Donepezil attenuates hippocampal neuronal damage and cognitive deficits after global cerebral ischemia in gerbils

Anti-oxidant activity of coenzyme Q10 against AlCl3/D-galactose in albino rat induced cognitive dysfunctions: Behavioral, biochemical, and BACE-1/GSK-3β alterations

The relationship between amyloid beta (Aβ) and oxidative stress (OS), both prominent factors in Alzheimer's disease-related neural degeneration, is deeply interconnected. The cleavage of the extracellular domain of Amyloid precursor protein (APP) and phosphorylating different substrates, respectively, the β-site amyloid precursor protein cleaving enzyme-1 (BACE-1) and Glycogen synthase kinase-3-beta (GSK-3β) enzymes initiate the synthesis of Aβ, which causes cognitive deficits in AD. This study aimed to explore the protective potential of Coenzyme Q10 (CoQ10). It also sought to uncover any synergistic effects when combined with donepezil, an acetylcholinesterase inhibitor, in treating Alzheimer's disease in male albino rats, focusing on the modulation of the BACE-1/GSK-3β pathway. The experiment involved 70 rats categorized into different groups: control, donepezil alone, CoQ10 alone, AD-model, donepezil co-treatment, CoQ10 co-treatment, and CoQ10 + donepezil combination. Various assessments, such as cholinesterase activity, oxidative stress, serum iron profile, Brain Derived Neurotrophic Factor (BDNF), Tau protein, β-site amyloid precursor protein cleaving enzyme-1 (BACE-1), phosphatase and tensin homolog (Pten), and Glycogen synthase kinase-3-beta (GSK-3β), were conducted on behavioral and biochemical aspects. CoQ10 treatment demonstrated memory improvement, enhanced locomotion, and increased neuronal differentiation, mainly through the inhibition of the dual BACE-1/GSK-3β. These findings were substantiated by histological and immunohistological examinations of the hippocampus.

Neuroprotective effect of Potentilla reptans L. root in the rat brain global ischemia/reperfusion model

Stroke is the most common cause of death among neurological diseases. The protective effects of Potentilla reptans L. include antioxidative, anti-inflammatory, and antiapoptotic effects. In this study, the brain protection and beta-amyloid effects of P. reptans root extract were investigated in the rat brain ischemia/reperfusion (IR) model. Forty male Wistar rats were randomly divided into five groups (n = 8), including IR, sham, and three groups receiving P. reptans with concentrations of 0.025, 0.05, and 0.1 (g/kg/b.w.), which were injected daily for 7 days. For the IR model, the common carotid artery was occluded bilaterally for 8 min. All injections were intraperitoneal (IP). The shuttle box test was used to measure passive avoidance memory. Then the brain tissue was extracted for the histological examination of neuron counts and β-amyloid plaques using a morphometric technique, and finally, Statistical Package for the Social Sciences software was used for statistical analysis of the data. Pretreatment with P. reptans improved memory impairment. Also, by examining the tissues of the CA1, CA3, and dentate gyrus areas of the hippocampus, it was observed that the number of plaques in the groups receiving P. reptans extract was reduced compared to the IR group, especially at the concentration of 0.05 g/kg/b.w. Also, P. reptans improved the number of neurons at all concentrations, in which the concentration of 0.05 g/kg/b.w. showed more effective therapeutic results. Taken together, we found that P. reptans root extract has beneficial effects on memory impairment, neuronal loss, and β-amyloid accumulation.

Is Target-Based Drug Discovery Efficient? Discovery and "Off-Target" Mechanisms of All Drugs

Target-based drug discovery is the dominant paradigm of drug discovery; however, a comprehensive evaluation of its real-world efficiency is lacking. Here, a manual systematic review of about 32000 articles and patents dating back to 150 years ago demonstrates its apparent inefficiency. Analyzing the origins of all approved drugs reveals that, despite several decades of dominance, only 9.4% of small-molecule drugs have been discovered through "target-based" assays. Moreover, the therapeutic effects of even this minimal share cannot be solely attributed and reduced to their purported targets, as they depend on numerous off-target mechanisms unconsciously incorporated by phenotypic observations. The data suggest that reductionist target-based drug discovery may be a cause of the productivity crisis in drug discovery. An evidence-based approach to enhance efficiency seems to be prioritizing, in selecting and optimizing molecules, higher-level phenotypic observations that are closer to the sought-after therapeutic effects using tools like artificial intelligence and machine learning.

Sericin improves memory and sociability impairments evoked by transient global cerebral ischemia through suppression of hippocampal oxidative stress, inflammation, and apoptosis

Sericin (Ser) is a natural neuroactive macromolecule with diverse pharmacological properties, and our previous findings have shown its neuroprotective potentials. This study aimed to investigate the therapeutic potential of Ser on cognitive dysfunction induced by transient global cerebral ischemia/reperfusion (tGI/R) and its mechanism of action. The tGI/R was induced in BALB/c mice by bilateral occlusion of the common carotid arteries for two 5 min followed by a 10-min reperfusion period. After 24 h, mice were treated with normal saline or different doses of Ser (100, 200, and 300 mg/kg) for 10 days. Cognitive performances were assessed using the Barnes maze and social interaction tasks. Oxidative stress markers including superoxide dismutase (SOD), glutathione peroxidase (GPx), total antioxidant capacity (TAC), and malondialdehyde (MDA) as well as pro-inflammatory cytokines (interleukin (IL)-6 and tumor necrosis factor-alpha) and anti-inflammatory cytokine (IL-10) were assessed in the hippocampus. Markers of apoptosis (pro- and cleaved caspase-9 and 3, Bax, and Bcl-2) were assessed by Western blotting. Besides, transferase-mediated dUTP nick end-labeling assay was used to detect apoptotic cell death. We show here that Ser administration improved tGI/R-induced cognitive deficits, enhanced the activity of SOD and GPx, increased TAC levels, while reduced MDA levels. Notably, Ser decreased neuronal apoptotic cell death in the hippocampal dentate gyrus (DG) region, accompanied by suppression of neuroinflammation, downregulation of pro-apoptotic proteins (caspase-9, caspases-3, and Bax), and upregulation of anti-apoptotic protein, Bcl-2. Taken together, Ser administration protected hippocampal neurons from apoptotic cell death by impeding oxidative stress and inflammatory responses and, in turn, improved cognitive function in the tGI/R mice.

