Effects of beta-carotene on antioxidant enzyme activity, intracellular reactive oxygen and membrane integrity within post confluent Caco-2 intestinal cells

Intestinal GLUT5 and FAT/CD36 transporters and blood glucose are reduced by a carotenoid/MUFA-rich oil in high-fat fed mice

AIMS

Intestinal nutrient absorption plays a vital role in developing obesity, and nutrient transporters expressed in the enterocytes facilitate this process. Moreover, previous studies have shown that specific foods and diets can affect their cell levels. Herein, we investigated the effects of pequi oil (PO), which is high in several bioactive compounds, on intestinal nutrient transporter levels as well as on intestinal morphology and metabolic biomarkers.

MAIN METHODS

Groups of male C57BL/6 mice were fed either a standard (C) or a high-fat diet (HFD) and pequi oil (CP and HFDP with PO by gavage at 150 mg/day) for eight weeks. Food intake and body weight were monitored, serum metabolic biomarkers, intestinal transporter levels and histological analyses were performed.

KEY FINDINGS

PO increased caloric intake without increasing body or fat mass regardless of diet. The HFD group treated with PO reduced fasting blood glucose and villus width. PO did not affect GLUT2, L-FABP, FATP4, NPC1L1, NHE3 or PEPT1 content in CP or HFDP groups. GLUT5 and FAT/CD36 levels were reduced in both CP and HFDP.

SIGNIFICANCE

Our data suggest that PO attenuated monosaccharide and fatty acid absorption, contributing to lower fasting glycemia and higher food intake without affecting body weight or visceral fat of high-fat feed mice.

Phytochemical analysis and evaluation of the antioxidant and antiproliferative effects of Tucumã oil nanocapsules in breast adenocarcinoma cells (MCF-7)

In this work was to develop an inedited nanocapsule with tucumã oil (Astrocaryum vulgare). The oil presents of phytosterols (squalene and β-sitosterol), all-trans-beta-carotene, acids oleic and palmitic. Antioxidant activity showed a good performance in DPPH and ABTS assays. The nanocapsules were prepared and demonstrated in their characterization particle size (206 ± 0.69 nm). The cytogenotoxicity evaluation was performed using the MTT, dichlorofluorescein, nitric oxide and dsDNA PicoGreen® assays. Antitumor efficacy assays in MCF-7 cells demonstrated that free oil and tucumã nanocapsules had IC₅₀ of 130 and 50 μg/mL, respectively. Thus, previous studies of toxicity are relevant, as they generate future subsidies, aiming at the potential application of nanostructures and in addition, the promising effect of NCs of tucumã oil on the antiproliferative effect in breast adenocarcinoma cells was evidenced.

Protective effect of bioaccessible fractions of citrus fruit pulps against H2O2-induced oxidative stress in Caco-2 cells

Fruit pulps from Navel (N) and Cara Cara (CC) oranges, and Clementine mandarin freshly harvested (M) and refrigerated stored (M12) were used to evaluate the cytoprotective effect of their bioaccessible fractions (BF) against H₂O₂-induced oxidative stress in Caco-2 cells. BF of samples preserved viability vs. H₂O₂ treated cells, reaching values similar to controls. Lipid peroxidation was reduced to levels of control cells, but M did not reach control values. ROS and mitochondrial membrane potential changes (Δψ_m) values were reduced compared with H₂O₂ treated cells, but without achieving control levels. A significant reduction in cell proportions in G1 phase and a significant increase in sub-G1 phase (apoptosis) of cell cycle was shown in H₂O₂ treated cells, and BF allowed a recovery close to control levels. Thus, BF of samples protect the cells from oxidative stress by preserving cell viability, mitochondrial membrane potential and correct cell cycle progression, and diminishing lipid peroxidation and ROS.

Antioxidant Activity of Methanol Extract of the Lotus Leaf (Nelumbo nucifera Gertn.)

