Progesterone and free-cholesterol (FC) obstructed each other’s effects against the H. pylori cell. Taken in sum, these results suggest that progesterone and FC may bind to the identical region on the H. pylori cell surface. We expect these findings to contribute to the development of a novel anti-H.

pylori steroidal agent. Helicobacter pylori colonizes the human gastric epithelium and causes chronic gastritis and peptic ulcers (Marshall & Warren, 1983; Wyatt & Dixon, 1988; Graham, 1991). Over longer periods, it also contributes to the development of gastric cancer and gastric mucosa-associated lymphoid tissue lymphoma (Wotherspoon et al., 1991; Forman, the Eurogast Study Group, 1993). This bacterium possesses the unique biological feature GPCR & G Protein inhibitor of steroid assimilation. A recent study by our group demonstrated that H. pylori selectively absorbs 3β-OH and 3-OH steroids,

glucosylates only the former, and uses both steroids, with or without glucosylation, as membrane lipid components (Hosoda et al., 2009). A number of investigations, including our own, have revealed the physiological significance of steroid assimilation in H. pylori. Wunder et al. (2006) demonstrated that H. pylori evades the host immune KU 57788 systems by glucosylating the absorbed free-cholesterol (FC). Our own study found that H. pylori retains the steroid (FC or estrone) in order to reinforce the membrane lipid barrier and thereby resists the bacteriolytic action of the phosphatidylcholines (Shimomura et al., 2009). This confirms that certain steroids are beneficial to the survival of H. pylori. Conversely, other steroids have been found to impair the viability of H. pylori. After examining Astemizole the anabolic use of 10 steroid hormones in H. pylori, our

group proposed that three hormones, namely, estradiol, androstenedione, and progesterone, may have the potential to inhibit the growth of H. pylori (Hosoda et al., 2009). These findings led to our interest in the development of antibacterial steroidal agents for H. pylori. To explore the potential for this, we must first precisely clarify the inhibitory effects of those steroids on the growth of H. pylori. In this study, we do so by analyzing the anti-H. pylori actions of the steroid hormones. Four strains of H. pylori were investigated: NCTC 11638, ATCC 43504, A-13, and A-19. The A-13 and A-19 strains were clinical isolates from a patient with a gastric ulcer and a patient with a duodenal ulcer, respectively. The cultures were all grown in an atmosphere of 5% O2, 10% CO2, and 85% N2 at 37 °C (Concept Plus: Ruskinn Technology, Leeds, UK).