Neuronal Sigma-1 Receptors: Signaling Functions and Protective Roles in Neurodegenerative Diseases

Sphingosylphosphorylcholine induces itch via activation of TRPM3 and TRPA1 in mice

Itch is a prevalent symptom in atopic dermatitis (AD), often leading to a strong urge to scratch. Elevated levels of sphingosylphosphorylcholine (SPC) are found in the stratum corneum of AD patients, and while SPC is known to induce itch, its molecular targets are not well understood. This study aims to identify the signaling pathway of SPC-induced itch under AD conditions. We demonstrate that SPC specifically activates the Transient Receptor Potential Melastatin 3 (TRPM3) channel in sensory neurons. In HEK293T cells expressing TRPM3, SPC treatment caused a significant increase in intracellular calcium, which was inhibited by TRPM3 antagonists. Among various TRP channels tested, TRPM3 exhibited the highest reactivity to SPC, followed by TRPA1. Molecular docking analysis also supported interactions between SPC and both TRPM3 and TRPA1. In an AD mouse model, SPC-induced responses were dependent on TRPM3 and TRPA1, and the expression of these channels increased in dorsal root ganglion neurons. SPC-induced scratching behaviors were significantly reduced by TRPM3 and TRPA1 antagonists, with TRPM3 playing a critical role in spontaneous scratching. This study identifies TRPM3 and TRPA1 as key mediators of SPC-induced itch, providing potential therapeutic targets for treating itch in AD patients.

The evolution of N, N-Dimethyltryptamine: from metabolic pathways to brain connectivity

RATIONALE

N, N-Dimethyltryptamine (DMT), a potent serotonergic psychedelic, bridges ancient wisdom and modern science. The mechanisms underlying its powerful psychedelic effects and out-of-body experiences continue to intrigue scientists. The functional role of DMT remains ambiguous. This paper explores the endogenous presence of DMT in the human body and its diverse neuroregulatory functions, which influence hierarchical brain connectivity, and the mechanisms driving its psychedelic effects.

OBJECTIVE

This paper aims to analyze DMT-receptor binding, its effects on neuronal modulation, brain oscillations, and connectivity, and its influence on hallucinations, out-of-body experiences, and cognitive functions.

RESULTS

DMT administration induces significant changes in brain wave dynamics, including reduced alpha power, increased delta power, and heightened Lempel-Ziv complexity, reflecting enhanced neural signal diversity. Functional neuroimaging studies reveal that DMT enhances global functional connectivity (GFC), particularly in transmodal association cortices such as the salience network, frontoparietal network, and default mode network, correlating with ego dissolution. The receptor density-dependent effects of DMT were mapped to brain regions rich in serotonin 5-HT2A receptors, supporting its role in modulating consciousness and neuroplasticity.

CONCLUSION

This integrated analysis provides insights into the profound effects of DMT on human cognition, and consciousness, and its role in enhancing natural well-being. As we uncover the endogenous functions of DMT, it becomes clear that the study of its biology reveals a complex interplay between brain chemistry and consciousness.

SIGMAR1 screened by a GPCR-related classifier regulates endoplasmic reticulum stress in bladder cancer

BACKGROUND

Bladder cancer (BC) is one of the most common malignancies worldwide. G protein-coupled receptors (GPCRs) are a large family of transmembrane proteins that are increasingly recognised as key players in cancer biology, affecting cell signalling and the tumour microenvironment. The sigma-1 receptor (SIGMAR1), although not a classical GPCR, has similar functions and is associated with the regulation of ER stress. However, its specific role and mechanism in bladder cancer are still unclear.

METHOD

The data sets pertaining to batch sequencing, single-cell RNA sequencing (scRNA-seq), immunotherapy response and clinical pathological characteristics were obtained from the public database. Thereafter, multiple algorithms were employed for the screening of GPCRs and immune cells related to the prognosis of BC. A GPCR-tumour microenvironment (TME) classifier was constructed and validated using different queues and multi-omics methods. The key biological pathways between GPCR-TME subgroups were identified through the utilisation of methodologies such as Gene Set Enrichment Analysis (GSEA), Weighted Gene Co-expression Network Analysis (WGCNA), and Tumour Immunophenotype Tracking (TIP). The expression of SIGMAR1 in BC cell lines and tissue samples was validated by western blotting. The Gene Ontology (GO) and GSEA were employed for biological process enrichment analysis. The biological role of SIGMAR1 in BC was investigated through functional experiments and subcutaneous tumour-bearing experiments in nude mice. The relationship between SIGMAR1 and immune cell infiltration was explored using the CIBERSORT method.

RESULTS

A total of 15 types of GPCR and 5 types of immune cells were identified and established as a GPCR-TME classifier. Patients in the GPCR-low + TME-high group exhibited the most favourable prognosis, whereas patients in the GPCR-high + TME-low group demonstrated the least favourable prognosis. The scRNA-seq results revealed an increase in GPCR expression in CD8 + T cells, endothelial cells, and NK cells. GPCR-TME was significantly correlated with overall survival (OS) in BC patients and outperformed a range of clinical parameters, making it an independent risk factor affecting the prognosis of BC patients. In comparison to normal tissues, SIGMAR1 was markedly expressed in BC tissues, and was associated with a poor prognosis. Functional experiments demonstrated that SIGMAR1 deficiency impeded the invasive capacity of cancer cells and restrained cellular proliferation. Moreover, in vivo experiments corroborated that SIGMAR1 deficiency curtailed the growth of xenografts in nude mice. Western blotting analysis revealed that SIGMAR1 silencing intensified endoplasmic reticulum (ER) stress in BC cells and promoted cell apoptosis. Additionally, the expression level of SIGMAR1 was correlated with the level of immune cell infiltration and immune-related functions.

CONCLUSION

The construction of a BC-related GPCR-TME classifier enabled the effective prediction of the OS of BC patients and the identification of SIGMAR1, a key factor regulating ER stress in BC. The knockout of SIGMAR1 can destroy its protective effect on ER stress, enhance apoptosis of BC cells, and facilitate further investigation of novel treatment strategies for cancer therapy.

Mutated sigma-1R disrupts cell homeostasis in dHMN patient cells

Hereditary-Motor-Neuropathies (dHMNs) are clinically and genetically heterogeneous neurological disorders characterized by degeneration of peripheral motoneurons. We previously identified two sigma-1 receptor (Sigma-1R) variants (p.E138Q; p.E150K) in dHMN Italian patients that behave as "loss-of-function" mutations in neuroblastoma cell lines. Here, we characterize the functional effects of Sigma-1R mutation in primary fibroblasts from homozygous patients bearing the E150K mutation, and matched controls, by performing biochemical, gene expression, immunofluorescence and Ca2+ imaging analysis. Our results show that Sigma-1R expression and distribution is significantly altered in patient fibroblasts. Moreover, patient cells present a general derangement of cell homeostasis as revealed by impairment of global Ca2+ dynamics, disorganization of the ER-mitochondria tethers, enhancement of the autophago-lysosomal pathway and blunting of mitochondrial aerobic metabolism compared to controls. These findings highlight the crucial role of Sigma-1R in the maintenance of cell and protein homeostasis, inter-organelle communication and intracellular Ca2+ signalling, supporting the notion that Sigma-1R is protective for motor neuron activity and its down-regulation and/or loss-of-function, as in the case of the E150K mutation, might play the key role in the neuronal degeneration in dHMN patients.

Unscrambling the cellular and molecular threads of Neuroplasticity: Insights into Alzheimer's disease pathogenesis

Alzheimer's disease (AD) is predominantly the most recurring and devastating neurological condition among the elderly population, characterized by the accumulation of amyloid-β (Aβ) and phosphorylated tau proteins, and is accompanied by progressive decline of learning and memory. Due to its complex and multifactorial etiology, a wide variety of therapeutic interventions have been developed. Despite constant advancements in the field, effective treatments that ameliorate the severity of Alzheimer's symptoms or cease their progression are still insufficient. Mounting evidence suggests that synaptic dysfunction could be an essential component of AD pathogenesis as synapse signaling is impaired in the aging brain, which contributes to synaptic decline. Therefore, improving neuroplasticity such as synaptic plasticity or neurogenesis could be a promising therapeutic approach for alleviating the effects of AD. This article reviews the cellular and molecular threads of neuroplasticity as well as targets that restore neuronal survival and plasticity to provide functional recoveries, including receptors, downstream signaling pathways, ion channels, transporters, enzymes, and neurotrophic factors.

