Environmental enrichment in combination with Bifidobacterium breve HNXY26M4 intervention amplifies neuroprotective benefits in a mouse model of Alzheimer's disease by modulating glutamine metabolism of the gut microbiome

The gut microbiota-brain axis has emerged as a novel target for Alzheimer's disease(AD),a neurodegenerative disease characterised by behavioural and cognitive impairment.However,most previous microbiome-based intervention studies have focused on single factors and yielded only modest cognitive improvements.Here,we proposed a multidomain intervention strategy that combined Bifidobacterium breve treatment with environmental enrichment(EE)training.In this study,we found that compared with EE or B.breve treatment alone,B.breve intervention combined with EE amplified its neuroprotective effects on AD mice,as reflected by improved cognition,inhibited neuroinflammation and enhanced synaptic function.Moreover,using microbiome and metabolome profiling,we found that the combination of B.breve and EE treatment restored AD-related gut microbiota dysbiosis and reversed microbial metabolite changes.Finally,by integrating behavioural and neurological data with metabolomic profiles,we revealed that the underlying mechanism may involve the modulation of microbiota-derived glutamine metabolism via gut-brain interactions.Collectively,combined B.breve intervention with EE treatment can alleviate AD-related cognitive impairment and improve brain function by regulating glutamine metabolism of the gut microbiome.Our findings provide a promising multidomain intervention strategy,with a combination of dietary microbiome-based and lifestyle-targeted interventions,to promote brain function and delay the progression of AD.

Molecular mechanisms underlying the neuroprotection of environmental enrichment in Parkinson’s disease

Parkinson’s disease is the most common movement disorder,affecting about 1%of the population over the age of 60 years.Parkinson’s disease is characterized clinically by resting tremor,bradykinesia,rigidity and postural instability,as a result of the progressive loss of nigrostriatal dopaminergic neurons.In addition to this neuronal cell loss,Parkinson’s disease is characterized by the accumulation of intracellular protein aggregates,Lewy bodies and Lewy neurites,composed primarily of the proteinα-synuclein.Although it was first described almost 200 years ago,there are no disease-modifying drugs to treat patients with Parkinson’s disease.In addition to conventional therapies,non-pharmacological treatment strategies are under investigation in patients and animal models of neurodegenerative disorders.Among such strategies,environmental enrichment,comprising physical exercise,cognitive stimulus,and social interactions,has been assessed in preclinical models of Parkinson’s disease.Environmental enrichment can cause structural and functional changes in the brain and promote neurogenesis and dendritic growth by modifying gene expression,enhancing the expression of neurotrophic factors and modulating neurotransmission.In this review article,we focus on the current knowledge about the molecular mechanisms underlying environmental enrichment neuroprotection in Parkinson’s disease,highlighting its influence on the dopaminergic,cholinergic,glutamatergic and GABAergic systems,as well as the involvement of neurotrophic factors.We describe experimental pre-clinical data showing how environmental enrichment can act as a modulator in a neurochemical and behavioral context in different animal models of Parkinson’s disease,highlighting the potential of environmental enrichment as an additional strategy in the management and prevention of this complex disease.

Environmental Enrichment and Its Effect on the Welfare of Two Asian Elephants in Africam Safari Wildlife Conservation Park (Puebla, Mexico)

Animal welfare is important in zoos to maintain the physical well-being and psychological health of individuals. An animal is considered to have welfare if it has good nutrition and also expresses its innate behavior, including sensations and feelings experienced as a result of physical health. The objective of this study was to evaluate the effect of environmental enrichment on the behaviors of two Asian elephants in a wildlife conservation park. The behavior of two Asian elephants, a 46-year-old male and a 59-year-old female, was observed. Behavior was measured by quantifying the frequency, latency, and duration of behavioral actions. Measurements were done with ad libitum sampling during 5 days of testing, then observations were recorded with focal sampling for 25 days with environmental enrichment and 25 days without enrichment. Data were analyzed with the Chi-square statistical test using the statistical program SPSS 20, observing significant differences (P the application of environmental enrichment. The frequency of maintenance behaviors was higher when environmental enrichment was provided, and the frequency of social conducts (affiliative and agonistic) decreased. In fact, the behaviors most frequently presented by elephants with and without environmental enrichment were definitely maintenance behaviors. The environmental enrichment program helped to reduce the duration of abnormal behaviors and increase the frequency of typical behaviors of the species. It also increased independent movements within the exhibition area and helped to know each of the elephants individually in order to apply each enrichment combination according to their needs.

