Cellular and molecular mechanisms of immunomodulation in the brain through environmental enrichment

HEP® (Homeostasis-Enrichment-Plasticity) Approach Changes Sensory-Motor Development Trajectory and Improves Parental Goals: A Single Subject Study of an Infant with Hemiparetic Cerebral Palsy and Twin Anemia Polycythemia Sequence (TAPS)

BACKGROUND

Early intervention (EI) for infants identified as being at high risk for cerebral palsy (CP), or who have been diagnosed with it, is critical for promotion of postnatal brain organization. The aim of this study was to explore the effectiveness of the Homeostasis-Enrichment-Plasticity (HEP) Approach, which is a contemporary EI model that applies the key principles of enriched environment paradigms and neuronal plasticity from experimental animal studies to ecological theories of human development on the motor development, sensory functions, and parental goals of an infant with twin anemia polycythemia sequence (TAPS) and CP.

METHODS

An AB phase with follow-up single case study design which consisted of multiple baseline assessments with the Peabody Developmental Motor Scales-2 (PDMS-2) and the Test of Sensory Functions in Infants (TSFI) was used. Non-overlapping confidence intervals analysis was used for pre-post PDMS-2 scores. The measurement of progress toward goals and objectives was conducted using the Goal Attainment Scale (GAS). The HEP Approach intervention consisted of 12 one-hour sessions implemented over a period of 3 months, where a physical therapist provided weekly clinic-based parental coaching.

RESULTS

Results found a stable baseline during Phase A and improvement in response to the HEP Approach intervention during Phase B in both the PDMS-2 and TSFI according to 2SD Band analysis. The confidence intervals for the PDMS-2 scores also indicated a significant improvement after HEP intervention. The scores for both the PDMS-2 and the TSFI were consistent or showed improvement throughout the Follow-Up phase. A GAS t-score of 77.14 indicated that the infant exceeded intervention goal expectations.

CONCLUSIONS

Although our findings suggest that the HEP Approach intervention has promise in enhancing sensory functions, motor skill outcomes, and parental goals in an infant with TAPS and CP, further research is required to validate and apply these results more broadly.

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

Microbiota-brain axis: Exploring the role of gut microbiota in psychiatric disorders - A comprehensive review

Mental illness is a hidden epidemic in modern science that has gradually spread worldwide. According to estimates from the World Health Organization (WHO), approximately 10% of the world's population suffers from various mental diseases each year. Worldwide, financial and health burdens on society are increasing annually. Therefore, understanding the different factors that can influence mental illness is required to formulate novel and effective treatments and interventions to combat mental illness. Gut microbiota, consisting of diverse microbial communities residing in the gastrointestinal tract, exert profound effects on the central nervous system through the gut-brain axis. The gut-brain axis serves as a conduit for bidirectional communication between the two systems, enabling the gut microbiota to affect emotional and cognitive functions. Dysbiosis, or an imbalance in the gut microbiota, is associated with an increased susceptibility to mental health disorders and psychiatric illnesses. Gut microbiota is one of the most diverse and abundant groups of microbes that have been found to interact with the central nervous system and play important physiological functions in the human gut, thus greatly affecting the development of mental illnesses. The interaction between gut microbiota and mental health-related illnesses is a multifaceted and promising field of study. This review explores the mechanisms by which gut microbiota influences mental health, encompassing the modulation of neurotransmitter production, neuroinflammation, and integrity of the gut barrier. In addition, it emphasizes a thorough understanding of how the gut microbiome affects various psychiatric conditions.

Spinal motor neuron development and metabolism are transcriptionally regulated by Nuclear Factor IA

Neural circuits governing all motor behaviors in vertebrates rely on the proper development of motor neurons and their precise targeting of limb muscles. Transcription factors are essential for motor neuron development, regulating their specification, migration, and axonal targeting. While transcriptional regulation of the early stages of motor neuron specification is well-established, much less is known about the role of transcription factors in the later stages of maturation and terminal arborization. Defining the molecular mechanisms of these later stages is critical for elucidating how motor circuits are constructed. Here, we demonstrate that the transcription factor Nuclear Factor-IA (NFIA) is required for motor neuron positioning, axonal branching, and neuromuscular junction formation. Moreover, we find that NFIA is required for proper mitochondrial function and ATP production, providing a new and important link between transcription factors and metabolism during motor neuron development. Together, these findings underscore the critical role of NFIA in instructing the assembly of spinal circuits for movement.

Effects of Environmental Enrichment on Exposure to Human-Relevant Mixtures of Endocrine Disrupting Chemicals in Zebrafish

Fish models used for chemical exposure in toxicological studies are normally kept in barren tanks without any structural environmental enrichment. Here, we tested the combined effects of environmental enrichment and exposure to two mixtures of endocrine disrupting chemicals (EDCs) in zebrafish. Firstly, we assessed whether developmental exposure to an EDC mixture (MIX G1) combined with rearing the fish in an enriched environment influenced behaviour later in life. This was evaluated using locomotion tracking one month after exposure, showing a significant interaction effect between enrichment and the MIX G1 exposure on the measured locomotion parameters. After three months, we assessed behaviour using custom-made behaviour tanks, and found that enrichment influenced swimming activity. Control fish from the enriched environment were more active than control fish from the barren environment. Secondly, we exposed adult zebrafish to a separate EDC mixture (MIX G0) after rearing them in a barren or enriched environment. Behaviour and hepatic mRNA expression for thyroid-related genes were assessed. There was a significant interaction effect between exposure and enrichment on swimming activity and an effect of environment on latency to approach the group of conspecifics, where enriched fish took more time to approach the group, possibly indicating that they were less anxious. Hepatic gene expression of a thyroid-related gene (thrb) was significantly affected by EDC exposure, while enrichment had no discernible impact on the expression of the measured genes. In conclusion, environmental enrichment is important to consider when studying the effects of EDCs in fish.

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

What Can Laboratory Animal Facility Managers Do to Improve the Welfare of Laboratory Animals and Laboratory Animal Facility Staff? A German Perspective

Laboratory animal facility managers must ensure that animal experiments can be carried out under optimal scientific conditions, that all legal requirements are met, and that animal welfare is maximized. Animal experimentation is stressful not only for the animals involved but also for the people who maintain these animals or carry out the experiments. Many of those involved find themselves in a constant conflict between scientific necessity, care, and harm. Under the term Culture of Care, procedures have been developed to reduce the burden of animal experimentation on the animals and the staff involved. The focus here is on what laboratory animal facility managers can do to improve the welfare of laboratory animals and the people working with them. Exemplary measures are the improvement of the housing conditions of laboratory animals, the introduction of uniform handling measures, clear and transparent structures via a quality management system, implementation of a no-blame culture of error (e.g., via Critical Incident Reporting System in Laboratory Animal Science [CIRS-LAS]), and open and respectful communication with all parties involved in animal experimentation, including the public and representatives of the authorities (public webpage, open house policy). The 6 Rs must be considered at all times: replacement, reduction, refinement, respect, responsibility, and reproducibility. We are writing this article from the perspective of laboratory animal facility managers in Germany.

Environmental Enrichment in Stroke Research: an Update

Environmental enrichment (EE) refers to different forms of stimulation, where the environment is designed to improve the levels of sensory, cognitive, and motor stimuli, inducing stroke recovery in animal models. Stroke is a leading cause of mortality and neurological disability among older adults, hence the importance of developing strategies to improve recovery for such patients. This review provides an update on recent findings, compiling information regarding the parameters affected by EE exposure in both preclinical and clinical studies. During stroke recovery, EE exposure has been shown to improve both the cognitive and locomotor aspects, inducing important neuroplastic alterations, increased angiogenesis and neurogenesis, and modified gene expression, among other effects. There is a need for further research in this field, particularly in those aspects where the evidence is inconclusive. Moreover, it is necessary refine and adapt the EE paradigms for application in human patients.

