Abstract: TH-PO887
Myo-Inositol Oxygenase Modulates the Progression of Renal Fibrosis in Diabetes via Oxidant and ER Stress
Session Information
- Diabetic Kidney Disease: Basic - I
October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 601 Diabetic Kidney Disease: Basic
Authors
- Sharma, Isha, Northwestern University, Chicago, Illinois, United States
- Deng, Fei, Northwestern University, Chicago, Illinois, United States
- Sun, Lin, Second Xiangya Hospital Central South University, Changsha, China
- Kanwar, Yashpal S., Northwestern University Medical School, Chicago, Illinois, United States
Background
Myo-inositol oxygenase (MIOX) is a renal tubular specific enzyme and its overexpression is associated with increased oxidant stress and renal fibrosis. Excessive ROS generation leads to accumulation of misfolded proteins in endoplasmic reticulum (ER) causing ER stress. How MIOX serves as a nodal molecule for regulating the progression of diabetic tubulopathy via oxidant and ER stress in hyperglycemia remains unexplored.
Methods
A diabetic state was induced with the administration of STZ in wild type (WT), MIOX transgenic (TG) and MIOX-/- (KO) mice. In addition, MIOX-/- (KO) mice were cross bred with Ins2 Akita mice to generate mice with double mutation (Ins2 Akita/MIOX-KO) to assess if genetic deletion of MIOX ameliorates the progression of tubulo-interstitial injury in Ins2 Akita mice.
Results
The expression of GRP78/Bip, a marker of ER stress, and another ER stress regulator, i.e., transcription factor X-BOX binding protein-1 (XBP-1), were increased in kidneys of WT and MIOX-TG mice with STZ-induced diabetes and Ins2 Akita mice. Interestingly, by EMSA and ChiP assays MIOX expression was noted to be regulated by XBP-1. MIOX-KO and Ins2 Akita/MIOX-KO had reduced expression of XBP1 and GRP78/Bip in diabetic state, and the kidneys of these mice had reduced tubulo-interstitial injury and fibrosis. Concomitantly, the extent of renal cellular redox was reduced in MIOX-KO and Ins2 Akita/MIOX-KO mice, while markedly accentuated in WT, MIOX-TG and Ins2 Akita mice, as indicated by perturbed NADPH:NADP ratios and increased DHE, and DCF staining in renal tissues. The assessment of relevant signaling molecules revealed an increase in the expression of p-PDK1, p-PKC in kidneys of MIOX-TG mice. Likewise, expression of TGF-β and Smad 3, 4 were relatively high in diabetic WT and MIOX-TG, and Ins2 Akita mice. The expression of the signaling molecules were marginally affected in KO mice. Similar results were observed in in vitro HK-2 cells studies with MIOX over-expression and gene disruption of MIOX as well as the XBP1, a hallmark of ER stress.
Conclusion
These findings identify a link between the biology of MIOX and oxidant and ER stress and delineate the role of MIOX as a nodal molecule in the pathogenesis of tubulo-interstitial fibrosing injury in diabetic state.
Funding
- NIDDK Support