Fucoxanthin enhances HO-1 and NQO1 expression in murine hepatic BNL CL.2 cells through activation of the Nrf2/ARE system partially by its pro-oxidant activity

Xanthophyll-Rich Extract of Phaeodactylum tricornutum Bohlin as New Photoprotective Cosmeceutical Agent: Safety and Efficacy Assessment on In Vitro Reconstructed Human Epidermis Model

The nutritional and health properties of algae make them perfect functional ingredients for nutraceutical and cosmeceutical applications. In this study, the Phaeodactylum tricornutum Bohlin (Phaeodactylaceae), a pleiomorphic diatom commonly found in marine ecosystems, was investigated. The in vitro culture conditions used favoured the fusiform morphotype, characterized by a high accumulation of neutral lipids, as detected by fluorescence microscopy after BODIPY staining. These data were confirmed by HPLC-DAD-APCI-MS/MS analyses carried out on the ethanolic extract (PTE), which showed a high content of xanthophylls (98.99%), and in particular of fucoxanthin (Fx, 6.67 g/100 g PTE). The antioxidant activity (ORAC, FRAP, TEAC and β-carotene bleaching) and photostability of PTE and Fx against UVA and UVB rays were firstly evaluated by in vitro cell-free assays. After this, phototoxicity and photoprotective studies were carried out on in vitro reconstructed human epidermidis models. Results demonstrated that PTE (0.1% Fx) and 0.1% Fx, both photostable, significantly (p < 0.05) reduce oxidative and inflammatory stress markers (ROS, NO and IL-1α), as well as cytotoxicity and sunburn cells induced by UVA and UVB doses simulating the solar radiation, with an excellent safety profile. However, PTE proved to be more effective than Fx, suggesting its effective and safe use in broad-spectrum sunscreens.

Ameliorative Effects of Peptide Phe-Leu-Ala-Pro on Acute Liver and Kidney Injury Caused by CCl4 via Attenuation of Oxidative Stress and Inflammation

Acute liver injury (ALI) and acute kidney injury (AKI) are significantly affected by the antioxidant status. In the present study, the protective effect and mechanism of the collagen peptide Phe-Leu-Ala-Pro (FLAP) in mice with ALI and AKI induced by carbon tetrachloride (CCl₄) were examined. The results showed that FLAP effectively improved the liver mass index, the renal mass index, and the histopathological morphology. FLAP treatment significantly decreased the levels of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea nitrogen (BUN), and creatinine (CRE) but increased the activity of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). The protein expression levels of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), p-protein kinase B (p-AKT), and p-phosphatidylinositol-3-kinase (p-PI3K) in the liver and kidneys were significantly up-regulated after FLAP treatment. FLAP down-regulated the levels of interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNF-α), and nuclear factor-κ B (NF-κB) in liver and kidney tissues. Thus, FLAP may play a protective role in ALI and AKI by attenuating oxidative stress and inflammation mediated by the Nrf2/anti-response element (ARE) and PI3K/AKT/NF-κB pathways.

Therapeutic Effect of Gypenosides on Antioxidant Stress Injury in Orbital Fibroblasts of Graves’ Orbitopathy

Purpose

To examine the impact of gypenosides (Gyps) on oxidative stress damage of orbital fibroblasts (OFs) from Graves' ophthalmopathy (GO) patients.

Methods

The relationship between Gyps and GO oxidative stress was understood by bioinformatics analysis. Orbital connective tissues of GO and non-GO patients were obtained for primary OF culture. The proliferation level of OFs was measured by Cell Counting Kit-8 method, and the appropriate intervention concentration of Gyps and H₂O₂ was obtained. The expression of apoptosis-related protein mRNA was analyzed by RT-qPCR technique. ROS and SOD test suites were employed to detect the oxidative stress level in OFs. Flow cytometry apoptosis detection, TUNEL detection, and lactate dehydrogenase detection were used to analyze the level of apoptosis. Western blotting detection was utilized to examine the regulatory pathway of oxidative stress, apoptosis, and autophagy-related proteins. The changes of cell morphology, autophagosome, and autophagy lysosome were observed by transmission electron microscope.

Results

The suitable intervention concentration of Gyps is 100 μg/mL, and the suitable intervention concentration of high concentration H₂O₂ is 350 μM. In comparison with the blank control group, the H₂O₂ intervention group enhanced the expression of apoptosis-related mRNA, the expression of ROS and SOD, the apoptosis rate, the expression of autophagy activation-related protein and Nrf2/ERK/HO-1 protein, and the number of autophagosomes and autophagy lysosomes. Compared with H₂O₂ intervention group, the expression of apoptosis-related mRNA decreased, ROS expression decreased, SOD expression increased, apoptosis rate decreased, autophagy activation-related protein expression decreased, Nrf2/ERK/HO-1 protein expression increased, and the quantity of autophagosomes and autophagy lysosomes decreased in H₂O₂ + Gyps intervention group.

Conclusion

Gyps can decrease the oxidative stress level of OFs generated by H₂O₂, reduce cell autophagy, and reduce apoptosis. Gyps may regulate the oxidative stress response of OFs in GO patients via the Nrf2/ERK/HO-1 signaling pathway.

Fucoxanthin: A Promising Phytochemical on Diverse Pharmacological Targets

Fucoxanthin (FX) is a special carotenoid having an allenic bond in its structure. FX is extracted from a variety of algae and edible seaweeds. It has been proved to contain numerous health benefits and preventive effects against diseases like diabetes, obesity, liver cirrhosis, malignant cancer, etc. Thus, FX can be used as a potent source of both pharmacological and nutritional ingredient to prevent infectious diseases. In this review, we gathered the information regarding the current findings on antimicrobial, antioxidant, anti-inflammatory, skin protective, anti-obesity, antidiabetic, hepatoprotective, and other properties of FX including its bioavailability and stability characteristics. This review aims to assist further biochemical studies in order to develop further pharmaceutical assets and nutritional products in combination with FX and its various metabolites.

