Hippocampus Of Mouse Brain Research Articles

Activation of 5-HT7 receptor stimulates neurite elongation through mTOR, Cdc42 and actin filaments dynamics.

Recent studies have indicated that the serotonin receptor subtype 7 (5-HT7R) plays a crucial role in shaping neuronal morphology during embryonic and early postnatal life. Here we show that pharmacological stimulation of 5-HT7R using a highly selective agonist, LP-211, enhances neurite outgrowth in neuronal primary cultures from the cortex, hippocampus and striatal complex of embryonic mouse brain, through multiple signal transduction pathways. All these signaling systems, involving mTOR, the Rho GTPase Cdc42, Cdk5, and ERK, are known to converge on the reorganization of cytoskeletal proteins that subserve neurite outgrowth. Indeed, our data indicate that neurite elongation stimulated by 5-HT7R is modulated by drugs affecting actin polymerization. In addition, we show, by 2D Western blot analyses, that treatment of neuronal cultures with LP-211 alters the expression profile of cofilin, an actin binding protein involved in microfilaments dynamics. Furthermore, by using microfluidic chambers that physically separate axons from the soma and dendrites, we demonstrate that agonist-dependent activation of 5-HT7R stimulates axonal elongation. Our results identify for the first time several signal transduction pathways, activated by stimulation of 5-HT7R, that converge to promote cytoskeleton reorganization and consequent modulation of axonal elongation. Therefore, the activation of 5-HT7R might represent one of the key elements regulating CNS connectivity and plasticity during development.

The effects of social defeat on behavior and dopaminergic markers in mice

The present study investigated the effects of chronic social defeat stress on several behavioral parameters, and the expression of dopaminergic markers, i.e., dopamine D1 receptors (D1Rs), dopamine D2 receptors (D2Rs), and dopamine and cyclic adenosine 3′,5′-monophosphate-regulated phosphoprotein-32 (DARPP-32), in the prefrontal cortex (PFC), amygdala (AMY), and hippocampus (HIP) of mouse brains. After 10days of social defeat stress, the defeated mice were divided into two groups: one group underwent a series of behavioral tests. The other group was sacrificed on the 11th day and tissue samples were collected for Western blotting. The behavioral tests comprised tests of locomotion, light/dark preference, social interaction, as well as the novel object recognition test (NORT), Morris water maze, and forced swimming test (FST). We measured the expression of D1Rs, D2Rs, total DARPP-32, phospho-Thr34 or Thr75-DARPP-32 using Western blotting. The defeated mice showed increased anxiety- and depression-like behaviors, and impaired cognition. No significant differences in D1Rs and D2Rs expression were shown between defeated and control mice in any area studied. A significantly increased expression in total DARPP-32, and phospho-DARPP-32 was observed in the PFC or AMY of defeated mice. These data suggest that alterations in dopaminergic markers may be involved in anxiety- and depression-like behaviors, and cognitive impairment induced by social defeat stress.

The Ameliorating Effect of Myrrh on Scopolamine-Induced Memory Impairments in Mice.

Myrrh has been used since ancient times for the treatment of various diseases such as inflammatory diseases, gynecological diseases, and hemiplegia. In the present study, we investigated the effects of aqueous extracts of myrrh resin (AEM) on scopolamine-induced memory impairments in mice. AEM was estimated with (2E,5E)-6-hydroxy-2,6-dimethylhepta-2,4-dienal as a representative constituent by HPLC. The oral administration of AEM for 7 days significantly reversed scopolamine-induced reduction of spontaneous alternation in the Y-maze test. In the passive avoidance task, AEM also restored the decreased latency time of the retention trial by scopolamine treatment. In addition, Western blot analysis and Immunohistochemistry revealed that AEM reversed scopolamine-decreased phosphorylation of Akt and extracellular signal-regulated kinase (ERK). Our study demonstrates for the first time that AEM ameliorates the scopolamine-induced memory impairments in mice and increases the phosphorylation of Akt and ERK in the hippocampus of mice brain. These results suggest that AEM has the therapeutic potential in memory impairments.

