Anthoxanthin Polyphenols Attenuate Aβ Oligomer-induced Neuronal Responses Associated with Alzheimer's Disease

Phytomedicine for neurodegenerative diseases: The road ahead

Neurodegenerative disorders (NDs) are among the most common causes of death across the globe. NDs are characterized by progressive damage to CNS neurons, leading to defects in specific brain functions such as memory, cognition, and movement. The most common NDs are Parkinson's, Alzheimer's, Huntington's, and amyotrophic lateral sclerosis (ALS). Despite extensive research, no therapeutics or medications against NDs have been proven to be effective. The current treatment of NDs involving symptom-based targeting of the disease pathogenesis has certain limitations, such as drug resistance, adverse side effects, poor blood-brain barrier permeability, and poor bioavailability of drugs. Some studies have shown that plant-derived natural compounds hold tremendous promise for treating and preventing NDs. Therefore, the primary objective of this review article is to critically analyze the properties and potency of some of the most studied phytomedicines, such as quercetin, curcumin, epigallocatechin gallate (EGCG), apigenin, and cannabinoids, and highlight their advantages and limitations for developing next-generation alternative treatments against NDs. Further extensive research on pre-clinical and clinical studies for developing plant-based drugs against NDs from bench to bedside is warranted.

Pharmacological Potential of Kaempferol, a Flavonoid in the Management of Pathogenesis via Modulation of Inflammation and Other Biological Activities

Natural products and their bioactive compounds have been used for centuries to prevent and treat numerous diseases. Kaempferol, a flavonoid found in vegetables, fruits, and spices, is recognized for its various beneficial properties, including its antioxidant and anti-inflammatory potential. This molecule has been identified as a potential means of managing different pathogenesis due to its capability to manage various biological activities. Moreover, this compound has a wide range of health-promoting benefits, such as cardioprotective, neuroprotective, hepatoprotective, and anti-diabetic, and has a role in maintaining eye, skin, and respiratory system health. Furthermore, it can also inhibit tumor growth and modulate various cell-signaling pathways. In vivo and in vitro studies have demonstrated that this compound has been shown to increase efficacy when combined with other natural products or drugs. In addition, kaempferol-based nano-formulations are more effective than kaempferol treatment alone. This review aims to provide detailed information about the sources of this compound, its bioavailability, and its role in various pathogenesis. Although there is promising evidence for its ability to manage diseases, it is crucial to conduct further investigations to know its toxicity, safety aspects, and mechanism of action in health management.

Kaempferol, a potential neuroprotective agent in neurodegenerative diseases: From chemistry to medicine

Neurodegenerative diseases (NDDs) encompass a range of conditions that involve progressive deterioration and dysfunction of the nervous system. Some of the common NDDs include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). Although significant progress has been made in understanding the pathological mechanisms of NDDs in recent years, the development of targeted and effective drugs for their treatment remains challenging. Kaempferol is a flavonoid whose derivatives include kaempferol-O-rhamnoside, 3-O-β-rutinoside/6-hydroxykaempferol 3,6-di-O-β-d-glucoside, and kaempferide. Emerging studies have suggested that kaempferol and its derivatives possess neuroprotective properties and may have potential therapeutic benefits in NDDs. Here, we aimed to provide a theoretical basis for the use of kaempferol and its derivatives in the clinical treatment of NDDs. We systematically reviewed the literature in the PubMed, Web of Science, and Science Direct databases until June 2022 using the search terms "kaempferol," "kaempferol derivatives," "NDDs," "pharmacokinetics," and "biosynthesis" according to the reporting items for systematic review (PRISMA) standard. Based on combined results of in vivo and in vitro studies, we summarize the basic mechanisms and targets of kaempferol and its derivatives in the management of AD, PD, HD, and ALS. Kaempferol and its derivatives exert a neuroprotective role mainly by preventing the deposition of amyloid fibrils (such as Aβ, tau, and α-synuclein), inhibiting microglia activation, reducing the release of inflammatory factors, restoring the mitochondrial membrane to prevent oxidative stress, protecting the blood-brain barrier, and inhibiting specific enzyme activities (such as cholinesterase). Kaempferol and its derivatives are promising natural neuroprotective agents. By determining their pharmacological mechanism, kaempferol and its derivatives may be new candidate drugs for the treatment of NDDs.

