Modulation of nicotinic receptor activity in the central nervous system: a novel approach to the treatment of Alzheimer disease

Emerging therapeutics agents and recent advances in drug repurposing for Alzheimer's disease

Alzheimer's disease (AD) is a multivariate and diversified disease and affects the most sensitive areas of the brain, the cerebral cortex, and the hippocampus. AD is a progressive age-related neurodegenerative disease most often associated with memory deficits and cognition that get more worsen over time. The central theory on the pathophysiological hallmark features of AD is characterized by the accumulation of amyloid β (Aβ) peptides, also associated with tau proteins (τ) dysfunctioning which leads to distorted microtubular structure, affects the cholinergic system, and mitochondrial biogenesis. This review emphasizes how simple it is to find novel treatments for AD and focuses on several recently developed medications through repurposing that can speed up traditional drug development.

Determinants of approved acetylcholinesterase inhibitor response outcomes in Alzheimer's disease: relevance for precision medicine in neurodegenerative diseases

Acetylcholinesterase inhibitors (ChEI) are the global standard of care for the symptomatic treatment of Alzheimer's disease (AD) and show significant positive effects in neurodegenerative diseases with cognitive and behavioral symptoms. Although experimental and large-scale clinical evidence indicates the potential long-term efficacy of ChEI, primary outcomes are generally heterogeneous across outpatient clinics and regional healthcare systems. Sub-optimal dosing or slow tapering, heterogeneous guidelines about the timing for therapy initiation (prodromal versus dementia stages), healthcare providers' ambivalence to treatment, lack of disease awareness, delayed medical consultation, prescription of ChEI in non-AD cognitive disorders, contribute to the negative outcomes. We present an evidence-based overview of determinants, spanning genetic, molecular, and large-scale networks, involved in the response to ChEI in patients with AD and other neurodegenerative diseases. A comprehensive understanding of cerebral and retinal cholinergic system dysfunctions along with ChEI response predictors in AD is crucial since disease-modifying therapies will frequently be prescribed in combination with ChEI. Therapeutic algorithms tailored to genetic, biological, clinical (endo)phenotypes, and disease stages will help leverage inter-drug synergy and attain optimal combined response outcomes, in line with the precision medicine model.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson’s Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Natural Products from Plants and Algae for Treatment of Alzheimer’s Disease: A Review

Neurodegenerative disorders including Parkinson’s disease (PD), Huntington’s disease (HD) and the most frequent, Alzheimer’s disease (AD), represent one of the most urgent medical needs worldwide. Despite a significantly developed understanding of disease development and pathology, treatments that stop AD progression are not yet available. The recent approval of sodium oligomannate (GV-971) for AD treatment in China emphasized the potential value of natural products for the treatment of neurodegenerative disorders. Many current clinical studies include the administration of a natural compound as a single and combination treatment. The most prominent mechanisms of action are anti-inflammatory and anti-oxidative activities, thus preserving cellular survival. Here, we review current natural products that are either approved or are in testing for a treatment of neurodegeneration in AD. In addition to the most important compounds of plant origin, we also put special emphasis on compounds from algae, given their neuroprotective activity and their underlying mechanisms of neuroprotection.

Decreased integrity of the monoaminergic tract is associated with a positive response to MPH in patients with vascular cognitive impairment - proof of principle study STREAM-VCI

Background

Patients with vascular cognitive impairment (VCI) are very heterogeneous in both symptoms and type of cerebrovascular pathology. This might be an important reason why there is no symptomatic treatment available for VCI patients. In this study, we investigated in patients with VCI, whether there was an association between a positive response to methylphenidate and galantamine and the type of cerebrovascular disease, structural damage to specific neurotransmitter systems, cerebral perfusion, and presence of co-morbid Alzheimer (AD) pathology.

Methods

We included 27 VCI patients (mean age 67 years ± 8,30% female) from the STREAM-VCI trial who received placebo, methylphenidate(10 mg), and galantamine(16 mg) in a single challenge, cross-over design. In this study, we classified patients improving on a task for executive functioning after methylphenidate compared to placebo as methylphenidate responders (MPH+; resp. non-responders, MPH-) and patients improving on a task for memory after galantamine compared to placebo as galantamine responders (GAL+; resp. non-responders, GAL-). On baseline MRI, we visually assessed measures of cerebrovascular disease, automatically segmented white matter hyperintensities, used diffusion tensor imaging to visualize the integrity of monoaminergic and cholinergic neurotransmitter systems with mean diffusivity (MD) and fractional anisotropy (FA). Comorbid AD pathology was assessed using CSF or amyloid-PET. We tested differences between responders and non-responders using ANOVA, adjusting for age and sex.

Results

Nine patients were MPH+ vs 18 MPH-. MPH+ had higher MD (1.22 ± 0.07 vs 0.94 ± 0.05); p = .001) and lower FA (0.38 ± .01 vs 0.43 ± .01); p = .04) in the monoaminergic tract compared to MPH-. Eight patients were GAL+ and 18 GAL-. We found no differences between GAL+ and GAL- in any of the MRI measures. Information on co-morbid AD pathology was present in 17 patients. AD pathology tended to be more frequent in GAL+ vs GAL- (5(71%) vs 2(20%); p = .06).

Conclusions

In patients with VCI, we found that decreased integrity of the monoaminergic tract is associated with a positive response to MPH. Responsiveness to galantamine may be related to co-morbid AD pathology.

Sub-acute oral toxicity study of aqueous extract of tobacco leaves (Nicotiana tabacum L.) on lipid profile, the tissue, and serum of the liver and kidney of male Wistar rats

CONTEXT

Tobacco consumption may pose a very serious threat to the physiological state of the body; yet, fewer records have been documented in that regard.

OBJECTIVE

We investigated the impact of aqueous extract of tobacco leaves on the lipid profile, the tissue, and serum levels of the liver and kidney of male Wister rats.

MATERIALS AND METHODS

Rats (n = 52; weight = 33 - 47 g; ∼ 2½ weeks old) were acclimatised for 7 days and administered aqueous extract of tobacco leaves at 100, 200, 400, 0 mg/kg of body weight (to group A, B, C, D) for 30 days.

RESULTS

Compared with the control group, the kidney tissue and serum (i.e., urea and creatinine) were not influenced, in contrast, indices of the liver such as AST, ALT, and ALP, dose-dependently increased. Changes such as coagulative necrosis resulted in the infiltration of mononuclear inflammatory cells and the vacuolar degeneration of the liver. Beside the reduction in the high-density lipoprotein of the rats, there was an increase in the concentration of triglycerides, very low-density lipoprotein, low-density lipoprotein, and the total cholesterol.

CONCLUSION

Thus, extract of tobacco leaves can greatly influence the body lipid profile, beside the serum and tissues of the liver.

Potential Astrocytic Receptors and Transporters in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by the progressive loss of memory and cognition in the aging population. However, the etiology of and therapies for AD remain far from understood. Astrocytes, the most abundant neuroglia in the brain, have recently aroused substantial concern due to their involvement in synaptotoxicity, amyloidosis, neuroinflammation, and oxidative stress. In this review, we summarize the candidate molecules of astrocytes, especially receptors and transporters, that may be involved in AD pathogenesis. These molecules include excitatory amino acid transporters (EAATs), metabotropic glutamate receptor 5 (mGluR5), the adenosine 2A receptor (A2AR), the α7-nicotinic acetylcholine receptor (α7-nAChR), the calcium-sensing receptor (CaSR), S100β, and cannabinoid receptors. We describe the characteristics of these molecules and the neurological and pharmacological underpinnings of these molecules in AD. Among these molecules, EAATs, A2AR, and mGluR5 are strongly related to glutamate-mediated synaptotoxicity and are involved in glutamate transmission or the clearance of extrasynaptic glutamate in the AD brain. The α7-nAChR, CaSR, and mGluR5 are receptors of Aβ and can induce a plethora of toxic effects, such as the production of excess Aβ, synaptotoxicity, and NO production triggered by changes in intracellular calcium signaling. Antagonists or positive allosteric modulators of these receptors can repair cognitive ability and modify neurobiological changes. Moreover, blocking S100β or activating cannabinoid receptors reduces neuroinflammation, oxidative stress, and reactive astrogliosis. Thus, targeting these molecules might provide alternative approaches for treating AD.

