Preclinical Models for Alzheimer's Disease: Past, Present, and Future Approaches

Intranasal amyloid model of Alzheimer's disease - potential opportunities and challenges

Amyloid beta 1-42 (Aβ1-42) peptide is one of the most studied disease-related amyloidogenic peptides implicated in the pathophysiology of Alzheimer's disease (AD). Despite significant scientific breakthroughs in the recent past, the existing non-transgenic animal models do not demonstrate accurate pathology of AD progression. This review has presented a concise mechanistic understanding of the intranasal amyloid-based animal model of AD, along with its advantages, challenges, and major limitations. Furthermore, discussions on how to combat these challenges to pave the road toward developing novel therapeutics for AD, have also been included. Preclinical exploration of repeated intranasal amyloid-beta exposure would certainly aid the translational development of a robust animal model of AD. This will also provide a better understanding of disease progression and pathology in the intranasal animal model.

Healing of ischemic injury in the retina

Neuro- and retinal degenerative diseases, including Alzheimer's, age-related macular degeneration, stroke, and central retinal artery occlusion, rob millions of their independence. Studying these diseases in human retinas has been hindered by the immediate loss of neuronal activity postmortem. While recent studies restored limited activity in postmortem CNS tissues, synchronized neuronal transmission >30 minutes postmortem remained elusive. Our study overcomes this barrier by reviving and sustaining light signal transmission in human retinas recovered up to four hours and stored 48 hours postmortem. We also establish infrared-based ex vivo imaging for precise sampling, a closed perfusion system for drug testing, and an ex vivo ischemia-reperfusion model in mouse and human retina. This platform enables testing of neuroprotective and neurotoxic effects of drugs targeting oxidative stress and glutamate excitotoxicity. Our advances question the irreversibility of ischemic injury, support preclinical vision restoration studies, offer new insights into treating ischemic CNS injuries, and pave the way for transplantation of human donor eyes.

Teaser

Reviving light signaling in postmortem human retinas challenges the irreversibility of ischemic injury and advances research to restore vision.

Efficacy of reminiscence therapy in improving cognitive decline: a systematic review and meta-analysis

BACKGROUND

‌ Reminiscence therapy(RT) is used in the care of people with dementia to help improve their quality of life, but the efficacy of RT in various cognitive decline populations is unclear, and long-term effects are not sufficiently evidenced.This systematic review and meta-analysis aims to determine the efficacy of RT in improving cognitive decline and provide evidence for its implementation in care.

METHODS

A comprehensive search strategy utilizing MeSH terms and free-text keywords was employed to systematically search the Embase, PubMed, and Cochrane databases up to January 24, 2024. Randomized controlled trials(RCTs) investigating RT monotherapy for improving cognitive decline were included. The primary outcomes of interest were the standard Mini-Mental State Examination (MMSE) scores. Additionally, all data analyses will be performed using RevMan5.4 software.

RESULTS

‌ We identified 612 studies, and 24 studies met the inclusion criteria, involving 2650 participants. This meta-analysis shows that RT significantly improves immediate and long-term cognitive decline with Standardized Mean Difference(SMD) and 95% CI of 0.55 [0.37, 0.73] and 0.50 [0.11, 0.88], respectively. However, there is no significant difference in efficacy between subgroups (P > 0.05).

CONCLUSION

‌ Our findings suggestS that RT significantly improves cognitive decline, with no significant differences between subgroups. This suggests that RT is universal in improving cognition and that the way RT is implemented has no significant effect on outcomes. These findings supportS the use of RT as a reliable non-pharmacological treatment option to enhance cognitive function.

Microglial Responses to Alzheimer's Disease Pathology: Insights From "Omics" Studies

Human genetics studies lent firm evidence that microglia are key to Alzheimer's disease (AD) pathogenesis over a decade ago following the identification of AD-associated genes that are expressed in a microglia-specific manner. However, while alterations in microglial morphology and gene expression are observed in human postmortem brain tissue, the mechanisms by which microglia drive and contribute to AD pathology remain ill-defined. Numerous mouse models have been developed to facilitate the disambiguation of the biological mechanisms underlying AD, incorporating amyloidosis, phosphorylated tau, or both. Over time, the use of multiple technologies including bulk tissue and single cell transcriptomics, epigenomics, spatial transcriptomics, proteomics, lipidomics, and metabolomics have shed light on the heterogeneity of microglial phenotypes and molecular patterns altered in AD mouse models. Each of these 'omics technologies provide unique information and biological insight. Here, we review the literature on the approaches and findings of these methods and provide a synthesis of the knowledge generated by applying these technologies to mouse models of AD.

Investigating the neuroprotective effects of Dracocephalum moldavica extract and its effect on metabolomic profile of rat model of sporadic Alzheimer's disease

Alzheimer's disease (AD) is a progressive condition marked by multiple underlying mechanisms. Therefore, the investigation of natural products that can target multiple pathways presents a potential gate for the understanding and management of AD. This study aimed to assess the neuroprotective effects of the hydroalcoholic extract of Dracocephalum moldavica (DM) on cognitive impairment, biomarker changes, and putative metabolic pathways in a rat model of AD induced by intracerebroventricular streptozotocin (ICV-STZ). The DM extract was standardized and quantified based on examining total phenolic, total flavonoid, rosmarinic acid, and quercetin contents using colorimetry and high-performance liquid chromatography (HPLC) methods. The antioxidant potential of the extract was evaluated by 2,2-Diphenyl-1-picrylhydrazyl and nitric oxide radical scavenging assays. Male Wistar rats were injected with STZ (3 mg/kg, single dose, bilateral ICV) to induce a sporadic AD (sAD) model. Following model induction, rats were orally administered with DM extract (100, 200, and 400 mg/kg/day) or donepezil (5 mg/kg/day) for 21 days. Cognitive function was assessed using the radial arm water maze behavioral test. The histopathological evaluations were conducted in the cortex and hippocampus regions. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) was used to assess metabolite changes in various brain regions. DM extract significantly attenuated cognitive dysfunction induced by ICV-STZ according to behavioral and histopathological investigations. Thirty-two discriminating metabolites related to the amino acid metabolism; the glutamate/gamma-aminobutyric acid/glutamine cycle; nucleotide metabolism; lipid metabolism (glycerophospholipids, sphingomyelins, ceramides, phosphatidylserines, and prostaglandins), and glucose metabolic pathways were identified in the brains of rats with sAD simultaneously for the first time in this model. Polyphenols in DM extract may contribute to the regulation of these pathways. After treatment with DM extract, 10 metabolites from the 32 identified ones were altered in the brain tissue of a rat model of sAD, most commonly at doses of 200 and 400 mg/kg. In conclusion, this study demonstrates the neuroprotective potential of DM by upregulation/downregulation of various pathophysiological biomarkers such as adenine, glycerophosphoglycerol, inosine, prostaglandins, and sphingomyelin induced by ICV-STZ in sAD. These findings are consistent with cognitive behavioral results and histopathological outcomes.