Kaempferol as a therapeutic agent in Alzheimer's disease: Evidence from preclinical studies

BACKGROUND

Alzheimer's disease (AD) is the most common type of dementia and seriously affects human life and health. Kaempferol (KMP) is a common flavonoid, that is mainly derived from the rhizomes of Kaempferol galanga L. and is widely found in various fruits and vegetables. Previous studies have suggested that KMP has multiple pharmacological activities. However, the anti-AD mechanism of KMP has not been elucidated.

METHODS

This systematic review aims to summarize the existing preclinical experiments on KMP, further confirm the therapeutic effect of KMP in an AD model, and summarize the possible mechanism by which KMP exerts anti-AD effects. Electronic databases, including PubMed, China National Knowledge Infrastructure (CNKI), Baidu Academic, and Wanfang, were searched using the keywords of 'Kaempferol,' 'KMP,' 'pharmacology,' and 'Alzheimer's disease'.

RESULTS

We evaluated the reliability of the 12 included studies, and the results showed that the anti-AD mechanism of KMP was reliable and that the prospect of KMP in the treatment of cognitive impairment was promising. We comprehensively assessed the neuroprotective effects of KMP in in vivo and in vitro models of AD. These studies shown that KMP ameliorated AD through several mechanisms, including its antioxidant, anti-inflammatory, anti-apoptotic, and anti-acetylcholinesterase effects.

CONCLUSION

KMP may exert anti-AD effects through various mechanisms and is a potential drug with broad prospects for the treatment of AD.

Molecular mechanisms of programmed cell death in methamphetamine-induced neuronal damage

Methamphetamine, commonly referred to as METH, is a highly addictive psychostimulant and one of the most commonly misused drugs on the planet. Using METH continuously can increase your risk for drug addiction, along with other health complications like attention deficit disorder, memory loss, and cognitive decline. Neurotoxicity caused by METH is thought to play a significant role in the onset of these neurological complications. The molecular mechanisms responsible for METH-caused neuronal damage are discussed in this review. According to our analysis, METH is closely associated with programmed cell death (PCD) in the process that causes neuronal impairment, such as apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. In reviewing this article, some insights are gained into how METH addiction is accompanied by cell death and may help to identify potential therapeutic targets for the neurological impairment caused by METH abuse.

SIRT7 Deficiency Protects against Aβ42-Induced Apoptosis through the Regulation of NOX4-Derived Reactive Oxygen Species Production in SH-SY5Y Cells

Alzheimer's disease (AD) is an age-related neurodegenerative disease that is characterized by irreversible memory loss and cognitive decline. The deposition of amyloid-β (Aβ), especially aggregation-prone Aβ₄₂, is considered to be an early event preceding neurodegeneration in AD. Sirtuins (SIRT1-7 in mammals) are nicotinamide adenine dinucleotide-dependent lysine deacetylases/deacylases, and several sirtuins play important roles in AD. However, the involvement of SIRT7 in AD pathogenesis is not known. Here, we demonstrate that SIRT7 mRNA expression is increased in the cortex, entorhinal cortex, and prefrontal cortex of AD patients. We also found that Aβ₄₂ treatment rapidly increased NADPH oxidase 4 (NOX4) expression at the post-transcriptional level, and induced reactive oxygen species (ROS) production and apoptosis in neuronal SH-SY5Y cells. In contrast, SIRT7 knockdown inhibited Aβ₄₂-induced ROS production and apoptosis by suppressing the upregulation of NOX4. Collectively, these findings suggest that the inhibition of SIRT7 may play a beneficial role in AD pathogenesis through the regulation of ROS production.

