Combination of chlorogenic acid and salvianolic acid B protects against polychlorinated biphenyls-induced oxidative stress through Nrf2

Caffeic acid derivatives (CADs) are well-known phytochemicals with multiple physiological and pharmacological activities. This study aimed to investigate the combined protective effects of CADs on PCB126-induced liver damages and oxidative stress in mice. Here, we used chemiluminescence and chose chlorogenic acid (CGA), salvianolic acid B (Sal B) as the best antioxidants. Then, mice were intragastrically administered with 60 mg/kg/d CGA, Sal B, and CGA plus Sal B (1:1) for 3 weeks before exposing to 0.05 mg/kg/d PCB126 for 2 weeks. We found that pretreatment with CGA, Sal B, and CGA plus Sal B effectively attenuated liver injury and cytotoxicity caused by PCB126, but improved the expressions of superoxide dismutase (SOD), glutathione reduced (GSH), heme oxygenase-1 (HO-1) and nuclear factor E2-related factor 2 (Nrf2), CGA plus Sal B especially, was found to have the best effects that indicated a synergetic protective effect. Taken together, as the Nrf2 regulates the cyto-protective response by up-regulating the expression of antioxidant genes, we suggested that CGA plus Sal B had a combined protection on PCB126-induced tissue damages and that the Nrf2 signaling might be involved.     

Nrf2/HO-1 pathway activation by manganese is associated with reactive oxygen species and ubiquitin-proteasome pathway, not MAPKs signaling

Manganese has been known to induce neurological disorders similar to Parkinson's disease. One of the features of manganese-induced neurotoxicity is oxidative stress. Accumulating data implicate NF-E2-related factor 2 (Nrf2) as a key regulator in the adaptive survival response to oxidative stress. Recent studies suggest that the activation of Nrf2 is induced by manganese in PC12 cells. In the present study, we investigated possible links between reactive oxygen species (ROS), proteasome or mitogen-activated protein kinase (MAPK) signaling and Nrf2/HO-1 activation in manganese-treated PC12 cells. After MnCl(2) treatment, there was an increase in nuclear localization and subsequent binding of Nrf2 to the antioxidant-responsive element (ARE) and upregulation of heme oxygenase-1 (HO-1) protein in PC12 cells. Pretreatment with N-acetyl cysteine, a scavenger of reactive oxygen species, suppressed MnCl(2) -induced Nrf2 activation, increase in Nrf2-ARE binding and subsequent upregulation of HO-1 expression. However, pretreatment with lactacystin, an inhibitor of proteasome activity, enhanced MnCl(2) -induced Nrf2 activation, increase in Nrf2-ARE binding and subsequent upregulation of HO-1 expression. Pretreatment of cells with a pharmacological inhibitor of MAPK (ERK inhibitor PD 98059, P38 inhibitor SB203580 or JNK inhibitor SP600125) did not affect the MnCl(2) -induced Nrf2 activation, increase in Nrf2-ARE binding or subsequent upregulation of HO-1 expression. These results suggest that Nrf2/HO-1 activation by Mn in PC12 cells is associated with ROS and the ubiquitin-proteasome pathway, not MAPK signaling.     

Protective mechanisms of anthocyanins from purple sweet potato against tert-butyl hydroperoxide-induced hepatotoxicity

Anthocyanins have been shown to exert anti-proliferative, anti-inflammatory effects and anti-carcinogenic activity. In the present work, we investigated the protective effects of anthocyanin fraction (AF) from purple sweet potato on tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity in HepG2 cell line and in rat liver. The result showed that the oral pretreatment of AF before t-BHP treatment significantly lowered the serum levels of the hepatic enzyme markers (ALT and AST) and reduced oxidative stress of the liver by evaluation of malondialdehyde and glutathione. Histopathological evaluation of the livers also revealed that AF reduced the incidence of liver lesions. The in vitro result showed that AF significantly reduced t-BHP-induced oxidative injury, as determined by cell cytotoxicity, intracellular glutathione content, lipid peroxidation, reactive oxygen species (ROS) levels, and caspases activation. Also, AF up-regulated antioxidant enzymes including heme oxygenase-1 (HO-1), NAD(P)H:quinone reductase, and glutathione S-transferase. Moreover, AF induced Nrf2 nuclear translocation and Akt and ERK1/2 activation, pathways that are involved in inducing Nrf2 nuclear translocation. Taken together, these results suggest that the protective effects of AF against t-BHP-induced hepatotoxicity may, at least in part, be due to its ability to scavenge ROS and to regulate the antioxidant enzyme HO-1 via the Akt and ERK1/2/Nrf2 signaling pathways.     

