Curcumin Downregulates GSK3 and Cdk5 in Scopolamine-Induced Alzheimer's Disease Rats Abrogating Aβ40/42 and Tau Hyperphosphorylation

Curcumin: A Golden Approach to Healthy Aging: A Systematic Review of the Evidence

Aging-related disorders pose significant challenges due to their complex interplay of physiological and metabolic factors, including inflammation, oxidative stress, and mitochondrial dysfunction. Curcumin, a natural compound with potent antioxidant and anti-inflammatory properties, has emerged as a promising candidate for mitigating these age-related processes. However, gaps in understanding the precise mechanisms of curcumin's effects and the optimal dosages for different conditions necessitate further investigation. This systematic review synthesizes current evidence on curcumin's potential in addressing age-related disorders, emphasizing its impact on cognitive function, neurodegeneration, and muscle health in older adults. By evaluating the safety, efficacy, and mechanisms of action of curcumin supplementation, this review aims to provide insights into its therapeutic potential for promoting healthy aging. A systematic search across three databases using specific keywords yielded 2256 documents, leading to the selection of 15 clinical trials for synthesis. Here, we highlight the promising potential of curcumin as a multifaceted therapeutic agent in combating age-related disorders. The findings of this review suggest that curcumin could offer a natural and effective approach to enhancing the quality of life of aging individuals. Further research and well-designed clinical trials are essential to validate these findings and optimize the use of curcumin in personalized medicine approaches for age-related conditions.

Design and in vitro evaluation of curcumin-loaded PLGA nanoparticle-embedded sodium alginate/gelatin 3D printed scaffolds for Alzheimer's disease

BACKGROUND

Targeted nanoparticles (NPs) are aimed at improving clinical outcomes by enhancing the diagnostic and therapeutic efficacy of drugs in the treatment of Alzheimer's disease (AD).

METHODS

Curcumin (CUR)-loaded poly-lactic-co-glycolic acid (PLGA) NPs (CNPs) were produced to demonstrate a prolonged release and successfully embedded into 3D printed sodium alginate (SA)/gelatin (GEL) scaffolds that can dissolve rapidly sublingually. Characterization and in vitro activity of the NPs and scaffolds were evaluated.

RESULTS

Based on the in vitro drug release studies, 99.6 % of the encapsulated CUR was released in a controlled manner within 18 days for the CNPs. In vitro cell culture studies showed that all samples exhibited cell viability above 84.2 % and no significant cytotoxic effect on SH-SY5Y cells. The samples were analyzed through 2 different pathways by PCR analysis. Real-time PCR results indicated that CNP and CNP-embedded SA/GEL scaffolds (CNPSGS) may show neuroprotective effects by modulating the Wnt/β-catenin pathway. The gene expression level of β-catenin slightly increased compared to the gene expression levels of other proteins and enzymes with these treatments. However, the PI3K/Akt/GSK-3β signaling pathway was regulated at the same time because of the crosstalk between these 2 pathways.

CONCLUSION

CNPSGS might be an effective therapeutic alternative for AD treatment.

Progress in the Treatment of Central Nervous System Diseases Based on Nanosized Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) is widely used in clinical practice to treat diseases related to central nervous system (CNS) damage. However, the blood-brain barrier (BBB) constitutes a significant impediment to the effective delivery of TCM, thus substantially diminishing its efficacy. Advances in nanotechnology and its applications in TCM (also known as nano-TCM) can deliver active ingredients or components of TCM across the BBB to the targeted brain region. This review provides an overview of the physiological and pathological mechanisms of the BBB and systematically classifies the common TCM used to treat CNS diseases and types of nanocarriers that effectively deliver TCM to the brain. Additionally, drug delivery strategies for nano-TCMs that utilize in vivo physiological properties or in vitro devices to bypass or cross the BBB are discussed. This review further focuses on the application of nano-TCMs in the treatment of various CNS diseases. Finally, this article anticipates a design strategy for nano-TCMs with higher delivery efficiency and probes their application potential in treating a wider range of CNS diseases.

Temporal and region-specific tau hyperphosphorylation in the medulla and forebrain coincides with development of functional changes in male obese Zucker rats

Metabolic syndrome (MetS) is associated with development of tauopathies that contribute to cognitive decline. Without functional leptin receptors, male obese Zucker rats (OZRs) develop MetS, and they have increased phosphorylated tau (ptau) with impaired cognitive function. In addition to regulating energy balance, leptin enhances activation of the hippocampus, which is essential for spatial learning and memory. Whether spatial learning and memory are always impaired in OZRs or develop with MetS is unknown. We hypothesized that male OZRs develop MetS traits that promote regional increases in ptau and functional deficits associated with those brain regions. In the medulla and cortex, tau-pSer199,202 and tau-pSer396 were comparable in juvenile (7-8 wk old) lean Zucker rats (LZRs) and OZRs but increased in 18- to 19-wk-old OZRs. Elevated tau-pSer396 was concentrated in the dorsal vagal complex of the medulla, and by this age OZRs had hypertension with increased arterial pressure variability. In the hippocampus, tau-pSer199,202 and tau-pSer396 were still comparable in 18- to 19-wk-old OZRs and LZRs but elevated in 28- to 29-wk-old OZRs, with emergence of deficits in Morris water maze performance. Comparable escape latencies observed during acquisition in 18- to 19-wk-old OZRs and LZRs were increased in 28- to 29-wk-old OZRs, with greater use of nonspatial search strategies. Increased ptau developed with changes in the insulin/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway in the hippocampus and cortex but not medulla, suggesting different underlying mechanisms. These data demonstrate that leptin is not required for spatial learning and memory in male OZRs. Furthermore, early development of MetS-associated autonomic dysfunction by the medulla may be predictive of later hippocampal dysfunction and cognitive impairment.NEW & NOTEWORTHY Male obese Zucker rats (OZRs) lack functional leptin receptors and develop metabolic syndrome (MetS). At 16-19 wk, OZRs are insulin resistant, with increased ptau in dorsal medulla and impaired autonomic regulation of AP. At 28-29 wk OZRs develop increased ptau in hippocampus with deficits in spatial learning and memory. Juvenile OZRs lack elevated ptau and these deficits, demonstrating that leptin is not essential for normal function. Elevated ptau and deficits emerge before the onset of diabetes in insulin-resistant OZRs.

