Sigma-1 receptor and seizures

Novel Emopamil-Binding Protein Inhibitors for Treating Multiple Sclerosis

Provided herein are novel Emopamil-Binding Protein (EBP) inhibitors, pharmaceutical compositions, use of such compounds in treating multiple sclerosis, and processes for preparing such compounds.

Exploring the Relationship Between Antipsychotic Drug Target Genes and Epilepsy: Evidence From Food and Drug Administration Adverse Event Reporting System Database and Mendelian Randomization

BACKGROUND

The effect of antipsychotic drugs on epilepsy is controversial, and we performed Food and Drug Administration Adverse Event Reporting System (FAERS) data mining and Mendelian Randomization (MR) analyses to clarify the effects of target genes on epilepsy.

METHOD

We explored antipsychotic-induced epilepsy AE signals in FAERS. Gene expression was obtained from the eQTLGen consortium and GTEx project. Epilepsy data were obtained from FinnGen and the International League Against Epilepsy (ILAE). MR, Summary-data-based Mendelian Randomization (SMR), and colocalization analysis were sequentially performed, and meta-analysis was performed on genes with significant expression in MR or SMR to assess the causal relationship between them and epilepsy.

RESULT

Through FAERS database mining, 63 antipsychotics reported 5121 adverse events in epilepsy. MR identified potential causal associations of 14 drug target genes for epilepsy and its subtypes. MCHR1 and SIGMAR1 were still significant for epilepsy after meta-analysis with no evidence of heterogeneity or pleiotropy. SMR showed that DRD4 and ADRA1D were strongly associated with epilepsy or its subtypes however, neither gene passed the HEIDI test.

CONCLUSION

Our study indicates that antipsychotic drugs are associated with a high incidence of epilepsy-related AEs. MR demonstrated a causal relationship between drug targets and epilepsy. Providing new insights for managing epilepsy patients with psychiatric disorders.

Berberine ameliorates seizure activity and cardiac dysfunction in pentylenetetrazol-kindling seizures in rats: Modulation of sigma1 receptor, Akt/eNOS signaling, and ferroptosis

Seizures can lead to cardiac dysfunction. Multiple pathways contribute to this phenomenon, of which the chaperone sigma-1 receptor (S1R) signaling represents a promising nexus between the abnormalities seen in both epilepsy and ensuing cardiac complications. The study explored the potential of Berberine (BER), a promising S1R agonist, in treating epilepsy and associated cardiac abnormalities in a pentylenetetrazol (PTZ) kindling rat model of epilepsy. Male Wistar albino rats received PTZ (35 mg/kg) every other day alone, with BER, with phenytoin (PHT), with both BER and PHT and with both BER and an S1R blocker (NE-100) over 27 days. BER decreased seizure severity and improved hemodynamic parameters. Histopathological abnormalities were more pronounced in the PTZ, and blocker group than in other groups, in heart tissue. In cardiac tissue, BER enhanced the AKT/eNOS signaling pathway and mitigated ferroptosis by boosting the cystine/glutamate transporter/Glutathione/Glutathione Peroxidase 4 (XCT/GSH/GPX4) system and ferritin heavy chain-1 (FTH-1) expression, while reducing iron and Transferrin receptor protein 1 (TFR1) levels. Such effects were largely negated by NE-100 pretreatment. In conclusion, BER shows protective effects on cardiac dysfunction induced by the PTZ kindling model by acting as an S1R agonist and influencing the AKT/eNOS signaling pathway and ferroptosis.

