ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: FR-PO413

PKC-δ Reduced DUSP4 Expression Causing NOX4 and Progressive Diabetic Nephropathy

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Rousseau, Marina, University of Sherbrooke, Sherbrooke, Quebec, Canada
  • Denhez, Benoit, University of Sherbrooke, Sherbrooke, Quebec, Canada
  • Lizotte, Farah, University of Sherbrooke, Sherbrooke, Quebec, Canada
  • Geraldes, Pedro Miguel, University of Sherbooke, Sherbrooke, Quebec, Canada
Background

Diabetic nephropathy is characterized by the loss of an important epithelial cell called podocytes. Podocytes are specialized cells that have a critical role in maintaining the integrity of the glomerular filtration barrier. A promising insight in the initiation of glomerular pathology begins with the loss of expression of the dual specificity phosphatase 4 (DUSP4), known for its role in MAPK inhibition. We have observed that cultured podocytes exposed to high glucose (HG; 25 mM) concentrations and glomeruli of diabetic (Ins2+/C96Y) mice exhibited significant reduction of DUSP4 which complied with glomerularsclerosis, podocyte foot process effacement and podocyte cell death. However, the exact mechanism of diabetes-induced DUSP4 reduction remained unknown but protein kinase C (PKC) activation has been shown to regulate DUSP expression in macrophages.

Methods

Non-diabetic (NDM) and diabetic (DM) mice with the deletion of DUSP4 (D4KO) and PKC-δ (Prckd-/-) were used after 6 months of diabetes. Mouse podocytes were exposed to normal (NG; 5.6 mM) or high (HG; 25 mM) glucose levels for 72 hours with or without the overexpression of DUSP4 and PKC-δ adenoviral vector to evaluate the oxidative stress pathway. Human blood and kidney sample were collected to measure DUSP4 mRNA levels and estimated glomerular filtration rate using the CKD-EPI formula.

Results

By overexpressing the dominant negative form of PKC-δ specifically, we were able to reestablish DUSP4 expression levels in podocytes. In addition, decreased DUSP4 expression observed in renal cortex of DM mice were not seen in DM mice that did not possess the PKC-δ gene. Podocytes exposed to HG concentrations showed a 52% increase of NOX4 expression which was prevented with the overexpression of DUSP4. DM mice had a 30% increase in NOX4 expression in the glomeruli, which was exacerbated by 31% in DM mice with a specific deletion in DUSP4. Interestingly, in humans, decreased mRNA expression of DUSP4 in the renal cortex of diabetic patients correlated with eGFR level decline.

Conclusion

Reduction of DUSP4 expression induced by PKC-δ activation increased NOX4 expression and podocyte dysfunction in diabetic nephropathy.

Funding

  • Government Support - Non-U.S.