Renal collecting duct epithelial cells regulate inflammation in tubulointerstitial damage in mice
Katsuhito Fujiu, Ichiro Manabe, Ryozo Nagai
Katsuhito Fujiu, Ichiro Manabe, Ryozo Nagai
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Research Article Nephrology

Renal collecting duct epithelial cells regulate inflammation in tubulointerstitial damage in mice

Abstract

Renal tubulointerstitial damage is the final common pathway leading from chronic kidney disease to end-stage renal disease. Inflammation is clearly involved in tubulointerstitial injury, but it remains unclear how the inflammatory processes are initiated and regulated. Here, we have shown that in the mouse kidney, the transcription factor Krüppel-like factor–5 (KLF5) is mainly expressed in collecting duct epithelial cells and that Klf5 haploinsufficient mice (Klf5+/– mice) exhibit ameliorated renal injury in the unilateral ureteral obstruction (UUO) model of tubulointerstitial disease. Additionally, Klf5 haploinsufficiency reduced accumulation of CD11b+F4/80lo cells, which expressed proinflammatory cytokines and induced apoptosis among renal epithelial cells, phenotypes indicative of M1-type macrophages. By contrast, it increased accumulation of CD11b+F4/80hi macrophages, which expressed CD206 and CD301 and contributed to fibrosis, in part via TGF-β production — phenotypes indicative of M2-type macrophages. Interestingly, KLF5, in concert with C/EBPα, was found to induce expression of the chemotactic proteins S100A8 and S100A9, which recruited inflammatory monocytes to the kidneys and promoted their activation into M1-type macrophages. Finally, assessing the effects of bone marrow–specific Klf5 haploinsufficiency or collecting duct– or myeloid cell–specific Klf5 deletion confirmed that collecting duct expression of Klf5 is essential for inflammatory responses to UUO. Taken together, our results demonstrate that the renal collecting duct plays a pivotal role in the initiation and progression of tubulointerstitial inflammation.

Authors

Katsuhito Fujiu, Ichiro Manabe, Ryozo Nagai

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Figure 6

KLF5 induces accumulation of M1 macrophages via S100A8 and S100A9.

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KLF5 induces accumulation of M1 macrophages via S100A8 and S100A9. (A) A...
(A) Activation of RAW264.7 macrophage migration by mIMCD-3 cells overexpressing KLF5. As shown schematically, mIMCD-3 and RAW264.7 cells were plated in the bottom wells and inserts, respectively. The mIMCD-3 cells were infected with empty adenovirus (Ad-empty), adenovirus expressing β-galactosidase (Ad-LacZ), or adenovirus expressing KLF5 (Ad-KLF5), as indicated. The numbers of cells that migrated through the porous membranes per high-power field (HPF) during the 8-hour incubation are shown. n = 12. *P < 0.05. (B and C) Levels of S100a8 and S100a9 transcription in mIMCD-3 cells overexpressing KLF5. Relative levels of S100a8 and S100a9 transcripts were determined by real-time PCR (B). n = 6. *P < 0.05. In C, expression of KLF5, S100A8, S100A9 protein and β-galactosidase were assessed by Western blotting. β-Tubulin was used as a loading control. (D) Effects of recombinant S100A8 and S100A9 on RAW264.7 cell migration. Recombinant S100A8 and/or S100A9 were added to the medium in the lower wells, as shown. n = 6. *P < 0.05 versus migrated cells without S100 proteins; #P < 0.05. (E) Effects of S100a8 and/or S100a9 knockdown in mIMCD-3 cells overexpressing KLF5 on RAW264.7 migration. mIMCD-3 cells overexpressing KLF5 were transfected with siRNAs against S100a8 and S100a9 or control siRNA (siCtrl), as indicated, after which they were plated in the bottom wells, as shown. The numbers of RAW264.7 cells that migrated during the 8-hour incubation are shown. n = 6. *P < 0.05.