In this study, hydrogen peroxide ( H 2 O 2)-mediated Caco-2 cytotoxicity was employed to investigate the potential antioxidant activity of the methanol extract from the lotus leaf (Nelumbo nucifera Gertn.). A dose-dependent protective effect against reactive oxygen species (ROS)-induced cytotoxicity was observed when Caco-2 cells were treated with 10 mM H 2 O 2 in combination with the methanol extract of the lotus leaf (0.1–0.3 mg/ml). However, no significant effect was found when co-treating Caco-2 cells with 10 mM H 2 O 2 and α-tocopherol. In vitro assay revealed that the extract exhibited scavenging activities on free radicals and hydroxyl radicals, and metal binding ability as well as reducing power, which may explain in part the mechanism behind the extract's ability to protect cells from oxidative damage. In addition, the extract also exhibited concentration-dependent antioxidant activities against hemoglobin-induced linoleic acid peroxidation and Fenton reaction-mediated plasmid DNA oxidation.

Antioxidant properties of lutein contribute to the protection against lipopolysaccharide-induced uveitis in mice

BACKGROUND

Lutein is an important eye-protective nutrient. This study investigates the protective effects and mechanisms of lutein on lipopolysaccharides (LPS)-induced uveitis in mice.

METHODS

Lutein, suspended in drinking water at a final concentration of 12.5 and 25 mg/mL, was administered to mice at 0.1 mL/10 g body weight for five consecutive days. Control and model group received drinking water only. Uveitis was induced by injecting LPS (100 mg per mouse) into the footpad in the model and lutein groups on day 5 after the last drug administration. Eyes of the mice were collected 24 hours after the LPS injection for the detection of indicators using commercial kits and reverse transcription-polymerase chain reaction.

RESULTS

LPS-induced uveitis was confirmed by significant pathological damage and increased the nitric oxide level in eye tissue of BALB/C mice 24 hours after the footpad injection. The elevated nitric oxide level was significantly reduced by oral administration of lutein (125 and 500 mg/kg/d for five days) before LPS injection. Moreover, lutein decreased the malondialdehyde content, increased the oxygen radical absorbance capacity level, glutathione, the vitamin C contents and total superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. Lutein further increased expressions of copper-zinc SOD, manganese SOD and GPx mRNA. Conclusion The antioxidant properties of lutein contribute to the protection against LPS-induced uveitis, partially through the intervention of inflammation process.

Induction of glutathione peroxidase 4 expression during enterocytic cell differentiation

Glutathione peroxidase 4 (GPx4), an abundant selenoenzyme, is ubiquitously expressed in a tissue-, cell- and differentiation-dependent manner, and it is localized in cytoplasmic, mitochondrial, and nuclear cellular compartments. Here, we report cytoplasmic and nuclear localization of GPx4 in Caco-2 intestinal epithelial cells. Enterocytic differentiation of Caco-2 cells triggers an increase in GPx4 mRNA and protein levels, mediated by enhanced promoter activity. We identified a combined cAMP response element (CREB) and CCAAT/enhancer binding protein (C/EBP) site as critical for the differentiation-triggered GPx4 promoter activity. Induction of GPx4 correlated with C/EBPα transcript levels during differentiation, suggesting a role of C/EBPα as regulator of enterocytic GPx4 expression. Consistent with the in vitro results, GPx4 protein was detected in cytoplasmic and nuclear compartments of enterocytes in human intestinal epithelia. GPx4 is uniformly expressed in colonic crypts and is differentially expressed along the crypt-to-villus axis in the small intestine with a more pronounced expression of GPx4 in the upper villi, which contain fully differentiated enterocytes. These data suggest that intestinal GPx4 expression is modulated by the enterocytic differentiation program, and the results support a direct role of nuclear GPx4 in the (selenium-dependent) prevention of oxidative damage in the gastrointestinal tract.

