Renal-Protective Effect of T- and L-Type Calcium Channel Blockers in Hypertensive Patients: An Amlodipine-to-Benidipine Changeover (ABC) Study

Protein kinase C epsilon-mediated modulation of T-type calcium channels underlies alcohol withdrawal hyperexcitability in the midline thalamus

BACKGROUND

Millions of people struggle with alcohol use disorder (AUD). Abrupt abstinence after a period of chronic alcohol use can precipitate the alcohol withdrawal syndrome (AWS), which includes hyperexcitability and, potentially, seizures. We have shown that T-type Ca2+ channels are novel, sensitive targets of alcohol, an effect that is dependent upon protein kinase C (PKC). The purpose of this study was to (1) understand midline thalamic neuronal hyperexcitability during alcohol withdrawal and its dependence on PKC; (2) characterize T channel functional changes using both current clamp and voltage clamp methods; and (3) determine which PKC isoform may be responsible for alcohol withdrawal (WD) effects.

METHODS

Whole-cell patch clamp recordings were performed in midline thalamic neurons in brain slices prepared from C57bl/6 mice that underwent chronic intermittent alcohol exposure in a standard vapor chamber model. The recordings were compared to those from air-exposed controls. T-channel inactivation curves and burst responses were acquired through voltage-clamp and current-clamp recordings, respectively.

RESULTS

Whole-cell voltage clamp recordings of native T-type current exhibited a depolarizing shift in the voltage-dependency of inactivation during alcohol withdrawal compared to air-exposed controls. A PKCε translocation inhibitor peptide mitigated this change. Current clamp recordings demonstrated more spikes per burst during alcohol withdrawal. Consistent with voltage clamp findings, the PKCɛ translocation inhibitor peptide reduced the number of spikes per burst after WD.

CONCLUSION

We found that alcohol WD produces T channel-mediated hyperexcitability in the midline thalamus, produced in part by a shift in the inactivation curve consistent with greater availability of T current. WD effects on T current inactivation were reduced to control levels by blocking PKCε translocation. Our results demonstrate that PKCε translocation plays an important role in the regulation of alcohol withdrawal-induced hyperexcitability in midline thalamic circuitry.

Structural bases of inhibitory mechanism of CaV1.2 channel inhibitors

The voltage-gated calcium channel CaV1.2 is essential for cardiac and vessel smooth muscle contractility and brain function. Accumulating evidence demonstrates that malfunctions of CaV1.2 are involved in brain and heart diseases. Pharmacological inhibition of CaV1.2 is therefore of therapeutic value. Here, we report cryo-EM structures of CaV1.2 in the absence or presence of the antirheumatic drug tetrandrine or antihypertensive drug benidipine. Tetrandrine acts as a pore blocker in a pocket composed of S6II, S6III, and S6IV helices and forms extensive hydrophobic interactions with CaV1.2. Our structure elucidates that benidipine is located in the DIII-DIV fenestration site. Its hydrophobic sidechain, phenylpiperidine, is positioned at the exterior of the pore domain and cradled within a hydrophobic pocket formed by S5DIII, S6DIII, and S6DIV helices, providing additional interactions to exert inhibitory effects on both L-type and T-type voltage gated calcium channels. These findings provide the structural foundation for the rational design and optimization of therapeutic inhibitors of voltage-gated calcium channels.

Calcium channel blocker in patients with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is involved in a progressive deterioration in renal function over the years and is now a global public health problem. Currently, reducing the number of patients progressing to end-stage renal failure is urgently necessary. Hypertension and CKD interact with each other, and good control of blood pressure (BP) can improve CKD patients' prognosis. With the current global trend for more strict BP control, the importance of BP management and the need for medication to achieve this strict goal are increasing. Calcium channel blockers (CCBs), which target voltage-dependent calcium channels, are frequently used in combination with renin-angiotensin-aldosterone system inhibitors for CKD patients because of their strong BP-lowering properties and relatively few adverse side effects. Calcium channels have several subtypes, including L, N, T, P/Q, and R, and three types of CCBs, L-type CCBs, L-/T-type CCBs, and L-/N-type CCBs, that are available. Nowadays, the new functions and effects of the CCBs are being elucidated.

CONCLUSION

We should use different types of CCBs properly depending on their pharmacological effects, such as the strength of antihypertensive effects and the organ protection effects, taking into account the pathophysiology of the patients. In this article, the role and the use of CCBs in CKD patients are reviewed.

