矢车菊素-3-葡萄糖苷在Caco-2细胞模型的吸收机制研究

目的研究花色苷矢车菊素-3-葡萄糖苷(Cy-3-G)在Caco-2细胞模型的吸收机制。方法建立Caco-2单层细胞模型,观察Cy-3-G的转运情况。加入不同浓度的维拉帕米(P-gp抑制剂)、MK571(MRP2抑制剂)、根皮苷(SGLT1抑制剂)及根皮素(GLUT2抑制剂),观察P-gp、MRP2、SGLT1及GLUT2等转运蛋白在Cy-3-G肠道吸收中的作用。结果 Cy-3-G在Caco-2细胞模型的吸收率随着时间延长逐渐升高,2 h时吸收率在0.76%~2.41%之间,但随着花色苷浓度的升高而降低。维拉帕米和MK571对Cy-3-G在Caco-2细胞模型的吸收无影响(P>0.05),根皮苷和根皮素可显著抑制Cy-3-G的吸收(P<0.05)。结论 P-gp和MRP2对Cy-3-G在肠道的吸收无影响,SGLT1和GLUT2均参与了Cy-3-G在小肠的吸收。[营养学报,2013,35(2):191-194,198]     

姜黄素抑制Caco-2细胞胆固醇吸收的作用及机制研究

目的探讨姜黄素对Caco-2细胞胆固醇吸收的影响以及可能机制。方法建立Caco-2细胞单层模型,分别用25、50、100μmol/L姜黄素或胆固醇吸收转运蛋白尼曼-匹克C1型类似蛋白1(NPC1L1)的抑制剂依折麦布孵育细胞24h或2h后,再用[14C]-胆固醇微胶溶液孵育细胞2h。用液闪计数仪检测细胞胆固醇吸收量,荧光定量PCR和Western blot检测NPC1L1的基因和蛋白表达量。结果 Caco-2细胞[14C]-胆固醇吸收可被依折麦布呈浓度依赖性地抑制,表明本研究建立的单层Caco-2细胞模型的胆固醇吸收是由NPC1L1所介导的。姜黄素能有效的下调NPC1L1的基因及蛋白表达水平,降低Caco-2细胞胆固醇吸收,100μmol/L姜黄素可引起40%胆固醇吸收下降。结论姜黄素能够降低Caco-2细胞胆固醇吸收,这可能与其抑制NPC1L1表达有关。     

The effect of lycopene on cytochrome P450 isoenzymes and P-glycoprotein by using human liver microsomes and Caco-2 cell monolayer model

Lycopene is widely used as a dietary supplement. However, the effects of lycopene on cytochrome P450 (CYP) enzymes or P-glycoprotein (P-gp) are not comprehensive. The present study was performed to investigate the effects of lycopene on the CYP enzymes and P-gp activity. A cocktail method was used to evaluate the activities of CYP3A4, CYP2C9, CYP2C19, CYP2D6 and CYP2E1. Caco-2 cell monolayer model was carried out to assay lycopene on P-gp activity. The results indicated that lycopene had a moderate inhibitory effect on CYP2E1, with IC50 value of 43.65?μM, whereas no inhibitory effects on CYP3A4, CYP2C19, CYP2D6 and CYP2E1, with IC50 values all over 100?μM. In addition, lycopene showed almost no inhibitory effect on rhodamine-123 efflux and uptake (p?>?.05), indicated no effects on P-gp activity. In conclusion, there should be required attention when lycopene are coadministered with other drugs that are metabolised by CYP2E1.     

