Novel critical role of Toll-like receptor 4 in lung ischemia-reperfusion injury and edema.
Toll-like receptors (TLRs) of the innate immune system contribute to noninfectious inflammatory processes. We employed a murine model of hilar clamping (1 h) with reperfusion times between 15 min and 3 h in TLR4-sufficient (C3H/OuJ) and TLR4-deficient (C3H/HeJ) anesthetized mice with additional studies in chimeric and myeloid differentiation factor 88 (MyD88)- and TLR4-deficient mice to determine the role of TLR4 in lung ischemia-reperfusion injury. Human pulmonary microvascular endothelial monolayers were subjected to simulated warm ischemia and reperfusion with and without CRX-526, a competitive TLR4 inhibitor. Functional TLR4 solely on pulmonary parenchymal cells, not bone marrow-derived cells, mediates early lung edema following ischemia-reperfusion independent of MyD88. Activation of MAPKs and NF-kappaB was significantly blunted and/or delayed in lungs of TLR4-deficient mice as a consequence of ischemia-reperfusion injury, but edema development appeared to be independent of activation of these signaling pathways. Pretreatment with a competitive TLR4 inhibitor prevented edema in vivo and reduced actin cytoskeletal rearrangement and gap formation in pulmonary microvascular endothelial monolayers subjected to simulated warm ischemia and reperfusion. In addition to its well-accepted role to alter gene transcription, functioning TLR4 on pulmonary parenchymal cells plays a key role in very early and profound pulmonary edema in murine lung ischemia-reperfusion injury. This may be due to a novel mechanism: regulation of endothelial cell cytoskeleton affecting microvascular endothelial cell permeability.
Zanotti
Giorgio
G
Division of Cardiothoracic Surgery, Cystic Fibrosis Pulmonary Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7065, USA.
Casiraghi
Monica
M
Abano
John B
JB
Tatreau
Jason R
JR
Sevala
Mayura
M
Berlin
Hilary
H
Smyth
Susan
S
Funkhouser
William K
WK
Burridge
Keith
K
Randell
Scott H
SH
Egan
Thomas M
TM
D000199:Actins / Q000378:metabolism; D000818:Animals; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005944:Glucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008024:Ligands; D008168:Lung / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019899:Paracrine Communication / Q000187:drug effects; D011654:Pulmonary Edema / Q000150:complications* / Q000201:enzymology / Q000378:metabolism* / Q000517:prevention & control; D015427:Reperfusion Injury / Q000150:complications* / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052096:Warm Ischemia
D000199:Actins; C501717:CRX-526; D008024:Ligands; D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D020928:Mitogen-Activated Protein Kinases; D005944:Glucosamine