Oxidation of carotenoids by heat and tobacco smoke

The stability to autoxidation of the polar carotenoids, lutein and zeaxanthin, was compared to that of the less polar carotenoids, beta-carotene and lycopene at physiologically or pathophysiologically relevant concentrations of 2 and 6 microM, after exposure to heat or cigarette smoke. Three methodological approaches were used: 1) Carotenoids dissolved in solvents with different polarities were incubated at 37 and 80 degrees C for different times. 2) Human plasma samples were subjected to the same temperature conditions. 3) Methanolic carotenoid solutions and plasma were also exposed to whole tobacco smoke from 1-5 unfiltered cigarettes. The concentrations of individual carotenoids in different solvents were determined spectrophotometrically. Carotenoids from plasma were extracted and analyzed using high performance liquid chromatography. Carotenoids were generally more stable at 37 than at 80 degrees C. In methanol and dichloromethane the thermal degradation of beta-carotene and lycopene was faster than that of lutein and zeaxanthin. However, in tetrahydrofuran beta-carotene and zeaxanthin degraded faster than lycopene and lutein. Plasma carotenoid levels at 37 degrees C did not change, but decreased at 80 degrees C. The decrease of beta-carotene and lycopene levels was higher than those for lutein and zeaxanthin. Also in the tobacco smoke experiments the highest autoxidation rates were found for beta-carotene and lycopene at 2 microM, but at 6 microM lutein and zeaxanthin depleted to the same extent as beta-carotene. These data support our previous studies suggesting that oxidative stress degrade beta-carotene and lycopene faster than lutein and zeaxanthin. The only exception was the thermal degradation of carotenoids solubilized in tetrahydrofuran, which favors faster breakdown of beta-carotene and zeaxanthin.     

Thermotropic phase behaviour of alpha-dipalmitoylphosphatidylcholine multibilayers is influenced to various extents by carotenoids containing different structural features--evidence from differential scanning calorimetry

Carotenoids are the effective modulators of physical properties of model and natural membranes. To demonstrate the relationship between the structure of carotenoids and their effect on the molecular dynamics of membranes, we have investigated the influence of five structurally different carotenoids: beta-carotene, lycopene, lutein, violaxanthin, zeaxanthin and additionally carotane--a fully saturated derivative of beta-carotene, on thermotropic phase behaviour of dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles by means of differential scanning calorimetry (DSC). The results obtained indicate that the carotenoids used modulated the thermotropic properties of multibilayers to various extents, broadening the pretransition and the main phase transition peaks and shifting them to lower temperatures. Pronounced decrease of pretransition enthalpy (DeltaH(p)) proves that carotenoids very strongly alter the membrane properties in its gel phase. Comparison of the influence of several carotenoids shows that a rigid, polyisoprenoid chain plays a basic role in altering the thermotropic properties of such membranes and the presence of rings without oxygen-containing groups has a minor significance for the observed interactions. Carotenoids containing epoxy and/or hydroxy groups attached to their rings modify the thermotropic phase behaviour of DPPC multilamellar vesicles stronger than carotenes--a result of their orientation in the DPPC bilayer.     

Interaction of peroxynitrite with carotenoids in human low density lipoproteins

Interaction of peroxynitrite, the product of the reaction between nitric oxide and superoxide, with carotenes (lycopene, alpha-carotene, and beta-carotene) and oxocarotenoids (beta-cryptoxanthin, zeaxanthin, and lutein) was studied both in homogeneous solution and in human low-density lipoproteins (LDL). All carotenoids prevented the formation of rhodamine 123 from dihydrorhodamine 123 caused by peroxynitrite, suggesting that the carotenoids react with peroxynitrite. Oxocarotenoids were as effective as biothiols, known scavengers of peroxynitrite, whereas lycopene, alpha-carotene, and beta-carotene exhibited a considerably more pronounced effect. Moreover, peroxynitrite caused a loss of carotenoids in LDL as was revealed by HPLC. The concentration of peroxynitrite causing half-maximal loss of carotenoids in LDL ranged from 13 +/- 3 to 68 +/- 3 microM for lycopene and lutein, respectively. Again, oxocarotenoids were less reactive in this system. A correlation between efficiency of carotenoids in the competitive assay with dihydrorhodamine 123 and the concentration of peroxynitrite causing half-maximal loss of carotenoids in LDL was observed (r(2) = 0.91). These findings suggest that carotenoids can efficiently react with peroxynitrite and perform the role of scavengers of peroxynitrite in vivo.     

cis-trans isomers of lycopene and beta-carotene in human serum and tissues.

