Changes in hippocampal synapses and learning-memory abilities in a streptozotocin-treated rat model and intervention by using fasudil hydrochloride

Methionine Aminopeptidase 2 (MetAP2) Inhibitor BL6 Attenuates Inflammation in Cultured Microglia and in a Mouse Model of Alzheimer's Disease

Methionine aminopeptidase 2 (MetAP2) plays an important role in the regulation of protein synthesis and post-translational processing. Preclinical/clinical applications of MetAP2 inhibitors for the treatment of various diseases have been explored because of their antiangiogenic, anticancer, antiobesity, antidiabetic, and immunosuppressive properties. However, the effects of MetAP2 inhibitors on CNS diseases are rarely examined despite the abundant presence of MetAP2 in the brain. Previously, we synthesized a novel boron-containing MetAP2 inhibitor, BL6, and found that it suppressed angiogenesis and adipogenesis yet improved glucose uptake. Here, we studied the anti-inflammatory effects of BL6 in SIM-A9 microglia and in a mouse model of Alzheimer's disease generated by the intracerebroventricular (icv) injection of streptozotocin (STZ). We found that BL6 reduced proinflammatory molecules, such as nitric oxide, iNOS, IL-1β, and IL-6, together with phospho-Akt and phospho-NF-κB p65, which were elevated in lipopolysaccharide (LPS)-activated microglial SIM-A9 cells. However, the LPS-induced reduction in Arg-1 and CD206 was attenuated by BL6, suggesting that BL6 promotes microglial M1 to M2 polarization. BL6 also decreased glial activation along with a reduction in phospho-tau and an elevation in synaptophysin in the icv-STZ mouse model. Thus, our experiments demonstrate an anti-neuroinflammatory action of BL6, suggesting possible clinical applications of MetAP2 inhibitors for brain disorders in which neuroinflammation is involved.

Drug Repurposing: A Leading Strategy for New Threats and Targets

Less than 6% of rare illnesses have an appropriate treatment option. Repurposed medications for new indications are a cost-effective and time-saving strategy that results in excellent success rates, which may significantly lower the risk associated with therapeutic development for rare illnesses. It is becoming a realistic alternative to repurposing "conventional" medications to treat joint and rare diseases considering the significant failure rates, high expenses, and sluggish stride of innovative medication advancement. This is due to delisted compounds, cheaper research fees, and faster development time frames. Repurposed drug competitors have been developed using strategic decisions based on data analysis, interpretation, and investigational approaches, but technical and regulatory restrictions must also be considered. Combining experimental and computational methodologies generates innovative new medicinal applications. It is a one-of-a-kind strategy for repurposing human-safe pharmaceuticals to treat uncommon and difficult-to-treat ailments. It is a very effective method for discovering and creating novel medications. Several pharmaceutical firms have developed novel therapies by repositioning old medications. Repurposing drugs is practical, cost-effective, and speedy and generally involves lower risks when compared to developing a new drug from the beginning.

Early chronic fasudil treatment rescues hippocampal alterations in the Ts65Dn model for down syndrome

Down syndrome (DS) is the most common genetic disorder associated with intellectual disability. To study this syndrome, several mouse models have been developed. Among the most common is the Ts65Dn model, which mimics most of the alterations observed in DS. Ts65Dn mice, as humans with DS, show defects in the structure, density, and distribution of dendritic spines in the cerebral cortex and hippocampus. Fasudil is a potent inhibitor of the RhoA kinase pathway, which is involved in the formation and stabilization of dendritic spines. Our study analysed the effect of early chronic fasudil treatment on the alterations observed in the hippocampus of the Ts65Dn model. We observed that treating Ts65Dn mice with fasudil induced an increase in neural plasticity in the hippocampus: there was an increment in the expression of PSA-NCAM and BDNF, in the dendritic branching and spine density of granule neurons, as well as in cell proliferation and neurogenesis in the subgranular zone. Finally, the treatment reduced the unbalance between excitation and inhibition present in this model. Overall, early chronic treatment with fasudil increases cell plasticity and eliminates differences with euploid animals.

Effect of the ROCK inhibitor fasudil on the brain proteomic profile in the tau transgenic mouse model of Alzheimer's disease

Introduction

The goal of this study is to explore the pharmacological potential of the amyloid-reducing vasodilator fasudil, a selective Ras homolog (Rho)-associated kinases (ROCK) inhibitor, in the P301S tau transgenic mouse model (Line PS19) of neurodegenerative tauopathy and Alzheimer's disease (AD).

Methods

We used LC-MS/MS, ELISA and bioinformatic approaches to investigate the effect of treatment with fasudil on the brain proteomic profile in PS19 tau transgenic mice. We also explored the efficacy of fasudil in reducing tau phosphorylation, and the potential beneficial and/or toxic effects of its administration in mice.

Results

Proteomic profiling of mice brains exposed to fasudil revealed the activation of the mitochondrial tricarboxylic acid (TCA) cycle and blood-brain barrier (BBB) gap junction metabolic pathways. We also observed a significant negative correlation between the brain levels of phosphorylated tau (pTau) at residue 396 and both fasudil and its metabolite hydroxyfasudil.

Conclusions

Our results provide evidence on the activation of proteins and pathways related to mitochondria and BBB functions by fasudil treatment and support its further development and therapeutic potential for AD.

Insights into early pathogenesis of sporadic Alzheimer's disease: role of oxidative stress and loss of synaptic proteins

Oxidative stress, induced by impaired insulin signaling in the brain contributes to cognitive loss in sporadic Alzheimer's disease (sAD). This study evaluated early hippocampal oxidative stress, pre- and post-synaptic proteins in intraperitoneal (IP) and intracerebroventricular (ICV) streptozotocin (STZ) models of impaired insulin signaling. Adult male Wistar rats were injected with STZ, IP, or ICV, and sacrificed 1-, 3-, or 6-weeks post injection. Rat's cognitive behavior was assessed using Morris water maze (MWM) tests at weeks 3 and 6. Hippocampal synaptosomal fractions were examined for oxidative stress markers and presynaptic [synapsin I, synaptophysin, growth-associated protein-43 (GAP-43), synaptosomal-associated protein-25 (SNAP-25)] and postsynaptic [drebrin, synapse-associated protein-97 (SAP-97), postsynaptic density protein-95 (PSD-95)] proteins. IP-STZ and ICV-STZ treatment impaired rat's cognition, decreased the levels of reduced glutathione (GSH) and increased the levels of thiobarbituric acid reactive species (TBARS) in a time dependent manner. In addition, it reduced the expression of pre- and post-synaptic proteins in the hippocampus. The decline in cognition is significantly correlated with the reduction in synaptic proteins in the hippocampus. In conclusion, impaired insulin signaling in the brain is deleterious in causing early synaptosomal oxidative damage and synaptic loss that exacerbates with time and correlates with cognitive impairments. Our data implicates oxidative stress and synaptic protein loss as an early feature of sAD and provides insights into early biochemical and behavioral changes during disease progression.

