Sustained administration of corticosterone at stress-like levels after stroke suppressed glial reactivity at sites of thalamic secondary neurodegeneration

Leonurus japonicus Houtt. modulates neuronal apoptosis in intracerebral hemorrhage: Insights from network pharmacology and molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

Leonurus japonicus Houtt. (Labiatae), commonly known as Chinese motherwort, is a herbaceous flowering plant that is native to Asia. It is widely acknowledged in traditional medicine for its diuretic, hypoglycemic, antiepileptic properties and neuroprotection. Currently, Leonurus japonicus (Leo) is included in the Pharmacopoeia of the People's Republic of China. Traditional Chinese Medicine (TCM) recognizes Leo for its myriad pharmacological attributes, but its efficacy against ICH-induced neuronal apoptosis is unclear.

AIMS OF THE STUDY

This study aimed to identify the potential targets and regulatory mechanisms of Leo in alleviating neuronal apoptosis after ICH.

MATERIALS AND METHODS

The study employed network pharmacology, UPLC-Q-TOF-MS technique, molecular docking, pharmacodynamic studies, western blotting, and immunofluorescence techniques to explore its potential mechanisms.

RESULTS

Leo was found to assist hematoma absorption, thus improving the neurological outlook in an ICH mouse model. Importantly, molecular docking highlighted JAK as Leo's potential therapeutic target in ICH scenarios. Further experimental evidence demonstrated that Leo adjusts JAK1 and STAT1 phosphorylation, curbing Bax while augmenting Bcl-2 expression.

CONCLUSION

Leo showcases potential in mitigating neuronal apoptosis post-ICH, predominantly via the JAK/STAT mechanism.

miR-96-5p alleviates cerebral ischemia-reperfusion injury in mice by inhibiting pyroptosis via downregulating caspase 1

Ischemic stroke is one of the leading causes of global mortality and disability. Nevertheless, successful treatment remains limited. In this study, we investigated the efficacy and the mechanism of miR-96-5p in protecting acute ischemic brain injury in adult mice. Focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) in adult male C57BL/6 mice. MiR-96-5p or the negative control was administered via intracerebroventricular injection. The expression of pyroptosis-related genes and activation of various resident cells in the brain was assessed by RT-qPCR, western blot, immunohistochemistry, and immunofluorescence. Modified neurological severity score, rotarod test, cylinder test, brain water content, and cerebral infarction volume were used to evaluate the behavioral deficits and the severity of brain injury after MCAO. Flow cytometry, TUNEL staining, and Nissl staining were employed to assess the neuron damage. MiR-96-5p decreased markedly in the ischemic stroke model in vivo and in vitro. MiR-96-5p mimics suppressed the expression of caspase 1 and alleviated the apoptosis rate in OGD/R treatment N2a cells, however, the miR-96-5p inhibitor caused the opposite results. Intracerebroventricular delivery of miR-96-5p agomir significantly mitigated behavioral deficits, brain water content, and cerebral infarction volume after MCAO. In addition, treatment with miR-96-5p agomir downregulated the expression of caspase 1/cleaved caspase 1 and Gsdmd/Gsdmd-N, while alleviating the neuron damage. In summary, overexpression of miR-96-5p suppresses pyroptosis and reduces brain damage in the acute phase of ischemic stroke, providing new insight into the treatment of acute ischemic stroke.

Acute ischemia induces spatially and transcriptionally distinct microglial subclusters

BACKGROUND

Damage in the ischemic core and penumbra after stroke affects patient prognosis. Microglia immediately respond to ischemic insult and initiate immune inflammation, playing an important role in the cellular injury after stroke. However, the microglial heterogeneity and the mechanisms involved remain unclear.

METHODS

We first performed single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomics (ST) on middle cerebral artery occlusion (MCAO) mice from three time points to determine stroke-associated microglial subclusters and their spatial distributions. Furthermore, the expression of microglial subcluster-specific marker genes and the localization of different microglial subclusters were verified on MCAO mice through RNAscope and immunofluorescence. Gene set variation analysis (GSVA) was performed to reveal functional characteristics of microglia sub-clusters. Additionally, ingenuity pathway analysis (IPA) was used to explore upstream regulators of microglial subclusters, which was confirmed by immunofluorescence, RT-qPCR, shRNA-mediated knockdown, and targeted metabolomics. Finally, the infarct size, neurological deficits, and neuronal apoptosis were evaluated in MCAO mice after manipulation of specific microglial subcluster.

