Overall objective of the proposal is to delineate the role of a proximal tubular specific enzyme, i.e., myo- inositol oxygenase (MIOX), in tubulo-interstitial pathobiology in the context of diabetic nephropathy (DN). The DN is characterized by perturbation in various metabolic/cellular signaling pathways in renal cells resulting in the generation of reactive oxygen species (ROS). The latter have emerged as central to the pathogenesis of DN. The metabolic/signaling events have been delineated largely in renal glomerular cells, and information relating to tubulointerstitial cells is limited. Glucose responsie MIOX catabolizes myo-inositol to D-glucuronate via Glucuronate-Xylulose (GX) pathway, as described in """"""""eye lens"""""""", and its metabolites enter pentose pathway. The GX pathway initiated by MIOX leads to """"""""redox imbalance"""""""" with perturbed NADPH:NADP+ and NAD+:NADH ratios at 4 steps [Fig. 1], akin to polyol pathway;suggesting that its activation would induce oxidant and hypoxic stress culminating into an increased synthesis of ECM proteins and tubulo-interstitial injury in DN [Fig. 2]. Perturbed NAD+/NADH ratio would also cause depletion of NAD+, as a result the activity of NAD-dependent deacetylases, Sirutins, are compromised. Targets of Sirutins include FOXO family transcription factors and transcriptional coactivator PGC-1?, which modulate mitochondrial biogenesis and various antioxidant genes. With these perturbations the tubular cells are likely to undergo energy stress and apoptosis. Our published (JBC 2011, AJP 2010) and preliminary data suggest that ROS are generated in the GX pathway, which in turn increases the transcription of MIOX, thus setting up cyclic generation of ROS. Data also suggest that GX pathway exist in the kidney [Fig. 4], and oxidant stress does occur in the tubular compartment in patients with DN [Fig. 3]. Also, MIOX over-expression in high glucose leads to accentuated synthesis of ECM proteins [Fig. 10]. With this background and to achieve objectives of the proposal the following 3 specific aims are proposed.
AIM I is to delineate mechanisms by which MIOX overexpression in vitro in tubular cells leads to accentuation of the oxidant stress, mitochondrial dysfunctions and ECM synthesis in the presence of high glucose. Status of NADPH:NADP+ &NAD+:NADH ratios, GSH, NOX4, PKC, TGF-, SIRTs, transcription factors, mitochondrial dynamics, and pro- and anti-apoptotic genes will be assessed. Specific inhibitors/activators will be used to test the specificity of MIOX effects.
AIM II is to characterie in vivo MIOX-induced GX pathway, redox imbalance and downstream signaling events leading to dysfunctions of SIRTs and mitochondria, apoptosis and tubulo- interstitial fibrosis. CD1 mice with STZ-induced diabetes and mice over-expressing MIOX cross bred with Akita mice will be used.
AIM III is to determine if MIOX gene deletion leads to amelioration in renal dysfunctions and progression to tubulo-interstitial injury in STZ-induced diabetes in heterozygote (+/-) mice and when the mutant Null (-/-) mice are cross bred with Akita mice. It is anticipated that the characterization of GX-SIRT pathway would aid in devising novel therapeutic strategies to decelerate tubulo-interstitial injury in DN.

Public Health Relevance

Diabetic nephropathy (DN) is one of the principal causes of end-stage renal disease (ESRD) leading to dialysis dependency in the US population, thus adding substantial amount of burden to the national expenditure. DN has a relentless course when both the glomerular and tubulo-interstitial compartments are affected. In fact, tubulo-interstitial changes in DN correlate relatively better with the derangements in renal functional parameters. The premise of this application is to delineate pathogenesis of tubulo-interstitial injury in the context of DN. Evidence is presented in this application that certain pathways are specific to the tubular compartment, and they are responsible for such an injury leading to tubulo-interstitial dysfunctions/fibrosis. Interruption of various events relevant to these pathway by pharmacologic or genetic means hold promise as novel therapeutic strategies to ameliorate the progression of diabetic nephropathy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK060635-13
Application #
8721924
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Rys-Sikora, Krystyna E
Project Start
2002-02-15
Project End
2017-06-30
Budget Start
2014-07-01
Budget End
2015-06-30
Support Year
13
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Pathology
Type
Schools of Medicine
DUNS #
City
Chicago
State
IL
Country
United States
Zip Code
60611
Wysocki, Jan; Ye, Minghao; Khattab, Ahmed M et al. (2016) Angiotensin-converting enzyme 2 amplification limited to the circulation does not protect mice from development of diabetic nephropathy. Kidney Int :
Zhu, Xuejing; Xiong, Xiaofen; Yuan, Shuguang et al. (2016) Validation of the interstitial fibrosis and tubular atrophy on the new pathological classification in patients with diabetic nephropathy: A single-center study in China. J Diabetes Complications 30:537-41
Tominaga, Tatsuya; Dutta, Rajesh K; Joladarashi, Darukeshwara et al. (2016) Transcriptional and Translational Modulation of myo-Inositol Oxygenase (Miox) by Fatty Acids: IMPLICATIONS IN RENAL TUBULAR INJURY INDUCED IN OBESITY AND DIABETES. J Biol Chem 291:1348-67
Nagasu, Hajime; Satoh, Minoru; Kiyokage, Emi et al. (2016) Activation of endothelial NAD(P)H oxidase accelerates early glomerular injury in diabetic mice. Lab Invest 96:25-36
Sun, Lin; Dutta, Rajesh K; Xie, Ping et al. (2016) myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience: A NEW MECHANISM RELEVANT TO THE PATHOGENESIS OF DIABETIC NEPHROPATHY. J Biol Chem 291:5688-707
Hu, C; Sun, L; Xiao, L et al. (2015) Insights into the Mechanisms Involved in the Expression and Regulation of Extracellular Matrix Proteins in Diabetic Nephropathy. Curr Med Chem 22:2858-70
Sun, Lin; Kanwar, Yashpal S (2015) Relevance of TNF-α in the context of other inflammatory cytokines in the progression of diabetic nephropathy. Kidney Int 88:662-5
Lerret, Nadine M; Li, Ting; Wang, Jiao-Jing et al. (2015) Recipient Myd88 Deficiency Promotes Spontaneous Resolution of Kidney Allograft Rejection. J Am Soc Nephrol 26:2753-64
Xiao, Li; Zhou, Xun; Liu, Fuyou et al. (2015) MicroRNA-129-5p modulates epithelial-to-mesenchymal transition by targeting SIP1 and SOX4 during peritoneal dialysis. Lab Invest 95:817-32
Zhan, Ming; Usman, Irtaza M; Sun, Lin et al. (2015) Disruption of renal tubular mitochondrial quality control by Myo-inositol oxygenase in diabetic kidney disease. J Am Soc Nephrol 26:1304-21

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