Neuroprotective Effects of Betulin in Pharmacological and Transgenic Caenorhabditis elegans Models of Parkinson's Disease

Antimicrobial drugs for Parkinson's disease: Existing therapeutic strategies and novel drugs exploration

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by loss of dopaminergic neurons in the substantia nigra, as well as the abnormal accumulation of misfolded α-synuclein. Clinically, PD is featured by typical motor symptoms and some non-motor symptoms. Up to now, although considerable progress has been made in understanding the pathogenesis of PD, there is still no effective therapeutic treatment for the disease. Thus, exploring new therapeutic strategies has been a topic that needs to be addressed urgently. Noteworthy, with the proposal of the microbiota-gut-brain axis theory, antimicrobial drugs have received significant attention due to their effects on regulating the intestinal microbiota. Nowadays, there is growing evidence showing that some antimicrobial drugs may be promising drugs for the treatment of PD. Data from pre-clinical and clinical studies have shown that some antimicrobial drugs may play neuroprotective roles in PD by modulating multiple biochemical and molecular pathways, including reducing α-synuclein aggregation, inhibiting neuroinflammation, regulating mitochondrial structure and function, as well as suppressing oxidative stress. In this paper, we summarized the effects of some antimicrobial drugs on PD treatment from recent pre-clinical and clinical studies. Then, we further discussed the potential of a few antimicrobial drugs for treating PD based on molecular docking and molecular dynamics simulation. Importantly, we highlighted the potential of clorobiocin as the therapeutic strategy for PD owing to its ability to inhibit α-synuclein aggregation. These results will help us to better understand the potential of antimicrobial drugs in treating PD and how antimicrobial drugs may alleviate or reverse the pathological symptoms of PD.

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.

Neuroprotective properties of Betulin, Betulinic acid, and Ursolic acid as triterpenoids derivatives: a comprehensive review of mechanistic studies

Cognitive deficits are the main outcome of neurological disorders whose occurrence has risen over the past three decades. Although there are some pharmacologic approaches approved for managing neurological disorders, it remains largely ineffective. Hence, exploring novel nature-based nutraceuticals is a pressing need to alleviate the results of neurodegenerative diseases, such as Alzheimer's disease (AD) and other neurodegenerative disorders. Some triterpenoids and their derivates can be considered potential therapeutics against neurological disorders due to their neuroprotective and cognitive-improving effects. Betulin (B), betulinic acid (BA), and ursolic acid (UA) are pentacyclic triterpenoid compounds with a variety of biological activities, including antioxidative, neuroprotective and anti-inflammatory properties. This review focuses on the therapeutic efficacy and probable molecular mechanisms of triterpenoids in damage prevention to neurons and restoring cognition in neurodegenerative diseases. Considering few studies on this concept, the precise mechanisms that mediate the effect of these compounds in neurodegenerative disorders have remained unknown. The findings can provide sufficient information about the advantages of these compounds against neurodegenerative diseases.

Exploring Caenorhabditis elegans as Parkinson's Disease Model: Neurotoxins and Genetic Implications

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, the first being Alzheimer's disease. Patients with PD have a loss of dopaminergic neurons in the substantia nigra of the basal ganglia, which controls voluntary movements, causing a motor impairment as a result of dopaminergic signaling impairment. Studies have shown that mutations in several genes, such as SNCA, PARK2, PINK1, DJ-1, ATP13A2, and LRRK2, and the exposure to neurotoxic agents can potentially increase the chances of PD development. The nematode Caenorhabditis elegans (C. elegans) plays an important role in studying the risk factors, such as genetic factors, aging, exposure to chemicals, disease progression, and drug treatments for PD. C. elegans has a conserved neurotransmission system during evolution; it produces dopamine, through the eight dopaminergic neurons; it can be used to study the effect of neurotoxins and also has strains that express human α-synuclein. Furthermore, the human PD-related genes, LRK-1, PINK-1, PDR-1, DJR-1.1, and CATP-6, are present and functional in this model. Therefore, this review focuses on highlighting and discussing the use of C. elegans an in vivo model in PD-related studies. Here, we identified that nematodes exposed to the neurotoxins, such as 6-OHDA, MPTP, paraquat, and rotenone, had a progressive loss of dopaminergic neurons, dopamine deficits, and decreased survival rate. Several studies have reported that expression of human LRRK2 (G2019S) caused neurodegeneration and pink-1, pdr-1, and djr-1.1 deletion caused several effects PD-related in C. elegans, including mitochondrial dysfunctions. Of note, the deletion of catp-6 in nematodes caused behavioral dysfunction, mitochondrial damage, and reduced survival. In addition, nematodes expressing α-synuclein had neurodegeneration and dopamine-dependent deficits. Therefore, C. elegans can be considered an accurate animal model of PD that can be used to elucidate to assess the underlying mechanisms implicated in PD to find novel therapeutic targets.

