Spongionella secondary metabolites protect mitochondrial function in cortical neurons against oxidative stress

Marine-Derived Components: Can They Be a Potential Therapeutic Approach to Parkinson's Disease?

The increase in the life expectancy average has led to a growing elderly population, thus leading to a prevalence of neurodegenerative disorders, such as Parkinson's disease (PD). PD is the second most common neurodegenerative disorder and is characterized by a progressive degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The marine environment has proven to be a source of unique and diverse chemical structures with great therapeutic potential to be used in the treatment of several pathologies, including neurodegenerative impairments. This review is focused on compounds isolated from marine organisms with neuroprotective activities on in vitro and in vivo models based on their chemical structures, taxonomy, neuroprotective effects, and their possible mechanism of action in PD. About 60 compounds isolated from marine bacteria, fungi, mollusk, sea cucumber, seaweed, soft coral, sponge, and starfish with neuroprotective potential on PD therapy are reported. Peptides, alkaloids, quinones, terpenes, polysaccharides, polyphenols, lipids, pigments, and mycotoxins were isolated from those marine organisms. They can act in several PD hallmarks, reducing oxidative stress, preventing mitochondrial dysfunction, α-synuclein aggregation, and blocking inflammatory pathways through the inhibition translocation of NF-kB factor, reduction of human tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6). This review gathers the marine natural products that have shown pharmacological activities acting on targets belonging to different intracellular signaling pathways related to PD development, which should be considered for future pre-clinical studies.

Terpenes extracted from marine sponges with antioxidant activity: a systematic review

Marine biodiversity has emerged as a very promising resource of bioactive compounds and secondary metabolites from different sea organisms. The sponge's secondary metabolites demonstrated various bioactivities and potential pharmacological properties. This systematic review of the literature focuses on the advances achieved in the antioxidant potential of marine sponges in vitro. The review was performed in accordance with PRISMA guidelines. The main inclusion criterion for analysis was articles with identification of compounds from terpene classes that demonstrate antioxidant activity in vitro. Searching in three different databases, two hundred articles were selected. After screening abstracts, titles and evaluating for eligibility of manuscripts 14 articles were included. The most performed analyzes to detect antioxidant activity were scavenging activity 2,2-diphenyl-1-picrylhydrazyl (DPPH) and measurement of intracellular reactive oxygen species (ROS). It was possible to identify 17 compounds of the terpene class with pronounced antioxidant activity in vitro. Scientific evidence of the studies included in this review was accessed by the GRADE analysis. Terpenes play an important ecological role, moreover these molecules have a pharmaceutical and industrial application.

Neuroprotective compounds from marine invertebrates

Background

Neuroinflammation is a key pathological feature of a wide variety of neurological disorders, including Parkinson’s, multiple sclerosis, Alzheimer’s, and Huntington’s disease. While current treatments for these disorders are primarily symptomatic, there is a growing interest in developing new therapeutics that target the underlying neuroinflammatory processes.

Main body

Marine invertebrates, such as coral, sea urchins, starfish, sponges, and sea cucumbers, have been found to contain a wide variety of biologically active compounds that have demonstrated potential therapeutic properties. These compounds are known to target various key proteins and pathways in neuroinflammation, including 6-hydroxydopamine (OHDH), caspase-3 and caspase-9, p-Akt, p-ERK, p-P38, acetylcholinesterase (AChE), amyloid-β (Aβ), HSF-1, α-synuclein, cellular prion protein, advanced glycation end products (AGEs), paraquat (PQ), and mitochondria DJ-1.

Short conclusion

This review focuses on the current state of research on the neuroprotective effects of compounds found in marine invertebrates and the potential therapeutic implications of these findings for treating neuroinflammatory disorders. We also discussed the challenges and limitations of using marine-based compounds as therapeutics, such as sourcing and sustainability concerns, and the need for more preclinical and clinical studies to establish their efficacy and safety.

