Overexpression of endophilin A1 exacerbates synaptic alterations in a mouse model of Alzheimer's disease

Treadmill exercise ameliorates hippocampal synaptic injury and recognition memory deficits by TREM2 in AD rat model

OBJECTIVE

The impairment of cognitive function has been associated with Alzheimer's disease (AD). Exercise exerts a positive modulatory effect on cognition by reducing synapse injury. However, limited in vivo evidence is available to validate the neuroprotective effect of TREM2 on synaptic function in this phenomenon. Here, we aim to explore whether physical exercise pretreatment alters Aβ-induced recognition memory impairment in structural synaptic plasticity within the hippocampus in AD rats. METHODS：: In study 1, fifty-two Sprague-Dawley (SD) rats were randomly divided into following four groups: control group (C group, n = 13), Alzheimer's disease group (AD group, n = 13), 4 weeks of physical exercise and Alzheimer's disease group (Exe+AD group, n = 13), 4 weeks of physical exercise and blank group (Exercise group, n = 13). Four weeks of treadmill exercise intervention was performed, and AD model were established by intra-cerebroventricular injection (ICV) injection of Aβ1-42 protein. After 3 weeks, we also conducted a novel object test to evaluate recognition memory in the behavior assessment. Golgi staining and transmission electron microscopy were used to evaluate the morphology and synaptic ultrastructure of neurons. Western blotting was used to measure the expression of hippocampal synaptic proteins. Extracellular neurotransmitters in the hippocampus were detected by microdialysis coupled with high-performance liquid chromatography. In study 2, 33 SD rats were randomly divided into three groups: 4 weeks of physical exercise and Alzheimer's disease group (Exe+AD group, n = 11), AAV-Control and physical exercise and Alzheimer's disease group (AAV-Control+Exe+AD group, n = 11), AAV-TREM2 and physical exercise and Alzheimer's disease group (AAV-TREM2 +Exe+AD group, n = 11). Stereotactic intracerebral injection in the bilateral hippocampus was performed to achieve microglial TREM2 down-expression by using adeno-associated virus (AAV) with CD68 promoter. After 4 weeks treadmill exercise and 3 weeks Aβ injection, all rats received behavior test and molecular experiment, which the same with experiment 2.

RESULTS

Novel recognition index in novel object recognition test significantly decreased, and western blot demonstrate that hippocampal TREM2 protein is significantly decreased (P < 0.001). But physical exercise reversed this phenomenon(P < 0.001). In addition, compared with Con group, the neuron from Exe+AD group exhibited a more complex branching pattern (P < 0.05). And impaired synaptic ultrastructure was observed in AD group. Hippocampal synaptic-related protein (SYX, SYP, GAP43, PSD95) and neurotransmitter (DA, Glu, GABA) was also significantly decreased (P < 0.01) in AD group. But the neuroprotection effect can be found in Exe+AD group, which are associated with the inhibition of synaptic injury by activate hippocampal TREM2 (P < 0.05). However, when blockade of hippocampal TREM2 reduced brain protective effect of exercise in AD rat model, including increased the damage of neuronal dendritic complexity, synaptic ultrastructure, and the decrease of hippocampal synapses-related protein, typical neurotransmitter.

CONCLUSION

Treadmill exercise facilitated recognition memory acquisition via TREM2-mediated structural synaptic plasticity of the hippocampus in an AD rat model.

Neurons Specialize in Presynaptic Autophagy: A Perspective to Ameliorate Neurodegeneration

The efficient and prolonged neurotransmission is reliant on the coordinated action of numerous synaptic proteins in the presynaptic compartment that remodels synaptic vesicles for neurotransmitter packaging and facilitates their exocytosis. Once a cycle of neurotransmission is completed, membranes and associated proteins are endocytosed into the cytoplasm for recycling or degradation. Both exocytosis and endocytosis are closely regulated in a timely and spatially constrained manner. Recent research demonstrated the impact of dysfunctional synaptic vesicle retrieval in causing retrograde degeneration of midbrain neurons and has highlighted the importance of such endocytic proteins, including auxilin, synaptojanin1 (SJ1), and endophilin A (EndoA) in neurodegenerative diseases. Additionally, the role of other associated proteins, including leucine-rich repeat kinase 2 (LRRK2), adaptor proteins, and retromer proteins, is being investigated for their roles in regulating synaptic vesicle recycling. Research suggests that the degradation of defective vesicles via presynaptic autophagy, followed by their recycling, not only revitalizes them in the active zone but also contributes to strengthening synaptic plasticity. The presynaptic autophagy rejuvenating terminals and maintaining neuroplasticity is unique in autophagosome formation. It involves several synaptic proteins to support autophagosome construction in tiny compartments and their retrograde trafficking toward the cell bodies. Despite having a comprehensive understanding of ATG proteins in autophagy, we still lack a framework to explain how autophagy is triggered and potentiated in compact presynaptic compartments. Here, we reviewed synaptic proteins' involvement in forming presynaptic autophagosomes and in retrograde trafficking of terminal cargos. The review also discusses the status of endocytic proteins and endocytosis-regulating proteins in neurodegenerative diseases and strategies to combat neurodegeneration.

Reduced 17β-estradiol following ovariectomy induces mitochondrial dysfunction and degradation of synaptic proteins in the entorhinal cortex

Reductions in circulating estrogens can contribute to cognitive decline, in part by impairing mitochondrial function within the hippocampal region. The entorhinal cortex provides the hippocampus with its main cortical inputs. To assess the impact of estrogen deficiency on mitochondrial respiration and synaptic proteins in the entorhinal cortex, female wildtype rats received either sham surgery, bilateral ovariectomy, or ovariectomy with implantation of a subdermal capsule to maintain low levels of circulating 17β-estradiol (E2). Mitochondrial respiration in the entorhinal cortex was not significantly affected two weeks following ovariectomy, but there was a reduction in oxygen consumption four weeks after ovariectomy that was prevented by E2 supplementation. The expression of mitochondrial membrane integrity element voltage-dependent anion channel protein (VDAC1) was also reduced four weeks after ovariectomy, suggesting that respiration was reduced due to a decline in mitochondrial density. Ovariectomy also increased mitochondrial and cytoplasmic cytochrome c and upregulated superoxide dismutase 2 (SOD2) both two and four weeks after ovariectomy, reflecting mitochondrial electron leakage and oxidative redox imbalance. Further, the ovariectomy-induced changes in mitochondrial proteins were associated with reductions in postsynaptic density protein 95 (PSD95) and the presynaptic protein synaptophysin. There were no changes in mitochondrial or synaptic proteins in ovariectomized animals that received E2 supplementation. Our findings indicate that reductions in circulating 17β-estradiol induced by ovariectomy disrupt mitochondrial functions in the entorhinal cortex, and suggest that a resulting increase in oxidative stress contributes to the degradation in synaptic proteins that may affect cognitive functions mediated by the hippocampal region.

