Benidipine improves endothelial function in renal resistance arteries of hypertensive rats

Interactions between renal vascular resistance and endothelium-derived hyperpolarization in hypertensive rats in vivo

Endothelium derived signaling mechanisms play an important role in regulating vascular tone and endothelial dysfunction is often found in hypertension. Endothelium-derived hyperpolarization (EDH) plays a significant role in smaller renal arteries and arterioles, but its significance in vivo in hypertension is unresolved. The aim of this study was to characterize the EDH-induced renal vasodilation in normotensive and hypertensive rats during acute intrarenal infusion of ACh. Our hypothesis was that the increased renal vascular resistance (RVR) found early in hypertension would significantly correlate with reduced EDH-induced vasodilation. In isoflurane-anesthetized 12-week-old normo- and hypertensive rats blood pressure and renal blood flow (RBF) was measured continuously. RBF responses to acute intrarenal ACh infusions were measured before and after inhibition of NO and prostacyclin. Additionally, RVR was decreased or increased using inhibition or activation of adrenergic receptors or by use of papaverine and angiotensin II. Intrarenal infusion of ACh elicited a larger increase in RBF in hypertensive rats compared to normotensive rats suggesting that endothelial dysfunction is not present in 12-week-old hypertensive rats. The EDH-induced renal vasodilation (after inhibition of NO and prostacyclin) was similar between normo- and hypertensive rats. Reducing RVR by inhibition of α1 -adrenergic receptors significantly increased the renal EDH response in hypertensive rats, but a similar increase was found after activating α-adrenergic receptors using norepinephrine. The results show that renal EDH is present and functional in 12-week-old normo- and hypertensive rats. Interestingly, both activation and inactivation of α1 -adrenergic receptors elicited an increase in the renal EDH-induced vasodilation.

Endothelium-Dependent Hyperpolarization (EDH) in Hypertension: The Role of Endothelial Ion Channels

Upon stimulation with agonists and shear stress, the vascular endothelium of different vessels selectively releases several vasodilator factors such as nitric oxide and prostacyclin. In addition, vascular endothelial cells of many vessels regulate the contractility of the vascular smooth muscle cells through the generation of endothelium-dependent hyperpolarization (EDH). There is a general consensus that the opening of small- and intermediate-conductance Ca2+-activated K⁺ channels (SKCa and IKCa) is the initial mechanistic step for the generation of EDH. In animal models and humans, EDH and EDH-mediated relaxations are impaired during hypertension, and anti-hypertensive treatments restore such impairments. However, the underlying mechanisms of reduced EDH and its improvement by lowering blood pressure are poorly understood. Emerging evidence suggests that alterations of endothelial ion channels such as SKCa channels, inward rectifier K⁺ channels, Ca2+-activated Cl- channels, and transient receptor potential vanilloid type 4 channels contribute to the impaired EDH during hypertension. In this review, we attempt to summarize the accumulating evidence regarding the pathophysiological role of endothelial ion channels, focusing on their relationship with EDH during hypertension.

A Single Resistance Exercise Session Improves Aortic Endothelial Function in Hypertensive Rats

BACKGROUND

Physical exercise is an important tool for the improvement of endothelial function.

OBJECTIVE

To assess the effects of acute dynamic resistance exercise on the endothelial function of spontaneously hypertensive rats (SHR).

METHODS

Ten minutes after exercise, the aorta was removed to evaluate the expression of endothelial nitric oxide synthase (eNOS), phosphorylated endothelial nitric oxide synthase (p-eNOS1177) and inducible nitric oxide synthase (iNOS) and to generate concentration-response curves to acetylcholine (ACh) and to phenylephrine (PHE). The PHE protocol was also performed with damaged endothelium and before and after NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin administration. The maximal response (Emax) and the sensitivity (EC50) to these drugs were evaluated.

RESULTS

ACh-induced relaxation increased in the aortic rings of exercised (Ex) rats (Emax= -80 ± 4.6%, p < 0.05) when compared to those of controls (Ct) (Emax = -50 ± 6.8%). The Emax to PHE was decreased following exercise conditions (95 ± 7.9%, p < 0.05) when compared to control conditions (120 ± 4.2%). This response was abolished after L-NAME administration or endothelial damage. In the presence of indomethacin, the aortic rings' reactivity to PHE was decreased in both groups (EC50= Ex -5.9 ± 0.14 vs. Ct -6.6 ± 0.33 log µM, p < 0.05 / Emax = Ex 9.5 ± 2.9 vs. Ct 17 ± 6.2%, p < 0.05). Exercise did not alter the expression of eNOS and iNOS, but increased the level of p-eNOS.

CONCLUSION

A single resistance exercise session improves endothelial function in hypertensive rats. This response seems to be mediated by increased NO production through eNOS activation.

Improvements in Augmentation Index and Urinary Albumin Excretion With Benidipine in Hypertensive Patients With Chronic Kidney Disease

Although calcium channel blockers (CCB) are expected to improve the augmentation index (AI) in CKD patients, the potential effect of benidipine on AI has been poorly studied.The present study aimed to compare the effect of benidipine and amlodipine in the treatment of CKD patients as measured through AI and urinary albumin excretion (UAE). Eligible patients with CKD were randomized to either the benidipine group or amlodipine group. Changes in UAE and AI were compared with target blood pressure level set at < 130/80 mmHg. A total of 108 patients were enrolled; 88 patients who were followed up were included in the analysis. Although no significant change in renal function was noted in either group, there was a significant improvement in AI only in the benidipine group (85.7 ± 13.3% to 81.4 ± 15.2%; P = 0.021) A subgroup analysis of 64 patients who achieved SBP < 140 mmHg at the end of follow-up (31 on amlodipine and 33 on benidipine) was carried out. Significant improvement in AI was noted only in the benidipine group (84.5 ± 13.6% to 79.5 ± 15.2%; P = 0.0138). In another subgroup of patients with UAE ≥ 300 mg/g Cr, a significant improvement in UAE in the benidipine group was found compared with the amlodipine group (-25 ± 46, 51 ± 60%, P = 0.031, respectively).These results suggest that benidipine might reduce significantly AI and might have potentially greater improvements in UAE than amlodipine in advanced CKD patients receiving RAS inhibitors.

The association between vitamin E intake and hypertension: results from the re-analysis of the National Health and Nutrition Survey

Recently, there has been an increasing concern about noncommunicable diseases (NCDs), in which oxidative damage plays a role. In this paper, we have re-analyzed the data from the National Health and Nutrition Survey (NHNS) 2007 to study the relationship between an NCD (e.g. hypertension) and the dietary intake of vitamin E, a potent anti-oxidative vitamin. The inclusion criteria were those aged 40 and over, excluding pregnant or lactating women, and data from 1,405 males and 2,102 females were analyzed. The mean ages were 63.5 and 62.4, respectively. Nutrients intake was evaluated from a semi-weighted, 1-d household dietary record. When the subjects were categorized into tertiles based on their vitamin E intake, higher vitamin E intake was associated with a lower percentage of subjects with hypertension (p for trend=0.01). Subjects with higher vitamin E intake had higher energy intake-adjusted intake of other nutrients which have been considered to be related to hypertension such as potassium, magnesium, and vitamin C. Logistic regression analysis was done with the low tertile of vitamin E intake as the reference. The medium and high tertiles of vitamin E intake were associated with a significantly lower odds ratio for hypertension, 0.73 (95% CI; 0.62-0.87) for the former and 0.81 (95% CI; 0.69-0.96) for the latter. Additional analyses, one adjusted for the indices associated with hypertension and one excluding the subjects with vitamin E supplementation, have yielded the similar results. In summary, re-analysis of data from NHNS has revealed that higher vitamin E intake was significantly associated with lower prevalence of hypertension.

