Abstract 5313: Reduction of S100A12 in Marfan Syndrome Aortic Smooth Muscle Cells Attenuates Inflammatory and Apoptotic Pathways
Marfan syndrome (MFS) is associated with thoracic aortic aneurysms. S100A12 has been associated with initiation of inflammatory pathways via activation of the receptor for advance glycation endproducts (RAGE) and is up regulated in smooth muscle cells of ruptured human coronary artery plaques. We tested the hypothesis that S100A12 is expressed in SMC in human aortic aneurysms of MFS, and that downregulation of S100A12 may suppress inflammatory and apoptosis pathways.
Methods: Aortic tissue from a patient undergoing surgery for MFS aneurysm and control aortic tissue were compared and several cell lines of primary SMC’s were established. SMC that carry a mutation in the FBN-1 gene (Arg529Term) and control SMC were each transfected with siRNA-S100A12-GFP and siRNA-control-GFP. GFP positve SMC were isolated by FACS, followed by qRT-RCR using arrays for inflammation and apoptosis pathways (RT2 profiler PCR Array, SA Biosciences).
Immunohistochemistry of aortic tissue from MFS revealed expression of S100A12 in SMC, but not in SMC of control aortic tissue. S100A12 was expressed strongest in SMC near the focal areas of medial degeneration.
Cultured SMC that carry the FBN-1 mutation strongly expressed S100A12 protein. S1090A12 expression was completely abolished by transfection with siRNA-S100A12-GFP construct but not with siRNA control-GFP construct.
S100A12 reduction in FBN-1 mutant SMC suppressed at least two fold the mRNA of 80% of genes on the inflammation array and of 91% of the genes on the apoptosis array.
The death receptor Fas, caspase 10 and effector caspases 3 and their substrate DFFA were probed using semi-quantitative immunoblotting. FBN-1 mutant SMC showed approximately 2-fold increase for Fas, and two fold increase in Casp3 and DFFA compared to control SMC. Treatment with Fas CH11 activating monoclonal antibody induced Casp3 approximately 12 fold in FBN-1 mutant SMC compared to a two fold induction in control SMC (p< 0.001). Reduction of S100A12 in FBN-1 mutant SMC reversed this pattern with s significant reduction in Fas, caspase 10 & 3, and DFFB. Summary: S100A12 is upregulated in SMC in thoracic aneurysms and reduction of S100A12 reduces Fas-mediated apoptosis in aortic SMC in MFS.
This research has received full or partial funding support from the American Heart Association, Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota & Wisconsin).