A methanolic extract of dried Schisandra fruit (Schisandra chinensis Baill.; Schisandraceae) significantly attenuated the neurotoxicity induced by L-glutamate in primary cultures of rat cortical cells. Five dibenzocyclooctadiene lignans (deoxyschisandrin, gomisin N, gomisin A, schisandrin, and wuweizisu C) were isolated from the methanolic extract; their protective effects against glutamate-induced neurotoxicity were then evaluated. Among the five lignans, deoxyschisandrin, gomisin N, and wuweizisu C significantly attenuated glutamate-induced neurotoxicity as measured by 1). an inhibition in the increase of intracellular [Ca(2+)]; 2). an improvement in the glutathione defense system, the level of glutathione, and the activity of glutathione peroxidase; and 3). an inhibition in the formation of cellular peroxide. These results suggest that dibenzocyclooctadiene lignans from Schisandra chinensis may possess therapeutic potential against oxidative neuronal damage induced by excitotoxin.

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BackgroundHelicobacter pylori (Hp), a human pathogen that is associated with gastritis, peptic ulcer, and gastric cancer, has been considered a microaerophile, but there is no general consensus about its specific O2 requirements. A clear understanding of Hp physiology is needed to elucidate the pathogenic mechanism(s) of Hp infection.ResultsWe cultured Hp under a range of O2 levels with or without 10% CO2 and evaluated growth profiles, morphology, intracellular pH, and energy metabolism. We found that, in the presence of 10% CO2, the normal atmospheric level of O2 inhibited Hp growth at low density but stimulated growth at a higher density. Field emission scanning electron microscopy and fluorescence microscopy of Hp cells cultured under 20% O2 tension revealed live spiral-shaped bacteria with outer membrane vesicles on a rugged cell surface, which became smooth during the stationary phase. Fermentation products including acetate, lactate, and succinate were detected in cell culture media grown under microaerobic conditions, but not under the aerobic condition. CO2 deprivation for less than 24 h did not markedly change cytoplasmic or periplasmic pH, suggesting that cellular pH homeostasis alone cannot account for the capnophilic nature of Hp. Further, CO2 deprivation significantly increased intracellular levels of ppGpp and ATP but significantly decreased cellular mRNA levels, suggesting induction of the stringent response.ConclusionsWe conclude, unlike previous reports, that H. pylori may be a capnophilic aerobe whose growth is promoted by atmospheric oxygen levels in the presence of 10% CO2. Our data also suggest that buffering of intracellular pH alone cannot account for the CO2 requirement of H. pylori and that CO2 deprivation initiates the stringent response in H. pylori. Our findings may provide new insight into the physiology of this fastidious human pathogen.

The ferric uptake regulator (Fur) protein is a Fe(2+)-dependent transcriptional repressor that binds to the Fur-box of bacterial promoters and down-regulates gene expression. In this study, to investigate global gene regulation by Fur in response to iron in Helicobacter pylori, a causative agent of human gastric diseases, we compared the proteome profiles of the H. pylori strain 26695 and its isogenic fur mutant grown under iron-rich and iron-depleted conditions. In total, 93 protein spots were found to be up- or down-regulated by more than 2-fold by either a fur mutation or iron-depletion. From these, 39 spots were identified by matrix-assisted laser desorption/ionization time of flight analysis to be 29 different proteins of diverse functions, including energy metabolism, transcription and translation, detoxification, biosynthesis of amino acids and nucleotides and production of the cell envelope. Expression of six proteins was found to be higher in the fur mutant than in the wild-type bacteria, indicating Fur-mediated repression. Eleven proteins were activated by Fur; five responded to iron and the others were not iron-responsive. The remaining 12 proteins were not under Fur-regulation but responded to iron in a positive or negative manner. Seven different types of gene regulation via Fur and iron were identified. These findings demonstrate that the H. pylori Fur protein functions as a classical transcriptional repressor but can also function as an activator, providing evidence for the presence of Fur-mediated positive regulation in H. pylori.

The lactoferrin sequestration in the gastric mucosa of HPIDA was remarkable, and this finding seems to give a clue that leads to the clarification of the mechanism by which H. pylori infection contributes to iron-deficiency anemia.