Functional characterization of multifunctional ligands targeting acetylcholinesterase and alpha 7 nicotinic acetylcholine receptor

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cholinergic dysfunction, provoking memory loss and cognitive dysfunction in elderly patients. The cholinergic hypothesis provided over the years with molecular targets for developing palliative treatments for AD, acting on the cholinergic system, namely, acetylcholinesterase and α7 nicotinic acetylcholine receptor (α7 nAChR). In our synthetic work, we used "click-chemistry" to synthesize two Multi Target Directed Ligands (MTDLs) MB105 and MB118 carrying tacrine and quinuclidine scaffolds which are known for their anticholinesterase and α7 nAChR agonist activities, respectively. Both, MB105 and MB118, inhibit human acetylcholinesterase and human butyrylcholinesterase in the nanomolar range. Electrophysiological recordings on Xenopus laevis oocytes expressing human α7 nAChR showed that MB105 and MB118 acted as partial agonists of the referred nicotinic receptor, albeit, with different potencies despite their similar structure. The different substitution at C-3 on the 2,3-disubstituted quinuclidine scaffold may account for the significantly lower potency of MB118 compared to MB105. Electrophysiological recordings also showed that the tacrine precursor MB320 behaved as a competitive antagonist of human α7 nAChR, in the micromolar range, while the quinuclidine synthetic precursor MB099 acted as a partial agonist. Taken all together, MB105 behaved as a partial agonist of α7 nAChR at concentrations where it completely inhibited human acetylcholinesterase activity paving the way for the design of novel MTDLs for palliative treatment of AD.

An update on the utility and safety of cholinesterase inhibitors for the treatment of Alzheimer's disease

Introduction: Alzheimer's disease (AD) is the most common cause of major neurocognitive disorders with a prevalence in the US of about 5.7 million in 2018. With the disease burden projected to increase dramatically in the coming years, it is imperative to review the current available treatment regimens for their safety and utility. The cholinesterase inhibitors (ChEIs) have continued to play a pivotal role in managing the symptoms and possibly slowing the rate of progression of AD since 1993. Owing to their being a mainstay in the treatment of AD, the safety and efficacy of prescribing these drugs needs to be reviewed often, especially with the approval of new formulations and doses.Areas covered: The three ChEIs currently approved by the FDA are donepezil, rivastigmine and galantamine. This article will review the safety and tolerability of these ChEIs and analyze the potential disease modifying properties of these drugs. The authors have reviewed all recent literature including review articles, meta-analyzes, clinical trials and more.Expert opinion: These ChEIs differ subtly in their mechanisms of action, in their tolerability and safety and FDA-approved indications. All are considered first-line, symptomatic treatments of the various phases of AD and may even have potentially disease-modifying effects.

Methylphenidate and galantamine in patients with vascular cognitive impairment-the proof-of-principle study STREAM-VCI

BACKGROUND

To date, no symptomatic treatment is available for patients with vascular cognitive impairment (VCI). In the proof-of-principle study Symptomatic Treatment of Vascular Cognitive Impairment (STREAM-VCI), we investigated whether a single dose of a monoaminergic drug (methylphenidate) improves executive functioning and whether a single dose of a cholinergic drug (galantamine) improves memory in VCI patients.

METHODS

STREAM-VCI is a single-center, double-blind, three-way crossover trial. We included 30 VCI patients (Mini-Mental State Examination (MMSE) ≥ 16 and Clinical Dementia Rating score 0.5-1.0) with cerebrovascular pathology on MRI. All patients received single doses of methylphenidate (10 mg), galantamine (16 mg), and placebo in random order on three separate study visits. We used the NeuroCart®, a computerized test battery, to assess drug-sensitive cognitive effects. Predefined main outcomes, measured directly after a single dose of a study drug, were (i) change in performance on the adaptive tracker for executive functioning and (ii) performance on the Visual Verbal Learning Test-15 (VVLT-15) for memory, compared to placebo. We performed mixed model analysis of variance.

RESULTS

The study population had a mean age of 67 ± 8 years and MMSE 26 ± 3, and 9 (30%) were female. Methylphenidate improved performance on the adaptive tracker more than placebo (mean difference 1.40%; 95% confidence interval [CI] 0.56-2.25; p = 0.002). In addition, methylphenidate led to better memory performance on the VVLT-15 compared to placebo (mean difference in recalled words 0.59; 95% CI 0.03-1.15; p = 0.04). Galantamine did not improve performance on the adaptive tracker and led to worse performance on delayed recall of the VVLT-15 (mean difference - 0.84; 95% CI - 1.65, - 0.03; p = 0.04). Methylphenidate was well tolerated while galantamine produced gastrointestinal side effects in a considerable number of patients.

CONCLUSIONS

In this proof-of-principle study, methylphenidate is well tolerated and improves executive functioning and immediate recall in patients with VCI. Galantamine did not improve memory or executive dysfunction. Results might be influenced by the considerable amount of side effects seen.

TRIAL REGISTRATION

http://www.clinicaltrials.gov. Registration number: NCT02098824. Registration date: March 28, 2014.

Symptomatic Treatment of Vascular Cognitive Impairment (STREAM-VCI): Protocol for a Cross-Over Trial

Background

People with vascular cognitive impairment (VCI) constitute a clinically heterogeneous group, but previous symptomatic drug trials in VCI did not take this clinical heterogeneity into account. Executive dysfunction and memory impairment are the cognitive domains that are most frequently impaired in VCI, and these impairments are likely to reflect vascular damage to specific neurotransmitter systems, which opens the possibility for targeted symptomatic treatment directed at specific neurotransmitters.

Objective

Here we describe the design of the “Symptomatic Treatment of Vascular Cognitive Impairment” (STREAM-VCI) trial. In this proof-of-concept study, we investigate whether people with VCI with executive dysfunction due to vascular damage to the monoaminergic neurotransmitter system differentially respond to a monoaminergic challenge, whereas people with VCI with memory dysfunction associated with vascular damage to the cholinergic system will in turn respond to a cholinergic challenge.

Methods

The STREAM-VCI is a single center, double blind, three-way cross-over trial among 30 people with VCI, in which subjects received a single dose of galantamine, methylphenidate, or placebo on separate occasions. The most important inclusion criteria were a diagnosis of VCI with a Mini-Mental State Examination score of ≥16 and a Clinical Dementia Rating of 0.5-1.0. For each person, the challenges consisted of a single 16 mg dose of galantamine, 10 mg of methylphenidate, and placebo, in random order on three separate visits. Change in performance in executive functioning and memory was assessed directly after the challenge using standardized neuropsychological tests. We will correlate a positive response to the cholinergic and monoaminergic treatment with differences in structural and functional connectivity at baseline using structural magnetic resonance imaging (MRI), diffusion tension MRI, and resting-state functional MRI.

Results

The protocol of this study is approved by the Medical Ethics Committee of VU University Medical Center and the competent authority. The first participant was enrolled in April 2014. In September 2017, enrolment for the study was completed. We expect to publish the results in 2018.