Graphical abstract

Potential candidates from marine and terrestrial resources targeting mitochondrial inhibition: Insights from the molecular approach

Mitochondria are the target sites for multiple disease manifestations, for which it is appealing to researchers' attention for advanced pharmacological interventions. Mitochondrial inhibitors from natural sources are of therapeutic interest due to their promising benefits on physiological complications. Mitochondrial complexes I, II, III, IV, and V are the most common sites for the induction of inhibition by drug candidates, henceforth alleviating the manifestations, prevalence, as well as severity of diseases. Though there are few therapeutic options currently available on the market. However, it is crucial to develop new candidates from natural resources, as mitochondria-targeting abnormalities are rising to a greater extent. Marine and terrestrial sources possess plenty of bioactive compounds that are appeared to be effective in this regard. Ample research investigations have been performed to appraise the potentiality of these compounds in terms of mitochondrial disorders. So, this review outlines the role of terrestrial and marine-derived compounds in mitochondrial inhibition as well as their clinical status too. Additionally, mitochondrial regulation and, therefore, the significance of mitochondrial inhibition by terrestrial and marine-derived compounds in drug discovery are also discussed.

From the North Sea to Drug Repurposing, the Antiseizure Activity of Halimide and Plinabulin

PharmaSea performed large-scale in vivo screening of marine natural product (MNP) extracts, using zebrafish embryos and larvae, to identify compounds with the potential to treat epilepsy. In this study, we report the discovery of two new antiseizure compounds, the 2,5-diketopiperazine halimide and its semi-synthetic analogue, plinabulin. Interestingly, these are both known microtubule destabilizing agents, and plinabulin could have the potential for drug repurposing, as it is already in clinical trials for the prevention of chemotherapy-induced neutropenia and treatment of non-small cell lung cancer. Both halimide and plinabulin were found to have antiseizure activity in the larval zebrafish pentylenetetrazole (PTZ) seizure model via automated locomotor analysis and non-invasive local field potential recordings. The efficacy of plinabulin was further characterized in animal models of drug-resistant seizures, i.e., the larval zebrafish ethyl ketopentenoate (EKP) seizure model and the mouse 6 Hz psychomotor seizure model. Plinabulin was observed to be highly effective against EKP-induced seizures, on the behavioral and electrophysiological level, and showed activity in the mouse model. These data suggest that plinabulin could be of interest for the treatment of drug-resistant seizures. Finally, the investigation of two functional analogues, colchicine and indibulin, which were observed to be inactive against EKP-induced seizures, suggests that microtubule depolymerization does not underpin plinabulin’s antiseizure action.

Neuroprotective effects of fluorophore-labelled manganese complexes: Determination of ROS production, mitochondrial membrane potential and confocal fluorescence microscopy studies in neuroblastoma cells

In this work, four manganese(II) complexes derived from the ligands H₂L¹-H₂L⁴, that incorporate dansyl or tosyl fluorescent dyes, have been investigated in term of their antioxidant properties. Two of the manganese(II) complexes have been newly prepared using the asymmetric half-salen ligand H₂L² and the thiosemicarbazone ligand H₂L³. The four organic strands and the manganese complexes have been characterized by different analytical and spectroscopic techniques. The study of the antioxidant behaviour of these two new complexes and other two fluorophore-labelled analogues was tested in SH-SY5Y neuroblastoma cells. These four model complexes 1-4 were found to protect cells from oxidative damage in this human neuronal model, by reducing the release of reactive oxygen species. Complexes 1-4 significantly improved cell survival, with levels between 79.1 ± 0.8% and 130.9 ± 4.1%. Moreover, complexes 3 and 4 were able to restore the mitochondrial membrane potential at 1 μM, with 4 reaching levels higher than 85%, similar to the percentages obtained by the positive control agent cyclosporin A. The incorporation of the fluorescent label in the complexes allowed the study of their ability to enter the human neuroblastoma cells by confocal microscopy.

