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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., (© 2021 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.)

Background: Mitochondrial dysfunction, bioenergetic deficit, and extensive oxidative stress underlie neuronal perturbation during the early stage of Alzheimer's disease (AD). Previously, we demonstrated that decreased PTEN-induced putative kinase 1 (PINK1) expression is associated with AD pathology in AD-affected human brains and AD mice., Objective: In the present study, we highlight the essential role of PINK1 in AD-relevant mitochondrial perturbation and neuronal malfunction., Methods: Using trans-mitochondrial "cybrid" (cytoplasmic hybrid) neuronal cells, whose mitochondria are transferred from platelets of patients with sporadic AD, we observed the effect of PINK1 in neuronal-like differentiation and synaptogenesis and mitochondrial functions., Results: In AD cybrid cells, the downregulation of PINK1 is correlated to the alterations in mitochondrial morphology and function and deficit in neuronal-like differentiation. Restoring/increasing PINK1 by lentivirus transduction of PINK1 robustly attenuates mitochondrial defects and rescues neurite-like outgrowth. Importantly, defective PINK1 kinase activity fails to reverse these detrimental effects. Mechanistically, AD cybrid cells reveal a significant decrease in PINK1-dependent phosphorylated mitofusin (Mfn) 2, a key mitochondrial membrane protein that participates in mitochondrial fusion, and an insufficient autophagic activity for the clearance of dysfunctional mitochondria. Overexpression of PINK1, but not mutant PINK1 elevates phosphorylation of Mfn2 and autophagy signaling LC3-II. Accordingly, PINK1-overexpressed AD cybrids exhibit increases in mitochondrial length and density and suppressed reactive oxygen species. These results imply that activation of PINK1 protects against AD-affected mitochondrial dysfunction and impairment in neuronal maturation and differentiation., Conclusion: PINK1-mediated mitophagy is important for maintaining mitochondrial health by clearance of dysfunctional mitochondria and therefore, improves energy homeostasis in AD.

