Chronic Cerebral Hypoperfusion In Rats Research Articles

Enriched environment remedies cognitive dysfunctions and synaptic plasticity through NMDAR-Ca2+-Activin A circuit in chronic cerebral hypoperfusion rats.

Chronic cerebral ischemia (CCI) is one of the critical factors in the occurrence and development of vascular cognitive impairment (VCI). Apoptosis of nerve cells and changes in synaptic activity after CCI are the key factors to induce VCI. Synaptic stimulation up-regulates intraneuronal Ca2+ level through N-methyl-D-aspartic acid receptor (NMDAR) via induction of the activity-regulated inhibitor of death (AID) expression to produce active-dependent neuroprotection. Moreover, the regulation of synaptic plasticity could improve cognition and learning ability. Activin A (ActA), an exocrine protein of AID, can promote NMDAR phosphorylation and participate in the regulation of synaptic plasticity. We previously found that exogenous ActA can improve the cognitive function of rats with chronic cerebral ischemia and enhance the oxygenated glucose deprivation of intracellular Ca2+ level. In addition to NMDAR, the Wnt pathway is critical in the positive regulation of LTP through activation or inhibition. It plays an essential role in synaptic transmission and activity-dependent synaptic plasticity. The enriched environment can increase ActA expression during CCI injury. We speculated that the NMDAR-Ca2+-ActA signal pathway has a loop-acting mode, and the environmental enrichment could improve chronic cerebral ischemia cognitive impairment via NMDAR-Ca2+-ActA, Wnt/β-catenin pathway is involved in this process. For the hypothesis verification, this study intends to establish chronic cerebral hypoperfusion (CCH) rat model, explore the improvement effect of enriched environment on VCI, detect the changes in plasticity of synaptic morphology and investigate the regulatory mechanism NMDAR-Ca2+-ActA-Wnt/β-catenin signaling loop, providing a therapeutic method for the treatment of CCH.

Dimethyl fumarate improves cognitive deficits in chronic cerebral hypoperfusion rats by alleviating inflammation, oxidative stress, and ferroptosis via NRF2/ARE/NF-κB signal pathway

Cerebrovascular disease and its risk factors cause persistent decrease of cerebral blood flow, chronic cerebral hypoperfusion (CCH) is the major foundation of vascular cognitive impairment (VCI). The hippocampus is extremely vulnerable to cerebral ischemia and hypoxia. Oxidative stress and neuroinflammation injury are important pathophysiological mechanisms of this process, which is closely related to hippocampal neurons damage and loss. Dimethyl fumarate (DMF), an FDA-approved therapeutic for multiple sclerosis (MS), plays a protective role in multiple neurological disorders. Studies have shown that DMF exerts anti-inflammatory and antioxidant effects via the NRF2/ARE/NF-κB signaling pathway. Thus, this study aimed to evaluate the neuroprotective effect of DMF in the CCH rat model. Ferroptosis, a novel defined iron-dependent cell death form, were found to be strongly associated with the pathophysiology of CCH. Emerging evidences have shown that inhibition of ferroptosis by targeting NRF2 exerted neuroprotective effect in neurodegeneration diseases. We also investigated whether DMF can alleviate cognitive deficits through inhibition of ferroptosis by the NRF2 signaling pathway in this study. DMF was intragastric for consecutive five weeks (100 mg/kg/day). Then behavior test and histological, molecular, and biochemical analysis were performed. We found that DMF treatment significantly improved cognitive deficits and partially reversed hippocampus neuronal damage and loss caused by CCH. And DMF treatment decreased hippocampus IL-1β, TNF-α, and IL-6 pro-inflammatory cytokines concentration, and mediated the NF-κB signaling pathway. And DMF also alleviated hippocampus oxidative stress through reducing MDA, and increasing GSH and SOD levels, which are also closely associated with ferroptosis. Besides, DMF treatment reduced the expression of PTGS2, and increased the expression of FTH1 and xCT, and the iron content is also reduced, which were the important features related to ferroptosis. Furthermore, DMF activated the NRF2/ARE signaling pathway and upregulated the expression of HO-1, NQO1 and GPX4. These outcomes indicated that DMF can improve cognitive impairment in rats with CCH, possibly through alleviating neuroinflammation, oxidative stress damage and inhibiting ferroptosis of hippocampal neurons. Overall, our results provide new evidence for the neuroprotective role of DMF.

