Reversal of the Detrimental Effects of Post-Stroke Social Isolation by Pair-Housing is Mediated by Activation of BDNF-MAPK/ERK in Aged Mice

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.

Reversal of the detrimental effects of social isolation on ischemic cerebral injury and stroke-associated pneumonia by inhibiting small intestinal T-cell migration into the brain and lung

Social isolation (ISO) is associated with an increased risk and poor outcomes of ischemic stroke. However, the roles and mechanisms of ISO in stroke-associated pneumonia (SAP) remain unclear. Adult male mice were single- or pair-housed with an ovariectomized female mouse and then subjected to transient middle cerebral artery occlusion. Isolated mice were treated with the natriuretic peptide receptor A antagonist A71915 or anti-gamma-delta (γδ) TCR monoclonal antibody, whereas pair-housed mice were treated with recombinant human atrial natriuretic peptide (rhANP). Subdiaphragmatic vagotomy (SDV) was performed 14 days before single- or pair-housed conditions. We found that ISO significantly worsened brain and lung injuries relative to pair housing, which was partially mediated by elevated interleukin (IL)-17A levels and the migration of small intestine-derived inflammatory γδ T-cells into the brain and lung. However, rhANP treatment or SDV could ameliorate ISO-exacerbated post-stroke brain and lung damage by reducing IL-17A levels and inhibiting the migration of inflammatory γδ T-cells into the brain and lung. Our results suggest that rhANP mitigated ISO-induced exacerbation of SAP and ischemic cerebral injury by inhibiting small intestine-derived γδ T-cell migration into the lung and brain, which could be mediated by the subdiaphragmatic vagus nerve.

Identification of a miRNA-mRNA regulatory network for post-stroke depression: a machine-learning approach

Objective

The study aimed to explore the miRNA and mRNA biomarkers in post-stroke depression (PSD) and to develop a miRNA-mRNA regulatory network to reveal its potential pathogenesis.

Methods

The transcriptomic expression profile was obtained from the GEO database using the accession numbers GSE117064 (miRNAs, stroke vs. control) and GSE76826 [mRNAs, late-onset major depressive disorder (MDD) vs. control]. Differentially expressed miRNAs (DE-miRNAs) were identified in blood samples collected from stroke patients vs. control using the Linear Models for Microarray Data (LIMMA) package, while the weighted correlation network analysis (WGCNA) revealed co-expressed gene modules correlated with the subject group. The intersection between DE-miRNAs and miRNAs identified by WGCNA was defined as stroke-related miRNAs, whose target mRNAs were stroke-related genes with the prediction based on three databases (miRDB, miRTarBase, and TargetScan). Using the GSE76826 dataset, the differentially expressed genes (DEGs) were identified. Overlapped DEGs between stroke-related genes and DEGs in late-onset MDD were retrieved, and these were potential mRNA biomarkers in PSD. With the overlapped DEGs, three machine-learning methods were employed to identify gene signatures for PSD, which were established with the intersection of gene sets identified by each algorithm. Based on the gene signatures, the upstream miRNAs were predicted, and a miRNA-mRNA network was constructed.

Results

Using the GSE117064 dataset, we retrieved a total of 667 DE-miRNAs, which included 420 upregulated and 247 downregulated ones. Meanwhile, WGCNA identified two modules (blue and brown) that were significantly correlated with the subject group. A total of 117 stroke-related miRNAs were identified with the intersection of DE-miRNAs and WGCNA-related ones. Based on the miRNA-mRNA databases, we identified a list of 2,387 stroke-related genes, among which 99 DEGs in MDD were also embedded. Based on the 99 overlapped DEGs, we identified three gene signatures (SPATA2, ZNF208, and YTHDC1) using three machine-learning classifiers. Predictions of the three mRNAs highlight four miRNAs as follows: miR-6883-5p, miR-6873-3p, miR-4776-3p, and miR-6738-3p. Subsequently, a miRNA-mRNA network was developed.

Conclusion

The study highlighted gene signatures for PSD with three genes (SPATA2, ZNF208, and YTHDC1) and four upstream miRNAs (miR-6883-5p, miR-6873-3p, miR-4776-3p, and miR-6738-3p). These biomarkers could further our understanding of the pathogenesis of PSD.

