Divergent Cytotoxic and Metabolically Stimulative Functions of Sigma-2 Receptors: Structure-Activity Relationships of 6-Acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one (SN79) Derivatives.

Sigma-2 receptors, recently identified as TMEM97, have been implicated in cancer and neurodegenerative disease. Structurally distinct sigma-2 receptor ligands induce cell death in tumor cells, linking sigma-2 receptors to apoptotic pathways. Recently, we reported that sigma-2 receptors can also stimulate glycolytic hallmarks, effects consistent with a prosurvival function and upregulation in cancer cells. Both apoptotic and metabolically stimulative effects were observed with compounds related to the canonical sigma-2 antagonist SN79. Here we investigate a series of 6-substituted SN79 analogs to assess the structural determinants governing these divergent effects. Substitutions on the benzoxazolone ring of the core SN79 structure resulted in high-affinity sigma-2 receptor ligands (K i = 0.56-17.9 nM), with replacement of the heterocyclic oxygen by N-methyl (producing N-methylbenzimidazolones) generally decreasing sigma-1 affinity and a sulfur substitution (producing benzothiazolones) imparting high affinity at both subtypes, lowering subtype selectivity. Substitution at the 6-position with COCH3, NO2, NH2, or F resulted in ligands that were not cytotoxic. Five of these ligands induced an increase in metabolic activity, as measured by increased reduction of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) in human SK-N-SH neuroblastoma cells, further supporting a role for sigma-2 receptors in metabolism. Substitution with 6-isothiocyanate resulted in ligands that were sigma-2 selective and that irreversibly bound to the sigma-2 receptor, but not to the sigma-1 receptor. These ligands induced cell death upon both acute and continuous treatment (EC50 = 7.6-32.8 µM), suggesting that irreversible receptor binding plays a role in cytotoxicity. These ligands will be useful for further study of these divergent roles of sigma-2 receptors.

Design and Investigation of a [18F]-Labeled Benzamide Derivative as a High Affinity Dual Sigma Receptor Subtype Radioligand for Prostate Tumor Imaging.

High overexpression of sigma (σ) receptors (σ1 and σ2 subtypes) in a variety of human solid tumors has prompted the development of σ receptor-targeting radioligands, as imaging agents for tumor detection. A majority of these radioligands to date target the σ2 receptor, a potential marker of tumor proliferative status. The identification of approximately equal proportions of both σ receptor subtypes in prostate tumors suggests that a high affinity, dual σ receptor-targeting radioligand could potentially provide enhanced tumor targeting efficacy in prostate cancer. To accomplish this goal, we designed a series of ligands which bind to both σ receptor subtypes with high affinity. Ligand 3a in this series, displaying optimal dual σ receptor subtype affinity (σ1, 6.3 nM; σ2, 10.2 nM) was radiolabeled with fluorine-18 (18F) to give [18F]3a and evaluated as a σ receptor-targeting radioligand in the mouse PC-3 prostate tumor model. Cellular assays with PC-3 cells demonstrated that a major proportion of [18F]3a was localized to cell surface σ receptors, while ∼10% of [18F]3a was internalized within cells after incubation for 3.5 h. Serial PET imaging in mice bearing PC-3 tumors revealed that uptake of [18F]3a was 1.6 ± 0.8, 4.4 ± 0.3, and 3.6 ± 0.6% ID/g (% injection dose per gram) in σ receptor-positive prostate tumors at 15 min, 1.5 h, and 3.5 h postinjection, respectively (n = 3) resulting in clear tumor visualization. Blocking studies conducted with haloperidol (a nonselective inhibitor for both σ receptor subtypes) confirmed that the uptake of [18F]3a was σ receptor-mediated. Histology analysis confirmed similar expression of σ1 and σ2 in PC-3 tumors which was significantly greater than its expression in normal organs/tissues such as liver, kidney, and muscle. Metabolite studies revealed that >50% of radioactivity in PC-3 tumors at 30 min postinjection represented intact [18F]3a. Prominent σ receptor-specific uptake of [18F]3a in prostate tumors and its subsequent clear visualization with PET imaging indicate potential utility for the diagnosis of prostate carcinoma.