CD2AP deficiency aggravates Alzheimer's disease phenotypes and pathology through p38 MAPK activation

BACKGROUND

Alzheimer's disease (AD) is the most common form of neurodegenerative disorder, which is characterized by a decline in cognitive abilities. Genome-wide association and clinicopathological studies have demonstrated that the CD2-associated protein (CD2AP) gene is one of the most important genetic risk factors for AD. However, the precise mechanisms by which CD2AP is linked to AD pathogenesis remain unclear.

METHODS

The spatiotemporal expression pattern of CD2AP was determined. Then, we generated and characterized an APP/PS1 mouse model with neuron-specific Cd2ap deletion, using immunoblotting, immunofluorescence, enzyme-linked immunosorbent assay, electrophysiology and behavioral tests. Additionally, we established a stable CD2AP-knockdown SH-SY5Y cell line to further elucidate the specific molecular mechanisms by which CD2AP contributes to AD pathogenesis. Finally, the APP/PS1 mice with neuron-specific Cd2ap deletion were treated with an inhibitor targeting the pathway identified above to further validate our findings.

RESULTS

CD2AP is widely expressed in various regions of the mouse brain, with predominant expression in neurons and vascular endothelial cells. In APP/PS1 mice, neuronal knockout of Cd2ap significantly aggravated tau pathology, synaptic impairments and cognitive deficits. Mechanistically, the knockout of Cd2ap activated p38 mitogen-activated protein kinase (MAPK) signaling, which contributed to increased tau phosphorylation, synaptic injury, neuronal apoptosis and cognitive impairment. Furthermore, the phenotypes of neuronal Cd2ap knockout were ameliorated by a p38 MAPK inhibitor.

CONCLUSION

Our study presents the first in vivo evidence that CD2AP deficiency exacerbates the phenotypes and pathology of AD through the p38 MAPK pathway, identifying CD2AP/p38 MAPK as promising therapeutic targets for AD.

Latest advances and clinical application prospects of resveratrol therapy for neurocognitive disorders

Neurocognitive disorders, such as Alzheimer's disease, vascular dementia, and postoperative cognitive dysfunction, are non-psychiatric brain syndromes in which a significant decline in cognitive function causes great trauma to the mental status of the patient. The lack of effective treatments for neurocognitive disorders imposes a considerable burden on society, including a substantial economic impact. Over the past few decades, the identification of resveratrol, a natural plant compound, has provided researchers with an opportunity to formulate novel strategies for the treatment of neurocognitive disorders. This is because resveratrol effectively protects the brain of those with neurocognitive disorders by targeting some mechanisms such as inflammation and oxidative stress. This article reviews the status of recent research investigating the use of resveratrol for the treatment of different neurocognitive disorders. By examining the possible mechanisms of action of resveratrol and the shared mechanisms of different neurocognitive disorders, treatments for neurocognitive disorders may be further clarified.

Remodeling brain pathological microenvironment to lessen cerebral ischemia injury by multifunctional injectable hydrogels

Ischemia stroke is one of the leading causes of death and disability worldwide. Owing to the limited delivery efficiency to the brain caused by the blood-brain barrier (BBB) and off-target effects of systemic treatment, it is crucial to develop an in situ drug delivery system to improve the therapeutic effect in ischemic stroke. Briefly, we report a multifunctional in situ hydrogel delivery system for the co-delivery of reactive oxygen species (ROS)-responsive nanoparticles loaded with atorvastatin calcium (DSPE-se-se-PEG@AC NPs) and β-nerve growth factor (NGF), which is expected to remodel pathological microenvironment for improving cerebral ischemia injury. The in vitro results exhibited the multifunctional hydrogel scavenged oxygen-glucose deprivation (OGD)-induced free radical, rescued the mitochondrial function, and maintained the survival and function of neurons, hence reducing neuronal apoptosis and neuroinflammation, consequently relieving ischemia injury in hippocampal neurons cell line (HT22). In the rat ischemia stroke model, the hydrogel significantly minified cerebral infarction by regulating inflammatory response, saving apoptotic neurons, and promoting angiogenesis and neurogenesis. Besides, the hydrogel distinctly improved the rats' neurological deficits after cerebral ischemia injury over the long-term observation. In conclusion, the in-situ hydrogel platform has demonstrated promising therapeutic effects in both in vitro and in vivo studies, indicating its potential as a new and effective therapy.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology (i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, primarily vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process requires neuronal activity and the kinase GSK3β. GCs also dramatically enhance trans-neuronal Tau spreading in vivo, and this effect is blocked by an inhibitor of Tau oligomerization and type 1 unconventional protein secretion. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Identification of the Shared Gene Signatures Between Alzheimer's Disease and Diabetes-Associated Cognitive Dysfunction by Bioinformatics Analysis Combined with Biological Experiment

Background

The connection between diabetes-associated cognitive dysfunction (DACD) and Alzheimer's disease (AD) has been shown in several observational studies. However, it remains controversial as to how the two related.

Objective

To explore shared genes and pathways between DACD and AD using bioinformatics analysis combined with biological experiment.

Methods

We analyzed GEO microarray data to identify DEGs in AD and type 2 diabetes mellitus (T2DM) induced-DACD datasets. Weighted gene co-expression network analysis was used to find modules, while R packages identified overlapping genes. A robust protein-protein interaction network was constructed, and hub genes were identified with Gene ontology enrichment and Kyoto Encyclopedia of Genome and Genome pathway analyses. HT22 cells were cultured under high glucose and amyloid-β 25-35 (Aβ25-35) conditions to establish DACD and AD models. Quantitative polymerase chain reaction with reverse transcription verification analysis was then performed on intersection genes.

Results

Three modules each in AD and T2DM induced-DACD were identified as the most relevant and 10 hub genes were screened, with analysis revealing enrichment in pathways such as synaptic vesicle cycle and GABAergic synapse. Through biological experimentation verification, 6 key genes were identified.

Conclusions

This study is the first to use bioinformatics tools to uncover the genetic link between AD and DACD. GAD1, UCHL1, GAP43, CARNS1, TAGLN3, and SH3GL2 were identified as key genes connecting AD and DACD. These findings offer new insights into the diseases' pathogenesis and potential diagnostic and therapeutic targets.

