Neuronal Signaling Research Articles

Mechanisms of fibrinogen trans-activation of the EGFR/Ca2+ signaling axis to regulate mitochondrial transport and energy transfer and inhibit axonal regeneration following cerebral ischemia.

Ischemic stroke results in inhibition of axonal regeneration but the roles of fibrinogen (Fg) in neuronal signaling and energy crises in experimental stroke are under-investigated. We explored the mechanism of Fg modulation of axonal regeneration and neuronal energy crisis after cerebral ischemia using a permanent middle cerebral artery occlusion (MCAO) rat model and primary cortical neurons under low glucose-low oxygen. Behavioral tests assessed neurological deficits; immunofluorescence, immunohistochemistry, and Western-blot analyzed Fg and protein levels. Fluo-3/AM fluorescence measured free Ca2+ and ATP levels were gauged via specific assays and F560nm/F510nm ratio calculations. Mito-Tracker Green labeled mitochondria and immunoprecipitation studied protein interactions. Our comprehensive study revealed that Fg inhibited axonal regeneration post-MCAO as indicated by reduced GAP43 expression along with elevated free Ca2+, both suggesting an energy crisis. Fg impeded mitochondrial function and mediated impairment through the EGFR/Ca2+ axis by trans-activating EGFR via integrin αvβ3 interaction. These results indicate that the binding of Fg with integrin αvβ3 leads to the trans-activation of the EGFR/Ca2+ signaling axis thereby disrupting mitochondrial energy transport and axonal regeneration and exacerbating the detrimental effects of ischemic neuronal injury.

Preliminary Evidence for Neuronal Dysfunction Following Adverse Childhood Experiences: An Investigation of Salivary MicroRNA Within a High-Risk Youth Sample

Background/Objectives: Adverse childhood experiences (ACEs) are potent drivers of psychopathology and neurological disorders, especially within minoritized populations. Nonetheless, we lack a coherent understanding of the neuronal mechanisms through which ACEs impact gene expression and, thereby, the development of psychopathology. Methods: This observational pilot study used a novel marker of neuronal functioning (brain-derived micro ribonucleic acids, or miRNAs) collected via saliva to explore the connection between ACEs and neuronal gene expression in 45 adolescents with a collectively high ACE exposure (26 males and 19 females of diverse races/ethnicities, with six cumulative ACEs on average). We aimed to determine the feasibility of using salivary microRNA for probing neuronal gene expression with the goal of identifying cellular processes and genetic pathways perturbed by childhood adversity. Results: A total of 274 miRNAs exhibited reliable salivary expression (raw counts > 10 in > 10% of samples). Fourteen (5.1%) were associated with cumulative ACE exposure (p < 0.05; r’s ≥ 0.31). ACE exposure correlated negatively with miR-92b-3p, 145a-5p, 31-5p, and 3065-5p, and positively with miR-15b-5p, 30b-5p, 30c-5p, 30e-3p, 199a-3p, 223-3p, 338-3p, 338-5p, 542-3p, and 582-5p. Most relations remained significant after controlling for multiple comparisons and potential retrospective bias in ACE reporting for miRNAs with particularly strong relations (p < 0.03). We examined KEGG pathways targeted by miRNAs associated with total ACE scores. Results indicated putative miRNA targets over-represented 47 KEGG pathways (adjusted p < 0.05) involved in neuronal signaling, brain development, and neuroinflammation. Conclusions: Although preliminary and with a small sample, the findings represent a novel contribution to the understanding of how childhood adversity impacts neuronal gene expression via miRNA signaling.

Alterations in store-operated calcium entry in neurodegenerative pathologies: history, facts, perspectives

Neurodegenerative disorders, along with cardiovascular and oncological pathologies, are one of the most actual issues facing modern medicine. Therefore, the study of the molecular mechanisms of their pathogenesis and the search for new drug targets is highly demanded. Neuronal calcium signalling has attracted close attention, as altered calcium homeostasis has been demonstrated in the pathogenesis of various neurodegenerative diseases. In this review, we focus on one of the most ubiquitous and important pathways for calcium uptake: store-operated calcium entry. Here we describe studies demonstrating disturbances in store-operated calcium entry in various neurodegenerative pathologies, including Alzheimer’s, Parkinson’s and Huntington’s diseases. Also, we analyse the molecular determinants underlying these disturbances and propose ways for pharmacological correction of altered calcium signaling. The information summarized in the review will allow us to consider store-operated calcium channels as promising targets for the drug development in order to treat neurodegenerative pathologies and outline further promising directions for the investigation.

