pylori, we examined the bacterial morphologies using a differential interference microscope (data not shown). When H. pylori (107 CFU mL−1) was incubated for 24 h in a simple-PPLO broth (3 mL) in the presence or absence of the steroids, the control cell suspension of H. pylori incubated without the steroids harbored the organisms in both mixed rod and coccoid forms. In contrast, the cell suspension of the H. pylori incubated with progesterone (100 μM) or 17αPSCE (100 μM) harbored hardly any organisms,

although objects such Daporinad in vitro as cellular debris were observed. Helicobacter pylori is known to aggressively absorb any FC present in a medium, although the FC-binding site on the H. pylori cell surface has yet to be identified. In light of this, we hypothesized that progesterone acts on FC-binding sites on the H. pylori cell surface when inducing cell lysis. To verify this hypothesis, we carried out the following

experiments using FC beads. After a 24-h preculture of H. pylori (106.3 CFU mL−1) with progesterone (5 or 10 μM) in a simple-PPLO broth (30 mL), the H. pylori cells (108.3 CFU mL−1) recovered were incubated for 4 h in a simple-PPLO broth (30 mL) containing FC beads (FC concentration: 250 μM). Thereafter, the amount of FC absorbed into the H. pylori cells was quantified. The amount of FC per CFU obviously tended to reduce by preculturing H. pylori with progesterone (Fig. 4a). These results suggest that progesterone strongly binds to the H. pylori cell surface Trametinib cost and thereby obstructs the FC absorption of H. pylori by inhibiting the cell surface binding of FC. Incidentally, progesterone had no influence on the growth of H. pylori at the 5 and 10 μM concentrations: the CFUs of the H. pylori cultured with progesterone were similar to the control CFU of the H. pylori cultured without progesterone (data not shown). Helicobacter pylori glucosylates the absorbed FC and synthesizes cholesteryl glucosides (CGs). With this in mind, we decided to examine the influence of progesterone on the glucosylation

of FC. After the 24-h preculture of H. pylori second (106.3 CFU mL−1) in the presence or absence of progesterone (10 μM) in a simple-PPLO broth (30 mL), the H. pylori (108.3 CFU mL−1) recovered was incubated for 4 h with FC beads (FC concentration: 250 μM) in a simple-PPLO broth (30 mL), and the membrane lipids were purified. The TLC analysis detected the CGs (CGL, CAG, and CPG) in the membrane lipids of H. pylori precultured with progesterone (Fig. 4b), although no FC was found to have accumulated within the lipids. Meanwhile, the CG levels detected in the membrane lipids of H. pylori precultured with progesterone were similar to the CG levels detected in the membrane lipids of H. pylori precultured without progesterone. These results indicate that progesterone exerts no inhibitory effects on the enzymes involved in the CG synthesis. Next, we examined whether FC conversely inhibits the anti-H. pylori action of progesterone. When the H.