Increased formation of the isoprostanes IPF2alpha-I and 8-epi-prostaglandin F2alpha in acute coronary angioplasty: evidence for oxidant stress during coronary reperfusion in humans

The Role of Potential Oxidative Biomarkers in the Prognosis of Acute Ischemic Stroke and the Exploration of Antioxidants as Possible Preventive and Treatment Options

Ischemic strokes occur when the blood supply to a part of the brain is interrupted or reduced due to arterial blockage, and it often leads to damage to brain cells or death. According to a myriad of experimental studies, oxidative stress is an important pathophysiological mechanism of ischemic stroke. In this narrative review, we aimed to identify how the alterations of oxidative stress biomarkers could suggest a severity-reflecting diagnosis of ischemic stroke and how these interactions may provide new molecular targets for neuroprotective therapies. We performed an eligibility criteria-based search on three main scientific databases. We found that patients with acute ischemic stroke are characterized by increased oxidative stress markers levels, such as the total antioxidant capacity, F2-isoprostanes, hydroxynonenal, total and perchloric acid oxygen radical absorbance capacity (ORACTOT and ORACPCA), malondialdehyde (MDA), myeloperoxidase, and urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine. Thus, acute ischemic stroke is causing significant oxidative stress and associated molecular and cellular damage. The assessment of these molecular markers could be useful in diagnosing ischemic stroke, finding its causes, predicting its severity and outcomes, reducing its impact on the cellular structures of the brain, and guiding preventive treatment towards antioxidant-based therapy as novel therapeutic alternatives.

Lipid Peroxidation in Atherosclerotic Cardiovascular Diseases

Significance: Atherosclerotic cardiovascular diseases (ACVDs) continue to be a primary cause of mortality worldwide in adults aged 35-70 years, occurring more often in countries with lower economic development, and they constitute an ever-growing global burden that has a considerable socioeconomic impact on society. The ACVDs encompass diverse pathologies such as coronary artery disease and heart failure (HF), among others. Recent Advances: It is known that oxidative stress plays a relevant role in ACVDs and some of its effects are mediated by lipid oxidation. In particular, lipid peroxidation (LPO) is a process under which oxidants such as reactive oxygen species attack unsaturated lipids, generating a wide array of oxidation products. These molecules can interact with circulating lipoproteins, to diffuse inside the cell and even to cross biological membranes, modifying target nucleophilic sites within biomolecules such as DNA, lipids, and proteins, and resulting in a plethora of biological effects. Critical Issues: This review summarizes the evidence of the effect of LPO in the development and progression of atherosclerosis-based diseases, HF, and other cardiovascular diseases, highlighting the role of protein adduct formation. Moreover, potential therapeutic strategies targeted at lipoxidation in ACVDs are also discussed. Future Directions: The identification of valid biomarkers for the detection of lipoxidation products and adducts may provide insights into the improvement of the cardiovascular risk stratification of patients and the development of therapeutic strategies against the oxidative effects that can then be applied within a clinical setting.

Targeting oxidative stress in disease: promise and limitations of antioxidant therapy

Oxidative stress is a component of many diseases, including atherosclerosis, chronic obstructive pulmonary disease, Alzheimer disease and cancer. Although numerous small molecules evaluated as antioxidants have exhibited therapeutic potential in preclinical studies, clinical trial results have been disappointing. A greater understanding of the mechanisms through which antioxidants act and where and when they are effective may provide a rational approach that leads to greater pharmacological success. Here, we review the relationships between oxidative stress, redox signalling and disease, the mechanisms through which oxidative stress can contribute to pathology, how antioxidant defences work, what limits their effectiveness and how antioxidant defences can be increased through physiological signalling, dietary components and potential pharmaceutical intervention.

Effects of cardiopulmonary bypass perfusion temperature on perioperative renal function in adult patients undergoing cardiac surgery

Aims and objective

The primary objective of this investigation was to study the effects of cardiopulmonary bypass (CPB) perfusion temperature on renal function parameters [serum creatinine, creatinine clearance, urine albumin, urine protein, and urine albumin/creatinine ratio (ACR)]. The secondary objective was to detect renal complications of CPB.

Materials and methods

This is a prospective longitudinal study of 30 adult patients (17 men, 13 women; mean age, 53.37 ± 16.02 years) who underwent valvular heart surgery [with or without coronary artery bypass grafting (CABG)]. Serum creatinine, creatinine clearance, urine protein, urine albumin, and urine ACR were collected during CPB (at 28 °C, 32 °C, and 37 °C) and postoperatively (at 12 hours, 24 hours, and 48 hours). Data were analyzed using one-way repeated-measures analysis of variance (ANOVA). A significant ANOVA was followed by a Bonferroni–Holm post hoc test.

Results

Although serum creatinine (p < 0.001) and creatinine clearance (p = 0.0016) underwent a significant ANOVA change (p < 0.001 and p = 0.0016, respectively) after CPB, there was no statistically significant change compared with their baseline values. Urine ACR showed a significant change at 28 °C (p < 0.01), 32 °C (p < 0.01), and 37 °C (p < 0.05) as compared with baseline values. No significant change in urine albumin was observed during CPB or up to 24 hours. A significant change occurred after 48 hours of CPB (p < 0.05). A significant increase in urine protein was noted after CPB at 12 hours (p < 0.01), 24 hours (p < 0.01), and 48 hours (p < 0.01). Overall, 12 (40%) patients had acute kidney injury (AKI). Ten (33.33%) patients had stage I AKI, one patient progressed to AKI stage II, and another to AKI stage III. Of the 10 patients who had stage I AKI, eight had complete recovery within 48 hours.

Conclusions

CPB with moderate hypothermia for valvular heart surgeries can be performed safely in patients with adequate renal functional reserve. The glomerular permeability across the Bowman’s capsule increases after CPB as evidenced by significant proteinuria at 12 hours and increased albuminuria at 48 hours after surgery. There is an increased risk of transient stage I AKI after CPB, from which patients recover within 48 hours.

Biochemical basis and metabolic interplay of redox regulation

Accumulated evidence strongly indicates that oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) production and antioxidants in favor of oxidants, plays an important role in disease pathogenesis. However, ROS can act as signaling molecules and fulfill essential physiological functions at basal levels. Each ROS would be different in the extent to stimulate and contribute to different pathophysiological effects. Importantly, multiple ROS generators can be activated either concomitantly or sequentially by relevant signaling molecules for redox biological functions. Here, we summarized the current knowledge related to chemical and biochemical features of primary ROS species and corresponding antioxidants. Metabolic pathways of five major ROS generators and five ROS clearance systems were described, including their ROS products, specific ROS enriched tissue, cell and organelle, and relevant functional implications. We provided an overview of ROS generation and induction at different levels of metabolism. We classified 11 ROS species into three types based on their reactivity and target selectivity and presented ROS homeostasis and functional implications in pathological and physiological status. This article intensively reviewed and refined biochemical basis, metabolic signaling and regulation, functional insights, and provided guidance for the identification of novel therapeutic targets.

Correlation of cardiopulmonary bypass duration with acute renal failure after cardiac surgery

OBJECTIVES

Prolonged cardiopulmonary bypass (CPB) is recognized as a risk factor for acute renal failure (ARF), but the dose effect of time on bypass is unknown. We therefore examined the risk of ARF associated with increasing CPB time stratified by preoperative renal function.

