Receptor Dysfunction Research Articles

Sphingosine 1-phosphate receptor subtype 1 (S1P1) activity in the course of Alzheimer's disease

Some specific lipid molecules in the brain act as signaling molecules, neurotransmitters, or neuromodulators, by binding to specific G protein-coupled receptors (GPCR) for neurolipids. One such receptor, sphingosine 1-phosphate receptor subtype 1 (S1P1), is coupled to Gi/o proteins and is involved in cell proliferation, growth, and neuroprotection. S1P1 constitutes an interesting target for neurodegenerative diseases like multiple sclerosis and Alzheimer's disease (AD), in which changes in the sphingolipid metabolism have been observed. This study analyzes S1P1 receptor-mediated activity in healthy brains and during AD progression using postmortem samples from controls and patients at different Braak's stages. Additionally, the distribution of S1P1 receptor activity in human brains is compared to that in commonly used rodent models, rats and mice, through functional autoradiography, measuring [35S]GTPγS binding stimulated by the S1P1 receptor selective agonist CYM-5442 to obtain the distribution of functional activity of S1P1 receptors.S1P1 receptor-mediated activity, along with that of the cannabinoid CB1 receptor, is one of the highest recorded for any GPCR in many gray matter areas of the brain, reaching maximum values in the cerebellar cortex, specific areas of the hippocampus and the basal forebrain. S1P1 signaling is crucial in areas that regulate learning, memory, motor control, and nociception, such as the basal forebrain and basal ganglia. In AD, S1P1 receptor activity is increased in the inner layers of the frontal cortex and underlying cortical white matter at early stages, but decreases in the hippocampus in advanced stages, indicating ongoing brain impairment. Importantly, we identified significant correlations between S1P1 receptor activity and Braak stages, suggesting that S1P1 receptor dysfunction is associated to disease progression, particularly in memory-related regions. The S1P signaling via S1P1 receptor is a promising neurological target due to its role in key neurophysiological functions and its potential to modify the progression of neurodegenerative diseases. Finally, rats are suggested as a preferred experimental model for studying S1P1 receptor-mediated responses in the human brain.

Mechanisms of glutamate receptors hypofunction dependent synaptic transmission impairment in the hippocampus of schizophrenia susceptibility gene Opcml-deficient mouse model

Schizophrenia is a severe psychiatric disorder with high heritability, characterized by positive and negative symptoms as well as cognitive abnormalities. Dysfunction in glutamate synapse is strongly implicated in the pathophysiology of schizophrenia. However, the precise role of the perturbed glutamatergic system in contributing to the cognitive abnormalities of schizophrenia at the synaptic level remains largely unknown. Although our previous work found that Opcml promotes spine maturation and Opcml-deficient mice exhibit schizophrenia-related cognitive impairments, the synaptic mechanism remains unclear. By using whole-cell patch clamp recording, we found that decreased neuronal excitability and alterations in intrinsic membrane properties of CA1 PNs in Opcml-deficient mice. Furthermore, Opcml deficiency leads to impaired glutamatergic transmission in hippocampus, which is closely related to postsynaptic AMPA/NMDA receptors dysfunction, resulting in the disturbances of E/I balance. Additionally, we found that the aripiprazole which we used to ameliorate abnormal cognitive behaviors also rescued the impaired glutamatergic transmission in Opcml-deficient mice. These findings will help to understand the synaptic mechanism in schizophrenia pathogenesis, providing insights into schizophrenia therapeutics with glutamatergic disruption.

Dysregulated renal tubular handling of filtered glucose in patients with type 2 diabetes mellitus: a descriptive study

