Synaptophysin Levels Research Articles

Whole body vibration (WBV) following spinal cord injury (SCI) in rats: Timing of intervention.

Following spinal cord injury (SCI), exercise training provides a wide range of benefits and promotes activity-dependent synaptic plasticity. Whole body vibration (WBV) in SCI patients improves walking and spasticity as well as bone and muscle mass. However, little is known about the effects of timing or frequency of intervention. To determine which WBV-onset improves locomotor and bladder functions and influences synaptic plasticity beneficially. SCI was followed by WBV starting 1, 7, 14, 28 days after injury (WBV1, WBV7, etc.) and continued for 12 weeks. Intact animals and those receiving SCI but no WBV (No WBV), SCI plus WBV twice daily (2×WBV) and SCI followed by passive hindlimb flexion-extension (PFE) served as controls. Locomotor [BBB rating, foot stepping angle (FSA) and rump-height index (RHI)] as well as bladder function were determined at 1, 3, 6, 9, and 12 weeks. Following perfusion fixation at 12 weeks, lesion volume and immunofluorescence for astrogliosis (GFAP), microglia (IBA1) and synaptic vesicles (synaptophysin, SYN) were determined. Compared to the No WBV group, the WB7 and WBV14 groups showed significantly faster speeds of BBB score recovery though this effect was temporary. Considering RHI we detected a sustained improvement in the WBV14 and PFE groups. Bladder function was better in the WBV14, WBV28, 2×WBV and PFE groups. Synaptophysin levels improved in response to WBV7 and WBV14, but worsened after WBV28 in parallel to an increased IBA1 expression. Correlation- and principal components analysis revealed complex relationships between behavioural (BBB, FSA, RHI) and morphological (GFAP, IBA1, SYN) measurements. WBV started 14 days after SCI provides the most benefit (RHI, bladder); starting at 1day after SCI provides no benefit and starting at 28 days may be detrimental. Increasing the intensity of WBV to twice daily did not provide additional benefit.

Learning and memory disabilities in IUGR babies: Functional and molecular analysis in a rat model.

1IntroductionIntrauterine growth restriction (IUGR) is the failure of the fetus to achieve its inherent growth potential, and it has frequently been associated with neurodevelopmental problems in childhood. Neurological disorders are mostly associated with IUGR babies with an abnormally high cephalization index (CI) and a brain sparing effect. However, a similar correlation has never been demonstrated in an animal model. The aim of this study was to determine the correlations between CI, functional deficits in learning and memory and alterations in synaptic proteins in a rat model of IUGR.2MethodsUtero‐placental insufficiency was induced by meso‐ovarian vessel cauterization (CMO) in pregnant rats at embryonic day 17 (E17). Learning performance in an aquatic learning test was evaluated 25 days after birth and during 10 days. Some synaptic proteins were analyzed (PSD95, Synaptophysin) by Western blot and immunohistochemistry.3ResultsPlacental insufficiency in CMO pups was associated with spatial memory deficits, which are correlated with a CI above the normal range. CMO pups presented altered levels of synaptic proteins PSD95 and synaptophysin in the hippocampus.4ConclusionsThe results of this study suggest that learning disabilities may be associated with altered development of excitatory neurotransmission and synaptic plasticity. Although interspecific differences in fetal response to placental insufficiency should be taken into account, the translation of these data to humans suggest that both IUGR babies and babies with a normal birth weight but with intrauterine Doppler alterations and abnormal CI should be closely followed to detect neurodevelopmental alterations during the postnatal period.

Effect of short-term exercise training on brain-derived neurotrophic factor signaling in spontaneously hypertensive rats.

Decreased brain-derived neurotrophic factor (BDNF) level has been reported in the hippocampus of hypertensive rats. The present study explored whether brain neurons and/or endothelial cells are targeted by hypertension with respect to BDNF expression and the potential of physical exercise to cope with hypertension. Physical exercise was induced in spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats. The hippocampus of sedentary and exercised rats (n = 6 for each group) were used for western blots to assess proBDNF, mature BDNF (mBDNF), tropomyosin-related kinase B (TrkB), P-TrkB (TrkB phosphorylated at tyrosine 816), synaptophysin, endothelial nitric oxide synthase (eNOS) and eNOS phosphorylated at serine 1177 protein levels. BDNF and proBDNF localization in the hippocampus was studied in WKY rats, SHR and exercised SHR (n = 5 each). mBDNF and proBDNF protein levels were also assessed in hippocampal slices prepared from SHR (n = 10) that were incubated for 24 h with the nitric oxide (NO) donor glyceryl trinitrate. SBP was measured by the tail-cuff method. Exercise modified blood pressure neither in SHR nor WKY. As compared with WKY rats, SHR displayed decreased levels of mBDNF, P-TrkB, synaptophysin, eNOS and eNOS phosphorylated at serine 1177 but no change in proBDNF and TrkB levels. These effects coincided with low BDNF staining in both endothelial cells and neurons. Exercise improved the endothelium-derived NO system and the BDNF pathway in both strains. The NO donor increased mBDNF but decreased proBDNF levels. Our results revealed that endothelial and neuronal BDNF expressions were both impaired in hypertension and that physical exercise improved hippocampal mBDNF levels and signaling through blood pressure-independent mechanisms.

