Direct Oral Anticoagulants (DOACs) for Therapeutic Targeting of Thrombin, a Key Mediator of Cerebrovascular and Neuronal Dysfunction in Alzheimer's Disease

Proteomic analysis and experimental validation reveal the blood-brain barrier protective of Huanshaodan in the treatment of SAMP8 mouse model of Alzheimer's disease

BACKGROUND

Huanshaodan (HSD) is a Chinese Herbal Compound which has a definite clinical effect on Alzheimer's disease (AD), however, the underlying mechanism remains unclear. The aim of this study is to preliminarily reveal the mechanism of HSD in the treatment of AD model of SAMP8 mice.

METHODS

Chemical composition of HSD and its drug-containing serum were identified by Q-Orbitrap high resolution liquid mass spectrometry. Six-month-old SAMP8 mice were treated with HSD and Donepezil hydrochloride by gavage for 2 months, and Wogonin for 28 days. Behavioral test was performed to test the learning and memory ability of mice. Immunofluorescence (IF) or Western-blot methods were used to detect the levels of pSer404-tau and β-amyloid (Aβ) in the brain of mice. Hematoxylin-eosin (H&E) staining and Transmission electron microscopy (TEM) assay was applied to observe the pathological changes of neurons. Proteomic technology was carried out to analyze and identify the protein network of HSD interventions in AD. Then the pathological process of the revealed AD-related differential proteins was investigated by IF, Q-PCR, Western-blot, Fluorescence in situ hybridization (FISH) and 16S rRNA sequencing methods.

RESULTS

The results showed that HSD and Wogonin, one of the components in its drug-containing serum, can effectively improve the cognitive impairments of SAMP8 mice, protect hippocampal neurons and synapses, and reduce the expression of pSer404-tau and Aβ. HSD and Wogonin reduced the levels of fibrinogen β chain (FGB) and γ chain (FGG), the potential therapeutic targets revealed by proteomics analysis, reduced the colocalization of FGB and FGG with Aβ, ionized calcium binding adaptor molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), increased level of and myelin basic protein (MBP). Meanwhile, HSD and Wogonin increased ZO-1 and Occludin levels, improved brain microvascular injury, and reduced levels of bacteria/bacterial DNA and lipopolysaccharide (LPS) in the brain of mice. In addition, 16S rRNA sequencing indicated that HSD regulated the structure of intestinal microbiota of mice.

CONCLUSION

The effects of HSD on AD may be achieved by inhibiting the levels of fibrinogen and the interactions on glia cells in the brain, and by modulating the structure of intestinal microbiota and improving the blood-brain barrier function.

In Search for Low-Molecular-Weight Ligands of Human Serum Albumin That Affect Its Affinity for Monomeric Amyloid β Peptide

An imbalance between production and excretion of amyloid β peptide (Aβ) in the brain tissues of Alzheimer's disease (AD) patients leads to Aβ accumulation and the formation of noxious Aβ oligomers/plaques. A promising approach to AD prevention is the reduction of free Aβ levels by directed enhancement of Aβ binding to its natural depot, human serum albumin (HSA). We previously demonstrated the ability of specific low-molecular-weight ligands (LMWLs) in HSA to improve its affinity for Aβ. Here we develop this approach through a bioinformatic search for the clinically approved AD-related LMWLs in HSA, followed by classification of the candidates according to the predicted location of their binding sites on the HSA surface, ranking of the candidates, and selective experimental validation of their impact on HSA affinity for Aβ. The top 100 candidate LMWLs were classified into five clusters. The specific representatives of the different clusters exhibit dramatically different behavior, with 3- to 13-fold changes in equilibrium dissociation constants for the HSA-Aβ40 interaction: prednisone favors HSA-Aβ interaction, mefenamic acid shows the opposite effect, and levothyroxine exhibits bidirectional effects. Overall, the LMWLs in HSA chosen here provide a basis for drug repurposing for AD prevention, and for the search of medications promoting AD progression.

Molecular Dynamics Studies of Atomistically Determined Fibrillar Assemblies: Comparison of the Rippled β-Sheet, Pleated β-Sheet, and Herringbone Structures

Pauling and Corey expected that a racemic mixture would result in a rippled β-sheet, however, it has been known from experiments that the racemic mixtures of triphenylalanine lead to a herringbone structure. Because of the theoretical limitations concerning crystal structures such as rippled β-sheet, it is inevitable to understand how the interplay of the amino acids prefers a specific structural motif. In this paper we use molecular dynamics to understand the sequence- and enantiomer-dependent structures by comparisons between rippled β-sheet and pleated β-sheet, solvated and anhydrous rippled β-sheet, and rippled β-sheet and the herringbone structure, based on thermodynamics and structures at the atomic level. The tripeptides select the favored structure that can be stabilized through aromatic or hydrogen bonding interactions between tripeptides. Furthermore, the solubility is determined by the environment of space that is created around the side chains. Our findings provide comprehensive insight into the crystallized fibril motif of the polypeptide.

