5,6,7,4'-Tetramethoxyflavanone attenuates NADPH oxidase 1/4 and promotes sirtuin-1 to inhibit cell stress, senescence and apoptosis in Aß25-35-mediated SK-N-SH dysfunction.

Amyloidogenesis is a fundamental step of amyloid beta (Aß) generation-induced toxicity that is commonly reported to disrupt neuronal circuits, function and survival in Alzheimer's disease (AD). The neuroprotective effect of 5,6,7,4'-tetramethoxyflavanone (TMF) from Chormolaela odorata extract on brain degeneration and amyloidogenesis has previously been demonstrated. However, the mechanistic evidence for TMF's effects is still unclear. In this study, we evaluated the neuroprotective effect of TMF in Aß25-35-induced toxicity in SK-N-SH neuroblastoma cells. Herein, we demonstrated that TMF exhibited potent antioxidant activity and significantly increased cell viability and decreased ROS production in a dose-dependent manner. Moreover, TMF reversed the effect of Aß25-35, which caused energy deprivation and apoptosis, by decreasing the ratio of Bax/Bcl-xL and reducing mitochondrial membrane potential (Δψm), caspase-3 expression, apoptotic cells, and attenuating glucose transporter (Glut-3) expression. In addition, TMF protected against Aß25-35-induced cellular senescence by attenuating ß-galactosidase, p-21 and p-53 expression and promoted the expression of Sirt-1 and p-Rb. In addition, the effects of TMF on Aß25-35 toxicity were related to the upregulation of phase II antioxidant and nuclear factor erythroid 2-related factor-2 (Nrf2) signaling, including superoxide dismutase (SOD), heme oxygenase (HO)-1, and nuclear translocation of Nrf2. Finally, we also found that TMF attenuated Aß25-35-reduced synaptic plasticity by increasing the expression of synaptophysin and PSD-95, which was correlated with a decrease in acetylcholine esterase (AChE). Importantly, we found that the protective effects of TMF on Aß25-35 were bidirectional, including marked inhibition of NADPH oxidase (NOX)-4 activity and partial activation of Sirt-1, which occurred prior to a reduction in the negative responses. Therefore, TMF may be useful for treating Aß toxicity in AD.

Protective effects of silk lutein extract from Bombyx mori cocoons on ß-Amyloid peptide-induced　apoptosis in PC12 cells.

Beta-amyloid (Aß) peptide, the hallmark of Alzheimer's disease (AD), invokes a cascade of oxidative damage to neurons and eventually leads to neuronal death. This study evaluated the protective effects of lutein extract from yellow cocoons of Bombyx mori, and its underlying mechanisms against was investigated to assess its protective effects and the underlying mechanisms against Aß25-35-induced neuronal cell death in cultured rat pheochromocytoma (PC12) cells. Aß25-35-induced neuronal toxicity is characterized by decrease in cell viability, increase in intracellular reactive oxygen species (ROS) production, activation of mitochondrial death pathway, and activation the phospholyration of mitogen-activated protein kinase (MAPKs) pathway. Pretreatment with silk lutein extract significantly attenuated Aß25-35-induced loss of cell viability, apoptosis, MAPKs pathway activation and ROS production. Taken together, our present study suggests that silk lutein extract protects PC12 cells from Aß25-35-induced neurotoxicity via the reduction of the ROS production, and subsequent attenuation of the mitochondrial death pathway and reduces the activation of the MAPK kinase pathways. This compound might beneficial as potential therapeutic agent to prevent or retard the development and progression of AD.

Cyanidin attenuates Aß25-35-induced neuroinflammation by suppressing NF-κB activity downstream of TLR4/NOX4 in human neuroblastoma cells.

Cyanidin is polyphenolic pigment found in plants. We have previously demonstrated that cyanidin protects nerve cells against Aß25-35-induced toxicity by decreasing oxidative stress and attenuating apoptosis mediated by both the mitochondrial apoptotic pathway and the ER stress pathway. To further elucidate the molecular mechanisms underlying the neuroprotective effects of cyanidin, we investigated the effects of cyanidin on neuroinflammation mediated by the TLR4/NOX4 pathway in Aß25-35-treated human neuroblastoma cell line (SK-N-SH). SK-N-SH cells were exposed to Aß25-35 (10 µmol/L) for 24 h. Pretreatment with cyanidin (20 µmol/L) or NAC (20 µmol/L) strongly inhibited the NF-κB signaling pathway in the cells evidenced by suppressing the degradation of IκBα, translocation of the p65 subunit of NF-κB from the cytoplasm to the nucleus, and thereby reducing the expression of iNOS protein and the production of NO. Furthermore, pretreatment with cyanidin greatly promoted the translocation of the Nrf2 protein from the cytoplasm to the nucleus; upregulating cytoprotective enzymes, including HO-1, NQO-1 and GCLC; and increased the activity of SOD enzymes. Pretreatment with cyanidin also decreased the expression of TLR4, directly improved intracellular ROS levels and regulated the activity of inflammation-related downstream pathways including NO production and SOD activity through TLR4/NOX4 signaling. These results demonstrate that TLR4 is a primary receptor in SK-N-SH cells, by which Aß25-35 triggers neuroinflammation, and cyanidin attenuates Aß-induced inflammation and ROS production mediated by the TLR4/NOX4 pathway, suggesting that inhibition of TLR4 by cyanidin could be beneficial in preventing neuronal cell death in the process of Alzheimer's disease.

