The evaluation of the N-type channel blocking properties of cilnidipine and other voltage-dependent calcium antagonists

Inhibition of Contractility of Isolated Caprine Detrusor by the Calcium Channel Blocker Cilnidipine and Reversal by Calcium Channel Openers

Background

Cilnidipine is a fourth-generation calcium channel blocker that is clinically used to treat hypertension. It is a dihydropyridine that blocks L- and N-type calcium channels. The inhibitory effect of cilnidipine on isolated detrusor muscle contractility has not been studied. This study investigated the inhibitory effect of cilnidipine on isolated caprine (goat) detrusor muscle contractility and the reversal of the inhibition by calcium channel openers.

Methods

Fourteen caprine detrusor strips were made to contract using 80 mM potassium chloride before and after addition of three concentrations (20, 40, and 60 µM) of cilnidipine. Two reversal agents, the L-type calcium channel opener FPL64716, and the N-type calcium channel opener GV-58, were investigated for their ability to reverse the inhibitory effect of 40 µΜ cilnidipine on potassium chloride-induced detrusor contractility.

Results

Cilnidipine caused a dose-dependent and statistically significant inhibition of detrusor contractility at all concentrations of cilnidipine used (20, 40, and 60 µΜ). The inhibitory effect of 40 µM cilnidipine on detrusor contractility was significantly reversed by the addition of FPL64716 and GV-58.

Conclusions

Cilnidipine inhibits the contractility of the isolated detrusor by blocking L- and N-type calcium channels. Cilnidipine could be evaluated for treating clinical conditions requiring relaxation of the detrusor such as overactive bladder.

New Insights into the Nephroprotective Potential of Lercanidipine

Kidneys are responsible for many crucial biological processes in the human body, including maintaining the water-electrolyte balance, pH, and blood pressure (BP), along with the elimination of toxins. Despite this, chronic kidney disease (CKD), which affects more and more people, is a disease that develops insidiously without causing any symptoms at first. The main purpose of this article is to summarize the existing literature on lercanidipine, with a particular focus on its nephroprotective properties. Lercanidipine is a third-generation dihydropyridine (DHP) blocker of calcium channels, and as such it possesses unique qualities such as high lipophilicity and high vascular selectivity. Furthermore, it acts by reversibly inhibiting L-type and T-type calcium channels responsible for exerting positive renal effects. It has been shown to reduce tissue inflammation and tubulointerstitial fibrosis, contributing to a decrease in proteinuria. Moreover, it exhibited antioxidative effects and increased expression of molecules responsible for repairing damaged tissues. It also decreased cell proliferation, preventing thickening of the vascular lumen. This article summarizes studies simultaneously comparing the effect of lercanidipine with other antihypertensive drugs. There is still a lack of studies on the medications used in patients with CKD, and an even greater lack of studies on those used in patients with concomitant hypertension. Therefore, further studies on lercanidipine and its potential in hypertensive patients with coexisting CKD are required.

Differential Effects of Ca2+ Channel Blockers Nifedipine and Cilnidipine on Arterial Elasticity in the Aortic and Femoral Arterial Segments of Anesthetized Rabbits

Ca2+ channel blockers have potent vasodilatory effects and excellent efficacy in preserving organ blood flow. These hemodynamic actions may be partly controlled by the functional stiffness of conduit arteries. In this study, we assessed the effects of the L-type Ca2+ channel blocker nifedipine on aortic and femoral arterial stiffness (referred to as aortic β and femoral β, respectively) in anesthetized rabbits. To further clarify the involvement of the autonomic nervous system, we compared the effects of nifedipine with those of the L/N-type Ca2+ channel blocker cilnidipine. Further, the effect of the α-adrenergic receptor blocker doxazosin on the effects of nifedipine on arterial elasticity was examined. An antihypertensive dose of nifedipine (300 µg/kg, administered intravenously) was found to increase the aortic β but hardly affected the femoral β. An antihypertensive dose of cilnidipine (30 µg/kg, administered intravenously) increased the aortic β but decreased the femoral β. Interestingly, nifedipine decreased the femoral β in the presence of the α-adrenoceptor blocker doxazosin (1 mg/kg, administered intravenously). These effects suggest that L-type Ca2+ channel blockers essentially increase vascular elasticity via the decrement in arterial stiffness in the femoral artery segment, which is modified by the presence or absence of the inhibitory effect of each drug on reflex sympathetic nerve activity, while decreasing vascular elasticity via the increment in arterial stiffness in the aortic segment independently of sympathetic nerve activity.

