Involvement of angiotensin converting enzyme in cerebral hypoperfusion induced anterograde memory impairment and cholinergic dysfunction in rats

Anethole Ameliorates Scopolamine-Induced Memory Deficits and Neuronal Damage Through Antioxidant, Anti-Inflammatory, and Anticholinesterase Activities in Rats

Scopolamine-induced memory impairment is a well-established model for studying the therapeutic potential of novel compounds in the pathogenesis of Alzheimer's disease (AD). This study aimed to evaluate the protective effects and underlying mechanisms of anethole against scopolamine-induced memory and cognitive disorders. Rats were treated with scopolamine (0.7 mg/kg, i.p.) for 14 consecutive days. Anethole (125, 250, and 500 mg/kg, i.g.) was administered one hour prior to scopolamine injection. Memory and cognitive performance were assessed using the Passive Avoidance Test (PAT) and the Novel Object Recognition Test (NORT). In addition, blood-brain barrier (BBB) permeability, brain water content (BWC), and hippocampal levels of oxidative stress markers, inflammatory cytokines, acetylcholine (ACh), and acetylcholinesterase (AChE) were evaluated following the behavioral tests. Histological changes in the hippocampus were examined using hematoxylin and eosin (H&E) staining. Anethole treatment significantly improved scopolamine-induced memory deficits in both NORT and PAT. Furthermore, anethole reduced BBB permeability and BWC in the AD rat model. Hippocampal levels of oxidative stress and inflammation were also attenuated following anethole administration. Additionally, anethole exerted cholinergic effects by inhibiting AChE and increasing ACh levels in the scopolamine-induced AD model. The neuroprotective effects of anethole were further confirmed by H&E staining. Our findings demonstrate that anethole effectively reverses scopolamine-induced memory and cognitive impairments through antioxidant, anti-inflammatory, and anticholinesterase mechanisms in rats. Therefore, anethole may be considered a promising therapeutic candidate for alleviating symptoms of AD and warrants further investigation in future studies.

Effects of Evodiamine on Behavior and Hippocampal Neurons through Inhibition of Angiotensin-Converting Enzyme and Modulation of the Renin Angiotensin Pathway in a Mouse Model of Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a persistent psychiatric condition that arises following exposure to traumatic events such as warfare, natural disasters, or other catastrophic incidents, typically characterized by heightened anxiety, depressive symptoms, and cognitive dysfunction. In this study, animals subjected to single prolonged stress (SPS) were administered evodiamine (EVO) and compared to a positive control group receiving sertraline. The animals were then assessed for alterations in anxiety, depression, and cognitive function. Histological analysis was conducted to examine neuronal changes in the hippocampus. In order to predict the core targets and related mechanisms of evodiamine intervention in PTSD, network pharmacology was used. The metabolic markers pre- and post-drug administration were identified using nontargeted serum metabolomics techniques, and the intersecting Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were screened. Finally, the core targets were validated through molecular docking, enzyme-linked immunosorbent assays, and immunofluorescence staining to confirm the anti-PTSD effects and mechanisms of these targets. As well as improving cognitive impairment, evodiamine reversed anxiety- and depression-like behaviors. It also inhibited the reduction in the number of hippocampal neuronal cells and Nissl bodies in SPS mice inhibited angiotensin converting enzyme (ACE) levels in the hippocampus of SPS mice, and modulated the renin angiotensin pathway and its associated serum metabolites in brain tissue. Evodiamine shows promise as a potential candidate for alleviating the symptoms of post-traumatic stress disorder.

BDNF Signaling in Vascular Dementia and Its Effects on Cerebrovascular Dysfunction, Synaptic Plasticity, and Cholinergic System Abnormality

Vascular dementia (VaD) is the second most common type of dementia and is characterized by memory impairment, blood-brain barrier disruption, neuronal cell loss, glia activation, impaired synaptic plasticity, and cholinergic system abnormalities. To effectively prevent and treat VaD a good understanding of the mechanisms underlying its neuropathology is needed. Brain-derived neurotrophic factor (BDNF) is an important neurotrophic factor with multiple functions in the systemic circulation and the central nervous system and is known to regulate neuronal cell survival, synaptic formation, glia activation, and cognitive decline. Recent studies indicate that when compared with normal subjects, patients with VaD have low serum BDNF levels and that BDNF deficiency in the serum and cerebrospinal fluid is an important indicator of VaD. Here, we review current knowledge on the role of BDNF signaling in the pathology of VaD, such as cerebrovascular dysfunction, synaptic dysfunction, and cholinergic system impairment.

The effect of curcumin on blood pressure and cognitive impairment in spontaneously hypertensive rats

BACKGROUND/OBJECTIVES

It is known that the renin-angiotensin system (RAS) in the brain could regulate cognitive functions as well as blood pressure. Inhibition of RAS for the improvement of cognitive function may be a new strategy, but studies so far have mostly reported on the effects of RAS inhibition by drugs, and there is no research on cognitive improvement through RAS inhibition of food ingredients. Therefore, this study investigated the effect of curcumin on blood pressure and cognitive function and its related mechanism in spontaneously hypertensive rat/Izm (SHR/Izm).

MATERIALS/METHODS

Six-week-old SHR/Izm rats were divided into 5 groups: control group (CON), scopolamine group (SCO, drug for inducing cognitive deficits), positive control (SCO and tacrine [TAC]), curcumin 100 group (CUR100, SCO + Cur 100 mg/kg), and curcumin 200 group (CUR200, SCO + Cur 200 mg/kg). Changes in blood pressure, RAS, cholinergic system, and cognitive function were compared before and after cognitive impairment.

RESULTS

The SCO group showed increased blood pressure and significantly reduced cognitive function based on the y-maze and passive avoidance test. Curcumin treatments significantly improved blood pressure and cognitive function compared with the SCO group. In both the CUR100 and CUR200 groups, the mRNA expressions of angiotensin-converting enzyme (ACE) and angiotensin II receptor type1 (AT1), as well as the concentrations of angiotensin II (Ang II) in brain tissue were significantly decreased. The mRNA expression of the muscarinic acetylcholine receptors (mAChRs) and acetylcholine (ACh) content was significantly increased, compared with the SCO group.

CONCLUSIONS

The administration of curcumin improved blood pressure and cognitive function in SCO-induced hypertensive mice, indicating that the cholinergic system was improved by suppressing RAS and AT1 receptor expression and increasing the mAChR expression.

Natural Product Co-Metabolism and the Microbiota-Gut-Brain Axis in Age-Related Diseases

Complementary alternative medicine approaches are growing treatments of diseases to standard medicine practice. Many of these concepts are being adopted into standard practice and orthomolecular medicine. Age-related diseases, in particular neurodegenerative disorders, are particularly difficult to treat and a cure is likely a distant expectation for many of them. Shifting attention from pharmaceuticals to phytoceuticals and "bugs as drugs" represents a paradigm shift and novel approaches to intervention and management of age-related diseases and downstream effects of aging. Although they have their own unique pathologies, a growing body of evidence suggests Alzheimer's disease (AD) and vascular dementia (VaD) share common pathology and features. Moreover, normal metabolic processes contribute to detrimental aging and age-related diseases such as AD. Recognizing the role that the cerebral and cardiovascular pathways play in AD and age-related diseases represents a common denominator in their pathobiology. Understanding how prosaic foods and medications are co-metabolized with the gut microbiota (GMB) would advance personalized medicine and represents a paradigm shift in our view of human physiology and biochemistry. Extending that advance to include a new physiology for the advanced age-related diseases would provide new treatment targets for mild cognitive impairment, dementia, and neurodegeneration and may speed up medical advancements for these particularly devastating and debilitating diseases. Here, we explore selected foods and their derivatives and suggest new dementia treatment approaches for age-related diseases that focus on reexamining the role of the GMB.