Protective effects of free radical scavenger edaravone against xanthine oxidase-mediated permeability increases in human intestinal epithelial cell monolayer

The barrier function of the intestinal mucosa can be disturbed under a variety of pathologic insults. Reactive oxygen species play an important role in intestinal mucosal injury. This in vitro study examines the hypothesis that a free radical scavenger, edaravone (ED), ameliorates gut epithelial permeability increase caused by xanthine oxidase (XO)-mediated oxidative stress in a cell monolayer model. Human intestinal epithelial (HIE) cells were grown as monolayer in bicameral chambers. Twenty milliunits per milliliter of XO+0.25 mM of xanthine (XO+X group) or saline (control) were administered into the basal chambers. Another set of chambers was treated with XO+X and 0.6 mg/ml of ED (XO+X+ED group). The permeability was assessed by quantifying the transepithelial passage of fluorescence in isothiocyanate-labeled dextran. In another series of experiments, Escherichia coli C-25 was also applied in an apical chamber to evaluate the bacterial translocation through the monolayer. The concentration of the fluorescence in isothiocyanate-labeled dextran in the basal chamber of the control group was significantly higher than the control (705 +/- 50.2 vs 155 +/- 45.4 mg/dl, P < .01). Treatment with ED prevented this permeability increase induced by the oxidative stress (P < .01). The incidence of bacterial translocation through the HIE monolayer in XO+X group was also higher than that of the control group (75 vs 13%, P < .05). Increased HIE cell monolayer permeability mediated by xanthine and XO was significantly attenuated with ED. This synthesized radical scavenger may have potential clinical applications against gut mucosal barrier dysfunction.

Carotenóides: uma possível proteção contra o desenvolvimento de câncer

Este artigo discute as possibilidades de proteção contra o desenvolvimento do câncer, proporcionadas por carotenóides provenientes da alimentação, com base em uma revisão da literatura. Os carotenóides têm demonstrado uma ação protetora contra a carcinogênese, tanto em estudos in vitro como in vivo, com animais e humanos. Entre eles, a beta-criptoxantina, a fucoxantina, a astaxantina, a capsantina, a crocetina e o fitoeno, têm sido pouco explorados, e a literatura ainda se mostra extremamente limitada e pouco conclusiva. Estudos experimentais com humanos demonstraram não haver efeito, ou efeito reverso, do beta-caroteno, no entanto, não incluíram anteriormente variáveis intervenientes e interativas que deveriam ter sido controladas. A partir da evidência científica, baseada em estudos epidemiológicos e ensaios experimentais recentes, e da elucidação dos mecanismos de atuação de fitoquímicos relacionados à maior proteção contra o câncer, conclui-se que a alimentação rica em carotenóides provenientes das frutas, legumes e verduras, representa um possível fator de proteção contra o desenvolvimento do câncer.

Update: effects of antioxidant and non-antioxidant vitamin supplementation on immune function

The purpose of this manuscript is to review the impact of supplementation with vitamins E and C, carotenoids, and the B vitamins on parameters of innate and adaptive immune function as reported from clinical trials in humans. There is evidence to support causal effects of supplementation with vitamins E and C and the carotenoids singly and in combination on selected aspects of immunity, including the functional capacity of innate immune cells, lymphocyte proliferation, and the delayed-type hypersensitivity (DTH) response. Controlled intervention trials of B vitamin-containing multivitamin supplements suggest beneficial effects on immune parameters and clinical outcomes in HIV-positive individuals.

Carotenoid actions and their relation to health and disease

Based on extensive epidemiological observation, fruits and vegetables that are a rich source of carotenoids are thought to provide health benefits by decreasing the risk of various diseases, particularly certain cancers and eye diseases. The carotenoids that have been most studied in this regard are beta-carotene, lycopene, lutein and zeaxanthin. In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. beta-Carotene may have added benefits due its ability to be converted to vitamin A. Additionally, lutein and zeaxanthin may be protective in eye disease because they absorb damaging blue light that enters the eye. Food sources of these compounds include a variety of fruits and vegetables, although the primary sources of lycopene are tomato and tomato products. Additionally, egg yolk is a highly bioavailable source of lutein and zeaxanthin. These carotenoids are available in supplement form. However, intervention trials with large doses of beta-carotene found an adverse effect on the incidence of lung cancer in smokers and workers exposed to asbestos. Until the efficacy and safety of taking supplements containing these nutrients can be determined, current dietary recommendations of diets high in fruits and vegetables are advised.