Methionine Aminopeptidase 2 (MetAP2) Inhibitor BL6 Attenuates Inflammation in Cultured Microglia and in a Mouse Model of Alzheimer's Disease

Methionine aminopeptidase 2 (MetAP2) plays an important role in the regulation of protein synthesis and post-translational processing. Preclinical/clinical applications of MetAP2 inhibitors for the treatment of various diseases have been explored because of their antiangiogenic, anticancer, antiobesity, antidiabetic, and immunosuppressive properties. However, the effects of MetAP2 inhibitors on CNS diseases are rarely examined despite the abundant presence of MetAP2 in the brain. Previously, we synthesized a novel boron-containing MetAP2 inhibitor, BL6, and found that it suppressed angiogenesis and adipogenesis yet improved glucose uptake. Here, we studied the anti-inflammatory effects of BL6 in SIM-A9 microglia and in a mouse model of Alzheimer's disease generated by the intracerebroventricular (icv) injection of streptozotocin (STZ). We found that BL6 reduced proinflammatory molecules, such as nitric oxide, iNOS, IL-1β, and IL-6, together with phospho-Akt and phospho-NF-κB p65, which were elevated in lipopolysaccharide (LPS)-activated microglial SIM-A9 cells. However, the LPS-induced reduction in Arg-1 and CD206 was attenuated by BL6, suggesting that BL6 promotes microglial M1 to M2 polarization. BL6 also decreased glial activation along with a reduction in phospho-tau and an elevation in synaptophysin in the icv-STZ mouse model. Thus, our experiments demonstrate an anti-neuroinflammatory action of BL6, suggesting possible clinical applications of MetAP2 inhibitors for brain disorders in which neuroinflammation is involved.

Therapeutic Potential of Experimental Stereotactic Hippocampal Cell Transplant in the Management of Alzheimer's Disease

Due to a continuous increase in life expectancy and the progress made in specialized healthcare, the incidence of Alzheimer's disease (AD) has dramatically increased to the point that it has become one of the main challenges of contemporary medicine. Despite a huge scientific and clinical effort, current treatments manage just a temporary alleviation of symptomatology but offer no cure. Modern trials involving cell transplantation in experimental animals require the involvement of neurosurgeons in the treatment protocol. CSF shunting, intraventricular infusions, or DBS for symptoms relief have been an integral part of the therapeutic arsenal from the very beginning. The development of stereotactic surgery has facilitated the experimental potential of cell transplantation in the hippocampus for Alzheimer's disease. We conducted a narrative review of the literature in the top three medical databases (PubMed, Science Direct, and Google Scholar) using the keywords "Alzheimer's disease", "hippocampus", and "transplant". After eliminating duplicates, 241 papers were selected and screened by title and abstract. Two reviewers independently analyzed the 88 papers and chose 32 experiments that involved stereotactic hippocampal transplantation of cells in experimental animals with AD. The stereotactic transplantation of cells such as mesenchymal stem cells (MSCs), neuronal stem cells (NSCs), induced pluripotent cells (iPSCs), astrocytes, and derivates from stem cells was analyzed. The experiments used either a chemically induced or transgenic AD model and observed the impact of the stereotactic transplantation with behavioral testing, MRS spectroscopy, and biochemical analysis. The stereotaxic method delivers minimal invasive treatment option by cell transplantation at the hippocampus. The results showed that amyloid deposits were lower after transplantation, showing a positive impact. Other impactful results involve proliferation of neurogenesis, downregulation of anti-inflammatory response, and increased neuronal plasticity. The increased precision with which the stereotaxic method manages to target deep structures of the brain and the results of the reviewed papers could represent an argument for future human trials. More studies are needed to confirm the viability of the transplanted cells and the long-term effects.

A Comprehensive Review on Preclinical Alzheimer's Disease Models: Evaluating their Clinical Relevance

Alzheimer's disease (AD) is a neurological disorder that increases with age and must be treated immediately by worldwide healthcare systems. Internal neurofibrillary tau tangles and extracellular amyloid accumulation have been widely recognized as the primary causes of Alzheimer's disease. These degenerative age-related ailments are expected to proliferate exponentially as life expectancy rises. Experimental models of AD are essential for acquiring a deep knowledge of its pathogenesis and determining the viability of novel therapy options. Although there isn't a model that encompasses all the characteristics of real AD, these models are nonetheless highly helpful for the research of various modifications associated with it, even though they are only partially indicative of the disease circumstances being studied. Better knowledge of the advantages and disadvantages of each of the different models, as well as the use of more than one model to evaluate potential medications, would increase the effectiveness of therapy translation from preclinical research to patients. We outline the pathogenic characteristics and limitations of the main experimental models of AD in this review, including transgenic mice, transgenic rats, primates and non-primate models along with in-vitro cell culture models in humans. Additionally, it highlights the possible future of experimental modeling of AD and includes the co-morbid models.

Ideal animal models according to multifaceted mechanisms and peculiarities in neurological disorders: present and challenges

Neurological disorders, encompassing conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), pose a significant global health challenge, affecting millions worldwide. With an aging population and increased life expectancy, the prevalence of these disorders is escalating rapidly, leading to substantial economic burdens exceeding trillions of dollars annually. Animal models play a crucial role in understanding the underlying mechanisms of these disorders and developing effective treatments. Various species, including rodents, non-human primates, and fruit flies, are utilized to replicate specific aspects of human neurological conditions. However, selecting the ideal animal model requires careful consideration of its proximity to human disease conditions and its ability to mimic disease pathobiology and pharmacological responses. An Animal Model Quality Assessment (AMQA) tool has been developed to facilitate this selection process, focusing on assessing models based on their similarity to human conditions and disease pathobiology. Therefore, integrating intrinsic and extrinsic factors linked to the disease into the study's objectives aids in constructing a biological information matrix for comparing disease progression between the animal model and human disease. Ultimately, selecting an ideal animal disease model depends on its predictive, face, and construct validity, ensuring relevance and reliability in translational research efforts.

Research on Alzheimer's Disease (AD) Involving the Use of In vivo and In vitro Models and Mechanisms

BACKGROUND

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by the progressive formation of extracellular amyloid plaques, intracellular neurofibrillary tangles, inflammation, and impaired antioxidant systems. Early detection and intervention are vital for managing AD effectively.

OBJECTIVES

This review scrutinizes both in-vivo and in-vitro screening models employed in Alzheimer's disease research. in-vivo models, including transgenic mice expressing AD-related mutations, offer profound insights into disease progression and potential therapeutic targets. A thorough understanding of these models and mechanisms will facilitate the development of novel therapies and interventions for Alzheimer's disease. This review aims to provide an overview of the current experimental models in AD research, assess their strengths and weaknesses as model systems, and underscore the future prospects of experimental AD modeling.