Possible Engagement of Nicotinic Acetylcholine Receptors in Pathophysiology of Brain Ischemia-Induced Cognitive Impairment

Post-stroke disabilities like cognitive impairment impose are complex conditions with great economic burdens on health care systems. For these comorbidities, no effective therapies have been identified yet. Nicotinic acetylcholine receptors (nAChRs) are multifunctional receptors participating in various behavioral and neurobiological functions. During brain ischemia, the increased glutamate accumulation leads to neuronal excitotoxicity as well as mitochondrial dysfunction. These abnormalities then cause the increased levels of oxidants, which play key roles in neuronal death and apoptosis in the infarct zone. Additionally, recall of cytokines and inflammatory factors play a prominent role in the exacerbation of ischemic injury. As well, neurotrophic factors' insufficiency results in synaptic dysfunction and cognitive impairments in ischemic brain. Of note, nAChRs through various signaling pathways can participate in therapeutic approaches such as cholinergic system's stimulation, and reduction of excitotoxicity, inflammation, apoptosis, oxidative stress, mitochondrial dysfunction, and autophagy. Moreover, the possible roles of nAChRs in neurogenesis, synaptogenesis, and stimulation of neurotrophic factors expression have been reported previously. On the other hand, the majority of the above-mentioned mechanisms were found to be common in both brain ischemia pathogenesis and cognitive function tuning. Therefore, it seems that nAChRs might be known as key regulators in the control of ischemia pathology, and their modulation could be considered as a new avenue in the multi-target treatment of post-stroke cognitive impairment.

Evaluation of hesperetin-loaded on multiple wall carbon nanotubes on cerebral ischemia/reperfusion injury in rats

The present study aimed to develop novel hesperetin-loaded on multiple wall carbon nanotubes (Hst-MWCNTs) to resolve the restricted bioavailability of hesperetin (Hst) and to enhance its preventive effect on cerebral ischemia-reperfusion (I/R). The physicochemical characteristics of Hst-MWCNTs were evaluated by Fourier-transform infrared spectra (FT-IR) and field emission scanning electron microscopy (FE-SEM). Forty male Wistar rats were randomly divided into five groups (control, I/R, MWCNTs, Hst, and Hst-MWCNTs). Hst, MWCNTs and Hst-MWCNTs (15 mg/kg orally) were pretreated for 14 days, and then I/R was induced by bilateral common carotid artery occlusion (BCCAO). Learning and memory deficits were evaluated using the novel object recognition test (NORT). The percentage of infarct size, catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GRx), glutathione peroxidase (GPx) activities, malondialdehyde (MDA), and glutathione (GSH) levels was evaluated. Caspase-3 and Bcl-2 expressions were detected by qRT-PCR and Western blot analysis. Compared to the I/R group, Hst-MWCNTs considerably reduced learning and memory deficits, infarct size, and MDA levels. CAT, SOD, GRx, GPx activities and GSH levels were significantly increased in the Hst-MWCNTs group than in the I/R group. Additionally, Hst-MWCNTs significantly reduced the Caspase-3 expression but increased the Bcl-2 expression. All these results indicated that MWCNTs could be used as a promising novel carrier to enhance the oral bioavailability of Hst and to treat cerebral I/R injury.

Epigenetic Blockade of Hippocampal SOD2 Via DNMT3b-Mediated DNA Methylation: Implications in Mild Traumatic Brain Injury-Induced Persistent Oxidative Damage

The recurrent events of mild trauma exacerbate the vulnerability for post-traumatic stress disorder; however, the underlying molecular mechanisms are scarcely known. The repeated mild traumatic brain injury (rMTBI) perturbs redox homeostasis which is primarily managed by superoxide dismutase 2 (SOD2). The current study investigates the role of DNA methylation in SOD2 gene regulation and its involvement in rMTBI-induced persistent neuropathology inflicted by weight drop injury paradigm. The oxidative damage, neurodegenerative indicators, and SOD2 function and its regulation in the hippocampus were analyzed after 48 h and 30 days of rMTBI. The temporal and episodic increase in ROS levels (oxidative stress) heightened 8-hydroxyguanosine levels indicating oxidative damage after rMTBI that was concomitant with decline in SOD2 function. In parallel, occupancy of DNMT3b at SOD2 promoter was higher post 30 days of the first episode of rMTBI causing hypermethylation at SOD2 promoter. This epigenetic silencing of SOD2 promoter was sustained after the second episode of rMTBI causing permanent blockade in SOD2 response. The resultant oxidative stress further culminated into the increasing number of degenerating neurons. The treatment with 5-azacytidine, a pan DNMT inhibitor, normalized DNA methylation levels and revived SOD2 function after the second episode of rMTBI. The release of blockade in SOD2 expression by DNMT inhibition also normalized the post-traumatic oxidative consequences and relieved the neurodegeneration and deficits in learning and memory as measured by novel object recognition test. In conclusion, DNMT3b-mediated DNA methylation plays a critical role in SOD2 gene regulation in the hippocampus, and the perturbations therein post rMTBI are detrimental to redox homeostasis manifesting into neurological consequences.

