Tsutomu Imaizumi

Single LDL Apheresis Improves Endothelium-Dependent Vasodilatation in Hypercholesterolemic Humans

BACKGROUNDnAlthough long-term lipid-lowering therapy improves endothelium-dependent vasodilatation in humans, it remains unknown whether the short-term removal of LDL per se ameliorates endothelial dysfunction.nnnMETHODS AND RESULTSnTo examine the effects of a single session of LDL apheresis on endothelial function in patients with hypercholesterolemia, we measured forearm blood flow (FBF) by strain-gauge plethysmography before and after single LDL apheresis while infusing acetylcholine (ACh; 4 to 24 micrograms/min) and sodium nitroprusside (SNP; 0.2 to 1.2 micrograms/min). The single session of LDL apheresis reduced total LDL (from 142.2 +/- 15.0 to 32.6 +/- 5.0 mg/mL, P < .0005) and oxidized LDL (from 111.6 +/- 22.8 to 30.0 +/- 5.4 ng/mL, P < .005). Although ACh and SNP increased FBF dose-dependently before and after LDL apheresis, the endothelium-dependent vasodilatation responses to ACh were significantly augmented (P < .01) after the single session of LDL apheresis without changes in the endothelium-independent vasodilatation responses to SNP. The plasma levels of total and oxidized LDL correlated with the degree of ACh-induced vasodilatation. Furthermore, the local production of nitrate/nitrite, metabolites of NO, during ACh infusion was significantly (P < .05) augmented by LDL apheresis, and there was a significant correlation between the degree of ACh-induced vasodilatation and the production in nitrate/nitrite (r = .99, P < .0005).nnnCONCLUSIONSnWe demonstrated that even a single session of LDL apheresis with the reduction of total LDL and oxidized LDL improved endothelial function. Our results suggest that total LDL and/or oxidized LDL may directly impair endothelial function in the human forearm vessel.

Asymmetrical Dimethylarginine, an Endogenous Nitric Oxide Synthase Inhibitor, in Experimental Hypertension

NG,NG-dimethyl-L-arginine (ADMA) is an endogenously synthesized nitric oxide (NO) synthase inhibitor which has potent pressor/vasoconstrictor effects. Dimethylargininase metabolizes ADMA to L-citrulline and plays a key role in determining the in vivo levels of ADMA. To investigate the role of ADMA in the pathogenesis of hypertension, we measured 24-hour urinary excretion of ADMA (UADMA) and nitrate/nitrite (NOx) in Dahl salt-sensitive hypertensive rats and spontaneously hypertensive rats (SHR). In Dahl salt-resistant rats, high-salt diet (8% NaCl) did not increase blood pressure and increased urinary NOx (P < .01) without changes in UADMA compared with low-salt diet (0.3% NaCl). In contrast, in Dahl salt-sensitive rats, high-salt diet increased blood pressure (P < .01), did not change urinary NOx excretion, and increased UADMA (P < .01). There was a significant (r = .65, P < .01) correlation between UADMA and the level of blood pressure in Dahl salt-sensitive rats. Plasma levels of NOx and ADMA and renal dimethylargininase content were comparable among them. These results may suggest that in Dahl salt-resistant rats, blood pressure is kept constant during high-salt intake, possibly due to the compensatory increased production of NO, and that in Dahl salt-sensitive rats, high-salt intake increases the production of ADMA, attenuates the compensatory increases in NO, and increases blood pressure. These results also suggest that the systemic production of ADMA is not dependent on renal dimethylargininase. SHR had significantly greater urinary NOx excretion (P < .05) and smaller UADMA than Wistar-Kyoto rats (P < .05), and UADMA was inversely correlated with their mean arterial pressure (r =.64, P < .05). In conclusion. ADMA, independently of the renal dimethylargininase content, may play a role in the pathogenesis in Dahl salt-sensitive hypertensive rats but not in SHR.