Ginsenoside Rb1 protects against 6-hydroxydopamine-induced oxidative stress by increasing heme oxygenase-1 expression through an estrogen receptor-related PI3K/Akt/Nrf2-dependent pathway in human dopaminergic cells

Phytoestrogens are polyphenolic non-steroidal plant compounds with estrogen-like biological activity. Ginseng, the root of Panax ginseng C.A. Meyer (Araliaceae), is a popular traditional herbal medicine. Ginsenoside Rb1 (Rb1), an active component commonly found in ginseng root, is a phytoestrogen that exerts estrogen-like activity. In this study, we demonstrate that the phytoestrogen Rb1 inhibits 6-hydroxydopamine (6-OHDA)-induced oxidative injury via an ER-dependent Gβ1/PI3K/Akt and heme oxygenase-1 (HO-1) pathway. Pretreatment of SH-SY5Y cells with Rb1 significantly reduced 6-OHDA-induced caspase-3 activation and subsequent cell death. Rb1 also up-regulated HO-1 expression, which conferred cytoprotection against 6-OHDA-induced oxidative injury. Moreover, Rb1 induced both Nrf2 nuclear translocation, which is upstream of HO-1 expression and PI3K activation, a pathway that is involved in induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection. Also, Rb1-mediated increases in PI3K activation and HO-1 induction were reversed by co-treatment with ICI 182,780 and pertussis toxin. Taken together, these results suggest that Rb1 augments the cellular antioxidant defenses through ER-dependent HO-1 induction via the Gβ1/PI3K/Akt-Nrf2 signaling pathway, thereby protecting cells from oxidative stress. Thus our study indicates that Rb1 has a partial cytoprotective role in dopaminergic cell culture systems.     

人参总皂苷在巨噬细胞RAW264.7中降低脂多糖诱导的炎症和氧化应激

目的:通过脂多糖诱导巨噬细胞RAW264.7建立炎症和氧化应激模型,探讨人参总皂苷的抗炎和抗氧化效果以及对脂多糖诱导的巨噬细胞RAW264.7自噬水平的影响。方法:培养RAW264.7细胞,给予脂多糖刺激并加入不同浓度人参总皂苷,使用硝酸还原酶法检测细胞内一氧化氮水平;ELISA法检测小鼠肿瘤坏死因子α(tumor necrosis factor-α,TNF-α)的分泌;DCFH-DA荧光探针法检测人参总皂苷处理后活性氧的变化;超氧化物阴离子荧光探针(dihydroethidium, DHE)检测细胞内超氧化物阴离子水平;吖啶橙染色法检测自噬体的形成;Western Blot法检测COX-2、NF-кB、Nrf2、HO-1、GCLC、GCLM、Beclin1、ATG7和LC3的蛋白表达。结果:与脂多糖模型组相比,随着TGS的浓度增加,细胞一氧化氮水平、TNF-α的分泌降低,细胞内活性氧和超氧阴离子的含量降低,巨噬细胞RAW264.7酸性自噬体的数量增加;Nrf2、HO-1、GCLC、GCLM、Beclin1、ATG7及LC3的蛋白表达提高,COX-2、NF-кB的蛋白表达降低。结论:在...     

