Reversal of age-associated cognitive deficits is accompanied by increased plasticity-related gene expression after chronic antidepressant administration in middle-aged mice

Depletion of PIEZO1 expression is accompanied by upregulating p53 signaling in mice with perioperative neurocognitive disorder

As the common complications observed in surgical elder patients, perioperative neurocognitive disorders (PND) cause a series of serious perioperative health problems. However, there are no effective treatments, and the exact mechanisms are still largely unknown. In this study, transcriptome sequencing was performed to investigate the differentially expressed genes (DEGs) in the hippocampus of C57BL/6J aged mice with or without PND. Compared with the Mock group, the expression of 352, 395, and 772 genes changed significantly in the PND group at days 1, 7, and 21 after surgery, respectively. Gene ontology (GO) and gene set enrichment analysis (GSEA) showed that DEGs were mainly associated with p53 signaling. Moreover, GSEA revealed potentially p53-related DEGs such as leucine-rich repeat serine/threonine-protein kinase 1 (LRRK1), monooxygenase DBH-like 1 (MOXD1), and piezo type mechanosensitive ion channel component 1 (PIEZO1). Furthermore, we confirmed the decreased interaction of PIEZO1 with p53 in PND, and upregulation of PIEZO1 resulted in a decrease in p53 protein levels through increased ubiquitination of p53. In conclusion, this study contributes to the knowledge of global changes in gene expression and mechanisms during PND.

Hypericin Ameliorates Depression-like Behaviors via Neurotrophin Signaling Pathway Mediating m6A Epitranscriptome Modification

Hypericin, one of the major antidepressant constituents of St. John's wort, was shown to exert antidepressant effects by affecting cerebral CYP enzymes, serotonin homeostasis, and neuroinflammatory signaling pathways. However, its exact mechanisms are unknown. Previous clinical studies reported that the mRNA modification N6-methyladenosine (m6A) interferes with the neurobiological mechanism in depressed patients, and it was also found that the antidepressant efficacy of tricyclic antidepressants (TCAs) is related to m6A modifications. Therefore, we hypothesize that the antidepressant effect of hypericin may relate to the m6A modification of epitranscriptomic regulation. We constructed a UCMS mouse depression model and found that hypericin ameliorated depressive-like behavior in UCMS mice. Molecular pharmacology experiments showed that hypericin treatment upregulated the expression of m6A-modifying enzymes METTL3 and WTAP in the hippocampi of UCMS mice. Next, we performed MeRIP-seq and RNA-seq to study m6A modifications and changes in mRNA expression on a genome-wide scale. The genome-wide m6A assay and MeRIP-qPCR results revealed that the m6A modifications of Akt3, Ntrk2, Braf, and Kidins220 mRNA were significantly altered in the hippocampi of UCMS mice after stress stimulation and were reversed by hypericin treatment. Transcriptome assays and qPCR results showed that the Camk4 and Arhgdig genes might be related to the antidepressant efficacy of hypericin. Further gene enrichment results showed that the differential genes were mainly involved in neurotrophic factor signaling pathways. In conclusion, our results show that hypericin upregulates m6A methyltransferase METTL3 and WTAP in the hippocampi of UCMS mice and stabilizes m6A modifications to exert antidepressant effects via the neurotrophin signaling pathway. This suggests that METTL3 and WTAP-mediated changes in m6A modifications may be a potential mechanism for the pathogenesis of depression and the efficacy of antidepressants, and that the neurotrophin signaling pathway plays a key role in this process.

Influence of Chronic Electroconvulsive Seizures on Plasticity-Associated Gene Expression and Perineuronal Nets Within the Hippocampi of Young Adult and Middle-Aged Sprague-Dawley Rats

BACKGROUND

Electroconvulsive seizure therapy is often used in both treatment-resistant and geriatric depression. However, preclinical studies identifying targets of chronic electroconvulsive seizure (ECS) are predominantly focused on animal models in young adulthood. Given that putative transcriptional, neurogenic, and neuroplastic mechanisms implicated in the behavioral effects of chronic ECS themselves exhibit age-dependent modulation, it remains unknown whether the molecular and cellular targets of chronic ECS vary with age.

METHODS

We subjected young adult (2-3 months) and middle-aged (12-13 months), male Sprague Dawley rats to sham or chronic ECS and assessed for despair-like behavior, hippocampal gene expression, hippocampal neurogenesis, and neuroplastic changes in the extracellular matrix, reelin, and perineuronal net numbers.

RESULTS

Chronic ECS reduced despair-like behavior at both ages, accompanied by overlapping and unique changes in activity-dependent and trophic factor gene expression. Although chronic ECS had a similar impact on quiescent neural progenitor numbers at both ages, the eventual increase in hippocampal progenitor proliferation was substantially higher in young adulthood. We noted a decline in reelin⁺ cell numbers following chronic ECS only in young adulthood. In contrast, an age-invariant, robust dissolution of perineuronal net numbers that encapsulate parvalbumin⁺ neurons in the hippocampus were observed following chronic ECS.

CONCLUSION

Our findings indicate that age is a key variable in determining the nature of chronic ECS-evoked molecular and cellular changes in the hippocampus. This raises the intriguing possibility that chronic ECS may recruit distinct, as well as overlapping, mechanisms to drive antidepressant-like behavioral changes in an age-dependent manner.

YY1 (Yin-Yang 1), a transcription factor regulating systemic inflammation, is involved in cognitive impairment of depression

AIM

Clinical and preclinical studies suggest that alterations in the peripheral and brain immune system are associated with the pathophysiology of depression, also leading to changes in local glucose metabolism in the brain. Here, the authors identified Yin-Yang 1 (YY1), a transcription factor closely associated with central and peripheral inflammation.

METHODS

Plasma levels of YY1, interleukin (IL) 6, and IL-1β in major depressive disorder (MDD) were collected before and after treatment with vortioxetine, and correlation with clinical and cognitive scores was studied. Chronic unpredictable mild stress was treated with vortioxetine. Micropositron emission tomography (microPET) was used to analyze glucose metabolism and mRNA, and the protein level of the YY1-nuclear factor κB (NF-κB)-IL-1β inflammatory pathway were measured in related brain regions.

RESULTS

Plasma levels of YY1 and IL-1β were significantly increased in MDD and decreased after treatment with vortioxetine. Meanwhile, the level of YY1 in plasma was negatively correlated with cognitive functions in patients with MDD and positively correlated with the level of IL-1β in plasma. Compared with the control group, in chronic unpredictable mild stress rats, (microPET) analysis showed that the decrease of glucose metabolism in the hippocampus, entorhinal cortex, amygdala, striatum, and medial prefrontal cortex was reversed after treatment. mRNA and protein level of related molecular in YY1-NF-κB-IL-1β inflammatory pathway decreased in the hippocampus and was reversed by vortioxetine.

CONCLUSION

The current study suggests that the YY1-NF-κB-IL-1β inflammatory pathway may play an essential role in both mood changes and cognitive impairment in depression, and may be associated with changes in glucose metabolism in emotion regulation and cognition. These findings provide new evidence for the inflammatory mechanisms of depression.

'Arc'-hitecture of normal cognitive aging

Arc is an effector immediate-early gene that is critical for forming long-term memories. Since its discovery 25 years ago, it has repeatedly surprised us with a number of intriguing properties, including the transport of its mRNA to recently-activated synapses, its master role in bidirectionally regulating synaptic strength, its evolutionary retroviral origins, its ability to mediate intercellular transfer between neurons via extracellular vesicles (EVs), and its exceptional regulation-both temporally and spatially. The current review discusses how Arc has been used as a tool to identify the neural networks involved in cognitive aging and how Arc itself may contribute to cognitive outcome in aging. In addition, we raise several outstanding questions, including whether Arc-containing EVs in peripheral blood might provide a noninvasive biomarker for memory-related synaptic failure in aging, and whether rectifying Arc dysregulation is likely to be an effective strategy for bending the arc of aging toward successful cognitive outcomes.

