Honokiol Alleviates Oxidative Stress-Induced Neurotoxicity via Activation of Nrf2

The Essential Oils and Eucalyptol From Artemisia vulgaris L. Prevent Acetaminophen-Induced Liver Injury by Activating Nrf2-Keap1 and Enhancing APAP Clearance Through Non-Toxic Metabolic Pathway

Artemisia has long been used in traditional medicine and as a food source for different functions in eastern Asia. Artemisia vulgaris L. (AV) is a species of the genus Artemisia. Essential oils (EOs) were extracted from AV by subcritical butane extraction. EO contents were detected by electronic nose and headspace solid-phase microextraction coupled with gas chromatography (HS-SPME-GC-MS). To investigate the hepatoprotective effects, mice subjected to liver injury were treated intragastrically with EOs or eucalyptol for 3 days. Acetaminophen (APAP) alone caused severe liver injury characterized by significantly increased serum AST and ALT levels, ROS and hepatic malondialdehyde (MDA), as well as liver superoxide dismutase (SOD) and catalase (CAT) depletions. EOs significantly attenuated APAP-induced liver damages. Further study confirmed that eucalyptol is an inhibitor of Keap1, the affinity K D of eucalyptol and Keap1 was 1.42 × 10-5, which increased the Nrf2 translocation from the cytoplasm into the mitochondria. The activated Nrf2 increased the mRNA expression of uridine diphosphate glucuronosyltransferases (UGTs) and sulfotransferases (SULTs), also inhibiting CYP2E1 activities. Thus, the activated Nrf2 suppressed toxic intermediate formation, promoting APAP hepatic non-toxicity, whereby APAP was metabolized into APAP-gluc and APAP-sulf. Collectively, APAP non-toxic metabolism was accelerated by eucalyptol in protecting the liver against APAP-induced injury, indicating eucalyptol or EOs from AV potentials as a natural source of hepatoprotective agent.

Lipoamide Ameliorates Oxidative Stress via Induction of Nrf2/ARE Signaling Pathway in PC12 Cells

The mechanisms underlying neurodegenerative diseases are not fully understood yet. However, an increasing amount of evidence has suggested that these disorders are related to oxidative stress. We reported herein that lipoamide (LM), a neutral amide derivative of lipoic acid (LA), could resist oxidative stress-mediated neuronal cell damage. LM is more potent than LA in alleviating hydrogen peroxide- or 6-hydroxydopamine-induced PC12 cell injury. Our results reveal that LM promotes the nuclear accumulation of NFE2-related factor 2 (Nrf2), following with the activation of expression of Nrf2-governed antioxidant and detoxifying enzymes. Notably, silencing Nrf2 gene annuls the protection of LM, which demonstrates that Nrf2 is engaged in this cytoprotection. Our findings suggest that LM might be used as a potential therapeutic candidate for oxidative stress-related neurological disorders.

Antioxidant, Anti-inflammatory, and Neuroprotective Effects of Novel Vinyl Sulfonate Compounds as Nrf2 Activator

The main pathway responsible for cellular regulation against oxidative stress is nuclear factor E2-related factor-2 (Nrf2) signaling. We previously synthesized and reported a novel vinyl sulfone (1) as an Nrf2 activator with therapeutic potential for Parkinson's disease (PD). In this study, we changed the vinyl sulfone to vinyl sulfonamide or vinyl sulfonate to improve Nrf2 activating efficacy. We observed that the introduction of vinyl sulfonamide led to a reduction of the effects on Nrf2 activation, whereas vinyl sulfonate compounds exhibited superior activity compared to the vinyl sulfone compounds. Among the vinyl sulfonates, 3c exhibited 6.9- and 83.5-fold higher effects on Nrf2 activation than the corresponding vinyl sulfone (1) and vinyl sulfonamide (2c), respectively. Compound 3c was confirmed to induce expression of the Nrf2-dependent antioxidant enzymes at the protein level in cells. In addition, 3c mitigated PD-associated behavioral deficits by protecting DAergic neurons in the MPTP-induced mouse model of PD.

Reversing ROS-mediated neurotoxicity by chlorogenic acid involves its direct antioxidant activity and activation of Nrf2-ARE signaling pathway

Chlorogenic acid (CA), the ester of caffeic acid and quinic acid, is one of the most abundant polyphenols in coffee, and has multiple pharmacological functions. The present study is designed to explore the protection provided by CA against hydrogen peroxide (H₂ O₂ )-induced oxidative damages in the rat pheochromocytoma cells, and the underlying mechanisms engaged in this process. CA displays robust free radical-scavenging activity in vitro. More importantly, CA strikingly rescues the cells from the H₂ O₂ -mediated oxidative insults. Mechanistic studies revealed that CA upregulates a panel of phase II cytoprotective species, such as heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, glutathione, thioredoxin reductase 1, and thioredoxin 1. This neuroprotection is dependent on the activation of the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), as knockdown of Nrf2 abolishes such effect. Our results demonstrate that CA provides dual neuroprotection via directly neutralizing free radicals and indirectly inducing expression of Nrf2-driven cytoprotective enzymes, and suggest a potential therapeutic usage of CA as a neuroprotective agent. Coffee is one of the most popular drinks in the world, and our discovery may also contribute to understanding the beneficial effects of regular coffee consumption. © 2019 BioFactors, 45 (4):616-626, 2019.