The cytoprotective effect of <Emphasis Type="Italic">Rumex Aquaticus Herba</Emphasis> extract against hydrogen peroxide-induced oxidative stress in AGS cells

The Rumex Aquaticus Herba extract containing quercetin-3-β-D-glucuronopyranoside (ECQ) has been reported to exhibit various pharmacological activities, including anti-inflammatory and anti-oxidative effects. This plant has been traditionally used for the treatment of diarrhea, disinfestation, edema and jaundice, and as an antipyretic drug. The aim of the present study was to investigate the ability of ECQ to protect against oxidative damage and to determine its signaling mechanism in AGS cells. The protein expressions of heme oxygenase-1 (HO-1) and nuclear factor-erythroid 2 related factor 2 (Nrf2) were measured by Western blots. Cell viability was measured by MTT assay. Intracellular reactive oxygen species (ROS) levels were measured using 2′,7′-dichlorofluorescein diacetate. Glutathione peroxidase levels were measured using kits. The protein expressions of HO-1 and its upstream mediator, Nrf2, increased after ECQ treatment. The HO-1 inhibitor, ZnPP, repressed the protective effect of ECQ on H₂O₂-induced cell damage. We found that LY294002, a specific PI3 K/Akt inhibitor, suppressed ECQ-induced HO-1 expression. ECQ significantly attenuated H₂O₂-induced cytotoxicity and ROS generation. Also, ECQ enhanced the antioxidant enzyme activities of glutathione peroxidase. These results suggest that ECQ exerts a cytoprotective effect against H₂O₂-induced oxidative stress by upregulation of Nrf2/HO-1 via the PI3 K/Akt pathway.     

黄芩素-7-甲醚对缺氧致PC12细胞损伤的保护作用

目的 研究黄芩素-7-甲醚对缺氧PC12细胞的保护作用。方法 将PC12细胞分为正常对照组、缺氧模型组、芦丁组和黄芩素-7-甲醚组,培养24 h后,MTT法检测黄芩素-7-甲醚对细胞活力的影响;酶标仪法检测细胞培养上清液中乳酸脱氢酶（lactate dehydrogenase,LDH）活性以及细胞内丙二醛（malondialdehyde,MDA）、超氧化物歧化酶（superoxide dismutase,SOD）和过氧化氢酶（catalase,CAT）水平;2'',7''-二氯荧光素探针法检测细胞内活性氧簇（reactive oxygen species,ROS）水平;实时荧光定量PCR和Western blot检测核因子E2相关因子2（Nrf2）和血红素氧合酶-1（heme oxygenase-1,HO-1）的mRNA和蛋白的表达。结果 与正常对照组相比,缺氧导致PC12细胞活力显著降低,LDH、MDA和ROS水平显著升高,抗氧化酶SOD和CAT的活力显著降低。黄芩素-7-甲醚预处理能够逆转这些变化。此外,缺氧能够诱导细胞内Nrf2、HO-1的mRNA和蛋白表达增加,而黄芩素-7-甲醚能够进一步提高Nrf2、HO-1的mRNA和蛋白表达。结论 黄芩素-7-甲醚对缺氧致PC12细胞损伤有一定的保护作用,其作用机制可能与激活Nrf2/HO-1通路,抑制氧化应激损伤有关。     

Anti-Apoptotic Effect of Flavokawain A on Ochratoxin-A-Induced Endothelial Cell Injury by Attenuation of Oxidative Stress via PI3K/AKT-Mediated Nrf2 Signaling Cascade

This study investigates the endothelial protective activity of flavokawain A (FKA) against oxidative stress induced by ochratoxin A (OTA), which acts as a mycotoxin, and its primary mechanisms in in vitro models. Reactive oxygen species, in general, regulate oxidative stress that significantly contributes to the pathophysiology of endothelial dysfunctions. OTA exerts toxicity through inflammation and the accumulation of ROS. This research is aimed at exploring the defensive function of FKA against the endothelial injury triggered by OTA through the Nrf2 pathway regulated by PI3K/AKT. OTA exposure significantly increased the nuclear translocation of NFκB, whereas we found a reduction in inflammation via NFκB inhibition with FKA treatment. FKA increased the PI3K and AKT phosphorylation, which may lead to the stimulation of antioxidative and antiapoptotic signaling in HUVECs. It also upregulated the phosphorylation of Nrf2 and a concomitant expression of antioxidant genes, such as HO-1, NQO-1, and γGCLC, depending on the dose under the oxidative stress triggered by OTA. Knockdown of Nrf2 through small interfering RNA (siRNA) impedes the protective role of FKA against the endothelial toxicity induced by OTA. In addition, FKA enhanced Bcl2 activation while suppressing apoptosis marker proteins. Therefore, FKA is regarded as a potential agent against endothelial oxidative stress caused by the deterioration of the endothelium. The research findings showed that FKA plays a key role in activating the p-PI3K/p-AKT and Nrf2 signaling pathways, while suppressing caspase-dependent apoptosis.     