Potential Therapeutic Benefits of Honey in Neurological Disorders: The Role of Polyphenols

Honey is the principal premier product of beekeeping familiar to Homo for centuries. In every geological era and culture, evidence can be traced to the potential usefulness of honey in several ailments. With the advent of recent scientific approaches, honey has been proclaimed as a potent complementary and alternative medicine for the management and treatment of several maladies including various neurological disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis, etc. In the literature archive, oxidative stress and the deprivation of antioxidants are believed to be the paramount cause of many of these neuropathies. Since different types of honey are abundant with certain antioxidants, primarily in the form of diverse polyphenols, honey is undoubtedly a strong pharmaceutic candidate against multiple neurological diseases. In this review, we have indexed and comprehended the involved mechanisms of various constituent polyphenols including different phenolic acids, flavonoids, and other phytochemicals that manifest multiple antioxidant effects in various neurological disorders. All these mechanistic interpretations of the nutritious components of honey explain and justify the potential recommendation of sweet nectar in ameliorating the burden of neurological disorders that have significantly increased across the world in the last few decades.

The neuroprotective effects of polyphenols, their role in innate immunity and the interplay with the microbiota

Neurodegenerative disorders, particularly in the elderly population, represent one of the most pressing social and health-care problems in the world. Besides the well-established role of both oxidative stress and inflammation, alterations of the immune response have been found to be closely linked to the development of neurodegenerative diseases. Interestingly, various scientific evidence reported that an altered gut microbiota composition may contribute to the development of neuroinflammatory disorders. This leads to the proposal of the concept of the gut-brain-immune axis. In this scenario, polyphenols play a pivotal role due to their ability to exert neuroprotective, immunomodulatory and microbiota-remodeling activities. In the present review, we summarized the available literature to provide a scientific evidence regarding this neuroprotective and immunomodulatory effects and the interaction with gut microbiota of polyphenols and, the main signaling pathways involved that can explain their potential therapeutic application in neurodegenerative diseases.

Antioxidant, Antihypertensive and Antimicrobial Properties of Phenolic Compounds Obtained from Native Plants by Different Extraction Methods

This study aims to evaluate the efficacy of two methods (agitation and ultra-sound) for extracting phenolic compounds from 15 native plants. Plant species collected in the Dehesa of Extremadura were used. The antioxidant, antihypertensive and antimicrobial activity of the phenolic extracts was investigated. Significantly different results were obtained when comparing the two extraction methods, with the highest concentrations of phenolic compounds found for ultrasound extraction. In addition, the extracts obtained for Cistus albidus, Cistus salviifolius, Rubus ulmifolius and Quercus ilex showed the highest concentrations of phenolic compounds. The antioxidant activity was higher in the extracts of Cistus and Q. ilex obtained by ultrasound, as was the antihypertensive activity. Antimicrobial activity was also higher in the extracts obtained by ultrasound from C. salviifolius and Q. ilex plants against bacteria and from Cistus ladanifer against yeasts. Therefore, it can be concluded that, with the ultrasound extraction of phenolic compounds from C. ladanifer, C. albidus and Q. ilex plants, it is possible to obtain extracts with important functional properties, so they could be studied for their use in food with the aim of obtaining healthy and safe products, favouring the sustainability of the environment of the Dehesa Extremeña.

Inhibition of Aβ aggregates in Alzheimer's disease by epigallocatechin and epicatechin-3-gallate from green tea

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive accumulation of senile plaques, which are primarily composed of misfolded amyloid β-peptide (Aβ). Aβ aggregates are believed to be a key factor in the pathogenesis of AD, affecting the nervous system in human body. The therapeutic potential of tea-derived polyphenolic compounds, (-)-epigallocatechin (EGC) and (-)-epicatechin-3-gallate (ECG), for AD was investigated by assessing their effects on the Cu²⁺/Zn²⁺-induced or self-assembled Aβ₄₀ aggregation using thioflavine T fluorescent spectrometry, inductively coupled plasma mass spectrometry, UV-Vis spectroscopy, transmission electron microscope, silver staining, immunohistochemistry, and immunofluorescence assays. EGC and ECG mildly bind to Cu²⁺ and Zn²⁺, and diminish the Cu²⁺- or Zn²⁺-induced or self-assembled Aβ aggregates; they also modulate the Cu²⁺/Zn²⁺-Aβ₄₀ induced neurotoxicity on mouse neuroblastoma Neuro-2a cells by reducing the production of ROS. Metal chelating, hydrogen bonding or Van Der Waals force may drive the interaction between the polyphenolic compounds and Aβ. The results demonstrate that green tea catechins EGC and ECG are able to alleviate the toxicity of Aβ oligomers and fibrils. Particularly, ECG can cross the blood-brain barrier to reduce the Aβ plaques in the brain of APP/PS1 mice, thereby protecting neurons from injuries. The results manifest the potential of green tea for preventing or ameliorating the symptoms of AD.

