Nrf2/ARE信号通路与胃癌耐药关系的研究进展

胃癌是癌症死亡的第二大原因。化疗是胃癌治疗的主要方法之一,胃癌化疗失败的主要原因是对化疗药物的耐受。Nrf2/ARE信号通路与肿瘤耐药的关系是当前的研究热点。转录因子Nrf2作为抗氧化反应中的关键转录因子,可以与抗氧化反应元件ARE结合,正向调节II相解毒酶、抗氧化酶及某些药物转运泵基因等靶基因的表达,诱导胃癌耐药性的产生。该综述整理归纳了Nrf2/ARE信号通路与胃癌耐药之间的关系。     

Allopurinol reduces oxidative stress and activates Nrf2/p62 to attenuate diabetic cardiomyopathy in rats

Allopurinol (ALP) attenuates oxidative stress and diabetic cardiomyopathy (DCM), but the mechanism is unclear. Activation of nuclear factor erythroid 2‐related factor 2 (Nrf2) following the disassociation with its repressor Keap1 under oxidative stress can maintain inner redox homeostasis and attenuate DCM with concomitant attenuation of autophagy. We postulated that ALP treatment may activate Nrf2 to mitigate autophagy over‐activation and consequently attenuate DCM. Streptozotocin‐induced type 1 diabetic rats were untreated or treated with ALP (100 mg/kg/d) for 4 weeks and terminated after heart function measurements by echocardiography and pressure‐volume conductance system. Cardiomyocyte H9C2 cells infected with Nrf2 siRNA or not were incubated with high glucose (HG, 25 mmol/L) concomitantly with ALP treatment. Cell viability, lactate dehydrogenase, 15‐F2t‐Isoprostane and superoxide dismutase (SOD) were measured with colorimetric enzyme‐linked immunosorbent assays. ROS, apoptosis, was assessed by dihydroethidium staining and TUNEL, respectively. The Western blot and qRT‐PCR were used to assess protein and mRNA variations. Diabetic rats showed significant reductions in heart rate (HR), left ventricular eject fraction (LVEF), stroke work (SW) and cardiac output (CO), left ventricular end‐systolic volume (LVVs) as compared to non‐diabetic control and ALP improved or normalized HR, LVEF, SW, CO and LVVs in diabetic rats (all P < .05). Hearts of diabetic rats displayed excessive oxidative stress manifested as increased levels of 15‐F2t‐Isoprostane and superoxide anion production, increased apoptotic cell death and cardiomyocytes autophagy that were concomitant with reduced expressions of Nrf2, heme oxygenase‐1 (HO‐1) and Keap1. ALP reverted all the above‐mentioned diabetes‐induced biochemical changes except that it did not affect the levels of Keap1. In vitro, ALP increased Nrf2 and reduced the hyperglycaemia‐induced increases of H9C2 cardiomyocyte hypertrophy, oxidative stress, apoptosis and autophagy, and enhanced cellular viability. Nrf2 gene silence cancelled these protective effects of ALP in H9C2 cells. Activation of Nrf2 subsequent to the suppression of Keap1 and the mitigation of autophagy over‐activation may represent major mechanisms whereby ALP attenuates DCM.     

2-Deoxy-D-glucose and 6-aminonicotinamide-mediated Nrf2 down regulation leads to radiosensitization of malignant cells via abrogation of GSH-mediated defense

Enhanced level of nuclear erythroid-related factor-2 (Nrf2) has been associated with cancer chemo/radioresistance. Therefore, the role of Nrf2 in radiosensitization of malignant cells induced by a combination of 2-deoxy-D-Glucose (2-DG) and 6-aminonicotinamide (6-AN) was investigated. Two established human malignant cells lines namely KB (head and neck squamous carcinoma) and BMG-1 (cerebral glioma) were used. Following treatment with a combination of 2-DG (5 mM) and 6-AN (5 μM), irradiated (2Gy) KB and BMG-1 cells were assessed for protein level of Nrf2, Keap1 and γ-glutamylcysteine synthetase (γ-GCS) by western blotting and mRNA expression of γ-GCS, glutathione reductase (GR) and glutathione peroxidase (GPx1) by RT-PCR at 24 hours post treatment. A significant decrease in the level of Nrf2 with a concomitant increase in Keap1 was observed in both the irradiated malignant cells at 24 hours following treatment with combination (2-DG + 6-AN). Down regulation of γ-GCS, GR and GPx1 at 24 hours following treatment with combination (2-DG + 6-AN) resulted in abrogation of glutathione (GSH)-mediated defense in both the irradiated malignant cells. Eventual accumulation of ROS led to radiosensitization of both the malignant cells. These results indicate that deregulated Nrf2-Keap1 signalling leads to the radiosensitization of malignant cells due to abrogated glutathione defense. Metabolic modification-mediated down regulation of Nfr2 and its downstream signalling may have a potential of improving tumour radiotherapy.     

