Novel insights for the treatment of Alzheimer's disease

Molecular Anti-inflammatory Mechanisms of Retinoids and Carotenoids in Alzheimer's Disease: a Review of Current Evidence

Alzheimer's disease (AD) is considered as one of the most prevalent neurodegenerative disorders characterized by progressive loss of mental function and ability to learn. AD is a multifactorial disorder. Various hypotheses are suggested for the pathophysiology of AD including "Aβ hypothesis," "tau hypothesis," and "cholinergic hypothesis." Recently, it has been demonstrated that neuroinflammation is involved in the pathogenesis of AD. Neuroinflammation causes synaptic dysfunction and neuronal death within the brain. Excessive production of pro-inflammatory mediators induces Aβ peptide production/accumulation and hyperphosphorylated tau generating inflammatory molecules and cytokines. These inflammatory molecules disrupt blood-brain barrier integrity and increase the production of Aβ42 oligomers. Retinoids and carotenoids are potent antioxidants and anti-inflammatory agents having neuroprotective properties. They are able to prevent disease progression through several mechanisms such as suppression of Aβ peptide production/accumulation, oxidative stress, and pro-inflammatory mediator's secretion as well as improvement of cognitive performance. These observations, therefore, confirm the neuroprotective role of retinoids and carotenoids through multiple pathways. Therefore, the administration of these nutrients is considered as a promising approach to the prevention and/or treatment of AD in the future. The aim of this review is to present existing evidences regarding the beneficial effects of retinoids and carotenoids on AD's risk and outcomes, seeking the mechanism of their action.

Interferon Gamma: Influence on Neural Stem Cell Function in Neurodegenerative and Neuroinflammatory Disease

Interferon-gamma (IFNγ), a pleiotropic cytokine, is expressed in diverse neurodegenerative and neuroinflammatory conditions. Its protective mechanisms are well documented during viral infections in the brain, where IFNγ mediates non-cytolytic viral control in infected neurons. However, IFNγ also plays both protective and pathological roles in other central nervous system (CNS) diseases. Of the many neural cells that respond to IFNγ, neural stem/progenitor cells (NSPCs), the only pluripotent cells in the developing and adult brain, are often altered during CNS insults. Recent studies highlight the complex effects of IFNγ on NSPC activity in neurodegenerative diseases. However, the mechanisms that mediate these effects, and the eventual outcomes for the host, are still being explored. Here, we review the effects of IFNγ on NSPC activity during different pathological insults. An improved understanding of the role of IFNγ would provide insight into the impact of immune responses on the progression and resolution of neurodegenerative diseases.

Effect of Huperzine A on Aβ-induced p65 of astrocyte in vitro

Alzheimer's disease (AD) is the most common cause of dementia. Its pathology often accompanies inflammatory action, and astrocytes play important roles in such procedure. Rela(p65) is one of significant message factors in NF-κB pathway which has been reported high expression in astrocyte treated by Aβ. HupA, an alkaloid isolated from Chinese herb Huperzia serrata, has been widely used to treat AD and observations reflected that it improves memory and cognitive capacity of AD patients. To reveal its molecular mechanisms on p65, we cultured astrocytes, built Aβ-induced AD model, treated astrocytes with HupA at different concentrations, assayed cell viability with MTT, and detected p65 expression by immunohistochemistry and PCR. Our results revealed that treatment with 10 μM Aβ1-42 for 24 h induced a significant increase of NF-κB in astrocytes; HupA significantly down-regulated p65 expression induced by Aβ in astrocytes. This study infers that HupA can regulate NF-κB pathway to treat AD.

Alzheimer's disease drug development based on Computer-Aided Drug Design

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the excessive deposition of amyloids in the brain. The pathological features mainly include the extracellular amyloid plaques and intracellular neurofibrillary tangles, which are the production of amyloid precursor protein (APP) processed by the α-, β- and γ-secretases. Based on the amyloid cascade hypotheses of AD, a large number of amyloid-β agents and secretase inhibitors against AD have been recently developed by using computational methods. This review article describes pathophysiology of AD and the structure of the Aβ plaques, β- and γ-secretases, and discusses the recent advances in the development of the amyloid agents for AD therapy and diagnosis by using Computer-Aided Drug Design approach.

