Kozo Yao

Blockade of T-type voltage-dependent Ca2+ channels by benidipine, a dihydropyridine calcium channel blocker, inhibits aldosterone production in human adrenocortical cell line NCI-H295R.

Benidipine, a long-lasting dihydropyridine calcium channel blocker, is used for treatment of hypertension and angina. Benidipine exerts pleiotropic pharmacological features, such as renoprotective and cardioprotective effects. In pathophysiological conditions, the antidiuretic hormone aldosterone causes development of renal and cardiovascular diseases. In adrenal glomerulosa cells, aldosterone is produced in response to extracellular potassium, which is mainly mediated by T-type voltage-dependent Ca2+ channels. More recently, it has been demonstrated that benidipine inhibits T-type Ca2+ channels in addition to L-type Ca2+ channels. Therefore, effect of calcium channel blockers, including benidipine, on aldosterone production and T-type Ca2+ channels using human adrenocortical cell line NCI-H295R was investigated. Benidipine efficiently inhibited KCl-induced aldosterone production at low concentration (3 and 10 nM), with inhibitory activity more potent than other calcium channel blockers. Patch clamp analysis indicated that benidipine concentration-dependently inhibited T-type Ca2+ currents at 10, 100 and 1000 nM. As for examined calcium channel blockers, inhibitory activity for T-type Ca2+ currents was well correlated with aldosterone production. L-type specific calcium channel blockers calciseptine and nifedipine showed no effect in both assays. These results indicate that inhibition of T-type Ca2+ channels is responsible for inhibition of aldosterone production in NCI-H295R cells. Benidipine efficiently inhibited KCl-induced upregulation of 11-beta-hydroxylase mRNA and aldosterone synthase mRNA as well as KCl-induced Ca2+ influx, indicating it as the most likely inhibition mechanism. Benidipine partially inhibited angiotensin II-induced aldosterone production, plus showed additive effects when used in combination with the angiotensin II type I receptor blocker valsartan. Benidipine also partially inhibited angiotensin II-induced upregulation of the above mRNAs and Ca2+ influx inhibitory activities of benidipine for aldosterone production. T-type Ca2+ channels may contribute to additional benefits of this drug for treating renal and cardiovascular diseases, beyond its primary anti-hypertensive effects from blocking L-type Ca2+ channels.

Protective effects of benidipine on hydrogen peroxide-induced injury in rat isolated hearts.

We investigated the effects of benidipine (hydrochloride), a calcium antagonist, on hydrogen peroxide (H2O2)‐induced injury in Langendorff‐perfused rat hearts. The hearts were aerobically perfused at a constant flow and exposed to H2O2 (600 μmol L−1) for 4 min, resulting in the oxidative stress‐induced myocardial dysfunction (e.g., decrease in the left ventricular developed pressure) and myocardial cell injury (e.g., increase in the release of lactate dehydrogenase). Pretreatment of the hearts with benidipine or nifedipine was performed for 20 min until the start of H2O2 exposure. Benidipine at 1 nmol L−1 and nifedipine at 10 nmol L−1 decreased the myocardial contractility and perfusion pressure to a similar degree in the hearts under normal conditions. Benidipine (1 nmol L−1) significantly reduced the H2O2‐induced myocardial damage. Nifedipine (10 nmol L−1) also tended to exhibit similar effects. Benidipine inhibited the increase in tissue lipid peroxidation induced by H2O2. The results suggest that, in addition to the calcium antagonism, benidipine possesses other actions responsible for the cardioprotective effects, to which the antioxidant activity of benidipine may partly contribute.

The selective adenosine A1 receptor antagonist KW-3902 prevents radiocontrast media-induced nephropathy in rats with chronic nitric oxide deficiency.

Several studies have recently suggested a principal role of adenosine in the pathogenesis of radiocontrast media-induced nephropathy. In the present experiments, we therefore investigated the renal protective effects of 8-(noradamantan-3-yl)-1,3-dipropylxanthine (KW-3902), a potent and selective adenosine A1 receptor antagonist, on radiocontrast media-induced nephropathy in the model of the N-pi-nitro-L-arginine methyl ester (L-NAME) hypertensive, chronic nitric oxide (NO)-depleted rat. Chronic NO depletion was induced by pretreatment with L-NAME, 50 mg/ml, added to drinking water for 8 weeks. Clearance experiments were performed in anesthetized rats and glomerular filtration rate was assessed prior to and following the application of high osmolar radiocontrast media (sodium diatrizoate, 3 ml/kg, i.v.) or an equivalent volume of isoosmolar mannitol to examine the role of hyperosmolarity in radiocontrast media-induced nephropathy. Subgroups received KW-3902 (0.1 mg/kg, i.v.), 20 min prior to radiocontrast media administration. Age-matched, untreated rats served as controls. Radiocontrast media application induced a significant decline in glomerular filtration rate in L-NAME hypertensive animals, whereas no effects were observed in control rats. KW-3902 fully prevented the drop in glomerular filtration rate in response to radiocontrast media in L-NAME hypertensive rats. No renal hemodynamic alterations were observed in mannitol-infused animals. The present experiments demonstrate that the decrease in glomerular filtration rate following radiocontrast media occurred independently of the osmotic load, and that KW-3902 effectively prevented the radiocontrast media-induced deterioration in renal function. KW-3902 may be especially beneficial in patients at high risk for developing acute renal failure following radiocontrast media application or in patients in which extracellular fluid volume expansion is limited by clinical conditions such as congestive heart failure.

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 (DiI-Ac-LDL) uptake and lectin binding under a fluorescent microscope. Incubation of PBMCs for 7 days with benidipine (0.01–1 μmol/l) significantly increased the number of DiI-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.

Effects of combination of angiotensin receptor blocker and calcium channel blocker on ox-LDL levels and cardiovascular dysfunction in Dahl rats.

In an effort to assess the cardiovascular benefits of combined angiotensin receptor blockage and calcium channel antagonism, we assessed the chronic effects of the angiotensin type 1 receptor blocker candesartan, the calcium channel blocker benidipine, and the use of a combination therapy in Dahl salt-sensitive (DS) rats. DS rats receiving a high salt diet were treated with either benidipine (4 mg/kg), candesartan (1 mg/kg) or both. Rat blood pressure was measured using a tail-cuff method. Following 12 weeks, the effect on heart weight, plasma-oxidized low-density lipoprotein (ox-LDL) level, endothelium-dependent vasorelaxation, and histology of the heart and aorta was assessed. Blood pressure, heart weight and plasma ox-LDL levels increased, while endothelium-dependent vasorelaxation decreased in the DS rats. Candesartan and benidipine inhibited the increase in blood pressure and heart weight, and the decrease in endothelium-dependent vasorelaxation. The use of benidipine alone or a combination significantly inhibited the increase in ox-LDL levels, whereas candesartan alone had no significant effect on ox-LDL levels. The present findings indicate that, if the monotherapy using ARB could not achieve adequate control of blood pressure, the combination therapy with ARB and benidipine provides the additional reductions in hypertension and cardiac hypertrophy. Moreover, the combination therapy inhibits cardiovascular dysfunction and ox-LDL levels more effectively than use of ARB alone. These results contribute to the possibility of lowering ox-LDL levels as a means of enhancing cardiovascular protection.