Targeting lncRNA NEAT1 Hampers Alzheimer's Disease Progression

Long noncoding RNA nuclear enriched abundant transcript 1 (lnc-NEAT1) is closely implicated in neurological diseases, while its implication in Alzheimer's disease (AD) is rarely reported. This study aimed to investigate the effect of lnc-NEAT1 knockdown on neuron injury, inflammation, and oxidative stress in AD, as well as its interaction with downstream targets and pathways. APPswe/PS1dE9 transgenic mice were injected with negative control or lnc-NEAT1 interference lentivirus. Besides, AD cellular model was constructed by amyloid β treatment in mice primary neuron cells; then, knockdown of lnc-NEAT1 and microRNA-193a was performed alone or in combination. In vivo experiments revealed that Lnc-NEAT1 knockdown improved cognition in AD mice reflected by Morrison water maze and Y-maze assays. Besides, lnc-NEAT1 knockdown reduced injury and apoptosis, decreased inflammatory cytokine levels, repressed oxidative stress level, and activated adenosine cyclophosphate response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF) and nuclear factor erythroid 2-related factor 2 (NRF2)/nicotinamide adenine dinucleotide phosphate dehydrogenase 1 (NQO1) pathways in hippocampi of AD mice. Notably, lnc-NEAT1 down-regulated microRNA-193a both in vitro and in vivo and acted as a decoy of microRNA-193a. In vitro experiments showed that lnc-NEAT1 knockdown decreased apoptosis and oxidative stress, improved cell viability, also activated CREB/BDNF and NRF2/NQO1 pathways in AD cellular model. Meanwhile, microRNA-193a knockdown showed the opposite effects, which also attenuated lnc-NEAT1 knockdown-mediated reduction in injury, oxidative stress, and CREB/BDNF and NRF2/NQO1 pathways of AD cellular model. In conclusion, lnc-NEAT1 knockdown reduces neuron injury, inflammation, and oxidative stress through activating microRNA-193a mediated CREB/BDNF and NRF2/NQO1 pathways in AD.

Regulation of Tau Expression in Superior Cervical Ganglion (SCG) Neurons In Vivo and In Vitro

The superior cervical ganglion (SCG) is part of the autonomic nervous system providing sympathetic innervation to the head and neck, and has been regularly used to prepare postnatal neuronal cultures for cell biological studies. We found that during development these neurons change tau expression from the low molecular weight (LMW) isoforms to Big tau, with the potential to affect functions associated with tau such as microtubule dynamic and axonal transport. Big tau contains the large 4a exon that transforms tau from LMW isoforms of 45-60 kDa to 110 kDa. We describe tau expression during postnatal development reporting that the transition from LMW tau to Big tau which started at late embryonic stages is completed by about 4-5 weeks postnatally. We confirmed the presence of Big tau in dissociated postnatal SCG neurons making them an ideal system to study the function of Big tau in neurons. We used SCG explants to examine the response of SCG neurons to lesion and found that Big tau expression returned gradually along the regrowing neurites suggesting that it does not drives regeneration, but facilitates the structure/function of mature SCG neurons. The structural/functional roles of Big tau remain unknown, but it is intriguing that neurons that express Big tau appear less vulnerable to tauopathies.

Etanercept Reduces Neuron Injury and Neuroinflammation via Inactivating c-Jun N-terminal Kinase and Nuclear Factor-κB Pathways in Alzheimer's Disease: An In Vitro and In Vivo Investigation

Inflammation contributes to amyloid beta (Aβ) aggregation and neuron loss in Alzheimer's disease (AD). Meanwhile, tumor necrosis factor-α (TNF-α) inhibitors present strong effect on suppressing inflammation. Thus, this study aimed to investigated the effect and molecular mechanism of etanercept (ETN) (a commonly used TNF-α inhibitor) on neuron injury and neuroinflammation in AD. AD cellular model was constructed by co-culture of primary embryonic neuron cells and microglial cells, followed by Aβ treatment. Subsequently, ETN was used to treat AD cellular model. Besides, APPswe/PS1M146V/tauP301L transgenic (AD) mice were respectively treated with saline or ETN by intravenous injection once per 3 days for 10 times. In vitro data revealed that cell viability and neurite outgrowth were increased, but apoptosis and levels of pro-inflammatory cytokines (including TNF-α, interleukin-1β, Interleukin-6 and C-C motif chemokine ligand 2 (CCL2)) were decreased by ETN treatment in AD cellular model. In vivo experiments found that ETN treatment improved spatial, long-term memory (reflected by Morrison water maze) and working memory (reflected by Y maze) in AD mice. Besides, ETN treatment reduced neuron injury (reflected by Hematoxylin-Eosin (HE) and terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assays) and levels of pro-inflammatory cytokines (including TNF-α, interleukin-1β, Interleukin-6 and CCL2) in AD mice. Moreover, ETN repressed the activation of c-Jun N-terminal kinase (JNK) and nuclear factor-κB (NF-κB) pathways in AD both in vitro and in vivo. In conclusion, ETN exerts neuroprotective function via inactivating JNK and NF-κB pathways in AD, indicating the potential of ETN for improving AD management.

