Rosmarinic acid protects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced dopaminergic neurotoxicity in zebrafish embryos

DJ-1: Potential target for treatment of myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a significant global health concern, resulting in high rates of mortality and disability among patients. Although coronary blood flow reperfusion is a key treatment for IHD, it often leads to acute myocardial ischemia-reperfusion injury (IRI). Current intervention strategies have limitations in providing adequate protection for the ischemic myocardium. DJ-1, originally known as a Parkinson's disease related protein, is a highly conserved cytoprotective protein. It is involved in enhancing mitochondrial function, scavenging reactive oxygen species (ROS), regulating autophagy, inhibiting apoptosis, modulating anaerobic metabolism, and exerting anti-inflammatory effects. DJ-1 is also required for protective strategies, such as ischemic preconditioning, ischemic postconditioning, remote ischemic preconditioning and pharmacological conditioning. Therefore, DJ-1 emerges as a potential target for the treatment of myocardial IRI. Our comprehensive review delves into its protective mechanisms in myocardial IRI and the structural foundations underlying its functions.

Role of Glutathione in Parkinson's Disease Pathophysiology and Therapeutic Potential of Polyphenols

Oxidative stress is recognized to have a central role in the initiation and progression of Parkinson's disease (PD). Within the brain, neurons are particularly sensitive to oxidation due in part to their weak intrinsic antioxidant defense. Theoretically, neurons mostly depend on neighboring astrocytes to provide antioxidant protection by supplying cysteine-containing products for glutathione (GSH) synthesis. Astrocytes and neurons possess several amino acid transport systems for GSH and its precursors. Indeed, GSH is the most abundant intrinsic antioxidant in the central nervous system. The GSH depletion and/or alterations in its metabolism in the brain contribute to the pathogenesis of PD. Noteworthy, polyphenols possess potent antioxidant activity and can augment the GSH redox system. Numerous in vitro and in vivo studies have indicated that polyphenols exhibit potent neuroprotective effects in PD. Epidemiological studies have found an association between the consumption of dietary polyphenols and a lower PD risk. In this review, we summarize current knowledge on the biosynthesis and metabolism of GSH in the brain, with an emphasis on their contribution and therapeutic potential in PD. In particular, we focus on polyphenols that can increase brain GSH levels against PD. Furthermore, some current challenges and future perspectives for polyphenol-based therapies are also discussed.

Phytochemicals regulate cancer metabolism through modulation of the AMPK/PGC-1α signaling pathway

BACKGROUND

Due to the complex pathophysiological mechanisms involved in cancer progression and metastasis, current therapeutic approaches lack efficacy and have significant adverse effects. Therefore, it is essential to establish novel strategies for combating cancer. Phytochemicals, which possess multiple biological activities, such as antioxidant, anti-inflammatory, antimutagenic, immunomodulatory, antiproliferative, anti-angiogenesis, and antimetastatic properties, can regulate cancer progression and interfere in various stages of cancer development by suppressing various signaling pathways.

METHODS

The current systematic and comprehensive review was conducted based on Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) criteria, using electronic databases, including PubMed, Scopus, and Science Direct, until the end of December 2023. After excluding unrelated articles, 111 related articles were included in this systematic review.

RESULTS

In this current review, the major signaling pathways of cancer metabolism are highlighted with the promising anticancer role of phytochemicals. This was through their ability to regulate the AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) signaling pathway. The AMPK/PGC-1α signaling pathway plays a crucial role in cancer cell metabolism via targeting energy homeostasis and mitochondria biogenesis, glucose oxidation, and fatty acid oxidation, thereby generating ATP for cell growth. As a result, targeting this signaling pathway may represent a novel approach to cancer treatment. Accordingly, alkaloids, phenolic compounds, terpene/terpenoids, and miscellaneous phytochemicals have been introduced as promising anticancer agents by regulating the AMPK/PGC-1α signaling pathway. Novel delivery systems of phytochemicals targeting the AMPK/PGC-1α pathway in combating cancer are also highlighted in this review.