Oxygen metabolism abnormality and Alzheimer's disease: An update

Oxygen metabolism abnormality plays a crucial role in the pathogenesis of Alzheimer's disease (AD) via several mechanisms, including hypoxia, oxidative stress, and mitochondrial dysfunction. Hypoxia condition usually results from living in a high-altitude habitat, cardiovascular and cerebrovascular diseases, and chronic obstructive sleep apnea. Chronic hypoxia has been identified as a significant risk factor for AD, showing an aggravation of various pathological components of AD, such as amyloid β-protein (Aβ) metabolism, tau phosphorylation, mitochondrial dysfunction, and neuroinflammation. It is known that hypoxia and excessive hyperoxia can both result in oxidative stress and mitochondrial dysfunction. Oxidative stress and mitochondrial dysfunction can increase Aβ and tau phosphorylation, and Aβ and tau proteins can lead to redox imbalance, thus forming a vicious cycle and exacerbating AD pathology. Hyperbaric oxygen therapy (HBOT) is a non-invasive intervention known for its capacity to significantly enhance cerebral oxygenation levels, which can significantly attenuate Aβ aggregation, tau phosphorylation, and neuroinflammation. However, further investigation is imperative to determine the optimal oxygen pressure, duration of exposure, and frequency of HBOT sessions. In this review, we explore the prospects of oxygen metabolism in AD, with the aim of enhancing our understanding of the underlying molecular mechanisms in AD. Current research aimed at attenuating abnormalities in oxygen metabolism holds promise for providing novel therapeutic approaches for AD.

The role of EndophilinA1 in chronic unpredicted mild stress-induced depression model mice

BACKGROUND

Depression is a common mental disease, accompanied by anxiety and persistent depression. Endophilin A1 (EPA1) is a brain-specific protein enriched in synaptic terminals that is primarily expressed in the central nervous system. It has been reported that EPA1 is involved in neurotransmitter release, which indicates that the protein may be involved in depression. However, it is unclear whether EPA1 is implicated in the development of depression.

METHODS

The mice depression model was established by chronic unpredicted mild stress (CUMS). Depression-like behaviors were detected by sucrose preference test (SPT), forced swim test (FST), tail-suspension test (TST) and open-field test (OFT). Neuronal histopathology was applied by hematoxylin and eosin stain (H&E), and Nissl stain. EPA1, NLRP1 inflammatory complexes, NADPH oxidase2 (NOX2), synaptic-related protein expression of the mice were tested by western blot. Immunofluorescence was applied to detect the expression of EPA1 and ROS in mice hippocampus. EPA1 knockdown was performed by an adeno-associated virus (AAV) vector containing EPA1-shRNA-EGFP infusion.

RESULT

CUMS exposure induced depressive-like behaviors and increased the expression of EPA1 in the hippocampus. Knockdown hippocampal EPA1 ameliorated CUMS-induced depressive-like behaviors, decreased calcium (Ca2+) overload, decreased ROS generation and NOX2 expression, inhibited NLRP1 inflammasome-driven neuroinflammation, and restored the levels of BDNF, PSD95, GAP-43, SYN, and MAP-2 in the hippocampus.

CONCLUSION

EPA1 contributes to CUMS induced depressive-like behaviors and the mechanism may be related to NLRP1 inflammasome-driven inflammatory response, regulating calcium ion homeostasis and ROS generation, and alleviating synaptic function damage. This indicated that EPA1 may participate in the occurrence and development of depression.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology (i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process occurs via type 1 unconventional protein secretion (UPS) and requires neuronal activity and the kinase GSK3b. GCs also dramatically enhance trans-neuronal Tau spreading in vivo, and this effect is blocked by an inhibitor of Tau oligomerization and type 1 UPS. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology ( i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process occurs via type 1 unconventional protein secretion (UPS) and requires neuronal activity and the kinase GSK3β. GCs also dramatically enhance trans-neuronal Tau spreading in vivo , and this effect is blocked by an inhibitor of Tau oligomerization and type 1 UPS. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Kai-Xin-San protects against mitochondrial dysfunction in Alzheimer's disease through SIRT3/NLRP3 pathway

BACKGROUND

Kai-Xin-San (KXS) has been reported to have a good curative impact on dementia. The purpose of the study was to determine whether KXS might ameliorate cognitive deficits in APP/PS1 mice and to evaluate its neuroprotective mechanism.

METHODS

APP/PS1 mice were employed as an AD animal model; Aβ_1-42 and KXS-containing serum were used in HT22 cells. Four different behavioral tests were used to determine the cognitive ability of mice. Nissl staining was utilized to detect hippocampal neuron changes. ROS, SOD, and MDA were used to detect oxidative stress levels. Transmission electron microscopy and Western blot were used to evaluate mitochondrial morphology, mitochondrial division, and fusion state. Western blotting and immunofluorescence identified PSD95, BDNF, NGF, SYN, SIRT3, and NLRP3 inflammasome levels.

RESULTS

The results indicated that KXS protected APP/PS1 mice against cognitive impairments. KXS suppressed neuronal apoptosis and oxidative stress among APP/PS1 mice. KXS and KXS-containing serum improved mitochondrial dysfunction and synaptic and neurotrophic factors regarding APP/PS1 mice. In addition, KXS and KXS-containing serum enhanced mitochondrial SIRT3 expression and reduced NLRP3 inflammasome expression in APP/PS1 mice.

CONCLUSION

KXS improves cognitive dysfunction among APP/PS1 mice via regulating SIRT3-mediated neuronal cell apoptosis. These results suggested that KXS was proposed as a neuroprotective agent for AD progression.

Small molecules targeting endocytic uptake and recycling pathways

Over the past years a growing number of studies highlighted the pivotal role of intracellular trafficking in cell physiology. Among the distinct transport itineraries connecting the endocytic system, both internalization (endocytosis) and recycling (endocytic recycling) pathways were found fundamental to ensure cellular sensing, cell-to-cell communication, cellular division, and collective cell migration in tissue specific-contexts. Consistently, the dysregulation of endocytic trafficking pathways is correlated with several human diseases including both cancers and neurodegeneration. Aimed at suppress specific intracellular trafficking routes involved in disease onset and progression, huge efforts have been made to identify small molecule inhibitors with suitable pharmacological properties for in vivo administration. Here, we review most used drugs and recently discovered small molecules able to block endocytosis and endocytic recycling pathways. We characterize such pharmacological inhibitors by emphasizing their target specificity, molecular affinity, biological activity and efficacy in both in vitro and in vivo experimental models.

Manganese-induced α-synuclein overexpression promotes the accumulation of dysfunctional synaptic vesicles and hippocampal synaptotoxicity by suppressing Rab26-dependent autophagy in presynaptic neurons

Manganese (Mn) overexposure induces learning and memory impairments in mice by disrupting the functions of synapses and synaptic vesicles (SVs) in the hippocampus, which is associated with α-synuclein (α-Syn) overexpression. Rab26-dependent autophagy is a key signaling step required for impaired SV clearance; however, it is unclear whether Mn-induced α-Syn overexpression is linked to dysregulated Rab26-dependent autophagy in presynaptic neurons. In this study, we developed manganism models in male C57BL/6 mice and hippocampal primary neurons to observe the associations between Mn-induced α-Syn overexpression and impaired SV accumulation. The results of the in vivo experiments showed that 100 and 200 μmol/kg Mn exposure significantly impaired memory and synaptic plasticity in the mice, which was related to the accumulation of impaired SVs in the hippocampus. Consistent with the in vivo outcomes, the level of in vitro injured SVs in the 50 and 100 μmol/L Mn-exposed neuron group were higher than that in the control group. Moreover, 100 μmol/L Mn suppressed the initiation of Rab26-dependent autophagy at the synapse. Then, we transfected neurons with LV-α-Syn short hairpin RNA (shRNA) and exposed the neurons to Mn for an additional 24 h. Surprisingly, the area of colocalization between Rab26 and Atg16L1 and the expression level of LC3II-positive SVs were both higher in Mn-exposed LV-α-Syn shRNA-transfected neurons than those in Mn-treated normal or Mn-treated LV-scrambled shRNA-transfected neurons. Thus, Mn-induced α-Syn overexpression was responsible for the dysregulation of Rab26-dependent autophagy, thereby promoting the accumulation of injured SVs, and causing synaptotoxicity and cognitive and memory deficits in mice.

