Whole plasma oxidation assay as a measure of lipoprotein oxidizability

Circulating Markers of Liver Function and Cardiovascular Disease Risk

Measurement of serum concentrations of various liver enzymes and other nonenzymatic proteins and metabolites of heme metabolism (eg, bilirubin) is often undertaken in clinical practice. Measurement of these liver function tests is simple, quick, and relatively inexpensive. However, interpreting the liver function test results in patients without evidence of liver disease is often challenging. Concentrations of some of liver enzymes, such as γ-glutamyltransferase or alkaline phosphatase, and concentrations of liver-derived metabolites, such as bilirubin, may be influenced by metabolic processes beyond the liver, sometimes making interpretation of the test results difficult. This scenario frequently occurs both in individuals at risk of cardiovascular disease and in patients with known cardiovascular disease, often resulting in the clinicians ignoring the test results. In this brief review, we discuss the evidence for associations between key serum liver function tests and cardiovascular disease risk and where associations are robust; we provide an interpretation for possible mechanistic links between the liver function test and cardiovascular disease.

Oxidative stress and modification of renal vascular permeability are associated with acute kidney injury during P. berghei ANKA infection

Malaria associated-acute kidney injury (AKI) is associated with 45% of mortality in adult patients hospitalized with severe form of the disease. However, the causes that lead to a framework of malaria-associated AKI are still poorly characterized. Some clinical studies speculate that oxidative stress products, a characteristic of Plasmodium infection, as well as proinflammatory response induced by the parasite are involved in its pathophysiology. Therefore, we aimed to investigate the development of malaria-associated AKI during infection by P. berghei ANKA, with special attention to the role played by the inflammatory response and the involvement of oxidative stress. For that, we took advantage of an experimental model of severe malaria that showed significant changes in the renal pathophysiology to investigate the role of malaria infection in the renal microvascular permeability and tissue injury. Therefore, BALB/c mice were infected with P. berghei ANKA. To assess renal function, creatinine, blood urea nitrogen, and ratio of proteinuria and creatininuria were evaluated. The products of oxidative stress, as well as cytokine profile were quantified in plasma and renal tissue. The change of renal microvascular permeability, tissue hypoxia and cellular apoptosis were also evaluated. Parasite infection resulted in renal dysfunction. Furthermore, we observed increased expression of adhesion molecule, proinflammatory cytokines and products of oxidative stress, associated with a decrease mRNA expression of HO-1 in kidney tissue of infected mice. The measurement of lipoprotein oxidizability also showed a significant increase in plasma of infected animals. Together, our findings support the idea that products of oxidative stress, as well as the immune response against the parasite are crucial to changes in kidney architecture and microvascular endothelial permeability of BALB/c mice infected with P. berghei ANKA.

The effect of oxidized low-density lipoprotein combined with adriamycin on the proliferation of Eca-109 cell line

Background

The purpose of this study was to identify the affect on the proliferation Eca-109 cells treated with oxidized low-density lipoprotein (ox-LDL) combined with adriamycin (ADM).

Methods

Eca-109 cell were cultured in the presence of oxLDL/ADM, and cell proliferation tested by MTT and cell apoptosis was monitored by the proportion of apoptosis and cell cycle by flow cytomester. We simultaneously evaluated the level of associated- apoptosis Bcl-2, Bax, and Caspase-3 gene mRNA and protein.

Results

OxLDL were cytotoxic and activate apoptosis. OxLDL combined with ADM significant enhanced the proportion rate of apoptosis on a time and dose dependency. The expressions of the inhibiting apoptosis Bcl-2 gene mRNA and protein were down regulated, whereas, the expressions of the promoting apoptosis Bax, and Caspase-3 genes mRNA and protein were up regulation.

Conclusion

These results suggested that oxLDL have cytotoxicity and activate apoptosis on the Eca-109 cells. OxLDL combined with ADM have a synergistic effect on the apoptosis induced Eca-109 cells. Furthermore, oxLDL may contribute to the improvement of clinical chemotherapy of cancer need to make further investigation.

