A mitochondrial superoxide theory for oxidative stress diseases and aging

Fridovich identified CuZnSOD in 1969 and manganese superoxide dismutase (MnSOD) in 1973, and proposed ”the Superoxide Theory,” which postulates that superoxide (O₂^•−) is the origin of most reactive oxygen species (ROS) and that it undergoes a chain reaction in a cell, playing a central role in the ROS producing system. Increased oxidative stress on an organism causes damage to cells, the smallest constituent unit of an organism, which can lead to the onset of a variety of chronic diseases, such as Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis and other neurological diseases caused by abnormalities in biological defenses or increased intracellular reactive oxygen levels. Oxidative stress also plays a role in aging. Antioxidant systems, including non-enzyme low-molecular-weight antioxidants (such as, vitamins A, C and E, polyphenols, glutathione, and coenzyme Q₁₀) and antioxidant enzymes, fight against oxidants in cells. Superoxide is considered to be a major factor in oxidant toxicity, and mitochondrial MnSOD enzymes constitute an essential defense against superoxide. Mitochondria are the major source of superoxide. The reaction of superoxide generated from mitochondria with nitric oxide is faster than SOD catalyzed reaction, and produces peroxynitrite. Thus, based on research conducted after Fridovich’s seminal studies, we now propose a modified superoxide theory; i.e., superoxide is the origin of reactive oxygen and nitrogen species (RONS) and, as such, causes various redox related diseases and aging.     

Combination of ZD55-MnSOD therapy with 5-FU enhances antitumor efficacy in colorectal cancer

Purpose ZD55-MnSOD is an E1B 55 kDa-deleted replication-competent adenovirus and armed with the therapeutic gene MnSOD. The expression of the therapeutic gene MnSOD increases with the selective replication of the oncolytic adenovirus (ZD55) so that ZD55-MnSOD has more significant activity than the replicate defective adenovirus Ad-MnSOD in vitro and in vivo. The tumor cannot be completely eradicated only with ZD55-MnSOD, although ZD55-MnSOD has obvious antitumor activity. 5-fluorouracil (5-FU) is still the most effective adjuvant therapy for patients with colorectal cancer. Methods We reasoned that combined treatment of cancer cells with ZD55-MnSOD and 5-FU might have a synergistic effect. In vitro experiments with SW620 colorectal carcinoma cell line demonstrated that it was sensitive to ZD55-MnSOD, especially most sensitive to ZD55-MnSOD plus 5-FU treatment. Treatment with both ZD55-MnSOD and 5-FU could induce more significant apoptosis in cancer cells compared with ZD55-MnSOD or 5-FU alone, respectively. A better antitumor activity was observed by ZD55-MnSOD plus 5-fluorouracil (5-FU) treatment. Tumor growth was greatly inhibited by this combined treatment, and animal survival time increased. Conclusion These results show that, by using the combination therapies, a significant decrease in tumor mass can be achieved, which suggest that ZD55-MnSOD in combination with 5-FU may have potential clinical implications.     

Myeloperoxidase gene polymorphism predicts fibrosis severity in women with hepatitis C

Oxidative stress plays an important role on liver fibrosis progression in the course of hepatitis C virus (HCV) infection. Myeloperoxidase (MPO) is an enzyme released by neutrophils and macrophages, responsible for generating hypochlorous acid and reactive oxygen species (ROS) that may lead to liver injury in HCV infection. On the other hand, antioxidant enzymes such as manganese superoxide dismutase (SOD) controls ROS-mediated damage. The aim of the present study was to investigate the influence of MPO G-463A and SOD2 Ala16Val polymorphisms in the severity of liver fibrosis in individuals with chronic HCV infection. The present study included 270 patients with chronic HCV recruited from the Gastrohepatology Service of the Oswaldo Cruz University Hospital/Liver Institute of Pernambuco (Recife, Northeastern Brazil). All patients underwent liver biopsy, which was classified according METAVIR score. The SNPs were determined by real-time PCR. After multivariate analysis adjustment, the GG genotype of MPO and the presence of metabolic syndrome were independently associated with fibrosis severity in women (P = 0.025 OR 2.25 CI 1.10–4.59 and P = 0.032 OR 2.32 CI 1.07–5.01, respectively). The presence of the GG genotype seems to be a risk factor for fibrosis severity in women with HCV.     

