2-(2-Benzofuranyl)-2-Imidazoline Mediates Neuroprotection by Regulating the Neurovascular Unit Integrity in a Rat Model of Focal Cerebral Ischemia

m6A methylation: Critical roles in aging and neurological diseases

N6-methyladenosine (m6A) is the most abundant internal RNA modification in eukaryotic cells, which participates in the functional regulation of various biological processes. It regulates the expression of targeted genes by affecting RNA translocation, alternative splicing, maturation, stability, and degradation. As recent evidence shows, of all organs, brain has the highest abundance of m6A methylation of RNAs, which indicates its regulating role in central nervous system (CNS) development and the remodeling of the cerebrovascular system. Recent studies have shown that altered m6A levels are crucial in the aging process and the onset and progression of age-related diseases. Considering that the incidence of cerebrovascular and degenerative neurologic diseases increase with aging, the importance of m6A in neurological manifestations cannot be ignored. In this manuscript, we focus on the role of m6A methylation in aging and neurological manifestations, hoping to provide a new direction for the molecular mechanism and novel therapeutic targets.

Xueshuantong Improves Functions of Lymphatic Ducts and Modulates Inflammatory Responses in Alzheimer's Disease Mice

Recent studies have revealed significant contributions of lymphatic vessels (LVs) to vital functions of the brain, especially related to clearance of waste from the brain and immune responses in the brain. These studies collectively indicate that enhancing the functions of LVs may improve brain functions during brain aging and in Alzheimer’s disease (AD) where LV functions are impaired. However, it is currently unknown whether this enhancement can be achieved using small molecules. We have previously shown that a widely used Chinese herbal medicine Xueshuantong (XST) significantly improves functions and reduces pathology in AD transgenic mice associated with elevated cerebral blood flow (CBF). Here, we show that XST partially rescues deficits in lymphatic structures, improves clearance of amyloid-β (Aβ) from the brain, and reduces the inflammatory responses in the serum and brains of transgenic AD mice. In addition, we showed that this improvement in the lymphatic system occurs independently of elevated CBF, suggesting independent modulation and limited interaction between blood circulation and lymphatic systems. Moreover, XST treatment leads to a significant increase in GLT-1 level and a significantly lower level of MMP-9 and restores AQP4 polarity in APP/PS1 mice. These results provide the basis for further exploration of XST to enhance or restore LV functions, which may be beneficial to treat neurodegenerative diseases or promote healthy aging.

2-(2-Benzofuranyl)-2-Imidazoline Attenuates the Disruption of the Blood-Brain Barrier in EAE via NMDAR

Blood-brain barrier (BBB) disruption has been recognized as an early hallmark of multiple sclerosis (MS) pathology. Our previous studies have shown that 2-(2-Benzofuranyl)-2-imidazoline (2-BFI) protected against experimental autoimmune encephalomyelitis (EAE), a classic animal model of MS. However, the potential effects of 2-BFI on BBB permeability have not yet been evaluated in the context of EAE. Herein, we aimed to investigate the effect of 2-BFI on BBB permeability in both an animal model and an in vitro BBB model using TNF-α to imitate the inflammatory damage to the BBB in MS. In the animal model, 2-BFI reduced neurological deficits and BBB permeability in EAE mice compared with saline treatment. The Western blot results indicated that 2-BFI not only alleviated the loss of the tight junction protein occludin caused by EAE but also inhibited the activation of the NR1-ERK signaling pathway. In an in vitro BBB model, 2-BFI (100 μM) alleviated the TNF-α-induced increase in permeability and reduction in expression of occludin in monolayer bEnd.3 cells. Similar protective effects were also observed after treatment with the NMDAR antagonist MK801. The Western blot results showed that the TNF-α-induced BBB breakdown and increase in NMDAR subunit 1 (NR1) levels and ERK phosphorylation could be blocked by pretreatment with 2-BFI or MK801. However, no additional effect was observed on BBB permeability or the expression of occludin and p-ERK after pretreatment with both 2-BFI and MK801. Our study indicates that 2-BFI alleviates the disruption of BBB in the context of inflammatory injury similar to that of MS by targeting NMDAR1, as well as by likely activating the subsequent ERK signaling pathway. These results provide further evidence for 2-BFI as a potential drug for the treatment of MS.

