Human colorectal cancer cells efficiently conjugate the cyclopentenone prostaglandin, prostaglandin J(2), to glutathione

Cyclopentenone prostaglandins (PGs), particularly those of the J-series, affect proliferation and differentiation in a number of cell lines. J-ring PGs have been shown to be ligands for the peroxisome proliferator-activated receptor (PPAR)-gamma and to modulate NF-kappaB-mediated gene transcription. We have previously reported that large quantities of eicosanoids, including PGJ(2), are produced by the human colorectal cancer cell line HCA-7 while lesser amounts of Delta(12)-PGJ(2) and 15-deoxy-Delta(12,14)-PGJ(2) are formed. In this and other cell lines, cyclopentenone PGs have been shown to increase cell proliferation, but factors that influence their formation and metabolism are poorly understood. Unlike other PGs, cyclopentenone PGs contain alpha,beta-unsaturated carbonyl groups that readily adduct various biomolecules such as glutathione (GSH) in vitro. We now report that in HCA-7 cells, PGJ(2) is largely metabolized by conjugation to GSH. Characterization of the adducts by liquid chromatography (LC)-mass spectrometry (MS) revealed two major metabolites consisting of (1) a novel GSH conjugate in which the carbonyl at C-11 of PGJ(2) is reduced and (2) intact PGJ(2) conjugated to GSH. Approximately 70% of the PGJ(2) added to HCA-7 cells was esterifed to GSH after 2 h of incubation, suggesting this pathway represents the major route of metabolic disposition of PGJ(2) in HCA-7 cells.

The cyclopentenone product of lipid peroxidation, 15-A(2t)-isoprostane (8-isoprostaglandin A(2)), is efficiently conjugated with glutathione by human and rat glutathione transferase A4-4

Glutathione transferases (GSTs) are a large family of enzymes that can be divided into different classes based on structure. There has been considerable interest in the ability of GSTs to conjugate and inactivate endogenously derived reactive lipid peroxidation products that contain alpha,beta-unsaturated carbonyl moieties such as 4-hydroxyalkenals. One enzyme with prominent activity toward these substrates is human GST A4-4. Recently, we described a novel series of compounds termed A(2)/J(2)-isoprostanes (IsoPs) that are formed endogenously in humans from the free radical-initiated peroxidation of arachidonic acid. These compounds contain alpha,beta-unsaturated carbonyl groups and have structures similar to cyclooxygenase-derived PGA(2) and PGJ(2). Because of their chemical reactivity, these compounds may mediate tissue injury associated with oxidant stress. Herein, we report that the A-ring IsoP 15-A(2t)-IsoP (8-iso-PGA(2)) is efficiently conjugated to glutathione (GSH) by human GST A4-4 with a k(cat)/K(m) value of >200 s(-)(1) mM(-)(1). The k(cat)/K(m) value for conjugation of 15-A(2t)-IsoP by the homologous rat GST A4-4 is >2000 s(-)(1) mM(-)(1). Similar high enzyme activities were observed when PGA(2) was used as a substrate. In contrast, the human GSTs A1-1, M1-1, M2-2, P1-1, and T1-1 and rat GST T2-2 did not significantly metabolize 15-A(2t)-IsoP. These studies have therefore defined a potentially important route by which cyclopentenone IsoPs are metabolized that may serve as a mechanism for the inactivation of these highly reactive compounds.

