The role of p38 MAPK in the induction of intestinal inflammation by dietary oxysterols: modulation by wine phenolics.

Dietary oxysterols are cholesterol auto-oxidation products widely present in cholesterol-rich foods. They are thought to affect the intestinal barrier function, playing a role in gut inflammation. This study has characterized specific cell signals that are up-regulated in differentiated CaCo-2 colonic epithelial cells by a mixture of oxysterols representative of a hyper-cholesterolemic diet. p38 MAPK activation plays a major role, while other signal branches, i.e. the JNK and ERK pathways, make minor contributions to the intestinal inflammation induced by dietary oxysterols. p38 transduction might be the missing link connecting the known NADPH oxidase activation, and the induction of NF-κB-dependent inflammatory events related to oxysterols' action in the intestine. A NOX1/p38 MAPK/NF-κB signaling axis was demonstrated by the quenched inflammation observed on blocking individual branches of this signal with specific chemical inhibitors. Furthermore, all these signaling sites were prevented when CaCo-2 cells were pre-incubated with phenolic compounds extracted from selected wines made of typical Sardinian grape varieties: red Cannonau and white Vermentino. Notably, Cannonau was more effective than Vermentino. The effect of Sardinian wine extracts on intestinal inflammation induced by dietary oxysterols might mainly be due to their phenolic content, more abundant in Cannonau than in Vermentino. Furthermore, among different phenolic components of both wines, epicatechin and caffeic acid exerted the strongest effects. These findings show a major role of the NOX1/p38 MAPK/NF-κB signaling axis in the activation of oxysterol-dependent intestinal inflammation, and confirm the concept that phenolics act as modulators at different sites of pro-oxidant and pro-inflammatory cell signals.

Phenolic compounds present in Sardinian wine extracts protect against the production of inflammatory cytokines induced by oxysterols in CaCo-2 human enterocyte-like cells.

Cholesterol auto-oxidation products, namely oxysterols, are widely present in cholesterol-rich foods. They are thought to potentially interfere with homeostasis of the human digestive tract, playing a role in intestinal mucosal damage. This report concerns the marked up-regulation in differentiated CaCo-2 colonic epithelial cells of two key inflammatory interleukins, IL-6 and IL-8, caused by a mixture of oxysterols representative of a high cholesterol diet. This strong pro-inflammatory effect appeared to be dependent on the net imbalance of red-ox equilibrium with the production of excessive levels of reactive oxygen species through the colonic NADPH-oxidase NOX1 activation. Induction of NOX1 was markedly while not fully inhibited by CaCo-2 cell pre-incubation with phenolic extracts obtained from well-selected wines from typical grape varieties grown in Sardinia. Oxysterol-dependent NOX1 activation, as well as interleukin synthesis, were completely prevented by Cannonau red wine extract that contains an abundant phenolic fraction, in particular phenolic acids and flavonoids. Conversely, cell pre-treatment with Vermentino white wine extract with smaller phenolic fraction showed only a partial NOX1 down-regulation and was ineffective in interleukin synthesis induced by dietary oxysterols. It is thus likely that the effects of Sardinian wine extracts against intestinal inflammation induced by dietary oxysterols are mainly due to their high phenolic content: low doses of phenolics would be responsible only for direct scavenging oxysterol-dependent ROS production. Besides this direct activity, an excess of phenolic compounds detectable in red wine, may exert an additional indirect action by blocking oxysterol-related NOX1 induction, thus totally preventing the pro-oxidant and pro-inflammatory events triggered by dietary oxysterols.

Wine extracts from Sardinian grape varieties attenuate membrane oxidative damage in Caco-2 cell monolayers.

One of the most important sites of polyphenol action seems to be in the gastrointestinal system before absorption. We investigated the ability of three wine phenolic extracts, obtained from grape varieties grown in Sardinia, Cannonau (red), Vermentino and Malvasia (white), to exert an antioxidant action against tert-butyl hydroperoxide (TBH)-induced oxidative damage to Caco-2 cell monolayers as a model system of the human intestine. TBH treatment caused the disruption of epithelial integrity, measured as transepithelial electrical resistance, and markers of the peroxidation process of membrane lipids, MDA, fatty acid hydroperoxides and 7-ketocholesterol. All wine extracts were able to counteract the oxidising action of TBH and, in spite of the differences in phenolic composition, exerted a comparable activity. Our findings point out a direct antioxidant action of the wine extracts on enterocytes exposed to oxidising species and further support the opinion that total phenolic content is not essential for antioxidant activity.

Hydroxytyrosol glucuronides protect renal tubular epithelial cells against H(2)O(2) induced oxidative damage.

Hydroxytyrosol (2-(3',4'-dihydroxyphenyl)ethanol; HT), the most active ortho-diphenolic compound, present either in free or esterified form in extravirgin olive oil, is extensively metabolized in vivo mainly to O-methylated, O-sulfated and glucuronide metabolites. We investigated the capacity of three glucuronide metabolites of HT, 3'-O-ß-d-glucuronide and 4'-O-ß-d-glucuronide derivatives and 2-(3',4'-dihydroxyphenyl)ethanol-1-O-ß-d-glucuronide, in comparison with the parent compound, to inhibit H(2)O(2) induced oxidative damage and cell death in LLC-PK1 cells, a porcine kidney epithelial cell line. H(2)O(2) treatment exerted a toxic effect inducing cell death, interacting selectively within the pro-death extracellular-signal relate kinase (ERK 1/2) and the pro-survival Akt/PKB signaling pathways. It also produced direct oxidative damage initiating the membrane lipid peroxidation process. None of the tested glucuronides exhibited any protection against the loss in renal cell viability. They also failed to prevent the changes in the phosphorylation states of ERK and Akt, probably reflecting their inability to enter the cells, while HT was highly effective. Notably, pretreatment with glucuronides exerted a protective effect at the highest concentration tested against membrane oxidative damage, comparable to that of HT: the formation of malondialdehyde, fatty acid hydroperoxides and 7-ketocholesterol was significantly inhibited.

Effect of aqueous and lipophilic mullet (Mugil cephalus) Bottarga extracts on the growth and lipid profile of intestinal Caco-2 cells.

The importance of n-3 polyunsaturated fatty acid (n-3 PUFA) intake has long been recognized in human nutrition. Although health benefits, n-3 PUFA are subject to rapid and/or extensive oxidation during processing and storage, resulting in potential alteration in nutritional composition and quality of food. Bottarga, a salted and semi-dried mullet ( Mugil cephalus ) ovary product, is proposed as an important source of n-3 PUFA, having high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In this work, we investigated the extent of lipid oxidation of grated bottarga samples during 7 months of storage at -20 °C and room temperature under light exposure. Cell viability, lipid composition, and lipid peroxidation were measured in intestinal differentiated Caco-2 cell monolayers after 6-48 h of incubation with lipid and hydrophilic extracts obtained from bottarga samples at different storage conditions. The storage of bottarga did not affect the n-3 PUFA level, but differences were observed in hydroperoxide levels in samples from different storage conditions. All tested bottarga extracts did not show a toxic effect on cell viability of differentiated Caco-2 cells. Epithelial cells incubated with bottarga oil had significant changes in fatty acid composition but not in cholesterol levels with an accumulation of EPA, DHA, and 22:5. Cell hydroperoxides were higher in treated cells, in relation to the oxidative status of bottarga oil. Moreover, the bottarga lipid extract showed an in vitro inhibitory effect on the growth of a colon cancer cell line (undifferentiated Caco-2 cells).