Targeted therapies for breast and lung cancers by using Propolis loaded albumin protein nanoparticles

BACKGROUND

Cancer is a popular disease among many others that can threaten human life. This is not only because of its invasiveness but also because of its resistance and the highly effective cost of its treatments. Propolis is rich in natural bioactive and polyphenolic compounds that have proven their strong effect on cancer cells such as MCF-7 and A549 cell lines.

METHODS

Propolis extract was immobilized into the bovine serum albumin (BSA) conjugated to folic acid (FA), to increase control of its delivery and to strengthen its cellular uptake.

RESULTS

The growth of MCF-7 was significantly decreased by propolis extract and BSA-propolis NPs after their incubation for 48 and 72 h by (54 ± 0.01 %, and 45 ± 0.005 %, P ≤ 0.001) and (20 ± 0.01 % and 10 ± 0.005 %, P ≤ 0.0001), respectively. Similarly, there is a significant inhibition in the growth of A549 obtained after their incubation with (propolis extract and albumin-propolis NPs) for 72 h (15 ± 0.03 % and 5 ± 0.01 %, P ≤ 0.00001). Propolis extract and BSA-propolis NPs exhibited a greater effect on protein expression of MCF-7 and A549, showing significant modulation of caspase-3, cyclin D1, and light chain 3 (LC3II). The result was supported by nuclear fragmentations and activation of acidic/neutral autophagosomes in acridine orange/ethidium bromide (AO/EB) and 4',6-diamidino-2-phenylindole (DAPI) nuclear stains. According to this study, the expression of phospho-GSK3β (Ser9) (p < 0.001) increased significantly in MCF-7 and A549 cells after their exposure to propolis extract and BSA-propolis NPs.

CONCLUSION

Results support the potency application of propolis and its encapsulation as an alternative therapeutic agent for cancer treatments instead of chemotherapies because of its action on multi-signaling pathways.

Curcumin hybrid molecules for the treatment of Alzheimer's disease: Structure and pharmacological activities

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly. Contemporary treatments can only relieve symptoms but fail to delay disease progression. Curcumin is a naturally derived compound that has demonstrated significant therapeutic effects in AD treatment. Recently, molecular hybridization has been utilized to combine the pharmacophoric groups present in curcumin with those of other AD drugs, resulting in a series of novel compounds that enhance the therapeutic efficacy through multiple mechanisms. In this review, we firstly provide a concise summary of various pathogenetic hypotheses of AD and the mechanism of action of curcumin in AD, as well as the concept of molecular hybridization. Subsequently, we focus on the recent development of hybrid molecules derived from curcumin, summarizing their structures and pharmacological activities, including cholinesterase inhibitory activity, Aβ aggregation inhibitory activity, antioxidant activity, and other activities. The structure-activity relationships were further discussed.

Triaging between post-translational modification of cell cycle regulators and their therapeutics in neurodegenerative diseases

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, present challenges in healthcare because of their complicated etiologies and absence of healing remedies. Lately, the emerging role of post-translational modifications (PTMs), in the context of cell cycle regulators, has garnered big interest as a potential avenue for therapeutic intervention. The review explores the problematic panorama of PTMs on cell cycle regulators and their implications in neurodegenerative diseases. We delve into the dynamic phosphorylation, acetylation, ubiquitination, SUMOylation, Glycation, and Neddylation that modulate the key cell cycle regulators, consisting of cyclins, cyclin-dependent kinases (CDKs), and their inhibitors. The dysregulation of these PTMs is related to aberrant cell cycle in neurons, which is one of the factors involved in neurodegenerative pathologies. Moreover, the effect of exogenous activation of CDKs and CDK inhibitors through PTMs on the signaling cascade was studied in postmitotic conditions of NDDs. Furthermore, the therapeutic implications of CDK inhibitors and associated alteration in PTMs were discussed. Lastly, we explored the putative mechanism of PTMs to restore normal neuronal function that might reverse NDDs.

Curcumin-derived carbon quantum dots: Dual actions in mitigating tau hyperphosphorylation and amyloid beta aggregation

The amyloid cascade and tau hypotheses both hold significant implications for the pathogenesis of Alzheimer's disease (AD). Curcumin shows potential by inhibiting the aggregation of amyloid beta (Aβ) and reducing tau hyperphosphorylation, however, its use is limited due to issues with solubility and bioavailability. Carbon dots, recognized for their high biocompatibility and optimal water solubility, have demonstrated the capability to inhibit either Aβ or tau aggregation. Nonetheless, their effects on tau hyperphosphorylation are yet to be extensively explored. This study aims to evaluate the water-soluble curcumin-derived carbon quantum dots (Cur-CQDs) synthesized via an eco-friendly method, designed to preserve the beneficial effects of curcumin while overcoming solubility challenges. The synthesis of Cur-CQDs involves a single-step dry heating process using curcumin, resulting in dots that exhibit negligible cytotoxicity to SH-SY5Y cells at the examined concentrations. Notably, Cur-CQDs have shown the ability to simultaneously mitigate Aβ aggregation and tau hyperphosphorylation. Therefore, it is suggested that Cur-CQDs may hold potential for AD treatment, a hypothesis deserving of further research.

Novel insights into D-Pinitol based therapies: a link between tau hyperphosphorylation and insulin resistance

Alzheimer's disease is a neurodegenerative disorder characterized by the amyloid accumulation in the brains of patients with Alzheimer's disease. The pathogenesis of Alzheimer's disease is mainly mediated by the phosphorylation and aggregation of tau protein. Among the multiple causes of tau hyperphosphorylation, brain insulin resistance has generated much attention, and inositols as insulin sensitizers, are currently considered candidates for drug development. The present narrative review revises the interactions between these three elements: Alzheimer's disease-tau-inositols, which can eventually identify targets for new disease modifiers capable of bringing hope to the millions of people affected by this devastating disease.

