Loss and microglia phagocytosis of synaptic proteins in frontotemporal lobar degeneration with TDP-43 proteinopathy

Cortical synaptic loss has emerged as an early abnormality in Alzheimer's disease (AD) with a strong relationship to cognitive performance. However, the status of synapses in frontotemporal lobar degeneration (FTLD) has received meager experimental attention. The purpose of this study was to investigate changes in cortical synaptic proteins in FTLD with tar DNA binding protein-43 (TDP-43) proteinopathy. A second aim was to study phagocytosis of synaptic proteins by microglia as a surrogate for synaptic pruning. Western blot analysis in frozen tissue from the middle frontal gyrus revealed decreased levels of the presynaptic protein synaptophysin, but slightly increased levels of the postsynaptic density protein 95 (PSD95) in FTLD-TDP. Levels of the dendritic spine protein spinophilin displayed the largest decrease. Double immunofluorescent staining visualized aggregate or punctate synaptic protein immunoreactivity in microglia. Overall, the proportion of microglia containing synaptic proteins was larger in FTLD-TDP when compared with normal controls. The increase in PSD95 levels may represent reactive upregulation of this protein, as suggested in AD. While greater numbers of microglia containing synaptic proteins is consistent with loss of synapses in FTLD-TDP, it may also be an indication of abnormal synaptic pruning by microglia.

Zexieyin formula alleviates atherosclerosis with cognitive impairment: A novel role in the treatment of comorbidities and its underlying mechanisms

ETHNOPHARMACOLOGICAL RELEVANCY

Zexieyin formula (ZXYF) has been identified to have therapeutic actions of atherosclerosis (AS). It's unknown that whether ZXYF has therapeutic potential of atherosclerosis (AS) with cognitive impairment (CI) and its underlying mechanisms.

AIM OF THE STUDY

To elucidate therapeutic effect of ZXYF for AS with CI as well as its underlying mechanisms in AS with CI mice model.

METHODS AND MATERIALS

To establish AS with CI model, we fed ApoE-/- mice with high-fat diet (HFD) for 8 weeks. Oil red O staining (ORO) and Hematoxylin-eosin staining (HE) were used to detect aortic plaque area. Morris water maze (MWM) and Y-maze were used to measure cognitive function and cognitive improvement after administration of ZXYF and atorvastatin (ATO). Network pharmacology was used to screen for potential mechanisms for improving cognitive function. Western blot was used to detect expressions of MAPK, Aβ and synaptic proteins in hippocampus.

RESULTS

HFD caused and accelerated the AS in ApoE-/- mice, while it was easier able to produce CI than normal mice. Administration of ZXYF or ATO for 8 weeks significantly reduced aortic plaque area in ORO and HE tests, and improved cognitive abilities in MWM and Y-maze tests. Network pharmacology results showed that MAPK or synaptic proteins were highly associated with CI. HFD contributed to abnormal expressions of MAPK (pERK, pP38, pJNK), NF-kB, synaptic proteins (PSD95, synapsin1) and β-amyloid (Aβ) in hippocampus, which were all reversed by ZXYF. However, ERK and PSD95 expressions were not reversed by ATO in hippocampus.

CONCLUSIONS

ZXYF mitigated AS, further alleviating CI by modulating MAPK signaling, relating to synaptic proteins enhancing and Aβ protein decreasing in the hippocampus. This study firstly lit up the new clinical application of ZXYF, which might promote the use of ZXYF in AS and CI patients.

Sericin Improves Memory Impairment Via Activation of the PKA-CREB-BDNF Signaling Pathway and Suppression of Oxidative Stress in Ovariectomized Mice

Menopause results in estrogen hormone deficiency which causes changes in brain morphology and cognitive impairments. The risk of breast and ovarian cancer increases with estrogen therapy. Thus, finding a substitute treatment option for women in menopause is necessary. In the current study, the impact of chronic sericin treatment (200 mg/kg/day for 6 weeks, gavage) on memory process, oxidative stress markers, synaptic neurotransmission, and acetylcholinesterase (AChE) activity in the hippocampus (HIP) of ovariectomized (OVX) mice was examined and compared to the effects of 17β-estradiol (Es; 20 µg/kg, s.c.). The results demonstrated that sericin and Es administration improved spatial and recognition memory of the OVX animals in the both Lashley III maze and novel object recognition tests. Moreover, sericin-treated OVX mice showed decreased ROS levels, increased endogenous antioxidant defense capacity, and decreased AChE activity in the HIP. Additionally, sericin and Es therapy up-regulated pre-and-post-synaptic protein markers and increased BDNF, CREB, and protein kinase A (PKA) protein expressions in the HIP of OVX mice. Overall, the activation of the PKA-CREB-BDNF signaling pathway by sericin can provide protection against OVX-induced cognitive dysfunction, making it a potential alternative for managing cognitive deficits in postmenopausal women.

Sleep deprivation aggravates lipopolysaccharide-induced anxiety, depression and cognitive impairment: The role of pro-inflammatory cytokines and synaptic plasticity-associated proteins

Growing evidence indicates that neuroinflammation plays a critical role in anxiety, depression, and cognitive impairment. Sleep loss disrupts the host's immune balance and increases neuroinflammation. This study explored whether chronic sleep deprivation aggravates lipopolysaccharide-induced anxiety, depression, and cognitive impairment and assessed the underlying mechanisms. Lipopolysaccharide (250 μg/kg) was administered to adult mice for 9 days, accompanied with daily intermittent sleep deprivation from 12:00 to 18:00 by using an activity wheel. Anxiety, depression, and cognitive function were evaluated using a task battery consisting of an open field, elevated plus maze, tail suspension, forced swimming, and Morris water maze tests. The levels of pro-inflammatory cytokines and synaptic plasticity-associated proteins were examined by enzyme-linked immunosorbent assay and western blot, respectively. The results showed that lipopolysaccharide increased anxiety- and depression-like behaviors, impaired cognitive function, uprelated interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and decreased brain-derived neurotrophic factor (BDNF), postsynaptic density-95 (PSD-95), and synaptophysin (SYN), which were aggravated by chronic sleep deprivation. These results suggest that chronic sleep deprivation exerted adverse effects on lipopolysaccharide-induced anxiety, depression, and cognitive impairment, which was associated with changes in pro-inflammatory cytokines and synaptic plasticity associated proteins.

Involvement of protein L-isoaspartyl methyltransferase in the physiopathology of neurodegenerative diseases: Possible substrates associated with synaptic function

Synaptic dysfunction is a typical pathophysiologic change in neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Hintington's disease (HD) and amyotrophic lateral sclerosis (ALS), which involves protein post-translational modifications (PTMs) including L-isoaspartate (L-isoAsp) formed by isomerization of aspartate or deamidation of asparagine. The formation of L-isoAsp could be repaired by protein L-isoaspartyl methyltransferase (PIMT). Some synaptic proteins have been identified as PIMT potential substrates and play an essential role in ensuring synaptic function. In this review, we discuss the role of certain synaptic proteins as PIMT substrates in neurodegenerative disease, thus providing therapeutic synapse-centered targets for the treatment of NDs.

Early postnatal development of the MDGA2+/- mouse model of synaptic dysfunction

Synaptic dysfunction underlies many neurodevelopmental disorders (NDDs). The membrane-associated mucin domain-containing glycosylphosphatidylinositol anchor proteins (MDGAs) regulate synaptic development by modulating neurexin-neuroligin complex formation. Since understanding the neurodevelopmental profile and the sex-based differences in the manifestation of the symptoms of NDDs is important for their early diagnosis, we tested a mouse model haploinsufficient for MDGA2 (MDGA2+/-) on a neurodevelopmental test battery, containing sensory, motor, and cognitive measures, as well as ultrasonic vocalizations. When male and female MDGA2+/- and wildtype (WT) C57BL/6 J mice were examined from 2 to 23 days of age using this test battery, genotype and sex differences in body weight, sensory-motor processes, and ultrasonic vocalizations were observed. The auditory startle reflex appeared earlier in the MDGA2+/- than in WT mice and the MDGA2+/- mice produced fewer ultrasonic vocalizations. The MDGA2+/- mice showed reduced locomotion and rearing than WT mice in the open field after 17 days of age and spent less time investigating a novel object than WT mice at 21 days of age. Female MDGA2+/- mice weighed less than WT females and showed lower grip strength, indicating a delay in sensory-motor development in MDGA2+/- mice, which appears to be more pronounced in females than males. The behavioural phenotypes resulting from MDGA2 haploinsufficiency suggests that it shows delayed development of motor behaviour, grip strength and exploratory behaviour, non-social phenotypes of NDDs.