An enriched environment increases the expression of fibronectin type Ⅲ domain-containing protein 5 and brain-derived neurotrophic factor in the cerebral cortex of the ischemic mouse brain

Many studies have shown that fibronectin type III domain-containing protein 5(FDNC5) and brain-derived neurotrophic factor(BDNF) play vital roles in plasticity after brain injury. An enriched environment refers to an environment that provides animals with multi-sensory stimulation and movement opportunities. An enriched environment has been shown to promote the regeneration of nerve cells, synapses, and blood vessels in the animal brain after cerebral ischemia;however, the exact mechanisms have not been clarified. This study aimed to determine whether an enriched environment could improve neurobehavioral functions after the experimental inducement of cerebral ischemia and whether neurobehavioral outcomes were associated with the expression of FDNC5 and BDNF. This study established ischemic mouse models using permanent middle cerebral artery occlusion(pMCAO) on the left side. On postoperative day 1, the mice were randomly assigned to either enriched environment or standard housing condition groups. Mice in the standard housing condition group were housed and fed under standard conditions. Mice in the enriched environment group were housed in a large cage, containing various toys, and fed with a standard diet. Sham-operated mice received the same procedure, but without artery occlusion, and were housed and fed under standard conditions. On postoperative days 7 and 14, a beam-walking test was used to assess coordination, balance, and spatial learning. On postoperative days 16–20, a Morris water maze test was used to assess spatial learning and memory. On postoperative day 15, the expression levels of FDNC5 and BDNF proteins in the ipsilateral cerebral cortex were analyzed by western blot assay. The results showed that compared with the standard housing condition group, the motor balance and coordination functions(based on beam-walking test scores 7 and 14 days after operation), spatial learning abilities(based on the spatial learning scores from the Morris water maze test 16–19 days after operation), and memory abilities(based on the memory scores of the Morris water maze test 20 days after operation) of the enriched environment group improved significantly. In addition, the expression levels of FDNC5 and BDNF proteins in the ipsilateral cerebral cortex increased in the enriched environment group compared with those in the standard housing condition group. Furthermore, the Pearson correlation coefficient showed that neurobehavioral functions were positively associated with the expression levels of FDNC5 and BDNF(r = 0.587 and r = 0.840, respectively). These findings suggest that an enriched environment upregulates FDNC5 protein expression in the ipsilateral cerebral cortex after cerebral ischemia, which then activates BDNF protein expression, improving neurological function. BDNF protein expression was positively correlated with improved neurological function. The experimental protocols were approved by the Institutional Animal Care and Use Committee of Fudan University, China(approval Nos. 20160858 A232, 20160860 A234) on February 24, 2016.

Environmental enrichment combined with fasudil promotes motor function recovery and axonal regeneration after stroke

Fasudil,a Rho-associated protein kinase(ROCK)inhibitor,has a protective effect on the central nervous system.In addition,environmental enrichment is a promising technique for inducing the recovery of motor impairments in ischemic stroke models.The present study aimed to explore whether environmental enrichment combined with fasudil can facilitate motor function recovery and induce cortical axonal regeneration after stroke.First,a mouse model of ischemic cerebral stroke was established by photochemical embolization of the left sensorimotor cortex.Fasudil solution(10 mg/kg per day)was injected intraperitoneally for 21 days after the photothrombotic stroke.An environmental enrichment intervention was performed on days 7-21 after the photothrombotic stroke.The results revealed that environmental enrichment combined with fasudil improved motor function,increased growth-associated protein 43 expression in the infarcted cerebral cortex,promoted axonal regeneration on the contralateral side,and downregulated ROCK,p-LIM domain kinase(LIMK)1,and p-cofilin expression.The combined intervention was superior to monotherapy.These findings suggest that environmental enrichment combined with fasudil treatment promotes motor recovery after stroke,at least partly by stimulating axonal regeneration.The underlying mechanism might involve ROCK/LIMK1/cofilin pathway regulation.This study was approved by the Institutional Animal Care and Use Committee of Fudan University,China(approval No.20160858A232)on February 24,2016.