Sigma-2 Receptors Play a Role in Cellular Metabolism: Stimulation of Glycolytic Hallmarks by CM764 in Human SK-N-SH Neuroblastoma.

Sigma-2 receptors are attractive antineoplastic targets due to their ability to induce apoptosis and their upregulation in rapidly proliferating cancer cells compared with healthy tissue. However, this role is inconsistent with overexpression in cancer, which is typically associated with upregulation of prosurvival factors. Here, we report a novel metabolic regulatory function for sigma-2 receptors. CM764 [6-acetyl-3-(4-(4-(2-amino-4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one] binds with Ki values of 86.6 ± 2.8 and 3.5 ± 0.9 nM at the sigma-1 and sigma-2 receptors, respectively. CM764 increased reduction of MTT [3-[4,5 dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide] in human SK-N-SH neuroblastoma compared with untreated cells, an effect not due to proliferation. This effect was attenuated by five different sigma antagonists, including CM572 [3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-6-isothiocyanatobenzo[d]oxazol-2(3H)-one], which has no significant affinity for sigma-1 receptors. This effect was also observed in MG-63 osteosarcoma and HEK293T cells, indicating that this function is not exclusive to neuroblastoma or to cancer cells. CM764 produced an immediate, robust, and transient increase in cytosolic calcium, consistent with sigma-2 receptor activation. Additionally, we observed an increase in the total NAD(+)/NADH level and the ATP level in CM764-treated SK-N-SH cells compared with untreated cells. After only 4 hours of treatment, basal levels of reactive oxygen species were reduced by 90% in cells treated with CM764 over untreated cells, and HIF1α and VEGF levels were increased after 3-24 hours of treatment. These data indicate that sigma-2 receptors may play a role in induction of glycolysis, representing a possible prosurvival function for the sigma-2 receptor that is consistent with its upregulation in cancer cells compared with healthy tissue.

Characterization of CM572, a Selective Irreversible Partial Agonist of the Sigma-2 Receptor with Antitumor Activity.

The sigma-2 receptors are promising therapeutic targets because of their significant upregulation in tumor cells compared with normal tissue. Here, we characterize CM572 [3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-6-isothiocyanatobenzo[d]oxazol-2(3H)-one] (sigma-1 Ki ≥ 10 µM, sigma-2 Ki = 14.6 ± 6.9 nM), a novel isothiocyanate derivative of the putative sigma-2 antagonist, SN79 [6-acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one]. CM572 bound irreversibly to sigma-2 receptors by virtue of the isothiocyanate moiety but not to sigma-1. Studies in human SK-N-SH neuroblastoma cells revealed that CM572 induced an immediate dose-dependent increase in cytosolic calcium concentration. A 24-hour treatment of SK-N-SH cells with CM572 induced dose-dependent cell death, with an EC50 = 7.6 ± 1.7 µM. This effect was sustained over 24 hours even after a 60-minute pretreatment with CM572, followed by extensive washing to remove ligand, indicating an irreversible effect consistent with the irreversible binding data. Western blot analysis revealed that CM572 also induced cleavage activation of proapoptotic BH3-interacting domain death agonist. These data suggest irreversible agonist-like activity. Low concentrations of CM572 that were minimally effective were able to attenuate significantly the calcium signal and cell death induced by the sigma-2 agonist CB-64D [(+)-1R,5R-(E)-8-benzylidene-5-(3-hydroxyphenyl)-2-methylmorphan-7-one]. CM572 was also cytotoxic against PANC-1 pancreatic and MCF-7 breast cancer cell lines. The cytotoxic activity of CM572 was selective for cancer cells over normal cells, being much less potent against primary human melanocytes and human mammary epithelial cells. Taken together, these data show that CM572 is a selective, irreversible sigma-2 receptor partial agonist. This novel irreversible ligand may further our understanding of the endogenous role of this receptor, in addition to having potential use in targeted cancer diagnosis and therapy.

Genome-scale RNAi profiling of cell division in human tissue culture cells.