Ginsenosides 20(S)-protopanaxadiol and Rh2 reduce cell proliferation and increase sub-G1 cells in two cultured intestinal cell lines, Int-407 and Caco-2

Ginsenosides derived from 20(S)-protopanaxatriol (PT) and 20(S)-protopanaxadiol (PD) groups had similar characteristic cytotoxic effects on the growth of two intestinal cells lines, Int-407 and Caco-2. Pure Rh2, a ginsenoside structurally related to PD, inhibited intestinal cell growth at greater than twice the concentration of PD, while Rh1, a ginsenoside structurally related to aglycone PT, had no cytotoxic effect. Concentrations causing growth inhibition of 50% of cells (LC50) for the compounds PD, PT, and Rh2 were 23, 26, and 53 microg/mL, respectively, for Int-407 cells. In comparison, the LC50 for PD and PT was determined to be 24 microg/mL, and that for Rh2 was 55 microg/mL in Caco-2 cells. A standardized North American ginseng extract with a known ginsenosides composition did not induce cytotoxicity in either of the intestinal cell lines. Cell cycle analysis showed characteristically different (P = 0.05) effects of ginsenosides PD, Rh2, and PT in both cell lines. Rh2 treatment of Int-407 caused a significantly (P = 0.05) higher production of sub-G1 (apoptotic) cells (35% +/- 1%) compared with untreated cells (14% +/- 0.3%) after 24 h. PD and Rh2 treatments were both significantly (P < 0.05) higher in apoptotic cells than in untreated cells after 48 and 72 h. Similar results were obtained for treatment of Caco-2 cells. Lactate dehydrogenase (LDH) activity in both cell lines was similar for PD and Rh2 and higher (P = 0.05) than for PT treatment at most time periods. These results show a specific structure-function relationship for bioactive ginsenosides in two contrasting intestinal cell types.

The effect of short-term kaempferol exposure on reactive oxygen levels and integrity of human (HL-60) leukaemic cells

Flavonoids may be a principal contributor to the cancer preventative activity of fruit- and vegetable-rich diets and there is interest in their use as dietary supplements. However, there is potential conflict between the cytoprotective and cytotoxic activities of flavonoids, and their efficacy as anti-cancer agents is unresolved. Here, the integrity and survival of HL-60 promyelocytic leukaemia cells following short-term (90 min) exposure to the dietary abundant flavonoid kaempferol (1-100 microM) is reported. Supplementation initially decreased reactive oxygen levels but, paradoxically, a dose-dependent increase in single-strand DNA breakage occurred. However, there was no increase in oxidised DNA purines or membrane damage. Following a 24-h recovery period in non-kaempferol supplemented media, DNA single-strand breakage had declined and kaempferol exposed and control cultures possessed similar reactive oxygen levels. A reduction in (3)H-thymidine incorporation occurred with > or =10 microM kaempferol. One hundred micromolar kaempefrol increased the proportion of cells in G(2)-M phase, the proportion of cells with a sub-G(1) DNA content and enhanced 'active' caspase-3 expression but only induced a loss of mitochondrial membrane potential within a minority of cells. The relevance of induced DNA damage within a non-overtly oxidatively stressed environment to the disease preventative and therapeutic use of kaempferol is discussed.

Antioxidant activity of sugar–lysine Maillard reaction products in cell free and cell culture systems

Model Maillard reaction (MR) products (MRPs) employing lysine with an aldohexose (e.g., glucose), ketohexose (e.g., fructose), and aldopentose (e.g., ribose) sugars were generated (e.g., pH 9.0; over 2h heating at 120 degrees ) and fractionated with ethanol into low (LMW) and high (HMW) molecular weight fractions. Characteristically different temporal patterns of fluorescence and ultraviolet/visible absorption spectra were obtained from the three distinct sugar-lysine MRPs, and corresponded to different yields of total and dialyzable carbon, indicating that relative reaction rates and degree of polymerization favored the Rib-Lys MRP, compared to Glu-Lys and Fru-Lys MRPs, respectively (p<0.05). Further characterization of antioxidant activity of the sugar specific-lysine MRPs in chemical (e.g., hydrophobic (1,1,-diphenyl-2-picryl-hydrazyl radical (DPPH) and hydrophilic (Fenton reaction-induced hydroxyl radical) in vitro scavenging assays showed that Rib-Lys HMW MRPs had the highest (p<0.05) affinity to scavenge free radicals. All sugar-Lys MRPs, however, displayed similar protection of cultured Caco-2 cells from exposure to H(2)O(2)-, 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH)-, ferrous (Fe(2+))-, and cupric (Cu(2+))-induced cytotoxicity, evaluated both from redox (e.g., MTT response) and cell membrane integrity (e.g., LDH secretion). HMW-MRPs exhibited stronger (p<0.05) antioxidant activity to scavenge hydroxyl and DPPH radicals, and a greater (p<0.05) protective effect against both Fe(2+)- and Cu(2+)-induced cytotoxicity in Caco-2 cells than corresponding LMW-MRPs. We conclude that HMW MRPs possess affective antioxidant protection against oxidizable substrates; however, the degree of polymerization of this product, characteristic to the source of monosaccharide used in the reaction, is not a distinguishable factor for this bioactivity.