Update on the gut microbiome in health and diseases

The Human Microbiome Project, Earth Microbiome Project, and next-generation sequencing have advanced novel genome association, host genetic linkages, and pathogen identification. The microbiome is the sum of the microbes, their genetic information, and their ecological niche. This study will describe how millions of bacteria in the gut affect the human body in health and disease. The gut microbiome changes in relation with age, with an increase in Bacteroidetes and Firmicutes. Host and environmental factors affecting the gut microbiome are diet, drugs, age, smoking, exercise, and host genetics. In addition, changes in the gut microbiome may affect the local gut immune system and systemic immune system. In this study, we discuss how the microbiome may affect the metabolism of healthy subjects or may affect the pathogenesis of metabolism-generating metabolic diseases. Due to the high number of publications on the argument, from a methodologically point of view, we decided to select the best papers published in referred journals in the last 3 years. Then we selected the previously published papers. The major goals of our study were to elucidate which microbiome and by which pathways are related to healthy and disease conditions.

Molecular insights into enriched environments and behavioral improvements in autism: a systematic review and meta-analysis

Aims

Autism is a multifaceted developmental disorder of the nervous system, that necessitates novel therapeutic approaches beyond traditional medications and psychosomatic therapy, such as appropriate sensory integration training. This systematic mapping review aims to synthesize existing knowledge on enriching environmental interventions as an alternative avenue for improving autism, guiding future research and practice.

Method

A comprehensive search using the terms ASD and Enriched Environment was conducted across PubMed, EMBASE, ISI, Cochrane, and OVID databases. Most of the literature included in this review was derived from animal model experiments, with a particular focus on assessing the effect of EE on autism-like behavior, along with related pathways and molecular mechanisms. Following extensive group discussion and screening, a total of 19 studies were included for analysis.

Results

Enriched environmental interventions exhibited the potential to induce both behavioral and biochemical changes, ameliorating autism-like behaviors in animal models. These improvements were attributed to the targeting of BDNF-related pathways, enhanced neurogenesis, and the regulation of glial inflammation.

Conclusion

This paper underscores the positive impact of enriched environmental interventions on autism through a review of existing literature. The findings contribute to a deeper understanding of the underlying brain mechanisms associated with this intervention.

Phosphorylation regulates tau's phase separation behavior and interactions with chromatin

Tau is a microtubule-associated protein often found in neurofibrillary tangles (NFTs) in the brains of patients with Alzheimer's disease (AD). Beyond this context, mounting evidence suggests that tau localizes into the nucleus, where it may play a role in DNA protection and heterochromatin regulation. Models of tau depletion or pathology show loss of genetically silent heterochromatin, aberrant expression of heterochromatic genes, and transposable element activation. The molecular mechanisms behind these observations are currently unclear. Using in vitro biophysical experiments, here we demonstrate that tau can undergo liquid-liquid phase separation (LLPS) with DNA, mononucleosomes, and reconstituted nucleosome arrays under low salt conditions. Low concentrations of tau promote chromatin compaction and protect DNA from digestion. While the material state of samples at physiological salt is dominated by chromatin oligomerization, tau can still associate strongly and reversibly with nucleosome arrays. These properties are driven by tau's strong interactions with linker and nucleosomal DNA, while magic angle spinning (MAS) solid-state NMR experiments show that tau binding does not drastically alter nucleosome structure and dynamics. In addition, tau co-localizes into droplets formed by nucleosome arrays and phosphorylated HP1α, a key heterochromatin constituent thought to function through an LLPS mechanism. Importantly, LLPS and chromatin interactions are disrupted by aberrant tau hyperphosphorylation. These biophysical properties suggest that tau may directly impact DNA and chromatin accessibility and that loss of these interactions could contribute to the aberrant nuclear effects seen in tau pathology.

Increased depression-like behaviors with altered brain dopamine metabolisms in male mice housed in large cages are alleviated by bupropion

Psycho-environmental stress-based animal models of anxiety and depression are useful for investigating pathological mechanisms and drug development. Although several rodent-based studies have reported the beneficial effects of environmental enrichment (EE) on brain plasticity and anxiety- and depression-like behaviors, other studies have reported inverse effects. Here, we found that housing male mice in EE involving large cages and other EE materials increased anxiety- and depression-like behaviors in open field and tail suspension tests (TST). We further confirmed that housing in large cages was sufficient to induce increased depression-like behaviors in the TST and reduce the saccharine preference percentage, a sign of anhedonia, in male mice. In these experiments, the number of animals per cage was equivalent to that in standard cage housing, suggesting that low density in large cages may be a determining factor for behavioral alteration. In mice housed in large cages, sex-specific dysregulation of brain monoamine systems was observed; dopamine turnover to homovanillic acid or norepinephrine in the prefrontal cortex was elevated in males, while serotonin turnover to 5-hydroxyindoleacetic acid in the amygdala was increased in females. Finally, we demonstrated that daily intraperitoneal injections of bupropion, a dopamine and norepinephrine reuptake inhibitor, counteracted large-cage housing-induced changes in depression- and anhedonia-like behaviors in male mice. Our results suggest that housing in large cages with a low density of mice is a novel paradigm to clarify the mechanisms of environmental stress-induced emotional dysregulation and to identify drugs or food factors to alleviate the dysregulation.

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.

Regulation of astrocyte metabolism by mitochondrial translocator protein 18kDa

The mitochondrial translocator protein 18kDa (TSPO) has been linked to a variety of functions from steroidogenesis to regulation of cellular metabolism and is an attractive therapeutic target for chronic CNS inflammation. Studies in the periphery using Leydig cells and hepatocytes, as well as work in microglia, indicate that the function of TSPO may vary between cells depending on their specialised roles. Astrocytes are critical for providing trophic and metabolic support in the brain as part of their role in maintaining brain homeostasis. Recent work has highlighted that TSPO expression increases in astrocytes under inflamed conditions and may drive astrocyte reactivity. However, relatively little is known about the role TSPO plays in regulating astrocyte metabolism and whether this protein is involved in immunometabolic processes in these cells. Using TSPO-deficient (TSPO-/-) mouse primary astrocytes in vitro (MPAs) and a human astrocytoma cell line (U373 cells), we performed metabolic flux analyses. We found that loss of TSPO reduced basal astrocyte respiration and increased the bioenergetic response to glucose reintroduction following glucopenia, while increasing fatty acid oxidation (FAO). Lactate production was significantly reduced in TSPO-/- astrocytes. Co-immunoprecipitation studies in U373 cells revealed that TSPO forms a complex with carnitine palmitoyltransferase 1a, which presents a mechanism wherein TSPO may regulate FAO in astrocytes. Compared to TSPO+/+ cells, inflammation induced by 3h lipopolysaccharide (LPS) stimulation of TSPO-/- MPAs revealed attenuated tumour necrosis factor release, which was enhanced in TSPO-/- MPAs at 24h LPS stimulation. Together these data suggest that while TSPO acts as a regulator of metabolic flexibility in astrocytes, loss of TSPO does not appear to modulate the metabolic response of astrocytes to inflammation, at least in response to the stimulus/time course used in this study.

Reduction of restricted repetitive behavior by environmental enrichment: Potential neurobiological mechanisms

Restricted repetitive behaviors (RRB) are one of two diagnostic criteria for autism spectrum disorder and common in other neurodevelopmental and psychiatric disorders. The term restricted repetitive behavior refers to a wide variety of inflexible patterns of behavior including stereotypy, self-injury, restricted interests, insistence on sameness, and ritualistic and compulsive behavior. However, despite their prevalence in clinical populations, their underlying causes remain poorly understood hampering the development of effective treatments. Intriguingly, numerous animal studies have demonstrated that these behaviors are reduced by rearing in enriched environments (EE). Understanding the processes responsible for the attenuation of repetitive behaviors by EE should offer insights into potential therapeutic approaches, as well as shed light on the underlying neurobiology of repetitive behaviors. This review summarizes the current knowledge of the relationship between EE and RRB and discusses potential mechanisms for EE's attenuation of RRB based on the broader EE literature. Existing gaps in the literature and future directions are also discussed.

