Dihydropyridine Analogue Research Articles

Cardioprotective Effect against Ischemia-Reperfusion Injury of PAK-200, a Dihydropyridine Analog with an Inhibitory Effect on Cl- but Not Ca2+ Current.

We examined the effects of a dihydropyridine analog, PAK-200, on guinea pig myocardium during experimental ischemia and reperfusion. In isolated ventricular cardiomyocytes, PAK-200 (1 μM) had no effect on the basal peak inward and steady-state currents but inhibited the isoprenaline-induced time-independent Cl- current. In the right atria, PAK-200 had no effect on the beating rate and the chronotropic response to isoprenaline. In an ischemia-reperfusion model with coronary-perfused right ventricular tissue, a decrease in contractile force and a rise in tension were observed during a period of 30-min no-flow ischemia. Upon reperfusion, contractile force returned to less than 50% of preischemic values. PAK-200 had no effect on the decline in contractile force during the no-flow ischemia but reduced the rise in resting tension. PAK-200 significantly improved the recovery of contractile force after reperfusion to about 70% of the preischemic value. PAK-200 was also shown to attenuate the decrease in tissue ATP during ischemia. Treatment of ventricular myocytes with an ischemia-mimetic solution resulted in depolarization of the mitochondrial membrane potential and an increase in cytoplasmic and mitochondrial Ca2+ concentrations. PAK-200 significantly delayed these changes. Thus, PAK-200 inhibits the cAMP-activated chloride current in cardiac muscle and may have protective effects against ischemia-reperfusion injury through novel mechanisms.

Spectroscopic evaluation of Zn (II) complexes with drug analogues: Interactions with BSA and the pH effect on the drug-Zn (II) system.

Using UV-Vis, FT-IR, fluorescence spectroscopy and protein-ligand docking, the interactions between the zinc complexes with drug analogues and bovine serum albumin were investigated. In addition, considering the ubiquitous presence of zinc ions in the human system, we studied the interactions between this ion with hymecromone, dihydropyridine analogue, and acetamide, as well as the pH influence on these systems. The complexes were synthesized by interaction between the ligands and the Zn (II) ion in a 2:1M ratio. Elemental analysis, FT-IR, and UV-Vis spectroscopy studies investigated the structure of the synthesized complexes. Fluorescence spectroscopy, UV-Vis, molecular docking and molecular dynamics were used to study the interactions of the Zn complexes with the BSA. The drug-Zn (II) system's pH effect was investigated using UV-Vis spectroscopy. After the complexation with the zinc, the drug molecules exhibited higher apparent binding affinity to BSA. BSA's fluorescence efficiency by the drug analogues was enhanced. In addition, molecular modelling was used to classify the residue of amino acids in the BSA playing key roles in this binding interaction. An increase in pH appears to contribute to alkaline hydrolysis of the Zn (II) molecules.

Synthesis, Biological Evaluation and Molecular Docking Studies of Novel Di-hydropyridine Analogs as Potent Antioxidants.

The aim of this study is to synthesize, characterize and biological evaluation of 3-ethyl 5- methyl2-(2-aminoethoxy)-4-(2-chlorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate derivatives. An efficient synthesis of two series of novel carbamate and sulfonamide derivatives of amlodipine, 3-ethyl 5-methyl 2-(2-aminoethoxy)-4-(2-chlorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate (amlodipine) 1 were chemical synthesized process. In this process, various chloroformates 2(a-e) and sulfonyl chlorides 4(a-e) on reaction with 1 in the presence of N,N-dimethylpiperazine as a base in THF at 50-550 oC, the corresponding title compounds 3(a-e) and 5(a-e) in high yields. Furthermore, the compounds 3(a-e) and 5(a-e) were evaluated for antioxidant activity (DPPH method), metal chelating activity, hemolytic activity, antioxidant assay (ABTS method), cytotoxicity, molecular docking and in silico ADMET properties. Results revealed that 5a, 5e, 3d, 3a and 5c exhibited high antioxidant, metal chelating activities, but 5a, 5e and 3d exhibited low activity. The molecular docking studies and ADMET of suggested ligands showed the best binding energies and non-toxic properties. The present in silico and in vitro evaluations suggested that these dihydropyridine derivatives act as potent antioxidants and chelating agents which may be useful in treating metals induced oxidative stress associated diseases.

