DL-3n-Butylphthalide Improves Blood-Brain Barrier Integrity in Rat After Middle Cerebral Artery Occlusion

The impact of cytokines in neuroinflammation-mediated stroke

Cerebral stroke is ranked as the third most common contributor to global mortality and disability. The involvement of inflammatory mechanisms, both peripherally and within the CNS, holds significance in the pathophysiological cascades following the initiation of stroke. After the onset of acute stroke, predominantly ischemic, a subsequent phase of neuroinflammation ensues. It is a dual-effect process that not only exacerbates injury, leading to cell death, but paradoxically, it also serves a shielding role in facilitating recovery. Cytokines serve as pivotal mediators within the inflammatory cascade, actively contributing to the progression of ischemic damage. Stroke is followed by increased expression of pro-inflammatory cytokines including TNF-α, IL-1β, IL-6, etc. leading to the recruitment and stimulation of glial cells and peripheral leukocytes at the site of injury, promoting neuroinflammation. Cytokines can directly induce neuronal injury and death through various mechanisms, including excitotoxicity, oxidative stress, HPA-axis activation, secretion of matrix metalloproteinase and apoptosis. They can also amplify the inflammatory response, leading to further neuronal damage. Therapeutic strategies aimed at modulating cytokine release, immune response and cytokine signalling or activity are being explored as potential interventions to mitigate neuroinflammation and its detrimental effects in stroke. In this review, we have given a concise summary of our current knowledge of the function of various cytokines, brain inflammation and various signalling and molecular pathways including JAK/STAT3, TGF-β/Smad, MAPK, HMGB1/TLR and NF-κB modulated cytokines regulation in stroke. Therapeutic agents such as MCC950, genistein, edaravone, minocycline, etc. targeting various cytokines-associated signalling pathways have shown efficacy in preclinical and clinical trials reducing the pathophysiology of the illness were also addressed in this study.

Neferine inhibits BMECs pyroptosis and maintains blood-brain barrier integrity in ischemic stroke by triggering a cascade reaction of PGC-1α

Blood-brain barrier disruption is a critical pathological event in the progression of ischemic stroke (IS). Most studies regarding the therapeutic potential of neferine (Nef) on IS have focused on neuroprotective effect. However, whether Nef attenuates BBB disruption during IS is unclear. We here used mice underwent transient middle cerebral artery occlusion (tMCAO) in vivo and bEnd.3 cells exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) injury in vitro to simulate cerebral ischemia. We showed that Nef reduced neurobehavioral dysfunction and protected brain microvascular endothelial cells and BBB integrity. Molecular docking, short interfering (Si) RNA and plasmid transfection results showed us that PGC-1α was the most binding affinity of biological activity protein for Nef. And verification experiments were showed that Nef upregulated PGC-1α expression to reduce mitochondrial oxidative stress and promote TJ proteins expression, further improves the integrity of BBB in mice. Intriguingly, our study showed that neferine is a natural PGC-1α activator and illustrated the mechanism of specific binding site. Furthermore, we have demonstrated Nef reduced mitochondria oxidative damage and ameliorates endothelial inflammation by inhibiting pyroptosis to improve BBB permeability through triggering a cascade reaction of PGC-1α via regulation of PGC-1α/NLRP3/GSDMD signaling pathway to maintain the integrity of BBB in ischemia/reperfusion injury.

Partial blood replacement ameliorates middle cerebral artery occlusion generated neurological aberrations by intervening TLR4 and NLRP3 cascades in rats

Acute ischemic stroke is a catastrophic medical condition that causes severe disability and mortality if the sufferer escapes treatment within a stipulated timeframe. While timely intervention with clot-bursting agents like tissue-plasminogen activators abrogates some post-stroke neurologic deficits, no neuroprotective therapy is yet promisingly addresses the post-recanalization neuroinflammation in post-stroke survivors. Herein, we investigated the effect of partial blood replacement therapy (BRT), obtained from healthy and treadmill-trained donor rats, on neurological deficits, and peripheral and central inflammatory cascades using the ischemia-reperfusion animal paradigm. The cerebral ischemia-reperfusion was induced in rats by occlusion of the middle cerebral artery (MCAO) for 90 min, followed by reperfusion. Rats underwent MCAO surgery displayed remarkable sensorimotor and motor deficits in rotarod, foot fault, adhesive removal, and paw whisker tests till 5 days post-surgery. These behavior abnormalities were ameliorated in the BRT-recipient MCAO rats. BRT also reduced the infarct volume and neuronal death in the ipsilateral hemisphere revealed by TTC and cresyl violet staining compared to the MCAO group. Rats received BRT infusion exhibited the reduced expression of glial fibrillary acidic protein, ionized calcium-binding adaptor molecule-1 (Iba-1), and MyD88 on day 5 post-MCAO in immunohistochemistry and immunofluorescent assays. Moreover, elevated levels of toll-like receptor 4 (TLR4) and mRNA expression of IL-1β, TNF-α, matrix metalloproteinase-9 and NLRP3, and decreased levels of zonula occludens-1 in MCAO rats, were reversed following BRT. These findings suggest that the partial BRT may rescind MCAO-induced neurological dysfunctions and cerebral injury by intervening in the TLR4 and NLRP3 pathways in rats.

