Dihydropyridine Compounds Research Articles

Synthesis of 1,2-dihydropyridine, Arylidene, Hydrazide, and Terthienylnicotinamidine Hydrochloride Analogs: Theoretical Studies, and Antioxidant Activity Assessment

: In the current work, we have utilized the reactivity of N-(4- acetylphenyl)-2-(4-formylphenoxy)acetamide for the synthesis of novel series of 1,2- dihydropyridines, Arylidenes, and hydrazides. Our strategies were prolonged for the synthesis of novel terthienylnicotinamidine hydrochloride salt through a Stille coupling reaction of 6-(5'-bromo-[2,2'-bithiophen]-5-yl)nicotinonitrile with 2-tributyltin thiophene followed by treatment with lithium trimethylsilylamide and subsequent hydrolysis. : The newly prepared structures were well-elucidated by analytical and spectral data (IR, 1H-NMR, 13C-NMR, MS, and elemental analysis). The theoretical studies of terthienylnicotinamidine verified that the other atoms that carry a high density of positive values are considered active centers for the electron acceptor. : The novel synthesized compounds were efficiently established by spectroscopic data and elemental analysis. The antioxidant activity of the synthesized arylidene, hydrazide, and dihydropyridine compounds was assessed by ABTS•+ free radical assay. : The results verified that the transformation of N-(4-acetylphenyl)-2-(4-formylphenoxy)acetamide (47.6%) into hydrazide analogs provided remarkable antioxidant activity (78.1, and 60.3%).

Identification of Chemical and Pharmacological Chaperones for Correction of Trafficking-Deficient Mutant Cyclic Nucleotide-Gated A3 Channels.

Trafficking deficiency caused by missense mutations is a well known phenomenon that occurs for mutant, misfolded proteins. Typically, the misfolded protein is retained by the protein quality-control system and degraded by the endoplasmic reticulum-associated protein degradation pathway and thus does not reach its destination, although residual function of the protein may be preserved. Chemical and pharmacological chaperones can improve the targeting of trafficking-deficient proteins and thus may be promising candidates for therapeutic applications. Here, we report the application of a cellular bioassay based on the bioluminescent calcium reporter aequorin to quantify surface expression of mutant CNGA3 channels associated with the autosomal recessively inherited retinal disease achromatopsia. A screening of 77 compounds enabled the identification of effective chemical and pharmacological chaperones that result in a 1.5- to 4.8-fold increase of surface expression of mutant CNGA3. Using selected compounds, we confirmed that the rescue of the defective trafficking is not limited to a single mutation in CNGA3. Active compounds and our structure-activity correlated data for the dihydropyridine compound class may provide valuable information for developing a treatment of the trafficking defect in achromatopsia. SIGNIFICANCE STATEMENT: This study describes a novel luminescence-based assay to detect the surface expression of mutant trafficking-deficient CNGA3 channels based on the calcium-sensitive photoprotein aequorin. Using this assay for a compound screening, this study identifies novel chemical and pharmacological chaperones that restore the surface localization of mutant trafficking-deficient CNGA3 channels. The results from this work may serve as starting point for the development of potent compounds that rescue trafficking deficiencies in the autosomal recessively inherited retinal disease achromatopsia.

A Synthesis of Two 1,4-Dihydropyridine Derivatives Labeled with Carbon-14 Using Conventional Heating, Microwave Irradiation, and Solid-State Reaction

Three modes of the reaction for labeling of dihydropyridine compounds were studied: thermal heating, microwave irradiation, and solid-state process.

Structural Basis of the Modulation of the Voltage‐Gated Calcium Ion Channel Cav1.1 by Dihydropyridine Compounds**

Abstract1,4‐Dihydropyridines (DHP), the most commonly used antihypertensives, function by inhibiting the L‐type voltage‐gated Ca2+ (Cav) channels. DHP compounds exhibit chirality‐specific antagonistic or agonistic effects. The structure of rabbit Cav1.1 bound to an achiral drug nifedipine reveals the general binding mode for DHP drugs, but the molecular basis for chiral specificity remained elusive. Herein, we report five cryo‐EM structures of nanodisc‐embedded Cav1.1 in the presence of the bestselling drug amlodipine, a DHP antagonist (R)‐(+)‐Bay K8644, and a titration of its agonistic enantiomer (S)‐(−)‐Bay K8644 at resolutions of 2.9–3.4 Å. The amlodipine‐bound structure reveals the molecular basis for the high efficacy of the drug. All structures with the addition of the Bay K8644 enantiomers exhibit similar inactivated conformations, suggesting that (S)‐(−)‐Bay K8644, when acting as an agonist, is insufficient to lock the activated state of the channel for a prolonged duration.