An Efficient One‐Pot, Multicomponent, and Green Solvent Protocol for the Synthesis of Dihydropyridine Derivatives

Highly prominent dihydropyridine analogs have been developed and screened for their yields by using different catalysts under eco‐friendly ethanol solvent condition. Triethylamine catalyst was identified as ro bust catalyst for this synthetic path. The key benefits of this procedure are environmentally benign procedure, mild reaction conditions, simplicity of operation, high yields, mild reaction period, and decent substrate generality.

The Role of Surface-Bound Dihydropyridine Analogues in Pyridine-Catalyzed CO2 Reduction over Semiconductor Photoelectrodes.

We propose a general reaction mechanism for the pyridine (Py)-catalyzed reduction of CO2 over GaP(111), CdTe(111), and CuInS2(112) photoelectrode surfaces. This mechanism proceeds via formation of a surface-bound dihydropyridine (DHP) analogue, which is a newly postulated intermediate in the Py-catalyzed mechanism. Using density functional theory, we calculate the standard reduction potential related to the formation of the DHP analogue, which demonstrates that it is thermodynamically feasible to form this intermediate on all three investigated electrode surfaces under photoelectrochemical conditions. Hydride transfer barriers from the intermediate to CO2 demonstrate that the surface-bound DHP analogue is as effective at reducing CO2 to HCOO– as the DHP(aq) molecule in solution. This intermediate is predicted to be both stable and active on many varying electrodes, therefore pointing to a mechanism that can be generalized across a variety of semiconductor surfaces, and explains the observed electrode dependence of the photocatalysis. Design principles that emerge are also outlined.

High affinity complexes of pannexin channels and L-type calcium channel splice-variants in human lung: Possible role in clevidipine-induced dyspnea relief in acute heart failure

Clevidipine, a dihydropyridine (DHP) analogue, lowers blood pressure (BP) by inhibiting l-type calcium channels (CaV1.2; gene CACNA1C) predominantly located in vascular smooth muscle (VSM). However, clinical observations suggest that clevidipine acts by a more complex mechanism. Clevidipine more potently reduces pulmonary vascular resistance (PVR) than systemic vascular resistance and its spectrum of effects on PVR are not shared by other DHPs. Clevidipine has potent spasmolytic effects in peripheral arteries at doses that are sub-clinical for BP lowering and, in hypertensive acute heart failure, clevidipine, but not other DHPs, provides dyspnea relief, partially independent of BP reduction. These observations suggest that a molecular variation in CaV1.2 may exist which confers unique pharmacology to different DHPs. We sequenced CACNA1C transcripts from human lungs and measured their affinity for clevidipine. Human lung tissue contains CACNA1C mRNA with many different splice variations. CaV1.2 channels with a specific combination of variable exons showed higher affinity for clevidipine, well below the concentration associated with BP reduction. Co-expression with pannexin 1 further increased the clevidipine affinity for this CaV1.2 splice variant. A high-affinity splice variant of CaV1.2 in combination with pannexin 1 could underlie the selective effects of clevidipine on pulmonary arterial pressure and on dyspnea. Research in ContextClevidipine lowers blood pressure by inhibiting calcium channels in vascular smooth muscle. In patients with acute heart failure, clevidipine was shown to relieve breathing problems. This was only partially related to the blood pressure lowering actions of clevidipine and not conferred by another calcium channel inhibitor. We here found calcium channel variants in human lung that are more selectively inhibited by clevidipine, especially when associated with pannexin channels. This study gives a possible mechanism for clevidipine's relief of breathing problems and supports future clinical trials testing the role of clevidipine in the treatment of acute heart failure.

Antihypertensive effects of new dihydropyridine derivatives on phenylephrine-raised blood pressure in rats.