Sigma-1 Receptor-Mediated High Mobility Group A1 Silencing Alleviates Endoplasmic Reticulum Stress-Induced Ovarian Granulosa Cell Apoptosis: An In Vitro Cell Experimental Study

OBJECTIVE

To investigate the role and underlying mechanism of sigma-1 receptor (SigmaR1)/high mobility group A1 (HMGA1) in the pathogenesis of diminished ovarian reserve (DOR).

DESIGN

In vitro cell experimental study.

SETTING

The Reproductive Medical Center, People's Hospital of Zhengzhou University.

SAMPLE

Serum, follicular fluid (FF), ovarian granulosa cells (GCs) and KGN cells.

METHODS

Samples were collected from DOR patients. Endoplasmic reticulum (ER) stress was induced in the GCs using thapsigargin (TG). mRNA and protein levels were determined using reverse transcription-quantitative polymerase chain reaction and western blotting. Cell apoptosis and viability were assessed using flow cytometry and cell counting kit-8. Protein colocalization was detected via immunofluorescence. Molecular interactions were validated using co-immunoprecipitation, luciferase reporter and chromatin immunoprecipitation assays.

MAIN OUTCOME MEASURES

Cell viability, cell apoptosis, SigmaR1, HMGA1 and ER stress-associated mRNA levels.

RESULTS

SigmaR1 expression decreased while HMGA1 expression increased in the serum, FF and GC samples of DOR patients and TG-treated GCs. TG induced ER stress and GC apoptosis; these effects were diminished by SigmaR1 overexpression or HMGA1 silencing. SigmaR1 expressed in the nuclear envelope forms a complex with gene repressor-specific protein 3 (SP3) and histone deacetylase (HDAC)1/2/3; however, TG reduced SigmaR1 in GCs and blocked the complex formation. HMGA1, a transcriptional target of SP3, was negatively modulated by the SigmaR1/SP3 complex. HMGA1 overexpression abolished the protective effect of SigmaR1 on TG-induced ER stress and GC apoptosis.

CONCLUSION

SigmaR1 formed a SmigaR1/SP3/HDAC complex to inhibit HMGA1 transcription, alleviating ER stress and GC apoptosis and providing new therapeutic targets for DOR.

Sigma-1 Receptor Specific Biological Functions, Protective Role, and Therapeutic Potential in Cardiovascular Diseases

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, and there is an urgent need for efficient and cost-effective treatments to decrease the risk of CVD. The sigma-1 receptor (S1R) plays a role in the development of cardiac hypertrophy, heart failure, ventricular remodeling, and various other cardiac diseases. Preclinical studies have shown that S1R activation has considerable beneficial effects on the cardiovascular system, and this knowledge might contribute to informing clinical trials associated with the prevention and treatment of CVDs. Therefore, the objective of this review was to investigate the mechanisms of S1R in CVD and how modulation of pathways contributes to cardiovascular protection to facilitate the development of new therapeutic agents targeting the cardiovascular system.

Targeting the sigma-1 receptor with pridopidine induces functional neurorestoration in spinal cord ischemia-reperfusion injury

Spinal cord ischemia reperfusion injury (IRI) occurs with an incidence of 1-32%, often leading to paraplegia with limited prevention options. Pridopidine (Prdpn), a highly selective sigma-1 receptor (Sig-1R) agonist, serves as a protein chaperone that is engaged in neuroplasticity and cellular defense. This research aimed to assess the neuroprotective properties of Prdpn in spinal cord IRI in rats and investigate the underlying mechanisms. Forty male Wistar albino rats were randomly allocated into 4 groups: control, sham, IRI, and IRI + Prdpn. Tarlov's test was used to examine behavioral performance, as well as withdrawal from agonizing stimuli and the placing/stepping reflex (SPR). Biochemical markers, including spinal malondialdehyde (MDA), AOPP, antioxidant GPX, TNF-α and IL-1β, and apoptotic caspase-3, were measured, along with BDNF, GDNF, and Sig-1R gene expression. Histopathological changes in spinal cord tissue were also evaluated. Spinal cord IRI significantly caused neurological deficits, evidenced by lower scores in Tarlov's test, withdrawal from agonizing stimuli, and SPR. Biochemically, spinal cord IRI led to decreased GPX and increased MDA, AOPP, TNF-α, IL-1β, caspase-3, and GDNF levels, along with downregulated BDNF and Sig-1R gene expression. Histopathologically, spinal cord IRI resulted in greater spinal neuronal degeneration, apoptosis, and demyelination. However, treatment with Prdpn significantly improved behavioral outcomes and partially reversed the biochemical and histopathological alterations. Prdpn improved spinal cord IRI-induced behavioral deficits through its antioxidant, anti-inflammatory, anti-apoptotic, and neurotrophic properties. It suggests promise as a potential treatment option to stop spinal cord IRI.

CNEURO-201, an Anti-amyloidogenic Agent and σ1-Receptor Agonist, Improves Cognition in the 3xTg Mouse Model of Alzheimer's Disease by Multiple Actions in the Pathology

The complexity of Alzheimer's disease (AD) pathophysiology represents a significant challenge in the development of effective therapeutic agents for its treatment. CNEURO-201 (CN, also Amylovis-201) is a novel pharmaceutical agent with dual activity as an anti-amyloid-β (Aβ) agent and σ1 receptor agonist. CN exhibits great efficacy at very low doses, delaying cognitive impairment and alleviating Aβ load in animal models of AD. However, CN functions on other remains related to this pathology remain to be investigated. The present study sought to evaluate the effects of CN treatment at a dosage of 0.1 mg kg-1 (p.o) over an eight-week period in the 3xTg-AD mouse model. In silico studies, as well as biochemical and immunofluorescence assays, were conducted on brain tissue to investigate the CN effects on acetylcholine metabolism, redox system, and glial cell activation-related biomarkers in brain regions that are relevant for memory. The results demonstrated that CN effectively rescues cognitive impairment of 3xTg-AD mice by influencing glial activity to reduce existing Aβ plaques but also modulating acetylcholine metabolism and the enzymatic response of proteins involved in the redox system. Our outcomes reinforced the potential of CN in treating AD by acting on multiple pathways altered in this disease.

Neuromodulating Alkaloids from Millipede Defensive Secretions

Millipedes have long been known to produce structurally diverse chemical defenses, including hydrogen cyanide, terpenoid alkaloids, and oxidized aromatics. Although the hydrogen cyanide and oxidized aromatic producing millipedes have been well studied, less than 10% of the terpenoid alkaloid producers have been chemically investigated. Several previous studies have shown that alkaloids disorient predators, but their biochemical target is currently unknown. Herein, we investigated the defensive secretions of a colobognath millipede, Ischnocybe plicata, and elucidated the constitution, absolute configuration, and conformation of four new highly oxidized terpenoid alkaloids, termed ischnocybines, using a range of analytical techniques. The ischnocybines are actively secreted from the defensive glands and were shown to disorient ants, a likely common predator. Evaluation of the ischnocybines in a panel of neuroreceptors revealed that ischnocybine A possesses potent (Ki 13.6 nM) and selective (100-fold) binding affinity for sigma-1, an orphan neuroreceptor, over sigma-2. These molecules represent the most complex alkaloids to be discovered from millipedes and provide the first potential insights into a biochemical target responsible for their defensive properties.

