Protection against oxidative stress in liver of four different vertebrates

Serum miR-96-5p is a novel and non-invasive marker of acute myocardial infarction associated with coronary artery disease

Acute myocardial infarction (AMI) is a severe cardiovascular disease. AMI associated with coronary artery disease (AMI-CAD) is a subtype of AMI, composed of AMI patients caused by CAD. This study aimed to evaluate the diagnostic value of miR-96-5p in AMI induced by coronary artery disease. Expression of miR-96-5p and BCL2L13 was evaluated by serum samples and cells utilizing Western blot and RT-qPCR assays. The diagnostic value of miR-96-5p in AMI-CAD was analyzed with a receiver operating characteristic (ROC) curves. The correlation between miR-96-5p and BCL2L13 was examined by Spearman's correlation analysis. The level of oxidative stress and apoptosis were estimated via relative commercial kit, flow cytometry apoptosis assay and TUNEL staining assay. Our study discovered that miR-96-5p was down-regulated while BCL2L13 was up-regulated in patients with AMI-CAD. miR-96-5p was a potential diagnostic parameter, which may help distinguish AMI-CAD patients from healthy controls. In vitro experiments, miR-96-5p expression was down regulated while BCL2L13 was up-regulated in hypoxic cardiomyocytes. After confirming the targeted link of miR-96-5p to BCL2L13 using luciferase reporter and RNA pull down assays, we discovered that miR-96-5p overexpression may restore oxidative stress and cell apoptosis induced by hypoxia treatment in H9c2 cells; meanwhile, co-transfection with BCL2L13 overexpressing plasmid might partly countervail the ameliorative effects of miR-96-5p on oxidative stress and apoptosis. Collectively, miR-96-5p may function as a potential diagnostic biomarker for AMI-CAD patients, and the up-regulation of miR-96-5p would ameliorate AMI-associated cardiomyocytes injury by targeting BCL2L13, hence contributing to the clinical treatment of AMI-CAD.

Antioxidant metabolism of Xenopus laevis embryos during the first days of development

Reactive oxygen species (ROS) are formed and degraded in all aerobic organisms, but their role during embryonic development has not yet been well established. In this paper, we report the activities of various enzymes involved in antioxidant metabolism during the first 7 days of embryonic development of Xenopus laevis embryos. During the first two days of development, embryo antioxidant metabolism is based on catalase and superoxide dismutase activities. Later, the glutathione system is activated, and the activity of all the enzymes involved increases. The results presented in this study, together with previously reported data, support the hypothesis that antioxidant defences may include enzymes that are genetically regulated, while the other systems that appear to be environmentally modulated become relevant later in development, probably to protect embryos from environmental and toxic factors.

Oxidative DNA damage and antioxidant defenses in the European common lizard (Lacerta vivipara) in supercooled and frozen states

The European common lizard (Lacerta vivipara) tolerates long periods at sub-zero temperatures, either in the supercooled or the frozen state. Both physiological conditions limit oxygen availability to tissues, compelling lizards to cope with potential oxidative stress during the transition from ischemic/anoxic conditions to reperfusion with aerated blood during recovery. To determine whether antioxidant defenses are implicated in the survival of lizards when facing sub-zero temperatures, we monitored the activities of antioxidant enzymes and oxidative stress either during supercooling or during freezing exposures (20 h at -2.5 degrees C) and 24 h after thawing in two organs of lizards--muscle and liver. Supercooling induced a significant increase in the total SOD and GPx activity in muscle (by 67 and 157%, respectively), but freezing had almost no effect on enzyme activity, either in muscle or in liver. By contrast, thawed lizards exhibited higher GPx activity in both organs (a 133% increase in muscle and 59% increase in liver) and a significant decrease in liver catalase activity (a 47% difference between control and thawed lizards). These data show that supercooling (but not freezing) triggers activation of the antioxidant system and this may be in anticipation of the overgeneration of oxyradicals when the temperature increases (while thawing or at the end of supercooling). Oxidative stress was assessed from the content of 8-oxodGuo and the different DNA adducts resulting from lipid peroxidation, but it was unaltered whatever the physiological state of the lizards, thus demonstrating the efficiency of the antioxidant system that has been developed by this species. Overall, antioxidant defenses appear to be part of the adaptive machinery for reptilian tolerance to sub-zero temperatures.

Antioxidants do not explain the disparate longevity between mice and the longest-living rodent, the naked mole-rat

The maximum lifespan of naked mole-rats (NMRs; Heterocephalus glaber) is greater than that of any other rodent. These hystricognaths survive in captivity >28 years, eight-times longer than similar-sized mice. The present study tested if NMRs possess superior antioxidant defenses compared to mice and if age-related interspecies changes in antioxidants were evident. Activities of Cu/Zn superoxide dismutase (Cu/Zn, SOD), Mn SOD, catalase and cellular glutathione peroxidase (cGPx) were measured in livers of physiologically equivalent age-matched NMRs (30, 75 and 130 months) and CB6F1 mice (4, 12 and 18 months). In mice, Mn SOD activity increased with age, while the activity of catalase and cGPx declined. None of the antioxidants changed with age in mole-rats. cGPx activity of NMRs was 70-times lower (p < 0.0001) than in mice, and resembled that of cGPx knock-out animals. NMRs may partially compensate for the lower cGPx when compared to mice, by having moderately higher activities of the other antioxidants. It is nonetheless unlikely that antioxidant defenses are responsible for the eight-fold longevity difference between these two species. Maintenance of constant antioxidant defenses with age in NMRs concurs with previous physiological data, suggesting delayed aging in this species.