Changes in the substitutions at C-3 and C-5 positions of 4-(1-methyl-5-nitro-2-imidazolyl) dihydropyridine analogs of nifedipine have led to changes in potency of the compounds. The objective of the present study was to examine the hypotensive effects of 5 newly synthesized dihydropyridine derivatives of nifedipine in rats with phenylephrine-raised blood pressure. Anesthetized Sprague-Dawley rats were randomly assigned to 19 groups of 7 animals each. Control group received the vehicle dimethylsulfoxide (0.05 mL), 3 groups were given nifedipine at 100, 300, or 1000 μg/kg, and 5 other groups each composed of 3 subgroups administered one of the 5 new dihydropyridine compound at 100, 300, or 1000 μg/kg. All animals were initially infused with 20 µg/kg/min phenylephrine for 45 min, and were then given a bolus of either dimethylsulfoxide, nifedipine, or new dihydropyridine compounds 20 min after the commencement of phenylephrine infusion. Blood pressure and heart rate (HR) of the animals were measured before and at the end of phenylephrine infusion, or 25 min after injection of vehicle or compounds. Compared to dimethylsulfoxide, nifedipine, and new 1, 4-dihydropyridine derivatives caused significant reductions in MBP. Moreover, cyclohexyl propyl, phenyl butyl, and cyclohexyl methyl analogs of 1, 4-dihydro-2,6-dimethyl-4-(1-methyl-5-nitro-2-imidazoyl)-3,5-pyridinedicarboxylase at 100 μg/kg, phenyl butyl, and cyclohexyl methyl analogs at 300 μg/kg, and cyclohexyl methyl analogs at 1000 μg/kg reduced MBP similar to nifedipine. There was no significant difference between HR of all groups before and after administration of the compounds. The findings indicated that changes in substitution at C-3 and C-5 positions of 2-(1-methyl-5-nitro-2-imidazolyl) dihydropyridine analogs of nifedipine were associated with changes in hypotensive activity of the compounds.

Arrhythmogenic effects of mutated L-type Ca 2+-channels on an optogenetically paced muscular pump in Caenorhabditis elegans.

Cardiac arrhythmias are often associated with mutations in ion channels or other proteins. To enable drug development for distinct arrhythmias, model systems are required that allow implementing patient-specific mutations. We assessed a muscular pump in Caenorhabditis elegans. The pharynx utilizes homologues of most of the ion channels, pumps and transporters defining human cardiac physiology. To yield precise rhythmicity, we optically paced the pharynx using channelrhodopsin-2. We assessed pharynx pumping by extracellular recordings (electropharyngeograms—EPGs), and by a novel video-microscopy based method we developed, which allows analyzing multiple animals simultaneously. Mutations in the L-type VGCC (voltage-gated Ca2+-channel) EGL-19 caused prolonged pump duration, as found for analogous mutations in the Cav1.2 channel, associated with long QT syndrome. egl-19 mutations affected ability to pump at high frequency and induced arrhythmicity. The pharyngeal neurons did not influence these effects. We tested whether drugs could ameliorate arrhythmia in the optogenetically paced pharynx. The dihydropyridine analog Nemadipine A prolonged pump duration in wild type, and reduced or prolonged pump duration of distinct egl-19 alleles, thus indicating allele-specific effects. In sum, our model may allow screening of drug candidates affecting specific VGCCs mutations, and permit to better understand the effects of distinct mutations on a macroscopic level.

1,4-Dihydropyridine derivatives with T-type calcium channel blocking activity attenuate inflammatory and neuropathic pain.

We have recently identified a class of dihydropyridine (DHP) analogues with 30-fold selectivity for T-type over L-type calcium channels that could be attributed to a modification of a key ester moiety. Based on these results, we examined a second series of compounds with similar attributes to determine if they had enhanced affinity for T-type channels. Whole-cell patch clamp experiments in transfected tsA-201 cells were used to screen these DHP derivatives for high affinity and selectivity for Cav3.2 over Cav1.2L-type channels. The effects of the two lead compounds, termed N10 and N12, on Cav3.2 channel activity and gating were characterized in detail. When delivered intrathecally or intraperitoneally, these compounds mediated analgesia in a mouse model of acute inflammatory pain. The best compound from the initial screening, N12, was also able to reverse mechanical hyperalgesia produced by nerve injury. The compounds were ineffective in Cav3.2 null mice. Altogether, our data reveal a novel class of T-type channel blocking DHPs for potential pain therapies.

