Oxidative stress and ischaemia-reperfusion injury in the heart

Induction of brain natriuretic peptide and monocyte chemotactic protein-1 gene expression by oxidized low-density lipoprotein: relevance to ischemic heart failure

Brain natriuretic peptide (BNP) and monocyte chemotactic protein-1 (MCP-1) are biomarkers of heart failure (HF). The aim of the present study was to determine the role of oxidized low-density lipoprotein (Ox-LDL) in the induction of these biomarkers and the signaling pathways involved in vitro. Incubation of HL-1 cardiomyocytes and human myocytes with Ox-LDL induced the expression of BNP and MCP-1 genes, while native LDL had no effect. When peroxides associated with Ox-LDL were reduced to hydroxides, the ability to induce BNP and MCP-1 gene expression was abolished. Furthermore, exposure of HL-1 cells to ischemic conditions alone had no effect on BNP gene expression, while ischemia followed by reperfusion resulted in increased expression of BNP gene. Inhibitors of ERK and JNK inhibited the induction of BNP. Signaling array results suggested that the induction of both MAPK and NF-κB pathways is involved in the induction of BNP by Ox-LDL. These results suggest that Ox-LDL or peroxidized lipids formed in oxidatively stressed myocytes during ischemia-reperfusion injury may play a role in the induction of BNP and MCP-1.

Tidal height influences the levels of enzymatic antioxidant defences in Mytilus edulis

We investigated the potential variability of enzymatic antioxidant activities in blue mussels Mytilus edulis from a single intertidal population but living at different tidal heights. Activity levels of antioxidant enzymes (Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione transferase) were measured in the gills and digestive gland of mussels sampled at high shore (HS, air-exposure>6h/12h) and low shore (LS, air-exposure<2h/12h) of an intertidal zone (Yport, Normandie, France) for two consecutive autumns. In both tissues, levels of each enzymatic activity (except GST) were clearly higher in HS mussels than in LS for the two years. These results suggest an ability to acclimate the enzymatic antioxidant defences to the degree of undergone stress, confirming the importance of environmental conditions in the antioxidant responses. Therefore, the location of organisms on the shore should be taken into account in sampling for ecotoxicological studies.

Differential pattern of Cu/Zn superoxide dismutase isoforms in relation to tidal spatio-temporal changes in the blue mussel Mytilus edulis

Inducible antioxidant defences in marine organisms such as mussel bivalves are commonly used as biomarkers of pollutant-induced oxidative stress and their variations proposed as one of the biological effect measurements for assessment of contamination impact in aquatic environments. Among them, the copper/zinc superoxide dismutases (Cu/Zn-SODs) are metalloenzymes which play a key role in the protection of cells in case of oxidative stress. In order to observe possible variations of an antioxidant response in relation to tidal oscillations, the copper/zinc superoxide dismutase activity (Cu/Zn-SOD) was characterized in the digestive gland and gills of blue mussels sampled at high and low shore throughout the tidal cycle. Determination of SOD activity was performed on gels after isoelectro-focusing, allowing the revelation of three isoforms. In both tissues, high-shore mussels exhibited a higher level of total SOD activity than low-shore mussels. During emersion, a decrease of total SOD activity appeared in digestive gland for both groups. In high-shore mussels, the less acidic form contributed to 75% of the total activity, the second one to 20% and the more acidic one to 5% in both tissues before air exposure. During emersion, the relative contribution of the three isoforms to the total activity was markedly changed with a significant decrease in intensity of the first isoform and parallel increases in the two other ones. After re-immersion a progressive recovery of proportions of SOD isoforms was observed. In low-shore mussels, the relative contribution of the three isoforms to the total SOD activity showed similar changes. The observed variations could correspond to changes in the redox status of the mussels during tidal oscillations.

Urate oxidation during percutaneous transluminal coronary angioplasty and thrombolysis in patients with coronary artery disease

Thrombolysis and percutaneous transluminal coronary angioplasty (PTCA) are kinds of procedures that can be used to restore the blood flow of previously ischemic myocardium that can be the result of excessive production of reactive oxygen and nitrogen species, such as superoxide and hydroxyl radical, hypochlorous acid and peroxynitrite. Reaction of urate with some of these potent oxidants results in allantoin production. In this study, we measured the serum allantoin levels, an oxidation product of urate, and "in vivo" marker of free radical generation in reperfusion of ischemic myocardium. After an overnight fasting state, blood samples were collected from 35 patients with coronary occlusive diseases (7 women and 28 men) and 31 healthy subjects (8 women and 23 men). Serum allantoin and urate levels were measured by a GC-MS method. Serum allantoin levels of patients on PTCA therapy (mean+/-SD, 27.4 +/- 15.2 micromol/l) and thrombolytic therapy (24.6 +/- 8.6 micromol/l) were significantly higher than those of the patients without therapy (15.8 +/- 6.2 micromol/l, p < 0.05 with PTCA and p < 0.006 with thrombolysis) and healthy controls (12.6 +/- 6.3 micromol/l, p < 0.002 with PTCA and p < 0.0001 with thrombolysis). Although serum urate levels in PTCA (380.1 +/- 72.6 micromol/l) and thrombolysis (359.5 +/- 60.0 micromol/l) were higher than those in the non-therapy patients (336.6 +/- 53.8 micromol/l) and controls (318.3 +/- 81.0 micromol/l), there were no significant differences among groups (p > 0.05). The results of the study are consistent with others which have demonstrated, higher urate levels are associated with coronary occlusive diseases. Our data support the hypothesis that generation of ROS occurs during myocardial reperfusion. Increased allantoin levels may be used as an index of increased oxidative stress during reperfusion.