Germline mutations in the X-linked gene, methyl-CpG-binding protein 2 (MECP2), underlie most cases of Rett syndrome (RTT), an autism spectrum disorder affecting approximately one in 10 000 female live births. The disease is characterized in affected girls by a latent appearance of symptoms between 12 and 18 months of age while boys usually die before the age of two. The nature of the latency is not known, but RTT-like phenotypes are recapitulated in mouse models, even when MeCP2 is removed at different postnatal stages, including juvenile and adolescent stages. Unexpectedly, here, we show that within a very brief developmental window, between 10 (adolescent) and 15 (adult) weeks after birth, symptom initiation and progression upon removal of MeCP2 in male mice transitions from 3 to 4 months to only several days, followed by lethality. We further show that this accelerated development of RTT phenotype and lethality occur at the transition to adult stage (15 weeks of age) and persists thereafter. Importantly, within this abbreviated time frame of days, the brain acquires dramatic anatomical, cellular and molecular abnormalities, typical of classical RTT. This study reveals a new postnatal developmental stage, which coincides with full-brain maturation, where the structure/function of the brain is extremely sensitive to levels of MeCP2 and loss of MeCP2 leads to precipitous collapse of the neuronal networks and incompatibility with life within days., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Infrasound, a kind of common environmental noise and a major contributor of vibroacoustic disease, can induce the central nervous system (CNS) damage. However, no relevant anti-infrasound drugs have been reported yet. Our recent studies have shown that infrasound resulted in excessive microglial activation rapidly and sequential inflammation, revealing a potential role of microglia in infrasound-induced CNS damage. Epigallocatechin gallate (EGCG), a major bioactive component in green tea, has the capacity of protecting against various neurodegenerative diseases via an anti-inflammatory mechanism. However, it is still unknown to date whether EGCG acts on infrasound-induced microglial activation and neuronal damage. We showed that, after 1-, 2- or 5-day exposure of rats to 16 Hz, 130 dB infrasound (2 h/day), EGCG significantly inhibited infrasound-induced microglial activation in rat hippocampal region, evidenced by reduced expressions of Iba-1 (a marker for microglia) and proinflammatory cytokines (IL-1β, IL-6, IL-18 and TNF-α). Moreover, infrasound-induced neuronal apoptosis in rat hippocampi was significantly suppressed by EGCG. EGCG also inhibited infrasound-induced activation of primary microglia in vitro and decreased the levels of proinflammatory cytokines in the supernatants of microglial culture, which were toxic to cultured neurons. Furthermore, EGCG attenuated infrasound-induced increases in nuclear NF-κB p65 and phosphorylated IκBα, and ameliorated infrasound-induced decrease in IκB in microglia. Therefore, our study provides the first evidence that EGCG acts against infrasound-induced neuronal impairment by inhibiting microglia-mediated inflammation through a potential NF-κB pathway-related mechanism, suggesting that EGCG can be used as a promising drug for the treatment of infrasound-induced CNS damage., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Synaptic dysfunction and degeneration is an early pathological feature of aging and age-related diseases, including Alzheimer's disease (AD). Aging is associated with increased generation and deposition of advanced glycation endproducts (AGEs), resulting from nonenzymatic glycation (or oxidation) proteins and lipids. AGE formation is accelerated in diabetes and AD-affected brain, contributing to cellular perturbation. The extent of AGEs' involvement, if at all, in alterations in synaptic structure and function is currently unknown. Here we analyze the contribution of neuronal receptor of AGEs (RAGE) signaling to AGE-mediated synaptic injury using novel transgenic neuronal RAGE knockout mice specifically targeted to the forebrain and transgenic mice expressing neuronal dominant-negative RAGE (DN-RAGE). Addition of AGEs to brain slices impaired hippocampal long-term potentiation (LTP). Similarly, treatment of hippocampal neurons with AGEs significantly decreases synaptic density. Such detrimental effects are largely reversed by genetic RAGE depletion. Notably, brain slices from mice with neuronal RAGE deficiency or DN-RAGE are resistant to AGE-induced LTP deficit. Further, RAGE deficiency or DN-RAGE blocks AGE-induced activation of p38 signaling. Taken together, these data show that neuronal RAGE functions as a signal transducer for AGE-induced synaptic dysfunction, thereby providing new insights into a mechanism by which the AGEs-RAGE-dependent signaling cascade contributes to synaptic injury via the p38 MAP kinase signal transduction pathway. Thus, RAGE blockade may be a target for development of interventions aimed at preventing the progression of cognitive decline in aging and age-related neurodegenerative diseases.

It is generally believed that cerebellar granule neurons originate exclusively from granule neuron precursors (GNPs) in the external germinal layer (EGL). Here we identified a rare population of neuronal progenitors in mouse developing cerebellum that expresses Nestin. Although Nestin is widely considered a marker for multipotent stem cells, these Nestin-expressing progenitors (NEPs) are committed to the granule neuron lineage. Unlike conventional GNPs, which reside in the outer EGL and proliferate extensively, NEPs reside in the deep part of the EGL and are quiescent. Expression profiling revealed that NEPs are distinct from GNPs and, in particular, express markedly reduced levels of genes associated with DNA repair. Consistent with this, upon aberrant activation of Sonic hedgehog (Shh) signaling, NEPs exhibited more severe genomic instability and gave rise to tumors more efficiently than GNPs. These studies revealed a previously unidentified progenitor for cerebellar granule neurons and a cell of origin for medulloblastoma.

