto PGF1alpha. The treatment also tended to increase plasma levels of bradykinin and cGMP, but not to a significant extent. The posttreatment NO level was inversely correlated with posttreatment systolic, diastolic, and mean blood pressure (n = 17, r= -.68, P< .01, n = 17, r= -.54, P < .05, and n = 17, r= -.66, P< .01, respectively). The posttreatment bradykinin level was also modestly correlated with posttreatment systolic and mean blood pressure (n = 17, r = -.51, P < .05 and n = 17, r = -.55, P < .05, respectively). In contrast, posttreatment 6-keto PGF1alpha and cGMP levels were not correlated with posttreatment systolic, diastolic, or mean blood pressure. These findings raise the possibility that increased formation of NO and bradykinin, as well as inhibition of the renin-angiotensin system, contribute to the hypotensive effect of the ACE inhibitor observed in our hypertensive patients.

[Pathophysiology of vascular complications in diabetes]

Hyperglycemia is an important causative factor in the development of micro- and macrovascular complications in diabetes. It activates polyol pathway and protein kinase C, which result in the increase in insulin resistance and oxidative stress in vascular tissues, leading to the accelerated atherosclerosis. Increased hematocrit and blood viscosity are observed in diabetes, which contribute to an increased risk of thrombosis and accelerated vasculopathy. Blood glucose control as well as blood pressure control are important in the prevention of diabetic vascular complications as evidenced by large-scale interventional studies.

Association between angiotensin-converting enzyme gene polymorphisms and regression of left ventricular hypertrophy in patients treated with angiotensin-converting enzyme inhibitors

PURPOSE

An insertion/deletion (ID) polymorphism of the angiotensin-converting enzyme (ACE) gene is associated with left ventricular hypertrophy. The present study examined polymorphisms of the ACE gene in patients with essential hypertension and left ventricular hypertrophy who were participants in a long-term trial of therapy with an ACE inhibitor.

PATIENTS AND METHODS

ACE inhibitor therapy was administered for >2 years to 54 patients with hypertension who had moderate or severe left ventricular hypertrophy. Cardiac dimensions were monitored by echocardiography before the initiation of therapy and after 1 and 2 years of treatment. Serum ACE activity and plasma concentrations of brain natriuretic peptide, a marker for left ventricular hypertrophy, were also monitored.

RESULTS

Eighteen patients had the II genotype for the angiotensin-converting enzyme gene, 19 had the ID genotype, and 17 had the DD genotype. Baseline (mean +/- SD) serum ACE activity was significantly greater (P <0.05) in the DD (18 +/- 7 IU/L) group than in the II (7 +/- 4 IU/L) or ID (12 +/- 6 IU/L) groups. ACE inhibitor therapy was effective in controlling blood pressure, and it reduced posterior and septal wall thickness, left ventricular mass index, and plasma brain natriuretic peptide concentration in all three groups. Despite similar blood pressure reductions, after 2 years, mean (+/- SD) regression in posterior wall thickness was significantly less (P <0.05) in the DD group (-9% +/- 5%) than in the ID (-21% +/- 7%) and II (-21% +/- 9%) groups. Similar results were seen for the reductions in brain natriuretic peptide levels. The magnitudes of regression of septal wall thickness and left ventricular mass index during therapy were less in the DD group than the II group (P <0.05).

CONCLUSION

Hypertensive patients with the DD genotype are less likely to have regression of left ventricular hypertrophy when treated with ACE inhibitors than are patients with other ACE genotypes.

Anti-atherosclerotic action of vascular D1 receptors

1. Vascular smooth muscle cell (VSMC) migration and proliferation are believed to play key roles in atherosclerosis. To elucidate the role of vascular dopamine D1-like (D1 and D5) receptors in atherosclerosis, the effects of dopamine and the specific D1-like receptor agonists SKF 38393 and YM 435 on platelet-derived growth factor (PDGF)-BB-mediated VSMC migration, proliferation and hypertrophy were investigated. 2. We observed that cell stimulated by 5 ng/mL PDGF-BB showed increased migration, proliferation and hypertrophy. These effects were prevented by co-incubation with dopamine, SKF 38393 or YM 435 at 1-10 mumol/L and this prevention was reversed by Sch 23390 (1-10 mumol/L), a specific D1-like receptor antagonist. These actions of D1-like receptor agonists were mimicked by 1-10 mumol/L forskolin, a direct activator of adenylate cyclase, and 0.1-1 mmol/L 8-bromo-cAMP. The actions were blocked by the specific protein kinase A (PKA) inhibitor N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinoline-sulphonamide (H 89), but were not blocked by its negative control N-[2-(N-formyl-p-chlorocinnamylamino) ethyl]-5-isoquinoline sulphonamide (H 85). Platelet-derived growth factor-BB (5 ng/mL)-mediated activation of phospholipase D (PLD), protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) activity was significantly suppressed by co-incubation with dopamine. 3. These results suggest that vascular D1-like receptor agonists inhibit migration, proliferation and hypertrophy of VSMC, possibly through the activation of PKA and the suppression of activated PLD, PKC and MAPK activity.

Antioxidants improve impaired insulin-mediated glucose uptake and prevent migration and proliferation of cultured rabbit coronary smooth muscle cells induced by high glucose

BACKGROUND

To explore the role of intracellular oxidative stress in high glucose-induced atherogenesis, we examined the effect of probucol and/or alpha-tocopherol on the migration and growth characteristics of cultured rabbit coronary vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

Chronic high-glucose-medium (22. 2 mmol/L) treatment increased platelet-derived growth factor (PDGF)-BB-mediated VSMC migration, [3H]thymidine incorporation, and cell number compared with VSMCs treated with normal-glucose medium (5.6 mmol/L+16.6 mmol/L mannose). Probucol and alpha-tocopherol significantly suppressed high glucose-induced increase in VSMC migration, cell number, and [3H]thymidine incorporation. Probucol and alpha-tocopherol suppressed high glucose-induced elevation of the cytosolic ratio of NADH/NAD+, phospholipase D, and membrane-bound protein kinase C activation. Probucol, alpha-tocopherol, and calphostin C improved the high glucose-induced suppression of insulin-mediated [3H]deoxyglucose uptake. Chronic high-glucose treatment increased the oxidative stress, which was significantly suppressed by probucol, alpha-tocopherol, suramin, and calphostin C.