Amlodipine Compared with Benidipine in the Management of Hypertension: A Systematic Review and Meta-Analysis

INTRODUCTION

Benidipine and amlodipine are two well-known drugs used in hypertensive patients with chronic kidney disease (CKD).

AIM

In this systematic review we aimed to compare benidipine and amlodipine in terms of efficacy in the management of hypertensive patients.

METHODS

We searched PubMed, Cochrane CENTRAL, SCOPUS and Web of Science for relevant clinical trials and excluded observational studies. Quality appraisal was evaluated according to GRADE and we assessed the risk of bias using the Cochrane's risk of bias tool. We included the following outcomes: Systolic blood pressure, diastolic blood pressure, heart rate, estimated glomerular filtration rate (eGFR), and urinary albumin/creatinine ratio. Data were pooled as mean differences (MD) with relative 95% confidence intervals (CI).

RESULTS

Eight studies were eligible for our meta-analysis. We found no significant difference between both drugs regarding systolic (MD = - 0.21 [- 1.48, 1.89], (P = 0.81) and diastolic (MD = 0.01[- 0.51, 0.53], (P = 0.97)) blood pressure measurements. The overall heart rate did not differ as well (MD = - 0.03 [- 1.63, 1.57], (P = 0.97)). We found that benidipine was statistically better than amlodipine in terms of eGFR (MD = 1.07 [0.43, 1.71], (P = 0.001)), and urinary albumin/creatinine ratio (MD = - 43.41 [- 53.53, - 33.29], (P < 0.00001)).

CONCLUSIONS

Finally we conclude that benidipine seems to show more positive and promising results in the management of hypertensive patients with chronic kidney disease.

Ion-Channel modulator TH1177 reduces glomerular injury and serum creatinine in chronic mesangial proliferative disease in rats

Background

T-type calcium channels (TTCC) are involved in mesangial cell proliferation. In acute thy-1 nephritis in the rat TTCC inhibition reduces glomerular damage and cell proliferation. This work is extended here by a study of the non-selective TTCC inhibitor TH1177 in a chronic model of proliferative glomerulonephritis (GN) including late treatment starting after the initial inflammation has resolved. The objective was to determine the effects of TH1177 in a model of chronic mesangioproliferative renal disease.

Methods

Chronic GN was induced in WKY rats by unilateral nephrectomy (day − 7) followed by day 0 injection of Ox7 thy-1 mAb. Treatment with TH1177 (10–20 mg/Kg daily IP) was started on day 2 (early treatment) or on day 14 (late treatment) and compared to vehicle-treated controls until sacrifice at day 42. Glomerular disease was assessed with a damage score, fibrosis assay, cellular counts and renal function measured by serum creatinine.

Results

Treatment with TH11777 was associated with reduced serum creatinine, less glomerular damage, reduced fibrosis and reduced glomerular cellularity. The results for early and late TH1177 treatments were essentially the same and differed significantly from vehicle.

Conclusions

The ion-channel modulator TH1177 is capable of improving glomerular outcome in chronic rat GN even when treatment starts 14 days after initiation of the disease. These data are discussed in the context of the possible targets of TH1177 including TTCC, TRP family, Stim/Orai group and other cation channels. The work supports the use of genetic models to examine the roles of individual cation channels in progressive glomerulonephritis to further define the targets of TH1177.

Pharmacokinetics, Safety and Tolerability of Tylerdipine Hydrochloride, a Novel Dihydropyridine Dual L/T-type Calcium Channel Blocker, after Single and Multiple Oral Doses in Healthy Chinese Subjects

BACKGROUND AND OBJECTIVE

Tylerdipine hydrochloride (KBP-5660) is a novel L/T-type dual calcium channel blocker developed for the treatment of hypertension. We aimed to study the pharmacokinetics, safety and tolerability of tylerdipine in healthy Chinese subjects.

METHODS

Two double-blind, randomized, dose-escalation studies were conducted that included a total of 88 healthy subjects: (1) a single-ascending dose (SAD) study; and (2) a multiple-ascending dose (MAD) study. In the SAD study, 64 subjects were randomly assigned to receive a single dose of 0.5, 2.5, 5, 10, 15, 20, 25, or 30 mg of tylerdipine or placebo. In the MAD study, 24 subjects were randomly assigned to receive 10 or 20 mg of tylerdipine or placebo once daily for 9 days. Blood samples were collected at the designated time points for pharmacokinetic analyses. Safety assessments were conducted throughout the study.