Ergovaline toxicity on Caco-2 cells as assessed by MTT, alamarBlue, and DNA assays

The exact mechanisms of fescue toxicity in animals have yet to be established, but it has been associated with an inability to thrive. Ergovaline is the major ergopeptine alkaloid associated with fungal infections of tall fescue. Gastrointestinal (GI) toxicity of ergovaline (10(-11) to 10(-4) M) was evaluated in Caco-2 cells (mimicking the GI epithelium) beginning on days 1, 8, and 18 of culture. Acute and chronic toxicity was assessed after 24 and 72 h of exposure. Treatment periods were chosen to study undifferentiated, semidifferentiated, and completely differentiated cells. Cell loss and metabolic activity were assessed by thiazolyl blue reduction (3-(4,5-dimethylthiozole-2-yl)-2,5,-biphenyl tetrazolium bromide [MTT], mitochondrial succinate dehyrdogenase activity), alamarBlue assay (cytochrome oxidase activity), and deoxyribonucleic acid (DNA) quantitation. Undifferentiated cells were sensitive to 1 x 10(-4) M ergovaline after acute exposure (from 52 to 74% of control values depending on assay). After 72 h of exposure to 1 x 10(-4) M ergovaline, in all three assays, treatment means were reduced to approximately 10% of the control means. By day 11 in culture, ergovaline toxicity to cells had decreased. With 24 h exposure, an apparent paradoxical increase in MTT was seen at some concentrations. This increase in MTT was also found in fully differentiated cells (day 21), whereas alamarBlue activity decreased. No change in DNA was found until 72 h of exposure, when DNA was reduced approximately 12% over most concentrations. These findings indicate differentiation state-dependent sensitivity of Caco-2 cells to ergovaline, potential problems of the MTT assay as an indicator of cellular toxicity, and usefulness of alamarBlue assay over DNA assay for toxicity assessment.

Beta-carotene regulates NF-kappaB DNA-binding activity by a redox mechanism in human leukemia and colon adenocarcinoma cells

We demonstrated previously that beta-carotene may affect cell growth by a redox mechanism. The purpose of this study was to determine whether the redox-sensitive transcription factor nuclear factor (NF)-kappaB may be involved in the growth-inhibitory and proapoptotic effects of the carotenoid. To test this hypothesis, human leukemic cells (HL-60) and colon adenocarcinoma cells (LS-174 and WiDr) were treated with beta-carotene, alone or in combination with alpha-tocopherol or N-acetylcysteine, and changes in 1) cell oxidative status, 2) cell growth and apoptosis, 3) DNA-binding activity of NF-kappaB and 4) expression of c-myc, a NF-kappaB target gene involved in apoptosis, were evaluated. In HL-60 cells, beta-carotene induced a significant increase in reactive oxygen species (ROS) production (P < 0.001) and in oxidized glutathione (GSSG) content (P < 0.005) at concentrations >/=10 micro mol/L. These effects were always accompanied by a sustained elevation of NF-kappaB and by a significant inhibition (P < 0.002) of cell growth. NF-kappaB DNA-binding activity increased at 3 h and persisted for at least 48 h. Colon adenocarcinoma cells displayed substantial differences in their sensitivity to beta-carotene, exhibiting increased ROS levels and activation of NF-kappaB at concentrations much lower in LS-174 cells (2.5-5.0 micro mol/L) than in WiDr cells (50-100 micro mol/L). In all cell lines studied, alpha-tocopherol and N-acetylcysteine inhibited the effects of beta-carotene on NF-kappaB, cell growth and apoptosis, and normalized the increased expression of c-myc induced by the carotenoid. These data suggest that the redox regulation of NF-kappaB induced by beta-carotene is involved in the growth-inhibitory and proapoptotic effects of the carotenoid in tumor cells.