Cynarin, a caffeoylquinic acid derivative in artichoke, inhibits exocytotic glutamate release from rat cortical nerve terminals (synaptosomes)

The purpose of this study was to evaluate the effect of cynarin, a caffeoylquinic acid derivative in artichoke, on glutamate release elicited by 4-aminopyridine (4-AP) in rat cortical nerve terminals (synaptosomes). We observed that cynarin decreased 4-aminopyridine-elicited glutamate release, which was prevented by the removal of external free Ca²⁺ with ethylene glycol bis (β-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) or the blockade of P/Q-type calcium channels with ω-agatoxin IVA. Molecular docking also revealed that cynarin formed a hydrogen bond with the P/Q-type Ca²⁺ channel, indicating a mechanism of action involving Ca²⁺ influx inhibition. Additionally, the inhibitory effect of cynarin on glutamate release is associated with a change in the available synaptic vesicles, as cynarin decreased 4-AP-elicited FM1-43 release or hypertonic sucrose-evoked glutamate release from synaptosomes. Furthermore, the suppression of protein kinase A (PKA) prevented the effect of cynarin on 4-AP-elicited glutamate release. 4-AP-elicited PKA and synapsin I or synaptosomal-associated protein of 25 kDa (SNAP-25) phosphorylation at PKA-specific residues were also attenuated by cynarin. Our data indicate that cynarin, through the suppression of P/Q-type Ca²⁺ channels, inhibits PKA activation and attenuates synapsin I and SNAP-25 phosphorylation at PKA-specific residues, thus decreasing synaptic vesicle availability and contributing to glutamate release inhibition in cerebral cortex terminals.

Translationally controlled tumor protein restores impaired memory and altered synaptic protein expression in animal models of dementia

This study describes the effects of translationally controlled tumor protein (TCTP) on mice with memory impairment caused by scopolamine (SCO) administration. Specifically, memory functions and expression levels of hippocampal synaptic proteins in 7- to 12-month-old SCO-treated wild-type (WT-SCO) mice were compared to those of TCTP-overexpressing (TG) and TCTP knocked-down (KD) mice similarly treated with SCO. Passive-avoidance tasks were performed with WT, TG, and KD mice for four weeks after intraperitoneal injection of SCO or saline followed by an acquisition test. After completing behavioral studies, hippocampi of all mice groups were collected and their synaptic protein contents were subjected to Western blotting or immunohistochemical analyses, and compared with those of 5x familial Alzheimer's disease (5xFAD) mice and postmortem AD patients. Results of passive avoidance tests revealed that SCO-induced memory impairment was repaired in TCTP-TG mice, but not in TCTP-KD mice. Hippocampal expression levels of synaptophysin, synapsin-1, and PSD-95 were increased in TCTP-TG mice treated with SCO (TG-SCO) but decreased in TCTP-KD mice treated with SCO (KD-SCO). Decreased levels of TCTP, synaptophysin, and PSD-95 were also found in hippocampi of 5xFAD mice and AD patients. Expression levels of p-CREB/CREB and brain-derived neurotrophic factor (BDNF) in TCTP-TG and TG-SCO mice were similar to or increased compared to those in WT mice, but decreased in TCTP-KD and KD-SCO mice. BDNF immunoreactivity was restored in CA1 regions of hippocampi of TG-SCO mice, but not in KD-SCO mice. These results suggest that TCTP can restore damaged memory in mice possibly through restored synaptic protein expression.

Delayed Outgrowth in Response to the BDNF and Altered Synaptic Proteins in Neurons From SHR Rats

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity symptoms. Neuroimaging studies have revealed a delayed cortical and subcortical development pattern in children diagnosed with ADHD. This study followed up on the development in vitro of frontal cortical neurons from Spontaneously hypertensive rats (SHR), an ADHD rat model, and Wistar-Kyoto rats (WKY), control strain, over their time in culture, and in response to BDNF treatment at two different days in vitro (DIV). These neurons were also evaluated for synaptic proteins, brain-derived neurotrophic factor (BDNF), and related protein levels. Frontal cortical neurons from the ADHD rat model exhibited shorter dendrites and less dendritic branching over their time in culture. While pro- and mature BDNF levels were not altered, the cAMP-response element-binding (CREB) decreased at 1 DIV and SNAP-25 decreased at 5 DIV. Different from control cultures, exogenous BDNF promoted less dendritic branching in neurons from the ADHD model. Our data revealed that neurons from the ADHD model showed decreased levels of an important transcription factor at the beginning of their development, and their delayed outgrowth and maturation had consequences in the levels of SNAP-25 and may be associated with less response to BDNF. These findings provide an alternative tool for studies on synaptic dysfunctions in ADHD. They may also offer a valuable tool for investigating drug effects and new treatment opportunities.

Acupuncture inhibits autophagy and repairs synapses by activating the mTOR pathway in Parkinson's disease depression model rats

Acupuncture is a good treatment for depression in Parkinson's disease (DPD), so the possible mechanism of acupuncture in the treatment of DPD was explored in this study. Firstly, observing the behavioral changes of the DPD rat model, the regulation of monoamine neurotransmitters dopamine (DA) and 5-hydroxytryptamine (5-HT) in the midbrain, the change of α-synuclein (α-syn) in the striatum, the efficacy of acupuncture in the treatment of DPD was discussed. Secondly, autophagy inhibitors and activators were selected to judge the effect of acupuncture on autophagy in the DPD rat model. Finally, an mTOR inhibitor was used to observe the effect of acupuncture on the mTOR pathway in the DPD rat model. The results showed that acupuncture could improve the motor and depressive symptoms of DPD model rats, increase the content of DA and 5-HT, and decrease the content of ɑ-syn in the striatum. Acupuncture inhibited the expression of autophagy in the striatum of DPD model rats. At the same time, acupuncture upregulates p-mTOR expression, inhibits autophagy, and promotes synaptic protein expression. Therefore, we concluded that acupuncture might improve the behavior of DPD model rats by activating the mTOR pathway, inhibiting autophagy from removing α-syn and repairing synapses.

Tunicamycin induces depression-like behaviors in male rats, accompanied by initiated chaperon-mediated autophagy and decreased synaptic protein expression in the hippocampus

BACKGROUND AND AIM

Endoplasmic reticulum (ER) stress participates in the occurrence and development of depression, but the underlying mechanism is not fully understood. This study aimed to investigate the behavioral performance and intracerebral molecular changes in an ER stress model of male rats.

METHODS

Intrahippocampal injection of tunicamycin (TM) was performed on male rats as a model of ER stress. The body weight was determined, and behavioral tests, including sucrose preference test (SPT), open field test (OFT), and forced swimming test (FST), were performed to evaluate depressive and anxiety-like phenotypes within 8 days after injection. The levels of chaperone-mediated autophagy (CMA), synaptic proteins, and neuroinflammation related factors in this model were measured via real-time quantitative PCR and Western blot analysis.

RESULTS

Intrahippocampal injection of TM (2 or 1 μg) induced depression-like behaviors in rats, as indicated by the reduced body weight, sucrose preference in SPT, central time in OFT, and increased immobility time in FST. The mRNA and protein levels of GRP78, ATF4, CHOP, LAMP2A, IL-1β, IL-6, and TNF-α were significantly increased, while the expressions of MEF2D, PSD95, SYN, p-CREB (Ser133), and BDNF were significantly decreased in the hippocampus in the model group compared with the sham group.

CONCLUSIONS

These results confirmed that intrahippocampal injection of TM was a valid method to induce an ER stress rat model with depression-like behaviors accompanied by decreased synaptic protein expression and neuroinflammation. The alteration in CMA-related proteins in this ER stress depression model indicated the involvement of CMA in the development of depression.

The antidepressant-like effect elicited by vitamin D3 is associated with BDNF/TrkB-related synaptic protein synthesis

Vitamin D₃ (cholecalciferol) has been shown to exert antidepressant-like responses, but the role BDNF/TrkB-related synaptic plasticity in this effect remains to be established. Thus, this study investigated the time-course antidepressant-like response of vitamin D₃ in female and male mice and the possible role of BDNF/TrkB signaling in this response. The repeated (7 and 21 days), but not acute (60 min), administration of vitamin D₃ (2.5 μg/kg, p.o.) exerted an antidepressant-like effect in female and male mice subjected to the tail suspension test, without altering the basal locomotor activity in the open-field test. Notably, vitamin D₃ caused a similar time-dependent antidepressant-like effect in male and female mice, suggesting that this behavioral response in the tail suspension test might not be affected by sex differences. Vitamin D₃ administration for 21 days, but not for 7 days or 1 h, augmented BDNF levels in the hippocampus and prefrontal cortex of mice. No effects on phospho-CREB/CREB levels were detected in the hippocampus and prefrontal cortex after chronic vitamin D₃ administration. Additionally, vitamin D₃ increased TrkB, GluA1, and PSD-95 levels in the prefrontal cortex, but not in the hippocampus. Furthermore, an upregulation of synapsin level was observed in both brain regions after vitamin D₃ administration. These findings reinforce and extend the notion that vitamin D₃ is effective to produce antidepressant-like responses in male and female mice and provide novel evidence that this effect could be associated with BDNF/TrkB-related synaptic protein synthesis. Finally, vitamin D₃ could be a feasible nutritional strategy for the management of depression.

Complexins: Ubiquitously Expressed Presynaptic Regulators of SNARE-Mediated Synaptic Vesicle Fusion

Neurotransmitter release is a spatially and temporally tightly regulated process, which requires assembly and disassembly of SNARE complexes to enable the exocytosis of transmitter-loaded synaptic vesicles (SVs) at presynaptic active zones (AZs). While the requirement for the core SNARE machinery is shared by most membrane fusion processes, SNARE-mediated fusion at AZs is uniquely regulated to allow very rapid Ca2+-triggered SV exocytosis following action potential (AP) arrival. To enable a sub-millisecond time course of AP-triggered SV fusion, synapse-specific accessory SNARE-binding proteins are required in addition to the core fusion machinery. Among the known SNARE regulators specific for Ca2+-triggered SV fusion are complexins, which are almost ubiquitously expressed in neurons. This chapter summarizes the structural features of complexins, models for their molecular interactions with SNAREs, and their roles in SV fusion.