Lipid peroxidation in aging brain and Alzheimer's disease

Lipid peroxidation is one of the major outcomes of free radical-mediated injury that directly damages membranes and generates a number of secondary products, both from fission and endocyclization of oxygenated fatty acids that possess neurotoxic activity. Numerous studies have demonstrated increased lipid peroxidation in brain of patients with Alzheimer's disease (AD) compared with age-matched controls. These data include quantification of fission and endocyclized products such as 4-hydroxy-2-nonenal, acrolein, isoprostanes, and neuroprostanes. Immunohistochemical and biochemical studies have localized the majority of lipid peroxidation products to neurons. A few studies have consistently demonstrated increased cerebrospinal fluid (CSF) levels of isoprostanes in AD patients early in the course of their dementia, and one study has suggested that CSF isoprostanes may improve the laboratory diagnostic accuracy for AD. Similar analyses of control individuals over a wide range of ages indicate that brain lipid peroxidation is not a significant feature of usual aging. Quantification of isoprostanes in plasma and urine of AD patients has yielded inconsistent results. These results indicate that brain lipid peroxidation is a potential therapeutic target in probable AD patients, and that CSF isoprostanes may aid in the assessment of antioxidant experimental therapeutics and the laboratory diagnosis of AD.

Plasma F2-isoprostane levels are elevated in chronic hemodialysis patients

AIMS

Cardiovascular mortality has been reported to be 10- to 20-fold higher in chronic dialysis patients than in the age-matched general population. It has been suggested that increased oxidant stress and resulting vascular wall injury due to uremia and the hemodialysis procedure may be one of the mechanisms predisposing to these cardiovascular complications. Further, hemodialysis membrane bioincompatibility can contribute to increased oxidative stress and prevalence of inflammation.

MATERIALS

We studied 18 chronic hemodialysis (CHD) patients (age 62.8 +/- 14.7 years, 39% male, 61% African-American, 44% insulin-dependent diabetic, 61% smokers, 61% with documented coronary artery disease) during hemodialysis with 2 membranes with different flux and complement activating properties.

METHODS

We have measured free and phospholipid-bound F2-isoprostane (F2-IsoP) levels, a sensitive marker of oxidative stress, in CHD patients and compared them to levels in healthy subjects. We have also examined the acute effects of the hemodialysis procedure using both biocompatible and bioincompatible membranes on F2-IsoP levels.

RESULTS

The results indicated that, compared to controls, both free (96.2 +/- 48.8 pg/ml versus 37.6 +/- 17.2 pg/ml) and bound F2-IsoP (220.4 +/- 154.8 pg/ml versus 146.8 +/- 58.4 pg/ml) levels were significantly higher (p < 0.05 for both). There was a statistically significant decrease in free F2-IsoP concentrations at 15 and 30 minutes of HD, which rebounded to baseline levels at the completion of the procedure. There were no significant differences in F2-IsoP concentrations between the 2 study dialyzers at any time point. Age, smoking status, diabetes mellitus and presence of cardiovascular disease were also not correlated with F2-IsoP levels in this patient population. There was a significant association between predialysis F2-IsoP and C-reactive protein concentrations.

CONCLUSION

Using a sensitive and specific assay for the measurement of F2-IsoP, we demonstrated that CHD patients are under increased oxidative stress. During a single hemodialysis treatment, the hemodialysis membrane appears to have no discernable effect on oxidative stress status. Measurement of F2-isoprostanes may be a useful biomarker of oxidative stress status as well as in developing new therapeutic strategies to ameliorate inflammatory and oxidative injury in this patient population.

Peripheral F2-isoprostanes and F4-neuroprostanes are not increased in Alzheimer's disease

Quantitative biomarkers of oxidative damage, such as the F(2)-isoprostanes (IsoPs) and F(4)-neuroprostanes (F(4)-NeuroPs), may be useful in assessing progression and response to therapeutics in patients with Alzheimer's disease. F(2)-IsoPs and F(4)-NeuroPs are reproducibly increased in brain and cerebrospinal fluid of Alzheimer's disease patients; however, results in blood and urine have been conflicting. We tested the hypothesis that F(2)-IsoPs and F(4)-NeuroPs in plasma or urine quantitatively reflect oxidative damage to the central nervous system. Our results showed that urine levels of F(2)-IsoPs or their major metabolite were not significantly different between 56 Alzheimer's disease patients and 34 controls. In addition, urine and cerebrospinal fluid F(2)-IsoP levels in 32 Alzheimer's disease patients did not correlate. Supporting these conclusions, elevated rat cerebral F(2)-IsoPs and F(4)-NeuroPs after systemic exposure to kainic acid were not associated with a significant change in their plasma or urine levels. These results show that plasma and urine F(2)-IsoPs and F(4)-NeuroPs do not accurately reflect central nervous system levels of these biomarkers and are not reproducibly elevated in body fluids outside of central nervous system in Alzheimer's disease patients. These results should guide the organization of clinical trials now being planned for patients with Alzheimer's disease.