Anti-RAGE antibody selectively blocks acute systemic inflammatory responses to LPS in serum, liver, CSF and striatum

Systemic inflammation induces transient or permanent dysfunction in the brain by exposing it to soluble inflammatory mediators. The receptor for advanced glycation endproducts (RAGE) binds to distinct ligands mediating and increasing inflammatory processes. In this study we used an LPS-induced systemic inflammation model in rats to investigate the effect of blocking RAGE in serum, liver, cerebrospinal fluid (CSF) and brain (striatum, prefrontal cortex, ventral tegmental area and substantia nigra). Intraperitoneal injection of RAGE antibody (50μg/kg) was followed after 1h by a single LPS (5mg/kg) intraperitoneal injection. Twenty-four hours later, tissues were isolated for analysis. RAGE antibody reduced LPS-induced inflammatory effects in both serum and liver; the levels of proinflammatory cytokines (TNF-α, IL-1β) were decreased and the phosphorylation/activation of RAGE downstream targets (ERK1/2, IκB and p65) in liver were significantly attenuated. RAGE antibody prevented LPS-induced effects on TNF-α and IL-1β in CSF. In striatum, RAGE antibody inhibited increases in IL-1β, Iba-1, GFAP, phospho-ERK1/2 and phospho-tau (ser202), as well as the decrease in synaptophysin levels. These effects were caused by systemic RAGE inhibition, as RAGE antibody did not cross the blood-brain barrier. RAGE antibody also prevented striatal lipoperoxidation and activation of mitochondrial complex II. In conclusion, blockade of RAGE is able to inhibit inflammatory responses induced by LPS in serum, liver, CSF and brain.

Time-course investigation of blood-brain barrier permeability and tight junction protein changes in a rat model of permanent focal ischemia.

Permanent middle cerebral artery occlusion (pMCAO) is an animal model that is widely used to simulate human ischemic stroke. However, the timing of the changes in the expression of tight junction (TJ) proteins and synaptic proteins associated with pMCAO remain incompletely understood. Therefore, to further explore the characteristics and mechanisms of blood-brain barrier (BBB) damage during cerebral ischemic stroke, we used a pMCAO rat model to define dynamic changes in BBB permeability within 120h after ischemia in order to examine the expression levels of the TJ proteins claudin-5 and occludin and the synaptic proteins synaptophysin (SYP) and postsynaptic density protein 95 (PSD95). In our study, Evans blue content began to increase at 4h and was highest at 8 and 120h after ischemia. TTC staining showed that cerebral infarction was observed at 4h and that the percentage of infarct volume increased with time after ischemia. The expression levels of claudin-5 and occludin began to decline at 1h and were lowest at 8 and 120h after ischemia. The expression levels of SYP and PSD95 decreased from 12 to 120h after ischemia. GFAP, an astrocyte marker, gradually increased in the cortex penumbra over time post-ischemia. Our study helps clarify the characteristics of pMCAO models and provides evidence supporting the translational potential of animal stroke models.

Glycine Administration Alters MAPK Signaling Pathways and Causes Neuronal Damage in Rat Brain: Putative Mechanisms Involved in the Neurological Dysfunction in Nonketotic Hyperglycinemia.

High glycine (GLY) levels have been suggested to induce neurotoxic effects in the central nervous system of patients with nonketotic hyperglycinemia (NKH). Since the mechanisms involved in the neuropathophysiology of NKH are not totally established, we evaluated the effect of a single intracerebroventricular administration of GLY on the content of proteins involved in neuronal damage and inflammatory response, as well as on the phosphorylation of the MAPK p38, ERK1/2, and JNK in rat striatum and cerebral cortex. We also examined glial fibrillary acidic protein (GFAP) staining, a marker of glial reactivity. The parameters were analyzed 30min or 24h after GLY administration. GLY decreased Tau phosphorylation in striatum and cerebral cortex 30min and 24h after its administration. On the other hand, synaptophysin levels were decreased in striatum at 30min and in cerebral cortex at 24h after GLY injection. GLY also decreased the phosphorylation of p38, ERK1/2, and JNK 30min after its administration in both brain structures. Moreover, GLY-induced decrease of p38 phosphorylation in striatum was attenuated by N-methyl-D-aspartate receptor antagonist MK-801. In contrast, synuclein, NF-κB, iκB, inducible nitric oxide synthase and nitrotyrosine content, and GFAP immunostaining were not altered by GLY infusion. It may be presumed that the decreased phosphorylation of MAPK associated with alterations of markers of neuronal injury induced by GLY may contribute to the neurological dysfunction observed in NKH.

