Effect of HMG-CoA reductase inhibitors on beta-amyloid peptide levels: implications for Alzheimer's disease

Statins and the risk of dementia: a meta-analysis

Clarify the relationship between the use of statins and the risk of dementia, and further guide the clinical application of statins. This paper uses computer search Chinese and foreign language databases Pubmed, Medline, Cochrane, Embase, Web of Science, Weipu, CBM, Wanfang, CNKI, etc., to include the literature that meets the standards from the establishment of the library to December 2020, and uses Revman 5.1 software and Stata15.0 software for meta-analysis. Of the 34 included observational studies, stratified subgroup analyses were performed based on the type of clinical trial, sex of participants, presence or absence of apolipoprotein E-4 (ApoEε4) allele, and duration of use. The conclusions showed that (1) the use of statins can significantly reduce the risk of dementia; (2) There is no significant sex difference in reducing the risk of dementia; (3) Continuous use of statins for ≥ 1 year can significantly reduce the risk of dementia compared with the time of taking the drug for < 1 year; (4) Compared with subjects with negative ApoEε4 allele, the use of statins has a more significant effect on reducing the risk of dementia in subjects carrying the ApoEε4 allele.

Statins' protective effects on focal epilepsy are independent of LDL-C

OBJECTIVE

This study evaluates the potential protective effects of statins against epilepsy, focusing on their differential impacts on focal and generalized epilepsy. It investigates the role of statins through the HMGCR gene and associated low-density lipoprotein (LDL) cholesterol levels.

METHODS

A two-sample Mendelian randomization (MR) and summary-data-based MR (SMR) approach were employed using genetic instruments from genome-wide association studies (GWASs) and expression quantitative trait loci (eQTLs). Subgroup analyses examined focal and generalized epilepsy, with sensitivity tests, including MR-Egger regression and MR-PRESSO, to assess horizontal pleiotropy and robustness.

RESULTS

SMR analysis found no significant association between HMGCR expression and epilepsy risk across subtypes (p > 0.05). However, inverse-variance-weighted MR (IVW-MR) showed that elevated LDL cholesterol mediated by HMGCR was linked to an increased risk of focal epilepsy (OR = 1.251, 95% CI = 1.135-1.378). No such association was observed for generalized epilepsy. Statins showed promise in reducing post-stroke epilepsy risk, likely through anti-inflammatory and neuroprotective effects.

SIGNIFICANCE

The findings suggest that statins' protective effects may be subtype-specific, particularly in post-stroke focal epilepsy. Further research is needed to elucidate underlying mechanisms and optimize their therapeutic potential in epilepsy management.

PLAIN LANGUAGE SUMMARY

Statins, drugs typically used to manage cholesterol, may also lower the risk of developing certain types of epilepsy, especially post-stroke focal epilepsy, by reducing inflammation and protecting brain cells. The research found no clear effect of statins on generalized epilepsy or epilepsy caused by other factors. These results could aid in creating better treatments for epilepsy in the future.

Mechanistic Insights into the Antibiofilm Activity of Simvastatin and Lovastatin against Bacillus subtilis

Statins have been reported for diverse pleiotropic activities, including antimicrobial and antibiofilm. However, due to the limited understanding of their mode of action, none of the statins have gained approval for antimicrobial or antibiofilm applications. In a recent drug repurposing study, we observed that two statins (i.e., Simvastatin and Lovastatin) interact stably with TasA(28-261), the principal extracellular matrix protein of Bacillus subtilis, and also induce inhibition of biofilm formation. Nevertheless, the underlying mechanism remained elusive. In the present study, we examined the impact of these statins on the physiological activity of TasA(28-261), specifically its interaction with TapA(33-253) and aggregation into the amyloid-like structure using purified recombinant TasA(28-261) and TapA(33-253) in amyloid detection-specific in vitro assays (i.e., CR binding and ThT staining assays). Results revealed that both statins interfered with amyloid formation by the TasA(28-261)-TapA(33-253) complex, while neither statin inhibited amyloid formation by lysozyme, a model amyloid-forming protein. Moreover, neither statin significantly altered the expressions of terminal regulatory genes (viz, sinR, sinI) and terminal effector genes (viz, tasA, tapA, and bslA) involved in biofilm formation by B. subtilis. While the intricate interplay between Simvastatin and Lovastatin with the diverse molecular constituents of B. subtilis biofilm remains to be elucidated conclusively, the findings obtained during the present study suggest that the underlying mechanism for Simvastatin- and Lovastatin-mediated inhibition of B. subtilis biofilm formation is manifested by interfering with the aggregation and amyloid formation by TasA(28-261)-TapA(33-253). These results represent one of the first experimental evidence for the underlying mechanism of antibiofilm activity of statins and offer valuable directions for future research to harness statins as antibiofilm therapeutics.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

