Protein Arc Research Articles

91 CAUSAL AND GENETIC EPIDEMIOLOGY OF URBANICITY AS A RISK FACTOR FOR PSYCHOSIS

Understanding resilience is a major challenge to improve current pharmacological therapies aimed at complementing psychological-based approaches of stress-related disorders. In particular, resilience is a multi-factorial construct where the complex network of molecular events that drive the process still needs to be resolved. Here, we exploit the acute escape deficit model, an animal model based on exposure to acute unavoidable stress followed by an escape test, to define vulnerable and resilient phenotypes in rats. Hippocampus and prefrontal cortex (PFC), two of the brain areas most involved in the stress response, were analysed for gene expression at two different time points (3 and 24 h) after the escape test. Total Brain-Derived Neurotrophic Factor (BDNF) was highly responsive in the PFC at 24-h after the escape test, while expression of BDNF transcript IV increased in the hippocampus of resistant animals 3 h post-test. Expression of memory enhancers like Neuronal PAS Domain Protein 4 (Npas4) and Activity-regulated cytoskeleton-associated protein (Arc) decreased in a time- and region-dependent fashion in both behavioural phenotypes. Also, the memory inhibitor Protein Phosphatase 1 (Ppp1ca) was increased in the hippocampus of resilient rats at 3 h post-test. Given the importance of neurotrophic factors and synaptic plasticity-related genes for the development of appropriate coping strategies, our data contribute to an additional step forward in the comprehension of the psychobiology of stress and resiliency.

Memantine Attenuates Salicylate-induced Tinnitus Possibly by Reducing NR2B Expression in Auditory Cortex of Rat.

Memantine, a noncompetitive antagonist of the N-methyl-d-aspartate (NMDA) receptor, suppresses the release of excessive levels of glutamate that may induce neuronal excitation. Here we investigated the effects of memantine on salicylate-induced tinnitus model. The expressions of the activity-regulated cytoskeleton-associated protein (ARC) and tumor necrosis factor-alpha (TNF α) genes; as well as the NMDA receptor subunit 2B (NR2B) gene and protein, were examined in the SH-SY5Y cells and the animal model. We also used gap-prepulse inhibition of the acoustic startle reflex (GPIAS) and noise burst prepulse inhibition of acoustic startle, and the auditory brainstem level (electrophysiological recordings of auditory brainstem responses, ABR) and NR2B expression level in the auditory cortex to evaluate whether memantine could reduce salicylate-mediated behavioral disturbances. NR2B was significantly upregulated in salicylate-treated cells, but downregulated after memantine treatment. Similarly, expression of the inflammatory cytokine genes TNFα and immediate-early gene ARC was significantly increased in the salicylate-treated cells, and decreased when the cells were treated with memantine. These results were confirmed by NR2B immunocytochemistry. GPIAS was attenuated to a significantly lesser extent in rats treated with a combination of salicylate and memantine than in those treated with salicylate only. The mean ABR threshold in both groups was not significant different before and 1 day after the end of treatment. Additionally, NR2B protein expression in the auditory cortex was markedly increased in the salicylate-treated group, whereas it was reduced in the memantine-treated group. These results indicate that memantine is useful for the treatment of salicylate-induced tinnitus.

Secreted Amyloid Precursor Protein-Alpha Promotes Arc Protein Synthesis in Hippocampal Neurons