Burdock (Arctium lappa L.) leaf flavonoids rich in morin and quercetin 3-O-rhamnoside ameliorate lipopolysaccharide-induced inflammation and oxidative stress in RAW264.7 cells

In this study, the anti-inflammatory and antioxidant activities and mechanism of burdock leaf flavonoids (BLF) on LPS-stimulated inflammation in RAW264.7 macrophage cells were explored. We have observed that BLF and main effective components morin and quercetin 3-O-rhamnoside pretreatment significantly inhibited LPS-stimulated inflammatory activation of RAW264.7 cells by lowering the levels of NO, PGE2, TNF-α, and IL-6 production (p < .05). At the same time, BLF not only had potent free radical scavenging ability in vitro (DPPH: 2025.33 ± 84.15 μmol Trolox/g, ABTS: 159.14 ± 5.28 μmol Trolox/g, and ORAC: 248.72 ± 9.74 μmol Trolox/g) but also effectively ameliorated cellular oxidative stress status by restoring the decreased activity of antioxidant enzymes (SOD, CAT, and GSH-Px) and decreasing the elevated levels of ROS and TBARS in LPS-stimulated macrophages (p < .05). The western blot analysis indicated that BLF and main components morin and quercetin 3-O-rhamnoside mainly inhibited LPS-stimulated inflammation by reducing the iNOS and COX-2 protein expression, decreasing cellular ROS, and blocking the activation of NF-κB signaling pathway in macrophages. Our results collectively imply that BLF could be used as a new type of functional factor for the development of antioxidant and anti-inflammatory foods.

Brown Algae as Functional Food Source of Fucoxanthin: A Review

Fucoxanthin is an algae-specific xanthophyll of aquatic carotenoid. It is prevalent in brown seaweed because it functions as a light-harvesting complex for algal photosynthesis and photoprotection. Its exceptional chemical structure exhibits numerous biological activities that benefit human health. Due to these valuable properties, fucoxanthin's potential as a potent source for functional food, feed, and medicine is being explored extensively today. This article has thoroughly reviewed the availability and biosynthesis of fucoxanthin in the brown seaweed, as well as the mechanism behind it. We included the literature findings concerning the beneficial bioactivities of fucoxanthin such as antioxidant, anti-inflammatory, anti-obesity, antidiabetic, anticancer, and other potential activities. Last, an additional view on its potential as a functional food ingredient has been discussed to facilitate a broader application of fucoxanthin as a promising bioactive compound.

Dietary phenolic-type Nrf2-activators: implications in the control of toxin-induced hepatic disorders

Numerous studies have exemplified the importance of nuclear factor erythroid 2-related factor 2 (Nrf2) activation in the alleviation of toxin-induced hepatic disorders primarily through eliminating oxidative stress. Whereafter, increasingly more efforts have been contributed to finding Nrf2-activators, especially from dietary polyphenols. The present review summarized the phenolic-type Nrf2-activators published in the past few decades, analyzed their effectiveness based on their structural characteristics and outlined their related mechanisms. It turns out that flavonoids are the largest group of phenolic-type Nrf2-activators, followed by nonflavonoids and phenolic acids. When counting on subgroups, the top three types are flavonols, flavones, and hydroxycinnamic acids, with curcuminoids having the highest effective doses. Moreover, most polyphenols work through the phosphorylation of Nrf2. Besides, mitogen-activated protein kinases (MAPKs) and protein kinase B (Akt) are the frequent targets of these Nrf2-activators, which indirectly mediate the behavior of Nrf2. However, current data are not sufficient to conclude any structure-activity relationship.

Targeting Nrf2-Mediated Oxidative Stress Response in Traumatic Brain Injury: Therapeutic Perspectives of Phytochemicals

Traumatic brain injury (TBI), known as mechanical damage to the brain, impairs the normal function of the brain seriously. Its clinical symptoms manifest as behavioral impairment, cognitive decline, communication difficulties, etc. The pathophysiological mechanisms of TBI are complex and involve inflammatory response, oxidative stress, mitochondrial dysfunction, blood-brain barrier (BBB) disruption, and so on. Among them, oxidative stress, one of the important mechanisms, occurs at the beginning and accompanies the whole process of TBI. Most importantly, excessive oxidative stress causes BBB disruption and brings injury to lipids, proteins, and DNA, leading to the generation of lipid peroxidation, damage of nuclear and mitochondrial DNA, neuronal apoptosis, and neuroinflammatory response. Transcription factor NF-E2 related factor 2 (Nrf2), a basic leucine zipper protein, plays an important role in the regulation of antioxidant proteins, such as oxygenase-1(HO-1), NAD(P)H Quinone Dehydrogenase 1 (NQO1), and glutathione peroxidase (GPx), to protect against oxidative stress, neuroinflammation, and neuronal apoptosis. Recently, emerging evidence indicated the knockout (KO) of Nrf2 aggravates the pathology of TBI, while the treatment of Nrf2 activators inhibits neuronal apoptosis and neuroinflammatory responses via reducing oxidative damage. Phytochemicals from fruits, vegetables, grains, and other medical herbs have been demonstrated to activate the Nrf2 signaling pathway and exert neuroprotective effects in TBI. In this review, we emphasized the contributive role of oxidative stress in the pathology of TBI and the protective mechanism of the Nrf2-mediated oxidative stress response for the treatment of TBI. In addition, we summarized the research advances of phytochemicals, including polyphenols, terpenoids, natural pigments, and otherwise, in the activation of Nrf2 signaling and their potential therapies for TBI. Although there is still limited clinical application evidence for these natural Nrf2 activators, we believe that the combinational use of phytochemicals such as Nrf2 activators with gene and stem cell therapy will be a promising therapeutic strategy for TBI in the future.

The edible seaweed Laminaria japonica contains cholesterol analogues that inhibit lipid peroxidation and cyclooxygenase enzymes

In this study, 5 sterols were isolated and purified from Laminaria japonica, commonly known as edible brown seaweed, and their structures were identified based on detailed chemical methods and spectroscopic analyses. Spectroscopic analyses characterized 5 sterols as 29-Hydroperoxy-stigmasta-5,24(28)-dien-3β-ol, saringosterol (24-vinyl-cholest-5-ene-3β,24-diol), 24-methylenecholesterol, fucosterol (stigmasta-5,24-diene-3β-ol), and 24-Hydroperoxy-24-vinyl-cholesterol. The bioactivities of these sterols were tested using lipid peroxidation (LPO) and cyclooxygenase (COX-1 and -2) enzyme inhibitory assays. Fucosterol exhibited the highest COX-1 and -2 enzyme inhibitory activities at 59 and 47%, respectively. Saringosterol, 24-methylenecholesterol and fucosterol showed higher LPO inhibitory activity at >50% than the other compounds. In addition, the results of molecular docking revealed that the 5 sterols were located in different pocket of COX-1 and -2 and fucosterol with tetracyclic skeletons and olefin methine achieved the highest binding energy (-7.85 and -9.02 kcal/mol) through hydrophobic interactions and hydrogen bond. Our results confirm the presence of 5 sterols in L. japonica and its significant anti-inflammatory and antioxidant activity.