Augmented Inhibition from Cannabinoid-Sensitive Interneurons Diminishes CA1 Output after Traumatic Brain Injury.

The neurological impairments associated with traumatic brain injury include learning and memory deficits and increased risk of seizures. The hippocampus is critically involved in both of these phenomena and highly susceptible to damage by traumatic brain injury. To examine network activity in the hippocampal CA1 region after lateral fluid percussion injury, we used a combination of voltage-sensitive dye, field potential, and patch clamp recording in mouse hippocampal brain slices. When the stratum radiatum (SR) was stimulated in slices from injured mice, we found decreased depolarization in SR and increased hyperpolarization in stratum oriens (SO), together with a decrease in the percentage of pyramidal neurons firing stimulus-evoked action potentials. Increased hyperpolarization in SO persisted when glutamatergic transmission was blocked. However, we found no changes in SO responses when the alveus was stimulated to directly activate SO. These results suggest that the increased SO hyperpolarization evoked by SR stimulation was mediated by interneurons that have cell bodies and/or axons in SR, and form synapses in stratum pyramidale and SO. A low concentration (100 nM) of the synthetic cannabinoid WIN55,212-2, restored CA1 output in slices from injured animals. These findings support the hypothesis that increased GABAergic signaling by cannabinoid-sensitive interneurons contributes to the reduced CA1 output following traumatic brain injury.

Intracellular accumulation of amyloid-β (Aβ) protein plays a major role in Aβ-induced alterations of glutamatergic synaptic transmission and plasticity.

Intracellular accumulation of amyloid-β (Aβ) protein has been proposed as an early event in AD pathogenesis. In patients with mild cognitive impairment, intraneuronal Aβ immunoreactivity was found especially in brain regions critically involved in the cognitive deficits of AD. Although a large body of evidence demonstrates that Aβ42 accumulates intraneuronally ((in)Aβ), the action and the role of Aβ42 buildup on synaptic function have been poorly investigated. Here, we demonstrate that basal synaptic transmission and LTP were markedly depressed following Aβ42 injection into the neuron through the patch pipette. Control experiments performed with the reverse peptide (Aβ42-1) allowed us to exclude that the effects of (in)Aβ depended on changes in oncotic pressure. To further investigate (in)Aβ synaptotoxicity we used an Aβ variant harboring oxidized methionine in position 35 that does not cross the neuronal plasma membrane and is not uploaded from the extracellular space. This Aβ42 variant had no effects on synaptic transmission and plasticity when applied extracellularly, but induced synaptic depression and LTP inhibition after patch-pipette dialysis. Finally, the injection of an antibody raised against human Aβ42 (6E10) in CA1 pyramidal neurons of mouse hippocampal brain slices and autaptic microcultures did not, per se, significantly affect LTP and basal synaptic transmission, but it protected against the toxic effects of extracellular Aβ42. Collectively, these findings suggest that Aβ42-induced impairment of glutamatergic synaptic function depends on its internalization and intracellular accumulation thus paving the way to a systemic proteomic analysis of intracellular targets/partners of Aβ42.

Activation of neuronal NMDA receptors triggers transient ATP-mediated microglial process outgrowth.

