| 1. |
- Denamur, Erick, et al.
(författare)
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High frequency of mutator strains among human uropathogenic Escherichia coli isolates.
- 2002
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 184:2, s. 605-9
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Tidskriftsartikel (refereegranskat)abstract
- By using a panel of 603 commensal and pathogenic Escherichia coli and Shigella isolates, we showed that mutation rates of strains vary considerably among different ecotypes. Uropathogenic strains had the highest frequency of mutators, while strains from patients with bacteremia had the lowest mutation rates. No correlation between the mutation rates and antibiotic resistance was observed among the studied strains.
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| 2. |
- Bambou, Jean-Christophe, et al.
(författare)
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In vitro and ex vivo activation of the TLR5 signaling pathway in intestinal epithelial cells by a commensal Escherichia coli strain.
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:41, s. 42984-92
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of non-pathogenic enteric bacteria to induce a pro-inflammatory response is under debate in terms of its effect on the symbiosis between the mammalian host and its commensal gut microflora. Activation of NF-kappaB and induction of interleukin-8 (IL-8) and CCL-20 by the commensal Escherichia coli strain MG1655 were first studied in vitro in the human intestinal epithelial cell (IECs) lines HT29-19A and Caco-2, transfected or not with plasmids encoding dominant negative Toll-like receptor (TLR) 5 and myeloid differentiation factor-88 (MyD88) adaptor protein. The response of enterocytes in situ was then assessed using murine ileal biopsies mounted in Ussing chambers. Commensal E. coli induced NF-kappaB DNA binding, NF-kappaB transcriptional activity, CCL-20 expression, and IL-8 secretion in the human IEC lines. E. coli MG1655 flagellin was necessary and sufficient to trigger this pro-inflammatory pathway via its interaction with TLR5 and the subsequent recruitment of the adaptor protein MyD88. Following epithelial cell polarization, signaling could be induced by live E. coli and flagellin on the apical side of HT29-19A. The in vivo relevance of our findings was confirmed, because immunohistochemical staining of murine ileum demonstrated expression of TLR5 in the apical part of enterocytes in situ. Furthermore, flagellin added on the mucosal side of murine ileal biopsies mounted in Ussing chambers induced a basolateral production of KC, a functional murine homolog of human IL-8. These findings provide strong evidence that flagellin released by flagellated commensal bacteria in the intestinal lumen can induce a pro-inflammatory response in enterocytes in vivo.
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| 3. |
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| 4. |
- Giraud, Antoine, 1972-
(författare)
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Axenic mice model.
- 2008
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Ingår i: Innate Immunity. - Totowa, NJ : Humana Press. - 9781588297464 - 9781597455701 ; , s. 321-336
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The interaction of an organism with surrounding microbial communities has a profound impact on its anatomy, physiology, and behavior. The innate immune system plays a major role in the crosstalk between bacteria and the hosts they colonize. Axenic mice provide a powerful in vivo controlled model to decipher the particular interactions between the host and one defined strain, or group of strains, isolated from the "noise" of the rest of the flora. This chapter briefly reviews the specificities of axenic mice and describes the main guidelines to derive, house, and work with axenic mice.
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| 5. |
- Giraud, Antoine, et al.
(författare)
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Costs and benefits of high mutation rates : adaptive evolution of bacteria in the mouse gut.
- 2001
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 291:5513, s. 2606-8
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Tidskriftsartikel (refereegranskat)abstract
- We have shown that bacterial mutation rates change during the experimental colonization of the mouse gut. A high mutation rate was initially beneficial because it allowed faster adaptation, but this benefit disappeared once adaptation was achieved. Mutator bacteria accumulated mutations that, although neutral in the mouse gut, are often deleterious in secondary environments. Consistently, the competitiveness of mutator bacteria is reduced during transmission to and re-colonization of similar hosts. The short-term advantages and long-term disadvantages of mutator bacteria could account for their frequency in nature.
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| 6. |
- Giraud, Antoine, et al.