Since cis or trans isomers of carotenoids may have different biological reactivities, the isomeric composition of lycopene and beta-carotene was measured in serum and seven human tissues. In addition to all-trans lycopene, at least three cis-isomers (9-, 13-, and 15-cis) were present, accounting for more than 50% of total lycopene. 13- and 15-cis-beta-carotene, however, were present at only 5% of the all-trans isomer. In addition, 9-cis-beta-carotene was present in tissue samples but not in serum. There were interindividual differences in carotenoid levels of the different tissue types, but liver, adrenal gland, and testes always contained significantly higher amounts of the carotenoids than kidney, ovary, and fat; carotenoids in brain stem tissue were below the detection limit. beta-Carotene was the major carotenoid in liver, adrenal gland, kidney, ovary, and fat, whereas lycopene was the predominant carotenoid in testes.     

Dietary intake of carotenoids and retinol and the risk of acute myocardial infarction in Italy

BACKGROUND: Carotenoids may reduce the risk of coronary heart disease through their antioxidant properties, but the results of epidemiological studies are controversial. We analysed the relation between the intake of selected carotenoids and retinol and risk of acute myocardial infarction (AMI). METHODS: A case-control study was conducted in Milan, Italy, in 1995-2003. Cases were 760 patients with nonfatal AMI, and controls 682 patients admitted to hospital. RESULTS: The risk of AMI decreased with increasing intake of alpha-carotene (odds ratios, OR = 0.71, 95% confidence intervals, CI 0.51-0.98, for the highest vs the lowest quartile of intake), beta-carotene (OR = 0.71, 95% CI 0.50-1.01) and beta-criptoxanthin (OR = 0.64, 95% CI 0.46-0.88). No associations emerged for total carotenoids, lycopene, lutein plus zeaxanthin and retinol. CONCLUSIONS: Our study suggests a weak protective effect of alpha-carotene, beta-carotene and beta-criptoxanthin on the risk of AMI. It also indicates that total carotenoids, lycopene, lutein plus zeaxanthin and retinol were not related to the risk of the disease.     

Lycopene and beta-carotene decompose more rapidly than lutein and zeaxanthin upon exposure to various pro-oxidants in vitro

Major carotenoids of human plasma and tissues were exposed to radical-initiated autoxidation conditions. The consumption of lutein and zeaxanthin, the only carotenoids in the retina, and lycopene and beta-carotene, the most effective quenchers of singlet oxygen in plasma, were compared. Under all conditions of free radical-initiated autoxidation of carotenoids which were investigated, the breakdown of lycopene and beta-carotene was much faster than that of lutein and zeaxanthin. Under the influence of UV light in presence of Rose Bengal, by far the highest breakdown rate was found for beta-carotene, followed by lycopene. Bleaching of carotenoid mixtures mediated by NaOCl, addition of azo-bis-isobutyronitril (AIBN), and the photoirradiation of carotenoid mixtures by natural sunlight lead to the following sequence of breakdown rates: lycopene > beta-carotene > zeaxanthin > lutein. The slow degradation of the xanthophylls zeaxanthin and lutein may be suggested to explain the majority of zeaxanthin and lutein in the retina of man and other species. In correspondence to that, the rapid degradation of beta-carotene and lycopene under the influence of natural sunlight and UV light is postulated to be the reason for the almost lack of those two carotenoids in the human retina. Nevertheless, a final proof of that theory is lacking.     