Neuroprotection of agomelatine against cerebral ischemia/reperfusion injury through an antiapoptotic pathway in rat.

Agomelatine is an agonist of the melatonergic MT1/MT2 receptors and an antagonist of the serotonergic 5-HT receptors. Its actions mimic melatonin in antioxidative and anti-inflammation. However, the protective mechanism of agomelatine in ischemic/reperfusion (I/R) injury has not been investigated. In this study, cerebral I/R injury rats were induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion. The rats were randomly divided into 6 groups (12 rats per group): sham-operated; vehicle-treated I/R; 20 mg/kg, 40 mg/kg, and 80 mg/kg agomelatine-treated I/R; and 10 mg/kg melatonin-treated I/R. Agomelatine and melatonin were intraperitoneally administrated to the rats 1 h before MCAO induction. After reperfusion for 24 h, the brain samples were harvested for evaluating the infarct volume, histological changes, terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining as well as cleaved caspase-3, Bax, Bcl-XL, nuclear factor erythroid-2-related factor (Nrf2), and heme oxygenase (HO-1) levels. Agomelatine treatment significantly decreased apoptosis, with decreases in Bax and cleaved caspase-3, and increased Bcl-XL, along with a decrease in apoptotic neuronal cells. Moreover, agomelatine was also found to markedly increase the expression of HO-1, the antioxidative enzymes, and the activity of superoxide dismutase (SOD) mediated by Nrf2 pathway. Agomelatine treatment protects the brain from cerebral I/R injury by suppressing apoptosis and agomelatine has antioxidant properties. Hence, there exists the possibility of developing agomelatine as a potential candidate for treating ischemic stroke.

Cyanidin-3-glucoside attenuates angiotensin II-induced oxidative stress and inflammation in vascular endothelial cells.

Angiotensin II (Ang II) causes oxidative stress and vascular inflammation, leading to vascular endothelial cell dysfunction, and is associated with the development of inflammatory cardiovascular diseases such as atherosclerosis. Therefore, interventions of oxidative stress and inflammation may contribute to the reduction of cardiovascular diseases. Cyanidin-3-glucoside (C3G) plays a role in the prevention of oxidative damage in several diseases. Here, we investigated the effect of C3G on Ang II-induced oxidative stress and vascular inflammation in human endothelial cells (EA.hy926). C3G dose-dependently suppressed the free radicals and inhibited the nuclear factor-kappa B (NF-κB) signaling pathway by protecting the degradation of inhibitor of kappa B-alpha (IκB-α), inhibiting the expression and translocation of NF-κB into the nucleus through the down-regulation of NF-κB p65 and reducing the expression of inducible nitric oxide synthase (iNOS). Pretreatment with C3G not only prohibited the NF-κB signaling pathway but also promoted the activity of the nuclear erythroid-related factor 2 (Nrf2) signaling pathway through the upregulation of endogenous antioxidant enzymes. Particularly, we observed that C3G significantly enhanced the production of superoxide dismutase (SOD) and induced the expression of heme oxygenase (HO-1). Our findings confirm that C3G can protect against vascular endothelial cell inflammation induced by AngII. C3G may represent a promising dietary supplement for the prevention of inflammation, thereby decreasing the risk for the development of atherosclerosis.

Neuroprotective effects of cyanidin against Aß-induced oxidative and ER stress in SK-N-SH cells.

