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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Research Article Nephrology

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 13

Functional TLR4 on intrinsic kidney cells makes the more significant contribution to kidney damage.

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Functional TLR4 on intrinsic kidney cells makes the more significant con...
WT/WTBM mice showed significant kidney dysfunction and injury at day 1 after ischemia/reperfusion, while TLR4–/–/TLR4–/–BM chimeric mice were protected from kidney IRI as measured by day 1 serum creatinine (A) and tubular damage (B). Creatinine levels and tubular injury scores replicated those observed in WT and TLR4–/– mice (Figures 5 and 6), excluding an effect of the BM transplant procedure per se on the response to renal ischemia. Moreover, TLR4–/–/WTBM chimeras were protected from kidney IRI to the same degree as TLR4–/–/TLR4–/–BM mice, while WT/TLR4–/–BM mice enjoyed only partial protection as assessed by day 1 serum creatinine and tubular damage (A and B). Data shown are mean ± SD. n = 7–10 per group. *P < 0.05, **P < 0.01, *** P < 0.001. Full replacement of hematopoietic cells in the chimeric mice was confirmed by genotyping of genomic DNA from whole blood using PCR. PCR products shown on representative gels (C). The top panel represents PCR products for the WT allele DNA, and the bottom panel represents PCR products for the mutated allele DNA (lanes 1–2: WT/WTBM; lanes 3–4: WT/TLR4–/–BM; lanes 5–6: TLR4–/–/WTBM; lanes 7–8: TLR4–/–/ TLR4–/–BM; lane 9: TLR4 heterozygous blood as positive controls; and lane 10: negative controls).