Targeting brain Renin-Angiotensin System for the prevention and treatment of Alzheimer's disease: Past, present and future

Alzheimer's disease (AD) is a well-known neurodegenerative disease characterized by the presence of two main hallmarks - Tau hyperphosphorylation and Aβ deposits. Notwithstanding, in the last few years the scientific evidence about the drivers of AD have been changing and nowadays age-related vascular alterations and several cardiovascular risk factors have been shown to trigger the development of AD. In this context, drugs targeting the Renin Angiotensin System (RAS), commonly used for the treatment of hypertension, are evidencing a high potential to delay AD development due to their action on brain RAS. Indeed, the ACE 1/Ang II/AT1R axis is believed to be upregulated in AD and to be responsible for deleterious effects such as increased oxidative stress, neuroinflammation, blood-brain barrier (BBB) hyperpermeability, astrocytes dysfunction and a decrease in cerebral blood flow. In contrast, the alternative axis - ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) - seems to counterbalance the deleterious effects of the principal axis and to exert beneficial effects on memory and cognition. Accordingly, retrospective studies demonstrate a reduced risk of developing AD among people taking RAS medication as well as several in vitro and in vivo pre-clinical studies as it is herein critically reviewed. In this review, we first revise, at a glance, the pathophysiology of AD focused on its classic hallmarks. Secondly, an overview about the impact of the RAS on the pathophysiology of AD is also provided, focused on their four essential axes ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) and ACE 1/Ang II/AT1R. Finally, the therapeutic potential of available drugs targeting RAS on AD, namely angiotensin II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs), is highlighted and data supporting this hope will be presented, from in vitro and in vivo pre-clinical to clinical studies.

Effects of Goldblatt hypertension on rats’ hippocampal cholinergic system

Background

The classical renin-angiotensin system (RAS) has an important role in the cardiovascular system and water homeostasis in the body. Recently, the existence of RAS with all of its components has been shown in the mammalian brain. RAS participates in many brain activities, including memory acquisition and consolidation. Since the cholinergic neurotransmission in the hippocampus is crucial for these functions, this study aims to evaluate the hippocampal angiotensin receptors (ATs) and choline acetyltransferase (ChAT) mRNA in the renovascular hypertensive rats in captopril- and losartan-treated hypertensive rats.

Methods

The rats were randomly divided into four groups of eight animals; sham, Goldblatt two kidney one clip (2K1C) hypertensive rats and Goldblatt 2K1C hypertensive rats received 5 mg/kg captopril and Goldblatt 2K1C hypertensive rats received 10 mg/kg losartan. After 8 days of treatment, the rats were sacrificed and angiotensin-converting enzyme (ACE), ChAT, AT1, and AT2 receptor mRNAs in the hippocampus of rats were assessed by real-time PCR. The Morris water maze test was applied to measure the cognitive functioning of the rats.

Results

Hypertensive rats showed impaired acquisition and memory function in the Morris water maze test. Treatment with ACE inhibitor (captopril) and AT1 receptor antagonist (losartan) reversed the observed acquisition and memory deficit in hypertensive rats. Overexpression of AChE, AT1, and AT2 and low expression of ChAT were noted in the hippocampus of rats with Goldblatt hypertension compared with that of the sham group. Treatment with captopril significantly reversed these changes, while treatment with losartan slightly reduced the mentioned effects.

Conclusion

The memory-enhancing effect of captopril in renovascular hypertensive rats might lead to increased hippocampal ChAT expression.

Crry silencing alleviates Alzheimer's disease injury by regulating neuroinflammatory cytokines and the complement system

Complement component (3b/4b) receptor 1 (CR1) expression is positively related to the abundance of phosphorylated microtubule-associated protein tau (tau), and CR1 expression is associated with susceptibility to Alzheimer’s disease. However, the exact role of CR1 in tau protein-associated neurodegenerative diseases is unknown. In this study, we show that the mouse Cr1-related protein Y (Crry) gene, Crry, is localized to microglia. We also found that Crry protein expression in the hippocampus and cortex was significantly elevated in P301S mice (a mouse model widely used for investigating tau pathology) compared with that in wild-type mice. Tau protein phosphorylation (at serine 202, threonine 205, threonine 231, and serine 262) and expression of the major tau kinases glycogen synthase kinase-3 beta and cyclin-dependent-like kinase 5 were greater in P301S mice than in wild-type mice. Crry silencing by lentivirus-transfected short hairpin RNA led to greatly reduced tau phosphorylation and glycogen synthase kinase-3 beta and cyclin-dependent-like kinase 5 activity. Crry silencing reduced neuronal apoptosis and rescued cognitive impairment of P301S mice. Crry silencing also reduced the levels of the neuroinflammatory factors interleukin-1 beta, tumor necrosis factor alpha, and interleukin-6 and the complement components complement 3 and complement component 3b. Our results suggest that Crry silencing in the P301S mouse model reduces tau protein phosphorylation by reducing the levels of neuroinflammation and complement components, thereby improving cognitive function.

12/15-Lipoxygenase debilitates mitochondrial health in intermittent hypobaric hypoxia induced neuronal damage: An in vivo study

High altitude cerebral edema does not fall in routine definition of hypoxia and requires alternative therapeutic strategies. 12/15-Lipoxygenase (12/15 LOX), a key proinflammatory lipid peroxidative enzyme which site specifically inserts into cellular and subcellular membranes and plays an instrumental role in hypobaric hypoxia induced neuropathogenesis. Mitochondria, the master regulator organelles for oxygen consumption and ATP generation are sensitive to intracellular oxygen perturbations and are associated with activation of apoptosis based cell death cascades that seal the fate of the cell. The mechanistic involvement of 12/15 LOX in mitochondria mediated cell death in brain microenvironment during hypobaric hypoxia conditions can be an interesting preposition. In the present study, we have investigated underlying involvement of 12/15 LOX in hypobaric hypoxia (HH) induced disturbance in mitochondrial integrity and its relation with neuronal apoptosis. Male Balb/c mice subjected to simulated HH condition for three consecutive days showed robust increase in intra-hippocampal 12(S)HETE (12/15 LOX metabolite), which was significantly reduced following baicalein (12/15 LOX Inhibitor) treatment. The elevated level of 12(S)HETE following hypobaric hypoxia condition correlated with simultaneous increase in expression of 12/15 LOX in neurons and microglia lining the hippocampal CA3 region. Further, 12/15 LOX gets embedded onto the periphery of mitochondria following HH and a strong correlation has been observed with loss of mitochondrial integrity as evident from increased cytochrome-c in the cytosolic compartment and a subsequent upregulated activity of Caspase-3 and Caspase-9 as well as Bax/Bcl-2 expression ratio. The observed effects seen under HH were reversed upon treatment with baicalein suggesting a critical role of 12/15 LOX in HH induced mitochondrial damage Further, the hypobaric hypoxia-mediated increase in hippocampal pAKT and pmTOR protein expression were significantly ameliorated following 12/15 LOX inhibition, suggesting a mitochondrial involvement. We hereby demonstrate the contribution of 12/15 LOX in disorienting mitochondrial integrity with subsequent release of cytochrome-c in cytosol which drives the neuronal cells to intrinsic mode of cell death during hypobaric hypoxia. The protective role of baicalein by inhibition of 12/15 LOX dependent neuronal cell death and preservation of mitochondrial integrity suggests it to be a plausible therapeutic target in CNS related disorders.

Melatonin attenuates cerebral hypoperfusion-induced hippocampal damage and memory deficits in rats by suppressing TRPM7 channels

This study was conducted to examine if modulating transporters like transient receptor potential cation channels, subfamily M, member 7 (TRPM7) underlies the hippocampal neuroprotection afforded by melatonin (Mel) in rats exposed to cerebral hypoperfusion (CHP). Experimental groups included control, Mel-treated (1.87 g/kg), CHP, and CHP + Mel (1.87 g/kg)-treated rats. CHP was induced by the permanent bilateral occlusion of the common carotid arteries (2VO) method and treatments were conducted for 7 days, orally. Mel prevented the damage of the dental gyrus and memory loss in CHP rats and inhibited the hippocampal reactive oxygen species (ROS), lipid peroxidation levels of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6), interleukine-1 beta (IL-1β), and prostaglandin E2 (PGE2). It also reduced the hippocampal transcription of the TRPM7 channels and lowered levels of calcium (Ca²⁺) and zinc (Zn²⁺). Mel Also enhanced the levels of total glutathione (GSH) and superoxide dismutase (SOD) in the hippocampus of the control and CHP-treated rats. In conclusion, downregulation of TRPM7 seems to be one mechanism underlying the neuroprotective effect of Mel against global ischemia and is triggered by its antioxidant potential.