Objective: To determine the frequency of suspected dysregulated renal tubular handling of filtered glucose, and its association with blood glucose levels in type 2 diabetes mellitus. Method: The analytical, cross-sectional study was conducted from November 2022 to June 2023 at the Department of Medicine along with the Department of Pathology and Biochemistry, Pakistan Railway Hospital, Islamic International Medical College, Rawalpindi, Pakistan, and comprised diabetics aged 19-80 years. Blood and urinary glucose were assessed at the point of contact. Blood glucose 80-180mg/dl was considered glucose in range and >180mg/dl glucose above range. Hyper-function of sodium glucose transport receptors was suspected if urinary glucose was <++ and the function of these receptors was considered normal if urinary sugar was ++ or more. Association of suspected receptors and their association with blood glucose levels was determined. Data was analysed using SPSS 26. Results: Of the 159 diabetics, 91(57%) were females and 68(43%) were males. The overall mean age was 57±11 years (range: 46-68 years). Of the total, 43(27%) patients had glucose in range and 116(73%) had glucose above range. Of the diabetics with glucose above range, 54(47%) patients had hyper-functioning sodium glucose transport receptors, and 62(53%) had normal functioning sodium glucose transport receptors. Of the patients with glucose in range, 11(26%) had hyper-functioning sodium glucose transport receptors, and 32(74%) had normal functioning sodium glucose transport receptors. There was a significant association between sodium glucose transport receptors’ function and blood glucose levels (p<0.001). Conclusion: Dysfunction of sodium glucose transport receptors affected the secretion of glucose in the urine, resulting in impaired glucose regulation in type 2 diabetes mellitus cases. Key Words: Blood glucose, Diabetes, Glycosuria, Sodium-glucose transporter 2.

The effect of Amantadine on recovery, postoperative cognitive dysfunction and pain after propofol anesthesia in mice

IntroductionPostoperative cognitive dysfunction (POCD) encompasses a spectrum of cognitive impairments following surgery, attributed to disruptions in brain homeostasis. The pathogenesis involves glutamate toxicity, GABA receptor dysfunction, and alterations in NMDA and AMPA receptors. This study aimed to investigate the impact of pre-anesthetic amantadine administration on postoperative recovery time, POCD, and stress-related pain levels when combined with propofol anesthesia. MethodsTwenty-four adult male BALB/C mice were divided into four groups: Control, Propofol, Amantadine, and Amantadine+Propofol. Amantadine and propofol doses were administered intraperitoneally based on previous literature. Recovery time, pain levels (assessed via tail pinch and hot plate tests), cognitive functions (evaluated through Morris Water Maze), and locomotor activity (measured via Open Field Test) were recorded. ResultsAmantadine administration significantly reduced recovery time from propofol anesthesia, prolonged pain perception, and preserved cognitive functions compared to propofol alone. The time spent in the target quadrant in the Morris Water Maze was significantly longer in groups receiving amantadine. Additionally, the distance covered until finding the platform was significantly shorter in the propofol-only group. DiscussionAmantadine's neuroprotective effects, attributed to its antagonistic action on glutamate and NMDA receptors, mitigate the detrimental effects of propofol on cognitive function and pain perception. This study highlights the potential of combining amantadine with propofol to enhance postoperative outcomes. ConclusionAmantadine administration before propofol anesthesia positively influenced postoperative recovery, cognitive function preservation, and stress-related pain perception in mice. These findings suggest a potential therapeutic strategy to mitigate POCD and pain associated with surgery.

8644 Dynamic Insights into Glucocorticoid Receptor Dysfunction: Novel patient-derived T437I Mutation and Its Impact on Glucocorticoid Receptor Function

Abstract Disclosure: T. Tettey: None. S. Kim: None. K. Wagh: None. Q. Lao: None. L.R. Schiltz: None. D.A. Stavreva: None. D.M. Presman: None. D.P. Merke: None. G.L. Hager: None. The glucocorticoid receptor (GR) is a hormone regulated transcription factor which binds chromatin to regulate many genes, including stress-response and inflammatory genes. Dexamethasone, a GR agonist, is widely used in the treatment of severe inflammation, including COVID-19. GR is vital for life and several GR mutations have been linked to severe pathophysiological conditions. Here we report a novel mutation in the DNA binding domain (DBD) of GR (T437I) in a patient with partial glucocorticoid resistance, a rare genetic disorder characterized by generalized insensitivity to glucocorticoids and a consequent hyperactivation of the hypothalamic pituitary adrenal axis. While the clinical manifestations of this hT437I GR mutation are apparent, its molecular mechanisms remain unexplored. Employing a comprehensive approach that integrates biophysical methods, molecular biology, and genomics, we investigate the molecular underpinnings of this genetic anomaly. Using CRISPR/Cas9 gene editing, we introduce GFP or Halo-tagged hT437I GR mutant into GR null mouse cells. Our findings indicate that the T437I GR variant exhibits normal hormone binding and nuclear translocation. Live-cell imaging using number and brightness analysis reveals that the mutant receptor maintains a wildtype-like oligomeric state but adopts a heterodimeric conformation in the presence of endogenous GR. Global transcriptomics analyses of the mouse hT437I mutant show that most dexamethasone-regulated genes are unresponsive following hormone treatment. We hypothesize that this mutation within the DBD compromises the binding of GR to regulatory sites of target genes. Leveraging fluorescence high-resolution microscopy, we employ single molecule tracking to study the dynamic behavior of Halo-tagged hT437I GR in mouse cells. Our results indicate that the GR mutant has a higher dwell-time on chromatin compared to the wild-type receptor. This suggests that the hT437I mutation impairs the receptor's binding to genomic sites, potentially leading to a failure in regulating GR target genes. This ongoing exploration of the molecular intricacies aims to deepen our understanding of the clinical phenotype observed in the patient. Presentation: 6/2/2024