Bixin and fucoxanthin sensitize human lung cancer and cervical cancer cell to cisplatin in vitro

Objective

Cisplatin is a conventional anticancer drug that generates reactive oxygen species and causes apoptosis. However, many cancer cells develop alterations in the ATP binding cassette transporter responsible for the uptake and efflux process, which leads to resistance. Many natural products have shown potential to compete with ATP binding cassette transporter and may sensitize resistant cells to cisplatin. Studies have shown pro-oxidant effect of carotenoids that promote apoptosis of cancer cells. Bixin and fucoxanthin are well-known carotenoids with known antioxidant properties, however their bioactivity in lung cancer cells, clinically known to develop resistance due to ATP binding cassette transporter, has been minimally studied. This study is the first to investigate the potential of bixin and fucoxanthin to sensitize human lung cancer cell line, A549 and cervical cancer cell line, HeLa, to cisplatin. Drug combination method developed by Chou and Talalay theorem was employed.

Result

Employing the best combination ratio, this study shows selective sensitization of cancer cells to cisplatin after bixin and fucoxanthin treatment. Further study on the mechanism of action in specific types of cancer cells is warranted. It may improve cisplatin sensitivity in tumors and rational use of cancer drugs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05866-4.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

Fucoxanthin Holds Potential to Become a Drug Adjuvant in Breast Cancer Treatment: Evidence from 2D and 3D Cell Cultures

Fucoxanthin (Fx) is a carotenoid derived from marine organisms that exhibits anticancer activities. However, its role as a potential drug adjuvant in breast cancer (BC) treatment is still poorly explored. Firstly, this study investigated the cytotoxic effects of Fx alone and combined with doxorubicin (Dox) and cisplatin (Cis) on a panel of 2D-cultured BC cell lines (MCF7, SKBR3 and MDA-MB-231) and one non-tumoral cell line (MCF12A). Fucoxanthin induced cytotoxicity against all the cell lines and potentiated Dox cytotoxic effects towards the SKBR3 and MDA-MB-231 cells. The combination triggering the highest cytotoxicity (Fx 10 µM + Dox 1 µM in MDA-MB-231) additionally showed significant induction of cell death and genotoxic effects, relative to control. In sequence, the same combination was tested on 3D cultures using a multi-endpoint approach involving bioactivity assays and microscopy techniques. Similar to 2D cultures, the combination of Fx and Dox showed higher cytotoxic effects on 3D cultures compared to the isolated compounds. Furthermore, this combination increased the number of apoptotic cells, decreased cell proliferation, and caused structural and ultrastructural damages on the 3D models. Overall, our findings suggest Fx has potential to become an adjuvant for Dox chemotherapy regimens in BC treatment.

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.

Fucoxanthin@Polyvinylpyrrolidone Nanoparticles Promoted Oxidative Stress-Induced Cell Death in Caco-2 Human Colon Cancer Cells

Fucoxanthin (FX), a natural carotenoid found in seaweed with multiple functional activities, is unstable with a poor water solubility that limits its utilization. This study aimed to improve FX's stability and bioavailability via the nano-encapsulation of FX in polyvinylpyrrolidone (PVP)-coated FX@PVP nanoparticles (NPs). The FX@PVP NPs were evaluated in terms of their morphology, stability, encapsulation efficiency (EE), loading capacity (LC), and in vitro release to optimize the encapsulation parameters, and a 1:8 FX:PVP ratio was found to perform the best with the highest EE (85.50 ± 0.19%) and LC (10.68 ± 0.15%) and improved FX stability. In addition, the FX@PVP NPs were shown to effectively deliver FX into Caco-2 cancer cells, and the accumulation of FX in these cancer cells showed pro-oxidative activities to ameliorate H2O2-induced damage and cell death. The FX@PVP NPs could potentially become a new therapeutical approach for targeted cancer treatment.

Meeting Sustainable Development Goals: Alternative Extraction Processes for Fucoxanthin in Algae

The ever-expanding human population puts tremendous pressure on global food security. With climate change threats lowering crop productivity and food nutritional quality, it is important to search for alternative and sustainable food sources. Microalgae are a promising carbon-neutral biomass with fast growth rate and do not compete with terrestrial crops for land use. More so, microalgae synthesize exclusive marine carotenoids shown to not only exert antioxidant activities but also anti-cancer properties. Unfortunately, the conventional method for fucoxanthin extraction is mainly based on solvent extraction, which is cheap but less environmentally friendly. With the emergence of greener extraction techniques, the extraction of fucoxanthin could adopt these strategies aligned to UN Sustainable Development Goals (SDGs). This is a timely review with a focus on existing fucoxanthin extraction processes, complemented with future outlook on the potential and limitations in alternative fucoxanthin extraction technologies. This review will serve as an important guide to the sustainable and environmentally friendly extraction of fucoxanthin and other carotenoids including but not limited to astaxanthin, lutein or zeaxanthin. This is aligned to the SDGs wherein it is envisaged that this review becomes an antecedent to further research work in extract standardization with the goal of meeting quality control and quality assurance benchmarks for future commercialization purposes.

A novel wheat germ polysaccharide: Structural characterization, potential antioxidant activities and mechanism

A wheat germ polysaccharide (WGP-1) was isolated from wheat germ through hot-water (pH = 7.3) extraction and further fractionated by anion-exchange column using DEAE-52 cellulose column and purified by gel-permeation chromatography using Sephacryl S-500 column. WGP-1 was mainly consisted with rhamnose, arabinose, xylose, mannose, galactose and glucose, and linked with 1→, 1 → 2, 1 → 4, 1 → 3 and 1 → 6 glucosidic bands. The present study was designed to evaluate the antioxidant activities of WGP-1 in oleic acid (OA)-induced HepG2 cell model with its related mechanisms. Results showed that WGP-1 remarkably elevated the expression of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and total antioxidant capacity (T-AOC), and decreased the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in OA-treated cell. WGP-1 was found to promote the expression of PI3K, the phosphorylation of AKT and the translocation of Nrf2, further increased the expression of HO-1 in OA-induced cells. These results demonstrate again that WGP-1 can effectively improve OA-induced oxidative damage, probably by up-regulating of PI3K expression, Nrf2 translocation, and AKT phosphorylation.