Propofol improves brain injury induced by chronic cerebral hypoperfusion in rats

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

Conventional cardiovascular risk factors in Transient Global Amnesia: Systematic review and proposition of a novel hypothesis

Transient Global Amnesia (TGA) is an enigmatic amnestic syndrome. We conducted a systematic review to investigate the relationship between the conventional cardiovascular risk factors and TGA. MEDLINE, CENTRAL, EMBASE and PsycINFO were comprehensively searched and 23 controlled observational studies were retrieved. The prevalence of hypertension, diabetes mellitus, dyslipidemia and smoking was lower among patients with TGA compared to Transient Ischemic Attack. Regarding the comparison of TGA with healthy individuals, there was strong evidence suggesting a protective effect of diabetes mellitus on TGA and weaker evidence for a protective effect of smoking. Hypertension was associated with TGA only in more severe stages, while dyslipidemia was not related. In view of these findings, a novel pathophysiological hypothesis is proposed, in which the functional interactions of Angiotensin-II type-1 and N-methyl-D-aspartate receptors are of pivotal importance. The whole body of clinical evidence (nature of precipitating events, associations with migraine, gender-based association patterns) was integrated.

Cognitive Impairment, P300, and Transforming Growth Factor β1 in Different Forms of Dementia

BACKGROUND

There are currently few biomarkers to assist in early diagnosis of dementias.

OBJECTIVE

To distinguish between different dementias: Alzheimer's disease (AD), vascular dementia (VaD), and Parkinson's disease dementia (PDD) using simple neurophysiologic (P300) and laboratory markers (transforming growth factor β1 "TGF-β1").

METHODS

The study included 15 patients for each type of dementia and 25 age- and sex-matched control subjects. Dementia patients were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders 4th edition-revised (DSM-IV-R). Modified Mini-Mental State Examination (3MS), Memory Assessment Scale (MAS), P300, and TGF-β1 were examined for each participant.

RESULTS

There were no significant differences between groups as regard to age, sex, and education, social, and economic levels. Significant differences between groups were observed in registration and naming variables of the 3MS. Compared with the control group, P300 latency was prolonged in all groups, although to a greater extent in AD and PDD than in VaD. A serum level of TGF-β1 was significantly elevated in all groups but was significantly higher in AD and VaD than in PDD. 3MS tended to correlate with P300 more than TGF-β1, and to be stronger in AD than the other groups.

CONCLUSION

Measurements of P300 latency and serum levels of TGF-β1 can help distinguish AD, PDD, and VaD. P300 was more prolonged in AD and PDD than VaD whereas TGF-β1 was significantly higher in AD and VaD than PDD. Thus P300 and TGF-β1 may be useful biomarkers for detection and evaluation of the extent of cognitive dysfunction.

Effects of Candesartan vs Lisinopril on Neurocognitive Function in Older Adults With Executive Mild Cognitive Impairment: A Randomized Clinical Trial

IMPORTANCE

Observational studies have suggested that angiotensin receptor blockers are associated with a unique cognitive protection. It is unclear if this is due to reduced blood pressure (BP) or angiotensin receptors type 1 blockade.

OBJECTIVE

To determine neurocognitive effects of candesartan vs lisinopril in older adults with mild cognitive impairment (MCI).

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical trial included participants aged 55 years or older with MCI and hypertension. Individuals were withdrawn from prior antihypertensive therapy and randomized in a 1 to 1 ratio to candesartan or lisinopril from June 2014 to December 2018. Participants underwent cognitive assessments at baseline and at 6 and 12 months. Brain magnetic resonance images were obtained at baseline and 12 months. This intent-to-treat study was double-blind and powered for a sample size accounting for 20% dropout. Data were analyzed from May to October 2019.

INTERVENTIONS

Escalating doses of oral candesartan (up to 32 mg) or lisinopril (up to 40 mg) once daily. Open-label antihypertensive drug treatments were added as needed to achieve BP less than 140/90 mm Hg.

MAIN OUTCOMES AND MEASURES

The primary outcome was executive function (measured using the Trail Making Test, Executive Abilities: Measures and Instruments for Neurobehavioral Evaluation and Research tool) and secondary outcomes were episodic memory (measured using the Hopkins Verbal Learning Test-Revised) and microvascular brain injury reflected by magnetic resonance images of white matter lesions.

RESULTS

Among 176 randomized participants (mean [SD] age, 66.0 [7.8] years; 101 [57.4%] women; 113 [64.2%] African American), 87 were assigned to candesartan and 89 were assigned to lisinopril. Among these, 141 participants completed the trial, including 77 in the candesartan group and 64 in the lisinopril group. Although the lisinopril vs candesartan groups achieved similar BP (12-month mean [SD] systolic BP: 130 [17] mm Hg vs 134 [20] mm Hg; P = .20; 12-month mean [SD] diastolic BP: 77 [10] mm Hg vs 78 [11] mm Hg; P = .52), candesartan was superior to lisinopril on the primary outcome of executive function measured by Trail Making Test Part B (effect size [ES] = -12.8 [95% CI, -22.5 to -3.1]) but not Executive Abilities: Measures and Instruments for Neurobehavioral Evaluation and Research score (ES = -0.03 [95% CI, -0.08 to 0.03]). Candesartan was also superior to lisinopril on the secondary outcome of Hopkins Verbal Learning Test-Revised delayed recall (ES = 0.4 [95% CI, 0.02 to 0.8]) and retention (ES = 5.1 [95% CI, 0.7 to 9.5]).

CONCLUSIONS AND RELEVANCE

These findings suggest that in older adults with MCI, 1-year treatment with candesartan had superior neurocognitive outcomes compared with lisinopril. These effects are likely independent of the BP-lowering effect of candesartan.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01984164.

Acetyl-L-Carnitine in Dementia and Other Cognitive Disorders: A Critical Update

Several studies explored the effects of acetyl-L-carnitine (ALC) in dementia, suggesting a role in slowing down cognitive decline. Nevertheless, in 2003 a systematic review concluded there was insufficient evidence to recommend a clinical use, although a meta-analysis in the same year showed a significant advantage for ALC for clinical scales and psychometric tests. Since then, other studies have been published; however, a critical review is still lacking. We provide an update of the studies on ALC in primary and secondary dementia, highlighting the current limitations and translational implications. Overall, the role of ALC in dementia is still under debate. The underlying mechanisms may include restoring of cell membranes and synaptic functioning, enhancing cholinergic activity, promoting mitochondrial energy metabolism, protecting against toxins, and exerting neurotrophic effects. The effects of ALC on the gut-liver-brain axis seem to identify the category of patients in which the new insights contribute most to the mechanisms of action of ALC, likely being the liver metabolism and the improvement of hepatic detoxifying mechanisms the primary targets. In this framework, our research group has dealt with this topic, focusing on the ALC-related cross-talk mechanisms. Further studies with homogeneous sample and longitudinal assessment are needed before a systematic clinical application.

Acetyl-L-Carnitine in Dementia and Other Cognitive Disorders: A Critical Update

Several studies explored the effects of acetyl-L-carnitine (ALC) in dementia, suggesting a role in slowing down cognitive decline. Nevertheless, in 2003 a systematic review concluded there was insufficient evidence to recommend a clinical use, although a meta-analysis in the same year showed a significant advantage for ALC for clinical scales and psychometric tests. Since then, other studies have been published; however, a critical review is still lacking. We provide an update of the studies on ALC in primary and secondary dementia, highlighting the current limitations and translational implications. Overall, the role of ALC in dementia is still under debate. The underlying mechanisms may include restoring of cell membranes and synaptic functioning, enhancing cholinergic activity, promoting mitochondrial energy metabolism, protecting against toxins, and exerting neurotrophic effects. The effects of ALC on the gut-liver-brain axis seem to identify the category of patients in which the new insights contribute most to the mechanisms of action of ALC, likely being the liver metabolism and the improvement of hepatic detoxifying mechanisms the primary targets. In this framework, our research group has dealt with this topic, focusing on the ALC-related cross-talk mechanisms. Further studies with homogeneous sample and longitudinal assessment are needed before a systematic clinical application.

