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Francisella tularensis infection induces macrophage cell death
Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
2004 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Francisella tularensis, the causative agent of tularemia, is a potent human and animal pathogen. Its principal survival mechanism is rapid intracellular multiplication. The mechanisms that enables it to multiply intracellularly have been ill-defined and the thesis focused on characterizing the outcome of the macrophage-Francisella interaction and also if the interactions differ between the various subspecies of F tularensis.

The nature of host cell death was examined and the correlation of macrophage killing with intramacrophage Francisella growth was investigated by in vitro infection of J774A.1 macrophages with either the live vaccine (LVS) strain of F. tularensis, belonging to subspecies holarctica, or the subspecies novicida strain U112 Macrophage entry was in both cases cytochalasin D-sensitive but the intramacrophage growth of the two Francisella strains led to distinct types of host cell death, i.e., apoptosis vs. necrosis.

The macrophage apoptosis induced by infection with the LVS strain was mediated via the intrinsic pathway with critical involvement of caspase-3 and the mitochondria. The infected and apoptotic macrophages were shrunken, their chromatin was specifically degraded and revealed a typical DNA ladder pattern upon electrophoresis. Moreover, they were TUNEL positive, indicating the occurrence of apoptosis-dependent DNA fragmentation. The necessity of intracellular growth for the apoptosis was shown by the use of an isogenic mutant, denoted iglC, which lacked the ability to multiply intracellularly and this infection did not result in apoptosis.

The F. novicida strain U112, on the other hand, inhibited NF- B activity and ultimately induced macrophage necrosis. The infected and necrotic macrophages were enlarged, their chromatin was randomly degraded which gave a diffuse DNA pattern typical of necrosis. There was no apoptosis-specific caspase activation. By the use of an isogenic mutant, denoted mglA, it was shown that intracellular replication was necessary for the induction of necrosis. A hemolytic protein, novilysin A, was found in the F. novicida strain U112 but lacking in other subspecies of F. tularensis. The protein is a putative virulence factor but most likely not involved in the induction of necrosis. Its significance for the pathogenesis of F. novicida remains to be determined.

The findings of the thesis provide a detailed picture of the interaction between the host cells and various subspecies of F. tularensis. It also shows that the outcome of the interaction is critically dependent on the type of F. tularensis subspecies. The findings also question the use of F. novicida as a model organism for understanding pathogenicity mechanisms of the species in general. The induction of the host cell death is presumably an important mechanism for the survival of F. tularensis since it allows the bacterium to escape from cells deplete of nutrients and subsequently to invade cells with an intact supply of nutrients necessary for its continuous multiplication.

Ort, förlag, år, upplaga, sidor
Umeå: Klinisk bakteriologi , 2004. , s. 89
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 899
Forskningsämne
klinisk bakteriologi
Identifikatorer
URN: urn:nbn:se:umu:diva-295ISBN: 91-7305-671-5 (tryckt)OAI: oai:DiVA.org:umu-295DiVA, id: diva2:142975
Disputation
2004-05-27, Sal E 04, By 6 E, Norrlands Universitetssjukhus, 13:00
Opponent
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2010-08-03Bibliografiskt granskad
Delarbeten
1. Fancisella tularensis induces cytopathogenicity and apaptosis in murine macrophages via a mechanism that requires intracellular bacterial multiplication
Öppna denna publikation i ny flik eller fönster >>Fancisella tularensis induces cytopathogenicity and apaptosis in murine macrophages via a mechanism that requires intracellular bacterial multiplication
2001 (Engelska)Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 69, nr 7, s. 4691-4694Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The murine macrophage-like cell line J774.A1 ingests and allows intracellular growth of Francisella tularensis. We demonstrate that, after 24 h of infection, a pronounced cytopathogenicity resulted and the J774 cells were undergoing apoptosis. Despite this host cell apoptosis, no decrease in bacterial numbers was observed. When internalization of bacteria was prevented or intracellularly located F. tularensis bacteria were eradicated within 12 h, the progression of host cell cytopathogenicity and apoptosis was prevented.

Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:umu:diva-4023 (URN)10.1128/IAI.69.7.4691-4694.2001 (DOI)11402018 (PubMedID)
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
2. Delineation of the molecular mechanisms of Francisella tularensis-induced apoptosis in murine macrophages
Öppna denna publikation i ny flik eller fönster >>Delineation of the molecular mechanisms of Francisella tularensis-induced apoptosis in murine macrophages
2003 (Engelska)Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 71, nr 8, s. 4642-4646Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Francisella tularensis is a facultative intracellular bacterium capable of inducing apoptosis in murine macrophages. Here we analyzed the pathway leading to apoptosis in the murine macrophage-like cell line J774A.1 after infection with F. tularensis strain LVS (named LVS for live vaccine strain). We obtained evidence that the infection affected the mitochondria of the macrophages, since it induced release of the mitochondrial molecule cytochrome c into the cytosol and changed the potential over the mitochondrial membrane. Moreover, activation of caspase 9 and the executioner caspase 3 was also observed in the LVS-infected J774A.1 macrophages. The activated caspase 3 degraded poly(ADP-ribose) polymerase (PARP). All of these events were observed within 9 to 12 h after the initiation of infection, and maximum degradation of a synthetic caspase 3 substrate occurred at 18 h. The internucleosomal fragmentation and PARP degradation resulting from activation of this apoptotic pathway was prevented by the caspase 3 inhibitor Z-DEVD-fmk. No involvement of caspase 1, caspase 8, Bcl-2, or Bid was observed. Thus, the F. tularensis infection induces macrophage apoptosis through a pathway partly resembling the intrinsic apoptotic pathway.

Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:umu:diva-4024 (URN)10.1128/IAI.71.8.4642-4646.2003 (DOI)12874344 (PubMedID)
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
3. Expression of iglC is mecessary for intracellular growth and induction of apoptosis in murine macrophages by Francisella tularensis
Öppna denna publikation i ny flik eller fönster >>Expression of iglC is mecessary for intracellular growth and induction of apoptosis in murine macrophages by Francisella tularensis
2004 (Engelska)Ingår i: Microbial Pathogenesis, ISSN 0882-4010, E-ISSN 1096-1208, Vol. 37, nr 5, s. 225-230Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Francisella tularensis is a facultative intracellular bacterium capable of inducing apoptosis in murine macrophages. In a previous study, an iglC null mutant of F. tularensis live vaccine strain LVS was generated by allelic replacement and in the current study this iglC mutant was successfully complemented in trans. We characterized the capacity of this iglC mutant and the complemented strain to induce macrophage apoptosis. The iglC mutant did not induce apoptosis in the infected cells. In contrast, the complemented iglC strain was able to multiply in the murine macrophage-like cell line J774A.1 and induced apoptosis similar to that of the wild-type strain. It is the first successful example of complementation in trans of a F. tularensis mutant strain and more importantly this work provides direct evidence that the intracellular growth ability is essential for F. tularensis to induce macrophage apoptosis.

Ort, förlag, år, upplaga, sidor
London: Academic P., 2004
Nyckelord
Intracellular bacterial growth, Francisella, Macrophage apoptosis, Intracellular growth locus C (iglC), Allelic replacement, Trans-complementation
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:umu:diva-4025 (URN)10.1016/j.micpath.2004.07.002 (DOI)15519043 (PubMedID)
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
4. Infection with Francisella novicida leads to killing of murine macrophages by necrosis
Öppna denna publikation i ny flik eller fönster >>Infection with Francisella novicida leads to killing of murine macrophages by necrosis
Visa övriga...
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:umu:diva-4026 (URN)
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
5. Francisella strains express hemolysins of distinct characteristics
Öppna denna publikation i ny flik eller fönster >>Francisella strains express hemolysins of distinct characteristics
2003 (Engelska)Ingår i: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 224, nr 1, s. 91-95Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Historically, Francisella strains have been described as nonhemolytic. In this study, we show by use of solid and liquid hemolysis assays that some Francisella strains have hemolytic properties. The Francisella novicida type strain U112 is hemolytic to horse erythrocytes and Francisella philomiragia type strain FSC144 is hemolytic towards both human and horse erythrocytes. The F. novicida strain U112 released a protein (novilysin A) into the culture supernatant which cross-reacted with antiserum against Escherichia coli HlyA whereas there was no similar protein detectable with this cross-reactive property from the supernatant of the F. philomiragia strain.

Ort, förlag, år, upplaga, sidor
Elsevier, 2003
Nyckelord
Hemolysin, Novilysin A, Virulence factor, Growth-phase dependence, Francisella
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:umu:diva-4027 (URN)10.1016/S0378-1097(03)00431-2 (DOI)12855173 (PubMedID)
Tillgänglig från: 2004-06-23 Skapad: 2004-06-23 Senast uppdaterad: 2019-01-22Bibliografiskt granskad

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