METHODS

We conducted a systematic literature search across multiple databases, such as Pub- Med, Bentham Science, Elsevier, Springer Nature, Wiley, and Research Gate. The search strategy incorporated pertinent keywords related to Alzheimer's disease, in-vivo models, in-vitro models, and screening mechanisms. Inclusion criteria were established to identify studies focused on in-vivo and in-vitro screening models and their mechanisms in Alzheimer's disease research. Studies not meeting the predefined criteria were excluded from the review.

RESULTS

A well-structured experimental animal model can yield significant insights into the neurobiology of AD, enhancing our comprehension of its pathogenesis and the potential for cutting-edge therapeutic strategies. Given the limited efficacy of current AD medications, there is a pressing need for the development of experimental models that can mimic the disease, particularly in pre-symptomatic stages, to investigate prevention and treatment approaches. To address this requirement, numerous experimental models replicating human AD pathology have been established, serving as invaluable tools for assessing potential treatments.

CONCLUSION

In summary, this comprehensive review underscores the pivotal role of in-vivo and in-vitro screening models in advancing our understanding of Alzheimer's disease. These models offer invaluable insights into disease progression, pathological mechanisms, and potential therapeutic targets. By conducting a rigorous investigation and evaluation of these models and mechanisms, effective screening and treatment methods for Alzheimer's disease can be devised. The review also outlines future research directions and areas for enhancing AD screening models.

Crotalaria quinquefolia L. Revealed as a Potential Source of Neuropharmacophore in Both Experimental and Computational Studies

Herbal remedies have shown great promise for improving human health. The plant Crotalaria quinquefolia is used in folk medicine to cure different diseases, including scabies, fever, discomfort, and lung infections. The present research was designed to explore bioactive compounds and evaluate the neuropharmacological effects of C. quinquefolia extract through in vivo and in silico approaches. Different secondary metabolites as well as the antioxidant activity were measured. Furthermore, chemical compounds were identified by HPLC and GCMS analysis. The neuropharmacological activity was examined by hole cross, hole board, open field, Y-maze, elevated plus maze, and thiopental sodium induced sleeping time tests in mice at doses of 100 mg/kg and 200 mg/kg b.w. (p.o). Besides, an in-silico study was performed on proteins related to Alzheimer disease. The extract showed a significant content of secondary metabolites and antioxidant potential. The in-silico analysis showed that myricetin, quercetin, rutin, and kaempferol have good binding affinity with studied proteins, and QSAR studies revealed potential benefits for treating dementia, and age-related macular degeneration. The findings of the present neurological activity collectively imply that the extract has strong CNS depressant and anxiolytic activity. Therefore, C. quinquefolia can be a potential source of compounds to treat Alzheimer disease.

Surface engineered nano architectonics: An evolving paradigm for tackling Alzheimer's disease

As per the World Health Organization (WHO) estimation, Alzheimer's disease (AD) will affect 100 million population across the globe by 2050. AD is an incurable neurodegenerative disease that remains a mystery for neurologists owing to its complex pathophysiology. Currently, available therapeutic regimens will only cause symptomatic relief by improving the cognitive and behavioral functions of AD. However, the major pitfalls in managing AD include tight junctions in the endothelial cells of the blood-brain barrier (BBB), diminished neuronal bioavailability, enzymatic degradation and reduced stability of the therapeutic moiety. In an effort to surmount the drawbacks mentioned above, researchers shifted their focus toward nanocarriers (NCs). Nevertheless, non-specific targeting of NCs imparts toxicity to the peripheral organs, thereby reducing the bioavailability of therapeutic moiety at the target site. To unravel this unmet clinical need, scientists came up with the idea of a novel intriguing strategy of surface engineering by targeting ligands. Surface-decorated NCs provide targeted drug delivery, controlled drug release, enhanced penetration and bioavailability. In this state-of-the-art review, we have highlighted in detail various molecular signalling pathways involved in AD pathogenesis. The significance of surface functionalization and its application in AD management have been deliberated. We have elaborated on the regulatory bottlenecks and clinical hurdles faced during lab-to-industrial scale translation along with possible solutions.

Oral administration of butylated hydroxytoluene induces neuroprotection in a streptozotocin-induced rat Alzheimer's disease model via inhibition of neuronal ferroptosis

BACKGROUND

Alzheimer's disease (AD) is the most common human neurodegenerative disorder worldwide. Owing to its chronic nature, our limited understanding of its pathophysiological mechanisms, and because of the lack of effective anti-AD drugs, AD represents a significant socio-economic challenge for all industrialized countries. Neuronal cell death is a key factor in AD pathogenesis and recent studies have suggested that neuronal ferroptosis may play a major patho-physiological role. Since ferroptosis involves free radical-mediated lipid peroxidation, we hypothesized that enteral administration of the radical scavenger butylated hydroxytoluene (BHT) might slow down or even prevent the development of AD-related symptoms in an in vivo animal AD model.

MATERIAL AND METHODS

To test this hypothesis, we employed the rat model of streptozotocin-induced AD and administered butylated hydroxytoluene orally at a dose of 120 mg/kg body weight. Following BHT treatment, neuronal cell death was induced by bilateral stereotactic intraventricular injection of streptozotocin at a dose of 3.0 mg/kg body weight. Three weeks after surgery, we assessed the learning capabilities and the short-term memory of three experimental groups using the conventional y-maze test: (i) streptozotocin-treated rats (BHT pre-treatment), (ii) streptozotocin-treated rats (no BHT pre-treatment), (iii) sham-operated rats (BHT pre-treatment but no streptozotocin administration). After the y-maze test, the animals were sacrificed, hippocampal tissue was prepared and several biochemical (malonyl dialdehyde formation, glutathione homeostasis, gene expression patterns) and histochemical (Congo-red staining, Nissl staining, Perls staining) readout parameters were quantified.

RESULTS

Intraventricular streptozotocin injection induced the development of AD-related symptoms, elevated the degree of lipid peroxidation and upregulated the expression of ferroptosis-related genes. Histochemical analysis indicated neuronal cell death and neuroinflammation, which were paralleled by aberrant intraneuronal iron deposition. The streptozotocin-induced alterations were significantly reduced and sometimes even abolished by oral BHT treatment.

CONCLUSION

Our data indicate that oral BHT treatment attenuated the development of AD-related symptoms in an in vivo rat model, most probably via inhibiting neuronal ferroptosis. These findings suggest that BHT might constitute a promising candidate as anti-AD drug. However, more work is needed to explore the potential applicability of BHT in other models of neurodegeneration and in additional ferroptosis-related disorders.