Vibroacoustic disease, a progressive and systemic disease, mainly involving the central nervous system, is caused by excessive exposure to low-frequency but high-intensity noise generated by various heavy transportations and machineries. Infrasound is a type of low-frequency noise. Our previous studies demonstrated that infrasound at a certain intensity caused neuronal injury in rats but the underlying mechanism(s) is still largely unknown. Here, we showed that glial cell-expressed TRPV4, a Ca(2+)-permeable mechanosensitive channel, mediated infrasound-induced neuronal injury. Among different frequencies and intensities, infrasound at 16 Hz and 130 dB impaired rat learning and memory abilities most severely after 7-14 days exposure, a time during which a prominent loss of hippocampal CA1 neurons was evident. Infrasound also induced significant astrocytic and microglial activation in hippocampal regions following 1- to 7-day exposure, prior to neuronal apoptosis. Moreover, pharmacological inhibition of glial activation in vivo protected against neuronal apoptosis. In vitro, activated glial cell-released proinflammatory cytokines IL-1β and TNF-α were found to be key factors for this neuronal apoptosis. Importantly, infrasound induced an increase in the expression level of TRPV4 both in vivo and in vitro. Knockdown of TRPV4 expression by siRNA or pharmacological inhibition of TRPV4 in cultured glial cells decreased the levels of IL-1β and TNF-α, attenuated neuronal apoptosis, and reduced TRPV4-mediated Ca(2+) influx and NF-κB nuclear translocation. Finally, using various antagonists we revealed that calmodulin and protein kinase C signaling pathways were involved in TRPV4-triggered NF-κB activation. Thus, our results provide the first evidence that glial cell-expressed TRPV4 is a potential key factor responsible for infrasound-induced neuronal impairment.

Although ischemic preconditioning (IP) can provide powerful protection on brain against ischemic insult, it is rarely used in clinic to prevent the occurrence of ischemic stroke because of safety concerns. It is therefore necessary to seek the safer stimuli to initiate pharmacological preconditioning. Our previous work demonstrated that ginkgolide B (GB) could protect neurons against ischemia-induced apoptosis. Astrocytes are the most numerous cells in mammalian central nervous system and there is a close bi-directional communication between neurons and astrocytes in brain. Besides neurons, whether GB can exert the role of preconditioning on astrocytes through which to further improve neuronal survival under ischemic condition is not yet known. In the present study, primary cultured astrocytes were treated with GB for 24h or short-term ischemia (ischemia for 3h, as ischemic preconditioning/IP), and then cultured back to normoxia and normal medium for 24h to induce the preconditioning response. Astrocyte-conditioned medium (ACM) was then collected and used to incubate the cultured neurons for 24h before neurons were subjected to severe ischemia. Our results demonstrated that not only GB and IP increased astrocytic viability in ischemia, but also the conditioned medium from astrocytes treated with GB or IP increased cell viability and decreased the number of apoptosis of neurons in ischemia. We also found that GB and IP significantly stimulated astrocytes to express and secrete erythropoietin (EPO) into ACM, and the addition of anti-EPO antibody blocked the protective effect of GB or IP-treated astrocytes culture medium on neurons in ischemia. Further study of above protection revealed that ACM from astrocytes treated with GB or IP induced the inactivation of proapoptotic factor Bad by phosphorylation at serine 136 and 112 ((136)p-Bad and (112)p-Bad) in neurons. Together, our results suggest that GB is capable of preconditioning on astrocytes as IP and then protects neurons against ischemia-induced apoptosis, which is mediated by EPO., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Mutations in the X-linked gene, methyl-CpG binding protein 2 (Mecp2), underlie a wide range of neuropsychiatric disorders, most commonly, Rett Syndrome (RTT), a severe autism spectrum disorder that affects approximately one in 10,000 female live births. Because mutations in the Mecp2 gene occur in the germ cells with onset of neurological symptoms occurring in early childhood, the role of MeCP2 has been ascribed to brain maturation at a specific developmental window. Here, we show similar kinetics of onset and progression of RTT-like symptoms in mice, including lethality, if MeCP2 is removed postnatally during the developmental stage that coincides with RTT onset, or adult stage. For the first time, we show that brains that lose MeCP2 at these two different stages are actively shrinking, resulting in higher than normal neuronal cell density. Furthermore, we show that mature dendritic arbors of pyramidal neurons are severely retracted and dendritic spine density is dramatically reduced. In addition, hippocampal astrocytes have significantly less complex ramified processes. These changes accompany a striking reduction in the levels of several synaptic proteins, including CaMKII α/β, AMPA, and NMDA receptors, and the synaptic vesicle proteins Vglut and Synapsin, which represent critical modifiers of synaptic function and dendritic arbor structure. Importantly, the mRNA levels of these synaptic proteins remains unchanged, suggesting that MeCP2 likely regulates these synaptic proteins post-transcriptionally, directly or indirectly. Our data suggest a crucial role for MeCP2 in post-transcriptional regulation of critical synaptic proteins involved in maintaining mature neuronal networks during late stages of postnatal brain development.

