TLR4 activation mediates kidney ischemia/reperfusion injury
Huiling Wu, … , Alexandra F. Sharland, Steven J. Chadban
Huiling Wu, … , Alexandra F. Sharland, Steven J. Chadban
Published October 1, 2007
Citation Information: J Clin Invest. 2007;117(10):2847-2859. https://doi.org/10.1172/JCI31008.
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TLR4 activation mediates kidney ischemia/reperfusion injury

Abstract

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.

Authors

Huiling Wu, Gang Chen, Kate R. Wyburn, Jianlin Yin, Patrick Bertolino, Josette M. Eris, Stephen I. Alexander, Alexandra F. Sharland, Steven J. Chadban

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Figure 11

Proinflammatory cytokine and chemokine gene expression in primary cultured TECs submitted to 1 hour ischemia in vitro.

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Proinflammatory cytokine and chemokine gene expression in primary cultur...
(A) Immunofluorescence staining of primary cultured TECs from C57BL/6 mice with mAbs against cytokeratin (green) and nuclear staining with DAPI in blue. Original magnification, ×400. (B) mRNA expression of proinflammatory cytokines (IL-6, IL-1β, and TNF-α) and chemokines (MIP-2 and MCP-1) in TLR4–/– and MyD88–/– primary cultured TECs submitted to 1 hour ischemia in vitro was significantly reduced at 1 hour after medium replacement as compared with WT controls. The results have been normalized by expressing the number of transcript copies as a ratio to GAPDH. These data are representative of 3 experiments. The comparison between TLR4–/– or MyD88–/– TECs and WT controls is indicated by asterisks. #P < 0.001.