Immunopharmacological profile of SR 31747: in vitro and in vivo studies on humoral and cellular responses

The immunomodulatory effects of classical psychedelics: A systematic review of preclinical studies

Emerging evidence suggests that classical psychedelics possess immunomodulatory and anti-inflammatory properties; however, these effects are yet to be well-established. This systematic review aims to provide a timely and comprehensive overview of the immunomodulatory effects of classical psychedelics in preclinical studies. A systematic search was conducted on six databases, including CINAHL, EMBASE, MEDLINE, PsychINFO, Scopus, and Web of Science. Eligible studies targeting classical psychedelics for evaluation of their effects on inflammatory markers and immunomodulation have been included for analysis. Data was extracted from 40 out of 2822 eligible articles, and their risk of bias was assessed using the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) tool and Quality Assessment Tool for In Vitro Studies (QUIN). Studies examined 2,5-dimethoxy-4-iodoamphetamine (DOI; n = 18); psilocybin (4-PO-DMT; n = 9); N,N-dimethyltryptamine (DMT; n = 8); lysergic acid diethylamide (LSD; n = 6); 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT; n = 3); psilocin (4-HO-DMT; n = 3); and mescaline (n = 2). In 36 studies where inflammatory cytokine levels were measured following psychedelic administration, a decrease in at least one inflammatory cytokine was observed in 29 studies. Immune cell activity was assessed in 10 studies and findings were mixed, with an equal number of studies (n = 5 out of 10) reporting either an increase or decrease in immune cell activity. Classical psychedelics were found to alleviate pre-existing inflammation but promote inflammation when administered under normal physiological conditions. This information is anticipated to inform future clinical trials, exploring classical psychedelics' potential to alleviate inflammation in various pathologies.

Sigma-1 Receptors and Neurodegenerative Diseases: Towards a Hypothesis of Sigma-1 Receptors as Amplifiers of Neurodegeneration and Neuroprotection

Sigma-1 receptors are molecular chaperones that may act as pathological mediators and targets for novel therapeutic applications in neurodegenerative diseases. Accumulating evidence indicates that sigma-1 ligands can either directly or indirectly modulate multiple neurodegenerative processes, including excitotoxicity, calcium dysregulation, mitochondrial and endoplasmic reticulum dysfunction, inflammation, and astrogliosis. In addition, sigma-1 ligands may act as disease-modifying agents in the treatment for central nervous system (CNS) diseases by promoting the activity of neurotrophic factors and neural plasticity. Here, we summarize their neuroprotective and neurorestorative effects in different animal models of acute brain injury and chronic neurodegenerative diseases, and highlight their potential role in mitigating disease. Notably, current data suggest that sigma-1 receptor dysfunction worsens disease progression, whereas enhancement amplifies pre-existing functional mechanisms of neuroprotection and/or restoration to slow disease progression. Collectively, the data support a model of the sigma-1 receptor as an amplifier of intracellular signaling, and suggest future clinical applications of sigma-1 ligands as part of multi-therapy approaches to treat neurodegenerative diseases.

Sigma1 Pharmacology in the Context of Cancer

Sigma1 (also known as sigma-1 receptor, Sig1R, σ1 receptor) is a unique pharmacologically regulated integral membrane chaperone or scaffolding protein. The majority of publications on the subject have focused on the neuropharmacology of Sigma1. However, a number of publications have also suggested a role for Sigma1 in cancer. Although there is currently no clinically used anti-cancer drug that targets Sigma1, a growing body of evidence supports the potential of Sigma1 ligands as therapeutic agents to treat cancer. In preclinical models, compounds with affinity for Sigma1 have been reported to inhibit cancer cell proliferation and survival, cell adhesion and migration, tumor growth, to alleviate cancer-associated pain, and to have immunomodulatory properties. This review will highlight that although the literature supports a role for Sigma1 in cancer, several fundamental questions regarding drug mechanism of action and the physiological relevance of aberrant SIGMAR1 transcript and Sigma1 protein expression in certain cancers remain unanswered or only partially answered. However, emerging lines of evidence suggest that Sigma1 is a component of the cancer cell support machinery, that it facilitates protein interaction networks, that it allosterically modulates the activity of its associated proteins, and that Sigma1 is a selectively multifunctional drug target.

High-affinity σ1 protein agonist reduces clinical and pathological signs of experimental autoimmune encephalomyelitis

BACKGROUND AND PURPOSE

Selective agonists of the sigma-1 receptor (σ1 protein) are generally reported to protect against neuronal damage and modulate oligodendrocyte differentiation. Human and rodent lymphocytes possess saturable, high-affinity binding sites for compounds binding to the σ1 protein and potential immunomodulatory properties have been described for σ1 protein ligands. Experimental autoimmune encephalomyelitis (EAE) is recognized as a valuable model of the inflammatory aspects of multiple sclerosis (MS). Here, we have assessed the role of a σ1 protein agonist, containing the tetrahydroisoquinoline-hydantoin structure, in EAE.

EXPERIMENTAL APPROACH

EAE was induced in SJL/J female mice by active immunization with myelin proteolipid protein (PLP)139-151 peptide. The σ1 protein agonist was injected i.p. at the time of immunization (day 0). Disease severity was assessed clinically and by histopathological evaluation of the CNS. Phenotyping of B-cell subsets and regulatory T-cells were performed by flow cytometry in spleen and cervical lymph nodes.

KEY RESULTS

Prophylactic treatment of EAE mice with the σ1 protein agonist prevented mononuclear cell accumulation and demyelination in brain and spinal cord and increased T2 B-cells and regulatory T-cells, resulting in an overall reduction in the clinical progression of EAE.

