TLR4 activation mediates kidney ischemia/reperfusion injury.
Ischemia/reperfusion injury (IRI) may activate innate immunity through the engagement of TLRs by endogenous ligands. TLR4 expressed within the kidney is a potential mediator of innate activation and inflammation. Using a mouse model of kidney IRI, we demonstrated a significant increase in TLR4 expression by tubular epithelial cells (TECs) and infiltrating leukocytes within the kidney following ischemia. TLR4 signaling through the MyD88-dependent pathway was required for the full development of kidney IRI, as both TLR4(-/-) and MyD88(-/-) mice were protected against kidney dysfunction, tubular damage, neutrophil and macrophage accumulation, and expression of proinflammatory cytokines and chemokines. In vitro, WT kidney TECs produced proinflammatory cytokines and chemokines and underwent apoptosis after ischemia. These effects were attenuated in TLR4(-/-) and MyD88(-/-) TECs. In addition, we demonstrated upregulation of the endogenous ligands high-mobility group box 1 (HMGB1), hyaluronan, and biglycan, providing circumstantial evidence that one or more of these ligands may be the source of TLR4 activation. To determine the relative contribution of TLR4 expression by parenchymal cells or leukocytes to kidney damage during IRI, we generated chimeric mice. TLR4(-/-) mice engrafted with WT hematopoietic cells had significantly lower serum creatinine and less tubular damage than WT mice reconstituted with TLR4(-/-) BM, suggesting that TLR4 signaling in intrinsic kidney cells plays the dominant role in mediating kidney damage.
Wu
Huiling
H
Collaborative Transplant Research Group, Royal Prince Alfred Hospital and Bosch Institute, Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia. huilingw@med.usyd.edu.au
Chen
Gang
G
Wyburn
Kate R
KR
Yin
Jianlin
J
Bertolino
Patrick
P
Eris
Josette M
JM
Alexander
Stephen I
SI
Sharland
Alexandra F
AF
Chadban
Steven J
SJ
D000818:Animals; D017209:Apoptosis; D058578:Biglycan; D018925:Chemokines / Q000235:genetics / Q000378:metabolism; D002678:Chimera / Q000378:metabolism; D003401:Creatine / Q000097:blood; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D024243:HMGB1 Protein / Q000378:metabolism; D006820:Hyaluronic Acid / Q000378:metabolism; D007668:Kidney / Q000098:blood supply* / Q000737:chemistry / Q000473:pathology; D008024:Ligands; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D015427:Reperfusion Injury / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism
C546885:Bgn protein, mouse; D058578:Biglycan; D018925:Chemokines; D016207:Cytokines; D016326:Extracellular Matrix Proteins; D024243:HMGB1 Protein; D008024:Ligands; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D011509:Proteoglycans; D012333:RNA, Messenger; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D006820:Hyaluronic Acid; D003401:Creatine