Cell division is fundamental for all organisms. Here we report a genome-scale RNA-mediated interference screen in HeLa cells designed to identify human genes that are important for cell division. We have used a library of endoribonuclease-prepared short interfering RNAs for gene silencing and have used DNA content analysis to identify genes that induced cell cycle arrest or altered ploidy on silencing. Validation and secondary assays were performed to generate a nine-parameter loss-of-function phenoprint for each of the genes. These phenotypic signatures allowed the assignment of genes to specific functional classes by combining hierarchical clustering, cross-species analysis and proteomic data mining. We highlight the richness of our dataset by ascribing novel functions to genes in mitosis and cytokinesis. In particular, we identify two evolutionarily conserved transcriptional regulatory networks that govern cytokinesis. Our work provides an experimental framework from which the systematic analysis of novel genes necessary for cell division in human cells can begin.

Trojan-horse nanotube on-command intracellular drug delivery.

A major challenge to nanomaterial-based medicine is the ability to release drugs on-command. Here, we describe an innovative drug delivery system based on carbon nanotubes (CNTs), in which compounds can be released inside cells from within the nanotube "on-command" by inductive heating with an external alternating current or pulsed magnetic field. Without inductive heating the drug remains safely inside the CNTs, showing no toxicity in cell viability tests. Similar to the "Trojan-Horse" in function, we demonstrate the delivery of a combination of chemotherapeutic agents with low aqueous solubility, paclitaxel (Taxol), and C6-ceramide, to multidrug resistant pancreatic cancer cells. Nanotube encapsulation permitted the drugs to be used at a 100-fold lower concentration compared to exogenous treatment yet achieve a comparable ~70% cancer kill rate.

Identification and characterization of MAM03055A: A novel bivalent sigma-2 receptor/TMEM97 ligand with cytotoxic activity.

Sigma-2 receptor/transmembrane protein 97 (TMEM97) is upregulated in cancer cells compared to normal cells. Traditional sigma-2 receptor agonists induce apoptosis and autophagy, making them of interest in cancer therapy. Recently, we reported a novel metabolically stimulative function of the sigma-2 receptor, showing increased 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and stimulation of glycolytic hallmarks. 6-Substituted analogs of the canonical sigma-2 receptor antagonist, 6-acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one (SN79), produce both metabolically stimulative and cytotoxic effects. Here, we compare the activities of two related compounds: 6-amino-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one (CM571), the 6-amino derivative of SN79, which binds with high affinity to both sigma-1 and sigma-2 receptors, and 1,3-bis(3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-2-oxo-2,3-dihydrobenzo[d]oxazol-6-yl)thiourea (MAM03055A), a homo-bivalent dimer of CM571. MAM03055A resulted from the degradation of 3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-6-isothiocyanatobenzo[d]oxazol-2(3H)-one (CM572), the cytotoxic 6-isothiocyanato SN79 derivative. MAM03055A exhibited high affinity and strong preference for sigma-2 receptors (sigma-1 Ki = 3371 nM; sigma-2 receptor Ki = 55.9 nM). Functionally, MAM03055A treatment potently induced cell death in SK-N-SH neuroblastoma, MDA-MB-231 breast, and both SW48 and SW480 colorectal cancer cell lines, causing proapoptotic BH3 interacting-domain death agonist (BID) cleavage in SK-N-SH cells. Conversely, CM571 induced metabolic stimulation. CM571 bound reversibly to both receptors, while MAM03055A bound pseudo-irreversibly to sigma-2 receptors and caused residual cytotoxic activity after acute exposure and removal of the compound from the media. Interestingly, MAM03055A induced a time-dependent loss of sigma-2 receptor/TMEM97 protein from cells, whereas monomer CM571 had no effect on receptor levels. These results suggest that monovalent and bivalent sigma-2 receptor ligands in this series interact differently with the receptor, thus resulting in divergent effects.

Proceedings from the Fourth International Symposium on σ-2 Receptors: Role in Health and Disease.

