Sicilian pistachio (Pistacia vera L.) nut inhibits expression and release of inflammatory mediators and reverts the increase of paracellular permeability in IL-1b-exposed human intestinal epithelial cells

Background Dietary approaches to control inflammatory bowel diseases (IBD) may include proanthocyanidin-rich foods. Our previous research showed that a hydrophilic extract from Sicilian pistachio nut (HPE) contains sub- stantial amounts of proanthocyanidins and possesses anti- inflammatory activities. Purpose We studied the effects of HPE and of its poly- meric proanthocyanidin fraction (PPF) in a cell model that simulated some conditions of IBD, consisting of interleukin (IL)-1b-stimulated Caco-2 cells. Methods HPE was prepared by Pistacia vera L. nuts, and PPF was isolated from HPE by adsorbance chromatogra- phy. Proanthocyanidins were quantified as anthocyanidins after acidic hydrolysis. Differentiated Caco-2 cells were pre-incubated with HPE or PPF and then were exposed to IL-1b. Cell viability and parameters associated with nuclear factor-kB (NF-kB) activation were assayed. Adsorption of polymeric proanthocyanidins to the cell membrane was investigated by transepithelial electrical resistance (TEER) measurements. Results HPE decreased prostaglandin (PG)E2 production, IL-6 and IL-8 release, and cyclooxygenase (COX)-2 expression. HPE also inhibited the increase in paracellular permeability and reduced NF-kB activation. Polymeric proanthocyanidins, tested at a concentration comparable with their content in HPE, produced effects comparable HPE. Finally, cell exposure to PPF increases TEER of the epithelial monolayers. Conclusion Our results provide evidence that pistachio nut components inhibit inflammatory response of intestinal epithelial cells in vitro and indicate polymeric proanthocyanidins as the major bioactive nut components. The protection implies inhibition of NF-jB activation and occurs in parallel with the adsorption of polymeric pro- anthocyanidins to cell membrane. Our findings suggest that intake of small amounts of pistachio nut can exert benefi- cial effects to gastrointestinal pathophysiology.