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Infectious and foodborne diseases pose significant global threats, with devastating consequences in low- and middle-income countries. Ozone, derived from atmospheric oxygen, exerts antimicrobial effects against various microorganisms, and degrades fungal toxins, which were initially recognized in the healthcare and food industries. However, highly concentrated ozone gas can be detrimental to human health. In addition, ozonated water is unstable and has a short half-life. Therefore, ultrafine-bubble technology is expected to overcome these issues. Ultrafine bubbles, which are nanoscale entitles that exist in water for considerable durations, have previously demonstrated bactericidal effects against various bacterial species, including antibiotic-resistant strains. This present study investigated the effects of ozone ultrafine bubble water (OUFBW) on various bacterial toxins. This study revealed that OUFBW treatment abolished the toxicity of pneumolysin, a pneumococcal pore-forming toxin, and leukotoxin, a toxin that causes leukocyte injury. Silver staining confirmed the degradation of pneumolysin, leukotoxin, and staphylococcal enterotoxin A, which are potent gastrointestinal toxins, following OUFB treatment. In addition, OUFBW treatment significantly inhibited NF-κB activation by Pam3CSK4, a synthetic triacylated lipopeptide that activates Toll-like receptor 2. Additionally, OUFBW exerted bactericidal activity against Staphylococcus aureus, including an antibiotic-resistant strain, without displaying significant toxicity toward human neutrophils or erythrocytes. These results suggest that OUFBW not only sterilizes bacteria but also degrades bacterial toxins. [ABSTRACT FROM AUTHOR]

Many bacterial pathogens can enter various host cells and then survive intracellularly, transiently evade humoral immunity, and further disseminate to other cells and tissues. When bacteria enter host cells and replicate intracellularly, the host cells sense the invading bacteria as damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) by way of various pattern recognition receptors. As a result, the host cells induce alarm signals that activate the innate immune system (1). Therefore, bacteria must modulate host inflammatory signalling and dampen these alarm signals (2-4). How pathogens do this after invading epithelial cells remains unclear, however. Here we show that OspI, a Shigella flexneri effector encoded by ORF169b on the large plasmid and delivered by the type III secretion system, dampens acute inflammatory responses during bacterial invasion by suppressing the tumour-necrosis factor (TNF)-receptor-associated factor 6 (TRAF6)-mediated signalling pathway. OspI is a glutamine deamidase that selectively deamidates the glutamine residue at position 100 in UBC13 to a glutamic acid residue. Consequently, the E2 ubiquitin-conjugating activity required for TRAF6 activation is inhibited, allowing S. flexneri OspI to modulate the diacylglycerol-CBM (CARD-BCL10-MALT1) complex-TRAF6-nuclear-factor-κB signalling pathway. We determined the 2.0 Å crystal structure of OspI, which contains a putative cysteine-histidine-aspartic acid catalytic triad. A mutational analysis showed this catalytic triad to be essential for the deamidation of UBC13. Our results suggest that S. flexneriinhibits acute inflammatory responses in the initial stage of infection by targeting the UBC13-TRAF6 complex, The rupture of host cell membranes by invasive bacteria such as S. flexneri and Listeria monocytogenes is sensed as DAMPs and triggers acute inflammatory responses by activating various cell signals [...]

The interactions of Helicobacter pylori pathogen with their host tissues are studied to explain the working of the eukaryotic regulatory circuits. The analysis has shown to be extremely helpful in understanding the control of epithelial cell structure and developmental fate.

