Calcium-/Calmodulin-Dependent Protein Kinase II (CaMKII) Inhibition Induces Learning and Memory Impairment and Apoptosis

Increased NaV1.2 expression and its interaction with CaM contribute to the hyperexcitability induced by prolonged inhibition of CaMKII

OBJECTIVE

Dysfunction of calcium/calmodulin (CaM)-dependent kinase II (CaMKII) has been involved in hyperexcitability-related disorders including epilepsy. However, the relationship between CaMKII and neuronal excitability remains unclear.

METHODS

Neuronal excitability was detected in vivo and in vitro by electroencephalography (EEG), patch clamp and multi-electrode array (MEA), respectively. Next, we assessed the currents of voltage-gated sodium channels (VGSCs) by patch clamp, and  mRNA and protein expressions of VGSCs were determined by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot, respectively. Meanwhile, the association between the nuclear receptor subfamily 4 group A member 2 (NR4A2) and promoters of Scn2a, was determined by chromatin immunoprecipitation (ChIP)-qPCR. In addition, we utilized co-immunoprecipitation (Co-IP), immunofluorescence labeling, and pull-down to determine the interaction between VGSCs and CaM.

RESULTS

Prolonged CaMKII inhibition by KN93, an inhibitor of CaMKII, for 24 h and CaMKII knockdown induced more seizure-like events in Wistar rats, TRM rats and C57BL/6 mice, and led to hyperexcitability in primary hippocampal neurons and human induced-pluripotent stem cell (hiPSC)-derived cortical neurons. In addition, prolonged CaMKII inhibition resulted in elevated persistent sodium current (INaP)/transient sodium current (INaT) and increased mRNA and protein expressions of NaV1.2. Meanwhile, prolonged CaMKII inhibition by KN93 decreased NR4A2 expression and contributed to a transcriptional repression role of NR4A2 in Scn2a regulation, leading to increased NaV1.2 expression. Moreover, an increased interaction between NaV1.2 and CaM was attributable to enhanced binding of CaM to the isoleucine-glutamine (IQ) domain at the C-terminus of the NaV1.2 channel, which may also lead to the potentiation in INaP/INaT and channel activity. Furthermore, a peptide that antagonized CaM binding to NaV1.2 IQ domain (ACNp) rescued hyperexcitability following prolonged CaMKII inhibition.

SIGNIFICANCE

We unveiled that prolonged CaMKII inhibition induced hyperexcitability through increasing the expression of NaV1.2 and its association with CaM. Thus, our study uncovers a novel signaling mechanism by which CaMKII maintains appropriate neuronal excitability.

Investigating the Impact of NMDA Receptor Organization and Biological Sex in the APPswe/PS1dE9 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by memory loss and cognitive decline, with women being disproportionately affected in both prevalence and severity. A key feature of AD is synaptic loss, particularly around amyloid-β (Aβ) aggregates, which correlates strongly with the severity of dementia. Oligomeric Aβ is believed to be the primary driver of synaptic dysfunction by impairing excitatory neurotransmission through interactions with synaptic receptors, including N-methyl-D-aspartate (NMDA) receptors. However, the influence of sex on these synaptic changes and NMDA receptor mislocalization in AD is not well understood. This study examined potential sex-specific differences in synaptotoxicity and the role of extrasynaptic GluN2B-containing NMDA receptors in AD pathogenesis using the APP/PS1 double transgenic mouse model. Although both male and female mice showed a similar amyloid burden and cognitive impairments, synaptic alterations were slightly less severe in females, suggesting subtle sex differences in synaptic pathology. Both sexes exhibited the mislocalization of GluN2B subunits to extrasynaptic areas, which was linked to reduced PSD-95 levels and the synaptic accumulation of Aβ1-42. Intrahippocampal injections of DL-TBOA confirmed the role of extrasynaptic GluN2B-containing NMDA receptors in memory dysfunction. These findings emphasize the importance of targeting synaptic receptor trafficking to address AD-related memory deficits, potentially offering a therapeutic approach for both sexes.

