Low-density lipoprotein oxidation in essential hypertension

Relationship of resting heart rate and blood pressure with all-cause and cardiovascular disease mortality

OBJECTIVES

This study aimed to investigate associations of resting heart rate (RHR) and blood pressure (BP) with all-cause and cardiovascular disease (CVD) mortality.

STUDY DESIGN

A retrospective cohort study.

METHODS

A total of 67,028 Chinese participants aged ≥60 years were included in the analysis. RHR, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were evaluated according to quartiles ([41-69, 70-74, 75-79, 80-127 beats/min], [80-119, 120-129, 130-139, 140-238 mm Hg], and [40-70, 71-79, 80-84, 85-133 mm Hg]). Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of all-cause and CVD mortality with RHR, SBP, and DBP. Restricted cubic splines were used to evaluate the dose-response association.

RESULTS

During the 361,975 person-year follow-up, 9326 deaths were recorded, of which 5039 deaths were due to CVD. The risk of all-cause mortality was increased by 25% with the quartiles four vs quartile one of RHR (HR [95% CI]:1.25 [1.17-1.33]), and CVD mortality was increased by 32% (HR [95% CI]: 1.32 [1.22-1.44]). Similar results were observed when comparing the quartiles four vs quartile one of SBP with the risk of all-cause and CVD mortality (HRs [95% CIs]: 1.14 [1.07, 1.22] and 1.23 [1.12. 1.34]) and DBP with the risk of all-cause and CVD mortality (HRs [95% CIs]: 1.17 [1.11. 1.24] and 1.36 [1.26. 1.47]). We found linear associations of RHR, SBP, and DBP with all-cause and CVD mortality (P_{non-linearity} >0.05), except for the approximately J-shaped association between DBP and all-cause mortality (P_{non-linearity} = 0.008). There was a significant interaction of RHR and SBP with all-cause and CVD mortality (P_interaction <0.05).

CONCLUSIONS

RHR and BP increased the risk of all-cause and CVD mortality, especially fast RHR combined with high SBP.

Ang II-Induced Hypertension Exacerbates the Pathogenesis of Tuberculosis

It has been known that infection plays a role in the development of hypertension. However, the role of hypertension in the progression of infectious diseases remain unknown. Many countries with high rates of hypertension show geographical overlaps with those showing high incidence rates of tuberculosis (TB). To explore the role of hypertension in tuberculosis, we compared the effects of hypertension during mycobacterial infection, we infected both hypertensive Angiotensin II (Ang II) and control mice with Mycobacterium tuberculosis (Mtb) strain H37Ra by intratracheal injection. Ang II-induced hypertension promotes cell death through both apoptosis and necrosis in Mtb H37Ra infected mouse lungs. Interestingly, we found that lipid accumulation in pulmonary tissues was significantly increased in the hypertension group compared to the normal controls. Ang II-induced hypertension increases the formation of foamy macrophages during Mtb infection and it leads to cell death. Moreover, the hypertension group showed more severe granuloma formation and fibrotic lesions in comparison with the control group. Finally, we observed that the total number of mycobacteria was increased in the lungs in the hypertension group compared to the normal controls. Taken together, these results suggest that hypertension increases intracellular survival of Mtb through formation of foamy macrophages, resulting in severe pathogenesis of TB.

Attenuation of fatty liver and prevention of hypercholesterolemia by extract of Curcuma longa through regulating the expression of CYP7A1, LDL-receptor, HO-1, and HMG-CoA reductase

The extract of Curcuma longa, better known as turmeric, was orally administered to experimental rats that were fed a high-cholesterol diet to investigate whether it could regulate plasma lipids and cholesterol levels and possibly improve hepatic conditions. With turmeric supplements, rats showed a significant decrease in total plasma cholesterol and low-density lipoprotein cholesterol but an increase in high-density lipoprotein cholesterol when compared with rats that were fed a high-cholesterol diet alone. Fatty liver developed in hypercholesterolemic rats with the high-cholesterol diet treatment, and this condition was markedly improved when rats were provided with turmeric supplements at 100 mg/kg or 300 mg/kg of body mass. The turmeric treatment resulted in a significant decrease in the total amount of hepatic lipid. Histological staining of liver tissues with Sudan III and hematoxylin showed that rats fed with a high-cholesterol diet alone had more and larger granular fat bodies than rats having turmeric extract supplementation in their high-cholesterol diet. Reverse-transcription polymerase chain reaction was used to assess the expression levels of enzymes involved in fat metabolism and cellular homeostasis in experimental rat livers. The results showed that rats fed a high-cholesterol diet supplemented with turmeric extract had a significant increase in the expression of cholesterol 7 α-hydroxylase, hemeoxygenase 1, and low-density lipoprotein receptors but a significant decrease in 3-hydroxy-3-methyl-glutaryl-CoA reductase level when compared with rats fed a normal or high-cholesterol diet, showing that turmeric prevents hypercholesterolemia and the formation of fatty liver by the modulation of expressions of enzymes that are important to cholesterol metabolism.

PRACTICAL APPLICATION

  Turmeric may be considered a functional food for regulating plasma cholesterol levels and preventing the development of fatty liver in people who frequently consume a high-cholesterol diet.

Early increase in autoantibodies against human oxidized low-density lipoprotein in hypertensive patients after blood pressure control

BACKGROUND

Oxidized lipoproteins and antioxidized low-density lipoprotein (anti-oxLDL) antibodies (Abs) have been detected in plasma in response to blood pressure (BP) elevation, suggesting the participation of the adaptive immune system. Therefore, treatment of hypertension may act on the immune response by decreasing oxidation stimuli. However, this issue has not been addressed. Thus, we have here analyzed anti-oxLDL Abs in untreated (naive) hypertensive patients shortly after initiation of antihypertensive therapeutic regimens.

METHODS

Titers of anti-oxLDL Abs were measured in subjects with recently diagnosed hypertension on stage 1 (n = 94), in primary prevention of coronary disease, with no other risk factors, and naive of antihypertensive medication at entry. Subjects were randomly assigned to receive perindopril, hydrochlorothiazide (HCTZ), or indapamide (INDA) for 12 weeks, with additional perindopril if necessary to achieve BP control. Abs against copper-oxidized LDL were measured by enzyme-linked immunosorbent assay.

RESULTS

Twelve-week antihypertensive treatment reduced both office-based and 24-h ambulatory BP measurements (P < 0.0005). The decrease in BP was accompanied by reduction in thiobarbituric acid-reactive substances (TBARS) (P < 0.05), increase in anti-oxLDL Ab titers (P < 0.005), and improvement in flow-mediated dilation (FMD) (P < 0.0005), independently of treatment. Although BP was reduced, we observed favorable changes in anti-oxLDL titers and FMD.

CONCLUSIONS

We observed that anti-oxLDL Ab titers increase after antihypertensive therapy in primary prevention when achieving BP targets. Our results are in agreement with the concept that propensity to oxidation is increased by essential hypertension and anti-oxLDL Abs may be protective and potential biomarkers for the follow-up of hypertension treatment.

Anti-oxidized LDL antibody levels are reduced in women with hypertension

BACKGROUND

Previous studies have suggested that hypertension may be associated with increased oxidized low-density lipoprotein (LDL). Increased in vitro oxidizability of LDL or elevated titers of anti-oxidized LDL antibodies have been shown in subjects with essential hypertension. However, the relationship between oxidized LDL and hypertension is equivocal. We examined the association between hypertension and levels of IgG anti-oxidized LDL antibodies in a group of women from the general population.

MATERIALS AND METHODS

The study included 619 women classified according to their blood pressure values. IgG anti-oxidized LDL antibodies were measured by enzyme-linked immunosorbent assay and the women were classified as being above or below the 50th percentile.

RESULTS

Hypertension was present in 54.3% of the women. These women had significantly lower levels of IgG anti-oxidized LDL antibodies than the normotensive women (0.280 +/- 0.117 vs. 0.336 +/- 0.125, P < 0.001). Both systolic and the diastolic blood pressures showed a significant negative correlation with the levels of IgG anti-oxidized LDL antibodies (r = -0.204, P < 0.001; r = -0.225, P < 0.001, respectively). Women with IgG anti-oxidized LDL antibody levels above the 50th percentile had a lower prevalence of hypertension than those with IgG anti-oxidized LDL antibody levels below the 50th percentile (40.2% vs. 59.8%) (P < 0.001).

CONCLUSIONS

Women with hypertension had lower levels of IgG anti-oxidized LDL antibodies than normotensive women.

Hypertensive status and lipoprotein oxidation in an elderly population at high cardiovascular risk

BACKGROUND

In elderly individuals, hypertension is a main risk factor for cardiovascular disease and oxidative damage is increased. Our aim was to assess the relationship between the degree of in vivo low-density lipoprotein (oxLDL) oxidation and the hypertensive status in a elderly population at high cardiovascular risk.

