Potential Application of Marine Algae and Their Bioactive Metabolites in Brain Disease Treatment: Pharmacognosy and Pharmacology Insights for Therapeutic Advances

Seaweeds, also known as edible marine algae, are an abundant source of phytosterols, carotenoids, and polysaccharides, among other bioactive substances. Studies conducted in the past few decades have demonstrated that substances derived from seaweed may be able to pass through the blood-brain barrier and act as neuroprotectants. According to preliminary clinical research, seaweed may also help prevent or lessen the symptoms of cerebrovascular illnesses by reducing mental fatigue, preventing endothelial damage to the vascular wall of brain vessels, and regulating internal pressure. They have the ability to control neurotransmitter levels, lessen neuroinflammation, lessen oxidative stress, and prevent the development of amyloid plaques. This review aims to understand the application potential of marine algae and their influence on brain development, highlighting the nutritional value of this "superfood" and providing current knowledge on the molecular mechanisms in the brain associated with their dietary introduction.

Rehashing Our Insight of Seaweeds as a Potential Source of Foods, Nutraceuticals, and Pharmaceuticals

In a few Southeast Asian nations, seaweeds have been a staple of the cuisine since prehistoric times. Seaweeds are currently becoming more and more popular around the world due to their superior nutritional value and medicinal properties. This is because of rising seaweed production on a global scale and substantial research on their composition and bioactivities over the past 20 years. By reviewing several articles in the literature, this review aimed to provide comprehensive information about the primary and secondary metabolites and various classes of bioactive compounds, such as polysaccharides, polyphenols, proteins, and essential fatty acids, along with their bioactivities, in a single article. This review also highlights the potential of seaweeds in the development of nutraceuticals, with a particular focus on their ability to enhance human health and overall well-being. In addition, we discuss the challenges and potential opportunities associated with the advancement of pharmaceuticals and nutraceuticals derived from seaweeds, as well as their incorporation into different industrial sectors. Furthermore, we find that many bioactive constituents found in seaweeds have demonstrated potential in terms of different therapeutic attributes, including antioxidative, anti-inflammatory, anticancer, and other properties. In conclusion, seaweed-based bioactive compounds have a huge potential to play an important role in the food, nutraceutical, and pharmaceutical sectors. However, future research should pay more attention to developing efficient techniques for the extraction and purification of compounds as well as their toxicity analysis, clinical efficacy, mode of action, and interactions with regular diets.

N-Acetylglucosamine Kinase-Small Nuclear Ribonucleoprotein Polypeptide N Interaction Promotes Axodendritic Branching in Neurons via Dynein-Mediated Microtubule Transport

N-acetylglucosamine kinase (NAGK) has been identified as an anchor protein that facilitates neurodevelopment with its non-canonical structural role. Similarly, small nuclear ribonucleoprotein polypeptide N (SNRPN) regulates neurodevelopment and cognitive ability. In our previous study, we revealed the interaction between NAGK and SNRPN in the neuron. However, the precise role in neurodevelopment is elusive. In this study, we investigate the role of NAGK and SNRPN in the axodendritic development of neurons. NAGK and SNRPN interaction is significantly increased in neurons at the crucial stages of neurodevelopment. Furthermore, overexpression of the NAGK and SNRPN proteins increases axodendritic branching and neuronal complexity, whereas the knockdown inhibits neurodevelopment. We also observe the interaction of NAGK and SNRPN with the dynein light-chain roadblock type 1 (DYNLRB1) protein variably during neurodevelopment, revealing the microtubule-associated delivery of the complex. Interestingly, NAGK and SNRPN proteins rescued impaired axodendritic development in an SNRPN depletion model of Prader-Willi syndrome (PWS) patient-derived induced pluripotent stem cell neurons. Taken together, these findings are crucial in developing therapeutic approaches for neurodegenerative diseases.

Neuronal Differentiation and Outgrowth Effect of Thymol in Trachyspermum ammi Seed Extract via BDNF/TrkB Signaling Pathway in Prenatal Maternal Supplementation and Primary Hippocampal Culture

Reviving the neuronal functions in neurodegenerative disorders requires the promotion of neurite outgrowth. Thymol, which is a principal component of Trachyspermum ammi seed extract (TASE), is reported to have neuroprotective effects. However, the effects of thymol and TASE on neuronal differentiation and outgrowth are yet to be studied. This study is the first report investigating the neuronal growth and maturation effects of TASE and thymol. Pregnant mice were orally supplemented with TASE (250 and 500 mg/kg), thymol (50 and 100 mg/kg), vehicle, and positive controls. The supplementation significantly upregulated the expression of brain-derived neurotrophic factor (BDNF) and early neuritogenesis markers in the pups' brains at post-natal day 1 (P1). Similarly, the BDNF level was significantly upregulated in the P12 pups' brains. Furthermore, TASE (75 and 100 µg/mL) and thymol (10 and 20 µM) enhanced the neuronal polarity, early neurite arborization, and maturation of hippocampal neurons in a dose-dependent manner in primary hippocampal cultures. The stimulatory activities of TASE and thymol on neurite extension involved TrkB signaling, as evidenced by attenuation via ANA-12 (5 µM), which is a specific TrkB inhibitor. Moreover, TASE and thymol rescued the nocodazole-induced blunted neurite extension in primary hippocampal cultures, suggesting their role as a potent microtubule stabilizing agent. These findings demonstrate the potent capacities of TASE and thymol in promoting neuronal development and reconstruction of neuronal circuitry, which are often compromised in neurodegenerative diseases and acute brain injuries.