Microglia are morphologically dynamic cells that rapidly extend their processes in response to various stimuli including extracellular ATP. In this study, we tested the hypothesis that stimulation of neuronal NMDARs trigger ATP release leading to communication with microglia. We used acute mouse hippocampal brain slices and two-photon laser scanning microscopy to study microglial dynamics and developed a novel protocol for fixation and immunolabeling of microglia processes. Similar to direct topical ATP application in vivo, short multiple applications of NMDA triggered transient microglia process outgrowth that was reversible and repeatable indicating that this was not due to excitotoxic damage. Stimulation of NMDAR was required as NMDAR antagonists, but not blockers of AMPA/kainate receptors or voltage-gated sodium channels, prevented microglial outgrowth. We report that ATP release, secondary to NMDAR activation, was the key mediator of this neuron-microglia communication as both blocking purinergic receptors and inhibiting hydrolysis of ATP to prevent locally generated gradients abolished outgrowth. Pharmacological and genetic analyses showed that the NMDA-triggered microglia process extension was independent of Pannexin 1, the ATP releasing channels, ATP release from astrocytes via connexins, and nitric oxide generation. Finally, using whole-cell patch clamping we demonstrate that activation of dendritic NMDAR on single neurons is sufficient to trigger microglia process outgrowth. Our results suggest that dendritic neuronal NMDAR activation triggers ATP release via a Pannexin 1-independent manner that induces outgrowth of microglia processes. This represents a novel uncharacterized form of neuron-microglial communication mediated by ATP.

Antidepressant-induced vascular dynamics in the hippocampus of adult mouse brain.

New neurons are continuously added to hippocampal circuitry involved with spatial learning and memory throughout life. These new neurons originate from neural stem/progenitor cells (NSPCs) in the subgranular zone (SGZ) of the dentate gyrus (DG). Recent studies indicate that vascular reconstruction is closely connected with neurogenesis, but little is known about its mechanism. We have examined vascular reconstruction in the hippocampus of adult mouse brain after the administration of the antidepressant fluoxetine, a potent inducer of hippocampal neurogenesis. The immunohistochemistry of laminin and CD31 showed that filopodia of endothelial cells sprouted from existing thick microvessels and often formed a bridge between two thick microvessels. These filopodia were frequently seen at the molecular layer and dentate hilus of the DG, the stratum lacunosum-moleculare of the CA1, and the stratum oriens of the CA3. The filopodia were exclusively localized along cellular processes of astrocytes, but such intimate association was not seen with cell bodies and processes of NSPCs. The administration of fluoxetine significantly increased vascular density by enlarging the luminal size of microvessels and eliminating the filopodia of endothelial cells in the molecular layer and dentate hilus. Treatment with fluoxetine increased the number of proliferating NSPCs in the granule cell layer and dentate hilus, and that of endothelial cells in the granule cell layer. Thus, antidepressant-induced vascular dynamics in the DG are possibly attributable to the alteration of the luminal size of microvessels rather than to proliferation of endothelial cells.

Melatonin pretreatment prevented the effect of dexamethasone negative alterations on behavior and hippocampal neurogenesis in the mouse brain

Glucocorticoids play various physiological functions via the glucocorticoid receptor (GR). Glucocorticoid is associated with the pathophysiology of depression. Dexamethasone (DEX), a synthetic GR agonist, has a greater affinity for GR than the mineralocorticoid receptor (MR) in the hippocampus of pigs and may mimic the effects of GR possession. DEX decreases neurogenesis and induces damage to hippocampal neurons that is associated with depressive-like behavior. Melatonin, a hormone mainly synthesized in the pineal gland, is a potent free radical scavenger and antioxidant. Melatonin alters noradrenergic transmission in depressed patients. It may be interesting to further explore the mechanism of melatonin that is associated with the role of stress as a key factor to precipitate depression and as a factor altering neurogenesis. In this study, we assessed the capability of melatonin to protect the hippocampus of mouse brains to counteract the effects of chronic DEX treatment for 21 days on depressive-like behavior and neurogenesis. Our results revealed that chronic administration of DEX induced depressive-like behavior and that this could be reversed by pretreatment with melatonin. Moreover, the number of 5-bromo-2-deoxyuridine (BrdU)-immunopositive cells and doublecortin (DCX; the neuronal-specific marker) protein levels were significantly reduced in the DEX-treated mice. Pretreatment with melatonin was found to renew BrdU and DCX expression in the dentate gyrus. Furthermore, pretreatment with melatonin prevented DEX-induced reductions in GR and an extracellular-signal-regulated kinase (ERK1/2) in the hippocampal area. Melatonin may protect hippocampal neurons from damage and reverse neurogenesis after chronic DEX by activating brain-derived neurotrophic (BDNF) and ERK1/2 cascades. These results revealed that melatonin pretreatment prevented the reduction of cell proliferation, immature neuron precursor cells, and GR and ERK1/2 expression. This finding indicates that melatonin attenuates the DEX-induced depressive-like behavior, supporting the notion that melatonin possesses anti-stress and neurogenic actions.

