Mammalian hybrid pre-autophagosomal structure HyPAS generates autophagosomes.

The biogenesis of mammalian autophagosomes remains to be fully defined. Here, we used cellular and in vitro membrane fusion analyses to show that autophagosomes are formed from a hitherto unappreciated hybrid membrane compartment. The autophagic precursors emerge through fusion of FIP200 vesicles, derived from the cis-Golgi, with endosomally derived ATG16L1 membranes to generate a hybrid pre-autophagosomal structure, HyPAS. A previously unrecognized apparatus defined here controls HyPAS biogenesis and mammalian autophagosomal precursor membranes. HyPAS can be modulated by pharmacological agents whereas its formation is inhibited upon severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or by expression of SARS-CoV-2 nsp6. These findings reveal the origin of mammalian autophagosomal membranes, which emerge via convergence of secretory and endosomal pathways, and show that this process is targeted by microbial factors such as coronaviral membrane-modulating proteins.

Sigma-1R Protects Retinal Ganglion Cells in Optic Nerve Crush Model for Glaucoma.

Purpose: The purpose of this study was to determine the effects of the Sigma-1R (σ-1r) on retinal ganglion cell (RGC) survival following optic nerve crush (ONC) and the signaling mechanism involved in the σ-1r protection. Methods: The overall strategy was to induce injury by ONC and mitigate RGC death by increasing σ-1r expression and/or activate σ-1r activity in σ-1r K/O mice and wild type (WT) mice. AAV2-σ-1r vector was used to increase σ-1r expression and σ-1r agonist used to activate the σ-1r and RGCs were counted. Immunohistochemical and Western blot analysis determined phosphorylated (p)-c-Jun, c-Jun, and Caspase-3. Pattern electroretinography (PERG) determined RGC activity. Results: RGC counts and function were similar in pentazocine-treated WT mice when compared to untreated mice and in WT mice when compared with σ-1r K/O mice. Pentazocine-induced effects and the effects of σ-1r K/O were only observable after ONC. ONC resulted in decreased RGC counts and activity in both WT and σ-1r K/O mice, with σ-1r K/O mice experiencing significant decreases compared with WT mice. The σ-1r transgenic expression resulted in increased RGC counts and activity following ONC. In WT mice, treatment with σ-1r agonist pentazocine resulted in increased RGC counts and increased activity when compared with untreated WT mice. There were time-dependent increases in c-jun, p-c-jun, and caspase-3 expression in ONC mice that were mitigated with pentazocine-treatment. Conclusions: These findings suggest that the apoptotic pathway is involved in RGC losses seen in an ONC model. The σ-1r offers neuroprotection, as activation and/or transgenic expression of σ-1r attenuated the apoptotic pathway and restored RGCs number and function following ONC.

Methamphetamine Induces Apoptosis of Microglia via the Intrinsic Mitochondrial-Dependent Pathway.

Methamphetamine (METH) is a drug of abuse, the acute and chronic use of which induces neurotoxic responses in the human brain, ultimately leading to neurocognitive disorders. Our goals were to understand the impact of METH on microglial mitochondrial respiration and to determine whether METH induces the activation of the mitochondrial-dependent intrinsic apoptosis pathway in microglia. We assessed the expression of pro- apoptosis genes using qPCR of RNA extracted from a human microglial cell line (HTHU). We examined the apoptosis-inducing effects of METH on microglial cells using digital holographic microscopy (DHM) to quantify real-time apoptotic volume decrease (AVD) in microglia in a noninvasive manner. METH treatment significantly increased AVD, activated Caspase 3/7, increased the gene expression levels of the pro- apoptosis proteins, APAF-1 and BAX, and decreased mitochondrial DNA content. Using immunofluorescence analysis, we found that METH increased the expression of the mitochondrial proteins cytochrome c and MCL-1, supporting the activation of mitochondrion-dependent (intrinsic) apoptosis pathway. Cellular bio-energetic flux analysis by Agilent Seahorse XF Analyzer revealed that METH treatment increased both oxidative and glycolytic respiration after 3 h, which was sustained for at least 24 h. Several events, such as oxidative stress, neuro-inflammatory responses, and mitochondrial dysfunction, may converge to mediate METH-induced apoptosis of microglia that may contribute to neurotoxicity of the CNS. Our study has important implications for therapeutic strategies aimed at preserving mitochondrial function in METH abusing patients.