Intranasal H102 Peptide-Loaded Liposomes for Brain Delivery to Treat Alzheimer's Disease

PURPOSE

H102, a novel β-sheet breaker peptide, was encapsulated into liposomes to reduce its degradation and increase its brain penetration through intranasal administration for the treatment of Alzheimer's disease (AD).

METHODS

The H102 liposomes were prepared using a modified thin film hydration method, and their transport characteristics were tested on Calu-3 cell monolayers. The pharmacokinetics in rats' blood and brains were also investigated. Behavioral experiments were performed to evaluate the improvements on AD rats' spatial memory impairment. The neuroprotective effects were tested by detecting acetylcholinesterase (AchE), choline acetyltransferase (ChAT) and insulin degrading enzyme (IDE) activity and conducting histological assays. The safety was evaluated on rats' nasal mucosa and cilia.

RESULTS

The liposomes prepared could penetrate Calu-3 cell monolayers consistently. After intranasal administration, H102 could be effectively delivered to the brain, and the AUC of H102 liposomes in the hippocampus was 2.92-fold larger than that of solution group. H102 liposomes could excellently ameliorate spatial memory impairment of AD model rats, increase the activities of ChAT and IDE and inhibit plaque deposition, even in a lower dosage compared with H102 intranasal solution. H102 nasal formulations showed no toxicity on nasal mucosa.

CONCLUSIONS

The H102-loaded liposome prepared in this study for nasal administration is stable, effective and safe, which has great potential for AD treatment.

A review on Alzheimer's disease pathophysiology and its management: an update

Alzheimer's disease acknowledged as progressive multifarious neurodegenerative disorder, is the leading cause of dementia in late adult life. Pathologically it is characterized by intracellular neurofibrillary tangles and extracellular amyloidal protein deposits contributing to senile plaques. Over the last two decades, advances in the field of pathogenesis have inspired the researchers for the investigation of novel pharmacological therapeutics centered more towards the pathophysiological events of the disease. Currently available treatments i.e. acetylcholinesterase inhibitors (rivastigmine, galantamine, donepezil) and N-methyl d-aspartate receptor antagonist (memantine) contribute minimal impact on the disease and target late aspects of the disease. These drugs decelerate the progression of the disease, provide symptomatic relief but fail to achieve a definite cure. While the neuropathological features of Alzheimer's disease are recognized but the intricacies of the mechanism have not been clearly defined. This lack of understanding regarding the pathogenic process may be the likely reason for the non-availability of effective treatment which can prevent onset and progression of the disease. Owing to the important progress in the field of pathophysiology in the last couple of years, new therapeutic targets are available that should render the underlying disease process to be tackled directly. In this review, authors will discusses the different aspects of pathophysiological mechanisms behind Alzheimer's disease and its management through conventional drug therapy, including modern investigational therapeutic strategies, recently completed and ongoing.

Add life to years: psychosocial interventions for people with cognitive disorders

As population longevity increases, living with cognitive disorders during a significant part of the remaining lifespan becomes a strong possibility for the majority of older adults. Therefore, the development of treatment strategies to address the principal causes of cognitive and functional decline is a healthcare priority. The aims of medical and psychological therapies vary according to clinical severity. In the stages of mild cognitive impairment and early dementia, maintaining personal independence and enjoyment of life is a major objective from individual, societal, and economical perspectives (Neugroschl and Wang, 2011; Mokhtariet al., 2012). Current anti-dementia drugs contribute to this goal to a very limited extent. In individuals with mild cognitive impairment these compounds do not prevent the onset of dementia (Raschettiet al., 2007), and in those diagnosed with early dementia, these compounds delay the worsening of symptoms only for several months (Kurz and Lautenschlager, 2010). Drugs with novel mechanisms of action are being developed for Alzheimer's disease and other neurodegenerative conditions. These have the potential to slow down the progression of pathology and expand the number of years for which patients remain at mild levels of cognitive and functional impairment. It is less likely that these treatments will stop cognitive and functional decline completely (Kurz and Perneczky, 2011). Therefore, psychosocial interventions are urgently needed in addition to current and future pharmacotherapy. At any level of cognitive and functional impairment the role of psychosocial interventions is to strengthen and make the best use of preserved skills in order to attain or maintain optimal levels of activity, participation, and interpersonal relationships. In contrast to drugs, psychosocial treatments primarily operate at the behavioral level. Some attempt to restore functions through cognitive, social, or physical activity, while others attempt to minimize disability through compensatory cognitive, behavioral, or environmental strategies. Recent research has shown that psychosocial interventions may increase regional cortical thickness or modify the pattern of neuronal network activation (Draganski and May, 2008; van Paasschenet al., 2009; Vosset al., 2010; Ericksonet al., 2011). These neurobiological effects clearly demonstrate that brain plasticity persists into old age, but the relationship to behavioral gains and the importance for the prevention of cognitive decline (Lautenschlageret al., 2012; Steffener and Stern, 2012; Valenzuelaet al., 2012) are currently unclear.