The Role of Endophilin A1 in Lipopolysaccharide-Induced Parkinson's Disease Model Mice

BACKGROUND

Endophilin A1 (EPA1) is encoded by the SH3GL2 gene, and SH3GL2 was designated as a Parkinson's disease (PD) risk locus by genome-wide association analysis, suggesting that EPA1 may be involved in the occurrence and development of PD.

OBJECTIVE

To investigate the role of EPA1 in lipopolysaccharide (LPS)-induced PD model mice.

METHODS

The mice PD model was prepared by injecting LPS into the substantia nigra (SN), and the changes in the behavioral data of mice in each group were observed. The damage of dopaminergic neurons, activation of microglia, and reactive oxygen species (ROS) generation were detected by immunofluorescence method; calcium ion concentration was detected by calcium content detection kit; EPA1 and inflammation and its related indicators were detected by western blot method. EPA1 knockdown was performed by an adeno-associated virus vector containing EPA1-shRNA-eGFP infusion.

RESULTS

LPS-induced PD model mice developed behavioral dysfunction, SN dopaminergic nerve damage, significantly increased calcium ion, calpain 1, and ROS production, activated NLRP1 inflammasome and promoted pro-inflammatory cell release, and SN EPA1 knockdown improves behavioral disorders, alleviates dopaminergic neuron damage, reduces calcium, calpain 1, ROS generation, and blocks NLRP1 inflammasome-driven inflammatory responses.

CONCLUSION

The expression of EPA1 in the SN of LPS-induced PD model mice was increased, and it played a role in promoting the occurrence and development of PD. EPA1 knockdown inhibited the NLRP1 inflammasome activation, decreased the release of inflammatory factors and ROS generation, and alleviated dopaminergic neuron damage. This indicated that EPA1 may participating in the occurrence and development of PD.

Inhibiting amyloid beta (1–42) peptide-induced mitochondrial dysfunction prevents the degradation of synaptic proteins in the entorhinal cortex

Increasing evidence suggests that mitochondrial dysfunction and aberrant release of mitochondrial reactive oxygen species (ROS) play crucial roles in early synaptic perturbations and neuropathology that drive memory deficits in Alzheimer’s disease (AD). We recently showed that solubilized human amyloid beta peptide 1–42 (hAβ_1–42) causes rapid alterations at glutamatergic synapses in the entorhinal cortex (EC) through the activation of both GluN2A- and GluN2B-containing NMDA receptors. However, whether disruption of mitochondrial dynamics and increased ROS contributes to mechanisms mediating hAβ_1–42-induced synaptic perturbations in the EC is unknown. Here we assessed the impact of hAβ_1–42 on mitochondrial respiratory functions, and the expression of key mitochondrial and synaptic proteins in the EC. Measurements of mitochondrial respiratory function in wild-type EC slices exposed to 1 μM hAβ_1–42 revealed marked reductions in tissue oxygen consumption and energy production efficiency relative to control. hAβ_1–42 also markedly reduced the immunoexpression of both mitochondrial superoxide dismutase (SOD2) and mitochondrial-cytochrome c protein but had no significant impact on cytosolic-cytochrome c expression, voltage-dependent anion channel protein (a marker for mitochondrial density/integrity), and the immunoexpression of protein markers for all five mitochondrial complexes. The rapid impairments in mitochondrial functions induced by hAβ_1–42 were accompanied by reductions in the presynaptic marker synaptophysin, postsynaptic density protein (PSD95), and the vesicular acetylcholine transporter, with no significant changes in the degradative enzyme acetylcholinesterase. We then assessed whether reducing hAβ_1–42-induced increases in ROS could prevent dysregulation of entorhinal synaptic proteins, and found that synaptic impairments induced by hAβ_1–42 were prevented by the mitochondria-targeted antioxidant drug mitoquinone mesylate, and by the SOD and catalase mimetic EUK134. These findings indicate that hAβ_1–2 can rapidly disrupt mitochondrial functions and increase ROS in the entorhinal, and that this may contribute to synaptic dysfunctions that may promote early AD-related neuropathology.

Nanocatalytic Biofunctional MOF Coating on Titanium Implants Promotes Osteoporotic Bone Regeneration through Cooperative Pro-osteoblastogenesis MSC Reprogramming

An elevated bone microenvironmental reactive oxygen species (ROS) level is a hallmark of osteoporosis that often leads to the dysfunction of bone-related mesenchymal stem cells (MSCs), which would induce MSC senescence and severely undermine their osteoblastic potential. Herein, we report the in situ construction of bone microenvironment-responsive biofunctional metal-organic framework (bio-MOF) coating on the titanium surface through the coordination between p-xylylenebisphosphonate (PXBP) and Ce/Sr ions by a hydrothermal method. Taking advantage of the anchored Ce and Sr ions, the AHT-Ce/SrMOF implants demonstrate on-demand superoxide dismutase and catalase-like catalytic activities to decompose ROS in MSCs and restore their mitochondrial functions. In vitro analysis showed that the AHT-Ce/SrMOF implants substantially activated the AMP-activated protein kinase (AMPK) signaling pathway in MSCs and reduced the ROS levels. Meanwhile, MSCs grown on AHT-Ce/SrMOF implants displayed significantly higher expressions of the mitochondrial fission marker (DRP1), mitochondrial fusion marker (MFN2 and OPA1), and mitophagy marker (PINK1 and LC3) than those of the AHT-CeMOF and AHT-SrMOF groups, which indicated that the bio-MOF could amend mitochondrial function in MSCs to reverse senescence. In vivo evaluations showed that the bio-MOF-coated Ti implants could restore MSC function in the implant site and promote new bone formation, leading to improved osteointegration in osteoporotic rat. This study may improve implant-mediated fracture healing in the clinics.