CONCLUSIONS

These findings suggest that probucol and alpha-tocopherol may suppress high glucose-induced VSMC migration and proliferation via suppression of increases in the cytosolic ratio of free NADH/NAD+, phospholipase D, and protein kinase C activation induced by high glucose, which result in reduction in intracellular oxidative stress.

Heparin inhibits human coronary artery smooth muscle cell migration

Heparin, an anticoagulant, has been shown to reduce neointimal proliferation and restenosis following vascular injury in experimental studies, but the clinical trials of heparin in coronary balloon angioplasty have been negative. The current study, therefore, examined the effect of heparin on basal or stimulated migration by serum and platelet-derived growth factor (PDGF)-BB in cultured human coronary artery smooth muscle cells (SMCs) by Boyden's chamber method. In addition, the reversibility of the heparin effect on human coronary artery SMC migration was examined. Fetal calf serum (FCS) and PDGF-BB stimulated SMC migration in a concentration-dependent manner. Heparin in moderate to high concentration (10 to 100 U/mL) exhibited concentration-related inhibition of FCS- and PDGF-BB-stimulated SMC migration; however, a low concentration (1 U/mL) of heparin had no inhibitory effects. Heparin also had weak inhibitory effects on nonstimulated SMC migration. The SMCs that were exposed to a high concentration (100 U/mL) of heparin for 6 hours were capable of migrating after a short lag period of removal of heparin from the culture medium. These SMCs also showed recovery of responses to FCS and PDGF-BB by migrating significantly greater than the nonstimulated level. Furthermore, heparin-containing medium did not contain detached cells. These results indicate that heparin inhibits human coronary artery SMC migration, especially when stimulated by FCS or PDGF-BB, and that this inhibitory effect of heparin is reversible and not simply a function of killing cells.

Induction by lysophosphatidylcholine, a major phospholipid component of atherogenic lipoproteins, of human coronary artery smooth muscle cell migration

BACKGROUND

The objectives of the present study were (1) to determine whether lysophosphatidylcholine (lyso-PC), a prominent component of oxidatively modified LDL, induces migration of human coronary artery smooth muscle cells (SMCs) and, if so, to clarify the mechanism, and (2) to investigate the possible interactions of lyso-PC and platelet-derived growth factor (PDGF)-BB, endothelin- (ET-1), adrenomedullin (AM), or vitamin E on SMC migration by the Boyden's chamber method.

METHODS AND RESULTS

Lyso-PC induced SMC migration in a concentration-dependent manner between 10(-6) and 5 x 10(-5) mol/L. By contrast, phosphatidylcholine was without significant activity, and lysophosphatidylinositol and lysophosphatidylserine were much less effective than lyso-PC. Lyso-PC increased basic fibroblast growth factor (bFGF) production in a concentration-dependent manner between 10(-6) and 5 x 10(-5) mol/L in these cells. Furthermore, lyso-PC-induced SMC migration was inhibited by neutralizing antibody to bFGF but not by neutralizing antibody to transforming growth factor-beta1. Lyso-PC-induced migration was significantly enhanced by PDGF-BB or ET-1 but was clearly inhibited by human AM and vitamin E.

CONCLUSIONS

These results indicate that (1) lyso-PC induces human coronary artery SMC migration at least in part through release of endogenous bFGF and (2) this lyso-PC-induced migration can be further induced by PDGF-BB and ET-1 and can be inhibited by human AM and vitamin E. Lyso-PC may recruit medial SMCs during the process of coronary atherosclerosis in part by releasing bFGF in concert with PDGF-BB or ET-1 in vascular tissues. This lyso-PC-induced SMC migration may be suppressed by AM and vitamin E under certain pathological conditions.

Vascular dopamine-I receptors and atherosclerosis

Vascular smooth muscle cell (VSMC) migration and proliferation are believed to play key roles in atherosclerosis. To elucidate the role of vascular dopamine D1-like receptors in atherosclerosis, the effects of dopamine, specific D1-like agonists SKF 38,393, and YM 435 on platelet-derived growth factor (PDGF) BB-mediated VSMC migration, proliferation, and hypertrophy were studied. We observed that cells stimulated by 5 ng/ml PDGF BB showed increased migration, proliferation and hypertrophy. These effects were prevented by coincubation with dopamine, SKF 38,393, or YM 435 at 1-10 mumol/l, and this prevention was reversed by Sch 23,390 (1-10 mumol/l), a specific D1-like antagonist. These actions are mimicked by 1-10 mumol/l forskolin, a direct activator of adenylate cyclase and 8-bromocyclic AMP at 0.1-1 mmol/l. The actions are blocked by a specific protein kinase A (PKA) inhibitor N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinoline-sulfonamide (H 89), but are not blocked by its negative control, N-[2-(N-formyl-p-chlorocinnamylamino) ethyl]-5-isoquinoline sulfonamide (H 85). PDGF-BB (5 ng/ml)-mediated activation of phospholipase D (PLD), protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) activity were significantly suppressed by coincubation with dopamine. These results suggest that vascular D1-like receptor agonists inhibit migration, proliferation and hypertrophy of VSMC, possibly through PKA activation and suppression of activated PLD, PKC and MAPK activity.

Suppression of endothelin-3-induced nitric oxide synthesis by triglyceride in human endothelial cells

Reduced endothelium-derived nitric oxide (NO) production characterizes several vascular diseases. This study examined the effect of triglyceride on NO production induced by endothelin-3 (ET-3) in cultured human umbilical vein endothelial cells. Triglyceride-rich human plasma obtained after a high-carbohydrate diet with white wine was used in an ex vivo study. The plasma triglyceride fraction was found to consist of large amounts of palmitic and oleic acids detected by gas-liquid chromatography. Therefore, the effect of synthetic tripalmitin and triolein emulsion on NO production was also examined. ET-3 stimulated NO and guanosine 3',5'-cyclic monophosphate production and increased cytosolic Ca2+ levels in the endothelial cells (ECs). After incubation of the ECs with the triglyceride-rich plasma for 2 h, these responses to ET-3 were ameliorated in a triglyceride concentration-dependent manner (50-200 mg/dl). A synthesized emulsion of tripalmitin (100 mg/dl) and triolein (100 mg/dl) also blunted the responses to ET-3. Neither endothelial constitutive NO synthase mRNA expression nor its protein level was affected by treatment with triglycerides. These results suggest that triglyceride suppresses ET-3-induced NO synthesis in human ECs by inhibiting cytosolic Ca2+ elevation.