The mechanisms of neuroprotection induced by hypoxic preconditioning (HP) and the effects of HP on iron metabolism proteins in the brain have not been fully elucidated. Based on the accumulated information, we hypothesized that HP would be able to affect the expression of iron metabolism proteins in the brain and that the changes in the expression of these proteins induced by HP might be partly associated with the HP-induced neuroprotection. Here, we demonstrated for the first time that HP could induce a significant increase in the expression of HIF-1alpha as well as iron uptake (TfR1 and DMT1) and release (Fpn1) proteins and thus increase transferrin-bound iron (Tf-Fe) and non-transferrin-bound iron (NTBI) uptake and iron release, and also a progressive increase in cellular iron content in the cultured neurons. We concluded that HP has the ability to speed iron transport rate and proposed that the increase in iron transport rate and cellular iron in neurons might be one of the mechanisms involved in neuroprotection in the HP neurons. We also demonstrated that Fpn1 expression was significantly affected by HIF-1alpha, implying that the gene encoding this iron efflux protein is hypoxia-inducible., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Our previous studies have demonstrated that ginsenoside Rd (GSRd), one of the principal ingredients of Pana notoginseng, has neuroprotective effects against ischemic stroke. However, the possible mechanism(s) underlying the neuroprotection of GSRd is/are still largely unknown. In this study, we treated glutamate-injured cultured rat hippocampal neurons with different concentrations of GSRd, and then examined the changes in neuronal apoptosis and intracellular free Ca(2+) concentration. Our MTT assay showed that GSRd significantly increased the survival of neurons injured by glutamate in a dose-dependent manner. Consistently, TUNEL and Caspase-3 staining showed that GSRd attenuated glutamate-induced cell death. Furthermore, calcium imaging assay revealed that GSRd significantly attenuated the glutamate-induced increase of intracellular free Ca(2+) and also inhibited NMDA-triggered Ca(2+) influx. Thus, the present study demonstrates that GSRd protects the cultured hippocampal neurons against glutamate-induced excitotoxicity, and that this neuroprotective effect may result from the inhibitory effects of GSRd on Ca(2+) influx.

It has been demonstrated that conditioned medium from astrocytes challenged by in vitro ischemia (oxygen-glucose deprivation, OGD) improved neuronal survival. In addition, preconditioning stimuli can be cross-tolerant, safeguarding against other types of injury. We therefore hypothesized that hyperthermia-conditioned astrocyte-cultured medium (ACM) might also have protective effect on neurons against ischemic injury. The cultured-media, named 38ACM and 40ACM respectively, were collected after astrocytes had been incubated at 38 °C or 40 °C for 6h, followed by incubation at 37 °C for 24h. It was found that ischemia for 6h induced a significant reduction in the number of neuronal cells and cell-viability, and an increase in lactate dehydrogenase (LDH) release and the percentage of apoptotic nuclei in neurons. Pre-treatment with 38ACM or 40ACM for 24h significantly diminished ischemia injury, enhanced cell viability, reduced LDH release and reversed apoptosis. Western blot analysis showed that treatment with 38ACM or 40ACM for 24h led to a significant increase in hypoxia-inducible factor-1 (HIF-1) alpha expression. The EMSA demonstrated that the ACM increased the binding activity of HIF-1 in ischemic neurons. The data implied that hyperthermia-conditioned ACM protects neurons from ischemic injury by up-regulating HIF-1 alpha, and the increased binding activity of HIF-1 and anti-apoptotic ability., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: Several studies demonstrate that neurogenesis may be induced or activated following vascular insults, which may be important for neuronal regeneration and functional recovery. Understanding the cellular mechanism underlying stroke-associated neurogenesis is of neurobiological as well as neurological/clinical relevance. The present study attempted to explore potential homing and early development of transplanted bone marrow stem cells in mouse forebrain after focal occlusion of the middle cerebral artery, an experimental model of ischemic stroke., Results: Bone marrow stem cells isolated from donor mice were confirmed by analysis of surface antigen profile, and were pre-labeled with a lipophilic fluorescent dye PKH26, and subsequently transfused into recipient mice with middle cerebral artery coagulation. A large number of PKH26-labeled cells were detected surrounding the infarct site, most of which colocalized with immunolabelings for the proliferating cell nuclear antigen (PCNA) and some also colocalized with the immature neuronal marker doublecortin (DCX) during 1-2 weeks after the bone marrow cells transfusion., Conclusions: The present study shows that transplanted bone marrow cells largely relocate to the infarct penumbra in ischemic mouse cerebrum. These transplanted bone marrow cells appear to undergo a process of in situ proliferation and develop into putative cortical interneurons during the early phase of experimental vascular injury.

