Photoprotective potential of lycopene,beta-carotene,vitamin E,vitamin C and carnosic acid in UVA-irradiated human skin fibroblasts

The photoprotective potential of the dietary antioxidants vitamin C, vitamin E, lycopene, beta-carotene, and the rosemary polyphenol, carnosic acid, was tested in human dermal fibroblasts exposed to ultraviolet-A (UVA) light. The carotenoids were prepared in special nanoparticle formulations together with vitamin C and/or vitamin E. Nanoparticle formulations, in contrast to dimethylsulphoxide, stablized lycopene in the cell culture medium and allowed efficient cellular uptake. The presence of vitamin E in the formulation further increased the stability and cellular uptake of lycopene. UVA irradiation of the human skin fibroblasts led to a 10-15-fold rise in metalloproteinase 1 (MMP-1) mRNA. This rise was suppressed in the presence of low microM concentrations of vitamin E, vitamin C, or carnosic acid but not with beta-carotene or lycopene. Indeed, in the presence of 0.5-1.0 microM beta-carotene or lycopene, the UVA-induced MMP-1 mRNA was further increased by 1.5-2-fold. This increase was totally suppressed when vitamin E was included in the nanoparticle formulation. Heme-oxygenase 1 (HO-1) mRNA expression was strongly induced by UVA irradiation but none of the antioxidants inhibited this effect at the concentrations used in this study. Indeed, beta-carotene or lycopene (0.5-1.0 microM) led to a further 1.5-fold rise in the UVA-induced HO-1 mRNA levels. In conclusion, vitamin C, vitamin E, and carnosic acid showed photoprotective potential. Lycopene and beta-carotene did not protect on their own but in the presence of vitamin E, their stability in culture was improved and the rise in MMP-1 mRNA expression was suppressed, suggesting a requirement for antioxidant protection of the carotenoids against formation of oxidative derivatives that can influence the cellular and molecular responses.     

Lycopene attenuates alcoholic apoptosis in HepG2 cells expressing CYP2E1

To test the hypothesis that ethanol-induced hepatic apoptosis is secondary to the oxidative stress generated by cytochrome P4502E1 (CYP2E1), we assessed the effects of the carotenoid lycopene, a potent antioxidant extracted from tomatoes, on oxidative stress and apoptosis in HepG2 cells overexpressing CYP2E1 (2E1 cells). These were exposed for 5 days to 100mM ethanol and 10 microM lycopene or an equal volume of placebo (vehicle). Ethanol significantly increased apoptosis measured by flow cytometry and by TUNEL assay. This was accompanied by an ethanol-induced oxidative stress: hydrogen peroxide production was significantly increased and mitochondrial GSH was strikingly decreased. Both were restored by lycopene, with a significant decrease in apoptosis. The placebo had no protective effect. In conclusion, Lycopene opposes the ethanol-induced oxidative stress and apoptosis in 2E1 cells. The parallelism between these effects suggests a causal link. Furthermore, these beneficial effects and the innocuity of lycopene now justify an in vivo trial.     

Chemically induced hepatotoxicity in human stem cell-induced hepatocytes compared with primary hepatocytes and HepG2

Stem cell-induced hepatocytes (SC-iHeps) have been suggested as a valuable model for evaluating drug toxicology. Here, human-induced pluripotent stem cells (QIA7) and embryonic stem cells (WA01) were differentiated into hepatocytes, and the hepatotoxic effects of acetaminophen (AAP) and aflatoxin B1 (AFB1) were compared with primary hepatocytes (p-Heps) and HepG2. In a cytotoxicity assay, the IC₅₀ of SC-iHeps was similar to that in p-Heps and HepG2 in the AAP groups but different from that in p-Heps of the AFB1 groups. In a multi-parameter assay, phenotypic changes in mitochondrial membrane potential, calcium influx and oxidative stress were similar between QIA7-iHeps and p-Heps following AAP and AFB1 treatment but relatively low in WA01-iHeps and HepG2. Most hepatic functional markers (hepatocyte-specific genes, albumin/urea secretion, and the CYP450 enzyme activity) were decreased in a dose-dependent manner following AAP and AFB1 treatment in SC-iHeps and p-Heps but not in HepG2. Regarding CYP450 inhibition, the cell viability of SC-iHeps and p-Heps was increased by ketoconazole, a CYP3A4 inhibitor. Collectively, SC-iHeps and p-Heps showed similar cytotoxicity and hepatocyte functional effects for AAP and AFB1 compared with HepG2. Therefore, SC-iHeps have phenotypic characteristics and sensitivity to cytotoxic chemicals that are more similar to p-Heps than to HepG2 cells.     

