Chemopreventive effects of α-tocopherol and its long-chain metabolites α-13'-hydroxy- and α-13'-carboxychromanol in LT97 colon adenoma cells

Anticancer effects of vitamin E (tocopherols) have been studied extensively. While in vitro and animal studies showed promising results regarding anticancer effects of tocopherols, human intervention studies failed to reproduce these results. In vivo, α-tocopherol (α-TOH) is metabolized to the long-chain metabolites (LCM) 13'-hydroxychromanol (α-13'-OH) and 13'-carboxychromanol (α-13'-COOH), which likely reach the large intestine. The LCM showed antiproliferative effects in different colon cancer cell lines, but the exact mechanism of action remains unclear. To further clarify the chemopreventive action of the LCM, premalignant LT97 colon adenoma cells were treated with α-TOH, α-13'-OH and α-13'-COOH to study their impact on growth, apoptosis, antigenotoxicity, and ROS-scavenging capacity as well as expression of selected genes involved in detoxification and the cell cycle. Growth inhibitory potential was observed for α-13'-OH (IC50: 37.4 μM) and α-13'-COOH (IC50: 5.8 μM) but not for α-TOH in the tested concentrations. Levels of caspase-3 activity and expression of genes regulating the cell cycle and detoxification remained unchanged. However, α-TOH, α-13'-OH and α-13'-COOH exhibited antigenotoxic and partly ROS-scavenging capacity. The results indicate that the LCM exert chemopreventive effects via ROS-scavenging capacity, the protection against DNA damage and the induction of cell death via caspase-independent mechanisms in premalignant colon cells.

Effect of a regular consumption of traditional and roasted oat and barley flakes on blood lipids and glucose metabolism-A randomized crossover trial

Background

Regular consumption of the soluble dietary fiber β-glucan is associated with decreased total cholesterol (TC), low-density lipoprotein (LDL) cholesterol and blood glucose. Barley and oat flakes as natural sources of β-glucan were roasted to improve sensory quality. The aim of this study was to investigate whether roasting of barley and oat flakes changes the physiological impact of the β-glucan-rich flakes on glucose and lipid metabolism.

Method

A five-armed randomized crossover trial design was used. The intervention study was conducted from May 2018 to May 2019 and included 32 healthy subjects with moderately increased LDL cholesterol (≥2.5 mmol/L). During the 3-week intervention periods, 80 g of roasted or traditional barley or oat flakes, or four slices of white toast bread per day were consumed for breakfast. At the start and the end of each intervention, fasting and postprandial blood was taken. The intervention periods were separated by 3-week wash-out periods.

Results

During the interventions with the cereal flakes, TC and LDL cholesterol concentrations were significantly reduced compared to baseline values by mean differences of 0.27-0.33 mmol/L and 0.21-0.30 mmol/L, respectively (p < 0.05), while high-density lipoprotein (HDL) cholesterol was only reduced after the intervention with barley flakes (p < 0.05). After the intervention period with toast, TC and HDL cholesterol increased (p < 0.05). The fasting levels of triglycerides, fasting blood glucose and insulin did not change in any group. The effects of traditional and roasted varieties on blood lipids did not differ between the groups.

Conclusion

The regular consumption of traditional or roasted barley and oat flakes contributes to the management of cardiovascular diseases by improving TC and LDL cholesterol.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03648112, identifier NCT03648112.

Impact of in vitro digested zinc oxide nanoparticles on intestinal model systems

Background

Zinc oxide nanoparticles (ZnO NP) offer beneficial properties for many applications, especially in the food sector. Consequently, as part of the human food chain, they are taken up orally. The toxicological evaluation of orally ingested ZnO NP is still controversial. In addition, their physicochemical properties can change during digestion, which leads to an altered biological behaviour. Therefore, the aim of our study was to investigate the fate of two different sized ZnO NP (< 50 nm and < 100 nm) during in vitro digestion and their effects on model systems of the intestinal barrier. Differentiated Caco-2 cells were used in mono- and coculture with mucus-producing HT29-MTX cells. The cellular uptake, the impact on the monolayer barrier integrity and cytotoxic effects were investigated after 24 h exposure to 123–614 µM ZnO NP.

Results

In vitro digested ZnO NP went through a morphological and chemical transformation with about 70% free zinc ions after the intestinal phase. The cellular zinc content increased dose-dependently up to threefold in the monoculture and fourfold in the coculture after treatment with digested ZnO NP. This led to reactive oxygen species but showed no impact on cellular organelles, the metabolic activity, and the mitochondrial membrane potential. Only very small amounts of zinc (< 0.7%) reached the basolateral area, which is due to the unmodified transepithelial electrical resistance, permeability, and cytoskeletal morphology.

Conclusions

Our results reveal that digested and, therefore, modified ZnO NP interact with cells of an intact intestinal barrier. But this is not associated with serious cell damage.

Olive Oil Extracts and Oleic Acid Attenuate the LPS-Induced Inflammatory Response in Murine RAW264.7 Macrophages but Induce the Release of Prostaglandin E2

Olive oil contains high amounts of oleic acid (OA). Although OA has been described to inhibit inflammatory processes, the effects of olive oil on cellular mechanisms remain poorly understood. Therefore, we compared the effects of major fatty acids (FA) from olive oil with those of olive oil extracts (OOE) on inflammatory mediators and alterations in the cellular phospholipid composition in murine macrophages. Upon treatment with different OOE, FA compositions of lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages were analyzed using gas chromatography. Olive oil extracts and OA significantly reduced the LPS-induced expression of inducible nitric oxide synthase (iNos), cyclooxygenase (Cox2), and interleukin-6 mRNA. In addition, a significant decrease in Cox2 and iNos protein expression was observed. The formation of nitric oxide was significantly reduced, while the formation of prostaglandin (PG) E₂ from arachidonic acid significantly increased after treatment with OOE or OA. The latter was associated with a shift in the phospholipid FA composition from arachidonic acid to OA, resulting in an elevated availability of arachidonic acid. Together, OOE and OA mediate anti-inflammatory effects in vitro but increase the release of arachidonic acid and hereinafter PGE₂, likely due to elongation of OA and competitive incorporation of fatty acids into membrane phospholipids.