Side effects based network construction and drug repositioning of ropinirole as a potential molecule for Alzheimer's disease: an in-silico, in-vitro, and in-vivo study

Alzheimer's disease (AD) is the leading cause of dementia in older adults. Drug repositioning is a process of finding new therapeutic applications for existing drugs. One of the methods in drug repositioning is to use the side-effect profile of a drug to identify a new therapeutic indication. The drugs with similar side-effects may act on similar biological targets and could affect the same biochemical process. In this study, we explored the Food and Drug Administration-approved drugs using PROMISCUOUS database to find those that have adverse effects profile comparable with the ligands being studied or used to treat AD. Here, we found that the ropinirole, a dopamine receptor agonist, shared a maximum number of side-effects with the drugs proven beneficial for treating AD. Furthermore, molecular modelling demonstrated that ropinirole exhibited strong binding affinity (-9.313 kcal/mol) and best ligand efficiency (0.49) with sigma-1 receptor. Here, we observed that the quaternary amino group of ropinirole is essential for binding with sigma-1 receptor. Molecular dynamic simulation indicated that the movement of the carboxy-terminal helices (α4/α5) could play a major role in the receptor's physiological functions. The neurotoxicity induced by Aβ25-35 in SH-SY5Y cells was reduced by ropinirole at concentrations 10, 30, and 50 µM. The effect on spatial learning and memory was examined in mice with Aβ25-35 induced memory deficit using the radial arm maze. Ropinirole (10 and 20 mg/kg) significantly improved the short and long-term memories in the radial arm maze test. Our results suggest that ropinirole has the potential to be repositioned for AD treatment.Communicated by Ramaswamy H. Sarma.

The Effect of Oral Simvastatin on the Clinical Outcome of Patients with Severe Traumatic Brain Injury: A Randomized Clinical Trial

Background

Despite recent promising pharmacological and technological advances in neurosurgical intensive care, the overall TBI-related mortality and morbidity remain high and still pose a major clinical problem. The aim of this study was to evaluate the effect of oral simvastatin on the clinical outcome of patients with severe TBI.

Methods

In a double-blind placebo-controlled randomized clinical trial a total of 98 patients with severe TBI in Imam Khomeini Hospital in Sari, Iran, were evaluated. Patients who meet the inclusion criteria were randomly allocated into two groups (n=49). In addition to supportive therapies, the intervention group received oral simvastatin (40 mg, daily) for 10 days, and the control group received the placebo (10 days). Patients' Glasgow coma scale (GCS) score, in hospital mortality, duration of mechanical ventilation and length of ICU and neurosurgery ward stay were evaluated during three-time intervals (T1: admission, T2: discharge and T3: one month after discharge).

Results

The percentage of conscious patients was 18.9% (7 cases) in the simvastatin group and 3.1% (1 case) in controls (P=0.06) at T2. One month after discharge (T3) the proportion of conscious patients significantly increased in the simvastatin group compared to control group (64.9 % versus 28.1 %; P=0.002). There was no significant difference for the mean of GCS score between the simvastatin group and control group at T1 (6.41 ± 1.30 versus 6.41 ± 1.28, respectively; P = 0.98). However, the mean score of GCS in patients who received simvastatin was significantly greater than controls at T2 and T3 (p<0.05). There was no significant differences between two group in-terms of length of mechanical ventilation, ICU and neurosurgery ward stay.

Conclusion

According to the results of this study it seems that using simvastatin may be an effective and promising therapeutic modality for improving GCS score during TBI recovery.

Identification of phytochemicals from North African plants for treating Alzheimer's diseases and of their molecular targets by in silico network pharmacology approach

BACKGROUND

The global social expenses of Alzheimer's disease (AD) have been increased to US$1 trillion due to high cost, side-effects, and low efficiency of the current AD-therapies. Another reason is the lack of preventive drugs and the low-income situation of Asian and African countries. Accordingly, patients rather prefer traditional herbal remedies. Network-pharmacology has been a well-established method for the visualization and the construction of disorder target protein-drug framework. This could aid in the identification of drugs molecular-mechanisms.

AIM

The aim of this study is to investigate the phytochemical constituents that could target Alzheimer's disease from the North African plants. This could be done by exploring their possible mechanisms of action through molecular network pharmacology-based approach.

EXPERIMENTAL PROCEDURE

The Phytochemical-compounds of North-African plants (NAP) have been accessed from open-databank. ADME-screening has been conducted for filtering of the NAP phytochemical-constituents utilizing Qikprop-software. The open STITCH databank has been utilized for the prediction of the phytochemical-constituents target-proteins; UniProt and TDD-DB databanks have been utilized for distinguishing AD-related proteins. Phytochemical constituent-target protein (C-T) and plant-phytochemical constituent-target protein (P-C-T) frameworks have been assembled utilizing Cytoscape to interpret the anti-Alzheimer's disease mechanism of action of the targeted phytochemical constituents.