Alzheimer, Parkinson, dementia, and phytochemicals: insight review

Alzheimer's, Parkinson's, and dementia are the leading neurodegenerative diseases that threaten the world with the aging population. Although the pathophysiology of each disease is unique, the steps to be taken to prevent diseases are similar. One of the changes that a person can make alone is to gain the habit of an antioxidant-rich diet. Phytochemicals known for their antioxidant properties have been reported to prevent neurodegenerative diseases in various studies. Phytochemicals with similar chemical structures are grouped. Accordingly, there are two main groups of phytochemicals, flavonoid and non-flavonoid. Various in vitro and in vivo studies on phytochemicals have proven neuroprotective effects by increasing cognitive function with their anti-inflammatory and antioxidant mechanisms. The purpose of this review is to summarize the in vitro and in vivo studies on phytochemicals with neuroprotective effects and to provide insight.

Common Signaling Pathways Involved in Alzheimer's Disease and Stroke: Two Faces of the Same Coin

Alzheimer's disease (AD) and stroke are two interrelated neurodegenerative disorders which are the leading cause of death and affect the neurons in the brain and central nervous system. Although amyloid-β aggregation, tau hyperphosphorylation, and inflammation are the hallmarks of AD, the exact cause and origin of AD are still undefined. Recent enormous fundamental discoveries suggest that the amyloid hypothesis of AD has not been proven and anti-amyloid therapies that remove amyloid deposition have not yet slowed cognitive decline. However, stroke, mainly ischemic stroke (IS), is caused by an interruption in the cerebral blood flow. Significant features of both disorders are the disruption of neuronal circuitry at different levels of cellular signaling, leading to the death of neurons and glial cells in the brain. Therefore, it is necessary to find out the common molecular mechanisms of these two diseases to understand their etiological connections. Here, we summarized the most common signaling cascades including autotoxicity, ApoE4, insulin signaling, inflammation, mTOR-autophagy, notch signaling, and microbiota-gut-brain axis, present in both AD and IS. These targeted signaling pathways reveal a better understanding of AD and IS and could provide a distinguished platform to develop improved therapeutics for these diseases.

Effect of Curcumin and Coenzyme Q10 Alone and in Combination on Learning and Memory in an Animal Model of Alzheimer's Disease

The most frequent neurodegenerative illness among senior people and the main cause of dementia is Alzheimer's disease. The present dementia medications available only help with the symptoms of cognitive deficits and have several negative effects. The current study's goal is to assess the effects of curcumin and coenzyme Q10, two herbal medicines, both separately and in combination, on learning and memory before comparing them to the industry standard drug. A total of 42 adult healthy Wistar rats were used in our study. In this experiment, rats were given daily doses of 2.5 mg/kg of body weight of scopolamine hydrobromide for 7 days to induce Alzheimer's disease. On the eighth day, behavioural testing was conducted. Following testing, scopolamine and the test medications were given daily for the following 21 days. On days 29 and 30, behavioural testing was conducted once more, and then animals were slaughtered. Brain homogenate was produced for the estimation of molecular and biochemical markers. Curcumin has demonstrated a dose-response relationship, with a higher dose (200 mg/kg b.w. p.o.) being more effective than a lower dose (100 mg/kg b.w. p.o.). Similar to the greater dose of curcumin, coenzyme Q10 (200 mg/kg b.w. p.o.) has also been found to improve memory and learning. Higher doses of curcumin and coenzyme Q10 had more pronounced and meaningful effects. Acetylcholinesterase and TNF levels increased in scopolamine-induced memory impairment, but these effects were restored by the test medications, and improved by the combined therapy. These outcomes are comparable to those of the common medication memantine. As a result, we may infer from our results that curcumin at higher doses and its combination with coenzyme Q10 (200 mg/kg b.w. p.o.) have a significant impact on cognitive impairment in animal models of Alzheimer's disease and can be utilised alone or as an add-on therapy for the condition.

A novel rhein-huprine hybrid ameliorates disease-modifying properties in preclinical mice model of Alzheimer's disease exacerbated with high fat diet

BACKGROUND

Alzheimer's disease (AD) is characterized by a polyetiological origin. Despite the global burden of AD and the advances made in AD drug research and development, the cure of the disease remains elusive, since any developed drug has demonstrated effectiveness to cure AD. Strikingly, an increasing number of studies indicate a linkage between AD and type 2 diabetes mellitus (T2DM), as both diseases share some common pathophysiological features. In fact, β-secretase (BACE1) and acetylcholinesterase (AChE), two enzymes involved in both conditions, have been considered promising targets for both pathologies. In this regard, due to the multifactorial origin of these diseases, current research efforts are focusing on the development of multi-target drugs as a very promising option to derive effective treatments for both conditions. In the present study, we evaluated the effect of rhein-huprine hybrid (RHE-HUP), a synthesized BACE1 and AChE inhibitor, both considered key factors not only in AD but also in metabolic pathologies. Thus, the aim of this study is to evaluate the effects of this compound in APP/PS1 female mice, a well-established familial AD mouse model, challenged by high-fat diet (HFD) consumption to concomitantly simulate a T2DM-like condition.

RESULTS

Intraperitoneal treatment with RHE-HUP in APP/PS1 mice for 4 weeks reduced the main hallmarks of AD, including Tau hyperphosphorylation, Aβ₄₂ peptide levels and plaque formation. Moreover, we found a decreased inflammatory response together with an increase in different synaptic proteins, such as drebrin 1 (DBN1) or synaptophysin, and in neurotrophic factors, especially in BDNF levels, correlated with a recovery in the number of dendritic spines, which resulted in memory improvement. Notably, the improvement observed in this model can be attributed directly to a protein regulation at central level, since no peripheral modification of those alterations induced by HFD consumption was observed.

CONCLUSIONS

Our results suggest that RHE-HUP could be a new candidate for the treatment of AD, even for individuals with high risk due to peripheral metabolic disturbances, given its multi-target profile which allows for the improvement of some of the most important hallmarks of the disease.

