Novel 4-(4-aryl)cyclohexyl-1-(2-pyridyl)piperazines as Delta(8)-Delta(7) sterol isomerase (emopamil binding protein) selective ligands with antiproliferative activity

Application of Graph Models to the Identification of Transcriptomic Oncometabolic Pathways in Human Hepatocellular Carcinoma

Whole-tissue transcriptomic analyses have been helpful to characterize molecular subtypes of hepatocellular carcinoma (HCC). Metabolic subtypes of human HCC have been defined, yet whether these different metabolic classes are clinically relevant or derive in actionable cancer vulnerabilities is still an unanswered question. Publicly available gene sets or gene signatures have been used to infer functional changes through gene set enrichment methods. However, metabolism-related gene signatures are poorly co-expressed when applied to a biological context. Here, we apply a simple method to infer highly consistent signatures using graph-based statistics. Using the Cancer Genome Atlas Liver Hepatocellular cohort (LIHC), we describe the main metabolic clusters and their relationship with commonly used molecular classes, and with the presence of TP53 or CTNNB1 driver mutations. We find similar results in our validation cohort, the LIRI-JP cohort. We describe how previously described metabolic subtypes could not have therapeutic relevance due to their overall downregulation when compared to non-tumoral liver, and identify N-glycan, mevalonate and sphingolipid biosynthetic pathways as the hallmark of the oncogenic shift of the use of acetyl-coenzyme A in HCC metabolism. Finally, using DepMap data, we demonstrate metabolic vulnerabilities in HCC cell lines.

Chemical Inhibition of Sterol Biosynthesis

Cholesterol is an essential molecule of life, and its synthesis can be inhibited by both genetic and nongenetic mechanisms. Hundreds of chemicals that we are exposed to in our daily lives can alter sterol biosynthesis. These also encompass various classes of FDA-approved medications, including (but not limited to) commonly used antipsychotic, antidepressant, antifungal, and cardiovascular medications. These medications can interfere with various enzymes of the post-lanosterol biosynthetic pathway, giving rise to complex biochemical changes throughout the body. The consequences of these short- and long-term homeostatic disruptions are mostly unknown. We performed a comprehensive review of the literature and built a catalogue of chemical agents capable of inhibiting post-lanosterol biosynthesis. This process identified significant gaps in existing knowledge, which fall into two main areas: mechanisms by which sterol biosynthesis is altered and consequences that arise from the inhibitions of the different steps in the sterol biosynthesis pathway. The outcome of our review also reinforced that sterol inhibition is an often-overlooked mechanism that can result in adverse consequences and that there is a need to develop new safety guidelines for the use of (novel and already approved) medications with sterol biosynthesis inhibiting side effects, especially during pregnancy.

Synthesis, biological evaluation, and molecular docking of novel hydroxyzine derivatives as potential AR antagonists

Prostate cancer (PCa) is a malignant tumor with a higher mortality rate in the male reproductive system. In this study, the hydroxyazine derivatives were synthesized with different structure from traditional anti-prostate cancer drugs. In the evaluation of in vitro cytotoxicity and antagonistic activity of PC-3, LNCaP, DU145 and androgen receptor, it was found that the mono-substituted derivatives on the phenyl group (4, 6, 7, and 9) displayed strong cytotoxic activities, and compounds 11–16 showed relatively strong antagonistic potency against AR (Inhibition% >55). Docking analysis showed that compounds 11 and 12 mainly bind to AR receptor through hydrogen bonds and hydrophobic bonds, and the structure-activity relationship was discussed based on activity data. These results suggested that these compounds may have instructive implications for drug structural modification in prostate cancer.