Dl-3-n-butylphthalide promotes synaptic plasticity by activating the Akt/ERK signaling pathway and reduces the blood-brain barrier leakage by inhibiting the HIF-1α/MMP signaling pathway in vascular dementia model mice

AIMS

DL-3-n-butylphthalide (NBP) exerts beneficial effects on global cognitive functions, but the underlying molecular mechanisms are still poorly understood. The present study aimed to investigate whether NBP mediates synaptic plasticity and blood-brain barrier (BBB) function, which play a pivotal role in the pathogenesis of vascular dementia (VaD), in a mouse model of bilateral common carotid artery stenosis (BCAS).

METHODS

NBP was administered to model mice at a dose of 80 mg/kg by gavage for 28 days after surgery. Cognitive function was evaluated by behavioral tests, and hippocampal synaptic plasticity was evaluated by in vivo electrophysiological recording. Cerebral blood flow (CBF), hippocampal volume, and white matter integrity were measured with laser speckle imaging (LSI) and MRI. In addition, BBB leakage and the expression of proteins related to the Akt/ERK and HIF-1α/MMP signaling pathways were assessed by biochemical assays.

RESULTS

NBP treatment alleviated cognitive impairment, hippocampal atrophy, and synaptic plasticity impairment induced by BCAS. In addition, NBP treatment increased CBF, promoted white matter integrity, and decreased BBB leakage. Regarding the molecular mechanisms, in mice  with BCAS, NBP may activate the Akt/ERK signaling pathway, which upregulates the expression of synapse-associated proteins, and it may also inhibit the HIF-1α/MMP signaling pathway, thereby increasing the expression of tight junction (TJ) proteins.

CONCLUSION

In conclusion, our results demonstrated the therapeutic effects of NBP in improving cognitive function via a wide range of targets in mice subjected to BCAS.

DL-3-n-butylphthalide for acute ischemic stroke: An updated systematic review and meta-analysis of randomized controlled trials

Background: DL -3-n-butylphthalide (NBP) is widely used as a neuroprotective drug in stroke patients in China. A systematic review in 2010 suggested NBP to be safe and effective at promoting neurological recovery, but could not conclude whether it decreased risk of long-term death or disability. Since numerous randomized controlled trials (RCTs) have been conducted on NBP since 2010, we performed an updated systematic review and meta-analysis of safety and efficacy data.

Method: We searched electronic databases and reference lists to identify RCTs that compared patients who received NBP or not (including placebo). Methodological quality of RCTs was assessed using the Revised Cochrane Risk of Bias Tool 2.0, and data were meta-analyzed using Review Manager 5.4 software.

Results: Fifty-seven RCTs involving 8,747 participants were included. Twenty trials examined NBP as a capsule, 29 as an injection, and 8 as sequential injection-capsule therapy. Meta-analyses showed that NBP treatment was associated with a reduction in composite outcome of death and dependency (risk ratio 0.59, 95% CI 0.42 to 0.83; 260 participants; 2 studies), death (risk ratio 0.32, 95% CI 0.13 to 0.75; 2,287 participants; 10 studies), modified Rankin Scale score (mean difference -0.80, 95% CI -0.88 to -0.72; 568 participants; 4 studies), and an increase in Barthel Index, which assesses the ability to engage in basic activities of daily living (mean difference 11.08, 95% CI 9.10 to 13.05; 2,968 participants; 22 studies). Meta-analyses found that NBP significantly reduced neurological deficit based on National Institute of Health Stroke Scale (mean difference -3.39, 95% CI -3.76 to -3.03; 7.283 participants; 46 studies) and Chinese Stroke Scale (mean difference -4.16, 95% CI -7.60 to -0.73; 543 participants; 4 studies). Of the adverse events reported in 31 trials, elevated transaminase (incidence, 1.39-17.53%), rash (0-1.96%) and gastrointestinal discomfort (1.09-6.15%) were most frequent and no serious adverse events were reported.

Conclusion: This update review confirms that NBP can help acute ischemic stroke patients regain the ability to perform activities of daily living, reduce their neurological deficit and short-term death rates. However, the available evidence on whether NBP reduces risk of long-term death or dependence after ischemic stroke remains insufficient.