Dihydro-CDDO-trifluoroethyl amide suppresses inflammatory responses in macrophages via activation of Nrf2

Nuclear factor erythroid 2-related factor (Nrf2) is the major regulator of cellular defenses against various pathological stresses in a variety of organ systems, thus Nrf2 has evolved to be an attractive drug target for the treatment and/or prevention of human disease. Several synthetic oleanolic triterpenoids including dihydro-CDDO-trifluoroethyl amide (dh404) appear to be potent activators of Nrf2 and exhibit chemopreventive promises in multiple disease models. While the pharmacological efficacy of Nrf2 activators may be dependent on the nature of Nrf2 activation in specific cell types of target organs, the precise role of Nrf2 in mediating biological effects of Nrf2 activating compounds in various cell types remains to be further explored. Herein we report a unique and Nrf2-dependent anti-inflammatory profile of dh404 in inflamed macrophages. In lipopolysaccharide (LPS)-inflamed RAW264.7 macrophages, dh404 dramatically suppressed the expression of pro-inflammatory cytokines including inducible nitric oxide synthase (iNOS), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1 beta (MIP-1β), while minimally regulating the expression of interleulin-6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNFα). Dh404 potently activated Nrf2 signaling; however, it did not affect LPS-induced NF-κB activity. Dh404 did not interrupt the interaction of Nrf2 with its endogenous inhibitor Kelch-like ECH associating protein 1 (Keap1) in macrophages. Moreover, knockout of Nrf2 blocked the dh404-induced anti-inflammatory responses in LPS-inflamed macrophages. These results demonstrated that dh404 suppresses pro-inflammatory responses in macrophages via an activation of Nrf2 independently of Keap1 and NF-κB, suggesting a unique therapeutic potential of dh404 for specific targeting a Nrf2-mediated resolution of inflammation.     

Nutritional strategies to modulate inflammation and oxidative stress pathways via activation of the master antioxidant switch Nrf2

The nuclear factor E2-related factor 2 (Nrf2) plays an important role in cellular protection against cancer, renal, pulmonary, cardiovascular and neurodegenerative diseases where oxidative stress and inflammation are common conditions. The Nrf2 regulates the expression of detoxifying enzymes by recognizing the human Antioxidant Response Element (ARE) binding site and it can regulate antioxidant and anti-inflammatory cellular responses, playing an important protective role on the development of the diseases. Studies designed to investigate how effective Nrf2 activators or modulators are need to be initiated. Several recent studies have shown that nutritional compounds can modulate the activation of Nrf2–Keap1 system. This review aims to discuss some of the key nutritional compounds that promote the activation of Nrf2, which may have impact on the human health.     

Nrf2及天然产物导向的Nrf2激活剂研究进展

氧化应激能够破坏细胞内氧化还原平衡,造成系统和组织损伤,最终引起一系列疾病的产生.转录因子E2相关因子2(Nrf2),受Kelch样环氧氯丙烷相关蛋白1(Keap1)蛋白的调控,是细胞氧化应激反应中的关键因子,在氧化应激条件下,Nrf2从Keap1中分离,然后进入细胞核与抗氧化反应元件(ARE)结合,增加了Ⅱ相解毒酶的...     

Inhibitor of Nrf2 (INrf2 or Keap1) protein degrades Bcl-xL via phosphoglycerate mutase 5 and controls cellular apoptosis

INrf2 (Keap1) is an adaptor protein that facilitates INrf2-Cul3-Rbx1-mediated ubiquitination/degradation of Nrf2, a master regulator of cytoprotective gene expression. Here, we present evidence that members of the phosphoglycerate mutase family 5 (PGAM5) proteins are involved in the INrf2-mediated ubiquitination/degradation of anti-apoptotic factor Bcl-xL. Mass spectrometry and co-immunoprecipitation assays revealed that INrf2, through its DGR domain, interacts with PGAM5, which in turn interacts with anti-apoptotic Bcl-xL protein. INrf2-Cul3-Rbx1 complex facilitates ubiquitination and degradation of both PGAM5 and Bcl-xL. Overexpression of PGAM5 protein increased INrf2-mediated degradation of Bcl-xL, whereas knocking down PGAM5 by siRNA decreased INrf2 degradation of Bcl-xL, resulting in increased stability of Bcl-xL. Mutation of PGMA5-E79A/S80A abolished INrf2/PGAM5/Bcl-xL interaction. Therefore, PGAM5 protein acts as a bridge between INrf2 and Bcl-xL interaction. Further studies showed that overexpression of INrf2 enhanced degradation of PGAM5-Bcl-xL complex, led to etoposide-mediated accumulation of Bax, increased release of cytochrome c from mitochondria, activated caspase-3/7, and enhanced DNA fragmentation and apoptosis. In addition, antioxidant (tert-butylhydroquinone) treatment destabilized the Nrf2-INrf2-PGAM5-Bcl-xL complex, which resulted in release of Nrf2 in cytosol and mitochondria, release of Bcl-xL in mitochondria, increase in Bcl-xL heterodimerization with Bax in mitochondria, and reduced cellular apoptosis. These data provide the first evidence that INrf2 controls Bcl-xL via PGAM5 and controls cellular apoptosis.     