RESULTS

We discovered stroke-associated microglial subclusters in the brains of MCAO mice. We also identified novel marker genes of these microglial subclusters and defined these cells as ischemic core-associated (ICAM) and ischemic penumbra-associated (IPAM) microglia, according to their spatial distribution. ICAM, induced by damage-associated molecular patterns, are probably fueled by glycolysis, and exhibit increased pro-inflammatory cytokines and chemokines production. BACH1 is a key transcription factor driving ICAM generation. In contrast, glucocorticoids, which are enriched in the penumbra, likely trigger IPAM formation, which are presumably powered by the citrate cycle and oxidative phosphorylation and are characterized by moderate pro-inflammatory responses, inflammation-alleviating metabolic features, and myelinotrophic properties.

CONCLUSIONS

ICAM could induce excessive neuroinflammation, aggravating brain injury, whereas IPAM probably exhibit neuroprotective features, which could be essential for the homeostasis and survival of cells in the penumbra. Our findings provide a biological basis for targeting specific microglial subclusters as a potential therapeutic strategy for ischemic stroke.

Clopidogrel Administration Impairs Post-Stroke Learning and Memory Recovery in Mice

Clopidogrel, which is one of the most prescribed antiplatelet medications in the world, is given to stroke survivors for the prevention of secondary cardiovascular events. Clopidogrel exerts its antiplatelet activity via antagonism of the P2Y12 receptor (P2RY12). Although not widely known or considered during the initial clinical trials for clopidogrel, P2RY12 is also expressed on microglia, which are the brain's immune cells, where the receptor facilitates chemotactic migration toward sites of cellular damage. If microglial P2RY12 is blocked, microglia lose the ability to migrate to damaged sites and carry out essential repair processes. We aimed to investigate whether administering clopidogrel to mice post-stroke was associated with (i) impaired motor skills and cognitive recovery; (ii) physiological changes, such as survival rate and body weight; (iii) changes in the neurovascular unit, including blood vessels, microglia, and neurons; and (iv) changes in immune cells. Photothrombotic stroke (or sham surgery) was induced in adult male mice. From 24 h post-stroke, mice were treated daily for 14 days with either clopidogrel or a control. Cognitive performance (memory and learning) was assessed using a mouse touchscreen platform (paired associated learning task), while motor impairment was assessed using the cylinder task for paw asymmetry. On day 15, the mice were euthanized and their brains were collected for immunohistochemistry analysis. Clopidogrel administration significantly impaired learning and memory recovery, reduced mouse survival rates, and reduced body weight post-stroke. Furthermore, clopidogrel significantly increased vascular leakage, significantly increased the number and appearance of microglia, and significantly reduced the number of T cells within the peri-infarct region post-stroke. These data suggest that clopidogrel hampers cognitive performance post-stroke. This effect is potentially mediated by an increase in vascular permeability post-stroke, providing a pathway for clopidogrel to access the central nervous system, and thus, interfere in repair and recovery processes.

Melatonin attenuates chronic stress-induced hippocampal inflammatory response and apoptosis by inhibiting ADAM17/TNF-α axis

Melatonin, as a dietary supplement, has a potent neuroprotective effect and exerts a certain antidepressant effect. This study explored the molecular mechanisms and targets of melatonin on chronic stress-induced hippocampal damage from the perspective of inhibiting inflammatory cytokines release. Our results indicated that melatonin alleviated chronic restraint stress (CRS)-induced inflammatory response and apoptosis, thus improving hippocampal structural damage and subsequent depression-like behaviors in rats. The radar map displayed that the change of TNF-α content was the most significant. Meanwhile, correlation analysis showed that TNF-α content was highly positively correlated with apoptosis. Molecular autodocking studies suggested that TNF-α converting enzyme ADAM17 as a potential target has a priority in docking with melatonin. Molecular mechanism studies indicated that melatonin inhibited CRS-induced activation of the ADAM17/TNF-α axis and its downstream proteins p38 and p53 phosphorylation in the hippocampus. Analogously, Both ADAM17 inhibitor TMI-1 and TNF-α inhibitor thalidomide relieved the effects of CRS on ADAM17/TNF-α axis and its downstream proteins phosphorylation, hippocampal apoptosis, hippocampal inflammatory response, and depression-like behaviors in rats. Altogether, these findings reveal that melatonin relieves CRS-induced inflammatory response and apoptosis, and subsequent depression-like behaviors by inhibiting ADAM17/TNF-α axis.