Factors associated with oxidative stress in human populations

Oxidation of biomolecules may play a role in susceptibility to a number of diseases. However, there are few large-scale survey data describing oxidative damage that occurs in humans and the demographic, physical, or nutritional factors that may be associated with it. Such information is essential for the design and analysis of studies investigating the role of oxidative stress in health and disease. This paper presents data on levels of two biomarkers of lipid peroxidation, malondialdehyde and F(2)-isoprostanes, in 298 healthy adults aged 19-78 years. The study was conducted in Berkeley and Oakland, California, in 1998-1999. Sex was the strongest predictor of lipid peroxidation as measured by both biomarkers (p < 0.0001); it was stronger than smoking. C-reactive protein was positively associated with lipid peroxidation (p = 0.004), as was plasma cholesterol. Plasma ascorbic acid had a strong inverse relation (p < 0.001) with both biomarkers. Plasma beta-carotene was also associated with F(2)-isoprostanes. Other plasma antioxidants were not associated with lipid peroxidation biomarkers, once ascorbic acid was included in the multivariate model. Future surveys and epidemiologic studies should measure at least one marker of oxidative damage, as well as plasma ascorbic acid. These data would permit a better understanding of the role that oxidants and antioxidants play in the health of human populations.

Herpes simplex virus type 1 encephalitis is associated with elevated levels of F2-isoprostanes and F4-neuroprostanes

To better understand the pathogenesis of herpes simplex virus type 1 (HSV-1) infections of the nervous system, concentrations of F(4)-neuroprostanes (F(4)-NP) and F(2)-isoprostanes (F(2)-IP) in the murine brain were determined following intracerebral inoculation of HSV-1 or normal saline. F(4)-NP are highly selective, quantitative markers of neuronal oxidative damage, while F(2)-IP are markers of oxidative damage to brain tissue not limited to a certain cell type. In contrast to saline-treated control animals, HSV-1-infected animals developed encephalitic symptoms associated with severe inflammation, widespread HSV-1 protein expression, and significantly elevated F(4)-NP and F(2)-IP levels in the brain. Survivors of acute HSV-1 infection showed no encephalitic symptoms 2 to 3 weeks following virus inoculation. Brain tissue derived from mice euthanized 2 month after virus inoculation demonstrated expression of HSV-1 latency-associated transcripts without detectable HSV-1 protein expression. However, brain tissue from these animals showed focal chronic inflammation, moderately elevated F(2)-IP levels, and normal levels of F(4)-NP. These observations provide novel biochemical evidence that oxidant tissue injury is a mechanism underlying neuronal damage during acute HSV-1 encephalitis and suggest that oxidative damage to tissue may continue in the mammalian brain until at least several weeks after recovery from the symptomatic phase of HSV-1 infection.

Formation of isoprostane bicyclic endoperoxides from the autoxidation of cholesteryl arachidonate

Autoxidation of polyunsaturated fatty acids and esters leads to a complex mixture containing hydroperoxides and cyclic peroxides. Prostaglandin bicyclic endoperoxides have been detected from the autoxidation of cholesteryl arachidonate by LC-MS and GC-MS techniques. All four possible types (I-IV) of bicyclic endoperoxides have been found starting from different regioisomeric hydroperoxides of cholesteryl arachidonate. Furthermore, the stereochemistry of Type IV bicyclic endoperoxides has been determined by conversion to pentafluorobenzyl (PFB) ester, trimethylsilyl (TMS) derivatives, and comparison with synthetic standards by the use of GC-MS. All eight possible diastereomers of the derivatized isoprostanes were observed and were separated by gas chromatography. The bicyclic endoperoxides with the two alkyl chains syn on the cyclopentane ring were formed preferentially to those with anti configuration, a result anticipated from earlier work. Substantial amounts of the anti-substituted isoprostanes, including PGF(2)(alpha), were, however, observed in the product mixture.