The Aqueous Extract from Ceratonia siliqua Leaves Protects Against 6-hydroxydopamine in Zebrafish: Understanding the Underlying Mechanism

Ceratonia siliqua L. is a Mediterranean medicinal plant traditionally cultivated for its ethnopharmacological benefits, such as antidiarrheal, antidiabetic, enhance acetylcholine, antioxidant, antiatherosclerotic, and for its possible anti-neurodegenerative potential. The aim of the present study was to evaluate the chemical composition, as well as the cognitive-enhancing, anxiolytic, and antioxidant activities of the aqueous extract from C. siliqua (CsAE) leaves against 6-hydroxydopamine (6-OHDA) zebrafish Parkinson’s disease (PD) model. CsAE (0.1, 0.3, and 1 mg/L) was administered by immersion to zebrafish (Danio rerio) for eight consecutive days and one hour before each behavioral test of each day, while 6-OHDA (250 µM) treatment was supplied one day before the novel tank diving test (NTT). Qualitative and quantitative analyses were performed by the ultra-high-performance liquid chromatography (UHPLC) analysis. The memory performance was evaluated through the NTT and Y-maze tests. Additionally, the in vitro and in vivo antioxidant status and acetylcholinesterase (AChE) activity was also assessed. Our finds demonstrated that CsAE presented positive antioxidant and anti-AChE activities, which contributed to the improvement of cognitive function in the 6-OHDA zebrafish PD model.

Electroacupuncture Improved Chronic Cerebral Hypoperfusion-Induced Anxiety-Like Behavior and Memory Impairments in Spontaneously Hypertensive Rats by Downregulating the ACE/Ang II/AT1R Axis and Upregulating the ACE2/Ang-(1-7)/MasR Axis

Electroacupuncture (EA) can effectively alleviate anxiety disorders and memory impairments caused by various neurodegenerative diseases; however, the molecular mechanisms underlying its neuroprotective effects are unclear. Previous studies have shown that the renin-angiotensin system (RAS) comprises of two axes with mutual antagonism: the classical angiotensin converting enzyme/angiotensin II/angiotensin II type 1 receptor (ACE/Ang II/AT1R) axis and the protective angiotensin converting enzyme 2/angiotensin-(1-7)/Mas receptor (ACE2/Ang-(1-7)/MasR) axis. In this study, we observed that chronic cerebral hypoperfusion (CCH) mediated anxiety-like behavior and memory impairments in spontaneously hypertensive rats (SHR) via upregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and the partial hippocampal protective axis (ACE2/Ang-(1-7)). However, Ang II levels were much higher than those of Ang-(1–7), indicating that the ACE/Ang II/AT1R axis plays a dominant role in the comorbidity of CCH and hypertension. Moreover, candesartan cilexetil (Canc) and perindopril (Peril) were used as positive control drugs. We found that EA, Canc, and Peril attenuated CCH-induced anxiety-like behavior and memory impairments in SHR, potentially via downregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and upregulation of the whole hippocampal protective axis (ACE2/Ang-(1-7)/MasR). These results suggest that EA therapy for CCH with hypertension may be mediated by two hippocampal RAS axes.

Effects of Phytochemicals on Blood Pressure and Neuroprotection Mediated Via Brain Renin-Angiotensin System

Background: The renin-angiotensin system (RAS) in the brain plays a crucial role in maintaining blood pressure as well as neuroprotection. This study compared the effects of curcumin, quercetin, and saponin on blood pressure, the brain RAS, and cholinergic system using perindopril, an angiotensin converting enzyme inhibitor (ACEI), as a positive control. Methods: Five-week-old male mice were stabilized and randomly assigned into a control group (n = 8), three phytochemical-treated groups (curcumin (n = 8), quercetin (n = 8), and saponin (n = 8)), and a positive control group (n = 8). The groups treated with the phytochemical were orally administered daily at a dose of 50 mg/kg body weight of phytochemicals. During the experiments, the weight and dietary intakes were measured regularly. After experiments, the brain tissue was homogenized and centrifuged for an additional assay. The concentrations of ACE, angiotensin II (AngII), and aldosterone levels were measured, and the mRNA expressions of renin and ACE were measured. As biomarkers of neuroprotection, the concentrations of acetylcholine (ACh) as well as the concentration and activity of acetylcholine esterase (AChE) were measured. Results: After 4 weeks of treatment, the perindopril group showed the lowest blood pressure. Among the groups treated with the phytochemicals, treatment with curcumin and saponin significantly reduced blood pressure, although such effect was not as high as that of perindopril. Among phytochemicals, curcumin treatment significantly inhibited the concentration and activity of ACE, concentration of AngII, and mRNA expression of ACE. All phytochemical treatments significantly increased the concentration of ACh. The levels of AChE activity in groups exposed to curcumin or saponin (not quercetin) were significantly inhibited, Conclusion: Curcumin administration in rats reduced blood pressure by blocking the brain RAS components and protected the cholinergic system in brain by inhibiting the activity of AChE.

Telmisartan Protects Against Aluminum-Induced Alzheimer-like Pathological Changes in Rats

Currently, there is no effective mean for treatment or prevention of Alzheimer's disease (AD). Commonly used AD drugs have a moderate effect and treat only the associated symptoms, therefore there is a strong need to search for more effective agents. Our goal is to examine telmisartan neuroprotective effect in aluminum-induced cognitive impairment in rats. Aluminum chloride (10 mg/kg, i.p) was administered for 2 months then behavioral tests (Y-maze and Morris water maze) were done. Hippocampal biochemical and histological analysis were then carried out. AD-like histological, biochemical, and behavioral alterations appeared in aluminum-treated rats. Telmisartan improved rats' condition on behavioral and histological levels. It reversed the increase in hippocampal amyloid beta protein, phosphorylated tau protein contents together with augmentation of neprilysin level, it also diminished levels of nuclear factor kappa-B, FAS ligand, tumor necrosis factor-alpha, malondialdehyde, and acetylcholinesterase content.These findings show the protective action of telmisartan against AD-like pathological alterations.

Preischemic treadmill exercise improves short-term memory by inhibiting hypoperfusion-induced disruption of blood-brain barrier after bilateral common carotid arteries occlusion

Bilateral common carotid arteries occlusion (BCCAO) causes an abrupt reduction of cerebral blood flow, and this method has been used to investigate the effects of chronic cerebral hypoperfusion on vascular dementia and neuronal injuries. Chronic cerebral hypoperfusion leads to functional changes in the hippocampus and then results in a cognitive impairment. We investigated the effect of preischemic treadmill exercise on short-term memory and blood-brain barrier integration following cerebral hypoperfusion caused by BCCAO. The rats in the preischemic treadmill exercise and BCCAO group were made to run on a treadmill for 30 min once a day for 4 weeks. At 4 weeks after performing treadmill exercise, right carotid artery was ligated, and 1 week after, left common carotid artery was ligated. At 20 days after BCCAO, short-term memory was evaluated. Half of the rats were sacrificed 2 days after BCCAO and the other rats were sacrificed at 3 weeks after BCCAO. Immunohistochemistry and western blot were performed. Preischemic treadmill exercise alleviated impairment of short-term memory in the step-down avoidance task. Preischemic treadmill exercise reduced microvascular injury in the hippocampus. Preischemic treadmill exercise prevented the reduction of zonula occludens-1 in the hippocampus and inhibited the activation of matrix metalloproteinase-9. Therefore, pre-conditioning treadmill exercise might be used as a therapeutic strategy for the prevention of stroke in patients.