RESULTS

Following a single oral dose of tylerdipine of 5-30 mg, the mean maximum plasma concentration (C_max) increased from 0.9993 to 10.11 ng/ml; mean area under the plasma-concentration curve (AUC) from time zero to 72 h increased from 4.332 to 73.95 h·ng/ml. AUC increased in a greater than dose-proportional manner, whereas C_max exhibited a rough but non-typical dose-proportionality increase. In the MAD study, steady-state conditions were achieved after 1 week of daily dosing in both dose groups. Accumulation of tylerdipine was low, with accumulation ratios (R_AUC) of less than 1.65. All adverse events were assessed as mild or moderate.

CONCLUSION

Tylerdipine hydrochloride was safe and well tolerated. The exposure (AUC) of tylerdipine over the dose range of 5-30 mg increased in a greater than dose-proportional manner, while C_max exhibited a rough but non-typical dose proportionality increase. A slight accumulation of tylerdipine was observed following multiple dosing.

STUDY REGISTRATIONS

CTR20140862 and CTR20150660.

T-type Calcium Channels in Health and Disease

Low Voltage-Activated (LVA) T-type calcium channels are characterized by transient current and Low Threshold Spikes (LTS) that trigger neuronal firing and oscillatory behavior. Combined with their preferential localization in dendrites and their specific "window current", T-type calcium channels are considered to be key players in signal amplification and synaptic integration. Assisted by the emerging pharmacological tools, the structural determinants of channel gating and kinetics, as well as novel physiological and pathological functions of T-type calcium channels, are being uncovered. In this review, we provide an overview of structural determinants in T-type calcium channels, their involvement in disorders and diseases, the development of novel channel modulators, as well as Structure-Activity Relationship (SAR) studies that lead to rational drug design.

Development and validation of two LC-MS/MS methods to assay urinary tylerdipine hydrochloride and its metabolites in healthy Chinese subjects

For quantitative assaying tylerdipine hydrochloride, and its two primary metabolites (M2 and M4) in human urine, two sensitive and accurate LC-MS/MS methods were firstly developed and validated, where multiple reaction monitoring (MRM) was applied under positive electrospray ionization mode for tylerdipine and negative electrospray ionization mode for M2/M4, respectively. Urinary proteins were precipitated using acetonitrile, and deuterated isotopes of tylerdipine and M4 ([D5]‑tylerdipine and [D6]-M4) were used as internal standards. Triton X-100, a good surfactant, was used to prevent the adsorption. An Agilent Poroshell 120 column was employed for chromatographic separation of the analytes with the mobile phases of 2 mM ammonium formate solution (containing 0.1% formic acid) and acetonitrile (45:55 for tylerdipine and 75:25 for the M2/M4, v/v). Flow rate was 0.3 mL/min. Calibration curves for tylerdipine, M2 and M4 in urine were linear over the ranges of 0.02-10 ng/mL, 2-1500 ng/mL and 0.5-200 ng/mL, respectively. The precision, accuracy, specificity and stability of two methods all evaluated and achieved the acceptable criteria. The LC-MS/MS methods were successfully applied to assay urinary excretion of tylerdipine and the metabolites in healthy Chinese subjects who orally received a single dose of 20 mg tylerdipine tablet. Generally, the urinary excretion of the two primary metabolites accounted for 11.7% of the total dose of tylerdipine in healthy Chinese subjects, while little tylerdipine was recovered in urine.

P/Q-type and T-type voltage-gated calcium channels are involved in the contraction of mammary and brain blood vessels from hypertensive patients

AIM

Calcium channel blockers are widely used in cardiovascular diseases. Besides L-type channels, T- and P/Q-type calcium channels are involved in the contraction of human renal blood vessels. It was hypothesized that T- and P/Q-type channels are involved in the contraction of human brain and mammary blood vessels.

METHODS

Internal mammary arteries from bypass surgery patients and cerebral arterioles from patients with brain tumours with and without hypertension were tested in a myograph and perfusion set-up. PCR and immunohistochemistry were performed on isolated blood vessels.

