Do antioxidants and polyunsaturated fatty acids have a combined association with coronary atherosclerosis?

High cholesterol diet promotes dysfunction of arginase and cholinergic enzymatic system in rats: ameliorative role of caffeic and chlorogenic acids

BACKGROUND

Dietary phenolic compounds intake have been reported to have an inverse relationship to the prevalence of hypercholesterolemia. The objective of this study is to determine the effect of caffeic acid (CFA) and chlorogenic acid (CGA) on rats fed with high cholesterol diet (HCD).

METHODS

Experimental animals were fed with high cholesterol diet (HCD) for a period of 21 days while simvastatin (0.2 mg/kg BWT), CFA and CGA (10 and 15 mg/kg BWT) were administered daily.

RESULTS

Activity of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and arginase were significantly (P<0.05) higher in the rats fed with HCD alone. Also, level of malondiadehyde equivalent compounds (MDA) was significantly (P<0.05) elevated in hypercholesterolemic rats. Nevertheless, treatment with simvastatin, CFA and CGA normalized altered AChE, BChE and arginase activities as well as improved antioxidant status in hypercholesterolemic rats.

CONCLUSION

CFA and CGA could offer protective role in hypercholeseterolemic rats via their antioxidant potentials as well as restoring altered activity of acetylcholinesterase, butrylcholinesterase and arginase. Based on our findings chlorogenic acid exhibits better attribute.

Oleic acid and derivatives affect human endothelial cell mitochondrial function and vasoactive mediator production

BACKGROUND

Inhalation of common air pollutants such as diesel and biodiesel combustion products can induce vascular changes in humans which may contribute to increased mortality and morbidity associated with fine particulate matter exposures. Diesel, biodiesel, and other combustion byproducts contain fatty acid components capable of entering the body through particulate matter inhalation. Fatty acids can also be endogenously released into circulation following a systemic stress response to some inhaled pollutants such as ozone. When in the circulation, bioactive fatty acids may interact with cells lining the blood vessels, potentially inducing endothelial dysfunction. To examine whether fatty acids could potentially be involved in human vascular responses to air pollutants, we determined the effects of fatty acids and derivatives on important vascular cell functions.

METHODS

Human umbilical vein endothelial cells (HUVEC) were exposed in vitro to oleic acid (OA) or OA metabolites for 4-48 h. Cytotoxicity, vasodilator production (by ELISA measurement), mitochondrial function (using Sea Horse assays), and iron metabolism (inferred by ICP-OES measurements) were examined, with standard statistical testing (ANOVA, t-tests) employed.

RESULTS

Dose-dependent cytotoxicity was noted at 24 h, with 12-hydroxy OA more potent than OA. Mitochondrial stress testing showed that 12-hydroxy OA and OA induce mitochondrial dysfunction. Analysis of soluble mediator release from HUVEC showed a dose-dependent increase in prostaglandin F2α, a lipid involved in control of vascular tone, at 24 h (85% above controls) after OA-BSA exposure. RT-PCR analysis revealed OA did not induce changes in gene expression at noncytotoxic concentrations in exposed HUVEC, but 12-OH OA did alter ICAM and COX2 gene expression.

CONCLUSIONS

Together, these data demonstrate that FA may be capable of inducing cytotoxic effects and altering expression of mediators of vascular function following inhalation exposure, and may be implicated in air pollutant-induced deaths and hospitalizations. (267 of max 350 words).

Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review

Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.

Effects of the Dietary Addition of Amaranth (Amaranthus mantegazzianus) Protein Isolate on Antioxidant Status, Lipid Profiles and Blood Pressure of Rats

The effects of the dietary addition of 2.5% (w/w) Amaranthus mantegazzianus protein isolate (AI) on blood pressure, lipid profiles and antioxidative status of Wistar rats were evaluated. Six diets were used to feed animals during 28 days: (base (AIN93G), Chol (cholesterol 1%, w/w), CE (α-tocopherol 0.005%, w/w), CholE (cholesterol 1% (w/w) + α-tocopherol 0.005%, w/w), CAI (AI 2.5% w/w), CholAI (cholesterol 1% (w/w) + AI 2.5%, w/w). Lipid profiles of plasma and liver and faecal cholesterol content were analyzed. Antioxidant status was evaluated by the ferric reducing activity of plasma (FRAP), the 2-thiobarbituric acid (TBA) assay and superoxide dismutase (SOD) activity in plasma and liver. Blood pressure was measured in the tail artery of rats. CholA group presented a significant (α < 0.05) reduction (16%) in the plasma total cholesterol. In liver, the intake of cholesterol (Chol group) induced a significant increment in cholesterol and triglycerides (2.5 and 2.3 times, respectively), which could be decreased (18% and 47%, respectively) by the addition of AI (CholA group). This last group also showed an increased faecal cholesterol excretion (20%). Increment (50%) in FRAP values, diminution of TBA value in plasma and liver (70% and 38%, respectively) and diminution of SOD activity (20%) in plasma of CholA group suggest an antioxidant effect because of the intake of AI. In addition, CA and CholA groups presented a diminution (18%) of blood pressure after 28 days.

Effects of thymol on B16-F10 melanoma cells

Aromatic monoterpene, thymol, shows several beneficial activities, such as an antioxidative effect. However, the mechanism of its toxicity remains to be fully defined. In preliminary studies, thymol was characterized as a melanin formation inhibitor in an enzymatic system; however, thymol showed moderate cytotoxicity but not an antimelanogenic effect on B16-F10 melanoma cells. Thymol exhibited cytotoxicity, with an IC(50) value of 400 μM (60.09 μg/mL). This moderate toxic effect was suppressed with the addition of vitamin C and vitamin D, and 20 and 40% of cell viability was increased, respectively. Subsequently, the treatment of L-cysteine on thymol-treated melanoma cells reversed the toxic effect of thymol. Moreover, a significant oxidative stress condition was observed when B16 melanoma cells were cultured with thymol. In conclusion, the antioxidant actions of thymol generate a stable phenoxy radical intermediate, which generates reactive oxygen species and quinone oxide derivatives. Thus, it is proposed that the primary mechanism of thymol toxicity at high doses is due to the formation of antioxidant-related radicals.