The 2-(2-benzofuranyl)-2-imidazoline provides neuroprotection against focal cerebral ischemia-reperfusion injury in diabetic rats: Influence of microglia and possible mechanisms of action

Increased microglial NADPH oxidase (NOX₂) production may make an important contribution to the increased incidence and severity of ischemic stroke associated with diabetes. Imidazoline receptors are closely associated with neuroprotection, but the neuroprotective effects of the selective I₂-imidazoline receptor ligand 2-(2-benzofuranyl)-2-imidazoline (2BFI) in diabetes has not been established. The effect of 2BFI on microglial NOX₂ production was investigated using a co-culture of neurons and microglia, and the effect on cerebral ischemia-reperfusion (IR) injury was determined in diabetic rats. Garcia neurological scores, brain infarct volumes, brain water content, TUNEL staining, blood-brain barrier, and immunofluorescent labeling for microglia were evaluated. Western blots were used to determine gp91^phox and Tyr1472 expression. Anti-inflammatory cytokine (IL-10) and inflammatory cytokine secretion was determined using ELISA kits. The brain infarct volumes, TUNEL-positive neurons, expression of microglia, brain water content, blood-brain barrier structure damage, and gp91^phox and Tyr1472 expression were increased, the Garcia neurological scores were significantly decreased in the IR group, and 2BFI relieved these alterations. The IL-10 concentration was increased in the IR group; 2BFI significantly improved this increase. The neuron apoptosis and necrosis rates, and production of reactive oxygen species (ROS) and inflammatory cytokines, including IL-6, IL-8, TNF-α, and 8-iso-PGF2α, were significantly increased by high glucose stimulation combined with oxygen-glucose deprivation treatment, which were inhibited by 2BFI. The 2BFI ameliorated cerebral ischemia-reperfusion injury in diabetes and decreased neuron death in an in vitro model. The mechanism underlying these findings may be related to the decreased production of inflammatory factors and reactive oxygen species from microglia.

2-BFI attenuates ischemic injury by modulating mTOR signaling and neuroinflammation in rats

Ischemic stroke is one of the major diseases that cause mortality and morbidity of human beings, but there is still lack of effective treatment and prevention. We found that 2-(2-Benzofuranyl)-2-Imidazoline (2-BFI) is potently protective against stroke and acute inflammatory immune disease. Moreover, the mammalian target of rapamycin (mTOR) signaling contributes effectively to the modulation of post-stroke neuroinflammatory response. However, whether the protection of 2-BFI against ischemic injury is through mTOR-mediated neuroinflammatory response remains unestablished. Here, we used 2-BFI to treat ischemic rats induced by distal middle cerebral artery occlusion (dMCAO). We found that 2-BFI administration after dMCAO improved the neurological deficits and decreased the infarct volume. 2-BFI reduced phosphorylation of mTOR and p70S6, increased IL-10 and TGF-β, and decreased IFN-γ levels in ischemic rats. Our results demonstrated that 2-BFI attenuates ischemic injury by inhibiting the activation of mTOR signaling and modulating neuroinflammation after stroke in rats.

Benzoinum from Styrax tonkinensis (Pierre) Craib ex Hart exerts a NVU protective effect by inhibiting cell apoptosis in cerebral ischaemia rats

ETHNOPHARMACOLOGICAL RELEVANCE

Benzoinum (Styraceae) is a traditional Chinese medicine used to treat stroke and other cardio-cerebrovascular diseases for thousands of years. Benzoinum has also proven to have diverse pharmacological activity, but the neuroprotection mechanism of apoptosis in ischaemic stroke was not determined.

AIM OF THIS STUDY

To investigate the protective effect of a neurovascular unit (NVU) and the mechanisms of benzoinum on cerebral ischaemic rats.

MATERIALS AND METHODS

The neuroprotective activity of benzoinum against middle cerebral artery occlusion (MCAO)-induced cerebral ischaemic injury. Neurological scores, 2,3,5-Triphenyltetrazolium chloride (TTC) staining, and hematoxylin-eosin staining (HE) staining were conducted to evaluate the neurological damage. Infarction rate and denatured cell index (DCI) were also calculated. The ultrastructure of neuron and blood-brain-barrier (BBB) was observed by transmission electron microscopy (TEM). Immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect Bax, Bcl-2 and Caspase 3 expression. Furthermore, Claudin 5 also was detected through immunohistochemistry.

RESULTS

Benzoinum could significantly improve neurological function score and reduce cerebral infarction rate and DCI. In addition, benzoinum alleviated pathomorphological change and apoptosis in the brain tissue of MCAO rats. The results of TEM and claudin 5 expression of immunohistochemistry showed that benzoinum could play a neuroprotective effect in NVU. Also, benzoinum-enhanced Bcl2, and reduced Bax and Bax/Bcl-2 and Caspase 3, suggest that benzoinum provided a neuroprotective effect by inhibited cell apoptosis.

