Differential effects of cytochrome P-450 induction on ligand binding to sigma receptors

Trends in Sigma-1 Receptor Research: A 25-Year Bibliometric Analysis

Purpose: There are previous reviews focused on Sigma-1 receptor but no bibliometric studies examining this field as a whole. This article aims to present a global view of Sigma-1 receptor research and its intellectual structure.

Methods: We used bibliometric indicators of a basic nature as well as techniques for the visualization and analysis of networks of scientific information extracted from Scopus database.

Results: In total, 1,102 articles from 1992 to 2017 were identified. The growth in the production of articles is not constant over time, with periods of stagnation of approximately 5 years. Only 247 authors have five or more publications. The authors appear grouped in relatively independent clusters, thus suggesting a low level of collaborations between those dedicated to the Sigma-1 receptor. The United States was the country with the highest production followed by Japan and Germany. Spain, Japan, and Italy showed the highest per million inhabitants ratio. The highest citation/article ratio was reached in France, United States, and Canada. The leading institutions were the University of Münster, the National Institutes of Health, ESTEVE, and INSERM. The top authors in number of publications were Wünsch-B, Schepmann-D, and Maurice-T. Hayashi-T, Su-TP and Bowen-WD showed the highest citations per article. The article by Hayashi-T and Su-TP in Cell (2007) describing the Sigma-1 receptor as a chaperone protein is the top cited reference. Cluster labeling from author co-citation analysis shows that research has been focused on specific diseases such as addiction, neuroprotection and neurodegenerative diseases, psychiatric disorders, and pain. High-frequency terms in author keywords suggest that the research efforts in some areas such as neuroimaging, cocaine addiction or psychiatric disorders have declined over time, while others such as neurodegenerative diseases or pain are currently most popular.

Perspective: A greater involvement of the scientific community, with an increase in the scientific production related to Sigma-1, is desirable. Additional boost needed to improve research performance is likely to come from combining data from different laboratories to overcome the limitations of individual approaches. The resulting maps are a useful and attractive tool for the Sigma-1 receptor research community, as they reveal the main lines of exploration at a glance.

Small molecule modulator of sigma 2 receptor is neuroprotective and reduces cognitive deficits and neuroinflammation in experimental models of Alzheimer's disease

Accumulating evidence suggests that modulating the sigma 2 receptor (Sig2R) can provide beneficial effects for neurodegenerative diseases. Herein, we report the identification of a novel class of Sig2R ligands and their cellular and in vivo activity in experimental models of Alzheimer's disease (AD). We report that SAS-0132 and DKR-1051, selective ligands of Sig2R, modulate intracellular Ca²⁺ levels in human SK-N-SH neuroblastoma cells. The Sig2R ligands SAS-0132 and JVW-1009 are neuroprotective in a C. elegans model of amyloid precursor protein-mediated neurodegeneration. Since this neuroprotective effect is replicated by genetic knockdown and knockout of vem-1, the ortholog of progesterone receptor membrane component-1 (PGRMC1), these results suggest that Sig2R ligands modulate a PGRMC1-related pathway. Last, we demonstrate that SAS-0132 improves cognitive performance both in the Thy-1 hAPP^Lond/Swe+ transgenic mouse model of AD and in healthy wild-type mice. These results demonstrate that Sig2R is a promising therapeutic target for neurocognitive disorders including AD.

Sigma (σ) receptors as potential therapeutic targets to mitigate psychostimulant effects

Many psychostimulants, including cocaine and methamphetamine, interact with sigma (σ) receptors at physiologically relevant concentrations. The potential therapeutic relevance of this interaction is underscored by the ability to selectively target σ receptors to mitigate many behavioral and physiological effects of psychostimulants in animal and cell-based model systems. This chapter begins with an overview of these enigmatic proteins. Provocative preclinical data showing that σ ligands modulate an array of cocaine and methamphetamine effects are summarized, along with emerging areas of research. Together, the literature suggests targeting of σ receptors as an innovative option for combating undesired actions of psychostimulants through both neuronal and glial mechanisms.