Guanidine transport across the apical and basolateral membranes of human intestinal Caco-2 cells is mediated by two different mechanisms

The functional characteristics of the intestinal absorption and secretion of guanidine as a model of a nutritionally and metabolically essential organic cation were examined in the Caco-2 human intestinal cell line. Both apical and basolateral transport of [14C]-guanidine were studied using Caco-2 cells grown on polycarbonate permeable membranes. The basolateral-to-apical flux of [14C]-guanidine (i.e., its secretion) was quantitatively higher than the apical-to-basolateral transport (i.e., its absorption). When Na+ was replaced by K+ or Li+, both apical and basolateral accumulation were significantly inhibited. Studies using the cell monolayers and apical membrane vesicles obtained from Caco-2 cells showed a potential-independent mechanism of guanidine apical uptake and efflux. Conversely, basolateral uptake and efflux were membrane potential dependent. Kinetic analysis revealed that both saturable and nonsaturable mechanisms accounted for the apical and basolateral accumulations. The [14C]-guanidine efflux from cells through the apical and basolateral membranes was significantly reduced at 4 degrees C, suggesting carrier-mediated mechanisms. Moreover, the apical efflux was stimulated by an inwardly directed H+ gradient. Influx and efflux of [14C]-guanidine were unaffected by the presence of tetraethylammonium, cimetidine or decynium-22 in the donor compartment. Only quinine significantly reduced [14C]-guanidine entrance through apical and basolateral membranes and its exit through the basolateral membrane. In conclusion, our results suggest that the influx and the efflux through the apical membrane is mediated by different transporters, whereas transport across the basolateral membrane is mediated by a member of the organic cation transporter family with high affinity for guanidine.     

姜黄素对人骨肉瘤细胞株/阿霉素多药耐药逆转作用的实验研究

目的观察姜黄素对多药耐受糖蛋白(P-gp)介导的人骨肉瘤细胞株/阿霉素(U-2OS/ADM)细胞多药耐药(MDR)的逆转作用。方法以阿霉素为诱导药物,人骨肉瘤细胞系U-2OS为诱导对象,采用大剂量冲击法建立人骨肉瘤多药耐药细胞系模型(U-2OS/ADM),采用MTT法检测姜黄素作用于U-2OS/ADM细胞前后对化疗药物的逆转;流式细胞仪检测细胞内罗丹明-123积聚和外排的影响。结果 MTT显示姜黄素20μmol/L能增加不同浓度阿霉素对U-2OS/ADM细胞的抑制作用(P<0.01),且姜黄素对阿霉素为2.0μg/ml时的U-2OS/ADM细胞抑制作用增加幅度达49%。FCM结果显示,姜黄素能增加阿霉素对U-2OS/ADM的细胞毒性作用,且呈剂量依赖关系。结论姜黄素可有效逆转U-2OS/ADM细胞的多药耐药现象的作用。     

铜对Caco-2细胞单层屏障功能的影响

目的研究铜对Caco2细胞单层细胞间通透性、P糖蛋白(Pgp)活性的影响。方法应用Caco2细胞单层模型,通过测定铜暴露后细胞单层的跨上皮细胞电阻(TEER)来反映通透性的改变;通过免疫荧光和荧光染色观察铜对紧密连接蛋白ZO1和F微丝的影响;通过测定细胞单层对罗丹明123的跨膜转运和细胞内罗丹明123的蓄积来反映P糖蛋白活性的改变。结果细胞单层顶面铜暴露(30～100μmol/L,Hanks缓冲溶液,0～3h)可导致TEER值呈浓度和时间依赖性降低,同时伴随着F微丝的解聚,但对紧密连接蛋白ZO1无显著影响;在不影响细胞活性和细胞单层通透性的剂量下,顶面铜暴露(300μmol/L,完全培养基,24h)后细胞单层对罗丹明123的表观通透系数(Papp)BL→AP从对照组的(737±020)10-6cm/s降低为(643±027)×10-6cm/s,PappAP→BL从对照组(123±005)×10-7cm/s增加为(341±008)×10-7cm/s,同时细胞内罗丹明-123的蓄积量从对照组的每膜(031±001)nmol增加为每膜(050±003)nmol。结论铜可显著增加Caco2细胞单层的通透性和抑制Pgp的活性,从而推测可能影响肠道上皮细胞的正常屏障功能。     

Macelignan: A New Modulator of P-Glycoprotein in Multidrug-Resistant Cancer Cells