Environmental modifications to rehabilitate social behavior deficits after acquired brain injury: What is the evidence?

Social behavior deficits are a common, debilitating consequence of traumatic brain injury and stroke, particularly when sustained during childhood. Numerous factors influence the manifestation of social problems after acquired brain injuries, raising the question of whether environmental manipulations can minimize or prevent such deficits. Here, we examine both clinical and preclinical evidence addressing this question, with a particular focus on environmental enrichment paradigms and differing housing conditions. We aimed to understand whether environmental manipulations can ameliorate injury-induced social behavior deficits. In summary, promising data from experimental models supports a beneficial role of environmental enrichment on social behavior. However, limited studies have considered social outcomes in the chronic setting, and few studies have addressed the social context specifically as an important component of the post-injury environment. Clinically, limited high-caliber evidence supports the use of specific interventions for social deficits after acquired brain injuries. An improved understanding of how the post-injury environment interacts with the injured brain, particularly during development, is needed to validate the implementation of rehabilitative interventions that involve manipulating an individuals' environment.

Activity-Induced MeCP2 Phosphorylation Regulates Retinogeniculate Synapse Refinement

Mutations in MECP2 give rise to Rett syndrome (RTT), an X-linked neurodevelopmental disorder that results in broad cognitive impairments in females. While the exact etiology of RTT symptoms remains unknown, one possible explanation for its clinical presentation is that loss of MeCP2 causes miswiring of neural circuits due to defects in the brain's capacity to respond to changes in neuronal activity and sensory experience. Here we show that MeCP2 is phosphorylated at four residues in the brain (S86, S274, T308, and S421) in response to neuronal activity, and we generate a quadruple knock-in (QKI) mouse line in which all four activity-dependent sites are mutated to alanines to prevent phosphorylation. QKI mice do not display overt RTT phenotypes or detectable gene expression changes in two brain regions. However, electrophysiological recordings from the retinogeniculate synapse of QKI mice reveal that while synapse elimination is initially normal at P14, it is significantly compromised at P20. Notably, this phenotype is distinct from that previously reported for Mecp2 null mice, where synapses initially refine but then regress after the third postnatal week. We thus propose a model in which activity-induced phosphorylation of MeCP2 is critical for the proper timing of retinogeniculate synapse maturation specifically during the early postnatal period.

SIGNIFICANCE STATEMENT

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder that predominantly affects girls. RTT is caused by loss of function mutations in a single gene MeCP2. Girls with RTT develop normally during their first year of life, but then experience neurological abnormalities including breathing and movement difficulties, loss of speech, and seizures. This study investigates the function of the MeCP2 protein in the brain, and how MeCP2 activity is modulated by sensory experience in early life. Evidence is presented that sensory experience affects MeCP2 function, and that this is required for synaptic pruning in the brain. These findings provide insight into MeCP2 function, and clues as to what goes awry in the brain when the function of MeCP2 is disrupted.

The influence of long-term housing in enriched environment on behavior of normal rats and subjected to neonatal pro-inflammatory challenge

It is well known that neonatal pro-inflammatory challenge (NPC) acquire a predisposition to the development of a number of neuropsychiatric diseases: depression, anxiety disorders, autism, attention deficit hyperactivity disorder. Symptoms of these diseases can manifest themselves in adulthood and adolescent after repeated exposure to negative influences. Preventing the development of the negative consequences of NPC is one of the main tasks for researchers. The exposure to an enriched environment (EE) was shown to have anxiolytic, anti-depressive, and pro-cognitive effects. The present work was aimed to investigate the effects of the long-term EE on anxious-depressive and conditioned fear behavior in normal male and female rats and subjected to NPC. The NPC was induced by subcutaneous administration of lipopolysaccharide (LPS, 50 μg/kg) on 3d and 5th PNDs. The control animals received saline (SAL). The rats were placed in the EE from 25 to 120 PND. Animals housed in the standard conditions (STAND) served as controls. In adult female and male rats of the STAND groups, LPS did not affect the anxiety, depressive-like behavior and conditioned fear. The EE increased motor and search activity in males and females. In the open field, the EE reduced anxiety in males of the SAL and LPS groups and in females of SAL groups compared to the STAND housed animals. In the elevated plus maze, the EE decreased anxiety only in males of the SAL group. In the sucrose preference test, the EE did not change sucrose consumption in males and females of SAL and LPS groups, while, in the forced swimming test, the EE reduced depressive-like behavior in females of both SAL and LPS groups. The enrichment decreased the contextual conditioned fear in male and female of SAL groups, but not of the LPS group, and did not affect the cue conditioned fear. The corticosterone reactivity to the forced swimming stress increased in males of the EE groups. The basal level of IL-1beta in blood serum decreased in males of the SAL-EE group. Thus, the EE reduced anxiety in males, depressive-like behavior in females, and contextual conditioned fear in males and females compared to the STAND housed animals. Although the NPC did not affect these behaviors in the STAND groups, LPS prevented the beneficial EE effects on anxiety and conditioned fear. The opposing effects of LPS were dependent on sex and type of testing.

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 protein α-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.

The Masticatory Activity Interference in Quantitative Estimation of CA1, CA3 and Dentate Gyrus Hippocampal Astrocytes of Aged Murine Models and under Environmental Stimulation

Studies indicating the influence of masticatory dysfunction, due to a soft diet or lack of molars, on impairing spatial memory and learning have led to research about neuronal connections between areas and cell populations possibly affected. In this sense, with scarce detailed data on the subfields of hippocampus in dementia neurodegeneration, there is no information about astrocytic responses in its different layers. Thus, considering this context, the present study evaluated the effects of deprivation and rehabilitation of masticatory activity, aging, and environmental enrichment on the stereological quantification of hippocampal astrocytes from layers CA1, CA3, and DG. For this purpose, we examined mature (6-month-old; 6M), and aged (18-month-old; 18M) mice, subjected to distinct masticatory regimens and environments. Three different regimens of masticatory activity were applied: continuous normal mastication with hard pellets (HD); normal mastication followed by deprived mastication with equal periods of pellets followed by soft powder (HD/SD); or rehabilitated masticatory activity with equal periods of HD, followed by powder, followed by pellets (HD/SD/HD). Under each specific regimen, half of the animals were raised in standard cages (impoverished environment (IE)) and the other half in enriched cages (enriched environment (EE)), mimicking sedentary or active lifestyles. Microscopic stereological, systematic, and random sampling approaches with an optical dissector of GFAP-immunolabeled astrocytes were done, allowing for an astrocyte numerical estimate. Stratum moleculare and hilus, from the dentate gyrus (DG) and Strata Lacunosum-Moleculare, Oriens, and Radiatum, similarly to the dentate gyrus, showed no significant change in any of the investigated variables (age, diet, or environment) in these layers. However, in Stratum radiatum, it was possible to observe significant differences associated with diet regimens and age. Therefore, diet-related differences were found when the HD 18M IE group was compared to the HD/SD/HD 18-month-old group in the same environment (IE) (p = 0.007). In the present study, we present modulatory factors (masticatory function, environmental enrichment, and aging) for the differentiated quantitative laminar response in the hippocampal regions, suggesting other studies to read the plasticity and responsiveness of astrocytes, including the molecular background.

Psychological dominant stressor modification to an animal model of depression with chronic unpredictable mild stress

Background and Aim

Chronic unpredictable mild stress (CUMS) is a protocol widely used to create an animal model of depression with food deprivation, water deprivation, and physical-dominant stressors as routine procedures. However, human depression mainly involves psychological stressors and does not always involve a lack of food and water; thus, CUMS procedures should be modified accordingly. Therefore, this study aimed to create an animal model of depression, mainly focusing on a psychologically dominant stressor without food and water deprivation.