Parkinson's disease model in zebrafish using intraperitoneal MPTP injection

Introduction

Parkinson's disease (PD) is the second most common neurodegenerative disease that severely affects the quality of life of patients and their family members. Exposure to 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been shown to reflect behavioral, molecular, and proteomic features of PD. This study aimed to assess the protocol for inducing PD following MPTP injection in adult zebrafish.

Methods

Fish were injected with 100 μg/g of MPTP intraperitoneally once or twice and then assessed on days 1 to 30 post-injection.

Results

Between one-time and two-time injections, there was no significant difference in most locomotor parameters, expressions of tyrosine hydroxylase-2 (th2) and dopamine transporter (dat) genes, and dopaminergic neurons (tyrosine hydroxylase positive, TH+ cells) counts. However, caspase-3 levels significantly differed between one- and two-time injections on the day 1 assessment.

Discussion

Over a 30-day period, the parameters showed significant differences in swimming speed, total distance traveled, tyrosine hydroxylase-1 (th1) and dat gene expressions, caspase-3 and glutathione protein levels, and TH+ cell counts. Days 3 and 5 showed the most changes compared to the control. In conclusion, a one-time injection of MPTP with delayed assessment on days 3 to 5 is a good PD model for animal studies.

LAR Downregulation Protects the Astrocytic U251 and Cocultured SH-SY5Y Cells in a Rotenone-Induced Parkinson's Disease Cell Model

Leukocyte common antigen-related protein tyrosine phosphatase (LAR) is a member of the protein tyrosine phosphatase family that serves as a key regulator of cellular survival. It is also involved in neurodevelopment and brain disorders. This study was designed to investigate the role of LAR in a cell-based model of Parkinson's disease (PD) in which U251 and SH-SY5Y cells were used as models of astrocytes and dopaminergic neurons, respectively. Cell viability, cell death, cell morphology, protein phosphorylation and expression, ATP levels, reactive oxygen species (ROS) generation, and mitochondrial membrane potential were analyzed in the wild-type (WT) and heterozygous LAR-knockout astrocytoma U251 cells to assess the cell state, signal transduction, and mitochondrial function. LAR downregulation showed a protective effect in rotenone-exposed U251 cells by increasing cell viability, reducing cell mortality, and restoring appropriate cellular morphology. LAR downregulation enhanced IGF-1R phosphorylation and downstream signal transduction as evidenced by increases in the Akt and GSK-3β phosphorylation, as well as the upregulation of NRF2 and HO-1. The downregulation of LAR also augmented DJ-1 levels in these cells. The enhanced Akt and GSK-3β phosphorylation contributed to a reduced Bax/Bcl2 ratio and suppressed apoptosis after rotenone exposure. Heterozygous LAR-knockout U251 cells exhibited higher mitochondrial function evidenced by increased mitochondrial membrane potential, ATP contents, and reduced ROS production compared to the WT cells following rotenone exposure. Further studies showed that the astrocytic protection mediated by the heterozygous knockout of LAR was associated with the activation of Akt. A specific Akt inhibitor, MK2206, reduced the cell viability, Akt and GSK3β phosphorylation, and HO-1 and NRF2 expression in U251 cells exposed to rotenone. Astrocytes provide structural and metabolic support to maintain neuronal health. Astrocytic glial cell-derived neurotrophic factor (GDNF) production is vital for dopaminergic neuron survival. Heterozygous LAR-knockout U251 cells produced higher amounts of GDNF than the WT cells. The SH-SY5Y cells cocultured with heterozygous LAR-knockout U251 cells exhibited greater viability than that of cells cocultured with WT U251 cells in response to rotenone. Together, these findings demonstrate that the heterozygous knockout of LAR in astrocytes can play a key role in protecting both astrocytic cells and cocultured neurons in a rotenone-induced cell-based model of PD. This neuroprotective effect is attributable to the augmentation of IGF1R-Akt-GDNF signaling and the maintenance of astrocytic mitochondrial function.