Whole Body Vibration Improves Spatial Memory, Anxiety-Like Behavior, and Motor Performance in Aged Male and Female Rats

Aging is a progressive process leading to functional decline in many domains. Recent studies have shown that physical exercise (PE) has a positive influence on the progression of age-related functional decline, including motor and brain functions. Whole body vibration (WBV) is a form of passive stimulation by mechanical vibration platforms, which offers an alternative for PE interventions, especially for aged individuals. WBV has been demonstrated to mimic the beneficial effects of PE on the musculoskeletal system, as well on the central nervous system. However, preclinical data with aged rodents are very limited. Hence, the purpose of this experiment was to investigate the effects of a 5-week WBV intervention with an aged animal model on memory functions, anxiety-related behavior, and motor performance. The 18-month old male (N = 14) and female (N = 14) Wistar rats were divided into two groups, namely, vibration and pseudo-vibration. Animals underwent a 5-week WBV intervention protocol with low intensity (frequency of 30 Hz and amplitude of 50–200 μm) stimulation. After 5 weeks, the following cognitive and motor tests were administered: open-field, novel and spatial object recognition, grip-hanging, and balance-beam. WBV-treated rats showed a decrease in their anxiety level in the open field test compared with those in the pseudo-treated controls. In addition, WBV-treated male animals showed significantly increased rearing in the open-field test compared to their pseudo controls. Spatial memory was significantly improved by WBV treatment, whereas WBV had no effect on object memory. Regarding motor performance, both grip strength and motor coordination were improved by WBV treatment. Our results indicate that WBV seems to have comparable beneficial effects on age-related emotional, cognitive, and motor decline as what has been reported for active PE. No striking differences were found between the sexes. As such, these findings further support the idea that WBV could be considered as a useful alternative for PE in case active PE cannot be performed due to physical or mental issues.

Heat Shock Factor 1 Directly Regulates Postsynaptic Scaffolding PSD-95 in Aging and Huntington's Disease and Influences Striatal Synaptic Density

PSD-95 (Dlg4) is an ionotropic glutamate receptor scaffolding protein essential in synapse stability and neurotransmission. PSD-95 levels are reduced during aging and in neurodegenerative diseases like Huntington's disease (HD), and it is believed to contribute to synaptic dysfunction and behavioral deficits. However, the mechanism responsible for PSD-95 dysregulation under these conditions is unknown. The Heat Shock transcription Factor 1 (HSF1), canonically known for its role in protein homeostasis, is also depleted in both aging and HD. Synaptic protein levels, including PSD-95, are influenced by alterations in HSF1 levels and activity, but the direct regulatory relationship between PSD-95 and HSF1 has yet to be determined. Here, we showed that HSF1 chronic or acute reduction in cell lines and mice decreased PSD-95 expression. Furthermore, Hsf1(+/-) mice had reduced PSD-95 synaptic puncta that paralleled a loss in thalamo-striatal excitatory synapses, an important circuit disrupted early in HD. We demonstrated that HSF1 binds to regulatory elements present in the PSD-95 gene and directly regulates PSD-95 expression. HSF1 DNA-binding on the PSD-95 gene was disrupted in an age-dependent manner in WT mice and worsened in HD cells and mice, leading to reduced PSD-95 levels. These results demonstrate a direct role of HSF1 in synaptic gene regulation that has important implications in synapse maintenance in basal and pathological conditions.

Einstein-Nathan Shock Center: translating the hallmarks of aging to extend human health span

The overarching mission of the Einstein-Nathan Shock Center (E-NSC) is to make scientific discoveries in geroscience, leveraging on the expertise in our center in 6 out of the 7 pillars of aging, and to translate their effects towards drug discovery. The relevance of this basic biology of aging discoveries to humans will be confirmed through the unique gero-human resource at E-NSC. This is achieved through services provided by E-NSC, connectivity among its members, attracting worldwide investigators, and providing them with the opportunities to become future leaders. The two central components of the E-NSC are (a) cutting-edge research programs and (b) unique E-NSC research support cores. E-NSC scientists lead NIH-supported cutting-edge research programs that integrate key hallmarks of aging including proteostasis/autophagy, metabolism/inflammaging, genetic/epigenetics, stem cells/regeneration, and translational aging/longevity. Since the inception of the E-NSC, the well-integrated, collaborative, and innovative nature of the multiple supporting state-of-the-art E-NSC research cores form the bedrock of research success at the E-NSC. The three state-of-the-art E-NSC research cores, (i) Proteostasis of Aging Core (PAC), (ii) the Health Span Core (HSC), and (iii) the Human Multi-Omics Core (HMOC), have allowed impressive expansion of translational biological research programs. Expansion was facilitated through the wealth of data coming from genomics/proteomics and metabolomic analysis on human longevity studies, due to access to a variety of biological samples from elderly subjects in clinical trials with aging-targeting drugs, and new drug design services via the PAC to target the hallmarks of aging.

Effects of a Tea Cultivar "MK5601" on Behaviors and Hippocampal Neurotrophin-3 Levels in Middle-Aged Mice

Dietary factors are thought to play an important role in the prevention of cognition diseases and depression in late life. In the present study, we compared the effects between the theogallin-rich tea cultivar, "MK5601" and a common Japanese tea cultivar, "Yabukita" on behaviors and hippocampal neurotrophin levels in experimental animals. Middle-aged mice (aged 8 mo) were given either of the tea infusions or water ad libitum for 4 mo. In the novel object location test, the middle-aged mice drinking water or "Yabukita" performed worse than young mice (aged 2-3 mo) although the middle-aged mice drinking "MK5601" retained spatial memory at the same level as the young mice. We also found that the middle-aged mice drinking "MK5601" showed high levels of neurotrophin-3 in the hippocampus. In conclusion, the "MK5601" tea infusion appears to be effective in preventing age-related changes in cognitive function, as compared with a common Japanese tea cultivar.

Episodic-like memory is preserved with age in cuttlefish

Episodic memory, remembering past experiences based on unique what–where–when components, declines during ageing in humans, as does episodic-like memory in non-human mammals. By contrast, semantic memory, remembering learnt knowledge without recalling unique what–where–when features, remains relatively intact with advancing age. The age-related decline in episodic memory likely stems from the deteriorating function of the hippocampus in the brain. Whether episodic memory can deteriorate with age in species that lack a hippocampus is unknown. Cuttlefish are molluscs that lack a hippocampus. We test both semantic-like and episodic-like memory in sub-adults and aged-adults nearing senescence (n = 6 per cohort). In the semantic-like memory task, cuttlefish had to learn that the location of a food resource was dependent on the time of day. Performance, measured as proportion of correct trials, was comparable across age groups. In the episodic-like memory task, cuttlefish had to solve a foraging task by retrieving what–where–when information about a past event with unique spatio-temporal features. In this task, performance was comparable across age groups; however, aged-adults reached the success criterion (8/10 correct choices in consecutive trials) significantly faster than sub-adults. Contrary to other animals, episodic-like memory is preserved in aged cuttlefish, suggesting that memory deterioration is delayed in this species.

Curcumin Attenuates Sarcopenia in Chronic Forced Exercise Executed Aged Mice by Regulating Muscle Degradation and Protein Synthesis with Antioxidant and Anti-inflammatory Effects

The aim of the current study is to investigate the effects of spray dry powders of Curcuma longa containing 40% curcumin (CM-SD), as a new aqueous curcumin formula, on sarcopenia in chronic forced exercise executed 10 month old ICR mice. CM-SD (80 and 40 mg/kg) increased calf thicknesses and strengths, total body and calf protein amounts, and muscle weights in both gastrocnemius and soleus muscles. mRNA expressions regarding muscle growth and protein synthesis were induced, while those of muscle degradation significantly declined in CM-SD treatment. CM-SD decreased serum biochemical markers, lipid peroxidation, and reactive oxygen species and increased endogenous antioxidants and enzyme activities. It also reduced immunoreactive myofibers for apoptosis and oxidative stress markers but increased ATPase in myofibers. These results suggest that CM-SD can be an adjunct therapy to exercise-based remedy that prevents muscle disorders including sarcopenia by anti-apoptosis, anti-inflammation, and antioxidation-mediated modulation of gene expressions related to muscle degradation and protein synthesis.

Vortioxetine ameliorates anhedonic-like behaviour and promotes strategic cognitive performance in a rodent touchscreen task

Depression-associated cognitive impairments are among the most prevalent and persistent symptoms during remission from a depressive episode and a major risk factor for relapse. Consequently, development of antidepressant drugs, which also alleviate cognitive impairments, is vital. One such potential antidepressant is vortioxetine that has been postulated to exhibit both antidepressant and pro-cognitive effects. Hence, we tested vortioxetine for combined antidepressant and pro-cognitive effects in male Long-Evans rats exposed to the chronic mild stress (CMS) paradigm. This well-established CMS paradigm evokes cognitive deficits in addition to anhedonia, a core symptom of depression. Learning and memory performance was assessed in the translational touchscreen version of the paired-associates learning task. To identify the mechanistic underpinning of the neurobehavioural results, transcriptional profiling of genes involved in the stress response, neuronal plasticity and genes of broad relevance in neuropsychiatric pathologies were assessed. Vortioxetine substantially relieved the anhedonic-like state in the CMS rats and promoted acquisition of the cognitive test independent of hedonic phenotype, potentially due to an altered cognitive strategy. Minor alterations in gene expression profiling in prefrontal cortex and hippocampus were found. In summary, our findings suggest that vortioxetine exhibits an antidepressant effect as well as behavioural changes in a translational learning task.