Innovative Approach to Enhance Bioavailability of Birch Bark Extracts: Novel Method of Oleogel Development Contrasted with Other Dispersed Systems

Birch outer bark extract (BBE), containing pentacyclic triterpenes such as betulin, lupeol, and betulinic acid, is a widely recognized natural product renowned for its diverse pharmacological effects. However, its limited water solubility restricts its bioavailability. Therefore, the main objective is to enhance the bioavailability of BBE for pharmaceutical use. In this study, we aimed to develop a dispersion system utilizing a unique oleogel-producing method through the recrystallization of BBE from an ethanol solution in the oil phase. We generated an oleogel that demonstrates a notable 42-80-fold improvement in betulin and lupeol peroral bioavailability from BBE in Wistar rats, respectively. A physical paste-like BBE hydrogel developed with antisolvent precipitation showed a 16-56-fold increase in the bioavailability of betulin and lupeol from BBE in rat blood plasma, respectively. We also observed that the repeated administration of the BBE oleogel did not exhibit any toxicity at the tested dose (38.5 mg/kg betulin, 5.2 mg/kg lupeol, 1.5 mg/kg betulinic acid daily for 7 days). Betulin and betulinic acid were not detected in rat heart, liver, kidney, or brain tissues after the peroral administration of the oleogel daily for 7 days. Lupeol was found in rat heart, liver, and kidney tissues.

Natural products for the treatment of neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are among the most common diseases in older adults worldwide. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common neurodegenerative diseases, and are accompanied by cerebral cortical atrophy, neuronal loss, protein accumulation, and excessive accumulation of metal ions. Natural products exhibit outstanding performance in improving cerebral circulatory disorders, promoting cerebral haematoma absorption, repairing damaged nerve tissue, and improving damaged nerve function. In recent years, studies have shown that neuroinflammatory mechanisms and signalling pathways closely related to the occurrence and development of neurological diseases include microglial activation, nuclear factor-κB (NF-κB) pathway, mitogen activated protein kinases (MAPK) pathway, reactive oxygen pathway, nucleotide binding oligomerisation domain-like receptor protein3 (NLRP3) inflammasomes, toll-like receptor4 (TLR4) pathway, nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, and intestinal flora. Therefore, this study considered the mechanism of neurological diseases as the starting point to review the mechanism of action of natural products in the prevention and treatment of AD and PD in recent years to provide a theoretical basis for clinical prevention and treatment.

AIM

Natural products are a promising source of novel lead structures that have long been used to treat various nervous system diseases.

METHODOLOGY

This review collected literature on neurological diseases and natural products from 2012 to 2022, which were mainly searched through databases such as ScienceDirect, Springer, PubMed, SciFinder, China National Knowledge Infrastructure (CNKI), Wanfang, Google Scholar, and Baidu Academic. The following keywords were searched: neurological disorders, natural products, signalling pathway, mechanism of action.

RESULTS

This review summarises the pathogenesis of degenerative neurological diseases, recent findings on natural products used in neurodegenerative diseases, and the molecular mechanisms underlying these effects.

Rose essential oil diminishes dopaminergic neuron degenerations and reduces α-synuclein aggregation in Caenorhabditis elegans models of Parkinson's disease

Parkinson's disease (P.D.) is the second most progressive neurodegenerative disorder in the elderly. Degeneration of dopaminergic (DA) neurons and α-synuclein (α-Syn) accumulated toxicity is the major contributor to this disease. At present, the disease has no effective treatment. Many recent studies focus on identifying novel therapeutics that provide benefits to stop the disease progression in P.D. patients. Screening novel and effective drugs in P.D. animal models is time- and cost-consuming. Rose Essential Oil (REO) extracted from Rosa Rugosa species (R. Setate × R. Rugosa). REO contains Citronellol, Geraniol, and Octadiene that possess anti-Aβ, anti-oxidative, and anti-depression-like properties, but no reports have defined the REO effect on P.D. yet. The present study examines the REO neuroprotective potential in transgenic Caenorhabditis elegans P.D. models. We observed that REO reduced α-Syn aggregations and diminished DA neuron degenerations induced by 6-OHDA, reduced food-sensing behavioural disabilities, and prolonged the lifespan of the nematode. Moreover, REO augmented the chymotrypsin-like proteasome and SOD-3 activities. Further, we observed the anti-oxidative role of REO by reducing internal cells ROS. Together, these findings supported REO as an anti-PD drug and may exert its effects by lowering oxidative stress via the anti-oxidative pathway.

Snake venom nerve growth factor-inspired designing of novel peptide therapeutics for the prevention of paraquat-induced apoptosis, neurodegeneration, and alteration of metabolic pathway genes in the rat pheochromocytoma PC-12 cell

Neurodegenerative disorders (ND), associated with the progressive loss of neurons, oxidative stress-mediated production of reactive oxygen species (ROS), and mitochondrial dysfunction, can be treated with synthetic peptides possessing innate neurotrophic effects and neuroprotective activity. Computational analysis of two small synthetic peptides (trideca-neuropeptide, TNP; heptadeca-neuropeptide, HNP) developed from the nerve growth factors from snake venoms predicted their significant interaction with the human TrkA receptor (TrkA). In silico results were validated by an in vitro binding study of the FITC-conjugated custom peptides to rat pheochromocytoma PC-12 cell TrkA receptors. Pre-treatment of PC-12 cells with TNP and HNP induced neuritogenesis and significantly reduced the paraquat (PT)-induced cellular toxicity, the release of lactate dehydrogenase from the cell cytoplasm, production of intracellular ROS, restored the level of antioxidants, prevented alteration of mitochondrial transmembrane potential (ΔΨm) and adenosine triphosphate (ATP) production, and inhibited cellular apoptosis. These peptides lack in vitro cytotoxicity, haemolytic activity, and platelet-modulating properties and do not interfere with the blood coagulation system. Functional proteomic analyses demonstrated the reversal of PT-induced upregulated and downregulated metabolic pathway genes in PC-12 cells that were pre-treated with HNP and revealed the metabolic pathways regulated by HNP to induce neuritogenesis and confer protection against PT-induced neuronal damage in PC-12. The quantitative RT-PCR analysis confirmed that the PT-induced increased and decreased expression of critical pro-apoptotic and anti-apoptotic genes had been restored in the PC-12 cells pre-treated with the custom peptides. A network gene expression profile was proposed to elucidate the molecular interactions among the regulatory proteins for HNP to salvage the PT-induced damage. Taken together, our results show how the peptides can rescue PT-induced oxidative stress, mitochondrial dysfunction, and cellular death and suggest new opportunities for developing neuroprotective drugs.