Heparin suppresses cyclosporine-induced endothelin-1 synthesis in rat endothelial cells

Cyclosporine stimulates vasoconstrictor endothelin-1 (ET-1) synthesis. This study examined the effect of heparin on cyclosporine-induced ET-1 synthesis in Wistar rat aortic endothelial cells in culture. Cyclosporine (0.01-5 mumol/L) stimulated ET-1 mRNA expression in a dose-dependent manner. A nitric oxide synthesis inhibitor, NG-monomethyl-L-arginine (L-NMMA) (10(-5) mol/L), did not affect cyclosporine-induced ET-1 mRNA expression. Heparin (1-20 U/ml) suppressed cyclosporine-induced ET-1 mRNA expression in a dose-dependent manner. The inhibitory effect of heparin was blunted in the presence of either L-NMMA (10(-5) mol/L) or calmodulin inhibitors such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) (5 x 10(-5) mol/L) or calmidazolium (5 x 10(-5) mol/L) in the presence of the phosphodiesterase inhibitor 3-isobutyl 1-methylxanthine (0.1 mmol/L). These results suggest that heparin suppresses cyclosporine-induced ET-1 mRNA expression via both NO- and calmodulin-dependent pathways.

Effect of the endothelin family of peptides on human coronary artery smooth-muscle cell migration

The migration of coronary artery medial smooth-muscle cells (SMCs) is one of the key events in the process of intimal thickening in coronary atherosclerotic lesions. The objectives of the present study were to determine whether any of the three isoforms of endothelin (ET), ET-1, ET-2, and ET-3, or an intermediate form of ET, big ET-1, induces migration of human coronary artery SMCs, and to investigate the possible interaction of ET peptides and well-known migration-stimulatory factors, platelet-derived growth factor (PDGF)-BB and angiotensin II (Ang II), on SMC migration by the Boyden's chamber method. None of the ET peptides alone induced SMC migration between 10(-9) and 10(-7) mol/L. In contrast, ET-1 and ET-2 significantly induced SMC migration in the presence of low concentrations of PDGF-BB (0.5 ng/mL) or Ang II (10(-9) mol/L), although ET-3 was less active (ET-1 = ET-2 > ET-3). In contrast, big ET-1 was without significant activity on PDGF-BB-or Ang II-induced SMC migration. The potentiation of SMC migration by ET peptides was clearly inhibited by the ETA receptor antagonist BG-123 in a concentration-dependent manner. These results suggest that the ET family of peptides, especially ET-1 and ET-2, can induce human coronary artery SMC migration in combination with PDGF-BB or Ang II, probably via ETA receptors. Taken together with the finding that the concentrations of ET, PDGF-BB and Ang II are locally increased at sites of endothelial injury, this indicates that ET may be an initial stimulus for human coronary artery medial SMC recruitment during coronary atherosclerosis, possibly in combination with PDGF-BB or Ang II.

Mechanisms of action of troglitazone in the prevention of high glucose-induced migration and proliferation of cultured coronary smooth muscle cells

Recent findings suggest that high glucose levels may promote atherosclerosis in coronary vascular smooth muscle cells (VSMCs). To explore the intracellular mechanisms of action by which troglitazone affects this process, we examined the effect of troglitazone on the migration and growth characteristics of cultured rabbit coronary VSMCs. Treatment with chronic high glucose medium (22.2 mmol/L) for 5 days increased VSMC migration by 92%, [3H]thymidine incorporation by 135%, and cell number by 32% compared with VSMCs treated with normal glucose (5.5 mmol/L glucose + 16.6 mmol/L mannose) medium. Trolitazone at 100 nmol/L and 1 mumol/L significantly suppressed high glucose-induced VSMC migration by 34% and 42%, respectively, the proliferative effect (as measured by cell number) by 17% and 27%, and [3H]thymidine incorporation by 45% and 60% (n = 6, P < .05). The high glucose-induced impairment of insulin-mediated [3H]deoxyglucose uptake was blocked by a protein kinase C (PKC) inhibitor (calphostin C, 1 mumol/L) and was also improved by troglitazone without any change in insulin receptor number and affinity. The high glucose-induced insulin-mediated increase in cell number and in [3H]thymidine incorporation was suppressed by troglitazone. Troglitazone (1 mumol/L) also suppressed high glucose-induced phospholipase D activation, elevation of the cytosolic NADH/NAD+ ratio (as measured by the cytosolic ratio of lactate/pyruvate), and membrane-bound PKC activation. Flow cytometric DNA histogram analysis of cell cycle stage showed that high glucose-induced increase in the percentage of cells in the S phase was suppressed by 1 mumol/L troglitazone. These findings suggest that PKC may be a link between impairment of insulin-mediated glucose uptake and the increase in migration and proliferation induced by high glucose levels and that troglitazone may be clinically useful for the treatment of high glucose-induced coronary atherosclerosis.

Dopamine as a novel antimigration and antiproliferative factor of vascular smooth muscle cells through dopamine D1-like receptors

Vascular smooth muscle cell (VSMC) migration and proliferation are believed to play key roles in atherosclerosis. To elucidate the role of vascular dopamine D1-like receptors in atherosclerosis, the effects of dopamine and specific D1-like agonists SKF 38,393 and YM 435 on platelet-derived growth factor (PDGF) BB-mediated VSMC migration and proliferation were studied. We observed that cells stimulated by PDGF-BB (5 ng/mL), showed increased migration and proliferation. These effects were prevented by coincubation with dopamine, SKF 38,393, or YM 435 (1 to 10 mumol/L), and this prevention was reversed by Sch 23,390 (1 to 10 mumol/l), a specific D1-like antagonist. These actions are mimicked by forskolin (1 to 10 mumol/L), a direct activator of adenylate cyclase and 8-bromo-cAMP at 0.1 to 1 mmol/L and are blocked by a specific protein kinase A inhibitor, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide (H 89), but not blocked by its negative control, N-[2-(N-formyl)-p-chlorociannamylamino)ethyl]-5-isoquinoline sulfonamide (H 85). PDGF-BB (5 ng/mL)-mediated activation of phospholipase D, protein kinase C, and mitogen activated protein kinase activity were significantly suppressed by coincubation with dopamine. These results suggest that vascular D1-like receptor agonists inhibit migration and proliferation of VSMC, possibly through protein kinase A activation and suppression of activated phospholipase D, protein kinase C, and mitogen-activated protein kinase activity.

