Evidence for oxidative stress in unstable angina

Objective—To determine whether unstable angina, which is characterised by recurring episodes of myocardial ischaemia and reperfusion, is associated with oxidative stress (that is, where there is an imbalance between oxidants, such as free radicals, which are in excess and antioxidants).

Design—Between group comparison of patients with unstable angina, stable angina, and healthy controls.

Setting—The coronary care unit and cardiac investigation ward of a regional cardiology centre.

Patients—Twenty five consecutive patients admitted to the coronary care unit with unstable angina. Twenty five consecutive patients admitted to the cardiac investigation ward (patients with stable angina undergoing coronary angiography) were used as control for the presence of [ill], drug treatment, and smoking habit. Thirty eight healthy controls (hospital staff and patients admitted for minor surgical procedures who were otherwise healthy) were also studied.

Main outcome

measures—Thiobarbituric acid related substances (TBARS) in plasma and plasma reduced thiol (PSH) as indicators of oxidative damage to lipids and proteins respectively were measured. Coronary angiography was performed in all patients with stable angina and roughly half of those with unstable angina.

Results—Mean (SEM) plasma TBARS in unstable angina and stable angina were 9·95 (0·36) nmol/ml and 9·14 (0·28) nmol/ml respectively (p = 0·08). Mean plasma TBARS in healthy controls were 8·09 (0·21) nmol/ml (p < 0·05 compared with both angina groups). Mean (SEM) PSH concentration in unstable angina was 4·21 (9) nmol/ml and in stable angina was 4·85 (9) nmol/ml (p < 0·05). Mean PSH in healthy controls was 5·64 (8) nmol/ml (p < 0·001 compared with both angina groups). The extent of coronary artery disease, use of medication, and smoking habit were not significantly different between the angina groups.

Conclusions—Biochemical indicators of oxidative stress are more abnormal in unstable than stable angina. This is in keeping with experimental evidence that episodes of ischaemia and reperfusion lead to generation of free radicals and toxic oxygen species and depression of endogenous antioxidant activity. The clinical significance of this finding remains to be determined, although, experimentally, free radicals and toxic oxygen species have adverse effects on myocardial contractile function, myocardial electrical stability, endothelial mediated vasodilatation, and coagulation.

     

Evidence for oxidative stress in unstable angina.

OBJECTIVE--To determine whether unstable angina, which is characterised by recurring episodes of myocardial ischaemia and reperfusion, is associated with oxidative stress (that is, where there is an imbalance between oxidants, such as free radicals, which are in excess and antioxidants). DESIGN--Between group comparison of patients with unstable angina, stable angina, and healthy controls. SETTING--The coronary care unit and cardiac investigation ward of a regional cardiology centre. PATIENTS--Twenty five consecutive patients admitted to the coronary care unit with unstable angina. Twenty five consecutive patients admitted to the cardiac investigation ward (patients with stable angina undergoing coronary angiography) were used as controls for the presence of atherosclerosis, drug treatment, and smoking habit. Thirty eight healthy controls (hospital staff and patients admitted for minor surgical procedures who were otherwise healthy) were also studied. MAIN OUTCOME MEASURES--Thiobarbituric acid related substances (TBARS) in plasma and plasma reduced thiol (PSH) as indicators of oxidative damage to lipids and proteins respectively were measured. Coronary angiography was performed in all patients with stable angina and roughly half of those with unstable angina. RESULTS--Mean (SEM) plasma TBARS in unstable angina and stable angina were 9.95 (0.36) nmol/ml and 9.14 (0.28) nmol/ml respectively (p = 0.08). Mean plasma TBARS in healthy controls were 8.09 (0.21) nmol/ml (p < 0.05 compared with both angina groups). Mean (SEM) PSH concentration in unstable angina was 4.21 (9) nmol/ml and in stable angina was 4.85 (9) nmol/ml (p < 0.05). Mean PSH in healthy controls was 5.64 (8) nmol/ml (p < 0.001 compared with both angina groups). The extent of coronary artery disease, use of medication, and smoking habit were not significantly different between the angina groups. CONCLUSIONS--Biochemical indicators of oxidative stress are more abnormal in unstable than stable angina. This is in keeping with experimental evidence that episodes of ischaemia and reperfusion lead to generation of free radicals and toxic oxygen species and depression of endogenous antioxidant activity. The clinical significance of this finding remains to be determined, although, experimentally, free radicals and toxic oxygen species have adverse effects on myocardial contractile function, myocardial electrical stability, endothelial mediated vasodilatation, and coagulation.     