Three-dimensional analysis of abnormal ultrastructural alteration in mitochondria of hippocampus of APP/PSEN1 transgenic mouse

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. The deterioration of subcellular organelles, including the mitochondria, is another major ultrastructural characteristic of AD pathogenesis, in addition to amyloid plaque deposition. However, the three-dimensional (3-D) study of mitochondrial structural alteration in AD remains poorly understood. Therefore, ultrastructural analysis, 3-D electron tomography, and immunogold electron microscopy were performed in the present study to clarify the abnormal structural alterations in mitochondria caused by the progression of AD in APP/PSEN1 transgenic mice, expressing human amyloid precursor protein, as a model for AD. Amyloid beta (A beta) plaques accumulated and dystrophic neurites (DN) developed in the hippocampus of transgenic AD mouse brains. We also identified the loss of peroxiredoxin 3, an endogenous cytoprotective antioxidant enzyme and the accumulation of A beta in the hippocampal mitochondria of transgenic mice, which differs from those in age-matched wild-type mice. The mitochondria in A beta plaque-detected regions were severely disrupted, and the patterns of ultrastructural abnormalities were classified into three groups: disappearance of cristae, swelling of cristae, and bulging of the outer membrane. These results demonstrated that morpho-functional alterations of mitochondria and AD progression are closely associated and may be beneficial in investigating the function of mitochondria in AD pathogenesis.

Farnesyltransferase Haplodeficiency Reduces Neuropathology and Rescues Cognitive Function in a Mouse Model of Alzheimer Disease

Isoprenoids and prenylated proteins have been implicated in the pathophysiology of Alzheimer disease (AD), including amyloid-β precursor protein metabolism, Tau phosphorylation, synaptic plasticity, and neuroinflammation. However, little is known about the relative importance of the two protein prenyltransferases, farnesyltransferase (FT) and geranylgeranyltransferase-1 (GGT), in the pathogenesis of AD. In this study, we defined the impact of deleting one copy of FT or GGT on the development of amyloid-β (Aβ)-associated neuropathology and learning/memory impairments in APPPS1 double transgenic mice, a well established model of AD. Heterozygous deletion of FT reduced Aβ deposition and neuroinflammation and rescued spatial learning and memory function in APPPS1 mice. Heterozygous deletion of GGT reduced the levels of Aβ and neuroinflammation but had no impact on learning and memory. These results document that farnesylation and geranylgeranylation play differential roles in AD pathogenesis and suggest that specific inhibition of protein farnesylation could be a potential strategy for effectively treating AD.

The effects of perindopril on cognitive impairment induced by d-galactose and aluminum trichloride via inhibition of acetylcholinesterase activity and oxidative stress

Preclinical and clinical studies indicate involvement of renin angiotensin system (RAS) in memory functions. However, exact role of RAS in cognition is still ambiguous. The present study investigated the effects of perindopril on dementia of Alzheimer's type induced by d-galactose (d-gal) and aluminum trichloride (AlCl3). Perindopril, an angiotensin converting enzyme inhibitor, was administered intragastrically (0.5mg/kg/day) for 60days after mice were given d-gal (150mg/kg/day) and AlCl3 (10mg/kg/day) intraperitoneally for 90days. Then, memory function was evaluated by Morris water maze test. The biochemical studies were conducted in cerebral cortex and hippocampus of mouse brain after the behavioral studies. d-Gal and AlCl3 caused significant memory impairment along with significant elevation of acetylcholinesterase (AChE) activity in cerebral cortex and hippocampus. Further, a significant reduction of superoxide dismutases (SOD) and glutathione peroxidase (GSH-Px) activities, and elevation of malondialdehyde (MDA) level in cerebral cortex and hippocampus were observed. Perindopril not only improved cognitive impairment but also restored the elevation of AChE activity induced by d-gal and AlCl3. In addition, perindopril significantly increased SOD and GSH-Px activities, reduced MDA level in cerebral cortex and hippocampus. Taken together, the above findings indicate that perindopril improves learning and memorizing probably by restoring cholinergic function and attenuating oxidative damage.