Objective: To observe the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in hippocampus neurons in rats after different time of neuron oxygen deprivation/oxygen supply, and to investigate the role of PPARgamma in neuron ischemia reperfusion injury., Methods: One day old newborn SD rats were chosen. Primary cultured hippocampus neurons were used to establish neuron ischemic reperfusion model in vitro by oxygen and glucose depriving 15 minutes and supplying again, and then the neuron structure was observed by transmission electron microscope of JEM-200EX. The expression of PPARgamma mRNA and protein were detected by RT-PCR and Western blot, respectively., Results: Neuron structure was damaged after neuron oxygen deprivation/oxygen supply. There was no significant difference between 0 h oxygen supply group and the control group. The expression of PPARgamma was decreased both at mRNA and protein level after 6 h of oxygen supply. The difference between 6 h oxygen supply group and the control group was significant (P<0.01), which decreased with the length of reperfusion and the lowest was at 48 h after the reperfusion. The difference among the different reperfusion groups and the control group was significant (P<0.01)., Conclusion: PPARgamma may participate in the pathological damage course of neuron ischemical reperfusion injury, and may become a new intervention target of treatment for ischemic cerebrovascular disease.

Ischaemic preconditioning (IP) has been reported to protect the brain against subsequent lethal ischaemia, but it has not been used clinically to prevent ischaemic injury because of safety concerns. The aim of the present study was to see whether Ginkgolide B (GB) is capable of preconditioning as IP to protect neurons against ischaemic injury; if so, which mechanism is involved. Cultured mouse cortical neurons at day 8 were pre-treated with GB (120 micromol/l) for 24 hrs or exposed to short-term ischaemia (1 hr) followed by 24-hr normal culture to induce IP before being treated with severe ischaemia (5 hrs). GB and IP significantly increased cell viability, expression of hypoxia-inducible factor-1 alpha (HIF-1alpha), erythropoietin (EPO), phosphorylated Bad at serine 136 (136p-Bad) and phosphorylated glycogen synthase kinase- 3beta at serine 9 (p-GSK-3beta), and decreased the percentage of apoptotic cells and the level of active caspase-3 in severely ischaemic neurons. Moreover, LY294002 that is a specific inhibitor of phosphatidylinositol 3-kinase (PI3K) significantly reduced the enhanced expression of HIF-1alpha, EPO and 136p-Bad induced by GB and IP. These results suggest that GB, like IP in neurons, is capable of preconditioning against ischaemia-induced apoptosis, the mechanism of which may involve the PI3K signalling pathway.

