(-)-Phenserine and Inhibiting Pre-Programmed Cell Death: In Pursuit of a Novel Intervention for Alzheimer's Disease

Gastroretentive Delivery Approach to Address pH-Dependent Degradation of (+)- and (-)-Phenserine

(-)-Phenserine ("phenserine") and (+)-phenserine (posiphen; buntanetap) are longer-acting enantiomeric analogs of physostigmine with demonstrated promise in the treatment of Alzheimer's and Parkinson's diseases. Both enantiomers have short plasma half-lives, and their pharmacokinetics might be improved through the use of either once or twice-daily administration of an extended-release dosage form. Phenserine was observed to form a colored degradation product in near-neutral and alkaline pH environments, and at pH 7, the half-life of posiphen was determined to be ~ 9 h (40 °C). To limit luminal degradation which would reduce bioavailability, a gastroretentive tablet composed of a polyethylene oxide-xanthan gum matrix was developed. When placed in simulated gastric fluid (pH 1.2), approximately 70% of the phenserine was released over a 12 h period, and no degradants were detected in the release medium. In comparison, a traditional hydrophilic-matrix, extended-release tablet showed measurable amounts of phenserine degradation in a pH 7.2 medium over an 8 h release interval. These results confirm that a gastroretentive tablet can reduce the luminal degradation of phenserine or posiphen by limiting exposure to neutral pH conditions while providing sustained release of the drug over at least 12 h. Additional advantages of the gastroretentive tablet include reduced gastric and intestinal concentrations of the drug resulting from the slower release from the gastroretentive tablet which may also limit the occurrence of the dose-limiting GI side effects previously observed with immediate-release phenserine capsules.

Phytochemical Compounds and Nanoparticles as Phytochemical Delivery Systems for Alzheimer's Disease Management

Alzheimer's disease remains one of the most widespread neurodegenerative reasons for dementia worldwide and is associated with considerable mortality and morbidity. Therefore, it has been considered a priority for research. Indeed, several risk factors are involved in the complexity of the therapeutic ways of this pathology, including age, traumatic brain injury, genetics, exposure to aluminum, infections, diabetes, vascular diseases, hypertension, dyslipidemia, and obesity. The pathophysiology of Alzheimer's disease is mostly associated with hyperphosphorylated protein in the neuronal cytoplasm and extracellular plaques of the insoluble β-amyloid peptide. Therefore, the management of this pathology needs the screening of drugs targeting different pathological levels, such as acetylcholinesterase (AchE), amyloid β formation, and lipoxygenase inhibitors. Among the pharmacological strategies used for the management of Alzheimer's disease, natural drugs are considered a promising therapeutic strategy. Indeed, bioactive compounds isolated from different natural sources exhibit important anti-Alzheimer effects by their effectiveness in promoting neuroplasticity and protecting against neurodegeneration as well as neuroinflammation and oxidative stress in the brain. These effects involve different sub-cellular, cellular, and/or molecular mechanisms, such as the inhibition of acetylcholinesterase (AchE), the modulation of signaling pathways, and the inhibition of oxidative stress. Moreover, some nanoparticles were recently used as phytochemical delivery systems to improve the effects of phytochemical compounds against Alzheimer's disease. Therefore, the present work aims to provide a comprehensive overview of the key advances concerning nano-drug delivery applications of phytochemicals for Alzheimer's disease management.

Recent advance on carbamate-based cholinesterase inhibitors as potential multifunctional agents against Alzheimer's disease

Alzheimer's disease (AD), as the fourth leading cause of death among the elderly worldwide, has brought enormous challenge to the society. Due to its extremely complex pathogeneses, the development of multi-target directed ligands (MTDLs) becomes the major strategy for combating AD. Carbamate moiety, as an essential building block in the development of MTDLs, exhibits structural similarity to neurotransmitter acetylcholine (ACh) and has piqued extensive attention in discovering multifunctional cholinesterase inhibitors. To date, numerous preclinical studies demonstrate that carbamate-based cholinesterase inhibitors can prominently increase the level of ACh and improve cognition impairments and behavioral deficits, providing a privileged strategy for the treatment of AD. Based on the recent research focus on the novel cholinesterase inhibitors with multiple biofunctions, this review aims at summarizing and discussing the most recent studies excavating the potential carbamate-based MTDLs with cholinesterase inhibition efficacy, to accelerate the pace of pleiotropic cholinesterase inhibitors for coping AD.

Blood Biomarkers Predict Future Cognitive Decline after Military-Related Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) has been associated with increased likelihood of late-life dementia; however, the mechanisms driving this relationship are elusive. Blood-based biomarkers may provide insight into these mechanisms and serve as useful prognostic indicators of cognitive recovery or decline following a TBI.

OBJECTIVE

The aim of this study was to examine blood biomarkers within one year of TBI and explore their relationship with cognitive decline.