METHODS

A retrospective analysis was performed on 3889 patients undergoing cardiac surgery on CPB without circulatory arrest between 2011 and 2017 excluding those with a diagnosis of dialysis-dependent renal failure and those who had an intra-aortic balloon pump. Postoperative ARF was defined as a 3-fold increase in creatinine level, creatinine level > 4 mg/dL, or requirement for dialysis. A logistic regression model was built to identify predictors of ARF and to determine the probability of ARF.

RESULTS

Postoperative ARF occurred in 72 patients (2%) overall. Of 100 patients with an estimated glomerular filtration rate <30 mL/min/1.73 m², 22% developed ARF, of which 16 required dialysis. Thirty-day mortality was 31% for those with ARF compared with <1% for those without ARF (P < .01). Risk factors for ARF included obesity (odds ratio, 3.03; P < .01), increasing preoperative creatinine level (odds ratio, 4.21; P < .01), CPB time scaled by a factor of 10 minutes (odds ratio, 1.06; P = .04), and postoperative transfusion (odds ratio, 11.94; P < .01). The adjusted probability of ARF as a function of CPB time was determined and stratified by preoperative glomerular filtration rate.

CONCLUSIONS

Increasing CPB duration is associated with postoperative ARF, particularly among those with preoperative renal impairment. For patients with an estimated glomerular filtration rate <30 mL/min/1.73 m² the risk increases exponentially with time.

Unraveling mechanisms of toxicant-induced oxidative stress in cardiovascular disease

To date, numerous clinical studies examining correlations between oxidative stress biomarkers and cardiovascular diseases (CVD) have repeatedly suggested a role for oxidant injury in the pathogenesis of diseases such as atherosclerosis. Despite this, antioxidant supplementation trials have not demonstrated a reduction in disease progression. Nevertheless, small animal and epidemiological studies have linked exposures to certain toxicants with increased CVD risk involving putative oxidative stress mechanisms. A few prototypical vascular toxicants will be discussed as examples of toxicants that likely act via oxidative stress mechanisms. For discussion, we will classify these toxicants as those that induce direct (e.g., arsenic, nucleoside reverse transcriptase inhibitors) versus indirect (particulate matter, ozone) oxidative stress mechanisms, and those that likely induce CVD through both direct and indirect mechanisms (cigarette smoke). Finally, new findings in oxidative stress research, including the emerging importance of reactive sulfur species, hydrogen peroxide as a presumed endothelium-derived hyperpolarizing factors, etc., will be discussed, as well as the need to determine the role of toxicants in modulating these newly identified pathways. Moreover, given the lack of success in conclusively demonstrating the roles of oxidative stress in CVD risk stratification, research probing the roles of toxicant exposures in propagating CVD pathogenesis may be a novel approach for more conclusively delineating the causal role of oxidative stress in CVD initiation and progression.

The Risk of Oxygen during Cardiac Surgery (ROCS) trial: study protocol for a randomized clinical trial

Background

Anesthesiologists administer excess supplemental oxygen (hyper-oxygenation) to patients during surgery to avoid hypoxia. Hyper-oxygenation, however, may increase the generation of reactive oxygen species and cause oxidative damage. In cardiac surgery, increased oxidative damage has been associated with postoperative kidney and brain injury. We hypothesize that maintenance of normoxia during cardiac surgery (physiologic oxygenation) decreases kidney injury and oxidative damage compared to hyper-oxygenation.

Methods/design

The Risk of Oxygen during Cardiac Surgery (ROCS) trial will randomly assign 200 cardiac surgery patients to receive physiologic oxygenation, defined as the lowest fraction of inspired oxygen (FIO₂) necessary to maintain an arterial hemoglobin saturation of 95 to 97%, or hyper-oxygenation (FIO₂ = 1.0) during surgery. The primary clinical endpoint is serum creatinine change from baseline to postoperative day 2, and the primary mechanism endpoint is change in plasma concentrations of F₂-isoprostanes and isofurans. Secondary endpoints include superoxide production, clinical delirium, myocardial injury, and length of stay. An endothelial function substudy will examine the effects of oxygen treatment and oxidative stress on endothelial function, measured using flow mediated dilation, peripheral arterial tonometry, and wire tension myography of epicardial fat arterioles.

Discussion

The ROCS trial will test the hypothesis that intraoperative physiologic oxygenation decreases oxidative damage and organ injury compared to hyper-oxygenation in patients undergoing cardiac surgery.

Trial registration

ClinicalTrials.gov, ID: NCT02361944. Registered on the 30th of January 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2021-5) contains supplementary material, which is available to authorized users.

The enigma ofin vivooxidative stress assessment: isoprostanes as an emerging target

Oxidative stress is believed to be one of the major factors behind several acute and chronic diseases, and may also be associated with ageing. Excess formation of free radicals in miscellaneous body environment may originate from endogenous response to cell injury, but also from exposure to a number of exogenous toxins. When the antioxidant defence system is overwhelmed, this leads to cell damage. However, the measurement of free radicals or their endproducts is tricky, since these compounds are reactive and short lived, and have diverse characteristics. Specific evidence for the involvement of free radicals in pathological situations has been difficult to obtain, partly owing to shortcomings in earlier described methods for the measurement of oxidative stress. Isoprostanes, which are prostaglandin-like bioactive compounds synthesized in vivo from oxidation of arachidonic acid, independently of cyclooxygenases, are involved in many human diseases, and their measurement therefore offers a way to assess oxidative stress. Elevated levels of F₂-isoprostanes have also been seen in the normal human pregnancy, but their physiological role has not yet been defined. Large amounts of bioactive F₂-isoprostanes are excreted in the urine in normal basal situations, with a wide interindividual variation. Their exact role in the regulation of normal physiological functions, however, needs to be explored further. Current understanding suggests that measurement of F₂-isoprostanes in body fluids provides a reliable analytical tool to study oxidative stress-related diseases and experimental inflammatory conditions, and also in the evaluation of various dietary antioxidants, as well as drugs with radical-scavenging properties. However, assessment of isoprostanes in plasma or urine does not necessarily reflect any specific tissue damage, nor does it provide information on the oxidation of lipids other than arachidonic acid.

Plasma apelin-12 levels may predict in-hospital major adverse cardiac events in ST-elevation myocardial infarction and the relationship between apelin-12 and the neutrophil/lymphocyte ratio in patients undergoing primary coronary intervention

OBJECTIVE

We aimed to investigate the compliance of plasma apelin-12 levels to show angiographic properties and hospital MACE in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

MATERIAL AND METHODS

The association of apelin-12 levels with the N/L ratio on admission was assessed in 170 consecutive patients with primary STEMI undergoing primary PCI. All patient SYNTAX scores and thrombolysis in myocardial infarction (TIMI) flow grades were also assessed. Patients were divided into two groups according to their TIMI flow grade. Patients with a TIMI 0-2 flow and TIMI 3 flow with grade 0/1 myocardial blush grade (MBG) score were defined as the no-reflow group and patients with TIMI grade 3 flow with ⩾2 MBG were considered as the normal flow group.

RESULTS

Baseline apelin-12 levels were significantly lower in the no-reflow group than in the normal flow group (3.3±1.81 vs 6.2±1.74, p<0.001). In-hospital events, including death, myocardial infarction (MI) and re-infarction were significantly higher in patients in the no-reflow group than normal flow group (23% vs 7%, p<0.001). Apelin-12 level was negative correlated with the N/L ratio (r= -0.352, p<0.001), Hs-Crp (r=-0.272, p=0.01) and SYNTAX score (r= -0.246, p=0.029). In the multivariate regression analysis, apelin-12, presence of no-reflow and the SYNTAX score were independent predictors of in-hospital MACE (odds ratio [OR] 1.41, 95% confidence interval (CI) [1.27 to 1.67], p=0.001 for apelin-12, OR 1.085, [0.981 to 1.203], p<0.001 for no-reflow and OR 0.201, 95% CI [0.05 to 0.47], p= 0.004 for SYNTAX score).

