Expression of manganese superoxide dismutase in esophageal and gastric cancers

The tumor-killing activity of radiotherapy and chemotherapy for cancer is closely associated with the production of active oxygen, and the relation between therapeutic resistance and active oxygen scavengers produced by the tumor itself is gaining more attention. It is considered that manganese superoxide dismutase (MnSOD) protects host cells from oxidative stress, in synergy with other antioxidant enzymes. In this study, we used a quantitative polymerase chain reaction assay to measure MnSOD mRNA in resected specimens from patients with esophageal and gastric cancers. In both esophageal and gastric cancers, the level of MnSOD mRNA was significantly elevated in cancer tissue compared to non-cancer tissue (P < 0.01). In gastric cancer tissue, the MnSOD mRNA level was significantly higher than in esophageal cancer tissue (P < 0.01). The significance of MnSOD in cancer tissue was investigated further by measuring MnSOD content in resected specimens using an enzyme-linked immunosorbent assay, and by examining its location by an immunohistochemical method. Upregulation of MnSOD in cancer tissue most likely serves as a protective mechanism against anti-cancer therapies known to produce superoxide radicals as a key component of their tumor-killing activity. (Received June 30, 1997; accepted June 26, 1998)     

Bilobalide protects astrocytes from oxygen and glucose deprivation‐induced oxidative injury by upregulating manganese superoxide dismutase

Bilobalide (BB), a constituent of the Ginkgo biloba extract, is a neuroprotective agent with multiple mechanisms of action. To further explore the potential therapeutic effects of BB in stroke, we investigated its effects on primary astrocytes using the oxygen and glucose deprivation‐reoxygenation (OGD‐R) model. Cell viability was measured by lactate dehydrogenase release assay and 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Cell death was measured by annexin 5 conjgated with fluorescein isothiocyanate (V‐FITC) assay, and reactive oxygen species (ROS) production was measured by 2′,7′‐Dichlorodihydrofluorescein Diacetate (DCFH‐DA) probe. Manganese superoxide dismutase (MnSOD) expression was measured by western blot and immunofluorescence. Mitochondrial membrane potential was monitored using JC‐1 staining. Our results show that OGD‐R downregulated MnSOD and impaired mitochondrial function, which further enhanced ROS production in primary astrocytes. As a result, cell viability was compromised, and cell death increased. BB treatment protected astrocytes from those injuries mainly by restoring MnSOD level as MnSOD inhibitor abolished the effects of BB. In conclusion, we demonstrated that OGD‐R induced astrocytic injury, but BB increased the expression of MnSOD, the ROS scavenger, to reverse the exacerbated astrocytic injury.     

Resistance of mitochondrial DNA-depleted cells against cell death: Potential relevance to aging

We studied the changes of gene expression in SK-Hep1 hepatoma ρ° cells to study the mechanism of their resistance to cell death. The expression of MnSOD and glutathione peroxidases was increased in ρ° cells. ρ° cells were resistant to ROS. ρ° cells were also resistant to p53. These results suggest that an increase in the expression of antioxidant enzymes renders cancer cells or aged cells with frequent mitochondrial DNA mutations to resist against oxidative stress or host surveillance.     

锰超氧化物歧化酶9Ala/Val基因多态性与冠心病的关系

目的:探讨锰超氧化物歧化酶9 Ala/Val(MnSOD9 Ala/Val)基因多态性与冠心病、血浆总超氧化物歧化酶(T-SOD)和锰超氧化物歧化酶(MnSOD)活性的关系。方法:采用ABI 3100 DNA测序仪检测147例冠心病患者和108例对照组的MnSOD9 Ala/Val基因多态性的基因型,采用比色法测定血浆T-SOD和MnSOD活性。结果:与对照组比较,冠心病患者的血浆T-SOD和MnSOD活性明显降低,C反应蛋白(CRP)和颈动脉内-中膜厚度(IMT)则显著增高;冠心病患者的MnSOD VV基因型和V等位基因携带者较对照组明显增多;MnSOD VV基因型的T-SOD和MnSOD活性较AA基因型明显降低,并且MnSOD 9V等位基因与T-SOD活力、MnSOD活力和高密度脂蛋白呈负相关;与空腹血糖、胆固醇、甘油三酯、低密度脂蛋白、收缩压、IMT和CRP呈正相关。结论:冠心病患者的抗氧化能力明显降低,因而炎症反应和动脉硬化程度加重;MnSOD 9 Ala/Val基因多态性通过影响血浆MnSOD活性和冠心病的危险因素而参与冠心病的发病。     