Fermentation profile, cholesterol-reducing properties and chemopreventive potential of β-glucans from Levilactobacillus brevis and Pediococcus claussenii - a comparative study with β-glucans from different sources

The aim of the present study was to investigate whether β-glucans obtained from the lactic acid bacteria (LAB) Levilactobacillus (L.) brevis and Pediococcus (P.) claussenii exhibit similar physiological effects such as cholesterol-binding capacity (CBC) as the structurally different β-glucans from oat, barley, and yeast as well as curdlan. After in vitro fermentation, fermentation supernatants (FSs) and/or -pellets (FPs) were analyzed regarding the concentrations of short-chain fatty acids (SCFAs), ammonia, bile acids, the relative abundance of bacterial taxa and chemopreventive effects (growth inhibition, apoptosis, genotoxicity) in LT97 colon adenoma cells. Compared to other glucans, the highest CBC was determined for oat β-glucan (65.9 ± 8.8 mg g^-1, p < 0.05). Concentrations of SCFA were increased in FSs of all β-glucans (up to 2.7-fold). The lowest concentrations of ammonia (down to 0.8 ± 0.3 mmol L^-1) and bile acids (2.5-5.2 μg mL^-1) were detected in FSs of the β-glucans from oat, barley, yeast, and curdlan. The various β-glucans differentially modulated the relative abundance of bacteria families and reduced the Firmicutes/Bacteroidetes ratio. Treatment of LT97 cells with the FSs led to a significant dose-dependent growth reduction and increase in caspase-3 activity without exhibiting genotoxic effects. Though the different β-glucans show different fermentation profiles as well as cholesterol- and bile acid-reducing properties, they exhibit comparable chemopreventive effects.

Impact of pH changes on metal oxide nanoparticle behaviour during artificial digestion

The physicochemical properties of orally ingested metal nanoparticles can be influenced by the conditions prevailing in the digestive tract. In our work, we demonstrate the strong influence of the pH value on particle fate using a simplified digestion approach to analyze magnesium oxide, copper oxide and zinc oxide nanoparticles and show why a separate consideration of the digestion parameters is necessary.

Thermal Processing has no Impact on Chemopreventive Effects of Oat and Barley Kernels in LT97 Colon Adenoma Cells

The unique dietary fiber composition with high contents of β-glucan contributes to the health-promoting properties of oat and barley and may mediate a reduction of colon cancer risk. In the present study, chemopreventive effects of oat and barley (beta^®barley) kernels were investigated. In order to address the impact of thermal processing on these effects, kernels were roasted (150-180 °C, approx. 20 min), digested and fermented using an In Vitro human digestion model. Concentrations of short-chain fatty acids (SCFA) and ammonia were determined in fermentation supernatants (FS). Growth inhibition, apoptosis, DNA integrity and gene expression of catalase were analyzed in LT97 colon adenoma cells. Concentrations of SCFA, particularly butyrate, were higher in oat/barley FS (2.2-fold, on average), while ammonia levels were significantly lower (0.7-fold, on average) than in the fermentation control. Treatment of LT97 cells with FS of oat/barley kernels led to a significant time- and dose-dependent growth reduction, a significant increase in caspase-3 activity and enhanced levels of catalase mRNA, without exhibiting genotoxic effects. In general, the results indicate a chemopreventive potential of In Vitro fermented oat and waxy winter barley mediated mainly by growth inhibitory and apoptotic effects, which are preserved after thermal processing.

Chemopreventive effects of raw and roasted oat flakes after in vitro fermentation with human faecal microbiota

The aim of the present study was to analyse chemopreventive effects of oat flakes under consideration of processing. Thin and thick flakes were roasted and subjected to an in vitro digestion and fermentation. Fermentation supernatants (FS) were characterised and chemopreventive effects were analysed in LT97 colon adenoma cells. Compared to the fermentation control, pH values were decreased (from pH 6.3 to pH 5.0) and concentrations of SCFA, in particular butyrate, were increased in oat FS (2.6-fold, on average). Ammonia levels were not altered. Oat FS significantly decreased cell growth time- and dose-dependently. Caspase 3 activity was significantly increased (9.7-fold, on average). Oat FS slightly increased the mRNA expression of CAT (2.0-fold), SOD2 (1.7-fold) and GSTP1 (2.8-fold), on average, while GPX1 mRNA (0.3-fold) was decreased. The results indicate a chemopreventive potential of in vitro digested oat flakes regarding colon cancer development mediated mostly by growth inhibition and apoptosis, unaffected by roasting.

Study on chemopreventive effects of raw and roasted β-glucan-rich waxy winter barley using an in vitro human colon digestion model

Fermentation supernatants of barley flakes exhibit chemopreventive effects in LT97 colon adenoma cells without impact of roasting.

Toxicological assessment of magnesium oxide nanoparticles in HT29 intestinal cells

Nanoparticles (NPs) are increasingly used in different consumer-related areas, for instance in food packaging or as additives, because of their enormous potential. Magnesium oxide (MgO) is an EU-approved food additive (E number 530). It is commonly used as a drying agent for powdered foods, for colour retention or as a food supplement. There are no consistent results regarding the effects of oral MgO NP uptake. Consequently, the aim of this study was to examine the effects of MgO NPs in the HT29 intestinal cell line. MgO NP concentrations ranged from 0.001 to 100 μg/ml and incubation times were up to 24 h. The cytotoxic and genotoxic potential were investigated. Apoptotic processes and cell cycle changes were analysed by flow cytometry. Finally, oxidative stress was examined. Transmission electron microscopy indicated that there was no cellular uptake. MgO NPs had no cytotoxic or genotoxic effects in HT29 cells and they did not induce apoptotic processes, cell cycle changes or oxidative stress.

Impact of different roasting conditions on chemical composition, sensory quality and physicochemical properties of waxy-barley products

Roasting improves sensory properties and differentially modulates health-related compounds of barley products.

Calcium and Phosphate Metabolism, Blood Lipids and Intestinal Sterols in Human Intervention Studies Using Different Sources of Phosphate as Supplements-Pooled Results and Literature Search

Phosphates are associated with negative physiological effects. The objectives of this publication were to compare differential effects of supplementation with calcium phosphate or phosphate alone in healthy humans. Four adult human studies were conducted with pentacalcium hydroxy-trisphosphate supplementation (CaP; 90 subjects) and their data were pooled for assessment. For literature search; PubMed and ISI Web of Knowledge were used and 21 items were assigned to three main topics. The pooled study results show that following CaP supplementation, faecal calcium and phosphorus and urinary calcium were increased, blood lipids were positively modulated, and faecal bile acids were increased, as compared with placebo. The literature search reveals that following calcium phosphate supplementation, urinary calcium was increased. Following solely phosphate supplementation, urinary phosphorus was increased and urinary calcium was decreased. Postprandial calcium concentrations were increased following calcium phosphate supplementation. Postprandial phosphate concentrations were increased following solely phosphate supplementation. Calcium phosphate supplementation resulted in rather positively modulated blood lipids and gut-related parameters. The presented results show the relevance to distinguish between calcium phosphate and solely phosphate supplementations, and the importance of a balanced calcium and phosphorus intake.

