Involvement of heme oxygenase-1 induction via Nrf2/ARE activation in protection against H2O2-induced PC12 cell death by a metabolite of sesamin contained in sesame seeds

Deinococcus radiodurans-derived membrane vesicles protect HaCaT cells against H2O2-induced oxidative stress via modulation of MAPK and Nrf2/ARE pathways

BACKGROUND

Deinococcus radiodurans is a robust bacterium that can withstand harsh environments that cause oxidative stress to macromolecules due to its cellular structure and physiological functions. Cells release extracellular vesicles for intercellular communication and the transfer of biological information; their payload reflects the status of the source cells. Yet, the biological role and mechanism of Deinococcus radiodurans-derived extracellular vesicles remain unclear.

AIM

This study investigated the protective effects of membrane vesicles derived from D. radiodurans (R1-MVs) against H₂O₂-induced oxidative stress in HaCaT cells.

RESULTS

R1-MVs were identified as 322 nm spherical molecules. Pretreatment with R1-MVs inhibited H₂O₂-mediated apoptosis in HaCaT cells by suppressing the loss of mitochondrial membrane potential and reactive oxygen species (ROS) production. R1-MVs increased the superoxide dismutase (SOD) and catalase (CAT) activities, restored glutathione (GSH) homeostasis, and reduced malondialdehyde (MDA) production in H₂O₂-exposed HaCaT cells. Moreover, the protective effect of R1-MVs against H₂O₂-induced oxidative stress in HaCaT cells was dependent on the downregulation of mitogen-activated protein kinase (MAPK) phosphorylation and the upregulation of the nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. Furthermore, the weaker protective capabilities of R1-MVs derived from ΔDR2577 mutant than that of the wild-type R1-MVs confirmed our inferences and indicated that SlpA protein plays a crucial role in R1-MVs against H₂O₂-induced oxidative stress.

CONCLUSION

Taken together, R1-MVs exert significant protective effects against H₂O₂-induced oxidative stress in keratinocytes and have the potential to be applied in radiation-induced oxidative stress models.

Novel Flavan-3,4-diol vernicidin B from Toxicodendron Vernicifluum (Anacardiaceae) as potent antioxidant via IL-6/Nrf2 cross-talks pathways

BACKGROUND

Oxidative stress is considered to be a pathological factor of various neurodegenerative diseases. Studies have confirmed the antioxidant activity of T. vernicifluum. However, the main active components responsible for antioxidant activity remain unknown.

OBJECTIVE

The aim of this study is to explore the activities of vernicidin B on oxidative stress injury induced by H₂O₂ in SH-SY5Y cells, and the underlying mechanism of vernicidin B in oxidative stress-related neurological diseases is further discussed.

METHODS

Various separation methods were used to isolate and identify the compounds in an EtOAc extract of T. vernicifluum. The structures of the isolates were clarified by HR-TOF-MS and 1D/2D NMR data and compared with findings in previous literature. The MTT assay was used to evaluate the potential antioxidant activity of the isolated flavonoids. The apoptosis rate, mitochondrial reactive oxygen species (ROS) level and mitochondrial potential were measured by flow cytometry and fluorescence microscope. The levels of related proteins were detected by Western blotting.

RESULTS

Four new flavan-3,4-diols (1-4, vernicidins A-D) and 11 known flavonoids (5-15) were purified from the EtOAc extract of T. vernicifluum. Among these compounds, vernicidin B showed the most promising potential for protecting SH-SY5Y cells from H₂O₂-induced oxidative stress. Moreover, pretreatment with vernicidin B decreased ROS production and mitochondrial membrane potential and significantly attenuated H₂O₂-induced apoptosis in a dose-dependent manner. Mechanistically, the antioxidant stress activities of vernicidin B were confirmed to be related to the IL-6/Nrf2 cross-talks pathway and its downstream pathways, including PI3K/Akt/mToR-Gsk3β, JAK2/STAT3 and MAPKs.