Experimental models of chemically induced Parkinson's disease in zebrafish at the embryonic larval stage: a systematic review

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra that results in a decrease in dopamine levels, resulting in motor-type disturbances. Different vertebrate models, such as rodents and fish, have been used to study PD. In recent decades, Danio rerio (zebrafish) has emerged as a potential model for the investigation of neurodegenerative diseases due to its homology to the nervous system of humans. In this context, this systematic review aimed to identify publications that reported the utilization of neurotoxins as an experimental model of parkinsonism in zebrafish embryos and larvae. Ultimately, 56 articles were identified by searching three databases (PubMed, Web of Science, and Google Scholar). Seventeen studies using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 4 1-methyl-4-phenylpyridinium (MPP+), 24 6-hydroxydopamine (6-OHDA), 6 paraquat/diquat, 2 rotenone, and 6 articles using other types of unusual neurotoxins to induce PD were selected. Neurobehavioral function, such as motor activity, dopaminergic neuron markers, oxidative stress biomarkers, and other relevant parameters in the zebrafish embryo-larval model were examined. In summary, this review provides information to help researchers determine which chemical model is suitable to study experimental parkinsonism, according to the effects induced by neurotoxins in zebrafish embryos and larvae.

Zebrafish as a Model Organism for Studying Pathologic Mechanisms of Neurodegenerative Diseases and other Neural Disorders

Zebrafish are widely considered an excellent vertebrate model for studying the pathogenesis of human diseases because of their transparency of embryonic development, easy breeding, high similarity with human genes, and easy gene manipulation. Previous studies have shown that zebrafish as a model organism provides an ideal operating platform for clarifying the pathological and molecular mechanisms of neurodegenerative diseases and related human diseases. This review mainly summarizes the achievements and prospects of zebrafish used as model organisms in the research of neurodegenerative diseases and other human diseases related to the nervous system in recent years. In the future study of human disease mechanisms, the application of the zebrafish model will continue to provide a valuable operating platform and technical support for investigating and finding better prevention and treatment of these diseases, which has broad application prospects and practical significance. Zebrafish models used in neurodegenerative diseases and other diseases related to the nervous system.

The Importance of Animal Models in Biomedical Research: Current Insights and Applications

Animal research is considered a key element in advance of biomedical science. Although its use is controversial and raises ethical challenges, the contribution of animal models in medicine is essential for understanding the physiopathology and novel treatment alternatives for several animal and human diseases. Current pandemics’ pathology, such as the 2019 Coronavirus disease, has been studied in primate, rodent, and porcine models to recognize infection routes and develop therapeutic protocols. Worldwide issues such as diabetes, obesity, neurological disorders, pain, rehabilitation medicine, and surgical techniques require studying the process in different animal species before testing them on humans. Due to their relevance, this article aims to discuss the importance of animal models in diverse lines of biomedical research by analyzing the contributions of the various species utilized in science over the past five years about key topics concerning human and animal health.

Rosmarinic acid alone or in combination with Lactobacillus rhamnosus ameliorated ammonia stress in the rainbow trout, Oncorhynchus mykiss: growth, immunity, antioxidant defense and liver functions

Rosmarinic acid (RS) and Lactobacillus rhamnosus (LR) were added singularly or in combination to rainbow trout (Oncorhynchus mykiss) diets to test their efficacy in the protection against ammonia stress. Fish (31.4±0.6 g) were randomly allocated to six groups in three replicates, as follows: T1: basic food as control, T2: LR with a concentration of 1.5 × 108 CFU/g, T3: LR with a concentration of 3 × 108 CFU/g, T4: 1 g RS/kg, T5: 3 g RS/kg, and T6: 1.5 × 108 CFU/g LR + 1 g RS/kg and T7: 3 × 108 CFU/g LR + 3 g RS/kg. After 60 days feeding, fish exposed to 0ammonia stress. After the feeding period, the supplemented fish had the highest final body weight (FW), weight gain (WG), and specific growth rate (SGR), and the lowest feed conversion ratio (FCR) as compared with the control group (P<0.05). Amylase, protease and lipase activities were noticed markedly higher in fish supplemented with 1.5 × 108 CFU/g LR + 1 g RS/kg and 1.5 × 108 CFU/g LR diets compared to the control (P<0.05). Generally, fish in supplemented diets, particularly T2 and T6 groups, had the highest lysozyme, alternative complement activity (ACH50), total Ig, nitroblue tetrazolium test (NBT), myeloperoxidase (MPO), complement component 3 (C3), complement component 4 (C4), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). On the other hand, T2 and T6 groups had the lowest malondialdehyde (MDA), glucose, and cortisol concentrations as well as alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) enzyme levels when were compared with the control (P<0.05). After ammonia stress, fish in the supplemented groups, particularly T2 and T6, generally showed significantly higher values of lysozyme, ACH50, total Ig, NBT, MPO, C3, C4, SOD, CAT, GPx and lower levels of MDA, glucose, cortisol, ALT, ALP, LDH when compared with the control (P<0.05). In conclusion, a combined administration of RS and L. rhamnosus effectively improved growth performance and health status as well as enhanced the resistance of rainbow trout against ammonia toxicity.

