The State of The Art on Acetylcholinesterase Inhibitors in the Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic disabling disease that affects the central nervous system. The main consequences of AD include the decline of cognitive functions and language disorders. One of the causes leading to AD is the decrease of neurotransmitter acetylcholine (ACh) levels in the brain, in part due to a higher activity of acetylcholinesterase (AChE), the enzyme responsible for its degradation. Many acetylcholinesterase inhibitors (AChEIs), both natural and synthetic, have been developed and used through the years to counteract the progression of the disease. The first of such drugs approved for a therapeutic use was tacrine, that binds through a reversible bond to the enzyme. However, tacrine has since been withdrawn because of its adverse effects. Currently, donepezil and galantamine are very promising AChEIs with clinical benefits. Moreover, rivastigmine is considered a pseudo-irreversible compound with anti-AChE action, providing similar effects at the clinical level. The purpose of this review is to provide an overview of what has been published over the last decade on the effectiveness of AChEIs in AD, analysing the most relevant issues under the clinical and methodological profiles and the consequent possible welfare effects for the whole world. Furthermore, novel drugs and possible therapeutic approaches are also discussed.

The Sphingosine 1-Phosphate Signaling Pathway in Epilepsy: A Possible Role for the Immunomodulator Drug Fingolimod in Epilepsy Treatment.

It is currently known that erythrocytes are the major source of sphingosine 1-phosphate (S1P) in the body. S1P acts both extracellularly as a cellular mediator and intracellularly as an important second messenger molecule. Its effects are mediated by interaction with five specific types of G proteincoupled S1P receptor. Fingolimod, is a recognized modulator of S1P receptors, and is the first orally active disease-modifying therapy that has been approved for the treatment of multiple sclerosis. Magnetic resonance imaging data suggest that fingolimod may be effective in multiple sclerosis by preventing blood-brain barrier disruption and brain atrophy. Fingolimod might also possess S1P receptorindependent effects and exerts both anti-inflammatory and neuroprotective effects. In the therapeutic management of epilepsy, there are a great number of antiepileptic drugs, but there is still a need for others that are more effective and safer. S1P and its receptors might represent a suitable novel target also in light of their involvement in neuroinflammation, a well-known process underlying seizures and epileptogenesis. The objective of this manuscript is to review the biological role of S1P and its receptors, focusing on their expression, effects and possible involvement in epilepsy; furthermore, we summarize the possible anti-seizure properties of fingolimod and discuss its possible usefulness in epilepsy treatment. We conclude that fingolimod, being already commercially available, might be easily tested for its possible therapeutic effectiveness in epileptic patients, both after a more comprehensive evaluation of the real potential of this drug and following a clear evaluation of the potential role of its main targets, including the S1P signaling pathway in epilepsy.

Antiepileptogenic effects of the selective COX-2 inhibitor etoricoxib, on the development of spontaneous absence seizures in WAG/Rij rats.

Different data suggest the involvement of specific inflammatory pathways in the pathogenesis of epilepsy. Cyclooxygenase (COX), which catalyses the production of pro-inflammatory prostaglandins, may play a significant role in seizure-induced neuroinflammation and neuronal hyperexcitability. COX-2 is constitutively expressed in the brain and also increased during/after seizures. COX-2 inhibitors may thus attenuate inflammation associated with brain disorders. We studied whether early long-term treatment (17 consecutive weeks starting from 45 days postnatal age) with the non-steroidal anti-inflammatory drug etoricoxib (10 mg/kg/day per os), a selective COX-2 inhibitor, was able to prevent/reduce the development of absence seizures in WAG/Rij rats, a recognized animal model of absence epilepsy and epileptogenesis. Drug effects on the incidence, duration and properties of absence seizure spike-wave discharges (SWDs) were measured both 1 and 5 months after treatment withdrawal; furthermore, the acute effects of etoricoxib on SWDs in 6-month-old WAG/Rij rats were measured. Early long-term treatment (ELTT) with etoricoxib led to an ∼40% long-lasting (5 months) reduction in the development of spontaneous absence seizures in adult WAG/Rij rats thus exhibiting antiepileptogenic effects. Acutely administered etoricoxib (10 and 20mg/kg i.p.) also had anti-absence properties, significantly reducing the number and duration of SWDs by ∼50%. These results confirm the antiepileptogenic effects of COX-2 inhibitors and suggest the possible role of COX-2, prostaglandin synthesis and consequent neuroinflammation in the epileptogenic process underlying the development of absence seizures in WAG/Rij rats.

