Synthesis and evaluation of (E)-2-(5-phenylpent-2-en-4-ynamido)cyclohex-1-ene-1-carboxylate derivatives as HCA2 receptor agonists.

Novel series of compounds consisting of 2-amidocyclohex-1-ene carboxylate and phenyl parts which are connected by enyne (compounds 2a-f), but-1-yne (compounds 4a-j), and phenylethylene (compounds 5a-f) linkers as HCA2 full agonists were designed and their functional activity using cAMP assay and binding affinity using radioligand (3H-niacin) binding assay were evaluated. In general, compounds of all three series exhibit similar HCA2 binding and activation profile. However, the activity is strongly dependent on the substituent at the aromatic part of the structure. Among the structures evaluated, the highest affinity and potency in all series were exhibited by compounds containing 4-hydroxy and/or 2-chloro or 2-fluoro substituents. The most active compounds in the enyne and but-1-yne series in the cAMP assay are 2-fluoro,4-hydroxy and 2-chloro,4-hydroxy phenyl derivatives 2f, 4f, and 4g showing potency similar to the previously described 4-hydroxy-biphenyl analogue 5c.

1,4-Dihydropyridine derivatives without Ca2+-antagonist activity up-regulate Psma6 mRNA expression in kidneys of intact and diabetic rats.

Impaired degradation of proteins by the ubiquitin-proteasome system (UPS) is observed in numerous pathologies including diabetes mellitus (DM) and its complications. Dysregulation of proteasomal degradation might be because of altered expression of genes and proteins involved in the UPS. The search for novel compounds able to normalize expression of the UPS appears to be a topical problem. A novel group of 1,4-dihydropyridine (1,4-DHP) derivatives lacking Ca2+-antagonists activities, but capable to produce antidiabetic, antioxidant and DNA repair enhancing effects, were tested for ability to modify Psma6 mRNA expression levels in rat kidneys and blood in healthy animals and in rats with streptozotocin (STZ) induced DM. Psma6 gene was chosen for the study, as polymorphisms of its human analogue are associated with DM and cardiovascular diseases. 1,4-DHP derivatives (metcarbatone, etcarbatone, glutapyrone, J-9-125 and AV-153-Na) were administered per os for three days (0.05 mg/kg and/or 0.5 mg/kg). Psma6 gene expression levels were evaluated by quantitative PCR. Psma6 expression was higher in kidneys compared to blood. Induction of diabetes caused increase of Psma6 expression in kidneys, although it was not changed in blood. Several 1,4-DHP derivatives increased expression of the gene both in kidneys and blood of control and model animals, but greater impact was observed in kidneys. The observed effect might reflect coupling of antioxidant and proteolysis-promoting activities of the compounds.

Direct Aminolysis of Ethoxycarbonylmethyl 1,4-Dihydropyridine-3-carboxylates.

The ethoxycarbonylmethyl esters of 1,4-dihydropyridines were directly converted into carbamoylmethyl esters in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in good to excellent yields under mild conditions. The use of TBD is crucial for the successful aminolysis of ethoxycarbonylmethyl ester of 1,4-dihydropyridines with secondary amines as without it the reaction does not proceed at all. The aminolysis reaction proceeded regioselectively, as the alkyl ester conjugated with the 1,4-dihydropyridine cycle was not involved in the reaction. Screening of other N-containing bases, such as triethylamine (TEA), pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), imidazole, tetramethyl guanidine (TMG) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) as catalysts revealed no activity in the studied reaction.

Thieno[2,3-b]pyridines--a new class of multidrug resistance (MDR) modulators.

