The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment and the combined interventions of EE and metformin enhance hippocampal neuron survival and hippocampal-dependent memory in type 2 diabetic rats under stress through the BDNF-TrkB signaling pathways

BACKGROUND

Type 2 diabetes (T2D) with depression causes severe cognitive impairments. The devastating conditions will further compromise the overall quality of life. The overconsumption of high-fat and high-sucrose (HFS) diet is one of the modifiable risk factors for T2D, depression, and cognitive impairments. Thus, it is essential to identify effective therapeutic strategies to overcome the cognitive impairments in T2D with depression. We proposed environmental enrichment (EE) which encompasses social, cognitive, and physical components as the alternative treatment for such impairments. We also investigated the potential neuroprotective properties of the antidiabetic drug metformin. This study aimed to investigate the effects of EE and metformin interventions on hippocampal neuronal death, and hippocampal-dependent memory impairment in T2D rats under stress.

METHODS

Thirty-two male rats (200-250 g) were divided into four groups: C group (standard diet + conventional cage), DS group [HFS-induced T2D + restraint stress (RS)], DSE group [HFS-induced T2D + RS + EE] and DSEM group [HFS + RS + EE + metformin]. Serum corticosterone (CORT) was measured to evaluate stress levels. The serum Free Oxygen Radicals Testing (FORT) and Free Oxygen Radicals Defence Test (FORD) were measured to evaluate the systemic oxidative status (OS). Serum brain-derived neurotrophic factor (BDNF) and T-maze tasks were performed to evaluate cognitive functions. Rats were humanely sacrificed to collect brains for histological, morphometric, and hippocampal gene expression studies.

RESULTS

The CORT and the serum FORT levels in the DSE and DSEM groups were lower than in the DS group. Meanwhile, the serum BDNF, T-maze scores, histological, and morphometric analysis were improved in the DSE and DSEM groups than in the DS group. These findings supported that EE and the combined interventions of EE and metformin had neuroprotective properties. The hippocampal gene expression analysis revealed that the DSE and DSEM groups showed improved regulation of BDNF-TrkB signalling pathways, including the BDNF/TrkB binding, PI3K - Akt pathway, Ras-MAPK pathway, PLCγ-Ca2+ pathway, and CREB transcription.

CONCLUSION

EE and the combined interventions of EE and metformin improved hippocampal neuron survival and hippocampal-dependent memory in T2D rats under stress by enhancing gene expression regulation of neurogenesis and synaptic plasticity.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Neurogenesis and pesticides: news of no new neurons

New hippocampal neurons are continuously generated in the adult human brain. Several studies have demonstrated that the proliferation of hippocampal cells is strongly influenced by a variety of stimuli, including pesticides exposure. These effects are particularly important because neurogenesis dysregulation could be associated with the decline of neuronal and cognitive functions and the possible development of neuropsychiatric disorders.

Hippocampal capillary pericytes in post-stroke and vascular dementias and Alzheimer's disease and experimental chronic cerebral hypoperfusion

Neurovascular unit mural cells called 'pericytes' maintain the blood-brain barrier and local cerebral blood flow. Pathological changes in the hippocampus predispose to cognitive impairment and dementia. The role of hippocampal pericytes in dementia is largely unknown. We investigated hippocampal pericytes in 90 post-mortem brains from post-stroke dementia (PSD), vascular dementia (VaD), Alzheimer's disease (AD), and AD-VaD (Mixed) subjects, and post-stroke non-demented survivors as well as similar age controls. We used collagen IV immunohistochemistry to determine pericyte densities and a mouse model of VaD to validate the effects of chronic cerebral hypoperfusion. Despite increased trends in hippocampal microvascular densities across all dementias, mean pericyte densities were reduced by ~25-40% in PSD, VaD and AD subjects compared to those in controls, which calculated to 14.1 ± 0.7 per mm capillary length, specifically in the cornu ammonis (CA) 1 region (P = 0.01). In mice with chronic bilateral carotid artery occlusion, hippocampal pericyte loss was ~60% relative to controls (P < 0.001). Pericyte densities were correlated with CA1 volumes (r = 0.54, P = 0.006) but not in any other sub-region. However, mice subjected to the full-time environmental enrichment (EE) paradigm showed remarkable attenuation of hippocampal CA1 pericyte loss in tandem with CA1 atrophy. Our results suggest loss of hippocampal microvascular pericytes across common dementias is explained by a vascular aetiology, whilst the EE paradigm offers significant protection.