The effect of macelignan, a phytoestrogen, on P-gp function was investigated using multidrug resistant cancer cells overexpressing P-gp (NCI/ADR-RES) and the fluorescent P-gp substrates, daunorubicin and rhodamine 123. Macelignan (40 μM) increased the cellular accumulation of daunorubicin by approximately threefold in NCI/ADR-RES cells, whereas it did not alter the cellular accumulation of daunorubicin in MCF-7/sensitive cells. Similarly, the presence of macelignan also enhanced significantly (P < 0.05) the cellular accumulation of rhodamine 123 in a concentration-dependent manner in NCI/ADR-RES cells. Furthermore, cancer cells were more susceptible to the cytotoxicity of vinblastine, a P-gp substrate, in the presence of macelignan. Those results suggest that macelignan has inhibitory effects on P-gp mediated cellular efflux. However, P-gp activity did not affect the cellular accumulation of macelignan itself. Taken all together, macelignan was identified as a novel inhibitor of P-gp activity and may be a promising lead compound for the rational design of more efficacious drugs to reverse multidrug resistance in cancer.     

The Role of Sodium-Dependent Glucose Transporter 1 and Glucose Transporter 2 in the Absorption of Cyanidin-3-O-β-Glucoside in Caco-2 Cells

Anthocyanins have multiple biological activities of benefit to human health. While a few studies have been conducted to evaluate the bioavailability of anthocyanins, the mechanisms of their absorption mechanism remain ill-defined. In the present study, we investigated the absorption mechanism of cyanidin-3-O-β-glucoside (Cy-3-G) in human intestinal epithelial (Caco-2) cells. Cy-3-G transport was assessed by measuring the absorptive and efflux direction. Inhibition studies were conducted using the pharmacological agents, phloridzin, an inhibitor of sodium-dependent glucose transporter 1 (SGLT1), or phloretin, an inhibitor of glucose transporter 2 (GLUT2). The results showed that phloridzin and phloretin significantly inhibited the absorption of Cy-3-G. In addition, Caco-2 cells transfected with small interfering RNA (siRNA) specific for SGLT1 or GLUT2 showed significantly decreased Cy-3-G absorption. These siRNA transfected cells also showed a significantly decreased rate of transport of Cy-3-G compared with the control group. These findings suggest that Cy-3-G absorption is dependent on the activities of SGLT1 and GLUT2 in the small intestine and that SGLT1 and GLUT2 could be a limiting step for the bioavailability of Cy-3-G.     

Carotenoid transport is decreased and expression of the lipid transporters SR-BI, NPC1L1, and ABCA1 is downregulated in Caco-2 cells treated with ezetimibe

Data suggest that intestinal carotenoid absorption is a facilitated process. The present study was conducted to determine whether carotenoids and cholesterol share common pathways (transporters) for their intestinal absorption. Differentiated Caco-2 cells on membranes were incubated (16 h) with a carotenoid (1 micromol/L) with or without ezetimibe (EZ; Zetia, an inhibitor of cholesterol transport), and with or without antibodies against the receptors, cluster determinant 36 (CD36) and scavenger receptor class B, type I (SR-BI). Carotenoid transport in Caco-2 cells (cellular uptake + secretion) was decreased by EZ (10 mg/L) as follows: beta-carotene approximately alpha-carotene (50% inhibition) > beta-cryptoxanthin approximately lycopene (20%) > lutein:zeaxanthin (1:1) (7%). EZ reduced cholesterol transport by 31%, but not retinol transport. beta-Carotene transport was also inhibited by anti-SR-BI, but not by anti-CD36. The inhibitory effects of EZ and anti-SR-BI on beta-carotene transport were additive, indicating that they may have different targets. Finally, differentiated Caco-2 cells treated with EZ showed a significant decrease in mRNA expression for the surface receptors SR-BI, Niemann-Pick type C1 Like 1 protein (NPC1L1), and ATP-binding cassette transporter, subfamily A (ABCA1) and for the nuclear receptors retinoid acid receptor (RAR)gamma, sterol-regulatory element binding proteins (SREBP)-1 and -2, and liver X receptor (LXR)beta as assessed by real-time PCR analysis. The data indicate that 1) EZ is an inhibitor of carotenoid transport, an effect that decreases with increasing polarity of the carotenoid molecule, 2) SR-BI is involved in carotenoid transport, and 3) EZ may act, not only by interacting physically with cholesterol transporters as previously suggested, but also by downregulating expression of these proteins. The cellular uptake and efflux of carotenoids, like that of cholesterol, likely involve more than one transporter.     