HPLC-DAD analysis of Hyssopus Cuspidatus Boriss extract and mensuration of its antioxygenation property

BACKGROUND

Hyssopus cuspidatus Boriss has been used as an important ethnomedicinal plant for long to eliminate phlegm, relieve cough and as well as having antibacterial, antioxygenation, and antitumor activities. In this study, the polyphenol contents, flavonoid contents, free radical scavenging assay and animal antioxygenation property assay of ethanol extract of H. cuspidatus were measured.

METHODS

This study determined the total polyphenol and flavonoid contents in H. cuspidatus by UV-VIS. Caffeic, ferulic, and rosmarinic acids were measured using HPLC-DAD. Free radical scavenging assay of H. cuspidatus was studied by colorimetric method. Animal antioxygenation property assay of H. cuspidatus was studied with mice by biochemical assay kits.

RESULTS

The total polyphenol and flavonoid contents of H. cuspidatus in 2017, 2018, 2019 were determined and the contents of H. cuspidatus in 2019 was the highest. In addition, rosmarinic acid was the phenolic acid with the highest content in H. cuspidatus. Compared with those of DPPH free radical, hydroxyl free radical, and superoxide anion free radical, the scavenging ability of H. cuspidatus of ABTS free radical was stronger, the average IC50 value was 0.0245 mg/mL. In animal antioxygenation property experiment, the model group was successfully established with decreased activities of SOD, CAT, and GSH-px and increased content of MDA. The ethanol extract of H. cuspidatus increased the activities of SOD, CAT, and GSH-px and reduced the content of MDA. Each group of samples and the ascorbic acid positive control group showed significant differences in the results of free radical scavenging and animal antioxygenation property experiments (P < 0.05).

CONCLUSIONS

These results suggest that H. cuspidatus exerts an antioxygenation property, which can be attributed to the contents of total polyphenol and flavonoid. Given its strong antioxygenation property, H. cuspidatus can be used as a new natural antioxidant in food preservation and disease treatment.

Luteolin alleviates methamphetamine-induced neurotoxicity by suppressing PI3K/Akt pathway-modulated apoptosis and autophagy in rats

Methamphetamine (METH) is a highly addictive stimulant that results in serious and persistent neurotoxic effects. Studies have indicated that luteolin, a flavonoid, may confer neuroprotection against neurotoxicity. Nevertheless, the effects of luteolin on METH-induced neurotoxicity have not been sufficiently verified. In the present study, Sprague Dawley rats were pretreated with luteolin (100 mg/kg) or sodium dodecyl sulfate water, followed by administration of METH (15 mg/kg) or saline. Rat striata were then collected for RNA-sequencing and subsequent analyses. A total of 347 differentially expressed genes (DEGs) were identified in the METH group with 20 pathways, including the phosphoinositol 3 kinase (PI3K)/protein kinase B (Akt), found to be enriched by the KEGG analysis. Seventy-five of the 347 DEGs were modulated in luteolin-pretreated rats, which were enriched into 12 pathways, containing the PI3K/Akt. Results further showed that luteolin pretreatment significantly repressed the METH-induced increases of PI3K, Akt, p-Akt, p53, Bax, caspase 3, normalized the ratio of p-Akt/Akt, and autophagy-related proteins (Beclin1, Atg5 and LC3-II) expression. Taken together, these findings indicate that luteolin attenuates METH-induced apoptosis and autophagy by suppressing the PI3K/Akt pathway. In this case, it exerts protection against METH-induced neurotoxicity. This provides a platform for development of potential therapies for METH treatment.