CONCLUSIONS AND IMPLICATIONS

This σ1 protein agonist, containing the tetrahydroisoquinoline-hydantoin structure, decreased the magnitude of inflammation in EAE. This effect was associated with increased proportions of B-cell subsets and regulatory T-cells with potential immunoregulatory functions. Targeting of the σ1 protein might thus provide new therapeutic opportunities in MS.

Inhibitory effects of sigma-2 receptor agonists on T lymphocyte activation

Sigma (σ) receptor ligands are essentially known for their effects on the nervous system although recent studies have shown their potential effects modulating some other pathophysiological processes as cell proliferation, cancer, and the immune response. Here, we have analyzed the actions of σ-1 and σ-2 receptors ligands on T cell activation. Our results show that treatment of Jurkat T cells with σ-2 agonists decreased the induction of the expression of Interleukin (IL)-2, Tumor necrosis factor (TNF)-α, and Cyclooxygenase (COX)-2 by activated T cells in a dose-dependent manner. These effects take place at the transcriptional level since σ-2 agonists BD-737 and CB-184 diminished the activity of the promoters of those genes. Those immunosuppressive effects could be attributable to interference with transcription factor activation. Induced transcription mediated by Nuclear factor (NF)-κB or Nuclear Factor of Activated T cells (NFAT) was inhibited by σ-2 agonists. These effects seem to be specific for σ-2 agonists as no significant effects on T cell activation by σ-1 ligands PRE-084 and BD-1063 were found. Our results provide new insights into the immunomodulatory actions of σ ligands and describe a new property of σ-2 agonists, through inhibition of activation of transcription factors as NFAT by which these compounds are regulating gene expression. This may have important consequences on the possible therapeutic use of those compounds.

Sigma-1 receptor alters the kinetics of Kv1.3 voltage gated potassium channels but not the sensitivity to receptor ligands

Sigma1 receptors (Sigma1R) are intracellular chaperone proteins that bind psychotropic drugs and also clinically used drugs such as ketamine and haloperidol. Co-expression of the Sigma1R has been reported to enhance the sensitivity of several voltage-gated ion channels to Sigma1R ligands. Kv1.3 is the predominant voltage-gated potassium channel expressed in T lymphocytes with a documented role in immune activation. To gain a better understanding of Sigma1R modulation of Kv ion channels, we investigated the effects of Sigma1R co-expression on Kv1.3 physiology and pharmacology in ion channels expressed in Xenopus oocytes. We also explored the protein domains of Kv1.3 necessary for protein:protein interaction between Kv1.3 and Sigma1R through co-immunoprecipitation studies. Slowly inactivating outward-going currents consistent with Kv1.3 expression were elicited on step depolarizations. The current characterized by E(rev), V(1/2), and slope factor remained unchanged when co-expressed with Sigma1R. Analysis of inactivation time constant revealed a faster Kv1.3 current decay when co-expressed with Sigma1R. However the sensitivity to Sigma1R ligands remained unaltered when co-expressed with the Sigma1R in contrast to the previously reported modulation of ligand sensitivity in closely related Kv1.4 and Kv1.5 voltage gated potassium channels. Co-immunoprecipitation assays of various Kv1.3 truncation constructs indicated that the transmembrane domain of the Kv1.3 protein was responsible for the protein:protein interaction with the Sigma1R. Sigma1R likely interacts with different domains of Kv ion channel family proteins resulting in distinct modulation of different channels.

Early development of sigma-receptor ligands

Sigma receptors (σ-1 and σ-2) are non-opioid proteins implicated in the pathophysiology of various neurological disorders and cancer. The σ-1 subtype is a chaperon protein widely distributed in the CNS and peripheral tissues. These receptors are involved in the modulation of K+- and Ca2+-dependent signaling cascades at the endoplasmic reticulum and modulation of neurotransmitter release. σ-1 receptors are emerging targets for the treatment of neurophychiatric diseases (schizophrenia and depression) and cocaine addiction. σ-2 receptors are lipid raft proteins. They are highly expressed on many tumor cells and hence considered potential targets for anticancer drugs. σ receptors bind to a diverse class of pharmacological compounds like cocaine, methamphetamine, benzomorphans like (±)-pentazocine, (±)-SKF-10,047 and endogenous neurosteroids and sphingolipids. In this review we focus on the early development of σ receptor-specific ligands and radiolabeling agents.

The sigma-1 receptor chaperone as an inter-organelle signaling modulator

Inter-organelle signaling plays important roles in many physiological functions. Endoplasmic reticulum (ER)-mitochondrion signaling affects intramitochondrial calcium (Ca(2+)) homeostasis and cellular bioenergetics. ER-nucleus signaling attenuates ER stress. ER-plasma membrane signaling regulates cytosolic Ca(2+) homeostasis and ER-mitochondrion-plasma membrane signaling regulates hippocampal dendritic spine formation. Here, we propose that the sigma-1 receptor (Sig-1R), an ER chaperone protein, acts as an inter-organelle signaling modulator. Sig-1Rs normally reside at the ER-mitochondrion contact called the MAM (mitochondrion-associated ER membrane), where Sig-1Rs regulate ER-mitochondrion signaling and ER-nucleus crosstalk. When cells are stimulated by ligands or undergo prolonged stress, Sig-1Rs translocate from the MAM to the ER reticular network and plasmalemma/plasma membrane to regulate a variety of functional proteins, including ion channels, receptors and kinases. Thus, the Sig-1R serves as an inter-organelle signaling modulator locally at the MAM and remotely at the plasmalemma/plasma membrane. Many pharmacological/physiological effects of Sig-1Rs might relate to this unique action of Sig-1Rs.