Stimulus-induced rotary saturation imaging of visually evoked response: A pilot study.

Spin-lock (SL) pulses have been proposed to directly detect neuronal activity otherwise inaccessible through standard functional magnetic resonance imaging. However, the practical limits of this technique remain unexplored. Key challenges in SL-based detection include ultra-weak signal variations, sensitivity to magnetic field inhomogeneities, and potential contamination from blood oxygen level-dependent effects, all of which hinder the reliable isolation of neuronal signals. This pilot study evaluates the performance of the stimulus-induced rotary saturation (SIRS) technique to map visual stimulation response in the human cortex. A rotary echo spin-lock (RESL) preparation followed by a 2D echo planar imaging readout was used to investigate 12 healthy subjects at rest and during continuous exposure to 8Hz flickering light. The SL amplitude was fixed to the target neuroelectric oscillations at that frequency. The signal variance was used as contrast metric, and two alternative post-processing pipelines (regression-filtering-rectification and normalized subtraction) were statistically evaluated. Higher variance in the SL signal was detected in four of the 12 subjects. Although group-level analysis indicated activation in the occipital pole, analysis of variance revealed that this difference was not statistically significant, highlighting the need for comparable control measures and more robust preparations. Further optimization in sensitivity and robustness is required to noninvasively detect physiological neuroelectric activity in the human brain.

Transcriptional Profiling of Tofacitinib Treatment in Juvenile Idiopathic Arthritis: Implications for Treatment Response Prediction.

To assess changes in gene expression following tofacitinib treatment and investigate transcription patterns as potential predictors of treatment response in patients with active juvenile idiopathic arthritis (JIA). Whole blood samples were collected from JIA patients at baseline and after 18 weeks of open-label tofacitinib treatment (clinical trial NCT02592434). Patients who achieved a JIA-American College of Rheumatology (ACR) response of 70 or above at week 18 were classified as treatment-responders (TR) while those with at most a JIA-ACR30 response were classified as poor-responders (PR). Differential gene expression and gene ontology (GO) over-representation analyses were performed to compare RNA expression between week 18 and baseline samples, as well as between PR and TR samples at baseline. Samples from 67 patients at baseline and 60 at week 18 were analyzed. Following 18 weeks of tofacitinib treatment across all JIA subjects, 883 genes showed significant differential expression (week 18 - baseline). The most strongly downregulated genes were over-represented within IL-7, type I, and type II interferon pathways, while upregulated genes were enriched in ontologies related to neuronal cell processes and cell signaling. Comparing PR and TR at baseline, 663 genes showed differential expression. Upregulated genes were over-represented within ontologies including activation of MAPK activity (p=9.40x10-5), myeloid cell development (p=8.13 x10-5), activation of GTPase activity (p=0.00015), and organelle transport along microtubules (p=0.00021). Tofacitinib treatment in JIA downregulated genes in interferon and IL-7 signaling pathways regardless of effectiveness. Furthermore, baseline upregulation of MAPK signaling may predict poor response to tofacitinib treatment in JIA.

Targeting GM2 Ganglioside Accumulation in Dementia: Current Therapeutic Approaches and Future Directions.

Dementia in neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB) is a progressive neurological condition affecting millions worldwide. The amphiphilic molecule GM2 gangliosides are abundant in the human brain and play important roles in neuronal development, intercellular recognition, myelin stabilization, and signal transduction. GM2 ganglioside's degradation requires hexosaminidase A (HexA), a heterodimer composed of an α subunit encoded by HEXA and a β subunit encoded by HEXB. The hydrolysis of GM2 also requires a non-enzymatic protein, the GM2 activator protein (GM2-AP), encoded by GM2A. Pathogenic mutations of HEXA, HEXB, and GM2A are responsible for autosomal recessive diseases known as GM2 gangliosidosis, caused by the excessive intralysosomal accumulation of GM2 gangliosides. In AD, PD and DLB, GM2 ganglioside accumulation is reported to facilitate Aβ and α-synuclein aggregation into toxic oligomers and plaques through activation of downstream signaling pathways, such as protein kinase C (PKC) and oxidative stress factors. This review explored the potential role of GM2 ganglioside alteration in toxic protein aggregations and its related signaling pathways leading to neurodegenerative diseases. Further review explored potential therapeutic approaches, which include synthetic and phytomolecules targeting GM2 ganglioside accumulation in the brain, holding a promise for providing new and effective management for dementia.