Materials and Methods

The CUMS and control groups, respectively, received CUMS modification (psychologically dominant stressors without food and water deprivation) for 21 days. A 24-h sucrose preference test (SPT) was used to assess the successful creation of an animal model of depression. Daily food intake measurements, weekly weight monitoring, and weight gain calculations were performed. Either an independent sample t-test or the Mann-Whitney test was used.

Results

Of the 42 rats included, 39 completed the study. Chronic unpredictable mild stress procedures for 21 days significantly reduced the SPT (p < 0.05), mean body weight (p < 0.05), and weekly weight gain (p < 0.05) in the CUMS group compared to the control group. However, the weekly average food intake did not statistically differ between the two groups.

Conclusion

Psychological dominant CUMS modification to an animal model of depression resulted in lower SPT, body weight, and weekly weight gain in the CUMS group than in the control group.

Gain-of-function p.F28S variant in RAC3 disrupts neuronal differentiation, migration and axonogenesis during cortical development, leading to neurodevelopmental disorder

BACKGROUND

RAC3 encodes a Rho family small GTPase that regulates the behaviour and organisation of actin cytoskeleton and intracellular signal transduction. Variants in RAC3 can cause a phenotypically heterogeneous neurodevelopmental disorder with structural brain anomalies and dysmorphic facies. The pathomechanism of this recently discovered genetic disorder remains unclear.

METHODS

We investigated an early adolescent female with intellectual disability, drug-responsive epilepsy and white matter abnormalities. Through exome sequencing, we identified the novel de novo variant (NM_005052.3): c.83T>C (p.Phe28Ser) in RAC3. We then examined the pathophysiological significance of the p.F28S variant in comparison with the recently reported disease-causing p.Q61L variant, which results in a constitutively activated version of RAC3.

RESULTS

In vitro analyses revealed that the p.F28S variant was spontaneously activated by substantially increased intrinsic GTP/GDP-exchange activity and bound to downstream effectors tested, such as PAK1 and MLK2. The variant suppressed the differentiation of primary cultured hippocampal neurons and caused cell rounding with lamellipodia. In vivo analyses using in utero electroporation showed that acute expression of the p.F28S variant caused migration defects of excitatory neurons and axon growth delay during corticogenesis. Notably, defective migration was rescued by a dominant negative version of PAK1 but not MLK2.

CONCLUSION

Our results indicate that RAC3 is critical for brain development and the p.F28S variant causes morphological and functional defects in cortical neurons, likely due to the hyperactivation of PAK1.

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).

[Improved immunity and mean lifespan in mature mice genetically deficient in catecholamine synthesis after living with wild type for two months]

INTRODUCTION

Mice hemizygous in tyrosine hydroxylase (TH-HZ), the limiting enzyme in catecholamine synthesis, show premature immunosenescence, which in females is associated with a shorter lifespan than the corresponding controls (WT). The coexistence of TH-Hz with WT improves the immune function in both males and females in adulthood.

OBJECTIVE

To test whether cohabitation for two months of mature male TH-HZ with WT improves the immune function of the former and whether this impacts the lifespan.

MATERIAL AND METHODS

Mature male ICR-CD1 mice (13 ± 1 months) TH-HZ coexisted with WT (2:4 ratio in each cage) for two months. Peritoneal leukocytes were extracted from all animals at baseline, one month, and two months after cohabitation, and macrophage phagocytic capacity, macrophage and lymphocyte chemotaxis, natural killer (NK) antitumor activity, and lymphoproliferative capacity in response to the mitogens concanavalin A and lipopolysaccharide (LPS) were assessed. The animals were maintained under these conditions until their natural death.

RESULTS

The TH-HZ, which start, in general, with lower values than the WT in the immune functions studied, improved them after two months of cohabitation, becoming similar to those of the controls. This improvement was already observed in NK activity after one month of cohabitation. The TH-HZ presented lower mean longevity than WT, but when they cohabited with WT, it was similar to the latter.

CONCLUSION

The coexistence of TH-HZ male mice with WT mice for two months at mature age improves these genetically modified animals' immune response and longevity.

Using SuperClomeleon to Measure Changes in Intracellular Chloride during Development and after Early Life Stress

Intraneuronal chloride concentrations ([Cl^-]_i) decrease during development resulting in a shift from depolarizing to hyperpolarizing GABA responses via chloride-permeable GABA_A receptors. This GABA shift plays a pivotal role in postnatal brain development, and can be strongly influenced by early life experience. Here, we assessed the applicability of the recently developed fluorescent SuperClomeleon (SClm) sensor to examine changes in [Cl^-]_i using two-photon microscopy in brain slices. We used SClm mice of both sexes to monitor the developmental decrease in neuronal chloride levels in organotypic hippocampal cultures. We could discern a clear reduction in [Cl^-]_i between day in vitro (DIV)3 and DIV9 (equivalent to the second postnatal week in vivo) and a further decrease in some cells until DIV22. In addition, we assessed alterations in [Cl^-]_i in the medial prefrontal cortex (mPFC) of postnatal day (P)9 male SClm mouse pups after early life stress (ELS). ELS was induced by limiting nesting material between P2 and P9. ELS induced a shift toward higher (i.e., immature) chloride levels in layer 2/3 cells in the mPFC. Although conversion from SClm fluorescence to absolute chloride concentrations proved difficult, our study underscores that the SClm sensor is a powerful tool to measure physiological changes in [Cl^-]_i in brain slices.

Enriched Environment Attenuates Enhanced Trait Anxiety in Association with Normalization of Aberrant Neuro-Inflammatory Events

Neuroinflammation is discussed to play a role in specific subgroups of different psychiatric disorders, including anxiety disorders. We have previously shown that a mouse model of trait anxiety (HAB) displays enhanced microglial density and phagocytic activity in key regions of anxiety circuits compared to normal-anxiety controls (NAB). Using minocycline, we provided causal evidence that reducing microglial activation within the dentate gyrus (DG) attenuated enhanced anxiety in HABs. Besides pharmacological intervention, "positive environmental stimuli", which have the advantage of exerting no side-effects, have been shown to modulate inflammation-related markers in human beings. Therefore, we now investigated whether environmental enrichment (EE) would be sufficient to modulate upregulated neuroinflammation in high-anxiety HABs. We show for the first time that EE can indeed attenuate enhanced trait anxiety, even when presented as late as adulthood. We further found that EE-induced anxiolysis was associated with the attenuation of enhanced microglial density (using Iba-1 as the marker) in the DG and medial prefrontal cortex. Additionally, EE reduced Iba1 + CD68+ microglia density within the anterior DG. Hence, the successful attenuation of trait anxiety by EE was associated in part with the normalization of neuro-inflammatory imbalances. These results suggest that pharmacological and/or positive behavioral therapies triggering microglia-targeted anti-inflammatory effects could be promising as novel alternatives or complimentary anxiolytic therapeutic approaches in specific subgroups of individuals predisposed to trait anxiety.

Enriched environment ameliorates propagation of tau pathology and improves cognition in rat model of tauopathy

Introduction

The typical symptoms of Alzheimer’s disease (AD) are cognitive impairment, disrupted spatial orientation, behavioral and psychiatric abnormalities, and later motor deficits. Neuropathologically, AD is characterized by deposits of pathological forms of endogenous proteins – amyloid-β, and neurofibrillary tau protein pathology. The latter closely correlates with brain atrophy and clinical impairment. Pharmacological therapies for these pathologies are largely absent, raising the question whether non-pharmacological interventions could be efficacious. Environmental factors can play a role in the manifestation of AD. It is unknown whether enriched environment (EE) can ameliorate the propagation of protein aggregates or their toxic components.

Methods

We injected insoluble tau extracts from human brains with AD (600 or 900 ng per animal) into hippocampi of SHR72 transgenic rats that express non-mutated truncated human tau 151-391/4R, but usually do not develop hippocampal tangles. The rats had either standard housing, or could access an EE 5×/week for 3 months. Behavioral analysis included the Morris Water Maze (MWM). Histological analysis was used to assess the propagation of tau pathology.