Chronic postnatal phencyclidine treatment on [3H](+) pentazocine binding in juvenile rat brain

Chronic phencyclidine (PCP) administrations in postnatal rats produce long-term behavioral changes. Here we report the effects of repeated postnatal PCP treatment on [3H](+)pentazocine binding in juvenile rats. Saturation analyses of the binding data showed no significant difference in any of the binding characteristics between chronic PCP-related rats and saline-treated controls suggesting that mechanisms other than alterations in sigma1 binding underlie the behavioral effects of repeated postnatal PCP administration in immature rats.

sigma recognition sites in brain and peripheral tissues. Characterization and effects of cytochrome P450 inhibitors

Binding to sigma sites in subcellular fractions of brain and in crude homogenates from peripheral tissues of the guinea pig was characterized with the [3H]ligands (+)pentazocine and di(2-tolyl)guanidine (DTG). The inhibitory effects of representative sigma compounds and cytochrome P450 inhibitors were evaluated in guinea pig tissues, and the effects of cytochrome P450 induction on sigma binding in the rat were investigated. For both ligands, the majority of sites were localized to the microsomal fractions. The KD values for [3H](+)pentazocine- or [3H]DTG-labeled sigma sites in guinea pig liver and testes were 2-fold lower than those in brain and heart. The number of sites labeled by [3H](+)pentazocine varied, with an order of liver > testes > brain > heart. In contrast, the Bmax values for [3H]DTG-defined sigma sites were greatest in testes, followed by liver, brain and heart. The rank order of potency for representative sigma and P450 compounds was similar in brain, liver and testes for both [3H]ligands, and the potency of selective compounds to displace sigma binding in guinea pig liver failed to correlate with their abilities to inhibit cytochrome P450IID1 activity in human liver. Following induction of cytochrome P450IIB1 with phenobarbital or cytochrome P450IA1 with beta-naphthoflavone, neither the affinity nor the number of sigma sites was altered in rat brain or liver. These results suggest that sigma sites in the periphery are similar to those in the brain, and that the sigma binding site is not identical with cytochrome P450IIB1, P450IA1 or P450IID1.

Multiple [3H]DTG binding sites in guinea pig cerebellum: evidence for the presence of non-specific binding

The characteristics of the low affinity component of 1,3-di(2-[5-3H]tolyl)guanidine binding to the guinea pig cerebellum were investigated. Saturation binding assays where sigma 1 receptors were masked with dextrallorphan indicated that 1,3-di(2-[5-3H]tolyl)guanidine bound to cerebellar membranes in a fashion best described by a 1 site+non-specific binding model with a low density of specific binding sites (Bmax approximately 200 fmol/mg protein). Boiling the cerebellar membranes before addition to the saturation assay had no effect on the density of 1,3-di(2-[5-3H]tolyl)guanidine binding. In contrast, both the Kd and Bmax for 1,3-di(2-[5-3H]tolyl)guanidine binding to liver membranes was significantly reduced by boiling, as was the density of [3H](+)-pentazocine binding to cerebellum and liver. Thus, a substantial component of 1,3-di(2-[5-3H]tolyl)guanidine binding in the guinea pig cerebellum is to non-specific, proteinaceous binding sites with some of the pharmacological characteristics of the sigma 2 binding site.

[3H](+)-pentazocine binding to rat brain sigma 1 receptors

[3H](+)-Pentazocine binding has been characterized in the rat brain. It binds to a single population of binding sites with affinity of about 7 nM and density of 280 fmol/mg protein. [3H](+)-Pentazocine binding is not enriched in the crude synaptic membrane, being about 1/6 of what we found in the crude membrane preparation. The binding, like that for other sigma ligands, was enriched in the microsomal and nuclear fractions. The inhibition by haloperidol, proadifen and d-fenfluramine was the same in the crude synaptic membrane, nuclear and microsomal fractions, suggesting that [3H](+)-pentazocine binds to a homogeneous protein in the different subcellular fractions. Our pharmacological characterization using 45 different drugs suggests that the [3H](+)-pentazocine binding site in rat brain differs from other sigma ligands, like N-propyl-3-(3-hydroxyphenyl)piperidine ([3H](+)-3PPP), N,N'-di(o-tolyl)guanidine ([3H]DTG) and (+)-N-allylnormetazocine ([3H](+)-SKF10,047). [3H](+)-Pentazocine binding in rat brain is inhibited by sigma compounds and some cytochrome P450 ligands, like proadifen and 1-[2-[bis(4-fluoro-phenyl) methoxy]ethyl]-4-[3-phenylpropyl] piperazine (GBR 12909), although with considerably lower potency than reported for other sigma ligands. Other inhibitors are some serotonin uptake blockers or their metabolites and phenylalkylamines.