Moringa oleifera leaf fractions attenuated Naje haje venom-induced cellular dysfunctions via modulation of Nrf2 and inflammatory signalling pathways in rats

Naja haje envenoming could activate multiple pathways linked to haematotoxic, neurological, and antioxidant systems dysfunctions. Moringa oleifera has been used in the management of different snake venom-induced toxicities, but there is no scientific information on its antivenom effects against Naja haje. This study thus, investigated the antivenom activities of different extract partitions of M. oleifera leaves against N. haje envenoming. Forty five male rats were divided into nine groups (n = 5). Groups 2 to 9 were envenomed with 0.025 mg/kg (LD₅₀) of N. haje venom while group 1 was given saline. Group 2 was left untreated, while group 3 was treated with polyvalent antivenom, groups 4, 6 and 8 were treated with 300 mg/kg^?1 of N-hexane, ethylacetate and ethanol partitions of M. oleifera, respectively. Groups 5, 7 and 9 were also treated with 600 mgkg^?1of the partitions, respectively. Ethanol extract and ethyl acetate partition of M. oleifera significantly improved haematological indices following acute anaemia induced by the venom. Likewise, haemorrhagic, haemolytic and anti-coagulant activities of N. haje venom were best inhibited by ethanol partition. Envenoming significantly down-regulated Nuclear factor erythroid 2-related factor 2 (Nrf2) with the consequent elevation of antioxidant enzymes activities in the serum and brain. Treatment with extract partitions however, elevated Nrf2 levels while normalising antioxidant enzyme activities. Furthermore, there were reduction in levels of pro-inflammatory cytokines (TNF-α and interleukin-1β) in tissues of treated envenomed rats. This study concludes that ethanol partition of M. oleifera was most effective against N. haje venom and could be considered as a potential source for antivenom metabolites.     

Aucubin inhibited lipid accumulation and oxidative stress via Nrf2/HO‐1 and AMPK signalling pathways

Aucubin (AU) is the main active ingredient of Aucuba japonica which has showed many positive effects such as anti‐inflammation and liver protection. Non‐alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. In this research, we explored the effects of AU on the tyloxapol‐induced NAFLD in mice and apolipoprotein C‐III (apoC‐III) induced‐3T3L1 cells. Tyloxapol (300 mg/kg) was injected to C57BL/6 mice with aucubin. The differentiated 3T3‐L1 cells were treated with or without aucubin after stimulation of apoC‐III (100 μg/mL). In results, aucubin inhibited hyperlipidaemia, oxidative stress and inflammation by influencing the content of total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), very low density lipoprotein (VLDL), myeloperoxidase (MPO), superoxide dismutase (SOD), tumour necrosis factor receptor‐α (TNF‐α), interleukin‐1β (IL‐1β), and IL‐6 in blood. AU activated NF‐E2‐related factor 2 (Nrf2), peroxisome proliferator‐activated receptor α (PPARα), PPARγ and hemeoxygenase‐1 (HO‐1) and promoted the phosphorylation of adenosine 5′‐monophosphate‐activated protein kinase (AMPKα), AMPKβ, acetyl‐CoA carboxylase (ACC) and protein kinase B (AKT). In conclusion, AU performed the function of hypolipidaemic by its obvious anti‐inflammation and antioxidant activity, which may become a kind of new drug targeting at NAFLD.     

依达拉奉通过Nrf2信号分子调节氧化应激减轻脑缺血再灌注诱导的神经损伤

本研究旨在探讨依达拉奉(edaravone,ED)在脑缺血再灌注损伤中发挥神经元保护作用与Nrf2信号分子间的关系。体内实验利用脑内脑中动脉闭塞(middle cerebral artery occlusion model,MCAO)建立SD大鼠脑缺血再灌注损伤模型,体外实验采用过氧化氢(H2O2)损伤PC12细胞建立氧化应激模型。通过TTC染色、HE染色、Nissl染色来检测大脑的病理状态。测定活性氧(reactive oxygen species,ROS)、丙二醛(malondialdehyde,MDA)含量、超氧化物歧化酶(superoxide dismutase,SOD)活性,来反映氧化应激水平。此外,通过Hoechst 33342染色和线粒体膜电位(mitochondrial membrane potential,MTP)测定,探究细胞水平的损伤。采用免疫组织化学和蛋白质印记测定Nrf2的表达。构建Nrf2敲除的PC12细胞系,证实Nrf2信号分子抑制氧化应激损伤的作用。结果提示,经依达拉奉给药后,在动物体内水平,TTC染色证实,脑缺血再灌注损伤(cerebral ischemia reperfusion injury,CIRI)大鼠的脑组织梗死体积减小(P<0.001),ROS和MDA水平下降(P<0.01),SOD活性上升(P<0.01);在细胞水平,凋亡细胞减少(P<0.05),MTP上升(P<0.01),ROS和MDA水平下降,SOD活性上升(P<0.01);在分子水平,免疫组化和Western印迹结果均提示,Nrf2蛋白质含量较正常组增加。H2O2诱导Nrf2基因敲除的PC12细胞损伤加重,且依达拉奉的治疗效果明显削弱。综上所述,Nrf2在依达拉奉减轻脑缺血再灌注诱导的氧化应激损伤中发挥关键作用。