[The activity of blood serum cholinesterases and neprilysin as potential biomarkers of mild-cognitive impairment and Alzheimer's disease]

Molecular basis of selective amyloid-β degrading enzymes in Alzheimer's disease

The accumulation of the small 42-residue long peptide amyloid-β (Aβ) has been proposed as a major trigger for the development of Alzheimer's disease (AD). Within the brain, the concentration of Aβ peptide is tightly controlled through production and clearance mechanisms. Substantial experimental evidence now shows that reduced levels of Aβ clearance are present in individuals living with AD. This accumulation of Aβ can lead to the formation of large aggregated amyloid plaques-one of two detectable hallmarks of the disease. Aβ-degrading enzymes (ADEs) are major players in the clearance of Aβ. Stimulating ADE activity or expression, in order to compensate for the decreased clearance in the AD phenotype, provides a promising therapeutic target. It has been reported in mice that upregulation of ADEs can reduce the levels of Aβ peptide and amyloid plaques-in some cases, this led to improved cognitive function. Among several known ADEs, neprilysin (NEP), endothelin-converting enzyme-1 (ECE-1), insulin degrading enzyme (IDE) and angiotensin-1 converting enzyme (ACE) from the zinc metalloprotease family have been identified as important. These ADEs have the capacity to digest soluble Aβ which, in turn, cannot form the toxic oligomeric species. While they are known for their amyloid degradation, they exhibit complexity through promiscuous nature and a broad range of substrates that they can degrade. This review highlights current structural and functional understanding of these key ADEs, giving some insight into the molecular interactions that leads to the hydrolysis of peptide substrates, the crucial tasks performed by them and the potential for therapeutic use in the future.

The Potential Role of Serum Tau Protein (MAPT), Neuronal Cell Adhesion Molecule (NrCAM) and Neprilysin (NEP) in Neurodegenerative Disorders Development in Psoriasis-Preliminary Results

Psoriasis is one of the most common dermatoses, which shortens patients’ lives because of the wide comorbidity. However, little is known about its association with neurodegenerative diseases (NDs). We aimed to investigate whether psoriatics are at increased risk of NDs. Sixty patients with plaque-type psoriasis were enrolled into the study. Serum concentrations of tau protein (MAPT), neuronal cell adhesion molecule (NrCAM) and neprilysin (NEP), which are NDs biomarkers and have been hardly studied in psoriasis before, were measured before and after 12 weeks of treatment with acitretin or methotrexate. NrCAM and NEP concentrations were significantly lower in patients than controls, whereas MAPT higher (all p < 0.05). There was no association between these markers and psoriasis severity, BMI or disease duration. After the treatment the concentration of NrCAM and NEP significantly increased and MAPT decreased (p < 0.001, p < 0.05, p < 0.01, respectively). Methotrexate had significant influence on the concentrations of all markers, hence it seems to have neuroprotective properties. Psoriasis severity and duration do not seem to affect the risk of neurodegenerative process. Our results suggest that NDs could be considered as another comorbidity of psoriasis and that further research are needed in order to establish their definite association.

Prospects for the use of graphene-based biological sensors in the early diagnosis of Alzheimer's disease (review of literature)

Among the most significant challenges presented to modern medicine is the problem of cognitive disorders. The relevance of her research is determined by the wide spread of disorders of the higher cortical functions, their significant negative impact on the quality of life of patients, as well as high economic costs on the part of the state and the patient's relatives aimed at organizing medical, diagnostic and rehabilitation processes. The main cause of cognitive impairment in the elderly is Alzheimer's disease. Currently, the criteria for the diagnosis of this nosological form have been developed and are widely used in practice. However, it should be noted that their use is most effective if the patient has a detailed clinical picture, at the stage of dementia. In addition, they provide for the study of biomarkers in a number of cases in the cerebrospinal fluid or using positron emission tomography, which presents certain technical difficulties. Especially significant problems arise in the pre-dement stages. This situation dictates the need to search for new promising diagnostic methods that will have high sensitivity and specificity, as well as the possibility of application in the early stages of Alzheimer's disease, including in outpatient settings. The article provides information about modern methods of computer neuroimaging, discusses the research directions of individual biomarkers, and also shows the prospects for using diagnostic test panels developed on the basis of graphene biosensors, taking into account the latest achievements of nanotechnology and their integration into medical science.