Bone marrow stromal cells promote neuromotor functional recovery, via upregulation of neurotrophic factors and synapse proteins following traumatic brain injury in rats.

It has previously been demonstrated that bone marrow stromal cells (BMSCs) exhibit great therapeutic potential in neuronal injuries; however, there is limited understanding of the precise underlying mechanisms that contribute to functional improvement following brain injury. The aim of the present study was to assess the effect of BMSC treatment on traumatic brain injury (TBI) in rats, and investigate if they migrate to injured areas and promote neuromotor functional recovery via upregulation of neurotrophic factors and synaptic proteins. BMSCs were cultured in vitro from female Sprague Dawley (SD) rat bone marrow and were subsequently infused into male adult SD rats via the tail vein, following induction of TBI. The results demonstrated that treatment with BMSCs significantly reduced TBI-induced neuromotor impairment and neuronal loss, as assessed by rota rod testing, western blot analysis, modified neurological severity score and immunohistochemistry. The distribution of transplanted BMSCs was tracked by monitoring the expression of sex determining region Y (SRY) in rats. The number of cells double-positive for SRY/neuronal nuclear antigen or SRY/glial fibrillary acidic protein was increased in the BMSC group, which demonstrated that BMSCs migrated to injured areas and differentiated into neurons and astrocytes, following TBI. Furthermore, administration of BMSCs increased expression of vascular endothelial growth factor and brain derived neurotrophic factor. Protein expression levels of synaptophysin were downregulated following TBI and this was reversed in part by treatment with BMSCs. These findings uncovered some underlying mechanisms of action of BMSCs, and may lead to their potential use as a future effective therapeutic agent for the treatment of TBI.

Astaxanthin improves cognitive performance in mice following mild traumatic brain injury

BackgroundTraumatic brain injury (TBI) produces lasting neurological deficits that plague patients and physicians. To date, there is no effective method to combat the source of this problem. Here, we utilized a mild, closed head TBI model to determine the modulatory effects of a natural dietary compound, astaxanthin (AST). AST is centrally active following oral administration and is neuroprotective in experimental brain ischemia/stroke and subarachnoid hemorrhage (SAH) models. We examined the effects of oral AST on the long-term neurological functional recovery and histological outcomes following moderate TBI in a mice model. MethodsMale adult ICR mice were divided into 3 groups: (1) Sham+olive oil vehicle treated, (2) TBI+olive oil vehicle treated, and (3) TBI+AST. The olive oil vehicle or AST were administered via oral gavage at scheduled time points. Closed head brain injury was applied using M.A. Flierl weight-drop method. NSS, Rotarod, ORT, and Y-maze were performed to test the behavioral or neurological outcome. The brain sections from the mice were stained with H&E and cresyl-violet to test the injured lesion volume and neuronal loss. Western blot analysis was performed to investigate the mechanisms of neuronal cell survival and neurological function improvement. ResultsAST administration improved the sensorimotor performance on the Neurological Severity Score (NSS) and rotarod test and enhanced cognitive function recovery in the object recognition test (ORT) and Y-maze test. Moreover, AST treatment reduced the lesion size and neuronal loss in the cortex compared with the vehicle-treated TBI group. AST also restored the levels of brain-derived neurotropic factor (BDNF), growth-associated protein-43 (GAP-43), synapsin, and synaptophysin (SYP) in the cerebral cortex, which indicates the promotion of neuronal survival and plasticity. ConclusionTo the best of our knowledge, this is the first study to demonstrate the protective role and the underlining mechanism of AST in TBI. Based on these neuroprotective actions and considering its longstanding clinical use, AST should be considered for the clinical treatment of TBI.

Neuroprotective effects of quercetin in diabetic rat retina.