Repositioning Canagliflozin for Mitigation of Aluminium Chloride-Induced Alzheimer's Disease: Involvement of TXNIP/NLRP3 Inflammasome Axis, Mitochondrial Dysfunction, and SIRT1/HMGB1 Signalling

Background and Objectives: Alzheimer's disease (AD) is the most common neurodegenerative disorder in the world. Due to failure of the traditional drugs to produce a complete cure for AD, the search for new safe and effective lines of therapy has attracted the attention of ongoing research. Canagliflozin is an anti-diabetic agent with proven efficacy in the treatment of neurological disorders in which mitochondrial dysfunction, oxidative stress, apoptosis, and autophagy play a pathophysiological role. Elucidation of the potential effects of different doses of canagliflozin on AD induced by aluminium chloride in rats and exploration of the molecular mechanisms that may contribute to these effects were the primary objectives of the current study. Materials and Methods: In a rat model of AD, the effect of three different doses of canagliflozin on the behavioural, biochemical, and histopathological alterations induced by aluminium chloride was assessed. Results: Canagliflozin administered to aluminium chloride-treated animals induced dose-dependent normalisation in the behavioural tests, augmentation of the antioxidant defence mechanisms, inhibition of TXNIP/NLRP3 inflammasome signalling, modulation of the SIRT1/HMGB1 axis, interference with the pro-inflammatory and the pro-apoptotic mechanisms, and restoration of the mitochondrial functions and autophagy in the hippocampal tissues to approximately baseline values. In addition, canagliflozin exhibited an interesting dose-dependent ability to repress aluminium chloride-induced histopathological changes in the brain. Conclusions: The effects of canagliflozin on oxidative stress, mitochondrial functions, inflammatory pathways, and autophagy signals may open new gates towards the mitigation of the pathologic features of AD.

Neuroprotective Effect of Ixeris dentata Extract on Trimethyltin-Induced Memory Impairment in Rats

Alzheimer's disease (AD) is a representative neurodegenerative disease characterized by the structural and functional degeneration of neurons. The present study investigated the neuroprotective effect of Ixeris dentata (ID) extract on trimethyltin (TMT)-induced memory deficit in the rat. Cognitive improving effect and neuronal activity of ID were assessed by using Morris water maze (MWM) test and choline acetyltransferase (ChAT), cAMP-response element-binding protein (CREB) immunohistochemistry. Seven days after TMT injection (8.0 mg/kg, i.p.), each group of rats was administered saline, water extract of ID (WID, 400 or 800 mg/kg, p.o.), ethanol extract of ID (EID, 400 or 800 mg/kg, p.o.), or caffeic acid (CAF, 30 mg/kg, i.p.) daily for fourteen days. Results: Treatment with EID and CAF produced a significant improvement in escape latency time of the acquisition, and retention time in the target area of the MWM task. Additionally, administration of EID or CAF markedly alleviated TMT-induced loss of ChAT- and CREB-immunoreactive cells in the hippocampus. The results demonstrated that EID has a protective effect against TMT-induced memory deficit, partly through increasing the CREB and cholinergic signaling pathway in the hippocampus. These results suggest that ethanol extracts of ID might be useful for improving cognitive functions in neurodegenerative diseases such as Alzheimer's disease.

Astrocyte dysfunction alters GABAergic communication and ammonia metabolism in the streptozotocin-induced sporadic Alzheimer's disease model

Background

In the sporadic model of Alzheimer's disease (AD), induced by intracerebroventricular streptozotocin (STZ) administration, cognitive impairment is accompanied by specific astrocytic changes in the hippocampus prior to amyloid deposition.

Objective

Hypothesizing that the synthesis of GABA, via MAO-B, contributes to ammonia elevation, thereby compromising antioxidant defense and ATP synthesis, and possibly contributing to cognitive damage, we determined the hippocampal levels of glutamine synthetase (GS), monoamine oxidase B (MAO-B) and other enzymes related to GABA metabolism.

Methods

Immunoblotting and RT-PCR assays were carried out in hippocampal samples of Wistar rats, at 4 and 16 weeks post-STZ, in the sporadic STZ-induced AD model, corresponding to the pre-amyloid and amyloid phases, respectively.

Results

We observed a reduction in GS activity and increased MAO-B content, both in 4 weeks and in 16 weeks, reinforcing the idea that astroglial dysfunction precedes the amyloid phase. These alterations were accompanied by an increase in the content of ornithine decarboxylase 1 (ODC1), which catalyzes the synthesis of putrescine (substrate for GABA synthesis, via MAO-B), and a reduction in the gene expression of arginine-glycine amidinotransferase (AGAT), an enzyme involved in the synthesis of creatine, and in the generation of GABA agonists. These changes were only seen in the amyloid phase of the AD model.

Conclusions

Our findings contribute to explain the greater damage that occurs in energy metabolism at this stage, in addition to the greater GABAergic loss. The changes reinforce the importance of the STZ model and further our understanding of the changes in both AD phases.

Calpeptin improves the cognitive function in Alzheimer's disease-like complications of diabetes mellitus rats by regulating TXNIP/NLRP3 inflammasome

AIMS

Diabetes mellitus (DM) is closely associated with Alzheimer's disease (AD), and is considered an accelerator of AD. Our previous study has confirmed that the Calpain inhibitor Calpeptin may alleviate AD-like complications of diabetes mellitus. This work further investigated its underlying mechanism.

MATERIALS AND METHODS

Diabetes mellitus rat model was constructed by a high-fat and high-sugar diet combined with streptozotocin, followed by the administration of Calpeptin. Moreover, rats were micro-injected with LV-TXNIP-OE/vector into the CA1 region of the hippocampus one day before streptozotocin injection. The Morris water maze test assessed the spatial learning and memory ability of rats. Immunohistochemistry and western blotting detected the expression of the pericyte marker PDGFRβ, tight junction proteins occludin and ZO-1, calpain-1, calpain-2, APP, Aβ, Aβ-related, and TXNIP/NLRP3 inflammasome-related proteins. Immunofluorescence staining examined the blood vessel density and neurons in the hippocampus. Evans blue extravasation and fluorescence detected the permeability of the blood-brain barrier (BBB) in rats. Additionally, the oxidative stress markers and inflammatory-related factors were assessed by enzyme-linked immunosorbent assay.

RESULTS

Calpeptin effectively reduced the expression of Calpain-2 and TXNIP/NLRP3 inflammasome-related proteins, improved the decreased pericyte marker (PDGFR-β) and cognitive impairment in hippocampus of DM rats. The neuronal loss, microvessel density, permeability of BBB, Aβ accumulation, inflammation, and oxidative stress injury in the hippocampus of DM rats were also partly rescued by calpeptin treatment. The influence conferred by calpeptin treatment was reversed by TXNIP overexpression.

CONCLUSIONS

These data demonstrated that calpeptin treatment alleviated AD-like symptoms in DM rats through regulating TXNIP/NLRP3 inflammasome. Thus, calpeptin may be a potential drug to treat AD-like complications of diabetes mellitus.

