Isoprostanes: potential markers of oxidant stress in atherothrombotic disease

BOLD-MRI assessment of intrarenal oxygenation and oxidative stress in patients with chronic kidney allograft dysfunction

Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) uses deoxyhemoglobin as an endogenous contrast agent for the noninvasive assessment of tissue oxygen bioavailability. We hypothesized that intrarenal oxygenation was impaired in patients with chronic allograft nephropathy (CAN). Ten kidney-transplant recipients with CAN and nine healthy volunteers underwent BOLD-MRI. Medullary R2* (MR2*) and cortical R2* (CR2*) levels (measures directly proportional to tissue deoxyhemoglobin levels) were determined alongside urine and serum markers of oxidative stress (OS): hydrogen peroxide (H(2)O(2)), F(2)-isoprostanes, total nitric oxide (NO), heat shock protein 27 (HSP27), and total antioxidant property (TAOP). Mean MR2* and CR2* levels were significantly decreased in CAN (increased local oxyhemoglobin concentration) compared with healthy volunteers (20.7 +/- 1.6 vs. 23.1 +/- 1.8/s, P = 0.03 and 15.9 +/- 1.9 vs. 13.6 +/- 2.3/s, P = 0.05, respectively). There was a significant increase in serum and urine levels of H(2)O(2) and serum HSP27 levels in patients with CAN. Conversely, urine NO levels and TAOP were significantly increased in healthy volunteers. Multiple linear regression analyses showed a significant association between MR2* and CR2* levels and serum/urine biomarkers of OS. BOLD-MRI demonstrated significant changes in medullary and cortical oxygen bioavailability in allografts with CAN. These correlated with serum/urine biomarkers of OS, suggesting an association between intrarenal oxygenation and OS.

Polyphenols synergistically inhibit oxidative stress in subjects given red and white wine

Aim of this study was to analyse the relationship between the plasma levels of polyphenols and the antioxidant activity of red and white wine. Twenty healthy subjects (HS) were randomly allocated to drink 300 ml of red (n = 10) or white n = 10 wine for 15 days. Ten HS who refrained from any alcohol beverage for 15 days were used as control. Urinary PGF-2alpha-III, a marker of oxidative stress and plasma levels of polyphenols were measured. Urinary PGF-2alpha-III significantly fell in subjects taking wine with a higher percentage decrease in subjects given red wine (-38.5 +/- 6%, p < 0.001) than in those given white wine (-23.1 +/- 6%). Subjects taking red wine had higher plasma polyphenols than those taking white wine (1.9 +/- 0.6 microM versus 1.5 +/- 0.33 microM, p < 0.001). Plasma polyphenols were inversely correlated with urinary PGF2alpha (r = 0.77, p < 0.001). No changes of urinary isoprostanes were observed in subjects who refrained from wine intake. In vitro study demonstrated that only a mixture of polyphenols, all in a range corresponding to that found in human circulation, inhibited LDL oxidation and PKC-mediated NADPH oxidase activation. Such inhibitory effects were more marked using the concentrations of polyphenols detected in human circulation after red wine intake. This study shows that red wine is more antioxidant than white wine in virtue of its higher content of polyphenols, an effect that may be dependent upon a synergism among polyphenols.

Lipoprotein-associated proteins involved in platelet signaling

Platelets and lipoproteins are both key elements in the development of atherosclerosis and thrombosis. Based on their density, five classes of lipoproteins have been identified which all influence platelets via distinct mechanisms. The activation of platelets starts with binding of apolipoproteins to different platelet receptors and is followed by the activation of signaling pathways resulting in activation or inhibition of platelet functions like aggregation or secretion. In addition to apolipoproteins, lipoproteins are also associated to a large amount of proteins, enzymes and lipids that also can induce platelet activation or inhibition. This review provides a summary of the activation of signaling pathways after platelet-lipoprotein interactions initiated by lipoprotein-associated proteins and lipids.

Aspirin therapy for inhibition of platelet reactivity in the presence of erythrocytes in patients with vascular disease

Inhibition of erythrocyte (RBC) promotion of platelet reactivity could improve the antiplatelet effect of aspirin (ASA). We tested different ASA regimens for optimal inhibition of platelets and the effects of RBC in patients with a history of vascular diseases. Collagen-induced platelet activation (14C-5HT, TXA2 release) and platelet recruitment (proaggregatory activity of cell-free releasates from activated platelets) were measured in PRP, platelet-RBC (Hct 40%), and whole blood (WB) in 206 patients initially on 200-300-mg ASA/day. Their regimen was modified to biweekly 500 mg (loading dose, L) plus daily or twice-daily low-dose ASA (50 or 100 mg). TXA2 was inhibited with all regimens. Percentage of patients with suboptimal inhibition of platelet recruitment in WB was 200-300 ASA/day (41%), L-50/day (87%), L-100/day (58%), L-50/twice-daily (39%), and L-100/twice-daily (20%; P < 0.05 vs other regimens). 14C-5HT release was inhibited to the greatest extent with L-100/twice-daily in PRP + RBC or WB (P < 0.05 vs other regimens) due to greater inhibition of the RBC prothrombotic effect. Compared with other ASA regimens, L-100 twice-daily (equivalent to 221-mg ASA/day in the 14-day cycle), reduced by >50% the proportion of patients with suboptimal inhibition of platelet recruitment in WB and inhibited 14C-5HT release to the greatest extent.

Oxidative stress and atherosclerosis

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the Western world. Its incidence has been increasing lately in developing countries. Several lines of evidence support a role for oxidative stress in atherogenesis. Growing evidence indicates that chronic and acute overproduction of reactive oxygen species (ROS) under pathophysiologic conditions is integral in the development of cardiovascular diseases (CVD). ROS mediate various signaling pathways that underlie vascular inflammation in atherogenesis from the initiation of fatty streak development through lesion progression to ultimate plaque rupture. Various animal models of oxidative stress support the notion that ROS have a causal role in atherosclerosis and other cardiovascular diseases. Human investigations also support the oxidative stress hypothesis of atherosclerosis. Oxidative stress is the unifying mechanism for many CVD risk factors, which additionally supports its central role in CVD. A main source of ROS in vascular cells is the reduced nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase system. This is a membrane-associated enzyme, composed of five subunits, catalyzing the one-electron reduction of oxygen, using NADH or NADPH as the electron donor. This system is an important target for genetic investigations. Identification of groups of patients with genetically prone or resistant of oxidative stress is therefore an obvious target of investigation. A better understanding of the complexity of cellular redox reactions, development of a new class of antioxidants targeted to specific subcellular sites, and the phenotype-genotype linkage analysis for oxidative stress will likely be avenues for future research with regards to the broader use of pharmacological therapies in the treatment and prevention of CVD.

Aldosterone blockade attenuates urinary monocyte chemoattractant protein-1 and oxidative stress in patients with type 2 diabetes complicated by diabetic nephropathy

CONTEXT

Aldosterone causes organic impairment by enhancement of oxidative stress and subsequent induction of proinflammatory cytokines and chemokines.

OBJECTIVE

This study was designed to investigate the effect of spironolactone, an aldosterone blocker, on oxidative stress and the level of urinary monocyte chemoattractant protein (MCP)-1, a cysteine-cysteine chemokine that may contribute to progression of various nephropathies in type 2 diabetic patients with diabetic nephropathy. DESIGN, SETTING, PATIENTS AND OTHER PARTICIPANTS, AND INTERVENTION: The patients were randomly assigned to two groups in which they received either spironolactone (50 mg/d; n = 23) or amlodipine (2.5 mg/d; n = 14).

MAIN OUTCOME MEASURES

Urinary 8-iso-prostaglandin (PG) F2alpha (a marker of oxidative stress), urinary MCP-1, and urinary albumin excretion (UAE) were measured at the start of administration (0 months) and after 3 months in each group. Baseline levels of these variables were also measured in 25 age-matched healthy subjects.

RESULTS

There were significant positive correlations between log(10)-transformed (log) 8-iso-PGF2alpha and log MCP-1 levels in control and diabetic subjects and all subjects combined, but no correlations between log UAE and log 8-iso-PGF2alpha or log MCP-1 were found in any group. Significant decreases in 8-iso-PGF2alpha, MCP-1, and UAE were observed with spironolactone (P = 0.0001, P = 0.0041, and P = 0.0037, respectively), and systolic blood pressure significantly decreased after both spironolactone and amlodipine therapy (P = 0.00011 and P = 0.0051, respectively).

CONCLUSIONS

Our data suggest that urinary MCP-1 is correlated with oxidative stress as measured by urinary 8-iso-PGF2alpha and that spironolactone can decrease urinary MCP-1 and oxidative stress.

Effect of a short-term diet and exercise intervention on oxidative stress, inflammation, MMP-9, and monocyte chemotactic activity in men with metabolic syndrome factors

The present study was designed to examine the effects of lifestyle modification on key contributing factors to atherogenesis, including oxidative stress, inflammation, chemotaxis, and cell adhesion. Obese men ( n = 31), 15 of whom had metabolic syndrome, were placed on a high-fiber, low-fat diet in a 3-wk residential program where food was provided ad libitum and daily aerobic exercise was performed. In each subject, pre- and postintervention fasting blood was drawn for circulating levels of serum lipids, glucose and insulin (for estimation of insulin sensitivity), oxidative stress-generating enzyme myeloperoxidase and marker 8-isoprostaglandin F2α, the inflammatory protein C-reactive protein, soluble ICAM-1 as an indicator of endothelial activation, sP-selectin as a marker of platelet activation, the chemokine macrophage inflammatory protein-1α, and total matrix metalloproteinase-9. Using subject sera and human aortic endothelial cell culture systems, we measured VCAM-1 cell surface abundance and monocyte chemotactic protein-1, nitric oxide, superoxide, and hydrogen peroxide production in vitro by fluorometric detection. Also determined in vitro was serum-induced, monocyte adhesion and monocyte chemotactic activity. After 3 wk, significant reductions ( P < 0.05) in body mass index, all serum lipids and lipid ratios, fasting glucose, insulin, homeostasis model assessment for insulin resistance, myeloperoxidase, 8-isoprostaglandin F2α, C-reactive protein, soluble ICAM-1, soluble P-selectin, macrophage inflammatory protein-1α, and matrix metalloproteinase-9 were noted. In vitro, serum-stimulated cellular VCAM-1 expression, monocyte chemotactic protein-1 production, and fluorometric detection of superoxide and hydrogen peroxide production decreased, whereas a concomitant increase in NO production was noted (all P < 0.01). Additionally, both monocyte adhesion ( P < 0.05) and MCA ( P < 0.01) decreased. Nine of 15 were no longer positive for metabolic syndrome postintervention. Intensive lifestyle modification may ameliorate novel coronary artery disease risk factors in men with metabolic syndrome factors before reversal of obesity.