Treatment with edaravone improves the structure and functional changes in the hippocampus after chronic cerebral hypoperfusion in rat

This study aimed to find out cellular and electrophysiological effects of the edaravone (EDR) administration following induction of vascular dementia (VaD) via bilateral-carotid vessel occlusion (2VO).The rats were randomly divided into control, sham, 2VO + V (vehicle), and 2VO + EDR groups. EDR was administered once a day from day 0–28 after surgery. The passive-avoidance, Morris water-maze, and open-field tests were used for evaluation of memory, locomotor, and anxiety. The field-potential recording was used for assessment of electrophysiological properties of the hippocampus; and after sacrificing, the cerebral hemispheres were removed for stereological study and evaluation of MDA levels. The long-term potentiation (LTP), paired-pulse ratio (PPR), and input-output (I/O) curves were evaluated as indexes for long-term and short-term synaptic plasticity, and basal-synaptic transmission (BST), respectively.The 2VO led to increases in MDA level with considerable neuronal loss and decreases in the volume of the hippocampus, along with a reduction in the BST and LTP induction which was associated with a decrement in PPR and ultimate loss in memory with higher anxiety behavior. However, administration of EDR caused a decline in MDA and prevented the neural loss and volume of the hippocampus, rescued BST and LTP depression, improved memory and anxiety without any effects on PPR.Therefore, most likely through the improvement of MDA level, and the hippocampal cell number and volume, EDR leads to recovery of synaptic plasticity and behavioral performance. Because of the LTP rescue, without recovery of PPR, it is likely that the EDR improved LTP through the post-synaptic neurons.

In vitro anti-cholinesterase activity and in vivo screening of Coccoloba uvifera, Mimusops elengi and Syzygium aqueum extracts on learning and memory function of chronic cerebral hypoperfusion rat

Vascular dementia (VaD), is one of the most common types of dementia in the ageing population, initiated by chronic cerebral hypoperfusion (CCH). At present, effective therapeutic approaches to cure VaD are still missing. Cholinergic system dysfunction in the central nervous system (CNS) has been recognised as one of the main reasons for learning and memory impairment in VaD patients. Therefore, medications that restore the level of acetylcholine (ACh) neurotransmitter by inhibiting cholinesterase activity were proposed as a potential candidate to treat VaD patients. Permanent occlusion of bilateral common carotid arteries (POBCCA) surgery method was performed to develop CCH model in rats. The present study evaluated the anti-cholinesterase activity of three Malaysian plant methanol leaf extracts in vitro and further validated its cognitive-enhancing effects in vivo using POBCCA rats. The selected plant extracts were Coccoloba uvifera (stems), Mimusops elengi (leaves) and Syzygium aqueum (leaves). The in vitro anti-cholinesterase activities of these plants were determined using Ellman's method. The effects of selected plant extracts (100 and 200 mg/kg, p.o.) on learning and memory functions were evaluated using a series of behavioural tests. All the selected plant extracts exhibited good anti-acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities in vitro, with IC50 ranging from 3.67 to 16.04 and 5.6 to 13.95 µg/mL, respectively. Extracts of S. aqueum (200 mg/kg) improve both short- and long-term recognition memories, whereas M. elengi and S. aqueum (200 mg/kg) extracts improve spatial learning. None of the extracts impaired motor and exploratory functions in POBCCA rats. In conclusion, methanol extracts of C. uvifera, M. elengi and S. aqueum showed good anti-cholinesterase activity in vitro. However, only M. elengi and S. aqueum improve learning and memory function in POBCCA rats.

Adalimumab ameliorates memory impairments and neuroinflammation in chronic cerebral hypoperfusion rats.

Vascular dementia (VaD) is the second most common type of dementia worldwide. Although there are five FDA-approved drugs for the treatment of Alzheimer’s disease (AD), none of them have been applied to treat VaD. Adalimumab is a TNF-α inhibitor that is used for the treatment of autoimmune diseases such as rheumatoid arthritis. In a recent retrospective case-control study, the application of adalimumab for rheumatoid or psoriasis was shown to decrease the risk of AD. However, whether adalimumab can be used for the treatment of VaD is not clear. In this study, we used 2VO surgery to generate a VaD rat model and treated the rats with adalimumab or vehicle. We demonstrated that VaD rats treated with adalimumab exhibited significant improvements in memory. In addition, adalimumab treatment significantly alleviated neuronal loss in the hippocampi of VaD rats. Moreover, adalimumab significantly reduced microglial activation and reversed M1/M2 polarization in VaD rats. Furthermore, adalimumab treatment suppressed the activity of NF-κB, an important neuroinflammatory transcription factor. Finally, adalimumab displayed a protective role against oxidative stress in VaD rats. Our results indicate that adalimumab may be applied for the treatment of human patients with VaD.

