Sustained release of vascular endothelial growth factor A and basic fibroblast growth factor from nanofiber membranes reduces oxygen/glucose deprivation-induced injury to neurovascular units

Upregulation of vascular endothelial growth factor A/basic fibroblast growth factor(VEGFA/b FGF)expression in the penumbra of cerebral ischemia can increase vascular volume,reduce lesion volume,and enhance neural cell proliferation and differentiation,thereby exerting neuroprotective effects.However,the beneficial effects of endogenous VEGFA/b FGF are limited as their expression is only transiently increased.In this study,we generated multilayered nanofiber membranes loaded with VEGFA/b FGF using layer-by-layer self-assembly and electrospinning techniques.We found that a membrane containing 10 layers had an ideal ultrastructure and could efficiently and stably release growth factors for more than 1 month.This 10-layered nanofiber membrane promoted brain microvascular endothelial cell tube formation and proliferation,inhibited neuronal apoptosis,upregulated the expression of tight junction proteins,and improved the viability of various cellular components of neurovascular units under conditions of oxygen/glucose deprivation.Furthermore,this nanofiber membrane decreased the expression of Janus kinase-2/signal transducer and activator of transcription-3(JAK2/STAT3),Bax/Bcl-2,and cleaved caspase-3.Therefore,this nanofiber membrane exhibits a neuroprotective effect on oxygen/glucose-deprived neurovascular units by inhibiting the JAK2/STAT3 pathway.

Fingolimod protects against neurovascular unit injury in a rat model of focal cerebral ischemia/reperfusion injury

Recent research on the underlying mechanisms of cerebral ischemia indicates that the neurovascular unit can be used as a novel subject for general surveys of neuronal damage and protein mechanisms.Fingolimod(FTY-720)is a newly developed immunosuppressant isolated from Cordyceps sinensis that exhibits a wide range of biological activities,and has recently attracted much attention for the treatment of ischemic cerebrovascular diseases.In the current research,the role of FTY-720 and its possible mechanisms were assessed from an neurovascular unit perspective using a rat cerebral ischemia model.Our results revealed that FTY-720 markedly decreased infarct volume,promoted neurological function recovery,and weakened the blood-brain barrier permeability of ischemic rats.The protective roles of FTY-720 in ischemic stroke are ascribed to a combination of sphingosin-1-phosphate receptor-1 and reduced expression of sphingosin-1-phosphate receptor-1 in microvessels and reduction of interleukin-17A protein levels.These findings indicate that FTY-720 has promise as a new therapy for neurovascular protection and functional recovery after ischemic stroke.

Dysfunction of the neurovascular unit in brain aging

An emerging concept termed the neurovascular unit(NVU)underlines neurovascular coupling.It has been reported that NVU impairment can result in neurodegenerative diseases,such as Alzheimer's disease and Parkinson's disease.Aging is a complex and irreversible process caused by programmed and damage-related factors.Loss of biological functions and increased susceptibility to additional neurodegenerative diseases are major characteristics of aging.In this review,we describe the basics of the NVU and discuss the effect of aging on NVU basics.Furthermore,we summarize the mechanisms that increase NVU susceptibility to neurodegenerative diseases,such as Alzheimer's disease and Parkinson's disease.Finally,we discuss new treatments for neurodegenerative diseases and methods of maintaining an intact NVU that may delay or diminish aging.