An enriched environment improves cognitive performance in mice from the senescence-accelerated prone mouse 8 strain Role of upregulated neurotrophic factor expression in the hippocampus

In this study,we examined 3-month-old female mice from the senescence-accelerated prone mouse 8 strain and age-matched homologous normal aging female mice from the senescence accelerated-resistant mouse 1 strain.Mice from each strain were housed in an enriched environment（including a platform,running wheels,tunnel,and some toys）or a standard environment for 3 months.The mice housed in the enriched environment exhibited shorter escape latencies and a greater percentage of time in the target quadrant in the Morris water maze test,and they exhibited reduced errors and longer latencies in step-down avoidance experiments compared with mice housed in the standard environment.Correspondently,brain-derived neurotrophic factor mRNA and protein ex- pression in the hippocampus was significantly higher in mice housed in the enriched environment compared with those housed in the standard environment,and the level of hippocampal brain-derived neurotrophic factor protein was positively correlated with the learning and memory abilities of mice from the senescence-accelerated prone mouse 8 strain.These results suggest that an enriched environment improved cognitive performance in mice form the senescence-accelerated prone mouse 8 strain by increasing brain-derived neurotrophic factor expression in the hippocampus.

An enriched environment reduces hippocampal inflammatory response and improves cognitive function in a mouse model of stroke

An enriched environment is used as a behavio ral intervention therapy that applies sensory,motor,and social stimulation,and has been used in basic and clinical research of va rious neurological diseases.In this study,we established mouse models of photothrombotic stroke and,24 hours later,raised them in a standard,enriched,or isolated environment for 4 weeks.Compared with the mice raised in a standard environment,the cognitive function of mice raised in an enriched environment was better and the pathological damage in the hippocampal CA1 region was remarkably alleviated.Furthermore,protein expression levels of tumor necrosis factor receptor-associated factor 6,nuclear factorκB p65,interleukin-6,and tumor necrosis factorα,and the mRNA expression level of tumor necrosis factor receptor-associated factor 6 were greatly lower,while the expression level of miR-146a-5p was higher.Compared with the mice raised in a standard environment,changes in these indices in mice raised in an isolated environment were opposite to mice raised in an enriched environment.These findings suggest that different living environments affect the hippocampal inflammatory response and cognitive function in a mouse model of stro ke.An enriched environment can improve cognitive function following stroke through up-regulation of miR-146a-5p expression and a reduction in the inflammatory response.

Memantine combined with environmental enrichment improves spatial memory and alleviates Alzheimer's disease-like pathology in senescence-accelerated prone-8(SAMP8) mice

Memantine is a N-methyl-D-aspartate (NMDA) receptor antagonist approved for the treatment of moderate to severe Alzheimer's disease (AD). Environmental enrichment (EE) has shown significant beneficial effects on func- tional improvement in AD. In this study, we sought to determine whether combining these two distinct therapies would yield greater benefit than either drug used alone. We investigated the effect of memantine combined with EE on spatial learning and memory and AD-like pathology in a widely used AD model, the senescence-accelerated prone mice (SAMP8). The SAMP8 mice were randomly assigned to enriched housing (EH) or standard housing (SH), where either memantine (20 mg/kg) or saline was given by gastric lavage once daily continuously for eight weeks. Our results showed that, when provided separately, memantine and EE significantly improved spatial learning and memory by shortening escape latencies and increasing the frequency of entrance into the target quadrant. When combined, memantine and EE showed additive effect on learning and memory as evidenced by significant shorter escape latencies and higher frequency of target entrance than either drug alone. Consistent with the behavior results, pathological studies showed that both memantine and EE significantly reduced hippocampal CA1 neurofibrilliary tangles (NFTs) as well as amyloid beta precursor protein (APP) levels. Combining both therapies synergistically lessened NFTs and APP expression compared to either drug alone in SAMP8 mice, indicating that the combination of memantine with EE could offer a novel and efficient therapeutic strategy for the treatment of AD.

