Abstract 14810: Sam68 Promotes Nf-kb Signaling and Inflammation and Impedes the Recovery of Arterial Injury
Background: The role of Src-associated in mitosis 68 kDa (Sam68) protein in cardiovascular biology has not been studied. A recent report suggests that Sam68 suppresses TNF-α-mediated NF-kB activation. Since NF-kB plays a critical role in vascular inflammation and injury via generation of inflammatory cytokines and recruitment of inflammatory cells, we sought to dissect the molecular mechanism by which Sam68 regulates NF-kB signaling and its functional significance during vascular injury.
Methods & Results: The endothelial denudation injury was induced in the carotid arteries of Sam68-null (Sam68-/-) and WT mice. Sam68-/- mice displayed an accelerated re-endothelialization (P<0.05 at day 5 post-injury) and attenuated neointima formation (by 2.2 folds, P<0.05, at day 14), which was associated with a reduced number of macrophages and lowered expression of pro-inflammatory cytokines (i.e., TNF-alpha, MCP-1 and IL-6) in the injured vessels. In cultured Raw264.7 macrophages, knockdown of Sam68 resulted in a significant reduction in the TNF-α-induced expression of TNF-α, MCP-1, and IL-6 and in the level of nuclear phospho-p65, which indicates attenuated NF-kB activation. These results were confirmed in peritoneal macrophages and macrophages differentiated from bone-marrow mononuclear cells of Sam68-/- and WT mice. To identify molecular mechanisms, Raw264.7 cells were treated with TNF-α and Vehicle, followed by Sam68 co-immunoprecipitation and mass-spectrometric identification of the Sam68-interacting proteins. We found that TNF-α treatment results in altered interactions of Sam68 with 22 cytosolic, cytoskeletal, and nuclear proteins. Further experiments are under way to validate their involvement in the NF-kB signaling.
Conclusions: Our results for the first time suggest that Sam68 promotes pro-inflammatory response in injured arteries and impedes recovery, and this effect may be partially attributable to the exaggerated NF-kB activity.
Author Disclosures: S. Han: None. J. Zhou: None. G. Qin: None.
This research has received full or partial funding support from the American Heart Association
- © 2014 by American Heart Association, Inc.