Aerobic Cytotoxicity of Aromatic N-Oxides: The Role of NAD(P)H:Quinone Oxidoreductase (NQO1)

Derivatives of tirapazamine and other heteroaromatic N-oxides (ArN→O) exhibit tumoricidal, antibacterial, and antiprotozoal activities, which are typically attributed to bioreductive activation and free radical generation. In this work, we aimed to clarify the role of NAD(P)H:quinone oxidoreductase (NQO1) in ArN→O aerobic cytotoxicity. We synthesized 9 representatives of ArN→O with uncharacterized redox properties and examined their single-electron reduction by rat NADPH:cytochrome P-450 reductase (P-450R) and Plasmodium falciparum ferredoxin:NADP⁺ oxidoreductase (PfFNR), and by rat NQO1. NQO1 catalyzed both redox cycling and the formation of stable reduction products of ArN→O. The reactivity of ArN→O in NQO1-catalyzed reactions did not correlate with the geometric average of their activity towards P-450R- and PfFNR, which was taken for the parameter of their redox cycling efficacy. The cytotoxicity of compounds in murine hepatoma MH22a cells was decreased by antioxidants and the inhibitor of NQO1, dicoumarol. The multiparameter regression analysis of the data of this and a previous study (DOI: 10.3390/ijms20184602) shows that the cytotoxicity of ArN→O (n = 18) in MH22a and human colon carcinoma HCT-116 cells increases with the geometric average of their reactivity towards P-450R and PfFNR, and with their reactivity towards NQO1. These data demonstrate that NQO1 is a potentially important target of action of heteroaromatic N-oxides.

Potential Anti-Aging Substances Derived from Seaweeds

Aging is a major risk factor for many chronic diseases, such as cancer, cardiovascular disease, and diabetes. The exact mechanisms underlying the aging process are not fully elucidated. However, a growing body of evidence suggests that several pathways, such as sirtuin, AMP-activated protein kinase, insulin-like growth factor, autophagy, and nuclear factor erythroid 2-related factor 2 play critical roles in regulating aging. Furthermore, genetic or dietary interventions of these pathways can extend lifespan by delaying the aging process. Seaweeds are a food source rich in many nutrients, including fibers, polyunsaturated fatty acids, vitamins, minerals, and other bioactive compounds. The health benefits of seaweeds include, but are not limited to, antioxidant, anti-inflammatory, and anti-obese activities. Interestingly, a body of studies shows that some seaweed-derived extracts or isolated compounds, can modulate these aging-regulating pathways or even extend lifespans of various animal models. However, few such studies have been conducted on higher animals or even humans. In this review, we focused on potential anti-aging bioactive substances in seaweeds that have been studied in cells and animals mainly based on their anti-aging cellular and molecular mechanisms.

Terpenoids as Potential Geroprotectors

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

Carotenoids and Chlorophylls as Antioxidants

Chlorophylls and carotenoids are natural pigments that are present in our daily diet, especially with the increasing tendency towards more natural and healthy behaviors among consumers. As disturbed antioxidant homeostasis capacities seem to be implicated in the progress of different pathologies, the antioxidant properties of both groups of lipophilic compounds have been studied. The objective of this review was to analyze the state-of-the-art advances in this field. We conducted a systematic bibliographic search (Web of Science™ and Scopus®), followed by a comprehensive and critical description of the results, with special emphasis on highly cited and more recently published research. In addition to an evaluative description of the methodologies, this review discussed different approaches used to obtain a physiological perspective, from in vitro studies to in vivo assays using oxidative biomarkers. From a chemical viewpoint, many studies have demonstrated how a pigment's structure influences its antioxidant response and the underlying mechanisms. The major outcome is that this knowledge is essential for interpreting new data in a metabolic networks context in the search for more direct applications to health. A promising era is coming where the term "antioxidant" is understood in terms of its broadest significance.

Fucoxanthin: A promising compound for human inflammation-related diseases

Fucoxanthin, a natural product of carotenoids, is a potential drug source obtained from marine algae. The special chemical structure of fucoxanthin has equipped it with a variety of biological activities. Several studies have indicated that fucoxanthin has a potential protective effect on a variety of inflammation-related diseases. This mechanism may be related to fucoxanthin's strong antioxidant capacity and gut microbiota regulation. The key molecules that require consideration include nuclear factor erythroid 2-related factor 2, Akt serine/threonine kinase/phosphatidylinositol-3-kinase, extracellular signal-regulated kinase, adenosine monophosphate (AMP)-dependent protein kinase, cAMP response element binding protein, and peroxisome proliferator-activated receptorγcoactivator-1α. The study summarizes the recent progress in the research based on the protective effect of fucoxanthin and its related molecular mechanism, in addition to the potential use of fucoxanthin as a promising compound for human inflammation-related diseases.

Impact of Antioxidant Natural Compounds on the Thyroid Gland and Implication of the Keap1/Nrf2 Signaling Pathway

BACKGROUND

Natural compounds with potential antioxidant properties have been used in the form of food supplements or extracts with the intent to prevent or treat various diseases. Many of these compounds can activate the cytoprotective Nrf2 pathway. Besides, some of them are known to impact the thyroid gland, often with potential side-effects, but in other instances, with potential utility in the treatment of thyroid disorders.

OBJECTIVE

In view of recent data regarding the multiple roles of Nrf2 in the thyroid, this review summarizes the current bibliography on natural compounds that can have an effect on thyroid gland physiology and pathophysiology, and it discusses the potential implication of the Nrf2 system in the respective mechanisms.

METHODS & RESULTS

Literature searches for articles from 1950 to 2018 were performed in PubMed and Google Scholar using relevant keywords about phytochemicals, Nrf2 and thyroid. Natural substances were categorized into phenolic compounds, sulfur-containing compounds, quinones, terpenoids, or under the general category of plant extracts. For individual compounds in each category, respective data were summarized, as derived from in vitro (cell lines), preclinical (animal models) and clinical studies. The main emerging themes were as follows: phenolic compounds often showed potential to affect the production of thyroid hormones; sulfur-containing compounds impacted the pathogenesis of goiter and the proliferation of thyroid cancer cells; while quinones and terpenoids modified Nrf2 signaling in thyroid cell lines.

CONCLUSION

Natural compounds that modify the activity of the Nrf2 pathway should be evaluated carefully, not only for their potential to be used as therapeutic agents for thyroid disorders, but also for their thyroidal safety when used for the prevention and treatment of non-thyroidal diseases.

