5). These results suggested that the cell death process may not be associated with activation of inflammasomes, but rather that IL-1β and ATP are released from damaged cells. Alternatively, oxidative stress may contribute to the cell death, because ROS inhibitor reduced the cell death of macrophages (Fig. 5). ROS generated from damaged mitochondoria are known to induce cell death in various ways (Ott et al.,

2007). In this regard, several oral streptococcal species including S. sanguinis are known to produce hydrogen peroxide (Chen et al., 2011). This bacterial product is a possible candidate for click here the virulence factor that mediates cellular damage in macrophages, because Streptococcus gordonii, another oral streptococcus, is reported to induce cell death of endothelial cells by peroxidogenesis (Stinson

et al., 2003). Our preliminary study suggested that the concentrations of hydrogen peroxide in the culture supernatants of S. sanguinis were <5 μM under the conditions of the infection assay, although its effect on macrophages was unknown. The involvement of hydrogen peroxide produced by S. sanguinis in the cell death of infected macrophages should be investigated further. To evaluate the molecular mechanisms underlying S. sanguinis-induced cell death, further study on the mitochondorial dysfunction induced by this microorganism will be required. This work was supported in part by Grants-in-Aid for Scientific Research (A) (#19209063), (B) (#20390465, #20390531) and (C) (#20592398), and Grants-in-Aid for Young Scientists (B) (#21792069,

#21791786) from the Japan Gefitinib in vitro Society for the Promotion of Science. We thank Dr M. Killian for providing 4-Aminobutyrate aminotransferase S. sanguinis strain SK36. “
“Ophiobolins are sesterterpene-type phytotoxins produced by fungi belonging mainly to the genus Bipolaris. In this study, the antifungal effect of ophiobolins A and B on different zygomycetes has been examined. Depending on the zygomycete tested, MIC values of 3.175–50 μg mL–1 were found for ophiobolin A and 25–50 μg mL–1 for ophiobolin B. Ophiobolin A inhibited sporangiospore germination of Mucor circinelloides and caused morphological changes; the fungus formed degenerated, thick or swollen cells with septa. Cytoplasm effusions from the damaged cells were also observed. Fluorescence microscopy after annexin and propidium iodide staining of the treated cells suggested that the drug induced an apoptosis-like cell death process in the fungus. Ophiobolins are secondary metabolites of certain fungi belonging to the genera Bipolaris, Drechslera, Cephalosporium and Aspergillus (Au et al., 2000a). These sesterterpene-type compounds (C25) are characterized by a unique tricyclic chemical structure (Fig. 1). More than 25 ophiobolin analogues have been described (Au et al., 2000a; Wei et al., 2004; Evidente et al., 2006) and various biological actions have been attributed to them, such as phytotoxic (Au et al.