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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Tilton, R.G. Diabetic vascular dysfunction: Links to glucose-induced reductive stress and VEGF. Microscopy Res. Technique, 57(5):390-407; 2002.
- 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.
- 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.
- 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.
- 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.
- 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.