The gastric proton pump inhibitor lansoprazole, its active analog AG-2000, and omeprazole dose dependently inhibited urease activity extracted with distilled water from Helicobacterpylori cells; the 50%1 inhibitory concentrations were between 3.6 and 9.5 ,M, which were more potent than those of urease inhibitors, such as acetohydroxamic acid, hydroxyurea, and thiourea. These compounds also inhibited urease activity in intact cells of H. pylori and Helicobacter mustelae but did not inhibit ureases from other bacteria, such as Proteus vulgaris, Proteus mirabilis, and Providencia rettgeri. The mechanism of urease inhibition was considered to be blockage of the SH groups of H. pylori urease, since SH residues in the enzyme decreased after preincubation with lansoprazole and glutathione or dithiothreitol completely abolished the inhibitory action. The SH-blocking reagents A -ethylmaleinide and idoacetamide were also examined for their inhibition of the urease activity; their 5W0 inhibitory tontentrations were 100-to 1,000-fold higher than those of lansoprazole. These results suggest that lansoprazole and omeprazole can potently and selectively inhibit H. pylori urease and that inhibition may be related to earlier findings indicating that these compounds have selective activity against HP growth.

Serum from Mycobacterium bovis BCG-infected mice that had been challenged with lipopolysaccharide (LPS) exhibited a marked ability to induce gamma interferon (IFN-y) in cultures of spleen cells of normal mice in the presence of interleukin-2 (IL-2). The inducing activity became detectable in the circulatory system about 90 min after LPS challenge, disappeared at around 5 h, and was observable upon 640x dilution of the serum. Addition of monoclonal anti-IL-2 receptor antibody to the culture inhibited the induction by the serum. The activity induced high levels of IFN-y even in nylon wool-nonadherent cells, while concanavalin A failed to do so. Serum from uninfected mice challenged with LPS contained no such activity. The molecular weight of the active substance, estimated by gel filtration, was about 70,000. There were pronounced differences among mouse strains in the activities of the sera prepared, which paralleled the amounts of IFN-y produced in vivo. However, the levels of IFN-y produced in whole spleen cells and in nylon wool-nonadherent cells from mice of various strains were the same when stimulated with competent serum. These results indicate the existence of an unidentified factor that induces IFN-y in cooperation with IL-2 in macrophage-depleted splenocytes. They also suggest that IFN-,y production in vivo is not genetically controlled at the lymphocyte level but, rather, at the level of synthesis of the unknown factor.

Administration of monoclonal anti-CD3 antibody to mice treated with Propionibacterium acnes induced secretion of a high level of gamma interferon (IFN-␥) into the circulation system, while it induced no significant release in untreated mice. In order to analyze this high-level induction of IFN-␥ in these bacterium-treated mice, we investigated the factors that might be involved. An activity that induces IFN-␥ in T cells was observed in the liver extracts of mice treated with P. acnes and subsequently challenged with lipopolysaccharide. Here, we purified an IFN-␥-inducing factor from the liver extract to homogeneity and characterized it. Its molecular mass was 18 to 19 kDa, and its pI was 4.9. The amino acid sequence of the NH 2-terminal portion was determined and shown to have no similarities to any protein in the EMBL, GenBank, and PIR data bases. The same molecule was also demonstrated in the serum factor that was previously reported to have an IFN-␥inducing activity and to have an apparent molecular mass of 75 kDa. Moreover, the activity of this serum factor was recovered in the fraction containing the 18-to 19-kDa protein under reducing conditions and was shown to have the same NH 2-terminal amino acid sequence as that of the factor from the liver extract. In addition to the ability to induce IFN-␥, this protein augmented T-cell proliferation and NK activity in the spleen cells. Thus, several of its biological activities were apparently similar to those of interleukin-12. These results indicated that this novel protein, which exhibited marked costimulatory activity on IFN-␥ production in vitro, was elevated in vivo in response to P. acnes treatment. This factor, probably released from the producing cells by lipopolysaccharide stimuli, may be involved in the high-level induction of IFN-␥ in the P. acnes-treated mice. Recently CD4 ϩ T (Th) cells were divided into distinct subsets according to the profiles of cytokine production (15, 22, 23, 25). This will help our understanding of the regulatory mechanism of immune responses caused by infections with a variety of pathogens. Accessory cells or cytokines produced in response to the initial contact with antigens were shown to exhibit important functions in the development of these cells, depending on the antigenic characteristics. Cells of the Th2 subset are thought to require interleukin-1 (IL-1) or IL-4 for their development (6, 9, 11, 12, 24), and it is shown that IL-12 induces the differentiation of Th1 cells from uncommitted T cells (7, 13, 21). Gamma interferon (IFN-␥), which is produced by activated CD4 ϩ T (Th1), CD8 ϩ T, or NK cells, has been demonstrated to play important roles in cell-mediated immunity. Each of these producer cells may be regulated in the same or different manners, when stimulated. IL-2 was shown to induce IFN-␥ production in NK cells (3, 8), and IL-12 was demonstrated to be involved in IFN-␥ induction in CD4 ϩ T cells or NK cells (7, 13, 21). However, the detailed mechanisms underlying IFN-␥ production as well as the mechanism of devel...

