Social isolation after stroke leads to depressive-like behavior and decreased BDNF levels in mice

Serum brain derived neurotrophic factor levels and post-stroke depression in ischemic stroke patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is crucial for neuronal survival and may be implicated in the pathophysiological process of depression. This study aimed to prospectively investigate the association between serum BDNF and post-stroke depression (PSD) at 3 months in a multicenter cohort study.

METHODS

A total of 611 ischemic stroke patients with serum BDNF measurements from the China Antihypertensive Trial in Acute Ischemic Stroke were included in this analysis. We used the 24-item Hamilton Depression Rating Scale to assess depression status at 3 months after ischemic stroke, and PSD was defined as a score of ≥8.

RESULTS

Baseline serum BDNF was inversely associated with the risk of depression after ischemic stroke. The multivariable-adjusted odds ratio of PSD for the highest tertile of BDNF was 0.53 (95 % confidence interval, 0.34-0.82; P for trend = 0.004) compared with the lowest tertile. Multivariable-adjusted spline regression model also showed a linear does-response association between serum BDNF levels and PSD at 3 months (P for linearity = 0.006). In addition, adding serum BDNF to conventional risk factors significantly improved the risk reclassification of PSD (net reclassification improvement: 16.98 %, P = 0.039; integrated discrimination index: 0.93 %, P = 0.026).

LIMITATIONS

All patients in this study were Chinese, so our findings should be applied to other populations cautiously.

CONCLUSIONS

Higher serum BDNF levels at baseline were significantly associated with a decreased risk of PSD at 3 months, suggesting that BDNF might be a valuable predictive biomarker and potential therapeutic target for PSD among ischemic stroke patients.

Impact of social isolation on corticosterone release and recovery after stroke in aged rats: A behavioral and biochemical analysis

Social isolation (SI) after stroke reduces recovery. The aim of this study was to evaluate the effects of SI on corticosterone release and recovery after stroke in aged rats. A total of 64 male Wistar rats (aged 24 months) were used in the present study. All rats were housed in pairs for two weeks. After two weeks, rats were randomly assigned to one of four groups: (1) rats underwent sham surgery and kept socially isolated (control/social isolated (CO/SI) group); (2) rats underwent sham surgery and kept pair housed (control/pair housed (CO/PH) group); (3) rats underwent middle cerebral artery occlusion (MCAO) surgery and kept socially isolated (stroke/isolated (ST/SI) group); (4) rats underwent MCAO surgery and kept pair housed (stroke/pair housed (ST/PH)) group. Behaviors were assessed using the adhesive removal test, rotarod test and social interaction test at 1st, 7th, 14th and 21st days after stroke. Serum biochemical analysis was also performed on the behavioral testing days. Results showed THAT serum corticosterone and MDA levels in CO/PH group were significantly lower than CO/SI group. Serum BDNF levels in CO/PH group was significantly higher than CO/SI group. Serum corticosterone and MDA levels in ST/PH group were lower than ST/SI group. In ST/PH group, serum Total antioxidant capacity (TAC) and BDNF levels were significantly higher than ST/SI group. Biochemical analysis of certain regions of the brain (hippocampus, striatum and cerebral cortex) was performed on 21st day after stroke. In the hippocampus of CO/PH group, BDNF and TAC levels were significantly higher than CO/SI group. The hippocampal MDA level of CO/PH group were significantly lower than CO/SI group. BDNF and TAC levels in the hippocampus, striatum and cerebral cortex of ST/PH group were significantly higher and MDA level was significantly lower as compared with ST/SI group. Both ischemic groups showed sensorimotor recovery over a 21-day period, but recovery of ST/PH group was significantly greater than ST/SI group. Total social interaction time in ST/PH group was significantly longer than ST/SI group. Based on the results of this study, social interaction after stroke enhances histologic and sensorimotor recovery through reduction of HPA activity and corticosterone release, leading to increased TAC and BDNF levels.

The oxytocin receptor is essential for the protective effect of pair housing on post-stroke depression in mice

The beneficial effect of social interaction in mitigating the incidence of post-stroke depression (PSD) and ameliorating depressive symptoms has been consistently demonstrated through preclinical and clinical studies. However, the underlying relationship with oxytocin requires further investigation. In light of this, the present study aimed to explore the protective effect of pair housing on the development of PSD and the potential relationship with oxytocin receptors. The PSD model was induced by middle cerebral artery occlusion (MCAO) for 50 min, followed by 4-week isolated housing and restrained stress. Subsequently, each mouse in the pair-housing group (PH) was pair-housed with an isosexual healthy partner. Another group was continuously administrated fluoxetine (10 mg/Kg, i.p, once a day) for 3 weeks. To elucidate the potential role of oxytocin, we subjected pair-housed PSD mice to treatment with an oxytocin receptor (OXTR) antagonist (L368,889) (5 mg/Kg, i.p, once a day) for 3 weeks. At 31 to 32 days after MCAO, anxiety- and depressive-like behaviors were assessed using sucrose consumption, forced swim test, and tail-suspension test. The results showed that pair housing significantly improved post-stroke depression to an extent comparable to that of fluoxetine treatment. Furthermore, pair housing significantly decreased corticosterone in serum, increasing OXT mRNA expression in the hypothalamus. Treatment with L368,889 essentially reversed the effect of pair housing, with no discernible sex differences apart from changes in body weight. Pair housing increased hippocampal serotonin (5-HT), but treatment with L368,889 had no significant impact. Additionally, pair housing effectively reduced the number of reactive astrocytes and increased Nissl's body in the cortex and hippocampal CA3 regions. Correspondingly, treatment with L368,889 significantly reversed the changes in the Nissl's body and reactive astrocytes. Moreover, pair housing downregulated mRNA levels of TNF-α, IL-1β, and IL-6 in the cortex caused by PSD, which was also reversed by treatment with L368,889. In conclusion, pair housing protects against the development of PSD depending on OXT and OXTR in the brain, with no significant divergence based on sex. These findings provide valuable insights into the potential of social interaction and oxytocin as therapeutic targets for PSD. Further research into the underlying mechanisms of these effects may contribute to the development of novel treatments for PSD.

Social isolation initiated post-weaning augments ischemic brain injury by promoting pro-inflammatory responses

Social isolation is associated with poor stroke outcome, but the underlying molecular mechanisms were largely unknown. In male Balb/C mice exposed to transient middle cerebral artery occlusion (MCAo), we examined the effects of social isolation initiated post-weaning on ischemic injury, cytokine/chemokine responses and cell signaling using a broad panel of techniques that involved immunocytochemistry, cytokine/chemokine array and Western blots. Social isolation initiated post-weaning elevated infarct size, brain edema and neuronal injury in the ischemic brain tissue 3 days after MCAo, and increased microglia/ macrophage and leukocyte accumulation. In line with the increased immune cell recruitment, levels of several proinflammatory cytokines (e.g., IL-1α, IL-1β, IL-13, IL-17, TNF-α, IFN-γ), chemokines (e.g., CCL3, CCL4, CCL12, CXCL2, CXCL9, CXCL12) and adhesion molecules (i.e., ICAM-1) were increased in the ischemic brain tissue of socially isolated compared with paired housing mice, whereas levels of selected cytokines (IL-5, IL-6, IL-16) and colony-stimulating factors (G-CSF, GM-CSF) were reduced. The activity of the transcription factor nuclear factor-ĸB (NF-ĸB), which promotes cell injury via pro-inflammatory responses, was increased by social isolation, whereas that of nuclear factor erythroid related factor-2 (Nrf-2), which mediates anti-oxidative responses under oxidative stress conditions, was reduced. Our study shows that social isolation profoundly alters post-ischemic cell signaling in a way promoting pro-inflammatory responses. Our results highlight the importance of social support in preventing deleterious health effects of social isolation.

Cognitive behavioral therapy for managing depressive and anxiety symptoms after brain injury: a meta-analysis

BACKGROUND

Individuals with traumatic brain injury (TBI) are at increased risk of depression and anxiety, leading to impaired recovery. While cognitive-behavioral therapy (CBT) addresses anxiety and depression maintenance factors, its efficacy among those with TBI has not been clearly demonstrated. This review aims to bridge this gap in the literature.