METHODS

Cross-sectional study with baseline data from the PREDIMED (PREvención con DIeta MEDiterránea) trial, an intervention study directed at testing the efficacy of the Mediterranean diet on the primary prevention of cardiovascular disease. Participants were 1,130 subjects at high cardiovascular risk aged 55-80. At baseline, in vivo circulating oxLDL was measured, and stages of hypertension determined according to the USA Joint National Committee guidelines.

RESULTS

A positive relationship between in vivo oxLDL and systolic and diastolic blood pressure (DBP) was observed after adjusting for confounding factors (P < 0.05). OxLDL concentrations increased in a linear manner from low to high hypertensive stages (P < 0.05).

CONCLUSIONS

Elderly individuals at high cardiovascular risk showed higher levels of circulating oxLDL when their hypertensive status increased. This fact identifies the hypertensive elderly population as a target for antioxidant preventive measures.

Beneficial effect of low ethanol intake on the cardiovascular system: possible biochemical mechanisms

Low ethanol intake is known to have a beneficial effect on cardiovascular disease. In cardiovascular disease, insulin resistance leads to altered glucose and lipid metabolism resulting in an increased production of aldehydes, including methylglyoxal. Aldehydes react non-enzymatically with sulfhydryl and amino groups of proteins forming advanced glycation end products (AGEs), altering protein structure and function. These alterations cause endothelial dysfunction with increased cytosolic free calcium, peripheral vascular resistance, and blood pressure. AGEs produce atherogenic effects including oxidative stress, platelet adhesion, inflammation, smooth muscle cell proliferation and modification of lipoproteins. Low ethanol intake attenuates hypertension and atherosclerosis but the mechanism of this effect is not clear. Ethanol at low concentrations is metabolized by low K_m alcohol dehydrogenase and aldehyde dehydrogenase, both reactions resulting in the production of reduced nicotinamide adenine dinucleotide (NADH). This creates a reductive environment, decreasing oxidative stress and secondary production of aldehydes through lipid peroxidation. NADH may also increase the tissue levels of the antioxidants cysteine and glutathione, which bind aldehydes and stimulate methylglyoxal catabolism. Low ethanol improves insulin resistance, increases high-density lipoprotein and stimulates activity of the antioxidant enzyme, paraoxonase. In conclusion, we suggest that chronic low ethanol intake confers its beneficial effect mainly through its ability to increase antioxidant capacity and lower AGEs.

Effects of combination of angiotensin receptor blocker and calcium channel blocker on ox-LDL levels and cardiovascular dysfunction in Dahl rats

In an effort to assess the cardiovascular benefits of combined angiotensin receptor blockage and calcium channel antagonism, we assessed the chronic effects of the angiotensin type 1 receptor blocker candesartan, the calcium channel blocker benidipine, and the use of a combination therapy in Dahl salt-sensitive (DS) rats. DS rats receiving a high salt diet were treated with either benidipine (4 mg/kg), candesartan (1 mg/kg) or both. Rat blood pressure was measured using a tail-cuff method. Following 12 weeks, the effect on heart weight, plasma-oxidized low-density lipoprotein (ox-LDL) level, endothelium-dependent vasorelaxation, and histology of the heart and aorta was assessed. Blood pressure, heart weight and plasma ox-LDL levels increased, while endothelium-dependent vasorelaxation decreased in the DS rats. Candesartan and benidipine inhibited the increase in blood pressure and heart weight, and the decrease in endothelium-dependent vasorelaxation. The use of benidipine alone or a combination significantly inhibited the increase in ox-LDL levels, whereas candesartan alone had no significant effect on ox-LDL levels. The present findings indicate that, if the monotherapy using ARB could not achieve adequate control of blood pressure, the combination therapy with ARB and benidipine provides the additional reductions in hypertension and cardiac hypertrophy. Moreover, the combination therapy inhibits cardiovascular dysfunction and ox-LDL levels more effectively than use of ARB alone. These results contribute to the possibility of lowering ox-LDL levels as a means of enhancing cardiovascular protection.

The association between pre-hypertension status and oxidative stress markers related to atherosclerotic disease: the ATTICA study

BACKGROUND

We sought to evaluate the association between pre-hypertension status and oxidative stress markers (total antioxidant capacity (TAC) and oxidized low density lipoprotein (LDL)), in a random sample of cardiovascular disease-free adults.

METHODS

The ATTICA study is a cross-sectional population-based survey that conducted in Attica region during 2001-2002. Based on a multistage and stratified random sampling, 1514 men and 1528 women (18-89 years old) were enrolled. The survey included a detailed interview; blood samples collected after 12h of fasting and, among other clinical measurements, status of blood pressure levels was evaluated.

RESULTS

Six hundred and fifty-three men (43%) and 535 women (35%) were defined as pre-hypertensives. Both systolic and diastolic blood pressures were inversely correlated with TAC (p<0.001) and positively correlated to oxidized LDL (p<0.001). Particularly, compared to normotensive subjects, pre-hypertensives had 7% lower TAC levels (p<0.001) and 15% higher oxidized LDL levels (p<0.05), after correcting for multiple comparisons and adjusting for age, body mass index, blood lipids, glucose, food groups consumed and other potential confounders.

CONCLUSIONS

Studying a large sample of cardiovascular disease-free adults, we revealed an association of pre-hypertension with oxidative stress markers linking to atherosclerotic process.

Nebivolol decreases oxidative stress in essential hypertensive patients and increases nitric oxide by reducing its oxidative inactivation

OBJECTIVE

To obtain further insight into the mechanism underlying the vasodilator effect of nebivolol. Since oxidative inactivation of nitric oxide (NO) is regarded as an important cause of its decreased biological activity, we studied (1) the effect of nebivolol on some oxidative parameters in essential hypertensive patients; (2) the effect of plasma of nebivolol-treated patients on reactive oxygen species production and NO availability in endothelial cells.

METHODS

A total of 20 healthy subjects and 20 matched essential hypertensive patients treated with atenolol or nebivolol according to a double-blind, randomized design participated in the study. We measured low-density lipoprotein (LDL) and plasma hydroperoxides, 8-isoprostanes, oxidized LDL, susceptibility of LDL to oxidation (lag phase) and LDL vitamin E and the effect of plasma of nebivolol- and atenolol-treated patients on reactive oxygen species production and NO availability in endothelial cells exposed to oxidative stress.

RESULTS

In hypertensive patients, nebivolol and atenolol significantly reduced blood pressure values after 4 weeks of treatment. Plasma and LDL hydroperoxides, plasma 8-isoprostanes, plasma ox-LDL and LDL lag phase were significantly improved only in the patients receiving nebivolol compared with the atenolol group. Similarly there was a reduction of reactive oxygen species (ROS) and O2*- concentration in endothelial cells exposed to oxidative stress after incubation of the cells with plasma of the patients enrolled in the trial only in the patients receiving nebivolol compared to atenolol group. Furthermore, the reduction of basal and stimulated NO induced by oxidative stress in endothelial cells was significantly lower in the patients receiving nebivolol compared to atenolol group.

CONCLUSIONS

The findings of the present study indicate that nebivolol, through its antioxidant properties, increases NO also by decreasing its oxidative inactivation.

Immunomodulation of atherosclerosis: implications for vaccine development

A number of studies have shown activation of the immune system throughout various stages of atherosclerosis. Recent observations have suggested that activation of immune responses may promote atherosclerosis on one hand by inducing and perpetuating arterial inflammation, whereas on the other hand, selective activation of certain immune functions may inhibit atherosclerosis and arterial inflammation. These observations suggest the possibility that selective suppression of proatherogenic immune responses or selective activation of antiatherogenic immune responses may provide new approaches for atherosclerosis prevention and treatment. Several antigens activating immune responses affecting development of atherosclerosis have been identified. These immune responses may be modulated by presenting the antigens together with different types of adjuvants as well as through the route of administration. In this review, we summarize recent experimental studies using immunomodulatory approaches for treatment of atherosclerosis.

Sulfhydryl angiotensin-converting enzyme inhibition induces sustained reduction of systemic oxidative stress and improves the nitric oxide pathway in patients with essential hypertension

BACKGROUND

Essential hypertension is associated with enhanced LDL oxidation and impaired endothelium-dependent vasodilation. The antioxidant status is linked to the nitric oxide (NO) pathway. Sulfhydryl angiotensin-converting enzyme (ACE) inhibitors inhibit oxidative stress and atherogenesis in experimental models; therefore we tested whether this beneficial antioxidant activity could be also clinically relevant in patients with essential hypertension.

METHODS

Plasma LDL oxidizability was investigated initially in untreated normocholesterolemic patients with moderate essential hypertension without clinically evident target organ damage (n = 96) and in control normotensive subjects (n = 46). Patients were then randomly assigned into two age- and sex-matched groups to receive the new sulfhydryl ACE inhibitor zofenopril (15 to 30 mg/d; n = 48) or enalapril (20 mg/d, n = 48). LDL oxidizability was evaluated (generation of malondialdehyde, MDA) and systemic oxidative stress was evaluated by isoprostanes (8-isoPGF2alpha). Asymmetrical dimethyl-L-arginine (ADMA), a competitive inhibitor of endothelial NO synthase, and plasma nitrite and nitrates (NOx) were also measured.

