Kidney Week

Abstract: FR-PO744

Genetic NRF2 Activation Worsens Kidney Injury in an Alport Syndrome Mouse Model

Session Information

• Glomerular Diseases: Mechanisms and Podocyte Biology
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology

Authors

• Ng, Desmond, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Desmond Ng

• Hartman, Hannah L., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Hannah L. Hartman

• Yeh, Hsuan, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Hsuan Yeh, MD

• Gilbert, Josie, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Josie Gilbert

• Stewart, Joy A., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Joy A. Stewart

• Bondi, Corry D., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Corry D. Bondi, MS, PhD

• Miner, Jeffrey H., Washington University in St Louis School of Medicine, St Louis, Missouri, United States

Jeffrey H. Miner, PhD, FASN

• Tan, Roderick J., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Roderick J. Tan, MD, PhD

Background

Alport syndrome (AS) is caused by mutations in type IV collagen, resulting in abnormal glomerular basement membrane, proteinuria, and progressive kidney disease. The KEAP1/NRF2 pathway mitigates cellular damage through upregulation of antioxidant and detoxifying genes. KEAP1 is an endogenous inhibitor of NRF2. Bardoxolone methyl (CDDO-Me) induces NRF2 through disruption of the KEAP1-NRF2 interaction and was tested as a treatment for AS in human clinical trials. While CDDO-Me increased estimated glomerular filtration rate (GFR), it was unclear if CDDO-Me meaningfully altered disease progression. In addition, CDDO-Me exposure was associated with paradoxical worsening of proteinuria. To determine the effects of NRF2 activation in AS, we examined how genetic reduction in Keap1 expression (hypomorphism) affected AS in a mouse model. We hypothesized that higher NRF2 activity would worsen proteinuria and overall kidney injury in AS.

Methods

AS mice possessing a deletion mutation in Col4a3 were bred with Keap1 hypomorphic (HM) mice to generate double mutant Col4a3^-/- Keap1^HM/HM progeny. Proteinuria was measured over the course of 30 weeks using an albumin ELISA. GFR was measured through the transdermal measurement of FITC-sinistrin clearance. We performed histology and qPCR for renal injury biomarkers to assess overall injury. We used electron microscopy to examine podocyte foot process effacement and basement membrane ultrastructure.

Results

Consistent with their lower expression of Keap1, the double mutant mice exhibited higher expression of Nrf2 target genes compared to single mutant Col4a3^-/- mice. The double mutants exhibited significantly more proteinuria throughout the time course and a lower GFR compared to mice with only the Col4a3^-/- mutation. Double mutants also exhibited more interstitial fibrosis and increased biomarkers of glomerular injury, tubular injury, and inflammation. Electron microscopy revealed extensive foot process effacement and basement membrane thickening that did not differ between groups.

Conclusion

Our findings demonstrate that excessive NRF2 activity worsens AS kidney injury in mice. These findings suggest that NRF2 has deleterious actions in AS and that NRF2 inducers such as CDDO-Me should be avoided in the treatment of this disease.

Funding

• NIDDK Support