Sigma-1 receptor activation produces faster antidepressant-like effect through enhancement of hippocampal neuroplasticity: Focus on sigma-1-5-HT1A heteroreceptor complex

The sigma-1 receptor (S1R) has garnered significant attention as a potential target for rapid-onset antidepressant-like effects, particularly owing to its ability to swiftly stimulate serotonergic neurons in the dorsal raphe nucleus (DRN). However, the precise mechanisms underlying its regulatory effects remain unclear. Therefore, this study aims to examine the interaction between SA-4503 (a selective S1R agonist) and 8-OH-DPAT (a serotonin1A (5-HT1A) receptor agonist) in mice with depressive-like behavior induced by chronic restraint stress (CRS). Preliminary studies were conducted to explore the potential mechanisms underlying the accelerated antidepressant-like effects resulting from the combined activation of S1R and 5-HT1A receptors. The results showed that the coadministration of SA4503 (1.0 mg/kg, orally) and 8-OH-DPAT (0.3 mg/kg, i. g.) produced antidepressant-like effects. However, the doses of 8-OH-DPAT used in this study did not exhibit intrinsic antidepressant-like activity in this model. Moreover, using an in-situ proximity ligation assay provided the first evidence of S1R-5-HT1A heteroreceptor complexes in the midbrain DRN and dentate gyrus (DG) of the forebrain in mice. The formation of these heterocomplexes was influenced by pharmacological agents and was closely associated with depressive-like behavior development in mice. Mechanistic analysis revealed that the combined activation of S1R and 5-HT1A receptors synergistically enhanced neurogenesis and plasticity in the dorsal DG region of the hippocampus in mice subjected to CRS. These findings significantly advance our understanding of S1R-mediated neuroplasticity, suggesting potential therapeutic strategies for developing rapid-acting antidepressants.

Sigma 1 Receptor and Its Pivotal Role in Neurological Disorders

Sigma 1 receptor (S1R) is a multifunctional, ligand-activated protein located in the membranes of the endoplasmic reticulum (ER). It mediates a variety of neurological disorders, including epilepsy, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease. The wide neuroprotective effects of S1R agonists are achieved by a variety of pro-survival and antiapoptotic S1R-mediated signaling functions. Nonetheless, relatively little is known about the specific molecular mechanisms underlying S1R activity. Many studies on S1R protein have highlighted the importance of maintaining normal cellular homeostasis through its control of calcium and lipid exchange between the ER and mitochondria, ER-stress response, and many other mechanisms. In this review, we will discuss S1R different cellular localization and explain S1R-associated biological activity, such as its localization in the ER-plasma membrane and Mitochondrion-Associated ER Membrane interfaces. While outlining the cellular mechanisms and important binding partners involved in these processes, we also explained how the dysregulation of these pathways contributes to neurodegenerative disorders.

Exploring the Role of Sigma Receptors in the Treatment of Cancer: A Narrative Review

This study investigated the association of sigma receptors (SRs) and their selective ligands (because the molecular characteristics of the same SRs, particularly sigma-2 receptor {S2R}, are not completely clear) in carcinogenesis, their potential use as antitumor agents, and their great utility in tumor imaging. The ion channels and transporters enhance the cell's ability to adapt to the metabolic conditions encountered in the tumor tissue. The high expression of SRs in the proliferating cells compared with those at rest indicates that this is a significant clinical biomarker for determining the proliferative status of solid tumors using functional PET imaging techniques. The association of SRs in the pathophysiology of cancer cells is a result of the high concentration of S1R and S2R binding sites observed in various tumor cell lines and tissues. It would also be remarkable to determine if SRs are involved in metastasis and other metastatic cell behaviors such as adhesion, secretion, motility, and penetration. An absolute challenge for research in this field is to develop an integrated model that describes the molecular mechanisms of sigma receptors, incorporating their known biological and pathophysiological roles.

Preclinical efficacy profiles of the sigma-1 modulator E1R and of fenfluramine in two chronic mouse epilepsy models

OBJECTIVE

Given its key homeostatic role affecting mitochondria, ionotropic and metabotropic receptors, and voltage-gated ion channels, sigma-1 receptor (Sig1R) represents an interesting target for epilepsy management. Antiseizure effects of the positive allosteric modulator E1R have already been reported in acute seizure models. Although modulation of serotonergic neurotransmission is considered the main mechanism of action of fenfluramine, its interaction with Sig1R may be of additional relevance.