Conclusions

STREAM-VCI is the first study to investigate the association of a response to a cholinergic and monoaminergic treatment with structural and functional connectivity of the monoaminergic and/or cholinergic systems on MRI. We aim to predict on an individual basis which individuals show a positive response to a cholinergic and/or monoaminergic challenge in people with VCI. This may be instrumental in moving in the direction of individually-tailored pharmacological interventions based on MRI measures in people with VCI.

Trial Registration

ClinicalTrials.gov NCT02098824; https://clinicaltrials.gov/ct2/show/NCT02098824 (Archived by WebCite at http://www.webcitation.org/6xhO7Ya1q)

Ethnopharmacological Approaches for Dementia Therapy and Significance of Natural Products and Herbal Drugs

Dementia is a clinical syndrome wherein gradual decline of mental and cognitive capabilities of an afflicted person takes place. Dementia is associated with various risk factors and conditions such as insufficient cerebral blood supply, toxin exposure, mitochondrial dysfunction, oxidative damage, and often coexisting with some neurodegenerative disorders such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD). Although there are well-established (semi-)synthetic drugs currently used for the management of AD and AD-associated dementia, most of them have several adverse effects. Thus, traditional medicine provides various plant-derived lead molecules that may be useful for further medical research. Herein we review the worldwide use of ethnomedicinal plants in dementia treatment. We have explored a number of recognized databases by using keywords and phrases such as “dementia”, “Alzheimer's,” “traditional medicine,” “ethnopharmacology,” “ethnobotany,” “herbs,” “medicinal plants” or other relevant terms, and summarized 90 medicinal plants that are traditionally used to treat dementia. Moreover, we highlight five medicinal plants or plant genera of prime importance and discuss the physiological effects, as well as the mechanism of action of their major bioactive compounds. Furthermore, the link between mitochondrial dysfunction and dementia is also discussed. We conclude that several drugs of plant origin may serve as promising therapeutics for the treatment of dementia, however, pivotal evidence for their therapeutic efficacy in advanced clinical studies is still lacking.

Efficacy of Galantamine on Cognition in Mild-to-Moderate Alzheimer's Dementia after Failure to Respond to Donepezil

OBJECTIVE

This study compares the efficacy of the cholinesterase inhibitor (ChEI) galantamine on cognition in patients with mild-to-moderate Alzheimer's dementia (AD) who were either naïve to ChEI drugs or who had failed a trial of the ChEI donepezil.

METHODS

Outpatients with AD were sequentially referred for screening and enrollment. Current outpatients who had taken donepezil for at least 6 months without demonstrated efficacy on cognition were switched to galantamine (switched group). New outpatients with no ChEI prescription history were classified as the naïve group and were given galantamine. The primary outcome measures for the between-group comparison were response rate on cognition at 26 and 52 weeks (categorical) and change on the Korean version of the Alzheimer's Disease Assessment Scale-cognitive subscale (dimensional). Secondary cognitive outcomes were measured using the subset of frontal executive function and the Korean Mini-Mental State Examination.

RESULTS

Seventy outpatients were enrolled and 66 were analyzed by Intent-to-treat (ITT). There were 42 cases in the naïve group and 24 in the switched group. Response rates did not differ at 26 weeks (71.4% naïve vs. 58.3% switched; p=0.277) or at 52 weeks (59.5% naïve vs. 41.6% switched; p=0.162). No significant differences were observed in the pattern of change over the 52 weeks on the primary and secondary cognitive scales.

CONCLUSION

As the efficacy of galantamine on cognition was not inferior in the switched group compared to that in the naïve group, switching ChEI drugs is clinically feasible for non-responding patients with mild-to-moderate AD.

Positive allosteric modulation of alpha-7 nicotinic receptors promotes cell death by inducing Ca(2+) release from the endoplasmic reticulum

Positive allosteric modulation of α7 isoform of nicotinic acetylcholine receptors (α7-nAChRs) is emerging as a promising therapeutic approach for central nervous system disorders such as schizophrenia or Alzheimer's disease. However, its effect on Ca(2+) signaling and cell viability remains controversial. This study focuses on how the type II positive allosteric modulator (PAM II) PNU120596 affects intracellular Ca(2+) signaling and cell viability. We used human SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH). We monitored cytoplasmic and endoplasmic reticulum (ER) Ca(2+) with Fura-2 and the genetically encoded cameleon targeting the ER, respectively. Nicotinic inward currents were measured using patch-clamp techniques. Viability was assessed using methylthiazolyl blue tetrazolium bromide or propidium iodide staining. We observed that in the presence of a nicotinic agonist, PNU120596 (i) reduced viability of α7-SH but not of C-SH cells; (ii) significantly increased inward nicotinic currents and cytosolic Ca(2+) concentration; (iii) released Ca(2+) from the ER by a Ca(2+) -induced Ca(2+) release mechanism only in α7-SH cells; (iv) was cytotoxic in rat organotypic hippocampal slice cultures; and, lastly, all these effects were prevented by selective blockade of α7-nAChRs, ryanodine receptors, or IP3 receptors. In conclusion, positive allosteric modulation of α7-nAChRs with the PAM II PNU120596 can lead to dysregulation of ER Ca(2+) , overloading of intracellular Ca(2+) , and neuronal cell death. This study focuses on how the type II positive allosteric modulator PNU120596 (PAM II PNU12) affects intracellular Ca(2+) signaling and cell viability. Using SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH), we find that PAM of α7-nAChRs with PNU120596: (i) increases inward calcium current (ICa ) and cytosolic Ca(2+) concentration ([Ca(2+) ]cyt ); (ii) releases Ca(2+) from the ER ([Ca(2+) ]ER ) by a Ca(2+) -induced Ca(2+) release mechanism; and (iv) reduces cell viability. These findings were corroborated in rat hippocampal organotypic cultures. [Ca(2+) ]cyt , cytosolic Ca(2+) concentration; [Ca(2+) ]ER , endoplasmic reticulum Ca(2+) concentration; α7 nAChR, α7 isoform of nicotinic acetylcholine receptors; α7-SH, SH-SY5Y stably overexpressing α7 nAChRs cells; C-SH, control SH-SY5Y cells; Nic, nicotine; PNU12, PNU120596.

Synaptic connectivity in engineered neuronal networks

We have developed a method to organize cells in dissociated cultures using engineered chemical clues on a culture surface and determined their connectivity patterns. Although almost all elements of the synaptic transmission machinery can be studied separately in single cell models in dissociated cultures, the complex physiological interactions between these elements are usually lost. Thus, factors affecting synaptic transmission are generally studied in organotypic cultures, brain slices, or in vivo where the cellular architecture generally remains intact. However, by utilizing engineered neuronal networks complex phenomenon such as synaptic transmission or synaptic plasticity can be studied in a simple, functional, cell culture-based system. We have utilized self-assembled monolayers and photolithography to create the surface templates. Embryonic hippocampal cells, plated on the resultant patterns in serum-free medium, followed the surface clues and formed the engineered neuronal networks. Basic whole-cell patch-clamp electrophysiology was applied to characterize the synaptic connectivity in these engineered two-cell networks. The same technology has been used to pattern other cell types such as cardiomyocytes or skeletal muscle fibers.

The warrior in the machine: neuroscience goes to war

Ever since Stone Age men discovered that knapping flint produced sharp stone edges that could be used in combat as well as for cooking and hunting, technological advances of all kinds have been adapted and adopted by the military.The opportunities provided by modern neuroscience are proving no exception, but their application in a military context is accompanied by complex practical and ethical considerations.