Environmental enrichment improves cognitive function, learning, memory and anxiety-related behaviours in rodent models of dementia: Implications for future study

Environmental enrichment (EE) is a process of brain stimulation by modifying the surroundings, for example, by changing the sensory, social, or physical conditions. Rodents have been used in such experimental strategies through exposure to diverse physical, social, and exploration conditions. The present study conducted an extensive analysis of the existing literature surrounding the impact of EE on dementia rodent models. The review emphasised the two principal aspects that are very closely related to dementia: cognitive function (learning and memory) as well as psychological factors (anxiety-related behaviours such as phobias and unrealistic worries). Also highlighted were the mechanisms involved in the rodent models of dementia showing EE effects. Two search engines, PubMed and Science Direct, were used for data collection using the following keywords: environmental enrichment, dementia, rodent model, cognitive performance, and anxiety-related behaviour. Fifty-five articles were chosen depending on the criteria for inclusion and exclusion. The rodent models with dementia demonstrated improved learning and memory in the form of hampered inflammatory responses, enhanced neuronal plasticity, and sustained neuronal activity. EE housing also prevented memory impairment through the prevention of amyloid beta (Aβ) seeding formation, an early stage of Aβ plaque formation. The rodents subjected to EE were observed to present increased exploratory activity and exert less anxiety-related behaviour, compared to those in standard housing. However, some studies have proposed that EE intervention through exercise would be too mild to counteract the anxiety-related behaviour and risk assessment behaviour deficits in the Alzheimer's disease rodent model. Future studies should be conducted on old-aged rodents and the duration of EE exposure that would elicit the greatest benefits since the existing studies have been conducted on a range of ages and EE durations. In summary, EE had a considerable effect on dementia rodent models, with the most evident being improved cognitive function.

Digital Therapeutics for Improving Effectiveness of Pharmaceutical Drugs and Biological Products: Preclinical and Clinical Studies Supporting Development of Drug + Digital Combination Therapies for Chronic Diseases

Limitations of pharmaceutical drugs and biologics for chronic diseases (e.g., medication non-adherence, adverse effects, toxicity, or inadequate efficacy) can be mitigated by mobile medical apps, known as digital therapeutics (DTx). Authorization of adjunct DTx by the US Food and Drug Administration and draft guidelines on "prescription drug use-related software" illustrate opportunities to create drug + digital combination therapies, ultimately leading towards drug-device combination products (DTx has a status of medical devices). Digital interventions (mobile, web-based, virtual reality, and video game applications) demonstrate clinically meaningful benefits for people living with Alzheimer's disease, dementia, rheumatoid arthritis, cancer, chronic pain, epilepsy, depression, and anxiety. In the respective animal disease models, preclinical studies on environmental enrichment and other non-pharmacological modalities (physical activity, social interactions, learning, and music) as surrogates for DTx "active ingredients" also show improved outcomes. In this narrative review, we discuss how drug + digital combination therapies can impact translational research, drug discovery and development, generic drug repurposing, and gene therapies. Market-driven incentives to create drug-device combination products are illustrated by Humira® (adalimumab) facing a "patent-cliff" competition with cheaper and more effective biosimilars seamlessly integrated with DTx. In conclusion, pharma and biotech companies, patients, and healthcare professionals will benefit from accelerating integration of digital interventions with pharmacotherapies.