Isorhamnetin protects against oxidative stress by activating Nrf2 and inducing the expression of its target genes

Isorhamentin is a 3′-O-methylated metabolite of quercetin, and has been reported to have anti-inflammatory and anti-proliferative effects. However, the effects of isorhamnetin on Nrf2 activation and on the expressions of its downstream genes in hepatocytes have not been elucidated. Here, we investigated whether isorhamnetin has the ability to activate Nrf2 and induce phase II antioxidant enzyme expression, and to determine the protective role of isorhamnetin on oxidative injury in hepatocytes. In HepG2 cells, isorhamnetin increased the nuclear translocation of Nrf2 in a dose- and time-dependent manner, and consistently, increased antioxidant response element (ARE) reporter gene activity and the protein levels of hemeoxygenase (HO-1) and of glutamate cysteine ligase (GCL), which resulted in intracellular GSH level increases. The specific role of Nrf2 in isorhamnetin-induced Nrf2 target gene expression was verified using an ARE-deletion mutant plasmid and Nrf2-knockout MEF cells. Deletion of the ARE in the promoter region of the sestrin2 gene, which is recently identified as the Nrf2 target gene by us, abolished the ability of isorhamnetin to increase luciferase activity. In addition, Nrf2 deficiency completely blocked the ability of isorhamnetin to induce HO-1 and GCL. Furthermore, isorhamnetin pretreatment blocked t-BHP-induced ROS production and reversed GSH depletion by t-BHP and consequently, due to reduced ROS levels, decreased t-BHP-induced cell death. In addition isorhamnetin increased ERK1/2, PKCδ and AMPK phosphorylation. Finally, we showed that Nrf2 deficiency blocked the ability of isorhamnetin to protect cells from injury induced by t-BHP. Taken together, our results demonstrate that isorhamnetin is efficacious in protecting hepatocytes against oxidative stress by Nrf2 activation and in inducing the expressions of its downstream genes.     

Protective effects of hesperidin against oxidative stress of tert-butyl hydroperoxide in human hepatocytes

Increasing evidence regarding free radical generating agents and the inflammatory process suggest that accumulation of reactive oxygen species (ROS) could involve hepatotoxicity. Hesperidin, a naturally occurring flavonoid presents in fruits and vegetables, has been reported to exert a wide range of pharmacological effects that include antioxidant, anti-inflammatory, antihypercholesterolemic, and anticarcinogenic actions. However, the cytoprotection and mechanism of hesperidin to neutralize oxidative stress in human hepatic L02 cells remain unclear. In this work, we assessed the capability of hesperidin to prevent tert-butyl hydroperoxide (t-BuOOH)-induced cell damage by augmenting cellular antioxidant defense. Hesperidin significantly protected hepatocytes against t-BuOOH-induced cell cytotoxicity, such as mitochondrial membrane potential (MMP) deplete and lactate dehydrogenase (LDH) release. Hesperidin also remarkably prevented indicators of oxidative stress, such as the ROS and lipid peroxidation level in a dose-dependent manner. Western blot showed that hesperidin facilitated ERK/MAPK phosphorylation which appeared to be responsible for nuclear translocation of Nrf2, thereby inducing cytoprotective heme oxygenase-1 (HO-1) expression. Based on the results described above, it suggested that hesperidin has potential as a therapeutic agent in the treatment of oxidative stress-related hepatocytes injury and liver dysfunctions.     