Secreted amyloid precursor protein-α (sAPPα) is a neuroprotective and memory-enhancing molecule, however, the mechanisms through which sAPPα promotes these effects are not well understood. Recently, we have shown that sAPPα enhances cell-surface expression of glutamate receptors. Activity-related cytoskeletal-associated protein Arc (Arg3.1) is an immediate early gene capable of modulating long-term potentiation, long-term depression and homeostatic plasticity through regulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor localization. Accordingly, we hypothesized that sAPPα may enhance synaptic plasticity, in part, by the de novo synthesis of Arc. Using primary cortical and hippocampal neuronal cultures we found that sAPPα (1 nM, 2 h) enhances levels of Arc mRNA and protein. Arc protein levels were increased in both the neuronal somata and dendrites in a Ca2+/calmodulin-dependent protein kinase II-dependent manner. Additionally, dendritic Arc expression was dependent upon activation of mitogen-activated protein kinase and protein kinase G. The enhancement of dendritic Arc protein was significantly reduced by antagonism of N-methyl-D-aspartate (NMDA) and nicotinic acetylcholine (α7nACh) receptors, and fully eliminated by dual application of these antagonists. This effect was further corroborated in area CA1 of acute hippocampal slices. These data suggest sAPPα-regulated plasticity within hippocampal neurons is mediated by cooperation of NMDA and α7nACh receptors to engage a cascade of signal transduction molecules to enhance the transcription and translation of Arc.

Lotus seedpod proanthocyanidins protect against neurotoxicity after methyl-mercuric chloride injury

In the present study, to investigate the prevention mechanism of proanthocyanidins from lotus seedpod (LSPCs) on methyl mercuric chloride (MMC) induced neurotoxicity, neuron/astrocyte cells were co-cultured to simulate the microenvironment in vivo to the greatest extent. The results showed that, compared with MMC group, pretreatment with LSPCs not only improved cell survival rate, decreased the release of lactate dehydrogenase (LDH), decreased the intracellular reactive oxygen species (ROS) level, and prevented the increase of intracellular [Ca2+]i, but also significantly increased the total anti-oxidation capacity (T-AOC) (p＜0.05), the levels of glutathione peroxidase (GSH-Px) (p＜0.05), glutathione (GSH) (p＜0.05), and mitochondrial membrane potential (MMP) (p＜0.01). Besides, LSPCs up-regulated the expression of transcriptional factor Nrf2/HO-1 in a concentration-dependent manner. Moreover, LSPCs reduced the expression of Bax protein, significantly increased the expression of Bcl-xl, Bcl-2, β-Ⅲ-Tubulin, SYN, and Arc proteins. The expression of these proteins is mainly regulated by genes and reflects the changes of genes functions. Taken together, these results suggested that LSPCs could enhance cellular antioxidant defense capacity through regulating the activation of Nrf2/HO-1, and involving the inhibition of mitochondria-mediated apoptotic signaling pathway.

Ancient foes and helpers: Research sheds new light on the role that retroviruses play in disease, innate immunity and neural plasticity.

Ancient retrovirus infections played a role in human evolution and are still involved in innate immunity and neural plasticity.

Assessment of genes involved in behavior, learning, memory, and synaptic plasticity following status epilepticus in rats

ObjectiveIn this study, it was aimed to evaluate cognitive and behavioral changes after status epilepticus (SE) induced by pentylenetetrazole in immature rats via Morris water maze and open-field area tests and to assess alterations in expression of 84 key genes involved in synaptic plasticity after SE. MethodThe study was conducted on 30 immature rats (12-days old). The rats were assigned into groups as control and experiment (SE) groups. The SE was induced by pentylenetetrazole in 12-days old rats. In addition, experiment group was divided into two groups as mature (n = 8) and immature SE (n = 8) subgroups. Again, the control group was divided into two groups as mature (n = 7) and immature control (n = 7) subgroups. Hippocampal tissue samples were prepared, and expression of 84 key genes involved in synaptic plasticity was assessed in Genome and Stem Cell Center of Erciyes University before behavioral tests in immature rats (22-days old) and after open-filed area and Morris water maze tests in mature rats (72-days old) in both experiment and control groups. ResultsNo significant difference was detected in behavioral tests assessing spatial memory and learning among groups. Significant differences were detected, ARC (activity-regulated cytoskeleton-associated protein), BDNF (brain-derived neurotrophic factor), MAPK1 (mitogen-activated protein kinase 1), NR4A1 (nuclear receptor subfamily 4 group A member 1), PPP3CA (protein phosphatase 3 catalytic subunit alpha), RGS2 (regulator of G protein signaling 2), and TNF (tumor necrosis factor) gene expressions between control and experiment groups in immature rats whereas in ADCY8 (adenylate cyclase 8), BDNF (brain-derived neurotrophic factor), EGR4 (early growth response 4), and KIF17 (kinesin family member 17) gene expressions between control and experiment groups in mature rats. DiscussionIn this study, differences detected in gene expressions of synaptic plasticity after SE indicate in which steps of synaptic plasticity may be problematic in epileptogenesis. The gene expressions in this study may be considered as potential biomarkers; however, epileptogenesis is a dynamic process and cannot be explained through a single mechanism. Future studies on epileptogenesis and studies specifically designed to evaluate genes detected in our study will further elucidate synaptic plasticity in epilepsy and epileptogenesis.