METHODS

Several databases, including Medline, PsycInfo and EMBASE, were used to identify studies published between 1990 and 2021. Studies were included if: (1) trials were randomized controlled trials (RCT) involving CBT-based intervention targeting anxiety and/or depression; (2) participants experienced brain injury at least 3-months previous; (3) participants were ≥18 years old. An SMD ± SE, 95% CI and heterogeneity were calculated for each outcome.

RESULTS

Thirteen RCTs were included in this meta-analysis. The pooled-sample analyses suggest that CBT interventions had small immediate post-treatment effects on reducing depression (SMD ± SE: 0.391 ± 0.126, p < 0.005) and anxiety (SMD ± SE: 0.247 ± 0.081, p < 0.005). Effects were sustained at a 3-months follow-up for depression. A larger effect for CBT was seen when compared with supportive therapy than control. Another sub-analysis found that individualized CBT resulted in a slightly higher effect compared to group-based CBT.

CONCLUSION

This meta-analysis provides substantial evidence for CBT in managing anxiety and depression post-TBI.

In silico and in vivo analysis of the relationship between ADHD and social isolation in pups rat model: Implication of redox mechanisms, and the neuroprotective impact of Punicalagin

Attention deficit hyperactivity disorder (ADHD) has high incidence rate among children which may be due to excessive monosodium glutamate (MSG) consumption and social isolation (SI).

AIM

We aimed to explore the relationships between MSG, SI, and ADHD development and to evaluate the neuroprotective potential of Punicalagin (PUN).

METHODS

Eighty male rat pups randomly distributed into eight groups. Group I is the control, and Group II is socially engaged rats treated with PUN. Groups III to VII were exposed to ADHD-inducing factors: Group III to SI, Group IV to MSG, and Group V to both SI and MSG. Furthermore, Groups VI to VIII were the same Groups III to V but additionally received PUN treatment.

KEY FINDINGS

Exposure to MSG and/or SI led to pronounced behavioral anomalies, histological changes and indicative of ADHD-like symptoms in rat pups which is accompanied by inhibition of the nuclear factor erythroid 2-related factor 2 (Nrf2)/Heme-oxygenase 1 (HO-1)/Glutathione (GSH) pathway, decline of the brain-derived neurotrophic factor (BDNF) expression and activation of the Toll-like receptor 4 (TLR4)/Nuclear factor kappa B (NF-kB)/NLR Family Pyrin Domain Containing 3 (NLRP3) pathway. This resulted in elevated inflammatory biomarker levels, neuronal apoptosis, and disrupted neurotransmitter equilibrium. Meanwhile, pretreatment with PUN protected against all the previous alterations.

SIGNIFICANCE

We established compelling associations between MSG consumption, SI, and ADHD progression. Moreover, we proved that PUN is a promising neuroprotective agent against all risk factors of ADHD.

Challenges in Translating Regenerative Therapies for Spinal Cord Injury

Regenerating the injured spinal cord is a substantial challenge with many obstacles that need to be overcome to achieve robust functional benefits. This abundance of hurdles can partly explain the limited success when applying regenerative intervention treatments in animal models and/or people. In this article, we elaborate on a few of these obstacles, starting with the applicability of animal models and how they compare to the clinical setting. We then discuss the requirement for combinatorial interventions and the associated problems in experimental design, including the addition of rehabilitative training. The article expands on differences in lesion sizes and locations between humans and common animal models, and how this difference can determine the success or failure of an intervention. An additional and frequently overlooked problem in the translation of interventions that applies beyond the field of neuroregeneration is the reporting bias and the lack of transparency in reporting findings. New data mandates are tackling this problem and will eventually result in a more balanced view of the field. Finally, we will discuss strategies to negotiate the challenging course of successful translation to facilitate successful translation of regeneration promoting interventions.

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.

Long-term behavioural alterations in mice following transient cerebral ischemia

Ischemic stroke is one of the leading causes of disability and mortality worldwide. Acute and chronic post-stroke changes have variable effects on the functional outcomes of the disease. Therefore, it is imperative to identify what daily activities are altered after stroke and to what extent, keeping in mind that ischemic stroke patients often have long-term post-stroke complications. Translational studies in stroke have also been challenging due to inconsistent study design of animal experiments. The objective of this study was to clarify whether and to what extent mouse behaviour was altered during a 6 months period after cerebral stroke. Experimental stroke was induced in mice by intraluminal filament insertion into the middle cerebral artery (fMCAo). Neurological deficits, recovery rate, motor performance, and circadian activity were evaluated following ischemia. We observed severe neurological deficits, motor impairments, and delay in the recovery rate of mice during the first 14 days after fMCAo. Aberrant circadian activity and distorted space map were seen in fMCAo mice starting one month after ischemia, similarly to altered new and familiar cage activity and sucrose preference using the IntelliCage, and was still evident 60- and 180- days following stroke in the voluntary running wheel using the PhenoMaster system. A preference towards ipsilateral side turns was observed in fMCAo mice both acutely and chronically after the stroke induction. Overall, our study shows the importance of determining time-dependent differences in the long-term post-stroke recovery (over 180 days after fMCAo) using multiple behavioural assessments.

Electroacupuncture treatment ameliorates depressive-like behavior and cognitive dysfunction via CB1R dependent mitochondria biogenesis after experimental global cerebral ischemic stroke

Introduction

This study aimed to identify the effect of electroacupuncture (EA) treatment on post-stroke depression (PSD) and explore whether cannabinoid receptor 1 (CB1R)-mediated mitochondrial biogenesis accounts for the treatment effect of EA.

Methods

The PSD mouse model was induced by a consecutive 14-day chronic unpredictable stress operation after 7 days of recovery from the bilateral common carotid artery occlusion surgery. Either EA treatment or sham stimulation was performed for 14 consecutive days from Day 7 after the BCCAO operation. Subjects’ PSD-like behaviors were tested via open field test, sucrose preference test, novelty suppressed feeding test, tail suspension test, and forced swim test, and subjects’ cognitive function was examined using Y-maze and novelty object recognition test. In addition, the levels of CB1R, mitochondrial biogenesis-related proteins (nuclear transcription factor 1, NRF1; mitochondrial transcription factor A, TFAM), proteins related to mitochondrial function (Cytochrome C, Cyto C; AIF, COX IV), and mitochondrial DNA were measured. To elucidate the role of CB1R in EA treatment, CB1R antagonists AM251 and CB1R-shRNA were given to mice before EA treatment. Likewise, subjects’ depressive-like behaviors, cognitive function, mitochondrial function, and mitochondrial biogenesis were examined after the PSD procedure.

Results

It has been showed that EA successfully ameliorated depressive-like behaviors, improved cognitive dysfunctions, and upregulated CB1R, NRF1 and TFAM expressions. However, the supplementation of AM251 and CB1R-shRNA blocked the antidepressant-like effects generated by EA, and EA failed to improve cognitive dysfunction, upregulate CB1R protein expression, and increase mitochondrial function and biogenesis.

Conclusion

Altogether, these results indicated that EA ameliorated PSD-like behaviors in mice, improved cognitive dysfunctions after PSD, and promoted mitochondrial biogenesis by activating CB1R, a novel mechanism underlying EA’s antidepressant-like effects in treating PSD.