Propofol improves brain injury induced by chronic cerebral hypoperfusion in rats.

To study effect of propofol on cognitive dysfunction and brain injury in a rat model of chronic cerebral hypoperfusion. The bilateral carotid artery ligation (bilateral common carotid artery occlusion and BCCAO) to establish rat model of chronic cerebral hypoperfusion and randomly assigned to 4 groups (n = 10): sham‐operation group treated with saline model group, propofol treatment model group, normal saline treatment, propofol treatment in the sham‐operation group; continuous intraperitoneal injection of propofol and saline for 12 weeks. Morris water maze was used to evaluate the learning and memory ability of rats. Determination of central cholinergic and oxidative stress in brain tissue by spectrophotometry. Detection of inflammatory response in brain tissue by immunohistochemistry and ELISA method. Detection of neuronal loss in brain tissue by Nissl and TUNEL staining. Compared with the saline‐treated model group, propofol in model group significantly increased the rat brain tissue SOD activity (p < .01) and GPX activity (p < .01), decreased the MDA levels (p < .01) and protein carbonyl compound levels (p < .01). The propofol treatment of model group rats hippocampal GFAP‐immunoreactive satellite glial cells (p < .01) and immune Iba1‐positive microglia cells (p < .01) area percent compared to saline‐treated model group decreased significantly. The number of normal propofol treatment of model group rats hippocampus neuron than in physiological saline treatment model group rats was significantly increased (p < .01). Propofol can improve chronic cerebral hypoperfusion in rats induced by cognitive dysfunction and brain damage.

Physical exercise modulates the astrocytes polarization, promotes myelin debris clearance and remyelination in chronic cerebral hypoperfusion rats

AimsWhite matter damage is the main pathological feature of chronic cerebral hypoperfusion (CCH) and glial activation is crucial in this process. Physical exercise has protective effects on CCH, but the mechanism is unclear. Therefore, this study focuses on investigating the influence of physical exercise on activated astrocytes polarization and its role in CCH. Main methodsRats were given wheel running 48 h after 2VO (2 vessel occlusion) surgery. The cognitive function was evaluated by Morris water maze and novel object recognition test. Inflammatory cytokines expressions were detected by ELISA. Astrocytes polarization was analyzed by immunofluorescence. Myelin debris clearance and remyelination were detected by immunofluorescence and transmission electron microscopy. Key findingsAstrocytes were activated and mainly switched to A1 phenotype in rats 2 and 3 months after 2VO. Myelin debris deposition and limited remyelination can be observed at the corresponding time. Whereas physical exercise can improve the cognitive function of 2VO rats, downregulate the expression of inflammatory factors IL-1α, C1q and TNF, upregulate the release of TGFβ, and promote activated astrocytes transformation from A1 to A2 phenotype. In addition, it can also enhance myelin debris removal and remyelination. SignificanceThese findings suggest that the benefits of physical exercise on white matter repair and cognition improvement may be related to its regulation of astrocytes polarization, which contributes to myelin debris clearance and effective remyelination in CCH.

Electroacupuncture Attenuates Cognitive Impairment in Rat Model of Chronic Cerebral Hypoperfusion via miR-137/NOX4 Axis.