Synthesis, bioactivity, and molecular docking of novel arylpiperazine derivatives as potential AR antagonists

Prostate cancer is one of the malignant tumors and the second most common malignant tumor in men. Clinically used androgen receptor (AR)–targeted drugs can antagonize androgen and inhibit tumor growth, but these drugs can cause serious resistance problems. To develop novel AR antagonists, 22 kinds of arylpiperazine derivatives were designed and synthesized, and the derivatives 5, 8, 12, 19, 21, 22, 25, and 26 not only showed strong antagonistic potency (>55% inhibition) and binding affinities (IC50 <3 μM) to AR, but also showed stronger inhibitory activity to LNCaP cells versus PC-3 cells. Among them, derivative 21 exhibited the highest binding affinity for AR (IC50 = 0.65 μM) and the highest antagonistic potency (76.2% inhibition). Docking studies suggested that the derivative 21 is primarily bound to the AR-LBP site by the hydrophobic interactions. Overall, those results provided experimental methods for developing novel arylpiperazine derivatives as potent AR antagonists.

A TMEDA-Iron Adduct Reaction Manifold in Iron-Catalyzed C(sp2 )-C(sp3 ) Cross-Coupling Reactions

Herein, we expand the current molecular-level understanding of one of the most important and effective additives in iron-catalyzed cross-coupling reactions, N,N,N',N'-tetramethylethylenediamine (TMEDA). Focusing on relevant phenyl and ethyl Grignard reagents and slow nucleophile addition protocols commonly used in effective catalytic systems, TMEDA-iron(II)-aryl intermediates are identified via in situ spectroscopy, X-ray crystallography, and detailed reaction studies to be a part of an iron(II)/(III)/(I) reaction cycle where radical recombination with FePhBr(TMEDA) (2Ph ) results in selective product formation in high yield. These results differ from prior studies with mesityl Grignard reagent, where poor product selectivity and low catalytic performance can be attributed to homoleptic iron-ate species. Overall, this study represents a critical advance in how amine additives such as TMEDA can modulate selectivity and reactivity of organoiron species in cross-coupling.

Development of novel phenoxyalkylpiperidines as high-affinity Sigma-1 (σ1) receptor ligands with potent anti-amnesic effect

The sigma-1 (σ1) receptor plays a significant role in many normal physiological functions and pathological disease states, and as such represents an attractive therapeutic target for both agonists and antagonists. Here, we describe a novel series of phenoxyalkylpiperidines based on the lead compound 1-[ω-(4-chlorophenoxy)ethyl]-4-methylpiperidine (1a) in which the degree of methylation at the carbon atoms alpha to the piperidine nitrogen was systematically varied. The affinity at σ1 and σ2 receptors and at Δ8-Δ7 sterol isomerase (SI) ranged from subnanomolar to micromolar Ki values. While the highest-affinity was displayed at the σ1, the increase of the degree of methylation in the piperidine ring progressively decreased the affinity. The subnanomolar affinity 1a and 1-[ω-(4-methoxyphenoxy)ethyl]-4-methylpiperidine (1b) displayed potent anti-amnesic effects associated with σ1 receptor agonism, in two memory tests. Automated receptor-small-molecule ligand docking provided a molecular structure-based rationale for the agonistic effects of 1a and 1b. Overall, the class of the phenoxyalkylpiperidines holds potential for the development of high affinity σ1 receptor agonists, and compound 1a, that appears as the best in class (exceeding by far the activity of the reference compound PRE-084) deserves further investigation.

The Deuterated "Magic Methyl" Group: A Guide to Site-Selective Trideuteromethyl Incorporation and Labeling by Using CD3 Reagents

In the field of medicinal chemistry, the precise installation of a trideuteromethyl group is gaining ever-increasing attention. Site-selective incorporation of the deuterated "magic methyl" group can provide profound pharmacological benefits and can be considered an important tool for drug optimization and development. This review provides a structured overview, according to trideuteromethylation reagent, of currently established methods for site-selective trideuteromethylation of carbon atoms. In addition to CD3 , the selective introduction of CD2 H and CDH2 groups is also considered. For all methods, the corresponding mechanism and scope are discussed whenever reported. As such, this review can be a starting point for synthetic chemists to further advance trideuteromethylation methodologies. At the same time, this review aims to be a guide for medicinal chemists, offering them the available C-CD3 formation strategies for the preparation of new or modified drugs.