Effects of thymol on mushroom tyrosinase-catalyzed melanin formation

The novel inhibitory mechanism of thymol (2-isopropyl-5-methylphenol) on dopachrome formation by mushroom tyrosinase (EC 1.14.18.1) was identified. The UV-vis spectrum and oxygen consumption assays showed dopachrome formation using L-tyrosine as a substrate was suppressed by thymol. This inhibitory activity was reversed by the addition of a well-known radical scavenger, butylated hydroxyanisole (BHA). Further investigations using N-acetyl-L-tyrosine as a substrate with HPLC analysis suggested that thymol inhibits chemical redox reactions between dopaquinone and leukodopachrome instead of enzymatic reaction. This redox inhibitory activity of thymol was examined by using a model redox reaction with L-dihydroxyphenylalanine (L-DOPA) and p-benzoquinone. Thymol successfully inhibited oxidation of L-DOPA to dopaquinone, coupled with reduction of p-benzoquinone. Hence, the suppression of dopachrome formation by thymol is due to the inhibition of conversion of leukodopachrome to dopachrome. The antioxidant property of thymol is a key characteristic for the inhibitory mechanism of melanin synthesis.

Effect of glutathione peroxidase mimic ebselen (PZ51) on endothelium and vascular structure of stroke‐prone spontaneously hypertensive rats

BACKGROUND

To investigate whether extrinsic antioxidant seleno-glutathione peroxidase mimic ebselen (PZ51) can protect endothelium and vascular structure of stroke-prone spontaneously hypertensive rats (SHRsp) during the chronic process of hypertension.

METHODS

Twenty-two 8-week-old SHRsp were randomized into a PZ51 group and a control group, and administered by gavage for 6 weeks. We examined the level of nitric oxide (NO) and malonaldehyde (MDA) in plasma. The intima-media thickness (IMT) of the common carotid artery (CCA) was measured by an image-analysis system. The endothelium of the CCA was observed by scanning electron microscopy. The eNOS protein of the major artery was assayed by immunohistochemistry and western blotting.

RESULTS

Compared with the control group, PZ51 decreased plasma MDA (7.88+/-1.06 vs 10.88+/-1.73 nmol/l, p<0.001) and increased plasma NO (40.02+/-9.74 vs 22.22+/-10.05 micromol/l, p<0.001), increased eNOS protein expression (8.25+/-2.36 vs 4.46+/-3.14, p=0.026), decreased IMT (69.85+/-5.47 vs 76.60+/-6.53 microm, p<0.05) significantly and alleviated the damage to the endothelium of the CCA.

CONCLUSION

Administration of PZ51 for 6 weeks can protect the endothelium and inhibit vascular remodeling, maybe due to its suppression of lipid peroxide formation and increase in eNOS protein expression.

Serum total antioxidant status and lipid peroxidation marker malondialdehyde levels in overt and subclinical hypothyroidism

BACKGROUND

Mitochondria are the main production site of free oxygen radicals, which can cause organ dysfunction by oxidation of cellular macromolecules such as carbohydrates, lipids and proteins. Oxidative stress may result from either overproduction of these species or from failure of the antioxidant defence systems. Thyroid hormones have well-known effects on mitochondrial oxygen consumption, but data about how hypothyroidism affects oxidative stress are controversial, and little is known about oxidative stress in subclinical hypothyroidism. Total antioxidant status (TAS) gives information about all of the antioxidants in the organism, while malondialdehyde (MDA) is a lipid peroxidation marker used to assess lipid peroxidation due to increased oxidative stress. We aimed to determine how hypothyroidism and subclinical hypothyroidism affect serum MDA and TAS.

SUBJECTS AND METHODS

Serum TAS, MDA, C-reactive protein levels and lipid compositions were studied in 20 hypothyroid, 40 subclinical hypothyroid and 40 healthy subjects.

RESULTS

MDA was elevated in both hypothyroid and subclinical hypothyroid patients compared with controls, while TAS levels show no significant differences between groups. Low-density lipoprotein (LDL) cholesterol levels were significantly high in both hypothyroid and subclinical hypothyroid patients. Triglyceride levels were high only in hypothyroid patients when compared with the controls. MDA showed a correlation with LDL cholesterol, total cholesterol and triglyceride.

CONCLUSIONS

These results suggest an increased oxidative stress in both hypothyroid and subclinical hypothyroidism states, which can be explained by both the insufficient increase in the antioxidant status and the altered lipid metabolism in these cases.

Triglyceride-rich lipoprotein lipolysis releases neutral and oxidized FFAs that induce endothelial cell inflammation

Triglyceride-rich lipoprotein (TGRL) lipolysis products provide a pro-inflammatory stimulus that can alter endothelial barrier function. To probe the mechanism of this lipolysis-induced event, we evaluated the pro-inflammatory potential of lipid classes derived from human postprandial TGRL by lipoprotein lipase (LpL). Incubation of TGRL with LpL for 30 min increased the saturated and unsaturated FFA content of the incubation solutions significantly. Furthermore, concentrations of the hydroxylated linoleates 9-hydroxy ocatadecadienoic acid (9-HODE) and 13-HODE were elevated by LpL lipolysis, more than other measured oxylipids. The FFA fractions elicited pro-inflammatory responses inducing TNFalpha and intracellular adhesion molecule expression and reactive oxygen species (ROS) production in human aortic endothelial cells (HAECs). The FFA-mediated increase in ROS was blocked by both the cytochrome P450 2C9 inhibitor sulfaphenazole and NADPH oxidase inhibitors. Compared with linoleate, 13-HODE was found to be a more potent inducer of ROS production in HAECs, an activity that was insensitive to both NADPH oxidase and cytochrome P450 inhibitors. Therefore, although the oxidative metabolism of FFA in endothelial cells can produce inflammatory responses, TGRL lipolysis can also release preformed mediators of oxidative stress (e.g., HODEs) that may influence endothelial cell function in vivo by stimulating intracellular ROS production.

Baroreflex sensitivity and oxidative stress in the LDL receptor knockout mice

This study aims at observing the effect of low-density lipoprotein (LDL) receptor deficiency in cholesterol blood levels, baroreflex sensitivity (BRS), nitric oxide (NO) bioavailability, and oxidative stress. The lack of LDL receptors in mice significantly increased the cholesterol blood levels (179+/-35 vs. 109+/-13mg/dL) in the knockout (KO) mice compared to control. There was no difference in basal mean arterial pressure and heart rate between the groups. However, in KO mice the BRS was significantly attenuated and the antioxidant enzyme activities, measured in erythrocytes and heart, were significantly decreased. On the other hand, the oxidative damage measured by chemiluminescence and carbonyls was increased, while total plasma nitrate levels were lower in KO mice, indicating a decrease in NO availability. In conclusion, these results indicate that the lack of LDL receptor increased cholesterol blood levels, induced oxidative stress and decreased BRS.