Disorders in the gut and liver are involved in depression contagion between isosexual post-stroke depression mice and the healthy cohabitors

Despite the accumulated evidence that pair housing could attenuate post-stroke depression (PSD), but less attention has been paid to the healthy cohabitors, and the underlying mechanisms remain unclear. This study aimed to determine whether there is depressive contagion between PSD mice and their healthy cohabitors. PSD was induced by middle cerebral artery occlusion (MCAO) plus restraint stress for four weeks. Three days after MCAO, the mice were restrained two hours per day and isosexually pair-housed for four weeks. The results showed that, compared with the partners pair housed with normal control mice (Ctrl group), the partners pair housed with PSD mice (CH group) displayed depressive-like behaviors, including decreased sucrose preference rate, significantly shorter duration in the center arena and reduced total distance in the open-field test, and extended immobile time in forced swimming test and tail-suspension test without sex differences. Regarding the change in the body weight, only the males showed a significant reduction on days 17 and 24 after treatment. Furthermore, the CH group showed significantly increased corticosterone and decreased oxytocin (OXT) levels in serum, while the mRNA levels of OXT, vasopressin and oxytocin receptor were remarkably upregulated in the hypothalamus of the CH group. However, there was no significant change in the vasopressin receptor V1a. Interestingly, compared with the Ctrl group, there was a significant decrease in butyrate in serum of the CH group. Consistently, they had mild liver dysfunction with increased alanine transaminase, extended hepatic sinus surrounded by enhanced SLC22A9, and significantly increased Iba1-positive macrophages. Moreover, the expression of tight junction protein (Occludin and ZO-1) obviously decreased in the colon with increasing Iba1-positive cells. These results suggest that isosexual pair-housing with PSD mice causes the healthy partners to develop depressive-like behaviors with disturbances in the gut and liver.

Potential neurobiological links between social isolation and Alzheimer's disease risk

It is estimated that 40% of dementia cases could be prevented by modification of lifestyle factors that associate with disease risk. One of these potentially modifiable lifestyle factors is social isolation. In this review, we discuss what is known about associations between social isolation and Alzheimer's disease, the most common cause of dementia. This is particularly relevant in the time of the COVID-19 pandemic when social isolation has been enforced with potential emerging negative impacts on cognition. While there are neurobiological mechanisms emerging that may account for the observed epidemiological associations between social isolation and Alzheimer's disease, more fundamental research is needed to fully understand the brain changes induced by isolation that may make people vulnerable to disease.

Music Upper Limb Therapy-Integrated Provides a Feasible Enriched Environment and Reduces Post-stroke Depression: A Pilot Randomized Controlled Trial

OBJECTIVE

This study's aims were to refine Music Upper Limb Therapy-Integrated (MULT-I) to create a feasible enriched environment for stroke rehabilitation and compare its biologic and behavioral effects with that of a home exercise program (HEP).

DESIGN

This was a randomized mixed-methods study of 30 adults with post-stroke hemiparesis. Serum brain-derived neurotrophic factor and oxytocin levels measured biologic effects, and upper limb function, disability, quality of life, and emotional well-being were assessed as behavioral outcomes. Participant experiences were explored using semistructured interviews.

RESULTS

MULT-I participants showed reduced depression from preintervention to postintervention as compared with HEP participants. Brain-derived neurotrophic factor levels significantly increased for MULT-I participants but decreased for HEP participants, with a significant difference between groups after excluding those with post-stroke depression. MULT-I participants additionally improved quality of life and self-perceived physical strength, mobility, activity, participation, and recovery from preintervention to postintervention. HEP participants improved upper limb function. Qualitatively, MULT-I provided psychosocial support and enjoyment, whereas HEP supported self-management of rehabilitation.

CONCLUSIONS

Implementation of a music-enriched environment is feasible, reduces post-stroke depression, and may enhance the neural environment for recovery via increases in brain-derived neurotrophic factor levels. Self-management of rehabilitation through an HEP may further improve upper limb function.

Effects of Social Isolation on the Development of Anxiety and Depression-Like Behavior in Model Experiments in Animals

This review describes the role of social isolation in the development of anxiety and depression-like behavior in rodents. The duration of social isolation, age from onset of social isolation, sex, species, and strain of animals, the nature of the model used, and other factors have been shown to have influences. The molecular-cellular mechanisms of development of anxiety and depression-like behavior under the influence of social isolation and the roles of the HHAS, oxidative and nitrosative stress, neuroinflammation, BDNF, neurogenesis, synaptic plasticity, as well as monoamines in these mechanisms are discussed. This review presents data on sex differences in the effects of social isolation, along with the effects of interactions with other types of stress, and the roles of an enriched environment and other factors in ameliorating the negative sequelae of social isolation.

New Possibilities in the Therapeutic Approach to Alzheimer's Disease

Despite the fact that Alzheimer's disease (AD) is the most common cause of dementia, after many years of research regarding this disease, there is no casual treatment. Regardless of the serious public health threat it poses, only five medical treatments for Alzheimer's disease have been authorized, and they only control symptoms rather than changing the course of the disease. Numerous clinical trials of single-agent therapy did not slow the development of disease or improve symptoms when compared to placebo. Evidence indicates that the pathological alterations linked to AD start many years earlier than a manifestation of the disease. In this pre-clinical period before the neurodegenerative process is established, pharmaceutical therapy might prove invaluable. Although recent findings from the testing of drugs such as aducanumab are encouraging, they should nevertheless be interpreted cautiously. Such medications may be able to delay the onset of dementia, significantly lowering the prevalence of the disease, but are still a long way from having a clinically effective disease-modifying therapy.

Mediation Analyses of the Role of Apathy on Motoric Cognitive Outcomes

Recent literature indicates that apathy is associated with poor cognitive and functional outcomes in older adults, including motoric cognitive risk syndrome (MCR), a predementia syndrome. However, the underlying biological pathway is unknown. The objectives of this study were to (1) examine the cross-sectional associations between inflammatory cytokines (Interleukin 6 (IL-6) and C-Reactive Protein (CRP)) and apathy and (2) explore the direct and indirect relationships of apathy and motoric cognitive outcomes as it relates to important cognitive risk factors. N = 347 older adults (≥65 years old) enrolled in the Central Control of Mobility in Aging Study (CCMA). Linear and logic regression models showed that IL-6, but not CRP was significantly associated with apathy adjusted for age, gender, and years of education (β = 0.037, 95% CI: 0.002-0.072, p = 0.04). Apathy was associated with a slower gait velocity (β = -14.45, 95% CI: -24.89-4.01, p = 0.01). Mediation analyses demonstrated that IL-6 modestly mediates the relationship between apathy and gait velocity, while apathy mediated the relationships between dysphoria and multimorbidity and gait velocity. Overall, our findings indicate that apathy may be an early predictor of motoric cognitive decline. Inflammation plays a modest role, but the underlying biology of apathy warrants further investigation.

Cognitive -behavioral therapy for managing depressive and anxiety symptoms after stroke: a systematic review and meta-analysis

BACKGROUND

Post-stroke anxiety and depression can be disabling and result in impaired recovery. Cognitive-behavioral therapy (CBT) has been demonstrated to be effective for anxiety and depression; however, determining its efficacy among those with stroke is warranted. Our objectives to evaluate CBT for anxiety and depression post-stroke .

METHODS

This review was registered with PROSPERO (REG# CRD42020186324). Medline, PsycInfo, and EMBR Cochrane were used to locate studies published before May 2020, using keywords such as stroke and CBT. A study was included if: (1) interventions were CBT-based, targeting anxiety and/or depression; (2) participants experienced a stroke at least 3 months previous; (3) participants were at least 18 years old. Standardized mean differences ± standard errors and 95% confidence intervals were calculated, and heterogeneity was determined. The Cochrane Risk of Bias tool was used.

RESULTS

The search yielded 563 articles, of which 10 (N = 672) were included;6 were randomized controlled trials. Primary reasons for exclusion included: (1) wrong population (2) insufficient data provided for a meta-analysis; (3) wrongoutcomes. CBT showed large effects on reducing overall anxiety (SMD ± SE: 1.01 ± 0.32, p < .001) and depression (SMD ± SE: 0.95 ± 0.22, p < .000) symptoms at the end of the studies. CBT moderately maintained anxiety (SDM ± SE: 0.779 ± 0.348, p ˂.025) and depression (SDM ± SE: 0.622 ± 0.285, p ˂ .029) scores after 3-months. Limitations included small sample size, limited comparators, and lack of follow-up data.

CONCLUSION

The results of this meta-analysis provide substantial evidence for the use of CBTto manage post-stroke anxiety and depression.