Significant correlations of dermal total carotenoids and dermal lycopene with their respective plasma levels in healthy adults

Carotenoids in skin have been known to play a role in photoprotection against UV radiation. We performed dermal biopsies of healthy humans (N = 27) and collected blood samples for pair-wise correlation analyses of total and individual carotenoid content by high performance liquid chromatography (HPLC). The hydrocarbon carotenoids (lycopene and beta-carotene) made up the majority of carotenoids in both skin and plasma, and skin was somewhat enriched in these carotenoids relative to plasma. Beta-cryptoxanthin, a monohydroxycarotenoid, was found in similar proportions in skin as in plasma. In contrast, the dihydroxycarotenoids, lutein and zeaxanthin, were relatively lacking in human skin in absolute and relative levels as compared to plasma. Total carotenoids were significantly correlated in skin and plasma (r = 0.53, p < 0.01). Our findings suggest that human skin is relatively enriched in lycopene and beta-carotene, compared to lutein and zeaxanthin, possibly reflecting a specific function of hydrocarbon carotenoids in human skin photoprotection.     

Enhancing the carotenoid content of <Emphasis Type="Italic">Brassica napus</Emphasis> seeds by downregulating lycopene epsilon cyclase

The accumulation of carotenoids in higher plants is regulated by the environment, tissue type and developmental stage. In Brassica napus leaves, beta-carotene and lutein were the main carotenoids present while petals primarily accumulated lutein and violaxanthin. Carotenoid accumulation in seeds was developmentally regulated with the highest levels detected at 35-40 days post anthesis. The carotenoid biosynthesis pathway branches after the formation of lycopene. One branch forms carotenoids with two beta rings such as beta-carotene, zeaxanthin and violaxanthin, while the other introduces both beta- and epsilon-rings in lycopene to form alpha-carotene and lutein. By reducing the expression of lycopene epsilon-cyclase (epsilon-CYC) using RNAi, we investigated altering carotenoid accumulation in seeds of B. napus. Transgenic seeds expressing this construct had increased levels of beta-carotene, zeaxanthin, violaxanthin and, unexpectedly, lutein. The higher total carotenoid content resulting from reduction of epsilon-CYC expression in seeds suggests that this gene is a rate-limiting step in the carotenoid biosynthesis pathway. epsilon-CYC activity and carotenoid production may also be related to fatty acid biosynthesis in seeds as transgenic seeds showed an overall decrease in total fatty acid content and minor changes in the proportions of various fatty acids.     

Carotenoids suppress proliferating cell nuclear antigen and cyclin D1 expression in oral carcinogenic models

The purpose of this study was to investigate the chemopreventive effect of carotenoids on proliferating cell nuclear antigen (PCNA) and cyclin D(1) expression in betel (Areca catechu) quid extract (BQE)-induced hamster oral cancer and human KB cell models, respectively. In the in vivo animal study, 41 hamsters were divided into six groups and treated with 0.3 ml of 0.5% 9,10-dimethyl-1,2-benz[a]-anthracene, BQE, alpha-tocopherol, beta-carotene, lycopene, lutein and mixed carotenoids for 12 weeks. After treatment, the pouches were excised and graded using an immunohistochemical assay of PCNA. In the in vitro cell experiment, KB cells were cultured, and the inhibitory effect of carotenoids (beta-carotene, lycopene and lutein) on cell proliferation was evaluated. Cyclin D(1) and PCNA were evaluated in terms of cell differentiation. In the results, most of the animal lesions showed no overexpression of PCNA. However, in dysplastic lesions, PCNA expressions by the beta-carotene, lutein, lycopene, mixed and vitamin E groups were less than that of the control group. In papilloma lesions, PCNA expressions by the beta-carotene, mixed and vitamin E groups were less severe than that of the control group. PCNA expression by the vitamin E-treated group was less severe than that of the control group. No carcinoma was found in the lycopene or mixed groups. In the cell study, all carotenoids exerted a significant inhibitory effect on KB cell proliferation. Although lycopene suppressed KB cell proliferation at the G(0)/G(1) phase with a significant decrease in PCNA expression, beta-carotene and lutein possessed less of an inhibitory effect and even exhibited elevated cell proliferation at the G(2)/M phase. These results indicate that different carotenoids present various suppressive abilities against PCNA and cyclin D(1) expressions in cell proliferation. In conclusion, carotenoids suppressed the carcinogenesis of induced hamster oral cancer and a cancer cell line by acting as a suppressor which inhibited the expressions of PCNA and cyclin D(1).     