It is unknown whether amyloid beta-protein 31-35 (Abeta[31-35]) has effects similar to Abeta[1-40] and Abeta[25-35] on the intracellular calcium ([Ca(2+)]i) to induce a disruption of calcium homeostasis. In this study, we investigated the effects of Abeta[31-35] on [Ca(2+)]i in primary cultured cortical neurons using real time fluorescence imaging technique and the Ca(2+)-sensitive dye Furo-2/AM. It was found that Abeta[31-35] (25 microM) could induce a significant elevation in [Ca(2+)]i and a decrease in the average latency in the cortical neurons in a dose-dependent manner. To examine whether the activation of group III mGluRs could block the changes in [Ca(2+)]i and protect neurons from apoptosis induced by Abeta[31-35], we then investigated the effects of L: -serine-O-phosphate (L: -SOP) and (R,S)-4-phosphonophenylglycine ((R,S)-PPG), the selective agonists of group III metabotropic glutamate receptors (mGluRs), on [Ca(2+)]i and apoptosis in neurons treated by Abeta[31-35]. We demonstrated that L: -SOP or (R,S)-PPG (100 microM) treatment suppresses significantly the elevation of [Ca(2+)]i induced by Abeta[31-35] and also induces an almost complete recovery of both the fluorescence intensity and apoptotic cells (%) to the control level in the neurons. These results suggest that Abeta[31-35] may be the shortest sequence responsible for the neuronal toxicity of Abeta protein and that the neuroprotective role of the activation of group III mGluRs from the apoptosis induced by Abeta[31-35] might be partly due to its ability to inhibit the increased calcium influx, which results from Abeta[31-35].

Previous studies showed that nerve growth factor (NGF) exerts protective effects on cultured neurons against various kinds of damage. However, a recent publication reported that exposure of NGF-treated PC12 cells to physical hypoxia resulted in a higher cell death rate when compared to the untreated controls. In the present study, we therefore investigated the effects of NGF on the hypoxic cortical neurons induced by potassium cyanide (KCN). We demonstrated that NGF at a higher concentration can significantly increase neuronal viability, decrease the release of lactate dehydrogenase and improve cellular morphology in the hypoxic cortical neurons. However, we also found that pretreatment of NGF was not able to completely revise the decreased cell viability and the increased leakage of lactate dehydrogenase (LDH) induced by KCN, although the indexes in the neurons treated with NGF and KCN were significantly higher than those in the neurons treated with KCN only. Analysis of the data showed that the incomplete revision of NGF should be not due to the dosage of NGF we used. It might be induced by the inability of NGF to inhibit all injury pathways induced by potassium cyanide.

This study aims to investigate the roles of the protein kinase A (PKA)- and caspase-dependent pathways in amyloid beta-peptide 31-35 (Abeta[31-35])-induced apoptosis, and the mechanisms of neuroprotection by group III metabotropic glutamate receptor (mGluR) activation against apoptosis induced by Abeta[31-35] in cortical neurons. We demonstrated that Abeta[31-35] induces neuronal apoptosis as well as a significant increase in caspase-3, -8 and -9. Activation of group III mGluRs by l-serine-O-phosphate and (R,S)-4-phosphonophenylglycine (two group III mGluR agonists), which attenuate the effects of Abeta[31-35], provides neuroprotection to the cortical neurons subjected to Abeta[31-35]. We also showed that Rp-cAMP, an inhibitor of cAMP-dependent PKA, has the ability to protect neurons from Abeta[31-35]-induced apoptosis and to reverse almost completely the effects of Abeta[31-35] on the activities of caspase-3. Further, we found that Sp-cAMP, an activator of cAMP-dependent PKA, can significantly abolish the l-serine-O-phosphate- and (R,S)-4-phosphonophenylglycine-induced neuroprotection against apoptosis, and decrease caspase-3, -8 and -9 in the Abeta[31-35]-treated neurons. Our findings suggest that neuronal apoptosis induced by Abeta[31-35] is mediated by the PKA-dependent pathway as well as the caspase-dependent intrinsic and extrinsic apoptotic pathways. Activation of group III mGluRs protects neurons from Abeta[31-35]-induced apoptosis by blocking the caspase-dependent pathways. Inhibition of the PKA-dependent pathway might also protect neurons from Abeta[31-35]-induced apoptosis by blocking the caspase-dependent pathways. Taken together, our observations suggest that Abeta[31-35] might have the ability to activate PKA, which in turn activates the caspase-dependent intrinsic and extrinsic apoptotic pathways, inducing apoptosis in the cortical neurons.