Floridoside Exhibits Antioxidant Properties by Activating HO-1 Expression via p38/ERK MAPK Pathway

Floridoside is a low-molecular-weight organic compound, which can be accumulated by red algae under stressful conditions to protect cells via its excellent antioxidant properties. In the present study, we investigated the antioxidant mechanism of floridoside toward human hepatocyte L-02 cells. We found that floridoside had no toxicity to L-02 cells, and no reactive oxidative species were induced by it either. However, the expression of hemoxygenase-1 (HO-1) protein was up-regulated upon exposure to floridoside, and two antioxidant enzymes, superoxide dismutase (SOD) and GSH-Px, were activated by floridoside. Moreover, we investigated the pathway involved in the production of these antioxidants, p38/extracellular signal-regulated kinase (ERK) MAPK-nuclear factor-erythroid-2-related factor 2 (Nrf2) pathway. ERK1/2 and p38 phosphorylation, nuclear translocation of Nrf2, and activation of ARE luciferase activity were observed upon exposure to floridoside. siRNA interference and inhibitor treatment suppressed the HO-1 expression and the phosphorylation of ERK1/2 and p38, respectively. These results indicated that floridoside exerted its antioxidant activity by activating HO-1 expression via p38/ERK MAPK-Nrf2 pathway in human hepatocyte L-02 cells.

Health benefits of fucoxanthin in the prevention of chronic diseases

Fucoxanthin is a xanthophyll carotenoid abundant in macroalgae, such as brown seaweeds. When fucoxanthin is consumed, it can be esterified or hydrolyzed to fucoxanthinol in the gastrointestinal tract and further converted into amarouciaxanthin A in the liver. It has a unique chemical structure that confers its biological effects. Fucoxanthin has a strong antioxidant capacity by scavenging singlet molecular oxygen and free radicals. Also, it exerts an anti-inflammatory effect. Studies have demonstrated potential health benefits of fucoxanthin for the prevention of chronic diseases, such as cancer, obesity, diabetes mellitus, and liver disease. Animal studies have shown that fucoxanthin supplementation has no adverse effects. However, investigation of the safety of fucoxanthin consumption in humans is lacking. Clinical trials are required to assess the safety of fucoxanthin in conjunction with the study of mechanisms by which fucoxanthin exhibits its health benefits. This review focuses on current knowledge of metabolism and functions of fucoxanthin with its potential health benefits. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Retracted Article: Anti-inflammatory potency of Locusta migratoria manilensis cyclopeptides in mast cells and macrophages

Locusts are esteemed as a traditional Chinese medicine, as well as tonic foods in Asian countries. While searching for natural anti-inflammatory agents in natural products, we isolated four novel locust cyclopeptides (LCPs) and the results show that [cyclo-(Trp-Leu-His-Thr)]∼LCP-3 has potent anti-inflammatory potency in RAW264.7 and HMC-1 cells under LPS (lipopolysaccharide) stimuli. Furthermore, mechanistic studies show that LCP-3 attenuates pro-inflammatory cytokine (TNF-α, IL-6, IL-1β, NO and PGE2) expression. Moreover, LCP-3 attenuates inflammatory damage associated with the direct inhibition of iNOS and COX-2 expression. LCP-3 also regulates the MAPK, PI3K/AKT and NF-κB pathways to attenuate LPS-induced damage. Of note, our study first reports the anti-inflammatory potency of LCPs and elucidates their underlying molecular mechanisms.

Increased fucoxanthin in Chaetoceros calcitrans extract exacerbates apoptosis in liver cancer cells via multiple targeted cellular pathways

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Both treatments inhibited cancer proliferation in a time and dose dependent manner.

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FxRF treatment were effective in inducing apoptosis in HepG2 cells than crude extract.

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Treatments stimulated regulation in cell signalling, apoptotic and antioxidant genes.

In this study, anti-proliferative effects of C. calcitrans extract and its fucoxanthin rich fraction (FxRF) were assessed on human liver HepG2 cancer cell line. Efficacy from each extract was determined by cytotoxicity assay, morphological observation, and cell cycle analysis. Mechanisms of action observed were evaluated using multiplex gene expression analysis. Results showed that CME and FxRF induced cytotoxicity to HepG2 cells in a dose and time-dependent manner. FxRF (IC₅₀: 18.89 μg.mL⁻¹) was found to be significantly more potent than CME (IC₅₀: 87.5 μg.mL⁻¹) (p < 0.05). Gene expression studies revealed that anti-proliferative effects in treated cells by C. calcitrans extracts were mediated partly through the modulation of numerous genes involved in cell signaling (AKT1, ERK1/2, JNK), apoptosis (BAX, BID, Bcl-2, APAF, CYCS) and oxidative stress (SOD1, SOD2, CAT). Overall, C. calcitrans extracts demonstrated effective intervention against HepG2 cancer cells where enhanced apoptotic activities were observed with increased fucoxanthin content.

Seaweeds as Source of Bioactive Substances and Skin Care Therapy—Cosmeceuticals, Algotheraphy, and Thalassotherapy

Riverine, estuarine, and coastal populations have always used algae in the development of home remedies that were then used to treat diverse health problems. The empirical knowledge of various generations originated these applications, and their mechanism of action is, in most cases, unknown, that is, few more scientific studies would have been described beyond simple collection and ethnographic recording. Nevertheless, recent investigations, carried out with the purpose of analyzing the components and causes that alter the functioning and the balance of our organism, are already giving their first results. Water, and especially sea water is considered as essential to life on our planet. It sings all the substances necessary and conducive to the development of the living being (minerals, catalysts, vitamins, amino acids, etc.). Oceans cover over 70% of Earth, being home to up to 90% of the organisms in the planet. Many rich resources and unique environments are provided by the ocean. Additionally, bioactive compounds that multiple marine organisms have a great potential to produce can be used as nutraceuticals, pharmaceuticals, and cosmeceuticals. Both primary and secondary metabolites are produced by algae. The first ones are directly implicated in development, normal growth, or reproduction conditions to perform physiological functions. Stress conditions, like temperature changes, salinity, environmental pollutants, or UV radiation exposure cause the performance of secondary metabolites. In algae, proteins, polysaccharides, fatty acids, and amino acids are primary metabolites and phenolic compounds, pigments, vitamins, sterols, and other bioactive agents, all produced in algae tissues, are secondary metabolites. These algal active constituents have direct relevance in cosmetics.