Donepezil attenuates injury following ischaemic stroke by stimulation of neurogenesis, angiogenesis, and inhibition of inflammation and apoptosis

Donepezil has proven to be an effective drug to reduce neuronal death and subsequently injury in neurodegenerative diseases. The current study evaluated the neuroprotective effects of donepezil in a rat model of ischaemic stroke and explored possible mechanisms which by this drug may reduce cell death. Temporary middle cerebral artery occlusion (tMCAO) was exerted for 45 min to induce ischaemic stroke. The animals were assigned into five groups: sham, control, and three groups treated with different doses of donepezil. Donepezil was intraperitoneally (IP) injected 4 h after reperfusion for 10 consecutive days. Infarct size was determined using TTC staining. The expression of proteins was evaluated using immunohistochemistry assays. Compared with the control group, infarct size was significantly reduced in tMCAO rats treated with different doses of donepezil. Moreover, our results showed significant decreased expression levels of apoptotic markers and pro-inflammatory mediators after treatment with different doses of donepezil for 10 days (P < 0.05). Likewise, significant increase of brain-derived neurotrophic factor (BDNF) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) proteins were found in tMCAO rats treated with donepezil compared with the control group (P < 0.05). Collectively, our findings show the validity of donepezil as a new therapeutic agent for attenuation of injury following ischaemic stroke through attenuation of inflammation and improvement of mitochondrial function, neurogenesis, and angiogenesis.

Long-Term Alternating Fasting Increases Interleukin-13 in the Gerbil Hippocampus, But Does Not Protect BBB and Pyramidal Neurons From Ischemia-Reperfusion Injury

It is questionable whether intermittent fasting (IF) protects against brain ischemic injury. This study examined whether IF increased anti-inflammatory cytokines and protected neurons from ischemia-reperfusion injury in the gerbil hippocampus. Gerbils were subjected to 1-day alternating fasting as IF for 1, 2, or 3 months and assigned to sham or 5 min of transient ischemia. We examined the changes in anti-inflammatory cytokines (IL-4 and IL-13), neurons and IgG by immunohistochemistry or immunofluorescence staining in the cornu ammonis 1 (CA1) region of the hippocampus before and after ischemia. IF increased IL-13 immunoreactivity in the CA1 region before ischemia, but did not affect IL-4 immunoreactivity. After ischemia, IL-13 and 4 immunoreactivities in the CA1 region were significantly lower in IF gerbils than in non-IF gerbils. In the IF gerbils, the CA1 pyramidal neurons were not protected from ischemic injury; in these gerbils, strong IgG immunoreactivity was seen in the CA1 parenchyma, indicating leakage of the BBB. In brief, IF increased IL-13 in the CA1 region, but these neurons were not protected from transient ischemic injury evidenced by IgG immunoreactivity in the CA1 parenchyma. This study indicates that IF increased some anti-inflammatory cytokines but did not afford neuroprotection against ischemic insults via BBB disruption.

Inhibition of JNK Alleviates Chronic Hypoperfusion-Related Ischemia Induces Oxidative Stress and Brain Degeneration via Nrf2/HO-1 and NF-κB Signaling

Cerebral ischemia is one of the leading causes of neurological disorders. The exact molecular mechanism related to chronic unilateral cerebral ischemia-induced neurodegeneration and memory deficit has not been precisely elucidated. In this study, we examined the effect of chronic ischemia on the induction of oxidative stress and c-Jun N-terminal kinase-associated detrimental effects and unveiled the inhibitory effect of specific JNK inhibitor (SP600125) on JNK-mediated brain degeneration in adult mice. Our behavioral, biochemical, and immunofluorescence studies revealed that chronic ischemic injuries sustained increased levels of oxidative stress-induced active JNK for a long time, whereas SP600125 significantly reduced the elevated level of active JNK and further regulated Nrf2/HO-1 and NF-κB signaling, which have been confirmed in vivo. Neuroinflammatory mediators and loss of neuronal cells was significantly reduced with the administration of SP600125. Ischemic brain injury caused synaptic dysfunction and memory impairment in mice. However, these were significantly improved with SP600125. On the whole, these findings suggest that elevated ROS-mediated JNK is a key mediator in chronic ischemic conditions and has a crucial role in neuroinflammation, neurodegeneration, and memory dysfunction. Our findings suggest that chronic oxidative stress associated JNK would be a potential target in time-dependent studies of chronic ischemic conditions induced brain degeneration.

Effect of low-dose Levamlodipine Besylate in the treatment of vascular dementia

Vascular dementia (VaD) is a complex disorder caused by reduced blood flow in the brain. However, there is no effective pharmacological treatment option available until now. Here, we reported that low-dose levamlodipine besylate could reverse the cognitive impairment in VaD mice model of right unilateral common carotid arteries occlusion (rUCCAO). Oral administration of levamlodipine besylate (0.1 mg/kg) could reduce the latency to find the hidden platform in the MWM test as compared to the vehicle group. Furthermore, vehicle-treated mice revealed reduced phospho-CaMKII (Thr286) levels in the hippocampus, which can be partially restored by levamlodipine besylate (0.1 mg/kg and 0.5 mg/kg) treatment. No significant outcome on microglia and astrocytes were observed following levamlodipine besylate treatment. This data reveal novel findings of the therapeutic potential of low-dose levamlodipine besylate that could considerably enhance the cognitive function in VaD mice.

Selenium nanoparticles for targeted stroke therapy through modulation of inflammatory and metabolic signaling

Ischemic cerebral stroke is a major cause of death and morbidity. Currently, no neuroprotective agents have been shown to impact the clinical outcomes in cerebral stroke cases. Here, we report therapeutic effects of Se nanoparticles on ischemic stroke in a murine model. Anti-transferrin receptor monoclonal antibody (OX26)-PEGylated Se nanoparticles (OX26-PEG-Se NPs) were designed and synthesized and their neuroprotective effects were measured using in vitro and in vivo approaches. We demonstrate that administration of the biodegradable nanoparticles leads to resolution of brain edema, protection of axons in hippocampus region, and myelination of hippocampal area after cerebral ischemic stroke. Our nanoparticle design ensures efficient targeting and minimal side effects. Hematological and biochemical analyses revealed no undesired NP-induced changes. To gain mechanistic insights into the therapeutic effects of these particles, we characterized the changes to the relevant inflammatory and metabolic signaling pathways. We assessed metabolic regulator mTOR and related signaling pathways such as hippo, Ubiquitin-proteasome system (ERK5), Tsc1/Tsc2 complex, FoxO1, wnt/β-catenine signaling pathway. Moreover, we examined the activity of jak2/stat3 signaling pathways and Adamts1, which are critically involved in inflammation. Together, our study provides a promising treatment strategy for cerebral stroke based on Se NP induced suppression of excessive inflammation and oxidative metabolism.