The phenotypic and genotypic spectrum of individuals with mono- or biallelic ANK3 variants.

ANK3 encodes ankyrin-G, a protein involved in neuronal development and signaling. Alternative splicing gives rise to three ankyrin-G isoforms comprising different domains with distinct expression patterns. Mono- or biallelic ANK3 variants are associated with non-specific syndromic intellectual disability in 14 individuals (seven with monoallelic and seven with biallelic variants). In this study, we describe the clinical features of 13 additional individuals and review the data on a total of 27 individuals (16 individuals with monoallelic and 11 with biallelic ANK3 variants) and demonstrate that the phenotype for biallelic variants is more severe. The phenotypic features include language delay (92%), autism spectrum disorder (76%), intellectual disability (78%), hypotonia (65%), motor delay (68%), attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD) (57%), sleep disturbances (50%), aggressivity/self-injury (37.5%), and epilepsy (35%). A notable phenotypic difference was presence of ataxia in three individuals with biallelic variants, but in none of the individuals with monoallelic variants. While the majority of the monoallelic variants are predicted to result in a truncated protein, biallelic variants are almost exclusively missense. Moreover, mono- and biallelic variants appear to be localized differently across the three different ankyrin-G isoforms, suggesting isoform-specific pathological mechanisms.

Effects of the two-pore potassium channel subunit Task5 on neuronal function and signal processing in the auditory brainstem

Processing of auditory signals critically depends on the neuron’s ability to fire brief, precisely timed action potentials (APs) at high frequencies and high fidelity for prolonged times. This requires the expression of specialized sets of ion channels to quickly repolarize neurons, prevent aberrant AP firing and tightly regulate neuronal excitability. Although critically important, the regulation of neuronal excitability has received little attention in the auditory system. Neuronal excitability is determined to a large extent by the resting membrane potential (RMP), which in turn depends on the kind and number of ion channels open at rest; mostly potassium channels. A large part of this resting potassium conductance is carried by two-pore potassium channels (K2P channels). Among the K2P channels, the subunit Task5 is expressed almost exclusively in the auditory brainstem, suggesting a specialized role in auditory processing. However, since it failed to form functional ion channels in heterologous expression systems, it was classified “non-functional” for a long time and its role in the auditory system remained elusive. Here, we generated Task5 knock-out (KO) mice. The loss of Task5 resulted in changes in neuronal excitability in bushy cells of the ventral cochlear nucleus (VCN) and principal neurons of the medial nucleus of the trapezoid body (MNTB). Moreover, auditory brainstem responses (ABRs) to loud sounds were altered in Tasko5-KO mice. Thus, our study provides evidence that Task5 is indeed a functional K2P subunit and contributes to sound processing in the auditory brainstem.

Rab11 suppresses neuronal stress signaling by localizing dual leucine zipper kinase to axon terminals for protein turnover.

Dual leucine zipper kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals for protein turnover and a failure of such transport can lead to neuronal loss. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling.

Somatostatin-expressing inhibitory neurons with mTORC1 activation in cortical layers 4/5 are involved in the epileptogenesis of mice

Aim: Patients with tuberous sclerosis complex (TSC) which is caused by hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1) often show giant cells in the brain. These giant cells are thought to be involved in epileptogenesis, but the underlying mechanisms are unknown. In this study, we focused on mTORC1 activation and γ-amino butyric acid (GABA)ergic signaling in somatostatin-expressing inhibitory neurons (SST-INs) using TSC-related epilepsy model mice. Methods: We analyzed the 8-week-old Tsc2 conditional knockout (Tsc2 cKO) mice, which have epileptic seizures that are cured by sirolimus, an mTORC1 inhibitor. After the occurrence of epileptic seizures was confirmed, Tsc2 cKO mice were treated with vehicle or sirolimus. Then, their brains were investigated by hematoxylin and eosin staining, immunohistochemical staining and immunoblotting assay. Results: As in TSC patients, giant cells with hyperactivation of mTORC1 were found in the cerebral cortex of Tsc2 cKO mice. These giant cells were mainly SST-INs in the cortical layers 4/5. Giant cells showed decreased expression of GABA type A receptor subunit α1 (GABAAR-α1) compared with normal size cells in control mice and Tsc2 cKO mice. In addition, decreased GABAAR-α1 expression was also confirmed by immunoblotting assay of the whole cerebral cortex. In the cerebral cortex of sirolimus-treated Tsc2 cKO mice, whose epileptic seizures were cured, decreased GABAAR-α1 expression was recovered to the same level as in control mice. Conclusions: These results suggest that the epileptic seizures in Tsc2 cKO mice are caused by the deregulation of GABAergic signaling through mTORC1 activation of SST-INs localized in cortical layers 4/5.