Endothelium-dependent relaxations in the aorta from K(2p)6.1 knockout mice

K2P6.1 or TWIK-2, a two-pore domain K channel, is an important regulator of cardiovascular function. K2P6.1 is highly expressed in vascular smooth muscle and endothelium. Mice (8-12 wk) lacking functional K2P6.1 (K2P6.1(-/-)) are hypertensive and have enhanced vascular contractility. It is not known whether the lack of functional K2P6.1 in endothelium has a role in the vascular dysfunction in K2P6.1(-/-) mice. We tested the hypothesis: K2P6.1(-/-) mice have impaired endothelium-dependent relaxations. K2P6.1(-/-) mice were ∼35 mmHg more hypertensive than WT mice at both 8-12 wk (young adult) and 20-24 wk (mature mice, P < 0.01; n = 8-10). Endothelium-dependent relaxations of the thoracic aorta were evaluated by isometric myography after contraction with phenylephrine (10(-6) M). Maximal ACh-dependent relaxations were increased from 65 ± 1% to 73 ± 1% in the aorta from young adult (P < 0.01; n = 6) and from 45 ± 1% to 74 ± 1% in the aorta from mature (P < 0.001; n = 5) K2P6.1(-/-) mice compared with K2P6.1(+/+) littermates. However, in the aorta from young adult and mature K2P6.1(+/+) mice, 10(-5) M indomethacin, a cyclooxygenase inhibitor, increased maximal ACh relaxations to knockout levels. Enhanced relaxation was also seen with ATP, a P2Y purinergic agonist, and A23187, a nonreceptor-based agonist in mature K2P6.1(-/-) mice. Mature adult aorta from K2P6.1(-/-) showed an attenuated ACh-mediated contraction in the presence of nitro-l-arginine methyl ester (l-NAME) and without precontraction of 0.97 mN vs. 7.5 mN in K2P6.1(-/-) and K2P6.1(+/+) (P < 0.001; n = 5). In summary, K2P6.1(-/-) mice, which are hypertensive, have enhanced endothelium-dependent relaxations in the aorta due to the suppression of an indomethacin-sensitive constrictor component.

The effect of mebudipine on cardiac function and activity of the myocardial nitric oxide system in ischaemia-reperfusion injury in rats

Objectives

Previous studies have suggested that failure of the synthesis of nitric oxide is involved in the pathophysiology of myocardial ischaemia–reperfusion injury. In this study, we investigated the effect of mebudipine, a new dihydropyridine calcium channel blocker, on cardiac function and activity of the myocardial nitric oxide system in ischaemia–reperfusion injury in isolated rat hearts.

Methods

Forty male Wistar rats (250–300 g) were divided into four groups (n = 10): sham, control, vehicle and drug groups. The animals were anesthetised with sodium pentobarbital (6 mg/kg intraperitoneal). The hearts were quickly removed, mounted on a Longendorff apparatus and perfused with Krebs-Henseleit solution under constant pressure at 37°C. After 20 min stabilisation period, the ischaemic groups received 30 min global ischaemia and 120 min reperfusion. For the drug and vehicle groups, before ischaemia the hearts were perfused with mebudipine (10^-3 µM) or ethanol-enriched solution (0.01%) for 25 min, respectively. Myocardial function, and creatine kinase, lactate dehydogenase and total nitric oxide metabolite (nitrite and nitrate) levels were analysed.

Results

Cardiac functions had recovered significantly in the mebudipine group (p < 0.01). Furthermore, mebudipine remarkably reduced the levels of lactate dehydogenase and creatine kinase in the coronary effluent and increased myocardial nitric oxide metabolite levels compared with the control group.

Conclusion

Our results indicate that mebudipine reduced the intensity of myocardial ischaemia–reperfusion injury, and that activation of the myocardial nitric oxide system played an important role in this regard.

Renoprotective effect of calcium channel blockers in combination with an angiotensin receptor blocker in elderly patients with hypertension. A randomized crossover trial between benidipine and amlodipine

Anti-hypertensive medication with an angiotensin II receptor blocker (ARB) is effective in slowing the progression of chronic kidney disease. The present study was designed to investigate whether calcium channel blockers (CCBs) in combination with an ARB differentially affect kidney function. Elderly hypertensive patients with chronic kidney disease (n = 17, 72 +/- 6 years old) were instructed to self-measure blood pressure. They were randomly assigned to receive either benidipine (4-8 mg/day) or amlodipine (5-10 mg/day) combined with olmesartan (10 mg/day). After 3 months, CCBs were switched in each patient and the same protocol was applied for another 3 months. At baseline, significant correlation was obtained between urine albumin (22.8 +/- 16.7 (median +/- median absolute deviation) mg/g creatinine) and self-measured blood pressure (170 +/- 23/87 +/- 10 (mean +/- SD) mmHg, r = 0.65, p < 0.01). Both regimens reduced blood pressure to a similar extent (139 +/- 22/75 +/- 11 mmHg and 133 +/- 17/72 +/- 10 mmHg, respectively; both p < 0.001), while urine albumin decreased only after combination therapy including benidipine (11.7 +/- 6.1 mg/g creatinine, p < 0.05). Benidipine, but not amlodipine, in combination with olmesartan, reduced urinary albumin excretion in elderly hypertensive patients with chronic kidney disease. The results suggest the importance of selecting medications used in combination with ARB in hypertensive patients with chronic kidney disease.

Endothelium-dependent contractions in SHR: a tale of prostanoid TP and IP receptors

In the aorta of spontaneously hypertensive rats (SHR), the endothelial dysfunction is due to the release of endothelium-derived contracting factors (EDCFs) that counteract the vasodilator effect of nitric oxide, with no or minor alteration of its production. The endothelium-dependent contractions elicited by acetylcholine (ACh) involve an increase in endothelial [Ca(2+)](i), the production of reactive oxygen species, the activation of endothelial cyclooxygenase-1, the diffusion of EDCF and the subsequent stimulation of smooth muscle cell TP receptors. The EDCFs released by ACh have been identified as PGH(2) and paradoxically prostacyclin. Prostacyclin generally acts as an endothelium-derived vasodilator, which, by stimulating IP receptors, produces hyperpolarization and relaxation of the smooth muscle and inhibits platelet aggregation. In the aorta of SHR and Wistar-Kyoto rats, prostacyclin is the principal metabolite of arachidonic acid released by ACh. However, in SHR aorta, prostacyclin does not produce relaxations but activates the TP receptors on vascular smooth muscle cells and produces contraction. The IP receptor is not functional in the aortic smooth muscle cells of SHR as early as 12 weeks of age, but its activity is not reduced in platelets. Therefore, prostacyclin in the rule protects the vascular wall, but in the SHR aorta it can contribute to endothelial dysfunction. Whether or not prostacyclin plays a detrimental role as an EDCF in other animal models or in human remains to be demonstrated. Nevertheless, because EDCFs converge to activate TP receptors, selective antagonists of this receptor, by preventing endothelium-dependent contractions, curtail the endothelial dysfunction in diseases such as hypertension and diabetes.

Endothelium-dependent contractions: when a good guy turns bad!