Structure-Activity Relationship and Neuroprotective Activity of 1,5-Dihydro-2H-naphtho[1,2-b][1,4]diazepine-2,4(3H)-diones as P2X4 Receptor Antagonists

We analyzed the P2X4 receptor structure-activity relationship of a known antagonist 5, a 1,5-dihydro-2H-naphtho[1,2-b][1,4]diazepine-2,4(3H)-dione. Following extensive modification of the reported synthetic route, 4-pyridyl 21u (MRS4719) and 6-methyl 22c (MRS4596) analogues were most potent at human (h) P2X4R (IC50 0.503 and 1.38 μM, respectively, and selective versus hP2X1R, hP2X2/3R, hP2X3R). Thus, the naphthalene 6-, but not 7-position was amenable to substitution, and an N-phenyl ring aza-scan identified 21u with 3-fold higher activity than 5. Compounds 21u and 22c showed neuroprotective and learning- and memory-enhancing activities in a mouse middle cerebral artery occlusion (MCAO) model of ischemic stroke, with potency of 21u > 22c. 21u dose-dependently reduced infarct volume and reduced brain atrophy at 3 and 35 days post-stroke, respectively. Relevant to clinical implication, 21u also reduced ATP-induced [Ca2+]i influx in primary human monocyte-derived macrophages. This study indicates the translational potential of P2X4R antagonists for treating ischemic stroke, including in aging populations.

p-hydroxy benzaldehyde revitalizes the microenvironment of peri-infarct cortex in rats after cerebral ischemia-reperfusion

BACKGROUND

The formation of glial scar around the ischemic core following cerebral blood interruption exerts a protective effect in the subacute phase but impedes neurorepair in the chronic phase. Therefore, the present study aimed to explore whether p-hydroxy benzaldehyde (p-HBA), a phenolic compound isolated from Gastrodia elata Blume, can cut the Gordian knot of glial scar and promote brain repair after cerebral ischemia.

METHODS

The effects of p-HBA on neurorepair were evaluated using a rat model of transient middle cerebral artery occlusion (tMCAO). The motor functions were evaluated by neurobehavioral tests, the pathophysiological processes in the peri-infarct cortex (PIC) were detected by viral-based lineage tracking or immunofluorescence staining, and the putative signaling pathway was analyzed by western blot.

RESULTS

Administration of p-HBA in the acute stage after stroke onset alleviated the motor impairment in tMCAO rats in a time-dependent manner. The corresponding cellular events were inhibition of astrogliosis, facilitating the conversion of reactive astrocytes (RAs) into neurons, and prompting angiogenesis in PIC, thereby protecting the structure of the neurovascular unit (NVU). One of the underlying molecular mechanisms is the activation of the neurogenic switch of the Wnt/β-catenin signaling pathway. Notably, p-HBA only promotes astrocyte-to-neuron conversion in the PIC, and only partial RAs were converted to neurons. This pattern of conversion ensures that the brain structure remains unaltered, and the beneficial role of glial scarring is preserved during the subacute phase after ischemia.

CONCLUSIONS

These results provided a potential approach to address the dilemma of glial scarring after brain injury, i.e., the pharmacological promotion of astrocyte-to-neuron conversion in the PIC without interfering with normal brain tissue, which mitigates but does not eliminate the glial scar. Subsequently, the neuron rescue-unfriendly environment is switched to a beneficial reconstruction milieu in PIC, which is conducive to neurorepair. Moreover, p-HBA could be a candidate for pharmacological intervention.

Microbes, metabolites and (synaptic) malleability, oh my! The effect of the microbiome on synaptic plasticity