To identify new potent multidrug resistance modulators, we have synthesized a series of novel thieno[2,3-b]pyridines and furo[2,3-b]pyridines, and examined their structure-activity relationships. All synthesized compounds were tested to determine BCRP1, P-gp, and MRP1 inhibitor activity, and most potent MDR modulators were also screened for their toxicity, cytotoxicity and Ca(2+) channel antagonist activity. Among these compounds, thieno[2,3-b]pyridine (6r) was found to exhibit a potent P-gp inhibitory action with EC50 = 0.3 ± 0.2 µM, MRP1 inhibitory action with EC50 = 1.1 ± 0.1 µM and BCRP1 inhibitory action with EC50 = 0.2 ± 0.05 µM and may represent suitable candidate for further pharmacological studies.

Synthesis and evaluation of (E)-2-(acrylamido)cyclohex-1-enecarboxylic acid derivatives as HCA1, HCA2, and HCA3 receptor agonists.

2-(3-(Naphthalen-2-yl)propanamido)cyclohex-1-enecarboxylic acid and its 6-hydroxynaphthalen-2-yl analogue are well-known hydroxyl-carboxylic acid (HCA) receptor HCA2 agonists. A series of novel aryl derivatives of 2-amidocyclohex-1-ene carboxylic acid that contained rigidity elements, such as an E-double bond, triple bond, and trans or cis-substituted cyclopropane rings, instead of the saturated ethane linker in the amide part of the molecules were designed and synthesized, and the derivatives' potency for the activation of HCA1, HCA2, and HCA3 receptors by 3'-5'-cyclic adenosine monophosphate (cAMP) assay were evaluated. The SAR studies revealed that the rigidifying of appropriate molecules enabled modulation of the potency and selectivity of the HCA2 receptor activation.

Genotoxic and genoprotective effects of 1,4-dihydropyridine derivatives: a brief review.

This review summarises current knowledge about the genotoxic and genoprotective effects of 1,4-dihydropyridines (DHP) with the main focus on the water-soluble 1,4-DHPs. Most of these water-soluble compounds manifest very low calcium channel blocking activity, which is considered "unusual" for 1,4-DHPs. Glutapyrone, diludine, and AV-153 decrease spontaneous mutagenesis and frequency of mutations induced by chemical mutagens. AV-153, glutapyrone, and carbatones protect DNA against the damage produced by hydrogen peroxide, radiation, and peroxynitrite. The ability of these molecules to bind to the DNA may not be the only mechanism of DNA protection, as other mechanisms such as radical scavenging or binding to other genotoxic compounds may take place and enhance DNA repair. These uncertainties and reports of high 1,4-DHP concentrations damaging the DNA call for further in vitro and in vivo preclinical research, pharmacokinetic in particular, as it can help pinpoint the exact mechanism(s) of the genotoxic and/or genoprotective action of 1,4-DHPs.

Styrylpyridinium Derivatives for Fluorescent Cell Imaging.

A set of styrylpyridinium (SP) compounds was synthesised in order to study their spectroscopic and cell labelling properties. The compounds comprised different electron donating parts (julolidine, p-dimethylaminophenyl, p-methoxyphenyl, 3,4,5-trimethoxyphenyl), conjugated linkers (vinyl, divinyl), and an electron-withdrawing N-alkylpyridinium part. Geminal or bis-compounds incorporating two styrylpyridinium (bis-SP) moieties at the 1,3-trimethylene unit were synthesised. Compounds comprising a divinyl linker and powerful electron-donating julolidine donor parts possessed intensive fluorescence in the near-infrared region (maximum at ~760 nm). The compounds had rather high cytotoxicity towards the cancerous cell lines HT-1080 and MH-22A; at the same time, basal cytotoxicity towards the NIH3T3 fibroblast cell line ranged from toxic to harmful. SP compound 6e had IC50 values of 1.0 ± 0.03 µg/mL to the cell line HT-1080 and 0.4 µg/mL to MH-22A; however, the basal toxicity LD50 was 477 mg/kg (harmful). The compounds showed large Stokes' shifts, including 195 nm for 6a,b, 240 nm for 6e, and 325 and 352 nm for 6d and 6c, respectively. The highest photoluminescence quantum yield (PLQY) values were observed for 6a,b, which were 15.1 and 12.2%, respectively. The PLQY values for the SP derivatives 6d,e (those with a julolidinyl moiety) were 0.5 and 0.7%, respectively. Cell staining with compound 6e revealed a strong fluorescent signal localised in the cell cytoplasm, whereas the cell nuclei were not stained. SP compound 6e possessed self-assembling properties and formed liposomes with an average diameter of 118 nm. The obtained novel data on near-infrared fluorescent probes could be useful for the development of biocompatible dyes for biomedical applications.