Effects of environmental pollution on the liver parenchymal cells and Kupffer-melanomacrophagic cells of the frog Rana esculenta

In vertebrates, the biotransformation processes of xenobiotics are performed mainly by the liver which involves both hepatocytes and Kupffer-melanomacrophagic cells through enzymatic and nonenzymatic mechanisms. In this study, we investigated the liver of Rana esculenta adult frogs collected at two sample rice fields, one heavily polluted and one relatively unpolluted. Water pollution was determined by chemical analysis on tadpoles. The specific activities of some enzymes (glucose-6-phosphate dehydrogenase (G6PDH), acid and alkaline phosphatases (AcPase and AlkPase), succinic dehydrogenase (SDH), and catalase) were studied in the liver of adult frogs to identify the possible changes induced by contamination in the metabolic processes which depend on the function of the liver. The production of reactive oxygen species (ROS) were also evaluated through histochemical techniques. In the polluted samples, hepatocytes showed variations in the activity of G6PDH, AlkPase, and SDH and a moderate to intense ROS expression. Prominent changes were observed in Kupffer cells (KCs) and melanomacrophages (MMPs), both showing intense reactivity for AcPase and catalase and variations in melanin content and distribution. Results thus indicate a general adaptive response of liver parenchyma to environmental pollution. The possible role of both KCs and MMPs as scavengers of foreign substances is discussed.

Differential susceptibility of fish and rat liver cells to oxidative stress and cytotoxicity upon exposure to prooxidants

Species differences in the ability to cope with pollutant-mediated oxidative stress can provide insight into the mechanisms behind both the mode of toxicity of a specific chemical as well as the different ways in which an organism may deal with such stressors. In this study, the effects of exposure to model prooxidants on parameters of oxidative stress were investigated in liver cells from both fish (PLHC-1) and rat (H4IIE). The goals of this study were to compare the oxidative stress response of these cell lines and to assess the relative utility of several different measures of oxidative stress as signals preceding cytotoxicity. Cellular response to two model prooxidants, copper and Fenton reagents (ferrous sulfate plus hydrogen peroxide), was assessed by measuring cytotoxicity, lipid peroxidation, total glutathione (GSHT), and percent glutathione disulfide (%GSSG). Additionally, transcriptional activation of an antioxidant response element (ARE) reporter gene was measured using the chloramphenicol acetyltransferase (CAT) assay in response to these chemicals. In general, the fish cells were more sensitive than rat cells to prooxidants, and the assays for lipid peroxidation and ARE reporter gene activation were more sensitive for measuring oxidative stress than GSH or %GSSG. Fish cells were significantly (P < 0.0001) more sensitive to copper sulfate and Fenton reagent induced oxidative stress, as measured through lipid peroxidation and ARE reporter gene transcriptional activation. Copper sulfate and Fenton reagents caused a two-fold increase in %GSSG in both cell lines. Basal levels of GSHT were higher in the HII4E cells than the PLHC-1 cells, and Fenton reagents significantly reduced GSHT in fish cells but showed no effect on the rat cells. Significant differences were also observed in the cytotoxicity of the test chemicals to both cell lines, with the fish cells demonstrating a higher level of cell death. Lipid peroxidation and ARE transcriptional activation appeared to better reflect subsequent cytotoxicity than a change in GSHT or %GSSG. These results suggest that HII4E (rat) cells are more protected from oxidative stress than PLHC-1 (fish) cells. Additional studies are addressing oxidative stress-mediated signal transduction pathways that may play a role in the differential responses of these cells lines.

Oxidative stress stimulates multiple MAPK signalling pathways and phosphorylation of the small HSP27 in the perfused amphibian heart

We investigated the activation of three subfamilies of MAPKs (ERK, JNKs and p38-MAPK) by oxidative stress in the isolated perfused amphibian heart. Activation of p43-ERK by 100 micro mol l(-1) H(2)O(2) was maximally observed within 5 min, remained elevated for 30 min and was comparable with the effect of 1 micro mol l(-1) PMA. p43-ERK activation by H(2)O(2) was inhibited by PD98059 but not by SB203580. The p46 and p52 species of JNKs were maximally activated by 2.5- and 2.1-fold, respectively, by 100 micro mol l(-1) H(2)O(2) within 2 min. JNK activation was still detectable after 15 min, reaching control values at 30 min of treatment. p38-MAPK was maximally activated by 9.75-fold by 100 micro mol l(-1) H(2)O(2) after 2 min and this activation progressively declined thereafter, reaching control values within 45 min of treatment. The observed dose-dependent profile of p38-MAPK activation by H(2)O(2) revealed that 30 micro mol l(-1) H(2)O(2) induced maximal phosphorylation, whereas 100-300 micro mol l(-1) H(2)O(2) induced considerable activation of the kinase. Our studies also showed that the phosphorylation of MAPKAPK2 by H(2)O(2) followed a parallel time-dependent pattern and that SB203580 abolished this phosphorylation. Furthermore, our experiments clearly showed that 30 micro mol l(-1) H(2)O(2) induced a strong, specific phosphorylation of HSP27. Our immunohistochemical studies showed that immune complexes of phosphorylated forms of both p38-MAPK and HSP27 were strongly enhanced by 30 micro mol l(-1) H(2)O(2) in the perinuclear region as well as dispersedly in the cytoplasm of ventricular cells and that SB203580 abolished this phosphorylation. These data indicate that oxidative stress is a powerful activator of all three MAPK subfamilies in the amphibian heart. Stimulation of p38-MAPK and the consequent phosphorylation of HSP27 may be important in cardioprotection under such conditions.