RESULTS

The P/Q-type antagonist ω-agatoxin IVA (10^-8  mol L^-1 ) and the T-type calcium blocker mibefradil (10^-7  mol L^-1 ) inhibited KCl depolarization-induced contraction in mammary arteries from hypertensive patients with no effect on blood vessels from normotensive patients. ω-Agatoxin IVA decreased contraction in cerebral arterioles from hypertensive patients. L-type blocker nifedipine abolished the contraction in mammary arteries. PCR analysis showed expression of P/Q-type (Ca_v 2.1), T-type (Ca_v 3.1 and Ca_v 3.2) and L-type (Ca_v 1.2) calcium channels in mammary and cerebral arteries. Immunohistochemical labelling of mammary and cerebral arteries revealed the presence of Ca_v 2.1 in endothelial and smooth muscle cells. Ca_v 3.1 was also detected in mammary arteries.

CONCLUSION

P/Q- and T-type Ca_v are present in human internal mammary arteries and in cerebral penetrating arterioles. P/Q- and T-type calcium channels are involved in the contraction of mammary arteries from hypertensive patients but not from normotensive patients. Furthermore, in cerebral arterioles P/Q-type channels importance was restricted to hypertensive patients might lead to that T- and P/Q-type channels could be a new target in hypertensive patients.

T-type Ca2+ channels and autoregulation of local blood flow

L-type voltage gated Ca²⁺ channels are considered to be the primary source of calcium influx during the myogenic response. However, many vascular beds also express T-type voltage gated Ca²⁺ channels. Recent studies suggest that these channels may also play a role in autoregulation. At low pressures (40-80 mmHg) T-type channels affect myogenic responses in cerebral and mesenteric vascular beds. T-type channels also seem to be involved in skeletal muscle autoregulation. This review discusses the expression and role of T-type voltage gated Ca²⁺ channels in the autoregulation of several different vascular beds. Lack of specific pharmacological inhibitors has been a huge challenge in the field. Now the research has been strengthened by genetically modified models such as mice lacking expression of T-type voltage gated Ca²⁺ channels (Ca_V3.1 and Ca_V3.2). Hopefully, these new tools will help further elucidate the role of voltage gated T-type Ca²⁺ channels in autoregulation and vascular function.

Calcium-permeable ion channels in the kidney

Calcium ions (Ca(2+)) are crucial for a variety of cellular functions. The extracellular and intracellular Ca(2+) concentrations are thus tightly regulated to maintain Ca(2+) homeostasis. The kidney, one of the major organs of the excretory system, regulates Ca(2+) homeostasis by filtration and reabsorption. Approximately 60% of the Ca(2+) in plasma is filtered, and 99% of that is reabsorbed by the kidney tubules. Ca(2+) is also a critical signaling molecule in kidney development, in all kidney cellular functions, and in the emergence of kidney diseases. Recently, studies using genetic and molecular biological approaches have identified several Ca(2+)-permeable ion channel families as important regulators of Ca(2+) homeostasis in kidney. These ion channel families include transient receptor potential channels (TRP), voltage-gated calcium channels, and others. In this review, we provide a brief and systematic summary of the expression, function, and pathological contribution for each of these Ca(2+)-permeable ion channels. Moreover, we discuss their potential as future therapeutic targets.

Functional importance of T-type voltage-gated calcium channels in the cardiovascular and renal system: news from the world of knockout mice

Over the years, it has been discussed whether T-type calcium channels Cav3 play a role in the cardiovascular and renal system. T-type channels have been reported to play an important role in renal hemodynamics, contractility of resistance vessels, and pacemaker activity in the heart. However, the lack of highly specific blockers cast doubt on the conclusions. As new T-type channel antagonists are being designed, the roles of T-type channels in cardiovascular and renal pathology need to be elucidated before T-type blockers can be clinically useful. Two types of T-type channels, Cav3.1 and Cav3.2, are expressed in blood vessels, the kidney, and the heart. Studies with gene-deficient mice have provided a way to investigate the Cav3.1 and Cav3.2 channels and their role in the cardiovascular system. This review discusses the results from these knockout mice. Evaluation of the literature leads to the conclusion that Cav3.1 and Cav3.2 channels have important, but different, functions in mice. T-type Cav3.1 channels affect heart rate, whereas Cav3.2 channels are involved in cardiac hypertrophy. In the vascular system, Cav3.2 activation leads to dilation of blood vessels, whereas Cav3.1 channels are mainly suggested to affect constriction. The Cav3.1 channel is also involved in neointima formation following vascular damage. In the kidney, Cav3.1 regulates plasma flow and Cav3.2 plays a role setting glomerular filtration rate. In conclusion, Cav3.1 and Cav3.2 are new therapeutic targets in several cardiovascular pathologies, but the use of T-type blockers should be specifically directed to the disease and to the channel subtype.