Impaired Insulin Signaling Alters Mediators of Hippocampal Synaptic Dynamics/Plasticity: A Possible Mechanism of Hyperglycemia-Induced Cognitive Impairment

Alzheimer's disease (AD) is a neurological condition that affects the elderly and is characterized by progressive and irreversible neurodegeneration in the cerebral cortex [...].

LIM Kinases, LIMK1 and LIMK2, Are Crucial Node Actors of the Cell Fate: Molecular to Pathological Features

LIM kinase 1 (LIMK1) and LIM kinase 2 (LIMK2) are serine/threonine and tyrosine kinases and the only two members of the LIM kinase family. They play a crucial role in the regulation of cytoskeleton dynamics by controlling actin filaments and microtubule turnover, especially through the phosphorylation of cofilin, an actin depolymerising factor. Thus, they are involved in many biological processes, such as cell cycle, cell migration, and neuronal differentiation. Consequently, they are also part of numerous pathological mechanisms, especially in cancer, where their involvement has been reported for a few years and has led to the development of a wide range of inhibitors. LIMK1 and LIMK2 are known to be part of the Rho family GTPase signal transduction pathways, but many more partners have been discovered over the decades, and both LIMKs are suspected to be part of an extended and various range of regulation pathways. In this review, we propose to consider the different molecular mechanisms involving LIM kinases and their associated signalling pathways, and to offer a better understanding of their variety of actions within the physiology and physiopathology of the cell.

Long-Term Paracetamol Treatment Impairs Cognitive Function and Brain-Derived Neurotrophic Factor in Adult Rat Brain

Paracetamol (acetaminophen, APAP) is known as a safe pain reliever; however, its negative effects on the central nervous system have gradually been reported. We examined alterations in learning and memory, and brain-derived neurotrophic factor (BDNF) expression in the frontal cortex and hippocampus at different durations of APAP treatment in rats. Novel object recognition (NOR) and Morris water maze (MWM) paradigms were used to assess learning and memory in rats fed with 200 mg/kg APAP at single-dose, 15-day or 30-day treatments. BDNF expression was evaluated through immunohistochemistry and Western blotting. The single-dose APAP treatment did not alter the NOR performance. However, deficits in the NOR and MWM capacities were detected in the rats with longer durations of APAP treatment. An analysis of BDNF expression revealed no significant change in BDNF expression in the single-dose APAP treatment, while rats given APAP for extended periods as treatment showed a significant decrement in this protein in the frontal cortex and hippocampus. Short-term APAP treatment has no effect on learning and memory, or BDNF expression; however, long-term APAP exposure causes cognitive impairment. The diminishment of the BDNF level in the frontal cortex and hippocampus due to the long period of treatment with APAP may at least in part be involved in altered learning and memory in rats.

Acupuncture Improves Synaptic Plasticity of SAMP8 Mice through the RhoA/ROCK Pathway

BACKGROUND

Studies have found synaptic plasticity damage to be an early marker of Alzheimer's disease (AD). RhoA/ROCK pathway is involved in the regulation of synaptic plasticity. Acupuncture can significantly improve the cognitive state of AD.

OBJECTIVE

We aimed to use modern biological technology to detect the changes in synaptic plasticity and RhoA/ROCK pathway in SAMP8 mice, as well as the intervention effect of acupuncture.

METHODS

Morris water maze and electrophysiological techniques were used in vivo to detect the changes in spatial memory and LTP of mice. Golgi Cox staining and CASEVIEWER2.1 software were used to quantitatively analyze the changes in the morphology and number of dendritic spines in the hippocampus of mice. The activity of RhoA and ROCK2 in the hippocampus of mice was detected, respectively, by pull-down technique and ELISA. WB technique was used to detect the protein expression of ROCK2 and phosphorylation level of MLC2, LIMK2, and CRMP2 in the hippocampus of mice.

RESULTS

The neurobehavior and synaptic plasticity of 8-month-old SAMP8 mice were found to be significantly impaired. Acupuncture could improve the spatial learning and memory ability of SAMP8 mice, and partially prevent the reduction in the number of spines on the secondary branches of the apical dendrites in the hippocampus and the attenuation of LTP. The RhoA/ROCK pathway was significantly activated in the hippocampus of 8-month-old SAMP8 mice, and acupuncture had an inhibitory effect on it.

CONCLUSION

Acupuncture can improve synaptic plasticity by inhibiting the abnormal activation of the RhoA/ROCK pathway, and improve the spatial learning and memory ability of AD, so as to achieve the purpose of treating AD.

Activating PPARβ/δ Protects against Endoplasmic Reticulum Stress-Induced Astrocytic Apoptosis via UCP2-Dependent Mitophagy in Depressive Model

As energy metabolism regulation factor, peroxisome proliferator-activated receptor (PPAR) is thought to be a potential target for the treatment of depression. The present study was performed to evaluate the effects of activating PPARβ/δ, the most highly expressed subtype in the brain, in depressive in vivo and in vitro models. We observed that PPARβ/δ agonist GW0742 significantly alleviated depressive behaviors in mice and promoted the formation of autophagosomes around the damaged mitochondria in hippocampal astrocytes. Our in vitro experiments showed that GW0742 could reduce mitochondrial oxidative stress, and thereby attenuate endoplasmic reticulum (ER) stress-mediated apoptosis pathway via inhibiting IRE1α phosphorylation, subsequently protect against astrocytic apoptosis and loss. Furthermore, we found that PPARβ/δ agonist induces astrocytic mitophagy companied with the upregulated UCP2 expressions. Knocking down UCP2 in astrocytes could block the anti-apoptosis and pro-mitophagy effects of GW0742. In conclusion, our findings reveal PPARβ/δ activation protects against ER stress-induced astrocytic apoptosis via enhancing UCP2-mediated mitophagy, which contribute to the anti-depressive action. The present study provides a new insight for depression therapy.

