Decreased miR-451a in cerebrospinal fluid, a marker for both cognitive impairment and depressive symptoms in Alzheimer's disease.

Background: Alzheimer's disease (AD) patients are often accompanied by depressive symptoms, but its underlying mechanism remains unclear. The present study aimed to explore the potential role of microRNAs in the comorbidity of AD and depression. Methods: The miRNAs associated with AD and depression were screened from databases and literature and then confirmed in the cerebrospinal fluid (CSF) of AD patients and different ages of transgenic APP/PS1 mice. AAV9-miR-451a-GFP was injected into the medial prefrontal cortex (mPFC) of APP/PS1 mice at seven months, and four weeks later, a series of behavioral and pathological analyses were performed. Results: AD patients had low CSF levels of miR-451a, which was positively correlated with the cognitive assessment score, but negatively with their depression scale. In the mPFC of APP/PS1 transgenic mice, the miR-451a levels also decreased significantly in the neurons and microglia. Specific virus vector-induced overexpression of miR-451a in the mPFC of APP/PS1 mice ameliorated AD-related behavior deficits and pathologies, including long-term memory defects, depression-like phenotype, ß-amyloid load, and neuroinflammation. Mechanistically, miR-451a decreased the expression of neuronal ß-secretase 1 of neurons through inhibiting Toll-like receptor 4/Inhibitor of kappa B Kinase ß/ Nuclear factor kappa-B signaling pathway and microglial activation by inhibiting activation of NOD-like receptor protein 3, respectively. Conclusion: This finding highlighted miR-451a as a potential target for diagnosing and treating AD, especially for those with coexisting symptoms of depression.

Early growth response 2 in the mPFC regulates mouse social and cooperative behaviors.

Adolescent social neglect impairs social performance, but the underlying molecular mechanisms remain unclear. Here we report that isolation rearing of juvenile mice caused cooperation defects that were rescued by immediate social reintroduction. We also identified the transcription factor early growth response 2 (Egr2) in the medial prefrontal cortex (mPFC) as a major target of social isolation and resocialization. Isolation rearing increased corticosteroid production, which reduced the expression of Egr2 in the mPFC, including in oligodendrocytes. Overexpressing Egr2 ubiquitously in the mPFC, but not specifically in neurons nor in oligodendroglia, protected mice from the isolation rearing-induced cooperation defect. In addition to synapse integrity, Egr2 also regulated the development of oligodendroglia, specifically the transition from undifferentiated oligodendrocyte precursor cells to premyelinating oligodendrocytes. In conclusion, this study reveals the importance of mPFC Egr2 in the cooperative behavior that is modulated by social experience, and its unexpected role in oligodendrocyte development.

B lymphocytes ameliorate Alzheimer's disease-like neuropathology via interleukin-35.

Increasing evidence supports the involvement of the peripheral immune system in the pathogenesis of Alzheimer's disease (AD). In the present study, we found that B lymphocytes could mitigate beta-Amyloid (Aß) pathology and memory impairments in a transgenic AD mouse model. Specifically, in young 5 × FAD mice, we evidenced increased B cells in the frontal cortex and meningeal tissues; depletion of mature B cells aggravated these mice's Aß load and memory deficits. The increased B cells produced more interleukin-35 (IL-35) in the front cortex. We further found IL-35 neutralization exacerbated Aß pathology, while injecting IL-35 mitigated Aß load and cognitive dysfunction in 5 × FAD mice with or without mature B cell deficiency. Mechanistically, IL-35 inhibited neuronal BACE1 transcription through modulating the SOCS1/STAT1 pathway, and reduced Aß production accordingly. Reanalysis of the single-cell RNA sequencing data from blood samples of AD patients suggested an increased population of IL-35-producing B cells. Together, the present study revealed a novel effect of B lymphocyte-derived IL-35 on inhibiting Aß production in the frontal cortex, which may serve as a potential target for future AD treatment.

Miconazole Promotes Cooperative Ability of a Mouse Model of Alzheimer Disease.

