Mitochondrial depolarisation and oxidative stress in rheumatoid arthritis patients

ObjectivesTo investigate mitochondrial membrane integrity, lipid peroxidation and cytotoxicity in peripheral lymphocytes (PL) from rheumatoid arthritis (RA) patients.Design and methodsSouth African black RA patients (HIV^?) were recruited into the study. Mitochondrial membrane potential (Δψ_m) was analysed in PL using the JC-1 dye distribution assay and flow cytometry. Correlations between Δψ_m and clinical parameters were tested for statistical significance. Cytotoxicity (LDH) and lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) was also determined.ResultsOur findings show significantly elevated levels of cytotoxicity (p = 0.0029) and lipid peroxidation (p = 0.0030) in RA. A significantly higher percentage of circulating PL contained depolarised mitochondria (p = 0.0003) which correlated with disease activity and C-reactive protein levels in patients. Collapse of Δψ_m also negatively correlated to absolute lymphocyte counts (r = ? 0.4041; p = 0.0197).ConclusionThese findings suggest a possible role for mitochondrial membrane alterations in the pathology of RA.     

Mitochondrial oxidative stress after carbon monoxide hypoxia in the rat brain.

To better understand the mechanisms of tissue injury during and after carbon monoxide (CO) hypoxia, we studied the generation of partially reduced oxygen species (PROS) in the brains of rats subjected to 1% CO for 30 min, and then reoxygenated on air for 0-180 min. By determining H2O2-dependent inactivation of catalase in the presence of 3-amino-1,2,4-triazole (ATZ), we found increased H2O2 production in the forebrain after reoxygenation. The localization of catalase to brain microperoxisomes indicated an intracellular site of H2O2 production; subsequent studies of forebrain mitochondria isolated during and after CO hypoxia implicated nearby mitochondria as the source of H2O2. In the mitochondria, two periods of PROS production were indicated by decreases in the ratio of reduced to oxidized glutathione (GSH/GSSG). These periods of oxidative stress occurred immediately after CO exposure and 120 min after reoxygenation, as indicated by 50 and 43% decreases in GSH/GSSG, respectively. The glutathione depletion data were supported by studies of hydroxyl radical generation using a salicylate probe. The salicylate hydroxylation products, 2,3 and 2,5-dihydroxybenzoic acid (DHBA), were detected in mitochondria from CO exposed rats in significantly increased amounts during the same time intervals as decreases in GSH/GSSG. The DHBA products were increased 3.4-fold immediately after CO exposure, and threefold after 120 min reoxygenation. Because these indications of oxidative stress were not prominent in the postmitochondrial fraction, we propose that PROS generated in the brain after CO hypoxia originate primarily from mitochondria. These PROS may contribute to CO-mediated neuronal damage during reoxygenation after severe CO intoxication.     

Mitochondrial metabolism mediates oxidative stress and inflammation in fatty liver

Mitochondria are critical for respiration in all tissues; however, in liver, these organelles also accommodate high-capacity anaplerotic/cataplerotic pathways that are essential to gluconeogenesis and other biosynthetic activities. During nonalcoholic fatty liver disease (NAFLD), mitochondria also produce ROS that damage hepatocytes, trigger inflammation, and contribute to insulin resistance. Here, we provide several lines of evidence indicating that induction of biosynthesis through hepatic anaplerotic/cataplerotic pathways is energetically backed by elevated oxidative metabolism and hence contributes to oxidative stress and inflammation during NAFLD. First, in murine livers, elevation of fatty acid delivery not only induced oxidative metabolism, but also amplified anaplerosis/cataplerosis and caused a proportional rise in oxidative stress and inflammation. Second, loss of anaplerosis/cataplerosis via genetic knockdown of phosphoenolpyruvate carboxykinase 1 (Pck1) prevented fatty acid–induced rise in oxidative flux, oxidative stress, and inflammation. Flux appeared to be regulated by redox state, energy charge, and metabolite concentration, which may also amplify antioxidant pathways. Third, preventing elevated oxidative metabolism with metformin also normalized hepatic anaplerosis/cataplerosis and reduced markers of inflammation. Finally, independent histological grades in human NAFLD biopsies were proportional to oxidative flux. Thus, hepatic oxidative stress and inflammation are associated with elevated oxidative metabolism during an obesogenic diet, and this link may be provoked by increased work through anabolic pathways.     