The Changes of Blood and CSF Ion Levels in Depressed Patients: a Systematic Review and Meta-analysis

Micronutrient deficiencies and excesses are closely related to developing and treating depression. Traditional and effective antidepressants include tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and lithium. There is no consensus on the fluctuation of zinc (Zn2+), magnesium (Mg2+), calcium (Ca2+), copper (Cu2+), iron (Fe2+), and manganese (Mn2+) ion levels in depressed individuals before and after therapy. In order to determine whether there were changes in blood and cerebrospinal fluid (CSF) levels of these ions in depressed patients compared with healthy controls and depressed patients treated with TCAs, SSRIs, or lithium, we applied a systematic review and meta-analysis. Using the Stata 17.0 software, we performed a systematic review and meta-analysis of the changes in ion levels in human samples from healthy controls, depressive patients, and patients treated with TCAs, SSRIs, and lithium, respectively. By searching the PubMed, EMBASE, Google Scholar, Web of Science, China National Knowledge Infrastructure (CNKI), and WAN FANG databases, 75 published analyzable papers were chosen. In the blood, the levels of Zn2+ and Mg2+ in depressed patients had decreased while the Ca2+ and Cu2+ levels had increased compared to healthy controls, Fe2+ and Mn2+ levels have not significantly changed. After treatment with SSRIs, the levels of Zn2+ and Ca2+ in depressed patients increased while Cu2+ levels decreased. Mg2+ and Ca2+ levels were increased in depressed patients after Lithium treatment. The findings of the meta-analysis revealed that micronutrient levels were closely associated with the onset of depression and prompted more research into the underlying mechanisms as well as the pathophysiological and therapeutic implications.

Effects of clitorienolactones from Clitoria ternatea root on calcium channel mediating hippocampal long-term potentiation in rats induced chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH) is a common mechanism of acute brain injury due to impairment of blood flow to the brain. Moreover, a prolonged lack of oxygen supply may result in cerebral infarction or global ischemia, which subsequently causes long-term memory impairment. Research on using Clitoria ternatea root extract for treating long-term memory has been studied extensively. However, the bioactive compound contributing to its neuroprotective effects remains uncertain. In the present study, we investigate the effects of clitorienolactone A (CLA) and B (CLB) from the roots of Clitoria ternatea extract on hippocampal neuroplasticity in rats induced by CCH. CLA and CLB were obtained using column chromatography. The rat model of CCH was induced using two-vessel occlusion surgery (2VO). The 2VO rats were given 10 mg/kg of CLA and CLB orally, followed by hippocampal neuroplasticity recording using in vivo electrophysiological. Rats received CLA and CLB (10 mg/kg) significantly reversed the impairment of long-term potentiation following 2VO surgery. Furthermore, we investigate the effect of CLA and CLB on the calcium channel using the calcium imaging technique. During hypoxia, CLA and CLB sustain the increase in intracellular calcium levels. We next predict the binding interactions of CLA and CLB against NMDA receptors containing GluN2A and GluN2B subunits using in silico molecular docking. Our result found that both CLA and CLB exhibited lower binding affinity against GluN2A and GluN2B subunits. Our findings demonstrated that bioactive compounds from Clitoria ternatea improved long-term memory deficits in the chronic cerebral hypoperfusion rat model via calcium uptake. Hence, CLA and CLB could be potential therapeutic tools for treating cognitive dysfunction.

Calcium-Associated Proteins in Neuroregeneration

The dysregulation of intracellular calcium levels is a critical factor in neurodegeneration, leading to the aberrant activation of calcium-dependent processes and, ultimately, cell death. Ca2+ signals vary in magnitude, duration, and the type of neuron affected. A moderate Ca2+ concentration can initiate certain cellular repair pathways and promote neuroregeneration. While the peripheral nervous system exhibits an intrinsic regenerative capability, the central nervous system has limited self-repair potential. There is evidence that significant variations exist in evoked calcium responses and axonal regeneration among neurons, and individual differences in regenerative capacity are apparent even within the same type of neurons. Furthermore, some studies have shown that neuronal activity could serve as a potent regulator of this process. The spatio-temporal patterns of calcium dynamics are intricately controlled by a variety of proteins, including channels, ion pumps, enzymes, and various calcium-binding proteins, each of which can exert either positive or negative effects on neural repair, depending on the cellular context. In this concise review, we focus on several calcium-associated proteins such as CaM kinase II, GAP-43, oncomodulin, caldendrin, calneuron, and NCS-1 in order to elaborate on their roles in the intrinsic mechanisms governing neuronal regeneration following traumatic damage processes.