Caenorhabditis elegans as a model system to evaluate neuroprotective potential of nano formulations

The impact of neurodegenerative illnesses on society is significant, but the mechanisms leading to neuronal malfunction and death in these conditions remain largely unknown despite identifying essential disease genes. To pinpoint the mechanisms behind the pathophysiology of neurodegenerative diseases, several researchers have turned to nematode C. elegans instead of using mammals. Since C. elegans is transparent, free-living, and amenable to culture, it has several benefits. As a result, all the neurons in C. elegans can be easily identified, and their connections are understood. Human proteins linked to Neurodegeneration can be made to express in them. It is also possible to analyze how C. elegans orthologs of the genes responsible for human neurodegenerative diseases function. In this article, we focused at some of the most important C. elegans neurodegeneration models that accurately represent many elements of human neurodegenerative illness. It has been observed that studies using the adaptable C. elegans have helped us in better understanding of human diseases. These studies have used it to replicate several aspects of human neurodegeneration. A nanotech approach involves engineering materials or equipments interacting with biological systems at the molecular level to trigger physiological responses by increasing stimulation, responding, and interacting with target sites while minimizing side effects, thus revolutionizing the treatment and diagnosis of neurodegenerative diseases. Nanotechnologies are being used to treat neurological disorders and deliver nanoscale drugs. This review explores the current and future uses of these nanotechnologies as innovative therapeutic modalities in treatment of neurodegenerative diseases using C elegans as an experimental model.

Neuroprotective effects of cannabidiol on dopaminergic neurodegeneration and α-synuclein accumulation in C. elegans models of Parkinson's disease

Parkinson disease (PD) is the second most progressive neurodegenerative disorder of the central nervous system (CNS) in the elderly, causing motor impediments and cognitive dysfunctions. Dopaminergic (DA) neuron degeneration and α-synuclein (α-Syn) accumulation in substantia nigra pars compacta (SNPc) are the major contributor to this disease. At present, the disease has no effective treatment. Many recent studies focus on identifying novel therapeutics that provide benefits to stop disease advancement in PD patients. Cannabidiol (CBD) is a cannabinoid derived from the Cannabis sativa plant and possesses anti-depressive, anti-inflammatory, and antioxidative effects. The present study aims to evaluate the neuroprotective effect of CBD in transgenic C. elegans PD models. We observed that CBD at 0.025 mM (24.66 %), 0.05 mM (52.41 %) and 0.1 mM (71.36 %) diminished DA neuron degenerations induced by 6-hydroxydopamine (6-OHDA), reduced (0.025, 27.1 %), (0.05, 38.9 %), (0.1, 51.3 %) food-sensing behavioural disabilities in BZ555, reduced 40.6 %, 56.3 %, 70.2 % the aggregative toxicity of α-Syn and expanded the nematodes' lifespan up to 11.5 %, 23.1 %, 28.8 %, dose-dependently. Moreover, CBD augmented the ubiquitin-like proteasomes 28.11 %, 43.27, 61.33 % and SOD-3 expressions by about 16.4 %, 21.2 %, 44.8 % in transgenic models. Further, we observed the antioxidative role of CBD by reducing 33.2 %, 41.4 %, 56.7 % reactive oxygen species in 6-OHDA intoxicated worms. Together, these findings supported CBD as an anti-parkinsonian drug and may exert its effects by raising lipid depositions to enhance proteasome activity and reduce oxidative stress via the antioxidative pathway.

Citri Reticulatae Semen extract promotes healthy aging and neuroprotection via autophagy induction in Caenorhabditis elegans

Nutrition intervention has emerged as a potential strategy to delay aging and promote healthy longevity. Citri Reticulatae Semen (CRS) has diverse beneficial effects and has been used for thousands of years to treat pain. However, the health benefits of CRS in prolonging healthspan and improving aging-related diseases and the exact mechanisms remain poorly characterized. In this study, Caenorhabditis elegans (C. elegans) was used as a model organism to study the anti-aging and healthspan promoting activities of 75% ethanol extract of CRS (CRSE). The results showed that treatment with CRSE at 1000 μg/mL significantly extended the lifespan of worms by 18.93% without detriment to healthspan and fitness, as evidenced by the delayed aging-related phenotypes and increased body length and width and reproductive output. In addition, CRSE treatment enhanced the ability of resistance under heat, oxidative, and pathogenic bacterial stress. Consistently, heat shock proteins and antioxidant enzyme-related and pathogenesis-related (PR) genes were up-regulated by CRSE treatment. Furthermore, CRSE supplementation also improved α-synuclein, 6-OHDA, and polyQ40-induced pathologies in transgenic C. elegans models of Parkinson's disease (PD) and Huntington's disease (HD). The mechanistic study demonstrated that CRSE induced autophagy in worms, while the RNAi knockdown of 4 key autophagy-related genes including lgg-1, bec-1, vps-34, and unc-51 remarkably abrogated the beneficial effects of CRSE on the extending of lifespan and healthspan and neuroprotection, demonstrating that CRSE exerts beneficial effects via autophagy induction in worms. Together, our current findings provide new insights into the practical application of CRS for the prevention of aging and aging-related diseases.