Long-term betamethasone 21-phosphate disodium treatment has distinct effects in CD1 and DBA/2 mice on animal behavior accompanied by opposite effects on neurogenesis.

One of the most peculiar characteristics of the stress response is the pronounced inter-individual and inter-strain variability both in behavioral and neurochemical outcomes. Several studies confirm that rodents belonging to the same or different strain and/or gender, when exposed to a stressor, may show behavioral and cognitive differences. We compared the effects of long-term betamethasone 21-phosphate disodium (BTM), a widely clinically used corticosteroid, on animal behavior and neurogenesis in CD1 and DBA/2 mice. BTM treatment, in CD1 mice, increased body weight gain and anxiety parameters while having pro-depressant effects. Furthermore, BTM significantly reduced neurogenesis in the dentate gyrus of the hippocampus. Finally, BTM treatment induced a significant impairment in memory and learning performance in the Morris water maze. At odds, BTM administration, in DBA/2 mice, caused a significant reduction in the body weight while not modifying anxiety parameters. In addition, both an increased synaptogenesis and neurogenesis were found. Similarly to CD1 mice, also in DBA/2 mice, memory and learning were impaired. Our data confirm that long-term exposure to corticosteroids can generate or aggravate psychiatric/neurologic disorders such as depression, anxiety, memory and learning. Our study did not reveal significant differences between corticosterone and BTM treatment in CD1 mice. In contrast, BTM treatment in mice with an anxious phenotype (DBA/2 mice) revealed some contrasting results indicating that genetic factors can influence corticosteroids dependent effects. Finally, our data further underline the need for a re-evaluation of neurogenesis role; the increased neurogenesis observed in DBA/2 mice and behavioral effects might be distinguished phenomena.

Lamotrigine positively affects the development of psychiatric comorbidity in epileptic animals, while psychiatric comorbidity aggravates seizures.

Several clinical and preclinical studies have focused on the relationship between epilepsy and psychological disturbances. Although behavior in some experimental models of epilepsy has been studied, only few of them can be considered as models of epilepsy and mood disorder comorbidity. Since several models of epilepsy or psychiatric disorders are already available, we wondered whether a mixture of the two could experimentally represent a valid alternative to study such comorbidity. Here, we present a possible experimental protocol to study drug effects and physiopathogenesis of psychiatric comorbidity in epileptic animals. Pentylentetrazol-kindled animals were subjected to the chronic mild stress (CMS) procedure; furthermore, we tested the effects of chronic lamotrigine treatment on the development of comorbidity. We found that epileptic-depressed animals showed more pronounced behavioral alterations in comparison to other mice groups, indicating that kindled animals develop more pronounced CMS-induced behavioral alterations than nonepileptic mice; lamotrigine was able to prevent the development of comorbidities such as anxiety, depression-like behavior, and memory impairment.

Huperzine a restores cortico-hippocampal functional connectivity after bilateral AMPA lesion of the nucleus basalis of meynert.

Huperzine A (Hup-A), an alkaloid isolated from Huperzia serrata (Thunb.) Trevis. (Lycopodiaceae), acts as a selective inhibitor of acetylcholinesterase and shows memory-enhancing properties. Although Hup-A has shown promising expectation for Alzheimer's disease (AD) patients, controlled clinical trials supporting its use are limited. The aim of this work was to study in vivo, in an animal model of AD, the pharmacological activity of systemic administration of Hup-A on cortex- and hippocampus-dependent memory. With this purpose, a set of experiments was planned to evaluate attention, learning, working and spatial memory with respect to cortical and hippocampal electroencephalogram (EEG) theta rhythm during the object recognition test and Morris water maze in animals with lesion of the nucleus basalis of Meynert (NBM). In NBM-lesioned animals, compared with control, an increased theta power in the cortex and a reduced theta rhythm oscillation in the hippocampus were found. These EEG changes were correlated with worse performance in learning and memory tasks. In rats with damaged NBM, Hup-A (0.5 mg/kg i.p.) was able to restore EEG architecture, producing cortical desynchronization and reduction in theta power, while in the hippocampus the drug increased theta oscillation and reduced the impairment in attention/working memory as well as spatial navigation performance in the behavioral tasks. Taken together, the present data suggest that Hup-A is able to restore cholinergic cortico-hippocampal functional connectivity. In conclusion, the present results are in agreement with other experimental evidence that promote the clinical use of this natural drug.