BACKGROUND: Cooperative defect is 1 of the earliest manifestations of disease patients with Alzheimer disease (AD) exhibit, but the underlying mechanism remains unclear. METHODS: We evaluated the cooperative function of APP/PS1 transgenic AD model mice at ages 2, 5, and 8 months by using a cooperative drinking task. We examined neuropathologic changes in the medial prefrontal cortex (mPFC). Another experiment was designed to observe whether miconazole, which has a repairing effect on myelin sheath, could promote the cooperative ability of APP/PS1 mice in the early AD-like stage. We also investigated the protective effects of miconazole on cultured mouse cortical oligodendrocytes exposed to human amyloid ß peptide (Aß1-42). RESULTS: We observed an age-dependent impairment of cooperative water drinking behavior in APP/PS1 mice. The AD mice with cooperative dysfunction showed decreases in myelin sheath thickness, oligodendrocyte nuclear heterochromatin percentage, and myelin basic protein expression levels in the mPFC. The cooperative ability was significantly improved in APP/PS1 mice treated with miconazole. Miconazole treatment increased oligodendrocyte maturation and myelin sheath thickness without reducing Aß plaque deposition, reactive gliosis, and inflammatory factor levels in the mPFC. Miconazole also protected cultured oligodendrocytes from the toxicity of Aß1-42. CONCLUSIONS: These results demonstrate that mPFC hypomyelination is involved in the cooperative deficits of APP/PS1 mice. Improving myelination through miconazole therapy may offer a potential therapeutic approach for early intervention in AD.

miR-124 regulates early isolation-induced social abnormalities via inhibiting myelinogenesis in the medial prefrontal cortex.

Patients with autism spectrum disorder (ASD) typically experience substantial social isolation, which may cause secondary adverse effects on their brain development. miR-124 is the most abundant miRNA in the human brain, acting as a pivotal molecule regulating neuronal fate determination. Alterations of miR-124 maturation or expression are observed in various neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. In the present study, we analyzed a panel of brain-enriched microRNAs in serums from 2 to 6 year old boys diagnosed with ASD. The hsa-miR-124 level was found significantly elevated in ASD boys than in age and sex-matched healthy controls. In an isolation-reared weanling mouse model, we evidenced elevated mmu-miR-124 level in the serum and the medial prefrontal cortex (mPFC). These mice displayed significant sociability deficits, as well as myelin abnormality in the mPFC, which was partially rescued by expressing the miR-124 sponge in the bilateral mPFC, ubiquitously or specifically in oligodendroglia. In cultured mouse oligodendrocyte precursor cells, introducing a synthetic mmu-miR-124 inhibited the differentiation process through suppressing expression of nuclear receptor subfamily 4 group A member 1 (Nr4a1). Overexpressing Nr4a1 in the bilateral mPFC also corrected the social behavioral deficits and myelin impairments in the isolation-reared mice. This study revealed an unanticipated role of the miR-124/Nr4a1 signaling in regulating early social experience-dependent mPFC myelination, which may serve as a potential therapy target for social neglect or social isolation-related neuropsychiatric disorders.

Drainage of senescent astrocytes from brain via meningeal lymphatic routes.

Recent progress on the central lymphatic system has greatly increased our understanding of how the brain maintains its own waste homeostasis. Here, we showed that perivascular spaces and meningeal lymphatic vessels form a functional route for clearance of senescent astrocytes from the aging brain. Blocking meningeal lymphatic drainage by ligation of the deep cervical lymph nodes impaired clearance of senescent astrocytes from brain parenchyma, subsequently increasing neuroinflammation in aged mice. By contrast, enhancing meningeal lymphatic vessel diameter by a recombinant adeno-associated virus encoding mouse vascular endothelial growth factor-C (VEGF-C) improved clearance of senescent astrocytes and mitigated neuroinflammation. Mechanistically, VEGF-C was highly expressed in senescent astrocytes, contributing themselves to migrate across lymphatic vessels along C-C motif chemokine ligand 21 (CCL21) gradient by interacting with VEGF receptor 3. Moreover, intra-cisternal injection of antibody against CCL21 hampered senescent astrocytes into the lymphatic vessels and exacerbated short memory defects of aged mice. Together, these findings reveal a new perspective for the meningeal lymphatics in the removal of senescent astrocytes, thus offering a valuable target for therapeutic intervention.

Temporal regulation of nicotinic acetylcholine receptor subunits supports central cholinergic synapse development in Drosophila.