It is currently unclear whether Shigella kills its phagocytic host cells by apoptosis or necrosis. This study shows that rapid necrosis ensues in macrophage-like cell lines (U937 cells differentiated by all-trans-retinoic acid and J774 cells) infected with the Shigella flexneri strain YSH6000. The infected cells rapidly lose membrane integrity, a typical feature of necrosis, as indicated by the release of the cytoplasmic lactate dehydrogenase and the exposure of phosphatidylserine (PS) associated with the rapid uptake of propidium iodide (PI). The infected cells exhibit DNA fragmentation without nuclear condensation, and substantial involvement of either caspase-3/-7 or caspase-1 was not detected, which is also contrary to what is normally observed in apoptosis. Cytochalasin D potently inhibited Shigella-induced cell death, indicating that only internalized Shigella can cause necrosis. Osmoprotectants such as polyethylene glycols could suppress cell death, suggesting that insertion of a pore by Shigella into the host cell membrane induces the necrosis. The pore was estimated to be 2*87 [+ or -] 0*4 nm in diameter. Shigella was also found to be able to induce apoptosis but only in one of the lines tested and under specific conditions, namely U937 cells differentiated with interferon-[gamma] (U9371FN). Caspase-3/-7 but not caspase-1 activation was observed in these infected cells and the exposure of PS occurred without the uptake of PI. An avirulent Shigella strain, wild-type Shigella killed with gentamicin, and even Escherichia coli strain JM109, could also induce apoptosis in U9371FN cells, and cytochalasin D could not prevent apoptosis. It appears therefore that Shigella-induced apoptosis of U9371FN cells is unrelated to Shigella pathogenicity and does not require bacterial internalization. Thus, Shigella can induce rapid necrosis of macrophage-like cells in a virulence-related manner by forming pores in the host cell membrane while some cells can be killed through apoptosis in a virulence-independent fashion.

Abstract Article retracted

Abstract Background The inflammatory response in Helicobacter pylori-infected gastric tissue is mediated by cag pathogenicity island (PAI)-dependent activation of nuclear factor-κB (NF-κB). Phosphatidylinositol 3-kinase (PI3K)/Akt signaling is known to play a role in NF-κB activation, but little information is available on the relationship between H. pylori and PI3K/Akt signaling in gastric epithelial cells. We examined whether H. pylori activates Akt in gastric epithelial cells, the role of cag PAI in this process and the role of Akt in regulating H. pylori-induced NF-κB activation. Results Phosphorylated Akt was detected in epithelial cells of H. pylori-positive gastric tissues. Although Akt was activated in MKN45 and AGS cells by coculture with cag PAI-positive H. pylori strains, a cag PAI-negative mutant showed no activation of Akt. H. pylori also induced p65 phosphorylation. PI3K inhibitor suppressed H. pylori-induced p65 phosphorylation and NF-κB transactivation, as well as interleukin-8 expression. Furthermore, transfection with a dominant-negative Akt inhibited H. pylori-induced NF-κB transactivation. Transfection with small interference RNAs for p65 and Akt also inhibited H. pylori-induced interleukin-8 expression. Conclusion The results suggest that cag PAI-positive H. pylori activates Akt in gastric epithelial cells and this may contribute to H. pylori-mediated NF-κB activation associated with mucosal inflammation and carcinogenesis.

Small intestinal mononuclear cells that express CX3CR1 (CX3CR1+ cells) regulate immune responses1-5. CX3CR1+ cells take up luminal antigens by protruding their dendrites into the lumen1-4,6. However, it remains unclear how dendrite protrusion by CX3CR1+ cells is induced in the intestine. Here we show in mice that the bacterial metabolites pyruvic acid and lactic acid induce dendrite protrusion via GPR31 in CX3CR1+ cells. Mice that lack GPR31, which was highly and selectively expressed in intestinal CX3CR1+ cells, showed defective dendrite protrusions of CX3CR1+ cells in the small intestine. A methanol-soluble fraction of the small intestinal contents of specific-pathogen-free mice, but not germ-free mice, induced dendrite extension of intestinal CX3CR1+ cells in vitro. We purified a GPR31-activating fraction, and identified lactic acid. Both lactic acid and pyruvic acid induced dendrite extension of CX3CR1+ cells of wild-type mice, but not of Gpr31b−/− mice. Oral administration of lactate and pyruvate enhanced dendrite protrusion of CX3CR1+ cells in the small intestine of wild-type mice, but not in that of Gpr31b−/− mice. Furthermore, wild-type mice treated with lactate or pyruvate showed an enhanced immune response and high resistance to intestinal Salmonella infection. These findings demonstrate that lactate and pyruvate, which are produced in the intestinal lumen in a bacteria-dependent manner, contribute to enhanced immune responses by inducing GPR31-mediated dendrite protrusion of intestinal CX3CR1+ cells. In the mouse intestine, pyruvate and lactate produced from bacterial metabolites enhance immune responses through inducing dendrite protrusion, mediated by GPR31, of small intestinal mononuclear cells that express CX3CR1. [ABSTRACT FROM AUTHOR]