Nonmutagenicity of curcumin and its antimutagenic action versus chili and capsaicin

Turmeric, which is one of the commonly used spices in Indian cooking, was tested for mutagenicity using the Ames test. The alcoholic extract of fresh or dried turmeric, its principal components, and pyrolyzed turmeric powder and curcumin were tested for mutagenicity in Salmonella typhimurium strains with and without metabolic activation. None of these were mutagenic in all the tester strains. Chilies (which are used with turmeric powder) and their principal alkaloid capsaicin were mutagenic in the TA 98 with S9 mixture. We tested curcumin, which is the principal component of turmeric, for its antimutagenic effect. It showed dose-dependent decreases in mutagenicity of chili extract and capsaicin. Also, we compared the antimutagenicity of curcumin with other known antioxidants, including BHA, vitamins E and C, and vegetable oils. These all showed dose-dependent decreases in mutagenicity of chili extract and capsaicin. These studies show that although there are few mutagenic principles in Indian food, there is still quite a large number of antimutagenic principles in the Indian diet that will modulate the activity of environmental mutagens.     

Nonmutagenicity of curcumin and its antimutagenic action versus chili and capsaicin

Turmeric, which is one of the commonly used spices in Indian cooking, was tested for mutagenicity using the Ames test. The alcoholic extract of fresh or dried turmeric, its principal components, and pyrolyzed turmeric powder and curcumin were tested for mutagenicity in Salmonella typhimurium strains with and without metabolic activation. None of these were mutagenic in all the tester strains. Chilies (which are used with turmeric powder) and their principal alkaloid capsaicin were mutagenic in the TA 98 with S9 mixture. We tested curcumin, which is the principal component of turmeric, for its antimutagenic effect. It showed dose‐dependent decreases in mutagenicity of chili extract and capsaicin. Also, we compared the antimutagenicity of curcumin with other known antioxidants, including BHA, vitamins E and C, and vegetable oils. These all showed dose‐dependent decreases in mutagenicity of chili extract and capsaicin. These studies show that although there are few mutagenic principles in Indian food, there is still quite a large number of antimutagenic principles in the Indian diet that will modulate the activity of environmental mutagens.     

Inhibitory effect of wheat fibre extract on calcium absorption in Caco-2 cells: evidence for a role of associated phytate rather than fibre per se