Vigabatrin has antiepileptogenic and antidepressant effects in an animal model of epilepsy and depression comorbidity.

To evaluate the effects of Vigabatrin (VGB) treatment, on both absence seizure and depressive-like behaviour development in the WAG/Rij rat model of absence seizures. Early long-term treatment with VGB could alter the development of absence pathology, by significantly reducing seizure generation and synchronization in contrast to its pro-absence effects observed after acute or subchronic administration. We have demonstrated the antidepressant effects of a sub-chronic treatment with VGB in both wistar and WAG/Rij rats. In contrast, following an early long-term treatment, VGB antidepressant effects were only observable in WAG/Rij rats. In conclusion, VGB has antiepileptogenic and antidepressant properties in the WAG/Rij rat model despite its pro-absence effects suggesting that epilepsy and depression, in this animal model, are directly related and that seizure development inhibition also reduces the development of depressive behaviour.

Enhancement of anti-absence effects of ethosuximide by low doses of a noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist in a genetic animal model of absence epilepsy.

N-Acetyl-1-(4-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (THIQ-10c) is a noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist that has been demonstrated to antagonize generalized tonic-clonic seizures in different animal models of epilepsy. In the study described here, we tested the potential effect of such a compound alone or co-administered with ethosuximide in a genetic animal model of absence epilepsy, the WAG/Rij rat. The intraperitoneal or intracerebroventricular microinjection of THIQ-10c alone was unable to significantly modify the number and duration of spike-and-wave discharges (SWDs). In contrast, intracerebroventricular administration of AMPA induced a dose-dependent increase in the number of SWDs. THIQ-10c dose-dependently antagonized this effect. Furthermore, co-administration of THIQ-1c with ethosuximide (50mg/kg, intraperitoneally) was able to significantly increase the efficacy of the anti-absence drug. In conclusion, although noncompetitive AMPA receptor antagonists alone might not be useful in the treatment of absence epilepsy because of their low therapeutic index, combining them with ethosuximide might be helpful in controlling absence seizures in patients not tolerating this drug or in refractory patients.

Choline pivaloyl ester enhances brain expression of both nerve growth factor and high-affinity receptor TrkA, and reverses memory and cognitive deficits, in rats with excitotoxic lesion of nucleus basalis magnocellularis.

The aim of present work was the evaluation of the effects on brain levels of nerve growth factor (NGF) and of its high-affinity tyrosine kinase A receptor (TrkA), induced in rats unilaterally lesioned at nucleus basalis magnocellularis (NBM), by treatment with choline pivaloyl ester (CPE). CPE was daily administered (60 micromol/Kg ip) during 3 weeks to rats selectively lesioned by AMPA infusion into right NBM; the intact left NBM serving as control. NGF levels were determined in cerebral cortex and hippocampus by Elisa assay. TrkA receptor expression was evaluated in right NBM by Western blotting analysis. CPE treatment significantly increased NGF levels in both hippocampus and neocortex in right NBM, compared with intact left counter-part and controls. Western blotting showed an evident enhancement in TrkA receptor expression in lesioned right NBM in comparison with intact left counter-part and controls. CPE treatment was also able to restore, in bilaterally NBM-lesioned rats, the disrupted cortical EEG and HVS activities as well as to reverse deficits in learning and memory in spatial navigation and probe trials, and cognitive capacities in object recognition task.

Effects of some neurosteroids injected into some brain areas of WAG/Rij rats, an animal model of generalized absence epilepsy.

Neurosteroids are synthesized in the brain and have been demonstrated to modulate various cerebral functions. Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), a naturally occurring neurosteroid, and ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one), a synthetic derivative, are two neurosteroids acting as positive allosteric modulators of the GABA(A) receptor complex acting on a specific steroid recognition site. Both agents antagonize generalized tonic-clonic seizures in various animal models of epilepsy. Pregnenolone sulphate (3beta-hydroxy-5alpha-pregnen-20-one 3-sulphate; PS) is a negative allosteric modulator of GABA(A) receptors and a positive modulator of the NMDA receptors. We have evaluated the effects of such compounds in a genetic animal model of absence epilepsy, the WAG/Rij rat. Animals were chronically implanted with five frontoparietal cortical electrodes for electrocorticogram (EEG) recordings and bilateral guide cannulae into specific brain areas of the cortico-thalamic circuit in order to evaluate the effects of these compounds on the number and duration of epileptic spike-wave discharges (SWDs). The focal and bilateral microinjection of the two GABA(A) positive modulators into some thalamic nuclei (nucleus ventralis posteromedialis, nucleus reticularis thalami, nucleus ventralis posterolateralis was usually able to significantly worsen the occurrence of SWDs in WAG/Rij rats. Whereas both compounds were able to reduce the number and duration of SWDs when microinjected into the peri-oral region of the primary somatosensory cortex. The effects of PS were more complex depending on both the dose and the site of administration, generally, at low doses in thalamic nuclei and cortex, PS induced an increase of absence activity and a reduction at higher doses. These findings suggest that neurosteroids might play a role in absence epilepsies and that it might depend on the involvement of specific neuronal areas.