CONCLUSIONS

Our findings suggested that vernicidin B can improve the oxidative stress injury induced by H₂O₂ through IL-6/Nrf2 cross-talks pathway, indicating that it may be a potential candidate drug for the treatment of oxidative stress-related neurodegenerative diseases.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

Sesamin Activates Nrf2/Cnc-Dependent Transcription in the Absence of Oxidative Stress in Drosophila Adult Brains

Sesamin, a major lignin in sesame seeds, possesses health-promoting properties. Sesamin feeding suppresses several aging-related phenotypes such as age-dependent accumulation of damaged proteins in the muscles and neuronal loss in the brains of Drosophila adults with high levels of reactive oxygen species. Sesamin promotes the transcription of several genes that are responsible for oxidative stress, although the underlying mechanism remains unclear. Here, we aimed to demonstrate that sesamin mediates its action through activation of a transcription factor, Nrf2 (Cnc in Drosophila), essential for anti-aging oxidative stress response. Nrf2/Cnc activation was determined using the antioxidant response element, Green Fluorescence Protein reporter, that can monitor Nrf2/Cnc-dependent transcription. We observed strong fluorescence in the entire bodies, particularly in the abdomens and brains, of adult flies fed sesamin. Interestingly, Nrf2/Cnc was strongly activated in neuronal cells, especially in several neuron types, including glutamatergic and cholinergic, and some dopaminergic and/or serotonergic neurons but not in GABAergic neurons or the mushroom bodies of flies fed sesamin. These results indicate that the anti-aging effects of sesamin are exerted via activation of Nrf2/Cnc-dependent transcription to circumvent oxidative stress accumulation in several types of neurons of adult brains. Sesamin could be explored as a potential dietary supplement for preventing neurodegeneration associated with accumulation of oxidative stress.

Natural Antioxidant and Anti-Inflammatory Compounds in Foodstuff or Medicinal Herbs Inducing Heme Oxygenase-1 Expression

Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme that catalyzes heme group degradation. Decreased level of HO-1 is correlated with disease progression, and HO-1 induction suppresses development of metabolic and neurological disorders. Natural compounds with antioxidant activities have emerged as a rich source of HO-1 inducers with marginal toxicity. Here we discuss the therapeutic role of HO-1 in obesity, hypertension, atherosclerosis, Parkinson's disease and hepatic fibrosis, and present important signaling pathway components that lead to HO-1 expression. We provide an updated, comprehensive list of natural HO-1 inducers in foodstuff and medicinal herbs categorized by their chemical structures. Based on the continued research in HO-1 signaling pathways and rapid development of their natural inducers, HO-1 may serve as a preventive and therapeutic target for metabolic and neurological disorders.

Anti-Inflammatory and Anticancer Properties of Bioactive Compounds from Sesamum indicum L.-A Review

The use of foodstuff as natural medicines has already been established through studies demonstrating the pharmacological activities that they exhibit. Knowing the nutritional and pharmacological significance of foods enables the understanding of their role against several diseases. Among the foods that can potentially be considered as medicine, is sesame or Sesamum indicum L., which is part of the Pedaliaceae family and is composed of its lignans such as sesamin, sesamol, sesaminol and sesamolin. Its lignans have been widely studied and are known to possess antiaging, anticancer, antidiabetes, anti-inflammatory and antioxidant properties. Modern chronic diseases, which can transform into clinical diseases, are potential targets of these lignans. The prime example of chronic diseases is rheumatic inflammatory diseases, which affect the support structures and the organs of the body and can also develop into malignancies. In line with this, studies emphasizing the anti-inflammatory and anticancer activities of sesame have been discussed in this review.

Sesame Lignans Suppress Age-Related Cognitive Decline in Senescence-Accelerated Mice

Sesame lignans, which are biologically active compounds present in sesame seeds and oil, are known to have neuroprotective effects in several models of brain dysfunction. However, the effects of sesame lignans on age-related brain dysfunction are not clear and were thus investigated in the present study using a senescence-accelerated mouse (SAMP10). Two-month-old male SAMP10 mice were administrated a basal diet with 0% or 0.05% sesame lignans for two months, or with 0%, 0.02%, or 0.05% sesame lignans for 10 months and subjected to step-through passive avoidance tasks and forced swim tests. Reactive carbonyl species (RCs) were evaluated as markers of oxidative stress using a recently developed comprehensive analytical method. Both learning time in passive avoidance tasks and immobile time in forced swim tests became longer with aging (p < 0.05). However, the administration of sesame lignans significantly ameliorated age-related effects in both tests (p < 0.05). Age-related increases in RCs such as 4-hydroxy-2-nonenal in the cerebral cortex and liver were reduced in mice fed sesame lignans. These results suggest that sesame lignans can prevent age-related brain dysfunction via anti-oxidative activity.