A novel viewpoint in glaucoma therapeutics: enriched environment

Glaucoma is one of the world’s most frequent visual impairment causes and leads to selective damage to retinal ganglion cells and their axons.Despite glaucoma’s most accepted risk factor is increased intraocular pressure(IOP),the mechanisms behind the disease have not been fully elucidated.To date,IOP lowering remains the gold standard;however,glaucoma patients may still lose vision regardless of effective IOP management.Therefore,the exclusive IOP control apparently is not enough to stop the disease progression,and developing new resources to protect the retina and optic nerve against glaucoma is a goal of vast clinical importance.Besides pharmacological treatments,environmental conditions have been shown to prevent neurodegeneration in the central nervous system.In this review,we discuss current concepts on key pathogenic mechanisms involved in glaucoma,the effect of enriched environment on these mechanisms in different experimental models,as well as recent evidence supporting the preventive and therapeutic effect of enriched environment exposure against experimental glaucomatous damage.Finally,we postulate that stimulating vision may become a non-invasive and rehabilitative therapy that could be eventually translated to the human disease,preventing glaucoma-induced terrible sequelae resulting in permanent visual disability.

The Effects of the Enriched Environment on Sympathetic Skin Response in Pentylenetetrazol-Kindled Rats

Epilepsy is a neurodegenerative disease that interrupts the normal electrical activity of the brain and promotes abnormal wiring in this organ.Epileptic seizures are often associated with significant changes in the functioning of the autonomic nervous system(ANS).

Impact of Vertically-Suspended Environmental Enrichment and Two Densities of Fish on Circular Tank Velocity Profiles

Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the velocity profile of a 3.63-m diameter circular tank containing juvenile landlocked fall Chinook salmon (Oncorhynchus tshawytscha) at two different densities (9.0 and 34.3 kg/m3). The addition of vertically-suspended structure to the tank significantly decreased velocities at nearly every sampling point, with velocities typically dropping from 15 cm/s without structure to less than 6 cm/s when structure was present. Fish density also significantly impacted in-tank velocities, with an inverse relationship observed between the density of fish and water velocity. Significant interactions were present among the presence or absence of structure and fish density. When structure and fish were absent, the velocity at the edge of the tank was 15.63 cm/s, which was significantly higher than the 4.75 cm/s velocity when both structure and the lower fish density were added, which was in turn significantly higher than the 2.29 cm/s velocity observed with structure and higher fish density. Despite the potentially unique features of this study, vertically-suspended environmental enrichment and the presence of fish clearly alter circular tank water velocities, which may at least partially explain the improvements in fish rearing performance observed with the use of suspended structure.

Vertically-Suspended Environmental Enrichment Improves Growth of Landlocked Fall Chinook Salmon during Initial Hatchery Rearing

Environmental enrichment has been shown to improve juvenile salmonid growth during hatchery rearing. This study examined the effects of vertically-suspended environmental enrichment starting seven days after feed training and continuing for the next 32 days of landlocked fall Chinook salmon (Oncorhynchus tshawytscha) rearing. At the end of this experiment, final tank weights, gain, percent gain, and feed conversion ratio were all significantly improved in the tanks of salmon with environmental enrichment compared to barren tanks, with a nearly 25% improvement in feed conversion ratio. Individual salmon in tanks with environmental enrichment were significantly longer and weighed significantly more than salmon from tanks without enrichment. Specific growth rate was also significantly improved with the use of enrichment. The use of vertically-suspended environmental enrichment to improve growth and rearing efficiency is recommended during the initial rearing of landlocked fall Chinook salmon.