Cellular Mechanisms of RET Receptor Dysfunction in Multiple Endocrine Neoplasia 2.

REarranged during Transfection (RET) is a developmentally important receptor tyrosine kinase that has been identified as an oncogenic driver in a number of cancers. Activating RET point-mutations give rise to the inherited cancer syndrome Multiple Endocrine Neoplasia type 2 (MEN2), characterized by medullary thyroid carcinoma. There are two MEN2 subtypes, MEN2A and MEN2B, that differ in tumour aggressiveness and the associated constellation of other disease features, which are caused by distinct patterns of RET amino acid substitution mutations. MEN2A-RET mutations affecting extracellular cysteine residues promote ligand independent dimerization and constitutive RET activity, while MEN2B is caused by a single amino acid change in the tyrosine kinase domain of RET, releasing autoinhibition and producing a more active MEN2B-RET kinase that can promote signalling as monomers or dimers in the absence of ligand. These mutations cause intrinsic biochemical changes in RET structure and activation but also trigger extrinsic effects that alter RET cellular location, interactions and mechanisms of downregulation that can prolong or mislocate RET activity, changing or enhancing functional outcomes. Together, changes in specific combinations of RET-mediated effects associated with different mutations give rise to the distinct MEN2 disease phenotypes. Here, we discuss the current understanding of the intrinsic and extrinsic characteristics of RET MEN2A cysteine and MEN2B mutants and how these contribute to transforming cellular processes and to differences in tumour progression and disease aggressiveness.

Dysfunction of the NMDA Receptor in the Pathophysiology of Schizophrenia and/or the Pathomechanisms of Treatment-Resistant Schizophrenia.

For several decades, the dopamine hypothesis contributed to the discovery of numerous typical and atypical antipsychotics and was the sole hypothesis for the pathophysiology of schizophrenia. However, neither typical nor atypical antipsychotics, other than clozapine, have been effective in addressing negative symptoms and cognitive impairments, which are indices for the prognostic and disability outcomes of schizophrenia. Following the development of atypical antipsychotics, the therapeutic targets for antipsychotics expanded beyond the blockade of dopamine D2 and serotonin 5-HT2A receptors to explore the partial agonism of the D2 receptor and the modulation of new targets, such as D3, 5-HT1A, 5-HT7, and metabotropic glutamate receptors. Despite these efforts, to date, psychiatry has not successfully developed antipsychotics with antipsychotic properties proven to be superior to those of clozapine. The glutamate hypothesis, another hypothesis regarding the pathophysiology/pathomechanism of schizophrenia, was proposed based on clinical findings that N-methyl-D-aspartate glutamate receptor (NMDAR) antagonists, such as phencyclidine and ketamine, induce schizophrenia-like psychotic episodes. Large-scale genome-wide association studies (GWASs) revealed that approximately 30% of the risk genes for schizophrenia (the total number was over one hundred) encode proteins associated with glutamatergic transmission. These findings supported the validation of the glutamate hypothesis, which was inspired by the clinical findings regarding NMDAR antagonists. Additionally, these clinical and genetic findings suggest that schizophrenia is possibly a syndrome with complicated pathomechanisms that are affected by multiple biological and genetic vulnerabilities. The glutamate hypothesis has been the most extensively investigated pathophysiology/pathomechanism hypothesis, other than the dopamine hypothesis. Studies have revealed the possibility that functional abnormalities of the NMDAR play important roles in the pathophysiology/pathomechanism of schizophrenia. However, no antipsychotics derived from the glutamatergic hypothesis have yet been approved for the treatment of schizophrenia or treatment-resistant schizophrenia. Considering the increasing evidence supporting the potential pro-cognitive effects of glutamatergic agents and the lack of sufficient medications to treat the cognitive impairments associated with schizophrenia, these previous setbacks cannot preclude research into potential novel glutamate modulators. Given this background, to emphasize the importance of the dysfunction of the NMDAR in the pathomechanism and/or pathophysiology of schizophrenia, this review introduces the increasing findings on the functional abnormalities in glutamatergic transmission associated with the NMDAR.