Evidence for early oxidative stress in acute pancreatitis

Summary Pancreatic oxidative stress with depletion of pancreatic glutathione is an early feature in all tested models of acute pancreatitis, and sooner or later the problem extends to the lung, irrespective of disease severity, whether toward spontaneous recovery or death from multisystem organ failure. We, therefore, sought evidence of oxidative stress in the human disease by analyzing admission blood samples. We found it from high concentrations of oxidatively altered linoleic acid in serum and vitamin C in plasma (p<0.001 vs controls or a group of other acute abdominal crises where the proportion of patients with admission Apache II scores <or> 8 was similar). These changes were accompanied by subnormal levels of ascorbic acid in plasma (p<0.001); selenium (p<0.001), β-carotene (p<0.001), and α-tocopherol in serum (p=0.005 for its molar ratio to cholesterol). Paradoxically, the plasma concentration ofS-adenosylmethionine was elevated (p=0.02), suggesting that this proximate bioactive metabolite of the essential amino acid had backtracked because its intracellular metabolism down the methionine trans-sulfuration pathway toward glutathione synthesis was disrupted. The aberrations transcended putative etiological factor, duration of symptoms, or disease severity. We conclude: (1) that oxidative stress has pervaded the vascular compartment by the time of admission in patients with acute pancreatitis, and, (2) that blood micronutrient antioxidant profiles at this stage are consistent not only with compromised intracellular capacity to synthesize/refurbish glutathione, but also vulnerability of intra- and extracellular lipid targets.     

Prenatal diagnosis of succinate semialdehyde dehydrogenase deficiency in non-identical twins

Prenatal diagnosis was performed by both DNA and enzymatic analysis on non-identical twins conceived by in vitro fertilization and at risk of succinate semialdehyde dehydrogenase deficiency. One fetus was predicted to be affected and one unaffected and selective fetal reduction was performed.     

Expression profiling reveals multiple myelin alterations in murine succinate semialdehyde dehydrogenase deficiency

Summary Succinic semialdehyde dehydrogenase (SSADH) deficiency, a rare genetic defect of GABA degradation recently modelled in mice (SSADH^−/− mice), manifests early absence seizures that evolve into generalized convulsive seizures and lethal status epilepticus in gene-ablated mice. Disrupted GABA homeostasis, in conjunction with the epileptic phenotype and increased gamma-hydroxybutyric acid (GHB), suggested that expression profiling with the U74Av2 Affymetrix system would reveal dysregulation of receptor genes associated with GABAergic and glutamatergic neurotransmission. Unexpectedly, we found significant downregulation for genes associated with myelin biogenesis and compaction, predominantly in hippocampus and cortex. These results were confirmed by: (1) myelin basic protein (MBP) immunohistochemistry; (2) western blotting of myelin-associated glycoprotein (MAG) and MBP; (3) qRT-PCR analyses of myelin-associated oligodendrocytic basic protein (MOBP), MAG, MBP and proteolipid protein (PLP) in hippocampus, cortex and spinal cord; (4) quantitation of ethanolamine and choline plasmalogens, all core myelin components; (5) evaluation of myelin content in brain sections employing toluidine blue staining; and (6) ultrastructural evaluation of myelin sheath thickness via electron microscopy. We speculate that increased GABA/GHB, acting through GABAergic systems, results in decreased levels of the neurosteroids progesterone and allopregnanolone [Gupta et al (2003) Ann Neurol 54(Supplement 6): S81–S90] and phosphorylation of mitogen-activated protein (MAP) kinase, with resulting myelin protein abnormalities primarily in the cortex of SSADH^−/− mice. These authors contributed equally to this study. Communicating editor: Verena Peters Competing interests: None declared     

Evidence that NADPH-dependent methemoglobin reductase and administered riboflavin protect tissues from oxidative injury