Using Caenorhabditis elegans to Model Therapeutic Interventions of Neurodegenerative Diseases Targeting Microbe-Host Interactions

Emerging evidence from both clinical studies and animal models indicates the importance of the interaction between the gut microbiome and the brain in the pathogenesis of neurodegenerative diseases (NDs). Although how microbes modulate neurodegeneration is still mostly unclear, recent studies have started to probe into the mechanisms for the communication between microbes and hosts in NDs. In this review, we highlight the advantages of using Caenorhabditis elegans (C. elegans) to disentangle the microbe-host interaction that regulates neurodegeneration. We summarize the microbial pro- and anti-neurodegenerative factors identified using the C. elegans ND models and the effects of many are confirmed in mouse models. Specifically, we focused on the role of bacterial amyloid proteins, such as curli, in promoting proteotoxicity and neurodegeneration by cross-seeding the aggregation of endogenous ND-related proteins, such as α-synuclein. Targeting bacterial amyloid production may serve as a novel therapeutic strategy for treating NDs, and several compounds, such as epigallocatechin-3-gallate (EGCG), were shown to suppress neurodegeneration at least partly by inhibiting curli production. Because bacterial amyloid fibrils contribute to biofilm formation, inhibition of amyloid production often leads to the disruption of biofilms. Interestingly, from a list of 59 compounds that showed neuroprotective effects in C. elegans and mouse ND models, we found that about half of them are known to inhibit bacterial growth or biofilm formation, suggesting a strong correlation between the neuroprotective and antibiofilm activities. Whether these potential therapeutics indeed protect neurons from proteotoxicity by inhibiting the cross-seeding between bacterial and human amyloid proteins awaits further investigations. Finally, we propose to screen the long list of antibiofilm agents, both FDA-approved drugs and novel compounds, for their neuroprotective effects and develop new pharmaceuticals that target the gut microbiome for the treatment of NDs. To this end, the C. elegans ND models can serve as a platform for fast, high-throughput, and low-cost drug screens that target the microbe-host interaction in NDs.

Using a Caenorhabditis elegans Parkinson's Disease Model to Assess Disease Progression and Therapy Efficiency

Despite Parkinson's Disease (PD) being the second most common neurodegenerative disease, treatment options are limited. Consequently, there is an urgent need to identify and screen new therapeutic compounds that slow or reverse the pathology of PD. Unfortunately, few new therapeutics are being produced, partly due to the low throughput and/or poor predictability of the currently used model organisms and in vivo screening methods. Our objective was to develop a simple and affordable platform for drug screening utilizing the nematode Caenorhabditis elegans. The effect of Levodopa, the "Gold standard" of PD treatment, was explored in nematodes expressing the disease-causing α-synuclein protein. We focused on two key hallmarks of PD: plaque formation and mobility. Exposure to Levodopa ameliorated the mobility defect in C. elegans, similar to people living with PD who take the drug. Further, long-term Levodopa exposure was not detrimental to lifespan. This C. elegans-based method was used to screen a selection of small-molecule drugs for an impact on α-synuclein aggregation and mobility, identifying several promising compounds worthy of further investigation, most notably Ambroxol. The simple methodology means it can be adopted in many labs to pre-screen candidate compounds for a positive impact on disease progression.

Para-Hydroxybenzyl Alcohol Delays the Progression of Neurodegenerative Diseases in Models of Caenorhabditis elegans through Activating Multiple Cellular Protective Pathways

The traditional Chinese medicine Gastrodia elata (commonly called “Tianma” in Chinese) has been widely used in the treatment of rheumatism, epilepsy, paralysis, headache, and dizziness. Phenolic compounds, such as gastrodin, para-hydroxybenzyl alcohol (HBA), p-hydroxybenzaldehyde, and vanillin are the main bioactive components isolated from Gastrodia elata. These compounds not only are structurally related but also share similar pharmacological activities, such as antioxidative and anti-inflammatory activities, and effects on the treatment of aging-related diseases. Here, we investigated the effect of para-hydroxybenzyl alcohol (HBA) on neurodegenerative diseases and aging in models of Caenorhabditis elegans (C. elegans). Our results showed that HBA effectively delayed the progression of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease in models of C. elegans. In addition, HBA could increase the average lifespan of N2 worms by more than 25% and significantly improve the age-related physiological functions of worms. Moreover, HBA improved the survival rate of worms under stresses of oxidation, heat, and pathogenic bacteria. Further mechanistic investigation revealed that HBA could activate FOXO/DAF-16 and SKN-1 to regulate antioxidative and xenobiotic metabolism pathway. HBA could also activate HSF-1 to regulate proteostasis maintenance pathway, mitochondrial unfolded stress response, endoplasmic stress response and autophagy pathways. The above results suggest that HBA activated multiple cellular protective pathways to increase stress resistance and protect against aging and aging-related diseases. Overall, our study indicates that HBA is a potential candidate for future development of antiaging pharmaceutical application.