Summary Background: In spite of the strong evidence for the beneficial heath effects of dietary fibres, one of the potential nutritional disadvantages of high fibre diets is the adverse effect on the bioavailability of micronutrients, especially minerals and trace elements. With regard to Ca, there is considerable evidence that phytate, which is associated with fibre in many foods, such as cereals and soya products, inhibits Ca absorption. However, there is some doubt as to whether fibres per se have an influence on Ca absorption. Aim of the study: Therefore, the purpose of this study was to investigate the effect on Ca absorption of two cereal-based fibre extracts (wheat bran and barley hull). In addition, in order to distinguish between the effect of the fibre components per se and the associated phytate content in these fibre extracts, we investigated the effect of dephytinised wheat and barley fibre extracts and the effect of phytate, as sodium phytate at levels present in the fibre extracts, on Ca absorption. Ca absorption was assessed in Caco-2 cells, as a model for studying Ca absorption in humans. Methods: The effect of wheat and barley fibre extracts, dephytinised wheat and barley fibre extracts, cellulose, and of sodium phytate on transepithelial ⁴⁵Ca transport and ⁴⁵Ca uptake was studied in differentiated Caco-2 cells grown on permeable filter supports. Wheat and barley fibre extracts were dephytinised with wheat phytase. Results: Wheat fibre extract had a 3.2-fold higher phytate content (48.0 mmol/kg) than barely fibre extract (15.1 mmol/kg). Enzymatic dephytinisation of both fibre extracts reduced the phytate content to undetectable levels. The rate of transepithelial ⁴⁵Ca transport across Caco-2 cell monolavers and the uptake of ⁴⁵Ca into Caco-2 cells were unaffected by cellulose or barley fibre extract. On the other hand, inclusion of wheat fibre extract in the Ca transport buffer (50 g fibre/l) significantly reduced the rate of ⁴⁵Ca transport (by 17 and 19% respectively) and the uptake of ⁴⁵Ca (by 24 and 25% respectively) relative to a fibre-free buffer and a control fibre (cellulose) transport buffer. Increasing the phytate concentration of the transport buffer from 0 to 2 mM (a level close to that in the wheat fibre containing buffer) significantly reduced the rate of ⁴⁵Ca transport (by 16%) and ⁴⁵Ca uptake (by 26%). Dephytinisation of the wheat fibre extract removed its inhibitory effects on ⁴⁵Ca transport and e. g. ⁴⁵Ca uptake. Conclusion: The results from the present study in Caco-2 cells suggest that it is the phytate in wheat fibre extract which is the major inhibitory factor of Ca absorption and that wheat fibre per se has little if any inhibitory effect on Ca absorption. In addition, the results of this study support the usefulness of Caco-2 cells for investigating the effects of dietary factors on the cellular uptake and transepithelial intestinal transport of Ca. Received: 22 March 1999, Accepted: 2 February 2000     

Drosophila melanogaster p-glycoprotein: a membrane detoxification system toward polycyclic aromatic hydrocarbon pollutants

Polycyclic aromatic hydrocarbons (PAHs) are well-known ubiquitous environmental contaminants. Permeability glycoprotein (P-gp) is a transmembrane detoxification efflux pump transporting various lipophilic xenobiotics, such as PAHs, out of the cells. The existence of a P-gp detoxification system inducible by PAHs was investigated in Drosophila melanogaster. Western blot experiments showed that D. melanogaster expressed a 140-kDa P-gp in S12 cells, embryos, and adult flies. Permeability glycoprotein was expressed in adult flies in the head, abdomen, and thorax and sublocalized in the sexual and olfactory organs. Flow cytometry experiments using Drosophila S12 cells in the presence of PAHs and target P-gp drug compounds revealed that Drosophila P-gp acted as an efflux detoxification pump. In Drosophila exposed to benzo[a]pyrene or to ambient air polluted by higher or lower PAH concentrations, P-gp expression was clearly showed a dose-dependent increase response. The P-gp induction was detected both in adult flies and in different fly parts, such as the head, thorax, and antennae. Drosophila P-gp acts as a membrane barrier against PAH pollutants.     

Glucosamine Reverses P-Glycoprotein-Mediated Multidrug Resistance in the Daunorubicin-Resistant Human Gastric Cancer Cells

Abstract

Glucosamine (GlcN) is a natural amino monosaccharide in the human body, and evidence of its anticancer effects is growing. In this study, we aimed to evaluate the effects of GlcN for its cytotoxicity, MDR reversal effects and inhibitory effects on function and expression of P-glycoprotein (P-gp) transporter in the daunorubicin-resistant human gastric cancer cells. Cell viability was measured by MTT assay to evaluate the cytotoxicity and multidrug resistance (MDR) reversal effects of GlcN. The effects of GlcN on function and mRNA expression level of P-gp transporter were assessed by flow cytometry and real-time RT-qPCR, respectively. Our results indicated that GlcN reduced the proliferation of human gastric cancer cell line EPG85-257 and its drug-resistant variant EPG85-257RD in a dose-dependent manner. GlcN (at the concentrations of 0.5 and 1?mM) also enhanced the sensitivity of EPG85-257RDB cells to daunorubicin. The cellular accumulation studies showed that GlcN inhibited efflux activity of P-gp and enhanced the mean fluorescent intensity of Rho123 while ^˙it had no effects on P-gp gene expression in these cells. This study suggested that the inhibition of P-gp activity is a novel mechanism of action by which GlcN could reverse MDR in EPG85-257RDB cells.     