Dl-3-n-Butylphthalide Reduced Neuroinflammation by Inhibiting Inflammasome in Microglia in Mice after Middle Cerebral Artery Occlusion

The inflammatory response is one of the key events in cerebral ischemia, causing secondary brain injury and neuronal death. Studies have shown that the NLRP3 inflammasome is a key factor in initiating the inflammatory response and that Dl-3-n-butylphthalide (NBP) can attenuate the inflammatory response and improve neuronal repair during ischemic stroke. However, whether NBP attenuates the inflammatory response via inhibition of NLRP3 remains unclear. A 90 min middle cerebral artery occlusion was induced in 62 2-month-old adult male ICR mice, and NBP was administered by gavage zero, one, or two days after ischemia. Brain infarct volume, neurological deficits, NLRP3, microglia, and neuronal death were examined in sacrificed mice to explore the correction between NBP effects and NLRP3 expression. NBP significantly reduced infarct volume and attenuated neurological deficits after ischemic stroke compared to controls (p < 0.05). Moreover, it inhibited ASC+ microglia activation and NLRP3 and CASP1 expression in ischemic mice. In addition, neuronal apoptosis was reduced in NBP-treated microglia cultures (p < 0.05). Our results indicate that NBP attenuates the inflammatory response in ischemic mouse brains, suggesting that NBP protects against microglia activation via the NLRP3 inflammasome.

Signaling pathways involved in ischemic stroke: molecular mechanisms and therapeutic interventions

Ischemic stroke is caused primarily by an interruption in cerebral blood flow, which induces severe neural injuries, and is one of the leading causes of death and disability worldwide. Thus, it is of great necessity to further detailly elucidate the mechanisms of ischemic stroke and find out new therapies against the disease. In recent years, efforts have been made to understand the pathophysiology of ischemic stroke, including cellular excitotoxicity, oxidative stress, cell death processes, and neuroinflammation. In the meantime, a plethora of signaling pathways, either detrimental or neuroprotective, are also highly involved in the forementioned pathophysiology. These pathways are closely intertwined and form a complex signaling network. Also, these signaling pathways reveal therapeutic potential, as targeting these signaling pathways could possibly serve as therapeutic approaches against ischemic stroke. In this review, we describe the signaling pathways involved in ischemic stroke and categorize them based on the pathophysiological processes they participate in. Therapeutic approaches targeting these signaling pathways, which are associated with the pathophysiology mentioned above, are also discussed. Meanwhile, clinical trials regarding ischemic stroke, which potentially target the pathophysiology and the signaling pathways involved, are summarized in details. Conclusively, this review elucidated potential molecular mechanisms and related signaling pathways underlying ischemic stroke, and summarize the therapeutic approaches targeted various pathophysiology, with particular reference to clinical trials and future prospects for treating ischemic stroke.

The glymphatic system and subarachnoid hemorrhage: disruption and recovery

The glymphatic system, or glial-lymphatic system, is a waste clearance system composed of perivascular channels formed by astrocytes that mediate the clearance of proteins and metabolites from the brain. These channels facilitate the movement of cerebrospinal fluid throughout brain parenchyma and are critical for homeostasis. Disruption of the glymphatic system leads to an accumulation of these waste products as well as increased interstitial fluid in the brain. These phenomena are also seen during and after subarachnoid hemorrhages (SAH), contributing to the brain damage seen after rupture of a major blood vessel. Herein this review provides an overview of the glymphatic system, its disruption during SAH, and its function in recovery following SAH. The review also outlines drugs which target the glymphatic system and may have therapeutic applications following SAH.

Microglial Activation Damages Dopaminergic Neurons through MMP-2/-9-Mediated Increase of Blood-Brain Barrier Permeability in a Parkinson's Disease Mouse Model

Chronic neuroinflammation has been considered to be involved in the progressive dopaminergic neurodegeneration in Parkinson’s disease (PD). However, the mechanisms remain unknown. Accumulating evidence indicated a key role of the blood–brain barrier (BBB) dysfunction in neurological disorders. This study is designed to elucidate whether chronic neuroinflammation damages dopaminergic neurons through BBB dysfunction by using a rotenone-induced mouse PD model. Results showed that rotenone dose-dependently induced nigral dopaminergic neurodegeneration, which was associated with increased Evans blue content and fibrinogen accumulation as well as reduced expressions of zonula occludens-1 (ZO-1), claudin-5 and occludin, three tight junction proteins for maintaining BBB permeability, in mice, indicating BBB disruption. Rotenone also induced nigral microglial activation. Depletion of microglia or inhibition of microglial activation by PLX3397 or minocycline, respectively, greatly attenuated BBB dysfunction in rotenone-lesioned mice. Mechanistic inquiry revealed that microglia-mediated activation of matrix metalloproteinases-2 and 9 (MMP-2/-9) contributed to rotenone-induced BBB disruption and dopaminergic neurodegeneration. Rotenone-induced activation of MMP-2/-9 was significantly attenuated by microglial depletion and inactivation. Furthermore, inhibition of MMP-2/-9 by a wide-range inhibitor, SB-3CT, abrogated elevation of BBB permeability and simultaneously increased tight junctions expression. Finally, we found that microglial depletion and inactivation as well as inhibition of MMP-2/-9 significantly ameliorated rotenone-elicited nigrostriatal dopaminergic neurodegeneration and motor dysfunction in mice. Altogether, our findings suggested that microglial MMP-2/-9 activation-mediated BBB dysfunction contributed to dopaminergic neurodegeneration in rotenone-induced mouse PD model, providing a novel view for the mechanisms of Parkinsonism.