Increased urinary excretion of 8-iso-prostaglandin F2alpha in patients with HFE-related hemochromatosis: a case-control study

The hypothesis according to which iron overload could be harmful has been extensively and controversially discussed in the literature. One underlying pathological mechanism may be elevated oxidative stress. Thus, we studied the correlation between hemochromatosis and an established marker of oxidative stress, 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha, iPF2alpha-III, 15-F2t-IsoP). We enrolled 21 patients with hemochromatosis, positive for the homozygous C282Y mutation in the HFE gene, and 21 healthy controls frequency-matched by age and gender in a case-control study design. The objective was to show that iron overload in HFE-related hemochromatosis is associated with increased oxidative stress assessed through 8-iso-PGF(2alpha) urinary excretion, and that oxidative stress is impacted by iron-removal treatment (phlebotomy). Study parameters were transferrin saturation, 8-iso-PGF(2alpha) urine excretion, transferrin, ferritin, serum iron, and vitamins A and E for all participants. Iron concentration in the liver and non-transferrin-bound iron were measured in patients only. We found a significant difference in 8-iso-PGF2alpha in patients (245 [interquartile range 157-348] pg/mg creatinine) compared with controls (128 [106-191] pg/mg creatinine, P = 0.002). Vitamin A was significantly reduced in cases (0.34 [0.25-1.83] microg/ml compared to 3.00 [2.11-3.39] microg/ml, P < 0.001), while vitamin E did not show a significant difference in cases (14.7 [11.5-18.1] microg/ml) compared with controls (14.9 [13.1-19.2] microg/ml, P = 0.52). After phlebotomy treatment and normalization of the iron parameters in the hemochromatosis group, serum vitamin A levels were significantly increased (1.36 [1.08-1.97] microg/ml, P = 0.035 vs. baseline, P < 0.001 vs. controls) and 8-iso-PGF2alpha urinary excretion was lowered to control levels (146 [117-198] pg/mg creatinine, P = 0.38 vs. controls). In our study, HFE-related hemochromatosis was associated with increased oxidative stress and hypovitaminemia A in C282Y homozygotes. The increased oxidative stress was reversible by normalization of the iron load by phlebotomy. Thus, phlebotomy is an effective and adequate means for reducing oxidative stress in these patients.

[Prevention of coronary heart disease: smoking]

Smoking is the leading preventable cause of illness and premature death in Germany, claiming over 110,000 lives a year because it directly increases the risk of dying from heart disease, stroke, emphysema and a variety of cancers. The overwhelming majority of smokers begin tobacco use before they reach adulthood. Among those young people who smoke, the average age is now 13-14. In Germany, about 39% of male and 31% of female adults (age 18-60 years) continue to smoke, despite information about the unequivocally negative health consequences of smoking. The exact mechanisms of smoking-related vascular disease are not yet known. Smoking causes acute hemodynamic alterations such as increase in heart rate, systematic and coronary vascular resistance, myocardial contractility, and myocardial oxygen demand. These short-term effects could lower the ischemic threshold in smokers with coronary artery disease and contribute to the increased risk for acute cardiovascular events. Endothelial damage is thought to be an initiating event in atherosclerosis and early studies have demonstrated that long-term smoking has direct toxic effects with structural changes of human endothelial cells. Recent research has shown the importance of the functional role of the endothelium in regulating vascular tone, platelet-endothelial interactions, leukocyte adhesion and smooth muscle cell proliferation via synthesis and release of a variety of substances such as nitric oxide. There is strong evidence that smoking leads to endothelial dysfunction mainly by increased inactivation of nitric oxide by oxygen-derived free radicals. Smoking also increases oxidative modification of LDL and is associated with lower HDL plasma levels. Smoking induces a systemic inflammatory response with increased leukocyte count and elevation of the C-reactive protein level. Importantly, the prothrombotic effects of smoking have been repeatedly demonstrated to cause alterations in platelet function, imbalance of antithrombotic vs prothrombotic factors, and decrease of fibrinolytic activity. Given the enormous health hazard of tobacco use, complete abstinence from smoking should be achieved. Smoking cessation counselling should be given to healthy subjects and even more vigorously to patients with manifested disease. Every effort should be undertaken to prevent children and adolescents from starting to smoke. Brief tobacco dependence treatment is effective, and every smoker should be offered at least brief treatment at every office visit. More intensive treatment is more effective in producing long-term abstinence from tobacco. Nicotine replacement therapy (nicotine patches or gum), clinician-delivered social support, and skills training are the three most effective components of smoking cessation treatment. A framework for tobacco control measures is necessary to reduce tobacco consumption and exposure to tobacco smoke. Recommendations on specific tobacco control interventions are: 1. increase in tobacco taxes; 2. comprehensive tobacco advertising bans; 3. legislation prohibiting smoking in work and public places; 4. prohibiting the sales of tobacco products to persons under 18; 5. comprehensive disclosure of the physical, chemical and design characteristics of all tobacco products; 6. training of health professionals to promote smoking prevention and cessation interventions; and 7. development of a national network of smoking cessation treatment services.

Isoprostanes and Oxidative Stress in Off-Pump and On-Pump Coronary Bypass Surgery

BACKGROUND

Conventional on-pump coronary artery bypass grafting (CABG) is associated with a systemic inflammatory response and by an increased production of reactive oxygen species, whereas off-pump coronary artery bypass grafting (OPCAB) is thought to be accompanied by less oxidative stress. Urinary isoprostane iPF2alpha-III is a new marker reflecting oxidative stress; it has emerged as the most reliable marker of oxidative stress status in vivo. This study was designed to ascertain whether OPCAB compared with CABG represents a surgical strategy that avoids oxidative stress. To this end urinary isoprostanes and other established oxidative stress markers were measured during the first 24 hours after CABG and OPCAB.

METHODS

Fifty low-risk coronary patients were randomly assigned to CABG or OPCAB. Urinary isoprostane iPF2alpha-III levels, plasma levels of free malondialdehyde, and total antioxidant status were measured before, during, and up to 24 hours after surgery.

RESULTS

In OPCAB iPF2alpha-III excretion remained unchanged throughout the study. As expected, in CABG iPF2alpha-III levels significantly increased during surgery and returned at baseline 24 hours later. Free malondialdehyde behaved similarly, with no change in OPCAB and sharp increases during CABG. Conversely, total antioxidant status showed a sharp drop during CABG, followed by a slow recovery, whereas a significantly lower drop occurred in OPCAB.

CONCLUSIONS

In this randomized study in low-risk coronary patients, OPCAB revealed less perioperative oxidative stress, as reflected by lack of excretion of iPF2alpha-III in urine, by lack of increase of plasma free malondialdehyde, and by lower decreases in plasma total antioxidant status.

Diabetes treatments have differential effects on nontraditional cardiovascular risk factors

OBJECTIVE

The aim of this study was to determine the effect of basal insulin, alone or with a sensitizer, or a combination of oral agents on nontraditional risk factors for cardiovascular disease (CVD).

RESEARCH DESIGN AND METHODS

We randomized 57 patients with T2DM to either (1) continuous subcutaneous basal Lispro insulin at a single rate using an insulin pump (basal insulin) or (2) basal insulin and oral pioglitazone 30 mg daily (basal insulin +Pio) or (3) a sulfonylurea and metformin (SU+M). We measured glycosylated hemoglobin (HbA1c), plasma high-sensitivity C-reactive protein (hs-CRP), plasminogen activator inhibitor-1 (PAI-1), 8-epi-prostaglandin F2 alpha (PGF2alpha), serum lipoprotein (a) [Lp (a)], and lipoprotein profile at baseline and after 20 weeks of treatment.

RESULTS

HbA1c decreased by >or=2% (P<.001) and to comparable levels (P=NS) in all groups. Despite improved glycemia, hsCRP did not change in any group, whereas plasma PAI-1 fell with basal insulin +Pio (P<.02) and SU+M (P<.01). PGF2alpha declined with basal insulin (P<.02) and SU+M (P<.001). High-density lipoprotein cholesterol (HDL-C) increased only with basal insulin +Pio (18.2%, P<.05). Lp (a) increased with basal insulin therapy alone (P<.01). Data were pooled from all groups to determine the overall effect of glycemic control-there was a significant (P<.001) decline in HbA1c, PAI-1, and PGF2alpha and an increase in HDL-C (P<.001). There was no correlation between HbA1c reduction and changes in these parameters.

CONCLUSIONS

We conclude that excellent glycemic control per se does not impact nontraditional risk factors for CVD equally, but various diabetes medications have different effects on these risk factors. These findings may have implications for making appropriate therapeutic choices for patients with Type 2 diabetes, although larger studies with more appropriate treatment comparisons may be necessary.

Augmented oxidative stress as well as antioxidant capacity in maternal circulation in preeclampsia

OBJECTIVES

Isoprostanes are stable markers of oxidative stress. We wanted to assess maternal circulating levels of total 8-isoprostane and indices of antioxidant capacity in preeclampsia compared to uneventful pregnancies.

STUDY DESIGN

Total 8-isoprostane concentrations, FRAP (ferric reducing ability of plasma), Vitamin E and d-ROM (diacron reactive oxygen metabolites) were measured in maternal venous blood samples from preeclamptic (n=21) and uncomplicated (n=38) pregnancies at cesarean section.

