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Abstract: PO0900

Proteasome Mediated NF-E2 Degradation Occurs Upstream of JNK Activation-Mediated CTGF Expression in Renal Tubules and Diabetic Kidneys

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Rane, Madhavi J., University of Louisville, Louisville, Kentucky, United States
  • Li, Jia, University of Louisville, Louisville, Kentucky, United States
  • Jin, Shunying, University of Louisville, Louisville, Kentucky, United States
  • Barati, Michelle T., University of Louisville, Louisville, Kentucky, United States
Background

TGF-β is a critical mediator of diabetes-induced renal fibrosis. We recently demonstrated that TGF-b and diabetes (Type 1 and type 2) decreased NF-E2 expression and promoted pro-fibrotic signaling in renal cells and kidneys. P38 MAPK and ERK MAPK pathways contributed to proteasome activation and NF-E2 degradation. As JNK pathway is known to induce CTGF expression, current studies examined the contribution of JNK pathway in mediating NF-E2 degradation in TGF-β treated renal tubule cells.

Methods

HK-11 cells were pre-treated with/without JNK inhibitor SP600125, p38 inhibitor SB203580, or p38 and MEK/ERK inhibitor PD98059, or proteasome inhibitor MG132, for an hour prior to treatment with TGF-b for 24 h. Cell lysates were immunoblotted with appropriate antibodies. Kidney homogenates from FVB and OVE26 diabetic mice treated with 10 µg/Kg MG132 daily for 3 mo starting at 3 mo of age when OVE26 mice already displayed significant albuminuria.were immunoblotted with appropriate antibodies. MG132 were injected intraperitoneally at a dose of 10 µg/kg daily for 3 mo starting at 3 mo of age when OVE26 mice already displayed significant albuminuria.

Results

Inhibition of p38 MAPK partially preserved NF-E2 expression but induced CTGF expression, as p38 blockade induced ERK phosphorylation. Blockade of both p38/ ERK, prevented NF-E2 degradation and inhibited CTGF expression. Blockade of JNK pathway, inhibited CTGF expression without preserving NF-E2 expression. Interestingly, proteasome inhibition in renal cells and OVE26 mice preserved NF-E2 expression and inhibited JNK activation and CTGF expression suggesting JNK activation occurs downstream of proteasome activation.

Conclusion

Our studies have demonstrated that p38 and ERK MAPK pathways promote proteasome activation and NF-E2 degradation while proteasome activation promotes JNK activation and CTGF expression in renal cells and diabetic kidneys. We have recently demonstrated that NF-E2 over-expression inhibited CTGF expression however; future studies will examine effects of NF-E2 over-expression on TGF-b-induced and diabetes-induced JNK activation in renal cells.