Mechanoregulation of Vascular Endothelial Growth Factor Receptor 2 in Angiogenesis

The endothelial cells that compose the vascular system in the body display a wide range of mechanotransductive behaviors and responses to biomechanical stimuli, which act in concert to control overall blood vessel structure and function. Such mechanosensitive activities allow blood vessels to constrict, dilate, grow, or remodel as needed during development as well as normal physiological functions, and the same processes can be dysregulated in various disease states. Mechanotransduction represents cellular responses to mechanical forces, translating such factors into chemical or electrical signals which alter the activation of various cell signaling pathways. Understanding how biomechanical forces drive vascular growth in healthy and diseased tissues could create new therapeutic strategies that would either enhance or halt these processes to assist with treatments of different diseases. In the cardiovascular system, new blood vessel formation from preexisting vasculature, in a process known as angiogenesis, is driven by vascular endothelial growth factor (VEGF) binding to VEGF receptor 2 (VEGFR-2) which promotes blood vessel development. However, physical forces such as shear stress, matrix stiffness, and interstitial flow are also major drivers and effectors of angiogenesis, and new research suggests that mechanical forces may regulate VEGFR-2 phosphorylation. In fact, VEGFR-2 activation has been linked to known mechanobiological agents including ERK/MAPK, c-Src, Rho/ROCK, and YAP/TAZ. In vascular disease states, endothelial cells can be subjected to altered mechanical stimuli which affect the pathways that control angiogenesis. Both normalizing and arresting angiogenesis associated with tumor growth have been strategies for anti-cancer treatments. In the field of regenerative medicine, harnessing biomechanical regulation of angiogenesis could enhance vascularization strategies for treating a variety of cardiovascular diseases, including ischemia or permit development of novel tissue engineering scaffolds. This review will focus on the impact of VEGFR-2 mechanosignaling in endothelial cells (ECs) and its interaction with other mechanotransductive pathways, as well as presenting a discussion on the relationship between VEGFR-2 activation and biomechanical forces in the extracellular matrix (ECM) that can help treat diseases with dysfunctional vascular growth.

Tau Cleavage Contributes to Cognitive Dysfunction in Strepto-Zotocin-Induced Sporadic Alzheimer's Disease (sAD) Mouse Model

Tau cleavage plays a crucial role in the onset and progression of Alzheimer’s Disease (AD), a widespread neurodegenerative disease whose incidence is expected to increase in the next years. While genetic and familial forms of AD (fAD) occurring early in life represent less than 1%, the sporadic and late-onset ones (sAD) are the most common, with ageing being an important risk factor. Intracerebroventricular (ICV) infusion of streptozotocin (STZ)—a compound used in the systemic induction of diabetes due to its ability to damage the pancreatic β cells and to induce insulin resistance—mimics in rodents several behavioral, molecular and histopathological hallmarks of sAD, including memory/learning disturbance, amyloid-β (Aβ) accumulation, tau hyperphosphorylation, oxidative stress and brain glucose hypometabolism. We have demonstrated that pathological truncation of tau at its N-terminal domain occurs into hippocampi from two well-established transgenic lines of fAD animal models, such as Tg2576 and 3xTg mice, and that it’s in vivo neutralization via intravenous (i.v.) administration of the cleavage-specific anti-tau 12A12 monoclonal antibody (mAb) is strongly neuroprotective. Here, we report the therapeutic efficacy of 12A12mAb in STZ-infused mice after 14 days (short-term immunization, STIR) and 21 days (long-term immunization regimen, LTIR) of i.v. delivery. A virtually complete recovery was detected after three weeks of 12A12mAb immunization in both novel object recognition test (NORT) and object place recognition task (OPRT). Consistently, three weeks of this immunization regimen relieved in hippocampi from ICV-STZ mice the AD-like up-regulation of amyloid precursor protein (APP), the tau hyperphosphorylation and neuroinflammation, likely due to modulation of the PI3K/AKT/GSK3-β axis and the AMP-activated protein kinase (AMPK) activities. Cerebral oxidative stress, mitochondrial impairment, synaptic and histological alterations occurring in STZ-infused mice were also strongly attenuated by 12A12mAb delivery. These results further strengthen the causal role of N-terminal tau cleavage in AD pathogenesis and indicate that its specific neutralization by non-invasive administration of 12A12mAb can be a therapeutic option for both fAD and sAD patients, as well as for those showing type 2 diabetes as a comorbidity.

LIM-Kinases in Synaptic Plasticity, Memory, and Brain Diseases

Learning and memory require structural and functional modifications of synaptic connections, and synaptic deficits are believed to underlie many brain disorders. The LIM-domain-containing protein kinases (LIMK1 and LIMK2) are key regulators of the actin cytoskeleton by affecting the actin-binding protein, cofilin. In addition, LIMK1 is implicated in the regulation of gene expression by interacting with the cAMP-response element-binding protein. Accumulating evidence indicates that LIMKs are critically involved in brain function and dysfunction. In this paper, we will review studies on the roles and underlying mechanisms of LIMKs in the regulation of long-term potentiation (LTP) and depression (LTD), the most extensively studied forms of long-lasting synaptic plasticity widely regarded as cellular mechanisms underlying learning and memory. We will also discuss the involvement of LIMKs in the regulation of the dendritic spine, the structural basis of synaptic plasticity, and memory formation. Finally, we will discuss recent progress on investigations of LIMKs in neurological and mental disorders, including Alzheimer’s, Parkinson’s, Williams–Beuren syndrome, schizophrenia, and autism spectrum disorders.

Nao-Fu-Cong ameliorates diabetic cognitive dysfunction by inhibition of JNK/CHOP/Bcl2-mediated apoptosis in vivo and in vitro

Chinese herbal compound Nao-Fu-Cong (NFC) has been mainly used to treat cognitive disorders in Traditional Chinese Medicine (TCM). The present study aimed to investigate whether its neuroprotective effects might be related to the inhibition of JNK/CHOP/Bcl2-mediated apoptosis pathway or not. We randomly assigned STZ (60 mg·kg^-1)-induced diabetic rats into control group, diabetic model group and NFC groups (low-dose, medium-dose and high-dose). The primary culture of hippocampal neurons were transferred into different culture media on the third day. The cells were then divided into control group, high-glucose group, NFC (low-dose, medium-dose and high-dose) groups, CHOP si-RNA intervention group, JNK pathway inhibitor SP600125 group and oxidative stress inhibitor N-acetylcysteine (NAC) group. NFC significantly improved the cognitive function of diabetic rats, and had neuroprotective effect on hippocampal neurons cultured in high glucose. Further research results showed that NFC could reduce the apoptosis of hippocampal neurons in rats with diabetic cognitive dysfunction. NFC had inhibitory effects on CHOP/JNK apoptosis pathway induced by high glucose, and also decreased the levels of ROS and increased the mitochondrial membrane potential. These suggested that the neuroprotective effect of NFC might be related to the inhibition of CHOP and JNK apoptotic signaling pathways, and the cross pathway between oxidative stress and mitochondrial damage pathway.