GABAergic neurons in the central amygdala promote emergence from isoflurane anesthesia in mice.

Recent evidence indicates that general anesthesia and sleep-wake behavior share some overlapping neural substrates. GABAergic neurons in the central amygdala (CeA) have a high firing rate during wakefulness and play a role in regulating arousal-related behaviors. The objective of this study is to investigate whether CeA GABAergic neurons participate in the regulation of isoflurane general anesthesia and uncover the underlying neural circuitry. Fiber photometry recording was used to determine the changes in calcium signals of CeA GABAergic neurons during isoflurane anesthesia in Vgat-Cre mice. Chemogenetic and optogenetic approaches were used to manipulate the activity of CeA GABAergic neurons, and a righting reflex test was used to determine the induction and emergence from isoflurane anesthesia. Cortical electroencephalogram (EEG) recording was used to assess the changes in EEG spectral power and burst-suppression ratio during 0.8% and 1.4% isoflurane anesthesia, respectively. Both male and female mice were used in this study. The calcium signals of CeA GABAergic neurons decreased during the induction of isoflurane anesthesia and was restored during the emergence. Chemogenetic activation of CeA GABAergic neurons delayed induction time (mean ± SD, vehicle vs. clozapine-N-oxide: 58.75±5.42 s vs. 67.63±5.01 s; n=8, P=0.0017) and shortened emergence time (385.50±66.26 s vs. 214.60±40.21 s; n=8, P=0.0017) from isoflurane anesthesia. Optogenetic activation of CeA GABAergic neurons produced a similar effect. Furthermore, optogenetic activation decreased EEG delta power (Pre-stim vs. Stim: 46.63%±4.40% vs. 34.16%±6.47%; n=8, P=0.0195) and burst-suppression ratio (83.39%±5.15% vs. 52.60%±12.98%; n=8, P=0.0002). Moreover, optogenetic stimulation of terminals of CeA GABAergic neurons in the basal forebrain (BF) also promoted cortical activation and accelerated behavioral emergence from isoflurane anesthesia. Our results suggest that CeA GABAergic neurons play a role in general anesthesia regulation, which facilitates behavioral and cortical emergence from isoflurane anesthesia through the GABAergic CeA-BF pathway.

Mefloquine-induced conformational shift in Cx36 N-terminal helix leading to channel closure mediated by lipid bilayer

Connexin 36 (Cx36) forms interneuronal gap junctions, establishing electrical synapses for rapid synaptic transmission. In disease conditions, inhibiting Cx36 gap junction channels (GJCs) is beneficial, as it prevents abnormal synchronous neuronal firing and apoptotic signal propagation, mitigating seizures and progressive cell death. Here, we present cryo-electron microscopy structures of human Cx36 GJC in complex with known channel inhibitors, such as mefloquine, arachidonic acid, and 1-hexanol. Notably, these inhibitors competitively bind to the binding pocket of the N-terminal helices (NTH), inducing a conformational shift from the pore-lining NTH (PLN) state to the flexible NTH (FN) state. This leads to the obstruction of the channel pore by flat double-layer densities of lipids. These studies elucidate the molecular mechanisms of how Cx36 GJC can be modulated by inhibitors, providing valuable insights into potential therapeutic applications.

Functionalized Nanodiamonds for Targeted Neuronal Electromagnetic Signal Detection.