MicroRNA-297 promotes cardiomyocyte hypertrophy via targeting sigma-1 receptor.

AIMS: Sigma-1 receptor (Sig-1R) is a ligand-regulated endoplasmic reticulum (ER) chaperone involved in cardiac hypertrophy, but it is not known whether Sig-1R is regulated by microRNAs (miRNAs). According to bioinformatic analysis, miR-297 was suggested as a potential target miRNA for Sig-1R. Therefore, we verified whether miR-297 could target Sig-1R and investigated the possible mechanisms underlying the role of miR-297 in cardiac hypertrophy. MAIN METHODS: Bioinformatic analysis combined with laboratory experiments, including quantitative RT-PCR, Western blotting, and luciferase assay, were performed to identify the target miRNA of Sig-1R. Transverse aortic constriction (TAC) model and neonatal rat cardiomyocytes (NCMs) stimulated with angiotensin II (AngII) were used to explore the relationship between miR-297 and Sig-1R. Additionally, the function of miR-297 in cardiomyocyte hypertrophy and ER stress/unfolded protein response (UPR) signaling pathway was investigated by transfecting miR-297 mimics/inhibitor. KEY FINDINGS: miR-297 levels were increased in both TAC-induced hypertrophic heart tissue and AngII-induced cardiomyocyte hypertrophy. Up-regulation of miR-297 by specific mimics exacerbated AngII-induced cardiomyocyte hypertrophy, whereas inhibition of miR-297 suppressed the process. During cardiomyocyte hypertrophy, Sig-1R expression, which was negatively regulated by miR-297 by directly targeting its 3'untranslated region (UTR), was decreased. Furthermore, attenuation of miR-297 inhibited the activation of X-box binding protein 1 (Xbp1) and activating transcriptional factor 4 (ATF4) signaling pathways in NCMs. SIGNIFICANCE: Our data demonstrate that miR-297 promotes cardiomyocyte hypertrophy by inhibiting the expression of Sig-1R and activation of ER stress signaling, which provides a novel interpretation for cardiac hypertrophy.

Effect of different concentrations of oxygen on expression of sigma 1 receptor and superoxide dismutases in human colon adenocarcinoma cell lines.

CONTEXT: Tumor cells due to distance from capillary vessels exist in different oxygenation conditions (anoxia, hypoxia, normoxia). Changes in cell oxygenation lead to reactive oxygen species production and oxidative stress. Sigma 1 receptor (Sig1R) is postulated to be stress responding agent and superoxide dismutases (SOD1 and SOD2) are key antioxidant enzymes. It is possible that they participate in tumor cells adaptation to different concentrations of oxygen. OBJECTIVE: Evaluation of Sig1R, SOD1, and SOD2 expression in different concentrations of oxygen (1%, 10%, 21%) in colon adenocarcinoma cell lines. MATERIALS AND METHODS: SW480 (primary adenocarcinoma) and SW620 (metastatic) cell lines were cultured in standard conditions in Dulbecco's modified Eagle's medium for 5 days, and next cultured in Hypoxic Chamber in 1% O2, 10% O2, 21% O2. Number of living cells was determined by trypan blue assay. Level of mRNA for Sig1R, SOD1, and SOD2 was determined by standard PCR method. Statistical analysis was conducted using Statistica 10.1 software. RESULTS: We observed significant changes in expression of Sig1R, SOD1, SOD2 due to different oxygen concentrations. ANOVA analysis revealed significant interactions between studied parameters mainly in hypoxia conditions in SW480 cells and between Sig1R and SOD2 in SW620 cells. It also showed that changes in expression of studied proteins depend significantly on type of the cell line. CONCLUSION: Changes of Sig1R and SOD2 expression point to mitochondria as main organelle responsible for survival of tumor cells exposed to hypoxia or oxidative stress. Studied proteins are involved in intracellular response to stress related with different concentrations of oxygen.