Diabetic retinopathy (DR) is a severe complication of diabetes and the leading cause of blindness among working adults worldwide. DR is being widely recognized as a neurodegenerative disease of the retina, since, retinal neurons are damaged soon after diabetes onset. Diabetes-induced oxidative stress is considered as central factor that dysregulates neurotrophic factors and activates apoptosis, thereby damages neurons in the diabetic retina. Flavonoids being a powerful antioxidant have been considered to protect neurons in diabetic retina. The purpose of this study was to analyze the beneficial effects of flavonoid, quercetin to protect neurons in the diabetic rat retina. We quantitated the expression levels of BDNF, NGF, TrkB, synaptophysin, Akt, Bcl-2, cytochrome c and caspase-3 using Western blotting techniques in the diabetic retina with and without quercetin treatments and compared with non-diabetic rats. In addition, we employed ELISA techniques to determine the level of BDNF. Caspase-3 activity and the level of glutathione were analyzed by biochemical methods. Our results indicate that quercetin treatment to diabetic rats caused a significant increase in the level of neurotrophic factors and inhibited the level of cytochrome c and caspase-3 activity in the diabetic retina. Furthermore, the level of an anti-apoptotic protein Bcl-2 was augmented in quercetin treated diabetic retina. Thus, quercetin, may protect the neuronal damage in diabetic retina by ameliorating the levels of neurotrophic factors and also by inhibiting the apoptosis of neurons. Therefore, this study suggests that quercetin can be a suitable therapeutic agent to prevent neurodegeneration in diabetic retinopathy.

Grafted c-kit+/SSEA1- eye-wall progenitor cells delay retinal degeneration in mice by regulating neural plasticity and forming new graft-to-host synapses.

BackgroundDespite diverse pathogenesis, the common pathological change observed in age-related macular degeneration and in most hereditary retinal degeneration (RD) diseases is photoreceptor loss. Photoreceptor replacement by cell transplantation may be a feasible treatment for RD. The major obstacles to clinical translation of stem cell-based cell therapy in RD remain the difficulty of obtaining sufficient quantities of appropriate and safe donor cells and the poor integration of grafted stem cell-derived photoreceptors into the remaining retinal circuitry.MethodsEye-wall c-kit+/stage-specific embryonic antigen 1 (SSEA1)− cells were isolated via fluorescence-activated cell sorting, and their self-renewal and differentiation potential were detected by immunochemistry and flow cytometry in vitro. After labeling with quantum nanocrystal dots and transplantation into the subretinal space of rd1 RD mice, differentiation and synapse formation by daughter cells of the eye-wall c-kit+/SSEA1− cells were evaluated by immunochemistry and western blotting. Morphological changes of the inner retina of rd1 mice after cell transplantation were demonstrated by immunochemistry. Retinal function of rd1 mice that received cell grafts was tested via flash electroretinograms and the light/dark transition test.ResultsEye-wall c-kit+/SSEA1− cells were self-renewing and clonogenic, and they retained their proliferative potential through more than 20 passages. Additionally, eye-wall c-kit+/SSEA1− cells were capable of differentiating into multiple retinal cell types including photoreceptors, bipolar cells, horizontal cells, amacrine cells, Müller cells, and retinal pigment epithelium cells and of transdifferentiating into smooth muscle cells and endothelial cells in vitro. The levels of synaptophysin and postsynaptic density-95 in the retinas of eye-wall c-kit+/SSEA1− cell-transplanted rd1 mice were significantly increased at 4 weeks post transplantation. The c-kit+/SSEA1− cells were capable of differentiating into functional photoreceptors that formed new synaptic connections with recipient retinas in rd1 mice. Transplantation also partially corrected the abnormalities of inner retina of rd1 mice. At 4 and 8 weeks post transplantation, the rd1 mice that received c-kit+/SSEA1− cells showed significant increases in a-wave and b-wave amplitude and the percentage of time spent in the dark area.ConclusionsGrafted c-kit+/SSEA1− cells restored the retinal function of rd1 mice via regulating neural plasticity and forming new graft-to-host synapses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-016-0451-8) contains supplementary material, which is available to authorized users.

Behavior-associated Neuronal Activation After Kainic Acid-induced Hippocampal Neurotoxicity is Modulated in Time.