The Edible Seaweed Gelidium amansii Promotes Structural Plasticity of Hippocampal Neurons and Improves Scopolamine-induced Learning and Memory Impairment in Mice

BACKGROUND

Gelidium amansii has been gaining profound interest in East Asian countries due to its enormous commercial value for agar production and its extensive pharmacological properties. Previous studies have shown that the ethanol extract of Gelidium amansii (GAE) has promising neurotrophic effects in in vitro conditions.

OBJECTIVES

The present study aimed at investigating the protective effects of GAE against scopolamine-induced cognitive deficits and its modulatory effects on hippocampal plasticity in mice.

METHODS

For memory-related behavioral studies, the passive avoidance test and radial arm maze paradigm were conducted. The brain slices of the hippocampus CA1 neurons of experimental mice were then prepared to perform Golgi staining for analyzing spine density and its characteristic shape, and immunohistochemistry for assessing the expression of different pre- and postsynaptic proteins.

RESULTS

Following oral administration of GAE (0.5 mg/g body weight), mice with memory deficits exhibited a significant increase in the latency time on the passive avoidance test and a decrease in the number of working and reference memory errors and latency time on the radial arm maze test. Microscopic observations of Golgi-impregnated tissue sections and immunohistochemistry of hippocampal slices showed that neurons from GAE-treated mice displayed higher spine density and spine dynamics, increased synaptic contact, and the recruitment of memory-associated proteins such as N-methyl-D-aspartate receptors (NR2A and NR2B) and postsynaptic density-95 (PSD-95) when compared with the control group.

CONCLUSION

With these memory-protective functions and a modulatory role in underlying memory-related events, GAE could be a potential functional food and a promising source of pharmacological agents for the prevention and treatment of memory-related brain disorders.

Mechanisms of the ethanol extract of Gelidium amansii for slow aging in high-fat male Drosophila by metabolomic analysis

Gelidium amansii (GA) is a kind of red alga homologous to medicine and food and is distributed all over the world. Studies on GA are mainly focused on its polysaccharides, with little research on the ethanol extract. The ethanol extract of Gelidium amansii (GAE) was subjected to a reverse-phase column to obtain 7 components. Among them, 100% methanol solution (GAM), enriched with phytene-1,2-diol, exhibited the strongest DPPH free radical scavenging activity (IC50 = 0.17 mg mL-1). Subsequently, high-fat male flies (HMFs) were used as a model to explore the antioxidant and anti-aging effects of GAM in vivo. Studies showed that GAM can effectively prolong the lifespan of HMFs. When GAM concentrations were 0.2 and 1.0 mg mL-1, the average lifespan of HMFs was increased by 28.7 and 40.7%, respectively, while the longest lifespan of HMFs was increased by 20.55% and 32.88%, respectively. Further research revealed that GAM can significantly downregulate the levels of malondialdehyde (MDA) and protein carbonyl (PCO), and can significantly upregulate the levels of catalase (CAT) and total superoxide dismutase (T-SOD). In addition, by analyzing differential metabolites, we found that GAM relieves aging caused by oxidative stress by regulating amino acid, lipid, sugar, and energy metabolism. The GAM group significantly regulated the levels of adenine, cholic acid, glutamate, L-proline, niacin, and stachyose which tend to recover to the levels of the normal diet male fly (NMF) group. In general, our research provides ideas for the high-value utilization of GA and provides a lead compound for the research and development of anti-aging food or medicine.

Unveiling the effect of Withania somnifera on neuronal cytoarchitecture and synaptogenesis: A combined in vitro and network pharmacology approach

Withania somnifera (WS), is known for its remarkable contribution in herbal medicine and Ayurveda, which is therapeutically applied to improve memory and anxiety in patients. However, the pharmacological details of this plant on memory boosting yet remained undefined. This study provides mechanistic insights on the effect of ethanol solution extract of the whole plant of WS (WSEE) on neuritogenesis by combining in vitro and in silico network pharmacology approaches. WSEE promoted significant neuronal growth through early differentiation, axodendritic arborization, and synaptogenesis on primary hippocampal neurons. The network pharmacological study confirmed that the neuritogenic activity is potentially mediated by modulating the neurotrophin signaling pathway, where NRTK1 (TrkA) was revealed as the primary target of WS secondary metabolites. This neurotrophic activity of WSEE was significantly stifled by the presence of TrkA inhibitor, which further confirms the TrkA-dependent activity of WSEE. In addition, a molecular docking study suggested steroidal lactones present in the WS might act as nerve growth factor (NGF)-mimetics, activating TrkA by binding to the NGF-binding domain. As a whole, the findings of the study suggest a significant role of WSEE on neuritogenesis and its potential to function as a therapeutic agent and in drug designing for the prevention and treatment of memory-related neurological disorders.

Seaweed Exhibits Therapeutic Properties against Chronic Diseases: An Overview

Seaweeds or marine macroalgae are known for producing potentially bioactive substances that exhibit a wide range of nutritional, therapeutic, and nutraceutical properties. These compounds can be applied to treat chronic diseases, such as cancer, cardiovascular disease, osteoporosis, neurodegenerative diseases, and diabetes mellitus. Several studies have shown that consumption of seaweeds in Asian countries, such as Japan and Korea, has been correlated with a lower incidence of chronic diseases. In this study, we conducted a review of published papers on seaweed consumption and chronic diseases. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method for this study. We identified and screened research articles published between 2000 and 2021. We used PubMed and ScienceDirect databases and identified 107 articles. This systematic review discusses the potential use of bioactive compounds of seaweed to treat chronic diseases and identifies gaps where further research in this field is needed. In this review, the therapeutic and nutraceutical properties of seaweed for the treatment of chronic diseases such as neurodegenerative diseases, obesity, diabetes, cancer, liver disease, cardiovascular disease, osteoporosis, and arthritis were discussed. We concluded that further study on the identification of bioactive compounds of seaweed, and further study at a clinical level, are needed.

