Isofurans: novel products of lipid peroxidation that define the occurrence of oxidant injury in settings of elevated oxygen tension

Immunosuppressive therapies attenuate paraquat-induced renal dysfunction by suppressing inflammatory responses and lipid peroxidation

Although paraquat (PQ) induces oxidative damage and inflammatory responses in the lungs, the mechanism underlying PQ-induced acute kidney injury in patients is unclear. Immunosuppressive therapy with glucocorticoids and the immunosuppressant cyclophosphamide (CP) has been employed to treat patients with PQ poisoning. This study examined whether PQ could concurrently cause renal injury, inflammatory responses, and oxidative damage in the kidneys, and whether CP and dexamethasone (DEX) could suppress PQ-induced alterations. Mice were assigned to eight groups: Control, PQ, DEX, PQ plus DEX, CP, PQ plus CP, DEX plus CP, and PQ plus DEX with CP. DEX, CP, and DEX plus CP reversed PQ-induced renal injury, as indicated by urinary albumin-to-creatinine ratios and urea nitrogen levels in serum. The treatments also attenuated PQ-induced renal infiltration of leukocytes and macrophages and induction of the Il6, Tnf, Icam, Cxcl2, Tlr4, and Tlr9 genes encoding the inflammatory mediators in the kidneys. However, DEX only partially suppressed the macrophage infiltration, whereas DEX plus CP provided stronger protection than DEX or CP alone for the induction of Il6 and Cxcl2. Moreover, through the detection of F₂-isoprostanes (F₂-IsoPs) and isofurans in the kidneys and lungs and F₂-IsoPs in the plasma and urine, the therapies were found to suppress PQ-induced lipid peroxidation, although DEX was less effective. Finally, PQ decreased ubiquinol-9:ubiquinone-9 ratios in the kidneys. This effect of PQ was not found under CP treatment, but the ratio was lower than that of the control group. Our findings suggest that the suppression of PQ-induced inflammatory responses by DEX and CP in the kidneys can mitigate oxidative damage and acute kidney injury.

Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids, and influence cellular function via effects on membrane properties, and also by acting as a precursor pool for lipid mediators. These lipid mediators are formed via activation of pathways involving at least one step of dioxygen-dependent oxidation, and are consequently called oxylipins. Their biosynthesis can be either enzymatically-dependent, utilising the promiscuous cyclooxygenase, lipoxygenase, or cytochrome P450 mixed function oxidase pathways, or nonenzymatic via free radical-catalyzed pathways. The oxylipins include the classical eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes, and also more recently identified lipid mediators. With the advent of new technologies there is growing interest in identifying these different lipid mediators and characterising their roles in health and disease. This review brings together contributions from some of those at the forefront of research into lipid mediators, who provide brief introductions and summaries of current understanding of the structure and functions of the main classes of nonclassical oxylipins. The topics covered include omega-3 and omega-6 PUFA biosynthesis pathways, focusing on the roles of the different fatty acid desaturase enzymes, oxidized linoleic acid metabolites, omega-3 PUFA-derived specialized pro-resolving mediators, elovanoids, nonenzymatically oxidized PUFAs, and fatty acid esters of hydroxy fatty acids.

High-Density Lipoproteins and Acute Kidney Injury

High-density lipoprotein (HDL) particles, best known for their anti-atherosclerotic effects, also may play a beneficial role during acute renal stress. HDL from healthy human beings also shows anti-inflammatory and anti-oxidant capacities, promotes endothelial function and repair, and serves as a systemic signaling mechanism facilitating rapid interorgan communication during times of physiologic stress. Higher concentrations of HDL are associated with less acute kidney injury after sepsis, cardiac and vascular surgery, and contrast-exposure during percutaneous coronary interventions. A better understanding of the interplay between HDL and the kidney both under homeostatic conditions and under acute physiologic stress could lead to the identification of novel risk factors and therapeutic targets for acute kidney injury prevention and treatment in the future.

Perioperative high density lipoproteins, oxidative stress, and kidney injury after cardiac surgery

Oxidative stress promotes acute kidney injury (AKI). Higher HDL cholesterol concentrations are associated with less AKI. To test the hypothesis that HDL antioxidant activity is associated with AKI after cardiac surgery, we quantified HDL particle (HDL-P) size and number, paraoxonase-1 (PON-1) activity, and isofuran concentrations in 75 patients who developed AKI and 75 matched control patients. Higher preoperative HDL-P was associated with less AKI (OR: 0.80; 95% CI, 0.71-0.91; P = 0.001), higher PON-1 activity ( P < 0.001), and lower plasma concentrations of isofurans immediately after surgery (P = 0.02). Similarly, higher preoperative small HDL-P was associated with less AKI, higher PON-1 activity, and lower isofuran concentrations. Higher intraoperative particle losses were associated with less AKI (OR: 0.79; 95% CI 0.67-0.93; P = 0.005), and with decreased postoperative isofuran concentrations (P = 0.04) . Additionally, higher preoperative small HDL-P and increased intraoperative small particle loss were associated with improved long-term renal function (P = 0.003, 0.01, respectively). In conclusion, a higher preoperative concentration of HDL-P, particularly small particles, is associated with lower oxidative damage and less AKI. Perioperative changes in HDL-P concentrations are also associated with AKI. Small HDL-P may represent a novel modifiable risk factor for AKI.

A Case of Carbon Monoxide-Induced Delayed Neurological Sequelae Successfully Treated with Hyperbaric Oxygen Therapy, N-Acetylcysteine, and Glucocorticoids: Clinical and Neuroimaging Follow-Up

Carbon monoxide (CO) poisoning is a leading cause of intentional and unintentional poisoning worldwide, associated with mortality and severe morbidity. Some survivors of CO poisoning develop, after a lucid interval, a potentially permanent encephalopathy in the form of cognitive impairment and movement disorders, such as Parkinsonism. One of the most frequent neuroimaging findings is a cerebral white matter damage, but so far its precise cause and specific therapy are still debated. We here report the case of a 33-year-old woman with severe carbon monoxide poisoning who, after a period of lucid interval, presented symptoms of declining motor and cognitive functions. She was treated with 40 sessions of Hyperbaric Oxygen Therapy (HBOT). The therapeutic use of oxygen at supraphysiological pressures might either increase systemic oxidative stress or cause an overproduction of oxygen free radicals as drawbacks. Concurrent use of antioxidants and anti-inflammatory drugs may prevent the side effects of oxygen therapy at supraphysiological pressure due to oxidative stress. For this reason, the patient was also treated with high-dose N-Acetylcysteine and glucocorticoids. Here, we describe the longitudinal monitoring of patient's cognitive abilities and leukoencephalopathy associated with her positive clinical outcome.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

GC-MS Analysis of Lipid Oxidation Products in Blood, Urine, and Tissue Samples

Oxidant stress has been identified as important in the pathology of many diseases. Oxidation products of polyunsaturated fatty acids collectively termed isoprostanes, neuroprostanes, and isofurans are considered the most reliable measures of in vivo lipid oxidation, and they are widely used to assess oxidant stress in various diseases. Here we describe the measurement of these lipid oxidation products using gas chromatography mass spectrometry with electron capture negative ionization.