RESULTS

The NAP 6842 phytochemical-constituents (from more than 1000 plants) have been exposed to ADME and CNS modulating filtration, generating 94 phytochemical-constituents which have been subjected to target-prediction investigation. The 94 phytochemical-constituents and the 4 AD-identified targets have been associated through 155 edges which formed the main pathways related to AD. Cuparene, alpha-selinene, beta-sesquiphellandrene, calamenene, 2-4-dimethylheptane, undecane, n-tetradecane, hexadecane, nonadecane, n-eicosane, and heneicosane have had C-T network highest combined-score, whilst the proteins MAO-B, HMG-CoA, BACE1, and GCR have been the most enriched ones by comprising the uppermost combined-scores of C-T. Hypericum perforatum, Piper nigrum, Juniperus communis, Levisticum officinale, Origanum vulgare acquired the uppermost number of P-C-Target interactions.

CONCLUSION

The phytochemical-targets prediction of NAP utilizing molecular-network pharmacology-based investigation has paved the way for networking multi-target, multi-constituent, and multi-pathway mechanisms. This may introduce potential future targets for the regulation and the management of Alzheimer's disease.

TAXONOMY CLASSIFICATION BY EVISE

Alzheimer's disease, Network pharmacology, In-silico computer based approach.

Effects of Statin Treatment on Outcomes after Traumatic Brain Injury

Neuroprotective treatments that have shown promise in reducing secondary injury and improving recovery in animal models of traumatic brain injury (TBI) have not been found effective to date in humans. One reason may be the delay after injury in initiating treatment. Statin medications are among the promising neuroprotective agents in animal models, and their presence in the bloodstream of many individuals at the time of injury might optimize their clinical impact. This observational study conducted by a subset of centers participating in the National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR)-funded TBI Model System program sought to examine the effects of taking statin medication at the time injury on functional outcomes. Participants >50 years of age were prospectively enrolled during patient rehabilitation. Demographic data, cardiovascular history, and brain injury history were obtained through chart abstraction and interview. Prescription medication use in the year prior to enrollment was determined from a national pharmacy search service. Propensity scoring was used to create 49 pairs of participants who were well matched on demographic and clinical attributes but discordant for statin use. The treated and untreated participants did not differ on initial Glasgow Coma Score, time until commands were followed, duration of post-traumatic amnesia, or Functional Independence Measure (FIM) scores at rehabilitation admission, discharge, or 1 year post-injury, or on acute or rehabilitation hospital lengths of stay. Evidence of greater and lesser statin compliance was not associated with outcome. This study did not provide support for a clinically important benefit of statin use at the time of moderate to severe TBI.

The beneficial effects of HMG-CoA reductase inhibitors in the processes of neurodegeneration

Statins, cholesterol lowering drugs, have been demonstrated to exert beneficial effects in other conditions such as primary and progressing neurodegenerative diseases beyond their original role. Observation that statins ameliorate the neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and cerebral ischemic stroke, the neuroprotective effects of these drugs are thought to be linked to their anti-inflammatory, anti-oxidative, and anti-excitotoxic properties. Despite the voluminous literature on the clinical advantages of 3-hydroxy-3-methylglutaryl Co-enzyme A reductase (HMGCR) inhibitors (statins) in cardiovascular system, the neuroprotective effects and the underlying mechanisms are little understood. Hence, the present review tries to provide a critical overview on the statin-induced neuroprotection, which are presumed to be associated with the ability to reduce cholesterol, Amyloid-β and apolipoprotein E (ApoE) levels, decrease reactive oxygen and nitrogen species (ROS and RNS) formation, inhibit excitotoxicity, modulate matrix metalloproteinases (MMPs), stimulate endothelial nitric oxide synthase (eNOS), and increase cerebral blood perfusion. This review is also aimed to illustrate that statins protect neurons against the neuro-inflammatory processes through balancing pro-inflammatory/anti-inflammatory cytokines. Ultimately, the beneficial role of statins in ameliorating the development of PD, AD, MS and cerebral ischemic stroke has been separately reviewed.

Current insights into pathogenesis of Parkinson's disease: Approach to mevalonate pathway and protective role of statins

Although Parkinson's disease (PD) is considered as the second most common life threatening age-related neurodegenerative disorder, but the underlying mechanisms for pathogenesis of PD are remained to be fully found. However, a complex relationship between genetic and environmental predisposing factors are involved in progression of PD. Dopaminergic neuronal cell death caused by mutations and accumulation of α-synuclein in Lewy bodies and neurites was suggested as the main strategy for PD, but current studies have paid attention to the role of mevalonate pathway in incidence of neurodegenerative diseases including PD. The discovery may change the therapeutic protocols from symptomatic treatment by dopamine precursors and agonists to neurodegenerative process halting drugs. Moreover, the downstream metabolites of mevalonate pathway may be used as diagnostic biomarkers for early diagnosis of PD. Statins, as cholesterol lowering drugs, may ameliorate the enzyme complex dysfunction, a key step in the progression of the neurodegenerative disorders, oxidative stress-induced damage and neuro-inflammation. Statins exert the neuroprotective effects on striatal dopaminergic neurons through blocking the mevalonate pathway. In the present review, we have focused on the new approaches to pathogenesis of PD regarding to mevalonate pathway, in addition to the previous understood mechanisms for the disease. It tries to elucidate the novel findings about PD for the development of future diagnostic and therapeutic strategies. Moreover, we explain the controversial role of statins in improvement or progression of PD and the position of these drugs in neuroprotection in PD patients.

