Myocardial infarction: Is bepridil,a new calcium antagonist,able to improve the course of the acute phase?

Summary Several calcium antagonists are useful in the treatment of ischemic heart disease. This open randomized study was designed to determine the effects of bepridil, a new long-acting calcium antagonist with antiarrhythmic properties, on the course of acute myocardial infarction (AMI). Two hundred patients with AMI of less than 48 hours duration (average 10.9 hours) were randomly assigned to two treatment groups: The first one was treated with bepridil (BEP, n=100), and the second one was considered as a control group, using isosorbide dinitrate at a low dosage (ISDN, n=100). BEP was administered intravenously for 48 hours at a dosage of 4 mg/kg/day; at the same time, an oral dose of 200 mg t.i.d. was started and continued for 21 days. In the control group, ISDN was given orally at the low dosage of 5 mg every 4 hours for 21 days. An uneventful course was seen in 28 BEP patients versus 15 in the control group (p<0.05). Mortality and recurrence of angina were lower in the BEP group than in the control group, but the difference is not significant. On the other hand, moderate and severe hemodynamic complications did not occur in 80 BEP patients versus 65 in the control group (p<0.05). Ventricular arrhythmias occurred in 36 BEP patients versus 50 in the control group (p<0.05). Antiarrhythmic therapy was required in 14 BEP patients versus 61 in the control group (p<0.001). These results show that bepridil seems capable of improving the hemodynamics and arrhythmologic course of AMI.     

Cicletanine与Bepridil对大鼠离体胸主动脉环收缩的抑制效应

采用雄性SD大鼠胸主动脉环标本,用累积给药法制备去甲肾上腺素(NE)与氯化钾(KCl)收缩主动脉环的量效曲线,观察Cicletanine(Cic)与Bepridil(Bep)的抑制效应,比较两者对NE或KCl最大收缩反应(E_(max))的抑制百分率(％)与ED_(50)。结果显示Cic主要抑制NE激动的主动脉环收缩;Bep主要抑制KCl激动的主动脉环收缩。Cic与Bep联孵时,Cic可增加Bep抑制NE激动主动脉环收缩的效应;Bep可增加Cic抑制KCl激动主动脉环收缩的效应。上述作用无内皮依赖性。     

HPLC测定血浆中吡咯地尔浓度

建立了测定吡咯地尔血浆药物浓度的HPLC.采用YWG-C_(18)柱(10μm,15cm×4.6mm I.D.),检测波UV254nm,流动相为甲醇:水:10%三乙胺磷酸缓冲液(pH4.5):二氯甲烷=75:15:10:5,流速1.0ml/min;1.0ml血浆用正己烷:异丁醇(98:2)提取,内标法定量.线性范围10～2000ng/ml,最低检测浓度3ng/ml.平均提取回收率90.02%,平均方法回收率100.33%,日内RSD<4.0%,日间RSD<5.5%.     

Bepridil facilitates early termination of spiral-wave reentry in two-dimensional cardiac muscle through an increase of intercellular electrical coupling

Bepridil is effective for conversion of atrial fibrillation to sinus rhythm and in the treatment of drug-refractory ventricular tachyarrhythmias. We investigated the effects of bepridil on electrophysiological properties and spiral-wave (SW) reentry in a 2-dimensional ventricular muscle layer of isolated rabbit hearts by optical mapping. Ventricular tachycardia (VT) induced in the presence of bepridil (1 μM) terminated earlier than in the control. Bepridil increased action potential duration (APD) by 5% – 8% under constant pacing and significantly increased the space constant. There was a linear relationship between the wavefront curvature (κ) and local conduction velocity: LCV = LCV₀ ? D·κ (D, diffusion coefficient; LCV₀, LCV at κ = 0). Bepridil significantly increased D and LCV₀. The regression lines with and without bepridil crossed at κ = 20 – 40 cm^?1, resulting in a paradoxical decrease of LCV at κ > 40 cm^?1. Dye transfer assay in cultured rat cardiomyocytes confirmed that bepridil increased intercellular coupling. SW reentry in the presence of bepridil was characterized by decremental conduction near the rotation center, prominent drift, and self-termination by collision with boundaries. These results indicate that bepridil causes an increase of intercellular coupling and a moderate APD prolongation, and this combination compromises wavefront propagation near the rotation center of SW reentry, leading to its drift and early termination.[Supplementary Figures: available only at http://dx.doi.org/10.1254/jphs.10233FP]     