Intracellular sensing technologies necessitate a delicate balance of spatial resolution, sensitivity, biocompatibility, and stability. While existing methods partially fulfill these criteria, none offer a comprehensive solution. Nanodiamonds (NDs) harboring nitrogen-vacancy (NV) centers have emerged as promising candidates due to their sensing capabilities under biological conditions and their ability to meet all aforementioned requirements. This study focuses on expanding the application of NDs and NV center-based sensing to neuronal contexts by investigating their functionalization and subsequent effects on three distinct cell lines relevant to neurodegenerative disease research. Our study concentrates on positioning fluorescent NDs (FNDs) with NV center point defects onto neuronal cell surfaces. Achieving this through specific antibody attachment enhances the proximity of FND to neurites, facilitating the detection of local action potentials. Targeting voltage-dependent calcium channels (Cav2.2) with biotin-streptavidin-bound antibodies enables the precise positioning of FNDs. The functionalized FNDs (f-FNDs) show increased size and zeta potential, confirming the antibody presence without compromising cell viability. Two-color confocal imaging and co-localization algorithms are employed to further attest to the success of the functionalization. The f-FNDs are applied to cell cultures of three cell lines: SH-SY5Y, differentiated dopaminergic neurons, and hippocampal rat neurons; their biocompatibility and effects on synaptic activity are explored. Moreover, preliminary total internal reflection fluorescence - optically detected magnetic resonance (TIRF-ODMR) experiments across cellular sites demonstrate the magnetic field sensitivity of our sensor network. The successful establishment of this sensor network provides a platform for characterizing neuronal signaling in healthy models and conditions mimicking Parkinson's disease.

Soluble form of Lingo2, an autism spectrum disorder-associated molecule, functions as an excitatory synapse organizer in neurons

Autism Spectrum Disorder (ASD) is a developmental disorder characterized by impaired social communication and repetitive behaviors. In recent years, a pharmacological mouse model of ASD involving maternal administration of valproic acid (VPA) has become widely used. Newborn pups in this model show an abnormal balance between excitatory and inhibitory (E/I) signaling in neurons and exhibit ASD-like behavior. However, the molecular basis of this model and its implications for the pathogenesis of ASD in humans remain unknown. Using quantitative secretome analysis, we found that the level of leucine-rich repeat and immunoglobulin domain-containing protein 2 (Lingo2) was upregulated in the conditioned medium of VPA model neurons. This upregulation was associated with excitatory synaptic organizer activity. The secreted form of the extracellular domain of Lingo2 (sLingo2) is produced by the transmembrane metalloprotease ADAM10 through proteolytic processing. sLingo2 was found to induce the formation of excitatory synapses in both mouse and human neurons, and treatment with sLingo2 resulted in an increased frequency of miniature excitatory postsynaptic currents in human neurons. These findings suggest that sLingo2 is an excitatory synapse organizer involved in ASD, and further understanding of the mechanisms by which sLingo2 induces excitatory synaptogenesis is expected to advance our understanding of the pathogenesis of ASD.

Pathway enrichment in genome-wide analysis of longitudinal Alzheimer's disease biomarker endophenotypes.

The genetic pathways that influence longitudinal heterogeneous changes in Alzheimer's disease (AD) may provide insight into disease mechanisms and potential therapeutic targets. Longitudinal endophenotypes from the Alzheimer's Disease Neuroimaging Initiative (ADNI) representing amyloid, tau, neurodegeneration (A/T/N), and cognition were selected. Genome-wide association analysis was performed using a linear mixed model (LMM) approach, followed by gene and pathway enrichment with significant and functionally relevant SNPs. A total of 33 and 19 statistically significant pathways were identified associating with the intercept and longitudinal trajectory, respectively. The longitudinal intercept pathways represent eight groups: immune, metabolic, cell growth and survival, DNA maintenance, neuronal signaling, RAS/MAPK/ERKsignalingpathways, vesicle and lysosomal transport, and transcription modification. Longitudinal trajectory pathways represented six groups: Immune, metabolic, cell signaling, cytoskeleton, and glycosylation. Longitudinal enrichment identified pathways that uniquely associate with trajectories of key AD biomarkers and cognition, providing new insight into AD course-related mechanisms and potential new therapeutic targets. A systematic genome-wide analysis with longitudinal AD biomarker endophenotypes was performed. Enriched pathways were identified with functionally derived SNP to gene analysis. Fifty-two pathways were associated with longitudinal trajectory and intercept. Many of the identified pathways are specific steps in larger pathways implicated in AD. The identified pathways may provide therapeutic targets and areas for further study.