Sesame Oil Attenuates Renal Oxidative Stress Induced by a High Fat Diet

The antioxidative effects of the bioactive compounds enriched sesame oil (e.g. lignans and tocopherols) are well established. This study aims to elucidate whether sesame oil could reduce renal oxidative stress induced by a high fat diet (HFD). Mice received HFD for 12 weeks (n=7 per group), which was prepared by adding 20% (w/w) lard (lard group) or sesame oil (sesame group) to the chow diet, respectively. Compared with mice in the lard group, renal lipid levels of those in the sesame group were reduced, shown by decreases in protein expression of transcription factors and enzymes involved in fatty acid synthesis (sterol regulatory element-binding protein-1 and acetyl coenzyme A carboxylase α) and an increase in β-oxidation (peroxisome proliferator-activated receptor α and carnitine palmitoyltransferase I) (P<0.05). In the sesame group, levels of peroxynitrite and thiobarbituric acid reactive substances were also reduced, whereas the level of glutathione was increased. In addition, there was elevated protein expression levels of antioxidant enzymes regulated by nuclear factor-like 2, such as superoxide dismutase, glutathione peroxidase, and glutathione S-transferase (P<0.05), and decreased expression for nuclear factor kappa B and cyclooxygenase 2 (P<0.05). These results suggest that sesame oil could ameliorate HFD-induced renal damage by suppressing oxidative stress and inflammation.

Mitochondria in Neuroprotection by Phytochemicals: Bioactive Polyphenols Modulate Mitochondrial Apoptosis System, Function and Structure

In aging and neurodegenerative diseases, loss of distinct type of neurons characterizes disease-specific pathological and clinical features, and mitochondria play a pivotal role in neuronal survival and death. Mitochondria are now considered as the organelle to modulate cellular signal pathways and functions, not only to produce energy and reactive oxygen species. Oxidative stress, deficit of neurotrophic factors, and multiple other factors impair mitochondrial function and induce cell death. Multi-functional plant polyphenols, major groups of phytochemicals, are proposed as one of most promising mitochondria-targeting medicine to preserve the activity and structure of mitochondria and neurons. Polyphenols can scavenge reactive oxygen and nitrogen species and activate redox-responsible transcription factors to regulate expression of genes, coding antioxidants, anti-apoptotic Bcl-2 protein family, and pro-survival neurotrophic factors. In mitochondria, polyphenols can directly regulate the mitochondrial apoptosis system either in preventing or promoting way. Polyphenols also modulate mitochondrial biogenesis, dynamics (fission and fusion), and autophagic degradation to keep the quality and number. This review presents the role of polyphenols in regulation of mitochondrial redox state, death signal system, and homeostasis. The dualistic redox properties of polyphenols are associated with controversial regulation of mitochondrial apoptosis system involved in the neuroprotective and anti-carcinogenic functions. Mitochondria-targeted phytochemical derivatives were synthesized based on the phenolic structure to develop a novel series of neuroprotective and anticancer compounds, which promote the bioavailability and effectiveness. Phytochemicals have shown the multiple beneficial effects in mitochondria, but further investigation is required for the clinical application.

Dr. Jekyll and Mr. Hyde: Oxidizable phenol-generated reactive oxygen species enhance sulforaphane's antioxidant response element activation, even as they suppress Nrf2 protein accumulation