Melatonin Improves Memory Deficits in Rats with Cerebral Hypoperfusion, Possibly, Through Decreasing the Expression of Small-Conductance Ca2+-Activated K+ Channels

This study investigated the expression pattern, regulation of expression, and the role of hippocampal small-conductance Ca²⁺-activated K⁺ (SK) channels in memory deficits after cerebral hypoperfusion (CHP) with or without melatonin treatment, in rats. Adults male Wistar rats (n = 20/group) were divided into (1) a sham (2) a sham + melatonin (3) a two-vessel occlusion (2-VO) model, and (4) a 2-VO + melatonin. Melatonin was administered (i.p.) to all rats at a daily dose of 10 mg kg^-1 for 7 days starting at the time of 2-VO-induction. In contrast to 2-VO rats, melatonin increased the latency of the passive avoidance learning test and decreased time to find the hidden platform in Water Morris Test in all tested rats. In addition, it concomitantly downregulated SK1, SK2, and SK3 channels, downregulated mRNA levels of TNFα and IL-1β, enhanced BDNF levels and activity of PKA levels, and restored the levels of cholinergic markers in the hippocampi of the treated-rats. Mechanistically, melatonin significantly prevented CHP-induced activation of ERK1/2, JNK, and P38 MAPK at least by inhibiting ROS generation and enhancing the total antioxidant potential. In cultured hypoxic hippocampal neurons, individual blockage of MAPK signaling by the MEK1/2 inhibitor (U0126), but not by the P38 inhibitor (SB203580) or JNK inhibitor (SP600125), completely prevented the upregulation of all three kinds of SK channels. These data clearly confirm that upregulation of SK channels plays a role in CHP-induced memory loss and indicate that melatonin reverses memory deficits after CHP in rats, at least by, downregulation of SK1, SK2, and SK3 channels in their hippocampi.

The Coming of Age of the Angiotensin Hypothesis in Alzheimer's Disease: Progress Toward Disease Prevention and Treatment?

There is wide recognition of a complex association between midlife hypertension and cardiovascular disease and later development of Alzheimer’s disease (AD) and cognitive impairment. While significant progress has been made in reducing rates of mortality and morbidity due to cardiovascular disease over the last thirty years, progress towards effective treatments for AD has been slower. Despite the known association between hypertension and dementia, research into each disease has largely been undertaken in parallel and independently. Yet over the last decade and a half, the emergence of converging findings from pre-clinical and clinical research has shown how the renin angiotensin system (RAS), which is very important in blood pressure regulation and cardiovascular disease, warrants careful consideration in the pathogenesis of AD. Numerous components of the RAS have now been found to be altered in AD such that the multifunctional and potent vasoconstrictor angiotensin II, and similarly acting angiotensin III, are greatly altered at the expense of other RAS signaling peptides considered to contribute to neuronal and cognitive function. Collectively these changes may contribute to many of the neuropathological hallmarks of AD, as well as observed progressive deficiencies in cognitive function, while also linking elements of a number of the proposed hypotheses for the cause of AD. This review discusses the emergence of the RAS and its likely importance in AD, not only because of the multiple facets of its involvement, but also perhaps fortuitously because of the ready availability of numerous RAS-acting drugs, that could be repurposed as interventions in AD.

The association of multiple anti-hypertensive medication classes with Alzheimer's disease incidence across sex, race, and ethnicity

BACKGROUND

Antihypertensive treatments have been shown to reduce the risk of Alzheimer's disease (AD). The renin-angiotensin system (RAS) has been implicated in AD, and thus RAS-acting AHTs (angiotensin converting enzyme inhibitors (ACEIs), and angiotensin-II receptor blockers (ARBs)) may offer differential and additional protective benefits against AD compared with other AHTs, in addition to hypertension management.

METHODS

In a retrospective cohort design, we examined the medical and pharmacy claims of a 20% sample of Medicare beneficiaries from 2007 to 2013, and compared rates of AD diagnosis for 1,343,334 users of six different AHT drug treatments, 65 years of age or older (4,215,338 person-years). We compared AD risk between RAS and non-RAS AHT drug users, and between ACEI users and ARB users, by sex and race/ethnicity. Models adjusted for age, socioeconomic status, underlying health, and comorbidities.

FINDINGS

RAS-acting AHTs were slightly more protective against onset of AD than non-RAS-acting AHTs for males, (male OR = 0.931 (CI: 0.895-0.969)), but not so for females (female OR = 0.985 (CI: 0.963-1.007)). Relative to other AHTs, ARBs were superior to ACEIs for both men (male ARB OR = 0.834 (CI: 0.788-0.884); male ACEI OR = 0.978 (CI: 0.939-1.019)) and women (female ARB OR = 0.941 (CI: 0.913-0.969); female ACEI OR = 1.022 (CI: 0.997-1.048)), but only in white men and white and black women. No association was shown for Hispanic men and women.

CONCLUSION

Hypertension management treatments that include RAS-acting ARBs may, in addition to lowering blood pressure, reduce AD risk, particularly for white and black women and white men. Additional studies and clinical trials that include men and women from different racial and ethnic groups are needed to confirm these findings. Understanding the potentially beneficial effects of certain RAS-acting AHTs in high-risk populations is of great importance.

A Multicenter, Randomized, Double-blind, Placebo-controlled Clinical Trial for Efficacy of Acetyl-L-carnitine in Patients with Dementia Associated with Cerebrovascular Disease

Background and Purpose

Acetyl-L-carnitine (ALC) is a widely used drug for various neurodegenerative diseases including dementia. The aim of the present study was to elucidate the efficacy of ALC in dementia patients with cerebrovascular disease (vascular cognitive impairment; VCI).

Methods

Fifty-six patients were randomized to treatment with 500 mg ter in die ALC, or placebo in this 28-week, double-blind, placebo-controlled trial. The primary outcome measure was the Korean version of Montreal Cognitive Assessment (MoCA-K).

Results

Following treatment with ALC, the cognitive function measured by the MoCA-K was significantly improved in the ALC-treated groups. However, other secondary outcomes were not statistically significant between ALC- and placebo-treated groups. In MoCA-K analysis, attention and language sub-items significantly favored the ALC-treated group.

Conclusions

Compared with placebo, treatment with ALC 1,500 mg/day produced significant changes in MoCA-K in dementia patients with VCI. ALC was well tolerated in this population. Despite the study limitations, the findings suggested the potential benefits associated with the use of ALC in dementia patients with VCI.

Within the Brain: The Renin Angiotensin System

For many years, modulators of the renin angiotensin system (RAS) have been trusted by clinicians for the control of essential hypertension. It was recently demonstrated that these modulators have other pleiotropic properties independent of their hypotensive effects, such as enhancement of cognition. Within the brain, different components of the RAS have been extensively studied in the context of neuroprotection and cognition. Interestingly, a crosstalk between the RAS and other systems such as cholinergic, dopaminergic and adrenergic systems have been demonstrated. In this review, the preclinical and clinical evidence for the impact of RAS modulators on cognitive impairment of multiple etiologies will be discussed. In addition, the expression and function of different receptor subtypes within the RAS such as: Angiotensin II type I receptor (AT1R), Angiotensin II type II receptor (AT2R), Angiotensin IV receptor (AT4R), Mas receptor (MasR), and Mas-related-G protein-coupled receptor (MrgD), on different cell types within the brain will be presented. We aim to direct the attention of the scientific community to the plethora of evidence on the importance of the RAS on cognition and to the different disease conditions in which these agents can be beneficial.

A Rodent Model for Chronic Brain Hypoperfusion Related Diseases: Permanent Bilateral Occlusion of the Common Carotid Arteries (2VO) in Rats

Permanent occlusion of bilateral common carotid arteries (2VO) in rat is considered as a suitable animal model to mimic chronic brain hypoperfusion status, which is proved to be a risk factor to precede the Alzheimer's disease or/and vascular dementia. In this protocol, we describe how to successfully ligate the bilateral common carotid arteries covered by anterior cervical muscle group, and provide the details for understanding the surgical procedures of 2VO.