Effects of high-intensity interval training and flaxseed oil supplement on learning, memory and immobility: relationship with BDNF and TrkB genes

This study examined the independent and combined effects of high-intensity interval training (HIIT) and flaxseed oil supplementation on cognitive/executive functions in middle-aged rats. Hippocampal neurotropic brain factor (BDNF) and tyrosine kinase receptor B (TrkB) gene expression were also measured. Animals were randomly divided into groups including no exercise control and saline (CS), no exercise control and flaxseed oil supplement (CF), exercise training-and saline (TS) and exercise training and flaxseed oil supplement (TF). The training groups undertook a program of HIIT (10 weeks, five sessions per week) and the supplement groups received flaxseed oil supplement (300 mg/kg). The results showed that HIIT and flaxseed oil supplementation independently had positive effects on memory and learning (P<0.05). HIIT and flaxseed oil independently decreased immobility behaviour and increased hippocampal BDNF and TrkB genes expression (P<0.05). HIIT and flaxseed oil combination had a greater effect on some variables (hippocampal TrkB gene expression, memory and immobility) compared to each intervention alone (P<0.05). In conclusion, HIIT and flaxseed oil can independently improve cognitive/executive functions. In addition, HIIT had a greater positive effect than flaxseed oil supplementation on memory and immobility. The combination of HIIT and flaxseed oil supplement had a more positive effect compared to each intervention alone on memory, and immobility. Hippocampal BDNF gene expression did not significantly differ in the combination or independent groups. Thus, future work is needed on several other genes in different segments of the brain to find the additive-mechanisms involved in memory and immobility regulation and younger and older species of rat should be examined.

Vortioxetine Prevents Lipopolysaccharide-Induced Memory Impairment Without Inhibiting the Initial Inflammatory Cascade

Vortioxetine is a novel multimodal antidepressant that modulates a wide range of neurotransmitters throughout the brain. Preclinical and clinical studies have shown that vortioxetine exerts positive effects on different cognitive domains and neuroprotective effects. Considering the key role of microglial cells in brain plasticity and cognition, we aimed at investigating the effects of pretreatment with vortioxetine in modulating behavioral and molecular effects induced by an immune challenge: peripheral injection of lipopolysaccharide (LPS). To this purpose, C57BL/6J male mice were first exposed to a 28-day standard diet or vortioxetine-enriched diet, which was followed by an acute immune challenge with LPS. Sickness symptoms and depressive-like behaviors (anhedonia and memory impairment) were tested 6 and 24 h after exposure to LPS, respectively. Moreover, the expressions of markers of immune activation and M1/M2 markers of microglia polarization were measured in the dorsal and ventral parts of the hippocampus. The pretreatment with vortioxetine did not affect both LPS-induced sickness behavior and anhedonia but prevented the deficit in the recognition memory induced by the immune challenge. At the transcriptional level, chronic exposure to vortioxetine did not prevent LPS-induced upregulation of proinflammatory cytokines 6 h after the immune challenge but rather seemed to potentiate the immune response to the challenge also by affecting the levels of expression of markers of microglia M1 phenotype, like cluster of differentiation (CD)14 and CD86, in an area-dependent manner. However, at the same time point, LPS injection significantly increased the expression of the M2 polarization inducer, interleukin 4, only in the hippocampus of animals chronically exposed to vortioxetine. These results demonstrate that a chronic administration of vortioxetine specifically prevents LPS-induced memory impairment, without affecting acute sickness behavior and anhedonia, and suggest that hippocampal microglia may represent a cellular target of this novel antidepressant medication. Moreover, we provide a useful model to further explore the molecular mechanisms specifically underlying cognitive impairments following an immune challenge.

Microbial memories: Sex-dependent impact of the gut microbiome on hippocampal plasticity

Germ‐free rodents, raised in the absence of a measurable gut microbiome, have been a key model to study the microbiome‐gut‐brain axis. Germ‐free mice exhibit marked behavioural and neurochemical differences to their conventionally raised counterparts. It is as yet unclear how these neurochemical differences lead to the behavioural differences. Here, we test the electrophysiological properties of hippocampal plasticity in adult germ‐free mice and compare them to conventionally raised counterparts. Whilst basal synaptic efficacy and pre‐synaptic short‐term plasticity appear normal, we find a striking alteration of hippocampal long‐term potentiation specifically in male germ‐free slices. However, the spike output of these neurons remains normal along with altered input‐output coupling, potentially indicating homeostatic compensatory mechanisms, or an altered excitation/inhibition balance. To our knowledge this is the first time the electrophysiological properties of the hippocampus have been assessed in a microbiome deficient animal. Our data indicate that the absence of a microbiome alters integration of dendritic signalling in the CA1 region in mice.

Interaction Between Neurogenic Stimuli and the Gene Network Controlling the Activation of Stem Cells of the Adult Neurogenic Niches, in Physiological and Pathological Conditions

In the adult mammalian brain new neurons are continuously generated throughout life in two niches, the dentate gyrus of the hippocampus and the subventricular zone. This process, called adult neurogenesis, starts from stem cells, which are activated and enter the cell cycle. The proliferative capability of stem cells progressively decreases during aging. The population of stem cells is generally quiescent, and it is not clear whether the potential for stem cells to expand is limited, or whether they can expand and then return to quiescence, remaining available for further activation. Certain conditions may deregulate stem cells quiescence and self-renewal. In fact we discuss the possibility of activation of stem cells by neurogenic stimuli as a function of the intensity of the stimulus (i.e., whether this is physiological or pathological), and of the deregulation of the system (i.e., whether the model is aged or carrying genetic mutations in the gene network controlling quiescence). It appears that when the system is aged and/or carrying mutations of quiescence-maintaining genes, preservation of the quiescent state of stem cells is more critical and stem cells can be activated by a neurogenic stimulus which is ineffective in normal conditions. Moreover, when a neurogenic stimulus is in itself a cause of brain damage (e.g., kainic acid treatment) the activation of stem cells occurs bypassing any inhibitory control. Plausibly, with strong neurogenic stimuli, such as kainic acid injected into the dentate gyrus, the self-renewal capacity of stem cells may undergo rapid exhaustion. However, the self-renewal capability of stem cells persists when normal stimuli are elicited in the presence of a mutation of one of the quiescence-maintaining genes, such as p16Ink4a, p21Cip1 or Btg1. In this case, stem cells become promptly activated by a neurogenic stimulus even during aging. This indicates that stem cells retain a high proliferative capability and plasticity, and suggests that stem cells are protected against the response to stimulus and are resilient to exhaustion. It will be interesting to assess at which functional degree of deregulation of the quiescence-maintaining system, stem cells will remain responsive to repeated neurogenic stimuli without undergoing exhaustion of their pool.

Vortioxetine administration attenuates cognitive and synaptic deficits in 5×FAD mice

RATIONALE AND OBJECTIVE

Vortioxetine has been reported to exhibit a variety of neurobiological functions and neuroprotective effects. In the present study, we aimed to investigate the effects of vortioxetine on cognitive performance in a transgenic mouse model of Alzheimer's disease (AD).

METHODS

We administered vortioxetine (10 mg/kg, i.p., every day, for approximately 6 weeks), which acts on multiple 5-serotonin (5-HT) receptors, to 3.5-month-old 5×FAD mice. Subsequently, we used the open field (OF) test to detect anxiety-like behavior in the mice. The novel object recognition (NOR) test and Morris water maze (MWM) were used to assess the cognitive states of the 5×FAD mice. We also measured the levels of insoluble amyloid plaques and soluble β-amyloid (Aβ) plaques. Finally, we explored the expression levels of postsynaptic density protein 95 (PSD95), synaptophysin (SYP), and synaptotagmin-1 (SYT1) in the hippocampus of the mice.