Estimation of carotenoid bioavailability from fresh stir-fried vegetables using an in vitro digestion/Caco-2 cell culture model

We previously developed an in vitro model to estimate the relative bioavailability of carotenoids from a meal prepared using commercial baby foods. The general applicability of this model was tested using a stir-fried meal consisting of fresh spinach, fresh carrots, tomato paste, and vegetable oil. After in vitro digestion of the cooked meal, the aqueous fraction was separated from residual oil droplet and solids by centrifugation to quantify micellarized carotenoids. The percentages of lutein, lycopene, α-carotene, and β-carotene transferred from the meal to the micellar fraction were 29.0 ± 0.6, 3.2 ± 0.1, 14.7 ± 0.3, and 16.0 ± 0.4, respectively. Carotenoid transfer from the meal to the aqueous fraction was inhibited when bile extract was omitted from the intestinal phase of digestion. The bioavailability of the micellarized carotenoids was validated using differentiated cultures of Caco-2 human intestinal cells. All four carotenoids were accumulated in a linear manner throughout a 6-hr incubation period. Metabolic integrity was not compromised by exposure of cultures to the diluted aqueous fraction from the digested meal. The addition of 500 μmol/L α-tocopherol to test medium significantly improved the stability of the micellar carotenoids within the tissue culture environment. These results support the utility of the in vitro digestion procedure for estimating the bioavailability of carotenoids from foods and meals.     

Resonance Raman spectroscopy of carotenoids in Photosystem I particles

Low-temperature resonance Raman (RR) spectroscopy was used for the first time to study the spectral properties, binding sites and composition of major carotenoids in spinach Photosystem I (PSI) particles. Excitation was provided by an argon ion laser at 457.9, 476.5, 488, 496.5, 502 and 514.5 nm. Raman spectra contained the four known groups of bands characteristic for carotenoids (called from nu(1) to nu4). Upon 514.5, 496.5 and 476.5 nm excitations, the nu(1)-nu(3) frequencies coincided with those established for lutein. Spectrum upon 502-nm excitation could be assigned to originate from violaxanthin, at 488 nm to 9-cis neoxanthin, and at 457.9 nm to beta-carotene and 9-cis neoxanthin. The overall configuration and composition of these bound carotenoid molecules in Photosystem I particles were compared with the composition of pigment extracts from the same PSI particles dissolved in pyridine, as well as to configuration in the main chlorophyll a/b light-harvesting protein complex of photosystem II. The absorption transitions for lutein, violaxanthin and 9-cis neoxanthin in spinach photosystem I particles are characterized, and the binding sites of lutein and neoxanthin are discussed. Resonance Raman data suggest that beta-carotene molecules are also present in all-trans and, probably, in 9-cis configurations.     

Dietary supplementation with beta-carotene, but not with lycopene, inhibits endothelial cell-mediated oxidation of low-density lipoprotein.

