Current drugs and future hopes in the treatment of Alzheimer's disease

Influence of Lentiviral β-Synuclein Overexpression in the Hippocampus of a Transgenic Mouse Model of Alzheimer's Disease on Amyloid Precursor Protein Metabolism and Pathology

BACKGROUND

β-Synuclein (β-Syn) is a member of the highly homologous synuclein protein family. The most prominent family member, α-synuclein (α-Syn), abnormally accumulates in so-called Lewy bodies, one of the major pathological hallmarks of α-synucleinopathies. Notably, parts of the peptide backbone, called the nonamyloid component, are also found in amyloid plaques. However, β-Syn seems to have beneficial effects by reducing α-Syn aggregation, and amyloid antiaggregatory activity has been described.

OBJECTIVE

The aim of the study was to analyze if wild-type β-Syn can counteract functional and pathological changes in a murine Alzheimer model over different time periods.

METHODS

At the onset of pathology, lentiviral particles expressing human β-Syn were injected into the hippocampus of transgenic mice overexpressing human amyloid precursor protein with Swedish and London mutations (APPSL). An empty vector served as the control. Behavioral analyses were performed 1, 3 and 6 months after injection followed by biochemical and histological examinations of brain samples.

RESULTS

β-Syn expression was locally concentrated and rather modest, but nevertheless changed its effect on APP expression and plaque load in a time- and concentration-dependent manner. Interestingly, the phosphorylation of glycogen synthase kinase 3 beta was enhanced in APPSL mice expressing human β-Syn, but an inverse trend was observed in wild-type animals.

CONCLUSION

The initially reported beneficial effects of β-Syn could be partially reproduced, but locally elevated levels of β-Syn might also cause neurodegeneration. To enlighten the controversial pathological mechanism of β-Syn, further examinations considering the relationship between concentration and exposure time of β-Syn are needed.

Ginsenosides compound K and Rh2 inhibit tumor necrosis factor-α-induced activation of the NF-κB and JNK pathways in human astroglial cells

Ginsenosides, the main component of Panax ginseng, have been known for the anti-inflammatory and anti-proliferative activities. In this study, we investigated the molecular mechanisms responsible for the anti-inflammatory effects of ginsenosides on activated astroglial cells. Among 13 different ginsenosides, intestinal bacterial metabolites Rh(2) and compound K (C-K) showed a significant inhibitory effect on tumor necrosis factor-alpha (TNF-alpha)-induced expression of intercellular adhesion molecule-1 in human astroglial cells. Pretreatment with C-K or Rh(2) suppressed TNF-alpha-induced phosphorylation of IkappaBalpha kinase and the subsequent phosphorylation and degradation of IkappaBalpha. Additionally, the same treatment inhibited TNF-alpha-induced phosphorylation of MKK4 and the subsequent activation of the JNK-AP-1 pathway. The inhibitory effect of ginsenosides on TNF-alpha-induced activation of the NF-kappaB and JNK pathways was not observed in human monocytic U937 cells. These results collectively indicate that ginsenoside metabolites C-K and Rh(2) exert anti-inflammatory effects by the inhibition of both NF-kappaB and JNK pathways in a cell-specific manner.

Therapeutic targets: progress of their exploration and investigation of their characteristics

Modern drug discovery is primarily based on the search and subsequent testing of drug candidates acting on a preselected therapeutic target. Progress in genomics, protein structure, proteomics, and disease mechanisms has led to a growing interest in and effort for finding new targets and more effective exploration of existing targets. The number of reported targets of marketed and investigational drugs has significantly increased in the past 8 years. There are 1535 targets collected in the therapeutic target database compared with approximately 500 targets reported in a 1996 review. Knowledge of these targets is helpful for molecular dissection of the mechanism of action of drugs and for predicting features that guide new drug design and the search for new targets. This article summarizes the progress of target exploration and investigates the characteristics of the currently explored targets to analyze their sequence, structure, family representation, pathway association, tissue distribution, and genome location features for finding clues useful for searching for new targets. Possible "rules" to guide the search for druggable proteins and the feasibility of using a statistical learning method for predicting druggable proteins directly from their sequences are discussed.