Characterization and Transcriptional Activation of the Immediate Early Gene ARC During a Neural Correlate of Classical Conditioning.

Plasticity and learning genes require regulatory mechanisms that have the flexibility to respond to a variety of sensory stimuli to generate adaptive behavioral responses. The immediate early gene (IEG) activity-regulated cytoskeleton-associated protein (ARC) is rapidly induced not only by neuronal stimulation but also during a variety of learning tasks. How ARC is regulated in response to complex stimuli during associative learning remains to be fully detailed. Here, we characterized the structure of the ARC gene in the pond turtle and mechanisms of its transcriptional activation during a neural correlate of eyeblink classical conditioning. The tARC gene is regulated in part by the presence of paused polymerase (RNAPII) that is poised at the promoter for rapid gene induction. Conditioning induces permissive chromatin modifications in the tARC promoter that allows binding by the transcription factor cAMP response element-binding protein (CREB) within 5min of training. During learning acquisition, the pausing factor negative elongation factor (NELF) dissociates from the promoter thereby releasing RNAPII for active transcription. Data additionally suggest that the DNA insulator protein CCCTC-binding factor (CTCF) is required for transcription by mediating a learning-induced interaction of the ARC promoter with an enhancer element. Our study suggests that the learning-inducible IEG tARC utilizes both paused RNAPII and rapid chromatin modifications that allow for dynamic gene responsiveness required when an organism is presented with a variety of environmental stimuli.

High-fat diet reduces novelty-induced expression of activity-regulated cytoskeleton-associated protein.

Chronic high-fat-diet (HFD) consumption can lead to the development of brain insulin resistance, which then exerts deleterious effects on learning and memory. Activity-regulated cytoskeleton-associated protein (Arc) is a memory-related protein, and its expression can be induced by insulin stimulation. In HFD-fed animals, their basal Arc protein levels in cerebral cortex and hippocampus are reduced. However, the effects of HFD on novelty-induced Arc protein expression that is important for cognitive function is still unknown. In the present study, after feeding HFD (60% kcal from fat) for 5 weeks, mice developed brain insulin resistance and had a significant reduction in the novelty-induced but not the basal Arc protein levels in their hippocampi. Further experiments were performed in primary rat hippocampal neurons. The results show that, under the condition of neuronal insulin resistance, acute insulin stimulation induced less activation of the phosphatidylinositol 3-kinase/protein kinase B/p70 ribosomal S6 kinase (PI3K/Akt/p70S6K) pathway, resulting in reduced induction of Arc protein expression. Accordingly, it is suggested that following HFD feeding, the reduction in novelty-induced Arc protein expression in animal's hippocampus is probably related to a suppressed activation of the PI3K/Akt/p70S6K pathway due to the existence of brain insulin resistance.