Role of Sigma 1 Receptor in Retinal Degeneration of the Ins2Akita/+ Murine Model of Diabetic Retinopathy.

PURPOSE: Sigma receptor 1 (Sigma1R), a nonopioid putative molecular chaperone, has neuroprotective properties in retina. This study sought to determine whether delaying administration of (+)-pentazocine, a high-affinity Sigma1R ligand after onset of diabetes in Ins2Akita/+ diabetic mice would afford retinal neuroprotection and to determine consequences on retinal phenotype in Ins2Akita/+ diabetic mice in the absence of Sigma1R. METHODS: Ins2Akita/+ diabetic and WT mice received intraperitoneal injections of (+)-pentazocine beginning 4 or 8 weeks after onset of diabetes; eyes were harvested at 25 weeks. Retinal histologic sections were analyzed to determine thicknesses of retinal layers, number of ganglion cells, and evidence of gliosis (increased glial fibrillary acidic protein levels). Ins2Akita/+/Sig1R-/-mice were generated and subjected to in vivo assessment of retinal architecture (optical coherence tomography [OCT]) and retinal vasculature using fluorescein angiography (FA) at 12 and 16 weeks compared with age-matched Ins2Akita/+ mice. Eyes were then harvested for retinal morphometric assessment and gliosis assessment. RESULTS: Wild-type mice had 13 ± 0.06 cells/100 µm retinal length; cell bodies in Ins2Akita/+ mice injected 4 and 8 weeks after onset of diabetes with (+)-pentazocine retained significantly more ganglion cells compared with Ins2Akita/+ mice (9 ± 0.04) and demonstrated significant attenuation of gliosis. Ins2Akita/+/Sig1R-/-mouse retinas, analyzed to determine whether the Ins2Akita/+ phenotype was accelerated when lacking Sigma1R, revealed increased nerve fiber layer thickness (OCT), evidence of vitreal opacities, and vessel beading (FA) compared with Ins2Akita/+ mice. Morphometric analysis revealed significantly fewer ganglion cells in Ins2Akita/+/Sig1R-/-mice compared with Ins2Akita/+ mice. CONCLUSIONS: Sigma1R may be a novel retinal stress modulator, and targeting it even after disease onset may afford retinal neuroprotection.

SIGMAR1 Regulates Membrane Electrical Activity in Response to Extracellular Matrix Stimulation to Drive Cancer Cell Invasiveness.

The sigma 1 receptor (Sig1R) is a stress-activated chaperone that regulates ion channels and is associated with pathologic conditions, such as stroke, neurodegenerative diseases, and addiction. Aberrant expression levels of ion channels and Sig1R have been detected in tumors and cancer cells, such as myeloid leukemia and colorectal cancer, but the link between ion channel regulation and Sig1R overexpression during malignancy has not been established. In this study, we found that Sig1R dynamically controls the membrane expression of the human voltage-dependent K(+) channel human ether-à-go-go-related gene (hERG) in myeloid leukemia and colorectal cancer cell lines. Sig1R promoted the formation of hERG/ß1-integrin signaling complexes upon extracellular matrix stimulation, triggering the activation of the PI3K/AKT pathway. Consequently, the presence of Sig1R in cancer cells increased motility and VEGF secretion. In vivo, Sig1R expression enhanced the aggressiveness of tumor cells by potentiating invasion and angiogenesis, leading to poor survival. Collectively, our findings highlight a novel function for Sig1R in mediating cross-talk between cancer cells and their microenvironment, thus driving oncogenesis by shaping cellular electrical activity in response to extracellular signals. Given the involvement of ion channels in promoting several hallmarks of cancer, our study also offers a potential strategy to therapeutically target ion channel function through Sig1R inhibition.