Kainic acid-induced (KA) hippocampal damage leads to neuronal death and further synaptic plasticity. Formation of aberrant as well as of functional connections after such procedure has been documented. However, the impact of such structural plasticity on cell activation along time after damage and in face of a behavioral demand has not been explored. We evaluated if the mRNA and protein levels of plasticity-related protein synaptophysin (Syp and SYP, respectively) and activity-regulated cytoskeleton-associated protein mRNA and protein levels (Arc and Arc, respectively) in the dentate gyrus were differentially modulated in time in response to a spatial-exploratory task after KA-induced hippocampal damage. In addition, we analyzed Arc+/NeuN+ immunopositive cells in the different experimental conditions. We infused KA intrahippocampally to young-adult rats and 10 or 30 days post-lesion (dpl) animals performed a hippocampus-activating spatial-exploratory task. Our results show that Syp mRNA levels significantly increase at 10dpl and return to control levels after 30dpl, whereas SYP protein levels are diminished at 10dpl, but significantly increase at 30dpl, as compared to 10dpl. Arc mRNA and protein levels are both increased at 30dpl as compared to sham. Also the number of NeuN+/Arc+ cells significantly increases at 30dpl in the group with a spatial-exploratory demand. These results provide information on the long-term modifications associated to structural plasticity and neuronal activation in the dentate gyrus after excitotoxic damage and in face of a spatial-exploratory behavior. Anat Rec, 300:425-432, 2017. © 2016 Wiley Periodicals, Inc.

Improved Brain Insulin/IGF Signaling andReduced Neuroinflammation withT3D-959 in an Experimental ModelofSporadic Alzheimer's Disease.

Alzheimer's disease (AD) is associated with progressive impairments in brain insulin, insulin-like growth factor (IGF), and insulin receptor substrate (IRS) signaling through Akt pathways that regulate neuronal growth, survival, metabolism, and plasticity. The intracerebral streptozotocin (i.c. STZ) model replicates the full range of abnormalities in sporadic AD. T3D-959, an orally active PPAR-delta/gamma agonist remediates neurocognitive deficits and AD neuropathology in the i.c. STZ model. This study characterizes the effects of T3D-959 on AD biomarkers, insulin/IGF/IRS signaling through Akt pathways, and neuroinflammation in an i.c. STZ model. Long Evans rats were treated with i.c. STZ or saline, followed by daily oral doses of T3D-959 (1 mg/kg) or saline initiated 1 day (T3D-959-E) or 7 days (T3D-959-L) later through Experimental Day 28. Protein and phospho-protein expression and pro-inflammatory cytokine activation were measured in temporal lobe homogenates by duplex or multiplex bead-based ELISAs. i.c. STZ treatments caused neurodegeneration with increased pTau, AβPP, Aβ42, ubiquitin, and SNAP-25, and reduced levels of synaptophysin, IGF-1 receptor (R), IRS-1, Akt, p70S6K, mTOR, and S9-GSK-3β. i.c. STZ also broadly increased neuroinflammation. T3D-959 abrogated or reduced most of the AD neuropathological and biomarker abnormalities, increased/normalized IGF-1R, IRS-1, Akt, p70S6K, and S9-GSK-3β, and decreased expression of multiple pro-inflammatory cytokines. T3D-959-E or -L effectively restored insulin/IGF signaling, whereas T3D-959-L more broadly resolved neuroinflammation. AD remediating effects of T3D-959 are potentially due to enhanced expression of key insulin/IGF signaling proteins and inhibition of GSK-3β and neuroinflammation. These effects lead to reduced neurodegeneration, cognitive impairment, and AD biomarker levels in the brain.

382 - Ablation of Gpx4 in Forebrain Neurons Leads to Ferroptotic Cell Death and Cognitive Impairment

Synaptic loss and neuron death are the underlying drivers of neurodegenerative diseases such as Alzheimer’s disease (AD); however, the modalities of cell death remain unclear. Although apoptosis has long been considered the major mechanism of neurodegeneration in AD, inconclusive results of clinical trials and pathological data indicate that non-apoptotic cell-death mechanisms may also be involved. Ferroptosis is a newly identified oxidative cell-death pathway regulated by lipid peroxidation that promotes inflammation. Recently, our lab found that motor neurons are particularly susceptible to ferroptosis in vivo . Here, we investigated whether neurons in forebrain regions that are severely afflicted in AD patients (cerebral cortex and hippocampus) might also be vulnerable to ferroptosis. To this end, we deleted the ferroptosis regulator Gpx4 exclusively in fore B rain neurons of 3 month old mice using a novel tamoxifen- I nducible K nock O ut model ( Gpx4 BiKO). At 12 weeks post Gpx4 knockout, the mice exhibited significant deficits in spatial learning and memory versus control mice as determined by Morris water maze task. Hippocampal tissues from Gpx4 BiKO mice also showed reduced levels of neural marker proteins NeuN, Synaptophysin, and SNAP25 indicating the occurrence of neurodegeneration. Interestingly, classical markers of apoptosis such as activation of caspase-3 were absent while several markers associated with ferroptosis were pronounced in both hippocampus and cortex of Gpx4 BiKO mice. These features, which included elevated lipid peroxidation (4-HNE adducts), elevated gliosis (GFAP, Iba1), increased pro-inflammatory cytokine production, and increased ERK1/2 phosphorylation strongly suggested that neurodegeneration in Gpx4 BiKO mice occurred via ferroptosis. Knowing that vitamin-E has anti-ferroptotic properties, we next examined the effects of vitamin-E deficiency on the rate of neurodegeneration in Gpx4 BiKO mice. As expected, Gpx4 BiKO on VED exhibited a noticeably expedited rate of hippocampal neurodegeneration appearing at 2 weeks post Gpx4 ablation. Taken together, our results indicate that forebrain neurons are indeed susceptible to ferroptosis and that ferroptosis may be an important degenerative mechanism of neurons in AD.