Co-exposure of chronic stress and alumina nanoparticles aggravates hippocampal microglia pyroptosis by activating cathepsin B/NLRP3 signaling pathway

Combined exposure of chronic stress and alumina nanoparticles (AlNPs) aggravates hippocampal injury, but the pathogenesis is unevaluated. This study aimed to investigate the effect and mechanism of co-exposure to chronic stress and AlNPs on hippocampal microglia pyroptosis. In this study, chronic restraint stress (CRS) alone caused NLRP3-mediated hippocampal microglia pyroptosis, but AlNPs did not. Moreover, co-exposure to CRS and AlNPs exacerbated hippocampal microglia pyroptosis, resulting in more severe hippocampal damage and behavioral deficits in rats. Protein-protein interaction network predicted that cathepsin B was a potential regulatory protein of NLRP3. CRS up-regulated cathepsin B expression which had a more pronounced increase in co-exposure group. Whereas, caspase-1 inhibitor VX-765 alleviated hippocampal microglia pyroptosis and behavioral deficits in rats. Consistent with in vivo results, co-exposure of corticosterone and AlNPs aggravated NLRP3-mediated pyroptosis and cathepsin B expression in HAPI cells. Nevertheless, the pyroptosis of HAPI cells was inhibited by cathepsin B inhibitor CA-074Me and NLRP3 knockout, respectively. NLRP3 agonist nigericin failed to promote the pyroptosis of HAPI cells in the presence of cathepsin B inhibition. These results demonstrated that co-exposure to chronic stress and AlNPs could aggravate hippocampal microglia pyroptosis by activating cathepsin B/NLRP3 signaling pathway, resulting in hippocampal damage and behavioral deficits.

Do P2Y12 receptor inhibitors prescribed poststroke modify the risk of cognitive disorder or dementia? Protocol for a target trial using multiple national Swedish registries

INTRODUCTION

The target of a class of antiplatelet medicines, P2Y12R inhibitors, exists both on platelets and on brain immune cells (microglia). This protocol aims to describe a causal (based on a counterfactual model) approach for analysing whether P2Y12R inhibitors prescribed for secondary prevention poststroke may increase the risk of cognitive disorder or dementia via their actions on microglia, using real-world evidence.

METHODS AND ANALYSIS

This will be a cohort study nested within the Swedish National Health and Medical Registers, including all people with incident stroke from 2006 to 2016. We developed directed acyclic graphs to operationalise the causal research question considering potential time-independent and time-dependent confounding, using input from several experts. We developed a study protocol following the components of the target trial approach described by Hernan et al and describe the data structure that would be required in order to make a causal inference. We also describe the statistical approach required to derive the causal estimand associated with this important clinical question; that is, a time-to-event analysis for the development of cognitive disorder or dementia at 1, 2 and 5-year follow-up, based on approaches for competing events to account for the risk of all-cause mortality. Causal effect estimates and the precision in these estimates will be quantified.

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee of the University of Gothenburg and Confidentiality Clearance at Statistics Sweden with Dnr 937-18, and an approved addendum with Dnr 2019-0157. The analysis and interpretation of the results will be heavily reliant on the structure, quality and potential for bias of the databases used. When we implement the protocol, we will consider and document any biases specific to the dataset and conduct appropriate sensitivity analyses. Findings will be disseminated to local stakeholders via conferences, and published in appropriate scientific journals.