Effects of long-term social isolation on central, behavioural and metabolic parameters in middle-aged mice

Social isolation gained discussion momentum due to the COVID-19 pandemic. Whereas many studies address the effects of long-term social isolation in post-weaning and adolescence and for periods ranging from 4 to 12 weeks, little is known about the repercussions of adult long-term social isolation in middle age. Thus, our aim was to investigate how long-term social isolation can influence metabolic, behavioural, and central nervous system-related areas in middle-aged mice. Adult male C57Bl/6 mice (4 months-old) were randomly divided into Social (2 cages, n = 5/cage) and Isolated (10 cages, n = 1/cage) housing groups, totalizing 30 weeks of social isolation, which ended concomitantly with the onset of middle age of mice. At the end of the trial, metabolic parameters, short-term memory, anxiety-like behaviour, and physical activity were assessed. Immunohistochemistry in the hippocampus (ΔFosB, BDNF, and 8OHDG) and hypothalamus (ΔFosB) was also performed. The Isolated group showed impaired memory along with a decrease in hippocampal ΔFosB at dentate gyrus and in BDNF at CA3. Food intake was also affected, but the direction depended on how it was measured in the Social group (individually or in the group) with no alteration in ΔFosB at the hypothalamus. Physical activity parameters increased with chronic isolation, but in the light cycle (inactive phase), with some evidence of anxiety-like behaviour. Future studies should better explore the timepoint at which the alterations found begin. In conclusion, long-term social isolation in adult mice contributes to alterations in feeding, physical activity pattern, and anxiety-like behaviour. Moreover, short-term memory deficit was associated with lower levels of hippocampal ΔFosB and BDNF in middle age.

Up-regulation of SETD3 may contribute to post-stroke depression in rat through negatively regulating VEGF expression

Post-stroke depression (PSD) is one of the most familiar complications of stroke, which refers to stroke patients who have varying degrees of depression (lasts for >2 weeks). SET domain-containing 3 (SETD3) is a conserved histone H3 methyltransferase, and the role of SETD3 in some diseases is increasingly being explored. However, the effects of SETD3 in PSD remain unclear. In this study, the PSD rat model was firstly constructed by Endothelin-1 injection combined with chronic unpredictable mild stress, and we discovered that SETD3 expression was up-regulated in PSD rat model. Additionally, SETD3 knockdown relieved the depressive symptom of PSD. Moreover, SETD3 knockdown promoted proliferation and differentiation of neural stem cells (NSCs). Due to the critical role of vascular endothelial growth factor (VEGF) in antidepressant and SETD3 can negatively regulate VEGF, we speculated that SETD3 may regulate PSD progression through VEGF. Our results demonstrated that SETD3 knockdown up-regulated VEGF expression. Furthermore, SETD3 modulated the proliferation and differentiation of NSCs through regulating VEGF expression. In conclusion, our study indicated that up-regulation of SETD3 contributed to PSD progression in rats through negatively regulating VEGF expression. The findings of this work suggest that SETD3 may be a promising target for treating PSD in the future.

Consequences of pandemic-associated social restrictions: Role of social support and the oxytocin system

During pandemics, governments take drastic actions to prevent the spreading of the disease, as seen during the present COVID-19 crisis. Sanctions of lockdown, social distancing and quarantine urge people to exclusively work and teach at home and to restrict social contacts to a minimum; lonely people get into further isolation, while families` nerves are strained to the extreme. Overall, this results in a dramatic and chronic increase in the level of psychosocial stress over several months mainly caused by i) social isolation and ii) psychosocial stress associated with overcrowding, social tension in families, and domestic violence. Moreover, pandemic-associated social restrictions are accompanied by loss of an essential stress buffer and important parameter for general mental and physical health: social support. Chronic psychosocial stress and, in particular, social isolation and lack of social support affect not only mental health, but also the brain oxytocin system and the immune system. Hence, pandemic-associated social restrictions are expected to increase the risk of developing psychopathologies, such as depression, anxiety-related and posttraumatic stress disorders, on the one hand, but also to induce a general inflammatory state and to impair the course of infectious disorders on the other. Due to its pro-social and stress-buffering effects, resulting in an anti-inflammatory state in case of disease, the role of the neuropeptide oxytocin will be discussed and critically considered as an emerging treatment option in cases of pandemic-induced psychosocial stress, viral infection and during recovery. In this review, we aim to critically focus on possible short- and long-term consequences of social restrictions on mental health and the immune system, while discussion oxytocin as a possible treatment option.

Progress and challenges in preclinical stroke recovery research

Significant innovations in the management of acute ischemic stroke have led to an increased incidence in the long-term complications of stroke. Therefore, there is an urgent need for improvements in and refinement of rehabilitation interventions that can lead to functional and neuropsychological recovery. The goal of this review is to summarize the current progress and challenges involved with preclinical stroke recovery research. Moving forward, stroke recovery research should be placing an increased emphasis on the incorporation of comorbid diseases and biological variables in preclinical models in order to overcome translational roadblocks to establishing successful clinical rehabilitation interventions.

Protective Role of Caregiver Preparedness on the Relationship Between Depression and Quality of Life in Stroke Dyads

BACKGROUND AND PURPOSE

Depression and quality of life (QOL) have an interdependent and transactional nature in stroke survivor-caregiver dyads. While the strong relationship between depression and physical and emotional QOL in stroke survivor-caregiver dyads is well known, it is less clear if this relationship is moderated by caregiver preparedness, which could easily be targeted with interventions. In this study, we examined the moderating role of caregiver preparedness on the association between depression and QOL in stroke survivor-caregiver dyads.

METHODS

We used a longitudinal design with follow-ups every 3 months over a 1-year period. Considering the nonindependent nature of the data (survivors and their caregivers), we used multilevel modeling to analyze data at the dyad level. We implemented 4 longitudinal dyadic moderation models (one for each QOL domain: physical, psychological, social, and environmental) using hierarchical linear modeling.

RESULTS

A sample of 222 stroke survivor-caregiver dyads was analyzed. Stroke survivors were older (M=70.8, SD=11.9) than their caregivers (M=52.4, SD=13.1). Stroke survivors predominantly had an ischemic stroke, equally distributed by site. Caregivers were primarily female (66%), with a medium to high educational level (57%). Caregiver preparedness significantly moderated the association between survivor depression and survivor psychological (B=0.56, P<0.01) and environmental (B=0.58, P<0.01) QOL at baseline and social QOL over time (B=0.24, P<0.05). Similarly, caregiver preparedness significantly moderated the association between caregiver depression and caregiver physical (B=0.25, P<0.01) and environmental (B=0.18, P<0.05) QOL over time.

CONCLUSIONS

Caregiver preparedness has a positive influence on both members of the dyad. Assessment of stroke-caregiver preparedness could be helpful to motivate clinicians to develop and implement interventions for stroke survivor-caregiver dyads.

(R,S)-Ketamine Promotes Striatal Neurogenesis and Sensorimotor Recovery Through Improving Poststroke Depression–Mediated Decrease in Atrial Natriuretic Peptide

Background

Poststroke social isolation could worsen poststroke depression and dampen neurogenesis. (R,S)-ketamine has antidepressant and neuroprotective effects; however, its roles and mechanisms in social isolation–mediated depressive-like behaviors and sensorimotor recovery remain unclear.

Methods

Mice were subjected to transient middle cerebral artery occlusion, and then were pair-housed with ovariectomized female mice or were housed isolated (ISO) starting at 3 days postischemia. ISO mice received 2 weeks of (R,S)-ketamine treatment starting at 14 days postischemia. Primary ependymal epithelial cells and choroid plexus epithelial cells were cultured and treated with recombinant human atrial natriuretic peptide (ANP) protein.

Results

The poststroke social isolation model was successfully established using middle cerebral artery occlusion combined with poststroke isolation, as demonstrated by a more prominent depression-like phenotype in ISO mice compared with pair-housed mice. (R,S)-ketamine reversed ISO-mediated depressive-like behaviors and increased ANP levels in the atrium. The depression-like phenotype was negatively correlated with ANP levels in both the atrium and plasma. Atrial GLP-1 and GLP-1 receptor signaling was essential to the promoting effects of (R,S)-ketamine on the synthesis and secretion of ANP from the atrium in ISO mice. (R,S)-ketamine also increased ANP and TGF-β1 levels in the choroid plexus of ISO mice. Recombinant human ANP increased TGF-β1 levels in both the primarily cultured ependymal epithelial cells and choroid plexus epithelial cells. Furthermore, (R,S)-ketamine increased TGF-β1 levels in the ischemic hemisphere and promoted striatal neurogenesis and sensorimotor recovery via ANP in ISO mice.