Regulation of cell cycle progression and apoptosis by beta-carotene in undifferentiated and differentiated HL-60 leukemia cells: possible involvement of a redox mechanism

Although epidemiologic studies have demonstrated that a high intake of vegetables containing beta-carotene lowers the risk of cancer, recent intervention studies have revealed that beta-carotene supplementation to smokers resulted in a high incidence of lung cancer. We hypothesized that beta-carotene may act as a pro- or anticancerogenic agent by modulating pathways involved in cell growth and that such a modulation may involve a redox mechanism. To test this hypothesis, cell proliferation, apoptosis and redox status were evaluated in undifferentiated and dimethylsulfoxide-differentiated HL-60 cells exposed to beta-carotene. The carotenoid modified cell cycle progression and induced apoptosis in a dose-dependent manner. These effects were more remarkable in undifferentiated cells than in differentiated cells. In accord with these findings, in undifferentiated cells, beta-carotene was more effective in decreasing cyclin A and Bcl-2 expression and in increasing p21 and p27 expression. Neither Bcl-xL nor Bax expression were significantly modified by the carotenoid. From a mechanistic point of view, the delay in cell growth by beta-carotene was highly coincident with the increased intracellular reactive oxygen species production and oxidized glutathione content induced by the carotenoid. Moreover, alpha-tocopherol minimized the effects of beta-carotene on cell growth. These data provide evidence that beta-carotene modulates molecular pathways involved in cell cycle progression and apoptosis and support the hypothesis that a redox mechanism may be implicated. They also suggest that differentiated cells may be less susceptible to the carotenoid than highly neoplastic undifferentiated cells.

Carotenoids as antioxidants

Larry Machlin had many and varied interests in nutrition in general and antioxidants in particular. Although he was interested primarily in vitamin E, he shared a curiosity about the actions of carotenoids that most nutritionists have. He served on the Organizing Committee of the 8th International Symposium on Carotenoids that was held in Boston in June 1987. In that role, he was an active participant in helping to select sessions and then identifying the speakers who spoke at those sessions. As part of that Organizing Committee, I had the opportunity to grasp his breadth of science and his knowledge about the most current work, even in fields in which he was not directly involved. His loss has been felt, not only for his scientific contributions but also the warmth and kindness of his personality.

Quercetin modifies reactive oxygen levels but exerts only partial protection against oxidative stress within HL-60 cells

Quercetin may contribute to the protection afforded by fruit- and vegetable-rich diets against diseases for which excess production of reactive oxygen species (ROS) has been implicated as a causal or contributory factor. We examine the effect of short term (90 min) quercetin (1-100 microM) exposure on the progress of menadione induced oxidative stress within HL-60 cells. 2',7'-dichlorofluorescein and rhodamine-123 fluorescence, resulting from oxidation of the ROS-sensitive dyes dichlorodihydrofluorescein and dihydrorhodamine-123 respectively, were utilised as indicators of general ROS levels. Ethidium fluorescence, resulting from oxidation of dihydroethidium, was used as a potentially more specific indicator of O(2)(-). Exposure to quercetin alone induced a decrease in DCF and rhodamine fluorescence. Conversely, ethidium fluorescence was enhanced by treatment with >or=40 microM quercetin. Incubation with 1-100 microM quercetin reduced the extent of menadione-induced increase in DCF and rhodamine fluorescence but the menadione-induced increase in ethidium fluorescence was further elevated for cells treated with >or=25 microM quercetin. Exposure to >or=10 microM quercetin abrogated menadione-induced DNA single-strand breaks but, paradoxically, quercetin exacerbated membrane damage and failed to enhance the viability of menadione-challenged cells. In conclusion, quercetin exerts only site-specific protection against oxidative stress.