RESULTS

LDL from hypertensive subjects had enhanced susceptibility to oxidation in vitro compared with that in control subjects (P <.05). Similarly, isoprostanes were significantly increased (P <.01) in hypertensive subjects versus control subjects. After 12-week treatment, MDA levels were significantly reduced by zofenopril (P <.05) but not enalapril treatment (P = not significant). Isoprostanes were normalized after zofenopril treatment (P <.03), whereas enalapril was ineffective. After treatment with both ACE inhibitors, plasma NOx concentrations were significantly reduced (P <.05). Similarly, hypertension increased ADMA concentration compared with the normotensive state, whereas ACE inihibition elicited a significant decrease. However, the reduction of ADMA concentration was significantly higher in patients receiving sulfhydryl ACE inhibition (P <.05 vs enalapril).

CONCLUSIONS

The sulfhydryl ACE inhibitor zofenopril reduces oxidative stress and improves the NO pathway in patients with essential hypertension. If confirmed in a large multicenter clinical trial, our data suggest a possible vasculoprotective effect of the compound in retarding vascular dysfunction and atherogenesis that often develops rapidly in hypertensive patients.

Platelet aggregation, blood viscosity and serum lipids in hypertensive and obese children

A group of 35 patients (median age 15.5 years, range 8-17 years) with juvenile essential hypertension, 15 with body mass index (BMI kg/m(2)) <25 and 20 with BMI >25, as well as 35 age and sex matched controls (BMI <25 n=20; BMI >25 n=15) were investigated to study the role of hypertension and obesity, separately and in combination, on in vitro platelet aggregation, blood and plasma viscosity, plasma lipid concentrations and lipid peroxidation as well as nitric oxide (NO) production. Obese children (hypertensive and controls) had significantly higher concentrations of total cholesterol and triglycerides. The levels of high density lipoprotein (HDL)-cholesterol were lower in obese hypertensive children than their non-obese counterparts. There was a significant increase in platelet aggregation and a decrease in NO levels in hypertensive patients (obese and non-obese) reflecting a significant negative correlation (r=-0.553 and -0.530, n=35; P<0.01, respectively). However, an increased tendency to aggregation was also evident in obese normotensive patients. A significant positive correlation was observed between the platelet aggregation and BMI (r=0.501, n=35; P<0.01). Plasma free thiols were decreased in hypertensive children independent of their BMI. An increased lipid peroxidation and higher blood and plasma viscosity were found only in obese patients with hypertension. Multivariate analysis revealed significant interactions in the effects of obesity and hypertension on platelet aggregation and thiol oxidation.

CONCLUSION

in obese children an increased platelet aggregation and oxidative insult contribute to the development of hypertension and to the promotion of vascular damage.

Lipoprotein oxidation and plasma vitamin E in nondiabetic normotensive obese patients

OBJECTIVE

To correlate the susceptibility of low-(LDL) and very-low-density lipoprotein to oxidation in vitro and the concentrations of serum antibodies against malondialdehyde-modified LDL and plasma vitamin E with the anthropometric and laboratory characteristics of obesity.

RESEARCH METHODS AND PROCEDURES

A total of 75 nondiabetic, normotensive obese patients were assigned to one of four groups according to their body mass index (BMI): moderately obese (30 <or= BMI <or= 34.9 kg/m(2), n = 11), severely obese (35 <or= BMI <or= 39.9 kg/m(2), n = 20), morbidly obese (40 <or= BMI <or= 50 kg/m(2), n = 29), and very severely obese (BMI > 50 kg/m(2), n = 15).

RESULTS

The oxidation lag time for LDL from patients with a BMI >or=35 kg/m(2) was shorter than that for LDL from non-obese controls (n = 13), whereas very-low-density lipoprotein oxidation lag times were not significantly different. The serum antibodies against modified LDL were similar in all groups, whereas the plasma vitamin E concentrations of obese patients were decreased (p <or= 0.01). There was a negative correlation between LDL oxidation lag time and BMI (r = -0.35, p = 0.0008), and between plasma vitamin E and BMI (r = -0.53, p < 0.0001) and waist-to-hip ratio (r = -0.40, p = 0.0003).

DISCUSSION

The LDL of nondiabetic, normotensive obese patients is more readily oxidized, and plasma vitamin E concentrations are low. These are both risk factors for coronary heart disease.

[Atherosclerosis and anti-oxidized low density lipoprotein antibodies in an elderly population]

BACKGROUND

Antibodies to oxidized LDL (anti-OxLDL) have been found to be associated with atherosclerosis. The aim of the study was to evaluate the relationship between anti-OxLDL antibodies and atherosclerosis in the elderly.

PATIENTS AND METHOD

We studied several risk factors and different clinical manifestations of atherosclerosis in 100 people older than 65 years and in 48 healthy blood donor controls (age range: 20 to 55 years). Anti-OxLDL antibodies were measured by ELISA.

RESULTS

Thirty-one percent of the patients tested positive for anti-OxLDL. This percentage increased in the group of subjects without any risk factor or clinical manifestation (66.6%) as it was the case of the mean optical density (O.D.) value (O.D. = 0.671 vs. 0.357 in our general geriatric population). Most of those with a proven atherosclerotic event tested negative for anti-OxLDL antibodies and a statistically significant difference was shown for those with a calcified aortic arch (P = 0.041, 95% CI 0.15-0.97). Mean value of risk factors and clinical manifestations was 3.50 among anti-OxLDL-negative patients, whereas it was 2.51 in the anti-OxLDL-positive group (P = 0.035, 95% CI 0.07-1.91). Actually, when more adverse effects were present, patients' trend to test negative for anti-OxLDL antibodies was higher. An inverse correlation was observed between anti-OxLDL titers and the relative risk of coronary heart disease (P = 0.020).

CONCLUSIONS

The cause of the decrease of free anti-OxLDL antibodies in situations that lead to an oxidative stress is unknown but it may be explained by the formation of immunocomplexes in an effort to ease the clearance of oxidized substrates.

Nutrition, antioxidants, and risk factor profile of nonsmokers, passive smokers and smokers of the Prevention Education Program (PEP) in Nuremberg, Germany

BACKGROUND

An elevated risk for coronary artery disease and lung cancer was reported for smokers and nonsmokers exposed to environmental tobacco smoke. Particularly in nonsmokers, in addition to the adverse effects of tobacco smoke, other factors which are associated with the exposure to environmental tobacco smoke may contribute to the health risks. We investigated both by questionnaires and biochemical analyses whether smokers influence the dietary habits of nonsmokers living in the same household.

METHODS

The study population was a subgroup of the Prevention Education Program in Nuremberg: 817 adults aged 27-66 years were allocated to one of the four groups: Nonsmokers living with a nonsmoker (Group 1), nonsmokers living with a smoker (Group 2), smokers living with a nonsmoker (Group 3), and smokers living with a smoker (Group 4).

RESULTS

The four groups did not differ in the body mass index, the concentration of lycopene, all-trans-retinol, and selenium in plasma. Plasma concentrations of high-density lipoprotein cholesterol, triglycerides, homocysteine, cobalamin, folate, beta-carotene, and alpha-tocopherol showed a gradient to unfavorable levels from Group 1 to Group 4. This trend was also reflected in the reported dietary intake of beta-carotene, alpha-tocopherol, ascorbic acid, fiber, and linoleic acid.

CONCLUSIONS

Our data show that nonsmokers living with smokers indulge in less healthy dietary habits than nonsmokers living with nonsmokers. This has to be considered when evaluating the health risks of exposure to environmental tobacco smoke.

Lipid-lowering therapy with fluvastatin inhibits oxidative modification of low density lipoprotein and improves vascular endothelial function in hypercholesterolemic patients

This prospective randomized trial was designed to elucidate clinically the effect of fluvastatin on inhibiting oxidation of the low density lipoprotein (LDL) and improving the vascular endothelial function as well as its lipid-lowering effects, in comparison with pravastatin. Of 64 consecutive dyslipidemic patients, 40 patients, whose level of total cholesterol or LDL-cholesterol maintained the criteria of the hypercholesterolemia in spite of 12-week dietary therapy, were randomly assigned to receive either fluvastatin (n=20) or pravastatin (n=20). We assessed the titer of antibody against oxidized LDL (anti-Ox-LDL) as a biomarker for LDL-oxidation, and the forearm blood flow response during reactive hyperemia by venous occlusion plethysmography, which indicates the endothelium-dependent vasodilator capacity. After the 16-week lipid-lowering therapy, the anti-Ox-LDL titer significantly decreased in the fluvastatin group (P<0.01) but did not change in the pravastatin group. The percent increase in the forearm blood flow at the peak reactive hyperemia from the baseline value (%RH) significantly increased in the fluvastatin group (P<0.001) but did not change in the pravastatin group. The ratio of the %RH after the therapy over the baseline value negatively correlated with that of the anti-Ox-LDL titer (R=0.73, P<0.001) in all patients. Fluvastatin may serve as an ideal drug for reducing the risk of atherosclerosis, not only by its cholesterol-lowering effect but also by its unique effects of inhibiting LDL oxidation and improving the vascular endothelial function.