Oxidized Low-density Lipoprotein and the Incidence of Age-related Macular Degeneration

PURPOSE

To examine the relationship between serum oxidized low-density lipoprotein (ox-LDL) cholesterol and the incidence of age-related macular degeneration (AMD) over a 25-year period in a sample of persons from the population-based Beaver Dam Eye Study (BDES).

DESIGN

Observational prospective cohort study.

PARTICIPANTS

A total of 4972 people from the BDES (aged 43-84 years and living in Beaver Dam, Wisconsin in 1988) seen during at least 1 of 6 examination phases at approximately 5-year intervals between 1988 and 2016.

METHODS

A 50% random sample of participants (N = 2468) was selected for ox-LDL measurements. Stored frozen specimens from every examination phase were processed using an enzyme-linked immunosorbent assay from a single batch. All available intervals were included for a person, resulting in 6586 person-visits.

MAIN OUTCOME MEASURES

Age-related macular degeneration was assessed using the Wisconsin Age-related Maculopathy Grading System, and severity was defined using a 5-step severity scale. The severity of the worse eye at each examination was used for analyses. A multi-state Markov (MSM) model was fit to simultaneously assess the ox-LDL relationship to all AMD transitions, including incidence of any AMD, incidence of late AMD, and worsening and improvement of AMD over the 25 years of the study.

RESULTS

The mean (standard deviation) level of ox-LDL was 75.3 (23.1) U/L at the baseline examination. When adjusting for age, sex, ARMS2 and CFH risk alleles, and examination phase, the ox-LDL at the beginning of a period was not statistically significantly associated with the incidence of any AMD (hazard ratio per 10 U/L ox-LDL was 1.03, 95% confidence interval 0.98,1.09). Furthermore, ox-LDL was not associated with worsening anywhere along the AMD severity scale, nor with incidence of late AMD. The lack of relationships of ox-LDL to the incidence of any AMD or worsening of AMD remained after adjustment for history of statin use, smoking status, body mass index, and history of cardiovascular disease (data not shown).

CONCLUSIONS

Our findings do not provide evidence for statistically significant relationships between ox-LDL and AMD disease development or worsening of AMD.

Hyperbaric oxygen therapy is not associated with oxidative stress assessed using plasma F2-isoprostanes and isofurans

BACKGROUND AND AIMS

Hyperbaric oxygen (HBO) therapy is increasingly used in medical practice as a means of enhancing the formation of collagen matrix and angiogenesis, thus promoting healing in wounds and necrotic tissue. However, there are concerns that oxygen can also associate with increased production of oxygen free radicals and oxidative stress. F₂-Isoprostanes (F₂-IsoPs) formed by non-enzymatic oxidation of arachidonic acid (AA) are reliable measures for assessing oxidative stress in vivo. In addition, under conditions of high oxygen tension isofurans (IsoFs) are preferentially formed from AA and are considered to better reflect oxidative stress in the setting of high oxygen tension. This study aimed to measure plasma IsoFs and F₂-IsoP in patients receiving HBO therapy to treat osteonecrosis secondary to radiation therapy. Our hypothesis was that IsoFs would continue to rise with increasing oxygen pressures in contrast to F₂-IsoPs whose synthesis would be reduced.

METHODS

Twelve patients receiving hyperbaric therapy to treat osteonecrosis secondary to radiation therapy were studied during hyperbaric treatment. Blood samples were collected prior to, during and after cessation of HBO therapy that lasted for 119min. Seven serial blood samples were collected for measurement of plasma F₂-IsoPs and IsoFs, blood gases and haemoglobin.

RESULTS

Oxygen saturation and venous oxygen partial pressure (PvO₂) rose significantly during hyperbaric therapy. However, there were no significant changes in plasma IsoFs or F₂-IsoPs during the hyperbaric therapy session.

CONCLUSION

In this study of patients with osteonecrosis, HBO therapy at a maximum pressure of 2.4atm with up to 100% oxygen did not worsen oxidative stress assessed using plasma F₂- IsoFs and IsoPs.

Role of mitochondria-derived reactive oxygen species in microvascular dysfunction in chronic kidney disease

Cardiovascular disease is the leading cause of mortality in chronic kidney disease (CKD). Mitochondrial dysfunction secondary to CKD is a potential source of oxidative stress that may impair vascular function. This study sought to determine if mitochondria-derived reactive oxygen species contribute to microvascular dysfunction in stage 3-5 CKD. Cutaneous vasodilation in response to local heating was assessed in 20 CKD patients [60 ± 13 yr; estimated glomerular filtration rate (eGFR) 46 ± 13 ml·kg^-1·1.73 m^-2] and 11 matched healthy participants (58 ± 2 yr; eGFR >90 ml·kg^-1·1.73 m^-2). Participants were instrumented with two microdialysis fibers for the delivery of 1) Ringer solution, and 2) the mitochondria- specific superoxide scavenger MitoTempo. Skin blood flow was measured via laser Doppler flowmetry during standardized local heating (42°C). Cutaneous vascular conductance (CVC) was calculated as a percentage of the maximum conductance achieved with sodium nitroprusside infusion at 43°C. Urinary isofuran/F₂-isoprostane ratios were assessed by gas-chromatography mass spectroscopy. Isofuran-to-F₂-isoprostane ratios were increased in CKD patients (3.08 ± 0.32 vs. 1.69 ± 0.12 arbitrary units; P < 0.01) indicative of mitochondria-derived oxidative stress. Cutaneous vasodilation was impaired in CKD compared with healthy controls (87 ± 1 vs. 92 ± 1%CVC_max; P < 0.01). Infusion of MitoTempo significantly increased the plateau phase CVC in CKD patients (CKD Ringer vs. CKD MitoTempo: 87 ± 1 vs. 93 ± 1%CVC_max; P < 0.01) to similar levels observed in healthy controls ( P = 0.9). These data provide in vivo evidence that mitochondria-derived reactive oxygen species contribute to microvascular dysfunction in CKD and suggest that mitochondrial dysfunction may be a potential therapeutic target to improve CKD-related vascular dysfunction.

