Simvastatin exerts antiamnesic effect in Aβ25-35 -injected mice

Panaxadiol carbamate derivatives: Synthesis and biological evaluation as potential multifunctional anti-Alzheimer agents

It is reported that panaxadiol has neuroprotective effects. Previous studies have found that compound with carbamate structure introduced at the 3-OH position of 20 (R) -panaxadiol showed the most effective neuroprotective activity with an EC50 of 13.17 μM. Therefore, we designed and synthesized a series of ginseng diol carbamate derivatives with ginseng diol as the lead compound, and tested their anti-AD activity. It was found that the protective effect of compound Q4 on adrenal pheochromocytoma was 80.6 ± 10.85 % (15 μM), and the EC50 was 4.32 μM. According to the ELISA results, Q4 reduced the expression of Aβ25-35 by decreasing β-secretase production. Molecular docking studies revealed that the binding affinity of Q4 to β-secretase was -49.67 kcal/mol, indicating a strong binding affinity of Q4 to β-secretase. Western blotting showed that compound Q4 decreased IL-1β levels, which may contribute to its anti-inflammatory effect. Furthermore, compound Q4 exhibits anti-AD activities by reducing abnormal phosphorylation of tau protein and activation of the mitogen activated protein kinase pathway. The learning and memory deficits in mice treated with Q4in vivo were significantly alleviated. Therefore, Q4 may be a promising multifunctional drug for the treatment of AD, providing a new way for anti-AD drugs.

Carbon dioxide and MAPK signalling: towards therapy for inflammation

Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.

Simvastatin rescues memory and granule cell maturation through the Wnt/β-catenin signaling pathway in a mouse model of Alzheimer's disease

We previously showed that simvastatin (SV) restored memory in a mouse model of Alzheimer disease (AD) concomitantly with normalization in protein levels of memory-related immediate early genes in hippocampal CA1 neurons. Here, we investigated age-related changes in the hippocampal memory pathway, and whether the beneficial effects of SV could be related to enhanced neurogenesis and signaling in the Wnt/β-catenin pathway. APP mice and wild-type (WT) littermate controls showed comparable number of proliferating (Ki67-positive nuclei) and immature (doublecortin (DCX)-positive) granule cells in the dentate gyrus until 3 months of age. At 4 months, Ki67 or DCX positive cells decreased sharply and remained less numerous until the endpoint (6 months) in both SV-treated and untreated APP mice. In 6 month-old APP mice, dendritic extensions of DCX immature neurons in the molecular layer were shorter, a deficit fully normalized by SV. Similarly, whereas mature granule cells (calbindin-immunopositive) were decreased in APP mice and not restored by SV, their dendritic arborizations were normalized to control levels by SV treatment. SV increased Prox1 protein levels (↑67.7%, p < 0.01), a Wnt/β-catenin signaling target, while significantly decreasing (↓61.2%, p < 0.05) the upregulated levels of the β-catenin-dependent Wnt pathway inhibitor DKK1 seen in APP mice. In APP mice, SV benefits were recapitulated by treatment with the Wnt/β-catenin specific agonist WAY-262611, whereas they were fully abolished in mice that received the Wnt/β-catenin pathway inhibitor XAV939 during the last month of SV treatment. Our results indicate that activation of the Wnt-β-catenin pathway through downregulation of DKK1 underlies SV neuronal and cognitive benefits.

Simvastatin Blocks Reinstatement of Cocaine-induced Conditioned Place Preference in Male Mice with Brain Lipidome Remodeling

Drug-associated reward memories are conducive to intense craving and often trigger relapse. Simvastatin has been shown to regulate lipids that are involved in memory formation but its influence on other cognitive processes is elusive. Here, we used a mass spectrometry-based lipidomic method to evaluate the impact of simvastatin on the mouse brain in a cocaine-induced reinstatement paradigm. We found that simvastatin blocked the reinstatement of cocaine-induced conditioned place preference (CPP) without affecting CPP acquisition. Specifically, only simvastatin administered during extinction prevented cocaine-primed reinstatement. Global lipidome analysis showed that the nucleus accumbens was the region with the greatest degree of change caused by simvastatin. The metabolism of fatty-acids, phospholipids, and triacylglycerol was profoundly affected. Simvastatin reversed most of the effects on phospholipids induced by cocaine. The correlation matrix showed that cocaine and simvastatin significantly reshaped the lipid metabolic pathways in specific brain regions. Furthermore, simvastatin almost reversed all changes in the fatty acyl profile and unsaturation caused by cocaine. In summary, pre-extinction treatment with simvastatin facilitates cocaine extinction and prevents cocaine relapse with brain lipidome remodeling.