Antidepressant-like activity of turmerone in behavioral despair tests in mice

BackgroundThe present study was undertaken to evaluate the anti-depressive activity of turmerone after one-week administration by using a mouse forced swimming test (FST) and tail suspension test (TST).MethodsAnimals were divided into four groups (n = 10 /group): control (0.9% saline), the three doses of turmerone (1.25, 2.5, 5.0 mg/kg) for one-week treatment. To assess the effect of turmerone on locomotor activity, mice were evaluated in the open-field paradigm. Forced swimming test (FST) and Tail suspension test (TST) were used to take as a measure of antidepressant activity. The probable mechanisms of action of the anti-depressive effect of turmerone was also investigated by measuring the activity of monoamine oxidase-A and corticosterone levels in the blood and the levels of monoamines in the cortex, striatum, hippocampus and hypothalamus of the mice.ResultsTurmerone (2.5, 5.0 mg/kg, p.o.) significantly reduced the immobility time of mice in both the FST and TST, but it did not significantly affect the ambulatory and total movements of mice. However, hyperactivity might explain the results. In addition, turmerone decreased the corticosterone level in the blood while it increased the levels of 5-HT in cortex, striatum, hippocampus, and hypothalamus, the level of NE in striatum and hippocampus, the levels of MHPG and DOPAC in hypothalamus, the level of 5-HIAA in striatum, and the level of DA in striatum, hippocampus, and hypothalamus. Turmerone (2.5, 5.0 mg/kg) decreased the activity of MAO-A in the frontal cortex and hippocampus of mouse brain.ConclusionsAfter one-week administration, turmerone produced antidepressant-like effects. The mechanisms of action of anti-depressive effect of turmerone seemed to involve an increase of the monoamines level decreasing the MAO-A activity and the stress of mice.

Sodium hydrosulfide prevents hypoxia-induced behavioral impairment in neonatal mice

Hypoxic encephalopathy is a common cause of neonatal seizures and long-term neurological abnormalities. Endogenous hydrogen sulfide (H2S) may have multiple functions in brain. The aim of this study is to investigate whether sodium hydrosulfide (NaHS), a H2S donor, provides protection against neonatal hypoxia-induced neurobehavioral deficits. Neonatal mice were subjected to hypoxia (5% oxygen for 120min) at postnatal day 1 and received NaHS (5.6mg/kg) once daily for 3d. Neurobehavioral toxicity was examined at 3–30d after hypoxia. Treatment with NaHS significantly attenuated the delayed development of sensory and motor reflexes induced by hypoxia up to two weeks after the insult. Moreover, NaHS improved the learning and memory performance of hypoxic animals as indicated in Morris water maze test at 30d after hypoxia. In mice exposed to hypoxia, treatment with NaHS enhanced expression of brain derived neurotrophic factor (BDNF) in the hippocampus. Furthermore, the protective effects of NaHS were associated with its ability to repress the hypoxia-induced nitric oxide synthase (NOS) activity and nitric oxide production in the hippocampus of mice brain. Taken together, these results suggest that the long-lasting beneficial effects of NaHS on hypoxia-induced neurobehavioral deficits are mediated, at least in part, by inducing BDNF expression and suppressing NOS activity in the brain of mice.