Differential effect of T-type voltage-gated Ca2+ channel disruption on renal plasma flow and glomerular filtration rate in vivo

Voltage-gated Ca(2+) (Cav) channels play an essential role in the regulation of renal blood flow and glomerular filtration rate (GFR). Because T-type Cav channels are differentially expressed in pre- and postglomerular vessels, it was hypothesized that they impact renal blood flow and GFR differentially. The question was addressed with the use of two T-type Cav knockout (Cav3.1(-/-) and Cav3.2(-/-)) mouse strains. Continuous recordings of blood pressure and heart rate, para-aminohippurate clearance (renal plasma flow), and inulin clearance (GFR) were performed in conscious, chronically catheterized, wild-type (WT) and Cav3.1(-/-) and Cav3.2(-/-) mice. The contractility of afferent and efferent arterioles was determined in isolated perfused blood vessels. Efferent arterioles from Cav3.2(-/-) mice constricted significantly more in response to a depolarization compared with WT mice. GFR was increased in Cav3.2(-/-) mice with no significant changes in renal plasma flow, heart rate, and blood pressure. Cav3.1(-/-) mice had a higher renal plasma flow compared with WT mice, whereas GFR was indistinguishable from WT mice. No difference in the concentration response to K(+) was observed in isolated afferent and efferent arterioles from Cav3.1(-/-) mice compared with WT mice. Heart rate was significantly lower in Cav3.1(-/-) mice compared with WT mice with no difference in blood pressure. T-type antagonists significantly inhibited the constriction of human intrarenal arteries in response to a small depolarization. In conclusion, Cav3.2 channels support dilatation of efferent arterioles and affect GFR, whereas Cav3.1 channels in vivo contribute to renal vascular resistance. It is suggested that endothelial and nerve localization of Cav3.2 and Cav3.1, respectively, may account for the observed effects.

Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels

Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers.

Ethanol inhibition of a T-type Ca²+ channel through activity of protein kinase C

BACKGROUND

T-type calcium channels (T-channels) are widely distributed in the central and peripheral nervous system, where they mediate calcium entry and regulate the intrinsic excitability of neurons. T-channels are dysregulated in response to alcohol administration and withdrawal. We therefore investigated acute ethanol (EtOH) effects and the underlying mechanism of action in human embryonic kidney (HEK) 293 cell lines, as well as effects on native currents recorded from dorsal root ganglion (DRG) neurons cultured from Long-Evans rats.

METHODS

Whole-cell voltage-clamp recordings were performed at 32 to 34°C in both HEK cell lines and DRG neurons. The recordings were taken after a 10-minute application of EtOH or protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate [PMA]).

RESULTS

We recorded T-type Ca²⁺ currents (T-currents) from 3 channel isoforms (CaV3.1, CaV3.2, and CaV3.3) before and during administration of EtOH. We found that only 1 isoform, CaV3.2, was significantly affected by EtOH. EtOH reduced current density as well as producing a hyperpolarizing shift in steady-state inactivation of both CaV3.2 currents from HEK 293 cell lines and in native T-currents from DRG neurons that are known to be enriched in CaV3.2. A myristoylated PKC peptide inhibitor (MPI) blocked the major EtOH effects, in both the cell lines and the DRG neurons. However, PMA effects were more complex. Lower concentration PMA (100 nM) replicated the major effects of EtOH, while higher concentration PMA (1 μM) did not, suggesting that the EtOH effects operate through activation of PKC and were mimicked by lower concentration of PMA.

CONCLUSIONS

EtOH primarily affects the CaV3.2 isoform of T-type Ca²⁺ channels acting through PKC, highlighting a novel target and mechanism for EtOH effects on excitable membranes.

Functional Importance of L- and P/Q-Type Voltage-Gated Calcium Channels in Human Renal Vasculature