Effects of CREB1 gene silencing on cognitive dysfunction by mediating PKA-CREB signaling pathway in mice with vascular dementia

Background

As a form of dementia primarily affecting the elderly, vascular dementia (VD) is characterized by changes in the supply of blood to the brain, resulting in cognitive impairment. The aim of the present study was to explore the effects involved with cyclic adenosine monophosphate (cAMP) response element-binding (CREB)1 gene silencing on cognitive dysfunction through meditation of the protein kinase A (PKA)-CREB signaling pathway in mice with VD.

Methods

Both the Morris water maze test and the step down test were applied to assess the cognitive function of the mice with VD. Immunohistochemical and TUNEL staining techniques were employed to evaluate the positive expression rates of the protein CREB1 and Cleaved Caspase-3, as well as neuronal apoptosis among hippocampal tissues in a respective manner. Flow cytometry was applied to determine the proliferation index and apoptosis rate of the hippocampal cells among each group. Reverse transcription quantitative polymerase chain reaction and Western blot analysis methods were applied to detect the expressions of cAMP, PKA and CREB in hippocampal cells.

Results

Compared with the normal group, all the other groups exhibited impaired cognitive function, reduced cell numbers in the CAI area, positive expressions of CREB1 as well as positive optical density (OD) values. Furthermore, increased Cleaved Caspase-3 positive expression, OD value, proliferation index, apoptosis rate of hippocampal cells and neurons, were observed in the other groups when compared with the normal group, as well as lower expressions of cAMP, PKA and CREB1 and p-CREB1 (the shCREB1–1, H89 and shCREB1–1 + H89 groups < the VD group).

Conclusion

The key findings of the present study demonstrated that CREB1 gene silencing results in aggravated VD that occurs as a result of inhibiting the PKA-CREB signaling pathway, thus exasperating cognitive dysfunction.

Using Drugs as Molecular Probes: A Computational Chemical Biology Approach in Neurodegenerative Diseases

Neurodegenerative diseases including Alzheimer’s disease are complex to tackle because of the complexity of the brain, both in structure and function. Such complexity is reflected by the involvement of various brain regions and multiple pathways in the etiology of neurodegenerative diseases that render single drug target approaches ineffective. Particularly in the area of neurodegeneration, attention has been drawn to repurposing existing drugs with proven efficacy and safety profiles. However, there is a lack of systematic analysis of the brain chemical space to predict the feasibility of repurposing strategies. Using a mechanism-based, drug-target interaction modeling approach, we have identified promising drug candidates for repositioning. Mechanistic cause-and-effect models consolidate relevant prior knowledge on drugs, targets, and pathways from the scientific literature and integrate insights derived from experimental data. We demonstrate the power of this approach by predicting two repositioning candidates for Alzheimer’s disease and one for amyotrophic lateral sclerosis.

Diverse Effects of an Acetylcholinesterase Inhibitor, Donepezil, on Hippocampal Neuronal Death after Pilocarpine-Induced Seizure

Epileptic seizures are short episodes of abnormal brain electrical activity. Many survivors of severe epilepsy display delayed neuronal death and permanent cognitive impairment. Donepezil is an acetylcholinesterase inhibitor and is an effective treatment agent for Alzheimer’s disease. However, the role of donepezil in seizure-induced hippocampal injury remains untested. Temporal lobe epilepsy (TLE) was induced by intraperitoneal injection of pilocarpine (25 mg/kg). Donepezil (2.5 mg/kg/day) was administered by gavage in three different settings: (1) pretreatment for three days before the seizure; (2) for one week immediately after the seizure; and (3) for three weeks from three weeks after the seizure. We found that donepezil showed mixed effects on seizure-induced brain injury, which were dependent on the treatment schedule. Pretreatment with donepezil aggravated neuronal death, oxidative injury, and microglia activation. Early treatment with donepezil for one week showed neither adverse nor beneficial effects; however, a treatment duration of three weeks starting three weeks after the seizure showed a significant reduction in neuronal death, oxidative injury, and microglia activation. In conclusion, donepezil has therapeutic effects when injected for three weeks after seizure activity subsides. Therefore, the present study suggests that the therapeutic use of donepezil for epilepsy patients requires a well-conceived strategy for administration.

Cerebral ischemic injury decreases α-synuclein expression in brain tissue and glutamate-exposed HT22 cells

α-Synuclein is abundantly expressed in neuronal tissue, plays an essential role in the pathogenesis of neurodegenerative disorders, and exerts a neuroprotective effect against oxidative stress. Cerebral ischemia causes severe neurological disorders and neuronal dysfunction. In this study, we examined α-synuclein expression in middle cerebral artery occlusion (MCAO)-induced cerebral ischemic injury and neuronal cells damaged by glutamate treatment. MCAO surgical operation was performed on male Sprague-Dawley rats, and brain samples were isolated 24 hours after MCAO. We confirmed neurological behavior deficit, infarction area, and histopathological changes following MCAO injury. A proteomic approach and Western blot analysis demonstrated a decrease in α-synuclein in the cerebral cortices after MCAO injury. Moreover, glutamate treatment induced neuronal cell death and decreased α-synuclein expression in a hippocampal-derived cell line in a dose-dependent manner. It is known that α-synuclein regulates neuronal survival, and low levels of α-synuclein expression result in cytotoxicity. Thus, these results suggest that cerebral ischemic injury leads to a reduction in α-synuclein and consequently causes serious brain damage.