Endothelial dysfunction and increased oxidative stress in mitochondrial diseases

MDs (mitochondrial diseases) are a clinically heterogeneous group of disorders characterized by impairment of the respiratory chain function with altered oxidative phosphorylation. We tested the hypothesis that the function of vascular endothelium is affected by increased oxidative stress in MDs. A total of 12 patients with MDs and pair-matched controls were studied. Endothelial function was assessed by measuring FMD (flow-mediated vasodilation) of brachial and common femoral arteries. The test was repeated after vitamin C (500 mg, twice a day) and E (400 mg, once a day) supplementation for 30 days and 90 days after vitamin withdrawal. FMD was reduced in patients compared with controls [AUC/τ (time-averaged area under the curve) for the brachial artery, 1.05±0.24 compared with 4.19±0.59% respectively, P<0.001; AUC/τ for the femoral artery, 0.98±0.19 compared with 2.36±0.29% respectively, P=0.001; values are means±S.E.M.] and correlated (brachial artery) with plasma lactate (r=-0.63, P<0.01). Urinary 8-iso-PGF2α (8-iso-prostaglandin F2α) was higher in patients than controls (505.6±85.9 compared with 302.5±38.7 pg/mg of creatinine; P<0.05) and correlated with plasma lactate (r=0.70, P<0.05). Immunohistochemical analysis showed 8-iso-PGF2α staining in MD-affected striated muscle cells and in blood vessels in muscle biopsies of patients. Antioxidant vitamins transiently restored FMD in patients [ΔAUC/τ (change in AUC/τ) for the brachial artery, +1.38±0.49%, P<0.05; ΔAUC/τ for the femoral artery, +0.98±0.24%, P<0.01] but had no effect on FMD in controls (brachial artery, -1.3±0.63%; and common femoral artery, -0.58±0.30%), thus abolishing the differences between patients and controls. The results of the present study indicate that oxidative stress is increased and is, at least partly, responsible for endothelial dysfunction in MDs.     

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.     

Mitochondrial antibodies--heterogeneity and effects on mitochondrial respiration.

Sera containing antimitochondrial antibodies (MTA) were tested for binding to intact mitochondria, sonic fragments (SMP), Complex I + III and to oligomycin sensitive ATPase (OS-ATPase) from bovine heart by indirect immunofluorescence. Antigens capable of binding to MTA were present in mitochondria and its fragments tested. Maximum binding was observed with SMP. It appears that one or more antigen binding sites are present on the matrix side of the inner mitochondrial membrane or some location exterior to the inner membrane. Normal human serum or sera containing MTA did not effect the respiration of intact mitochondria or sonic particles. However, NADH-cytochrome c reductase activity of complex I + III was enhanced by 10-60% by sera containing MTA antibodies.     

荧光实时定量PCR检测线粒体DNA氧化损伤方法初探

目的体外构建DNA氧化损伤模型,荧光实时定量PCR检测线粒体DNA氧化损伤。方法体外应用亚甲蓝联合可见光(MBL)方法建立DNA氧化损伤模型,通过8-羟基鸟嘌呤DNA糖苷酶(OGG1)特异性切割氧化损伤位点8-羟基鸟嘌呤(8-oxoG),运用荧光实时定量PCR法检测不同比例混匀的OGG1酶切与未酶切的DNA氧化损伤模板。结果成功构建体外氧化损伤DNA模型,OGG1酶能特异切割氧化损伤位点;OGG1酶切DNA在定量PCR体系模板中所占比例,与线粒体DNA编码基因COⅡ扩增Ct值呈正相关。结论自制OGG1酶具有良好的生物活性,可以联合荧光实时定量PCR检测DNA氧化损伤。     

Mitochondrial redox studies of oxidative stress in kidneys from diabetic mice

Chronic hyperglycemia during diabetes leads to increased production of reactive oxygen species (ROS) and increased oxidative stress (OS). Here we investigated whether changes in the metabolic state can be used as a marker of OS progression in kidneys. We examined redox states of kidneys from diabetic mice, Akita(/+) and Akita(/+);TSP1(-/-) mice (Akita mice lacking thrombospondin-1, TSP1) with increasing duration of diabetes. OS as measured by mitochondrial redox ratio (NADH/FAD) was detectable shortly after the onset of diabetes and further increased with the duration of diabetes. Thus, cryo fluorescence redox imaging was used as a quantitative marker of OS progression in kidneys from diabetic mice and demonstrated that alterations in the oxidative state of kidneys occur during the early stages of diabetes.     