The Potentials of Melatonin in the Prevention and Treatment of Bacterial Meningitis Disease

Bacterial meningitis (BM) is an acute infectious central nervous system (CNS) disease worldwide, occurring with 50% of the survivors left with a long-term serious sequela. Acute bacterial meningitis is more prevalent in resource-poor than resource-rich areas. The pathogenesis of BM involves complex mechanisms that are related to bacterial survival and multiplication in the bloodstream, increased permeability of blood-brain barrier (BBB), oxidative stress, and excessive inflammatory response in CNS. Considering drug-resistant bacteria increases the difficulty of meningitis treatment and the vaccine also has been limited to several serotypes, and the morbidity rate of BM still is very high. With recent development in neurology, there is promising progress for drug supplements of effectively preventing and treating BM. Several in vivo and in vitro studies have elaborated on understanding the significant mechanism of melatonin on BM. Melatonin is mainly secreted in the pineal gland and can cross the BBB. Melatonin and its metabolite have been reported as effective antioxidants and anti-inflammation, which are potentially useful as prevention and treatment therapy of BM. In bacterial meningitis, melatonin can play multiple protection effects in BM through various mechanisms, including immune response, antibacterial ability, the protection of BBB integrity, free radical scavenging, anti-inflammation, signaling pathways, and gut microbiome. This manuscript summarizes the major neuroprotective mechanisms of melatonin and explores the potential prevention and treatment approaches aimed at reducing morbidity and alleviating nerve injury of BM.

Long-noncoding RNA Peg13 alleviates epilepsy progression in mice via the miR-490-3p/Psmd11 axis to inactivate the Wnt/β-catenin pathway

Epilepsy, one of the most common neurological diseases with spontaneous recurrent seizures, is a severe health problem globally. The present study aimed to study the role and upstream mechanism of 26S proteasome non-ATPase regulatory subunit 11 (Psmd11) in epilepsy. In the current paper, epileptic mice models were successfully established. Hematoxylin and eosin (HE) staining was performed to reveal morphology of hippocampal tissues. Nissl's staining was performed for detection of neuron injury. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect concentrations of pro-inflammatory cytokines. The expression of Psmd11 was downregulated in the hippocampal tissues of epileptic mice, and overexpression of Psmd11 improved the spatial learning and memory of epileptic mice. Further, upregulation of Psmd11 protected epileptic hippocampal neurons from injury. Moreover, Psmd11 overexpression inhibited cell apoptosis, suppressed the activities of microglia and astrocytes, as well as reduced inflammatory response in epileptic hippocampi. Psmd11 was a downstream target of miR-490-3p. Long noncoding RNA (lncRNA) Peg13 bound with miR-490-3p to upregulate Psmd11. Subsequently, rescue experiments revealed that Peg13 suppressed the progression of epilepsy via upregulating Psmd11. Furthermore, Psmd11 was verified to inactivate the Wnt/β-catenin pathway. Peg13 repressed the Wnt/β-catenin pathway via upregulation of Peg13. In conclusion, this paper illuminated the function and upstream mechanism of Psmd11 in epilepsy. Psmd11 was upregulated by Peg13 at a miR-490-3p dependent way, thus inactivating the Wnt/β-catenin pathway and alleviating epilepsy course in mice, which may be a promising approach for epilepsy treatment.