The fourth-generation Calcium channel blocker: cilnidipine

Several classes of antihypertensive agents have been in clinical use, including diuretics, α-blockers, β-blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II type 1 receptor blockers (ARB), and organic calcium channel blockers (CCBs). All these drugs are being currently used in the treatment of Hypertension & various disease conditions of the heart either alone or in combination. Cilnidipine is a new antihypertensive drug distinguished from other L-type Ca(2+) channel blockers or even other antihypertensives, which will be useful for selection of antihypertensive drugs according to the pathophysiological condition of a patient.

Comparison of the effects of cilnidipine and amlodipine on cardiac remodeling and diastolic dysfunction in Dahl salt-sensitive rats

OBJECTIVE

The L/N-type calcium channel blocker (CCB) cilnidipine suppresses sympathetic nerve activity and has a superior renoprotective effect compared with L-type CCBs such as amlodipine. The cardioprotective action of cilnidipine has remained largely uncharacterized, however. We have now investigated the effects of cilnidipine, in comparison with amlodipine, on cardiac pathophysiology in rats with salt-sensitive hypertension.

METHODS

Dahl salt-sensitive rats fed a high-salt diet from 6 weeks of age were treated with vehicle (LVH group), amlodipine (3 mg/kg per day), or cilnidipine (3 mg/kg per day) from 7 to 11 weeks.

RESULTS

The salt-induced increase in SBP apparent in LVH rats was attenuated to a similar extent by treatment with amlodipine or cilnidipine. The two drugs also similarly inhibited the development of left ventricular (LV) hypertrophy. However, cilnidipine attenuated the increase in relative wall thickness as well as ameliorated LV perivascular and interstitial fibrosis and diastolic dysfunction to a greater extent than did amlodipine. In addition, cilnidipine treatment was associated with greater inhibition of cardiac oxidative stress, inflammation, and renin-angiotensin system (RAS) gene expression. The decrease in cardiac norepinephrine content apparent in LVH rats was similarly inhibited by both drugs.

CONCLUSIONS

Cilnidipine attenuated LV fibrosis and diastolic dysfunction as well as LV concentricity to a greater extent than did amlodipine in Dahl salt-sensitive rats. The superior cardioprotective action of cilnidipine is likely attributable, at least in part, to the greater antioxidant and anti-inflammatory effects associated with inhibition of cardiac RAS gene expression observed with this drug.

Renoprotective and antioxidant effects of cilnidipine in hypertensive patients

Cilnidipine, an L/N-type calcium channel blocker (CCB), has been reported to have more beneficial effects on proteinuria progression in hypertensive patients than amlodipine, an L-type CCB. The N-type calcium channel blockade that inhibits renal sympathetic nerve activity might reduce glomerular hypertension by facilitating vasodilation of the efferent arterioles. However, the precise mechanism of the renoprotective effect of cilnidipine remains unknown. Because cilnidipine exerted significantly higher antioxidant activity than amlodipine in cultured human mesangial cells, we hypothesized that cilnidipine might exert a renoprotective effect by suppressing oxidative stress. A total of 35 hypertensive patients receiving a renin-angiotensin system inhibitor were randomly assigned to a cilnidipine (n=18; 10 mg per day cilnidipine titrated to 20 mg per day) or amlodipine (n=17; 5 mg per day amlodipine titrated to 10 mg per day) group; the target blood pressure (BP) was set at 130/85 mmHg. After 6 months of treatment, systolic and diastolic BPs were significantly reduced in both of the groups, without any significant difference between the groups. The urinary albumin, 8-hydroxy-2'-deoxyguanosine (OHdG) and liver-type fatty-acid-binding protein (L-FABP) to creatinine ratios significantly decreased in the cilnidipine group (P<0.05) compared with those in the amlodipine group. The reductions in urinary albumin, 8-OHdG and L-FABP were not correlated with the change in systolic BP. In conclusion, cilnidipine, but not amlodipine, ameliorated urinary albumin excretion and decreased urinary 8-OHdG and L-FABP in the hypertensive patients. Cilnidipine probably exerts a greater renoprotective effect through its antioxidative properties.