Enzymes in the Cholesterol Synthesis Pathway: Interactomics in the Cancer Context

A global protein interactome ensures the maintenance of regulatory, signaling and structural processes in cells, but at the same time, aberrations in the repertoire of protein-protein interactions usually cause a disease onset. Many metabolic enzymes catalyze multistage transformation of cholesterol precursors in the cholesterol biosynthesis pathway. Cancer-associated deregulation of these enzymes through various molecular mechanisms results in pathological cholesterol accumulation (its precursors) which can be disease risk factors. This work is aimed at systematization and bioinformatic analysis of the available interactomics data on seventeen enzymes in the cholesterol pathway, encoded by HMGCR, MVK, PMVK, MVD, FDPS, FDFT1, SQLE, LSS, DHCR24, CYP51A1, TM7SF2, MSMO1, NSDHL, HSD17B7, EBP, SC5D, DHCR7 genes. The spectrum of 165 unique and 21 common protein partners that physically interact with target enzymes was selected from several interatomic resources. Among them there were 47 modifying proteins from different protein kinases/phosphatases and ubiquitin-protein ligases/deubiquitinases families. A literature search, enrichment and gene co-expression analysis showed that about a quarter of the identified protein partners was associated with cancer hallmarks and over-represented in cancer pathways. Our results allow to update the current fundamental view on protein-protein interactions and regulatory aspects of the cholesterol synthesis enzymes and annotate of their sub-interactomes in term of possible involvement in cancers that will contribute to prioritization of protein targets for future drug development.

Recent Advances in the Development of Sigma Receptor Ligands as Cytotoxic Agents: A Medicinal Chemistry Perspective

Since their discovery as distinct receptor proteins, the specific physiopathological role of sigma receptors (σRs) has been deeply investigated. It has been reported that these proteins, classified into two subtypes indicated as σ₁ and σ₂, might play a pivotal role in cancer growth, cell proliferation, and tumor aggressiveness. As a result, the development of selective σR ligands with potential antitumor properties attracted significant attention as an emerging theme in cancer research. This perspective deals with the recent advances of σR ligands as novel cytotoxic agents, covering articles published between 2010 and 2020. An up-to-date description of the medicinal chemistry of selective σ₁R and σ₂R ligands with antiproliferative and cytotoxic activities has been provided, including major pharmacophore models and comprehensive structure–activity relationships for each main class of σR ligands.

Crystal structure of 1-(3-chlorophenyl)-4-(4-(((2,3-dihydro-1H-inden-5-yl)oxy)methyl)phenethyl)piperazine, C28H31ClN2O

C28H31ClN2O, monoclinic, P1̄ (no. 2), a = 21.9309(11) Å, b = 9.9648(5) Å, c = 11.0049(7) Å, β = 93.403(6)°, V = 2400.7(2) Å3, Z = 4, R gt(F) = 0.0566, wR ref(F 2) = 0.1355, T = 293 K.

Synthesis and pharmacological evaluation of naftopidil-based arylpiperazine derivatives containing the bromophenol moiety

BACKGROUND

Prostate cancer (PCa) is the most common malignancy in men and in the absence of any effective treatments available.

METHODS

For the development of potential anticancer agents, 24 kinds of naftopidil-based arylpiperazine derivatives containing the bromophenol moiety were synthesized and characterized by using spectroscopic methods. Their pharmacological activities were evaluated against human PCa cell lines (PC-3 and LNCaP) and a₁-adrenergic receptors (a₁-ARs; α_1a, α_1b, and α_1d-ARs). The structure-activity relationship of these designed arylpiperazine derivatives was rationally explored and discussed.