A novel tri-culture model for neuroinflammation

Neuroinflammation is believed to play a primary role in the pathogenesis of most neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and schizophrenia. Currently, suitable in vitro neuroinflammation models for studying cellular interactions and inflammatory mechanisms at the neurovascular unit are still scarce. In this study, we established an experimentally flexible tri-culture neuroinflammation model combining murine microglial cells (N11), mouse neuroblastoma Nuro2A cell lines and brain microvascular endothelial MVEC(B3) cells in a transwell co-culture system stimulated with lipopolysaccharides. Neuroinflammation was induced in this tri-culture model as manifested by activated N11 cells via toll-like receptor 4, resulting in increased release of proinflammatory mediators (nitric oxide, interleukin-6 and tumour necrosis factor-α) through the activation of nuclear factor-κB signalling pathway. The released inflammatory cytokines from N11 in turn, damaged the tight junction in microvascular endothelial MVEC(B3) cells, increased permeability of endothelial barrier, and induced tau phosphorylation and up-regulated caspase-3 expression in mouse neuroblastoma Nuro2A cell lines, leading to neuroinflammation injury. In summary, this tri-culture inflammation model mimics the microenvironment, the cellular crosstalk and the molecular events that take place during neuroinflammation. It provides a robust in vitro model for studying neuroinflammation mechanisms and screening for potential therapeutics to treat various neurodegenerative diseases.

Beading of injured axons driven by tension- and adhesion-regulated membrane shape instability

The formation of multiple beads along an injured axon will lead to blockage of axonal transport and eventually neuron death, and this has been widely recognized as a hallmark of nervous system degeneration. Nevertheless, the underlying mechanisms remain poorly understood. Here, we report a combined experimental and theoretical study to reveal key factors governing axon beading. Specifically, by transecting well-developed axons with a sharp atomic force microscope probe, significant beading of the axons was triggered. We showed that adhesion was not required for beading to occur, although when present strong axon–substrate attachments seemed to set the locations for bead formation. In addition, the beading wavelength, representing the average distance between beads, was found to correlate with the size and cytoskeleton integrity of axon, with a thinner axon or a disrupted actin cytoskeleton both leading to a shorter beading wavelength. A model was also developed to explain these observations which suggest that axon beading originates from the shape instability of the membrane and is driven by the release of work done by axonal tension as well as the reduction of membrane surface energy. The beading wavelength predicted from this theory was in good agreement with our experiments under various conditions. By elucidating the essential physics behind axon beading, the current study could enhance our understanding of how axonal injury and neurodegeneration progress as well as provide insights for the development of possible treatment strategies.

Chronic treatment with the complex I inhibitor MPP+ depletes endogenous PTEN-induced kinase 1 (PINK1) via up-regulation of Bcl-2-associated athanogene 6 (BAG6)

Mitochondrial dysfunction is implicated in sporadic and familial Parkinson's disease (PD). However, the mechanisms that impair homeostatic responses to mitochondrial dysfunction remain unclear. Previously, we found that chronic, low-dose administration of the mitochondrial complex I inhibitor 1-methyl-4-phenylpyridinium (MPP⁺) dysregulates mitochondrial fission-fusion, mitophagy, and mitochondrial biogenesis. Given that PTEN-induced kinase 1 (PINK1) regulates mitochondrial function, dynamics, and turnover, we hypothesized that alterations in endogenous PINK1 levels contribute to depletion of mitochondria during chronic complex I injury. Here we found that chronic MPP⁺ treatment of differentiated SH-SY5Y neuronal cells significantly decreases PINK1 expression prior to reductions in other mitochondrial components. Furthermore, Bcl2-associated athanogene 6 (BAG6, BAT3, or Scythe), a protein involved in protein quality control and degradation, was highly up-regulated during the chronic MPP⁺ treatment. BAG6 interacted with PINK1, and BAG6 overexpression decreased the half-life of PINK1. Conversely, siRNA-mediated BAG6 knockdown prevented chronic MPP⁺ stress-induced loss of PINK1, reversed MPP⁺-provoked mitochondrial changes, increased cell viability, and prevented MPP⁺-induced dendrite shrinkage in primary neurons. These results indicate that BAG6 up-regulation during chronic complex I inhibition contributes to mitochondrial pathology by decreasing the levels of endogenous PINK1. Given that recessive mutations in PINK1 cause familial PD, the finding of accelerated PINK1 degradation in the chronic MPP⁺ model suggests that PINK1 loss of function represents a point of convergence between the neurotoxic and genetic causes of PD.