Calcium channel antagonists part V: Second-generation agents

Summary Second-generation agents include new dihydropyridines, such as amlodipine, felodipine, isradipine, nicardipine, nimodipine, nisoldipine, and nitrendipine. Verapamil-like agents include tiapamil, gallopamil, and anipamil. Among the diphenylalkylamines, bepridil is of special interest. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. From all these agents will be selected those that are longeracting and provide higher vascular selectivity.[This article appeared in Cardiovascular Drugs and Therapy, 2:191–203, 1988.]     

Bepridil up-regulates cardiac Na+ channels as a long-term effect by blunting proteasome signals through inhibition of calmodulin activity

Background and purpose:

Bepridil is an anti-arrhythmic agent with anti-electrical remodelling effects that target many cardiac ion channels, including the voltage-gated Na⁺ channel. However, long-term effects of bepridil on the Na⁺ channel remain unclear. We explored the long-term effect of bepridil on the Na⁺ channel in isolated neonatal rat cardiomyocytes and in a heterologous expression system of human Na_v1.5 channel.

Experimental approach:

Na⁺ currents were recorded by whole-cell voltage-clamp technique. Na⁺ channel message and protein were evaluated by real-time RT-PCR and Western blot analysis.

Key results:

Treatment of cardiomyocytes with 10 µmol·L⁻¹ bepridil for 24 h augmented Na⁺ channel current (I_Na) in a dose- and time-dependent manner. This long-term effect of bepridil was mimicked or masked by application of W-7, a calmodulin inhibitor, but not KN93 [2-[N-(2-hydroxyethyl)-N-(4-methoxy benzenesulphonyl)]-amino-N-(4-chlorocinnamyl)-N-methylbenzylamine], a Ca²⁺/calmodulin-dependent kinase inhibitor. During inhibition of protein synthesis by cycloheximide, the I_Na increase due to bepridil was larger than the increase without cycloheximide. Bepridil and W-7 significantly slowed the time course of Na_v1.5 protein degradation in neonatal cardiomyocytes, although the mRNA levels of Na_v1.5 were not modified. Bepridil and W-7 did not increase I_Na any further in the presence of the proteasome inhibitor MG132 [N-[(phenylmethoxy)carbonyl]-L-leucyl-N-[(1S)-1-formyl-3-methylbutyl]-L-leucinamide]. Bepridil, W-7 and MG132 but not KN93 significantly decreased 20S proteasome activity in a concentration-dependent manner.

Conclusions and implications:

We conclude that long-term exposure of cardiomyocytes to bepridil at therapeutic concentrations inhibits calmodulin action, which decreased degradation of the Na_v1.5 α-subunit, which in turn increased Na⁺ current.     

苄普地尔对豚鼠甲亢性肥厚心肌中延迟整流钾电流的抑制作用

目的　研究苄普地尔(bepridil)对肥厚心肌细胞延迟整流钾电流(I_K)中快激活成份(I_Kr)和慢激活成份(I_Ks)及内向整流钾电流(I_K1)的作用。方法　全细胞膜片钳技术。结果　在肥厚心肌细胞中,Bepridil 30 μmol·L- 1 对I_Kr及I_Ks有阻断作用,抑制率分别为20.9% (0 mV)和27.2 % (+50 mV)。“Envelopeoftail”显示bepridil对I_Ks的阻断作用大于I_Kr。Bepridil(1 - 100 μmol·L^-1 )浓度依赖性的阻断I_Ks及I_Kr,其IC₅₀ 分别为23.8μmol·L^-1 和46.7μmol·L^-1 。Bepridil 30 μmol·L^-1 也能阻断I_K1 ,抑制率为15.1% (- 100 mV) ,但不影响其反转电位。结论　Bepridil对甲亢性豚鼠肥厚心肌中I_Ks,I_Kr及I_K1有阻断作用     