CONCLUSION

We have shown that lower apelin-12 level on admission is associated with higher SYNTAX scores and no-reflow phenomenon and may be used as a prognostic marker for hospital MACE in patients with STEMI.

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.

Acute kidney injury following cardiac surgery: current understanding and future directions

Acute kidney injury (AKI) complicates recovery from cardiac surgery in up to 30 % of patients, injures and impairs the function of the brain, lungs, and gut, and places patients at a 5-fold increased risk of death during hospitalization. Renal ischemia, reperfusion, inflammation, hemolysis, oxidative stress, cholesterol emboli, and toxins contribute to the development and progression of AKI. Preventive strategies are limited, but current evidence supports maintenance of renal perfusion and intravascular volume while avoiding venous congestion, administration of balanced salt as opposed to high-chloride intravenous fluids, and the avoidance or limitation of cardiopulmonary bypass exposure. AKI that requires renal replacement therapy occurs in 2–5 % of patients following cardiac surgery and is associated with 50 % mortality. For those who recover from renal replacement therapy or even mild AKI, progression to chronic kidney disease in the ensuing months and years is more likely than for those who do not develop AKI. Cardiac surgery continues to be a popular clinical model to evaluate novel therapeutics, off-label use of existing medications, and nonpharmacologic treatments for AKI, since cardiac surgery is fairly common, typically elective, provides a relatively standardized insult, and patients remain hospitalized and monitored following surgery. More efficient and time-sensitive methods to diagnose AKI are imperative to reduce this negative outcome. The discovery and validation of renal damage biomarkers should in time supplant creatinine-based criteria for the clinical diagnosis of AKI.

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.

Prognosis of STEMI Patients with Multi-Vessel Disease Undergoing Culprit-Only PCI without Significant Residual Ischemia on Non-Invasive Stress Testing

Aims

In about 50–80% of ST-segment elevation myocardial infarction (STEMI) patients there is significant atherosclerotic disease in other coronary arteries in addition to the culprit vessel. There is substantial controversy as to the optimal revascularization approach in these patients. We sought to compare the outcomes of STEMI patients with multi-vessel disease (MVD) treated with culprit-only primary percutaneous coronary intervention (PPCI) without significant ischemia on subsequent non-invasive testing, to those of STEMI patients with single-vessel disease (SVD).

Methods and Results

Between 2001–2010, 1,540 consecutive patients treated with primary PCI for STEMI were prospectively observed and entered into a comprehensive clinical database. The primary end point was a composite of major adverse cardiac events (MACE), consisting of mortality, re-infarction and revascularization within 1 and 3 years following PPCI (excluding events occurring during the first 30 days). Patients with cardiogenic shock were excluded. The study included 720 patients with SVD and 185 patients with MVD who underwent culprit-only PPCI and had no residual ischemia on subsequent non-invasive stress testing. Patients with MVD were older, more likely to have hypertension or previous MI and less likely to be smokers and present with anterior MI than patients with SVD. One and 3-year MACE rates were similar between the groups. On cox proportional-hazards regression MVD without residual ischemia was not independently associated with MACE and its components.

Conclusions

STEMI patients with MVD treated with culprit only-PCI without significant residual ischemia on non-invasive stress testing appear to have similar prognosis to STEMI patients with SVD.

Pathophysiology of isoprostanes in the cardiovascular system: implications of isoprostane-mediated thromboxane A2 receptor activation

Isoprostanes are free radical-catalysed PG-like products of unsaturated fatty acids, such as arachidonic acid, which are widely recognized as reliable markers of systemic lipid peroxidation and oxidative stress in vivo. Moreover, activation of enzymes, such as COX-2, may contribute to isoprostane formation. Indeed, formation of isoprostanes is considerably increased in various diseases which have been linked to oxidative stress, such as cardiovascular disease (CVD), and may predict the atherosclerotic burden and the risk of cardiovascular complications in the latter patients. In addition, several isoprostanes may directly contribute to the functional consequences of oxidant stress via activation of the TxA2 prostanoid receptor (TP), for example, by affecting endothelial cell function and regeneration, vascular tone, haemostasis and ischaemia/reperfusion injury. In this context, experimental and clinical data suggest that selected isoprostanes may represent important alternative activators of the TP receptor when endogenous TxA2 levels are low, for example, in aspirin-treated individuals with CVD. In this review, we will summarize the current understanding of isoprostane formation, biochemistry and (patho) physiology in the cardiovascular context.

Effect of common single nucleotide polymorphisms in COX-1 gene on related metabolic activity in diabetic patients treated with acetylsalicylic acid

INTRODUCTION

The objective of this study was to investigate the effect of common single nucleotide genomic polymorphisms in the cyclooxygenase-1 (COX-1) gene on the thromboxane A2 (TxA2) metabolite concentrations in serum and urine, as well as on prostaglandin F2α (PGF2α) urinary excretion in the diabetic population on acetylsalicylic acid (ASA) therapy.

MATERIAL AND METHODS

The study cohort consisted of 284 Caucasians with diabetes type 2 who had been taking ASA tablets at the dose of 75 mg/day for at least 3 months. Genotyping for the 4 selected SNPs within the COX-1 gene (two nonsynonymous-coding variants, rs3842787 [C50T, P17L] and rs5789 [C174A, L237M]; and two other synonymous SNPs, rs3842788 [G128A, Q41Q] and rs5788 [C644A]) was performed using the Sequenom iPLEX platform.

RESULTS

No statistically significant results were observed for the investigated SNPs and measured metabolites in the investigated cohort of patients. Statistically significant differences in S-TxB2 could however be observed for rs5788 in the subgroup of patients with very high S-TxB2 concentrations. In particular, more patients who were carriers of the minor allele for this polymorphism were observed in the group with S-TxB2 levels > 95(th) percentile, when compared with similar carriers in the group with S-TxB2 < 95(th) percentile (20% vs. 1.1%, respectively, p < 0.001, Mann-Whitney test).

CONCLUSIONS

The results of our study suggest that the four investigated common SNPs in the COX1 gene are not associated with obviously altered TxA2 metabolism and PGF2α synthesis in the investigated diabetic cohort treated with ASA.

Testing cardiovascular drug safety and efficacy in randomized trials

Randomized trials provide the gold standard evidence on which rests the decision to approve novel therapeutics for clinical use. They are large and expensive and provide average but unbiased estimates of efficacy and risk. Concern has been expressed about how unrepresentative populations and conditions that pertain in randomized trials might be of the real world, including concerns about the homogeneity of the biomedical and adherence characteristics of volunteers entered into such trials, the dose and constancy of drug administration and the mixture of additional medications that are restricted in such trials but might influence outcome in practice. A distinction has been drawn between trials that establish efficacy and those that demonstrate effectiveness, drugs that patients actually consume in the real world for clinical benefit. However, randomized controlled trials remain the gold standard for establishing efficacy and the testing of effectiveness with less rigorous approaches is a secondary, albeit important consideration. Despite this, there is an appreciation that average results may conceal considerable interindividual variation in drug response, leading to a failure to appreciate clinical value or risk in subsets of patients. Thus, attempts are now being made to individualize risk estimates by modulating those derived from large randomized trials with the individual baseline risk estimates based on demographic and biological criteria-the individual Numbers Needed to Treat to obtain a benefit, such as a life saved. Here, I will consider some reasons why large phase 3 trials-by far the most expensive element of drug development-may fail to address the unmet medical needs, which should justify such effort and investment.