A Comprehensive Exploration of the Multifaceted Neuroprotective Role of Cannabinoids in Alzheimer's Disease across a Decade of Research

Alzheimer's disease (AD), a progressive neurodegenerative disorder, manifests through dysregulation of brain function and subsequent loss of bodily control, attributed to β-amyloid plaque deposition and TAU protein hyperphosphorylation and aggregation, leading to neuronal death. Concurrently, similar cannabinoids to the ones derived from Cannabis sativa are present in the endocannabinoid system, acting through receptors CB1R and CB2R and other related receptors such as Trpv-1 and GPR-55, and are being extensively investigated for AD therapy. Given the limited efficacy and adverse effects of current available treatments, alternative approaches are crucial. Therefore, this review aims to identify effective natural and synthetic cannabinoids and elucidate their beneficial actions for AD treatment. PubMed and Scopus databases were queried (2014-2024) using keywords such as "Alzheimer's disease" and "cannabinoids". The majority of natural (Δ9-THC, CBD, AEA, etc.) and synthetic (JWH-133, WIN55,212-2, CP55-940, etc.) cannabinoids included showed promise in improving memory, cognition, and behavioral symptoms, potentially via pathways involving antioxidant effects of selective CB1R agonists (such as the BDNF/TrkB/Akt pathway) and immunomodulatory effects of selective CB2R agonists (TLR4/NF-κB p65 pathway). Combining anticholinesterase properties with a cannabinoid moiety may enhance therapeutic responses, addressing cholinergic deficits of AD brains. Thus, the positive outcomes of the vast majority of studies discussed support further advancing cannabinoids in clinical trials for AD treatment.

Revolutionizing Alzheimer's treatment: Harnessing human serum albumin for targeted drug delivery and therapy advancements

Alzheimer's disease (AD) is a neurodegenerative disorder initiated by amyloid-beta (Aβ) accumulation, leading to impaired cognitive function. Several delivery approaches have been improved for AD management. Among them, human serum albumin (HSA) is broadly employed for drug delivery and targeting the Aβ in AD owing to its biocompatibility, Aβ inhibitory effect, and nanoform, which showed blood-brain barrier (BBB) crossing ability via glycoprotein 60 (gp60) receptor and secreted protein acidic and rich in cysteine (SPARC) protein to transfer the drug molecules in the brain. Thus far, there is no previous review focusing on HSA and its drug delivery system in AD. Hence, the reviewed article aimed to critically compile the HSA therapeutic as well as drug delivery role in AD management. It also delivers information on how HSA-incorporated nanoparticles with surfaced embedded ligands such as TAT, GM1, and so on, not only improve BBB permeability but also increase neuron cell targetability in AD brain. Additionally, Aβ and tau pathology, including various metabolic markers likely BACE1 and BACE2, etc., are discussed. Besides, the molecular interaction of HSA with Aβ and its distinctive forms are critically reviewed that HSA can segregate Zn(II) and Cu(II) metal ions from Aβ owing to high affinity. Furthermore, the BBB drug delivery challenges in AD are addressed. Finally, the clinical formulation of HSA for the management of AD is critically discussed on how the HSA inhibits Aβ oligomer and fibril, while glycated HSA participates in amyloid plaque formation, i.e., β-structure sheet formation. This review report provides theoretical background on HSA-based AD drug delivery and makes suggestions for future prospect-related work.

Changes in Astroglial Water Flow in the Pre-amyloid Phase of the STZ Model of AD Dementia

Alzheimer's disease (AD) is an age-dependent neurodegenerative disease that is typically sporadic and has a high social and economic cost. We utilized the intracerebroventricular administration of streptozotocin (STZ), an established preclinical model for sporadic AD, to investigate hippocampal astroglial changes during the first 4 weeks post-STZ, a period during which amyloid deposition has yet to occur. Astroglial proteins aquaporin 4 (AQP-4) and connexin-43 (Cx-43) were evaluated, as well as claudins, which are tight junction (TJ) proteins in brain barriers, to try to identify changes in the glymphatic system and brain barrier during the pre-amyloid phase. Glial commitment, glucose hypometabolism and cognitive impairment were characterized during this phase. Astroglial involvement was confirmed by an increase in glial fibrillary acidic protein (GFAP); concurrent proteolysis was also observed, possibly mediated by calpain. Levels of AQP-4 and Cx-43 were elevated in the fourth week post-STZ, possibly accelerating the clearance of extracellular proteins, since these proteins actively participate in the glymphatic system. Moreover, although we did not see a functional disruption of the blood-brain barrier (BBB) at this time, claudin 5 (present in the TJ of the BBB) and claudin 2 (present in the TJ of the blood-cerebrospinal fluid barrier) were reduced. Taken together, data support a role for astrocytes in STZ brain damage, and suggest that astroglial dysfunction accompanies or precedes neuronal damage in AD.

Alcohol Use Disorder and Dementia: A Review

PURPOSE

By 2040, 21.6% of Americans will be over age 65, and the population of those older than age 85 is estimated to reach 14.4 million. Although not causative, older age is a risk factor for dementia: every 5 years beyond age 65, the risk doubles; approximately one-third of those older than age 85 are diagnosed with dementia. As current alcohol consumption among older adults is significantly higher compared to previous generations, a pressing question is whether drinking alcohol increases the risk for Alzheimer's disease or other forms of dementia.

SEARCH METHODS

Databases explored included PubMed, Web of Science, and ScienceDirect. To accomplish this narrative review on the effects of alcohol consumption on dementia risk, the literature covered included clinical diagnoses, epidemiology, neuropsychology, postmortem pathology, neuroimaging and other biomarkers, and translational studies. Searches conducted between January 12 and August 1, 2023, included the following terms and combinations: "aging," "alcoholism," "alcohol use disorder (AUD)," "brain," "CNS," "dementia," "Wernicke," "Korsakoff," "Alzheimer," "vascular," "frontotemporal," "Lewy body," "clinical," "diagnosis," "epidemiology," "pathology," "autopsy," "postmortem," "histology," "cognitive," "motor," "neuropsychological," "magnetic resonance," "imaging," "PET," "ligand," "degeneration," "atrophy," "translational," "rodent," "rat," "mouse," "model," "amyloid," "neurofibrillary tangles," "α-synuclein," or "presenilin." When relevant, "species" (i.e., "humans" or "other animals") was selected as an additional filter. Review articles were avoided when possible.

SEARCH RESULTS

The two terms "alcoholism" and "aging" retrieved about 1,350 papers; adding phrases-for example, "postmortem" or "magnetic resonance"-limited the number to fewer than 100 papers. Using the traditional term, "alcoholism" with "dementia" resulted in 876 citations, but using the currently accepted term "alcohol use disorder (AUD)" with "dementia" produced only 87 papers. Similarly, whereas the terms "Alzheimer's" and "alcoholism" yielded 318 results, "Alzheimer's" and "alcohol use disorder (AUD)" returned only 40 citations. As pertinent postmortem pathology papers were published in the 1950s and recent animal models of Alzheimer's disease were created in the early 2000s, articles referenced span the years 1957 to 2024. In total, more than 5,000 articles were considered; about 400 are herein referenced.

DISCUSSION AND CONCLUSIONS

Chronic alcohol misuse accelerates brain aging and contributes to cognitive impairments, including those in the mnemonic domain. The consensus among studies from multiple disciplines, however, is that alcohol misuse can increase the risk for dementia, but not necessarily Alzheimer's disease. Key issues to consider include the reversibility of brain damage following abstinence from chronic alcohol misuse compared to the degenerative and progressive course of Alzheimer's disease, and the characteristic presence of protein inclusions in the brains of people with Alzheimer's disease, which are absent in the brains of those with AUD.