An interference study of the copper-induced plasma oxidizability test

OBJECTIVES

The aim of this study is to investigate the effect of cristaloid cardioplegic fluid (CCF) and its contents on the susceptibility of plasma to copper-catalyzed lipid peroxidation test.

DESIGN AND METHODS

The plasma pool was divided into eight groups. Equal volumes of CCF or one of its contents were added to each group of the plasma pool. The accumulation of conjugated diene (CD) by copper-induced oxidation was monitored for a period of 5 h. Thiobarbituric acid-reactive substances (TBARS) formed during the incubation of plasma with copper was also measured.

RESULTS

It was found that, the production of CD and TBARS were inhibited and the lag time had increased, when the plasma was mixed with CCF or its contents.

CONCLUSIONS

As a result, we conclude that that the susceptibility of plasma to copper-induced lipid peroxidation is interfered by CCF. The chloride ions, which major content of CCF, may play an important role on this effect.

Improved resistance to serum oxidation in Gilbert's syndrome: a mechanism for cardiovascular protection

Bilirubin is a potent antioxidant, however, uncertainty surrounds its physiological importance. Individuals with Gilbert's syndrome (GS) have increased circulating bilirubin and a reduced prevalence of cardiovascular disease (CVD). The aim of this study was to investigate mechanisms that may link bilirubin to protection from CVD seen in GS by examining markers of antioxidant and oxidative stress status and the susceptibility of serum to oxidation. Nine individuals with GS and twelve controls, matched for age, height and weight, were assessed for plasma antioxidant status, red blood cell antioxidant enzyme activities, plasma malondialdehyde, the susceptibility of serum to copper (Cu(2+)) induced oxidation and blood lipid profile. Individuals with GS had significantly elevated unconjugated bilirubin (GS: 26.0+/-6.4; control: 9.7+/-3.0 micromol/L; P<0.001), increased trolox equivalent antioxidant capacity (GS: 1.59+/-0.07; control: 1.52+/-0.07 mmol/L trolox Equ; P=0.035) and ferric reducing ability of plasma (GS: 1.09+/-0.16; control: 0.92+/-0.14 mmol/L Fe(2+) Equ; P=0.024). The lag phase of serum oxidation was significantly longer in the GS group (GS: 121.4+/-10.5; control: 106.8+/-14.6 min; P=0.020) and was positively correlated with the bilirubin concentration (r=0.451, P=0.040). A trend toward elevated HDL:LDL ratio was observed in GS (GS 0.96+/-0.31; control: 0.73+/-0.21; P=0.072). In summary, individuals with GS have an increased circulating antioxidant status and an improved resistance to serum oxidation which may partially explain their reduced prevalence of CVD.

Oxidized LDL, serum oxidizability and serum lipid levels in patients with breast or ovarian cancer

OBJECTIVES

The aim of this study was to evaluate the extent of oxidative stress in patients with breast or ovarian cancer by analyzing the magnitude of serum oxidizability and the involvement of oxidized low-density lipoproteins (oxLDL) in the disease.

DESIGN AND METHODS

The study was conducted on 32 patients diagnosed with breast or ovarian cancer but who had not undergone any kind of treatment and 30 healthy individuals of similar age. The evaluation of oxidative stress was assessed by: (a) the ex-vivo susceptibility of serum lipids to oxidation and (b) the detection of oxLDL and anti-oxLDL autoantibodies. Total cholesterol, LDL-cholesterol and HDL-cholesterol were co-estimated.

RESULTS

The results indicated that the levels of oxLDL were increased among both breast and ovarian cancer patients as compared to the control subjects. Additionally in patients with breast cancer, serum total cholesterol, LDL-cholesterol, anti-oxLDL antibodies and the maximal rate of diene formation (RA), the index of oxidizable components load, were increased in comparison to controls. There is statistically significant evidence that serum oxLDL levels are associated with increased risk of breast and ovarian cancer.