A Non-Invasive and DNA-free Approach to Upregulate Mammalian Voltage-Gated Calcium Channels and Neuronal Calcium Signaling via Terahertz Stimulation.

Mammalian voltage-gated calcium channels (CaV) play critical roles in cardiac excitability, synaptic transmission, and gene transcription. Dysfunctions in CaV are implicated in a variety of cardiac and neurodevelopmental disorders. Current pharmacological approaches to enhance CaV activity are limited by off-target effects, drug metabolism issues, cytotoxicity, and imprecise modulation. Additionally, genetically-encoded channel activators and optogenetic tools are restricted by gene delivery challenges and biosafety concerns. Here a novel terahertz (THz) wave-based method to upregulate CaV1.2, a key subtype of CaV, and boost CaV1-mediated Ca2+ signaling in neurons without introducing exogenous DNA is presented. Using molecular dynamics simulations, it is shown that 42.5 THz (7.05µm, 1418cm-1) waves enhance Ca2+ conductance in CaV1.2 by resonating with the stretching mode of the -COO- group in the selectivity filter. Electrophysiological recordings and Ca2+ imaging confirm that these waves rapidly, reversibly, and non-thermally increase calcium influx of CaV1.2 in HEK293 cells and induce acute Ca2+ signals in neurons. Furthermore, this irradiation upregulates critical CaV1 signals, including CREB phosphorylation and c-Fos expression, in vitro and in vivo, without raising significant biosafety risks. This DNA-free, non-invasive approach offers a promising approach for modulating CaV gating and Ca2+ signaling and treating diseases characterized by deficits in CaV functions.

Deciphering Spectroscopic Signatures of Competing Ca2+ - Peptide Interactions.

Calcium-protein interactions are of paramount importance in biochemistry. They are a key element in a number of biological processes, such as neuronal signaling. Therefore, an understanding of the interaction at the molecular level is highly desirable. Here, we study the zwitterionic model peptide l-alanyl-l-alanine (2Ala), which has two distinct and competing binding sites for Ca2+: The carbonyl of the peptide bond and the C-terminus, the carboxylate group. We perform linear and two-dimensional IR spectroscopy experiments and find that the spectroscopic signatures of both moieties in the IR spectra change in amplitude and peak position upon the addition of CaCl2: A blueshift of the asymmetric carboxylate band and a redshift for the amide I mode. Ab initio molecular dynamics simulations confirm the direct interaction of the Ca2+ ion at both the carboxylate and the amide CO site leading to different spectral responses. The blueshift of the asymmetric carboxylate band is caused by a localization of the charge, leading to a decoupling of the CO stretching modes of the carboxylate group. The slight redshift of the amide I mode of 2Ala upon the addition of CaCl2 contrasts the blueshift that has been observed for isolated amide motifs, such as N-methylacetamide (NMA). This difference is caused by the smaller number of water molecules being replaced by the Ca2+ ion for 2Ala's amide compared to less sterically hindered, isolated amide carbonyls, in conjunction with vibrational Stark effects. Our results highlight the importance of considering potential competing binding sites, such as the amide CO backbone, the termini and residues, as well as the nature of the hydration of both peptide and ion, when exploring ions' interacting with small peptides and larger proteins.

Impairment of neuronal tyrosine phosphatase STEP worsens post-ischemic inflammation and brain injury under hypertensive condition

Hypertension is associated with poor outcome and higher mortality in patients with ischemic stroke. The impairment of adaptive vascular mechanisms under hypertensive condition compromises collateral blood flow after arterial occlusion in patients with acute ischemic stroke resulting in hypoperfusion. The increased oxidative stress caused by hypoperfusion is thought to be a trigger for the rapid evolution of ischemic infarct volume under hypertensive condition. However, the cellular factors and pathways that contribute to the exacerbation of ischemic brain injury under hypertensive condition is not yet understood. The current study reveals that predisposition to hypertension leads to basal loss of function of the neuron-specific tyrosine phosphatase STEP, which plays a crucial role in neuroprotection against excitotoxic insult. The findings further show that a mild ischemic insult in hypertensive rats triggers an early onset and sustained activation of the neuronal extracellular signal regulated kinase (ERK MAPK), a member of the mitogen activated protein kinase family and a substrate of STEP. This leads to rapid increase in the activation of neuronal NF-κB, expression of neuronal cyclooxygenase-2 and subsequent biosynthesis of the pro-inflammatory mediator prostaglandin E2, resulting in rapid morphological transformation of microglia to the pro-inflammatory state and subsequent exacerbation of ischemic brain injury. Restoration of STEP signaling with intravenous administration of a STEP-derived peptide mimetic reduces the pro-inflammatory response in neurons, activation of microglia, and ischemic brain injury. The findings suggest that the basal loss of STEP function under hypertensive condition contributes to the exacerbation of ischemic brain injury by enhancing post-ischemic inflammatory response. The study not only presents a novel role of STEP in regulating neuroimmune communication but also highlights the therapeutic potential of a STEP-mimetic in mitigating ischemic brain damage under hypertensive condition.

