Vitis vinifera L.: anti-inflammatory activity on the gastrointestinal tract

The gastrointestinal tract represents an important barrier between the human host and microbial populations. One potential consequence of this interaction is the development of mucosal inflammation, which can lead to gastritis and ulcer in the stomach, and inflammatory bowel diseases (IBDs, i.e. ulcerative colitis and Crohn’s disease) in the gut. Helicobacter pylori is the bacterium mainly involved in the pathogenesis of gastric diseases. In gastric inflammation, macrophages produce pro- inflammatory cytokines, including TNFα and IL-1β, which determine the activation of NF-kB. It has been extensively reported that NF-kB plays a crucial role in the pathogenesis of gastritis, ulcer and IBDs. This nuclear factor mediates the transcription and secretion of different pro- inflammatory mediators including IL-8, a potent chemokine leading to the activation of macrophages and neutrophils, and contributing to the maintenance of the inflammatory status. It has been previously demonstrated that different extracts from grape juice, skin and seeds show anti- inflammatory effects. The water extract of Vitis vinifera L. leaves is a component of various food supplements; however, there are no studies in the literature on the anti-inflammatory activity in the gastrointestinal tract. The aim of this study was to evaluate in vitro the effect of the water extract from Vitis vinifera L. against gastrointestinal inflammation. The extract was obtained from dried leaves of Vitis vinifera L., var. Teinturiers and characterized by pH differential method and HPLC- DAD analysis; the extract was assayed on human gastric epithelial cells (AGS) and colonocytes (Caco-2) stimulated with TNFα and IL-1β (both at 10 ng/mL). NF-kB driven transcription was evaluated by transient transfection assay with a plasmid containing the luciferase gene under the control of three NF-kB responsive elements. NF-kB nuclear translocation and IL-8 secretion were performed by an ELISA assay. Quantitative analysis showed that kaempferol-3-O-glucoside was the most abundant flavonoid, and cyanidin-3-O-glucoside the main anthocyanoside. In AGS cells, the extract inhibited NF-kB driven transcription in concentration-dependent way, after stimulation with both TNFα and IL-1β, with statistically significant inhibition starting from 5 μg/mL and 25 μg/mL, respectively. When TNF-α was used as stimulus, the extract exhibited 50% of inhibition at 25 μg/mL, while the effect on IL-1β-induced transcription was significant at 200 μg/mL (-40%). The extract inhibited also the NF-kB nuclear translocation in a concentration-dependent manner. Similarly to what was observed in AGS cells, inhibitory effect of the extract was dependent on the pro-inflammatory stimulus used in Caco-2 cells as well; water extract inhibited in a concentration- dependent manner both NF-kB driven transcription and nuclear translocation induced by TNFα, with a maximum effect at 50 μg/mL whereas the effect on IL-1β-induced NF-kB driven transcription was lower. Although TNFα was not able to induce IL-8 release in Caco-2 cells, the extract (50 μg/mL) significantly inhibited IL-1β-induced IL-8 release. Results obtained in this study provide some experimental evidence on the anti-inflammatory activity of Vitis vinifera L. water extract in the gastrointestinal tract. If these data will be confirmed by in vivo studies, the use of Vitis vinifera L. extracts might be useful against gastrointestinal inflammatory diseases.