Application of the Movable Type Free Energy Method to the Caspase-Inhibitor BindingAffinity Study

Many studies have provided evidence suggesting that caspases not only contribute to the neurodegeneration associated with Alzheimer’s disease (AD) but also play essential roles in promoting the underlying pathology of this disease. Studies regarding the caspase inhibition draw researchers’ attention through time due to its therapeutic value in the treatment of AD. In this work, we apply the “Movable Type” (MT) free energy method, a Monte Carlo sampling method extrapolating the binding free energy by simulating the partition functions for both free-state and bound-state protein and ligand configurations, to the caspase-inhibitor binding affinity study. Two test benchmarks are introduced to examine the robustness and sensitivity of the MT method concerning the caspase inhibition complexing. The first benchmark employs a large-scale test set including more than a hundred active inhibitors binding to caspase-3. The second benchmark includes several smaller test sets studying the relative binding free energy differences for minor structural changes at the caspase-inhibitor interaction interfaces. Calculation results show that the RMS errors for all test sets are below 1.5 kcal/mol compared to the experimental binding affinity values, demonstrating good performance in simulating the caspase-inhibitor complexing. For better understanding the protein-ligand interaction mechanism, we then take a closer look at the global minimum binding modes and free-state ligand conformations to study two pairs of caspase-inhibitor complexes with (1) different caspase targets binding to the same inhibitor, and (2) different polypeptide inhibitors targeting the same caspase target. By comparing the contact maps at the binding site of different complexes, we revealed how small structural changes affect the caspase-inhibitor interaction energies. Overall, this work provides a new free energy approach for studying the caspase inhibition, with structural insight revealed for both free-state and bound-state molecular configurations.

LC-ESI-QTOF/MS Characterisation of Phenolic Acids and Flavonoids in Polyphenol-Rich Fruits and Vegetables and Their Potential Antioxidant Activities

Polyphenols are naturally occurring compounds found largely in fruits and vegetables. The antioxidant properties of these polyphenols including total phenolic content (TPC), total flavonoid content (TFC), tannin content, 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), 2,2'-azinobis-(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS) scavenging abilities and ferric ion reducing antioxidant power (FRAP) were measured among sixteen (16) plant foods (mango, blueberry, strawberry, black carrot, raspberry, dark grapes, garlic, ginger, onion, cherry, plum, apple, papaya, peach, pear and apricot) by modifying, standardising and translating existing antioxidant methods using a 96-well plate reader. Eighteen targeted phenolic acids and flavonoids were characterised and quantified using high-performance liquid chromatography-photometric diode array (HPLC-PDA) and verified by modifying an existing method of liquid chromatography coupled with electrospray-ionisation triple quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). While most of these compounds were accurately detected by the HPLC-PDA at a low concentration, a few polyphenols in low concentrations could be only be characterised using the LC-ESI-QTOF/MS method. Our results showed that mango possessed the highest overall antioxidant activity, phenolic acid and flavonoid content among the selected fruits. Factor analysis (FA) and Pearson's correlation tests showed high correlations among ABTS, DPPH, FRAP and phenolic acids, implying the comparable capabilities of scavenging the DPPH/ABTS free radicals and reducing ferric ions from the antioxidant compounds in the samples. Phenolic acids contributed significantly to the antioxidant activities, and flavonoids contributed more to tannin content based on the correlations. Overall, methods modified and standardized in this study can provide better understanding of high throughput technologies and increase the reliability of antioxidant data of different plant foods.

Multicomponent Synthesis of Polyphenols and their in vitro Evaluation as Potential β-Amyloid Aggregation Inhibitors

While plant polyphenols possess a variety of biological properties, exploration of chemical diversity around them is still problematic. Here, an example of application of the Ugi multicomponent reaction to the combinatorial assembly of artificial, yet "natural-like", polyphenols is presented. The synthesized compounds represent a second-generation library directed to the inhibition of β-amyloid protein aggregation. Chiral enantiopure compounds, and polyphenol-β-lactam hybrids have been prepared too. The biochemical assays have highlighted the importance of the key pharmacophores in these compounds. A lead for inhibition of aggregation of truncated protein AβpE3-42 was selected.