The Seaweed Diet in Prevention and Treatment of the Neurodegenerative Diseases

Edible marine algae are rich in bioactive compounds and are, therefore, a source of bioavailable proteins, long chain polysaccharides that behave as low-calorie soluble fibers, metabolically necessary minerals, vitamins, polyunsaturated fatty acids, and antioxidants. Marine algae were used primarily as gelling agents and thickeners (phycocolloids) in food and pharmaceutical industries in the last century, but recent research has revealed their potential as a source of useful compounds for the pharmaceutical, medical, and cosmetic industries. The green, red, and brown algae have been shown to have useful therapeutic properties in the prevention and treatment of neurodegenerative diseases: Parkinson, Alzheimer’s, and Multiple Sclerosis, and other chronic diseases. In this review are listed and described the main components of a suitable diet for patients with these diseases. In addition, compounds derived from macroalgae and their neurophysiological activities are described.

Centella asiatica promotes early differentiation, axodendritic maturation and synaptic formation in primary hippocampal neurons

BACKGROUND

Centella asiatica is a 'medhya-rasayana (nootrophic or memory booster)' herb that has been indicated in Ayurveda for improving memory function and treating dementia disorders. Although the neuroprotective effects of C. asiatica have been reported in earlier studies, the information on whether this nootropic herb could promote early differentiation and development of axon and dendrites in primary hippocampal neurons is currently limited.

THE AIM OF THE STUDY

To investigate the effects of C. asiatica and asiatic acid, one of the principal active constituents of C. asiatica, on the various stages of neuronal polarity, including early neuronal differentiation, axonal outgrowth, dendritic arborization, axonal maturation, and synaptic formation.

MATERIALS AND METHODS

Embryonic rat hippocampal neurons were incubated with C. asiatica leaf extract (CAE) or asiatic acid. After an indicated time, neurons were fixed and immunolabeled to visualize the neuronal morphology. Morphometric analyses for early neuronal differentiation, axonal and dendritic maturation and synaptogenesis were performed using Image J software. Neuronal viability was determined using trypan blue exclusion assay.

RESULTS

CAE at varying concentrations ranging from 3.75 to 15 μg/mL enhanced neurite outgrowth with the highest optimal concentration of 7.5 μg/mL. The effects of CAE commenced immediately after cell seeding, as indicated by its accelerating effect on neuronal differentiation. Subsequently, CAE significantly elaborated dendritic and axonal morphology and facilitated synapse formation. Asiatic acid also facilitated neurite outgrowth, but to a lesser extent than CAE.

CONCLUSION

These findings revealed that CAE exerted its modulatory effects in every stage of neuronal development, supporting its previously claimed neurotrophic function and suggest that this natural nootropic and its active component asiatic acid can be further investigated to explore a promising solution for degenerative brain disorders and injuries.

Pharmaceutical and Nutraceutical Potential Applications of Sargassum fulvellum

Sargassum fulvellum is a brown seaweed of the Sargassaceae family which has been demonstrated to exhibit antipyretic, analgesic, antiedema, antimicrobial, antioxidant, antitumor, neuroprotective, anticoagulative, anti-inflammatory, and hepatoprotective activities. It has been widely used as a food additive and as a medicine in oriental medicine to treat lumps, dropsy, swelling, testicular pains, and urinary problems. S. fulvellum has been identified as a potential producer of a wide spectrum of natural compounds such as carotenoids, fucoidans, and phlorotannins, showing different biological activities in various industrial applications including pharmaceutical, nutraceutical, cosmeceutical, and functional food. However, the promising health effects associated with the extracts and compounds isolated from S. fulvellum have not been reviewed to date. The present review thus focuses on the biological activity of S. fulvellum as reported by previous publications, which include antioxidant, anticoagulant, anti-inflammatory, neuroprotective, immunomodulatory, antidiabetic, and anticancer effects. Thus, this review might serve to increase the utilization of this invaluable natural source as a potential component in pharmaceutical and nutraceutical applications.

Neuroprotection Against Oxidative Stress: Phytochemicals Targeting TrkB Signaling and the Nrf2-ARE Antioxidant System