(författare)
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Dissecting the genetic components of adaptation of Escherichia coli to the mouse gut
- 2008
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- While pleiotropic adaptive mutations are thought to be central for evolution, little is known on the downstream molecular effects allowing adaptation to complex ecologically relevant environments. Here we show that Escherichia coli MG1655 adapts rapidly to the intestine of germ-free mice by single point mutations in EnvZ/OmpR two-component signal transduction system, which controls more than 100 genes. The selective advantage conferred by the mutations that modulate EnvZ/OmpR activities was the result of their independent and additive effects on flagellin expression and permeability. These results obtained in vivo thus suggest that global regulators may have evolved to coordinate activities that need to be fine-tuned simultaneously during adaptation to complex environments and that mutations in such regulators permit adjustment of the boundaries of physiological adaptation when switching between two very distinct environments.
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| 7. |
- Giraud, Antoine, et al.
(författare)
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Mutator bacteria as a risk factor in treatment of infectious diseases.
- 2002
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Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804 .- 1098-6596. ; 46:3, s. 863-5
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Tidskriftsartikel (refereegranskat)abstract
- We show in a gnotobiotic mouse model that, in addition to direct selection of antibiotic-resistant bacteria, some antibiotic treatments also select for mutator alleles. Because of these mutator alleles' high mutation rates, the initial treatment failure increases the probability of failures in subsequent treatments with other drugs.
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| 8. |
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| 9. |
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| 10. |
- Lawrenson, Kate, et al.
(författare)
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Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 × 10-20), ER-negative BC (P=1.1 × 10-13), BRCA1-associated BC (P=7.7 × 10-16) and triple negative BC (P-diff=2 × 10-5). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 × 10-3) and ABHD8 (P<2 × 10-3). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3′-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk.
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| 11. |
- Liu, Haoyu, et al.
(författare)
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Distinct B cell subsets in Peyer's patches convey probiotic effects by Limosilactobacillus reuteri
- 2021
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Ingår i: Microbiome. - : Springer Nature. - 2049-2618. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Intestinal Peyer's patches (PPs) form unique niches for bacteria-immune cell interactions that direct host immunity and shape the microbiome. Here we investigate how peroral administration of probiotic bacterium Limosilactobacillus reuteri R2LC affects B lymphocytes and IgA induction in the PPs, as well as the downstream consequences on intestinal microbiota and susceptibility to inflammation.Results: The B cells of PPs were separated by size to circumvent activation-dependent cell identification biases due to dynamic expression of markers, which resulted in two phenotypically, transcriptionally, and spatially distinct subsets: small IgD(+)/GL7(-)/S1PR1(+)/Bcl6, CCR6-expressing pre-germinal center (GC)-like B cells with innate-like functions located subepithelially, and large GL7(+)/S1PR1(-)/Ki67(+)/Bcl6, CD69-expressing B cells with strong metabolic activity found in the GC. Peroral L. reuteri administration expanded both B cell subsets and enhanced the innate-like properties of pre-GC-like B cells while retaining them in the sub-epithelial compartment by increased sphingosine-1-phosphate/S1PR1 signaling. Furthermore, L. reuteri promoted GC-like B cell differentiation, which involved expansion of the GC area and autocrine TGF beta-1 activation. Consequently, PD-1-T follicular helper cell-dependent IgA induction and production was increased by L. reuteri, which shifted the intestinal microbiome and protected against dextran-sulfate-sodium induced colitis and dysbiosis.Conclusions: The Peyer's patches sense, enhance and transmit probiotic signals by increasing the numbers and effector functions of distinct B cell subsets, resulting in increased IgA production, altered intestinal microbiota, and protection against inflammation.
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| 12. |
- Lo, Ying-Chu, et al.