SynCAM1 deficiency in the hippocampal parvalbumin interneurons contributes to sevoflurane-induced cognitive impairment in neonatal rats

AIMS

Sevoflurane is widely used for general anesthesia in children. Previous studies reported that multiple neonatal exposures to sevoflurane can induce long-term cognitive impairment in adolescent rats, but the underlying mechanisms were not defined.

METHODS

Postnatal day 6 (P6) to P8 rat pups were exposed to 30% oxygen with or without 3% sevoflurane balanced with air. The Y maze test (YMT) and Morris water maze (MWM) tests were performed in some cohorts from age P35 to assess cognitive functions, and their brain samples were harvested at age P14, 21, 28, 35, and 42 for measurements of various molecular entities and in vivo electrophysiology experiments at age P35.

RESULTS

Sevoflurane exposure resulted in cognitive impairment that was associated with decreased synCAM1 expression in parvalbumin (PV) interneurons, a reduction of PV phenotype, disturbed gamma oscillations, and dendritic spine loss in the hippocampal CA3 region. Enriched environment (EE) increased synCAM1 expression in the PV interneurons and attenuated sevoflurane-induced cognitive impairment. The synCAM1 overexpression by the adeno-associated virus vector in the hippocampal CA3 region restored sevoflurane-induced cognitive impairment, PV phenotype loss, gamma oscillations decrease, and dendritic spine loss.

CONCLUSION

Our data suggested that neonatal sevoflurane exposure results in cognitive impairment through decreased synCAM1 expression in PV interneurons in the hippocampus.

Land/Water Aerobic Activities: Two Sides of the Same Coin. A Comparative Analysis on the Effects in Cognition of Alzheimer's Disease

 Evidence in the literature indicates that aerobic physical activity may have a protective role in aging pathologies. However, it has not been clarified whether different types of aerobic exercise produce different effects. In particular, these potential differences have not been explored in patients with Alzheimer's disease (AD). The present narrative review has the specific aim of evaluating whether land (walking/running) and water (swimming) aerobic activities exert different effects on cognitive functions and neural correlates in AD patients. In particular, the investigation is carried out by comparing the evidence provided from studies on AD animal models and on patients. On the whole, we ascertained that both human and animal studies documented beneficial effects of land and water aerobic exercise on cognition in AD. Also, the modulation of numerous biological processes is documented in association with structural modifications. Remarkably, we found that aerobic activity appears to improve cognition per se, independently from the specific kind of exercise performed. Aerobic exercise promotes brain functioning through the secretion of molecular factors from skeletal muscles and liver. These molecular factors stimulate neuroplasticity, reduce neuroinflammation, and inhibit neurodegenerative processes leading to amyloid-β accumulation. Additionally, aerobic exercise improves mitochondrial activity, reducing oxidative stress and enhancing ATP production. Aerobic activities protect against AD, but implementing exercise protocols for patients is challenging. We suggest that health policies and specialized institutions should direct increasing attention on aerobic activity as lifestyle modifiable factor for successful aging and age-related conditions.

Environmental Enrichment in Cancer as a Possible Tool to Combat Tumor Development: A Systematic Review

This systematic review aims to evaluate the influence of environmental enrichment (EE) on oncological factors in experimental studies involving various types of cancer models. A comprehensive search was conducted in three databases: PubMed (161 articles), Embase (335 articles), and Scopus (274 articles). Eligibility criteria were applied based on the PICOS strategy to minimize bias. Two independent researchers performed the searches, with a third participant resolving any discrepancies. The selected articles were analyzed, and data regarding sample characteristics and EE protocols were extracted. The outcomes focused solely on cancer and tumor-related parameters, including cancer type, description of the cancer model, angiogenesis, tumor occurrence, volume, weight, mice with tumors, and tumor inhibition rate. A total of 770 articles were identified across the three databases, with 12 studies meeting the inclusion criteria for this systematic review. The findings demonstrated that different EE protocols were effective in significantly reducing various aspects of tumor growth and development, such as angiogenesis, volume, weight, and the number of mice with tumors. Furthermore, EE enhanced the rate of tumor inhibition in mouse cancer models. This systematic review qualitatively demonstrates the impacts of EE protocols on multiple parameters associated with tumor growth and development, including angiogenesis, occurrence, volume, weight, and tumor incidence. Moreover, EE demonstrated the potential to increase the rate of tumor inhibition. These findings underscore the importance of EE as a valuable tool in the management of cancer.