High phosphorus intake and gut-related parameters - results of a randomized placebo-controlled human intervention study

Background

In recent years, high phosphate intakes were discussed critically. In the small intestine, a part of the ingested phosphate and calcium precipitates to amorphous calcium phosphate (ACP), which in turn can precipitate other intestinal substances, thus leading to a beneficial modulation of the intestinal environment. Therefore, we analysed faecal samples obtained from a human intervention study regarding gut-related parameters.

Methods

Sixty-two healthy subjects (men, n = 30; women, n = 32) completed the double-blind, placebo-controlled and parallel designed study (mean age: 29 ± 7 years; mean BMI: 24 ± 3 kg/m²). Supplements were monosodium phosphate and calcium carbonate. During the first 2 weeks, all groups consumed a placebo sherbet powder, and afterwards a sherbet powder for 8 weeks according to the intervention group: P1000/Ca0 (1000 mg/d phosphorus), P1000/Ca500 (1000 mg/d phosphorus and 500 mg/d calcium) and P1000/Ca1000 (1000 mg/d phosphorus and 1000 mg/d calcium). After the placebo period and after 8 weeks of intervention faecal collections took place. We determined in faeces: short-chain fatty acids (SCFA) and fat as well as the composition of the microbiome (subgroup) and cyto- and genotoxicity of faecal water (FW). By questionnaire evaluation we examined tolerability of the used phosphorus supplement.

Results

Faecal fat concentrations did not change significantly due to the interventions. Concentrations of faecal total SCFA and acetate were significantly higher after 8 weeks of P1000/Ca500 supplementation compared to the P1000/Ca0 supplementation. In men, faecal total SCFA and acetate concentrations were significantly higher after 8 weeks in the P1000/Ca1000 group compared to the P1000/Ca0 one. None of the interventions markedly affected cyto- and genotoxic activity of FW. Men of the P1000/Ca1000 intervention had a significantly different gut microbial community compared to the men of the P1000/Ca0 and P1000/Ca500 ones. The genus Clostridium XVIII was significantly more abundant in men of the P1000/Ca1000 intervention group compared to the other groups. Supplementations did not cause increased intestinal distress.

Conclusions

The used high phosphorus diet did not influence cyto- and genotoxicity of FW and the concentrations of faecal fat independent of calcium intake. Our study provides first hints for a potential phosphorus-induced modulation of the gut community and the faecal total SCFA content.

Trial registration

The trial is registered at ClinicalTrials.gov as NCT02095392.

Electronic supplementary material

The online version of this article (10.1186/s12937-018-0331-4) contains supplementary material, which is available to authorized users.

Habitual Intakes, Food Sources and Excretions of Phosphorus and Calcium in Three German Study Collectives

Phosphorus intake in Europe is far above recommendations. We present baseline data from three human intervention studies between 2006 and 2014 regarding intake and excretion of phosphorus and calcium. All subjects documented their nutritional habits in weighed dietary records. Fasting blood samples were drawn, and feces and urine were quantitatively collected. Dietary phosphorus intake was estimated based on weighed dietary records and urine phosphorus excretions. Food sources were identified by allocation to defined food product groups. Average phosphorus consumption was 1338 mg/day and did not change from 2006 to 2014, while calcium intake decreased during this period (1150 to 895 mg/day). The main sources for phosphorus intake were bread/cereal products, milk/milk products and meat/meat products/sausage products and the main sources of calcium intake included milk/milk products/cheese, bread/cereal products and beverages. There was no difference between estimated phosphorus intake from the weighed dietary records and urine phosphorus excretion. In conclusion, we demonstrated constant phosphorus intakes far above the recommendations and decreasing calcium intakes below the recommendations in three German collectives from 2006 to 2014. Furthermore, we could show in case of usual intakes that an estimated phosphorus intake from urine phosphorus excretion is similar to the calculated intake from weighed dietary records.

Chemopreventive Potential of In Vitro Fermented Raw and Roasted Hazelnuts in LT97 Colon Adenoma Cells

BACKGROUND/AIM

Due to their unique composition of health-promoting compounds, the consumption of hazelnuts may contribute to the prevention of colon cancer.

MATERIALS AND METHODS

Since hazelnuts are often consumed roasted, the impact of different roasting conditions (RC1=140.6°C/25 min, RC2=155.1°C/20 min and RC3=180.4°C/21 min) on chemopreventive effects of in vitro fermented hazelnuts was analyzed in LT97 colon adenoma cells.

RESULTS

FS (2.5%) of raw and roasted hazelnuts reduced H₂O₂-induced DNA damage while 5% FS significantly induced gene expression of SOD2 (3.0-fold) and GSTP1 (2.1-fold). GPx1 mRNA levels were significantly decreased (0.6-fold) by FS (2.5%). The growth of LT97 cells was significantly reduced by hazelnut FS in a time- and dose-dependent manner. Hazelnut FS (5%) increased the numbers of early apoptotic cells (9.6% on average) and caspase-3 activities (6.4-fold on average).

CONCLUSION

These results indicate a chemopreventive potential of in vitro fermented hazelnuts which is largely unaffected by the roasting process.

Influence of roasting on the chemopreventive potential of in vitro fermented almonds in LT97 colon adenoma cells

The consumption of almonds may contribute to the prevention of colon cancer due to their unique composition of health promoting compounds. Since almonds are often consumed roasted, the impact of different roasting (R) conditions (R1 = 139.2 °C/25 min, R2 = 161.5 °C/20 min and R3 = 170.8 °C/15 min) on chemopreventive effects of in vitro-fermented almonds was analysed in LT97 colon adenoma cells. Fermentation supernatants (FS) of raw and roasted almonds had no genotoxic effects. FS obtained from raw or mildly roasted almonds (R1) significantly increased mRNA levels of CAT (4.6-fold), SOD2 (5.6-fold) and GSTP1 (3.9-fold) but not of GPx1. FS of almonds significantly reduced the growth of LT97 cells in a time- and dose-dependent manner. Treatment with 5% almonds FS increased the number of early apoptotic cells (17.4%, on average) and caspase-3 activity (4.9-fold, on average). The results indicate a chemopreventive potential of in vitro-fermented almonds which is largely independent of the roasting process.