This study evaluated the mechanisms underlying the protective effect of cyanidin against Aß25-35-induced neuronal cell death in SK-N-SH cells. Aß25-35-induced neurotoxicity is characterized by a decrease in cell viability, inducing the expression of endoplasmic reticulum (ER) stress proteins; an increase in intracellular reactive oxygen species (ROS) production; and an increase in intracellular calcium release. Aß25-35 also induces neuronal toxicity through the disturbance of ER calcium levels. Pretreatment with cyanidin significantly attenuated the Aß25-35-induced loss of cell viability, reducing the expression of endoplasmic reticulum (ER) stress response proteins with regard to the down-regulation of the expression levels of 78 kDa glucose regulated protein (Grp78), phosphorylated forms of pancreatic ER elF2α kinase (PERK), eukaryotic initiation factor 2 α (eIF2α), and inositol-requiring enzyme 1 (IRE1), and the expression levels of X-box binding protein 1 (XBP-1), activating transcription factor 6 (ATF6), and CCAAT/enhancer binding protein homologous transcription factor (C/EBP) homologous protein (CHOP); decreased intracellular ROS production; decreased intracellular calcium release; and reduced down-regulation of the protein expression levels of calpain and cleaved caspase-12. This result suggests that cyanidin may be an alternative agent in preventing neurodegenerative diseases.

Di-O-demethylcurcumin protects SK-N-SH cells against mitochondrial and endoplasmic reticulum-mediated apoptotic cell death induced by Aß25-35.

Alzheimer's disease (AD) is a neurodegenerative and progressive disorder. The hallmark of pathological AD is amyloid plaque which is the accumulation of amyloid ß (Aß) in extracellular neuronal cells and neurofibrillary tangles (NFT) in neuronal cells, which lead to neurotoxicity via reactive oxygen species (ROS) generation related apoptosis. Loss of synapses and synaptic damage are the best correlates of cognitive decline in AD. Neuronal cell death is the main cause of brain dysfunction and cognitive impairment. Aß activates neuronal death via endoplasmic reticulum (ER) stress and mitochondria apoptosis pathway. This study investigated the underlying mechanisms and effects of di-O-demethylcurcumin in preventing Aß-induced apoptosis. Pretreatment with di-O-demethylcurcumin for 2 h, which was followed by Aß25-35 (10 µM) in human neuroblastoma SK-N-SH cells improved cell viability by using MTS assay and decreased neuronal cell apoptosis. Pretreatment with di-O-demethylcurcumin attenuated the number of nuclear condensations and number of apoptotic cells in Aß25-35-induced group in a concentration-dependent manner by using transmission electron microscope (TEM) and flow cytometry, respectively. Di-O-demethylcurcumin also increased the ratio of Bcl-XL/Bax protein, and reduced intracellular ROS level, cytochrome c protein expression, cleaved caspase-9 protein expression, and cleaved caspase-3 protein expression. Additionally, di-O-demethylcurcumin treatment also reduced the expression of ER stress protein markers, including protein kinase RNA like endoplasmic reticulum kinase (PERK) phosphorylation, eukaryotic translation initiation factor 2 alpha (eIF2α) phosphorylation, inositol-requiring enzyme 1 (IRE1) phosphorylation, X-box-binding protein-1 (XBP-1), activating transcription factor (ATF6), C/EBP homologous protein (CHOP), and cleaved caspase-12 protein. CHOP and cleaved caspase-12 protein are the key mediators of apoptosis. Our data suggest that di-O-demethylcurcumin is a candidate protectant against neuronal death through its suppression of the apoptosis mediated by mitochondrial death and ER stress pathway.

Neuroprotective effect of purple rice extract and its constituent against amyloid beta-induced neuronal cell death in SK-N-SH cells.

This study evaluated the protective effects of purple rice (Oryza sativa L.) extract (PRE) and its major constituent, cyanidin, and their underlying mechanisms against Aß 25-35-induced neuronal cell death in SK-N-SH cells. Aß 25-35-induced neuronal toxicity is characterized by decrease in cell viability, the release of lactate dehydrogenase (LDH), decrease superoxide dismutase (SOD) activity, increase in reactive oxygen species (ROS) production, morphological alteration, and activation of mitochondrial death pathway. Pretreatment with PRE and cyanidin significantly attenuated Aß 25-35-induced loss of cell viability, apoptosis, and increase in ROS and RNS production in a dose-dependent manner. In addition, PRE and cyanidin also helped to bring about the downregulation of the expression of Bax, cytochrome c, cleavage caspase-9, and cleavage caspase-3 proteins, and the upregulation of the Bcl-XL protein in cascade. Therefore, it is evident that PRE and its major constituent, cyanidin, were successful in protecting from the cytotoxic effect of Aß 25-35 through attenuation ROS and RNS production and modulation of mitochondrial death pathway in SK-N-SH cells. This result suggests that PRE and its major constituent, cyanidin, might be beneficial as potential therapeutic agents in preventing neurodegenerative diseases.