RESULTS

The administration of vortioxetine effectively reversed the reduction in anxiety-type behaviors in 5×FAD mice and improved the impairment in recognition memory and spatial reference memory. However, we did not find that vortioxetine decreased or delayed the formation of amyloid plaques or Aβ. Interestingly, we found a significant increase in the expression levels of PSD95, SYP, and SYT1 in the 5×FAD mice after vortioxetine treatment compared with the control group.

CONCLUSION

These results demonstrate that vortioxetine may improve cognitive impairment in 5×FAD mice. The role in cognitive improvement may be related to the beneficial effects of vortioxetine on synaptic function.

Effect of amyloid toxicity or chronic cerebral hypoperfusion on brain insulin resistance in a rat model with intracerebroventricular streptozotocin

Sporadic Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder affected by amyloid and vascular pathogenesis. Brain insulin resistance (BIR) has been suggested as one of the pathomechanisms of sporadic AD. We investigated how the amyloid and vascular pathogenesis of AD interacts with BIR. We examined experimental groups mimicking amyloid pathogenesis following intracerebroventriculr (icv) injection of amyloid β or vascular pathogenesis following permanent ligation of the bilateral common carotid arteries in Wistar rats that had undergone icv injection of streptozotocin. Behavioral tests and pathologic studies were performed. Cognitive impairments were induced by BIR superimposed by amyloid or vascular pathogenesis. Neuroinflammation in the white matter and hippocampus was aggravated by an interaction between BIR and vascular pathogenesis. Amyloid-associated pathology in the white matter was enhanced by BIR and vascular pathogenesis. Tau-associated pathology in the hippocampus was altered by BIR in a relation with amyloid or vascular pathogenesis. Our study may provide useful experimental insights based on an integrated approach to the influence of amyloid and vascular pathogenesis on BIR, permitting better understanding of the heterogeneous pathogenesis of sporadic AD. Pathologic responses in sporadic AD may differ depending on amyloid and vascular pathogenesis and may sometimes be synergistically aggravated when combined with BIR.

Effects of aging on the motor, cognitive and affective behaviors, neuroimmune responses and hippocampal gene expression

The known effects of aging on the brain and behavior include impaired cognition, increases in anxiety and depressive-like behaviors, and reduced locomotor activity. Environmental exposures and interventions also influence brain functions during aging. We investigated the effects of normal aging under controlled environmental conditions and in the absence of external interventions on locomotor activity, cognition, anxiety and depressive-like behaviors, immune function and hippocampal gene expression in C57BL/6 mice. Healthy mice at 4, 9, and 14 months of age underwent behavioral testing using an established behavioral battery, followed by cellular and molecular analysis using flow cytometry, immunohistochemistry, and quantitative PCR. We found that 14-month-old mice showed significantly reduced baseline locomotion, increased anxiety, and impaired spatial memory compared to younger counterparts. However, no significant differences were observed for depressive-like behavior in the forced-swim test. Microglia numbers in the dentate gyrus, as well as CD8+ memory T cells increased towards late middle age. Aging processes exerted a significant effect on the expression of 43 genes of interest in the hippocampus. We conclude that aging is associated with specific changes in locomotor activity, cognition, anxiety-like behaviors, neuroimmune responses and hippocampal gene expression.

Rolipram treatment during consolidation ameliorates long-term object location memory in aged male mice

Normal aging is accompanied by cognitive and memory impairments that negatively impact quality of life for the growing elderly population. Hippocampal function is most vulnerable to the deleterious effects of aging, and deficits in hippocampus-dependent memories are common amongst aged individuals. Moreover, signaling networks such as the cAMP/PKA/CREB pathway, which are critical for memory consolidation, are dampened in healthy aged subjects. Phosphodiesterase (PDE) enzymes that break down cAMP are also affected by aging, and increased break down of cAMP by PDEs may contribute to reduced activity of the cAMP/PKA/CREB signaling network in the brain of aged individuals. Here, we report that the PDE4 inhibitor rolipram administered during consolidation of hippocampus-dependent object location memory improves aged-related spatial memory deficits in aged mice.

Exercise Modalities Improve Aversive Memory and Survival Rate in Aged Rats: Role of Hippocampal Epigenetic Modifications

We aimed to investigate the effects of aging and different exercise modalities on aversive memory and epigenetic landscapes at brain-derived neurotrophic factor, cFos, and DNA methyltransferase 3 alpha (Bdnf, cFos, and Dnmt3a, respectively) gene promoters in hippocampus of rats. Specifically, active epigenetic histone markers (H3K9ac, H3K4me3, and H4K8ac) and a repressive mark (H3K9me2) were evaluated. Adult and aged male Wistar rats (2 and 22 months old) were subjected to aerobic, acrobatic, resistance, or combined exercise modalities for 20 min, 3 times a week, during 12 weeks. Aging per se altered histone modifications at the promoters of Bdnf, cFos, and Dnmt3a. All exercise modalities improved both survival rate and aversive memory performance in aged animals (n = 7-10). Exercise altered hippocampal epigenetic marks in an age- and modality-dependent manner (n = 4-5). Aerobic and resistance modalities attenuated age-induced effects on hippocampal Bdnf promoter H3K4me3. Besides, exercise modalities which improved memory performance in aged rats were able to modify H3K9ac or H3K4me3 at the cFos promoter, which could increase gene transcription. Our results highlight biological mechanisms which support the efficacy of all tested exercise modalities attenuating memory deficits induced by aging.

Rigor and reproducibility in rodent behavioral research

Behavioral neuroscience research incorporates the identical high level of meticulous methodologies and exacting attention to detail as all other scientific disciplines. To achieve maximal rigor and reproducibility of findings, well-trained investigators employ a variety of established best practices. Here we explicate some of the requirements for rigorous experimental design and accurate data analysis in conducting mouse and rat behavioral tests. Novel object recognition is used as an example of a cognitive assay which has been conducted successfully with a range of methods, all based on common principles of appropriate procedures, controls, and statistics. Directors of Rodent Core facilities within Intellectual and Developmental Disabilities Research Centers contribute key aspects of their own novel object recognition protocols, offering insights into essential similarities and less-critical differences. Literature cited in this review article will lead the interested reader to source papers that provide step-by-step protocols which illustrate optimized methods for many standard rodent behavioral assays. Adhering to best practices in behavioral neuroscience will enhance the value of animal models for the multiple goals of understanding biological mechanisms, evaluating consequences of genetic mutations, and discovering efficacious therapeutics.

Vortioxetine reverses medial prefrontal cortex-mediated cognitive deficits in male rats induced by castration as a model of androgen deprivation therapy for prostate cancer

RATIONALE

Androgen deprivation therapy (ADT) is an effective treatment for prostate cancer, but induces profound cognitive impairment. Little research has addressed mechanisms underlying these deficits or potential treatments. This is an unmet need to improve quality of life for prostate cancer survivors.

OBJECTIVES

We investigated mechanisms of cognitive impairment after ADT in rats and potential utility of the multimodal serotonin-targeting drug, vortioxetine, to improve the impairment, as vortioxetine has specific efficacy against cognitive impairment in depression.

METHODS

Male Sprague-Dawley rats were surgically castrated. Vortioxetine (28 mg/kg/day) was administered in the diet. The attentional set-shifting test was used to assess medial prefrontal cortex (mPFC) executive function. Afferent-evoked field potentials were recorded in the mPFC of anesthetized rats after stimulating the ventral hippocampus (vHipp) or medial dorsal thalamus (MDT). Gene expression changes were assessed by microarray. Effects of vortioxetine on growth of prostate cancer cells were assessed in vitro.

RESULTS

ADT impaired cognitive set shifting and attenuated responses evoked in the mPFC by the vHipp afferent, but not the MDT. Both the cognitive impairment and attenuated vHipp-evoked responses were reversed by chronic vortioxetine treatment. Preliminary investigation of gene expression in the mPFC indicates that factors involved in neuronal plasticity and synaptic transmission were down-regulated by castration and up-regulated by vortioxetine in castrated animals. Vortioxetine neither altered the growth of prostate cancer cells in vitro nor interfered with the antiproliferative effects of the androgen antagonist, enzalutamide.