Opposite effects of cyclooxygenase-1 and -2 activity on the pressor response to angiotensin II

Therapeutic use of cyclooxygenase-inhibiting (COX-inhibiting) nonsteroidal antiinflammatory drugs (NSAIDs) is often complicated by renal side effects including hypertension and edema. The present studies were undertaken to elucidate the roles of COX1 and COX2 in regulating blood pressure and renal function. COX2 inhibitors or gene knockout dramatically augment the pressor effect of angiotensin II (Ang II). Unexpectedly, after a brief increase, the pressor effect of Ang II was abolished by COX1 deficiency (either inhibitor or knockout). Ang II infusion also reduced medullary blood flow in COX2-deficient but not in control or COX1-deficient animals, suggesting synthesis of COX2-dependent vasodilators in the renal medulla. Consistent with this, Ang II failed to stimulate renal medullary prostaglandin E(2) and prostaglandin I(2) production in COX2-deficient animals. Ang II infusion normally promotes natriuresis and diuresis, but COX2 deficiency blocked this effect. Thus, COX1 and COX2 exert opposite effects on systemic blood pressure and renal function. COX2 inhibitors reduce renal medullary blood flow, decrease urine flow, and enhance the pressor effect of Ang II. In contrast, the pressor effect of Ang II is blunted by COX1 inhibition. These results suggest that, rather than having similar cardiovascular effects, the activities of COX1 and COX2 are functionally antagonistic.

Increasing plasma fatty acids elevates F2-isoprostanes in humans: implications for the cardiovascular risk factor cluster

OBJECTIVE

To determine whether raised concentrations of non-esterified fatty acids (NEFAs) may contribute to the cardiovascular risk factor cluster by increasing oxidative stress in vivo.

DESIGN AND METHODS

Plasma and urine F2-isoprostanes, biomarkers of oxidative stress, were measured after an overnight fast and during a 4 h infusion of Intralipid and heparin to increase NEFAs in 10 obese hypertensive patients with and 12 healthy normotensive individuals without evidence of insulin resistance. A time-control group of nine healthy normotensive individuals received saline and heparin.

RESULTS

Plasma F2-isoprostanes increased more in obese hypertensive individuals than in lean normotensive individuals after 2 h (14.9 +/- 2.8 ng/ml compared with 4.6 +/- 2.8 ng/ml; P < 0.05) but not after 4 h (10.3 +/- 2.5 ng/ml compared with 8.1 +/- 4.1 ng/ml; NS) of the Intralipid and heparin infusion. When obese and lean individuals were combined, plasma (+9.1 +/- 2.5 ng/ml; P < 0.05) and urine (+0.7 +/- 0.3 ng/mg creatinine; P < 0.05) F2-isoprostanes increased by about 20% after 4 h of Intralipid and heparin, whereas plasma F2-isoprostanes decreased by approximately 20% (-9.7 +/- 4.5 ng/ml; P < 0.05) after 4 h of saline and heparin. When individuals from both infusions were combined, the correlation between changes in plasma NEFAs and F2-isoprostanes after 4 h persisted after controlling for changes in triglyceride concentrations (partial r = 0.49; P < 0.01), whereas the correlation between changes in triglycerides and F2-isoprostanes did not persist after controlling for changes in NEFA concentrations (partial r = 0.33, NS).

CONCLUSIONS

The findings indicate that an acute increase in plasma lipids increases the concentration of F2-isoprostanes, biomarkers of oxidative stress, especially in obese hypertensive individuals. The observations raise the possibility that increased concentrations of NEFAs contribute to the cardiovascular risk factor cluster through oxidative-stress-sensitive mechanisms.