The transcription factor Nrf2 is a master regulator of antioxidant and cytoprotective genes, binding to antioxidant response elements (AREs) in their promoter regions. Due to the therapeutic role of the Nrf2/ARE system in oxidative homeostasis, its activation has been investigated in many pre-clinical and clinical trials for common chronic diseases. One of the most promising Nrf2 activators is sulforaphane, the subject of over 50 clinical trials. In this work, we examine the effect of reactive oxygen species (ROS) on sulforaphane's Nrf2/ARE activation in the non-tumorigenic keratinocyte cell line HaCaT, with the non-arylating oxidizable phenol, 2,5-di-tert-butylhydroquinone (dtBHQ), as the source of ROS. We find that, in combination with 2.5 µM sulforaphane, dtBHQ markedly enhances ARE-regulated gene expression, including expression of the cytoprotective proteins aldo-keto reductase family 1 member C1 (AKR1C1) and heme oxygenase-1 (HO-1). Additionally, sulforaphane's therapeutic window is widened by 12.5 µM dtBHQ. Our data suggest that H₂O₂ generated by dtBHQ oxidation is responsible for these effects, as shown by inclusion of catalase and by co-treatment with sulforaphane and H₂O₂. While sulforaphane treatment causes Nrf2 protein to accumulate as expected, interestingly, dtBHQ and H₂O₂ appear to act on targets downstream of Nrf2 protein accumulation to enhance sulforaphane's ARE-regulated gene expression. Inclusion of dtBHQ or H₂O₂ with sulforaphane does not increase Nrf2 protein levels, and catalase has little effect on Nrf2 protein levels in the presence of sulforaphane and dtBHQ. Surprisingly, dtBHQ suppresses Nrf2 protein synthesis. Inclusion of a superoxide dismutase mimetic with sulforaphane and dtBHQ partly rescues Nrf2 suppression and significantly further increases sulforaphane's efficacy for ARE-reporter expression. Thus, there is a "Dr. Jekyll and Mr. Hyde" effect of ROS: ROS enhance sulforaphane's ARE-regulated gene expression even as they also inhibit Nrf2 protein synthesis. This unexpected finding reveals the degree to which targets in the ARE pathway downstream of Nrf2 protein accumulation contribute to gene expression. The results presented here provide a model system for significant enhancement of sulforaphane's potency with small molecule co-treatment.

Neuroprotection of a sesamin derivative, 1, 2-bis [(3-methoxyphenyl) methyl] ethane-1, 2-dicaroxylic acid (MMEDA) against ischemic and hypoxic neuronal injury

Objective(s):

Stroke may cause severe neuronal damage. The sesamin have been demonstrated to possess neuroprotection by its antioxidant and anti-inflammatory properties. One sesamin derivative was artificially composited, 1, 2-bis [(3-methoxyphenyl) methyl] ethane-1, 2-dicaroxylic acid (MMEDA) had been developed to study its antioxidative activity and neuroprotection.

Materials and Methods:

The infaction of Sprague Dawley (SD) rats and hypoxia models of BV-2 microglia or PC12 cells were investigated for in vivo and in vitro test respectively. Lipid peroxidation and reactive oxygen species (ROS), prostaglandin E₂ (PGE₂) and related signaling pathways from hypoxic cells were analyzed by ELISA or Western blot assay, respectively.

Results:

MMEDA showed a protective effect when given 90 min after the focal cerebral ischemia. The neuroprotection of MMEDA was further confirmed by attenuating ROS and PGE₂ release from hypoxic BV-2 or PC12 cells. MMEDA significantly reduced hypoxia-induced JNK and caspase-3 (survival and apoptotic pathways) in PC12 cells.

Conclusion:

The neuroprotective effect of MMEDA on ischemia/hypoxia models was involved with its antioxidative activity and anti-inflammatory effects. These results suggest that MMEDA exert effective neuroprotection against ischemia/hypoxia injury.

Sesamin extends lifespan through pathways related to dietary restriction in Caenorhabditis elegans

PURPOSE

Sesamin, a polyphenolic compound found in sesame seeds, has been reported to exert a variety of beneficial health effects. We have previously reported that sesamin increases the lifespan of Caenorhabditis elegans. In this study, we investigated the molecular mechanisms underlying the longevity effect of sesamin in C. elegans.

METHODS

Starting from three days of age, Caenorhabditis elegans animals were fed a standard diet alone or supplemented with sesamin. A C. elegans genome array was used to perform a comprehensive expression analysis. Genes that showed differential expression were validated using real-time PCR. Mutant or RNAi-treated animals were fed sesamin, and the lifespan was determined to identify the genes involved in the longevity effects of sesamin.

RESULTS

The microarray analysis revealed that endoplasmic reticulum unfolded protein response-related genes, which have been reported to show decreased expression under conditions of SIR-2.1/Sirtuin 1 (SIRT1) overexpression, were downregulated in animals supplemented with sesamin. Sesamin failed to extend the lifespan of sir-2.1 knockdown animals and of sir-2.1 loss-of-function mutants. Sesamin was also ineffective in bec-1 RNAi-treated animals; bec-1 is a key regulator of autophagy, and is necessary for longevity induced by sir-2.1 overexpression. Furthermore, the heterozygotic mutation of daf-15, which encodes the target of rapamycin (TOR)-binding partner Raptor, abolished lifespan extension by sesamin. Moreover, sesamin did not prolong the lifespan of loss-of-function mutants of aak-2, which encodes the AMP-activated protein kinase (AMPK).