Potential links between platelets and amyloid-β in the pathogenesis of Alzheimer's disease: Evidence from in vitro, in vivo, and clinical studies

Cerebral amyloid angiopathy (CAA) is a prevalent comorbidity among patients with Alzheimer's disease (AD), present in up to 80% of cases with varying levels of severity. There is evidence to suggest that CAA might intensify cognitive deterioration in AD patients, thereby accelerating the development of AD pathology. As a source of amyloids, it has been postulated that platelets play a significant role in the pathogenesis of both AD and CAA. Although several studies have demonstrated that platelet activation plays an important role in the pathogenesis of AD and CAA, a clear understanding of the mechanisms involved in the three steps: platelet activation, platelet adhesion, and platelet aggregation in AD pathogenesis still remains elusive. Moreover, potential therapeutic targets in platelet-mediated AD pathogenesis have not been explicitly addressed. Therefore, the aim of this review is to collate and discuss the in vitro, in vivo, and clinical evidence related to platelet dysfunction, including associated activation, adhesion, and aggregation, with specific reference to amyloid-related AD pathogenesis. Potential therapeutic targets of platelet-mediated AD pathogenesis are also discussed. By enriching the understanding of the intricate relationship between platelet dysfunction and onset of AD, researchers may unveil new therapeutic targets or strategies to tackle this devastating neurodegeneration.

Heart-brain interaction in cardiogenic dementia: pathophysiology and therapeutic potential

Diagnosis and treatment of patients with cardiovascular and neurologic diseases primarily focus on the heart and brain, respectively. An increasing number of preclinical and clinical studies have confirmed a causal relationship between heart and brain diseases. Cardiogenic dementia is a cognitive impairment caused by heart dysfunction and has received increasing research attention. The prevention and treatment of cardiogenic dementia are essential to improve the quality of life, particularly in the elderly and aging population. This study describes the changes in cognitive function associated with coronary artery disease, myocardial infarction, heart failure, atrial fibrillation and heart valve disease. An updated understanding of the two known pathogenic mechanisms of cardiogenic dementia is presented and discussed. One is a cascade of events caused by cerebral hypoperfusion due to long-term reduction of cardiac output after heart disease, and the other is cognitive impairment regardless of the changes in cerebral blood flow after cardiac injury. Furthermore, potential medications for the prevention and treatment of cardiogenic dementia are reviewed, with particular attention to multicomponent herbal medicines.

Cardiovascular and Neurological Outcomes in Patients Treated with Edoxaban for Atrial Fibrillation and Characteristics in Patients with Cancer

BACKGROUND

Direct oral anticoagulants (DOACs) outperform warfarin in vascular and bleeding events in atrial fibrillation (AF) patients. Yet, effects of DOACs on congestive heart failure (CHF) and Alzheimer's disease (AD) remain less explored.

METHODS

Using the Taiwan National Health Insurance Research Database, a nationwide retrospective cohort study was conducted. The study matched 5,683 non-valvular atrial fibrillation (NVAF) edoxaban patients with 11,366 warfarin patients, and 703 NVAF with cancer (NVAF-C) edoxaban patients with 1,406 warfarin patients. Vasular and non-vascular outcomes, with focuses on CHF and AD, were compared between the edoxaban and warfarin users.

RESULTS

Edoxaban significantly lowered adjusted hazrad ratio (aHR) of all-cause mortality, hospitalization for gastrointestinal bleeding, and CHF (0.37, 0.74, and 0.26, respectively, in NVAF; 0.39, 0.67, and 0.31, respectively, in NVAF-C, all p < 0.05), compared to warfarin. Edoxaban was associated with significantly lower aHRs of acute myocardial infarction, peripheral artery disease, venous thromboembolism, pulmonary embolism, and AD (0.71, 0.48, 0.55, 0.20, and 0.66, respectively; all p < 0.05) in NVAF patients versus warfarin. However, edoxaban had higher aHR of hospitalized bleeding (1.19, p = 0.002) than warfarin in NVAF patients, but not in NVAF-C patients.