Mitochondrial Modulators: The Defender

Mitochondria are widely considered the "power hub" of the cell because of their pivotal roles in energy metabolism and oxidative phosphorylation. However, beyond the production of ATP, which is the major source of chemical energy supply in eukaryotes, mitochondria are also central to calcium homeostasis, reactive oxygen species (ROS) balance, and cell apoptosis. The mitochondria also perform crucial multifaceted roles in biosynthetic pathways, serving as an important source of building blocks for the biosynthesis of fatty acid, cholesterol, amino acid, glucose, and heme. Since mitochondria play multiple vital roles in the cell, it is not surprising that disruption of mitochondrial function has been linked to a myriad of diseases, including neurodegenerative diseases, cancer, and metabolic disorders. In this review, we discuss the key physiological and pathological functions of mitochondria and present bioactive compounds with protective effects on the mitochondria and their mechanisms of action. We highlight promising compounds and existing difficulties limiting the therapeutic use of these compounds and potential solutions. We also provide insights and perspectives into future research windows on mitochondrial modulators.

Protective Effects of Hippophae rhamnoides L. Phenylpropanoids on Doxorubicin-Induced Cardiotoxicity in Zebrafish

Hippophae rhamnoides L. is a deciduous shrub that contains many unique bioactive substances. This sea buckthorn possesses anticancer, antioxidant, anti-inflammatory, and cardiovascular protective properties. Herein, the effects of phenylpropyl compounds extracted from H. rhamnoides L. on doxorubicin (Dox)-induced cardiotoxicity were evaluated in zebrafish. Cardiac injury in zebrafish was induced using 35 μM Dox for 96 h, and 30 μM phenylpropanoid compounds were used as the protective treatment. The cardioprotective effects and mechanisms of the four phenylpropanoids were investigated using microscopy, behavioral analysis, acridine orange staining, western blotting, flow cytometry, and real-time quantitative polymerase chain reaction. The extracted phenylpropanoids could significantly relieve Dox-induced cardiac injury in zebrafish and inhibit cardiomyocyte apoptosis. The mechanisms of action were mainly related to the stability of mitochondrial biogenesis and function maintained by phenylpropanoids in zebrafish. To our knowledge, this is the first report on the protective effect of sea buckthorn against myocardial injury in zebrafish. Our findings provide support for the further research and development of sea buckthorn and its components.

Anxiolytic and antidepressive potentials of rosmarinic acid: A review with a focus on antioxidant and anti-inflammatory effects

Depression and anxiety are the most prevalent neuropsychiatric disorders that have emerged as global health concerns. Anxiolytic and antidepressant drugs, such as benzodiazepines, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, and tricyclics, are the first line used in treating anxiety and depression. Although these drugs lack efficacy and have a delayed response time and numerous side effects, their widespread abuse and market continue to grow. Over time, traditional practices using natural and phytochemicals as alternative therapies to chemical drugs have emerged to treat many pathological conditions, including anxiety and depression. Recent preclinical studies have demonstrated that the phenolic compound, rosmarinic acid, is effective against several neuropsychiatric disorders, including anxiety and depression. In addition, rosmarinic acid showed various pharmacological effects, such as cardioprotective, hepatoprotective, lung protective, antioxidant, anti-inflammatory, and neuroprotective effects. However, the potentialities of the use of rosmarinic acid in the treatment of nervous system-related disorders, such as anxiety and depression, are less or not yet reviewed. Therefore, the purpose of this review was to present several preclinical and clinical studies, when available, from different databases investigating the effects of rosmarinic acid on anxiety and depression. These studies showed that rosmarinic acid produces advantageous effects on anxiety and depression through its powerful antioxidant and anti-inflammatory properties. This review will examine and discuss the possibility that the anxiolytic and anti-depressive effects of rosmarinic acid could be associated with its potent antioxidant and anti-inflammatory activities.