Mechanism of phytoestrogen puerarin-mediated cytoprotection following oxidative injury: estrogen receptor-dependent up-regulation of PI3K/Akt and HO-1

Phytoestrogens are polyphenolic non-steroidal plant compounds with estrogen-like biological activity. The phytoestrogen puerarin, the main isoflavone glycoside found in the root of Pueraria lobata, has been used for various medicinal purposes in traditional Chinese medicines for thousands of years. Recent studies have indicated that the estrogen receptor (ER), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, non-nuclear function of ER that may be relevant in cytoprotection. In this study, we demonstrate that the phytoestrogen puerarin inhibits tert-butyl hydroperoxide (t-BHP)-induced oxidative injury via an ER-dependent Gβ1/PI3K/Akt and heme oxygenase-1 (HO-1) pathway. Pretreatment of Hepa1c1c7 and HepG2 cells with puerarin significantly reduced t-BHP-induced caspase-3 activation and subsequent cell death. Also, puerarin up-regulated HO-1 expression and this expression conferred cytoprotection against oxidative injury induced by t-BHP. Moreover, puerarin induced Nrf2 nuclear translocation, which is upstream of puerarin-induced HO-1 expression, and PI3K activation, a pathway that is involved in induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection. Puerarin-induced up-regulation of HO-1 and cytoprotection against t-BHP were abolished by silencing Nrf2 expression with specific siRNA. Also, puerarin-mediated increases in PI3K activation and HO-1 induction were reversed by co-treatment with ICI 182,780 and pertussis toxin. Taken together, these results suggest that puerarin augments cellular antioxidant defense capacity through ER-dependent HO-1 induction via the Gβ1/PI3K/Akt-Nrf2 signaling pathway, thereby protecting cells from oxidative stress.     

Attenuation of Aβ25–35-induced parallel autophagic and apoptotic cell death by gypenoside XVII through the estrogen receptor-dependent activation of Nrf2/ARE pathways

Amyloid-beta (Aβ) has a pivotal function in the pathogenesis of Alzheimer's disease. To investigate Aβ neurotoxicity, we used an in vitro model that involves Aβ_25–35-induced cell death in the nerve growth factor-induced differentiation of PC12 cells. Aβ_25–35 (20 μM) treatment for 24 h caused apoptotic cell death, as evidenced by significant cell viability reduction, LDH release, phosphatidylserine externalization, mitochondrial membrane potential disruption, cytochrome c release, caspase-3 activation, PARP cleavage, and DNA fragmentation in PC12 cells. Aβ_25–35 treatment led to autophagic cell death, as evidenced by augmented GFP-LC3 puncta, conversion of LC3-I to LC3-II, and increased LC3-II/LC3-I ratio. Aβ_25–35 treatment induced oxidative stress, as evidenced by intracellular ROS accumulation and increased production of mitochondrial superoxide, malondialdehyde, protein carbonyl, and 8-OHdG. Phytoestrogens have been proved to be protective against Aβ-induced neurotoxicity and regarded as relatively safe targets for AD drug development. Gypenoside XVII (GP-17) is a novel phytoestrogen isolated from Gynostemma pentaphyllum or Panax notoginseng. Pretreatment with GP-17 (10 μM) for 12 h increased estrogen response element reporter activity, activated PI3K/Akt pathways, inhibited GSK-3β, induced Nrf2 nuclear translocation, augmented antioxidant responsive element enhancer activity, upregulated heme oxygenase 1 (HO-1) expression and activity, and provided protective effects against Aβ_25–35-induced neurotoxicity, including oxidative stress, apoptosis, and autophagic cell death. In conclusion, GP-17 conferred protection against Aβ_25–35-induced neurotoxicity through estrogen receptor-dependent activation of PI3K/Akt pathways, inactivation of GSK-3β and activation of Nrf2/ARE/HO-1 pathways. This finding might provide novel insights into understanding the mechanism for neuroprotective effects of phytoestrogens or gypenosides.     