Statin treatment reduces the risk of poststroke seizures

OBJECTIVE

To examine the potential efficacy of statin treatment in reducing the risk of poststroke seizures.

METHODS

In this cohort study, patients with a first-ever ischemic stroke and no history of epilepsy before stroke were enrolled. After a mean follow-up period of 2.5 years, a follow-up assessment was performed to identify poststroke epilepsy. Logistic regression and Cox regression analyses were used to assess the relationship between statin use and poststroke early-onset seizures or poststroke epilepsy.

RESULTS

Of 1,832 enrolled patients, 63 (3.4%) patients had poststroke early-onset seizures and 91 (5.0%) patients had poststroke epilepsy. Statin use was associated with a lower risk of poststroke early-onset seizures (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.20-0.60, p < 0.001), and this reduced risk was seen mainly in patients who used a statin only in the acute phase (OR 0.36, 95% CI 0.20-0.62, p < 0.001). No significant association was found between statin use and poststroke epilepsy (OR 0.81, 95% CI 0.52-1.26, p = 0.349). In 63 patients who presented with early-onset seizures, statin use was associated with reduced risk of poststroke epilepsy (OR 0.34, 95% CI 0.13-0.88, p = 0.026).

CONCLUSIONS

Statin use, especially in the acute phase, may reduce the risk of poststroke early-onset seizures. In addition, statin treatment may prevent the progression of initial poststroke seizure-induced neurodegeneration into chronic epilepsy. Because of the observational nature of the study, more studies are needed to confirm the results.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that in patients with a first-ever ischemic stroke, the early use of statins reduces the risk of early poststroke seizures.

Statins, cognition, and dementia—systematic review and methodological commentary

Firm conclusions about whether mid-life or long-term statin use has an impact on cognitive decline and dementia remain elusive. Here, our objective was to systematically review, synthesize and critique the epidemiological literature that examines the relationship between statin use and cognition, so as to assess the current state of knowledge, identify gaps in our understanding, and make recommendations for future research. We summarize the findings of randomized controlled trials (RCTs) and observational studies, grouped according to study design. We discuss the methods for each, and consider likely sources of bias, such as reverse causation and confounding. Although observational studies that considered statin use at or near the time of dementia diagnosis suggest a protective effect of statins, these findings could be attributable to reverse causation. RCTs and well-conducted observational studies of baseline statin use and subsequent cognition over several years of follow-up do not support a causal preventative effect of late-life statin use on cognitive decline or dementia. Given that much of the human research on statins and cognition in the future will be observational, careful study design and analysis will be essential.

Increasing membrane cholesterol of neurons in culture recapitulates Alzheimer's disease early phenotypes

BACKGROUND

It is suspected that excess of brain cholesterol plays a role in Alzheimer's disease (AD). Membrane-associated cholesterol was shown to be increased in the brain of individuals with sporadic AD and to correlate with the severity of the disease. We hypothesized that an increase of membrane cholesterol could trigger sporadic AD early phenotypes.

RESULTS

We thus acutely loaded the plasma membrane of cultured neurons with cholesterol to reach the 30% increase observed in AD brains. We found changes in gene expression profiles that are reminiscent of early AD stages. We also observed early AD cellular phenotypes. Indeed we found enlarged and aggregated early endosomes using confocal and electron microscopy after immunocytochemistry. In addition amyloid precursor protein vesicular transport was inhibited in neuronal processes, as seen by live-imaging. Finally transient membrane cholesterol loading lead to significantly increased amyloid-β42 secretion.

CONCLUSIONS

Membrane cholesterol increase in cultured neurons reproduces most early AD changes and could thus be a relevant model for deciphering AD mechanisms and identifying new therapeutic targets.

Maternal pravastatin prevents altered fetal brain development in a preeclamptic CD-1 mouse model

Objective

Using an animal model, we have previously shown that preeclampsia results in long-term adverse neuromotor outcomes in the offspring, and this phenotype was prevented by antenatal treatment with pravastatin. This study aims to localize the altered neuromotor programming in this animal model and to evaluate the role of pravastatin in its prevention.