Characterization of the cocaine binding site on the sigma-1 receptor

The cocaine photoaffinity label 3-iodo-4-azidococaine ([125I]IACoc) binds to the sigma-1 receptor with an affinity that is 2-3 orders of magnitude higher than the parent compound cocaine [Kahoun, J. R., and Ruoho, A. E. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1393-1397]. In the present study, the binding properties of several cocaine derivatives to the guinea pig liver sigma-1 receptor were determined. The results from assessing the affinity of various derivatives of cocaine which were substituted on the phenyl ring indicated that an important determinant of binding to the guinea pig sigma-1 receptor binding site may be the development of a dipole in the ring in which the pi electron density of the phenyl ring is reduced. This implies that an electron-rich source is present in the sigma-1 receptor binding site, such as the pi system of an aromatic ring or other electron-rich side chains, which interact with the phenyl ring of cocaine. The precise [125I]IACoc derivatization site in the guinea pig sigma-1 receptor was identified using chemical cleavage and purification of the resulting labeled peptides. Cyanogen bromide cleavage of the [125I]IACoc photolabeled sigma-1 receptor followed by radiosequencing identified Asp188, which is located in the putative steroid binding domain-like II (SBDL II) near the carboxyl terminus, as the site of [125I]IACoc insertion. Systematic truncation of the C-terminus indicated the requirement for the last 15 amino acid residues of the receptor for [125I]IACoc photolabeling.

Assessment of the genotoxic potential of the antipsychotic sigma receptor ligand E-5842

The genotoxic potential of E-5842, a sigma ligand compound being developed as an antipsychotic drug, was evaluated by means of an extensive battery of in vitro and in vivo assays. Negative results were obtained in an Ames test (up to 5000 μg/plate), a mouse lymphoma assay (up to 535.1 μg/ml (-S9) and 891.8 μg/ml (+S9)), an in vivo rat hepatocyte micronucleus assay (up to 100 mg/kg/day on 2 days), and a two-dose mouse micronucleus assay (up to 40 mg/kg/day on 2 days). In a single-dose mouse bone-marrow micronucleus assay (up to 400 mg/kg; 24, 48 and 72 h sampling) a slight and non-statistically significant increase in the frequency of micronucleated polychromatic erythrocytes (MNPCE) was observed 48 h after administration of a 200 mg/kg dose, in the absence of bone-marrow toxicity. This minor increase in MNPCE frequency was considered of questionable biological relevance, because it was observed under conditions of marked animal toxicity including mortality. In addition, it occurred in association with a strong hypothermic effect produced by administration of E-5842. A clear increase in the frequency of structural chromosomal aberrations was observed in human lymphocytes at concentrations ≥350.6 and 1685.4 μg/ml in the presence and absence of S9, respectively. Mitotic accumulation was observed at those concentrations at which clastogenic effects were observed, a condition that may have masked toxicity. Concentrations lacking clastogenic effects in this chromosome aberration assay (300.7 and 173.2 μg/ml in the presence and absence of S9, respectively) were well in excess of maximum human plasma concentrations attained in clinical studies at the maximum tolerated dose (19.1 ng/ml). A weight-of-evidence analysis, taking into consideration the results obtained in the different in vitro and in vivo assays and the conditions of clinical use, suggest that E-5842 would not pose a genotoxic risk under clinical conditions.

The Sigma1 Protein as a Target for the Non-genomic Effects of Neuro(active)steroids: Molecular, Physiological, and Behavioral Aspects

Steroids synthesized in the periphery or de novo in the brain, so called 'neurosteroids', exert both genomic and nongenomic actions on neurotransmission systems. Through rapid modulatory effects on neurotransmitter receptors, they influence inhibitory and excitatory neurotransmission. In particular, progesterone derivatives like 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone) are positive allosteric modulators of the gamma-aminobutyric acid type A (GABA(A)) receptor and therefore act as inhibitory steroids, while pregnenolone sulphate (PREGS) and dehydroepiandrosterone sulphate (DHEAS) are negative modulators of the GABA(A) receptor and positive modulators of the N-methyl-D-aspartate (NMDA) receptor, therefore acting as excitatory neurosteroids. Some steroids also interact with atypical proteins, the sigma (sigma) receptors. Recent studies particularly demonstrated that the sigma1 receptor contributes effectively to their pharmacological actions. The present article will review the data demonstrating that the sigma1 receptor binds neurosteroids in physiological conditions. The physiological relevance of this interaction will be analyzed and the impact on physiopathological outcomes in memory and drug addiction will be illustrated. We will particularly highlight, first, the importance of the sigma1-receptor activation by PREGS and DHEAS which may contribute to their modulatory effect on calcium homeostasis and, second, the importance of the steroid tonus in the pharmacological development of selective sigma1 drugs.

IL-10 mediates sigma 1 receptor-dependent suppression of antitumor immunity

Sigma receptors are unique endoplasmic reticulum proteins that mediate signaling for a variety of drugs. We determined the effect of sigma(1) receptor agonists on immune responses in a syngeneic lung cancer model. Sigma(1) receptor agonists, including cocaine, up-regulated splenocyte IL-10 mRNA and protein production in vitro in a sigma receptor-dependent, pertussis toxin-sensitive manner. In vivo, sigma(1) receptor agonists promoted tumor growth and induced IL-10 at the tumor site. Increased tumor growth was prevented by administration of specific Abs to IL-10 or by administration of specific sigma(1) receptor antagonists. We report that sigma(1) receptor ligands, including cocaine, augment tumor growth through an IL-10 dependent mechanism.