Ultrasonicated sour Jujube seed flavonoids extract exerts ameliorative antioxidant capacity and reduces Aβ-induced toxicity in Caenorhabditis elegans

ETHNOPHARMACOLOGICAL RELEVANCE

Sour Jujube seed from Ziziphus jujuba Mill. var. Spinosa (Bunge) Hu ex H. F. Chow is a traditional Chinese herb. It was demonstrated with significant activities in anti-depression and antioxidant by numerous pharmacological studies. Flavonoids is one of the main constituents in sour Jujube seed.

AIM OF THE STUDY

The aim of this study was to propose a green ultrasound-assisted extraction (UAE) process of flavonoids from sour Jujube seed.

MATERIALS AND METHODS

The extraction parameters were investigated and optimized using single factor experiments, Plackett-Burman design (PBD) and response surface methodology (RSM). Moreover, a comparative analysis between ultrasound-assisted extraction and heat reflux extraction was performed to verify the ameliorating effects of ultrasound-assisted extraction on the flavonoids yield, the composition, antioxidant capacities in vitro and ROS scavenging capacity in PC12 cells. Meanwhile, the effects of flavonoids extract (FE) on Aβ transgenic Caenorhabditis elegans (GMC101) behavior were investigated.

RESULTS

The optimal extracting conditions of total flavonoids were as follows: ethanol concentration 70.60 (v/v%), liquid-solid ratio 15.02:1 mL/g, ultrasonic power 404 W, extraction time 60.03 min. The highest extraction yield was 1.59%. When compared to Heat reflux extraction (HRE) that only has gained a yield of 1.356%. Approximately, the UAE method was able to increase the yield by 17.11%. Moreover, FE extracted by UAE displayed larger capacity of scavenging ABTS, DPPH, superoxide, and hydroxyl radicals and reducing the level of ROS accumulation in PC12 cells, suggesting the biological functions of these compounds could be also better protected under UAE conditions. Furthermore, FE could also increase the chemotaxis and heat stress resistance ability, delay the paralysis and extend the lifespan of Caenorhabditis elegans.

CONCLUSION

UAE is a green and efficient technique for the preparation of flavonoids from sour Jujube seed. The flavonoids extract can reduce Aβ-induced toxicity in Caenorhabditis elegans.

Oroxylum indicum (L.) extract protects human neuroblastoma SH‑SY5Y cells against β‑amyloid‑induced cell injury

It has been reported that amyloid β peptide, the major component of senile plaques, serves a critical role in the development and progression of Alzheimer's disease (AD) by generating reactive oxygen species (ROS), leading to oxidative stress. The aim of the present study was to investigate the protective effect of Oroxylum indicum (L.) extract against Aβ25‑35‑induced oxidative stress and cell injury using SH‑SY5Y cells as a model, and at exploring the underlying mechanisms. The results revealed that the exposure of cells to 20 µM Aβ25‑35 significantly increased cellular oxidative stress, as evidenced by the increased ROS levels. Aβ25‑35 treatment also increased caspase‑3/7 activity and lactate dehydrogenase (LDH) release, and caused viability loss. Oroxylum indicum treatment not only attenuated the generation of ROS and suppressed caspase‑3/7 activity but also reduced the neurotoxicity of Aβ25‑35 in a concentration‑dependent manner, as evidenced by the increased cell viability and decreased LDH release. Treatment with Oroxylum indicum also increased superoxide dismutase (SOD) and catalase (CAT) activity, increased the phosphorylation of Akt and cAMP‑responsive element binding protein (CREB), and contributed to the upregulation of Bcl‑2 protein. In combination, these results indicated that Oroxylum indicum extract could protect SH‑SY5Y cells against Aβ25‑35‑induced cell injury, at least partly, by inhibiting oxidative stress, increasing SOD and CAT activity, attenuating caspase 3/7 activity and promoting the cell survival pathway, Akt/CREB/Bcl‑2. The approach used in the present study may also be useful for preventing the neurotoxicity induced by Aβ in AD and related neurodegenerative diseases. Further studies investigating the activity of Oroxylum indicum extract in vivo are now required.