Copulation induces expression of the immediate early gene Arc in mating-relevant brain regions of the male rat

The medial amygdala (MeA), bed nucleus of the stria terminalis (BNST), and medial preoptic area (mPOA) are important for the regulation of male sexual behavior. Sexual experience facilitates sexual behaviors and influences activity in these regions. The goal of this study was to determine whether sexual experience or copulation induces plasticity in the MeA, BNST, or mPOA of male rats, as indicated by changes in levels of Arc, which is indicative of activity-dependent synaptic plasticity in the brain. To this end, sexually naïve or experienced males were placed in mating arenas either alone, with an inaccessible estrus female, or with an accessible estrus female. Arc protein levels were then quantified in these three regions using immunohistochemistry. As expected, sexual experience facilitated copulation, as evidenced by a reduction in latencies to mount, intromit, and ejaculate. Copulation also increased the number of Arc-positive cells in the MeA, anterior BNST, posterior BNST, and the posterior mPOA, but not in the central-rostral region of the mPOA. Surprisingly, prior sexual experience did not impact levels of Arc, suggesting that copulation-induced Arc occurs in both sexually naïve and experienced males.

Influence of acupuncture plus moxibustion on changes of synaptic structure and expression of synaptic skeleton related genes and proteins in prefrontal cortex of heroin re-addicted rats

To observe the effect of acupuncture plus moxibustion on the synaptic ultrastructure and expression of synaptic skeleton related proteins in the prefrontal cortex (PFC) of heroin re-addicted rats, so as to reveal its mechanisms underlying improvement of heroin addiction. Twenty-four Wister rats (half male and half female) were randomly divi-ded into normal control, model and acupuncture groups (n＝8 in each group). The heroin re-addicted model was established by muscular injection of heroin into the hind limbs for 8 days (incremental 0.8-3.6 mg, once daily for 6 days, and twice daily for 2 days), followed by conventional breeding for 5 days (detoxification), the procedure (addition－detoxification) was repeated 3 cycles. For rats of the acupuncture group, "Baihui" (GV20) was needled with filiform needles which were retained for 30 min, and moxibustion was then applied to bilateral "Shenshu" (BL23) for 30 min. The treatment was conducted once daily during the deto-xification. On the 39th day of experiment, the bilateral prefrontal cortex tissues were sampled for examining the ultrastructure by using transmission electron microscope (TEM) after fixative solution immersion and for determining the expression of genes and proteins of activity-regulated cytoskeleton-associated protein (Arc), microtubule-asso-ciated protein-2 (MAP-2) and microtubule-associated protein Tau (Tau) with quantitative real-time PCR and Western blot, respectively. After modeling, the expression levels of Arc mRNA and protein were significantly up-regulated, and those of MAP-2 and Tau mRNA and proteins ob-viously down-regulated in the model group relevant to the normal control group (P<0.05). Following the intervention, the up-regulated Arc protein and mRNA and the down-regulated MAP-2 and Tau were obviously reversed relevant to the model group (P<0.05). Outcomes of TEM showed unclear pre- and post-membranes of the synapses, narrowing of the synaptic gap and non-uniform of the density of the thickened dense plaque after modeling, which was relatively milder in the acupuncture group. Acupuncture plus moxibustion can improve changes of synaptic ultrastructure in heroin re-addicted rats, which may be related to their effect in regulating the expression of some synaptic skeleton proteins and genes.

The Capsid Domain of Arc Changes Its Oligomerization Propensity through Direct Interaction with the NMDA Receptor

The activity-regulated cytoskeleton-associated protein, Arc, is highly expressed in neuronal dendrites and is involved in synaptic scaling and plasticity. Arc exhibits homology to the capsid-forming Gag proteins from retroviruses and can encapsulate its own mRNA and transport it to neighboring neurons. However, the molecular events that lead to the assembly of Arc capsids and how the capsid formation is regulated are not known. Here we show that the capsid domain of Arc may transiently form homogeneous oligomers of similar size as capsids formed byfull-length Arc. We determined a high-resolution structure of the monomeric Arc capsid domain and mapped the initial structural change in the oligomerization process to the N-terminal part of the capsid domain. Peptide ligands from the NMDA receptor subunits inhibit oligomerization, which suggests that Arc's ability to transfer mRNA between cells may be regulated by protein-protein interactions at the synapse.