Local regulation of extracellular vesicle traffic by the synaptic endocytic machinery

Neuronal extracellular vesicles (EVs) are locally released from presynaptic terminals, carrying cargoes critical for intercellular signaling and disease. EVs are derived from endosomes, but it is unknown how these cargoes are directed to the EV pathway rather than for conventional endolysosomal degradation. Here, we find that endocytic machinery plays an unexpected role in maintaining a release-competent pool of EV cargoes at synapses. Endocytic mutants, including nervous wreck (nwk), shibire/dynamin, and AP-2, unexpectedly exhibit local presynaptic depletion specifically of EV cargoes. Accordingly, nwk mutants phenocopy synaptic plasticity defects associated with loss of the EV cargo synaptotagmin-4 (Syt4) and suppress lethality upon overexpression of the EV cargo amyloid precursor protein (APP). These EV defects are genetically separable from canonical endocytic functions in synaptic vesicle recycling and synaptic growth. Endocytic machinery opposes the endosomal retromer complex to regulate EV cargo levels and acts upstream of synaptic cargo removal by retrograde axonal transport. Our data suggest a novel molecular mechanism that locally promotes cargo loading into synaptic EVs.

Mitochondrial-Respiration-Improving Effects of Three Different Gardeniae Fructus Preparations and Their Components

The processing method for Chinese traditional herbal medicine is "Pao Zhi" in Chinese. This study examined the efficacy of the Pao Zhi on the preparations of Gardeniae Fructus (GF) on a mitochondrial respiratory function in rats. To determine the efficacy of Pao Zhi, we investigated the effects of GF heat processing on mitochondrial respiratory function. To test the GF components, the rats were randomly divided into a geniposide-alone group, crocin-alone group, and combination groups and treated with geniposide and crocin at different ratios. The results showed that a high dose, raw GF was more effective in improving the neurological function, mitochondrial respiratory function, and activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase than the preparations that underwent heating. Moreover, mitochondrial ROS production was the lowest in the raw GF-treated group. In addition, treatments with crocin and GC3 were more effective than geniposide in improving the functional deficit in MCAO rats. In conclusion, our results suggest that raw GF is the most suitable preparation for the treatment of cerebral ischemia, and its underlying mechanisms may be associated with the improvement of mitochondrial respiratory function, increased activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase, and reduced oxidative stress in mitochondria. Our findings suggest that raw GF, especially crocin, could be an ideal therapeutic agent for ischemic stroke.

Disentangling Mitochondria in Alzheimer's Disease

Alzheimer's disease (AD) is a major cause of dementia in older adults and is fast becoming a major societal and economic burden due to an increase in life expectancy. Age seems to be the major factor driving AD, and currently, only symptomatic treatments are available. AD has a complex etiology, although mitochondrial dysfunction, oxidative stress, inflammation, and metabolic abnormalities have been widely and deeply investigated as plausible mechanisms for its neuropathology. Aβ plaques and hyperphosphorylated tau aggregates, along with cognitive deficits and behavioral problems, are the hallmarks of the disease. Restoration of mitochondrial bioenergetics, prevention of oxidative stress, and diet and exercise seem to be effective in reducing Aβ and in ameliorating learning and memory problems. Many mitochondria-targeted antioxidants have been tested in AD and are currently in development. However, larger streamlined clinical studies are needed to provide hard evidence of benefits in AD. This review discusses the causative factors, as well as potential therapeutics employed in the treatment of AD.

TUFM is involved in Alzheimer's disease-like pathologies that are associated with ROS

Mitochondrial Tu translation elongation factor (TUFM or EF-Tu) is part of the mitochondrial translation machinery. It is reported that TUFM expression is reduced in the brain of Alzheimer's disease (AD), suggesting that TUFM might play a role in the pathophysiology. In this study, we found that TUFM protein level was decreased in the hippocampus and cortex especially in the aged APP/PS1 mice, an animal model of AD. In HEK cells that stably express full-length human amyloid-β precursor protein (HEK-APP), TUFM knockdown or overexpression increased or reduced the protein levels of β-amyloid protein (Aβ) and β-amyloid converting enzyme 1 (BACE1), respectively. TUFM-mediated reduction of BACE1 was attenuated by translation inhibitor cycloheximide (CHX) or α-[2-[4-(3,4-Dichlorophenyl)-2-thiazolyl]hydrazinylidene]-2-nitro-benzenepropanoic acid (4EGI1), and in cells overexpressing BACE1 constructs deleting the 5' untranslated region (5'UTR). TUFM silencing increased the half-life of BACE1 mRNA, suggesting that RNA stability was affected by TUFM. In support, transcription inhibitor Actinomycin D (ActD) and silencing of nuclear factor κB (NFκB) failed to abolish TUFM-mediated regulation of BACE1 protein and mRNA. We further found that the mitochondria-targeted antioxidant TEMPO diminished the effects of TUFM on BACE1, suggesting that reactive oxygen species (ROS) played an important role. Indeed, cellular ROS levels were affected by TUFM knockdown or overexpression, and TUFM-mediated regulation of apoptosis and Tau phosphorylation at selective sites was attenuated by TEMPO. Collectively, TUFM protein levels were decreased in APP/PS1 mice. TUFM is involved in AD pathology by regulating BACE1 translation, apoptosis, and Tau phosphorylation, in which ROS plays an important role.

Endophilin A1 drives acute structural plasticity of dendritic spines in response to Ca2+/calmodulin

Induction of long-term potentiation (LTP) in excitatory neurons triggers a large transient increase in the volume of dendritic spines followed by decays to sustained size expansion, a process termed structural LTP (sLTP) that contributes to the cellular basis of learning and memory. Although mechanisms regulating the early and sustained phases of sLTP have been studied intensively, how the acute spine enlargement immediately after LTP stimulation is achieved remains elusive. Here, we report that endophilin A1 orchestrates membrane dynamics with actin polymerization to initiate spine enlargement in NMDAR-mediated LTP. Upon LTP induction, Ca²⁺/calmodulin enhances binding of endophilin A1 to both membrane and p140Cap, a cytoskeletal regulator. Consequently, endophilin A1 rapidly localizes to the plasma membrane and recruits p140Cap to promote local actin polymerization, leading to spine head expansion. Moreover, its molecular functions in activity-induced rapid spine growth are required for LTP and long-term memory. Thus, endophilin A1 serves as a calmodulin effector to drive acute structural plasticity necessary for learning and memory.

A γ-adducin cleavage fragment induces neurite deficits and synaptic dysfunction in Alzheimer's disease

Neurite deficits and synaptic dysfunction contribute to cognitive impairments in Alzheimer's disease (AD). However, the underlying molecular mechanisms remain unclear. Here, we show that γ-adducin, a cytoskeleton-associated protein that assembles the spectrin-actin framework, is cleaved by a lysosomal cysteine proteinase named asparagine endopeptidase (AEP). AEP is upregulated and activated during aging and cleaves γ-adducin at N357, disrupting spectrin-actin assembly. Moreover, γ-adducin (1-357) fragment downregulates the expression of Rac2, leading to defects in neurite outgrowth. Expression of the γ-adducin (1-357) fragment in the hippocampus of tau P301S transgenic mice resulted in significant AD-like pathology and cognitive deficits. In summary, AEP-mediated fragmentation of γ-adducin plays a vital role in AD. Blocking the activity of AEP might be a novel therapeutic target for AD.