Protective effect of borneol combined with safflower on neurovascular unit in rats with ischemic stroke

Background:Compatibility is a characteristic of the clinical application of traditional Chinese medicine,often leading to enhanced therapeutic effects.In the treatment of cerebral ischemia,blood-activating and open orifices herbs are frequently used individually;however,their combination is not commonly practiced.This study aims to investigate the impact of combining safflower and borneol as examples of open orifices herbs and blood-activating herbs on the neurovascular unit in rats with ischemic stroke.The objective is to determine whether this combination exhibits superior therapeutic efficacy compared to using borneol or safflower alone while exploring its underlying mechanism.These findings may provide novel insights for clinical treatments.Methods:SD male rats were randomly divided into 6 groups:sham operation group,model group,borneol group(0.1 g/kg),safflower group(5 g/kg),borneol combined with safflower group(0.1 g/kg+5 g/kg)and nimodipine group(0.01 g/kg).The middle cerebral artery cerebral ischemia(MCAO)model were prepared after continuous intragastric administration for 7 days in each group,the neurological function of each group were scored 24h after operation,and water content in brain tissue were measured by weighing method.The activity of superoxide dismutase(SOD)and the contents of nitric oxide(NO)and malondialdehyde(MDA)in brain tissue and serum were determined by spectrophotometry,and the mRNA expressions of matrix metalloproteinase 2(MMP-2),tight junction protein 1(ZO-1),vascular endothelial growth factor(VEGF)and brain-derived neurotrophic factor(BDNF)were detected by Real time PCR.Result:Compared with the model group,the group treated with borneol combined with safflower exhibited a significant decrease in the neural function score of MCAO rats(P<0.01).Additionally,it led to a reduction in brain tissue water content(P<0.01),elevated SOD activity,and reduced levels of NO and MDA in both serum and brain tissue(P<0.01 or P<0.05).Moreover,this treatment resulted in a decrease in the mRNA expression of MMP-2 and an increase in ZO-1 in brain tissue,along with an increase in the mRNA expression of VEGF and BDNF(P<0.01).Conclusion:Borneol combined with safflower demonstrates a protective effect on the neurovascular unit in rats with ischemic stroke.This effect is likely associated with increased SOD activity,reduced MDA and NO content in both serum and brain tissue of MCAO rats,and a decrease in MMP-2 mRNA expression in brain tissue,coupled with an increase in ZO-1,VEGF,and BDNF mRNA expression.These effects were superior to those observed with borneol or safflower administered alone.

Houshiheisan compound prescription protects neurovascular units after cerebral ischemia

Houshiheisan is composed of wind-dispelling （chrysanthemun fower, divaricate saposhnikovia root, Manchurian wild ginger, cassia twig, Szechwan lovage rhizome, and platycodon root） and deficiency-nourishing （ginseng, Chinese angelica, large-head atractylodes rhizome, Indian bread, and zingiber） drugs. In this study, we assumed these drugs have protective effects against cerebral ischemia, on neurovascular units. Houshiheisan was intragastrically administered in a rat model of focal cerebral ischemia. Hematoxylin-eosin staining, transmission electron microscopy, immu- nofluorescence staining, and western blot assays showed that Houshiheisan reduced pathological injury to the ischemic penumbra, protected neurovascular units, visibly up-regtflated neuronal nuclear antigen expression, and down-regulated amyloid precursor protein and amyloid-[3 42 expression. Wind-dispelling and deficiency-nourishing drugs maintained NeuN expression to varying degrees, but did not affect amyloid precursor protein or amyloid-~ 42 expression in the ischemic penumbra. Our results suggest that the compound prescription Houshiheisan effectively suppresses abnormal amyloid precursor protein accumulation, reduces amyloid substance depo- sition, maintains stabilization of the internal environment of neurovascular units, and minimizes injury to neurovascular units in the ischemic penumbra.

Abnormal Glu/mGluR2/3/PI3K pathway in the hippocampal neurovascular unit leads to diabetesrelated depression