Resveratrol Regulates BDNF, trkB, PSA-NCAM, and Arc Expression in the Rat Cerebral Cortex after Bilateral Common Carotid Artery Occlusion and Reperfusion.

The polyphenol resveratrol (RVT) may drive protective mechanisms of cerebral homeostasis during the hypoperfusion/reperfusion triggered by the transient bilateral common carotid artery occlusion followed by reperfusion (BCCAO/R). This immunochemical study investigates if a single dose of RVT modulates the plasticity-related markers brain-derived neurotrophic factor (BDNF), the tyrosine kinase trkB receptor, Polysialylated-Neural Cell Adhesion Molecule (PSA-NCAM), and Activity-regulated cytoskeleton-associated (Arc) protein in the brain cortex after BCCAO/R. Frontal and temporal-occipital cortical regions were examined in male Wistar rats randomly subdivided in two groups, sham-operated and submitted to BCCAO/R. Six hours prior to surgery, half the rats were gavage fed a dose of RVT (180 mg·kg−1 in 300 µL of sunflower oil as the vehicle), while the second half was given the vehicle alone. In the frontal cortex of BCCAO/R vehicle-treated rats, BDNF and PSA-NCAM decreased, while trkB increased. RVT pre-treatment elicited an increment of all examined markers in both sham- and BCCAO/R rats. No variations occurred in the temporal-occipital cortex. The results highlight a role for RVT in modulating neuronal plasticity through the BDNF-trkB system and upregulation of PSA-NCAM and Arc, which may provide both trophic and structural local support in the dynamic changes occurring during the BCCAO/R, and further suggest that dietary supplements such as RVT are effective in preserving the tissue potential to engage plasticity-related events and control the functional response to the hypoperfusion/reperfusion challenge.

An evidence-based approach for the development of therapy recommendations in integrative paediatrics

Biomarkers associated with inflammation and immune function are increasingly being used to examine mechanisms of the effects of mind-body therapies. Less researched are biomarkers associated with cognitive and executive functioning in the study of mind-body therapy mechanisms and effects. This study explored the feasibility of recruiting breast cancer patients (BCPs) and implementation fidelity of participation in a research project utilizing the 4-stage Creative Psychosocial Genomic Healing Experience (CPGHE), a mind-body protocol that is theorized to create epigenetic effects via targeted psychological change in emotional triggers in coping with cancer.Eight BCPs were identified as eligible (stages I, II, III, early phases of treatment) and five consented to one of two intervention groups (allocated to a single session or two sessions of CPGHE). Blood draws were examined pre- and post-intervention for a stress/inflammation gene expression marker, Nuclear Factor kappa-B (NF-kB), and three markers associated with synaptic plasticity undergirding cognitive and executive functioning: Early Growth Response 1 (EGR1), activity-regulated cytoskeleton-associated protein (Arc), and brain-derived neurotrophic factor (BDNF).One consented BCP dropped out due to illness. The remaining four adhered to the 4-stage CPGHE protocol and found the CPGHE experience beneficial. Blood samples for the gene expression results were collected and processed according to planned protocol without incident.Implementing the CPGHE and achieving good adherence among a sample of BCPs is feasible. Processing of blood samples collected from BCPs for gene expression data is also feasible.