Reduction of IL-10 and nitric oxide synthesis by SR31747A (sigma ligand) in RAW murine macrophages

BACKGROUND

There are several subtypes of sigma receptor, one of which is found throughout the immune system. SR31747A is a unique sigma ligand that possesses potent immune modulatory properties. Previous in vivo studies have documented that administration of SR31747A in murine models of sepsis resulted in decreased proinflammatory (IL-1, IL-6, TNF-alpha) and increased anti-inflammatory (IL-10) response (serum, splenocyte). Studies regarding the effect of this sigma ligand on purified macrophages are lacking. We therefore sought to investigate the effect of SR31747A in LPS-stimulated murine macrophages (RAW 264.7).

METHODS

RAW cells were incubated at 2.5 x 10(5) cells/well; controls were incubated with media alone, experimental groups contained LPS (0.01 microg) and SR31747A (1 nM, 10 nM, 100 nM, 1 microM, 10 microM). Supernatant and cells were harvested at 24 and 48 h. Concentrations of nitric oxide (Greiss reaction) and IL-10 were determined in the supernatant; cellular IL-10 mRNA was assessed.

RESULTS

SR31747A induced a dose-dependent reduction in NO and IL-10 protein release in LPS-stimulated murine macrophages. The decrease in IL-10 protein synthesis was paralleled by a significant dose-dependent reduction in IL-10 mRNA.

CONCLUSION

SR31747A is a novel immunomodulator that down regulates nitric oxide and IL-10 protein and mRNA expression. This in vitro reduction of IL-10 protein and mRNA expression is in contrast to previous in vivo murine studies. These data suggest that peripheral macrophages are not the source of the increased anti-inflammatory (IL-10) response induced by SR31747A.

SSR125329A, a high affinity sigma receptor ligand with potent anti-inflammatory properties

SSR125329A ([(Z)-3-(4-Adamantan-2-yl-3,5-dichloro-phenyl)-allyl]-cyclohexyl-ethyl-amine) is a new ligand exhibiting high affinity for sigma(1) and sigma(2) receptors and for the human Delta8-Delta7-sterol isomerase. Here we show that this molecule has potent immunoregulatory properties both in vitro and in vivo. SSR125329A inhibited staphylococcal enterotoxin B-induced mouse splenocyte proliferation in vitro, whereas in vivo it enhanced lipopolysaccharide-induced systemic release of interleukin-10 while simultaneously inhibiting tumor necrosis factor-alpha (TNF-alpha) synthesis. It also prevented graft-versus-host disease in B6D2F1 mice and protected Mrl/lpr mice against the development of its spontaneous rheumatoid-like syndrome. There is high interplay of pro- and anti-inflammatory cytokines in inflammatory processes, particularly in human rheumatoid arthritis. The results of this study provide substantial evidence that sigma receptor ligands may represent a new effective approach for rheumatoid arthritis treatment.

A DNA microarray-based approach to elucidate the effects of the immunosuppressant SR31747A on gene expression in Saccharomyces cerevisiae

SR31747A is an immunosuppressive agent that arrests cell proliferation in the yeast Saccharomyces cerevisiae. In this microorganism, SR31747A was shown to inhibit the ERG2 gene product, namely the delta8-delta7 sterol isomerase, involved in the ergosterol biosynthesis pathway. Although previous genetic experiments pointed to this enzyme as the target for SR31747A in yeast, the existence of other potential targets could not be ruled out. To enlighten this issue, we undertook a DNA microarray-based approach in which the expression profile of SR31747A-treated wild-type cells defining the "drug signature" was compared with the "mutant signature," the expression profile of the corresponding ERG2-deleted strain. We observed that treatment of ERG2-positive cells with SR31747A resulted in the modulation of mRNA levels of numerous genes. Among them, 121 werealso affected in untreated ERG2-disrupted cells compared with wild-type cells. By contrast, drug exposure did not induce any significant transcriptional change in the ERG2 null mutant. These results were consistent with SR31747A being an inhibitor of the sterol isomerase and demonstrated the absence of any additional SR31747A target. The detailed analysis of the observed 121 modulated genes provides new insights into the cellular response to ergosterol deprivation induced by SR31747A through inhibition of the ERG2 gene product.

Expression pattern of the type 1 sigma receptor in the brain and identity of critical anionic amino acid residues in the ligand-binding domain of the receptor

The type 1 sigma receptor (sigmaR1) has been shown to participate in a variety of functions in the central nervous system. To identify the specific regions of the brain that are involved in sigmaR1 function, we analyzed the expression pattern of the receptor mRNA in the mouse brain by in situ hybridization. SigmaR1 mRNA was detectable primarily in the cerebral cortex, hippocampus, and Purkinje cells of cerebellum. To identify the critical anionic amino acid residues in the ligand-binding domain of sigmaR1, we employed two different approaches: chemical modification of anionic amino acid residues and site-directed mutagenesis. Chemical modification of anionic amino acids in sigmaR1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide reduced the ligand-binding activity markedly. Since it is known that a splice variant of this receptor which lacks exon 3 does not have the ability to bind sigma ligands, the ligand-binding domain with its critical anionic amino acid residues is likely to be present in or around the region coded by exon 3. Therefore, each of the anionic amino acids in this region was mutated individually and the influence of each mutation on ligand binding was assessed. These studies have identified two anionic amino acids, D126 and E172, that are obligatory for ligand binding. Even though the ligand-binding function was abolished by these two mutations, the expression of these mutants was normal at the protein level. These results show that sigmaR1 is expressed at high levels in specific areas of the brain that are involved in memory, emotion and motor functions. The results also provide important information on the chemical nature of the ligand-binding site of sigmaR1 that may be of use in the design of sigmaR1-specific ligands with potential for modulation of sigmaR1-related brain functions.

