FIG. 6.

The level of cellular cholesterol influenced the CagA-induced responses of infected AGS cells. (A) The hummingbird phenotype of infected AGS cells induced by CagA was blocked by cholesterol depletion. AGS cells were pretreated with or without MβCD, which was followed by infection with wild-type H. pylori or the ΔCagA mutant, and then viewed by phase-contrast microscopy. MβCD−, without MβCD treatment; MβCD+, with 5.0 mM MβCD treatment; Cho recover+, MβCD-treated cells that were replenished with 400 μg/ml cholesterol for 1 h; WT Hp+, cells infected by wild-type H. pylori; Hp−, noninfected cells; ΔCagA+, cells infected by H. pylori ΔCagA. In each experiment, AGS cells were added to mid-logarithmic-phase bacteria at a synchronized MOI of 100 and incubated at 37°C for 6 h. Scale bar, 20 μm. (B) The proportion of elongated cells was determined from the results shown in panel A. Cho, cholesterol; Hp, H. pylori; WT, wild type. (C) Induction of IL-8 involves CagA and host cellular cholesterol. AGS cells were treated with lovastatin (0, 10, 20, and 50 μM) and infected with wild-type H. pylori (filled bars) or the ΔCagA mutant (open bars). After 6 h of infection, the level of IL-8 in the culture supernatant was determined by a standard ELISA method. The data are the means and standard deviations of at least three independent experiments. Statistical significance was evaluated using Student's t test (one asterisk, P < 0.05; two asterisks, P < 0.01; n.s., not significant).