CONCLUSIONS

Sesamin extends the lifespan of C. elegans through several dietary restriction-related signaling pathways, including processes requiring SIRT1, TOR, and AMPK.

Neuroprotective and Antioxidant Activities of 4-Methylcoumarins: Development of Structure-Activity Relationships

Coumarins are a major class of polyphenols that are abundantly present in many dietary plants and possess different biological activities. Neuroprotective effect of 28 variously substituted 4-methylcoumarins was evaluated in a cell model of oxidative stress-induced neurodegeneration, which measures viability in PC12 cells challenged with hydrogen peroxide by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The inhibitory activity of these compounds against intracellular reactive oxygen species (ROS) formation was also determined by 2',7'-dichlorofluorescein diacetate method in the same cells. Chemical redox-based assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) tests were employed to explore structure-antioxidant activity relationships in a cell-free environment. The results demonstrated that 4-methylcoumarins containing ortho-dihydroxy or ortho-diacetoxy substituents on the benzenoid ring possess considerable neuroprotective effects. ortho-Dihydroxy compounds inhibited cytotoxicity (44.7-62.9%) and ROS formation (41.6-71.1%) at 50 µM and showed considerable antioxidant effects. We conclude that 4-methylcoumarins are promising neuroprotective and antioxidant scaffolds potentially usefull for management of neurodegenerative diseases.

Curative effect of sesame oil in a rat model of chronic kidney disease

AIM

Chronic kidney disease causes a progressive and irreversible loss of renal function. We investigated the curative effect of sesame oil, a natural, nutrient-rich, potent antioxidant, in a rat model of chronic kidney disease.

METHODS

Chronic kidney disease was induced by subcutaneously injecting uni-nephrectomized rats with deoxycorticosterone acetate (DOCA) and 1% NaCl [DOCA/salt] in drinking water. Four weeks later, the rats were gavaged with sesame oil (0.5 or 1 mL/kg per day) for 7 days. Renal injury, histopathological changes, hydroxyl radical, peroxynitrite, lipid peroxidation, Nrf2, osteopontin expression, and collagen were assessed 24 h after the last dose of sesame oil.

RESULTS

Blood urea nitrogen, creatinine, urine volume, and albuminuria were significantly higher in the DOCA/salt treated rats than in control rats. Sesame oil significantly decreased these four tested parameters in DOCA/salt treated rats. In addition, creatinine clearance rate and nuclear Nrf2 expression were significantly decreased in the DOCA/salt treated rats compared to control rats. Sesame oil significantly decreased hydroxyl radical, peroxynitrite level, lipid peroxidation, osteopontin, and renal collagen deposition, but increased creatinine clearance rate and nuclear Nrf2 expression in DOCA/salt treated rats.

CONCLUSION

We conclude that supplementation of sesame oil mitigates DOCA/salt induced chronic kidney disease in rats by activating Nrf2 and attenuating osteopontin expression and inhibiting renal fibrosis in rats.

Biliverdin reductase isozymes in metabolism

The biliverdin reductase (BVR) isozymes BVRA and BVRB are cell surface membrane receptors with pleiotropic functions. This review compares, for the first time, the structural and functional differences between the isozymes. They reduce biliverdin, a byproduct of heme catabolism, to bilirubin, display kinase activity, and BVRA, but not BVRB, can act as a transcription factor. The binding motifs present in the BVR isozymes allow a wide range of interactions with components of metabolically important signaling pathways such as the insulin receptor kinase cascades, protein kinases (PKs), and inflammatory mediators. In addition, serum bilirubin levels have been negatively associated with abdominal obesity and hypertriglyceridemia. We discuss the roles of the BVR isozymes in metabolism and their potential as therapeutic targets.