Materials and Methods

For the preeclampsia model, pregnant CD-1 mice were randomly allocated to injection of adenovirus carrying sFlt-1 or its control virus carrying mFc into the tail vein. Thereafter they received pravastatin (sFlt-1-pra “experimental group”) or water (sFlt-1 “positive control”) until weaning. The mFc group (“negative control”) received water. Offspring at 6 months of age were sacrificed, and whole brains underwent magnetic resonance imaging (MRI). MRIs were performed using an 11.7 Tesla vertical bore MRI scanner. T2 weighted images were acquired to evaluate the volumes of 28 regions of interest, including areas involved in adaptation and motor, spatial and sensory function. Cytochemistry and cell quantification was performed using neuron-specific Nissl stain. One-way ANOVA with multiple comparison testing was used for statistical analysis.

Results

Compared with control offspring, male sFlt-1 offspring have decreased volumes in the fimbria, periaquaductal gray, stria medullaris, and ventricles and increased volumes in the lateral globus pallidus and neocortex; however, female sFlt-1 offspring showed increased volumes in the ventricles, stria medullaris, and fasciculus retroflexus and decreased volumes in the inferior colliculus, thalamus, and lateral globus pallidus. Neuronal quantification via Nissl staining exhibited decreased cell counts in sFlt-1 offspring neocortex, more pronounced in males. Prenatal pravastatin treatment prevented these changes.

Conclusion

Preeclampsia alters brain development in sex-specific patterns, and prenatal pravastatin therapy prevents altered neuroanatomic programming in this animal model.

Protective effect of HMG CoA reductase inhibitors against running wheel activity induced fatigue, anxiety like behavior, oxidative stress and mitochondrial dysfunction in mice

BACKGROUND

Chronic fatigue stress (CFS) is an important health problem with unknown causes and unsatisfactory prevention strategies, often characterized by long-lasting and debilitating fatigue, myalgia, impairment of neuro-cognitive functions along with other common symptoms. The present study has been designed to explore the protective effect of statins against running wheel activity induced fatigue anxiety.

METHODS

Male albino Laca mice (20-30 g) were subjected to swim stress induced fatigue in a running wheel activity apparatus. Atorvastatin (10, 20 mg/kg, po) and fluvastatin (5, 10 mg/kg, po) were administered daily for 21 days, one hour prior to the animals being subjected to running wheel activity test session of 6 min. Various behavioral tests (running wheel activity, locomotor activity and elevated plus maze test), biochemical parameters (lipid peroxidation, nitrite concentration, glutathione levels and catalase activity) and mitochondrial complex enzyme dysfunctions (complex I, II, III and IV) were subsequently assessed.

RESULTS

Animals exposed to 6 min test session on running wheel for 21 days showed a significant decrease in number of wheel rotations per 6 min indicating fatigue stress like behavior. Treatment with atorvastatin (10 and 20 mg/kg) and fluvastatin (10 mg/kg) for 21 days significantly improved the behavioral alterations [increased number of wheel rotations and locomotor activity, and anxiety like behavior (decreased number of entries and time spent in open arm)], oxidative defence and mitochondrial complex enzyme activities in brain.

CONCLUSION

Present study suggests the protective role of statins against chronic fatigue induced behavioral, biochemical and mitochondrial dysfunctions.

The genetic architecture of Alzheimer's disease: beyond APP, PSENs and APOE

Alzheimer's disease (AD) is a complex disorder with a clear genetic component. Three genes have been identified as the cause of early onset familial AD (EOAD). The most common form of the disease, late onset Alzheimer's disease (LOAD), is, however, a sporadic one presenting itself in later stages of life. The genetic component of this late onset form of AD has been the target of a large number of studies, because only one genetic risk factor (APOE4) has been consistently associated with the disease. However, technological advances allow new approaches in the study of complex disorders. In this review, we discuss the new results produced by genome wide association studies, in light of the current knowledge of the complexity of AD genetics.

The neuroprotective effect of two statins: simvastatin and pravastatin on a streptozotocin-induced model of Alzheimer's disease in rats

Astrocytes play a fundamental role in glutamate metabolism by regulating the extracellular levels of glutamate and intracellular levels of glutamine. They also participate in antioxidant defenses, due to the synthesis of glutathione, coupled to glutamate metabolism. Although the cause of Alzheimer's disease (AD) remains elusive, some changes in neurochemical parameters, such as glutamate uptake, glutamine synthetase activity and glutathione have been investigated in this disease. A possible neuroprotective effect of two statins, simvastatin and pravastatin (administered p.o.), was evaluated using a model of dementia, based on the intracerebroventricular (ICV) administration of streptozotocin (STZ), and astrocyte parameters were determined. We confirmed a cognitive deficit in rats submitted to ICV-STZ, and a prevention of this deficit by statin administration. Moreover, both statins were able to prevent the decrease in glutathione content and glutamine synthetase activity in this model of AD. Interestingly, simvastatin increased per se glutamate uptake activity, while both statins increased glutamine synthetase activity per se. These results support the idea that these drugs could be effective for the prevention of alterations observed in the STZ dementia model and may contribute to reduce the cognitive impairment and brain damage observed in AD patients.