Trehalose intake induces chaperone molecules along with autophagy in a mouse model of Lewy body disease.

The accumulation of mis-folded and/or abnormally modified proteins is a major characteristic of many neurodegenerative diseases. In Lewy body disease (LBD), which includes Parkinson's disease and dementia with Lewy bodies, insoluble α-synuclein is widely deposited in the presynaptic terminals as well as in the neuronal cytoplasm in distinct brain regions. It is well known that the autophagy-lysosome system serves as an efficient degradation pathway for abnormal molecules within cells. To test the possibility that activated autophagy can degrade abnormal molecules, we investigated the effect of trehalose on abnormal aggregation of α-synuclein in a model of LBD. Trehalose is a natural disaccharide composed of two glucose units and functions as an autophagy inducer. Consistent with previous studies, trehalose increased level of the autophagosomal protein LC3, especially a lipidated form LC3-II in cultured cells and mice brain. Also, trehalose increased levels of several chaperon molecules, such as HSP90 and SigmaR1, in the brains of LBD model mice. Further studies revealed that level of detergent-insoluble α-synuclein was suppressed in mice following oral administration of trehalose, despite an apparent alteration was not observed regarding abnormal aggregation of α-synuclein. These results suggest that the oral intake of trehalose modulates propensity of molecules prior to aggregation formation.

Stimulation of Sigma-1 Receptor Ameliorates Depressive-like Behaviors in CaMKIV Null Mice.

Sigma-1 receptor (Sig-1R) is a molecular chaperone regulating calcium efflux from the neuronal endoplasmic reticulum to the mitochondria. Calcium/calmodulin-dependent protein kinase IV (CaMKIV) null mice exhibit depressive-like behaviors and impaired neurogenesis as assessed by bromodeoxyuridine (BrdU) incorporation into newborn cells of the hippocampal dentate gyrus (DG). Here, we demonstrate that chronic stimulation of Sig-1R by treatment with the agonist SA4503 or the SSRI fluvoxamine for 14 days improves depressive-like behaviors in CaMKIV null mice. By contrast, treatment with paroxetine, which lacks affinity for Sig-1R, did not alter these behaviors. Reduced numbers of BrdU-positive cells and decreased brain-derived neurotrophic factor (BDNF) mRNA expression and protein kinase B (Akt; Ser-473) phosphorylation seen in the DG of CaMKIV null mice were significantly rescued by chronic Sig-1R stimulation. Interestingly, reduced ATP production observed in the DG of CaMKIV null mice was improved by chronic Sig-1R stimulation. Such stimulation also improved hippocampal long-term potentiation (LTP) induction and maintenance, which are impaired in the DG of CaMKIV null mice. LTP rescue was closely associated with both increases in calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation and GluA1 (Ser-831) phosphorylation. Taken together, Sig-1R stimulation by SA4503 or fluvoxamine treatment increased hippocampal neurogenesis, which is closely associated with amelioration of depressive-like behaviors in CaMKIV null mice.

Sigma-1 receptor chaperones in neurodegenerative and psychiatric disorders.