Calcium channel blockers are widely used for treatment of hypertension, because they decrease peripheral vascular resistance through inhibition of voltage-gated calcium channels. Animal studies of renal vasculature have shown expression of several types of calcium channels that are involved in kidney function. It was hypothesized that human renal vascular excitation-contraction coupling involves different subtypes of channels. In human renal artery and dissected intrarenal blood vessels from nephrectomies, PCR analysis showed expression of L-type (Ca v 1.2), P/Q-type (Ca v 2.1), and T-type subtype (Ca v 3.1 and Ca v 3.2) voltage-gated calcium channels (Ca v s), and quantitative PCR showed highest expression of L-type channels in renal arteries and variable expression between patients of subtypes of calcium channels in intrarenal vessels. Immunohistochemical labeling of kidney sections revealed signals for Ca v 2.1 and Ca v 3.1 associated with smooth muscle cells of preglomerular and postglomerular vessels. In human intrarenal arteries, depolarization with potassium induced a contraction inhibited by the L-type antagonist nifedipine, EC 50 1.2×10 −8 mol/L. The T-type antagonist mibefradil inhibited the potassium-induced constriction with large variations between patients. Interestingly, the P/Q-type antagonist, ω-agatoxin IVA, inhibited significantly the contraction with 24% at 10 −9 mol/L. In conclusion L-, P/Q, and T-type channels are expressed in human renal blood vessels, and L- and P/Q-type channels are of functional importance for the depolarization-induced vasoconstriction. The contribution of P/Q-type channels to contraction in the human vasculature is a novel mechanism for the regulation of renal blood flow and suggests that clinical treatment with calcium blockers might affect vascular reactivity also through P/Q-type channel inhibition.

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.

Benidipine, a dihydropyridine L-type/T-type calcium channel blocker, affords additive benefits for prevention of cardiorenal injury in hypertensive rats

OBJECTIVES

Benidipine is a dihydropyridine calcium channel blocker inhibiting not only L-type but also T-type calcium channels. To elucidate potential additive benefit of benidipine for prevention of cardiorenal injury, we compared the cardiac and renal protective effects of equihypotensive doses of benidipine and cilnidipine in stroke-prone spontaneously hypertensive rats (SHRSP).

METHODS

SHRSP were divided into five groups, and were given vehicle, benidipine at 1 or 3 mg/kg per day, or cilnidipine at 1 or 3 mg/kg per day for 7 weeks, and the protective effects against cardiorenal injury were compared among each group.

RESULTS

Benidipine and cilnidipine at the same doses exerted comparable hypotensive effects on SHRSP throughout the treatment. Despite equihypotensive effects between both drugs, benidipine prevented cardiac hypertrophy, fibrosis, and inflammation to a greater extent than cilnidipine. Moreover, benidipine prevented glomerulosclerosis, tubulointerstitial injury, and renal inflammation more than cilnidipine. To elucidate the underlying mechanism of more beneficial effects of benidipine than cilnidipine, we compared the effects of these drugs on cardiac and renal oxidative stress, and aldosterone in SHRSP. Benidipine reduced both cardiac and renal NADPH oxidase activities in SHRSP more than cilnidipine, being associated with more attenuation of cardiac and renal superoxide by benidipine. Furthermore, serum aldosterone was significantly reduced by benidipine but not by cilnidipine.

CONCLUSION

Benidipine exerted more protective effects against cardiorenal injury of hypertensive rats than cilnidipine, through more attenuation of oxidative stress than cilnidipine, and the reduction of aldosterone. Benidipine, via blockade of T-type calcium channels, seems to elicit additive benefits for prevention of hypertensive cardiorenal injury.

Effect of cilnidipine on normal to marginally elevated urine albumin-creatinine ratio in asymptomatic non-diabetic hypertensive patients: an exponential decay curve analysis

BACKGROUND

High-normal urinary albumin excretion has been reported to have clinical significance with respect to progression of proteinuria and hypertension.

OBJECTIVE

We analysed the effect of cilnidipine (10 mg/day) on morning systolic blood pressure (SBP) and urine albumin-creatinine ratio (UACR) in 16 non-diabetic hypertensive patients with a normal to marginally elevated UACR (mean +/- SD 29.4 +/- 21.7; range 7.5-72.9 mg/g creatinine).

METHODS

Sequential home BP and UACR data were fitted to a simple exponential function as follows: where y is SBP (mmHg) or UACR (mg/g creatinine); alpha is the extent of the SBP (mmHg)- or UACR (mg/g creatinine)-lowering effect; beta (days) is the time-constant for SBP or UACR decrease; t is the number of days after the start of cilnidipine administration; and gamma is the finally stabilized SBP (mmHg) or UACR (mg/g creatinine).

RESULTS

Mean +/- SD morning SBP and UACR decreased by 20.4 +/- 11.4 mmHg and 15.2 +/- 13.1 mg/g creatinine, respectively, as determined by coefficient alpha. The mean +/- SD time-constant for UACR decrease was significantly longer than that for BP decrease (43.5 +/- 22.9 vs 15.4 +/- 7.1 days). UACR reduction correlated with pre-treatment UACR values (correlation coefficient [R] = 0.88, p < 0.01) but not with BP decrease.