Long-term Smoking Impairs Platelet-Derived Nitric Oxide Release

BACKGROUNDnLong-term smoking impairs endothelium-dependent vasodilation, which is mediated by nitric oxide (NO). However, it is unknown whether long-term smoking impairs the platelet-derived NO release, which regulates platelet aggregation.nnnMETHODS AND RESULTSnPlatelet-derived electrical current induced by collagen was measured with an NO-selective electrode in 12 smokers and 11 nonsmokers. Collagen-induced intraplatelet cGMP and platelet aggregation was measured in smokers and nonsmokers. S-nitroso-N-acetyl-dl-penicillamine, a direct NO donor, dose dependently increased in electrical current (r = .99). Collagen induced platelet aggregation and dose dependently increased electrical current (r = .94). Collagen-induced electrical current and cGMP were significantly augmented by L-arginine, a precursor of NO, and attenuated by NG-monomethyl-L-arginine, an inhibitor of NO synthesis. Significant correlation was found between collagen-induced electrical current and cGMP (r = .73). These findings indicate that the change in electrical current reflects the NO release through the L-arginine-NO pathway in platelets. Collagen-induced electrical current (6.7 versus 13.8 pA; P < .001) and cGMP (1.2 versus 3.0 pmol/10(9) platelets; P < .005) were significantly lower in smokers than in nonsmokers. Although L-arginine increased cGMP levels in both smokers and nonsmokers, the level was still lower in smokers than in nonsmokers. The inhibitory effect of L-arginine on collagen-induced platelet aggregation was significantly lower in smokers than in nonsmokers (P < .05).nnnCONCLUSIONSnThese findings provide evidence that platelet-derived NO release is significantly impaired in long-term smokers, resulting in the augmentation of platelet aggregability.

Inhibition of Intimal Hyperplasia After Balloon Injury by Antibodies to Intercellular Adhesion Molecule-1 and Lymphocyte Function–Associated Antigen-1

BACKGROUNDnAlthough intercellular adhesion molecule-1 (ICAM-1) is known to be expressed in balloon-injured arteries, it remains unknown whether ICAM-1 plays a role in the progression of intimal hyperplasia (IH) induced by balloon injury.nnnMETHODS AND RESULTSnWe examined the ICAM-1 expression in rat carotid arteries at 1, 2, 5, 7, 10, and 14 days after injury by immunohistochemistry. Medial smooth muscle cells (SMC) expressed ICAM-1 intensely at 1 to 2 days after injury. The regenerating endothelial cells expressed ICAM-1 more than did those of intact carotid arteries. To investigate the effects of monoclonal antibodies (MAbs) on IH, we examined the intima/ medial ratio of arteries at 2 weeks after injury in five treatment groups: nonimmune IgG, anti-membrane glycoprotein MAb, anti-lymphocyte function-associated antigen-1 (LFA-1) MAb, anti-ICAM-1 MAb, and anti-ICAM/LFA-1 MAb. Treatments were administered intravenously into rats for 6 consecutive days after injury. MAb against LFA-1 alone or membrane glycoprotein had no effect on IH. The intima/media ratios in anti-ICAM-1 MAb-treated and anti-ICAM-1/LFA-1 MAb-treated animals were significantly less than those in nonimmune IgG-treated and anti-membrane glycoprotein MAb-treated animals (P < .05).nnnCONCLUSIONSnBalloon injury induced or upregulated the ICAM-1 expression on vascular SMC and on regenerating endothelial cells. MAb against ICAM-1 or ICAM-1/LFA-1 attenuated IH. These results suggest that ICAM-1 may play a role in the progression of IH after injury in rats.

Effects of Monoclonal Antibody to P-Selectin and Analogue of Sialyl Lewis X on Cyclic Flow Variations in Stenosed and Endothelium-Injured Canine Coronary Arteries