N, N-dimethyltryptamine (DMT) in rodent brain: Concentrations, distribution, and recent pharmacological data

Renewed interest in the clinical use of psychedelic drugs acknowledges their therapeutic effectiveness. It has also provided a changing frame of reference for older psychedelic drug study data, especially regarding concentrations of N, N-dimethyltryptamine (DMT) reported in rodent brains and recent discoveries in DMT receptor interactions in rat brain neurons and select brain areas. The mode of action of DMT in its newly defined role as a neuroplastogen, its effectiveness in treating neuropsychiatric disorders, and its binding to intracellular sigma-1 and 5HT2a receptors may define these possible roles. Recent data also show psychedelics promote neuroplasticity via activation of sigma-1 receptors associated with the endoplasmic reticulum and binding to 5-HT2a receptors predominantly related to the intracellular membrane of the Golgi apparatus in cortical neurons and the failure of DMT to occupy cell surface 5-HT2a receptors. While DMT has been proposed as the endogenous ligand for sigma-1, there is no identified ligand for intracellular 5-HT2a receptors, which serotonin cannot acquire. DMT is proposed to be the missing endogenous ligand. These data further suggest that DMT may be involved in brain development in rat pups. Brain levels of DMT have also been shown to be elevated by stress in the rat and appear to be under an inducible, adaptive, physiological regulatory system control. With DMT acting as the natural ligand for intracellular 5HT2a receptors in the Golgi, it may also explain the subjective effects observed from the administration of psychedelics in general and define some of the natural roles for DMT in particular.

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.

Age-dependent changes in visceral adiposity are associated with decreased plasma levels of DHEA-S in sigma-1 receptor knockout male mice

The sigma-1 receptor (S1R) is involved in intracellular lipid synthesis and transport. Recent studies have shown that its genetic inactivation impairs adipogenic differentiation in vitro. This study investigated the role of S1R in adipose tissue physiology and metabolic health using adult and old WT and S1R KO mice. Visceral fat mass was increased in adult, but not old S1R-KO male mice compared to that of WT mice, despite having similar body weights, food intake, and energy expenditure. The average adipocyte size was 64 % larger in adult KO mice than in adult WT mice. Adult S1R-KO mice showed reduced plasma dehydroepiandrosterone sulfate (DHEA-S) and elevated fasting plasma leptin concentrations. Lipidomic analysis revealed alterations in plasma metabolite concentrations, particularly reduced levels of sphingomyelins, ceramides, phosphatidylcholines, lysophosphatidylcholines, and cholesteryl esters in adult mice. Decreased expression of Pparγ, Adipoq, and Atgl was detected in visceral white adipose tissue (vWAT) isolated from adult KO mice. Additionally, Fabp4 and Adipoq expression levels were significantly lower in KO adipose-derived stromal cells than in WT adipose-derived stromal cells. A fivefold increase in the mitochondrial fatty acid oxidation rate and a 43 % increase in electron transfer coupling capacity were detected in adult S1R-KO vWAT. In summary, our investigation revealed an age-dependent association between increased visceral adiposity and decreased plasma levels of DHEA-S in S1R-deficient male mice. These findings underscore the potential role of S1R in regulating metabolic processes in adipose tissue and suggest that DHEA-S is a potential mediator of adiposity changes in the absence of S1R.

The next frontier in multiple sclerosis therapies: Current advances and evolving targets

Recent advancements in research have significantly enhanced our comprehension of the intricate immune components that contribute to multiple sclerosis (MS) pathogenesis. By conducting an in-depth analysis of complex molecular interactions involved in the immunological cascade of the disease, researchers have successfully identified novel therapeutic targets, leading to the development of innovative therapies. Leveraging pioneering technologies in proteomics, genomics, and the assessment of environmental factors has expedited our understanding of the vulnerability and impact of these factors on the progression of MS. Furthermore, these advances have facilitated the detection of significant biomarkers for evaluating disease activity. By integrating these findings, researchers can design novel molecules to identify new targets, paving the way for improved treatments and enhanced patient care. Our review presents recent discoveries regarding the pathogenesis of MS, highlights their genetic implications, and proposes an insightful approach for engaging with newer therapeutic targets in effectively managing this debilitating condition.

Sigma-1 receptor signaling: A potential therapeutic approach for ischemic stroke

Strokes constitute over 50% of all neurological diseases, standing as the foremost cause of physical and mental disability. Currently, there are no widely accepted gold standard treatments for ischemic strokes beyond intravenous thrombolysis and mechanical thrombectomy applied during the acute therapeutic window. Therefore, the need for novel treatments targeting crucial signaling mediators involved in ischemic stroke is of utmost importance. The sigma-1 receptor (S1R), a molecular chaperone located at mitochondria-associated endoplasmic reticulum membranes (MAM), has exhibited neuroprotective effects when modulated by synthetic and endogenous agents across various cerebrovascular diseases. In this review, we describe the emerging therapeutic role of S1R agonists and antagonists in regulating blood-brain barrier (BBB) dysfunction, neuroinflammation, and neurocognitive impairment following ischemic stroke.

Treatment of Stroke at a Delayed Timepoint with a Repurposed Drug Targeting Sigma 1 Receptors

Sigma 1 receptors are intracellular chaperone proteins that have been explored as a subacute treatment to enhance post-stroke recovery. We recently identified the antitussive oxeladin as a selective sigma 1 receptor agonist with the ability to stimulate the release of brain-derived neurotrophic factor from neurons in vitro. In this study, we hypothesized that oral oxeladin citrate would stimulate BDNF secretion and improve stroke outcomes when administered to male rats starting 48 h after transient middle cerebral artery occlusion. Oxeladin did not alter blood clotting and crossed the blood brain barrier within 30 min of oral administration. Rats underwent 90 min of transient middle cerebral artery occlusion. Forty-eight hours later rats began receiving daily oxeladin (135 mg/kg) for 11 days. Oxeladin significantly improved neurological function on days 3, 7, and 14 following MCAO. Infarct size was not altered by a single dose, but the final extent of infarct after 14 days was decreased. However, there was no significant reduction in astrogliosis or microgliosis compared to vehicle-treated control rats. In agreement with in vitro studies, oxeladin increased the amount of mature BDNF in the cerebral cortex 2, 6, and 24 h after single oral dose. However, the increase in BDNF did not result in increases in cellular proliferation in the subventricular zone or dentate gyrus when compared to vehicle-treated controls. These results suggest that oxeladin may reduce the extent of infarct expansion in the subacute phase of stroke, although this action does not appear to involve a reduction in inflammation or increased cell proliferation.

"Sigma-1 receptor modulation by clemastine highlights its repurposing as neuroprotective agent against seizures and cognitive deficits in PTZ-kindled rats"

Epilepsy is a neurological disorder characterized by recurrent spontaneous seizures alongside other neurological comorbidities. Cognitive impairment is the most frequent comorbidity secondary to progressive neurologic changes in epilepsy. Sigma 1 receptors (σ1 receptors) are involved in the neuroprotection and pathophysiology of both conditions and targeting these receptors may have the potential to modulate both seizures and comorbidities. The current research demonstrated the effect of clemastine (10 mg/kg, P.O.), a non-selective σ1 receptor agonist, on pentylenetetrazol (PTZ) (35 mg/kg, i.p., every 48 h for 14 doses)-kindling rats by acting on σ1 receptors through its anti-inflammatory/antioxidant capacity. Clemastine and phenytoin (30 mg/kg, P.O.) or their combination were given once daily. Clemastine treatment showed a significant effect on neurochemical, behavioural, and histopathological analyses through modulation of σ1 receptors. It protected the kindling animals from seizures and attenuated their cognitive impairment in the Morris water maze test by reversing the PTZ hippocampal neuroinflammation/oxidative stress state through a significant increase in inositol-requiring enzyme 1 (IRE1), x-box binding protein 1 (XBP1), along with a reduction of total reactive oxygen species (TROS) and amyloid beta protein (Aβ). The involvement of σ1 receptors in the protective effects of clemastine was confirmed by their abrogation when utilizing NE-100, a selective σ1 receptor antagonist. In light of our findings, modulating σ1 receptors emerges as a compelling therapeutic strategy for epilepsy and its associated cognitive impairments. The significant neuroprotective effects observed with clemastine underscore the potential of σ1 receptor-targeted treatments to address both the primary symptoms and comorbidities of neurological disorders.