Effective blood pressure treatment improves LDL-cholesterol susceptibility to oxidation in patients with essential hypertension

OBJECTIVES

LDL-cholesterol particles from hypertensive patients exhibit enhanced susceptibility to in vitro oxidation, an abnormality thought to increase cardiovascular risk. We tested whether blood pressure (BP) normalization can reverse this abnormality.

DESIGN

Double-blind, randomized pharmacological intervention trial.

SETTING

Clinical research centre. Subjects. A total of 29 nondiabetic, normolipidaemic patients with essential hypertension (BP= 151 +/- 3/99 +/- 1 mmHg) and 11 normotensive controls (BP=125 +/- 3/85 +/- 1 mmHg) matched for gender, age, obesity, glucose tolerance and lipid profile. Intervention. Anti-hypertensive treatment for 3 months with a calcium-antagonist in randomized combination with either an ACE inhibitor or a beta-blocker.

MAIN OUTCOME MEASURES

Lag phase of copper-induced LDL oxidation, cell-mediated (human umbilical vein endothelium) generation of malondialdehyde (MDA) by LDL and vitamin E content in LDL.

RESULTS

At baseline in hypertensives versus controls, lag phase was shorter (89 +/- 3 vs. 107 +/- 6 min, P < 0.04), MDA generation was higher (5.8 +/- 0.1 vs. 5.1 +/- 0.2 nmol L(-1), P=0.002), and vitamin E was reduced (6.40 +/- 0.05 vs. 6.67 +/- 0.11 microg mg(-1), P=0.03). At 3 months, BP was normalized (124 +/- 3/81 +/- 1, P < 0.0001 vs. baseline, P=ns versus controls), lag phase was prolonged (to 98 +/- 3 min, P=0.0005), MDA generation was reduced (5.6 +/- 0.1 nmol L-1, P = 0.001), and vitamin E was increased (6.53 +/- 0.05 microg mg(-1), P=0.003), with no significant differences between the randomized groups.

CONCLUSIONS

In nondiabetic, nonobese, normolipidaemic patients with essential hypertension, LDL susceptibility to copper- and cell-mediated oxidation is increased. BP normalization is associated with a significant improvement, but not a full reversal, of this abnormality.

Effect of calcium antagonist or beta blockade treatment on nitric oxide-dependent vasodilation and oxidative stress in essential hypertensive patients

OBJECTIVES

Essential hypertension is associated with impaired endothelium-dependent vasodilation caused by oxygen free radical-induced nitric oxide (NO) breakdown. Since calcium antagonists can improve endothelial function in hypertensive patients, we tested whether this beneficial effect could be related to restoration of NO availability by antioxidant activity.

METHODS

In 10 healthy subjects and 20 essential hypertensive patients, we studied forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (from 0.15-15 microg/100 ml per min), bradykinin (0.005-0.05 microg/100 ml per min), two endothelium-dependent vasodilators, and sodium nitroprusside (1-4 microg/100 ml forearm tissue per min), an endothelium independent vasodilator, in the absence and presence of NG-monomethyl-L-arginine (L-NMMA) (100 microg/100 ml forearm tissue per min), an NO synthase inhibitor.

RESULTS

In controls, vasodilation to acetylcholine and bradykinin was inhibited by L-NMMA. In hypertensive patients, vasodilation to acetylcholine and bradykinin, but not to sodium nitroprusside, was blunted and resistant to L-NMMA. Hypertensive patients were randomized to a 12-week treatment with lacidipine (4-6 mg/daily) or atenolol (50-100 mg/daily) (n = 10 each group). Lacidipine but not atenolol increased the vasodilation to acetylcholine and bradykinin and restored the inhibiting effect of L-NMMA on endothelium-dependent vasodilation, without affecting the response to sodium nitroprusside. Moreover, lacidipine reduced circulating markers of oxidative stress including plasma and low-density lipoprotein (LDL) hydroperoxides, the susceptibility of LDL to Cu2+-induced oxidation and the reactive oxygen species generated from human umbilical vein endothelial cells after incubation with LDL derived from plasma of the patients.

CONCLUSIONS

Lacidipine increases endothelium-dependent vasodilation by restoring NO availability, and this effect possibly is related to antioxidant activity.

Consumption of flavonoids in onions and black tea: lack of effect on F2-isoprostanes and autoantibodies to oxidized LDL in healthy humans

BACKGROUND

Oxidative damage to lipids in vivo may be involved in the development of atherosclerosis and cancer. Onions and black tea are foods rich in flavonoids, predominantly the flavonoid quercetin, which is a potent in vitro inhibitor of membrane lipid peroxidation and LDL oxidation.

OBJECTIVE

Our objective was to investigate the effects of consuming a high-flavonoid (HF) diet enriched with onions and black tea on indexes of oxidative damage in vivo compared with a low-flavonoid (LF) diet.

DESIGN

Thirty-two healthy humans were studied in a randomized crossover design. Indexes of oxidative damage used were plasma F2-isoprostanes (a biomarker of lipid peroxidation in vivo) and the titer of antibodies to malondialdehyde (MDA)-modified LDL.

RESULTS

There were no significant differences in the intake of macronutrients or assessed micronutrients, plasma F2-isoprostane concentrations, and MDA-LDL autoantibody titer between the HF and LF dietary treatments. In the men, however, plasma concentrations of the F2-isoprostane 8-epi-prostaglandin F2alpha were slightly higher after the HF treatment phase than after the LF treatment [0.31 +/- 0.029 nmol/L (111 +/- 10.4 ng/L) compared with 0.26 +/- 0.022 nmol/L (92 +/- 7.8 ng/L); P = 0.041]. In all subjects, plasma quercetin concentrations were significantly higher after the HF treatment phase than after the LF treatment: 221.6 +/- 37.4 nmol/L compared with less than the limit of detection of 66.2 nmol/L.

CONCLUSION

Flavonoid consumption in onions and tea had no significant effect on plasma F2-isoprostane concentrations and MDA-LDL autoantibody titer in this study and thus does not seem to inhibit lipid peroxidation in humans.

Immunological response to oxidized LDL occurs in association with oxidative DNA damage independently of serum LDL concentrations in dyslipidemic patients

Oxidative modification of LDL induces immunogenic epitopes in the LDL molecule, and the presence of antibodies against oxidized LDL (anti-Ox-LDL) has been demonstrated in human sera. However, little is known about the clinical significance of anti-Ox-LDL. To elucidate a clinical relationship between the immunological response to oxidized LDL and cellular oxidative stress, we measured serum titers of anti-Ox-LDL in 45 unselected patients with hypercholesterolemia and serum 8-hydroxy-2'-deoxyguanosine (8-OHdG), considered a biomarker of the oxidative damage to DNA. The anti-Ox-LDL titer was not correlated with the serum LDL-C concentration, but was correlated with the 8-OHdG concentration (r = 0.300, P < 0.05) in a simple linear regression. Multiple regression analysis indicated that 8-OHdG was independently correlated with anti-Ox-LDL (r = 0.429, P < 0.05), but no other variables, including LDL-C concentrations and smoking habit, were correlated with anti-Ox-LDL. In 16 subgroup patients, the concentrations of TC, TG and LDL-C decreased and the HDL-C concentration increased after cholesterol-lowering therapy with fluvastatin. In addition, both the anti-Ox LDL titer (14.0 +/- 9.5 to 11.4 +/- 6.6 AcU/ml, P < 0.05) and the 8-OHdG concentration (1.19 +/- 0.41 to 0.85 +/- 0.43 ng/ml, P < 0.05) also decreased after fluvastatin therapy. The immunological response to LDL oxidation on vascular wall tissues or cells appear to occur in association with oxidative DNA damage. The measurement of anti-Ox-LDL may be a useful indicator for lipid-lowering therapy.

