Abstract: SA-PO607
Epidermal Growth Factor Receptor-Dependent TLR7 Signaling in Macrophages Promotes Kidney Injury in Crescentic Glomerulonephritis
Session Information
- Glomerular Diseases: Immunology, Inflammation - II
November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1202 Glomerular Diseases: Immunology and Inflammation
Authors
- Tatsumoto, Narihito, Cedars Sinai Medical Center, Los Angeles, California, United States
- Leal, Daniel N., Cedars Sinai Medical Center, Los Angeles, California, United States
- Rifkin, Ian R., Boston University School of Medicine, Boston, Massachusetts, United States
- Arditi, Moshe, Cedars-Sinai Medical Center, Los Angeles, California, United States
- Yamashita, Michifumi, Cedars-Sinai Medical Center, Los Angeles, California, United States
Background
Epidermal growth factor receptor (EGFR) has been shown to promote glomerular injury in crescentic glomerulonephritis (CRGN) and we showed that EGFR plays pivotal roles in the signaling of endosomal Toll-like receptors (TLRs): TLR3 (Sci Signal. 2012), TLR4 (EMBO Rep. 2015), and TLR9 (J Immunol. 2018). Polymorphisms in TLR7, a sensor for endogenous danger signal, are linked with the development of SLE, and TLR7 activation is implicated in lupus nephritis. Here, we show that EGFR has a critical role in macrophages (MΦs) for TLR7-dependent CRGN.
Methods
To induce nephrotoxic serum nephritis (NTN), a model of CRGN, C57Bl/6 (WT) mice or TLR7-/- mice were immunized with normal rabbit IgG and IFA, and injected with nephrotoxic serum (NTS). These mice were also treated with or without treatment of Gefitinib, an EGFR inhibitor. Seven days after NTS injection, kidney injury was analyzed by proteinuria and histology. In cell culture system, TLR7-mediated gene induction, cytokine production, and cell migration were assessed using bone marrow-derived MΦs and RAW 264.7 cells. The physical interaction between EGFR and TLR7, and tyrosine phosphorylation of TLR7 were analyzed by immunoprecipitation assay.
Results
TLR7-/- mice were resistant to NTN compared to WT mice: TLR7-/- mice showed less severe proteinuria, GBM rupture, crescent formation, and less number of Mac-2 positive MΦs infiltration into glomeruli. None of the glomerular resident cells expressed TLR7 confirmed by protein expression and functional assays in vitro and ex vivo. Only inflammatory MΦs expressed significant amount of functional TLR7. Mechanistically, upon a TLR7 ligand stimulation, TLR7 physically interacted with EGFR in MΦs by co-immunoprecipitation, and tyrosine residue(s) of TLR7 is phosphorylated. However, such a TLR7 phosphorylation is completely blocked by Gefitinib, an EGFR kinase inhibitor. In addition, Gefitinib blocked subsequent cellular function (e.g. cell migration) and cytokine production (e.g. IL-6 production). Finally, Gefitinib treatment on TLR7-/- mice did not show significant additional protective effects on NTN at an early time point (Day 7), compared to TLR7-/- mice without Gefitinib.
Conclusion
These results indicate that regulation of TLR7 signaling in MΦs by EGFR has a critical role in the early pathogenesis of CRGN.
Funding
- Other NIH Support