Hyperglycemia induces memory impairment linked to increased acetylcholinesterase activity in zebrafish (Danio rerio)

Diabetes mellitus, which causes hyperglycemia, affects the central nervous system and can impairs cognitive functions, such as memory. The aim of this study was to investigate the effects of hyperglycemia on memory as well as on the activity of acethylcholinesterase. Hyperglycemia was induced in adult zebrafish by immersion in glucose 111mM by 14 days. The animals were divided in 4 groups: control, glucose-treated, glucose-washout 7-days and glucose-washout 14-days. We evaluated the performance in inhibitory avoidance task and locomotor activity. We also determined acethylcholinesterase activity and gene expression from whole brain. In order to counteract the effect of hyperglycemia underlined by effects on acethylcholinesterase activity, we treated the animals with galantamine (0.05ng/g), an inhibitor of this enzyme. Also we evaluated the gene expression of insulin receptor and glucose transporter from zebrafish brain. The hyperglycemia promoted memory deficit in adult zebrafish, which can be explained by increased AChE activity. The ache mRNA levels from zebrafish brain were decrease in 111mM glucose group and returned to normal levels after 7 days of glucose withdrawal. Insulin receptors (insra-1, insra-2, insrb-1 and insrb-2) and glut-3 mRNA levels were not significantly changed. Our results also demonstrated that galantamine was able to reverse the memory deficit caused by hyperglycemia, demonstrating that these effects involve modulation of AChE activity. These data suggest that the memory impairment induced by hyperglycemia is underlined by the cholinergic dysfunction caused by the mechanisms involving the control of acetylcholinesterase function and gene expression.

CHRNA7 polymorphisms and response to cholinesterase inhibitors in Alzheimer's disease

Background

CHRNA7 encodes the α7 nicotinic acetylcholine receptor subunit, which is important to Alzheimer's disease (AD) pathogenesis and cholinergic neurotransmission. Previously, CHRNA7 polymorphisms have not been related to cholinesterase inhibitors (ChEI) response.

Methods

Mild to moderate AD patients received ChEIs were recruited from the neurology clinics of three teaching hospitals from 2007 to 2010 (n = 204). Nine haplotype-tagging single nucleotide polymorphisms of CHRNA7 were genotyped. Cognitive responders were those showing improvement in the Mini-Mental State Examination score ≧2 between baseline and 6 months after ChEI treatment.

Results

AD women carrying rs8024987 variants [GG+GC vs. CC: adjusted odds ratio (AOR) = 3.62, 95% confidence interval (CI) = 1.47–8.89] and GG haplotype in block1 (AOR = 3.34, 95% CI = 1.38–8.06) had significantly better response to ChEIs (false discovery rate <0.05). These variant carriers using galantamine were 11 times more likely to be responders than female non-carriers using donepezil or rivastigmine.

Conclusion

For the first time, this study found a significant association between CHRNA7 polymorphisms and better ChEI response. If confirmed by further studies, CHRNA7 polymorphisms may aid in predicting ChEI response and refining treatment choice.

The vagus nerve and the inflammatory reflex--linking immunity and metabolism

The vagus nerve has an important role in regulation of metabolic homeostasis, and efferent vagus nerve-mediated cholinergic signalling controls immune function and proinflammatory responses via the inflammatory reflex. Dysregulation of metabolism and immune function in obesity are associated with chronic inflammation, a critical step in the pathogenesis of insulin resistance and type 2 diabetes mellitus. Cholinergic mechanisms within the inflammatory reflex have, in the past 2 years, been implicated in attenuating obesity-related inflammation and metabolic complications. This knowledge has led to the exploration of novel therapeutic approaches in the treatment of obesity-related disorders.

Effects of α7 positive allosteric modulators in murine inflammatory and chronic neuropathic pain models

Agonists and positive allosteric modulators (PAMs) of α7 nicotinic acetylcholine receptors (nAChRs) are currently being considered as novel therapeutic approaches for managing cognitive deficits in schizophrenia and Alzheimer's disease. Though α7 agonists were recently found to possess antinociceptive and anti-inflammatory properties in rodent models of chronic neuropathic pain and inflammation, the effects of α7 nAChRs PAMs on chronic pain and inflammation remain largely unknown. The present study investigated whether PAMs, by increasing endogenous cholinergic tone, potentiate α7 nAChRs function to attenuate inflammatory and chronic neuropathic pain in mice. We tested two types of PAMS, type I (NS1738) and type II (PNU-120596) in carrageenan-induced inflammatory pain and chronic constriction injury (CCI) neuropathic pain models. We found that both NS1738 and PNU-120596 significantly reduced thermal hyperalgesia, while only PNU-120596 significantly reduced edema caused by a hind paw infusion of carrageenan. Importantly, PNU-120596 reversed established thermal hyperalgesia and edema induced by carrageenan. In the CCI model, PNU-120596 had long-lasting (up to 6 h), dose-dependent anti-hyperalgesic and anti-allodynic effects after a single injection, while NS1738 was inactive. Systemic administration of the α7 nAChR antagonist MLA reversed PNU-120596's effects, suggesting the involvement of central and peripheral α7 nAChRs. Furthermore, PNU-120596 enhanced an ineffective dose of selective agonist PHA-543613 to produce anti-allodynic effects in the CCI model. Our results indicate that the type II α7 nAChRs PAM PNU-120596, but not the type I α7 nAChRs PAM NS1738, shows significant anti-edematous and anti-allodynic effects in inflammatory and CCI pain models in mice.

Galantamine alleviates inflammation and other obesity-associated complications in high-fat diet-fed mice

Obesity, a serious and growing health threat, is associated with low-grade inflammation that plays a role in mediating its adverse consequences. Previously, we have discovered a role for neural cholinergic signaling in controlling inflammation, and demonstrated that the cholinergic agent galantamine suppresses excessive proinflammatory cytokine release. The main objective of this study was to examine the efficacy of galantamine, a clinically-approved drug, in alleviating obesity-related inflammation and associated complications. After 8 wks on a high-fat diet, C57BL/6J mice were treated with either galantamine (4 mg/kg, intraperitoneally [i.p.]) or saline for 4 wks in parallel with mice on a low-fat diet and treated with saline. Galantamine treatment of obese mice significantly reduced body weight, food intake, abdominal adiposity, plasma cytokine and adipokine levels, and significantly improved blood glucose, insulin resistance and hepatic steatosis. In addition, galantamine alleviated impaired insulin sensitivity and glucose intolerance significantly. These results indicate a previously unrecognized potential of galantamine in alleviating obesity, inflammation and other obesity-related complications in mice. These findings are of interest for studying the efficacy of this clinically-approved drug in the context of human obesity and metabolic syndrome.

Galantamine: an update

SUMMARY Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that impairs cognitive function. Currently, the main purpose of pharmacological treatment is to slow down the progression by relieving its symptoms. Galantamine is one of the three cholinesterase inhibitors that are commonly used, either alone or in conjunction with memantine, to treat AD. Four fixed-dose pivotal trials with the immediate-release form and one with the extended-release form established its effectiveness in treating mild-to-moderate AD, without causing excessive adverse events. Both forms possess similar efficacy, but the extended-release form has better compliance.