Our previous studies have shown that glutamate and hippocampal neuron apoptosis are key signals and direct factors associated with diabetes-related depression,and structural and functional damage to the hippocampal neurovascular unit has been associated with diabetesrelated depression.However,the underlying mechanism remains unclear.We hypothesized that diabetes-related depression might be associated with the glutamate(Glu)/metabotropic glutamate receptor2/3(mGluR2/3)/phosphoinositide 3-kinase(PI3K)pathway,activated by glucocorticoid receptors in the hippocampal neurovascular unit.To test this hypothesis,rat hippocampal neurovascular unit models,containing hippocampal neurons,astrocytes,and brain microvascular endothelial cells,were treated with 150 mM glucose and 200μM corticosterone,to induce diabetes-related depression.Our results showed that under conditions of diabetes complicated by depression,hippocampal neurovascular units were damaged,leading to decreased barrier function;elevated Glu levels;upregulated glucocorticoid receptor,vesicular glutamate transporter 3(VGLUT-3),and metabotropic glutamate receptor 2/3(mGluR2/3)expression;downregulated excitatory amino acid transporter 1(EAAT-1)expression;and alteration of the balance of key proteins associated with the extracellular signal-regulated kinase(ERK)/glial cell-derived neurotrophic factor(GDNF)/PI3K signaling pathway.Moreover,the viability of neurons was dramatically reduced in the model of diabetes-related depression,and neuronal apoptosis,and caspase-3 and caspase-9 expression levels,were increased.Our results suggest that the Glu/mGluR2/3/PI3K pathway,induced by glucocorticoid receptor activation in the hippocampal neurovascular unit,may be associated with diabetes-related depression.This study was approved by the Laboratory Animal Ethics Committee of The First Hospital of Hunan University of Chinese Medicine,China(approval No.HN-ZYFY-2019-11-12)on November 12,2019.

Toward three-dimensional in vitro models to study neurovascular unit functions in health and disease

The high metabolic demands of the brain require an efficient vascular system to be coupled with neural activity to supply adequate nutrients and oxygen.This supply is coordinated by the action of neurons,glial and vascular cells,known collectively as the neurovascular unit,which temporally and spatially regulate local cerebral blood flow through a process known as neurovascular coupling.In many neurodegenerative diseases,changes in functions of the neurovascular unit not only impair neurovascular coupling but also permeability of the blood-brain barrier,cerebral blood flow and clearance of waste from the brain.In order to study disease mechanisms,we need improved physiologicallyrelevant human models of the neurovascular unit.Advances towards modeling the cellular complexity of the neurovascular unit in vitro have been made using stem-cell derived organoids and more recently,vascularized organoids,enabling intricate studies of non-cell autonomous processes.Engineering and design innovations in microfluidic devices and tissue engineering are progressing our ability to interrogate the cerebrovasculature.These advanced models are being used to gain a better understanding of neurodegenerative disease processes and potential therapeutics.Continued innovation is required to build more physiologically-relevant models of the neurovascular unit encompassing both the cellular complexity and designed features to interrogate neurovascular unit functionality.

Protective Effects of Activated Protein C on Neurovascular Unit in a Rat Model of Intrauterine Infection-Induced Neonatal White Matter Injury

Summary： Activated protein C （APC）, a natural anticoagulant, has been reported to exert direct vascu- loprotective, neural protective, anti-inflammatory, and proneurogenic activities in the central nervous system. This study was aimed to explore the neuroprotective effects and potential mechanisms of APC on the neurovascular unit of neonatal rats with intrauterine infection-induced white matter injury. In- traperitoneal injection of 300 ~tg/kg lipopolysaccharide （LPS） was administered consecutively to preg- nant Sprague-Dawley rats at embryonic days 19 and 20 to establish the rat model of intrauterine infec- tion-induced white matter injury. Control rats were injected with an equivalent amount of sterile saline on the same time. APC at the dosage of 0.2 mg/kg was intraperitoneally injected to neonatal rats imme- diately after birth. Brain tissues were collected at postnatal day 7 and stained with hematoxylin and eo- sin （H＆E）. Immunohistochemistry was used to evaluate myelin basic protein （MBP） expression in the periventricular white matter region. Blood-brain barrier （BBB） permeability and brain water content ~were measured using Evens Blue dye and wet/dry weight method. Double immunofluorescence staining and real-time quantitative PCR were performed to detect microglial activation and the expression of protease activated receptor 1 （PAR1）. Typical pathological changes of white matter injury were ob- served in rat brains exposed to LPS, and MBP expression in the periventricular region was significantly decreased. BBB was disrupted and the brain water content was increased. Microglia were largely acti- vated and the mRNA and protein levels of PAR1 were elevated. APC administration ameliorated the pathological lesions of the white matter and increased MBP expression. BBB permeability and brain water content were reduced. Microglia activation was inhibited and the PAR1 mRNA and protein ex- pression levels were both down-regulated. Our results suggested that APC exerted neuroprotective ef- fects on multiple components of the neurovascular unit in neonatal rats with intrauterine infec- tion-induced white matter injury, and the underlying mechanisms might involve decreased expression of PAR1.