Types of memory, dementia, Alzheimer's disease, and their various pathological cascades as targets for potential pharmacological drugs

Alzheimer's disease (AD) is the most common type of dementia accounting for 90% of cases; however, frontotemporal dementia, vascular dementia, etc. prevails only in a minority of populations. The term dementia is defined as loss of memory which further takes several other categories of memories like working memory, spatial memory, fear memory, and long-term, and short-term memory into consideration. In this review, these memories have critically been elaborated based on context, duration, events, appearance, intensity, etc. The most important part and purpose of the review is the various pathological cascades as well as molecular levels of targets of AD, which have extracellular amyloid plaques and intracellular hyperphosphorylated tau protein as major disease hallmarks. There is another phenomenon that either leads to or arises from the above-mentioned hallmarks, such as oxidative stress, mitochondrial dysfunction, neuroinflammation, cholinergic dysfunction, and insulin resistance. Several potential drugs like antioxidants, anti-inflammatory drugs, acetylcholinesterase inhibitors, insulin mimetics or sensitizers, etc. studied in various previous preclinical or clinical reports were put as having the capacity to act on these pathological targets. Additionally, agents directly or indirectly targeting amyloid and tau were also discussed. This could be further investigated in future research.

Cognitive decline, Aβ pathology, and blood-brain barrier function in aged 5xFAD mice

BACKGROUND

Patients with Alzheimer's disease (AD) develop blood-brain barrier dysfunction to varying degrees. How aging impacts Aβ pathology, blood-brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aβ levels, barrier function, and cognitive decline over time.

METHODS

5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the brain by two-photon microscopy. Images were processed and segmented to obtain intravascular intensity, extravascular intensity, and vessel diameters as a measure of barrier integrity. Mice were sacrificed after in vivo imaging to isolate brain and plasma for measuring Aβ levels. The effect of age and genotype were evaluated for each assay using generalized or cumulative-linked logistic mixed-level modeling and model selection by Akaike Information Criterion (AICc). Pairwise comparisons were used to identify outcome differences between the two groups.

RESULTS

5xFAD mice displayed spatial memory deficits compared to age-matched WT mice in the MWM assay, which worsened with age. Memory impairment was evident in 5xFAD mice by 2-threefold higher escape latencies, twofold greater cumulative distances until they reach the platform, and twice as frequent use of repetitive search strategies in the pool when compared with age-matched WT mice. Presence of the rd1 allele worsened MWM performance in 5xFAD mice at all ages but did not alter the rate of learning or probe trial outcomes. 9.5-month-old 15.5-month-old 5xFAD mice had twofold higher brain Aβ40 and Aβ42 levels (p < 0.001) and 2.5-fold higher (p = 0.007) plasma Aβ40 levels compared to 9.5-month-old 5xFAD mice. Image analysis showed that vessel diameters and intra- and extravascular dextran intensities were not significantly different in 9.5- and 15.5-month-old 5xFAD mice compared to age-matched WT mice.

CONCLUSION

5xFAD mice continue to develop spatial memory deficits and increased Aβ brain levels while aging. Given in vivo MP imaging limitations, further investigation with smaller molecular weight markers combined with advanced imaging techniques would be needed to reliably assess subtle differences in barrier integrity in aged mice.

Neuropathogenesis-on-chips for neurodegenerative diseases

Developing diagnostics and treatments for neurodegenerative diseases (NDs) is challenging due to multifactorial pathogenesis that progresses gradually. Advanced in vitro systems that recapitulate patient-like pathophysiology are emerging as alternatives to conventional animal-based models. In this review, we explore the interconnected pathogenic features of different types of ND, discuss the general strategy to modelling NDs using a microfluidic chip, and introduce the organoid-on-a-chip as the next advanced relevant model. Lastly, we overview how these models are being applied in academic and industrial drug development. The integration of microfluidic chips, stem cells, and biotechnological devices promises to provide valuable insights for biomedical research and developing diagnostic and therapeutic solutions for NDs.

Evolving therapeutic interventions for the management and treatment of Alzheimer's disease

Alzheimer's Disease (AD) patients experience diverse symptoms, including memory loss, cognitive impairment, behavioral abnormalities, mood changes, and mental issues. The fundamental objective of this review is to discuss novel therapeutic approaches, with special emphasis on recently approved marketed formulations for the treatment of AD, especially Aducanumab, the first FDA approved moiety that surpasses the blood-brain barrier (BBB) and reduces amyloid plaques in the brain, thereby reducing associated cognitive decline. However, it is still in the phase IV trial and is to be completed by 2030. Other drugs such as lecanemab are also under clinical trial and has recently been approved by the FDA and is also discussed here. In this review, we also focus on active and passive immunotherapy for AD as well as several vaccines, such as amyloid-beta epitope-based vaccines, amyloid-beta DNA vaccines, and stem cell therapy for AD, which are in clinical trials. Furthermore, ongoing pre-clinical trials associated with AD and other novel strategies such as curcumin-loaded nanoparticles, Crispr/ cas9, precision medicine, as well as some emerging therapies like anti-sense therapy are also highlighted. Additionally, we discuss some off-labeled drugs like non-steroidal anti-inflammatory drugs (NSAID), anti-diabetic drugs, and lithium, which can manage symptoms of AD and different non-pharmacological approaches are also covered which can help to manage AD. In summary, we have tried to cover all the therapeutic interventions which are available for the treatment and management of AD under sections approved, clinical phase, pre-clinical phase or futuristic interventions, off-labelled drugs, and non-pharmacological interventions for AD, offering positive findings and well as challenges that remain.

Butylated Hydroxytoluene (BHT) Protects SH-SY5Y Neuroblastoma Cells from Ferroptotic Cell Death: Insights from In Vitro and In Vivo Studies

Ferroptosis is a special kind of programmed cell death that has been implicated in the pathogenesis of a large number of human diseases. It involves dysregulated intracellular iron metabolism and uncontrolled lipid peroxidation, which together initiate intracellular ferroptotic signalling pathways leading to cellular suicide. Pharmacological interference with ferroptotic signal transduction may prevent cell death, and thus patients suffering from ferroptosis-related diseases may benefit from such treatment. Butylated hydroxytoluene (BHT) is an effective anti-oxidant that is frequently used in oil chemistry and in cosmetics to prevent free-radical-mediated lipid peroxidation. Since it functions as a radical scavenger, it has previously been reported to interfere with ferroptotic signalling. Here, we show that BHT prevents RSL3- and ML162-induced ferroptotic cell death in cultured human neuroblastoma cells (SH-SY5Y) in a dose-dependent manner. It prevents the RSL3-induced oxidation of membrane lipids and normalises the RSL3-induced inhibition of the intracellular catalytic activity of glutathione peroxidase 4. The systemic application of BHT in a rat Alzheimer's disease model prevented the upregulation of the expression of ferroptosis-related genes. Taken together, these data indicate that BHT interferes with ferroptotic signalling in cultured neuroblastoma cells and may prevent ferroptotic cell death in an animal Alzheimer's disease model.