Rehabilitation on a treadmill induces plastic changes in the dendritic spines of spinal motoneurons associated with improved execution after a pharmacological injury to the motor cortex in rats

Lesions to the corticospinal tract result in several neurological symptoms and several rehabilitation protocols have proven useful in attempts to direct underlying plastic phenomena. However, the effects that such protocols may exert on the dendritic spines of motoneurons to enhance accuracy during rehabilitation are unknown. Thirty three female Sprague-Dawley adult rats were injected stereotaxically at the primary motor cerebral cortex (Fr1) with saline (CTL), or kainic acid (INJ), or kainic acid and further rehabilitation on a treadmill 16 days after lesion (INJ+RB). Motor performance was evaluated with the the Basso, Beatie and Bresnahan (BBB) locomotion scale and in the Rotarod. Spine density was quantified in a primary dendrite of motoneurons in Lamina IX in the ventral horn of the thoracolumbar spinal cord as well as spine morphology. AMPA, BDNF, PSD-95 and synaptophysin expression was evaluated by Western blot. INJ+RB group showed higher scores in motor performance. Animals from the INJ+RB group showed more thin, mushroom, stubby and wide spines than the CTL group, while the content of AMPA, BDNF, PSD-95 and Synaptophysin was not different between the groups INJ+RB and CTL. AMPA and synaptophysin content was greater in INJ group than in CTL and INJ+RB groups. The increase in the proportion of each type of spine observed in INJ+RB group suggest spinogenesis and a greater capability to integrate the afferent information to motoneurons under relatively stable molecular conditions at the synaptic level.

Cognitive dysfunctions and spontaneous EEG alterations induced by hippocampal amyloid pathology in rats

PURPOSE

We aimed to determine the effects of different doses of amyloid-beta (Aβ) peptide on learning and memory, and whether the changes in brain oscillations induced by dose-dependent accumulation of Aβ could be used as biomarkers to detect early stages of Alzheimer's disease (AD).

MATERIAL AND METHODS

Male albino Wistar rats aged 3 months were randomly divided into four groups (n ​= ​12/group) obtained by i. h. Injection (to the dorsal hippocampus) of saline or different doses of 0.01 ​μg/μl, 0.1 ​μg/μl, and 1 ​μg/μl of Aβ. After two weeks of recovery period, open field and novel object recognition tests were performed and spontaneous EEG recordings were obtained. Later, hippocampus tissues were collected for Western blot and ELISA analysis.

RESULTS

A significant decrement in recognition memory was observed in 0.1 ​μg/μl, and 1 ​μg/μl injected groups. In addition, Aβ accumulation induced significant decrement of the expression of NeuN, SNAP-25, SYP, and PSD-95 proteins, and led to the increment of GFAP expression in hippocampus. Moreover, we detected remarkable alterations in spontaneous brain activity. The hippocampal Aβ levels were negatively correlated with hippocampal gamma power and positively correlated with hippocampal theta power. Also, we observed significant changes in coherence values, indicating the functional connectivity between different brain regions, after the accumulation of Aβ. Especially, there was a significant correlation between changes in frontohippocampal theta coherence and in frontotemporal theta coherence.

CONCLUSIONS

Our findings indicate that Aβ peptide induces AD-like molecular changes at certain doses, and these changes could be detected by evaluating brain oscillations.

Nicotine exposure through breastfeeding affects BDNF and synaptic proteins levels in the brain of stressed adult female mice

Nicotine has been used during pregnancy and lactation as a tobacco harm reduction strategy. However, it is unclear whether nicotine exposure during a critical development period negatively impacts stress responses in adulthood. This study investigated how nicotine, administered via breastfeeding, affects the brain-derived neurotrophic factor (BDNF), synaptic proteins levels, and anxiety-like behavior in adult female mice subjected to stress. Female Swiss mice were exposed to saline or nicotine (8 mg/kg/day) through breastfeeding between their fourth and 17th postnatal days (P) via implanted osmotic mini pumps. The unpredictable chronic mild stress (UCMS) protocol was performed during their adulthood (P65) for 10 consecutive days, followed by the elevated plus maze (EPM) test one day after the protocol. Animals were euthanized and their blood, collected for plasma corticosterone measurements and their brain structures, dissected for BDNF and synaptic proteins analyses. We found no significant differences in corticosterone levels between groups (Saline/Non-stress, Nicotine/Non-stress, Saline/Stress, and Nicotine/Stress). The UCMS protocol hindered weight gain. Mice exposed to nicotine through breastfeeding with or without the UCMS protocol in adulthood showed higher grooming and head dipping frequency; decreased BDNF levels in cerebellum and striatum; increased postsynaptic density protein 95 (PSD-95), synapsin I, and synaptophysin levels in cerebellum; and decreased PSD-95 and synapsin I levels in brainstem. Our results indicate that nicotine exposure through breastfeeding leads to long-lasting behavioral effects and synaptic protein changes, most of which were independent of the UCMS protocol, even after a long nicotine-free period, highlighting the importance of further studies on nicotine exposure during development.

Microglial polarization differentially affects neuronal vulnerability to the β-amyloid protein: Modulation by melatonin

Microglial cells play a central but yet debated role in neuroinflammatory events occurring in Alzheimer's disease (AD). We here explored how microglial features are modulated by melatonin following β-amyloid (Aβ42)-induced activation and examined the cross-talk with Aβ-challenged neuronal cells. Human microglial HMC3 cells were exposed to Aβ42 (200 nM) in the presence of melatonin (MEL; 1 μM) added since the beginning (MELco) or after a 72 h-exposure to Aβ42 (MELpost). In both conditions, MEL favored an anti-inflammatory activation and rescued SIRT1 and BDNF expression/release. Caspase-1 up-regulation and phospho-ERK induction following a prolonged exposure to Aβ42 were prevented by MEL. In addition, MEL partially restored proteasome functionality that was altered by long-term Aβ42 treatment, re-establishing both 20S and 26S chymotrypsin-like activity. Differentiated neuronal-like SH-SY5Y cells were exposed to Aβ42 (200 nM for 24 h) in basal medium or in the presence of conditioned medium (CM) collected from microglia exposed for different times to Aβ42 alone or in combination with MELco or MELpost. Aβ42 significantly reduced pre-synaptic proteins synaptophysin and VAMP2 and mean neuritic length. These effects were prevented by CM from anti-inflammatory microglia (Aβ42 for 6 h), or from MELco and MELpost microglia, but the reduction of neuritic length was not rescued when the SIRT1 inhibitor EX527 was added. In conclusion, our data add to the concept that melatonin shows a promising anti-inflammatory action on microglia that is retained even after pro-inflammatory activation, involving modulation of proteasome function and translating into neuroprotective microglial effects.

Prenatal Activation of Glucocorticoid Receptors Induces Memory Impairment in a Sex-Dependent Manner: Role of Cyclooxygenase-2

Prenatal exposure to dexamethasone (DEX) results in long-lasting effects on cognitive functions such as learning and memory impairment. However, the mechanisms underlying these DEX-induced deleterious effects are not well known. Here, we assessed whether cyclooxygenase-2 (COX-2) is involved in the impact of prenatal exposure to DEX on learning and memory during adulthood. Pregnant Sprague-Dawley rats received daily injections of either DEX (0.2 mg/kg; i.p.) or saline from gestation day (GD) 14 until GD21. Gene and protein expression of COX-2, as well as presynaptic (synaptophysin) and postsynaptic (postsynaptic density protein-95) proteins, were monitored in the dorsal and ventral hippocampi of adult male and female offspring. A different cohort of adult male and female rat offspring was given daily injections of either vehicle or a specific COX-2 inhibitor (celecoxib 10 mg/kg, i.p.) for 5 consecutive days and was subsequently subjected to Morris water maze memory test. Prenatal DEX enhanced the expression of COX-2 protein and cox-2 mRNA in the dorsal hippocampus of adult female but not male rats. This enhanced COX-2 expression was associated with reduced expression in pre- and postsynaptic proteins and altered memory acquisition and retention. Administration of COX-2-specific inhibitor alleviated prenatal DEX-induced memory impairment in adult female rats. This study suggests that prenatal activation of glucocorticoid receptors stimulates COX-2 gene and protein expression and impairs hippocampal-dependent spatial memory in female but not male rat offspring. Furthermore, COX-2 selective inhibitors can be used to alleviate the long-lasting deleterious effects of corticosteroid medication during pregnancy.

Cognitive impairments in type 1 diabetes mellitus model mice are associated with synaptic protein disorders

An association between type 1 diabetes mellitus (T1DM) and cognitive impairment was recently reported. However, the mechanisms by which T1DM induces cognitive impairment are still unknown. Here, we confirmed that T1DM mice induced by streptozotocin (STZ) injection had impaired working memory and spatial memory. We observed long-term potentiation (LTP) induction defects and synaptic loss in mice 20 weeks after STZ injection. We also found decreased levels of synaptic proteins, including the N-methyl-D-aspartic acid receptor (NMDAR) subunit NR2A, synaptophysin (SYP), and postsynaptic density 95 (PSD95), in the hippocampus and prefrontal cortex, revealing similarities in the alteration patterns of these synaptic proteins in aged Alzheimer's disease (AD) APP/PS1 mice and T1DM mice. Taken together, these findings expand our understanding of the mechanisms underlying T1DM-induced cognitive impairment.

