The role of antioxidants in the prevention of t-butyl hydroperoxide-induced chemiluminescence

How does glucose generate oxidative stress in peripheral nerve?

Diabetes-associated oxidative stress is clearly manifest in peripheral nerve, dorsal root, and sympathetic ganglia of the peripheral nervous system and endothelial cells and is implicated in nerve blood flow and conduction deficits, impaired neurotrophic support, changes in signal transduction and metabolism, and morphological abnormalities characteristic of peripheral diabetic neuropathy (diabetic peripheral neuropathy). Hyperglycemia has a key role in oxidative stress in diabetic nerve, whereas the contribution of other factors, such as endoneurial hypoxia, transition metal imbalance, and hyperlipidemia, has not been rigorously proven. It has been suggested that oxidative stress, particularly mitochondrial superoxide production, is responsible for sorbitol pathway hyperactivity, nonenzymatic glycation/glycooxidation, and activation of protein kinase C. However, this concept is not supported by in vivo studies demonstrating the lack of any inhibition of the sorbitol pathway activity in peripheral nerve, retina, and lens by antioxidants, including potent superoxide scavengers. Its has been also hypothesized that aldose reductase (AR) detoxifies lipid peroxidation products, and therefore, the enzyme inhibition in diabetes is detrimental rather than benefical. However, the role for AR in lipid peroxdation product metabolism has never been demonstrated in vivo, and the effects of aldose reductase inhibitors and antioxidants on diabetic peripheral neuropathy are unidirectional, i.e., both classes of agents prevent and correct functional, metabolic, neurotrophic, and morphological changes in diabetic nerve. Growing evidence indicates that AR has a key role in oxidative stress in the peripheral nerve and contributes to superoxide production by the vascular endothelium. The potential mechanisms of this phenonmenon are discussed.

A chemiluminescence assay detecting the antioxidative effects of glutathione and uric acid on erythrocytes and hemolysates exposed to t-butyl hydroperoxide

The aim of this study was to compare the antioxidative effects of glutathione (GSH) and uric acid (UA) on erythrocytes and hemolysates exposed to t-butyl hydroperoxide, by using a chemiluminescence (CL) technique. CL formation was induced by t-butyl hydroperoxide in an experimental system consisting of erythrocytes and hemolysates in Tris-HCl buffer (pH 7.4). GSH or UA was added as an antioxidant. In erythrocytes, 10 microM and 50 microM concentrations of either GSH or UA reduced the maximum chemiluminescence values (MCVs) significantly when compared to those of controls. In erythrocytes, MCVs observed in the 50 microM GSH group were significantly lower than those of the 50 microM UA group. In hemolysates, while 10 microM concentration of GSH or UA did not alter MCVs, 50 microM concentration of either GSH or UA reduced MCVs. The reduction of MCVs observed in the 50 microM GSH group was greater than that of the 50 microM UA group. When the effects of equimolar concentrations of GSH or UA on erythrocytes and hemolysates were compared, the MCVs of hemolysates were lower than those of erythrocytes. These results can be attributed to the fact that antioxidant agents react much more easily in the hemolysate medium.

Increased resistance to oxidative stress in normal and glucose-6-phosphate dehydrogenase-deficient hemolysates in the presence of enzyme substrates

Erythrocytes and hemolysates from 10 normal and 10 glucose-6-phosphate dehydrogenase-deficient individuals were incubated with cumene hydroperoxide, and free radical-induced lipid peroxidation was monitored by chemiluminescence. Chemiluminescence intensities in erythrocytes of normal and deficient subjects were similar in the presence or absence of glucose-6-phosphate dehydrogenase substrates. Hemolysates of normal and deficient subjects also showed similar chemiluminescence in the absence of substrates. However, with the addition of substrates to the incubation medium, deficient hemolysates reached maximum chemiluminescence intensity within a shorter period, and maximum values were higher than in normal hemolysates. We believe this offers a new means of detection of glucose-6-phosphate dehydrogenase-deficient patients.

The effects of detergents on t-butyl hydroperoxide-induced chemiluminescence

We examined the effects of Triton X-100, digitonin, sodium dodecyl sulfate, taurocholic acid, and cetylpyridinium chloride on hemoglobin-catalyzed and t-butyl hydroperoxide-induced chemiluminescence. The experimental system contained hemoglobin, luminol, t-butyl hydroperoxide, and different concentrations of detergents (5-100 mg/dl) in TRIS-HCl buffer. Control assays were performed by excluding detergents. Chemiluminescence was detected using a liquid scintillation counter in single photon mode. All concentrations chosen for each detergent reduced the maximum chemiluminescence value and retarded the time that maximum chemiluminescence occurred. The most prominent reduction in maximum chemiluminescence was observed with 50 and 100 mg/dl digitonin. The smallest reduction was observed with 5 mg/dl sodium dodecyl sulfate, without retardation of the time that maximum chemiluminescence occurred. Our aim was to use detergents in membrane-containing experimental systems and hence to identify the detergent with the least effect on chemiluminescence. Our results suggest that sodium dodecyl sulfate is the most suitable detergent for chemiluminescence studies in membrane systems.