The σ-2 receptor (S2R) complex has been implicated in CNS disorders ranging from anxiety and depression to neurodegenerative disorders such as Alzheimer's disease (AD). The proteins comprising the S2R complex impact processes including autophagy, cholesterol synthesis, progesterone signaling, lipid membrane-bound protein trafficking, and receptor stabilization at the cell surface. While there has been much progress in understanding the role of S2R in cellular processes and its potential therapeutic value, a great deal remains unknown. The International Symposium on Sigma-2 Receptors is held in conjunction with the annual Society for Neuroscience (SfN) conference to promote collaboration and advance the field of S2R research. This review summarizes updates presented at the Fourth International Symposium on Sigma-2 Receptors: Role in Health and Disease, a Satellite Symposium held at the 2019 SfN conference. Interdisciplinary members of the S2R research community presented both previously published and preliminary results from ongoing studies of the role of S2R in cellular metabolism, the anatomic and cellular expression patterns of S2R, the relationship between S2R and amyloid ß (Aß) in AD, the role of S2R complex protein PGRMC1 in health and disease, and the efforts to design new S2R ligands for the purposes of research and drug development. The proceedings from this symposium are reported here as an update on the field of S2R research, as well as to highlight the value of the symposia that occur yearly in conjunction with the SfN conference.

Signaling pathways from cannabinoid receptor-1 activation to inhibition of N-methyl-D-aspartic acid mediated calcium influx and neurotoxicity in dorsal root ganglion neurons.

Although the activation of cannabinoid receptor-1 (CB1) receptors by cannabinoids is known to inhibit neuronal hyperexcitability and reduce excitotoxic cell death, the mechanistic links between these two actions remain elusive. We tested the hypothesis that activation of CB1 receptors inhibits N-methyl-d-aspartic acid (NMDA)-mediated calcium influx and cell death via the inositol triphosphate (IP(3)) signaling pathway in both primary dorsal root ganglia neurons and a cultured neuronal cell line (F-11 cells). These cells were pretreated with the cannabinoid agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de)-1,4-benzoxazin-6-yl]-1-napthalenylmethanone (R-(+)-WIN 55,212-2; WIN) before exposure to NMDA. Concentrations of cytosolic calcium were measured with the ratiometric calcium indicator, Fura-2, and cell death was determined by a cell viability test. WIN dose-dependently attenuated both the calcium influx and cell death induced by NMDA. These effects were blocked by selective cannabinoid CB1 receptor antagonists N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A) or N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251), but not CB2 receptor antagonist N-[(1S)-endo-1,3,3,-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methyl-benzyl)-pyrazole-3-carboxamide (SR144528). It is interesting to note that a transient Ca(2+) signal was observed after the acute application of WIN. This Ca(2+) increase was blocked by a CB1 receptor antagonist AM251, IP(3) receptor antagonist 2- aminoethyl diphenylborinate, or by depleting intracellular Ca(2+) stores with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin. Removal of extracellular Ca(2+), on the other hand, had no effect on the CB1 receptor-induced Ca(2+) increase. These data suggest that WIN triggers a cascade of events: it activates the CB1 receptor and the IP(3) signaling pathway, stimulates the release of Ca(2+) from intracellular stores, raises the cytosolic Ca(2+) levels, and inhibits the NMDA-mediated Ca(2+) influx and cell death through a process that remains to be determined.

A Comparative Study of Fluorescence Assays in Screening for BRD4.

Fluorescence assay technologies are commonly used in high-throughput screening because of their sensitivity and ease of use. Different technologies have their characteristics and the rationale for choosing one over the other can differ between projects because of factors such as availability of reagents, assay performance, and cost. Another important factor to consider is the assay susceptibility to artifacts, which is almost as important as the ability of the assay to pick up active compounds. Spending time and money on false positives or missing the opportunity to build chemistry around false negatives is something that every drug project tries to avoid. We used a BET family Bromodomain, BRD4(1), to explore the outcome of a screening campaign using three fluorescent assay technologies as primary assays. A diverse 7,038 compound set was screened in fluorescence lifetime, fluorescence polarization, and homogeneous time-resolved fluorescence to look at primary hit rates, compound overlap, and hit confirmation rates. The results show a difference between the fluorescence assay technologies with three separate hit lists and some overlap. The confirmed hits from each assay were further evaluated for translation into cells (NanoBRET™). Most of the actives confirmed in cells originated from compounds that overlapped between the assays. In addition, a well-annotated set of compounds with undesirable mechanism of inhibition was screened against BRD4(1) to compare the ability to discriminate true hits from artifact compounds. The results indicate a difference between the assays in their ability to generate false positives and negatives.