Methyl 6-oxo-4-phenyl-2-[(Z)-2-(pyridin-2-yl)ethen-yl]-1,4,5,6-tetra-hydro-pyridine-3-carboxyl-ate.

In the title mol-ecule, C20H18N2O3, an intra-molecular N-H⋯O hydrogen bond leads to a cis conformation of the pyridinyl-vinyl fragment. The phenyl and pyridine rings are inclined to one another by 77.3 (1) °. In the crystal, mol-ecules are linked via pairs of C-H⋯O hydrogen bonds, forming inversion dimers. The dimers are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming a three-dimensional structure.

Search for stroke-protecting agents in endothelin-1-induced ischemic stroke model in rats.

BACKGROUND AND OBJECTIVE: Ischemic stroke may initiate a reperfusion injury leading to brain damage cascades where inflammatory mechanisms play a major role. Therefore, the necessity for the novel stroke-protecting agents whose the mechanism of action is focused on their anti-inflammatory potency is still on the agenda for drug designers. Our previous studies demonstrated that cerebrocrast (a 1,4-dihydropyridine derivative) and mildronate (a representative of the aza-butyrobetaine class) possessed considerable anti-inflammatory and neuroprotective properties in different in vitro and in vivo model systems. The present study investigated their stroke-protecting ability in an endothelin-1 (ET-1)-induced ischemic stroke model in rats. MATERIAL AND METHODS: Male Wistar rats were pretreated (for 7 days, per os) with cerebrocrast (0.1 mg/kg), mildronate (100 mg/kg), or their combination, followed by the intracerebral injection of ET-1. Functional and behavioral tests were carried out up to 14 days after the ET-1 injection. Ex vivo, the number of degenerated neurons and the infarction size in the cerebral cortical tissue were assessed histologically. RESULTS: Cerebrocrast and mildronate effectively normalized ET-1-induced disturbances in neurological status, improved the muscle tone, and decreased the number of degenerated cortical cells. Both drugs also reduced the infarction size, and cerebrocrast showed at least a 2-fold higher activity than mildronate. The combination of both drugs did not cause a more pronounced effect in comparison with the action of drugs administered separately. CONCLUSIONS: The 1,4-dihydropyridine and aza-butyrobetaine structures may serve for the design of novel stroke-protecting agents to prevent severe neurological poststroke consequences.

Design and Synthesis of Hepatitis B Virus (HBV) Capsid Assembly Modulators and Evaluation of Their Activity in Mammalian Cell Model.

Capsid assembly modulators (CAMs) have emerged as a promising class of antiviral agents. We studied the effects of twenty-one newly designed and synthesized CAMs including heteroaryldihydropyrimidine compounds (HAPs), their analogs and standard compounds on hepatitis B virus (HBV) capsid assembly. Cytoplasmic expression of the HBV core (HBc) gene driven by the exogenously delivered recombinant alphavirus RNA replicon was used for high level production of the full-length HBc protein in mammalian cells. HBV capsid assembly was assessed by native agarose gel immunoblot analysis, electron microscopy and inhibition of virion secretion in HepG2.2.15 HBV producing cell line. Induced fit docking simulation was applied for modelling the structural relationships of the synthesized compounds and HBc. The most efficient were the HAP class compounds-dihydropyrimidine 5-carboxylic acid n-alkoxyalkyl esters, which induced the formation of incorrectly assembled capsid products and their accumulation within the cells. HBc product accumulation in the cells was not detected with the reference HAP compound Bay 41-4109, suggesting different modes of action. A significant antiviral effect and substantially reduced toxicity were revealed for two of the synthesized compounds. Two new HAP compounds revealed a significant antiviral effect and a favorable toxicity profile that allows these compounds to be considered promising leads and drug candidates for the treatment of HBV infection. The established alphavirus based HBc expression approach allows for the specific selection of capsid assembly modulators directly in the natural cell environment.