Synergistic neuroprotective effect of combined low concentrations of galantamine and melatonin against oxidative stress in SH-SY5Y neuroblastoma cells

Melatonin is a potent free radical scavenger, antioxidant and neuroprotective drug. On the other hand, galantamine is a cholinergic drug with antioxidant and neuroprotective properties linked to inhibition of acetylcholinesterase and allosteric modulation of nicotinic receptors. This investigation evaluated a possible synergistic neuroprotective effect of subeffective concentrations of combined galantamine and melatonin. Human neuroblastoma SH-SY5Y cells were subjected to a mitochondrial oxidative stress, by blockade of mitochondrial complexes I and V with rotenone and oligomycin-A (R/O); cells were treated for 24 hr with R/O. This caused 40% of the cell to die as measured by lactate dehydrogenase (LDH) release. Cell incubation with increasing concentrations of galantamine (10-300 nm) or melatonin (0.3-10 nm) for 24 hr, followed by a 24-hr period with R/O, caused a concentration-dependent protection; maximum protection was achieved with 300 nm galantamine (56% protection) and 10 nm melatonin (50% protection). Combination of subeffective concentrations of melatonin (0.3 nm) and galantamine (30 nm) caused a synergistic and significant protection that was similar to the maximum protection afforded by effective concentrations of melatonin or galantamine alone. This protective effect was completely reversed when nicotinic and melatonin receptors were blocked respectively by mecamylamine and luzindole. The neuroprotective effect was prevented by chelerythrine, LY294002, and Sn (IV) protoporphyrin IX dichloride (SnPP), indicating the participation of the PKC/PI3K/Akt activation and induction of the antioxidant enzyme heme oxygenase-1. The synthesis of novel multitarget compounds having in a single molecule the combined neuroprotective properties of galantamine and melatonin could be a new strategy for potential therapeutic agents in neurodegenerative diseases.

Emerging cognitive enhancing drugs

BACKGROUND

Advances in health sciences during the last century have increased the average age in industrialized nations. Despite this progress, neurodegenerative diseases that affect higher order thinking and memory continue to increase in prevalence as they take a devastating toll on human productivity in the later years. There is an acute need for new drugs and therapeutic approaches for treating these severe diseases, and also for improving the quality of cognitive function associated with normal aging and in many other disorders and syndromes that present with cognitive dysfunction.

OBJECTIVE

The purpose of this review is to ascertain the pharmacological approaches being exploited to improve cognition and memory and to determine the most relevant and effective directions taken for new drug discovery. Limitations and difficulties encountered in this effort also are discussed.

METHODS

This review focuses primarily on compounds already undergoing clinical trials for improving cognition and memory with some discussion of rising new drug targets.

RESULTS/CONCLUSION

Compounds that act on allosteric sites on neurotransmitter receptors are expected to lead the field with new levels of specificity and reduced side effects. New multi-functional compounds can be designed that can both improve cognition and slow the process of disease.

Structural model for the binding sites of allosterically potentiating ligands on nicotinic acetylcholine receptors

Current treatments of Alzheimer's disease include the allosteric potentiation of nicotinic acetylcholine receptor (nAChR) response. The location of the binding site for allosteric potentiating ligands (APLs) within the receptor is not yet fully understood. Based on homology models for the ligand binding domain of human alpha7, human alpha4beta2, and chicken alpha7 receptors, as well as blind docking experiments with galanthamine, physostigmine, codeine, and 5HT, we identified T197 as an essential element of the APL binding site at the outer surface of the ligand binding domain (LBD) of nAChR. We also found the previously known galanthamine binding site in the region of K123 at the inside of the receptor funnel, which, however, was shown to not be part of the APL site. Our results are verified by site-directed mutagenesis and electrophysiological experiments, and suggest that APL and ACh bind to different sites on nicotinic receptors and that allosteric potentiation may arise from a direct interplay between both these sites.

The nicotinic receptor of cochlear hair cells: a possible pharmacotherapeutic target?

Mechanosensory hair cells of the organ of Corti transmit information regarding sound to the central nervous system by way of peripheral afferent neurons. In return, the central nervous system provides feedback and modulates the afferent stream of information through efferent neurons. The medial olivocochlear efferent system makes direct synaptic contacts with outer hair cells and inhibits amplification brought about by the active mechanical process inherent to these cells. This feedback system offers the potential to improve the detection of signals in background noise, to selectively attend to particular signals, and to protect the periphery from damage caused by overly loud sounds. Acetylcholine released at the synapse between efferent terminals and outer hair cells activates a peculiar nicotinic cholinergic receptor subtype, the alpha9alpha10 receptor. At present no pharmacotherapeutic approaches have been designed that target this cholinergic receptor to treat pathologies of the auditory system. The potential use of alpha9alpha10 selective drugs in conditions such as noise-induced hearing loss, tinnitus and auditory processing disorders is discussed.

Desensitization of nicotinic acetylcholine receptors as a strategy for drug development

The specific pharmacological response evoked by a nicotinic acetylcholine receptor (nAChR) agonist is governed by the anatomical distribution and expression of each receptor subtype and by the stoichiometry of subunits comprising each subtype. Contributing to this complexity is the ability of agonists that bind to the orthosteric site of the receptor to alter the affinity state of the receptor and induce desensitization and the observation that, at low doses, some nAChR antagonists evoke agonist-like nicotinic responses. Brain concentrations of nicotine rarely increase to the low-mid micromolar concentrations that have been reported to evoke direct agonist-like responses, such as calcium influx or neurotransmitter release. Low microgram per kilogram doses of nicotine administered to humans or to nonhuman primates to improve cognition and working memory probably result only in low nanomolar brain concentrations--more in line with the ability of nicotine to induce receptor desensitization. Here we review data illustrating that nicotine, its major metabolite cotinine, and two novel analogs of choline, JWB1-84-1 [2-(4-(pyridin-3-ylmethyl)piperazin-1-yl)ethanol] and JAY2-22-33, JWB1-84-1 [2-(methyl(pyridine-3-ylmethyl)amino)-ethanol], improve working memory in macaques. The effectiveness of these four compounds in the task was linearly related to their effectiveness in producing desensitization of the pressor response to ganglionic stimulation evoked by a nAChR agonist in rats. Only nicotine evoked an agonist-like action (increased resting blood pressure). Therefore, it is possible to develop new chemical entities that have the ability to desensitize nAChRs without an antecedent agonist action. Because these "silent desensitizers" are probably acting allosterically, an additional degree of subtype specificity could be attained.

Is long-term treatment of Alzheimer's disease with cholinesterase inhibitor therapy justified?

The cholinesterase inhibitors (ChEIs) donepezil, rivastigmine and galantamine are the current mainstays in the drug treatment of Alzheimer's disease (AD). There is convincing evidence that these agents provide at least modest cognitive, behavioural and functional benefit for 6-12 months at all stages of the disease. Longer term benefits cannot be directly examined by placebo-controlled trials. Nevertheless, the results of virtually all open-label extensions of the pivotal trials, studies of patients with AD at different levels of severity and clinical trials using other designs favour treatment over no treatment for periods of up to 5 years. There are plausible biological reasons why ChEIs might be expected to work over a prolonged period of time although, to date, studies using various markers to chart the effects of medication on long-term disease progression have yielded mixed results. The most contentious issue regarding long-term treatment is economic, but the majority of available economic analyses suggest net savings over the long term if patients with AD receive persistent treatment with ChEIs.

Cognitive deficits in schizophrenia: focus on neuronal nicotinic acetylcholine receptors and smoking

Patients with schizophrenia present with deficits in specific areas of cognition. These are quantifiable by neuropsychological testing and can be clinically observable as negative signs. Concomitantly, they self-administer nicotine in the form of cigarette smoking. Nicotine dependence is more prevalent in this patient population when compared to other psychiatric conditions or to non-mentally ill people. The target for nicotine is the neuronal nicotinic acetylcholine receptor (nAChR). There is ample evidence that these receptors are involved in normal cognitive operations within the brain. This review describes neuronal nAChR structure and function, focusing on both cholinergic agonist-induced nAChR desensitization and nAChR up-regulation. The several mechanisms proposed for the nAChR up-regulation are examined in detail. Desensitization and up-regulation of nAChRs may be relevant to the physiopathology of schizophrenia. The participation of several subtypes of neuronal nAChRs in the cognitive processing of non-mentally ill persons and schizophrenic patients is reviewed. The role of smoking is then examined as a possible cognitive remediator in this psychiatric condition. Finally, pharmacological strategies focused on neuronal nAChRs are discussed as possible therapeutic avenues that may ameliorate the cognitive deficits of schizophrenia.