Gene expression changes in the brain of a Cushing's syndrome mouse model

Excess glucocorticoid exposure affects emotional and cognitive brain functions. The extreme form, Cushing's syndrome, is adequately modelled in the AdKO_2.0 mouse, consequential to adrenocortical hypertrophy and hypercorticosteronemia. We previously reported that the AdKO_2.0 mouse brain undergoes volumetric changes that resemble closely those of Cushing's syndrome human patients, as well as changes in expression of glial related marker proteins. In the present work, the expression of genes related to glial and neuronal cell populations and functions was assessed in regions of the anterior brain, hippocampus, amygdala and hypothalamus. Glucocorticoid target genes were consistently regulated, including CRH mRNA suppression in the hypothalamus and induction in amygdala and hippocampus, even if glucocorticoid receptor protein was downregulated. Expression of glial genes was also affected in the AdKO_2.0 mouse brain, indicating a different activation status in glial cells. Generic markers for neuronal cell populations, and cellular integrity were only slightly affected. Our findings highlight the vulnerability of glial cell populations to chronic high levels of circulating glucocorticoids.

More than motor impairment: A spatiotemporal analysis of cognitive impairment and associated neuropathological changes following cortical photothrombotic stroke

There is emerging evidence suggesting that a cortical stroke can cause delayed and remote hippocampal dysregulation, leading to cognitive impairment. In this study, we aimed to investigate motor and cognitive outcomes after experimental stroke, and their association with secondary neurodegenerative processes. Specifically, we used a photothrombotic stroke model targeting the motor and somatosensory cortices of mice. Motor function was assessed using the cylinder and grid walk tasks. Changes in cognition were assessed using a mouse touchscreen platform. Neuronal loss, gliosis and amyloid-β accumulation were investigated in the peri-infarct and ipsilateral hippocampal regions at 7, 28 and 84 days post-stroke. Our findings showed persistent impairment in cognitive function post-stroke, whilst there was a modest spontaneous motor recovery over the investigated period of 84 days. In the peri-infarct region, we detected a reduction in neuronal loss and decreased neuroinflammation over time post-stroke, which potentially explains the spontaneous motor recovery. Conversely, we observed persistent neuronal loss together with concomitant increased neuroinflammation and amyloid-β accumulation in the hippocampus, which likely accounts for the persistent cognitive dysfunction. Our findings indicate that cortical stroke induces secondary neurodegenerative processes in the hippocampus, a region remote from the primary infarct, potentially contributing to the progression of post-stroke cognitive impairment.

Corticosterone Administration Alters White Matter Tract Structure and Reduces Gliosis in the Sub-Acute Phase of Experimental Stroke

White matter tract (WMT) degeneration has been reported to occur following a stroke, and it is associated with post-stroke functional disturbances. White matter pathology has been suggested to be an independent predictor of post-stroke recovery. However, the factors that influence WMT remodeling are poorly understood. Cortisol is a steroid hormone released in response to prolonged stress, and elevated levels of cortisol have been reported to interfere with brain recovery. The objective of this study was to investigate the influence of corticosterone (CORT; the rodent equivalent of cortisol) on WMT structure post-stroke. Photothrombotic stroke (or sham surgery) was induced in 8-week-old male C57BL/6 mice. At 72 h, mice were exposed to standard drinking water ± CORT (100 µg/mL). After two weeks of CORT administration, mice were euthanised and brain tissue collected for histological and biochemical analysis of WMT (particularly the corpus callosum and corticospinal tract). CORT administration was associated with increased tissue loss within the ipsilateral hemisphere, and modest and inconsistent WMT reorganization. Further, a structural and molecular analysis of the WMT components suggested that CORT exerted effects over axons and glial cells. Our findings highlight that CORT at stress-like levels can moderately influence the reorganization and microstructure of WMT post-stroke.

Behavioral Assessment of Sensory, Motor, Emotion, and Cognition in Rodent Models of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the second most common type of stroke and has one of the highest fatality rates of any disease. There are many clinical signs and symptoms after ICH due to brain cell injury and network disruption resulted from the rupture of a tiny artery and activation of inflammatory cells, such as motor dysfunction, sensory impairment, cognitive impairment, and emotional disturbance, etc. Thus, researchers have established many tests to evaluate behavioral changes in rodent ICH models, in order to achieve a better understanding and thus improvements in the prognosis for the clinical treatment of stroke. This review summarizes existing protocols that have been applied to assess neurologic function outcomes in the rodent ICH models such as pain, motor, cognition, and emotion tests. Pain tests include mechanical, hot, and cold pain tests; motor tests include the following 12 types: neurologic deficit scale test, staircase test, rotarod test, cylinder test, grid walk test, forelimb placing test, wire hanging test, modified neurologic severity score, beam walking test, horizontal ladder test, and adhesive removal test; learning and memory tests include Morris water maze, Y-maze, and novel object recognition test; emotion tests include elevated plus maze, sucrose preference test, tail suspension test, open field test, and forced swim test. This review discusses these assessments by examining their rationale, setup, duration, baseline, procedures as well as comparing their pros and cons, thus guiding researchers to select the most appropriate behavioral tests for preclinical ICH research.