In vitro uptake and toxicity studies of metal nanoparticles and metal oxide nanoparticles in human HT29 cells

In this paper, we investigated the toxicological behavior of metal nanoparticles (gold, silver) and metal oxide nanoparticles (copper oxide, zinc oxide, titanium dioxide) in vitro in human colorectal adenocarcinoma cells (HT29). We analyzed the cellular uptake by ICP-MS and TEM, the influence on cell viability by MTT assay and trypan blue exclusion test, their effect on DNA damage and/or generation of oxidized bases by alkaline comet assay, and their potential to induce apoptosis by flow cytometry after 24-h nanoparticle treatment with concentrations between 2 and 10 µg/ml. We determined the amount of metal taken up by a single HT29 cell, ranging from 0.02 pg/cell up to 1.39 pg/cell. Cell viability assays showed a significantly decrease for metal oxide nanoparticles using trypan blue exclusion test and for all nanoparticles, except titanium dioxide, using MTT assay. Genotoxic effects after nanoparticle treatment were not observed for the tested concentrations. Apoptosis induction was significantly increased for silver nanoparticles (tested for two sizes) as well as for titanium dioxide and zinc oxide nanoparticles. Our results indicate potential health risks of oral NP uptake by food ingredients or food contamination, making further mechanistic investigations on cellular uptake and toxicity necessary.

Consequences of a high phosphorus intake on mineral metabolism and bone remodeling in dependence of calcium intake in healthy subjects - a randomized placebo-controlled human intervention study

Background

Epidemiological studies reported an association between plasma phosphate concentrations and a higher risk for death and cardiovascular events in subjects free of chronic kidney diseases. The main aims of the present study were to determine the influence of a high phosphorus intake in combination with different calcium supplies on phosphorus, calcium, magnesium and iron metabolism as well as fibroblast growth factor 23 (FGF23) concentrations within eight weeks of supplementation.

Methods

Sixty-two healthy subjects completed the double-blind, placebo-controlled parallel designed study. Supplements were monosodium phosphate and calcium carbonate. During the first two weeks, all groups consumed a placebo sherbet powder, and afterwards, for eight weeks, a sherbet powder according to the intervention group: P1000/Ca0 (1 g/d phosphorus), P1000/Ca500 (1 g/d phosphorus and 0.5 g/d calcium) and P1000/Ca1000 (1 g/d phosphorus and 1 g/d calcium). Dietary records, fasting blood samplings, urine and fecal collections took place.

Results

Fasting plasma phosphate concentrations did not change after any intervention. After all interventions, renal excretions and fecal concentrations of phosphorus increased significantly after eight weeks. Renal calcium and magnesium excretion decreased significantly after eight weeks of P1000/Ca0 intervention compared to placebo. Plasma FGF23 concentrations were significantly higher after four weeks compared to eight weeks of all interventions.

Conclusions

The long-term study showed in healthy adults no influence of high phosphorus intakes on fasting plasma phosphate concentrations. A high phosphorus intake without adequate calcium intake seems to have negative impact on calcium metabolism. Plasma FGF23 concentrations increased four weeks after high phosphorus intake and normalized after eight weeks.

Trial registration

The trial is registered at ClinicalTrials.gov as NCT02095392.

α-Tocopherol long-chain metabolite α-13'-COOH affects the inflammatory response of lipopolysaccharide-activated murine RAW264.7 macrophages

SCOPE

Inflammatory response of macrophages is regulated by vitamin E forms. The long-chain metabolite α-13'-carboxychromanol (α-13'-COOH) is formed by hepatic α-tocopherol (α-TOH) catabolism and acts as a regulatory metabolite via pathways that are different from its metabolic precursor.

METHODS AND RESULTS

Using semisynthetically-derived α-13'-COOH we profiled its action on LPS-induced expression of pro- and anti-inflammatory genes using RT-qPCR and of key proteins by Western blotting. Effects on inflammatory response were assessed by measuring production of nitric oxide and prostaglandin (PG) E2 , PGD2 , and PGF2α. α-13'-COOH inhibits proinflammatory pathways in LPS-stimulated RAW264.7 macrophages more efficiently than α-TOH. Profiling inflammation-related genes showed significant blocking of interleukin (Il)1β by the metabolite and its precursor as well, while upregulation of Il6 was not impaired. However, induction of Il10, cyclooxygenase 2 (Cox2) and inducible nitric oxide synthase (iNos) by LPS and consequently the formation of nitric oxide and PG was significantly reduced by α-13'-COOH. Interestingly, α-13'-COOH acted independently from translocation of NFκB subunit p65.

CONCLUSION

Our study sheds new light on the mode of action of α-TOH on the inflammatory response in macrophages, which may be mediated in vivo at least in part by its metabolite α-13'-COOH. Our data show that α-13'-COOH is a potent anti-inflammatory molecule.

Influence of roasting conditions on health-related compounds in different nuts

Due to their health-beneficial ingredients the consumption of nuts can contribute to a healthy diet. The composition of hazelnuts, almonds, macadamia nuts, pistachios and walnuts regarding health-promoting and potentially harmful compounds was examined before and after roasting under different time and temperature conditions. Fatty acid compositions were not affected by roasting. Malondialdehyde increased with higher roasting temperatures (17-fold in walnuts). Levels of tocopherol isomers were reduced after roasting (α-T: 38%, β-T: 40%, γ-T: 70%) and hydrophilic antioxidant capacity decreased significantly in hazelnuts (1.4-fold), macadamia nuts (1.7-fold) and walnuts (3.7-fold). Increasing roasting temperatures supported the formation of significant amounts of acrylamide only in almonds (1220 μg kg(-1)). In general, nuts roasted at low/middle temperatures (120-160°C) exhibited best sensory properties. Therefore, desired sensory quality along with a favourable healthy nut composition may be achieved by roasting over a low to medium temperature range.

Butyrate modulates antioxidant enzyme expression in malignant and non-malignant human colon tissues

The induction of antioxidant enzymes is an important mechanism in colon cancer chemoprevention, but the response of human colon tissue to butyrate, a gut fermentation product derived from dietary fiber, remains largely unknown. Therefore, our study investigated the effect of a butyrate treatment on catalase (CAT) and superoxide dismutase (SOD2) in matched human colon tissues of different transformation stages (n = 3-15 in each group) ex vivo. By performing quantitative real-time PCR, Western blot, and spectrophotometric measurements, we found an increase in SOD2 at expression and activity level in colonic adenocarcinomas (mRNA: 1.96-fold; protein: 1.41-fold, activity: 1.8-fold; P < 0.05). No difference was detectable for CAT between normal, adenoma, and carcinoma colon tissues. Treatment of normal colon epithelium (12 h) with a physiologically relevant concentration of butyrate (10 mM) resulted in a significant increase (P < 0.05) in CAT mRNA (1.24-fold) and protein (1.39-fold), without affecting the enzymatic activity. Consequently, preliminary experiments failed to show any protective effect of butyrate against H2 O2 -mediated DNA damage. Despite a significantly lowered SOD2 transcript (0.51-fold, P < 0.01) and, to a lesser extent, protein level (0.86-fold) after butyrate exposure of normal colon cells, the catalytic activity was significantly enhanced (1.19-fold, P < 0.05), suggesting an increased protection against tissue superoxide radicals. In malignant tissues, greater variations in response to butyrate were observed. Furthermore, both enzymes showed an age-dependent decrease in activity in normal colon epithelium (CAT: r = -0.49, P = 0.09; SOD2: r = -0.58, P = 0.049). In conclusion, butyrate exhibited potential antioxidant features ex vivo but cellular consequences need to be investigated more in depth.