Immunocytochemical assessment of sigma-1 receptor and human sterol isomerase in breast cancer and their relationship with a series of prognostic factors

The purpose of this study was to immunocytochemically investigate two new markers, the sigma-1 receptor and the human sterol isomerase (hSI), in comparison with a series of clinicopathological and immunocytochemical prognostic factors in a trial including 95 patients with operable primary breast cancers. Our results showed no statistically significant relationship between these two markers and the age of the patients, their menopausal status, the tumour size and its histological grade, the nodal status and the expression of the Ki-67 proliferative marker. However, we evidenced a close correlation between the sigma-1 receptor expression and the hormonal receptor positivity (P = 0.008), essentially due to a link with the progesterone receptor status (P = 0.01). By contrast there was an inverse relationship between hSI expression and the oestrogen receptor and/or progesterone receptor positivity (P = 0.098). A significant relationship was shown between both the sigma-1 receptor, hSI expressions and Bcl2 expression, with P= 0.017 and 0.035 respectively. We also assessed whether the expression of the sigma-1 receptor or hSI might be linked with disease-free survival (DFS) and found that the presence of hSI and the absence of sigma-1 receptor expression were associated with a poorer disease-free survival (P= 0.007). Altogether these results suggest that in primary breast carcinomas in association with the evaluation of the steroid receptor status, the sigma-1 receptor and hSI may be interesting new markers useful to identify those patients who might be able to benefit from an adjuvant therapy.

Sterol metabolism and ERG2 gene regulation in the yeast Saccharomyces cerevisiae

Certain exogenously-supplied sterols, like ergost-8-enol, are efficiently converted into ergosterol in yeast. We have taken advantage of this property to study the regulation of the Delta8-Delta7-sterol isomerase-encoding ERG2 gene in an ergosterol auxotrophic mutant devoid of squalene-synthase activity. Ergosterol starvation leads to an 8-16-fold increase in ERG2 gene expression. Such an increase was also observed in wild-type cells either grown anaerobically or treated with SR31747A a sterol isomerase inhibitor. Exogenously-supplied zymosterol is entirely transformed into ergosterol, which represses ERG2 transcription. By contrast, exogenously-supplied ergosterol has little or no effect on ERG2 transcription.

Colocalization of sterol isomerase and sigma(1) receptor at endoplasmic reticulum and nuclear envelope level

SR31747A is a sigma ligand previously described as having original immunosuppressive properties. Two SR31747A targets were recently identified and termed sigma(1) or SR-BP-1 (SR31747A-binding protein-1) and hSI (human sterol isomerase). In order to characterize these proteins further, we examined their expression and localization at the subcellular level. Based on the amino acid sequence deduced from the cloned hSI, anti-hSI polyclonal antibody was raised against the N-terminal fragment of the protein. Using this antibody, we performed Western-blot experiments to demonstrate the presence of hSI in various B and T cell lines, and hSI expression was quantified in these cell lines by flow cytometry and estimated at 15 000-30 000 sites per cell. Subcellular localization studies by both confocal and electron microscopy, performed on THP1 cells with anti-hSI antibody and with the previously described anti-(SR-BP-1) monoclonal antibody, demonstrated that: (a) hSI was colocalized with SR-BP-1; (b) hSI and SR-BP-1 were associated with the endoplasmic reticulum and with the outer and inner membranes of the nuclear envelope; (c) both proteins were delocalized during the cell cycle at the mitosis step when the nuclear membranes disappeared. Taken together our results suggest that both SR31747A-binding proteins not only play a role in sterol metabolism but indirectly affect lipoprotein functions.

Drugs of abuse and placental transport

The placenta provides the only link between the mother and the developing fetus. The function of the placenta as a transport organ is obligatory for fetal development because this process, mediated by a variety of transport systems, is responsible for the delivery of nutrients from the mother to the fetus. Some of the transport systems in the placenta also play a role in the clearance of vasoactive compounds, thus maintaining optimal blood flow to this organ. There is strong supporting evidence to indicate that several of these placental transport systems are either direct or indirect targets for the abusable drugs cocaine, amphetamines, nicotine, and cannabinoids. These drugs of abuse compromise the placental transport function and consequently produce detrimental effects on the developing fetus.

Increased binding to sigma sites of N-[1'(2-piperidinyl)ethyl)-4-[I-125]-iodobenzamide (I-125-PAB) with onset of tumor cell proliferation

This study evaluated if the density of sigma sites was modulated following stimulation of mitosis and progression through the cell cycle. The sigma ligand N-[1'(2-piperidinyl)ethyl)-4-[I-125]-iodobenzamide (I-125-PAB) was a binding probe on the mammary tumor cell lines T47D and MCF-7, and the prostate tumor cell line DU-145. Cells at low density and in log phase growth bound more I-125-IPAB than those at high density at or the near plateau phase. Stimulation of mitosis with insulin or fresh 10% serum increased I-125-IPAB binding in all three cell lines. In cell-cycle synchronized cells, the highest amount of binding was found in cells treated with colcemid to block cells in the M-phase, while the lowest amount of binding was found in cells treated with low serum to block the cells in G1. Cells treated with aphidicolin to block cells at G1/S also bound less than cells block in the M-phase. Collectively, these results support a direct correlation between I-125-PAB binding and proliferative status, and suggest an up-regulation of sigma binding sites prior to mitosis.