Neuroprotective effect of curcumin on okadaic acid induced memory impairment in mice

Okadaic acid (OKA) has been observed to cause memory impairment in human subjects having seafood contaminated with dinoflagellate (Helicondria okadai). OKA induces tau hyperphosphorylation and oxidative stress leading to memory impairment as our previous study has shown. Curcumin a natural antioxidant has demonstrated neuroprotection in various models of neurodegeneration. However, the effect of curcumin has not been explored in OKA induced memory impairment. Therefore, present study evaluated the effect of curcumin on OKA (100ng, intracerebrally) induced memory impairment in male Swiss albino mice as evaluated in Morris water maze (MWM) and passive avoidance tests (PAT). OKA administration resulted in memory impairment with a decreased cerebral blood flow (CBF) (measured by laser doppler flowmetry), ATP level and increased mitochondrial (Ca2+)i, neuroinflammation (increased TNF-α, IL-1β, COX-2 and GFAP), oxidative-nitrosative stress, increased Caspase-9 and cholinergic dysfunction (decreased AChE activity/expression and α7 nicotinic acetylcholine receptor expression) in cerebral cortex and hippocampus of mice brain. Oral administration of curcumin (50mg/kg) for 13 days significantly improved memory function in both MWM and PAT along with brain energy metabolism, CBF and cholinergic function. It decreased mitochondrial (Ca2+)i, and ameliorated neuroinflammation and oxidative-nitrostative stress in different brain regions of OKA treated mice. Curcumin also inhibited astrocyte activation as evidenced by decreased GFAP expression. This neuroprotective effect of curcumin is due to its potent anti-oxidant action thus confirming previous studies. Therefore, use of curcumin should be encouraged in people consuming sea food (contaminated with dinoflagellates) to prevent cognitive impairment.

B-Raf and CRHR1 Internalization Mediate Biphasic ERK1/2 Activation by CRH in Hippocampal HT22 Cells

CRH is a key regulator of neuroendocrine, autonomic, and behavioral response to stress. CRH-stimulated CRH receptor 1 (CRHR1) activates ERK1/2 depending on intracellular context. In a previous work, we demonstrated that CRH activates ERK1/2 in limbic areas of the mouse brain (hippocampus and basolateral amygdala). ERK1/2 is an essential mediator of hippocampal physiological processes including emotional behavior, synaptic plasticity, learning, and memory. To elucidate the molecular mechanisms by which CRH activates ERK1/2 in hippocampal neurons, we used the mouse hippocampal cell line HT22. We document for the first time that ERK1/2 activation in response to CRH is biphasic, involving a first cAMP- and B-Raf-dependent early phase and a second phase that critically depends on CRHR1 internalization and β-arrestin2. By means of mass-spectrometry-based screening, we identified B-Raf-associated proteins that coimmunoprecipitate with endogenous B-Raf after CRHR1 activation. Using molecular and pharmacological tools, the functional impact of selected B-Raf partners in CRH-dependent ERK1/2 activation was dissected. These results indicate that 14-3-3 proteins, protein kinase A, and Rap1, are essential for early CRH-induced ERK1/2 activation, whereas dynamin and vimentin are required for the CRHR1 internalization-dependent phase. Both phases of ERK1/2 activation depend on calcium influx and are affected by calcium/calmodulin-dependent protein kinase II inactivation. Thus, this report describes the dynamics and biphasic nature of ERK1/2 activation downstream neuronal CRHR1 and identifies several new critical components of the CRHR1 signaling machinery that selectively controls the early and late phases of ERK1/2 activation, thus providing new potential therapeutic targets for stress-related disorders.

Dynamic Change of Hydrogen Sulfide After Traumatic Brain Injury and its Effect in Mice