RESULTS

Among these derivatives, 3c, 3d, 3h, 3k, 3o, and 3s exhibited the most potent activity against the tested cancer cells, and some derivatives with potent anticancer activities exhibited better a₁-AR subtype selectivity than others did (selectivity ratio > 10).

CONCLUSION

This work provided a potential lead compound for the further development of anticancer agents for PCa therapy.

Crystal structure of 2-(3-(2-(4-phenylpiperazin-1-yl)ethyl)benzyl)isoindoline-1,3-dione, C27H27N3O2

C27H27N3O2, triclinic, P1̄ (no. 2), a = 6.9263(4) Å, b = 10.0832(7) Å, c = 17.3531(10) Å, α = 75.708(5)°, β = 87.142(5)°, γ = 74.935(6)°, V = 1133.92(13) Å3, Z = 2, Rgt(F) = 0.0605, wRref(F2) = 0.1661, T = 290(1) K.

High Catalytic Activity of Pd Nanoparticles Synthesized from Green Alga Chlorella vulgaris in Buchwald-hartwig Synthesis of N-Aryl Piperazines

Background:

The N-aryl piperazines are an important component of many drug products used for the treatment of malaria, depression, anxiety and Parkinson diseases. Buchwald-Hartwig amination is the latest and well-known reaction for Pd catalyzed direct synthesis of N-aryl piperazine from aryl halides. Although several Pd-ligand systems have already been discovered for this conversion, Pd nanoparticles are recently being used for this useful coupling reaction due to their recyclability and durability. Metal nanoparticles show enhanced catalytic activity compared to their bulk counterparts due to increased surface area at the edges and corners. The use of green algal extract in place of chemical ligands makes this process more environment-friendly and cost-effective. In this research, Pd nanoparticles synthesized using green alga C. Vulgaris were utilized as an alternative approach for the coupling reaction during the preparation of N-aryl piperazines.

Methods:

Synthesized Pd nanoparticles from C. Vulgaris were characterized by FTIR, SEM and XRD techniques. The catalytic activity of the synthesized nanoparticles was monitored for the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction. The synthesized N-aryl piperazines were characterized by NMR, FTIR and mass analysis.

Results:

A very good catalytic activity of the synthesized Pd nanoparticles from green alga Chlorella vulgaris extract was observed. The green alga not only reduces the size of the Pd metal to nanoparticles but also acts as a green ligand for reduction of Pd(II) to Pd(0) during nanoparticle synthesis. Using this Pd nanoparticles-green ligand system, several N-aryl piperazines were synthesized in good to excellent yields. Reaction conditions for better conversion were optimized. The comparative advantage of the catalytic system with recently published works on Buchwald-Hartwig C-N coupling reaction is given. Recyclability and durability of the catalyst were explored and the results were found to be promising. A plausible mechanism of Pd nanoparticle catalyzed reaction is also proposed.

Conclusion:

Catalytic activity of the Pd nanoparticle synthesized from Chlorella vulagris in the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction is reported first time to the best of our knowledge and understanding. The green approach of Pd catalyst to facilitate the reaction and its environmental impact is the main characteristic of the process.

A comparative study of the crystal structures of 2-(4-(2-(4-(3-chlorophenyl)pipera -zinyl)ethyl) benzyl)isoindoline-1,3-dione by synchrotron radiation X-ray powder diffraction and single-crystal X-ray diffraction

The crystal structures of the title compound, C27H26ClN3O2, were established by single-crystal X-ray diffraction and synchrotron radiation X-ray powder diffraction. The simulated annealing approach and rigid-body Rietveld refinement were applied to the structure solution from powder data. Direct methods and full-matrix least-squares techniques were used to solve and refine the crystal structure from single-crystal data. The title compound crystallized in space group P $\bar{1}$ with lattice parameters a=17.396(7) Å, b= 10.010(4) Å, c=6.833(3) Å, α=77.345(12) °, β= 93.534(6) °, γ=97.210(9) °, unit-cell volume V= 1151.0(2) Å3, Z=2 from powder data, and in space group P $\bar{1}$with lattice parameters α=82.485(2) °, β= 86.5110(10) °, γ=77.518(2) °, a=6.8159(6) Å, b= 10.0003(9) Å, c=17.4140(15) Å, unit-cell volume V =1148.3(2) Å3, Z=2 from single-crystal data. No detectable impurities were observed.