Huprine X Attenuates The Neurotoxicity Induced by Kainic Acid, Especially Brain Inflammation

Huprine X (HX) is a synthetic anticholinesterasic compound that exerts a potent inhibitory action on acetylcholinesterase (AChE) activity, an agonist effect on cholinergic receptors, neuroprotective activity in different neurotoxicity models in vivo and in vitro and cognition enhancing effects in non-transgenic (C57BL/6) and transgenic (3xTg-AD, APPswe) mice. In this study, we assessed the ability of HX (0.8 mg/kg, 21 days) to prevent the damage induced by kainic acid (KA; 28 mg/kg) regarding apoptosis, glia reactivity and neurogenesis in mouse brain. KA administration significantly modified the levels of pAkt1, Bcl2, pGSK3β, p25/p35, increased the glial cell markers and reduced the neurogenesis process. We also observed that pre-treatment with HX significantly reduced the p25/p35 ratio and increased synaptophysin levels, which suggests a protective effect against apoptosis and an improvement of neuroplasticity. The increase in GFAP (88%) and Iba-1 (72%) induced by KA was totally prevented by HX pre-treatment, underlying a relevant anti-inflammatory action of the anticholinesterasic drug. Our findings highlight the potential of HX, in particular, and of AChEIs, in general, to treat a number of diseases that course with both cognitive deficits and chronic inflammatory processes.

CD74-immunoreactive activated M1 microglia are shown late in the gerbil hippocampal CA1 region following transient cerebral ischemia

Activated M1 microglia secrete proinflammatory cytokines into damaged brain areas. The present study examined activated M1 microglial morphology and expression in the hippocampal Cornu Ammonis (CA) 1 region, which is vulnerable to transient ischemia. Transient cerebral ischemia was performed for 5 min in gerbils, and neuronal death in the CA1 region following transient cerebral ischemia was confirmed using cresyl violet staining, neuronal nuclear antigen immunohistochemistry and Fluoro-Jade B histofluorescent staining. In addition, CA1 regions were stained for cluster of differentiation (CD) 74, a marker for activated M1 microglia and a ligand for macrophage migration inhibitory factor In sham-operated animals, no CD74 immunoreactivity was observed in the hippocampal CA1 region. CD74 immunoreactivity was not observed in the hippocampal CA1 region until 3 days post-ischemic insult; however, elevated CD74 immunoreactivity was detected in the CA1 region from 5 days post-ischemia. Double immunofluorescence staining for CD74 and ionized calcium-binding adapter molecule 1, a marker for M1 microglial cells, confirmed the expression of CD74 on this microglial subtype. These results indicated that M1 microglia are activated late in the hippocampal CA1 region following ischemic stroke. Therefore, optimizing the timing of therapeutic intervention may reduce activated M1 microglial-induced neuronal damage.

Inhibitory effects of cholinesterase inhibitor donepezil on the Kv1.5 potassium channel

Kv1.5 channels carry ultra-rapid delayed rectifier K⁺ currents in excitable cells, including neurons and cardiac myocytes. In the current study, the effects of cholinesterase inhibitor donepezil on cloned Kv1.5 channels expressed in HEK29 cells were explored using whole-cell recording technique. Exposure to donepezil resulted in a rapid and reversible block of Kv1.5 currents, with an IC₅₀ value of 72.5 μM. The mutant R476V significantly reduced the binding affinity of donepezil to Kv1.5 channels, showing the target site in the outer mouth region. Donepezil produced a significant delay in the duration of activation and deactivation, and mutant R476V potentiated these effects without altering activation curves. In response to slowed deactivation time course, a typical crossover of Kv1.5 tail currents was clearly evident after bath application of donepezil. In addition, both this chemical and mutant R476V accelerated current decay during channel inactivation in a voltage-dependent way, but barely changed the inactivation and recovery curves. The presence of donepezil exhibited the use-dependent block of Kv1.5 currents in response to a series of depolarizing pulses. Our data indicate that donepezil can directly block Kv1.5 channels in its open and closed states.

Update on Inflammatory Biomarkers and Treatments in Ischemic Stroke

After an acute ischemic stroke (AIS), inflammatory processes are able to concomitantly induce both beneficial and detrimental effects. In this narrative review, we updated evidence on the inflammatory pathways and mediators that are investigated as promising therapeutic targets. We searched for papers on PubMed and MEDLINE up to August 2016. The terms searched alone or in combination were: ischemic stroke, inflammation, oxidative stress, ischemia reperfusion, innate immunity, adaptive immunity, autoimmunity. Inflammation in AIS is characterized by a storm of cytokines, chemokines, and Damage-Associated Molecular Patterns (DAMPs) released by several cells contributing to exacerbate the tissue injury both in the acute and reparative phases. Interestingly, many biomarkers have been studied, but none of these reflected the complexity of systemic immune response. Reperfusion therapies showed a good efficacy in the recovery after an AIS. New therapies appear promising both in pre-clinical and clinical studies, but still need more detailed studies to be translated in the ordinary clinical practice. In spite of clinical progresses, no beneficial long-term interventions targeting inflammation are currently available. Our knowledge about cells, biomarkers, and inflammatory markers is growing and is hoped to better evaluate the impact of new treatments, such as monoclonal antibodies and cell-based therapies.

(-)-SCR1693 Protects against Memory Impairment and Hippocampal Damage in a Chronic Cerebral Hypoperfusion Rat Model

Chronic cerebral hypoperfusion (CCH) is one of the most common causes of vascular dementia (VaD) and is recognised as an etiological factor in the development of Alzheimer’s disease (AD). CCH can induce severe cognitive deficits, as assessed by the water maze task, along with neuronal loss in the hippocampus. However, there are currently no effective, approved pharmacological treatments available for VaD. In the present study, we created a rat model of CCH using bilateral common carotid artery occlusion and found that (-)-SCR1693, a novel compound, prevented rats from developing memory deficits and neuronal damage in the hippocampus by rectifying cholinergic dysfunction and decreasing the accumulation of the phospho-tau protein. These results strongly suggest that (-)-SCR1693 has therapeutic potential for the treatment of CCH-induced VaD.