Mitochondrial impairment triggers cytosolic oxidative stress and cell death following proteasome inhibition

Dysfunctions of the mitochondria and the ubiquitin–proteasome system, as well as generation of reactive oxygen species (ROS), are linked to many aging-related neurodegenerative disorders. However, the order of these events remains unclear. Here, we show that the initial impairment occurs in mitochondria under proteasome inhibition. Fluorescent redox probe measurements revealed that proteasome inhibition led to mitochondrial oxidation followed by cytosolic oxidation, which could be prevented by a mitochondrial-targeted antioxidant or antioxidative enzyme. These observations demonstrated that proteasome dysfunction causes damage to mitochondria, leading them to increase their ROS production and resulting in cytosolic oxidation. Moreover, several antioxidants found in foods prevented intracellular oxidation and improved cell survival by maintaining mitochondrial membrane potential and reducing mitochondrial ROS generation. However, these antioxidant treatments did not decrease the accumulation of protein aggregates caused by inhibition of the proteasome. These results suggested that antioxidative protection of mitochondria maintains cellular integrity, providing novel insights into the mechanisms of cell death caused by proteasome dysfunction.

Polyhydroxylated fullerene attenuates oxidative stress-induced apoptosis via a fortifying Nrf2-regulated cellular antioxidant defence system

Polyhydroxylated derivatives of fullerene C60, named fullerenols (C60[OH]n), have stimulated great interest because of their potent antioxidant properties in various chemical and biological systems, which enable them to be used as a new promising pharmaceutical for the future treatment of oxidative stress-related diseases, but the details remain unknown. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a principal transcription factor that regulates expression of several antioxidant genes via binding to the antioxidant response element and plays a crucial role in cellular defence against oxidative stress. In this study we investigated whether activation of the Nrf2/antioxidant response element pathway contributes to the cytoprotective effects of C60(OH)24. Our results showed that C60(OH)24 enhanced nuclear translocation of Nrf2 and upregulated expression of phase II antioxidant enzymes, including heme oxygenase-1 (HO-1), NAD(P)H: quinine oxidoreductase 1, and γ-glutamate cysteine ligase in A549 cells. Treatment with C60(OH)24 resulted in phosphorylation of p38 mitogen-activated protein kinases (p38 MAPK), extracellular signal-regulated kinases, and c-Jun-N-terminal kinases. By using inhibitors of cellular kinases, we showed that pretreatment of A549 cells with SB203580, a specific inhibitor of p38 MAPK, abolished nuclear translocation of Nrf2 and induction of HO-1 protein induced by C60(OH)24, indicating an involvement of p38 MAPK in Nrf2/HO-1 activation by C 60(OH)24. Furthermore, pretreatment with C60(OH)24 attenuated hydrogen peroxide-induced apoptotic cell death in A549 cells, and knockdown of Nrf2 by small interfering ribonucleic acid diminished C60(OH)24-mediated cytoprotection. Taken together, these findings demonstrate that C60(OH)24 may attenuate oxidative stress-induced apoptosis via augmentation of Nrf2-regulated cellular antioxidant capacity, thus providing insights into the mechanisms of the antioxidant properties of C60(OH)24.

Protective effect of a sesamin derivative, 3-bis (3-methoxybenzyl) butane-1, 4-diol on ischemic and hypoxic neuronal injury

Background

Stroke is one of the leading causes of neuronal death. Sesamin is known for neuroprotection by its antioxidant and anti-inflammatory properties but it lacks blood–brain barrier (BBB) activity. A panel of sesamin derivatives was screened and 3-bis (3-methoxybenzyl) butane-1,4-diol (BBD) was selected for high BBB activity and tested for its neuroprotective effect.

Methods

The focal cerebral ischemia of Sprague–Dawley rats and hypoxia models of murine BV-2 microglia or PC12 cells under oxygen/glucose deprivation were used for in vivo and in vitro test, respectively. Lipid peroxidation and superoxide dismutase (SOD) activity from the ischemic brain were tested and reactive oxygen species (ROS), cytokine production, prostaglandin (PGE₂) and related signaling pathways from hypoxic cells were examined by ELISA or Western blot assay, respectively.

Results

BBD showed a protective effect when given 90 min after the focal cerebral ischemia. It also reduced lipid peroxidation and preserved SOD activity from the ischemic brain. The mechanism of BBD was further confirmed by attenuating ROS, cytokine production, and PGE₂ release from hypoxic BV-2 or PC12 cells. BBD significantly reduced hypoxia-induced c-Jun N-terminal kinases (JNK) and modulated AKT-1 and caspase-3 (survival and apoptotic pathways) in BV-2 cells, and inhibited hypoxia-induced JNK and cyclooxygenase-2 activation in PC12 cells.

Conclusions

The neuroprotective effect of BBD on ischemia/hypoxia models was involved with antioxidant and anti-inflammatory effects. The result would help the development of new CNS drug for protection of ischemia/hypoxia injury.