Differential effects of sigma1 receptor blockade on self-administration and conditioned reinstatement motivated by cocaine vs natural reward.

Growing evidence suggests a role for sigma(1) (sigma(1)) receptors in cognitive function, anxiety, depression, regulation of stress responses, and, recently, the appetitive effects of cocaine as measured by conditioned place preference. This study was designed to extend understanding of the role of sigma(1) receptors in addiction-relevant conditioned effects of cocaine by testing the effects of a potent and selective sigma(1) receptor antagonist, BD1047, on conditioned reinstatement of cocaine-seeking. To determine whether modification of conditioned reinstatement by BD1047 is selective for drug-directed behavior or reflects general suppressant effects on motivated behavior, BD1047 was tested also on reinstatement induced by stimuli conditioned to a natural reward, sweetened condensed milk (SCM). Additionally, because sigma(1) receptors have been implicated also in processes linked to the acute reinforcing actions of cocaine, tests of the effects of BD1047 on cocaine self-administration-including a comparison with the sigma(1) antagonist effects on SCM self-administration-were conducted as well. Cocaine self-administering male Wistar rats were trained to associate a discriminative stimulus (S(D)) with the availability of cocaine or SCM, and then subjected to reinstatement tests following extinction of cocaine or SCM-reinforced behavior. BD1047 (1-30 mg/kg) reversed response reinstatement induced by the cocaine S(D) at 20 and 30 mg/kg but did not modify SCM S(D)-induced responding at all but the highest 30 mg dose, at which responding was reversed to extinction levels. BD1047 did not modify responding reinforced directly by SCM or cocaine. The findings support a role for sigma(1) receptors in regulating conditioned responses to cocaine-related contextual stimuli and identify this receptor as a potential treatment target for the prevention of craving and relapse.

Determination of cell colony formation in a high-content screening assay.

The use of cell colony formation assays for research and clinical applications to assess the functional integrity of cells after in vitro manipulations is extensive. Key areas include hematopoietic stem cell research, cell transformation studies, and predicting the response of tumors to chemotherapeutic agents. Traditionally, enumeration of colonies has involved laborious and subjective counting by hand using a microscope. Here, laser scanning microplate cytometry has been used to provide an automated high-content readout of the effects of cytostatic agents on colony formation. This approach determines colony number through the application of a volume algorithm. Such an approach permits the differentiation of cytostatic effects where the number of colonies and size remains constant, and cytotoxic effects where the size and number may be reduced. Application of microplate cytometry thus offers significant benefits over alternative analytical methods in the search for novel chemotherapeutic agents.

Application of laser-scanning fluorescence microplate cytometry in high content screening.

The resolution of cell-based assays down to the cellular level has created new opportunities for the drug discovery process. Aptly named high content analysis, such an approach is enabling new methods of analysis for the broad range of therapeutic targets emerging in the post-genomics era, and offering alternative multiparametric readouts for some traditional analyses. Microplate cytometry is one of the technologies that is being applied to a broad range of assays utilizing fluorescent labeling, at throughputs compatible with primary screening campaigns. Cellular resolution is achieved using scanning laser excitation coupled to photomultiplier detection. This configuration results in area-based scanning across a large field of view, plus simultaneous detection of up to four emission colors for efficient multiplexing. Microplate cytometry is being used most extensively in the field of oncology research because of its usefulness for numerous applications, including protein kinase activity, cell cycle analysis, and cell colony formation. The review focuses on the Acumen Explorer microplate cytometer (TTP LabTech Ltd., Melbourn, Hertfordshire, UK), detailing the principal components of the instrument and providing an overview of its use in high content screening.