CONCLUSIONS

The findings exhibit a correlation between oxLDL and malignancy, supporting the contribution of oxidative stress to carcinogenesis and the possible involvement of oxLDL in the process of malignancy. The clinical evaluation of the oxLDL measurement is under investigation.

Oxidative Susceptibility of Unfractionated Serum or Plasma: Response to Antioxidants in Vitro and to Antioxidant Supplementation

Background: The susceptibility of plasma lipids to oxidation is thought to be a factor contributing to atherogenic risk. Various groups have studied the in vitro oxidizability of isolated LDL and examined the effects of conventional antioxidants. The drawbacks associated with the isolation of LDL for evaluation of in vitro oxidizability, however, have limited the application of this measurement in large-scale studies.

Methods: We developed and evaluated an assay that can be used to directly assess the oxidative susceptibility of unfractionated serum or plasma lipids, obviating the need for isolation of lipoprotein fractions. Oxidative conditions were initiated in vitro with cuprous chloride and 2,2′-azobis(2-amidinopropane) hydrochloride. The effects of antioxidants added in vitro, and as an oral supplement, were monitored by conjugated diene formation.

Results: The addition of ascorbic acid (0–50 μmol/L) in vitro elicited a dose-dependent protective effect, increasing the lag time to oxidation (P &lt;0.001). In contrast, α-tocopherol demonstrated prooxidant behavior at increasing concentrations (0–50 μmol/L), although we observed a decrease in the maximum rate of oxidation. Our findings are supported by the results from plasma samples of participants in a randomized antioxidant (vitamins C and E) intervention study after acute ischemic stroke. The group receiving vitamins C and E for 14 days showed an increased lag time to plasma lipid oxidation in vitro compared with the nonsupplemented group (P &lt;0.05).

Conclusion: The susceptibility of unfractionated plasma or serum lipids to oxidation in vitro offers an alternative to LDL for evaluating the efficacy of antioxidant regimens.

Improvement of serum oxidation by pravastatin might be one of the mechanisms by which endothelial function in dilated coronary artery segments is ameliorated

BACKGROUND

Oxidation susceptibility of lipids in vitro is considered to reflect the exposure of lipids to oxidation stress in vivo which is related to cardiovascular morbidity. This study examined the effect of pravastatin therapy on serum oxidation susceptibility, particularly in relation to endothelial function of coronary arteries.

METHODS

The participants were recruited from the Pravastatin-Related Effects Following Angioplasty on Coronary Endothelium trial, a double-blinded, placebo-controlled, randomized, multi-center study designed to analyze the effect of pravastatin treatment on endothelial function in previously dilated and normal coronary arteries. Serial, graded, intra-coronary acetylcholine infusions were used to assess endothelial function. In vitro, copper-induced, serum oxidation parameters were determined at randomization and at time of coronary endothelial function assessment.

RESULTS

Oxidation parameters were determined in 45 patients (pravastatin 23, placebo 22). Pravastatin therapy significantly improved serum oxidation lag time (+8%, P<0.05), maximal diene formation rate (-22%, P<0.01) and total amount of dienes formed after 5 h (-16%, P<0.01). These parameters remained essentially unchanged in the placebo group. Acetylcholine-evoked responses were positively correlated to therapy-induced change in serum oxidation susceptibility in the dilated segment group (r2=0.56, P=0.006).

CONCLUSION

Pravastatin's beneficial effect on endothelial dysfunction of dilated coronary segments may be secondary to pravastatin's improvement of oxidation susceptibility.

Soy protein with isoflavones has favorable effects on endothelial function that are independent of lipid and antioxidant effects in healthy postmenopausal women

BACKGROUND

Controversy exists about the ability of soy protein and isoflavones to modulate vascular reactivity and biochemical cardiovascular disease risk markers in healthy, normolipidemic postmenopausal women.

