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Diminished NF-kappaB activation and PDGF-B expression in glomerular endothelial cells subjected to chronic shear
Eudora Eng1, Barbara J Ballermann
1Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. e-eng@northwestern.edu
Insights
Chronic arterial shear stress represses nuclear factor-kappaB (NF-kappaB) activation, decreasing platelet-derived growth factor (PDGF)-B gene transcription in endothelial cells. This finding impacts understanding of vascular gene regulation.
Area of Science:
- Endothelial cell biology
- Molecular biology
- Cardiovascular research
Background:
- Platelet-derived growth factor (PDGF)-B is crucial for vascular cell function.
- Nuclear factor-kappaB (NF-kappaB) is a key transcription factor involved in cellular responses.
- Arterial shear stress influences endothelial cell behavior and gene expression.
Purpose of the Study:
- To investigate the effect of chronic arterial shear stress on NF-kappaB and PDGF-B gene transcription in endothelial cells.
- To determine the mechanism by which shear stress impacts PDGF-B expression.
Main Methods:
- Bovine aortic endothelial (BAE) and glomerular capillary endothelial (GEN) cells were exposed to chronic (9 days) and acute (4 hours) arterial shear stress.
- Quantification of PDGF-B mRNA levels and stability.
- Assessment of nuclear and cytoplasmic NF-kappaB and I-kappaB levels.
- Investigation of NF-kappaB activation using interleukin (IL)-1beta and inhibition using MG-132.
Main Results:
- Chronic shear stress significantly reduced PDGF-B transcripts in both BAE and GEN cells.
- Shear stress led to decreased nuclear NF-kappaB levels and increased cytoplasmic NF-kappaB/I-kappaB.
- PDGF-B mRNA stability remained unchanged.
- IL-1beta-induced NF-kappaB activation increased PDGF-B transcripts, while MG-132 inhibited basal PDGF-B expression and IL-1beta response.
Conclusions:
- Repression of NF-kappaB activation by chronic shear stress in endothelial cells decreases PDGF-B gene expression.
- NF-kappaB plays a critical role in regulating PDGF-B transcription in response to shear stress.
- These findings elucidate a molecular mechanism linking mechanical forces to vascular gene expression.
Abstract:
We tested the hypothesis that in endothelial cells, chronic arterial shear stress represses both the transactivator nuclear factor-kappaB (NF-kappaB) and subsequent platelet-derived growth factor (PDGF)-B gene transcription. Bovine aortic endothelial (BAE) and glomerular capillary endothelial (GEN) cells were subjected to chronic (9 days) arterial shear stress (10 dyne/cm(2)). Chronic shear stress reduced PDGF-B transcripts in BAE cells by 59 +/- 23% compared to controls, and by 70 +/- 14% in GEN cells. While PDGF-B mRNA levels were not significantly changed in BAE cells subjected to acute (4 h) shear stress, in GEN cells PDGF-B transcript abundance fell by 59 +/- 3%. PDGF-B mRNA stability was unchanged. We investigated the possibility that these effects were due to decreased nuclear NF-kappaB. NF-kappaB levels were much lower in nuclei of chronic shear stress-treated cells compared to controls. This represents classical inactivation of NF-kappaB since cytoplasmic NF-kappaB/I-kappaB (the inhibitory protein of NF-kappaB) levels were elevated in shear stress-treated cells. Further supporting NF-kappaB regulation of PDGF-B, activation of NF-kappaB by interleukin (IL)-1beta resulted in increased PDGF-B transcript levels. Treatment of cells with MG-132, an inhibitor of NF-kappaB activation, resulted in a dramatic decrease in basal PDGF-B transcript levels, and essentially abrogated the response to IL-1beta. Thus, repression of NF-kappaB activation in endothelial cells by shear stress decreases PDGF-B gene expression, while activators of NF-kappaB increase PDGF-B transcription.