Inhibitors of Alzheimer's BACE-1 with 3,5-bis-N-(aryl/heteroaryl) carbamoyl-4-aryl-1,4-dihydropyridine structure.

β-site amyloid precursor protein cleaving enzyme (BACE-1) is a validated target for Alzheimer therapy due to its distinctive role in pathogenesis of AD. In the present contribution, a series of new 3,5-bis-N-(aryl/heteroaryl) carbamoyl-4-aryl-1,4-dihydropyridine structures were synthesized as BACE-1 inhibitors (6a-6n). In vitro BACE-1 inhibitory activities were determined by enzymatic fluorescence resonance energy transfer assay. Synthesized dihydropyridine (DHP) analogues exhibited weak to good inhibitory activities while 6i, 6n and 6a were found to be the most potent molecules with 83.76, 79.45 and 72.47% BACE-1 inhibition at 10μM, respectively. Structure binding/activity relationship elucidations revealed that superior BACE-1 inhibitory activities were observed for DHP derivatives bearing fused/non-fused thiazole groups and particularly 3,5-bis-N-(6-ethoxy-2-benzothiazolyl) moiety. Binding maps showed that enhanced activity may be attributed to the additional H-bond and hydrophobic interactions with S2-S3 subpockets of BACE-1.

1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity of novel dihydropyridine derivatives

Thirteen dihydropyridine analogues 1 - 13 were synthesized and evaluated for their DPPH radical scavenging activity. A good to moderate antioxidant activity ranging from 127.4 to 284.5 μM was observed and structure-activity relationship was established. The 3'-fluoro derivative 8 (IC 50 = 127.4±3.5 μM) was found to exhibit highest activity among the dihydro pyridine derivatives 1 - 13 , while the other derivatives 11 (IC 50 = 132.5±3.32 μM), 6 (IC 50 = 142.2±0.60 μM), 10 (IC 50 = 144.7±2.46 μM), 12 (IC 50 = 153.7±0.50 μM), 5 (IC 50 = 161.4±2.81 μM) and 5 (IC 50 = 164.4±2.50 μM) possess moderate activity, depends upon the C-4 and C-6 substituted groups. The compounds 7 , 13 , 4 , 3 and 2 have lowest IC 50 values, ranging between 172.8 and 284.5 μM. Dihydropyridine analogues were characterized by spectroscopic techniques.

Abstract 135: A Novel TGFb Selective Inhibitor Drives Cardiogenesis in Embryonic Stem Cells

The early signals that drive embryonic stem cells (ESC) to cardiomyocytes are well characterized, but little is known about the pathways that control the later stages of differentiation. Genetic studies in animals are however challenging to study these later steps of heart development and are thus incapable of providing useful information for controlling ESC differentiation. Therefore, we have implemented unbiased high throughput screens on mouse ESC (mESC) to discover small molecules that probe these steps of differentiation to unravel novel biological mechanisms that control cardiac fate. From over 17000 unique molecules, screened in a serum assay relying on a cardiac specific Myh6-GFP reporter to monitor cardiogenesis, we identified a dihydropyridine (DHP), which are well-known L-type calcium channel inhibitors. Subsequent pathway analysis in combination with a structure activity relationship study of over 200 DHP analogs pinpointed the activity specifically to the Activin A/TGFb pathway, with high inhibition efficiency for TGFb signals and poor to none for Activin A signals. Further functional characterization of DHP in the TGFb pathway demonstrated that DHP acts upstream of Smad2/3, positioning the activity at the receptor level, where DHP downregulates the amount of TGFb receptors on the cell surface and targets them for degradation. This TGFb selective inhibitor was then applied in mESC to probe the effects of inhibiting TGFb specifically at several stages of differentiation. When given early in differentiation DHP blocked all mesoderm, indicating that, in serum differentiated cultures, TGFb is essential for mesoderm induction. Secondly, when DHP was added during mesoderm patterning, cardiogenesis was enhanced specifically, whereas other cardiovascular lineages such as smooth muscle, blood and endothelial cells were not affected. In summary, we have identified a new probe of TGFb signaling that shows that TGFb signaling governs cardiopoietic fate by inhibiting formation of cardiomyocytes. Additionally, our molecule and its mechanism have important implications for congenital heart disease, since deficient TGFb signaling leads to vascular and cardiac defects, and elevated signaling underlies Loeys-Deitz syndrome.

