Sealy Center for Molecular Medicine

Research summary

 My research program is focused on understanding the pathogenesis of diabetic complications with an emphasis on diabetic nephropathy and retinopathy.  We are interested in the role of VEGF in the pathogenesis of diabetic complications, and our previous studies have indicated that vascular endothelial growth factor (VEGF) is upregulated in animal models of diabetic nephropathy and inhibition of VEGF signaling attenuates diabetes-induced functional and structural changes. These findings strongly implicate elevated VEGF levels in the pathogenesis of diabetes.  Our overall objective for this research is to identify all proteins globally affected by increased VEGF expression in the diabetic eye and kidney, then use bioinformatics-based tools to explore molecular mechanisms of VEGF action in the pathogenesis of diabetic complications. This research represents a multidisciplinary approach to build and compare systems biology linkages between dysregulated protein pathways and networks in retina and in glomeruli and proximal tubules of diabetic rodents and humans. Our approach utilizes a method to globally identify and quantify dysregulated proteins, involving endoprotease-catalyzed, 18O-labeling of tryptic peptides. 2D-LC-MS/MS is used to sequence peptides, and web-based analysis of the identified proteins, together with commercially available and in-house developed software for in silico modeling of identified pathways and networks are used to provide novel insights into tissue- and organ-level protein networks and molecular functions affected by diabetes.  Our use of bioinformatics and mathematics tools to build predictive models of diabetes allows perturbation-based reiterative refinement of the model using relevant interventions. This process of acquiring proteomic data, integrating the data with bioinformatics tools to build a predictive model, and refining the model by iterative hypothesis testing provides unique, systems level approaches for understanding diabetes pathogenesis. Our research group also has focused on NF-κB activation in diabetes. We use a human pTEC tissue culture system to probe molecular mechanisms involved in canonical vs noncanonical NF-κB pathway activaton in response to stimuli that mimic the in vivo diabetic milieu, including exposure to elevated glucose, advanced glycated endproducts (AGE), and angiotensin-II. Results obtained in tissue culture, combined with our animal experiments provide invaluable insights into molecular mechanisms by which diabetes induces and maintains chronic inflammation in the kidney.

Selected Publications

1. Sadygov, R.G., Zhao, Y., Haidacher, S.J., Starkey, J.M., Tilton, R.G., Denner, L.:  Using power spectrum analysis to evaluate 18O-water labeling data acquired from low resolution mass spectrometers.  J. Proteomic Res., 9(8):4306-4312, 2010.
   
   
2. Starkey, J.M., Zhao, Y., Sadygov, R.G., Haidacher, S.J., LeJeune, W.S., Dey, N., Luxon, B.A., Kane, M.A., Napoli, J.L., Denner, L., Tilton, R.G.:  Altered retinoic acid metabolism in diabetic mouse renal cortex identified by 18O isotopic labeling and 2D LC-MS/MS proteomics.  PLoS ONE, Jun 14, 5(6):e11095, 2010.
   
   
3. Ido, Y., Nyengaard, J.R., Chang, K., Tilton, R.G., Kilo, C., Mylari, B.L., Oates, P.J., Williamson, J.R.:  Early neural and vascular dysfunction in diabetic rats are largely sequelae of increased sorbitol oxidation.  Antioxidants Redox Signaling, 12(1):39-51, 2010.
   
   
4. Tieu, B.C., Lee, C.Y., Sun, H., Lejeune, W.S., Recinos, A., Milewicz, D., Tilton, R.G., Brasier, A.R.:  IL-6 production in the adventitia accelerates vascular inflammation leading to dissecting aneurysms.  J. Clin. Invest., 119(12):3637-3651, 2009.
   
   
5. Irani, Y., Brereton, H.M., Tilton, R.G., Coster, D.J., Williams, K.A.:  Production of scFv antibody fragments from a hybridoma with functional activity against human vascular endothelial growth factor.  Hybridoma, 28(3):205-209, 2009.
   
   
6. Zhao, Y., Haidacher, S.J., LeJeune, W.S., Denner, L.A., Tilton, R.G.:  Comprehensive analysis of the mouse renal cortical proteome using two dimensional HPLC – tandem mass spectrometrey.  Proteome Science, 6:15, 2008.
   
   
7. Tilton, R.G., Haidacher, S.J., LeJeune, W.S., Zhao, Y., Kurosky, A., Brasier, A.R., Denner, L.A.:  Diabetes-induced changes in the renal cortical proteome assessed with two-dimensional gel electrophoresis and mass spectrometry.  Proteomics J., 7:1729-1742, 2007.
   
   
8. Starkey, J.M., Haidacher, S.J., LeJeune, W.S., Zhang, X., Tieu, B.C., Choudhary, S., Brasier, A.R., Denner, L.A., Tilton, R.G.:  Diabetes-induced activation of canonical and noncanonical nuclear factor-κB pathways in renal cortex.  Diabetes, 55(5):1252-1259, 2006.
   
   
9.  Williamson, J.R., Ido, Y., Kilo, C., Tilton, R.G.:  Hyperglycemic pseudohypoxia and diabetes complications: sorbitol pathway-generated NADHc mediates diabetes complications.  In Commentaries on Perspectives in Diabetes. Vol. 2. Robertson, R.P., Ed.  Alexandria, VA, American Diabetes Association, 2006, pp. 39-41.
   
   
10. Tilton, R.G.  Diabetic vascular dysfunction:  Links to glucose-induced reductive stress and VEGF.  Microscopy Res. Technique, 57(5):390-407; 2002.
    
    
11. Flyvbjerg, A., Schrijvers, B.F., De Vriese, A.S., Tilton, R.G., Rasch, R.  Compensatory glomerular growth following unilateral nephrectomy is VEGF dependent.  Am. J. Physiol. Endocrinol. Metab., 283(2):E362-E366; 2002.
    
    
12. De Vriese, A.S., Tilton, R.G., Elger, M., Stephan, C.C., Kriz, W., Lameire, N.H.  Antibodies against vascular endothelial growth factor improve early renal dysfunction in experimental diabetes.  J. Am. Soc. Nephrol., 12(5):993-1000; 2001.
    
    
13. Tilton, R.G., Chang, K.C., LeJeune, W.S., Stephan, C.C., Brock, T.A., Williamson, J.R.  Role for nitric oxide in the hyperpermeability and hemodynamic changes induced by intravenous VEGF.  Invest. Ophthalmol. Vis. Sci., 40(3):689-696; 1999.
    
    
14. Tilton, R.G., Kawamura, T., Chang, K.C., Allison W., Faller, A.M., Ido, Y., Stephan, C.C., Brock, T.A., Williamson, J.R.  Vascular dysfunction induced by elevated glucose levels in rats is mediated by vascular endothelial growth factor.  J. Clin. Invest., 99(9):2192-2202; 1997.
    
    
15. Tilton, R.G., Chang, K., Nyengaard, J.R., Van den Enden, M., Ido, Y., Williamson, J.R.  Inhibition of sorbitol dehydrogenase:  Effects on vascular and neural dysfunction in streptozocin-induced diabetic rats.  Diabetes 44(2):234-242; 1995.