Targeting impaired nutrient sensing with repurposed therapeutics to prevent or treat age-related cognitive decline and dementia: A systematic review

BACKGROUND

Dementia is a debilitating syndrome that significantly impacts individuals over the age of 65 years. There are currently no disease-modifying treatments for dementia. Impairment of nutrient sensing pathways has been implicated in the pathogenesis of dementia, and may offer a novel treatment approach for dementia.

AIMS

This systematic review collates all available evidence for Food and Drug Administration (FDA)-approved therapeutics that modify nutrient sensing in the context of preventing cognitive decline or improving cognition in ageing, mild cognitive impairment (MCI), and dementia populations.

METHODS

PubMed, Embase and Web of Science databases were searched using key search terms focusing on available therapeutics such as 'metformin', 'GLP1', 'insulin' and the dementias including 'Alzheimer's disease' and 'Parkinson's disease'. Articles were screened using Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). The risk of bias was assessed using the Cochrane Risk of Bias tool v 2.0 for human studies and SYRCLE's risk of bias tool for animal studies.

RESULTS

Out of 2619 articles, 114 were included describing 31 different 'modulation of nutrient sensing pathway' therapeutics, 13 of which specifically were utilized in human interventional trials for normal ageing or dementia. Growth hormone secretagogues improved cognitive outcomes in human mild cognitive impairment, and potentially normal ageing populations. In animals, all investigated therapeutic classes exhibited some cognitive benefits in dementia models. While the risk of bias was relatively low in human studies, this risk in animal studies was largely unclear.

CONCLUSIONS

Modulation of nutrient sensing pathway therapeutics, particularly growth hormone secretagogues, have the potential to improve cognitive outcomes. Overall, there is a clear lack of translation from animal models to human populations.

Amyloid-β (25-35) regulates neuronal damage and memory loss via SIRT1/Nrf2 in the cortex of mice

Alzheimer's disease (AD) is the most common type of dementia. AD is pathologically characterized by synaptic dysfunction and cognitive decline due to the aggregation of a large amount of amyloid-β (Aβ) protein in the brain. However, recent studies have discovered that the Aβ is produced as an antimicrobial peptide that acts against bacteria and viruses. This has renewed interest in the effect of Aβ on AD. Thus, in this study, we investigated the different concentrations of Aβ_25-35 on neuroprotection and further explore the related mechanisms. Firstly, we detected the cognitive function using the Y-maze test, novel object recognition memory task and Morris water maze test. Then, we analyzed the ultrastructure of synapses and mitochondria, in addition to evaluating SOD levels. We also examined the effect of Aβ_25-35 on the viability and structure of the primary neurons. The western blot analysis was used to measure the protein levels. The results showed that mice treated with high concentration of Aβ_25-35 impaired the learning-memory ability and disordered the structure of neurons and mitochondria. Meanwhile, high concentration of Aβ_25-35 decreased the SIRT1/Nrf2 related antioxidant capacity and induced apoptosis. In contrast, mice treated with low concentration of Aβ_25-35 increased SOD levels and SIRT1/Nrf2 expressions, and induced autophagy. Our data suggest that low concentration of Aβ_25-35 may increase SOD levels through SIRT1/Nrf2 and induce autophagy.

Pleiotropic effects of statins on brain cells

Starting with cholesterol homeostasis, the first part of the review addresses various aspects of cholesterol metabolism in neuronal and glial cells and the mutual crosstalk between the two cell types, particularly the transport of cholesterol from its site of synthesis to its target loci in neuronal cells, discussing the multiple mechanistic aspects and transporter systems involved. Statins are next analyzed from the point of view of their chemical structure and its impingement on their pharmacological properties and permeability through cell membranes and the blood-brain barrier in particular. The following section then discusses the transcriptional effects of statins and the changes they induce in brain cell genes associated with a variety of processes, including cell growth, signaling and trafficking, uptake and synthesis of cholesterol. We review the effects of statins at the cellular level, analyzing their impact on the cholesterol composition of the nerve and glial cell plasmalemma, neurotransmitter receptor mobilization, myelination, dendritic arborization of neurons, synaptic vesicle release, and cell viability. Finally, the role of statins in disease is exemplified by Alzheimer and Parkinson diseases and some forms of epilepsy, both in animal models and in the human form of these pathologies.