Effect of natriuretic peptide family on the oxidized LDL-induced migration of human coronary artery smooth muscle cells

The migration of medial smooth muscle cells (SMCs) into the intima is proposed to be an important process of intimal thickening in atherosclerotic lesions. The present study examined the possible effect of a novel endothelium-derived relaxing peptide, C-type natriuretic peptide (CNP), on oxidized low-density lipoprotein (LDL)-induced migration of cultured human coronary artery SMCs by the Boyden's chamber method. The effect of CNP was compared with that of atrial and brain natriuretic peptides (ANP and BNP, respectively). Oxidized LDL stimulates SMC migration in a concentration-dependent manner between 20 and 200 micrograms/mL. This stimulation was chemotactic in nature but was not chemokinetic. By contrast, native LDL was without significant activity. CNP-22 clearly inhibited SMC migration stimulated with 200 micrograms/mL oxidized LDL in a concentration-dependent manner between 10(-9) and 10(-6) mol/L. ANP-(1-28) and BNP-32 also inhibited oxidized LDL-induced SMC migration at concentrations of 10(-7) and 10(-6) mol/L, but these effects were weaker than the effect of CNP-22. Such inhibition by these natriuretic peptides was paralleled by an increase in the cellular level of cGMP. Oxidized LDL-induced migration was significantly inhibited by a stable analogue of cGMP, 8-bromo-cGMP, or an activator of the cytosolic guanylate cyclase, sodium nitroprusside. These natriuretic peptides did not suppress the cell adhesion either in the absence or presence of oxidized LDL. These data indicate that oxidized LDL stimulates migration of human coronary artery SMCs and that natriuretic peptides, especially CNP, inhibit this stimulated SMC migration, at least in part, through a cGMP-dependent process. Taken together with the finding that oxidized LDL is present in the intima, CNP may play a role as a local antimigration factor during the process of intimal thickening in hypercholesterolemia-induced coronary atherosclerosis.

Renoprotective effects of a combined endothelin type A/type B receptor antagonist in experimental malignant hypertension

We previously showed that plasma endothelin-1 (ET-1) concentration was increased in deoxycorticosterone acetate (DOCA)-salt-induced malignant hypertension in spontaneously hypertensive rats (SHR). In contrast, in normal SHR, this value is similar to that seen in Wistar-Kyoto (WKY) rats. The purpose of this study was to examine the effects of the new combined ET type A/type B (ETA/B) receptor antagonist, TAK-044, on the development of hypertension in this model of malignant hypertension. TAK-044 10 mg/kg, which effectively blocks both ETA and ETB receptors, was administered intraperitoneally once per day for 4 weeks in DOCA-salt SHR, and the effects on ET-1 and other parameters were compared with the same values in untreated WKY rats, untreated DOCA-salt SHR, and hydralazine-treated DOCA-salt SHR. DOCA-salt caused marked increases in blood pressure, blood urea nitrogen (BUN), serum creatinine, and plasma ET-1 concentrations in SHR. Both TAK-044 and hydralazine significantly suppressed the increase in blood pressure in DOCA-salt SHR to the same extent. Both treatments also suppressed the increase in BUN and serum creatinine, but this attenuation was less marked with hydralazine than with TAK-044. Neither TAK-044 nor hydralazine affected plasma ET-1 concentration in this model. TAK-044 significantly reduced kidney weight in DOCA-salt SHR, whereas the decrease seen with hydralazine was less marked. Prevention of DOCA-salt-induced renal structural injury (mesangial hypercellularity, glomerular sclerotic changes, and tubulointerstitial damage) in this model was clearly greater with TAK-044 treatment than with hydralazine treatment. These results suggest that endogenous ET-1 may, at least in part, contribute to renal functional and structural damage in malignant DOCA-salt SHR. Our results raise the possibility of renoprotective effects of ETA/B receptor blockers in certain forms of malignant hypertension.

Adrenomedullin is a potent inhibitor of angiotensin II-induced migration of human coronary artery smooth muscle cells

The migration of coronary artery medial smooth muscle cells (SMCs) into the intima is proposed to be an important process of intimal thickening in coronary atherosclerotic lesions. In the current study, we examined the possible interaction of adrenomedullin, a novel vasorelaxant peptide, and angiotensin II (Ang II) on human coronary artery SMC migration using Boyden's chamber method. Ang II stimulated SMC migration in a concentration-dependent manner between 10(6) and 10(8) mol/L. This stimulation was clearly blocked by the Ang II type 1 receptor antagonist losartan but not by the type 2 receptor antagonist PD 123319. The migration stimulatory effect of Ang II was chemotactic in nature for cultured human coronary artery SMCs but was not chemokinetic. Human adrenomedullin clearly inhibited Ang II-induced migration in a concentration-dependent manner. Human adrenomedullin stimulated cAMP formation in these cells. Inhibition by adrenomedullin of Ang II-induced SMC migration was paralleled by an increase in the cellular level of cAMP. 8-Bromo-cAMP, a cAMP analogue, and forskolin, an activator of adenylate cyclase, inhibited the Ang II-induced SMC migration. These results suggest that Ang II stimulates SMC migration via type 1 receptors in human coronary artery and adrenomedullin inhibits Ang II-induced migration at least partly through a cAMP-dependent mechanism. Taken together with the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, this peptide may play a role as a local antimigration factor in certain pathological conditions.

Natriuretic peptide family as a novel antimigration factor of vascular smooth muscle cells

Vascular smooth muscle cell (SMC) migration is proposed to be an important process in the initiation and/or progression of atherosclerosis. The present study examined the effects of the natriuretic peptide family (atrial, brain, and C-type natriuretic peptides; ANP, BNP, and CNP) on the migration of cultured rat SMCs, using Boyden's chamber methods. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)-BB potently stimulated SMC migration. Rat ANP(1-28), rat BNP-45, and rat CNP-22 clearly inhibited SMC migration stimulated with FCS or PDGF-BB in a concentration-dependent manner. CNP-22 had the most potent inhibitory effect compared with other natriuretic peptides. When PDGF-BB-induced migration was separated into chemotactic and chemokinetic activities, the chemotactic component was strongly inhibited by these natriuretic peptides. Such inhibition by these natriuretic peptides was paralleled by an increase in the cellular level of cyclic GMP. The addition of a cyclic GMP analogue, 8-bromo cyclic GMP, and an activator of the cytosolic guanylate cyclase, sodium nitroprusside, significantly inhibited FCS- and PDGF-BB-stimulated migration in a concentration-dependent manner. These results suggest that natriuretic peptides, especially CNP-22, inhibit FCS- or PDGF-BB-stimulated SMC migration at least in part through a cyclic GMP-dependent process. Thus, the natriuretic peptide family may play a role as an antimigration factor of SMCs under certain circumstances.