Modulation of the ubiquitin-proteasome system by marine natural products

The ubiquitin-proteasome system (UPS) is a key player in the maintenance of cellular protein homeostasis (proteostasis). Since proteasome function declines upon aging leading to the acceleration of its progression and the manifestation of age-related pathologies, many attempts have been performed towards proteasome activation as a strategy to promote healthspan and longevity. The marine environment hosts a plethora of organisms that produce a vast array of primary and secondary metabolites, the majority of which are unique, exhibiting a wide spectrum of biological activities. The fact that these biologically important compounds are also present in edible marine organisms has sparked the interest for elucidating their potential health-related applications. In this review, we focus on the antioxidant, anti-aging, anti-aggregation and anti-photoaging properties of various marine constituents. We further discuss representatives of marine compounds classes with regard to their potential (direct or indirect) action on UPS components that could serve as UPS modulators and exert beneficial effects on conditions such as oxidative stress, aging and age-related diseases.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

Anti-Alzheimer's Molecules Derived from Marine Life: Understanding Molecular Mechanisms and Therapeutic Potential

Alzheimer’s disease (AD) is a devastating neurodegenerative disease and the most common cause of dementia. It has been confirmed that the pathological processes that intervene in AD development are linked with oxidative damage to neurons, neuroinflammation, tau phosphorylation, amyloid beta (Aβ) aggregation, glutamate excitotoxicity, and cholinergic deficit. Still, there is no available therapy that can cure AD. Available therapies only manage some of the AD symptoms at the early stages of AD. Various studies have revealed that bioactive compounds derived from marine organisms and plants can exert neuroprotective activities with fewer adverse events, as compared with synthetic drugs. Furthermore, marine organisms have been identified as a source of novel compounds with therapeutic potential. Thus, there is a growing interest regarding bioactive compounds derived from marine sources that have anti-AD potentials. Various marine drugs including bryostatin-1, homotaurine, anabaseine and its derivative, rifampicins, anhydroexfoliamycin, undecylprodigioisin, gracilins, 13-desmethyl spirolide-C, and dictyostatin displayed excellent bioavailability and efficacy against AD. Most of these marine drugs were found to be well-tolerated in AD patients, along with no significant drug-associated adverse events. In this review, we focus on the drugs derived from marine life that can be useful in AD treatment and also summarize the therapeutic agents that are currently used to treat AD.

Cyclophilins A, B, and C Role in Human T Lymphocytes Upon Inflammatory Conditions

Cyclophilins (Cyps) are a group of peptidyl-prolyl cis/trans isomerases that play crucial roles in regulatory mechanisms of cellular physiology and pathology in several inflammatory conditions. Their receptor, CD147, also participates in the development and progression of the inflammatory response. Nevertheless, the main function of Cyps and their receptor are yet to be deciphered. The release of CypA and the expression of the CD147 receptor in activated T lymphocytes were already described, however, no data are available about other Cyps in these cells. Therefore, in the present work intra and extracellular CypA, B and C levels were measured followed by induced inflammatory conditions. After activation of T lymphocytes by incubation with concanavalin A, both intra and extracellular Cyps levels and the CD147 membrane receptor expression were increased leading to cell migration towards circulating CypA and CypB as chemoattractants. When CypA was modulated by natural and synthetic compounds, the inflammatory cascade was avoided including T cell migration. Our results strengthen the relationship between CypA, B, and C, their receptor, and the inflammatory process in human T lymphocytes, associating CypC with these cells for the first time.

Natural Compounds for the Prevention and Treatment of Cardiovascular and Neurodegenerative Diseases

Secondary metabolites from plants and fungi are stimulating growing interest in consumers and, consequently, in the food and supplement industries. The beneficial effects of these natural compounds are being thoroughly studied and there are frequent updates about the biological activities of old and new molecules isolated from plants and fungi. In this article, we present a review of the most recent literature regarding the recent discovery of secondary metabolites through isolation and structural elucidation, as well as the in vitro and/or in vivo evaluation of their biological effects. In particular, the possibility of using these bioactive molecules in the prevention and/or treatment of widely spread pathologies such as cardiovascular and neurodegenerative diseases is discussed.