Synthesis, biological evaluation and molecular docking of 4-Amino-2H-benzo[h]chromen-2-one (ABO) analogs containing the piperazine moiety

Prostate cancer (PCa) is a major cause of cancer-related male death in worldwide. To develop of potential anti-prostate cancer agents, 22 kinds of 4-Amino-2H-benzo[h]chromen-2-one analogs were designed and synthesized as potent androgen receptor (AR) antagonist through rational drug modification leading to the discovery of a series of novel antiproliferative compounds. Analogs (3, 4, 5, 7, 8, 10, 11, 12, 16, 18, 21, 23, and 24) exhibited potent antagonistic potency against AR (inhibition >50%), and exhibited potent AR binding affinities as well as displayed the higher activities than finasteride toward LNCaP cells (AR-rich) versus PC-3 cells (AR-deficient). Moreover, the docking study suggested that the most potent antagonist 23 mainly bind to AR ligand binding pocket (LBP) site through Van der Waals' force interactions. The structure-activity relationship (SAR) of these designed 4-Amino-2H-benzo[h]chromen-2-one analogs was rationally explored and discussed. Collectively, this work provides a potential lead compound for anticancer agent development related to prostate cancer therapy, and took a step forward towards the development of novel and improved AR antagonists.

Synthesis and biological evaluation of estrone 3-O-ether derivatives containing the piperazine moiety

A series of new estrone derivatives were designed and synthesized, and their structures were confirmed by spectroscopic methods. All new estrone derivatives were investigated for their in vitro cytotoxic efficacies against a panel of three human prostate cancer cell lines (PC-3, LNCaP, and DU145). The derivatives 6, 7, 10, 15, 16, 20, 21, 22, 24 and 26 showed important cytotoxic actions against individual carcinoma cell line collections. Moreover, antagonistic activities of compounds (7, 15, 16 and 21) towards a₁-ARs (α_1A, α_1B, and α_1D) were further evaluated using dual-luciferase reporter assays, and the compounds 16 and 21 exhibited better a₁-ARs subtype selectivity. The structure-activity relationship (SAR) suggested that the substitute's type and position on the phenyl group leads to the interesting variations within pharmacological effects of resultant molecular systems.

Crystal structure of 2-(4-(2-(4-(2-fluorophenyl)piperazin-1-yl)ethyl)benzyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide, C26H26FN3O3S – a saccharin dervative

C26H26F1N3O3S1, triclinic, P1̅ (no. 2), a = 7.0252(14) Å, b = 9.3017(19) Å, c = 19.388(4) Å, α = 97.80(3)°, β = 97.77(3)°, γ = 106.84(3)°, V = 1180.9(5) Å3, Z = 2, R gt(F) = 0.0729, wR ref(F 2) = 0.1854, T = 296.15 K.

Crystal structure of 1-(4-((benzo[d][1,3]dioxol-5-yloxy)methyl)phenethyl)-4-(3-chlorophenyl) piperazin-1-ium chloride, C26H28Cl2N2O3

C26H28Cl2N2O3, monoclinic, P21/c (no. 14), a = 13.422(3) Å, b = 7.0011(14) Å, c = 26.249(5) Å, β = 101.06(3)°, V = 2420.8(9) Å3, Z = 4, R gt(F) = 0.0516, wR ref(F 2) = 0.1370, T = 296 K.