GJ-4 ameliorates memory impairment in focal cerebral ischemia/reperfusion of rats via inhibiting JAK2/STAT1-mediated neuroinflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Gardenia jasminoides J. Ellis (Fructus Gardenia) is a traditional Chinese medicine with diverse pharmacological functions, such as anti-inflammation, anti-depression, as well as improvement of cognition and ischemia brain injury. GJ-4 is a natural extract from Gardenia jasminoides J. Ellis (Fructus Gardenia) and has been proved to improve memory impairment in Alzheimer's disease (AD) mouse model in our previous studies.

AIM OF THE STUDY

This study aimed to evaluate the therapeutic effects of GJ-4 on vascular dementia (VD) and explore the potential mechanisms.

MATERIAL AND METHODS

In our experiment, a focal cerebral ischemia and reperfusion rat model was successfully developed by the middle cerebral artery occlusion and reperfusion (MCAO/R). GJ-4 (10 mg/kg, 25 mg/kg, 50 mg/kg) and nimodipine (10 mg/kg) were orally administered to rats once a day for consecutive 12 days. Learning and memory behavioral performance was assayed by step-down test and Morris water maze test. The neurological scoring test was performed to evaluate the neurological function of rats. 2,3,5-Triphenyltetrazolium chloride (TTC) staining and Nissl staining were respectively employed to determine the infarct condition and neuronal injury of the brain. Iba1 immunohistochemistry was used to show the activation of microglia. Moreover, the synaptic damage and inflammatory level were detected by Western blot.

RESULTS

GJ-4 could significantly improve memory impairment, cerebral infraction, as well as neurological deficits of VD rats induced by MCAO/R. Further research indicated VD-induced neuronal injury was alleviated by GJ-4. In addition, GJ-4 could protect synapse of VD rats by upregulating synaptophysin (SYP) expression, post synaptic density 95 protein (PSD95) expression, and downregulating N-Methyl-D-Aspartate receptor 1 (NMDAR1) expression. Subsequent investigation of the underlying mechanisms identified that GJ-4 could suppress neuroinflammatory responses, supported by inhibited activation of microglia and reduced expression of inflammatory proteins, which ultimately exerted neuroprotective effects on VD. Further mechanistic study indicated that janus kinase 2 (JAK2)/signal transducer and activator of transcription 1 (STAT1) pathway was inhibited by GJ-4 treatment.

CONCLUSION

These results suggested that GJ-4 might serve as a potential drug to improve VD. In addition, our study indicated that inhibition of neuroinflammation might be a promising target to treat VD.

Drug repositioning and repurposing for Alzheimer disease

Drug repositioning and repurposing can enhance traditional drug development efforts and could accelerate the identification of new treatments for individuals with Alzheimer disease (AD) dementia and mild cognitive impairment. Transcriptional profiling offers a new and highly efficient approach to the identification of novel candidates for repositioning and repurposing. In the future, novel AD transcriptional signatures from cells isolated at early stages of disease, or from human neurons or microglia that carry mutations that increase the risk of AD, might be used as probes to identify additional candidate drugs. Phase II trials assessing repurposed agents must consider the best target population for a specific candidate therapy as well as the mechanism of action of the treatment. In this Review, we highlight promising compounds to prioritize for clinical trials in individuals with AD, and discuss the value of Delphi consensus methodology and evidence-based reviews to inform this prioritization process. We also describe emerging work, focusing on the potential value of transcript signatures as a cost-effective approach to the identification of novel candidates for repositioning.

Alterations in Synaptic Plasticity and Oxidative Stress Following Long-Term Paracetamol Treatment in Rat Brain

Several studies have recently revealed that cognitive function can be affected by paracetamol (APAP) treatment. However, the exact impact of this drug treatment on learning and memory has not been clarified. This study aimed to investigate the effect of APAP treatment on the alteration of synapses and oxidative stress in the rat frontal cortex and hippocampus. APAP at a dose of 200 mg/kg bw was fed to adult male Wistar rats through either acute (n = 10), 15-day (n = 10), or 30-day (n = 10) treatment regimens. The synaptic ultrastructure and proteins, synaptophysin (SYP) and postsynaptic density-95 (PSD-95), were monitored. The amount of protein carbonyl oxidation (PCO) and glutathione (GSH) levels were examined. Our results demonstrated that acute treatment with APAP had no effect on synapses and oxidative stress. However, the synapses obtained from rats with 15-day APAP treatment showed a marked shortening of active zones and widening of the synaptic cleft. Decrement of SYP and PSD-95 proteins were demonstrated in these rats as well. With 30-day APAP treatment, the alteration of the synaptic ultrastructure and proteins was more evident. Moreover, the depletion of GSH and the elevation of PCO levels were demonstrated in the rats treated with APAP for 30 days. These results suggest that long-term APAP treatment can induce synaptic degeneration in the hippocampus and frontal cortex. The increase in oxidative stress in these brain areas may be due to the deleterious effect of this drug.

Combination of drug and stem cells neurotherapy: Potential interventions in neurotrauma and traumatic brain injury

Traumatic brain injury (TBI) has been recognized as one of the major public health issues that leads to devastating neurological disability. As a consequence of primary and secondary injury phases, neuronal loss following brain trauma leads to pathophysiological alterations on the molecular and cellular levels that severely impact the neuropsycho-behavioral and motor outcomes. Thus, to mitigate the neuropathological sequelae post-TBI such as cerebral edema, inflammation and neural degeneration, several neurotherapeutic options have been investigated including drug intervention, stem cell use and combinational therapies. These treatments aim to ameliorate cellular degeneration, motor decline, cognitive and behavioral deficits. Recently, the use of neural stem cells (NSCs) coupled with selective drug therapy has emerged as an alternative treatment option for neural regeneration and behavioral rehabilitation post-neural injury. Given their neuroprotective abilities, NSC-based neurotherapy has been widely investigated and well-reported in numerous disease models, notably in trauma studies. In this review, we will elaborate on current updates in cell replacement therapy in the area of neurotrauma. In addition, we will discuss novel combination drug therapy treatments that have been investigated in conjunction with stem cells to overcome the limitations associated with stem cell transplantation. Understanding the regenerative capacities of stem cell and drug combination therapy will help improve functional recovery and brain repair post-TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Luteolin Ameliorates Cognitive Impairments by Suppressing the Expression of Inflammatory Cytokines and Enhancing Synapse-Associated Proteins GAP-43 and SYN Levels in Streptozotocin-Induced Diabetic Rats

Luteolin, a flavonoid isolated from Cirsium japonicum, has antioxidant, anti-inflammatory and neuroprotective activities. Our previous studies brought a prospect that luteolin benefited diabetic rats with cognitive impairments. In this study, we examined whether luteolin could suppress the inflammatory cytokines, thus increasing synapse-associated proteins in streptozotocin (STZ)-induced diabetes in rat models. The model rats underwent luteolin treatment for 8 consecutive weeks, followed by assessment of cognitive performances with MWM test. Nissl staining was employed to assess the neuropathological changes in the hippocampus and the effects of luteolin on diabetic rats. With animals sacrificed, expressions of inflammatory cytokines including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) and synapse-associated proteins including growth-associated protein-43 (GAP-43) and synaptophysin (SYN) were determined. The results affirmed improvement of behavioral performances in the MWM test, downexpression of glycation end products (AGEs) in the plasma and the receptor for advanced glycation end products in the hippocampus, inhibition of IL-1β and TNF-α in both the hippocampus and plasma in diabetic rats. Furthermore, luteolin treatment upregulated the expressions of GAP-43 and SYN in the hippocampus. Thus, luteolin could ameliorate the cognitive dysfunctions in STZ-induced diabetic rat model.

