Kidney Week

Abstract: FR-PO126

Regnase-3 in Kidney-Resident MØ Controls Severity of AKI and AKI-CKD Transition by Degrading Pre-mRNAs That Drive Their Polarization Towards a Pro-Inflammatory M1 Phenotype

Session Information

• AKI: Mechanisms - II
  November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Li, Chenyu, Klinikum der Universitat Munchen Medizinische Klinik und Poliklinik IV - Standort Ziemssenstrasse, Munchen, Bayern, Germany

Chenyu Li,

• Marschner, Julian A., Klinikum der Universitat Munchen Medizinische Klinik und Poliklinik IV - Standort Ziemssenstrasse, Munchen, Bayern, Germany

Julian A. Marschner,

• Steiger, Stefanie, Klinikum der Universitat Munchen Medizinische Klinik und Poliklinik IV - Standort Ziemssenstrasse, Munchen, Bayern, Germany

Stefanie Steiger,

• Zhao, Zhibo, Klinikum der Universitat Munchen Medizinische Klinik und Poliklinik IV - Standort Ziemssenstrasse, Munchen, Bayern, Germany

Zhibo Zhao,

• Anders, Hans J., Klinikum der Universitat Munchen Medizinische Klinik und Poliklinik IV - Standort Ziemssenstrasse, Munchen, Bayern, Germany

Hans J. Anders,

Background

Kidney resident macrophages (Mø) are involved in regulating AKI-CKD transition (PNAS 2021). The mRNA regulatory enzyme Regnase-3 is specifically expressed in Mø and involved in the interferon-γ signaling pathway (J Exp Med. 2019). Here we speculated that Regnase-3 would represent a kidney resident Mø-specific immune checkpoint that limits necroinflammation in AKI and AKI-CKD transition.

Methods

We generated transgenic mice with a conditional resident-Mø-specific Regnase-3 KO (Rank^Cre/WT; Regnase3^flox/flox, [Reg3cKO]) that bred at Mendelian ratios. 6-8 week-old mice were subjected to a unilateral ischemia-reperfusion injury (IRI) with or without nephrectomy (uNX). We measured GFR before and 1, 3, 7, 14, and 21 days after uIRI. In vitro, we stimulated Reg3cKO bone-marrow-derived Mø with H₂O₂ and assessed cell metabolism, migration, and phagocytosis.

Results

After uIRI, the GFR significantly dropped in both WT and Reg3cKO mice at day 1. However, in Reg3cKO mice kidney function failed to fully recover compared with WT mice as indicated by the GFR at day 21 after uIRI. Serum creatinine as well as intrarenal Kim-1, Ngal, Timp2, and Tnfα mRNA levels were also higher in Reg3cKO mice together with more IFTA and interstitial F4/80+ cell infiltrates. Because uIRI is a model of persistent post-AKI ischemia, we turned to uIRI+uNX, an AKI model that restores reperfusion. Similarly, Reg3cKO mice showed delayed GFR recovery with only ~30% of baseline GFR at day 3 but ~50% for WT mice. In both Reg3cKO and WT mice the GFR fully recovered at day 14 after uIRI+uNX. However, the levels of Kim-1 and Ngal remained still higher in Reg3cKO mice with more IFTA and F4/80+ cell infiltrates. In vitro, after H₂O₂ incubation, M0 and M1 but not M2 Reg3cKO Mø showed higher metabolic, migratory, and phagocytic capacity, as well as higher expression levels of CCR2/5, IL6, and TNFα T than WT, indicative of M1 Mø.

Conclusion

Regnase-3 might act as a negative regulator of resident Mø polarization towards an M1 phenotype, which contributes to the early injury phase of AKI and AKI-CKD transition. Mechanistically, Regnase-3 is likely to degrade certain preRNAs to limit the expression of pro-inflammatory cytokines/chemokines and chemokine receptors during kidney necroinflammation.