CONCLUSION

Benzoinum could play a neuroprotective role and regulate apoptosis for repair and stabilisation of NVU. This anti-apoptosis activity might be associated with the downregulation of Bax and Caspase 3, and the upregulation of Bcl2. Our present findings provide a promising medication for the treatment of ischaemic stroke.

Effect of acupuncture on neurovascular units after cerebral infarction in rats through PI3K/AKT signaling pathway

OBJECTIVE

To study the effect of acupuncture on neurovascular units after cerebral infarction (CI) in rats through the phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/AKT) signaling pathway.

METHODS

A total of 36 Sprague-Dawley rats were randomly divided into sham group (n = 12), model group (n = 12) and acupuncture group (n = 12). The external carotid artery was only exposed in model group, while the post-CI ischemia-reperfusion model was established using the suture method in the other 2 groups. After modeling, the rats in sham group and model group were fixed and sampled, while those in acupuncture group were treated with acupuncture intervention for 2 weeks and sampled. The neurological deficits of rats were evaluated using the Zea-Longa score, and the spatial learning and memory of rats were detected via water maze test. Moreover, the expressions of vascular endothelial growth factor (VEGF), growth associated protein-43 (GAP-43) and synuclein (SYN) in brain tissues were detected via immunohistochemistry, and the relative protein expressions of PI3K p85, PI3K p110 and p-AKT were detected via Western blotting. The messenger ribonucleic acid (mRNA) expressions of VEGF, GAP-43 and SYN were detected via quantitative polymerase chain reaction (qPCR).

RESULTS

The Zea-Longa score was significantly increased in model group and acupuncture group compared with that in sham group (p < 0.05), while it significantly declined in acupuncture group compared with that in model group (p < 0.05). The escape latency was significantly prolonged and the times of crossing platform were significantly reduced in model group and acupuncture group compared with those in sham group (p < 0.05), while the escape latency was significantly shortened and the times of crossing platform were significantly increased in acupuncture group compared with those in model group (p < 0.05). The positive expressions of VEGF, GAP-43 and SYN were obviously increased in model group and acupuncture group compared with those in sham group (p < 0.05), while they were obviously increased in acupuncture group compared with those in model group (p < 0.05). Besides, model group and acupuncture group had significantly higher relative protein expressions of PI3K p85, PI3K p110 and p-AKT than sham group (p < 0.05), while acupuncture group also had significantly higher relative protein expressions of PI3K p85, PI3K p110 and p-AKT than model group (p < 0.05). The relative mRNA expressions of VEGF, GAP-43 and SYN were remarkably increased in model group and acupuncture group compared with those in sham group (p < 0.05), while they were remarkably increased in acupuncture group compared with those in model group (p < 0.05).

CONCLUSION

Acupuncture promotes the repair of neurovascular units after CI in rats through activating the PI3K/AKT signaling pathway, thereby exerting a protective effect on neurovascular units.

The Neurovascular Unit: Focus on the Regulation of Arterial Smooth Muscle Cells

The neurovascular unit is a physiological unit present in the brain, which is constituted by elements of the nervous system (neurons and astrocytes) and the vascular system (endothelial and mural cells). This unit is responsible for the homeostasis and regulation of cerebral blood flow. There are two major types of mural cells in the brain, pericytes and smooth muscle cells. At the arterial level, smooth muscle cells are the main components that wrap around the outside of cerebral blood vessels and the major contributors to basal tone maintenance, blood pressure and blood flow distribution. They present several mechanisms by which they regulate both vasodilation and vasoconstriction of cerebral blood vessels and their regulation becomes even more important in situations of injury or pathology. In this review, we discuss the main regulatory mechanisms of brain smooth muscle cells and their contributions to the correct brain homeostasis.