Rho GTPases in Intellectual Disability: From Genetics to Therapeutic Opportunities

Rho-class small GTPases are implicated in basic cellular processes at nearly all brain developmental steps, from neurogenesis and migration to axon guidance and synaptic plasticity. GTPases are key signal transducing enzymes that link extracellular cues to the neuronal responses required for the construction of neuronal networks, as well as for synaptic function and plasticity. Rho GTPases are highly regulated by a complex set of activating (GEFs) and inactivating (GAPs) partners, via protein:protein interactions (PPI). Misregulated RhoA, Rac1/Rac3 and cdc42 activity has been linked with intellectual disability (ID) and other neurodevelopmental conditions that comprise ID. All genetic evidences indicate that in these disorders the RhoA pathway is hyperactive while the Rac1 and cdc42 pathways are consistently hypoactive. Adopting cultured neurons for in vitro testing and specific animal models of ID for in vivo examination, the endophenotypes associated with these conditions are emerging and include altered neuronal networking, unbalanced excitation/inhibition and altered synaptic activity and plasticity. As we approach a clearer definition of these phenotype(s) and the role of hyper- and hypo-active GTPases in the construction of neuronal networks, there is an increasing possibility that selective inhibitors and activators might be designed via PPI, or identified by screening, that counteract the misregulation of small GTPases and result in alleviation of the cognitive condition. Here we review all knowledge in support of this possibility.

Rho-associated protein kinases as therapeutic targets for both vascular and parenchymal pathologies in Alzheimer's disease

The causes of late-onset Alzheimer's disease are unclear and likely multifactorial. Rho-associated protein kinases (ROCKs) are ubiquitously expressed signaling messengers that mediate a wide array of cellular processes. Interestingly, they play an important role in several vascular and brain pathologies implicated in Alzheimer's etiology, including hypertension, hypercholesterolemia, blood-brain barrier disruption, oxidative stress, deposition of vascular and parenchymal amyloid-beta peptides, tau hyperphosphorylation, and cognitive decline. The current review summarizes the functions of ROCKs with respect to the various risk factors and pathologies on both sides of the blood-brain barrier and present support for targeting ROCK signaling as a multifactorial and multi-effect approach for the prevention and amelioration of late-onset Alzheimer's disease. This article is part of the Special Issue "Vascular Dementia".

RhoA Signaling and Synaptic Damage Occur Within Hours in a Live Pig Model of CNS Injury, Retinal Detachment

PURPOSE

The RhoA pathway is activated after retinal injury. However, the time of onset and consequences of activation are unknown in vivo. Based on in vitro studies we focused on a period 2 hours after retinal detachment, in pig, an animal whose retina is holangiotic and contains cones.

METHODS

Under anesthesia, retinal detachments were created by subretinal injection of a balanced salt solution. Two hours later, animals were sacrificed and enucleated for GTPase activity assays and quantitative Western blot and confocal microscopy analyses.

RESULTS

RhoA activity with detachment was increased 1.5-fold compared to that in normal eyes or in eyes that had undergone vitrectomy only. Increased phosphorylation of myosin light chain, a RhoA effector, also occurred. By 2 hours, rod cells had retracted their terminals toward their cell bodies, disrupting the photoreceptor-to-bipolar synapse and producing significant numbers of spherules with SV2 immunolabel in the outer nuclear layer of the retina. In eyes with detachment, distant retina that remained attached also showed significant increases in RhoA activity and synaptic disjunction. Increases in RAC1 activity and glial fibrillary acidic protein (GFAP) were not specific for detachment, and sprouting of bipolar dendrites, reported for longer detachments, was not seen. The RhoA kinase inhibitor Y27632 significantly reduced axonal retraction by rod cells.

CONCLUSIONS

Activation of the RhoA pathway occurs quickly after injury and promotes synaptic damage that can be controlled by RhoA kinase inhibition. We suggest that retinal detachment joins the list of central nervous system injuries, such as stroke and spinal cord injury, that should be considered for rapid therapeutic intervention.

Stem cells and combination therapy for the treatment of traumatic brain injury

TBI is a nondegenerative, noncongenital insult to the brain from an external mechanical force; for instance a violent blow in a car accident. It is a complex injury with a broad spectrum of symptoms and has become a major cause of death and disability in addition to being a burden on public health and societies worldwide. As such, finding a therapy for TBI has become a major health concern for many countries, which has led to the emergence of many monotherapies that have shown promising effects in animal models of TBI, but have not yet proven any significant efficacy in clinical trials. In this paper, we will review existing and novel TBI treatment options. We will first shed light on the complex pathophysiology and molecular mechanisms of this disorder, understanding of which is a necessity for launching any treatment option. We will then review most of the currently available treatments for TBI including the recent approaches in the field of stem cell therapy as an optimal solution to treat TBI. Therapy using endogenous stem cells will be reviewed, followed by therapies utilizing exogenous stem cells from embryonic, induced pluripotent, mesenchymal, and neural origin. Combination therapy is also discussed as an emergent novel approach to treat TBI. Two approaches are highlighted, an approach concerning growth factors and another using ROCK inhibitors. These approaches are highlighted with regard to their benefits in minimizing the outcomes of TBI. Finally, we focus on the consequent improvements in motor and cognitive functions after stem cell therapy. Overall, this review will cover existing treatment options and recent advancements in TBI therapy, with a focus on the potential application of these strategies as a solution to improve the functional outcomes of TBI.

The ROCK Inhibitor Fasudil Prevents Chronic Restraint Stress-Induced Depressive-Like Behaviors and Dendritic Spine Loss in Rat Hippocampus

BACKGROUND

Dendritic arbor simplification and dendritic spine loss in the hippocampus, a limbic structure implicated in mood disorders, are assumed to contribute to symptoms of depression. These morphological changes imply modifications in dendritic cytoskeleton. Rho GTPases are regulators of actin dynamics through their effector Rho kinase. We have reported that chronic stress promotes depressive-like behaviors in rats along with dendritic spine loss in apical dendrites of hippocampal pyramidal neurons, changes associated with Rho kinase activation. The present study proposes that the Rho kinase inhibitor Fasudil may prevent the stress-induced behavior and dendritic spine loss.