Protective role of phenylethanoid glycosides, Torenoside B and Savatiside A, in Alzheimer's disease

The current study assessed the efficacy of two phenylethanoid glycosides (PhGs), Torenoside B (TB) and Savatiside A (SA), in the treatment of Alzheimer's disease (AD). The effects of TB and SA compounds were first assessed following amyloid beta (Aβ)_25-35 induction in SH-SY5Y cells at a range of concentrations. Their effects on cell viability and reactive oxygen species (ROS) were determined by performing MTT and dichlorofluorescin diacetate assays, respectively. The concentration of intracellular Ca²⁺ was determined using Fluo-3AM to stain SH-SY5Y cells. SA and TB treatments were also assessed in Aβ_25-35-induced mice. Y-maze and Morris water maze methods were utilized to assess murine learning and memory capability. The pathological changes of murine hippocampi was determined using H&E and Nissl staining. In addition, biochemical parameters associated with intracellular reactive oxygen pathways including Maleic dialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), acetylcholinesterase (AChE) and Calnexin were also assessed. TB and SA treatment in Aβ_25-35-induced SH-SY5Y cells resulted in the restoration of cell morphology, an increase of SOD and GSH-Px activity, a decrease in ROS, Ca²⁺ and MDA content, and a decrease in Calnexin expression. Furthermore, SA or TB treatment administered to Aβ_25-35-induced mice improved their spatial/non-spatial learning and memory capabilities. The efficacy of treatment was also supported by a marked change in the morphological structure of pyramidal neurons in the CA1 areas of murine hippocampi, as well as an increase of SOD and GSH-Px activity. Treatment also resulted in a decrease in MDA content, AchE activity and Calnexin expression in murine hippocampal tissue. As potential AD treatment drugs, SA and TB compounds have been demonstrated to alleviate the oxidative stress induced by Aβ_25-35 via the regulation of intracellular calcium homeostasis and Calnexin, preventing AD development.

Silencing the ACAT1 Gene in Human SH-SY5Y Neuroblastoma Cells Inhibits the Expression of Cyclo-Oxygenase 2 (COX2) and Reduces β-Amyloid-Induced Toxicity Due to Activation of Protein Kinase C (PKC) and ERK

Background

Acyl-coenzymeA: cholesterol acyltransferase (ACAT) 1, a key enzyme converting excess free cholesterol to cholesterol esters, has been demonstrated to be associated with the pathogenesis of Alzheimer disease (AD). However, the mechanism underlying the protective role of ACAT1 blockage in AD progression remains elusive.

Material/Methods

Human neuroblastoma SH-SY5Y cells were treated for 24 h with increasing concentrations of aggregated Aβ_25–35 (5, 15, 25, and 45 μmol) with or without the ACAT1 siRNA pretreatment. Cell viability analysis was measured by CCK-8 assay. The genome-wide correlation between ACAT1 and all other probe sets was measured by the Pearson correlation coefficient (r). Western blotting was used to detect the ACAT1 protein expression in the hippocampus of APP/PSN transgenic AD mice. The mRNA level for each target was analyzed by qPCR. Western blotting was used to detect the ACAT1, cyclo-oxygenase-2 (Cox2), Calcium voltage-gated channel subunits (CACNAs), and ERK/PKC proteins in SH-SY5Y cells with or without the ACAT1 siRNA pretreatment in the presence of Aβ_25–35.

Results

The expression of ACAT1 was significantly increased in the hippocampus of APP/PSN mice, and also showed an increasing trend when SH-SY5Y cells were exposed to Aβ_25–35. Silencing ACAT1 significantly attenuated Aβ-induced cytotoxicity and cell apoptosis in SH-SY5Y cells. The genome-wide correlation analysis showed that Ptgs2 had the most significant correlation with Acat1 in the hippocampus of BXD RI mice. We further determined the regulatory effect of ACAT1 on COX2 expression by silencing or over-expressing ACAT1 in SH-SY5Y cells and found that silencing ACAT1 played a protective role in AD progression by regulating CACNAs and PKC/ERK signaling cascades.

Conclusions

Silencing ACAT1 attenuates Aβ_25–35-induced cytotoxicity and cell apoptosis in SH-SY5Y cells, which may due to the synergistic effect of ACAT1 and COX2 through PKC/ERK pathways.

Ellagic acid ameliorates learning and memory deficits in a rat model of Alzheimer's disease: an exploration of underlying mechanisms

RATIONALE

Alzheimer's disease (AD) is a neurodegenerative disorder with irreversible loss of intellectual abilities. Current therapies for AD are still insufficient.

