Biomarkers of oxidative stress study II: are oxidation products of lipids, proteins, and DNA markers of CCl4 poisoning?

Oxidation products of lipids, proteins, and DNA in the blood, plasma, and urine of rats were measured as part of a comprehensive, multilaboratory validation study searching for noninvasive biomarkers of oxidative stress. This article is the second report of the nationwide Biomarkers of Oxidative Stress Study using acute CCl4 poisoning as a rodent model for oxidative stress. The time-dependent (2, 7, and 16 h) and dose-dependent (120 and 1200 mg/kg i.p.) effects of CCl4 on concentrations of lipid hydroperoxides, TBARS, malondialdehyde (MDA), isoprostanes, protein carbonyls, methionine sulfoxidation, tyrosine products, 8-hydroxy-2'-deoxyguanosine (8-OHdG), leukocyte DNA-MDA adducts, and DNA-strand breaks were investigated to determine whether the oxidative effects of CCl4 would result in increased generation of these oxidation products. Plasma concentrations of MDA and isoprostanes (both measured by GC-MS) and urinary concentrations of isoprostanes (measured with an immunoassay or LC/MS/MS) were increased in both low-dose and high-dose CCl4-treated rats at more than one time point. The other urinary markers (MDA and 8-OHdG) showed significant elevations with treatment under three of the four conditions tested. It is concluded that measurements of MDA and isoprostanes in plasma and urine as well as 8-OHdG in urine are potential candidates for general biomarkers of oxidative stress. All other products were not changed by CCl4 or showed fewer significant effects.

Biomarkers of oxidative stress study III. Effects of the nonsteroidal anti-inflammatory agents indomethacin and meclofenamic acid on measurements of oxidative products of lipids in CCl4 poisoning.

Plasma and urinary levels of malondialdehyde-like products (MDA) and isoprostanes were identified as markers of in vivo lipid peroxidation in an animal model of CCl4 poisoning. We sought to determine the extent to which the formation of these oxidation products is influenced by inhibition of the cyclooxygenase enzymes which catalytically generate proinflammatory lipid peroxidation products known as prostaglandins and thromboxane. In the present studies, after induction of oxidant stress in rats with CCl4, lipid peroxidation products measured in plasma and urine demonstrate that isoprostanes and MDA can be partially inhibited by cyclooxygenase inhibitors, albeit to different extents. The lowering of isoprostane and MDA formation, however, may not to due primarily to the diminution of catalytic generation of isoprostanes or MDA by the cyclooxygenases but, rather, may be the result of the suppression of nonenzymatic lipid peroxidation. This is suggested since 8,12-iso-iPF2alpha-VI is also reduced by indomethacin, yet, unlike other isoprostanes and MDA, it is not generated catalytically by the cyclooxygenase. Thus, although the two cyclooxygenase inhibitors we tested have statistically significant effects on the measurements of both isoprostanes and MDA in this study, the results provide evidence that these lipid-degradation products primarily constitute markers of oxidative stress.

Moderate alcohol consumption and levels of antioxidant vitamins and isoprostanes in postmenopausal women.

BACKGROUND: Although alcohol intake has been positively associated with breast cancer risk in epidemiologic studies, the mechanisms mediating this association are speculative. OBJECTIVE: The Postmenopausal Women's Alcohol Study was designed to explore the effects of moderate alcohol consumption on potential risk factors for breast cancer. In the present analysis, we evaluated the relationship of alcohol consumption with antioxidant nutrients and a biomarker of oxidative stress. DESIGN: Participants (n=53) consumed a controlled diet plus each of three treatments (15 or 30 g alcohol/day or a no-alcohol placebo beverage), during three 8-week periods in random order. We measured the antioxidants, vitamin E (alpha (alpha)- and gamma (gamma)-tocopherols), selenium, and vitamin C in fasting blood samples which were collected at the end of diet periods, treated and frozen for assay at the end of the study. We also measured 15-F(2t)-IsoP isoprostane, produced by lipid peroxidation, which serves as an indicator of oxidative stress and may serve as a biomarker for conditions favorable to carcinogenesis. RESULTS: After adjusting for BMI (all models) and total serum cholesterol (tocopherol and isoprostane models) we observed a significant 4.6% decrease (P=0.02) in alpha-tocopherol and a marginally significant 4.9% increase (P=0.07) in isoprostane levels when women consumed 30 g alcohol/day (P=0.06 and 0.05 for overall effect of alcohol on alpha-tocopherol and isoprostanes, respectively). The other antioxidants were not significantly modified by the alcohol treatment. CONCLUSIONS: These results suggest that moderate alcohol consumption increases some biomarkers of oxidative stress in postmenopausal women.

