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Many neurotropic strains of Escherichia coli cause potentially lethal bacteraemia and meningitis in newborn infants by virtue of their capacity to elaborate the protective polysialic acid (polySia) K1 capsule. Recombinant capsule depolymerase, endosialidase E (endoE), selectively removes polySia from the bacterial surface; when administered intraperitoneally to infected neonatal rats, the enzyme interrupts the transit of E. coli K1 from gut to brain via the blood circulation and prevents death from systemic infection. We now show that experimental E. coli K1 infection is accompanied by extensive modulation of host gene expression in the liver, spleen and brain tissues of neonatal rats. Bacterial invasion of the brain resulted in a threefold or greater upregulation of approximately 400 genes, a large number of which were associated with the induction of inflammation and the immune and stress responses: these included genes encoding C-X-C and C-C chemokines, lipocalins, cytokines, apolipoproteins and enzymes involved in the synthesis of low-molecular-mass inflammatory mediators. Administration of a single dose of endoE, 24 h after initiation of systemic infection, markedly reduced, but did not completely abrogate, these changes in gene expression, suggesting that attenuation of E. coli K1 virulence by removal of the polySia capsule may minimize the attendant inflammatory processes that contribute to poor outcome in these severe systemic infections. DOI 10.1099/mic.0.036145-0

Escherichia coli K1 isolates synthesize a polysialic acid (polySia) capsule, are components of the adult gastrointestinal microbiota and may cause lethal bacteraemia and meningitis if acquired maternally by newborn infants. We used a neonatal rat pup K1 infection model to establish that prompt administration of a selective capsule depolymerase reverses the bacteraemic state and prevents death of almost all pups. In untreated animals, bacteria colonize the gastrointestinal tract and gain entry to the blood compartment, where they express the non-O-acetylated form of polySia. The bacteria invade the major organs of the host; histological and histochemical analysis of brain sections revealed that at least some bacteria enter the central nervous system through the blood-cerebrospinal fluid barrier at the choroid plexus prior to colonization of the meninges. Once in this location, they cease expression of polySia. The unexpected abrogation of polySia, a factor associated with the pathogenesis of meningitis and essential for transit through the blood, suggests that the neuropathogen dispenses with its protective capsule once it has colonized protected niches. Thus, systemic infections due to encapsulated pathogens may be resolved by capsule depolymerization only if the enzyme modifies the bacteria whilst they are in the blood compartment.

The cold-inducible RNA-binding motif protein 3 (RBM3) is involved in the protection of neurons in hypoxic-ischemic and neurodegenerative disorders. RBM3 belongs to a small group of proteins whose synthesis increases during hypothermia while global protein production is slowed down. To investigate the molecular mechanisms underlying RBM3 action, we subjected hippocampal organotypic slice cultures from RBM3 knockout mice to various stressors and found exuberant signaling of the endoplasmic reticulum (ER) stress pathway PRKR-like ER kinase (PERK)-eukaryotic translation initiation factor 2α (eIF2α)-CCAAT/enhancer-binding protein homologous protein (CHOP) as compared with wild-type mice. Further, blocking RBM3 expression in human embryonic kidney HEK293 cells by specific small interfering RNAs increased phosphorylation of PERK and eIF2α, whereas overexpression of RBM3 prevented PERK-eIF2α-CHOP signaling during ER stress induced by thapsigargin or tunicamycin. RBM3 did not affect expression of the ER stress sensor immunoglobulin binding protein/GRP78. However, based on affinity purification coupled with mass spectrometry, coimmunoprecipitation, and proximity ligation assay, we revealed that nuclear factor 90 (NF90) is a novel protein interactor of PERK and that this interaction is essential for RBM3-mediated regulation of PERK activity, which requires an RNA-dependent interaction. In conclusion, our data provide evidence for a central role of RBM3 in preventing cell death by inhibiting the PERK-eIF2α-CHOP ER stress pathway through cooperation with NF90. [ABSTRACT FROM AUTHOR]