Results

Animals exposed to EE performed better in the MWM (spatial acquisition duration and total distance, probe test); unexposed animals improved over the course of acquisition trials, but their mean performance remained below that of the EE group. Enriched environment abrogated tau propagation and hippocampal tangle formation in the 600 ng group; in the 900 ng group, tangle formation was ∼10-fold of the 600 ng group, and unaffected by EE.

Conclusion

Even a small difference in the amount of injected human AD tau can cause a pronounced difference in the number of resulting tangles. EE leads to a noticeably better spatial navigation performance of tau-injected animals. Furthermore, EE seems to be able to slow down tau pathology progression, indicating the possible utility of similar interventions in early stages of AD where tangle loads are still low.

Pre-Exposure to Environmental Enrichment Protects against Learning and Memory Deficits Caused by Infrasound Exposure

With the development of industrialization in recent years, infrasound has become an important component of public noise. To date, diverse studies have revealed the negative effects of infrasound on the central nervous system (CNS), especially the learning and memory ability. It is widely reported that environmental enrichment (EE) ameliorates the learning and memory deficits in different models of brain injury. Therefore, the present study was designed to determine the possible benefits of pre-exposure to EE in preventing functional deficits following infrasound exposure and their related mechanism. Adult male rats were given enriched or standard housing for 30 days. Following enrichment, the rats were exposed to 16 Hz, 130 dB infrasound for 14 days, and then their learning and memory ability was assessed. Changes to neuroinflammation, apoptosis, and oxidative stress in the hippocampus were also detected. Our results showed that the infrasound-induced deficit in learning and memory was attenuated significantly in EE pre-exposed rats. Pre-exposure to EE could induce a decrease in proinflammatory cytokines and increased anti-inflammatory cytokines and antioxidant properties in the hippocampus. Moreover, pre-exposure to EE also exerted antiapoptosis functions by upregulating the B-cell lymphoma/leukemia-2 (Bcl-2) level and downregulating the P53 level in the hippocampus. In conclusion, the results of the present study suggested that EE is neuroprotective when applied before infrasound exposure, resulting in an improved learning and memory ability by enhancing antioxidant, anti-inflammatory, and antiapoptosis capacities.

Enriched Environment and Exercise Enhance Stem Cell Therapy for Stroke, Parkinson’s Disease, and Huntington’s Disease

Stem cells, specifically embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), induced pluripotent stem cells (IPSCs), and neural progenitor stem cells (NSCs), are a possible treatment for stroke, Parkinson’s disease (PD), and Huntington’s disease (HD). Current preclinical data suggest stem cell transplantation is a potential treatment for these chronic conditions that lack effective long-term treatment options. Finding treatments with a wider therapeutic window and harnessing a disease-modifying approach will likely improve clinical outcomes. The overarching concept of stem cell therapy entails the use of immature cells, while key in recapitulating brain development and presents the challenge of young grafted cells forming neural circuitry with the mature host brain cells. To this end, exploring strategies designed to nurture graft-host integration will likely enhance the reconstruction of the elusive neural circuitry. Enriched environment (EE) and exercise facilitate stem cell graft-host reconstruction of neural circuitry. It may involve at least a two-pronged mechanism whereby EE and exercise create a conducive microenvironment in the host brain, allowing the newly transplanted cells to survive, proliferate, and differentiate into neural cells; vice versa, EE and exercise may also train the transplanted immature cells to learn the neurochemical, physiological, and anatomical signals in the brain towards better functional graft-host connectivity.

The Relative Benefits of Environmental Enrichment on Learning and Memory are Greater When Stressed: A Meta-analysis of Interactions in Rodents

Environmental enrichment ("EE") is expected to alleviate the negative effects of stress on cognitive performance. However, there are complexities associated with interpreting interactions that obscure determining the benefit EE may play in mitigating the negative effects of stress. To clarify these complexities, we conducted a systematic review with meta-analysis on the main and interactive effects of EE and stress on learning and memory in rodents. We show that EE and stress interact 'synergistically' where EE provides a greater relative benefit to stressed individuals compared to those reared in conventional housing. Importantly, EE can fully-compensate for the negative effects of stress where stressed individuals with EE performed equally to enriched individuals without a stress manipulation. Additionally, we show the importance of other mediating factors, including the order of treatment exposure, duration and type of stress, type of EE, and type of cognitive assays used. This study not only quantifies the interactions between EE and stress, but also provides a clear example for how to conduct and interpret meta-analysis of interactions.

Suppression of active phase voluntary wheel running in male rats by unilateral chronic constriction injury: Enduring therapeutic effects of a brief treatment of morphine combined with TLR4 or P2X7 antagonists

The present series of studies examine the impact of systemically administered therapeutics on peripheral nerve injury (males; unilateral sciatic chronic constriction injury [CCI])-induced suppression of voluntary wheel running, across weeks after dosing cessation. Following CCI, active phase running distance and speed are suppressed throughout the 7-week observation period. A brief course of morphine, however, increased active phase running distance and speed throughout this same period, an effect apparent only in sham rats. For CCI rats, systemic co-administration of morphine with antagonists of either P2X7 (A438079) or TLR4 ((+)-naloxone) (receptors critical to the activation of NLRP3 inflammasomes and consequent inflammatory cascades) returned running behavior of CCI rats to that of shams through 5+ weeks after dosing ceased. This is a striking difference in effect compared to our prior CCI allodynia results using systemic morphine plus intrathecal delivery of these same antagonists, wherein a sustained albeit partial suppression of neuropathic pain was observed. This may point to actions of the systemic drugs at multiple sites along the neuraxis, modulating injury-induced, inflammasome-mediated effects at the injured sciatic nerve and/or dorsal root ganglia, spinal cord, and potentially higher levels. Given that our data to date point to morphine amplifying neuroinflammatory processes put into motion by nerve injury, it is intriguing to speculate that co-administration of TLR4 and/or P2X7 antagonists can intervene in these inflammatory processes in a beneficial way. That is, that systemic administration of such compounds may suppress inflammatory damage at multiple sites, rapidly and persistently returning neuropathic animals to sham levels of response.

Reduced ccl11/eotaxin mediates the beneficial effects of environmental stimulation on the aged hippocampus

A deterioration in cognitive performance accompanies brain aging, even in the absence of neurodegenerative pathologies. However, the rate of cognitive decline can be slowed down by enhanced cognitive and sensorimotor stimulation protocols, such as environmental enrichment (EE). Understanding how EE exerts its beneficial effects on the aged brain pathophysiology can help in identifying new therapeutic targets. In this regard, the inflammatory chemokine ccl11/eotaxin-1 is a marker of aging with a strong relevance for neurodegenerative processes. Here, we demonstrate that EE in both elderly humans and aged mice decreases circulating levels of ccl11. Interfering, in mice, with the ccl11 decrease induced by EE ablated the beneficial effects on long-term memory retention, hippocampal neurogenesis, activation of local microglia and of ribosomal protein S6. On the other hand, treatment of standard-reared aged mice with an anti-ccl11 antibody resulted in EE-like improvements in spatial memory, hippocampal neurogenesis, and microglial activation. Taken together, our findings point to a decrease in circulating ccl11 concentration as a key mediator of the enhanced hippocampal function resulting from exposure to EE.