Fucoxanthin Exerts Cytoprotective Effects against Hydrogen Peroxide-induced Oxidative Damage in L02 Cells

Several previous studies have demonstrated the excellent antioxidant activity of fucoxanthin against oxidative stress which is closely related to the pathogenesis of liver diseases. The present work was to investigate whether fucoxanthin could protect human hepatic L02 cells against hydrogen peroxide- (H₂O₂-) induced oxidative damage. Its effects on H₂O₂-induced cell viability, lactate dehydrogenase (LDH) leakage, intracellular reduced glutathione, and reactive oxygen species (ROS) contents, along with mRNA and protein relative levels of the cytoprotective genes including Nrf2, HO-1, and NQO1, were investigated. The results showed that fucoxanthin could upregulate the mRNA and protein levels of the cytoprotective genes and promote the nuclear translocation of Nrf2, which could be inhibited by the PI3K inhibitor of LY294002. Pretreatment of fucoxanthin resulted in decreased LDH leakage and intracellular ROS content but enhanced intracellular reduced glutathione. Interestingly, pretreatment using fucoxanthin protected against the oxidative damage in a nonconcentration-dependent manner, with fucoxanthin of 5 μM demonstrating the optimal effects. The results suggest that fucoxanthin exerts cytoprotective effects against H₂O₂-induced oxidative damage in L02 cells, which may be through the PI3K-dependent activation of Nrf2 signaling.

Hepatoprotective effect of ginsenoside Rg1 from Panax ginseng on carbon tetrachloride-induced acute liver injury by activating Nrf2 signaling pathway in mice

Oxidative stress and inflammatory response are well known to be involved in the pathogenesis of acute liver injury. This study was performed to examine the hepatoprotective effect of ginsenoside Rg1 (Rg1) against CCl4 -induced acute liver injury, and further to elucidate the involvement of Nrf2 signaling pathway in vivo and in vitro. Mice were orally administered Rg1 (15, 30, and 60 mg/kg) or sulforaphane (SFN) once daily for 1 week prior to 750 μL/kg CCl4 injection. The results showed that Rg1 markedly altered relative liver weights, promoted liver repair, increased the serum level of TP and decreased the serum levels of ALT, AST and ALP. Hepatic oxidative stress was inhibited by Rg1, as evidenced by the decrease in MDA, and increases in GSH, SOD, and CAT in the liver. Further research demonstrated that Rg1 suppressed liver inflammation response through repressing the expression levels of inflammation-related genes including TNF-α, IL-1β, IL-6, COX-2, and iNOS. In addition, Rg1 enhanced antioxidative stress and liver detoxification abilities by up-regulating Nrf2 and its target-genes such as GCLC, GCLM, HO-1, NQO1, Besp, Mrp2, Mrp3, Mrp4, and down-regulating Cyp2e1. However, the changes in Nrf2 target-genes, as well as ameliorative liver histology induced by Rg1 were abrogated by Nrf2 antagonist all-transretinoic acid in vivo and Nrf2 siRNA in vitro. Overall, the findings indicated that Rg1 might be an effective approach for the prevention against acute liver injury by activating Nrf2 signaling pathway.

Phycochemical Constituents and Biological Activities of Fucus spp

Seaweeds are known to be a good supply of key nutrients including carbohydrates, protein, minerals, polyunsaturated lipids, as well as several other health-promoting compounds capable of acting on a wide spectrum of disorders and/or diseases. While these marine macroalgae are deeply rooted in the East Asian culture and dietary habits, their major application in Western countries has been in the phycocolloid industry. This scenario has however been gradually changing, since seaweed consumption is becoming more common worldwide. Among the numerous edible seaweeds, members of the genus Fucus have a high nutritional value and are considered good sources of dietary fibers and minerals, especially iodine. Additionally, their wealth of bioactive compounds such as fucoidan, phlorotannins, fucoxanthin and others make them strong candidates for multiple therapeutic applications (e.g., antioxidant, anti-inflammatory, anti-tumor, anti-obesity, anti-coagulant, anti-diabetes and others). This review presents an overview of the nutritional and phytochemical composition of Fucus spp., and their claimed biological activities, as well as the beneficial effects associated to their consumption. Furthermore, the use of Fucus seaweeds and/or their components as functional ingredients for formulation of novel and enhanced foods is also discussed.

Activation of Nrf2 by Ginsenoside Rh3 protects retinal pigment epithelium cells and retinal ganglion cells from UV

Excessive Ultra-violet (UV) radiation shall induce damages to resident retinal pigment epithelium (RPE) cells (RPEs) and retinal ganglion cells (RGCs). Here we tested the potential activity of Ginsenoside Rh3 ("Rh3") against the process. In cultured human RPEs and RGCs, pretreatment with Rh3 inhibited UV-induced reactive oxygen species (ROS) production and following apoptotic/non-apoptotic cell death. Rh3 treatment in retinal cells induced nuclear-factor-E2-related factor 2 (Nrf2) activation, which was evidenced by Nrf2 protein stabilization and its nuclear translocation, along with transcription of antioxidant responsive element (ARE)-dependent genes (HO1, NOQ1 and GCLC). Nrf2 knockdown by targeted-shRNA almost abolished Rh3-induced retinal cell protection against UV. Further studies found that Rh3 induced microRNA-141 ("miR-141") expression, causing downregulation of its targeted gene Keap1 in RPEs and RGCs. On the other hand, Rh3-induced Nrf2 activation and retinal cell protection were largely attenuated by the miR-141's inhibitor, antagomiR-141. In vivo, intravitreal injection of Rh3 inhibited retinal dysfunction by light damage in mice. Rh3 intravitreal injection also induced miR-141 expression, Keap1 downregulation and Nrf2 activation in mouse retinas. We conclude that Rh3 protects retinal cells from UV via activating Nrf2 signaling.

Astaxanthin Induces the Nrf2/HO-1 Antioxidant Pathway in Human Umbilical Vein Endothelial Cells by Generating Trace Amounts of ROS

Astaxanthin is a powerful antioxidant that possesses potent protective effects against various human diseases and physiological disorders. However, the mechanisms underlying its antioxidant functions in cells are not fully understood. In the present study, the effects of astaxanthin on reactive oxygen species (ROS) production and antioxidant enzyme activity, as well as mitogen-activated protein kinases (MAPKs), phosphatidylinositol 3-kinase (PI3K)/Akt, and the nuclear factor erythroid 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1) pathways in human umbilical vein endothelial cells (HUVECs), were examined. It was shown that astaxanthin (0.1, 1, and 10 μM) induced ROS production by 9.35%, 14.8%, and 18.06% compared to control, respectively, in HUVECs. In addition, astaxanthin increased the mRNA levels of phase II enzymes HO-1 and also promoted GSH-Px enzyme activity. Furthermore, we observed ERK phosphorylation, nuclear translocation of Nrf-2, and activation of antioxidant response element-driven luciferase activity upon astaxanthin treatment. Knockdown of Nrf-2 by small interfering RNA inhibited HO-1 mRNA expression by 60%, indicating that the Nrf-2/ARE signaling pathway is activated by astaxanthin. Our results suggest that astaxanthin activates the Nrf-2/HO-1 antioxidant pathway by generating small amounts of ROS.