CONCLUSIONS

The present study demonstrated that cilnidipine reduced UACR in hypertensive patients with normal to marginally elevated UACR independent of its BP-lowering effect.

Voltage-gated divalent currents in descending vasa recta pericytes

Multiple voltage-gated Ca(2+) channel (Ca(V)) subtypes have been reported to participate in control of the juxtamedullary glomerular arterioles of the kidney. Using the patch-clamp technique, we examined whole cell Ca(V) currents of pericytes that contract descending vasa recta (DVR). The dihydropyridine Ca(V) agonist FPL64176 (FPL) stimulated inward Ca(2+) and Ba(2+) currents that activated with threshold depolarizations to -40 mV and maximized between -20 and -10 mV. These currents were blocked by nifedipine (1 μM) and Ni(2+) (100 and 1,000 μM), exhibited slow inactivation, and conducted Ba(2+) > Ca(2+) at a ratio of 2.3:1, consistent with "long-lasting" L-type Ca(V). In FPL, with 1 mM Ca(2+) as charge carrier, Boltzmann fits yielded half-maximal activation potential (V(1/2)) and slope factors of -57.9 mV and 11.0 for inactivation and -33.3 mV and 4.4 for activation. In the absence of FPL stimulation, higher concentrations of divalent charge carriers were needed to measure basal currents. In 10 mM Ba(2+), pericyte Ca(V) currents activated with threshold depolarizations to -30 mV, were blocked by nifedipine, exhibited voltage-dependent block by diltiazem (10 μM), and conducted Ba(2+) > Ca(2+) at a ratio of ∼2:1. In Ca(2+), Boltzmann fits to the data yielded V(1/2) and slope factors of -39.6 mV and 10.0 for inactivation and 2.8 mV and 7.7 for activation. In Ba(2+), V(1/2) and slope factors were -29.2 mV and 9.2 for inactivation and -5.6 mV and 6.1 for activation. Neither calciseptine (10 nM), mibefradil (1 μM), nor ω-agatoxin IVA (20 and 100 nM) blocked basal Ba(2+) currents. Calciseptine (10 nM) and mibefradil (1 μM) also failed to reverse ANG II-induced DVR vasoconstriction, although raising mibefradil concentration to 10 μM was partially effective. We conclude that DVR pericytes predominantly express voltage-gated divalent currents that are carried by L-type channels.

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.

Comparative effects of benidipine and amlodipine on proteinuria, urinary 8-OHdG, urinary L-FABP, and inflammatory and atherosclerosis markers in early-stage chronic kidney disease

INTRODUCTION

We examined the effects of 2 calcium channel blockers, benidipine (T-, L-, and N-type) and amlodipine (L- and N-type), on renal, inflammatory, oxidative, and atherosclerosis markers in hypertensive patients with mild chronic kidney disease (CKD).

METHODS

Forty hypertensive patients with CKD were assigned randomly to either of the 2 treatments: 8 mg benidipine once daily (n = 20, group A) or 5 mg amlodipine once daily (n = 20, group B). Treatment was continued for 12 months. Blood pressure, serum creatinine, estimated glomerular filtration rate, urinary protein excretion, urinary liver-type fatty acid-binding protein, interleukin-6, high mobility group box-1 protein, urinary 8-hydroxy-2'-deoxyguanosine, pulse wave velocity, intima-media thickness, and blood asymmetric dimethylarginine were monitored.

RESULTS

Blood pressure decreased equally in both groups (P < 0.001, at 6 and 12 months versus before treatment). Serum creatinine and estimated glomerular filtration rate changed little during the experimental period in each group. However, urinary protein excretion (P < 0.001), urinary liver-type fatty acid-binding protein (P < 0.001), urinary 8-hydroxy-2'-deoxyguanosine (P < 0.001), blood interleukin-6 (P < 0.001), blood high mobility group box-1 (P < 0.05), and pulse wave velocity (P < 0.01) decreased more in group A than in group B with 12 months of treatment. The percent reductions in intima-media thickness and blood asymmetric dimethylarginine were significantly greater in group A than in group B (P < 0.001).

CONCLUSIONS

Benidipine is more effective than amlodipine for protecting renal function and potentially for ameliorating atherosclerosis in hypertensive patients with mild CKD. T-type calcium channel blockers may be effective in patients with CKD.

