Inhibitory effects of fucoidan on NMDA receptors and l-type Ca2+ channels regulating the Ca2+ responses in rat neurons

Acute Treatment with Fucoidan Ameliorates Traumatic Brain Injury-Induced Neurological Damages and Memory Deficits in Rats: Role of BBB Integrity, Microglial Activity, Neuroinflammation, and Oxidative Stress

There is no acquiesced remedy for the treatment of traumatic brain injury (TBI)-associated impairment, especially cognitive decline. The first 24 h after TBI is a golden time for preventing the progress of the impairments. The present study aimed to examine the acute effects of fucoidan on neurological outcomes and memory performance and investigate its potential mechanisms in rats with TBI. Fucoidan (25, 50, and 100 mg/kg, i.p.) was injected immediately after TBI induction. Veterinary coma scale (VCS), brain edema, blood-brain barrier (BBB) integrity, passive avoidance memory and spatial memory, neuroplasticity, myeloperoxidase (MPO) activity, oxidative stress, and histological alteration were evaluated after TBI induction and fucoidan treatment. The findings revealed that TBI resulted in an enhancement in brain water content and BBB permeability and diminished the performance of passive avoidance memory and spatial memory. These were accompanied by long-term potentiation (LTP) suppression in the hippocampus and the prevention of activities of SOD, catalase, and GPx and enhancement of MPO activity, TNF-α, IL-6, and lipid peroxidation levels in the hippocampus as well as hippocampal neuronal loss. Fascinatingly, acute treatment of TBI rats with fucoidan especially in the higher doses (50 and 100 mg/kg) significantly ameliorated (p < 0.05) neurological outcomes of VCS, cerebral edema, BBB integrity, passive avoidance memory, spatial memory, LTP impairment, and oxidative-antioxidative balance. Also, fucoidan significantly ameliorated hippocampal neuronal loss, TNF-α and IL-6 levels, and MPO activity as an indicator of microglial activation. These outcomes imply that fucoidan can be a hopeful remedy for TBI-associated neuronal impairments. However, further research is necessary to endorse this issue.

Fucoxanthin Inhibits the NMDA and AMPA Receptors Through Regulating the Calcium Response on Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Juvenile Mice

Glutamate excitotoxicity is considered as the etiology of stroke and neurodegenerative diseases, namely, Parkinson's disease (PD), Alzheimer's disease (AD), and others. Meanwhile, substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc), a pivotal site in regulating orofacial nociceptive transmission via Aδ and C primary afferent fibers, majorly utilize glutamate as the principal excitatory neurotransmitter. Fucoxanthin (FCX), a carotenoid pigment extracted from brown seaweed, possesses various pharmaceutical properties including neuroprotective effect in multiple neuronal populations. To date, the direct activity of FCX on the SG of the Vc has not been extensively clarified. Consequently, we investigated the effect of FCX on excitatory signaling mediated by ionotropic glutamate receptors (iGluRs), using the patch-clamp technique recorded from SG neurons of the Vc. Here, FCX directly acted on glutamate receptors independent of voltage-gated sodium channel and γ-aminobutyric acid (GABA)A/glycine receptors in the voltage-clamp mode. Specifically, the N-methyl-D-aspartic acid (NMDA)- and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced responses but not the kainic acid receptor (KAR)-mediated response were suppressed by FCX in standard extracellular solution. Additionally, the inhibitory effect of FCX on NMDA currents was repeatable and concentration-dependent. The FCX blockade of NMDA-mediated excitotoxicity was associated with the modulation of Ca2+ response without affecting Na+ ions. The Ca2+-dependent fluorescence intensity of brain slice was reduced in the presence of FCX. Notably, FCX significantly attenuated the spontaneous firing activity of SG neurons. Altogether, these results reveal that FCX may protect SG neurons against glutamate excitotoxicity via primarily regulating Ca2+ response, thereby inhibiting the excitatory signaling induced by NMDA and AMPA receptors (AMPARs).

The molecular mechanism of polysaccharides in combating major depressive disorder: A comprehensive review

Major depressive disorder (MDD) is a complex psychiatric condition with diverse etiological factors. Typical pathological features include decreased cerebral cortex, subcortical structures, and grey matter volumes, as well as monoamine transmitter dysregulation. Although medications exist to treat MDD, unmet needs persist due to limited efficacy, induced side effects, and relapse upon drug withdrawal. Polysaccharides offer promising new therapies for MDD, demonstrating antidepressant effects with minimal side effects and multiple targets. These include neurotransmitter, neurotrophin, neuroinflammation, hypothalamic-pituitary-adrenal axis, mitochondrial function, oxidative stress, and intestinal flora regulation. This review explores the latest advancements in understanding the pharmacological actions and mechanisms of polysaccharides in treating major depression. We discuss the impact of polysaccharides' diverse structures and properties on their pharmacological actions, aiming to inspire new research directions and facilitate the discovery of novel anti-depressive drugs.