A combination of curcumin, vorinostat and silibinin reverses Aβ-induced nerve cell toxicity via activation of AKT-MDM2-p53 pathway

Alzheimer’s disease (AD) is a significant health issue for the elderly and becoming increasingly common as the global population ages. Although many efforts have been made to elucidate its pathology, there is still a lack of effective clinical anti-AD agents. Previous research has shown the neuroprotective properties of a combination of curcumin and vorinostat. In this study, nine other neuroprotective agents were investigated to examine whether a three-drug combination of curcumin, vorinostat, and a new drug is more advantageous than the previous two-drug combination in alleviating amyloid beta (Aβ)-induced nerve cell toxicity. Cell viability assay was performed to screen these agents, and further validation tests, including determination of cellular oxidative stress, apoptosis, and activity of the AKT/MDM2/p53 pathway, were performed. Among the nine candidate compounds, only silibinin at 1 µM reduced Aβ_25–35-induced toxicity in PC12 cells. The neuroprotective effects of 1 µM silibinin in combination with 5 µM curcumin and 0.5 µM vorinostat (CVS) was shown in PC12 cells, in which it decreased apoptosis and oxidative stress marker levels that were increased by 20 µM Aβ_25–35. Western blotting results showed that CVS pretreatment significantly increased the phosphorylation of AKT, BAD, and MDM2, which resulted in decreased intracellular expression of p53. Further, immunofluorescence results showed reduced p53 levels in the nuclei of PC12 cells following CVS pretreatment, indicating a reduction in the p53-mediated transcriptional activity associated with Aβ_25–35 exposure. In conclusion, our findings suggested that pretreatment with CVS protected PC12 cells from Aβ_25–35-induced toxicity through modulation of the AKT/MDM2/p53 pathway. Thus, CVS may present a new therapeutic option for treating AD.

Anti-Neuroinflammatory Property of Phlorotannins from Ecklonia cava on Aβ25-35-Induced Damage in PC12 Cells

Alzheimer disease (AD) is a neurodegenerative disorder characterized by excessive accumulation of amyloid-beta peptide (Aβ) and progressive loss of neurons. Therefore, the inhibition of Aβ-induced neurotoxicity is a potential therapeutic approach for the treatment of AD. Ecklonia cava is an edible brown seaweed, which has been recognized as a rich source of bioactive derivatives, mainly phlorotannins. In this study, phlorotannins including eckol, dieckol, 8,8'-bieckol were used as potential neuroprotective candidates for their anti-apoptotic and anti-inflammatory effects against Aβ25-35-induced damage in PC12 cells. Among the tested compounds, dieckol showed the highest effect in both suppressing intracellular oxidative stress and mitochondrial dysfunction and activation of caspase family. Three phlorotannins were found to inhibit TNF-α, IL-1β and PGE₂ production at the protein levels. These result showed that the anti-inflammatory properties of our compounds are related to the down-regulation of proinflammatory enzymes, iNOS and COX-2, through the negative regulation of the NF-κB pathway in Aβ25-35-stimulated PC12 cells. Especially, dieckol showed the strong anti-inflammatory effects via suppression of p38, ERK and JNK. However, 8,8'-bieckol markedly decreased the phosphorylation of p38 and JNK and eckol suppressed the activation of p38. Therefore, the results of this study indicated that dieckol from E. cava might be applied as a drug candidate for the development of new generation therapeutic agents against AD.

The Potential Use of Plant Natural Products and Plant Extracts with Antioxidant Properties for the Prevention/Treatment of Neurodegenerative Diseases: In Vitro, In Vivo and Clinical Trials

Neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease and Huntington's disease, present a major health issue and financial burden for health care systems around the world. The impact of these diseases will further increase over the next decades due to increasing life expectancies. No cure is currently available for the treatment of these conditions; only drugs, which merely alleviate the symptoms. Oxidative stress has long been associated with neurodegeneration, whether as a cause or as part of the downstream results caused by other factors. Thus, the use of antioxidants to counter cellular oxidative stress within the nervous system has been suggested as a potential treatment option for neurological disorders. Over the last decade, significant research has focused on the potential use of natural antioxidants to target oxidative stress. However, clinical trial results have lacked success for the treatment of patients with neurological disorders. The knowledge that natural extracts show other positive molecular activities in addition to antioxidant activity, however, has led to further research of natural extracts for their potential use as prevention or treatment/management of neurodegenerative diseases. This review will cover several in vitro and in vivo research studies, as well as clinical trials, and highlight the potential of natural antioxidants.