Cyclooxygenase-2-dependent prostacyclin formation is regulated by low density lipoprotein cholesterol in vitro

Reduction of plasma low density lipoprotein (LDL) levels is associated with a reduced risk of myocardial infarction, stroke, and death. Some of this clinical benefit may be derived from an improvement in endothelium-dependent vasodilation. In the present study, we examined the effects of LDL reduction on cyclooxygenase (COX) activity and prostacyclin (PGI2) production. Human umbilical vein endothelial cells exposed to reduced concentrations of LDL demonstrated increased PGI2 production in a dose-dependent manner (from 0.75+/-0.2 to 2.6+/-0.2 ng/mL, P<0.0001). This alteration in PGI2 production did not result from LDL-induced changes in PGI2 synthase expression. However, selective inhibition of COX-2, but not COX-1, blocked PGI2 production under low cholesterol conditions. Addition of exogenous cholesterol induces dose-dependent reductions in endothelial COX-2 expression as measured by reverse transcription-polymerase chain reaction and by Western blotting. Pretreatment of cells with actinomycin D, a transcription inhibitor, reduced COX-2-derived PGI2 production by 45.9% (from 0.55+/-0.09 to 0.25+/-0.08 ng/mL). Taken together, these observations indicate that endothelial PGI2 production is regulated by cholesterol at the transcriptional level and that cholesterol-sensitive transcriptional pathways that regulate COX-2 expression are present in vascular tissue.

Influence of vitamin C supplementation on oxidative and immune changes after an ultramarathon

The purpose of this randomized study was to measure the influence of vitamin C (n = 15 runners) compared with placebo (n = 13 runners) supplementation on oxidative and immune changes in runners competing in an ultramarathon race. During the 7-day period before the race and on race day, subjects ingested in randomized, double-blind fashion 1,500 mg/day vitamin C or placebo. On race day, blood samples were collected 1 h before race, after 32 km of running, and then again immediately after race. Subjects in both groups maintained an intensity of approximately 75% maximal heart rate throughout the ultramarathon race and ran a mean of 69 km (range: 48-80 km) in 9.8 h (range: 5-12 h). Plasma ascorbic acid was markedly higher in the vitamin C compared with placebo group prerace and rose more strongly in the vitamin C group during the race (postrace: 3.21 +/- 0.29 and 1.28 +/- 0.12 microg/100 microl, respectively, P < 0.001). No significant group or interaction effects were measured for lipid hydroperoxide, F2-isoprostane, immune cell counts, plasma interleukin (IL)-6, IL-10, IL-1-receptor antagonist, or IL-8 concentrations, or mitogen-stimulated lymphocyte proliferation and IL-2 and IFN-gamma production. These data indicate that vitamin C supplementation in carbohydrate-fed runners does not serve as a countermeasure to oxidative and immune changes during or after a competitive ultramarathon race.

Products of the isoprostane pathway: unique bioactive compounds and markers of lipid peroxidation

We previously reported the discovery of prostaglandin F2-like compounds (F2-isoprostanes) formed by nonenzymatic free-radical-induced peroxidation of arachidonic acid. Quantification of F2-isoprostanes has proven to be a major advance in assessing oxidative stress status in vivo. Central in the pathway of formation of isoprostanes are prostaglandin H2-like endoperoxides, which also undergo rearrangement in vivo to form E-ring, D-ring, and thromboxane-ring compounds. E2- and D2-isoprostanes also undergo dehydration in vivo to form reactive cyclopentenone A2- and J2-isoprostanes, which are susceptible to Michael addition reactions with thiols. Recently, we described the formation of highly reactive gamma-ketoaldehydes (now termed isoketals) as products of isoprostane endoperoxide rearrangement which readily adduct to lysine residues on proteins and induce cross-links at rates that far exceed other aldehyde products of lipid peroxidation. Isoprostane-like compounds (neuroprostanes) and isoketal-like compounds (neuroketals) are formed from oxidation of docosahexaenoic acid, which is enriched in the brain, and measurement of neuroprostanes may provide a unique marker of oxidative neuronal injury.

