Kidney Week

Abstract: TH-PO469

Macrophage IRF4 Deletion Protects Against Renal Fibrosis as a Result of Decreased Macrophage Recruitment and Activation

Session Information

• CKD: Mechanisms - I
  November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2103 CKD (Non-Dialysis): Mechanisms

Authors

• Sasaki, Kensuke, Vanderbilt University Medical School, Nashville, Tennessee, United States

Kensuke Sasaki,

• Pan, Yu, Vanderbilt University Medical School, Nashville, Tennessee, United States

Yu Pan,

• Jin, Guannan, Vanderbilt University Medical School, Nashville, Tennessee, United States

Guannan Jin,

• Niu, Aolei, Vanderbilt University Medical School, Nashville, Tennessee, United States

Aolei Niu,

• Wang, Yinqiu, Vanderbilt University Medical School, Nashville, Tennessee, United States

Yinqiu Wang,

• Wang, Suwan, Vanderbilt University Medical School, Nashville, Tennessee, United States

Suwan Wang,

• Fan, Xiaofeng, Vanderbilt University Medical School, Nashville, Tennessee, United States

Xiaofeng Fan,

• Harris, Raymond C., Vanderbilt University Medical School, Nashville, Tennessee, United States

Raymond C. Harris,

• Zhang, Ming-Zhi, Vanderbilt University Medical School, Nashville, Tennessee, United States

Ming-Zhi Zhang,

Background

Macrophage infiltration and polarization plays a key role in recovery from acute kidney injury (AKI). Previous studies have indicated that persistent and aberrant presence of M2 macrophages leads to renal fibrosis after AKI. Interferon regulatory factor 4 (IRF4) plays an important role in macrophage M2 polarization. We examined the role of macrophage IRF4 in renal macrophage polarization and development of fibrosis after AKI.

Methods

Wild type (WT, IRF4^f/f) or LysM-Cre; IRF4^f/f (macrophage IRF4^-/-) mice (male, 3 months, C57BL/6) were uninephrectomized, immediately followed by 32 min ischemia-reperfusion injury. Renal macrophages were isolated with a mixture of CD11b and CD11c microbeads. Bone marrow derived monocytes (BMDMs) were isolated and used for in vitro transwell migration and in vivo PHK26-labeled BMDM migration into injury WT kidneys. Peritonitis was induced by peritoneal injection of 3 ml of 4% thioglycolate.

Results

Compared to WT mice, LysM-Cre; IRF4^f/f mice developed less renal fibrosis 4 weeks after severe AKI, as indicated by Sirius red staining and decreased profibrotic and fibrotic components including TGF-β1, TGF-β2, CTGF, α-SMA, fibronectin, and collagens I, III, IV. LysM-Cre; IRF4^f/f mice had significantly fewer renal macrophages with less activation, as indicated by decreases in both Th1/M1 proinflammatory cytokines (TNF-α, MCP-1, IL-1α, IL-6, and IL-23α) and Th2/M2 pro-fibrotic cytokines (FIZZ1, CD206, CD209, B7-H4, IL-4Rα, and arginase 1). Flow cytometry and qPCR also determined low number and less activated renal macrophages (low levels of both Th1/M1 and Th2/M2 cytokines) in LysM-Cre; IRF4^f/f compared to WT mice at 1 and 5 days after AKI. An in vitro migration assay showed that IRF4-/- BMDMs had decreased migratory ability. IRF4-/- BMDMs also had decreased ability to infiltrate into injured kidney as indicated by fewer renal PKH26 and F4/80 double positive cells. Finally, LysM-Cre; IRF4^f/f mice had attenuated peritoneal macrophage infiltration in thioglycolate-induced peritonitis.

Conclusion

Macrophage IRF4 deletion protects against renal fibrosis after severe AKI, at least due in part to attenuated macrophage recruitment and activation in response to kidney injury, leading to decreased renal pro-fibrotic M2 macrophages.

Funding

• NIDDK Support