Bridging the gap between natural product synthesis and drug discovery

Covering: 1986 to 2020Natural products are an enduring source of chemical information useful for probing biologically relevant chemical space. Toward gathering further structure-activity relationship (SAR) information for a particular natural product, synthetic chemists traditionally proceeded first by a total synthesis effort followed by the synthesis of simplified derivatives. While this approach has proven fruitful, it often does not incorporate hypotheses regarding structural features necessary for bioactivity at the synthetic planning stage, but rather focuses on the rapid assembly of the targeted natural product; a goal that often supersedes the opportunity to gather SAR information en route to the natural product. Furthermore, access to simplified variants of a natural product possessing only the proposed essential structural features necessary for bioactivity, typically at lower oxidation states overall, is sometimes non-trivial from the original established synthetic route. In recent years, several synthetic design strategies were described to streamline the process of finding bioactive molecules in concert with fathering further SAR studies for targeted natural products. This review article will briefly discuss traditional retrosynthetic strategies and contrast them to selected examples of recent synthetic strategies for the investigation of biologically relevant chemical space revealed by natural products. These strategies include: diversity-oriented synthesis (DOS), biology-oriented synthesis (BIOS), diverted-total synthesis (DTS), analogue-oriented synthesis (AOS), two-phase synthesis, function-oriented synthesis (FOS), and computed affinity/dynamically ordered retrosynthesis (CANDOR). Finally, a description of pharmacophore-directed retrosynthesis (PDR) developed in our laboratory and initial applications will be presented that was initially inspired by a retrospective analysis of our synthetic route to pateamine A completed in 1998.

Gracilin A Derivatives Target Early Events in Alzheimer's Disease: in Vitro Effects on Neuroinflammation and Oxidative Stress

The search for compounds capable of targeting early pathological changes of Alzheimer̀s disease (AD), such as oxidative stress and neuroinflammation, is an important challenge. Gracilin A derivatives were recently synthesized, using a pharmacophore-directed retrosynthesis (PDR) strategy, and found to possess potent neuroprotective effects. In this work, the previously described derivatives 1-7 which demonstrated mitochondrial-mediated, antioxidant effects were chosen for further study. The ability of compounds to modulate the expression of antioxidant genes (CAT, GPx, SODs, and Nrf2) was determined in SH-SY5Y cells, and the simplified derivatives 2 and 3 were found to be the most effective. The anti-neuroinflammatory properties of all derivatives were assessed in BV2 microglial cells activated with lipopolysaccharide (LPS). Several derivatives decreased the release of cytokines (Il-1β, IL-6, GM-CSF, and TNF-α) and other damaging molecules (ROS, NO) and also regulated the translocation of Nrf2 and NFκB, and reduced p38 activation. These protective effects were confirmed in a trans-well coculture with BV2 and SH-SY5Y cells and several derivatives increased SH-SY5Y survival. This present work demonstrates the neuroprotective properties of gracilin A derivatives, making them promising candidate drugs for AD. Particularly, derivatives 2 and 3 showed the greatest potential as lead compounds for further development.

Bromotryptamine and Bromotyramine Derivatives from the Tropical Southwestern Pacific Sponge Narrabeena nigra

So far, the Futuna Islands located in the Central Indo-Pacific Ocean have not been inventoried for their diversity in marine sponges and associated chemical diversity. As part of the Tara Pacific expedition, the first chemical investigation of the sponge Narrabeena nigra collected around the Futuna Islands yielded 18 brominated alkaloids: seven new bromotryptamine derivatives 1-7 and one new bromotyramine derivative 8 together with 10 known metabolites of both families 9-18. Their structures were deduced from extensive analyses of nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) data. In silico metabolite anticipation using the online tool MetWork revealed the presence of a key and minor biosynthetic intermediates. These 18 compounds showed almost no cytotoxic effect up to 10 µM on human neuroblastoma SH-SY5Y and microglia BV2 cells, and some of them exhibited an interesting neuroprotective activity by reducing oxidative damage.