Natural Scaffolds with Multi-Target Activity for the Potential Treatment of Alzheimer's Disease

A few symptomatic drugs are currently available for Alzheimer’s Disease (AD) therapy, but these molecules are only able to temporary improve the cognitive capacity of the patients if administered in the first stages of the pathology. Recently, important advances have been achieved about the knowledge of this complex condition, which is now considered a multi-factorial disease. Researchers are, thus, more oriented toward the preparation of molecules being able to contemporaneously act on different pathological features. To date, the inhibition of acetylcholinesterase (AChE) and of β-amyloid (Aβ) aggregation as well as the antioxidant activity and the removal and/or redistribution of metal ions at the level of the nervous system are the most common investigated targets for the treatment of AD. Since many natural compounds show multiple biological properties, a series of secondary metabolites of plants or fungi with suitable structural characteristics have been selected and assayed in order to evaluate their potential role in the preparation of multi-target agents. Out of six compounds evaluated, 1 showed the best activity as an antioxidant (EC₅₀ = 2.6 ± 0.2 μmol/µmol of DPPH) while compound 2 proved to be effective in the inhibition of AChE (IC₅₀ = 6.86 ± 0.67 μM) and Aβ_1–40 aggregation (IC₅₀ = 74 ± 1 μM). Furthermore, compound 6 inhibited BChE (IC₅₀ = 1.75 ± 0.59 μM) with a good selectivity toward AChE (IC₅₀ = 86.0 ± 15.0 μM). Moreover, preliminary tests on metal chelation suggested a possible interaction between compounds 1, 3 and 4 and copper (II). Molecules with the best multi-target profiles will be used as starting hit compounds to appropriately address future studies of Structure-Activity Relationships (SARs).

Identification of novel immune-relevant drug target genes for Alzheimer's Disease by combining ontology inference with network analysis

AIMS

Alzheimer's disease (AD) is one of the leading causes of death in elderly people. Its pathogenesis is greatly associated with the abnormality of immune system. However, only a few immune-relevant AD drug target genes have been discovered up to now, and it is speculated that there are still many potential drug target genes of AD (at least immune-relevant genes) to be discovered. Thus, this study was designed to identify novel AD drug target genes and explore their biological properties.

METHODS

A combinatorial approach was adopted for the first time to discover AD drug targets by collectively considering ontology inference and network analysis. Moreover, a novel strategy limiting the distance of reasoning and in turn reducing noise interference was further proposed to improve inference performance. Potential AD drug target genes were discovered by integrating information of multiple popular databases (TTD, DrugBank, PharmGKB, AlzGene, and BioGRID). Then, the enrichment analyses of the identified drug targets genes based on nine well-known pathway-related databases were conducted to explore the function of the identified potential drug target genes.

RESULTS

Eighteen potential drug target genes were finally identified, and 13 of them had been reported to be closely associated with AD. Enrichment analyses of these identified drug target genes, based on nine pathway-related databases, revealed that the enriched terms were primarily focus on immune-relevant biological processes. Four of those identified drug target genes are involved in the classical complement pathway and process of antigen presenting.

CONCLUSION

The well-reproducible results showed the good performance of the combinatorial approach, and the remaining five new targets could be a good starting point for our understanding of the pathogenesis and drug discovery of AD. Moreover, this study supported validity of the combinatorial approach integrating ontology inference with network analysis in the discovery of novel drug target for neurological diseases.

Multicomponent, fragment-based synthesis of polyphenol-containing peptidomimetics and their inhibiting activity on beta-amyloid oligomerization

A new and short fragment-based approach towards artificial (but “natural-based”) complex polyphenols has been developed, exploiting the Ugi multicomponent reaction of phenol-containing simple substrates.