Bertrand Caporiccio

Both direct and indirect effects account for the pro-inflammatory activity of enteropathogenic mycotoxins on the human intestinal epithelium : Stimulation of interleukin-8 secretion, potentiation of interleukin-1β effect and increase in the transepithelial passage of commensal bacteria

Mycotoxins are fungal secondary metabolites responsible of food-mediated intoxication in animals and humans. Deoxynivalenol, ochratoxin A and patulin are the best known enteropathogenic mycotoxins able to alter intestinal functions resulting in malnutrition, diarrhea, vomiting and intestinal inflammation in vivo. Although their effects on intestinal barrier and transport activities have been extensively characterized, the mechanisms responsible for their pro-inflammatory effect are still poorly understood. Here we investigated if mycotoxin-induced intestinal inflammation results from a direct and/or indirect pro-inflammatory activity of these mycotoxins on human intestinal epithelial cells, using differentiated Caco-2 cells as model and interleukin 8 (IL-8) as an indicator of intestinal inflammation. Deoxynivalenol was the only mycotoxin able to directly increase IL-8 secretion (10- to 15-fold increase). We also investigated if these mycotoxins could indirectly stimulate IL-8 secretion through: (i) a modulation of the action of pro-inflammatory molecules such as the interleukin-1beta (IL-1beta), and/or (ii) an increase in the transepithelial passage of non-invasive commensal Escherichia coli. We found that deoxynivalenol, ochratoxin A and patulin all potentiated the effect of IL-1beta on IL-8 secretion (ranging from 35% to 138% increase) and increased the transepithelial passage of commensal bacteria (ranging from 12- to 1544-fold increase). In addition to potentially exacerbate established intestinal inflammation, these mycotoxins may thus participate in the induction of sepsis and intestinal inflammation in vivo. Taken together, our results suggest that the pro-inflammatory activity of enteropathogenic mycotoxins is mediated by both direct and indirect effects.

Hydrogen Peroxide Generation in Caco-2 Cell Culture Medium by Addition of Phenolic Compounds: Effect of Ascorbic Acid

Phenolic compounds have recently attracted special attention due to their beneficial health effects; their intestinal absorption and bioavailability need, therefore, to be investigated and Caco-2 cell culture model appeared as a promising tool. We have shown herein that the addition of a grape seed extract (GSE) to Dulbeccos modified Eagles medium (DMEM) used for Caco-2 cell culture leads to a substantial loss of catechin, epicatechin and B2 and B3 dimers from GSE in the medium after 24 h and to a production of hydrogen peroxide (H2O2). When 1420 microM ascorbic acid is added to the DMEM, such H2O2 production was prevented. This hydrogen peroxide generation substantially involves inorganic salts from the DMEM. We recommend that ascorbic acid be added to circumvent such a risk.

Superoxide production: A procalcifying cell signalling event in osteoblastic differentiation of vascular smooth muscle cells exposed to calcification media

Recent studies showed that hydrogen peroxide (H2O2) enhanced bone markers expression in vascular smooth muscle cells (VSMCs) implicated in osteoblastic differentiation. This study aimed at investigating the role of NAD(P)H oxidase in vascular calcification processes. A7r5 rat VSMCs were incubated with β-glycerophosphate (10 mm) or uremic serum to induce a diffuse mineralization. H2O2 production by VSMCs was determinated by chemiluminescence. NAD(P)H oxidase sub-unit (p22phox), Cbfa-1, ERK phosphorylation and bone alkaline phosphatase (ALP) expressions were measured by Western blotting. VSMCs exhibited higher production of H2O2 and early expression of p22phox with β-glycerophosphate or uremic serum within 24 h of treatment. β-glycerophosphate-induced oxidative stress was associated with Cbfa-1 expression followed by ALP expression and activity, meanwhile the VSMCs expressing ALP diffusely calcified their extracellular matrix. Interestingly, diphenyleneiodonium partly prevented the osteoblastic differentiation. Results from this model strongly suggest a major implication of vascular NAD(P)H oxidase in vascular calcification supported by VSMCs osteoblastic differentiation.