The construction and maturation of the postsynaptic apparatus are crucial for synapse and dendrite development. The fundamental mechanisms underlying these processes are most often studied in glutamatergic central synapses in vertebrates. Whether the same principles apply to excitatory cholinergic synapses, such as those found in the insect central nervous system, is not known. To address this question, we investigated a group of projection neurons in the Drosophila larval visual system, the ventral lateral neurons (LNvs), and identified nAchRα1 (Dα1) and nAchRα6 (Dα6) as the main functional nicotinic acetylcholine receptor (nAchR) subunits in the larval LNvs. Using morphological analyses and calcium imaging studies, we demonstrated critical roles of these two subunits in supporting dendrite morphogenesis and synaptic transmission. Furthermore, our RNA sequencing analyses and endogenous tagging approach identified distinct transcriptional controls over the two subunits in the LNvs, which led to the up-regulation of Dα1 and down-regulation of Dα6 during larval development as well as to an activity-dependent suppression of Dα1 Additional functional analyses of synapse formation and dendrite dynamics further revealed a close association between the temporal regulation of individual nAchR subunits and their sequential requirements during the cholinergic synapse maturation. Together, our findings support transcriptional control of nAchR subunits as a core element of developmental and activity-dependent regulation of central cholinergic synapses.

Brain-specific lipoprotein receptors interact with astrocyte derived apolipoprotein and mediate neuron-glia lipid shuttling.

Lipid shuttling between neurons and glia contributes to the development, function, and stress responses of the nervous system. To understand how a neuron acquires its lipid supply from specific lipoproteins and their receptors, we perform combined genetic, transcriptome, and biochemical analyses in the developing Drosophila larval brain. Here we report, the astrocyte-derived secreted lipocalin Glial Lazarillo (GLaz), a homolog of human Apolipoprotein D (APOD), and its neuronal receptor, the brain-specific short isoforms of Drosophila lipophorin receptor 1 (LpR1-short), cooperatively mediate neuron-glia lipid shuttling and support dendrite morphogenesis. The isoform specificity of LpR1 defines its distribution, binding partners, and ability to support proper dendrite growth and synaptic connectivity. By demonstrating physical and functional interactions between GLaz/APOD and LpR1, we elucidate molecular pathways mediating lipid trafficking in the fly brain, and provide in vivo evidence indicating isoform-specific expression of lipoprotein receptors as a key mechanism for regulating cell-type specific lipid recruitment.

Time-lapse Live Imaging and Quantification of Fast Dendritic Branch Dynamics in Developing Drosophila Neurons.

Highly motile dendritic filopodia are widely present in neurons at early developmental stages. These exploratory dynamic branches sample the surrounding environment and initiate contacts with potential synaptic partners. Although the connection between dendritic branch dynamics and synaptogenesis is well established, how developmental and activity-dependent processes regulate dendritic branch dynamics is not well understood. This is partly due to the technical difficulties associated with the live imaging and quantitative analyses of these fine structures using an in vivo system. We established a method to study dendrite dynamics using Drosophila larval ventral lateral neurons (LNvs), which can be individually labeled using genetic approaches and are accessible for live imaging. Taking advantage of this system, we developed protocols to capture branch dynamics of the whole dendritic arbor of a single labeled LNv through time-lapse live imaging. We then performed post-processing to improve image quality through drift correction and deconvolution, followed by analyzing branch dynamics at the single-branch level by annotating spatial positions of all branch terminals. Lastly, we developed R scripts (Supplementary File) and specific parameters to quantify branch dynamics using the coordinate information generated by the terminal tracing. Collectively, this protocol allows us to achieve a detailed quantitative description of branch dynamics of the neuronal dendritic arbor with high temporal and spatial resolution. The methods we developed are generally applicable to sparsely labeled neurons in both in vitro and in vivo conditions.

Transcriptional Regulation of Lipophorin Receptors Supports Neuronal Adaptation to Chronic Elevations of Activity.