Intramolecular C-H···O hydrogen bonding in 1,4-dihydropyridine derivatives.

The diastereotopy of the methylene protons at positions 2 and 6 in 1,4-dihydropiridine derivatives with various substituents has been investigated. NMR spectroscopy and quantum chemistry calculations show that the CH···O intramolecular hydrogen bond is one of the factors amplifying the chemical shift differences in the 1H-NMR spectra.

Growth modulation of human cells in vitro by mild oxidative stress and 1,4-dihydropyridine derivative antioxidants.

Reactive oxygen species and lipid peroxidation products are not only cytotoxic but may also modulate signal transduction in cells. Accordingly, antioxidants may be considered as modifiers of cellular redox signaling. Therefore, the effects of two novel synthetic antioxidants, analogues of 1,4-dihydropyridine derivatives, cerebrocrast and Z41-74 were analysed in vitro on human osteosarcoma cell line HOS, the growth of which can be modulated by lipid peroxidation. The cells were pretreated with either cerebrocrast or Z41-74 and afterwards exposed to mild, copper induced lipid peroxidation or to 4-hydroxynonenal (HNE), the end product of lipid peroxidation. The results obtained have shown that both antioxidants exert growth modulating effects interfering with the lipid peroxidation. Namely, cells treated with antioxidants showed increased metabolic rate and cell growth, thereby attenuating the effects of lipid peroxidation. Such biomodulating effects of cerebrocrast and Z41-74 resembled growth modulating effects of HNE, suggesting that the antioxidants could eventually promote cellular adaptation to oxidative stress interacting with redox signaling and hydroxynonenal HNE-signal transduction pathways. This may be of particular relevance for better understanding the beneficial role of hydroxynonenal HNE in cell growth control. Therefore, cerebrocrast and Z41-74 could be convenient to study further oxidative homeostasis involving lipid peroxidation.

1,4-dihydropyridine derivatives increase mRNA expression of Psma3, Psmb5, and Psmc6 in rats.

The ubiquitin-proteasome system modifies different cellular and protein functions. Its dysregulation may lead to disrupted proteostasis associated with multiple pathologies and aging. Pharmacological regulation of proteasome functions is already an important part of the treatment of several diseases. 1,4-dihydropyridine (1,4-DHP) derivatives possess different pharmacological activities, including antiaging and neuroprotective. The aim of this study was to investigate the effects of several 1,4-DHP derivatives on mRNA expression levels of proteasomal genes Psma3, Psmb5, and Psmc6 in several organs of rats. Rats were treated with metcarbatone, etcarbatone, glutapyrone, styrylcarbatone, AV-153-Na, or AV-153-Ca per os for three days. mRNA expression levels were determined with real-time polymerase chain reaction (PCR). For AV-153-Na and AV-153-Ca, we also determined the expression of the Psma6 gene. In the kidney, metcarbatone, etcarbatone, styrylcarbatone, and AV-153-Na increased the expression of all analysed genes. Glutapyrone increased the expression of Psmb5 and Psmc6 but did not affect the expression of Psma3. In the blood, glutapyrone increased Psmb5 expression. In the liver, AV-153-Na increased the expression of Psma6 and Psmc6 but lowered the expression of Psmb5, while AV-153-Ca only increased Psma6 expression. The ability of 1,4-DHP derivatives to increase the expression of proteasome subunit genes might hold a therapeutic potential in conditions associated with impaired proteasomal functions, but further research is needed.

