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Crohn's Disease Forum » Books, Multimedia, Research & News » Subversion of Autophagy in AIEC-Infected Neutrophils Induces Inflammation and Cell Death


12-21-2012, 05:53 PM   #1
kiny
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Subversion of Autophagy in AIEC-Infected Neutrophils Induces Inflammation and Cell Death

FULL: http://www.plosone.org/article/info%...l.pone.0051727


Subversion of Autophagy in Adherent Invasive Escherichia coli-Infected Neutrophils Induces Inflammation and Cell Death


Abderrahman Chargui, Annabelle Cesaro, Sanda Mimouna, Mohamed Fareh, Patrick Brest, Philippe Naquet, Arlette Darfeuille-Michaud, Xavier Hébuterne, Baharia Mograbi , Valérie Vouret-Craviari , Paul Hofman

Faculté de Médecine, Nice, France

December 14, 2012

Abstract

Invading bacteria are recognized, captured and killed by a specialized form of autophagy, called xenophagy. Recently, defects in xenophagy in Crohn’s disease (CD) have been implicated in the pathogenesis of human chronic inflammatory diseases of uncertain etiology of the gastrointestinal tract. We show here that pathogenic adherent-invasive Escherichia coli (AIEC) isolated from CD patients are able to adhere and invade neutrophils, which represent the first line of defense against bacteria. Of particular interest, AIEC infection of neutrophil-like PLB-985 cells blocked autophagy at the autolysosomal step, which allowed intracellular survival of bacteria and exacerbated interleukin-8 (IL-8) production. Interestingly, this block in autophagy correlated with the induction of autophagic cell death. Likewise, stimulation of autophagy by nutrient starvation or rapamycin treatment reduced intracellular AIEC survival and IL-8 production. Finally, treatment with an inhibitor of autophagy decreased cell death of AIEC-infected neutrophil-like PLB-985 cells. In conclusion, excessive autophagy in AIEC infection triggered cell death of neutrophils.



figure 2. Inhibition of autophagic flux by AIEC LF82 infection.

Human neutrophils or neutrophil-like PLB-985 cells were infected with AIEC LF82 at a MOI of 50 for 1 h than gentamicin (100 µg/ml) was added for 3 h.

Cells were and processed for immunoblotting (A, left panel, B), quantitative RT-PCR (A rigth panel), immunofluorescence (C, D) and ultrastructural TEM analysis (E).

(A)
Time-dependent accumulation (1–8 h) of LC3-II and p62 in infected human neutrophils or neutrophil-like PLB-985 cells compared to uninfected cells analyzed at the end time point. Longer exposure detects the LC3-I band. We checked that AIEC infection did not affect p62 mRNA levels by qRT-PCR analysis

(A right panel). Data are means ± SEM of three experiments. ** p<0.001.

(B) Autophagic flux was analysed by immunoblot analysis in differentiated PLB-985 cells infected for 3 h with AIEC LF82 bacteria (MOI 50) in the absence or in the presence of E64d/PEPS. Actin was used as a loading control. Control unstimulated cells were analysed at the end time point.

(C) Representative confocal images of control (0) or infected cells (LF82) (3 h post infection) showed the colocalization of bacteria with LC3-II and LAMP-1 proteins as indicated by yellow punctiform staining. Insets highlight individual staining of bacteria (DNA staining, blue), LC3-II (Alexa 488, green) and LAMP-1 (Alexa 594, red).

(D) Representative confocal micrographs of control (0) and LF82 infected cells (LF82) showing the co-localization of bacteria (DNA staining, blue) within autophagic (LC3-II positive, Alexa 594, red) but not acidic compartments (LysoTracker negative, green).

(E) Representative TEM images showing bacteria within endosomes (asterisk), autophagosomes (arrowheads) or free in the cytosol (arrow) in LF82-infected cells (3 h post infection). Bar = 2 µm.

Last edited by kiny; 12-21-2012 at 06:15 PM.
12-24-2012, 12:20 AM   #2
Mark in Seattle
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Another great article. I'm afraid however that I'm going to have to wait for the movie to come out before I can fully understand and appreciate many of the fine details mentioned herein.
12-24-2012, 01:37 AM   #3
kiny
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Another great article. I'm afraid however that I'm going to have to wait for the movie to come out before I can fully understand and appreciate many of the fine details mentioned herein.
idk, I do not understand everything, but I do understand a lot more than I used to. I rewrote it in a summary, hope everything is correct.



-Neuthrophils activate autophagy in response to LF82 infection and try to limit inflammation.

-But LF82 disturb authopagy and neutrophils that are supposed to control LF82 die through autophagic cell death.

-LF82 infection upregulates IL-8 production resulting in inflammation.

-Some people with crohn's disease already have genetic immune deficiencies through ATG16L1 and NOD2 mutations wich limits bacterial recognition and impairs autophagy, promoting long-term chronic inflammation.


Some other study said it nicely, AIEC are trojan horses. They exploit the host's defense mechanism, and their genetic predisposition, to ensure their survival.
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Mutations of genes responsible for autophagy woud not result in one disease, lots of pathogens would exploit hosts with a weakened immune response. Crohn's disease is not one disease, it's an umbrella of diseases that are clinically similar.

Last edited by kiny; 12-24-2012 at 02:48 AM.
12-24-2012, 03:24 AM   #4
helena101
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Very interesting. Thanks for the summary Kiny, it helped a lot.
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