Ethanol alters calcium signaling in axonal growth cones

Calcium (Ca2+) channels are sensitive to ethanol and Ca2+ signaling is a critical regulator of axonal growth and guidance. Effects of acute and chronic exposure to ethanol (22, 43, or 87 mM) on voltage-gated Ca2+ channels (VGCCs) in whole cells, and KCl-induced Ca2+ transients in axonal growth cones, were examined using dissociated hippocampal cultures. Whole-cell patch-clamp analysis in neurons with newly-formed axons (Stage 3) revealed that rapidly inactivating, low-voltage activated (LVA) and non-inactivating, high-voltage activated (HVA) currents were both inhibited in a dose-dependent manner by acute ethanol, with relatively greater inhibition of HVA currents. When assessed by Fluo-4-AM imaging, baseline fluorescence and Ca2+ response to ethanol in Stage 3 neurons was similar compared to neurons without axons, but peak Ca2+ transient amplitudes in response to bath-applied KCl were greater in Stage 3 neurons and were decreased by acute ethanol. The amplitude of Ca2+ transients elicited specifically in axonal growth cones by focal application of KCl was also inhibited by acute exposure to moderate-to-high concentrations of ethanol (43 or 87 mM), whereas a lower concentration (22 mM) had no effect. When 43 or 87 mM ethanol was present continuously in the medium, KCl-evoked Ca2+ transient amplitudes were also reduced in growth cones. In contrast, Ca2+ transients were increased by continuous exposure to 22 mM ethanol. Visualization using a fluorescent dihydropyridine analog revealed that neurons continuously exposed to ethanol expressed increased amounts of L-type Ca2+ channels, with greater increases in axonal growth cones than cell bodies. Thus, acute ethanol reduces Ca2+ current and KCl-induced Ca2+ responses in whole cells and axonal growth cones, respectively, and chronic exposure is also generally inhibitory despite apparent up-regulation of L-type channel expression. These results are consistent with a role for altered growth cone Ca2+ signaling in abnormal neuromorphogenesis associated with fetal alcohol spectrum disorders.

Leishmania donovani: Oral therapy with glycosyl 1,4-dihydropyridine analogue showing apoptosis like phenotypes targeting pteridine reductase 1 in intracellular amastigotes

Glycosyl 1,4-dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-β-l-threo pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester) synthesized in our laboratory, inhibited Leishmania donovani infection in vitro and in hamsters (Mesocricetus auratus) when administered orally. This analogue is nontoxic, cell-permeable and orally effective. This glycosyl dihydropyridine analogue functioned through arrest of cells in sub-G0/G1-phase, triggering mitochondrial membrane depolarization-mediated programmed cell death of the intracellular amastigotes.

The dihydropyridine analogue cerebrocrast blocks both T-type and L-type calcium currents

Cerebrocrast is a novel lipophilic dihydropyridine derivative with potential neuroprotective and antidiabetic properties. We have analyzed its interaction with L-type (CaV1.2b) and T-type (CaV3.1) calcium channels using a whole-cell patch clamp in HEK 293 cells. Cerebrocrast inhibited current flux through both CaV1.2b and CaV3.1 channels. In both cases, the drug was about 10-fold less effective than neutral dihydropyridines, but more efficient than the charged dihydropyridine amlodipine. IC50 values for the CaV1.2b channel were 586 +/- 96 nmol/L and 178 +/- 78 nmol/L at holding potentials of -80 mV and -50 mV, respectively. Approximately 50 micromol/L of cerebrocrast was needed to block 50% of the current amplitude in the CaV3.1 channel, but this inhibition was not facilitated by shifting the holding potential from -100 mV to -70 mV. Cerebrocrast did not alter current kinetics in either investigated channel, and the inhibition of calcium current was partly reversible or irreversible. In conclusion, the interaction of cerebrocrast with CaV3.1 lacked the typical characteristics of a state-dependent interaction, and voltage-dependent inhibition of CaV1.2b was consistent with partial interaction with the inactivated state of the channel.