Orientin Prolongs the Longevity of Caenorhabditis elegans and Postpones the Development of Neurodegenerative Diseases via Nutrition Sensing and Cellular Protective Pathways

Age is the major risk factor for most of the deadliest diseases. Developing small molecule drugs with antiaging effects could improve the health of aged people and retard the onset and progress of aging-associated disorders. Bioactive secondary metabolites from medicinal plants are the main source for development of medication. Orientin is a water-soluble flavonoid monomer compound widely found in many medicinal plants. Orientin inhibits fat production, antioxidation, and anti-inflammatory activities. In this study, we explored whether orientin could affect the aging of C. elegans. We found that orientin improved heat, oxidative, and pathogenic stress resistances through activating stress responses, including HSF-1-mediated heat shock response, SKN-1-mediated xenobiotic and oxidation response, mitochondria unfolded responses, endoplasmic unfolded protein response, and increased autophagy activity. Orientin also could activate key regulators of the nutrient sensing pathway, including AMPK and insulin downstream transcription factor FOXO/DAF-16 to further improve the cellular health status. The above effects of orientin reduced the accumulation of toxic proteins (α-synuclein, β-amyloid, and poly-Q) and delayed the onset of neurodegenerative disorders in AD, PD, and HD models of C. elegans and finally increased the longevity and health span of C. elegans. Our results suggest that orientin has promising antiaging effects and could be a potential natural source for developing novel therapeutic drugs for aging and its related diseases.

Relevance of bioassay of biologically active substances (BAS) with geroprotective properties in the model of the nematode Caenorhabditis elegans in experiments in vivo

Aging is a process global in nature. The age of living organisms contributes to the appearance of chronic diseases, which not only reduce the quality of life, but also significantly damage it. Modern medicines can successfully fight multiple diseases and prolong life. At the same time, medications have a large number of side effects. New research indicates that bioactive phytochemicals have great potential for treating even the most severe diseases and can become an alternative to medicines. Despite many studies in this area, the effects of many plant ingredients on living organisms are poorly understood. Analysis of the mechanisms through which herbal preparations influence the aging process helps to select the right active substances, determine the optimal doses to obtain the maximum positive effect. It is preferable to check the effectiveness of plant extracts and biologically active components with geroprotective properties in vivo. For these purposes, live model systems such as Rattus rattus, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans are used. These models help to comprehensively study the impact of the developed new drugs on the aging process. The model organism C. elegans is gaining increasing popularity in these studies because of its many advantages. This review article discusses the advantages of the nematode C. elegans as a model organism for studying the processes associated with aging. The influence of various BAS and plant extracts on the increase in the life span of the nematode, on the increase in its stress resistance and on other markers of aging is also considered. The review showed that the nematode C. elegans has a number of advantages over other organisms and is a promising model system for studying the geroprotective properties of BAS.

Natural products are an important source for proteasome regulating agents

BACKGROUND

Natural medicines have a long history in the prevention and treatment of various diseases in East Asian region, especially in China. Modern research has proved that the pharmacological effects of numerous natural medicines involve the participation of ubiquitin proteasome system (UPS). UPS can degrade the unwanted and damaged proteins widely distributed in the nucleus and cytoplasm of various eukaryotes.

PURPOSE

The objective of the present study was to review and discuss the regulatory effects of natural products and extracts on proteasome components, which may help to find new proteasome regulators for drug development and clinical applications.

METHODS

The related information was compiled using the major scientific databases, such as CNKI, Elsevier, ScienceDirect, PubMed, SpringerLink, Wiley Online, and GeenMedical. The keywords "natural product" and "proteasome" were applied to extract the literature. Nature derived extracts, compounds and their derivatives involved in proteasome regulation were included, and the publications related to synthetic proteasome agents were excluded.

RESULTS

The pharmacological effects of more than 80 natural products and extracts derived from phytomedicines related to the proteasome regulation were reviewed. These natural products were classified according to their chemical properties. We also summarized some laws of action of natural products as proteasome regulators in the treatment of diseases, and listed the action characteristics of the typical natural products.

CONCLUSION

Natural products derived from nature can induce the degradation of damaged proteins through UPS or act as regulators to directly regulate the activity of proteasome. But few proteasome modulators are applied clinically. Summary of known rules for proteasome modulators will contribute to discover, modify and synthesize more proteasome modulators for clinical applications.

The dopaminergic neuroprotective effects of different phytosterols identified in rice bran and rice bran oil

Phytosterols are important bioactive compounds in rice bran and rice bran oil, and the compositions of different phytosterols in rice bran and rice bran oil were investigated in our previous research. In this study, the dopaminergic neuroprotective effects and the underlying mechanisms of sitosterol, cycloartenyl ferulate, 24-methylenecycloartanyl ferulate and campesteryl ferulate identified in rice bran and rice bran oil were investigated in a rotenone-treated C. elegans model. The results indicated that the increased oxidative stress resistance induced by the activation of the DAF-16/FOXO pathway and the inhibition of the apoptotic protein CED-3 overexpression might play an important role in protecting the dopaminergic neurons. The results of this research reveal a new bioactivity of different phytosterols and are helpful for the further nutritional evaluation of rice bran and rice bran oil.

N-γ-(L-glutamyl)-L-selenomethionine shows neuroprotective effects against Parkinson's disease associated with SKN-1/Nrf2 and TRXR-1 in Caenorhabditis elegans

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease, yet fundamental treatments for the disease remain sparse. Thus, the search for potentially efficacious compounds from medicinal plants that can be used in the treatment of PD has gained significant interest.

PURPOSE

In many medicinal plants, selenium is primarily found in an organic form. We investigated the neuroprotective potential of an organic form of selenium, N-γ-(L-glutamyl)-L-selenomethionine (Glu-SeMet) in a Caenorhabditis elegans PD model and its possible molecular mechanisms.