(författare)
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Domestication in dry-cured meat Penicillium fungi : convergent specific phenotypes and horizontal gene transfers without strong genetic subdivision
- 2023
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Ingår i: Evolutionary Applications. - : John Wiley & Sons. - 1752-4571. ; 16:9, s. 1637-1660
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Tidskriftsartikel (refereegranskat)abstract
- Some fungi have been domesticated for food production, with genetic differentiation between populations from food and wild environments, and food populations often acquiring beneficial traits through horizontal gene transfers (HGTs). Studying their adaptation to human-made substrates is of fundamental and applied importance for understanding adaptation processes and for further strain improvement. We studied here the population structures and phenotypes of two distantly related Penicillium species used for dry-cured meat production, P. nalgiovense, the most common species in the dry-cured meat food industry, and P. salamii, used locally by farms. Both species displayed low genetic diversity, lacking differentiation between strains isolated from dry-cured meat and those from other environments. Nevertheless, the strains collected from dry-cured meat within each species displayed slower proteolysis and lipolysis than their wild conspecifics, and those of P. nalgiovense were whiter. Phenotypically, the non-dry-cured meat strains were more similar to their sister species than to their conspecific dry-cured meat strains, indicating an evolution of specific phenotypes in dry-cured meat strains. A comparison of available Penicillium genomes from various environments revealed HGTs, particularly between P. nalgiovense and P. salamii (representing almost 1.5 Mb of cumulative length). HGTs additionally involved P. biforme, also found in dry-cured meat products. We further detected positive selection based on amino acid changes. Our findings suggest that selection by humans has shaped the P. salamii and P. nalgiovense populations used for dry-cured meat production, which constitutes domestication. Several genetic and phenotypic changes were similar in P. salamii, P. nalgiovense and P. biforme, indicating convergent adaptation to the same human-made environment. Our findings have implications for fundamental knowledge on adaptation and for the food industry: the discovery of different phenotypes and of two mating types paves the way for strain improvement by conventional breeding, to elucidate the genomic bases of beneficial phenotypes and to generate diversity.
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| 13. |
- Lomei, Jalal, 1980-, et al.
(författare)
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Characterization of pro-angiogenic neutrophils
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The roles of neutrophils in immune defense have been investigated for decades. These cells are well equipped to protect the body in several ways against invaders such as microorganism. Recently it has been reported that neutrophils also contribute to angiogenesis; they are recruited to the site of hypoxia where they can promote blood vessel formation, as demonstrated both in vivo and in vitro. We found that these neutrophils with proangiogenic actions form a specific subset of the circulating neutrophils. The proangiogenic neutrophils (PANs) exclusively express the adhesion molecule CD49d and vascular endothelial growth factor receptor 1 (VEGFR1), and contribute to angiogenesis by delivering MMP-9 (matrix metalloproteinase 9). In this study, PANs were compared to classic neutrophils in respect to physical features as well as functionality. We found that PANs in humans were smaller and in human and mice PANs had higher granularity compared to the classic neutrophils. Moreover, they were more efficient phagocytes than classic neutrophils. In the aortic ring model of angiogenesis, vessel neo-formation was increased by the presence of pro-angiogenic neutrophils. Finally, by using neutrophils from mice with impaired VEGFR1 receptor (Flt-1 tk-/- mice) we demonstrated the role of VEGFR1 in neutrophil recruitment towards angiogenic endothelium. Together these results show clear differences between the pro-angiogenic subpopulation and the classic neutrophils, which further solidify the conclusion of a specific neutrophil subpopulation.
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| 14. |
- Massena, Sara, et al.
(författare)
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Identification and characterization of VEGF-A-responsive neutrophils expressing CD49d, VEGFR1, and CXCR4 in mice and humans
- 2015
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 126:17, s. 2016-2026
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Tidskriftsartikel (refereegranskat)abstract
- Vascular endothelial growth factor A (VEGF-A) is upregulated during hypoxia and is the major regulator of angiogenesis. VEGF-A expression has also been found to recruit myeloid cells to ischemic tissues where they contribute to angiogenesis. This study investigates the mechanisms underlying neutrophil recruitment to VEGF-A as well as the characteristics of these neutrophils. A previously undefined circulating subset of neutrophils shown to be CD49d(+)VEGFR1(high)CXCR4(high) was identified in mice and humans. By using chimeric mice with impaired VEGF receptor 1 (VEGFR1) or VEGFR2 signaling (Flt-1tk(-/-), tsad(-/-)), we found that parallel activation of VEGFR1 on neutrophils and VEGFR2 on endothelial cells was required for VEGF-A-induced recruitment of circulating neutrophils to tissue. Intravital microscopy of mouse microcirculation revealed that neutrophil recruitment by VEGF-A versus by the chemokine macrophage inflammatory protein 2 (MIP-2 [CXCL2]) involved the same steps of the recruitment cascade but that an additional neutrophil integrin (eg, VLA-4 [CD49d/CD29]) played a crucial role in neutrophil crawling and emigration to VEGF-A. Isolated CD49d(+) neutrophils featured increased chemokinesis but not chemotaxis compared with CD49d(-) neutrophils in the presence of VEGF-A. Finally, by targeting the integrin α4 subunit (CD49d) in a transplantation-based angiogenesis model that used avascular pancreatic islets transplanted to striated muscle, we demonstrated that inhibiting the recruitment of circulating proangiogenic neutrophils to hypoxic tissue impairs vessel neoformation. Thus, angiogenesis can be modulated by targeting cell-surface receptors specifically involved in VEGF-A-dependent recruitment of proangiogenic neutrophils without compromising recruitment of the neutrophil population involved in the immune response to pathogens.