Analysis of DNA damage and repair by comet fluorescence in situ hybridization (Comet-FISH)

A useful tool in the detection of overall and region-specific DNA damage is the Comet-FISH technique. This method combines two well-established methods, the Comet assay (single cell gel electrophoresis), which makes it possible to detect and quantify DNA damage at the single cell level, and FISH (fluorescence in situ hybridization), a technique that allows the specific detection of selected DNA sequences. The influence of specific substances such as water pollutants or food ingredients on individual cells can be measured with the alkaline version of the Comet assay, which involves the embedding of cells in agarose on microscopic slides, lysis of cells, and separation of DNA via electrophoresis. In damaged cells a "comet tail" is formed by fractured DNA migrating from the nucleus (head of the comet) in the electric field.The damaged DNA (DNA strand breaks) correlates with the percentage of DNA in the tail. In combination with the FISH method, DNA damage or repair capacity in single cells can be measured using labelled probes, which hybridize to specific DNA sequences of interest. This protocol exemplarily provides a description of the Comet-FISH technique for the detection of DNA damage using hydrogen peroxide as a genotoxic model substance.

First molecular cytogenetic high resolution characterization of the NIH 3T3 cell line by murine multicolor banding

Since being established in 1963, the murine fibroblast cell line NIH 3T3 has been used in thousands of studies. NIH 3T3 immortalized spontaneously and became tetraploid shortly after its establishment. Here we report the first molecular cytogenetic characterization of NIH 3T3 using fluorescence in situ hybridization based multicolor banding (mcb). Overall, a complex rearranged karyotype presenting 16 breakpoints was characterized. Also it was possible to deduce the resulting gains and losses of copy numbers in NIH 3T3. Overall, only 1.8% of the NIH 3T3 genome is disome, 26.2% tri-, 60% tetra-, 10.8% quinta-, and 1.2% hexasome. Strikingly, the cell line gained only 4 derivative chromosomes since its first cytogenetic description in 1989. An attempt to align the observed imbalances of the studied cell line with their homologous regions in humans gave the following surprising result: NIH 3T3 shows imbalances as typically seen in human solid cancers of ectodermal origin.

Molecular cytogenetic evaluation of the efficacy of photodynamic therapy by indocyanine green in breast adenocarcinoma MCF-7 cells

BACKGROUND

Photodynamic therapy (PDT) is used for the treatment of many types of predominantly epithelial cancers. Photosensitizer is taken up by fast growing tumor cells more actively than by other body cells and is activated by light, generating reactive oxygen species that cause cell death by necrosis or apoptosis. This study aimed to evaluate the efficacy of PDT with indocyanine green (ICG) through the investigation of TP53, HER-2 and TOP2A genes signals as breast cancer gene markers by interphase fluorescence in situ hybridization (nuc-FISH).

METHODS

The photosynthetizer ICG (200 μM) was applied to breast cancer cell line MCF-7 cells (adenocarcinoma) in combination with laser irradiation (807 nm) exposure for 20 min and then incubated for 12, 24 and 48 h. Cell viability was evaluated using trypan blue. The signals for nuc-FISH was investigated and counted for probes specific for the genes TP53 (17p13), HER-2 (17q11.2-q12), and TOP2A (17q21-q22), and BAC-probes RP11-746M1 in 17p11.2 and RP11-403E9 in 17q11.2.

RESULTS

The cell viability of MCF-7 did not reduced significantly when the cells were treated with ICG (200 μM) or exposed to laser irradiation for 20 min followed by incubation for 24 h. ICG/PDT treatment with laser irradiation exposure for 20 min reduced the cell viability after incubating cells for 12, 24 and 48 h highly significantly in a time dependent manner. For nuc-FISH analysis, TP53, HER-2, TOP2A, RP11-746M1 and RP11-403E9 signals did not reduce or increase in a significant manner when the cells were treated with ICG or exposed to laser irradiation for 20 min then incubated for 24h. PDT enhanced amplification of TP53 signals from nuc ish 17p13(TP53×2) to nuc ish 17p13(TP53×3) or nuc ish 17p13(TP53×4). However, the signals of HER-2 gene, TOP2A gene and BAC probes were reduced highly significantly when MCF-7 cells were treated with PDT with all time intervals.

CONCLUSION

ICG/PDT and laser induced cytotoxic effect in MCF-7 cells. Also, PDT enhanced TP53 gene amplification, and reduced HER-2, TOP2A, and BAC probes RP11-746M1 and RP11-403E9 signals. Therefore ICG/PDT can be used for breast cancer treatment. It has the potential to induce apoptotic effect and reduce HER-2 and TOP2A genes propagation. Further in vivo studies are needed to evaluate ICG/PDT as a promising therapeutic approach for breast cancer.

Gut fermentation products of inulin-type fructans modulate the expression of xenobiotic-metabolising enzymes in human colonic tumour cells

Epidemiological studies suggest that nutrition plays an important role in colonic cancer prevention. A possible mechanism of this prevention may be the modulation of carcinogen metabolism and scavenging of reactive intermediates. In particular, dietary fibres are discussed as potentially protective food ingredients. Therefore, the aim of this study was to analyse if the expression of genes related to biotransformation is modulated by fermentation samples of dietary fibres. HT29 (human colonic carcinoma) and LT97 (human adenoma) cells were incubated with fermentation supernatant (SFS), produced by in vitro fermentation of inulin enriched with oligofructose. Possible mechanisms of de-toxification were investigated by analysing the expression of catalase and glutathione-S-transferase (GST) A4 mRNA and the enzyme activity of catalase and GST. In addition, protection of both cell lines against DNA damage, induced by H(2)O(2) or 4-hydroxynonenal (HNE), was analysed using the comet assay. Incubation with SFS resulted in significantly increased GSTA4 mRNA expression, significantly enhanced catalase activity and a significant reduction in the amount of H(2)O(2)-induced DNA damage in HT29 cells. Our results show that complex fermentation samples of inulin-type fructans favourably modulate expression of genes related to biotransformation in carcinoma cells, which in turn supports the important role of dietary fibres in primary chemoprevention.