METHODS

To further explore the potential of Sig1R as a target, we assessed the efficacy and tolerability of E1R and fenfluramine in two chronic mouse models, including an amygdala kindling paradigm and the intrahippocampal kainate model. The relative contribution of the interaction with Sig1R was analyzed using combination experiments with the Sig1R antagonist NE-100.

RESULTS

Whereas E1R exerted pronounced dose-dependent antiseizure effects at well-tolerated doses in fully kindled mice, only limited effects were observed in response to fenfluramine, without a clear dose dependency. In the intrahippocampal kainate model, E1R failed to influence electrographic seizure activity. In contrast, fenfluramine significantly reduced the frequency of electrographic seizure events and their cumulative duration. Pretreatment with NE-100 reduced the effects of E1R and fenfluramine in the kindling model. Surprisingly, pre-exposure to NE-100 in the intrahippocampal kainate model rather enhanced and prolonged fenfluramine's antiseizure effects.

SIGNIFICANCE

In conclusion, the kindling data further support Sig1R as an interesting target for novel antiseizure medications. However, it is necessary to further explore the preclinical profile of E1R in chronic epilepsy models with spontaneous seizures. Despite the rather limited effects in the kindling paradigm, the findings from the intrahippocampal kainate model suggest that it is of interest to further assess a possible broad-spectrum potential of fenfluramine.

The classical D1 dopamine receptor antagonist SCH23390 is a functional sigma-1 receptor allosteric modulator

SCH23390 is a widely used D1 dopamine receptor (D1R) antagonist that also elicits some D1R-independent effects. We previously found that the benzazepine, SKF83959, an analog of SCH23390, produces positive allosteric modulation of the Sigma-1 receptor (Sig1R). SCH23390 does not bind to the orthodoxic site of Sig1R but enhances the binding of 3H (+)-pentazocine to Sig1R. In this study, we investigated whether SCH23390 functions as an allosteric modulator of Sig1R. We detected increased Sig1R dissociation from binding immunoglobulin protein (BiP) and translocation of Sig1R to the plasma membrane in response to SCH23390 in transfected HEK293T and SH-SY5Y cells, respectively. Activation of Sig1R by SCH23390 was further confirmed by inhibition of GSK3β activity in a time- and dose-dependent manner; this effect was blocked by pretreatment with the Sig1R antagonist, BD1047, and by knockdown of Sig1R. SCH23390 also inhibited GSK3β in wild-type mice but not in Sig1R knockout mice. Finally, we showed that SCH23390 allosterically modulated the effect of the Sig1R agonist SKF10047 on inhibition of GSK3β. This positive allosteric effect of SCH23390 was further confirmed via promotion of neuronal protection afforded by SKF10047 in primary cortical neurons challenged with MPP+. These results provide the first evidence that SCH23390 elicits functional allosteric modulation of Sig1R. Our findings not only reveal novel pharmacological effects of SCH23390 but also indicate a potential mechanism for SCH23390-mediated D1R-independent effects. Therefore, attention should be paid to these Sig1R-mediated effects when explaining pharmacological responses to SCH23390.

Astrocyte-specific activation of sigma-1 receptors in mPFC mediates the faster onset antidepressant effect by inhibiting NF-κB-induced neuroinflammation

Major depressive disorder (MDD) is a global health burden characterized by persistent low mood, deprivation of pleasure, recurrent thoughts of death, and physical and cognitive deficits. The current understanding of the pathophysiology of MDD is lacking, resulting in few rapid and effective antidepressant therapies. Recent studies have pointed to the sigma-1 (σ-1) receptor as a potential rapid antidepressant target; σ-1 agonists have shown promise in a variety of preclinical depression models. Hypidone hydrochloride (YL-0919), an independently developed antidepressant by our institute with faster onset of action and low rate of side effects, has recently emerged as a highly selective σ-1 receptor agonist; however, its underlying astrocyte-specific mechanism is unknown. In this study, we investigated the effect of YL-0919 treatment on gene expression in the prefrontal cortex of depressive-like mice by single-cell RNA sequencing. Furthermore, we knocked down σ-1 receptors on astrocytes in the medial prefrontal cortex of mice to explore the effects of YL-0919 on depressive-like behavior and neuroinflammation in mice. Our results demonstrated that astrocyte-specific knockdown of σ-1 receptor resulted in depressive-like behavior in mice, which was reversed by YL-0919 administration. In addition, astrocytic σ-1 receptor deficiency led to activation of the NF-κB inflammatory pathway, and crosstalk between reactive astrocytes and activated microglia amplified neuroinflammation, exacerbating stress-induced neuronal apoptosis. Furthermore, the depressive-like behavior induced by astrocyte-specific knockdown of the σ-1 receptor was improved by a selective NF-κB inhibitor, JSH-23, in mice. Our study not only reaffirms the σ-1 receptor as a key target of the faster antidepressant effect of YL-0919, but also contributes to the development of astrocytic σ-1 receptor-based novel drugs.