Oxidative stress (OS) plays a critical role in the pathophysiology of several brain-related disorders, including neurodegenerative diseases and ischemic stroke, which are the major causes of dementia. The Nrf2-ARE (nuclear factor erythroid 2-related factor 2/antioxidant responsive element antioxidant) system, the primary cellular defense against OS, plays an essential role in neuroprotection by regulating the expressions of antioxidant molecules and enzymes. However, simultaneous events resulting in the overproduction of reactive oxygen species (ROS) and deregulation of the Nrf2-ARE system damage essential cell components and cause loss of neuron structural and functional integrity. On the other hand, TrkB (tropomyosin-related kinase B) signaling, a classical neurotrophin signaling pathway, regulates neuronal survival and synaptic plasticity, which play pivotal roles in memory and cognition. Also, TrkB signaling, specifically the TrkB/PI3K/Akt (TrkB/phosphatidylinositol 3 kinase/protein kinase B) pathway promotes the activation and nuclear translocation of Nrf2, and thus, confers neuroprotection against OS. However, the TrkB signaling pathway is also known to be downregulated in brain disorders due to lack of neurotrophin support. Therefore, activations of TrkB and the Nrf2-ARE signaling system offer a potential approach to the design of novel therapeutic agents for brain disorders. Here, we briefly overview the development of OS and the association between OS and the pathogenesis of neurodegenerative diseases and brain injury. We propose the cellular antioxidant defense and TrkB signaling-mediated cell survival systems be considered pharmacological targets for the treatment of neurodegenerative diseases, and review the literature on the neuroprotective effects of phytochemicals that can co-activate these neuronal defense systems.

Neuroprotective Potentials of Marine Algae and Their Bioactive Metabolites: Pharmacological Insights and Therapeutic Advances

Beyond their significant contribution to the dietary and industrial supplies, marine algae are considered to be a potential source of some unique metabolites with diverse health benefits. The pharmacological properties, such as antioxidant, anti-inflammatory, cholesterol homeostasis, protein clearance and anti-amyloidogenic potentials of algal metabolites endorse their protective efficacy against oxidative stress, neuroinflammation, mitochondrial dysfunction, and impaired proteostasis which are known to be implicated in the pathophysiology of neurodegenerative disorders and the associated complications after cerebral ischemia and brain injuries. As was evident in various preclinical studies, algal compounds conferred neuroprotection against a wide range of neurotoxic stressors, such as oxygen/glucose deprivation, hydrogen peroxide, glutamate, amyloid β, or 1-methyl-4-phenylpyridinium (MPP+) and, therefore, hold therapeutic promise for brain disorders. While a significant number of algal compounds with promising neuroprotective capacity have been identified over the last decades, a few of them have had access to clinical trials. However, the recent approval of an algal oligosaccharide, sodium oligomannate, for the treatment of Alzheimer's disease enlightened the future of marine algae-based drug discovery. In this review, we briefly outline the pathophysiology of neurodegenerative diseases and brain injuries for identifying the targets of pharmacological intervention, and then review the literature on the neuroprotective potentials of algal compounds along with the underlying pharmacological mechanism, and present an appraisal on the recent therapeutic advances. We also propose a rational strategy to facilitate algal metabolites-based drug development.

Gelidium amansii Attenuates Hypoxia/Reoxygenation-Induced Oxidative Injury in Primary Hippocampal Neurons through Suppressing GluN2B Expression

Oxidative stress is known to be critically implicated in the pathophysiology of several neurological disorders, including Alzheimer’s disease and ischemic stroke. The remarkable neurotrophic activity of Gelidium amansii, which has been reported consistently in a series of our previous studies, inspired us to investigate whether this popular agarophyte could protect against hypoxia/reoxygenation (H/R)-induced oxidative injury in hippocampal neurons. The primary culture of hippocampal neurons challenged with H/R suffered from a significant loss of cell survival, accompanied by apoptosis and necrosis, DNA damage, generation of reactive oxygen species (ROS), and dissipation of mitochondrial membrane potential (ΔΨ_m), which were successfully attenuated when the neuronal cultures were preconditioned with ethanolic extract of G. amansii (GAE). GAE also attenuated an H/R-mediated increase of BAX and caspase 3 expressions while promoting Bcl-2 expression. Moreover, the expression of N-methyl-d-acetate receptor subunit 2B (GluN2B), an extrasynaptic glutamate receptor, was significantly repressed, while synaptic GluN2A expression was preserved in GAE-treated neurons as compared to those without GAE intervention. Together, this study demonstrates that GAE attenuated H/R-induced oxidative injury in hippocampal neurons through, at least in part, a potential neuroprotective mechanism that involves inhibition of GluN2B-mediated excitotoxicity and suppression of ROS production, and suggests that this edible seaweed could be a potential source of bioactive metabolites with therapeutic significance against oxidative stress-related neurodegeneration, including ischemic stroke and neurodegenerative diseases.

3β, 6β-dichloro-5-hydroxy-5α-cholestane facilitates neuronal development through modulating TrkA signaling regulated proteins in primary hippocampal neuron

Potentiating neuritogenesis through pharmacological intervention might hold therapeutic promise in neurodegenerative disorders and acute brain injury. Here, we investigated the novel neuritogenic potentials of a steroidal chlorohydrin, 3β, 6β-dichloro-5-hydroxy-5α-cholestane (hereafter, SCH) and the change in cellular proteome to gain insight into the underlying mechanism of its neurotrophic activity in hippocampal neurons. Morphometric analysis showed that SCH promoted early neuronal differentiation, dendritic arborization and axonal maturation. Proteomic and bioinformatic analysis revealed that SCH induced upregulation of several proteins, including those associated with neuronal differentiation and development. Immunocytochemical data further indicates that SCH-treated neurons showed upregulation of Hnrnpa2b1 and Map1b, validating their proteomic profiles. In addition, a protein-protein interaction network analysis identified TrkA as a potential target connecting most of the upregulated proteins. The neurite outgrowth effect of SCH was suppressed by TrkA inhibitor, GW441756, verifying TrkA-dependent activity of SCH, which further supports the connection of TrkA with the upregulated proteins. Also, the computational analysis revealed that SCH interacts with the NGF-binding domain of TrkA through Phe327 and Asn355. Collectively, our findings provide evidence that SCH promotes neuronal development via upregulating TrkA-signaling proteins and suggest that SCH could be a promising therapeutic agent in the prevention and treatment of neurodegenerative disorders.