CONCLUSIONS

These results suggest that vortioxetine may be useful in mitigating cognitive impairment associated with ADT for prostate cancer.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

Efficacy of a low-dose melatonin pretreatment in protecting against the neurobehavioral consequences of chronic hypoperfusion in middle-aged female rats

Mild cognitive impairment (MCI) is characterized by a reduction in cerebral blood flow. Permanent ligation of the common carotid arteries (2VO) in the rat mimics the chronic decrease in CBF that characterizes aMCI. The current study determined if melatonin (a pineal hormone with neuroprotective properties) can attenuate the neurobehavioral consequences of 2VO using middle-aged female rats. Two weeks following 2VO or sham surgery, rats were tested on various learning and memory tasks. 2VO resulted in hyperlocomotion on the open field. Melatonin attenuated this 2VO-induced hyperactivity. 2VO impaired visual memory however this was not attenuated by melatonin administration. Neither 2VO nor melatonin affected spatial memory performance on the MWM or spatial recognition task. Y-maze testing revealed 2VO rats exhibited a lower spontaneous alternation pattern and performed a greater number of alternate arm returns compared to 2VO rats treated with melatonin. 2VO resulted in a significant loss of CA1 hippocampal neurons which was attenuated with melatonin treatment. Chronic melatonin was found to attenuate the neuronal consequences of chronic cerebral hypoperfusion but only conferred partial behavioral protection in middle-aged female rats. Our results demonstrate that inclusion of older rodents is important in neuroprotection studies as neuroprotective agents may act differently in an aged brain.

Fluoxetine and Vortioxetine Reverse Depressive-Like Phenotype and Memory Deficits Induced by Aβ1-42 Oligomers in Mice: A Key Role of Transforming Growth Factor-β1

Depression is a risk factor for the development of Alzheimer’s disease (AD), and the presence of depressive symptoms significantly increases the conversion of mild cognitive impairment (MCI) into AD. A long-term treatment with antidepressants reduces the risk to develop AD, and different second-generation antidepressants such as selective serotonin reuptake inhibitors (SSRIs) are currently being studied for their neuroprotective properties in AD. In the present work, the SSRI fluoxetine and the new multimodal antidepressant vortioxetine were tested for their ability to prevent memory deficits and depressive-like phenotype induced by intracerebroventricular injection of amyloid-β (1-42) (Aβ_1-42) oligomers in 2-month-old C57BL/6 mice. Starting from 7 days before Aβ injection, fluoxetine (10 mg/kg) and vortioxetine (5 and 10 mg/kg) were intraperitoneally injected daily for 24 days. Chronic treatment with fluoxetine and vortioxetine (both at the dose of 10 mg/kg) was able to rescue the loss of memory assessed 14 days after Aβ injection by the passive avoidance task and the object recognition test. Both antidepressants reversed the increase in immobility time detected 19 days after Aβ injection by forced swim test. Vortioxetine exerted significant antidepressant effects also at the dose of 5 mg/kg. A significant deficit of transforming growth factor-β1 (TGF-β1), paralleling memory deficits and depressive-like phenotype, was found in the hippocampus of Aβ-injected mice in combination with a significant reduction of the synaptic proteins synaptophysin and PSD-95. Fluoxetine and vortioxetine completely rescued hippocampal TGF-β1 levels in Aβ-injected mice as well as synaptophysin and PSD-95 levels. This is the first evidence that a chronic treatment with fluoxetine or vortioxetine can prevent both cognitive deficits and depressive-like phenotype in a non-transgenic animal model of AD with a key contribution of TGF-β1.

Vortioxetine for Cognitive Enhancement in Major Depression: From Animal Models to Clinical Research

Objectives: Vortioxetine has already shown its efficacy in the acute and long-term treatment of major depressive disorder (MDD) and its potential interest in the prevention of relapse. The aim of this study was to review the current status of knowledge regarding its cognitive effects. Methods: We conducted a review of key data obtained from preclinical behavioral models and clinical trials in MDD focusing on vortioxetine-induced cognitive changes. Results: In animals, acute and chronic administration of vortioxetine improves performance on objective measures that cover a broad range of cognitive domains. In human, vortioxetine appears to be a useful treatment option in MDD patients with cognitive dysfunction. Conclusion: Vortioxetine constitutes a promising treatment for treatment of cognitive impairment in MDD, but its place in the therapeutic armamentarium still needs to be determined.

Inhibition of microRNA-124-3p as a novel therapeutic strategy for the treatment of Gulf War Illness: Evaluation in a rat model

Gulf War Illness (GWI) is a chronic, multisymptom illness that continues to affect up to 30% of veterans deployed to the Persian Gulf during the 1990-1991 Gulf War. After nearly 30 years, useful treatments for GWI are lacking and underlying cellular and molecular mechanisms involved in its pathobiology remain poorly understood, although exposures to pyridostigmine bromide (PB) and pesticides are consistently identified to be among the strongest risk factors. Alleviation of the broad range of symptoms manifested in GWI, which involve the central nervous system, the neuroendocrine system, and the immune system likely requires therapies that are able to activate and inactivate a large set of orchestrated genes. Previous work in our laboratory using an established rat model of GWI identified persistent elevation of microRNA-124-3p (miR-124) levels in the hippocampus whose numerous gene targets are involved in cognition-associated pathways and neuroendocrine function. This study aimed to investigate the broad effects of miR-124 inhibition in the brain 9 months after completion of a 28-day exposure regimen of PB, DEET (N,N-diethyl-3-methylbenzamide), permethrin, and mild stress by profiling the hippocampal expression of genes known to play a critical role in synaptic plasticity, glucocorticoid signaling, and neurogenesis. We determined that intracerebroventricular infusion of a miR-124 antisense oligonucleotide (miR-124 inhibitor; 0.05-0.5 nmol/day/28 days), but not a negative control oligonucleotide, into the lateral ventricle of the brain caused increased protein expression of multiple validated miR-124 targets and increased expression of downstream target genes important for cognition and neuroendocrine signaling in the hippocampus. Off-target cardiotoxic effects were revealed in GWI rats receiving 0.1 nmol/day as indicated by the detection in plasma of 5 highly elevated protein cardiac injury markers and 6 upregulated cardiac-enriched miRNAs in plasma exosomes determined by next-generation sequencing. Results from this study suggest that in vivo inhibition of miR-124 function in the hippocampus is a promising, novel therapeutic approach to improve cognition and neuroendocrine dysfunction in GWI. Additional preclinical studies in animal models to assess feasibility and safety by developing a practical, noninvasive drug delivery system to the brain and exploring potential adverse toxicologic effects of miR-124 inhibition are warranted.

Reduced Efficacy of d-Amphetamine and 3,4-Methylenedioxymethamphetamine in Inducing Hyperactivity in Mice Lacking the Postsynaptic Scaffolding Protein SHANK1

Genetic defects in the three SH3 and multiple ankyrin repeat domains (SHANK) genes (SHANK1, SHANK2, and SHANK3) are associated with multiple major neuropsychiatric disorders, including autism spectrum disorder (ASD), schizophrenia (SCZ), and bipolar disorder (BPD). Psychostimulant-induced hyperactivity is a commonly applied paradigm to assess behavioral phenotypes related to BPD and considered to be the gold standard for modeling mania-like elevated drive in mouse models. Therefore, the goal of our present study was to test whether Shank1 plays a role in the behavioral effects of psychostimulants and whether this is associated with genotype-dependent neurochemical alterations. To this aim, male and female null mutant Shank1^-/- mice were treated with d-amphetamine (AMPH; 2.5 mg/kg) and 3,4-methylenedioxymethamphetamine (MDMA, commonly known as ecstasy; 20 mg/kg), and psychostimulant-induced hyperactivity was compared to heterozygous Shank1^+/- and wildtype Shank1^+/+ littermate controls. Results show that Shank1^-/- mice display reduced psychostimulant-induced hyperactivity, although psychostimulants robustly stimulated locomotor activity in littermate controls. Shank1 deletion effects emerged throughout development, were particularly prominent in adulthood, and seen in response to both psychostimulants, i.e., AMPH and MDMA. Specifically, while AMPH-induced hyperactivity was reduced but still detectable in Shank1^-/- mice, MDMA-induced hyperactivity was robustly blocked and completely absent in Shank1^-/- mice. Reduced efficacy of psychostimulants to stimulate hyperactivity in Shank1^-/- mice might be associated with alterations in the neurochemical architecture in prefrontal cortex, nucleus accumbens, and hypothalamus. Our observation that psychostimulant-induced hyperactivity is reduced rather than enhanced in Shank1^-/- mice clearly speaks against a behavioral phenotype with relevance to BPD. Lack of BPD-like phenotype is consistent with currently available human data linking mutations in SHANK2 and SHANK3 but not SHANK1 to BPD.