Electroacupuncture has shown protective effects on cognitive decline. However, the underlying molecular mechanisms are not clear. The present study was conducted to determine whether the cognitive function was ameliorated in cerebral hypoperfusion rats following electroacupuncture and to investigate the role of miR-137/NOX4 axis. In this study, chronic cerebral hypoperfusion (CCH) model was established by bilateral common carotid artery occlusion. Electroacupuncture treatment attenuated brain injury in CCH model group via regulating miR-137/NOX4 axis. Furthermore, the data of neuronal apoptosis and oxidative stress were observed. Our findings indicated that (1) neuronal apoptosis and oxidative stress in CCH rats were significantly increased compared with control group; (2) the animal cognitive performance was evaluated using the Morris water maze (MWM). The results showed that electroacupuncture therapy ameliorated spatial learning and memory impairment in cerebral hypoperfusion rats; and (3) electroacupuncture therapy reduces neuronal apoptosis and oxidative stress by activating miR-137/NOX4 axis. These results suggest that electroacupuncture therapy for CCH may be mediated by miR-137/NOX4 axis. Electroacupuncture therapy may act as a potential therapeutic approach for chronic cerebral hypoperfusion.

Dl-3-n-Butylphthalide Alleviates Hippocampal Neuron Damage in Chronic Cerebral Hypoperfusion via Regulation of the CNTF/CNTFRα/JAK2/STAT3 Signaling Pathways.

Chronic cerebral hypoperfusion (CCH) contributes to cognitive impairments, and hippocampal neuronal death is one of the key factors involved in this process. Dl-3-n-butylphthalide (D3NB) is a synthetic compound originally isolated from the seeds of Apium graveolens, which exhibits neuroprotective effects against some neurological diseases. However, the protective mechanisms of D3NB in a CCH model mimicking vascular cognitive impairment remains to be explored. We induced CCH in rats by a bilateral common carotid artery occlusion (BCCAO) operation. Animals were randomly divided into a sham-operated group, CCH 4-week group, CCH 8-week group, and the corresponding D3NB-treatment groups. Cultured primary hippocampal neurons were exposed to oxygen-glucose deprivation/reperfusion (OGD/R) to mimic CCH in vitro. We aimed to explore the effects of D3NB treatment on hippocampal neuronal death after CCH as well as its underlying molecular mechanism. We observed memory impairment and increased hippocampal neuronal apoptosis in the CCH groups, combined with inhibition of CNTF/CNTFRα/JAK2/STAT3 signaling, as compared with that of sham control rats. D3NB significantly attenuated cognitive impairment in CCH rats and decreased hippocampal neuronal apoptosis after BCCAO in vivo or OGD/R in vitro. More importantly, D3NB reversed the inhibition of CNTF/CNTFRα expression and activated the JAK2/STAT3 pathway. Additionally, JAK2/STAT3 pathway inhibitor AG490 counteracted the protective effects of D3NB in vitro. Our results suggest that D3NB could improve cognitive function after CCH and that this neuroprotective effect may be associated with reduced hippocampal neuronal apoptosis via modulation of CNTF/CNTFRα/JAK2/STAT3 signaling pathways. D3NB may be a promising therapeutic strategy for vascular cognitive impairment induced by CCH.

The Minocycline Ameliorated the Synaptic Plasticity Impairment in Vascular Dementia.

Chronic cerebral hypoperfusion (CCH) leads to vascular dementia with progressive hippocampal damage and cognitive impairments. In the present study, we compared early and late Minocycline (MINO) treatment on cognitive function, long and short-term synaptic-plasticity following CCH. We used bilateral common carotid arteries occlusion model (2VO) for induction of hypoperfusion. Male Sprague-Dawley rats were divided into 5 following groups (each having 2 subgroups): 2VO + V (vehicle), 2VO+MINO-E (early treatment of MINO on days 0 to 3 after 2VO), 2VO+MINO-L (late-treatment on days 21 to 32 after 2VO), control, and sham. Passive-avoidance (PA) and radial arm maze (RAM) tests were used to investigate learning and memory. Long term and short term synaptic plasticity were assessed by field potential recording, the brains were removed after recording and preserved for histological study to count pyramidal cells in CA1 region.Cerebral hypoperfusion could impair memory performance, synaptic plasticity, and basal synaptic transmission (BST) along with hippocampal cell loss. Thus, we found a significant reduction in step-through latency (STL) of PA test with a higher number of working and reference errors in RAM in CCH rats. However, only late treatment with MINO improved memory performance, synaptic plasticity, hippocampal cell loss, and increased neurotransmitter pool (NP) in CCH rats, but early treatment could not produce long-lasting beneficial effects 32 days after 2VO. MINO may improve synaptic plasticity and memory performance in hypo-perfused rats directly and indirectly by increasing NP and/or suppressing inflammatory factors, respectively.