NPC-16, a novel naphthalimide–polyamine conjugate,induced apoptosis and autophagy in human hepatoma HepG2 cells and Bel-7402 cells

The antitumor effects and molecular mechanism of NPC-16, a novel naphthalimide–polyamine conjugate, were evaluated in HepG2 cells and Bel-7402 cells. Apoptosis and necrosis were evaluated by Annexin V-FITC detection kit, and autophagy by acridine orange and Lyso-Tracker Red staining. The change of mitochondrial transmembrane potential was measured using rhodamine 123 staining. The protein expression of Beclin 1, LC3 II and mTOR, p70S6 K, 14-3-3, caspase, and Bcl-2 family members was detected by immunofluorescence assays and Western Blot. Here, we elucidated the nature of cellular response of HepG2 cells and Bel-7402 cells to NPC-16 at IC₅₀. NPC-16 induced caspase-dependent apoptosis via the mitochondrial pathway and death receptor pathway in Bel-7402 cells. Differently, NPC-16 triggered HepG2 cells both apoptosis and autophagy, further autophagy facilitated cellular apoptosis. Furthermore, mTOR signal pathway was involved in NPC-16-mediated autophagy in HepG2 cells. Thus, NPC-16 may be useful as a potential template for investigation the molecular mechanism of naphthalimide–polyamine conjugate against hepatocellular carcinoma.     

Antioxidant and pro-oxidant effects of lycopene in comparison with beta-carotene on oxidant-induced damage in Hs68 cells

Lycopene has become a focal point in recent research following clinical trials that suggest that beta-carotene may promote lung cancer in smokers. Because lycopene only differs from beta-carotene in lacking the beta-ionone structure, and beta-carotene is known to have pro-oxidant activity in vitro, we sought to determine whether lycopene might also have pro-oxidant activity in vitro in comparison with beta-carotene. Human foreskin fibroblasts (Hs68 cells) were first enriched with 10 and 20 μM lycopene or beta-carotene for 1 hr followed by incubation with various oxidants. Lipid peroxidation was measured as thiobarbituric acid-reactive substances (TBARS) released into the medium and DNA damage was measured as formation of comet and 8-hydroxy-2'-deoxyguanosine. The results showed that lycopene at 20 μM significantly decreased levels of TBARS induced by ferric nitrilotriacetate (Fe/NTA) but enhanced levels of TBARS induced by a lipid-soluble radical generator (2,2'-azobis[2,4-dimethylvaleronitrile]; AMVN). Both the antioxidant and pro-oxidant effects of lycopene tended to be dose-dependent. beta-Carotene at 20 μM did not significantly decrease TBARS induced by Fe/NTA but significantly increased TBARS induced by AMVN. Lipid peroxidation induced by a water-soluble radical generator 2,2'-azobis(2-amidinopropane)dihydrochloride was not significantly affected by either lycopene or beta-carotene. Neither lycopene nor beta-carotene affected DNA damage or changes in cell morphology induced by any of the three oxidants tested. The present study in Hs68 cells demonstrates that lycopene can be either an antioxidant or a pro-oxidant depending on the oxidants used, and that lycopene and beta-carotene behave similarly under the in vitro oxidative conditions. Although it is unclear whether lycopene may have pro-oxidant activity in vivo, our results caution that it may be premature to undertake clinical trials with lycopene.     