The microbiome influences the emotional and cognitive phenotype of its host, as well as the neurodevelopment and pathophysiology of various brain processes and disorders, via the well‐established microbiome–gut–brain axis. Rapidly accumulating data link the microbiome to severe neuropsychiatric disorders in humans, including schizophrenia, Alzheimer's and Parkinson's. Moreover, preclinical work has shown that perturbation of the microbiome is closely associated with social, cognitive and behavioural deficits. The potential of the microbiome as a diagnostic and therapeutic tool is currently undercut by a lack of clear mechanistic understanding of the microbiome–gut–brain axis. This review establishes the hypothesis that the mechanism by which this influence is carried out is synaptic plasticity – long‐term changes to the physical and functional neuronal structures that enable the brain to undertake learning, memory formation, emotional regulation and more. By examining the different constituents of the microbiome–gut–brain axis through the lens of synaptic plasticity, this review explores the diverse aspects by which the microbiome shapes the behaviour and mental wellbeing of the host. Key elements of this complex bi‐directional relationship include neurotransmitters, neuronal electrophysiology, immune mediators that engage with both the central and enteric nervous systems and signalling cascades that trigger long‐term potentiation of synapses. The importance of establishing mechanistic correlations along the microbiome–gut–brain axis cannot be overstated as they hold the potential for furthering current understanding regarding the vast fields of neuroscience and neuropsychiatry. This review strives to elucidate the promising theory of microbiome‐driven synaptic plasticity in the hope of enlightening current researchers and inspiring future ones.

Social isolation: An underappreciated determinant of physical health

While a sizable body of research demonstrates the associations between social connection and health, much of the recent focus in the broader public and to some extent among academics has been on loneliness, with more objective/structural aspects often assumed to be proxies for more influential relationship factors such as relationship functions and quality. However, evidence suggests the actual presence of others (proximity and regular contact) is essential, and many studies document these structural indicators have just as powerful and, in some cases, more potent effects on indicators of health and well-being. This paper summarizes the evidence on social isolation and health and provides a framework for why social isolation may be a powerful predictor of health and mortality.

Functional analysis of brain derived neurotrophic factor (BDNF) in Huntington's disease

The aim of this study is to determine the molecular functions of brain derived neurotrophic factor (BDNF) in Huntington's disease (HD). A total of 1,675 differentially expressed genes (DEGs) were overlapped from HD versus control and BDNF-low versus high groups. Five co-expression modules were constructed using weight gene correlation network analysis, among which the blue and turquoise modules were most strongly correlated with HD and low BDNF. Functional enrichment analyses revealed DEGs in these modules significantly enriched in GABAergic synapse, phagosome, cyclic adenosine monophosphate (cAMP), mitogen-activated protein kinase (MAPK), renin-angiotensin system (Ras), Ras-associated protein-1 and retrograde endocannabinoid signaling pathways. The intersection pathways of BDNF, such as cAMP, MAPK and Ras signaling pathways, were identified in global regulatory network. Further performance evaluation of low BDNF accurately predicted HD occurrence according to the area under the curve of 82.4%. In aggregate, our findings highlighted the involvement of low BDNF expression in HD pathogenesis, potentially mediated by cAMP, MAPK and Ras signaling pathways.

Crosstalk between gut microbiome and immunology in the management of ischemic brain injury

Ischemic brain injury is a serious neurological complication, which accrues an immense activation of neuroinflammatory responses. Several lines of research suggested the interconnection of gut microbiota perturbation with the activation of proinflammatory mediators. Intestinal microbial communities also interchange information with the brain through various afferent and efferent channels and microbial by-products. Herein, we discuss the different microelements of gut microbiota and its connection with the host immune system and how change in immune-microbial signatures correlates with the stroke incidence and post-injury neurological sequelae. The activated inflammatory cells increase the production of proinflammatory cytokines, chemokines, proteases and adhesive proteins that are involved in the systemic inflammation, blood brain barrier disruption, gut dysbiosis and aggravation of ischemic brain injury. We suggest that fine-tuning of commensal gut microbiota (eubiosis) may regulate the activation of CNS resident cells like microglial, astrocytes, mast cells and natural killer cells.

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.

Long-Term Impact of Social Isolation and Molecular Underpinnings

Prolonged periods of social isolation can have detrimental effects on the physiology and behavior of exposed individuals in humans and animal models. This involves complex molecular mechanisms across tissues in the body which remain partly identified. This review discusses the biology of social isolation and describes the acute and lasting effects of prolonged periods of social isolation with a focus on the molecular events leading to behavioral alterations. We highlight the role of epigenetic mechanisms and non-coding RNA in the control of gene expression as a response to social isolation, and the consequences for behavior. Considering the use of strict quarantine during epidemics, like currently with COVID-19, we provide a cautionary tale on the indiscriminate implementation of such form of social isolation and its potential damaging and lasting effects in mental health.