Calotropis gigantea Promotes Neuritogenesis and Synaptogenesis through Activation of NGF-TrkA-Erk1/2 Signaling in Rat Hippocampal Neurons

Calotropis gigantea (L.) R. Br (Apocynaceae) (commonly known as milkweed or crown flower) is a large shrub native to temperate regions of Asia, including China, Bangladesh and India and has a long history of use in traditional medicines. In this study, we investigated the neuromodulatory effects of the ethanol extracts of C. gigantea leaves (CGE) during synaptogenesis in the late stage of neuronal development and during early stage neuritogenesis in cultured rat hippocampal neurons. Maximum neuritogenic activity was achieved at a CGE concentration of 7.5[Formula: see text][Formula: see text]g/ml. At this concentration, CGE facilitated the early development of cytoarchitecture, as evidenced by increases in morphometric parameters, such as, the numbers, lengths, and number of branches of initial neurites, axon and dendrites. During the synaptogenic stage (DIV 14), immunocytochemistry (ICC) showed that CGE upregulated synaptic vesicle 2 (SV2, a marker of axon terminals) and postsynaptic density-95 (PSD-95, a postsynaptic marker) and their colocalization. CGE upregulated nerve growth factor (NGF) and activated extracellular signal-regulated kinase 1/2 (Erk1/2), which is blocked by a TrkA-specific inhibitor suggesting the neuritogenic and synaptogenic potential of CGE was due to the activation of NGF-TrkA-Erk1/2 signaling. Moreover, UPLC of CGE did not detect stigmasterol, an active component of C. gigantea. However, the chloroform-methanol and ethyl acetate subfractions of CGE exhibited initial neuritogenic activity, suggesting that multiple active components were responsible for the neurotrophic-mimetic properties of CGE. Our data prove the neuromodulatory ability of CGE and provide a means of identifying new active phytochemicals with potential nootropic, preventative or therapeutic effects on the human brain.

Neurotrophic Activity of the Carrageenophyte Kappaphycus alvarezii Cultivated at Different Depths and for Different Growth Periods in Various Areas of Indonesia

The carrageenophyte Kappaphycus alvarezii (Rhodophyta) has neurotrophic activity in primary hippocampal neurons. This seaweed is abundant and easily cultivated in tropical coastal areas. To determine the best growth conditions for neurotrophic activity, thalli were grown at different depths and for different periods in various areas of Indonesia. Neurotrophic activity was measured based on the number of primary neurites, the total length of the primary neurites, and the length of the longest neurite. K. alvarezii had higher neurotrophic activity than carrageenophytes K. striatum and Eucheuma denticulatum cultured under the same conditions. K. alvarezii grown at the surface for 45 days had higher (1.4- to 1.8-fold) neurotrophic activity than thalli grown at depth (2 m) or harvested sooner (15 days) (P < 0.05). Relatively high activities were detected in thalli cultured at Ternate and Garut, Indonesia. Therefore, from a commercial perspective, the culture conditions at the surface for 45 days were optimal for the production of both neurotrophic compounds and carrageenan. K. alvarezii produced neurotrophic compounds under various environmental conditions, although some conditions were optimal.

Stigmasterol upregulates immediate early genes and promotes neuronal cytoarchitecture in primary hippocampal neurons as revealed by transcriptome analysis

BACKGROUND

The hippocampus is a vulnerable brain region that is implicated in learning and memory impairment by two pathophysiological features, that is, neurite regression and synaptic dysfunction, and stigmasterol (ST), a cholesterol-equivalent phytosterol, is known to facilitate neuromodulatory effects.

PURPOSE

To investigate the neuromodulatory effects of ST on the development of central nervous system neurons and the molecular bases of these effects in primary hippocampal neurons.

METHODS

Rat embryonic (E18-19) brain neurons were cultured in the absence or presence of ST (75 µM). Neuritogenic activities of ST were evident by increases in various morphometric parameters. To identify underlying affected genes, total RNA was isolated on day in vitro 12 (DIV 12) and mRNA high throughput sequencing (mRNA-Seq) was performed. Affected key genes for neuronal development were identified using bioinformatics tools and their upregulations were confirmed by immunocytochemistry.

RESULTS

Among the differentially expressed 17,337 RefSeq genes, 445 genes (up/down 293/157) passed the p-value < 0.05 criterion, 52 genes (up/down; 37/13) had a p-value < 0.05 and a false discovery rate (FDR) q-value of < 0.2, and 24 genes (up/down; 20/4) passed the more stringent criterion of both p < 0.05 and q < 0.05. After applying a stringent FDR q-value cutoff of < 0.2, it was found ST induced many immediate early genes (IEGs), and that a major proportion of upregulated genes were related to central nervous system (CNS) development (neurite outgrowth or synaptic transmission). In a Venn diagram for CNS development Gene Ontologies (GOs) (i.e., axon development, dendrite development, modulation of synaptic transmission), Reln emerged as a central player in these processes, and highly interconnected 'hub' genes, including Dcx, Egr1, Ntrk2, and Slc24a2, were revealed by gene co-expression networks. Finally, transcriptomic data was confirmed by immunocytochemistry of primary hippocampal neurons.