Advancements in the study of synaptic plasticity and mitochondrial autophagy relationship

Synapses serve as the points of communication between neurons, consisting primarily of three components: the presynaptic membrane, synaptic cleft, and postsynaptic membrane. They transmit signals through the release and reception of neurotransmitters. Synaptic plasticity, the ability of synapses to undergo structural and functional changes, is influenced by proteins such as growth-associated proteins, synaptic vesicle proteins, postsynaptic density proteins, and neurotrophic growth factors. Furthermore, maintaining synaptic plasticity consumes more than half of the brain's energy, with a significant portion of this energy originating from ATP generated through mitochondrial energy metabolism. Consequently, the quantity, distribution, transport, and function of mitochondria impact the stability of brain energy metabolism, thereby participating in the regulation of fundamental processes in synaptic plasticity, including neuronal differentiation, neurite outgrowth, synapse formation, and neurotransmitter release. This article provides a comprehensive overview of the proteins associated with presynaptic plasticity, postsynaptic plasticity, and common factors between the two, as well as the relationship between mitochondrial energy metabolism and synaptic plasticity.

Necroptosis involved in sevoflurane-induced cognitive dysfunction in aged mice by activating NMDA receptors increasing intracellular calcium

Perioperative neurocognitive disorders are a common surgical and postanesthesia complication. Necroptosis contributes to the emergence of various neurological disorders. We conjecture that cognitive impairment is associated with necroptosis of hippocampal neurons, which is mediated by NMDA receptors leading to cytoplasmic calcium imbalance. C57BL/6 J male mice ( 18 months) were randomly divided into the C ( control group), S ( sevoflurane group), S+M ( sevoflurane plus the NMDA receptor antagonist memantine group) and S+N ( sevoflurane plus necrostatin-1) group. We exposed the mice to 3% sevoflurane for 2 h a day for three consecutive days in the S, S+M and S+N groups. Memantine ( 20 mg/kg) or Nec-1 ( 10 mg/kg) was injected intraperitoneally 1 h before sevoflurane anesthesia in the S+M or S+N group. We used the animal behavior tests to evaluate the cognitive function. Pathological damage, the rate of necroptosis, [Ca2+]i, and the expression of necroptosis-related proteins were evaluated. The cognitive function tests, pathological damage, the rate of necroptosis, the expression of necroptosis-related proteins, NMDAR2A and NMDAR2B were significantly different in the S group ( P < 0.05). Alleviated pathological damage, decreased the rate of necroptosis and down-regulated the expression of necroptosis-related proteins occurred in the S+M and S+N group ( P < 0.05). The lower elevated [Ca2+]i, expression of NMDAR2A and NMDAR2B were found in the S+M group. Our findings highlighted sevoflurane-induced cognitive dysfunction is associated with an imbalance in cytoplasmic calcium homeostasis by activating NMDA receptors, which causes hippocampus neurons to undergo necroptosis and ultimately affects cognitive performance in aged mice.