Anomalous Behavior of Disease-Inflicting Polymorphic Variants of Nuclear Receptor THRβ of Indian Origin

Thyroid hormone receptor β (THRβ) binds to thyroid hormones to execute various cellular and physiological processes as a ligand-inducible transcriptional factor. THRs, especially THRβ, are key players in the central regulation of the HPT axis. They ensure a delicate balance between thyroid hormone production and feedback control, allowing the body to adapt to changing environmental conditions. Polymorphisms in THRβ can lead to multiple clinical manifestations like resistance to thyroid hormone β, neurological or psychological disorders (like autism, intellectual disabilities, etc), and several types of cancers (papillary thyroid cancer, breast cancer, etc). This study examined two disease-inflicting polymorphic variants of THRβ, P323L, and P453S of Indian origin. It was observed that these variants exhibit impaired subcellular localization patterns, transcriptional functions, and compromised receptor stability. The study provides valuable insight into the cellular mechanism underlying receptor dysfunction and inflicting disease states. It is anticipated that disease-inflicting polymorphic variants of THRβ influence the structural and functional behavior of the receptor, contributing to the onset of disease. A concerted effort to gain the molecular basis of receptor dysregulation will help improve the assessment and management of THRβ-mediated diseases.

Exploring the Iris haynei essential oil: analysis of phytochemical composition, evaluation of cytotoxicity, antimicrobial properties, and AMPA receptor modulation

BackgroundThe complex composition of essential oils (EOs) derived from plants offers potential therapeutic approaches for treating various medical conditions, including neurological disorders and infectious diseases. This research aimed to comprehensively analyze the phytochemical composition of Iris haynei EO and evaluate its pharmacological properties, specifically its cytotoxicity, antimicrobial activity, and modulation of AMPA receptors.ResultsThe analysis of I. haynei EO, conducted using gas chromatography and mass spectroscopy, identified diethyl phthalate, α-terpineol, and benzyl acetate as the main components. Cytotoxicity experiments on several cancer cell lines revealed a dose-dependent impact. Electrophysiological recordings on HEK293T cells expressing AMPARs showed varying levels of inhibition across different subunits, with receptors encoding GluA2 exhibiting the most significant effects. The EO also demonstrated significant antibacterial activity against both Gram-positive and Gram-negative bacteria, as well as fungi.ConclusionsThe findings of this study underscore the potential therapeutic benefits of I. haynei EO, particularly in treating neurological conditions associated with AMPA receptor dysfunction and exhibiting antimicrobial activity against infectious agents. The promising results warrant further investigation into the pharmacological effects of the EO, suggesting a novel approach for addressing cerebral ischemia and related neurological diseases.Graphical

Amyloid-β Causes NMDA Receptor Dysfunction and Dendritic Spine Loss through mGluR1 and AKAP150-Anchored Calcineurin Signaling.

Neuronal excitatory synapses are primarily located on small dendritic protrusions called spines. During synaptic plasticity underlying learning and memory, Ca2+ influx through postsynaptic NMDA-type glutamate receptors (NMDARs) initiates signaling pathways that coordinate changes in dendritic spine structure and synaptic function. During long-term potentiation (LTP), high levels of NMDAR Ca2+ influx promote increases in both synaptic strength and dendritic spine size through activation of Ca2+-dependent protein kinases. In contrast, during long-term depression (LTD), low levels of NMDAR Ca2+ influx promote decreased synaptic strength and spine shrinkage and elimination through activation of the Ca2+-dependent protein phosphatase calcineurin (CaN), which is anchored at synapses via the scaffold protein A-kinase anchoring protein (AKAP)150. In Alzheimer's disease (AD), the pathological agent amyloid-β (Aβ) may impair learning and memory through biasing NMDAR Ca2+ signaling pathways toward LTD and spine elimination. By employing AKAP150 knock-in mice of both sexes with a mutation that disrupts CaN anchoring to AKAP150, we revealed that local, postsynaptic AKAP-CaN-LTD signaling was required for Aβ-mediated impairment of NMDAR synaptic Ca2+ influx, inhibition of LTP, and dendritic spine loss. Additionally, we found that Aβ acutely engages AKAP-CaN signaling through activation of G-protein-coupled metabotropic glutamate receptor 1 (mGluR1) leading to dephosphorylation of NMDAR GluN2B subunits, which decreases Ca2+ influx to favor LTD over LTP, and cofilin, which promotes F-actin severing to destabilize dendritic spines. These findings reveal a novel interplay between NMDAR and mGluR1 signaling that converges on AKAP-anchored CaN to coordinate dephosphorylation of postsynaptic substrates linked to multiple aspects of Aβ-mediated synaptic dysfunction.