Application of Marine Natural Products against Alzheimer's Disease: Past, Present and Future

Alzheimer's disease (AD), a neurodegenerative disease, is one of the most intractable illnesses which affects the elderly. Clinically manifested as various impairments in memory, language, cognition, visuospatial skills, executive function, etc., the symptoms gradually aggravated over time. The drugs currently used clinically can slow down the deterioration of AD and relieve symptoms but cannot completely cure them. The drugs are mainly acetylcholinesterase inhibitors (AChEI) and non-competitive N-methyl-D-aspartate receptor (NDMAR) antagonists. The pathogenesis of AD is inconclusive, but it is often associated with the expression of beta-amyloid. Abnormal deposition of amyloid and hyperphosphorylation of tau protein in the brain have been key targets for past, current, and future drug development for the disease. At present, researchers are paying more and more attention to excavate natural compounds which can be effective against Alzheimer's disease and other neurodegenerative pathologies. Marine natural products have been demonstrated to be the most prospective candidates of these compounds, and some have presented significant neuroprotection functions. Consequently, we intend to describe the potential effect of bioactive compounds derived from marine organisms, including polysaccharides, carotenoids, polyphenols, sterols and alkaloids as drug candidates, to further discover novel and efficacious drug compounds which are effective against AD.

Identification of novel inhibitors for SARS-CoV-2 as therapeutic options using machine learning-based virtual screening, molecular docking and MD simulation

The new coronavirus SARS-COV-2, which emerged in late 2019 from Wuhan city of China was regarded as causing agent of the COVID-19 pandemic. The primary protease which is also known by various synonymous i.e., main protease, 3-Chymotrypsin-like protease (3CL^PRO) has a vital role in the replication of the virus, which can be used as a potential drug target. The current study aimed to identify novel phytochemical therapeutics for 3CL^PRO by machine learning-based virtual screening. A total of 4,000 phytochemicals were collected from deep literature surveys and various other sources. The 2D structures of these phytochemicals were retrieved from the PubChem database, and with the use of a molecular operating environment, 2D descriptors were calculated. Machine learning-based virtual screening was performed to predict the active phytochemicals against the SARS-CoV-2 3CL^PRO. Random forest achieved 98% accuracy on the train and test set among the different machine learning algorithms. Random forest model was used to screen 4,000 phytochemicals which leads to the identification of 26 inhibitors against the 3CL^PRO. These hits were then docked into the active site of 3CL^PRO. Based on docking scores and protein-ligand interactions, MD simulations have been performed using 100 ns for the top 5 novel inhibitors, ivermectin, and the APO state of 3CL^PRO. The post-dynamic analysis i.e,. Root means square deviation (RMSD), Root mean square fluctuation analysis (RMSF), and MM-GBSA analysis reveal that our newly identified phytochemicals form significant interactions in the binding pocket of 3CL^PRO and form stable complexes, indicating that these phytochemicals could be used as potential antagonists for SARS-COV-2.

Complementarity of Raman and Infrared spectroscopy for rapid characterization of fucoidan extracts

BACKGROUND

Fucoidans are sulfated polysaccharides from the cell-wall of brown algae. They have a wide range of applications in medicine, including regenerative medicine, ophthalmology, cancer, and autoimmune disease. Biological activity of fucoidans directly depends on their structure, which remains poorly understood. This is primarily because the polymeric nature of these molecules limits the use of nuclear magnetic resonance and mass spectrometry, classical tools of structural biology for their structural characterization. Raman and Infrared spectroscopies are non-invasive and non-destructive techniques that can be used to probe the structural organization of biological specimens. In this study, we investigate the potential of Raman and Infrared spectroscopy for structural analysis of several fucoidan extracts.

RESULTS

Our results show that Infrared and Raman provide different but complimentary information about the structure of crude extracts of fucoidans, revealing the presence of minor impurities from co-extractants. We also found that at high extraction temperatures acidic conditions limit formation of melanoidins, while also yielding relatively high sulfate ester fucoidan. However, at high temperatures, water extraction may potentially result in formation of advanced glycation end products. Their presence could be problematic for fucoidan extracts intended for medicinal use, as advanced glycation end products have been linked to endocrine interruption mechanisms in vivo by crosslinking to and permanently altering extracellular matrix proteins.

CONCLUSION

Raman and Infrared can be used as complementary tools for rapid screening of crude fucoidan extracts, which can be a valuable tool for assessing impurities that remain after extraction.