Exogenous platelet-derived growth factor improves neurovascular unit recovery after spinal cord injury

The blood-spinal cord barrier plays a vital role in recovery after spinal cord injury.The neurovascular unit concept emphasizes the relationship between nerves and vessels in the brain,while the effect of the blood-spinal cord barrier on the neurovascular unit is rarely reported in spinal cord injury studies.Mouse models of spinal cord injury were established by heavy object impact and then immediately injected with plateletderived growth factor(80μg/kg)at the injury site.Our results showed that after platelet-derived growth factor administration,spinal cord injury,neuronal apoptosis,and blood-spinal cord barrier permeability were reduced,excessive astrocyte proliferation and the autophagyrelated apoptosis signaling pathway were inhibited,collagen synthesis was increased,and mouse locomotor function was improved.In vitro,human umbilical vein endothelial cells were established by exposure to 200μM H2O2.At 2 hours prior to injury,in vitro cell models were treated with 5 ng/mL platelet-derived growth factor.Our results showed that expression of blood-spinal cord barrier-related proteins,including Occludin,Claudin 5,andβ-catenin,was significantly decreased and autophagy was significantly reduced.Additionally,the protective effects of platelet-derived growth factor could be reversed by intraperitoneal injection of 80 mg/kg chloroquine,an autophagy inhibitor,for 3 successive days prior to spinal cord injury.Our findings suggest that platelet-derived growth factor can promote endothelial cell repair by regulating autophagy,improve the function of the blood-spinal cord barrier,and promote the recovery of locomotor function post-spinal cord injury.Approval for animal experiments was obtained from the Animal Ethics Committee,Wenzhou Medical University,China(approval No.wydw2018-0043)in July 2018.

A neurovascular unit-on-a-chip:culture and differentiation of human neural stem cells in a three-dimensional microfluidic environment

Biological studies typically rely on a simple monolayer cell culture,which does not reflect the complex functional characteristics of human tissues and organs,or their real response to external stimuli.Microfluidic technology has advantages of high-throughput screening,accurate control of the fluid velocity,low cell consumption,long-term culture,and high integration.By combining the multipotential differentiation of neural stem cells with high throughput and the integrated characteristics of microfluidic technology,an in vitro model of a functionalized neurovascular unit was established using human neural stem cell-derived neurons,astrocytes,oligodendrocytes,and a functional microvascular barrier.The model comprises a multi-layer vertical neural module and vascular module,both of which were connected with a syringe pump.This provides controllable conditions for cell inoculation and nutrient supply,and simultaneously simulates the process of ischemic/hypoxic injury and the process of inflammatory factors in the circulatory system passing through the blood-brain barrier and then acting on the nerve tissue in the brain.The in vitro functionalized neurovascular unit model will be conducive to central nervous system disease research,drug screening,and new drug development.