Screening Novel Molecular Targets of Metformin in Breast Cancer by Proteomic Approach

Metformin is a commonly prescribed antihyperglycemic drug, and has been investigated in vivo and in vitro for its effect to improve the comorbidity of diabetes and various types of cancers. Several studies investigated the therapeutic mechanisms of metformin on cancer cells, but the exact mechanism of metformin’s effect on the proteomic pathways of cancer cells is yet to be further investigated. The main objective of our research line is to discover safe and alternative therapeutic options for breast cancer, we aimed in this study to design a novel “bottom up proteomics workflow” in which proteins were first broken into peptides to reveal their identity, then the proteomes were precisely evaluated using spectrometry analysis. In our study, metformin suppressed cell proliferation and induced apoptosis in human breast carcinoma cell line MCF-7 with minimal toxicity to normal breast epithelial cells MCF-10. Metformin induced apoptosis by arresting cells in G1 phase as evaluated by flow cytometric analysis. Moreover, The G1 phase arrest for the MCF-7 has been confirmed by increased expression levels of p21 and reduction in cyclin D1 level. Additionally, metformin increased the expression levels of p53, Bax, Bad while it reduced expression levels of Akt, Bcl-2, and Mdm2. The study employed a serviceable strategy that investigates metformin-dependent changes in the proteome using a literature-derived network. The protein extracts of the treated and untreated cell lines were analyzed employing proteomic approaches; the findings conveyed a proposed mechanism of the effectual tactics of metformin on breast cancer cells. Metformin proposed an antibreast cancer effect through the examination of the proteomic pathways upon the MCF-7 and MCF-10A exposure to the drug. Our findings proposed prolific proteomic changes that revealed the therapeutic mechanisms of metformin on breast cancer cells upon their exposure. In conclusion, the reported proteomic pathways lead to increase the understanding of breast cancer prognosis and permit future studies to examine the effect of metformin on the proteomic pathways against other types of cancers. Finally, it suggests the possibility to develop further therapeutic generations of metformin with increased anticancer effect through targeting specific proteomes.

Sonochemistry – an innovative opportunity towards a one-pot three-component synthesis of novel pyridylpiperazine derivatives catalysed by meglumine in water

An unprecedented and expeditious synthetic strategy for rapid access to a diversity-oriented library of novel functionalized pyridyl piperazine derivatives is reported.

Pd-Catalyzed Synthesis of Piperazine Scaffolds Under Aerobic and Solvent-Free Conditions

A facile Pd-catalyzed methodology providing an efficient synthetic route to biologically relevant arylpiperazines under aerobic conditions is reported. Electron donating and sterically hindered aryl chlorides were aminated to afford yields up to 97%, with examples using piperazine as solvent, illustrating an ecofriendly, cost-effective synthesis of these privileged structures.

Optimization of TRPV6 Calcium Channel Inhibitors Using a 3D Ligand-Based Virtual Screening Method

Herein, we report the discovery of the first potent and selective inhibitor of TRPV6, a calcium channel overexpressed in breast and prostate cancer, and its use to test the effect of blocking TRPV6-mediated Ca(2+)-influx on cell growth. The inhibitor was discovered through a computational method, xLOS, a 3D-shape and pharmacophore similarity algorithm, a type of ligand-based virtual screening (LBVS) method described briefly here. Starting with a single weakly active seed molecule, two successive rounds of LBVS followed by optimization by chemical synthesis led to a selective molecule with 0.3 μM inhibition of TRPV6. The ability of xLOS to identify different scaffolds early in LBVS was essential to success. The xLOS method may be generally useful to develop tool compounds for poorly characterized targets.