Structural Basis of the Modulation of the Voltage-Gated Calcium Ion Channel Cav 1.1 by Dihydropyridine Compounds*.

1,4‐Dihydropyridines (DHP), the most commonly used antihypertensives, function by inhibiting the L‐type voltage‐gated Ca2+ (Cav) channels. DHP compounds exhibit chirality‐specific antagonistic or agonistic effects. The structure of rabbit Cav1.1 bound to an achiral drug nifedipine reveals the general binding mode for DHP drugs, but the molecular basis for chiral specificity remained elusive. Herein, we report five cryo‐EM structures of nanodisc‐embedded Cav1.1 in the presence of the bestselling drug amlodipine, a DHP antagonist (R)‐(+)‐Bay K8644, and a titration of its agonistic enantiomer (S)‐(−)‐Bay K8644 at resolutions of 2.9–3.4 Å. The amlodipine‐bound structure reveals the molecular basis for the high efficacy of the drug. All structures with the addition of the Bay K8644 enantiomers exhibit similar inactivated conformations, suggesting that (S)‐(−)‐Bay K8644, when acting as an agonist, is insufficient to lock the activated state of the channel for a prolonged duration.

Synthetic Dihydropyridines as Novel Antiacanthamoebic Agents.

Acanthamoeba is an opportunistic pathogen widely spread in the environment. Acanthamoeba causes excruciating keratitis which can lead to blindness. The lack of effective drugs and its ability to form highly resistant cyst are one of the foremost limitations against successful prognosis. Current treatment involves mixture of drugs at high doses but still recurrence of infection can occur due to ineffectiveness of drugs against the cyst form. Pyridine and its natural and synthetic derivatives are potential chemotherapeutic agents due to their diverse biological activities. To study the antiamoebic effects of four novel synthetic dihydropyridine (DHP) compounds against Acanthamoeba castellanii belonging to the T4 genotype. Furthermore, to evaluate their activity against amoeba-mediated host cells cytopathogenicity as well as their cytotoxicity against human cells. Dihydropyridines were synthesized by cyclic dimerization of alkylidene malononitrile derivatives. Four analogues of functionally diverse DHPs were tested against Acanthamoeba castellanii by using amoebicidal, encystation and excystation assays. Moreover, Lactate dehydrogenase assays were carried out to study cytopathogenicity and cytotoxicity against human cells. These compounds showed significant amoebicidal and cysticidal effects at 50 μM concentration, whereas, two of the DHP derivatives also significantly reduced Acanthamoebamediated host cell cytotoxicity. Moreover, these DHPs were found to have low cytotoxicity against human cells suggesting a good safety profile. The results suggest that DHPs have potential against Acanthamoeba especially against the more resistant cyst stage and can be assessed further for drug development.

Repurposing Approved Drugs as Inhibitors of Kv7.1 and Nav1.8 to Treat Pitt Hopkins Syndrome.

Pitt Hopkins Syndrome (PTHS) is a rare genetic disorder caused by mutations of a specific gene, transcription factor 4 (TCF4), located on chromosome 18. PTHS results in individuals that have moderate to severe intellectual disability, with most exhibiting psychomotor delay. PTHS also exhibits features of autistic spectrum disorders, which are characterized by the impaired ability to communicate and socialize. PTHS is comorbid with a higher prevalence of epileptic seizures which can be present from birth or which commonly develop in childhood. Attenuated or absent TCF4 expression results in increased translation of peripheral ion channels Kv7.1 and Nav1.8 which triggers an increase in after-hyperpolarization and altered firing properties. We now describe a high throughput screen (HTS) of 1280 approved drugs and machine learning models developed from this data. The ion channels were expressed in either CHO (KV7.1) or HEK293 (Nav1.8) cells and the HTS used either 86Rb+ efflux (KV7.1) or a FLIPR assay (Nav1.8). The HTS delivered 55 inhibitors of Kv7.1 (4.2% hit rate) and 93 inhibitors of Nav1.8 (7.2% hit rate) at a screening concentration of 10μM. These datasets also enabled us to generate and validate Bayesian machine learning models for these ion channels. We also describe a structure activity relationship for several dihydropyridine compounds as inhibitors of Nav1.8. This work could lead to the potential repurposing of nicardipine or other dihydropyridine calcium channel antagonists as potential treatments for PTHS acting via Nav1.8, as there are currently no approved treatments for this rare disorder.

Chemical Constituents from Hericium erinaceus Promote Neuronal Survival and Potentiate Neurite Outgrowth via the TrkA/Erk1/2 Pathway.