Leishmania donovani: A glycosyl dihydropyridine analogue induces apoptosis like cell death via targeting pteridine reductase 1 in promastigotes

Targeting of pteridine reductase 1 (PTR1) in Leishmania is essential for development of successful antifolate chemotherapy. In search for specific inhibitors of PTR1 we have previously reported phenyl 1,4-dihydropyridine ring as the lead structure showing antileishmanial efficacy in vitro and by the oral route in vivo. In this study, we present programmed cell death inducing potential of this glycosyl dihydropyridine analogue (2,6-dimethyl-4-(3- O-benzyl-1,2- O-isopropylidene-β- l- threo-pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester). Flow cytometric analysis revealed that this analogue induces cell cycle arrest at G2/M phase with subsequent increase in sub-G1 peak. Incubation of Leishmania promastigotes with this analogue causes exposure of phosphatidylserine to the outer leaflet of plasma membrane, formation of reactive oxygen species, depolarization of mitochondrial membrane potential and concomitant nuclear alterations that included DNA fragmentation. The results from this study on promastigotes give important lead to investigate further in intracellular amastigotes, the biologically relevant parasite stage in host macrophages.

Synthesis of Dihydropyridine Analogues for Sperm Immobilizing Activity

Synthesis of Dihydropyridine Analogues for Sperm Immobilizing Activity

Actions of Mibefradil, Efonidipine and Nifedipine Block of Recombinant T- and L-Type Ca2+ Channels with Distinct Inhibitory Mechanisms

We compared detailed efficacy of efonidipine and nifedipine, dihydropyridine analogues, and mibefradil using recombinant T- and L-type Ca²⁺ channels expressed separately in mammalian cells. All these Ca²⁺ channel antagonists blocked T-type Ca²⁺ channel currents (I_Ca(T)) with distinct blocking manners: I_Ca(T) was blocked mainly by a tonic manner by nifedipine, by a use-dependent manner by mibefradil, and by a combination of both manners by efonidipine. IC₅₀s of these Ca²⁺ channel antagonists to I_Ca(T) and L-type Ca²⁺ channel current (I_Ca(L)) were 1.2 µmol/l and 0.14 nmol/l for nifedipine; 0.87 and 1.4 µmol/l for mibefradil, and 0.35 µmol/l and 1.8 nmol/l for efonidipine, respectively. Efonidipine, a dihydropyridine analogue, showed high affinity to T-type Ca²⁺ channel.

Physiological genomics in PG and beyond: October to December 2005

physiological genomics ( PG ) publishes, on a quarterly basis, brief editorial perspectives entitled “Physiological genomics in PG and beyond.” These editorial perspectives provide brief, accessible highlights of the studies published in PG in the most recent quarter, and relate those studies to

Determination of benidipine in human plasma using liquid chromatography–tandem mass spectrometry

We developed a method for determining benidipine, a dihydropyridine analogue calcium-channel blocker, in plasma using liquid chromatography–tandem mass spectrometry (LC–MS–MS). Benidipine and benidipine-d 5, an internal standard, were extracted from plasma using diethyl ether in the presence of 5 M NaOH. After drying the organic layer, the residue was reconstituted in acetonitrile and injected onto a reversed-phase C 18 column. The isocratic mobile phase (acetonitrile–5 mM ammonium acetate, 90:10, v/v) was eluted at 0.2 ml/min. The ion transitions monitored in multiple reaction-monitoring mode were m/ z 506–174 for benidipine and m/ z 511–179 for the internal standard. The coefficient of variation of the assay precision was less than 13%, and the accuracy exceeded 92%, except at the limit of quantification, 0.05 ng/ml with 1 ml of plasma, when it was 85%. This method was used to measure the benidipine concentration in plasma from healthy subjects after a single 4-mg oral dose of benidipine. This method is a very simple, sensitive, and accurate way to determine the plasma benidipine concentration.