Timely N-Acetyl-Cysteine and Environmental Enrichment Rescue Oxidative Stress-Induced Parvalbumin Interneuron Impairments via MMP9/RAGE Pathway: A Translational Approach for Early Intervention in Psychosis

Research in schizophrenia (SZ) emphasizes the need for new therapeutic approaches based on antioxidant/anti-inflammatory compounds and psycho-social therapy. A hallmark of SZ is a dysfunction of parvalbumin-expressing fast-spiking interneurons (PVI), which are essential for neuronal synchrony during sensory/cognitive processing. Oxidative stress and inflammation during early brain development, as observed in SZ, affect PVI maturation. We compared the efficacy of N-acetyl-cysteine (NAC) and/or environmental enrichment (EE) provided during juvenile and/or adolescent periods in rescuing PVI impairments induced by an additional oxidative insult during childhood in a transgenic mouse model with gluthation deficit (Gclm KO), relevant for SZ. We tested whether this rescue was promoted by the inhibition of MMP9/RAGE mechanism, both in the mouse model and in early psychosis (EP) patients, enrolled in a double-blind, randomized, placebo-controlled clinical trial of NAC supplementation for 6 months. We show that a sequential combination of NAC+EE applied after an early-life oxidative insult recovers integrity and function of PVI network in adult Gclm KO, via the inhibition of MMP9/RAGE. Six-month NAC treatment in EP patients reduces plasma sRAGE in association with increased prefrontal GABA, improvement of cognition and clinical symptoms, suggesting similar neuroprotective mechanisms. The sequential combination of NAC+EE reverses long-lasting effects of an early oxidative insult on PVI/perineuronal net (PNN) through the inhibition of MMP9/RAGE mechanism. In analogy, patients vulnerable to early-life insults could benefit from a combined pharmacological and psycho-social therapy.

Maternal Gut Dysbiosis Alters Offspring Microbiota and Social Interactions

Increasing application of antibiotics changes the gut microbiota composition, leading to dysbiosis of the gut microbiota. Although growing evidence suggests the potential role of gut dysbiosis as the cause of neurodevelopmental disorders and behavioral defects, a broad gap of knowledge remains to be narrowed to better understand the exact mechanisms by which maternal gut dysbiosis alters microbiota development and social interactions of offspring. Here, we showed that maternal gut dysbiosis during gestation is a critical determinant of gut microbiota and social interactions off mouse offspring. Gut microbiota of 2-week-old offspring showed significant changes in response to maternal antibiotic treatment. We even detected distinct effects of maternal oral antibiotics on gut microbiota of 14-week-old offspring. Compared to controls, offspring born to antibiotics-treated mothers displayed reduction in sociability and preference for social novelty, suggesting that the altered offspring social behavior was closely linked to dysbiosis of maternal gut microbiota. Our study opens the possibility to better understand the mechanism of how maternal gut microbiota vertically impairs social interactions of offspring in animal models, providing support to the maternal gut microbiota as a potential mediator between offspring microbiota and behaviors.

Microglial Morphology Across Distantly Related Species: Phylogenetic, Environmental and Age Influences on Microglia Reactivity and Surveillance States

Microglial immunosurveillance of the brain parenchyma to detect local perturbations in homeostasis, in all species, results in the adoption of a spectrum of morphological changes that reflect functional adaptations. Here, we review the contribution of these changes in microglia morphology in distantly related species, in homeostatic and non-homeostatic conditions, with three principal goals (1): to review the phylogenetic influences on the morphological diversity of microglia during homeostasis (2); to explore the impact of homeostatic perturbations (Dengue virus challenge) in distantly related species (Mus musculus and Callithrix penicillata) as a proxy for the differential immune response in small and large brains; and (3) to examine the influences of environmental enrichment and aging on the plasticity of the microglial morphological response following an immunological challenge (neurotropic arbovirus infection). Our findings reveal that the differences in microglia morphology across distantly related species under homeostatic condition cannot be attributed to the phylogenetic origin of the species. However, large and small brains, under similar non-homeostatic conditions, display differential microglial morphological responses, and we argue that age and environment interact to affect the microglia morphology after an immunological challenge; in particular, mice living in an enriched environment exhibit a more efficient immune response to the virus resulting in earlier removal of the virus and earlier return to the homeostatic morphological phenotype of microglia than it is observed in sedentary mice.

Short-Term Environmental Enrichment is a Stronger Modulator of Brain Glial Cells and Cervical Lymph Node T Cell Subtypes than Exercise or Combined Exercise and Enrichment

Physical exercise (PE) and environmental enrichment (EE) can modulate immunity. However, the differential effects of short-term PE, EE, and PE + EE on neuroimmune mechanisms during normal aging has not been elucidated. Hence, a cohort of 3-, 8-, and 13-month-old immunologically unchallenged C57BL/6 wild-type mice were randomly assigned to either Control, PE, EE, or PE + EE groups and provided with either no treatment, a running wheel, a variety of plastic and wooden objects alone or in combination with a running wheel for seven weeks, respectively. Immunohistochemistry and 8-color flow cytometry were used to determine the numbers of dentate gyrus glial cells, and the proportions of CD4+ and CD8+ T cell numbers and their subsets from cervical lymph nodes, respectively. An increase in the number of IBA1+ microglia in the dentate gyrus at 5 and 10 months was observed after EE, while PE and PE + EE increased it only at 10 months. No change in astroglia number in comparison to controls were observed in any of the treatment groups. Also, all treatments induced significant differences in the proportion of specific T cell subsets, i.e., CD4+ and CD8+ T naïve (TN), central memory (TCM), and effector memory (TEM) cells. Our results suggest that in the short-term, EE is a stronger modulator of microglial and peripheral T cell subset numbers than PE and PE + EE, and the combination of short-term PE and EE has no additive effects.

TNF signaling via TNF receptors does not mediate the effects of short-term exercise on cognition, anxiety and depressive-like behaviors in middle-aged mice

BACKGROUND

We recently reported that tumor necrosis factor (TNF) signaling via the TNFR1 and TNFR2 receptors mediates the effects of long-term exercise on locomotion, cognition and anxiety, but not depressive-like behavior. We now investigated whether the TNF signaling via its receptors also mediates the effects of short-term exercise on cognition, anxiety and depressive-like behaviors.

METHODS

Thirteen-month-old C57BL/6 (WT), TNF^-/-, TNFR1^-/-, and TNFR2^-/- mice were provided with 4 weeks of voluntary wheel running followed by behavioral testing using an established behavioral battery. Each genotype had a respective non-exercise control.

RESULTS

There was no interaction between genotype and exercise in any of the tests but the main effect of genotype, and not exercise, were found to be significant in the open field (OF), forced-swim test (FST) and Barnes maze (BM). In the OF, the control and exercise TNFR2^-/- mice spent significantly less time in the inner zone than mice in the control and exercise WT and TNF^-/- cohorts. In the FST, control and exercise WT mice showed significantly higher immobility time than their control and exercise TNF^-/-, TNFR1^-/- and TNFR2^-/- cohorts. In the BM, the latency to escape over 4 days of training was significantly higher in all KO groups compared to WT, irrespective of exercise. Also, the latency to escape to the original location during the probe trial was higher for control and exercise WT compared to corresponding TNFR1^-/- mice. In contrast, the latency to escape to the new location was lower for control and exercise WT compared to control and exercise TNFR1^-/- and TNFR2^-/- mice. The latency to escape to the new location in exercise groups was longer compared to control within all genotypes.

CONCLUSION

While TNF signaling via the TNF receptors mediates cognition, anxiety and depressive-like behaviors independently, it does not mediate the effects of short-term exercise on these behaviors in middle-aged mice.

Limbic Encephalitis Brain Damage Induced by Cocal Virus in Adult Mice Is Reduced by Environmental Enrichment: Neuropathological and Behavioral Studies

We previously demonstrated, using the Piry virus model, that environmental enrichment promotes higher T-cell infiltration, fewer microglial changes, and faster central nervous system (CNS) virus clearance in adult mice. However, little is known about disease progression, behavioral changes, CNS cytokine concentration, and neuropathology in limbic encephalitis in experimental models. Using Cocal virus, we infected C57Bl6 adult mice and studied the neuroanatomical distribution of viral antigens in correlation with the microglial morphological response, measured the CNS cytokine concentration, and assessed behavioral changes. C57Bl6 adult mice were maintained in an impoverished environment (IE) or enriched environment (EE) for four months and then subjected to the open field test. Afterwards, an equal volume of normal or virus-infected brain homogenate was nasally instilled. The brains were processed to detect viral antigens and microglial morphological changes using selective immunolabeling. We demonstrated earlier significant weight loss and higher mortality in IE mice. Additionally, behavioral analysis revealed a significant influence of the environment on locomotor and exploratory activity that was associated with less neuroinvasion and a reduced microglial response. Thus, environmental enrichment was associated with a more effective immune response in a mouse model of limbic encephalitis, allowing faster viral clearance/decreased viral dissemination, reduced disease progression, and less CNS damage.