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| 15. |
- Nikpour, Maryam, et al.
(författare)
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Shb deficiency in endothelium but not in leukocytes is responsible for impaired vascular performance during hindlimb ischemia.
- 2015
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 214:2, s. 200-209
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Myeloid cells have been suggested to participate in angiogenesis and regulation of vascular function. Shb-deficient mice display both vascular and myeloid cell abnormalities with possible consequences for recovery after hindlimb ischemia. This study was conducted in order to assess the contribution of Shb-deficiency in myeloid cells to impaired vascular function in ischemia. Methods: Wild type and Shb-deficient mice were subjected to peritoneal VEGFA followed by intraperitoneal lavage, after which blood and peritoneal cells were stained for myeloid markers. VEGFA-induced leukocyte recruitment to cremaster muscle was investigated using intravital microscopy of both mouse strains. Blood flow after femoral artery ligation was determined on chimeric mice after bone marrow transplantation. Results: No differences in neutrophil numbers or cell surface phenotypes were detected. Moreover, neutrophil extravasation in VEGFA-activated cremaster muscle was unaffected by Shb deficiency. However, blood and peritoneal CXCR4+ monocytes/macrophages were reduced in response to intraperitoneal VEGFA but not LPS in the absence of Shb. Furthermore, the macrophage population in ischemic muscle was unaffected by Shb-deficiency after two days but reduced seven days after injury. The bone marrow transplantation experiments revealed that mice with wild type vasculature showed better blood flow than those with Shb-deficient vasculature irrespective of leukocyte genotype. Conclusion: The observed aberrations in myeloid cell properties in Shb-deficient mice are likely consequences of an abnormal vascular compartment and are not responsible for reduced muscle blood flow. Structural vascular abnormalities seem to be the primary cause of poor vascular performance under provoked vascular stress in this genetic model.
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| 16. |
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| 17. |
- Sedin, John, 1982-, et al.
(författare)
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High Resolution Intravital Imaging of the Renal Immune Response to Injury and Infection in Mice
- 2019
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Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- We developed an experimental set up that enables longitudinal studies of immune cell behavior in situ in the challenged as well as unchallenged kidney of anesthetized mice over several hours. Using highly controlled vacuum to stabilize the kidney, the superficial renal cortex could continuously be visualized with minimal disruption of the local microenvironment. No visible changes in blood flow or neutrophils and macrophages numbers were observed after several hours of visualizing the unchallenged kidney, indicating a stable tissue preparation without apparent tissue damage. Applying this set up to monocyte/macrophage (CX(3)CR1(GFP/+)) reporter mice, we observed the extensive network of stellate-shaped CX(3)CR1 positive cells (previously identified as renal mononuclear phagocytes). The extended dendrites of the CX(3)CR1 positive cells were found to bridge multiple capillaries and tubules and were constantly moving. Light induced sterile tissue injury resulted in rapid neutrophil accumulation to the site of injury. Similarly, microinfusion of uropathogenic Escherichia coli into a single nephron induced a rapid and massive recruitment of neutrophils to the site of infection, in addition to active bacterial clearance by neutrophils. In contrast, the kidney resident mononuclear phagocytes were observed to not increase in numbers or migrate toward the site of injury or infection. In conclusion, this model allows for longitudinal imaging of responses to localized kidney challenges in the mouse.