The role of obesity and related metabolic disturbances in cancers of the colon, prostate, and pancreas

Recent evidence indicates that obesity and related metabolic abnormalities are associated with increased incidence or mortality for a number of cancers, including those of the colon, prostate, and pancreas. Obesity, physical inactivity, visceral adiposity, hyperglycemia, and hyperinsulinemia are relatively consistent risk factors for colon cancer and adenoma. Also, patients with type 2 diabetes mellitus have a higher risk of colon cancer. For prostate cancer, the relationship to obesity appears more complex. Obesity seems to contribute to a greater risk of aggressive or fatal prostate cancer but perhaps to a lower risk of nonaggressive prostate cancer. Furthermore, men with type 2 diabetes mellitus are at lower risk of developing prostate cancer. Long-standing type 2 diabetes increases the risk of pancreatic cancer by approximately 50%. Furthermore, over the past 6 years, a large number of cohort studies have reported positive associations between obesity and pancreatic cancer. Together with data from prediagnostic blood specimens showing positive associations between glucose levels and pancreatic cancer up to 25 years later, sufficient evidence now supports a strong role for diabetes and obesity in pancreatic cancer etiology. The mechanisms for these associations, however, remain speculative and deserve further study. Hyperinsulinemia may be important, but the role of oxidative stress initiated by hyperglycemia also deserves further attention.     

A neuronal model of Alzheimer's disease: an insight into the mechanisms of oxidative stress-mediated mitochondrial injury

Alzheimer's disease (AD) is associated with beta-amyloid accumulation, oxidative stress and mitochondrial dysfunction. However, the effects of genetic mutation of AD on oxidative status and mitochondrial manganese superoxide dismutase (MnSOD) production during neuronal development are unclear. To investigate the consequences of genetic mutation of AD on oxidative damages and production of MnSOD during neuronal development, we used primary neurons from new born wild-type (WT/WT) and amyloid precursor protein (APP) (NLh/NLh) and presenilin 1 (PS1) (P264L) knock-in mice (APP/PS1) which incorporated humanized mutations in the genome. Increasing levels of oxidative damages, including protein carbonyl, 4-hydroxynonenal (4-HNE) and 3-nitrotyrosine (3-NT), were accompanied by a reduction in mitochondrial membrane potential in both developing and mature APP/PS1 neurons compared with WT/WT neurons suggesting mitochondrial dysfunction under oxidative stress. Interestingly, developing APP/PS1 neurons were significantly more resistant to beta-amyloid 1-42 treatment, whereas mature APP/PS1 neurons were more vulnerable than WT/WT neurons of the same age. Consistent with the protective function of MnSOD, developing APP/PS1 neurons have increased MnSOD protein and activity, indicating an adaptive response to oxidative stress in developing neurons. In contrast, mature APP/PS1 neurons exhibited lower MnSOD levels compared with mature WT/WT neurons indicating that mature APP/PS1 neurons lost the adaptive response. Moreover, mature APP/PS1 neurons had more co-localization of MnSOD with nitrotyrosine indicating a greater inhibition of MnSOD by nitrotyrosine. Overexpression of MnSOD or addition of MnTE-2-PyP(5+) (SOD mimetic) protected against beta-amyloid-induced neuronal death and improved mitochondrial respiratory function. Together, the results demonstrate that compensatory induction of MnSOD in response to an early increase in oxidative stress protects developing neurons against beta-amyloid toxicity. However, continuing development of neurons under oxidative damage conditions may suppress the expression of MnSOD and enhance cell death in mature neurons.     

