Mucosal reactive oxygen species production in oesophagitis and Barrett's oesophagus.

Reactive oxygen species (ROS) produced by inflammatory cells can contribute to tissue destruction. ROS have been implicated in various gastrointestinal abnormalities, including the acid related peptic diseases. Although the development of oesophagitis and Barrett's columnar epithelium is associated with prolonged reflux of gastric acid, the exact mechanism by which tissue damage occurs is not known. To discover if ROS are involved in damage to the oesophageal mucosa, this study measured in vitro the mucosal ROS concentrations of biopsied mucosal samples taken from patients with reflux oesophagitis using luminol enhanced chemiluminescence (LECL). Mucosal biopsy specimens were taken from 83 patients: 19 with normal oesophageal mucosa (group I); 20 with macroscopic oesophagitis (group II); 20 with biopsy confirmed Barrett's epithelium without macroscopic oesophagitis (group III); and 24 with Barrett's epithelium with macroscopic oesophagitis (group IV). The mucosa from patients exhibited significantly higher LECL values than the mucosa from controls. But, there were no significant differences between groups II, III, and IV. Addition of the myeloperoxidase inhibitor, azide, or the hydrogen peroxide scavenger, catalase, to the tissue suspension caused a decrease in LECL values of 32% and 45%, respectively, suggesting that neutrophils--although important--are not the only source of mucosal LECL. These data are consistent with the proposal that ROS play an important part in the tissue injury associated with oesophagitis and Barrett's columnar epithelium.     

醛固酮对脂肪细胞因子表达及活性氧簇生成的影响

目的 探讨醛固酮对3T3-L1脂肪细胞脂肪细胞因子表达、分泌,活性氧簇(ROS)生成水平的影响.方法 诱导分化成熟的3T3-L1脂肪细胞经醛固酮(1μmol/L)孵育4h、24h,实时定量PCR检测脂肪细胞因子脂联素、白细胞介素-6(IL-6)、纤溶酶原激活物抑制剂-1(PAI-1)、单核细胞趋化蛋白-1( MCP-1...     

雌激素与活性氧

大量证据表明活性氧(ROS)对心脑血管疾病的发生和发展有重要影响。它可以直接氧化膜脂质和DNA,造成细胞氧化损伤和异常;同时还作为信使参与细胞各种生理和病理活动,例如调节基因表达和信号转导。近几年,雌激素对心脑血管疾病的保护作用越来越受到人们的重视,它主要参与细胞内的氧化应激反应,但在某些方面也存在争议。     

Metformin decreases intracellular production of reactive oxygen species in aortic endothelial cells

Beyond its antidiabetic activity justifying its use in the treatment of the type 2 diabetes, metformin (MET [dimethylguanidine, Glucophage]) has been shown to exhibit antioxidant properties in vitro, which could contribute to limit the deleterious vascular complications of diabetes. We investigated whether MET, at the pharmacological level of 10 -5 mol/L, was able to modulate intracellular production of reactive oxygen species (ROS) both in quiescent bovine aortic endothelial cells (BAECs) and in BAECs stimulated by a short incubation with high levels of glucose (30 mmol/L, 2 hours) or angiotensin II (10 -7 mol/L, 1 hour). Intracellular ROS production was measured by fluorescence of the DCF (2,7-dichlorodihydrofluorescein) probe. Our results showed that MET was able to reduce the intracellular production of ROS in both nonstimulated BAECs (-20%, P < .05) and BAEC stimulated by high levels of glucose or angiotensin II (-28% and -72%, respectively, P < .01). Experiments performed in the presence of the nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase inhibitor apocynin or the respiratory mitochondrial chain inhibitor rotenone indicated that MET exerted its effect partly through an inhibition of the formation of ROS produced mainly by NAD(P)H oxidase and also, to a lesser extent, by the respiratory mitochondrial chain.     