Neuroprotection of Chrysanthemum indicum Linne against cerebral ischemia/reperfusion injury by anti-inflammatory effect in gerbils

In this study, we tried to verify the neuroprotective effect of Chrysanthemum indicum Linne (CIL) extract, which has been used as a botanical drug in East Asia, against ischemic damage and to explore the underlying mechanism involving the anti-inflammatory approach. A gerbil was given CIL extract for 7 consecutive days followed by bilateral carotid artery occlusion to make a cerebral ischemia/reperfusion model. Then, we found that CIL extracts protected pyramidal neurons in the hippocampal CA1 region (CA1) from ischemic damage using neuronal nucleus immunohistochemistry and Fluoro-Jade B histofluorescence. Accordingly, interleukin-13 immunoreactivities in the CA1 pyramidal neurons of CIL-pretreated animals were maintained or increased after cerebral ischemia/reperfusion. These findings indicate that the pre-treatment of CIL can attenuate neuronal damage/death in the brain after cerebral ischemia/reperfusion via an anti-inflammatory approach.

Baicalin alleviates ischemia-induced memory impairment by inhibiting the phosphorylation of CaMKII in hippocampus

Baicalin has a significant neuroprotective effect in stroke. However, the mechanism remains unclear. This study was to reveal the mechanisms by which baicalin protected hippocampal neurons and improved learning and memory impairment after global cerebral ischemia/reperfusion in gerbil. In the present study, the Morris water maze test showed that baicalin significantly improved learning and memory impairment after global cerebral ischemia/reperfusion in gerbils. Laser scanning confocal fluorescence microscope examination showed that baicalin suppressed OGD-induced augmentation of intracellular calcium concentration. Western blotting analysis indicated that baicalin suppressed ischemia-caused elevated phosphorylation level of CaMKII in vivo, in hippocampal neurons in culture, and in SH-SY5Y cells in culture. Western blotting, TUNEL and RNA interference technology were applied to detect effects of baicalin on neuronal apoptosis. We found that baicalin, a CaMKII inhibitor and knocking down the CaMKII prevented OGD-induced apoptosis of hippocampal or SH-SY5Y cells in culture. Therefore, these results suggested that baicalin improves learning and memory impairment induced by global cerebral ischemia/reperfusion in gerbils via attenuating the phosphorylation level of CaMKII and further preventing hippocampal neuronal apoptosis.

Rolipram stimulates angiogenesis and attenuates neuronal apoptosis through the cAMP/cAMP-responsive element binding protein pathway following ischemic stroke in rats

Rolipram, a phosphodiesterase-4 inhibitor, can activate the cyclic adenosine monophosphate (cAMP)/cAMP-responsive element binding protein (CREB) pathway to facilitate functional recovery following ischemic stroke. However, to date, the effects of rolipram on angiogenesis and cerebral ischemia-induced neuronal apoptosis are yet to be fully elucidated. In this study, the aim was to reveal the effect of rolipram on the angiogenesis and neuronal apoptosis following brain cerebral ischemia. Rat models of ischemic stroke were established following transient middle cerebral artery occlusion and rolipram was administered for three, seven and 14 days. The results were examined using behavioral tests, triphenyl tetrazolium chloride staining, immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) to evaluate the effects of rolipram therapy on functional outcome, angiogenesis and apoptosis. Western blot analysis was used to show the phosphorylated- (p-)CREB protein level in the ischemic hemisphere. The rolipram treatment group exhibited a marked reduction in infarct size and modified neurological severity score compared with the vehicle group, and rolipram treatment significantly promoted the microvessel density in the ischemic boundary region and increased p-CREB protein levels in the ischemic hemisphere. Furthermore, a significant reduction in the number of TUNEL-positive cells was observed in the rolipram group compared with the vehicle group. These findings suggest that rolipram has the ability to attenuate cerebral ischemic injury, stimulate angiogenesis and reduce neuronal apoptosis though the cAMP/CREB pathway.

Monocarboxylate transporter 4 plays a significant role in the neuroprotective mechanism of ischemic preconditioning in transient cerebral ischemia

Monocarboxylate transporters (MCTs), which carry monocarboxylates such as lactate across biological membranes, have been associated with cerebral ischemia/reperfusion process. In this study, we studied the effect of ischemic preconditioning (IPC) on MCT4 immunoreactivity after 5 minutes of transient cerebral ischemia in the gerbil. Animals were randomly designated to four groups (sham-operated group, ischemia only group, IPC + sham-operated group and IPC + ischemia group). A serious loss of neuron was found in the stratum pyramidale of the hippocampal CA1 region (CA1), not CA2/3, of the ischemia-only group at 5 days post-ischemia; however, in the IPC + ischemia groups, neurons in the stratum pyramidale of the CA1 were well protected. Weak MCT4 immunoreactivity was found in the stratum pyramidale of the CA1 in the sham-operated group. MCT4 immunoreactivity in the stratum pyramidale began to decrease at 2 days post-ischemia and was hardly detected at 5 days post-ischemia; at this time point, MCT4 immunoreactivity was newly expressed in astrocytes. In the IPC + sham-operated group, MCT4 immunoreactivity in the stratum pyramidale of the CA1 was increased compared with the sham-operated group, and, in the IPC + ischemia group, MCT4 immunoreactivity was also increased in the stratum pyramidale compared with the ischemia only group. Briefly, present findings show that IPC apparently protected CA1 pyramidal neurons and increased or maintained MCT4 expression in the stratum pyramidale of the CA1 after transient cerebral ischemia. Our findings suggest that MCT4 appears to play a significant role in the neuroprotective mechanism of IPC in the gerbil with transient cerebral ischemia.