Acupuncture attenuates cognitive deficits through α7nAChR mediated anti-inflammatory pathway in chronic cerebral hypoperfusion rats

AimsChronic cerebral hypoperfusion (CCH) elicits inflammatory response, which contributes to the pathology of cognitive impairment. Several studies demonstrate that the alpha-7 nicotinic acetylcholine receptor (α7nAChR) can be a key component to modulate the inflammatory responses. We have reported previously that acupuncture attenuated cognitive deficits induced by CCH. In present study, whether effect of acupuncture was related to α7nAChR mediated anti-inflammatory pathway in CCH rats was further explored. Main methodsAcupuncture was performed in CCH rats induced by bilateral common carotid arteries occlusion. Neuronal injury, the activation of microglia, the release of inflammatory cytokines, the expression of α7nAChR, and the activation of JAK2/STAT3 signaling pathways were detected. Cognitive function and central inflammation were evaluated after the intraperitoneal injection of an α7nAChR agonist PNU282987, or intracerebroventricular injection of an α7nAChR antagonist α-bungarotoxin (α-BGT). Key findingsWe found that there were neuronal damage and inflammation, accompanied with the decreased expressions of α7nAChR in the hippocampus under CCH condition. Acupuncture inhibited neuronal damage, activation of microglia, and inflammatory cytokines. The expressions of α7nAChR, together with its downstream JAK2/STAT3 pathways were up regulated by acupuncture. PNU282987 mimicked the anti-inflammatory and neuroprotective effects as well as the cognitive improvements of acupuncture. Meanwhile, the benefit effects of acupuncture above were blocked by α-BGT. SignificanceIt was demonstrated that acupuncture promoted cognitive function and afforded neuroprotective effects against inflammation via activation of α7nAChR and its downstream JAK2-STAT3 pathway in CCH rats. It provides a new insight for acupuncture as an anti-inflammatory intervention for cognitive impairment.

Improvement of autophagy dysfunction as a potential mechanism for environmental enrichment to protect blood-brain barrier in rats with vascular cognitive impairment

Vascular cognitive impairment (VCI) is the second most common cause of dementia after Alzheimer’s disease, and the cognitive impairment is one of the common effects of VCI. Unfortunately, it lacks effective therapeutic treatments at present. In our previous study, environmental enrichment (EE), as an early intervention for lifestyle modification, can ameliorate cognitive impairment by attenuating hippocampal blood-brain barrier (BBB) injury in chronic cerebral hypoperfusion (CCH) rats. However, the underlying mechanism remains unclear. Here, we found CCH rats in the standard environment (SE) developed cognitive impairment and BBB damage, which were significantly alleviated with the EE intervention. Meantime, EE improved the autophagy dysfunction caused by CCH in the hippocampus of rats, suggesting that the effect of EE on cognitive function and BBB may be related to the improvement of autophagy pathway.

VEGF-PLGA controlled-release microspheres enhanced angiogenesis in encephalomyosynangiosis-based chronic cerebral hypoperfusion

Treatments enhancing angiogenesis for chronic cerebral hypoperfusion (CCH) are still in the research stage. Although encephalomyosynangiosis (EMS) is a common indirect anastomosis for the treatment of CCH, the effectiveness to promote angiogenesis is not satisfactory. Vascular endothelial growth factors (VEGF) is a cytokine found to specifically act directly on vascular endothelial cells, promote neovascularization, and enhance capillary permeability. However, the short half life and unstable property of VEGF underlies the need to explore available delivery system. In this study, poly (lactide-co-glycolide) (PLGA) was used to prepare VEGF controlled-release microspheres. In vitro and in vivo analysis of release kinetics showed that the microspheres could release VEGF continuously within 30 days. Then, modified chronic cerebral hypoperfusion rat model was established by ligation of bilateral internal carotid artery and one vertebral artery. At 14 days after ischemia, the EMS and the VEGF microspheres injection were performed. At 30 days after the injection, the result of Morris water maze displayed that combinating VEGF microspheres and EMS significantly ameliorated cognitive deficit after ischemia. We observed that combinating VEGF microspheres and EMS could further significantly increase cerebral blood flow. We speculated that this enhancement of cerebral blood flow was attributed to more angiogenesis induced by combination of VEGF microspheres and EMS, which verified by more collateral circulation with cerebral angiography and higher expression of CD31 or α-SMA. Our study demonstrated that combinating VEGF-PLGA controlled-release microspheres could significantly promote angiogenesis in EMS-based CCH rats model, providing new ideas for clinical treatment of CCH.