OBJECTIVE

The objective was to investigate whether the consumption of soy protein with isoflavones would result in improved vascular reactivity and decreased biochemical markers of endothelial dysfunction and inflammation, independent of enhanced lipid and antioxidant effects.

DESIGN

Healthy postmenopausal women (n = 28) were enrolled in a randomized, double-blind, crossover study, and they consumed 25 g of 3 protein products/d for 6 wk each, with intervening washout periods. The products were isolated soy protein with isoflavones, ethanol-washed isolated soy protein with trace isoflavones, and total milk protein, which supplied 107, 2, and 0 mg total isoflavone (aglycone) units/d, respectively. We studied vascular function by using brachial artery reactivity values, plasma concentrations of vasoactive factors, endothelial inflammatory markers, and plasma isoflavone concentrations. The resistance of whole plasma and isolated LDL to copper-mediated oxidation was measured by conjugated diene formation.

RESULTS

Postocclusion peak flow velocity of the brachial artery was significantly (P = 0.03) lower after treatment with isolated soy protein with isoflavones, which is consistent with a vasodilatory response, than after treatment with total milk protein. Plasma isoflavones and metabolites were significantly (P < 0.01) higher after treatment with isolated soy protein with isoflavones. There were no significant changes in biochemical cardiovascular disease risk markers or conjugated diene formation between the 3 dietary groups.

CONCLUSION

Daily consumption of soy protein with isoflavones can result in positive vascular effects that are independent of lipid and antioxidant effects in healthy postmenopausal women.

Neonatal blood plasma is less susceptible to oxidation than adult plasma owing to its higher content of bilirubin and lower content of oxidizable Fatty acids

Newborn infants are susceptible to a range of problems attributed to excessive production of free radicals. Because of a higher content of antioxidants, above all bilirubin, and a lower content of oxidizable lipids, newborn plasma should be better protected against oxidation than adult plasma. To test this hypothesis, we measured the susceptibility of plasma to in vitro oxidation in microsamples (7 microL) from 57 healthy newborns and 18 adults. Heparin plasma was diluted 150-fold and oxidized by 50 microM Cu2+. Oxidation was monitored as an increase in sample absorbance at 234 nm. Plasma oxidizability was found to be significantly lower in newborns than in adults. Accordingly, the level of bilirubin, an important antioxidant, was significantly higher, and the level of polyunsaturated fatty acids, a major substrate of lipid peroxidation, was significantly lower in newborn plasma. In addition, plasma oxidizability correlated positively with the level of polyunsaturated fatty acids and negatively with that of bilirubin. These data indicate that plasma is better protected against oxidative stress in newborns than in adults, owing to its higher content of antioxidants like bilirubin and its lower content of oxidizable lipids.

Exposure to automotive pollution increases plasma susceptibility to oxidation

Low-density lipoprotein oxidation is implicated in the development of atherosclerosis. Plasma susceptibility to oxidation may be used as a marker of low-density lipoprotein oxidation and thus predict atherosclerotic risk. In this study the authors investigated the relationship between plasma susceptibility to oxidation and exposure to automotive pollution in a group of automobile mechanics (n = 16) exposed to high levels of automotive pollution, vs. matched controls (n = 13). The authors induced plasma oxidation by a free radical initiator and they determined susceptibility to oxidation by (1) change in absorbance at 234 nm, (2) lag time to conjugated diene formation, and (3) linear slope of the oxidation curve. Mechanics had significantly higher values (mean +/- standard error) for change in absorbance (1.60 +/- 0.05 vs. 1.36 +/- 0.05; p < .002), and slope (1.6 x 10(-3) +/- 0.1 x 10(-3) vs. 1.3 x 10(-3) +/- 0.1 x 10(-3); p < .001), compared with controls. These results indicate that regular exposure to automotive pollutants increases plasma susceptibility to oxidation and may, in the long-term, increase the risk of developing atherosclerosis.