Efficacy of an environmental enrichment intervention for endometriosis: a pilot study

Introduction

We have previously shown that Environmental Enrichment (EE), a multi-modal psychosocial intervention consisting of increased social interaction, novelty, and open spaces, improved disease presentation, anxiety, and immune-related disturbances in the rat model of endometriosis. However, there is a knowledge gap regarding the effects of EE interventions in patients with this painful, inflammatory chronic disease.

Aim

To adapt and test the efficacy of an EE intervention on pelvic pain, mental health, perceived stress, quality of life, and systemic inflammation in endometriosis patients through a randomized clinical trial (RCT).

Materials and methods

A multidisciplinary team with expertise in physiology, neuroscience, psychology, and women's health adapted and implemented a two-arm RCT comparing an EE intervention with a wait-list control group. Six EE modules administered on alternate weeks were provided to patients in the intervention (N = 29); controls received education only. Survey data and biospecimens were collected at baseline, end-of-study, and 3-months post-intervention to assess pain (Brief Pain Inventory, BPI), endometriosis-related quality of life-QoL (Endometriosis Health Profile-30, EHP30), anxiety (Generalized Anxiety Disorder 7, GAD7), depression (Patient Health Questionnaire for Depression 8, PHQ8), pain catastrophizing (Pain Catastrophizing Score, PCS), stress (Perceived Stress Scale-14, PSS14), and saliva cortisol levels (AM, PM).

Results

Compared to the wait-list controls, participants in the EE intervention showed significantly decreased GAD-7 scores at the end of the intervention and 3-month follow-up. Depression, perceived stress, and QoL improved at the 3-month follow-up compared to baseline. While pain levels did not improve, they significantly correlated with anxiety, depression, QoL and pain catastrophizing scores.

Conclusion

This pilot RCT demonstrated significant improvements in anxiety and depressive symptoms, QoL, and perceived stress, supporting enriched environments as an integrative psychosocial intervention to be used as adjuvant to the standard of care for endometriosis pain.

Environmental enrichment through virtual reality as multisensory stimulation to mitigate the negative effects of prolonged bed rest

Prolonged bed rest causes a multitude of deleterious physiological changes in the human body that require interventions even during immobilization to prevent or minimize these negative effects. In addition to other interventions such as physical and nutritional therapy, non-physical interventions such as cognitive training, motor imagery, and action observation have demonstrated efficacy in mitigating or improving not only cognitive but also motor outcomes in bedridden patients. Recent technological advances have opened new opportunities to implement such non-physical interventions in semi- or fully-immersive environments to enable the development of bed rest countermeasures. Extended Reality (XR), which covers augmented reality (AR), mixed reality (MR), and virtual reality (VR), can enhance the training process by further engaging the kinesthetic, visual, and auditory senses. XR-based enriched environments offer a promising research avenue to investigate the effects of multisensory stimulation on motor rehabilitation and to counteract dysfunctional brain mechanisms that occur during prolonged bed rest. This review discussed the use of enriched environment applications in bedridden patients as a promising tool to improve patient rehabilitation outcomes and suggested their integration into existing treatment protocols to improve patient care. Finally, the neurobiological mechanisms associated with the positive cognitive and motor effects of an enriched environment are highlighted.