Purification and characterization of the human SR 31747A-binding protein. A nuclear membrane protein related to yeast sterol isomerase

SR 31747A, defined as a sigma ligand, is a novel immunosuppressive agent that blocks proliferation of human and mouse lymphocytes. Using a radiolabeled chemical probe, we here purified a target of SR 31747A and called it SR 31747A-binding protein (SR-BP). Purified SR-BP retained its binding properties and migrated on SDS-polyacrylamide gel as a Mr 28,000 protein. Cloning of the cDNA encoding human SR-BP shows an open reading frame for a 223-amino acid protein, which is homologous to the recently cloned sigma 1 receptor. Interestingly, the deduced amino acid sequence was found to be related to fungal C8-C7 sterol isomerase, encoded by the ERG2 gene. The ERG2 gene product has been identified recently as the molecular target of SR 31747A that mediates antiproliferative effects of the drug in yeast. Northern blot analysis of SR-BP gene expression revealed a single transcript of 2 kilobases which was widely expressed among organs, with the highest abundance in liver and the lowest abundance in brain. Subcellular localization analysis in various cells, using a specific monoclonal antibody raised against SR-BP, demonstrated that this protein was associated with the nuclear envelope. When studying the binding of SR 31747A on membranes from yeast expressing SR-BP, we found a pharmacological profile of sigma 1 receptors; binding was displaced by (+)-pentazocine, haloperidol, and (+)-SKF 10,047, with (+)-SKF 10, 047 being a more potent competitor than (-)-SKF 10,047. Scatchard plot analysis revealed Kd values of 7.1 nM and 0.15 nM for (+)-pentazocine and SR 31747A, respectively, indicating an affinity of SR-BP 50-fold higher for SR 31747A than for pentazocine. Additionally, we showed that pentazocine, a competitive inhibitor of SR 31747A binding, also prevents the immunosuppressive effect of SR 31747A. Taken together, these findings strongly suggest that SR-BP represents the molecular target for SR 31747A in mammalian tissues, which could be critical for T cell proliferation.

Differential localization of three distinct binding sites for sigma receptor ligands in rat spleen

In vitro receptor autoradiography was used to localize sigma 1 receptors, sigma 2 receptors, and novel haloperidol/DTG-inaccessible sites for sigma and opiate ligands in rat spleen. Sigma-1 receptors were present throughout the spleen, but were most concentrated in the T cell zones. Binding under "sigma 2 receptor-selective' conditions was 70% nonspecific, and sigma 2 receptors could not be detected. Haloperidol/DTG-inaccessible sites had a coarse, punctate distribution in the red pulp and marginal zones of the white pulp. This anatomical localization suggests types of cells and functions that should be examined for modulation by sigma receptors.

Stereoselective inhibition of natural killer activity by the sigma ligand (+)-pentazocine

The effect of sigma (sigma) receptor ligands on natural killer (NK) activity was examined both in vivo and in vitro. Following injection of mice with sigma receptor ligands such as (+)-pentazocine, (-)-pentazocine, BD 1073, BD 1165 and BD 737, NK activity was measured in poly-I.C.-stimulated mouse splenocytes. (+)-Pentazocine reduced NK cell activity in a dose-dependent fashion, while the (-) enantiomer was inactive in this measure. For example, at a dose of 50 mg/kg, (+)-pentazocine suppressed NK activity (using effector to target cell ratios of 200:1, 100:1 and 50:1) by > 70%, 24 h after injection while (-)-pentazocine was inactive. The other sigma ligands examined either slightly enhanced or had no effect on NK activity. Nonetheless, parenteral administration of the sigma receptor ligand BD 1165 blocked (+)-pentazocine-induced suppression of NK activity, while the opiate receptor antagonist naltrexone was ineffective. Addition of sigma receptor ligands (10(-11)-10(-5) M) to splenocyte cultures for 24 h did not affect NK activity. These findings indicate that while sigma receptor ligands are capable of modulating NK activity, this effect is not the result of an action on splenocyte sigma receptors, but may be mediated via sigma receptors either in the central or peripheral nervous systems.

[3H]1,3-di(2-tolyl) guanidine binds to a sigma 2 receptor on Jurkat cell membranes, but sigma compounds fail to influence immunomodulatory events in human peripheral blood lymphocytes

The binding characteristics of the sigma ligand [3H]1.3-di(2-tolyl)guanidine (DTG) were investigated in membranes prepared from the Jurkat T cell line. Binding was saturable with a KD of 56 +/- 3 nM and a Bmax of 11706 +/- 3173 fmol/mg protein (n = 3). The rank order of potency for sigma reference compounds to inhibit binding in the Jurkat cell line was ifenprodil > 1,3-di(2-tolyl)guanidine > haloperidol > carbetapentane > (+)3-(3-hydroxyphenyl)-N-propylpiperidine ((+)3-PPP) > (-)pentazocine > caramiphen > (+)pentazocine, and significantly correlated with potency at sigma 2 binding sites in guinea pig brain (r = 0.90, p < 0.01). The immunomodulatory activities of the sigma ligands 1,3-di(2-tolyl)guanidine, haloperidol. (-)pentazocine and (+)pentazocine on CD3-induced proliferation, IL-2 production and Ca2+ flux in human lymphocytes did not reveal any consistent pharmacology that could be ascribed to potency of these compounds at sigma binding sites. Collectively the data demonstrate that the [3H]1,3-di(2-tolyl)guanidine binding site on Jurkat cell membranes has a pharmacology consistent with sigma receptors, but no modulation of functional activity or intracellular events in human peripheral blood lymphocytes correlating with sigma receptors was found.