Hericium erinaceus is a culinary-medicinal mushroom used traditionally in Eastern Asia to improve memory. In this work, we investigated the neuroprotective and neuritogenic effects of the secondary metabolites isolated from the MeOH extract of cultured mycelium of H. erinaceus and the primary mechanisms involved. One new dihydropyridine compound (6) and one new natural product (2) together with five known compounds (1,3–5,7) were obtained and their structures were elucidated by spectroscopic analysis, including 2D NMR and HRMS. The cell-based screening for bioactivity showed that 4-chloro-3,5-dimethoxybenzoic methyl ester (1) and a cyathane diterpenoid, erincine A (3), not only potentiated NGF-induced neurite outgrowth but also protected neuronally-differentiated cells against deprivation of NGF in PC12 pheochromocytoma cells. Additionally, compound 3 induced neuritogenesis in primary rat cortex neurons. Furthermore, our results revealed that TrkA-mediated and Erk1/2-dependant pathways could be involved in 1 and 3-promoted NGF-induced neurite outgrowth in PC12 cells.

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.

Development of an 111In-labeled dihydropyridine complex for L-type calcium channel imaging

[111In]-DTPA-Amlodipine complex ([111In]-DTPA-AMLO) was prepared starting high purity [111In]indium chloride and conjugated DTPA-AMLO in 30 min at room temperature in acetate buffer in high radiochemical purity (>99 %, RTLC/HPLC; specific activity: 8–10 GBq/mmol). The log P, stability, biodistribution studies and imaging studies in untreated and amlodipine-pretreated rats were determined. The tracer is mostly washed out through kidneys as expected for a dihydropyridine compound. Blocking studies demonstrated high specific binding of the tracer in calcium channel-rich organs including intestine, heart and colon. SPECT images fully supported above results in normal and treated rats.

A novel dihydropyridine with 3-aryl meta-hydroxyl substitution blocks L-type calcium channels in rat cardiomyocytes

RationaleDihydropyridines are widely used for the treatment of several cardiac diseases due to their blocking activity on L-type Ca2+ channels and their renowned antioxidant properties. MethodsWe synthesized six novel dihydropyridine molecules and performed docking studies on the binding site of the L-type Ca2+ channel. We used biochemical techniques on isolated adult rat cardiomyocytes to assess the efficacy of these molecules on their Ca2+ channel-blocking activity and antioxidant properties. The Ca2+ channel-blocking activity was evaluated by confocal microscopy on fluo-3AM loaded cardiomyocytes, as well as using patch clamp experiments. Antioxidant properties were evaluated by flow cytometry using the ROS sensitive dye 1,2,3 DHR. ResultsOur docking studies show that a novel compound with 3-OH substitution inserts into the active binding site of the L-type Ca2+ channel previously described for nitrendipine. In biochemical assays, the novel meta-OH group in the aryl in C4 showed a high blocking effect on L-type Ca2+ channel as opposed to para-substituted compounds. In the tests we performed, none of the molecules showed antioxidant properties. ConclusionsOnly substitutions in C2, C3 and C5 of the aryl ring render dihydropyridine compounds with the capacity of blocking LTCC. Based on our docking studies, we postulate that the antioxidant activity requires a larger group than the meta-OH substitution in C2, C3 or C5 of the dihydropyridine ring.

Selectivity Problems with Drugs Acting on Cardiac Na<sup>+</sup> and Ca<sup>2+</sup> Channels

With the increase of our knowledge on cardioactive agents it comes more and more clear that practically none of the currently used compounds shows absolute selectivity to one or another ion channel type. This is particularly true for Na(+) and Ca(2+) channel modulators, which are widely applied in the clinical practice and biomedical research. The best example might be probably the marine guanidine poison tetrodotoxin, which has long been considered as a selective Na(+) channel blocker, while recently it turned out to effectively inhibit cardiac Ca(2+) currents as well. In the present study the cross actions observed between the effects of various blockers of Na(+) channels (such as toxin inhibitors, class I antiarrhythmics and local anesthetics) and Ca(2+) channels (like phenylalkylamines, dihydropyridine compounds, diltiazem and mibefradil) are overviewed in light of the known details of the respective channel structures. Similarly, activators of Na(+) channels, including veratridine and batrachotoxin, are also compared. The binding of tetrodotoxin and saxitoxin to Cav1.2 and Nav1.5 channel proteins is presented by construction of theoretical models to reveal common structures in their pore forming regions to explain cross reactions. Since these four domain channels can be traced back to a common ancestor, a close similarity in their structure can well be demonstrated. Thus, the poor selectivity of agents acting on cardiac Na(+) and Ca(2+) channels is a consequence of evolution. As a conclusion, since the limited selectivity is an intrinsic property of drug receptors, it has to be taken into account when designing new cardioactive compounds for either medical therapy or experimental research in the future.