Antifungal activity of styrylpyridinium compounds against Candida albicans.

We synthesized a set of 13 new and earlier described styrylpyridinium compounds (N-alkyl styrylpyridinium salts with bromide or tosylate anions) in order to evaluate antifungal activity against C. albicans cells, to assay the possible synergism with fluconazole, and to estimate cytotoxicity to mammalian cells. All compounds were synthesized according to a well-known two-step procedure involving alkylation of γ-picoline with appropriate alkyl bromide and further condensation with substituted benzaldehyde. Compounds with long N-alkyl chains (C18 H37 -C20 H41 ) had no antifungal activity against the cells of all tested C. albicans strains. Other styrylpyridinium compounds were able to inhibit yeast growth at the concentrations of 0.06-16 µg/ml. At fungicidal concentrations, the compound with the CN- group was least toxic to mammalian cells, showed the most effective synergism with fluconazole, and only slightly inhibited the respiration of C. albicans. The compound with the 4'-diethylamino group exhibited the strongest fungicidal properties and effectively blocked the respiration of C. albicans cells. However, toxicity to mammalian cells was also high. Summarizing, the results of our study indicate that styrylpyridinium compounds are promising candidates in the development of new antifungal drugs.

The Specificity and Broad Multitarget Properties of Ligands for the Free Fatty Acid Receptors FFA3/GPR41 and FFA2/GPR43 and the Related Hydroxycarboxylic Acid Receptor HCA2/GPR109A.

The paradigm of ligand-receptor interactions postulated as "one compound-one target" has been evolving; a multi-target, pleiotropic approach is now considered to be realistic. Novel series of 1,4,5,6,7,8-hexahydro-5-oxoquinolines, pyranopyrimidines and S-alkyl derivatives of pyranopyrimidines have been synthesized in order to characterise their pleiotropic, multitarget activity on the FFA3/GPR41, FFA2/GPR43, and HCA2/GPR109A receptors. Hexahydroquinoline derivatives have been known to exhibit characteristic activity as FFA3/GPR41 ligands, but during this study we observed their impact on FFA2/GPR43 and HCA2/GPR109A receptors as well as their electron-donating activity. Oxopyranopyrimidine and thioxopyranopyrimidine type compounds have been studied as ligands of the HCA2/GPR109A receptor; nevertheless, they exhibited equal or higher activity towards FFA3/GPR41 and FFA2/GPR43 receptors. S-Alkyl derivatives of pyranopyrimidines that have not yet been studied as ligands of GPCRs were more active towards HCA2/GPR109A and FFA3/GPR41 receptors than towards FFA2/GPR43. Representative compounds from each synthesized series were able to decrease the lipopolysaccharide-induced gene expression and secretion of proinflammatory cytokines (IL-6, TNF-α) and of a chemokine (MCP-1) in THP-1 macrophages, resembling the effect of HCA2/GPR109A ligand niacin and the endogenous ligand propionate. This study revealed groups of compounds possessing multitarget activity towards several receptors. The obtained data could be useful for further development of multitarget ligands.

Screening of SIRT6 inhibitors and activators: A novel activator has an impact on breast cancer cells.