Depression and adult neurogenesis: Positive effects of the antidepressant fluoxetine and of physical exercise

Of wide interest for health is the relation existing between depression, a very common psychological illness, accompanied by anxiety and reduced ability to concentrate, and adult neurogenesis. We will focus on two neurogenic stimuli, fluoxetine and physical exercise, both endowed with the ability to activate adult neurogenesis in the dentate gyrus of the hippocampus, known to be required for learning and memory, and both able to counteract depression. Fluoxetine belongs to the class of selective serotonin reuptake inhibitor (SSRI) antidepressants, which represent the most used pharmacological therapy; physical exercise has also been shown to effectively counteract depression symptoms in rodents as well as in humans. While there is evidence that the antidepressant effect of fluoxetine requires its pro-neurogenic action, exerted by promoting proliferation, differentiation and survival of progenitor cells of the hippocampus, on the other hand fluoxetine exerts also neurogenesis-independent antidepressant effects by influencing the plasticity of the new neurons generated. Similarly, the antidepressant action of running also correlates with an increase of hippocampal neurogenesis and plasticity, although the gene pathways involved are only partially coincident with those of fluoxetine, such as those involved in serotonin metabolism and synapse formation. We further discuss how extra-neurogenic actions are also suggested by the fact that, unlike running, fluoxetine is unable to stimulate neurogenesis during aging, but still displays antidepressant effects. Moreover, in specific conditions, fluoxetine or running activate not only progenitor but also stem cells, which normally are not stimulated; this fact reveals how stem cells have a long-term, hidden ability to self-renew and, more generally, that neurogenesis is subject to complex controls that may play a role in depression, such as the type of neurogenic stimulus or the state of the local niche. Finally, we discuss how fluoxetine or running are effective in counteracting depression originated from stress or neurodegenerative diseases.

Fluoxetine or Sox2 reactivate proliferation-defective stem and progenitor cells of the adult and aged dentate gyrus

The dentate gyrus of the hippocampus and the subventricular zone are neurogenic niches where the production of new neurons from glia-like stem cells continues throughout adult life. It is not clear whether the pool of stem cells is fated to be exhausted or is conserved until old age. We observed that the antiproliferative gene Btg1 maintains the quiescence of stem cells, and its ablation causes an increase of stem/progenitor cells proliferation in neonatal mice followed by progressive loss of proliferation during adulthood. Fluoxetine is an antidepressant, which exerts a powerful neurogenic effect on dentate gyrus progenitor cells, but is ineffective on stem cells. Here we show that adult dentate gyrus stem cells in the Btg1 knockout mice, with reduced self-renewal and proliferative capability, can be reactivated by fluoxetine, which increases their number greatly above the level of control or fluoxetine-treated wild-type mice. The increase of mitotic index above wild-type in Btg1 knockout fluoxetine-treated stem cells indicates that fluoxetine forces quiescent stem cells to enter the cycle. Stem cell proliferation undergoes continuous reactivation until fluoxetine is administered. Remarkably, fluoxetine reactivates proliferation-defective stem cells also in aged Btg1 knockout mice (15-month-old), an effect absent in wild-type aged mice. Moreover, overexpression of Sox2 retrovirally transduced in Btg1 knockout dentate gyrus cells significantly increases the number of neuroblasts, indicating that Sox2 is able to promote the self-renewal of proliferation-defective stem cells. Overall, the deletion of an antiproliferative gene, such as Btg1, reveals that dentate gyrus stem cells retain a hidden plasticity for self-renewal also in old age, in agreement with a model of permanent self-renewal.

Centella asiatica increases hippocampal synaptic density and improves memory and executive function in aged mice

INTRODUCTION

Centella asiatica is a plant used for centuries to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates age-related spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its mechanism of improving age-related cognitive impairment. This study investigates the effects of CAW on a variety of cognitive tasks as well as on synaptic density and mitochondrial and antioxidant pathways.

METHODS

Twenty-month-old CB6F1 mice were treated with CAW (2 mg/ml) in their drinking water for 2 weeks prior to behavioral testing. Learning, memory, and executive function were assessed using the novel object recognition task (NORT), object location memory task (OLM), and odor discrimination reversal learning (ODRL) test. Tissue was collected for Golgi analysis of spine density as well as assessment of mitochondrial, antioxidant, and synaptic proteins.

RESULTS

CAW improved performance in all behavioral tests suggesting effects on hippocampal and cortical dependent memory as well as on prefrontal cortex mediated executive function. There was also an increase in synaptic density in the treated animals, which was accompanied by increased expression of the antioxidant response gene NRF2 as well as the mitochondrial marker porin.

CONCLUSIONS

These data show that CAW can increase synaptic density as well as antioxidant and mitochondrial proteins and improve multiple facets of age-related cognitive impairment. Because mitochondrial dysfunction and oxidative stress also accompany cognitive impairment in many pathological conditions this suggests a broad therapeutic utility of CAW.

(R)-fluoxetine enhances cognitive flexibility and hippocampal cell proliferation in mice

Fluoxetine is a clinically successful antidepressant. It is a racemic mixture of (R) and (S) stereoisomers. In preclinical studies, chronic treatment with fluoxetine (10 mg/kg) had antidepressant effects correlated with increased hippocampal cell proliferation in adult rodents. However, the contribution of the enantiomers of fluoxetine is largely unknown. We investigated the effects of treatment with (R)- and (S)-fluoxetine on cognitive behavioral paradigms and examined cell proliferation in the hippocampus of C57BL/6J female mice. In a behavioral sequencing task using the IntelliCage system in which discriminated spatial patterns of rewarded and never-rewarded corners were reversed serially, (R)-fluoxetine-treated mice showed rapid acquisition of behavioral sequencing (compared with S-fluoxetine) and cognitive flexibility in subsequent reversal stages in intra- and inter-session analysis. (R)-fluoxetine also increased cell proliferation in the hippocampus, in particular in the suprapyramidal blade of the dentate gyrus. (R)-fluoxetine had superior effects to (S)-fluoxetine in elevated plus maze, forced-swim and tail-suspension tests. These results suggest that (R)-fluoxetine, which has been reported to have a shorter half-life than (S)-fluoxetine, has superior antidepressant effects and more consistently improves spatial learning and memory. This profile offers advantages in depression treatment and may also aid management of the neurocognitive impairments associated with depression.

Characterizing age-related decline of recognition memory and brain activation profile in mice

Episodic memory decline is one of the earlier deficits occurring during normal aging in humans. The question of spatial versus non-spatial sensitivity to age-related memory decline is of importance for a full understanding of these changes. Here, we characterized the effect of normal aging on both non-spatial (object) and spatial (object location) memory performances as well as on associated neuronal activation in mice. Novel-object (NOR) and object-location (OLR) recognition tests, respectively assessing the identity and spatial features of object memory, were examined at different ages. We show that memory performances in both tests were altered by aging as early as 15 months of age: NOR memory was partially impaired whereas OLR memory was found to be fully disrupted at 15 months of age. Brain activation profiles were assessed for both tests using immunohistochemical detection of c-Fos (neuronal activation marker) in 3and 15 month-old mice. Normal performances in NOR task by 3 month-old mice were associated to an activation of the hippocampus and a trend towards an activation in the perirhinal cortex, in a way that did significantly differ with 15 month-old mice. During OLR task, brain activation took place in the hippocampus in 3 month-old but not significantly in 15 month-old mice, which were fully impaired at this task. These differential alterations of the object- and object-location recognition memory may be linked to differential alteration of the neuronal networks supporting these tasks.

A Critical Role of Mitochondria in BDNF-Associated Synaptic Plasticity After One-Week Vortioxetine Treatment

BACKGROUND

Preclinical studies have indicated that antidepressant effect of vortioxetine involves increased synaptic plasticity and promotion of spine maturation. Mitochondria dysfunction may contribute to the pathophysiological basis of major depressive disorder. Taking into consideration that vortioxetine increases spine number and dendritic branching in hippocampus CA1 faster than fluoxetine, we hypothesize that new spines induced by vortioxetine can rapidly form functional synapses by mitochondrial support, accompanied by increased brain-derived neurotrophic factor signaling.

METHODS

Rats were treated for 1 week with vortioxetine or fluoxetine at pharmacologically relevant doses. Number of synapses and mitochondria in hippocampus CA1 were quantified by electron microscopy. Brain-derived neurotrophic factor protein levels were visualized with immunohistochemistry. Gene and protein expression of synapse and mitochondria-related markers were investigated with real-time quantitative polymerase chain reaction and immunoblotting.

