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Cellular and molecular response of human macrophages exposed to Aggregatibacter actinomycetemcomitans leukotoxin.

Kelk P, Abd H, Claesson R, Sandström G, Sjöstedt A, Johansson A - Cell Death Dis (2011)

Bottom Line: This toxin selectively kills human leukocytes by inducing apoptosis and lysis.A. actinomycetemcomitans leukotoxin-induced several cellular and molecular mechanisms in human macrophages that led to a specific and excessive pro-inflammatory response with particular secretion of both interleukin (IL)-1β and IL-18.In addition, this pro-inflammatory cell death was inhibited by oxidized ATP, which indicates involvement of the purinergic receptor P2X(7) in this process.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Periodontology, Department of Odontology, Faculty of Medicine, Umeå University, Umeå, Sweden. peyman.kelk@odont.umu.se

ABSTRACT
Aggregatibacter (Actinobacillus) actinomycetemcomitans is a facultative anaerobic gram-negative bacterium associated with severe forms of periodontitis. A leukotoxin, which belongs to the repeats-in-toxin family, is believed to be one of its virulence factors and to have an important role in the bacterium's pathogenicity. This toxin selectively kills human leukocytes by inducing apoptosis and lysis. Here, we report that leukotoxin-induced cell death of macrophages proceeded through a process that differs from the classical characteristics of apoptosis and necrosis. A. actinomycetemcomitans leukotoxin-induced several cellular and molecular mechanisms in human macrophages that led to a specific and excessive pro-inflammatory response with particular secretion of both interleukin (IL)-1β and IL-18. In addition, this pro-inflammatory cell death was inhibited by oxidized ATP, which indicates involvement of the purinergic receptor P2X(7) in this process. This novel virulence mechanism of the leukotoxin may have an important role in the pathogenic potential of this bacterium and can be a target for future therapeutic agents.

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Related in: MedlinePlus

Effects of oATP on leukotoxin-exposed MNL. The cell morphology (FSC/SSC) and viability (PI-uptake) of leukotoxin-exposed MNL were analyzed by FACS. MNL were exposed to 10 ng/ml leukotoxin with and without oATP (500μM) for up to 60 min. (a) Distribution of FSC/SSC in MNL during leukotoxin exposure. (b) Histogram of FSC of the exposed MNL (Co=0 min exposure, Ltx=10 min exposure). Mean FCS of the MNL population are indicated (c) PI-uptake in MNL during leukotoxin-exposure. Mean values of PI-positive cells are indicated. All the figures show representative results from three experiments with different macrophage donors. Mean values±S.D. are shown
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fig5: Effects of oATP on leukotoxin-exposed MNL. The cell morphology (FSC/SSC) and viability (PI-uptake) of leukotoxin-exposed MNL were analyzed by FACS. MNL were exposed to 10 ng/ml leukotoxin with and without oATP (500μM) for up to 60 min. (a) Distribution of FSC/SSC in MNL during leukotoxin exposure. (b) Histogram of FSC of the exposed MNL (Co=0 min exposure, Ltx=10 min exposure). Mean FCS of the MNL population are indicated (c) PI-uptake in MNL during leukotoxin-exposure. Mean values of PI-positive cells are indicated. All the figures show representative results from three experiments with different macrophage donors. Mean values±S.D. are shown

Mentions: Analysis of MNL structure (forward scatter (FSC)–side scatter (SSC)) examined by FACS showed a time-dependant selective depletion of the macrophage population (with high FSC/SSC) caused by the leukotoxin (10 ng/ml) that was blocked in presence of oATP (Figure 5a). Leukotoxin (10 ng/ml) caused also an enhanced FSC after 10 min exposure, which was not affected by the added oATP (Figure 5b). The PI-uptake analysis by FACS showed that leukotoxin (10 ng/ml) caused a time-dependant cell death of MNL that was inhibited by oATP (Figure 5c).