Sirtuin 6 (SIRT6), a member of sirtuin family (SIRT1-7), regulates a variety of cellular processes involved in aging, metabolism, and cancer. Dysregulation of SIRT6 is widely observed in different breast cancer subtypes; however, the role and function of SIRT6 in cancer development remain largely unexplored. The aim of this study was to identify novel compounds targeting SIRT6 which may provide a new approach in development of anti-cancer therapy for breast cancer. Virtual screening was utilized to discover potential compounds targeting SIRT6 for in vitro screening. In addition, novel 1,4-dihydropyridine derivatives were synthetized and further subjected for the screening. The impact of the compounds on the deacetylation activity of SIRT6 was determined with HPLC method. The anti-cancer activities were screened for a panel of breast cancer cells. A set of 1,4-dihydropyridine derivatives was identified as SIRT6 inhibitors. A SIRT6 activating compound, (2,4-dihydroxy-phenyl)-2-oxoethyl 2-(3-methyl-4-oxo-2-phenyl-4H-chromen-8-yl)acetate (later called as 4H-chromen), was discovered and it provided 30-40-fold maximal activation. 4H-chromen was proposed to bind similarly to quercetin and place to previously reported SIRT6 activator sites. 4H-chromen was investigated in various breast cancer cells, and it decreased cell proliferation in all cells as well as arrested cell cycle in triple negative cells. Overall, this study describes a highly potent SIRT6 activator and new inhibitors that represent a novel tool to study the mechanism of SIRT6 function.

Interaction of Styrylpyridinium Compound with Pathogenic Candida albicans Yeasts and Human Embryonic Kidney HEK-293 Cells.

Candida albicans-caused local and systemic diseases are a serious health issue worldwide, leading to high mycosis-associated morbidity and mortality. Efficient combinations of novel compounds with commonly used antifungals could be an important tool for fighting infections. The aim of this study was to evaluate the interaction of synthesized 4-(4-cyanostyryl)-1-dodecylpyridin-1-ium (CSDP+) bromide alone or in combination with fluconazole with yeast and mammalian cells. We investigated cytotoxicity of the tested agents to mammalian HEK-293 cells and the influence of CSDP+ on the ability of C. albicans wt and a clinical isolate to adhere to HEK-293. Accumulation of lipophilic cation ethidium (Et+) was used to monitor the activity of efflux pumps in HEK-293 cells. The effect of CSDP+ on the expression of the main efflux transporter genes and transcription factors in C.albicans cells as well as HEK-293 efflux pump gene ABCB1 was determined. The study showed that CSDP+ alone and in combination with fluconazole was nontoxic to HEK-293 cells and was able to reduce C.albicans adhesion. The treatment of C.albicans cells with CSDP+ in combination with fluconazole resulted in a considerable overexpression of the MDR1 and MRR1 genes. The findings suggest that these genes could be associated with efflux-related resistance to fluconazole. Measurements of Et+ fluorescence and analysis of ABCB1 gene expression demonstrated that mammalian cells were not sensitive to concentrations of CSDP+ affecting C. albicans.

Data for the cytotoxicity, self-assembling properties and synthesis of 4-pyridinium-1,4-dihydropyridines.

In this data file the synthetic procedures for preparation of the original 4-pyridinium-1,4-dihydropyridines (4-Py-1,4-DHP) and their parent compounds - dialkyl 2,6-dimethyl-4-(3-pyridyl)-1,4-dihydropyridine-3,5-dicarboxylates were described. In total, 5 unpublished compounds were obtained and characterised. All the structures of original compounds were confirmed by Nuclear Magnetic Resonance (NMR, including 1H NMR and 13C NMR) and low resolution mass spectra (MS) data. Additionally, the cytotoxic properties of four 4-Py-1,4-DHPs were evaluated on 3 cell lines - normal NIH3T3 (mouse embryonic fibroblast), cancerous HT-1080 (human lung fibrosarcoma) and MH-22A (mouse hepatoma) and self-assembling properties were studied and characterisation of formed nanoparticles were performed using dynamic light scattering technique. In this article provided data are directly related to the previously published research articles - "Novel cationic amphiphilic 1,4-dihydropyridine derivatives for DNA delivery" [1] where compound 5 was tested as gene delivery agent without full physico-chemical characterisation and "Synthesis and studies of calcium channel blocking and antioxidant activities of novel 4-pyridinium and/or N-propargyl substituted 1,4-dihydropyridine derivatives" [2] where synthesis and physico-chemical characterisation as well as calcium channel blocking and antioxidant activities were described for compound 6. Synthesis of other compounds - parent 1,4-DHPs 1 and 2, and 4-Py-1,4-DHPs 3-5, their characterisation, estimation of cytotoxicity and self-assembling properties for all 4-Py-1,4-DHPs 3-6 are reported herein for the first time. Information provided in this data file can be used in medicinal chemistry by other scientists to estimate structure-activity relationships for the analysis and construction of various cationic 1,4-dihydropyridine derivatives and related heterocycles.

