Abstract: SA-PO741
Nrf2 Deletion Attenuates Kidney Injury Caused by Cullin Ring Ligase Dysfunction
Session Information
- CKD: Mechanisms - III
November 09, 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
- Cornelius, Ryan J., Oregon Health and Science University, Portland, Oregon, United States
- Nelson, Jonathan W., Oregon Health and Science University, Portland, Oregon, United States
- Yang, Chao-Ling, Oregon Health and Science University, Portland, Oregon, United States
- Ellison, David H., Oregon Health and Science University, Portland, Oregon, United States
Background
Nrf2 is postulated to play a protective role in oxidative stress-induced kidney injury; conversely, multiple studies have shown that aberrant Nrf2 activity can be damaging. Nrf2 abundance is determined by cullin-RING ligases (CRLs), which control the regulated degradation of proteins through the ubiquitin proteasome system. CRLs, in turn, are regulated by the COP9 Signalosome (CSN). We previously reported that nephron-specific CSN disruption (KS-Jab1-/- mice) causes progressive renal injury, with increased Nrf2. Here, we tested the hypothesis that direct Nrf2 accumulation exacerbates kidney injury in this model, using KS-Jab1 and Nrf2 double knock out mice (DKO).
Methods
The Pax8-rtTA mouse system was used to generate inducible mice with genetic deletion of the catalytically active CSN subunit, Jab1, only along the nephron (KS-Jab1-/-). KS-Jab1-/- were bred to mice with global and constitutive deletion of Nrf2 (DKO). Kidney damage was evaluated at 1 week (early) and 8 weeks (late) after Jab1 deletion.
Results
KS-Jab1-/- showed an increase in Nrf2 activity which was attenuated in DKO at both time points. Early KS-Jab1-/- demonstrated an increase in blood urea nitrogen (BUN; 34 ± 2 vs. 26 ± 1 mg/dl in controls), and kidney weight (6.8 ± 0.3 vs. 5.3 ± 0.2 mg/g BW in controls). Analysis of the proximal tubule injury marker KIM-1 (kidney injury molecule-1) via Western blot revealed an increase in KS-Jab1-/- compared to controls. Furthermore, immunofluorescent staining using antibodies against the proliferation marker Ki-67 demonstrated an increase in the number of proliferating cells located in kidney medulla (208 ± 27 vs. 42 ± 4 cells/field in controls). Nrf2 deletion in early DKO significantly attenuated the rise in BUN (29 ± 2 mg/dl), KIM-1 abundance, and medullary Ki-67 positive cells (96 ± 13 cells/field). Kidney weight trended lower (6.0 ± 0.5 mg/g BW), but was not significantly different. Late DKO showed no significant differences in BUN, kidney weight, or KIM-1 abundance compared to time-matched KS-Jab1-/-.
Conclusion
Disrupting the CRL pathway in mouse tubules, which leads to kidney damage, also increases Nrf2 activity. Nrf2 deficiency reduces kidney injury after Jab1 deletion early, but not at later time points. The results suggest that treatment via modulation of Nrf2 activity in progressive kidney disease may have unexpected effects.
Funding
- NIDDK Support