Search Results (12)

Sex differences in the neurobiology of responses to chronic stress have been widely discussed but remain poorly understood. We found that chronic unpredictable mild stress (CUMS) experienced during adolescence induced different behavioral patterns in adult males and females. Immunohistochemical analysis of the CA1 field of the dorsal and ventral hippocampus revealed no quantitative or morphological changes in astrocytes in the long term after CUMS. Real-time PCR analysis showed no increase in the expression level of SigmaR1 after CUMS relative to individual housekeeping genes. Analysis of mouse cerebral cortex homogenates showed that IL-1β levels only decreased after CUMS in males. However, the SigmaR1 levels were significantly higher in the CUMS groups than in the control groups in both sexes. It can be concluded that biological sex and age influence the response to CUMS, although not in all cases. Further studies are needed to understand the effects of chronic stress on males and females. This is important because men and women have different risks for stress and mental disorders. Full article

Background/Objectives: The Sigma-1 receptor (Sigmar1), an intracellular chaperone protein, is ubiquitously expressed throughout the body, but its role in peripheral organs, such as the kidneys, remains unclear. Here, we investigated the protective effects and molecular mechanisms of SA4503, a selective Sigmar1 agonist, on Adriamycin (ADR)-induced renal glomerular injury. Methods: Using in vitro and in vivo models, we evaluated the effects of SA4503 on ADR-induced podocyte injury, including podocyte survival, albumin permeability, urinary albumin levels, and Sigmar1-nephrin interactions. NE-100, a Sigmar1 antagonist, was co-administered to validate the specificity of the effects of SA4503. Results: Sigmar1 was highly expressed in podocytes and mouse kidney tissues. SA4503 significantly reduced ADR-induced podocyte injury and urinary albumin leakage in mice. Mechanistically, SA4503 preserved Sigmar1-nephrin interactions, which were disrupted in ADR-treated kidneys. This protective effect was abolished by NE-100 co-treatment, confirming the Sigmar1-dependency of SA4503’s action. Conclusions: These findings demonstrate that the activation of Sigmar1 by SA4503 protects against ADR-induced podocyte injury and glomerular damage, likely by stabilizing Sigmar1-nephrin interactions. Therefore, Sigmar1 represents a promising therapeutic target for glomerular diseases such as nephrotic syndrome. Full article

Long regarded as illicit substances with no clinical value, N-dimethylated tryptamines—such as N,N-dimethyltryptamine, 5-methoxy-N,N-dimethyltryptamine, and bufotenine—have been found to produce naturally in a wide variety of species, including humans. Known for their psychoactive effects through serotonin receptors (5-HTRs), N-dimethylated tryptamines are currently being reinvestigated clinically for their long-term benefits in mental disorders. Endogenous tryptamine is methylated by indolethylamine-N-methyltransferase (INMT), which can then serve as an agonist to pro-survival pathways, such as sigma non-opioid intracellular receptor 1 (SIGMAR1) signaling. Fibrogenic diseases, like metabolic-associated fatty liver disease (MAFLD), steatohepatitis (MASH), and chronic kidney disease (CKD) have shown changes in INMT and SIGMAR1 activity in the progression of disease pathogenesis. At the cellular level, endothelial cells and fibroblasts have been found to express INMT in various tissues; however, little is known about tryptamines in endothelial injury and fibrosis. In this review, I will give an overview of the biochemistry, molecular biology, and current evidence of INMT’s role in hepatic fibrogenesis. I will also discuss current pre-clinical and clinical findings of N-methylated tryptamines and highlight new and upcoming therapeutic strategies that may be adapted for mitigating fibrogenic diseases. Finally, I will mention recent findings for mutualistic gut bacteria influencing endogenous tryptamine signaling and metabolism. Full article

Emerging evidence suggests that aberrant expression levels of Sigma1 (SIGMAR1, also known as sigma-1 receptor) have been implicated in the progression of various diseases, including cancer. However, its significance in oral cancer (OC) has not been thoroughly explored. To advance in this field, the present study aimed to investigate the impact of SIGMAR1 knockdown in oral cancer cells. To do so, we included in this study our cohort of human OC samples and OC cell lines, which were utilized for experimental verification through several in vitro assays. Our findings revealed that SIGMAR1 overexpression was associated with poor survival rates and positively correlated with PD-L1 overexpression in human oral cancer samples. Furthermore, SIGMAR1 inhibition led to a decrease in PD-L1 expression and sensitized oral cancer cells to cisplatin treatment by enhancing apoptosis. These results suggest that SIGMAR1 knockdown may present a promising strategy worthy of further exploration in the management of oral cancer. Full article

