Rap1 ameliorates renal tubular injury in diabetic nephropathy

  1. Lin Sun1
  1. 1Department of Nephrology
  2. 2Diabetes Center, Institute of Metabolism and Endocrinology, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
  3. 3Departments of Pathology & Medicine, Northwestern University, Chicago, Illinois, USA
  1. Correspondence address: Lin Sun, E-mail:zndxsunlin11{at}163.com

Abstract

Rap1b ameliorates high glucose (HG)-induced mitochondrial dysfunction in tubular cells. However, its role and precise mechanism in diabetic nephropathy (DN) in vivo remains unclear. We hypothesize that Rap1 plays a protective role in tubular damage of DN by modulating primarily the mitochondria-derived oxidative stress.The role and precise mechanisms of Rap1b on mitochondrial dysfunction and of tubular cells in DN was examined in rats with Streptozotocin (STZ)-induced diabetes that have Rap1b gene transfer using an ultrasound microbubble-mediated technique as well as in renal proximal epithelial tubular cell line (HK-2) exposed to HG ambiance. The results showed that Rap1b expression decreased significantly in tubules of renal biopsies from patients with DN. Over-expression of a constitutively active Rap1b G12V notably ameliorated renal tubular mitochondrial dysfunction, oxidative stress, apoptosis in the kidneys of STZ-induced rats, which was accompanied with increased expression of transcription factor C/EBP-β and PGC-1α. Furthermore, Rap1b G12V also decreased phosphorylation of Drp1, a key mitochondrial fission protein, while boosting the expression of genes related to mitochondrial biogenesis and antioxidants in HK-2 cells induced treated with HG. These effects were imitated by transfection with C/EBP-β or PGC-1α siRNA. In addition, Rap1b could modulate C/EBP-β binding to the endogenous PGC-1α promoter and the interaction between PGC-1α and Catalase or mitochondrial superoxide dismutase. Indicating that Rap1b ameliorates tubular injury and slows the progression of DN by modulation of mitochondrial dysfunction via C/EBP-β:PGC-1α signaling.

Footnotes

  • * Li Xiao and Xuejing Zhu contributed equally to this work.

  • Received September 15, 2013.
  • Accepted December 3, 2013.

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