Conclusions

(R,S)-ketamine alleviated poststroke ISO-mediated depressive-like behaviors and thus promoted striatal neurogenesis and sensorimotor recovery via ANP.

Neural Contributions of the Hypothalamus to Parental Behaviour

Parental behaviour is a comprehensive set of neural responses to social cues. The neural circuits that govern parental behaviour reside in several putative nuclei in the brain. Melanin concentrating hormone (MCH), a neuromodulator that integrates physiological functions, has been confirmed to be involved in parental behaviour, particularly in crouching behaviour during nursing. Abolishing MCH neurons in innate MCH knockout males promotes infanticide in virgin male mice. To understand the mechanism and function of neural networks underlying parental care and aggression against pups, it is essential to understand the basic organisation and function of the involved nuclei. This review presents newly discovered aspects of neural circuits within the hypothalamus that regulate parental behaviours.

Brain-Derived Neurotrophic Factor as a Clinical Biomarker in Predicting the Development of Post-Stroke Depression: A Review of Evidence

Studying the relationship between brain-derived neurotrophic factor (BDNF) and post-stroke depression (PSD) may help determine the potential for depression in stroke patients at the earliest stage possible. Current research has identified changes in BDNF levels in PSD patients. Thus, this article was intended as a review of evidence with respect to changes in the expression of BDNF in patients with PSD by integrating extant findings.

We conducted a search in the electronic databases PubMed, EMBASE, and PsycINFO (all records from January 1, 2000, through October 20, 2020) using keywords: “brain-derived neurotrophic factor OR BDNF,” “post-stroke depression OR PSD,” “expression level,” “association,” and “relationship.” Returned articles were considered for inclusion in this review if they were empirical studies investigating the association between BDNF expression and PSD.

Seven original papers were selected for review and revealed inconsistent findings. Five out of seven studies reported a significant decrease in BDNF levels in PSD patients at a certain stage (most likely the early stage) of stroke after admission, whereas the other two showed contrasting findings.

Overall, this review reveals associations between changes in serum BDNF levels and depression following stroke. Whether serum BDNF levels, especially in the early phase of stroke, can be a potentially effective biomarker for predicting the risk of subsequent PSD development is still open to debate.

Gadd45b is a novel mediator of depression-like behaviors and neuroinflammation after cerebral ischemia

BACKGROUND

Poststroke depression (PSD) is an important consequence after stroke, with a negative impact on stroke outcome. Recent evidence points to a modulatory role of Growth arrest and DNA-damage-inducible protein 45 beta (Gadd45b) in depression. Herein, we evaluated the antidepressant efficacy and mechanism underlying the potent therapeutic effects of Gadd45b after cerebral ischemia.

METHODS

Adult male Sprague-Dawley rats were subjected to cerebral ischemia by permanent middle cerebral artery occlusion (MCAO). The sucrose preference test (SPT), forced swim test (FST), and tail suspension test (TST) were performed after completing MCAO to study the antidepressant-like effects. The expression of brain-derived neurotrophic factor (BDNF) and neuroinflammation were determined in the hippocampus.

RESULTS

We showed that Gadd45b knockdown induced depression-like behaviors after cerebral ischemia, including increased immobility time in the FST and TST and reduced sucrose preference. Gadd45b knockdown enhanced the expression of pro-inflammatory cytokines IL-6 and TNF-α, accompanying with decreased protein levels of BDNF in the hippocampus. Moreover, the levels of phosphorylated ERK and CREB, which have been implicated in events downstream of BDNF signaling, were also decreased after cerebral ischemia.

CONCLUSION

Hence, the results showed that Gadd45b is a promising drug candidate for treating PSD and possibly other nervous system diseases associated with neuroinflammation. Gadd45b may have therapeutic potential for PSD through BDNF-ERK-CREB pathway and neuroinflammation.

CD36 deficiency reduces chronic BBB dysfunction and scar formation and improves activity, hedonic and memory deficits in ischemic stroke

Ameliorating blood-brain barrier disruption and altering scar formation dynamics are potential strategies that may improve post-stroke recovery. CD36 is a class B scavenger receptor that plays a role in innate immunity, inflammation and vascular dysfunction and regulates post-stroke injury, neovascularization, reactive astrogliosis and scar formation. By subjecting WT and CD36KO mice to different MCAo occlusion durations to generate comparable acute lesion sizes, we addressed the role of CD36 in BBB dysfunction, scar formation and recovery. The majority of stroke recovery studies primarily focus on motor function. Here, we employed an extensive behavioral test arsenal to evaluate psychological and cognitive endpoints. While not evident during the acute phase, CD36 deficient mice displayed significantly attenuated BBB leakage and scar formation at three months after stroke compared to wild-type littermates. Assessment of motor (open field, rotarod), anxiety (plus maze, light-dark box), depression (forced swim, sucrose preference) and memory tests (water maze) revealed that CD36 deficiency ameliorated stroke-induced behavioral impairments in activity, hedonic responses and spatial learning and strategy switching. Our findings indicate that CD36 contributes to stroke-induced BBB dysfunction and scar formation in an injury-independent manner, as well as to the chronic motor and neurophysiological deficits in chronic stroke.

Neuropsychiatric Complications after Stroke

Neuropsychiatric disturbances represent a common and uniquely challenging consequence of stroke. These disorders arise at the intersection of lesion-related brain dysfunction and psychological distress related to the event and its aftermath, making it difficult to identify what symptom is a direct physiological consequence of the stroke. Depression, anxiety, fatigue, apathy, emotionalism, and anger are the most common of these syndromes, and posttraumatic stress disorder related to the stroke event has become increasingly recognized as a relevant entity. Mania, obsessive-compulsive disorder, and psychosis are less commonly encountered but potentially highly debilitating conditions that may be underrecognized. Early identification and treatment may mitigate functional impairment and improve quality of life. Evidence-based guidelines from the general population are often relied upon to guide treatment. Further research is needed to understand and tailor treatment of these disorders in the poststroke population.

A novel murine model to study the impact of maternal depression and antidepressant treatment on biobehavioral functions in the offspring

Antenatal psychopathology negatively affects obstetric outcomes and exerts long-term consequences on the offspring's wellbeing and mental health. However, the precise mechanisms underlying these associations remain largely unknown. Here, we present a novel model system in mice that allows for experimental investigations into the effects of antenatal depression-like psychopathology and for evaluating the influence of maternal pharmacological treatments on long-term outcomes in the offspring. This model system in based on rearing nulliparous female mice in social isolation prior to mating, leading to a depressive-like state that is initiated before and continued throughout pregnancy. Using this model, we show that the maternal depressive-like state induced by social isolation can be partially rescued by chronic treatment with the selective serotonin reuptake inhibitor, fluoxetine (FLX). Moreover, we identify numerous and partly sex-dependent behavioral and molecular abnormalities, including increased anxiety-like behavior, cognitive impairments and alterations of the amygdalar transcriptome, in offspring born to socially isolated mothers relative to offspring born to mothers that were maintained in social groups prior to conception. We also found that maternal FLX treatment was effective in preventing some of the behavioral and molecular abnormalities emerging in offspring born to socially isolated mothers. Taken together, our findings suggest that the presence of a depressive-like state during preconception and pregnancy has sex-dependent consequences on brain and behavioral functions in the offspring. At the same time, our study highlights that FLX treatment in dams with a depression-like state can prevent abnormal behavioral development in the offspring.