Increased arterial intima-media thickness and in vivo LDL oxidation in young men with borderline hypertension

We used borderline hypertension as a model for prehypertension to examine the early influences of elevated blood pressure on subclinical atherosclerosis, lipoprotein oxidation, and cardiac adaptation. Healthy men (age 37+/-4 years) were classified prospectively into 2 groups on the basis of having either borderline hypertension (systolic 130 to 140 mm Hg or diastolic 85 to 89 mm Hg, n=16) or normal (<130/85 mm Hg, n=22) blood pressure values during the previous 2 years. The groups were matched for age, body size, and serum cholesterol levels. High-resolution ultrasound was used to measure intima-media thickness (IMT) of the carotid and brachial arteries, cardiac dimensions, and brachial artery endothelial function. Baseline low-density lipoprotein (LDL)-diene conjugation was measured as an estimate of in vivo LDL oxidation (ox-LDL). Compared with normotensive controls, men with borderline hypertension had higher IMT of the carotid artery (0.58+/-0.06 versus 0.75+/-0.07 mm, P<0.001) and IMT of the brachial artery (0.45+/-0.05 versus 0.57+/-0.07 mm, P<0.001), and increased levels of ox-LDL (29+/-9 versus 47+/-17 mol/L, P<0.001), but similar endothelial function. Left ventricular mass was similar in both groups, but there were significant differences in left ventricular geometry. In multivariate analyses, the predictors of carotid IMT were 24-hour systolic blood pressure (P<0.001) and ox-LDL (P=0.10). The current study demonstrates evidence of increased subclinical atherosclerosis and ox-LDL in borderline hypertension. These results are consistent with the idea that enhanced ox-LDL may be one of the pathophysiological events related to development of atherosclerosis in men with borderline elevated blood pressure.

Antioxidants and vitamins to reduce cardiovascular disease

Cardiovascular disease is the leading cause of morbidity and mortality in Western populations. Several lines of evidence support the role of oxidative stress in atherogenesis. Dietary micronutrients with antioxidant properties and vitamins have also been shown to have a benefit with regards to cardiovascular disease. The most persuasive evidence relates to alpha tocopherol and folate and vitamin B(12). Although the evidence is mounting for supplementation with alpha tocopherol and folate and B(12) for secondary prevention of cardiovascular disease, no clear consensus can be reached for primary prevention of cardiovascular disease. This will have to await results of ongoing clinical trials.

Analysis of process impurities in the basic drug SB-253149 using capillary electrophoresis and on-line mass spectrometric detection

Capillary electrophoresis with on-line electrospray ionisation mass spectrometry (CE/ESI-MS) has been used to identify process impurities in a batch of the anti-atherosclerotic drug, SB-253149. The impurities were separated from the main drug compound by capillary electrophoresis (CE) using an ammonium formate buffer at low pH in an untreated fused silica capillary. The CE method was initially developed using UV as the detection mode and then later structural elucidation work was achieved using an ion trap mass spectrometer. To maintain peak resolution and peak shape when the CE system was coupled to the mass spectrometer, a modified capillary cassette linked to a coaxial sheath flow electrospray ionisation (ESI) interface was used. By performing MS/MS experiments in conjunction with chemical knowledge of the reactivities of SB-253149, it was possible to propose molecular structures for impurities detected in the batch of SB-253149. The results from this study revealed that most of the process impurities in SB-253149 were dimeric derivatives of the parent molecule as well as trace levels of the starting material. This type of information was vital in process control and optimisation for the synthetic route for this drug.

Evidence that acute insulin administration enhances LDL cholesterol susceptibility to oxidation in healthy humans

Increased free radical production and hyperinsulinemia are thought to play a role in experimental and human atherosclerosis, but the relation between the 2 abnormalities has not been studied. In 23 healthy volunteers, we measured the susceptibility of circulating low-density lipoprotein (LDL) cholesterol particles to in vitro copper sulfate oxidation (measured as the lag phase) and cell-mediated oxidative modification (measured as malondialdehyde generation in LDL during incubation with human umbilical vein endothelial cells), as well as the vitamin E content of LDL cholesterol at baseline and after 2 hours of physiological hyperinsulinemia (euglycemic insulin clamp). The lag time of LDL oxidation decreased from control values of 108+/-3 and 107+/-3 minutes (at baseline and after 2 hours of saline infusion) to 101+/-3 minutes after 2 hours of clamping (P<0.0001). At corresponding times, cell-mediated malondialdehyde generation in LDL rose from 4.96+/-0.11 and 4.98+/-0.10 to 5.28+/-0.10 nmol/L (P=0. 0006), whereas the LDL vitamin E content decreased from 6.78+/-0.06 and 6.77+/-0.06 to 6.64+/-0.06 microg/mg (P<0.04). The insulin-induced shortening of the lag phase was directly related to the decrement of vitamin E in LDL; furthermore, in subjects with higher baseline serum triglyceride levels, insulin induced a greater shortening of the lag phase than in subjects with low baseline triglycerides. We conclude that in healthy humans acute physiological hyperinsulinemia enhances the oxidative susceptibility of LDL cholesterol particles. This effect may have pathogenic significance for atherogenesis in insulin resistant states.

Serum and placental lipid peroxides in chronic hypertension during pregnancy with and without superimposed preeclampsia

OBJECTIVE

To evaluate the circulating levels of lipid peroxides and vitamin E, and the placental levels of lipid peroxides in chronic hypertensive pregnant women, with and without superimposed preeclampsia, as compared to controls and women with primary preeclampsia.

METHODS

Lipid peroxides were measured in serum and placenta by the thiobarbituric acid method and high-pressure liquid chromatography (HPLC), and vitamin E by HPLC. Patients were 36 healthy pregnant women, 34 previously nonhypertensive women diagnosed with preeclampsia, 20 women with uncomplicated chronic hypertension, and 11 women with chronic hypertension complicated by superimposed preeclampsia.

RESULTS

Lipid peroxides in serum and placental tissue were significantly increased, and vitamin E levels in serum were significantly decreased in women with primary preeclampsia and superimposed preeclampsia, as compared to controls. The group of uncomplicated chronic hypertension presented with similar values of lipid peroxides and vitamin E to controls.

CONCLUSIONS

Our results support the clinical assumption that chronic hypertension aggravated by the development of proteinuria represents a superimposed condition associated with placental disease. The data further support the concept that increased lipid peroxides are not merely associated with the presence of hypertension in pregnancy, but they are implicated in the pathophysiology of preeclampsia.

Automated high-performance liquid chromatographic method with precolumn reduction for the determination of ubiquinol and ubiquinone in human plasma

We developed a gradient HPLC method with automated precolumn reduction for direct electrochemical detection of ubiquinol-10 (CoQ10H2) and total coenzyme Q10 (TQ10) in human plasma. The concentration of ubiquinone-10 (CoQ10) was calculated by subtraction of CoQ10H2 from TQ10. Preparation of reducing agent and precolumn reduction was performed by a programmable auto-injector. The two mobile phases used were: A, 100% of methanol containing 50 mM sodium perchlorate and 10 mM perchloric acid; and B, a mixture of ethanol and tert.-butanol (80:20, v/v). Sample preparation was simply a deproteinisation process with 10-fold ethanol. A good linear relationship was obtained for CoQ10H2 concentration from 0.1 to 3 micromol/l. The detection limit was 2.5 nmol/l with an injection volume of 20 microl. The analytical recovery and reproduciblity were generally >90%. To validate the method, 18 freshly collected plasma samples of normal healthy subjects were analysed. The mean ratio of CoQ10H2/CoQ10 was 93:7. The proposed method is sensitive, reliable and can be used for clinical investigation.

Abnormal flow-mediated epicardial vasomotion in human coronary arteries is improved by angiotensin-converting enzyme inhibition: a potential role of bradykinin

OBJECTIVES

This study was performed to determine whether angiotensin converting enzyme (ACE) inhibition improves endothelium-dependent flow-mediated vasodilation in patients with atherosclerosis or its risk factors and whether this is mediated by enhanced bradykinin activity.

BACKGROUND

Abnormal coronary vasomotion due to endothelial dysfunction contributes to myocardial ischemia in patients with atherosclerosis, and its reversal may have an antiischemic action. Previous studies have shown that ACE inhibition improves coronary endothelial responses to acetylcholine, but whether this is accompanied by improved responses to shear stress remains unknown.

METHODS

In 19 patients with mild atherosclerosis, metabolic vasodilation was assessed during cardiac pacing. Pacing was repeated during separate intracoronary infusions of low-dose bradykinin (BK) and enalaprilat. Endothelium-dependent and -independent vasodilation was estimated with intracoronary BK and sodium nitroprusside respectively.

RESULTS

Enalaprilat did not alter either resting coronary vascular tone or dilation with sodium nitroprusside, but potentiated BK-mediated dilation. Epicardial segments that constricted abnormally with pacing (-5+/-1%) dilated (3+/-2%) with pacing in the presence of enalaprilat (p = 0.002). Similarly, BK at a concentration (62.5 ng/min) that did not alter resting diameter in the constricting segments also improved the abnormal response to a 6+/-1% dilation (p < 0.001). Cardiac pacing-induced reduction in coronary vascular resistance of 27+/-4% (p < 0.001) remained unchanged after enalaprilat.

CONCLUSIONS

Thus ACE inhibition: A) selectively improved endothelium-dependent but not-independent dilation, and B) abolished abnormal flow-mediated epicardial vasomotion in patients with endothelial dysfunction, in part, by increasing endogenous BK activity.