An evaluation of the metabolic basis of aflatoxin B1 toxicity by using buffalo granulocytes and agranulocytes in vitro

This study was aimed at monitoring cytotoxic changes in buffalo leukocyte subpopulations exposed to aflatoxin B1 (AFB1), since no such information is available for this species. The effects of AFB1 on glutathione (GSH) S-transferase, Ca2+Mg2+ATPase and protein synthesis in leukocyte subpopulations, namely, mononuclear (MN) cells and polymorphonuclear (PMN) cells isolated from the blood of the domestic buffalo (Bos bubalis), were studied. The cells were separated by using Ficoll-Paque and incubated in the presence of AFB1. GSH S-transferase activity was found to increase in cells exposed to AFB1, but there was no difference in activity between MN and PMN cells. PMN cell ATPase activity increased after AFB1 treatment, whereas no such effect was observed in the MN cells, which showed higher basal levels of ATPase activity. In the presence of AFB1, all the cells showed significant decreases in 14C-leucine incorporation, but the MN cells showed higher 14C-leucine incorporation than the PMN cells. Nevertheless, both cell types were affected by AFB1 and participated in its detoxification. There was also an appreciable decrease in the release of myeloperoxidase by activated PMN cells in the presence of AFB1.     

Hepatocellular toxicity of kava leaf and root extracts.

Kava extracts are used widely for different purposes and were thought to be safe. Recently, several cases of hepatotoxicity have been published. To explore possible mechanisms of kava hepatotoxicity, we prepared and analyzed three different kava extracts (a methanolic and an acetonic root and a methanolic leaf extract), and investigated their toxicity on HepG2 cells and isolated rat liver mitochondria. All three extracts showed cytotoxicity starting at a concentration of 50 microg/ml (lactate dehydrogenase leakage) or 1 microg/ml (MTT test). The mitochondrial membrane potential was decreased (root extracts starting at 50 microg/ml) and the respiratory chain inhibited and uncoupled (root extracts) or only uncoupled (leaf extract) at 150 microg/ml, and mitochondrial beta-oxidation was inhibited by all extracts starting at 100 microg/ml. The ratio oxidized to reduced glutathione was increased in HepG2 cells, whereas the cellular ATP content was maintained. Induction of apoptosis was demonstrated by all extracts at a concentration of 150 microg/ml. These results indicate that the kava extracts are toxic to mitochondria, leading to inhibition of the respiratory chain, increased ROS production, a decrease in the mitochondrial membrane potential and eventually to apoptosis of exposed cells. In predisposed patients, mitochondrial toxicity of kava extract may explain hepatic adverse reactions of this drug.     

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.     

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.     

Geldanamycin, an inhibitor of Hsp90 increases cytochrome P450 2E1 mediated toxicity in HepG2 cells through sustained activation of the p38MAPK pathway

Cytochrome P450 2E1 (CYP2E1) can mediate reactive oxygen species (ROS) induced cell death through its catalytic processes. Heat shock protein 90 (Hsp90) is an important molecular chaperone which is essential for cellular integrity. We previously showed that inhibition of Hsp90 with Geldanamycin (GA), an inhibitor of Hsp90 increased CYP2E1 mediated toxicity in CYP2E1 over-expressing HepG2 cells (E47 cells) but not in C34-HepG2 cells devoid of CYP2E1 expression. The aim of the present study was to test the hypothesis that the potentiation of CYP2E1 toxicity in E47 cells with GA may involve changes in mitogen activated protein kinase signal transduction pathways. GA was toxic to E47 cells and SB203580, an inhibitor of p38 MAPK prevented this decrease in viability. The protective effects of SB203580 were effective only when SB203580 was added before GA treatment. GA activated p38 MAPK in E47 cells and this activation was an early and a sustained event. GA elevated ROS levels and lipid peroxidation and lowered GSH levels in E47 cells and these changes were blunted or prevented by treatment with SB203580. Apoptosis was increased by GA and prevented by pre-treatment with SB203580. The loss in mitochondrial membrane potential in E47 cells after GA treatment was also decreased significantly with SB203580 treatment. The activity and expression of CYP2E1 and Hsp90 levels were not altered by SB203580. In conclusion, the inhibition of Hsp90 with GA increases the toxicity of CYP2E1 in HepG2 cells through an early and sustained activation of the p38 MAPK pathway.     

Toll-like receptor-3-induced mitochondrial dysfunction in cultured human hepatocytes

Several studies have shown the presence of liver mitochondrial dysfunction during sepsis. TLR3 recognizes viral double-stranded RNA and host endogenous cellular mRNA released from damaged cells. TLR3 ligand amplifies the systemic hyperinflammatory response observed during sepsis and in sepsis RNA escaping from damaged tissues/cells may serve as an endogenous ligand for TLR3 thereby modulating immune responses. This study addressed the hypothesis that TLR3 might regulate mitochondrial function in cultured human hepatocytes.HepG2 cells were exposed to TLR-3 ligand (dsRNA — polyinosine–polycytidylic acid; Poly I:C) and mitochondrial respiration was measured. Poly I:C induced a reduction in maximal mitochondrial respiration of human hepatocytes which was prevented partially by preincubation with cyclosporine A (a mitochondrial permeability transition pore-opening inhibitor). Poly-I:C induced activation of NF-κB, and the mitochondrial dysfunction was accompanied by caspase-8 but not caspase-3 activation and by no major alterations in cellular or mitochondrial ultrastructure.     