Phosphodiesterase 10A Inhibition Leads to Brain Region-Specific Recovery Based on Stroke Type

Stroke is the leading cause of adult disability. Recovery of function after stroke involves signaling events that are mediated by cAMP and cGMP pathways, such as axonal sprouting, neurogenesis, and synaptic plasticity. cAMP and cGMP are degraded by phosphodiesterases (PDEs), which are differentially expressed in brain regions. PDE10A is highly expressed in the basal ganglia/striatum. We tested a novel PDE10A inhibitor (TAK-063) for its effects on functional recovery. Stroke was produced in mice in the cortex or the striatum. Behavioral recovery was measured to 9 weeks. Tissue outcome measures included analysis of growth factor levels, angiogenesis, neurogenesis, gliogenesis, and inflammation. TAK-063 improved motor recovery after striatal stroke in a dose-related manner, but not in cortical stroke. Recovery of motor function correlated with increases in striatal brain-derived neurotrophic factor. TAK-063 treatment also increased motor system axonal connections. Stroke affects distinct brain regions, with each comprising different cellular and molecular elements. Inhibition of PDE10A improved recovery of function after striatal but not cortical stroke, consistent with its brain localization. This experiment is the first demonstration of brain region-specific enhanced functional recovery after stroke, and indicates that differential molecular signaling between brain regions can be exploited to improve recovery based on stroke subtype.

Neuroprotective and neuro-rehabilitative effects of acute purinergic receptor P2X4 (P2X4R) blockade after ischemic stroke

Stroke remains a leading cause of disability in the United States. Despite recent advances, interventions to reduce damage and enhance recovery after stroke are lacking. P2X4R, a receptor for adenosine triphosphate (ATP), regulates activation of myeloid immune cells (infiltrating monocytes/macrophages and brain-resident microglia) after stroke injury. However, over-stimulation of P2X4Rs due to excessive ATP release from dying or damaged neuronal cells can contribute to ischemic injury. Therefore, we pharmacologically inhibited P2X4R to limit the over-stimulated myeloid cell immune response and improve both acute and chronic stroke recovery. We subjected 8-12-week-old male and female wild type mice to a 60 min right middle cerebral artery occlusion (MCAo) followed by 3 or 30 days of reperfusion. We performed histological, RNA sequencing, behavioral (sensorimotor, anxiety, and depressive), and biochemical (Evans blue dye extravasation, western blot, quantitative PCR, and flow cytometry) analyses to determine the acute (3 days after MCAo) and chronic (30 days after MCAo) effects of P2X4R antagonist 5-BDBD (1 mg/kg P.O. daily x 3 days post 4 h of MCAo) treatment. 5-BDBD treatment significantly (p < .05) reduced infarct volume, neurological deficit (ND) score, levels of cytokine interleukin-1 beta (IL-1β) and blood brain barrier (BBB) permeability in the 3-day group. Chronically, 5-BDBD treatment also conferred progressive recovery (p < .05) of motor balance and coordination using a rotarod test, as well as reduced anxiety-like behavior over 30 days. Interestingly, depressive-type behavior was not observed in mice treated with 5-BDBD for 3 days. In addition, flow cytometric analysis revealed that 5-BDBD treatment decreased the total number of infiltrated leukocytes, and among those infiltrated leukocytes, pro-inflammatory cells of myeloid origin were specifically reduced. 5-BDBD treatment reduced the cell surface expression of P2X4R in flow cytometry-sorted monocytes and microglia without reducing the total P2X4R level in brain tissue. In summary, acute P2X4R inhibition protects against ischemic injury at both acute and chronic time-points after stroke. Reduced numbers of infiltrating pro-inflammatory myeloid cells, decreased surface P2X4R expression, and reduced BBB disruption are likely its mechanism of neuroprotection and neuro-rehabilitation.

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.

Mood and behavioral problems are important predictors of quality of life of nursing home residents with moderate to severe dementia: A cross-sectional study

Objectives

To examine the predictors associated with quality of life of nursing home residents with dementia, in order to identify which predictors are most important and hold most promise for future intervention studies.