Three different pathways for human LDL oxidation are inhibited in vitro by water extracts of the medicinal herb Achyrocline satureoides

In this study we investigated the antioxidant properties of one herbal preparation widely used in complementary and alternative medicine in large areas of the world: Achyrocline satureoides (AS), popularly known as "marcela". Although rich in flavonoids, the ethnopharmacological uses of this plant do not include atherosclerosis prevention. Furthermore, no study had been conducted so far exploring the antioxidant activity of Achyrocline satureoides vis-à-vis human LDL oxidation, which is the compelling issue in pinpointing potential cardioprotective new uses for a traditional remedy. We explored the effects of AS extracts on human LDL oxidation, employing 3 different systems which are thought to play a role in oxidation of LDL in the arterial wall: copper, peroxynitrite, and lipoxygenase. Oxidation was monitored by conjugate dienes, TBARS formation and aggregation of apoB using SDS-PAGE. In copper-initiated oxidation a dose dependent inhibition of the initiation and propagation of lipid oxidation is shown by an increase in the lag phase for conjugate diene production which was 60 +/- 15 min in the absence and 120 +/- 20 min in the presence of 4 microg/ml AS extracts (p < 0.001). TBARS production was reduced by 95% after 3 h incubation at 5 microg/ml. Aggregation of apoB was abolished at the same concentrations. SIN-1 (3-morpholinosydnonimine) produces peroxynitrite via generation of NO and O2-. When LDL was incubated in its presence, a milder oxidation was observed as compared with Cu2+, and AS produced over 70% inhibition. Finally, we show a striking dose-dependent inhibitory effect of lipoxygenase conjugate diene production, which is over 95% at AS concentrations of 5 microg/ml. When compared with other antioxidants, AS effect is greater but in the same order of magnitude than that of ascorbic acid and similar to the popular herbal tea Ilex paraguariensis. In all three systems employed an effect is already substantiated at a concentration of the AS extract of 4 microg/ml, which corresponds to a 1/100 dilution of the preparations usually drunk.

Antioxidative functions of natto, a kind of fermented soybeans: effect on LDL oxidation and lipid metabolism in cholesterol-fed rats

Natto water-soluble fractions, low-molecular-weight viscous substance, and soybean water extract, which had an inhibitory effect on the oxidation of low-density lipoproteins (LDL) in vitro, were fed to rats for 3 weeks. These fractions had no influence on the growth of rats, which were fed a basal diet containing 1% cholesterol, but lowered plasma triglyceride and total cholesterol. Inhibition of copper-oxidation of plasma and LDL ex vivo, and a reduction in lipid peroxidation in liver and aorta in vivo, were also observed. The antioxidant enzymes were not induced in rats fed natto fraction diets. These results demonstrate that ingestion of the natto fractions led to inhibition of LDL oxidation, and that the fractions perform direct antioxidant action in the body. It is suggested that natto fractions might help to prevent arteriosclerosis, as they appear to reduce lipid peroxidation and improve lipid metabolism.

Simple and rapid assessment of lipoprotein susceptibility to oxidation in the macromolecule fraction of plasma

BACKGROUND

Susceptibility of lipoprotein to oxidation is usually studied using purified lipoproteins. However, for large clinical studies or routine clinical assessment, a rapid, less time-consuming method that minimizes hydroperoxide accumulation in lipoprotein during preparation is desirable. Methods using whole plasma are complicated by the presence of an anticoagulant that may affect oxidation and the presence of antioxidants in the plasma aqueous phase. Lipoproteins in serum are relatively unprotected from initiation of oxidation.

METHODS

We studied copper-mediated oxidation of a macromolecule fraction of plasma prepared by simple molecular sieve chromatography.

RESULTS

LDL was more susceptible to oxidation than plasma macromolecules. The lag times approached zero as the copper concentration increased. The propagation rate was linear for PM vs. the copper concentration while LDL became saturated at 10-20 micromol/l. The interassay CVs for the lag phase rate, lag time, PR and maximal DeltaA(max) were 23%, 7.7%, 4.9%, and 3.3%, respectively.