超氧化物歧化酶(Val16Ala)基因的克隆及其真核表达载体的构建

目的获得锰超氧化物歧化酶(MnSOD)基因并进行Val16Ala(GTT→GCT)位点的定点突变,构建MnSOD(Val)及MnSOD(Ala)基因的真核表达载体。方法采用RT-PCR法从人乳腺癌细胞MCF-7中扩增MnSOD(Val)基因;PCR引物延伸法对Val16Ala进行定点突变以获得MnSOD(Ala)基因;通过EcoRⅠ+XhoⅠ双酶切PCR产物与相应质粒pEGFP-N1连接构建两基因的真核表达载体pEGFP-N1-MnSOD(Val)和pEGFP-N1-MnSOD(Ala)。结果突变位点经测序证明正确,重组质粒经双酶切及测序鉴定证明正确。结论本实验成功获得了MnSOD(Val)及MnSOD(Ala)基因并成功构建了两基因的真核表达载体。     

Antioxidant enzyme activities are not broadly correlated with longevity in 14 vertebrate endotherm species

The free radical theory of ageing posits that accrual of oxidative damage underlies the increased cellular, tissue and organ dysfunction and failure associated with advanced age. In support of this theory, cellular resistance to oxidative stress is highly correlated with life span, suggesting that prevention or repair of oxidative damage might indeed be essential for longevity. To test the hypothesis that the prevention of oxidative damage underlies longevity, we measured the activities of the five major intracellular antioxidant enzymes in brain, heart and liver tissue of 14 mammalian and avian species with maximum life spans (MLSPs) ranging from 3 years to over 100 years. Our data set included Snell dwarf mice in which life span is increased by ∼50% compared to their normal littermates. We found that CuZn superoxide dismutase, the major cytosolic superoxide dismutase, showed no correlation with MLSP in any of the three organs. Similarly, neither glutathione peroxidase nor glutathione reductase activities correlated with MLSP. MnSOD, the sole mitochondrial superoxide dismutase in mammals and birds, was positively correlated with MLSP only for brain tissue. This same trend was observed for catalase. For all correlational data, effects of body mass and phylogenetic relatedness were removed using residual analysis and Felsenstein’s phylogenetically independent contrasts. Our results are not consistent with a causal role for intracellular antioxidant enzymes in longevity, similar to recent reports from studies utilising genetic modifications of mice (Pérez et al., Biochim Biophys Acta 1790:1005–1014, 2009). However, our results indicate a specific augmentation of reactive oxygen species neutralising activities in brain associated with longevity.     

利多卡因联合庆大霉素含漱对小儿鼾症术后疼痛及8-iso-PG、MnSOD水平的影响

目的观察利多卡因联合庆大霉素含漱对小儿鼾症术后疼痛及8-异构前列腺素(8-iso-PG)、锰超氧化物歧化酶(MnSOD)水平的影响。方法前瞻性选取阜阳市人民医院耳鼻咽喉头颈外科于2019年3月至2020年3月收治的小儿鼾症患者100例,所有患者均择期在气管插管麻醉下行扁桃体和(或)腺样体切除术治疗。根据奇偶数分组法分为两组,其中对照组50例术后给予冰袋冰敷等常规处理,同时联合0.9%氯化钠溶液含漱作为安慰剂,观察组50例术后在常规处理基础上给予利多卡因联合庆大霉素含漱。记录两组术后疼痛程度、咽部黏膜消肿时间、首次进流食时间、住院时间和并发症情况,检测两组8-iso-PG、MnSOD的水平。结果观察组术后24、48、72 h时的疼痛视觉模拟(VAS)评分分别为(4.12±0.54)、(3.24±0.43)、(2.32±0.34)分,均明显低于对照组[(5.08±0.51)、(4.18±0.47)、(3.51±0.42)分],差异均有统计学意义(P<0.05)。观察组咽部黏膜消肿时间、首次进流食时间、住院时间为(28.89±3.64)h、(4.91±0.86)d、(5.04±0.91)d,均短于对照组[(33.05±4.51)h、(5.85±1.04)d、(5.91±1.13)d],差异均有统计学意义(P<0.05)。术后72 h,观察组8-iso-PG为(107.25±16.42)ng/L,显著低于对照组[(121.33±18.56)ng/L],MnSOD为(6.58±1.21)U/mL,显著高于对照组[(6.04±1.14)U/mL],差异均有统计学意义(P<0.05)。观察组术后发热和总并发症的发生率分别为4.00%和6.00%,低于对照组(16.00%、28.00%),但总出血、饮水反流、感染的发生率与对照组比较,差异无统计学意义(P>0.05)。结论利多卡因联合庆大霉素含漱可有效减轻小儿鼾症术后的疼痛程度,减轻机体应激反应,促进术后康复,且可降低并发症的发生。