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Abstract: TH-PO192

MDM2 Promotes Diabetic Nephropathy by Targeting Integrin β8 for Ubiquitin Degradation in Renal Pericytes

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Cao, Yiling, Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
  • Zeng, Jieyu, Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
  • Yaru, Xie, Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
  • Zhang, Chun, Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
Background

Diabetic nephropathy (DN) is one of the most frequent diabetic chronic microvascular complications. Renal pericytes play a critical role in maintaining vascular homeostasis and are the major source of interstitial myofibroblasts in the fibrotic kidney. We previously reported that murine double minute 2 (MDM2), an E3 ubiquitin ligase, is essential in mediating mesangial cell proliferation and extracellular matrix accumulation. However, the mechanism of MDM2 in renal pericytes injury remains to be unknown. Transforming growth factor beta 1 (TGF-β1) is a pivotal profibrotic mediator and integrin β8 sequesters latent TGF-β1 to prevent its activation in mesangial cells. The present study sought to determine whether MDM2 could induce the activation of TGF-β1 through integrin β8 ubiquitination, and lead to pericytes differentiation and endothelial cell damage.

Methods

We established STZ-induced DN mice model. Primary cultured pericytes and HBZY-1 were stimulated with high glucose (30 mM). The expressions of MDM2, Integrin β8, TGF-β1, relative fibrotic markers and injury markers were measured by western blot and immunofluorescence. Inflammatory cytokines in culture medium were detected by Elisa kits.

Results

MDM2 and TGF-β1 elevated, while integrin β8 decreased in pericytes of DN mice. After inhibiting MDM2 in pericytes and HBZY-1, the expression of integrin β8 increased. Silenced MDM2 or overexpressed integrin β8 could alleviate high glucose-induced TGF-β1 expression and fibrosis and inflammatory response. Meanwhile, the levels of TNF-α, IL-6, TGF-β1 in HBZY-1 culture medium were reduced after MDM2 knockdown or integrin β8 overexpression. GECs were cultured with the aforementioned medium. The injuries of GECs were reversed in the MDM2 knockdown or integrin β8 overexpression medium. MG132 prevented the decline of integrin β8 and immunoprecipitation showed integrin β8 ubiquitination was increased under high-glucose conditions. In vivo, immunofluorescence staining indicated pericytes differentiation into myofibroblasts and the microvascular rarefaction in DN mice.

Conclusion

These data indicated that the release of TGF-β1 by ubiquitination-mediated integrin β8 degradation in pericytes is one of the downstream mechanisms of MDM2 profibrotic property, which contributes to pericytes differentiation into myofibroblasts and endothelial cell damage.

Funding

  • Government Support – Non-U.S.