Natural Compounds for Alzheimer's Disease Therapy: A Systematic Review of Preclinical and Clinical Studies

Alzheimer's Disease (AD) is a neurodegenerative disorder related with the increase of age and it is the main cause of dementia in the world. AD affects cognitive functions, such as memory, with an intensity that leads to several functional losses. The continuous increase of AD incidence demands for an urgent development of effective therapeutic strategies. Despite the extensive research on this disease, only a few drugs able to delay the progression of the disease are currently available. In the last years, several compounds with pharmacological activities isolated from plants, animals and microorganisms, revealed to have beneficial effects for the treatment of AD, targeting different pathological mechanisms. Thus, a wide range of natural compounds may play a relevant role in the prevention of AD and have proven to be efficient in different preclinical and clinical studies. This work aims to review the natural compounds that until this date were described as having significant benefits for this neurological disease, focusing on studies that present clinical trials.

Marine-Derived Natural Compounds for the Treatment of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder caused by the loss of dopaminergic neurons, leading to the motor dysfunctions of patients. Although the etiology of PD is still unclear, the death of dopaminergic neurons during PD progress was revealed to be associated with the abnormal aggregation of α-synuclein, the elevation of oxidative stress, the dysfunction of mitochondrial functions, and the increase of neuroinflammation. However, current anti-PD therapies could only produce symptom-relieving effects, because they could not provide neuroprotective effects, stop or delay the degeneration of dopaminergic neurons. Marine-derived natural compounds, with their novel chemical structures and unique biological activities, may provide anti-PD neuroprotective effects. In this study, we have summarized anti-PD marine-derived natural products which have shown pharmacological activities by acting on various PD targets, such as α-synuclein, monoamine oxidase B, and reactive oxygen species. Moreover, marine-derived natural compounds currently evaluated in the clinical trials for the treatment of PD are also discussed.

Simplified immunosuppressive and neuroprotective agents based on gracilin A

The architecture and bioactivity of natural products frequently serve as embarkation points for the exploration of biologically relevant chemical space. Total synthesis followed by derivative synthesis has historically enabled a deeper understanding of structure-activity relationships. However, synthetic strategies towards a natural product are not always guided by hypotheses regarding the structural features required for bioactivity. Here, we report an approach to natural product total synthesis that we term 'pharmacophore-directed retrosynthesis'. A hypothesized, pharmacophore of a natural product is selected as an early synthetic target and this dictates the retrosynthetic analysis. In an ideal application, sequential increases in the structural complexity of this minimal structure enable development of a structure-activity relationship profile throughout the course of the total synthesis effort. This approach enables the identification of simpler congeners retaining bioactivity at a much earlier stage of a synthetic effort, as demonstrated here for the spongiane diterpenoid, gracilin A, leading to simplified derivatives with potent neuroprotective and immunosuppressive activity.

Cognitive Impairment in Chronic Obstructive Pulmonary Disease (COPD): Possible Utility of Marine Bioactive Compounds

Chronic obstructive pulmonary disease (COPD) is characterized by long-term airflow limitation. Early-onset COPD in non-smoker subjects is ≥60 years and in the elderly is often associated with different comorbidities. Cognitive impairment is one of the most common feature in patients with COPD, and is associated with COPD severity and comorbidities. Cognitive impairment in COPD enhances the assistance requirement in different aspects of daily living, treatment adherence, and effectual self-management.This review describes various bioactive compounds of natural marine sources that modulate different targets shared by both COPD and cognitive impairment and hypothesizes a possible link between these two syndromes.

Selective Toxicity of Non Polar Bioactive Compounds of Persian Gulf Sea Squirt Phallusia Nigra on Skin Mitochondria Isolated from Rat Model of Melanoma

Background:

Skin cancer is the most prevalent cancer and one of the major causes of mortality worldwide. Marin animals have attracted much attention in recent years as useful substances having application in medicine. It was shown that Phallusia nigra (P. nigra) known as sea squirt could play an important role in cancer therapy.