1-Trifluoromethoxyphenyl-3-(1-Propionylpiperidin-4-yl) Urea Protects the Blood-Brain Barrier Against Ischemic Injury by Upregulating Tight Junction Protein Expression, Mitigating Apoptosis and Inflammation In Vivo and In Vitro Model

We previously have revealed that 1-trifluoromethoxyphenyl-3-(1- propionylpiperidin-4-yl) urea (TPPU), as a soluble epoxide hydrolase (sEH) inhibitor can reduce infarct volume, protect blood-brain barrier (BBB) and brain against ischemic injury in rats. Here, we investigated the potential mechanisms of TPPU on BBB integrity in both in permanent middle cerebral artery occlusion (pMCAO) rat model and in oxygen-glucose deprivation/reperfusion (OGD/R)-induced human brain microvascular endothelial cells (HBMVECs) model. In pMCAO rat, TPPU administration decreased brain edema and Evans blue content, increased tight junction proteins (TJs) expression of claudin-5, occludin, and zonula occludens-1 (ZO-1). In OGD/R model, OGD/R significantly increased permeability and cell apoptosis, downregulated the expression of claudin-5, ZO-1, occludin, and lymphoma (Bcl)-2. Notably, TPPU pretreatment effectively protected the BBB integrity by reducing the permeability, promoting expression of claudin-5, ZO-1, occluding and Bcl-2, mitigating reactive oxygen species (ROS) injury and release of interleukin-1β (IL-1β), IL-6β, and tumor necrosis factor-α (TNF-α), downregulating expression of matrix metalloproteinase-9 (MMP-9), MMP-2, bcl-2-associated X protein (Bax), IL-1β, IL-6β, and TNF-α. Moreover, OGD/R induced the up-regulation of p-p65, p-IκB, and p-p38, which were effectively decreased after TPPU pretreatment in comparison with that of the OGD/R group. Furthermore, pyrrolidinedithiocarbamate (PDTC, a selective inhibitor of NF-κB p65) not only alleviated the OGD/R-induced HBMVECs injury and permeability, but also reduced the expression of TNF-α, IL-6, IL-1β, p-p65, and p-IκB, and the protective effect of PDTC was equivalent to that of TPPU. These results indicate that TPPU protects BBB integrity against ischemic injury by multiple protective mechanisms, at least in part, by reducing ROS, inflammation, apoptosis, and suppressing the nuclear factor-κB (NF-κB) and p38 signaling pathways.

Role of the neurovascular unit in the process of cerebral ischemic injury

Cerebral ischemic injury exhibits both high morbidity and mortality worldwide. Traditional research of the pathogenesis of cerebral ischemic injury has focused on separate analyses of the involved cell types. In recent years, the neurovascular unit (NVU) mechanism of cerebral ischemic injury has been proposed in modern medicine. Hence, more effective strategies for the treatment of cerebral ischemic injury may be provided through comprehensive analysis of brain cells and the extracellular matrix. However, recent studies that have investigated the function of the NVU in cerebral ischemic injury have been insufficient. In addition, the metabolism and energy conversion of the NVU depend on interactions among multiple cell types, which make it difficult to identify the unique contribution of each cell type. Therefore, in the present review, we comprehensively summarize the regulatory effects and recovery mechanisms of four major cell types (i.e., astrocytes, microglia, brain-microvascular endothelial cells, and neurons) in the NVU under cerebral ischemic injury, as well as discuss the interactions among these cell types in the NVU. Furthermore, we discuss the common signaling pathways and signaling factors that mediate cerebral ischemic injury in the NVU, which may help to provide a theoretical basis for the comprehensive elucidation of cerebral ischemic injury.

Combined Treatment With 2-(2-Benzofu-Ranyl)-2-Imidazoline and Recombinant Tissue Plasminogen Activator Protects Blood-Brain Barrier Integrity in a Rat Model of Embolic Middle Cerebral Artery Occlusion

Recombinant tissue plasminogen activator (rt-PA) is used to treat acute ischemic stroke but is only effective if administered within 4.5 h after stroke onset. Delayed rt-PA treatment causes blood-brain barrier (BBB) disruption and hemorrhagic transformation. The compound 2-(-2-benzofuranyl)-2-imidazoline (2-BFI), a newly discovered antagonist of high-affinity postsynaptic N-methyl-D-aspartate (NMDA) receptors, has been shown to have neuroprotective effects in ischemia. Here, we investigated whether combining 2-BFI and rt-PA can ameliorate BBB disruption and prolong the therapeutic window in a rat model of embolic middle cerebral artery occlusion (eMCAO). Ischemia was induced in male Sprague Dawley rats by eMCAO, after which they were treated with 2-BFI (3 mg/kg) at 0.5 h in combination with rt-PA (10 mg/kg) at 6 or 8 h. Control rats were treated with saline or 2-BFI or rt-PA. Combined therapy with 2-BFI and rt-PA (6 h) reduced the infarct volume, denatured cell index, BBB permeability, and brain edema. This was associated with increased expression of aquaporin 4 (AQP4) and tight junction proteins (occludin and ZO-1) and downregulation of intercellular adhesion molecule 1 (ICAM-1) and matrix metalloproteinases 2 and 9 (MMP2 and MMP9). We conclude that 2-BFI protects the BBB from damage caused by delayed rt-PA treatment in ischemia. 2-BFI may therefore extend the therapeutic window up to 6 h after stroke onset in rats and may be a promising therapeutic strategy for humans. However, mechanisms to explain the effects oberved in the present study are not yet elucidated.