The Gut-Brain Axis: How Microbiota and Host Inflammasome Influence Brain Physiology and Pathology

The human microbiota has a fundamental role in host physiology and pathology. Gut microbial alteration, also known as dysbiosis, is a condition associated not only with gastrointestinal disorders but also with diseases affecting other distal organs. Recently it became evident that the intestinal bacteria can affect the central nervous system (CNS) physiology and inflammation. The nervous system and the gastrointestinal tract are communicating through a bidirectional network of signaling pathways called the gut-brain axis, which consists of multiple connections, including the vagus nerve, the immune system, and bacterial metabolites and products. During dysbiosis, these pathways are dysregulated and associated with altered permeability of the blood-brain barrier (BBB) and neuroinflammation. However, numerous mechanisms behind the impact of the gut microbiota in neuro-development and -pathogenesis remain poorly understood. There are several immune pathways involved in CNS homeostasis and inflammation. Among those, the inflammasome pathway has been linked to neuroinflammatory conditions such as multiple sclerosis, Alzheimer's and Parkinson's diseases, but also anxiety and depressive-like disorders. The inflammasome complex assembles upon cell activation due to exposure to microbes, danger signals, or stress and lead to the production of pro-inflammatory cytokines (interleukin-1β and interleukin-18) and to pyroptosis. Evidences suggest that there is a reciprocal influence of microbiota and inflammasome activation in the brain. However, how this influence is precisely working is yet to be discovered. Herein, we discuss the status of the knowledge and the open questions in the field focusing on the function of intestinal microbial metabolites or products on CNS cells during healthy and inflammatory conditions, such as multiple sclerosis, Alzheimer's and Parkinson's diseases, and also neuropsychiatric disorders. In particular, we focus on the innate inflammasome pathway as immune mechanism that can be involved in several of these conditions, upon exposure to certain microbes.

Effect of Tank Size on Zebrafish Behavior and Physiology

Simple Summary

Living space is an important aspect of animal welfare. Understanding the effects of welfare on experimental animals would help in drawing a precise conclusion. In this work, zebrafish in different tank sizes were studied through behavioral and physiology tests. Results showed that changes in the tank size affected zebrafish behavior; those that lived in small tanks behaved less boldly, had poor stamina, and spent much time on movement. Therefore, researchers should focus on zebrafish’s living space to generate valid data from laboratory studies.

Abstract

Environmental conditions strongly affect experimental animals. As a model organism, zebrafish has become important in life science studies. However, the potential effect of living environment on their behavior and physiology is often overlooked. This work aimed to determine whether tank size affects zebrafish behavior and physiology. Tests on shelter leaving, shelter seeking, shoaling, stamina, and pepsin and cortisol levels were conducted. Results showed that zebrafish behavior is easily affected by changes on the tank size. Fish that lived in small tanks behaved less boldly, had poor stamina, and spent much time on movement. Sex differences in behavior were only evident in the shelter seeking tests. Tank size had no effect on pepsin and cortisol, but cortisol concentrations in males were lower than those in females. This study suggests that zebrafish behavior is easily influenced by their living environment, and future related studies should consider their living space.

Enduring neuroimmunological consequences of developmental experiences: From vulnerability to resilience

The immune system is crucial for normal neuronal development and function (neuroimmune system). Both immune and neuronal systems undergo significant postnatal development and are sensitive to developmental programming by environmental experiences. Negative experiences from infection to psychological stress at a range of different time points (in utero to adolescence) can permanently alter the function of the neuroimmune system: given its prominent role in normal brain development and function this dysregulation may increase vulnerability to psychiatric illness. In contrast, positive experiences such as exercise and environmental enrichment are protective and can promote resilience, even restoring the detrimental effects of negative experiences on the neuroimmune system. This suggests the neuroimmune system is a viable therapeutic target for treatment and prevention of psychiatric illnesses, especially those related to stress. In this review we will summarise the main cells, molecules and functions of the immune system in general and with specific reference to central nervous system development and function. We will then discuss the effects of negative and positive environmental experiences, especially during development, in programming the long-term functioning of the neuroimmune system. Finally, we will review the sparse but growing literature on sex differences in neuroimmune development and response to environmental experiences.

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The immune system is essential for development and function of the central nervous system (neuroimmune system)

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Environmental experiences can permanently alter neuroimmune function and associated brain development

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Altered neuroimmune function following negative developmental experiences may play a role in psychiatric illnesses

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Positive experiences can promote resilience and rescue the effects of negative experiences on the neuroimmune system

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The neuroimmune system is therefore a viable therapeutic target for preventing and treating psychiatric illnesses

Alternative splicing of neurexins 1-3 is modulated by neuroinflammation in the prefrontal cortex of a murine model of multiple sclerosis

Mounting evidence points to immune-mediated synaptopathy and impaired plasticity as early pathogenic events underlying cognitive decline (CD) in Multiple sclerosis (MS) and in the experimental autoimmune encephalomyelitis (EAE) mouse model of the disease. However, knowledge of the neurobiology of synaptic dysfunction is still incomplete. Splicing regulation represents a flexible and powerful mechanism involved in dynamic remodeling of the synapse, which allows the expression of synaptic protein variants that dynamically control the specificity of contacts between neurons. The pre-synaptic adhesion molecules neurexins (NRXNs) 1-3 play a relevant role in cognition and are alternatively spliced to yield variants that differentially cluster specific ligands in the postsynaptic compartment and modulate functional properties of the synaptic contact. Notably, mutations in these genes or disruption of their splicing program are associated with neuropsychiatric disorders. Herein, we have investigated how inflammatory changes imposed by EAE impact on alternative splicing of the Nrxn 1-3 mouse genes in the acute phase of disease. Due to its relevance in cognition, we focused on the prefrontal cortex (PFC) of SJL/J mice, in which EAE-induced inflammatory lesions extend to the rostral forebrain. We found that inclusion of the Nrxn 1-3 AS4 exon is significantly increased in the PFC of EAE mice and that splicing changes are correlated with local Il1β-expression levels. This correlation is sustained by the concomitant downregulation of SLM2, the main splicing factor involved in skipping of the AS4 exon, in EAE mice displaying high levels of Il1β- expression. We also observed that Il1β-expression levels correlate with changes in parvalbumin (PV)-positive interneuron connectivity. Moreover, exposure to environmental enrichment (EE), a condition known to stimulate neuronal connectivity and to improve cognitive functions in mice and humans, modified PFC phenotypes of EAE mice with respect to Il1β-, Slm2-expression, Nrxn AS4 splicing and PV-expression, by limiting changes associated with high levels of inflammation. Our results reveal that local inflammation results in early splicing modulation of key synaptic proteins and in remodeling of GABAergic circuitry in the PFC of SJL/J mice. We also suggest EE as a tool to counteract these inflammation-associated events, thus highlighting potential therapeutic targets for limiting the progressive CD occurring in MS.

Differential impact of stress and environmental enrichment on corticolimbic circuits

Stress exposure can produce profound changes in physiology and behavior that can impair health and well-being. Of note, stress exposure is linked to anxiety disorders and depression in humans. The widespread impact of these disorders warrants investigation into treatments to mitigate the harmful effects of stress. Pharmacological treatments fail to help many with these disorders, so recent work has focused on non-pharmacological alternatives. One of the most promising of these alternatives is environmental enrichment (EE). In rodents, EE includes social, physical, and cognitive stimulation for the animal, in the form of larger cages, running wheels, and toys. EE successfully reduces the maladaptive effects of various stressors, both as treatment and prophylaxis. While we know that EE can have beneficial effects under stress conditions, the morphological and molecular mechanisms underlying these behavioral effects are still not well understood. EE is known to alter neurogenesis, dendrite development, and expression of neurotrophic growth factors, effects that vary by type of enrichment, age, and sex. To add to this complexity, EE has differential effects in different brain regions. Understanding how EE exerts its protective effects on morphological and molecular levels could hold the key to developing more targeted pharmacological treatments. In this review, we summarize the literature on the morphological and molecular consequences of EE and stress in key emotional regulatory pathways in the brain, the hippocampus, prefrontal cortex, and amygdala. The similarities and differences among these regions provide some insight into stress-EE interaction that may be exploited in future efforts toward prevention of, and intervention in, stress-related diseases.