Biomarkers of mercury toxicity: Past, present, and future trends

Mercury (Hg) toxicity continues to represent a global health concern. Given that human populations are mostly exposed to low chronic levels of mercurial compounds (methylmercury through fish, mercury vapor from dental amalgams, and ethylmercury from vaccines), the need for more sensitive and refined tools to assess the effects and/or susceptibility to adverse metal-mediated health risks remains. Traditional biomarkers, such as hair or blood Hg levels, are practical and provide a reliable measure of exposure, but given intra-population variability, it is difficult to establish accurate cause-effect relationships. It is therefore important to identify and validate biomarkers that are predictive of early adverse effects prior to adverse health outcomes becoming irreversible. This review describes the predominant biomarkers used by toxicologists and epidemiologists to evaluate exposure, effect and susceptibility to Hg compounds, weighing on their advantages and disadvantages. Most importantly, and in light of recent findings on the molecular mechanisms underlying Hg-mediated toxicity, potential novel biomarkers that might be predictive of toxic effect are presented, and the applicability of these parameters in risk assessment is examined.

Effect of Coenzyme Q10 on Biomarkers of Oxidative Stress and Cardiac Function in Hemodialysis Patients: The CoQ10 Biomarker Trial

BACKGROUND

Oxidative stress is highly prevalent in patients with end-stage renal disease and is linked to excess cardiovascular risk. Identifying therapies that reduce oxidative stress has the potential to improve cardiovascular outcomes in patients undergoing maintenance dialysis.

STUDY DESIGN

Placebo-controlled, 3-arm, double-blind, randomized, clinical trial.

SETTING & PARTICIPANTS

65 patients undergoing thrice-weekly maintenance hemodialysis.

INTERVENTION

Patients were randomly assigned in a 1:1:1 ratio to receive once-daily coenzyme Q10 (CoQ10; 600 or 1,200mg) or matching placebo for 4 months.

OUTCOMES

The primary outcome was plasma oxidative stress, defined as plasma concentration of F2-isoprotanes. Secondary outcomes included levels of plasma isofurans, levels of cardiac biomarkers, predialysis blood pressure, and safety/tolerability.

MEASUREMENTS

F2-isoprostanes and isofurans were measured as plasma markers of oxidative stress, and N-terminal pro-brain natriuretic peptide and troponin T were measured as cardiac biomarkers at baseline and 1, 2, and 4 months.

RESULTS

Of 80 randomly assigned patients, 15 were excluded due to not completing at least 1 postbaseline study visit and 65 were included in the primary intention-to-treat analysis. No treatment-related major adverse events occurred. Daily treatment with 1,200mg, but not 600mg, of CoQ10 significantly reduced plasma F2-isoprostanes concentrations at 4 months compared to placebo (adjusted mean changes of -10.7 [95% CI, -7.1 to -14.3] pg/mL [P<0.001] and -8.3 [95% CI, -5.5 to -11.0] pg/mL [P=0.1], respectively). There were no significant effects of CoQ10 treatment on levels of plasma isofurans, cardiac biomarkers, or predialysis blood pressures.

LIMITATIONS

Study not powered to detect small treatment effects; difference in baseline characteristics among randomized groups.

CONCLUSIONS

In patients undergoing maintenance hemodialysis, daily supplementation with 1,200mg of CoQ10 is safe and results in a reduction in plasma concentrations of F2-isoprostanes, a marker of oxidative stress. Future studies are needed to determine whether CoQ10 supplementation improves clinical outcomes for patients undergoing maintenance hemodialysis.

Intraoperative cerebral oxygenation, oxidative injury, and delirium following cardiac surgery

BACKGROUND

Delirium affects 20-30% of patients after cardiac surgery and is associated with increased mortality and persistent cognitive decline. Hyperoxic reperfusion of ischemic tissues increases oxidative injury, but oxygen administration remains high during cardiac surgery. We tested the hypothesis that intraoperative hyperoxic cerebral reperfusion is associated with increased postoperative delirium and that oxidative injury mediates this association.

METHODS

We prospectively measured cerebral oxygenation with bilateral oximetry monitors in 310 cardiac surgery patients, quantified intraoperative hyperoxic cerebral reperfusion by measuring the magnitude of cerebral oxygenation above baseline after any ischemic event, and assessed patients for delirium twice daily in the ICU following surgery using the confusion assessment method for ICU (CAM-ICU). We examined the association between hyperoxic cerebral reperfusion and postoperative delirium, adjusted for the extent of cerebral hypoxia, the extent of cerebral hyperoxia prior to any ischemia, and additional potential confounders and risk factors for delirium. To assess oxidative injury mediation, we examined the association between hyperoxic cerebral reperfusion and delirium after further adjusting for plasma levels of F₂-isoprostanes and isofurans at baseline and ICU admission, the association between hyperoxic cerebral reperfusion and these markers of oxidative injury, and the association between these markers and delirium.

RESULTS

Ninety of the 310 patients developed delirium following surgery. Every 10%·hour of intraoperative hyperoxic cerebral reperfusion was independently associated with a 65% increase in the odds of delirium (OR, 1.65 [95% CI, 1.12-2.44]; P=0.01). Hyperoxia prior to ischemia was also independently associated with delirium (1.10 [1.01-1.19]; P=0.02), but hypoxia was not (1.12 [0.97-1.29]; P=0.11). Increased hyperoxic cerebral reperfusion was associated with increased concentrations of F₂-isoprostanes and isofurans at ICU admission, increased concentrations of these markers were associated with increased delirium, and the association between hyperoxic cerebral reperfusion and delirium was weaker after adjusting for these markers of oxidative injury.

CONCLUSIONS

Intraoperative hyperoxic cerebral reperfusion was associated with increased postoperative delirium, and increased oxidative injury following hyperoxic cerebral reperfusion may partially mediate this association. Further research is needed to assess the potential deleterious role of cerebral hyper-oxygenation during surgery.