Beneficial effects of L- and N-type calcium channel blocker on glucose and lipid metabolism and renal function in patients with hypertension and type II diabetes mellitus

It has been proved that cilnidipine has N-type calcium channels inhibitory activity as well as L-type calcium channels and inhibits excessive release of norepinephrine from the sympathetic nerve ending. This study was undertaken to compare the efficacy of amlodipine (an inhibitor of L-type calcium channels) and cilnidipine (an inhibitor of both L-type and N-type calcium channels) in patients with hypertension and type II diabetes mellitus. Seventy-seven hypertensive patients were divided into two groups according to presence/absence of type II diabetes mellitus. In these two groups of patients, the effects of amlodipine and cilnidipine on glucose and lipid metabolism and renal function were compared. As for glucose and lipid metabolism, homeostasis model assessment insulin resistance (HOMA-R) level in the non-diabetic group and triglyceride in the diabetes group were significantly lower with cilnidipine than with amlodipine. As regards renal function in the diabetic group, estimated glomerular filtration rate (eGFR) was significantly higher and urinary albumin/creatinine ratio was significantly lower with cilnidipine than with amlodipine. Cilnidipine which inhibits N-type calcium channels is more useful for patients with hypertension and diabetes mellitus from its effects on glucose and lipid metabolism and renal function.

Comparison between the antiproteinuric effects of the calcium channel blockers benidipine and cilnidipine in combination with angiotensin receptor blockers in hypertensive patients with chronic kidney disease

AIMS

Benidipine, an L-/T-type calcium channel blocker, dilates renal efferent and afferent arterioles and reduces glomerular pressure; therefore, it may exert renoprotective effects. We conducted an open-labeled randomized trial to compare the effects of benidipine with cilnidipine in hypertensive patients with chronic kidney disease (CKD).

METHODS

The patients who were already being treated with angiotensin receptor blockers (ARBs) received one of the following treatment regimens: benidipine at a dose of 2 mg/day that was increased up to a dose of 8 mg/day (benidipine group; n=118) or cilnidipine at a dose of 5 mg/day that was increased up to a dose of 20 mg/day (cilnidipine group; n=115).

RESULTS

After 12 months of treatment, we observed a significant and comparable reduction in the systolic and diastolic blood pressure in both groups. The urinary protein:creatinine ratio was significantly decreased in both groups after 3 months of treatment and thereafter; however, the difference between both groups was not significant after 12 months of treatment. Benidipine exerted an antiproteinuric effect to a greater extent than cilnidipine in patients with diabetes.

CONCLUSION

The addition of benidipine as well as cilnidipine reduces urinary protein excretion in hypertensive patients with CKD who are already being administered ARBs.

T-type Ca channel blockade as a determinant of kidney protection

Voltage-dependent Ca channels are classified into several subtypes based on the isoform of their α1 subunits. Traditional Ca channels blockers (CCBs), including nifedipine and amlodipine, act predominantly on L-type Ca channels, whereas novel CCBs such as efonidipine, benidipine and azelnidipine inhibit both L-type and T-type Ca channels. Furthermore, cilnidipine blocks L-type and N-type Ca channels. These CCBs exert divergent actions on renal microvessels. L-type CCBs preferentially dilate afferent arterioles, whereas both L-/T-type and L-/N-type CCBs potently dilate afferent and efferent arterioles. The distinct actions of CCBs on the renal microcirculation are reflected by changes in glomerular capillary pressure and subsequent renal injury: L-type CCBs favor an increase in glomerular capillary pressure, whereas L-/T-type and L-/N-type CCBs alleviate glomerular hypertension. The renal protective action of L-/T-type CCBs is also mediated by non-hemodynamic mechanisms, i.e., inhibition of the inflammatory process and inhibition of Rho kinase and aldosterone secretion. Finally, a growing body of evidence indicates that T-type CCBs offer more beneficial action on proteinuria and renal survival rate than L-type CCBs in patients with chronic kidney disease (CKD). Similarly, in CKD patients treated with renin-angiotensin blockers, add-on therapy with N-type CCBs is more potent in reducing proteinuria than that with L-type CCBs, although no difference is found in the subgroup with diabetic nephropathy. Thus, the strategy for hypertension treatment with CCBs has entered a new era: treatment selection depends not only on blood pressure control but also on the subtypes of CCBs.