Cellular and molecular response of human macrophages exposed to Aggregatibacter actinomycetemcomitans leukotoxin.

Kelk P, Abd H, Claesson R, Sandström G, Sjöstedt A, Johansson A - Cell Death Dis (2011)

Effects of oATP on leukotoxin-exposed MNL. The cell morphology (FSC/SSC) and viability (PI-uptake) of leukotoxin-exposed MNL were analyzed by FACS. MNL were exposed to 10 ng/ml leukotoxin with and without oATP (500μM) for up to 60 min. (a) Distribution of FSC/SSC in MNL during leukotoxin exposure. (b) Histogram of FSC of the exposed MNL (Co=0 min exposure, Ltx=10 min exposure). Mean FCS of the MNL population are indicated (c) PI-uptake in MNL during leukotoxin-exposure. Mean values of PI-positive cells are indicated. All the figures show representative results from three experiments with different macrophage donors. Mean values±S.D. are shown
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3101819&req=5

fig5: Effects of oATP on leukotoxin-exposed MNL. The cell morphology (FSC/SSC) and viability (PI-uptake) of leukotoxin-exposed MNL were analyzed by FACS. MNL were exposed to 10 ng/ml leukotoxin with and without oATP (500μM) for up to 60 min. (a) Distribution of FSC/SSC in MNL during leukotoxin exposure. (b) Histogram of FSC of the exposed MNL (Co=0 min exposure, Ltx=10 min exposure). Mean FCS of the MNL population are indicated (c) PI-uptake in MNL during leukotoxin-exposure. Mean values of PI-positive cells are indicated. All the figures show representative results from three experiments with different macrophage donors. Mean values±S.D. are shown
Mentions: Analysis of MNL structure (forward scatter (FSC)–side scatter (SSC)) examined by FACS showed a time-dependant selective depletion of the macrophage population (with high FSC/SSC) caused by the leukotoxin (10 ng/ml) that was blocked in presence of oATP (Figure 5a). Leukotoxin (10 ng/ml) caused also an enhanced FSC after 10 min exposure, which was not affected by the added oATP (Figure 5b). The PI-uptake analysis by FACS showed that leukotoxin (10 ng/ml) caused a time-dependant cell death of MNL that was inhibited by oATP (Figure 5c).

Bottom Line: This toxin selectively kills human leukocytes by inducing apoptosis and lysis.A. actinomycetemcomitans leukotoxin-induced several cellular and molecular mechanisms in human macrophages that led to a specific and excessive pro-inflammatory response with particular secretion of both interleukin (IL)-1β and IL-18.In addition, this pro-inflammatory cell death was inhibited by oxidized ATP, which indicates involvement of the purinergic receptor P2X(7) in this process.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Periodontology, Department of Odontology, Faculty of Medicine, Umeå University, Umeå, Sweden. peyman.kelk@odont.umu.se

ABSTRACT
Aggregatibacter (Actinobacillus) actinomycetemcomitans is a facultative anaerobic gram-negative bacterium associated with severe forms of periodontitis. A leukotoxin, which belongs to the repeats-in-toxin family, is believed to be one of its virulence factors and to have an important role in the bacterium's pathogenicity. This toxin selectively kills human leukocytes by inducing apoptosis and lysis. Here, we report that leukotoxin-induced cell death of macrophages proceeded through a process that differs from the classical characteristics of apoptosis and necrosis. A. actinomycetemcomitans leukotoxin-induced several cellular and molecular mechanisms in human macrophages that led to a specific and excessive pro-inflammatory response with particular secretion of both interleukin (IL)-1β and IL-18. In addition, this pro-inflammatory cell death was inhibited by oxidized ATP, which indicates involvement of the purinergic receptor P2X(7) in this process. This novel virulence mechanism of the leukotoxin may have an important role in the pathogenic potential of this bacterium and can be a target for future therapeutic agents.

Show MeSH
Related in: MedlinePlus