Highly dynamic inflammatory and excitability transcriptional profiles in hippocampal CA1 following status epilepticus

Transient brain insults including status epilepticus (SE) can initiate a process termed 'epileptogenesis' that results in chronic temporal lobe epilepsy. As a consequence, the entire tri-synaptic circuit of the hippocampus is fundamentally impaired. A key role in epileptogenesis has been attributed to the CA1 region as the last relay station in the hippocampal circuit and as site of aberrant plasticity, e.g. mediated by acquired channelopathies. The transcriptional profiles of the distinct hippocampal neurons are highly dynamic during epileptogenesis. Here, we aimed to elucidate the early SE-elicited mRNA signature changes and the respective upstream regulatory cascades in CA1. RNA sequencing of CA1 was performed in the mouse pilocarpine-induced SE model at multiple time points ranging from 6 to 72 h after the initial insult. Bioinformatics was used to decipher altered gene expression, signalling cascades and their corresponding cell type profiles. Robust transcriptomic changes were detected at 6 h after SE and at subsequent time points during early epileptogenesis. Major differentially expressed mRNAs encoded primarily immediate early and excitability-related gene products, as well as genes encoding immune signalling factors. Binding sites for the transcription factors Nfkb1, Spi1, Irf8, and two Runx family members, were enriched within promoters of differentially expressed genes related to major inflammatory processes, whereas the transcriptional repressors Suz12, Nfe2l2 and Rest were associated with hyperexcitability and GABA / glutamate receptor activity. CA1 quickly responds to SE by inducing transcription of genes linked to inflammation and excitation stress. Transcription factors mediating this transcriptomic switch represent targets for new highly selected, cell type and time window-specific anti-epileptogenic strategies.

Shotgun Proteomic-Based Approach with a Q-Exactive Hybrid Quadrupole-Orbitrap High-Resolution Mass Spectrometer for Protein Adductomics on a 3D Human Brain Tumor Neurospheroid Culture Model: The Identification of Adduct Formation in Calmodulin-Dependent Protein Kinase-2 and Annexin-A1 Induced by Pesticide Mixture

Pesticides are increasingly used in combinations in crop protection, resulting in enhanced toxicities for various organisms. Although protein adductomics is challenging, it remains a powerful bioanalytical tool to check environmental exposure and characterize xenobiotic adducts as putative toxicity biomarkers with high accuracy, facilitated by recent advances in proteomic methodologies and a mass spectrometry high-throughput technique. The present study aims to predict the potential neurotoxicity effect of imidacloprid and λ-cyhalothrin insecticides on human neural cells. Our protocol consisted first of 3D in vitro developing neurospheroids derived from human brain tumors and then treatment by pesticide mixture. Furthermore, we adopted a bottom-up proteomic-based approach using nanoflow ultraperformance liquid chromatography coupled with a high-resolution mass spectrometer for protein-adduct analysis with prediction of altered sites. Two proteins were selected, namely, calcium-calmodulin-dependent protein kinase-II (CaMK2) and annexin-A1 (ANXA1), as key targets endowed with primordial roles. De novo sequencing revealed several adduct formations in the active site of 82-ANXA1 and 228-CaMK2 as a result of neurotoxicity, predicted by the added mass shifts for the structure of electrophilic precursors. To the best of our knowledge, our study is the first to adopt a proteomic-based approach to investigate in depth pesticide molecular interactions and their potential to adduct proteins which play a crucial role in the neurotoxicity mechanism.

Differential Proteome Profiling Analysis under Pesticide Stress by the Use of a Nano-UHPLC-MS/MS Untargeted Proteomic-Based Approach on a 3D-Developed Neurospheroid Model: Identification of Protein Interactions, Prognostic Biomarkers, and Potential Therapeutic Targets in Human IDH Mutant High-Grade Gliomas

High-grade gliomas represent the most common group of infiltrative primary brain tumors in adults associated with high invasiveness, agressivity, and resistance to therapy, which highlights the need to develop potent drugs with novel mechanisms of action. The aim of this study is to reveal changes in proteome profiles under stressful conditions to identify prognostic biomarkers and altered apoptogenic pathways involved in the anticancer action of human isocitrate dehydrogenase (IDH) mutant high-grade gliomas. Our protocol consists first of a 3D in vitro developing neurospheroid model and then treatment by a pesticide mixture at relevant concentrations. Furthermore, we adopted an untargeted proteomic-based approach with high-resolution mass spectrometry for a comparative analysis of the differentially expressed proteins between treated and nontreated spheroids. Our analysis revealed that the majority of altered proteins were key members in glioma pathogenesis, implicated in the cellular metabolism, biological regulation, binding, and catalytic and structural activity and linked to many cascading regulatory pathways. Our finding revealed that grade-IV astrocytomas promote the downstream of the mitogen-activated-protein-kinases/extracellular-signal-regulated kinase (MAPK1/ERK2) pathway involving massive calcium influx. The gonadotrophin-releasing-hormone signaling enhances MAKP activity and may serve as a negative feedback compensating regulator. Thus, our study can pave the way for effective new therapeutic and diagnostic strategies to improve the overall survival.