CONCLUSION

The study indicates that ST upregulates genes for neuritogenesis and synaptogenesis, and suggests ST be viewed as a potential resource for improving brain functions.

Alleviation of Hippocampal Endoplasmic Reticulum Stress by Allomyrina dichotoma Larvae Extract

In the brain, endoplasmic reticulum (ER) stress results in synaptic dysfunction and eventually leads to neurodegeneration. Allomyrina dichotoma larvae are a Chinese ethnomedicine and are widely used in East Asia. In the present study, we investigated the ability of ethanol extract of A. dichotoma larvae (ADE) to improve synaptic structure and function by activating unfolded protein response (UPR) under ER stress in animal and neuron culture models. ER stress was induced in obese mice fed a high fat diet (HFD) or by treating dissociated cultures of rat embryonic (E19) hippocampal neurons with tunicamycin (TM). Western blot and real-time or conventional RT-PCR were performed to analyze the expressions of ER stress marker proteins. In dissociated hippocampal cultures, immunocytochemistry was performed for synaptic proteins, and cultures were stained with styryl dye FM1-43 to assess presynaptic activities. In HFD-fed obese mice, ADE efficiently reduced the expressions of ER stress markers, such as, xbp-1, chop, atf4, erdi4, and eIf2a, and those of the ER chaperone/foldases Bip/grp78, Ero-1l, and PDI. Unconventionally spliced xbp-1s mRNA was not detected. In primary rat hippocampal cultures under ER stress, ADE significantly lowered the nuclear expression of CHOP, inhibited the downregulations of postsynaptic proteins, such as, GluN2A, GluN2B, and PSD-95, and maintained the pool size of recycling presynaptic vesicles. The study shows that ADE potently suppressed the induction of ER stress and maintained the structure and function of hippocampal neurons, and suggests that ADE is a potentially valuable food supplement and preventive therapeutic for ER stress-related nervous disorders.

Acute anti-obesity effects of intracerebroventricular 11β-HSD1 inhibitor administration in diet-induced obese mice

The hypothalamus is the regulatory centre of both appetite and energy balance and endoplasmic reticulum (ER) stress in the hypothalamus is involved in the pathogenesis of obesity. Recently, inhibition of 11 β hydroxysteroid dehydrogenase type1 (11β-HSD1) was reported to have an anti-obesity effect by reducing fat mass. However, the link between the role of 11β-HSD1 in the hypothalamus and obesity has yet to be determined. In the present study, embryonal primary hypothalamic neurones and high-fat diet (HFD) fed mice were used to investigate the anorexigenic effects of 11β-HSD1 inhibitors both in vitro and in vivo. In hypothalamic neurones, carbenoxolone (a non selecitve 11β-HSD inhibitor) alleviated ER stress and ER stress-induced neuropeptide alterations. In HFD mice, i.c.v. administration of carbenoxolone or KR67500 (nonselective and selective 11β-HSD1 inhibitors, respectively) was associated with less weight gain compared to control mice for 24 hours after treatment, presumably by reducing food intake. Furthermore, glucose regulated protein (Grp78), spliced X-box binding protein (Xbp-1s), c/EBP homologous protein (chop) and ER DnaJ homologue protein (Erdj4) expression was decreased in the hypothalami of mice administrated 11β-HSD1 inhibitors compared to controls. Conversely, the phosphorylation of protein kinase B (PKB/Akt), signal transducer and activator of transcription 3 (Stat3), mitogen-activated protein kinase (MAPK/ERK) and S6 kinase1 (S6K1) in the hypothalamus was induced more in mice treated using the same regimes. In conclusion, acute 11β-HSD1 inhibition in the hypothalamus could reduce food intake by decreasing ER stress and increasing insulin, leptin, and mammalian target of rapamycin complex 1 (mTORC1) signalling.

The Edible Red Alga Porphyra yezoensis Promotes Neuronal Survival and Cytoarchitecture in Primary Hippocampal Neurons

The edible red alga Porphyra yezoensis is among the most popular marine algae and is of economic and medicinal importance. In the present study, the neurotrophic and neuroprotective activities of the ethanol extract of P. yezoensis (PYE) were investigated in primary cultures of hippocampal neurons. Results revealed that PYE significantly increased neurite outgrowth at an optimal concentration of 15 µg/mL. PYE dose-dependently increased viable cells, significantly accelerated the rate of neuronal differentiation in cultures, promoted axodendritic arborization, and eventually induced synaptogenesis. In addition to morphological development, PYE also promoted functional maturation as indicated by the staining of live cultures with FM 1-43. Moreover, PYE increased neuronal survivability, which was attributed to reduced apoptosis and its ROS scavenging activity. Taurine, a major organic acid in PYE (2.584/100 mg of dry PYE) promoted neurite outgrowth in a dose-dependent manner, and this promotion was suppressed by the taurine antagonist isethionic acid. The study indicates that PYE and its active component, taurine, facilitate neuronal development and maturation and have a neuroprotective effect.