The Anti-Inflammatory Role of Minocycline in Alzheimer´s Disease.

Alzheimer's disease (AD) is a neurodegenerative disorder where the main risk factor is age, since its incidence increases dramatically after the age of 60. It is the most common form of dementia, and is accompanied by memory loss and cognitive impairment. Although AD was discovered over a century ago, the only drugs approved by the US Food and Drug Administration for use in its treatment are four cholinesterase inhibitors and memantine. However, these drugs are not fully effective in the treatment of AD. Therefore, the incessant search for new methods of treating AD continues, with the hope of improving both the effectiveness of therapies and the quality of life for patients suffering with AD. Current evidence suggests that the antibiotic minocycline could be a potential therapeutic drug for use in the treatment of AD due to its anti-neuroinflammatory effects. Minocycline is a tetracycline derivative that combines an anti-inflammatory property that is capable of crossing the blood brain barrier with neuroprotective properties that work by limiting inflammation and oxidative stress. Several studies have established the presence of inflammatory markers in the brains of patients suffering with AD, including elevated levels of cytokines/chemokines and microgliosis in damaged regions. Cytokines have been associated with increased tau phosphorylation and decreased levels of synaptophysin, establishing their roles in the cytoskeletal and synaptic alterations that take place in AD. Therefore, pharmacological approaches that allow for the discovery and development of new anti-inflammatory agents such as minocycline will be welcomed in the continuing struggle against AD. Considering these facts, this review will discuss the anti-inflammatory mechanisms underlying the neuroprotective effects of minocycline as a novel therapeutic approach for the treatment of AD.

Perinatal exposure to lead (Pb) induces ultrastructural and molecular alterations in synapses of rat offspring.

Lead (Pb), environmentally abundant heavy-metal pollutant, is a strong toxicant for the developing central nervous system. Pb intoxication in children, even at low doses, is found to affect learning and memorizing, with devastating effects on cognitive function and intellectual development. However, the precise mechanism by which Pb impairs synaptic plasticity is not fully elucidated. The purpose of this study was to investigate the effect of pre- and neonatal exposure to low dose of Pb (with Pb concentrations in whole blood below 10μg/dL) on the synaptic structure and the pre- and postsynaptic proteins expression in the developing rat brain. Furthermore, the level of brain-derived neurotrophic factor (BDNF) was analyzed. Pregnant female Wistar rats received 0.1% lead acetate (PbAc) in drinking water from the first day of gestation until weaning of the offspring, while the control animals received drinking water. During the feeding of pups, mothers from the Pb-group were continuously receiving PbAc. Pups of both groups were weaned at postnatal day 21 and then until postnatal day 28 received only drinking water. 28-day old pups were sacrificed and the ultrastructural changes as well as expression of presynaptic (VAMP1/2, synaptophysin, synaptotagmin-1, SNAP25, syntaxin-1) and postsynaptic (PSD-95) proteins were analyzed in: forebrain cortex, cerebellum and hippocampus. Our data revealed that pre- and neonatal exposure to low dose of Pb promotes pathological changes in synapses, including nerve endings swelling, blurred and thickened synaptic cleft structure as well as enhanced density of synaptic vesicles in the presynaptic area. Moreover, synaptic mitochondria were elongated, swollen or shrunken in Pb-treated animals. These structural abnormalities were accompanied by decrease in the level of key synaptic proteins: synaptotagmin-1 in cerebellum, SNAP25 in hippocampus and syntaxin-1 in cerebellum and hippocampus. In turn, increased level of synaptophysin was noticed in the cerebellum, while the expression of postsynaptic PSD-95 was significantly decreased in forebrain cortex and cerebellum, and raised in hippocampus. Additionally, we observed the lower level of BDNF in all brain structures in comparison to control animals. In conclusion, perinatal exposure to low doses of Pb caused pathological changes in nerve endings associated with the alterations in the level of key synaptic proteins. All these changes can lead to synaptic dysfunction, expressed by the impairment of the secretory mechanism and thereby to the abnormalities in neurotransmission as well as to the neuronal dysfunction.