Methods:

This study was designed to figure out the probable selective toxicity of n-hexane, diethyl ether, methanolic and aqueous extracts of P. nigra on cancerous mitochondria isolated from the skin of melanoma induced rats. In our study, mitochondria were isolated from the skin tissue of both melanoma induced and normal healthyrats. Different concentrations of four different extracts of P. nigra (250, 500 and 1000 µg/ml) were added to mitochondrial samples obtained from both groups, separately.

Results:

Our results showed that n-hexane, diethyl ether and methanolic extracts (but not aqueous extract) of P. nigra in all concentrations applied (250, 500 and 1000 µg/ml) significantly induced toxic alterations only in the cancerous but not normal healthy skin mitochondria including; increased reactive oxygen species (ROS) formation, mitochondrial swelling, decreased mitochondrial membrane potential (MMP) and cytochrome c release. Flow-cytometry analysis demonstrated that n-hexane, diethyl ether and methanolic extracts of P. nigra progressively induced apoptosis and necrosis only on melanoma cells but not healthy skin cells.

Conclusions:

Our results suggest that non polar bioactive compounds in P. nigra may be hopeful candidates for further studies including molecular identification, confirmatory in vivo experiments and finally clinical trials designed for new drug treatment of melanoma skin cancer.

Evaluation of the Antioxidant Activity of the Marine Pyrroloiminoquinone Makaluvamines

Makaluvamines are pyrroloiminoquinones isolated from Zyzzya sponges. Until now, they have been described as topoisomerase II inhibitors with cytotoxic effects in diverse tumor cell lines. In the present work, seven makaluvamines were tested in several antioxidant assays in primary cortical neurons and neuroblastoma cells. Among the alkaloids studied, makaluvamine J was the most active in all the assays. This compound was able to reduce the mitochondrial damage elicited by the well-known stressor H₂O₂. The antioxidant properties of makaluvamine J are related to an improvement of the endogenous antioxidant defenses of glutathione and catalase. SHSY5Y assays proved that this compound acts as a Nrf2 activator leading to an improvement of antioxidant defenses. A low concentration of 10 nM is able to reduce the reactive oxygen species release and maintain a correct mitochondrial function. Based on these results, non-substituted nitrogen in the pyrrole plus the presence of a p-hydroxystyryl without a double bond seems to be the most active structure with a complete antioxidant effect in neuronal cells.

Spongionella Secondary Metabolites, Promising Modulators of Immune Response through CD147 Receptor Modulation

The modulation of the immune system can have multiple applications such as cancer treatment, and a wide type of processes involving inflammation where the potent chemotactic agent cyclophilin A (Cyp A) is implicated. The Porifera phylum, in which Spongionella is encompassed, is the main producer of marine bioactive compounds. Four secondary metabolites obtained from Spongionella (Gracilin H, A, L, and Tetrahydroaplysulphurin-1) were described to hit Cyp A and to block the release of inflammation mediators. Based on these results, some role of Spongionella compounds on other steps of the signaling pathway mediated by this chemotactic agent can be hypothesized. In the present paper, we studied the effect of these four compounds on the surface membrane CD147 receptor expression, on the extracellular levels of Cyp A and on the ability to migrate of concanavalin (Con A)-activated T lymphocytes. Similar to a well-known immunosuppressive agent cyclosporine A (CsA), Gracilin H, A, L, and tetrahydroaplysulphurin-1 were able to reduce the CD147 membrane expression and to block the release of Cyp A to the medium. Besides, by using Cyp A as chemotactic agent, T cell migration was inhibited when cells were previously incubated with Gracilin A and Gracilin L. These positive results lead us to test the in vivo effect of Gracilin H and L in a mouse ear delayed hypersensitive reaction. Thus, both compounds efficiently reduce the ear swelling as well as the inflammatory cell infiltration. These results provide more evidences for their potential therapeutic application in immune-related diseases of Spongionella compounds.

