Antioxidative Properties of Pyruvate and Protection of the Ischemic Rat Heart During Cardioplegia

Abstract

Formation of oxygen free radicals during heart transplantation seems to be related to the alterations occurring during ischemia and reperfusion and could explain the short preservation time of donor hearts. The aim of our study was (a) to analyze the protective effects of pyruvate during cold cardioplegia and ischemia/reperfusion sequence, and (b) to investigate in vitro the radical scavenging properties of this compound. After 30 min of perfusion, isolated working rat hearts were arrested by cardioplegic solution, stored 4 h in B21 solutions at 4 degrees C, and reperfused with Krebs-Henseleit buffer for 45 min. Pyruvate (2 mM) was added to Krebs-Henseleit, cardioplegic, and storage solutions, and functional parameters were recorded throughout the experiments. In a second part, control hearts and hearts treated with pyruvate were cannulated via the aorta and perfused for 30 min by the Langendorff method, arrested by cardioplegic solution, stored 4 h in B21 solutions at 4 degrees C, and reperfused for 45 min by the Langendorff method. Malonedialdehyde and alpha-tocopherol levels were determined on heart homogenate. In situ detection of apoptotic cells also was performed on tissue samples (left ventricle) at the end of the ischemia/reperfusion sequence. To demonstrate in vitro the antioxidant effects of pyruvate, we monitored (a) its hydroxyl radical scavenging properties by using electron paramagnetic resonance (EPR) spectroscopy, and (b) the decrease of fluorescence of allophycocyanin, in the presence of a Fenton system (H2O2/Cu2+). Ischemia for 4 h, followed by myocardial reperfusion, resulted in substantially reduced mechanical function. Hearts subjected to this ischemia and pretreated with pyruvate showed a significant improvement in the function recovery. After the ischemia/reperfusion protocol, no significant decrease of malonedialdehyde levels was shown on hearts treated with pyruvate. However, alpha-tocopherol levels were higher in the pyruvate group compared with the control group. At the end of the reperfusion period, levels of apoptotic cells were significantly lower in hearts treated with pyruvate compared with control hearts. EPR studies showed that pyruvate was an efficient hydroxyl scavenger, with a median inhibitory concentration (IC50) of 8 mM. The allophycocyanin assay also showed a dose-dependent effect of pyruvate against hydroxyl radicals. In conclusion, these findings showed that pyruvate could prevent reperfusion injuries in the isolated heart, probably by its antioxidative properties. The application of pyruvate may contribute to the preservation of hearts for organ transplantation.

Apoptotic insults impair Na+, K+-ATPase activity as a mechanism of neuronal death mediated by concurrent ATP deficiency and oxidant stress

“…Previously observed anti-apoptotic effects of ROS scavengers (Lieberthal et al, 1998;Pong et al, 2001) are consistent with the preserved Na + , K + -pump function observed in this study. Pyruvate is well-known for its direct antioxidant effect of reacting with H2O2 to form water and carbon dioxide (Crestanello et al, 1998;Varma et al, 1998); it may also possess a hydroxyl radical scavenging property (Dobsak et al, 1999) or stimulate NADPH-dependent peroxide scavenging systems (Cavallini et al, 1990). In our study both exogenous H2O2 and endogenous ROS induced by menadione, DMNQ, or apoptotic insults inhibited Ipump.…”

Evidence That Glutathione Depletion Is a Mechanism Responsible for the Anti-Inflammatory Effects of Ethyl Pyruvate in Cultured Lipopolysaccharide-Stimulated RAW 264.7 Cells

“…It is well known that pyruvate is an ROS scavenger (Adickes and Andresen, 1943;Bunton, 1949;Melzer and Schmidt, 1988;Dobsak et al, 1999), and data are available suggesting that EP is as well (Varma et al, 1998;Tawadrous et al, 2002). NAC, a derivative of the amino acid L-cysteine, is both an ROS scavenger itself (Aruoma et al, 1989) and a precursor for the synthesis of the important endogenous antioxidant, GSH (Fernandez et al, 1999).…”

“…One possibility is suggested by the close chemical similarity between EP and pyruvate, a compound that is known to be an effective scavenger of reactive oxygen species (ROS) (Adickes and Andresen, 1943;Bunton, 1949;Melzer and Schmidt, 1988;Dobsak et al, 1999). An oxidizing environment, particularly in the cytosol, has been implicated in the activation of proinflammatory signaling molecules, such as NF-B (Schreck et al, 1992;Oka et al, 2000;Schoonbroodt et al, 2000;Livolsi et al, 2001;Rahman et al, 2001) and p38 mitogen-activated protein kinase .…”

Higher Hypochlorous Acid Scavenging Activity of Ethyl Pyruvate Compared to Its Sodium Salt

“…The concentrations used in the study were based on previous works. 7,10,13,15) Ascorbic acid was used as a reference antioxidant in all the experiments. A stock solution of NaOCl was prepared in water, and its concentration was determined spectrophotometrically at 290 nm, using a molar extinction coefficient of 350 M À1 cm À1 .…”

“…5) It reduces hydrogen peroxide to water 6) and scavenges the hydroxyl radical 7) by non-enzymatic decarboxylation.…”