Endothelial cells can induce contractions of the underlying vascular smooth muscle by generating vasoconstrictor prostanoids (endothelium-dependent contracting factor; EDCF). The endothelial COX-1 isoform of cyclooxygenase appears to play the dominant role in the phenomenon. Its activation requires an increase in intracellular Ca(2+) concentration. The production of EDCF is inhibited acutely and chronically by nitric oxide (NO), and possibly by endothelium-dependent hyperpolarizing factor (EDHF). The main prostanoids involved in endothelium-dependent contractions appear to be endoperoxides (PGH(2)) and prostacyclin, which activate thromboxane-prostanoid (TP) receptors of the vascular smooth muscle cells. Oxygen-derived free radicals can facilitate the production and/or the action of EDCF. Endothelium-dependent contractions are exacerbated by ageing, obesity, hypertension and diabetes, and thus are likely to contribute to the endothelial dysfunction observed in older people and in essential hypertensive patients.

Electron paramagnetic resonance investigation on modulatory effect of benidipine on membrane fluidity of erythrocytes in essential hypertension

It has been shown that benidipine, a long-lasting calcium (Ca) channel blocker, may exert its protective effect against vascular disorders by increasing nitric oxide (NO) production. The purpose of the present study was to investigate whether orally administered benidipine might influence the membrane function in patients with essential hypertension. We measured the membrane fluidity of erythrocytes by using an electron paramagnetic resonance (EPR) and spin-labeling method. In the preliminary study using erythrocytes obtained from healthy volunteers, benidipine decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-NS in the EPR spectra in vitro. The finding indicated that benidipine increased the membrane fluidity and improved the microviscosity of erythrocytes. In addition, it was demonstrated that the effect of benidipine on membrane fluidity of erythrocytes was significantly potentiated by the NO-substrate, L-arginine. In the separate series of the study, we observed that orally administered benidipine for 4 weeks significantly increased the membrane fluidity of erythrocytes with a concomitant increase in plasma NO metabolite levels in hypertensive subjects. The results of the present study demonstrated that benidipine might increase the membrane fluidity and improve the microviscosity of erythrocytes both in vitro and in vivo, to some extent, by the NO-dependent mechanism. Furthermore, it is strongly suggested that orally administered benidipine might have a beneficial effect on the rheologic behavior of erythrocytes and the improvement of the microcirculation in hypertensive subjects.

Benidipine, a dihydropyridine-Ca2+ channel blocker, increases the endothelial differentiation of endothelial progenitor cells in vitro

Benidipine is a dihydropyridine-Ca2+ channel blocker used in the treatment of hypertension and angina pectoris. In the present study, we examined the effects of benidipine on the endothelial differentiation of circulating endothelial progenitor cells (EPCs) using an in vitro culture method. Peripheral blood derived mononuclear cells (PBMCs) containing EPCs were isolated from C57BL/6 mice, and then the cells were cultured on vitronectin/gelatin-coated slide glasses. After 7 days of culture, endothelial cells differentiated from EPCs were identified as adherent cells with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine-labeled acetylated low density lipoprotein (Dil-Ac-LDL) uptake and lectin binding under a fluorescent microscope. Incubation of PBMCs for 7 days with benidipine (0.01-1 micromol/l) significantly increased the number of Dil-Ac-LDL+/fluorescein isothiocyanate-lectin (FITC-Lectin)+ cells. Wortmannin, a phosphoinositide-3 kinase (PI3K) inhibitor, selectively attenuated the effect of benidipine on the endothelial differentiation. In addition, benidipine treatment augmented the phosphorylation of Akt, indicating that the PI3K/Akt pathway contributed, at least in part, to the endothelial differentiation induced by benidipine. These results suggest that the treatment with benidipine may increase the endothelial differentiation of circulating EPCs and contribute to endothelial protection, prevention of cardiovascular disease, and/or an improvement of the prognosis after ischemic damage.

Increased oxidative stress impairs endothelial modulation of contractions in arteries from spontaneously hypertensive rats

OBJECTIVES

The endothelium modulates vascular contractions. We investigated the effects of oxidative stress on endothelial modulation of contractions in hypertension.

METHODS

Changes in isometric tension of femoral arterial rings from spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats were recorded.

RESULTS

The contractile response to norepinephrine of arteries with endothelium was greater in SHR than in WKY rats (P < 0.0001). Endothelium removal augmented the norepinephrine-induced contraction (P < 0.05). The augmentation was more pronounced in WKY than in SHR, which resulted in comparable contraction of arteries without endothelium in both strains. Nomega-nitro-L-arginine methyl ester (100 micromol/l) mimicked the effect of endothelium removal. Production of nitric oxide (NO, assessed by measuring nitrite/nitrate concentrations) during the contraction was not different between SHR and WKY. Vitamin C suppressed the contraction of arteries with endothelium from SHR but not from WKY (P < 0.05). Diphenyleneiodonium and apocynin, inhibitors of nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase, attenuated the contraction of arteries with endothelium from SHR (P < 0.001) but not WKY, but did not affect contractions induced by serotonin. Superoxide generated by xanthine oxidase/hypoxanthine enhanced the norepinephrine-induced contraction of arteries with endothelium from WKY (P < 0.0001), and this effect was reversed by vitamin C.

CONCLUSIONS

In rat femoral arteries, NO released from the endothelium modulates vascular contraction. In SHR, production of superoxide by NADH/NADPH oxidase, which may be activated by norepinephrine, is enhanced, resulting in the inactivation of NO and impairment of endothelial modulation of vascular contractions. Vascular oxidative stress may contribute to the altered circulation in hypertension by impairing endothelial modulation of vascular contractions.

Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability. Endothelial dysfunction has been associated with a number of pathophysiological processes. Oxidative stress appears to be a common denominator underlying endothelial dysfunction in cardiovascular diseases. However, depending on the pathology, the vascular bed studied, the stimulant, and additional factors such as age, sex, salt intake, cholesterolemia, glycemia, and hyperhomocysteinemia, the mechanisms underlying the endothelial dysfunction can be markedly different. A reduced bioavailability of nitric oxide (NO), an alteration in the production of prostanoids, including prostacyclin, thromboxane A2, and/or isoprostanes, an impairment of endothelium-dependent hyperpolarization, as well as an increased release of endothelin-1, can individually or in association contribute to endothelial dysfunction. Therapeutic interventions do not necessarily restore a proper endothelial function and, when they do, may improve only part of these variables.

Pharmacological, Pharmacokinetic, and Clinical Properties of Benidipine Hydrochloride, a Novel, Long-Acting Calcium Channel Blocker

Benidipine is a dihydropyridine-derived calcium channel blocker developed in Japan, with several unique mechanisms of action, that is, triple calcium channels (L, N, and T) blocking action with a membrane approach. Benidipine has relatively high vascular selectivity and is expected to show protective effects on vascular endothelial cells. Renal protective effects of benidipine also have been shown in several basic and clinical studies. Moreover, anti-oxidative action and enhancing nitric oxide production have been noted with this drug, following its cardio-protective effects in patients with ischemic heart diseases. In fact, benidipine exerted a better prognostic effect than other calcium channel blockers in the therapy for patients with vasospastic angina. In addition, benidipine showed reliable antihypertensive, renoprotective effects if used in combination with angiotensin II type 1 receptor blockers (ARBs) when adequate anti-hypertensive effects are not achieved by ARBs alone, indicating that benidipine is an useful calcium channel blocker in combination therapy for hypertension. Benidipine was launched on the Japanese market 14 years ago, but few severe side effects have been reported, suggesting that this is a drug with established safety and long-acting pharmacological effects.