Photoinduced Cycloadditions in the Diversity-Oriented Synthesis Toolbox: Increasing Complexity with Straightforward Postphotochemical Modifications

Rapid growth of complexity and unprecedented molecular architectures are realized via the excited-state intramolecular proton transfer (ESIPT) in o-acylamidobenzaldehydes and ketones followed by [4+2] or [4+4] cycloadditions with subsequent postphotochemical modifications. The approach is congruent with Diversity-Oriented Synthesis: photoprecursors are synthesized in a modular fashion allowing for up to four diversity inputs. The complexity of the primary photoproducts is further enhanced using straightforward and high-yielding postphotochemical modification steps such as reactions with nitrile oxides, nitrones, Povarov reaction, and oxa-Diels-Alder reaction.

Bromoalkaloids protect primary cortical neurons from induced oxidative stress

Bromoalkaloids are secondary metabolites with a demonstrated high activity in several therapeutic areas. In this research, we probe the neuroprotective and antioxidant activities of hymenialdisine and hymenin. Both structures were tested in an oxidative stress cellular model, consisting of cortical neurons that are incubated with the oxidative stress inducer hydrogen peroxide and the tested compound. Several oxidation biomarkers were analyzed, and the results of the oxidative stress induced neurons in the presence and absence of bromoalkaloids were compared. Both compounds demonstrated significant neuroprotective ability under stress conditions at low nanomolar concentrations, with hymenialdisine highlighted for demonstrating a more complete protection. Also, the activity of hymenialdisine and hymenin was studied in the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway, and, for the first time, these halogenated metabolites are described as Nrf2 inducers, reinforcing the antioxidant capacity observed and therefore opening a new path of investigation. These results, added to the previously described effect of this compound family in negatively modulating several kinases and proinflammatory cytokines, position hymenialdisine and hymenin as good candidates for the development of new drugs for neurodegenerative diseases.

Chitooligosaccharides attenuate Cu2+-induced cellular oxidative damage and cell apoptosis involving Nrf2 activation

Alzheimer's disease (AD) is one of the common neurodegenerative diseases. Increase of labile copper pool plays an important role in the pathogenesis of AD. Nrf2(NF-E2-related factor-2)-ARE (antioxidant response element) signaling is an important intracellular manner to defend against oxidative stress. In this study, we used SH-SY5Y cells as a model of neuron to test the effect of chitooligosaccharides (COSs) on Cu(2+)-induced oxidative damage. SH-SY5Y cells were treated with different concentrations of COSs (100-800 mg/L) before incubated with Cu(2+). Cell viability and cell damage and apoptosis were assessed. Both extracellular H(2)O(2) and intracellular ROS were measured and the relative levels of Nrf2, phosphorylated Nrf2, and HO-1 were analyzed by Western blotting, and further HO-1 mRNA was relatively quantified by real-time quantitative PCR. The results indicated that Cu(2+)-induced decrease of cell viability and increase of LDH release. In cell-free solution, COSs alone or with Cu(2+) cannot scavenge O(2)(-); however, COSs downregulate the levels of cellular oxidative stress and activated Caspase-3 induced by Cu(2+). Further, the levels of pSer40-Nrf2 protein and both the transcription and the translation of HO-1 gene are dramatically increased in COSs-protective group compared with Cu(2+) damage group. Therefore, these results indicate that Nrf2 activation might be involved in the protection of COSs against Cu(2+)-induced cellular oxidative damage. COSs contribute to the attenuation of oxidative damage and could be used as a nutritional agent for AD treatment.

Natural products from marine organisms with neuroprotective activity in the experimental models of Alzheimer's disease, Parkinson's disease and ischemic brain stroke: their molecular targets and action mechanisms

Continuous increases in the incidence of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and brain stroke demand the urgent development of therapeutics. Marine organisms are well-known producers of natural products with diverse structures and pharmacological activities. Therefore, researchers have endeavored to identify marine natural products with neuroprotective effects. In this regard, this review summarizes therapeutic targets for AD, PD, and ischemic brain stroke and marine natural products with pharmacological activities on the targets according to taxonomies of marine organisms. Furthermore, several marine natural products on the clinical trials for the treatment of neurological disorders are discussed.