Methods/Design

This cross-sectional analysis of data collected in two intervention trials included 143 participants with moderate to severe dementia who resided in 40 psychogeriatric wards in 13 nursing homes. The outcome measure quality of life was assessed with the Qualidem. Predictors examined were demographic factors, cognition, mood, behavioral problems, and comorbid conditions.

Results

Linear mixed regression analyses showed that all nine domains of quality of life showed independent (negative) associations with either depression, agitation, apathy, or a combination of these predictors. Agitation, apathy, depression, and the presence of neurological disease explained 50% of the variance in total quality of life. Male gender, psychiatric/mood disorders, and having one or more comorbid conditions was associated with worse social relations, while the presence of comorbid neurological diseases was associated with more social isolation and a worse care relationship. The presence of endocrine/metabolic disorders and pulmonary disorders was associated with less restless tense behavior.

Conclusions

Different domains of quality of life showed different associations, confirming the multidimensionality of quality of life in nursing home residents with dementia. Quality of life is independently associated with mood and behavioral problems, comorbid conditions, and gender. This knowledge may help to identify older persons at risk of a lower quality of life, and to offer targeted interventions to improve quality of life.

Trial registration

Dutch Trial registration NTR5641

High Frequency Repetitive Transcranial Magnetic Stimulation Alleviates Cognitive Impairment and Modulates Hippocampal Synaptic Structural Plasticity in Aged Mice

Normal aging is accompanied by hippocampus-dependent cognitive impairment, which is a risk factor of Alzheimer’s disease. This study aims to investigate the effect of high frequency-repetitive transcranial magnetic stimulation (HF-rTMS) on hippocampus-dependent learning and memory in aged mice and explore its underlying mechanisms. Forty-five male Kunming mice (15 months old) were randomly divided into three groups: aged sham, 5 Hz rTMS, and 25 Hz rTMS. Two sessions of 5 Hz or 25 Hz rTMS comprising 1,000 pulses in 10 trains were delivered once a day for 14 consecutive days. The aged sham group was treated by the reverse side of the coil. In the adult sham group, 15 male Kunming mice (3 months old) were treated the same way as the aged sham group. A Morris water maze (MWM) was conducted following the stimulation, and synaptic ultrastructure was observed through a transmission electron microscope. HF-rTMS improved spatial learning and memory impairment in the aged mice, and 5 Hz was more significant than 25 Hz. Synaptic plasticity-associated gene profiles were modified by HF-rTMS, especially neurotrophin signaling pathways and cyclic adenosine monophosphate response element binding protein (CREB) cofactors. Compared to the aged sham group, synaptic plasticity-associated proteins, i.e., synaptophysin (SYN) and postsynaptic density (PSD)-95 were increased; brain-derived neurotrophic factor (BDNF) and phosphorylated CREB (pCREB) significantly increased after the 5 Hz HF-rTMS treatment. Collectively, our results suggest that HF-rTMS ameliorated cognitive deficits in naturally aged mice. The 5 Hz rTMS treatment significantly enhanced synaptic structural plasticity and activated the BDNF/CREB pathway in the hippocampus.

Corticosterone-Mediated Body Weight Loss Is an Important Catabolic Process for Poststroke Immunity and Survival

Background and Purpose- Stroke-induced acute severe body weight (BW) loss is associated with a high rate of mortality during a critical poststroke period. Several interventions to reduce weight loss, however, have not been successful. Currently, the biological significance of this extraordinary catabolic process is not well understood. Spleen-derived monocytes/macrophages (MMs) are the major immune cells recruited to the injured brain. The trafficking of MMs has been shown to be important for tissue repair and recovery. The purpose of the study is to investigate whether the BW reduction is essential for MM-mediated immune response for mice to survive and whether a corticosterone-mediated catabolic event underlies the processes. Methods- C57BL/6 male mice (12-week-old) were subjected to transient middle cerebral artery occlusion. BW, total MMs, and their Ly-6Chigh and Ly-6Clow subsets were determined in the spleen, blood, and the brain in poststroke mice. Poststroke survival rate and MM subsets were determined in mice with adrenalectomy, sham-adrenalectomy, and adrenalectomy mice supplemented with corticosterone. Results- Stroke reduced BW with a maximum reduction at day 3 poststroke (17.2±5.2%). The reduction at day 3 was positively linked to injury severity and selective depletion of MMs, but no other types of immune cells, in the spleen. Notably, the splenic MM depletion was significantly greater in mice with severe BW reduction (≥18% at day 3). In the blood, stroke depleted circulating MMs to a similar degree in animals with moderate and severe BW loss. Ly-6C+ monocyte infiltration in the poststroke brain was greater in mice with severe BW loss. Blocking the catabolic process by adrenalectomy significantly increased poststroke mortality, but the mortality was partially rescued by corticosterone supplement in adrenalectomy mice. Conclusions- Stroke-induced BW loss facilitates MM-mediated immune response, and the adrenal corticosterone-mediated catabolic process is necessary for poststroke survival. Visual Overview- An online visual overview is available for this article.