OBJECTIVE

In this study, the effect of ellagic acid on learning and memory deficits was evaluated in intrahippocampal amyloid beta (Aβ_25-35)-microinjected rats and its modes of action were also explored.

METHODS

AD rat model was induced by bilateral intrahippocampal microinjection of Aβ_25-35 and ellagic acid was daily administered (10, 50, and 100 mg/kg), and learning, recognition memory, and spatial memory were evaluated in addition to histochemical assessment, oxidative stress, cholinesterases activity, and level of nuclear factor-kappaB (NF-κB), Toll-like receptor 4 (TLR4), and nuclear factor (erythroid-derived 2)-like 2 (Nrf2).

RESULTS

The amyloid beta-microinjected rats showed a lower discrimination ratio in novel object and alternation score in Y maze tasks and exhibited an impairment of retention and recall capability in passive avoidance paradigm and higher working and reference memory errors in radial arm maze (RAM). In addition, amyloid beta group showed a lower number of Nissl-stained neurons in CA1 area in addition to enhanced oxidative stress, higher activity of cholinesterases, greater level of NF-κB and TLR4, and lower level of nuclear/cytoplasmic ratio for Nrf2 and ellagic acid at a dose of 100 mg/kg significantly prevented most of these abnormal alterations.

CONCLUSIONS

Ellagic acid pretreatment of intrahippocampal amyloid beta-microinjected rats could dose-dependently improve learning and memory deficits via neuronal protection and at molecular level through mitigation of oxidative stress and acetylcholinesterase (AChE) activity and modulation of NF-κB/Nrf2/TLR4 signaling pathway.

Simvastatin Attenuates Endothelial Activation through 15-Epi-Lipoxin A4 Production in Murine Chronic Chagas Cardiomyopathy

Current treatments for chronic Chagas cardiomyopathy, a disease with high mortality rates and caused by the protozoan Trypanosoma cruzi, are unsatisfactory. Myocardial inflammation, including endothelial activation, is responsible for the structural and functional damage seen in the chronic phase. The clinical efficacy of benznidazole could be improved by decreasing chronic inflammation. Statins, which have anti-inflammatory properties, may improve the action of benznidazole. Here, the action of simvastatin in a murine model of chronic Chagas cardiomyopathy and the link with the production of the proresolving eicosanoid 15-epi-lipoxin A4, produced by 5-lipoxygenase, are evaluated. Simvastatin decreased the expression of the adhesion molecules E-selectin, intracellular adhesion molecule type 1 (ICAM-1), and vascular cell adhesion molecule type 1 (VCAM-1) in T. cruzi-infected mice. However, when this drug was administered to 5-lipoxygenase-deficient mice, the anti-inflammatory effect was not observed unless exogenous 15-epi-lipoxin A4 was administered. Thus, in chronic Chagas disease, 5-epi-lipoxin A4 induced by simvastatin treatment could improve the pathophysiological condition of patients by increasing the trypanocidal action of benznidazole.

Diurnal Variation of the Peripheral Cholinergic Antiinflammatory Function in Mice

AIMS

Cholinergic antiinflammatory (CAI) pathway functions importantly in inflammation via α7 nicotinic acetylcholine receptors (α7nAChR). The present work tested circadian rhythm in peripheral CAI activity and validities of CAI activity and glucocorticoids in chronotherapy for lipopolysaccharide (LPS)-induced shock.

METHODS

Vesicular acetylcholine transporter (VAChT) expressed in liver and kidney was examined every 3 h in C57BL/6 mice. Proinflammatory cytokines in serum and survival time in shock were monitored after LPS injection every 3 h. Mifepristone, antagonist of glucocorticoid receptors, and methyllycaconitine (MLA), antagonist of α7nAChR, were administrated before LPS to block antiinflammatory function of endogenous glucocorticoids and acetylcholine.

RESULTS

Both levels of tumor necrosis factor α, interleukin 1β, and interleukin 6 and mortality exhibited diurnal variations with prominent peaks when LPS was given at 15:00, and the minimum mortality occurred at 00:00. Expression of VAChT increased during resting period. MLA increased serum proinflammatory cytokines slightly, but not affected survival rate. Both differences in cytokines and in survival times between LPS injection at 15:00 and 00:00 were eliminated by mifepristone, but not by MLA.

CONCLUSION

Peripheral CAI pathway exerts more powerful antiinflammatory effect during resting period. Glucocorticoids appear to be efficient in chronotherapy for septic shock.