Soybean Meal Extract Preserves Memory Ability by Increasing Presynaptic Function and Modulating Gut Microbiota in Rats

Age-related degenerative brain diseases frequently manifest as memory deficits. Dietary interventions or nutraceuticals may provide efficacious treatments through prevention and cure. Soybean meal, a byproduct of soy oil refining, has health benefits, but its effect on memory function is unknown. Therefore, we evaluated the effect of the oral administration of soybean meal extract (SME) for 2 weeks on memory function using the Morris water maze (MWM) test in healthy rats and investigated the possible underlying mechanisms. First, analysis of the composition revealed that SME is rich in isoflavones; SME did not exhibit hepatotoxicity or renal toxicity at the different doses tested. The MWM results revealed that the escape latency and movement distance of rats were significantly shorter in the SME group than in the control group, indicating that SME can help in memory preservation. In addition, SME increased the levels of presynaptic proteins such as synaptophysin, synaptobrevin, synaptotagmin, syntaxin, synapsin I, and 25-kDa synaptosome-associated protein as well as protein kinases and their phosphorylated expression, including extracellular signal-regulated kinases 1 and 2 (ERK1/2), protein kinase C (PKC), and Ca2+/calmodulin-dependent protein kinase II (CaMKII) in the hippocampal nerve terminals (synaptosomes). Transmission electron microscopy also indicated that SME increased the number of synaptic vesicles in hippocampal synaptosomes. Furthermore, SME rats exhibited altered microbiota composition compared with control rats. Therefore, our data suggest that SME can increase presynaptic function and modulate gut microbiota, thus aiding in memory preservation in rats.

A Guide to Analysis of Relative Synaptic Protein Abundance by Quantitative Fluorescent Western Blotting

The introduction of fluorescent detection systems has revolutionized the applicability of Western blotting for quantitative protein expression analyses. The fundamental premise behind fluorescent Western blotting is the combination of distinct fluorescent dye-conjugated secondary antibodies and high performance digital imaging solutions in which the fluorescence signal is directly proportional to the amount of protein enabling quantitative measurements and simultaneous detection of several target proteins. This aspect of Western blotting is now widely used, especially in preclinical research, to detect quantitative changes in protein levels and phosphorylation status between experimental groups. This chapter provides a detailed step-by-step guide for best practice procedures during the entire process from sample preparation, SDS polyacrylamide gel electrophoresis to electrotransfer of proteins and highlights approaches that can be applied to increase data output.

Rats bred for low intrinsic aerobic exercise capacity link obesity with brain inflammation and reduced structural plasticity of the hippocampus

BACKGROUND

Increasing evidence shows obesity and poor metabolic health are associated with cognitive deficits, but the mechanistic connections have yet to be resolved. We studied rats selectively bred for low and high intrinsic aerobic capacity in order to test the association between low physical fitness, a genetic predisposition for obesity, and brain health. We hypothesized that low-capacity runner (LCR) rats with concurrently greater levels of adiposity would have increased hippocampal inflammation and reduced plasticity compared to the more physically fit high-capacity runner (HCR) rats.

METHODS

We examined markers for inflammation and brain plasticity in the hippocampi of LCR rats and compared them to HCR rats. The effect of age was determined by studying the rats at a young age (8 weeks) and later in life (40 weeks). We used western blots and immunohistochemistry to quantify the expression of target proteins.

RESULTS

Our study showed that the number of adult-born new neurons in the hippocampus was significantly lower in LCR rats than it was in HCR rats already at a young age and that the difference became more pronounced with age. The expression of synaptic proteins was higher in young animals relative to older ones. Brain inflammation tended to be higher in LCR rats than it was in the HCR rats, and more prominent in older rats than in young ones.

CONCLUSION

Our study is the first to demonstrate that low intrinsic aerobic fitness that is associated with obesity and poor metabolic health is also linked with reduced hippocampal structural plasticity at a young age. Our results also suggest that inflammation of the brain could be one factor mediating the link between obesity and poor cognitive performance.

Neuroplasticity induced by the retention period of a complex motor skill learning in rats

Learning complex motor skills is an essential process in our daily lives. Moreover, it is an important aspect for the development of therapeutic strategies that refer to rehabilitation processes since motor skills previously acquired can be transferred to similar tasks (motor skill transfer) or recovered without further practice after longer delays (motor skill retention). Different acrobatic exercise training (AE) protocols induce plastic changes in areas involved in motor control and improvement in motor performance. However, the plastic mechanisms involved in the retention of a complex motor skill, essential for motor learning, are not well described. Thus, our objective was to analyze the brain plasticity mechanisms involved in motor skill retention in AE . Motor behavior tests, and the expression of synaptophysin (SYP), synapsin-I (SYS), and early growth response protein 1 (Egr-1) in brain areas involved in motor learning were evaluated. Young male Wistar rats were randomly divided into 3 groups: sedentary (SED), AE, and AE with retention period (AER). AE was performed three times a week for 8 weeks, with 5 rounds in the circuit. After a fifteen-day retention interval, the AER animals was again exposed to the acrobatic circuit. Our results revealed motor performance improvement in the AE and AER groups. In the elevated beam test, the AER group presented a lower time and greater distance, suggesting retention period is important for optimizing motor learning consolidation. Moreover, AE promoted significant plastic changes in the expression of proteins in important areas involved in control and motor learning, some of which were maintained in the AER group. In summary, these data contribute to the understanding of neural mechanisms involved in motor learning in an animal model, and can be useful to the construction of therapeutics strategies that optimize motor learning in a rehabilitative context.

Prefrontal cortex VAMP1 gene network moderates the effect of the early environment on cognitive flexibility in children

During development, genetic and environmental factors interact to modify specific phenotypes. Both in humans and in animal models, early adversities influence cognitive flexibility, an important brain function related to behavioral adaptation to variations in the environment. Abnormalities in cognitive functions are related to changes in synaptic connectivity in the prefrontal cortex (PFC), and altered levels of synaptic proteins. We investigated if individual variations in the expression of a network of genes co-expressed with the synaptic protein VAMP1 in the prefrontal cortex moderate the effect of early environmental quality on the performance of children in cognitive flexibility tasks. Genes overexpressed in early childhood and co-expressed with the VAMP1 gene in the PFC were selected for study. SNPs from these genes (post-clumping) were compiled in an expression-based polygenic score (PFC-ePRS-VAMP1). We evaluated cognitive performance of the 4 years-old children in two cohorts using similar cognitive flexibility tasks. In the first cohort (MAVAN) we utilized two CANTAB tasks: (a) the Intra-/Extra-dimensional Set Shift (IED) task, and (b) the Spatial Working Memory (SWM) task. In the second cohort, GUSTO, we used the Dimensional Change Card Sort (DCCS) task. The results show that in 4 years-old children, the PFC-ePRS-VAMP1 network moderates responsiveness to the effects of early adversities on the performance in attentional flexibility tests. The same result was observed for a spatial working memory task. Compared to attentional flexibility, reversal learning showed opposite effects of the environment, as moderated by the ePRS. A parallel ICA analysis was performed to identify relationships between whole-brain voxel based gray matter density and SNPs that comprise the PFC-ePRS-VAMP1. The early environment predicts differences in gray matter content in regions such as prefrontal and temporal cortices, significantly associated with a genetic component related to Wnt signaling pathways. Our data suggest that a network of genes co-expressed with VAMP1 in the PFC moderates the influence of early environment on cognitive function in children.

Optimization of protocols for pre-embedding immunogold electron microscopy of neurons in cell cultures and brains

Immunogold labeling allows localization of proteins at the electron microscopy (EM) level of resolution, and quantification of signals. The present paper summarizes methodological issues and experiences gained from studies on the distribution of synaptic and other neuron-specific proteins in cell cultures and brain tissues via a pre-embedding method. An optimal protocol includes careful determination of a fixation condition for any particular antibody, a well-planned tissue processing procedure, and a strict evaluation of the credibility of the labeling. Here, tips and caveats on different steps of the sample preparation protocol are illustrated with examples. A good starting condition for EM-compatible fixation and permeabilization is 4% paraformaldehyde in PBS for 30 min at room temperature, followed by 30 min incubation with 0.1% saponin. An optimal condition can then be readjusted for each particular antibody. Each lot of the secondary antibody (conjugated with a 1.4 nm small gold particle) needs to be evaluated against known standards for labeling efficiency. Silver enhancement is required to make the small gold visible, and quality of the silver-enhanced signals can be affected by subsequent steps of osmium tetroxide treatment, uranyl acetate en bloc staining, and by detergent or ethanol used to clean the diamond knife for cutting thin sections. Most importantly, verification of signals requires understanding of the protein of interest in order to validate for correct localization of antibodies at expected epitopes on particular organelles, and quantification of signals needs to take into consideration the penetration gradient of reagents and clumping of secondary antibodies.