Distinguishing Lewy body dementias from Alzheimer's disease

Lewy body dementia (LBD) is the second most common dementia after Alzheimer's disease (AD). LBD is characterized clinically by visual hallucinations, extrapyramidal symptoms, cognitive fluctuations and neuroleptic sensitivity. LBD and AD share many common features in pathology, genetics and biochemical alterations; however, correct clinical distinction between these disorders has prognostic and therapeutic implications. There are currently no definitive radiological or biological markers for LBD, but studies suggest that premorbid differences in cognitive domains and personality traits, differences in clinical presentation, and alterations in autonomic function and sleep may improve diagnosis. Cholinergic dysfunction plays a major role in both AD and LBD; however, dysfunction is greater in LBD. This may account for the more prominent hallucinations, and offers the possibility of a greater response to cholinesterase inhibitors in LBD. The treatment of LBD is symptomatic and is based on a limited number of clinical trials and extension of results from trials in AD. Current research is focused on the role of synuclein aggregation with possible roles for synuclein-derived peptides as aggregation inhibitors. Other approaches target amyloid, neuroinflammation, oxidative injury, proteolysis, lipid peroxidation and immunotherapies with variable results. Improved understanding of disease mechanisms may open new therapeutic avenues for LBD in the future.

Synthesis of desformylflustrabromine and its evaluation as an alpha4beta2 and alpha7 nACh receptor modulator

Desformylflustrabromine (dFBr; 1) and desformylflustrabromine-B (dFBr-B; 2) have been previously isolated from natural sources, and the former has been demonstrated to be a novel and selective positive allosteric modulator of alpha4beta2 nicotinic acetylcholine (nACh) receptors. The present study describes the synthesis of water-soluble salts of 1 and 2, and confirms and further investigates the actions of 1 and 2 using two-electrode voltage clamp recordings.

Synaptic connectivity in engineered neuronal networks

In this study, we have demonstrated a method to organize cells in dissociated cultures using engineered chemical clues on the culture surface and determined their connectivity patterns. Although almost all elements of the synaptic transmission machinery between neurons or between neurons and muscle fibers can be studied separately in single-cell models in dissociated cultures, the difficulty of clarifying the complex interactions between these elements makes random cultures not particularly suitable for specific studies. Factors affecting synaptic transmission are generally studied in organotypic cultures, brain slices, or in vivo where the cellular architecture generally remains intact. However, by utilizing engineered neuronal networks, complex phenomenon such as synaptic transmission can be studied in a simple, functional, cell culture-based system. We have utilized self-assembled monolayers (SAMs) and photolithography to create the surface templates. Embryonic hippocampal cells, plated on the resultant patterns in serum-free medium, followed the surface clues and formed the engineered neuronal networks. Basic electrophysiological methods were applied to characterize the synaptic connectivity in these engineered two-cell networks.

Development and application of acute exposure guideline levels (AEGLs) for chemical warfare nerve and sulfur mustard agents

Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrations greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios.

Physostigmine modulation of acetylcholine currents in COS cells transfected with mouse muscle nicotinic receptor

Physostigmine (Phy), a reversible inhibitor of acetylcholine (ACh) esterase (AChE), may also act as a low potency agonist and a modulator of the nicotinic receptor. The actions of Phy on mouse muscle nicotinic receptors in the COS-7 cell line were studied by the patch-clamp technique. Currents were recorded in the whole-cell mode 3-7 days after cell transfection by plasmids coding alphabetagammadelta combination of receptor subunits. The application of ACh to cells clamped at -10 mV produced inward currents which displayed desensitization. The application of Phy in concentrations up to 1 x 10(-3) M did not give reliable specific whole-cell membrane responses. The application of Phy in concentrations of 10(-6)-10(-4) M together with ACh modulated the amplitude; accelerated desensitization of currents induced by ACh and increased the final extent of desensitization in a concentration-dependent manner. This finding is in contrast to the suppression and slowing down of desensitization by Phy and 1-methyl-galanthamine observed in Torpedo receptors.

Allosteric modulation of ligand-gated ion channels

Ligand-gated ion channels (LGICs) are cell surface proteins that play an important role in fast synaptic transmission and in the modulation of cellular activity. Due to their intrinsic properties, LGICs respond to neurotransmitters and other effectors (e.g. pH) and transduce the binding of a ligand into an electrical current on a microsecond timescale. Following activation, LGICs open allowing an ion flux across the cell membrane. Depending upon the charge and concentration of ions, the flux can cause a depolarization or hyperpolarization, thus modulating excitability of the cell. While our understanding of LGICs has significantly progressed during the past decade, many properties of these proteins are still poorly understood, in particular their modulation by allosteric effectors. LGICs are often thought as a simple on-off switches. However, a closer look at these receptors reveals a complex behavior and a wide repertoire of subtle modulation by intrinsic and extrinsic factors. From a physiological point of view, this modulation can be seen as an additional level of complexity in the cell signaling process. Here we review the allosteric modulation of LGICs in light of the latest findings and discuss the suitability of this approach to the design of new therapeutic molecules.

Loss of cholinergic pathways in vascular dementia of the Binswanger type

We sought to determine the changes in the cholinergic pathways, which project from the nucleus basalis of Meynert (nBM) and travel in the subinsular region, in vascular dementia of the Binswanger type (VDBT) and Alzheimer's disease (AD). The subinsular regions were examined in 6 autopsied brains with VDBT, 5 brains with AD and 4 control brains without any neurologic diseases. The cholinergic pathway was labeled either by histochemistry for acetylcholine esterase (AChE), a degradatory enzyme of ACh, or by immunohistochemistry for choline acetyltransferase, its synthetic enzyme. The numerical density of nBM neurons did not differ significantly between these groups (163 +/- 49 in the VDBT, 105 +/- 82 in the AD and 198 +/- 76 in the control groups), but with a tendency towards a decrease in the AD group. The subinsular cholinergic fibers were impaired, with relative preservation of the nBM neurons in VDBT, whereas both the subinsular cholinergic fibers and the nBM neurons were degraded in AD. These results indicate that the cholinergic pathway is damaged not only in AD, but also in VDBT, and may further provide a pharmacological basis for treatment with AChE inhibitors in VDBT.

A novel positive allosteric modulator of the alpha7 neuronal nicotinic acetylcholine receptor: in vitro and in vivo characterization

Several lines of evidence suggest a link between the alpha7 neuronal nicotinic acetylcholine receptor (nAChR) and brain disorders including schizophrenia, Alzheimer's disease, and traumatic brain injury. The present work describes a novel molecule, 1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5-methyl-isoxazol-3-yl)-urea (PNU-120596), which acts as a powerful positive allosteric modulator of the alpha7 nAChR. Discovered in a high-throughput screen, PNU-120596 increased agonist-evoked calcium flux mediated by an engineered variant of the human alpha7 nAChR. Electrophysiology studies confirmed that PNU-120596 increased peak agonist-evoked currents mediated by wild-type receptors and also demonstrated a pronounced prolongation of the evoked response in the continued presence of agonist. In contrast, PNU-120596 produced no detectable change in currents mediated by alpha4beta2, alpha3beta4, and alpha9alpha10 nAChRs. PNU-120596 increased the channel mean open time of alpha7 nAChRs but had no effect on ion selectivity and relatively little, if any, effect on unitary conductance. When applied to acute hippocampal slices, PNU-120596 increased the frequency of ACh-evoked GABAergic postsynaptic currents measured in pyramidal neurons; this effect was suppressed by TTX, suggesting that PNU-120596 modulated the function of alpha7 nAChRs located on the somatodendritic membrane of hippocampal interneurons. Accordingly, PNU-120596 greatly enhanced the ACh-evoked inward currents in these interneurons. Systemic administration of PNU-120596 to rats improved the auditory gating deficit caused by amphetamine, a model proposed to reflect a circuit level disturbance associated with schizophrenia. Together, these results suggest that PNU-120596 represents a new class of molecule that enhances alpha7 nAChR function and thus has the potential to treat psychiatric and neurological disorders.

