The podocyte synthesizes a major portion of the glomerular basement membrane (GBM) to which it anchors via the alphabeta31 integrin, and it maintains the integrity of the filtration barrier that restricts the permeability of proteins. Podocyte dysfunction contributes greatly to the pathogenesis of diabetic glomerulopathy, as reflected by altered GBM composition, decreased podocyte number, and albuminuria. The mechanisms of these changes are incompletely understood, but up-regulation of Vascular Endothelial Growth Factor (VEGF) production by the podocyte may be implicated. The target cell of podocyte-derived VEGF is believed to be the glomerular endothelium, but exciting recent data showing that podocytes possess functional VEGF receptor(s) strongly suggest that VEGF can act on the podocyte itself in an autocrine loop. In fact, over activity of this VEGF loop can exert untoward effects on the podocyte by stimulating production of alpha3 (IV) collagen and decreasing expression of the alpha3 integrin subunit. These cell-matrix interactions may contribute to GBM thickening, podocyte detachment/loss, and altered macromolecular permeability. Our hypothesis is that high levels of intrarenal Angiotensin II and Transforming Growth Factor-( TGF-beta), two of the principal culprits in diabetic kidney disease, cause podocyte overproduction of VEGF that in turn acts in an autocrine loop to promote GBM thickening, cell detachment and albuminuria.
Aim 1 will examine the mechanisms whereby diabetic mediators, notably Angiotensin II, stimulate VEGF expression in differentiated mouse podocytes and assess the intermediary role of the up-regulated TGF-beta/Smad pathway in accentuating VEGF expression.
Aim 2 will delve into the mechanisms of how the up-regulated EGF autocrine loop causes collagen IV stimulation and a3(1 integrin suppression in podocytes; the VEGF receptor(s) involved and the downstream signal transduction pathways will be elucidated.
Aim 3 will explore with in vivo experiments the extent to which individual cytokine systems participate in the development of albuminuria and other lesions of diabetic glomerulopathy; kidney structure and function will be examined in diabetic vs. non-diabetic transgenic mice produced by Cre/LoxP recombination to yield podocyte-specific knockouts of candidate signaling receptors that engage Angiotensin II, TGF-beta, and VEGF (i.e., AT1A, TGF-beta type II receptor, and VEGFR-l/Flt-1, respectively). Selectively ablating the ability of glomerular podocytes to respond to each of these relevant stimuli will allow us to dissect the relative contribution of these systems to podocyte dysfunction in diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK044513-13
Application #
7491449
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Kimmel, Paul
Project Start
1992-02-01
Project End
2010-02-28
Budget Start
2008-03-01
Budget End
2009-02-28
Support Year
13
Fiscal Year
2008
Total Cost
$329,734
Indirect Cost
Name
Northwestern University at Chicago
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
Khoury, Charbel C; Khayat, Mark F; Yeo, Tet-Kin et al. (2012) Visualizing the mouse podocyte with multiphoton microscopy. Biochem Biophys Res Commun 427:525-30
Kanwar, Yashpal S; Sun, Lin; Xie, Ping et al. (2011) A glimpse of various pathogenetic mechanisms of diabetic nephropathy. Annu Rev Pathol 6:395-423
Lee, Eun Young; Chung, Choon Hee; Khoury, Charbel C et al. (2009) The monocyte chemoattractant protein-1/CCR2 loop, inducible by TGF-beta, increases podocyte motility and albumin permeability. Am J Physiol Renal Physiol 297:F85-94
Chen, Sheldon; Ziyadeh, Fuad N (2008) Vascular endothelial growth factor and diabetic nephropathy. Curr Diab Rep 8:470-6
Wolf, Gunter; Ziyadeh, Fuad N (2007) Cellular and molecular mechanisms of proteinuria in diabetic nephropathy. Nephron Physiol 106:p26-31
Wang, Amy; Ziyadeh, Fuad N; Lee, Eun Young et al. (2007) Interference with TGF-beta signaling by Smad3-knockout in mice limits diabetic glomerulosclerosis without affecting albuminuria. Am J Physiol Renal Physiol 293:F1657-65
Sung, Sun Hee; Ziyadeh, Fuad N; Wang, Amy et al. (2006) Blockade of vascular endothelial growth factor signaling ameliorates diabetic albuminuria in mice. J Am Soc Nephrol 17:3093-104
Cohen, Margo P; Ziyadeh, Fuad N; Chen, Sheldon (2006) Amadori-modified glycated serum proteins and accelerated atherosclerosis in diabetes: pathogenic and therapeutic implications. J Lab Clin Med 147:211-9
Cohen, Margo P; Chen, Sheldon; Ziyadeh, Fuad N et al. (2005) Evidence linking glycated albumin to altered glomerular nephrin and VEGF expression, proteinuria, and diabetic nephropathy. Kidney Int 68:1554-61
Wolf, Gunter; Chen, Sheldon; Ziyadeh, Fuad N (2005) From the periphery of the glomerular capillary wall toward the center of disease: podocyte injury comes of age in diabetic nephropathy. Diabetes 54:1626-34

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