Protective effects of efonidipine, a T- and L-type calcium channel blocker, on renal function and arterial stiffness in type 2 diabetic patients with hypertension and nephropathy

AIM

The three types of calcium channel blocker (CCB), L-, T- and N-type, possess heterogeneous actions on endothelial function and renal microvascular function. In the present study, we evaluated the effects of two CCBs, efonidipine and amlodipine, on renal function and arterial stiffness.

METHODS

Forty type 2 diabetic patients with hypertension and nephropathy receiving angiotensin receptor II blockers were enrolled and randomly divided into two groups: the efonidipine group was administered efonidipine hydrochloride ethanolate 40 mg/day and the amlodipine group was admin-istered amlodipine besilate 5 mg/day for 12 months. Arterial stiffness was evaluated by the cardio-ankle vascular index (CAVI).

RESULTS

Changes in blood pressure during the study were almost the same in the two groups. Sig-nificant increases in serum creatinine and urinary albumin and a significant decrease in the esti-mated glomerular filtration rate were observed in the amlodipine group, but not in the efonidipine group. On the other hand, significant decreases in plasma aldosterone, urinary 8-hydroxy-2'-deoxy-guanosine and CAVI were observed after 12 months in the efonidipine group, but not in the amlo-dipine group.

CONCLUSIONS

These results suggest that efonidipine, which is both a T-type and L-type calcium chan-nel blocker, has more favorable effects on renal function, oxidative stress and arterial stiffness than amlodipine, an L-type calcium channel blocker.

Influence of T-calcium channel blocker treatment on deterioration of renal function in chronic kidney disease

Some calcium channel blockers (CCBs) have renoprotective effects. Our aim was to compare the effects of different subclasses of CCBs on the deterioration of renal function in chronic kidney disease (CKD). This is a prospective, observational cohort study in a single center. The subjects were 107 nondiabetic CKD patients. The rate of deterioration of estimated glomerular filtration rate (DeltaeGFR) was calculated by [last visit eGFR - baseline eGFR/follow-up duration]. Multivariate analysis was performed using the change in urinary protein (DeltaUP) and DeltaeGFR during follow-up as response variables. CCB subclasses were L-type in 76 patients, T- and L-type in 28 patients, and nondihydropyridines in 6 patients. Multiregression analysis indicated that higher baseline proteinuria (UP) and the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers were associated with the decrease of UP, while the use of L-type CCBs, prednisolone, and probucol was associated with the increase of UP. The use of T- and L-type CCBs, ACEIs and diuretics was associated with a good outcome in terms of DeltaeGFR, whereas chronic glomerulonephritis, polycystic kidney disease, and higher baseline eGFR and UP were associated with a poor outcome. It is suggested that the use of T- and L-type CCB among other subclasses may improve the outcome of patients with nondiabetic CKD in terms of renal function.

Comparison of the antiproteinuric effects of the calcium channel blockers benidipine and amlodipine administered in combination with angiotensin receptor blockers to hypertensive patients with stage 3-5 chronic kidney disease

Benidipine, an L- and T-type calcium channel blocker, dilates both efferent and afferent arterioles and reduces glomerular pressure. Thus, it may exert renoprotective effects. We conducted an open-labeled, randomized trial to compare the blood pressure (BP)-lowering effect and antiproteinuric effect of benidipine with those of amlodipine in hypertensive patients with moderate-to-advanced-stage chronic kidney disease (CKD) (stages 3-5). These patients were already being administered the current maximum recommended doses of angiotensin receptor blockers (ARBs). Patients with BP >or=140/90 mm Hg, despite treatment with the maximum recommended dose of ARBs, were randomly assigned to two groups. The patients received either of the following treatment regimens: 4 mg day(-1) of benidipine, which was increased up to a dose of 16 mg day(-1) (B group; n=24), and 2.5 mg day(-1) of amlodipine, which was increased up to a dose of 10 mg day(-1) amlodipine (A group; n=23). After 6 months of treatment, a significant and comparable reduction in the systolic and diastolic BP was seen in both groups. The decrease in the urinary protein to creatinine ratio in the B group was significantly lower than that in the A group. Benidipine exerted antiproteinuric effect to a greater extent than did amlodipine, even in patients with diabetic nephropathy. We conclude that the addition of benidipine, rather than amlodipine, ameliorates urinary protein excretion in hypertensive patients with CKD who are already being administered ARBs. Therefore, we propose a combination therapy with benidipine and ARBs, even for patients with moderate-to-advanced-stage CKD.