Construction and imaging of a neurovascular unit model

In 2001,the concept of the neurovascular unit was introduced at the Stroke Progress Review Group meeting.The neurovascular unit is an important element of the health and disease status of blood vessels and nerves in the central nervous system.Since then,the neurovascular unit has attracted increasing interest from research teams,who have contributed greatly to the prevention,treatment,and prognosis of stroke and neurodegenerative diseases.However,additional research is needed to establish an efficient,low-cost,and low-energy in vitro model of the neurovascular unit,as well as enable noninvasive observation of neurovascular units in vivo and in vitro.In this review,we first summarize the composition of neurovascular units,then investigate the efficacy of different types of stem cells and cell culture methods in the construction of neurovascular unit models,and finally assess the progress of imaging methods used to observe neurovascular units in recent years and their positive role in the monitoring and investigation of the mechanisms of a variety of central nervous system diseases.

Structural and functional damage to the hippocampal neurovascular unit in diabetes-related depression

Previous studies have shown that models of depression exhibit structural and functional changes to the neurovascular unit. Thus, we hypothesized that diabetes-related depression might be associated with damage to the hippocampal neurovascular unit. To test this hypothesis, neurons, astrocytes and endothelial cells were isolated from the brain tissues of rat embryos and newborn rats. Hippocampal neurovascular unit co-cultures were produced using the Transwell chamber co-culture system. A model of diabetes-related depression was generated by adding 150 mM glucose and 200 μM corticosterone to the culture system and compared with the neuron + astrocyte and astrocyte + endothelial cell co-culture systems. Western blot assay was used to measure levels of structural proteins in the hippocampal neurovascular unit co-culture system. Levels of basic fibroblast growth factor, angiogenic factor 1, glial cell line–derived neurotrophic factor, transforming growth factor β1, leukemia inhibitory factor and 5-hydroxytryptamine in the hippocampal neurovascular unit co-culture system were measured by enzyme-linked immunosorbent assay. Flow cytometry and terminal deoxynucleotidyl transferase(TdT)-mediated dUTP nick end labeling staining was used to assess neuronal apoptosis in the hippocampal neurovascular unit. The neurovascular unit triple cell co-culture system had better barrier function and higher levels of structural and secretory proteins than the double cell co-culture systems. In comparison, in the model of diabetes-related depression, the neurovascular unit was damaged with decreased barrier function, poor structural integrity and impaired secretory function. Moreover, neuronal apoptosis was markedly increased, and 5-hydroxytryptamine levels were reduced. These results suggest that diabetes-related depression is associated with structural and functional damage to the neurovascular unit. Our findings provide a foundation for further studies on the pathogenesis of diabetes-related depression.

Hyodeoxycholic acid protects the neurovascular unit against oxygen-glucose deprivation and reoxygenation-induced injury in vitro

Calculus bovis is commonly used for the treatment of stroke in traditional Chinese medicine. Hyodeoxycholic acid(HDCA) is a bioactive compound extracted from calculus bovis. When combined with cholic acid, baicalin and jas-minoidin, HDCA prevents hypoxia-reoxygenation-induced brain injury by suppressing endoplasmic reticulum stress-mediated apoptotic signaling. However, the effects of HDCA in ischemic stroke injury have not yet been studied. Neurovascular unit(NVU) dysfunction occurs in ischemic stroke. Therefore, in this study, we investigated the effects of HDCA on the NVU under ischemic conditions in vitro. We co-cultured primary brain microvascular endothelial cells, neurons and astrocytes using a transwell chamber co-culture system. The NVU was pre-treated with 10.16 or 2.54 μg/mL HDCA for 24 hours before exposure to oxygen-glucose deprivation for 1 hour. The cell counting kit-8 assay was used to detect cell activity. Flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling were used to assess apoptosis. Enzyme-linked immunosorbent assay was used to measure the expression levels of inflammatory cytokines, including interleukin-1β, interleukin-6 and tumor necrosis factor-α, and neurotrophic factors, including brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor. Oxidative stress-related factors, such as superoxide dismutase, nitric oxide, malondialdehyde and γ-glutamyltransferase, were measured using kits. Pretreatment with HDCA significantly decreased blood-brain barrier permeability and neuronal apoptosis, significantly increased transendothelial electrical resistance and γ-glutamyltransferase activity, attenuated oxidative stress damage and the release of inflammatory cytokines, and increased brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor expression. Our findings suggest that HDCA maintains NVU morphological integrity and function by modulating inflammation, oxidation stress, apoptosis, and the expression of neurotrophic factors. Therefore, HDCA may have therapeutic potential in the clinical management of ischemic stroke. This study was approved by the Ethics Committee of Experimental Animals of Beijing University of Chinese Medicine(approval No. BUCM-3-2016040201-2003) in April 2016.