The transcriptional regulation of several dozen genes in response to low oxygen tension is mediated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric protein composed of two subunits, HIF-1α and HIF-1β. In the HIF-1α-deficient human leukemic cell line, Z-33, exposed to mild (8% O2) or severe (1% O2) hypoxia, we found significant upregulation of two related heterogenous nuclear ribonucleoproteins, RNA-binding motif protein 3 (RBM3) and cold inducible RNA-binding protein (CIRP), which are highly conserved cold stress proteins with RNA-binding properties. Hypoxia also induced upregulation of RBM3 and CIRP in the murine HIF-1β-deficient cell line, Hepa-1 c4. In various HIF-1 competent cells, RBM3 and CIRP were induced by moderate hypothermia (32°C) but hypothermia was ineffective in increasing HIF-1α or vascular endothelial growth factor (VEGF), a known HIF-1 target. In contrast, iron chelators induced VEGF but not RBM3 or CIRP. The RBM3 and CIRP mRNA increase after hypoxia was inhibited by actinomycin-D, and in vitro nuclear run-on assays demonstrated specific increases in RBM3 and CIRP mRNA after hypoxia, which suggests that regulation takes place at the level of gene transcription. Hypoxia-induced RBM3 or CIRP transcription was inhibited by the respiratory chain inhibitors NaN3 and cyanide in a dose-dependent fashion. However, cells depleted of mitochondria were still able to upregulate RBM3 and CIRP in response to hypoxia. Thus, RBM3 and CIRP are adaptatively expressed in response to hypoxia by a mechanism that involves neither HIF-1 nor mitochondria. [ABSTRACT FROM AUTHOR]

The cold-inducible RNA-binding motif protein 3 (RBM3) is involved in the protection of neurons in hypoxic-ischemic and neurodegenerative disorders. RBM3 belongs to a small group of proteins whose synthesis increases during hypothermia while global protein production is slowed down. To investigate the molecular mechanisms underlying RBM3 action, we subjected hippocampal organotypic slice cultures from RBM3 knockout mice to various stressors and found exuberant signaling of the endoplasmic reticulum (ER) stress pathway PRKR-like ER kinase (PERK)-eukaryotic translation initiation factor 2α (eIF2α)-CCAAT/enhancer-binding protein homologous protein (CHOP) as compared with wild-type mice. Further, blocking RBM3 expression in human embryonic kidney HEK293 cells by specific small interfering RNAs increased phosphorylation of PERK and eIF2α, whereas overexpression of RBM3 prevented PERK-eIF2α-CHOP signaling during ER stress induced by thapsigargin or tunicamycin. RBM3 did not affect expression of the ER stress sensor immunoglobulin binding protein/GRP78. However, based on affinity purification coupled with mass spectrometry, coimmunoprecipitation, and proximity ligation assay, we revealed that nuclear factor 90 (NF90) is a novel protein interactor of PERK and that this interaction is essential for RBM3-mediated regulation of PERK activity, which requires an RNA-dependent interaction. In conclusion, our data provide evidence for a central role of RBM3 in preventing cell death by inhibiting the PERK-eIF2α-CHOP ER stress pathway through cooperation with NF90., (© FASEB.)

According to World Health Organization estimates, infectious organisms are responsible for approximately one in four deaths worldwide. Animal models play an essential role in the development of vaccines and therapeutic agents but large numbers of animals are required to obtain quantitative microbiological data by tissue sampling. Biophotonic imaging (BPI) is a highly sensitive, nontoxic technique based on the detection of visible light, produced by luciferase-catalysed reactions (bioluminescence) or by excitation of fluorescent molecules, using sensitive photon detectors. The development of bioluminescent/fluorescent microorganisms therefore allows the real-time noninvasive detection of microorganisms within intact living animals. Multiple imaging of the same animal throughout an experiment allows disease progression to be followed with extreme accuracy, reducing the number of animals required to yield statistically meaningful data. In the study of infectious disease, the use of BPI is becoming widespread due to the novel insights it can provide into established models, as well as the impact of the technique on two of the guiding principles of using animals in research, namely reduction and refinement. Here, we review the technology of BPI, from the instrumentation through to the generation of a photonic signal, and illustrate how the technique is shedding light on infection dynamics in vivo., (© 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)