High Dietary Advanced Glycation End Products Impair Mitochondrial and Cognitive Function

BACKGROUND

Advanced glycation end products (AGEs) are an important risk factor for the development of cognitive decline in aging and late-onset neurodegenerative diseases including Alzheimer's disease. However, whether and how dietary AGEs exacerbate cognitive impairment and brain mitochondrial dysfunction in the aging process remains largely unknown.

OBJECTIVE

We investigated the direct effects of dietary AGEs on AGE adducts accumulation, mitochondrial function, and cognitive performance in mice.

METHODS

Mice were fed the AGE+ diet or AGE- diet. We examined levels of AGE adducts in serum and cerebral cortexes by immunodetection and immunohistochemistry, determined levels of reactive oxygen species by biochemical analysis, detected enzyme activity associated with mitochondrial respiratory chain complexes I & IV and ATP levels, and assessed learning and memory ability by Morris Water Maze and nesting behavior.

RESULTS

Levels of AGE adducts (MG-H1 and CEL) were robustly increased in the serum and brain of AGE+ diet fed mice compared to the AGE- group. Furthermore, greatly elevated levels of reactive oxygen species, decreased activities of mitochondrial respiratory chain complexes I & IV, reduced ATP levels, and impaired learning and memory were evident in AGE+ diet fed mice compared to the AGE- group.

CONCLUSION

These results indicate that dietary AGEs are important sources of AGE accumulation in vivo, resulting in mitochondrial dysfunction, impairment of energy metabolism, and subsequent cognitive impairment. Thus, reducing AGEs intake to lower accumulation of AGEs could hold therapeutic potential for the prevention and treatment of AGEs-induced mitochondrial dysfunction linked to cognitive decline.

Gain of PITRM1 peptidase in cortical neurons affords protection of mitochondrial and synaptic function in an advanced age mouse model of Alzheimer's disease

Mitochondrial dysfunction is one of the early pathological features of Alzheimer's disease (AD). Accumulation of cerebral and mitochondrial Aβ links to mitochondrial and synaptic toxicity. We have previously demonstrated the mechanism by which presequence peptidase (PITRM1)‐mediated clearance of mitochondrial Aβ contributes to mitochondrial and cerebral amyloid pathology and mitochondrial and synaptic stress in adult transgenic AD mice overexpressing Aβ up to 12 months old. Here, we investigate the effect of PITRM1 in an advanced age AD mouse model (up to 19–24 months) to address the fundamental unexplored question of whether restoration/gain of PITRM1 function protects against mitochondrial and synaptic dysfunction associated with Aβ accumulation and whether this protection is maintained even at later ages featuring profound amyloid pathology and synaptic failure. Using newly developed aged PITRM1/Aβ‐producing AD mice, we first uncovered reduction in PITRM1 expression in AD‐affected cortex of AD mice at 19–24 months of age. Increasing neuronal PITRM1 activity/expression re‐established mitochondrial respiration, suppressed reactive oxygen species, improved synaptic function, and reduced loss of synapses even at advanced ages (up to 19–24 months). Notably, loss of PITRM1 proteolytic activity resulted in Aβ accumulation and failure to rescue mitochondrial and synaptic function, suggesting that PITRM1 activity is required for the degradation and clearance of mitochondrial Aβ and Aβ deposition. These data indicate that augmenting PITRM1 function results in persistent life‐long protection against Aβ toxicity in an AD mouse model. Therefore, augmenting PITRM1 function may enhance Aβ clearance in mitochondria, thereby maintaining mitochondrial integrity and ultimately slowing the progression of AD.

Targeting redox-altered plasticity to reactivate synaptic function: A novel therapeutic strategy for cognitive disorder

Redox-altered plasticity refers to redox-dependent reversible changes in synaptic plasticity via altering functions of key proteins, such as N-methyl-d-aspartate receptor (NMDAR). Age-related cognitive disorders includes Alzheimer's disease (AD), vascular dementia (VD), and age-associated memory impairment (AAMI). Based on the critical role of NMDAR-dependent long-term potentiation (LTP) in memory, the increase of reactive oxygen species in cognitive disorders, and the sensitivity of NMDAR to the redox status, converging lines have suggested the redox-altered NMDAR-dependent plasticity might underlie the synaptic dysfunctions associated with cognitive disorders. In this review, we summarize the involvement of redox-altered plasticity in cognitive disorders by presenting the available evidence. According to reports from our laboratory and other groups, this "redox-altered plasticity" is more similar to functional changes rather than organic injuries, and strategies targeting redox-altered plasticity using pharmacological agents might reverse synaptic dysfunctions and memory abnormalities in the early stage of cognitive disorders. Targeting redox modifications for NMDARs may serve as a novel therapeutic strategy for memory deficits.

Age-dependent accumulation of dicarbonyls and advanced glycation endproducts (AGEs) associates with mitochondrial stress

Aging is a strong risk factor for brain dementia and cognitive decline. Age-related accumulation of metabolites such as advanced glycation end products (AGEs) could serve as danger signals to initiate and accelerate disease process and neurodegeneration. The underlying causes and consequences of cerebral AGEs accumulation remain largely unknown. Here, we comprehensively investigate age-related accumulation of AGEs and dicarbonyls, including methylglyoxal (MG), glyoxal (GO), and 3-deoxyglucosone (3-DG), and the effects of mitochondrial reactive oxygen species (ROS) on cerebral AGEs accumulation, mitochondrial function, and oxidative stress in the aging human and mouse brain. We demonstrate that AGEs, including arginine and lysine derived N(6)-carboxymethyl lysine (CML), Nε-(1-Carboxyethyl)-l-lysine (CEL), and methylglyoxal-derived hydroimidazolone-1 (MG-H1), were significantly elevated in the cerebral cortex and hippocampus with advanced age in mice. Accordingly, aging mouse and human brains revealed decrease in activities of mitochondrial respiratory chain complexes I & IV and ATP levels, and increased ROS. Notably, administration of mitoTEMPO (2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (mTEMPO), a scavenger of mitochondrial ROS, not only suppressed ROS production but also reduced aged-induced accumulation of AGEs and dicarbonyls. mTEMPO treatment improved mitochondrial respiratory function and restored ATP levels. Our findings provide evidence linking age-related accumulation of toxic metabolites (AGEs) to mitochondrial oxidative stress. This highlights a novel mechanism by which AGEs-dependent signaling promotes carbonyl stress and sustained mitochondrial dysfunction. Eliminating formation and accumulation of AGEs may represent a new therapeutic avenue for combating cognitive decline and mitochondrial degeneration relevant to aging and neurodegenerative diseases including Alzheimer's disease.

