No abstract

Copper (Cu) is a vital mineral essential for many biological processes. The vast majority of all Cu in healthy humans is associated with enzyme prosthetic groups or bound to proteins. Cu homeostasis is tightly regulated through a complex system of Cu transporters and chaperone proteins. Excess or toxicity of Cu, which is associated with the pathogenesis of hepatic disorder, neurodegenerative changes and other disease conditions, can occur when Cu homeostasis is disrupted. The capacity to initiate oxidative damage is most commonly attributed to Cu-induced cellular toxicity. Recently, altered cellular events, including lipid metabolism, gene expression, alpha-synuclein aggregation, activation of acidic sphingomyelinase and release of ceramide, and temporal and spatial distribution of Cu in hepatocytes, as well as Cu-protein interaction in the nerve system, have been suggested to play a role in Cu toxicity. However, whether these changes are independent of, or secondary to, an altered cellular redox state of Cu remain to be elucidated.

No abstract

A method has been developed to measure malondial‐dehyde (MDA) in biological systems. MDA was reacted with 2‐thiobarbituric acid (TBA) in the presence of butylated hydroxytoluene (BHT) to minimize formation of artifacts. Initial separation of the TBA‐MDA adduct was accomplished by isobutanol extraction. Further elimination and separation of interfering substances was achieved by high performance liquid chromatography. The mobile phase consisted of a 1∶1 (v/v) mixture of methanol and water with 0.05% (w/v) tetrabutyl ammonium dihydrogen phosphate added as an ion pairing reagent. At a flow rate of 1 ml/min, the TBA‐MDA adduct was eluted from a 15‐cm, c‐18, reversed phase column in approximately 4.9 min. The TBA‐MDA adduct was quantitated with a fluorescence detector set at 515 nm excitation and 550 nm emission. Using this method, picomole quantities of MDA can be easily detected in plasma and liver samples.

The generation of reactive oxygen species (ROS) is a steady-state cellular event in respiring cells. Their production can be grossly amplified in response to a variety of pathophysiological conditions such as inflammation, immunologic disorders, hypoxia, hyperoxia, metabolism of drug or alcohol, exposure to UV or therapeutic radiation, and deficiency in antioxidant vitamins. Uncontrolled production of ROS often leads to damage of cellular macromolecules (DNA, protein, and lipids) and other small antioxidant molecules. A number of major cellular defense mechanisms exist to neutralize and combat the damaging effects of these reactive substances. The enzymic system functions by direct or sequential removal of ROS (superoxide dismutase, catalase, and glutathione peroxidase), thereby terminating their activities. Metal binding proteins, targeted to bind iron and copper ions, ensure that these Fenton metals are cryptic. Nonenzymic defense consists of scavenging molecules that are endogenously produced (GSH, ubiquinols, uric acid) or those derived from the diet (vitamins C and E, lipoic acid, selenium, riboflavin, zinc, and the carotenoids). These antioxidant nutrients occupy distinct cellular compartments and among them, there are active recycling. For example, oxidized vitamin E (tocopheroxy radical) has been shown to be regenerated by ascorbate, GSH, lipoic acid, or ubiquinols. GSH disulfides (GSSG) can be regenerated by GSSG reductase (a riboflavin-dependent protein), and enzymic pathways have been identified for the recycling of ascorbate radical and dehydroascorbate. The electrons that are used to fuel these recycling reactions (NADH and NADPH) are ultimately derived from the oxidation of foods. Sickle cell anemia, thalassemia, and glucose-6-phosphate-dehydrogenase deficiency are all hereditary disorders with higher potential for oxidative damage due to chronic redox imbalance in red cells that often results in clinical manifestation of mild to serve hemolysis in patients with these disorders. The release of hemoglobin during hemolysis and the subsequent therapeutic transfusion in some cases lead to systemic iron overloading that further potentiates the generation of ROS. Antioxidant status in anemia will be examined, and the potential application of antioxidant treatment as an adjunct therapy under these conditions will be discussed.