Post-stroke depression: Chaos to exposition

Cerebral ischemia contributes to significant disabilities worldwide, impairing cognitive function and motor coordination in affected individuals. Stroke has severe neuropsychological outcomes, the major one being a stroke. Stroke survivors begin to show symptoms of depression within a few months of the incidence that overtime progresses to become a long-term ailment. As the pathophysiology for the progression of the disease is multifactorial and complex, it limits the understanding of the disease mechanism completely. Meta-analyses and randomized clinical trials have shown that intervening early with tricyclic antidepressants and selective serotonin receptor inhibitors can be effective. However, these pharmacotherapies possess several limitations that have given rise to newer approaches such as brain stimulation, psychotherapy and rehabilitation therapy, which in today's time are gaining attention for their beneficial results in post-stroke depression (PSD). The present review highlights numerous factors like lesion location, inflammatory mediators and genetic abnormalities that play a crucial role in the development of depression in stroke patients. Further, we have also discussed various mechanisms involved in post-stroke depression (PSD) and strategies for early detection and diagnosis using biomarkers that may revolutionize treatment for the affected population. Towards the end, along with the preclinical scenario, we have also discussed the various treatment approaches like pharmacotherapy, traditional medicines, psychotherapy, electrical stimulation and microRNAs being utilized for effectively managing PSD.

Post-Stroke Social Isolation Reduces Cell Proliferation in the Dentate Gyrus and Alters miRNA Profiles in the Aged Female Mice Brain

Social isolation and loneliness are risk factors for stroke. Elderly women are more likely to be isolated. Census data shows that in homeowners over the age of 65, women are much more likely to live alone. However, the underlying mechanisms of the detrimental effects of isolation have not been well studied in older females. In this study, we hypothesized that isolation impairs post-stroke recovery in aged female mice, leading to dysregulated microRNAs (miRNAs) in the brain, including those previously shown to be involved in response to social isolation (SI). Aged C57BL/6 female mice were subjected to a 60-min middle cerebral artery occlusion and were randomly assigned to either single housing (SI) or continued pair housing (PH) immediately after stroke for 15 days. SI immediately after stroke led to significantly more brain tissue loss after stroke and higher mortality. Furthermore, SI significantly delayed motor and sensory recovery and worsened cognitive function, compared to PH. A decrease in cell proliferation was seen in the dentate gyrus of SI mice assessed by bromodeoxyuridine (BrdU) labeling. miRNAome data analysis revealed changes in several miRNAs in the brain, such as miR-297a-3p and miR-200c-3p, which are known to regulate pathways involved in cell proliferation. In conclusion, our data suggest that SI can lead to a poor post-stroke recovery in aged females and dysregulation of miRNAs and reduced hippocampal cell proliferation.

Social isolation alters behavior, the gut-immune-brain axis, and neurochemical circuits in male and female prairie voles

The absence of social support, or social isolation, can be stressful, leading to a suite of physical and psychological health issues. Growing evidence suggests that disruption of the gut-immune-brain axis plays a crucial role in the negative outcomes seen from social isolation stress. However, the mechanisms remain largely unknown. The socially monogamous prairie vole (Microtus ochrogaster) has been validated as a useful model for studying negative effects of social isolation on the brain and behaviors, yet how the gut microbiome and central immune system are altered in isolated prairie voles are still unknown. Here, we utilized this social rodent to examine how social isolation stress alters the gut-immune-brain axis and relevant behaviors. Adult male and female prairie voles (n = 48 per sex) experienced social isolation or were cohoused with a same-sex cagemate (control) for six weeks. Thereafter, their social and anxiety-like behaviors, neuronal circuit activation, neurochemical expression, and microgliosis in key brain regions, as well as gut microbiome alterations from the isolation treatment were examined. Social isolation increased anxiety-like behaviors and impaired social affiliation. Isolation also resulted in sex- and brain region-specific alterations in neuronal activation, neurochemical expression, and microgliosis. Further, social isolation resulted in alterations to the gut microbiome that were correlated with key brain and behavioral measures. Our data suggest that social isolation alters the gut-immune-brain axis in a sex-dependent manner and that gut microbes, central glial cells, and neurochemical systems may play a critical, integrative role in mediating negative outcomes from social isolation.

Vitamin D3/vitamin D receptor signaling mitigates symptoms of post-stroke depression in mice by upregulating hippocampal BDNF expression

Elucidation of the pathogenic mechanisms underlying post-stroke depression (PSD) could aid in the development of effective treatments. The present study explored whether Vitamin D3 (VitD3) can function as an antidepressant in PSD model mice and whether the effect is mediated by upregulation of brain-derived neurotrophic factor (BDNF). Mice were subjected to middle cerebral artery occlusion (MCAO) combined with chronic unpredicted mild stress (CUMS) to established the PSD model. For the mice in each group, Longa and Berderson behavioral tests were performed to evaluate motor function, sucrose preference and forced swimming tests were conducted to assess the cardinal depression-like behaviors anhedonia and helplessness, and western blot and immunohistochemistry were conducted to measure the levels of vitamin D receptor (VDR) and BDNF expression levels in mouse hippocampus. Compared to MCAO alone, subsequent CUMS aggravated motor dysfunction and depression-like behaviors, whereas injection of calcitriol (VitD3) enhanced expression levels of VDR and BDNF in the hippocampus as well as ameliorated both motor dysfunction and depression-like behaviors of PSD model mice, with optimal efficacy at 25 μg/kg. Injection of a BDNF-binding protein (TrkB-IgG) almost completely reversed the antidepressant and neuroprotective effects of VitD3, strongly suggesting that VitD3 improved motor dysfunction and depression-like behaviors in PSD model mice by promoting hippocampal BDNF signaling. Modulation of hippocampal BDNF by VitD3 treatment could be an effective strategy for prevention and treatment of PSD.

The effect of voluntary wheel running on the antioxidant status is dependent on sociability conditions

Voluntary wheel running is widely used as a physical activity (PA) model in rodents, but most studies investigate the beneficial effects of this intervention in socially isolated mice. Social isolation stress (SIS) is associated with vulnerability to oxidative stress and reduced mitochondrial activity. Thus, the aim of this study was to investigate the effects of free access to a running wheel for 21 days on the various markers of the cellular redox/antioxidant status as well as mitochondrial function of mice subjected to SIS or maintained in groups of 3 in the homecage. SIS increased thiobarbituric acid reactive substance (TBARS) levels in the cerebral cortex, and PA intervention was not able to reverse such alteration. PA reduced TBARS levels in the liver of grouped mice and gastrocnemius of socially isolated mice. PA increased nonprotein thiol (NPSH) levels in the cerebral cortex of grouped mice. Furthermore, socially isolated mice presented lower glutathione peroxidase (GPx) activity in the cerebellum and gastrocnemius, and glutathione reductase (GR) activity in the cerebral cortex and liver. By contrast, SIS induced higher GPx activity in the cerebral cortex and heart. PA reduced GPx (cerebral cortex) and GR (cerebral cortex and liver) activities of socially isolated mice. SIS caused higher activity of mitochondrial complexes I and II in the cerebral cortex, and the PA paradigm was not able to alter this effect. Interestingly, the PA produced antidepressant-like effect at both SIS and control groups. In conclusion, the results showed the influence of SIS for the effects of PA on the antioxidant status, but not on the mitochondrial function and emotionality.

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PA intervention produces antioxidant responses dependent on sociability conditions.

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SIS induces mitochondria function and antioxidant defense abnormalities.

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Running produces antidepressant-like behavior and does not change the ambulation.

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The distance travelled on the running wheel is correlated with immobility time in the TST.

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The lipoperoxidation index is negatively correlated with time spent on the running wheel.

Differential Association of Serum BDNF With Poststroke Depression and Poststroke Anxiety

OBJECTIVES

To investigate the correlation between brain-derived neurotrophic factor (BDNF) and risk factors, as well as functional outcome in poststroke depression (PSD) or poststroke anxiety (PSA).

DESIGN

Cohort study.

SETTING

Stroke patients admitted to an urban rehabilitation hospital.

PARTICIPANTS

Stroke patients (N=162) without any previous history of depression and anxiety.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Sociodemographic information and comorbidities were recorded during hospital admission. Functional outcomes were assessed using FIM scores at time of admission and discharge. The influence of various factors such as BDNF and patient characteristics on functional outcome was investigated. Single-factor effect was examined using simple logistic regression, as was multi-factor effect using multiple logistic regression. The goodness-of-fit of those regression models was evaluated by the integrated area under ROC curve.