Haloperidol and spiperone potentiate murine splenic B cell proliferation

The neuroleptics haloperidol and spiperone potentiated anti-mu induced murine B-lymphocyte proliferation in vitro and lowered the threshold of anti-mu antibody needed to trigger proliferation. Because haloperidol and spiperone are best known for actions at D2, 5HT2, alpha 1 and sigma (sigma) receptors, a series of agonists and antagonists of these receptors were tested. Dopamine and norepinephrine inhibited, and serotonin (5HT) enhanced B-cell proliferation. Spiperone opposed the suppression of proliferation by dopamine and norepinephrine. However, antagonists of D1, D2, D3, D5, 5HT2, 5HT1A, and alpha 1 receptors did not mimic the effect of haloperidol and spiperone. Furthermore, a series of sigma agonists failed to affect B-cell proliferation. Therefore it is likely that the effects of haloperidol and spiperone are not due to actions at known dopamine, 5HT, alpha 1, or sigma receptors. These findings indicate neuroleptics act not only in the CNS, but also directly on B-lymphocytes of the immune system. The pharmacological site of this action is not clear at this time.

A sigma ligand, SR 31747A, potently modulates Staphylococcal enterotoxin B-induced cytokine production in mice

Sigma receptors originally described in distinct regions of the central nervous system are expressed on cells of the immune system. A sigma ligand, SR 31747A, was observed here to inhibit in vitro the Staphylococcal enterotoxin B (SEB)-driven lymphocyte proliferation. In mice, the drug confers a potent protection against the lethality induced by SEB, stimulates the SEB-induced serum release of interleukin (IL)-10 and inhibits at the same time the systemic release of IL-2, IL-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6 and tumour necrosis factor-alpha (TNF-alpha). The enhancement of IL-10 production by this compound is also effective in nude mice treated with SEB, indicating that IL-10 of T-cell origin is not involved in this process. The finding that a sigma ligand protects against the SEB-induced toxicity provides insights into the clinical use of this family of compounds, particularly in food poisoning and septic shock where Staphylococcal enterotoxins are involved. The observation that this compound stimulates IL-10 synthesis indicates that it could be a potent regulatory agent of chronic inflammatory diseases.

Kappa opioid receptor agonists inhibit sigma-1 (sigma 1) receptor binding in guinea-pig brain, liver and spleen: autoradiographical evidence

The present study examined whether the kappa-opioid agonists U50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N[-2-(1-pyrrolidinyl)- cyclohexyl]-benzeacetamide methane sulphonate), bremazocine, spiradoline and ICI 197067 bind to sigma sites in guinea-pig tissues using in vitro, semi-quantitative receptor autoradiography and receptor binding, and compared the binding profile so obtained with those for several selective sigma ligands. Guinea-pigs were killed and their brians, livers and spleens were removed, tissue sections cut and processed for sigma binding site autoradiography using (+)-[3H]-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-[3H]-3-PPP), or tissue was wiped and determined by liquid scintillation. Serial slide-mounted sections were incubated with 9-10 concentrations (1 nM-10 microM) of kappa opioids and their potency to inhibit (+)-[3H]-3-PPP binding compared with that of the sigma ligands haloperidol, DTG (1,3 di(o)-tolylguanidine), (+)-3-PPP, (+) and (-)pentazocine, SR 31742A and rimcazole (n = 3, duplicate determinations). Binding of (+)-[3H]-3-PPP to untreated, matched serial tissue sections was used as control. Kd values were estimated in brain, liver and spleen using quantitative, saturation binding analysis, IC50 values were determined from the binding data obtained by slide wiping experiments for each drug, and Ki values were calculated using the Cheng-Prussoff equation. All four kappa opioids inhibited (+)-[3H]-3-PPP binding to sigma 1-receptors with order of potency: brain: U50,488H = spiradoline > bremazocine > ICI 197067; liver: spiradoline > U50,488H > ICI 197067 > bremazocine; spleen: U50,488H > spiradoline > ICI 197067 > bremazocine. By comparison, the sigma ligands inhibited (+)-[3H]-3-PPP binding to matched, serial slide-mounted brain tissue sections (similar results in liver and spleen) with order of potency: SR 31742A > haloperidol > (+)pentazocine > (+)-3-PPP > DTG > (-)pentazocine > rimcazole. (+)-[3H]-3-PPP autoradiography confirmed these binding data. It is concluded that the kappa opioids tested moderately inhibit (+)-[3H]-3-PPP binding to sigma 1-receptors in guinea-pig brain, liver and spleen tissue with Ki values comparable to some selective sigma ligands and therefore are not opioid selective.

Initial characterization and autoradiographic localization of a novel sigma/opioid binding site in immune tissues

High concentrations of novel, haloperidol- and DTG-inaccessible (+)-[3H]-3-PPP binding sites were found in human peripheral blood leukocytes rat spleen and splenocytes, but not in rat brain. Splenic sites were localized in a course punctate pattern in the marginal zones and red pulp. The pharmacology of the splenic sites was: (-)-SKF 10,047 > or = naltrexone = (-)-pentazocine > (+)-pentazocine = (-)-3-PPP = (+)-SKF 10,047 > or = (+)-3-PPP > or = dextrorphan > dextromethorphan > PCP > clorgyline. DTG, haloperidol, TCP, (-)-deprenyl and SKF 525-A did not complete. Binding activity was destroyed by heating and phospholipase C, but not by proteases or glycosidases. These sites may be involved in immunomodulation by opiate and sigma receptor agonists.