Papaverine, a Phosphodiesterase 10A Inhibitor, Ameliorates Quinolinic Acid-Induced Synaptotoxicity in Human Cortical Neurons

Phosphodiesterase-10A (PDE10A) hydrolyse the secondary messengers cGMP and cAMP, two molecules playing important roles in neurodevelopment and brain functions. PDE10A is associated to progression of neurodegenerative diseases like Alzheimer's, Parkinson's, Huntington's diseases, and a critical role in cognitive functions. The present study was undertaken to determine the possible neuroprotective effects and the associated mechanism of papaverine (PAP), a PDE10A isoenzyme inhibitor, against quinolinic acid (QUIN)-induced excitotoxicity using human primary cortical neurons. Cytotoxicity potential of PAP was analysed using MTS assay. Reactive oxygen species (ROS) and mitochondrial membrane potential were measured by DCF-DA and JC10 staining, respectively. Caspase 3/7 and cAMP levels were measured using ELISA kits. Effect of PAP on the CREB, BNDF and synaptic proteins such as SAP-97, synaptophysin, synapsin-I, and PSD-95 expression was analysed by Western blot. Pre-treatment with PAP increased intracellular cAMP and nicotinamide adenine dinucleotide (NAD⁺) levels, restored mitochondrial membrane potential (ΔΨm), and decreased ROS and caspase 3/7 content in QUIN exposed neurons. PAP up-regulated CREB and BDNF, and synaptic protein expression. In summary, these data indicate that PDE10A is involved in QUIN-mediated synaptotoxicity and its inhibition elicit neuroprotection by reducing the oxidative stress and protecting synaptic proteins via up-regulation of cAMP signalling cascade.

Sensorimotor Perturbation Induces Late and Transient Molecular Synaptic Proteins Activation and Expression Changes

Plasticity of the cerebral cortex following a modification of the sensorimotor experience takes place in several steps that can last from few hours to several months. Among the mechanisms involved in the dynamic modulation of the cerebral cortex in adults, it is commonly proposed that short-term plasticity reflects changes in synaptic connections. Here, we were interested in the time-course of synaptic plasticity taking place in the somatosensory primary cortex all along a 14-day period of sensorimotor perturbation (SMP), as well as during a recovery phase up to 24 h. Activation and expression level of pre- (synapsin 1, synaptophysin, synaptotagmin 1) and postsynaptic (AMPA and NMDA receptors) proteins, postsynaptic density scaffold proteins (PSD-95 and Shank2), and cytoskeletal proteins (neurofilaments-L and M, β3-tubulin, synaptopodin, N-cadherin) were determined in cortical tissue enriched in synaptic proteins. During the SMP period, most changes were observed as soon as D7 in the presynaptic compartment and were followed, at D14, by changes in the postsynaptic compartment. These changes persisted at least until 24 h of recovery. Proteins involved in synapse structure (scaffolding, adhesion, cytoskeletal) were mildly affected and almost exclusively at D14. We concluded that experience-dependent reorganization of somatotopic cortical maps is accompanied by changes in synaptic transmission with a very close time-course.

Selected tools to visualize membrane interactions

In the past decade, we developed various fluorescence-based methods for monitoring membrane fusion, membrane docking, distances between membranes, and membrane curvature. These tools were mainly developed using liposomes as model systems, which allows for the dissection of specific interactions mediated by, for example, fusion proteins. Here, we provide an overview of these methods, including two-photon fluorescence cross-correlation spectroscopy and intramembrane Förster energy transfer, with asymmetric labelling of inner and outer membrane leaflets and the calibrated use of transmembrane energy transfer to determine membrane distances below 10 nm. We discuss their application range and their limitations using examples from our work on protein-mediated vesicle docking and fusion.

Neonatal Sevoflurane Exposure Impairs Learning and Memory by the Hypermethylation of Hippocampal Synaptic Genes

Sevoflurane anesthesia is widely used in pediatric patients. Clinical studies report memory impairment in those exposed to general anesthesia early in life. DNA methylation is essential for the modulation of synaptic plasticity through regulating the transcription of synaptic genes. Therefore, we tested whether neonatal sevoflurane exposure affects learning and memory underlying the hippocampal DNA methylation of synaptic genes. Male Sprague-Dawley rats were exposed to 3% sevoflurane or air for 2 h daily from postnatal day 7 (P7) to P9. 5-aza-2-deoxycytidine (5-AZA), an inhibitor of DNA methyltransferases (DNMTs), was intraperitoneally injected 30 min before sevoflurane or air exposure on P7-9. The rats were euthanized 6, 12, 24 h, and 28 days after the last sevoflurane exposure, followed by the determination of global and gene-specific DNA methylation. The expression of synaptic proteins and synaptic density and the transcription of Dnmts and ten eleven translocations (Tets) in the hippocampus were measured. The ability of learning and memory was assessed using Morris water maze, novel object recognition, and intruder tests. Repeated neonatal sevoflurane exposure impaired cognitive, social, and spatial memory. The memory impairment was associated with the increased Dnmt1, Dnmt3a, and 5-methylcytosine level and the decreased Tet1 and 5-hydromethylcytosine level. Sevoflurane subsequently induced hypermethylation of Shank2, Psd95, Syn1, and Syp gene and down-regulated the expression of synaptic proteins, which finally led to the decrease of synaptic density in a time-dependent manner. Notably, 5-AZA pretreatment ameliorated learning and memory in sevoflurane-treated rats. In conclusion, neonatal exposure to sevoflurane can impair learning and memory through DNA methylation of synaptic genes.

Maternal stress programs accelerated aging of the basal ganglia motor system in offspring

Early-life stress involved in the programming of stress-related illnesses can have a toxic influence on the functioning of the nigrostriatal motor system during aging. We examined the effects of perinatal stress (PRS) on the neurochemical, electrophysiological, histological, neuroimaging, and behavioral correlates of striatal motor function in adult (4 months of age) and old (21 months of age) male rats. Adult PRS offspring rats showed reduced dopamine (DA) release in the striatum associated with reductions in tyrosine hydroxylase-positive (TH⁺) cells and DA transporter (DAT) levels, with no loss of striatal dopaminergic terminals as assessed by positron emission tomography analysis with fluorine-18-l-dihydroxyphenylalanine. Striatal levels of DA and its metabolites were increased in PRS rats. In contrast, D₂ DA receptor signaling was reduced and A_2A adenosine receptor signaling was increased in the striatum of adult PRS rats. This indicated enhanced activity of the indirect pathway of the basal ganglia motor circuit. Adult PRS rats also showed poorer performance in the grip strength test and motor learning tasks. The aged PRS rats also showed a persistent reduction in striatal DA release and defective motor skills in the pasta matrix and ladder rung walking tests. In addition, the old rats showed large increases in the levels of SNAP-25 and synaptophysin, which are synaptic vesicle-related proteins in the striatum, and in the PRS group only, reductions in Syntaxin-1 and Rab3a protein levels were observed. Our findings indicated that the age-dependent threshold for motor dysfunction was lowered in PRS rats. This area of research is underdeveloped, and our study suggests that early-life stress can contribute to an increased understanding of how aging diseases are programmed in early-life.

Whole body vibration training improves depression-like behaviors in a rat chronic restraint stress model

Major depressive disorder (MDD) is a prevalent psychiatric disorder that brings great harm and burden to both patients and society. This study aimed to examine the effects of whole-body vibration (WBV) training on a chronic restraint stress (CRS) induced depression rat model and provide an initial understanding of related molecular mechanisms. Adult Sprague-Dawley male rats were randomly divided into the following three groups: a) control group, b) depressive disorder group, and c) depression with WBV training treatment group. Daily food intake, body weight, sucrose preference test, open field test, elevated plus maze, forced swimming test, and Barnes maze task tests were performed. Immunofluorescence staining and ELISA analysis were used to assess neuronal damage, synaptic proteins, glial cells, and trophic factors. The data of behavioral tests and related biochemical indicators were statistically analyzed and compared between groups. Rats undergoing CRS showed increased anxiety-like behavior and memory impairment, along with synaptic atrophy and neuronal degeneration. WBV could reverse behavioral dysfunction, inhibit the degeneration of neurons, alleviate the damage of neurons and the pathological changes of glial cells, enhance trophic factor expression, and ameliorate the downregulation of dendritic and synaptic proteins after CRS. The effect of WBV in rats may be mediated via the reduction of hippocampal neuronal degeneration and by improving expression of synaptic proteins. WBV training exerts multifactorial benefits on MDD that supports its use as a promising new therapeutic option for improving depression-like behaviors in the depressive and/or potentially depressive.

Patchouli alcohol protects against chronic unpredictable mild stress-induced depressant-like behavior through inhibiting excessive autophagy via activation of mTOR signaling pathway

Patchouli alcohol (PA), a tricyclic sesquiterpene, is the major chemical component of patchouli oil. This study investigated the antidepressant-like effect and mechanism of PA in chronic unpredictable mild stress (CUMS). Our results showed that PA markedly attenuated CUMS-induced depressant-like behaviors, including an effective increase of sucrose preference and spontaneous exploratory capacity, as well as reduction of immobility time. In addition, PA markedly attenuated CUMS-induced mTOR, p70S6K, and 4E-BP-1 phosphorylation reduction in the hippocampus. Furthermore, PA reversed CUMS-induced increases in LC3-II and p62 levels and CUMS-induced decrease in PSD-95 and SYN-I levels. These results indicated that the antidepressant-like effect of PA was correlated with the activation of the mTOR signaling pathway. Moreover, behavioral experimental results showed that the antidepressant-like effect of PA was blocked by rapamycin (autophagy inducer and mTOR inhibitor) and chloroquine (autophagic flux inhibitor). These results suggest that PA exerted antidepressant-like effect in CUMS rats through inhibiting autophagy, repairing synapse, and restoring autophagic flux in the hippocampus by activating the mTOR signaling pathway. The results render PA a promising antidepressant agent worthy of further development into a pharmaceutical drug for the treatment of depression.