Simvastatin enhances NMDA receptor GluN2B expression and phosphorylation of GluN2B and GluN2A through increased histone acetylation and Src signaling in hippocampal CA1 neurons

Simvastatin (SV) can improve cognitive deficits in Alzheimer's disease patients and mice. Herein, we report that the administration of SV (20 mg/kg) for 5 days in mice (SV-mice) or the treatment of slices with SV (10 μM) for 4 h (SV-slices) could increase the density of NMDA-evoked inward currents (INMDA) in hippocampal CA1 pyramidal cells, which were blocked by farnesol (FOH) that converts farnesyl pyrophosphate (FPP), but not geranylgeraniol (GGOH) that increases geranylgeranylpyrophosphate (GGPP). Sensitivity of INMDA to ifenprodil in SV-mice or SV-slices was significantly increased. The levels of hippocampal GluN2B and GluN2A or Src phosphorylation in SV-mice or SV-slices were higher than controls, which were sensitive to FOH. The Src inhibitor PP2 could inhibit the SV-enhanced phosphorylation of GluN2B and GluN2A and SV-augmented INMDA, but PI3K inhibitor LY294002 did not. The levels of GluN2B mRNA and protein were elevated in SV-mice, which was abolished by FOH, but not by GGOH or PP2. Furthermore, the histone H3K9 and H3K27 acetylation of GluN2B promoter was increased in SV-mice, which was suppressed by FOH rather than GGOH or PP2. In control mice and slices, the reduction of FPP by farnesyl transferase inhibitor could increase the levels of GluN2B expression, the histone H3K9 and H3K27 acetylation and enhance the phosphorylation of GluN2B, GluN2A and Src. The findings indicate that the administration of SV can enhance GluN2B expression and GluN2B and GluN2A phosphorylation leading to augmentation of NMDAR activity through reducing FPP to increase histone acetylation of GluN2B and Src signaling.

A novel acetylcholinesterase inhibitor and calcium channel blocker SCR-1693 improves Aβ25-35-impaired mouse cognitive function

RATIONALE

The mechanism involved in AD is complex, which has prompted to develop compounds that could simultaneously interact with several potential targets. Here, we report a new synthesized compound SCR-1693 which is designed to target both AChE and calcium channels that are potential for AD therapy.

OBJECTIVES

We investigated the effects of SCR-1693 on AChE and calcium channels, the effects of neuroprotection and anti-amnesia in icv-Aβ25-35-injected mice, and the potential mechanisms.

METHODS

AChE activity assay, intracellular Ca(2+) content and calcium currents measurement, and Aβ25-35-induced cellular death determine were performed for validation of designed targets and neuroprotection of SCR-1693. Mice were orally administrated with SCR-1693 once daily after an Aβ25-35 injection. The Morris water maze and Y-maze test, and hippocampal protein detection were conducted on days 5-10, day 11, and day 8. The pyramidal neuron number, hippocampal AChE activity, and synaptic transmission were measured on day 12.

RESULTS

SCR-1693 acted as a selective, reversible, and noncompetitive inhibitor of AChE, and a nonselective voltage-gated calcium channel blocker. SCR-1693 also inhibited the increase of AChE activity in the mouse hippocampus. SCR-1693 was more effective than donepezil and memantine in preventing Aβ25-35-induced long-term and short-term memory impairment, maintaining the basal transmission of Schaffer collateral-CA1 synapses, and sustaining LTP in mouse hippocampus. SCR-1693 attenuated Aβ25-35-induced death of SH-SY5Y cell and the loss of hippocampal pyramidal neurons, and regulated Aβ25-35-induced signal cascade in neurons.

CONCLUSIONS

All these findings indicated that SCR-1693, as a double-target-direction agent, is a considerable candidate for AD therapy.

Role of the nicotinic acetylcholine receptor in Alzheimer's disease pathology and treatment

Alzheimer's Disease (AD) is the major form of senile dementia, characterized by neuronal loss, extracellular deposits, and neurofibrillary tangles. It is accompanied by a loss of cholinergic tone, and acetylcholine (ACh) levels in the brain, which were hypothesized to be responsible for the cognitive decline observed in AD. Current medication is restricted to enhancing cholinergic signalling for symptomatic treatment of AD patients. The nicotinic acetylcholine receptor family (nAChR) and the muscarinic acetylcholine receptor family (mAChR) are the target of ACh in the brain. Both families of receptors are affected in AD. It was demonstrated that amyloid beta (Aβ) interacts with nAChRs. Here we discuss how Aβ activates or inhibits nAChRs, and how this interaction contributes to AD pathology. We will discuss the potential role of nAChRs as therapeutic targets. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.