The relationship between plasma lipid peroxidation products and primary graft dysfunction after lung transplantation is modified by donor smoking and reperfusion hyperoxia

BACKGROUND

Donor smoking history and higher fraction of inspired oxygen (FIO2) at reperfusion are associated with primary graft dysfunction (PGD) after lung transplantation. We hypothesized that oxidative injury biomarkers would be elevated in PGD, with higher levels associated with donor exposure to cigarette smoke and recipient hyperoxia at reperfusion.

METHODS

We performed a nested case-control study of 72 lung transplant recipients from the Lung Transplant Outcomes Group cohort. Using mass spectroscopy, F2-isoprostanes and isofurans were measured in plasma collected after transplantation. Cases were defined in 2 ways: grade 3 PGD present at day 2 or day 3 after reperfusion (severe PGD) or any grade 3 PGD (any PGD).

RESULTS

There were 31 severe PGD cases with 41 controls and 35 any PGD cases with 37 controls. Plasma F2-isoprostane levels were higher in severe PGD cases compared with controls (28.6 pg/ml vs 19.8 pg/ml, p = 0.03). Plasma F2-isoprostane levels were higher in severe PGD cases compared with controls (29.6 pg/ml vs 19.0 pg/ml, p = 0.03) among patients reperfused with FIO2 >40%. Among recipients of lungs from donors with smoke exposure, plasma F2-isoprostane (38.2 pg/ml vs 22.5 pg/ml, p = 0.046) and isofuran (66.9 pg/ml vs 34.6 pg/ml, p = 0.046) levels were higher in severe PGD compared with control subjects.

CONCLUSIONS

Plasma levels of lipid peroxidation products are higher in patients with severe PGD, in recipients of lungs from donors with smoke exposure, and in recipients exposed to higher Fio2 at reperfusion. Oxidative injury is an important mechanism of PGD and may be magnified by donor exposure to cigarette smoke and hyperoxia at reperfusion.

Association of plasma F2-isoprostanes and isofurans concentrations with erythropoiesis-stimulating agent resistance in maintenance hemodialysis patients

Background

In patients undergoing maintenance hemodialysis (HD), hyporesponsiveness to erythropoiesis stimulating agents (ESAs) is associated with adverse clinical outcomes. Systemic inflammation is highly prevalent in HD patients and is associated with ESA hyporesponsiveness. Oxidative stress is also highly prevalent in HD patients, but no previous study has determined its association with ESA response. This study assessed the association of plasma markers of oxidative stress and inflammation with ESA resistance in patients undergoing maintenance HD.

Methods

We analyzed data from 165 patients enrolled in the Provision of Antioxidant Therapy in Hemodialysis study, a randomized controlled trial evaluating antioxidant therapy in prevalent HD patients. Linear and mixed-effects regression were used to assess the association of baseline and time-averaged high sensitivity F2-isoprostanes, isofurans, C-reactive protein (hsCRP), and interleukin-6 (IL-6) with ESA resistance index (ERI), defined as the weekly weight-adjusted ESA dose divided by blood hemoglobin level. Unadjusted models as well as models adjusted for potential confounders were examined. Predicted changes in ERI per month over study follow-up among baseline biomarker quartiles were also assessed.

Results

Patients with time-averaged isofurans in the highest quartile had higher adjusted mean ERI compared with patients in the lowest quartile (β = 14.9 ng/ml; 95 % CI 7.70, 22.2; reference group <0.26 ng/ml). The highest quartiles of hsCRP and IL-6 were also associated with higher adjusted mean ERI (β = 10.8 mg/l; 95 % CI 3.52, 18.1 for hsCRP; β = 10.2 pg/ml; 95 % CI 2.98, 17.5 for IL-6). No significant association of F2-isoprostanes concentrations with ERI was observed. Analyses restricted to baseline exposures and ERI showed similar results. Baseline hsCRP, IL-6, and isofurans concentrations in the highest quartiles were associated with greater predicted change in ERI over study follow-up compared to the lowest quartiles (P = 0.008, P = 0.004, and P = 0.04, respectively). There was no association between baseline F2-isoprostanes quartile and change in ERI.

Conclusions

In conclusion, higher concentrations of isofurans, hsCRP and IL-6, but not F2-isoprostanes, were associated with greater resistance to ESAs in prevalent HD patients. Further research is needed to test whether interventions that successfully decrease oxidative stress and inflammation in patients undergoing maintenance HD improve ESA responsiveness.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0074-9) contains supplementary material, which is available to authorized users.

Oxidative Stress Biomarkers and Incidence of Postoperative Atrial Fibrillation in the Omega-3 Fatty Acids for Prevention of Postoperative Atrial Fibrillation (OPERA) Trial

BACKGROUND

Animal study results point to oxidative stress as a key mechanism triggering postoperative atrial fibrillation (PoAF), yet the extent to which specific biomarkers of oxidative stress might relate to PoAF risk in humans remains speculative.

METHODS AND RESULTS

We assessed the association of validated, fatty acid-derived oxidative stress biomarkers (F2-isoprostanes, isofurans, and F3-isoprostanes) in plasma and urine, with incident PoAF among 551 cardiac surgery patients. Biomarkers were measured at enrollment, the end of surgery, and postoperative day 2. PoAF lasting ≥30 seconds was confirmed with rhythm strip or electrocardiography and centrally adjudicated. Outcomes were assessed until hospital discharge or postoperative day 10, whichever occurred first. Urine level of each oxidative stress biomarker rose at the end of surgery (2- to 3-fold over baseline, P<0.001) and subsequently declined to concentrations comparable to baseline by postoperative day 2. In contrast, plasma concentrations remained relatively stable throughout the perioperative course. Urine F2-isoprostanes and isofurans at the end of surgery were 20% and 50% higher in subjects who developed PoAF (P≤0.009). While baseline biomarker levels did not associate significantly with PoAF, end of surgery and postoperative day 2 isoprostanes and isofurans demonstrated relatively linear associations with PoAF. For example, the end of surgery extreme quartile multivariate adjusted OR (95% CI) for urine isofurans and F3-isoprostanes were 1.95 (1.05 to 3.62; P for trend=0.01) and 2.10 (1.04 to 2.25, P for trend=0.04), respectively. The associations of biomarkers with PoAF varied little by demographics, surgery type, and medication use (P≥0.29 for each).

CONCLUSIONS

These novel results add to accumulating evidence supporting the likely key pathogenic role of elevated oxidative stress in PoAF.