Bone marrow stromal cells promote neuroplasticity of cerebral ischemic rats via a phosphorylated CRMP2-mediated mechanism

Collapsin response mediator protein 2 (CRMP2), an important protein involved in axonal growth and the maintenance of neuronal membrane integrity, has proved to be altered in nervous system diseases. This study was aimed to investigate the role of CRMP2 in bone marrow stromal cells (BMSCs) treating rats with cerebral ischemia. BMSCs were isolated from shaft of the femurs, tibiae, and humeri and were intra-carotid administrated immediately after middle cerebral artery occlusion (MCAO). Modified Neurological Severity Scores (mNSS) was conducted at 3, 7, 14dpo and the electrophysiologic evaluation was evaluated at 14dpo. Then all rats were sacrificed and brain tissues were harvested for RT-PCR, Western blot and Immunohistochemistry analysis. We found BMSCs treatment significantly improved the neurobehavioral performance impaired by ischemic brain injury, accompanied with the notably increasing levels of Synaptophysin (SYP) and Growth associated protein 43 (GAP43). We also found the protein level of phosphorylated CRMP2 (p-CRMP2) and phosphorylation-mediated protein including Glycogen synthase kinase 3 Beta (GSK3β), Cyclin-dependent kinase 5 (CDK5) were dramatically downregulated in ischemic rats following BMSCs transplant. Furthermore, the GSK3β-mediated factors including neurotrophic and signaling factors were all significantly upregulated in BMSCs-treated group. On the basis of these findings, we suggest that the neuroplasticity effect of BMSCs on cerebral ischemia may be associated with the phosphorylated modulation of CRMP2.

Blast waves from detonated military explosive reduce GluR1 and synaptophysin levels in hippocampal slice cultures

Explosives create shockwaves that cause blast-induced neurotrauma, one of the most common types of traumatic brain injury (TBI) linked to military service. Blast-induced TBIs are often associated with reduced cognitive and behavioral functions due to a variety of factors. To study the direct effects of military explosive blasts on brain tissue, we removed systemic factors by utilizing rat hippocampal slice cultures. The long-term slice cultures were briefly sealed air-tight in serum-free medium, lowered into a 37°C water-filled tank, and small 1.7-gram assemblies of cyclotrimethylene trinitramine (RDX) were detonated 15cm outside the tank, creating a distinct shockwave recorded at the culture plate position. Compared to control mock-treated groups of slices that received equal submerge time, 1–3 blast impacts caused a dose-dependent reduction in the AMPA receptor subunit GluR1. While only a small reduction was found in hippocampal slices exposed to a single RDX blast and harvested 1–2days later, slices that received two consecutive RDX blasts 4min apart exhibited a 26–40% reduction in GluR1, and the receptor subunit was further reduced by 64–72% after three consecutive blasts. Such loss correlated with increased levels of HDAC2, a histone deacetylase implicated in stress-induced reduction of glutamatergic transmission. No evidence of synaptic marker recovery was found at 72h post-blast. The presynaptic marker synaptophysin was found to have similar susceptibility as GluR1 to the multiple explosive detonations. In contrast to the synaptic protein reductions, actin levels were unchanged, spectrin breakdown was not detected, and Fluoro-Jade B staining found no indication of degenerating neurons in slices exposed to three RDX blasts, suggesting that small, sub-lethal explosives are capable of producing selective alterations to synaptic integrity. Together, these results indicate that blast waves from military explosive cause signs of synaptic compromise without producing severe neurodegeneration, perhaps explaining the cognitive and behavioral changes in those blast-induced TBI sufferers that have no detectable neuropathology.

An enriched environment enhances synaptic plasticity and cognition post-stroke

Objective To observe the effects of an enriched environment (EE) on cognitive functioning and the synaptic plasticity of mice modeling post-stroke cognitive impairment (PSCI) and explore the possible mechanisms involved. Methods Mice modeling PSCI and sham-operated mice were randomly divided into 3 groups: sham-operated mice in a standard environment (the Sham+ SE group), PSCI mice in a standard environment (the PSCI+ SE group) and PSCI mice in an enriched environment (the PSCI+ EE group). The cognitive functioning of all of the mice was quantified using a Morris water maze and their hippocampal long-term potentiation (LTP) was recorded using an electrophysiological method. The level of synaptophysin was detected using Western blotting. Synaptic ultrastructure in the hippocampus was imaged using electron microscopy. Results Compared with the Sham+ SE group, the PSCI+ SE group showed significantly poorer water maze performance and failed induction of contralateral LTP. Their average level of synaptophysin was significantly lower, and significant adverse changes in the synaptic ultrastructure of the hippocampus were observed, including a decreased number of synapses. The average width of the synaptic cleft, postsynaptic density and the interface curvature of the synapses were all less desirable. All of the measurements of the PSCI+ EE group improved significantly compared to those of the PSCI+ SE group, but were still significantly poorer than those of the Sham+ SE group. Conclusions An enhanced environment can improve the cognitive functioning of mice modelling PSCI. It may be that an EE can improve synaptic plasticity in the hippocampus contralateral to the stroke. Key words: Stroke; Cognitive impairment; Enriched environments; Synaptic plasticity