Hypoxia-inducible factor-1 (HIF-1) is a master regulator of cellular and systemic oxygen homeostasis. Recently, we demonstrated that ginkgolides, the main constituents of the non-flavone fraction of the standardized Ginkgo biloba (Ginkgoaceae) extract EGb 761, have a significant protective role against chemical and physical hypoxia-induced injury in neurons and PC12 cells. Based on the findings and the function of HIF-1 as a master regulator of oxygen homeostasis, we speculate that the protective role of ginkgolides might be mediated by HIF-1. In this study, we therefore investigated the effects of ginkgolides on the expression of HIF-1alpha, the cell viability and the lactate dehydrogenase (LDH) release in the hypoxic cortical neuron. We demonstrated that ginkgolides significantly increase the expression of HIF-1alpha and the cell viability as well as decrease the release of LDH in the hypoxic neuron. The findings suggested that the neuroprotective role of ginkgolides against hypoxia-induced injury might be associated with its role to up-regulate the expression of HIF-1alpha in the hypoxic neurons.

In this study, we investigated the effects of ginkgolides (Gins A, B, C and J), the main constituent of the non-flavone fraction of EGb 761, on hypoxic injury induced by potassium cyanide (KCN) in primary cortical neurons. The neurons were pretreated with or without ginkgolides for 24 h before incubation with KCN for 4 h. Cell viability was then determined by a MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyletrazolium bromide] assay and lactate dehydrogenase (LDH) release from neurons into the medium was measured. The morphological changes of neurons were observed under inverse microscopy and electron microscopy. The results demonstrated that KCN (0.05 mmol/l) significantly decreased cell viability and increased LDH release (P < 0.05 versus the control). The characteristic changes of neuronal morphology induced by KCN were observed. However, pretreatment of neurons with 37.5 microg/ml of ginkgolides (ginkgolides + KCN group) led to a significant increase in cell viability, a decrease in LDH release (P < 0.05 versus the KCN group) and a remarkable improvement in cellular morphology in hypoxic neurons compared with the KCN group. The data suggested that ginkgolides have a significant role to protect the primary cortical neurons from hypoxic injury induced by KCN.

Objective: To observe whether the dopaminergic neuroprotective effect of (-)-epigallocatechin gallate (EGCG) is associated with its inhibition of microglial cell activation in vivo., Methods: The effects of EGCG at different doses on dopaminergic neuronal survival were tested in a methyl-4-phenyl-pyridinium (MPP+)-induced dopaminergic neuronal injury model in the primary mesencephalic cell cultures. With unbiased stereological method, tyrosine hydroxylase-immunoreactive (TH-ir) cells were counted in the A8, A9 and A10 regions of the substantia nigra (SN) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated C57BL/6 mice. The effect of EGCG on microglial activation in the SN was also investigated., Results: Pretreatment with EGCG (1 to 100 micromol/L) significantly attenuated MPP+-induced TH-ir cell loss by 22.2% to 80.5% in the mesencephalic cell cultures. In MPTP-treated C57BL/6 mice, EGCG at a low concentration (1 mg/kg) provided significant protection against MPTP-induced TH-ir cell loss by 50.9% in the whole nigral area and by 71.7% in the A9 region. EGCG at 5 mg/kg showed more prominent protective effect than at 1 or 10 mg/kg. EGCG pretreatment significantly inhibited microglial activation and CD11b expression induced by MPTP., Conclusion: EGCG exerts potent dopaminergic neuroprotective activity by means of microglial inhibition, which shed light on the potential use of EGCG in treatment of Parkinson's disease.

Anti-parkinsonian agents, pramipexole (PPX) and ropinirole (ROP), have been reported to possess neuroprotective properties, both in vitro and in vivo. The mechanisms underlying neuroprotection afforded by the D3-preferring receptor agonists remain poorly understood. The present study demonstrates that incubation of primary mesencephalic cultures with PPX and ROP or the conditioned medium from PPX- or ROP-treated primary cultures induced a marked increase in the number of dopamine (DA) neurons in the cultures. Similar effects can be observed after incubating with the conditioned medium derived from PPX- and ROP-treated substantia nigra astroglia. Meanwhile, PPX and ROP can protect the primary cells from insult of 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Furthermore, the neurotrophic effects of PPX and ROP on mesencephalic dopamine neurons could be significantly blocked by D3 receptor antagonist, but not by D2 receptor antagonist. Moreover, we found that the levels of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in the conditioned medium of mesencephalic cultures treated with PPX and ROP were significantly increased. Blocking GDNF and BDNF with the neutralizing antibodies, the neurotrophic effects of PPX and ROP were greatly diminished. These results suggest that D3 dopamine receptor-preferring agonists, PPX and ROP, exert neurotrophic effects on cultured DA neurons by modulating the production of endogenous GDNF and BDNF, which may participate in their neuroprotection.