An improved GC/MS-based procedure for the quantitation of the isoprostane 15-F2t-IsoP in rat plasma.

This article describes a procedure for the quantitation of the isoprostane 15-F2t-IsoP (9a,11a,15S-trihydroxy-(8b)-prosta-5Z,13E-dien-1-oic acid [CAS#27415-26-5] formerly known as 8-epi-PGF2a or 8-iso-PGF2a, and also as iPF2a-III). We have combined features from several earlier methods for 15-F2t-IsoP and prostaglandins, and identified and modified those steps that may lead to poor recoveries. The resulting protocol is precise and reliable, and was validated by a blind time-course study of plasma levels in rats treated with 120 and 1200 mg CCl4/kg body weight. Plasma levels of 15-F2t-IsoP, as measured according to the procedure described above, are good indicators of acute oxidative stress as induced by CCl4. The precision of the measurements allows detection of elevated plasma 15-F2t-IsoP levels as long as 16 h after an acute exposure of 120 mg CCl4/kg body weight, and 2 h after an exposure of 1 mg CCl4/kg body weight. The results of this low-dose, pilot study suggest that this method has sufficient analytical precision to allow the detection of the small changes in plasma isoprostane levels, which result from chronic and/or lower-level exposures to agents causing oxidative stress.

Pulmonary endothelial and epithelial integrity and neutrophil infiltration after endotoxin in interleukin-1 receptor knockout mice.

Previously we found the structural integrity of the aortic endothelium was maintained after the administration of endotoxin in type 1 interleukin-1 (IL-1) receptor knockout mice. In this study, we investigated further the integrity of pulmonary vascular endothelium, airway epithelial, pulmonary microvasculature, and neutrophil infiltration into the microvasculature and respiratory air spaces. Adult male C57BL/129J wild-type mice and C57BL/129J knockout mice possessing a homozygous deletion of the type 1 IL-1 receptor received the following intraperitoneal injections; 1) Escherichia coli endotoxin (ENDT) (10 mg/kg), 2) ENDT (2 mg/kg given for 4 days), or (3) saline vehicle. Wild-type and knockout control animals receiving saline vehicle showed normal endothelial and epithelial ultrastructure with intact membranes. Pulmonary endothelial cell damage was found only in wild-type mice given a single 10 mg/kg endotoxin dose. Airway epithelial damage was found only in wild-type mice given a repetitive dose of endotoxin (2 mg/kg for 4 days). Neutrophil infiltration increased only in mice given a single dose of endotoxin (10 mg/kg) with the wild-type increasing by 32% and the knockouts by 6% compared with the saline control for that group respectively. Serum IL-6 and nitric oxide (indicators of septic shock severity and lethality) significantly increased only in the mice given 10 mg/kg of endotoxin. The maintenance of pulmonary endothelial and epithelial cell integrity and the decrease of neutrophil infiltration in the IL-1 knockout mice suggest that IL-1 contributes significantly to the severity of endotoxin-induced sepsis.

Nitric oxide (NO) and interleukin-1beta (IL-1beta) in follicular fluid and their correlation with fertilization and embryo cleavage.

PROBLEM: Using an IVF model, the goal of the study was to investigate the relationship between follicular fluid (ff) NO and IL-1beta levels, as well as their correlation with fertilization of mature oocytes and embryo cleavage rates. METHOD OF STUDY: Follicular fluid was collected from 17 patients at the time of transvaginal oocyte retrieval following controlled ovarian stimulation. Oocytes harvested from these follicles were followed through fertilization and embryo cleavage. The NO metabolites nitrate/nitrite (NO3/NO2) were measured using the Griess reaction as an indirect assessment of NO activity. IL-1beta was measured using a high sensitivity ELISA system (Amersham, UK). The Student's t-test was utilized for unpaired data with the means considered significantly different when P < or = 0.05. RESULTS: Follicular fluid NO3/NO2 levels were significantly lower in follicles containing mature oocytes that fertilized (n = 30; 9.7 +/- 1.0 microM), versus those that did not fertilize (n = 23; 15.4 +/- 2.4 microM; P < 0.05). Follicles that contained oocytes that fertilized and went on to divide beyond the 6 cell stage had significantly lower ff levels of NO3/NO2 (n = 18; 7.5 +/- 0.9 microM), as compared to ff that contained oocytes that did not fertilize or failed to develop beyond the 5 cell stage (n = 35; 14.6 +/- 1.7 microM; P < 0.01). No correlation was found between ff NO3/NO2 levels (n = 28; 13.8 +/- 2.0 microM) and ff IL-1beta levels (n = 28; 0.5 +/- 0.08 pg/mL). An analysis of ff IL-1beta levels in relation to fertilization and embryo cleavage rates revealed no correlation. CONCLUSIONS: Lower ff NO3/NO2 levels at the time of oocyte retrieval are associated with adequate fertilization and embryo cleavage rates. In our IVF model, no correlation was found between ff IL-1beta levels and ff NO3/NO2, fertilization, or embryo cleavage rates.