Improvement of erythrocyte deformability by cholesterol-lowering therapy with pravastatin in hypercholesterolemic patients

Erythrocyte deformation is an important regulatory factor of the microcirculation. The present study was designed to examine whether erythrocyte deformability is altered in hypercholesterolemic patients and, if so, whether cholesterol-lowering therapy affects this parameter in these patients. The erythrocyte deformability of 37 hypercholesterolemic patients was evaluated before and after 1 year of therapy with pravastatin, an inhibitor of hepatic hydroxymethyl glutaryl coenzyme A reductase, under various shear stresses (4.7, 9.5, 23.6, 47.3, 118.1, and 236.2 dyne/cm2) using laser diffractometry. At study entry, erythrocyte deformability under 4.7 and 9.5 dyne/cm2 shear stress, which is actually observed in human vessels, was reduced compared with that in 20 age-matched normocholesterolemic subjects and was inversely correlated with serum cholesterol and low-density lipoprotein (LDL) cholesterol. Pravastatin therapy for 1 year, which reduced serum cholesterol from 288 +/- 28 to 223 +/- 20 mg/dL, significantly improved erythrocyte deformability by approximately 20%. There was a significant relation between the improvement of erythrocyte deformability and the reduction of serum cholesterol or LDL cholesterol. The results suggest that erythrocyte deformability is reduced in hypercholesterolemic patients, and that long-term cholesterol-lowering therapy can improve reduced erythrocyte deformability, which may contribute to the improvement of organ perfusion.

Dopamine D1-like receptor stimulation inhibits hypertrophy induced by platelet-derived growth factor in cultured rat renal vascular smooth muscle cells

Vascular smooth muscle cell (VSMC) hypertrophy is believed to play some roles in atherosclerosis. To elucidate the role of vascular D1-like receptors in VSMC hypertrophy, the effects of dopamine and specific D1-like receptor agonists SKF 38393 and YM 435 on platelet-derived growth factor (PDGF) BB-mediated VSMC hypertrophy was studied. We observed that cells stimulated by PDGF-BB 5 ng/mL showed increased VSMC hypertrophy. These effects were prevented by coincubation with dopamine, SKF 38393, and YM 435 1-10 mumol/L, and this prevention was reversed by Sch 23390 1 to 10 mumol/L, a specific D1-like receptor antagonist. These actions are mimicked by forskolin 1 to 10 mumol/L, a direct activator of adenylate cyclase and 8-bromo-cAMP 0.1 to 1 mmol/L, and are blocked by a specific protein kinase A (PKA) inhibitor N-[2-(P-bromcoinnamylamino)ethyl]-5-isoquinoline-sulfonamide (H89) but not blocked by its negative control. PDGF-BB (5 ng/mL)-mediated mitogen-activated protein kinase (MAPK) activity was significantly suppressed by coincubation with D1-like receptor agonists, which were reversed by PKA inhibitor H 89. These results suggest that vascular D1-like receptor agonists inhibit hypertrophy of VSMC, possibly through PKA activation and suppression of activated MAPK activity.

Changes in plasma cardiac natriuretic peptides concentrations during 1 year treatment with angiotensin-converting enzyme inhibitor in elderly hypertensive patients with left ventricular hypertrophy

Plasma concentrations of atrial and brain natriuretic peptides (ANP and BNP) are high in patients with hypertension and congestive heart failure. The present study examined changes in plasma ANP and BNP concentrations during 1 year of monotherapy with enalapril in elderly hypertensive patients with left ventricular (LV) hypertrophy. Eight elderly hypertensive patients with LV hypertrophy were treated with enalapril for 1 year, during which time serial changes were recorded in LV mass index, LV systolic function, and plasma concentrations of ANP and BNP. Enalapril maintained systolic and diastolic blood pressure in the normal range for over 1 year. Treatment significantly reduced posterior wall thickness at 6 months, and more so at 1 year, and tended to reduce septal wall thickness and LV mass index at 1 year. LV ejection fraction was slightly but significantly increased at 1 year. Plasma ANP and BNP, which were markedly elevated at study entry, both decreased after 1 year of enalapril. These results suggest that 1 year of treatment with enalapril caused both a modest regression of LV hypertrophy and a modest improvement in LV systolic function in our selected group of elderly hypertensive patients. The drug reduced elevated plasma ANP and BNP levels but did not alter BUN and serum creatinine levels. Enalapril appears to be useful for the treatment of elderly hypertensive patients with LV hypertrophy.

Plasma brain natriuretic peptide during ergometric exercise in hypertensive patients with left ventricular hypertrophy

Cardiac ventricle is shown to be an important source of circulating brain natriuretic peptide (BNP) in hypertensive rats with left ventricular hypertrophy (LVH). This study examined the effect of short-term exercise with a bicycle ergometer on plasma BNP concentrations in 21 essential hypertension patients with LVH established by echocardiography. The results were compared with those from 24 age-matched hypertensives without LVH. Blood pressure, heart rate, plasma renin activity (PRA), and plasma norepinephrine level increased during exercise, but the mean increases of these parameters were not different in the two groups. Resting BNP levels were slightly but significantly higher in the LVH group than in the non-LVH group. This peptide increased during exercise in the two groups, but the exercise-induced increase (percent increase) in plasma BNP was significantly greater in the LVH group than in the non-LVH group (207% +/- 50% v 141% +/- 36%, P < .05). The exercise-induced increase in BNP was significantly correlated with the left ventricular (LV) mass index (N = 45, r = .60, P < .01). By contrast, the exercise-induced increase in BNP was not correlated with the exercise-induced increase in heart rate, systolic blood pressure, diastolic blood pressure, mean blood pressure, PRA, or noradrenaline level. These results suggest that short-term exercise induces an accelerated increase of plasma BNP in hypertensive subjects with LVH. The LV mass appeared to be related to the observed increase of plasma BNP concentration, at least in our hypertensive patients with LVH.