Sphingolipidomics Investigation of the Temporal Dynamics after Ischemic Brain Injury

Sphingolipids (SPLs) have been proposed as potential therapeutic targets for strokes, but no reports have ever profiled the changes of the entire range of SPLs after a stroke. This study applied sphingolipidomic methods to investigate the temporal and individual changes in the sphingolipidome including the effect of atorvastatin after ischemic brain injury. We conducted sphingolipidomic profiling of mouse brain tissue by liquid chromatography-electrospray ionization tandem mass spectrometry at 3 h and 24 h after 1 h of middle cerebral artery occlusion (MCAO), and SPL levels were compared with those of the Sham control group. At 3 h post-MCAO, ceramides (Cers) exhibited an increase in levels of long-chain Cers but a decrease in very-long-chain Cers. Moreover, sphingosine, the precursor of sphingosine-1-phosphate (S1P), decreased and S1P increased at 3 h after MCAO. In contrast to 3 h, both long-chain and very-long-chain Cers showed an increased trend at 24 h post-MCAO. Most important, the administration of atorvastatin improved the neurological function of the mice and significantly reversed the SPL changes resulting from the ischemic injury. Furthermore, we used plasma samples from nonstroke control and stroke patients at time points of 72 h after a stroke, and found a similar trend of Cers as in the MCAO model. This study successfully elucidated the overall effect of ischemic injury on SPL metabolism with and without atorvastatin treatment. The network of SPL components that change upon ischemic damage may provide novel therapeutic targets for ischemic stroke.

Suppression of REDD1 attenuates oxygen glucose deprivation/reoxygenation-evoked ischemic injury in neuron by suppressing mTOR-mediated excessive autophagy

Cerebral ischemia/reperfusion (I/R) typically occurs after mechanical thrombectomy to treat ischemic stroke, generation of reactive oxygen species (ROS) after reperfusion may result in neuronal insult, ultimately leading to disability and death. Regulated in development and DNA damage responses 1 (REDD1) is a conserved stress response protein under various pathogenic conditions. Recent research confirms the controversial role of REDD1 in injury processes. Nevertheless, the role of REDD1 in cerebral I/R remains poorly defined. In the current study, increased expression of REDD1 was observed in neurons exposed to simulated I/R via oxygen glucose deprivation/reoxygenation (OGD/R) treatment. Knockdown of REDD1 enhanced OGD/R-inhibited cell viability, but suppressed lactate dehydrogenase (LDH) release in neurons upon OGD/R. Simultaneously, suppression of REDD1 also antagonized OGD/R-evoked cell apoptosis, Bax expression, and caspase-3 activity. Intriguingly, REDD1 depression abrogated neuronal oxidative stress under OGD/R condition by suppressing ROS, MDA generation, and increasing antioxidant SOD levels. Further mechanism analysis corroborated the excessive activation of autophagy in neurons upon OGD/R with increased expression of autophagy-related LC3 and Beclin-1, but decreased autophagy substrate p62 expression. Notably, REDD1 inhibition reversed OGD/R-triggered excessive neuronal autophagy. More importantly, depression of REDD1 also elevated the expression of p-mTOR. Preconditioning with mTOR inhibitor rapamycin engendered not only a reduction in mTOR activation, but also a reactivation of autophagy in REDD1 knockdown-neurons upon OGD/R. In addition, blocking the mTOR pathway muted the protective roles of REDD1 inhibition against OGD/R-induced neuron injury and oxidative stress. Together these data suggested that REDD1 may regulate I/R-induced oxidative stress injury in neurons by mediating mTOR-autophagy signaling, supporting a promising therapeutic strategy against brain ischemic diseases.

Hyperglycemia Induced by Chronic Restraint Stress in Mice Is Associated With Nucleus Tractus Solitarius Injury and Not Just the Direct Effect of Glucocorticoids