BCNU-induced gR2 DEFECT mediates S-glutathionylation of Complex I and respiratory uncoupling in myocardium

A deficiency of mitochondrial glutathione reductase (or GR2) is capable of adversely affecting the reduction of GSSG and increasing mitochondrial oxidative stress. BCNU [1,3-bis (2-chloroethyl)-1-nitrosourea] is an anticancer agent and known inhibitor of cytosolic GR ex vivo and in vivo. Here we tested the hypothesis that a BCNU-induced GR2 defect contributes to mitochondrial dysfunction and subsequent impairment of heart function. Intraperitoneal administration of BCNU (40 mg/kg) specifically inhibited GR2 activity by 79.8 ± 2.7% in the mitochondria of rat heart. However, BCNU treatment modestly enhanced the activities of mitochondrial Complex I and other ETC components. The cardiac function of BCNU-treated rats was analyzed by echocardiography, revealing a systolic dysfunction associated with decreased ejection fraction, decreased cardiac output, and an increase in left ventricular internal dimension and left ventricular volume in systole. The respiratory control index of isolated mitochondria from the myocardium was moderately decreased after BCNU treatment, whereas NADH-linked uncoupling of oxygen consumption was significantly enhanced. Extracellular flux analysis to measure the fatty acid oxidation of myocytes indicated a 20% enhancement after BCNU treatment. When the mitochondria were immunoblotted with antibodies against GSH and UCP3, both protein S-glutathionylation of Complex I and expression of UCP3 were significantly up-regulated. Overexpression of SOD2 in the myocardium significantly reversed BCNU-induced GR2 inhibition and mitochondrial impairment. In conclusion, BCNU-mediated cardiotoxicity is characterized by the GR2 deficiency that negatively regulates heart function by impairing mitochondrial integrity, increasing oxidative stress with Complex I S-glutathionylation, and enhancing uncoupling of mitochondrial respiration.     

AP-2α对肺腺癌A549细胞MnSOD表达的作用研究

目的：探讨转录因子激活蛋白-2α(activator protein-2 alpha,AP-2α)对锰超氧化物歧化酶(manganese superoxide dismutase,MnSOD)mRNA和蛋白表达的影响,探讨AP-2α下调MnSOD表达的可能的分子机制。方法：转染Ad-AP-2α和AP-2α siRNA进入A549细胞,上调和下调AP-2α后,采用实时定量RT-PCR及Western blot检测A549细胞内MnSOD的mRNA及蛋白质的表达水平。结果：1)Ad-AP-2α转染A549细胞后,MnSOD mRNA和蛋白质表达均下降;2)AP-2α siRNA转染A549细胞后,MnSOD mRNA及蛋白质表达均增加。结论：AP-2α对肺腺癌A549细胞MnSOD的mRNA和蛋白表达起下调作用。     

Dihydroartemisinin induces autophagy by suppressing NF-κB activation

Nuclear factor-kappa B (NF-κB) and autophagy are two major regulators involved in both tumor initiation and progression. However, the association between these two signaling pathways still remains obscure. In this work, we demonstrate that dihydroartemisinin (DHA) stimulates the induction of autophagy in several cancer cell lines through repression of NF-κB activity. We also show that inhibiting NF-κB results in an accumulation of reactive oxygen species (ROS), which participate in the stimulation of autophagy. These findings present a pathway by which DHA promotes autophagy in cancer cells and provide evidence for the DHA-induced sensitization effect of some chemotherapeutics.