Neutrophil migration and production of reactive oxygen species during treatment with a fully human anti-tumor necrosis factor-alpha monoclonal antibody in patients with rheumatoid arthritis

OBJECTIVE: To evaluate the effects of therapy with a fully human anti-tumor necrosis factor (TNF)-alpha monoclonal antibody on the production of superoxide and other reactive oxygen species (ROS) and on the migration capacity of neutrophils in patients with rheumatoid arthritis (RA). METHODS: A total of 29 patients with active RA and 25 healthy controls participated. Assessments were performed at baseline and 2 weeks after the first administration of anti-TNF-alpha. The production of ROS was studied in unstimulated conditions and after stimulation of receptor dependent (serum treated zymosan, STZ) and receptor independent (phorbol mystrate acetate, PMA) pathways by luminol enhanced chemiluminescence. As well, the PMA induced burst production of superoxide was measured using the cytochrome-c reduction assay. Potential changes in neutrophil migration to joints were assessed by scintigraphy with autologous leukocytes. RESULTS: Baseline production of ROS (both spontaneously and after STZ stimulation) and superoxide and the ex vivo chemotaxis were similar in RA patients (n = 25) and controls (n = 25) and remained unchanged after administration of anti-TNF-alpha. The production of ROS after PMA stimulation was slightly higher in patients than in controls (p = 0.04) and this difference disappeared 2 weeks after the first dose of anti-TNF-alpha (p < 0.05). The scintigraphic study showed that a single dose of anti-TNF-alpha, but not placebo, markedly decreased the influx of leukocytes to inflamed joints. CONCLUSION: In patients with RA, anti-TNF-alpha therapy rapidly decreases the influx of leukocytes into inflamed joints but does not impair neutrophil chemotaxis and production of ROS.     

Hemoglobin potentiates the production of reactive oxygen species by alveolar macrophages

The objectives of this investigation were (1) to determine the effects of hemoglobin on the production of reactive oxygen species by activated rat alveolar macrophages, (2) to determine a possible mechanism for these effects, and (3) to determine which part of the hemoglobin molecule is responsible for these effects. Production of reactive oxygen species by phorbol myristate acetate (PMA)-stimulated cells was assessed by measuring luminol-enhanced chemiluminescence (CL). Hemoglobin enhances PMA-stimulated CL in a dose-dependent manner. The effect is maximal at 0.5-1.0 microM hemoglobin where PMA-induced CL is increased by approximately 20-fold. Superoxide anion release from PMA-stimulated cells is not affected by hemoglobin. However, the hemoglobin-induced enhancement of PMA-stimulated CL is inhibited by superoxide dismutase, catalase, dimethylthiourea, or deferoxamine. These results suggest that hydroxyl radical may be formed from hydrogen peroxide which is derived from superoxide anion. Measurements of electron spin resonance spectra following spin trapping of radicals verify that hydroxyl radicals are produced by the cells in the presence of PMA and hemoglobin. The hemoglobin effects appear to require iron in a protoporphyrin complex, because hemin stimulates PMA-induced CL, whereas neither ferrous nor ferric iron has any effect. These findings taken together suggest that hemoglobin can act as a biological Fenton reagent to enhance the production of reactive oxygen species from alveolar macrophages and potentially contribute to lung damage during leakage of blood into the alveolar spaces.     

Nitroglycerine causes mitochondrial reactive oxygen species production: in vitro mechanistic insights

BACKGROUND: Nitroglycerine (GTN) is an organic nitrate that has been used for more than 100 years. Despite its widespread clinical use, several aspects of the pharmacology of GTN remain elusive. In a recent study, the authors of the present study showed that GTN causes opening of the mitochondrial permeability transition pore (mPTP) and mitochondrial production of reactive oxygen species (ROS). OBJECTIVE: In the present study, it was tested whether GTN-induced ROS production depends on mitochondrial potassium ATP-dependent channel or mPTP opening, and/or GTN biotransformation. METHODS AND RESULTS: Isolated rat heart mitochondria were incubated with succinate (a substrate for complex II) and GTN, causing immediate ROS production, as manifested by chemiluminescence. This ROS production was prevented by concomitant vitamin C incubation. Conversely, inhibitors of potassium ATP-dependent channels, mPTP opening or of GTN biotransformation did not modify ROS production. CONCLUSIONS: GTN triggers mitochondrial ROS production independently of the opening of mitochondrial channels and/or of GTN biotransformation. The present data, coupled with previous evidence published by the same authors that GTN causes opening of mPTPs, provide further evidence on the pharmacology of GTN. It is proposed that GTN causes direct uncoupling of the respiratory chain, which determines ROS production and subsequent mPTP opening. The clinical implications of these findings are also discussed.     