Treatments for schizophrenia: a critical review of pharmacology and mechanisms of action of antipsychotic drugs

The treatment of schizophrenia has evolved over the past half century primarily in the context of antipsychotic drug development. Although there has been significant progress resulting in the availability and use of numerous medications, these reflect three basic classes of medications (conventional (typical), atypical and dopamine partial agonist antipsychotics) all of which, despite working by varying mechanisms of actions, act principally on dopamine systems. Many of the second-generation (atypical and dopamine partial agonist) antipsychotics are believed to offer advantages over first-generation agents in the treatment for schizophrenia. However, the pharmacological properties that confer the different therapeutic effects of the new generation of antipsychotic drugs have remained elusive, and certain side effects can still impact patient health and quality of life. Moreover, the efficacy of antipsychotic drugs is limited prompting the clinical use of adjunctive pharmacy to augment the effects of treatment. In addition, the search for novel and nondopaminergic antipsychotic drugs has not been successful to date, though numerous development strategies continue to be pursued, guided by various pathophysiologic hypotheses. This article provides a brief review and critique of the current therapeutic armamentarium for treating schizophrenia and drug development strategies and theories of mechanisms of action of antipsychotics, and focuses on novel targets for therapeutic agents for future drug development.

Early Diagnosis and Treatment of Dementia Presenting as Transient Global Amnesia in a 76-Year-Old Man

This article reports the case of a high-functioning patient who had an "event" diagnosed as probable transient global amnesia (TGA) 1 year before being diagnosed with evolving cognitive impairment. Formal psychometric testing was necessary to make this diagnosis owing to the insensitivity of simple tests in this high-functioning individual. Neuropsychological evaluation showed impairment of short-term verbal memory, compounded by observed fluctuations in attention. In light of its reported benefits for cognitive function and attention, galantamine was administered starting at 4 mg b.i.d., then increasing to 8 mg b.i.d. and finally to 12 mg b.i.d. During galantamine dose escalation, the patient experienced transient vomiting on the first day of taking 12 mg b.i.d. With reassurance, he returned to the same dose and tolerated it during long-term treatment without problems. His cognitive function has remained at an improved level for 18 months on galantamine administration.

Pharmacotherapeutic approaches to the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), a progressive degenerative disorder of the brain, is the most common cause of cognitive impairment in the elderly. The pharmacotherapy of AD is evolving rapidly. Cholinergic stabilization with cholinesterase-inhibitor (ChEI) therapy implies neuroprotection and a resultant slowing of disability and disease progression. The moderate-affinity N-methyl-d-aspartate (NMDA)-receptor antagonist memantine may block neural excitotoxicity.

OBJECTIVE

The purpose of this review was to examine the evidence for the responsiveness to pharmacotherapy of established AD; specifically, the extent to which the benefits of therapy have been proved, the extent to which currently available ChEIs support cholinergic neurotransmission, and the extent to which currently available ChEIs and memantine provide neuroprotection.

METHODS

Relevant studies were identified through a comprehensive search of MEDLINE for articles published between January 1999 and February 2004 using the terms Alzheimer's pharmacotherapy, cholinesterase inhibitor therapy, Alzheimer's disease, donepezil, rivastigmine, galantamine, glutamatergic system modifiers, and memantine; a search of the reference lists of identified articles; and a manual search of pertinent journals. Articles were selected that contained higher-level evidence, based on explicit validated criteria.

RESULTS

ChEI therapy was associated with quality-of-life improvements that included enhanced performance of activities of daily living, reduced behavioral disturbances, stabilized cognitive impairment, decreased caregiver stress, and delay in the first dementia-related nursing home placement. In large clinical trials in moderate to severe AD (a stage that is associated with distress for patients and caregiver burden, and for which other treatments are not available), memantine showed an ability to delay cognitive and functional deterioration. The combination of memantine and ChEI therapy was significantly more efficacious than ChEI therapy alone (P < 0.001) and was well tolerated.

CONCLUSIONS

The idea that AD is pharmacologically unresponsive appears to be changing. With the use of ChEI and NMDA-receptor antagonist therapy, the symptoms and outcomes of this devastating neurodegenerative disease can be improved and its course altered.

Psychosis in Parkinson's disease

Psychosis in Parkinson's disease (PD) is a fairly common and vexing problem. Although it can occur at any stage of the illness, it is a particularly important issue for patients who are in the later stages of PD and have been chronically treated with anti-PD medications. The exact pathophysiology of PD-related psychosis remains a mystery. Neurochemical imbalances, sleep disturbances, and visual processing abnormalities in PD have been implicated in its pathogenesis. Treatment of psychotic symptoms should occur only after potential medical and environmental causes of delirium have been eliminated or addressed. Initial pharmacologic changes should include limiting the patient's anti-PD medications to those that are necessary to preserve motor function. Should that fail, an atypical antipsychotic agent is presently the treatment of choice. An emerging treatment option is the use of acetylcholinesterase inhibitors. This article reviews what is known about the epidemiology, risk factors, pathophysiology, and treatment of PD-related psychosis.

A long-term comparison of galantamine and donepezil in the treatment of Alzheimer's disease

OBJECTIVE

To compare the long-term efficacy and safety of galantamine 24 mg/day and donepezil 10 mg/day in patients with Alzheimer's disease.

PATIENTS AND STUDY DESIGN

This was a rater-blinded, randomised, parallel-group multicentre study (18 outpatient clinics) in the UK. 182 patients (69 male, 113 female) with Alzheimer's disease were randomised to galantamine (n = 94) or donepezil (n = 88) for 52 weeks.

MAIN OUTCOME MEASURES

The effects of galantamine and donepezil on function using the Bristol Activities of Daily Living Scale (BrADL); cognition using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog/11); behaviour using the Neuropsychiatric Inventory (NPI); caregiver burden using the Screen for Caregiver Burden; and safety were assessed.

RESULTS

BrADL total scores showed no significant difference between treatment groups in mean change from baseline to week 52. In the total population, in terms of cognition, galantamine patients' scores on the MMSE at week 52 did not differ significantly from baseline (-0.52 +/- 0.39, p < 0.5 vs baseline), whereas donepezil patients' scores deteriorated significantly from baseline (-1.58 +/- 0.42, p < 0.0005 vs baseline). The between-group difference in MMSE change, which showed a trend for superiority of galantamine, did not reach statistical significance (p < or = 0.1). In the ADAS-cog/11 analysis, between-group differences for the total population were not significant, whereas galantamine-treated patients with MMSE scores of 12-18 demonstrated an increase (worsening) in the ADAS-cog/11 score of 1.61 +/- 0.80 versus baseline, compared with an increase of 4.08 +/- 0.84 for patients treated with donepezil, with a significant between-group difference in favour of galantamine (p < or = 0.05). More caregivers of patients receiving galantamine reported reductions in burden compared with donepezil. Changes from baseline in NPI were similar for both treatments. Both treatments were well tolerated; most adverse events were transient and of mild-to-moderate intensity, and were consistent with the findings of previous clinical trials.