CLINICAL TRIAL REGISTRATION

URL: Clinicaltrials.gov Unique identifier: NCT00970489.

Hyperoxia elevates adrenic acid peroxidation in marine fish and is associated with reproductive pheromone mediators

The development of oxidative stress in the marine ecosystem is a concurring concern in fish reproductive behavior. Marine fish being rich in polyunsaturated fatty acids (PUFA) are precursors of prostaglandin pheromone mediators but also vulnerable to lipid peroxidation. It is yet to be determined if hypoxia or hyperoxia environment, a cumulative effect in the marine ecosystem affect pheromone mediators in fish, and to understand if this is associated with the generation of oxidized lipid products of PUFA. Novel oxidized lipid metabolites, isoprostanoids (15-F_2t-isoprostane, 7(RS)-7-F_2t-dihomo-isoprostane, 17(RS)-17-F_2t-dihomo-isoprostane, 8-F_3t-isoprostane, 4(RS)-4-F_4t-neuroprostane, 10-F_4t-neuroprostane), isofuranoids (isofurans, 10-epi-17(RS)-SC-Δ¹⁵-11-dihomo-isofuran and neurofurans), hydroxyeicosatetraenoic acids and resolvins, PUFA (arachidonic, adrenic, eicosapentaenoic and docosahexaenoic acids) and prostaglandin pheromone mediators in fish muscle were determined in marine male and female fish muscles before and after interaction in a hypoxia or hyperoxia environment. Reproductive behaviors were also assessed. Our study showed oxidized lipid metabolites of arachidonic, eicosapentaenoic, and docosahexaenoic acids were not influenced by hypoxia and hyperoxia exposure in the fishes and no gender differences were found. However, adrenic acid and its oxidized products, 17(RS)-17-F_2t-dihomo-isoprostane and 10-epi-17(RS)-SC-Δ¹⁵-11-dihomo-isofuran showed strong correspondence with male fish pheromone mediators and reproductive behavior when under oxidative stress especially, hyperoxia. The occurrence of hypoxia and hyperoxia in the marine ecosystem may not be detrimental to marine fish and instead presents as being beneficial in reproductive behavior.

Markers of inflammation, oxidative stress, and endothelial dysfunction and the 20-year cumulative incidence of early age-related macular degeneration: the Beaver Dam Eye Study

IMPORTANCE Modifying levels of factors associated with age-related macular degeneration (AMD) may decrease the risk for visual impairment in older persons. OBJECTIVE To examine the relationships of markers of inflammation, oxidative stress, and endothelial dysfunction to the 20-year cumulative incidence of early AMD. DESIGN, SETTING, AND PARTICIPANTS This longitudinal population-based cohort study involved a random sample of 975 persons in the Beaver Dam Eye Study without signs of AMD who participated in the baseline examination in 1988-1990 and up to 4 follow-up examinations in 1993-1995, 1998-2000, 2003-2005, and 2008-2010. EXPOSURES Serum markers of inflammation (high-sensitivity C-reactive protein, tumor necrosis factor-α receptor 2, interleukin-6, and white blood cell count), oxidative stress (8-isoprostane and total carbonyl content), and endothelial dysfunction (soluble vascular cell adhesion molecule-1 and soluble intercellular adhesion molecule-1) were measured. Interactions with complement factor H (rs1061170), age-related maculopathy susceptibility 2 (rs10490924), complement component 3 (rs2230199), and complement component 2/complement factor B (rs4151667) were examined using multiplicative models. Age-related macular degeneration was assessed from fundus photographs. MAIN OUTCOMES AND MEASURES Early AMD defined by the presence of any size drusen and the presence of pigmentary abnormalities or by the presence of large-sized drusen (≥125-μm diameter) in the absence of late AMD. RESULTS The 20-year cumulative incidence of early AMD was 23.0%. Adjusting for age, sex, and other risk factors, high-sensitivity C-reactive protein (odds ratio comparing fourth with first quartile, 2.18; P = .005), tumor necrosis factor-α receptor 2 (odds ratio, 1.78; P = .04), and interleukin-6 (odds ratio, 1.78; P = .03) were associated with the incidence of early AMD. Increased incidence of early AMD was associated with soluble vascular cell adhesion molecule-1 (odds ratio per SD on the logarithmic scale, 1.21; P = .04). CONCLUSIONS AND RELEVANCE We found modest evidence of relationships of serum high-sensitivity C-reactive protein, tumor necrosis factor-α receptor 2, interleukin-6, and soluble vascular cell adhesion molecule-1 to the 20-year cumulative incidence of early AMD independent of age, smoking status, and other factors. It is not known whether these associations represent a cause and effect relationship or whether other unknown confounders accounted for the findings. Even if inflammatory processes are a cause of early AMD, it is not known whether interventions that reduce systemic inflammatory processes will reduce the incidence of early AMD.

Hyperoxia synergizes with mutant bone morphogenic protein receptor 2 to cause metabolic stress, oxidant injury, and pulmonary hypertension

Pulmonary arterial hypertension (PAH) has been associated with a number of different but interrelated pathogenic mechanisms. Metabolic and oxidative stresses have been shown to play important pathogenic roles in a variety of model systems. However, many of these relationships remain at the level of association. We sought to establish a direct role for metabolic stress and oxidant injury in the pathogenesis of PAH. Mice that universally express a disease-causing mutation in bone morphogenic protein receptor 2 (Bmpr2) were exposed to room air or to brief daily hyperoxia (95% oxygen for 3 h) for 6 weeks, and were compared with wild-type animals undergoing identical exposures. In both murine tissues and cultured endothelial cells, the expression of mutant Bmpr2 was sufficient to cause oxidant injury that was particularly pronounced in mitochondrial membranes. With the enhancement of mitochondrial generation of reactive oxygen species by hyperoxia, oxidant injury was substantially enhanced in mitochondrial membranes, even in tissues distant from the lung. Hyperoxia, despite its vasodilatory actions in the pulmonary circulation, significantly worsened the PAH phenotype (elevated right ventricular systolic pressure, decreased cardiac output, and increased pulmonary vascular occlusion) in Bmpr2 mutant animals. These experiments demonstrate that oxidant injury and metabolic stress contribute directly to disease development, and provide further evidence for PAH as a systemic disease with life-limiting cardiopulmonary manifestations.