Lycopene Protects against Hypoxia/Reoxygenation-Induced Apoptosis by Preventing Mitochondrial Dysfunction in Primary Neonatal Mouse Cardiomyocytes

Background

Hypoxia/reoxygenation(H/R)-induced apoptosis of cardiomyocytes plays an important role in myocardial injury. Lycopene is a potent antioxidant carotenoid that has been shown to have protective properties on cardiovascular system. The aim of the present study is to investigate the potential for lycopene to protect the cardiomyocytes exposed to H/R. Moreover, the effect on mitochondrial function upon lycopene exposure was assessed.

Methods and Findings

Primary cardiomyocytes were isolated from neonatal mouse and established an in vitro model of H/R which resembles ischemia/reperfusion in vivo. The pretreatment of cardiomyocytes with 5 µM lycopene significantly reduced the extent of apoptosis detected by TUNEL assays. To further study the mechanism underlying the benefits of lycopene, interactions between lycopene and the process of mitochondria-mediated apoptosis were examined. Lycopene pretreatment of cardiomyocytes suppressed the activation of the mitochondrial permeability transition pore (mPTP) by reducing the intracellular reactive oxygen species (ROS) levels and inhibiting the increase of malondialdehyde (MDA) levels caused by H/R. Moreover, the loss of mitochondrial membrane potential, a decline in cellular ATP levels, a reduction in the amount of cytochrome c translocated to the cytoplasm and caspase-3 activation were observed in lycopene-treated cultures.

Conclusion

The present results suggested that lycopene possesses great pharmacological potential in protecting against H/R-induced apoptosis. Importantly, the protective effects of lycopene may be attributed to its roles in improving mitochondrial function in H/R-treated cardiomyocytes.     

Spin trapping agents (Tempol and POBN) protect HepG2 cells overexpressing CYP2E1 against arachidonic acid toxicity

Polyunsaturated fatty acids such as arachidonic acid were previously shown to be toxic to HepG2 cells expressing CYP2E1 by a mechanism involving oxidative stress and lipid peroxidation. This study investigated the effects of the spin trapping agents Tempol and POBN on the arachidonic acid toxicity. Arachidonic acid caused toxicity and induced lipid peroxidation and mitochondrial membrane damage in cells overexpressing CYP2E1 but had little or no effect in control cells not expressing CYP2E1. The toxicity appeared to be both apoptotic and necrotic in nature. 4-Hydroxy-[2,2,6,6-tetramethylpiperidine-1-oxyl] (Tempol) and alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (POBN) protected against the decrease in cell viability and the apoptosis and necrosis. These spin traps prevented the enhanced lipid peroxidation and the loss of mitochondrial membrane potential. Tempol and POBN had little or no effect on cellular viability or on CYP2E1 activity at concentrations which were protective. It is proposed that elevated production of reactive oxygen intermediates by cells expressing CYP2E1 can cause lipid peroxidation, which subsequently damages the mitochondrial membrane leading to a loss in cell viability when the cells are enriched with arachidonic acid. Tempol and POBN, which scavenge various radical intermediates, prevent in this way the enhanced lipid peroxidation, mitochondrial dysfunction, and the cell toxicity. Since oxidative stress appears to play a key role in ethanol hepatotoxicity, it may be of interest to evaluate whether such spin trapping agents are useful candidates for the prevention or improvement of ethanol-induced liver injury.     