Longitudinal hippocampal volumetric changes in mice following brain infarction

Hippocampal atrophy is increasingly described in many neurodegenerative syndromes in humans, including stroke and vascular cognitive impairment. However, the progression of brain volume changes after stroke in rodent models is poorly characterized. We aimed to monitor hippocampal atrophy occurring in mice up to 48-weeks post-stroke. Male C57BL/6J mice were subjected to an intraluminal filament-induced middle cerebral artery occlusion (MCAO). At baseline, 3-days, and 1-, 4-, 12-, 24-, 36- and 48-weeks post-surgery, we measured sensorimotor behavior and hippocampal volumes from T₂-weighted MRI scans. Hippocampal volume-both ipsilateral and contralateral-increased over the life-span of sham-operated mice. In MCAO-subjected mice, different trajectories of ipsilateral hippocampal volume change were observed dependent on whether the hippocampus contained direct infarction, with a decrease in directly infarcted tissue and an increase in non-infarcted tissue. To further investigate these volume changes, neuronal and glial cell densities were assessed in histological brain sections from the subset of MCAO mice lacking hippocampal infarction. Our findings demonstrate previously uncharacterized changes in hippocampal volume and potentially brain parenchymal cell density up to 48-weeks in both sham- and MCAO-operated mice.

Lesions in the right Rolandic operculum are associated with self-rating affective and apathetic depressive symptoms for post-stroke patients

Stroke survivors majorly suffered from post-stroke depression (PSD). The PSD diagnosis is commonly performed based on the clinical cut-off for psychometric inventories. However, we hypothesized that PSD involves spectrum symptoms (e.g., apathy, depression, anxiety, and stress domains) and severity levels. Therefore, instead of using the clinical cut-off, we suggested a data-driven analysis to interpret patient spectrum conditions. The patients’ psychological conditions were categorized in an unsupervised manner using the k-means clustering method, and the relationships between psychological conditions and quantitative lesion degrees were evaluated. This study involved one hundred sixty-five patient data; all patients were able to understand and perform self-rating psychological conditions (i.e., no aphasia). Four severity levels—low, low-to-moderate, moderate-to-high, and high—were observed for each combination of two psychological domains. Patients with worse conditions showed the significantly greater lesion degree at the right Rolandic operculum (part of Brodmann area 43). The dissimilarities between stress and other domains were also suggested. Patients with high stress were specifically associated with lesions in the left thalamus. Impaired emotion processing and stress-affected functions have been frequently related to those lesion regions. Those lesions were also robust and localized, suggesting the possibility of an objective for predicting psychological conditions from brain lesions.

Advances in Studies on Stroke-Induced Secondary Neurodegeneration (SND) and Its Treatment

Background:

The occurrence of secondary neurodegeneration has exclusively been observed after the first incidence of stroke. In humans and rodents, post-stroke secondary neurodegeneration (SND) is an inevitable event that can lead to progressive neuronal loss at a region distant to initial infarct. SND can lead to cognitive and motor function impairment, finally causing dementia. The exact pathophysiology of the event is yet to be explored. It is seen that the thalami, in particular, are susceptible to cause SND. The reason behind this is because the thalamus functioning as the relay center and is positioned as an interlocked structure with direct synaptic signaling connection with the cortex. As SND proceeds, accumulation of misfolded proteins and microglial activation are seen in the thalamus. This leads to increased neuronal loss and worsening of functional and cognitive impairment.

Objective:

There is a necessity of specific interventions to prevent post-stroke SND, which are not properly investigated to date owing to sparsely reproducible pre-clinical and clinical data. The basis of this review is to investigate about post-stroke SND and its updated treatment approaches carefully.

Methods:

Our article presents a detailed survey of advances in studies on stroke-induced secondary neurodegeneration (SND) and its treatment.

Results:

This article aims to put forward the pathophysiology of SND. We have also tabulated the latest treatment approaches along with different neuroimaging systems that will be helpful for future reference to explore.