METHODS

Service members and veterans (n=224) without injury (n=77), or with history of bodily injury (n=37), uncomplicated mild TBI (n=55), or more severe TBI (n=55), underwent a blood draw and neuropsychological assessment within one year of their injury as part of a case-control study. A subsample (n=87) completed follow-up cognitive assessment.

RESULTS

In the more severe TBI group, baseline glial fibrillary acidic protein (p=.008) and ubiquitin C-terminal hydrolase-L1 (p=.026) were associated with processing speed at baseline, and baseline ubiquitin C-terminal hydrolase-L1 predicted change in immediate (R2Δ=.244, p=.005) and delayed memory (R2Δ=.390, p=.003) over time. In the mild TBI group, higher baseline tau predicted greater negative change in perceptual reasoning (R2Δ=.188, p=.033) and executive functioning (R2Δ=.298, p=.007); higher baseline neurofilament light predicted greater negative change in perceptual reasoning (R2Δ=.211, p=.012).

CONCLUSION

Baseline ubiquitin C-terminal hydrolase-L1 strongly predicted memory decline in the more severe TBI group, while tau and neurofilament light strongly predicted decline in the mild TBI group. A panel including these biomarkers could be particularly helpful in identifying those at risk for future cognitive decline following TBI.

In Silico and Ex Vivo Analyses of the Inhibitory Action of the Alzheimer Drug Posiphen and Primary Metabolites with Human Acetyl- and Butyrylcholinesterase Enzymes

Alzheimer’s disease (AD) is the most common neurodegenerative disorder worldwide. Ongoing research to develop AD treatments has characterized multiple drug targets including the cholinergic system, amyloid-β peptide, phosphorylated tau, and neuroinflammation. These systems have the potential to interact to either drive or slow AD progression. Promising agents that simultaneously impact many of these drug targets are the AD experimental drug Posiphen and its enantiomer phenserine that, currently, are separately being evaluated in clinical trials. To define the cholinergic component of these agents, the anticholinesterase activities of a ligand dataset comprising Posiphen and primary metabolites ((+)-N1-norPosiphen, (+)-N8-norPosiphen, and (+)-N1,N8-bisnorPosiphen) were characterized and compared to those of the enantiomer phenserine. The “target” dataset involved the human cholinesterase enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Binding interactions between the ligands and targets were analyzed using Autodock 4.2. The computationally determined inhibitory action of these ligands was then compared to ex vivo laboratory-measured values versus human AChE and BChE. While Posiphen lacked AChE inhibitory action, its major and minor metabolites (+)-N1-norPosiphen and (+)-N1,N8-bisnorPosiphen, respectively, possessed modest AChE inhibitory activity, and Posiphen and all metabolites lacked BChE action. Phenserine, as a positive control, demonstrated AChE-selective inhibitory action. In light of AChE inhibitory action deriving from a major and minor Posiphen metabolite, current Posiphen clinical trials in AD and related disorders should additionally evaluate AChE inhibition; particularly if Posiphen should be combined with a known anticholinesterase, since this drug class is clinically approved and the standard of care for AD subjects, and excessive AChE inhibition may impact drug tolerability.

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.

Targeting Impaired Antimicrobial Immunity in the Brain for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and aging is the most common risk factor for developing the disease. The etiology of AD is not known but AD may be considered as a clinical syndrome with multiple causal pathways contributing to it. The amyloid cascade hypothesis, claiming that excess production or reduced clearance of amyloid-beta (Aβ) and its aggregation into amyloid plaques, was accepted for a long time as the main cause of AD. However, many studies showed that Aβ is a frequent consequence of many challenges/pathologic processes occurring in the brain for decades. A key factor, sustained by experimental data, is that low-grade infection leading to production and deposition of Aβ, which has antimicrobial activity, precedes the development of clinically apparent AD. This infection is chronic, low grade, largely clinically silent for decades because of a nearly efficient antimicrobial immune response in the brain. A chronic inflammatory state is induced that results in neurodegeneration. Interventions that appear to prevent, retard or mitigate the development of AD also appear to modify the disease. In this review, we conceptualize further that the changes in the brain antimicrobial immune response during aging and especially in AD sufferers serve as a foundation that could lead to improved treatment strategies for preventing or decreasing the progression of AD in a disease-modifying treatment.

Drug repositioning and repurposing for Alzheimer disease

Drug repositioning and repurposing can enhance traditional drug development efforts and could accelerate the identification of new treatments for individuals with Alzheimer disease (AD) dementia and mild cognitive impairment. Transcriptional profiling offers a new and highly efficient approach to the identification of novel candidates for repositioning and repurposing. In the future, novel AD transcriptional signatures from cells isolated at early stages of disease, or from human neurons or microglia that carry mutations that increase the risk of AD, might be used as probes to identify additional candidate drugs. Phase II trials assessing repurposed agents must consider the best target population for a specific candidate therapy as well as the mechanism of action of the treatment. In this Review, we highlight promising compounds to prioritize for clinical trials in individuals with AD, and discuss the value of Delphi consensus methodology and evidence-based reviews to inform this prioritization process. We also describe emerging work, focusing on the potential value of transcript signatures as a cost-effective approach to the identification of novel candidates for repositioning.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury

Aim

Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury‐associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI‐linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism‐targeted drug unlikely.