Tat-Endophilin A1 Fusion Protein Protects Neurons from Ischemic Damage in the Gerbil Hippocampus: A Possible Mechanism of Lipid Peroxidation and Neuroinflammation Mitigation as Well as Synaptic Plasticity

The present study explored the effects of endophilin A1 (SH3GL2) against oxidative damage brought about by H₂O₂ in HT22 cells and ischemic damage induced upon transient forebrain ischemia in gerbils. Tat-SH3GL2 and its control protein (Control-SH3GL2) were synthesized to deliver it to the cells by penetrating the cell membrane and blood–brain barrier. Tat-SH3GL2, but not Control-SH3GL2, could be delivered into HT22 cells in a concentration- and time-dependent manner and the hippocampus 8 h after treatment in gerbils. Tat-SH3GL2 was stably present in HT22 cells and degraded with time, by 36 h post treatment. Pre-incubation with Tat-SH3GL2, but not Control-SH3GL2, significantly ameliorated H₂O₂-induced cell death, DNA fragmentation, and reactive oxygen species formation. SH3GL2 immunoreactivity was decreased in the gerbil hippocampal CA1 region with time after ischemia, but it was maintained in the other regions after ischemia. Tat-SH3GL2 treatment in gerbils appreciably improved ischemia-induced hyperactivity 1 day after ischemia and the percentage of NeuN-immunoreactive surviving cells increased 4 days after ischemia. In addition, Tat-SH3GL2 treatment in gerbils alleviated the increase in lipid peroxidation as assessed by the levels of malondialdehyde and 8-iso-prostaglandin F2α and in pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, and interleukin-6; while the reduction of protein levels in markers for synaptic plasticity, such as postsynaptic density 95, synaptophysin, and synaptosome associated protein 25 after transient forebrain ischemia was also observed. These results suggest that Tat-SH3GL2 protects neurons from oxidative and ischemic damage by reducing lipid peroxidation and inflammation and improving synaptic plasticity after ischemia.

The Role of Exosomal microRNAs and Oxidative Stress in Neurodegenerative Diseases

Neurodegenerative diseases including Alzheimer's disease and Parkinson's disease are aging-associated diseases with irreversible damage of brain tissue. Oxidative stress is commonly detected in neurodegenerative diseases and related to neuronal injury and pathological progress. Exosome, one of the extracellular vesicles, is demonstrated to carry microRNAs (miRNAs) and build up a cell-cell communication in neurons. Recent research has found that exosomal miRNAs regulate the activity of multiple physiological pathways, including the oxidative stress response, in neurodegenerative diseases. Here, we review the role of exosomal miRNAs and oxidative stress in neurodegenerative diseases. Firstly, we explore the relationship between oxidative stress and neurodegenerative diseases. Secondly, we introduce the characteristics of exosomes and roles of exosome-related miRNAs. Thirdly, we summarized the crosstalk between exosomal miRNAs and oxidative stress in neurodegenerative diseases. Fourthly, we discuss the potential of exosomes to be a biomarker in neurodegenerative diseases. Finally, we summarize the advantages of exosome-based delivery and present situation of research on exosome-based delivery of therapeutic miRNA. Our work is aimed at probing and reinforcing the recognition of the pathomechanism of neurodegenerative diseases and providing the basis for novel strategies of clinical diagnosis and treatment.

Involvement of p38 MAPK in Synaptic Function and Dysfunction

Many studies have revealed a central role of p38 MAPK in neuronal plasticity and the regulation of long-term changes in synaptic efficacy, such as long-term potentiation (LTP) and long-term depression (LTD). However, p38 MAPK is classically known as a responsive element to stress stimuli, including neuroinflammation. Specific to the pathophysiology of Alzheimer’s disease (AD), several studies have shown that the p38 MAPK cascade is activated either in response to the Aβ peptide or in the presence of tauopathies. Here, we describe the role of p38 MAPK in the regulation of synaptic plasticity and its implication in an animal model of neurodegeneration. In particular, recent evidence suggests the p38 MAPK α isoform as a potential neurotherapeutic target, and specific inhibitors have been developed and have proven to be effective in ameliorating synaptic and memory deficits in AD mouse models.

Discovery of a novel small molecule PT109 with multi-targeted effects against Alzheimer's disease in vitro and in vivo

Alzheimer's disease (AD), which is characterized by impairment of cognitive functions, is a chronic neurodegenerative disease that mainly affects the elderly. Currently available anti-AD drugs can only offer limited symptom-relieving effects. "One-compound-Multitargeted Strategy" have been recognized as the promising way to win the war against AD. Herein we report a potential anti-AD agent PT109 with multi-functions. First, an 81-kinase screening was carried out and results showed that PT109 potently inhibited c-Jun N-terminal kinases and Serum and glucocorticoid-inducible kinase 1, which are the important signaling molecules involved in neurogenesis, neuroprotection and neuroinflammation and mildly inhibit glycogen synthase kinase-3β as well as protein kinase C gamma, both are involved in AD pathological processes. In addition, invitro studies of immunofluorescent staining and Western blot showed that PT109 might promote the neurogenesis of C17.2 cells and induce synaptogenesis in primary cultured rat hippocampal neurons. We detected and confirmed the neuroprotective effect of PT109 in cultured HT22 cells by MTT assay, dehydrogenase assay, glutathione assay and reactive oxygen species assay. Furthermore, the results of Western blot, ELISA assay and immunofluorescent staining indicated that PT109 attenuated lipopolysaccharide-induced inflammation in BV2 cells and primary astrocytes. The results of Morris water maze and Step-through test indicated that PT109 improved the spatial learning ability in APP/PS1 mice. More importantly, the invivo pharmacokinetic parameters indicated that PT109 had better medicinal properties. Taken together, our findings suggest that PT109 may be a promising candidate for treating AD through multiple targets although further studies are ought to be conducted.

Molecular mechanism of Fast Endophilin-Mediated Endocytosis

Endocytosis mediates the cellular uptake of micronutrients and cell surface proteins. Clathrin-mediated endocytosis (CME) is the housekeeping pathway in resting cells but additional Clathrin-independent endocytic (CIE) routes, including Fast Endophilin-Mediated Endocytosis (FEME), internalize specific cargoes and support diverse cellular functions. FEME is part of the Dynamin-dependent subgroup of CIE pathways. Here, we review our current understanding of the molecular mechanism of FEME. Key steps are: (i) priming, (ii) cargo selection, (iii) membrane curvature and carrier formation, (iv) membrane scission and (v) cytosolic transport. All steps are controlled by regulatory mechanisms mediated by phosphoinositides and by kinases such as Src, LRRK2, Cdk5 and GSK3β. A key feature of FEME is that it is not constitutively active but triggered upon the stimulation of selected cell surface receptors by their ligands. In resting cells, there is a priming cycle that concentrates Endophilin into clusters on discrete locations of the plasma membrane. In the absence of receptor activation, the patches quickly abort and new cycles are initiated nearby, constantly priming the plasma membrane for FEME. Upon activation, receptors are swiftly sorted into pre-existing Endophilin clusters, which then bud to form FEME carriers within 10 s. We summarize the hallmarks of FEME and the techniques and assays required to identify it. Next, we review similarities and differences with other CIE pathways and proposed cargoes that may use FEME to enter cells. Finally, we submit pending questions and future milestones and discuss the exciting perspectives that targeting FEME may boost treatments against cancer and neurodegenerative diseases.