Ameliorative effects of bromelain on aluminum-induced Alzheimer's disease in rats through modulation of TXNIP pathway

Alzheimer's disease (AD) is known as "type 3 diabetes". As thioredoxin binding protein (TXNIP) has been shown to be involved in brain insulin resistance, the present study evaluated the roles of TXNIP, phospho-insulin receptor substrate 1 (P-IRS-1), and phosphatidyl inositol-3 kinase (PI3K) in the pathogenesis of AD. The potential ameliorative effect of bromelain compared to donepezil was evaluated in an aluminum chloride (AlCl3)-induced AD in rats. Behavioral tests demonstrated similar improvements in exploratory activity, cognitive and spatial memory functions, anxiety, and depression levels between rats treated with bromelain and donepezil. Donepezil was superior to bromelain in improving locomotor activity. Histopathological examinations demonstrated neuronal degeneration in the AlCl3 group that was almost normalized by bromelain and donepezil. Moreover, there was deposition of amyloid plaques in the AlCl3 group that was improved by bromelain and donepezil. Acetylcholine esterase levels were significantly increased in rats treated with AlCl3 group and significantly decreased in rats treated with bromelain and donepezil. Furthermore, AlCl3 group showed a significantly increased TXNIP and P-IRS1 and a significantly reduced PI3K levels. These effects were ameliorated by bromelain and donepezil treatment. The present study demonstrates a previously unreported modulatory effect of bromelain on the TXNIP/P-IRS-1/PI3K axis in AD model.

Impaired Dopamine Release and Latent Learning in Alzheimer's Disease Model Zebrafish

Alzheimer's disease (AD) is a progressive, fatal, neurodegenerative disorder for which only treatments of limited efficacy are available. Despite early mentions of dementia in the ancient literature and the first patient diagnosed in 1906, the underlying causes of AD are not well understood. This study examined the possible role of dopamine, a neurotransmitter that is involved in cognitive and motor function, in AD. We treated adult zebrafish (Danio rerio) with okadaic acid (OKA) to model AD and assessed the resulting behavioral and neurochemical changes. We then employed a latent learning paradigm to assess cognitive and motor function followed by neurochemical analysis with fast-scan cyclic voltammetry (FSCV) at carbon fiber microelectrodes to measure the electrically stimulated dopamine release. The behavioral assay showed that OKA treatment caused fish to have lower motivation to reach the goal chamber, resulting in impeded learning and decreased locomotor activity compared to controls. Our voltammetric measurements revealed that the peak dopamine overflow in OKA-treated fish was about one-third of that measured in controls. These findings highlight the profound neurochemical changes that may occur in AD. Furthermore, they demonstrate that applying the latent learning paradigm and FSCV to zebrafish is a promising tool for future neurochemical studies and may be useful for screening drugs for the treatment of AD.

Recent advances of small molecule JNK3 inhibitors for Alzheimer's disease

C-Jun N-terminal kinase (JNK) is a member of mitogen-activated protein kinases (MAPKs) family, with three isoforms, JNK1, JNK2 and JNK3. Alzheimer's disease (AD) is a neurological disorder and the most common type of dementia. Two well-established AD pathologies are the deposition of Aβ amyloid plaques and neurofibrillary tangles caused by Tau hyperphosphorylation. JNK3 is involved in forming amyloid Aβ and neurofibrillary tangles, suggesting that JNK3 may represent a target to develop treatments for AD. Therefore, this review will discuss the roles of JNK3 in the pathogenesis and treatment of AD, and the latest progress in the development of JNK3 inhibitors.

A Flavonoid on the Brain: Quercetin as a Potential Therapeutic Agent in Central Nervous System Disorders

Quercetin is one of the most common, naturally occurring flavonoids, structurally classified to the flavonol subfamily. This compound, found in many edible and medicinal plants either as a free or glycosidated form, has been scientifically exploited for many years, and one could hardly expect it could be a hero of some additional story. Commonly recognized as an anti-inflammatory agent, quercetin not only limits capillary vessel permeability by inhibiting hyaluronidase but also blocks cyclooxygenases and lipoxygenases. As a typical flavonoid, it is also known for its antioxidant effect, which was confirmed by many in vitro and in vivo studies. Throughout the years, numerous other activities were reported for quercetin, including antidiabetic, anti-proliferative, or anti-viral. Of note, recent data have revealed its potential role as a therapeutic agent for several central nervous system disorders. This review provides an overview of available experimental data on quercetin and its complexes with respect to central nervous system diseases, with a main focus on some aspects that were not discussed previously, such as anti-anxiolytic effects, anti-Huntington’s disease activity, or therapeutic potential in brain cancer. Moreover, quercetin’s protective role in some of these diseases is discussed, especially as an anti-neuroinflammatory agent. Bearing in mind the poor bioavailability of this compound, possible options that would enhance its delivery to the site of action are also presented.

Discovery of a Potent and Selective JNK3 Inhibitor with Neuroprotective Effect Against Amyloid β-Induced Neurotoxicity in Primary Rat Neurons

As members of the MAPK family, c-Jun-N-terminal kinases (JNKs) regulate the biological processes of apoptosis. In particular, the isoform JNK3 is expressed explicitly in the brain at high levels and is involved in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). In this study, we prepared a series of five 6-dihydroxy-1H-benzo[d]imidazoles as JNK3 inhibitors and found them have potential as neuroprotective agents. Following a previous lead scaffold, benzimidazole moiety was modified with various aryl groups and hydroxylation, and the resulting compounds exhibited JNK3 inhibitory activity with improved potency and selectivity. Out of 37 analogues synthesized, (S)-cyclopropyl(3-((4-(2-(2,3-dihydrobenzo[b][1,4]dioxin -6-yl)-5,6-dihydroxy-1H-benzo[d]imidazol-1-yl)pyrimidin-2-yl)amino) piperidin-1-yl)methanone (35b) demonstrated the highest JNK3 inhibition (IC₅₀ = 9.7 nM), as well as neuroprotective effects against Aβ-induced neuronal cell death. As a protein kinase inhibitor, it also showed excellent selectivity over other protein kinases including isoforms JNK1 (>1000 fold) and JNK2 (−10 fold).