Cholinergic Dysfunction Involvement in Chronic Cerebral Hypoperfusion-Induced Impairment of Medial Septum-dCA1 Neurocircuit in Rats.

Chronic cerebral hypoperfusion (CCH) is considered a preclinical condition of mild cognitive impairment and thought to precede dementia. However, as the principal cholinergic source of hippocampus, whether the septo-hippocampal neurocircuit was impaired after CCH is still unknown. In this study, we established the CCH rat model by bilateral common carotid artery occlusion (2VO). Under anesthesia, the medial septum (MS) of rats was stimulated to evoke the field excitatory post-synaptic potential (fEPSP) in the pyramidal cell layer of dCA1. Consequently, we observed decreased amplitude of fEPSP and increased paired-pulse ratio (PPR) after 8-week CCH. After tail pinch, we also found decreased peak frequency and shortened duration of hippocampal theta rhythm in 2VO rats, indicating the dysfunction of septo-hippocampal neurocircuit. Besides, by intracerebroventricularly injecting GABAergic inhibitor (bicuculline) and cholinergic inhibitors (scopolamine and mecamylamine), we found that CCH impaired both the pre-synaptic cholinergic release and the post-synaptic nAChR function in MS–dCA1 circuits. These results gave an insight into the role of CCH in the impairment of cholinergic MS–dCA1 neurocircuits. These findings may provide a new idea about the CCH-induced neurodegenerative changes.

Xanthone-enriched fraction of Garcinia mangostana and α-mangostin improve the spatial learning and memory of chronic cerebral hypoperfusion rats.

Xanthones isolated from the pericarp of Garcinia mangostana has been reported to exhibit neuroprotective effect. In this study, the effect of xanthone-enriched fraction of Garcinia mangostana (XEFGM) and α-mangostin (α-MG) were investigated on cognitive functions of the chronic cerebral hypoperfusion (CCH) rats. HPLC analysis revealed that XEFGM contained 55.84% of α-MG. Acute oral administration of XEFGM (25, 50 and 100mg/kg) and α-MG (25 and 50mg/kg) before locomotor activity and Morris water maze (MWM) tests showed no significant difference between the groups for locomotor activity. However, α-MG (50mg/kg) and XEFGM (100mg/kg) reversed the cognitive impairment induced by CCH in MWM test. α-MG (50mg/kg) was further tested upon sub-acute 14-day treatment in CCH rats. Cognitive improvement was shown in MWM test but not in long-term potentiation (LTP). BDNF but not CaMKII was found to be down-regulated in CCH rats; however, both parameters were not affected by α-MG. In conclusion, α-MG ameliorated learning and memory deficits in both acute and sub-acute treatments in CCH rats by improving the spatial learning but not hippocampal LTP. Hence, α-MG may be a promising lead compound for CCH-associated neurodegenerative diseases, including vascular dementia and Alzheimer's disease.

Neurovascular integrative effects of long-term environmental enrichment on chronic cerebral hypoperfusion rat model

Vascular dementia (VaD) is one of the most common types of dementia followed by Alzheimer's disease (AD). Recent studies showed that approximately 30 %–35 % of patients with AD at post-mortem exhibited vascular pathologies, which suggested that mixed dementia may be the most common type of dementia. Permanent bilateral common carotid artery occlusion (2VO) is a well-characterized method for investigating cognitive functions and the histopathological consequences of chronic cerebral hypoperfusion (CCH) in rats. In the present study, we investigated the effects of environmental enrichment (EE) on cognitive impairment after CCH, as well as the effects of CCH-induced neurovascular damage on cognitive function. Wistar rats were randomly allocated to a sham group, a 2VO group, and a 2VO + EE group. The 2VO procedure was performed at 12 weeks, while EE was performed for 8 weeks before and 6 weeks after 2VO. The effect of EE on cognitive functions in 2VO rats was investigated using the radial-arm maze and Morris Water Maze tests. Neurovascular integrity was assessed based on immunoreactivity for glial fibrillary acidic protein (GFAP), morphological changes in microvessels, and the expression of matrix metalloproteinase-9 (MMP-9) and zonula occludens-1 (ZO-1) in the motor cortex and hippocampus. EE ameliorated microvessel fragmentation by sustaining the tight junction through increases of ZO-1 expression after CCH, resulting in preserving the neurovascular unit. In summary, EE mitigated cognitive impairment by restoring neurovascular integrity. These findings suggest that EE can be a valuable and meaningful environmental intervention for patients with cognitive impairment.