Supporting daily activities and indoor travel of persons with moderate Alzheimer's disease through standard technology resources

These two studies were aimed at evaluating standard technology resources for supporting activity and travel among patients with moderate Alzheimer's disease. Specifically, Study I assessed a pictorial instruction program relying on the use of a portable computer and a commercially available and inexpensive video editing software for supporting the performance of daily activities with three patients. Study II assessed the indoor travel performance of four patients (i.e., the three involved in Study I and a fourth patient with no previous research exposure) using a commercially available, basic doorbell system with sound and light cues. The percentages of correct activity steps obtained with the instruction program used in Study I were relatively high and largely similar to the percentages reported in previous studies using more sophisticated technology. During Study II, the percentages of correct travels of two patients matched the data of the most successful patients involved in previous studies with more sophisticated technology. The percentages of the other two patients tended to be lower than those obtained previously, but were still practically relevant. The implications of the results of the two studies and a number of issues for new research are discussed.

2,3-dihydro-1H-cyclopenta[b]quinoline derivatives as acetylcholinesterase inhibitors-synthesis, radiolabeling and biodistribution

In the present study we describe the synthesis and biological assessment of new tacrine analogs in the course of inhibition of acetylcholinesterase. The obtained molecules were synthesized in a condensation reaction between activated 6-BOC-hydrazinopyridine-3-carboxylic acid and 8-aminoalkyl derivatives of 2,3-dihydro-1H-cyclopenta[b]quinoline. Activities of the newly synthesized compounds were estimated by means of Ellman’s method. Compound 6h (IC₅₀ = 3.65 nM) was found to be most active. All obtained novel compounds present comparable activity to that of tacrine towards acetylcholinesterase (AChE) and, simultaneously, lower activity towards butyrylcholinesterase (BChE). Apart from 6a, all synthesized compounds are characterized by a higher affinity for AChE and a lower affinity for BChE in comparison with tacrine. Among all obtained molecules, compound 6h presented the highest selectivity towards inhibition of acetylcholinesterase. Molecular modeling showed that all compounds demonstrated a similar binding mode with AChE and interacted with catalytic and peripheral sites of AChE. Also, a biodistribution study of compound 6a radiolabeled with ^99mTc was performed.

The effect of crebanine on memory and cognition impairment via the alpha-7 nicotinic acetylcholine receptor

AIMS

The aims of the present study were to investigate the effect of crebanine on memory and cognition impairment in mice and to elucidate the underlying molecular mechanisms.

MAIN METHODS

The memory-enhancing effects of crebanine were assessed with a water maze test using scopolamine-induced amnesic mice. The molecular mechanism was explored in silico by docking crebanine against acetylcholine binding proteins (AChBPs) and in vitro with a radioligand competition assay using (±)-[(3)H]-epibatidine. The pharmacological behavior was assessed by observing changes to the functional activity of α7-nAChRs expressed in Xenopus oocytes and by fluorescent assays on recombinant ligand gated ion channel (LGIC) receptors expressed in mammalian cells.

KEY FINDINGS

The administration of crebanine significantly improved the cognitive deficits induced by scopolamine, as measured by the water maze test. The docking results demonstrated that crebanine bound to the active binding site of the AChBP template with a good docking energy. Crebanine significantly inhibited the binding of (±)-[(3)H]-epibatidine to AChBPs with K(i) values of 179 nM and 538 nM for Ls and Ac, respectively. Further functional assays performed using two separate protocols indicated that crebanine is an antagonist of the α7-nAChR with an IC(50) of 19.1μM.