Conclusion:

In this article, we have reviewed the available reports on SND pathophysiology, detection techniques, and possible treatment modalities that have not been attempted to date.

Growth Hormone Promotes Motor Function after Experimental Stroke and Enhances Recovery-Promoting Mechanisms within the Peri-Infarct Area

Motor impairment is the most common and widely recognised clinical outcome after stroke. Current clinical practice in stroke rehabilitation focuses mainly on physical therapy, with no pharmacological intervention approved to facilitate functional recovery. Several studies have documented positive effects of growth hormone (GH) on cognitive function after stroke, but surprisingly, the effects on motor function remain unclear. In this study, photothrombotic occlusion targeting the motor and sensory cortex was induced in adult male mice. Two days post-stroke, mice were administered with recombinant human GH or saline, continuing for 28 days, followed by evaluation of motor function. Three days after initiation of the treatment, bromodeoxyuridine was administered for subsequent assessment of cell proliferation. Known neurorestorative processes within the peri-infarct area were evaluated by histological and biochemical analyses at 30 days post-stroke. This study demonstrated that GH treatment improves motor function after stroke by 50%–60%, as assessed using the cylinder and grid walk tests. Furthermore, the observed functional improvements occurred in parallel with a reduction in brain tissue loss, as well as increased cell proliferation, neurogenesis, increased synaptic plasticity and angiogenesis within the peri-infarct area. These findings provide new evidence about the potential therapeutic effects of GH in stroke recovery.

Cognitive dysfunction in mice lacking proper glucocorticoid receptor dimerization

Stress is a major risk factor for depression and anxiety. One of the effects of stress is the (over-) activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of stress hormones such as glucocorticoids (GCs). Chronically increased stress hormone levels have been shown to have detrimental effects on neuronal networks by inhibiting neurotrophic processes particularly in the hippocampus proper. Centrally, GCs modulate metabolic as well as behavioural processes by activating two classes of corticoid receptors, high-affinity mineralocorticoid receptors (MR) and low-affinity glucocorticoid receptors (GR). Upon activation, GR can modulate gene transcription either as a monomeric protein, or as a dimer interacting directly with DNA. GR can also modulate cellular processes via non-genomic mechanisms, for example via a GPCR-protein interaction. We evaluated the behavioral phenotype in mice with a targeted mutation in the GR in a FVB/NJ background. In GRdim/dim mice, GR proteins form poor homodimers, while the GR monomer remains intact. We evaluated the effect of poor GR dimerization on hippocampus-dependent cognition as well as on exploration and emotional behavior under baseline and chronically increased stress hormone levels. We found that GRdim/dim mice did not behave differently from GRwt/wt littermates under baseline conditions. However, after chronic elevation of stress hormone levels, GRdim/dim mice displayed a significant impairment in hippocampus-dependent memory compared to GRwt/wt mice, which correlated with differential expression of hippocampal Bdnf/TrkB and Fkbp5.

Visual discrimination impairment after experimental stroke is associated with disturbances in the polarization of the astrocytic aquaporin-4 and increased accumulation of neurotoxic proteins

Numerous clinical studies have documented the high incidence of cognitive impairment after stroke. However, there is only limited knowledge about the underlying mechanisms. Interestingly, there is emerging evidence suggesting that cognitive function after stroke may be affected due to reduced waste clearance and subsequent accumulation of neurotoxic proteins. To further explore this potential association, we utilised a model of experimental stroke in mice. Specifically, a photothrombotic vascular occlusion targeting motor and sensory parts of the cerebral cortex was induced in young adult mice, and changes in cognition were assessed using a touchscreen platform for pairwise visual discrimination. The results showed that the execution of the visual discrimination task was impaired in mice 10 to 14 days post-stroke compared to sham. Stroke also induced significant neuronal loss within the peri-infarct, thalamus and the CA1 sub-region of the hippocampus. Further, immunohistochemical and protein analyses of the selected brain regions revealed an increased accumulation and aggregation of both amyloid-β and α-synuclein. These alterations were associated with significant disturbances in the aquaporin-4 protein expression and polarization at the astrocytic end-feet. The results suggest a link between the increased accumulation of neurotoxic proteins and the stroke-induced cognitive impairment. Given that the neurotoxic protein accumulation appeared alongside changes in astrocytic aquaporin-4 distribution, we suggest that the function of the waste clearance pathways in the brain post-stroke may represent a therapeutic target to improve brain recovery.