Discussion

We review recent data indicating that the small molecular weight drug (−)‐phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI‐ and modTBI‐induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury‐induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well‐characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman.

Conclusion

In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast‐tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

Alzheimer's Disease and Its Potential Alternative Therapeutics

Alzheimer’s Disease (AD) is a chronic neurodegenerative disease that affects over 5 million individuals in the United States alone. Currently, there are only two kinds of pharmacological interventions available for symptomatic relief of AD; Acetyl Cholinesterase Inhibitors (AChEI) and N-methyl-D-aspartic Acid (NMDA) receptor antagonists and these drugs do not slow down or stop the progression of the disease. Several molecular targets have been implicated in the pathophysiology of AD, such as the tau (τ) protein, Amyloid-beta (Aβ), the Amyloid Precursor Protein (APP) and more and several responses have also been observed in the advancement of the disease, such as reduced neurogenesis, neuroinflammation, oxidative stress and iron overload. In this review, we discuss general features of AD and several small molecules across different experimental AD drug classes that have been studied for their effects in the context of the molecular targets and responses associated with the AD progression. These drugs include: Paroxetine, Desferrioxamine (DFO), N-acetylcysteine (NAC), Posiphen/-(−)Phenserine, JTR-009, Carvedilol, LY450139, Intravenous immunoglobulin G 10%, Indomethacin and Lithium Carbonate (Li₂CO₃).

Cholinesterase inhibitors as Alzheimer's therapeutics (Review)

Alzheimer's disease (AD) is one of the most common forms of dementia. AD is a chronic syndrome of the central nervous system that causes a decline in cognitive function and language ability. Cholinergic deficiency is associated with AD, and various cholinesterase inhibitors have been developed for the treatment of AD, including naturally‑derived inhibitors, synthetic analogues and hybrids. Currently, the available drugs for AD are predominantly cholinesterase inhibitors. However, the efficacy of these drugs is limited as they may cause adverse side effects and are not able to completely arrest the progression of the disease. Since AD is multifactorial disease, dual and multi‑target inhibitors have been developed. The clinical applications and the limitations of the inhibitors used to treat AD are discussed in the present review. Additionally, this review presents the current status and future directions for the development of novel drugs with reduced toxicity and preserved pharmacological activity.

Canine Cognitive Dysfunction and Alzheimer's Disease - Two Facets of the Same Disease?

Neurodegenerative diseases present a major and increasing burden in the societies worldwide. With aging populations, the prevalence of neurodegenerative diseases is increasing, yet there are no effective cures and very few treatment options are available. Alzheimer's disease is one of the most prevalent neurodegenerative conditions and although the pathology is well studied, the pathogenesis of this debilitating illness is still poorly understood. This is, among other reasons, also due to the lack of good animal models as laboratory rodents do not develop spontaneous neurodegenerative diseases and human Alzheimer's disease is only partially mimicked by transgenic rodent models. On the other hand, older dogs commonly develop canine cognitive dysfunction, a disease that is similar to Alzheimer's disease in many aspects. Dogs show cognitive deficits that could be paralleled to human symptoms such as disorientation, memory loss, changes in behavior, and in their brains, beta amyloid plaques are commonly detected both in extracellular space as senile plaques and around the blood vessels. Dogs could be therefore potentially a very good model for studying pathological process and novel treatment options for Alzheimer's disease. In the present article, we will review the current knowledge about the pathogenesis of canine cognitive dysfunction, its similarities and dissimilarities with Alzheimer's disease, and developments of novel treatments for these two diseases with a focus on canine cognitive dysfunction.

Geriatric pharmacotherapy: Appraising new drugs for neurologic disorders in older patients

New drug development for neurologic disorders has one of the highest attrition rates of all clinical drug developments. This is problematic when, with innovative technology available in so many aspects of life, modern societies expect to have effective treatments for neurodegenerative disorders and mental health conditions that provide something beyond simple symptomatic relief-the expectation is treatment that impacts and mitigates fundamental mechanisms that drive these disorders. The disease burden of neurologic disorders remains extremely high, whereas the proportion of patients receiving effective therapy is relatively low, demonstrating a sizeable unmet medical need. Whether for novel breakthrough therapies or for drugs considered successful, deciding on the basis of clinical trial data whether a particular treatment will be effective for a specific patient is always a leap of faith. However, expertise at reading trial results combined with knowledge of the patient and of his or her disease, together with an understanding of the effect of age on drug pharmacokinetics and pharmacodynamics, the effect of age on the patient's condition, and the effect of age on the patient's life and outlook will ensure the landing is safe. The focus of this article is to provide such knowledge and thereby optimize this expertise.