Towards a WPA Position Document on the Human Rights of Older Adults with Mental Health Conditions: К документу с изложением позиции Всемирной психиатрической ассоциации по вопросу соблюдения прав пожилых людей с психическими расстройствами

The increasing number of older adults in countries across the world is a huge challenge to those that are in charge of promoting, protecting, and implementing their human rights. This task is particularly difficult in the absence of a strong international framework addressing the principles required to guide the actions to combat all human rights violations. The existence of such a specific framework for older adults with mental health conditions is justified in view of the particular vulnerability of this section of the population by virtue of societal ageism, stigmatization, exclusion, as well as the disability and dependency which mental health conditions in old age may confer. The present article is a development of a previous statement by the International Psychogeriatric Association and the World Psychiatric Association Section of Old Age Psychiatry. As there is a call to all organizations to support efforts to combat Human Rights violations among older adults, a text will be submitted to the Executive Committee of the World Psychiatric Association to approve an official position statement on Human Rights of Older Persons with Mental Health Conditions.

The Evolution of Diagnostic Boundaries of Alzheimer's Disease and Novel Therapeutic Options: Эволюция диагностических границ болезни Альцгеймера и новые терапевтические возможности

Over the past three decades, the definition and diagnostic boundaries of Alzheimer's disease (AD) have been repeatedly revised due to significant progress in understanding of the pathogenesis of neurodegeneration associated with Alzheimer's disease and in the development of high-tech diagnostic methods. The current approach to AD diagnostics relies on the detection of biomarkers that reflect two main neuropathological processes involved in the primary neurodegeneration that underlies AD: abnormal amyloidogenesis, and neuronal degeneration. The currently available diagnostic tools are limited to the detection of cerebrospinal biomarkers and/or assessment of the abnormal amyloid and tau protein burden in the brain via amyloid and tau positron emission tomography (PET) ligands. Practical implementation (mostly in the research field) of the biological model of AD diagnosis has led to a significant expansion of its diagnostic boundaries with the inclusion of predementia AD stages: asymptomatic and symptomatic, the latter is clinically corresponding to amnestic mild cognitive impairment (aMCI-amnestic mild cognitive impairment). On the one hand, this approach significantly expands the possibilities to study and use preventive technologies aiming to avert or delay the progression of predementia cognitive impairment to dementia but, on the other, it is associated with a number of negative implications from both the clinical and ethical points of view. A significant limitation of purely biological diagnosis of AD based on biomarker levels is due to the low prognostic value of biomarkers, which can cause diagnostic confusion in certain circumstances. Moreover, since the future evolution of the asymptomatic stage is not yet clear and there are still no reliable ways to prevent the cognitive and behavioral symptoms associated with AD, disclosure of stressful information about this "terrifying" diagnosis to patients can cause irreversible damage by triggering depressive disorder, which is a risk factor of AD itself. The current knowledge about AD prognosis in amyloid-positive cognitively unimpaired patients is insufficient.The most adequate approach to early AD diagnostics appears to be the clinical and biological model, as recommended by the International Working Group (IWG 2021), which requires a combination of the clinical AD phenotype and the detection of biomarkers specific to this disease. The article discusses the potential directions for the development of biological diagnostic methods, including those based on the so-called peripheral (serum) biomarker technologies and promising directions for the development of biological methods of secondary AD prevention.

An Overview of Combination Treatment with Citicoline in Dementia

INTRODUCTION

The present article reports an overview of the studies about combination treatment with citicoline of Alzheimer's (AD) and mixed dementia (MD).

METHODS

A Medline search was carried out by using the keywords Alzheimer's dementia, mixed dementia, older people, treatment with citicoline, memantine, and acetylcholinesterase inhibitors (AchEIs).