Rosmarinic Acid Attenuates Rotenone-Induced Neurotoxicity in SH-SY5Y Parkinson’s Disease Cell Model through Abl Inhibition

Rosmarinic acid (RA) is a natural polyphenolic compound with antioxidative property. With the present study, we aimed to evaluate the neuroprotective role of RA on Parkinson’s disease using rotenone induced SH-SY5Y cell model of Parkinson’s disease, the underlying mechanism of action of RA was also investigated. Cell viability, cell morphology, apoptosis, signaling protein phosphorylation and expression, cellular reactive oxygen species (ROS) production, ATP content, and mitochondrial membrane potential were tested in SH-SY5Y cells. RA showed a neuroprotective effect in a rotenone-induced SH-SY5Y cell model of Parkinson’s disease with dose-dependent manner, it reduced cell apoptosis and restored normal cell morphology. RA not only decreased levels of α-synuclein and Tau phosphorylation but also elevated the contents of AMPK phosphorylation, Akt phosphorylation, and PGC-1α. RA restored the reduced mitochondrial membrane potential and ATP content as well as inhibited rotenone-induced ROS overproduction. Further findings demonstrated that the neuroprotective role of RA was partially due to the inhibition of Abl tyrosine kinase. RA treatment suppressed the hyperphosphorylation of Abl Y412 and CrkII Y221 induced by rotenone. Nilotinib, a specific inhibitor of Abl, elicited a similar neuroprotective effect as that of RA. The present study indicates that RA has a property of neuroprotection against rotenone, and the neuroprotective effect is partially attributed to the inhibition of Abl.

Rosmarinic Acid Inhibits Mitochondrial Damage by Alleviating Unfolded Protein Response

Mitochondria are essential organelles that perform important roles in cell biologies such as ATP synthesis, metabolic regulation, immunomodulatory, and apoptosis. Parkinson’s disease (PD) is connected with mitochondrial neuronal damage related to mitochondrial unfolded protein response (mtUPR). Rosmarinic acid (RA) is a naturally occurring hydroxylated polyphenolic chemical found in the Boraginaceae and the Labiatae subfamily Nepetoideae. This study looked into RA’s protective effect against mitochondrial loss in the substantia nigra (SN) caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the underlying mechanism associated with the mtUPR. Pretreatment with RA reduced motor impairments and dopaminergic neuronal degeneration in the SN of a mouse model injected with MPTP. Pretreatment of SH-SY5Y cells from cell viability loss, morphological damage, and oxidative stress. Furthermore, RA pre-injection suppressed MPTP-induced mtUPR, lowered the expression of HSPA9, HSPE1, CLPP, LONP1, and SIRT 4, and protected the MPTP-mice and SH-SY5Y cells from mitochondrial failure. These findings imply that RA can prevent Parkinson’s disease by preventing mitochondrial damage in dopaminergic neurons in Parkinson’s disease via alleviating mitochondrial unfolded protein response.