Dynamic Changes in the Renin-Angiotensin-Aldosterone System and the Beneficial Effects of Renin-Angiotensin-Aldosterone Inhibitors on Spatial Learning and Memory in a Rat Model of Chronic Cerebral Ischemia

Renin-angiotensin-aldosterone system (RAAS) plays an important role in the regulation of blood pressure and brain function. Therefore, we studied the dynamic changes in the RAAS in the blood, cerebral cortex, and hippocampus and the effects of RAAS inhibitors on spatial learning and memory and hippocampal apoptosis in a rat model of chronic cerebral ischemia (CCI) established by bilateral ligation of the common carotid arteries of rats. The levels of renin, angiotensin II (Ang II), and aldosterone (ALD) in the plasma, and the homogenates of the left side of cerebral cortex and whole hippocampus of rats were detected on day 1, 3, 7, 14, 21, and 30 by radioimmunoassay. Spatial learning and memory and hippocampal apoptosis were evaluated on day 30 by Morris water maze test (navigation and space exploration tests) and terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay, respectively, after rats were orally administered with distilled water (DW), renin inhibitor aliskiren (30 mg/kg), Ang converting enzyme inhibitor enalapril (4 mg/kg), or Ang II receptor antagonist candesartan (2 mg/kg) daily for 30 days. The results showed that the levels of renin and Ang II were significantly higher but ALD fluctuated in the blood, cerebral cortex, and hippocampus in CCI rats compared to normal rats. However, aliskiren and enalapril could significantly decrease (p < 0.05) the levels of renin, Ang II and ALD in the blood, cerebral cortex, and hippocampus compared to DW treatment; while candesartan had similar effect on renin and ALD but no effect on Ang II in CCI rats. Furthermore, spatial learning and memory were significantly decreased but apoptosis in the hippocampus was obviously increased in CCI rats compared to normal rats (p < 0.05). However, aliskiren, enalapril, and candesartan were equally effective to improve spatial learning and memory and decrease apoptosis in the hippocampus. Therefore, RAAS plays an important role in the development of cerebral ischemia and RAAS inhibitors aliskiren, enalapril, and candesartan improve spatial learning and memory and protect brain injury by inhibiting hippocampal apoptosis in CCI rats.

Captopril and Valsartan May Improve Cognitive Function Through Potentiation of the Brain Antioxidant Defense System and Attenuation of Oxidative/Nitrosative Damage in STZ-Induced Dementia in Rat

Purpose: Previous findings have shown the crucial roles of brain renin-angiotensin system (RAS) in pathogenesis of Alzheimer's disease (AD). Since RAS inhibitors may have beneficial effects on dementia and cognitive function in elderly people, the aim of present study was to examine the neuroprotective actions of captopril and valsartan on memory function and neuronal damage in experimental model of AD. Methods: Adult forty male Wistar rats (220-280g) were randomly divided into 5 groups; Control, Vehicle, Alzheimer and treatment groups. AD was induced by the injections of streptozotocin (3mg/kg, bilateral intracerebroventricular) at days 1&3. Treated rats received orally captopril (50mg/kg/day) and valsartan (30mg/kg/day). Memory function and histological assessments were done at termination of experiment. Finally, superoxide dismutase (SOD) and catalase (CAT) activities as well as malondialdehyde (MDA) and NOx contents were determined. Results: There was a significant increase in the mean value of latency in Alzheimer group (66%). Captopril and valsartan considerably decreased this value in both treatment groups (45% and 72%, respectively). In Alzheimer group the activities of brain's SOD and CAT reduced (40% and 47%, respectively) in accompany with an increase in MDA and NOx contents (49% and 50%, respectively). Captopril and valsartan significantly increased the activities of brain's SOD and CAT concomitant reduction in MDA and NOx contents. Also, histopathological damages noticeably decreased in both treatment groups. Conclusion: Our findings indicate that RAS inhibition by using captopril and valsartan potentiates the antioxidant defense system of brain and reduces oxidative/nitrosative stress in accompany with neuronal damage during AD.

Rutin protects against cognitive deficits and brain damage in rats with chronic cerebral hypoperfusion

BACKGROUND AND PURPOSE

Chronic cerebral hypoperfusion is a critical causative factor for the development of cognitive decline and dementia in the elderly, which involves many pathophysiological processes. Consequently, inhibition of several pathophysiological pathways is an attractive therapeutic strategy for this disorder. Rutin, a biologically active flavonoid, protects the brain against several insults through its antioxidant and anti-inflammatory properties, but its effect on cognitive deficits and brain damage caused by chronic cerebral hypoperfusion remains unknown. Here, we investigated the neuroprotective effect of rutin on cognitive impairments and the potential mechanisms underlying its action in rats with chronic cerebral hypoperfusion.

EXPERIMENTAL APPROACH

We used Sprague-Dawley rats with permanent bilateral common carotid artery occlusion (BCCAO), a well-established model of chronic cerebral hypoperfusion. After rutin treatment for 12 weeks, the neuroprotective effect of rutin in rats was evaluated by behavioural tests, biochemical and histopathological analyses.

KEY RESULTS

BCCAO rats showed marked cognitive deficits, which were improved by rutin treatment. Moreover, BCCAO rats exhibited central cholinergic dysfunction, oxidative damage, inflammatory responses and neuronal damage in the cerebral cortex and hippocampus, compared with sham-operated rats. All these effects were significantly alleviated by treatment with rutin.

CONCLUSION AND IMPLICATIONS

Our results provide new insights into the pharmacological actions of rutin and suggest that rutin has multi-targeted therapeutical potential on cognitive deficits associated with conditions with chronic cerebral hypoperfusion such as vascular dementia and Alzheimer's disease.

Fructus mume extracts alleviate cognitive impairments in 5XFAD transgenic mice

Background

Fructus mume (F. mume) has been used as a traditional treatment for ulcer, cough, and digestive problems for many years in Asian countries. Previous studies have demonstrated that F. mume extracts alleviate cognitive deficits in rats with chronic cerebral hypoperfusion and in mice with scopolamine treatments. The present experiment was conducted to examine the effects of F. mume on cognitive impairments in 5XFAD transgenic mice with five familial Alzheimer’s disease (AD) mutations.

Methods

F. mume was administered daily to 5XFAD mice at 12 weeks of age and continued for 90 days. Cognitive function was evaluated using a spatial memory version of the Morris water maze task, the object/location novelty recognition test, and contextual fear conditioning at 24 weeks of age. To elucidate the possible mechanisms underlying the memory improving effects of F. mume in 5XFAD mice, we examined alterations in hippocampal cholinergic function.

Results

Vehicle-treated 5XFAD mice exhibited hippocampus-dependent memory impairments compared with non-transgenic littermates, which was reversed in F. mume-treated 5XFAD mice. In addition, reduced hippocampal choline acetyltransferase (ChAT) levels in 5XFAD mice were reversed by F. mume treatment, indicating that F. mume enhances the effects of cholinergic neuronal function.

Conclusions

F. mume may have therapeutic effects on cognitive impairments in AD.

Electric stimulation of the ears ameliorated learning and memory impairment in rats with cerebral ischemia-reperfusion injury

Ear acupuncture enhances the secretion of acetylcholine, which has anti-inflammatory effects. Here we want to investigate the effect of electric stimulation (ES) of the ears on learning and memory impairment in rats with cerebral ischemia-reperfusion injury. At 24 h after reperfusion, 2-Hz ES was applied to the ears for 20 min/day (10 min for each ear) for 7 days continuously. The step-through time of the passive avoidance test was greater in the ES group than in the control group (300.0 ± 0.0 s vs 45.0 ± 26.7 s, p < 0.05). Our results showed that neither neurological deficit score nor motor functions were improved after 2-Hz ES (4.0 ± 0 vs 4.5 ± 0.8, p > 0.05). The numbers of nicotinic acetylcholine receptor α4 positively stained cells in the CA2 and dentate gyrus of the hippocampus were 19.0 ± 11.5 and 269.2 ± 79.3, respectively, in the ES group, which were greater than those in the control group (7.0 ± 5.9 and 165.5 ± 30.8, respectively) (both p < 0.05). These results suggested that 2-Hz ES of the ears ameliorated learning and memory impairment in rats with ischemia-reperfusion injury. ES of the ears has neuroprotective effects, which are related to acetylcholine release.