METHODS

Adult male Sprague-Dawley rats were injected with saline or Fasudil (i.p., 10 mg/kg) starting 4 days prior to and maintained during the restraint stress procedure (2.5 h/d for 14 days). Nonstressed control animals were injected with saline or Fasudil for 18 days. At 24 hours after treatment, forced swimming test, Golgi-staining, and immuno-western blot were performed.

RESULTS

Fasudil prevented stress-induced immobility observed in the forced swimming test. On the other hand, Fasudil-treated control animals showed behavioral patterns similar to those of saline-treated controls. Furthermore, we observed that stress induced an increase in the phosphorylation of MYPT1 in the hippocampus, an exclusive target of Rho kinase. This change was accompanied by dendritic spine loss of apical dendrites of pyramidal hippocampal neurons. Interestingly, increased pMYPT1 levels and spine loss were both prevented by Fasudil administration.

CONCLUSION

Our findings suggest that Fasudil may prevent the development of abnormal behavior and spine loss induced by chronic stress by blocking Rho kinase activity.

Melatonin attenuates the high-fat diet and streptozotocin-induced reduction in rat hippocampal neurogenesis

A deviant level of melatonin in blood circulation has been associated with the development of diabetes and with learning and memory deficiencies. Melatonin might have an important function in diabetes control; however, the mechanism of melatonin in diabetes remains unknown. The present study aimed to investigate the hyperglycemic condition induced by high-fat diet (HFD) feeding and streptozotocin (STZ) injection and to examine the effect of melatonin on adult hippocampal functions. HFD-fed and STZ-treated rats significantly increased blood glucose level. The present study showed that HFD-fed and STZ-treated rats significantly impaired memory in the Morris Water Maze task, reduced neurogenesis in the hippocampus shown by a reduction in nestin, doublecortin (DCX) and β-III tubulin immunoreactivities, reduced axon terminal markers, synaptophysin, reduced dendritic marker including postsynaptic density 95 (PSD-95) and the glutamate receptor subunit NR2A. Moreover, a significant downregulation of melatonin receptor, insulin receptor-β (IR-β) and both p-IR-β and phosphorylated extracellular signal-regulated kinase (p-ERK) occurred in HFD-fed and STZ-treated rats, while the level of glial fibrillary acidic protein (GFAP) increased. Treatment of melatonin, rats had shorter escape latencies and remained in the target quadrant longer compared to the HFD-fed and STZ-treated rats. Melatonin attenuated the reduction of neurogenesis, synaptogenesis and the induction of astrogliosis. Moreover, melatonin countered the reduction of melatonin receptor, insulin receptor and downstream signaling pathway for insulin. Our data suggested that the dysfunction of insulin signaling pathway occurred in the diabetes may provide a convergent mechanism of hippocampal impaired neurogenesis and synaptogenesis lead to impair memory while melatonin reverses these effects, suggesting that melatonin may reduce the pathogenesis of diabetes.

Fasudil treatment in adult reverses behavioural changes and brain ventricular enlargement in Oligophrenin-1 mouse model of intellectual disability

Loss of function mutations in human Oligophrenin1 (OPHN1) gene are responsible for syndromic intellectual disability (ID) associated with cerebellar hypoplasia and cerebral ventricles enlargement. Functional studies in rodent models suggest that OPHN1 linked ID is a consequence of abnormal synaptic transmission and shares common pathophysiological mechanisms with other cognitive disorders. Variants of this gene have been also identified in autism spectrum disorder and schizophrenia. The advanced understanding of the mechanisms underlying OPHN1-related ID, allowed us to develop a therapeutic approach targeting the Ras homolog gene family, member A (RHOA) signalling pathway and repurpose Fasudil- a well-tolerated Rho Kinase (ROCK) and Protein Kinase A (PKA) inhibitor- as a treatment of ID. We have previously shown ex-vivo its beneficial effect on synaptic transmission and plasticity in a mouse model of the OPHN1 loss of function. Here, we report that chronic treatment in adult mouse with Fasudil, is able to counteract vertical and horizontal hyperactivities, restores recognition memory and limits the brain ventricular dilatation observed in Ophn1^-/y However, deficits in working and spatial memories are partially or not rescued by the treatment. These results highlight the potential of Fasudil treatment in synaptopathies and also the need for multiple therapeutic approaches especially in adult where brain plasticity is reduced.

Rho Kinases in Health and Disease: From Basic Science to Translational Research

Rho-associated kinases ROCK1 and ROCK2 are key regulators of actin cytoskeleton dynamics downstream of Rho GTPases that participate in the control of important physiologic functions, S including cell contraction, migration, proliferation, adhesion, and inflammation. Several excellent review articles dealing with ROCK function and regulation have been published over the past few years. Although a brief overview of general molecular, biochemical, and functional properties of ROCKs is included, an effort has been made to produce an original work by collecting and synthesizing recent studies aimed at translating basic discoveries from cell and experimental models into knowledge of human physiology, pathophysiological mechanisms, and medical therapeutics. This review points out the specificity and distinct roles of ROCK1 and ROCK2 isoforms highlighted in the last few years. Results obtained from genetically modified mice and genetic analysis in humans are discussed. This review also addresses the involvement of ROCKs in human diseases and the potential use of ROCK activity as a biomarker or a pharmacological target for specific inhibitors.

The role of Rho/Rho-kinase pathway and the neuroprotective effects of fasudil in chronic cerebral ischemia

The Rho/Rho-kinase signaling pathway plays an important role in cerebral ischemia/reperfusion injury. However, very few studies have examined in detail the changes in the Rho/Rho-kinase signaling pathway in chronic cerebral ischemia. In this study, rat models of chronic cerebral ischemia were established by permanent bilateral common carotid artery occlusion and intragastrically administered 9 mg/kg fasudil, a powerful ROCK inhibitor, for 9 weeks. Morris water maze results showed that cognitive impairment progressively worsened as the cerebral ischemia proceeded. Immunohistochemistry, semi-quantitative RT-PCR and western blot analysis showed that the expression levels of Rho-kinase, its substrate myosin-binding subunit, and its related protein alpha smooth muscle actin, significantly increased after chronic cerebral ischemia. TUNEL staining showed that chronic cerebral ischemia could lead to an increase in neuronal apoptosis, as well as the expression level of caspase-3 in the frontal cortex of rats subjected to chronic cerebral ischemia. Fasudil treatment alleviated the cognitive impairment in rats with chronic cerebral ischemia, and decreased the expression level of Rho-kinase, myosin-binding subunit and alpha smooth muscle actin. Furthermore, fasudil could regulate cerebral injury by reducing cell apoptosis and decreasing caspase-3 expression in the frontal cortex. These findings demonstrate that fasudil can protect against cognitive impairment induced by chronic cerebral ischemia via the Rho/Rho-kinase signaling pathway and anti-apoptosis mechanism.