NADPH-dependent methemoglobin reductase, first detected in erythrocytes sixty years ago, has subsequently been purified and characterized as a methylene blue reductase and a flavin reductase. The reductase plays no role in methemoglobin reduction under normal conditions, but its activity serves as the basis for the treatment of methemoglobinemia with methylene blue or flavin. On-going studies demonstrate that this cytosolic protein is also present in liver and that its primary structure distinguishes it from other known proteins. The bovine erythrocyte reductase tightly binds hemes, porphyrins, and fatty acids with resulting loss of activity. Pyrroloquinoline quinone serves as a high-affinity substrate of the reductase, suggesting that this naturally-occurring compound may be a physiological substrate. The ability of the reductase to catalyze the intracellular reduction of administered riboflavin to dihydroriboflavin suggested that this system might be exploited to protect tissues from oxidative damage. This hypothesis was supported by our finding that dihydroriboflavin reacts rapidly with Fe(IV)O and Fe(V)O oxidation states of hemeproteins, states that have been implicated in tissue damage associated with ischemia and reperfusion. Preliminary studies demonstrate that, as predicted, administration of low concentrations of riboflavin protects isolated rabbit heart from reoxygenation injury, rat lung from injury resulting from systemic activation of complement, and rat brain from damage caused by four hours of ischemia. Data from these animal studies suggest that flavin therapy holds promise in protecting tissue from the oxidative injuries of myocardial infarction, acute lung injury, stroke, and a number of other clinical conditions. © 1993 Wiley-Liss, Inc.     

Succinic semialdehyde dehydrogenase deficiency: Lessons from mice and men

Summary  Succinic semialdehyde dehydrogenase (SSADH) deficiency, a disorder of GABA degradation with subsequent elevations in brain GABA and GHB, is a neurometabolic disorder with intellectual disability, epilepsy, hypotonia, ataxia, sleep disorders, and psychiatric disturbances. Neuroimaging reveals increased T2-weighted MRI signal usually affecting the globus pallidus, cerebellar dentate nucleus, and subthalamic nucleus, and often cerebral and cerebellar atrophy. EEG abnormalities are usually generalized spike-wave, consistent with a predilection for generalized epilepsy. The murine phenotype is characterized by failure-to-thrive, progressive ataxia, and a transition from generalized absence to tonic-clonic to ultimately fatal convulsive status epilepticus. Binding and electrophysiological studies demonstrate use-dependent downregulation of GABA(A) and (B) receptors in the mutant mouse. Translational human studies similarly reveal downregulation of GABAergic activity in patients, utilizing flumazenil-PET and transcranial magnetic stimulation for GABA(A) and (B) activity, respectively. Sleep studies reveal decreased stage REM with prolonged REM latencies and diminished percentage of stage REM. An ad libitum ketogenic diet was reported as effective in the mouse model, with unclear applicability to the human condition. Acute application of SGS–742, a GABA(B) antagonist, leads to improvement in epileptiform activity on electrocorticography. Promising mouse data using compounds available for clinical use, including taurine and SGS–742, form the framework for human trials. Competing interests: None declared References to electronic databases: Succinic semialdehyde dehydrogenase deficiency: OMIM #271980. Presented at the 2nd Pediatric Neurotransmitter Disease (PND) Association Symposium, ‘Medical Management of Pediatric Neurotransmitter Disorders: A Multidisciplinary Approach’, 18–19 July 2008, Hyatt Dulles Hotel, Herndon, VA, USA.     

Evidence for oxidative/nitrosative stress in the pathogenesis of hepatic encephalopathy

Hepatic encephalopathy (HE) is a serious complication of liver failure. HE manifests as a series of neuropsychiatric and neuromuscular symptoms including personality changes, sleep abnormalities, asterixis and muscle rigidity progressing through stupor to coma. The pathophysiologic basis of HE remains unclear. There is general agreement that ammonia plays a key role. In recent years, it has been suggested that oxidative/nitrosative stress constitutes part of the pathophysiologic cascade in HE. Direct evidence for oxidative/nitrosative stress in the pathogenesis of HE has been demonstrated in experimental animal models of acute or chronic liver failure. However, evidence from studies in HE patients is limited. This review summarizes this evidence for a role of oxidative/nitrosative stress in relation to ammonia toxicity and to the pathogenesis of HE.     