The effect of intravenous vitamin C infusion on periprocedural myocardial injury for patients undergoing elective percutaneous coronary intervention

BACKGROUND

This small study has determined the effect of vitamin C on myocardial reperfusion in patients undergoing elective percutaneous coronary intervention (PCI). This study was to explore whether antioxidant vitamin C infusion before the procedure is able to affect the incidence of periprocedural myocardial injury (PMI) in patients undergoing PCI.

METHODS

In this prospective single-centre randomized study, 532 patients were randomized into 2 groups: the vitamin C group, which received a 3-g vitamin C infusion within 6 hours before PCI, and a control group, which received normal saline. The primary end point was the troponin I-defined PMI, and the second end point was the creatine kinase (CK)-MB-defined PMI. Separate analyses using both end points were performed. PMI was defined as an elevation of cardiac biomarker values (CK-MB or troponin I) > 5 times the upper limit of normal (ULN), alone or associated with chest pain or ST-segment or T-wave changes.

RESULTS

After PCI, the incidence of PMI was reduced, whether defined by troponin or by CK-MB, compared with the control group (troponin I, 10.9% vs 18.4%; P = 0.016; CK-MB, 4.2% vs 8.6%; P = 0.035). Logistic multivariate analysis showed that preprocedure use of vitamin C is an independent predictor of PMI either defined by troponin I (odds ratio [OR], 0.56; 95% confidence interval [CI], 0.33-0.97; P = 0.037) or by CK-MB (OR, 0.37; 95% CI, 0.14-0.99; P = 0.048).

CONCLUSIONS

In patients undergoing elective PCI, preprocedure intravenous treatment with vitamin C is associated with less myocardial injury.

A novel single-site manganese(II) complex of a pyridine derivative as a catalase mimetic for disproportionation of H2O2 in water

A novel single site Mn(II) complex was successfully synthesized and tested in the aqueous disproportionation of hydrogen peroxide. The complex was found to be stable (HR-XAS) and exhibits catalase-like activity in neutral pH. Theoretical calculations suggested a reaction mechanism involving two complexes, changes in metal oxidation state and proton shuttling.

Patients with microvascular obstruction after primary percutaneous coronary intervention show a gp91phox (NOX2) mediated persistent oxidative stress after reperfusion

BACKGROUND

Persistent oxidative stress may play a key role in microvascular obstruction (MVO). We aimed at assessing the role of platelet gp91phox (NOX2), the catalytic subunit of NADPH oxidase in MVO.

METHODS

We enrolled 40 patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention within 12 h from symptoms onset, either with angiographic MVO (n=20) or good angiographic myocardial reperfusion (MR) (n=20). Angiographic MVO was defined as a final thrombolysis in myocardial infarction (TIMI) flow ≤2 or TIMI flow of 3 with myocardial blush grade <2. NOX2 and isoprostanes (8-iso-PGF2α) levels, as assessed by enzyme-linked immunoadsorbent assay (ELISA) or by an enzyme immunoassays, respectively, were measured on admission, at 24 h and pre-discharge.

RESULTS

NOX2 levels increased from baseline to pre-discharge in patients with angiographic MVO (20.25 (15-24.75) pg/ml vs 25.50 (17-29.25) pg/ml, p=0.02), but not in MR patients (p=0.45), with a significant interaction between baseline and pre-discharge levels among the two groups (p=0.04). The levels of 8-iso-PGF2α showed a trend to increase from baseline to pre-discharge in angiographic MVO patients (295 (183.50-389.25) pmol/l vs 322 (206-370) pmol/l, p=0.06), but not in patients with MR (p=0.56), with a trend for interaction between baseline and pre-discharge levels among the two groups (p=0.09).

CONCLUSION

Patients with MVO, but not those with myocardial reperfusion, have a sustained increase of NOX2 and 8-iso-PGF2α. Therapies targeting NOX2 or high dosage antioxidants should be tested for MVO prevention and treatment.

F2-isoprostanes as markers of oxidant stress: an overview

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo via a non-enzymatic mechanism involving the free radical-initiated peroxidation of arachidonic acid. This unit summarizes selected aspects regarding current knowledge of these compounds and their value as markers of oxidative injury. Novel aspects related to the biochemistry of isoprostane formation are discussed and methods by which these compounds can be analyzed and quantified are summarized. A considerable portion of this unit examines the utility of F(2)-isoprostanes as markers of oxidant injury in vitro and in vivo. Numerous studies carried out over the past decade have shown that these compounds are extremely accurate measures of lipid peroxidation in animals and humans and have illuminated the role of oxidant injury in a number of human diseases.

Glucagon-like peptide-1 preserves coronary microvascular endothelial function after cardiac arrest and resuscitation: potential antioxidant effects

Glucagon-like peptide-1 (GLP-1) has protective effects in the heart. We hypothesized that GLP-1 would mitigate coronary microvascular and left ventricular (LV) dysfunction if administered after cardiac arrest and resuscitation (CAR). Eighteen swine were subjected to ventricular fibrillation followed by resuscitation. Swine surviving to return of spontaneous circulation (ROSC) were randomized to receive an intravenous infusion of either human rGLP-1 (10 pmol·kg(-1)·min(-1); n = 8) or 0.9% saline (n = 8) for 4 h, beginning 1 min after ROSC. CAR caused a decline in coronary flow reserve (CFR) in control animals (pre-arrest, 1.86 ± 0.20; 1 h post-ROSC, 1.3 ± 0.05; 4 h post-ROSC, 1.25 ± 0.06; P < 0.05). GLP-1 preserved CFR for up to 4 h after ROSC (pre-arrest, 1.31 ± 0.17; 1 h post-ROSC, 1.5 ± 0.01; 4 h post-ROSC, 1.55 ± 0.22). Although there was a trend toward improvement in LV relaxation in the GLP-1-treated animals, overall LV function was not consistently different between groups. 8-iso-PGF(2α), a measure of reactive oxygen species load, was decreased in post-ROSC GLP-1-treated animals [placebo, control (NS): 38.1 ± 1.54 pg/ml; GLP-1: 26.59 ± 1.56 pg/ml; P < 0.05]. Infusion of GLP-1 after CAR preserved coronary microvascular and LV diastolic function. These effects may be mediated through a reduction in oxidative stress.

