Abstract 16125: Pla2g7 is Crucial in Stem Cell Differentiation into Smooth Muscle Cells and Involves in Atherosclerosis
Background: Accumulating evidence suggests that phospholipase A2 group 7 (Pla2g7) is involved in cardiovascular development and vascular diseases because of its divergent functions in inflammation and oxidative stress/reactive oxygen species (ROS) balance. Our previous studies have demonstrated that embryonic stem (ES) cells can differentiate into smooth muscle cells (SMC) resulting from the maintenance of the ROS balance. In the present study, we aim to investigate the functional role of Pla2g7 in SMC differentiation.
Methods and Results: When ES cells were cultivated on collagen IV-coated plates, Pla2g7 was up-regulated significantly in parallel with SMC marker genes (SM22, SM alpha-actin, calponin and SM myosin heavy chain) following 4–14 days of cell differentiation, and co-localized with SMC markers in the differentiated ES cells. Knockdown of Pla2g7 resulted in down-regulation of smooth muscle specific markers, while enforced expression of Pla2g7 enhanced SMC differentiation and increased ROS generation in a dose-dependent manner. Interestingly, free radical scavenger NMPG and flavoprotein inhibitor DPI, but not hydrogen peroxide inhibitor catalase, retard Pla2g7-induced SMC differentiation gene expression. Moreover, we demonstrated that overexpression of nuclear factor erythroid 2-related factor 3 (Nrf3) resulted in increase of Pla2g7 production, while knockdown Nrf3 ablated the Pla2g7 gene expression and enzyme activity. Most importantly, we further demonstrated that NAPDH oxidase 4 (Nox4), another important mediator for SMC differentiation and ROS generation, is required for Nrf3-indueced Pla2g7 gene expression. Finally, Pla2g7 is up-regulated in mature SMC phenotype switching in the culture, highly expressed in atherosclerotic lesions of apoE−/− mice and decreased significantly in the vessels after injury.
Conclusions: Our findings demonstrated for the first time that Pla2g7 has a crucial role in SMC differentiation from stem cells, and the fine interactions between Nrf3, Nox4 and Pla2g7 is essential for ROS balance and SMC differentiation in vitro and in vivo, implicating that Pla2g7 could be potential new targets for switching SMC differentiation in vascular disease.
- © 2010 by American Heart Association, Inc.