Lipid peroxidation and its toxicological implications

Lipid peroxidation is a free radical oxidation of polyunsaturated fatty acids such as linoleic acid or arachidonic acid. This process has been related with various pathologies and disease status mainly because of the oxidation products formed during the process. The oxidation products include reactive aldehydes such as malondialdehyde and 4-hydroxynonenal. These reactive aldehydes can form adducts with DNAs and proteins, leading to the alterations in their functions to cause various diseases. This review will provide a short summary on the implication of lipid peroxidation on cancer, atherosclerosis, and neurodegeneration as well as chemical and biochemical mechanisms by which these adducts affect the pathological conditions. In addition, select examples will be presented where antioxidants were used to counteract oxidative damage caused by lipid peroxidation. At the end, isoprostanes are discussed as a gold standard for the assessment of oxidative damages.

New insights regarding tissue Se and Hg interactions on oxidative stress from plasma IsoP and IsoF measures in the Canadian Inuit population

Despite animal and in vitro studies demonstrating pro-oxidative effects of Hg, previous human work showed no relationship between tissue Hg and plasma levels of F2-isoprostanes (IsoPs), a whole-body oxidative stress marker. We hypothesized that another IsoP species, isofurans (IsoFs), was a more sensitive indicator of Hg-mediated oxidative stress, which can be modified by tissue Se status. A cross-sectional study was carried out involving individuals from a random subset (n = 233) of Inuit adults from a population-based survey (n = 2,595) of 36 Canadian Arctic Inuit communities to assess the relationships of plasma IsoPs to Se and Hg status indicators. F2-IsoPs were inversely correlated with blood Se (r = -0.186, P = 0.005) and toenail Se (r = -0.146, P = 0.044), but not correlated with Hg. IsoFs were inversely correlated with blood Se (r = -0.164, P = 0.014) and positively correlated with Hg (r = 0.228, P < 0.001) and Hg:Se (r = 0.340, P < 0.001). The strength of the correlations remained unchanged after multivariate adjustments. Multivariate analysis showed that F2-IsoPs were not positively associated with Hg but with Hg:Se (β = 0.148, P = 0.021). We conclude that Se and Hg status and their interactions are important factors modulating F2-IsoP and IsoF levels such that the Inuit may be protected from Hg-induced oxidative stress because of their high Se status.

Isoprostanes and neuroprostanes: total synthesis, biological activity and biomarkers of oxidative stress in humans

Isoprostanes (IsoPs) and neuroprostanes (NeuroPs) are formed in vivo by a free radical non-enzymatic mechanism involving peroxidation of arachidonic acid (AA, C20:4 n-6) and docosahexaenoic acid (DHA, C22:6 n-3) respectively. This review summarises our research in the total synthesis of these lipid metabolites, as well as their biological activities and their utility as biomarkers of oxidative stress in humans.

The short-term effects of antioxidant and zinc supplements on oxidative stress biomarker levels in plasma: a pilot investigation

PURPOSE

To determine if short-term Age-Related Eye Disease Study (AREDS) antioxidant and zinc supplementation affects biomarkers of oxidative stress, possibly serving as a predictor of their efficacy.

DESIGN

Prospective interventional case series.

METHODS

Nineteen subjects, 12 with intermediate or advanced age-related macular degeneration (AMD) (AREDS categories 3 or 4) and 7 non-AMD controls, were admitted to the Vanderbilt General Clinical Research Center and placed on a controlled diet for 7 days. Antioxidant and zinc supplements were stopped 2 weeks prior to study enrollment. Dietary supplementation with 500 mg vitamin C, 400 IU vitamin E, 15 mg β-carotene, 80 mg zinc oxide, and 2 mg cupric oxide per day was instituted on study day 2. Blood was drawn on study days 2 and 7, and plasma concentrations of cysteine (Cys), cystine (CySS), glutathione (GSH), isoprostane (IsoP), and isofuran (IsoF) were determined.

RESULTS

Short-term AREDS supplementation significantly lowered mean plasma levels of CySS in participants on a regulated diet (P = .034). No significant differences were observed for Cys, GSH, IsoP, or IsoF. There were no significant differences between AMD patients and controls.

CONCLUSIONS

This pilot interventional study shows that a 5-day course of antioxidant and zinc supplements can modify plasma levels of CySS, suggesting that this oxidative stress biomarker could help predict how likely an individual is to benefit from AREDS supplementation. Further, CySS may be useful for the evaluation of new AMD therapies, particularly those hypothesized to affect redox status.

Radical decisions in cancer: redox control of cell growth and death

Free radicals play a key role in many physiological decisions in cells. Since free radicals are toxic to cellular components, it is known that they cause DNA damage, contribute to DNA instability and mutation and thus favor carcinogenesis. However, nowadays it is assumed that free radicals play a further complex role in cancer. Low levels of free radicals and steady state levels of antioxidant enzymes are responsible for the fine tuning of redox status inside cells. A change in redox state is a way to modify the physiological status of the cell, in fact, a more reduced status is found in resting cells while a more oxidative status is associated with proliferative cells. The mechanisms by which redox status can change the proliferative activity of cancer cells are related to transcriptional and posttranscriptional modifications of proteins that play a critical role in cell cycle control. Since cancer cells show higher levels of free radicals compared with their normal counterparts, it is believed that the anti-oxidative stress mechanism is also increased in cancer cells. In fact, the levels of some of the most important antioxidant enzymes are elevated in advanced status of some types of tumors. Anti-cancer treatment is compromised by survival mechanisms in cancer cells and collateral damage in normal non-pathological tissues. Though some resistance mechanisms have been described, they do not yet explain why treatment of cancer fails in several tumors. Given that some antitumoral treatments are based on the generation of free radicals, we will discuss in this review the possible role of antioxidant enzymes in the survival mechanism in cancer cells and then, its participation in the failure of cancer treatments.

Plasma biomarkers of oxidative stress and genetic variants in age-related macular degeneration

PURPOSE

To compare plasma levels of oxidative stress biomarkers in patients with age-related macular degeneration (AMD) and controls and to evaluate a potential relationship between biochemical markers of oxidative stress and AMD susceptibility genotypes.

DESIGN

Prospective case-control study.

METHODS

Plasma levels of oxidative stress biomarkers were determined in 77 AMD patients and 75 controls recruited from a clinical practice. Cysteine, cystine (CySS), glutathione, isoprostane, and isofuran were measured, and participants were genotyped for polymorphisms in the complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) genes.