New therapeutics beyond amyloid-β and tau for the treatment of Alzheimer's disease

As the population ages, Alzheimer's disease (AD), the most common neurodegenerative disease in elderly people, will impose social and economic burdens to the world. Currently approved drugs for the treatment of AD including cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) and an N-methyl-D-aspartic acid receptor antagonist (memantine) are symptomatic but poorly affect the progression of the disease. In recent decades, the concept of amyloid-β (Aβ) cascade and tau hyperphosphorylation leading to AD has dominated AD drug development. However, pharmacotherapies targeting Aβ and tau have limited success. It is generally believed that AD is caused by multiple pathological processes resulting from Aβ abnormality, tau phosphorylation, neuroinflammation, neurotransmitter dysregulation, and oxidative stress. In this review we updated the recent development of new therapeutics that regulate neurotransmitters, inflammation, lipid metabolism, autophagy, microbiota, circadian rhythm, and disease-modified genes for AD in preclinical research and clinical trials. It is to emphasize the importance of early diagnosis and multiple-target intervention, which may provide a promising outcome for AD treatment.

GSK-3β, FYN, and DYRK1A: Master Regulators in Neurodegenerative Pathways

Protein kinases (PKs) have been recognized as central nervous system (CNS)-disease-relevant targets due to their master regulatory role in different signal transduction cascades in the neuroscience space. Among them, GSK-3β, FYN, and DYRK1A play a crucial role in the neurodegeneration context, and the deregulation of all three PKs has been linked to different CNS disorders with unmet medical needs, including Alzheimer’s disease (AD), Parkinson’s disease (PD), frontotemporal lobar degeneration (FTLD), and several neuromuscular disorders. The multifactorial nature of these diseases, along with the failure of many advanced CNS clinical trials, and the lengthy approval process of a novel CNS drug have strongly limited the CNS drug discovery. However, in the near-decade from 2010 to 2020, several computer-assisted drug design strategies have been combined with synthetic efforts to develop potent and selective GSK-3β, FYN, and DYRK1A inhibitors as disease-modifying agents. In this review, we described both structural and functional aspects of GSK-3β, FYN, and DYRK1A and their involvement and crosstalk in different CNS pathological signaling pathways. Moreover, we outlined attractive medicinal chemistry approaches including multi-target drug design strategies applied to overcome some limitations of known PKs inhibitors and discover improved modulators with suitable blood–brain barrier (BBB) permeability and drug-like properties.

Phenolic Profiling and Therapeutic Potential of Certain Isolated Compounds from Parkia roxburghii against AChE Activity as well as GABAA α5, GSK-3β, and p38α MAP-Kinase Genes

Parkia roxburghii belongs to the family Mimosaceae; it has been used since ancient times as a cure for different health complications; such as inflammatory and gynecological diseases and hemiplegia. In this investigation, a reversed-phase-high-performance liquid chromatography (RP-HPLC) profile was carried out for P. roxburghii; also, the isolated bioactive compounds including quercetin, catechin, and biochaninA were individually and/or in combination investigated for their inhibitory effects on scopolamine-induced memory impairments in mice, implying that they have the ability to reduce the neurodegenerative effects of scopolamine and thus could be employed as a more effective therapeutic agent in the treatment of Alzheimer's disease (AD) in humans. The possible interactions of Parkia flavonoids with acetylcholinesterase (AChE), γ-aminobutyric acid A receptor, alpha5 (GABA_A α5), glycogen synthase kinase-3 (GSK-3), p38 mitogen-activated protein kinase (p38MAP-kinase), signal-regulated kinase (ERK), and protein-serine/threonine kinase (Akt) were then determined using molecular docking.

Pharmacological relevance of CDK inhibitors in Alzheimer's disease

Evidence suggests that cell cycle activation plays a role in the pathophysiology of neurodegenerative diseases. Alzheimer's disease is a progressive, terminal neurodegenerative disease that affects memory and other important mental functions. Intracellular deposition of Tau protein, a hyperphosphorylated form of a microtubule-associated protein, and extracellular aggregation of Amyloid β protein, which manifests as neurofibrillary tangles (NFT) and senile plaques, respectively, characterize this condition. In recent years, however, several studies have concluded that cell cycle re-entry is one of the key causes of neuronal death in the pathogenesis of Alzheimer's disease. The eukaryotic cell cycle is well-coordinated machinery that performs critical functions in cell replenishment, such as DNA replication, cell creation, repair, and the birth of new daughter cells from the mother cell. The complex interplay between the levels of various cyclins and cyclin-dependent kinases (CDKs) at different checkpoints is needed for cell cycle synchronization. CDKIs (cyclin-dependent kinase inhibitors) prevent cyclin degradation and CDK inactivation. Different external and internal factors regulate them differently, and they have different tissue expression and developmental functions. The checkpoints ensure that the previous step is completed correctly before starting the new cell cycle phase, and they protect against the transfer of defects to the daughter cells. Due to the development of more selective and potent ATP-competitive CDK inhibitors, CDK inhibitors appear to be on the verge of having a clinical impact. This avenue is likely to yield new and effective medicines for the treatment of cancer and other neurodegenerative diseases. These new methods for recognizing CDK inhibitors may be used to create non-ATP-competitive agents that target CDK4, CDK5, and other CDKs that have been recognized as important therapeutic targets in Alzheimer's disease treatment.

Neuroprotective Studies of Evodiamine in an Okadaic Acid-Induced Neurotoxicity

Background: Alzheimer’s disease (AD) is the most common neurodegenerative disease, and it manifests as progressive memory loss and cognitive decline. However, there are no effective therapies for AD, which is an urgent problem to solve. Evodiamine, one of the main bioactive ingredients of Evodia rutaecarpa, has been reported to ameliorate blood–brain barrier (BBB) permeability and improve cognitive impairment in ischemia and AD mouse models. However, whether evodiamine alleviates tauopathy remains unclear. This study aimed to examine whether evodiamine ameliorates tau phosphorylation and cognitive deficits in AD models. Methods: A protein phosphatase 2A inhibitor, okadaic acid (OA), was used to induce tau phosphorylation to mimic AD-like models in neuronal cells. Protein expression and cell apoptosis were detected using Western blotting and flow cytometry, respectively. Spatial memory/cognition was assessed using water maze, passive avoidance tests, and magnetic resonance imaging assay in OA-induced mice models, and brain slices were evaluated further by immunohistochemistry. Results: The results showed that evodiamine significantly reduced the expression of phosphor-tau, and further decreased tau aggregation and neuronal cell death in response to OA treatment. This inhibition was found to be via the inhibition of glycogen synthase kinase 3β, cyclin-dependent kinase 5, and mitogen-activated protein kinase pathways. In vivo results indicated that evodiamine treatment ameliorated learning and memory impairments in mice, whereas Western blotting and immunohistochemical analysis of the mouse brain also confirmed the neuroprotective effects of evodiamine. Conclusions: Evodiamine can decrease the neurotoxicity of tau aggregation and exhibit a neuroprotective effect. Our results demonstrate that evodiamine has a therapeutic potential for AD treatment.

