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The subendothelial extracellular matrix modulates NF-kappaB activation by flow: a potential role in atherosclerosis.

Orr AW, Sanders JM, Bevard M, Coleman E, Sarembock IJ, Schwartz MA - J. Cell Biol. (2005)

Bottom Line: Flow-induced NF-kappaB activation is downstream of conformational activation of integrins, resulting in new integrin binding to the subendothelial extracellular matrix and signaling.Whereas endothelial cells plated on fibronectin or fibrinogen activate NF-kappaB in response to flow, cells on collagen or laminin do not.Furthermore, altering the extracellular matrix to promote p38 activation in cells on fibronectin suppresses NF-kappaB activation, suggesting a novel therapeutic strategy for treating atherosclerosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA.

ABSTRACT
Atherosclerotic plaque forms in regions of the vasculature exposed to disturbed flow. NF-kappaB activation by fluid flow, leading to expression of target genes such as E-selectin, ICAM-1, and VCAM-1, may regulate early monocyte recruitment and fatty streak formation. Flow-induced NF-kappaB activation is downstream of conformational activation of integrins, resulting in new integrin binding to the subendothelial extracellular matrix and signaling. Therefore, we examined the involvement of the extracellular matrix in this process. Whereas endothelial cells plated on fibronectin or fibrinogen activate NF-kappaB in response to flow, cells on collagen or laminin do not. In vivo, fibronectin and fibrinogen are deposited at atherosclerosis-prone sites before other signs of atherosclerosis. Ligation of integrin alpha2beta1 on collagen prevents flow-induced NF-kappaB activation through a p38-dependent pathway that is activated locally at adhesion sites. Furthermore, altering the extracellular matrix to promote p38 activation in cells on fibronectin suppresses NF-kappaB activation, suggesting a novel therapeutic strategy for treating atherosclerosis.

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Localized activation of p38 and IKK at adhesion sites. (A) Cells were plated on Coll or FN, sheared for 5 min or kept under static conditions, and stained for phosphorylated p38 and β1 integrin. Images are representative of four experiments. (B) BAE cells were plated on Coll, LN, FN, or FG and sheared for the indicated times, and IKK phosphorylation was assessed by Western blotting. Results are representative of four to six experiments. (C) Cells were plated on Coll or FN, sheared for 30 min or kept as static controls, and stained for phosphorylated IKK and β1 integrin. Results are representative of three experiments. (D) Cells on Coll or FN were treated with 10 U/ml TNFα and stained for phosphorylated IKK and β1 integrin. Images are representative of three experiments.
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fig6: Localized activation of p38 and IKK at adhesion sites. (A) Cells were plated on Coll or FN, sheared for 5 min or kept under static conditions, and stained for phosphorylated p38 and β1 integrin. Images are representative of four experiments. (B) BAE cells were plated on Coll, LN, FN, or FG and sheared for the indicated times, and IKK phosphorylation was assessed by Western blotting. Results are representative of four to six experiments. (C) Cells were plated on Coll or FN, sheared for 30 min or kept as static controls, and stained for phosphorylated IKK and β1 integrin. Results are representative of three experiments. (D) Cells on Coll or FN were treated with 10 U/ml TNFα and stained for phosphorylated IKK and β1 integrin. Images are representative of three experiments.

Mentions: These results appear paradoxical but could be explained if the inhibitory p38 signal from Coll occurs locally within a specific compartment. To test this hypothesis, endothelial cells on Coll or FN were sheared for 5 min and active p38 was localized. Cells on Coll showed colocalization of phospho-p38 with β1 integrins, which was increased by shear stress (Fig. 6 A). Cells on FN showed only low levels of phospho-p38 staining, which is consistent with results from Western blotting.


The subendothelial extracellular matrix modulates NF-kappaB activation by flow: a potential role in atherosclerosis.

Orr AW, Sanders JM, Bevard M, Coleman E, Sarembock IJ, Schwartz MA - J. Cell Biol. (2005)

Localized activation of p38 and IKK at adhesion sites. (A) Cells were plated on Coll or FN, sheared for 5 min or kept under static conditions, and stained for phosphorylated p38 and β1 integrin. Images are representative of four experiments. (B) BAE cells were plated on Coll, LN, FN, or FG and sheared for the indicated times, and IKK phosphorylation was assessed by Western blotting. Results are representative of four to six experiments. (C) Cells were plated on Coll or FN, sheared for 30 min or kept as static controls, and stained for phosphorylated IKK and β1 integrin. Results are representative of three experiments. (D) Cells on Coll or FN were treated with 10 U/ml TNFα and stained for phosphorylated IKK and β1 integrin. Images are representative of three experiments.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171897&req=5

fig6: Localized activation of p38 and IKK at adhesion sites. (A) Cells were plated on Coll or FN, sheared for 5 min or kept under static conditions, and stained for phosphorylated p38 and β1 integrin. Images are representative of four experiments. (B) BAE cells were plated on Coll, LN, FN, or FG and sheared for the indicated times, and IKK phosphorylation was assessed by Western blotting. Results are representative of four to six experiments. (C) Cells were plated on Coll or FN, sheared for 30 min or kept as static controls, and stained for phosphorylated IKK and β1 integrin. Results are representative of three experiments. (D) Cells on Coll or FN were treated with 10 U/ml TNFα and stained for phosphorylated IKK and β1 integrin. Images are representative of three experiments.
Mentions: These results appear paradoxical but could be explained if the inhibitory p38 signal from Coll occurs locally within a specific compartment. To test this hypothesis, endothelial cells on Coll or FN were sheared for 5 min and active p38 was localized. Cells on Coll showed colocalization of phospho-p38 with β1 integrins, which was increased by shear stress (Fig. 6 A). Cells on FN showed only low levels of phospho-p38 staining, which is consistent with results from Western blotting.

Bottom Line: Flow-induced NF-kappaB activation is downstream of conformational activation of integrins, resulting in new integrin binding to the subendothelial extracellular matrix and signaling.Whereas endothelial cells plated on fibronectin or fibrinogen activate NF-kappaB in response to flow, cells on collagen or laminin do not.Furthermore, altering the extracellular matrix to promote p38 activation in cells on fibronectin suppresses NF-kappaB activation, suggesting a novel therapeutic strategy for treating atherosclerosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA.

ABSTRACT
Atherosclerotic plaque forms in regions of the vasculature exposed to disturbed flow. NF-kappaB activation by fluid flow, leading to expression of target genes such as E-selectin, ICAM-1, and VCAM-1, may regulate early monocyte recruitment and fatty streak formation. Flow-induced NF-kappaB activation is downstream of conformational activation of integrins, resulting in new integrin binding to the subendothelial extracellular matrix and signaling. Therefore, we examined the involvement of the extracellular matrix in this process. Whereas endothelial cells plated on fibronectin or fibrinogen activate NF-kappaB in response to flow, cells on collagen or laminin do not. In vivo, fibronectin and fibrinogen are deposited at atherosclerosis-prone sites before other signs of atherosclerosis. Ligation of integrin alpha2beta1 on collagen prevents flow-induced NF-kappaB activation through a p38-dependent pathway that is activated locally at adhesion sites. Furthermore, altering the extracellular matrix to promote p38 activation in cells on fibronectin suppresses NF-kappaB activation, suggesting a novel therapeutic strategy for treating atherosclerosis.

Show MeSH
Related in: MedlinePlus