Dynorphin A (1-8) inhibits oxidative stress and apoptosis in MCAO rats, affording neuroprotection through NMDA receptor and κ-opioid receptor channels

The contents of Dynorphin A(1-8) decreased gradually in ischemic cortices in rats and an intracerebroventricular administration of synthetic Dynorphin A(1-8) reduced the volume of cerebral infarction in our previous research. However, the specific protective mechanism is unclear and Dynorphin A(1-8) is unlikely to cross the blood-brain barrier (BBB) by noninvasive oral or intravenous administration as a macromolecule neuropeptide. In this study, intranasal administration was used to middle cerebral artery occlusion(MCAO) rats to assessed the therapeutic effects of Dynorphin A(1-8) by evaluating behavior, volume of cerebral infarct, cerebral edema ratio, histological observation. Then apoptosis neuron rate was detected by TUNEL staining. Immunohistochemical staining was carried out to explore the alteration of Bcl-2, Bax and Caspase-3. Finally, κ-opioid receptor antagonist and N-methyl-d-aspartate(NMDA) receptor antagonist were used to explore its possible mechanism. We found that MCAO rats under intranasal administration of Dynorphin A(1-8) showed better behavioral improvement, higher extent of Bcl-2, activity of SOD along with much lower level of infarction volume, brain water content, number of cell apoptosis, extent of Bax and Caspase-3, and concentration of MDA compared with those in MCAO model group and intravenous Dynorphin A(1-8) group. Administration of nor-BNI or MK-801 reversed these neuroprotective effects of intranasal Dynorphin A(1-8). In summary, Dynorphin A(1-8), with advantages of intranasal administration, could be effectively delivered to central nervous system(CNS). Dynorphin A(1-8) inhibited oxidative stress and apoptosis against cerebral ischemia/reperfusion injury, affording neuroprotection through NMDA receptor and κ-opioid receptor channels.

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.

LC/MS Analysis of Saponin Fraction from the Leaves of Elaeagnus rhamnoides (L.) A. Nelson and Its Biological Properties in Different In Vitro Models

This study focuses on saponin fraction from sea buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) leaves. It has known that for example teas from sea buckthorn leaves have anti-obesity properties. The objective of our present experiments was to investigate both the chemical composition of saponin fraction, as well as their biological properties in different in vitro models (using human plasma, blood platelets, and peripheral blood mononuclear cells (PBMCs)). We observed that saponin fraction reduces plasma lipid peroxidation and protein carbonylation induced by H₂O₂/Fe. This fraction also decreased DNA oxidative damage induced by H₂O₂ in PBMCs. Regarding the cytotoxicity of saponin fraction (0.5–50 µg/mL) none was found to cause lysis of blood platelets, and PBMCs. Our results, for the first time indicate that saponin fraction from sea buckthorn leaves may be a new promising source of compounds for prophylaxis and treatment of diseases associated with oxidative stress.

Potential Beneficial Actions of Fucoidan in Brain and Liver Injury, Disease, and Intoxication-Potential Implication of Sirtuins

Increased interest in natural antioxidants has brought to light the fucoidans (sulfated polysaccharides present in brown marine algae) as highly valued nutrients as well as effective and safe therapeutics against several diseases. Based on their satisfactory in vitro antioxidant potency, researchers have identified this molecule as an efficient remedy for neuropathological as well as metabolic disorders. Some of this therapeutic activity is accomplished by upregulation of cytoprotective molecular pathways capable of restoring the enzymatic antioxidant activity and normal mitochondrial functions. Sirtuin-3 has been discovered as a key player for achieving the neuroprotective role of fucoidan by managing these pathways, whose ultimate goal is retrieving the entirety of the antioxidant response and preventing apoptosis of neurons, thereby averting neurodegeneration and brain injuries. Another pathway whereby fucoidan exerts neuroprotective capabilities is by interactions with P-selectin on endothelial cells, thereby preventing macrophages from entering the brain proper. Furthermore, beneficial influences of fucoidan have been established in hepatocytes after xenobiotic induced liver injury by decreasing transaminase leakage and autophagy as well as obtaining optimal levels of intracellular fiber, which ultimately prevents fibrosis. The hepatoprotective role of this marine polysaccharide also includes a sirtuin, namely sirtuin-1 overexpression, which alleviates obesity and insulin resistance through suppression of hyperglycemia, reducing inflammation and stimulation of enzymatic antioxidant response. While fucoidan is very effective in animal models for brain injury and neuronal degeneration, in general, it is accepted that fucoidan shows somewhat limited potency in liver. Thus far, it has been used in large doses for treatment of acute liver injuries. Thus, it appears that further optimization of fucoidan derivatives may establish enhanced versatility for treatments of various disorders, in addition to brain injury and disease.