Cardioprotection against ischaemia/reperfusion by vitamins C and E plus n-3 fatty acids: molecular mechanisms and potential clinical applications. Clin Sci (Lond). 2013;124:1-15. [PMID: 22963444 DOI: 10.1042/cs20110663]

The role of oxidative stress in ischaemic heart disease has been thoroughly investigated in humans. Increased levels of ROS (reactive oxygen species) and RNS (reactive nitrogen species) have been demonstrated during ischaemia and post-ischaemic reperfusion in humans. Depending on their concentrations, these reactive species can act either as benevolent molecules that promote cell survival (at low-to-moderate concentrations) or can induce irreversible cellular damage and death (at high concentrations). Although high ROS levels can induce NF-κB (nuclear factor κB) activation, inflammation, apoptosis or necrosis, low-to-moderate levels can enhance the antioxidant response, via Nrf2 (nuclear factor-erythroid 2-related factor 2) activation. However, a clear definition of these concentration thresholds remains to be established. Although a number of experimental studies have demonstrated that oxidative stress plays a major role in heart ischaemia/reperfusion pathophysiology, controlled clinical trials have failed to prove the efficacy of antioxidants in acute or long-term treatments of ischaemic heart disease. Oral doses of vitamin C are not sufficient to promote ROS scavenging and only down-regulate their production via NADPH oxidase, a biological effect shared by vitamin E to abrogate oxidative stress. However, infusion of vitamin C at doses high enough to achieve plasma levels of 10 mmol/l should prevent superoxide production and the pathophysiological cascade of deleterious heart effects. In turn, n-3 PUFA (polyunsaturated fatty acid) exposure leads to enhanced activity of antioxidant enzymes. In the present review, we present evidence to support the molecular basis for a novel pharmacological strategy using these antioxidant vitamins plus n-3 PUFAs for cardioprotection in clinical settings, such as post-operative atrial fibrillation, percutaneous coronary intervention following acute myocardial infarction and other events that are associated with ischaemia/reperfusion.

Controlled reoxygenation cardiopulmonary bypass is associated with reduced transcriptomic changes in cyanotic tetralogy of Fallot patients undergoing surgery

In cyanotic patients undergoing repair of heart defects, high level of oxygen during cardiopulmonary bypass (CPB) leads to greater susceptibility to myocardial ischemia and reoxygenation injury. This study investigates the effects of controlled reoxygenation CPB on gene expression changes in cyanotic hearts of patients undergoing surgical correction of tetralogy of Fallot (TOF). We randomized 49 cyanotic TOF patients undergoing corrective cardiac surgery to receive either controlled reoxygenation or hyperoxic/standard CPB. Ventricular myocardium biopsies were obtained immediately after starting and before discontinuing CPB. Microarray analyses were performed on samples, and array results validated with real-time PCR. Gene expression profiles before and after hyperoxic/standard CPB revealed 35 differentially expressed genes with three upregulated and 32 downregulated. Upregulated genes included two E3 Ubiquitin ligases. The products of downregulated genes included intracellular signaling kinases, metabolic process proteins, and transport factors. In contrast, gene expression profiles before and after controlled reoxygenation CPB revealed only 11 differentially expressed genes with 10 upregulated including extracellular matrix proteins, transport factors, and one downregulated. The comparison of gene expression following hyperoxic/standard vs. controlled reoxygenation CPB revealed 59 differentially expressed genes, with six upregulated and 53 downregulated. Upregulated genes included PDE1A, MOSC1, and CRIP3. Downregulated genes functionally clustered into four major classes: extracellular matrix/cell adhesion, transcription, transport, and cellular metabolic process. This study provides direct evidence that hyperoxic CPB decreases the adaptation and remodeling capacity in cyanotic patients undergoing TOF repair. This simple CPB strategy of controlled reoxygenation reduced the number of genes whose expression was altered following hyperoxic/standard CPB.

The cellular and molecular origin of reactive oxygen species generation during myocardial ischemia and reperfusion

Myocardial ischemia-reperfusion injury is an important cause of impaired heart function in the early postoperative period subsequent to cardiac surgery. Reactive oxygen species (ROS) generation increases during both ischemia and reperfusion and it plays a central role in the pathophysiology of intraoperative myocardial injury. Unfortunately, the cellular source of these ROS during ischemia and reperfusion is often poorly defined. Similarly, individual ROS members tend to be grouped together as free radicals with a uniform reactivity towards biomolecules and with deleterious effects collectively ascribed under the vague umbrella of oxidative stress. This review aims to clarify the identity, origin, and progression of ROS during myocardial ischemia and reperfusion. Additionally, this review aims to describe the biochemical reactions and cellular processes that are initiated by specific ROS that work in concert to ultimately yield the clinical manifestations of myocardial ischemia-reperfusion. Lastly, this review provides an overview of several key cardioprotective strategies that target myocardial ischemia-reperfusion injury from the perspective of ROS generation. This overview is illustrated with example clinical studies that have attempted to translate these strategies to reduce the severity of ischemia-reperfusion injury during coronary artery bypass grafting surgery.

Reactive oxygen species in cardiovascular disease

Based on the "free radical theory" of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that reactive oxygen species and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding of reactive oxygen species has evolved to the point at which we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review addresses our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology.

Intravenous ascorbic acid infusion improves myocardial perfusion grade during elective percutaneous coronary intervention: relationship with oxidative stress markers. JACC Cardiovasc Interv. 2010;3:221-229. [PMID: 20170881 DOI: 10.1016/j.jcin.2009.10.025]

OBJECTIVES

Our goal was to explore whether antioxidant vitamin C infusion is able to affect the microcirculation perfusion in patients undergoing elective percutaneous coronary intervention for stable angina.

BACKGROUND

Periprocedural myocardial injury in the setting of elective percutaneous coronary intervention is associated with increased risk of death, recurrent infarction, and revascularization at follow-up. Despite excellent epicardial blood flow, impaired microcirculatory reperfusion may persist and increases the risk of vascular recurrences. Post-percutaneous coronary intervention induced-oxidative stress is one of the potential mechanisms accounting for impaired perfusion.

METHODS

Fifty-six patients were enrolled in a prospective, single-center, randomized study comparing 1 g vitamin C infusion (16.6 mg/min, over 1 h before percutaneous coronary intervention) versus placebo.

RESULTS

At the baseline, Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade <2 was observed in 89% and in 86% of patients randomized to the placebo or vitamin C infusion group, respectively (p > 0.05). After percutaneous coronary intervention, these percentages decreased in the placebo group (32%) and in greater measure in the vitamin C group (4%, p < 0.01). Complete microcirculatory reperfusion (TIMI myocardial perfusion grade = 3) was achieved in 79% of the vitamin C-treated group compared with 39% of the placebo group (p < 0.01); 8-hydroxy-2-deoxyguanosine (p < 0.002) and 8-iso-prostaglandin F(2alpha) (p < 0.02) plasma levels significantly increased in the placebo group while they were significantly reduced in the vitamin C-treated group (p < 0.0001). TIMI myocardial perfusion grade changes from the baseline showed significant correlation with 8-hydroxy-2-deoxyguanosine (p < 0.006) or 8-iso-prostaglandin F(2alpha) (p < 0.01) plasma levels changes.

CONCLUSIONS

In patients undergoing elective percutaneous coronary intervention, impaired microcirculatory reperfusion is improved by vitamin C infusion suggesting that oxidative stress is implicated in such a phenomenon.

The first clinical pilot study of intravenous adrenomedullin administration in patients with acute myocardial infarction. J Cardiovasc Pharmacol. 2010;56:413-419. [PMID: 20930593 DOI: 10.1097/FJC.0b013e3181f15b45]

Adrenomedullin (AM) is a 52-amino-acid vasodilator peptide that was originally isolated from human pheochromocytoma. In the previous experimental study with rat ischemia/reperfusion model, AM reduced infarct size and inhibited myocyte apoptosis. AM also suppressed the production of oxygen-free radicals. The present study was designed to evaluate the feasibility of intravenous administration of AM in patients with acute myocardial infarction. We studied 10 patients with first acute myocardial infarction [male to female ratio: 9 to 1, age: 65 ± 9 (mean ± SD) years, peak creatine phosphokinase level: 4215 ± 1933 (SD) U/L], who were hospitalized within 12 hours of symptom onset. Proceeding reperfusion therapy, AM infusion was initiated and continued at concentration of 0.0125-0.025 μg·kg·min for 12 hours. Follow-up coronary angiography and left ventriculography were performed at 3 months. Cardiac magnetic resonance was examined at 1 month and 3 months after AM therapy. During infusion of AM, hemodynamics kept stable except 2 patients. Wall motion index in the infarct area at 3 months was significantly improved compared with that at baseline, and infarct size evaluated by cardiac magnetic resonance was significantly decreased at 3 months. In conclusion, intravenous administration of AM, which possesses a variety of potential cardiovascular protective actions, can be adjunctive to percutaneous coronary intervention.

