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- Boekel, Jorrit, et al.
(författare)
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Comparative tissue transcriptomics reveal prompt inter-organ communication in response to local bacterial kidney infection
- 2011
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 12, s. 123-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Mucosal infections elicit inflammatory responses via regulated signaling pathways. Infection outcome depends strongly on early events occurring immediately when bacteria start interacting with cells in the mucosal membrane. Hitherto reported transcription profiles on host-pathogen interactions are strongly biased towards in vitro studies. To detail the local in vivo genetic response to infection, we here profiled host gene expression in a recent experimental model that assures high spatial and temporal control of uropathogenic Escherichia coli (UPEC) infection within the kidney of a live rat. Results: Transcriptional profiling of tissue biopsies from UPEC-infected kidney tissue revealed 59 differentially expressed genes 8 h post-infection. Their relevance for the infection process was supported by a Gene Ontology (GO) analysis. Early differential expression at 3 h and 5 h post-infection was of low statistical significance, which correlated to the low degree of infection. Comparative transcriptomics analysis of the 8 h data set and online available studies of early local infection and inflammation defined a core of 80 genes constituting a "General tissue response to early local bacterial infections". Among these, 25% were annotated as interferon-gamma (IFN-gamma) regulated. Subsequent experimental analyses confirmed a systemic increase of IFN-gamma in rats with an ongoing local kidney infection, correlating to splenic, rather than renal Ifng induction and suggested this inter-organ communication to be mediated by interleukin (IL)-23. The use of comparative transcriptomics allowed expansion of the statistical data handling, whereby relevant data could also be extracted from the 5 h data set. Out of the 31 differentially expressed core genes, some represented specific 5 h responses, illustrating the value of comparative transcriptomics when studying the dynamic nature of gene regulation in response to infections. Conclusion: Our hypothesis-free approach identified components of infection-associated multi-cellular tissue responses and demonstrated how a comparative analysis allows retrieval of relevant information from lower-quality data sets. The data further define marked representation of IFN-gamma responsive genes and a prompt inter-organ communication as a hallmark of an early local tissue response to infection.
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| 2. |
- Boekel, Jorrit
(författare)
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Tissue responses and host transcriptomics in bacterial infections
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bacterial infections can damage host tissue and are as such a potential threat to their hosts. To protect themselves from pathogens, hosts therefore can employ diverse immune reactions. When bacteria are recognized by their hosts, complex signaling cascades are triggered that lead to an influx of specialized immune cells into the infected tissue and a change in tissue integrity. The inflammation that is mounted may eliminate the pathogens, but will also cause substantial tissue damage. The foundation for the inflammatory process is laid early, in the first 12 hours of infection. This thesis aims to reveal host responses within this early time frame. While in vitro studies can yield highly detailed data on subjects as protein-protein and cell-bacterial interactions, they cannot reproduce all aspects that occur in a live animal, such as immune infiltration, nerve, and hormone effects. We have developed a kidney infection model of bacterial infection to study early whole-host responses to bacteria. Using micropuncture techniques, we delivered bacteria to a known nephron, from where the infection progressed. Within hours, we observed numerous physiological changes of the tissue volume bordering the infection. Infection kinetics could be visualized and showed markedly faster host responses to haemolysin (Hlγ)-carrying bacteria compared to Hlγ-knockouts. Tissue oxygen levels decreased in response to infection, possibly caused both by blood ow restriction combined with epithelial oxygen consumption. Blood ow shutdown at the infected nephron was due to activation of the coagulation cascade. Coagulation also protected against sepsis, as animals died due to bacteremia when this cascade was inhibited. Some of these phenomena could be found in the host transcriptome. We also found that a core of common gene expression exists in live host innate immune responses by applying bioinformatic methods on the gene expression measurements. This core had a strong IFN-γ signature, a cytokine which we consequently found increased in the blood stream, and expressed by cells in the spleen. We go on to show that IFN-γ downregulates transcription of several neutrophil-attracting chemokines, and that this does not occur through canonical effectors of either IFN-γ or inflammatory signaling pathways. The data I present here show that using a live host infection model can reveal host processes that cannot be found using in vitro models. By combining this model with analysis methods that yield detailed data, early responses could be studied. The data show the importance of live models for discovering unknown contributors and functions in inflammation, which may lead to possible future medicine development.
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