Cdk5 Inhibitory Peptide Prevents Loss of Neurons and Alleviates Behavioral Changes in p25 Transgenic Mice

BACKGROUND

Accumulation of p25 is thought to be a causative risk factor for Alzheimer's disease (AD). As a cleaved product of p35, p25 binds to cyclin-dependent kinase 5 (Cdk5) and leads to the hyperactivity of Cdk5. Then, Cdk5/p25 phosphorylates many pathological substrates related to neurodegenerative diseases. p25 transgenic (Tg) mouse model recaptures some pathological changes of AD, including tau hyperphosphorylation, neurofibrillary tangles, neuroinflammation, and neuronal death, which can be prevented by transgenic expression of Cdk5 inhibitory peptide (CIP) before the insult of p25.

OBJECTIVE

In the present study, we would like to know whether adeno-associated virus serotype-9 (AAV9)-mediated CIP can protect neurons after insult of p25 in p25Tg mice.

METHODS

Administration of AAV9-CIP or control virus were delivered in the brain of p25Tg mice via intracerebroventricular infusions following the induction of p25. Western blotting, immunohistochemistry and immunofluorescence assessment, and animal behavioral evaluation were performed.

RESULTS

Brain atrophy, neuronal death, tau phosphorylation and inflammation in the hippocampus, and cognitive decline were observed in p25Tg mice. Administration of CIP but not the control virus in p25Tg mice reduced levels of tau phosphorylation and inflammation in the hippocampus, which is correlated with inhibition of brain atrophy and neuronal apoptosis in the hippocampus, and improvement of cognitive decline.

CONCLUSION

Our results provide further evidence that the neurotoxicity of p25 can be alleviated by CIP.

Inhibitory Effect of Hexahydrocurcumin on Memory Impairment and Amyloidogenesis in Dexamethasone-Treated Mice

A high dose of dexamethasone induces neurodegeneration by initiating the inflammatory processes that lead to neural apoptosis. A dexamethasone administration model induces overproduction of amyloid-β (Aβ) and tau protein hyperphosphorylation and shows abnormalities of cholinergic function similar to Alzheimer's disease (AD). This study aimed to investigate the protective effect of hexahydrocurcumin on the brain of dexamethasone-induced mice. The results showed that hexahydrocurcumin and donepezil attenuated the levels of amyloid precursor protein and β-secretase mRNA by reverse transcription polymerase chain reaction, decreased the expression of hyperphosphorylated tau, and improved synaptic function. Moreover, we found that hexahydrocurcumin treatment could decrease interleukin-6 levels by attenuating p65 of nuclear factor kappa-light-chain-enhancer (NF-κB) of activated beta cells. In addition, hexahydrocurcumin also decreased oxidative stress, as demonstrated by the expression of 4-hydroxynonenal and thereby prevented apoptosis. Therefore, our finding suggests that hexahydrocurcumin prevents dexamethasone-induced AD-like pathology and improves memory impairment.

[Network pharmacology-based study of the therapeutic mechanism of resveratrol for Alzheimer's disease]

OBJECTIVE

To investigate the therapeutic mechanism of resveratrol (RES) for Alzheimer's disease (AD) in light of network pharmacology.

METHODS

We searched PubChem, BATMAN-TCM, Genecards, AD, TTD, String 11.0, AlzData, SwissTargetPrediction, Metascape and other databases for the therapeutic targets of RES and human AD-related targets. The intersection was determined using Venny 2.1 to obtain the therapeutic targets of RES for AD. The protein-protein interaction (PPI) network was constructed, the gene ontology (GO) was enriched and the Kyoto Encyclopedia of Genes and Genomes pathway (KEGG pathway) were analyzed. Cytoscape 3.7.1 software was used to construct a target-signaling pathway network of RES in the treatment of AD. Molecular docking verification was carried out on SwissDock (http://www.swissdock.ch/docking). We examined a 293Tau cell model of AD for changes in protein levels of pS396, pS199, Tau5, CDK5, glycogen synthase kinase 3β (GSK3β) and p-GSK3β in response to RES treatment using Western blotting.

RESULTS

We obtained 182 targets of RES, 525 targets related to AD, and 36 targets of RES for AD treatment, among which 34.6% of the targets were protein-modifying enzymes, 27.7% were metabolite invertase, 13.8% were gene-specific transcriptional regulators, and 10.3% were transporters. The core key targets of RES in the treatment of AD included INS, APP, ESR1, MMP9, IGF1R, CACNA1C, MAPT (microtubule- associated protein Tau), MMP2, TGFB1 and GSK3B. Enrichment analysis of GO biological process suggested that the biological function of RES in AD treatment mainly involved the response to β-amyloid protein, positive regulation of transferase activity, the transmembrane receptor protein tyrosine kinase signaling pathway, regulation of behavior, learning or memory, aging, and transmembrane transport. KEGG pathway enrichment analysis showed that the most significantly enriched signaling pathways were AD pathway, PI3K-AKT signaling pathway, cGMP-PKG signaling pathway, and MAPK signaling pathway. Molecular docking results showed that RES had strong binding with ESR1, GSK3B, MMP9, IGF1R, APP and INS. In the cell model of AD, treatment with 50 μmol/L RES for 12 h significantly reduced the levels of pS396 and pS199 by regulating CDK5 and GSK3β activity (P < 0.001).

CONCLUSIONS

RES produces therapeutic effects on AD by acting on multiple targets and affecting multiple signaling pathways and improves AD-associated pathologies via a direct action on Aβ and Tau pathological processes.