RESULTS

PSD was diagnosed in 61 (37.7%) patients, and PSA was diagnosed in 40 (24.7%). Multiple logistic analysis showed that BDNF, divorce or separation, and history of smoking were significantly associated with the occurrence of PSD but not with the occurrence of PSA. The model combining low BDNF level and divorce or separation improved the prediction for PSD. Among the variables analyzed for prediction of functional outcome, serum BDNF had a minimum correlation with motor FIM scores in PSD but no significant correlation with motor FIM scores in PSA.

CONCLUSIONS

BDNF is a valuable prediction for the occurrence of PSD but not for PSA. More strikingly, ischemic stroke patients who are divorced or separated with low serum BDNF have a much higher risk for PSD. BDNF has a minimum correlation with motor function outcome in PSD but no significant correlation with motor outcome in PSA.

Improving the Social Relevance of Experimental Stroke Models: Social Isolation, Social Defeat Stress and Stroke Outcome in Animals and Humans

The outcome of ischemic stroke varies across socioeconomic strata, even among countries with universal health care. Emerging evidence suggests that psychosocial aspects of low socioeconomic status such as social isolation and social defeat stress interact with, and contribute to, stroke pathophysiology. However, experimental investigations of stroke rarely account for such socioeconomic influences. Social isolation in stroke survivors is associated with increased infarction volume, increased risk of post-stroke depression, and worse long-term functional outcome. Social defeat is thought to contribute significantly to chronic stress in low socioeconomic status groups and is associated with poor health outcomes. Chronic stress is also associated with worse post-stroke functional outcome and greater disability even after accounting for stroke severity, vascular risk factors, and access to acute stroke care. Experimental stroke studies which incorporate social isolation or social defeat stress have shown that both tissue and functional stroke outcome is affected by the increased expression of TNF-α and IL-6, increased glucocorticoid production, and suppression of the protooncogene bcl-2. This review explores the consequences of social isolation and social defeat stress on stroke, preclinical stroke models that have been used to investigate these factors, and possible molecular mechanisms underlying the influence of socioeconomic disparities on stroke outcome.

Gut Microbiota-Derived Short-Chain Fatty Acids Promote Poststroke Recovery in Aged Mice

RATIONALE

The elderly experience profound systemic responses after stroke, which contribute to higher mortality and more severe long-term disability. Recent studies have revealed that stroke outcomes can be influenced by the composition of gut microbiome. However, the potential benefits of manipulating the gut microbiome after injury is unknown.

OBJECTIVE

To determine if restoring youthful gut microbiota after stroke aids in recovery in aged subjects, we altered the gut microbiome through young fecal transplant gavage in aged mice after experimental stroke. Further, the effect of direct enrichment of selective bacteria producing short-chain fatty acids (SCFAs) was tested as a more targeted and refined microbiome therapy.

METHODS AND RESULTS

Aged male mice (18-20 months) were subjected to ischemic stroke by middle cerebral artery occlusion. We performed fecal transplant gavage 3 days after middle cerebral artery occlusion using young donor biome (2-3 months) or aged biome (18-20 months). At day 14 after stroke, aged stroke mice receiving young fecal transplant gavage had less behavioral impairment, and reduced brain and gut inflammation. Based on data from microbial sequencing and metabolomics analysis demonstrating that young fecal transplants contained much higher SCFA levels and related bacterial strains, we selected 4 SCFA-producers (Bifidobacterium longum, Clostridium symbiosum, Faecalibacterium prausnitzii, and Lactobacillus fermentum) for transplantation. These SCFA-producers alleviated poststroke neurological deficits and inflammation, and elevated gut, brain and plasma SCFA concentrations in aged stroke mice.

CONCLUSIONS

This is the first study suggesting that the poor stroke recovery in aged mice can be reversed via poststroke bacteriotherapy following the replenishment of youthful gut microbiome via modulation of immunologic, microbial, and metabolomic profiles in the host.

EMMPRIN/CD147 plays a detrimental role in clinical and experimental ischemic stroke

Background: Ischemic stroke is a devastating disease, often resulting in death or permanent neurological deficits. EMMPRIN/CD147 is a plasma membrane protein that induces the production of matrix metalloproteinases (MMPs), which contribute to secondary damage after stroke by disrupting the blood brain barrier (BBB) and facilitating peripheral leukocyte infiltration into the brain.

Results: CD147 surface expression increased significantly after stroke on infiltrating leukocytes, astrocytes and endothelial cells, but not on resident microglia. Inhibition of CD147 reduced MMP levels, decreased ischemic damage, and improved functional, cognitive and histological outcomes after experimental ischemic stroke in both young and aged mice. In stroke patients, high levels of serum CD147 24 hours after stroke predicted poor functional outcome at 12 months. Brain CD147 levels were correlated with MMP-9 and secondary hemorrhage in post-mortem samples from stroke patients.

Conclusions: Acute inhibition of CD147 decreases levels of MMP-9, limits tissue loss, and improves long-term cognitive outcomes following experimental stroke in aged mice. High serum CD147 correlates with poor outcomes in stroke patients. This study identifies CD147 as a novel, clinically relevant target in ischemic stroke.

Micro RNA 181c-5p: A promising target for post-stroke recovery in socially isolated mice

Dysregulation of microRNAs (miRNAs) has been tied to several neurological disorders, including ischemic stroke. It has also been established that social environments can modulate miRNA profiles. We have previously shown that post-stroke social isolation (SI) is linked to poor stroke outcomes and that miR-181c-5p emerged as one of few lead miRNAs that was downregulated in both stroke and SI. Therefore, in this study we examined the potential role of miR-181c-5p mimic in reversing the detrimental effects of post-stroke SI. Two to three-month-old C57BL/6 male mice were pair-housed (PH) for at least two weeks. After two weeks, mice underwent stroke survival surgery using middle cerebral artery occlusion (MCAO) and were randomly assigned to one of two housing conditions: stroke isolation (ST-ISO) or stroke pair-housing with a healthy partner (ST-PH). ST-ISO mice were randomized to receive either miR-181c-5p mimic or a scrambled RNA (7 mg/kg i.v./day×drug) control at 24 h and 48 h after stroke. The effects of miR-181c-5p mimic treatment were evaluated at 1, 3, and 7 days after stroke at histological, behavioral, and biochemical levels. Target genes of miR-181c-5p were then analyzed by qPCR using an RT2 Profiler qPCR Array of pre-coated miR-181c gene targets. Temporal profile expression data suggested that miR-181c-5p was significantly downregulated (p < 0.05 vs ST-PH) up to 7 days after post-stroke SI. MiR-181c-5p mimic treatment significantly increased miR-181c-5p expression in brain tissue and showed partial swift recovery in sensorimotor deficit. Target gene analysis identified downregulation of several calcium signaling-related genes, e.g., Cpne2 and Gria 1 & 2 after miR-181c-5p mimic treatment. In summary, present data suggests that miR-181c-5p is a potential target for post-stroke SI. Data also suggests that genes related to calcium and glutamate signaling might be involved in the beneficial effect of the miR-181c-5p mimic.

A Retrospective Study to Identify Novel Factors Associated with Post-stroke Anxiety

BACKGROUND AND PURPOSE

Post-stroke anxiety (PSA) is common and disabling. PSA should be considered as an important outcome in stroke. However, there is a lack of understanding of factors that may be linked to PSA. The purpose of this study was to determine the frequency of PSA and sociodemographic and clinical factors associated with PSA in a cohort of racially and ethnically diverse stroke patients.

METHODS

We conducted a retrospective study of ischemic and hemorrhagic stroke patients seen in a stroke outpatient clinic from August 1, 2017 to June 30, 2018. Patients were eligible if a Generalized Anxiety Disorder 7-Item (GAD-7) instrument was available. GAD-7 scores greater than or equal to 10 indicated the presence of moderate to severe PSA. Multivariable logistic regression was used to identify independent sociodemographic and clinical factors associated with PSA.