Human colon cell culture models of different transformation stages to assess conjugated linoleic acid and conjugated linolenic acid metabolism: Challenges and chances

Both cellular transformation status and cell culture conditions affect fatty acid metabolism. Hence, the incorporation and metabolism of c9,t11-CLA (conjugated linoleic acid) and other CFAs (conjugated fatty acids) were compared in colon cells (LT-97, adenoma; HT-29, adenocarcinoma). Growth inhibition by CFA in LT-97 cells was assessed via the DAPI (4',6-diamidino-2-phenylindole dihydrochloride) assay. Basal gene expression of desaturases (Δ5, Δ6 and Δ9) and elongases (1, 2, 5 and 6) was determined in LT-97 using PCR. Analysis of cellular fatty acids revealed a 2-fold higher incorporation of c9,t11-CLA (40 and 80μM) in HT-29 cells compared to LT-97 cells. The β-oxidized and elongated conjugated dienoic (CD) fatty acids differed by 8-fold (CD-C16:2/CD-C20:2; HT-29: 8:1; LT-97: 1:1). Notably, LT-97 cells were shown to convert conjugated linolenic acid (CLnA) to CLA. Moreover, LT-97 cells revealed no basal expression of elongase 2. CLnA caused stronger growth inhibition (≤80μM) compared to CLA (200μM). The results indicate that LT-97 cells represent a superior model to carry out elongation and desaturation studies of unsaturated and conjugated fatty acids compared to HT-29 cells. Nevertheless, further in-depth metabolic and transcriptomic analyses are required to confirm this suggestion.

Detection of DNA damage by comet fluorescence in situ hybridization

Comet fluorescence in situ hybridization (Comet-FISH) is a useful method to detect overall and region-specific DNA damage in individual cells. Two well-established methods are combined, the Comet assay (single cell gel electrophoresis) and fluorescence in situ hybridization (FISH). The Comet assay is the method of choice for the detection of DNA damage. With the alkaline version the influence of specific substances such as water pollutants or ingredients of food on individual cells can be easily measured. The Comet assay involves the embedding of cells in agarose on microscopic slides, lysis of cells, and separation of DNA via electrophoresis. Damaged DNA migrates from the nucleus (head of the comet) forming a tail. The percentage of DNA in the tail correlates with the degree of DNA strand breaks (DNA damage). The combination of FISH with the Comet assay uses labeled probes which hybridize specifically to selected DNA sequences. This allows the detection of specific DNA damage or repair capacity in single cells. Here we present exemplarily the Comet-FISH method by detection of DNA damage using hydrogen peroxide as a genotoxic model substrate.

Chemopreventive effects of in vitro digested and fermented bread in human colon cells

PURPOSE

Bread as a staple food product represents an important source for dietary fibre consumption. Effects of wheat bread, wholemeal wheat bread and wholemeal rye bread on mechanisms which could have impact on chemoprevention were analysed in colon cells after in vitro fermentation.

METHODS

Effects of fermented bread samples on gene expression, glutathione S-transferase activity and glutathione content, differentiation, growth and apoptosis were investigated using the human colon adenoma cell line LT97. Additionally, apoptosis was studied in normal and tumour colon tissue by determination of caspase activities.

RESULTS

The expression of 76 genes (biotransformation, differentiation, apoptosis) was significantly upregulated (1.5-fold) in LT97 cells. The fermented bread samples were able to significantly increase glutathione S-transferase activity (1.8-fold) and glutathione content (1.4-fold) of the cells. Alkaline phosphatase activity as a marker of differentiation was also significantly enhanced (1.7-fold). The fermented bread samples significantly inhibited LT97 cell growth and increased the level of apoptotic cells (1.8-fold). Only marginal effects on apoptosis in tumour compared to normal tissue were observed.

CONCLUSIONS

This is the first study which presents chemopreventive effects of different breads after in vitro fermentation. In spite of differences in composition, the results were comparable between the bread types. Nevertheless, they indicate a potential involvement of this staple food product regarding the prevention of colon cancer.

Impact of butyrate on PKM2 and HSP90β expression in human colon tissues of different transformation stages: a comparison of gene and protein data

Due to protection of oncogenic proteins from degradation and enhancement of glycolytic phosphometabolites for synthetic processes, respectively, heat shock protein 90 (HSP90) and pyruvate kinase type M2 (PKM2) are important proteins for tumor growth. The present study was undertaken to investigate the susceptibility of both proteins and their encoding genes to the chemopreventive agent butyrate in human colon cells. Matched tissue of different transformation stages derived from 20 individual colon cancer patients was used for the experiments. The results of quantitative real-time PCR revealed a moderate increase of HSP90β and PKM2 mRNA in colon tumors (P < 0.01) compared to normal tissues without relation to clinical parameters. The expression pattern could be confirmed for PKM2 protein by Western blot but not for HSP90β. During culturing with butyrate, the amount of PKM2 transcripts decreased in all three tissue types with the strongest effects observed in tumors (median fold decrease 45%, P < 0.05). The protein data have not reflected this influence supposing a more gradual degradation rate due to a longer half-life of PKM2. In contrast, the mRNA expression of HSP90β in normal tissue was found 1.38-fold increased by butyrate (P < 0.05), but not the corresponding protein level. HSP90β expression in adenomas and tumors remained generally insensitive. Only in malignant tissue, however, a significant correlation was found between the individual effects observed on gene and protein expression level. In conclusion, the present study identified PKM2 as a potential direct target of butyrate in neoplastic colon tissue, whereas HSP90β is none of it.

The effect of probiotics on faecal microbiota and genotoxic activity of faecal water in patients with atopic dermatitis: a randomized, placebo-controlled study

BACKGROUND

Colonic microbiota is involved in the etiology of colon cancer according to several reports. Studies also indicate that the microbiota differs between atopic patients and healthy subjects.

OBJECTIVE

To evaluate whether a probiotic mix containing Lactobacillus paracasei Lpc-37, Lactobacillus acidophilus 74-2, and Bifidobacterium animalis subsp. lactis DGCC 420 can affect the microbiota and its genotoxic activity in healthy subjects and patients with atopic dermatitis (AD).

METHODS

A placebo-controlled cross-over study was conducted. Fifteen healthy adults and 15 adult AD patients consumed 2×100 ml/d of either a probiotic or a placebo drink for 8 weeks followed by a wash out period of 2 weeks before crossing the intervention. Faecal water was isolated from stool samples collected at the end of each period. HT29c19a cells incubated with faecal water were measured for DNA damage using single-cell gel electrophoresis ("comet assay"). Bacterial species were determined by qPCR and concentrations of short-chain fatty acids were measured by means of gas chromatography.