Antioxidants from Rabdosia japonica

The antioxidant activities of phenolic compounds: pedalitin, quercetin, rutin, isoquercitrin, and rosmarinic acid, isolated from the dried leaves of Rabdosia japonica Hara (Labiatae) were elucidated. All the phenolics tested exhibited superoxide scavenging activity and an inhibitory effect on xanthine oxidase (EC 1.1.3.22), and pedalitin showed the most potent antioxidant activity. Pedalitin prevents the generation of superoxide radicals in part by inhibiting xanthine oxidase competitively. Both pedalitin and quercetin inhibited uric acid formation by xanthine oxidase, and the inhibition kinetics analysed by Lineweaver-Burk plots found both flavonoids to be competitive inhibitors. On the other hand, isoquercitrin, rutin and rosmarinic acid were effective in scavenging superoxide radicals generated by the xanthine-xanthine oxidase system without inhibiting the enzyme.

Role of lupeol and lupeol linoleate on lipemic–oxidative stress in experimental hypercholesterolemia

Epidemiological studies have shown that there is a positive correlation between the incidence of coronary heart disease (CHD) and the blood cholesterol level. To study the effect of plant derived triterpene, lupeol and its ester lupeol linoleate, on blood lipid status and oxidant stress in heart and hemolysate, male albino Wistar rats were fed high cholesterol diet (normal rat chow supplemented with 4% cholesterol and 1% cholic acid; HCD) for 30 days. A significant increase (p<0.05) in plasma total cholesterol (4.22 fold) and triglycerides (1.7 fold) was observed in HCD fed rats, along with elevated LDL (3.56 fold) and VLDL (1.99 fold) cholesterol and decreased HDL cholesterol (34.14%). Treatment with lupeol and its derivative normalized the lipid profile. The significant increase (p<0.05) in lipid peroxidation (LPO) was paralleled by significantly diminished (p<0.05) activities of antioxidant enzymes (SOD, CAT and GPx) and decreased (p<0.05) concentration of antioxidant molecules (GSH, Vit C and Vit E) in cardiac tissue and hemolysate of HCD fed rats. The oxidative tissue injury in hypercholesterolemic rats was substantiated by the increase in cardiac marker, serum CPK and the drop in its activity in the heart tissue. Lupeol and lupeol linoleate treatment decreased the LPO levels and increased enzymatic and nonenzymatic antioxidants. CPK activity in the treated group was comparable with that of the control. These observations highlight the beneficial effects of the triterpene, lupeol and its linoleate ester derivative, in ameliorating the lipidemic-oxidative abnormalities in the early stage of hypercholesterolemic atherosclerosis.

Unsaturated fatty acids isolated from human lipoproteins activate protein phosphatase type 2Cβ and induce apoptosis in endothelial cells

Activity of serine/threonine protein phosphatase type 2C is known to be stimulated by certain unsaturated fatty acids and this enzyme dephosphorylates Bad, thus acting on apoptosis. This prompted us to investigate endothelial cell death. Here, we present evidence for the presence of protein phosphatase type 2Cbeta (PP2Cbeta) in human umbilical vein endothelial cells (HUVECs) and report on colocalization of PP2Cbeta and Bad in the cytosol of endothelial cells. Lipophilic compounds that stimulated PP2Cbeta activity in vitro were found to induce cell death of HUVECs. Lipoproteins did neither influence PP2Cbeta activity nor affect cell behaviour. Lipoproteins treated with the lipoprotein lipase, however, stimulated the activity of PP2Cbeta at least 10-fold concomitantly triggering cell death. Analytical methods revealed that both effects - stimulation of PP2Cbeta and apoptosis - were caused by free fatty acids liberated from VLDL, LDL and HDL with oleic acid and linoleic acid as major constituents. The results provide novel insights in endothelial apoptosis and suggest that PP2Cbeta participates in the development and progress of atherosclerosis.

Quercetin protects against linoleic acid-induced porcine endothelial cell dysfunction

Consumption of plant phenolics, such as quercetin, may be associated with decreased risk of cardiovascular disease by stabilizing and protecting vascular endothelial cells against oxidative and proinflammatory insults. The present study focused on the effect of quercetin on linoleic acid-induced oxidative stress and the inflammatory pathways of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). Because the transcription factor peroxisome proliferator activated receptor gamma (PPARgamma) was reported to downregulate inflammatory pathways, we further investigated the effect of quercetin on PPARgamma. Porcine pulmonary-arterial endothelial cells were activated with linoleic acid in the presence or absence of quercetin. Oxidative stress was markedly induced by endothelial cell exposure to linoleic acid and diminished by treatment with quercetin as measured via the oxidation of 2',7'-dichlorofluorescin. Quercetin reduced linoleic acid-mediated binding activity of NF-kappaB and AP-1 and mRNA levels of inflammatory genes such as interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (VCAM-1). Cotreatment of linoleic acid plus quercetin or vitamin E also decreased linoleic acid-induced binding activity of PPARgamma. These data suggest that quercetin has potent antioxidative and anti-inflammatory properties and protects endothelial cells against linoleic acid-mediated cell dysfunction.

Linoleic acid-induced endothelial activation: role of calcium and peroxynitrite signaling

Hypertriglyceridemia, an important risk factor of atherosclerosis, is associated with increased circulating free fatty acids. Research to date indicates that linoleic acid (LA), the major fatty acid in the American diet, may be atherogenic by activating vascular endothelial cells. However, the exact signaling mechanisms involved in LA-mediated proinflammatory events in endothelial cells still remain unclear. We previously reported increased superoxide formation after LA exposure in endothelial cells. The objective of the present investigation is to determine the role of calcium and peroxynitrite in mediating the proinflammatory effect of LA in vascular endothelial cells. LA exposure increased intracellular calcium, nitric oxide, and tetrahydrodiopterin levels as well as the expression of E-selectin. Inhibiting calcium signaling using 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid and heparin decreased the expression of E-selectin. Also, LA-mediated nuclear factor kappa B activation and E-selectin gene expression were suppressed by Mn (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (a superoxide scavenger), N(G)-monomethyl-l-arginine (an endothelial nitric oxide synthase inhibitor), and 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron (III) chloride (a peroxynitrite scavenger). LA exposure resulted in increased nitrotyrosine levels, as observed by Western blotting and immunofluorescence. Our data suggest that the proinflammatory effects of LA can be mediated through calcium and peroxynitrite signaling.