BACKGROUNDnA fundamental role of cell adhesion molecules is implicated in the disease processes of acute coronary syndromes. We have shown an increase in the soluble form of P-selectin in these syndromes, suggesting the important interaction between P-selectin and sialyl Lewis X (SLe(x)) for the pathophysiology of these syndromes. To further test this, we examined the effects of a monoclonal antibody against P-selectin (PB1.3) and a carbohydrate analogue of SLe(x) (SLe(x)-OS) on cyclic flow variations (CFVs) in stenosed and endothelium-injured canine coronary arteries.nnnMETHODS AND RESULTSnAnesthetized, open-chest dogs (n = 48) were divided into six groups after CFVs were established. Dogs received intravenous normal saline, PB1.3 (1 mg/kg bolus), a low dose (5 mg/kg bolus) or a high dose (40 mg/kg bolus) of SLe(x)-OS followed by an infusion (5 mg.kg-1.h-1) for 60 minutes, a combination of PB1.3 and SLe(x)-OS (low dose), or a combination of a nonblocking antibody against P-selectin (PNB1.6, 1 mg/kg) and SLe(x)-OS (low dose). Although saline, PB1.3, SLe(x)-OS (low dose), and the combination of PNB1.6 and SLe(x)-OS (low dose) did not affect CFVs, the high dose of SLe(x)-OS and the combination of PB1.3 and SLe(x)-OS (low dose) significantly reduced CFVs.nnnCONCLUSIONSnThese findings indicate that the high dose of SLe(x)-OS and the combination of PB1.3 and the low dose of SLe(x)-OS provide protection against CFVs. Thus, the adhesive interaction between P-selectin and SLe(x) may play an important role in mediating CFVs in this model.

Hyperinsulinaemia as a predictor of hypertension : an 11-year follow-up study in Japan

Objective To examine the hypothesis that hyperinsulinaemia is associated with the development of borderline hypertension or hypertension. Design Blood pressure status in non-obese normotensives (< 140/90 mmHg, n = 135) people were re-examined after 11 years after the baseline examination. Participants were selected from a 1981 population-based health examination and had a high blood glucose level or more than a trace of glucose in their urine. Out of 319 people recruited for further examination of glucose tolerance status, 135 normotensive participants with body mass index < 26 kg/m2 and without diabetes according to World Health Organization criteria were re-examined at the follow-up survey. Results Sixty-two (46%) out of 135 normotensive participants were hypertensive (defined as blood pressure ≥ 140/90 mmHg) or receiving antihypertensive medication (n = 8) at the follow-up survey. Significant associations between the development of hypertension and baseline parameters were observed for systolic and diastolic blood pressure, serum triglycerides, high-density lipoprotein (HDL)-cholesterol, fasting and 60 min post-load insulin levels, and the sum of insulin concentrations from fasting to 180 min after glucose challenge after adjustments for age and sex. Odds ratios (95% confidence intervals) for the future development of hypertension between the highest and the lowest tertiles of insulin levels were 4.06 (1.40–11.76) for fasting insulin, 4.25 (1.45–12.45) for 60 min post-glucose load insulin, and 3.88 (1.34–11.20) for the sum of insulin concentrations, after adjustment for age, sex, systolic blood pressure, body mass index and alcohol consumption. Further adjustments for serum triglycerides and serum creatinine did not affect the insulin–hypertension relationship. Conclusion The present study suggests that hyperinsulinemia is significantly related to the development of hypertension in non-obese and non-diabetic Japanese people.

Renal Denervation Prevents Intraglomerular Platelet Aggregation and Glomerular Injury Induced by Chronic Inhibition of Nitric Oxide Synthesis

Nitric oxide (NO) inhibits platelet adhesion and aggregation in vitro. In vivo, chronic inhibition of NO synthesis induces nephrosclerosis and hypertension. Although the pathophysiological mechanism of this glomerular injury has not been clarified, sympathetic nerve activation, a potent procoagulant stimulus elicited by NO inhibition, may play a role. To investigate the role of renal sympathetic nerves in the development of renal injury induced by NG-nitro-L-arginine methyl ester (L-NAME), a specific NO synthesis inhibitor, we examined renal histological changes in four groups of Sprague-Dawley rats: (1) sham operated, vehicle treated; (2) sham operated, L-NAME treated; (3) denervated, vehicle treated, and (4) denervated, L-NAME treated. Following renal denervation or sham operation, L-NAME was administered orally for 4 weeks. Chronic NO inhibition induced platelet aggregation and erythrocyte stasis in the glomerular capillary lumen accompanied by electron-microscopic glomerular injury. Renal denervation abrogated platelet aggregation and glomerular injury in L-NAME-treated animals. Thus, chronic NO synthesis inhibition induced intraglomerular platelet aggregation and glomerular injury, which was attenuated by renal nerve denervation. These results suggest that intrinsic NO may have an antithrombotic effect in the glomeruli and may play a protective role in the progression of glomerular injury possibly mediated by renal sympathetic nerves.