Efficacy of Sailuotong(塞络通)on neurovascular unit in amyloid precursor protein/presenilin-1 transgenic mice with Alzheimer's disease

OBJECTIVE:To discuss the influence of Sailuotong(塞络通,SLT)on the Neurovascular Unit(NVUs)of amyloid precursor protein(APP)/presenilin-1(PS1)mice and evaluate the role of gas supplementation in activating blood circulation during the progression of Alzheimer's disease(AD).METHODS:The mice were allocated into the following nine groups:(a)the C57 Black(C57BL)sham-operated group(control group),(b)ischaemic treatment in C57BL mice(the C57 ischaemic group),(c)the APP/PS1 sham surgery group(APP/PS1 model group),(d)ischaemic treatment in APP/PS1 mice(APP/PS1 ischaemic group),(e)C57BL mice treated with aspirin following ischaemic treatment(C57BL ischaemic+aspirin group),(f)C57BL mice treated with SLT following ischaemic treatment(C57BL ischaemic+SLT group),(g)APP/PS1 mice treated with SLT(APP/PS1+SLT group),(h)APP/PS1 mice treated with donepezil hydrochloride following ischaemic treatment(APP/PS1 ischaemic+donepezil hydrochloride group)and(i)APP/PS1 mice treated with SLT following ischaemic treatment(APP/PS1 ischaemic+SLT group).The ischaemic model was established by operating on the bilateral common carotid arteries and creating a microembolism.The Morris water maze and step-down tests were used to detect the spatial behaviour and memory ability of mice.The hippocampus of each mouse was observed by haematoxylin and eosin(HE)and Congo red staining.The ultrastructure of NVUs in each group was observed by electron microscopy,and various biochemical indicators were detected by enzymelinked immunosorbent assay(ELISA).The protein expression level was detected by Western blot.The mRNA expression was detected by quantitative real-time polymerase chain reaction(qRT-PCR).RESULTS:The results of the Morris water maze and step-down tests showed that ischemia reduced learning and memory in the mice,which were restored by SLT.The results of HE staining showed that SLT restored the pathological changes of the NVUs.The Congo red staining results revealed that SLT also improved the scattered orange-red sediments in the upper cortex and hippocampus of the APP/PS1 and APP/PS1 ischaemic mice.Furthermore,SLT significantly reduced the content of Aβ,improved the vascular endothelium and repaired the mitochondrial structures.The ELISA detection,western blot detection and qRT-PCR showed that SLT significantly increased the vascular endothelial growth factor(VEGF),angiopoietin and basic fibroblast growth factor,as well as the levels of gene and protein expression of low-density lipoprotein receptor-related protein-1(LRP-1)and VEGF in brain tissue.CONCLUSIONS:By increasing the expression of VEGF,SLT can promote vascular proliferation,up-regulate the expression of LRP-1,promote the clearance of Aβand improve the cognitive impairment of APP/PS1 mice.These results confirm that SLT can improve AD by promoting vascular proliferation and Aβclearance to protect the function of NVUs.