RESULTS

CySS was elevated in cases compared with controls (P = .013). After adjustment for age, sex, and smoking, this association was not significant. In all participants, CySS levels were associated with the CFH polymorphism rs3753394 (P = .028) as well as an 8-allele CFH haplotype (P = .029) after correction for age, gender, and smoking. None of the other plasma markers was related to AMD status in our cohort.

CONCLUSIONS

Our investigation of the gene-environment interaction involved in AMD revealed a relationship between a plasma biomarker of oxidative stress, CySS, and CFH genotype. These data suggest a potential association between inflammatory regulators and redox status in AMD pathogenesis.

Hemoglobin attenuates the effects of inspired oxygen on plasma isofurans in humans during upper-limb surgery

Reperfusion injury is characterized by significant oxidative stress. F(2)-isoprostanes (F(2)-IsoP's) and isofurans (IsoF's), the latter preferentially produced during increased oxygen tension, are recognized markers of in vivo oxidative stress. We aimed to determine whether increasing oxygen tension during reperfusion modified levels of plasma total IsoF's and F(2)-IsoP's. Forty-five patients undergoing upper-limb surgery were randomized to receive inspired oxygen concentrations of 30, 50, or 80% during the last 15 min of surgery. Venous blood samples were taken before the change in inspired oxygen, after 10 min (before reperfusion), and after 15 min (5 min after reperfusion). IsoF's and F(2)-IsoP's were measured by gas chromatography-mass spectrometry. Venous oxygen tension and hemoglobin concentrations were also measured. Plasma IsoF and F(2)-IsoP levels in the 50 and 80% O(2) groups were not significantly different from those of the 30% O(2) group. In secondary analyses, using data combining all groups, levels of IsoF's, but not F(2)-IsoP's, associated with higher venous oxygen tension (P=0.038). Hemoglobin negatively modified the influence of oxygen tension on levels of IsoF's (P=0.014). This study has shown, for the first time, that plasma IsoF levels associate with higher oxygen tension in a human model of reperfusion, and this effect is significantly attenuated by hemoglobin.

Plasma biomarkers of oxidant stress and development of organ failure in severe sepsis

We hypothesized that circulating levels of lipid peroxidation products in patients with severe sepsis are associated with the development of pulmonary, renal, hepatic, circulatory, and coagulation failure. Plasma levels of F2-isoprostanes and isofurans were measured by mass spectroscopy on intensive care unit day 2 in 50 critically ill patients with severe sepsis. Plasma F2-isoprostane levels were higher in patients who developed renal failure compared with those who did not (65 pg/mL [interquartile range {IQR} 44-112] vs. 44 pg/mL [IQR 29-54], P = 0.009) as were isofuran levels (1,223 pg/mL [IQR 348-2,531] vs. 329 pg/mL [IQR 156-1,127], P = 0.009). Plasma F2-isoprostane levels were higher in patients who developed hepatic failure compared with those who did not (72 pg/mL [IQR 44-112] vs. 44 pg/mL [IQR 30-65], P = 0.023), and there was also a trend for higher isofuran levels (1,411 pg/mL [IQR 298-1,965] vs. 525 pg/mL [IQR 160-1,223], P = 0.14). Coagulation failure (thrombocytopenia) was associated with higher isofuran levels. Circulatory failure and acute lung injury were not associated with elevated levels of isoprostanes or isofurans. Patients with isoprostane levels above the 25th percentile had higher mortality (42%) compared with patients with levels below the 25th percentile (8%, P = 0.03). Plasma levels of F2-isoprostanes and isofurans are associated with renal, hepatic, and coagulation failure, but not with circulatory or pulmonary failure in severe sepsis, suggesting that lipid peroxidation is a prominent feature of septic multisystem organ failure. Plasma isoprostanes and isofurans may be useful for monitoring oxidative stress in treatment trials of antioxidant therapies in severe sepsis.

Effects of spinal or general anesthesia on F₂-isoprostanes and isofurans during ischemia/reperfusion of the leg in patients undergoing knee replacement surgery

General and spinal anesthesia are used extensively in orthopedic surgery. However, these methods of anesthesia may result in different amounts of oxygen being delivered to the patient. Ischemia/reperfusion injury after release of the tourniquet initiates free radical-mediated oxidative stress. F₂-isoprostanes are reliable markers of in vivo lipid peroxidation. However, under conditions of high oxygen tension, isofurans are formed. We aimed to compare plasma isofurans and F₂-isoprostanes in spinal versus general anesthesia in patients undergoing knee-replacement surgery in a randomized, blinded study. Thirty-nine patients were randomized to spinal (SA; n = 19) or general anesthesia (GA; n = 20). Blood was collected before anesthesia, and a tourniquet was then applied to the limb during surgery. After release of the tourniquet, blood samples were collected at 30 min, 2 h, and 24 h for measurement of plasma F₂-isoprostanes and isofurans by gas chromatography-mass spectrometry. The two groups were comparable in age and body mass index. Plasma F₂-isoprostanes were significantly lower in the GA patients compared with the SA patients (p = 0.045). In contrast, the GA patients had significantly elevated plasma isofurans (p = 0.032). Increased isofurans during GA compared with SA are likely to reflect increased oxidative stress due to elevated oxygen concentrations during GA. Further studies are required to assess the implications of these findings on perioperative outcomes.

Evidence of oxidative stress in relation to feeding type during early life in premature infants

Morbidity in the premature (PT) infant may reflect difficult adaptation to oxygen. We hypothesized that feeding including formula feeding (F) and feeding mother's milk (HM) with added fortifier would affect redox status. Therefore, 65 PT infants (birth weight: 1146 ± 261 g; GA: 29 ± 2.5 wk; mean ± SD) were followed biweekly, once oral feeds were introduced. Feeding groups: F (>75% total feeds) and HM (>75% total feeds) were further subdivided according to human milk fortifier (HMF) content of 0-19, 20-49, and ≥ 50%. Oxidative stress was quantified by F2-isoprostanes (F2-IsoPs) in urine, protein carbonyls, and oxygen radical absorbance capacity (ORAC) in plasma. F2-IsoPs (ng/mg creatinine): 0-2 wk, 125 ± 63; 3-4 wk, 191 ± 171; 5-6 wk, 172 ± 83; 7-8 wk, 211 ± 149; 9-10 wk, 222 ± 121; and >10 wk, 183 ± 67. Protein carbonyls from highest [2.41 ± 0.75 (n = 9)] and lowest [2.25 ± 0.89 (n = 12) pmol/μg protein] isoprostane groups did not differ. ORAC: baseline, 6778 ± 1093; discharge, 6639 ± 735 [full term 4 and 12 M, 9010 ± 600 mg (n = 12) TE]. Highest isoprostane values occurred in infants with >50% of their mother's milk fortified. Further research on HMF is warranted.