Evidence of a systemic phenomenon for oxidative stress in cholestatic liver disease

BACKGROUND: There is considerable evidence indicating that the severity of hepatic damage in individuals with cholestatic liver disease is causally associated with the extent of intrahepatic oxidative stress. Increased levels or accelerated generation of reactive oxygen species and toxic degradative products of lipid peroxidation have been reported in the plasma of individuals with chronic liver disease and animal models of liver disease. Hence, by virtue of their increased presence in the circulation, it is not unreasonable to suppose that they may account for extrahepatic tissue damage in chronic liver disease. MATERIALS AND METHODS: This hypothesis was tested by determining plasma levels of the ubiquitous antioxidant glutathione (GSH) and lipid peroxides (LP), together with assessment of the extent of lipid peroxidation in the kidney, brain, and heart, in 24 day chronically bile duct ligated (CBDL) rats. The extent of lipid peroxidation in tissues was based on measurement of conjugated dienes, lipid peroxides, and malondialdehyde (MDA) content. Data were compared with identical data collected from unoperated control, pair fed, 24 day bile duct manipulated (sham operated), and pair fed sham operated rats. RESULTS: In CBDL rats, total and reduced plasma GSH levels were almost half those determined in all control rats. Plasma, kidney, and heart LP levels were significantly increased in CBDL rats compared with controls. MDA levels were significantly higher in the kidney, brain, and heart homogenates prepared from CBDL rats compared with MDA content measured in tissue homogenates prepared from the four groups of control rats. CONCLUSIONS: Our data show that experimental cholestatic liver disease is associated with increased lipid peroxidation in the kidney, brain, and heart. Hence we have concluded that the oxidative stress in cholestatic liver disease is a systemic phenomenon probably encompassing all tissues and organs, even those separated by the blood-brain barrier.     

Evidence of oxidative stress in chronic heart failure in humans

Chronic heart failure (CHF) due to coronary artery disease (CAD)has been shown to be associated with increased plasma thiobarbituricreactive substances (TBARS) and reduced plasma thiol (PSH) concentrations,suggesting oxidative stress (OS). The aims of the present studieswere (a) to determine whether OS is due to CAD or CHF per seand (b) to determine if a wider range of more specific markersof OS are abnormal in CHF. In the first study, two groups of patients (n = 15 each) werecompared. Group 1 (11 male, mean age 56 years) had CHF due toCAD and group 2 (12 male, mean age 53 years) had non-CAD CHF.Median plasma TBARS in controls was 7.6 nmol . ml^–1 ,10.0 nmol . m^–1 in group 1 and 9.3 nmol. ml^–1 ingroup 2 (P < 0.01 both groups vs control). Median PSH was505 384 and 364 nmol. ml^–1 (P < 0.05 and P < 0.01vs control) respectively. Fifty-three patients with CHF were recruited in the second study.Malondialdehyde and PSH were 10.3 and 409 nmol. ml^–1 respectively,compared to control values of 7.9 and 560 nmol. ml^.1 (both P< 0.001). The median values for the following additionalmeasures of OS in controls and patients were: erythrocyte superoxidedismustase 131 vs 114 U . l^–1 (P = 0.005); caeruloplasminoxidase 97 vs 197 U. l^–1 (P < 0.01); erythrocyte glutathione1.56 nmol . ml^–1 vs 1.77 nmol . ml^–1 (P < 0.02);plasma conjugated dienes 0.28 vs 0.33 optical density units(P = ns). Chronic heart failure, regardless of aetiology, is associatedwith abnormalities of a range of markers of OS.     

Effects of repaglinide on oxidative stress in tissues of diabetic rabbits

In this study, the antioxidative properties of repaglinide were examined in tissues of alloxan-induced diabetic rabbits. Glutathione (GSH), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R) and protein carbonyl groups (PCG) were measured after 4 and 8 weeks treatment with repaglinide (0.3 mg/kg daily). In liver, diabetic versus control values (mean +/- S.E.M., p<0.05) for GSH-Px were 181.0 +/- 5.4 mU/mg protein versus 203.1 +/- 1.9 mU/mg protein and 187.4 +/- 6.6 mU/mg protein versus 240.9 +/- 18.8 mU/mg protein. The respective values for GSH were 33.7 +/- 0.4 nmol/mg protein versus 49.0 +/- 1.6 nmol/mg protein and 37.7 +/- 1.0 nmol/mg protein versus 41.2 +/- 0.7 nmol/mg protein. In diabetic kidney, GSSG-R activity (20.6 +/- 1.6 mU/mg protein versus 32.4 +/- 1.5 mU/mg protein and 23.6 +/- 0.6 mU/mg protein versus 36.3 +/- 0.3 mU/mg protein) and GSH level (16.6 +/- 0.5 nmol/mg protein versus 23.2 +/- 0.9 nmol/mg protein and 17.9 +/- 0.5 nmol/mg protein versus 23.2 +/- 0.6 nmol/mg protein) were reduced compared to control. PCG level was elevated in diabetic liver (0.58 +/- 0.02 nmol/mg protein versus 0.16 +/- 0.03 nmol/mg protein at 4 weeks and 0.64 +/- 0.04 nmol/mg protein versus 0.16 +/- 0.03 nmol/mg protein at 8 weeks) and in diabetic kidney (0.32 +/- 0.03 nmol/mg protein versus 0.11 +/- 0.02 nmol/mg protein and 0.35 +/- 0.03 nmol/mg protein versus 0.16 +/- 0.03 nmol/mg protein). Repaglinide did not affect the glucose level but reduced to some extent the oxidative stress enhanced by chronic hyperglycemia. In diabetic kidney, it restored to control values GSSG-R activity (45.4 +/- 2.0 mU/mg protein at 4 weeks and 41.1 +/- 0.07 mU/mg protein at 8 weeks), GSH level (27.0 +/- 0.8 and 26.8 +/- 0.9 nmol/mg protein), and partly PCG level (0.17 +/- 0.02 nmol/mg protein at 8 weeks). The treatment partly affected GSH-Px activity (262.7 +/- 17.6 mU/mg protein) and GSH level (40.4 +/- 1.4 nmol/mg protein) in diabetic liver. This study shows that repaglinide produces measurable antioxidative effects at therapeutic dose.     