Abstract Tu078: Mechanistic basis of protein phosphatase 2A inhibition by I2PP2A dimerization: A key step in βAR resensitization

Dysfunction of beta-adrenergic receptor (βAR) is a key hallmark of heart failure, wherein mechanisms of phosphorylation-mediated desensitization of βARs are well understood. However, less is known about dephosphorylation-mediated resensitization of βARs that is regulated by protein phosphatase 2A (PP2A) in heart failure. Our previous studies have shown that agonist stimulation of βAR activates phosphoinositide 3-kinase γ (PI3Kγ) which phosphorylates endogenous inhibitor of PP2A (I2PP2A) on serine residues 9 & 93. Phosphorylated I2PP2A (pI2PP2A) binds to PP2A inhibiting its activity thereby, impairing βAR resensitization. Although structural studies have shown I2PP2A to be a dimer, yet little is understood about the mechanistic basis of PP2A inhibition by I2PP2A. We therefore hypothesized that phosphorylation of I2PP2A promotes dimerization driving robust interaction with PP2A resulting in inhibition of PP2A and impairment in βAR resensitization. To test for dimerization, hemagglutinin (HA)-tagged I2PP2A and Myc-tagged I2PP2A were generated and co-expressed in HEK 293 cells. Immunoprecipitation of HA-I2PP2A led to significant co-immunoprecipitation of Myc-I2PP2A reflecting the ability of I2PP2A to dimerize. To determine whether phosphorylation is key for dimerization, phospho-mimetic mutants of I2PP2A (S9,93A (inactive) or S9,93D (active)) were generated. Immunoblotting of cellular lysates with expression of these phospho-mimetics showed that S9,93D exclusively formed dimers, while S9,93A I2PP2A only formed monomers suggesting that phosphorylation is key facilitator of dimerization. The role of I2PP2A phosphorylation in its dimerization and PP2A interaction with consequences on βAR resensitization will be presented. Determining the mechanistic basis of this understudied pathway is critical as human heart failure is associated with increased PI3Kγ activity, elevated expression of I2PP2A and reduced βAR function. Key words: Desensitization, Resensitization, I2PP2A, PP2A, Dimerization

Abstract We107: Reduction of Six-Month Heart Failure Readmission Rates in Patients Undergoing MitraClip with Beta Receptor Blockade

Introduction: MitraClip has been shown to reduce heart failure readmissions in patients with moderate to severe mitral valve regurgitation. Likewise, beta-blocker (BB) therapy has been shown to reduce morbidity and mortality in select heart failure patients. At the cellular level, chronic myocardial insult from ongoing heart failure and mitral regurgitation leads to persistent overstimulation of myocardial beta-receptors, ultimately reducing cardiac inotropic reserve and contributing to myocardial injury. Thus, we hypothesized that patients on beta-blocker therapy before the MitraClip procedure would have fewer heart failure-related readmissions. Hypothesis: We assessed the hypothesis that beta-blocker therapy before the MitraClip procedure would lead to fewer heart failure-related readmissions by conducting a retrospective cohort study. This would help us better understand the pathogenesis of re-admissions in this patient population as well as help us decide whether prophylactic initiation of BB therapy before the procedure would reduce the risk of heart failure readmissions. Methods: We reviewed the records of patients who underwent the MitraClip procedure at our institution from January 2017 to July 2022. Patients without listed home medications, as well as non-heart failure-related readmissions and deaths, were excluded. Patients were split into those on BB therapy and those with no BB therapy. Of the 401 charts screened, 324 met the inclusion criteria. Results: From those who met the inclusion criteria, 226 patients were on beta-blocker therapy, while 98 patients were not. Of those who had at least one heart failure-related readmission within 6 months of the MitraClip procedure, 18 patients were on beta-blocker therapy and 16 patients were not. Meaning a 7.96% readmission rate for patients on beta-blocker therapy, and a 16.32% readmission rate for those who were not (OR 2.05, 95% CI: 1.004 to 4.186, p<0.05), with the number needed to treat being 11.9. Conclusions: Our data shows that the use of beta-blocker therapy was associated with a statistically significant decrease in 6-month heart failure readmissions in those undergoing the MitraClip procedure. This suggests that at the cellular level, cardiac beta receptor dysfunction plays an integral part in future hospitalizations in this population. In conclusion, beta-blocker therapy should be considered in heart failure patients planning to undergo the MitraClip procedure to reduce heart failure-related readmissions.

