Diabetic nephropathy (DN) is a complication associated with diabetes and is characterized by proteinuria and a progressive loss of kidney function. The disease morphologically manifests as an increase in the extracellular matrix (ECM) produced by kidney cells including specialized mesangial cells found in the kidney glomeruli. The mesangial cells undergo increased proliferation and hypertrophy, produce ECM components at an elevated rate and in turn the ECM itself is broken down at a reduced rate. This leads to fibrosis, or the scarring of the glomeruli. The process of fibrosis is known to be promoted by pro-fibrotic factors such as transforming growth factor beta-1 (TGF-β1), which is activated by various proteins including thrombospondin-1 (TSP-1). Both of these proteins are known to have an increased rate of expression and activation in a high glucose environment and in the kidneys of diabetic patients. Glucose-regulate protein 78 (GRP78) is another protein altered by high glucose, as it is translocated to cell surface in DN (cell surface GRP78, csGRP78). In this study, we investigate the role csGRP78 has in the regulation of TSP-1 and downstream signaling by high glucose, using primary rat mesangial cell cultures. Our results confirm that TSP-1 protein levels are increased in the cell lysate and in the ECM of cells treated with high glucose. We further show that inhibitors of csGRP78 and downstream PI3K/Akt reduce the high glucose-induced increase in TSP1 at both protein and transcript levels, and attenuate TGF-β1 signaling. / Thesis / Master of Science (MSc) / Diabetic nephropathy is a condition that is associated with a gradual loss of kidney function as well as the presence of protein in the urine. As the name implies, diabetic nephropathy occurs as a result of diabetes mellitus. The disease causes the mesangial cells in the kidney to produce excess extracellular matrix leading to scarring in the kidney, a process called fibrosis. One of the key fibrotic proteins is called transforming growth factor beta-1 (TGF-β1), stored in a latent form. A major activator of TGF-β1 is thrombospondin-1 (TSP-1). Our results demonstrate that the cell surface localization of glucose regulated protein 78 (GRP78) is required for the upregulation of TSP-1 in a high glucose environment, leading to activation of profibrotic pathways that are well known to perpetuate the fibrotic phenotype seen in diabetic nephropathy.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25816 |
| Date | January 2020 |
| Creators | Ahmed, Usman |
| Contributors | Krepinsky, Joan, Medical Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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