The enduring effects of antimicrobials and lipopolysaccharide on the cellular mechanisms and behaviours associated with neurodegeneration in pubertal male and female CD1 mice

Puberty is a sensitive developmental period during which stressors can cause lasting brain and behavioural deficits. While the acute effects of pubertal lipopolysaccharide (LPS) and antimicrobial (AMNS) treatments are known, their enduring impacts on neurodegeneration-related mechanisms and behaviours remain unclear. This study examined these effects in male and female mice. At five weeks old, mice received 200ul of either broad-spectrum antimicrobials or water through oral gavage twice daily for seven days. At six weeks of age, they received an intraperitoneal injection of either saline or LPS. Four weeks later, adult mice underwent neurodegeneration-related behavioural tests, including the rotarod, forepaw stride length, reversed grid hang, open field, and buried pellet tests. Two days after the final test, brain and ileal samples were collected. Results showed that female mice treated with both AMNS and LPS exhibited deficits in neuromuscular strength, while males treated with LPS alone showed increased anxiety-like behaviours. Males treated with AMNS alone had decreased sigma-1 receptor (S1R) expression in the cornu ammonis 1 (CA1) and dentate gyrus (DG), while females treated with both AMNS and LPS had decreased S1R expression. Additionally, males treated with either LPS or AMNS had lower glial-derived neurotrophic factor receptor alpha-1 (GFRA1) expression in the primary motor cortex (M1) than females. Mice treated with LPS alone had decreased GFRA1 expression in the DG and decreased S1R expression in the secondary motor cortex (M2). These findings suggest that pubertal AMNS and LPS treatments may lead to enduring changes in biomarkers and behaviours related to neurodegeneration.

Endoplasmic reticulum stress, autophagy, neuroinflammation, and sigma 1 receptors as contributors to depression and its treatment

The etiological factors contributing to depression and other neuropsychiatric disorders are largely undefined. Endoplasmic reticulum stress pathways and autophagy are well-defined mechanisms that play critical functions in recognizing and resolving cellular stress and are possible targets for the pathophysiology and treatment of psychiatric and neurologic illnesses. An increasing number of studies indicate the involvement of endoplasmic reticulum stress and autophagy in the control of neuroinflammation, a contributing factor to multiple neuropsychiatric illnesses. Initial inflammatory triggers induce endoplasmic reticulum stress, leading to neuroinflammatory responses. Subsequently, induction of autophagy by neurosteroids and other signaling pathways that converge on autophagy induction are thought to participate in resolving neuroinflammation. The aim of this review is to summarize our current understanding of the molecular mechanisms governing the induction of endoplasmic reticulum stress, autophagy, and neuroinflammation in the central nervous system. Studies focused on innate immune factors, including neurosteroids with anti-inflammatory roles will be reviewed. In the context of depression, animal models that led to our current understanding of molecular mechanisms underlying depression will be highlighted, including the roles of sigma 1 receptors and pharmacological agents that dampen endoplasmic reticulum stress and associated neuroinflammation.

Blocking Sigmar1 exacerbates methamphetamine-induced hypertension

AIM

Methamphetamine (METH) chronic exposure is an important risk factor for hypertension development. However, the mechanisms behind METH-induced hypertension remain unclear. Therefore, we aimed to reveal the potential mechanisms underlying METH-induced hypertension.

METHODS AND RESULTS

We structured the mouse hypertension model by METH, and observed that METH-treated mice have presented vascular remodeling (large-and small-size arteries) with collagen deposit around the vessel and increasing blood pressure (BP) and Sigma1 receptor (Sigmar1) in vascular tissue. We hypothesized that Sigmar1 is crucial in METH-induced hypertension and vascular remodeling. Sigmar1 knockout (KO) mice and antagonist (BD1047) pretreated mice exposed to METH for six-week showed higher BP and more collagen deposited around vessels than wild-type (WT) mice exposed to METH for six-week, in contrast, mice pretreated with Sigmar1 agonist (PRE-084) had unchanged BP and perivascular collagen despite the six-week METH exposure. Furthermore, we found that METH exposure induced vascular smooth muscle cells (VSMCs) and mesenchymal stem cells to differentiate into the myofibroblast-like cell and secrete collagen into surrounding vessels. Mechanically, Sigmar1 can suppress the COL1A1 expression by blocking the classical fibrotic TGF-β/Smad2/3 signaling pathway in METH-exposed VSMCs and mesenchymal stem cells.

CONCLUSION

Our results suggest that Sigmar1 is involved in METH-induced hypertension and vascular fibrosis by blocking the activation of the TGF-β/Smad2/3 signaling pathway. Accordingly, Sigmar1 may be a novel therapeutic target for METH-induced hypertension and vascular fibrosis.

Advancements in Pharmacological Treatment of Alzheimer's Disease: The Advent of Disease-Modifying Therapies (DMTs)

The landscape of pharmacological treatment for Alzheimer's disease (AD) has undergone significant transformations with the advent of disease-modifying therapies (DMTs) targeting β-Amyloid (Aβ) accumulation, one of the hallmark pathologies of AD. The approval and market introduction of monoclonal antibodies mark the dawn of a new era in AD therapeutics as well. Furthermore, considerable progress has also been made in the development of new drugs targeting non-Aβ and non-Tau protein pathways. These advancements are key in tackling the root causes of AD, offering hope for treatments that both relieve symptoms and slow disease progression, improving patient outcomes and quality of life. This review aims to provide a comprehensive update on the advances in drug development and application for AD, including those currently in clinical trials and those already approved for the market to treat patients.

SAL0114: a novel deuterated dextromethorphan-bupropion combination with improved antidepressant efficacy and safety profile

Background

Esketamine, the first Food and Drug Administration-approved fast-acting antidepressant, has limited use because of its addictive properties. Although the combination of dextromethorphan and bupropion partially addresses the limitations of esketamine, concerns remain regarding neurologic side effects related to dextromethorphan metabolites, and seizure risks associated with high-dose bupropion. SAL0114, a novel formulation combining deuterated dextromethorphan (in which hydrogen atoms are replaced with deuterium) with bupropion, seeks to enhance dextromethorphan stability through deuteration of its metabolic sites. This approach is expected to increase antidepressant efficacy, reduce metabolite-induced safety issues, and allow for lower bupropion dosages.

Methods

Radioligand competition binding assays were used to evaluate the impact of deuterium substitution on the in vitro activity of dextromethorphan and its metabolite, dextrorphan. In vitro hepatic microsomal stability and in vivo mouse pharmacokinetic assays were performed to assess the effects of deuteration on dextromethorphan stability. Two mouse models of behavioral despair were used to determine the antidepressant and synergistic effects of deuterated dextromethorphan and bupropion. Additionally, a reserpine-induced hypothermia rat model and an ammonia-induced cough mouse model were used to assess the in vivo effects from a pathological perspective.

Results

Deuterated dextromethorphan maintained the same in vitro activity as dextromethorphan while exhibiting twice the metabolic stability both in vitro and in vivo. Combination with bupropion further improved its in vivo stability, increasing the exposure by 2.4 times. The combination demonstrated efficacy and synergistic effects in all tested animal models, showing superior efficacy compared with the dextromethorphan-bupropion combination.

Conclusion

Deuteration improved dextromethorphan metabolic stability without altering its in vitro activity. Bupropion enhanced this stability and synergistically boosted the antidepressant effect by increasing deuterated dextromethorphan exposure in vivo. This enhanced metabolic stability suggests a reduction in dextromethorphan metabolites associated with clinical neurological side effects. Consequently, SAL0114 is hypothesized to offer improved efficacy and safety compared with the non-deuterated combination, potentially allowing for lower bupropion dosages. Further clinical studies are required to confirm these preclinical findings.

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.

Identification of Psychoplastogenic Tropanes Lacking Muscarinic Activity

Tropane-containing small molecules like scopolamine are a promising class of psychoplastogens. However, their potent antagonism of all muscarinic receptor subtypes presents the potential for undesirable anticholinergic side effects. In an effort to decouple their neuroplasticity-promoting effects from their muscarinic activity, we performed phenotypic structure-activity relationship studies across a variety of structurally distinct subclasses of tropanes. We discovered several novel tropanes capable of significantly increasing cortical neuronal growth while exhibiting drastically reduced activity at all muscarinic receptor subtypes compared to scopolamine.