Endothelial mitochondrial oxidative stress determines podocyte depletion in segmental glomerulosclerosis

Focal segmental glomerular sclerosis (FSGS) is a primary kidney disease that is commonly associated with proteinuria and progressive loss of glomerular function, leading to development of chronic kidney disease (CKD). FSGS is characterized by podocyte injury and depletion and collapse of glomerular capillary segments. Progression of FSGS is associated with TGF-β activation in podocytes; however, it is not clear how TGF-β signaling promotes disease. Here, we determined that podocyte-specific activation of TGF-β signaling in transgenic mice and BALB/c mice with Adriamycin-induced glomerulosclerosis is associated with endothelin-1 (EDN1) release by podocytes, which mediates mitochondrial oxidative stress and dysfunction in adjacent endothelial cells via paracrine EDN1 receptor type A (EDNRA) activation. Endothelial dysfunction promoted podocyte apoptosis, and inhibition of EDNRA or scavenging of mitochondrial-targeted ROS prevented podocyte loss, albuminuria, glomerulosclerosis, and renal failure. We confirmed reciprocal crosstalk between podocytes and endothelial cells in a coculture system. Biopsies from patients with FSGS exhibited increased mitochondrial DNA damage, consistent with EDNRA-mediated glomerular endothelial mitochondrial oxidative stress. Our studies indicate that segmental glomerulosclerosis develops as a result of podocyte-endothelial crosstalk mediated by EDN1/EDNRA-dependent mitochondrial dysfunction and suggest that targeting the reciprocal interaction between podocytes and endothelia may provide opportunities for therapeutic intervention in FSGS.     

线粒体功能障碍和氧化应激在脂肪肝中的作用机制

目前各种病因引起的肝脏脂肪变性甚至发展为脂肪性肝炎或脂肪性肝硬化成为当今严重的公共卫生及医疗问题。氧化应激、NO信号通路的中断和线粒体功能障碍等被认为是加速脂肪变性和启动脂肪肝和纤维化进程的关键机制。线粒体损伤和氧化应激之间相互作用的复杂机制,也使得临床治疗脂肪性肝炎效果不佳。因此找到一种多基因、多靶点安全有效阻断氧化应激和线粒体损伤的分子靶向药物和治疗方案成为了学术界的难题。     

Neurodegenerative diseases and oxidative stress.

Oxidative stress is now recognized as accountable for redox regulation involving reactive oxygen species (ROS) and reactive nitrogen species (RNS). Its role is pivotal for the modulation of critical cellular functions, notably for neurons astrocytes and microglia, such as apoptosis program activation, and ion transport, calcium mobilization, involved in excitotoxicity. Excitotoxicity and apoptosis are the two main causes of neuronal death. The role of mitochondria in apoptosis is crucial. Multiple apoptotic pathways emanate from the mitochondria. The respiratory chain of mitochondria that by oxidative phosphorylation, is the fount of cellular energy, i.e. ATP synthesis, is responsible for most of ROS and notably the first produced, superoxide anion (O(2)(;-)). Mitochondrial dysfunction, i.e. cell energy impairment, apoptosis and overproduction of ROS, is a final common pathogenic mechanism in aging and in neurodegenerative disease such as Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Nitric oxide (NO(;)), an RNS, which can be produced by three isoforms of NO-synthase in brain, plays a prominent role. The research on the genetics of inherited forms notably ALS, AD, PD, has improved our understanding of the pathobiology of the sporadic forms of neurodegenerative diseases or of aging of the brain. ROS and RNS, i.e. oxidative stress, are not the origin of neuronal death. The cascade of events that leads to neurons, death is complex. In addition to mitochondrial dysfunction (apoptosis), excitotoxicity, oxidative stress (inflammation), the mechanisms from gene to disease involve also protein misfolding leading to aggregates and proteasome dysfunction on ubiquinited material.     