A calcium channel blocker amlodipine increases coronary blood flow via both adenosine- and NO-dependent mechanisms in ischemic hearts

Amlodipine reduces oxidative stress that decreases NO and adenosine release. This study was undertaken to examine whether amlodipine mediates coronary vasodilation and improves myocardial metabolism and contractility in ischemic hearts via either adenosine- or NO-dependent mechanisms. In open-chest dogs, amlodipine (2 mug kg per min) was infused at the minimum dose that caused maximal coronary vasodilation. The perfusion pressure was reduced in the left anterior descending coronary artery so that coronary blood flow (CBF) decreased by 50%. Amlodipine increased the difference of the adenosine level (VAD (Ado): 119+/-14 to 281+/-46 nM) and the nitrate+nitrite level (VAD (NOx): 7.8+/-1.3 to 16.1+/-1.1 muM) between coronary venous and coronary arterial blood, and also increased CBF (50+/-3 to 69+/-6 ml/100 g/min). These changes were partially reversed by either 8-sulfophenyeltheophylline (8SPT) or l(omega)-nitro arginine methyl ester (l-NAME), and were completely blocked by both 8SPT and l-NAME. The reduction of CBF increased VAD (8-iso-prostaglandin F(2alpha)), and this increase was reduced by amlodipine (10.8+/-1.1 to 5.0+/-0.5 pg/ml). In addition, pretreatment with superoxide dismutase mimicked the coronary effects of amlodipine and blunted the response to amlodipine administration. Amlodipine-induced coronary vasodilation via both adenosine- and NO-dependent mechanisms. Adenosine and NO may interact in ischemic hearts to mediate coronary vasodilation by amlodipine.

Benidipine, a dihydropyridine-calcium channel blocker, prevents lysophosphatidylcholine-induced injury and reactive oxygen species production in human aortic endothelial cells

Lysophosphatidylcholine (lysoPC) is a component of oxidized low-density lipoproteins (oxLDLs), which play an important role in the pathogenesis of atherosclerosis. In this study, we examined whether benidipine hydrochloride (benidipine), a dihydropyridine-calcium channel blocker with antioxidant activity, prevents lysoPC (C 16:0)-induced injury of human aortic endothelial cells (HAEC). Treatment of HAECs with lysoPC changed cell morphology, decreased cell viability and induced DNA fragmentation, leading to apoptosis. Additionally, lysoPC species containing palmitoyl (C 16:0) or stearoyl (C 18:0), which are the major components of oxLDLs, stimulated reactive oxygen species (ROS) production and induced caspase-3/7-like activity in HAECs, but lysoPC species with short acyl chains did not affect either ROS production or caspase-3/7-like activity. Pretreatment with benidipine (0.3-3 micromol/L) for 24 h protected against lysoPC-induced cytotoxicity in the endothelial cells and the drug inhibited both lysoPC-stimulated ROS production and caspase-3/7-like activation with a similar potency. Since caspase-3/7 is involved in executing the apoptotic process, the reduction of the activity of this enzyme by benedipine may explain the anti-apoptotic effect of the drug. However, benidipine did not suppress lysoPC-induced phosphorylation of mitogen-activated protein kinases and Ca2+ influx in HAECs. These results suggest that the anti-oxidant properties of benidipine may be responsible for its ability to inhibit ROS production, resulting in reduced activation of caspase-3/7. In conclusion, benidipine suppresses lysoPC-induced endothelial dysfunction through inhibition of ROS production, which is due at least in part to its antioxidant effect, and not through the inhibition of L-type voltage-dependent calcium channels.

Benidipine improves oxidized LDL-dependent monocyte and endothelial dysfunction in hypertensive patients with type 2 diabetes mellitus

We investigated the effects of long-term benidipine treatment on levels of monocyte and endothelial cell activation markers in hypertensive patients with (n = 28) and without (n = 10) type 2 diabetes mellitus. Benidipine, 4 mg/day, was administered for 6 months; there were no other changes in any of the patients pharmacologic regimens during benidipine treatment. Clinical and biochemical data obtained before and after benidipine administration were compared; all markers were measured by ELISA. The levels of platelet activation markers (CD62P, CD63, and PAC-1), microparticles (monocyte-derived microparticles: MDMPs, and endothelial cell-derived microparticles: EDMPs), chemokines (monocyte chemotactic peptide 1: MCP-1, regulated on activation normally T-cell expressed and secreted: RANTES) and soluble adhesion markers (soluble E-selectin and soluble ICAM-1) differed in the control and hypertension groups. In addition, levels of platelet, monocyte, and endothelial cell activation markers, microparticles, chemokines, and soluble adhesion molecules were higher in hypertensive patients than in those without type 2 diabetes. Furthermore, benidipine administration decreased the concentrations of all these markers. The effect of this drug was significant in diabetes patients with high levels of antioxidized low-density lipoprotein (LDL) antibody. These results suggest that benidipine is effective for the treatment of oxLDL-dependent vascular disorders in hypertensive patients with type 2 diabetes.

Long-Term Anti-Hypertensive Therapy with Benidipine Improves Arterial Stiffness over Blood Pressure Lowering

Pulse wave velocity (PWV) reflects arterial stiffness and is an independent predictor of cardiovascular mortality and morbidity. However, because it is closely related to blood pressure (BP), PWV is an imperfect measure for evaluating the effects of anti-hypertensive drugs on arterial wall properties. To clarify the effect of benidipine on arterial properties, we first derived the regression line between BP and PWV changes in a short-term experiment. Using this line, we evaluated the long-term effect of benidipine on PWV changes. In the short-term experiment, 29 participants were intravenously administered nicardipine for 90 min. Maximum decreases of brachial-ankle PWV (baPWV) were plotted against the corresponding decreases in BP. In the long-term experiment, 9 hypertensive patients were treated with benidipine for 1 year, during which BP and baPWV were monitored. After 1 year, benidipine was suspended for 2 weeks, and BP and baPWV were reevaluated. In the short-term experiment, PWV was dependent on BP only, and the equation of the regression line was deltaPWV (cm/s) =10.114 x deltaMBP (mmHg) (r=0.913) or deltaPWV (%) =0.719 x deltaMBP (%) (r=0.926). In the long-term therapy, benidipine treatment achieved stable BP control within 3 months; the real PWV decreases (r-PWV) were almost identical to the PWV decrease estimated (e-PWV) from BP lowering at 3 months. However, r-PWV exceeded e-PWV after 6 months. Relative BP and PWV improvements compared to the control were maintained 2 weeks after suspension of benidipine. In conclusion, long-term benidipine administration improves arterial wall properties beyond what can be accounted for by changes in BP.

Benidipine Reduces Myocardial Infarct Size Involving Reduction of Hydroxyl Radicals and Production of Protein Kinase C-Dependent Nitric Oxide in Rabbits

Japanese white rabbits underwent 30 minutes of ischemia and 48 hours of reperfusion. Benidipine (3 or 10 microg/kg, i.v.) was administered 10 minutes before ischemia with and without pretreatment with L-NAME (10 mg/kg, i.v., a NOS inhibitor), chelerythrine (5 mg/kg, i.v., a PKC blocker) or 5-HD (5 mg/kg, i.v. a mitochondrial KATP channel blocker), genistein (5 mg/kg, i.v. a protein tyrosin kinase blocker). SNAP (2.5 mg/kg/min x 70 minutes, i.v., an NO donor) was also administered 10 minutes before ischemia. Benidipine significantly reduced the infarct size in a dose-dependent manner (3 microg/kg: 29.0 +/- 2.7%, n = 8, 10 microg/kg: 23.0 +/- 2.4%, n = 10) compared with the control (41.6 +/- 3.3%, n = 10). This effect was completely blocked by L-NAME (39.9 +/- 3.6%, n = 8) and chelerythrine (35.5 +/- 2.4%, n = 8) but not by 5-HD (23.0 +/- 2.4%, n = 10) or genistein (24.6 +/- 3.1%, n = 10). SNAP also reduced the infarct size (24.6 +/- 3.1%, n = 8). Benidipine significantly increased the expression of eNOS mRNA at 30 minutes after reperfusion and significantly increased the expression of eNOS protein at 3 hours after reperfusion in the ischemic area of the left ventricle. Benidipine and SNAP significantly decreased myocardial interstitial 2,5-DHBA levels, an indicator of hydroxyl radicals, during ischemia and reperfusion. Benidipine increased myocardial interstitial NOx levels, which effect was blocked by chelerythrine, during 0 to 30 minutes and 150 to 180 minutes after reperfusion. Benidipine reduces the infarct size through PKC-dependent production of nitric oxide and decreasing hydroxyl radicals but not through involving protein tyrosine kinase or mitochondrial KATP channels in rabbits.