Notoginsenoside R1-mediated neuroprotection involves estrogen receptor-dependent crosstalk between Akt and ERK1/2 pathways: a novel mechanism of Nrf2/ARE signaling activation

Notoginsenoside R1 (NGR1), a novel phytoestrogen isolated from Panax notoginseng, has antioxidant and anti-apoptotic properties. Oxidative stress plays a pivotal role in neurodegenerative diseases. To mimic oxidative stress in neurons and explore the neuroprotection of NGR1, H₂O₂-induced neurotoxicity in NGF-induced differentiation of PC12 cells was used. In this study, NGR1 preconditioning provided neuroprotective effects via suppressing H₂O₂-induced the intracellular ROS accumulation, the increase in the product of lipid peroxidation (MDA), protein oxidation (protein carbonyl), and DNA fragmentation (8-OHdG), and mitochondrial membrane depolarization as well as caspase-3 activation. Moreover, NGR1 treatment alone potently increased the nuclear translocation of Nrf2, augmented ARE enhancer activity, and upregulated the expression and activity of phase II antioxidant enzymes including HO-1, NQO-1, and γ-GCSc. NGR1 could also increase the ERE activity and activate Akt and ERK1/2 pathways. NGR1-mediated activation of Nrf2/ARE signaling and neuroprotection were abolished by genetic silencing of Nrf2 using siRNA or the pharmacological blockade of estrogen receptors using ICI-182780, and partially inhibited by Akt siRNA or ERK siRNA transfection. In addition, the phosphorylation of ERK1/2 mediated by NGR1 was markedly inhibited in PC12 cells transfected with Akt siRNA. On the contrary, ERK1/2 siRNA transfection hardly had any effect on the phosphorylation of Akt mediated by NGR1. NGR1-mediated activation of Akt and ERK1/2 pathways was blocked by ICI-182780. In conclusion, NGR1 provided neuroprotection via inducing an estrogen receptor-dependent crosstalk between Akt and ERK1/2 pathways, subsequently activating Nrf2/ARE signaling and thereby up-regulating phase II antioxidant enzymes.

The protective effects of oxyresveratrol imine derivative against hydrogen peroxide-induced cell death in PC12 cells

Oxyresveratrol (2',3,4',5-tetrahydroxystilbene) is a naturally occurring ingredient found in mulberries that shows potential as an antioxidant, anti-inflammatory, and neuroprotective agent. This study was performed to identify materials similar to oxyresveratrol that may have more effective antioxidant properties. We synthesized a stilbene analog referred to as Compound 1 (2',3,4',5-tetramethoxystilbene); a benzamide analog referred to as Compound 2 ((2,4-dimethoxyphenyl)-3,5-dimethoxybenzamide); and three imine analogs referred to as Compound 3 (3,5-dimethoxybenzylidene)-(2,4-dimethoxyphenylamine), Compound 4 ((4-methoxybenzylidene)-(3-methoxyphenyl)amine), and Compound 5 ((4-methoxybenzylidene)phenylamine). The cytoprotective effects of these compounds were subsequently evaluated using hydrogen peroxide-treated PC12 cells. The cytoprotective effects of the imine analogs were greater than the effects of oxyresveratrol and the other analogs at concentrations of 200 μM. The Compound 3, which is the most effective imine analog of oxyresveratrol, exhibited these cytoprotective effects against hydrogen peroxide-induced oxidative stress through the regulation of heme oxygenase-1 (HO-1) expression and the translocation of nuclear factor E2-related factor 2 (Nrf2). Our results suggest that imine analogs of oxyresveratrol may be useful agents in reducing neuronal oxidative damage.

Lipocalin-type prostaglandin D synthase protects against oxidative stress-induced neuronal cell death