Evidence that 2-methylacetoacetate induces oxidative stress in rat brain

In the present study we investigated the effects of 2-methylacetoacetate (MAA) and 2-methyl-3-hydroxybutyrate (MHB), the major metabolites accumulating in mitochondrial 2-methylacetoacetyl-CoA thiolase (KT) and 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiencies, on important parameters of oxidative stress in cerebral cortex from young rats. We verified that MAA induced lipid peroxidation (increase of thiobarbituric acid-reactive substances (TBA-RS) and chemiluminescence values), whereas MHB did not alter these parameters. MAA-induced increase of TBA-RS levels was fully prevented by free radical scavengers, indicating that free radicals were involved in this effect. Furthermore, MAA, but not MHB, significantly induced sulfhydryl oxidation, implying that this organic acid provokes protein oxidative damage. It was also observed that MAA reduced GSH, a naturally-occurring brain antioxidant, whereas MHB did not change this parameter. Furthermore, the decrease of GSH levels caused by MAA was not due to a direct oxidative action, since this organic acid did not alter the sulfhydryl content of a commercial solution of GSH in a cell free medium. Finally, MAA and MHB did not raise nitric oxide production. The data indicate that MAA induces oxidative stress in vitro in cerebral cortex. It is presumed that this pathomechanism may be involved in the brain damage found in patients affected by KT deficiency.     

Evidence that oxidative stress is increased in plasma from patients with maple syrup urine disease

Maple syrup urine disease (MSUD) or branched-chain α-keto aciduria (BCKA) is an inherited disorder caused by a deficiency of the branched-chain α-keto acid dehydrogenase complex (BCKAD) activity. The blockage of this pathway leads to tissue accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine and valine and their respective keto-acids. The clinical features presented by MSUD patients include ketoacidosis, convulsions, coma, psychomotor delay and mental retardation. The mechanism of brain damage in this disease is still poorly understood. However, an increase in lipid peroxidation in vitro in cerebral cortex of young rats as well as a decrease in the antioxidant defenses has been previously observed. In the present work we evaluated different oxidative stress parameters, named reactive species of thiobarbituric acid (TBARS), total antioxidant reactivity (TAR) and total antioxidant status (TAS) in plasma of MSUD patients in order to evaluate whether oxidative stress is involved in this disorder. We verified a marked increase of plasma TBARS measurements, which is indicative of increased lipid peroxidation, as well as a decrease on plasma TAR reflecting a deficient capacity to efficiently modulate the damage associated with an increased production of reactive species. In contrast, TAS was not changed indicating that the total content of antioxidants in plasma of patients affected by MSUD was not altered. These results suggest that free radical generation is elicited in MSUD and is possibly involved in the pathophysiology of the tissue damage found in this disorder.     