Neurovascular unit in diabetic retinopathy:pathophysiological roles and potential therapeutical targets

Diabetic retinopathy(DR),one of the common complications of diabetes,is the leading cause of visual loss in working-age individuals in many industrialized countries.It has been traditionally regarded as a purely microvascular disease in the retina.However,an increasing number of studies have shown that DR is a complex neurovascular disorder that affects not only vascular structure but also neural tissue of the retina.Deterioration of neural retina could precede microvascular abnormalities in the DR,leading to microvascular changes.Furthermore,disruption of interactions among neurons,vascular cells,glia and local immune cells,which collectively form the neurovascular unit,is considered to be associated with the progression of DR early on in the disease.Therefore,it makes sense to develop new therapeutic strategies to prevent or reverse retinal neurodegeneration,neuroinflammation and impaired cell-cell interactions of the neurovascular unit in early stage DR.Here,we present current perspectives on the pathophysiology of DR as a neurovascular disease,especially at the early stage.Potential novel treatments for preventing or reversing neurovascular injuries in DR are discussed as well.

Neurovascular unit in diabetic retinopathy:pathophysiological roles and potential therapeutical targets

Diabetic retinopathy(DR),one of the common complications of diabetes,is the leading cause of visual loss in working-age individuals in many industrialized countries.It has been traditionally regarded as a purely microvascular disease in the retina.However,an increasing number of studies have shown that DR is a complex neurovascular disorder that affects not only vascular structure but also neural tissue of the retina.Deterioration of neural retina could precede microvascular abnormalities in the DR,leading to microvascular changes.Furthermore,disruption of interactions among neurons,vascular cells,glia and local immune cells,which collectively form the neurovascular unit,is considered to be associated with the progression of DR early on in the disease.Therefore,it makes sense to develop new therapeutic strategies to prevent or reverse retinal neurodegeneration,neuroinflammation and impaired cell-cell interactions of the neurovascular unit in early stage DR.Here,we present current perspectives on the pathophysiology of DR as a neurovascular disease,especially at the early stage.Potential novel treatments for preventing or reversing neurovascular injuries in DR are discussed as well.

Effects of Ferulic Acid on Regulating the Neurovascular Unit:Implications for Ischemic Stroke Treatment

Ferulic acid(FA)is a phenolic phytochemical with antioxidant and anti-inflammatory pharmacological effects.In recent years,the neuroprotective effects of FA have been studied extensively.Many researchers have attempted to use FA to prevent and treat neurological diseases and have made some progress.This paper mainly collated the study of the protective effect of FA on stroke and summarized the protective effect of FA on ischemic stroke and the potential protective effects of FA on neurovascular units.

Iptakalim,an ATP-sensitive potassium channel opener,confers neuroprotection against cerebral ischemia/reperfusion injury in rats by protecting neurovascular unit cells

Objective:To investigate the role of iptakalim,an ATP-sensitive potassium channel opener,in transient cerebral ischemia/reperfusion (I/R) injury and its involved mechanisms.Methods:Intraluminal occlusion of middle cerebral artery (MCAO) in a rat model was used to investigate the effect of iptakalim at different time points.Infarct volume was measured by staining with 2,3,5-triphenyltetrazolium chloride,and immunohistochemistry was used to evaluate the expressions of Bcl-2 and Bax.In vitro,neurovascular unit (NVU) cells,including rat primary cortical neurons,astrocytes,and cerebral microvascular endothelial cells,were cultured and underwent oxygen-glucose deprivation (OGD).The protective effect of iptakalim on NVU cells was investigated by cell viability and injury assessments,which were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and release of lactate dehydrogenase.Caspase-3,Bcl-2 and Bax mRNA expressions were evaluated by real-time polymerase chain reaction (PCR).Results:Administration of iptakalim 0 or 1 h after reperfusion significantly reduced infarct volumes,improved neurological scores,and attenuated brain edema after cerebral I/R injury.Iptakalim treatment (0 h after reperfusion) also reduced caspase-3 expression and increased the ratio of Bcl-2 to Bax by immunohistochemistry.Iptakalim inhibited OGD-induced cell death in cultured neurons and astrocytes,and lactate dehydrogenase release from cerebral microvascular endothelial cells.Iptakalim reduced mRNA expression of caspase-3 and increased the ratio of Bcl-2 to Bax in NVU cells.Conclusions:Iptakalim confers neuroprotection against cerebral I/R injury by protecting NVU cells via inhibiting of apoptosis.