Electroencephalographic effects induced by choline pivaloyl esters in scopolamine-treated or nucleus basalis magnocellularis lesioned rats.

The electroencephalographic (EEG) effects of two choline pivaloyl esters, [2-(2,2-dimethylpropionyloxy)ethyl]trimethylammonium iodide (1) and [2-(2,2-dimethylpropionyloxy)ethyl]trimethylammonium 2,2-dimethylpropionate (2), were evaluated in scopolamine-treated or nucleus basalis magnocellularis (NBM) lesioned rats. In scopolamine-treated animals, Compounds 1 and 2 prevented or reduced EEG effects, such as increased amplitude of total spectra and high-voltage spindle (HVS) activity as well. Furthermore, choline esters showed a noticeable effectiveness in reversing the EEG changes produced in rats by AMPA-induced lesion of NBM. Indeed, Compounds 1 and 2 were able to induce EEG desynchronisation, a significant decrease in the total EEG power (0.25-16 Hz) and in the lower frequency delta and theta bands (0.25-3 and 3-6 Hz, respectively). The EEG effects produced by Compounds 1 and 2 were well comparable with that evoked by Tacrine, used as a reference compound. The results of the present work allow us to put forward the hypothesis that the EEG effects observed are most likely mediated through the stimulation of the cholinergic neurotransmission ensuing from enhanced cerebral levels of acetylcholine (ACh) consequent upon acetylcholinesterase (AChE) inhibition by choline pivaloyl esters.

Seizure susceptibility to various convulsant stimuli in dystrophin-deficient mdx mice.

In the present study, the susceptibility of the mdx mouse, a dystrophin-deficient genetic model of Duchenne muscular dystrophy (DMD), to various convulsant stimuli has been evaluated and compared to three related mice strains (C57BL/6J, C57BL/10 and DBA/2 mice). Animals were treated with chemical convulsants impairing gamma-aminobutyric acid (GABA) neurotransmission [pentylenetetrazole, picrotoxin, bicuculline, methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), methyl-beta-carboline-3-carboxylate (beta-CCM)], enhancing glutamatergic neurotransmission [N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and kainic acid (KA)] or a K(+) channel blocker (4-aminopyridine). Occurrence of clonic and/or tonic seizures was evaluated to observe possible differences in seizure susceptibility. In addition, all strains of mice were repeatedly treated with a subconvulsant dose of pentylenetetrazole (PTZ) for possible differences in kindling development. The mdx mice exhibited no difference in seizure susceptibility for all convulsant drugs with the exception of a significantly lower sensitivity to AMPA and KA than the other mice strains. This study demonstrates that mdx mice possess a decreased susceptibility to some convulsant stimuli. However, mdx mice showed an enhanced seizure severity and a shorter latency in the development of chemical kindling produced by administration of PTZ. The present data suggests that the dystrophin deficiency in mdx mice affects the pathophysiology and pharmacology of acute and chronic epileptic seizures in an opposite manner.

Choline pivaloyl esters improve in rats cognitive and memory performances impaired by scopolamine treatment or lesions of the nucleus basalis of Meynert.

The effects of two choline pivaloyl esters, [2-(2,2-dimethylpropionyloxy)ethyl]trimethylammonium iodide (1) and [2-(2,2-dimethylpropionyloxy)ethyl]trimethylammonium 2,2-dimethylpropionate (2), on learning and memory impairments induced in rats by scopolamine or lesions of nucleus basalis magnocellularis (NBM) have been evaluated by object recognition and Morris water maze tests in comparison with Tacrine (THA). Both 1 and 2 restored discrimination in object recognition test for assessing working-episodic memory and improved spatial memory in scopolamine or NBM-lesioned rats as well. The positive effects produced by 1 and 2 on cognitive and memory deficits were well comparable with those evoked by THA, used as reference compound.