A calcium channel blocker activates both ecto-5′-nucleotidase and NO synthase in HUVEC

Since amlodipine, a long-acting Ca channel blocker, increases both NO and adenosine production in canine hearts, we investigated that amlodipine activates both ecto-5(')-nucleotidase responsible for adenosine production and NO synthase (NOS) for NO production in human umbilical venous endothelial cells (HUVECs), and its cellular signaling. We measured activities of ecto-5(')-nucleotidase and NOS in HUVECs in the condition with additions of xanthine (100 microM)+xanthine oxidase (1.6 x 10(-3)U/ml) in the presence or absence of amlodipine (1 x 10(-9)-1 x 10(-6)M). Amlodipine increased both ecto-5(')-nucleotidase and NOS activities. Xanthine+xanthine oxidase deactivated both NOS and ecto-5(')-nucleotidase, and amlodipine increased both activities of NOS and ecto-5(')-nucleotidase by 117+/-33% and 48+/-6%, respectively. Amlodipine phosphorylated p38MAP kinase and that an inhibitor of p38MAP kinase inhibited the amlodipine-induced activation of both NOS and ecto-5(')-nucleotidase. Furthermore, amlodipine increased both adenosine and NO production in the canine ischemic hearts. We concluded that amlodipine activates both NOS and ecto-5(')-nucleotidase via p38MAP kinase in vitro and enhances both NO and adenosine production in vivo.

[Endothelium-derived factors in hypertensive blood vessels, especially nitric oxide and hypertension]

Endothelium-dependent relaxation (EDR) in the blood vessels of spontaneously hypertensive rats (SHR) and the role of nitric oxide (NO) in the initiation of hypertension are reviewed. EDR was impaired in blood vessels of SHR depending on age and degree of hypertension when compared with those of normotensive rats. The cause of the impairment varied among the type of blood vessels: a decrease in the production of NO and endothelium-derived relaxing factor (EDRF) and an increase in the production of endothelium-derived contracting factor (EDCF) are the main causes of the impairment in large arteries, while a decrease in endothelium-dependent hyperpolarization and increased release of EDCF are the main causes of the impairment in small arteries. Interactions among these endothelium-derived factors and changes in the interactions are also causes of impairment. Superoxide may be involved in the impairment of EDR by destroying NO. The endothelium depresses smooth muscle contraction, including spontaneous tone developed in vascular smooth muscle, and the depressing effect of the endothelium is impaired in the preparations from SHR. The endothelium of blood vessels of SHR are structurally injured as demonstrated by scanning electron microscopy. Antihypertensive treatment prevented these functional and structural changes. Chronic treatment with inhibitors of NO production in normotensive rats impaired EDR and elevated blood pressure. The impairment of EDR is a secondary change due to continued hypertension, and early initiation of antihypertensive therapy is recommended.

Circulating thrombomodulin levels are related to latent progression of atherosclerosis in hypertensive patients

The present study was designed to test the hypothesis that circulating levels of thrombomodulin are elevated in patients with hypertension in proportion to the severity of the vascular damage. A cross-sectional study was carried out using a population consisting of 96 patients with essential hypertension without clinically evident cardiovascular disease (mean age: 65 +/- 10 years) and 99 healthy normotensive control subjects (64 +/- 9 years). Blood was sampled and serum concentrations of soluble thrombomodulin were measured using an enzyme immunoassay method. We calculated the ratio of the concentration of thrombomodulin to that of creatinine, because soluble thrombomodulin is excreted by the kidney and the serum level of thrombomodulin was correlated with that of creatinine (p < 0.05). The association between the ratio and other clinical variables was investigated. The ratio of the thrombomodulin to creatinine concentrations was higher in hypertensive (29.3 +/- 10.9) than in control subjects (24.4 +/- 5.9; p < 0.0001). Systolic blood pressure was correlated with the ratio but the ratio showed no correlation with serum lipid levels when analyzed using data from all subjects. In hypertensive patients, the ratio correlated with the grade of sclerotic, but not hypertensive, changes in the fundus oculi (Scheie's classification, p < 0.001). Furthermore, the ratio correlated with brachial-ankle pulse wave velocity (p < 0.001). However, no correlation was detected between the ratio and blood pressure. These results suggest that circulating levels of thrombomodulin are elevated in hypertensive patients as compared to normotensive subjects and that the thrombomodulin level may be a molecular marker of the latent progression of atherosclerosis in hypertensive patients.

Altered effect of cyclopiazonic acid on endothelium-dependent relaxation in femoral arteries from hypertensive rats

The function of endoplasmic reticulum in hypertensive vascular endothelium has not been intensively studied. The current study was designed to investigate a role of intracellular Ca2+ stores in endothelium-dependent relaxations to acetylcholine using femoral arteries obtained from Wistar-Kyoto (WKYs) and spontaneously hypertensive rats (SHRs). Rings were prepared from the femoral arteries and changes in isometric tension were recorded. Endothelium-dependent relaxations induced by acetylcholine in rings contracted with serotonin were identical in WKYs and SHRs. Cyclopiazonic acid (CPA) inhibited the relaxation in SHRs but not in WKYs. In WKYs, acetylcholine evoked smaller relaxations in rings contracted with KCl than in those contracted with serotonin, whereas in SHRs the relaxation was not affected by the contractile agonists used. The relaxation in rings contracted with KCl was abolished by Nw-nitro-l-arginine methyl ester (l-NAME) and was reduced by CPA to a similar extent in both strains. In rings contracted with serotonin, l-NAME abolished the relaxation in SHRs, but the inhibitor only partially reduced the relaxation in WKYs. CPA did not alter the relaxation in the presence of l-NAME. Endothelium-independent relaxations to sodium nitroprusside were not affected by CPA. These results suggest that acetylcholine relaxes rat femoral arteries by releasing both nitric oxide and endothelium-derived hyperpolarizing factor (EDHF). In SHRs, the relaxation is preserved, but the release of EDHF is absent. CPA inhibits the relaxation mediated by nitric oxide, but not EDHF and, thus, inhibits the relaxation in SHRs but not in WKYs. Functional alteration of endoplasmic reticulum in the hypertensive endothelium cannot be detected.

Role of endogenous reactive oxygen derived species and cyclooxygenase mediators in 5-hydroxytryptamine-induced contractions in rat aorta: relationship to nitric oxide

Endogenous reactive oxygen species (superoxide anion, hydroxyl radical and hydrogen peroxide), endothelium-derived nitric oxide and cyclooxygenase mediators are involved in the regulation of vascular smooth muscle tone. An imbalance of these mediators can have profound implications in various cardiovascular disorders. Involvement of endogenous reactive oxygen species, endothelium-derived nitric oxide (NO) and cyclooxygenase mediators in 5-hydroxytryptamine- (5-HT-) induced contractions of endothelium intact rat aortic rings have been investigated in the present study. The contribution of each of the endogenous reactive oxygen species in mediating 5-HT-induced contractions was studied by pretreating the rings with their respective scavengers. Pretreatment of the rings with superoxide dismutase (superoxide radical scavenger), catalase (H (2)O (2)inactivator), mannitol (extracellular OH. scavenger), or thiourea (intracellular OH. radical scavenger) significantly depressed the 5-HT-induced contractions in the aortic rings. The responses to 5-HT in the presence of SOD or catalase were augmented byL -NAME pretreatment. Though aminotriazole partially inhibited the catalase activity, it inhibited 5-HT-induced contractions significantly. The results obtained thus suggest that endogenous generation of ROS (O(2).(-), H (2)O (2)and OH.) modulates 5-HT-induced rat aortic ring contractions. In addition, H (2)O (2)generated in the endothelium seems to regulate the vascular response and also act as a mediator to release other vasoactive substances. Basal production of NO by the endothelium seems to affect the vascular response due to its interaction with ROS mediators.