The Sigma-1 Receptor (Sigmar1) is a stress-activated chaperone and a promising target for pharmacological modulation due to its ability to induce multiple cellular responses. Yet, it is unknown how Sigmar1 is involved in cardiorenal syndrome type 4 (CRS4) in which renal damage results in cardiac dysfunction. This study explored the role of Sigmar1 and its ligands in a CRS4 model induced by unilateral ureteral obstruction (UUO) in male and female C57BL/6 mice. We evaluated renal and cardiac dysfunction markers, Sigmar1 expression, and cardiac remodeling through time (7, 12, and 21 days) and after chronically administering the Sigmar1 agonists PRE-084 (1 mg/kg/day) and SA4503 (1 mg/kg/day), and the antagonist haloperidol (2 mg/kg/day), for 21 days after UUO using colorimetric analysis, RT-qPCR, histology, immunohistochemistry, enzyme-linked immunosorbent assay, RNA-seq, and bioinformatics. We found that obstructive nephropathy induces Sigmar1 expression in the kidneys and heart, and that Sigmar1 stimulation with its agonists PRE-084 and SA4503 aggravates cardiac dysfunction and remodeling in both sexes. Still, their effects are significantly more potent in males. Our findings reveal essential differences associated with sex in the development of CRS4 and should be considered when contemplating Sigmar1 as a pharmacological target. Full article

Takotsubo syndrome (TTS) is a stress-induced cardiomyopathy that presents with sudden onset of chest pain and dyspneic and cardiac dysfunction as a result of extreme physical or emotional stress. The sigma-1 receptor (Sigmar1) is a ligand-dependent molecular chaperone that is postulated to be involved in various processes related to cardiovascular disease. However, the role of Sigmar1 in TTS remains unresolved. In this study, we established a mouse model of TTS using wild-type and Sigmar1 knockout mice to investigate the involvement of Sigmar1 in TTS development. Our results revealed that Sigmar1 knockout exacerbated cardiac dysfunction, with a noticeable decrease in ejection fraction (EF) and fractional shortening (FS) compared to the wild-type model. In terms of the gut microbiome, we observed regulation of Firmicutes and Bacteroidetes ratios; suppression of probiotic Lactobacillus growth; and a rise in pathogenic bacterial species, such as Colidextribacter. Metabolomic and transcriptomic analyses further suggested that Sigmar1 plays a role in regulating tryptophan metabolism and several signaling pathways, including MAPK, HIF-1, calcium signaling, and apoptosis pathways, which may be crucial in TTS pathogenesis. These findings offer valuable insight into the function of Sigmar1 in TTS, and this receptor may represent a promising therapeutic target for TTS. Full article

Despite the major progress in treating breast cancer, recurrence remains a problem and types such as triple-negative breast cancer still lack targeted medicine. The orphan Sigma receptor1 (SigmaR1) has emerged as a target in breast cancer, but its mechanism of action is unclear and hinders clinical utility. SigmaR1 is widely expressed in organ tissues and localized to various sub-cellular compartments, particularly the endoplasmic reticulum (ER), the mitochondrial-associated membranes (MAMs) and the nuclear envelope. As such, it involves diverse cellular functions, including protein quality control/ER stress, calcium signaling, cholesterol homeostasis, mitochondrial integrity and energy metabolism. Consequently, SigmaR1 has been implicated in a number of cancers and degenerative diseases and thus has been intensively pursued as a therapeutic target. Because SigmaR1 binds a number of structurally unrelated ligands, it presents an excellent context-dependent therapeutic target. Here, we review its role in breast cancer and the current therapies that have been considered based on its known functions. As SigmaR1 is not classified as an oncoprotein, we propose a model in which it serves as an oligomerization adaptor in key cellular pathways, which may help illuminate its association with variable diseases and pave the way for clinical utility in personalized medicine. Full article

The sigma-1 receptor (SIGMAR1) is one of a kind: a receptor chaperone protein. This 223 amino acid-long protein is enriched at the mitochondria-associated endoplasmic reticulum membrane (MAM), a specialized microdomain of the endoplasmic reticulum that is structurally and functionally connected to the mitochondria. As a receptor, SIGMAR1 binds a wide spectrum of ligands. Numerous molecules targeting SIGMAR1 are currently in pre-clinical or clinical development. Interestingly, the range of pathologies covered by these studies is broad, especially with regard to neurodegenerative disorders. Upon activation, SIGMAR1 can translocate and interact with other proteins, mostly at the MAM but also in other organelles, which allows SIGMAR1 to affect many cellular functions. During these interactions, SIGMAR1 exhibits chaperone protein behavior by participating in the folding and stabilization of its partner. In this short communication, we will shed light on how SIGMAR1 confers protection against neurodegeneration to the cells of the nervous system and why this ability makes SIGMAR1 a multifunctional therapeutic prospect. Full article