RESULTS

Records from 289 stroke patients with a GAD-7 instrument were analyzed. PSA was common (21%; GAD-7 ≥ 10). Fifty-seven percent of females had a GAD-7 greater than or equal to 10 compared to 41% of females who had a GAD-7 less than 10 (P = .03). Multivariable analysis found that self-reported nonmarried status (odds ratio, 3.27; 95% confidence interval, 1.44-7.44), excessive fatigue (odds ratio, 4.46; 95% confidence interval, 1.87-10.63), and depression (odds ratio, 1.24; 95% confidence interval, 1.16-1.33) were independently associated with PSA.

CONCLUSIONS

PSA may occur more frequently in those who report non-married, excessive fatigue, or depression. Trials of PSA interventions should consider the potential impact of social support, depression, and comorbid conditions contributing to post-stroke fatigue, including sleep apnea.

Optimizing functional outcome endpoints for stroke recovery studies

Novel therapeutic intervention that aims to enhance the endogenous recovery potential of the brain during the subacute phase of stroke has produced promising results. The paradigm shift in treatment approaches presents new challenges to preclinical and clinical researchers alike, especially in the functional endpoints domain. Shortcomings of the "neuroprotection" era of stroke research are yet to be fully addressed. Proportional recovery observed in clinics, and potentially in animal models, requires a thorough reevaluation of the methods used to assess recovery. To this end, this review aims to give a detailed evaluation of functional outcome measures used in clinics and preclinical studies. Impairments observed in clinics and animal models will be discussed from a functional testing perspective. Approaches needed to bridge the gap between clinical and preclinical research, along with potential means to measure the moving target recovery, will be discussed. Concepts such as true recovery of function and compensation and methods that are suitable for distinguishing the two are examined. Often-neglected outcomes of stroke, such as emotional disturbances, are discussed to draw attention to the need for further research in this area.

Sex as a biological variable in the pathology and pharmacology of neurodegenerative and neurovascular diseases

The incidence of dementia, most commonly caused by cerebrovascular and neurodegenerative diseases, continues to grow as our population ages. Alzheimer disease (AD) and vascular cognitive impairment (VCI) are responsible for more than 80% of all cases of dementia. There are few effective, long-term treatments for AD and VCI-related conditions (e.g., stroke and cerebral amyloid angiopathy (CAA)). This review focuses on AD (as the most common "neurodegenerative" cause of dementia), CAA (as an "emerging" cause of dementia), and stroke (as the most common cause of "vascular" dementia). We will discuss the available literature on the pharmacological therapies that demonstrate sex differences, which refer to any combination of structural, chromosomal, gonadal, or hormonal differences between males and females. We will emphasize the importance of considering sex as a biological variable in the design of preclinical and clinical studies that investigate underlying pathologies or response to pharmacological interventions in dementia. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Mir363-3p attenuates post-stroke depressive-like behaviors in middle-aged female rats

Women are more likely to develop Post Stroke Depression (PSD) than men and generally do not respond well to anti-depressants with age. This study investigated the effect of microRNA mir363-3p treatment on PSD using a physiologically-relevant animal model. Our previous work showed that mir363-3p treatment, delivered post-stroke, effectively reduces infarct volume in the acute phase of stroke in middle-aged females but not males. Middle-aged female Sprague Dawley rats were tested for baseline sensory motor function and depressive-like behaviors, and then subjected to ischemic stroke via middle cerebral artery occlusion (MCAo) or sham surgery. Animals received either control oligos (MCAo+scrambled, Sham+scrambled) or mir363-3p (MCAo+mir363-3p, Sham+mir363-3p) treatment 4 h later. Sensory motor function and depressive-like behaviors were reassessed up to 100 d after stroke, and circulating levels of IL-6, TNF-alpha and Brain-Derived Neurotrophic Factor (BDNF) were quantified at regular intervals. Prior to termination, Fluorogold was injected into the striatum to assess meso-striatal projections. MCAo+scrambled animals had impaired sensorimotor performance in the acute phase (5 days) of stroke and developed anhedonia, decreased sociability and increased helplessness in the chronic phase. MCAo+mir363-3p animals showed significantly less sensory motor impairment and fewer depressive-like behaviors. IL-6 and TNF-alpha were elevated transiently at 4 weeks after MCAo in both groups. BDNF levels decreased progressively after stroke in the MCAo+scrambled group, and this was attenuated in the mir363-3p group. The number of retrogradely-labeled SNc and VTA cells was reduced in the ischemic hemisphere of the MCAo+scrambled group. In contrast, there was no interhemispheric difference in the number of retrogradely-labeled SNc and VTA cells of MCAo+mir363-3p treated animals. Our results support a therapeutic role for mir363-3p for long-term stroke disability.

Indoleamine 2,3-Dioxygenase-Dependent Neurotoxic Kynurenine Metabolism Contributes to Poststroke Depression Induced in Mice by Ischemic Stroke along with Spatial Restraint Stress

Aim

Poststroke depression (PSD), which occurs in approximately one-third of stroke survivors, is clinically important because of its association with slow functional recovery and increased mortality. In addition, the underlying pathophysiological mechanisms are still poorly understood.

Methods

We used a mouse model of PSD to examine the neurobiological mechanisms of PSD and the beneficial effects of aripiprazole, an atypical antipsychotic drug. PSD was induced in mice by combining middle cerebral artery occlusion (MCAO) with spatial restraint stress. The body weight, sucrose preference, and forced swim tests were performed at 5, 7, and 9 weeks and the Morris water maze test at 10 weeks after completing MCAO and spatial restraint stress.

Results

Mice subjected to MCAO and spatial restraint stress showed significant depressive-like behavior in the sucrose preference test and forced swim test as well as cognitive impairment in the Morris water maze test. The PSD-like phenotype was accompanied by an indoleamine 2,3-dioxygenase 1 (IDO1) expression increase in the nucleus accumbens, hippocampus, and hypothalamus, but not in the striatum. Furthermore, the increased IDO1 levels were localized in Iba-1(+) cells but not in NeuN(+) or GFAP(+) cells, indicating that microglia-induced IDO1 expression was prominent in the PSD mouse brain. Moreover, 3-hydroxyanthranilate 3,4-dioxygenase (HAAO), quinolinic acid (QUIN), and reactive oxygen species (ROS) were significantly increased in the nucleus accumbens, hippocampus, and hypothalamus of PSD mice. Importantly, a 2-week aripiprazole (1 mg/kg, per os) regimen, which was initiated 1 day after MCAO, ameliorated depressive-like behavior and impairment of cognitive functions in PSD mice that was accompanied by downregulation of IDO1, HAAO, QUIN, and ROS.

Conclusions

Our results suggest that the IDO1-dependent neurotoxic kynurenine metabolism induced by microglia functions in PSD pathogenesis. The beneficial effect of aripiprazole on depressive-like behavior and cognitive impairment may be mediated by inhibition of IDO1, HAAO, QUIN, and ROS.

Central Nervous System Responses to Simulated Galactic Cosmic Rays

In preparation for lunar and Mars missions it is essential to consider the challenges to human health that are posed by long-duration deep space habitation via multiple stressors, including ionizing radiation, gravitational changes during flight and in orbit, other aspects of the space environment such as high level of carbon dioxide, and psychological stress from confined environment and social isolation. It remains unclear how these stressors individually or in combination impact the central nervous system (CNS), presenting potential obstacles for astronauts engaged in deep space travel. Although human spaceflight research only within the last decade has started to include the effects of radiation transmitted by galactic cosmic rays to the CNS, radiation is currently considered to be one of the main stressors for prolonged spaceflight and deep space exploration. Here we will review the current knowledge of CNS damage caused by simulated space radiation with an emphasis on neuronal and glial responses along with cognitive functions. Furthermore, we will present novel experimental approaches to integrate the knowledge into more comprehensive studies, including multiple stressors at once and potential translation to human functions. Finally, we will discuss the need for developing biomarkers as predictors for cognitive decline and therapeutic countermeasures to prevent CNS damage and the loss of cognitive abilities.