Effects of carvedilol and its analog BM-910228 on mitochondrial function and oxidative stress

The antioxidant effects of carvedilol and its analog BM-910228 (also known as SB 211475) were studied in rat liver mitochondria as well as their action on mitochondrial bioenergetics. Carvedilol and BM-910228 inhibited ADP/Fe(2+)-initiated lipid peroxidation (measured in mitochondrial membranes as thiobarbituric acid reactive substances and oxygen consumption) with IC(50) values of 10.9 and 0. 33 microM, respectively. Under the same conditions, the IC(50) value for Trolox C was 18.8 microM. At the same concentration range showing antioxidant activity both compounds prevent the collapse of transmembranar electric potential induced by ADP/Fe(2+) on respiring mitochondria. Furthermore, both carvedilol and BM-910228 do not display toxic effects on mitochondria up to the concentration showing maximal antioxidant effects ( approximately 40 microM for carvedilol and approximately 1 microM for BM-910228). At higher concentrations of carvedilol (>40 microM), however, the phosphorylation efficiency of mitochondria is depressed as deduced from a decrease in respiratory control and in the ADP/oxygen ratio. The Brand approach was used to assess the effects of carvedilol on oxidative phosphorylation. We found that carvedilol stimulated membrane proton leak and inhibited substrate oxidation, but had no measurable effect on phosphorylation reactions. Because carvedilol exerts its antioxidant properties for nontoxic concentrations, its therapeutic interest is reinforced because it may potentially prevent mitochondrial dysfunctions associated to cell death in several pathophysiological states where excessive production of reactive oxygen species by mitochondria is well documented (e.g., ischemia/reperfusion). Additionally, its hydroxylated analog BM-910228 with notable superior antioxidant activity may significantly contribute to the known therapeutic effects of carvedilol.     

Increased DNA damage and oxidative stress in patients with rheumatoid arthritis

OBJECTIVES: Oxidative stress has been described as an important mechanism that underlies chronic inflammation in rheumatoid arthritis (RA). The aim of the study was to investigate the peripheral DNA damage, total antioxidant status (TAS), and total oxidative status (TOS) in patients with RA. DESIGN AND METHODS: The study population contained 25 patients with RA and 26 healthy controls. DNA damage was assessed by alkaline comet assay in peripheral lymphocyte, plasma levels of total antioxidant status (TAS) and total oxidative status (TOS) were determined, and OSI was calculated using a novel automated measurement method. Disease activity was evaluated by DAS-28 score. RESULTS: In RA patients, DNA damage was significantly higher than in controls (20.0+/-9.6 AU, 7.6+/-4.3 AU; p<0.001). Plasma TOS and OSI were higher in patients than in healthy controls (9.9+/-2.6 vs. 7.3+/-1.1, p<0.001; 1.04+/-0.4 vs. 0.7+/-0.1, p<0.001, respectively). Plasma TAS level in patients was lower than in healthy controls (0.9+/-0.7 vs. 1.01+/-0.7, p<0.001). DNA damage was correlated with TOS, OSI, and DAS-28 scores (r=0.682, p<0.001; r=0.753, p<0.001; r=0.519, p=0.008, respectively). CONCLUSIONS: The findings indicated that lymphocyte DNA damage level increases in patients with RA. Elevated DNA damage may be related with increased oxidative stress and decreased antioxidant capacity. However, the mechanism of this association, and whether it is direct or indirect, remains to be explored.     

Mitochondrial DNA and disease

The small circle of mitochondrial DNA (mtDNA) present in all human cells has proven to be a veritable Pandora's box of pathogenic mutations and rearrangements. In this review, we summarize the distinctive rules of mitochondrial genetics (maternal inheritance, mitotic segregation, heteroplasmy and threshold effect), stress the relatively high prevalence of mtDNA‐related diseases, and consider recent additions to the already long list of pathogenic mutations (especially mutations affecting protein‐coding genes). We then discuss more controversial issues, including the functional or pathological role of mtDNA haplotypes, the pathogenicity of homoplasmic mutations and the still largely obscure pathophysiology of mtDNA mutations.     

Mitochondrial DNA and aging

Among the numerous theories that explain the process of aging, the mitochondrial theory of aging has received the most attention. This theory states that electrons leaking from the ETC (electron transfer chain) reduce molecular oxygen to form O2*- (superoxide anion radicals). O2*-, through both enzymic and non-enzymic reactions, can cause the generation of other ROS (reactive oxygen species). The ensuing state of oxidative stress results in damage to ETC components and mtDNA (mitochondrial DNA), thus increasing further the production of ROS. Ultimately, this 'vicious cycle' leads to a physiological decline in function, or aging. This review focuses on recent developments in aging research related to the role played by mtDNA. Both supportive and contradictory evidence is discussed.     

