Increasing evidence strongly supports a role for growth factors and oxidized lipids in the pathogenesis of Diabetic Nephropathy (DN), largely due to their pro-fibrotic and growth promoting effects. However the molecular events involved are not well understood. In the previous funding period, we identified novel signaling mechanisms by which key factors associated with DN, namely transforming growth factor-beta1 (TGF-b), Angiotensin II and high glucose (HG), could cross talk with the lipoxygenase (LO) pathway of arachidonate metabolism and its oxidized lipid products to augment hypertrophy and extracellular matrix (ECM) gene expression in glomerular mesangial cells (MC). But the precise nuclear epigenetic mechanisms involved are not clear and will therefore be evaluated in this renewal. Gene transcription can be regulated by epigenetic mechanisms in the chromatin that include posttranslational modifications (PTMs) of nucleosomal histones. Histone PTMs, such as Histone H3 -lysine methylation (H3Kme), can modulate chromatin states to dictate the 'active'or 'inactive'states of gene promoters. Our preliminary results demonstrate that key epigenetic histone H3Kme dependent mechanisms are involved in the expression of fibrotic genes in MC in response to TGF-b and diabetic conditions. We now propose to extend these new observations to evaluate the MC epigenomic states and their functional relevance to DN. We will use state-of the-art approaches to determine epigenetic mechanisms by which TGF-b, HG and LO products induce transcriptional regulation and sustained expression of fibrotic genes in renal MC. We will also examine whether agents that block these diabetogenic stimuli can reverse the epigenetic events in vitro and in vivo in mouse models. The Central Hypothesis is that, under diabetic conditions, increased activity and expression of TGF-b and 12/15-LO and their cross-talk can lead to enhanced expression of extracellular matrix genes in MC via novel epigenetic mechanisms.
Specific Aim 1 is to perform candidate and genome-wide profiling of key H3Kme marks in MC treated with and without TGF-b, and then determine potential associations between the identified methylated candidates and gene expression levels.
Specific Aim 2 is to determine whether the effects of TGF-b and HG can be mediated by 12/15-LO.
Specific Aim 3 is to examine the in vivo relevance of TGF-b and 12/15-LO induced chromatin histone PTMs in mouse models of DN. The results of these conceptually and technologically innovative studies can greatly increase our understanding of the epigenetic mechanisms involved in the persistent microvascular complications of diabetes such as DN, with major therapeutic implications.

Public Health Relevance

Diabetic Nephropathy is a major complication associated with diabetes that can lead to significantly increased rates of end stage renal disease and painful dialysis. Despite the availability of several therapies, the rates of diabetic nephropathy are soaring, leading to a drain on our healthcare resources. Since transforming growth factor-beta1 and 12/15-lipoxygenase have been implicated in these pathologies, we propose to identify new mechanisms by which these agents can induce the expression of pathologic genes in glomerular mesangial cells and promote renal dysfunction and diabetic nephropathy. We will use state-of-the-art technologies to achieve our Specific Aims and thereby advance our long-term goal to identify novel mechanisms and drug targets for diabetic nephropathy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK058191-10A1
Application #
8320024
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Rys-Sikora, Krystyna E
Project Start
2000-07-01
Project End
2017-03-31
Budget Start
2012-04-10
Budget End
2013-03-31
Support Year
10
Fiscal Year
2012
Total Cost
$365,400
Indirect Cost
$147,900
Name
City of Hope/Beckman Research Institute
Department
Type
DUNS #
027176833
City
Duarte
State
CA
Country
United States
Zip Code
91010
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Reddy, Marpadga A; Sumanth, Putta; Lanting, Linda et al. (2014) Losartan reverses permissive epigenetic changes in renal glomeruli of diabetic db/db mice. Kidney Int 85:362-73
Leung, Amy; Natarajan, Rama (2014) Noncoding RNAs in vascular disease. Curr Opin Cardiol 29:199-206
Miao, Feng; Chen, Zhuo; Genuth, Saul et al. (2014) Evaluating the role of epigenetic histone modifications in the metabolic memory of type 1 diabetes. Diabetes 63:1748-62
Castro, Nancy E; Kato, Mitsuo; Park, Jung Tak et al. (2014) Transforming growth factor ?1 (TGF-?1) enhances expression of profibrotic genes through a novel signaling cascade and microRNAs in renal mesangial cells. J Biol Chem 289:29001-13
Kato, Mitsuo; Castro, Nancy E; Natarajan, Rama (2013) MicroRNAs: potential mediators and biomarkers of diabetic complications. Free Radic Biol Med 64:85-94
Deshpande, Supriya D; Putta, Sumanth; Wang, Mei et al. (2013) Transforming growth factor-*-induced cross talk between p53 and a microRNA in the pathogenesis of diabetic nephropathy. Diabetes 62:3151-62
Yuan, Hang; Reddy, Marpadga A; Sun, Guangdong et al. (2013) Involvement of p300/CBP and epigenetic histone acetylation in TGF-?1-mediated gene transcription in mesangial cells. Am J Physiol Renal Physiol 304:F601-13
Park, Jung Tak; Kato, Mitsuo; Yuan, Hang et al. (2013) FOG2 protein down-regulation by transforming growth factor-*1-induced microRNA-200b/c leads to Akt kinase activation and glomerular mesangial hypertrophy related to diabetic nephropathy. J Biol Chem 288:22469-80
Reddy, Marpadga A; Tak Park, Jung; Natarajan, Rama (2013) Epigenetic modifications in the pathogenesis of diabetic nephropathy. Semin Nephrol 33:341-53

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