Characterization of LPS-induced lung inflammation in cftr-/- mice and the effect of docosahexaenoic acid

The mechanism by which Pseudomonas causes excessive inflammation in the cystic fibrosis lung is unclear. We have reported that arachidonic acid is increased and docosahexaenoic acid (DHA) decreased in lung, pancreas, and ileum from cftr-/- mice. Oral DHA corrected this defect and reversed the pathology. To determine which mediators regulate inflammation in lungs from cftr-/- mice and whether inhibition occurs with DHA, cftr-/- and wild-type (WT) mice were exposed to aerosolized Pseudomonas lipopolysaccharide (LPS). After 2 days of LPS, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2, and KC levels in bronchoalveolar lavage fluid were increased in cftr-/- compared with WT mice and not suppressed by pretreatment with oral DHA. Neutrophil levels were not different between cftr-/- and WT mice. After 3 days of aerosolized LPS, neutrophil concentration, TNF-alpha, and the eicosanoids 6-keto-PGF1alpha, PGF2alpha, PGE2, and thromboxane B2 were all increased in bronchoalveolar lavage fluid from cftr-/- mice compared with WT controls. Oral DHA had no significant effect on TNF-alpha levels in cftr-/- mice. In contrast, neutrophils and eicosanoids were decreased in cftr-/- but not in WT mice treated with DHA, indicating that the effects of DHA on these inflammatory parameters may be related to correction of the membrane lipid defect.

Cyclooxygenase-2 promotes early atherosclerotic lesion formation in LDL receptor-deficient mice

BACKGROUND

Atherosclerosis has features of an inflammatory disease. Because cyclooxygenase (COX)-2 is expressed in atherosclerotic lesions and promotes inflammation, we tested the hypotheses that selective COX-2 inhibition would reduce early lesion formation in LDL receptor-deficient (LDLR-/-) mice and that macrophage COX-2 expression contributes to atherogenesis in LDLR-/- mice.

METHODS AND RESULTS

Treatment of male LDLR-/- mice fed the Western diet with rofecoxib or indomethacin for 6 weeks resulted in significant reductions in atherosclerosis in the proximal aorta (25% and 37%) and in the aorta en face (58% and 57%), respectively. Rofecoxib treatment did not inhibit platelet thromboxane production, a COX-1-mediated process, but it significantly reduced the urinary prostacyclin metabolite 2,3-dinor-6-keto-PGF1alpha. Fetal liver cell transplantation was used to generate LDLR-/- mice null for expression of the COX-2 gene by macrophages. After 8 weeks on the Western diet, COX-2-/- --> LDLR-/- mice developed significantly less (33% to 39%) atherosclerosis than control COX-2+/+ --> LDLR-/- mice. In both the inhibitor studies and the transplant studies, serum lipids did not differ significantly between groups.

CONCLUSIONS

The present studies provide strong pharmacological and genetic evidence that COX-2 promotes early atherosclerotic lesion formation in LDLR-/- mice in vivo. These results support the potential of anti-inflammatory approaches to the prevention of atherosclerosis.

Selective cyclooxygenase-1 and -2 inhibitors each increase allergic inflammation and airway hyperresponsiveness in mice

Nonselective cyclooxygenase (COX) inhibition during allergic sensitization with ovalbumin in a murine model leads to an increase in the Type 2 cytokines interleukin-5 (IL-5) and IL-13; however, the effect of selective COX-1 and COX-2 inhibitors on these cytokines is unknown. We found that COX-1 protein was constitutively expressed in lung tissue. Expression of COX-1 protein did not increase with ovalbumin sensitization, but expression of COX-2 protein did. Ovalbumin-sensitized mice treated with either selective COX-1 inhibitor SC58560 (OVA-COX-1 inhibitor) or selective COX-2 inhibitor SC58236 (OVA-COX-2 inhibitor) had significantly greater airway hyperresponsiveness (p < 0.05) and higher levels of IL-13 (p < 0.05) in lung supernatants than did untreated mice that were ovalbumin sensitized (OVA). Lung mRNA levels for the chemokine receptors CCR1 through CCR5 (expressed on eosinophils, basophils, lymphocytes, and dendritic cells) were increased in the OVA-COX-2 inhibitor and OVA-indomethacin groups. We conclude that in the BALB/c mouse, COX inhibition with either a COX-1 or COX-2 inhibitor during allergen sensitization augments production of IL-13 and increases airway hyperresponsiveness.

