Influence of Acetylcholine Esterase Inhibitors and Memantine, Clinically Approved for Alzheimer's Dementia Treatment, on Intestinal Properties of the Mouse

A distinctive subgingival microbiome in patients with periodontitis and Alzheimer's disease compared with cognitively unimpaired periodontitis patients

AIM

Periodontitis is caused by dysbiosis of oral microbes and is associated with increased cognitive decline in Alzheimer's disease (AD), and recently, a potential functional link was proposed between oral microbes and AD. We compared the oral microbiomes of patients with or without AD to evaluate the association between oral microbes and AD in periodontitis.

MATERIALS AND METHODS

Periodontitis patients with AD (n = 15) and cognitively unimpaired periodontitis patients (CU) (n = 14) were recruited for this study. Each patient underwent an oral examination and neuropsychological evaluation. Buccal, supragingival and subgingival plaque samples were collected, and microbiomes were analysed by next-generation sequencing. Alpha diversity, beta diversity, linear discriminant analysis effect size, analysis of variance-like differential expression analysis and network analysis were used to compare group oral microbiomes.

RESULTS

All 29 participants had moderate to severe periodontitis. Group buccal and supragingival samples were indistinguishable, but subgingival samples demonstrated significant alpha and beta diversity differences. Differential analysis showed subgingival samples of the AD group had higher prevalence of Atopobium rimae, Dialister pneumosintes, Olsenella sp. HMT 807, Saccharibacteria (TM7) sp. HMT 348 and several species of Prevotella than the CU group. Furthermore, subgingival microbiome network analysis revealed a distinct, closely connected network in the AD group comprised of various Prevotella spp. and several anaerobic bacteria.

CONCLUSIONS

A unique microbial composition was discovered in the subgingival region in the AD group. Specifically, potential periodontal pathogens were found to be more prevalent in the subgingival plaque samples of the AD group. These bacteria may possess a potential to worsen periodontitis and other systemic diseases. We recommend that AD patients receive regular, careful dental check-ups to ensure proper oral hygiene management.

Epigenetics of Alzheimer’s Disease: Past, Present and Future

Alzheimer’s disease (AD) exemplifies a looming epidemic lacking effective treatment and manifests with the accumulation of neurofibrillary tangles, amyloid-β plaques, neuroinflammation, behavioral changes, and acute cognitive impairments. It is a complex, multifactorial disorder that arises from the intricate interaction between environment and genetic factors, restrained via epigenetic machinery. Though the research progress has improved the understanding of clinical manifestations and disease advancement, the causal mechanism of detrimental consequences remains undefined. Despite the substantial improvement in recent diagnostic modalities, it is challenging to distinguish AD from other forms of dementia. Accurate diagnosis is a major glitch in AD as it banks on the symptoms and clinical criteria. Several studies are underway in exploring novel and reliable biomarkers for AD. In this direction, epigenetic alterations have transpired as key modulators in AD pathogenesis with the impeding inferences for the management of this neurological disorder. The present chapter aims to discuss the significance of epigenetic modifications reported in the pathophysiology of AD such as DNA methylation, hydroxy-methylation, methylation of mtDNA, histone modifications, and noncoding RNAs. Additionally, the chapter also describes the possible therapeutic avenues that target epigenetic modifications in AD.

Chrysophanol improves memory impairment and cell injury by reducing the level of ferroptosis in Aβ25-35 treated rat and PC12 cells

Alzheimer's disease (AD) is a common age-related chronic and neurodegenerative disease that has become a global health problem. AD pathogenesis is complex, and the clinical efficacy of commonly used anti-AD drugs is suboptimal. Recent research has revealed a close association between AD-induced damage and the activation of ferroptosis signaling pathways. Chrysophanol (CHR) the principal medicinal component of Rhubarb, has been reported to have anti-AD effects and can reduce ROS levels in AD-damaged models. AD has been linked to the activation of ferroptosis signaling pathways, which has an important feature of higher levels of reactive oxygen species (ROS). Therefore, the present study explored whether CHR had an anti-AD effect by regulating the ferroptosis levels in AD injury models. Morris water maze, novel object recognition test, Y-maze test, Hematoxylin-eosin (H&E) staining, western blotting, ROS measurement, GPx activity measurement, LPO measurement, transmission electron microscopy, live/dead cell staining were used to investigate the changes in spatial memory level and ferroptosis level in AD model, and the intervention effect of CHR. CHR improved the spatial memory level of AD rat models, reduced the level of hippocampal neuron damage, and improved the survival rate of PC12 cells damaged by β-amyloid (Aβ). Meanwhile, CHR increased glutathione peroxidase-4 (GPX4) protein expression, GPx activity, and GSH, decreased ROS and LPO levels in AD rat models and Aβ-damaged PC12 cells, and improved mitochondrial pathological damage. Our findings suggest that CHR may play a protective role in AD injury by lowering ferroptosis levels, which may provide a potential pathway for developing drugs for AD. However, the mechanism of CHR's role requires further investigation.