Memantine: a review of its use in Alzheimer's disease

Memantine (Ebixa, Axura, Namenda, Akatinol) is a moderate-affinity, uncompetitive, voltage-dependent, NMDA-receptor antagonist with fast on/off kinetics that inhibits excessive calcium influx induced by chronic overstimulation of the NMDA receptor. Memantine is approved in the US and the EU for the treatment of patients with moderate to severe dementia of the Alzheimer's type. In well designed clinical trials, oral memantine, as monotherapy or in addition to a stable dose of acetylcholinesterase inhibitors, was well tolerated during the treatment of mild to severe Alzheimer's disease for up to 52 weeks. Memantine generally modified the progressive symptomatic decline in global status, cognition, function and behaviour exhibited by patients with moderate to severe Alzheimer's disease in four 12- to 28-week trials. In patients with mild to moderate Alzheimer's disease, data from three 24-week trials are equivocal, although meta-analyses indicate beneficial effects on global status and cognition. Memantine is an effective pharmacotherapeutic agent, and currently the only approved option, for the treatment of moderate to severe Alzheimer's disease.

Progress and problems in the exploration of therapeutic targets

Drugs exert their therapeutic effect by binding and regulating the activity of a particular protein or nucleic acid target. A large number of targets have been explored for drug discovery. Continuous effort has been directed at the search for new targets and more-extensive exploration of existing targets. Knowledge of these targets facilitates the understanding of molecular mechanisms of drugs and the effort required for drug discovery and target searches. Areas of progress, current focuses of research and development and the difficulties in target exploration are reviewed. The characteristics of the currently explored targets and their correlation to the level of difficulty for target exploration are analyzed. From these characteristics, simple rules can be derived for estimating the difficulty level of target exploration. The feasibility of predicting druggable proteins by using simple rules and sequence-derived physicochemical properties is also discussed.

Current Status and Future Promise of Pharmacotherapeutic Strategies for Alzheimer’s Disease

BACKGROUND AND OBJECTIVE

The pharmacotherapy of Alzheimer's disease (AD) is evolving rapidly. Unless new discoveries continue to emerge to facilitate prevention and effective treatment of the disease, the anticipated burden of this disease on caregivers and society at large will overwhelm resources. The objective of this paper is to review the state of development of approaches likely to yield effective interventional measures with regard to AD in the future.

DESIGN

A comprehensive systematic search of MEDLINE using focused search criteria, a search of reference lists from these studies and reviews, a review of the Cochrane Database of Systematic Reviews, and a hand search of relevant journals was conducted. Selection of articles was based on the clinical focus. Additional inclusion criteria preferentially selected key articles that contained higher-level evidence in accordance with explicit, validated criteria.

RESULTS

Pharmaceutical interventions are being developed and tested that confer neuroprotective benefits by targeting causative mechanisms.

CONCLUSION

The paradigm that AD is pharmacologically unresponsive is shifting. Our understanding of the molecular mechanisms of neurodegeneration will soon allow us to more specifically target and interrupt the processes that contribute to this dementia.

Current Status and Future Promise of Pharmacotherapeutic Strategies for Alzheimer’s Disease

BACKGROUND AND OBJECTIVE

The pharmacotherapy of Alzheimer's disease (AD) is evolving rapidly. Unless new discoveries continue to emerge to facilitate prevention and effective treatment of the disease, the anticipated burden of this disease on caregivers and society at large will overwhelm resources. The objective of this paper is to review the state of development of approaches likely to yield effective interventional measures with regard to AD in the future.

DESIGN

A comprehensive systematic search of MEDLINE using focused search criteria, a search of reference lists from these studies and reviews, a review of the Cochrane Database of Systematic Reviews, and a hand search of relevant journals was conducted. Selection of articles was based on the clinical focus. Additional inclusion criteria preferentially selected key articles that contained higher-level evidence in accordance with explicit, validated criteria.

RESULTS

Pharmaceutical interventions are being developed and tested that confer neuroprotective benefits by targeting causative mechanisms.

CONCLUSION

The paradigm that AD is pharmacologically unresponsive is shifting. Our understanding of the molecular mechanisms of neurodegeneration will soon allow us to more specifically target and interrupt the processes that contribute to this dementia.