Thioredoxin reductase reduces lipid hydroperoxides and spares alpha-tocopherol

We investigated whether and how rat liver thioredoxin reductase spares alpha-tocopherol in biomembranes. Purified hydroperoxides of beta-linoleoyl-gamma-palmitoylphosphatidylcholine were decreased 35% by treatment with thioredoxin reductase and 54% by thioredoxin reductase plus E. coli thioredoxin. Thioredoxin reductase also halved the amount of hydroperoxides that had been formed during photoperoxidation of liposomes composed of beta-linoleoyl-gamma-palmitoylphosphatidylcholine, and of emulsions of both cholesterol and cholesteryl linolenate. In erythrocyte ghosts, thioredoxin reductase spared alpha-tocopherol from oxidation by both soybean lipoxygenase and ferricyanide. Thioredoxin reductase also decreased F(2)-isoprostanes in ghosts oxidized by ferricyanide, suggesting that its ability to spare alpha-tocopherol relates to reduction of lipid hydroperoxides.

Mouse cerebral prostaglandins, but not oxidative damage, change with age and are responsive to indomethacin treatment

Epidemiological and clinical trial data indicate that at least some non-steroidal anti-inflammatory drugs (NSAIDs) reduce the risk of developing Alzheimer's disease (AD). Advancing age is the most robust risk factor for AD. If NSAIDs mitigate the initiation of AD by affecting processes of aging, and if the target of NSAIDs are cyclooxygenases (COX), then COX activity would be hypothesized to increase with advancing age in brain regions affected by AD. We tested this hypothesis in mouse cerebrum by measuring two outcomes of increased COX activity, prostaglandin (PG) levels and markers of oxidative damage. Our results showed that frontal cortical PGE(2) and 6-keto-PGF(1alpha) levels were significantly increased at 14 months compared to 2 months, but that frontal cortical levels of these PGs at 26 months returned to levels observed at 2 months of age. At all ages, 2-week treatment with indomethacin (14 microg/ml drinking water, or approximately 2.2 mg/kg per day) equally suppressed frontal cortical levels of both PGs. In contrast, basal levels of oxidative damage to cerebral cortex did not increase in mice aged up to 26 months, and indomethacin treatment did not significantly alter basal levels of oxidative damage as assayed by F(2)-isoprostanes or protein carbonyls. These results suggest that indomethacin may influence the initiation of AD by reducing cerebral PG elevation that may occur in middle age, but that it is unlikely to have a direct effect on levels of oxidative damage.

Association between low serum enterolactone and increased plasma F2-isoprostanes, a measure of lipid peroxidation

Evidence suggests that low serum enterolactone concentration might be an independent risk factor for acute coronary events. Enterolactone is a lignan, which is formed by intestinal bacteria from precursors in plant foods. Due to the biphenolic structure of enterolactone, it could act as an antioxidant and through this contribute to cardiovascular health. The aim of this study was to test the hypothesis that a low serum enterolactone concentration is associated with increased in vivo lipid peroxidation, assessed by plasma F2-isoprostane concentrations. We investigated this association in a subset of participants in 'The Antioxidant Supplementation in Atherosclerosis Prevention' (ASAP) study. Out of 256 male participants a subsample of 100 consecutive men from baseline was selected for F2-isoprostane assays. The mean serum enterolactone concentration was 16.6 nmol/l and that of F2-isoprostanes 29.6 ng/l. The correlation coefficient for association between serum enterolactone and F2-isoprostane concentrations was -0.30 (P<0.003). Plasma F2-isoprostane levels decreased linearly across quintiles of serum enterolactone concentration (P=0.008 for a linear trend). In a multivariate model, enterolactone persisted as a significant predictor after adjustment for vitamins and other variables, with the strongest associations with F2-isoprostanes. Our present data suggest that low serum enterolactone concentration is associated with enhanced in vivo lipid peroxidation in men.