The potential applications of traditional Chinese medicine in Parkinson's disease: A new opportunity

Parkinson's disease (PD) presents a common challenge for people all over the world and has become a major research hotspot due to the large population affected by the illness and the difficulty of clinical treatment. The prevalence of PD is increasing every year, the pathogenesis is complex, and the current treatment is ineffective. Therefore, it has become imperative to find effective drugs for PD. With the advantages of low cost, high safety and high biological activity, Chinese medicine has great advantages in the prevention and treatment of PD. This review systematically summarizes the potential of Chinese medicine for the treatment of PD, showing that Chinese medicine can exert anti-PD effects through various pathways, such as anti-inflammatory and antioxidant pathways, reducing mitochondrial dysfunction, inhibiting endoplasmic reticulum stress and iron death, and regulating intestinal flora. These mainly involve HMGB1/TLR4, PI3K/Akt, NLRP3/ caspase-1/IL-1β, Nrf2/HO-1, SIRT1/Akt1, PINK1/parkin, Bcl-2/Bax, BDNF-TrkB and other signaling pathways. In sum, based on modern phytochemistry, pharmacology and genomic proteomics, Chinese medicine is likely to be a potential candidate for PD treatment, which requires more clinical trials to further elucidate its importance in the treatment of PD.

Biomedical features and therapeutic potential of rosmarinic acid

For decades, the use of secondary metabolites of various herbs has been an attractive strategy in combating human diseases. Rosmarinic acid (RA) is a bioactive phenolic compound commonly found in plants of Lamiaceae and Boraginaceae families. RA is biosynthesized using amino acids tyrosine and phenylalanine via enzyme-catalyzed reactions. However, the chemical synthesis of RA involves an esterification reaction between caffeic acid and 3,4-dihydroxy phenyl lactic acid contributing two phenolic rings to the structure of RA. Several studies have ascertained multiple therapeutic benefits of RA in various diseases, including cancer, diabetes, inflammatory disorders, neurodegenerative disorders, and liver diseases. Many previous scientific papers indicate that RA can be used as an anti-plasmodic, anti-viral and anti-bacterial drug. In addition, due to its high anti-oxidant capacity, this natural polyphenol has recently gained attention for its possible application as a nutraceutical compound in the food industry. Here we provide state-of-the-art, flexible therapeutic potential and biomedical features of RA, its implications and multiple uses. Along with various valuable applications in safeguarding human health, this review further summarizes the therapeutic advantages of RA in various human diseases, including cancer, diabetes, neurodegenerative diseases. Furthermore, the challenges associated with the clinical applicability of RA have also been discussed.

Anti-Parkinson's Disease Activity of Sanghuangprous vaninii Extracts in the MPTP-Induced Zebrafish Model

Parkinson's disease (PD) is a devastating disease of the central nervous system that occurs mainly in the elderly age group, affecting their quality of life. The PD pathogenesis is not yet fully understood and lacks the disease-modifying treatment strategies. Sanghuangprous vaninii (S. vaninii) is a perennial fungus with a plethora of pharmacological activities including anti-cancer and antioxidant activity and so on. However, no study till date has reported its neuroprotective effect against symptoms that are similar to PD in pre-clinical investigation. In the current study, we investigated anti-PD-like effects of S. vaninii mycelium extracts (SvMEs) on MPTP-induced PD in zebrafish. We observed that the loss of dopaminergic neurons and neurovascular reduction were reversed by using SvMEs in the zebrafish brain in a concentration-independent manner. Moreover, it also relieved locomotor impairments in MPTP-induced PD zebrafish. In addition, SvMEs exerted significant antioxidant activity in vitro, which was also demonstrated in vivo on ktr4:NTR-hKikGR zebrafish. Upon investigating the underlying mechanism, we found that SvMEs may alleviate oxidant stress and accelerate α-synuclein degradation and then alleviate PD-like symptoms. Antioxidant-related genes (sod1, gss, gpx4a, gclm, and cat) implied that the SvMEs exhibited anti-PD activity due to the antioxidation mechanism. Finally, upon analysis of chemical composition of SvMEs by liquid chromatography-mass spectrometry, we identified 10 compounds that are plausibly responsible for the anti-PD-like effect of SvMEs. On the limiting part, the finding of the study would have been more robust had we investigated the protein expression of genes related to PD and oxidative stress and compared the effects of SvMEs with any standard anti-PD therapy. Despite this, our results indicated that SvMEs possess anti-PD effects, indicating SvMEs as a potential candidate that is worth exploring further in this avenue.