Current landscape of fecal microbiota transplantation in treating depression

Depression, projected to be the predominant contributor to the global disease burden, is a complex condition with diverse symptoms including mood disturbances and cognitive impairments. Traditional treatments such as medication and psychotherapy often fall short, prompting the pursuit of alternative interventions. Recent research has highlighted the significant role of gut microbiota in mental health, influencing emotional and neural regulation. Fecal microbiota transplantation (FMT), the infusion of fecal matter from a healthy donor into the gut of a patient, emerges as a promising strategy to ameliorate depressive symptoms by restoring gut microbial balance. The microbial-gut-brain (MGB) axis represents a critical pathway through which to potentially rectify dysbiosis and modulate neuropsychiatric outcomes. Preclinical studies reveal that FMT can enhance neurochemicals and reduce inflammatory markers, thereby alleviating depressive behaviors. Moreover, FMT has shown promise in clinical settings, improving gastrointestinal symptoms and overall quality of life in patients with depression. The review highlights the role of the gut-brain axis in depression and the need for further research to validate the long-term safety and efficacy of FMT, identify specific therapeutic microbial strains, and develop targeted microbial modulation strategies. Advancing our understanding of FMT could revolutionize depression treatment, shifting the paradigm toward microbiome-targeting therapies.

Navigating the future of retinitis pigmentosa treatments: A comprehensive analysis of therapeutic approaches in rd10 mice

Retinitis pigmentosa (RP) is a degenerative disease, caused by genetic mutations that lead to a loss in photoreceptors. For research on RP, rd10 mice, which carry mutations in the phosphodiesterase (PDE) gene, exhibit degenerative patterns comparable to those of patients with RP, making them an ideal model for investigating potential treatments. Although numerous studies have reported the potential of biochemical drugs, gene correction, and stem cell transplantation in decelerating rd10 retinal degeneration, a comprehensive review of these studies has yet to be conducted. Therefore, here, a comparative analysis of rd10 mouse treatment research over the past decade was performed. Our findings suggest that biochemical drugs capable of inhibiting the inflammatory response may be promising therapeutics. Additionally, significant progress has been made in the field of gene therapy; nevertheless, challenges such as strict delivery requirements, bystander editing, and off-target effects still need to be resolved. Nevertheless, secretory function is the only unequivocal protective effect of stem cell transplantation. In summary, this review presents a comprehensive analysis and synthesis of the treatment approaches employing rd10 mice as experimental subjects, describing a clear pathway for future RP treatment research and identifies potential clinical interventions.

The Protective Role of Mitochondria-Associated Endoplasmic Reticulum Membrane (MAM) Protein Sigma-1 Receptor in Regulating Endothelial Inflammation and Permeability Associated with Acute Lung Injury