Carotenoids may protect low-density lipoprotein from oxidation, a process implicated in the development of atherosclerosis. Our previous studies showed that in vitro enrichment of low-density lipoprotein (LDL) with beta-carotene protected it from cell-mediated oxidation. However, in vitro enrichment with either lutein or lycopene actually enhanced oxidation of the LDL. In the present studies we have examined the impact of LDL carotenoid content on its oxidation by human aortic endothelial cells (EaHy-1) in culture, comparing the effects of in vivo supplementation with in vitro enrichments. The beta-carotene content in human LDL was increased three- to sixfold by daily supplementation with 15 mg beta-carotene for 4 weeks, and the lycopene content of LDL in other individuals was increased two- to threefold by ingestion of one glass (12 ounce) of tomato juice daily for 3 weeks. LDL isolated from these healthy, normolipidemic donors not taking supplemental carotenoid was incubated at 0.25 mg protein/ml with EaHy-1 cells in Ham's F-10 medium for up to 48 h. Following dietary beta-carotene supplementation, LDL oxidation (as assessed by formation of lipid hydroperoxides) was markedly inhibited, to an even greater extent than was observed for LDL enriched in vitro with beta-carotene (that resulted in an 11- to 12-fold increase in LDL beta-carotene). No effect on cell-mediated oxidation was observed, however, for LDL enriched in vivo with lycopene. Thus, beta-carotene appears to function as an antioxidant in protecting LDL from cell-mediated oxidation although lycopene does not. The fact that the three- to sixfold enrichments of LDL with beta-carotene achieved by dietary supplementation were more effective in inhibiting oxidation than the 11- to 12-fold enrichments achieved by an in vitro method suggests that dietary supplementation is a more appropriate procedure for studies involving the enrichment of lipoprotein with carotenoids.     

Addition of lutein, lycopene, or β-carotene to LDL or serum in vitro: Effects on carotenoid distribution, LDL composition, and LDL oxidation

Carotenoids are dietary antioxidants transported with plasma lipoproteins, primarily low-density lipoprotein (LDL). In this study in vitro methods were used to increase the amounts of specific, individual carotenoids in LDL. By addition of carotenoid to isolated LDL or to serum, followed by (re)isolation of the lipoproteins, samples of LDL were enriched 4- to 150-fold with lutein, 2- to 15-fold with lycopene, or 3- to 25-fold with β-carotene. Enrichment with specific carotenoids was achieved without affecting the electrophoretic mobility of the lipoprotein, its cholesterol to protein ratio, or the levels of other cartenoids or -tocopherol. The distributions among lipoproteins of carotenoid added to serum were similar, but not identical, to the distributions of the endogenous carotenoids. In particular, for added lutein, a greater proportion was found in HDL, and for added β-carotene, more was found in very low-density lipoprotein (VLDL). We then studied the effect of enriching LDL with specific carotenoids on its susceptibility to oxidation by copper ions. Lutein, β-cryptoxanthin, lycopene, and β-carotene, the four major plasma carotenoids, and -tocopherol were destroyed before the formation of lipid peroxidation products. The rates of destruction of the individual carotenoids differed; lycopene was destroyed most rapidly and lutein most slowly. Upon oxidation of β-carotene-enriched LDL, the rates of destruction of β-carotene, lycopene, and lutein were slowed and the lag times before the initiation of lipid peroxidation increased from 19 to 65 min. Neither effect was observed in LDL enriched with lutein or lycopene. Thus, β-carotene was unique among the carotenoids studied in having a small, but significant effect on LDL oxidation in vitro.     

High dietary intake of phytosterol esters decreases carotenoids and increases plasma plant sterol levels with no additional cholesterol lowering

The objective of this study was to measure the effects on serum lipids and plasma phytosterols of 6.6 g/day phytosterols from three foods (bread, breakfast cereal, and spread) consumed for 12 weeks compared with a diet that was not enriched with phytosterols. Thirty-five subjects undertook a nonrandomized, single-blind study consisting of a 2 week baseline period, 6 weeks on high-phytosterol intake, 6 weeks on high-phytosterol intake plus increased fruit and vegetable intake, and a final 2 week washout period. Serum total cholesterol decreased by 8.3% from 6.59 to 6.04 mmol/l, and LDL cholesterol decreased by 12.6% from 4.44 to 3.88 mmol/l. Plasma phytosterol levels increased by 45% (sitosterol) and 105% (campesterol). Cholesterol-adjusted plasma alpha- and beta-carotene levels decreased by 19-23%, lutein by 14%, and lycopene by 11%. Levels of alpha-carotene and lutein increased with extra fruit and vegetables. Only lycopene failed to increase during the washout phase. There were no significant changes in biochemical parameters. Serum LDL cholesterol lowering with 6.6 g/day ingested phytosterols was in the range seen with 1.6-3.2 g/day phytosterols. Lowering of plasma carotenoids was greater than that seen with lower phytosterol intake and was partially reversed by increased fruit and vegetable intake.     