CONCLUSIONS

This procedure should be applicable to large numbers of individuals in investigations regarding the effects of drugs and diets on lipid composition and oxidative susceptibility.

Fluvastatin depresses the enhanced lipid peroxidation in vitamin E-deficient hamsters

Fluvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has recently been reported to have the antioxidative activity in vitro. However, it is still unclear whether chronic treatment with this drug actually leads to amelioration of the redox status in the body. In this study, we investigated the antioxidative effect of fluvastatin in vivo, using a vitamin E-deficient hamster model, an in vivo model of enhanced oxidative stress. After pre-treatment with a vitamin E-deficient diet for 2 months, fluvastatin, pravastatin or probucol was added to the diet for 1 month. Vitamin E deficiency caused a significant increase in the levels of plasma oxidative stress markers such as 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) and hydroperoxides. Furthermore, there was a significant increase in the oxidizability of plasma lipids in the vitamin E-deficient animals, indicating that the oxidative stress was increased in the circulation. Fluvastatin markedly depressed the above oxidative stress markers in plasma, and significantly decreased the oxidizability of plasma lipids without affecting their levels. Probucol, a reference antioxidant, also showed a similar effect while pravastatin, another HMG-CoA reductase inhibitor, showed only a weak improvement. We suggest that the treatment with fluvastatin leads to a reduction of oxidative stress in vivo, which is mainly derived from its antioxidative property rather than its lipid-lowering activity.

Potential role of oxidized lipids and lipoproteins in antioxidant defense

The atherogenic oxidative modification of low-density lipoprotein is suggested to occur in the aortic intima. There is reasonable evidence to suggest that antioxidants might be beneficial in preventing or retarding the progression of atherosclerosis. Exercise, estrogens, and substitution of polyunsaturated fat for saturated fat are beneficial in the prevention of atherosclerosis. Yet, paradoxically, they are capable of inducing an oxidative stress. To reconcile with this paradox, we postulate that under certain conditions an oxidative stress might be beneficial by inducing antioxidant enzymes in arterial cells. However, those with genetic deficiency in antioxidant enzymes or those who poorly respond to oxidative stress or those with overwhelming plasma oxidative stress might need additional antioxidant protection.

Plasma thyroxine and cholesterol concentrations of miniature pigs are influenced by thermally oxidized dietary lipids

To investigate the effect of a dietary oxidized oil on thyroid hormone status and circulating cholesterol, we conducted a study with 16 male miniature pigs fed a nutritionally adequate diet with 15% of either fresh or thermoxidized oil for 35 d (n = 8/group). The thermoxidized oil was prepared by heating sunflower oil at 110 degrees C for 48 h. The fresh oil consisted of a mixture of sunflower oil and lard (94:6, v/v) which had a fatty acid composition similar to the thermoxidized oil. At the end of the study, there were no differences in body weight gains and plasma clinicochemical variables between groups, suggesting that the thermoxidized oil did not induce general toxic symptoms. However, pigs fed the thermoxidized oil had significantly higher plasma concentrations of total and free thyroxine (P < 0.05) and a tendency for a higher plasma concentration of thyroid hormone-stimulating hormone (P < 0.1) than pigs fed the fresh oil. Additionally, pigs fed the thermoxidized oil had lower concentrations of cholesterol in plasma, LDL and HDL (P < 0.05). There were significant negative correlations between the plasma concentrations of total (r = -0.29) and free thyroxine (r = -0.40) and that of cholesterol (P < 0.05), suggesting that there is a causal relationship between the changes in thyroxine concentration and the reduction of plasma cholesterol. Our results indicate that there is a close relationship between alterations of thyroid hormone status and cholesterol metabolism in pigs fed a thermoxidized oil, and dietary oxidized fats should be considered in thyroid hormone disorders.