Synthetically modified bioisosteres of salicyl alcohol and their gastroulcerogenic assessment versus aspirin: biochemical and histological correlates

The present study was conducted to synthesize nitrogen containing derivatives of salicyl alcohol and to investigate in vivo their ulcerogenic potential in comparison with aspirin in rats. The compounds [4-(2-hydroxybenzyl) morpholin-4-iumchloride (I)] and [1,4-bis(2-hydroxybenzyl) piperazine-1,4-diium chloride (II)] were synthesized and their chemical structures were characterized using spectral data. In our previous study (Ali et al., Afr J Pharm Pharmacol 7:585-596, 2013), both compounds showed anti-inflammatory, antinociceptive, and antipyretic properties in standard animal models and a greater binding affinity for cyclooxygenase-2 versus cyclooxygenase-1 in molecular docking and dynamics analysis. For in vivo studies, animals were randomly divided into four groups. The synthetic compounds (both at 100 or 150 mg/kg), aspirin (150 mg/kg), or saline vehicle was administered orally, once daily for 6 days and then tested for ulcerogenic activity. At the end of the procedure, gastric juice and tissues were collected and subjected to biochemical and histological analyses. The results of the study revealed that in the case of the aspirin-treated group, there was a significant increase in gastric juice volume, free acidity, total acidity, and ulcer score and a decrease in gastric pH. Moreover, histological examination of the gastric mucosa of the aspirin-treated group indicated morphological changes while neither of the synthetic compounds showed any significant ulcerogenic or cytotoxic properties. The results of the present study suggest that both compounds are free from ulcerogenic side effects and may represent a better alternative to aspirin.

1-Cyclohexyl-4-(4-arylcyclohexyl)piperazines: Mixed σ and human Δ(8)-Δ(7) sterol isomerase ligands with antiproliferative and P-glycoprotein inhibitory activity

Many new chemotherapeutic agents are under preclinical investigation and, despite efforts to more selectively target cancer cells, limitations such as toxicity and inherent resistance are often encountered. Therefore, alternative strategies are needed to treat cancer and overcome such limitations. We describe novel cyclohexylpiperazine derivatives, designed as mixed affinity ligands for sigma (σ) receptors and human Δ₈-Δ₇ sterol isomerase (HSI) ligands, which also exhibit P-glycoprotein (P-gp) inhibitory activity, with the aim of exploiting the antiproliferative effects mediated by σ and HSI sites while overcoming P-gp-mediated resistance. All of the compounds displayed high affinities for σ receptors and HSI sites, P-gp inhibitory activity, and σ₂ receptor agonist antiproliferative activity. Antiproliferative activity was also tested in PC-3 cells to establish σ₁ and HSI contribution. Compound cis-11, which displayed the best antiproliferative and P-gp inhibitory activities, was co-administered with 0.1 μM doxorubicin in MDCK-MDR1 cells. Compound cis-11 caused 70 % and 90 % cell death when co-administered at 30 μM and 50 μm, respectively. When administered alone, cis-11 resulted in 50 % cell death, demonstrating its single agent antitumor properties in a tumor cell line overexpressing P-gp.

Novel potent and selective σ ligands: evaluation of their agonist and antagonist properties

Novel enantiomers and diastereoisomers structurally related to σ ligand (+)-MR200 were synthesized to improve σ(1)/σ(2) subtype selectivity. The selective σ(1) ligand (-)-8 showed an antagonist profile determined by phenytoin differential modulation of binding affinity in vitro, confirmed in vivo by an increase of κ opioid analgesia. The σ(2) ligand (-)-9 displayed agonist properties in an in vitro isolated organ bath assay and antiproliferative effects on LNCaP and PC3 prostate cancer cell lines.

Molecular imaging of σ receptors: synthesis and evaluation of the potent σ1 selective radioligand [18F]fluspidine

PURPOSE

Neuroimaging of σ(1) receptors in the human brain has been proposed for the investigation of the pathophysiology of neurodegenerative and psychiatric diseases. However, there is a lack of suitable (18)F-labelled PET radioligands for that purpose.