Vertically-Suspended Environmental Enrichment Alters the Velocity Profiles of Circular Fish Rearing Tanks

The inclusion of vertically-suspended environmental enrichment in circular tanks has produced substantial benefits during fish rearing. This study examined the tank water velocity profiles of four different vertically-suspended structures?(rod array, extended rod array, single angle array, double angle array) and a control (no environmental enrichment) at two incoming water velocities (18.3 cm/s and 54.9 cm/s) in 1.8-m diameter circular tanks. At both of the incoming water velocities, overall water velocities throughout the tank were significantly reduced with the addition of any environmental enrichment in comparison to the control. In addition, the overall water velocities in the double angle array were significantly lower than the other three enrichment treatments. The pattern of significant reductions in velocity with the use of any environmental enrichment, with further significant velocity reductions in the double angle treatment, was repeated when the data were?combined for each sampling depth, radius from the center, and degree (circular arc). Although considerable variation in water velocity was observed at each specific sampling location with both incoming velocities, significantly lower velocities?were observed at nearly every sampling location with the addition of any environmental enrichment to the circular tank. In addition, the double angle array consistently produced the lowest velocities among the environmental enrichment treatments. The changes in velocity profiles from vertically-suspended?environmental enrichment may be at least partially-responsible for the frequently-observed improvements in fish growth.

Influence of environmental enrichment on hippocampal synapses in adolescent offspring of mothers exposed to prenatal stress

Environmental enrichment attenuates hippocampal synaptic injury induced by prenatal stress in offspring. However, the influence of hippocampal synaptic changes and regional differences in prenatal stress remains poorly understood. The present study induced stress in Sprague Dawley rats, which were at gestational age 13-19 days. Following weaning, the offspring were raised in an enriched environment to establish models of stress ＋ enriched environment. Dendritic spine density and synaptophysin expression were detected in hippocampal neurons using Golgi staining and western blot analysis, respectively. Results showed that enriched environment increased dendritic spine density of apical dendrites in CA1 pyramidal cells and basal dendrites of granular cells in the outer layer of the dentate gyrus. In addition, hippocampal synaptophysin expression increased and the effects of prenatal stress on neuronal dendritic spines were reversed in adolescence.

Environmental enrichment promotes neural remodeling in newborn rats with hypoxic-ischemic brain damage

We evaluated the effect of hypoxic-ischemic brain damage and treatment with early environmental enrichment intervention on development of newborn rats, as evaluated by light and electron microscopy and morphometry. Early intervention with environmental enrichment intelligence training attenuated brain edema and neuronal injury, promoted neuronal repair, and increased neuronal plasticity in the frontal lobe cortex of the newborn rats with hypoxic-ischemic brain damage.

Environmental enrichment and mouse models: Current perspectives

The provision of environmental enrichment to numerous species of laboratory animals is generally considered routine husbandry. However, mouse enrichment has proven to be very complex due to the often contradictory outcomes(animal health and welfare, variability in scientific data, etc.) associated with strain, age of the animal when enrichment is provided, gender of the animal, scientific use of the animal,and other housing attributes. While this has led to some suggesting that mice should not be provided enrichment, more recently opinion is trending toward acknowledging that enrichment actually normalizes the animal and data obtained from a mouse living in a barren environment are likely not to be representative or even reliable. This article offers an overview of the types of impact enrichment can have on various strains of mice and demonstrates that enrichment not only has a role in mouse husbandry, but also can lead to new areas of scientific enquiry in a number of different fields.

An enriched environment promotes synaptic plasticity and cognitive recovery after permanent middle cerebral artery occlusion in mice

Cerebral ischemia activates an endogenous repair program that induces plastic changes in neurons. In this study, we investigated the effects of environmental enrichment on spatial learning and memory as well as on synaptic remodeling in a mouse model of chronic cerebral ischemia, produced by subjecting adult male C57 BL/6 mice to permanent left middle cerebral artery occlusion. Three days postoperatively, mice were randomly assigned to the environmental enrichment and standard housing groups. Mice in the standard housing group were housed and fed a standard diet. Mice in the environmental enrichment group were housed in a cage with various toys and fed a standard diet. Then, 28 days postoperatively, spatial learning and memory were tested using the Morris water maze. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 in the hippocampus were analyzed by western blot assay. The number of synapses was evaluated by electron microscopy. In the water maze test, mice in the environmental enrichment group had a shorter escape latency, traveled markedly longer distances, spent more time in the correct quadrant(northeast zone), and had a higher frequency of crossings compared with the standard housing group. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 were substantially upregulated in the hippocampus in the environmental enrichment group compared with the standard housing group. Furthermore, electron microscopy revealed that environmental enrichment increased the number of synapses in the hippocampal CA1 region. Collectively, these findings suggest that environmental enrichment ameliorates the spatial learning and memory impairment induced by permanent middle cerebral artery occlusion. Environmental enrichment in mice with cerebral ischemia likely promotes cognitive recovery by inducing plastic changes in synapses.