Statins promote the degradation of extracellular amyloid {beta}-peptide by microglia via stimulation of exosome-associated insulin-degrading enzyme (IDE) secretion

Epidemiological studies indicate that intake of statins decrease the risk of developing Alzheimer disease. Cellular and in vivo studies suggested that statins might decrease the generation of the amyloid β-peptide (Aβ) from the β-amyloid precursor protein. Here, we show that statins potently stimulate the degradation of extracellular Aβ by microglia. The statin-dependent clearance of extracellular Aβ is mainly exerted by insulin-degrading enzyme (IDE) that is secreted in a nonconventional pathway in association with exosomes. Stimulated IDE secretion and Aβ degradation were also observed in blood of mice upon peripheral treatment with lovastatin. Importantly, increased IDE secretion upon lovastatin treatment was dependent on protein isoprenylation and up-regulation of exosome secretion by fusion of multivesicular bodies with the plasma membrane. These data demonstrate a novel pathway for the nonconventional secretion of IDE via exosomes. The modulation of this pathway could provide a new strategy to enhance the extracellular clearance of Aβ.

Synergistic benefits of erythropoietin and simvastatin after traumatic brain injury

Simvastatin and recombinant human erythropoietin (rhEpo) are implicated as potential therapeutic candidates for traumatic brain injury (TBI). Prominent effects of simvastatin include its anti-inflammatory, neurotrophic and neuroregenerative actions studied in various models of neuronal injury. On the other hand, rhEpo has been shown to promote cell survival mechanisms by producing anti-apoptotic and cell proliferative actions. Beneficial effects of rhEpo and statin monotherapies have been well studied. However, there are no reports showing combined use of rhEpo and statins after TBI. This investigation examined if combined efficacy of cell proliferative ability of rhEpo along with the neuroregenerative ability of simvastatin will render maximum recovery in a controlled cortical impact (CCI) mouse model of TBI. Results showed that compared to baseline TBI, rhEpo was more effective than simvastatin in promoting cell proliferation while simvastatin was more effective than rhEpo in restoring axonal damage following TBI. Combined treatment with simvastatin and rhEpo maximally restored axonal integrity while simultaneously inducing greater proliferation of newly formed cells resulting in better functional recovery after TBI than either alone. This is the first study showing the efficacy of erythropoietin-simvastatin combinational therapeutic approach in achieving greater structural and cognitive recovery after TBI.

[Course modifying therapy of Alzheimer's dementia]

The current therapy of Alzheimer's disease is primarily symptomatic. Drugs which aim to modify the course of the disease are currently being developed and tested in clinical trials. Given the complex and partly unknown pathogenesis of the disease, failure of such forms of therapy has to be taken into account. Clinical epidemiology suggests a possible neuroprotective effect of statins and non-steroidal anti-inflammatory drugs, however, the molecular basis of these effects has to be further unraveled. Therapies that modify the course of Alzheimer's disease are only likely to be effective years if not decades before the disease becomes clinically apparent. Thus, the therapy of risk factors including arterial hypertension and obesity in midlife as well as a Mediterranean diet currently provides the highest chance of modifying the course of the disease.

Neurite-like structures induced by mevalonate pathway blockade are due to the stability of cell adhesion foci and are enhanced by the presence of APP

Epidemiological studies have shown an association between statin use and a decreased risk of dementia. However, the mechanism by which this beneficial effect is brought about is unclear. In the context of Alzheimer's disease, at least three possibilities have been studied; reduction in amyloid beta peptide (Abeta) production, the promotion of alpha-secretase cleavage and positive effects on neurite outgrowth. By investigating the effects of mevalonate pathway blockade on neurite outgrowth using real-time imaging, we found that rather than promote the production of neurite extensions, inhibition rapidly induced cell rounding. Crucially, neurite-like structures were generated through the persistence of cell-cell and cell-substrate adhesions and not through a mechanism of positive outgrowth. This effect can be strikingly enhanced by the over-expression of human amyloid precursor protein and is isoprenoid rather than cholesterol dependent.

ACAT inhibition and amyloid beta reduction

Alzheimer's disease (AD) is a devastating neurodegenerative disorder. Accumulation and deposition of the beta-amyloid (Abeta) peptide generated from its larger amyloid precursor protein (APP) is one of the pathophysiological hallmarks of AD. Intracellular cholesterol was shown to regulate Abeta production. Recent genetic and biochemical studies indicate that not only the amount, but also the distribution of intracellular cholesterol is critical to regulate Abeta generation. Acyl-coenzyme A: cholesterol acyl-transferase (ACAT) is a family of enzymes that regulates the cellular distribution of cholesterol by converting membrane cholesterol into hydrophobic cholesteryl esters for cholesterol storage and transport. Using pharmacological inhibitors and transgenic animal models, we and others have identified ACAT1 as a potential therapeutic target to lower Abeta generation and accumulation. Here we discuss data focusing on ACAT inhibition as an effective strategy for the prevention and treatment of AD.