The systemic effects of the enriched environment on the conditioned fear reaction

In this review, a hypothesis is proposed to explain the beneficial effect of an enriched environment (EE) on the conditioned fear reaction (CFR) from the perspective of a functional system of behavioral control. According to the hypothesis, the EE affects all behavioral act components, including the processing of sensory information, memory, motivational and reinforcing systems, and motor activities, which weakens the CFR. Animals raised in the EE have effects that are comparable to those of context (CTX) and CS pre-exposures at latent inhibition. An abundance of stimuli in the EE and constant contact with them provide the formation of CS-noUS and CTX-noUS connections that later, during CFR learning, slow down and diminish fear. The EE also contributes to faster processing of information and habituation to it. As a result, many stimuli in the context lose their significance, and subjects simply ignore them. And finally, the EE affects the motivational and reinforcing brain mechanisms, induces an impairment of search activity, and worsens memory consolidation, which leads to a reduction of CFR.

Neuroprotection in metabolic syndrome by environmental enrichment. A lifespan perspective

Metabolic syndrome (MetS) is defined by the concurrence of different metabolic conditions: obesity, hypertension, dyslipidemia, and hyperglycemia. Its incidence has been increasingly rising over the past decades and has become a global health problem. MetS has deleterious consequences on the central nervous system (CNS) and neurological development. MetS can last several years or be lifelong, affecting the CNS in different ways and treatments can help manage condition, though there is no known cure. The early childhood years are extremely important in neurodevelopment, which extends beyond, encompassing a lifetime. Neuroplastic changes take place all life through - childhood, adolescence, adulthood, and old age - are highly sensitive to environmental input. Environmental factors have an important role in the etiopathogenesis and treatment of MetS, so environmental enrichment (EE) stands as a promising non-invasive therapeutic approach. While the EE paradigm has been designed for animal housing, its principles can be and actually are applied in cognitive, sensory, social, and physical stimulation programs for humans. Here, we briefly review the central milestones in neurodevelopment at each life stage, along with the research studies carried out on how MetS affects neurodevelopment at each life stage and the contributions that EE models can provide to improve health over the lifespan.

MSK1 is required for the beneficial synaptic and cognitive effects of enriched experience across the lifespan

Positive experiences, such as social interaction, cognitive training and physical exercise, have been shown to ameliorate some of the harms to cognition associated with ageing. Animal models of positive interventions, commonly known as environmental enrichment, strongly influence neuronal morphology and synaptic function and enhance cognitive performance. While the profound structural and functional benefits of enrichment have been appreciated for decades, little is known as to how the environment influences neurons to respond and adapt to these positive sensory experiences. We show that adult and aged male wild-type mice that underwent a 10-week environmental enrichment protocol demonstrated improved performance in a variety of behavioural tasks, including those testing spatial working and spatial reference memory, and an enhancement in hippocampal LTP. Aged animals in particular benefitted from enrichment, performing spatial memory tasks at levels similar to healthy adult mice. Many of these benefits, including in gene expression, were absent in mice with a mutation in an enzyme, MSK1, which is activated by BDNF, a growth factor implicated in rodent and human cognition. We conclude that enrichment is beneficial across the lifespan and that MSK1 is required for the full extent of these experience-induced improvements of cognitive abilities, synaptic plasticity and gene expression.

Life Experience Matters: Enrichment and Stress Can Influence the Likelihood of Developing Alzheimer's Disease via Gut Microbiome

Alzheimer's disease (AD) is a chronic neurodegenerative disease, characterized by the presence of β-amyloid (Aβ) plaques and neurofibrillary tangles (NFTs) formed from abnormally phosphorylated tau proteins (ptau). To date, there is no cure for AD. Earlier therapeutic efforts have focused on the clinical stages of AD. Despite paramount efforts and costs, pharmaceutical interventions including antibody therapies targeting Aβ have largely failed. This highlights the need to alternate treatment strategies and a shift of focus to early pre-clinical stages. Approximately 25-40% of AD cases can be attributed to environmental factors including chronic stress. Gut dysbiosis has been associated with stress and the pathogenesis of AD and can increase both Aβ and NFTs in animal models of the disease. Both stress and enrichment have been shown to alter AD progression and gut health. Targeting stress-induced gut dysbiosis through probiotic supplementation could provide a promising intervention to delay disease progression. In this review, we discuss the effects of stress, enrichment, and gut dysbiosis in AD models and the promising evidence from probiotic intervention studies.