Zebrafish, Medaka and Turquoise Killifish for Understanding Human Neurodegenerative/Neurodevelopmental Disorders

In recent years, small fishes such as zebrafish and medaka have been widely recognized as model animals. They have high homology in genetics and tissue structure with humans and unique features that mammalian model animals do not have, such as transparency of embryos and larvae, a small body size and ease of experiments, including genetic manipulation. Zebrafish and medaka have been used extensively in the field of neurology, especially to unveil the mechanisms of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, and recently, these fishes have also been utilized to understand neurodevelopmental disorders such as autism spectrum disorder. The turquoise killifish has emerged as a new and unique model animal, especially for ageing research due to its unique life cycle, and this fish also seems to be useful for age-related neurological diseases. These small fishes are excellent animal models for the analysis of human neurological disorders and are expected to play increasing roles in this field. Here, we introduce various applications of these model fishes to improve our understanding of human neurological disorders.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Cerebroventricular Microinjections of MPTP on Adult Zebrafish Induces Dopaminergic Neuronal Death, Mitochondrial Fragmentation, and Sensorimotor Impairments

Mitochondria are dynamic organelles that mediate the energetic supply to cells and mitigate oxidative stress through the intricate balance of fission and fusion. Mitochondrial dysfunction is a prominent feature within Parkinson disease (PD) etiologies. To date, there have been conflicting studies of neurotoxin impact on dopaminergic cell death, mitochondrial function and behavioral impairment using adult zebrafish. Here, we performed cerebroventricular microinjections (CVMIs) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on adult transgenic zebrafish that resulted in significant reductions in dopaminergic neurons within the telencephalon and olfactory bulbs (OB) of Tg(dat:eGFP) fish. Visualization of mCherry and mitochondrial gene expression analysis in Tg(dat:tom20 MLS:mCherry) fish reveal that MPTP induces mitochondrial fragmentation in dopaminergic neurons and the activation of the pink1/parkin pathway involved mitophagy. Moreover, the loss of dopaminergic neurons translated into a transient locomotor and olfactory phenotype. Taken together, these data can contribute to a better understanding of the mitochondrial impact on dopaminergic survivability.

Natural products attenuate PI3K/Akt/mTOR signaling pathway: A promising strategy in regulating neurodegeneration

BACKGROUND

As common, progressive, and chronic causes of disability and death, neurodegenerative diseases (NDDs) significantly threaten human health, while no effective treatment is available. Given the engagement of multiple dysregulated pathways in neurodegeneration, there is an imperative need to target the axis and provide effective/multi-target agents to tackle neurodegeneration. Recent studies have revealed the role of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) in some diseases and natural products with therapeutic potentials.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating various neuronal disorders via the PI3K/Akt/mTOR signaling pathway.

STUDY DESIGN AND METHODS

A systematic and comprehensive review was done based on the PubMed, Scopus, Web of Science, and Cochrane electronic databases. Two independent investigators followed the PRISMA guidelines and included papers on PI3K/Akt/mTOR and interconnected pathways/mediators targeted by phytochemicals in NDDs.

RESULTS

Natural products are multi-target agents with diverse pharmacological and biological activities and rich sources for discovering and developing novel therapeutic agents. Accordingly, recent studies have shown increasing phytochemicals in combating Alzheimer's disease, aging, Parkinson's disease, brain/spinal cord damages, depression, and other neuronal-associated dysfunctions. Amongst the emerging targets in neurodegeneration, PI3K/Akt/mTOR is of great importance. Therefore, attenuation of these mediators would be a great step towards neuroprotection in such NDDs.

CONCLUSION

The application of plant-derived secondary metabolites in managing and/or treating various neuronal disorders through the PI3K/Akt/mTOR signaling pathway is a promising strategy towards neuroprotection.