Reactive oxygen species and the pathogenesis of radiocontrast-induced nephropathy. Invest Radiol. 2010;45:188-195. [PMID: 20195159 DOI: 10.1097/rli.0b013e3181d2eed8]

Experimental findings in vitro and in vivo illustrate enhanced hypoxia and the formation of reactive oxygen species (ROS) within the kidney following the administration of iodinated contrast media, which may play a role in the development of contrast media-induced nephropathy. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging or reduced ROS formation with the administration of N-acetyl cysteine and bicarbonate infusion, respectively. Furthermore, most risk factors, predisposing to contrast-induced nephropathy are prone to enhanced renal parenchymal hypoxia and ROS formation. In this review, the association of renal hypoxia and ROS-mediated injury is outlined. Generated during contrast-induced renal parenchymal hypoxia, ROS may exert direct tubular and vascular endothelial injury and might further intensify renal parenchymal hypoxia by virtue of endothelial dysfunction and dysregulation of tubular transport. Preventive strategies conceivably should include inhibition of ROS generation or ROS scavenging.

Thromboxane and the thromboxane receptor in cardiovascular disease

Thromboxane A(2) (TXA(2)), the primary product of COX-1-dependent metabolism of arachidonic acid, mediates its biological actions through the TXA(2) receptor, termed the TP. Irreversible inhibition of platelet COX-1-derived TXA(2) with low-dose aspirin affords protection against primary and secondary vascular thrombotic events, underscoring the central role of TXA(2) as a platelet agonist in cardiovascular disease. The limitations associated with aspirin use include significant gastrointestinal toxicity, bleeding complications, potential interindividual response variability and poor efficacy in some disease states. This, together with the broad role of TXA(2) in cardiovascular disease beyond the platelet, has refocused interest towards additional TXA(2)-associated drug targets, in particular TXA(2) synthase and the TP. The superiority of these agents over low-dose aspirin, in terms of clinical efficacy, tolerability and commercial viability, remain open questions that are the focus of ongoing research.

Nutritional and exercise-based interventions in the treatment of amyotrophic lateral sclerosis

BACKGROUND & AIMS

Disease pathogenesis in amyotrophic lateral sclerosis (ALS) involves a number of interconnected mechanisms all resulting in the rapid deterioration of motor neurons. The main mechanisms include enhanced free radical production, protein misfolding, aberrant protein aggregation, excitotoxicity, mitochondrial dysfunction, neuroinflammation and apoptosis. The aim of this review is to assess the efficacy of using nutrition- and exercise-related interventions to improve disease outcomes in ALS.

METHODS

Studies involving nutrition or exercise in human and animal models of ALS were reviewed.

RESULTS

Treatments conducted in animal models of ALS have not consistently translated into beneficial results in clinical trials due to poor design, lack of power and short study duration, as well as differences in the genetic backgrounds, treatment dosages and disease pathology between animals and humans. However, vitamin E, folic acid, alpha lipoic acid, lyophilized red wine, coenzyme Q10, epigallocatechin gallate, Ginkgo biloba, melatonin, Cu chelators, and regular low and moderate intensity exercise, as well as treatments with catalase and l-carnitine, hold promise to mitigating the effects of ALS, whereas caloric restriction, malnutrition and high-intensity exercise are contraindicated in this disease model.

CONCLUSIONS

Improved nutritional status is of utmost importance in mitigating the detrimental effects of ALS.

Oxidative Stress and Myocardial Damage during Elective Percutaneous Coronary Interventions and Coronary AngiographyA Comparison of Blood-borne Isoprostane and Troponin Release

The role of oxidative stress in clinical cardiology is still controversial. The aims of the present study were to examine if minor ischaemic episodes as may occur during elective percutaneous coronary intervention (PCI) induce oxidative stress and, eventually, if oxygen stress correlates with myocardial injury. Thirty eight and nine patients underwent PCI and diagnostic coronary angiography, respectively. Peripheral blood was sampled at different time points for plasma analyses of: 8-iso-PGF2alpha (free radical-mediated oxidative stress); 15-keto-dihydro-PGF2alpha (cyclooxygenase-mediated inflammation); troponin-T (myocardial injury); hsCRP, vitamin A and vitamin E; and, total antioxidants status (TAS). In both groups 8-iso-PGF2alpha increased transiently by approximately 80% (p < 0.001) during the procedure. There was a minor troponin-T release (p < 0.001) after PCI, but no correlation with 8-iso-PGF2alpha. Troponin-T did not increase after angiography. 15-keto-dihydro-PGF2alpha decreased by 50% after ended procedure, but increased by 100% after 24 h compared to baseline. hsCRP increased significantly (p < 0.001) from baseline to the next day in the PCI-group, but not in the angiography group. Vitamins and TAS decreased slightly after the procedures. It is concluded that a moderate oxidative stress was induced by both elective PCI and coronary angiography but that no correlation was found between oxidative stress and myocardial injury in this setting. This indicates that other mechanisms than ischaemia-reperfusion episodes caused an elevation in plasma isoprostane such like the injury at a vascular site mutual for both procedures. A secondary finding from the study was elevated markers of early inflammatory response, not only after PCI, but also after angiography.

Novel eicosapentaenoic acid-derived F3-isoprostanes as biomarkers of lipid peroxidation

Isoprostanes (iPs) are prostaglandin (PG) isomers generated by free radical-catalyzed peroxidation of polyunsaturated fatty acids (PUFAs). Urinary F(2)-iPs, PGF(2alpha) isomers derived from arachidonic acid (AA) are used as indices of lipid peroxidation in vivo. We now report the characterization of two major F(3)-iPs, 5-epi-8,12-iso-iPF(3alpha)-VI and 8,12-iso-iPF(3alpha)-VI, derived from the omega-3 fatty acid, eicosapentaenoic acid (EPA). Although the potential therapeutic benefits of EPA receive much attention, a shift toward a diet rich in omega-3 PUFAs may also predispose to enhanced lipid peroxidation. Urinary 5-epi-8,12-iso-iPF(3alpha)-VI and 8,12-iso-iPF(3alpha)-VI are highly correlated and unaltered by cyclooxygenase inhibition in humans. Fish oil dose-dependently elevates urinary F(3)-iPs in mice and a shift in dietary omega-3/omega-6 PUFAs is reflected by an increasing slope [m] of the line relating urinary 8, 12-iso-iPF(3alpha)-VI and 8,12-iso-iPF(2alpha)-VI. Administration of bacterial lipopolysaccharide evokes a reversible increase in both urinary 8,12-iso-iPF(3alpha)-VI and 8,12-iso-iPF(2alpha)-VI in humans on an ad lib diet. However, while excretion of the iPs is highly correlated (R(2) median = 0.8), [m] varies by an order of magnitude, reflecting marked inter-individual variability in the relative peroxidation of omega-3 versus omega-6 substrates. Clustered analysis of F(2)- and F(3)-iPs refines assessment of the oxidant stress response to an inflammatory stimulus in vivo by integrating variability in dietary intake of omega-3/omega-6 PUFAs.