RESULTS

Probiotic supplementation resulted in a significant increase in lactobacilli, whereas numbers of Bifidobacteria and Bacteroidetes remained unchanged. Clostridium perfringens cluster I-II was significantly reduced in healthy subjects. Genotoxic potential (expressed as tail intensity) of faecal water, was not affected. However, tail intensity decreased significantly in the probiotic period compared to placebo (23.5 vs. 16.7%) in AD patients. Although faecal concentrations of short-chain fatty acids were not affected, faecal pH was significantly reduced (7.0 vs. 6.6) in AD patients after probiotics.

CONCLUSION

The results indicate that probiotics lower the genotoxic potential of faecal water in AD patients. The faecal C. perfringens cluster I-II levels remained unaffected suggesting either a change in their activity, or the fact that other bacterial species are responsible for the reduced genotoxic activity of faecal water.

Impact of polyphenol metabolites produced by colonic microbiota on expression of COX-2 and GSTT2 in human colon cells (LT97)

Polyphenols may play an important role in colon cancer prevention. After entering the colon, they are subjected to metabolism by the human gut microbiota. The objective of the present study was to analyze the impact of selected intestinal metabolites on modulation of enzymes involved in detoxification and inflammation in human adenoma cells LT97. LT97 cells were incubated with 3,4-dihydroxyphenylacetic acid (ES) and 3-(3,4-dihydroxyphenyl)-propionic acid (PS), metabolites of quercetin and chlorogenic acid/caffeic acid, respectively. The effect on cell number was analyzed using 4'- 6-diamino-2-phenylindole-dihydrochloride (DAPI)-staining. Modulation of glutathione S-transferase T2 (GSTT2) and cyclooxygenase-2 (COX-2) was measured by real-time PCR and Western blot. Comet assay was performed to assess the impact on DNA damage caused by the GSTT2 substrate cumene hydroperoxide (CumOOH). Polyphenol metabolites did not affect cell number but significantly upregulated GSTT2 expression and decreased COX-2. The latter was confirmed via Western blot. CumOOH-induced DNA damage was significantly reduced compared to the control. An upregulation of GSTT2 and downregulation of COX-2 could possibly contribute to the chemopreventive potential of polyphenols after degradation in the gut. Working with polyphenol metabolites is an important prerequisite to better understand the in vivo effects of pure polyphenols.

Effects of synbiotic fermentation products on primary chemoprevention in human colon cells

The consumption of synbiotics, a mixture of probiotics and indigestible food constituents such as dietary fiber, has been reported to reduce colon cancer risk. We investigated the effects of fermented wheat aleurone enriched with the probiotics Lactobacillus rhamnosus GG/Bifidobacterium animalis supsp. lactis on the gene expression and functional end points related to cellular defence in HT29 and primary human colon cells. Aleurone was digested and fermented in vitro with/without probiotics. The resulting fermentation supernatants (fs) were analyzed for concentrations of deoxycholic acid and ammonia. The cells were treated with the fs, and effects on gene expression of catalase, GSTP1 and SULT2B1, enzyme activity of catalase and glutathione S-transferase as well as H₂O₂-induced DNA damage were examined. Fermentation of aleurone reduced deoxycholic acid concentration by 84%, while the probiotics enhanced this effect. Ammonia was increased by fs aleurone, whereas a reduction occurred by the addition of L. rhamnosus GG/B. animalis supsp. lactis 12. GSTP1 expression tended to result in an increase by the fs aleurone in both cell types, whereas the probiotics could not additionally increase the effect. Catalase was not modulated by fs aleurone enriched with probiotics. Only in HT29 cells, expression of SULT2B1 was enhanced by fs aleurone. Enzyme activity of catalase and glutathione S-transferase was induced (2-3.6 fold, 72 h) in HT29 cells only. Addition of probiotics had no influence on this effect. In HT29 cells, a reduced H₂O₂-induced DNA damage by the fs aleurone after 48 h, enhanced by the addition of probiotics, was detected. The observed effects could improve detoxification of xenobiotics and therefore may lower colon cancer risk.

Fermented wheat aleurone enriched with probiotic strains LGG and Bb12 modulates markers of tumor progression in human colon cells

Fermentation of dietary fiber by the microflora enhances the levels of effective metabolites, which are potentially protective against colon cancer. The specific addition of probiotics may enhance the efficiency of fermentation of wheat aleurone, a source of dietary fiber. We investigated the effects of aleurone, fermented with fecal slurries with the addition of the probiotics LGG and Bb12 (aleurone(+)), on cell growth, apoptosis, and differentiation, as well as expression of genes related to growth and apoptosis using two different human colon cell lines (HT29: adenocarcinoma cells; LT97: adenoma cells). The efficiency of fermentation of aleurone was only slightly enhanced by the addition of LGG/Bb12, resulting in an increased concentration of butyrate. In LT97 cells, the growth inhibition of aleurone(+) was stronger than in HT29 cells. In HT29 cells, a cell cycle arrest in G(0)/G(1) and the alkaline phosphatase activity, a marker of differentiation, were enhanced by the fs aleurone(+). Treatment with all fermentation supernatants resulted in a significant increase in apoptosis and an upregulation of genes involved in cell growth and apoptosis (p21 and WNT2B). In conclusion, fs aleurone(+) modulated markers of cancer prevention, namely inhibition of cell growth and promotion of apoptosis as well as differentiation.

Butyrate suppresses mRNA increase of osteopontin and cyclooxygenase-2 in human colon tumor tissue

The short chain fatty acid (SCFA) butyrate, a product of fermentation of dietary fiber in the human colon, is found to exert multiple regulatory processes in colon carcinogenesis. The aim of this study was to find out whether butyrate affects the tumor-promoting genes osteopontin (OPN) and cyclooxygenase (COX)-2, their respective proteins and/or their functional activity in matched normal, adenoma and tumor colon tissues obtained from 20 individuals at colon cancer surgery. Quantitative real-time polymerase chain reaction experiments showed increased levels of OPN and COX-2 messenger RNA in tumor tissues when compared with the adjacent normal samples (P < 0.001). The addition of butyrate reduced OPN and COX-2 mRNA expression in all tissue types compared with the related medium controls (tumor: P < 0.05). In tumor samples, a downregulation of up to median 35% (COX-2) and 50% (OPN) was observed, respectively. Thereby, tumors with lower levels of OPN basal expression were more sensitive to inhibition and vice versa for COX-2 in normal tissue. At the protein and enzyme level, which were determined by using western blot and enzyme immunometric assays, the impact of the SCFA was not clearly visible anymore. The active proteins of OPN and COX-2 (determined by prostaglandin E(2)) were found to correlate with their respective mRNA expression only in 50-63% of analyzed donors. For the first time, our data reveal new insights into the chemoprotective potential of butyrate by showing the suppression of OPN and COX-2 mRNA in primary human colon tissue with the strongest effects observed in tumors.