Dual actions of cilnidipine in human internal thoracic artery: inhibition of calcium channels and enhancement of endothelial nitric oxide synthase

OBJECTIVE

Cilnidipine is a novel, long-action L/N-type dihydropyridine calcium channel blocker that has recently been used for antihypertensive therapy. We investigated the vasorelaxation effect of cilnidipine with regard to its calcium channel blockage and nitric oxide-cyclic guanosine monophosphate-dependent mechanism in human internal thoracic artery.

METHODS

Fresh human internal thoracic arteries taken from discarded tissues of patients undergoing coronary artery bypass surgery were studied. Concentration-relaxation curves for cilnidipine in comparison with nifedipine were studied. The expression level of endothelial nitric oxide synthase mRNA was assayed by quantitative real-time polymerase chain reaction, and the phosphorylation of endothelial nitric oxide synthase at Ser(1177) was determined by Western blotting analysis.

RESULTS

Cilnidipine and nifedipine caused nearly full relaxation in potassium-precontracted internal thoracic artery. Pretreatment with cilnidipine at the clinical plasma concentration significantly depressed the maximal contraction. Endothelium denudation (47.7% ± 7.0%, P < .05) and inhibition of endothelial nitric oxide synthase (48.6% ± 6.1%, P < .05) or guanylate cyclase (41.6% ± 3.8%, P < .01) significantly reduced the cilnidipine-induced endothelium-dependent relaxation (73.9% ± 6.4%). Cilnidipine increased the expression of endothelial nitric oxide synthase mRNA by 42.4% (P < .05) and enhanced phosphorylation level of endothelial nitric oxide synthase at Ser(1177) by 37.0% (P < .05).

CONCLUSIONS

The new generation of calcium channel antagonist cilnidipine relaxes human arteries through calcium channel antagonism and increases production of nitric oxide by enhancement of endothelial nitric oxide synthase. The dual mechanisms of cilnidipine in human arteries demonstrated in this study may prove particularly important in vasorelaxing therapy in cardiovascular diseases.

Oral administration of cilnidipine to patients with hypertensive intracerebral hemorrhage in the acute stage: significance and role of an N-type calcium channel blocker

BACKGROUND

Elevated blood pressure (BP) causes rebleeding or enlargement of intracerebral hematomas.

AIMS

How a long-acting oral calcium channel blocker, cilnidipine, could control BP in the acute stage of cerebral hemorrhage was evaluated.

METHODS AND RESULTS

Cilnidipine given within 3 days of hospitalization has more benefit than cilnidipine given after 4 days of hospitalization; it can reduce the amount of intravenous nicardipine, and it can help to maintain the BP below 80% of the initial BP. Surgical removal of the hematoma has no benefit in reducing the amount of intravenous nicardipine and maintaining the BP below 80% of the initial BP.

CONCLUSION

In order to reduce the total amount of intravenous nicardipine and to maintain the BP below 80% of the initial BP, oral administration of a long-acting N-type calcium channel blocker, cilnidipine, is useful and important, independent of whether the hematomas are surgically removed.

Cardiac effects of L/N-type Ca2+ channel blocker cilnidipine in anesthetized dogs

Cardiac effects of L/N-type Ca2+ channel blocker cilnidipine were assessed using the halothane-anesthetized canine model. Cilnidipine (1 and 3 microg/kg, i.v.) lowered the mean blood pressure by -5 and -14 mm Hg, respectively, without affecting the heart rate or maximum upstroke velocity of left ventricular pressure. Isoproterenol or acetylcholine was intravenously injected to directly or indirectly induce the positive chronotropic responses, respectively. Cilnidipine hardly affected the isoproterenol-induced cardiac responses, but it attenuated the acetylcholine-induced reflex tachycardia to 63-78% of the pre-drug control level. These results suggest that clinically relevant doses of cilnidipine can directly attenuate the sympathetic tone.