Algae Undaria pinnatifida Protects Hypothalamic Neurons against Endoplasmic Reticulum Stress through Akt/mTOR Signaling

Increased endoplasmic reticulum (ER) stress is known to be one of the causes of hypothalamic neuronal damage, as well as a cause of metabolic disorders such as obesity and diabetes. Recent evidence has suggested that Undaria pinnatifida (UP), an edible brown algae, has antioxidant activity. However, the neuroprotective effect of UP has yet to be examined. In this study, to investigate the neuroprotective effect of UP on ER stress-induced neuronal damage in mouse hypothalamic neurons, mice immortal hypothalamic neurons (GT1-7) were incubated with extract of UP. ER stress was induced by treating with tunicamycin. Tunicamycin induced apoptotic cell death was compared with the vehicle treatment through excessive ER stress. However UP protected GT1-7 cells from cell death, occurring after treatment with tunicamycin by reducing ER stress. Treatment with UP resulted in reduced increment of ATF6 and CHOP, and recovered the decrease of phosphorylation of Akt/mTOR by tunicamycin and the increment of autophagy. These results show that UP protects GT1-7 cells from ER stress induced cell death through the Akt/mTOR pathway. The current study suggests that UP may have a beneficial effect on cerebral neuronal degeneration in metabolic diseases with elevated ER stress.

Protective effect of carbenoxolone on ER stress-induced cell death in hypothalamic neurons

Hypothalamic endoplasmic reticulum (ER) stress is known to be increased in obesity. Induction of ER stress on hypothalamic neurons has been reported to cause hypothalamic neuronal apoptosis and malfunction of energy balance, leading to obesity. Carbenoxolone is an 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitor that converts inactive glucocorticoid into an active form. In addition to its metabolic effect via enzyme inhibitory action, carbenoxolone has shown anti-apoptotic activity in several studies. In this study, the direct effects of carbenoxolone on ER stress and cell death in hypothalamic neurons were investigated. Carbenoxolone attenuated tunicamycin induced ER stress-mediated molecules such as spliced XBP1, ATF4, ATF6, CHOP, and ROS generation. In vivo study also revealed that carbenoxolone decreased tunicamycin-induced ER stress in the hypothalamus. In conclusion, the results of this study show that carbenoxolone has protective effects against tunicamycin induced-ER stress and apoptosis in hypothalamic neurons, suggesting its direct protective effects against obesity. Further study is warranted to clarify the effects of carbenoxolone on hypothalamic regulation of energy balance in obesity.

The Edible Marine Alga Gracilariopsis chorda Alleviates Hypoxia/Reoxygenation-Induced Oxidative Stress in Cultured Hippocampal Neurons

Age-related neurological disorders are of growing concern among the elderly, and natural products with neuroprotective properties have been attracting increasing attention as candidates for the prevention or treatment of neurological disorders induced by oxidative stress. In an effort to explore natural resources, we collected some common marine seaweed from the Korean peninsula and Indonesia and screened them for neuroprotective activity against hypoxia/reoxygenation (H/R)-induced oxidative stress. Of the 23 seaweeds examined, the ethanol extract of Gracilariopsis chorda (GCE) provided maximum neuroprotection at an optimum concentration of 15 μg/mL, followed by Undaria pinnatifida. GCE increased cell viability after H/R, decreased the formation of reactive oxygen species (measured by 2',7'-dichlorodihydrofluorescein diacetate [DCF-DA] staining), and inhibited the double-stranded DNA breaks (measured by H2AX immunocytochemistry), apoptosis (measured by Annexin V/propidium iodide staining), internucleosomal DNA fragmentation (measured by DNA laddering), and dissipation of mitochondrial membrane potential (measured by JC-1 staining). Using reverse-phase high-pressure liquid chromatography, we quantitated the arachidonic acid (AA) in GCE, which provides neuroprotection against H/R-induced oxidative stress. This neuroprotective effect of AA was comparable to that of GCE. These findings suggest that the neuroprotective effect of GCE against H/R-induced neuronal death is due, at least in part, to the AA content that suppresses neuronal apoptosis.

Undaria pinnatifida Promotes Spinogenesis and Synaptogenesis and Potentiates Functional Presynaptic Plasticity in Hippocampal Neurons

Reductions in neurotrophic factors are implicated in synaptic dysfunction in the central nervous system, but exogenous neurotrophic factors with potential effects on neuritic regeneration and synaptic reconstruction could offer therapeutic and preventive strategies for treating memory-related neurological disorders. In an earlier effort to identify natural neurotrophic agents, we found that the ethanol extract of the edible marine alga Undaria pinnatifida (UPE) had promising effects on the neuritogenesis of cultured hippocampal neurons. Here, we further investigated the ability of UPE to promote spinogenesis and synaptogenesis in primary cultures of hippocampal neurons. It was found that UPE triggered significant increase in numbers of dendritic filopodia and spines, promoted the formation of excitatory and inhibitory synapses, and potentiated synaptic transmission by increasing the sizes of reserve vesicle pools at presynaptic terminals. These findings indicate a substantial role for UPE in the morphological and functional maturation of neurons and suggest that UPE is a possible therapeutic preventative measure and treatment for neurodegenerative diseases, such as those involving cognitive disorders and memory impairments.

Moringa oleifera with promising neuronal survival and neurite outgrowth promoting potentials

ETHNOPHARMACOLOGICAL RELEVANCE

Moringa oleifera Lam. (Moringaceae) by virtue of its high nutritional as well as ethnomedical values has been gaining profound interest both in nutrition and medicinal research. The leaf of this plant is used in ayurvedic medicine to treat paralysis, nervous debility and other nerve disorders. In addition, research evidence also suggests the nootropic as well as neuroprotective roles of Moringa oleifera leaf in animal models. The aim of the present study was to evaluate the effect of Moringa oleifera leaf in the primary hippocampal neurons regarding its neurotrophic and neuroprotective properties.