Activity-dependent modifications strongly influence neural development. However, molecular programs underlying their context and circuit-specific effects are not well understood. To study global transcriptional changes associated with chronic elevation of synaptic activity, we performed cell-type-specific transcriptome profiling of Drosophila ventral lateral neurons (LNvs) in the developing visual circuit and identified activity-modified transcripts that are enriched in neuron morphogenesis, circadian regulation, and lipid metabolism and trafficking. Using bioinformatics and genetic analyses, we validated activity-induced isoform-specific upregulation of Drosophila lipophorin receptors LpR1 and LpR2, the homologs of mammalian low-density lipoprotein receptor (LDLR) family proteins. Furthermore, our morphological and physiological studies uncovered critical functions of neuronal lipophorin receptors (LpRs) in maintaining the structural and functional integrities in neurons challenged by chronic elevations of activity. Together, our findings identify LpRs as molecular targets for activity-dependent transcriptional regulation and reveal the functional significance of cell-type-specific regulation of neuronal lipid uptake in experience-dependent plasticity and adaptive responses.

Experience-dependent structural plasticity targets dynamic filopodia in regulating dendrite maturation and synaptogenesis.

Highly motile dendritic protrusions are hallmarks of developing neurons. These exploratory filopodia sample the environment and initiate contacts with potential synaptic partners. To understand the role for dynamic filopodia in dendrite morphogenesis and experience-dependent structural plasticity, we analyzed dendrite dynamics, synapse formation, and dendrite volume expansion in developing ventral lateral neurons (LNvs) of the Drosophila larval visual circuit. Our findings reveal the temporal coordination between heightened dendrite dynamics with synaptogenesis in LNvs and illustrate the strong influence imposed by sensory experience on the prevalence of dendritic filopodia, which regulate the formation of synapses and the expansion of dendritic arbors. Using genetic analyses, we further identified Amphiphysin (Amph), a BAR (Bin/Amphiphysin/Rvs) domain-containing protein as a required component for tuning the dynamic state of LNv dendrites and promoting dendrite maturation. Taken together, our study establishes dynamic filopodia as the key cellular target for experience-dependent regulation of dendrite development.

Macrophages activate iNOS signaling in adventitial fibroblasts and contribute to adventitia fibrosis.

A large amount of NO is generated through the inducible nitric oxide synthase (iNOS) pathway from the vascular adventitia in various vascular diseases. However, it is currently not fully understood how the iNOS signaling pathway is activated. In the present study, this question was addressed in the context of adventitial cellular interactions. A rat model of acute hypertension in the contralateral carotid arteries was established through transverse aortic constriction (TAC) surgery. In this model, activated macrophages were found surrounded by a large quantity of iNOS-expressing adventitial fibroblasts (AFs), suggesting a possible causal relationship between macrophages and iNOS activation of the neighboring AFs. In an in vitro model, a macrophage-like cell line RAW 264.7 was first activated by LPS treatment. The supernatant was then harvested and applied to treat primary rat AFs. iNOS in AFs was activated robustly by the supernatant treatment but not by LPS itself. Treating AFs with interleukin-1ß (IL-1ß) also activated iNOS signaling, suggesting that the IL-1ß pathway might be a possible mediator. As a consequence of the iNOS activation, total protein nitration and S-nitrosylation significantly increased in those AFs. Additionally, increased deposition of type I and type III collagens was observed in both in vitro and in vivo models. The collagen deposition was partially restored by an iNOS inhibitor, 1400 W. These findings highlight the importance of iNOS signaling during vascular inflammation, and advance our understanding of its activation through a cellular interaction perspective.

DJ-1 deficiency perturbs microtubule dynamics and impairs striatal neurite outgrowth.

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the selective loss of the dopaminergic (DA) neurons in substantia nigra. The degeneration leads to decreased levels of DA in striatum and causes uncontrolled firing of innervated medium spiny neurons (MSNs), thus preventing the patient to act smoothly. Gene-specific deficient mouse models for the recessive forms of PD were generated in the past decade, although most failed to exhibit degeneration of DA neurons or decreased DA level, as evidenced in PD patients. Here by using DJ-1-knockdown neuroblastoma SH-SY5Y cells and Neuro-2a cells as well as DJ-1-deficient mice, we found DJ-1 deficiency could downregulate ß-tubulin III via a hypoxia-inducible factor 1α (HIF-1α) pathway, and, correspondingly, we observed reduced microtubule dynamics. With Golgi-Cox impregnation, we also observed declined dendritic complexity and the loss of dendritic spines in striatal MSNs of DJ-1-deficient mice. Our results revealed a novel role of DJ-1 in the regulation of microtubule dynamics and suggested that striatal impairments may also play an important role as loss of DA neurons in the pathogenesis of PD.