Alzheimer's Disease-Related Proteins Targeted by Secondary Metabolite Compounds from Streptomyces: A Scoping Review

Background

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized as rapid and progressive cognitive decline affecting 26 million people worldwide. Although immunotherapies are ideal, its clinical safety and effectiveness are controversial, hence, treatments are still reliant on symptomatic medications. Concurrently, the Streptomyces genus has attracted attention given its pharmaceutically beneficial secondary metabolites to treat neurodegenerative diseases.

Objective

To present secondary metabolites from Streptomyces sp. with regulatory effects on proteins and identified prospective target proteins for AD treatment.

Methods

Research articles published between 2010 and 2021 were collected from five databases and 83 relevant research articles were identified. Post-screening, only 12 research articles on AD-related proteins were selected for further review. Bioinformatics analyses were performed through the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) network, PANTHER Go-Slim classification system (PANTHER17.0), and Kyoto Encyclopedia of Genes and Genomes (KEGG) Mapper.

Results

A total of 20 target proteins were identified from the 12 shortlisted articles. Amyloid-β, BACE1, Nrf-2, Beclin-1, and ATG5 were identified as the potential target proteins, given their role in initiating AD, mitigating neuroinflammation, and autophagy. Besides, 10 compounds from Streptomyces sp., including rapamycin, alborixin, enterocin, bonnevillamides D and E, caniferolide A, anhydroexfoliamycin, rhizolutin, streptocyclinone A and B, were identified to exhibit considerable regulatory effects on these target proteins.

Conclusions

The review highlights several prospective target proteins that can be regulated through treatments with Streptomyces sp. compounds to prevent AD's early stages and progression. Further identification of Streptomyces sp. compounds with potential anti-AD properties is recommended.

Insight into the emerging and common experimental in-vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial, rapidly progressing neurodegenerative disorder. As the exact cause of the disease is still unclear, the drug development is very challenging. This review encompasses the commonly used AD models involving various chemicals, heavy metals and endogenous substances induced models and the transgenic models. It also provides insight into the reliable emerging models of AD that may overcome the shortcomings associated with available models. Chemicals like streptozotocin, scopolamine, colchicine and okadaic acid render the animal susceptible to neuroinflammation and oxidative stress induced neurodegeneration along with amyloid-β deposition and tau hyperphosphorylation. Similarly, endogenous substances like acrolein and amyloid-β 1-42 are efficient in inducing the major pathologies of AD. Heavy metals like aluminum and fluoride and mixture of these have been reported to induce neurotoxicity therefore are used as animal models for AD. Transgenic models developed as a result of knock-in or knock-out of certain genes associated with AD including PDAPP, APP23, Tg2576, APP/PS1, 3 × Tg and 5 × FAD have also been incorporated in this study. Further, emerging and advanced pathomimetic models of AD are provided particular interest here which will add on to the current knowledge of animal models and may aid in the drug development process and deepen our understanding related to AD pathogenesis. These newly discovered models include oAβ25-35 model, transgenic model expressing 82-kDa ChAT, oDGal mouse and APP knock-in rat. This study may aid in the selection of suitable model for development of novel potent therapeutics and for exploring detailed pathogenic mechanism of AD.

Neuromodulatory effect of vardenafil on aluminium chloride/D-galactose induced Alzheimer's disease in rats: emphasis on amyloid-beta, p-tau, PI3K/Akt/p53 pathway, endoplasmic reticulum stress, and cellular senescence

Dysregulation of protein homeostasis, proteostasis, is a distinctive hallmark of many neurodegenerative disorders and aging. Deleteriously, the accumulation of aberrant proteins in Alzheimer's disease (AD) is accompanied with a marked collapse in proteostasis network. The current study explored the potential therapeutic effect of vardenafil (VAR), a phosphodiesterase-5 inhibitor, in AlCl3/D-galactose (D-gal)-induced AD in rats and its possible underlying mechanisms. The impact of VAR treatment on neurobehavioral function, hippocampal tissue architecture, and the activity of the cholinergic system main enzymes were assessed utilizing VAR at doses of 0.3 mg/kg and 1 mg/kg. Additionally, the expression level of amyloid-beta and phosphorylated tau proteins in the hippocampus were figured out. Accordingly, VAR higher dose was selected to contemplate the possible underlying mechanisms. Intriguingly, VAR elevated the cyclic guanosine monophosphate level in the hippocampus and averted the repressed proteasome activity by AlCl3/D-gal; hence, VAR might alleviate the burden of toxic protein aggregates in AD. In addition, a substantial reduction in the activating transcription factor 6-mediated endoplasmic reticulum stress was demonstrated with VAR treatment. Notably, VAR counteracted the AlCl3/D-gal-induced depletion of nuclear factor erythroid 2-related factor 2 level. Moreover, the anti-senescence activity of VAR was demonstrated via its ability to restore the balance of the redox circuit. The modulation of phosphatidylinositol-3-kinase/protein kinase B/p53 pathway and the reduction of nuclear factor kappa B level, the key regulator of senescence-associated secretory phenotype mediators release, with VAR treatment were also elucidated. Altogether, these findings insinuate the possible therapeutic benefits of VAR in AD management.

Isolation, Identification, Activity Evaluation, and Mechanism of Action of Neuroprotective Peptides from Walnuts: A Review

As human life expectancy increases, the incidence of neurodegenerative diseases in older adults has increased in parallel. Walnuts contain bioactive peptides with demonstrated neuroprotective effects, making them a valuable addition to the diet. We here present a comprehensive review of the various methods used to prepare, isolate, purify, and identify the neuroprotective peptides found in walnuts. We further summarise the different approaches currently used to evaluate the activity of these peptides in experimental settings, highlighting their potential to reduce oxidative stress, neuroinflammation, and promote autophagy, as well as to regulate the gut microflora and balance the cholinergic system. Finally, we offer suggestions for future research concerning bioavailability and improving or masking the bitter taste and sensory properties of final products containing the identified walnut neuroprotective peptides to ensure successful adoption of these peptides as functional food ingredients for neurohealth promotion.