阿托伐他汀对高胆固醇-动脉粥样硬化兔脑组织的抗氧化应激作用研究

目的建立兔高胆固醇-动脉粥样硬化模型，观察阿托伐他汀对脑组织的抗氧化应激保护作用。方法24只健康新西兰白兔随机分为3组：（A组）正常对照组、（B组）高脂饮食组和（C组）高脂饮食加阿托伐他汀组。喂饲8周后，测定兔血清总胆固醇（TC）及低密度脂蛋白（LDL）浓度，取脑组织检测血红素氧合酶（HO-1）水平、超氧化物歧化酶（SOD）活力及丙二醛（MDA）含量的变化。结果ABC三组HO-1平均吸光度值分别为0．418200±0．001874，0．682100±0．001853，0．918800±0．001549；SOD值分别为424．03±14．45、271．79±13．46和402．38±7．35；MDA值分别为16．66±2．55、40．87±2．78和21．57±2．19。与对照组相比，高脂饮食组HO-1表达显著上调，SOD活力下降，MDA含量增加（P〈0．05）；阿托伐他汀组较高脂饮食组HO-1表达进一步上调，SOD活力升高，MDA含量降低（P〈0．05）。结论兔动脉粥样硬化过程中，脑组织处于氧化应激状态，阿托伐他汀可对抗氧化应激损伤，从而减缓动脉粥样硬化的形成。     

Characterization of oxidative stress in various tissues of diabetic and galactose-fed rats

Rats fed a galactose-rich diet have been used for several years as a model for diabetes to study, particularly in the eye, the effects of excess blood hexoses. This study sought to determine the utility of galactosemia as a model for oxidative stress in extraocular tissues by examining biomarkers of oxidative stress in galactose-fed rats and experimentally-induced diabetic rats. Sprague-Dawley rats were divided into four groups: experimental control; streptozotocin-induced diabetic; insulin-treated diabetic; and galactose-fed. The rats were maintained on these regimens for 30 days, at which point the activities of catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as levels of lipid peroxidation and reduced and oxidized glutathione were determined in heart, liver, and kidney. This study indicates that while there are some similarities between galactosemic and diabetic rats in these measured indices of oxidative stress (hepatic catalase activity levels and hepatic and renal levels of oxidized glutathione in both diabetic and galactosemic rats were significantly decreased when compared to normal), overall the galactosemic rat model is not closely parallel to the diabetic rat model in extra-ocular tissues. In addition, several effects of diabetes (increased hepatic glutathione peroxidase activity, increased superoxide dismutase activity in kidney and heart, decreased renal and increased cardiac catalase activity) were not mimicked in galactosemic rats, and glutathione concentration in both liver and heart was affected in opposite ways in diabetic rats and galactose-fed rats. Insulin treatment reversed/prevented the activity changes in renal and cardiac superoxide dismutase, renal and cardiac catalase, and hepatic glutathione peroxidase as well as the hepatic changes in lipid peroxidation and reduced and oxidized glutathione, and the increase in cardiac glutathione. Thus, prudence should be exercised in the use of experimentally galactosemic rats as a model for diabetes until the correspondence of the models has been more fully characterized.     

Induction of heme oxygenase-1 in vivo suppresses NADPH oxidase derived oxidative stress

Our previous studies suggest that heme oxygenase (HO)-1 induction and/or subsequent bilirubin generation in endothelial cells may suppress superoxide generation of from reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase. In this study, we examined the consequence of HO-1 induction in vivo on NADPH oxidase activity. Three doses of hemin (25 mg x kg(-1), IP, every 48 hours), with or without cotreatment with the HO inhibitor tin protoporphyrin-IX (15 mg x kg(-1), IP), were given to apolipoprotein E-deficient mice, which display vascular oxidative stress. Hemin treatment increased HO-1 expression and activity in aorta (undetectable at baseline) and kidney (by 3-fold) and significantly reduced both NADPH oxidase activity (by approximately 25% to 50%) and superoxide generation in situ. The increase in HO-1 activity and inhibition of NADPH oxidase activity by hemin were reversed by tin protoporphyrin-IX and were not associated with changes in Nox2 or Nox4 protein levels. Hemin also reduced plasma F(2)-isoprostane levels by 23%. The inhibition of NADPH oxidase activity by hemin in the aorta was mimicked by bilirubin in vitro (0.01 to 1 micromol/L). Bilirubin also concentration-dependently reduced NADPH oxidase-dependent superoxide production stimulated by angiotensin II in rat vascular smooth muscle cells and by phorbol 12-myristate 13-acetate in human neutrophil-like HL-60 cells. HO-1 overexpression by plasmid-mediated gene transfer in rat vascular smooth muscle cells decreased NADPH-stimulated superoxide production. Thus, systemic expression of HO-1 suppresses NADPH oxidase activity by mechanisms at least partly mediated by the bile pigment bilirubin, thereby reducing oxidative stress.