RESULTS

Median total 8-isoprostane concentration was elevated in preeclampsia compared to uncomplicated pregnancies (354 and 218 pg/mL, P=0.02). Median FRAP level was also elevated in preeclampsia compared to uncomplicated pregnancies, but to a lesser degree than 8-isoprostane. A positive correlation between 8-isoprostane and previously analyzed placenta-derived sFlt1 (soluble fms-like tyrosine kinase 1) levels in the maternal circulation was found in preeclampsia.

CONCLUSION

We found a relative more increase for the oxidative stress marker (8-isoprostane) than for the antioxidant capacity (FRAP) in preeclampsia compared to uneventful pregnancies.

Human health implications of environmental contaminants in Arctic Canada: A review

The objectives of this paper are to: assess the impact of exposure to current levels of environmental contaminants in the Canadian Arctic on human health; identify the data and knowledge gaps that need to be filled by future human health research and monitoring; examine how these issues have changed since our first assessment [Van Oostdam, J., Gilman, A., Dewailly, E., Usher, P., Wheatley, B., Kuhnlein, H. et al., 1999. Human health implications of environmental contaminants in Arctic Canada: a review. Sci Total Environ 230, 1-82]. The primary exposure pathway for contaminants for various organochlorines (OCs) and toxic metals is through the traditional northern diet. Exposures tend to be higher in the eastern than the western Canadian Arctic. In recent dietary surveys among five Inuit regions, mean intakes by 20- to 40-year-old adults in Baffin, Kivalliq and Inuvialuit communities exceeded the provisional tolerable daily intakes (pTDIs) for the OCs, chlordane and toxaphene. The most recent findings in NWT and Nunavut indicate that almost half of the blood samples from Inuit mothers exceeded the level of concern value of 5 microg/L for PCBs, but none exceeded the action level of 100 microg/L. For Dene/Métis and Caucasians of the Northwest Territories exposure to OCs are mostly below this level of concern. Based on the exceedances of the pTDI and of various blood guidelines, mercury and to a lesser extent lead (from the use of lead shot in hunting game) are also concerns among Arctic peoples. The developing foetus is likely to be more sensitive to the effects of OCs and metals than adults, and is the age groups of greatest risk in the Arctic. Studies of infant development in Nunavik have linked deficits in immune function, an increase in childhood respiratory infections and birth weight to prenatal exposure to OCs. Balancing the risks and benefits of a diet of country foods is very difficult. The nutritional benefits of country food and its contribution to the total diet are substantial. Country food contributes significantly more protein, iron and zinc to the diets of consumers than southern/market foods. The increase in obesity, diabetes and cardiovascular disease has been linked to a shift away from a country food diet and a less active lifestyle. These foods are an integral component of good health among Aboriginal peoples. The social, cultural, spiritual, nutritional and economic benefits of these foods must be considered in concert with the risks of exposure to environmental contaminants through their exposure. Consequently, the contamination of country food raises problems which go far beyond the usual confines of public health and cannot be resolved simply by risk-based health advisories or food substitutions alone. All decisions should involve the community and consider many aspects of socio-cultural stability to arrive at a decision that will be the most protective and least detrimental to the communities.

The role of exercise on platelet aggregation in patients with stable coronary artery disease: exercise induces aspirin resistant platelet activation

OBJECTIVES

The aim of our study was to determine the relation between exercise stress test and aspirin resistance in patients with stable coronary artery disease.

BACKGROUND

Clinically aspirin resistance is defined as having thrombotic and embolic cardiovascular events despite regular aspirin therapy.

METHODS

We studied platelet functions of 62 patients with stable coronary artery disease and 20 subjects with normal coronary arteries by Platelet Function Analyzer (PFA-100, Dade Behring, Germany) at rest and after exertion with collagen and/or epinephrine (Col/Epi) and collagen and/or ADP cartridges. Closure time (CT)<186 seconds was defined as aspirin resistance with Col/Epi cartridges of PFA-100. Symptom limited treadmill stress test (protocol of Bruce) was performed with Oxford Streslink TD-1 system.

RESULTS

8 (12.9%) patients were aspirin resistant by PFA-100 (CT<186s despite regular aspirin therapy) at rest. At the first minute of the recovery period of exercise stress test 14 (22.5%) patients were aspirin resistant by PFA-100. CTs with Col/ADP were respectively 89+/-6 s (83--100s) and 89+/-5 s (82--104s) at rest and after exercise (p=0.107). 20.3% (11/54) of patients known as in vitro aspirin sensitives at rest had shorter CTs and 11.1% (6/54) had aspirin resistance after exercise (p=0.004). There was no statistically significiant difference in platelet functions in the control group after exertion.

CONCLUSION

We conclude that 11.1% of in vitro aspirin sensitive subjects at rest had aspirin resistance after exercise by PFA-100. In some individuals, exercise induced platelet activation is aspirin insensitive at usual antiplatelet doses. We need further clinical trials to optimize antiplatelet therapy in patients with coronary artery disease.

Thromboxane, prostacyclin and isoprostanes: therapeutic targets in atherogenesis

Atherosclerosis is a chronic disease of the vasculature that is influenced by multiple factors that involve a complex interplay between some components of the blood and the arterial wall. Inflammation and oxidative stress have key roles in atherogenesis. The production of F2-isoprostanes (F2-IPs), thromboxane A2 (TxA2) and prostacyclin (PGI2) increases in atherosclerosis, and recent studies show that pharmacological modulation of their biosynthesis and biological activities are important therapeutic targets for managing atherosclerosis. In this review, we highlight recent breakthroughs in the roles of F2-IPs, TxA2 and PGI2 in atherogenesis, and identify pertinent therapeutic targets.

Reduced in vivo oxidative stress following 5-methyltetrahydrofolate supplementation in patients with early-onset thrombosis and 677TT methylenetetrahydrofolate reductase genotype

The protective role of folate in vascular disease has been related to antioxidant effects. In 45 patients with previous early-onset (at age <50 years) thrombotic episodes and the 677TT methylenetetrahydrofolate reductase genotype, we evaluated the effects of a 28 d-course (15 mg/d) of 5-methyltetrahydrofolate (MTHF) on homocysteine metabolism and on in vivo generation of 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), a reliable marker of oxidative stress. At baseline, patients' fasting total homocysteine (tHcy) was 11.5 micromol/l (geometric mean) and urinary excretion of 8-iso-PGF2alpha was 304 pg/mg creatinine, with the highest metabolite levels in the lowest quartile of plasma folate distribution (P < 0.05). After 5-MTHF supplementation, plasma folate levels increased approximately 13-fold (P < 0.0001 versus baseline); tHcy levels (6.7 micromol/l, P < 0.0001) and urinary 8-iso-PGF2alpha (254 pg/mg creatinine, P < 0.001) were both significantly lowered, their reduction being proportional to baseline values (r = 0.98 and r = 0.77, respectively) and maximal in patients with the lowest pre-supplementation folate levels (P < 0.05). The effects on folate (P < 0.0001) and tHcy (P = 0.0004) persisted for at least up to 2 months after withdrawing 5-MTHF. In parallel with long-lasting tHcy-lowering effects, a short-course 5-MTHF supplementation reduces in vivo formation of 8-iso-PGF2alpha in this population, supporting the antioxidant protective effects of folate in vascular disease.

Recent advances in the biochemistry and clinical relevance of the isoprostane pathway

Isoprostanes (IsoPs), lipid peroxidation products formed via the free radical-mediated oxidation of arachidonic acid, have become the "gold standard" biomarker of oxidative stress in vivo over the past 15 yr. Significant advances have been made in understanding this important pathway of lipid peroxidation. Recent studies from our laboratory are discussed that have provided insights into the mechanism of formation and regioisomeric distribution of these compounds and that have identified novel products of the IsoP pathway such as cyclized dioxolane IsoPs, IsoP-derived racemic prostaglandins, and reactive cyclopentenone IsoP, the latter of which possess potent biological actions. 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.

Vitamin E, oxidative stress, and inflammation

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the Western world. Its incidence has also been increasing lately in developing countries. Several lines of evidence support a role for oxidative stress and inflammation in atherogenesis. Oxidation of lipoproteins is a hallmark in atherosclerosis. Oxidized low-density lipoprotein induces inflammation as it induces adhesion and influx of monocytes and influences cytokine release by monocytes. A number of proinflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) modulate monocyte adhesion to endothelium. C-reactive protein (CRP), a prototypic marker of inflammation, is a risk marker for CVD and it could contribute to atherosclerosis. Hence, dietary micronutrients having anti-inflammatory and antioxidant properties may have a potential beneficial effect with regard to cardiovascular disease. Vitamin E is a potent antioxidant with anti-inflammatory properties. Several lines of evidence suggest that among different forms of vitamin E, alpha-tocopherol (AT) has potential beneficial effects with regard to cardiovascular disease. AT supplementation in human subjects and animal models has been shown to decrease lipid peroxidation, superoxide (O2-) production by impairing the assembly of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase as well as by decreasing the expression of scavenger receptors (SR-A and CD36), particularly important in the formation of foam cells. AT therapy, especially at high doses, has been shown to decrease the release of proinflammatory cytokines, the chemokine IL-8 and plasminogen activator inhibitor-1 (PAI-1) levels as well as decrease adhesion of monocytes to endothelium. In addition, AT has been shown to decrease CRP levels, in patients with CVD and in those with risk factors for CVD. The mechanisms that account for nonantioxidant effects of AT include the inhibition of protein kinase C, 5-lipoxygenase, tyrosine-kinase as well as cyclooxygenase-2. Based on its antioxidant and anti-inflammatory activities, AT (at the appropriate dose and form) could have beneficial effects on cardiovascular disease in a high-risk population.