METHODS

We used a C. elegans pharmacological PD strain (BZ555) that specifically expresses green fluorescent protein (GFP) in dopaminergic neurons and a transgenic PD strain (NL5901) that expresses human α-synuclein (α-syn) in muscle cells to investigate the neuroprotective potential of Glu-SeMet against PD.

RESULTS

We found that Glu-SeMet significantly ameliorated 6-hydroxydopamine (6-OHDA)-induced dopaminergic neuron damage in the transgenic BZ555 strain, with corresponding improvements in slowing behavior and intracellular ROS levels. In addition, compared with clinical PD drugs (L-DOPA and selegiline), Glu-SeMet demonstrated stronger ameliorated effects on 6-OHDA-induced toxicity. Glu-SeMet also triggered the nuclear translocation of SKN-1/Nrf2 and significantly increased SKN-1, GST-4, and GCS-1 mRNA levels in the BZ555 strain. However, Glu-SeMet did not increase mRNA levels or ameliorate the damage to dopaminergic neurons when the BZ555 strain was subjected to skn-1 RNA interference (RNAi). Glu-SeMet also upregulated the mRNA levels of the selenoprotein TRXR-1 in both the BZ555 and BZ555; skn-1 RNAi strains and significantly decreased α-syn accumulation in the NL5901 strain, although this was not observed in the NL5901; trxr-1 strain.

CONCLUSION

We found that Glu-SeMet has a neuroprotective effect against PD in a C. elegans PD model and that the anti-PD effects of Glu-SeMet were associated with SKN-1/Nrf2 and TRXR-1. Glu-SeMet may thus have the potential for use in therapeutic applications or supplements to slow the progression of PD.

Novel pentacyclic triterpenes exhibiting strong neuroprotective activity in SH-SY5Y cells in salsolinol- and glutamate-induced neurodegeneration models

Novel triterpene derivatives were prepared and evaluated in salsolinol (SAL)- and glutamate (Glu)-induced models of neurodegeneration in neuron-like SH-SY5Y cells. Among the tested compounds, betulin triazole 4 bearing a tetraacetyl-β-d-glucose substituent showed a highly potent neuroprotective effect. Further studies revealed that removal of tetraacetyl-β-d-glucose part (free triazole derivative 10) resulted in strong neuroprotection in the SAL model at 1 μM, but this derivative suffered from cytotoxicity at higher concentrations. Both compounds modulated oxidative stress and caspase-3,7 activity, but 10 showed a superior effect comparable to the Ac-DEVD-CHO inhibitor. Interestingly, while both 4 and 10 outperformed the positive controls in blocking mitochondrial permeability transition pore opening, only 4 demonstrated potent restoration of the mitochondrial membrane potential (MMP) in the model. Derivatives 4 and 10 also showed neuroprotection in the Glu model, with 10 exhibiting the strongest oxidative stress reducing effect among the tested compounds, while the neuroprotective activity of 4 was probably due recovery of the MMP.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

A Dihydroflavonoid Naringin Extends the Lifespan of C. elegans and Delays the Progression of Aging-Related Diseases in PD/AD Models via DAF-16

Naringin is a dihydroflavonoid, which is rich in several plant species used for herbal medicine. It has a wide range of biological activities, including antineoplastic, anti-inflammatory, antiphotoaging, and antioxidative activities. So it would be interesting to know if naringin has an effect on aging and aging-related diseases. We examined the effect of naringin on the aging of Caenorhabditis elegans (C. elegans). Our results showed that naringin could extend the lifespan of C. elegans. Moreover, naringin could also increase the thermal and oxidative stress tolerance, reduce the accumulation of lipofuscin, and delay the progress of aging-related diseases in C. elegans models of AD and PD. Naringin could not significantly extend the lifespan of long-lived mutants from genes in insulin/IGF-1 signaling (IIS) and nutrient-sensing pathways, such as daf-2, akt-2, akt-1, eat-2, sir-2.1, and rsks-1. Naringin treatment prolonged the lifespan of long-lived glp-1 mutants, which have decreased reproductive stem cells. Naringin could not extend the lifespan of a null mutant of the fox-head transcription factor DAF-16. Moreover, naringin could increase the mRNA expression of genes regulated by daf-16 and itself. In conclusion, we show that a natural product naringin could extend the lifespan of C. elegans and delay the progression of aging-related diseases in C. elegans models via DAF-16.

Intergenerational toxicity of nonylphenol ethoxylate (NP-9) in Caenorhabditis elegans

The ethoxylated isomers of nonylphenol (NPEs, NP-9) are one of the main active ingredients present in nonionic surfactants employed as herbicides, cosmetics, paints, plastics, disinfectants and detergents. These chemicals and their metabolites are commonly found in environmental matrices. The aim of this work was to evaluate the intergenerational toxicity of NP-9 in Caenorhabditis elegans. The lethality, length, width, locomotion and lifespan were investigated in the larval stage L4 of the wild strain N2. Transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. RT-qPCR was utilized to measure mRNA expression for neurotoxicity-related genes (unc-30, unc-25, dop-3, dat-1, mgl-1, and eat-4). Data were obtained from parent worms (P0) and the first generation (F1). Lethality of the nematode was concentration-dependent, with 48 h-LC₅₀ values of 3215 and 1983 μM in P0 and F1, respectively. Non-lethal concentrations of NP-9 reduced locomotion. Lifespan was also decreased by the xenobiotic, but the negative effect was greater in P0 than in F1. Non-monotonic concentration-response curves were observed for body length and width in both generations. The gene expression profile in P0 was different from that registered in F1, although the expression of sod-4, hsp-70, gpx-6 and mtl-2 increased with the surfactant concentration in both generations. None of the tested genes followed a classical concentration-neurotoxicity relationship. In P0, dopamine presented an inverted-U curve, while GABA and glutamate displayed a bimodal type. However, in F1, inverted U-shaped curves were revealed for these genes. In summary, NP-9 induced intergenerational responses in C. elegans through mechanisms involving ROS, and alterations of the GABA, glutamate, and dopamine pathways.

