Plasma Amyloid-β and Alzheimer's Disease-Related Changes in Late-Life Depression

Sleep deprivation enhances amyloid beta peptide, p-tau and serotonin in the brain: Neuroprotective effects of nanowired delivery of cerebrolysin with monoclonal antibodies to amyloid beta peptide, p-tau and serotonin

Sleep deprivation is quite frequent in military during combat, intelligence gathering or peacekeeping operations. Even one night of sleep deprivation leads to accumulation of amyloid beta peptide burden that would lead to precipitation of Alzheimer's disease over the years. Thus, efforts are needed to slow down or neutralize accumulation of amyloid beta peptide (AβP) and associated Alzheimer's disease brain pathology including phosphorylated tau (p-tau) within the brain fluid environment. Sleep deprivation also alters serotonin (5-hydroxytryptamine) metabolism in the brain microenvironment and impair upregulation of several neurotrophic factors. Thus, blockade or neutralization of AβP, p-tau and serotonin in sleep deprivation may attenuate brain pathology. In this investigation this hypothesis is examined using nanodelivery of cerebrolysin- a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies against AβP, p-tau and serotonin (5-hydroxytryptamine, 5-HT). Our observations suggest that sleep deprivation induced pathophysiology is significantly reduced following nanodelivery of cerebrolysin together with monoclonal antibodies to AβP, p-tau and 5-HT, not reported earlier.

Beneficial effects of QTC-4-MeOBnE in an LPS-induced mouse model of depression and cognitive impairments: The role of blood-brain barrier permeability, NF-κB signaling, and microglial activation

Clinical and preclinical investigations have suggested a possible biological link betweenmajor depressive disorder (MDD) and Alzheimer's disease (AD). Therefore, a pharmacologic approach to treating MDD could be envisioned as a preventative therapy for some AD cases. In line with this, 1-(7-chloroquinolin-4-yl)-N-(4-methoxybenzyl)-5-methyl-1H-1,2,3-triazole-4 carboxamide (QTC-4-MeOBnE) is characterized as an inhibitor of β-secretase, glycogen synthase kinase 3β, and acetylcholinesterase and has also shown secondary effects underlying the modulation of neurogenesis and synaptic plasticity pathways. Therefore, we investigated the effects of QTC-4-MeOBnE treatment (0.1 or 1 mg/kg) on depressive-like behavior and cognitive impairments elicited by repeated injections of lipopolysaccharide (LPS; 250 μg/kg) in mice. Injections of LPS for seven days led to memory impairments and depressive-like behavior, as evidenced in the Y-maze/object recognition test and forced swimming/splash tests, respectively. However, these impairments were prevented in mice that, after the last LPS injection, were also treated with QTC-4-MeOBnE (1 mg/kg). This effect was associated with restoring blood-brain barrier permeability, reducing oxidative/nitrosative biomarkers, and decreasing neuroinflammation mediated NF-κB signaling in the hippocampus and cortex of the mice. To further investigate the involvement with NF-κB signaling, we evaluated the effects of QTC-4-MeOBnE on microglial cell activation through canonical and non-canonical pathways and the modulation of the involved components. Together, our findings highlight the pharmacological benefits of QTC-4-MeOBnE in a mouse model of sickness behavior and memory impairments, supporting the novel concept that since this molecule produces anti-depressant activity, it could also be beneficial for preventing AD onset and related dementias in subjects suffering from MDD through inflammatory pathway modulation.

Mental Illness and Amyloid: A Scoping Review of Scientific Evidence over the Last 10 Years (2011 to 2021)

Amyloid precursor protein and its derivates represent a central factor in the process of neurodegeneration in Alzheimer’s disease (AD). Since mental illnesses share with AD cognitive impairment, amyloid indicators have been used to explore the unknown pathophysiologic mechanisms underlining psychiatric illness. This work aims to compare the role of amyloid markers, together with tau proteins, among various mental disorders evaluating the possible role of altered amyloid metabolism in the onset and in the course of psychiatric diseases, considering the relationship with cognitive impairment in dementia. This review includes articles written in English, published between 1 January 2011 and 31 January 2021, which evaluated amyloid and tau proteins in psychiatric patients. After screening, 31 studies were included in the review. Results suggest that amyloid metabolism is altered in major psychiatric disorders and that it could be a marker of cognitive impairment. Nevertheless, the role of amyloid in mental diseases seems to be related to neurodevelopmental alteration as well as neurodegeneration processes, like in AD. The role of amyloid in the pathogenesis of mental disorders is still unknown. Amyloid should not be only considered as a marker of cognitive impairment in mental illness, but also for altered neurodevelopment.

The Neurobiological Basis of Cognitive Side Effects of Electroconvulsive Therapy: A Systematic Review

Decades of research have consistently demonstrated the efficacy of electroconvulsive therapy (ECT) for the treatment of major depressive disorder (MDD), but its clinical use remains somewhat restricted because of its cognitive side effects. The aim of this systematic review is to comprehensively summarize current evidence assessing potential biomarkers of ECT-related cognitive side effects. Based on our systematic search of human studies indexed in PubMed, Scopus, and Web of Knowledge, a total of 29 studies evaluating patients with MDD undergoing ECT were reviewed. Molecular biomarkers studies did not consistently identify concentration changes in plasma S-100 protein, neuron-specific enolase (NSE), or Aβ peptides significantly associated with cognitive performance after ECT. Importantly, these findings suggest that ECT-related cognitive side effects cannot be explained by mechanisms of neural cell damage. Notwithstanding, S-100b protein and Aβ40 peptide concentrations, as well as brain-derived neurotrophic factor (BDNF) polymorphisms, have been suggested as potential predictive biomarkers of cognitive dysfunction after ECT. In addition, recent advances in brain imaging have allowed us to identify ECT-induced volumetric and functional changes in several brain structures closely related to memory performance such as the hippocampus. We provide a preliminary framework to further evaluate neurobiological cognitive vulnerability profiles of patients with MDD treated with ECT.