Amyotrophic lateral sclerosis (ALS) is regarded as a fatal neurodegenerative disease that is featured by progressive damage of the upper and lower motor neurons. To date, over 45 genes have been found to be connected with ALS pathology. The aim of this work was to computationally identify unique sets of protein hydrolysate peptides that could serve as therapeutic agents against ALS. Computational methods which include target prediction, protein-protein interaction, and peptide-protein molecular docking were used. The results showed that the network of critical ALS-associated genes consists of ATG16L2, SCFD1, VAC15, VEGFA, KEAP1, KIF5A, FIG4, TUBA4A, SIGMAR1, SETX, ANXA11, HNRNPL, NEK1, C9orf72, VCP, RPSA, ATP5B, and SOD1 together with predicted kinases such as AKT1, CDK4, DNAPK, MAPK14, and ERK2 in addition to transcription factors such as MYC, RELA, ZMIZ1, EGR1, TRIM28, and FOXA2. The identified molecular targets of the peptides that support multi-metabolic components in ALS pathogenesis include cyclooxygenase-2, angiotensin I-converting enzyme, dipeptidyl peptidase IV, X-linked inhibitor of apoptosis protein 3, and endothelin receptor ET-A. Overall, the results showed that AGL, APL, AVK, IIW, PVI, and VAY peptides are promising candidates for further study. Future work would be needed to validate the therapeutic properties of these hydrolysate peptides by in vitro and in vivo approaches. Full article

Obesity is increasing at epidemic rates across the US and worldwide, as are its co-morbidities, including type-2 diabetes and cardiovascular disease. Thus, targeted interventions to reduce the prevalence of obesity are of the utmost importance. The sigma-1 receptor (S1R) and sigma-2 receptor (S2R; encoded by Tmem97) belong to the same class of drug-binding sites, yet they are genetically distinct. There are multiple ongoing clinical trials focused on sigma receptors, targeting diseases ranging from Alzheimer’s disease through chronic pain to COVID-19. However, little is known regarding their gene-specific role in obesity. In this study, we measured body composition, used a comprehensive laboratory-animal monitoring system, and determined the glucose and insulin tolerance in mice fed a high-fat diet. Compared to Sigmar1+/+ mice of the same sex, the male and female Sigmar1−/− mice had lower fat mass (17% and 12% lower, respectively), and elevated lean mass (16% and 10% higher, respectively), but S1R ablation had no effect on their metabolism. The male Tmem97−/− mice exhibited 7% lower fat mass, 8% higher lean mass, increased volumes of O₂ and CO₂, a decreased respiratory exchange ratio indicating elevated fatty-acid oxidation, and improved insulin tolerance, compared to the male Tmem97+/+ mice. There were no changes in any of these parameters in the female Tmem97−/− mice. Together, these data indicate that the S1R ablation in male and female mice or the S2R ablation in male mice protects against diet-induced adiposity, and that S2R ablation, but not S1R deletion, improves insulin tolerance and enhances fatty-acid oxidation in male mice. Further mechanistic investigations may lead to translational strategies to target differential S1R/S2R regulations and sexual dimorphism for precision treatments of obesity. Full article

Sigma (σ) receptors have attracted great interest since they are implicated in various cellular functions and biological processes and diseases, including various types of cancer. The receptor family consists of two subtypes: sigma-1 (σ1) and sigma-2 (σ2). Both σ receptor subtypes have been proposed as therapeutic targets for various types of cancers, and many studies have provided evidence that their selective ligands (agonists and antagonists) exhibit antiproliferative and cytotoxic activity. Still, the precise mechanism of action of both σ receptors and their ligands remains unclear and needs to be elucidated. In this study, we aimed to simultaneously determine the expression levels of both σ receptor subtypes in several human cancer cell lines. Additionally, we investigated the in vitro antiproliferative activity of some widely used σ1 and σ2 ligands against those cell lines to study the relationship between σ receptor expression levels and σ ligand activity. Finally, we ran the NCI60 COMPARE algorithm to further elucidate the cytotoxic mechanism of action of the selected σ ligands studied herein. Full article

Autophagy is an important stress response pathway responsible for the removal and recycling of damaged or redundant cytosolic constituents. Mitochondrial damage triggers selective mitochondrial autophagy (mitophagy), mediated by a variety of response factors including the Pink1/Parkin system. Using human retinal pigment epithelial cells stably expressing autophagy and mitophagy reporters, we have conducted parallel screens of regulators of endoplasmic reticulum (ER) and mitochondrial morphology and function contributing to starvation-induced autophagy and damage-induced mitophagy. These screens identified the ER chaperone and Ca²⁺ flux modulator, sigma non-opioid intracellular receptor 1 (SIGMAR1), as a regulator of autophagosome expansion during starvation. Screens also identified phosphatidyl ethanolamine methyl transferase (PEMT) and the IP3-receptors (IP3Rs) as mediators of Parkin-induced mitophagy. Further experiments suggested that IP3R-mediated transfer of Ca²⁺ from the ER lumen to the mitochondrial matrix via the mitochondrial Ca²⁺ uniporter (MCU) primes mitochondria for mitophagy. Importantly, recruitment of Parkin to damaged mitochondria did not require IP3R-mediated ER-to-mitochondrial Ca²⁺ transfer, but mitochondrial clustering downstream of Parkin recruitment was impaired, suggesting involvement of regulators of mitochondrial dynamics and/or transport. Our data suggest that Ca²⁺ flux between ER and mitochondria at presumed ER/mitochondrial contact sites is needed both for starvation-induced autophagy and for Parkin-mediated mitophagy, further highlighting the importance of inter-organellar communication for effective cellular homeostasis. Full article