advances in inflammatory bowel diseases hollywood fl, 2013 pro-inflammatory cytokines alter tight...
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Advances in Inflammatory Bowel DiseasesHollywood FL, 2013
Pro-inflammatory cytokines alter tight junction self-assembly and barrier function through
claudin heterotypic incompatibility.
Christopher T. Capaldo, Ph.D.Emory University
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DISCLOSURES
• Nothing to disclose
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• Barrier defects are linked to IBD.
• Epithelial Tight Junctions provide the paracellular barrier.
• Barrier properties depend on transmembrane claudins.
• Pro-inflammatory cytokines, such as IFN-g and TNF-a, disrupt Tight Junctions and claudin function.
• Tight Junctions are dynamic structures.(Sasaki PNAS, 2003. Shen J Cell Bio.2008)
• Fluorescence Recovery After Photobleaching (FRAP)
• Are these dynamics disrupted in the presence of pro inflammatory cytokines?
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IFN-g/TNF- a increase claudin-4 dynamics
(48hrs)
Fluorescence Recovery After Photobleaching (FRAP)
• Increased recovery• Little or no planar TJ
diffusion.
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IFN-g/TNF- a increases claudin-4 partitioning into the mobile Junction sub-pool.
• Cytokine alter Mf/If partitioning.
• Cytokines do not alter t1/2 of recovery.
• Does this reflect a change in TJ structure?
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cont
rol
Freeze fracture EM
Susanne Krug, Fromm Lab
IFN-g/TNF-a treatment does not alter gross TJ structure.
IFN
-g/T
NF
-a
(200nm)
IFN
-g/T
NF
-a
1 20
20
40
60
80
100
120
140
Ohm
s*cm
2control IFN-g
TNF-a
n=6
If not TJ structure, then is TJ composition changed?
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Claudin-4 excludes claudin-2 from the TJ.
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• Claudin 2 and 4 are heterotypically incompatible across cells, but not within the same cell.
(Daugherty 2007, Piontek, 2011)
• Is this responsible for cytokine-induced changes in mobility?
• Does this play a role in cytokine –induced barrier loss?
Claudin-4 excludes claudin-2 from the TJ.
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Claudin 4 rescues cytokine-induced changes in mobility and barrier function
***
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TJ Immobile stands
Lateral pool
TJ mobile pool
Summary and working model
IFN-g/TNF-a Claudin 4
Claudin 2• IFN-g/TNF- a increase
claudin 2 levels (1).• Claudin 2 competes
with claudin 4 at the junction.
• Resulting in increased mobile pool claudin 4 and lower barrier function over time.
(1. Mankertz, 2009)
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Nusrat labAsma NusratRoland HilgarthMattie FeasleMike KwonAttila FarkasJeremy Benedik
Koval LabParkos LabShroyer Lab
Fromm LabSusanne Krug
Funded by a CCFA Career Development Award