Donepezil attenuates inflammation and apoptosis in ulcerative colitis via regulating LRP1/AMPK/NF-κB signaling

This article focuses on the specific effects and mechanisms of donepezil (DNPZ) hydrochloride on inflammation and apoptosis in ulcerative colitis (UC). In vivo and in vitro models of UC were established using dextran sodium sulfate (DSS)-induced mice and NCM460 cells, respectively. Following oral administration of DNPZ, body weight, disease activity index (DAI) scores and colon lengths of mice were recorded. Histopathological damage was detected employing hematoxylin and eosin (H&E) staining. Inflammatory factors were tested using enzyme-linked immunosorbent assay and quantitative reverse transcription polymerase chain reaction, respectively. Apoptosis was estimated utilizing terminal deoxynucleotidyl transferase dUTP nick-end labeling and western blot. Low-density lipoprotein receptor-related protein 1 (LRP1)/AMP activated protein kinase (AMPK)/nuclear factor-κB (NF- κB) signaling proteins were detected utilizing western blot. NCM460 cell viability was assessed by cell counting kit (CCK)-8. We found that DNPZ partially restored body weight, reduced DAI scores and attenuated intestinal pathological damage in DSS-induced mice. Additionally, inflammatory factors decreased significantly after DNPZ treatment, accompanied by reduced apoptosis level. Phosphorylation (p)-AMPK increased and p-p65 decreased after DNPZ treatment, whereas LRP1 knockdown showed the opposite effect. Moreover, DNPZ treatment greatly restored NCM460 cell viability after DSS stimulation. DNPZ attenuated DSS-induced inflammation and apoptosis in NCM460 cells, which was reversed by LRP1 knockdown. In summary, DNPZ hydrochloride attenuates inflammation and apoptosis in UC via LRP1/AMPK/NF-κB signaling.

Pharmacological evaluations of amide carboxylates as potential anti-Alzheimer agents: anti-radicals, enzyme inhibition, simulation and behavioral studies in animal models

Alzheimer's disease (AD) is a neurological disorder that progresses gradually but irreversibly leading to dementia and is difficult to prevent and treat. There is a considerable time window in which the progression of the disease can be intervened. Scientific advances were required to help the researchers to identify the effective methods for the prevention and treatment of disease. This research was designed to investigate potential mediators for the remedy of AD, five new carboxylate amide zinc complexes (AAZ9-AAZ13) were synthesized and characterized by spectroscopic and physicochemical techniques. The biological evaluation was carried out based on the cholinesterase inhibitory mechanism. The preparation methodology provided the effective synthesis of targeted moieties. The in vitro pharmacological activities were evaluated involving AChE/BChE inhibition and antioxidant potential. All synthesized compounds displayed activity against both enzymes in higher or comparable to the standard drug Galantamine, a reversible inhibitor but the results displayed by compound AAZ10 indicated IC50 of 0.0013 µM (AChE) and 0.061 µM (BChE) as high values for dual AChE/BChE inhibition with potent anti-oxidant results. Structure activity relationship (SAR) indicated that the potent activity of compound AAZ10 appeared due to the presence of nitro clusters at the ortho position of an aromatic ring. The potent synthesized compound AAZ10 was also explored for the in-vivo Anti-Alzheimer activity and anti-oxidant activity. Binding approaches of all synthesized compounds were revealed through molecular docking studies concerning binding pockets of enzymes that analyzed the best posture interaction with amino acid (AA) residues providing an appreciable understanding of enzyme inhibitory mechanisms. Results indicate that synthesized zinc (II) amide carboxylates can behave as an effective remedy in the treatment of Alzheimer's disease.Communicated by Ramaswamy H. Sarma.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

Modulating the Gut Microbiota as a Therapeutic Intervention for Alzheimer's Disease

Growing evidence suggested that the change of composition and proportion of intestinal microbiota may be related to many diseases, such as irritable bowel syndrome, bipolar disorder, Parkinson's disease, as well as Alzheimer's disease. Current literature supports the fact that unbalanced gut microbial composition (gut dysbiosis) is a risk factor for AD. In our review, we briefly sum up the recent progress regarding the correlations between the gut microbiota and AD. Therapeutic interventions capable of modulating the make-up of the gut microflora may exert beneficial effects on AD, preventing or delaying the beginning of AD or counteracting its development. Additionally, well-documented approaches that can positively influence AD may exert their beneficial effects through modifying the gut microbiota. Therefore, other novel interventions which can target on gut microbiota will also be potential therapies for AD. The chances and challenges that AD is confronted with in the research field of microbiomics are also discussed in this review.

Discovery of effective phosphodiesterase 2 inhibitors with antioxidant activities for the treatment of Alzheimer's disease

The multi-target-directed-ligand (MTDL) strategy has been widely applied in the discovery of novel drugs for the treatment of Alzheimer's disease (AD) because of the multifactorial pathological mechanisms of AD. Phosphodiesterase-2 (PDE2) has been identified to be a novel and promising target for AD. However, MTDL combining with the inhibitory activity against PDE2A and other anti-AD factors such as antioxidants has not been developed yet. Herein, a novel series of PDE2 inhibitors with antioxidant capacities were designed, synthesized, and evaluated. Most compounds showed remarkable inhibitory activities against PDE2A as well as antioxidant activities. Compound 6d was selected, which showed good IC₅₀ of 6.1 nM against PDE2A, good antioxidant activity (ORAC (Trolox) = 8.4 eq.) and no cytotoxicity to SH-SY5Y cells. Molecular docking and dynamics simulations were applied for the rational design and explanation of structure-activity relationship (SAR) of lead compounds.