Lipopolysaccharide-Induced Spatial Memory and Synaptic Plasticity Impairment Is Preventable by Captopril

Introduction. Renin-angiotensin system has a role in inflammation and also is involved in many brain functions such as learning, memory, and emotion. Neuroimmune factors have been proposed as the contributors to the pathogenesis of memory impairments. In the present study, the effect of captopril on spatial memory and synaptic plasticity impairments induced by lipopolysaccharide (LPS) was investigated. Methods. The rats were divided and treated into control (saline), LPS (1 mg/kg), LPS-captopril (LPS-Capto; 50 mg/kg captopril before LPS), and captopril groups (50 mg/kg) before saline. Morris water maze was done. Long-term potentiation (LTP) from CA1 area of hippocampus was assessed by 100 Hz stimulation in the ipsilateral Schaffer collateral pathway. Results. In the LPS group, the spent time and traveled path to reach the platform were longer than those in the control, while, in the LPS-Capto group, they were shorter than those in the LPS group. Moreover, the slope and amplitude of field excitatory postsynaptic potential (fEPSP) decreased in the LPS group, as compared to the control group, whereas, in the LPS-Capto group, they increased compared to the LPS group. Conclusion. The results of the present study showed that captopril improved the LPS-induced memory and LTP impairments induced by LPS in rats. Further investigations are required in order to better understand the exact responsible mechanism(s).

MicroRNA-9 induces defective trafficking of Nav1.1 and Nav1.2 by targeting Navβ2 protein coding region in rat with chronic brain hypoperfusion

Background

Previous studies have demonstrated that the trafficking defects of Nav1.1/Nav1.2 are involved in the dementia pathophysiology. However, the detailed mechanisms are not fully understood. Moreover, whether the impaired miRNAs regulation linked to dementia is a key player in sodium channel trafficking disturbance remains unclear. The cognitive impairment induced by chronic cerebral ischemia through chronic brain hypoperfusion (CBH) is likely reason to precede dementia. Therefore, our goal in the present study was to examine the role of microRNA-9 (miR-9) in regulating Nav1.1/Nav1.2 trafficking under CBH generated by bilateral common carotid artery occlusion (2VO).

Results

The impairment of Nav1.1/Nav1.2 trafficking and decreased expression of Navβ2 were found in the hippocampi and cortices of rats following CBH generated by bilateral 2VO. MiR-9 was increased in both the hippocampi and cortices of rats following CBH by qRT-PCR. Intriguingly, miR-9 suppressed, while AMO-miR-9 enhanced, the trafficking of Nav1.1/Nav1.2 from cytoplasm to cell membrane. Further study showed that overexpression of miR-9 inhibited the Navβ2 expression by targeting on its coding sequence (CDS) domain by dual luciferase assay. However, binding-site mutation or miR-masks failed to influence Navβ2 expression as well as Nav1.1/Nav1.2 trafficking process, indicating that Navβ2 is a potential target for miR-9. Lentivirus-mediated miR-9 overexpression also inhibited Navβ2 expression and elicited translocation deficits to cell membrane of Nav1.1/Nav1.2 in rats, whereas injection of lentivirus-mediated miR-9 knockdown could reverse the impaired trafficking of Nav1.1/Nav1.2 triggered by 2VO.

Conclusions

We conclude that miR-9 may play a key role in regulating the process of Nav1.1/Nav1.2 trafficking via targeting on Navβ2 protein in 2VO rats at post-transcriptional level, and inhibition of miR-9 may be a potentially valuable approach to prevent Nav1.1/Nav1.2 trafficking disturbance induced by CBH.

Ameliorating Effects of Ethanol Extract of Fructus mume on Scopolamine-Induced Memory Impairment in Mice

We previously reported that Fructus mume (F. mume) extract shows protective effects on memory impairments and anti-inflammatory effects induced by chronic cerebral hypoperfusion. Neurodegeneration of basal cholinergic neurons is also observed in the brain with chronic cerebral hypoperfusion. Therefore, the present study was conducted to examine whether F. mume extracts enhance cognitive function via the action of cholinergic neuron using a scopolamine-induced animal model of memory impairments. F. mume (50, 100, or 200 mg/kg) was administered to C57BL/6 mice for 14 days (days 1-14) and memory impairment was induced by scopolamine (1 mg/kg), a muscarinic receptor antagonist for 7 days (days 8-14). Spatial memory was assessed using Morris water maze and hippocampal level of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) was examined by ELISA and immunoblotting. Mice that received scopolamine alone showed impairments in acquisition and retention in Morris water maze task and increased activity of AChE in the hippocampus. Mice that received F. mume and scopolamine showed no scopolamine-induced memory impairment and increased activity of AChE. In addition, treatments of F. mume increased ChAT expression in the hippocampus. These results indicated that F. mume might enhance cognitive function via action of cholinergic neurons.

Perindopril increases the swallowing reflex by inhibiting substance P degradation and tyrosine hydroxylase activation in a rat model of dysphagia

Patients with hypertension have a high risk of ischemic stroke and subsequent stroke-associated pneumonia. Stroke-associated pneumonia is most likely to develop in patients with dysphagia. The present study was designed to compare the ameliorative effects of different treatments in rat model of dysphagia. Spontaneously hypertensive rats were treated with bilateral common carotid artery occlusion (BCAO) to induce chronic cerebral hypoperfusion causing disorders of the swallowing reflex. Angiotensin-converting enzyme (ACE) inhibitors (perindopril, imidapril and enalapril), an angiotensin II type 1-receptor blocker (losartan), a vasodilator (hydralazine) and an indirect dopamine agonist (amantadine) were dissolved in drinking water and administered to the rats for six weeks. The blood pressure, the swallowing reflex under anesthesia, the substance P content in the striatum and the tyrosine hydroxylase (TH) expression in the substantial nigra were measured. Compared to the vehicle control, the decrease in the swallowing reflex induced by BCAO was attenuated significantly by enalapril, imidapril and perindopril, but only slightly by losartan. Hydralazine had no effect on the swallowing reflex. Amantadine significantly attenuated the decreased swallowing reflex but increased the blood pressure. Cerebral hypoperfusion for six weeks decreased the TH expression and substance P level. Perindopril improved both the TH expressions and substance P level, but imidapril, enalapril and amantadine only improved the substance P level. The present findings indicate that perindopril could be useful for preventing dysphagia in the chronic stage of stroke by attenuating the decrease in TH expression and the decrease in the substance P level.

Animal models of vascular dementia: translational potential at the present time and in 2050

ABSTRACT: Vascular dementia is a heterogeneous syndrome, and includes subcortical ischemic vascular dementia. For translational research, subcortical ischemic vascular dementia is an appropriate target since this is the most prevalent subtype and exhibits relatively uniform clinical and neuropathological changes. These changes consist of hypertensive arteriolar changes, lacunar infarctions, hypertensive hemorrhage and white matter lesions. Among various species, rodents are most frequently used, but their small volume of white matter may impede analysis of white matter lesions. Primate models have a larger volume, but the degree of white matter lesions is inconsistent. Animal models should accommodate the effect of aging and comorbidities, and in the case of primate models, low accessibility should be overcome by repeated and quantitative examinations using modern neuroimaging techniques and functional measures, especially for memory and motor function. There is no model that replicates all features of subcortical ischemic vascular dementia and, therefore, rodent and primate models should be selected appropriately for translational research.

Beneficial effect of candesartan and lisinopril against haloperidol-induced tardive dyskinesia in rat

INTRODUCTION

Tardive dyskinesia is a serious motor disorder of the orofacial region, resulting from chronic neuroleptic treatment of schizophrenia. Candesartan (AT1 antagonist) and lisinopril (ACE inhibitor) has been reported to possess antioxidant and neuroprotective effects. The present study is designed to investigate the effect of candesartan and lisinopril on haloperidol-induced orofacial dyskinesia and oxidative damage in rats.

MATERIALS AND METHODS

Tardive dyskinesia was induced by administering haloperidol (1 mg/kg i.p.) and concomitantly treated with candesartan (3 and 5 mg/kg p.o.) and lisinopril (10 and 15 mg/kg p.o.) for 3 weeks in male Wistar rats. Various behavioral parameters were assessed on days 0, 7, 14 and 21 and biochemical parameters were estimated at day 22.

RESULTS

Chronic administration of haloperidol significantly increased stereotypic behaviors in rats, which were significantly improved by administration of candesartan and lisinopril. Chronic administration of haloperidol significantly increased oxidative stress and neuro-inflammation in the striatum region of the rat's brain. Co-administration of candesartan and lisinopril significantly attenuated the oxidative damage and neuro-inflammation in the haloperidol-treated rat.

CONCLUSIONS

The present study supports the therapeutic use of candesartan and lisinopril in the treatment of typical antipsychotic-induced orofacial dyskinesia and possible antioxidant and neuro-inflammatory mechanisms.