The nootropic and anticholinesterase activities of Clitoria ternatea Linn. root extract: Potential treatment for cognitive decline

BackgroundClitoria ternatea (CT) is an herbal plant that has been used as a memory booster in folk medicine. CT root extract has been proven to restore chronic cerebral hypoperfusion (CCH)-induced memory deficits in a rat model, but the underlying mechanisms and the toxicity profile following repeated exposure have yet to be explored. The aim of the studyTo investigate the effects of the chronic (28 days) oral administration of CT root extract on CCH-induced cognitive impairment, neuronal damage and cholinergic deficit, and its toxicity profile in the CCH rat model. Materials and methodsThe permanent bilateral occlusion of common carotid arteries (PBOCCA) surgery method was employed to develop a CCH model in male Sprague Dawley (SD) rats. Then, these rats were given oral administration of CT root extract at doses of 100, 200, and 300 mg/kg, respectively for 28 days and subjected to behavioural tests. At the end of the experiment, the brain was harvested for histological analysis and cholinesterase activities. Then, blood samples were collected and organs such as liver, kidney, lung, heart, and spleen were procured for toxicity assessment. ResultsChronic treatment of CT root extract at doses of 200 and 300 mg/kg, restored memory impairments induced by CCH. CT root extract was also found to diminish CCH-induced neuronal damage in the CA1 region of the hippocampus. High dose (300 mg/kg) of the CT root extract was significantly inhibited the increased acetylcholinesterase (AChE) activity in the frontal cortex and hippocampus of the PBOCCA rats. In toxicity study, repeated doses of CT root extract were found to be safe in PBOCCA rats after 28 days of treatment. ConclusionsOur findings provided scientific evidence supporting the therapeutic potential of CT root extract in the treatment of vascular dementia (VaD)-related cholinergic abnormalities and subsequent cognitive decline.

Effects of Geniposide on the Neuroinflammation in Chronic Cerebral Hypoperfusion Rat Model

To investigate the effects and the mechanism of geniposide on the neuroinflammation occured in the neurodegeneration course of a chronic cerebral hypoperfusion rat model. Permanent bilateral common carotid arteries occlusions was performed to induce gradient cognitive deficit in rats. The sham group was used as control group. Then 18 rats that met the Screening Criteria were randomly selected 8 weeks post surgery, and were randomly divided into three groups, the 2-VO rats with saline solution group (2-VO+saline group), 2-VO rats with 50 mg/kg per day geniposide group (2-VO+G50) and 2-VO rats with 100 mg/kg per day geniposide group (2-VO+G100). All intervention groups were daily administered with geniposide or saline for 4 weeks. The sham-operated rats were administrated with saline. Then the rats were tested for Morris water maze to evaluate the memory and learning ability. Rats were sacrificed to obtain cortex and hippocampus tissues for HE staining and to detect expression level of glial fibrillary acidic protein (GFAP), inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-κB), and the level of inflammatory factors tumor necrosis factor-α (TNF-α) and interleukin (IL)-6. The 2-VO+saline group rats showed significant longer escape latency and less percent time in target quadrant, compared with sham-operation group ( P<0.05). The escape latency of 2-VO+G50 and 2-VO+G100 groups were shorter than the 2-VO+saline group ( P<0.05), but still longer than the sham group ( P<0.05), the percent time in target quadrant of which were more than the 2-VO+saline group and less than the sham group. However, there was no significant difference between these two groups. HE staining of sham group showed that neurons in the cortex and hippocampus lined up in order, cellar nucleus were big and globular. HE staining results showed that there were obviously neuoral cells loss, severe cytomorphosis, structural disappearance and nuclear fragmentation in the 2-VO+saline group. The 2-VO+G50 and 2-VO+G100 groups showed less neurodamage than the 2-VO+saline group with less neuoral cells loss, cytomorphosis and ambiguous nucleus. GFAP, iNOS, NF-κB were all highly expressed in the process of cognitive dysfunction in rats after chronic cerebral ischemia, however geniposide intervention (50 and 100 mg/kg per day) significantly decreased the expression of the above proteins. In addition, much more TNF-α and IL-6 were released in brain induced by chronic cerebral ischemia, and the levels were decreased after chronic geniposide oral treatment. No significant differences were detected between 2-VO+G50 and 2-VO+G100 groups. These findings demonstrated that geniposide significantly prevented cognition deterioration induced by chronic cerebral hypoperfusion in rats. Geniposide inhibited neuroinflammation occurred in the process of chronic cerebral ischemia probably via reducing iNOS and NF-κB expression and suppressing the release of inflammatory factor TNF-α and IL-6.