Combined treatment with valproic acid and estrogen has neuroprotective effects in ovariectomized mice with Alzheimer's disease

Postmenopausal women with Alzheimer’s disease (AD) exhibit dramatically reduced sensitivity to estrogen replacement therapy, which is though to be related to an estrogen receptor (ER)α/ERβ ratio imbalance arising from a significantly decreased level of ERs of the brain. The aim of our study was to investigate whether valproic acid (VPA) can enhance the beneficial effects of estrogen on cognitive function through restoration of ERα and ERβ expression in the brain. We removed the ovaries of female APP/PS1 mice to simulate the low estrogen levels present in postmenopausal women and then administered VPA (30 mg/kg, intraperitoneal injection, once daily), 17β-estradiol (E2) (2.4 μg, intraperitoneal injection, once daily), liquiritigenin (LG) (50 μg/kg, intragastric infusion, once daily), VPA + E2, or VPA + LG for 4 successive weeks. Compared with treatment with a single drug, treatment with VPA + E2 or VPA + LG significantly increased the level of glycogen synthase kinase 3β, increased the expression of estrogen receptor α, reduced the expression of small ubiquitin-like modifiers, and increased the level of estrogen receptor β. This resulted in enhanced sensitivity to estrogen therapy, reduced amyloid β aggregation, reduced abnormal phosphorylation of the tau protein, reduced neuronal loss, increased dendritic spine and postsynaptic density, and significantly alleviated memory loss and learning impairment in mice. This study was approved by the Chongqing Medical University Animal Protection and Ethics Committee, China on March 6, 2013.

The neuroprotective effects of phosphocreatine on Amyloid Beta 25-35-induced differentiated neuronal cell death through inhibition of AKT /GSK-3β /Tau/APP /CDK5 pathways in vivo and vitro

Alzheimer (AD) is a degenerative disease that can lead memory loss and behavioral dysfunction. Aβ protein and phosphorylation of Tau protein are related to the onset of AD. However, at present, its treatment and drugs are limited. The purpose of our study is to evaluate whether phosphocreatine (PCr) could protect neuronal injury induced by Aβ protein in vivo and in vitro through AKT/GSK-3β/Tau/APP/CDK5 pathways. Differentiated PC-12 cells were cultured with Aβ25-35 for 24 h, while the mice were injected with D-Galactose for eight weeks, both of them were pretreated with PCr for 2 h. The results showed PCr could obviously induce cells and hippocampus apoptosis using DAPI and TUNEL. PCr decreased the levels of intercellular reactive oxygen species (ROS) and malondialdehyde (MDA), and increased the activities of superoxide dismutase (SOD). Besides, the apoptosis pathway was detected using Western blot, showing that PCr could significantly reduce caspase-3, caspase-9, Bcl-2/Bax expression in vivo and in vitro. At the same time, PCr could decreased Ca²⁺ and apoptosis by Flow Cytometry in PC-12 cells. We observed that the morphological alteration of hippocampus injury was mitigated with the pretreatment of PCr. Furthermore, PCr pretreatment could decrease Aβ25-35-induced PC-12 cells apoptosis with APP cDNA transfection, which up-regulated AKT/GSK-3β/CDK5 pathways and induced Tau phosphorylation. In summary, PCr could reduce Aβ25-35 toxicity to protect neuronal cells via AKT/GSK-3β/CDK5 pathways.

Vaccinium bracteatum Improves Spatial Learning and Memory by Regulating N-methyl-D-aspartate Receptors and Tau Phosphorylation in Chronic Restraint Stress-Induced Memory Impaired Mice

Vaccinium bracteatum Thunb. Leaves (VBL) are a component of traditional herbal medicines. However, molecular mechanisms of VBL in stress-related memory impairment are still unclear. This study aimed to investigate the spatial memory improvement effects of VBL in an animal model of chronic restraint stress (CRS) by using Y maze test and identified possible protective mechanisms against oxidative stress inducers (e.g., corticosterone and hydrogen peroxide [H2O2]) in SH-SY5Y neuronal cells. VBL showed neuroprotective effects via reduced release of lactate dehydrogenase (LDH) in corticosterone or H2O2-induced cell death that was mediated through the regulation of cleaved caspase-3 and Nrf2 pathways. Furthermore, CRS-exposed mice were orally administered VBL (10, 50, 100, and 200 mg/kg) daily for 21 days. CRS-exposed mice treated with VBL showed significantly increased spontaneous alternation in short-term memory (STM) and long-term memory (LTM) trials, and number of total arm entries in LTM trials as measured by the Y maze test. Moreover, VBL (50, 100, and 200 mg/kg) decreased acetylcholinesterase (AChE) activity in the hippocampus (HC, [Formula: see text] ¡ 0.01 and [Formula: see text] ¡ 0.001, respectively) and prefrontal cortex (PFC). CRS-exposed mice treated with VBL had dramatically decreased total Tau and Tau phosphorylation in the synapse of the HC and PFC which might be mediated by the regulation of CaMKII and GSK3[Formula: see text] phosphorylation. Additionally, VBL reduced CRS-induced upregulation of N-methyl-D-aspartate (NMDA) receptor subunits (NMDAR1, 2A, and 2B). Thus, VBL exerts spatial memory improvement by regulating CRS-induced NMDA receptor neurotoxicity and Tau hyperphosphorylation.

Brain delivery of quercetin-loaded exosomes improved cognitive function in AD mice by inhibiting phosphorylated tau-mediated neurofibrillary tangles

It is reported that quercetin (Que) can prevent tau pathology and induce neuroprotection by improving cognitive and functional symptoms in the treatment of Alzheimer's disease (AD). However, its clinical application has been limited due to its poor brain targeting and bioavailability. Exosomes are considered as cargo carriers for intercellular communication and especially serve as a natural and important drug brain delivery platform for achieving better treatment of central neurological diseases. Here, we developed plasma exosomes (Exo) loaded with Que (Exo-Que) to improve the drug bioavailability, enhance the brain targeting of Que and potently ameliorate cognitive dysfunction in okadaic acid (OA)-induced AD mice. Our results showed that Exo-Que improved brain targeting of Que as well as significantly enhanced bioavailability of Que. Furthermore, compared with free Que, Exo-Que better relieved the symptoms of AD by inhibiting cyclin-dependent kinase 5 (CDK5)-mediated phosphorylation of Tau and reducing formation of insoluble neurofibrillary tangles (NFTs), suggesting its therapeutic potential for better treatment of AD.