The mechanism of 5-lipoxygenase in the impairment of learning and memory in rats subjected to chronic unpredictable mild stress

ObjectivesTo examine the mechanism of 5-lipoxygenase (5-LO) in the learning and memory dysfunction in rats subjected to chronic unpredictable mild stress (CUMS). MethodsEighty rats were divided into eight groups: the 0.5% sodium carboxymethyl cellulose solution (NaCMC)-treated group, empty vector (LV-Mock)-treated group, CUMS+NaCMC-treated group, CUMS+sertraline-treated group, CUMS+caffeic acid (10mg/kg)-treated group, CUMS+caffeic acid (30mg/kg)-treated group, CUMS+LV-Mock-treated group, and CUMS+5-LO-silencers lentiviral vectors (LV-si-5-LO)-treated group, n=10. Sucrose preference tests were performed to assess depression-like behavior. The Morris water maze and step-down tests were used to evaluate learning and memory performance. The levels of inflammatory cytokines, malondialdehyde, and the activity of superoxide dismutase (SOD) were detected to estimate inflammation and oxidative stress. Changes in 5-LO mRNA and protein were detected using reverse transcription polymerase chain reaction and Western blotting. The expression of synaptophysin, postsynaptic density-95 (PSD-95), and brain-derived neurotrophic factor (BDNF) in the hippocampus were measured using immunohistochemical staining. ResultsTreatment with caffeic acid or LV-si-5-LO increased sucrose consumption, decreased escape latency and increased the number of platform crosses in the Morris water maze test, and decreased the number of errors and prolonged the latency in the step-down test. We observed a decreased expression of 5-LO, and levels of malondialdehyde, leukotriene-B4, tumor necrosis factor-α, and interleukin-6, while the protein levels of synaptophysin, PSD-95, BDNF, and the activity of SOD were increased in the hippocampus of the CUMS-treated rats. ConclusionsCUMS-induced impairment in learning and memory could be triggered by an inflammatory response in the rat hippocampus, which results in oxidative stress injury and impacts the synaptic plasticity of hippocampal neurons. Inhibition of the activity or expression of 5-LO could suppress hippocampal inflammation, enhance synaptic plasticity, and improve learning and memory function in depressed rats.

Decreased synaptic proteins in neuronal exosomes of frontotemporal dementia and Alzheimer's disease.

Synaptic dysfunction occurs early in senile dementias, presumably as a result of decreased levels of functional synaptic proteins as found in autopsied brains of patients with Alzheimer's disease (AD) or frontotemporal dementia (FTD). Plasma neuronal-derived exosomes (NDEs) were recovered by precipitation and immunoabsorption from 12 patients with AD, 16 with FTD, and 28 controls in a cross-sectional study, and from 9 patients with AD, 10 with FTD, and 19 controls in a longitudinal study. Six synaptic proteins in NDE extracts were quantified by ELISAs and normalized for exosome amounts. NDE levels of synaptophysin, synaptopodin, synaptotagmin-2, and neurogranin were significantly lower in patients with FTD and AD than in controls, but those of growth-associated protein 43 and synapsin 1 were reduced only in patients with AD. Functionally relevant phosphorylation of synapsin 1 serine 9 was reduced in patients with FTD and AD, although total synapsin 1 protein was higher in FTD than in controls. NDE levels of synaptotagmin, synaptophysin, and neurogranin were decreased years before dementia in patients with FTD and AD. NDE levels of synaptopodin, synaptotagmin, and synaptophysin, but not of amyloid β-peptide 42 or P-T181-tau, were correlated significantly with cognition assessed by mini-mental state examination or AD assessment scale-cognitive subscale. NDE synaptic proteins may be useful preclinical indices and progression measures in senile dementias.-Goetzl, E. J., Kapogiannis, D., Schwartz, J. B., Lobach, I. V., Goetzl, L., Abner, E. L., Jicha, G. A., Karydas, A. M., Boxer, A., Miller, B. L. Decreased synaptic proteins in neuronal exosomes of frontotemporal dementia and Alzheimer's disease.