This study aims to investigate the roles of the protein kinase A (PKA)- and caspase-dependent pathways in amyloid β-peptide 31–35 (Aβ[31–35])-induced apoptosis, and the mechanisms of neuroprotection by group III metabotropic glutamate receptor (mGluR) activation against apoptosis induced by Aβ[31–35] in cortical neurons. We demonstrated that Aβ[31–35] induces neuronal apoptosis as well as a significant increase in caspase-3, -8 and -9. Activation of group III mGluRs byl-serine- O-phosphate and ( R, S)-4-phosphonophenylglycine (two group III mGluR agonists), which attenuate the effects of Aβ[31–35], provides neuroprotection to the cortical neurons subjected to Aβ[31–35]. We also showed that Rp-cAMP, an inhibitor of cAMP-dependent PKA, has the ability to protect neurons from Aβ[31–35]-induced apoptosis and to reverse almost completely the effects of Aβ[31–35] on the activities of caspase-3. Further, we found that Sp-cAMP, an activator of cAMP-dependent PKA, can significantly abolish thel-serine- O-phosphate- and ( R, S)-4-phosphonophenylglycine-induced neuroprotection against apoptosis, and decrease caspase-3, -8 and -9 in the Aβ[31–35]-treated neurons. Our findings suggest that neuronal apoptosis induced by Aβ[31–35] is mediated by the PKA-dependent pathway as well as the caspase-dependent intrinsic and extrinsic apoptotic pathways. Activation of group III mGluRs protects neurons from Aβ[31–35]-induced apoptosis by blocking the caspase-dependent pathways. Inhibition of the PKA-dependent pathway might also protect neurons from Aβ[31–35]-induced apoptosis by blocking the caspase-dependent pathways. Taken together, our observations suggest that Aβ[31–35] might have the ability to activate PKA, which in turn activates the caspase-dependent intrinsic and extrinsic apoptotic pathways, inducing apoptosis in the cortical neurons. [ABSTRACT FROM AUTHOR]

Abstract: Infrasound is a kind of environmental noise. It can evoke biological resonance in organismic tissues including the central nervous system (CNS), causing displacement and distortion of cellular architectures. Several studies have revealed that certain intensity infrasound can impair normal functions of the brain, but the underlying mechanisms still remain largely unknown. Growing evidence has demonstrated that axonal degeneration is responsible for a variety of CNS dysfunctions. To explore whether neuronal axons are affected under infrasonic insults, we exposed cultured hippocampal neurons to infrasound with a frequency of 16Hz and a pressure level of 130dB for 1h, and examined the morphological and molecular changes of neuronal axons by immunocytochemistry and Western blotting, respectively. Our results showed that infrasound exposure significantly resulted in axonal degeneration of cultured hippocampal neurons, which was relatively independent of neuronal cell death. This infrasound-induced axonal degeneration can be significantly blocked by Ca2+ chelator EGTA and Rho kinase inhibitor Fasudil, but not by proteasome inhibitor MG132. Moreover, calcium imaging and RhoA activation assays revealed a great enhancement of Ca2+ influx within axons and RhoA activation after infrasound exposure, respectively. Depletion of Ca2+ by EGTA markedly inhibited this Ca2+ influx and attenuated RhoA activation as well. Thus, our findings revealed that axonal degeneration may be one of the important mechanisms underlying infrasound-induced CNS impairment, and Ca2+ influx pathway is likely implicated in the process. [Copyright &y& Elsevier]