Environmental Enrichment Protects against Neurotoxic Effects of Lipopolysaccharide: A Comprehensive Overview

Neuroinflammation is a pathophysiological condition associated with damage to the nervous system. Maternal immune activation and early immune activation have adverse effects on the development of the nervous system and cognitive functions. Neuroinflammation during adulthood leads to neurodegenerative diseases. Lipopolysaccharide (LPS) is used in preclinical research to mimic neurotoxic effects leading to systemic inflammation. Environmental enrichment (EE) has been reported to cause a wide range of beneficial changes in the brain. Based on the above, the purpose of the present review is to describe the effects of exposure to EE paradigms in counteracting LPS-induced neuroinflammation throughout the lifespan. Up to October 2022, a methodical search of studies in the literature, using the PubMed and Scopus databases, was performed, focusing on exposure to LPS, as an inflammatory mediator, and to EE paradigms in preclinical murine models. On the basis of the inclusion criteria, 22 articles were considered and analyzed in the present review. EE exerts sex- and age-dependent neuroprotective and therapeutic effects in animals exposed to the neurotoxic action of LPS. EE’s beneficial effects are present throughout the various ages of life. A healthy lifestyle and stimulating environments are essential to counteract the damages induced by neurotoxic exposure to LPS.

Promoting Endogenous Neurogenesis as a Treatment for Alzheimer's Disease

Alzheimer's disease (AD) is the most universal neurodegenerative disorder characterized by memory loss and cognitive impairment. AD is biologically defined by production and aggregation of misfolded protein including extracellular amyloid β (Aβ) peptide and intracellular microtubule-associated protein tau tangles in neurons, leading to irreversible neuronal loss. At present, regulation of endogenous neurogenesis to supplement lost neurons has been proposed as a promising strategy for treatment of AD. However, the exact underlying mechanisms of impaired neurogenesis in AD have not been fully explained and effective treatments targeting neurogenesis for AD are limited. In this review, we mainly focus on the latest research of impaired neurogenesis in AD. Then we discuss the factors affecting stages of neurogenesis and the interplay between neural stem cells (NSCs) and neurogenic niche under AD pathological conditions. This review aims to explore potential therapeutic strategies that promote endogenous neurogenesis for AD treatments.

Feasibility and acceptability of an adapted environmental enrichment intervention for endometriosis: A pilot study

Introduction

We have previously shown that Environmental Enrichment (EE)-consisting of social support, novelty, and open spaces-decreased disease progression and anxiety in a rat model of endometriosis. We developed a novel EE intervention to be tested in a pilot randomized clinical trial (RCT) in patients with endometriosis, a painful, stressful disease.

Objective

To translate and evaluate the feasibility and acceptability of an adapted EE intervention as an adjuvant to standard-of-care for endometriosis patients.

Methods

Feasibility was assessed through recruitment, enrollment, and adherence rates. Acceptability was evaluated through a post-intervention survey and focus group discussion 3-months after the end of the intervention.

Results

Of the 103 subjects recruited, 64 were randomized to the intervention group and 39 to the control group. At the start of the intervention, the study groups consisted of 29 (intervention) and 27 (control) subjects. Enrollment rates were 45.3% and 69.2%, and adherence rates were 41.4% and 100% for the intervention and control groups, respectively. Delays resulting from natural events (earthquakes, the COVID-19 pandemic) impacted enrollment and adherence rates. The most common reasons for missing an intervention were period pain (39.1%) and work-study (34.8%). There was high acceptability (>80%) of the intervention's logistics. The majority (82.4%) of subjects would continue participating in support groups regularly, and 95.7% would recommend the intervention to other patients.