Electroacupuncture protective effects after cerebral ischemia are mediated through miR-219a inhibition

BACKGROUND

Electroacupuncture (EA) is a complementary and alternative therapy which has shown protective effects on vascular cognitive impairment (VCI). However, the underlying mechanisms are not entirely understood.

METHODS

Rat models of VCI were established with cerebral ischemia using occlusion of the middle cerebral artery or bilateral common carotid artery. The brain structure and function imaging were measured through animal MRI. miRNA expression was detected by chip and qPCR. Synaptic functional plasticity was detected using electrophysiological techniques.

RESULTS

This study demonstrated the enhancement of Regional Homogeneity (ReHo) activity of blood oxygen level-dependent (BOLD) signal in the entorhinal cortical (EC) and hippocampus (HIP) in response to EA treatment. miR-219a was selected and confirmed to be elevated in HIP and EC in VCI but decreased after EA. N-methyl-D-aspartic acid receptor1 (NMDAR1) was identified as the target gene of miR-219a. miR-219a regulated NMDAR-mediated autaptic currents, spontaneous excitatory postsynaptic currents (sEPSC), and long-term potentiation (LTP) of the EC-HIP CA1 circuit influencing synaptic plasticity. EA was able to inhibit miR-219a, enhancing synaptic plasticity of the EC-HIP CA1 circuit and increasing expression of NMDAR1 while promoting the phosphorylation of downstream calcium/calmodulin-dependent protein kinase II (CaMKII), improving overall learning and memory in VCI rat models.

CONCLUSION

Inhibition of miR-219a ameliorates VCI by regulating NMDAR-mediated synaptic plasticity in animal models of cerebral ischemia.

Effects of Apamin on MPP+-Induced Calcium Overload and Neurotoxicity by Targeting CaMKII/ERK/p65/STAT3 Signaling Pathways in Dopaminergic Neuronal Cells

Parkinson's disease (PD), a neurodegenerative disorder, is characterized by the loss of dopaminergic (DA) neurons. The pathogenesis of PD is associated with several factors including oxidative stress, inflammation, and mitochondrial dysfunction. Ca2+ signaling plays a vital role in neuronal signaling and altered Ca2+ homeostasis has been implicated in many neuronal diseases including PD. Recently, we reported that apamin (APM), a selective antagonist of the small-conductivity Ca2+-activated K+ (SK) channel, suppresses neuroinflammatory response. However, the mechanism(s) underlying the vulnerability of DA neurons were not fully understood. In this study, we investigated whether APM affected 1-methyl-4-phenyl pyridinium (MPP+)-mediated neurotoxicity in SH-SY5Y cells and rat embryo primary mesencephalic neurons. We found that APM decreased Ca2+ overload arising from MPP+-induced neurotoxicity response through downregulating the level of CaMKII, phosphorylation of ERK, and translocation of nuclear factor NFκB/signal transducer and activator of transcription (STAT)3. Furthermore, we showed that the correlation of MPP+-mediated Ca2+ overload and ERK/NFκB/STAT3 in the neurotoxicity responses, and dopaminergic neuronal cells loss, was verified through inhibitors. Our findings showed that APM might prevent loss of DA neurons via inhibition of Ca2+-overload-mediated signaling pathway and provide insights regarding the potential use of APM in treating neurodegenerative diseases.