Hydrogen sulfide (H2S) is a lipid-soluble, endogenously produced gaseous messenger molecule collectively known as gasotransmitter. Over the last several decades, gasotransmitters have emerged as potent cytoprotective mediators in various models of tissue and cellular injury. In this study, we performed a weight-drop traumatic brain injury (TBI) model in adult mice and investigated changes of H2S and its possible role in the pathogenesis after TBI. Expression of Cystathionine-β-synthase (CBS) mRNA as H2S-producing enzymes in mouse brain was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). From the results of RT-PCR, it was found that the expression of CBS was down-regulated in mouse brain cortex and hippocampus after brain injury. Western blot analysis revealed that CBS was present in normal mouse brain cortex and the hippocampus. It gradually decreased, reached its lowest level and then increased. Hydrogen sulfide in the cortex and hippocampus exhibited dynamic changes after brain injury, in parallel with CBS mRNA and protein expression. Moreover, pretreatment with the H2S donor (NaHS) could protect the neuron against the injury induced by TBI. Noticeably, the H2S donor NaHS could reduce TBI-induced injury assessed with lesion volume. These data suggested that H2S may have a therapeutic potential against neuron damage.

The effects of lignan-riched extract of Shisandra chinensis on amyloid-β-induced cognitive impairment and neurotoxicity in the cortex and hippocampus of mouse

Ethnopharmacological relevanceThe fruits of Schisandra chinensis (Trucz.) Baill. (Schisandraceae) which have been used as a tonic especially for kidney yin deficiency in Chinese traditional medicine are recently receiving attention for its preventive activity on age-related neurodegenerative diseases. A variety of studies demonstrated the cognitive-enhancing effects of Schisandra chinensis through animal tests and also in clinical trials. Aim of studyIn this study, we attempted to investigate the effects of the lignan-riched extract of Schisandra chinensis fruits (ESP-806) on neurotoxicity and memory impairment induced by Aβ1–42 injection in mice. Materials and methodsThe fruits of Schisandra chinensis were extracted with the mixture of n-hexane:ethanol (9:1), which is riched with bioactive dibenzocyclooctadiene lignans, schizandrin, gomisin N, wuweigisu C. After oral treatment of ESP-806 (100mg/kg body weight) followed by injection of Aβ1–42 (2μg/mouse, i.c.v.), novel object recognition and passive avoidance tests were evaluated. To verify the cognition enhancing effects of ESP-806, we examined the effects of ESP-806 on the activities of β-secretase and acetylcholinesterase, and the contents of Aβ and the reduced glutathione within the cortex and hippocampus of Aβ-injected mice. ResultsOral treatment of ESP-806 (100mg/kg body weight) significantly attenuated Aβ1–42-induced memory impairment evaluated by behavioral tests. Furthermore, the treatment of ESP-806 attenuated the elevation of β-secretase activity accompanying the reduced level of Aβ1–42 in the cortex and hippocampus of the brain. ESP-806 also significantly inhibited the acetylcholinesterase activity in the hippocampus and increased the content of the reduced glutathione in the cortex and hippocampus of mouse brain. ConclusionsThese data suggested that the extract of Schisandra chinensis fruits riched with dibenzocyclooctadiene lignans may be useful in the prevention and treatment of Alzheimer's disease.

Intrahippocampal injection of Aβ1-42 inhibits neurogenesis and down-regulates IFN-γ and NF-κB expression in hippocampus of adult mouse brain

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by accumulation of amyloid plaques and neurofibrillary tangles. Amyloid-β (Aβ) is widely recognized as a key factor in the pathogenesis of AD. Aβ1-42, a major component of amyloid plaques, has shown synaptotoxicity associated with impaired long-term potentiation and cognitive deficits. Alteration of neurogenesis in AD patients has been reported, while little is known about how Aβ1-42 affects hippocampal neurogenesis in the adult brain. In this study, we injected human Aβ1-42 peptide into hippocampal CA1 area of adult mouse brain bilaterally and evaluated histological change and neurogenesis in the hippocampus. Hematoxylin and eosin (HE) stain showed that Aβ1-42-injection resulted in an extensive neurodegeneration in the Aβ-accumulated area and CA3 in hippocampus. Immunostaining showed that intrahippocampal Aβ1-42-injection dramatically decreased the number of bromodeoxyuridine (BrdU)-positive cells in the dentate gyrus (DG) compared to the vehicle injection. Moreover, a significant decrease in the number of BrdU/double-cortin double-positive cells in Aβ1-42-injected hippocampus was observed, suggesting that Aβ1-42-injection inhibited progenitor cell proliferation and neurogenesis in subgranular zone of the DG in the adult brain. We also found that the Aβ1-42-mediated decline of neurogenesis was associated with decreased protein levels of cytokines interferon-γ (IFN-γ) and transcription factor nuclear factor-kappa B (NF-κB) in the hippocampus. These results suggest that Aβ1-42 inhibits hippocampal neurogenesis in the adult brain possibly through down-regulation of INF-γ and NF-κB signaling pathway. This study provides a new insight into Aβ1-42-mediated decrease in hippocampal neurogenesis in the adult central nervous system.Abbreviations: Aβ, Amyloid-β; AD, Alzheimer’s disease; AβPP (APP), Amyloid β precursor protein; BrdU, Bromodeoxyuridine; CNS, central nervous system; DCX, doublecortin; DG, dentate gyrus; IFN-γ, interferon-γ; NF-κB, nuclear factor-kappa B; NS, normal saline; RT, room temperature; SGZ, subgranular zone; SVZ, subventricular zone.