INTRODUCTION: Sigma-1 receptors (Sig-1Rs) are molecular chaperones that reside mainly in the endoplasmic reticulum (ER) but exist also in the proximity of the plasma membrane. Sig-1Rs are highly expressed in the CNS and are involved in many cellular processes including cell differentiation, neuritogenesis, microglia activation, protein quality control, calcium-mediated ER stress and ion channel modulation. Disturbance in any of the above cellular processes can accelerate the progression of many neurological disorders; therefore, the Sig-1R has been implicated in several neurological diseases. AREAS COVERED: This review broadly covers the functions of Sig-1Rs including several neurodegenerative disorders in humans and drug addiction-associated neurological disturbance in the case of HIV infection. We discuss how several Sig-1R ligands could be utilized in therapeutic approaches to treat those disorders. EXPERT OPINION: Emerging understanding of the cellular functions of this unique transmembrane chaperone may lead to the use of new agents or broaden the use of certain available ligands as therapeutic targets in those neurological disorders.

Overexpression of Sig1R is closely associated with tumor progression and poor outcome in patients with hilar cholangiocarcinoma.

Nonopioid Sigma1 receptor (Sig1R), which regulates various metabolism functions, has been implicated in cancers; yet, its role in hilar cholangiocarcinoma remains unclear. In the present study, we examined Sig1R expression in hilar cholangiocarcinoma (HC) tissues and explored its possible clinical values. Tissue microarray blocks containing 92 HC tissues and matched non-cancerous bile duct tissues were examined immunohistochemically for expression of Sig1R protein. Overexpression of Sig1R was found in 43 (46.7%) of the 92 primary tumor tissues. Overexpression of Sig1R was significantly associated with poor/undifferentiation (P = 0.011), tumor invasion (P = 0.001), lymph node metastasis (P = 0.047), and advanced disease stage (P = 0.024) of HC patients. Kaplan-Meier analysis showed that patients overexpressing Sig1R had an earlier recurrence and worse overall survival than those not overexpressing Sig1R. Cox regression analysis revealed that Sig1R was an independent factor to predict HC recurrence and prognosis of HC patients. Our results suggest that Sig1R is frequently activated in human HC tissue and overexpression of Sig1R might serve as a predictor for tumor recurrence and a prognostic biomarker for HC patients.

Sigma receptor ligand, (+)-pentazocine, suppresses inflammatory responses of retinal microglia.

PURPOSE: To evaluate the effects of the σ 1 receptor (σR1) agonist, (+)-pentazocine, on lipopolysaccharide (LPS)-induced inflammatory changes in retinal microglia cells. METHODS: Retinal microglia cells were isolated from Sprague-Dawley rat pups. Cells were treated with LPS with or without (+)-pentazocine and with or without the σR1 antagonist BD1063. Morphologic changes were assayed. Cell viability was assessed by using MTT assay. Supernatant levels of tumor necrosis factor α (TNF-α), interleukin 10, (IL-10), monocyte chemoattractant protein-1 (MCP-1), and nitric oxide (NO) were determined. Reactive oxygen species (ROS) formation was assayed, and levels of mitogen-activated protein kinases (MAPKs) were analyzed by using Western blot. RESULTS: The σR1 protein was expressed in retinal microglia. Incubation with LPS and/or (+)-pentazocine did not alter cell viability or σR1 protein levels. Incubation with LPS for 24 hours induced a marked change in microglial morphology and a significant increase in secreted levels of TNF-α, IL-10, MCP-1, and NO. Pretreatment with (+)-pentazocine inhibited the LPS-induced morphologic changes. Release of TNF-α, IL-10, MCP-1, and NO was reduced with (+)-pentazocine. Intracellular ROS formation was suppressed with (+)-pentazocine. Phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was reduced in the presence of (+)-pentazocine. The σR1 antagonist BD1063 blocked the (+)-pentazocine-mediated inhibition of LPS-induced morphologic changes. In addition, BD1063 treatment blocked (+)-pentazocine-mediated suppression of LPS-induced TNF-α, IL-10, MCP-1, NO, and intracellular ROS release. CONCLUSIONS: Treatment with (+)-pentazocine suppressed inflammatory responses of retinal microglia and inhibited LPS-induced activation of ERK/JNK MAPK. In neurodegenerative disease, (+)-pentazocine may exert neuroprotective effects through manipulation of microglia.