Cholesterol attenuates linoleic acid-induced endothelial cell activation

Vascular endothelial cell activation and dysfunction are critical early events in atherosclerosis. Even though very low or high levels of cholesterol can compromise cellular functions, cholesterol is a critical membrane component and may protect the vascular endothelium from oxidative stress and polyunsaturated fatty acid-mediated inflammatory responses. We have previously shown that the parent omega-6 fatty acid linoleic acid can markedly activate vascular endothelial cells. We now propose that membrane cholesterol can modify and inhibit linoleic acid-mediated endothelial cell dysfunction. To test this hypothesis, pulmonary artery endothelial cells were incubated with cholesterol (0 to 100 micromol/L) for 24 hours and then treated with 90 micromol/L of linoleic acid (18:2n-6) for 6 to 24 hours. In control cells, treatment with linoleic acid reduced intracellular glutathione levels and induced the DNA binding activity of nuclear factor-kappaB (NF-kappaB) leading to the upregulation of interleukin-6 (IL-6). In addition, the expression of endothelial nitric oxide synthase (eNOS) was altered, with linoleic acid increasing eNOS activity. In contrast, enrichment with cholesterol enhanced glutathione levels and reduced the linoleic acid-induced activation of NF-kappaBand the production of IL-6. Prior exposure to 50 micromol/L cholesterol also prevented the fatty acid-induced increase in eNOS activation. Cholesterol loading activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor that can decrease inflammatory responses. Furthermore, the PPAR-gamma agonist thiazolidinedione markedly downregulated the NF-kappaB activation mediated by linoleic acid. Our data suggest that signaling pathways linked to endothelial cell activation by prooxidant and proinflammatory insults may be influenced by cellular cholesterol levels.

Selenium supplementation acting through the induction of thioredoxin reductase and glutathione peroxidase protects the human endothelial cell line EAhy926 from damage by lipid hydroperoxides

The human endothelial cell line EAhy926 was used to determine the importance of selenium in preventing oxidative damage induced by tert-butyl hydroperoxide (tert-BuOOH) or oxidised low density lipoprotein (LDLox). In cells grown in a low selenium medium, tert-BuOOH and LDLox killed cells in a dose-dependent manner. At 555 mg/l LDLox or 300 microM tert-BuOOH, >80% of cells were killed after 20 h. No significant cell kill was achieved by these agents if cells were pre-incubated for 48 h with 40 nM sodium selenite, a concentration that maximally induced the activities of cytoplasmic glutathione peroxidase (cyGPX; 5.1-fold), phospholipid hydroperoxide glutathione peroxidase (PHGPX;1.9-fold) and thioredoxin reductase (TR; 3.1-fold). Selenium-deficient cells pre-treated with 1 microM gold thioglucose (GTG) (a concentration that inhibited 25% of TR activity but had no inhibitory effect on cyGPX or PHGPX activity) were significantly (P<0.05) more susceptible to tert-BuOOH toxicity (LC(50) 110 microM) than selenium-deficient cells (LC(50) 175 microM). This was also the case for LDLox. In contrast, cells pre-treated with 40 nM selenite prior to exposure to GTG were significantly more resistant to damage from tert-BuOOH and LDLox than Se-deficient cells. Treatment with GTG or selenite had no significant effect on intracellular total glutathione concentrations. These results suggest that selenium supplementation, acting through induction of TR and GPX, has the potential to protect the human endothelium from oxidative damage.

Selenoprotein expression in endothelial cells from different human vasculature and species

Selenium (Se) can protect endothelial cells (EC) from oxidative damage by altering the expression of selenoproteins with antioxidant function such as cytoplasmic glutathione peroxidase (cyGPX), phospholipid hydroperoxide glutathione peroxidase (PHGPX) and thioredoxin reductase (TR). If the role of Se on EC function is to be studied, it is essential that a model system be chosen which reflects selenoprotein expression in human EC derived from vessels prone to developing atheroma. We have used [75Se]-selenite labelling and selenoenzyme measurements to compare the selenoproteins expressed by cultures of EC isolated from different human vasculature with EC bovine and porcine aorta. Only small differences were observed in selenoprotein expression and activity in EC originating from human coronary artery, human umbilical vein (HUVEC), human umbilical artery and the human EC line EAhy926. The selenoprotein profile in HUVEC was consistent over eight passages and HUVEC isolated from four cords also showed little variability. In contrast, EC isolated from pig and bovine aorta showed marked differences in selenoprotein expression when compared to human cells. This study firmly establishes the suitability and consistency of using HUVEC (and possibly the human cell line EAhy926) as a model to study the effects of Se on EC function in relation to atheroma development in the coronary artery. Bovine or porcine EC appear to be an inappropriate model.

Serum free fatty acid pattern and risk of myocardial infarction: a case-control study

OBJECTIVES

To investigate the association between composition of serum free fatty acid (FFA) fraction and risk of a first myocardial infarction (MI).

DESIGN

A case-control design.

SETTING

The patients were recruited from Ullevål Hospital in Oslo and Ostfold Central Hospital in Fredrikstad and Sarpsborg, Norway.

SUBJECTS

A total of 103 patients with first MI and 104 population controls, both men and postmenopausal women, age 45-75 years.

RESULTS

The mean molar percentage content of docosahexaenoic (DHA), eicosapentaenoic (EPA), stearic and myristic acid in the serum FFA fraction was significantly lower in cases than in controls, whereas that of oleic and linoleic acid was higher in cases. Increased percentage content of total very long-chain omega-3 fatty acids (VLC n-3) in serum FFA was associated with decreased risk of MI. Multivariate odds ratio (OR), adjusted for age, sex, waist-hip ratio, smoking, family history of coronary heart disease (CHD) and years of education was 0.20 (95% CI 0.06-0.63) for the highest vs. lowest quartile. Also increased content of stearic acid was associated with decreased risk. Multivariate OR adjusted as above was 0.38 (95% CI 0.14-1.04) for the highest versus lowest quartile. After adjustment for oleic acid, however, the inverse linear trend was no longer significant.

CONCLUSIONS

The percentage content of VLC n-3 as well as of stearic acid in serum FFA was inversely associated with risk of myocardial infarction. That of VLC n-3 may reflect diet, but additionally these free fatty acids might in some way be related to the pathogenetic process and not only reflect their content in adipose tissue.