Amantadine for Traumatic Brain Injury-Supporting Evidence and Mode of Action

Traumatic brain injury (TBI) is an important global clinical issue, requiring not only prevention but also effective treatment. Following TBI, diverse parallel and intertwined pathological mechanisms affecting biochemical, neurochemical, and inflammatory pathways can have a severe impact on the patient's quality of life. The current review summarizes the evidence for the utility of amantadine in TBI in connection to its mechanism of action. Amantadine, the drug combining multiple mechanisms of action, may offer both neuroprotective and neuroactivating effects in TBI patients. Indeed, the use of amantadine in TBI has been encouraged by several clinical practice guidelines/recommendations. Amantadine is also available as an infusion, which may be of particular benefit in unconscious patients with TBI due to immediate delivery to the central nervous system and the possibility of precise dosing. In other situations, orally administered amantadine may be used. There are several questions that remain to be addressed: can amantadine be effective in disorders of consciousness requiring long-term treatment and in combination with drugs approved for the treatment of TBI? Do the observed beneficial effects of amantadine extend to disorders of consciousness due to factors other than TBI? Well-controlled clinical studies are warranted to ultimately confirm its utility in the TBI and provide answers to these questions.

Multi-target drugs for Alzheimer's disease

Alzheimer's disease (AD), a leading cause of dementia, increasingly challenges our healthcare systems and society. Traditional therapies aimed at single targets have fallen short owing to the complex, multifactorial nature of AD that necessitates simultaneous targeting of various disease mechanisms for clinical success. Therefore, targeting multiple pathologies at the same time could provide a synergistic therapeutic effect. The identification of new disease targets beyond the classical hallmarks of AD offers a fertile ground for the design of new multi-target drugs (MTDs), and building on existing compounds have the potential to yield in successful disease modifying therapies. This review discusses the evolving landscape of MTDs, focusing on their potential as AD therapeutics. Analysis of past and current trials of compounds with multi-target activity underscores the capacity of MTDs to offer synergistic therapeutic effects, and the flourishing genetic understanding of AD will inform and inspire the development of MTD-based AD therapies.

Ethanol drinking at adulthood is sensitive to S1-R antagonism and is promoted by binge ethanol self-administration at adolescence

BACKGROUND

Binge drinking at adolescence is a risk factor for problematic alcohol (ethanol) consumption later in life, yet the murine studies that modelled this phenomenon via ethanol self-administration have provided mixed findings. Antagonism of the sigma-1 receptor (S1-R) system at adolescence modulates ethanol's motivational effects and intake. It is still unknown, however, whether this antagonism would protect against enhanced ethanol intake at adulthood after adolescent binge ethanol exposure.

METHODS

Exp. 1 and 2 tested adults male or female Wistar rats -exposed or not to ethanol self-administration at adolescence (postnatal days 31-49; nine 2-hour sessions of access to 8-10% ethanol)- for ethanol intake using 24-h two-bottle choice test (Exp. 1) or time restricted, single-bottle, tests (Exp. 2). Experiments 2-5 evaluated, in adolescent or adult rats, the effects of the S1-R antagonist S1RA on ethanol intake and on ethanol-induced conditioned taste or place aversion. Ancillary tests (e.g., novel object recognition, ethanol-induced locomotor activity) were also conducted.

RESULTS

Adolescent ethanol exposure promoted ethanol consumption at both the restricted, single-bottle, and at the two-bottle choice tests conducted at adulthood. S1RA administration reduced ethanol intake at adulthood and facilitated the development of ethanol-induced taste (but not place) aversion.

CONCLUSIONS

S1RA holds promise for lessening ethanol intake after chronic and substantial ethanol exposure in adolescence that results in heightened ethanol exposure at adulthood. This putative protective effect of S1-R antagonism may relate to S1RA exacerbating the aversive effects of this drug.

N, N-Dimethyltryptamine, a natural hallucinogen, ameliorates Alzheimer's disease by restoring neuronal Sigma-1 receptor-mediated endoplasmic reticulum-mitochondria crosstalk

BACKGROUND

Aberrant neuronal Sigma-1 receptor (Sig-1r)-mediated endoplasmic reticulum (ER)- mitochondria signaling plays a key role in the neuronal cytopathology of Alzheimer's disease (AD). The natural psychedelic N, N-dimethyltryptamine (DMT) is a Sig-1r agonist that may have the anti-AD potential through protecting neuronal ER-mitochondrial interplay.

METHODS

3×TG-AD transgenic mice were administered with chronic DMT (2 mg/kg) for 3 weeks and then performed water maze test. The Aβ accumulation in the mice brain were determined. The Sig-1r level upon DMT treatment was tested. The effect of DMT on the ER-mitochondrial contacts site and multiple mitochondria-associated membrane (MAM)-associated proteins were examined. The effect of DMT on calcium transport between ER and mitochondria and the mitochondrial function were also evaluated.

RESULTS

chronic DMT (2 mg/kg) markedly alleviated cognitive impairment of 3×TG-AD mice. In parallel, it largely diminished Aβ accumulation in the hippocampus and prefrontal cortex. DMT restored the decreased Sig-1r levels of 3×TG-AD transgenic mice. The hallucinogen reinstated the expression of multiple MAM-associated proteins in the brain of 3×TG-AD mice. DMT also prevented physical contact and calcium dynamic between the two organelles in in vitro and in vivo pathological circumstances. DMT modulated oxidative phosphorylation (OXPHOS) and ATP synthase in the in vitro model of AD.

CONCLUSION

The anti-AD effects of DMT are associated with its protection of neuronal ER-mitochondria crosstalk via the activation of Sig-1r. DMT has the potential to serve as a novel preventive and therapeutic agent against AD.

Benzomorphan and non-benzomorphan agonists differentially alter sigma-1 receptor quaternary structure, as does types of cellular stress

Sigma-1 receptor (S1R) is a calcium-sensitive, ligand-operated receptor chaperone present on the endoplasmic reticulum (ER) membrane. S1R plays an important role in ER-mitochondrial inter-organelle calcium signaling and cell survival. S1R and its agonists confer resilience against various neurodegenerative diseases; however, the molecular mechanism of S1R is not yet fully understood. At resting state, S1R is either in a monomeric or oligomeric state but the ratio of these concentrations seems to change upon activation of S1R. S1R is activated by either cellular stress, such as ER-calcium depletion, or ligands. While the effect of ligands on S1R quaternary structure remains unclear, the effect of cellular stress has not been studied. In this study we utilize cellular and an in-vivo model to study changes in quaternary structure of S1R upon activation. We incubated cells with cellular stressors (H2O2 and thapsigargin) or exogenous ligands, then quantified monomeric and oligomeric forms. We observed that benzomorphan-based S1R agonists induce monomerization of S1R and decrease oligomerization, which was confirmed in the liver tissue of mice injected with (+)-Pentazocine. Antagonists block this effect but do not induce any changes when used alone. Oxidative stress (H2O2) increases the monomeric/oligomeric S1R ratio whereas ER calcium depletion (thapsigargin) has no effect. We also analyzed the oligomerization ability of various truncated S1R fragments and identified the fragments favorizing oligomerization. In this publication we demonstrate that quaternary structural changes differ according to the mechanism of S1R activation. Therefore, we offer a novel perspective on S1R activation as a nuanced phenomenon dependent on the type of stimulus.

Neuroactive steroids and Parkinson's disease: Review of human and animal studies

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

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.

Radiotracers in the Diagnosis of Pain: A Mini Review

The diagnosis and understanding of pain is challenging in clinical practice. Assessing pain relies heavily on self-reporting by patients, rendering it inherently subjective. Traditional clinical imaging methods such as computed tomography and magnetic resonance imaging can only detect anatomical abnormalities, offering limited sensitivity and specificity in identifying pain-causing conditions. Radiotracers play a vital role in molecular imaging that aims to identify abnormal biological processes at the cellular level, even in apparently normal anatomical structures. Therefore, molecular imaging is an important area of research as a prospective diagnostic modality for pain-causing pathophysiology. We present a mini review of the current knowledge base regarding radiotracers for identification of pain in vivo. We also describe radiocaine, a novel positron emission tomography imaging agent for sodium channels that has shown great potential for identifying/labeling pain-producing nerves and producing an objectively measurable pain intensity signal.