Sigma-2 receptor agonists activate a novel apoptotic pathway and potentiate antineoplastic drugs in breast tumor cell lines.

We have reported previously that sigma-2 receptors are expressed in high densities in a variety of tumor cell types (B. J. Vilner et al., Cancer Res., 55: 408-413, 1995) and that various sigma ligands have cytotoxic effects (B. J. Vilner et al., J. Neurosci., 15: 117-134, 1995). Other investigators have demonstrated increased expression of sigma-2 receptors in rapidly proliferating tumors (R. H. Mach et al., Cancer Res., 57: 156-161, 1997) and the ability of some sigma ligands to inhibit proliferation (P. J. Brent and G. T. Pang, Eur. J. Pharmacol., 278: 151-160, 1995). We demonstrate here the ability of sigma-2 receptor agonists to induce cell death by a mechanism consistent with apoptosis. In breast tumor cell lines that are sensitive (MCF-7) and resistant (MCF-7/Adr-, T47D, and SKBr3) to antineoplastic agents, incubation with the sigma-2 subtype-selective agonists CB-64D and CB-184 produced dose-dependent cytotoxicity (measured by lactate dehydrogenase release into medium). The EC(50) for this response was similar across cell lines, irrespective of p53 genotype and drug-resistance phenotype. CB-64D and the subtype nonselective sigma-2 agonists haloperidol and reduced haloperidol induced terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining in MCF-7 and T47D cells, indicating that cell death occurs via apoptosis. Apoptosis was also indicated by increases in Annexin V binding caused by CB-64D. In MCF-7 cells, cytotoxicity and Annexin V binding induced by the antineoplastics doxorubicin and actinomycin D was partially or completely abrogated by certain specific and general inhibitors of caspases. In contrast, caspase inhibitors had no effect on sigma-2 receptor-mediated (CB-64D and CB-184) cytotoxicity or Annexin V binding. Marked potentiation of cytotoxicity was observed when a subtoxic dose of CB-184 was combined with doxorubicin or actinomycin D, both in drug-sensitive (MCF-7) and drug-resistant (MCF-7/Adr-) cell lines. Haloperidol potentiated doxorubicin only in drug-resistant cells. These findings suggest the involvement of a novel p53- and caspase-independent apoptotic pathway used by sigma-2 receptors, which is distinct from mechanisms used by some DNA-damaging, antineoplastic agents and other apoptotic stimuli. These observations further suggest that sigma-2 receptors may be targets that can be therapeutically exploited in the treatment of both drug-sensitive and drug-resistant metastatic tumors.

Sigma 1 receptor-related neuroactive steroids modulate cocaine-induced reward.

The sigma1 receptor is critically involved in the rewarding effect of cocaine, as measured using the conditioned place preference (CPP) procedure in mice. Neuroactive steroids exert rapid neuromodulatory effects in the brain by interacting with GABA(A), NMDA, and sigma1 receptors. At the sigma1 receptor level, 3beta-hydroxy-5-androsten-17-one [dehydroepiandrosterone (DHEA)] and 3beta-hydroxy-5-pregnen-20-one (pregnenolone) act as agonists, whereas 4-pregnene-3,20-dione (progesterone) is an efficient antagonist. The present study sought to investigate the action of neuroactive steroids in acquisition of cocaine-induced CPP in C57BL/6 mice. None of these steroids induced CPP alone. However, pretreatment with DHEA or pregnenolone (5-20 mg/kg, s.c.) during conditioning with cocaine (10 mg/kg, i.p.) increased the conditioned score. On the contrary, pretreatment with either progesterone (10 or 20 mg/kg, s.c.) or finasteride (25 mg/kg, twice a day), a 5alpha-reductase inhibitor, blocked acquisition of cocaine (20 mg/kg)-induced CPP. A crossed pharmacology was observed between steroids and sigma1 ligands. The sigma1 antagonist N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino)ethylamine blocked cocaine-induced CPP and its potentiation by DHEA or pregnenolone. Progesterone blocked cocaine-induced CPP and its potentiation by the sigma1 agonist igmesine. These results showed that neuroactive steroids play a role in cocaine-induced appetence, through their interaction with the sigma1 receptor. Therefore, neuroendocrine control of cocaine addiction may not involve solely glucocorticoids. The importance of neuroactive steroids as factors of individual vulnerability to drug addiction should, thus, be considered.