RESULTS

Six studies were found to match the combination treatment of citicoline with AcheIs and/or memantine. The CITIRIVAD and CITICHOLINAGE studies were the first to report the potential benefits of adding citicoline to acetylcholinesterase inhibitors (AchEIs). Then, we added citicoline to memantine in the CITIMEM study, and finally, we demonstrated benefits in terms of delay in cognitive worsening with the triple therapy (citicoline + AchEIs + memantine). Other authors also reinforced our hypothesis through two further studies.

CONCLUSIONS

Open, prospective studies are advised to confirm the utility of combination therapy with citicoline for the treatment of AD and MD.

[Citicoline in the treatment of cognitive impairment in first-degree relatives of AD patients: the influence of the ApoE genotype]

OBJECTIVE

To study the effects of a three-month course of therapy with citicoline, aimed at preventing the progression of cognitive deficit in 1st-degree relatives of patients with Alzheimer's disease (AD), depending on the carriage of the ApoE4(+) genotype.

MATERIAL AND METHODS

Study participants: 82 blood relatives of AD patients, 66 of them with signs of minimal cognitive dysfunction (group 1) objectively confirmed by clinical neuropsychological examination and 16 people with mild cognitive decline syndrome (group 2). Open comparative multidisciplinary study of the dynamics of cognitive status in relatives of AD patients who received a three-month course of citicoline therapy. The baseline indicators of the cognitive functioning of the relatives of the two groups were compared with the indicators at the end of the three-month course of therapy with citicoline in a daily dose of 1000 mg, depending on whether the treated persons had genotypes ApoE4(+) or ApoE4(-). Clinical-psychopathological, neuropsychological, psychometric, molecular-genetic, statistical.

RESULTS

An association of the ApoE4(-) genotype with a significantly more pronounced positive effect of the course therapy with citicoline was established according to the general clinical impression (CGI-I scale), indicators of cognitive functioning (MMSE and MoCA scales), as well as according to most psychometric tests (with the exception of the number repetition test in reverse order), as well as for almost all indicators of the neuropsychological «express method» (excluding the parameter of the volume of visual memory).

CONCLUSION

The results of course therapy with citicoline showed a negative effect of the carriage of the ε4 allele of the ApoE gene on the efficiency of treatment of blood relatives of AD patients who had signs of cognitive decline before the start of therapy, which did not reach the level of dementia. The obtained data can serve as the basis for the development of preventive therapeutic measures aimed at preventing the progression of cognitive deficit and the development of dementia in the group at high risk of developing dementia - in 1st degree relatives of AD patients, especially in carriers of the ApoE4(+) genotype.

Exosomal Aβ-Binding Proteins Identified by "In Silico" Analysis Represent Putative Blood-Derived Biomarker Candidates for Alzheimer´s Disease

The potential of exosomes as biomarker resources for diagnostics and even for therapeutics has intensified research in the field, including in the context of Alzheimer´s disease (AD). The search for disease biomarkers in peripheral biofluids is advancing mainly due to the easy access it offers. In the study presented here, emphasis was given to the bioinformatic identification of putative exosomal candidates for AD. The exosomal proteomes of cerebrospinal fluid (CSF), serum and plasma, were obtained from three databases (ExoCarta, EVpedia and Vesiclepedia), and complemented with additional exosomal proteins already associated with AD but not found in the databases. The final biofluids’ proteomes were submitted to gene ontology (GO) enrichment analysis and the exosomal Aβ-binding proteins that can constitute putative candidates were identified. Among these candidates, gelsolin, a protein known to be involved in inhibiting Abeta fibril formation, was identified, and it was tested in human samples. The levels of this Aβ-binding protein, with anti-amyloidogenic properties, were assessed in serum-derived exosomes isolated from controls and individuals with dementia, including AD cases, and revealed altered expression patterns. Identification of potential peripheral biomarker candidates for AD may be useful, not only for early disease diagnosis but also in drug trials and to monitor disease progression, allowing for a timely therapeutic intervention, which will positively impact the patient’s quality of life.