Protective role of L-carnitine on liver and heart lipid peroxidation in atherosclerotic rats

Lipid peroxides are considered to be the initiation factor for atherosclerosis. Present study depicts that L-carnitine treatment (300 mg/kg body weight/day) for 7 and 14 days caused significant reduction in the tissue lipid peroxidations. It also shows marked improvement in the antioxidant status. By this way carnitine maintain the normal function of the cells.

The role of methyl-linoleic acid epoxide and diol metabolites in the amplified toxicity of linoleic acid and polychlorinated biphenyls to vascular endothelial cells

Selected dietary lipids may increase the atherogenic effects of environmental chemicals, such as polychlorinated biphenyls (PCBs), by cross-amplifying mechanisms leading to dysfunction of the vascular endothelium. We have shown previously that the omega-6 parent fatty acid, linoleic acid, or 3,3',4,4'-tetrachlorobiphenyl (PCB 77), an aryl hydrocarbon (Ah) receptor agonist, independently can cause disruption of endothelial barrier function. Furthermore, cellular enrichment with linoleic acid can amplify PCB-induced endothelial cell dysfunction. We hypothesize that the amplified toxicity of linoleic acid and PCBs to endothelial cells could be mediated in part by cytotoxic epoxide metabolites of linoleic acid called leukotoxins (LTX) or their diol derivatives (LTXD). Exposure to LTXD resulted in a dose-dependent increase in albumin transfer across endothelial cell monolayers, whereas this disruption of endothelial barrier function was observed only at a high concentration of LTX. Pretreatment with the cytosolic epoxide hydrolase inhibitor 1-cyclohexyl-3-dodecyl urea partially protected against the observed LTX-induced endothelial dysfunction. Endothelial cell activation mediated by LTX and/or LTXD also enhanced nuclear translocation of the transcription factor NF-kappa B and gene expression of the inflammatory cytokine IL-6. Inhibiting cytosolic epoxide hydrolase decreased the LTX-mediated induction of both NF-kappa B and the IL-6 gene, whereas the antioxidant vitamin E did not block LTX-induced endothelial cell activation. Most importantly, inhibition of cytosolic epoxide hydrolase blocked both linoleic acid-induced cytotoxicity, as well as the additive toxicity of linoleic acid plus PCB 77 to endothelial cells. Interestingly, cellular uptake and accumulation of linoleic acid was markedly enhanced in the presence of PCB 77. These data suggest that cytotoxic epoxide metabolites of linoleic acid play a critical role in linoleic acid-induced endothelial cell dysfunction. Furthermore, the severe toxicity of PCBs in the presence of linoleic acid may be due in part to the generation of epoxide and diol metabolites. These findings have implications in understanding interactive mechanisms of how dietary fats can modulate dysfunction of the vascular endothelium mediated by certain environmental contaminants.

Antimicrobial activity of tannin components from Vaccinium vitis-idaea L

Reactive oxygen species have been implicated as important pathological mediators in many clinical disorders, including periodontal disease. As a possible alternative for the treatment of periodontal disease, the antimicrobial activity of six tannins isolated from Vaccinium vitis-idaea L., with confirmed antioxidant activity, were assayed by the agar dilution method against selected periodontal pathogens, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia. The results showed that epicatechin-(4beta-->8)-epicatechin-(4beta-->8, 2beta-->O-->7)-catechin had strong antimicrobial activity against P. gingivalis and P. intermedia, but not A. actinomycetemcomitans. The other tannins tested did not show antimicrobial activity. We conclude that tannins isolated from V. vitis-idaea L. with antimicrobial activity could potentially be used for the treatment of periodontal disease.

A diet high in whole and unrefined foods favorably alters lipids, antioxidant defenses, and colon function

OBJECTIVE

Diets rich in whole and unrefined foods, like whole grains, dark green and yellow/orange-fleshed vegetables and fruits, legumes, nuts and seeds, contain high concentrations of antioxidant phenolics, fibers and numerous other phytochemicals that may be protective against chronic diseases. This study compared the effects of a phytochemical-rich diet versus a refined-food diet on lipoproteins, antioxidant defenses and colon function.

METHODS

Twelve hyperlipidemic women followed two diets for four weeks starting with a refined-food diet. Subjects then directly crossed over to the phytochemical-rich diet. Duplicate, fasting serum lipids and single, fasting antioxidant enzymes were measured at the end of the four-week refined-food diet period (baseline) and again at the end of the phytochemical-rich diet period.

RESULTS

Total energy and total fat intake were similar during both diet periods, but there was a decrease in saturated fat (SFA) of 61% in the phytochemical-rich diet group. Dietary fiber, vitamin E, vitamin C and carotene intakes were 160%, 145%, 160% and 500% more, respectively, than during the refined-food diet period. The phytochemical-rich diet induced a drop of 13% in total cholesterol (TC) (p < 0.05) and 16% (p < 0.001) in low density lipoprotein-cholesterol (LDL-C). Erythrocyte superoxide dismutase decreased 69% (p < 0.01) and glutathione peroxidase dropped 35% (p < 0.01). Colon function was improved on the phytochemical-rich diet.

CONCLUSIONS

A diet abundant in phytochemically-rich foods beneficially affected lipoproteins, decreased need for oxidative defense mechanisms and improved colon function.

The susceptibility of red blood cells to autoxidation in type 2 diabetic patients with angiopathy

We examined the in vitro susceptibility of red blood cell (RBC) lipids to oxidation in type 2 diabetic patients with or without angiopathy. Lipid peroxidation was assessed by quantifying thiobarbituric acid (TBA) reactivity as malondialdehyde (MDA). We also examined the RBC antioxidant status by determining glutathione (GSH) levels. Before in vitro oxidation, RBC MDA levels were significantly higher in both diabetic groups than in the controls (P < .001), and a significant difference was found between the two diabetic groups (P < .05). After in vitro treatment of RBCs with hydrogen peroxide, the degree of lipid peroxidative damage was significantly higher in diabetic patients with angiopathy versus diabetics without angiopathy (P < .001). Diabetic patients have low RBC GSH levels compared with controls, and after in vitro oxidation, the levels were significantly decreased in diabetics (P < .001). There was not a significant correlation between RBC MDA levels and glycated hemoglobin (GHb), plasma cholesterol, and triglyceride. The correlation between RBC MDA and GSH was weak (P < .001). We suggest that the results of this study might help to clarify the role of oxidative mechanisms as an in vitro model of degenerative damage in type 2 diabetic angiopathic complications.