Accumulation of the sigma-1 receptor is common to neuronal nuclear inclusions in various neurodegenerative diseases.

The sigma-1 receptor (SIGMAR1) is now known to be one of the endoplasmic reticulum (ER) chaperones, which participate in the degradation of misfolded proteins in cells via the ER-related degradation machinery linked to the ubiquitin-proteasome pathway. Mutations of the SIGMAR1 gene are implicated in the pathogenesis of familial frontotemporal lobar degeneration and motor neuron disease. Involvement of ER dysfunction in the formation of inclusion bodies in various neurodegenerative diseases has also become evident. We performed immunohistochemical staining to clarify the localization of SIGMAR1 in the brains of patients with neurodegenerative disorders, including trans-activation response DNA protein 43 (TDP-43) proteinopathy, tauopathy, α-synucleinopathy, polyglutamine disease and intranuclear inclusion body disease (INIBD). Double-immunocytofluorescence and Western blot analyses of cultured cells were also performed to investigate the role of SIGMAR1 using a specific exportin 1 inhibitor, leptomycin B and an ER stress inducer, thapsigargin. SIGMAR1 was consistently shown to be co-localized with neuronal nuclear inclusions in TDP-43 proteinopathy, five polyglutamine diseases and INIBD, as well as in intranuclear Marinesco bodies in aged normal controls. Cytoplasmic inclusions in neurons and glial cells were unreactive for SIGMAR1. In cultured cells, immunocytofluorescent study showed that leptomycin B and thapsigargin were shown to sequester SIGMAR1 within the nucleus, acting together with p62. This finding was also supported by immunoblot analysis. These results indicate that SIGMAR1 might shuttle between the nucleus and the cytoplasm. Neurodegenerative diseases characterized by neuronal nuclear inclusions might utilize the ER-related degradation machinery as a common pathway for the degradation of aberrant proteins.

Altered expression level of Sigma1 receptor gene in human colorectal cancer.

Nonopioid Sigma1 receptor (Sig1R) influences numerous metabolism functions including regulation of ion channels, reaction on stress and response to growth signals. Due to this influence, Sigma1 receptor ligands show anti-proliferative and cytotoxic action on tumor cells. Additionally its increased level is observed in some types of tumors. Colorectal cancer is one of the most common cancers worldwide and its clinical development is well described. The aim of the study was evaluation of Sigma1 receptor mRNA expression level in human colorectal cancer and colorectal cancer liver metastases at different stages of tumor development. The mRNA was isolated from 30 patients: 18 with colorectal cancer (CRC) and 12 with colorectal cancer liver metastases (CRCLM). The cDNA of Sig1R gene was amplified by polymerase chain reaction using specific primers. The level of Sig1R mRNA expression was determined by measurement of optical density. Sig1R expression level was increased in CRC and CRCLM. The highest level of Sig1R mRNA was observed in UICC stage III. We also showed significant interactions of UICC stage and tumor localization with Sig1R expression level. There were no interactions between UICC stage and age of patients, although we observed significantly decreased level of Sig1R mRNA in older patients. Clinical advancement stage, localization of tumor and age of patients seems to be an important factors influencing Sigma1 receptor expression level. It is probably due to double nature of Sig1R action - in certain conditions it could act pro- or antiapoptotic. This action might depend on Sig1R activity resulting from its expression level.

Development of the sigma-1 receptor in C-terminals of motoneurons and colocalization with the N,N'-dimethyltryptamine forming enzyme, indole-N-methyl transferase.