Advances in laser scanning imaging cytometry for high-content screening.

The advent of high-content screening more than a decade ago remodeled drug discovery workflows by recasting the role of cell-based approaches in target identification, primary screening, lead optimization, and toxicity. The ability to identify and quantify compound effects on multiple cellular functions allows for rapid characterization of chemical libraries. Laser scanning imaging cytometry (LSIC) is one of the technologies that is being applied to a broad range of assays utilizing fluorescent labeling, at throughputs compatible with primary screening campaigns. Cellular resolution is achieved using laser scanning excitation through a specialized F-theta scan lens. This configuration results in rapid whole well scanning and large depth of field. The recent availability of systems equipped with multiple sources of laser excitation and arrays of detectors for spectral analysis has significantly increased its applicability through enabling more fluorescent reagents and higher levels of multiplexing. LSIC is being used most extensively for phenotypic screening especially in areas such as cell health, RNA interference (RNAi) screening, and three-dimensional cell models. This review communicates advances in LSIC and how it is being applied by presenting an overview of the technology and a range of real-world case studies.

Involvement of sigma receptors in the behavioral effects of cocaine: evidence from novel ligands and antisense oligodeoxynucleotides.

Pharmacological and molecular biological tools were used to validate the involvement of sigma receptors in the actions of cocaine. Radioligand binding studies demonstrated significant levels of sigma receptors in the brain and heart, where cocaine interacts preferentially with the sigma(1) subtype. In behavioral pharmacological studies using mice, nine novel sigma receptor antagonists significantly attenuated cocaine-induced convulsions, while structural analogs with weak interactions with sigma receptors were ineffective. In contrast to the protection provided by the antagonists, a classical sigma receptor agonist exacerbated the convulsive effects of cocaine. The antagonists also attenuated cocaine-induced lethality, with the best compound protecting against death even when administered as a post-treatment. At doses where the antagonists had no effect on baseline locomotor activity, they significantly attenuated the locomotor stimulatory effects of cocaine, suggesting their ability to block the psychomotor as well as the toxic effects of cocaine. To further validate that the anti-cocaine effects were achieved by interfering with cocaine's access to sigma receptors, antisense oligodeoxynucleotides against sigma(1) receptors were shown to attenuate the convulsive and locomotor stimulatory effects of cocaine. Together, the studies support the involvement of sigma receptors, particularly the sigma(1) subtype, in the behavioral effects of cocaine.

Dual probes for the dopamine transporter and sigma1 receptors: novel piperazinyl alkyl-bis(4'-fluorophenyl)amine analogues as potential cocaine-abuse therapeutic agents.

Both dopamine uptake inhibitors and sigma(1) receptor antagonists have been implicated as potential pharmacotherapeutics for the treatment of cocaine abuse. While the dopamine uptake inhibitors may share with cocaine neurochemical mechanisms underlying reinforcing properties, sigma(1) antagonists have been shown to attenuate some behavioral actions and toxic side effects associated with cocaine overdose. Rimcazole, a sigma(1) receptor antagonist that binds to the DAT (K(i) = 224 nM), is not behaviorally cocaine-like and attenuates some of the behavioral actions of cocaine. To determine the roles of both DAT and sigma(1) receptors in the behavioral actions of rimcazole, a series of analogues was synthesized. Initial studies identified two analogues (1 and 4) that showed high to moderate affinities for both DAT and sigma(1) receptors and failed to show cocaine-like discriminative stimulus (DS) effects. A second series of bis(4'-fluorophenyl)amine analogues have now been prepared in which the most potent DAT compound, 19 (K(i) = 8.5 nM), was selective over serotonin transporter (SERT/DAT = 94), norepinephrine transporter (NET/DAT = 63), and sigma(1) receptor binding (sigma(1)/DAT = 44). In addition, two other analogues 10 and 17 showed superior selectivity for DAT over SERT (170- and 140-fold, respectively) and DAT over NET (219- and 190-fold, respectively) but were essentially equipotent at DAT and sigma(1) receptors (10; K(i) = 77 and 124 nM, respectively, 17; K(i) = 28 and 13 nM, respectively). CoMFA studies at both DAT and sigma(1) receptors were performed to examine structural requirements for optimal binding at these two targets as well as to assess differences between them. Behavioral evaluation of analogues with varying affinities for both DAT and sigma(1) receptors may provide a novel approach toward designing medications for cocaine abuse.