Red blood cells: reservoirs of cis- and trans-epoxyeicosatrienoic acids

Epoxyeicosatrienoic acids (EETs) are candidate endothelium-derived hyperpolarizing factors that demonstrate a wide range of biological effects. The presence of both cis- and trans-EETs in rat plasma was identified with HPLC-electrospray ionization tandem mass spectrometry in this study. The total EETs in plasma are 38.2 ng/ml with cis-EETs representing 21.4 +/- 0.4 ng/ml and trans-EETs 16.8 +/- 0.4 ng/ml. EETs in RBCs were estimated to be 20.2 ng/10(9) RBCs, which corresponds to 200 ng in RBCs contained in 1 ml blood. RBC incubation with 10 mM tert-butyl hydroperoxide resulted in 4.4-fold increase of total cis-EETs (from 9.2 to 40.2 ng/10(9) RBCs) and 5.5-fold increase of total trans-EETs (from 11.0 to 60.8 ng/10(9) RBCs). EETs were released (2 ng/ml) from RBCs after incubation at 37 degrees C for 10 min even after being washed 3 times, indicating that RBCs are reservoirs of plasma EETs. The identification of cis- and trans-EETs in RBCs and in plasma as well as their release from RBCs suggest a vasoregulatory role of RBCs in view of their potent vasoactivity.

N-(carboxymethyl)valine residues in hemoglobin (CMV-Hb) reflect accumulation of oxidative stress in diabetic patients

While carboxymethylated proteins are considered to be advanced glycation end products (AGE), they can also be induced by reactive oxygen species (ROS) independently of the AGE-forming process. To clarify whether N-(carboxymethyl)valine residues in hemoglobin (CMV-Hb) were a useful marker of the accumulation of ROS in diabetes, we evaluated CMV-Hb formation in vitro and in vivo. For the in vitro studying, purified human hemoglobin was incubated with D-glucose or D-glucose and hydrogen peroxide. For the in vivo study, CMV-Hb was extracted from peripheral red blood cells in diabetic patients and compared with that from non-diabetic subjects. Furthermore, the effect of antioxidants was evaluated after 6 months in 15 diabetic patients showing very high CMV-Hb levels. In vitro CMV-Hb formation increased in a glucose concentration and time-dependent manner. Co-incubation with glucose and hydrogen peroxide synergistically increased CMV-Hb formation. The CMV-Hb level was higher in the diabetic group than the non-diabetic group, and CMV-Hb was correlated with the plasma total cholesterol and serum creatinine levels. The CMV-Hb level was decreased by antioxidant therapy, whereas HbA1c did not change. These results demonstrate that CMV-Hb may be a useful marker for accumulation of oxidative stress in diabetic patients.

Oxidative stress — mediated alterations in glucose dynamics in a genetic animal model of type II diabetes

Insulin resistance, characterized by an inexorable decline in skeletal muscle glucose utilization and/or an excessive hepatic glucose production, constitutes a major pathogenic importance in a cluster of clinical disorders including diabetes mellitus, hypertension, dyslipidemia, central obesity and coronary artery disease. A novel concept suggests that heightened state of oxidative stress during diabetes contributes, at least in part, to the development of insulin resistance. Several key predictions of this premise were subjected to experimental testing using Goto-Kakizaki (GK) rats as a genetic animal model for non-obese type II diabetes. Euglycemic-hyperinsulinemic clamp studies with an insulin infusion index of 5 mU/kg bw/min were used to measure endogenous glucose production (EGP), glucose infusion rate (GIR), glucose disposal rate (GDR) and skeletal muscle glucose utilization index (GUI). Moreover, the status of oxidative stress as reflected by the urinary levels of isoprostane and protein carbonyl formation were also assessed as a function of diabetes. Post-absorptive basal EGP and circulating levels of insulin, glucose and free fatty acid (FFA) were elevated in GK rats, compared to their corresponding control values. In contrast, steady state GIR and GDR of the hyperglycemic/hyperinsulinemic animals were reduced, concomitantly with impaired insulin's ability to suppress EGP. Insulin stimulated [3H]-2-deoxyglucose (2-DG) uptake (a measure of glucose transport activity) by various types of skeletal muscle fibers both in vivo and in vitro (isolated muscle, cultured myoblasts) was diminished in diabetic GK rats. This diabetes-related suppression of skeletal muscle glucose utilization was associated with a decrease in insulin's ability to promote the phosphorylation of tyrosine residues of insulin receptor substrate-1 (IRS-1). Similarly, the translocation of GLUT-4 from intracellular compartment to plasma membrane in response to insulin was also reduced in these animals. Oxidative stress-based markers (e.g. urinary isoprostane, carbonyl-bound proteins) were elevated as a function of diabetes. Nullification of the heightened state of oxidative stress in the GK rats with alpha-lipoic acid resulted in a partial amelioration of the diabetes-related impairment of the in vivo and in vitro insulin actions. Collectively, the above data suggest that 1) insulin resistance in GK rats occurs at the hepatic and skeletal muscle levels, 2) muscle cell glucose transport exhibited a blunted response to insulin and it is associated with a major defect in key molecules of both GLUT-4 trafficking and insulin signaling pathways, 3) skeletal muscle insulin resistance in GK rats appears to be of genetic origin and not merely related to a paracrine or autocrine effect, since this phenomenon is also observed in cultured myoblasts over several passages and finally heightened state of oxidative stress may mediate the development of insulin resistance during diabetes.

Inflammatory mediators are associated with 1-year mortality in critical limb ischemia

OBJECTIVE

The atherosclerotic process has inflammatory features. Patients with peripheral atherosclerosis and critical limb ischemia have a poor prognosis. This study evaluated the hypothesis that inflammatory markers are associated with mortality among patients admitted to the hospital because of critical limb ischemia.

METHODS

This was a prospective, single-center, 1-year, follow-up study of 259 consecutive patients with critical limb ischemia who were admitted to a secondary referral center of vascular diseases. Interventions included evaluation of intercurrent disease, ankle and arm blood pressures, plasma glucose and lipid levels, plasma homocysteine, cardiolipin antibodies, resistance to activated protein C, plasma endothelin-1, and the inflammatory mediators tumor necrosis factor-alpha, interleukin-6, neopterin, high-sensitivity C-reactive protein, CD40 ligand, and 8-iso-prostaglandin F alpha in plasma. The main outcome measure was total mortality and causes of death assessed 1 year after admission.

RESULTS

During the first year after admission, 61 patients (24%) died. These patients were older (P < .0001), showed a higher leukocyte count (P = .0011) and levels of serum creatinine (P < .0001), lower levels of high-density lipoprotein (HDL) cholesterol (P = .003) and frequency of active treatment (P = .014) than the 198 (76%) survivors. More nonsurvivors had gangrene (P < .0001), and fewer (P = .004) had lipid-lowering treatment. The plasma levels of interleukin-6 (P < .0001), tumor necrosis factor-alpha (P < .0001), neopterin (P < .0001), and high-sensitivity C-reactive protein (P = .002) at admission for critical limb ischemia were all significantly lower in the survivors, whereas there was no difference concerning CD40 ligand. In logistic regression adjusted for age, sex, lipid-lowering therapy, active treatment, gangrene, leukocyte count, creatinine, and serum HDL cholesterol, the inflammatory mediators tumor necrosis factor-alpha (P = .0084), neopterin (P = .0035), but not interleukin-6 (P = .585) or high-sensitivity C-reactive protein (P = .314) were independent risk variables of death within 1 year.

CONCLUSIONS

Increased age, leukocyte count, creatinine, and inflammatory mediators, together with gangrene, were associated with 1-year mortality despite intervention in critical limb ischemia. For tumor necrosis factor-alpha and neopterin in plasma, this association was independent of the other parameters.

Insulin resistance and type 2 diabetes in high-fat-fed mice are linked to high glycotoxin intake

Dietary advanced glycosylation end products (AGEs) have been linked to insulin resistance in db/db(++) mice. To test whether dietary AGEs play a role in the progression of insulin resistance in normal mice fed high-fat diets, normal C57/BL6 mice were randomly assigned to high-fat diets (35% g fat), either high (HAGE-HF group; 995.4 units/mg AGE) or low (by 2.4-fold LAGE-HF group; 329.6 units/mg AGE) in AGE content for 6 months. Age-matched C57/BL6 and db/db(++) mice fed regular diet (5% g fat, 117.4 units/mg AGE) served as controls. After 6 months, 75% of HAGE-HF mice were diabetic and exhibited higher body weight (P < 0.001), fasting glucose (P < 0.001), insulin (P < 0.001), and serum AGEs (P < 0.01) than control mice, while none of the LAGE-HF mice were diabetic despite a similar rise in body weight and plasma lipids. The HAGE-HF group displayed markedly impaired glucose and insulin responses during glucose tolerance tests and euglycemic and hyperglycemic clamps and altered pancreatic islet structure and function compared with those of LAGE-HF mice, in which findings resembled those of control mice. The HAGE-HF group had more visceral fat (by two- and fourfold) and more AGE-modified fat (by two- and fivefold) than LAGE-HF and control mice, respectively. In the HAGE-HF group, plasma 8-isoprostane was higher (P < 0.01) and adiponectin lower (P < 0.001) than control mice, while in the LAGE-HF group, these were more modestly affected (P < 0.05). These results demonstrate that the development of insulin resistance and type 2 diabetes during prolonged high-fat feeding are linked to the excess AGEs/advanced lipoxidation end products inherent in fatty diets.

The specific thromboxane receptor antagonist S18886: pharmacokinetic and pharmacodynamic studies

OBJECTIVES AND PATIENTS

We conducted a multicenter double-blind pharmacokinetic/pharmacodynamic (PK/PD) study of the new oral thromboxane receptor antagonist S18886 in 30 patients with peripheral artery disease, who were randomized to receive five different oral dosages of S18886 (1, 2.5, 5, 10 or 30 mg) for 12 weeks (83 days). Primary objective was to determine the effect of S18886 on platelet aggregation ex vivo.