The function of the sigma-1 receptor (S1R) has been linked to modulating the activities of ion channels and G-protein-coupled receptors (GPCR). In the CNS, the S1R is expressed ubiquitously but is enriched in mouse motoneurons (MN), where it is localized to subsurface cisternae of cholinergic postsynaptic densities, also known as C-terminals. We found that S1R is enriched in mouse spinal MN at late stages of embryonic development when it is first visualized in the endoplasmic reticulum. S1Rs appear to concentrate at C-terminals of mouse MN only on the second week of postnatal development. We found that indole-N-methyl transferase (INMT), an enzyme that converts tryptamine into the sigma-1 ligand dimethyltryptamine (DMT), is also localized to postsynaptic sites of C-terminals in close proximity to the S1R. This close association of INMT and S1Rs suggest that DMT is synthesized locally to effectively activate S1R in MN.

Expression of sigma receptor 1 mRNA and protein in rat retina.

Sigma receptor (sigmaR), known as a unique nonopiate, nonphencyclidine brain receptor, can bind diverse classes of psychotropic drugs, neurosteroids and other synthetic compounds, such as (+)pentazocine, etc. Two types of sigmaRs have been identified: sigmaR1 and sigmaR2. In this work, we examined the expression of sigmaR1 in rat retina by reverse transcription-polymerase chain reactive (RT-PCR) analysis and immunofluorescence double labeling. RT-PCR analysis showed that sigmaR1 mRNA was present in rat retina. Furthermore, labeling for sigmaR1 was diffusely distributed in the outer and inner plexiform layers. The sigmaR1-immunoreactivity (IR) was also observed in many cells in the inner nuclear layer and the ganglion cell layer. In the outer retina sigmaR1 was expressed in all horizontal cells labeled by calbindin. In contrast, no sigmaR1-IR was detected in several subtypes of bipolar cells, including rod-dominant ON-type bipolar cells, types 2, 3, 5 and 8 bipolar cells, labeled by protein kinase C (PKC), recoverin and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4) respectively. In the inner retina, most of GABAergic amacrine cells, including dopaminergic and cholinergic ones, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) respectively, expressed sigmaR1. Some glycinergic amacrine cells were also labeled by sigmaR1, but glycinergic AII amacrine cells were not labeled. In addition, sigmaR1-IR was seen in almost all somata of the ganglion cells retrogradely labeled by fluorogold. These results suggest that sigmaR1 may have neuromodulatory and neuroprotective roles in the retina.

Regulation of sigma-1 receptors and endoplasmic reticulum chaperones in the brain of methamphetamine self-administering rats.

sigma-1 Receptors are endoplasmic reticulum (ER) chaperones that are implicated in the neuroplasticity associated with psychostimulant abuse. We immunocytochemically examined the distribution of sigma-1 receptors in the brain of drug-naive rats and then examined the dynamics of sigma-1 receptors and other ER chaperones in specific brain subregions of rats that self-administered methamphetamine, received methamphetamine passively, or received only saline injections. sigma-1 Receptors were found to be expressed in moderate to high levels in the olfactory bulb, striatum, nucleus accumbens shell, olfactory tubercle, amygdala, hippocampus, red nucleus, ventral tegmental area, substantia nigra, and locus ceruleus. Methamphetamine, whether self-administered or passively received, significantly elevated ER chaperones including the sigma-1 receptor, BiP, and calreticulin in the ventral tegmental area and substantia nigra. In the olfactory bulb, however, only the sigma-1 receptor chaperone was increased, and this increase occurred only in rats that actively self-administered methamphetamine. Consistent with an increase in sigma-1 receptors, extracellular signal-regulated kinase was found to be activated and protein kinase A attenuated in the olfactory bulb of methamphetamine self-administering rats. sigma-1 Receptors in the olfactory bulb were found to be colocalized with dopamine D1 receptors. These results indicate that methamphetamine induces ER stress in the ventral tegmental area and substantia nigra in rats whether the drug is received actively or passively. However, the changes seen only in rats that actively self-administered methamphetamine suggest that D1 and sigma-1 receptors in the olfactory bulb might play an important role in the motivational conditioning/learning aspects of methamphetamine self-administration in the rat.

Sigma-2 receptor expression in bovine papillomavirus-associated urinary bladder tumours.