Association of Neuropathological Markers in the Parietal Cortex With Antemortem Cognitive Function in Persons With Mild Cognitive Impairment and Alzheimer Disease

The associations between cognitive function and neuropathological markers in patients with mild cognitive impairment (MCI) and Alzheimer disease (AD) remain only partly defined. We investigated relationships between antemortem global cognitive scores and β-amyloid (Aβ), tau, TDP-43, synaptic proteins and other key AD neuropathological markers assessed by biochemical approaches in postmortem anterior parietal cortex samples from 36 subjects (12 MCI, 12 AD and 12 not cognitively impaired) from the Religious Orders Study. Overall, the strongest negative correlation coefficients associated with global cognitive scores were obtained for insoluble phosphorylated tau (r2 = -0.484), insoluble Aβ42 (r2 = -0.389) and neurofibrillary tangle counts (r2 = -0.494) (all p < 0.001). Robust inverse associations with cognition scores were also established for TDP-43-positive cytoplasmic inclusions (r2 = -0.476), total insoluble tau (r2 = -0.385) and Aβ plaque counts (r2 = -0.426). Sarkosyl (SK)- or formic acid (FA)-extracted tau showed similar interrelations. On the other hand, synaptophysin (r2 = +0.335), pS403/404 TDP-43 (r2 = +0.265) and septin-3 (r2 = +0.257) proteins positively correlated with cognitive scores. This study suggests that tau and Aβ42 in their insoluble aggregated forms, synaptic proteins and TDP-43 are the markers in the parietal cortex that are most strongly associated with cognitive function. This further substantiates the relevance of investigating these markers to understand the pathogenesis of AD and develop therapeutic tools.

Ascorbic acid presents rapid behavioral and hippocampal synaptic plasticity effects

Growing evidence has suggested that ascorbic acid may exhibit rapid anxiolytic and antidepressant-like effects. In this study the effects of a single administration of ascorbic acid (1 mg/kg, p.o.), ketamine (1 mg/kg, i.p., a fast-acting antidepressant) and fluoxetine (10 mg/kg, p.o., conventional antidepressant) were investigated on: a) behavioral performance in the novelty suppressed feeding (NSF) test; b) hippocampal synaptic protein immunocontent; c) dendritic spine density and morphology in the dorsal and ventral dentate gyrus (DG) of the hippocampus and d) hippocampal dendritic arborization. Ascorbic acid or ketamine, but not fluoxetine, decreased the latency to feed in the NSF test in mice. This effect was accompanied by increased p70S6K (Thr³⁸⁹) phosphorylation 1 h after ascorbic acid or ketamine treatment, although only ascorbic acid increased synapsin I immunocontent. Ketamine administration increased the dendritic spine density in the dorsal DG, but none of the treatments affected the maturation of dendritic spines in this region. In addition, both ascorbic acid and ketamine increased the dendritic spine density in the ventral DG, particularly the mature spines. Sholl analysis demonstrated no effect of any treatment on hippocampal dendritic arborization. Altogether, the results provide evidence that the behavioral and synaptic responses observed following ascorbic acid administration might occur via the upregulation of synaptic proteins, dendritic spine density, and maturation in the ventral DG, similar to ketamine. These findings contribute to understand the cellular targets implicated in its antidepressant/anxiolytic behavioral responses and support the notion that ascorbic acid may share with ketamine the ability to increase synaptic function.

Methylation in Syn and Psd95 genes underlie the inhibitory effect of oxytocin on oxycodone-induced conditioned place preference

Oxycodone (Oxy) is one of the most effective analgesics in medicine, but is associated with the development of dependence. Recent studies demonstrating epigenetic changes in the brain after exposure to opiates have provided an insight into possible mechanisms underlying addiction. Oxytocin (OT), an endogenous neuropeptide well known for preventing drug abuse, is a promising pharmacotherapy to counteract addiction. Therefore, we explored the mechanism of Oxy addiction and the role of OT in Oxy-induced epigenetic alterations. In this study, drug-induced changes in conditioned place preference (CPP), i.e. the expression of synaptic proteins and synaptic density in the ventral tegmental area (VTA) were measured. We also sought to identify DNA methyltransferases (DNMTs), ten-eleven translocations (TETs), global 5-methylcytosine (5-mC), and DNA methylation of two genes implicated in plasticity (Synaptophysin, Syn; Post-synaptic density protein 95, Psd95). Oxy (3.0 mg/kg, i.p.) induced CPP acquisition in Sprague-Dawley rats. Oxy down-regulated DNMT1 and up-regulated TET1-3, leading to a decrease in global 5-mC levels and differential demethylation at exon 1 of Syn and exon 2 of Psd95. These changes in DNA methylation of Syn and Psd95 elevated the expression of synaptic proteins (SYN, PSD95) and synaptic density in the VTA. Pretreatment with OT (2.5 µg, i.c.v.) via its receptor specifically blocked Oxy CPP, normalized synaptic density, and regulated DNMT1 and TET2-3 causing reverse of DNA demethylation of Syn and Psd95. DNA methylation is an important gene regulation mechanism underlying Oxy CPP, and OT - via its receptor - could specifically inhibit Oxy addiction.

Early treatment with C1 esterase inhibitor improves weight but not memory deficits in a rat model of status epilepticus

BACKGROUND

Status epilepticus (SE) is a prolonged and continuous seizure that lasts for at least 5 min. An episode of SE in a healthy system can lead to the development of spontaneous seizures and cognitive deficits which may be accompanied by hippocampal injury and microgliosis. Although the direct mechanisms underlying the SE-induced pathophysiology remain unknown, a candidate mechanism is hyperactivation of the classical complement pathway (C1q-C3 signaling). We recently reported that SE triggered an increase in C1q-C3 signaling in the hippocampus that closely paralleled cognitive decline. Thus, we hypothesized that blocking activation of the classical complement pathway immediately after SE may prevent the development of SE-induced hippocampal-dependent learning and memory deficits.

METHODS

Because C1 esterase inhibitor (C1-INH) negatively regulates activation of the classical complement pathway, we used this drug to test our hypothesis. Two groups of male rats were subjected to 1 hr of SE with pilocarpine (280-300 mg/kg, i.p.), and treated with either C1-INH (SE+C1-INH, 20 U/kg, s.c.) or vehicle (SE+veh) at 4, 24, and 48 h after SE. Control rats were treated with saline. Body weight was recorded for up to 23 days after SE. At two weeks post SE, recognition and spatial memory were determined using Novel Object Recognition (NOR) and Barnes maze (BM), respectively, as well as locomotion and anxiety-like behaviors using Open Field (OF). Histological and biochemical methods were used to measure hippocampal injury including cell death, microgliosis, and inflammation.

RESULTS

One day after SE, both SE groups had a significant loss of body weight compared to controls (p<0.05). By day 14, the weight of SE+C1-INH rats was significantly higher than SE+veh rats (p<0.05), and was not different from controls (p>0.05). At 14 days post-SE, SE+C1-INH rats displayed higher mobility (distance travelled and average speed, p<0.05) and had reduced anxiety-like behaviors (outer duration, p<0.05) than control or SE+veh rats. In NOR, control rats spent significantly more time exploring the novel object vs. the familiar (p<0.05), while rats in both SE groups spent similar amount of time exploring both objects. During days 1-4 of BM training, the escape latency of the control group significantly decreased over time (p<0.05), whereas that of the SE groups did not improve (p>0.05). Compared to vehicle-treated SE rats, SE+C1-INH rats had increased levels of C3 and microglia in the hippocampus, but lower levels of caspase-3 and synaptic markers.

CONCLUSIONS

These findings suggest that acute treatment with C1-INH after SE may have some protective, albeit limited, effects on the physiological recovery of rats' weight and some anxiolytic effects, but does not attenuate SE-induced deficits in hippocampal-dependent learning and memory. Reduced levels of caspase-3 suggest that treatment with C1-INH may protect against cell death, perhaps by regulating inflammatory pathways and promoting phagocytic/clearance pathways.

Implications of the Sap47 null mutation for synapsin phosphorylation, longevity, climbing proficiency and behavioural plasticity in adult Drosophila

The Sap47 gene of Drosophila melanogaster encodes a highly abundant 47 kDa synaptic vesicle-associated protein. Sap47 null mutants show defects in synaptic plasticity and larval olfactory associative learning but the molecular function of Sap47 at the synapse is unknown. We demonstrate that Sap47 modulates the phosphorylation of another highly abundant conserved presynaptic protein, synapsin. Site-specific phosphorylation of Drosophila synapsin has repeatedly been shown to be important for behavioural plasticity but it was not known where these phospho-synapsin isoforms are localized in the brain. Here, we report the distribution of serine-6-phosphorylated synapsin in the adult brain and show that it is highly enriched in rings of synapses in the ellipsoid body and in large synapses near the lateral triangle. The effects of knockout of Sap47 or synapsin on olfactory associative learning/memory support the hypothesis that both proteins operate in the same molecular pathway. We therefore asked if this might also be true for other aspects of their function. We show that knockout of Sap47 but not synapsin reduces lifespan, whereas knockout of Sap47 and synapsin, either individually or together, affects climbing proficiency, as well as plasticity in circadian rhythms and sleep. Furthermore, electrophysiological assessment of synaptic properties at the larval neuromuscular junction (NMJ) reveals increased spontaneous synaptic vesicle fusion and reduced paired pulse facilitation in Sap47 and synapsin single and double mutants. Our results imply that Sap47 and synapsin cooperate non-uniformly in the control of synaptic properties in different behaviourally relevant neuronal networks of the fruitfly.