Effects of aflatoxin and carotenoids on growth performance and immune response in mule ducklings

The purpose of this study was to investigate if carotenoids could alleviate the adverse effects caused by aflatoxin with respect to growth performance and immune response. In two experiments, a total of 320 mule ducklings were assigned to 5 treatments, i.e. control, aflatoxin B(1) (AFB(1)) 200 ppb, AFB(1) +beta-carotene (BC) 200 ppm, AFB(1)+BC 400 ppm, and AFB(1)+astaxanthin (AS) 200 ppm. In experiment 1, the addition of beta-carotene or astaxanthin in the diet containing AFB(1) 200 ppb resulted in a significant decrease in average daily gain as compared with the control. AFB(1) 200 ppb alone and the addition of BC or AS on top of AFB(1) resulted in a significantly lower daily feed intake than for the control group. There were no significant differences in relative organ weights among treatment groups. Both treatments of BC 400 ppm and AS 200 ppm had significantly more macrophages harvested per duck than the control and AFB(1) 200 ppb treatments. However, there were no significant differences among treatments in percentages of phagocytotic macrophages and number of Candida albican phagocytized by phagocytotic macrophages. In experiment 2, blood biochemical parameters and antibody titers were evaluated. There were no significant differences among treatments in total bilirubin content and alkaline phosphatase activity in the serum or in antibody titers against fowl cholera. However, AFB(1) treatment had the highest activities of AST and ALT in the serum. The addition of BC 400 ppm on top of AFB(1) significantly reduced ALT activity as compared with the AFB(1) 200 ppb treatment. These results suggest that carotenoids could provide a slightly toxic alleviating effect on growth performance, enhance the chemotaxis ability of macrophages, and reduce ALT activity elevated by AFB(1).     

Photoprotective potential of lycopene, β-carotene, vitamin E, vitamin C and carnosic acid in UVA-irradiated human skin fibroblasts

The photoprotective potential of the dietary antioxidants vitamin C, vitamin E, lycopene, β-carotene, and the rosemary polyphenol, carnosic acid, was tested in human dermal fibroblasts exposed to ultraviolet-A (UVA) light. The carotenoids were prepared in special nanoparticle formulations together with vitamin C and/or vitamin E. Nanoparticle formulations, in contrast to dimethylsulphoxide, stablized lycopene in the cell culture medium and allowed efficient cellular uptake. The presence of vitamin E in the formulation further increased the stability and cellular uptake of lycopene. UVA irradiation of the human skin fibroblasts led to a 10–15-fold rise in metalloproteinase 1 (MMP-1) mRNA. This rise was suppressed in the presence of low μM concentrations of vitamin E, vitamin C, or carnosic acid but not with β-carotene or lycopene. Indeed, in the presence of 0.5–1.0 μM β-carotene or lycopene, the UVA-induced MMP-1 mRNA was further increased by 1.5–2-fold. This increase was totally suppressed when vitamin E was included in the nanoparticle formulation. Heme-oxygenase 1 (HO-1) mRNA expression was strongly induced by UVA irradiation but none of the antioxidants inhibited this effect at the concentrations used in this study. Indeed, β-carotene or lycopene (0.5–1.0 μM) led to a further 1.5-fold rise in the UVA-induced HO-1 mRNA levels. In conclusion, vitamin C, vitamin E, and carnosic acid showed photoprotective potential. Lycopene and β-carotene did not protect on their own but in the presence of vitamin E, their stability in culture was improved and the rise in MMP-1 mRNA expression was suppressed, suggesting a requirement for antioxidant protection of the carotenoids against formation of oxidative derivatives that can influence the cellular and molecular responses.     

Ultrastructural changes in murine lymphocytes induced by aflatoxin B1

This investigation sought to determine whether splenic lymphocytes obtained from Balb/C mice exposed to aflatoxin B1 (AFB1) showed any ultrastructural changes which could account for the immunodysfunction attributable to aflatoxins. Lymphocytes obtained from Balb/C mice administered aflatoxin B1 in olive oil daily for three weeks were studied using both transmission and scanning electron microscopy. The lymphocytes demonstrated ultrastructural changes primarily in the mitochondria where marked internal dissociation of the cristae was revealed by transmission electron microscopy. All other cellular organelles were unaffected. No significant alterations in external structure were observed under scanning electron microscopy. The findings of this study indicate that AFB1 administration does not affect the surface topography of lymphocytes, but AFB1, by causing extensive mitochondrial damage, may affect the way in which these cells function. This could be a possible explanation for the immunodysfunction associated with AFB1.Abbreviations AFB1 Aflatoxin B1 - SEM scanning electron microscopy - TEM transmission electron microscopy     

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.     

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.