Neuroprotection of Ischemic Preconditioning is Mediated by Anti-inflammatory, Not Pro-inflammatory, Cytokines in the Gerbil Hippocampus Induced by a Subsequent Lethal Transient Cerebral Ischemia

Ischemic preconditioning (IPC) induced by sublethal transient cerebral ischemia could reduce neuronal damage/death following a subsequent lethal transient cerebral ischemia. We, in this study, compared expressions of interleukin (IL)-2 and tumor necrosis factor (TNF)-α as pro-inflammatory cytokines, and IL-4 and IL-13 as anti-inflammatory cytokines in the gerbil hippocampal CA1 region between animals with lethal ischemia and ones with IPC followed by lethal ischemia. In the animals with lethal ischemia, pyramidal neurons in the stratum pyramidale (SP) of the hippocampal CA1 region were dead at 5 days post-ischemia; however, IPC protected the CA1 pyramidal neurons from lethal ischemic injury. Expressions of all cytokines were significantly decreased in the SP after lethal ischemia and hardly detected in the SP at 5 days post-ischemia because the CA1 pyramidal neurons were dead. IPC increased expressions of anti-inflammatory cytokines (IL-4 and IL-13) in the stratum pyramidale of the CA1 region following no lethal ischemia (sham-operation), and the increased expressions of IL-4 and IL-13 by IPC were continuously maintained is the SP of the CA1 region after lethal ischemia. However, pro-inflammatory cytokines (IL-2 and TNF-α) in the SP of the CA1 region were similar those in the sham-operated animals with IPC, and the IL-4 and IL-13 expressions in the SP were maintained after lethal ischemia. In conclusion, this study shows that anti-inflammatory cytokines significantly increased and longer maintained by IPC and this might be closely associated with neuroprotection after lethal transient cerebral ischemia.

Baicalin alleviates diabetes‑associated cognitive deficits via modulation of mitogen-activated protein kinase signaling, brain‑derived neurotrophic factor and apoptosis

Baicalin is an important active component of the medicinal herb Scutellaria baicalensis Georgi and has shown a variety of pharmacological actions. The present study aimed to evaluate the neuroprotective effects of baicalin against diabetes‑associated cognitive deficits (DACD) in rats and to elucidate the potential molecular mechanisms of action. A rat model of diabetes mellitus was prepared by intraperitoneal injection of streptozotocin. After the successful establishment of the diabetic rat model, baicalin (50, 100 and 200 mg/kg) or vehicle was administrated for seven weeks. Learning and memory function were assessed using the Morris water maze test. At the end of the experiment, the activities of acetylcholinesterase (AChE) and choline acetylase (ChAT) were determined using commercial kits. Furthermore, the expression of proteins involved in mitogen‑activated protein kinase (MAPK) cascades [extracellular signal‑regulated kinase (ERK), c‑Jun N‑terminal kinase (JNK) and p38], brain‑derived neurotrophic factor (BDNF) and apoptosis‑associated proteins [caspase‑3, B-cell lymphoma 2 (Bcl‑2) and Bcl-2-associated X protein (Bax)] were detected by western blot analysis. Caspase‑3 activity was also analyzed using a commercial kit. The results demonstrated that diabetic rats exhibited decreases in body weight, decreases in the percentage of time spent in the target quadrant and the number of times of crossing the platform in the water maze test, as well as decreases in neuronal survival, ChAT, phosphorylated (p)ERK, BDNF and Bcl‑2. Furthermore, diabetic rats showed increases in escape latency and mean path length in the water maze test, increases in the levels of hippocampal AChE, p‑JNK, p‑p38, caspase‑3 and Bax as well as plasma glucose. However, in diabetic rats treated with baicalin, all of the abovementioned observations were obviously reversed. The findings suggested that baicalin exerts neuroprotective effects against DACD via modulation of MAPK cascades, BDNF and apoptosis.

Phase II anti-inflammatory and immune-modulating drugs for acute ischaemic stroke

INTRODUCTION

Stroke is the second leading cause of death worldwide and the leading cause of adult neurological disability. Despite advances in stroke unit care, and increasing use of thrombolysis, there remains an urgent need for safe and effective treatments for acute ischaemic stroke. However, this is against a backdrop of multiple failures in translational drug development. Cerebral ischaemia initiates a complex cascade of immune and inflammatory pathways in the brain microvasculature and periphery, which contribute to the evolution of cerebral injury, resolution and repair. Targeting specific inflammatory or immune pathways, therefore, represents an attractive treatment strategy in acute ischaemic stroke. Although anti-inflammatory drugs have already failed in clinical trial development, several are currently at the Phase II developmental stage.

AREAS COVERED

The authors highlight several candidate drugs, which modulate a range of inflammatory and immune pathways, and have been investigated in pre-clinical and Phase II studies to date.

EXPERT OPINION

Drugs targeting inflammatory and immune pathways offer theoretical advantages including potentially longer therapeutic time windows and effects complementary to thrombolysis (ameliorating reperfusion injury). Fundamental changes in the approach to pre-clinical and clinical drug development are required to facilitate successful translation of promising candidate drugs into clinical practice.

Neocortical pCREB and BDNF expression under different modes of hypobaric hypoxia: role in brain hypoxic tolerance in rats

Preconditioning with repetitive mild hypobaric hypoxia is known to increase tolerance of susceptible brain neurons to severe hypoxia, whereas a single trial of mild hypoxia has been ineffective. In the present study, the effects of three-trial and one-trial hypobaric preconditioning on the expression of the protective transcription factor phosphorylated CREB (pCREB) and neurotrophin BDNF, before and after severe hypobaric hypoxia, have been comparatively studied in the neocortex of rats. As revealed by quantitative immunocytochemistry, the severe hypobaric hypoxia (180 Torr, 3h) substantially down-regulated the levels of pCREB and BDNF in cortical neurons assessed 24h after the treatment. One trial of mild hypoxia (360 Torr, 2h) also reduced by half the number of BDNF-expressing cells, but had no effect on pCREB expression in the neocortex. In contrast, the exposure to three trials of mild hypoxia at 24h intervals considerably up-regulated pCREB and BDNF levels in the neocortex of rats. Only preconditioning by three trials of mild hypoxia (360 Torr, 2h, 24h intervals), but not a single trial preconditioning, was neuroprotective significantly enhancing the pCREB and BDNF neuronal expression in response to severe hypoxic challenge. The results of the present study indicate that development of the neuronal hypoxic tolerance induced by the three-trial mild hypoxic preconditioning is apparently associated with activation of CREB and BDNF expression.