Metal-induced neurotoxicity in a RAGE-expressing C. elegans model

Environmental and occupational metal exposure poses serious global concerns. Metal exposure have severally been associated with neurotoxicity and brain damage. Furthermore, receptor for advanced glycation end products (RAGE) is also implicated in neurological disorders, particularly those with altered glucose metabolism. Here, we examine potential compounding effect of metal exposure and RAGE expression on dopamine (DA) and serotonin (SER) neurons in C. elegans. In addition, we evaluate the effect of RAGE expression on DA and SER neurons in hyperglycemic conditions. Newly generated RAGE-expressing C. elegans tagged with green fluorescent proteins (GFP) in DAergic and SERergic neurons were treated with cadmium (Cd) or manganese (Mn). Additionally, the RAGE-expressing worms were also exposed to high glucose conditions. Results showed metals induced neurodegeneration both in the presence and absence of RAGE expression, but the manner of degeneration differed between Cd and Mn treated nematodes. Furthermore, RAGE-expressing worms showed significant neurodegeneration in both DAergic and SERergic neurons. Our results indicate co-occurrence of metal exposure and RAGE expression can induce neurodegeneration. Additionally, we show that RAGE expression can exacerbate hyperglycemic induced neurodegeneration.

Maackiain Ameliorates 6-Hydroxydopamine and SNCA Pathologies by Modulating the PINK1/Parkin Pathway in Models of Parkinson's Disease in Caenorhabditis elegans and the SH-SY5Y Cell Line

The movement disorder Parkinson's disease (PD) is the second most frequently diagnosed neurodegenerative disease, and is associated with aging, the environment, and genetic factors. The intracellular aggregation of α-synuclein and the loss of dopaminergic neurons in the substantia nigra pars compacta are the pathological hallmark of PD. At present, there is no successful treatment for PD. Maackiain (MK) is a flavonoid extracted from dried roots of Sophora flavescens Aiton. MK has emerged as a novel agent for PD treatment that acts by inhibiting monoamine oxidase B. In this study, we assessed the neuroprotective potential of MK in Caenorhabditis elegans and investigated possible mechanism of this neuroprotection in the human SH-SY5Y cell line. We found that MK significantly reduced dopaminergic neuron damage in 6-hydroxydopamine (6-OHDA)-exposed worms of the BZ555 strain, with corresponding improvements in food-sensing behavior and life-span. In transgenic worms of strain NL5901 treated with 0.25 mM MK, the accumulation of α-synuclein was diminished by 27% (p < 0.01) compared with that in untreated worms. Moreover, in worms and the SH-SY5Y cell line, we confirmed that the mechanism of MK-mediated protection against PD pathology may include blocking apoptosis, enhancing the ubiquitin-proteasome system, and augmenting autophagy by increasing PINK1/parkin expression. The use of small interfering RNA to downregulate parkin expression in vivo and in vitro could reverse the benefits of MK in PD models. MK may have considerable therapeutic applications in PD.

Terpenoids as Potential Geroprotectors

Terpenes and terpenoids are the largest groups of plant secondary metabolites. However, unlike polyphenols, they are rarely associated with geroprotective properties. Here we evaluated the conformity of the biological effects of terpenoids with the criteria of geroprotectors, including primary criteria (lifespan-extending effects in model organisms, improvement of aging biomarkers, low toxicity, minimal adverse effects, improvement of the quality of life) and secondary criteria (evolutionarily conserved mechanisms of action, reproducibility of the effects on different models, prevention of age-associated diseases, increasing of stress-resistance). The number of substances that demonstrate the greatest compliance with both primary and secondary criteria of geroprotectors were found among different classes of terpenoids. Thus, terpenoids are an underestimated source of potential geroprotectors that can effectively influence the mechanisms of aging and age-related diseases.

A novel semi-supervised multi-view clustering framework for screening Parkinson's disease

In recent years, there are many research cases for the diagnosis of Parkinson's disease (PD) with the brain magnetic resonance imaging (MRI) by utilizing the traditional unsupervised machine learning methods and the supervised deep learning models. However, unsupervised learning methods are not good at extracting accurate features among MRIs and it is difficult to collect enough data in the field of PD to satisfy the need of training deep learning models. Moreover, most of the existing studies are based on single-view MRI data, of which data characteristics are not sufficient enough. In this paper, therefore, in order to tackle the drawbacks mentioned above, we propose a novel semi-supervised learning framework called Semi-supervised Multi-view learning Clustering architecture technology (SMC). The model firstly introduces the sliding window method to grasp different features, and then uses the dimensionality reduction algorithms of Linear Discriminant Analysis (LDA) to process the data with different features. Finally, the traditional single-view clustering and multi-view clustering methods are employed on multiple feature views to obtain the results. Experiments show that our proposed method is superior to the state-of-art unsupervised learning models on the clustering effect. As a result, it may be noted that, our work could contribute to improving the effectiveness of identifying PD by previous labeled and subsequent unlabeled medical MRI data in the realistic medical environment.