The sigma1 (sigma1) receptor activation is a key step for the reactivation of cocaine conditioned place preference by drug priming.

RATIONALE: Cocaine-seeking behavior can be investigated in rodents using the conditioned place preference (CPP) paradigm, in which the drug-paired environment serves as a conditioned stimulus. Such approach allowed to previously demonstrate the importance of the neuromodulatory sigma1 (sigma1) receptor in acquisition of cocaine-induced CPP. CPP can be extinguished and then reactivated, notably using a cocaine challenge (i.e., priming). OBJECTIVES AND METHODS: In order to examine the role of the sigma1 receptor in reinstatement of Cocaine-seeking, Swiss mice acquired CPP with cocaine (30 mg/kg, i.p.) and then CPP was extinguished. RESULTS: A challenge cocaine priming (15 mg/kg) reactivated CPP up to 140% of the post-conditioning response. Pre-administration of the sigma1 receptor antagonist BD1047 (330 mg/kg, i.p.) or repeated treatment with an antisense probe targeting the sigma1 receptor prevented CPP reactivation. The sigma1 agonist igmesine (1-10 mg/kg, i.p.) or the steroid dehydroepiandrosterone (DHEA, 10-40 mg/kg, s.c.) reactivated CPP, in a BD1047-sensitive manner. Moreover, the in vivo [3H](+)-SKF-10,047 binding levels to the sigma1 receptor were increased after cocaine conditioning in numerous brain structures and these increases subsisted after extinction. Finally, cross-reactivation of cocaine-induced CPP was observed after phencyclidine (PCP), morphine, nicotine and ethanol administration. However, BD1047 blocked reactivation of CPP induced by PCP, morphine and nicotine but not ethanol. CONCLUSIONS: Since activation of the sigma1 receptor is not sufficient to sustain CPP in naive animals [Neuropsychopharmacology 26 (2002) 444], it is concluded that sigma1 receptor activation is a key event for relapse to drug seeking. Activation may occur via sensitization due to enhanced in vivo available of receptors.

Sigma-2 receptors are specifically localized to lipid rafts in rat liver membranes.

We have previously shown that sigma-2 receptors are relatively difficult to solubilize (Eur. J. Pharmacol. 304 (1996) 201), suggesting possible localization in detergent-resistant lipid raft domains. Rat liver membranes were treated on ice with 1% Triton X-100 or 20 mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), and the extract subjected to centrifugation on a discontinuous gradient of 5%, 38%, and 40% sucrose. Gradient fractions were analyzed for sigma-1 receptors using [3H]+-pentazocine and for sigma-2 receptors using [3H]1,3-di-o-tolylguanidine ([3H]DTG), in the presence of dextrallorphan. Flotillin-2 was assessed by immunoblotting as a marker for lipid rafts. Sigma-2 receptors were found to discretely co-localize with flotillin-2 in lipid raft fractions. However, sigma-1 receptors were found throughout the gradient. Rafts prepared in CHAPS had sigma-2 receptors with normal pharmacological characteristics, whereas those in Triton X-100-prepared rafts had about seven-fold lower affinity for [3H]DTG and other ligands. Thus, sigma-2 receptors are resident in membrane lipid rafts, whereas sigma-1 receptors appear in both raft and non-raft membrane domains. Lipid rafts may play an important role in the mechanism of sigma-2 receptor-induced apoptosis.