Expression of Ang II/TGF beta 1 signaling pathway in kidney of diabetic nephropathy rats and effects of polydatin on it

Biomarkers associated with inflammation and immune function are increasingly being used to examine mechanisms of the effects of mind-body therapies. Less researched are biomarkers associated with cognitive and executive functioning in the study of mind-body therapy mechanisms and effects. This study explored the feasibility of recruiting breast cancer patients (BCPs) and implementation fidelity of participation in a research project utilizing the 4-stage Creative Psychosocial Genomic Healing Experience (CPGHE), a mind-body protocol that is theorized to create epigenetic effects via targeted psychological change in emotional triggers in coping with cancer.Eight BCPs were identified as eligible (stages I, II, III, early phases of treatment) and five consented to one of two intervention groups (allocated to a single session or two sessions of CPGHE). Blood draws were examined pre- and post-intervention for a stress/inflammation gene expression marker, Nuclear Factor kappa-B (NF-kB), and three markers associated with synaptic plasticity undergirding cognitive and executive functioning: Early Growth Response 1 (EGR1), activity-regulated cytoskeleton-associated protein (Arc), and brain-derived neurotrophic factor (BDNF).One consented BCP dropped out due to illness. The remaining four adhered to the 4-stage CPGHE protocol and found the CPGHE experience beneficial. Blood samples for the gene expression results were collected and processed according to planned protocol without incident.Implementing the CPGHE and achieving good adherence among a sample of BCPs is feasible. Processing of blood samples collected from BCPs for gene expression data is also feasible.

Activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) regulates anxiety- and novelty-related behaviors.

The activity-regulated cytoskeleton-associated protein (Arc, also known as Arg3.1) regulates glutamatergic synapse plasticity and has been linked to neuropsychiatric illness; however, its role in behaviors associated with mood and anxiety disorders remains unclear. We find that stress upregulates Arc expression in the adult mouse nucleus accumbens (NAc)-a brain region implicated in mood and anxiety behaviors. Global Arc knockout mice have altered AMPAR-subunit surface levels in the adult NAc, and the Arc-deficient mice show reductions in anxiety-like behavior, deficits in social novelty preference, and antidepressive-like behavior. Viral-mediated expression of Arc in the adult NAc of male, global Arc KO mice restores normal levels of anxiety-like behavior in the elevated plus maze (EPM). Consistent with this finding, viral-mediated reduction of Arc in the adult NAc reduces anxiety-like behavior in male, but not female, mice in the EPM. NAc-specific reduction of Arc also produced significant deficits in both object and social novelty preference tasks. Together our findings indicate that Arc is essential for regulating normal mood- and anxiety-related behaviors and novelty discrimination, and that Arc's function within the adult NAc contributes to these behavioral effects.

Hippocampal Arc protein expression and conditioned fear.

Arc (Activity-regulated cytoskeleton-associated protein) is an effector neuronal immediate-early gene (IEG) and has been closely linked to behaviorally-induced neuronal plasticity. The present studies examined the regionally-selective, dissociable patterns of Arc expression induced by Pavlovian trace fear conditioning, delay fear conditioning, and contextual fear conditioning as well as novel context exposure. This research was guided by anatomical studies identifying heterogeneity of connectivity across the transverse (CA1, CA3) and septo-temporal (dorsal vs. ventral) axes of the hippocampus; companion neuropsychological experiments suggest that these subregions likely play functionally dissociable roles in different forms of hippocampal-dependent learning. Hence the primary goal of the present study was to characterize the expression of Arc protein across both the septotemporal and transverse axes of the hippocampus induced by hippocampal dependent trace fear conditioning and compare these expression patterns to those induced by other fear conditioning paradigms. A second goal of these studies was to explore which specific paradigmatic features of the fear conditioning task itself are responsible for the observed patterns of Arc expression. The results of these studies suggest that, within the dorsal hippocampus, Arc expression in CA3 induced by trace fear conditioning may play a unique role in representing the context, while Arc protein expression within ventral CA3 may reflect CS processing. Arc protein expression in dorsal and ventral CA1 are likely not meaningfully involved in trace fear conditioning as there is either a lack of significant enhancement (dorsal CA1) or enhancement is not unique to subjects trained in trace fear conditioning (ventral CA1). The specific regional pattern of Arc protein enhancement induced by trace fear conditioning may reflect the unique temporal parameters of the task which critically engages the hippocampus in processing both contextual representations as well as the explicit CS. This additional hippocampal processing may account for the greater enhancement in Arc protein in dorsal and ventral CA3 for subjects trained in trace fear conditioning compared to novel context exposure, or contextual and delay fear conditioning.