METHODS

The selective σ(1) receptor ligand [(18)F]fluspidine (1'-benzyl-3-(2-[(18)F]fluoroethyl)-3H-spiro[[2]benzofuran-1,4'-piperidine]) was synthesized by nucleophilic (18)F(-) substitution of the tosyl precursor. In vitro receptor binding affinity and selectivity were assessed by radioligand competition in tissue homogenate and autoradiographic approaches. In female CD-1 mice, in vivo properties of [(18)F]fluspidine were evaluated by ex vivo brain section imaging and organ distribution of intravenously administered radiotracer. Target specificity was validated by organ distribution of [(18)F]fluspidine after treatment with 1 mg/kg i.p. of the σ receptor antagonist haloperidol or the emopamil binding protein (EBP) inhibitor tamoxifen. In vitro metabolic stability and in vivo metabolism were investigated by LC-MS(n) and radio-HPLC analysis.

RESULTS

[(18)F]Fluspidine was obtained with a radiochemical yield of 35-45%, a radiochemical purity of ≥ 99.6% and a specific activity of 150-350 GBq/μmol (n = 6) within a total synthesis time of 90-120 min. In vitro, fluspidine bound specifically and with high affinity to σ(1) receptors (K (i) = 0.59 nM). In mice, [(18)F]fluspidine rapidly accumulated in brain with uptake values of 3.9 and 4.7%ID/g and brain to blood ratios of 7 and 13 at 5 and 30 min after intravenous application of the radiotracer, respectively. By ex vivo autoradiography of brain slices, resemblance between binding site occupancy of [(18)F]fluspidine and the expression of σ(1) receptors was shown. The radiotracer uptake in the brain as well as in peripheral σ(1) receptor expressing organs was significantly inhibited by haloperidol but not by tamoxifen. Incubation with rat liver microsomes led to a fast biotransformation of fluspidine. After an incubation period of 30 min only 13% of the parent compound was left. Seven metabolites were identified by HPLC-UV and LC-MS(n) techniques. However, [(18)F]fluspidine showed a higher metabolic stability in vivo. In plasma samples ∼ 94% of parent compound remained at 30 min and ∼ 67% at 60 min post-injection. Only one major radiometabolite was detected. None of the radiometabolites crossed the blood-brain barrier.

CONCLUSION

[(18)F]Fluspidine demonstrated favourable target affinity and specificity as well as metabolic stability both in vitro and in animal experiments. The in vivo properties of [(18)F]fluspidine offer a high potential of this radiotracer for neuroimaging and quantitation of σ(1) receptors in vivo.

Interaction of the sigma(2) receptor ligand PB28 with the human nucleosome: computational and experimental probes of interaction with the H2A/H2B dimer

Sigma-2 (sigma(2)) binding sites are an emerging target for anti-neoplastic agents due to the strong apoptotic effect exhibited by sigma(2) agonists in vitro and the overexpression of these sites in tumor cells. Nonetheless, no sigma(2) receptor protein has been identified. Affinity chromatography using the high-affinity sigma(2) ligand PB28 and human SK-N-SH neuroblastoma cells was previously utilized to identify sigma(2) ligand binding proteins, specifically histones H1, H2A, H2B, and H3.3a. To rationalize this finding, homology modeling and automated docking studies were employed to probe intermolecular interactions between PB28 and human nucleosomal proteins. These studies predicted interaction of PB28 with the H2A/H2B dimer at a series of sites previously found to be implicated in chromatin compaction and nucleosomal assembly. To experimentally verify this prediction, a competitive binding assay was performed on the reconstituted H2A/H2B dimer using [(3)H]PB28 as radioligand, and an IC(50) value of 0.50 nM was determined for PB28 binding. In addition, [(3)H]PB28 was found to accumulate with up to a fivefold excess in nuclear fractions over cytosolic fractions of SK-N-SH and MCF7 cells, indicating that PB28 is capable of entering the nucleus to interact with histone proteins. In conjunction with computational results, these data suggest that PB28 may exert its cytotoxic effect through direct interaction with nuclear material.