Neprilysin expression and functions in development, ageing and disease

Neprilysin (NEP) is an integral membrane-bound metallopeptidase with a wide spectrum of substrates and physiological functions. It plays an important role in proteolytic processes in the kidney, cardiovascular regulation, immune response, cell proliferation, foetal development etc. It is an important neuropeptidase and amyloid-degrading enzyme which makes NEP a therapeutic target in Alzheimer's disease (AD). Moreover, it plays a preventive role in development of cancer, obesity and type-2 diabetes. Recently a role of NEP in COVID-19 pathogenesis has also been suggested. Despite intensive research into NEP structure and functions in different organisms, changes in its expression and regulation during brain development and ageing, especially in age-related pathologies, is still not fully understood. This prevents development of pharmacological treatments from various diseases in which NEP is implicated although recently a dual-acting drug sacubitril-valsartan (LCZ696) combining a NEP inhibitor and angiotensin receptor blocker has been approved for treatment of heart failure. Also, various natural compounds capable of upregulating NEP expression, including green tea (EGCG), have been proposed as a preventive medicine in prostate cancer and AD. This review summarizes the existing literature and our own research on the expression and activity of NEP in normal brain development, ageing and under pathological conditions.

The Importance of Citicoline in Combined Treatment in Dementia: What did the Citimem Study Teach us?

BACKGROUND

Citicoline is a drug used both in degenerative and in vascular cognitive decline; memantine is a drug used for the treatment of mild to moderate Alzheimer's disease (AD). Our hypothesis is that their combined use could have enhanced action in patients having AD and mixed dementia (MD). We report the main tips from a recent study on the use of these drugs, the CITIMEM study.

METHODS

The study was retrospective and was performed on 126 patients aged 65 years old or older affected with AD or MD (mean age 80.7 ± 5.2 years old) who had been visited between 2015 and 2017 in four different centers for dementia all over Italy. Neuropsychological and functional tests were administered at baseline (T0), after 6 (T1), and 12 months (T2). The effects of combined treatment versus memantine alone on cognitive functions assessed by Mini-Mental State Examination (MMSE) and the possible onset of side effects or adverse events, as well as the influence on daily life functions and behavioral symptoms, were investigated.

RESULTS

Patients undergoing combined treatment showed a significant increase in MMSE vs. memantine alone, both at T1 (p=0.003) and T2 (p =0.000).

CONCLUSION

The CITIMEM study confirms our hypothesis that the combined administration of memantine plus citicoline is safe and more effective than memantine alone on cognition in patients suffering from AD or MD.

Potential Enzymatic Targets in Alzheimer's: A Comprehensive Review

Alzheimer's, a degenerative cause of the brain cells, is called as a progressive neurodegenerative disease and appears to have a heterogeneous etiology with main emphasis on amyloid-cascade and hyperphosphorylated tau-cascade hypotheses, that are directly linked with macromolecules called enzymes such as β- & γ-secretases, colinesterases, transglutaminases, and glycogen synthase kinase (GSK-3), cyclin-dependent kinase (cdk-5), microtubule affinity-regulating kinase (MARK). The catalytic activity of the above enzymes is the result of cognitive deficits, memory impairment and synaptic dysfunction and loss, and ultimately neuronal death. However, some other enzymes also lead to these dysfunctional events when reduced to their normal activities and levels in the brain, such as α- secretase, protein kinase C, phosphatases etc; metabolized to neurotransmitters, enzymes like monoamine oxidase (MAO), catechol-O-methyltransferase (COMT) etc. or these abnormalities can occur when enzymes act by other mechanisms such as phosphodiesterase reduces brain nucleotides (cGMP and cAMP) levels, phospholipase A2: PLA2 is associated with reactive oxygen species (ROS) production etc. On therapeutic fronts, several significant clinical trials are underway by targeting different enzymes for development of new therapeutics to treat Alzheimer's, such as inhibitors for β-secretase, GSK-3, MAO, phosphodiesterase, PLA2, cholinesterases etc, modulators of α- & γ-secretase activities and activators for protein kinase C, sirtuins etc. The last decades have perceived an increasing focus on findings and search for new putative and novel enzymatic targets for Alzheimer's. Here, we review the functions, pathological roles, and worth of almost all the Alzheimer's associated enzymes that address to therapeutic strategies and preventive approaches for treatment of Alzheimer's.