Oxidative injury is a common consequence of BMPR2 mutations

Hereditary pulmonary arterial hypertension (PAH) is usually caused by mutations in BMPR2. Mutations are found throughout the gene, and common molecular consequences of different types of mutation are not known. Knowledge of common molecular consequences would provide insight into the molecular etiology of the disease. The objective of this study was to determine the common molecular consequences across classes of BMPR2 mutation. Increased superoxide and peroxide production and alterations in genes associated with oxidative stress were a common consequence of stable transfection of the vascular smooth muscle cells, with three distinct classes of BMPR2 mutation, in the ligand binding domain, the kinase domain and the cytoplasmic tail domain. Measurement of oxidized lipids in whole lung from transgenic mice expressing a mutation in the BMPR2 cytoplasmic tail showed a 50% increase in isoprostanes and a two-fold increase in isofurans, suggesting increased reactive oxygen species (ROS) of mitochondrial origin. Immunohistochemistry on BMPR2 transgenic mouse lung showed that oxidative stress was vascular-specific. Electron microscopy showed decreased mitochondrial size and variability in the pulmonary vessels from BMPR2-mutant mice. Measurement of oxidized lipids in urine from humans with BMPR2 mutations demonstrated increased ROS, regardless of disease status. Immunohistochemistry on hereditary PAH patient lung confirmed oxidative stress specific to the vasculature. Increased oxidative stress, likely of mitochondrial origin, is a common consequence of BMPR2 mutation across mutation types in cell culture, mice and humans.

Oxidative lipidomics of hyperoxic acute lung injury: mass spectrometric characterization of cardiolipin and phosphatidylserine peroxidation

Reactive oxygen species have been shown to play a significant role in hyperoxia-induced acute lung injury, in part, by inducing apoptosis of pulmonary endothelium. However, the signaling roles of phospholipid oxidation products in pulmonary endothelial apoptosis have not been studied. Using an oxidative lipidomics approach, we identified individual molecular species of phospholipids involved in the apoptosis-associated peroxidation process in a hyperoxic lung. C57BL/6 mice were killed 72 h after exposure to hyperoxia (100% oxygen). We found that hyperoxia-induced apoptosis (documented by activation of caspase-3 and -7 and histochemical terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining of pulmonary endothelium) was accompanied by nonrandom oxidation of pulmonary lipids. Two anionic phospholipids, mitochondria-specific cardiolipin (CL) and extramitochondrial phosphatidylserine (PS), were the two major oxidized phospholipids in hyperoxic lung. Using electrospray ionization mass spectrometry, we identified several oxygenation products in CL and PS. Quantitative assessments revealed a significant decrease of CL and PS molecular species containing C(18:2), C(20:4), C(22:5), and C(22:6) fatty acids. Similarly, exposure of mouse pulmonary endothelial cells (MLEC) to hyperoxia (95% oxygen; 72 h) resulted in activation of caspase-3 and -7 and significantly decreased the content of CL molecular species containing C(18:2) and C(20:4) as well as PS molecular species containing C(22:5) and C(22:6). Oxygenated molecular species were found in the same two anionic phospholipids, CL and PS, in MLEC exposed to hyperoxia. Treatment of MLEC with a mitochondria-targeted radical scavenger, a conjugate of hemi-gramicidin S with nitroxide, XJB-5-131, resulted in significantly lower oxidation of both CL and PS and a decrease in hyperoxia-induced changes in caspase-3 and -7 activation. We speculate that cytochrome c driven oxidation of CL and PS is associated with the signaling role of these oxygenated species participating in the execution of apoptosis and clearance of pulmonary endothelial cells, thus contributing to hyperoxic lung injury.

Seizure-induced formation of isofurans: novel products of lipid peroxidation whose formation is positively modulated by oxygen tension

We have previously shown that seizures induce the formation of F(2)-isoprostanes (F(2)-IsoPs), one of the most reliable indices of oxidative stress in vivo. Isofurans (IsoFs) are novel products of lipid peroxidation whose formation is favored by high oxygen tensions. In contrast, high oxygen tensions suppress the formation of F(2)-IsoPs. The present study determined seizure-induced formation of IsoFs and its relationship with cellular oxygen levels (pO2). Status epilepticus (SE) resulted in F(2)-IsoP and IsoF formation, with overlapping but distinct time courses in hippocampal subregions. IsoF, but not F(2)-IsoP formation coincided with mitochondrial oxidative stress. SE resulted in a transient decrease in hippocampal pO2 measured by in vivo electron paramagnetic resonance oximetry suggesting an early phase of seizure-induced hypoxia. Seizure-induced F(2)-IsoP formation coincided with the peak hypoxia phase, whereas IsoF formation coincided with the 'reoxygenation' phase. These results demonstrate seizure-induced increase in IsoF formation and its correlation with changes in hippocampal pO2 and mitochondrial dysfunction.

Proteasomal dysfunction: a common feature of neurodegenerative diseases? Implications for the environmental origins of neurodegeneration

The neurodegenerative diseases that afflict humans affect different part of the nervous system and have different symptoms and prognoses, yet they have certain things in common. One of them is defects in the clearance of abnormal or other "unwanted" proteins, particularly affecting the proteasome system. In this review, I advance two concepts: (a) that defects in protein clearance can be a fundamental cause of neurodegeneration, and (b) that because proteasome inhibitors are widespread in nature, their ingestion may contribute to "spontaneous" neurodegeneration.

Isoprostanes and related compounds: update 2006

Last year Antioxidants and Redox Signaling devoted a special Forum issue (Volume 7, 2005) to reviewing the current literature on isoprostanes (IsoPs) and related compounds. Awide variety of topics provided readers of that issue with important information on the chemistry and biology of these molecules. During the past year, more than 200 articles have been published in the field of IsoP research, and noteworthy advances in the area have been made. This editorial highlights selected aspects of these advances as they relate to the Forum issue. The main focus of this discussion is on the role of the IsoPs as biomarkers and mediators of oxidant stress in human disease, their mechanism of formation and metabolism, and their biologic activities.