Abstract 489: The Role of Hemodynamics in Modulating p120 and Kaiso Expression and Activity in Atherogenesis

Introduction. The generation of atherosclerosis has been shown to be a non-random process, with endothelial cells (ECs) in regions of disturbed hemodynamics developing an atheroprone (pro-inflammatory) phenotype. While a great deal of research has focused on hemodynamic regulation of EC phenotype, the mechanisms that mediate ECs’ response to local shear stress environment remain elusive. p120-catenin (p120) and its transcription factor binding partner Kaiso are expressed in ECs and possess a variety of functions that potentially contribute to the hemodynamic regulation of EC phenotype in atherosclerosis. Specifically, p120 has been shown to regulate adherens junction stability and regulate gene transcription through interaction with Kaiso. Hypothesis. We hypothesize hemodynamic forces modulate the activity of p120 and Kaiso in a manner that alters local endothelial susceptibility to atherogenesis. Methods. Atheroprone/protective hemodynamic profiles obtained by human carotid artery imaging were applied to human ECs in vitro . Protein/gene expression was then analyzed by Western blot, RT-PCR, and imaging. To determine Kaiso-dependent regulation of target gene expression, siRNAs were used to knockdown Kaiso expression. For in vivo validation, vasculature from Apolipoprotein E -/- mice was isolated, fixed, and stained. Results. In vitro, atheroprotective flow upregulates p120 expression and increases its junctional continuity and nuclear accumulation. There is a flow-dependent increase in Kaiso expression over time in both flow conditions, but p120/Kaiso interaction is increased under atheroprone flow. Kaiso knockdown under protective flow results in decreased expression of the anti-inflammatory genes eNOS (0.49 fold) and KLF2 (0.68 fold) and increased expression of the inflammatory marker VCAM (1.44 fold), suggesting a previously unknown anti-atherogenic function of Kaiso. In preliminary mouse studies, Kaiso is expressed in ECs overlying both healthy and diseased regions, as well as being highly expressed within the lesions. Conclusions. p120 and Kaiso expression are regulated in a flow-dependent manner and are potentially a mechanism by which hemodynamics modulate susceptibility to atherogenesis.