Chronic restraint stress (CRS) can affect hypothalamic-pituitary-adrenal (HPA) axis activity and increase glucocorticoid levels. Glucocorticoids are stress hormones that regulate multiple aspects of energy homeostasis. Stress also impairs glucose tolerance. The aim of this study was to investigate the cause of insulin-resistant hyperglycemia during CRS. We produced the CRS models (a 7-day restraint followed by a 3-day free moving procedure, total of 4 cycles for 40 days) in mice, detected the parameters related to glucose metabolism, and compared them to those of the dexamethasone (DEX) injection (0.2 mg/kg i.p., also a 4 cycle procedure as the CRS). The results showed that the CRS induced a moderate (not higher than 11 mmol/L) and irreversible insulin-resistant hyperglycemia in about 1/3 of the individuals, and all the restrained mice had adrenal hypertrophy. CRS induced the apoptosis of neurons in the anterior part of commissural subnucleus of nucleus tractus solitarius (acNTS) in the hyperglycemic mice, and acNTS mechanical damage also led to insulin-resistant hyperglycemia. In contrast, in the DEX-treated mice, adrenal gland atrophy was evident. The glucose and insulin tolerance varied with the delay of determination. DEX exposure in vivo does not induce the apoptosis of neurons in NTS. This study indicates that restraint stress and DEX induce metabolic disorders through different mechanisms. During CRS, injury (apoptosis) of glucose-sensitive acNTS neurons cause dysregulation of blood glucose. This study also suggests the mouse restraint stress model has value as a potential application in the study of stress-induced hyperglycemia.

Adapentpronitrile, a New Dipeptidyl Peptidase-IV Inhibitor, Ameliorates Diabetic Neuronal Injury Through Inhibiting Mitochondria-Related Oxidative Stress and Apoptosis

Our previous studies indicated that adapentpronitrile, a new adamantane-based dipeptidyl peptidase-IV (DPP-IV) inhibitor, has a hypoglycemic effect and ameliorates rat pancreatic β cell dysfunction in type 2 diabetes mellitus through inhibiting DPP-IV activity. However, the effect of adapentpronitrile on the neurodegenerative diseases has not been studied. In the present study, we first found that adapentpronitrile significantly ameliorated neuronal injury and decreased amyloid precursor protein (APP) and amyloid beta (Aβ) expression in the hippocampus and cortex in the high fat diet/STZ rat model of diabetes. Furthermore, adapentpronitrile significantly attenuated oxidative stress, downregulated expression of the pro-apoptotic proteins BAX, cytochrome c, caspase-9, and caspase-3, and upregulated expression of the anti-apoptotic protein Bcl-2, although there was no effect on GLP-1R expression. At 30 min post-injection of adapentpronitrile (50 mg/kg) via the tail vein, its concentration in normal rat brain was 0.2034 ± 0.0094 μg/g. Subsequently, we further confirmed the neuroprotective effects and mechanism of adapentpronitrile in HT22 cells treated with high glucose (HG) and aluminum maltolate [Al(mal)₃] overload, respectively. Our results showed significant decreases in mitochondrial membrane potential (MTP) and Bcl-2 expression, accompanied by a significant increase in apoptosis, reactive oxygen species (ROS) generation, and the expression of pro-apoptotic proteins in HT22 cells exposed to these stimuli. Adapentpronitrile treatment protected against neuronal injury, suppressed ROS generation, and reduced MTP and mitochondrial apoptosis in HT22 cells; however, DPP-IV activity was not detected. Our results suggest that adapentpronitrile protects against diabetic neuronal injury, at least partially, by inhibiting mitochondrial oxidative stress and the apoptotic pathway in a DPP-IV-independent manner.

Catalpol protects synaptic proteins from beta-amyloid induced neuron injury and improves cognitive functions in aged rats

Synapse loss is one of the common factors contributing to cognitive disorders, such as Alzheimer’s disease (AD), which is manifested by the impairment of basic cognitive functions including memory processing, perception, problem solving, and language. The current therapies for patients with cognitive disorders are mainly palliative; thus, regimens preventing and/or delaying dementia progression are urgently needed. In this study, we evaluated the effects of catalpol, isolated from traditional Chinese medicine Rehmannia glutinosa, on synaptic plasticity in aged rat models. We found that catalpol markedly improved the cognitive function of aged male Sprague-Dawley rats and simultaneously increased the expression of synaptic proteins (dynamin 1, PSD-95, and synaptophysin) in the cerebral cortex and hippocampus, respectively. In beta-amyloid (Aβ) injured primary rat’s cortical neuron, catalpol did not increase the viability of neuron but extended the length of microtubule-associated protein 2 (MAP-2) positive neurites and reversed the suppressive effects on expression of synaptic proteins induced by Aβ. Additionally, the effects of catalpol on stimulating the growth of MAP-2 positive neurites and the expression of synaptic proteins were diminished by a PKC inhibitor, bisindolylmaleimide I, suggesting that PKC may be implicated in catalpol’s function of preventing the neurodegeneration induced by Aβ. Altogether, our study indicates that catalpol could be a potential disease-modifying drug for cognitive disorders such as AD.