Biomarkers of oxidative stress study V: ozone exposure of rats and its effect on lipids, proteins, and DNA in plasma and urine.

Ozone exposure effect on free radical-catalyzed oxidation products of lipids, proteins, and DNA in the plasma and urine of rats was studied as a continuation of the international Biomarker of Oxidative Stress Study (BOSS) sponsored by NIEHS/NIH. The goal was to identify a biomarker for ozone-induced oxidative stress and to assess whether inconsistent results often reported in the literature might be due to the limitations of the available methods for measuring the various types of oxidative products. The time- and dose-dependent effects of ozone exposure on rat plasma lipid hydroperoxides, malondialdehyde, F2-isoprostanes, protein carbonyls, methionine oxidation, and tyrosine- and phenylalanine oxidation products, as well as urinary malondialdehyde and F2-isoprostanes were investigated with various techniques. The criterion used to recognize a marker in the model of ozone exposure was that a significant effect could be identified and measured in a biological fluid seen at both doses at more than one time point. No statistically significant differences between the experimental and the control groups at either ozone dose and time point studied could be identified in this study. Tissue samples were not included. Despite all the work accomplished in the BOSS study of ozone, no available product of oxidation in biological fluid has yet met the required criteria of being a biomarker. The current negative findings as a consequence of ozone exposure are of great importance, because they document that in complex systems, as the present in vivo experiment, the assays used may not provide meaningful data of ozone oxidation, especially in human studies.

Effect of FIO2 on oxidative stress during interval training at moderate altitude.

PURPOSE: To evaluate the effect of different fractions of inspired oxygen (FIO2) on oxidative stress during a high-intensity interval workout in trained endurance athletes residing at altitude. METHODS: Subjects (N = 19) were trained male cyclists who were residents of moderate altitude (1800-1900 m). Testing was conducted at 1860 m (PB 610-612 torr, PIO2 approximately 128 torr). Subjects performed three randomized, single-blind trials consisting of a standardized interval workout (6 x 100 kJ) while inspiring a medical-grade gas with FIO2 0.21 (PIO2 approximately 128 torr), FIO2 0.26 (PIO2 approximately 159 torr), and FIO2 0.60 (PIO2 approximately 366 torr). Serum lipid hydroperoxides (LOOH) and whole-blood reduced glutathione (GSH) were measured 60 min preexercise and immediately postexercise, and analyzed using standard colorimetric assays. Urinary malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were measured 24 h preexercise and 24 h postexercise, and analyzed via HPLC and ELISA, respectively. RESULTS: Compared with the control trial (FIO2 0.21), total time (min:s) for the 100-kJ work interval was faster (5% in FIO2 0.26; 8% in FIO2 0.60 (P < 0.05)) and power output (W) was higher (5% in FIO2 0.26, 8% in FIO2 0.60 (P < 0.05)) in the supplemental oxygen trials. There was a significant pre- versus postexercise main effect (P < 0.05) for LOOH and GSH; however, there were no significant differences in LOOH or GSH between the FIO2 trials. MDA and 8-OHdG were unaffected by either the interval training session or FIO2. CONCLUSION: Supplemental oxygen used in conjunction with high-intensity interval training at altitude ("live high + train low via supplemental O2" (LH + TLO2)) results in a significant improvement in exercise performance without inducing additional free radical oxidative stress as reflected in hematological and urinary biomarkers.

Lipid peroxidation in the skeletal muscle of hamsters with emphysema.

Current evidence suggests that skeletal muscle functional impairments present in emphysema and COPD patients may in part be a consequence of the disease condition per se. The mechanistic basis for these impairments is uncertain. Within the human population, it is difficult to control for confounding effects of concomitantly reduced activity levels. To explore this issue, malondialdehyde (MDA), a marker of lipid peroxidation, and enzymes of the glutathione redox system were measured in selected hindlimb muscles of Syrian Golden hamsters 6 months following intratracheal instillation of either saline (CON, n=7) or elastase (25 U/100 g body weight, EMP, n=5) in an accepted model where physical activity levels between control and EMP groups could be equated. Excised lung volume increased with EMP (CON, 1.3+/-0.2 g; EMP, 3.2+/-0.4 g, P<0.01). MDA was increased in the gastrocnemius (CON, 238+/-87; EMP, 371+/-122 nmol/g protein, P<0.05) of EMP hamsters. Antioxidant concentrations had a disparate response; glutathione (CON, 7.68+/-1.53; and EMP, 10.25+/-0.67 &mgr;mol/g protein, P<0.01) and the activity of glutathione reductase (GR) were increased (CON, 1.87+/-0.17; and EMP, 2.46+/-0.31 U/g protein, P<0.01) in the gastrocnemius, whereas the activity of glutathione peroxidase (GPx) was decreased (CON, 12.7+/-2.65; and EMP, 9.46+/-1.88 U/g protein, P<0.05) in the vastus lateralis of EMP hamsters. CONCLUSION: These data indicate that EMP may induce oxidative stress in peripheral skeletal muscle.