Juvenile bright light exposure ameliorates adult behavioral abnormalities by enhancing neurogenesis in a N-methyl-D-aspartate receptor dysfunction mouse model relevant for cognitive impairment in schizophrenia

Exposure to light has been demonstrated to stimulate brain regions associated with cognition; however, investigations into its cognitive-enhancing effects have primarily focused on wild-type rodents. This study seeks to elucidate how bright light exposure mitigates cognitive deficits associated with schizophrenia by examining its impact on hippocampal neurogenesis and its potential to alleviate sub-chronic MK-801-induced cognitive impairments in mice. Following three weeks of juvenile bright light exposure (5–8 weeks old), significant increases in proliferating neurons (BrdU+) and immature neurons (DCX+ cells) were observed in the dentate gyrus (DG) and lateral ventricle of MK-801-treated mice. Long-term bright light treatment further promoted the differentiation of BrdU+ cells into immature neurons (BrdU+ DCX+ cells), mature neurons (BrdU+ NeuN+ cells), or astrocytes (BrdU+ GFAP+ cells) in the hippocampal DG. This augmented neurogenesis correlated with the attenuation of sub-chronic MK- 801-induced cognitive deficits, as evidenced by enhancements in Y-maze, novel object recognition (NOR), novel location recognition (NLR), and Morris water maze (MWM) test performances. These findings suggest a promising noninvasive clinical approach for alleviating cognitive impairments associated with neuropsychiatric disorders.

Ginsenoside Rb1 reduces oxidative/carbonyl stress damage and dysfunction of RyR2 in the heart of streptozotocin-induced diabetic rats

BackgroundOxidative stress may contribute to cardiac ryanodine receptor (RyR2) dysfunction in diabetic cardiomyopathy. Ginsenoside Rb1 (Rb1) is a major pharmacologically active component of ginseng to treat cardiovascular diseases. Whether Rb1 treat diabetes injured heart remains unknown. This study was to investigate the effect of Rb1 on diabetes injured cardiac muscle tissue and to further investigate its possible molecular pharmacology mechanisms.MethodsMale Sprague-Dawley rats were injected streptozotocin solution for 2 weeks, followed 6 weeks Rb1 or insulin treatment. The activity of SOD, CAT, Gpx, and the levels of MDA was measured; histological and ultrastructure analyses, RyR2 activity and phosphorylated RyR2(Ser2808) protein expression analyses; and Tunel assay were performed.ResultsThere was decreased activity of SOD, CAT, Gpx and increased levels of MDA in the diabetic group from control. Rb1 treatment increased activity of SOD, CAT, Gpx and decreased the levels of MDA as compared with diabetic rats. Neutralizing the RyR2 activity significantly decreased in diabetes from control, and increased in Rb1 treatment group from diabetic group. The expression of phosphorylation of RyR2 Ser2808 was increased in diabetic rats from control, and were attenuated with insulin and Rb1 treatment. Diabetes increased the apoptosis rate, and Rb1 treatment decreased the apoptosis rate. Rb1 and insulin ameliorated myocardial injury in diabetic rats.ConclusionsThese data indicate that Rb1 could be useful for mitigating oxidative damage, reduced phosphorylation of RyR2 Ser2808 and decreased the apoptosis rate of cardiomyocytes in diabetic cardiomyopathy.