RESULTS

Pharmacokinetics of S18886 was linear, with peak plasma levels being reached between 30 min and 2 h and a terminal half-life of 5.8-10 h. No significant accumulation of S18886 in plasma was observed after repeated dosing. The relationship between the S18886 concentration and platelet inhibition was examined in terms of U46619-induced platelet aggregation. Over the range of doses studied, there was a predictable relation between the plasma drug concentration and the degree of platelet inhibition at each dose. Maximal inhibition of U46619-induced platelet aggregation was achieved within 1 h with all oral doses of S18886, and this effect was maintained for at least 12 h. The PK/PD relationship was direct, and U46619-induced platelet aggregation was strongly inhibited by S18886 plasma concentrations above 10 ng mL(-1). This concentration was thus the minimal effective antiplatelet level in this population, and was maintained only by the dosages of 10 and 30 mg. The safety profile of S18886 was excellent, whatever the unit dose, with no attributable adverse events.

CONCLUSION

The results of this study, which included modeling and simulation, help identify the minimal effective plasma concentration of S18886 required for potent antiplatelet efficacy in patients with stable peripheral arterial disease.

Enhanced oxidative stress in coronary heart disease and chronic heart failure as indicated by an increased 8-epi-PGF(2alpha)

The role of oxidation injury as an important factor in the pathophysiology of cardiomyopathy (CMP) has recently gained increasing interest. Semiquantitative analysis for isoprostane, 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)), and oxidised low-density lipoprotein (ox-LDL) of coronary vascular tissue samples derived from CMP patients revealed an increased extent and intensity of uptake as compared to the respective controls. To evaluate oxidative stress in vivo, we examined plasma, serum, salivary, and urinary 8-epi-PGF(2alpha) in patients with dilated CMP (n=20) and ischemic CMP (n=20) with decreased left ventricular ejection fraction (LVEF). Patients with coronary heart disease (CHD) (n=20) and 20 healthy, age-matched, and sex-matched controls were investigated in parallel. 8-Epi-PGF(2alpha) levels were correlated with the functional severity of heart failure [New York Heart Association (NYHA) classification] and LVEF. 8-Epi-PGF(2alpha) levels were matched according to risk factors (smoking and hypercholesterolemia) and were significantly higher in patients with CMP as compared to healthy controls and patients with CHD in all investigated compartments. A positive correlation between NYHA stages and 8-epi-PGF(2alpha), as well as a negative correlation to LVEF, could be demonstrated in a subgroup analysis. These findings reflect the enhanced oxidation injury in patients with CMP and, to a lesser extent, in CHD as compared to healthy controls, thus highly indicating the relevance of oxidative stress for the pathogenesis and progression of cardiovascular disease.

Early activation of vascular endothelial cells and platelets in obese children

Obesity in adulthood is combined with vascular endothelial cell and platelet activation. In this study we evaluated whether or not such activation is already present in obese children. Forty obese (10.3 +/- 2.5 yr) and 40 nonobese (10.3 +/- 2.3 yr) children were studied. Circulating levels of soluble (s) intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, as indices of vascular endothelial cell activation, were assessed in both groups. Plasma concentrations of sP-selectin and sCD40 ligand, as indices of platelet activation, were also measured. Circulating levels of highly sensitive C-reactive protein (hs-CRP) and the lipid peroxidation product 8-iso-prostaglandin (PG)F(2alpha) were evaluated because of their ability to promote vascular endothelial cell and platelet activation. Circulating levels of all of the assessed markers were higher in obese than in nonobese children (sICAM-1, +38.8 +/- 13.3%; sVCAM-1, +26.5 +/- 13.7%; sE-selectin, +31.3 +/- 17.3%; sP-selectin, +31.7 +/- 16.9%; sCD40 ligand, +36.9 +/- 22.1%; total 8-iso-PGF(2alpha), +24.0 +/- 20.2%; hs-CRP, +76.6 +/- 12.9%; P < 0.0001). Significant correlations (P < 0.004) between plasma total 8-iso-PGF(2alpha) levels and circulating sICAM-1 (r = 0.485), sVCAM-1 (r = 0.506), sP-selectin (r = 0.449), sCD40 ligand (r = 0.498), and hs-CRP (r = 0.520) concentrations were found in obese children. In conclusion, an early activation of vascular endothelial cells and platelets was present in obese children. Increased lipid peroxidation was also present in these children and likely contributed to the observed proinflammatory phenotype.

Oxidative stress, diet, and the etiology of preeclampsia

BACKGROUND

A current theory holds that oxidative stress, ie, an imbalance between maternal prooxidants and antioxidants, is a component of preeclampsia. It is uncertain whether such an imbalance occurs before clinical recognition of the syndrome or whether it is related to diet.

OBJECTIVE

We measured urinary excretion of the isoprostane 8-iso-prostaglandin F(2alpha), which is an indicator of oxidative damage to lipids, and the total antioxidant power, which is a global measure of antioxidant status, at the entry to prenatal care. We also examined the relation of these indexes to diet during pregnancy.

DESIGN

A cohort of 307 gravidae from Camden, NJ, was studied from entry to prenatal care (at 15.0 +/- 0.49 wk gestation). Measures of the maternal diet were obtained by 24-h recall.

RESULTS

Risk of preeclampsia was increased 5-fold with higher urinary isoprostane excretion and decreased 3-fold with higher total antioxidant power. Over the course of pregnancy, there were significant trends for an association of higher isoprostane excretion with increased consumption of energy-adjusted fat, polyunsaturated fat, and polyunsaturated fatty acids (n-3, n-6, and linoleic and linolenic fatty acids), whereas total antioxidant power was not related to diet.

CONCLUSIONS

Increased urinary excretion of isoprostane and decreased antioxidant production is an imbalance that is consistent with oxidative stress, and it precedes clinical recognition of preeclampsia. The maternal diet is an underlying factor that provides an environment for free radical generation.

Age-related differences in vasoconstrictor responses to isoprostanes in piglet pulmonary and mesenteric vascular smooth muscle

Isoprostanes are prostaglandin (PG)-like compounds produced nonenzymatically by free radical-catalyzed peroxidation of arachidonic acid. Isoprostanes evoke potent vascular effects but their actions in the neonatal vasculature are poorly known. We aimed to study the effects of 8-iso-PGE(1), 8-iso-PGE(2), 8-iso-PGF(1alpha), 8-iso-PGF(1beta), 8-iso-PGF(2alpha), and 8-iso-PGF(2beta) in pulmonary arteries (PA), pulmonary veins (PV), and mesenteric arteries (MA) from newborn and 2-wk-old piglets. Isoprostanes produced concentration-dependent contractions of PA, PV, and MA (magnitudes up to 1.5- to 2-fold greater than the responses to 62.5 mM KCl) but they were markedly less potent vasoconstrictors than the thromboxane A(2) (TXA(2)) mimetic U46619. Neonatal PA were more sensitive to 8-iso-PGF(1alpha), 8-iso-PGF(1beta), and 8-iso-PGF(2beta) than 2-wk-old PA. Neonatal PV were more sensitive to 8-iso-PGE(2) and 8-iso-PGF(1alpha), and neonatal MA were more sensitive to 8-iso-PGE(2), 8-iso-PGF(1alpha), 8-iso-PGF(1beta), 8-iso-PGF(2alpha), and 8-iso-PGF(2beta) than the corresponding 2-wk-old vessels. The sensitivity to U46619 decreased with postnatal age in MA but did not change in PA and PV. The contractile responses to all the isoprostanes and to U46619 were reverted by the TXA(2) receptor (TP) antagonist SQ 29,548. Moreover, isoprostane-evoked contractions in 2-wk-old PA were reduced by inhibitors of tyrosine kinase (genistein) and Rho kinase (Y 27632 and hydroxyfasudil) but not by inhibitors of protein kinase C (chelerythrine), mitogen-activated protein kinase kinase (PD 98059) or p38-kinase (SB 203580). In conclusion, isoprostanes produced compound-, tissue-, and age-dependent constriction of neonatal porcine pulmonary and mesenteric vascular smooth muscle. Isoprostane-evoked PA vasoconstriction involved TP receptors and activation of tyrosine kinases and Rho kinases.

Endothelial function and dysfunction. Part I: Methodological issues for assessment in the different vascular beds: a statement by the Working Group on Endothelin and Endothelial Factors of the European Society of Hypertension

An enormous number of studies in the last two decades have been devoted to investigating the role of the endothelium in cardiovascular diseases. Nonetheless, the optimal methodology for investigating the multifaceted aspects of endothelial dysfunction is still under debate. Biochemical markers, molecular genetic tests and invasive and non-invasive tools with and without pharmacological and physiological stimuli have been introduced. Furthermore newer pharmacological tools have been proposed. However, the application of these methodologies should fulfil a number of requirements in order to provide conclusive answers in this area of research. Thus, the most relevant methodological issues in the research on endothelial function and dysfunction are summarized in this paper.

Effects of exercise and diet on chronic disease

Currently, modern chronic diseases, including cardiovascular diseases, Type 2 diabetes, metabolic syndrome, and cancer, are the leading killers in Westernized society and are increasing rampantly in developing nations. In fact, obesity, diabetes, and hypertension are now even commonplace in children. Clearly, however, there is a solution to this epidemic of metabolic disease that is inundating today's societies worldwide: exercise and diet. Overwhelming evidence from a variety of sources, including epidemiological, prospective cohort, and intervention studies, links most chronic diseases seen in the world today to physical inactivity and inappropriate diet consumption. The purpose of this review is to 1) discuss the effects of exercise and diet in the prevention of chronic disease, 2) highlight the effects of lifestyle modification for both mitigating disease progression and reversing existing disease, and 3) suggest potential mechanisms for beneficial effects.

Isoprostanes: markers and mediators of oxidative stress

Some years ago it was discovered that prostaglandin F2-like compounds are formed in vivo by nonenzymatic free radical-catalyzed peroxidation of arachidonic acid. Because these compounds are a series of isomers that contain the prostane ring of prostaglandins, they were termed F2-isoprostanes. Intermediates in the isoprostane pathway are prostaglandin H2-like compounds that become reduced to form F2-isoprostanes but also undergo rearrangement in vivo to form E2-, D2-, A2-, J2-isoprostanes, isothromboxanes, and highly reactive gamma-ketoaldehydes, termed isoketals. Analogous compounds have also been shown to be formed from free radical mediated oxidation of docosoahexaenoic acid. Because docosahexaenoic acid is highly enriched in neurons, these compounds have been termed neuroprostanes and neuroketals. An important aspect of the discovery of isoprostanes is that measurement of F2-isoprostanes has emerged as one of the most reliable approaches to assess oxidative stress status in vivo, providing an important tool to explore the role of oxidative stress in the pathogenesis of human disease. Measurement of F4-neuroprostanes has also proved of value in exploring the role of oxidative stress in neurodegenerative diseases. Products of the isoprostane pathway have been found to exert potent biological actions and therefore may participate as physiological mediators of disease.