Chemistry, Biological Activities and In Silico Bioprospection of Sterols and Triterpenes from Mexican Columnar Cactaceae

The Cactaceae family is an important source of triterpenes and sterols. The wide uses of those plants include food, gathering, medicinal, and live fences. Several studies have led to the isolation and characterization of many bioactive compounds. This review is focused on the chemistry and biological properties of sterols and triterpenes isolated mainly from some species with columnar and arborescent growth forms of Mexican Cactaceae. Regarding the biological properties of those compounds, apart from a few cases, their molecular mechanisms displayed are not still fully understand. To contribute to the above, computational chemistry tools have given a boost to traditional methods used in natural products research, allowing a more comprehensive exploration of chemistry and biological activities of isolated compounds and extracts. From this information an in silico bioprospection was carried out. The results suggest that sterols and triterpenoids present in Cactaceae have interesting substitution patterns that allow them to interact with some bio targets related to inflammation, metabolic diseases, and neurodegenerative processes. Thus, they should be considered as attractive leads for the development of drugs for the management of chronic degenerative diseases.

Betula utilis extract prolongs life expectancy, protects against amyloid-β toxicity and reduces Alpha Synuclien in Caenorhabditis elegans via DAF-16 and SKN-1

Betula utilis (BU), an important medicinal plant that grows in high altitudes of the Himalayan region, has been utilized traditionally due to it's antibacterial, hepatoprotective, and anti-tumor properties. Here, we demonstrated the longevity and amyloid-β toxicity attenuating activity of B. utilis ethanolic extract (BUE) in Caenorhabditis elegans. Lifespan of the worms was observed under both the standard laboratory and stress (oxidative and thermal) conditions. Effect of BUE was also observed on the attenuation of age-dependent physiological parameters. Further, gene-specific mutants and green fluorescent protein (GFP)-tagged strains were used to investigate the molecular mechanism underlying the beneficial effects mediated by BUE supplementation. Our results showed that BUE (50 μg/ml) extended the mean lifespan of C. elegans by 35.99% and increased its survival under stress conditions. The BUE also reduced the levels of intracellular reactive oxygen species (ROS) by 22.47%. A delayed amyloid-β induced paralyses was observed in CL4176 transgenic worms. Interestingly, the BUE supplementation was also able to reduce the α-synuclein aggregation in NL5901 transgenic strain. Gene-specific mutant studies suggested that the BUE-mediated lifespan extension was dependent on daf-16, hsf-1, and skn-1 but not on sir-2.1 gene. Furthermore, transgenic reporter gene expression assay showed that BUE treatment enhanced the expression of stress-protective genes such as sod-3 and gst-4. Present findings suggested that ROS scavenging activity, together with multiple longevity mechanisms, were involved in BUE-mediated lifespan extension. Thus, BUE might have potential to increase the lifespan and to attenuate neuro-related disease progression.

Betulin and its derivatives as novel compounds with different pharmacological effects

Betulin (B) and Betulinic acid (BA) are natural pentacyclic lupane-structure triterpenoids which possess a wide range of pharmacological activities. Recent evidence indicates that B and BA have several properties useful for the treatment of metabolic disorders, infectious diseases, cardiovascular disorders, and neurological disorders. In the current review, we discuss B and BA structures and derivatives and then comprehensively explain their pharmacological effects in relation to various diseases. We also explain antiviral, antibacterial and anti-cancer effects of B and BA. Finally, we discuss the delivery methods, in which these compounds most effectively target different systems.

Studying Parkinson’s disease using Caenorhabditis elegans models in microfluidic devices

Parkinson’s disease (PD) is a progressive neurological disorder associated with the loss of dopaminergic neurons (DNs) in the substantia nigra and the widespread accumulation of α-synuclein (α-syn) protein, leading to motor impairments and eventual cognitive dysfunction. In-vitro cell cultures and in-vivo animal models have provided the opportunity to investigate the PD pathological hallmarks and identify different therapeutic compounds. However, PD pathogenesis and causes are still not well understood, and effective inhibitory drugs for PD are yet to be discovered. Biologically simple but pathologically relevant disease models and advanced screening technologies are needed to reveal the mechanisms underpinning protein aggregation and PD progression. For instance, Caenorhabditis elegans (C. elegans) offers many advantages for fundamental PD neurobehavioral studies including a simple, well-mapped, and accessible neuronal system, genetic homology to humans, body transparency and amenability to genetic manipulation. Several transgenic worm strains that exhibit multiple PD-related phenotypes have been developed to perform neuronal and behavioral assays and drug screening. However, in conventional worm-based assays, the commonly used techniques are equipment-intensive, slow and low in throughput. Over the past two decades, microfluidics technology has contributed significantly to automation and control of C. elegans assays. In this review, we focus on C. elegans PD models and the recent advancements in microfluidic platforms used for manipulation, handling and neurobehavioral screening of these models. Moreover, we highlight the potential of C. elegans to elucidate the in-vivo mechanisms of neuron-to-neuron protein transfer that may underlie spreading Lewy pathology in PD, and its suitability for in-vitro studies. Given the advantages of C. elegans and microfluidics technology, their integration has the potential to facilitate the investigation of disease pathology and discovery of potential chemical leads for PD.

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.