Enhanced eMAGE applied to identify genetic factors of nuclear hormone receptor dysfunction via combinatorial gene editing

Technologies that generate precise combinatorial genome modifications are well suited to dissect the polygenic basis of complex phenotypes and engineer synthetic genomes. Genome modifications with engineered nucleases can lead to undesirable repair outcomes through imprecise homology-directed repair, requiring non-cleavable gene editing strategies. Eukaryotic multiplex genome engineering (eMAGE) generates precise combinatorial genome modifications in Saccharomyces cerevisiae without generating DNA breaks or using engineered nucleases. Here, we systematically optimize eMAGE to achieve 90% editing frequency, reduce workflow time, and extend editing distance to 20 kb. We further engineer an inducible dominant negative mismatch repair system, allowing for high-efficiency editing via eMAGE while suppressing the elevated background mutation rate 17-fold resulting from mismatch repair inactivation. We apply these advances to construct a library of cancer-associated mutations in the ligand-binding domains of human estrogen receptor alpha and progesterone receptor to understand their impact on ligand-independent autoactivation. We validate that this yeast model captures autoactivation mutations characterized in human breast cancer models and further leads to the discovery of several previously uncharacterized autoactivating mutations. This work demonstrates the development and optimization of a cleavage-free method of genome editing well suited for applications requiring efficient multiplex editing with minimal background mutations.

Effects of (S)-3,4-DCPG, an mGlu8 receptor agonist, on hippocampal long-term potentiation at perforant pathway-dentate gyrus synapses in prenatal valproic acid-induced rat model of autism

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental condition characterized by social interaction deficits, communication impairments, repetitive behaviors, and sensory sensitivities. While the etiology of ASD is multifaceted, abnormalities in glutamatergic neurotransmission and synaptic plasticity have been implicated. This study investigated the role of metabotropic glutamate receptor 8 (mGlu8) in modulating long-term potentiation (LTP) in a rat model of ASD induced by prenatal valproic acid (VPA) exposure. To induce an animal model with autism-like characteristics, pregnant rats received an intraperitoneal injection of 500 mg/kg of sodium valproate (NaVPA) on embryonic day 12.5. High-frequency stimulation was applied to the perforant path-dentate gyrus (PP-DG) synapse to induce LTP, while the mGlu8 receptor agonist (S)-3,4-dicarboxyphenylglycine (DCPG) was administered into the DG. The results revealed that VPA-exposed rats exhibited reduced LTP compared to controls. DCPG had contrasting effects, inhibiting LTP in controls and enhancing it in VPA-exposed rats. Moreover, reduced social novelty preference index (SNPI) in VPA-exposed rats was reversed by intra-DG administration of S-3,4-DCPG. In conclusion, our study advances our understanding of the complex relationship between glutamatergic neurotransmission, synaptic plasticity, and VPA-induced autism model. The findings suggest that mGlu8 receptor dysfunction plays a role in the impaired synaptic plasticity seen in ASD.

The antipsychotic agent sulpiride microinjected into the ventral pallidum restores positive symptom-like habituation disturbance in MAM-E17 schizophrenia model rats

Dysfunction of subcortical D2-like dopamine receptors (D2Rs) can lead to positive symptoms of schizophrenia, and their analog, the increased locomotor activity in schizophrenia model MAM-E17 rats. The ventral pallidum (VP) is a limbic structure containing D2Rs. The D2R antagonist sulpiride is a widespread antipsychotic drug, which can alleviate positive symptoms in human patients. However, it is still not known how sulpiride can influence positive symptoms via VP D2Rs. We hypothesize that the microinjection of sulpiride into the VP can normalize hyperactivity in MAM-E17 rats. In addition, recently, we showed that the microinjection of sulpirid into the VP induces place preference in neurotypical rats. Thus, we aimed to test whether intra-VP sulpiride can also have a rewarding effect in MAM-E17 rats. Therefore, open field-based conditioned place preference (CPP) test was applied in neurotypical (SAL-E17) and MAM-E17 schizophrenia model rats to test locomotor activity and the potential locomotor-reducing and rewarding effects of sulpiride. Sulpiride was microinjected bilaterally in three different doses into the VP, and the controls received only vehicle. The results of the present study demonstrated that the increased locomotor activity of the MAM-E17 rats was caused by habituation disturbance. Accordingly, larger doses of sulpiride in the VP reduce the positive symptom-analog habituation disturbance of the MAM-E17 animals. Furthermore, we showed that the largest dose of sulpiride administered into the VP induced CPP in the SAL-E17 animals but not in the MAM-E17 animals. These findings revealed that VP D2Rs play an important role in the formation of positive symptom-like habituation disturbances in MAM-E17 rats.