Mitochondrial DNA and disease

The small circle of mitochondrial DNA (mtDNA) present in all human cells has proven to be a veritable Pandora's box of pathogenic mutations and rearrangements. In this review, we summarize the distinctive rules of mitochondrial genetics (maternal inheritance, mitotic segregation, heteroplasmy and threshold effect), stress the relatively high prevalence of mtDNA-related diseases, and consider recent additions to the already long list of pathogenic mutations (especially mutations affecting protein-coding genes). We then discuss more controversial issues, including the functional or pathological role of mtDNA haplotypes, the pathogenicity of homoplasmic mutations and the still largely obscure pathophysiology of mtDNA mutations.     

沉默囊性纤维化跨膜传导调节因子对大鼠海马神经元细胞线粒体功能及氧化应激的影响

目的探讨沉默囊性纤维化跨膜传导调节因子(cystic fibrosis transmembrane conductance regulator,CFTR)在大鼠海马神经元细胞线粒体功能及氧化应激中的作用。方法18只SD大鼠随机分为CFTR小干扰RNA(small interfering RNA,siRNA)组、阴性对照组、空白对照组各6只。分离3组海马神经元细胞,取对数生长期细胞进行实验。CFTR siRNA组神经元细胞转染CFTR siRNA,阴性对照组转染阴性对照siRNA,空白对照组不转染。转染后培养48 h,采用Western blot法检测3组神经元细胞线粒体CFTR蛋白相对表达量,JC-1荧光探针检测线粒体膜电位,荧光分光光度法检测线粒体活性氧(reactive oxygen species,ROS)和过氧化氢(hydrogen peroxide,H2O2)表达,氧电极法测定线粒体呼吸控制率(respiratory control rate,RCR),荧光素酶发光法检测线粒体三磷酸腺苷(adenosine triphosphate,ATP)浓度,高效液相色谱法检测线粒体谷胱甘肽(glutathione,GSH)和氧化型谷胱甘肽(oxidized glutathione,GSSG)表达。结果转染后培养48 h,CFTR siRNA组神经元细胞线粒体CFTR蛋白相对表达量(0.09±0.01)、线粒体膜电位[(247.16±34.28)mV]、ATP[(11.71±2.54)mol/g]、RCR(4.69±0.82)、GSH[(0.71±0.12)nmol/μg]、GSH/GSSG值(0.31±0.08)低于空白对照组[0.42±0.07、(432.18±56.04)mV、(24.18±3.64)mol/g、7.94±1.21、(1.62±0.23)nmol/μg、1.65±0.27]和阴性对照组[0.38±0.06、(434.07±52.13)mV、(22.97±3.43)mol/g、7.83±1.18、(1.57±0.21)nmol/μg、1.63±0.24](P<0.05),线粒体H2O2水平(1.73±0.11)高于空白对照组(1.00±0.02)和阴性对照组(1.08±0.06)(P<0.05);空白对照组神经元细胞线粒体CFTR蛋白相对表达量及线粒体膜电位、ATP、RCR、H2O2、GSH、GSH/GSSG值与阴性对照组比较差异均无统计学意义(P>0.05)。结论沉默大鼠神经元细胞线粒体CFTR可引起海马神经元细胞线粒体功能障碍,增强氧化应激反应。     

Effects of amphetamines on mitochondrial function: role of free radicals and oxidative stress

Amphetamine-like psychostimulants are associated with long-term decreases in markers for monoaminergic neurons, suggesting neuronal loss and/or damage within the brain. This long-term "toxicity" results from formation of free radicals, particularly reactive oxygen species (ROS) and reactive nitrogen species (RNS), although the mechanism(s) of ROS and RNS formation are unclear. Mitochondria are a major source of ROS and mitochondrial dysfunction has been linked to some neurodegenerative disorders. Amphetamines also inhibit mitochondrial function, although the mechanism involved in the inhibition is uncertain. This review coordinates findings on the multiple pathways for ROS and RNS and describes a hypothesis involving mitochondrial inhibition in the initiation of amphetamine-induced cellular necrosis.