(R,S)-trihexyphenidyl, acting via a muscarinic receptor-independent mechanism, inhibits hippocampal glutamatergic and GABAergic synaptic transmissions: Potential relevance for treatment of organophosphorus intoxication

Preclinical studies have reported that, compared to the muscarinic receptor (mAChR) antagonist atropine, (R,S)-trihexyphenidyl (THP) more effectively counters the cholinergic crisis, seizures, and neuropathology triggered by organophosphorus (OP)-induced acetylcholinesterase (AChE) inhibition. The greater effectiveness of THP was attributed to its ability to block mAChRs and N-methyl-d-aspartate-type glutamatergic receptors (NMDARs) in the brain. However, THP also inhibits α7 nicotinic receptors (nAChRs). The present study examined whether THP-induced inhibition of mAChRs, α7 nAChRs, and NMDARs is required to suppress glutamatergic synaptic transmission, whose overstimulation sustains OP-induced seizures. In primary hippocampal cultures, THP (1-30 μM) suppressed the frequency of excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) recorded from neurons in nominally Mg2+-free solution. A single sigmoidal function adequately fit the overlapping concentration-response relationships for THP-induced suppression of IPSC and EPSC frequencies yielding an IC50 of 6.3 ± 1.3 μM. Atropine (1 μM), the NMDAR antagonist d,l-2-amino-5-phosphonopentanoic acid (D,L-AP5, 50 μM), and the α7 nAChR antagonist methyllycaconitine (MLA, 10 nM) did not prevent THP-induced inhibition of synaptic transmission. THP (10 μM) did not affect the probability of transmitter release because it had no effect on the frequency of miniature IPSCs and EPSCs recorded in the presence of tetrodotoxin. Additionally, THP had no effect on the amplitudes and decay-time constants of miniature IPSCs and EPSCs; therefore, it did not affect the activity of postsynaptic GABAA and glutamate receptors. This study provides the first demonstration that THP can suppress action potential-dependent synaptic transmission via a mechanism independent of NMDAR, mAChR, and α7 nAChR inhibition.

The potential of psychedelics for the treatment of Alzheimer's disease and related dementias

Alzheimer's Disease (AD) is a currently incurable but increasingly prevalent fatal and progressive neurodegenerative disease, demanding consideration of therapeutically relevant natural products and their synthetic analogues. This paper reviews evidence for effectiveness of natural and synthetic psychedelics in the treatment of AD causes and symptoms. The plastogenic effects of serotonergic psychedelics illustrate that they have efficacy for addressing multiple facets of AD pathology. We review findings illustrating neuroplasticity mechanisms of classic (serotonergic) and non-classic psychedelics that indicate their potential as treatments for AD and related dementias. Classic psychedelics modulate glutamatergic neurotransmission and stimulate synaptic and network remodeling that facilitates synaptic, structural and behavioral plasticity. Up-regulation of neurotrophic factors enable psychedelics to promote neuronal survival and glutamate-driven neuroplasticity. Muscimol modulation of GABAAR reduces Aβ-induced neurotoxicity and psychedelic Sig-1R agonists provide protective roles in Aβ toxicity. Classic psychedelics also activate mTOR intracellular effector pathways in brain regions that show atrophy in AD. The potential of psychedelics to treat AD involves their ability to induce structural and functional neural plasticity in brain circuits and slow or reverse brain atrophy. Psychedelics stimulate neurotrophic pathways, increase neurogenesis and produce long-lasting neural changes through rewiring pathological neurocircuitry. Psychedelic effects on 5-HT receptor target genes and induction of synaptic, structural, and functional changes in neurons and networks enable them to promote and enhance brain functional connectivity and address diverse mechanisms underlying degenerative neurological disorders. These findings provide a rationale for immediate investigation of psychedelics as treatments for AD patients.

Phenylacetyl-/Trolox- Amides: Synthesis, Sigma-1, HDAC-6, and Antioxidant Activities

In search of novel multi-mechanistic approaches for treating Alzheimer's disease (AD), we have embarked on synthesizing single small molecules for probing contributory roles of the following combined disease targets: sigma-1 (σ-1), class IIb histone deacetylase-6 (HDAC-6), and oxidative stress (OS). Herein, we report the synthesis and partial evaluation of 20 amides (i.e., phenylacetic and Trolox or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid derivatives). Target compounds were conveniently synthesized via amidation by either directly reacting acyl chlorides with amines or condensing acids with amines in the presence of coupling agents 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b] pyridinium 3-oxide hexafluorophosphate (HATU) or 1,1'-carbonyldiimidazole (CDI). Overall, this project afforded compound 8 as a promising lead with σ-1 affinity (Ki = 2.1 μM), HDAC-6 (IC50 = 17 nM), and antioxidant (1.92 Trolox antioxidant equivalents or TEs) activities for optimization in ensuing structure-activity relationship (SAR) studies.

Targeting Sigma-1 Receptor: A Promising Strategy in the Treatment of Parkinson's Disease

Parkinson's disease is a neurodegenerative disease affecting mainly the elderly population. It is characterized by the loss of dopaminergic neurons of the substantia nigra pars compacta region. Parkinson's disease patients exhibit motor symptoms like tremors, rigidity, bradykinesia/hypokinesia, and non-motor symptoms like depression, cognitive decline, delusion, and pain. Major pathophysiological factors which contribute to neuron loss include excess/misfolded alpha-synuclein aggregates, microglial cell-mediated neuroinflammation, excitotoxicity, oxidative stress, and defective mitochondrial function. Sigma-1 receptors are molecular chaperones located at mitochondria-associated ER membrane. Their activation (by endogenous ligands or agonists) has shown neuroprotective and neurorestorative effects in various diseases. This review discusses the roles of activated Sig-1 receptors in modulating various pathophysiological features of Parkinson's disease like alpha-synuclein aggregates, neuroinflammation, excitotoxicity, and oxidative stress.

Sigma Receptors: Novel Regulators of Iron/Heme Homeostasis and Ferroptosis

Sigma receptors are non-opiate/non-phencyclidine receptors that bind progesterone and/or heme and also several unrelated xenobiotics/chemicals. They reside in the plasma membrane and in the membranes of the endoplasmic reticulum, mitochondria, and nucleus. Until recently, the biology/pharmacology of these proteins focused primarily on their role in neuronal functions in the brain/retina. However, there have been recent developments in the field with the discovery of unexpected roles for these proteins in iron/heme homeostasis. Sigma receptor 1 (S1R) regulates the oxidative stress-related transcription factor NRF2 and protects against ferroptosis, an iron-induced cell death process. Sigma receptor 2 (S2R), which is structurally unrelated to S1R, complexes with progesterone receptor membrane components PGRMC1 and PGRMC2. S2R, PGRMC1, and PGRMC2, either independently or as protein-protein complexes, elicit a multitude of effects with a profound influence on iron/heme homeostasis. This includes the regulation of the secretion of the iron-regulatory hormone hepcidin, the modulation of the activity of mitochondrial ferrochelatase, which catalyzes iron incorporation into protoporphyrin IX to form heme, chaperoning heme to specific hemoproteins thereby influencing their biological activity and stability, and protection against ferroptosis. Consequently, S1R, S2R, PGRMC1, and PGRMC2 potentiate disease progression in hemochromatosis and cancer. These new discoveries usher this intriguing group of non-traditional progesterone receptors into an unchartered territory in biology and medicine.

Discovery and computational studies of piperidine/piperazine-based compounds endowed with sigma receptor affinity

Herein, we describe our efforts to identify sigma receptor 1 (S1R) ligands through a screening campaign on our in-house collection of piperidine/piperazine-based compounds. Our investigations led to the discovery of the potent compound 2-[4-(benzyl)-1-piperidin-1-yl]-1-4-(4-phenylpiperazin-1-yl)ethanone (1) with high affinity toward S1R (Ki value of 3.2 nM) that was comparable to reference compound haloperidol (Ki value of 2.5 nM). Functional assay revealed that compound 1 acted as S1R agonist. To decipher the binding mode of this promising S1R ligand as a starting point for further structure-based optimization, we analysed the docking pose by using a S1R-structure derived from cocrystal structures of potent ligands in complex with target protein. The computational study was enriched with molecular dynamic simulations that revealed the crucial amino acid residues that interacted with the most interesting compound 1.