Carotenoid biosynthesis in the primitive red alga Cyanidioschyzon merolae

Cyanidioschyzon merolae is considered to be one of the most primitive of eukaryotic photosynthetic organisms. To obtain insights into the origin and evolution of the pathway of carotenoid biosynthesis in eukaryotic plants, the carotenoid content of C. merolae was ascertained, genes encoding enzymes of carotenoid biosynthesis in this unicellular red alga were identified, and the activities of two candidate pathway enzymes of particular interest, lycopene cyclase and beta-carotene hydroxylase, were examined. C. merolae contains perhaps the simplest assortment of chlorophylls and carotenoids found in any eukaryotic photosynthetic organism: chlorophyll a, beta-carotene, and zeaxanthin. Carotenoids with epsilon-rings (e.g., lutein), found in many other red algae and in green algae and land plants, were not detected, and the lycopene cyclase of C. merolae quite specifically produced only beta-ringed carotenoids when provided with lycopene as the substrate in Escherichia coli. Lycopene beta-ring cyclases from several bacteria, cyanobacteria, and land plants also proved to be high-fidelity enzymes, whereas the structurally related epsilon-ring cyclases from several plant species were found to be less specific, yielding products with beta-rings as well as epsilon-rings. C. merolae lacks orthologs of genes that encode the two types of beta-carotene hydroxylase found in land plants, one a nonheme diiron oxygenase and the other a cytochrome P450. A C. merolae chloroplast gene specifies a polypeptide similar to members of a third class of beta-carotene hydroxylases, common in cyanobacteria, but this gene did not produce an active enzyme when expressed in E. coli. The identity of the C. merolae beta-carotene hydroxylase therefore remains uncertain.     

Impact of water-dispersible beadlets as a vehicle for the delivery of carotenoids to cultured cells

Water-dispersible beadlets of carotenoids were used as supplements for human umbilical vein endothelial cells (HUVECs), human peripheral blood mononuclear cells (PBMCs) and human monocytes. Stability, cellular association and cytotoxicity of the carotenoid beadlets were compared with carotenoids delivered with tetrahydrofuran (THF). Incubations with lycopene, beta-carotene, lutein and astaxanthin dissolved in THF resulted in a lower stability in the medium, lower cellular association, and a higher standard deviation. Beadlets provided 60, 4, 6, and 2 times greater accumulation of lycopene, beta-carotene, lutein and astaxanthin, respectively, by PBMCs than THF. The cellular association of carotenoids delivered by THF seems to be more carotenoid-specific than when carotenoids are delivered by beadlets. After 48 h of incubation under cell culture conditions all of the four carotenoids (1 microM) delivered by beadlets to the medium showed a reduction less than 30%. In addition, no cytotoxic effect of the carotenoid beadlets or the vehicle alone was detected in a concentration range of 0.5-5 microM. The results show that beadlets are a non-toxic vehicle for supplementing and stabilizing carotenoids in culture media offering a reasonable compromise in term of cell accumulation efficiency.     

Carotenoids and fatty liver disease: Current knowledge and research gaps

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to β-carotene and lycopene, but also including β-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from β-carotene and β-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from β-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.     

Carotenoids and cardiovascular disease: what research gaps remain?

