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Renal TGF-beta regulation in spontaneously diabetic NOD mice with correlations in mesangial cells
O G Pankewycz1, J X Guan, W K Bolton
1Health Sciences Center, University of Virginia, Charlottesville.
Abstract:
Diabetic nephropathy is characterized by excessive glomerular matrix accumulation, basement membrane thickening and sclerosis. Although it is clear that systemic metabolic disturbances precipitate such renal changes, the signals and pathways involved in this process are not fully elucidated. Recent evidence suggests that growth factors/cytokines are intimately involved in the pathogenesis of diabetic nephropathy. Because of its prosclerotic properties, transforming growth factor-beta (TGF-beta) is a prime candidate mediator of diabetic nephrosclerosis. We examined perfused kidney tissues isolated from spontaneously diabetic, non-obese diabetic mice (NOD) for TGF-beta content. By using murine isotype specific TGF-beta probes, we demonstrate that within 5 to 10 days of hyperglycuria renal TGF-beta 2 mRNA and protein content increases. By immunohistochemical analysis, de novo TGF-beta immunoreactivity was detected within both glomeruli and the interstitium. In order to determine the signals involved in promoting kidney TGF-beta content in vivo, TGF-beta regulation was examined in renal mesangial cells in vitro. Murine mesangial cells stimulated with glycosylated protein secrete bioactive TGF-beta and demonstrate a disproportionate increase in the steady state levels of TGF-beta 2 mRNA. These data suggest that a major early renal response in NOD mice to hyperglycemia or to glycosylated proteins is characterized by increases in TGF-beta.
Insights
Diabetic nephropathy involves kidney damage. This study shows hyperglycemia increases transforming growth factor-beta (TGF-beta) in diabetic mouse kidneys, suggesting TGF-beta plays a key role in diabetic kidney disease progression.
Area of Science:
- Nephrology
- Endocrinology
- Molecular Biology
Background:
- Diabetic nephropathy is a complication of diabetes mellitus characterized by kidney damage.
- The exact molecular mechanisms driving diabetic nephropathy are not fully understood.
- Transforming growth factor-beta (TGF-beta) is implicated in kidney fibrosis.
Purpose of the Study:
- To investigate the role of TGF-beta in the early stages of diabetic nephropathy.
- To examine TGF-beta expression in the kidneys of diabetic mice.
- To explore the in vitro regulation of TGF-beta by hyperglycemic conditions.
Main Methods:
- Analysis of kidney tissues from spontaneously diabetic non-obese diabetic (NOD) mice.
- Measurement of TGF-beta 2 mRNA and protein levels using specific probes.
- Immunohistochemical analysis to detect TGF-beta.
- In vitro studies using murine mesangial cells stimulated with glycosylated proteins.
Main Results:
- Hyperglycemia in NOD mice led to increased renal TGF-beta 2 mRNA and protein within 5-10 days.
- Immunohistochemistry revealed TGF-beta expression in both glomeruli and interstitium.
- Stimulation of mesangial cells with glycosylated proteins induced TGF-beta secretion and increased TGF-beta 2 mRNA levels.
Conclusions:
- Early hyperglycemia or exposure to glycosylated proteins in diabetic mice significantly increases renal TGF-beta.
- TGF-beta is a key mediator in the early renal response to hyperglycemia in diabetic nephropathy.
- These findings highlight TGF-beta as a potential therapeutic target for diabetic kidney disease.