Adeno-associated virus gene therapy with cholesterol 24-hydroxylase reduces the amyloid pathology before or after the onset of amyloid plaques in mouse models of Alzheimer's disease

The development of Alzheimer's disease (AD) is closely connected with cholesterol metabolism. Cholesterol increases the production and deposition of amyloid-beta (Abeta) peptides that result in the formation of amyloid plaques, a hallmark of the pathology. In the brain, cholesterol is synthesized in situ but cannot be degraded nor cross the blood-brain barrier. The major exportable form of brain cholesterol is 24S-hydroxycholesterol, an oxysterol generated by the neuronal cholesterol 24-hydroxylase encoded by the CYP46A1 gene. We report that the injection of adeno-associated vector (AAV) encoding CYP46A1 in the cortex and hippocampus of APP23 mice before the onset of amyloid deposits markedly reduces Abeta peptides, amyloid deposits and trimeric oligomers at 12 months of age. The Morris water maze (MWM) procedure also demonstrated improvement of spatial memory at 6 months, before the onset of amyloid deposits. AAV5-wtCYP46A1 vector injection in the cortex and hippocampus of amyloid precursor protein/presenilin 1 (APP/PS) mice after the onset of amyloid deposits also reduced markedly the number of amyloid plaques in the hippocampus, and to a less extent in the cortex, 3 months after the injection. Our data demonstrate that neuronal overexpression of CYP46A1 before or after the onset of amyloid plaques significantly reduces Abeta pathology in mouse models of AD.

Pharmacological Treatment of Alzheimer's Disease: Is it Progressing Adequately?

INTRODUCTION

Between 1993 and 2000 four acetylcholinesterase inhibitors were marketed as a symptomatic treatment for Alzheimer's disease (AD), as well as memantine in 2003. Current research is focused on finding drugs that favorably modify the course of the disease. However, their entrance into the market does not seem to be imminent.

RESEARCH DEVELOPMENT

The aim of AD research is to find substances that inhibit certain elements of the AD pathogenic chain (beta- and gamma-secretase inhibitors, alpha-secretase stimulants, beta-amyloid aggregability reducers or disaggregation and elimination inductors, as well as tau-hyperphosphorylation, glutamate excitotoxicity, oxidative stress and mitochondrial damage reducers, among other action mechanisms). Demonstrating a disease's retarding effect demands longer trials than those necessary to ascertain symptomatic improvement. Besides, a high number of patients (thousands of them) is necessary, all of which turns out to be difficult and costly. Furthermore, it would be necessary to count on diagnosis and progression markers in the disease's pre-clinical stage, markers for specific phenotypes, as well as high-selectivity molecules acting only where necessary. In order to compensate these difficulties, drugs acting on several defects of the pathogenic chain or showing both symptomatic and neuroprotective action simultaneously are being researched.

CONCLUSIONS

There are multiple molecules used in research to modify AD progression. Although it turns out to be difficult to obtain drugs with sufficient efficacy so that their marketing is approved, if they were achieved they would lead to a reduction of AD prevalence.

High serum Abeta and vascular risk factors in first-degree relatives of Alzheimer's disease patients

The main objective of this study was to determine whether elevated blood beta-amyloid (Abeta) levels among the first-degree relatives of patients with Alzheimer's Disease (AD) are associated with vascular risk factors of AD. Serum Abeta was measured in samples from 197 cognitively normal first-degree relatives of patients with AD-like dementia. Study participants were recruited as part of an ancillary study of the Alzheimer's Disease Anti-inflammatory Prevention Trial (ADAPT subpopulation). The ADAPT subpopulation was found to be similar in age, sex, and ethnicity to another cognitively normal cohort (n = 98). Using cross-sectional analyses, we examined the association of Abeta with blood pressure, lipid levels, apolipoprotein E genotypes, and the use of prescribed medication to treat vascular risk factors in the ADAPT subpopulation. Abeta(1-40) was positively associated with age, use of antihypertensives, and serum creatinine, and we observed a marginal negative interaction on Abeta(1-40) associated with systolic blood pressure and use of antihypertensives. Serum Abeta(1-42) was associated with statin use and a positive correlation of Abeta (1-42) with HDL was observed among statin nonusers. These findings suggest that high Abeta in the periphery among the family history-enriched cohorts may be due to enrichment of vascular risk factors and may reflect presymptomatic AD pathology. It remains to be determined whether the association of Abeta with medications used for treating vascular risk factors indicates prevention of AD. Longitudinal evaluation of blood Abeta in this cohort will provide a better understanding of the significance of this association in AD etiology.