RESULTS

Vortioxetine increased number of synapses and mitochondria significantly, whereas fluoxetine had no effect after 1-week dosing. BDNF levels in hippocampus DG and CA1 were significantly higher after vortioxetine treatment. Gene expression levels of Rac1 after vortioxetine treatment were significantly increased. There was a tendency towards increased gene expression levels of Drp1 and protein levels of Rac1. However, both gene and protein levels of c-Fos were significantly decreased. Furthermore, there was a significant positive correlation between BDNF levels and mitochondria and synapse numbers.

CONCLUSION

Our results imply that mitochondria play a critical role in synaptic plasticity accompanied by increased BDNF levels. Rapid changes in BDNF levels and synaptic/mitochondria plasticity of hippocampus following vortioxetine compared with fluoxetine may be ascribed to vortioxetine's modulation of serotonin receptors.

Shortened Spadin Analogs Display Better TREK-1 Inhibition, In Vivo Stability and Antidepressant Activity

Depression is a devastating mental disorder that affects 20% of the population worldwide. Despite their proven efficacy, antidepressants present a delayed onset of action and serious adverse effects. Seven years ago, we described spadin (PE 12-28) as a promising endogenous peptide with antidepressant activity. Spadin specifically blocks the TREK-1 channel. Previously, we showed in vivo that, spadin activity disappeared beyond 7 h after administration. In order to improve in vivo spadin stability and bioavailability, we screened spadin analogs and derivatives. From the study of spadin blood degradation products, we designed a 7 amino-acid peptide, PE 22-28. In vitro studies on hTREK-1/HEK cells by using patch-clamp technique, showed that PE 22-28 displayed a better specificity and affinity for TREK-1 channel compared to spadin, IC₅₀ of 0.12 nM vs. 40–60 nM for spadin. In the same conditions, we also pointed out that different modifications of its N or C-terminal ends maintained or abolished TREK-1 channel activity without affecting PE 22-28 affinity. In vivo, the antidepressant properties of PE 22-28 and its derivatives were demonstrated in behavioral models of depression, such as the forced swimming test. Mice treated with spadin-analogs showed a significant reduction of the immobility time. Moreover, in the novelty suppressed feeding test after a 4-day sub-chronic treatment PE 22-28 reduced significantly the latency to eat the food pellet. PE 22-28 and its analogs were able to induce neurogenesis after only a 4-day treatment with a prominent effect of the G/A-PE 22-28. On mouse cortical neurons, PE 22-28 and its derivatives enhanced synaptogenesis measured by the increase of PSD-95 expression level. Finally, the action duration of PE 22-28 and its analogs was largely improved in comparison with that of spadin, up to 23 h instead of 7 h. Taken together, our results demonstrated that PE 22-28 and its derivatives represent other promising molecules that could be an alternative to spadin in the treatment of depression.

Arc restores juvenile plasticity in adult mouse visual cortex

The molecular basis for the decline in experience-dependent neural plasticity over age remains poorly understood. In visual cortex, the robust plasticity induced in juvenile mice by brief monocular deprivation during the critical period is abrogated by genetic deletion of Arc, an activity-dependent regulator of excitatory synaptic modification. Here, we report that augmenting Arc expression in adult mice prolongs juvenile-like plasticity in visual cortex, as assessed by recordings of ocular dominance (OD) plasticity in vivo. A distinguishing characteristic of juvenile OD plasticity is the weakening of deprived-eye responses, believed to be accounted for by the mechanisms of homosynaptic long-term depression (LTD). Accordingly, we also found increased LTD in visual cortex of adult mice with augmented Arc expression and impaired LTD in visual cortex of juvenile mice that lack Arc or have been treated in vivo with a protein synthesis inhibitor. Further, we found that although activity-dependent expression of Arc mRNA does not change with age, expression of Arc protein is maximal during the critical period and declines in adulthood. Finally, we show that acute augmentation of Arc expression in wild-type adult mouse visual cortex is sufficient to restore juvenile-like plasticity. Together, our findings suggest a unifying molecular explanation for the age- and activity-dependent modulation of synaptic sensitivity to deprivation.

Neuroplasticity pathways and protein-interaction networks are modulated by vortioxetine in rodents

Background

The identification of biomarkers that predict susceptibility to major depressive disorder and treatment response to antidepressants is a major challenge. Vortioxetine is a novel multimodal antidepressant that possesses pro-cognitive properties and differentiates from other conventional antidepressants on various cognitive and plasticity measures. The aim of the present study was to identify biological systems rather than single biomarkers that may underlie vortioxetine’s treatment effects.

Results

We show that the biological systems regulated by vortioxetine are overlapping between mouse and rat in response to distinct treatment regimens and in different brain regions. Furthermore, analysis of complexes of physically-interacting proteins reveal that biomarkers involved in transcriptional regulation, neurodevelopment, neuroplasticity, and endocytosis are modulated by vortioxetine. A subsequent qPCR study examining the expression of targets in the protein–protein interactome space in response to chronic vortioxetine treatment over a range of doses provides further biological validation that vortioxetine engages neuroplasticity networks. Thus, the same biology is regulated in different species and sexes, different brain regions, and in response to distinct routes of administration and regimens.

Conclusions

A recurring theme, based on the present study as well as previous findings, is that networks related to synaptic plasticity, synaptic transmission, signal transduction, and neurodevelopment are modulated in response to vortioxetine treatment. Regulation of these signaling pathways by vortioxetine may underlie vortioxetine’s cognitive-enhancing properties.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-017-0376-x) contains supplementary material, which is available to authorized users.

Frameworking memory and serotonergic markers

The evidence for neural markers and memory is continuously being revised, and as evidence continues to accumulate, herein, we frame earlier and new evidence. Hence, in this work, the aim is to provide an appropriate conceptual framework of serotonergic markers associated with neural activity and memory. Serotonin (5-hydroxytryptamine [5-HT]) has multiple pharmacological tools, well-characterized downstream signaling in mammals’ species, and established 5-HT neural markers showing new insights about memory functions and dysfunctions, including receptors (5-HT1A/1B/1D, 5-HT2A/2B/2C, and 5-HT3-7), transporter (serotonin transporter [SERT]) and volume transmission present in brain areas involved in memory. Bidirectional influence occurs between 5-HT markers and memory/amnesia. A growing number of researchers report that memory, amnesia, or forgetting modifies neural markers. Diverse approaches support the translatability of using neural markers and cerebral functions/dysfunctions, including memory formation and amnesia. At least, 5-HT1A, 5-HT4, 5-HT6, and 5-HT7receptors and SERT seem to be useful neural markers and therapeutic targets. Hence, several mechanisms cooperate to achieve synaptic plasticity or memory, including changes in the expression of neurotransmitter receptors and transporters.

Serotonin Transporter-Independent Actions of the Antidepressant Vortioxetine As Revealed Using the SERT Met172 Mouse

Selective serotonin (5-HT, SERT) reuptake inhibitors (SSRIs) are the most commonly prescribed treatments for depression. However, they have delayed efficacy and can induce side-effects that can encourage discontinuation. Recently, agents have been developed, including vortioxetine (Trintellix), that augment SERT blockade with interactions at other targets. At therapeutic doses, vortioxetine interacts with SERT as well as 5-HT_1A, 5-HT_1B, 5-HT₃, and 5-HT₇ receptors. We assessed the SERT-dependency of vortioxetine action using the SERT Met172 mouse model, which disrupts high-affinity interactions of many antidepressants with the transporter. We demonstrate that the SERT Met172 substitution induces an ∼19-fold loss in vortioxetine potency for SERT inhibition in midbrain synaptosomes. Moreover, in these mice, we observed reduced SERT occupancy, a diminished ability to prolong 5-HT clearance, and a reduced capacity to elevate extracellular 5-HT. Despite reduced interactions with SERT, vortioxetine maintained its ability to enhance mobility in tail suspension and forced swim tests, reduce consumption latency in the novelty induced hypophagia test, and promoted proliferation and survival of subgranular zone hippocampal stem cells. Our findings suggest that the antidepressant actions of vortioxetine may be SERT-independent, and encourage consideration of agents that mimic one or more actions of the drug in the development of improved depression treatments.

