Abstract: SA-PO239

Impact of Tryptophan Metabolism Alteration by Kynurenine 3-Monooxygenase Inhibition on Renal Cells and Its Role in Diabetic Kidney Disease

Session Information

  • Glomerular: Cell Biology
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Authors

  • Bolanos-Palmieri, Patricia, Hannover Medical School, Hannover, Germany
  • Schroder, Patricia Ann, Mount Desert Island Biological Laboratory, Salisbury Cove, Maine, United States
  • Schenk, Heiko Joachim, Hannover Medical School, Hannover, Germany
  • Müller-Deile, Janina, Hannover Medical School, Hannover, Germany
  • Haller, Hermann G., Hannover Medical School, Hannover, Germany
  • Schiffer, Mario, Hannover Medical School, Hannover, Germany
Background

The kynurenine pathway (KP) is the major route for tryptophan catabolism, and changes in KP metabolites correlate with renal complications in a diverse range of pathologies. Previous work from our group identified the enzyme kynurenine 3-monooxygenase (KMO) as a factor underlying the onset of proteinuria in diabetes by contributing to morphological changes in podocyte foot processes. However, in spite of the correlational evidence for kynurenine involvement in the worsening of renal function, the pathological and functional significance of the increase in KP metabolites on renal cells remains unkown.

Methods

To assess if the enzymes of the KP are altered in diabetic kidney disease we performed IF staining of mouse kidney sections after Streptozotocin (STZ) injections, as a model for type I diabetes. Alongside this, cultured murine and human podocytes were analyzed upon inhibition of KMO to define the impact of KP dysregulation. Cell shape, size and substrate adherence were monitored. Finally, since KMO is an integral part of the mitochondrial membrane and the KP plays a role in the production of NAD+, we assessed mitochondrial function of podocytes after KMO inhibition by measuring bioenergetics parameters in a microplate-based live-cell metabolic assay.

Results

In line with our previous results, STZ-injected mice show reduced KMO expression in the renal cortex. Similarly, the expression of Arylformamidase, that catalyzes the production of kynurenine, is altered in diabetes. This change is more prominent in the glomeruli, where a reduction in the nuclear localization of AFMID was observed. Furthermore, KMO inhibition in cultured podocytes resulted in a substantial reduction in average cell size, and changes in Paxillin staining show alterations in the focal adhesions, which correlate with an increase in cellular detachment. Moreover, the changes in spare respiratory capacity observed after KMO inhibition are consistent with mitochondrial dysfunction which could affect the cells’ ability to respond to variations in energy demand.

Conclusion

Taken together, these results highlight the prominent role of the KP in the maintenance of podocyte function as its dysregulation has an impact on cell morphology, substrate adherence and metabolic profile.

Funding

  • Government Support - Non-U.S.