Circulating exosomal microRNAs reveal the mechanism of Fructus Meliae Toosendan-induced liver injury in mice

The toxicological mechanisms of liver injury caused by most traditional Chinese medicine (TCM) remain largely unknown. Due to the unique features, exosomal microRNAs (miRNAs) are currently attracting major interests to provide further insights into toxicological mechanisms. Thus, taking Fructus Meliae Toosendan as an example of hepatoxic TCM, this study aimed to elucidate its hepatotoxicity mechanisms through profiling miRNAs in circulating exosomes of Fructus Meliae Toosendan water extract (FMT)-exposed mice. Biological pathway analysis of the 64 differentially expressed exosomal miRNAs (DEMs) showed that hepatic dysfunction induced by FMT likely related to apoptosis, mitochondrial dysfunction, and cell cycle dysregulation. Integrated analysis of serum exosomal DEMs and hepatic differentially expressed mRNAs further enriched oxidative stress and apoptosis related pathways. In vitro validation studies for omics results suggested that FMT-induced DNA damage was mediated by generating intracellular reactive oxygen species, leading to cell apoptosis through p53-dependent mitochondrial damage and S-phase arrest. Nrf2-mediated antioxidant response was activated to protect liver cells. Moreover, serum exosomal miR-370-3p, the most down-regulated miRNA involving in these pathways, might be the momentous event in aggravating cytotoxic effect of FMT by elevating p21 and Cyclin E. In conclusion, circulating exosomal miRNAs profiling could contribute to deepen the understanding of TCM-induced hepatotoxicity.

SC79 protects retinal pigment epithelium cells from UV radiation via activating Akt-Nrf2 signaling

Excessive Ultra-violet (UV) radiation causes oxidative damages and apoptosis in retinal pigment epithelium (RPE) cells. Here we tested the potential activity of SC79, a novel small molecule activator of Akt, against the process. We showed that SC79 activated Akt in primary and established (ARPE-19 line) RPE cells. It protected RPE cells from UV damages possibly via inhibiting cell apoptosis. Akt inhibition, via an Akt specific inhibitor (MK-2206) or Akt1 shRNA silence, almost abolished SC79-induced RPE cytoprotection. Further studies showed that SC79 activated Akt-dependent NF-E2-related factor 2 (Nrf2) signaling and inhibited UV-induced oxidative stress in RPE cells. Reversely, Nrf2 shRNA knockdown or S40T mutation attenuated SC79-induced anti-UV activity. For the in vivo studies, we showed that intravitreal injection of SC79 significantly protected mouse retina from light damages. Based on these results, we suggest that SC79 protects RPE cells from UV damages possibly via activating Akt-Nrf2 signaling axis.

Screening active components of modified Xiaoyao powder as NRF2 agonists

Nuclear factor (erythroid-derived 2)-like 2 (NRF2) regulates antioxidant enzymes and phase II detoxifying enzymes, such as NAD(P)H: quinone oxidoreductase 1 (NQO1). Modified Xiaoyao powder (MXP) is most frequently used in the prevention and treatment of breast cancer in China. This study aimed to screen active components of MXP for antioxidant stress and chemoprevention, which depend on NRF2-NQO1 signalling pathway. A total of 25 monomeric compounds contained in MXP were screened using an antioxidant response element-luciferase reporter. The most potent antioxidant response element-luciferase inducers were chosen to further examine their effects on NRF2 and NQO1 in MCF-7 cells. These results were then confirmed by determining the oxidative stress levels and chemopreventive effect on inhibiting carcinogenesis transformation in NRF2 knockdown (NRF2^KD ) and NRF2 wild-type MCF-10A cells. We found that quercetin, kaempferol, and atractylenolide II in MXP were potent NRF2 inducers, which could up-regulate the expression of NRF2 and its downstream enzymes NQO1. In addition, these components could decrease reduced oxidative stress and inhibit carcinogenesis transformation, which depended on NRF2-NQO1 pathway. In conclusion, NRF2-NQO1 pathway plays an essential role in mediating the activity of MXP and its active components, at least in part; some beneficial effects of MXP may be applicable to breast cancer chemoprevention. Our study firstly found MXP active components including quercetin, kaempferol, and atractylenolide II. Our results firstly demonstrate that NRF2-NQO1 pathway plays an essential role in mediating the activity of MXP and its active components in breast cancer chemoprevention. Our study firstly found that atractylenolide II is a novel NRF2 inducer.

Fucoxanthin attenuates fatty acid-induced lipid accumulation in FL83B hepatocytes through regulated Sirt1/AMPK signaling pathway

The fucoxanthin, isolated from brown algae, was reported to have multiple biological functions to anti-inflammation, anti-tumor, and ameliorated obesity in mice. In this study we investigated whether fucoxanthin could inhibit lipids accumulation in FL83B hepatocytes. FL83B cells were induced as fatty liver cell model by 0.5 mM oleic acid for 48 h, and treated with various concentration of fucoxanthin for 24 h. The results demonstrated that fucoxanthin significantly suppressed lipid accumulation and decreased lipid peroxidation in hepatocytes. Fucoxanthin could decrease lipogenesis-related transcription factor expression, including sterol regulatory element-binding proteins 1c and peroxisome proliferator-activated receptor γ. It also reduced fatty acid synthase expression and increased adipose triglyceride lipase and the phosphorylation of hormone-sensitive lipase production for lipolysis. Furthermore, fucoxanthin significantly increased phosphorylation of AMP-activated protein kinase (AMPK), and decreased activity of acetyl-CoA carboxylase for regulating fatty acid synthesis. The results suggest that fucoxanthin is an effective marine nature compound for increasing lipolysis and inhibiting lipogenesis in oleic acid induced fatty liver cells through promoted Sirt1/AMPK pathway.