Long-term effects of benidipine on cerebral vasoreactivity in hypertensive rats

We tested the hypothesis that long-term application of a Ca2+ channel blocker would ameliorate the functional and morphological deterioration of the cerebral arteries during hypertension. Male spontaneously hypertensive rats (SHR) were fed a standard rat chow, containing a low (3 mg/kg/day) or high dose (6 mg/kg/day) of benidipine, a Ca2+ channel blocker, for 2 months. Using a cranial window, we examined responses of the basilar artery to acetylcholine, sodium nitroprusside, (-)-(3S,4R)-4-(N-acetyl-N-hydroxyamino)-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ol (Y-26763; an opener of ATP-sensitive K+ channels), and (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632; an inhibitor of Rho-associated kinase). Mean arterial pressure of the control group was 193+/-5 mm Hg (mean+/-S.E.M.), while that of the low-dose benidipine group was 183+/-5 mm Hg and that of the high-dose group was 159+/-4 mm Hg. Dilator responses of the basilar artery to acetylcholine and Y-26763 were impaired in SHR compared with those of normotensive Wistar-Kyoto (WKY) rats and treatment with benidipine enhanced the vasodilator responses to acetylcholine and Y-26763 in SHR. Y-27632-induced dilatation of the basilar artery was enhanced in SHR compared to that in WKY rats and the vasodilatation was reduced by benidipine in SHR. Sodium nitroprusside caused similar dilatation of the basilar artery, in both WKY rats and the SHR control group, and benidipine did not affect nitroprusside-induced dilatation of the artery in SHR. The wall of the basilar artery was significantly thicker in SHR than in WKY rats and benidipine treatment reduced the wall thickness of the artery in SHR. These findings suggest that chronic treatment with a Ca2+ channel blocker may enhance the dilator capacity and reduce contractility of the basilar artery during hypertension. Benidipine may also ameliorate the morphological changes of the basilar artery in hypertension.

Paradoxical release of nitric oxide by an L-type calcium channel antagonist, the R+ enantiomer of amlodipine

Amlodipine is a mixture of two enantiomers, one having L-type channel blocking activity (S-) and the other about 1,000-fold weaker activity and of little known other activity (R+). To determine whether the R+ enantiomer releases nitric oxide, the ability of amlodipine, its enantiomers, and nitrendipine to release nitric oxide in isolated coronary microvessels and to regulate cardiac tissue oxygen consumption via nitric oxide release was studied in vitro. Amlodipine and the R+ enantiomer released nitric oxide in a concentration-dependent fashion, increasing nitrite release from coronary microvessels by 57 +/- 12 and 45 +/- 5 pmol/mg/20 min at 10(-6) M (p < 0.05 from control). Nitrite release was entirely blocked by N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, and HOE-140, a B2-kinin receptor antagonist. The S- enantiomer had no effect on nitrite release at any concentration. Amlodipine and the R+ enantiomer also reduced oxygen consumption in canine cardiac tissue in vitro and this was in an L-NAME-blockable manner. The S- enantiomer of amlodipine had no effect. This study shows that the R+ enantiomer of amlodipine is responsible for the release of nitric oxide and not the S- enantiomer (the L-type calcium channel blocking portion of amlodipine). Interestingly, nitric oxide release is dependent on the production of kinins because it is blocked by HOE-140. This study defines a potentially important property by which calcium channel blockers may release nitric oxide and may contribute to their use in the treatment of cardiovascular disease.

Effects of calcium antagonist, benidipine, on the progression of chronic renal failure in the elderly: a 1-year follow-up

The number of patients who needs for dialysis therapy is increasing rapidly among the older population. Although control of hypertension can delay or arrest the progression of renal failure, there are lacking of studies about antihypertensive treatment of chronic renal failure in the elderly. We have studied the effects of treating hypertension with a calcium antagonist, benidipine, on renal function and blood pressure in 58 patients (mean age: 71 +/- 9) with hypertension and chronic renal insufficiency (the levels of creatinine ranging from 1.5 to 4.0 mg/dl). The underlying disease included glomerulopathies (in 33), diabetic nephropathy (in 15), and other causes (in 10). Forty two patients who had been treated with other antihypertensive drugs other than angiotensin converting enzyme (ACE) inhibitors, antihypertensive drugs were withdrawn 2 weeks before the entry. At the entry, patients should have sitting systolic blood pressure (SBP) of above 160 mmHg and diastolic blood pressure (DBP) of above 90 mmHg. In total, both SBP and DBP decreased from 169/95+/-12.5/8.9 to 148/81+/-16.1/8.0 mmHg (p<0.001) with remaining the serum creatinine levels from 2.2+/-0.8 vs 2.4+/-1.3 mg/dl (P>0.05). Retrospective analysis revealed that in 4 of 4 patients treated with benidipine and 2 of 3 patients with benidipine and ACE inhibitors with systolic blood pressure more than 160 mmHg at the end of the study, the levels of serum creatinine increased from 2.5+/-0.3 to 2.8+/-0.4 with significance (P<0.05). If systolic blood pressure was reduced less than 159 mmHg, 38 of 48 patients did not show any deterioration of renal function. Compared to the significance of SBP in preserving renal function, DBP did not associate with the changes in renal function. No patients died during the study. One patient had transient ischemic attack and one patient had stroke in benidipine treated group. One patient had angina pectoris in benidipine-ACE inhibitors treated group. The results of our trial seem to give some support for the idea that long-acting calcium antagonists such as benidipine are renoprotective through reduction of SBP in the elderly people with hypertension and chronic renal insufficiency. However, if systolic blood pressure was not reduced below 160 mmHg throughout a year, the substantial declines in renal function would be expected.

A calcium channel blocker, benidipine, inhibits intimal thickening in the carotid artery of mice by increasing nitric oxide production

OBJECTIVE

Recent studies suggest that several calcium channel blockers exert their protective effects against vascular disorders by increasing nitric oxide (NO) production from the endothelium. The purpose of this study was to clarify the effects of a long-lasting calcium channel blocker, benidipine, on vascular remodeling.

METHODS

The left common carotid arteries of mice were completely ligated just proximal to the carotid bifurcation. Treatment with benidipine (3 mg/kg per day) or vehicle was started 1 week before the carotid ligation, and continued throughout the experiments. Four weeks after the carotid ligation, these mice were killed and vascular remodeling was analyzed. Moreover, NO production and endothelial NO synthase (eNOS) expression were assessed.

RESULTS

At 4 weeks after ligation, the neointimal area in the vehicle-treated mice was 39,400 +/- 4,900 microm2 (n = 8), whereas that in the drug-treated mice was reduced to 18,300 +/- 3,800 microm2 (n = 10). Consequently, the luminal area was 35% larger in the drug-treated mice. Benidipine increased the basal as well as agonist-induced NO production from the endothelium, detected by Griess method or NOx analyzer. Endothelial NOS expression in vessels of the drug-treated mice was increased compared with that of the vehicle-treated mice.