The Effect of Turmeric (Curcuma longa) Extract on the Functionality of the Solute Carrier Protein 22 A4 (SLC22A4) and Interleukin-10 (IL-10) Variants Associated with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic relapsing disease. Genetic predisposition to the disease reduces an individual’s capacity to respond appropriately to environmental challenges in the intestine leading to inappropriate inflammation. IBD patients often modify their diet to mitigate or reduce the severity of inflammation. Turmeric (Curcuma longa L., Zingiberaceae) has historically been used in Chinese, Hindu, and Ayurvedic medicine over several centuries to treat inflammatory disorders. To understand how turmeric may influence the consequences of a genetic predisposition to inappropriate inflammation, we used HEK293 cells to examine the in vitro capacity of turmeric extract and fractions to affect the functionality of two gene variants, solute carrier protein 22 A4 (SLC22A4, rs1050152) and interleukin-10 (IL-10, rs1800896) associated with IBD. We found that a turmeric extract and several chromatographically separated fractions beneficially affected the variants of SLC22A4 and IL-10 associated with IBD, by reducing inappropriate epithelial cell transport (SLC22A4, 503F) and increasing anti-inflammatory cytokine gene promoter activity (IL-10, −1082A). The effect of turmeric on the IL-10 variant was strongly associated with the curcumin content of the extract and its fractions.     

Ascorbic acid offsets the inhibitory effect of bioactive dietary polyphenolic compounds on transepithelial iron transport in Caco-2 intestinal cells

We previously reported that (-)-epigallocatechin-3-gallate (EGCG) and grape seed extract (GSE) at high concentration nearly blocked intestinal iron transport across the enterocyte. In this study, we aimed to determine whether small amounts of EGCG, GSE, and green tea extract (GT) are capable of inhibiting iron absorption, to examine if ascorbic acid counteracts the inhibitory action of polyphenols on iron absorption, and to explore the mechanisms of polyphenol-mediated apical iron uptake and basolateral iron release. An(55)Fe absorption study was conducted by adding various concentrations of EGCG, GSE, and GT using Caco-2 intestinal cells. Polyphenols were found to inhibit the transepithelial (55)Fe transport in a dose-dependent manner. The addition of ascorbic acid offset the inhibitory effects of polyphenols on iron transport. Ascorbic acid modulated the transepithelial iron transport without changing the apical iron uptake and the expression of ferroportin-1 protein in the presence of EGCG. The polyphenol-mediated apical iron uptake was inhibited by membrane impermeable Fe(2+) chelators (P < 0.001), but at a low temperature (4°C), the apical iron uptake was still higher than the control values at 37°C (P < 0.001). These results suggest that polyphenols enhance the apical iron uptake partially by reducing the conversion of ferric to ferrous ions and possibly by increasing the uptake of polyphenol-iron complexes via the energy-independent pathway. The present results indicate that the inhibitory effects of dietary polyphenols on iron absorption can be offset by ascorbic acid. Further studies are needed to confirm the current findings in vivo.     

Dietary components inhibit lipid peroxidation in erythrocyte membrane

Lipid peroxidation induced by ascorbic acid and ferrous sulphate in erythrocyte membrane was effectively inhibited by curcumin and capsaicin, active principles in turmeric (Curcuma longa) and red pepper (Capsaicin annuum) with are commonly used spices in the Indian diet. The concentration of curcumin required to quench the peroxidation to about 80% was only 4 μM. Whereas, chemical antioxidants such as butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT) at 40 μM resulted only in 53% and 59% inhibition. Further, fresh onion (Allium cepa) and radish (Raphanus sativus) extract also inhibited the erythrocyte membrane lipid peroxidation effectively in a dose dependent manner. These results suggest that dietary components could offer effective defence mechanism against free radical induced lipid peroxidation which in turn may lead to cellular damage and eventually even to promotion of transformation.     