Activation of c-Jun N-terminal kinase and p38 after cerebral ischemia upregulates cerebral sodium-glucose transporter type 1

Cerebral ischemic stress increases cerebral sodium-glucose transporter type 1 (SGLT-1). However, the mechanism by which cerebral ischemia leads to the up-regulation of SGLT-1 remains unclear. In peripheral tissue, the activation of mitogen-activated protein kinases (MAPKs) increases SGLT-1. MAPK pathways [c-Jun N-terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated protein kinase (ERK)] are activated by cerebral ischemic stress. Therefore, we confirmed the involvement of MAPKs in the up-regulation of cerebral SGLT-1 after cerebral ischemia. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO). Protein expression was assessed by western blotting. Mice received an intracerebroventricular (i.c.v.) injection of SP600125 (JNK inhibitor), SB203580 (p38 inhibitor), and PD98059 (MEK inhibitor) immediately after reperfusion. The infarction and behavioral abnormalities were assessed on days 1 and 3 after MCAO. The MAPK inhibitors suppressed the activation of JNK, p38, and ERK 3 h after MCAO. SP600125 and SB203580 administration ameliorated cerebral ischemic neuronal damage, whereas PD98059 administration exacerbated cerebral ischemic neuronal damage. SP600125 and SB203580 significantly suppressed the increase in SGLT-1 12 h after MCAO. PD98059 had no effect on SGLT-1 expression after MCAO. Our results indicate that the activation of JNK and p38 participate in the up-regulation of cerebral SGLT-1 after MCAO.

Inhibition of miR-141-3p Ameliorates the Negative Effects of Poststroke Social Isolation in Aged Mice

BACKGROUND AND PURPOSE

Social isolation increases mortality and impairs recovery after stroke in clinical populations. These detrimental effects have been recapitulated in animal models, although the exact mechanism mediating these effects remains unclear. Dysregulation of microRNAs (miRNAs) occurs in both strokes as well as after social isolation, which trigger changes in many downstream genes. We hypothesized that miRNA regulation is involved in the detrimental effects of poststroke social isolation in aged animals.

METHODS

We pair-housed 18-month-old C57BL/6 male mice for 2 weeks before a 60-minute right middle cerebral artery occlusion or sham surgery and then randomly assigned mice to isolation or continued pair housing immediately after surgery. We euthanized mice either at 3, 7, or 15 days after surgery and isolated the perilesional frontal cortex for whole microRNAome analysis. In an additional cohort, we treated mice 1 day after stroke onset with an in vivo-ready antagomiR-141 for 3 days.

RESULTS

Using whole microRNAome analysis of 752 miRNAs, we identified miR-141-3p as a unique miRNA that was significantly upregulated in isolated mice in a time-dependent manner up to 2 weeks after stroke. Posttreatment with an antagomiR-141-3p reduced the postisolation-induced increase in miR-141-3p to levels almost equal to those of pair-housed stroke controls. This treatment significantly reduced mortality (by 21%) and normalized infarct volume and neurological scores in poststroke-isolated mice. Quantitative PCR analysis revealed a significant upregulation of Tgfβr1 (transforming growth factor beta receptor 1, a direct target of miR-141-3p) and Igf-1 (insulin-like growth factor 1) mRNA after treatment with antagomiR. Treatment also increased the expression of other pleiotropic cytokines such as Il-6 (interleukin 6) and Tnf-α (tumor necrosis factor-α), an indirect or secondary target) in brain tissue.