Anti-Inflammatory and Tau Phosphorylation-Inhibitory Effects of Eupatin

Alzheimer's disease (AD), which is among the most prevalent neurodegenerative diseases, manifests as increasing memory loss and cognitive decline. Tau phosphorylation and aggregation are strongly linked to neurodegeneration, as well as associated with chronic neuroinflammatory processes. The anti-inflammation effects of natural products have led to wide recognition of their potential for use in treating and preventing AD. This study investigated whether eupatin, a polymethoxyflavonoid found in Artemisia species, has inhibitory effects on neuroinflammation and tau phosphorylation. We treated mouse macrophages and microglia cells with lipopolysaccharides (LPSs) to activate inflammatory signals, and we treated neuronal cells with a protein phosphatase 2A inhibitor, okadaic acid (OA), or transfection with pRK5-EGFP-Tau P301L plasmid to induce tau phosphorylation. The results indicated that eupatin significantly reduced the LPS-induced protein expression and phosphorylation of p65 and inducible nitric oxide synthase as well as downstream products interleukin 6 and nitrite, respectively. Furthermore, eupatin markedly inhibited the expression of phospho-tau in response to OA treatment and plasmid transfection. We discovered that this inhibition was achieved through the inhibition of glycogen synthase kinase 3β (GSK3β), and molecular docking results suggested that eupatin can sufficiently bind to the GSK3β active site. Our results demonstrate that eupatin has neuroprotective effects, making it suitable for AD treatment.

In silico docking and comparative ADMET profile of different glycogen synthase kinase 3 beta inhibitors as the potential leads for the development of anti-Alzheimer drug therapy

Glycogen synthase kinase 3 beta (GSK3 β) plays a key role in pathologic hyper phosphorylation of tau and plays an important role in the pathogenesis of Alzheimer's disease. In the present study, we have screened a set of potential hits in in silico platform to gain insight regarding binding profile with the target (GSK3 β) from molecular docking, ADME/T, and molecular dynamics (MD) simulations. The three screened compounds 6-BIBEO, 6-BIO, and SB216763 topped the docking score chart when subjected to hard scoring function extraprecision of GLIDE. The active site dynamics study through MD simulations provides insights on residues Asp133, Val135, and Ile62 which are in a state of minimum deviation from their mean special position while they interact with the respective ligands. The same molecules also displayed favorable pharmacokinetic profile, negative Ames test and falls correctly within drug-likeliness rules. These agents can be taken forward further for the development of anti-Alzheimer's drug therapy.

Resveratrol targeting tau proteins, amyloid-beta aggregations, and their adverse effects: An updated review

Resveratrol (Res) is a non-flavonoid compound with pharmacological actions such as antioxidant, antiinflammatory, hepatoprotective, antidiabetes, and antitumor. This plant-derived chemical has a long history usage in treatment of diseases. The excellent therapeutic impacts of Res and its capability in penetration into blood-brain barrier have made it an appropriate candidate in the treatment of neurological disorders (NDs). Tau protein aggregations and amyloid-beta (Aβ) deposits are responsible for the induction of NDs. A variety of studies have elucidated the role of these aggregations in NDs and the underlying molecular pathways in their development. In the present review, based on the recently published articles, we describe that how Res administration could inhibit amyloidogenic pathway and stimulate processes such as autophagy to degrade Aβ aggregations. Besides, we demonstrate that Res supplementation is beneficial in dephosphorylation of tau proteins and suppressing their aggregations. Then, we discuss molecular pathways and relate them to the treatment of NDs.

Experimental evidence for alpha enolase as one potential autoantigen in the pathogenesis of both autoimmune thyroiditis and its related encephalopathy

Alpha-enolase (ENO1) is a ubiquitous protein. Patients with autoimmune thyroiditis-associated encephalopathy have high serum ENO1Ab titers. We aimed to explore whether ENO1Ab was the pathogenic antibody in the thyroid and brain. The serum ENO1Ab titers were significantly increased in the mice immunized with Thyroglobulin (Tg). And in the mice immunized with ENO1, serum levels of both TgAb and thyroid-stimulating hormone (TSH) were significantly increased. Obvious CD16⁺ cell infiltration, IgG deposit and cleaved caspase-3 were observed in the thyroid of ENO1-immunized mice. Spatial learning and memory abilities and synaptic functions were impaired in ENO1-immunized mice. Furthermore, the expression levels of Iba-1, GFAP, interlukin-6, CDK5, and phosphorylated tau were increased, and endothelial tight junction proteins were decreased in the brain of ENO1-immunized mice. These results suggest that ENO1Ab can cause thyrocyte damage via ADCC effect and impair cerebral function by disrupting the blood-brain barrier.

Discovery of 1-Pyrimidinyl-2-Aryl-4,6-Dihydropyrrolo [3,4-d]Imidazole-5(1H)-Carboxamide as a Novel JNK Inhibitor

We designed and synthesized 1-pyrimidinyl-2-aryl-4, 6-dihydropyrrolo [3,4-d] imidazole-5(1H)-carboxamide derivatives as selective inhibitors of c-Jun-N-terminal Kinase 3 (JNK3), a target for the treatment of neurodegenerative diseases. Based on the compounds found in previous studies, a novel scaffold was designed to improve pharmacokinetic characters and activity, and compound 18a, (R)-1-(2-((1-(cyclopropanecarbonyl)pyrrolidin-3-yl)amino)pyrimidin-4-yl)-2-(3,4-dichlorophenyl)-4,6-dihydro pyrrolo [3,4-d]imidazole-5(1H)-carboxamide, showed the highest IC₅₀ value of 2.69 nM. Kinase profiling results also showed high selectivity for JNK3 among 38 kinases, having mild activity against JNK2, RIPK3, and GSK3β, which also known to involve in neuronal apoptosis.