Real-time quantitation of renal ischemia using targeted microbubbles: in-vivo measurement of P-selectin expression

INTRODUCTION

Ischemia-reperfusion injury (IRI) results in cellular damage, production of free oxygen radicals, and subsequent apoptosis. During partial nephrectomy, the renal hilum is temporarily clamped to optimize resection of renal masses in a bloodless field. The trade-off for this maneuver is IRI. It is not known definitively how long a period of renal artery clamping will result in irreversible cellular death, nor in which region of the kidney the injury primarily occurs. An established marker of inflammation and ischemic injury is P-selectin, a cell adhesion molecule expressed on endothelial cells and activated platelets. The goal of this project was to use targeted microbubbles outfitted with anti-P-selectin antibodies to quantitate for the first time the microvascular reperfusion injury and regional blood flow in the kidney during IRI.

MATERIALS AND METHODS

Using the protocol approved by the Institutional Animal Care and Use Committee (IACUC), 20 renal units obtained from C57/BL6J female mice were studied. The left renal artery and vein were ligated for 30 minutes. Microbubbles coated with anti-P-selectin antibodies were injected after hilar unclamping, and both kidneys were scanned. As a control, perfusion and re-perfusion of the left kidney was performed using pulse-wave Doppler mode. Subsequently, a Vevo 770 micro-ultrasound system with a resolution of 40 mum was used to noninvasively measure the microvascular flow and quantitate targeted microbubbles bound to P-selectin. Negative controls consisted of sham animals and microbubbles coated with isotype serum. Customized software produced digital subtraction video intensity units (VIU), which allowed comparison of the different regions of the kidney.

RESULTS

Regional blood flow was measured in three areas: cortex, medulla, and corticomedullary junction (CMJ). In the sham left kidney, the CMJ had the highest blood volume and flow (141.1) compared with renal medulla (43.7) and cortex (100.6) VIU (p < 0.01). After hilar unclamping, blood flow rate to the left kidney decreased from 554 mm/s to 182 mm/s, despite improvement in the color of the kidney from cyanotic to pink. After 30 minutes of ischemia, P-selectin expression increased by 41%, 25%, and 14% in the CMJ, cortex, and the medulla, respectively, compared to controls. P-selectin expression, and therefore the greatest area of ischemic injury, was highest in the CMJ region (432.1) compared with the cortex (369.4) and medulla (86.5) (p < 0.01).

CONCLUSION

This pilot study quantitates for the first time in an in-vivo model of IRI that the CMJ region sustains the highest degree of nephron and microvascular damage. This region is the most susceptible to ischemic injury as indicated by 41% increase in expression of P-selectin immediately postunclamping.

The effects of normoxic versus hyperoxic cardiopulmonary bypass on oxidative stress and inflammatory response in cyanotic pediatric patients undergoing open cardiac surgery: a randomized controlled trial

OBJECTIVES

This study investigates the effects of controlled reoxygenation cardiopulmonary bypass on oxidative stress, inflammatory response, and organ function in children undergoing repair of cyanotic congenital heart defects.

METHODS

Sixty-seven cyanotic patients (median age 15 months, interquartile range 6-49 months) undergoing corrective cardiac surgery were randomized to receive either controlled normoxic (50-0 mm Hg; n = 35) or hyperoxic (150-180 mm Hg; n = 32) cardiopulmonary bypass. Troponin I and 8-isoprostane, C3a, interleukins 6, 8, and 10, cortisol, protein S100, and alpha-glutamate transferase were measured preoperatively and 10 and 30 minutes after starting bypass, on removal of the aortic crossclamp, and 12 and 24 hours thereafter.

RESULTS

Overall, troponin I and 8-isoprostane levels were lower in the controlled normoxic group (-29%, 95% CI -48% to -3%, P = .03, and -26%, 95% CI -44% to -2%, P = .03, respectively). Protein S100 release was also lower in the normoxic group 10 minutes after starting bypass (-26%, 95% CI -40% to -9%, P = .005) and 10 minutes after aortic crossclamp removal (-23%, 95% CI -38% to -3%, P = .02, respectively), but similar at other time points in the two groups (P >or= .17). The alpha-glutamate transferase release was significantly lower in the normoxic group 10 minutes after aortic crossclamp removal (-28%, 95% CI -44% to -9%, P = .006, respectively) but was similar at other times (P >or= .11). Release of C3a, interleukins 6, 8, and 10, and cortisol was similar in the two groups throughout (P >or= .15).

CONCLUSION

Controlled reoxygenation on starting cardiopulmonary bypass is associated with reduced myocardial damage, oxidative stress, and cerebral and hepatic injury compared with hyperoxic bypass and similar whole body inflammatory and stress response in cyanotic children undergoing open cardiac surgery.

Beyond prostaglandins--chemistry and biology of cyclic oxygenated metabolites formed by free-radical pathways from polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) are important constituents in all organisms. They fulfil many functions, ranging from modulating the structure of membranes to acting as precursors of physiologically important molecules, such as the prostaglandins, which for a long time were the most prominent cyclic PUFA metabolites. However, since the beginning of the 1990s a large variety of cyclic metabolites have been discovered that form under autoxidative conditions in vivo to a much larger extent than do prostaglandins. These compounds--isoprostanes, neuroprostanes, phytoprostanes, and isofurans--proved subsequently to be ubiquitous in nature. They display a wide range of biological activities, and isoprostanes have become the currently most reliable indicators of oxidative stress in humans. In a relatively short time, the structural variety, properties, and applications of the autoxidatively formed cyclic PUFA derivatives have been uncovered.

Microglia are the major cellular source of inducible nitric oxide synthase during experimental herpes encephalitis

Although production of reactive nitrogen and reactive oxygen species (RNS and ROS) is a component of innate defense against viral infection, their overproduction in the brain may also lead to deleterious consequences. To investigate potential immunopathologic roles of oxidative stress during herpes encephalitis, the authors examined the expression kinetics of inducible nitric oxide synthase (iNOS) as well as heme oxygenase-1 (HO-1), a marker of oxidative stress, and evaluated infection-induced oxidative brain damage. Results from these studies showed that both iNOS and HO-1 gene expression were highly elevated in the brain within 7 days post infection (d.p.i.) and remained elevated through 21 d.p.i. Real-time bioluminescence imaging of HO-1 promoter-luciferase transgenic mice confirmed HO-1 promoter activity in the brains of HSV-1-infected animals within 3 d.p.i., which peaked between 5 and 7 d.p.i. Immunohistochemical staining for both 3-nitrotyrosine and 8-hydroxydeoxyguanosine (8-OH-dG), as well as quantitative assessment of 8-isoprostane levels, demonstrated the presence of viral infection-induced oxidative brain damage. In addition, when brain leukocytes obtained from animals with experimental herpes encephalitis were sorted using fluorescence-activated cell sorting (FACS) and the individual cell populations analyzed, CD45(int)/CD11b(+) resident microglia were found to be the major cellular source of iNOS expression.