Imidazoles as Serotonin Receptor Modulators for Treatment of Depression: Structural Insights and Structure-Activity Relationship Studies

Serotoninergic signaling is identified as a crucial player in psychiatric disorders (notably depression), presenting it as a significant therapeutic target for treating such conditions. Inhibitors of serotoninergic signaling (especially selective serotonin reuptake inhibitors (SSRI) or serotonin and norepinephrine reuptake inhibitors (SNRI)) are prominently selected as first-line therapy for the treatment of depression, which benefits via increasing low serotonin levels and norepinephrine by blocking serotonin/norepinephrine reuptake and thereby increasing activity. While developing newer heterocyclic scaffolds to target/modulate the serotonergic systems, imidazole-bearing pharmacophores have emerged. The imidazole-derived pharmacophore already demonstrated unique structural characteristics and an electron-rich environment, ultimately resulting in a diverse range of bioactivities. Therefore, the current manuscript discloses such a specific modification and structural activity relationship (SAR) of attempted derivatization in terms of the serotonergic efficacy of the resultant inhibitor. We also featured a landscape of imidazole-based development, focusing on SAR studies against the serotoninergic system to target depression. This study covers the recent advancements in synthetic methodologies for imidazole derivatives and the development of new molecules having antidepressant activity via modulating serotonergic systems, along with their SAR studies. The focus of the study is to provide structural insights into imidazole-based derivatives as serotonergic system modulators for the treatment of depression.

Impact of common ALDH2 inactivating mutation and alcohol consumption on Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme found in the mitochondrial matrix that plays a central role in alcohol and aldehyde metabolism. A common ALDH2 polymorphism in East Asians descent (called ALDH2*2 or E504K missense variant, SNP ID: rs671), present in approximately 8% of the world's population, has been associated with a variety of diseases. Recent meta-analyses support the relationship between this ALDH2 polymorphism and Alzheimer's disease (AD). And AD-like pathology observed in ALDH2-/- null mice and ALDH2*2 overexpressing transgenic mice indicate that ALDH2 deficiency plays an important role in the pathogenesis of AD. Recently, the worldwide increase in alcohol consumption has drawn attention to the relationship between heavy alcohol consumption and AD. Of potential clinical significance, chronic administration of alcohol in ALDH2*2/*2 knock-in mice exacerbates the pathogenesis of AD-like symptoms. Therefore, ALDH2 polymorphism and alcohol consumption likely play an important role in the onset and progression of AD. Here, we review the data on the relationship between ALDH2 polymorphism, alcohol, and AD, and summarize what is currently known about the role of the common ALDH2 inactivating mutation, ALDH2*2, and alcohol in the onset and progression of AD.

The Role of Hydrogen Sulfide (H2S) in Epigenetic Regulation of Neurodegenerative Diseases: A Systematic Review

This review explores the emerging role of hydrogen sulfide (H2S) in modulating epigenetic mechanisms involved in neurodegenerative diseases. Accumulating evidence has begun to elucidate the multifaceted ways in which H2S influences the epigenetic landscape and, subsequently, the progression of various neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease. H2S can modulate key components of the epigenetic machinery, such as DNA methylation, histone modifications, and non-coding RNAs, impacting gene expression and cellular functions relevant to neuronal survival, inflammation, and synaptic plasticity. We synthesize recent research that positions H2S as an essential player within this intricate network, with the potential to open new therapeutic avenues for these currently incurable conditions. Despite significant progress, there remains a considerable gap in our understanding of the precise molecular mechanisms and the potential therapeutic implications of modulating H2S levels or its downstream targets. We conclude by identifying future directions for research aimed at exploiting the therapeutic potential of H2S in neurodegenerative diseases.

Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma ameliorate scopolamine-induced cognitive impairment by regulating the cholinergic and synaptic associated proteins

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Polygoni Multiflori Radix Praeparata (PMRP) and Acori Tatarinowii Rhizoma (ATR) is often used in traditional Chinese medicine to prevent and treat Alzheimer's disease (AD). However, it is not clear whether the effects and mechanisms of the decoction prepared by traditional decocting method (PA) is different from that prepared by modern decocting method (P + A).

AIM OF THE STUDY

The present study aimed to investigate the differences in the protective effects of PA and P + A on scopolamine induced cognitive impairment, and to explore its potential mechanism.

MATERIALS AND METHODS

To assess the protective effect of PA and P + A on cognitive dysfunction, the mice were orally administrated with PA (1.56, 6.24 g kg^-1•day^-1) and P + A (1.56, 6.24 g kg^-1•day^-1) for 26 days before co-treatment with scopolamine (4 mg kg^-1•day^-1, i.p.). The learning and memory abilities of mice were examined by Morris water maze test, and the expressions of proteins related to cholinergic system and synaptic function were detected by the methods of ELISA, real-time PCR and Western blotting. Then, molecular docking technique was used to verify the effect of active compounds in plasma after PA administration on Acetylcholinesterase (AChE) protein. Finally, the Ellman method was used to evaluate the effects of different concentrations of PA, P + A (1 μg/mL-100 mg/mL) and the compounds (1-100 μM) on AChE activity in vitro.

RESULTS

On one hand, in the scopolamine-induced cognitive impairment mouse model, both of PA and P + A could improve the cognitive impairment, while the effect of PA on cognitive amelioration was better than that of P + A. Moreover, PA regulated the cholinergic and synaptic functions by enhancing the concentration of acetylcholine (ACh), the mRNA levels of CHT1, Syn, GAP-43 and PSD-95, and the related proteins (CHT1, VACHT, Syn, GAP-43 and PSD-95), and significantly inhibiting the expression of AChE protein. Meanwhile, P + A only up-regulated the mRNA levels of GAP-43 and PSD-95, increased the expressions of CHT1, VACHT, Syn, GAP-43 and PSD-95 proteins, and inhibited the expression of AChE protein. On the other hand, the in vitro study showed that some compounds including emodin-8-o-β-d-Glucopyranoside, THSG and α-Asarone inhibited AChE protein activity with the IC₅₀ values 3.65 μM, 5.42 μM and 9.43 μM, respectively.

CONCLUSIONS

These findings demonstrate that both of PA and P + A can ameliorate the cognitive deficits by enhancing cholinergic and synaptic related proteins, while PA has the stronger improvement effect on the cholinergic function, which may be attributed to the compounds including THSG, emodin, emodin-8-O-β-D-glucopyranoside and α-asarone. The present study indicated that PA has more therapeutic potential in the treatment of neurodegenerative diseases such as AD. The results provide the experimental basis for the clinical use of PA.

Spontaneous and familial models of Alzheimer's disease: Challenges and advances in preclinical research

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder that is progressive and irreversible in nature. Even after decades of dedicated research and paradigm-shifting hypotheses of AD etiology, very few well-founded credible improvements have been foreseen in understanding the actual underlying mechanisms involved in the development of the disorder. As for any disease to be well-comprehended, AD also requires optimal modelling strategies, which will then pave way for effective therapeutic interventions. Most of the clinical trials and research towards better treatment of AD fail in translation, due to the inefficacy of explored animal models to mimic the actual AD pathology, precisely. The majority of the existing AD models are developed based on the mutations found in the familial form of AD (fAD) which accounts for less than 5 % of the incidence of AD. Further, the investigations also face more challenges due to the additional complexities and lacunae found in etiology of sporadic form of AD (sAD), which accounts for 95 % of total AD. This review illustrates the gaps found in different models of AD, both sporadic and familial variants with additional focus on recent avenues for accurate simulation of AD pathology using in vitro and chimeric AD models.