Roles of LIM kinases in central nervous system function and dysfunction

LIM kinase 1 (LIMK1) and LIM kinase 2 (LIMK2) regulate actin dynamics by phosphorylating cofilin. In this review, we outline studies that have shown an involvement of LIMKs in neuronal function and we detail some of the pathways and molecular mechanisms involving LIMKs in neurodevelopment and synaptic plasticity. We also review the involvement of LIMKs in neuronal diseases and emphasize the differences in the regulation of LIMKs expression and mode of action. We finally present the existence of a cofilin-independent pathway also involved in neuronal function. A better understanding of the differences between both LIMKs and of the precise molecular mechanisms involved in their mode of action and regulation is now required to improve our understanding of the physiopathology of the neuronal diseases associated with LIMKs.

Fasudil, a rho kinase inhibitor, limits motor neuron loss in experimental models of amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with no effective treatment. Fasudil hydrochloride (fasudil), a potent rho kinase (ROCK) inhibitor, is useful for the treatment of ischaemic diseases. In previous reports, fasudil improved pathology in mouse models of Alzheimer's disease and spinal muscular atrophy, but there is no evidence in that it can affect ALS. We therefore investigated its effects on experimental models of ALS.

EXPERIMENTAL APPROACH

In mice motor neuron (NSC34) cells, the neuroprotective effect of hydroxyfasudil (M3), an active metabolite of fasudil, and its mechanism were evaluated. Moreover, the effects of fasudil, 30 and 100 mg·kg(-1), administered via drinking water to mutant superoxide dismutase 1 (SOD1(G93A)) mice were tested by measuring motor performance, survival time and histological changes, and its mechanism investigated.

KEY RESULTS

M3 prevented motor neuron cell death induced by SOD1(G93A). Furthermore, M3 suppressed both the increase in ROCK activity and phosphorylated phosphatase and tensin homologue deleted on chromosome 10 (PTEN), and the reduction in phosphorylated Akt induced by SOD1(G93A). These effects of M3 were attenuated by treatment with a PI3K inhibitor (LY294002). Moreover, fasudil slowed disease progression, increased survival time and reduced motor neuron loss, in SOD1(G93A) mice. Fasudil also attenuated the increase in ROCK activity and PTEN, and the reduction in Akt in SOD1(G93A) mice.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that fasudil may be effective at suppressing motor neuron degeneration and symptom progression in ALS. Hence, fasudil may have potential as a therapeutic agent for ALS treatment.

Intracranial injection of PEG-PEI/ROCK II-siRNA improves cognitive impairment in a mouse model of Alzheimer's disease

PURPOSE

A plenty of studies have demonstrated that the Rho/ROCK pathway is involved in the neuronal loss and inhibition of axonal regeneration observed in Alzheimer's disease (AD). Therefore, we conducted this study to evaluate whether intracranial injection of PEG-PEI/ROCK II siRNA (PPRS) would improve the cognitive impairments in a senescence-accelerated mouse (SAM) model of AD.

MATERIALS AND METHODS

Five male senescence-resistant inbred strain (SAMR1) mice and 15 male senescence-accelerated mouse prone-8 (SAMP8) strain mice were divided into the following three groups:PPRS group, PEG-PEI/ ROCK II-Scramble (PPRScr) siRNA group, and normal group (SAMR1). Total volumes of 2.3 μl of nanoparticles or saline were intracranially injected under the guidance of a stereotaxic apparatus. The injections were performed every three days and lasted for two weeks. Four weeks after injection, the Morris water maze (MWM) was used to evaluate the spatial learning and memory functions of the mice. Choline acetyltransferase (ChAT) activity was detected by immunohistochemistry.

RESULTS

Mice in the PPRS-treated group exhibited decreases in escape latencies over the three successive days of navigating the test and crossing the target quadrant during the spatial probe test more frequently than did the mice in the PPRScr-treated group. Analyses of ChAT activity revealed that greater numbers of ChAT-positive cells were present in the hippocampal regions of the PPRS-treated mice than in the PPRScr group.

CONCLUSIONS

Intracranial injection of PPRS improved the cognitive impairments of SAM mice, and this improvement may have been mediated by enhancement of ChAT activity in the hippocampus.

Clitoria ternatea ameliorated the intracerebroventricularly injected streptozotocin induced cognitive impairment in rats: behavioral and biochemical evidence

RATIONALE

Clitoria ternatea, commonly known as Aparajita, is used as Medhya rasayana in Ayurveda. The role of C. ternatea in experimental models of cognitive impairment is yet to be explored.

OBJECTIVES

The present study was designed to study the effect of aqueous and hydroalcoholic extracts of C. ternatea on biochemical and behavioral parameters related to cognitive impairment in in vitro and in vivo studies.

METHODS

In vitro free radical scavenging and enzyme-inhibitory (cholinesterase, glycogen synthase kinase-3-β, rho kinase, prolyl endopeptidase, catechol-O-methyl transferase, and lipoxygenase) activities of aqueous and hydroalcoholic extracts of C. ternatea plant were evaluated. Based on in vitro results, hydroalcoholic extract of C. ternatea (100, 300, and 500 mg/kg, p.o.) was selected for evaluation in intracerebroventricularly injected streptozotocin (STZ)-induced cognitive impairment in male Wistar rats. Behavioral assessment was performed at baseline and on the 14th, 21st, and 28th days after STZ injection using elevated plus maze, passive avoidance, Morris water maze, and photoactometer. Oxidative stress parameters (malondialdehyde, reduced glutathione, nitric oxide levels, and superoxide dismutase activity), cholinesterase activity, and rho kinase (ROCK II) expression were studied in cerebral cortex and hippocampus of rats' brain at the end of the study.

RESULTS

The hydroalcoholic extract possessed significantly more in vitro antioxidant and enzyme-inhibitory activities as compared to aqueous extract. The hydroalcoholic extract of C. ternatea prevented STZ-induced cognitive impairment dose dependently by reducing oxidative stress, cholinesterase activity, and ROCK II expression.

CONCLUSION

In vitro and in vivo results suggest the potential of hydroalcoholic extract of C. ternatea for treatment of cognitive deficit in neurological disorders.