SIGNIFICANCE

The observed actions of crebanine against amnesia and its effect on α7-nAChRs will be beneficial for target-based drug design; crebanine or its scaffold can be used as the starting point to develop a drug for Alzheimer's disease. The cognition-enhancing effects of crebanine and the underlying mechanism based on α7-nAChRs are consistent with its traditional use. These findings demonstrate the potential utility of crebanine in the development of neurodegenerative therapy.

Radio electric asymmetric brain stimulation in the treatment of behavioral and psychiatric symptoms in Alzheimer disease

PURPOSE

Behavioral and psychiatric symptoms of dementia (BPSD) are common in Alzheimer's disease (AD) and disrupt the effective management of AD patients. The present study explores the use of radio electric asymmetric brain stimulation (REAC) in patients who have had a poor response to pharmacological treatment.

PATIENTS AND METHODS

Eight patients (five females and three males; mean [±standard deviation] age at study baseline: 69.9 ± 3.0 years) diagnosed with AD according to the DSM-IV-TR criteria (mean onset age of AD: 65.4 ± 3.5 years) were cognitively and psychometrically assessed with the Mini-Mental State Examination (MMSE), the Activity of Daily Living (ADL), the Instrumental Activity of Daily Living (IADL), and the Neuropsychiatric Inventory (NPI), prior to and after each of 2 REAC treatment cycles.

RESULTS

Scores on the MMSE and all subscales of the NPI (frequency, severity, and distress), the ADL, and the IADL were significantly improved following the initial REAC treatment. There was further significant improvement in all measurements (with a tendency for improvement in the IADL) after the second REAC treatment cycle.

CONCLUSION

The improvement of cognitive and behavioral/psychiatric functioning following REAC treatment suggests that this innovative approach may be an effective, safe, and tolerable alternative to pharmacological treatment of AD patients, especially in the area of BPSD. Elderly patients suffering from other types of dementia may also benefit from REAC treatment.

Tau mediated neurodegeneration: an insight into Alzheimer's disease pathology

Extracellular accumulations of Aβ, hyperphosphorylation of tau and intracellular neurofibrillary tangle formation have been the hallmarks of Alzheimer's Disease (AD). Although tau and its phosphorylation play a pivotal role in the normal physiology yet its hyperphosphorylation has been a pathological manifestation in neurodegenerative disorders like AD. In this review physiology of tau, its phosphorylation, hyperphosphorylation with the intervention of various kinases, aggregation and formation of paired helical filaments has been discussed. A brief account of various animal models employed to study the pathological manifestation of tau in AD and therapeutic strategies streamlined to counter the tau induced pathology has been given. The reasons for the failure to have suitable animal model to study AD pathology and recent success in achieving this has been included. The role of caspase cascade in tau cleavage has been emphasized. The summary of current studies on tau and the need for future studies has been accentuated.

Category cued recall following controlled encoding as a neuropsychological tool in the diagnosis of Alzheimer's disease: a review of the evidence

Aim of the present review paper was to evaluate the hypothesis (included in the proposal of new research criteria for Alzheimer's disease; Dubois et al., Lancet Neurology, 6, 734-746, 2007) that a neuropsychological tool which provides support for the semantic encoding of memorandum at the time of study and supplies category cues at the time of retrieval (i.e. the Grober-Buschke paradigm) is more effective than traditional measures of free recall in 1) differentiating patients affected by the amnestic form of Mild Cognitive Impairment (MCI) or by mild to moderate forms of Alzheimer's disease (AD) from healthy matches, 2) predicting the conversion of individuals with MCI to AD, and 3) differentiating AD patients from individuals affected by other forms of dementia. Results of the review are controversial regarding the superiority of the Grober-Buschke procedure in differentiating individuals affected by AD or MCI from healthy individuals. The only study that evaluated this issue directly found that the Grober-Buschke procedure was more sensitive and specific than more traditional memory tests in predicting the conversion of MCI patients to AD. Finally, two studies reported that patients affected by AD or other forms of dementia showed different performance patterns in the free and cued recall tasks of the Grober-Buschke procedure. In conclusion, although encouraging results are reported in the few studies that investigated the ability of this procedure to predict the evolution of individuals with amnestic MCI and to differentiate AD patients from patients with other forms of cortical and subcortical dementia, more experimental work is needed to confirm these positive findings.