CONCLUSIONS

miR-141-3p is increased with poststroke isolation. Inhibition of miR-141-3p improved mortality, neurological deficits, and decreased infarct volumes. Importantly, these therapeutic effects occurred in aged animals, the population most at risk for stroke and poststroke isolation.

Diazoxide inhibits of ER stress‑mediated apoptosis during oxygen‑glucose deprivation in vitro and cerebral ischemia‑reperfusion in vivo

Neuroprotective strategies using diazoxide (DZX) have been demonstrated to limit ischemia/reperfusion (I/R)-induced injury and cell apoptosis. In type 2 diabetes mellitus, DZX has been reported to improve β-cell function and reduce their apoptosis, through suppressing endoplasmic reticulum (ER) stress. However, the effects of DZX on ER stress during I/R-induced neuronal apoptosis in the hippocampus remains to be elucidated. In the present study, pretreatment of hippocampal neurons with DZX was revealed to inhibit oxygen-glucose deprivation (OGD)-stimulated apoptosis in vitro and to alleviate I/R-induced hippocampal injury and behavioral deficits in rats in vivo. Furthermore, OGD and I/R were demonstrated to induce ER stress via upregulating the expression of ER stress-associated proteins, including C/EBP homologous protein, 78 kDa glucose-regulated protein and caspase-12, whereas the exogenous administration of DZX effectively downregulated ER stress-associated protein expression following OGD and I/R. In addition, DZX was revealed to significantly increase the protein expression of B-cell lymphoma (Bcl)-2 and suppress the expression of caspase-3 and Bcl-2-associated X protein. These findings suggested that DZX may protect cells against apoptosis via regulating the expression of ER stress-associated proteins in vitro and in vivo, thus enhancing the survival of hippocampal cells. The present results suggested a novel mechanism that may underlie the protective effect of DZX administration in the central nervous system.

Sodium-glucose transporter as a novel therapeutic target in disease

Glucose is the primary energy fuel of life. A glucose transporter, the sodium-glucose transporter (SGLT), is receiving attention as a novel therapeutic target in disease. This review summarizes the physiological role of SGLT in cerebral ischemia, cancer, cardiac disease, and intestinal ischemia, which has encouraged analysis of SGLT function. In cerebral ischemia and cardiomyopathy, SGLT-1 is involved in worsening of the injury. In addition, SGLT-1 promotes the development of cancer. On the other hand, SGLT-1 has a protective effect against cardiac and intestinal ischemia. Interestingly, SGLT-1 expression levels are increased in some diseased tissue, such as in cerebral ischemia and cancer. This suggests that SGLT-1 may have an important role in many diseases. This review discusses the potential of SGLT as a target for novel therapeutic agents.

Splenectomy protects aged mice from injury after experimental stroke

Elderly stroke patients and aged animals subjected to experimental stroke have significantly worse functional recovery and higher mortality compared to younger subjects. Activation of the peripheral immune system is known to influence stroke outcome. Prior studies have shown that splenectomy reduces ischemic brain injury in young mice. As immune function changes with aging, it is unclear whether splenectomy will confer similar benefits in aged animals. We investigated the contribution of spleen to brain injury after cerebral ischemia in aged male mice. Splenic architecture and immune cell composition were altered in aged mice. Splenectomy 2 weeks before stroke resulted in improved neurobehavioral and infarct outcomes in aged male mice. In addition, there was a reduction in peripheral immune cell infiltration into the brain and decreased levels of peripheral inflammatory cytokines after stroke in aged splenectomized mice. Splenectomy immediately after reperfusion also improved behavioral and infarct outcomes. This study suggests that inhibition of the splenic immune response is a translationally relevant target to pursue for stroke treatment in aged individuals.

Deletion of the P2X4 receptor is neuroprotective acutely, but induces a depressive phenotype during recovery from ischemic stroke

INTRODUCTION

Acute ischemic injury leads to severe neuronal loss. One of the key mechanisms responsible for this effect is inflammation, which is characterized by the activation of myeloid cells, including resident microglia and infiltrating monocytes/macrophages. P2X4 receptors (P2X4Rs) present on these immune cells modulate the inflammatory response. For example, excessive release of adenosine triphosphate during acute ischemic stroke triggers stimulation of P2X4Rs, leading to myeloid cell activation and proliferation and further exacerbating post-ischemic inflammation. In contrast, during recovery P2X4Rs activation on microglia leads to the release of brain-derived neurotrophic factor (BDNF), which alleviate depression, maintain synaptic plasticity and hasten post-stroke behavioral recovery. Therefore, we hypothesized that deletion of the P2X4R specifically from myeloid cells would have differential effects on acute versus chronic recovery following stroke.