Sulforaphane protects against acetaminophen-induced hepatotoxicity

Oxidative stress is closely associated with acetaminophen (APAP)-induced toxicity. Heme oxygenase-1 (HO-1), an antioxidant defense enzyme, has been shown to protect against oxidant-induced tissue injury. This study investigated whether sulforaphane (SFN), as a HO-1 inducer, plays a protective role against APAP hepatotoxicity in vitro and in vivo. Pretreatment of primary hepatocyte with SFN induced nuclear factor E2-factor related factor (Nrf2) target gene expression, especially HO-1 mRNA and protein expression, and suppressed APAP-induced glutathione (GSH) depletion and lipid peroxidation, which eventually leads to hepatocyte cell death. A comparable effect was observed in mice treated with APAP. Mice were treated with 300 mg/kg APAP 30 min after SFN (5 mg/kg) administration and were then sacrificed after 6 h. APAP alone caused severe liver injuries as characterized by increased plasma AST and ALT levels, GSH depletion, apoptosis, and 4-hydroxynonenal (4-HNE) formations. This APAP-induced liver damage was significantly attenuated by pretreatment with SFN. Furthermore, while hepatic reactive oxygen species (ROS) levels were increased by APAP exposure, pretreatment with SFN completely blocked ROS formation. These results suggest that SFN plays a protective role against APAP-mediated hepatotoxicity through antioxidant effects mediated by HO-1 induction. SFN has preventive action in oxidative stress-mediated liver injury.     

The role of ANXA5 in DBP-induced oxidative stress through ERK/Nrf2 pathway

Di-N-butylphthalate (DBP) have given rise to more and more attention due to its unique endocrine toxicity to male reproductive system. Our previous studies have demonstrated antioxidative Nrf2 (nuclear factor erythroid related factor 2) pathway play a vital role in DBP induced oxidative stress injury. ANXA5 (annexin A5), which is highly expressed in testicular Leydig and Sertoli cells, was found upregulated after DBP stimulation. Mouse Leydig and Sertoli cells were exposed to different concentration of DBP for 24 h to examine the ROS (Reactive oxygen species), MDA (Malondialdehyde), SOD (superoxide dismutase) level and ANXA5, Nrf2, NQO1 (NAD(P)H-quinone oxidoreductase 1), HO-1 (heme oxygenase 1) and ERK/P-ERK protein expression by DHE (Dihydroethidium) staining, ELISA (enzyme-linked immunosorbent assay) and Western blot respectively. Firstly, the oxidative stress injury induced by DBP was re-validated. Then, we confirmed the change of Nrf2 pathway and ANXA5 level after DBP exposure to testicular cells. Additionally, overexpressed ANXA5 could activate Nrf2/HO-1/NQO1 antioxidant pathway and significantly attenuate DBP-induced oxidative stress. Ultimately, we demonstrated ANXA5 could increase ERK phosphorylated level and the activated role of ANXA5 on ERK/Nrf2 pathway could be reversed by ERK inhibitor. Overall, this study illuminated that ANXA5 could defend testicle Leydig and Sertoli cells against DBP-induced oxidative stress injury through ERK/Nrf2 pathway.     

<Emphasis Type="Italic">In vitro</Emphasis> protective effects of Hoveniae Semen cum Fructus extracts against oxidative stress

We evaluated the in vitro cytoprotective effects of Hoveniae Semen cum Fructus (HSCF) extracts against oxidative stress-mediated cell damage using HepG2 cells. Cytotoxic effects of HSCF extracts were observed in HepG2 cells, and the 50% inhibitory concentration was determined. Cytoprotective effects of sublethal doses of HSCF extracts were evaluated using a tert-butyl hydroperoxide (tBHP)-induced cellular damage model. We also assessed whether NFE2-related factor-2 (Nrf2) was transactivated by HSCF extracts. The antioxidant capacity of HSCF extracts was evaluated with superoxide dismutase (SOD) and catalase (CAT) activities and the expression of the antioxidant genes glutamate cysteine ligase catalytic subunit (GCLC), hemeoxygenase-1 (HO1), and NAD (P)H dehydrogenase quinone 1 (NQO1). HSCF extracts up to 1,000 μg/mL showed no cytotoxic effect in HepG2 cells. Indeed, 300 and 1,000 μg/mL of HSCF extracts significantly protected HepG2 cells from oxidative stress-mediated cell death by tBHP. As a molecular mechanism, HSCF extracts at 1,000 μg/mL significantly increased Nrf2 transactivation and induced expression of its target genes (GCLC, HO1, NQO1). Furthermore, 1,000 μg/mL of HSCF extracts enhanced SOD activity. Although treatment with 300 and 1,000 μg/mL of HSCF extracts tended to slightly increase CAT activity, the increases were not statistically significant. These findings provide direct evident that HSCF extracts have favorable hepatoprotective effects against oxidative stress through Nrf2-mediated antioxidant gene induction.