Proapoptotic effects of long-chain vitamin E metabolites in HepG2 cells are mediated by oxidative stress

Although the metabolism of vitamin E has been extensively studied in cell culture, animals, and humans, biochemical analyses of intermediate metabolites are scarce. We here describe the synthesis and proapoptotic properties of long-chain metabolites of α- and δ-tocopherol. Several long-chain vitamin E metabolites, namely 13'-hydroxy- and 13'-carboxychromanols, were synthesized from garcinoic acid, a δ-tocotrienol derivative extracted from the African bitter nut Garcinia kola. Both α- and δ-13'-carboxychromanol induced cell death in HepG2 cells at EC(50) of 13.5 and 6.5 μM, respectively. Apoptosis was quantified by annexin V/7-AAD staining and flow cytometry analysis. By immunoblot analyses, we observed activation of both caspase-3 and caspase-9 as well as PARP-1 cleavage. Parameters of mitochondrial dysfunction including reduced mitochondrial membrane potential and increased intracellular and intramitochondrial reactive oxygen species formation were observed after metabolite treatment. Last, long-chain hydroxychromanols were readily metabolized to the corresponding carboxychromanols in HepG2 cells. Taken together, these results indicate that long-chain metabolites may be responsible for antiproliferative properties of vitamin E vitamers.

Defensin alpha 6 (DEFA 6) overexpression threshold of over 60 fold can distinguish between adenoma and fully blown colon carcinoma in individual patients

Background

It is known that alpha-defensin expression is enhanced in colon cancer. However, the expression of human alpha defensin 6 (DEFA 6) in earlier stages, such as adenoma, has so far not yet been studied in a patient resolved manner.

Methods

By using quantitative Real Time-PCR, the gene expression pattern of DEFA 1-3 and DEFA 6 was analyzed in tissue of different stages of carcinogenesis, derived from colorectal cancer patients. In addition to paired normal and tumor tissue, matched normal near tumor and adenoma tissue samples were examined.

Results

The median gene expression of human defensin alpha 6 (DEFA 6) has been found to be moderately increased (~ 5 fold) in tumor samples derived from individuals with colorectal cancer (CRC) when compared to their normal counterparts. However, when the data were analyzed in a patient-wise manner, a large expression variation among individual patients is found, making the use of DEFA 6 for individual diagnosis of fully blown colon carcinoma difficult. Surprisingly, in adenoma the gene expression analysis revealed a 100 fold increased median expression of DEFA 6 relative to normal colon tissue. 13/18 samples had an individual overexpression of more than 60 fold in adenoma but only 3/17 in carcinoma. In each of the individual patients, at least either the adenoma or the carcinoma showed strong DEFA 6 overexpression.

Conclusions

We suggest that the expression of DEFA 6 preferably can be used as a potential diagnostic marker for adenoma and not as a marker for fully blown carcinoma. This is supported by the fact that DEFA 6 is a downstream target of the Wnt pathway, which is mutational active during the earliest stage of cancer development.

Fish fatty acids alter markers of apoptosis in colorectal adenoma and adenocarcinoma cell lines but fish consumption has no impact on apoptosis-induction ex vivo

Previous studies suggest that the n-3 polyunsaturated fatty acids (PUFAs) eicosapenteinoic acid (EPA) and docosahexaenoic acid (DHA), constituents of fish oil, exert chemopreventive activity in colon cancer. One of the mechanisms involved is the facilitation of apoptosis. While a pro-apoptotic potential of n-3 PUFAs has been suggested, it is still unclear whether additional consumption of fish will also lead to comparable results. The aim of this study was to assess EPA- and DHA-mediated effects on endpoints of apoptosis and to use a novel biomarker-approach to measure modulation of apoptosis by consumption of fish. LT97 human colon adenoma and HT29 human colon adenocarcinoma cells were used to investigate modulation of apoptosis by EPA, DHA or linoleic acid (LA) using a set of endpoints, namely phosphatidylserine staining with Annexin-V (flow cytometry), Bcl-2 expression (Real-time RT-PCR), and Bid, caspase 3, 8 and 9 expression as well as PARP cleavage (Western Blot). Furthermore, faecal water (FW) of volunteers (n = 89) from a human trial intervening with fish was used to investigate changes in apoptosis by flow cytometry. DHA was more effective at inducing apoptosis than EPA. LT97 cells were more prone to DHA and EPA induced apoptosis than HT29 cells. Treatment of LT97 cells with FW from volunteers consuming fish did not result in any changes in apoptosis. Taken together, our results show that adenoma cells are highly susceptible to n-3 PUFA-induced apoptosis. By using a biomarker-approach (FW) to measure apoptosis-induction ex vivo no change in apoptosis after additional fish consumption was detectable.

Impact of apple polyphenols on GSTT2 gene expression, subsequent protection of DNA and modulation of proliferation using LT97 human colon adenoma cells

Apple extract (AE) enhances expression of glutathione S-transferases (e.g., GSTT2) in human colon cells (LT97). Therefore, aim of the present study was to identify functional consequences of GSTT2 induction by AE and to determine the relation of AE effects to isolated compounds. Polyphenol composition of AE was analyzed. LT97 cells were treated with AE or synthetic polyphenol mixture (SPM) under conditions that induced GSTT2, and challenged with GSTT2-2 substrate cumene hydroperoxide (CumOOH) to determine DNA damage using comet assay. Modulation of GSTT2 expression (real-time PCR) was reassessed, and the influence on cell proliferation and pro-oxidative potential of AE and SPM were assessed to understand additional mechanisms. Induction of GSTT2 by AE was accompanied by protection of LT97 cells from CumOOH-induced genotoxicity. Although SPM was unable to reflect AE-specific bioactivity related to GSTT2 modulation and anti-genotoxicity, inhibition of LT97 cell proliferation by SPM was comparable. Storage of AE caused changes in phenolic composition along with loss of activity regarding GSTT2 induction and amplified growth inhibition. At the applied concentrations, no H(2)O(2) formation was detectable with any of the substances. AE can protect against oxidatively induced DNA damage. Nevertheless, chemopreventive effects of AE strongly depend on the specific composition, which is modified by storage.