Two weeks of exercise alters neuronal extracellular vesicle insulin signaling proteins and pro-BDNF in older adults with prediabetes.

Adults with prediabetes are at risk for Alzheimer's Disease and Related Dementia (ADRD). While exercise may lower ADRD risk, the exact mechanism is unclear. We tested the hypothesis that short-term exercise would raise neuronal insulin signaling and pro-BDNF in neuronal extracellular vesicles (nEVs) in prediabetes. Twenty-one older adults (18F, 60.0 ± 8.6 yrs.; BMI: 33.5 ± 1.1 kg/m2) with prediabetes (ADA criteria; 75 g OGTT) were randomized to 12 supervised work-matched continuous (n = 13, 70% HRpeak) or interval (n = 8, 90% HRpeak and 50% HRpeak for 3 min each) sessions over 2-wks for 60 min/d. Aerobic fitness (VO2peak) and body weight were assessed. After an overnight fast, whole-body glucose tolerance (total area under the curve, tAUC) and insulin sensitivity (SIis) were determined from a 120 min 75 g OGTT. nEVs were acquired from 0 and 60 min time-points of the OGTT, and levels of insulin signaling proteins (i.e., p-IRS-1, total-/p-Akt, pERK1/2, pJNK1/2, and pp38) and pro-BNDF were measured. OGTT stimulatory effects were calculated from protein differences (i.e., OGTT 60-0 min). Adults were collapsed into a single group as exercise intensity did not affect nEV outcomes. Exercise raised VO2peak (+1.4 ± 2.0 mL/kg/min, p = 0.008) and insulin sensitivity (p = 0.01) as well as decreased weight (-0.4 ± 0.9 kg, p = 0.04) and whole-body glucose tAUC120min (p = 0.02). Training lowered 0-min pro-BDNF (704.1 ± 1019.0 vs. 414.5 ± 533.5, p = 0.04) and increased OGTT-stimulated tAkt (-51.8 ± 147.2 vs. 95 ± 204.5 a.u., p = 0.01), which was paralleled by reduced pAkt/tAkt at 60 min of the OGTT (1.3 ± 0.2 vs. 1.2 ± 0.1 a.u., p = 0.04). Thus, 2 weeks of exercise altered neuronal insulin signaling responses to glucose ingestion and lowered pro-BNDF among adults with prediabetes, thereby potentially lowering ADRD risk.

A new variant of the electromagnetic field theory of consciousness: approaches to empirical confirmation.

There are various electromagnetic (EM) field theories of consciousness. They postulate an epineural EM field which, due to its binding properties, unifies the different neuronal information differences originating from various sensory and cognitive processes. Only through a real physical integration in space within this field could phenomenal consciousness arise. This would solve the binding problem mentioned in the philosophy of mind. On closer inspection, the electromagnetic interaction not only provides an explanation for the integrative property of the EM field, but also for the necessary differentiating contrasts of information. This article will take a closer look at the physical properties of a postulated EM field. It will also show how the problem of qualia in connection with emergentism could be solved by a new variant of EM field theory. If it can be clearly demonstrated that the postulated epineural EM field plays a decisive role in the origin of consciousness in addition to neuronal "wired" information processing, this also leaves less room for metaphysical assumptions that attempt to solve the binding problem. In experiments to prove the postulated epineural EM field by means of external electromagnetic manipulations, it can never be ruled out that these also have a direct effect on the "wired" neuronal signal processing. Therefore, on the way to proving the EM field theory of consciousness, an experimental method is needed that must ensure that external manipulations only affect the extensions of the EM field without directly influencing the neuronal network. A method will be discussed here that works with the shielding of EM fields instead of external electromagnetic stimuli.