Activation of caspase-3 is associated with oxidative stress in the hydropic guinea pig cochlea

The aim of this study was to investigate the involvement of oxidative stress and apoptosis in an animal model of Meniere's disease. Endolymphatic hydrops (ELH) is generally accepted as the decisive histological characteristic of Meniere's disease. Closure of the endolymphatic duct (Kimura's method) was used to induce endolymphatic hydrops in guinea pigs. Sham-operated animals served as controls. After 4 weeks the animals operated showed a significant elevation of the hearing thresholds as measured by audiometric brainstem responses (ABR) pre- and postoperatively. Immediately after the second ABR measurement, the animals were sacrificed for further immunohistological examinations of the inner ear with specific antibodies to active caspase-3 (cas-3) as a marker for apoptosis and antibodies to 8-isoprostane (8-iso) and nitrotyrosine (NT) as indicators of oxidative stress. Compared with the sham-operated controls, hydropic cochleae showed strong immunostaining for both oxidative stress markers in spiral ganglion cells, in the blood-vessels and fibrocytes of the lateral wall, as well as in supporting cells of the organ of Corti. Activation of cas-3 in spiral ganglion cells and the lateral wall was found exclusively in hydropic cochleae. Our findings suggest that oxidative stress is involved in the development of endolymphatic hydrops and may lead to cellular damage which induces apoptosis by activation of cas-3. Apoptotic cell death might contribute to the sensorineural hearing loss found in later stages of Meniere's disease.

Associations between apolipoprotein E genotype and circulating F2-isoprostane levels in humans

Apolipoprotein E (apoE), an important determinant of plasma lipoprotein metabolism, has three common alleles (epsilon2, epsilon3, and epsilon4). Population studies have shown that the risk of diseases characterized by oxidative damage, such as coronary heart disease and Alzheimer's disease, is significantly higher in epsilon4 carriers. We evaluated the association between apoE genotypes and plasma F2-isoprostane levels, an index of lipid peroxidation, in humans. Two hundred seventy-four healthy subjects (104 males, 170 females; 46.9 +/- 13.0 yr; 200 whites, 74 blacks; 81 nonsmokers, 64 passive smokers, and 129 active smokers) recruited for a randomized clinical antioxidant intervention trial were included in this analysis. ApoE genotype was determined by PCR and restriction enzyme digestion. Free plasma F2-isoprostane was measured by GC-MS. Genotype groups were compared using multiple regression analysis with adjustment for sex, age, race, smoking status, body mass index, plasma ascorbic acid, and beta-carotene. Subjects with epsilon3/epsilon4 and epsilon4/epsilon4 genotype (epsilon4-carriers) and with epsilon2/epsilon3 and epsilon3/epsilon3 (non-epsilon4-carriers) were pooled for analysis. In subjects with high cholesterol levels (total cholesterol above 200 mg/dl), plasma F2-isoprostane levels were 29% higher in epsilon4 carriers than in non-epsilon4-carriers (P= 0.0056). High-cholesterol subjects that are epsilon4 carriers have significantly higher levels of lipid peroxidation as assessed by circulating F2-isoprostane levels.

The role of platelet glycoprotein IIIa polymorphism in the high prevalence of in vitro aspirin resistance in patients with intracoronary stent restenosis

OBJECTIVES

The aim of our study was to determine the relation between platelet glycoprotein IIIa (Pl A ) polymorphism and aspirin resistance in patients with intracoronary stent restenosis.

BACKGROUND

Clinically, aspirin resistance is defined as having thrombotic and embolic cardiovascular events despite regular aspirin therapy. Platelet glycoprotein IIIa polymorphism is said to be a possible mechanism of aspirin resistance.

METHODS

We studied the prevalence of aspirin resistance in 204 previously intracoronary stent-implanted patients with stable coronary artery disease. In 102 of these patients, intracoronary stent restenosis was present. Platelet functions were analyzed in a platelet function analyzer (PFA-100, Dade Behring, Germany) with collagen and/or epinephrine (Col/Epi) and collagen and/or adenosine diphosphate cartridges. Closure time <186 seconds was defined as aspirin resistance with Col/Epi cartridges of PFA-100. The Pl A polymorphisms of 43 aspirin-resistant and 51 aspirin-sensitive subjects were determined with polymerase chain reaction and restriction fragments length polymorphism.

RESULTS

A total of 31.3% (n = 32) of patients with intracoronary stent restenosis and 10.7% (n = 11) of patients with patent intracoronary stents were resistant to aspirin by PFA-100. The Pl A1,A1 allele of glycoprotein IIIa was present in 36 subjects (83.7.%) and the Pl A1,A2 allele was present in 7 subjects (16.2.%) in the aspirin-resistant patients group. The Pl A1,A1 allele of glycoprotein IIIa was present in 37 subjects (72.5%) and the Pl A1,A2 allele was present in 14 subjects (27.5%) in the aspirin-sensitive patients group ( P = .195).

CONCLUSION

Our results suggest that platelets of patients with intracoronary stent restenosis with or without Pl A2 heterozygosity of glycoprotein IIIa are more likely to be resistant to low-dose aspirin therapy.

Nitric oxide dynamics and endothelial dysfunction in type II model of genetic diabetes

Although diabetes is a major risk factor for vascular diseases, e.g., hypertension and atherosclerosis, mechanisms that underlie the "risky" aspects of diabetes remain obscure. The current study is intended to examine the notion that diabetic endothelial dysfunction stems from a heightened state of oxidative stress induced by an imbalance between vascular production and scavenging of reactive oxygen/nitrogen species. Goto-Kakizaki (GK) rats were used as a genetic animal model for non-obese type II diabetes. Nitric oxide (NO) bioavailability and O2- generation in aortic tissues of GK rats were assessed using the Griess reaction and a lucigenin-chemiluminescence-based technique, respectively. Organ chamber-based isometric tension studies revealed that aortas from GK rats had impaired relaxation responses to acetylcholine whereas a rightward shift in the dose-response curve was noticed in the endothelium-independent vasorelaxation exerted by the NO donor sodium nitroprusside. An enhancement in superoxide (O2-) production and a diminuation in NO bioavailability were evident in aortic tissues of GK diabetic rats. Immunoblotting and high-performance liquid chromatography (HPLC)-based techniques revealed, respectively, that the above inverse relationship between O2- and NO was associated with a marked increase in the protein expression of nitric oxide synthase (eNOS) and a decrease in the level of its cofactor tetrahydrobiopterin (BH4) in diabetic aortas. Endothelial denudation by rubbing or the addition of pharmacological inhibitors of eNOS (e.g. N(omega)-nitro-L-arginine methyl ester (L-NAME)), and NAD(P)H oxidase (e.g. diphenyleneiodonium, apocynin) strikingly reduced the diabetes-induced enhancement in vascular O2- production. Aortic contents of key markers of oxidative stress (isoprostane F2alpha III, protein-bound carbonyls, nitrosylated protein) in connection with the protein expression of superoxide generating enzyme NAD(P)H oxidase (e.g. p47phox, pg91phox), a major source of reactive oxygen species in vascular tissue, were elevated as a function of diabetes. In contrast, the process involves in the vascular inactivation of reactive oxygen species exemplified by the activity of CuZnSOD was reduced in this diseased state. Our studies suggest that diabetes produces a cascade of events involving production of reactive oxygen species from the NADPH oxidase leading to oxidation of BH4 and uncoupling of NOS. This promotes the oxidative inactivation of NO with subsequent formation of peroxynitrite. An alteration in the balance of these bioactive radicals in concert with a defect in the antioxidant defense counteracting mechanism may favor a heightened state of oxidative stress. This phenomenon could play a potentially important role in the pathogenesis of diabetic endothelial dysfunction.

Inhibition of lipoprotein lipid oxidation

According to the oxidative modification hypothesis, antioxidants that inhibit the oxidation of low-density lipoprotein (LDL) are expected to attenuate atherosclerosis, yet not all antioxidants that inhibit LDL oxidation in vitro inhibit disease in animal models of atherosclerosis. As with animal studies, a benefit with dietary supplements of antioxidants in general and vitamin E in particular was anticipated in humans, yet the overall outcome of large, randomized controlled studies has been disappointing. However, in recent years it has become clear that the role of vitamin E in LDL oxidation and the relationship between in vitro and in vivo inhibition of LDL oxidation are more complex than previously appreciated, and that oxidative events in addition to LDL oxidation in the extracellular space need to be considered in the context of an antioxidant as a therapeutic drug against atherosclerosis. This review focuses on some of these complexities, proposes a novel method to assess in vitro 'oxidizability' of lipoprotein lipids, and summarizes the present situation of development of antioxidant compounds as drugs against atherosclerosis and related cardiovascular disorders.