Impact of apolipoprotein E isoforms on sporadic Alzheimer's disease:beyond the role of amyloid beta

The impact of apolipoprotein E(ApoE)isoforms on sporadic Alzheimer's disease has long been studied;however,the influences of apolipoprotein E gene(APOE)on healthy and pathological human brains are not fully understood.ApoE exists as three common isoforms(ApoE2,ApoE3,and ApoE4),which differ in two amino acid residues.Traditionally,ApoE binds cholesterol and phospholipids and ApoE isoforms display diffe rent affinities for their receptors,lipids transport and distribution in the brain and periphery.The role of ApoE in the human depends on ApoE isoforms,brain regions,aging,and neural injury.APOE E4 is the strongest genetic risk factor for sporadic Alzheimer's disease,considering its role in influencing amyloid-beta metabolism.The exact mechanisms by which APOE gene variants may increase or decrease Alzheimer's disease risk are not fully understood,but APOE was also known to affect directly and indirectly tau-mediated neurodegeneration,lipids metabolism,neurovascular unit,and microglial function.Consistent with the biological function of ApoE,ApoE4 isoform significantly alte red signaling pathways associated with cholesterol homeostasis,transport,and myelination.Also,the rare protective APOE variants confirm that ApoE plays an important role in Alzheimer's disease pathogenesis.The objectives of the present mini-review were to describe classical and new roles of various ApoE isoforms in Alzheimer's disease pathophysiology beyond the deposition of amyloid-beta and to establish a functional link between APOE,brain function,and memory,from a molecular to a clinical level.APOE genotype also exerted a heterogeneous effect on clinical Alzheimer's disease phenotype and its outcomes.Not only in learning and memory but also in neuro psychiatric symptoms that occur in a premorbid condition.Cla rifying the relationships between Alzheimer's disease-related pathology with neuropsychiatric symptoms,particularly suicidal ideation in Alzheimer's disease patients,may be useful for elucidating also the underlying pathophysiological process and its prognosis.Also,the effects of anti-amyloid-beta drugs,recently approved for the treatment of Alzheimer's disease,could be influenced by the APOE genotype.

On implications of somatostatin in diabetic retinopathy

Somatostatin,a naturally produced neuroprotective peptide,depresses excitatory neurotransmission and exerts anti-proliferative and anti-inflammatory effects on the retina.In this review,we summarize the progress of somatostatin treatment of diabetic retinopathy through analysis of relevant studies published from February 2019 to February 2023 extracted from the PubMed and Google Scholar databases.Insufficient neuroprotection,which occurs as a consequence of declined expression or dysregulation of retinal somatostatin in the very early stages of diabetic retinopathy,triggers retinal neurovascular unit impairment and microvascular damage.Somatostatin replacement is a promising treatment for retinal neurodegeneration in diabetic retinopathy.Numerous pre-clinical and clinical trials of somatostatin analog treatment for early diabetic retinopathy have been initiated.In one such trial(EUROCONDOR),topical administration of somatostatin was found to exert neuroprotective effects in patients with pre-existing retinal neurodysfunction,but had no impact on the onset of diabetic retinopathy.Overall,we concluded that somatostatin restoration may be especially beneficial for the growing population of patients with early-stage retinopathy.In order to achieve early prevention of diabetic retinopathy initiation,and thereby salvage visual function before the appearance of moderate non-proliferative diabetic retinopathy,several issues need to be addressed.These include the needs to:a)update and standardize the retinal screening scheme to incorporate the detection of early neurodegeneration,b)identify patient subgroups who would benefit from somatostatin analog supplementation,c)elucidate the interactions of somatostatin,particularly exogenously-delivered somatostatin analogs,with other retinal peptides in the context of hyperglycemia,and d)design safe,feasible,low cost,and effective administration routes.