Conclusions

We showed that EE could be translated into an acceptable integrative multi-modal therapy perceived as valuable among participants who completed the intervention. High attrition/low adherence indicates that additional refinements would be needed to improve feasibility. Acceptability data indicate that EE has the potential to be integrated into the clinical management of patients with endometriosis and other inflammatory, painful disorders. Studies are ongoing to assess the efficacy of EE in improving pain symptoms, mental health, and quality of life (QoL).

Long-term environmental enrichment overcomes depression, learning, and memory impairment in elderly CD-1 mice with maternal sleep deprivation exposure

Early-life stress disrupts central nervous system development and increases the risk of neuropsychiatric disorder in offspring based on rodent studies. Maternal sleep deprivation (MSD) in rodents has also been associated with depression and cognitive decline in adult offspring. However, it is not known whether these issues persist into old age. Environmental enrichment is a non-pharmacological intervention with proven benefits in improving depression and cognitive impairment; however, it is unclear whether these benefits hold for aging mice following MSD exposure. The aim of this study was to explore the effects of MSD on depression and cognition in elderly offspring CD-1 mice and to determine whether long-term environmental enrichment could alleviate these effects by improving neuroinflammation and synaptic plasticity. The offspring mice subjected to MSD were randomly assigned to either a standard environment or an enriched environment. At 18 months of age, the forced swimming and tail suspension tests were used to evaluated depression-like behaviors, and the Morris water maze test was used to evaluate cognitive function. The expression levels of hippocampal proinflammatory cytokines and synaptic plasticity-associated proteins were also measured. MSD increased depression-like behaviors and impaired cognition function in aging CD-1 offspring mice. These effects were accompanied by upregulated interleukin (IL)-1β, IL-6, and tumor necrosis factor-α expression, and downregulated brain-derived neurotrophic factor, tyrosine kinase receptor B, postsynaptic density-95, and synaptophysin expression in the hippocampus. All of these changes were reversed by long-term exposure to an enriched environment. These findings suggest that MSD exerts long-term effects on the behaviors of offspring in mice, leading to depression and cognitive impairment in older age. Importantly, long-term environmental enrichment could counteract the behavior difficulties induced by MSD through improving hippocampal proinflammatory cytokines and synaptic plasticity-associated proteins.

Effect of a combined program of running exercise and environmental enrichment on memory function and neurogenesis markers in amyloid-beta-induced Alzheimer-like model

Objectives

It is urgent to develop non-pharmacological interventions or multifactor combination approaches to combat Alzheimer's disease (AD). The effect of exercise (EX) combined with environmental enrichment (EE) on behavioral phenotypes and neurogenesis markers in an Alzheimer-like rat model was investigated.

Materials and Methods

The groups consisted of AD, sham-operated, AD+EX, AD+EE, and AD+EX+EE. AD was produced by injection of amyloid-beta (1-42, 6 µg) intrahippocampally, and a daily treadmill for 3 consecutive weeks was used for EX animals. EE was a large cage (50× 50× 50 cm) containing differently shaped objects. Spatial learning and memory were evaluated in the Morris water maze (MWM), and a shuttle box was used to evaluate inhibitory avoidance memory. RT-PCR was performed to assess the expression of early neurogenesis markers, DCX, and Sox2 within the hippocampus.

Results

Pretreatment with exercise and EE, both individually and in combination, could provide protection from memory impairments in AD rats. Combined treatment led to a significantly more pronounced improvement in memory deficits of AD rats than either paradigm alone. Combination therapy with exercise and EE could also reverse the passive avoidance memory impairment and hippocampal DCX expression of AD rats to the control levels.

Conclusion

These data suggest that exercise in combination with cognitive engagement can provide a non-pharmacological and multidomain policy that may prevent or delay AD symptoms.