Neuroprotective effects of ginsenoside Rb1 on high glucose-induced neurotoxicity in primary cultured rat hippocampal neurons

Ginsenoside Rb1 is one of the main active principles in traditional herb ginseng and has been reported to have a wide variety of neuroprotective effects. Endoplasmic reticulum (ER) stress has been implicated in neurodegenerative diseases, so the present study aimed to observe the effects of ginsenoside Rb1 on ER stress signaling pathways in high glucose-treated hippocampal neurons. The results from MTT, TUNEL labeling and Annexin V-FITC/PI/Hoechst assays showed that incubating neurons with 50 mM high glucose for 72h decreased cell viability and increased the number of apoptotic cells whereas treating neurons with 1 μM Rb1 for 72h protected the neurons against high glucose-induced cell damage. Further molecular mechanism study demonstrated that Rb1 suppressed the activation of ER stress-associated proteins including protein kinase RNA (PKR)-like ER kinase (PERK) and C/EBP homology protein (CHOP) and downregulation of Bcl-2 induced by high glucose. Moreover, Rb1 inhibited both the elevation of intracellular reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential induced by high glucose. In addition, the high glucose-induced cell apoptosis, activation of ER stress, ROS accumulation and mitochondrial dysfunction can also be attenuated by the inhibitor of ER stress 4-phenylbutyric acid (4-PBA) and anti-oxidant N-acetylcysteine(NAC). In conclusion, these results suggest that Rb1 may protect neurons against high glucose-induced cell injury through inhibiting CHOP signaling pathway as well as oxidative stress and mitochondrial dysfunction.

Advances in the studies of roles of Rho/Rho-kinase in diseases and the development of its inhibitors

RhoA/Rho-kinase pathway plays a pivotal role in numerous fundamental cellular functions including contraction, motility, proliferation, differentiation and apoptosis. The pathway is also involved in the development of many diseases such as vasospasm, pulmonary hypertension, cancer and central nervous systems (CNS) disorders. The inhibitors of Rho kinase have been extensively studied since the Rho/Rho-kinase pathway was verified as a target for a number of diseases. Herein, we reviewed the advances in the studies of the roles of Rho/Rho-kinase in diseases and the development of Rho-kinase inhibitors in recent five years.

Contribution of single-minded 2 to hyperglycaemia-induced neurotoxicity

Diabetes mellitus is associated to central nervous system damage, which results in impairment of brain functions and cognitive deficits and decline in memory. However, the mechanisms mediating the actions of glucose on the neurons remained elusive. Single-minded 2 (Sim2), a basic helix-loop-helix (bHLH)-PAS transcriptional repressor, is thought to be involved in some symptoms of Down syndrome. We hypothesized that Sim2 mediated hyperglycaemia-induced neuronal injury and impairment of learning and memory. It was found that expression of Sim2 protein in cortical neurons was increased in streptozotocin-induced diabetes mellitus rat model. Drebrin, down-regulated by Sim2, was subsequently decreased as detected by confocal laser scanning microscopy and Western blot analysis. The expression pattern of Sim2 and Drebrin correspond to 50mmol/L glucose (hyperglycaemia) was also found in primary cultured neurons. Curcumin, one neuroprotective agent, inhibited hyperglycaemia-induced neurotoxicity. Moreover, curcumin alleviated Sim2 expression, and reversely raised Drebrin expression in neurons treated with hyperglycaemia. Finally, we found that silencing Sim2 expression decreased hyperglycaemia-induced neuronal injury. In conclusion, Sim2 may mediate neurotoxicity during hyperglycaemia and thereby play a critical role in the development of hyperglycaemia-induced cognitive deficits.

Dietary cholesterol alters memory and synaptic structural plasticity in young rat brain

Cholesterol plays an important role in synaptic plasticity, learning and memory. To better explore how dietary cholesterol contributes to learning and memory and the related changes in synaptic structural plasticity, rats were categorized into a regular diet (RD) group and a cholesterol-enriched diet (CD) group, and were fed with respective diet for 2 months. Dietary cholesterol impacts on learning and memory, hippocampal synaptic ultrastructure, expression levels of postsynaptic density-95 (PSD-95), synaptophysin (SYP) and cannabinoid receptor type 1 (CB1R) were investigated. We found CD rats had better performances in learning and memory using Morris water maze and object recognition test than RD rats. The memory improvement was accompanied with alterations of synaptic ultrastructure in the CA1 area of the hippocampus evaluated by electron microscopy, enhanced immunoreactivity of SYP, a presynaptic marker in hippocampus detected by immunocytochemistry, as well as increased levels of PSD-95, SYP and decreased level of CB1R in brains of CD rats determined by Western blot. Taken together, the results suggest that the improvement of learning and memory abilities of the young adult rats induced by dietary cholesterol may be linked with changes in synaptic structural plasticity in the brain.

Amelioration of intracerebroventricular streptozotocin induced cognitive impairment by Evolvulus alsinoides in rats: in vitro and in vivo evidence

Evolvulus alsinoides, also known as Shankpushapi, is a commonly used traditional medicine for enhancing memory. We evaluated the in vitro free radical scavenging and enzymes [acetylcholinesterase, butyrylcholinestrase, glycogen synthase kinase-3-β (GSK-3-β), rho kinase (ROCK II), prolyl endopeptidase (PEP), catechol-O-methyl transferase (COMT) and lipoxygenase (LOX)] inhibitory activities of aqueous and hydro-alcoholic extracts of E. alsinoides. Hydro-alcoholic extract of E. alsinoides demonstrated more free radical scavenging activity as compared to aqueous extract. Hydro-alcoholic extract also showed higher cholinesterase, GSK-3-β, ROCK II, PEP, COMT and LOX enzyme inhibitory activities as compared to aqueous extract. Phytochemical analysis revealed more flavanoids in hydro-alcoholic extract as compared to aqueous extract but no significant difference in phenolic content of the two extracts was observed. Based on in vitro data, hydro-alcoholic extract (100, 300 and 500mg/kg, p.o.) was selected for in vivo study in intracerebroventricularly injected streptozotocin (STZ) induced cognitive impairment in male Wistar rats. Elevated plus maze, passive avoidance and Morris water maze were used for assessment of cognitive function on 14th, 21st and 28th day after STZ injection. Oxidative stress parameters (malondialdehyde, reduced glutathione, nitric oxide levels and superoxide dismutase activity), cholinergic dysfunction and rho kinase (ROCK II) expression were studied in cerebral cortex and hippocampus of rat brain at the end of the study. Hydro-alcoholic extract of E. alsinoides dose dependently prevented STZ induced cognitive impairment by reducing the oxidative stress, improving cholinergic function and preventing the increase in rho kinase expression. The results suggest an anti-Alzheimer potential of hydro-alcoholic extract of E. alsinoides.