The expression of sigma-2 receptors was investigated in nine urothelial tumours of the urinary bladder of cattle. Each tumour was associated with the presence of DNA of bovine papillomavirus type-2 (BPV-2) and expression of the E5 viral oncoprotein. Five tumours were classified as low-grade carcinoma on the basis of morphological criteria and calculation of mean nuclear area (MNA) and mean nuclear perimeter (MNP). Four tumours were classified as high-grade carcinoma. Sigma-2 receptors were overexpressed in both types of carcinoma. In control normal bovine bladder tissue the density of receptors (expressed as the B(max)) was 0.37 pmol/mg of protein. Low-grade carcinomas had a mean B(max) of 1.37+/-0.32 pmol/mg of protein (range 1.03-1.86) and in high-grade carcinomas the mean B(max) was 10.9+/-2.8 pmol/mg of protein (range 8.2-14). The difference in B(max) between low- and high-grade carcinomas was statistically significant (P=0.0001).

In vitro and ex vivo characterization of sigma-1 and sigma-2 receptors: agonists and antagonists in biological assays.

Methods for addressing sigma receptor affinity and activity have been explored and although several protocols have been employed, only few procedures resulted reliable. Sigma-1 receptor affinity protocol using guinea-pig brain and (+)-[(3)H]-pentazocine and sigma-2 receptor affinity protocol employing rat liver and [(3)H]-DTG are usually reported by authors as standard procedures. By contrast, the intrinsic activity evaluation of sigma ligands has been performed in several manners: tumor cell lines, isolated organ bath, in vivo animal model. The last is not considered in the present paper because this method studied the physiological role of sigma receptors. The studies carried out in tumor cell lines involved the role of sigma receptors in tumors progression while, although isolated organ bath experiment employed physiological samples, the pharmacokinetic properties of ligands, a strictly requirement for the in vivo assays, did not affect the pharmacodynamic properties of tested compounds. The advances in the above mentioned assays have been reported.

Intrathecal injection of the sigma(1) receptor antagonist BD1047 blocks both mechanical allodynia and increases in spinal NR1 expression during the induction phase of rodent neuropathic pain.

BACKGROUND: Selective blockade of spinal sigma(1) receptors (Sig-1R) suppresses nociceptive behaviors in the mouse formalin test. The current study was designed to verify whether intrathecal Sig-1R antagonists can also suppress chronic neuropathic pain. METHODS: Neuropathic pain was produced by chronic constriction injury (CCI) of the right sciatic nerve in rats. The Sig-1R antagonist BD1047 was administered intrathecally twice daily from postoperative days 0 to 5 (induction phase of neuropathic pain) or from days 15 to 20 (maintenance phase). Western blot and immunohistochemistry were performed to determine changes in Sig-1R expression and to examine the effect of BD1047 on N-methyl-D-aspartate receptor subunit 1 expression and phosphorylation in spinal cord dorsal horn from neuropathic rats. RESULTS: BD1047 administered on postoperative days 0-5 significantly attenuated CCI-induced mechanical allodynia, but not thermal hyperalgesia, and this suppression was blocked by intrathecal administration of the Sig-1R agonist PRE084. In contrast, BD1047 treatment during the maintenance phase of neuropathic pain had no effect on mechanical allodynia. Sig-1R expression significantly increased in the ipsilateral spinal cord dorsal horn from days 1 to 3 after CCI. Importantly, BD1047 (30 nmol) administered intrathecally during the induction, but not the maintenance phase, blocked the CCI-induced increase in N-methyl-D-aspartate receptor subunit 1 expression and phosphorylation. CONCLUSIONS: These results demonstrate that spinal Sig-1Rs play a critical role in both the induction of mechanical allodynia and the activation of spinal N-methyl-d-aspartate receptors in CCI rats and suggest a potential therapeutic role for the use of Sig-1R antagonists in the clinical management of neuropathic pain.