Inhibitory effect of ponciretin on Helicobacter pylori VacA toxin-induced vacuolation in HeLa cells

The inhibitory effects of flavanone derivatives on Helicobacter pylori (HP) growth, infection and VacA toxin-induced vacuolation were investigated. Among flavanones tested, ponciretin potently inhibited the growth of HP with a MIC value of 0.01 mg/ml and VacA toxin-induced vacuolation in HeLa cells with IC50 value of 0.078 mM. However, other flavanones inhibited neither HP growth nor VacA toxin-induced vacuolation. All flavanones tested did not inhibit HP infection to KATO III cells. Ponciretin also inhibited activation of procaspase-3 to caspase-3 in HeLa cell induced by HP VacA toxin, but did not affect Bax and Bcl-2 protein levels. These findings indicate that ponciretin inhibits growth as well as vacuolation by HP VacA toxin, which induces cell death via proteolytic activation of a cascade of caspases.