Neutral Endopeptidase (Neprilysin) in Therapy and Diagnostics: Yin and Yang

Neprilysin (NEP) is a zinc-dependent metalloproteinase that exists in organisms in both transmembrane and soluble forms. NEP substrates are involved in regulating the cardiovascular and nervous systems. In this review, we discuss some of the biochemical characteristics and physiological functions of this enzyme with special emphasis on the use of NEP as a therapeutic target. The history and various physiological aspects of applying NEP inhibitors for treating heart failure and attempts to increase NEP activity when treating Alzheimer's disease using gene and cell therapies are described. Another important issue discussed is the role of NEP as a potential marker for predicting the risk of cardiovascular disease complications. The diagnostic and prognostic performance of soluble NEP in various types of heart failure is analyzed and presented. We also discuss the methods and approaches for measuring NEP activity for prognosis and diagnosis, as well as a possible new role of natriuretic peptides (NEP substrates) in cardiovascular diagnostics.

Targeting amyloid clearance in Alzheimer's disease as a therapeutic strategy

Targeting the amyloid-β (Aβ) peptide cascade has been at the heart of therapeutic developments in Alzheimer's disease (AD) research for more than 25 years, yet no successful drugs have reached the marketplace based on this hypothesis. Nevertheless, the genetic and other evidence remains strong, if not overwhelming, that Aβ is central to the disease process. Most attention has focused on the biosynthesis of Aβ from its precursor protein through the successive actions of the β- and γ-secretases leading to the development of inhibitors of these membrane proteases. However, the levels of Aβ are maintained through a balance of its biosynthesis and clearance, which occurs both through further proteolysis by a family of amyloid-degrading enzymes (ADEs) and by a variety of transport processes. The development of late-onset AD appears to arise from a failure of these clearance mechanisms rather than by overproduction of the peptide. This review focuses on the nature of these clearance mechanisms, particularly the various proteases known to be involved, and their regulation and potential as therapeutic targets in AD drug development. The majority of the ADEs are zinc metalloproteases [e.g., the neprilysin (NEP) family, insulin-degrading enzyme, and angiotensin converting enzymes (ACE)]. Strategies for up-regulating the expression and activity of these enzymes, such as genetic, epigenetic, stem cell technology, and other pharmacological approaches, will be highlighted. Modifiable physiological mechanisms affecting the efficiency of Aβ clearance, including brain perfusion, obesity, diabetes, and sleep, will also be outlined. These new insights provide optimism for future therapeutic developments in AD research. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Vascular Dysfunction in Alzheimer's Disease: A Prelude to the Pathological Process or a Consequence of It?

Alzheimer's disease (AD) is the most prevalent form of dementia. Despite decades of research following several theoretical and clinical lines, all existing treatments for the disorder are purely symptomatic. AD research has traditionally been focused on neuronal and glial dysfunction. Although there is a wealth of evidence pointing to a significant vascular component in the disease, this angle has been relatively poorly explored. In this review, we consider the various aspects of vascular dysfunction in AD, which has a significant impact on brain metabolism and homeostasis and the clearance of β-amyloid and other toxic metabolites. This may potentially precede the onset of the hallmark pathophysiological and cognitive symptoms of the disease. Pathological changes in vessel haemodynamics, angiogenesis, vascular cell function, vascular coverage, blood-brain barrier permeability and immune cell migration may be related to amyloid toxicity, oxidative stress and apolipoprotein E (APOE) genotype. These vascular deficits may in turn contribute to parenchymal amyloid deposition, neurotoxicity, glial activation and metabolic dysfunction in multiple cell types. A vicious feedback cycle ensues, with progressively worsening neuronal and vascular pathology through the course of the disease. Thus, a better appreciation for the importance of vascular dysfunction in AD may open new avenues for research and therapy.

