Procyanidin B2 rich cocoa extracts inhibit inflammation in Caco-2 cell model of in vitro celiac disease by down-regulating interferon-gamma- or gliadin peptide 31-43-induced transglutaminase-2 and interleukin-15

Abstract The objective of this research was to investigate the efficacy of procyanidin B2 rich cocoa extracts on interferon-gamma (IFN-γ) or gliadin peptide p31-43-induced transglutaminase-2 and interleukin-15 (IL-15) in Caco-2 cell model of in vitro celiac disease. Cysteamine was used as a positive control inhibitor of TG2. Procyanidin B2-rich extract reduced IFN-γ- and gliadin p31-43-induced TG2 activity by 77% and 45%, respectively. Cocoa extract containing 4.9–289 µg/mL of procyanidin B2 dose-dependently reduced IFN-γ-induced IL-15 secretion to the level of IL-15 in control cells. Similarly, cocoa extract containing 4.9–289 µg/mL of procyanidin B2 dose-dependently reduced gliadin p31-43-induced IL-15 to the level in control cells. Procyanidin B2-rich cocoa extracts reduced the activities of other inflammatory biomarkers including COX-2, IL-1β, IL-6, and IL-8 in both IFN-γ and p31-43-treated Caco-2 cells. Caffeine or theobromine, at the concentration found in the cocoa extracts, did not contribute to the activity of procyanidin B2 against TG2 or IL-15.