Preservation of alpha-tocopherol in sunflower oil by herbs and spices

The ability of some commercially available herb and spice extracts to preserve alpha-tocopherol in sunflower oil during heating at 85-105°C was assessed using sunflower oil as a model system. The Rancimat® was evaluated for the heating stage and was used throughout as it was shown to be viable: α-tocopherol did not evaporate under the test conditions. The delay in the onset of rancidity was found to be directly related to the initial α-tocopherol concentration (P < 0.01). Rosemary, thyme, turmeric, sage, oregano and cumin extracts (2000 mg.kg^?1) delayed rancidity (P < 0.01) and preserved α-tocopherol (P < 0.01). Some preservation was observed with clove extract but coriander and cardamom extracts were pro-oxidants. With thyme extract, the log of the induction time (as an indicator of the delay in rancidity) was directly proportional to the temperature (85-100°C). The ethyl acetate, hexane and methanol extracts of fresh sage were effective for preserving α-tocopherol (P < 0.01). With thyme, rosemary and sage extracts, the increase in the preservation of α-tocopherol was directly related to the concentration of the herb extract (P < 0.01) and was quite effective even at 100 mg.kg^?1. The increased delay in the onset of rancidity was due directly to the improved preservation of α-tocopherol (P < 0.01). In further experiments, the preservative effect of turmeric was shown not to be due to its reported major antioxidant, curcumin, even though it delayed rancidity. When herb/spice extracts were examined mixed with thyme, bay and turmeric showed synergism (P < 0.01) whereas bay alone was slightly inhibitory. The mode of action appeared to be due to free radical activity rather than through singlet oxygen generation.     

铜对人类肠道上皮Caco-2细胞的毒性研究

目的　了解铜对人类肠道上皮Caco 2细胞的毒性影响。方法　应用噻唑蓝 (MTT)实验、P 糖蛋白(P gp)活性检测实验、活性氧检测及克隆形成实验研究铜对肠道上皮Caco 2细胞的毒性及可能作用机制 ,同时利用Caco 2细胞和肠炎沙门氏菌为模型 ,研究铜对Caco 2细胞对细菌侵入和存活易感性的影响。结果　在一定的暴露场景下 ,铜可明显地降低细胞的活力 ,抑制细胞膜表面P gp的活性 ,促进细胞内活性氧自由基的产生 ,降低细胞的克隆形成能力。此外 ,细胞经铜暴露后 ,肠炎沙门氏菌侵入细胞的数量增加 ,但细胞内存活的细菌数量却下降。结论　过量的铜可导致Caco 2细胞氧化损伤 ,从而引起更广泛的细胞毒性效应 ,但其对细胞对细菌侵入和存活易感性的影响有待进一步研究。     

Curcumin and Turmeric Modulate the Tumor-Promoting Effects of Iron In Vitro

Free or loosely chelated iron has tumor-promoting properties in vitro. Curcumin, a polyphenol derived from the food spice turmeric (Curcuma longa), is a potent antioxidant that binds iron. The primary aim of this study was to investigate whether curcuminoids prevent tumor-promoting effects of iron in T51B cells, a non-neoplastic rat liver epithelial cell line. Purified curcuminoids (curcumin) or a standardized turmeric extract similarly reduced oxidative stress and cytotoxicity associated with iron overload (IC₅₀ values near 10 μM, P < 0.05). Inhibition of iron-induced tumor promotion (seen upon treatment with 200 μM ferric ammonium citrate ± curcumin/turmeric for 16 wk in culture; subsequently assayed by soft agar colony formation) was nearly complete at 20 μM of total curcuminoids (P < 0.05), a concentration predicted to only partially chelate the added iron. Surprisingly, lower curcumin concentrations (10 μM) increased tumor promotion (P < 0.01). Curcuminoids delivered as a standardized turmeric extract were taken up better by cells, had a longer half-life, and appeared more effective in blocking tumor promotion (P < 0.01), suggesting enhanced curcuminoid delivery to cells in culture. The primary finding that curcuminoids can inhibit tumor promotion caused by iron in T51B cells is tempered by evidence for an underlying increase in neoplastic transformation at lower concentrations.