The immunosuppressant SR 31747 blocks cell proliferation by inhibiting a steroid isomerase in Saccharomyces cerevisiae

SR 31747 is a novel immunosuppressant agent that arrests cell proliferation in the yeast Saccharomyces cerevisiae, SR 31747-treated cells accumulate the same aberrant sterols as those found in a mutant impaired in delta 8- delta 7-sterol isomerase. Sterol isomerase activity is also inhibited by SR 31747 in in vitro assays. Overexpression of the sterol isomerase-encoding gene, ERG2, confers enhanced SR resistance. Cells growing anaerobically on ergosterol-containing medium are not sensitive to SR. Disruption of the sterol isomerase-encoding gene is lethal in cells growing in the absence of exogenous ergosterol, except in SR-resistant mutants lacking either the SUR4 or the FEN1 gene product. The results suggest that sterol isomerase is the target of SR 31747 and that both the SUR4 and FEN1 gene products are required to mediate the proliferation arrest induced by ergosterol depletion.

Development of a radioimmunoassay for SR 31747A, a new sigma ligand, in human plasma

A specific and sensitive radioimmunoassay was developed for SR 31747A, a new sigma ligand, using a monoclonal antibody. This antibody was produced from spleen lymphocytes of a mouse immunized with SR 31747A coupled to bovine serum albumin via a peptide bond using SR 120684A, a succinamic acid derivative of SR 31747A. Negligible binding occurred when metabolites, obtained by chemical synthesis or by "in-vitro" incubation with hepatic microsomal fraction, were tested for cross-reactivity. A quantitative recovery in serum of the exogenous analyte was obtained for all the concentrations tested and the quantification limit was found to be 0.25 ng ml-1 of SR 31747 (the non-salified derivative). Intra- and inter-assay relative standard deviations ranged from 6.3-10.9 and from 5.3% to 15.4% respectively. Furthermore, comparison of results from samples which were assayed by radioimmunoassay and gas chromatography demonstrated an excellent correlation (r = 0.984).

In vivo effects of a new immunosuppressive sigma ligand, SR 31747, on mouse thymus

SR 31747 is a new sigma ligand which has immunosuppressive properties. The immunopharmacology of SR 31747 was investigated in vivo by studying its effects on the thymuses of C3H mice. The action of SR 31747 was compared with the reference drugs cyclosporin-A and dexamethasone on the basis of several parameters which were: the thymus weight; the number of thymocytes per organ; the percentages of mature CD4+ or CD8+ thymocytes and of immature CD4+ CD8+ thymocytes. SR 31747 slightly but significantly decreased the thymus weight at the dose of 50 mg/kg whereas the number of thymocytes per organ was significantly decreased from 6.25 mg/kg to the 50 mg/kg dose. It had rather no effect on the percentages of immature and mature subsets. These data led to the conclusion that the effects of SR 31747 on the thymuses of C3H mice were close to those obtained with cyclosporin-A and different from those obtained with dexamethasone.

Enhancement of endotoxin-induced interleukin-10 production by SR 31747A, a sigma ligand

SR 31747A is a new sigma ligand eliciting immunosuppressive and anti-inflammatory properties. Here, we show that SR 31747A greatly enhances lipopolysaccharide (LPS)-induced systemic release of interleukin (IL)-10, while it inhibits the secretion of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. In line with this finding, we also show by using quantitative reverse transcription-polymerase chain reaction analysis that SR 31747A increased LPS-induced IL-10 mRNA accumulation in spleen cells, whereas the level of both TNF-alpha and IFN-gamma mRNA was dramatically decreased. The enhancement of IL-10 production by SR 31747A treatment was also apparent in nude and severe-combined immunodeficient mice treated with LPS, clearly indicating that T and B cells were not involved. Finally, SR 31747A conferred protection against the lethal effect of LPS. The finding that SR 31747A strongly stimulates the synthesis of the natural anti-inflammatory cytokine IL-10, a property not observed with dexamethasone, provides new insights for the clinical use of this original compound, particularly in chronic inflammatory diseases where IL-10 is believed to be a pivotal regulatory component.

Characterization of a new gene family developing pleiotropic phenotypes upon mutation in Saccharomyces cerevisiae

The aim of this paper is to gather and complete data about four members of a new gene family. Mutation in SUR4 gene was originally selected as a suppressor of defects caused by mutations in RVS161 or RVS167 genes. Cloning and sequencing of the SUR4 gene were performed. The deduced protein contains six putative transmembrane domains. Sequence comparison revealed that two yeast genes, FEN1 and JO343, shared significant similarities with SUR4. Mutants for SUR4 and FEN1 have the same pleiotropic phenotype, including bud localization defects, resistance to an immunosuppressor and resistance to ergosterol biosynthesis inhibitors. The double inactivation of SUR4 and FEN1 genes is lethal. These data and other aspects implicating SUR4 in glucose metabolism, suggest an involvement of these genes in the dynamics of cortical actin cytoskeleton in response to nutrient availability. Moreover, the existence of a fourth homologous gene in C. elegans extends the family to pluricellular organisms.

The sigma ligand SR 31747 prevents the development of acute graft-versus-host disease in mice by blocking IFN-gamma and GM-CSF mRNA expression

SR 31747 is a sigma ligand which prevents the development of acute graft-versus-host reaction (GvHR) in hybrid B6D2F1 mice injected with C57BL/6 parental spleen cells. In the present study, we showed that this drug dramatically impaired the GvHR-associated increase in the numbers of both B-lymphocytes and polymorphonuclear cells (PMNs) in the spleen. Because SR 31747 blocked the GvHR-induced expression of both interleukin-2 and transferrin receptors on T-lymphocytes, it is very likely that this molecule prevented the disease through an inhibition of T-lymphocyte activation. Cytokine messenger RNA analyses on spleen cells revealed that SR 31747 blocked IFN-gamma and GM-CSF but not IL-4 transcription. These effects, which are different from those observed with either cyclosporin-A or dexamethasone, strongly suggest that SR 31747 preferentially inhibits the Th1 lymphocyte subset.