MATERIALS AND METHODS

The primary culture of embryonic hippocampal neurons was incubated with the ethanol extract of Moringa oleifera leaf (MOE). After an indicated time, cultures were either stained directly with a lipophilic dye, DiO, or fixed and immunolabeled to visualize the neuronal morphology. Morphometric analyses for neurite maturation and synaptogenesis were performed using Image J software. Neuronal viability was evaluated using trypan blue exclusion and lactate dehydrogenase assays.

RESULTS

MOE promoted neurite outgrowth in a concentration-dependent manner with an optimal concentration of 30 μg/mL. As a very initial effect, MOE significantly promoted the earlier stages of neuronal differentiation. Subsequently, MOE significantly increased the number and length of dendrites, the length of axon, and the number and length of both dendrite and axonal branches, and eventually facilitated synaptogenesis. The β-carotene, one major compound of MOE, promoted neuritogensis, but the increase was not comparable with the effect of MOE. In addition, MOE supported neuronal survival by protecting neurons from naturally occurring cell death in vitro.

CONCLUSIONS

Our findings indicate that MOE promotes axodendritic maturation as well as provides neuroprotection suggesting a promising pharmacological importance of this nutritionally and ethnomedically important plant for the well-being of nervous system.

Differential neuritogenic activities of two edible brown macroalgae, Undaria pinnatifida and Saccharina japonica

Undaria pinnatifida (Harvey) Suringar and Saccharina japonica Areschoug are two common seaweeds, and both are known to have numerous pharmacological properties that include neuroprotective effects. In a previous study, we found that the ethanol extracts of U. pinnatifida (UPE) and S. japonica (SJE) had neurite promoting activities on developing hippocampal neurons. In the present study, we studied and compared the effects of UPE and SJE on neuronal maturation. Both UPE and SJE promoted neurite outgrowth in a dose-dependent manner with optimal concentrations of 5 and 15 μg/mL, respectively. Initial neuronal differentiation was significantly promoted by UPE and SJE. Subsequently, treatment with both increased indices of axonal and dendritic cytoarchitecture, such as, the numbers and lengths of primary processes, although only UPE had a significant effect on branching frequencies. In addition, UPE and SJE showed no evidence of cytotoxicity, rather they protected neurons from naturally occurring death in vitro. These results indicate that UPE and SJE promote axodendritic maturation and neuronal survival and suggest that these algal extracts, especially UPE, have beneficial effects on the nervous system.

Hexane fraction from Sargassum fulvellum inhibits lipopolysaccharide-induced inducible nitric oxide synthase expression in RAW 264.7 cells via NF-κB pathways

Sargassum fulvellum (Turner) C. Agardh has been used to treat various inflammatory diseases, including lump, dropsy, swollen and painful scrotum, and urination problems for several centuries with no side effects. This study aims to investigate the anti-inflammatory effect of the hexane fraction of S. fulvellum (HFS) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and phorbol 12-myristate 13-acetate (PMA)-induced mouse-ear edema. The anti-inflammatory activity of HFS in LPS-stimulated RAW 264.7 cells was investigated by assessing the inhibition of nitric oxide (NO) and pro-inflammatory cytokine production during Griess reaction and enzyme-linked immunosorbent assay (ELISA), respectively. The molecular mechanisms that underlie the anti-inflammatory action of HFS were investigated by analyzing the activation of transcription factor and its upstream signaling proteins. Additionally, an in vivo study of the anti-inflammatory effect of HFS was carried out using PMA-induced mouse-ear edema. HFS inhibited LPS-induced NO production in a dose-dependent manner and suppressed the expression of inducible NO synthase (iNOS) in the RAW 264.7 cells. Further, HFS reduced the production of pro-inflammatory cytokines in the LPS-stimulated RAW 264.7 cells. HFS significantly inhibited LPS-induced nuclear factor kappa B (NF-κB) transcriptional activity and NF-κB translocation into the nucleus by preventing degradation of inhibitor κB-α. Moreover, HFS inhibited the activation of Akt and mitogen-activated protein kinases (MAPKs) in the LPS-stimulated RAW 264.7 cells. Furthermore, HFS suppressed PMA-induced mouse-ear edema. The above data indicate that the anti-inflammatory effects of HFS on LPS-stimulated cells are associated with the suppression of NF-κB through the inhibition of MAPKs and Akt phosphorylation.

A brown alga Sargassum fulvellum facilitates neuronal maturation and synaptogenesis

Sargassum fulvellum (Turner) C. Agardh is an edible brown macroalgae having pharmacological importance. In previous reports, we described the screening of marine algae for their neuritogenic activity in developing hippocampal neurons and found that ethanol extract of S. fulvellum (SFE) possesses promising neurite-outgrowth-promoting activity. In this study, we evaluated whether the initial neurite promoting effect of SFE was followed on the further neuronal maturation and synapse formation. SFE exhibited dose-dependent effect on neurite maturation with an optimum concentration of 5 μg/mL. The initial neuronal differentiation is significantly promoted by SFE. Subsequently, compared with control culture, SFE increased the indices of axonal and dendritic developments such as the number and the length of primary processes, and branching frequencies. In addition to its effect on neurite development, SFE significantly increased the number of puncta for postsynaptic density-95, synaptic vesicle 2, and synapse (about 35%, 67%, and 125%, respectively, of control). Moreover, SFE dose-dependently protects neurons from naturally occurring death in normal culture condition. Taken together, our data demonstrate that SFE can promote neuronal maturation and synaptogenesis and support neuronal survival, suggesting the beneficial effect of this alga in nervous system.