(-)-Phenserine and the prevention of pre-programmed cell death and neuroinflammation in mild traumatic brain injury and Alzheimer's disease challenged mice

Mild traumatic brain injury (mTBI) is a risk factor for neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). TBI-derived neuropathologies are promoted by inflammatory processes: chronic microgliosis and release of pro-inflammatory cytokines that further promote neuronal dysfunction and loss. Herein, we evaluated the effect on pre-programmed cell death/neuroinflammation/synaptic integrity and function of (-)-Phenserine tartrate (Phen), an agent originally developed for AD. This was studied at two clinically translatable doses (2.5 and 5.0 mg/kg, BID), in a weight drop (concussive) mTBI model in wild type (WT) and AD APP/PSEN1 transgenic mice. Phen mitigated mTBI-induced cognitive impairment, assessed by Novel Object Recognition and Y-maze behavioral paradigms, in WT mice. Phen fully abated mTBI-induced neurodegeneration, evaluated by counting Fluoro-Jade C-positive (FJC+) cells, in hippocampus and cortex of WT mice. In APP/PSEN1 mice, degenerating cell counts were consistently greater across all experimental groups vs. WT mice. mTBI elevated FJC+ cell counts vs. the APP/PSEN1 control (sham) group, and Phen similarly mitigated this. Anti-inflammatory effects on microglial activation (IBA1-immunoreactivity (IR)) and the pro-inflammatory cytokine TNF-α were evaluated. mTBI increased IBA1-IR and TNF-α/IBA1 colocalization vs. sham, both in WT and APP/PSEN1 mice. Phen decreased IBA1-IR throughout hippocampi and cortices of WT mice, and in cortices of AD mice. Phen, likewise, reduced levels of IBA1/TNF-α-IR colocalization volume across all areas in WT animals, with a similar trend in APP/PSEN1 mice. Actions on astrocyte activation by mTBI were followed by evaluating GFAP, and were similarly mitigated by Phen. Synaptic density was evaluated by quantifying PSD-95+ dendritic spines and Synaptophysin (Syn)-IR. Both were significantly reduced in mTBI vs. sham in both WT and APP/PSEN1 mice. Phen fully reversed the PSD-95+ spine loss in WT and Syn-IR decrease in both WT and APP/PSEN1 mice. To associate immunohistochemical changes in synaptic markers with function, hippocampal long term potentiation (LTP) was induced in WT mice. LTP was impaired by mTBI, and this impairment was mitigated by Phen. In synopsis, clinically translatable doses of Phen ameliorated mTBI-mediated pre-programmed cell death/neuroinflammation/synaptic dysfunction in WT mice, consistent with fully mitigating mTBI-induced cognitive impairments. Phen additionally demonstrated positive actions in the more pathologic brain microenvironment of AD mice, further supporting consideration of its repurposing as a treatment for mTBI.

Environmental enrichment restores the reduced expression of cerebellar synaptophysin and the motor coordination impairment in rats prenatally treated with betamethasone

Preterm babies treated with synthetic glucocorticoids in utero exhibit behavioural alterations and disturbances in brain maturation during postnatal life. Accordingly, it has been shown in preclinical studies that SGC exposure at a clinical dose alters the presynaptic and postsynaptic structures and results in synaptic impairments. However, the precise mechanism by which SGC exposure impairs synaptic protein expression and its implications are not fully elucidated. Therefore, the purpose of this study was to investigate the effect of prenatal exposure to a clinical dose of betamethasone on the pre- and postsynaptic proteins expression in the developing rat cerebellum and prefrontal cortex, whose synchronized synaptic activity is crucial for motor control and learning. Consequently, the first objective of the present study was to determine whether prenatal betamethasone -equivalent to the clinically used dose- alters cerebellar vermal and cortical expression of synaptophysin, synaptotagmin I, post-synaptic density protein 95 and gephyrin - four important pre- and post-synaptic proteins, respectively- at a relevant adolescent stage. In addition, our second objective was to assess whether prenatal betamethasone administration induced coordination impairment using a rotarod test. On the other hand, it has been shown that the environmental enrichment is capable of improving synaptic transmission and recovering various behavioural impairments. Nevertheless, there is not enough information about the effect of this non-pharmacological preclinical approach on the regulation of this cerebellar and cortical synaptic proteins. Therefore, the third objective of this study was to examine whether environmental enrichment exposure could recover the possible molecular and behavioural impairments in the offspring at the same developmental stage. The principal data showed that adolescent rats prenatally treated with betamethasone exhibited underexpression of synaptophysin in the vermal cerebellum, but not change in levels of synaptotagmin I, post-synaptic density protein 95 and gephyrin. Analysis of the same pre- and post-synaptic proteins no showed differences in the frontal cortex of the same rats. These results were accompanied by an increase in the number of falls in the rotarod test, when the speed of rotation was fixed and when it was in acceleration, which means motor coordination impairments. Importantly, we found that environmental enrichment restores the betamethasone-induced reduction in the cerebellar synaptophysin together with a recover in the motor coordination impairments in prenatally betamethasone-exposed adolescent rats.

Synaptic structure and alterations in the hippocampus in neonatal rats exposed to lipopolysaccharide

Synaptic structure integrity plays a key role in learning and memory. Previous studies have shown that there is cognitive dysfunction in septic neonates in later life. In this study, intraperitoneal injection of lipopolysaccharide (LPS) in the developing rats was used as a sepsis model to determine whether hippocampal synapses would be affected. Expression of synaptophysin (Syn), synaptosomal associated protein of 25 kD (SNAP-25), and N-methyl d-aspartate receptor (NMDAR) in the hippocampus in septic brain were significantly reduced. Consistent with this, the number of dendritic spines associated with the pyramidal neurons in the CA1 region of hippocampus at 28d after LPS administration was decreased. Additionally, the number of synapse and synaptic vesicles were reduced and appeared swollen. The number of neurons in the CA1 and CA3 of hippocampus at 14, and 28d after LPS injection remained unchanged. Coupled with the above was upregulated expression of interleukin-1β (IL-1β), IL-1 receptor 1 (IL-R1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) at 1-3d after LPS injection. IL-1β expression was specifically detected in activated microglia. The plasma corticosterone (CORT) concentration in the LPS treatment rats was increased; but the glucocorticoid receptor (GR) expression in the hippocampus was decreased. We conclude that LPS injection in neonatal rats can cause synaptic disruption in the hippocampus which may be attributed to inflammatory response due to excess production of proinflammatory cytokines e.g., IL-1β derived from activated microglia. The significance of increased plasma CORT concentration and decreased GR expression in the hippocampus is discussed.

Herpesviruses, autoimmunity and epilepsy: Peptide sharing and potential cross-reactivity with human synaptic proteins

Aggregation of immuno-proteomic data reveals that i) herpesviruses and synaptic proteins -in particular Synapsin-1 and Bassoon - share a large number of hexapeptides that also recur in hundreds of epitopes experimentally validated as immunopositive in the human host, and ii) the shared peptides are also spread among human epilepsy-related proteins. The data indicate that cross-reactive processes may be associated with pathogenetic mechanisms in epilepsy, thus suggesting a role of autoimmunity in etiopathology of epilepsies after herpesvirus-infections.

Coincident Pre- and Post-Synaptic Cortical Remodelling Disengages Episodic Memory from Its Original Context

The view that the neocortex is remotely recruited for long-term episodic memory recall is challenged by data showing that an intense transcriptional and synaptic activity is detected in this region immediately after training. By measuring markers of synaptic activity at recent and remote time points from contextual fear conditioning (CFC), we could show that pre-synaptic changes are selectively detected 1 day post-training when the memory is anchored to the training context. Differently, pre- and post-synaptic changes are detected 14 days post-training when the memory generalizes to other contexts. Confirming that coincident pre- and post-synaptic remodelling mediates the disengagement of memory from its original context, DREADDs-mediated enhancement of cortical neuron activity during CFC training anticipates expression of a schematic memory and observation of bilateral synaptic remodelling. Together, our data show that the plastic properties of cortical synapses vary over time and specialise in relation to the quality of memory.

CYP46A1 Activation by Efavirenz Leads to Behavioral Improvement without Significant Changes in Amyloid Plaque Load in the Brain of 5XFAD Mice

Efavirenz, the FDA-approved anti-retroviral medication, is evaluated in the clinical trial in patients with mild cognitive impairment or early dementia due to Alzheimer's disease. Efavirenz is assessed for activation of cytochrome P450 46A1 (CYP46A1), a CNS-specific enzyme that converts cholesterol to 24-hydroxycholesterol. Cholesterol 24-hydroxylation is the major pathway for brain cholesterol removal, and a mechanism that controls brain cholesterol turnover. The present study tested efavirenz on 5XFAD mice (an Alzheimer's model) at a very low daily dose of 0.1 mg/kg body weight. Efavirenz treatment started from three months of age, after amyloid plague appearance, and continued for 6 months. This treatment led to CYP46A1 activation in the brain, enhancement of brain cholesterol turnover, behavioral improvements, reduction in microglia activation but increased astrocyte reactivity. The levels of the soluble and insoluble amyloid 40 and 42 peptides were unchanged while the number and area of the dense core amyloid plaques were slightly decreased. The measurements of the brain levels of several pre- and post-synaptic proteins (Munc13-1, PSD-95, gephyrin, synaptophysin, synapsin-1, and calbindin-D28k) suggested efavirenz effect at the synaptic level. Efavirenz treatment in the present work seems to represent a model of behavioral and other improvements independent of the levels of the amyloid peptides and provides insight into potential outcomes of the future clinical trial.