Protective effect of donepezil hydrochloride on cerebral ischemia/reperfusion injury in mice

The aim of this study was to investigate the effects of donepezil hydrochloride (DH) on the expression of the calpain I-cyclin-dependent kinase5/p25 (CDK5/p25) pathway in the hippocampal CA1 region in mice with cerebral ischemia-reperfusion (I/R). Mice were randomly divided and assigned to the sham operation group (SO), the model group (MG) and the DH treatment group (TG). The pathological appearance of the hippocampal CA1 region and the expression of calpain I and CDK5/p25, were observed on the 4th, 6th and 8th week of the I/R surgery. Within the same time periods, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were also determined. At each postoperative time point, the normal neuron count in the hippocampal CA1 region in the MG was significantly lower than that in the SO (P<0.05), whereas the calpain I and CDK5/p25 expression, SOD activity and MDA content in the MG were significantly higher than those in the SO (P<0.05). The normal neuron count of the hippocampal CA1 region in the TG increased significantly (P<0.05), whereas the calpain I and CDK5/p25 expression, SOD activity and MDA content in the TG were significantly lower than those in the MG (P<0.05). DH has protective effects against ischemic damage. The ability of DH to improve learning and memory in mice may be due to its ability to decrease the expression of the calpain I-CDK5/p25 pathway and reduce oxidative damage.

Undifferentiated and differentiated PC12 cells protected by huprines against injury induced by hydrogen peroxide

Oxidative stress is implicated in the pathogenesis of neurodegenerative disorders and hydrogen peroxide (H₂O₂) plays a central role in the stress. Huprines, a group of potent acetylcholinesterase inhibitors (AChEIs), have shown a broad cholinergic pharmacological profile. Recently, it has been observed that huprine X (HX) improves cognition in non transgenic middle aged mice and shows a neuroprotective activity (increased synaptophysin expression) in 3xTg-AD mice. Consequently, in the present experiments the potential neuroprotective effect of huprines (HX, HY, HZ) has been analyzed in two different in vitro conditions: undifferentiated and NGF-differentiated PC12 cells. Cells were subjected to oxidative insult (H₂O₂, 200 µM) and the protective effects of HX, HY and HZ (0.01 µM–1 µM) were analyzed after a pre-incubation period of 24 and 48 hours. All huprines showed protective effects in both undifferentiated and NGF-differentiated cells, however only in differentiated cells the effect was dependent on cholinergic receptors as atropine (muscarinic antagonist, 0.1 µM) and mecamylamine (nicotinic antagonist, 100 µM) reverted the neuroprotection action of huprines. The decrease in SOD activity observed after oxidative insult was overcome in the presence of huprines and this effect was not mediated by muscarinic or nicotinic receptors. In conclusion, huprines displayed neuroprotective properties as previously observed in in vivo studies. In addition, these effects were mediated by cholinergic receptors only in differentiated cells. However, a non-cholinergic mechanism, probably through an increase in SOD activity, seems to be also involved in the neuroprotective effects of huprines.

Neuroprotective effects of donepezil against Aβ42-induced neuronal toxicity are mediated through not only enhancing PP2A activity but also regulating GSK-3β and nAChRs activity

The main purpose of this study was to evaluate whether donepezil, acetylcholinesterase inhibitor, shown to play a protective role through inhibiting glycogen synthesis kinase-3β (GSK-3β) activity, could also exert neuroprotective effects by stimulating protein phosphatase 2A (PP2A) activity in the amyloid-beta (Aβ)42-induced neuronal toxicity model of Alzheimer's disease. In Aβ42-induced toxic conditions, each PP2A and GSK-3β activity measured at different times showed time-dependent reverse pattern toward the direction of accelerating neuronal deaths with the passage of time. In addition, donepezil pre-treatment showed dose-dependent stepwise increase of neuronal viability and stimulation of PP2A activity. However, such effects on them were significantly reduced through the depletion of PP2A activity with either okadaic acid or PP2Ac siRNA. In spite of blocked PP2A activity in this Aβ42 insult, however, donepezil pretreatment showed additional significant recovering effect on neuronal viability when compared to the value without donepezil. Moreover, donepezil partially recovered its dephosphorylating effect on hyperphosphorylated tau induced by Aβ42. This observation led us to assume that additional mechanisms of donepezil, including its inhibitory effect on GSK-3β activity and/or the activation role of nicotinic acetylcholine receptors (nAChRs), might be involved. Taken together, our results suggest that the neuroprotective effects of donepezil against Aβ42-induced neurotoxicity are mediated through activation of PP2A, but its additional mechanisms including regulation of GSK-3β and nAChRs activity would partially contribute to its effects. We investigated neuroprotective mechanisms of donepezil against Aβ42 toxicity: Donepezil increased neuronal viability with reduced p-tau by enhancing PP2A activity. Despite of blocked PP2A activity, donepezil showed additional recovering effect on neuronal viability, which findings led us to assume that additional mechanisms of donepezil including its inhibitory effect on GSK-3β activity and activating role of nicotinic AChRs might be involved.

Nimodipine improves regional cerebral blood flow and suppresses inflammatory factors in the hippocampus of rats with vascular dementia

OBJECTIVE

To study the effect of nimodipine on hippocampal regional cerebral blood flow (rCBF) and proinflammatory cytokines in rats with experimental vascular dementia.

METHODS

Male Sprague Dawley rats were randomly divided into four groups (n = 15/group): sham operated controls (group A); focal cerebral ischaemia (group B); vascular dementia (group C); and vascular dementia treated with 20 mg/kg nimodipine daily (group D). The Morris water maze test evaluated learning and memory, and magnetic resonance perfusion-weighted imaging was used to measure rCBF. Hippocampal levels of nuclear factor-κB (NF-κB), tumour necrosis factor-α (TNF-α) and interleukin 1β (IL-1β) were measured.

RESULTS

Compared with group C, rats in group D demonstrated significantly improved learning ability and significantly increased hippocampal rCBF. The levels of NF-κB, TNF-α and IL-1β were significantly lower in group D than in group C. Hippocampal nerve cell morphology was abnormal in group C but near normal in group D.

CONCLUSIONS

Nimodipine improved the symptoms of cognitive impairment, increased rCBF, reduced hippocampal cytokine levels and alleviated neuronal injury in the hippocampus of rats with experimental vascular dementia.