Newer Options for Treating Drug-Resistant (MDR+) Cancer Cells using Photoradiation Therapy

Emergence of drug resistance with conventional cytotoxic therapy is a major challenge towards the curability of many cancers, especially in patients undergoing autologous BMT with ex-vivo purged hematopoietic support. We have explored the potential role of photoradiation therapy in purging hematopoietic stem cells of various hematological malignancies. Benzoporphyrin derivative, monoacid ring A (BPD-MA), dihematoporphyrin ether (DHE), and MC-540 were evaluated for the “ex-vivo” purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large cell lymphoma cell lines and colony forming-unit leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments four log elimination of tumor cell lines was observed after 1 hr of incubation with BPD-MA or DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA or DHE, the mean recovery of normal BM progenitors was 4-5.2% for granulocyte-macrophage colony forming unit (CFU-GM) and 5-9.8% for burst forming unit erythroid (BFUE).

The T lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL₁₀₀. along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. Our results demonstrated the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation would be useful for “ex-vivo” purging of malignant cells. Other methods to deal with decreasing drug resistance are also detailed.     

Effects of Bepridil Versus E‐4031 on Transmural Ventricular Repolarization and Inducibility of Ventricular Tachyarrhythmias in the Dog

Background: Bepridil (a multiple channel blocker) may markedly prolong the QT interval and induce polymorphic ventricular tachyarrhythmias (VTA). We compared the transmural ventricular repolarization characteristics and inducibility of polymorphic VTA after administration of bepridil versus the pure I_Kr blocker, E‐4031, each administered to five open‐chest dogs. Methods: We used plunge needle electrode to record transmural left ventricular (LV) repolarization and activation‐recovery interval (ARI) to estimate local repolarization. The correlation between paced cycle length and ARI was separately examined in the LV endocardium, mid‐myocardium (Mid), and epicardium. Attempts to induce VTA were made during bradycardia and sympathetic stimulation. Results: Bepridil and E‐4031 prolonged QT interval and ARI in all LV layers, though the magnitude of prolongation was greatest in Mid, increasing the transmural ARI dispersion, particularly during bradycardia. Compared with E‐4031, bepridil caused mild, reverse use‐dependent changes in ventricular repolarization, and less ARI dispersion than E‐4031 during slow ventricular pacing. Both drugs increased ARI_max and cycle length at 50% of ARI_max, though the changes were smaller after bepridil than after E‐4031 administration. Bradycardia after the administration of each drug induced no VTA; however, sympathetic stimulation induced sustained polymorphic VTA in two of five dogs treated with E‐4031 versus no dog treated with bepridil. Conclusions: Unlike the pure I_kr blocker, E‐4031, bepridil exhibited weak properties of reverse use‐dependency and protected against sympathetic stimulation‐induced VTA. It may be an effective supplemental treatment for recipients of implantable cardioverter defibrillator. (PACE 2010; 950–959)     

小分子p53-MDM2抑制剂先导化合物苄普地尔的研究

目的采用老药新用药物设计方法,探寻p53-MDM2蛋白结合小分子抑制剂的先导化合物。方法通过荧光偏振(FP)法和蛋白印迹试验法,分别测定化合物的p53-MDM2蛋白结合抑制活性和相关蛋白的表达变化,采用四甲基偶氮唑盐微量酶反应比色法(MTT法)测试其体外抗肿瘤活性,并且测定人肝微粒体中代谢产物。结果发现苄普地尔具有优秀的体外抗肿瘤活性和较强的p53-MDM2蛋白结合抑制活性,能显著降低MDM2蛋白的表达,而且呈剂量依赖性。在人肝微粒体中的代谢产物主要为苯环羟基单氧化代谢产物。结论苄普地尔可作为p53-MDM2蛋白结合小分子抑制剂先导化合物,用于后续的结构优化设计研究。