Different Sides of Depression in the Elderly: An In-depth View on the Role of Aβ Peptides

BACKGROUND

Late-onset depression (LOD) is the most common neuropsychiatric disorder associated with Alzheimer's disease (AD), often associated with structural and functional brain changes, neuropsychological impairments and negative family history for affective disorders. LOD could be a risk factor or a prodromal phase of AD; this has led to the investigation of the link between depression and amyloid-β (Aβ) peptides by measuring Aβ levels in plasma, cerebrospinal fluid (CSF) and brains of elderly depressed subjects.

OBJECTIVE

Clarify the complex relationship between depression, Aβ peptides and AD.

METHOD

We evaluated all articles published up to 2019 in PubMed in which Aβ was measured in serum (or plasma), CSF or brain in elderly with Major Depressive Disorder or depressive symptoms evaluated with standard scales.

RESULTS

Low plasma Aβ42 levels are strongly associated with depression severity. Plasma Aβ40 levels are higher in younger depressed, drug-resistant and those with more severe symptoms. CSF Aβ42 levels are lower in depressed than controls. PET-detected global and region-specific increases in Aβ deposition are sometimes associated with LOD, cognitive impairment, anxiety but not with Cardiovascular Diseases (CVDs)/CVD risk factors. Elderly depressed with CVDs/CVD risk factors have more frequently high plasma Aβ40 levels and drug-resistance; those without these co-morbidities have low plasma Aβ42 levels and a greater cognitive impairment.

CONCLUSION

Two specific Aβ profiles emerge in elderly depressed. One is associated with Aβ42 reductions in plasma and CSF, possibly reflecting increased brain amyloid deposition and prodromal AD. The other one is characterized by high plasma Aβ40 levels, cerebrovascular disease and clinically associated with increased AD risk.

The Emerging Role of Circular RNAs in Alzheimer's Disease and Parkinson's Disease

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are two neurodegenerative diseases (NDDs) commonly found in elderly patients that are difficult to diagnose and lack effective treatment. Currently, the available diagnostic methods for these two NDDs do not meet clinical diagnostic expectations. Circular RNAs (circRNAs) are a diverse group of endogenous non-coding RNAs (ncRNAs) found in eukaryotic cells. Emerging studies suggest that altered expression of circRNAs is involved in the pathological processes of NDDs. CircRNAs could also prove to be promising biomarkers for the early diagnosis of NDDs such as AD and PD. Growing evidence has improved our knowledge of the roles of circRNAs in NDDs, which may lead to new therapeutic approaches that target transcription for preventing neurodegeneration. In this review, we describe the formation mechanisms and functions of circRNAs as well as methods of validation. We also discuss the emerging role of circRNAs in the pathophysiology of AD and PD and their potential value as biomarkers and therapeutic targets for AD and PD in the future.

Decrease in 130 kDa- amyloid protein precursor protein (APP) and APP protein ratio in schizophrenia platelets

Cognitive dysfunction is common among people with schizophrenia. The molecular substrates underlying this remain poorly understood. To address this, we analyzed changes in amyloid precursor protein (APP) in platelets of people with acute schizophrenia (n=24) and control subjects (n=20) by ECL-immunoblotting. APP bands corresponding to molecular masses of ∼130, ∼110 and ∼100 kDa, and the APP ratio (APPr: highest APP molecular mass vs lowest APP molecular mass bands) were quantified. The intensity of 130 kDa-APP and the APPr were significantly reduced in schizophrenia patients compared to control subjects. The age-associated decreases in the 130 kDa, ∼110 kDa proteins and APPr were present in patients, but not controls. Our results confirm peripheral APP metabolism is altered in people with schizophrenia. Further work is now warranted on a larger sample of diseased subjects with detailed cognitive assessment to determine the APP role in cognitive processing in schizophrenia, how it is related to severity and disease progression, as well as outcomes.

Depression related cerebral pathology and its relationship with cognitive functioning: A systematic review

BACKGROUND

Depression's relationship with cerebral abnormalities and cognitive decline is temporally dynamic. Despite clear clinical utility, understanding depression's effect on cerebral structures, cognitive impairment and the interaction between these symptoms has had limited consideration.

METHODS

This review summarised studies examining a clinical depression diagnosis or validated scales measuring depressive symptoms, data concerning amyloid-beta (Aβ) levels, brain structure and function focusing on hippocampal alterations, or white matter hyperintensities (WMH), and at least one validated neuropsychological test. Online database searches of: PsycINFO, EMBASE, MEDLINE, and Scopus were conducted to identify potential articles.

RESULTS

While depression was consistently associated with cross-sectionally cognitive decline across multiple domains, the neuropathological basis of this dysfunction remained unclear. Hippocampal, frontal, and limbic dysfunction as well as cortical thinning, WMH, and Aβ burden all provide inconsistent findings, likely due to depression subtypes. The consistency of these findings additionally decreases when examining this relationship longitudinally, as these results are further confounded by pre-dementia states. The therapeutic interventions examined were more efficacious in the younger compared with the older samples, who were characterised by greater WMH and Aβ burden.

LIMITATIONS

The limited number of longitudinal and interventional studies in addition to the heterogeneity of the samples restricts their generalisability.

CONCLUSIONS

Symptomatological differences between early-onset and late-onset depression (EOD and LOD) appear crucial in understanding whether late-life depression is the primary or secondary source of cerebral pathology. Though severe cognitive impairments and clearer neuropathological underpinnings are more characteristic of LOD than EOD, the inconsistency of valid biomarkers remains problematic.