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| 18. |
- Vigorito, Elena, et al.
(författare)
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Fine-Scale Mapping at 9p22.2 Identifies Candidate Causal Variants That Modify Ovarian Cancer Risk in BRCA1 and BRCA2 Mutation Carriers
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- Population-based genome wide association studies have identified a locus at 9p22.2 associated with ovarian cancer risk, which also modifies ovarian cancer risk in BRCA1 and BRCA2 mutation carriers. We conducted fine-scale mapping at 9p22.2 to identify potential causal variants in BRCA1 and BRCA2 mutation carriers. Genotype data were available for 15,252 (2,462 ovarian cancer cases) BRCA1 and 8,211 (631 ovarian cancer cases) BRCA2 mutation carriers. Following genotype imputation, ovarian cancer associations were assessed for 4,873 and 5,020 SNPs in BRCA1 and BRCA2 mutation carriers respectively, within a retrospective cohort analytical framework. In BRCA1 mutation carriers one set of eight correlated candidate causal variants for ovarian cancer risk modification was identified (top SNP rs10124837, HR: 0.73, 95% CI: 0.68 to 0.79, p-value 2x 10-16). These variants were located up to 20 kb upstream of BNC2. In BRCA2 mutation carriers one region, up to 45 kb upstream of BNC2, and containing 100 correlated SNPs was identified as candidate causal (top SNP rs62543585, HR: 0.69, 95% CI: 0.59 to 0.80, p-value 1.0 x 10-6). The candidate causal in BRCA1 mutation carriers did not include the strongest associated variant at this locus in the general population. In sum, we identified a set of candidate causal variants in a region that encompasses the BNC2 transcription start site. The ovarian cancer association at 9p22.2 may be mediated by different variants in BRCA1 mutation carriers and in the general population. Thus, potentially different mechanisms may underlie ovarian cancer risk for mutation carriers and the general population.
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| 19. |
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| 20. |
- Vågesjö, Evelina, et al.
(författare)
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Perivascular macrophages regulate blood flow following tissue damage
- 2021
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Ingår i: Circulation Research. - : Lippincott Williams & Wilkins. - 0009-7330 .- 1524-4571. ; 128:11, s. 1694-1707
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Tidskriftsartikel (refereegranskat)abstract
- Rationale: Ischemic injuries remain a leading cause of mortality and morbidity worldwide, and restoration of functional blood perfusion is vital to limit tissue damage and support healing.Objective: To reveal a novel role of macrophages in reestablishment of functional tissue perfusion following ischemic injury that can be targeted to improve tissue restoration.Methods and Results: Using intravital microscopy of ischemic hindlimb muscle in mice, and confocal microscopy of human tissues from amputated legs, we found that macrophages accumulated perivascularly in ischemic muscles, where they expressed high levels of iNOS (inducible nitric oxide [NO] synthase). Genetic depletion of iNOS specifically in macrophages (Cx3cr1-CreERT2;Nos2(fl/fl) or LysM-Cre;Nos2(fl/fl)) did not affect vascular architecture but highly compromised blood flow regulation in ischemic but not healthy muscle, which resulted in aggravated ischemic damage. Thus, the ability to upregulate blood flow was shifted from eNOS (endothelial)-dependence in healthy muscles to completely rely on macrophage-derived iNOS during ischemia. Macrophages in ischemic muscles expressed high levels of CXCR4 (C-X-C chemokine receptor type 4) and CCR2 (C-C chemokine receptor type 2), and local overexpression by DNA plasmids encoding the corresponding chemokines CXCL12 (stromal-derived factor 1) or CCL2 (chemokine [C-C motif] ligand 2) increased macrophage numbers, while CXCL12 but not CCL2 induced their perivascular positioning. As a result, CXCL12-overexpression increased the number of perfused blood vessels in the ischemic muscles, improved functional muscle perfusion in a macrophage-iNOS-dependent manner, and ultimately restored limb function.Conclusions: This study establishes a new function for macrophages during tissue repair, as they regulate blood flow through the release of iNOS-produced NO. Further, we demonstrate that macrophages can be therapeutically targeted to improve blood flow regulation and functional recovery of ischemic tissues.
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