Perindopril may improve the hippocampal reduced glutathione content in rats

PURPOSE

Oxidative stress and renin- angiotensin system are both involved in the pathophysiology of most of the systemic and central disorders as well as in aging. Angiotensin converting enzyme (ACE) inhibitors, well known for their cardiovascular beneficial effects, have also shown antioxidant properties in pathologic conditions. This study aimed to evaluate the central effect of ACE inhibitors on oxidative status under no pathologic condition.

METHODS

Adult male rats were divided into four groups of 9 rats each. Groups were treated orally by perindopril at the doses of 1, 2, 4 mg/kg/day or normal saline as the control for four consecutive weeks. At the end of the treatment period the reduced and oxidized glutathione (GSH and GSSG respectively) and malondialdehyde (MDA), the product of lipid peroxidation, were measured in the rats' hippocampus.

RESULTS

The GSH increased dose dependently and was significantly higher in the 2 mg/kg perindopril treated group than the control group (p<0.05) while the GSSG level remained unchanged. As a consequent, the ratio of GSH to GSSG increased significantly in a dose dependent manner. There was not any significant change in MDA.

CONCLUSION

This study demonstrated that ACE inhibition may cause an increase in GSH as an anti- oxidant defense in the hippocampus.

Inhibition of central angiotensin II enhances memory function and reduces oxidative stress status in rat hippocampus

While it is now well established that the independent brain renin-angiotensin system (RAS) has some important central functions besides the vascular ones, the relevance of its main bioactive peptide angiotensin II (Ang II) on the memory processes, as well as on oxidative stress status is not completely understood. The purpose of the present work was to evaluate the effects of central Ang II administration, as well as the effects of Ang II inhibition with either AT1 and AT 2 receptor specific blockers (losartan and PD-123177, respectively) or an angiotensin-converting enzyme (ACE) inhibitor (captopril). These effects were studied on the short-term memory (assessed through Y-maze) or long-term memory (as determined in passive avoidance) and on the oxidative stress status of the hippocampus. Our results demonstrate memory deficits induced by the administration of Ang II, as showed by the significant decrease of the spontaneous alternation in Y-maze (p=0.015) and latency-time in passive avoidance task (p=0.001) when compared to saline. On the other side, the administration of all the aforementioned Ang II blockers significantly improved the spontaneous alternation in Y-maze task, while losartan also increased the latency time as compared to saline in step-through passive avoidance (p=0.042). Also, increased oxidative stress status was induced in the hippocampus by the administration of Ang II, as demonstrated by increased levels of lipid peroxidation markers (malondialdehyde-MDA concentration) (p<0.0001) and a decrease in both antioxidant enzymes determined: superoxide dismutase-SOD (p<0.0001) and glutathione peroxidase-GPX (p=0.01), as compared to saline. Additionally, the administration of captopril resulted in an increase of both antioxidant enzymes and decreased levels of lipid peroxidation (p=0.001), while PD-123177 significantly decreased MDA concentration (p>0.0001) vs. saline. Moreover, significant correlations were found between all of the memory related behavioral parameters and the main oxidative stress markers from the hippocampus, which is known for its implication in the processes of memory and also where RAS components are well expressed. This could be relevant for the complex interactions between Ang II, behavioral processes and neuronal oxidative stress, and could generate important therapeutic approaches.

MicroRNA-195 protects against dementia induced by chronic brain hypoperfusion via its anti-amyloidogenic effect in rats

Previous studies have demonstrated that chronic brain hypoperfusion (CBH) causes Aβ aggregation by upregulating expression of amyloid precursor protein (APP) and β-site APP cleaving enzyme 1 (BACE1) protein, which is accompanied by cognitive impairment, but the mechanisms are not fully understood. In this study, we evaluated the effect of microRNA on memory impairment in rats induced by CBH. We show here that CBH generated by bilateral common carotid artery occlusion (2VO) significantly decreased the learning and memory ability in rats, as assessed by Morris water maze, and upregulated expression of APP and BACE1 proteins in the hippocampus and cortex of rats, as evaluated by Western blot and immunofluorescence. In reciprocal, qRT-PCR analysis showed that microRNA-195 (miR-195) was downregulated in both the hippocampus and cortex of rats following CBH, and in the plasma of dementia patients. APP and BACE1 proteins were downregulated by miR-195 overexpression, upregulated by miR-195 inhibition, and unchanged by binding-site mutation or miR-masks, indicating that APP and BACE1 are two potential targets for miR-195. Knockdown of endogenous miR-195 by lentiviral vector-mediated overexpression of its antisense molecule (lenti-pre-AMO-miR-195) elicited dementia in rats, whereas overexpression of miR-195 using lenti-pre-miR-195 reduced dementia vulnerability triggered by 2VO. Additionally, chromatin immunoprecipitation analysis showed that NFκB was bound to the promoter region of miR-195 and inhibited its expression. We conclude that miR-195 may play a key role in determining dementia susceptibility in 2VO rats by regulating APP and BACE1 expression at the post-transcriptional level, and exogenous complement of miR-195 may be a potentially valuable anti-dementia approach.

The effects of ramipril in individuals at risk for Alzheimer's disease: results of a pilot clinical trial

Research shows that certain antihypertensives taken during midlife confer Alzheimer's disease (AD) related benefits in later life. We conducted a clinical trial to evaluate the extent to which the angiotensin converting enzyme inhibitor (ACE-I), ramipril, affects AD biomarkers including cerebrospinal fluid (CSF) amyloid-β (Aβ) levels and ACE activity, arterial function, and cognition in participants with a parental history of AD. This four month randomized, double-blind, placebo-controlled, pilot clinical trial evaluated the effects of ramipril, a blood-brain-barrier crossing ACE-I, in cognitively healthy individuals with mild, or Stage I hypertension. Fourteen participants were stratified by gender and apolipoprotein E ε4 (APOE ε4) status and randomized to receive 5 mg of ramipril or matching placebo daily. Participants were assessed at baseline and month 4 on measures of CSF Aβ(1-42) and ACE activity, arterial function, and cognition. Participants were middle-aged (mean 54 y) and highly educated (mean 15.4 y), and included 50% men and 50% APOE ε4 carriers. While results did not show a treatment effect on CSF Aβ(1-42) (p = 0.836), data revealed that ramipril can inhibit CSF ACE activity (p = 0.009) and improve blood pressure, however, there were no differences between groups in arterial function or cognition. In this study, ramipril therapy inhibited CSF ACE activity and improved blood pressure, but did not influence CSF Aβ1-42. While larger trials are needed to confirm our CSF Aβ results, it is possible that prior research reporting benefits of ACE-I during midlife may be attributed to alternative mechanisms including improvements in cerebral blood flow or the prevention of angiotensin II-mediated inhibition of acetylcholine.

Effects of lisinopril on NMDA receptor subunits 2A and 2B levels in the hippocampus of rats with L-NAME-induced hypertension

Hypertension is major risk factor leading to cerebrovascular pathologies. N-methyl D-aspartate receptors (NMDARs) and renin-angiotensin system are involved in neuronal plasticity, as well as cognitive functions in the hippocampus. In this study, we examined the effects of lisinopril, an ACE inhibitor, on the levels of hippocampal NMDAR subunits; NR2A and NR2B in L-NAME (N(ε)-nitro-L-arginine Methyl Ester)-induced hypertensive rats. In addition, malondialdehyde (MDA) levels were measured as a marker for lipid peroxidation. Compared with the control group, the MDA level was significantly increased after 8 weeks in the L-NAME-treated group. Rats treated with lisinopril and L-NAME plus lisinopril were found to have significantly decreased hippocampal MDA levels. Regarding the hippocampal concentrations of NR2A and NR2B, there were no statistically significant differences between groups. We demonstrated that lisinopril treatment has no direct regulatory effect on the levels of NR2A and NR2B in the rat hippocampus. Our results showed that Lisinopril could act as an antioxidant agent against hypertension-induced oxidative stress in rat hippocampus. The findings support that the use of lisinopril may offer a good alternative in the treatment of hypertension by reducing not only blood pressure but also prevent hypertensive complications in the brain.