TRPM4 inhibition improves spatial memory impairment and hippocampal long-term potentiation deficit in chronic cerebral hypoperfused rats

Chronic cerebral hypoperfusion (CCH) been well characterized as a common pathological status contributing to neurodegenerative diseases such as Alzheimer’s disease and vascular dementia. CCH is an important factor that leads to cognitive impairment, but the underlying neurobiological mechanism is poorly understood and no effective treatment is available. Recently, transient receptor potential melastatin 4 (TRPM4) cation channel has been identified as an important molecular element in focal cerebral ischemia. Over activation of the channel is a major molecular mechanism of oncotic cell death. However, the role of TRPM4 in CCH that propagates global brain hypoxia have not been explored. Therefore, the present study is designed to investigate the effect of TRPM4 inhibition on the cognitive functions of the rats following CCH via permanent bilateral occlusion of common carotid arteries (PBOCCA) model. In this model, treatment with siRNA suppressed TRPM4 expression at both the mRNA and protein levels and improved cognitive deficits of the CCH rats without affecting their motor function. Furthermore, treatment with siRNA rescued the LTP impairment in CCH-induced rats. Consistent with the restored of LTP, western blot analysis revealed that siRNA treatment prevented the reduction of synaptic proteins, including calcium/calmodulin-dependent kinase II alpha (CaMKIIα) and brain-derived neurotrophic factor (BDNF) in brain regions of CCH rats. The present findings provide a novel role of TRPM4 in restricting cognitive functions in CCH and suggest inhibiting TRPM4 may represent a promising therapeutic strategy in targeting ion channels to prevent the progression of cognitive deficits induced by ischemia.

Epimedium flavonoids protect neurons and synapses in the brain via activating NRG1/ErbB4 and BDNF/Fyn signaling pathways in a chronic cerebral hypoperfusion rat model

Cerebral hypoperfusion is a common feature of cerebral small vascular disease (CSVD), which has been considered as one of the causes of cognitive decline in recent years. Epimedium flavonoids (EF) are the main ingredients extracted from Epimedium. The purpose of this study was to investigate the effects of EF on cognitive impairment, and the underlying mechanisms in rats with permanent occlusion of the bilateral common carotid artery (2VO). EF (50, 100, and 200 mg/kg) was intragastrically administered for 12 weeks starting 2 weeks after 2VO surgery. The results showed that EF treatment improved learning and memory impairment in 2VO rats evaluated by novel object recognition and Y-maze tests. NeuN immunohistochemical staining indicated that EF alleviated neuronal loss in the hippocampus and cerebral cortex of 2VO rats. MAP-2 immunofluorescence staining and western blotting showed that EF protected neuronal dendrites and increased the expression of cytoskeleton proteins MAP-2 and NF200 in the hippocampus of 2VO rats. Moreover, EF protected the synapse ultrastructure detected by transmission electron microscopy, and increased the expression of synaptic plasticity-related proteins, including synaptophysin, synaptotagmin-I, synapsin I, PSD-95, p-NMDA2B, and p-CaMKII-α in the hippocampus of 2VO rats. In addition, EF increased the expression of neuregulin-1 (NRG-1), p-ErbB4, brain-derived neurotrophic factor (BDNF), p-Fyn, PI3K, p-Akt, and p-CREB in the hippocampus of 2VO rats. These results suggest that EF may protect neurons and synapses by activating the NRG1/ErbB4, BDNF/Fyn, and P13 K/Akt/CREB pathways in the hippocampus and cerebral cortex, thus improving cognitive impairment induced by chronic cerebral hypoperfusion. EF may be a potential candidate drug for chronic cerebral hypoperfusion and CSVD therapy.