Possible involvement of phospholipase D and protein kinase C in vascular growth induced by elevated glucose concentration

Hyperglycemia is believed to be a major cause of diabetic vascular complications. To elucidate the effect of hyperglycemia on vascular response, we studied hyperproliferation, hypertrophy, and the natriuretic peptide response of vascular smooth muscle cells under high-glucose conditions. We observed that cells cultured in high glucose (22.2 mmol/L) showed hyper-proliferation and hypertrophy and that natriuretic peptide receptor responses were suppressed compared with cells cultured in normal glucose (5.6 mmol/L). We also examined phospholipase D and protein kinase C activities and found that in high-glucose conditions such activities are higher than in cells cultured in normal glucose. The activation of phospholipase D was not prevented by coincubation with 1 mumol/L protein kinase C(19-36), a specific protein kinase C inhibitor, but the activation of protein kinase C was. Protein kinase C(19-36) also markedly attenuated vascular hyperproliferation and hypertrophy as well as glucose-induced suppression of natriuretic peptide receptor response. These results show that hyperglycemia may be linked to vascular hyperproliferation, hypertrophy, and a suppressed natriuretic peptide receptor response, which are caused by increased phospholipase D and protein kinase C activities.

Interaction of adrenomedullin and platelet-derived growth factor on rat mesangial cell production of endothelin

Adrenomedullin has recently been isolated from human pheochromocytoma. We designed the present study to examine the effect of adrenomedullin on the production of the vasoconstrictive and growth-promoting peptide endothelin-1 (ET-1) after stimulation with platelet-derived growth factor (PDGF) in cultured rat glomerular mesangial cells. PDGF stimulated ET-1 production in a concentration-dependent manner. Rat adrenomedullin inhibited this stimulated ET-1 production in a concentration-dependent manner between 10(-7) and 10(-8) mol/L. Rat adrenomedullin also increased the cellular level of cAMP in a concentration-dependent manner between 10(-7) and 10(-8) mol/L. Human adrenomedullin was less effective than rat adrenomedullin with respect to inhibiting ET-1 production and increasing cAMP levels. The addition of 8-bromo-cAMP (10(-3) and 10(-4) mol/L) reduced PDGF-induced ET-1 production. Furthermore, forskolin (10(-4) and 10(-5) mol/L), an activator of adenylate cyclase, reduced PDGF-induced ET-1 production. In contrast, the basal production of ET-1 was not significantly altered by rat and human adrenomedullin. These results indicate that adrenomedullin inhibits PDGF-induced ET-1 production in cultured rat mesangial cells, probably through a cAMP-dependent process.

Adrenomedullin as a novel antiproliferative factor of vascular smooth muscle cells

OBJECTIVE

The present study was designed to examine whether adrenomedullin affects fetal calf serum (FCS)-stimulated proliferation in cultured rat vascular smooth muscle cells (VSMCs).

METHODS

Rat VSMCs were grown from explants of Sprague-Dawley rat aorta and were grown using the standard cell culture method. After incubation for 24 h with various concentrations of adrenomedullin in the presence of 5% FCS, trichloroacetic acid-insoluble tritiated thymidine was measured in a liquid scintillation counter. After incubation for 48 h, cell counts were performed. Cyclic adenosine 3',5'-monophosphate (AMP) levels were determined by radioimmunoassay.

RESULTS

Rat adrenomedullin exhibited concentration-dependent inhibition of the FCS-stimulated increase in thymidine incorporation between 10(-7) and 10(-9) mol/l and of cell number at 10(-7) mol/l. However, the calcitonin generelated peptide (CGRP) receptor antagonist human CGRP(8-37) abolished these antiproliferative effects of rat adrenomedullin. Inhibition by adrenomedullin of FCS-stimulated cellular proliferation was paralleled by an increase in the cellular level of cyclic AMP. 8-Bromocyclic AMP, a cyclic AMP analogue, and forskolin, an activator of adenylate cyclase, inhibited the FCS-stimulated increase in thymidine incorporation and cell number.

CONCLUSIONS

These results suggest that adrenomedullin inhibits FCS-stimulated proliferation in cultured rat VSMCs, probably through a cyclic AMP-dependent process. Taken together with the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, adrenomedullin may play a role as an antiproliferative factor for VSMCs in a paracrine fashion.

Plasma adrenomedullin concentrations in essential hypertension

We designed the present study to assess any changes in plasma concentrations of the novel vasorelaxant peptide adrenomedullin in patients with essential hypertension. Plasma adrenomedullin concentrations were measured in 45 patients with untreated essential hypertension, 15 patients with borderline hypertension, and 30 normotensive control subjects. After 4 weeks of effective calcium channel blocker-based antihypertensive therapy, adrenomedullin concentrations were measured again. The concentrations were higher in hypertensive patients with increased serum creatinine levels or decreased glomerular filtration rates compared with borderline hypertensive patients and normotensive subjects, although values in normotensive and hypertensive individuals overlapped. Plasma adrenomedullin concentrations were positively correlated with serum creatinine levels and inversely correlated with glomerular filtration rates in the hypertensive patients, whereas adrenomedullin values were not correlated with blood pressure level, left ventricular mass index, or left ventricular ejection fraction. Despite blood pressure control with antihypertensive therapy, plasma adrenomedullin concentrations were not changed. Reversed-phase high-performance liquid chromatographic analysis showed that a major component of immunoreactive adrenomedullin in the plasma of normotensive subjects and hypertensive patients is human adrenomedullin-(1-52). These results indicate that plasma adrenomedullin concentrations are elevated in many hypertensive patients with renal dysfunction and its major component is human adrenomedullin-(1-52).

Promotion of nitric oxide formation by heparin in cultured aortic endothelial cells from spontaneously hypertensive rats

1. The present study examined the effect of heparin on nitric oxide (NO) formation and cyclic guanosine 3', 5'-monophosphate (cGMP) levels in cultured aortic endothelial cells (EC) from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. 2. Bradykinin (BK), adenosine diphosphate (ADP), Ca2+ ionophore A23187 (Io) and endothelin-3 (ET-3) stimulated the production of NO and cGMP. No significant difference was observed in both NO and cGMP production in EC between WKY and SHR. 3. Heparin enhanced BK-, ADP-, Io- and ET-3-stimulated NO and cGMP production. These enhancements by heparin in EC were significantly greater in SHR than in WKY. 4. Both NO formation and cGMP production stimulated by the agonists and/or heparin were blocked in the presence of NG-monomethyl-L-arginine (LNMMA, 10(-5) mol/L). 5. Increased sulphur level was observed on heparin-treated SHR EC surface compared with that on control SHR EC or on heparin-treated WKY EC surface. 6. These results suggest that heparin promotes agonist-induced NO-cGMP response in cultured EC from SHR.