L-PGDS [lipocalin-type PGD (prostaglandin D) synthase] is a dual-functional protein, acting as a PGD2-producing enzyme and a lipid transporter. L-PGDS is a member of the lipocalin superfamily and can bind a wide variety of lipophilic molecules. In the present study we demonstrate the protective effect of L-PGDS on H2O2-induced apoptosis in neuroblastoma cell line SH-SY5Y. L-PGDS expression was increased in H2O2-treated neuronal cells, and the L-PGDS level was highly associated with H2O2-induced apoptosis, indicating that L-PGDS protected the neuronal cells against H2O2-mediated cell death. A cell viability assay revealed that L-PGDS protected against H2O2-induced cell death in a concentration-dependent manner. Furthermore, the titration of free thiols in H2O2-treated L-PGDS revealed that H2O2 reacted with the thiol of Cys65 of L-PGDS. The MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight)-MS spectrum of H2O2-treated L-PGDS showed a 32 Da increase in the mass relative to that of the untreated protein, showing that the thiol was oxidized to sulfinic acid. The binding affinities of oxidized L-PGDS for lipophilic molecules were comparable with those of untreated L-PGDS. Taken together, these results demonstrate that L-PGDS protected against neuronal cell death by scavenging reactive oxygen species without losing its ligand-binding function. The novel function of L-PGDS could be useful for the suppression of oxidative stress-mediated neurodegenerative diseases.

Sesamolinol glucoside, disaminyl ether, and other lignans from sesame seeds

The application of a procedure based on XAD-4 adsorption resin permitted the obtainment of an enriched polyphenolic extract from Sesamum indicum seeds. Chemical analysis of the obtained extract led to the identification of 12 lignans. Among them, 2 lignans, (+)-sesamolinol-4'-O-β-D-glucoside and disaminyl ether, are reported for the first time as natural compounds. Their structure has been determined by spectroscopic methods, mainly by the application of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) techniques [heteronuclear multiple-quantum coherence (HMQC), heteronuclear multiple-bond correlation (HMBC), and nuclear Overhauser effect spectrometry (NOESY)] and mass spectroscopy. The isolated compounds were evaluated for their antimutagenic activity. Among the tested lignans, the most active lignan was found to be sesamolin, followed by sesamolinol and samin, against H(2)O(2). Additionally, some of the tested lignans showed desmutagenic activity against benzo[a]pyrene (BaP).

Oxidative stress in neurodegenerative diseases: mechanisms and therapeutic perspectives

The incidence and prevalence of neurodegenerative diseases (ND) increase with life expectancy. This paper reviews the role of oxidative stress (OS) in ND and pharmacological attempts to fight against reactive oxygen species (ROS)-induced neurodegeneration. Several mechanisms involved in ROS generation in neurodegeneration have been proposed. Recent articles about molecular pathways involved in ROS generation were reviewed. The progress in the development of neuroprotective therapies has been hampered because it is difficult to define targets for treatment and determine what should be considered as neuroprotective. Therefore, the attention was focused on researches about pharmacological targets that could protect neurons against OS. Since it is necessary to look for genes as the ultimate controllers of all biological processes, this paper also tried to identify gerontogenes involved in OS and neurodegeneration. Since neurons depend on glial cells to survive, recent articles about the functioning of these cells in aging and ND were also reviewed. Finally, clinical trials testing potential neuroprotective agents were critically reviewed. Although several potential drugs have been screened in in vitro and in vivo models of ND, these results were not translated in benefit of patients, and disappointing results were obtained in the majority of clinical trials.

Gene categories differentially expressed in C. elegans age-1 mutants of extraordinary longevity: new insights from novel data-mining procedures

Two nonsense mutants of age-1, the Caenorhabditis elegans gene encoding phosphoinositide 3-kinase, live nearly 10-fold longer than wild-type controls and are exceptionally resistant to several stresses. Genome-wide expression analyses implicated downregulation of many more genes than were upregulated in second-generation age-1 homozygotes. Functional-annotation analysis, based on Gene Ontology terms, suggested that novel mechanisms may mediate the stronger phenotypes observed for these worms than with milder age-1 disruption. For the current study, the same microarray data were reanalyzed using novel meta-analytic procedures that we developed recently. First, gene p values were corrected for systematic biases based on the observed distribution for nonexpressed genes; these values were then combined to derive an aggregate p value for each functional-annotation term while adjusting for intergene covariance. This resulted in much better coverage of relevant gene categories, including many that were independently supported by other data. The number of nonredundant GO categories significantly distinguishing age-1 alleles of exceptional longevity increased from sevenfold to greater than ninefold, improving both sensitivity and specificity of selection for altered pathways and implicating previously unsuspected longevity mechanisms. Of 150 genes whose differential expression underlay significant GO terms in both comparisons, over half were up- or down-regulated in accord with longevity, whereas one third showed altered expression uniquely in the longest-lived age-1-null strains, consistent with the activation or suppression of pathways peculiar to strong age-1 mutants.