Dual Biological Functions of a Cytoprotective Effect and Apoptosis Induction by Bioavailable Marine Carotenoid Fucoxanthinol through Modulation of the Nrf2 Activation in RAW264.7 Macrophage Cells

In this study, the function of fucoxanthinol (FxOH) as a bioavailable marine carotenoid together with the pre-metabolite, fucoxanthin (Fx), was examined through the Nrf2-ARE pathway. The antioxidant activity in the low concentration range of the compounds (1–4 μM) with a peroxyl radical scavenging capacity was proved by the ORAC (Oxygen Radical Absorbance Capacity) method and an ESR study. Similar concentrations of the compound also activated the Nrf2-ARE signaling with the Nrf2 translocation into the nuclear, then the expression of the antioxidant protein HO-1 increased. On the other hand, the high concentrations of both compounds (>10 μM) induced apoptosis with caspase 3/7 activation during suppression of the anti-apoptotic proteins, such as Bcl-_XL and phosphorous Akt (pAkt). The Nrf2 expression was then activated in the nuclear, indicating that the Nrf2 plays a significant role in the cytoprotective effect against the toxicity of the compounds. These results indicated that the compounds have the dual functions of a cytoprotective effect and the apoptosis induction dependent on the treated concentrations through the Nrf2 activation. In addition, the results of all the assays involved in our previous studies suggested that the metabolite FxOH having a higher activity than the Fx, will be a bioavailable compound in biological systems.

miRNA-141 attenuates UV-induced oxidative stress via activating Keap1-Nrf2 signaling in human retinal pigment epithelium cells and retinal ganglion cells

Activation of NF-E2-related factor 2 (Nrf2) signaling could protect cells from ultra violet (UV) radiation. We aim to provoke Nrf2 activation via downregulating its inhibitor Keap1 by microRNA-141 (“miR-141”). In both human retinal pigment epithelium cells (RPEs) and retinal ganglion cells (RGCs), forced-expression of miR-141 downregulated Keap1, causing Nrf2 stabilization, accumulation and nuclear translocation, which led to transcription of multiple antioxidant-responsive element (ARE) genes (HO1, NOQ1 and GCLC). Further, UV-induced reactive oxygen species (ROS) production and cell death were significantly attenuated in miR-141-expressing RPEs and RGCs. On the other hand, depletion of miR-141 via expressing its inhibitor antagomiR-141 led to Keap1 upregulation and Nrf2 degradation, which aggravated UV-induced death of RPEs and RGCs. Significantly, Nrf2 shRNA knockdown almost abolished miR-141-mediated cytoprotection against UV in RPEs. These results demonstrate that miR-141 targets Keap1 to activate Nrf2 signaling, which protects RPEs and RGCs from UV radiation.

Fucoxanthin Inhibits β-Amyloid Assembly and Attenuates β-Amyloid Oligomer-Induced Cognitive Impairments

β-Amyloid (Aβ) can form aggregates through self-assembly and produce neurotoxicity in the early stage of Alzheimer's disease (AD). Therefore, the inhibition of Aβ assembly is considered as the primary target for AD therapy. In this study, we reported that fucoxanthin, a marine carotenoid, potently reduced the formation of Aβ fibrils and oligomers. Moreover, the fucoxanthin-triggered modification significantly reduced the neurotoxicity of Aβ oligomers in vitro. Molecular dynamics simulation analysis further revealed a hydrophobic interaction between fucoxanthin and Aβ peptide, which might prevent the conformational transition and self-assembly of Aβ. Most importantly, fucoxanthin could attenuate cognitive impairments in Aβ oligomer-injected mice. In addition, fucoxanthin significantly inhibited oxidative stress, enhanced the expression of brain-derived neurotrophic factor, and increased ChAT-positive regions in the hippocampus of mice. On the basis of these novel findings, we anticipated that fucoxanthin might ameliorate AD via inhibiting Aβ assembly and attenuating Aβ neurotoxicity.

Fucoxanthin provides neuroprotection in models of traumatic brain injury via the Nrf2-ARE and Nrf2-autophagy pathways

Fucoxanthin is abundant in seaweed and is considered as a powerful antioxidant. It has been proposed to possess anti-cancer, anti-obesity and anti-diabetes effects. However, its roles in brain injury models have not been fully understood. The objective of this study was to investigate the neuroprotection of fucoxanthin in models of traumatic brain injury (TBI) and the role of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant-response element (ARE) and Nrf2-autophagy pathways in the putative neuroprotection. We found that fucoxanthin alleviated TBI-induced secondary brain injury, including neurological deficits, cerebral edema, brain lesion and neuronal apoptosis. Moreover, the up-regulation of malondialdehyde (MDA) and the activity of glutathione peroxidase (GPx) were reversed by fucoxanthin treatment. Furthermore, our in vitro studies demonstrated that fucoxanthin increased the neuron survival and reduced the reactive oxygen species (ROS) level. In addition, fucoxanthin activated the Nrf2-ARE pathway and autophagy both in vivo and in vitro, which was proven by the results of immunohistochemistry, western blot and electrophoretic mobility shift assay (EMSA). However, fucoxanthin failed to provide neuroprotection and activated autophagy following TBI in Nrf2^−/− mice. In conclusion, our studies indicated that fucoxanthin provided neuroprotective effects in models of TBI, potentially via regulation of the Nrf2-ARE and Nrf2-autophagy pathways.

SC79 rescues osteoblasts from dexamethasone though activating Akt-Nrf2 signaling

Dexamethasone (Dex) causes osteoblast cell injuries. In the present research, we tested the potential effect of SC79, a novel and specific Akt activator, against Dex in osteoblasts. In primary murine osteoblasts and osteoblastic MC3T3-E1 cells, pretreatment with SC79 significantly attenuated Dex-induced cell death. Further, Dex-induced mitochondrial permeability transition pore (mPTP) opening, cytochrome C release and apoptosis activation were dramatically alleviated with SC79 pretreatment in above cells. At the molecular level, SC79 activated Akt, which was indispensable for subsequent osteoblast protection against Dex. Akt inhibitors (LY294002, perifosine and MK-2206) blocked SC79-induced Akt activation and abolished its anti-Dex actions in osteoblasts. Further, SC79 activated Akt downstream Nrf2 (NF-E2-related factor 2) signaling and attenuated Dex-induced oxidative stress in osteoblasts. Nrf2 shRNA knockdown or S40T mutation almost reversed SC79-mediated anti-oxidant and cytoprotective activities in osteoblasts. Together, these results suggest that SC79 activates Akt-Nrf2 signaling to protect osteoblasts from Dex.