Antioxidant supplementation decreases lipid peroxidation biomarker F(2)-isoprostanes in plasma of smokers

Free radicals in cigarette smoke (CS) cause oxidative damage to proteins, DNA, and lipids, contributing to the pathobiology of atherosclerosis, heart disease, and cancer. In vitro studies have shown that antioxidants quench free radicals and ameliorate certain aspects of biomolecular damage caused by CS. It is hypothesized that a combination of antioxidants is more effective than a single antioxidant, due to their interactions. To investigate whether supplemental antioxidants reduce CS-related lipid peroxidation in vivo and whether they are more effective in combination, we conducted an intervention study in smokers. In a randomized double-blind placebo-controlled trial, we investigated whether vitamin C or an antioxidant mixture containing vitamin C, alpha-lipoic acid, and vitamin E decreases plasma F(2)-isoprostane levels, an index of oxidant stress, in smokers. Plasma of 126 smokers (mean age, 46 years; age range, 20-78 years) was analyzed for F(2)-isoprostanes at baseline and after intervention with antioxidants and placebo. In smokers with a body mass index (BMI) above the median, 2 months of daily supplementation with 500 mg of vitamin C decreased plasma F(2)-isoprostane levels by 28.8 pmol/liter when compared with the placebo group (P = 0.001); levels in the mixture group were 7.45 pmol/liter lower after treatment, but this difference was not statistically significant (P = 0.14). There was no treatment effect in smokers with a low BMI. BMI was significantly positively associated with plasma F(2)-isoprostane levels (trend P = 0.001). Antioxidants decrease smoking-related lipid peroxidation markers of oxidative stress in humans with high BMI. Our results do not indicate that an antioxidant combination is more effective than vitamin C alone. The intake of antioxidants may help prevent smoking-related diseases. Smoking cessation should still be considered the most effective way to prevent smoking-related diseases.

In-vivo effects of Glu298Asp endothelial nitric oxide synthase polymorphism

Endothelial nitric oxide synthase catalyses the formation of the vasodilator nitric oxide, a major regulator of vascular tone. The Asp298 polymorphism of the nitric oxide synthase gene is associated with altered function and expression of the enzyme in vitro and myocardial infarction and coronary artery spasm in vivo. We examined the effect of the Glu298Asp polymorphism on: (1) local vascular responses to phenylephrine, acetylcholine, glyceryl trinitrate and prostaglandin E1 in the dorsal hand vein; (2) changes in forearm blood flow during mental stress, a measure of nitric oxide-mediated effect on resistance vessels; (3) excretion of urinary nitrite/nitrate as a measure of total body nitric oxide production; and (4) F2-isoprostane metabolite, a measure of oxidative stress, in healthy Glu298 (n = 12) and Asp298 (n = 13) homozygotes. There were no significant differences in acetylcholine dose responses (P = 0.29) in Glu298 and Asp298 homozygotes. Responses to glyceryl trinitrate, prostaglandin E1 and the alpha-adrenergic agonist phenylephrine did not differ by genotype. Forearm blood flow was similar at rest and increased significantly (from 7.5 ml/min/100 ml to 12.2 ml/min/100 ml; P = 0.003), but similarly (P = 0.2), during mental stress in both genotypes. Asp298 homozygotes excreted significantly less nitrate/nitrite than Glu298 homozygotes (nitrate + nitrite/creatinine ratio 0.05 +/- 0.01 vs. 0.09 +/- 0.01, respectively; P < 0.005). Urinary F2-isoprostane metabolite excretion did not differ (Glu298, 2.04 +/- 0.25 ng/mg creatinine; Asp298, 1.85 +/- 0.37 ng/mg creatinine; P = 0.7). We conclude that in healthy volunteers the Glu298Asp polymorphism affects endogenous nitric oxide production without affecting nitric oxide-mediated vascular responses. This polymorphism may only have clinical significance in the presence of endothelial dysfunction.