Long-lived Indy induces reduced mitochondrial reactive oxygen species production and oxidative damage

Decreased Indy activity extends lifespan in D. melanogaster without significant reduction in fecundity, metabolic rate, or locomotion. To understand the underlying mechanisms leading to lifespan extension in this mutant strain, we compared the genome-wide gene expression changes in the head and thorax of adult Indy mutant with control flies over the course of their lifespan. A signature enrichment analysis of metabolic and signaling pathways revealed that expression levels of genes in the oxidative phosphorylation pathway are significantly lower in Indy starting at day 20. We confirmed experimentally that complexes I and III of the electron transport chain have lower enzyme activity in Indy long-lived flies by Day 20 and predicted that reactive oxygen species (ROS) production in mitochondria could be reduced. Consistently, we found that both ROS production and protein damage are reduced in Indy with respect to control. However, we did not detect significant differences in total ATP, a phenotype that could be explained by our finding of a higher mitochondrial density in Indy mutants. Thus, one potential mechanism by which Indy mutants extend life span could be through an alteration in mitochondrial physiology leading to an increased efficiency in the ATP/ROS ratio.     

Differential production of reactive oxygen species in distinct brain regions of hypoglycemic mice

Hypoglycemia is a serious complication of insulin therapy in patients suffering from type 1 Diabetes Mellitus. Severe hypoglycemia leading to coma (isoelectricity) induces massive neuronal death in vulnerable brain regions such as the hippocampus, the striatum and the cerebral cortex. It has been suggested that the production of reactive oxygen species (ROS) and oxidative stress is involved in hypoglycemic brain damage, and that ROS generation is stimulated by glucose reintroduction (GR) after the hypoglycemic coma. However, the distribution of ROS in discrete brain regions has not been studied in detail. Using the oxidation sensitive marker dihydroethidium (DHE) we have investigated the distribution of ROS in different regions of the mouse brain during prolonged severe hypoglycemia without isoelectricity, as well as the effect of GR on ROS levels. Results show that ROS generation increases in the hippocampus, the cerebral cortex and the striatum after prolonged severe hypoglycemia before the coma. The hippocampus showed the largest increases in ROS levels. GR further stimulated ROS production in the hippocampus and the striatum while in the cerebral cortex, only the somatosensory and parietal areas were significantly affected by GR. Results suggest that ROS are differentially produced during the hypoglycemic insult and that a different response to GR is present among distinct brain regions.     

Nuclear factor-kappaB activation on the reactive oxygen species in acute necrotizing pancreatitic rats

AIM: To investigate the potential role of nuclear factor kappa-B (NF-KB) activation on the reactive oxygen species in rat acute necrotizing pancreatitis (ANP) and to assess the effect of pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-KB). METHODS: Rat ANP model was established by retrograde injection of 5% sodium taurocholate into biliopancreatic duct. Rats were randomly assigned to three groups (10 rats each): Control group, ANP group and PDTC group. At the 6th h of the model, the changes of the serum amylase, nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD) and pancreatic morphological damage were observed. The expressions of inducible nitric oxide (iNOS) were observed by SP immunohistochemistry. And the expressions of NF-κB p65 subunit mRNA were observed by hybridization in situ. RESULTS: Serum amylase and NO level decreased significantly in ANP group as compared with PDTC administrated group [(7170.40±1308.63) U/L vs(4 074.10±1719.78) U/L, P<0.05], [(76.95±9.04) μmol/L vs(65.18±9.02)μmol/L, P<0.05] respectively. MDA in both ANP and PDTC group rose significantly over that in control group [(9.88±1.52) nmol/L, (8.60±1.41) nmol/L, vs(6.04±1.78) nmol/L, P<0.05], while there was no significant difference between them. SOD levels in both ANP and PDTC group underwent a significant decrease as compared with that in control t(3 214.59±297.74) NU/mL, (3 260.62±229.44) NU/mL, vs(3 977.80±309.09) NU/mL, P<0.05], but there was no significant difference between them. Though they were still higher than those in Control group, pancreas destruction was slighter in PDTC group, iNOS expression and NF-κB p65 subunit mRNA expression were lower in PDTC group as compared with ANP group. CONCLUSION: We conclude that correlation among NF-KB activation, serum amylase, reactive oxygen species level and tissue damage suggests a key role of NF-κB in the pathogenesis of ANP. Inhibition of NF-κB activation may reverse the pancreatic damage of rat ANP and the production of reactive oxygen species.     