Spectroscopic and electrochemical study of interactions between DNA and different salts of 1,4-dihydropyridine AV-153.

1,4-dihydropyridines (1,4-DHP) possess important biochemical and pharmacological properties, including antimutagenic and DNA-binding activity. The latter activity was first described for water-soluble 1,4-DHP with carboxylic group in position 4, the sodium salt of the 1,4-DHP derivative AV-153 among others. Some data show the modification of physicochemical properties and biological activities of organic compounds by metal ions that form the salts. We demonstrated the different affinity to DNA and DNA-protecting capacity of AV-153 salts, depending on the salt-forming ion (Na, K, Li, Rb, Ca, Mg). This study aimed to use different approaches to collate data on the DNA-binding mode of AV-153-Na and five other AV-153 salts. All the AV-153 salts in this study quenched the ethidium bromide and DNA complex fluorescence, which points to an intercalation binding mode. For some of them, the intercalation binding was confirmed using cyclic voltammetry and circular dichroism spectroscopy. It was shown that in vitro all AV-153 salts can interact with four DNA bases. The FTIR spectroscopy data showed the interaction of AV-153 salts with both DNA bases and phosphate groups. A preference for base interaction was observed as the AV-153 salts interacted mostly with G and C bases. However, the highest differences were detected in the spectral region assigned to phosphate groups, which might indicate either conformational changes of DNA molecule (B form to A or H form) or partial denaturation of the molecule. According to the UV/VIS spectroscopy data, the salts also interact with the human telomere repeat, both in guanine quadruplex (G4) and single-stranded form; Na and K salts manifested higher affinity to G4, Li and Rb -to single-stranded DNA.

4-Pyridinio-1,4-Dihydropyridines as Calcium Ion Transport Modulators: Antagonist, Agonist, and Dual Action.

A set of six new 4-pyridinio-1,4-dihydropyridine (1,4-DHP) compounds has been synthesized. The calcium channel modulating activity of these compounds was evaluated in an aorta vascular smooth muscle cell line (A7R5), in an isolated rat aortic ring model, and in human neuroblastoma cell lines (SH-SY5Y). The antagonistic effect of these 1,4-DHP was tested by modulating the impact of carbachol-dependent mobilization of intracellular Ca2+ in SH-SY5Y cells. The intracellular free Ca2+ concentration was measured in confluent monolayers of SH-SY5Y cells and A7R5 cells with the Ca2+-sensitive fluorescent indicator Fluo-4 NW. Only four compounds showed calcium channel blocking activity in SH-SY5Y and A7R5 cells as well as in the aortic ring model. Among them, compound 3 was the most active calcium channel antagonist, which had 3 times higher activity on carbachol-activated SH-SY5Y cells than amlodipine. Two of the compounds were inactive. Compound 4 had 9 times higher calcium agonist activity than the classic DHP calcium agonist Bay K8644. The intracellular mechanism for the action of compound 4 using inhibitor analysis was elucidated. Nicotinic as well as muscarinic receptors were not involved. Sarcoplasmic reticulum (ER) Ca2+ (SERCA) stores were not affected. Ryanodine receptors (RyRs), another class of intracellular Ca2+ releasing channels, participated in the agonist response evoked by compound 4. The electrooxidation data suggest that the studied compounds could serve as antioxidants in OS.