Enriched environment effect on lipopolysaccharide-induced spatial learning, memory impairment and hippocampal inflammatory cytokine levels in male rats

Neuro-inflammation is responsible for cognitive impairments and neurodegenerative diseases such as Alzheimer's disease. In this study, we aimed to investigate the enriched environment (EE) effect on learning and memory impairment as well as on pro-inflammatory cytokines changes induced by lipopolysaccharide (LPS). LPS injection (1 mg/kg/i.p, days 1, 3, 5, and 7) was used to develop the animal model of neuro-inflammation. Twenty-eight male Wistar rats were used in the experiment and randomly divided into 4 groups: 1) sham (S), 2) sham + enriched environment (SE), 3) LPS (L), and 4) LPS + EE (LE). Two different housing conditions, including standard environment (SE) and enriched environment, were used. The Morris Water Maze (MWM) test was used to examine animals learning and memory. IL-1β, IL-10, and TNF-α levels were measured in the brain using ELISA. We found that LPS significantly impaired learning and memory (p < 0.05) in the MWM task, but EE could significantly improve learning and memory impairment (p < 0.05). IL-1 and IL-10 levels dramatically increased in the LPS group (P < 0.05), whereas EE could decrease and increase IL-1β and IL-10 values in the LPS + EE group (P < 0.05), respectively. TNF-α levels were traced but had not detectable values in the hippocampus. Thus, we can conclude that EE has healing effects on LPS induced neuro-inflammation and can improve learning and memory deficit; however, further studies are needed to support the findings of our study.

Social Environment Ameliorates Behavioral and Immune Impairments in Tyrosine Hydroxylase Haploinsufficient Female Mice

The social environment can influence the functional capacity of nervous and immune systems, and consequently the state of health, especially in aged individuals. Adult female tyrosine hydroxylase haploinsufficient (TH-HZ) mice exhibit behavioral impairments, premature immunosenescence and oxidative- inflammatory stress. All these deteriorations are associated with a lower lifespan than wild type (WT) counterparts. The aim was to analyze whether the cohabitation with WT animals could revert or at least ameliorate the deterioration in the nervous and immune systems that female TH-HZ mice show at adult age. Female TH-HZ and WT mice at age of 3-4 weeks were divided into following groups: control TH-HZ (5 TH-HZ mice in the cage; TH-HZ100%), control WT (5 WT mice in the cage; WT100%), TH-HZ > 50% and WT < 50% (5 TH-HZ with 2 WT mice in each cage) as well as TH-HZ < 50% and WT > 50% (2 TH-HZ and 5 WT mice in each cage). At the age of 37-38 weeks, all mice were submitted to a battery of behavioral tests, evaluating sensorimotor abilities, exploratory capacities and anxiety-like behaviors. Subsequently, peritoneal leukocytes were extracted and several immune functions as well as oxidative and inflammatory stress parameters were analyzed. The results showed that the TH-HZ < 50% group had improved behavioral responses, especially anxiety-like behaviors, and the immunosenescence and oxidative stress of their peritoneal leukocytes were ameliorated. However, WT mice that cohabited with TH-HZ mice presented higher anxiety-like behaviors and deterioration in immune functions and in their inflammatory stress parameters. Thus, this social environment is capable of ameliorating the impairments associated with a haploinsufficiency of the th gene. Graphical Abstract.

The Link Between Stress and Endometriosis: from Animal Models to the Clinical Scenario

There is strong evidence from humans and animal models showing that abnormal functioning of the hypothalamic-pituitary-adrenal (HPA) axis and/or the inflammatory response system disrupts feedback regulation of both neuroendocrine and immune systems, contributing to disease. Stress is known to affect the physiology of pelvic organs and to disturb the HPA axis leading to chronic, painful, inflammatory disorders. A link between stress and disease has already been documented for many chronic conditions. Endometriosis is a complex chronic gynecological disease associated with severe pelvic pain and infertility that affects 10% of reproductive-aged women. Patients report the negative impact of endometriosis symptoms on quality of life, work/study productivity, and personal relationships, which in turn cause high levels of psychological and emotional distress. The relationship between stress and endometriosis is not clear. Still, we have recently demonstrated that stress increases the size and severity of the lesions as well as inflammatory parameters in an animal model. Furthermore, the "controllability" of stress influences the pathophysiology in this model, offering the possibility of using stress management techniques in patients. The crosstalk between stress-inflammation-pain through HPA axis activity indicates that stress relief should alleviate inflammation and, in turn, decrease painful responses. This opens up the opportunity of altering brain-body-brain pathways as potential new therapeutic option for endometriosis. The goal of this review is to gather the research evidence regarding the interaction between stress (psychological and physiological) and the development and progression of endometriosis on the exacerbation of its symptoms with the purpose of proposing new lines of emerging research and possible treatment modalities for this still incurable disease.

The effects of environmental enrichment on skin barrier recovery in humans: a randomised trial

This study investigated whether environmental enrichment (EE) could reduce stress and improve wound healing in humans. 120 participants underwent a standardised tape-stripping procedure and were then randomised to interact for 30 minutes with one of three EE interventions (comfort blankets as tactile enrichment, music as auditory enrichment or a Paro robot as multi-sensory enrichment) or to a control group. Skin barrier recovery (SBR) was measured using transepidermal water loss at baseline, after tape-stripping and after the intervention. Psychological variables, cortisol and alpha-amylase were measured at the three time-points. SBR did not significantly differ between the EE conditions and the control condition. The music condition had higher stimulation levels than the control condition, and the comfort condition had significantly lower relaxation levels than the control condition after the intervention. The EE interventions tested were not beneficial for wound healing compared to a control group. Limitations were that the sample were not stressed and an active control condition was used.

Duration of Environmental Enrichment Determines Astrocyte Number and Cervical Lymph Node T Lymphocyte Proportions but Not the Microglial Number in Middle-Aged C57BL/6 Mice

Environmental enrichment (EE) has been shown to modulate behavior and immunity. We recently reported that both short and long-term EE enhance baseline locomotion and alleviate depressive-like behavior, but only long-term EE affects locomotion adversely in a threatening environment and enhances anxiety-like behavior in middle-age mice. We have now investigated whether the observed changes in behavior after short- and long-term EE were associated with underlying immune changes. Hence, at the end of behavioral testing, mice were sacrificed, and brains and cervical lymph nodes were collected to investigate the differential effects of the duration of EE (short- and long-term) on the number of immunopositive glial cells in the dentate gyrus, CA1, CA2, and CA3 regions of the hippocampus and proportions of T cell subsets in the cervical lymph nodes using immunohistochemistry and flow cytometry, respectively. EE, regardless of duration, caused an increase in microglia number within the dentate gyrus, CA1 and CA3 hippocampal regions, but only long-term EE increased astrocytes number within the dentate gyrus and CA3 hippocampal regions. A significantly higher proportion of CD8⁺ naive T cells was observed after long-term EE vs. short-term EE. No significant differences were observed in the proportion of central memory and effector memory T cells or early activated CD25⁺ cells between any of the test groups. Our results suggest that EE, irrespective of duration, enhances the numbers of microglia, but long-term EE is required to modify astrocyte number and peripheral T cell proportions in middle-aged mice. Our findings provide new insights into the therapeutic effects of EE on various brain disorders, which may be at least partly mediated by glial and neuroimmune modulation.