The effects of asthma medications on reactive oxygen species production in human monocytes

Objective: Asthma is a chronic inflammatory airway disease induced by many environmental factors. The inhalation of allergens and pollutants promotes the production of reactive oxygen species (ROS) leading to airway inflammation, hyper-responsiveness, and remodeling in allergic asthma. The effects of asthma medications on ROS production are unclear. The present study investigated the anti-ROS effects of current asthma medications including inhaled corticosteroid (ICS; budesonide and fluticasone), leukotriene receptor antagonist (LTRA; montelukast), long-acting β2 agonists (LABAs; salmeterol and formoterol), and a new extra-LABA (indacaterol). Methods: The human monocyte cell line THP-1 cells were pre-treated with different concentrations of the asthma medications at different time points after hydrogen peroxide (H₂O₂) stimulation. H₂O₂ production was measured with DCFH-DA by flow cytometry. Results: Montelukast, fluticasone, and salmeterol suppressed H₂O₂-induced ROS production. Indacaterol enhanced H₂O₂-induced ROS production. Budesonide and formoterol alone had no anti-ROS effects, but the combination of these two drugs significantly suppressed H₂O₂-induced ROS production. Conclusions: Different asthma medications have different anti-ROS effects on monocytes. The combination therapy with LABA and ICS seemed not to be the only choice for asthma control. Montelukast may also be a good supplemental treatment for the poorly controlled asthma because of its powerful anti-ROS effects. Our findings provide a novel therapeutic view in asthma.     

Influence of dichloromethylene diphosphonate on reactive oxygen species production by human neutrophils

Summary Biphosphonates suppress bone destruction in various diseases. Several studies have demonstrated the potential use of biphosphonates in arthritis. The results of these studies indicate that the effectiveness of the biphosphonates, for inhibiting the arthritic process, is related to their antiresorptive properties. It has been shown that the generation of reactive oxygen species is associated with the formation of new osteoclasts and enhanced bone resorption. We studied the effects of the dichloromethylene diphosphonate on the reactive oxygen species production by activated polymorphonuclear leucocytes, measured by chemiluminescence. Our results indicate a dose-dependent inhibitory effect of dichloromethylene diphosphonate on reactive oxygen species production by polymorphonuclear leucocytes stimulated with N-formil-methionyl-leucyl-phenylalanine, the calcium ionophore A23187 and phorbol myristate acetate. The mechanisms by which this biphosphonate inhibits the reactive oxygen species production by activated polymorphonuclear leucocytes are discussed.     

Mitochondrial oxygen consumption and reactive oxygen species production are independently modulated: implications for aging studies

Various recent investigations relevant to the study of aging mechanisms have recently found that increases in longevity during dietary restriction can occur together with lack of decreases or even increases in O2 consumption. This is frequently interpreted as contradictory with the mitochondrial free radical theory of aging. But this is based on the erroneous assumption that increasing O2 consumption must increase the rate of mitochondrial oxygen radical generation. Here it is shown that the opposite occurs in many important situations. Strong decreases in absolute and relative (per unit of O2 consumed) mitochondrial oxygen radical production occur during aerobic exercise bouts, chronic exercise training, and hyperthyroidism, and notably, during dietary restriction. Mitochondrial oxygen radical generation is also lower in long-lived birds than in short-lived mammals of similar body size and metabolic rate. Total rates of reactive oxygen species generation can also vary between tissues in a way not linked to their differences in oxygen consumption. All this indicates that mitochondrial reactive oxygen species (ROS) production is not a simple byproduct of mitochondrial respiration. Instead, it is regulated independently of O2 consumption in many different physiologic situations, tissues, and animal species. Thus, the apparently paradoxical increases in O2 consumption observed in some models of dietary restriction do not discredit the mitochondrial free radical theory of aging, and they can further strengthen it.