CONCLUSION

Our data provide evidence that benidipine increases NO production via increment of eNOS protein in vessels and prevents intimal thickening in mice. These results show the possibility of benidipine as a protective tool against vascular remodeling independent of its effect on blood pressure.

Dual mode of action of dihydropyridine calcium antagonists: a role for nitric oxide

Dihydropyridine calcium antagonists have been used for many years in the treatment of angina pectoris and hypertension. According to the common view, their mechanism of action is based on an inhibition of the smooth muscle L-type calcium current, thus decreasing intracellular calcium concentration and inducing smooth muscular relaxation. However, in recent years evidence has accumulated that besides the smooth muscle effects of these agents, their effect on the endothelium must also to be taken into account. It was shown that dihydropyridines can induce the release of nitric oxide (NO) from the vascular endothelium of various vessels and in different species. This was first shown by Günther and colleagues by assaying the methaemoglobin formation in the presence of intact endothelium (in porcine coronary arteries) with and without treatment with nitrendipine. These findings were later confirmed by direct measurement of NO or of nitrite production. In addition, in several preparations, including micro- and macrovasculature, the sensitivity of the vasorelaxing effect of the dihydropyridines to inhibitors of NO-synthase, such as L-N(G)-nitroarginine (LNNA) or L-N-nitro-arginine-methyl-ester (L-NAME), has been shown. With these studies it became evident that the NO-releasing effect was not unique to nitrendipine but was a group phenomenon shared by the dihydropyridines and several nondihydropyridine calcium antagonists. In addition to their action on vascular endothelium, NO release by nifedipine has also been detected in platelets. There are also studies showing long term effects of calcium antagonists involving NO release. Regarding the underlying mechanism of NO release, nitrendipine was shown, not to decrease but to increase intracellular Ca2+ in cultured endothelial cells. This increase was sensitive to both Ca2+-free extracellular superfusion and to gadolinium, a lanthanide known to inhibit shear-stress activated cation channels. This increase in intracellular calcium can activate endothelial NO-synthase, thus inducing the release of NO. These findings on a dual mode of action, i.e. the direct relaxing effect by inhibition of the smooth muscle L-type calcium current and indirect relaxing effect by release of NO from vascular endothelium may help to understand the beneficial antihypertensive effects of the dihydropyridine calcium antagonists and the preferential effect of certain drugs in certain vascular regions (resistance versus conductive vessels). In addition, NO release from both vascular endothelium and platelets may contribute to the antiatherosclerotic and antithrombotic effects described for certain dihydropyridines.

Effects of amlodipine on nitric oxide synthase mRNA expression and coronary microcirculation in prolonged nitric oxide blockade-induced hypertensive rats

We evaluated the effects of long-term treatment with amlodipine, a calcium antagonist, on nitric oxide synthase (NOS) activity and NOS messenger RNA (mRNA) expression in the left ventricle (LV) and its relation to coronary reserve, and microvascular remodeling in Nomega-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Seventeen male Sprague-Dawley rats were given L-NAME (60 mg/kg/day) in drinking water for 6 weeks to induce hypertension, and then treated with amlodipine (L-NAME + A, 5 mg/kg/day, n = 9), or a vehicle (L-NAME + V, n = 8) for 4 weeks. Age-matched rats (C, n = 8) served as the control group. An increased blood pressure in L-NAME + V was significantly decreased in L-NAME + A. Nitrite production and endothelial cell (e) NOS mRNA in the LV were significantly decreased in L-NAME + V compared with C, and were significantly increased in L-NAME + A compared with C and L-NAME + V. L-NAME + V had a significantly decreased coronary reserve and capillary density, and a significantly increased type I collagen mRNA expression, wall-to-lumen ratio, perivascular fibrosis, myocardial fibrosis, and myocyte cross-sectional area. These parameters in the microvasculature were significantly improved by amlodipine. We concluded that NOS activity and eNOS mRNA were significantly increased by amlodipine in the LV of L-NAME-induced hypertensive rats, and that these increase NOS activity and eNOS mRNA expression may play a role in the amelioration of coronary reserve and microvascular remodeling.

Effects of a novel calcium antagonist, benidipine hydrochloride, on platelet responsiveness to mental stress in patients with essential hypertension

The effects of a novel calcium antagonist, benidipine hydrochloride, on responses of platelets to mental stress were evaluated in nine patients with essential hypertension. Before and 12 weeks after the monotherapy with benidipine (2-4 mg/day), platelet aggregability and plasma beta-thromboglobulin were determined during rest and after a 10-min arithmetic stress. Before the treatment, arithmetic stress significantly increased platelet aggregability in response to adenosine diphosphate (ADP) and plasma beta-thromboglobulin level. Blood pressure, pulse rate, and plasma catecholamines also increased during arithmetic stress. The treatment with benidipine did not affect resting values of platelet functions, but attenuated significantly stress-induced alterations in primary aggregation to 1.0 microM ADP (34 +/- 4% to 40 +/- 3% before treatment vs. 32 +/- 2% to 34 +/- 3% after benidipine), ADP threshold for biphasic aggregation (2.2 +/- 0.4 to 1.8 +/- 0.3 microM before treatment vs. 2.2 +/- 0.3 to 2.2 +/- 0.4 microM after benidipine) and plasma beta-thromboglobulin level (74 +/- 16 to 104 +/- 15 ng/ml before treatment vs. 60 +/- 10 to 52 +/- 8 ng/ml after benidipine; p < 0.05 for Stress x Treatment interactions in all values). The pretreatment elevations in blood pressure and sympathetic activity with stress were not modified by benidipine treatment. In conclusion, the monotherapy with benidipine did not affect platelet function during the resting condition, but significantly suppressed the platelet activation induced by arithmetic stress in patients with essential hypertension.

Effect of prolonged treatment with amlodipine on enhanced vascular contractility in cardiomyopathic hamsters

This study examined the effects of prolonged treatment with amlodipine on the enhanced vascular contractions in dilated cardiomyopathic (CM) hamsters. From the ages of 5 to 20 weeks, CM hamsters (BIO 53.58) orally received amlodipine. Then we compared the contractile responses to vasoconstrictors in aortas and mesenteric arteries from CM hamsters with or without treatment with those in the arteries from controls (F1b). We also investigated the effect of amlodipine treatment on the Ca2+ sensitivity of tension in beta-escin-skinned smooth muscle of mesenteric artery. The contractile responses to phenylephrine, angiotensin II, and high K+ in both aorta and mesenteric artery were greatly enhanced in CM hamsters compared with controls. Amlodipine treatment slightly but significantly inhibited the enhanced responses in aorta but did not alter the responses in mesenteric arteries. The Ca2+ sensitivity of tension was significantly increased in CM hamster preparations, which was unaffected by amlodipine treatment. These data indicate that amlodipine treatment differentially affects the enhanced responses to vasoconstrictors between large and small blood vessels from CM hamsters. The lack of effect of amlodipine treatment on the responsiveness of CM mesenteric artery leads to the suggestion that the preventive effect of amlodipine on focal myocytolytic necrosis of cardiomyocytes, which was previously reported to be the main cause of cardiomyopathy, results from an action on cardiomyocytes.

Flow-mediated vasodilation and distensibility of the brachial artery in renal allograft recipients

BACKGROUND

Alterations of large artery function and structure are frequently observed in renal allograft recipients. However, endothelial function has not yet been assessed in this population.