Age exacerbates abnormal protein expression in a mouse model of Down syndrome

The Ts65Dn is a popular mouse model of Down syndrome (DS). It displays DS-relevant features of learning/memory deficits and age-related loss of functional markers in basal forebrain cholinergic neurons. Here we describe protein expression abnormalities in brain regions of 12-month-old male Ts65Dn mice. We show that the magnitudes of abnormalities of human chromosome 21 and non-human chromosome 21 orthologous proteins are greater at 12 months than at ∼6 months. Age-related exacerbations involve the number of components affected in the mechanistic target of rapamycin pathway, the levels of components of the mitogen-activated protein kinase pathway, and proteins associated with Alzheimer's disease. Among brain regions, the number of abnormalities in cerebellum decreased while the number in cortex greatly increased with age. The Ts65Dn is being used in preclinical evaluations of drugs for cognition in DS. Most commonly, drug evaluations are tested in ∼4- to 6-month-old mice. Data on age-related changes in magnitude and specificity of protein perturbations can be used to understand the molecular basis of changes in cognitive ability and to predict potential age-related specificities in drug efficacies.

New drugs in psychiatry: focus on new pharmacological targets

The approval of psychotropic drugs with novel mechanisms of action has been rare in recent years. To address this issue, further analysis of the pathophysiology of neuropsychiatric disorders is essential for identifying new pharmacological targets for psychotropic medications. In this report, we detail drug candidates being examined as treatments for psychiatric disorders. Particular emphasis is placed on agents with novel mechanisms of action that are being tested as therapies for depression, schizophrenia, or Alzheimer’s disease. All of the compounds considered were recently approved for human use or are in advanced clinical trials. Drugs included here are new antipsychotic medications endowed with a preferential affinity at dopamine D3 receptor (cariprazine) or at glutamatergic or cannabinoid receptors, as well as vortioxetine, a drug approved for managing the cognitive deficits associated with major depression. New mechanistic approaches for the treatment of depression include intravenous ketamine or esketamine or intranasal esketamine. As for Alzheimer’s disease, the possible value of passive immunotherapy with agents such as aducanumab is considered to be a potential disease-modifying approach that could slow or halt the progressive decline associated with this devastating disorder.

In vivo and in vitro effects of vortioxetine on molecules associated with neuroplasticity

Neuroplasticity is fundamental for brain functions, abnormal changes of which are associated with mood disorders and cognitive impairment. Neuroplasticity can be affected by neuroactive medications and by aging. Vortioxetine, a multimodal antidepressant, has shown positive effects on cognitive functions in both pre-clinical and clinical studies. In rodent studies, vortioxetine increases glutamate neurotransmission, promotes dendritic branching and spine maturation, and elevates hippocampal expression of the activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) at the transcript level. The present study aims to assess the effects of vortioxetine on several neuroplasticity-related molecules in different experimental systems. Chronic (1 month) vortioxetine increased Arc/Arg3.1 protein levels in the cortical synaptosomes of young and middle-aged mice. In young mice, this was accompanied by an increase in actin-depolymerizing factor (ADF)/cofilin serine 3 phosphorylation without altering the total ADF/cofilin protein level, and an increase in the GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor phosphorylation at serine 845 (S845) without altering serine 831 (S831) GluA1 phosphorylation nor the total GluA1 protein level. Similar effects were detected in cultured rat hippocampal neurons: Acute vortioxetine increased S845 GluA1 phosphorylation without changing S831 GluA1 phosphorylation or the total GluA1 protein level. These changes were accompanied by an increase in α subunit of Ca²⁺/calmodulin-dependent kinase (CaMKIIα) phosphorylation (at threonine 286) without changing the total CaMKIIα protein level in cultured neurons. In addition, chronic (1 month) vortioxetine, but not fluoxetine, restored the age-associated reduction in Arc/Arg3.1 and c-Fos transcripts in the frontal cortex of middle-aged mice. Taken together, these results demonstrated that vortioxetine modulates molecular targets that are related to neuroplasticity.

Distinct Antidepressant-Like and Cognitive Effects of Antidepressants with Different Mechanisms of Action in Middle-Aged Female Mice

BACKGROUND

Cognitive dysfunction is among the key symptoms of major depressive disorder and can be affected by antidepressants. Cognitive decline also occurs in normal aging. The effects of different antidepressants on affective and cognitive domains in older subjects are seldom assessed simultaneously.

METHODS

Healthy middle-aged female mice received vehicle or antidepressant (vortioxetine, vilazodone, duloxetine, or fluoxetine) at therapeutic doses. After 1 month treatment, mice were accessed for visuospatial memory and depression-like behavior. A separate cohort of mice received 3 months of treatment and was test for recognition memory and depression-like behavior.

RESULTS

After 1 month treatment, vortioxetine improved visuospatial memory and reduced depression-like behavior. Vilazodone reduced depression-like behavior. Duloxetine and fluoxetine were ineffective in both tests. After 3 months treatment, vortioxetine reduced depression-like behavior without affecting recognition memory, while fluoxetine impaired recognition memory. Duloxetine and vilazodone had no effect in both tests.

CONCLUSION

Different antidepressants have distinct effects in middle-aged female mice.

Chronic vortioxetine treatment in rodents modulates gene expression of neurodevelopmental and plasticity markers

The multimodal antidepressant vortioxetine displays an antidepressant profile distinct from those of conventional selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) and possesses cognitive-enhancing properties in preclinical and clinical studies. Recent studies have begun to investigate molecular mechanisms that may differentiate vortioxetine from other antidepressants. Acute studies in adult rats and chronic studies in a middle-aged mouse model reveal upregulation of several markers that play a central role in synaptic plasticity. However, the effect of chronic vortioxetine treatment on expression of neuroplasticity and neurodevelopmental biomarkers in naïve rats has not been evaluated. In the present study, we demonstrate that vortioxetine at a range of doses regulates expression of genes associated with plasticity in the frontal cortex, hippocampus, region encompassing the amygdala, as well as in blood, and displays similar effects relative to the SSRI fluoxetine in adult naïve rats. These genes encode immediate early genes (IEGs), translational regulators, and the neurodevelopmental marker Sema4g. Similar findings detected in brain regions and in blood provide a potential translational impact, and vortioxetine appears to consistently regulate signaling in these networks of neuroplasticity and developmental markers.

Comparison of the Antidepressant-Like Effects of Estradiol and That of Selective Serotonin Reuptake Inhibitors in Middle-Aged Ovariectomized Rats

This study investigated the effect of age and that of the post-ovariectomy (OVX) time interval on the antidepressant (AD)-like effects of estradiol (E₂) and selective serotonin reuptake inhibitors (SSRIs) in middle-aged (10 month) OVX rats (10m-OVX). Acute or chronic effects of these treatments in 10m-OVX were compared with those (1) in young adult (4-month) OVX rats (4m-OVX) or with older (14-month) OVX rats (14m-OVX), at a short time: 2 weeks post-OVX (+2w) and (2) in 10m-OVX rats after a longer times: 4 or 8 months post-OVX (+4m or +8m). Using in vivo chronoamperometry in the CA3 region of the hippocampus, E₂ at 20 pmol, a dose shown previously to inhibit the serotonin transporter (SERT) in 4m-OVX, had no effect in 10m-OVX+2w. A higher dose of E₂ (40 pmol) increased T80 value, a measure of serotonin or 5-hydroxytryptamine (5-HT) clearance, and also blocked the ability of fluvoxamine to increase T80. By contrast, estradiol had no effects on SERT function in 10m-OVX+4m, even at a higher dose than 40 pmol. Fluvoxamine slowed 5-HT clearance in 10m-OVX at +2w, +4m and +8m post-OVX as it did in the 4m-OVX. Using the forced swim test, 2 weeks treatment with E₂ (5 μg/day), a dose shown previously to induce AD-like effects in 4m-OVX, had no effect in 10m-OVX+2w. However, a higher dose (10 μg/day) of E₂ induced an AD-like effect as demonstrated by significantly increased swimming behavior and decreased immobility. This effect was not seen in 10m-OVX+4m. By contrast, significant AD-like effects were obtained in 14m-OVX+2w, thereby demonstrating that the lack of an AD effect of E₂ is due to the 4-month hormone withdrawal and not to an age effect. After 2 weeks treatment with the SSRI sertraline, similar AD-like effects were obtained in 10m-OVX tested at +2w, +4m or +8m post-OVX as those found in 4m-OVX. Thus, the potency of estradiol to produce effects consistent with inhibition of the SERT was not only decreased in older rats but its effects were markedly diminished the longer hormonal depletion occurred. By contrast, the ability of SSRIs to inhibit the SERT was not affected either by age or the length of hormonal depletion.