D-serine and D-amino acid oxidase levels in patients with schizophrenia spectrum disorders in the first episode and 6-month follow-up

BackgroundD-serine and the D-amino acid oxidase (DAO) enzyme, which breaks down d-amino acids, may be involved in the pathophysiology of schizophrenia by affecting the N-methyl-D-aspartate (NMDA) receptor. The exact role of D-serine and DAO, as well as the consequences of increased DAO activity in patients with schizophrenia, remain unclear. We aimed to investigate D-serine and DAO levels in patients with first-episode schizophrenia spectrum disorders before treatment and after six months of treatment. MethodComparisons for the serum levels of D-serine and DAO were made between 81 healthy controls and 89 patients with first-episode schizophrenia spectrum disorders without a history of treatment. Further comparisons were made after 6 months for changes in these levels in the 41 patients in follow-up. The Positive and Negative Syndrome Scale (PANNS), Calgary Scale for Depression in Schizophrenia (CDSS), Montreal Cognitive Assessment Scale (MoCA), Global Assessment Scale (GAS), and Clinical Global Impression Scale (CGI) were used to evaluate the symptom severity and functionality. Secondary results included comparisons related to antipsychotic equivalent doses. ResultsBefore treatment, patients had significantly lower levels of D-serine, DAO, and D-serine/DAO ratio compared to healthy individuals (p < 0.001; p < 0.001; p = 0.004). DAO and D-serine levels of the patients were higher after six months of treatment (p = 0.025; p = 0.001). There was correlation of DAO levels with antipsychotic dosage and with PANSS negative and total subscale scores (rho = 0.421, p = 0.01; rho = 0.280, p = 0.008; rho = 0.371, p = 0.000). No correlation was found between serum D-serine level, DAO level, and the D-serine/DAO ratio with cognitive function. ConclusionsThe results suggest that D-serine and DAO may play a role that is sensitive to treatment effects in schizophrenia spectrum disorders. To gain a more comprehensive understanding of the impact antipsychotic drugs have on NMDA receptor dysfunction, there is a requirement for studies that directly evaluates the activity of the DAO enzyme.

Interleukin 1β receptor and synaptic dysfunction in recurrent brain infection with Herpes simplex virus type-1.

Several experimental evidence suggests a link between brain Herpes simplex virus type-1 infection and the occurrence of Alzheimer's disease. However, the molecular mechanisms underlying this association are not completely understood. Among the molecular mediators of synaptic and cognitive dysfunction occurring after Herpes simplex virus type-1 infection and reactivation in the brain neuroinflammatory cytokines seem to occupy a central role. Here, we specifically reviewed literature reports dealing with the impact of neuroinflammation on synaptic dysfunction observed after recurrent Herpes simplex virus type-1 reactivation in the brain, highlighting the role of interleukins and, in particular, interleukin 1β as a possible target against Herpes simplex virus type-1-induced neuronal dysfunctions.

Limb-Clasping Response in NMDA Receptor Palmitoylation-Deficient Mice.

Proper regulation of N-methyl-D-aspartate-type glutamate receptor (NMDA receptor) expression is responsible for excitatory synaptic functions in the mammalian brain. NMDA receptor dysfunction can cause various neuropsychiatric disorders and neurodegenerative diseases. Posttranslational protein S-palmitoylation, the covalent attachment of palmitic acid to intracellular cysteine residues via thioester bonds, occurs in the carboxyl terminus of GluN2B, which is the major regulatory NMDA receptor subunit. Mutations of three palmitoylatable cysteine residues in the membrane-proximal cluster of GluN2B to non-palmitoylatable serine (3CS) lead to the dephosphorylation of GluN2B Tyr1472 in the hippocampus and cerebral cortex, inducing a reduction in the surface expression of GluN2B-containig NMDA receptors. Furthermore, adult GluN2B 3CS homozygous mice demonstrated a definite clasping response without abnormalities in the gross brain structure, other neurological reflexes, or expression levels of synaptic proteins in the cerebrum. This behavioral disorder, observed in the GluN2B 3CS knock-in mice, indicated that complex higher brain functions are coordinated through the palmitoylation-dependent regulation of NMDA receptors in excitatory synapses.