Dihydropyridine receptors actively control gating of ryanodine receptors in resting mouse skeletal muscle fibres

Contraction of skeletal muscle is triggered by the release of Ca(2+) from the sarcoplasmic reticulum (SR) in response to depolarization of the muscle membrane. Depolarization is known to elicit a conformational change of the dihydropyridine receptor (DHPR) in the tubular membrane that controls in a time- and voltage-dependent manner the opening of the ryanodine receptor (RyR), the SR Ca(2+) release channel. At rest, it is assumed that RyRs are kept in a closed state imposed by the repressive action of DHPRs; however, a direct control of the RyR gating by the DHPR has up to now never been demonstrated in resting adult muscle. In this study, we monitored slow changes in SR Ca(2+) content using the Ca(2+) indicator fluo-5N loaded in the SR of voltage-clamped mouse muscle fibres. We first show that external Ca(2+) removal induced a reversible SR Ca(2+) efflux at -80 mV and prevented SR Ca(2+) refilling following depolarization-evoked SR Ca(2+) depletion. The dihydropyridine compound nifedipine induced similar effects. The rate of SR Ca(2+) efflux was also shown to be controlled in a time- and voltage-dependent manner within a membrane potential range more negative than -50 mV. Finally, intracellular addition of ryanodine produced an irreversible SR Ca(2+) efflux and kept the SR in a highly depleted state following depolarization-evoked SR Ca(2+) depletion. The fact that resting SR Ca(2+) efflux is modulated by conformational changes of DHPRs induced by external Ca(2+), nifedipine and voltage demonstrates that DHPRs exert an active control on gating of RyRs in resting skeletal muscle.

Effects of Calcium Antagonists on the Erythrocyte Membrane

The effects of dihydropyridine compounds nimodipine, nicardipine and NB818 (isopropyl methyl-6-carbamoyloxymethyl-4-(2,3-dichlorophenyl)-1,4-dihydro-2-methyl- 3,5- pyridine-dicarboxylate) on erythrocyte membranes have been studied. These compounds showed protective effects against hypotonic haemolysis, but not against heat-induced haemolysis. An increase in deformability of erythrocytes by these calcium antagonists was observed using a capillary tube centrifugal method. The erythrocytes showed slight stomatocytosis after 30 min of incubation with calcium antagonists, but did not show significant changes in mean corpuscular volume and ATP levels.

Selective dihydropyiridine compounds facilitate the clearance of β-amyloid across the blood–brain barrier

Increasing evidence suggests that the soluble form of the β-amyloid peptide (Aβ) plays a critical role in the pathogenesis of Alzheimer's disease. Previously, we reported that treatment with certain antihypertensive dihydropyridine (DHP) compounds can mitigate Aβ production in whole cells and reduce brain Aβ burden in a mouse model of Alzheimer's disease. As Aβ clearance across the blood–brain barrier (BBB) is a key regulatory step in the deposition of Aβ in the brain, we examined the effect of DHP treatment on Aβ brain clearance. Treatment with certain DHP compounds significantly increased Aβ(1–42) transcytosis across the BBB in an in vitro model. The rank order of these compounds was nitrendipine > nicardipine = cilnidipine = lercanidipine > nimodipine > azelnidipine = nilvadipine. Conversely, amlodipine, felodipine, isradipine, and nifedipine had no effect on Aβ(1–42) BBB transcytosis. In an in vivo paradigm of Aβ clearance across the BBB, peripheral administration of nitrendipine, cilnidipine, and nilvadipine to wild-type animals facilitated the brain clearance of centrally administered exogenous Aβ(1–42), whereas with amlodipine, there was no effect. We also observed improved cognitive function in mice treated with nilvadipine following central Aβ(1–42) insult. Thus, in addition to the effect of certain DHP compounds on Aβ production, we demonstrate that certain DHP compounds also facilitate the clearance of Aβ across the BBB. This dual mechanism of action may be particularly effective in attenuating Aβ brain burden in Alzheimer's disease and could open the door to a new class of therapies for the treatment of this disease.