Protective Effects of the Soluble Epoxide Hydrolase Inhibitor 1-Trifluoromethoxyphenyl-3-(1-Propionylpiperidin-4-yl) Urea in a Rat Model of Permanent Middle Cerebral Artery Occlusion

Acute ischemic stroke is a serious disease that endangers human health. In our efforts to develop an effective therapy, we previously showed that the potent, highly selective inhibitor of soluble epoxide hydrolase called 1-trifuoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) protects the brain against focal ischemia in rats. Here we explored the mechanism of TPPU action by assessing whether it could preserve blood-brain barrier integrity and reduce apoptosis in the brain during permanent middle cerebral artery occlusion in male Sprague-Dawley rats. TPPU administration at the onset of stroke and once daily thereafter led to smaller infarct volume and brain edema as well as milder neurological deficits. TPPU significantly inhibited the activity of soluble epoxide hydrolase and matrix metalloproteases 2 and 9, reducing 14,15-DHET levels, while increasing expression of tight junction proteins. TPPU decreased numbers of apoptotic cells by down-regulating the pro-apoptotic proteins BAX and Caspase-3, while up-regulating the anti-apoptotic protein BCL-2. Our results suggest that TPPU can protect the blood-brain barrier and reduce the apoptosis of brain tissue caused by ischemia.

NLRP3 inflammasome contributes to neurovascular unit damage in stroke

Recently, a wealth of information has emerged connecting the activation of the NLRP3 (NOD-like receptor family pyrin domain-containing 3) inflammasome to stroke pathogenesis, although the exact influence of the NLRP3 inflammasome on stroke is still in the stage of preliminary study and is awaiting further confirmation. In this paper, we will review the structure, assembly and activation of the NLRP3 inflammasome and its expression in the neurovascular units and will speculate on its possible roles in neurovascular injury post-stroke. Evidence on this topic suggests that targeting NLRP3-mediated inflammation at multiple levels may provide a new therapeutic strategy to prevent the deterioration of neurovascular units after stroke. However, many aspects of the biological link between the NLRP3 inflammasome and stroke remain ill-defined or even completely unknown. As fresh insights come to light regarding the NLRP3 inflammasome, the opportunities to develop new therapeutic strategies for stroke patients are expected to improve accordingly.

Protective effects of 2-(2-benzonfuranyl)-2-imidazoline combined with tissue plasminogen activator after embolic stroke in rats

Stroke is the third leading cause of death and disability in developing countries. The effective therapy for acute ischemic stroke is thrombolysis with recombinant tissue plasminogen activator (rt-PA) within 4.5 h of stroke onset. An effective post-ischemic neuroprotectant would extend the advantages of rt-PA, and protect against complications of thrombolysis. We previously reported that 2-(2-benzofuranyl)-2-imidazoline (2-BFI), a newly discovered ligand for high-affinity type 2 imidazoline receptor (I2R), provides neuroprotection against ischemic stroke in rats. Here we investigated the protective effects of 2-BFI in combination with delayed intravenous rt-PA after stroke induced by embolic middle cerebral artery occlusion (eMCAO) in rats. Infarct size was determined using 2,3,5-triphenyltrazolium chloride staining, while neurological deficit was assessed based on neurological score. Numbers of apoptotic cells in vivo were estimated using TUNEL stain, and expression of the pro-apoptotic protein BAX and anti-apoptotic protein BCL-2 were quantified by Western blotting. The results showed that 2-BFI (3 mg/kg) administered at 0.5 h after embolic MCAO combined with rt-PA (10 mg/kg) administered at 6 h reduced brain infarct size, mitigated neurological deficit, decreased the number of TUNEL-positive cells, down-regulated BAX expression, and up-regulated BCL-2 expression. These findings suggest that 2-BFI may extend the therapeutic window of rt-PA to 6 h after embolic stroke onset in rats.