Integrative CUT&Tag-RNA-Seq analysis of histone variant macroH2A1-dependent orchestration of human induced pluripotent stem cell reprogramming

Aim: Human induced pluripotent stem cells (iPSCs) are inefficiently derived from somatic cells by overexpression of defined transcription factors. Overexpression of H2A histone variant macroH2A1.1, but not macroH2A1.2, leads to increased iPSC reprogramming by unclear mechanisms. Materials & methods: Cleavage under targets and tagmentation (CUT&Tag) allows robust epigenomic profiling of a low cell number. We performed an integrative CUT&Tag-RNA-Seq analysis of macroH2A1-dependent orchestration of iPSCs reprogramming using human endothelial cells. Results: We demonstrate wider genome occupancy, predicted transcription factors binding, and gene expression regulated by macroH2A1.1 during reprogramming, compared to macroH2A1.2. MacroH2A1.1, previously associated with neurodegenerative pathologies, specifically activated ectoderm/neural processes. Conclusion: CUT&Tag and RNA-Seq data integration is a powerful tool to investigate the epigenetic mechanisms occurring during cell reprogramming.

Structure-Based Modeling of Sigma 1 Receptor Interactions with Ligands and Cholesterol and Implications for Its Biological Function

The sigma 1 receptor (S1R) is a 223-amino-acid-long transmembrane endoplasmic reticulum (ER) protein. The S1R plays an important role in neuronal health and it is an established therapeutic target for neurodegenerative and neuropsychiatric disorders. Despite its importance in physiology and disease, the biological function of S1R is poorly understood. To gain insight into the biological and signaling functions of S1R, we took advantage of recently reported crystal structures of human and Xenopus S1Rs and performed structural modeling of S1R interactions with ligands and cholesterol in the presence of the membrane. By combining bioinformatics analysis of S1R sequence and structural modelling approaches, we proposed a model that suggests that S1R may exist in two distinct conformations-"dynamic monomer" (DM) and "anchored monomer" (AM). We further propose that equilibrium between AM and DM conformations of S1R is essential for its biological function in cells, with AM conformation facilitating the oligomerization of S1R and DM conformation facilitating deoligomerization. Consistent with experimental evidence, our hypothesis predicts that increased levels of membrane cholesterol and S1R antagonists should promote the oligomeric state of S1R, but S1R agonists and pathogenic mutations should promote its deoligomerization. Obtained results provide mechanistic insights into signaling functions of S1R in cells, and the proposed model may help to explain neuroprotective effects of S1R modulators.

Sigma-1 Receptor Activation Is Protective against TGFβ2-Induced Extracellular Matrix Changes in Human Trabecular Meshwork Cells

The trabecular meshwork (TM) route is the principal outflow egress of the aqueous humor. Actin cytoskeletal remodeling in the TM and extracellular matrix (ECM) deposition increase TM stiffness, outflow resistance, and elevate intraocular pressure (IOP). These alterations are strongly linked to transforming growth factor-β2 (TGFβ2), a known profibrotic cytokine that is markedly elevated in the aqueous humor of glaucomatous eyes. Sigma-1 receptor (S1R) has been shown to have neuroprotective effects in the retina, but data are lacking about its role in the TM. In this study, we identified the presence of S1R in mouse TM tissue and investigated the effect of an S1R agonist fluvoxamine (FLU) on TGFβ2-induced human TM cells regarding cell proliferation; ECM-related functions, including F-actin reorganization; and the accumulation of ECM elements. TGFβ2 increased the proliferation, cytoskeletal remodeling, and protein levels of fibronectin, collagen type IV, and connective tissue growth factor, and decreased the level of matrix metalloproteinase-2. Most importantly, FLU reversed all these effects of TGFβ2, suggesting that S1R agonists could be potential candidates for preserving TM function and thus maintaining normal IOP.

Sigma-1 Receptor Agonist Fluvoxamine Ameliorates Fibrotic Response of Trabecular Meshwork Cells

Primary open-angle glaucoma remains a global issue, lacking a definitive treatment. Increased intraocular pressure (IOP) is considered the primary risk factor of the disease and it can be caused by fibrotic-like changes in the trabecular meshwork (TM) such as increased tissue stiffness and outflow resistance. Previously, we demonstrated that the sigma-1 receptor (S1R) agonist fluvoxamine (FLU) has anti-fibrotic properties in the kidney and lung. In this study, the localization of the S1R in TM cells was determined, and the anti-fibrotic efficacy of FLU was examined in both mouse and human TM cells. Treatment with FLU reduced the F-actin rearrangement, inhibited cell proliferation and migration induced by the platelet-derived growth factor and decreased the levels of fibrotic proteins. The protective role of the S1R in fibrosis was confirmed by a more pronounced increase in alpha smooth muscle actin and F-actin bundle and clump formation in primary mouse S1R knockout TM cells. Furthermore, FLU demonstrated its protective effects by increasing the production of nitric oxide and facilitating the degradation of the extracellular matrix through the elevation of cathepsin K. These findings suggest that the S1R could be a novel target for the development of anti-fibrotic drugs and offer a new therapeutic approach for glaucoma.

Experimental Study of Antidepressant Properties of Afobazole

We studied the effects of oral administration of Afobazole in a dose of 10 mg/kg for 5 days on depressive-like behavior of male C57BL/6 mice in the tail suspension test in comparison with amitriptyline (10 mg/kg) or fluoxetine (20 mg/kg) treatment. Afobazole produced an antidepressant effect similar to amitriptyline, but inferior to fluoxetine. The σ1 receptor antagonist BD-1047 in a dose of 5 mg/kg blocked the antidepressant effect of Afobazole, which indicates the involvement of σ1 receptors in the antidepressant effect of the drug.

Pridopidine Does Not Significantly Prolong the QTc Interval at the Clinically Relevant Therapeutic Dose

INTRODUCTION

Pridopidine is a highly selective sigma-1 receptor (S1R) agonist in development for the treatment of Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS). Pridopidine's activation of S1R enhances cellular processes that are crucial for neuronal function and survival but are impaired in neurodegenerative diseases. Human brain positron emission tomography (PET) imaging studies show that at the therapeutic dose of 45 mg twice daily (bid), pridopidine selectively and robustly occupies the S1R. We conducted concentration-QTc (C-QTc) analyses to assess pridopidine's effect on the QT interval and investigated its cardiac safety profile.

METHODS

C-QTc analysis was conducted using data from PRIDE-HD, a phase 2, placebo-controlled trial evaluating four pridopidine doses (45, 67.5, 90, 112.5 mg bid) or placebo over 52 weeks in HD patients. Triplicate electrocardiograms (ECGs) with simultaneous plasma drug concentrations were determined in 402 patients with HD. The effect of pridopidine on the Fridericia-corrected QT interval (QTcF) was evaluated. Cardiac-related adverse events (AEs) were analyzed from PRIDE-HD alone and from pooled safety data of three double-blind, placebo-controlled trials with pridopidine in HD (HART, MermaiHD, and PRIDE-HD).

RESULTS

A concentration-dependent effect of pridopidine on the change from baseline in the Fridericia-corrected QT interval (ΔQTcF) was observed, with a slope of 0.012 ms (ms) per ng/mL (90% confidence interval (CI), 0.0109-0.0127). At the therapeutic dose of 45 mg bid, the predicted placebo-corrected ΔQTcF (ΔΔQTcF) was 6.6 ms (upper bound 90% CI, 8.0 ms), which is below the level of concern and not clinically relevant. Analysis of pooled safety data from three HD trials demonstrates that at 45 mg bid, pridopidine cardiac-related AE frequencies are similar to those with placebo. No patients reached a QTcF of 500 ms and no patients experienced torsade de pointes (TdP) at any pridopidine dose.

