Abstract 14741: CaMKIIδ Controls Neointimal Formation After Carotid Ligation and Vascular Smooth Muscle Cells Proliferation Through Regulation of the Akt/mdm2 Pathway
Smooth muscle proliferation contributes to vascular remodeling, obstructive vasculopathies and restenosis after percutaneous coronary interventions. The multifunctional Ca (2+)/calmodulin-dependent protein kinase II (CaMKII) regulates vascular smooth muscle cells proliferation, but the signaling pathways are poorly defined. We assessed the hypothesis that CaMKIIδ is critical in regulating smooth muscle cells proliferation through regulating cell cycle checkpoint proteins and further elucidated the signaling pathways. Carotid artery ligation was performed on CaMKIIδ−/− and control mice. CaMKII was strongly expressed in the neointima of littermate controls after carotid artery ligation by immunofluorescence. Control mice had prominent neointimal hyperplasia 2 weeks after carotid ligation (n=16, neointimal area 0.022±0.00373 mm2). In contrast, minimal neointimal hyperplasia was present in CaMKIIδ−/− mice (n=14, neointimal area 0.0039±0.003 mm2, p<0.01). This was mainly due to decreased cell proliferation in CaMKIIδ−/− mice without affecting apoptosis (BrdU-positive cells in neointima after 14 days: 0.2±0.7% vs. 14.17±5.5%, n=14, p<0.0001). Two weeks after carotid ligation, the cell cycle-dependent kinase cdk2 and its cognate cyclins E were increased in control mice by western blot compared with the sham side. In contrast, CaMKIIδ deletion enhanced the expression of the cdk inhibitor p21 but down-regulated cdk2 and cyclin E expression. In vitro, aortic smooth muscle cells from CaMKIIδ−/− mice were replication-deficient in culture. The expression of p21 was significantly increased and there was increased association of p21 with cdk4 and cdk2, which subsequently led to decreased cdk2 and 4 kinase activities. Finally, we detected decreased phosphorylation of Akt kinase and Mdm2, a regulator of p21 transcription under CaMKIIδ deletion. In addition, p21 expression was increased under Akt inhibition. In conclusion, CaMKII plays an essential role in smooth muscle proliferation by promoting cell cycle progression. Deletion of CaMKIIδ decreases cdk2 and cyclin E and increases p21 expression through regulating Akt phosphorylation. Our data provide a potential mechanistic link between CaMKII and neointimal proliferation.
- © 2010 by American Heart Association, Inc.