Methylene blue induces macroautophagy through 5′ adenosine monophosphate-activated protein kinase pathway to protect neurons from serum deprivation

Methylene blue has been shown to be neuroprotective in multiple experimental neurodegenerative disease models. However, the mechanisms underlying the neuroprotective effects have not been fully elucidated. Previous studies have shown that macroautophagy has multiple beneficial roles for maintaining normal cellular homeostasis and that induction of macroautophagy after myocardial ischemia is protective. In the present study we demonstrated that methylene blue could protect HT22 hippocampal cell death induced by serum deprivation, companied by induction of macroautophagy. We also found that methylene blue-mediated neuroprotection was abolished by macroautophagy inhibition. Interestingly, 5′ adenosine monophosphate-activated protein kinase (AMPK) signaling, but not inhibition of mammalian target of rapamycin signaling, was activated at 12 and 24 h after methylene blue treatment in a dose-dependent manner. Methylene blue-induced macroautophagy was blocked by AMPK inhibitor. Consistent with in vitro data, macroautophagy was induced in the cortex and hippocampus of mouse brains treated with methylene blue. Our findings suggest that methylene blue-induced neuroprotection is mediated, at least in part, by macroautophagy though activation of AMPK signaling.

Beta Amyloid-Induced Depression of Hippocampal Long-Term Potentiation Is Mediated through the Amylin Receptor

Alzheimer's disease (AD) is characterized by accumulation of amyloid-β peptide (Aβ) in the brain regions that subserve memory and cognition. The amylin receptor is a potential target receptor for expression of the deleterious actions of soluble oligomeric Aβ species. We investigated whether the amylin receptor antagonist, AC253, neutralizes the depressant effects of Aβ(1-42) and human amylin on hippocampal long-term potentiation (LTP). Furthermore, we examined whether depressed levels of LTP observed in transgenic mice, which overexpress amyloid precursor protein (TgCRND8), could be restored with AC253. In mouse hippocampal brain slices, field EPSPs were recorded from the stratum radiatum layer of the CA1 area (cornu ammonis 1 region of the hippocampus) in response to electrical stimulation of Schaeffer collateral afferents. LTP was induced by 3-theta burst stimulation protocols. Aβ(1-42) (50 nM) and human amylin (50 nM), but not Aβ(42-1) (50 nM), depressed LTP evoked using both stimulation protocols. Preapplication of AC253 (250 nM) blocked Aβ- and human amylin-induced reduction of LTP without affecting baseline transmission or LTP on its own. In contrast to wild-type controls, where robust LTP is observed, 6- to 12-month-old TgCRND8 mice show blunted LTP that is significantly enhanced by application of AC253. Our data demonstrate that the effects of Aβ(1-42) and human amylin on LTP are expressed via the amylin receptor, and moreover, blockade of this receptor increases LTP in transgenic mice that show increased brain amyloid burden. Amylin receptor antagonists could serve as potentially useful therapeutic agents in AD.