Low oxygen post conditioning prevents thalamic secondary neuronal loss caused by excitotoxicity after cortical stroke

In the current study, we were interested in investigating whether Low oxygen post-conditioning (LOPC) was capable of limiting the severity of stroke-induced secondary neurodegeneration (SND). To investigate the effect of LOPC we exposed adult male C57/BL6 mice to photothrombotic occlusion (PTO) of the motor and somatosensory cortex. This is known to induce progressive neurodegeneration in the thalamus within two weeks of infarction. Two days after PTO induction mice were randomly assigned to one of four groups: (i) LOPC-15 day exposure group; (ii) a LOPC 15 day exposure followed by a 15 day exposure to normal atmosphere; (iii) normal atmosphere for 15 days and (iv) normal atmosphere for 30 days (n = 20/group). We observed that LOPC reduced the extent of neuronal loss, as indicated by assessment of both area of loss and NeuN⁺ cell counts, within the thalamus. Additionally, we identified that LOPC reduced microglial activity and decreased activity within the excitotoxic signalling pathway of the NMDAR axis. Together, these findings suggest that LOPC limits neuronal death caused by excitotoxicity in sites of secondary damage and promotes neuronal survival. In conclusion, this work supports the potential of utilising LOPC to intervene in the sub-acute phase post-stroke to restrict the severity of SND.

Low Oxygen Post Conditioning as an Efficient Non-pharmacological Strategy to Promote Motor Function After Stroke

Low oxygen post conditioning (LOPC) has shown promising results in terms of neuroprotection after stroke, but the effects on motor function have not been considered. Cortical stroke targeting the motor and sensory cortex was induced by photothrombotic occlusion and after 48 h allocated to LOPC (11% O₂) for 2 weeks. Motor impairment was assessed using the cylinder and grid walk tests during the exposure period and for two further weeks upon completion of the intervention. Neuroprotection was evaluated by histological and molecular analysis at two time points. Two weeks of LOPC was sufficient to significantly reduce motor deficits and tissue loss after stroke. This functional improvement was associated with increased capillary density, enhanced levels of BDNF, decreased neuronal loss and decreased microglia activation. These improvements, in most instances, were maintained up to 2 weeks after the end of the treatment. To our knowledge, this is the first study to demonstrate that LOPC induces a persistent improvement in motor function and neuroprotection after stroke, and in doing so provides evidence to support a case for considering taking LOPC forward to early stage clinical research.

Growth Hormone Improves Cognitive Function After Experimental Stroke

BACKGROUND AND PURPOSE

Cognitive impairment is a common outcome for stroke survivors. Growth hormone (GH) could represent a potential therapeutic option as this peptide hormone has been shown to improve cognition in various clinical conditions. In this study, we evaluated the effects of peripheral administration of GH at 48 hours poststroke for 28 days on cognitive function and the underlying mechanisms.

METHODS

Experimental stroke was induced by photothrombotic occlusion in young adult mice. We assessed the associative memory cognitive domain using mouse touchscreen platform for paired-associate learning task. We also evaluated neural tissue loss, neurotrophic factors, and markers of neuroplasticity and cerebrovascular remodeling using biochemical and histology analyses.

RESULTS

Our results show that GH-treated stroked mice made a significant improvement on the paired-associate learning task relative to non-GH-treated mice at the end of the study. Furthermore, we observed reduction of neural tissue loss in GH-treated stroked mice. We identified that GH treatment resulted in significantly higher levels of neurotrophic factors (IGF-1 [insulin-like growth factor-1] and VEGF [vascular endothelial growth factor]) in both the circulatory and peri-infarct regions. GH treatment in stroked mice not only promoted protein levels and density of presynaptic marker (SYN-1 [synapsin-1]) and marker of myelination (MBP [myelin basic protein]) but also increased the density and area coverage of 2 major vasculature markers (CD31 and collagen-IV), within the peri-infarct region.

CONCLUSIONS

These findings provide compelling preclinical evidence for the usage of GH as a potential therapeutic tool in the recovery phase of patients after stroke.