Advances of Zebrafish in Neurodegenerative Disease: From Models to Drug Discovery

Neurodegenerative disease (NDD), including Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis, are characterized by the progressive loss of neurons which leads to the decline of motor and/or cognitive function. Currently, the prevalence of NDD is rapidly increasing in the aging population. However, valid drugs or treatment for NDD are still lacking. The clinical heterogeneity and complex pathogenesis of NDD pose a great challenge for the development of disease-modifying therapies. Numerous animal models have been generated to mimic the pathological conditions of these diseases for drug discovery. Among them, zebrafish (Danio rerio) models are progressively emerging and becoming a powerful tool for in vivo study of NDD. Extensive use of zebrafish in pharmacology research or drug screening is due to the high conserved evolution and 87% homology to humans. In this review, we summarize the zebrafish models used in NDD studies, and highlight the recent findings on pharmacological targets for NDD treatment. As high-throughput platforms in zebrafish research have rapidly developed in recent years, we also discuss the application prospects of these new technologies in future NDD research.

DJ-1 in neurodegenerative diseases: Pathogenesis and clinical application

Neurodegenerative diseases (NDs) are one of the major health threats to human characterized by selective and progressive neuronal loss. The mechanisms of NDs are still not fully understood. The study of genetic defects and disease-related proteins offers us a window into the mystery of it, and the extension of knowledge indicates that different NDs share similar features, mechanisms, and even genetic or protein abnormalities. Among these findings, PARK7 and its production DJ-1 protein, which was initially found implicated in PD, have also been found altered in other NDs. PARK7 mutations, altered expression and posttranslational modification (PTM) cause DJ-1 abnormalities, which in turn lead to downstream mechanisms shared by most NDs, such as mitochondrial dysfunction, oxidative stress, protein aggregation, autophagy defects, and so on. The knowledge of DJ-1 derived from PD researches might apply to other NDs in both basic research and clinical application, and might yield novel insights into and alternative approaches for dealing with NDs.

Herbal Resources to Combat a Progressive & Degenerative Nervous System Disorder- Parkinson's Disease

Parkinson's disease is one of the most common adult-onset, a chronic disorder involving neurodegeneration, which progressively leads to deprivation of dopaminergic neurons in substantia nigra, causing a subsequent reduction of dopamine levels in the striatum resulting in tremor, myotonia, and dyskinesia. Genetics and environmental factors are believed to be responsible for the onset of Parkinson's disease. The exact pathogenesis of Parkinson's disease is quite complicated and the present anti-Parkinson's disease treatments appear to be clinically insufficient. Comprehensive researches have demonstrated the use of natural products such as ginseng, curcumin, ashwagandha, baicalein, etc. for the symptomatic treatment of this disease. The neuroprotective effects exhibited by these natural products are mainly due to their ability to increase dopamine levels in the striatum, manage oxidative stress, mitochondrial dysfunction, glutathione levels, clear the aggregation of α- synuclein, induce autophagy and decrease the pro-inflammatory cytokines and lipid peroxidation. This paper reviews various natural product studies conducted by scientists to establish the role of natural products (both metabolite extracts as well as pure metabolites) as adjunctive neuroprotective agents.

Studying CNS effects of Traditional Chinese Medicine using zebrafish models

ETHNOPHARMACOLOGICAL RELEVANCE

Although Traditional Chinese Medicine (TCM) has a millennia-long history of treating human brain disorders, its complex multi-target mechanisms of action remain poorly understood. Animal models are currently widely used to probe the effects of various TCMs on brain and behavior. The zebrafish (Danio rerio) has recently emerged as a novel vertebrate model organism for neuroscience research, and is increasingly applied for CNS drug screening and development.

AIM OF THE STUDY

As zebrafish models are only beginning to be applied to studying TCM, we aim to provide a comprehensive review of the TCM effects on brain and behavior in this fish model species.

MATERIALS AND METHODS

A comprehensive search of published literature was conducted using biomedical databases (Web of Science, Pubmed, Sciencedirect, Google Scholar and China National Knowledge Internet, CNKI), with key search words zebrafish, brain, Traditional Chinese Medicine, herbs, CNS, behavior.

RESULTS

We recognize the developing utility of zebrafish for studying TCM, as well as outline the existing model limitations, problems and challenges, as well as future directions of research in this field.

CONCLUSIONS

We demonstrate the growing value of zebrafish models for studying TCM, aiming to improve our understanding of TCM' therapeutic mechanisms and potential in treating brain disorders.