Intracellular Trafficking Mechanisms of Synaptic Dysfunction in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss. Although AD neuropathological hallmarks are extracellular amyloid plaques and intracellular tau tangles, the best correlate of disease progression is synapse loss. What causes synapse loss has been the focus of several researchers in the AD field. Synapses become dysfunctional before plaques and tangles form. Studies based on early-onset familial AD (eFAD) models have supported that synaptic transmission is depressed by β-amyloid (Aβ) triggered mechanisms. Since eFAD is rare, affecting only 1% of patients, research has shifted to the study of the most common late-onset AD (LOAD). Intracellular trafficking has emerged as one of the pathways of LOAD genes. Few studies have assessed the impact of trafficking LOAD genes on synapse dysfunction. Since endocytic traffic is essential for synaptic function, we reviewed Aβ-dependent and independent mechanisms of the earliest synaptic dysfunction in AD. We have focused on the role of intraneuronal and secreted Aβ oligomers, highlighting the dysfunction of endocytic trafficking as an Aβ-dependent mechanism of synapse dysfunction in AD. Here, we reviewed the LOAD trafficking genes APOE4, ABCA7, BIN1, CD2AP, PICALM, EPH1A, and SORL1, for which there is a synaptic link. We conclude that in eFAD and LOAD, the earliest synaptic dysfunctions are characterized by disruptions of the presynaptic vesicle exo- and endocytosis and of postsynaptic glutamate receptor endocytosis. While in eFAD synapse dysfunction seems to be triggered by Aβ, in LOAD, there might be a direct synaptic disruption by LOAD trafficking genes. To identify promising therapeutic targets and biomarkers of the earliest synaptic dysfunction in AD, it will be necessary to join efforts in further dissecting the mechanisms used by Aβ and by LOAD genes to disrupt synapses.

Ferrostatin-1 mitigates cognitive impairment of epileptic rats by inhibiting P38 MAPK activation

Evidence indicates that ferrostain-1 (Fer-1), a specific inhibitor of ferroptosis, could ameliorate cognitive dysfunction of rats with kainic acid (KA)-induced temporal lobe epilepsy (TLE) by suppressing ferroptosis processes. Recent studies suggest that P38 mitogen-activated protein kinase (MAPK) pathway could be mediated by ferroptosis processes. The activation of P38 MAPK results in cognitive impairment by suppressing the expression of synaptic plasticity-related proteins. However, it is unclear whether Fer-1 can mitigate cognitive impairment of rats with KA-induced TLE by inhibiting P38 MAPK activation. In the present study, treatment with Fer-1 blocked the activation of P38 MAPK, which resulted in an increased expression of synaptophysin (SYP) and postsynaptic density protein 95 (PSD-95) in the hippocampus of rats with KA-induced TLE, hence, ameliorating their cognitive impairment. Also, P38 MAPK activation in the hippocampus of the rats reduced the expression of both PSD-95 and SYP proteins. Treatment of the rats with SB203580, a P38 MAPK-specific inhibitor, prevented the activation of P38 MAPK, which resulted in an increase in SYP and PSD95 protein levels in the hippocampus. These results suggest that Fer-1 could mitigate the cognitive impairment by suppressing P38 MAPK activation thus restoring the expression of synaptic proteins. Ferroptosis processes might be involved in suppressing synaptic protein expression.

Plasma protein profiling reveals candidate biomarkers for multiple sclerosis treatment

Multiple sclerosis (MS) treatment options have improved significantly over the past decades, but the consequences of MS can still be devastating and the needs for monitoring treatment surveillance are considerable. In the current study we used affinity proteomics technology to identify potential biomarkers which could ultimately be used to as facilitate treatment decisions. We profiled the intra-individual changes in the levels of 59 target proteins using an antibody suspension bead array in serial plasma samples from 44 MS patients during treatment with natalizumab followed by fingolimod. Nine proteins showed decreasing plasma levels during natalizumab treatment, with PEBP1 and RTN3 displaying the most significant changes. Protein levels remained stable during fingolimod treatment for both proteins. The decreasing PEBP1 levels during natalizumab treatment could be validated using ELISA and replicated in an independent cohort. These results support the use of this technology as a high throughput method of identifying potentially useful biomarkers of MS treatment.

A Brief Ischemic Postconditioning Protects Against Amyloid-β Peptide Neurotoxicity by Downregulating MLK3-MKK3/6-P38MAPK Signal in Rat Hippocampus

BACKGROUND

Oligomeric amyloid-β peptide (Aβ) is associated with dysfunctional neuronal networks and neuronal loss in the development of Alzheimer's disease (AD). Ischemic postconditioning protects against post-ischemic excitotoxicity, oxidative stress, and inflammatory process that have also been implicated in the pathogenesis of AD. Evaluating the roles of ischemic postconditioning in oligomeric Aβ-induced neurotoxicity and underlying signal events may provide potential strategy for medical therapy in AD.

OBJECTIVES

The aim of the present study was to explore whether and how a brief ischemic postconditioning protects against Aβ neurotoxicity in rat hippocampus.

METHODS

Oligomeric Aβ25-35 (20 nmol/rat) or Aβ1-42 (5 nmol/rat) was infused by intracerebroventricular injection in adult male Sprague-Dawley rats. Ischemic postconditioning, a brief episode of global brain ischemia (3 min), was conducted at 1, 3, or 7 days after Aβ treatment, respectively.

RESULTS

A brief ischemic postconditioning reduced neuronal loss and inhibited the activation of MLK3, MKK3/6, and P38MAPKs in rat hippocampal CA1 and CA3 subfields after Aβ oligomer infusion. An N-methyl-D-aspartate (NMDA) receptor antagonist amantadine, but not non-NMDA receptor antagonist CNQX, reversed the MLK3-MKK3/6-P38MAPK signal events and beneficial effect of ischemic postconditioning on neuronal survival. Such reversion was also realized by NVP-AAM077, a GluN2A-subunit-selective NMDA receptor antagonist. Moreover, posttreatment with low doses of NMDA (5 nmol-40 nmol/rat) suppressed the Aβ-induced P38MAPK signaling and imitated the neuroprotection of ischemic postconditioning against Aβ neurotoxicity.

CONCLUSIONS

Ischemic postconditioning provides neuroprotection against Aβ neurotoxicity by moderate upregulation of NMDA receptor signaling, especially GluN2A-containing NMDA receptor pathway, and thereafter downregulation of MLK3-MKK3/6-P38MAPK signal events.