Promotion of nitric oxide formation by heparin in cultured aortic endothelial cells from spontaneously hypertensive rats

1. The present study examined the effect of heparin on nitric oxide (NO) formation and cyclic guanosine 3', 5'-monophosphate (cGMP) levels in cultured aortic endothelial cells (EC) from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. 2. Bradykinin (BK), adenosine diphosphate (ADP), Ca2+ ionophore A23187 (Io) and endothelin-3 (ET-3) stimulated the production of NO and cGMP. No significant difference was observed in both NO and cGMP production in EC between WKY and SHR. 3. Heparin enhanced BK-, ADP-, Io- and ET-3-stimulated NO and cGMP production. These enhancements by heparin in EC were significantly greater in SHR than in WKY. 4. Both NO formation and cGMP production stimulated by the agonists and/or heparin were blocked in the presence of NG-monomethyl-L-arginine (LNMMA, 10(-5) mol/L). 5. Increased sulphur level was observed on heparin-treated SHR EC surface compared with that on control SHR EC or on heparin-treated WKY EC surface. 6. These results suggest that heparin promotes agonist-induced NO-cGMP response in cultured EC from SHR.

Enhanced phosphoinositide turnover signalling stimulated by endothelin B-type receptor in endothelial cells from spontaneously hypertensive rats

1. Endothelin (ET) B-type (ETB) receptor-mediated signal transduction was examined after stimulation with ET-3 in cultured aortic endothelial cells (EC) from spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats (8 weeks old). 2. The EC from both rat strains expressed only ETB receptor mRNA. The receptor densities and affinities, which were non-selective for ET-1, -2, -3 and Sarafotoxin S6c, and mRNA expression were similar in WKY and SHR. 3. The cytosolic Ca2+ level in the absence of extracellular Ca2+, inositol 1,4,5-trisphosphate levels, protein kinase C and phospholipase C activities in response to ET-3 were greater in SHR EC than in WKY EC. 4. The 45Ca uptake in response to ET-3, which was blocked by Ni2+, was smaller in SHR EC than in WKY EC. 5. The 6-keto-PGF1alpha production was augmented in SHR, though nitric oxide formation after stimulation with ET-3 was similar. 6. These results suggest that ETB receptor-mediated phosphoinositide turnover signalling is augmented in SHR EC through postreceptor mechanism.

Elevated glucose concentration and natriuretic peptides receptor response on vascular smooth muscle of spontaneously hypertensive rats

1. Hyperglycaemia is believed to be a major cause of diabetic vascular complications such as accelerated atherosclerosis. In order to elucidate the effect of hyperglycaemia on vascular response in spontaneously hypertensive rats (SHR), the natriuretic peptides receptor responses to vascular smooth muscle cells (VSMC) which are thought to suppress atherosclerosis were studied under high glucose (HG:22.2 mmol/L) conditions. 2. The total number of cells in SHR is higher and natriuretic peptides receptor response is smaller than that of cells in the Wistar-Kyoto (WKY) rat. Membrane bound protein kinase C (PKC) activity in HG or SHR is higher compared to that of cells in normal glucose (NG:5.6 mmol/L) or WKY. Cells cultured in HG for at least 2 passages had higher total cell number and receptor mediated cGMP formation were suppressed compared to cells cultured in NG both in SHR and WKY. Specific PKC inhibitor PKC (19-36) 1 mu mol/L prevented HG induced suppression of natriuretic peptides response. 3. These results show that hyperglycaemia may be linked to suppressed natriuretic peptides receptor response which is caused by increased PKC activity both in WKY and SHR. This suppressed response may cause the accelerated atherosclerosis by hyperglycaemia.

Effect of thrombin and PDGF on endothelin production in cultured mesangial cells derived from spontaneously hypertensive rats

1. Basal endothelin-1 (ET-1) production in mesangial cells of spontaneously hypertensive rats (SHR) was not different from that of Wistar-Kyoto (WKY) rats, although a trend toward increased ET-1 production was observed in these cells of SHR. 2. Thrombin and platelet-derived growth factor (PDGF) stimulated ET-1 production in a concentration-dependent manner in these cells of both rat strains, but thrombin- and PDGF-induced stimulation of ET-1 production were clearly greater in cells of SHR than WKY rats. 3. The protein kinase C (PKC)-activating phorbol ester, phorbol myristate acetate, stimulated ET-1 production in cells of both rat strains, but this stimulation was significantly greater in cells of SHR than in cells of WKY rats. 4. An inactive enantiomer of phorbol ester, 4alpha-PDD, had no effect on the ET-1 production in these cells of both rat strains. 5. Neither thrombin nor PDGF stimulated ET-1 production in PKC-depleted cells of both rat strains.

Aldose reductase inhibitor prevents hyperproliferation and hypertrophy of cultured rat vascular smooth muscle cells induced by high glucose

Vascular remodeling is a key process in the pathophysiology of atherosclerosis. Recent evidence suggests that high glucose levels may function as a vascular smooth muscle growth and proliferation-promoting substance. To explore the role of the polyol pathway in this process, we examined the effect of an aldose reductase inhibitor (ARI), epalrestat, on the growth characteristics of cultured rat vascular smooth muscle cells (VSMCs). Epalrestat (10 nmol/L, 1 mumol/L) significantly suppressed the high glucose-induced proliferative effect as measured by [3H]thymidine incorporation by 67% and 82% in cell number, suggesting ARI as an antimitogenic factor. In VSMCs, epalrestat (10 nmol/L, 1 mumol/L) significantly suppressed the high glucose-induced incorporation of [3H]leucine by 45% and 58% with the concomitant reduction of the cell size estimated by flowcytometry. Epalrestat (1 mumol/L) also suppressed high glucose-induced intracellular NADH/NAD+ increase and membrane-bound protein kinase C activation. These results indicate that this ARI possesses an antiproliferative and antihypertrophic action on VSMCs induced by high glucose possibly through protein kinase C suppression.