Grapefruit juices impair the bioaccessibility of β-carotene from orange-fleshed sweet potato but not its intestinal uptake by Caco-2 cells.

Among various factors influencing β-carotene (Bc) bioavailability, information on interactions between carotenoids or other micronutrients such as flavonoids during a meal that contains different plant-derived foods is quite limited. Because orange-fleshed sweet potato (OFSP) is an important Bc-rich staple food, a source of vitamin A in developing countries, this study focused on the effect of citrus fruit juice carotenoids and flavonoids on Bc bioaccessibility from OFSP. In vitro digestion coupled with the Caco-2 cell culture model was used to evaluate the bioaccessibility and cellular uptake of Bc from OFSP in the presence of pink grapefruit (pGF) or white grapefruit (wGF) juices. The addition of grapefruit juices significantly decreased the bioaccessibility, by up to 30%, but not the cellular uptake of Bc from boiled OFSP. Lycopene, but more probably naringin, present in grapefruit juices was suspected to be responsible for the inhibitory effect of the citrus juices on Bc bioaccessibility. This inhibition was apparently due in part to competition for incorporation between Bc and naringin into mixed micelles during in vitro digestion. In contrast, Bc uptake from dietary micelles was not impaired by naringin.

Nutritional value and intestinal effects of dipeptides and tripeptides. Comparison with their issuing bovine plasma protein in rats.

A hydrolysate containing 75% di- and tripeptides (DTP) was prepared from bovine plasma proteins (BP) and the original protein and hydrolysate were compared for nutritional value. Food intake, protein efficiency ratio (PER), nitrogen balance and digestibility and plasma amino acid concentrations were measured in young rats receiving the diets over 17 days. Moreover, intestinal adaptation was evaluated in duodenum, jejunum and ileum, with the aid of light microscopy and enzyme analyses; tritiated thymidine incorporation was also measured. In DTP- and BP-fed rats, food intake, body weight gain, nitrogen balance and digestibility as well as PER were similar. Plasma amino acid concentration analyses showed an increased concentration of threonine and valine in the BP-fed group. Measurements of mucosal enzyme activities suggest adaptation to the diets especially in the ileum as indicated by increasing aminopeptidase N and dipeptidyl peptidase IV specific activities in the BP-fed group. This group also displayed substantial 3H-thymidine incorporation. It is concluded that the hydrolysate containing di- and tripeptides is efficiently utilized in healthy growing rats, though the efficacy is not higher than with the BP diet except for the difference in 3H-thymidine incorporation.

Staphylococcal enterotoxin A: Partial unfolding caused by high pressure or denaturing agents enhances superantigenicity

The effect of transient exposure of Staphylococcus aureus enterotoxin A (SEA) to high pressure and/or denaturing agents was examined by assessing the toxin superantigenicity and immunoreactivity, and by monitoring pressure-induced changes in fluorescence emission spectra. Pressurization of SEA at 600 MPa and 45 degrees C in Tris-HCl buffer (20 mM, pH 7.4) resulted in a marked increase in both T-cell proliferation (superantigenicity) and immunoreactivity. In opposite, pressurization at 20 degrees C did not change significantly SEA superantigenicity and immunoreactivity, indicating some toxin baro-resistance. Exposure of SEA to 8 M urea at atmospheric pressure or at 600 MPa and 20 degrees C, also led to a marked increase of superantigenicity (but not of immunoreactivity). In contrast, exposure of SEA to sodium-dodecylsulfate (30 mM) led to an increase of immunoreactivity with some effect on superantigenicity after pressurization at 45 degrees C only. High pressure up to 600 MPa induced spectral changes which at 20 degrees C were fully reversible upon decompression. At 45 degrees C, however, a sharp break of the centre of spectral mass mainly due to tryptophan residues was observed at 300 MPa, and irreversible spectral changes mainly related to tyrosine residues subsisted after pressure release, indicating a marked protein conformational transition. Urea 8 M further increased SEA structural changes at 600 MPa and 20 degrees C. These results indicate that SEA, under a combination of high pressure and mild temperature, as well as in the presence of urea, partly unfolds to a structure of strongly increased T-cell proliferative ability.