F2-isoprostanes in human health and diseases: from molecular mechanisms to clinical implications

Oxidative stress is implicated as one of the major underlying mechanisms behind many acute and chronic diseases, and involved in normal aging. However, the measurement of free radicals or their end products is complicated. Thus, proof of association of free radicals in pathologic conditions has been absent. Isoprostanes are prostaglandin-like bioactive compounds that are biosynthesized in vivo independent of cyclooxygenases, principally through free-radical catalyzation of arachidonic acid. Isoprostanes are now considered to be reliable biomarkers of oxidative stress, as evidenced by an autonomous study organized recently by the National Institutes of Health (NIH) in the United States. A number of these compounds have potent biologic activities such as vasoconstrictive and certain inflammatory properties. Isoprostanes are involved in many human diseases. Additionally, elevated levels of F(2)-isoprostanes have been seen in normal human pregnancy and after intake of some fatty acids, but their physiologic assignments have not yet been distinctive. This evidence indicates that measurement of bioactive F(2)-isoprostanes in body fluids offers a unique noninvasive analytic utensil to study the role of free radicals in physiology, oxidative stress-related diseases, experimental acute or chronic inflammatory conditions, and also in the assessment of various antioxidants, radical scavengers, and drugs.

Increased isoprostane content in coronary plaques obtained from vulnerable patients

8-Iso-prostaglandin F(2)(alpha) (8-iso-PGF(2)(alpha)), a representative isoprostane, is a reliable biomarker for enhanced oxidant stress in vivo. Its urinary excretion has been proposed as a risk marker in patients with coronary heart disease. Isoprostane content has not yet been well elucidated so far in human coronary plaques. The aim of this study was to evaluate content of immunoreactive 8-iso-PGF(2)(alpha) in directional coronary atherectomy (DCA) specimens from patients with coronary heart diseases. Twenty-seven patients with stable angina pectoris (SAP) and 8 vulnerable patients (5 patients with unstable angina pectoris and 3 with recent myocardial infarction) were subjected to DCA. The specimens from SAP consisted of 14 de novo and 13 restenotic lesions, whereas those from the vulnerable patients were all de novo lesions. Total 8-iso-PGF(2)(alpha) content in the DCA specimens from the vulnerable patients was significantly greater than that from patients with SAP (5.48 (2.70-10.43) versus 2.38 (1.19-4.32)ng/g tissue, median (interquartile range), P<0.05). There was no significant difference in total 8-iso-PGF(2)(alpha) content between de novo and restenotic lesions from patients with SAP (3.25 (1.48-5.05) versus 1.57 (0.62-2.47)ng/g tissue, respectively, P=0.895). Total 8-iso-PGF(2)(alpha) content in apparently normal peripheral artery specimens was only 0.34 (0.26-0.46)ng/g tissue. In conclusion, 8-iso-PGF(2)(alpha) was enriched in the DCA specimens from vulnerable patients, suggesting a crucial role of free radicals in formation of vulnerable plaques and a putative benefit of anti-oxidant therapy on these patients.

Isoprostanes constrict human radial artery by stimulation of thromboxane receptors, Ca2+ release, and RhoA activation

OBJECTIVES

Radial artery vasospasm remains a potential cause of early graft failure after coronary bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. We examined the roles of isoprostanes and prostanoid receptors selective for thromboxane A2 in the vasoconstriction of human radial arteries.

METHODS

Human radial arterial segments were pretreated intraoperatively with verapamil/papaverine or nitroglycerine/phenoxybenzamine, or not treated. In the laboratory, we measured isometric contractions in ring segments, vasoconstriction in pressurized segments, and changes in [Ca2+] and K+ currents in single cells.

RESULTS

Although phenoxybenzamine eliminated adrenergic responses, the isoprostane 15-F(2t)-IsoP and 2 closely related E-ring molecules (15-E(1t)-IsoP and 15-E(2t)-IsoP) still evoked powerful contractions; 15-E(2t)-IsoP was approximately 10-fold more potent than the other 2 agents. Responses were mediated through thromboxane receptors because they were sensitive to ICI-192605. Furthermore, they were sensitive to the Rho-kinase inhibitors Y-27632 or H-1152 (both 10(-5) mol/L) or to cyclopiazonic acid (which depletes the internal Ca2+ pool), but not to nifedipine. In single cells, 15-E(2t)-IsoP elevated [Ca2+]i and suppressed K+ current.

CONCLUSIONS

Isoprostanes accumulate after coronary artery bypass graft surgery, yet none of the currently available antispasm treatments for radial artery grafts is effective against isoprostane-induced vasoconstriction. It is imperative that more specific treatment strategies be developed. We found that isoprostane responses in radial arteries are mediated by prostanoid receptors selective for thromboxane A2 with activation of Rho-kinase and release of Ca2+. Pretreatment of radial artery grafts with Rho-associated kinase inhibitors may potentially reduce postoperative graft spasm. Clinical studies to test this are indicated.

F2-isoprostanes are not just markers of oxidative stress

F(2)-isoprostanes are not just markers of oxidative stress. The discovery of F(2)-isoprostanes (F(2)-IsoPs) as specific and reliable markers of oxidative stress in vivo is briefly summarized here. F(2)-IsoPs are also agonists of important biological effects, such as the vasoconstriction of renal glomerular arterioles, the retinal vessel, and the brain microcirculature. In addition to the F(2)-IsoPs, E(2)- and D(2)-IsoPs can be formed by rearrangement of H(2)-IsoP endoperoxides and can give rise to cyclopentenone IsoPs, which are very reactive alpha,beta-unsaturated aldehydes. The same type of reactivity is also shown by acyclic gamma-ketoaldehydes formed as products of the IsoP pathway. Because previous studies suggested a relation between oxidative stress and collagen hyperproduction, it was investigated whether collagen synthesis is induced by F(2)-IsoPs, the most proximal products of lipid peroxidation. In contrast to aldehydes, F(2)-IsoPs act through receptors able to elicit definite signal transduction pathways. In a rat model of carbon tetrachloride-induced hepatic fibrosis, plasma F(2)-IsoPs were markedly elevated for the entire experimental period; hepatic collagen content was also increased. When hepatic stellate cells from normal liver were cultured up to activation (expression of smooth muscle alpha-actin) and then treated with F(2)-IsoPs in the concentration range found in the in vivo studies (10(-9) to 10(-8) M), a striking increase in DNA synthesis, cell proliferation, and collagen synthesis was observed. Total collagen content was similarly increased. All these stimulatory effects were reversed by the specific antagonist of the thromboxane A(2) receptor, SQ 29 548, whereas the receptor agonist, I-BOP, also had a stimulatory effect. Therefore F(2)-IsoPs generated by lipid peroxidation in hepatocytes may mediate hepatic stellate cell proliferation and collagen hyperproduction seen in hepatic fibrosis.

New techniques to detect oxidative stress markers: mass spectrometry-based methods to detect isoprostanes as the gold standard for oxidative stress in vivo

Free radical-induced lipid oxidation under oxidative stress has been implicated in a number of human diseases. Isoprostanes (IsoPs), isomers of prostaglandins, are one of the major classes of oxidation products derived from this oxidation process. Measurement of the levels of IsoPs by Mass Spectrometry-based methods has become the "gold standard" biomarker of oxidative stress in vivo. Significant advances have been made in understanding this important pathway of lipid peroxidation since the discovery of IsoP formation in vivo 18 years ago. Studies from our laboratory and others are discussed that have provided insights into the mechanism of formation. Furthermore, new independent studies have demonstrated that IsoPs are the most reliable available marker of lipid peroxidation in vivo, and recent work examining IsoP formation has provided valuable information about the pathogenesis of numerous human diseases. Thus, the complexity of the IsoP pathway has expanded, providing novel insights into mechanisms of lipid peroxidation in vivo and allowing investigators to explore the role of oxidative stress in human disease.