CONCLUSIONS

Edoxaban demonstrated lowered CHF risks in both NVAF and NVAF-C patients, and reduced AD occurrence in NVAF patients versus warfarin. These findings advocate for edoxaban's use in AF cases.

CLINICAL PERSPECTIVE

What Is New?: The study reveals that in patients with atrial fibrillation (AF), edoxaban, a direct oral anticoagulant (DOAC), demonstrates significant advantages over warfarin. Notably, edoxaban is associated with a reduced risk of congestive heart failure (CHF) and Alzheimer's disease (AD) when compared to warfarin.Clinical Implications?: These findings have important clinical implications. Edoxaban appears to be a superior anticoagulant choice for AF patients, as it lowers the risk of CHF and AD. This highlights the potential of edoxaban to improve patient outcomes and underscores its relevance for managing AF cases.

A comparison of the effects of NOAC and VKA therapy on the incidence of dementia in patients with atrial fibrillation: A systematic review and meta-analysis

Atrial fibrillation (AF) patients are more susceptible to dementia, but the results about the effect of oral anticoagulants (OACs) on the risk of dementia are not consistent. We hypothesize that OAC is associated with a reduced risk of dementia with AF and that nonvitamin K antagonist oral anticoagulants (NOAC) are superior to vitamin K antagonists (VKA). Four databases were systematically searched until July 1, 2022. Two reviewers independently selected literature, evaluated quality, and extracted data. Data were examined using pooled hazard ratios (HRs) and 95% confidence intervals (CIs). Fourteen research studies involving 910 patients were enrolled. The findings indicated that OACs were associated with a decreased risk of dementia (pooled HR: 0.68, 95% CI: 0.55-0.82, I2  = 87.7%), and NOACs had a stronger effect than VKAs (pooled HR: 0.87, 95% CI: 0.79-0.95, I2  = 72%), especially in participants with a CHA2DS2VASc score ≥ 2 (pooled HR: 0.85, 95% CI: 0.72-0.99). Subgroup analysis demonstrated no statistical significance among patients aged <65 years old (pooled HR: 0.83, 95% CI: 0.64-1.07), patients in "based on treatment" studies (pooled HR: 0.89, 95% CI: 0.75-1.06), or people with no stroke background (pooled HR: 0.90, 95% CI: 0.71-1.15). This analysis revealed that OACs were related to the reduction of dementia incidence in AF individuals, and NOACs were better than VKAs, remarkably in people with a CHA2DS2VASc score ≥ 2. The results should be confirmed by further prospective studies, particularly in patients in "based on treatment" studies aged <65 years old with a CHA2DS2VASc score < 2 or without a stroke background.

Thrombin, a Key Driver of Pathological Inflammation in the Brain

Neurodegenerative diseases, including Alzheimer's disease (AD), are major contributors to death and disability worldwide. A multitude of evidence suggests that neuroinflammation is critical in neurodegenerative disease processes. Exploring the key mediators of neuroinflammation in AD, a prototypical neurodegenerative disease, could help identify pathologic inflammatory mediators and mechanisms in other neurodegenerative diseases. Elevated levels of the multifunctional inflammatory protein thrombin are commonly found in conditions that increase AD risk, including diabetes, atherosclerosis, and traumatic brain injury. Thrombin, a main driver of the coagulation cascade, has been identified as important to pathological events in AD and other neurodegenerative diseases. Furthermore, recent evidence suggests that coagulation cascade-associated proteins act as drivers of inflammation in the AD brain, and studies in both human populations and animal models support the view that abnormalities in thrombin generation promote AD pathology. Thrombin drives neuroinflammation through its pro-inflammatory activation of microglia, astrocytes, and endothelial cells. Due to the wide-ranging pro-inflammatory effects of thrombin in the brain, inhibiting thrombin could be an effective strategy for interrupting the inflammatory cascade which contributes to neurodegenerative disease progression and, as such, may be a potential therapeutic target for AD and other neurodegenerative diseases.

Relationship of Apolipoprotein E with Alzheimer's Disease and Other Neurological Disorders: An Updated Review

Alzheimer's disease (AD) and other neurodegenerative diseases, for which there is no effective cure, cause great social burden. Apolipoprotein E (APOE) is an important lipid transporter, which has been shown to have a close relationship with AD and other neurological disorders in an increasing number of studies, suggesting its potential as a therapeutic target. In this review, we summarize the recent advances in clinical and basic research on the role of APOE in the pathogenesis of multiple neurological diseases, with an emphasis on the new associations between APOE and AD, and between APOE and depression. The progress of APOE research in Parkinson's disease (PD) and some other neurological diseases is briefly discussed.