Earlier studies from our lab identified endoplasmic reticulum (ER) chaperone BiP/GRP78, an important component of MAM, to be a novel determinant of endothelial cell (EC) dysfunction associated with acute lung injury (ALI). Sigma1R (Sig1R) is another unique ER receptor chaperone that has been identified to associate with BiP/GRP78 at the MAM and is known to be a pluripotent modulator of cellular homeostasis. However, it is unclear if Sig1R also plays a role in regulating the EC inflammation and permeability associated with ALI. Our data using human pulmonary artery endothelial cells (HPAECs) showed that siRNA-mediated knockdown of Sig1R potentiated LPS-induced the expression of proinflammatory molecules ICAM-1, VCAM-1 and IL-8. Consistent with this, Sig1R agonist, PRE-084, known to activate Sig1R by inducing its dissociation from BiP/GRP78, blunted the above response. Notably, PRE-084 failed to blunt LPS-induced inflammatory responses in Sig1R-depleted cells, confirming that the effect of PRE-084 is driven by Sig1R. Furthermore, Sig1R antagonist, NE-100, known to inactivate Sig1R by blocking its dissociation from BiP/GRP78, failed to block LPS-induced inflammatory responses, establishing that dissociation from BiP/GRP78 is required for Sig1R to exert its anti-inflammatory action. Unlike Sig1R, the siRNA-mediated knockdown or Subtilase AB-mediated inactivation of BiP/GRP78 protected against LPS-induced EC inflammation. Interestingly, the protective effect of BiP/GRP78 knockdown or inactivation was abolished in cells that were depleted of Sig1R, confirming that BiP/GRP78 knockdown/inactivation-mediated suppression of EC inflammation is mediated via Sig1R. In view of these findings, we determined the in vivo relevance of Sig1R in a mouse model of sepsis-induced ALI. The intraperitoneal injection of PRE-084 mitigated sepsis-induced ALI, as evidenced by a decrease in ICAM-1, IL-6 levels, lung PMN infiltration, and lung vascular leakage. Together, these data evidence a protective role of Sig1R against endothelial dysfunction associated with ALI and identify it as a viable target in terms of controlling ALI in sepsis.

The Intriguing Sigma-1 and Sigma-2 Receptors and Their Potential Therapeutic Roles 2.0

For some time now, the research on sigma receptors has been at a high level of maturity but, despite everything that has already been achieved, further work in this field still holds huge appeal, with vast possibilities for original discoveries [...].

The Psychedelic N,N-Dipropyltryptamine Prevents Seizures in a Mouse Model of Fragile X Syndrome via a Mechanism that Appears Independent of Serotonin and Sigma1 Receptors

The serotonergic psychedelic psilocybin shows efficacy in treating neuropsychiatric disorders, though the mechanism(s) underlying its therapeutic effects remain unclear. We show that a similar psychedelic tryptamine, N,N-dipropyltryptamine (DPT), completely prevents audiogenic seizures (AGS) in an Fmr1 knockout mouse model of fragile X syndrome at a 10 mg/kg dose but not at lower doses (3 or 5.6 mg/kg). Despite showing in vitro that DPT is a serotonin 5-HT2A, 5-HT1B, and 5-HT1A receptor agonist (with that rank order of functional potency, determined with TRUPATH Gα/βγ biosensors), pretreatment with selective inhibitors of 5-HT2A/2C, 5-HT1B, or 5-HT1A receptors did not block DPT's antiepileptic effects; a pan-serotonin receptor antagonist was also ineffective. Because 5-HT1A receptor activation blocks AGS in Fmr1 knockout mice, we performed a dose-response experiment to evaluate DPT's engagement of 5-HT1A receptors in vivo. DPT elicited 5-HT1A-dependent effects only at doses greater than 10 mg/kg, further supporting that DPT's antiepileptic effects were not 5-HT1A-mediated. We also observed that the selective sigma1 receptor antagonist, NE-100, did not impact DPT's antiepileptic effects, suggesting DPT engagement of sigma1 receptors was not a crucial mechanism. Separately, we observed that DPT and NE-100 at high doses caused convulsions on their own that were qualitatively distinct from AGS. In conclusion, DPT dose-dependently blocked AGS in Fmr1 knockout mice, but neither serotonin nor sigma1 receptor antagonists prevented this action. Thus, DPT might have neurotherapeutic effects independent of its serotonergic psychedelic properties. However, DPT also caused seizures at high doses, showing that DPT has complex dose-dependent in vivo polypharmacology.