CONCLUSIONS

Significant advantages were found in the treatment response to galantamine (versus donepezil) on cognition as measured by response rates on the MMSE and ADAS-cog/11.

The nicotinic acetylcholine receptor subtypes and their function in the hippocampus and cerebral cortex

Nicotinic acetylcholine receptors (nAChRs) are widely distributed in the central nervous system and have been implicated in multiple behavioral paradigms and pathological conditions. Nicotinic therapeutic interventions require an extensive characterization of native nAChRs including mapping of their distribution and function in different brain regions. Here, we describe the roles played by different nAChRs in affecting neuronal activity in the hippocampus and cerebral cortex. At least three distinct functional nAChR subtypes (alpha 7, alpha 4 beta 2, alpha 3 beta 4) can be detected in the hippocampal region, and in many instances a single neuron type is found to be influenced by all three nAChRs. Further, it became clear that GABAergic and glutamatergic inputs to the hippocampal interneurons are modulated via different subtypes of nAChRs. In the cerebral cortex, GABAergic inhibition to the layer V pyramidal neurons is enhanced predominantly via activation of alpha 4 beta 2 nAChR and to a minor extent via activation of alpha 7 nAChR. Such diversity offers pathways by which nicotinic drugs affect brain function.

Psychoactive drugs and pilot performance: a comparison of nicotine, donepezil, and alcohol effects

The cholinergic system plays a major role in cognitive abilities that are essential to piloting an aircraft: attention, learning, and memory. In previous studies, drugs that enhance the cholinergic system through different pharmacologic mechanisms have shown beneficial effects on cognition; but dissimilar cognitive measures were used and samples were not comparable. A comparison within the same cognitive tasks, within comparable samples appears desirable. Toward this aim, we compared effect sizes (ES) of performance-enhancing doses of nicotine (a nicotinic receptor agonist) and donepezil (an acetylcholinesterase inhibitor) as found in our prior work on pilot performance. We also compared cholinergic ES to those of performance-impairing doses of alcohol. In three randomized, placebo-controlled trials, we assessed the flight performance of aircraft pilots in a Frasca 141 simulator, testing I: the acute effects of nicotine gum 2 mg; II: the effects of administration of 5 mg donepezil/day for 30 days; and III: the acute and 8 h-carryover effects of alcohol after a target peak BAC of 0.10%. We calculated the ES of nicotine, donepezil, and alcohol on a flight summary score and on four flight component scores. Compared to placebo, nicotine and donepezil significantly improved, while alcohol significantly impaired overall flight performance: ES (nicotine)=0.80; ES (donepezil)=1.02; ES (alcohol acute)=-3.66; ES (alcohol 8 h)=-0.82. Both cholinergic drugs showed the largest effects on flight tasks requiring sustained visual attention. Although the two tested cholinergic drugs have different pharmacologic mechanisms, their effects on flight performance were similar in kind and size. The beneficial effects of the cholinergic drugs on overall flight performance were large and the absolute (ie nondirectional) sizes were about one-fourth of the absolute ES of acute alcohol intoxication and roughly the same as the absolute 8 h-carryover ES of alcohol.

Cognitive decline and treatment options for patients with vascular dementia

Cognitive impairment is the primary symptom of vascular dementia (VaD). Animal and human studies indicate that, as with Alzheimer's disease (AD), deficits in cholinergic transmission -- including nicotinic receptor binding abnormalities -- may be responsible for the development of cognitive impairment associated with VaD. Therefore, studies of acetylcholinesterase inhibitors (AChEIs) have been initiated and have shown promising results to date. These agents have demonstrated cognitive and global benefits in patients with VaD. Additionally, functional and behavioral benefits have been reported with the dual-mechanism AChEI galantamine. These studies suggest a potential role for AChEIs in the management of cognitive impairment associated with VaD.

The rationale behind cholinergic drug treatment for dementia related to cerebrovascular disease

Common to all subtypes of dementia, including Alzheimer's disease (AD), and those associated cerebrovascular disease (CVD), Lewy body pathology and Parkinson's disease, is degeneration of cholinergic neurotransmission. The cholinergic hypothesis of AD is based on evidence of reduced cholinergic markers and decreased numbers of cholinergic neurons and nicotinic acetylcholine receptors (nAChR) in the hippocampus and cortex of the brain-both areas associated with memory, learning and executive function impairments characteristic of cognitive decline in AD. There is growing evidence for the involvement of the cholinergic system in vascular dementia (VaD). Attention has, therefore, recently turned to the use of cholinergic treatments such as galantamine (Reminyl), which has demonstrated broad-spectrum and long-term efficacy in AD, for the treatment of patients with VaD or AD with CVD. Galantamine is both a moderate, reversible, competitive acetylcholinesterase inhibitor, and an allosteric modulator of nAChR. Recent evidence suggests that the unmatched efficacy of galantamine in cognitive as well as behavioral and functional symptoms in patients with AD, as well as those with VaD or AD with CVD, may at least partly result from its unique dual cholinergic mode of action. Here, the rationale for using galantamine to treat dementia related to CVD is discussed. In particular, some interesting findings are covered which indicate the potential of galantamine to modulate other neurotransmitter systems (e.g. serotonergic, dopaminergic), which may be of specific relevance in the behavioral symptoms of dementia related to CVD.

Galantamine--a novel cholinergic drug with a unique dual mode of action for the treatment of patients with Alzheimer's disease

Galantamine hydrobromide is a tertiary alkaloid drug that has been developed and approved in a number of countries including the USA and several countries in Europe as a treatment for mild-to-moderate Alzheimer's disease (AD). Galantamine has a unique, dual mode of action. It is a reversible, competitive inhibitor of acetylcholinesterase (AChE), and is the only drug actively marketed for the treatment of AD with proven activity as an allosteric modulator of nicotinic acetylcholine receptors (nAChRs). This latter activity is thought to be particularly important since decreases in the expression and activity of nAChRs make a large contribution to the reduction in central cholinergic neurotransmission in patients with AD. Galantamine exhibits favorable pharmacokinetic characteristics including predictable linear elimination kinetics at the recommended maintenance doses (16 and 24 mg/day), a relatively short half-life (approximately 7 h) and high bioavailability. It is extensively metabolized in numerous pathways, mainly in the liver via cytochrome P450 enzymes CYP2D6 and CYP3A4, and has a low potential for clinically significant drug-drug interactions. During four large randomized, double-blind, placebo-controlled trials of up to 6 months duration, galantamine 16 and 24 mg/day significantly benefited cognitive and global function, ability to perform activities of daily living (ADL) and behavior, relative to placebo and baseline, for up to 6 months. Caregiver burden (time spent by caregivers supervising patients or assisting them with ADL), and caregiver distress (related to patients' behavioral symptoms) were also reduced. Cognitive and functional abilities were preserved at or near baseline for at least 12 months in patients who received galantamine 24 mg/day for 12 months in a long-term US study. These benefits were maximized by early and continued galantamine treatment and, again, were associated with significant reductions in caregiver burden. Trials of the efficacy of galantamine in dementia related to cerebrovascular disease have also yielded positive results. There are no safety concerns associated with the use of galantamine. The incidence of adverse events, particularly cholinergically mediated events affecting the gastrointestinal system, is generally low and can be minimized using the recommended slow dose-escalation scheme. Galantamine may, therefore, help to reduce the overall burden and cost involved in caring for dementia patients. Taking all evidence into account, galantamine has the potential to become a first-line therapy for dementia.