METHODS

Flow-mediated vasodilation is a useful index of endothelial function. We measured the diameter and distensibility of the brachial artery at rest using high-resolution ultrasound and Doppler frequency analysis of vessel wall movements in the M mode. Thereafter, changes in brachial artery diameter were measured during reactive hyperemia (after 4 min of forearm occlusion) in 16 cyclosporine-treated renal allograft recipients and 16 normal controls of similar age and sex ratio. Nitroglycerin-mediated vasodilation was measured to assess endothelium-independent vasodilation. Brachial artery blood pressure was measured using an automatic sphygmomanometer, and brachial artery flow was estimated using pulsed Doppler.

RESULTS

Distensibility was reduced in renal allograft recipients (5.31 +/- 0. 74 vs. 9.10 +/- 0.94 x 10-3/kPa, P = 0.003, mean +/- sem), while the brachial artery diameter at rest was higher (4.13 +/- 0.14 vs. 3.25 +/- 0.14 mm, P < 0.001). Flow-mediated vasodilation was significantly reduced in renal allograft recipients (0.13 +/- 0.08 vs. 0.60 +/- 0.08 mm or 3 +/- 2 vs. 19 +/- 3%, both P < 0.001). However, nitroglycerin-mediated vasodilation was similar in renal allograft recipients and controls (0.76 +/- 0.10 vs. 0.77 +/- 0.09 mm, NS, or 19 +/- 3 vs. 22 +/- 2%, NS). There were no significant differences in brachial artery flow at rest and during reactive hyperemia between both groups. The impairments of flow-mediated vasodilation and distensibility in renal allograft recipients remained significant after correction for serum cholesterol, creatinine, parathyroid hormone concentrations, end-diastolic diameter, as well as blood pressure levels, and were also present in eight renal allograft recipients not treated with cyclosporine. Flow-mediated vasodilation was not related to distensibility in either group.

CONCLUSIONS

The results show impaired endothelial function and reduced brachial artery distensibility in renal allograft recipients. The impairments of flow-mediated vasodilation and distensibility are not attributable to a diminished brachial artery vasodilator capacity, because endothelium-independent vasodilation was preserved in renal allograft recipients.

Protection against endothelial abnormalities by a novel calcium channel blocker, AE0047, in stroke-prone spontaneously hypertensive rats

We investigated the protective effect of chronic treatment with AE0047, a dihydropyridine-type calcium channel blocker, on vascular endothelial abnormalities in stroke-prone spontaneously hypertensive rats (SHRSP). Ten-week repeated antihypertensive treatment with AE0047 inhibited blood pressure elevation and improved endothelium-dependent relaxation in response to acetylcholine in aorta isolated from SHRSP. Furthermore, the abnormal production of prostaglandin I2 and thromboxane A2 in the aorta was normalized to a level equivalent to that in Wistar-Kyoto rats. These results suggest that chronic treatment with AE0047 exerts protective effects against endothelial abnormalities associated with the development of hypertension.

A Ca channel blocker, benidipine, increases coronary blood flow and attenuates the severity of myocardial ischemia via NO-dependent mechanisms in dogs

OBJECTIVES

This study was undertaken to examine whether a dihydropyridine Ca channel blocker, benidipine, increases cardiac NO levels, and thus coronary blood flow (CBF) in ischemic hearts.

BACKGROUND

Benidipine protects endothelial cells against ischemia and reperfusion injury in hearts.

METHODS AND RESULTS

In open chest dogs, coronary perfusion pressure (CPP) of the left anterior descending coronary artery was reduced so that CBF decreased to one-third of the control CBF, and thereafter CPP was maintained constant (103+/-8 to 42+/-1 mmHg). Both fractional shortening (FS: 6.1+/-1.0%) and lactate extraction ratio (LER: -41+/-4%) decreased. Ten minutes after the onset of an intracoronary infusion of benidipine (100 ng/kg/min), CBF increased from 32+/-1 to 48+/-4 ml/100g/ min during 20 min without changing CPP (42+/-2 mmHg). Both FS (10.7+/-1.2%) and LER (-16+/-4%) also increased. Benidipine increased cardiac NO levels (11+/-2 to 17+/-3 nmol/ml). The increases in CBF, FS, LER and cardiac NO levels due to benidipine were blunted by L-NAME. Benidipine increased cyclic GMP contents of the coronary artery of ischemic myocardium (139+/-13 to 208+/-15 fmol/mg protein), which was blunted by L-NAME.

CONCLUSION

Thus, we conclude that benidipine mediates coronary vasodilation and improves myocardial ischemia through NO-cyclic GMP-dependent mechanisms.

Forearm vasorelaxation in hypertensive renal transplant patients: the impact of withdrawal of cyclosporine

OBJECTIVE

To determine whether cyclosporine A-induced hypertension in renal transplant recipients is accompanied by impairment of endothelium-dependent vasodilatation, which has been suggested by in-vitro and in-vivo animal experiments.

DESIGN AND METHODS

In-vivo endothelium-dependent and endothelium-independent vasodilatation, and plasma concentrations of vasoactive hormones in 16 renal transplant patients were determined while they were being treated with cyclosporine A, and 16 weeks later, after their treatment had been changed to azathioprine therapy. The vasodilator response of the forearm vascular bed was measured by strain gauge venous occlusion plethysmography during intra-arterial infusion of acetylcholine (endothelium-dependent vasodilatation) and nitroprusside (endothelium-independent vasodilatation). Postischemic reactive flow was measured after 10 min of arterial occlusion. In addition, plasma concentrations of norepinephrine, and the prostanoids prostaglandin E2 and thromboxane B2, and also concentration of cyclosporine A in blood, were measured. Glomerular filtration rate and renal blood flow were estimated 1 day before the plethysmography study during each treatment period.

RESULTS

Upon changing from cyclosporine A to azathioprine treatment, mean arterial pressure fell significantly by 12+/-3% (P< 0.05). Glomerular filtration rate and renal blood flow increased by 13+/-5 and 19+/-8%, respectively (both P< 0.05), while renal vascular resistance fell by 48+/-11% (P< 0.01). Both baseline forearm blood flow and baseline forearm resistance did not change after conversion (5.7+/-0.7 versus 4.9+/-0.6 ml/100 ml/min, and 27.3+/-4.2 versus 26.2+/-3.2 arbitrary units). The absolute and relative forearm blood flow responses, and forearm vascular resistance responses to infusions of acetylcholine and nitroprusside were similar during treatments with cyclosporine A and azathioprine. Peak postischaemic forearm blood flow was 42+/-12% higher during cyclosporine A treatment than it was during azathioprine treatment (P< 0.05), but the minimal postischaemic forearm vascular resistance did not differ for these treatments. Plasma prostaglandin E2 and thromboxane B2 levels decreased by 34+/-7 and 45+/-8%, respectively, after changing treatment, but norepinephrine levels did not change.

CONCLUSIONS

Our data indicate that cyclosporine A-induced hypertension in renal transplant recipients is not accompanied by an increase in forearm vascular resistance. In addition, changing from cyclosporine A to azathioprine treatment did not cause changes in endothelial vasodilator functioning, although mean arterial pressure decreased significantly. Our results do not support the hypothesis that attenuation of endothelial vasodilator functioning contributes to the development of cyclosporine A-induced hypertension.

Heterogeneity of endothelial function within the circulation

As our understanding of endothelial function continues to evolve, it has become increasingly clear that the peripheral vasculature exhibits striking regional and segmental heterogeneity in the influence of the endothelial cell layer on vascular tone. This heterogeneity encompasses not only the normal interactions between endothelium-derived factors and vascular smooth muscle, but also the way in which these interactions can change during juvenile growth or in disease states such as hypertension. The underlying causes of this heterogeneity are multifactorial and include intrinsic differences among endothelial cell populations and differences in the endothelial cell microenvironment.