PURPOSE OF REVIEW: Dietary and blood carotenoids, including alpha-carotene, beta-carotene, lycopene, lutein/zeaxanthin, and beta-cryptoxanthin, have been examined in a number of epidemiological studies in recent years for the risk of cardiovascular disease. This review assimilated the existing and recent literature on carotenoids and cardiovascular disease and considered what research gaps may remain. RECENT FINDINGS: Numerous large cohort studies have been published in largely American men and women that have examined dietary intake or blood levels of total or individual carotenoids with the risk of various cardiovascular endpoints. Overall, early, promising results have grown increasingly inconsistent over time. More recently, studies examining lycopene and lutein/zeaxanthin have offered more promising data on a possible, but not yet established, inverse association with the risk of cardiovascular disease. Recent epidemiological data on beta-cryptoxanthin and cardiovascular disease are lacking. Primary and secondary prevention trials have extensively examined beta-carotene, but not other carotenoids, for the risk of cardiovascular disease as either the primary or secondary endpoint with largely null results. More recent studies have focused on individual carotenoids in relation to cardiovascular disease and require a more careful evaluation of potential mechanisms of effect. SUMMARY: The promise of early epidemiological studies on carotenoids and cardiovascular disease paved the way to largely disappointing results from several large prevention trials of beta-carotene. Emerging recent evidence of potential cardioprotective effects for lycopene and other carotenoids besides beta-carotene in the diet and blood suggest that there is more to be learned in the story of carotenoids and both atherosclerotic progression and clinically manifested cardiovascular disease.     

Can vitamin A modify the activity of docetaxel in MCF-7 breast cancer cells?

Docetaxel is one of the most effective chemotherapeutic agents in the treatment of breast cancer. On the other hand, the vitamin A family compounds play the essential roles in many biological processes in mammary gland. The aim of our study was to investigate the effect of all-trans retinol, carotenoids (beta-carotene, lycopene) and retinoids (9-cis, 13-cis and all-trans retinoic acid) on the activity of docetaxel and to compare these effects with the estradiol and tamoxifen actions on human ER(+) MCF-7 breast cancer cell line. The evaluation was based on [3H] thymidine incorporation and the proliferative activity of PCNA and Ki 67 positive cells. In our study, the incorporation of [3H] thymidine into cancer cells was inhibited to 50% by 0.2, 0.5 and 1 microM of docetaxel in the 24-hour culture and addition of estradiol (0.001 microM) didn't influence the results. However, addition of tamoxifen caused a statistically significant decrease of the percentage of the proliferating cells in the culture medium with 0.2 and 0.5 microM of docetaxel (38.99 +/- 2.84%, p<0.01 and 40.67 +/- 5.62%, p<0.01) in comparison to the docetaxel only group. The above-mentioned observations were also confirmed with the use of the immunohistochemical investigations. Among the examined vitamin A family compounds, the simultaneous application of beta-carotene (0.1 microM) and docetaxel (0.2 microM) resulted in a statistically significant reduction in the percentage of proliferating cells (40.25 +/- 14.62%, p<0.01). Lycopene (0.1 microM), which stimulates the growth of breast cancer cells in a 24-hour culture, had an inhibitory effect (42.97 +/- 9.58%, p<0.01) when combined with docetaxel (0.2 microM). Although, beta-carotene and lycopene belong to the different chemical groups, they surprisingly had a similar inhibitory influence on both growth and proliferation of MCF-7 breast cancer cells when combined with docetaxel. The application of docetaxel either with beta-carotene or lycopene had comparable inhibitory effect on breast cells growth and proliferation as tamoxifen. Therefore, it may suggest a possible important role of these carotenoids in the breast cancer therapy in women especially when docetaxel is applied.     

Macular pigments lutein and zeaxanthin as blue light filters studied in liposomes.

Lutein and zeaxanthin are the predominant carotenoids in the human macula lutea. Epidemiological data suggest that an increased intake of a lutein-rich diet correlates with a diminished risk for age-related macular degeneration, a major cause of impaired vision in the elderly. Filtering of blue light has been proposed as a possible mechanism of protection. Here, the blue light filter efficacy of carotenoids was investigated in unilamellar liposomes loaded in the hydrophilic core space with a fluorescent dye, Lucifer yellow, excitable by blue light. Carotenoids were incorporated into the lipophilic membrane. Fluorescence emission in carotenoid-containing liposomes was lower than in carotenoid-free controls when exposed to blue light, indicating a filter effect. Filter efficacy was in the order lutein > zeaxanthin > beta-carotene > lycopene. Some of the difference in blue light filter efficacy of carotenoids is attributable to differences in extinction coefficients, and a major further contribution is suggested to be related to the orientation of the incorporated molecules in the liposomal membrane.