Adrenomedullin as a novel antimigration factor of vascular smooth muscle cells

The present study investigated the effect of adrenomedullin, a novel vasorelaxant peptide, on the migration of cultured rat vascular smooth muscle cells (SMCs) by using the Boyden-chamber method. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)-BB strongly stimulated SMC migration. Adrenomedullin clearly inhibited SMC migration stimulated with 5% and 10% FCS in a concentration-dependent manner. The migration induced by 10 and 25 ng/mL PDGF-BB was also inhibited by adrenomedullin in a concentration-dependent manner. Inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration was paralleled by an increase in the cellular level of cAMP. In fact, the percent increase in cAMP level was strongly correlated with the percent decrease in migration activity of SMCs after treatment with adrenomedullin. 8-Bromo cAMP, a cAMP analogue, reproduced the inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration. An activator of adenylate cyclase, forskolin, also reduced FCS- and PDGF-induced SMC migration. These data indicate that adrenomedullin inhibits the migration of SMCs stimulated with FCS and PDGF, probably through a cAMP-dependent process. On the basis of these results and the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, adrenomedullin may play a role as a local antimigration factor in some pathophysiological states.

Increased nitric oxide production in patients with hypotension during hemodialysis

OBJECTIVE

To determine the involvement of nitric oxide production in hemodialysis-induced hypotension.

DESIGN

Examination of nitric oxide synthesis, cyclic guanosine 3'5'-monophosphate (cGMP) levels, and endothelin-1 levels in plasma before and after hemodialysis.

SETTING

Veterans Affairs medical center.

PATIENTS

13 patients with end-stage renal failure who were receiving hemodialysis: Six patients had hypotensive episodes during dialysis and 7 did not.

INTERVENTION

Patients received heparin at a bolus dose of 2000 U at the initiation of dialysis followed by 1000 U/h during 4-hour hemodialysis sessions.

RESULTS

Nitric oxide production markedly increased during hemodialysis-induced hypotensive episodes; this increase was not seen in patients who did not have a hypotensive episode. In both groups, the plasma cGMP and endothelin-1 levels decreased after hemodialysis. According to multiple regression analysis, standard coefficients of nitric oxide production, plasma cGMP levels, and endothelin-1 levels with mean blood pressure after hemodialysis were -0.743, -0.07, and 0.31, respectively.

CONCLUSION

Nitric oxide production increased in patients who had a hypotensive episode during hemodialysis but did not increase in those who did not have a hypotensive episode.

Vascular dopamine-I receptors

The modulation of dopamine DA1 receptors of cultured rat renal arterial smooth muscle cells by phorbol ester, glucocorticoid and sodium chloride was studied. The extent of [3H]Sch-23390 binding to phorbol ester-treated cell was increased without any change in the dissociation constant (Kd). At a concentration of 10 nmol/l, the synthetic glucocorticoid dexamethasone increased maximum receptor binding (Bmax) but had no effect on the Kd. 100 mmol/l sodium chloride did not change Bmax, but increased the Kd for DA1 receptor. The production of cAMP in response to DA1 receptor stimulation was enhanced without any change of the adenylate cyclase activity. The glucocorticoid effect on DA1 of arterial smooth muscle cells became apparent after hours of incubation in the presence of the steroid and was significantly inhibited by cycloheximide (10 micrograms/ml) and by the glucocorticoid receptor antagonist RU-38486, indicating that the effect required protein synthesis through glucocorticoid receptors. Treatment of cells with 1 mumol/l dexamethasone for 24 h increased basal and DA1-stimulated adenylate cyclase activity. Basal adenylate cyclase was decreased by sodium chloride in a dose-dependent manner. These results suggest differential control of DA1 receptors on vascular smooth muscle cells by protein kinase C, glucocorticoid or sodium chloride.

Inhibition of endothelin production by adrenomedullin in vascular smooth muscle cells

Adrenomedullin recently has been found to potently stimulate cAMP formation in cultured rat vascular smooth muscle cells (VSMCs). In the present study, we examined the effect of adrenomedullin on the production of a vasoconstrictive and growth-promoting peptide, endothelin-1, after stimulation with a clotting enzyme, thrombin, and a potent mitogen, platelet-derived growth factor (PDGF), in cultured rat VSMCs. Thrombin and PDGF stimulated endothelin-1 production in a dose-dependent manner. Rat adrenomedullin significantly inhibited thrombin- and PDGF-stimulated endothelin-1 production in a dose-dependent manner between 10(-7) and 10(-9) mol/L. Inhibition by rat adrenomedullin of thrombin- and PDGF-stimulated endothelin-1 production was paralleled by an increase in the cellular level of cAMP. Human adrenomedullin also inhibited thrombin- and PDGF-stimulated endothelin-1 production and increased cAMP levels. The addition of 8-bromo-cAMP, a cAMP analogue, reduced thrombin- and PDGF-induced endothelin-1 production. Furthermore, forskolin, a potent activator of adenylate cyclase, reduced thrombin- and PDGF-induced endothelin-1 production. In contrast, basal production of endothelin-1 was not altered by rat or human adrenomedullin. These results indicate that adrenomedullin inhibits not basal but thrombin- and PDGF-induced ET-1 production in cultured VSMCs probably through a cAMP-dependent process. Taken together with the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, adrenomedullin may modulate vascular tone as a paracrine regulator partially through the inhibition of VSMC endothelin-1 production in some pathophysiological states.

Brain natriuretic peptide as a marker for hypertensive left ventricular hypertrophy: changes during 1-year antihypertensive therapy with angiotensin-converting enzyme inhibitor

PURPOSE

Secretion of brain natriuretic peptide (BNP), a cardiac hormone, is accelerated via hypertrophied ventricles in experimental hypertension. The present study examined whether regression of left ventricular (LV) hypertrophy by long-term treatment with an angiotensin-converting enzyme inhibitor (ACEI) affects plasma BNP concentration in patients with essential hypertension.

PATIENTS AND METHODS

Thirty-one hypertensive patients with LV hypertrophy were treated with ACEI (16 with enalapril; 15 with lisinopril) for 1 year. Serial changes were recorded in LV mass index, LV systolic function, and plasma concentrations of BNP and atrial natriuretic peptide (ANP).

RESULTS

ACEI therapy significantly reduced LV mass index at 6 months, and more so at 1 year. Septal and posterior wall thicknesses were also reduced. Plasma BNP and ANP were markedly elevated at study entry, but only BNP levels correlated with LV mass index. Both peptide levels declined after 6 months, and this decline was enhanced at 1 year. There was a close relation between BNP decline and LV mass index reduction overall and with enalapril and lisinopril separately. Changes in ANP and in LV mass index were not related.

CONCLUSION

Long-term ACEI therapy can reduce elevated plasma BNP. In this study, changes in BNP reflected the magnitude of regression of LVH. Plasma BNP may be a useful marker for LVH during antihypertensive therapy in patients with essential hypertension and LVH.