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Kidney Week

Abstract: PO0902

Rab27b Repression by Foxo1 Leads to Decreased Exosome Production in Diabetic Kidneys

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Zeng, Mengru, Department of Nephrology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
  • Wen, Jin, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
  • Dong, Zheng, Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, Georgia, Georgia
Background

Diabetic kidney disease (DKD) is associated with changes in exosomes. However, it is unclear whether the production or secretion of exosomes is affected in DKD. This study aims to investigate whether and how the secretion of exosomes is affected in DKD using in vivo and in vitro diabetic models.

Methods

In vivo, exosomes were isolated from kidney cortical tissues of Akita and streptozotocin-induced diabetic mice for analysis. In vitro, mouse kidney proximal tubular BUMPT cells were incubated with high glucose (30mM, HG) or mannitol (control) for 8 days to collect exosomes in culture medium. Exosomes were examined by electron microscopy (EM), nanoparticle tracking analysis (NTA), and immunoblotting. Knockdown and overexpression were used to study the roles of Rab27b and Foxo1 on exosome secretion.

Results

In vivo, diabetic mice had a reduced number of exosomes in renal cortical tissues compared with non-diabetic mice. In vitro, HG treatment led to a significant decrease in exosome secretion in BUMPT cells, which was associated with the specific downregulation of Rab27b, a key GTPase for exosome secretion. Overexpression of Rab27b restored exosome secretion in HG-treated cells, suggesting a role of Rab27b downregulation in decreased exosome secretion in DKD. For the mechanism of Rab27b downregulation, bioinformatic analysis predicted Foxo1-binding sites at Rab27b gene promoter. We demonstrated the phosphorylation of Foxo1 in HG-treated cells, accompanied by less Foxo1 accumulation in the nucleus. Overexpression of Foxo1 increased Rab27b expression, whereas Knockdown of Foxo1 had opposite effects. Moreover, expression of non-phosphorylatable (constitutively active) Foxo1 led to the upregulation of Rab27b and increases in exosome secretion in HG treated cells.

Conclusion

In diabetic kidney cells and tissues, Foxo1 is phosphorylated and inactivated, leading to decreases in Rab27b expression and consequential secretion of exosomes.

Funding

  • NIDDK Support