Antioxidant activity of tannin components from Vaccinium vitis-idaea L

Reactive oxygen molecules have been implicated as important pathological mediators in many clinical disorders and periodontal disease. To provide possible alternative treatment of periodontal disease, six tannins isolated from Vaccinium vitis-idaea L. were evaluated for anti-lipid peroxidation, anti-superoxide formation and free radical scavenging activity. The results showed that cinnamtannin B1 displayed the strongest anti-lipid peroxidation activity, proanthocyanidin A-1 displayed the strongest superoxide scavenging activity, and epicatechin-(4beta--> 6)-epicatechin-(4beta-->8, 2beta-->O--> 7)-catechin had the strongest anti-superoxide formation effect. We conclude that tannins isolated from V. vitis-idaea L. exhibited multiple antioxidant activity, and could be used for the treatment of periodontal disease.

The role of linoleic acid in endothelial cell gene expression. Relationship to atherosclerosis

There is evidence that linoleic acid plays a critical role in gene expression and vascular function as it relates to the pathogenesis of atherosclerosis. The lipid environment, particularly linoleic acid and its derivatives, of the vascular endothelium may profoundly influence the inflammatory response mediated by cytokines. Modulations in the level of activity of a select set of endothelial transcription factors appear to provide a mechanism for linking lipid/cytokine-mediated vessel wall dysfunction, including endothelial cell activation, altered proteoglycan metabolism, and endothelial barrier dysfunction, with the onset of atherosclerotic lesion formation. The activity of endothelial transcription factors is in part regulated by the balance of cellular oxidative stress and antioxidant status. Our data suggest that linoleic acid can activate the vascular endothelium and may thus be an atherogenic fatty acid. Furthermore, nutrients/chemicals with antioxidant properties can protect endothelial cells against lipid-mediated cell injury, suggesting that oxidative stress is a critical component in linoleic acid-mediated gene expression. Our discoveries that linoleic acid can influence significantly the cytokine-mediated inflammatory response may open new fields in dietary intervention of atherosclerosis.

Antioxidant activity of the microalga Spirulina maxima

Spirulina maxima, which is used as a food additive, is a microalga rich in protein and other essential nutrients. Spirulina contains phenolic acids, tocopherols and beta-carotene which are known to exhibit antioxidant properties. The aim of the present study was to evaluate the antioxidant capacity of a Spirulina extract. The antioxidant activity of a methanolic extract of Spirulina was determined in vitro and in vivo. The in vitro antioxidant capacity was tested on a brain homogenate incubated with and without the extract at 37 degrees C. The IC50 (concentration which causes a 50% reduction of oxidation) of the extract in this system was 0.18 mg/ml. The in vivo antioxidant capacity was evaluated in plasma and liver of animals receiving a daily dose of 5 mg for 2 and 7 weeks. Plasma antioxidant capacity was measured in brain homogenate incubated for 1 h at 37 degrees C. The production of oxidized compounds in liver after 2 h of incubation at 37 degrees C was measured in terms of thiobarbituric acid reactant substances (TBARS) in control and experimental groups. Upon treatment, the antioxidant capacity of plasma was 71% for the experimental group and 54% for the control group. Data from liver spontaneous peroxidation studies were not significantly different between groups. The amounts of phenolic acids, alpha-tocopherol and beta-carotene were determined in Spirulina extracts. The results obtained indicate that Spirulina provides some antioxidant protection for both in vitro and in vivo systems.

Antioxidant activity of the microalga Spirulina maxima

Spirulina maxima, which is used as a food additive, is a microalga rich in protein and other essential nutrients. Spirulina contains phenolic acids, tocopherols and beta-carotene which are known to exhibit antioxidant properties. The aim of the present study was to evaluate the antioxidant capacity of a Spirulina extract. The antioxidant activity of a methanolic extract of Spirulina was determined in vitro and in vivo. The in vitro antioxidant capacity was tested on a brain homogenate incubated with and without the extract at 37 degrees C. The IC50 (concentration which causes a 50% reduction of oxidation) of the extract in this system was 0.18 mg/ml. The in vivo antioxidant capacity was evaluated in plasma and liver of animals receiving a daily dose of 5 mg for 2 and 7 weeks. Plasma antioxidant capacity was measured in brain homogenate incubated for 1 h at 37 degrees C. The production of oxidized compounds in liver after 2 h of incubation at 37 degrees C was measured in terms of thiobarbituric acid reactant substances (TBARS) in control and experimental groups. Upon treatment, the antioxidant capacity of plasma was 71% for the experimental group and 54% for the control group. Data from liver spontaneous peroxidation studies were not significantly different between groups. The amounts of phenolic acids, alpha-tocopherol and beta-carotene were determined in Spirulina extracts. The results obtained indicate that Spirulina provides some antioxidant protection for both in vitro and in vivo systems.

Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata

Licochalcone A, B, C, D and echinatin, retrochalcones isolated from the roots of Glycyrrhiza inflata (licorice), along with an ordinary chalcone isoliquiritigenin, were assessed for their inhibitory activities on lipid peroxidation in various systems and radical scavenging activity. Among those tested, licochalcones B and D strongly inhibited superoxide anion production in the xanthine/xanthine oxidase system. These two compounds also showed potent scavenging activity on DPPH radical. Microsomal lipid peroxidation induced by Fe(III)-ADP/NAPDH was inhibited almost completely by 3 micrograms/ml of licochalcones B and D. Mitochondrial lipid peroxidation induced by Fe(III)-ADP/NADH was more sensitive to these retrochalcones; almost complete inhibition was observed at 10 micrograms/ml of all retrochalcones tested. Licochalcones B and D scavenged superoxide anion in microsome. Furthermore, these retrochalcones protected red cells against oxidative hemolysis. These phenolic compounds were shown to be effective to protect biological systems against various oxidative stresses.