Ca2+ channel subtypes and pharmacology in the kidney

A large body of evidence has accrued indicating that voltage-gated Ca(2+) channel subtypes, including L-, T-, N-, and P/Q-type, are present within renal vascular and tubular tissues, and the blockade of these Ca(2+) channels produces diverse actions on renal microcirculation. Because nifedipine acts exclusively on L-type Ca(2+) channels, the observation that nifedipine predominantly dilates afferent arterioles implicates intrarenal heterogeneity in the distribution of L-type Ca(2+) channels and suggests that it potentially causes glomerular hypertension. In contrast, recently developed Ca(2+) channel blockers (CCBs), including mibefradil and efonidipine, exert blocking action on L-type and T-type Ca(2+) channels and elicit vasodilation of afferent and efferent arterioles, which suggests the presence of T-type Ca(2+) channels in both arterioles and the distinct impact on intraglomerular pressure. Recently, aldosterone has been established as an aggravating factor in kidney disease, and T-type Ca(2+) channels mediate aldosterone release as well as its effect on renal efferent arteriolar tone. Furthermore, T-type CCBs are reported to exert inhibitory action on inflammatory process and renin secretion. Similarly, N-type Ca(2+) channels are present in nerve terminals, and the inhibition of neurotransmitter release by N-type CCBs (eg, cilnidipine) elicits dilation of afferent and efferent arterioles and reduces glomerular pressure. Collectively, the kidney is endowed with a variety of Ca(2+) channel subtypes, and the inhibition of these channels by their specific CCBs leads to variable impact on renal microcirculation. Furthermore, multifaceted activity of CCBs on T- and N-type Ca(2+) channels may offer additive benefits through nonhemodynamic mechanisms in the progression of chronic kidney disease.

Effects of Benidipine in a Rat Model of Experimental Angina

To compare the antianginal effects of 1,4-dihydropyridine-type calcium-channel blockers, we evaluated the effects of benidipine, amlodipine, nifedipine, and efonidipine on vasopressin-induced myocardial ischemia in rats, an experimental model of angina. Intravenous administration of benidipine (3 microg/kg), amlodipine (1000 microg/kg), and nifedipine (100 microg/kg) suppressed the vasopressin-induced S-wave depression, an index of myocardial ischemia. Efonidipine (100 microg/kg, i.v.) tended to inhibit the S-wave depression. At the antianginal dose of each drug, amlodipine, nifedipine, and efonidipine decreased blood pressure significantly, whereas benidipine had little effect on blood pressure at a dose of 3 microg/kg. These results indicate that benidipine, unlike the other 1,4-dihydropyridine-type calcium-channel blockers examined in this study, inhibits vasopressin-induced coronary vasospasm with fewer undesirable effects such as hypotension in rats, suggesting that benidipine may be useful in the treatment of angina pectoris.

Involvement of different calcium channels in the depolarization-evoked release of noradrenaline from sympathetic neurones in rabbit carotid artery

The calcium channels coupled to noradrenaline release from sympathetic neurones in the rabbit isolated carotid artery were examined. Rings of carotid artery were preloaded with (-)-[(3)H]noradrenaline and the fractional (3)H overflow evoked by electrical-field stimulation was determined by liquid scintillation spectrometry. The N-type Ca(2+) channel blocking agent omega-conotoxin GVIA (3x10(-9)-6x10(-8) M) reduced the stimulation-evoked (3)H overflow. The maximal inhibition was seen with 3x10(-8) M. The maximal reduction was more marked at a low (2 Hz) stimulation frequency than at a high one (30 Hz). Mibefradil (10(-6) M) irreversibly reduced the (3)H overflow evoked by field stimulation (2 Hz). At 30 Hz, the reduction was more marked than at 2 Hz. Mibefradil (3x10(-6)-10(-5) M) enhanced the passive (3)H outflow. The reduction of the stimulation (30 Hz)-evoked (3)H overflow seen with omega-conotoxin GVIA (3x10(-8) M) was enhanced by mibefradil (10(-6) M) and unaffected by nimodipine (10(-5) M) and omega-agatoxin IVA (10(-8) M). We conclude that the stimulation-evoked release of noradrenaline from sympathetic neurones in rabbit carotid artery at a low frequency (2 Hz) is mediated mainly by the N-type calcium channels. At a high frequency (30 Hz), T-type Ca(2+) channels are also involved.