2nd Annual Meeting, March 17-19, 2016, Marriott Marquis, NYC
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Shear-Sensitive miRNA-181b Impairs Anti-Inflammatory Signaling in the Aortic Valve Endothelium
Jack Heath, Joan Fernandez Esmerats, Rachel Simmons, Sandeep Kumar, Hanjoong Jo.
Emory University, Atlanta, GA, USA.

Background: Aortic valve (AV) disease is a significant contributor to cardiovascular mortality. The process is regulated by both endothelial cells (ECs) at the valve surface and interstitial cells within the tissue. Tissue dysfunction occurs preferentially on the valve’s aortic side, where ECs are subjected to disturbed blood flow and oscillatory shear stress (OS). These ECs exhibit an inflammatory phenotype, whereas ECs on the opposite (ventricular) side experience laminar shear stress (LS) and an anti-inflammatory phenotype. Our research seeks to determine mechanisms responsible for differential endothelial responses to shear stress and potential therapeutic targets for AV disease.
Methods: In vitro shear stress experiments were carried out using our cone-and-plate shear system, as pictured above. LS was induced by parallel force of 20 dynes/cm2, and OS was induced at ± 5 dynes/cm2 for 24 hours. Gene knockdown, immunoprecipitation, and quantitative gene expression analysis were performed as previously described by our group.
Results: We have performed microarray studies revealing several endothelial shear-sensitive microRNAs (miRNAs), small molecules which repress messenger RNA (mRNA) translation by targeting the 3’ untranslated region matching the mRNA seed sequence. We found one miRNA, miRNA-181b, is upregulated in OS, correlating with increased expression of inflammatory adhesion molecules and decreased anti-inflammatory marker Klf2. OS also decreases expression of a predicted target of miRNA-181b, O-GlcNAc transferase (OGT), which adds the O-GlcNAc signaling moiety onto key amino acids of target proteins. Knockdown of OGT resulted in increased inflammation even in response to normally protective LS, suggesting a link between OGT and inflammation. Via immunoprecipitation studies, we discovered OGT binds specifically to MEF2C, a key anti-inflammatory transcription factor, and this binding is impaired in OS. The decreased binding of OGT to MEF2C results in an inhibition of MEF2C O-GlcNAc modification, which may affect the protein’s transcriptional activity.
Conclusions: Our results show an important pathway of transcriptional regulation of post-translational modification. Future studies are focused on mechanisms linking miRNA-181b to inflammatory signaling, and ex vivo/in vivo methods to determine therapeutic potential of inhibiting miRNA-181b. These studies may lead to new targets for AV disease treatment without surgical intervention.


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