Effect of vitamin E and probucol on dietary cholesterol-induced atherosclerosis in rabbits

The preventive effect of vitamin E and Probucol against atherosclerosis in rabbits were compared. Atherosclerosis was induced by a 2% cholesterol-containing vitamin E-poor diet (5-10 ppm). Six groups of five rabbits each were studied. Group I (control) was fed on a vitamin E-poor diet. The other groups had the following supplements: group II, 50 mg/kg vitamin E i.m.; group III, 2% cholesterol; group IV, 2% cholesterol plus 50 mg/kg vitamin E i.m., group V, 2% cholesterol plus 1% Probucol; group VI, 2% cholesterol + 1% Probucol plus 50 mg/kg vitamin E i.m. After 4 weeks, aortas were removed and analyzed by light and scanning electron microscopy for atherosclerotic lesions. Samples of the media were analyzed for protein kinase C activity. The aortas of cholesterol-fed rabbits showed typical atherosclerotic lesions, detected by microscopic examination, their media smooth muscle cells exhibited an increase in protein kinase C activity. Vitamin E fully prevented cholesterol-induced atherosclerotic lesions and the induction of protein kinase C activity. Probucol was not effective in preventing either cholesterol-induced atherosclerotic lesions or the induction of protein kinase C activity. These results show that the protective effect of vitamin E against hypercholesterolemic atherosclerosis is not produced by an other antioxidant such as Probucol, and therefore, may not be linked to the antioxidant properties of this vitamin. The effects observed at the level of smooth muscle cells ex vivo suggest an involvement of signal transduction events in the protective effect of vitamin E against atherosclerosis.

Lipid peroxidation and antioxidant status in experimental animals: effects of aging and hypercholesterolemic diet

Effects of aging and hypercholesterolemic diet on lipid peroxidation and antioxidant status were investigated in rats. The rats were divided into four groups of ten: Group I; young rats receiving standard lab chow; Group II; young rats on hypercholesterolemic diet (0.4 g/rat/day); Group III; aged rates receiving standard lab chow; Group IV; aged rats on hypercholesterolemic diet (0.4 g/rat/day). Plasma lipid peroxidation end product level was determined as thiobarbutiric acid reactive substances (TBARS). Plasma cholesterol concentration was analyzed by a kinetic enzymatic method. Erythrocyte superoxide dismutase (CuZn SOD), glutathione peroxidase (GSH Px) and glutathione (GSH) levels were determined spectrophotometrically. Cholesterol values were found to be significantly high (p < 0.001), TBARS (0.05 > p > 0.02) and GSH (p < 0.001) levels significantly low in aged rats in comparison with young rats. Hypercholesterolemic diet induced significant increases in GSH (p < 0.001) and CuZn SOD (p < 0.001) levels, whereas a significant decrease in GSH Px activity (0.05 > p > 0.02) was observed in aged rats. In young rats hypercholesterolemic diet caused a significant increase in both GSH and CuZnSOD levels. Our results indicate an imbalance between radical production and destruction in favour of prooxidant conditions in the young rats and the induction by hypercholesterolemic diet of the antioxidative response in erythrocytes.

Antiperoxidative activity of neolignans from Magnolia obovata

Honokiol and magnolol, neolignans in Magnolia obovata, have been evaluated as antioxidants. Microsomal lipid peroxidation induced by Fe(III)-ADP/NADPH and mitochondrial lipid peroxidation induced by Fe(III)-ADP/NADH were inhibited by these compounds. These neolignans protected mitochondrial respiratory chain enzyme activity against NADPH-induced peroxidative stress and protected red cells against oxidative haemolysis. The anti-oxidative activity of honokiol was more potent than that of magnolol. Neolignans in M. obovata were shown to be effective in protecting biological systems and functions against oxidative stress.

[Vitamin E distribution of lipoproteins in patients with coronary heart disease]

The oxidative modification of LDL could play an important role for the development of atherosclerosis. The present study was undertaken to compare the concentration of vitamin E in serum and lipoproteins between patients with coronary heart disease and a healthy control group. The study included 36 male patients with angiographically established coronary three-vessel disease and 32 healthy volunteers. Cholesterin, triglyceride, LDL-cholesterin, HDL-cholesterin, and vitamin E in serum and in lipoproteins were determined. The serum vitamin E concentration in the patients group was significantly higher than in controls. However, vitamin E was correlated with cholesterin in both groups. The distribution of vitamin E in healthy volunteers was LDL 53%, HDL 34% and VLDL 13%, whereas that in patients was LDL 57%, HDL 26% and VLDL 16%. The level of vitamin E in LDL was in the patient group significantly higher and correlated with the vitamin E- and the cholesterin-concentration in serum. The ratio vitamin E/cholesterin in LDL was in patients discretely lower, whereas the same ratio in HDL was higher. The results suggest that also in patients with coronary artery disease vitamin E is related to the lipid concentration. The decreased ratio vitamin E/cholesterin in LDL could be attributed to the oxidative modification of LDL.

Inhibition of lipid peroxidation by diterpenoid from Podocarpus nagi

A diterpenoid, totarol (1), from Podocarpus nagi was evaluated as an antioxidant. This diterpenoid inhibited autoxidation of linoleic acid. Mitochondrial and microsomal lipid peroxidation induced by Fe(III)-ADP/NADH or Fe(III)-ADP/NADPH were also inhibited. Nagilactone E (2), a norditerpene lactone isolated from the same source, had no antioxidative activity. Furthermore, totarol protected red cells against oxidative hemolysis. This diterpene was shown to be effective in protecting biological systems against oxidative stresses.

Inhibition of lipid peroxidation by sesquiterpenoid in Heterotheca inuloides

A sesquiterpenoid, 7-hydroxy-3,4-dihydrocadalin, isolated from a Mexican medicinal plant Heterotheca inuloides was evaluated as an antioxidant. This sesquiterpenoid inhibited mitochondrial and microsomal lipid peroxidation induced by Fe(III)-ADP/NADH or Fe(III)-ADP/NADPH. Furthermore, 7-hydroxy-3,4-dihydrocadalin protected red cells against oxidative haemolysis. This sesquiterpene was thus shown to be effective in protecting biological systems against oxidative stresses.

Role of fatty acids and eicosanoids in modulating proteoglycan metabolism in endothelial cells

Endothelial cell dysfunction is considered to be a critical event in the etiology of atherosclerosis. Thus, the preservation of endothelial structure and function are a prerequisite for normal control of vascular permeability properties, mediation of both inflammatory and immunologic responses and the general 'communication' between blood-borne cells and abluminal tissues. Many of these properties can be influenced by proteoglycans present in vascular tissues. There is evidence that selected lipids can be atherogenic by altering endothelial proteoglycan metabolism. Little is known about the role of fatty acids in modulating proteoglycan composition in endothelial cells. Data suggest, however, that linoleic acid in particular can adversely alter proteoglycan metabolism, which may be related to an imbalance in eicosanoid synthesis patterns. These events could be sufficient to disrupt normal endothelial barrier function, initiate smooth muscle migration and proliferation, and result in other metabolic dysfunctions associated with the etiology of vascular diseases such as atherosclerosis. Thus, the focus of this review is on fatty acids and eicosanoids as they may alter proteoglycan metabolism of vascular tissues and in particular of the endothelium.