Transthyretin-related hereditary amyloidosis in a Chinese family with TTR Y114C mutation.

BACKGROUND: Transthyretin-related hereditary amyloidosis is an autosomal dominant inherited disease caused by mutations in the transthyretin (TTR) gene. Corresponding to the various transthyretin gene mutations and a wide range of geographical distribution, transthyretin-related hereditary amyloidosis presents diverse characteristics in genotype-phenotype correlation. OBJECTIVE/METHOD: Here, we identify the clinical characteristics of a Chinese family affected by transthyretin-related hereditary amyloidosis with TTR Tyr114Cys mutation. RESULTS/CONCLUSION: The pathogenic mechanism studies showed that the protein encoded by TTR Tyr114Cys is more easily depolymerized to form amyloid fibrils. Moreover, the cytotoxicity of the TTR Tyr114Cys may be attributed to its ability to persistently activate the extracellular-signal-regulated kinase 1/2 pathway.

Amyloid-beta1-42 induces reactive oxygen species-mediated autophagic cell death in U87 and SH-SY5Y cells.

Alzheimer's disease (AD) is a neurodegenerative disorder initiated by the aggregation of amyloid-beta peptide (Abeta). Macroautophagy, which is essential for cell survival as well as the promotion of cell death, has been observed extensively in AD brains or transgenic mice overexpressing Abeta protein precursor. However, the role of macroautophagy in the pathogenesis of AD is unclear. In this study, we showed that Abeta1-42 triggered autophagic cell death in both human glioma cell line (U87 cell) and human neuroblastoma cell line (SH-SY5Y cell). Abeta1-42-induced cytotoxicity and autophagic cell death were blocked by the autophagy inhibitor 3-methyladenine (3-MA) or by small interfering RNA against the autophagy gene Beclin-1. Reactive oxygen species (ROS) accumulation was also detected in both Abeta1-42 treated cell lines and this accumulation was not affected by 3-MA. Moreover, pretreatment with the ROS scavenger N-acetylcysteine inhibited ROS accumulation and autophagic cell death induced by Abeta1-42, suggesting that Abeta1-42-induced ROS accumulation might trigger the onset of autophagy and subsequent autophagic cell death. These findings provide further insights into the mechanisms underlying Abeta-induced cytotoxicity.

Blockade of the translocation and activation of c-Jun N-terminal kinase 3 (JNK3) attenuates dopaminergic neuronal damage in mouse model of Parkinson's disease.

Increasing evidence suggests that c-Jun N-terminal kinase (JNK) is an important kinase mediating neuronal death in Parkinson's disease (PD) model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). JNK3, the only neural-specific isoform, may play an important role in mediating the neurotoxic effects of MPTP in dopaminergic neuronal injury. To analyze the variation in JNK3 activation, the levels of phospho-JNK3 were measured at the various time points of occurrence of MPTP-induced lesions. In our study, we observed that during MPTP intoxication, two peaks of JNK3 activation appeared at 8 and 24h. To further define the mechanism of JNK3 activation and translocation, the antioxidant N-acetylcysteine (NAC), the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine, and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate (KA) receptor antagonist 6,7-dinitroquinoxaline-2,3(1H,4H)-dione (DNQX) were administered to the mice 30 min after each of the four MPTP injections. The results revealed that NAC clearly inhibited JNK3 activation during the early intoxication, whereas ketamine preferably attenuated JNK3 activation during the latter intoxication. DNQX had no significant effects on JNK3 activation during intoxication. Consequently, reactive oxygen species (ROS) and the NMDA receptor were closely associated with JNK3 activation following MPTP intoxication. NAC and ketamine exerted a preventive effect against MPTP-induced loss of tyrosine hydroxylase-positive neurons and suppressed the nuclear translocation of JNK3, suggesting that NAC and ketamine can prevent MPTP-induced dopaminergic neuronal death by suppressing JNK3 activation.