Magnesium bioavailability from magnesium-fortified spirulina in cultured human intestinal Caco-2 cells

Abstract The role of magnesium (Mg) for health promotion and disease prevention is generally accepted world wide. The aim of this study was to examine magnesium availability from Mg-fortified spirulina. We have used an in vitro digestion/Caco-2 cell culture system to measure magnesium spirulina availability. Magnesium concentration measurements were performed by atomic absorption spectrometry in digests containing the same amount of magnesium and at the basal side of Caco-2 cells exposed to these digests. Comparison was made with crude spirulina, Banania, Kellogs all bran and Magnogene (magnesium chloride) as a reference. Our results show that Mg-fortification of spirulina does not improve Mg availability and that crude spirulina represents an adequate source of Mg as efficient as All bran and Banania.

Glutathione-related enzymic activities in rats receiving high cholesterol or standard diets supplemented with two forms of selenium

Selenium deficiency was produced in rats fed a high cholesterol diet for 57 days (Group 1). It was characterized by an increase in malondialdehyde (MDA) an end product of lipid peroxidation and by the dramatic collapse of selenium-dependent glutathione peroxidase activity (GSHPx) in plasma, erythrocytes and in homogenate supernatant fraction of liver, kidney and heart compared with rats fed a standard diet containing sodium selenite (Group 3). A compensatory rise in the activity of liver glutathione S-transferase (GST) activity and also in glutathione reductase (GSSGR) activity was accompanied by an increase in NADPH-generating enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Adequate dietary selenium supplementation by Se-rich Spirulina corrected all the selenium deficiency effects (Group 2), then, GSHPx and NADPH-consuming enzymes activities were of the same magnitude as those exhibited by rats fed a standard diet containing adequate selenium in the form of sodium selenite. Based on this study, it is concluded that Se-enriched Spirulina behave as an excellent selenium carrier.

Comparative study of nutritional qualities of defatted cottonseed and soybean meals

Abstract Experiments were conducted on rats to investigate the quality of glandless cottonseed flour compared to soybean flour prepared in the same way. In order to inactivate toxic residual factors, an additional heat treatment (steaming at 112°C for 15 min) was applied on both flour samples. Cottonseed flour contained 39% protein and about 1·7% ether extract. Dietary fibres ranged from 19·2 to 20·6%. Antinutritional compounds were absent, except phytic acid (4·4%) which was still present after steaming. Nutritional parameters, used as criteria in this work, i.e. protein efficiency ratio (PER), biological value (BV) and net protein utilization (NPU), demonstrated a good intrinsic nutritional quality for cottonseed protein (unless it had a low lysine content), when compared with casein and soybean. Moreover, enzymic and light microscopic studies, which were performed on the digestive tract of animals, showed no noxious effect.

Nutritional rehabilitation of malnourished rats by di- and tripeptides: nitrogen metabolism and intestinal response☆

Abstract An enzymic hydrolysate (DTP) rich in di- and tripeptides (75%) was prepared from bovine plasma proteins (BP). Protein-calorie malnourished rats were subjected to refeeding tests with diets having the same nitrogen and caloric contents and differing only in the molecular form of the nitrogen supply: BP, DTP, or an equivalent amino acid mixture (AAM). Growth, food intake, and food efficiency were measured after an eight-day period of rehabilitation; nitrogen balance and digestibility were also determined. Animals refed the DTP diet exhibited the best nutritional parameters, AAM failed to support any rehabilitation. In the intestine measurements of mucosal enzyme activities and morphometric studies strongly suggested the beneficial effect of DTP as indicated by increased both amino-peptidase N level and villus height. The results showed an adaptive response of rats to the molecular form of the nitrogen supply and demonstrated the superior efficacy of DTP for a rapid recovery from protein-calorie malnutrition.