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Kidney Week

Abstract: PO2240

Mechanisms of Suppressed Autophagic Flux in the Kidney Caused by Sham Surgery and Unilateral Nephrectomy

Session Information

Category: Pathology and Lab Medicine

  • 1601 Pathology and Lab Medicine: Basic

Authors

  • Brown, Carolyn Nicole, Univ Colorado, Aurora, Colorado, United States
  • Atwood, Daniel, Univ Colorado, Aurora, Colorado, United States
  • Pokhrel, Deepak, Univ Colorado, Aurora, Colorado, United States
  • Altmann, Chris, Univ Colorado, Aurora, Colorado, United States
  • Faubel, Sarah, Univ Colorado, Aurora, Colorado, United States
  • Edelstein, Charles L., Univ Colorado, Aurora, Colorado, United States
Background

Compensatory renal hypertrophy resulting from loss of nephron mass has been implicated in promoting further nephron damage. Unilateral nephrectomy (UNX) is a model of compensatory hypertrophy in the remaining kidney. We previously reported that in the remaining mouse kidney that both sham surgery (SS) and UNX vs. normal kidney (N) resulted in increased mTORC1/2, decreased lysosomal function, suppressed autophagic flux. P62/SQSTM1, is an autophagy receptor that links cargo proteins with the autophagosome membrane. p62 is destroyed by the lysosome and is a marker of autophagic flux, a decrease usually indicating increased autophagic flux. The aim of the study was to measure p62 and other potential mechanisms of suppressed autophagy caused by SS and UNX.

Methods

C57BL6 mice. p62 and ERK was measured by quantitative immunoblot analysis. Cytokines were measured by MesoScale. Mice were treated with the MEK1/2 inhibitor Trametinib (T) (1 mg/kg/d for 3 days) that is a potent ERK1/2 inhibitor

Results

There was an increase in p62 in SS and UNX kidneys. p62/GAPDH (densitometry units) was 0.6 in N, 1.0 in SS (P<0.05 vs N) and 1.0 in UNX kidneys (P<0.05 vs N). p62 is known to modulate pro-inflammatory cytokines. In the serum, there were increases (fold) in IL-1b (50), IL-4 (10), IL-6 (100), IL-8 (5), IL-12 (5), GMCSF (2), IFNγ (2), IL-10 (0), TNFα (0) in SS and UNX vs N. Pro-inflammatory cytokines can activate ERK1/2, a known autophagy suppressor. There was a large increase in ERK1/2 in SS and UNX kidneys. Phospho/total ERK (densitometry units) was 0.2 in N, 1.4 in SS (P<0.001 vs N) and 2.0 in UNX kidneys (P<0.001 vs N). Trametinib blocked the increase in pERK in sham surgery and UNX kidneys and resulted in a significant decrease in p62. Phospho/total ERK (densitometry units) was 1.0 in N, 0 in SS+T (P<0.001 vs N) and 0 in UNX+T kidneys (P<0.001 vs N). p62/GAPDH (densitometry units) was 1.6 in N, 0.4 in SS +T (P<0.05 vs N) and 0.4 in UNX+T kidneys (P<0.05 vs N).

Conclusion

The mechanism of suppressed autophagy with SS and UNX may be related to an intense systemic inflammatory response and an ERK-mediated increase in p62. It is important that researchers are aware that changes in ERK1/2, systemic pro-inflammatory cytokines and autophagy can be caused by sham surgery as well as the kidney injury/disease itself.

Funding

  • Veterans Affairs Support