Transcranial focused ultrasound stimulation reduces vasogenic edema after middle cerebral artery occlusion in mice

Blood-brain barrier (BBB) disruption underlies the vasogenic edema and neuronal cell death induced by acute ischemic stroke. Reducing this disruption has therapeutic potential. Transcranial focused ultrasound stimulation has shown neuromodulatory and neuroprotective effects in various brain diseases including ischemic stroke. Ultrasound stimulation can reduce inflammation and promote angiogenesis and neural circuit remodeling. However, its effect on the BBB in the acute phase of ischemic stroke is unknown. In this study of mice subjected to middle cerebral artery occlusion for 90 minutes, low-intensity low-frequency (0.5 MHz) transcranial focused ultrasound stimulation was applied 2, 4, and 8 hours after occlusion. Ultrasound stimulation reduced edema volume, improved neurobehavioral outcomes, improved BBB integrity (enhanced tight junction protein ZO-1 expression and reduced IgG leakage), and reduced secretion of the inflammatory factors tumor necrosis factor-α and activation of matrix metalloproteinase-9 in the ischemic brain. Our results show that low-intensity ultrasound stimulation attenuated BBB disruption and edema formation, which suggests it may have therapeutic use in ischemic brain disease as a protector of BBB integrity.

Stroke subtype-dependent synapse elimination by reactive gliosis in mice

The pathological role of reactive gliosis in CNS repair remains controversial. In this study, using murine ischemic and hemorrhagic stroke models, we demonstrated that microglia/macrophages and astrocytes are differentially involved in engulfing synapses in the reactive gliosis region. By specifically deleting MEGF10 and MERTK phagocytic receptors, we determined that inhibiting phagocytosis of microglia/macrophages or astrocytes in ischemic stroke improved neurobehavioral outcomes and attenuated brain damage. In hemorrhagic stroke, inhibiting phagocytosis of microglia/macrophages but not astrocytes improved neurobehavioral outcomes. Single-cell RNA sequencing revealed that phagocytosis related biological processes and pathways were downregulated in astrocytes of the hemorrhagic brain compared to the ischemic brain. Together, these findings suggest that reactive microgliosis and astrogliosis play individual roles in mediating synapse engulfment in pathologically distinct murine stroke models and preventing this process could rescue synapse loss.

Plasma from healthy donors protects blood-brain barrier integrity via FGF21 and improves the recovery in a mouse model of cerebral ischaemia

Background

Healthy plasma therapy reverses cognitive deficits and promotes neuroplasticity in ageing brain disease. However, whether healthy plasma therapy improve blood–brain barrier integrity after stroke remains unknown.

Methods

Here, we intravenously injected healthy female mouse plasma into adult female ischaemic stroke C57BL/6 mouse induced by 90 min transient middle cerebral artery occlusion for eight consecutive days. Infarct volume, brain atrophy and neurobehavioural tests were examined to assess the outcomes of plasma treatment. Cell apoptosis, blood–brain barrier integrity and fibroblast growth factor 21 knockout mice were used to explore the underlying mechanism.

Results

Plasma injection improved neurobehavioural recovery and decreased infarct volume, brain oedema and atrophy after stroke. Immunostaining showed that the number of transferase dUTP nick end labelling⁺/NeuN⁺ cells decreased in the plasma-injected group. Meanwhile, plasma injection reduced ZO-1, occluding and claudin-5 tight junction gap formation and IgG extravasation at 3 days after ischaemic stroke. Western blot results showed that the FGF21 expression increased in the plasma-injected mice. However, using FGF21 knockout mouse plasma injecting to the ischaemic wild-type mice diminished the neuroprotective effects.

Conclusions

Our study demonstrated that healthy adult plasma treatment protected the structural and functional integrity of blood–brain barrier, reduced neuronal apoptosis and improved functional recovery via FGF21, opening a new avenue for ischaemic stroke therapy.