Neuronal nitric oxide synthase/reactive oxygen species pathway is involved in apoptosis and pyroptosis in epilepsy

Dysfunction of neuronal nitric oxide synthase contributes to neurotoxicity, which triggers cell death in various neuropathological diseases, including epilepsy. Studies have shown that inhibition of neuronal nitric oxide synthase activity increases the epilepsy threshold, that is, has an anticonvulsant effect. However, the exact role and potential mechanism of neuronal nitric oxide synthase in seizures are still unclear. In this study, we performed RNA sequencing, functional enrichment analysis, and weighted gene coexpression network analysis of the hippocampus of tremor rats, a rat model of genetic epilepsy. We found damaged hippocampal mitochondria and abnormal succinate dehydrogenase level and Na⁺-K⁺-ATPase activity. In addition, we used a pilocarpine-induced N2a cell model to mimic epileptic injury. After application of neuronal nitric oxide synthase inhibitor 7-nitroindazole, changes in malondialdehyde, lactate dehydrogenase and superoxide dismutase, which are associated with oxidative stress, were reversed, and the increase in reactive oxygen species level was reversed by 7-nitroindazole or reactive oxygen species inhibitor N-acetylcysteine. Application of 7-nitroindazole or N-acetylcysteine downregulated the expression of caspase-3 and cytochrome c and reversed the apoptosis of epileptic cells. Furthermore, 7-nitroindazole or N-acetylcysteine downregulated the abnormally high expression of NLRP3, gasdermin-D, interleukin-1β and interleukin-18. This indicated that 7-nitroindazole and N-acetylcysteine each reversed epileptic cell death. Taken together, our findings suggest that the neuronal nitric oxide synthase/reactive oxygen species pathway is involved in pyroptosis of epileptic cells, and inhibiting neuronal nitric oxide synthase activity or its induced oxidative stress may play a neuroprotective role in epilepsy.

Effects and potential mechanism of Ca2+/calmodulin‑dependent protein kinase II pathway inhibitor KN93 on the development of ovarian follicle

Adequate regulation of the speed of follicular development has been reported to prolong the reproductive life of the ovary. The aim of the present study was to assess the potential effects and mechanism of the Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) pathway on the development of ovarian follicle. In the present study, the expression of CaMKII was measured in the ovary of mice at different developmental stages by immunofluorescence, confirming that CaMKII has a role in follicular development. Subsequently, the 17.5 days post-coitus (dpc) embryonic ovaries were collected and cultured with KN93 for 4 days in vitro. It was revealed that KN93 inhibited the development of follicles, where it reduced the expression levels of oocyte and granulosa cell markers DEAD-box helicase 4 (DDX4) and forkhead box L2 (FOXL2). These results suggested that KN93 could delay follicular development. Proteomics technology was then used to find that 262 proteins of KN93 treated 17.5 dpc embryonic ovaries were significantly altered after in vitro culture. Bioinformatics analysis was used to analyze these altered proteins. In total, four important Kyoto Encyclopedia of Genes and Genome pathways, namely steroid biosynthesis, p53 signaling pathway and retinol metabolism and metabolic pathways, were particularly enriched. Further analysis revealed that the upregulated proteins NADP-dependent steroid dehydrogenase-like (Nsdhl), lanosterol synthase (Lss), farnesyl-diphosphate farnesyltransferase 1 (Fdft1), cytochrome P450 family 51 family A member 1 (Cyp51a1), hydroxymethylglutaryl-CoA synthase 1 (Hmgcs1), fatty acid synthase (Fasn) and dimethylallyltranstransferase (Fdps) were directly interacting with each other in the four enriched pathways. In summary, the potential mechanism of KN93 in slowing down follicular development most likely lies in its inhibitory effects on CaMKII, which upregulated the expression of Nsdhl, Lss, Fdft1, Cyp51a1, Hmgcs1, Fasn and Fdps. This downregulated the expression of oocyte and granulosa cell markers DDX4 and FOXL2 in the follicles, thereby delaying follicular development. Overall, these results provide novel insight into the potential mechanism by which KN93 and CaMKII can delay follicular development.

Mechanism of cell death pathways in status epilepticus and related therapeutic agents

The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.