[Alzheimer's disease]

Alzheimer's disease (AD) is a serious medical and social problem of our time, while remaining the most common cause of dementia in the elderly. The leading symptom in the clinical picture of the disease is a progressive loss of memory with further development of behavioral disorders. In the early stages of AD, patients are mostly managed by neurologists and differential diagnosis is carried out with a variety of neurodegenerative diseases. The authors present clinical criteria of AD diagnosis and consider diagnostic possibilities in the predementia stage using biological markers. With this purpose, modern concepts of the etiology and pathogenesis of AD and genetic aspects of pathology are considered. Contribution of many environmental factors to the initiation and progression of the disease process is evaluated. Mechanisms of cerebral amyloidosis and its characteristic neurological manifestations are considered.

Meta-analysis of expression and function of neprilysin in Alzheimer's disease

Neprilysin (NEP) is one of the most important Aβ-degrading enzymes, and its expression and activity in Alzheimer's brain have been widely reported, but the results remain debatable. Thus, the meta-analysis was performed to elucidate the role of NEP in Alzheimer's disease (AD). The relevant case-control or cohort studies were retrieved according to our inclusion/exclusion criteria. Six studies with 123 controls and 141 AD cases, seven studies with 102 controls and 90 AD cases, and four studies with 93 controls and 132 AD cases were included in meta-analysis of NEP's protein, mRNA, and enzyme activity respectively. We conducted Meta regression to detect the sources of heterogeneity and further performed cumulative meta-analysis or subgroup analysis. Our meta-analysis revealed a significantly lower level of NEP mRNA (SMD=-0.44, 95%CI: -0.87, -0.00, p=0.049) in AD cases than in non-AD cases, and such pattern was not altered over time in the cumulative meta-analysis. However, the decrease of NEP protein (SMD=-0.18, 95%CI: -0.62, 0.25) and enzyme activity (SMD=-0.35, 95%CI: -1.03, 0.32) in AD cases did not pass the significance check, while the cumulative meta-analysis by average age showed the pooled effect became insignificant as adding the studies with younger subjects, which indicates that the protein expression and enzyme activity of NEP in the cortex are affected by age. Therefore, the present meta-analysis suggests the need of further investigation of roles of NEP in AD pathogenesis and treatment.

The CITIRIVAD Study: CITIcoline plus RIVAstigmine in Elderly Patients Affected with Dementia Study

BACKGROUND

Acetylcholinesterase inhibitors (AchEIs), such as rivastigmine, coadministered with cholinergic precursors, such as citicoline, could be effective in Alzheimer's disease (AD) and in mixed dementia (MD), because they are able to increase the intrasynaptic levels of acetylcholine more than the single drugs given alone.

OBJECTIVE

The aim of the present study was to show the effectiveness of oral citicoline plus rivastigmine in patients with AD and MD.

METHODS

The CITIRIVAD study was a retrospective case-control study on 174 consecutive outpatients aged ≥65 years, affected with AD or MD, mean age 81.3 ± 4.5 years. Of the 174 patients, 92 had been treated with rivastigmine + citicoline 1000 mg/day given orally (group A); 82 patients had been treated with rivastigmine (group B). In both groups rivastigmine patch had been used for at least six months at the highest tolerated dosage. Group A comprised 62 patients affected with AD and 30 patients with MD. Group B comprised 53 patients affected with AD and 29 with MD. Cognitive functions had been assessed by Mini Mental State Examination (MMSE), daily life functions by activities of daily living (ADL) and instrumental activities (IADL), behavioral symptoms by neuropsychiatric inventory (NPI), comorbidities by the Cumulative Illness Rating Scale and mood by geriatric depression scale (GDS)-short form tests, which had been administered at baseline, 3 and 9 months.

RESULTS AND CONCLUSIONS

Data show the effectiveness of combined administration versus the AchEI alone, mainly in slowing disease progression and consequently in disease management, both in AD and in MD. No differences regarding the combined treatment were found between the two groups. Treatment with citicoline plus rivastigmine was safe and well tolerated.