Influence of nutrients and cytokines on endothelial cell metabolism

The vascular endothelium plays an active role in physiological processes such as hemostasis, regulation of vessel tone and vascular permeability. Cell injury, or any event which disrupts endothelial integrity and thus endothelial permeability properties, may be involved in the early events leading to atherosclerotic lesion formation. Because of its constant exposure to blood components, including prooxidants, diet-derived fats and their derivatives, the endothelium is susceptible to oxidative stress and to injury mediated by blood lipid components. It is likely that these events potentiate the overall inflammatory response to injury by increasing cytokine release in proximity to the endothelium, which then could further disrupt endothelial barrier function. Even though mechanisms associated with lipid/cytokine-mediated endothelial cell dysfunction are unclear, our data suggest that they may be both oxidative and non-oxidative in nature. We suggest that dietary fats, rich in certain unsaturated fatty acids are atherogenic by enhancing the formation of reactive oxygen intermediates. These intermediates can activate oxidative stress-responsive transcription factors, such as NF-kappa B, which in turn may promote cytokine production, adhesion molecule expression and ultimately endothelial barrier dysfunction. The resulting disturbances in endothelial integrity possibly allow increased penetration of cholesterol-rich lipoprotein remnants into the arterial wall, a critical event in the etiology of atherosclerosis. Data suggest that certain nutrients, which have antioxidant and/or membrane stabilizing properties, protect endothelial cells by interfering with the above proposed mechanisms of endothelial cell dysfunction.

Absence of antioxidant effects of nifedipine and diltiazem on myocardial membrane lipid peroxidation in contrast with those of nisoldipine and propranolol

Both the production of active oxygen species and cellular damage due to concurrent lipid peroxidation are believed to be important factors in the pathogenesis of cardiovascular diseases and the ageing process. Since cardiovascular drugs are often administered over a long term, it might be advantageous if they reduced lipid peroxidation. There have been conflicting reports concerning the antiperoxidant effect of nifedipine. Therefore, we investigated whether nifedipine could inhibit lipid peroxidation in a nonenzymatic active oxygen-generating system, utilizing rat crude myocardial membranes, and compared its effect with those of propranolol, nisoldipine, and diltiazem. Nifedipine and diltiazem had no inhibitory effects on the lipid peroxidation of myocardial membranes. In contrast, nisoldipine and propranolol had a concentration-dependent antiperoxidant effect, with IC50 values of 28.2 and 50.1 microM, respectively. In addition, nisoldipine appeared to possess dual antiperoxidant mechanisms, involving both preventive and chain-breaking properties.

Changes in drinking water selenium and mortality for coronary disease in a residential cohort

In a part of the municipal territory of Reggio Emilia, northern Italy, selenium in drinking water decreased from 7 micrograms/L to less than 1 micrograms/L. In a cohort of 4419 individuals, previously exposed for at least 5 yr to the drinking water with higher selenium content, the 7-yr temporal distribution of deaths for coronary disease and for stroke was analyzed to examine a possible relationship with changes in drinking water selenium. From January 1986 until August 1988, when tap water selenium was 7 micrograms/L, deaths for coronary disease were one in males and two in females. After the decrease in drinking water selenium, 21 and 10 coronary deaths were observed, respectively, in males and in females from September 1988 to December 1992. No significant difference in the temporal distribution of stroke deaths was observed both in males and in females. Even if an effect of chance and aging in the temporal distribution of coronary deaths may not be excluded, findings of the study seem to be consistent with the hypothesis of a beneficial effect of selenium on coronary disease mortality.

Nutrition, endothelial cell metabolism, and atherosclerosis

The vascular endothelium that forms an interface between the blood and the surrounding tissues is continuously exposed to both physiologic and pathophysiologic stimuli. These stimuli are often mediated by nutrients that can contribute to the overall function of the endothelial cell in the regulation of vascular tone, coagulation and fibrinolysis, cellular growth and differentiation, and immune and inflammatory responses. Therefore, nutrient-mediated functional changes of the endothelium and the underlying tissues may be significantly involved in the atherosclerotic disease process. There is evidence that individual nutrients or nutrient derivatives may either provoke or prevent metabolic and physiologic perturbations of the vascular endothelium. Preservation of nutrients that exhibit antiatherogenic properties may, therefore, be a critical issue in the preparation and processing of foods. This review focuses on selected nutrients as they affect endothelial cell metabolism and their possible implications in atherosclerosis.

Molecular and cellular concepts in atherosclerosis

Atherosclerosis is a complex disease of uncertain cause. Its pathobiology is believed to represent an abnormal expression of the processes of vascular healing. Etiologic models derive from a 'response to injury' paradigm and can be divided into three separate disease stages: endothelial dysfunction, smooth muscle proliferation and architectural disruption. The initiating event of endothelial dysfunction is unknown, but is believed to be related to low-density lipoproteins and/or their oxidized derivatives. Endothelial injury is signalled to the smooth muscle cells of the media by three routes: direct cell-cell interaction, secretion of soluble growth factors and monocyte-derived cytokines. Monocytes are recruited by the endothelium and invade the subintimal space by a complex interaction of a variety of adhesion proteins and receptors on both cell types. Smooth muscle cell proliferation is initiated by a change in phenotype expression from 'contractile' to 'synthetic' resulting from the binding of fibronectin to specific integrin receptors. Three functionally distinct activities may represent separate subtypes of the 'synthetic phenotype': migration from the media to the intima, increased proliferation and inappropriate extracellular matrix synthesis. The loss of normal regulatory control and anchorage independence of proliferation suggest a relationship to oncogenic transformation. Both migration and proliferation result from the binding of platelet-derived growth factor-like factors to smooth muscle cell receptors, which initiates a cascade of intracellular molecular events leading either to cytoskeletal locomotory restructuring or cell cycle activation. Both pathways also appear to be coregulated by integrin receptors and both depend upon phosphorylation of cell membrane, cytosolic and nuclear regulatory proteins. Clinical expression of atherosclerosis may follow sudden loss of architectural integrity of the intimal plaque by three different mechanisms: plaque fissuring, intraluminal plaque rupture or intramural hemorrhage related to abnormal vessel wall stress and/or biochemistry.