Statins: mechanisms of neuroprotection

Clinical trials report that the class of drugs known as statins may be neuroprotective in Alzheimer's and Parkinson's disease, and further trials are currently underway to test whether these drugs are also beneficial in multiple sclerosis and acute stroke treatment. Since statins are well tolerated and have relatively few side effects, they may be considered as viable drugs to ameliorate neurodegenerative diseases. However, the mechanism of their neuroprotective effects is only partly understood. In this article, we review the current data on the neuroprotective effects of statins and their underlying mechanisms. In the first section, we detail the mechanisms by which statins affect cellular signalling. The primary action of statins is to inhibit cellular cholesterol synthesis. However, the cholesterol synthesis pathway also has several by-products, the non-sterol isoprenoids that are also important in cellular functioning. Furthermore, reduced cholesterol levels may deplete the cholesterol-rich membrane domains known as lipid rafts, which in turn could affect cellular signalling. In the second section, we summarize how the effects on signalling translate into general neuroprotective effects through peripheral systems. Statins improve blood-flow, reduce coagulation, modulate the immune system and reduce oxidative damage. The final section deals with the effects of statins on the central nervous system, particularly during Alzheimer's and Parkinson's disease, stroke and multiple sclerosis.

Reduction of cholesterol synthesis in the mouse brain does not affect amyloid formation in Alzheimer's disease, but does extend lifespan

Alterations in cellular cholesterol synthesis or content in cultured neurons affect the cleavage of amyloid precursor protein to amyloidogenic Abeta(40) and Abeta(42) peptides characteristic of Alzheimer's disease. To determine whether a decrease in cholesterol synthesis affects amyloid precursor protein processing in vivo, we crossed cholesterol 24-hydroxylase knockout mice, which exhibit a 50% reduction in brain sterol synthesis, with transgenic mice [B6.Cg-Tg(APPswe, PSEN1E9)85Dbo/J] that develop Alzheimer's disease-like pathology. Amyloid precursor protein expression and amyloid plaque deposition in the cortex and hippocampus of male and female Alzheimer's disease mice between the ages of 3 to 15 months were similar in the presence and absence of cholesterol 24-hydroxylase. A modest but statistically significant decline in insoluble Abeta(42) peptide levels was detected in the hippocampus of 12-month-old knockout/Alzheimer's disease males. The levels of insoluble Abeta(40) and Abeta(42) peptides in 15-month-old knockout/Alzheimer's disease females were also reduced slightly. Although amyloid plaque accumulation did not affect brain sterol or fatty acid synthesis rates in 24-hydroxylase WT or knockout mice, loss of one or both cholesterol 24-hydroxylase alleles increased longevity in Alzheimer's disease mice. These studies suggest that reducing de novo cholesterol synthesis in the brain will not substantially alter the course of Alzheimer's disease, but may confer a survival advantage.

[Alzheimer's disease. Molecular pathology, animal models, and current treatment]

The currently approved but only mildly efficient drugs against Alzheimer's disease treat merely the symptoms. Genetic, neuropathological, and biochemical data support the importance of the amyloid hypothesis of Alzheimer's disease, at the moment the most influential hypothesis. Many treatment strategies have been performed based on this hypothesis and were markedly successful in preclinical animal models. Unfortunately the treatment is still unsuccessful in humans. This could be due to the animal models showing marginal behavioural deficits but no Alzheimer-like nerve cell loss, although they all developed a more or less pronounced plaque load. Today we know however that Alzheimer plaques are not mainly responsible for the cell loss. Therefore novel animal models have been developed that show age-dependent axonal degeneration, massive neuronal loss, and robust behavioural deficits. Successful treatment of an animal model with such robust deficits would be very likely better suited to transferral into the clinic. The final validation or disproof of individual Alzheimer hypotheses and their resulting treatment strategies can however be obtained only after clinical proof.

Abeta(25-35) attenuated SREBP level in nuclear extracts of serum-deprived human neuroblastoma cells

Disturbance in cholesterol homeostasis appears to be an important factor in the pathogenesis of neurodegenerative disorders. The aim of the present study was to investigate sterol regulatory element binding protein (SREBP) levels in the nuclear extracts of human neuroblastoma cells and the possible interaction of beta-amyloid peptide (Abeta) and cholesterol with this transcription factor. In this study, cultured human neuroblastoma cells (SHSY-5Y) were incubated in serum-deprived media in the presence or absence of Abeta((25-35)) (1 microM) or cholesterol (300 microM) for 24 h. Nuclear extracts were subjected to SDS-PAGE, and SREBP cleavage product (68 kDa) was detected by immunoblotting. SREBP levels were elevated in the cells incubated 24 h in serum-deprived experimental media and were attenuated by Abeta or cholesterol-supplementation. It is likely that the ability of Abeta to release cholesterol into the medium and downregulate SREBP is due to a feedback mechanism.