Molecular mechanisms of the copper dependent oxidation of low-density lipoprotein

There is little doubt that oxidative modification of low-density lipoprotein (LDL) is an important process during atherogenesis. This conclusion has been derived in a relatively short period of time since the initial descriptions of LDL oxidation with a significant contribution from Professor Esterbauer and colleagues. In this short overview, we have described the mechanisms by which copper promotes LDL oxidation focussing on the importance of lipid hydroperoxides in this process. These mechanisms are discussed in the context of the ongoing debate as to relevance of metal dependent LDL oxidation in vivo and as a model reaction for assessing antioxidants.

Plasma ubiquinol-10 as a marker for disease: is the assay worthwhile?

Ubiquinol-10 and ubiquinone-10 were measured in plasma of patients with several pathologies known to be associated with increased oxidative stress. Plasma ubiquinol-10, expressed as a percentage of total ubiquinol-10 + ubiquinone-10, was found to be significantly lower in hyperlipidaemic patients and in patients with liver diseases than in age-matched control subjects. In contrast, no decrease in ubiquinol-10 was detected in plasma of patients with coronary heart disease and Alzheimer's disease. Except for ubiquinol-10, no other lipophilic antioxidant was found to be decreased in patients with liver diseases. These data suggest that the level of ubiquinol-10 in human plasma may serve as a marker for liver dysfunction, reflecting its diminished reduction by the liver rather than increased consumption by oxidants.

Cu(I) availability paradoxically antagonizes antioxidant consumption and lipid peroxidation during the initiation phase of copper-induced LDL oxidation

The incubation of isolated human low-density lipoprotein (LDL) with Cu(II) promoted extensive oxidation of both the lipid and protein moieties of the lipoprotein particle. When the Cu(II) to LDL molar ratio was equal or higher than 50, the removal of Cu(I) formed by the contemporary presence of the Cu(I) chelator bathocuproine disulphonate (BC) markedly accelerated the formation of end-products of lipid peroxidation. Moreover, the initial rate of Cu(II)-induced consumption of either endogenous antioxidants in LDL or free alpha-tocopherol in suspension was increased in the presence of BC, thus indicating that the continuous removal of Cu(I) enhanced both antioxidant consumption and LDL oxidation promoted by copper. Furthermore, the direct addition of Cu(I), together with Cu(II), to a suspension of isolated LDL efficiently delayed the onset of extensive lipid peroxidation and decreased the rate of antioxidant consumption. The latter effect, however, was detectable exclusively on LDL-associated alpha-tocopherol and not on alpha-tocopherol in suspension, thus suggesting that the competition between Cu(I) and Cu(II) was taking place at discrete sites associated with the LDL particle. Finally, the inclusion of Cu(I) in the incubation medium of LDL already undergoing extensive peroxidation did not inhibit but rather markedly stimulated the rate of peroxidation. Although apparently in contrast with the common view that Cu(I) and not Cu(II) is the real trigger species of LDL oxidation in the copper model, the results reported here indicate that the availability of Cu(I) during the initiation phase of LDL oxidation promoted by copper antagonizes both antioxidant consumption and the onset of extensive oxidation.

Different mechanisms are progressively recruited to promote Cu(II) reduction by isolated human low-density lipoprotein undergoing oxidation

The kinetics of Cu(II) reduction and its relationship to the process of low density lipoprotein (LDL) oxidation were investigated in isolated human LDL incubated with CuSO4 by using the Cu(I) chelator and indicator dye bathocuproine disulfonate (BC). The inclusion of BC in the incubation medium containing isolated LDL and different concentrations of CuSO4 revealed a biphasic kinetics of Cu(II) reduction consisting of an early phase followed by a plateau phase and a subsequent extensive reduction phase. The amount of Cu(I) formed during the early phase, as well as the rate of its generation, were strictly dependent on both the level of Cu(II) available (saturation was observed at 20 and 50 microM CuSO4) and the concentration of alpha-tocopherol within native LDL particles. Artificial enrichment of LDL with different concentrations of alpha-tocopherol led to a parallel increase of both the amount of Cu(II) reduced and the rate of reduction. The late phase of Cu(II) reduction was strictly related to the availability of copper but was largely independent from alpha-tocopherol. Neither the amount of Cu(I) generated nor the rate of generation were saturated at concentrations of copper up to 100 microM. Comparable results were obtained by adding BC at different time-points to the LDL-copper mixture, in order to measure at the same time-points both the true rate of Cu(II) reduction and the generation of TBARS during the dynamic process of LDL oxidation. The rate of Cu(II) reduction was already high during the lag-phase of the LDL oxidation profile and progressively decreased as alpha-tocopherol concentration decreased. The subsequent increase in the rate of Cu(II) reduction paralleled the formation of TBARS during the extensive LDL oxidation phase. These results suggest that different mechanisms of Cu(II) reduction, namely alpha-tocopherol-dependent and independent (likely lipid peroxide-dependent), are progressively recruited during copper-promoted LDL oxidation.

Low-density lipoprotein oxidation and vitamins E and C in sustained and white-coat hypertension

Low-density lipoprotein oxidation and antioxidant vitamins E and C were investigated in white-coat hypertension in comparison with sustained hypertension and normotension. We selected 21 sustained hypertensive subjects, 21 white-coat hypertensive subjects, and 21 normotensive subjects matched for gender, age, and body mass index. White-coat hypertension was defined as clinical hypertension and daytime ambulatory blood pressure <139/90 (subjects were also reclassified using 134/90 and 135/85 mm Hg as cutoff points for daytime blood pressure). Blood samples were drawn for lipid profile determination, assessment of fluorescent products of lipid peroxidation in native LDL, evaluation of susceptibility to LDL oxidation in vitro (lag phase and propagation rate), and determination of LDL vitamin E and plasma vitamins E and C contents. Compared with sustained hypertensive subjects, white-coat hypertensives had significantly lower fluorescent products of lipid peroxidation (15.4+/-3.4 versus 10.2+/-3 units of relative fluorescence/mg LDL protein, P<.05), longer lag phase (54+/-10 versus 88+/-10 minutes, P<.05), lower propagation rate (8.2+/-2.5 versus 5.95+/-2.1 nmol diene/min per mg LDL cholesterol, P<.05), higher LDL vitamin E content (8.3+/-1.1 versus 10.1+/-1.8 nmol/mg LDL cholesterol, P<.05), and plasma vitamin C content (40+/-13 versus 57+9 micromol/L, P<. 05). No significant difference was observed between white-coat hypertensive and normotensive subjects. The results did not change after reclassification of subjects. Our data show that white-coat hypertensive subjects do not show an enhanced propensity to LDL oxidation or reduction in antioxidant vitamins. Given the role of LDL oxidation in the development of atherosclerosis and that of vitamin E and C in protecting against it, these findings suggest that white-coat hypertension per se carries a low atherogenic risk.

In search of biological markers of high-risk carotid artery atherosclerotic plaque: enhanced LDL oxidation

The oxidation of low density lipoprotein (LDL) is a key event in the development and progression of atherosclerosis because it generates molecular epitopes that are more atherogenic than parent LDL. We found previously that patients with carotid atherosclerosis have a significantly higher titer of autoantibodies against oxidatively modified LDL than normal subjects. The aim of this study is to correlate biological markers of in vivo LDL oxidation with the degree of carotid stenosis and of plaque ulceration (PU) in a series of patients undergoing carotid endoarteriectomy (CEA). Ninety-four consecutive patients (68M and 26F, aged 67.3 +/- 8.2 years) who underwent CEA at our institution between June 1993 and January 1994 were included in the study. The degree of carotid stenosis and the presence and extent of PU were correlated with the level of autoantibodies (IgG) against oxidatively modified LDL (Cu++-oxidized [oxLDL] or malondialdehyde derivatized LDL [MDA-LDL]), that consistently mirrors the occurrence of oxidative modifications in vivo. A statistically significant correlation (r = 0.23, p = 0.039) was found between the degree of carotid stenosis and antiMDA-LDL specific ratio (a parameter that describes the specificity of LDL towards other proteins as target for oxidative modification). A statistically significant correlation was also found between the PU score and antioxLDL IgG (r = 0.32, p = 0.011), antiMDA-LDL IgG (r = 0.25, p = 0.045) and antiMDA-LDL IgG specific ratio (r = 0.38, p = 0.002). None of the classical biochemical parameters (total, LDL and HDL cholesterol and triglycerides) correlated with the above-mentioned plaque characteristics. The results shown, support the use of biological markers of in vivo LDL oxidation (antioxidatively modified LDL autoantibody titers) to evaluate the clinical setting of high-risk carotid atherosclerosis both in screening and in follow-up studies.