The High Atherosclerotic Risk Among Epileptics: the Atheroprotective Role of Multivitamins

Neurologists have little concern about the high atherosclerotic risk among epileptics. Recent evidences mount that chronic epilepsy and prolonged use of antiepileptic drugs (AEDs) are associated with multiple risk factors that are critically implicated in pathobiology and dysfunction of the vessel wall through complex molecular mechanisms that promote atherogenesis. This review is concerned with three metabolic alterations, which are attributed as major risk factors for atherosclerosis among epileptics: altered metabolism of a) homocysteine (Hcy), b) lipids and lipoproteins, and c) uric acid. Most conventional AEDs reduce folic acid levels, thereby raising Hcy levels. Hyperhomosysteinemia is recently believed to induce endothelial dysfunction and promote atherosclerosis through complex oxidative and excitatory neurotoxic molecular mechanisms. However, Hcy itself is a convulsing substance with increased seizure recurrence and intractability to antiepileptic medications. AEDs can disturb lipid metabolism with resultant hypercholestrolemia and dyslipidemia, common recognized risks for atherosclerosis. Altered uric acid metabolism is common among epileptics. Uric acid has been implicated in endothelial cell damage and decreased endothelial nitric oxide bioavailability. In the presence of atherosclerotic milieu, uric acid interacts with other substrate toxicities and increased reactive oxygen species, accelerating atherosclerosis. The above information forms the rationale for future routine screening and correction of such metabolic alterations in epileptics. A convincing argument now develops that routine polyvitamin supplementation (folic acid, vitamin B12, vitamin B6, vitamin C, vitamin E, and beta-carotene) becomes increasingly important for women and men receiving AEDs at all ages. The atheroprotective effect of multivitamins is through their antioxidant and anti-inflammatory effects together with their lipid and Hcy lowering effects.

Effects of thiol antioxidant on reduced nicotinamide adenine dinucleotide phosphate oxidase in hypertensive Dahl salt-sensitive rats

Recent studies implicate of reactive oxygen species (ROS) in hypertension; however, whether reactive oxygen species promote hypertensive derangements is not fully clear. We thus investigated the effects of an antioxidant, N-acetyl-L-cysteine, on hypertensive Dahl salt-sensitive rats. High-salt intake for 4 weeks markedly elevated systolic arterial pressure, urinary excretion of protein, 8-isoprostane, and H(2)O(2), and the enzyme activity of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase along with the elevated expression of its subunits gp91phox and p47phox at the levels of mRNA and protein. Supplement with N-acetyl-L-cysteine reduced the increase in systolic arterial pressure and counteracted the elevation of urinary excretion of protein, 8-isoprostane, and H(2)O(2), and the increases in NADPH oxidase activity/expression in high-salt-loaded Dahl salt-sensitive rats. N-acetyl-L-cysteine supplement ameliorated plasma and urinary levels of thromboxane B(2) (an end metabolite of thromboxane A(2)), associated with improvement of both the abnormal contraction and the impaired nitric oxide-dependent relaxation in renal arteries. These results revealed that oxidative stress mediates hypertensive changes in Dahl salt-sensitive rats, because thiol antioxidant N-acetyl-L-cysteine attenuated the augmentation of local ROS production by diminishing the elevation of NADPH oxidase expression and ameliorated renal/vascular hypertensive changes.

Role of oxidative modifications in atherosclerosis

This review focuses on the role of oxidative processes in atherosclerosis and its resultant cardiovascular events. There is now a consensus that atherosclerosis represents a state of heightened oxidative stress characterized by lipid and protein oxidation in the vascular wall. The oxidative modification hypothesis of atherosclerosis predicts that low-density lipoprotein (LDL) oxidation is an early event in atherosclerosis and that oxidized LDL contributes to atherogenesis. In support of this hypothesis, oxidized LDL can support foam cell formation in vitro, the lipid in human lesions is substantially oxidized, there is evidence for the presence of oxidized LDL in vivo, oxidized LDL has a number of potentially proatherogenic activities, and several structurally unrelated antioxidants inhibit atherosclerosis in animals. An emerging consensus also underscores the importance in vascular disease of oxidative events in addition to LDL oxidation. These include the production of reactive oxygen and nitrogen species by vascular cells, as well as oxidative modifications contributing to important clinical manifestations of coronary artery disease such as endothelial dysfunction and plaque disruption. Despite these abundant data however, fundamental problems remain with implicating oxidative modification as a (requisite) pathophysiologically important cause for atherosclerosis. These include the poor performance of antioxidant strategies in limiting either atherosclerosis or cardiovascular events from atherosclerosis, and observations in animals that suggest dissociation between atherosclerosis and lipoprotein oxidation. Indeed, it remains to be established that oxidative events are a cause rather than an injurious response to atherogenesis. In this context, inflammation needs to be considered as a primary process of atherosclerosis, and oxidative stress as a secondary event. To address this issue, we have proposed an "oxidative response to inflammation" model as a means of reconciling the response-to-injury and oxidative modification hypotheses of atherosclerosis.

Oxidative stress and its association with coronary artery disease and different atherogenic risk factors

OBJECTIVE

It is well known that free radicals contribute to endothelial dysfunction and are involved in the pathogenesis and development of cardiovascular diseases, such as atherosclerosis. The aim of this study was to provide evidence for enhanced oxidative stress in coronary artery disease (CAD).

METHODS

Plasma levels of 8-isoprostane (8-epiPGF(2alpha)), marker of lipid peroxidation, were measured in 68 subjects (age: 60 +/- 2 years, mean +/- SEM). Subjects included 30 healthy control subjects and 38 patients with angiographically proven CAD. In addition, the total antioxidant power (PAO) was evaluated in a subgroup (40 subjects, 12 healthy and 28 CAD).

RESULTS

Levels of 8-epiPGF(2alpha) increased with the number of affected vessels (one- and multi-vessel disease versus control subjects, P < 0.001) and considering different risk determinants for atherosclerosis (i.e. hypertension, gender, hypercholesterolaemia, P < 0.01). In multivariate regression models the number of affected vessels was independently correlated with 8-epiPGF(2alpha) (P < 0.05). PAO values significantly decreased with increased number of affected vessels (P < 0.05) and in hypertensive patients when compared with those without hypertension (P < 0.05). In multivariate regression models the number of affected vessels resulted an independent determinant for PAO (P < 0.05). Concentration of 8-epiPGF(2alpha) and PAO also correlated with the number of cardiovascular risk factors (P < 0.01 and P = 0.07, respectively).

CONCLUSION

These findings indicate that elevated levels of plasma 8-epiPGF(2alpha) and reduced antioxidant capacity are associated with the extent and the severity of CAD and with the occurrence and number of different atherogenic risk factors. This observation may assist in providing more information as to how oxidative stress may predispose to atherogenesis and suggest attractive therapeutic strategies in the prevention and treatment of cardiovascular disease.

Serum total 8-iso-prostaglandin F2α: A new and independent predictor of peripheral arterial disease

OBJECTIVE

Circulating 8-iso-prostaglandin F 2alpha (8-iso-PGF 2alpha ) has been proposed as new indicator of oxidative stress, which is involved in the pathophysiologic changes of atherosclerosis. We proposed to test the hypothesis that 8-iso-PGF 2alpha is an independent predictor of symptomatic peripheral arterial disease (PAD).

METHODS

A case-control study in 100 patients with symptomatic PAD and 100 control subjects matched for age, sex, and diabetes mellitus was conducted. Smokers and subjects using lipid-lowering drugs were excluded. Serum total 8-iso-PGF 2alpha was quantified with an enzyme immunoassay.

RESULTS

Median 8-iso-PGF 2alpha was higher in patients with PAD than in control subjects (63 vs 42 pg/mL; P = .001). Logistic regression with hypertension, body mass index, and creatinine, low-density lipoprotein (LDL) cholesterol, triglyceride, high-sensitivity C-reactive protein (hs-CRP), 8-iso-PGF 2alpha , and total homocysteine concentrations as independent variables and case-control status as dependent variable revealed significant odds ratios (OR) for hypertension (OR, 3.74; 95% confidence interval [CI], 1.85-7.53), low-density lipoprotein cholesterol (OR, 1.16, for an increment of 10 mg/dL; 95% CI, 1.07-1.27), high-sensitivity C-reactive protein (OR, 1.02, for an increment of 1 mg/L; 95% CI, 1.00-1.03), and 8-iso-PGF 2alpha (OR, 1.11, for an increment of 10 pg/mL; 95% CI, 1.03-1.20).

CONCLUSIONS

Serum total 8-iso-PGF 2alpha was an independent predictor of PAD in the population studied. This finding supports the hypothesis that 8-iso-PGF 2alpha is a risk marker for PAD. Our results indicate increased systemic oxidative stress in patients with PAD.

Oxidative stress and antioxidant defense in relation to the severity of diabetic polyneuropathy and cardiovascular autonomic neuropathy

OBJECTIVE

Oxidative stress resulting from enhanced free-radical formation and/or a defect in antioxidant defenses has been implicated in the pathogenesis of experimental diabetic neuropathy. The objective of this study was to evaluate plasma levels of various biomarkers of oxidative stress in diabetic subjects in relation to the presence or absence of polyneuropathy (PN) and/or cardiovascular autonomic neuropathy (CAN).

RESEARCH DESIGN AND METHODS

Plasma 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)), superoxide anion (O(2)(.-)) generation, lag phase to peroxidation by peroxynitrite (ONOO(-)), vitamin E-to-lipid ratio, and vitamin C were measured in nonsmoking diabetic patients without PN and CAN (PN(-)/CAN(-) group; n = 62), in a group with PN but without CAN (PN(+)/CAN(-) group; n = 105), in those with both PN and CAN (PN(+)/CAN(+) group; n = 22), and in healthy control subjects (n = 85).

RESULTS

All three markers of oxidative stress were significantly increased, and both markers of antioxidant defense were decreased in the PN(+)/CAN(-) group compared with the control group (all P < 0.05). PN(-)/CAN(-) subjects showed a significant increase compared with control subjects for 8-iso-PGF(2alpha), O(2)(.-), and ONOO(-) and a decrease for the vitamin E-to-lipid ratio (all P < 0.05). In the PN(+)/CAN(-) group, a significant increase compared with the PN(-)/CAN(-) group was noted for O(2)(.-), whereas the vitamin E-to-lipid ratio and vitamin C were reduced (all P < 0.05). No significant differences were noted between the PN(+)/CAN(-) and PN(+)/CAN(+) groups for each of the five markers of oxidative stress. In multivariate models, O(2)(.-) and ONOO(-) were independently associated with neuropathic deficits, but diabetes duration and triglyceride levels were also independent determinants.

CONCLUSIONS

Oxidative stress is enhanced in diabetic patients before the development of PN but to an even higher degree in those with PN, without further significant increase in relation to superimposed autonomic neuropathy. However, apart from oxidative stress, diabetes duration and triglyceride levels are also related to the severity of PN.

Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men

BACKGROUND

We recently showed that trans-10,cis-12 (t10,c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men. However, metabolic effects of the c9,t11 CLA isomer are still unknown in obese men. Because c9,t11 CLA is the predominant CLA isomer in foods and is included in dietary weight-loss products, it is important to conduct randomized controlled studies that use c9,t11 CLA preparations.

OBJECTIVE

We investigated the effects of c9,t11 CLA supplementation on insulin sensitivity, body composition, and lipid peroxidation in a group at high risk for cardiovascular disease.

DESIGN

In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo (olive oil). Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism, body composition, and urinary 8-iso-prostaglandin F(2alpha) (a major F(2)-isoprostane) and 15-keto-dihydro-prostaglandin F(2alpha), markers of in vivo oxidative stress and inflammation, respectively.

RESULTS

All subjects completed the study. Compared with placebo, c9,t11 CLA decreased insulin sensitivity by 15% (P < 0.05) and increased 8-iso-prostaglandin F(2alpha) and 15-keto-dihydro-prostaglandin F(2alpha) excretion by 50% (P < 0.01) and 15% (P < 0.05), respectively. The decreased insulin sensitivity was independent of changes in serum lipids, glycemia, body mass index, and body fat but was abolished after adjustment for changes in 8-iso-prostaglandin F(2alpha) concentrations. There were no differences between groups in body composition.

CONCLUSIONS

A CLA preparation containing the purified c9,t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t11 CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women.

Revascularization decreases 8-isoprostaglandin F2alpha excretion in chronic lower limb ischemia

8-Isoprostaglandin F2alpha is one of a series of isoprostanes formed by free radical catalysed peroxidation of arachidonic acid. Urinary 8-isoprostaglandin F2alpha is a new marker which reflects oxidative stress in vivo and can be utilized as a diagnostic tool to assess the extent of oxidative stress in various disease states associated with lipid peroxidation. Increased levels of 8-isoprostaglandin F2alpha in cardiac ischemia/reperfusion provide evidence for oxidative stress during coronary perfusion. In animal studies, the restoration of blood flow after lower limb ischemia is followed by reperfusion syndrome. In this study we investigated whether lower limb ischemia/reperfusion is associated with oxidative stress, as reflected by urinary levels of 8-isoprostaglandin F2alpha. Ten patients (mean age 72 years, range 61-82 years) suffering from chronic lower limb ischemia and 10 healthy volunteers (mean age 69 years, range 60-79 years) participated in the study. In all patients, diagnostic angiography had revealed stenosis or occlusion either in the aortoiliac or femoropopliteal region. Surgical revascularization consisted of femoropopliteal reconstruction, femorofemoral reconstruction, aortobifemorial reconstruction, or femoral endartectomy. Urine samples from patients were collected a day before surgery and in the second postoperative day. Urinary 8-isoprostaglandin F2alpha was extracted on a C2 silica cartridge and determinated by radioimmunoassay. After revascularization, 8-isoprostaglandin F2alpha excretion (pg/micromol creatinine, mean +/- SD) was decreased by 2.5-fold (preoperative 48.9 +/- 8.9, postoperative 19.1 +/- 9.5, P < 0.001). The postoperative values were similar to the concentrations measured in healthy volunteers (18.0 +/- 11.0). All revascularizations were successful, and the increase in ankle-brachial index (preoperative 0-0.6, postoperative 0.4-0.8) revealed improved blood flow in the ischemic lower limb. We suggest that, as assessed by the quantitation of urinary 8-isoprostaglandin F2alpha, chronic lower limb ischemia is associated with increased oxidative stress, which is decreased by revascularization.

Identification of 5,6-trans-Epoxyeicosatrienoic Acid in the Phospholipids of Red Blood Cells

A novel eicosanoid, 5,6-trans-epoxy-8Z,11Z,14Z-eicosatrienoic acid (5,6-trans-EET), was identified in rat red blood cells. Characterization of 5,6-trans-EET in the sn-2 position of the phospholipids was accomplished by hydrolysis with phospholipase A(2) followed by gas chromatography/mass spectrometry as well as electrospray ionization-tandem mass spectrometry analyses. The electron ionization spectrum of 5,6-erythro-dihydroxyeicosatrienoic acid (5,6-erythro-DHET), converted from 5,6-trans-EET in the samples, matches that of the authentic standard. Hydrogenation of the extracted 5,6-erythro-DHET with platinum(IV) oxide/hydrogen resulted in an increase of the molecular mass by 6 daltons and the same retention time shift as an authentic standard in gas chromatography, suggesting the existence of three olefins as well as the 5,6-erythro-dihydroxyl structure in the metabolite. Match of retention times by chromatography indicated identity of the stereochemistry of the red blood cell 5,6-erythro-DHET vis à vis the synthetic standard. High pressure liquid chromatography-electrospray ionization-tandem mass spectrometry analysis of the phospholipase A(2)-hydrolyzed lipid extracts from red blood cells revealed match of the mass spectrum and retention time of the compound with the authentic 5,6-trans-EET standard, providing direct evidence of the existence of 5,6-trans-EET in red blood cells. The presence of other trans-EETs was also demonstrated. The ability of both 5,6-trans-EET and its product 5,6-erythro-DHET to relax preconstricted renal interlobar arteries was significantly greater than that of 5,6-cis-EET. In contrast, 5,6-cis-EET and 5,6-trans-EET were equipotent in their capacity to inhibit collagen-induced rat platelet aggregation, whereas 5,6-erythro-DHET was without effect. We propose that the red blood cells serve as a reservoir for epoxides which on release may act in a vasoregulatory capacity.

Platelet activation in type 2 diabetes mellitus

The abnormal metabolic state that accompanies diabetes renders arteries susceptible to atherosclerosis, being capable of altering the functional properties of multiple cell types, including endothelium and platelets. In particular, an altered platelet metabolism and changes in intraplatelet signaling pathways may contribute to the pathogenesis of atherothrombotic complications of diabetes. A variety of mechanisms may be responsible for enhanced platelet aggregation. Among them, hyperglycemia may represent a causal factor for in vivo platelet activation, and may be responsible for nonenzymatic glycation of platelet glycoproteins, causing changes in their structure and conformation, as well as alterations of membrane lipid dynamics. Furthermore, hyperglycemia-induced oxidative stress is responsible for enhanced peroxidation of arachidonic acid to form biologically active isoprostanes, which represents an important biochemical link between impaired glycemic control and persistent platelet activation. Finally, increased oxidative stress is responsible for activation of transcription factors and expression of redox-sensitive genes leading to a phenotypic switch of endothelium toward an adhesive, pro-thrombotic condition, initial platelet activation, adhesion and subsequent platelet aggregate formation. All this evidence is strengthened by the results of clinical trials documenting the beneficial effects of metabolic control on platelet function, and by the finding that aspirin treatment may even be more beneficial in diabetic than in high-risk non-diabetic patients. Attention to appropriate medical management of diabetic patients will have great impact on long-term outcome in this high-risk population.

Overexpression of human heme oxygenase-1 attenuates endothelial cell sloughing in experimental diabetes

Heme oxygenase (HO)-1 represents a key defense mechanism against oxidative injury. Hyperglycemia produces oxidative stress and various perturbations of cell physiology. The effect of streptozotocin (STZ)-induced diabetes on aortic HO activity, heme content, the number of circulating endothelial cells, and urinary 8-epi-isoprostane PGF2alpha (8-Epi) levels in control rats and rats overexpressing or underexpressing HO-1 was measured. HO activity was decreased in hyperglycemic rats. Hyperglycemia increased urinary 8-Epi, and this increase was augmented in rats underexpressing HO-1 and diminished in rats overexpressing HO-1. The number of detached endothelial cells and O2- formation increased in diabetic rats and in hyperglycemic animals underexpressing HO-1 and decreased in diabetic animals overexpressing HO-1 compared with controls. These data demonstrate that HO-1 gene transfer in hyperglycemic rats brings about a reduction in O2- production and a decrease in endothelial cell sloughing. Upregulation of HO-1 decreases oxidant production and endothelial cell damage and shedding and may attenuate vascular complications in diabetes.

8-isoprostane increases scavenger receptor A and matrix metalloproteinase activity in THP-1 macrophages, resulting in long-lived foam cells

BACKGROUND

Oxidative stress is a key factor in atherogenesis, in which it is closely associated with the inflammation and formation of bioactive lipids. Although 8-isoprostane is regarded as a reliable marker of oxidative stress in vivo, the pathogenic role of this F(2)-isoprostane in atherogenesis is far from clear. Based on the important role of foam cells in the initiation and progression of atherosclerosis we hereby examined the ability of 8-isoprostane to modulate oxidized (ox)LDL-induced foam cell formation and the function of these cells, particularly focusing on the effect on matrix degradation.

METHODS AND RESULTS

8-isoprostane (10 micro M) augmented the oxLDL-induced (20 micro g mL(-1)) lipid accumulation of THP-1 macrophages evaluated by Oil-Red-O staining and lipid mass quantification (colourimetric assay). Additionally, 8-isoprostane induced the expression of the scavenger receptor A type 1 (MSR-1) [mRNA and protein level], assessed by RT-PCR and Western blotting, respectively. Moreover, 8-isoprostane counteracted the oxLDL-induced apoptosis of these cells, involving both mitochondrial-protective and caspase-suppressive mechanisms. Along with these changes, 8-isoprostane increased the oxLDL-induced gene expression of matrix metalloproteinase (MMP)-9 and its endogenous inhibitor [i.e. tissue inhibitor of MMP (TIMP)-1] accompanied by enhanced total MMP activity.

CONCLUSIONS

We show that 8-isoprostane increases foam cell formation at least partly by enhancing MSR-1 expression and by inhibiting apoptosis of these cells, inducing long-lived foam cells with enhanced matrix degrading capacity. Our findings further support a role for 8-isoprostane not only as a marker of oxidative stress in patients with atherosclerotic disorders, but also as a mediator in atherogenesis and plaque destabilization.