Neuroprotection and recovery from early-life adversity: considerations for environmental enrichment

In the laboratory,environmental enrichment（EE）is used as a protocol to understand the functional,behavioral and molecular mechanisms that underlie neural plasticity（van Praag et al.,2000;Sale et al.,2014）.In addition,it is utilized to provide supplementary resources to animals in order to maintain their well-being and to preserve the scientific validity of the study at hand（see http：//www.nap.edu/catalog/12910/guide-for-thecare-and-use-of-laboratory-animals-eighth）.

Axon regeneration induced by environmental enrichment-epigenetic mechanisms

Environmental enrichment is known to be beneficial for cognitive improvement.In many animal models of neurological disorders and brain injury,EE has also demonstrated neuroprotective benefits in neurodegenerative diseases and in improving recovery after stroke or traumatic brain injury.The exact underlying mechanism for these phenomena has been unclear.Recent findings have now indicated that neuronal activity elicited by environmental enrichment induces Ca2+influx in dorsal root ganglion neurons results in lasting enhancement of CREB-binding protein-mediated histone acetylation.This,in turn,increases the expression of pro-regeneration genes and promotes axonal regeneration.This mechanism associated with neuronal activity elicited by environmental enrichment-mediated pathway is one of several epigenetic mechanisms which modulate axon regeneration upon injury that has recently come to light.The other prominent mechanisms,albeit not yet directly associated with environmental enrichment,include DNA methylation/demethylation and N6-methyladenosine modification of transcripts.In this brief review,I highlight recent work that has shed light on the epigenetic basis of environmental enrichment-based axon regeneration,and discuss the mechanism and pathways involved.I further speculate on the implications of the findings,in conjunction with the other epigenetic mechanisms,that could be harness to promote axon regeneration upon injury.

A Study on Multi-Enriched Housing Environment in Blue Foxes

A traditional fox cage was furnished with both activating environmental enrichments (EE) (a bone, a scratching plate, a hockey buck, a ceiling rope and a wall rope and straw) and EEs enabling resting or observation (a wire-mesh platform and a top nest box). The aim was to find out to which extent blue foxes (Vulpes lagopus) utilized these EEs, and to collect practical experiences of the EEs. The experimental animals were 12 adult blue fox vixens that had been housed in cages furnished with a platform and a bone for about 1.5 years before they were transferred to the multi-enriched cages. The frequency and duration of the active contacts with the EEs were measured with continuous recording on Days 1, 2, 7 and 16 after the transfer, with three hours (13:30 - 14:30, 18:00 - 19:00 and 2:00 - 3:00) on each day. The total use of the EEs was 15 times per hour and more than 20% of the time. For most EEs both the time spent in contact and the frequency of contacts with the EEs declined steeply after Day 1, reflecting a novelty effect of the EEs. This decline was not so evident for the platform, top nest box and wall rope. These three EEs were also the ones used the most by the foxes. The ropes were badly damaged during the experiments, whereas other EEs remained in good condition. Explorativity markedly increased when animals were transferred from home cage to enriched cages. Explorativity remained high during entire study period when foxes were kept in enriched enrichment. Furthermore, it remained high also after transferring of animals back to home cages. Capture reaction was quite similar in home and enriched cages. The amount of stereotypy varied among recording days (P < 0.05). When foxes were transferred from home cages to multi-enriched cages, no change was found in the amount stereotypy during Days 1 and 2. Thereafter, the amount of stereotypy showed a declined trend. Stereotypy tended to increase when foxes were transferred back to home cages. Our results indicated that foxes used readily the opportunities for more diverse behaviours.