During studies of the bactericidal action of nitric oxide (NO), we found that it reversibly inhibited the respiration of Escherichia coli and irreversibly inhibited the respiration of Helicobacter pylori. Peroxynitrite, a reaction product of NO and superoxide, irreversibly inhibited the respiration of both H. pylori and E. coli. H. pylori, but not E. coli, generated substantial amounts of superoxide radicals. These results suggest that NO directly inhibits the respiration of E. coli whereas it rapidly reacts with endogenously generated superoxide radicals in H. pylori. The resulting peroxynitrite inactivates the respiration of H. pylori. Nitric oxide (NO)1 is a multifunctional gaseous free radical produced by NO synthase in various types of cells, such as endothelial cells, neurons, neutrophils, and macrophages (1). Nitric oxide is also generated from nitrite in saliva and from food by microorganisms in the oral cavity as well as by nonenzymatic mechanisms under acidic conditions, such as in gastric juice (12). Because NO synthase is also present in gastric mucosa (13,14), physiological concentrations of NO in gastric juice are fairly high.We have shown that the biological activity of NO is augmented significantly by physiologically low levels of oxygen tension (2-5). Although NO plays important roles in defense mechanisms against enteric bacteria (6, 7), few studies have explored the mechanism of its bactericidal action at physiological levels of oxygen tension.Helicobacter pylori is a Gram-negative and microaerophilic bacterium that resides in the mucus layer overlying the gastric epithelium of the human stomach. This organism is thought to play essential roles in the pathogenesis of gastric inflammation, ulceration, and carcinogenesis (8 -11). Although H. pylori is exposed to fairly high concentrations of NO in gastric juice, which has low oxygen tension, the effect of NO on the metabolism of H. pylori remains to be defined. We therefore studied the effects of NO on the respiration of H. pylori and Escherichia coli under physiologically low levels of oxygen tension. MATERIALS AND METHODSReagents-Peroxynitrite solution and carboxy-2-phenyl-4,4,5,5-tetramethylimidazolin-1-oxyl-3-oxide (cPTIO) were obtained from Dojin Co. (Kumamoto, Japan). Mn-type superoxide dismutase (SOD) from E. coli and 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazol[1,2-␣]pyra zin-3-one (MCLA) were obtained from Sigma and Tokyo Kasei Kogyo Co. (Tokyo, Japan), respectively. Nitric oxide solution was prepared as described previously (5).Bacterial Strains and Their Culture-Two types of enteric bacteria, E. coli K-12 JM109 and H. pylori NCTC-11637, were used in all experiments. E. coli was cultured at 37°C with shaking in nutrient broth (Difco) containing 0.5% NaCl. H. pylori was cultured in Brucella broth containing 5% horse serum under a microaerophilic atmosphere, produced with the use of a gas pack BBL CampyPak (Becton, MD), at 37°C for 20 h as described previously (15). The cultured E. coli and H. pylori were harvested at the logarithmic...

Besides various gastroduodenal diseases,