Atorvastatin attenuates lysophosphatidic acid‐induced tau hyperphosphorylation through p38 MAPK kinase pathway in an Alzheimer's disease model

The prevalence of Alzheimer's disease (AD) is currently estimated to be around 6 million cases and is predicted to rapidly increase in the coming decades. The currently approved treatments fail to alter the underlying pathophysiology, provide only modest and temporary symptomatic relief and are associated with several side effects. Recent evidence suggests that vascular factors, in particular, lysophosphatidic acid (LPA), the most bioactive component of oxidized low‐density lipoprotein (oxLDL), play a crucial role in the pathophysiology of AD. Increased levels of LPA lead to activation of several intracellular signaling cascades thereby leading to neuroinflammation and neurodegeneration. Statins are cholesterol lowering agents of proven benefit in vascular disease and are also associated with reduction in circulating oxLDL levels. Additionally, several clinical studies suggest the risk of AD was substantially reduced with statins. Hence, the goal of the proposed research is to evaluate the role of the LPA signaling in AD pathogenesis and the effect of statin (atorvastatin) in attenuating LPA induced cognitive dysfunction. In vitro studies utilizing ShSy5y neuronal cell line showed atorvastatin attenuated LPA induced Amyloid beta and tau hyperphosphorylation. The effect of LPA on p38 MAPK Kinase and it's downstream signaling markers of apoptosis (BAX, BCL2) and inflammation (NF‐Kβ, IL‐6, TNFα) was analyzed through biochemical assays. We will utilize a high fat diet mouse model, to investigate the neuroprotective effects of atorvastatin. Novel object location test, Y‐maze and contextual fear conditioning will be performed to evaluate cognitive and behavioral deficits. To assess the effects of LPA and atorvastatin on hippocampal synaptic plasticity, we will measure long term potentiation and long‐term depression, which are the cellular correlates of learning and memory. Golgi cox staining to study the effect of LPA and atorvastatin on dendritic spine morphology is being performed. Western blot will also be used to measure levels of AMPA and NMDA receptor subunits. Biochemical assays will be performed to quantify levels of PSD‐95, synaptophysin, and ARC protein, which are proteins essential for synaptic maturity and plasticity. Finally, the neuroprotective effect of atorvastatin on LPA induced cognitive dysfunction will be analyzed by measuring the levels of autotaxin (ATX), an enzyme important for LPA synthesis. 4, 8‐ and 12‐months aged age. We believe our study will demonstrate that that atorvastatin through its pleotropic effects, attenuate LPA induced cognitive dysfunction by improving behavioral and cognitive deficits, synaptic dysfunction, and reducing the pathologies of AD thereby uncovering a molecular mechanism of LPA induced dyshomeostasis in AD.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

3'-Daidzein Sulfonate Sodium Protects Against Chronic Cerebral Hypoperfusion-Mediated Cognitive Impairment and Hippocampal Damage via Activity-Regulated Cytoskeleton-Associated Protein Upregulation.