METHODS

We subjected global or myeloid-specific (MS) P2X4R knock-out (KO) mice and wild-type littermates of both sexes to right middle cerebral artery occlusion (60min). We performed histological, behavioral (sensorimotor and depressive), and biochemical (quantitative PCR and flow cytometry) analyses to determine the acute (three days after occlusion) and chronic (30days after occlusion) effects of receptor deletion.

RESULTS

Global P2X4R deletion led to reduced infarct size in both sexes. In MS P2X4R KO mice, only females showed reduced infarct size, an effect that did not change with ovariectomy. MS P2X4R KO mice of both sexes showed swift recovery from sensorimotor deficits during acute recovery but exhibited a more pronounced post-stroke depressive behavior phenotype that was independent of infarct size. Quantitative PCR analysis of whole cell lysate as well as flow-sorted myeloid cells from the perilesional cortex showed increased cellular interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α) mRNA levels but reduced plasma levels of these cytokines in MS P2X4R KO mice after stroke. The expression levels of BDNF and other depression-associated genes were reduced in MS P2X4R KO mice after stroke.

CONCLUSIONS

P2X4R deletion protects against stroke acutely but predisposes to depression-like behavior chronically after stroke. Thus, a time-sensitive approach should be considered when targeting P2X4Rs after stroke.

Neurotrophy and immunomodulation of induced neural stem cell grafts in a mouse model of closed head injury

Closed head injury (CHI) usually results in severe and permanent neurological impairments, which are caused by several intertwined phenomena, such as cerebral edema, blood-brain barrier (BBB) disruption, neuronal loss, astroglial scarring and inflammation. We previously reported that induced neural stem cells (iNSCs), similar to neural stem cells (NSCs), can accelerate neurological recovery in vivo and produce neurotrophic factors in vitro. However, the effects of iNSC neurotrophy following CHI were not determined. Moreover, whether iNSCs have immunomodulatory properties is unknown. Mouse models of CHI were established using a standardized weight-drop device and assessed by neurological severity score (NSS). Although these models fail to mimic the complete spectrum of human CHI, they reproduce impairment in neurological function observed in clinical patients. Syngeneic iNSCs or NSCs were separately transplanted into the brains of CHI mice at 12h after CHI. Neurological impairment post-CHI was evaluated by several tests. Animals were sacrificed for morphological and molecular biological analyses. We discovered that iNSC administration promoted neurological functional recovery in CHI mice and reduced cerebral edema, BBB disruption, cell death and astroglial scarring following trauma. Implanted iNSCs could up-regulate brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) levels to support the survival of existing neurons after CHI. In addition, engrafted iNSCs decreased immune cell recruitment and pro-inflammatory cytokine expression in the brain post-injury. Moreover, we found significant nuclear factor-kappaB (NF-κB) inhibition in the presence of iNSC grafts. In short, iNSCs exert neurotrophic and immunomodulatory effects that mitigate CHI-induced neurological impairment.

Assessed and Emerging Biomarkers in Stroke and Training-Mediated Stroke Recovery: State of the Art

Since the increasing update of the biomolecular scientific literature, biomarkers in stroke have reached an outstanding and remarkable revision in the very recent years. Besides the diagnostic and prognostic role of some inflammatory markers, many further molecules and biological factors have been added to the list, including tissue derived cytokines, growth factor-like molecules, hormones, and microRNAs. The literatures on brain derived growth factor and other neuroimmune mediators, bone-skeletal muscle biomarkers, cellular and immunity biomarkers, and the role of microRNAs in stroke recovery were reviewed. To date, biomarkers represent a possible challenge in the diagnostic and prognostic evaluation of stroke onset, pathogenesis, and recovery. Many molecules are still under investigation and may become promising and encouraging biomarkers. Experimental and clinical research should increase this list and promote new discoveries in this field, to improve stroke diagnosis and treatment.