Novel MicroRNA-455-3p and its protective effects against abnormal APP processing and amyloid beta toxicity in Alzheimer's disease

The purpose of our study is to understand the protective role of miR-455-3p against abnormal amyloid precursor protein (APP) processing, amyloid beta (Aβ) formation, defective mitochondrial biogenesis/dynamics and synaptic damage in AD progression. In-silico analysis of miR-455-3p has identified the APP gene as a putative target. Using mutant APP cells, miR-455-3p construct, biochemical and molecular assays, immunofluorescence and transmission electron microscopy (TEM) analyses, we studied the protective effects of miR-455-3p on - 1) APP regulation, amyloid beta (Aβ)(1-40) & (1-42) levels, mitochondrial biogenesis & dynamics; 3) synaptic activities and 4) cell viability & apoptosis. Our luciferase reporter assay confirmed the binding of miR-455-3p at the 3'UTR of APP gene. Immunoblot, sandwich ELISA and immunostaining analyses revealed that the reduced levels of the mutant APP, Aβ(1-40) & Aβ(1-42), and C99 by miR-455-3p. We also found the reduced levels of mRNA and proteins of mitochondrial biogenesis (PGC1α, NRF1, NRF2, and TFAM) and synaptic genes (synaptophysin and PSD95) in mutant APP cells; on the other hand, mutant APP cells that express miR-455-3p showed increased mRNA and protein levels of biogenesis and synaptic genes. Additionally, expression of mitochondrial fission proteins (DRP1 and FIS1) were decreased while the fusion proteins (OPA1, Mfn1 and Mfn2) were increased by miR-455-3p. Our TEM analysis showed a decrease in mitochondria number and an increase in the size of mitochondrial length in mutant APP cells transfected with miR-455-3p. Based on these observations, we cautiously conclude that miR-455-3p regulate APP processing and protective against mutant APP-induced mitochondrial and synaptic abnormalities in AD.

Palmitoylation-mediated synaptic regulation of AMPA receptor trafficking and function

The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is a major glutamate-gated ion channel in the brain and is important for synaptic transmission, synaptic plasticity, and learning. Palmitoylation, a post-translational modification, is a critical process regulating AMPAR trafficking, synaptic function and plasticity, and learning and memory in health and diseases. In this review, we discuss current knowledge on the palmitoylation-dependent regulation of AMPAR trafficking and functions. We focus on the palmitoylation of AMPARs and other synaptic proteins that directly or indirectly interact with AMPARs, including postsynaptic density 95, glutamate receptor-interacting protein/AMPAR-binding protein, A-kinase anchoring protein 79/150, and protein interacting with C kinase 1. Finally, we discuss what future studies should address in the field of palmitoylation-dependent AMPAR trafficking and function with regard to physiology and neurodegenerative 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.

SNAP-25 in Serum Is Carried by Exosomes of Neuronal Origin and Is a Potential Biomarker of Alzheimer's Disease

A loss of synaptic density and connectivity is observed in multiple brain regions of Alzheimer's disease (AD) patients, resulting in a reduced expression of synaptic proteins such as SNAP-25 (synaptosomal-associated-protein-25). SNAP-25 alterations thus could be an index of the degree of synaptic degeneration in the central nervous system (CNS). We isolated from serum of both AD patients and healthy controls (HC) a population of neuron-derived exosomes (NDEs) and measured the concentrations of SNAP-25 contained in such NDEs. The levels of SNAP-25 carried by NDEs were reduced in AD patients (mean 459.05 ng/ml, SD 146.35 ng/ml) compared to HC (mean 686.42 ng/ml, SD 204.08 ng/ml) (p < 0.001). As a further confirmation of these results, ROC (receiver operating characteristic) analyses indicated that the level of SNAP-25 carried by NDEs has the power to discriminate between AD and HC (AUC = 0.826, sensitivity = 87.5%, specificity = 70.6%, p < 0.0001, cut-off value 587.07 ng/ml). Notably, a correlation between the levels of SNAP-25 carried by NDEs and levels and cognitive status measured by MMSE score (r = 0.465, 95% CI 0.11 to 0.714, p = 0.01) was detected. This is the first report of SNAP-25 measurement in serum. These data suggest that NDE-carried SNAP-25 could be an effective and accessible biomarker that reflects synapses integrity in the brain.

Postnatal exposure to poly (I:C) impairs learning and memory through changes in synaptic plasticity gene expression in developing rat brain

Viral infection during early stage of life influences brain development and results in several neurodevelopmental disorders such as schizophrenia, autism and behavioral abnormalities. However, the mechanism through which infection causes long-term behavioral defects is not well known. To elucidate this, we have used synthetic polyinosinic-polycytidylic acid [poly (I:C)] which acts as a dsRNA molecule and interacts with toll-like receptor-3 (TLR-3) of microglia cells to evoke the immune system, thus mimicking the viral infection. Rat pups of postnatal day (PND) 7 were infused with a single dose of poly (I:C) (5 mg/kg BW) and vehicle alone to controls. When these pups grew to 3, 6 and 12 weeks, their spatial and fear conditioning memory were impaired as assessed by Morris water maze and passive avoidance test, respectively. We checked the immune activation by staining of TNF-α in the hippocampus and observed that poly (I:C) exposure elevated the number of TNF-α positive cells immediately after 12 h of infusion in one week rat and it persisted up to postnatal age of 3 and 12 weeks. Moreover, poly (I:C) significantly decreased the binding of ³H-QNB to the cholinergic receptors in the frontal cortex and hippocampus of 3 and 6 weeks rats as compared to control but did not change significantly in 12 weeks rats. RT-PCR and immunoblotting results showed that poly (I:C) exposure upregulated the expression of memory associated genes (BDNF, Arc, EGR1) at mRNA and protein level in frontal cortex and hippocampus of 3 weeks rats as compared to control. However, long-time persistence of poly (I:C) effects significantly decreased the expression of these genes in both brain regions of 12 weeks rats. Taken together, it is evident that early life exposure to poly (I:C) has a long-term effect and impairs learning and memory, probably through TNF-α mediated neuroinflammation and alteration in the expression of memory associated genes in frontal cortex and hippocampus of rats.

Chronic Toxoplasma infection is associated with distinct alterations in the synaptic protein composition

Background

Chronic infection with the neurotropic parasite Toxoplasma gondii has been implicated in the risk for several neuropsychiatric disorders. The mechanisms, by which the parasite may alter neural function and behavior of the host, are not yet understood completely.

Methods

Here, a novel proteomic approach using mass spectrometry was employed to investigate the alterations in synaptic protein composition in a murine model of chronic toxoplasmosis. In a candidate-based strategy, immunoblot analysis and immunohistochemistry were applied to investigate the expression levels of key synaptic proteins in glutamatergic signaling.

Results

A comparison of the synaptosomal protein composition revealed distinct changes upon infection, with multiple proteins such as EAAT2, Shank3, AMPA receptor, and NMDA receptor subunits being downregulated, whereas inflammation-related proteins showed an upregulation. Treatment with the antiparasitic agent sulfadiazine strongly reduced tachyzoite levels and diminished neuroinflammatory mediators. However, in both conditions, a significant number of latent cysts persisted in the brain. Conversely, infection-related alterations of key synaptic protein levels could be partly reversed by the treatment.

Conclusion

These results provide evidence for profound changes especially in synaptic protein composition in T. gondii-infected mice with a downregulation of pivotal components of glutamatergic neurotransmission. Our results suggest that the detected synaptic alterations are a consequence of the distinct neuroinflammatory milieu caused by the neurotropic parasite.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1242-1) contains supplementary material, which is available to authorized users.

Improved synaptic and cognitive function in aged 3 × Tg-AD mice with reduced amyloid-β after immunotherapy with a novel recombinant 6Aβ15-TF chimeric vaccine

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder impairing memory and cognition. In this study, we describe the immunogenicity and protective efficacy of the novel recombinant 6Aβ15-TF chimeric antigen as a subunit protein vaccine for AD. Recombinant 6Aβ15-TF chimeric vaccine induced strong Aβ-specific humoral immune responses without Aβ-specific T cell immunity in C57/BL6 and 3 × Tg-AD mice at different ages. As an early immunotherapy model for AD, this vaccine induced high titers of long-lasting anti-Aβ42 antibodies in aged 3 × Tg-AD mice, which led to improve behavioral performance and markedly reduced the levels of insoluble and soluble Aβ and Aβ oligomers. In agreement with these findings, immunotherapy with 6Aβ15-TF prevented the Aβ-induced decrease of presynaptic and postsynaptic proteins in aged 3 × Tg-AD mice. Our results suggest that this novel and highly immunogenic recombinant 6Aβ15-TF chimeric vaccine provides neuroprotection in AD mice and can be considered an effective AD candidate vaccine.