Alpha- and beta-carotenes in low density lipoprotein are the preferred target for nitric oxide-induced oxidation

Whereas low plasma levels of carotenes are strongly associated with the elevated risk of atherosclerosis, the reason for this is still unknown. We hypothesized that lipoprotein oxidation in the arterial wall might selectively deplete carotenes, thus explaining the observed effects. In order to assess this hypothesis, we incubated plasma low density lipoprotein (LDL) with different oxidants and measured the consumption of carotenes and tocopherols. We found that when LDL oxidation was induced by nitric oxide, both alpha- and beta-carotene were consumed at a significantly higher relative rate than alpha- or gamma-tocopherol. In contrast, superoxide, peroxynitrite, hypochlorite or transition metal ions were unable to induce selective consumption of carotenes in LDL. These data suggest that the decreased plasma levels of alpha- and beta-carotene frequently measured in atherosclerosis may be related to their preferred consumption by reactive nitrogen species in the arterial wall.

Cerebrospinal fluid lipoproteins are more vulnerable to oxidation in Alzheimer's disease and are neurotoxic when oxidized ex vivo

Brain regional oxidative damage is thought to be a central mechanism in the pathogenesis of Alzheimer's disease (AD). Recent studies of cerebrospinal fluid (CSF) have suggested that increased lipid peroxidation of CSF and CSF lipoproteins also may occur in AD patients. In the present study, we determined the susceptibility of human CSF to ex vivo lipid peroxidation and tested the hypothesis that oxidized CSF lipoproteins may be neurotoxic. Whole CSF or a CSF lipoprotein fraction (d < 1.210 g/mL) was oxidized with 2,2'-azobis(2-amidino-propane)dihydrochloride (AAPH), a hydrophilic free-radical generator. Kinetics of CSF lipid peroxidation were followed by a standard fluorescence product accumulation assay. Oxidation of AD CSF yielded significantly shorter fluorescent lag times than controls, indicating reduced antioxidant capacity. Electrophoretic mobilities of CSF apolipoproteins were specifically reduced upon oxidation of CSF with AAPH, suggesting that lipoproteins are primary targets of CSF lipid peroxidation. Cultured neuronal cells were exposed to physiological concentrations of isolated CSF lipoproteins oxidized with increasing concentrations of AAPH; the resulting neurotoxicity showed a significant linear AAPH concentration-response relationship. These results suggest that oxidized CSF lipoproteins may contribute to the pathogenesis of neurodegeneration in AD.

Coenzyme Q10 enrichment decreases oxidative DNA damage in human lymphocytes

Ubiquinol-10, the reduced form of coenzyme Q10, is a powerful antioxidant in plasma and lipoproteins. It has been suggested that endogenous ubiquinol-10 also exerts a protective role even towards DNA oxidation mediated by lipid peroxidation. Even though the antioxidant activity of coenzyme Q10 is mainly ascribed to ubiquinol-10, a role for ubiquinone-10 (the oxidized form), has been suggested not only if appropriate reducing systems are present. To investigate whether the concentration of ubiquinol-10 or ubiquinone-10 affects the extent of DNA damage induced by H2O2, we supplemented in vitro human lymphocytes with both forms of coenzyme Q10 and evaluated the DNA strand breaks by Comet assay. The exposure of lymphocytes to 100 microM H2O2 resulted in rapid decrease of cellular ubiquinol-10 content both in ubiquinol-10-enriched and in control cells, whereas alpha-tocopherol and beta-carotene concentration were unchanged. After 30 min from H2O2 exposure, the amount of DNA strand breaks was lower and cells' viability was significantly higher in ubiquinol-10-enriched cells compared with control cells. A similar trend was observed in ubiquinone-10-enriched lymphocytes when compared with control cells. Our experiments suggest that coenzyme Q10 in vitro supplementation enhances DNA resistance towards H2O2-induced oxidation, but it doesn't inhibit directly DNA strand break formation.