Xanthohumol Analogues as Potent Nrf2 Activators against Oxidative Stress Mediated Damages of PC12 Cells

The nuclear factor erythroid 2-related factor 2 (Nrf2), a master transcription factor controlling a series of cytoprotective genes, is closely associated with scavenging the reactive oxygen species and maintaining the intracellular redox balance. Accumulating evidence has indicated that activation of Nrf2 is efficient to block or retard oxidative stress mediated neurodegenerative disorders. Small molecules that contribute directly or indirectly to the Nrf2 activation thus are promising therapeutic agents. Herein, we screened xanthohumol and its analogues, and two analogues (11 and 12) were disclosed to possess low cytotoxicity and rescue PC12 cells from the hydrogen peroxide or 6-hydroxydopamine induced injuries. Molecular mechanism studies demonstrated that compounds 11 and 12 are potent Nrf2 activators by promoting the nuclear accumulation of Nrf2 and enhancing the cellular antioxidant defense system. More importantly, genetically silencing the Nrf2 expression shuts down the observed cytoprotection conferred by both compounds, supporting the critical involvement of Nrf2 for the cellular actions of compounds 11 and 12.

Neuroprotection of mangiferin against oxidative damage via arousing Nrf2 signaling pathway in PC12 cells

Accumulating evidence demonstrates that oxidative stress is involved in the pathogenesis and progression of neurodegeneration. As NF-E2-related factor 2 (Nrf2) plays a crucial role in maintaining cellular redox homeostasis, small molecules with the ability in activation of Nrf2 pathway are promising neuroprotective agents. Mangiferin (Mg) is a xanthone glucoside extracted from mangoes and papayas, and has been reported to possess multiple pharmacological activities. In this study, we investigated neuroprotective effects of Mg in the neuron-like rat pheochromocytoma cell line (PC12 cells). Mg scavenges different kinds of free radicals in vitro and attenuates hydrogen peroxide- or 6-hydroxydopamine-induced cell death. After treatment with Mg, a range of antioxidant genes governed by Nrf2 were upregulated, and the expressions and activities of these gene products were also elevated. Moreover, knockdown of Nrf2 antagonized the protective effect of Mg, indicating that Nrf2 is an essential factor in this cytoprotective process. In summary, our study demonstrates that Mg is a potent antioxidant that can provide neuroprotection against oxidative stress-mediated damage of PC12 cells. © 2019 BioFactors, 45(3):381-392, 2019.

(±)-Alternamgin, a Pair of Enantiomeric Polyketides, from the Endophytic Fungi Alternaria sp. MG1

A pair of enantiomeric polyketides, (+)- and (-)-alternamgin (1), featuring an unprecedented 6/6/6/6/5/6/6 seven ring backbone, were isolated from the endophytic fungi Alternaria sp. MG1. The relative configuration of 1 was determined using X-ray diffraction, and the absolute configurations of (±)-1 were confirmed by comparing the experimental and calculated ECD data. Plausible biosynthetic pathways for 1 were proposed. Compound (-)-1 exhibited moderate necrosis rates to Hela and HepG2 cells, but (+)-1 only showed similar necrosis rates to HepG2 cells.

Activation of anti-oxidant of curcumin pyrazole derivatives through preservation of mitochondria function and Nrf2 signaling pathway

Oxidative stress is an important cause of neurodegenerative diseases. Antioxidant is an potential important method to treat such diseases. The aim of this study is to discover new and effective antioxidants and their mechanism. The neuroprotective effect of six curcumin pyrozole compounds were first evaluated on sodium nitroprusside (SNP) - induced PC12 cell injury by testing cell viability and LDH release. The results showed that four compounds (C1-C4) have more significant protective effects compared to curcumin and edaravone. Furthermore, compounds C1-C4 can attenuate the intracellular ROS, and compound C3 is the most effective one which can preservate the mitochondria function by inhibiting the mitochondrial membrane potential loss and enhance nuclear translocation of Nrf2 in PC12 cell. These results indicated that C3 may be a potential candidate drug for treating neurodegenerative diseases.

Depletion of protein thiols and the accumulation of oxidized thioredoxin in Parkinsonism disclosed by a red-emitting and environment-sensitive probe

Protein sulfhydryl groups play a vital role in maintaining cellular redox homeostasis and protein functions and have attracted increasing interests for the selective detection of protein thiols over low-molecular-weight thiols (LMWTs).