Synthesis and structural study of bis-perfluoropyridyl bridged by 1,4 and 1,2 dihydropyridine

Bis-perfluoropyridyl bridged by 1,4 and 1,2 dihydropyridine compounds was synthesized by reaction of 2 and 4 aminopridine derivatives with pentafluoropyridine. The structures were determined by X-ray crystallography. Compound 3a comprises two crystallographically independent molecules in the asymmetric unit in which one of them shows 1-D infinite chains along [0 1 0] direction due to the intermolecular C–H⋯N hydrogen bonds. In compound 5 intermolecular C–H⋯F and C–H⋯N hydrogen bonds link neighbouring molecules to each other. In addition, in both structures a series of C–F⋯π interactions stabilize the crystal packing.

Novel Lipofuscin Bisretinoids Prominent in Human Retina and in a Model of Recessive Stargardt Disease

Bisretinoid adducts accumulate as lipofuscin in retinal pigment epithelial (RPE) cells of the eye and are implicated in the pathology of inherited and age-related macular degeneration. Characterization of the bisretinoids A2E and the all-trans-retinal dimer series has shown that these pigments form from reactions in photoreceptor cell outer segments that involve all-trans-retinal, the product of photoisomerization of the visual chromophore 11-cis-retinal. Here we have identified two related but previously unknown RPE lipofuscin compounds. By high performance liquid chromatography-electrospray ionization-tandem mass spectrometry, we determined that the first of these compounds is a phosphatidyl-dihydropyridine bisretinoid; to indicate this structure and its formation from two vitamin A-aldehyde (A2), we will refer to it as A2-dihydropyridine-phosphatidylethanolamine (A2-DHP-PE). The second pigment, A2-dihydropyridine-ethanolamine, forms from phosphate hydrolysis of A2-DHP-PE. The structure of A2-DHP-PE was corroborated by Fourier transform infrared spectroscopy, and density functional theory confirmed the presence of a dihydropyridine ring. This lipofuscin pigment is a fluorescent compound with absorbance maxima at approximately 490 and 330 nm, and it was identified in human, mouse, and bovine eyes. We found that A2-DHP-PE forms in reaction mixtures of all-trans-retinal and phosphatidylethanolamine, and in mouse eyecups we observed an age-related accumulation. As compared with wild-type mice, A2-DHP-PE is more abundant in mice with a null mutation in Abca4 (ATP-binding cassette transporter 4), the gene causative for recessive Stargardt macular degeneration. Efforts to clarify the composition of RPE lipofuscin are important because these compounds are targets of gene-based and drug therapies that aim to alleviate ABCA4-related retinal disease.

Synthesis, Evaluation of Pharmacological Activities and Quantitative Structure–Activity Relationship Studies of a Novel Group of bis(4‐Nitroaryl‐1,4‐dihyropyridine)

Voltage-dependent calcium channels are crucial targets for a wide range of clinically active pharmacological agents. From these agents, 1,4-dihydropyridines constitute a group of small organic compounds are based on a core pyridine structure which can both block and enhance calcium currents. They are considered specific for L-Type calcium channels; however, other channel types, and in particular certain T-Type channels, may show sensitivity to dihydropyridine compounds. In this study, we synthesized a novel group of bis-1,4-dihydropyridines using the procedure reported by Dagnino that involved the condensation of n-alkyl diacetoacetate (n = 2-7) with methyl-3-aminocrotonate and nitrophenylaldehyde. The synthesis was run under two conditions: (i) reflux and (ii) microwave. Calcium channels antagonist activity were determined in vitro using guinea-pig ileum longitudinal smooth muscle assay. Synthesis of these compounds was confirmed with 1H-NMR, IR and mass spectrometry. Then IC(50) of them are calculated and compared with Nifedipine. Finally, the result of this pharmacological assay was used in quantitative structure-activity relationship studies utilizing multiple linear regression analysis. Most of these compounds are less active compared with Nifedipine. Decrease in activity is the result of increase in steric hindrance. The quantitative structure-activity relationship study indicates that the activity is related to the electrostatic and topological parameters and the distance between two C5-esteric groups of 1,4-dihydropyridine rings.

Photodegradation Products of New Dihydropyridine Derivatives

Photodegradation of two dihydropyridine compounds has been studied in accordance with the recommendations of the first version of the ICH guidelines. Photodecomposition was monitored by UV–visible spectroscopy, LC, and LC–MS. Quantum yields and kinetic data were obtained for the photochemical reactions. The new dihydropyridine derivatives were found to decompose into different numbers of photoproducts with different rate constants. The derivative with two chlorine atoms in the phenyl ring proved to be more stable than the nitro derivative.

Rethinking the role of L-type voltage-gated calcium channels in fear memory extinction

Rethinking the role of L-type voltage-gated calcium channels in fear memory extinction