The learning and memory impairment caused by chronic cerebral hypoperfusion (CCH) is permanent and seriously affects the daily life of patients and their families. The compound 3′-daidzein sulfonate sodium (DSS) protects against CCH-mediated memory impairment and hippocampal damage in a rat model. In the present study, we further investigated the underlying mechanisms of this effect in the rat two-vessel occlusion (2VO) and the oxygen and glucose deprivation (OGD) primary hippocampal neuron models. The hippocampal expression of the activity-regulated cytoskeleton associated protein (Arc) following DSS administration was detected in vivo and in vitro and behavioral testing was used to investigate the role of Arc in the DSS-mediated rescue of CCH-induced neurotoxicity. DSS increased hippocampal Arc expression both in vivo and in vitro. Arc overexpression increased and Arc knockdown decreased hippocampal neuronal densities in rat 2VO model, when compared to DSS treatment alone. Arc overexpression decreased and Arc knockdown increased apoptotic hippocampal neurons in rat 2VO and OGD primary hippocampal neuron models, when compared to DSS treatment alone. Arc overexpression enhanced and Arc knockdown inhibited the beneficial effect of DSS on 2VO-induced cognitive impairment. DSS restored the neuronal OGD-mediated phosphorylation decrease in protein kinase alpha (PKA), extracellular signal-regulated protein kinases 1/2 (ERK1/2) and cAMP response element binding protein (CREB), in vitro. PKA and ERK1/2 inhibition blocked the DSS-mediated effects on neuronal apoptosis and OGD-induced Arc downregulation. In conclusion, DSS protects against CCH-mediated cognitive impairment and hippocampal damage via Arc upregulation, which is activated by the PKA/CREB and ERK/CREB signaling pathways. Our study further confirms the potential use of DSS as an effective treatment for CCH-associated diseases.

27-Hydroxycholesterol Alters Synaptic Structural and Functional Plasticity in Hippocampal Neuronal Cultures.

This study aimed to explore the neurotoxic effects of 27-hydroxycholesterol (27-OHC), a major circulating cholesterol active derivative in brain on synaptic structural and functional plasticity in primary hippocampal neurons. Newborn SD rat primary hippocampal neurons were treated with 0, 1, 3, 10, and 30 μM 27-OHC for 24 hours. MTT and CCK-8 assays were used to monitor the cell viability of neurons with different treatments. Neurite morphology was assessed by staining for microtubule-associated protein-2 (MAP2) and analyzed by immunofluorescence. Synaptic ultrastructure was evaluated by transmission electron microscopy. Real-time polymerase chain reaction and Western blot analyses were used to evaluate the expression of key synaptic proteins: synaptophysin (SYP), postsynaptic density protein-95 (PSD-95), synaptosomal-associated protein 25 (SNAP-25), growth-associated protein-43 (GAP-43), MAP2, and activity-regulated cytoskeleton-associated protein (Arc). Treatment with 27-OHC at various doses stimulated cell death and resulted in significant decreases in neurite number and length, alteration of synaptic ultrastructure, and downregulated expression of synaptic proteins in a dose-dependent manner. These results suggest that 27-OHC is deleterious for synaptic structural and functional plasticity, which may partially account for its neurotoxic effects.

A Specific Role of Hippocampal NMDA Receptors and Arc Protein in Rapid Encoding of Novel Environmental Representations and a More General Long-Term Consolidation Function.

Activation of the NMDA receptor (NMDAR) has been proposed to be a key event responsible for the structural changes that occur in neurons during learning and memory formation. It has been extensively studied yet no consensus has been reached on its mnemonic role as both NMDAR dependent and independent forms of learning have been observed. We investigated the role that hippocampal NMDAR have in rapid spatial learning and memory across training environments. Hippocampal NMDAR was blocked via intra-hippocampal injection of the competitive antagonist CPP. Groups of rats were pre-trained on a spatial version of the Morris water task, and then mass reversal training under NMDAR blockade occurred in the same or different training environments as pre-training. We measured expression of Arc protein throughout the main hippocampal subfields, CA1, CA3, and dentate gyrus, after mass-training. We observed that NMDAR blockade allowed for rapid spatial learning, but not consolidation, when the SUBJECTS used previously acquired environmental information. Interestingly, NMDAR blockade impaired rapid spatial learning when rats were mass-trained in a novel context. Arc protein expression in the dentate gyrus followed this pattern of NMDAR dependent spatial behavior, with high levels of expression observed after being trained in the new environment, and low levels when trained in the same environment. CPP significantly reduced Arc expression in the dentate gyrus. These results implicate dentate NMDAR in the acquisition of novel environmental information.