Low-density lipoprotein and oxidised low-density lipoprotein: their role in the development of atherosclerosis

Oxidation of low-density lipoprotein (LDL) may be implicated in the development of atherosclerotic disease. Oxidised LDL is taken up more readily by monocyte-derived macrophages than LDL. Antibodies to oxidised LDL are found in atherosclerotic lesions, Increased risk of ischaemic heart disease is associated with a preponderance of small dense LDL particles, which are more susceptible to oxidation. Proatherogenic alterations in cell biochemistry and signalling pathways occur in the presence of LDL and more markedly oxidised LDL. In vitro antioxidants inhibit changes in cell biochemistry, while in vivo, they have been shown to attenuate or reverse development of atherosclerosis.

Dose-response comparison of RRR-alpha-tocopherol and all-racemic alpha-tocopherol on LDL oxidation

Much data have accrued in support of the concept that oxidation of LDL is a key early step in atherogenesis. The most consistent data with respect to micronutrient antioxidants and atherosclerosis appear to relate to alpha-tocopherol (AT), the predominant lipid-soluble antioxidant in LDL. There are scant data on the direct comparison of RRR-AT and all-racemic (rac)-AT on LDL oxidizability. Hence, the aim of the present study was to examine the relative effects of RRR-AT and all-rac-AT on plasma antioxidant levels and LDL oxidation in healthy persons in a dose-response study. The effect of RRR-AT and all-rac-AT at doses of 100, 200, 400, and 800 IU/d on plasma and LDL AT levels and LDL oxidation was tested in a randomized, placebo-controlled study of 79 healthy subjects. Copper-catalyzed oxidation of LDL was monitored by measuring the formation of conjugated dienes and lipid peroxides over an 8-hour time course at baseline and again after 8 weeks. Plasma AT, lipid-standardized AT, and LDL AT levels rose in a dose-dependent fashion in both the RRR-AT and all-rac-AT groups compared with baseline. There were no significant differences in plasma, lipid-standardized, and LDL AT levels between RRR-AT and all-rac-AT supplementation at any dose comparison. The lag phases of oxidation were significantly prolonged with doses > or = 400 IU/d of RRR-AT and all-rac-AT, as measured by conjugated-dienes assay and at 400 IU/d of RRR-AT and 800 IU/d of both forms of AT by lipid peroxide assay. Again, there were no significant differences in the lag phase of oxidation at each dose for RRR-AT when compared with all-rac-AT. Also, there were no significant differences in LDL oxidation after in vitro enrichment of LDL with RRR-AT and all-rac-AT. Thus, supplementation with either RRR-AT or all-rac-AT resulted in similar increases in plasma and LDL AT levels at equivalent IU doses, and the degree of protection against copper-catalyzed LDL oxidation was only evident at doses > or = 400 IU/d for both forms.

Decreased low-density lipoprotein oxidation after repeated selective apheresis in homozygous familial hypercholesterolemia

Familial hypercholesterolemia was the first genetic disorder recognized to cause myocardial infarction. Patients with homozygous familial hypercholesterolemia have rapidly progressive coronary atherosclerosis with angina pectoris, myocardial infarction, or sudden death at a young age. Selective apheresis on dextran sulfate cellulose columns reduces mortality and may induce regression of coronary lesions. These patients have both increased levels and prolonged circulation residence time of low-density lipoprotein (LDL), which is not removed by cellular receptor. LDL oxidation may play a pivotal role in atherogenesis. LDL undergoes oxidation before being taken up by macrophages and then transformed into arterial wall foam cells. The aim of this study was to investigate LDL oxidation in eight homozygous patients with familial hypercholesterolemia during repeated LDL apheresis. LDL lipid peroxidation, estimated by conjugated-diene absorbance at 234 nm, lipid peroxides, and malondialdehyde showed an increased resistance against oxidation after repeated LDL apheresis. This phenomenon was also observed in the oxidative indexes of protein moiety of LDL (apolipoprotein-B100 fragmentation, trinitrobenzenesulfonic acid reactivity, and electrophoresis agarose mobility). Similarly, cholesteryl esterification was decreased after LDL apheresis. Thus selective LDL apheresis not only decreases the pool of LDL, but it also induces changes that render LDL less susceptible to oxidation. This phenomenon might contribute to reduce coronary atherosclerosis and thus mortality of these particular patients.

The formation of some antigenic epitopes in oxidized human low-density lipoprotein is inhibited by nitric oxide

NO and NO-donors are able to inhibit the peroxidation of polyunsaturated fatty acids in human low-density lipoproteins (LDL) exposed to Cu+2. Here we report that 1-hydroxy-2-oxo-3,3-bis(3-aminoethyl)-1-triazene (NOC-18), a compound which releases NO at low rate in aqueous solutions, powerfully inhibits the peroxidation of polyunsaturated fatty acids, tryptophan loss, the formation of fluorescent aldehydic adducts in apo B100 and the increase of electrophoretic mobility in isolated LDL undergoing oxidation. The inhibitory effect is not restricted to Cu+2-induced peroxidation but is also detectable with other oxidizing conditions such as the free radical generator 2,2'-azobis-(2-amidino propane) hydrochloride (AAPH), the combination of horseradish peroxidase and H2O2 (HRP), and peroxynitrite (ONOO-). The recognition of Cu+2-, AAPH-, and ONOO(-)-modified LDL by specific autoantibodies present in serum of atherosclerotic patients is almost completely inhibited when the oxidation procedure is performed in the presence of NOC-18. However, NOC-18 is completely ineffective in preventing the formation of recognizable antigens in HRP-modified LDL. These findings suggest that NO may efficiently prevent the formation of some, but not all, the antigenic epitopes recognized by human autoantibodies and thus likely formed during in vivo LDL oxidation.

Plasma ubiquinol-10 is decreased in patients with hyperlipidaemia

Ubiquinol-10, the reduced form of ubiquinone-10 (coenzyme Q10), is a potent lipophilic antioxidant present in nearly all human tissues. The exceptional oxidative lability of ubiquinol-10 implies that it may represent a sensitive index of oxidative stress. The present study was undertaken to assess the hypothesis that the level of ubiquinol-10 in human plasma can discriminate between healthy subjects and patients who are expected to be subjected to an increased oxidative stress in vivo. Using a newly developed method, we measured plasma ubiquinol-10 in 38 hyperlipidaemic patients with and without further complications, such as coronary heart disease, hypertension, or liver disease, and in 30 healthy subjects. The oxidizability of plasma samples obtained from hyperlipidaemic patients was found to be increased in comparison with control subjects, suggesting that the patients were subjected to a higher oxidative stress in vivo than the controls. Plasma ubiquinol-10, expressed as a percentage of total ubiquinol-10 + ubiquinone-10 or normalized to plasma lipids, was lower in the patients than in controls (P = 0.001 and 0.008, respectively). The proportion of ubiquinol-10 decreased in the order young controls > aged controls > hyperlipidaemic patients without complications > hyperlipidaemic patients with complications (P = 0.003). A negative correlation was found between the proportion of ubiquinol-10 and plasma triglycerides. The hyperlipidaemic patients with hypertension had a lower proportion of ubiquinol-10 than subjects without. When the study population was divided into smokers and non-smokers, plasma ubiquinol-10 was found to be reduced amongst smokers, independently of whether it was expressed as a percentage of total ubiquinol-10 + ubiquinone-10 (P = 0.006) or normalized to plasma lipids (P = 0.009). These data suggest that the level of ubiquinol-10 in human plasma may represent a sensitive index of oxidative stress in vivo especially indicative of early oxidative damage. Measuring plasma ubiquinol-10 can be proposed as a practical approach to assess oxidative stress in humans.

Oxidative damage and fibrogenesis

Various chronic disease processes are characterized by progressive accumulation of connective tissue under-going fibrotic degeneration. Evidence of oxidative reactions is often associated with fibrogenesis occurring in liver, lung, arteries, and nervous system. Moreover, an increasing bulk of experimental and clinical data supports a contributory role of oxidative stress in the pathogenesis of this kind of disease. Indeed, many etiological agents of fibrogenesis stimulate free radical reactions either directly or through inflammatory stimuli. Free radicals, as well as products of their reaction with biomolecules, appear to modulate the activity of the two cellular types mainly involved in the process, namely phagocytes and extracellular matrix-producing cells. Lipid peroxidation and certain lipid peroxidation products induce genetic overexpression of fibrogenic cytokines, the key molecules in the pathomechanisms of fibrosis, as well as increased transcription and synthesis of collagen. Both these events can be downregulated, at least in experimental models, by the use of antioxidants. The effect of oxidative stress on cytokine gene expression appears to be an important mechanism by which it promotes connective tissue deposition.