CONCLUSIONS

At the 45 mg bid therapeutic dose, pridopidine demonstrates a favorable cardiac safety profile, with an effect on the QTc interval that is below the level of concern and not clinically relevant.

TRIAL REGISTRATION

PRIDE-HD (TV7820-CNS-20002) trial registration: ClinicalTrials.gov identifier, NCT02006472, EudraCT 2013-001888-23; HART (ACR16C009) trial registration: ClinicalTrials.gov identifier, NCT00724048; MermaiHD (ACR16C008) trial registration: ClinicalTrials.gov identifier, NCT00665223, EudraCT No. 2007-004988-22.

Design and Synthesis of New Acyl Urea Analogs as Potential σ1R Ligands

In search of synthetically accessible open-ring analogs of PD144418 or 5-(1-propyl-1,2,5,6-tetrahydropyridin-3-yl)-3-(p-tolyl)isoxazole, a highly potent sigma-1 receptor (σ1R) ligand, we herein report the design and synthesis of sixteen arylated acyl urea derivatives. Design aspects included modeling the target compounds for drug-likeness, docking at σ1R crystal structure 5HK1, and contrasting the lower energy molecular conformers with that of the receptor-embedded PD144418-a molecule we opined that our compounds could mimic pharmacologically. Synthesis of our acyl urea target compounds was achieved in two facile steps which involved first generating the N-(phenoxycarbonyl) benzamide intermediate and then coupling it with the appropriate amines weakly to strongly nucleophilic amines. Two potential leads (compounds 10 and 12, with respective in vitro σ1R binding affinities of 2.18 and 9.54 μM) emerged from this series. These leads will undergo further structure optimization with the ultimate goal of developing novel σ1R ligands for testing in neurodegeneration models of Alzheimer's disease (AD).

Design and Synthesis of Orally Active Quinolyl Pyrazinamides as Sigma 2 Receptor Ligands for the Treatment of Pancreatic Cancer

Sigma 2 receptor (σ2R) is overexpressed in select cancers and is regarded as a biomarker for tumor proliferation. σ2R ligands are emerging as promising theranostics for cancer and neurodegenerative diseases. Herein, we describe the design and synthesis of a series of novel quinolyl pyrazinamides as selective and potent σ2R ligands that show sub-micromolar potency in pancreatic cancer cell lines. Compounds 14 (JR1-157) and 17 (JR2-298) bind σ2R with K_i of 47 and 10 nM, respectively. Importantly, compound 14 has an oral bioavailability of 60% and shows significant in vivo efficacy without obvious toxicity in a syngeneic model of pancreatic cancer. The cytotoxicity of the quinolyl pyrazinamides significantly enhanced in the presence of copper and diminished in the presence of the copper-chelator tetrathiomolybdate. In conclusion, compound 14 is water-soluble, metabolically stable, orally active, and increases the expression of the autophagy marker LC3B and warrants further development for the treatment of pancreatic cancer.

Sphingoid Bases Regulate the Sigma-1 Receptor-Sphingosine and N,N'-Dimethylsphingosine Are Endogenous Agonists

Both bioactive sphingolipids and Sigma-1 receptor (S1R) chaperones occur ubiquitously in mammalian cell membranes. Endogenous compounds that regulate the S1R are important for controlling S1R responses to cellular stress. Herein, we interrogated the S1R in intact Retinal Pigment Epithelial cells (ARPE-19) with the bioactive sphingoid base, sphingosine (SPH), or the pain-provoking dimethylated SPH derivative, N,N'-dimethylsphingosine (DMS). As informed by a modified native gel approach, the basal and antagonist (BD-1047)-stabilized S1R oligomers dissociated to protomeric forms in the presence of SPH or DMS (PRE-084 as control). We, thus, posited that SPH and DMS are endogenous S1R agonists. Consistently, in silico docking of SPH and DMS to the S1R protomer showed strong associations with Asp126 and Glu172 in the cupin beta barrel and extensive van der Waals interactions of the C18 alkyl chains with the binding site including residues in helices 4 and 5. Mean docking free energies were 8.73-8.93 kcal/mol for SPH and 8.56-8.15 kcal/mol for DMS, and calculated binding constants were ~40 nM for SPH and ~120 nM for DMS. We hypothesize that SPH, DMS, and similar sphingoid bases access the S1R beta barrel via a membrane bilayer pathway. We further propose that the enzymatic control of ceramide concentrations in intracellular membranes as the primary sources of SPH dictates availability of endogenous SPH and DMS to the S1R and the subsequent control of S1R activity within the same cell and/or in cellular environments.

Overview of Sigma-1R Subcellular Specific Biological Functions and Role in Neuroprotection

For the past several years, fundamental research on Sigma-1R (S1R) protein has unveiled its necessity for maintaining proper cellular homeostasis through modulation of calcium and lipid exchange between the endoplasmic reticulum (ER) and mitochondria, ER-stress response, and many other mechanisms. Most of these processes, such as ER-stress response and autophagy, have been associated with neuroprotective roles. In fact, improving these mechanisms using S1R agonists was beneficial in several brain disorders including neurodegenerative diseases. In this review, we will examine S1R subcellular localization and describe S1R-associated biological activity within these specific compartments, i.e., the Mitochondrion-Associated ER Membrane (MAM), ER-Lipid Droplet (ER-LD) interface, ER-Plasma Membreane (ER-PM) interface, and the Nuclear Envelope (NE). We also discussed how the dysregulation of these pathways contributes to neurodegenerative diseases, while highlighting the cellular mechanisms and key binding partners engaged in these processes.

Sigma-1 Receptor Signaling: In Search of New Therapeutic Alternatives for Cardiovascular and Renal Diseases

Cardiovascular and renal diseases are among the leading causes of death worldwide, and regardless of current efforts, there is a demanding need for therapeutic alternatives to reduce their progression to advanced stages. The stress caused by diseases leads to the activation of protective mechanisms in the cell, including chaperone proteins. The Sigma-1 receptor (Sig-1R) is a ligand-operated chaperone protein that modulates signal transduction during cellular stress processes. Sig-1R interacts with various ligands and proteins to elicit distinct cellular responses, thus, making it a potential target for pharmacological modulation. Furthermore, Sig-1R ligands activate signaling pathways that promote cardioprotection, ameliorate ischemic injury, and drive myofibroblast activation and fibrosis. The role of Sig-1R in diseases has also made it a point of interest in developing clinical trials for pain, neurodegeneration, ischemic stroke, depression in patients with heart failure, and COVID-19. Sig-1R ligands in preclinical models have significantly beneficial effects associated with improved cardiac function, ventricular remodeling, hypertrophy reduction, and, in the kidney, reduced ischemic damage. These basic discoveries could inform clinical trials for heart failure (HF), myocardial hypertrophy, acute kidney injury (AKI), and chronic kidney disease (CKD). Here, we review Sig-1R signaling pathways and the evidence of Sig-1R modulation in preclinical cardiac and renal injury models to support the potential therapeutic use of Sig-1R agonists and antagonists in these diseases.

The Bright Side of Psychedelics: Latest Advances and Challenges in Neuropharmacology

The need to identify effective therapies for the treatment of psychiatric disorders is a particularly important issue in modern societies. In addition, difficulties in finding new drugs have led pharmacologists to review and re-evaluate some past molecules, including psychedelics. For several years there has been growing interest among psychotherapists in psilocybin or lysergic acid diethylamide for the treatment of obsessive-compulsive disorder, of depression, or of post-traumatic stress disorder, although results are not always clear and definitive. In fact, the mechanisms of action of psychedelics are not yet fully understood and some molecular aspects have yet to be well defined. Thus, this review aims to summarize the ethnobotanical uses of the best-known psychedelic plants and the pharmacological mechanisms of the main active ingredients they contain. Furthermore, an up-to-date overview of structural and computational studies performed to evaluate the affinity and binding modes to biologically relevant receptors of ibogaine, mescaline, N,N-dimethyltryptamine, psilocin, and lysergic acid diethylamide is presented. Finally, the most recent clinical studies evaluating the efficacy of psychedelic molecules in some psychiatric disorders are discussed and compared with drugs already used in therapy.