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Differences in binding of glucocorticoid receptor to DNA in chronic renal graft rejection
N Ichimaru1, S Takahara, J D Wang
1Department of Urology, Osaka University Medical School, Suita, Japan.
Abstract:
Although chronic rejection is the most common reason for late allograft loss, its pathophysiology and etiology are unclear. Attempts to prevent chronic rejection are now focused on the modulation of transcriptional regulation. We evaluated the ability of glucocorticoid receptors (GR) to bind to the DNA binding site in peripheral blood mononuclear cells (PBMC) of five patients with chronic rejection and seven without it. Using an electrophoretic mobility shift assay, we measured the amount of nuclear glucocorticoid receptor capable of binding to its specific DNA recognition sequences, termed glucocorticoid response elements (GRE). GR binding was significantly greater in control patients than in those with chronic rejection (P < 0.01). The retarded band was almost undetectable in two patients with chronic rejection even though they were taking more prednisolone than the seven control patients, all of whom had clearly identifiable retarded bands. These results suggest a decreased ability of GR to bind to GRE in chronic rejection, resulting in a reduced ability to block key proinflammatory promoter sites. This reduced binding may be one molecular basis of chronic rejection.
Insights
Glucocorticoid receptor (GR) binding to DNA is reduced in chronic rejection patients, potentially explaining transplant loss. This impaired binding affects the ability to control inflammatory genes.
Area of Science:
- Transplantation immunology
- Molecular biology
- Genetics
Background:
- Chronic rejection is the primary cause of late allograft failure.
- Understanding the molecular mechanisms of chronic rejection is crucial for developing new therapies.
- Transcriptional regulation is a key focus for preventing chronic rejection.
Purpose of the Study:
- To investigate the role of glucocorticoid receptors (GR) in the pathophysiology of chronic rejection.
- To evaluate the DNA-binding ability of GR in patients with and without chronic rejection.
Main Methods:
- Peripheral blood mononuclear cells (PBMC) were collected from patients with chronic rejection and healthy controls.
- Electrophoretic mobility shift assay (EMSA) was used to measure nuclear GR binding to glucocorticoid response elements (GRE).
- GR binding was quantified and compared between the two groups.
Main Results:
- GR binding to GRE was significantly lower in patients experiencing chronic rejection compared to controls (P < 0.01).
- Reduced GR binding was observed even in patients taking higher doses of prednisolone.
- These findings suggest a diminished capacity for GR to bind its DNA targets in chronic rejection.
Conclusions:
- Decreased GR binding to GRE may represent a molecular basis for chronic rejection.
- This impaired binding could lead to a reduced ability to suppress pro-inflammatory gene expression.
- Targeting GR function may offer a novel therapeutic strategy for preventing chronic rejection.