Antioxidants inhibit the expression of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 induced by oxidized LDL on human umbilical vein endothelial cells

The oxidative modification of low density lipoprotein (LDL) and the endothelial expression of adhesion molecules are key events in the pathogenesis of atherosclerosis. In this study we evaluated the effect of oxidized LDL on the expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin on human umbilical vein endothelial cells (HUVECs). The hypothesis that oxidized LDL functions as a prooxidant signal was also evaluated, by studying the effect of different radical-scavenging antioxidants on expression of adhesion molecules. LDL was oxidized by using Cu2+, HUVECs or phospholipase A2 (PLA2)/ soybean lipoxygenase (SLO), the degree of oxidation being measured as thiobarbituric acid-reactive substances (TBARS) and conjugated dienes (CD). Exposure of 200 micrograms/ml of native LDL to 1 microns Cu2+, HUVECs and to PLA2/ SLO resulted in four- to fivefold higher levels of TBARS and CD than in native LDL. Cu(2+)-(1 microM), HUVEC-, and PLA2/SLO-oxidized LDL caused a dose-dependent, significant increase of ICAM-1 and VCAM-1 (p < .01). The expression of E-selectin did not change. LDL oxidized with a 2.5 and 5 microM Cu2+ did not increase ICAM-1 and VCAM-1 significantly. Both the Cu(2+)- and HUVEC-oxidized LDL, subjected to dialysis and ultrafiltration, induced ICAM-1 and VCAM-1 expression. After incubation with the ultrafiltrate, the expression of ICAM-1 and VCAM-1 was not significantly different from that obtained with native LDL. LDL pretreated with different antioxidants (vitamin E and probucol) and subjected to oxidation by Cu2+ and HUVECs induced a significantly lower expression of ICAM-1 and VCAM-1 than nonloaded LDL (p < .01). The pretreatment of HUVECs with vitamin E and probucol significantly reduced the expression of VCAM-1 on HUVECs induced by oxidized LDL (p < .01); the effect on ICAM-1 was much less evident. In conclusion, oxidized LDL can induce the expression of different adhesion molecules on HUVECs; this induction can be prevented by pretreating either the LDL or the cells with radical-scavenging antioxidant.

Decreased susceptibility of low-density lipoproteins to in-vitro oxidation after dextran-sulfate LDL-apheresis treatment

Low-density lipoproteins (LDL)-apheresis is a well established treatment of severe hypercholesterolemia resulting in fast clinical improvement and angiographically proven regression after 6 months of therapy. The underlying mechanisms, beside lipoprotein removal, are still under debate. Recently, oxidized LDL were shown to be of key importance in foam cell formation and atherosclerotic lesion development. We examined the influence of dextran-sulfate LDL-apheresis on the susceptibility of LDL to oxidation in 6 patients (5 males, 1 female, age: 41-60 years) suffering from severe heterozygous hypercholesterolemia or combined hyperlipidemia. LDL-apheresis influenced the oxidizability of LDL by a significant (P < 0.01) prolongation of the median of lag time (min) for LDL samples (before treatment 75, range: 31-176 versus after treatment 129.5, range 45-286). A significant (P < 0.01) difference could be also observed in the amount of conjugated dienes as expressed by the maximum rate in absorbance (before treatment 15.39, range: 5.29-21.22 versus after treatment 20.20, range 12.88-72.33). Thiobarbituric acid reactive substances (TBARS) formation was significantly decreased in LDL obtained after apheresis treatment as compared to pretreatment LDL. Electrophoretic mobility (EM) of LDL obtained before and after LDL-apheresis revealed a significant increase (P < 0.05) from a mean of 8.8 +/- 0.5 to a mean of 10.5 +/- 0.5 mm. The titers of plasma autoantibodies against oxLDL (oLAb) which varied considerably interindividually, were not influenced by LDL-apheresis treatment. Levels of F2-isoprostanes, as measured by plasma levels of 8-iso-prostaglandin-F2 alpha (8-iso-PGF2 alpha), reflecting oxidative stress, did not change, either. In summary, our findings provide evidence that even one single dextran sulfate LDL-apheresis treatment decreases LDL-oxidizability, which is an additional beneficial effect to that of lipid lowering.

Oxidative modification of low-density lipoprotein by the human hepatoma cell line HepG2

The human hepatoblastoma cell line HepG2 is a liver model commonly used for lipid metabolism studies. Numerous cell types have been found to oxidize low-density lipoprotein (LDL) but, to our knowledge, the effects of HepG2 cells on LDL have not been investigated. We found that LDL is modified by HepG2 cells through a peroxidative mechanism, as judged by an increase in TBARS content (which was prevented in the presence of the antioxidants vitamin E, 2,6-di-tertbutyl-cresol and probucol), increased degradation by J774 macrophages, decreased internalization by MRC5 fibroblasts, and aggregation of apo B. Aspirin and allopurinol, which inhibit cyclooxygenase and xanthine-oxidase activities, respectively, had no effect on HepG2-induced LDL modification, and neither did catalase, which dismutates hydrogen peroxide; or mannitol, which scavenges hydroxyl radicals. In contrast, superoxide dismutase, a superoxide anion scavenger, and glutamate and threonine, which alter cellular cystine uptake, prevented LDL modifications, as did the removal of cysteine/cystine from the culture medium. Oxidation of LDL by HepG2 cells might thus involve superoxide anion production and/or thiol metabolism.

Insulin decreases circulating vitamin E levels in humans

Both hyperinsulinemia and free oxygen radicals have been implicated in the pathogenesis of atherosclerosis, but the relationship between insulin levels or insulin action and the oxidant/antioxidant balance has not been explored. We measured the effect of physiologic hyperinsulinemia on plasma concentrations of vitamin E, a major free radical scavenger molecule. Isoglycemic clamps (at an insulin infusion rate of 6 pmol . min-1 . kg-1) were performed in four groups of subjects: (1) 12 non-insulin-dependent diabetic (NIDDM) patients, (2) eight patients with essential hypertension, (3) 11 nondiabetic obese individuals, and (4) 12 healthy subjects. In 10 healthy volunteers, a time-control experiment was performed by replacing the insulin infusion with normal saline. Vitamin E and plasma lipid levels were determined at baseline and after 2 hours of insulin/saline infusion. Insulin sensitivity was reduced in diabetic, obese, and hypertensive groups in comparison to healthy controls, but fasting plasma vitamin E concentrations were similar in all groups. A consistent decrement in plasma vitamin E concentrations (averaging 12% of baseline, P < .0001) was observed in all subjects receiving insulin regardless of the level of insulin sensitivity, whereas no significant changes in plasma vitamin E were seen in subjects receiving saline infusion (P < .001 v insulin infusion groups). The insulin-induced decrement persisted in all study groups when plasma vitamin E concentrations were corrected for total serum cholesterol levels (-8.9% +/- 1.2% v -0.4 +/- 2.3% of saline controls, P = .0004) or serum low-density lipoprotein (LDL(-10.0% +/- 1.2% v -0.4% +/- 2.2%, P = .0002). We conclude that insulin infusion acutely depletes vitamin E in circulating lipids regardless of insulin resistance. This effect may represent a physiologic means of transferring vitamin E into cell membranes; alternatively, it might reflect a pro-oxidant action of insulin in vivo.

Protective effects of carvedilol, a vasodilating beta-adrenoceptor blocker, against in vivo low density lipoprotein oxidation in essential hypertension

Low density lipoprotein (LDL) oxidation plays a crucial role in the development and progression of atherosclerosis and is enhanced in patients with essential hypertension. This finding has stimulated a search for antihypertensive drugs with high intrinsic antioxidant properties. We investigated the antihypertensive and antioxidant effects of carvedilol, a new vasodilating beta-adrenoceptor blocking agent in a group of patients with mild to moderate essential hypertension after 4-month treatment. Carvedilol administration markedly increased the resistance to oxidation of LDL isolated from treated patients to values comparable to those of control, nonhypertensive subjects. This effect was achieved despite a significant loss in LDL-associated vitamin E. The increased resistance of LDL to oxidation promoted by carvedilol was not related to the normalization of previously increased blood pressure (BP). Indeed, the administration of other conventional antihypertensive drugs, capable of decreasing arterial BP but without high intrinsic antioxidant properties, to a control group of matched hypertensive patients failed to ameliorate LDL oxidation parameters. Carvedilol treatment also reduced the extent of in vivo LDL oxidation, as reflected by the decrease in antioxidized LDL autoantibody titer. This effect as well was detected only in the group of carvedilol-treated hypertensive patients and not after the simple reduction in BP obtained with antihypertensive drugs different from carvedilol.

AL0671, a new potassium channel opener, inhibits nonenzymatic glycation of protein and LDL oxidation

1. The effects of AL0671, a novel potassium channel opener, on protein glycation and low-density lipoprotein (LDL) oxidation were tested. 2. AL0671 dose-dependently inhibited both fluorescence development of bovine serum albumin and cross-linking of lysozyme. These inhibitory effects for glycation were no less potent than aminoguanidine. 3. AL0671 dose-dependently inhibited both increase in negative charge and apo B-100 fragmentation during incubation of LDL with Cu2+. In addition, AL0671 significantly decreased the LDL degradation in rat peritoneal macrophages. 4. Neither pinacidil nor levcromakalim inhibited protein glycation and LDL oxidation. 5. Antioxidant properties of AL0671 might be due to its potent electron-donating ability, and this agent is expected to be useful for hypertensive diabetes.