Endotoxin-induced atrial natriuretic factor release: in vivo and in vitro studies.

OBJECTIVE: We evaluated the effects of coliform endotoxin on the circulating levels of atrial natriuretic factor and renal function. To understand the direct effects of endotoxin in the release of atrial natriuretic factor by cardiac tissue, studies in isolated rat atria were performed. STUDY DESIGN: In vivo studies were used. Anesthetized dogs were studied, with one group receiving isotonic saline solution (n = 6) and the other group receiving 50 microg/kg of coliform endotoxin (n = 7) as a continuous infusion over a 4-hour period. Cardiovascular parameters, renal function, and circulating levels of atrial natriuretic factor were measured at specified time intervals. In another set of experiments with in vitro studies left atria from Sprague-Dawley rats were isolated and perfused. In the control group (n = 9) the standard Krebs perfusate was used. In the endotoxin group (n = 9) coliform endotoxin was added at a concentration of 250 microg/mL to the standard perfusate. Atrial pressure was used as an index of stretch, and atrial natriuretic factor was measured from the perfusate. RESULTS: Administration of endotoxin resulted in decreased blood pressure (P < .05) with a concomitant increase in heart rate. Renal artery flow, however, showed an increase (P < .05) initially followed by a return to its baseline value, with a sustained increase occurring in the saline solution control group. A significant (P < .05) and sustained increase in the circulating levels of atrial natriuretic factor after endotoxin infusion did not prevent the decrease in fractional sodium excretion (P < .05) and creatinine clearance despite an increase in the urinary output. Serum sodium, serum potassium, and osmolalities, however, remained relatively stable. The study pertaining to isolated atria showed that in the presence of low atrial pressures, addition of endotoxin had no significant effect on the release of atrial natriuretic factor. With the increase in atrial pressure atrial natriuretic factor release was significantly higher in the group directly exposed to endotoxin compared with the control group. CONCLUSIONS: These studies demonstrate that the slow infusion of coliform endotoxin results in increased circulating levels of atrial natriuretic factor. This increase is in part due to the direct effect of endotoxin on the heart as indicated by studies in isolated atria. Our data suggest that atrial natriuretic factor in endotoxemia acts in an integrative manner with other hormones on a variety of target organs to modulate cardiovascular function and fluid balance.

Chronic disease mortality in Maine: assessing the targets for prevention.

From 1982 through 1991, nine chronic diseases accounted for over 55 percent of deaths in Maine. Using the lowest age-specific death rates as theoretically achievable rates, there were over 8,000 excess deaths. Over 25,000 deaths could be attributed to preventable causes over the 10-year period. Cigarette smoking was the single largest contributor to chronic disease mortality, accounting for 17,688 deaths, followed by physical inactivity, high blood pressure, and diet. This assessment provides a measure of the size of the chronic disease prevention target in Maine and is a first step in assessing the potential impact of prevention programs.

Atrial natriuretic peptide, oestradiol and progesterone in women undergoing spontaneous and gonadotrophin-stimulated ovulatory cycles.

The objective of this study was to examine the relationship between the concentrations of oestradiol and progesterone on the one hand and atrial natriuretic peptide (ANP) concentrations on the other, during the follicular and luteal phases of spontaneous and gonadotrophin-stimulated ovulatory menstrual cycles. A total of 27 ovulatory women undergoing either a spontaneous (n = 9) or a gonadotrophin-stimulated (n = 18) cycle were selected for inclusion in this study. In comparison with spontaneous cycles, gonadotrophin-stimulated cycles had increased peak follicular oestradiol (mean +/- SE; 937 +/- 150 versus 195 +/- 18 pg/ml; P < 0.05) and midluteal progesterone (mean +/- SE; 44.0 +/- 7.4 versus 14.1 +/- 2.4 ng/ml; P < 0.05) concentrations. There were no differences in the circulating ANP concentrations between the follicular and luteal phases of the menstrual cycle. Despite the increased oestradiol and progesterone concentrations following gonadotrophin stimulation, no difference in ANP concentrations was seen between stimulated and spontaneous cycles. There was no correlation between circulating concentrations of oestradiol, progesterone (at physiological and supraphysiological concentrations) and ANP throughout the menstrual cycle.